title: Rate of return

text: Ordinary returns and logarithmic returns are only equal when they are zero, but they are approximately equal when they are small. The difference between them is large only when percent changes are high. For example, an arithmetic return of +50% is equivalent to a logarithmic return of 40.55%, while an arithmetic return of −50% is equivalent to a logarithmic return of −69.31%.


title: Rate of return

text: The geometric average rate of return is in general less than the arithmetic average return. The two averages are equal if (and only if) all the sub-period returns are equal. This is a consequence of the AM–GM inequality. The difference between the annualized return and average annual return increases with the variance of the returns – the more volatile the performance, the greater the difference.


title: Rate of return

text: For example, a return of +10%, followed by −10%, gives an arithmetic average return of 0%, but the overall result over the 2 subperiods is 110% x 90% = 99% for an overall return of −1%. The order in which the loss and gain occurs does not affect the result.


title: Rate of return

text: For a return of +20%, followed by −20%, this again has an average return of 0%, but an overall return of −4%.


title: Rate of return

text: A return of +100%, followed by −100%, has an average return of 0% but an overall return of −100% since the final value is 0.


title: Rate of return

text: In cases of leveraged investments, even more extreme results are possible: A return of +200%, followed by −200%, has an average return of 0% but an overall return of −300%.


title: Rate of return

text: This pattern is not followed in the case of logarithmic returns, due to their symmetry, as noted above. A logarithmic return of +10%, followed by −10%, gives an overall return of 10% − 10% = 0% and an average rate of return of zero also.


title: Rate of return

text: Investment returns are often published as "average returns". In order to translate average returns into overall returns, compound the average returns over the number of periods.


title: Rate of return

text: The geometric average rate of return was 5%. Over 4 years, this translates into an overall return of:


title: Rate of return

text: The geometric average return over the 4-year period was −1.64%. Over 4 years, this translates into an overall return of:


title: Rate of return

text: The geometric average return over the 4-year period was −42.74%. Over 4 years, this translates back into an overall return of:


title: Rate of return

text: Care must be taken not to confuse annual with annualized returns. An annual rate of return is a return over a period of one year, such as January 1 through December 31, or June 3, 2006, through June 2, 2007, whereas an annualized rate of return is a rate of return per year, measured over a period either longer or shorter than one year, such as a month, or two years, annualized for comparison with a one-year return.


title: Rate of return

text: For example, a return over one month of 1% converts to an annualized rate of return of 12.7% = ((1+0.01) − 1). This means if reinvested, earning 1% return every month, the return over 12 months would compound to give a return of 12.7%.


title: Rate of return

text: As another example, a two-year return of 10% converts to an annualized rate of return of 4.88% = ((1+0.1) − 1), assuming reinvestment at the end of the first year. In other words, the geometric average return per year is 4.88%.


title: Rate of return

text: In the cash flow example below, the dollar returns for the four years add up to $265. Assuming no reinvestment, the annualized rate of return for the four years is:


title: Rate of return

text: Factors that investors may use to determine the rate of return at which they are willing to invest money include:


title: Rate of return

text: The time value of money is reflected in the interest rate that a bank offers for deposit accounts, and also in the interest rate that a bank charges for a loan such as a home mortgage. The "risk-free" rate on US dollar investments is the rate on U.S. Treasury bills, because this is the highest rate available without risking capital.


title: Rate of return

text: The rate of return which an investor requires from a particular investment is called the discount rate, and is also referred to as the (opportunity) cost of capital. The higher the risk, the higher the discount rate (rate of return) the investor will demand from the investment.


title: Rate of return

text: The annualized return of an investment depends on whether or not the return, including interest and dividends, from one period is reinvested in the next period. If the return is reinvested, it contributes to the starting value of capital invested for the next period (or reduces it, in the case of a negative return). Compounding reflects the effect of the return in one period on the return in the next period, resulting from the change in the capital base at the start of the latter period.


title: Rate of return

text: For example, if an investor puts $1,000 in a 1-year certificate of deposit (CD) that pays an annual interest rate of 4%, paid quarterly, the CD would earn 1% interest per quarter on the account balance. The account uses compound interest, meaning the account balance is cumulative, including interest previously reinvested and credited to the account. Unless the interest is withdrawn at the end of each quarter, it will earn more interest in the next quarter.


title: Rate of return

text: At the beginning of the second quarter, the account balance is $1,010.00, which then earns $10.10 interest altogether during the second quarter. The extra dime was interest on the additional $10 investment from the previous interest accumulated in the account. The annualized return (annual percentage yield, compound interest) is higher than for simple interest because the interest is reinvested as capital and then itself earns interest. The yield or annualized return on the above investment is formula_80.


title: Rate of return

text: As explained above, the return, or rate or return, depends on the currency of measurement. In the example given above, a US dollar cash deposit which returns 2% over a year, measured in US dollars, returns 12.2% measured in Japanese yen, over the same period, if the US dollar increases in value by 10% against the Japanese yen over the same period.


title: Rate of return

text: The return in Japanese yen is the result of compounding the 2% US dollar return on the cash deposit with the 10% return on US dollars against Japanese yen:


title: Rate of return

text: In more general terms, the return in a second currency is the result of compounding together the two returns:


title: Rate of return

text: This holds true if either the time-weighted method is used, or there are no flows in or out over the period. If using one of the money-weighted methods, and there are flows, it is necessary to recalculate the return in the second currency using one of the methods for compensating for flows.


title: Rate of return

text: It is not meaningful to compound together returns for consecutive periods measured in different currencies. Before compounding together returns over consecutive periods, recalculate or adjust the returns using a single currency of measurement.


title: Rate of return

text: A portfolio increases in value in Singapore dollars by 10% over the 2015 calendar year (with no flows in or out of the portfolio over the year). In the first month of 2016, it increases in value by another 7%, in US dollars. (Again, there are no inflows or outflows over the January 2016 period.)


title: Rate of return

text: The answer is that there is insufficient data to compute a return, in any currency, without knowing the return for both periods in the same currency.


title: Rate of return

text: If the return in 2015 was 10% in Singapore dollars, and the Singapore dollar rose by 5% against the US dollar over 2015, then so long as there were no flows in 2015, the return over 2015 in US dollars is:


title: Rate of return

text: Investments carry varying amounts of risk that the investor will lose some or all of the invested capital. For example, investments in company stock shares put capital at risk. Unlike capital invested in a savings account, the share price, which is the market value of a stock share at a certain point in time, depends on what someone is willing to pay for it, and the price of a stock share tends to change continually when the market for that share is open. If the price is relatively stable, the stock is said to have "low volatility". If the price often changes a great deal, the stock has "high volatility".


title: Rate of return

text: To the right is an example of a stock investment of one share purchased at the beginning of the year for $100.


title: Rate of return

text: To calculate the capital gain for US income tax purposes, include the reinvested dividends in the cost basis. The investor received a total of $4.06 in dividends over the year, all of which were reinvested, so the cost basis increased by $4.06.


title: Rate of return

text: For U.S. income tax purposes therefore, dividends were $4.06, the cost basis of the investment was $104.06 and if the shares were sold at the end of the year, the sale value would be $103.02, and the capital loss would be $1.04.


title: Rate of return

text: Mutual funds, unit investment trusts or UITs, insurance separate accounts and related variable products such as variable universal life insurance policies and variable annuity contracts, and bank-sponsored commingled funds, collective benefit funds or common trust funds, all derive their value from an underlying investment portfolio. Investors and other parties are interested to know how the investment has performed over various periods of time.


title: Rate of return

text: Performance is usually quantified by a fund's total return. In the 1990s, many different fund companies were advertising various total returns—some cumulative, some averaged, some with or without deduction of sales loads or commissions, etc. To level the playing field and help investors compare performance returns of one fund to another, the U.S. Securities and Exchange Commission (SEC) began requiring funds to compute and report total returns based upon a standardized formula—so-called "SEC Standardized total return", which is the average annual total return assuming reinvestment of dividends and distributions and deduction of sales loads or charges. Funds may compute and advertise returns on other bases (so-called "non-standardized" returns), so long as they also publish no less prominently the "standardized" return data.


title: Rate of return

text: Subsequent to this, apparently investors who had sold their fund shares after a large increase in the share price in the late 1990s and early 2000s were ignorant of how significant the impact of income/capital gain taxes was on their fund "gross" returns. That is, they had little idea how significant the difference could be between "gross" returns (returns before federal taxes) and "net" returns (after-tax returns). In reaction to this apparent investor ignorance, and perhaps for other reasons, the SEC made further rulemaking to require mutual funds to publish in their annual prospectus, among other things, total returns before and after the impact of US federal individual income taxes. And further, the after-tax returns would include 1) returns on a hypothetical taxable account after deducting taxes on dividends and capital gain distributions received during the illustrated periods and 2) the impacts of the items in #1) as well as assuming the entire investment shares were sold at the end of the period (realizing capital gain/loss on liquidation of the shares). These after-tax returns would apply of course only to taxable accounts and not to tax-deferred or retirement accounts such as IRAs.


title: Rate of return

text: Lastly, in more recent years, "personalized" brokerage account statements have been demanded by investors. In other words, the investors are saying more or less that the fund returns may not be what their actual account returns are, based upon the actual investment account transaction history. This is because investments may have been made on various dates and additional purchases and withdrawals may have occurred which vary in amount and date and thus are unique to the particular account. More and more funds and brokerage firms are now providing personalized account returns on investor's account statements in response to this need.


title: Rate of return

text: With that out of the way, here's how basic earnings and gains/losses work on a mutual fund. The fund records income for dividends and interest earned which typically increases the value of the mutual fund shares, while expenses set aside have an offsetting impact to share value. When the fund's investments increase (decrease) in market value, so too the fund shares value increases (or decreases). When the fund sells investments at a profit, it turns or reclassifies that paper profit or unrealized gain into an actual or realized gain. The sale has no effect on the value of fund shares but it has reclassified a component of its value from one bucket to another on the fund books—which will have future impact to investors. At least annually, a fund usually pays dividends from its net income (income less expenses) and net capital gains realized out to shareholders as an IRS requirement. This way, the fund pays no taxes but rather all the investors in taxable accounts do. Mutual fund share prices are typically valued each day the stock or bond markets are open and typically the value of a share is the net asset value of the fund shares investors own.


title: Rate of return

text: Mutual funds report total returns assuming reinvestment of dividend and capital gain distributions. That is, the dollar amounts distributed are used to purchase additional shares of the funds as of the reinvestment/ex-dividend date. Reinvestment rates or factors are based on total distributions (dividends plus capital gains) during each period.


title: Rate of return

text: US mutual funds are to compute average annual total return as prescribed by the U.S. Securities and Exchange Commission (SEC) in instructions to form N-1A (the fund prospectus) as the average annual compounded rates of return for 1-year, 5-year, and 10-year periods (or inception of the fund if shorter) as the "average annual total return" for each fund. The following formula is used:


title: Rate of return

text: ERV = ending redeemable value of a hypothetical $1,000 payment made at the beginning of the 1-, 5-, or 10-year periods at the end of the 1-, 5-, or 10-year periods (or fractional portion)


title: Rate of return

text: Mutual funds include capital gains as well as dividends in their return calculations. Since the market price of a mutual fund share is based on net asset value, a capital gain distribution is offset by an equal decrease in mutual fund share value/price. From the shareholder's perspective, a capital gain distribution is not a net gain in assets, but it is a realized capital gain (coupled with an equivalent decrease in unrealized capital gain).


title: High-temperature superconductivity

text: High-temperature superconductors (abbreviated high- or HTS) are defined as materials that behave as superconductors at temperatures above , the boiling point of liquid nitrogen. The adjective "high temperature" is only in respect to previously known superconductors, which function at even colder temperatures close to absolute zero. In absolute terms, these "high temperatures" are still far below ambient, and therefore require cooling. The first high-temperature superconductor was discovered in 1986, by IBM researchers Bednorz and Müller, who were awarded the Nobel Prize in Physics in 1987 "for their important break-through in the discovery of superconductivity in ceramic materials". Most high- materials are type-II superconductors.


title: High-temperature superconductivity

text: The major advantage of high-temperature superconductors is that they can be cooled by using liquid nitrogen, as opposed to the previously known superconductors which require expensive and hard-to-handle coolants, primarily liquid helium. A second advantage of high- materials is they retain their superconductivity in higher magnetic fields than previous materials. This is important when constructing superconducting magnets, a primary application of high- materials.


title: High-temperature superconductivity

text: The majority of high-temperature superconductors are ceramic materials, as opposed to the previously known metallic materials. Ceramic superconductors are suitable for some practical uses but they still have many manufacturing issues. For example, most ceramics are brittle which makes the fabrication of wires from them very problematic. However, overcoming these drawbacks is the subject of considerable research, and progress is ongoing.


title: High-temperature superconductivity

text: The main class of high-temperature superconductors is copper oxides combined with other metals, especially the Rare-earth barium copper oxides (REBCOs) such as Yttrium barium copper oxide (YBCO). The second class of high-temperature superconductors in the practical classification is the iron-based compounds.


title: High-temperature superconductivity

text: Magnesium diboride is sometimes included in high-temperature superconductors: It is relatively simple to manufacture, but it superconducts only below 43°K, which makes it unsuitable for liquid nitrogen cooling (approximately 30 °K below nitrogen triple point temperature). Some extremely-high pressure superhydride compounds are usually categorized as high-temperature superconductors. In fact, many articles on high-temperature superconductors can be found on this research on high pressure gases, which are not suitable for practical applications. The current record holder is carbonaceous sulfur hydride, beating the previous record held by lanthanum decahydride by nearly 30 °K. The superconductivity in these compounds, however, has recently come under question.


title: High-temperature superconductivity

text: Superconductivity was discovered by Kamerlingh Onnes in 1911, in a metal solid. Ever since, researchers have attempted to observe superconductivity at increasing temperatures with the goal of finding a room-temperature superconductor.


title: High-temperature superconductivity

text: By the late 1970s, superconductivity was observed in several metallic compounds (in particular Nb-based, such as NbTi, NbSn, and NbGe) at temperatures that were much higher than those for elemental metals and which could even exceed .


title: High-temperature superconductivity

text: In 1986, at the IBM research lab near Zurich, in Switzerland, Bednorz and Müller were looking for superconductivity in a new class of ceramics: the "copper oxides", or "cuprates".


title: High-temperature superconductivity

text: Bednorz encountered a particular copper oxide whose resistance dropped to zero at a temperature around . Their results were soon confirmed by many groups, notably Paul Chu at the University of Houston and Shoji Tanaka at the University of Tokyo.


title: High-temperature superconductivity

text: In 1987, Anderson gave the first theoretical description of these materials, based on the resonating valence bond theory, but a full understanding of these materials is still developing today. These superconductors are now known to possess a "d"-wave pair symmetry. The first proposal that high-temperature cuprate superconductivity involves "d"-wave pairing was made in 1987 by Bickers, Scalapino and Scalettar, followed by three subsequent theories in 1988 by Inui, Doniach, Hirschfeld and Ruckenstein, using spin-fluctuation theory, and by Gros, Poilblanc, Rice and Zhang, and by Kotliar and Liu identifying "d"-wave pairing as a natural consequence of the RVB theory. The confirmation of the "d"-wave nature of the cuprate superconductors was made by a variety of experiments, including the direct observation of the "d"-wave nodes in the excitation spectrum through Angle Resolved Photoemission Spectroscopy, the observation of a half-integer flux in tunneling experiments, and indirectly from the temperature dependence of the penetration depth, specific heat and thermal conductivity.


title: High-temperature superconductivity

text: As of 2021, the superconductor with the highest transition temperature at ambient pressure is the cuprate of mercury, barium, and calcium, at around 133 K. There are other superconductors with higher recorded transition temperaturesfor example lanthanum superhydride at 250 K, but these only occur at very high pressures.


title: High-temperature superconductivity

text: The origin of high-temperature superconductivity is still not clear, but it seems that instead of "electron-phonon" attraction mechanisms, as in conventional superconductivity, one is dealing with genuine "electronic" mechanisms (e.g. by antiferromagnetic correlations), and instead of conventional, purely "s"-wave pairing, more exotic pairing symmetries are thought to be involved ("d"-wave in the case of the cuprates; primarily extended "s"-wave, but occasionally "d"-wave, in the case of the iron-based superconductors).


title: High-temperature superconductivity

text: In 2014, evidence showing that fractional particles can happen in quasi two-dimensional magnetic materials, was found by EPFL scientists lending support for Anderson's theory of high-temperature superconductivity.


title: High-temperature superconductivity

text: Unfortunately, the "High-temperature" superconductor class has had many definitions in the context of superconductivity.


title: High-temperature superconductivity

text: The label high- should be reserved for materials with critical temperatures greater than the boiling point of liquid nitrogen. However, a number of materialsincluding the original discovery and recently discovered pnictide superconductorshave critical temperatures below 77 K but nonetheless, are commonly referred to in publications as high- class.


title: High-temperature superconductivity

text: A substance with a critical temperature above the boiling point of liquid nitrogen, together with a high critical magnetic field and critical current density (above which superconductivity is destroyed), would greatly benefit technological applications. In magnet applications, the high critical magnetic field may prove more valuable than the high itself. Some cuprates have an upper critical field of about 100 tesla. However, cuprate materials are brittle ceramics which are expensive to manufacture and not easily turned into wires or other useful shapes. Furthermore, high-temperature superconductors do not form large, continuous superconducting domains, rather clusters of microdomains within which superconductivity occurs. They are therefore unsuitable for applications requiring actual superconductive currents, such as magnets for magnetic resonance spectrometers. For a solution to this (powders), see HTS_wire.


title: High-temperature superconductivity

text: There has been considerable debate regarding high-temperature superconductivity coexisting with magnetic ordering in YBCO, iron-based superconductors, several ruthenocuprates and other exotic superconductors, and the search continues for other families of materials. HTS are Type-II superconductors, which allow magnetic fields to penetrate their interior in quantized units of flux, meaning that much higher magnetic fields are required to suppress superconductivity. The layered structure also gives a directional dependence to the magnetic field response.


title: High-temperature superconductivity

text: All known high- superconductors are Type-II superconductors. In contrast to Type-I superconductors, which expel all magnetic fields due to the Meissner effect, Type-II superconductors allow magnetic fields to penetrate their interior in quantized units of flux, creating "holes" or "tubes" of normal metallic regions in the superconducting bulk called vortices. Consequently, high- superconductors can sustain much higher magnetic fields.


title: High-temperature superconductivity

text: Cuprates are layered materials, consisting of superconducting layers of copper oxide, separated by spacer layers.


title: High-temperature superconductivity

text: Cuprates generally have a structure close to that of a two-dimensional material. Their superconducting properties are determined by electrons moving within weakly coupled copper-oxide (CuO) layers. Neighbouring layers contain ions such as lanthanum, barium, strontium, or other atoms which act to stabilize the structure and dope electrons or holes onto the copper-oxide layers. The undoped "parent" or "mother" compounds are Mott insulators with long-range antiferromagnetic order at sufficiently low temperatures. Single band models are generally considered to be enough to describe the electronic properties.


title: High-temperature superconductivity

text: The cuprate superconductors adopt a perovskite structure. The copper-oxide planes are checkerboard lattices with squares of O ions with a Cu ion at the centre of each square. The unit cell is rotated by 45° from these squares. Chemical formulae of superconducting materials generally contain fractional numbers to describe the doping required for superconductivity. There are several families of cuprate superconductors and they can be categorized by the elements they contain and the number of adjacent copper-oxide layers in each superconducting block. For example, YBCO and BSCCO can alternatively be referred to as "Y123" and Bi2201/Bi2212/Bi2223 depending on the number of layers in each superconducting block (). The superconducting transition temperature has been found to peak at an optimal doping value (=0.16) and an optimal number of layers in each superconducting block, typically =3.


title: High-temperature superconductivity

text: Possible mechanisms for superconductivity in the cuprates continue to be the subject of considerable debate and further research. Certain aspects common to all materials have been identified. Similarities between the antiferromagnetic the low-temperature state of undoped materials and the superconducting state that emerges upon doping, primarily the orbital state of the Cu ions, suggest that electron-electron interactions are more significant than electron-phonon interactions in cupratesmaking the superconductivity unconventional. Recent work on the Fermi surface has shown that nesting occurs at four points in the antiferromagnetic Brillouin zone where spin waves exist and that the superconducting energy gap is larger at these points. The weak isotope effects observed for most cuprates contrast with conventional superconductors that are well described by BCS theory.


title: High-temperature superconductivity

text: The electronic structure of superconducting cuprates is highly anisotropic (see the crystal structure of YBCO or BSCCO). Therefore, the Fermi surface of HTSC is very close to the Fermi surface of the doped CuO plane (or multi-planes, in case of multi-layer cuprates) and can be presented on the 2‑D reciprocal space (or momentum space) of the CuO lattice. The typical Fermi surface within the first CuO Brillouin zone is sketched in Fig. 1 (left). It can be derived from the band structure calculations or measured by angle resolved photoemission spectroscopy (ARPES). Fig. 1 (right) shows the Fermi surface of BSCCO measured by ARPES. In a wide range of charge carrier concentration (doping level), in which the hole-doped HTSC are superconducting, the Fermi surface is hole-like ("i.e." open, as shown in Fig. 1). This results in an inherent in-plane anisotropy of the electronic properties of HTSC. In 2018, the full three dimensional Fermi surface structure was derived from soft x-ray ARPES.


title: High-temperature superconductivity

text: Iron-based superconductors contain layers of iron and a pnictogensuch as arsenic or phosphorusor a chalcogen. This is currently the family with the second highest critical temperature, behind the cuprates. Interest in their superconducting properties began in 2006 with the discovery of superconductivity in LaFePO at 4 K and gained much greater attention in 2008 after the analogous material LaFeAs(O,F) was found to superconduct at up to 43 K under pressure.


title: High-temperature superconductivity

text: The highest critical temperatures in the iron-based superconductor family exist in thin films of FeSe, where a critical temperature in excess of 100 K was reported in 2014.


title: High-temperature superconductivity

text: Most undoped iron-based superconductors show a tetragonal-orthorhombic structural phase transition followed at lower temperature by magnetic ordering, similar to the cuprate superconductors. However, they are poor metals rather than Mott insulators and have five bands at the Fermi surface rather than one.


title: High-temperature superconductivity

text: The phase diagram emerging as the iron-arsenide layers are doped is remarkably similar, with the superconducting phase close to or overlapping the magnetic phase. Strong evidence that the value varies with the As-Fe-As bond angles has already emerged and shows that the optimal value is obtained with undistorted FeAs tetrahedra. The symmetry of the pairing wavefunction is still widely debated, but an extended "s"-wave scenario is currently favoured.


title: High-temperature superconductivity

text: Magnesium diboride is occasionally referred to as a high-temperature superconductor because its value of 39 K is above that historically expected for BCS superconductors. However, it is more generally regarded as the highest conventional superconductor, the increased resulting from two separate bands being present at the Fermi level.


title: High-temperature superconductivity

text: In 1991 Hebard et al discovered Fulleride superconductors, where alkali-metal atoms are intercalated into C molecules.


title: High-temperature superconductivity

text: P-doped Graphane was proposed in 2010 to be capable of sustaining high-temperature superconductivity.


title: High-temperature superconductivity

text: In 1999, Anisimov et al. conjectured superconductivity in nickelates, proposing nickel oxides as direct analogs to the cuprate superconductors. Superconductivity in an infinite-layer nickelate, NdSrNiO, was reported at the end of 2019 with a superconducting transition temperature between 9 and 15 K. This superconducting phase is observed in oxygen-reduced thin films created by the pulsed laser deposition of NdSrNiO onto SrTiO substrates that is then reduced to NdSrNiO via annealing the thin films at in the presence of CaH. The superconducting phase is only observed in the oxygen reduced film and is not seen in oxygen reduced bulk material of the same stoichiometry, suggesting that the strain induced by the oxygen reduction of the NdSrNiO thin film changes the phase space to allow for superconductivity.


title: High-temperature superconductivity

text: Of important is further to extract access hydrogen from the reduction with CaH, otherwise topotactic hydrogen may prevent superconductivity.


title: High-temperature superconductivity

text: The structure of cuprates which are superconductors are often closely related to perovskite structure, and the structure of these compounds has been described as a distorted, oxygen deficient multi-layered perovskite structure. One of the properties of the crystal structure of oxide superconductors is an alternating multi-layer of CuO planes with superconductivity taking place between these layers. The more layers of CuO, the higher . This structure causes a large anisotropy in normal conducting and superconducting properties, since electrical currents are carried by holes induced in the oxygen sites of the CuO sheets. The electrical conduction is highly anisotropic, with a much higher conductivity parallel to the CuO plane than in the perpendicular direction. Generally, critical temperatures depend on the chemical compositions, cations substitutions and oxygen content. They can be classified as superstripes; i.e., particular realizations of superlattices at atomic limit made of superconducting atomic layers, wires, dots separated by spacer layers, that gives multiband and multigap superconductivity.


title: High-temperature superconductivity

text: An yttrium–barium cuprate, YBaCuO (or Y123), was the first superconductor found above liquid nitrogen boiling point. There are two atoms of Barium for each atom of Yttrium.


title: High-temperature superconductivity

text: The proportions of the three different metals in the YBaCuO superconductor are in the mole ratio of 1 to 2 to 3 for yttrium to barium to copper, respectively: this particular superconductor has also often been referred to as the 123 superconductor.


title: High-temperature superconductivity

text: The unit cell of YBaCuO consists of three perovskite unit cells, which is pseudocubic, nearly orthorombic. The other superconducting cuprates have another structure: they have a tetragonal cell.


title: High-temperature superconductivity

text: Each perovskite cell contains a Y or Ba atom at the center: Ba in the bottom unit cell, Y in the middle one, and Ba in the top unit cell. Thus, Y and Ba are stacked in the sequence [Ba–Y–Ba] along the c-axis. All corner sites of the unit cell are occupied by Cu, which has two different coordinations, Cu(1) and Cu(2), with respect to oxygen. There are four possible crystallographic sites for oxygen: O(1), O(2), O(3) and O(4). The coordination polyhedra of Y and Ba with respect to oxygen are different. The tripling of the perovskite unit cell leads to nine oxygen atoms, whereas YBaCuO has seven oxygen atoms and, therefore, is referred to as an oxygen-deficient perovskite structure. The structure has a stacking of different layers: (CuO)(BaO)(CuO)(Y)(CuO)(BaO)(CuO). One of the key feature of the unit cell of YBaCuO (YBCO) is the presence of two layers of CuO. The role of the Y plane is to serve as a spacer between two CuO planes. In YBCO, the Cu–O chains are known to play an important role for superconductivity. is maximal near 92 K when "x" ≈ 0.15 and the structure is orthorhombic. Superconductivity disappears at "x" ≈ 0.6, where the structural transformation of YBCO occurs from orthorhombic to tetragonal.


title: High-temperature superconductivity

text: Problems in these superconductors arise because of the existence of three or more phases having a similar layered structure.


title: High-temperature superconductivity

text: Moreover, the crystal structure of other tested cuprate superconductors are very similar. Like YBCO, the perovskite-type feature and the presence of simple copper oxide (CuO) layers also exist in these superconductors. However, unlike YBCO, Cu–O chains are not present in these superconductors. The YBCO superconductor has an orthorhombic structure, whereas the other high- superconductors have a tetragonal structure.


title: High-temperature superconductivity

text: There are three main classes of superconducting cuprates: bismuth-based, thallium-based and mercury-based.


title: High-temperature superconductivity

text: The second cuprate by practical importance is currently BSCCO, a compound of Bi–Sr–Ca-Cu-O. The content of bismuth and strontium creates some chemical issues.


title: High-temperature superconductivity

text: These three phases are Bi-2201, Bi-2212 and Bi-2223, having transition temperatures of 20, 85 and 110 K, respectively, where the numbering system represent number of atoms for Bi Sr, Ca and Cu respectively. The two phases have a tetragonal structure which consists of two sheared crystallographic unit cells. The unit cell of these phases has double Bi–O planes which are stacked in a way that the Bi atom of one plane sits below the oxygen atom of the next consecutive plane. The Ca atom forms a layer within the interior of the CuO layers in both Bi-2212 and Bi-2223; there is no Ca layer in the Bi-2201 phase. The three phases differ with each other in the number of cuprate planes; Bi-2201, Bi-2212 and Bi-2223 phases have one, two and three CuO planes, respectively. The "c" axis lattice constants of these phases increases with the number of cuprate planes (see table below). The coordination of the Cu atom is different in the three phases. The Cu atom forms an octahedral coordination with respect to oxygen atoms in the 2201 phase, whereas in 2212, the Cu atom is surrounded by five oxygen atoms in a pyramidal arrangement. In the 2223 structure, Cu has two coordinations with respect to oxygen: one Cu atom is bonded with four oxygen atoms in square planar configuration and another Cu atom is coordinated with five oxygen atoms in a pyramidal arrangement.


title: High-temperature superconductivity

text: Cuprate of Tl–Ba–Ca: The first series of the Tl-based superconductor containing one Tl–O layer has the general formula TlBaCaCuO, whereas the second series containing two Tl–O layers has a formula of TlBaCaCuO with "n" =1, 2 and 3. In the structure of TlBaCuO (Tl-2201), there is one CuO layer with the stacking sequence (Tl–O) (Tl–O) (Ba–O) (Cu–O) (Ba–O) (Tl–O) (Tl–O). In TlBaCaCuO (Tl-2212), there are two Cu–O layers with a Ca layer in between. Similar to the TlBaCuO structure, Tl–O layers are present outside the Ba–O layers. In TlBaCaCuO (Tl-2223), there are three CuO layers enclosing Ca layers between each of these. In Tl-based superconductors, is found to increase with the increase in CuO layers. However, the value of decreases after four CuO layers in TlBaCaCuO, and in the TlBaCaCuO compound, it decreases after three CuO layers.


title: High-temperature superconductivity

text: Cuprate of Hg–Ba–Ca The crystal structure of HgBaCuO (Hg-1201), HgBaCaCuO (Hg-1212) and HgBaCaCuO (Hg-1223) is similar to that of Tl-1201, Tl-1212 and Tl-1223, with Hg in place of Tl. It is noteworthy that the of the Hg compound (Hg-1201) containing one CuO layer is much larger as compared to the one-CuO-layer compound of thallium (Tl-1201). In the Hg-based superconductor, is also found to increase as the CuO layer increases. For Hg-1201, Hg-1212 and Hg-1223, the values of are 94, 128, and the record value at ambient pressure 134 K, respectively, as shown in table below. The observation that the of Hg-1223 increases to 153 K under high pressure indicates that the of this compound is very sensitive to the structure of the compound.


title: High-temperature superconductivity

text: The simplest method for preparing ceramic superconductors is a solid-state thermochemical reaction involving mixing, calcination and sintering.


title: High-temperature superconductivity

text: The appropriate amounts of precursor powders, usually oxides and carbonates, are mixed thoroughly using a Ball mill. Solution chemistry processes such as coprecipitation, freeze-drying and sol–gel methods are alternative ways for preparing a homogeneous mixture. These powders are calcined in the temperature range from 800–950 °C for several hours. The powders are cooled, reground and calcined again. This process is repeated several times to get homogeneous material. The powders are subsequently compacted to pellets and sintered. The sintering environment such as temperature, annealing time, atmosphere and cooling rate play a very important role in getting good high- superconducting materials. The YBaCuO compound is prepared by calcination and sintering of a homogeneous mixture of YO, BaCO and CuO in the appropriate atomic ratio. Calcination is done at 900–950 °C, whereas sintering is done at 950 °C in an oxygen atmosphere. The oxygen stoichiometry in this material is very crucial for obtaining a superconducting YBaCuO compound. At the time of sintering, the semiconducting tetragonal YBaCuO compound is formed, which, on slow cooling in oxygen atmosphere, turns into superconducting YBaCuO. The uptake and loss of oxygen are reversible in YBaCuO. A fully oxygenated orthorhombic YBaCuO sample can be transformed into tetragonal YBaCuO by heating in a vacuum at temperature above 700 °C.


title: High-temperature superconductivity

text: The preparation of Bi-, Tl- and Hg-based high- superconductors is more difficult than the YBCO preparation. Problems in these superconductors arise because of the existence of three or more phases having a similar layered structure. Thus, syntactic intergrowth and defects such as stacking faults occur during synthesis and it becomes difficult to isolate a single superconducting phase. For Bi–Sr–Ca–Cu–O, it is relatively simple to prepare the Bi-2212 ( ≈ 85 K) phase, whereas it is very difficult to prepare a single phase of Bi-2223 ( ≈ 110 K). The Bi-2212 phase appears only after few hours of sintering at 860–870 °C, but the larger fraction of the Bi-2223 phase is formed after a long reaction time of more than a week at 870 °C. Although the substitution of Pb in the Bi–Sr–Ca–Cu–O compound has been found to promote the growth of the high- phase, a long sintering time is still required.


title: High-temperature superconductivity

text: The question of how superconductivity arises in high-temperature superconductors is one of the major unsolved problems of theoretical condensed matter physics. The mechanism that causes the electrons in these crystals to form pairs is not known. Despite intensive research and many promising leads, an explanation has so far eluded scientists. One reason for this is that the materials in question are generally very complex, multi-layered crystals (for example, BSCCO), making theoretical modelling difficult.


title: High-temperature superconductivity

text: Improving the quality and variety of samples also gives rise to considerable research, both with the aim of improved characterisation of the physical properties of existing compounds, and synthesizing new materials, often with the hope of increasing . Technological research focuses on making HTS materials in sufficient quantities to make their use economically viable and optimizing their properties in relation to applications.


title: High-temperature superconductivity

text: Metallic Hydrogen has been proposed as a room-temperature superconductor, some experimental observations have detected the occurrence of the Meissner effect


title: High-temperature superconductivity

text: There have been two representative theories for high-temperature or unconventional superconductivity.


title: High-temperature superconductivity

text: Firstly, weak coupling theory suggests superconductivity emerges from antiferromagnetic spin fluctuations in a doped system. According to this theory, the pairing wave function of the cuprate HTS should have a "d" symmetry. Thus, determining whether the pairing wave function has "d"-wave symmetry is essential to test the spin fluctuation mechanism. That is, if the HTS order parameter (a pairing wave function like in Ginzburg–Landau theory) does not have "d"-wave symmetry, then a pairing mechanism related to spin fluctuations can be ruled out. (Similar arguments can be made for iron-based superconductors but the different material properties allow a different pairing symmetry.) Secondly, there was the interlayer coupling model, according to which a layered structure consisting of BCS-type ("s"-wave symmetry) superconductors can enhance the superconductivity by itself. By introducing an additional tunnelling interaction between each layer, this model successfully explained the anisotropic symmetry of the order parameter as well as the emergence of the HTS. Thus, in order to solve this unsettled problem, there have been numerous experiments such as photoemission spectroscopy, NMR, specific heat measurements, etc. Up to date the results were ambiguous, some reports supported the "d" symmetry for the HTS whereas others supported the "s" symmetry. This muddy situation possibly originated from the indirect nature of the experimental evidence, as well as experimental issues such as sample quality, impurity scattering, twinning, etc.


title: High-temperature superconductivity

text: This summary makes an implicit assumption: superconductive properties can be treated by mean-field theory. It also fails to mention that in addition to the superconductive gap, there is a second gap, the pseudogap. The cuprate layers are insulating, and the superconductors are doped with interlayer impurities to make them metallic. The superconductive transition temperature can be maximized by varying the dopant concentration. The simplest example is LaCuO, which consist of alternating CuO and LaO layers which are insulating when pure. When 8% of the La is replaced by Sr, the latter act as dopants, contributing holes to the CuO layers, and making the sample metallic. The Sr impurities also act as electronic bridges, enabling interlayer coupling. Proceeding from this picture, some theories argue that the basic pairing interaction is still interaction with phonons, as in the conventional superconductors with Cooper pairs. While the undoped materials are antiferromagnetic, even a few percent of impurity dopants introduce a smaller pseudogap in the CuO planes which is also caused by phonons. The gap decreases with increasing charge carriers, and as it nears the superconductive gap, the latter reaches its maximum. The reason for the high transition temperature is then argued to be due to the percolating behaviour of the carriersthe carriers follow zig-zag percolative paths, largely in metallic domains in the CuO planes, until blocked by charge density wave domain walls, where they use dopant bridges to cross over to a metallic domain of an adjacent CuO plane. The transition temperature maxima are reached when the host lattice has weak bond-bending forces, which produce strong electron-phonon interactions at the interlayer dopants.


title: High-temperature superconductivity

text: An experiment based on flux quantization of a three-grain ring of YBaCuO (YBCO) was proposed to test the symmetry of the order parameter in the HTS. The symmetry of the order parameter could best be probed at the junction interface as the Cooper pairs tunnel across a Josephson junction or weak link.


title: High-temperature superconductivity

text: It was expected that a half-integer flux, that is, a spontaneous magnetization could only occur for a junction of "d" symmetry superconductors. But, even if the junction experiment is the strongest method to determine the symmetry of the HTS order parameter, the results have been ambiguous. John R. Kirtley and C. C. Tsuei thought that the ambiguous results came from the defects inside the HTS, so that they designed an experiment where both clean limit (no defects) and dirty limit (maximal defects) were considered simultaneously. In the experiment, the spontaneous magnetization was clearly observed in YBCO, which supported the "d" symmetry of the order parameter in YBCO. But, since YBCO is orthorhombic, it might inherently have an admixture of "s" symmetry. So, by tuning their technique further, they found that there was an admixture of "s" symmetry in YBCO within about 3%. Also, they found that there was a pure "d" order parameter symmetry in the tetragonal TlBaCuO.


title: High-temperature superconductivity

text: Despite all these years, the mechanism of high- superconductivity is still highly controversial, mostly due to the lack of exact theoretical computations on such strongly interacting electron systems. However, most rigorous theoretical calculations, including phenomenological and diagrammatic approaches, converge on magnetic fluctuations as the pairing mechanism for these systems. The qualitative explanation is as follows:


title: High-temperature superconductivity

text: In a superconductor, the flow of electrons cannot be resolved into individual electrons, but instead consists of many pairs of bound electrons, called Cooper pairs. In conventional superconductors, these pairs are formed when an electron moving through the material distorts the surrounding crystal lattice, which in turn attracts another electron and forms a bound pair. This is sometimes called the "water bed" effect. Each Cooper pair requires a certain minimum energy to be displaced, and if the thermal fluctuations in the crystal lattice are smaller than this energy the pair can flow without dissipating energy. This ability of the electrons to flow without resistance leads to superconductivity.


title: High-temperature superconductivity

text: In a high- superconductor, the mechanism is extremely similar to a conventional superconductor, except, in this case, phonons virtually play no role and their role is replaced by spin-density waves. Just as all known conventional superconductors are strong phonon systems, all known high- superconductors are strong spin-density wave systems, within close vicinity of a magnetic transition to, for example, an antiferromagnet. When an electron moves in a high- superconductor, its spin creates a spin-density wave around it. This spin-density wave in turn causes a nearby electron to fall into the spin depression created by the first electron (water-bed effect again). Hence, again, a Cooper pair is formed. When the system temperature is lowered, more spin density waves and Cooper pairs are created, eventually leading to superconductivity. Note that in high- systems, as these systems are magnetic systems due to the Coulomb interaction, there is a strong Coulomb repulsion between electrons. This Coulomb repulsion prevents pairing of the Cooper pairs on the same lattice site. The pairing of the electrons occur at near-neighbor lattice sites as a result. This is the so-called "d"-wave pairing, where the pairing state has a node (zero) at the origin.


title: High-temperature superconductivity

text: Examples of high- cuprate superconductors include YBCO and BSCCO, which are the most known materials that achieve superconductivity above the boiling point of liquid nitrogen.


title: Algeciras

text: Algeciras ( , ) is a municipality of Spain belonging to the province of Cádiz, Andalusia. Located in the southern end of the Iberian Peninsula, near the Strait of Gibraltar, it is the largest city on the Bay of Gibraltar (). The Port of Algeciras is one of the largest ports in Europe and the world in three categories: container, cargo and transshipment. The urban area straddles the small Río de la Miel, which is the southernmost river of continental Europe. As of 1 January 2020, the municipality had a registered population of 123,078, second in its province after Jerez de la Frontera and greater than Cádiz city population. It forms part of the "comarca" of Campo de Gibraltar.


title: Algeciras

text: The surrounding metro area also includes the municipalities of Los Barrios, La Línea de la Concepción, Castellar de la Frontera, Jimena de la Frontera, San Roque and Tarifa, with a population of 263,739.


title: Algeciras

text: Algeciras' site was also that of Roman cities called ("White Harbor"), (current Getares) and . In the later "Byzantine" period, the site would come to be known in Greek as (), meaning "between rivers/canals". The Arabic name for the settlement founded after the Islamic conquest of the Iberian Peninsula was (, "The Green Island"), in reference to Isla Verde. gave the modern Spanish .


title: Algeciras

text: The area of the city has been populated since prehistory, and the earliest remains belong to Neanderthal populations from the Paleolithic era.


title: Algeciras

text: Due to its strategic position it was an important port under the Phoenicians, and was the site of the relevant Roman port of "Portus Albus" ("White Port"), with two nearby cities called "Caetaria" (possibly founded by the Iberians) and "Iulia Traducta", founded by the Romans.


title: Algeciras

text: Recently it has been proposed that the site of "Iulia Transducta" was the "Villa Vieja" of Algeciras.


title: Algeciras

text: After being destroyed by the Goths and their Vandal allies, Tarik landed in Algeciras and Tarifa in April 711.


title: Algeciras

text: In the year 859 AD Viking troops on board 62 drekars and commanded by the leaders Hastein and Björn Ironside besieged the city for three days and subsequently laid waste to much of it. After looting the houses of the rich, they burnt the Aljama mosque and the Banderas mosque. Reorganized near the medina, the inhabitants managed to recover the city and make the invaders run away, capturing two boats.


title: Algeciras

text: It enjoyed a brief period of independence as a taifa state from 1035 to 1058. It was named "al-Jazirah al-Khadra"' ("Green Island") after the offshore Isla Verde; the modern name is derived from this original Arabic name (compare also Algiers and Al Jazeera). In 1055 Emir Al-Mutadid of Seville drove the Berbers from Algeciras, claiming it for Arabs.


title: Algeciras

text: Vowing to counter the Castilian expansion initiated by 1265, Nasrid Granada required assistance from Fez in late 1274 and ceded the place of Algeciras (together with Tarifa) to the Marinids.


title: Algeciras

text: In 1278, Algeciras was besieged by the forces of the Kingdom of Castile under the command of Alfonso X of Castile and his son, Sancho. This siege was the first of a series of attempts to take the city and ended in failure for the Castilian forces. An armada sent by Castile was also annihilated whilst trying to blockade the city's harbor.


title: Algeciras

text: The Marinid grip over the town further increased in the ensuing decades, and the place turned into a Marinid stronghold from which razzias were launched into the still incipient Christian settlements in the Lower Guadalquivir and the Guadalete area.


title: Algeciras

text: In July 1309 Ferdinand IV of Castile laid siege to Algeciras as well as Gibraltar. The latter fell into Christian hands, but Muslim Algeciras held on for the following three decades, until Alfonso XI of Castile resumed its siege. Juan Núñez de Lara, Juan Manuel, Pedro Fernández de Castro, Juan Alfonso de la Cerda, lord of Gibraleón all participated in the siege, as did knights from France, England and Germany, and even King Philip III of Navarre, king consort of Navarra, who came accompanied by 100 horsemen and 300 infantry. In March 1344, after several years of siege, Algeciras surrendered.


title: Algeciras

text: On winning the city, Alfonso XI made it the seat of a new diocese, established by Pope Clement VI's bull "Gaudemus et exultamus" of 30 April 1344, and entrusted to the governance of the bishop of Cadiz. The bishops of Cadiz continued to hold the title of Aliezira, as it called, until 1851, when in accordance with a concordat between Spain and the Holy See its territory was incorporated into the diocese of Cadiz. No longer a residential bishopric, Aliezira is today listed by the Catholic Church as a titular see.


title: Algeciras

text: Left relatively unguarded during the Castilian Civil War, the town was easily seized in 1369 by the Nasrids from Granada with assistance from a Marinid fleet. It was destroyed on the orders of Muhammed V of Granada. While tradition asserts that it was torn down immediately after the 1369 occupation, the Nasrid scorched-earth policy has been also dated to 1375, once Granadan repopulation efforts should have failed. The garrison was thus relocated to Gibraltar, with a worse port but more easily defensible, in Nasrid control after the Marinid retreat from the Iberian Peninsula. While the jurisdiction was ceded to Gibraltar in 1462 after the Castilian conquest of the latter place, there are hints about the continued existence of informal settlements by farmers and sepherds in the area, at least after 1466.


title: Algeciras

text: Algeciras was refounded after 1704 by refugees from Gibraltar following the territory's capture by Anglo-Dutch forces in the War of the Spanish Succession. As early as 1705, the place was described as "...a heap of stones...only a few hovels scattered here and there, amidst an infinity of ruins". The sense of temporariness among the displaced population and the hopes for a return to Gibraltar were shattered by the 1713 Treaty of Utrecht. Besides Gibraltarians, throughout the 18th century repopulation was also participated by settlers from the rest of the Iberian Peninsula and from elsewhere, standing out Italians in the latter regard. Population rapidly increased (from 1,845 in 1725 to 6,241 in 1787). The Algeciras' social structure featured a comparatively small number of nobles and comparatively larger weight of clergy. Just like the rest of the Campo de Gibraltar, husbandry (cattle in particular) played an important role in the economy during the 18th century thanks to the rich pastures. Given the abundance of international conflicts in the Strait area during the 18th century, corsair activities against ships belligerent with Spain or neutral ships provisioning the enemy also became an important part of the economy.


title: Algeciras

text: It was fortified to guard against British raids with installations such as the Fuerte de Isla Verde built to guard key points. The city was rebuilt on its present rectangular plan by Charles III in 1760. In July 1801, the French and Spanish navies fought the British Royal Navy offshore in the Battle of Algeciras, which ended in a British victory.


title: Algeciras

text: The city became the scene for settling a major international crisis as it hosted the Algeciras Conference in 1906. The international forum to discuss the future of Morocco which was held in the Casa Consistorial (town hall). It confirmed the independence of Morocco against threats from Germany, and gave France control of banking and police interests. In July 1942 Italian frogmen set up in a secret base in the Italian tanker Olterra, which was interned in Algeciras, in order to attack shipping in Gibraltar. During the Franco era, Algeciras underwent substantial industrial development, creating many new jobs for the local workers made unemployed when the border between Gibraltar and Spain was sealed by Franco between 1969 and 1982.


title: Algeciras

text: In 1982 there was a failed plan codenamed Operation Algeciras conceived by the Argentinian military to sabotage the British military facilities in Gibraltar during the Falklands War. The Spanish authorities intervened just before the attack, and deported the two Argentine Montoneros and military liaison officer involved.


title: Algeciras

text: Algeciras is located in the southern end of the Iberian Peninsula, in the "comarca" of Campo de Gibraltar. Its strategic location near the Strait of Gibraltar—the choke point connecting the Atlantic Ocean and the Mediterranean Sea also entailing the nearest distance between Europe and the African continent—has historically powered the importance of the port. The city proper lies on the western bank of the Bay of Gibraltar, fronting the Rock of Gibraltar, which dominates the eastern bank.


title: Algeciras

text: The municipality spans across a total area of , bordering with the municipalities of Los Barrios and Tarifa. The lower course of the river Palmones forms part of the boundary of Algeciras with the municipality of Los Barrios.


title: Algeciras

text: The urban agglomeration formed by Algeciras and the surrounding settlements is the sixth largest in Andalusia and the third largest off the region's coast.


title: Algeciras

text: Algeciras has a Mediterranean subtropical climate (Köppen: "Csa") with very mild, rainy winters and warm, dry summers with occasional heat waves, and temperature fluctuations are small because of the strong Oceanic influence. There are not snow registers in the city since the 19th century.


title: Algeciras

text: Algeciras is principally a transport hub and industrial city. Its main activities are connected with the Port of Algeciras, which serves as the main embarkation point between Spain and Tangier and other ports in Morocco as well as the Canary Islands and the Spanish enclaves of Ceuta and Melilla. It is ranked as the 16th busiest port in the world. The city also has a substantial fishing industry and exports a range of agricultural products from the surrounding area, including cereals, tobacco and farm animals.


title: Algeciras

text: In recent years it has become a significant tourist destination, with popular day trips to Tarifa to see bird migrations; to Gibraltar to see the territory's sights and culture; and to the Bay of Gibraltar on whale watching excursions.


title: Algeciras

text: Algeciras is the southern terminus of two principal north–south Euroroutes, the E05 and E15. Both routes, moreover, run to Scotland (the E05 terminates at Greenock and the E15 at Inverness) via France and England.


title: Algeciras

text: The Algeciras Gibraltar Railway Company built the Algeciras-Bobadilla railway line, which connects Algeciras railway station to Bobadilla, Antequera and continues to the rest of Spain, the train line terminates near the port of Algeciras.


title: Algeciras

text: The main bus station is located next to the train station. Several bus companies operate intercity bus services from and to Algeciras.


title: Algeciras

text: In addition, the Algeciras Heliport is being built for transport to Ceuta and other areas in the region.


title: Algeciras

text: Algeciras CF, the association football club, founded in 1912, plays usually in the third-tier Segunda División B, with past spells in the lower Tercera División and the higher Segunda División. They play home games at the Estadio Nuevo Mirador.


title: Algeciras

text: Algeciras BM, the professional handball club, played in the Liga ASOBAL between 2005 and 2008. The team was dissolved due to enormous debts after relegation to second level in 2008.


title: Grass Mud Horse

text: The Grass Mud Horse or Cǎonímǎ () is a Chinese Internet meme based on a pun. Homophonic puns in Standard Chinese delight many Chinese people, and they have become an important component of Chinese culture.


title: Grass Mud Horse

text: It is a word play on the Mandarin words "cào nǐ mā" (), literally, "fuck your mother", and is one of the 10 mythical creatures created in a hoax article on Baidu Baike in early 2009 whose names form obscene puns. It has become an Internet chat forum cult phenomenon in China and has garnered worldwide press attention, with videos, cartoons and merchandise of the animal (which is said to resemble the alpaca) having appeared.


title: Grass Mud Horse

text: The "Caonima", literally "Grass Mud Horse", is supposedly a species of alpaca. The name is similar to a profanity (), which translates as "fuck your mother". The comparison with the "animal" name is not an actual homophone: the two terms have the same consonants and vowels with different tones, and are represented by different characters.


title: Grass Mud Horse

text: According to the original, anonymous article from Baidu Baike, Grass Mud Horses originate from an area known as the "Mahler Gobi" Desert (, "Mǎlè Gēbì", which resembles the Chinese characters , "māle ge bī", meaning "your mother's fucking cunt"). Some variants of the animal are known as "Fertile Grass Mud Horses" (, "Wò Cǎonímǎ", which resembles , "Wǒ cào nǐ mā", meaning "I fuck your mother"). The Grass Mud Horse can only eat fertile grass (, "wò cǎo", which resembles , "Wǒ cào", meaning "I fuck!" or simply "Fuck!"). Other subspecies are known as "Crazy/Violent/Insane Grass Mud Horses" (, "Kuáng Cǎonímǎ"), which are considered the "kings" of the Caonima. The initial image found in the original Baidu Baike article was a zebra, but was replaced with an alpaca in subsequent revisions.


title: Grass Mud Horse

text: Because the Grass Mud Horse is said to be the dominant species which lives within the Mahler Gobi Desert, the region is also called the "Grass Mud Horse Gobi" (, "Cǎonímǎ Gēbì", which is close in pronunciation to , "cào nǐ mā ge bī", meaning "fuck your mother's cunt"). The animal is characterised as "lively, intelligent and tenacious". However, their existence is said to be threatened by "river crabs" which are invading their habitat.


title: Grass Mud Horse

text: The river crab (, "héxiè") symbolises internet censorship in China. Its pronunciation resembles the word for "harmony" (, "héxié"), in reference to the "harmonious society", to which the Chinese leadership professes to aspire, and which Chinese internet censors use to justify internet censorship. As a result, when a post on a microblog is deleted, the censorship notice says that the post has been "harmonized" (, "héxié"), which is pronounced similar to "river crab" (, "héxiè") in Mandarin Chinese, so the netizens say that the post has been eaten by the "river crab". The term "crab" itself is rural slang, meaning "a bully who uses power through force", and the "river crab" has become a symbol of crude censorship backed with the threat of force. The river crab is often depicted wearing three wristwatches, since 带三个表 ("dài sān ge biǎo", "wears three watches") can be rearranged and altered to ("Sāngè Dàibiǎo"), the ideology of the "Three Represents", an interpretation of communism promoted by former Chinese leader Jiang Zemin.


title: Grass Mud Horse

text: Music videos, "documentaries", and cartoons about the Grass Mud Horse started appearing on the internet in 2009. The original Grass Mud Horse music video's musical arrangement of a children's choir has been compared to "It's a Small World", and it scored 1.4 million hits in its first three months. A cartoon about the Grass Mud Horse attracted a quarter million views, and a nature documentary on its habits received 180,000 more hits in the same amount of time. Even though some Grass Mud Horse videos were not technically blocked by Chinese censors, some had their sound blocked, with a message saying "This video contains an audio track that has not been authorized by WMG."


title: Grass Mud Horse

text: "Yazhou Zhoukan" () reported that Zhan Bin, a teacher at the Beijing Institute of Fashion Technology, created a new Chinese character by fusing the three Chinese character radicals for "grass", "mud", and "horse". The word has no official pronunciation. Official "cleanup" of the internet, which threatens the Caonima, has led Chinese internet users to create other "Mud Horse" variants, such as the ("Gǔnnímǎ", "Rolling Mud Horse") and the "" ("Gànnímǎ", "Working Mud Horse"). "Gunnima" and "Gannima" are puns for "fuck off" and "fuck your mother" respectively.


title: Grass Mud Horse

text: The "Grass Mud Horse" became widely known on the English-language web following the publication of a "New York Times" article on the phenomenon on 11 March 2009, which sparked widespread discussion on blogs. In March 2011, "Grass Mud Horse" themed merchandise, such as plush dolls, began being sold over the Internet. One Guangzhou toy manufacturer reportedly produced its first batch of 150 Grass Mud Horse cuddly toys with official birth certificates issued by Mahler Gebi Mystical Creatures Bureau. The animals come in brown and white, named "Ma Le" () and "Ge Bi" () respectively, and sell for 40 yuan each. To accompany these, a user's and feeding manual have been created. Whereas they were called 'Caonima' before the crackdown, Internet sellers now list them using the correct Chinese term, " (Alpaca).


title: Grass Mud Horse

text: In 2009, renowned artist Ai Weiwei published an image of himself nude with only a 'Caonima' hiding his genitals, with a caption "草泥马挡中央" ("cǎonímǎ dǎng zhōngyāng", literally "a Grass Mud Horse covering the center". One interpretation of the caption is: "fuck your mother, Communist Party Central Committee". Political observers speculated that the photo may have contributed to Ai's arrest in 2011 by angering Chinese Communist Party hardliners.


title: Grass Mud Horse

text: In 2012, Chinese netizens started to designate the date 1 July as the "Grass Mud Horse Day". The date coincides with the "Party Day" in China which is to celebrate the founding of the Chinese Communist Party.


title: Grass Mud Horse

text: The China Digital Times sees Caonima as the "de facto mascot of netizens in China fighting for free expression, inspiring poetry, photos and videos, artwork, lines of clothing, and more." It is an illustration of the "resistance discourse" of Chinese internet users with "increasingly dynamic and sometimes surprising presence of an alternative political discourse: images, frames, metaphors and narratives that have been generated from Internet memes [that] undermine the values and ideology that reproduce compliance with the Chinese Communist Party's authoritarian regime, and, as such, force an opening for free expression and civil society in China."


title: Grass Mud Horse

text: Caonima is an expression of a broader Chinese internet culture of spoofing, mockery, punning, and parody known as e'gao, which includes video mash-ups and other types of bricolage.


title: Grass Mud Horse

text: The Beijing Television Cultural Center fire led to Chinese internet users creating a number of digitally manipulated image parodies, including one with a Caonima's outline in the smoke.


title: Grass Mud Horse

text: On 20 March 2009, "the New York Times" reported that a Chinese contributor to Global Voices Online posted a message from an Internet administrator to managers of online bulletin boards warning that "any content related with Grass-Mud Horse should not be promoted and hyped" because "the issue has been elevated to a political level ... The overseas media has exaggerated the incident as a confrontation between netizens and the government."


title: Grass Mud Horse

text: In a press conference on 25 March, the Foreign Ministry confirmed that China's access to YouTube had been officially blocked since two days earlier. According to Reporters Without Borders, the block was an attempt to stem videos showing Chinese repression of the Tibetan population in the run-up to the 50th anniversary of the Tibetan uprising of 10 March 1959, and to block access to the popular Grass Mud Horse video posted in early March.


title: Grass Mud Horse

text: The State Administration of Radio, Film, and Television issued a directive on 30 March 2009 to highlight 31 categories of content prohibited online, including violence, pornography, and content which may "incite ethnic discrimination or undermine social stability". Many netizens believe the instruction follows the official embarrassment over the rise of the "Grass Mud Horse" phenomenon. Industry observers believe that the move was designed to stop the spread of parodies or other comments on politically sensitive issues in the runup to the 20th anniversary of the 4 June Tiananmen Square protests. Following the government's directive, most Chinese essays and blog postings made about the Grass Mud Horse have been removed from the Internet after being discovered by government censors. Some of these citizen efforts to keep the Grass Mud Horse alive have moved offshore to the U.S. and elsewhere, including for example the creation of an independent Canadian publishing house (see Mudgrass Press) referencing the meme.


title: Grass Mud Horse

text: The Caonima reappeared as a subject of online cartoon satire following the announcement of the Green Dam Youth Escort pornography blocking software project.


title: Grass Mud Horse

text: The trickster figure is a character found across the study of myth, folklore religion as a type of archetypal character across cultures. The trickster figure is characterised by intelligence and a trait for playing with social norms and taboos, often enticing or deceiving others into breaking rules. Tricksters therefore might avoid stricture by authorities or figures in power even to the extent of making those authorities look foolish. For these reasons the anthropologist James Cuffe has called the Grass Mud Horse an example of an online trickster- mythic and duplicitous in nature. Rather than the Grass Mud Horse being simply subversive in the face of internet censorship, Cuffe proposes the trickster as a liminal character that carries a cultural function as a heuristic device; This allows the audience to "reevaluate their own experiential understanding against that of their communities. By framing itself against and in spite of limits the trickster offers new coordinates by which one can reassess and judge one's own experiences." In the case of China this can be the communication of the experience of censorship to those who have not experienced censorship but can come to understand it as something that happens within their community through shared stories.


The Metropolitan Atlanta Rapid Transit Authority (MARTA, ) is the principal public transport operator in the Atlanta metropolitan area. Formed in 1971 as strictly a bus system, MARTA operates a network of bus routes linked to a rapid transit system consisting of of rail track with 38 train stations. MARTA's rapid transit system is the eighth-largest rapid transit system in the United States by ridership.


title: Metropolitan Atlanta Rapid Transit Authority

text: MARTA operates almost exclusively in Fulton, Clayton, and DeKalb counties, although they maintain bus service to two destinations in neighboring Cobb County (Six Flags Over Georgia and the Cumberland Transfer Center next to the Cumberland Mall), while Doraville station serves portions of Gwinnett County via Gwinnett Transit buses. MARTA also operates Mobility, a separate paratransit service for disabled customers.


text: MARTA was originally proposed as a rapid transit agency for DeKalb, Fulton, Clayton, Gwinnett, and Cobb counties. These were the five original counties in the Atlanta metropolitan area, and to this day are the five largest counties in the region and state. MARTA was formed by an act of the Georgia General Assembly in 1965. In the same year, four of the five metropolitan area counties (Clayton, DeKalb, Fulton, and Gwinnett) and the City of Atlanta passed a referendum authorizing participation in the system, but the referendum failed in Cobb.


text: Although a 1968 referendum to actually fund MARTA failed, in 1971, voters in Fulton and DeKalb counties successfully passed a 1% sales tax increase to pay for MARTA operations, while Clayton and Gwinnett counties overwhelmingly rejected the tax in the referendum. Gwinnett County remains outside of the MARTA system. In November 2014, however, Clayton County voters passed a 1% sales tax to join the MARTA system, reversing its 1971 decision. Also in 1971, the agency agreed to purchase the existing, bus-only Atlanta Transit Company; the sale of the company closed on February 17, 1972, giving the agency control over all public transit in the immediate Atlanta area.


text: Construction began on MARTA's heavy rail system in 1975, with the first rail service commencing on June 30, 1979. The system has since built most of the proposed rail lines, as well as stations in Dunwoody, Sandy Springs, and North Springs, which were not included in the original plan. The missing rail segments from the original plan include a Tucker-North DeKalb line with service to Emory University and North Druid Hills, a Northwest line with service to Brookwood and Northside Drive, extension of the West line to Brownlee-Boulder Park near Fairburn Road, extension of the Proctor Creek line to West Highlands, and a branch off the south line to Hapeville and Clayton County.


text: MARTA is composed of a heavy rail rapid transit system, a light rail system, and a bus system, all of which operate primarily within the boundaries of Fulton, Clayton and DeKalb counties. In addition to Atlanta itself, the transit agency serves various suburbs within its service area, including Alpharetta, Avondale Estates, Brookhaven, Chamblee, Clarkston, College Park, Decatur, Doraville, Dunwoody, East Point, Ellenwood, Fairburn, Forest Park, Hapeville, Jonesboro, Lake City, Lovejoy, Lithonia, Morrow, Palmetto, Riverdale, Roswell, Sandy Springs, Stone Mountain, and Union City. MARTA also serves the airport via a station located next to the main terminal. Although Cobb County is not part of the MARTA system, the agency operates one limited bus route to the Cumberland Boulevard Transfer Center and another to Six Flags Over Georgia.


text: MARTA allows bicycles on its trains, and buses have room for two bicycles on racks mounted on the front of the bus. At the airport, bicycles can be locked up in all of the parking decks, so long as they are not obstructing either pedestrian or vehicular traffic.


text: In 2007, MARTA had 4,729 full and part-time employees, of whom 1,719 were bus drivers or train operators. Rail and bus operators, station agents, rail maintenance workers, and many other employees of MARTA are represented in negotiations by the Amalgamated Transit Union's Local 732.


text: MARTA's rapid transit system has of route and 38 rail stations located on four lines: the Red Line (prior to October 2009, known as the North-South Line), Gold Line (former Northeast-South Line), Blue Line (former East-West Line), and Green Line (former Proctor Creek Line). The tracks for this system are a combination of elevated, ground-level, and underground tracks.


text: The deepest station in the MARTA system is the Peachtree Center station, which is located in a hard-rock tunnel, beneath downtown Atlanta, where the highest hills in Atlanta are above sea level. No tunnel lining was installed in this station, or the adjacent tunnels. The architects and civil engineers decided to leave these with their rugged gneiss rock walls. The highest station in the MARTA system is the King Memorial station. It rises over a former CSX rail yard.


text: MARTA switched to a color-based identification system in October 2009. Formerly, the lines were named based upon their terminal stations, namely: Airport, Doraville, North Springs, H. E. Holmes, Bankhead, King Memorial, Candler Park, Indian Creek; or by their compass direction. During the transition between the two naming systems, all stations on the Red and Gold lines used their original orange signs, and all stations on the Blue and Green lines used their original blue signs.


text: All rapid transit lines have an ultimate nexus at the Five Points station, located in downtown Atlanta. MARTA trains are operated using the Automatic Train Control system, with one human operator per train to make announcements, operate doors, and to operate the trains manually in case of a control system malfunction or an emergency. Many of the suburban stations have free daily and paid long-term parking in park and ride lots. These stations also have designated Park and Ride passenger drop-off areas close to the stations' entrances.


text: The Atlanta Streetcar is a modern streetcar route that is powered by an overhead line and operates in mixed vehicle traffic. The system was constructed by the City of Atlanta and was integrated into MARTA operations on July 1, 2018. The streetcar operates on a pinched loop system in Downtown Atlanta.


text: The Atlanta Streetcar system uses Siemens S70 light rail vehicles (LRVs). A total of four S70 cars were purchased and were built at two different facilities; the cars themselves were built in Sacramento, California while most other major components, like the propulsion system, were assembled at a plant about north of Atlanta, in Alpharetta. They were delivered in the first months of 2014 and are numbered 1001–1004.


text: MARTA's bus system serves a wider area than the rail system, serving areas in Fulton, Clayton and DeKalb counties such as the cities of Roswell and Alpharetta in North Fulton, along with South DeKalb. MARTA bus service for Clayton County became effective March 21, 2015. As of 2010, MARTA has 554 diesel and compressed natural gas buses that covers over 110 bus routes that operated 25.9 million annual vehicle miles (41.7 million kilometers). MARTA has one bus route providing limited service in Cobb County (Route 12 has been extended to Cobb County's Cumberland Boulevard Transfer Center). As of June 2016, MARTA purchased 18 New Flyer Industries, Xcelsior XN60. All of the MARTA bus lines, except for route 142, feed into or intersect MARTA rail lines as well. MARTA shuttle service is available to Six Flags Over Georgia during the park's summer season.


text: In addition to the free parking adjacent to many rail stations, MARTA also operates five park and ride lots serviced only by bus routes (Windward Parkway, Mansell Road, Stone Mountain, Barge Road, and South Fulton).


text: In compliance with the Americans with Disabilities Act (ADA), MARTA provides the Mobility paratransit service for those persons defined as disabled by the ADA. MARTA uses 211 special lift-equipped vehicles for this service, and can either deliver passengers to their final destination (curb-to-curb service) or can deliver the passenger to the closest accessible bus stop or rail station (feeder service). Mobility is limited to existing rail and bus routes and cannot extend more than a radius from any existing route. Mobility service is only provided during the hours of the fixed route servicing the area. An application for acceptance into the Mobility service is required; reservations are required for each trip. In fiscal year 2006, MARTA provided 289,258 Mobility trips.


text: The average cost to MARTA for providing a one-way trip for an individual Mobility passenger is US$31.88. This is much greater than the US$4.00 fare the Mobility rider is required to pay. The Americans with Disabilities Act forbids MARTA from charging a Mobility fare more than twice the normal fixed route fare.


text: A 2001 federal civil lawsuit, "Martin v. Metropolitan Atlanta Rapid Transit Authority", was brought by several disabled riders who alleged MARTA was violating the ADA by failing to provide: bus schedule and route information in an accessible format, buses with working wheelchair lifts, stop announcements on rail and bus routes, and adequate staff to schedule and provide on-time Mobility service. The district court ruled in 2002 that MARTA had violated the ADA and granted the plaintiffs an injunction requiring MARTA to improve service to the disabled.


text: Currently, the one-way full fare for MARTA costs US$2.50. New Breeze cards are $2. Breeze Tickets carry an extra fee of $1. Passengers over 65, passengers with disabilities and Medicare recipients are eligible to receive a discounted fare of $1. A one-way paratransit fare is $4. Ten full fare one-way trips can be purchased for $25, and twenty full fare trips can be purchased at a discount for $42.50. MARTA also offers unlimited travel through multiple transit pass options: 24-Hour pass $9, 2-day pass $14, 3-day pass $16, 4-day pass $19, 7-day pass $23.75, and a 30-day pass for $95. Additional discounted pass programs allow for university students and staff to purchase calendar monthly passes. Additional discounts are available to corporate partners who sell monthly MARTA passes to employees and also to groups and conventions visiting Atlanta. Some employers (at their own expense) also provide reduced cost or free MARTA passes to employees to encourage the use of public transportation. Children up to can ride for free with fare-paying rider; limit is 2.


text: Free shuttles also operate within the MARTA area, but are not part of MARTA. The Buckhead Uptown Connection (The BUC) goes around Buckhead, Atlanta's uptown section and its third major business district behind downtown and midtown. This includes Lenox Square mall and the many high-rises and skyscrapers built along Peachtree Road. The Atlantic Station Shuttle offers service between the Arts Center MARTA Station and the Atlantic Station neighborhood of Midtown. Georgia Tech operates the Tech trolley between central campus, Technology Square, and the Midtown MARTA Station, as well as "Stinger" buses around its campus. Emory University operates "The Cliff" shuttle buses in and around its campus. The Clifton Corridor Transportation Management Association (CCTMA) operates a shuttle connecting Emory with downtown Decatur and the Decatur MARTA station.


text: Due to the COVID-19 outbreak, in March 2020 MARTA introduced free fares to bus rides, which ended early September 2020. The free fare modification did not apply to rail fares.


text: MARTA finished implementing the "Breeze" smart card electronic fare collection system in September 2006, replacing the previous token-based fare collection system. The new Breeze Card allows riders to load money on the card for use over time, and to add unlimited day passes that are not fixed to a calendar period. The Breeze Card is for every passenger riding MARTA. The new Breeze fare gates are designed to help prevent fare evasion; with the older fare collection system fare evasion was much easier and was estimated to cost MARTA $10 million per year. Other connecting transit systems such as GRTA Xpress and CobbLinc also use the Breeze system.


text: MARTA stopped selling tokens after the Breeze conversion. Cards (without fare) were sent by mail for free to those who requested them when the system was first implemented.


text: To protect against hacking problems experienced by the then-current Breeze Card, MARTA rolled out a new Breeze Card in January 2016. The new card costs $2.


text: MARTA operates every day. Rail service is provided from approximately 4:45 am to 1:00 am, Monday to Friday, and 6:00 am to 1:00 am on Saturday, Sunday & most holidays. During certain events (New Year's Eve) trains run until 2:00 a.m. (Trains also run all night during winter storms, though not in passenger service, to prevent ice from forming on non-underground lines.) On weekdays, trains run every 20 minutes on all rail lines from the beginning of service until 6:00 am. From 6:00 am-9:00 am and 3:00 pm-7:00 pm, trains run every 10 minutes on all rail lines. From 9:00 am-3:00 pm and 7:00 pm-8:30 pm, trains run every 12 minutes on all rail lines. From 8:30 pm until the end of service, trains run every 20 minutes on all rail lines. MARTA's Red Line rail service only operates between North Springs and Lindbergh Center stations after 8:30 pm. MARTA's Green Line rail service only operates between Bankhead and Vine City stations after 8:30 pm; Monday-Friday (with the exception of public holidays and track work performed by the authority). On weekends and public holidays, trains run every 20 minutes on all rail lines. Bus routes have varying frequencies dependent upon passenger demand.


text: Through formal fare reciprocity agreements, MARTA riders are able to transfer for free to the three other metro-Atlanta transit systems: Gwinnett County Transit, CobbLinc and GRTA Xpress. Some of these agreements require that neither system have significantly more transfers than the other. MARTA has stated that this is the case, that inbound (to MARTA from another system) and outbound (from MARTA to another system) transfers are approximately equal (for second quarter 2006, 8888 daily passengers transferred inbound and 8843 transferred outbound). Analysis of morning transfers (5 to 9 am) to MARTA shows that Cobb County had 718 inbound transfers but only 528 outbound, Gwinnett County had 239 inbound and 269 outbound, and GRTA Xpress had 1,175 inbound but 615 outbound. Some have suggested that more people from the other systems may benefit from free transfers than those living in the MARTA service area. It has also been noted that workers traveling in the morning to Atlanta from another system will more than likely make the return trip home, resulting in an equal number of transfers.


text: In addition to fare collections, the MARTA budget is funded by a 1% sales tax in Fulton, Clayton and DeKalb counties along with limited federal money. In 2017, the City of Atlanta raised their sales tax for MARTA to 1.5% to improve and expand MARTA. For fiscal year 2007, MARTA had a farebox recovery ratio of 31.8%. By law, funds from the 1% sales tax must be split evenly between MARTA's operational and Capital expenditure budgets. This restriction does not apply to other sources of revenue, including passenger revenue. The split was written into MARTA legislation at MARTA's formation with the rationale that MARTA should continue expanding and investing in the system. Nonetheless, MARTA has no active rail construction projects. Capital funds continue to decrease every year, creating a shortfall. The operations funds limit the amount of service MARTA provides. The sales tax law was amended by the state legislature in 2002 to allow a temporary three-year 45% capital/55% operations split. This additional 5% for operations expired in 2005. A 2005 bill to renew the split was tabled by the legislature's MARTA Oversight Committee, forcing MARTA to pass a new budget with cuts in service. The temporary 45%/55% capital/operations split was renewed again in the 2006 state legislative session. The capital funds surplus has resulted in projects, such as a new US$100 million Breeze Card fare collection system and US$1.1 million automatic toilets in the MARTA Five Points station, occurring at the same time that MARTA is struggling to pay for bus and rail operations. In 2015, the Georgia General Assembly approved a new bill that no longer requires MARTA to split the 1% Sales Tax. Due to low Sales Tax Revenue and no source of funding from the State of Georgia, MARTA was forced to eliminate 43 bus routes, eliminate shuttles, (Excluding the Six Flags Over Georgia and Braves Shuttle) and reduce Rail Service frequencies and hours. MARTA also closed the majority of its station restrooms. There are 13 station restrooms open to the public, most of which are located at the terminus of each line, and which include College Park, Arts Center, Peachtree Center, West End, Avondale, Kensington and Lindbergh Center. There are two Ridestores available, located at the Airport and Five Points Rail Stations. Despite the massive cuts, MARTA predicted the system would still come up 69.34 million dollars short for FY 2011, which was pulled from their Reserved Account. A $9 million addition was posted for 2013. This money was reinvested into the system by adding frequency to trains and bus routes.


text: The current 1% sales tax was set to be reduced to 0.5% in 2032. In early 2007 MARTA made a request to the City of Atlanta, DeKalb County, and Fulton County to seek a 15-year extension of the 1% sales tax from 2032 to 2047, with a 0.5% sales tax from 2047 to 2057. This is the fourth time in its history that MARTA sought the extension, the most recent in 1990. MARTA said the commitment to the tax is needed for the agency to secure long-term financing in the form of bonds to pay for any future expansions to the system. The resolution called for four new routes: bus rapid transit from H.E. Holmes station to Fulton Industrial Boulevard, bus rapid transit from Garnett station to Stonecrest Mall, transit for the BeltLine, and a direct transit link from Lindbergh Center to Emory University (formerly called the "C-Loop"). To approve the tax extension, two of the three government agencies needed to agree to the extension. In March 2007 the City of Atlanta voted 12–1 to approve the extension. In April 2007 the DeKalb County Commission also approved the sales tax extension. Some Fulton county officials opposed the sales tax extension on the basis that the proposed service expansions did not include previously proposed expansion of the North Rail line to Roswell and Alpharetta in North Fulton County.


text: MARTA was formed through the Metropolitan Atlanta Rapid Transit Authority Act of 1965, an act of the Georgia General Assembly. In addition to allowing the formation of the agency, and the collection of revenue from taxes, the legislation previously placed restrictions on how the agency managed its funds. In particular, the legislation established that any funds raised from the sale of bonds and capital goods would be spent on capital expenditures, and that any extra proceeds be put aside for paying off bond debt. While the enabling legislation put restrictions on how MARTA could manage its money, MARTA has never received any operational funding from the State of Georgia, making it the largest public transportation agency in the United States and the second-largest transit agency in Anglo-America (after the Toronto Transit Commission) not to receive state or provincial funding for operational expenses. The funding restrictions on MARTA were removed in 2015, with the passage of House Bill 213 by the General Assembly.


text: In early April 2009, MARTA experienced a budget crisis when the Georgia General Assembly failed to pass a bill that would allow MARTA to access its own capital reserve account, in order to compensate for a severe drop in sales-tax revenue during the late-2000s recession. MARTA stated that this could force the agency to discontinue operations one day out of the week, possibly a weekday. The agency's budget crisis forced MARTA to lay off 700 employees. Service cuts and other budget-stabilizing measures began in fiscal year 2011, with the first affected service mark-up in September 2010. Governor Sonny Perdue refused to call a special session as requested, and did not issue an executive order as he stated it would not be legal to do so.


text: MARTA is a multi-county authority that is governed by a board of directors, consisting of representatives appointed from the city of Atlanta (3 members), and the remainder of the counties of Fulton (3 members), Clayton (2 members) and DeKalb (4 members). Additionally, there is 1 member from the Georgia Department of Transportation, and 1 member from Georgia Regional Transportation Authority who also serve on the MARTA Board of Directors.


text: Positions on the MARTA board are directly appointed by the organizations they represent. Although the state of Georgia does not contribute to MARTA's operational funding, it still has voting members on the MARTA board. A similar situation existed for both Clayton and Gwinnett counties during most of MARTA's history; as a consequence of passing the authorization referendum but not the funding referendum. Gwinnett County have representation on the MARTA Board of Directors without paying into the system. This situation became controversial in 2004 when Gwinnett's representative Mychal Walker was found to have accepted US$20,000 from a lobbyist trying to secure a US$100 million contract with MARTA. Despite the controversy, as well as a MARTA board ruling that Walker violated the MARTA ethics policy, the Gwinnett County Commission initially failed to remove Mr. Walker from his position on the MARTA Board. Eventually, the state legislature was called upon to change the law governing MARTA's Board to allow for the removal of a member whose appointing county did not act on a request for removal. Before the new law could be used, Mr. Walker was arrested on an unrelated child support violation, which resulted in his firing by the Gwinnett County Commission.


text: The highest position at MARTA is the general manager and chief executive officer. Below is a list of people that have held the position:


text: The Georgia General Assembly has a standing committee that is charged with financial oversight of the agency. During the 2009 legislative session, Representative Jill Chambers, the MARTOC chairperson at the time, introduced a bill that would place MARTA under GRTA, and permanently remove the requirement that MARTA split its expenditures 50/50 between capital and operations. This would allow MARTA to avoid service cuts at times when sales tax revenue is low due to recession, without having to ask the state legislature for temporary exemptions (typically a 55/45 split) as it has received before. The bill was not passed, but the funding restrictions were removed in 2015.


text: During the 2005 fiscal year, MARTA had a customer satisfaction rate of 79%. On-time performance for rail service was 91.64%. The mean distance between rail service interruptions was and the mean distance between bus failures was .


text: MARTA has had two fatal accidents that resulted in a formal investigation by the National Transportation Safety Board. On February 25, 2000, a train near Avondale station struck two automatic train control technicians who were inspecting a relay box; one was fatally injured and the other technician suffered serious injuries. The workers had failed to apply for a safe clearance restriction for the track work. In addition, the rail system center controller, who was aware of the workers, failed to notify train drivers of the technicians' presence. A second accident occurred on April 10, 2000, when a train struck a bucket lift containing two contract workers at Lenox station; the workers were fatally injured. Although the MARTA employee who was accompanying the workers notified the rail control center of the work over the track, the control center employee failed to block off the section of the track in the automated rail control system and also failed to notify the unscheduled southbound train of the workers' presence. In 2001 MARTA settled with the families of the two killed workers for US$10.5 million.


text: In addition to these accidents, MARTA trains have derailed five times in recent years. The most recent incident occurred in January 2019 when an out of service train derailed between Airport station and College Park station. The operator was not injured. A previous derailment occurred on December 4, 2006 Medical Center station when a train carrying passengers was moved over a rail switch. No injuries were reported. In July 1996 during Atlanta's hosting of the Olympics, a paired car on a train that had developed mechanical problems was uncoupled from other cars at Indian Creek station (the last station on the east line). The train began rolling, crashing through the bumper at the end of the rail line and running off of the track. The train operator, the only person on board, received minor injuries. In June 1996 a minor derailment occurred at the junction between the North and Northeast lines; MARTA estimated 150 people were aboard. The derailment occurred when a rail supervisor told the train driver to reverse the train after realizing the train had gone the wrong way at a track split; a MARTA investigation of the incident showed the derailment caused $125,000 of damage to the train and track and caused injury to 16 passengers. And in August 1994 a minor derailment occurred at a switch between Candler Park and Inman Park. Approximately 20 passengers were on board and no one was injured.


text: On December 31, 2007, MARTA had three separate escalator accidents that injured at least 11 people. The incidents occurred as large crowds were going to the Chick-fil-A Bowl. Two escalators failed at Five Points station, and one escalator failed at Dome/GWCC/Philips Arena/CNN Center station. MARTA initially blamed the incidents on rowdy patrons jumping on the escalator. A subsequent formal investigation showed that the braking systems and a weak motor were to blame for the incidents.