title: Optical rotation

text: Optical activity is normally observed for transmitted light. However, in 1988, M. P. Silverman discovered that polarization rotation can also occur for light reflected from chiral substances. Shortly after, it was observed that chiral media can also reflect left-handed and right-handed circularly polarized waves with different efficiencies. These phenomena of specular circular birefringence and specular circular dichroism are jointly known as specular optical activity. Specular optical activity is very weak in natural materials.


title: Optical rotation

text: In 1898 Jagadish Chandra Bose described the ability of twisted artificial structures to rotate the polarization of microwaves. Since the early 21st century, the development of artificial materials has led to the prediction and realization of chiral metamaterials with optical activity exceeding that of natural media by orders of magnitude in the optical part of the spectrum. Extrinsic chirality associated with oblique illumination of metasurfaces lacking two-fold rotational symmetry has been observed to lead to large linear optical activity in transmission and reflection, as well as nonlinear optical activity exceeding that of lithium iodate by 30 million times.


title: Optical rotation

text: Optical activity occurs due to molecules dissolved in a fluid or due to the fluid itself only if the molecules are one of two (or more) stereoisomers; this is known as an enantiomer. The structure of such a molecule is such that it is "not" identical to its mirror image (which would be that of a different stereoisomer, or the "opposite enantiomer"). In mathematics, this property is also known as chirality. For instance, a metal rod is "not" chiral, since its appearance in a mirror is not distinct from itself. However a screw or light bulb base (or any sort of helix) "is" chiral; an ordinary right-handed screw thread, viewed in a mirror, would appear as a left-handed screw (very uncommon) which could not possibly screw into an ordinary (right-handed) nut. A human viewed in a mirror would have their heart on the right side, clear evidence of chirality, whereas the mirror reflection of a doll might well be indistinguishable from the doll itself.


title: Optical rotation

text: In order to display optical activity, a fluid must contain only one, or a preponderance of one, stereoisomer. If two enantiomers are present in equal proportions then their effects cancel out and no optical activity is observed; this is termed a racemic mixture. But when there is an enantiomeric excess, more of one enantiomer than the other, the cancellation is incomplete and optical activity is observed. Many naturally occurring molecules are present as only one enantiomer (such as many sugars). Chiral molecules produced within the fields of organic chemistry or inorganic chemistry are racemic unless a chiral reagent was employed in the same reaction.


title: Optical rotation

text: At the fundamental level, polarization rotation in an optically active medium is caused by circular birefringence, and can best be understood in that way. Whereas linear birefringence in a crystal involves a small difference in the phase velocity of light of two different linear polarizations, circular birefringence implies a small difference in the velocities between right and left-handed "circular polarizations". Think of one enantiomer in a solution as a large number of little helices (or screws), all right-handed, but in random orientations. Birefringence of this sort is possible even in a fluid because the handedness of the helices is not dependent on their orientation: even when the direction of one helix is reversed, it still appears right handed. And circularly polarized light itself is chiral: as the wave proceeds in one direction the electric (and magnetic) fields composing it are rotating clockwise (or counterclockwise for the opposite circular polarization), tracing out a right (or left) handed screw pattern in space. In addition to the bulk refractive index which substantially lowers the phase velocity of light in any dielectric (transparent) material compared to the speed of light (in vacuum), "there is an additional interaction between the chirality of the wave and the chirality of the molecules." Where their chiralities are the same, there will be a small additional effect on the wave's velocity, but the opposite circular polarization will experience an opposite small effect as its chirality is opposite that of the molecules.


title: Optical rotation

text: Unlike linear birefringence, however, natural optical rotation (in the absence of a magnetic field) cannot be explained in terms of a local material permittivity tensor (i.e., a charge response that only depends on the local electric field vector), as symmetry considerations forbid this. Rather, circular birefringence only appears when considering nonlocality of the material response, a phenomenon known as spatial dispersion. Nonlocality means that electric fields in one location of the material drive currents in another location of the material. Light travels at a finite speed, and even though it is much faster than the electrons, it makes a difference whether the charge response naturally wants to travel along with the electromagnetic wavefront, or opposite to it. Spatial dispersion means that light travelling in different directions (different wavevectors) sees a slightly different permittivity tensor. Natural optical rotation requires a special material, but it also relies on the fact that the wavevector of light is nonzero, and a nonzero wavevector bypasses the symmetry restrictions on the local (zero-wavevector) response. However, there is still reversal symmetry, which is why the direction of natural optical rotation must be 'reversed' when the direction of the light is reversed, in contrast to magnetic Faraday rotation. All optical phenomena have some nonlocality/wavevector influence but it is usually negligible; natural optical rotation, rather uniquely, absolutely requires it.


title: Optical rotation

text: The phase velocity of light in a medium is commonly expressed using the index of refraction "n", defined as the speed of light (in free space) divided by its speed in the medium. The difference in the refractive indices between the two circular polarizations quantifies the strength of the circular birefringence (polarization rotation),


title: Optical rotation

text: While formula_2 is small in natural materials, examples of giant circular birefringence resulting in a negative refractive index for one circular polarization have been reported for chiral metamaterials.


title: Optical rotation

text: The familiar rotation of the axis of "linear" polarization relies on the understanding that a linearly polarized wave can as well be described as the superposition (addition) of a left and right circularly polarized wave in equal proportion. The phase difference between these two waves is dependent on the orientation of the linear polarization which we'll call formula_3, and their electric fields have a relative phase difference of formula_4 which then add to produce linear polarization:


title: Optical rotation

text: where formula_6 is the electric field of the net wave, while formula_7 and formula_8 are the two circularly polarized basis functions (having zero phase difference). Assuming propagation in the "+z" direction, we could write formula_7 and formula_8 in terms of their "x" and "y" components as follows:


title: Optical rotation

text: where formula_13 and formula_14 are unit vectors, and "i" is the imaginary unit, in this case representing the 90 degree phase shift between the "x" and "y" components that we have decomposed each circular polarization into. As usual when dealing with phasor notation, it is understood that such quantities are to be multiplied by formula_15 and then the actual electric field at any instant is given by the "real part" of that product.


title: Optical rotation

text: Substituting these expressions for formula_7 and formula_8 into the equation for formula_6 we obtain:


title: Optical rotation

text: The last equation shows that the resulting vector has the "x" and "y" components in phase and oriented exactly in the formula_3 direction, as we had intended, justifying the representation of any linearly polarized state at angle formula_23 as the superposition of right and left circularly polarized components with a relative phase difference of formula_24. Now let us assume transmission through an optically active material which induces an additional phase difference between the right and left circularly polarized waves of formula_25. Let us call formula_26 the result of passing the original wave linearly polarized at angle formula_23 through this medium. This will apply additional phase factors of formula_28 and formula_29 to the right and left circularly polarized components of formula_30:


title: Optical rotation

text: thus describing a wave linearly polarized at angle formula_33, thus rotated by formula_34 relative to the incoming wave: formula_30


title: Optical rotation

text: We defined above the difference in the refractive indices for right and left circularly polarized waves of formula_2. Considering propagation through a length "L" in such a material, there will be an additional phase difference induced between them of formula_25 (as we used above) given by:


title: Optical rotation

text: where formula_39 is the wavelength of the light (in vacuum). This will cause a rotation of the linear axis of polarization by formula_29 as we have shown.


title: Optical rotation

text: In general, the refractive index depends on wavelength (see dispersion) and the differential refractive index formula_2 will also be wavelength dependent. The resulting variation in rotation with the wavelength of the light is called optical rotatory dispersion (ORD). ORD spectra and circular dichroism spectra are related through the Kramers–Kronig relations. Complete knowledge of one spectrum allows the calculation of the other.


title: Optical rotation

text: So we find that the degree of rotation depends on the color of the light (the yellow sodium D line near 589 nm wavelength is commonly used for measurements), and is directly proportional to the path length formula_42 through the substance and the amount of circular birefringence of the material formula_2 which, for a solution, may be computed from the substance's specific rotation and its concentration in solution.


title: Optical rotation

text: Although optical activity is normally thought of as a property of fluids, particularly aqueous solutions, it has also been observed in crystals such as quartz (SiO). Although quartz has a substantial linear birefringence, that effect is cancelled when propagation is along the optic axis. In that case, rotation of the plane of polarization is observed due to the relative rotation between crystal planes, thus making the crystal formally chiral as we have defined it above. The rotation of the crystal planes can be right or left-handed, again producing opposite optical activities. On the other hand, amorphous forms of silica such as fused quartz, like a racemic mixture of chiral molecules, has no net optical activity since one or the other crystal structure does not dominate the substance's internal molecular structure.


title: Optical rotation

text: For a pure substance in solution, if the color and path length are fixed and the specific rotation is known, the observed rotation can be used to calculate the concentration. This usage makes a polarimeter a tool of great importance to those trading in or using sugar syrups in bulk.


title: Optical rotation

text: Rotation of light's plane of polarization may also occur through the Faraday effect which involves a static magnetic field. However, this is a distinct phenomenon that is not classified as "optical activity." Optical activity is reciprocal, i.e. it is the same for opposite directions of wave propagation through an optically active medium, for example clockwise polarization rotation from the point of view of an observer. In case of optically active isotropic media, the rotation is the same for any direction of wave propagation. In contrast, the Faraday effect is non-reciprocal, i.e opposite directions of wave propagation through a Faraday medium will result in clockwise and anti-clockwise polarization rotation from the point of view of an observer. Faraday rotation depends on the propagation direction relative to that of the applied magnetic field. All compounds can exhibit polarization rotation in the presence of an applied magnetic field, provided that (a component of) the magnetic field is oriented in the direction of light propagation. The Faraday effect is one of the first discoveries of the relationship between light and electromagnetic effects.


title: Froude number

text: In continuum mechanics, the Froude number (, after William Froude, ) is a dimensionless number defined as the ratio of the flow inertia to the external field (the latter in many applications simply due to gravity). The Froude number is based on the speed–length ratio which he defined as:


title: Froude number

text: where is the local flow velocity, is the local external field, and is a characteristic length. The Froude number has some analogy with the Mach number. In theoretical fluid dynamics the Froude number is not frequently considered since usually the equations are considered in the high Froude limit of negligible external field, leading to homogeneous equations that preserve the mathematical aspects. For example, homogeneous Euler equations are conservation equations.


title: Froude number

text: However, in naval architecture the Froude number is a significant figure used to determine the resistance of a partially submerged object moving through water.


title: Froude number

text: In open channel flows, introduced first the ratio of the flow velocity to the square root of the gravity acceleration times the flow depth. When the ratio was less than unity, the flow behaved like a fluvial motion (i.e., subcritical flow), and like a torrential flow motion when the ratio was greater than unity.


title: Froude number

text: The term was converted into non-dimensional terms and was given Froude's name in recognition of the work he did. In France, it is sometimes called Reech–Froude number after Frederic Reech.


title: Froude number

text: To show how the Froude number is linked to general continuum mechanics and not only to hydrodynamics we start from the Cauchy momentum equation in its dimensionless (nondimensional) form.


title: Froude number

text: In order to make the equations dimensionless, a characteristic length r, and a characteristic velocity u, need to be defined. These should be chosen such that the dimensionless variables are all of order one. The following dimensionless variables are thus obtained:


title: Froude number

text: Substitution of these inverse relations in the Euler momentum equations, and definition of the Froude number:


title: Froude number

text: Cauchy-type equations in the high Froude limit (corresponding to negligible external field) are named free equations. On the other hand, in the low Euler limit (corresponding to negligible stress) general Cauchy momentum equation becomes an inhomogeneous Burgers equation (here we make explicit the material derivative):


title: Froude number

text: This is an inhomogeneous pure advection equation, as much as the Stokes equation is a pure diffusion equation.


title: Froude number

text: Euler momentum equation is a Cauchy momentum equation with the Pascal law being the stress constitutive relation:


title: Froude number

text: Free Euler equations are conservative. The limit of high Froude numbers (low external field) is thus notable and can be studied with perturbation theory.


title: Froude number

text: Incompressible Navier–Stokes momentum equation is a Cauchy momentum equation with the Pascal law and Stokes's law being the stress constitutive relations:


title: Froude number

text: In marine hydrodynamic applications, the Froude number is usually referenced with the notation and is defined as:


title: Froude number

text: where is the relative flow velocity between the sea and ship, is in particular the acceleration due to gravity, and is the length of the ship at the water line level, or in some notations. It is an important parameter with respect to the ship's drag, or resistance, especially in terms of wave making resistance.


title: Froude number

text: In the case of planing crafts, where the waterline length is too speed-dependent to be meaningful, the Froude number is best defined as "displacement Froude number" and the reference length is taken as the cubic root of the volumetric displacement of the hull:


title: Froude number

text: For shallow water waves, such as tsunamis and hydraulic jumps, the characteristic velocity is the average flow velocity, averaged over the cross-section perpendicular to the flow direction. The wave velocity, termed celerity , is equal to the square root of gravitational acceleration , times cross-sectional area , divided by free-surface width :


title: Froude number

text: For the flow is called a subcritical flow, further for the flow is characterised as supercritical flow. When the flow is denoted as critical flow.


title: Froude number

text: When considering wind effects on dynamically sensitive structures such as suspension bridges it is sometimes necessary to simulate the combined effect of the vibrating mass of the structure with the fluctuating force of the wind. In such cases, the Froude number should be respected.


title: Froude number

text: Similarly, when simulating hot smoke plumes combined with natural wind, Froude number scaling is necessary to maintain the correct balance between buoyancy forces and the momentum of the wind.


title: Froude number

text: The Froude number has also been applied in allometry to studying the locomotion of terrestrial animals, including antelope and dinosaurs.


title: Froude number

text: Geophysical mass flows such as avalanches and debris flows take place on inclined slopes which then merge into gentle and flat run-out zones.


title: Froude number

text: So, these flows are associated with the elevation of the topographic slopes that induce the gravity potential energy together with the pressure potential energy during the flow. Therefore, the classical Froude number should include this additional effect. For such a situation, Froude number needs to be re-defined. The extended Froude number is defined as the ratio between the kinetic and the potential energy:


title: Froude number

text: where is the mean flow velocity, , ( is the earth pressure coefficient, is the slope), , is the channel downslope position and formula_16 is the distance from the point of the mass release along the channel to the point where the flow hits the horizontal reference datum; and are the pressure potential and gravity potential energies, respectively. In the classical definition of the shallow-water or granular flow Froude number, the potential energy associated with the surface elevation, , is not considered. The extended Froude number differs substantially from the classical Froude number for higher surface elevations. The term emerges from the change of the geometry of the moving mass along the slope. Dimensional analysis suggests that for shallow flows , while and are both of order unity. If the mass is shallow with a virtually bed-parallel free-surface, then can be disregarded. In this situation, if the gravity potential is not taken into account, then is unbounded even though the kinetic energy is bounded. So, formally considering the additional contribution due to the gravitational potential energy, the singularity in Fr is removed.


title: Froude number

text: In the study of stirred tanks, the Froude number governs the formation of surface vortices. Since the impeller tip velocity is (circular motion), where is the impeller frequency (usually in rpm) and is the impeller radius (in engineering the diameter is much more frequently employed), the Froude number then takes the following form:


title: Froude number

text: The Froude number finds also a similar application in powder mixers. It will indeed be used to determine in which mixing regime the blender is working. If Fr<1, the particles are just stirred, but if Fr>1, centrifugal forces applied to the powder overcome gravity and the bed of particles becomes fluidized, at least in some part of the blender, promoting mixing


title: Froude number

text: The densimetric Froude number is usually preferred by modellers who wish to nondimensionalize a speed preference to the Richardson number which is more commonly encountered when considering stratified shear layers. For example, the leading edge of a gravity current moves with a front Froude number of about unity.


title: Froude number

text: The Froude number may be used to study trends in animal gait patterns. In analyses of the dynamics of legged locomotion, a walking limb is often modeled as an inverted pendulum, where the center of mass goes through a circular arc centered at the foot. The Froude number is the ratio of the centripetal force around the center of motion, the foot, and the weight of the animal walking:


title: Froude number

text: where is the mass, is the characteristic length, is the acceleration due to gravity and is the velocity. The characteristic length may be chosen to suit the study at hand. For instance, some studies have used the vertical distance of the hip joint from the ground, while others have used total leg length.


title: Froude number

text: If total leg length is used as the characteristic length, then the theoretical maximum speed of walking has a Froude number of 1.0 since any higher value would result in takeoff and the foot missing the ground. The typical transition speed from bipedal walking to running occurs with . R. M. Alexander found that animals of different sizes and masses travelling at different speeds, but with the same Froude number, consistently exhibit similar gaits. This study found that animals typically switch from an amble to a symmetric running gait (e.g., a trot or pace) around a Froude number of 1.0. A preference for asymmetric gaits (e.g., a canter, transverse gallop, rotary gallop, bound, or pronk) was observed at Froude numbers between 2.0 and 3.0.


title: Froude number

text: The Froude number is used to compare the wave making resistance between bodies of various sizes and shapes.


title: Froude number

text: In free-surface flow, the nature of the flow (supercritical or subcritical) depends upon whether the Froude number is greater than or less than unity.


title: Froude number

text: One can easily see the line of "critical" flow in a kitchen or bathroom sink. Leave it unplugged and let the faucet run. Near the place where the stream of water hits the sink, the flow is supercritical. It 'hugs' the surface and moves quickly. On the outer edge of the flow pattern the flow is subcritical. This flow is thicker and moves more slowly. The boundary between the two areas is called a "hydraulic jump". The jump starts where the flow is just critical and Froude number is equal to 1.0.


title: Froude number

text: The Froude number has been used to study trends in animal locomotion in order to better understand why animals use different gait patterns as well as to form hypotheses about the gaits of extinct species.


title: Froude number

text: In addition particle bed behavior can be quantified by Froude number (Fr) in order to establish the optimum operating window.


title: Code of Ur-Nammu

text: The Code of Ur-Nammu is the oldest known law code surviving today. It is from Mesopotamia and is written on tablets, in the Sumerian language c. 2100–2050 BCE.


title: Code of Ur-Nammu

text: The first copy of the code, in two fragments found at Nippur, in what is now Iraq, was translated by Samuel Kramer in 1952. These fragments are held at the Istanbul Archaeological Museums. Owing to its partial preservation, only the prologue and five of the laws were discernible. Kramer noted that luck was involved in the discovery:


title: Code of Ur-Nammu

text: Further tablets were found in Ur and translated in 1965, allowing some 30 of the 57 laws to be reconstructed. Another copy found in Sippar contains slight variants.


title: Code of Ur-Nammu

text: The preface directly credits the laws to king Ur-Nammu of Ur (2112–2095 BCE). The author who had the laws written onto cuneiform tablets is still somewhat under dispute. Some scholars have attributed it to Ur-Nammu's son Shulgi.


title: Code of Ur-Nammu

text: Although it is known that earlier law-codes existed, such as the Code of Urukagina, this represents the earliest extant legal text. It is three centuries older than the Code of Hammurabi. The laws are arranged in casuistic form of IF (crime) THEN (punishment)—a pattern followed in nearly all later codes. It institutes fines of monetary compensation for bodily damage as opposed to the later "lex talionis" ('eye for an eye') principle of Babylonian law. However, murder, robbery, adultery and rape were capital offenses.


title: Code of Ur-Nammu

text: The code reveals a glimpse at societal structure during Ur's Third Dynasty. Beneath the "lugal" ("great man" or king), all members of society belonged to one of two basic strata: the "lu" or free person, or the slave (male, "arad"; female "geme"). The son of a "lu" was called a "dumu-nita" until he married, becoming a "young man" ("gurus"). A woman ("munus") went from being a daughter ("dumu-mi") to a wife ("dam"), then if she outlived her husband, a widow ("nu-ma-su"), who could remarry.


title: Code of Ur-Nammu

text: The prologue, typical of Mesopotamian law codes, invokes the deities for Ur-Nammu's kingship, Nanna and Utu, and decrees "equity in the land".


title: Krystian Bielik

text: Krystian Bielik (; born 4 January 1998) is a Polish professional footballer who plays as a centre back and defensive midfielder for club Birmingham City, on loan from club Derby County, and for the Poland national team.


title: Krystian Bielik

text: He first played senior football with Legia Warsaw in 2014, and after joining Arsenal in 2015, spent the second half of the 2016–17 season on loan at EFL Championship club Birmingham City, and then the 2018–19 season on loan at Charlton Athletic, helping them gain promotion from League One. He joined Derby in August 2019.


title: Krystian Bielik

text: Bielik started playing football for his hometown club, Górnik Konin before being spotted by Lech Poznań scouts in 2012, and later joining their developmental academy. He won the Polish U-17 Championships with the club in early 2014. However, in July 2014, Bielik joined Lech's archrivals, Legia Warszawa for 50,000 zł (£9,000), and on 24 August, he made his Ekstraklasa debut against Korona Kielce.


title: Krystian Bielik

text: Arsenal completed a reported £2.4 million deal for the 17-year-old Bielik on 21 January 2015; the fee was officially undisclosed.


title: Krystian Bielik

text: Bielik made his senior Arsenal debut in the League Cup fourth round on 27 October 2015, replacing fellow debutant Glen Kamara after 60 minutes of a 3–0 loss at Sheffield Wednesday. He was a member of the Arsenal under-21 team that reached the 2015–16 U21 Premier League Division 2 play-off final, held at the Emirates Stadium in May 2016, in which they beat Aston Villa U21 3–1.


title: Krystian Bielik

text: On 31 January 2017, Bielik joined EFL Championship club Birmingham City on loan until the end of the 2016–17 season. He made his debut in the starting eleven for the visit to Preston North End on 14 February, and played the whole match as Birmingham lost 2–1. His next appearance was ten days later, as a substitute after centre-back Paul Robinson was sent off with Birmingham 2–0 up away to Wolverhampton Wanderers. Bielik partnered Ryan Shotton in central defence as Birmingham conceded once but, thanks in part to his "two last-ditch challenges in the closing stages", managed to hold on for the win. Playing on the right of a back three alongside Shotton and Robinson in mid-March against Newcastle United, Bielik contributed to a clean sheet, a performance that confirmed his place in the starting eleven for the next few weeks and encouraged manager Gianfranco Zola to consider trying to loan him again in 2017–18.


title: Krystian Bielik

text: Zola's dismissal coincided with the return to fitness of Michael Morrison and Birmingham's need for points, and incoming manager Harry Redknapp reverted to a back four and prioritised playing to the team's strengths for the last three matches of the season. He used Bielik only in the final match, away to Bristol City, as a substitute playing in front of the defence to help the team hold on to their one-goal lead and thus avoid relegation to League One.


title: Krystian Bielik

text: A shoulder injury that required surgery prevented Bielik going out on loan in the summer 2017 transfer window, but on 31 January 2018, he signed for Walsall of League One on loan until the end of the season.


title: Krystian Bielik

text: On 16 August 2018, Bielik joined Charlton Athletic on a season-long loan. His first senior goal gave Charlton a 2–1 win against Southend United on 1 September. He scored in the League One play-off semifinals against Doncaster Rovers, and was awarded Man of the Match in the final against Sunderland, a 2–1 victory at Wembley Stadium by which Charlton Athletic secured promotion to the Championship.


title: Krystian Bielik

text: He played 34 games in all competitions and scored 4 goals during his spell at Charlton, used in both centre back and defensive midfielder positions.


title: Krystian Bielik

text: On 2 August 2019, Bielik joined Derby County on a five-year contract. The fee was undisclosed, but reported by the "Telegraph" as an initial fee of below Derby's record fee paid of £8 million, plus performance-related clauses that could take it "towards the £10 million mark".


title: Krystian Bielik

text: In January 2020, Bielik was stretchered off in an under-23 match with what proved to be an anterior cruciate ligament injury. This kept him out of action for the remainder of the 2019–20 season. Bielik made his return to action in November 2020, returning in a 2–0 home defeat to Barnsley that saw Derby fall to bottom of the Championship. He scored his first goal for Derby in a 4–0 win over Birmingham City on 29 December.


title: Krystian Bielik

text: On 30 January 2021, Bielik suffered another ACL injury that kept him out for the rest of the year. Bielik made his long-awaited return a year to the day since he suffered it, coming off of the bench and scoring a 96th-minute equaliser with an overhead kick as Derby got a much-needed 2–2 draw with Birmingham City. He made 15 appearances by the end of the season as Derby were relegated to League One, and regained his international place, but was told by Poland's manager Czesław Michniewicz that he would not be considered for the 2022 World Cup if he were a third-tier player.


title: Krystian Bielik

text: Bielik was named in Poland's squad for the 2017 UEFA European Under-21 Championship, but did not play.


title: Krystian Bielik

text: He was called up for the 2019 UEFA European Under-21 Championship, at which he scored twice in three matches.


title: Krystian Bielik

text: Bielik received his first call-up to Poland's senior team for UEFA Euro 2020 qualifiers in September 2019. He made his debut on 6 September 2019 as a 70th-minute substitute in a 2–0 loss to Slovenia, and started three days later in a goalless draw with Austria.


title: Krystian Bielik

text: Bielik can play either as a centre back or as a defensive midfielder. He is known for his technique, passing ability and also his aerial dominance.


title: Niqqud

text: In Hebrew orthography, niqqud or nikud ( or ) is a system of diacritical signs used to represent vowels or distinguish between alternative pronunciations of letters of the Hebrew alphabet. Several such diacritical systems were developed in the Early Middle Ages. The most widespread system, and the only one still used to a significant degree today, was created by the Masoretes of Tiberias in the second half of the first millennium AD in the Land of Israel (see Masoretic Text, Tiberian Hebrew). Text written with niqqud is called "ktiv menuqad".


title: Niqqud

text: Niqqud marks are small compared to the letters, so they can be added without retranscribing texts whose writers did not anticipate them.


title: Niqqud

text: In modern Israeli orthography "niqqud" is seldom used, except in specialised texts such as dictionaries, poetry, or texts for children or for new immigrants to Israel. For purposes of disambiguation, a system of spelling without niqqud, known in Hebrew as "ktiv maleh" (, literally "full spelling") has developed. This was formally standardised in the "Rules for Spelling without Niqqud" () enacted by the Academy of the Hebrew Language in 1996, and updated in 2017.


title: Niqqud

text: One reason for the lesser use of niqqud is that it no longer reflects the current pronunciation. In modern Hebrew, "tzere" is pronounced the same as "segol", although they were distinct in Tiberian Hebrew, and "pataḥ" the same as "qamatz". To the younger generation of native Hebrew speakers, these distinctions seem arbitrary and meaningless; on the other hand, Hebrew language purists have rejected out of hand the idea of changing the basics of niqqud and fitting them to the current pronunciation – with the result that in practice niqqud is increasingly going out of use.


title: Niqqud

text: According to Ghil'ad Zuckermann, the lack of "nikúd" in what he calls "Israeli" (Modern Hebrew) often results in "mispronunciations". For example, the Israeli lexical item מתאבנים is often pronounced as "mitabním" (literally "becoming fossilized (masculine plural)") instead of "metaavním" "appetizers", the latter deriving from תאבון "teavón" "appetite", whereas the former deriving from אבן "éven" "stone". Another example is the toponym מעלה אדומים, which is often pronounced as "maalé edomím" instead of "maalé adumím", the latter appearing in the Hebrew Bible (Joshua 15:7 and 18:17). The hypercorrect "yotvetá" is used instead of "yotváta" for the toponym יטבתה, mentioned in Deuteronomy 10:7. The surname of American actress Farrah Fawcett (פארהפוסט) is often pronounced "fost" instead of "fóset" by many Israelis.


title: Niqqud

text: This table uses the consonant letters ', ' or , where appropriate, to demonstrate where the niqqud is placed in relation to the consonant it is pronounced after. Any other letters shown are actually part of the vowel. Note that there is some variation among different traditions in exactly how some vowel points are pronounced. The table below shows how most Israelis would pronounce them, but the classic Ashkenazi pronunciation, for example, differs in several respects.


title: Niqqud

text: Note concerning IPA: the transcription symbols are linked to the articles about the sounds they represent. The diacritic ˘ (breve) indicates a short vowel; the triangular colon symbol ː indicates that the vowel is long.


title: Niqqud

text: Both consonants and niqqud can be typed from virtual graphical keyboards available on the World Wide Web, or by methods integrated into particular operating systems.


title: Niqqud

text: In GTK+ Linux systems, niqqud can be entered by holding down AltGR and pressing the same keys as for Windows, above, or by pressing ctrl+shift+u followed by the appropriate 4 digit Unicode.


title: Niqqud

text: Using the Hebrew keyboard layout in Mac OS X, the typist can enter niqqud by pressing the Option key together with a number on the top row of the keyboard. Other combinations such as sofit and hataf can also be entered by pressing either the Shift key and a number, or by pressing the Shift key, Option key, and a number at the same time.


title: Niqqud

text: SIL International have developed another standard, which is based on Tiro, but adds the Niqqud along the home keys. Linux comes with "Israel — Biblical Hebrew (Tiro)" as a standard layout. With this layout, niqqud can be typed without pressing the Caps Lock key.


title: Ricardo Antonio Chavira

text: Ricardo Antonio Chavira (born September 1, 1971) is an American actor. He is best known for his role as Carlos Solis in the ABC television series "Desperate Housewives" (2004–2012). He also played Abraham Quintanilla in the Netflix original series "" (2020).


title: Ricardo Antonio Chavira

text: Chavira was born in Austin, Texas, the son of a Bexar County judge, Juan Antonio Chavira. Raised in San Antonio, he graduated from Robert E. Lee High School and the University of the Incarnate Word. He is a '00 UC San Diego Alumnus and received his Master of Fine Arts in Acting from the University of California San Diego's graduate acting program in 2000, and moved to Los Angeles shortly thereafter. Since then, he has worked in film, television and theatre.


title: Ricardo Antonio Chavira

text: Chavira began his career playing guest-starring roles on television shows, include "NYPD Blue", "24", "The Division", "Joan of Arcadia" and "JAG". In 2002, he had a recurring role in the HBO comedy-drama "Six Feet Under" and was series regular on the unaired Fox sitcom "The Grubbs". In 2004, he made his big screen debut appearing in a supporting role playing private José Gregorio Esparza in the western film "The Alamo" (2004).


title: Ricardo Antonio Chavira

text: In 2004, Chavira was cast as Carlos Solis, the husband of Eva Longoria’s character, Gabrielle Solis, in the ABC comedy-drama series "Desperate Housewives". The series was a breakthrough hit for ABC receiving wide coverage. In 2005, Chavira listed on the "50 Most Beautiful" list in "People en Español", and the following year named one of "TV's Sexiest Men" by "TV Guide". Along with cast, he received two Screen Actors Guild Award for Outstanding Performance by an Ensemble in a Comedy Series in 2005 and 2006, and well as three ALMA Awards nominations for Outstanding Actor in a Comedy Series. The series ended in 2012 after eight seasons.


title: Ricardo Antonio Chavira

text: Chavira starred in a production of "Tracers" at the Odyssey Theatre in Los Angeles, and also starred in a co-production of "Living Out". He played Stanley Kowalski in the Guthrie Theater's production of Tennessee Williams' "A Streetcar Named Desire", from July 3 to August 21 of 2010 in Minneapolis. He also had voice roles as Alejandro Borges in the film "" and as John Carver in the video game "Dead Space 3". He also appeared in a number of movies, including "Days of Wrath" (2008), "Saving God" (2008), and "Piranha 3D" (2010).


title: Ricardo Antonio Chavira

text: Following "Desperate Housewives", Chavira guest-starred on two episodes of USA Network drama series, "Burn Notice" in 2013, playing crime leader Rafael Serrano. Later that year, he went to star in the NBC sitcom "Welcome to the Family". The series was canceled after three episodes. In 2015, Chavira guest starred on "Castle" episode "At Close Range", and in 2016 reunited with Eva Longoria in her short-lived sitcom "Telenovela".


title: Ricardo Antonio Chavira

text: From 2016 to 2017, Chavira had a major recurring role in the ABC political thriller "Scandal" during the fifth and sixth seasons as democratic Governor Francisco “Frankie” Vargas who runs for president. At the same time, he had a recurring role in The CW comedy series, "Jane the Virgin" during the third season as Bruce, Xiomara's (Andrea Navedo) lover. In 2017, Chavira also had a recurring role in the Netflix horror-comedy "Santa Clarita Diet" alongside Timothy Olyphant and Drew Barrymore. In 2020, Chavira was cast as Abraham Quintanilla, the father of late singer Selena in the Netflix limited biographical series, "". He was a guest star on Chicago P.D. (S9:E6) in 2021.


title: Ricardo Antonio Chavira

text: Chavira is a supporter of breast cancer research as his mother, Elizabeth Ries Chavira, died of breast and ovarian cancer when she was 43 years old. Chavira is San Antonio's honorary spokesman for the charity Susan G. Komen for the Cure, and last June served as the National Team Captain for the Race for the Cure in Washington, D.C. Chavira and James Denton were the 2005 spokespeople for the Lee National Denim Day breast cancer fundraiser.


title: Ricardo Antonio Chavira

text: He has been married to Marcea Dietzel since September 22, 2007. They have two children, a son, Tomás Antonio (b. January 8th, 2003) and a daughter, Belén Elysabeth (b. July 28th 2008).


title: Ricardo Antonio Chavira

text: In October 2019, Chavira talked on Twitter about the relatively light prison sentence that his former "Desperate Housewives" castmate Felicity Huffman received for her role in the 2019 college admissions bribery scandal, citing "White Privilege."


title: Festina lente

text: Festina lente () or "speûde bradéōs" (, ) is a classical adage and oxymoron meaning "make haste slowly" (sometimes rendered in English as "more haste, less speed"). It has been adopted as a motto numerous times, particularly by the emperors Augustus and Titus, the Medicis and the Onslows.


title: Festina lente

text: The original form of the saying, "speũde bradéōs", is Classical Greek, of which "festina lente" is the Latin translation. The words and "festina" are second-person-singular present active imperatives, meaning "make haste", while and "lente" are adverbs, meaning "slowly".


title: Festina lente

text: The Roman historian Suetonius, in "De vita Caesarum", tells that Augustus deplored rashness in a military commander, thus "" was one of his favourite sayings:


title: Festina lente

text: Certain gold coins minted for Augustus bore images of a crab and a butterfly to attempt an emblem for the adage. Other such visualizations include a hare in a snail shell; a chameleon with a fish; a diamond ring entwined with foliage; and perhaps most recognizably, a dolphin entwined around an anchor.


title: Festina lente

text: Cosimo I de' Medici, Grand Duke of Tuscany took "festina lente" as his motto and symbolised it with a sail-backed tortoise. This emblem appears repeatedly throughout his Palazzo Vecchio where it was painted by the artist Giorgio Vasari. There are about 100 instances in the palace decorations and frescos and there are now tours with the object of finding them all.


title: Festina lente

text: The Renaissance printer Aldus Manutius adopted the symbol of the dolphin and anchor as his printer's mark. Erasmus (whose books were published by Manutius) featured the phrase in his "Adagia" and used it to compliment his printer: "Aldus, making haste slowly, has acquired as much gold as he has reputation, and richly deserves both." Manutius showed Erasmus a Roman silver coin, given to him by Cardinal Bembo, which bore the dolphin-and-anchor symbol on the reverse side.


title: Festina lente

text: The adage was popular in the Renaissance era and Shakespeare alluded to it repeatedly. In "Love's Labour's Lost", he copied the crab and butterfly imagery with the characters Moth and Armado.


title: Festina lente

text: The French poet and critic Nicolas Boileau, in his "Art poétique (The Art of Poetry)" (1674) applied the dictum specifically to the work of the writer, whom he advised in those words:


title: Festina lente

text: Jean de la Fontaine alluded to the motto in his famous fable of "The Hare and the Tortoise" ("Fables", 1668–94), writing that the tortoise "with a prudent wisdom hastens slowly".


title: Festina lente

text: The Onslow family of Shropshire has the adage as its motto, generating a pun upon the family name: "on-slow".


title: Festina lente

text: The meaning of the phrase is that activities should be performed with a proper balance of urgency and diligence. If tasks are rushed too quickly then mistakes are made and good long-term results are not achieved. Work is best done in a state of flow in which one is fully engaged by the task and there is no sense of time passing.


title: Festina lente

text: In physics, the name "Festina Lente Limit" has been applied to the Strong Confinement Limit, which is a mode of an atom laser in which the frequency of emission of the Bose–Einstein condensate is less than the confinement frequency of the trap.


title: Festina lente

text: Composer Arvo Pärt wrote "Festina lente" for strings and harp, in which some instruments play the melody at half-speed while others play it at double-speed, so the music is both fast and slow.


title: Festina lente

text: Goethe refers to both the proverb and Augustus' adoption of it in his poem "Hermann und Dorothea" (helpfully for poetry, the German rendition itself rhymes—""Eile mit Weile""):


title: Festina lente

text: The Lord Chancellor uses the phrase in W S Gilbert's "Iolanthe": "Recollect yourself I pray, and be careful what you say — as the ancient Romans said, "festina lente"."


title: Festina lente

text: "He has all along, since his coming, been trying his power, slowly but surely; that big child-brain of his is working. Well for us, it is, as yet, a child brain; for had he dared, at the first, to attempt certain things he would long ago have been beyond our power. However, he means to succeed, and a man who has centuries before him can afford to wait and to go slow. "Festina lente" may well be his motto."


title: Festina lente

text: The novel "Mr. Penumbra's 24-Hour Bookstore" by Robin Sloan involves a secret society devoted to Aldus Manutius, whose members use "Festina lente" as a motto/greeting.


title: Stellar corona

text: The Sun's corona lies above the chromosphere and extends millions of kilometres into outer space. It is most easily seen during a total solar eclipse, but it is also observable with a coronagraph. Spectroscopic measurements indicate strong ionization in the corona and a plasma temperature in excess of , much hotter than the surface of the Sun, known as the photosphere.


title: Stellar corona

text: In 1724, French-Italian astronomer Giacomo F. Maraldi recognized that the aura visible during a solar eclipse belongs to the Sun, not to the Moon. In 1809, Spanish astronomer José Joaquín de Ferrer coined the term 'corona'. Based in his own observations of the 1806 solar eclipse at Kinderhook (New York), de Ferrer also proposed that the corona was part of the Sun and not of the Moon. English astronomer Norman Lockyer identified the first element unknown on Earth in the Sun's chromosphere, which was called helium. French astronomer Jules Jenssen noted, after comparing his readings between the 1871 and 1878 eclipses, that the size and shape of the corona changes with the sunspot cycle. In 1930, Bernard Lyot invented the coronograph, which allows viewing the corona without a total eclipse. In 1952, American astronomer Eugene Parker proposed that the solar corona might be heated by myriad tiny 'nanoflares', miniature brightenings resembling solar flares that would occur all over the surface of the Sun.


title: Stellar corona

text: The high temperature of the Sun's corona gives it unusual spectral features, which led some in the 19th century to suggest that it contained a previously unknown element, "coronium". Instead, these spectral features have since been explained by highly ionized iron (Fe-XIV, or Fe). Bengt Edlén, following the work of Grotrian (1939), first identified the coronal spectral lines in 1940 (observed since 1869) as transitions from low-lying metastable levels of the ground configuration of highly ionised metals (the green Fe-XIV line from Fe at , but also the red Fe-X line from Fe at ).


title: Stellar corona

text: The Sun's corona is much hotter (by a factor from 150 to 450) than the visible surface of the Sun: the photosphere's average temperature is around compared to the corona's 1 to 3 million kelvin. The corona is 10 times as dense as the photosphere, and so produces about one-millionth as much visible light. The corona is separated from the photosphere by the relatively shallow chromosphere. The exact mechanism by which the corona is heated is still the subject of some debate, but likely possibilities include induction by the Sun's magnetic field and magnetohydrodynamic waves from below. The outer edges of the Sun's corona are constantly being transported away due to open magnetic flux and hence generating the solar wind.


title: Stellar corona

text: The corona is not always evenly distributed across the surface of the Sun. During periods of quiet, the corona is more or less confined to the equatorial regions, with coronal holes covering the polar regions. However, during the Sun's active periods, the corona is evenly distributed over the equatorial and polar regions, though it is most prominent in areas with sunspot activity. The solar cycle spans approximately 11 years, from solar minimum to the following minimum. Since the solar magnetic field is continually wound up due to the faster rotation of mass at the Sun's equator (differential rotation), sunspot activity will be more pronounced at solar maximum where the magnetic field is more twisted. Associated with sunspots are coronal loops, loops of magnetic flux, upwelling from the solar interior. The magnetic flux pushes the hotter photosphere aside, exposing the cooler plasma below, thus creating the relatively dark sun spots.


title: Stellar corona

text: Since the corona has been photographed at high resolution in the X-ray range of the spectrum by the satellite Skylab in 1973, and then later by Yohkoh and the other following space instruments, it has been seen that the structure of the corona is quite varied and complex: different zones have been immediately classified on the coronal disc.


title: Stellar corona

text: Active regions are ensembles of loop structures connecting points of opposite magnetic polarity in the photosphere, the so-called coronal loops.


title: Stellar corona

text: They generally distribute in two zones of activity, which are parallel to the solar equator. The average temperature is between two and four million kelvin, while the density goes from 10 to 10 particles per cm.


title: Stellar corona

text: Active regions involve all the phenomena directly linked to the magnetic field, which occur at different heights above the Sun's surface: sunspots and faculae occur in the photosphere; spicules, Hα filaments and plages in the chromosphere; prominences in the chromosphere and transition region; and flares and coronal mass ejections (CME) happen in the corona and chromosphere. If flares are very violent, they can also perturb the photosphere and generate a Moreton wave. On the contrary, quiescent prominences are large, cool, dense structures which are observed as dark, "snake-like" Hα ribbons (appearing like filaments) on the solar disc. Their temperature is about –, and so they are usually considered as chromospheric features.


title: Stellar corona

text: In 2013, images from the High Resolution Coronal Imager revealed never-before-seen "magnetic braids" of plasma within the outer layers of these active regions.


title: Stellar corona

text: Coronal loops are the basic structures of the magnetic solar corona. These loops are the closed-magnetic flux cousins of the open-magnetic flux that can be found in coronal holes and the solar wind. Loops of magnetic flux well up from the solar body and fill with hot solar plasma. Due to the heightened magnetic activity in these coronal loop regions, coronal loops can often be the precursor to solar flares and CMEs.


title: Stellar corona

text: The solar plasma that feeds these structures is heated from under to well over 10 K from the photosphere, through the transition region, and into the corona. Often, the solar plasma will fill these loops from one point and drain to another, called foot points (siphon flow due to a pressure difference, or asymmetric flow due to some other driver).


title: Stellar corona

text: When the plasma rises from the foot points towards the loop top, as always occurs during the initial phase of a compact flare, it is defined as chromospheric evaporation. When the plasma rapidly cools and falls toward the photosphere, it is called chromospheric condensation. There may also be symmetric flow from both loop foot points, causing a build-up of mass in the loop structure. The plasma may cool rapidly in this region (for a thermal instability), its dark filaments obvious against the solar disk or prominences off the Sun's limb.


title: Stellar corona

text: Coronal loops may have lifetimes in the order of seconds (in the case of flare events), minutes, hours or days. Where there is a balance in loop energy sources and sinks, coronal loops can last for long periods of time and are known as "steady state" or "quiescent" coronal loops ().


title: Stellar corona

text: Coronal loops are very important to our understanding of the current "coronal heating problem". Coronal loops are highly radiating sources of plasma and are therefore easy to observe by instruments such as "TRACE". An explanation of the coronal heating problem remains as these structures are being observed remotely, where many ambiguities are present (i.e., radiation contributions along the line-of-sight propagation). "In-situ" measurements are required before a definitive answer can be determined, but due to the high plasma temperatures in the corona, "in-situ" measurements are, at present, impossible. The next mission of the NASA Parker Solar Probe will approach the Sun very closely, allowing more direct observations.


title: Stellar corona

text: Large-scale structures are very long arcs which can cover over a quarter of the solar disk but contain plasma less dense than in the coronal loops of the active regions.


title: Stellar corona

text: The large-scale structure of the corona changes over the 11-year solar cycle and becomes particularly simple during the minimum period, when the magnetic field of the Sun is almost similar to a dipolar configuration (plus a quadrupolar component).


title: Stellar corona

text: The interconnections of active regions are arcs connecting zones of opposite magnetic field, of different active regions. Significant variations of these structures are often seen after a flare.


title: Stellar corona

text: Some other features of this kind are helmet streamers — large, cap-like coronal structures with long, pointed peaks that usually overlie sunspots and active regions. Coronal streamers are considered to be sources of the slow solar wind.


title: Stellar corona

text: Filament cavities are zones which look dark in the X-rays and are above the regions where Hα filaments are observed in the chromosphere. They were first observed in the two 1970 rocket flights which also detected "coronal holes".


title: Stellar corona

text: Filament cavities are cooler clouds of plasma suspended above the Sun's surface by magnetic forces. The regions of intense magnetic field look dark in images because they are empty of hot plasma. In fact, the sum of the magnetic pressure and plasma pressure must be constant everywhere on the heliosphere in order to have an equilibrium configuration: where the magnetic field is higher, the plasma must be cooler or less dense. The plasma pressure formula_1 can be calculated by the state equation of a perfect gas: formula_2, where formula_3 is the particle number density, formula_4 the Boltzmann constant and formula_5 the plasma temperature. It is evident from the equation that the plasma pressure lowers when the plasma temperature decreases with respect to the surrounding regions or when the zone of intense magnetic field empties. The same physical effect renders sunspots apparently dark in the photosphere.


title: Stellar corona

text: Bright points are small active regions found on the solar disk. X-ray bright points were first detected on April 8, 1969, during a rocket flight.


title: Stellar corona

text: The fraction of the solar surface covered by bright points varies with the solar cycle. They are associated with small bipolar regions of the magnetic field. Their average temperature ranges from 1.1 MK to 3.4 MK. The variations in temperature are often correlated with changes in the X-ray emission.


title: Stellar corona

text: Coronal holes are unipolar regions which look dark in the X-rays since they do not emit much radiation. These are wide zones of the Sun where the magnetic field is unipolar and opens towards the interplanetary space. The high speed solar wind arises mainly from these regions.


title: Stellar corona

text: In the UV images of the coronal holes, some small structures, similar to elongated bubbles, are often seen as they were suspended in the solar wind. These are the coronal plumes. More precisely, they are long thin streamers that project outward from the Sun's north and south poles.


title: Stellar corona

text: The solar regions which are not part of active regions and coronal holes are commonly identified as the quiet Sun.


title: Stellar corona

text: The equatorial region has a faster rotation speed than the polar zones. The result of the Sun's differential rotation is that the active regions always arise in two bands parallel to the equator and their extension increases during the periods of maximum of the solar cycle, while they almost disappear during each minimum. Therefore, the quiet Sun always coincides with the equatorial zone and its surface is less active during the maximum of the solar cycle. Approaching the minimum of the solar cycle (also named butterfly cycle), the extension of the quiet Sun increases until it covers the whole disk surface excluding some bright points on the hemisphere and the poles, where there are coronal holes.


title: Stellar corona

text: The Alfvén surface is the boundary separating the corona from the solar wind defined as where the coronal plasma's Alfvén speed and the large-scale solar wind speed are equal.


title: Stellar corona

text: Researchers were unsure exactly where the Alfvén critical surface of the Sun lay. Based on remote images of the corona, estimates had put it somewhere between 10 to 20 solar radii from the surface of the Sun. On April 28, 2021, during its eighth flyby of the Sun, NASA's Parker Solar Probe encountered the specific magnetic and particle conditions at 18.8 solar radii that indicated that it penetrated the Alfvén surface.


title: Stellar corona

text: A portrait, as diversified as the one already pointed out for the coronal features, is emphasized by the analysis of the dynamics of the main structures of the corona, which evolve at differential times. Studying coronal variability in its complexity is not easy because the times of evolution of the different structures can vary considerably: from seconds to several months. The typical sizes of the regions where coronal events take place vary in the same way, as it is shown in the following table.


title: Stellar corona

text: Flares take place in active regions and are characterized by a sudden increase of the radiative flux emitted from small regions of the corona. They are very complex phenomena, visible at different wavelengths; they involve several zones of the solar atmosphere and many physical effects, thermal and not thermal, and sometimes wide reconnections of the magnetic field lines with material expulsion.


title: Stellar corona

text: Flares are impulsive phenomena, of average duration of 15 minutes, and the most energetic events can last several hours. Flares produce a high and rapid increase of the density and temperature.


title: Stellar corona

text: An emission in white light is only seldom observed: usually, flares are only seen at extreme UV wavelengths and into the X-rays, typical of the chromospheric and coronal emission.


title: Stellar corona

text: In the corona, the morphology of flares is described by observations in the UV, soft and hard X-rays, and in Hα wavelengths, and is very complex. However, two kinds of basic structures can be distinguished:


title: Stellar corona

text: As for temporal dynamics, three different phases are generally distinguished, whose duration are not comparable. The durations of those periods depend on the range of wavelengths used to observe the event:


title: Stellar corona

text: Often accompanying large solar flares and prominences are coronal mass ejections (CME). These are enormous emissions of coronal material and magnetic field that travel outward from the Sun at over a million kilometers per hour, containing roughly 10 times the energy of the solar flare or prominence that accompanies them. Some larger CMEs can propel hundreds of millions of tons of material into interplanetary space at roughly 1.5 million kilometers an hour.


title: Stellar corona

text: Coronal stars are ubiquitous among the stars in the cool half of the Hertzsprung–Russell diagram. These coronae can be detected using X-ray telescopes. Some stellar coronae, particularly in young stars, are much more luminous than the Sun's. For example, FK Comae Berenices is the prototype for the FK Com class of variable star. These are giants of spectral types G and K with an unusually rapid rotation and signs of extreme activity. Their X-ray coronae are among the most luminous ("L" ≥ 10 erg·s or 10W) and the hottest known with dominant temperatures up to 40 MK.


title: Stellar corona

text: The astronomical observations planned with the Einstein Observatory by Giuseppe Vaiana and his group showed that F-, G-, K- and M-stars have chromospheres and often coronae much like our Sun.


title: Stellar corona

text: The "O-B stars", which do not have surface convection zones, have a strong X-ray emission. However these stars do not have coronae, but the outer stellar envelopes emit this radiation during shocks due to thermal instabilities in rapidly moving gas blobs.


title: Stellar corona

text: Also A-stars do not have convection zones but they do not emit at the UV and X-ray wavelengths. Thus they appear to have neither chromospheres nor coronae.


title: Stellar corona

text: The matter in the external part of the solar atmosphere is in the state of plasma, at very high temperature (a few million kelvin) and at very low density (of the order of 10 particles/m).


title: Stellar corona

text: According to the definition of plasma, it is a quasi-neutral ensemble of particles which exhibits a collective behaviour.


title: Stellar corona

text: The composition is similar to that in the Sun's interior, mainly hydrogen, but with much greater ionization of its heavier elements than that found in the photosphere. Heavier metals, such as iron, are partially ionized and have lost most of the external electrons. The ionization state of a chemical element depends strictly on the temperature and is regulated by the Saha equation in the lowest atmosphere, but by collisional equilibrium in the optically-thin corona. Historically, the presence of the spectral lines emitted from highly ionized states of iron allowed determination of the high temperature of the coronal plasma, revealing that the corona is much hotter than the internal layers of the chromosphere.


title: Stellar corona

text: The corona behaves like a gas which is very hot but very light at the same time: the pressure in the corona is usually only 0.1 to 0.6 Pa in active regions, while on the Earth the atmospheric pressure is about 100 kPa, approximately a million times higher than on the solar surface. However it is not properly a gas, because it is made of charged particles, basically protons and electrons, moving at different velocities. Supposing that they have the same kinetic energy on average


title: Stellar corona

text: (for the equipartition theorem), electrons have a mass roughly times smaller than protons, therefore they acquire more velocity. Metal ions are always slower. This fact has relevant physical consequences either on radiative processes (that are very different from the photospheric radiative processes), or on thermal conduction.


title: Stellar corona

text: Furthermore, the presence of electric charges induces the generation of electric currents and high magnetic fields.


title: Stellar corona

text: Magnetohydrodynamic waves (MHD waves) can also propagate in this plasma, even though it is still not clear how they can be transmitted or generated in the corona.


title: Stellar corona

text: Coronal plasma is optically-thin and therefore transparent to the electromagnetic radiation that it emits and to that coming from lower layers. The plasma is very rarefied and the photon mean free path overcomes by far all the other length-scales, including the typical sizes of common coronal features.


title: Stellar corona

text: Electromagnetic radiation from the corona has been identified coming from three main sources, located in the same volume of space:


title: Stellar corona

text: In the corona thermal conduction occurs from the external hotter atmosphere towards the inner cooler layers. Responsible for the diffusion process of the heat are the electrons, which are much lighter than ions and move faster, as explained above.


title: Stellar corona

text: When there is a magnetic field the thermal conductivity of the plasma becomes higher in the direction which is parallel to the field lines rather than in the perpendicular direction.


title: Stellar corona

text: A charged particle moving in the direction perpendicular to the magnetic field line is subject to the Lorentz force which is normal to the plane individuated by the velocity and the magnetic field. This force bends the path of the particle. In general, since particles also have a velocity component along the magnetic field line, the Lorentz force constrains them to bend and move along spirals around the field lines at the cyclotron frequency.


title: Stellar corona

text: If collisions between the particles are very frequent, they are scattered in every direction. This happens in the photosphere, where the plasma carries the magnetic field in its motion. In the corona, on the contrary, the mean free-path of the electrons is of the order of kilometres and even more, so each electron can do a helicoidal motion long before being scattered after a collision. Therefore, the heat transfer is enhanced along the magnetic field lines and inhibited in the perpendicular direction.


title: Stellar corona

text: where formula_4 is the Boltzmann constant, formula_5 is the temperature in kelvin, formula_9 is the electron mass, formula_10 is the electric charge of the electron,


title: Stellar corona

text: is the Debye length of the plasma with particle density formula_3. The Coulomb logarithm formula_14 is roughly 20 in the corona, with a mean temperature of 1 MK and a density of 10 particles/m, and about 10 in the chromosphere, where the temperature is approximately 10kK and the particle density is of the order of 10 particles/m, and in practice it can be assumed constant.


title: Stellar corona

text: Thence, if we indicate with formula_15 the heat for a volume unit, expressed in J m, the Fourier equation of heat transfer, to be computed only along the direction formula_16 of the field line, becomes


title: Stellar corona

text: Numerical calculations have shown that the thermal conductivity of the corona is comparable to that of copper.


title: Stellar corona

text: Coronal seismology is a method of studying the plasma of the solar corona with the use of magnetohydrodynamic (MHD) waves. MHD studies the dynamics of electrically conducting fluids — in this case, the fluid is the coronal plasma. Philosophically, coronal seismology is similar to the Earth's seismology, the Sun's helioseismology, and MHD spectroscopy of laboratory plasma devices. In all these approaches, waves of various kinds are used to probe a medium. The potential of coronal seismology in the estimation of the coronal magnetic field, density scale height, fine structure and heating has been demonstrated by different research groups.


title: Stellar corona

text: The coronal heating problem in solar physics relates to the question of why the temperature of the Sun's corona is millions of kelvins versus the thousands of kelvins of the surface. Several theories have been proposed to explain this phenomenon but it is still challenging to determine which of these is correct. The problem first emerged when Bengt Edlen and Walter Grotrian identified Fe IX and Ca XIV lines in the solar spectrum. This led to the discovery that the emission lines seen during solar eclipses are not caused by an unknown element called "coronium" but known elements at very high stages of ionization. The comparison of the coronal and the photospheric temperatures of 6,000K, leads to the question of how the 200 times hotter coronal temperature can be maintained. The problem is primarily concerned with how the energy is transported up into the corona and then converted into heat within a few solar radii.


title: Stellar corona

text: The high temperatures require energy to be carried from the solar interior to the corona by non-thermal processes, because the second law of thermodynamics prevents heat from flowing directly from the solar photosphere (surface), which is at about , to the much hotter corona at about 1 to 3 MK (parts of the corona can even reach ).


title: Stellar corona

text: Between the photosphere and the corona, the thin region through which the temperature increases is known as the transition region. It ranges from only tens to hundreds of kilometers thick. Energy cannot be transferred from the cooler photosphere to the corona by conventional heat transfer as this would violate the second law of thermodynamics. An analogy of this would be a light bulb raising the temperature of the air surrounding it to something greater than its glass surface. Hence, some other manner of energy transfer must be involved in the heating of the corona.


title: Stellar corona

text: The amount of power required to heat the solar corona can easily be calculated as the difference between coronal radiative losses and heating by thermal conduction toward the chromosphere through the transition region. It is about 1 kilowatt for every square meter of surface area on the Sun's chromosphere, or 1/ of the amount of light energy that escapes the Sun.


title: Stellar corona

text: Many coronal heating theories have been proposed, but two theories have remained as the most likely candidates: wave heating and magnetic reconnection (or nanoflares). Through most of the past 50 years, neither theory has been able to account for the extreme coronal temperatures.


title: Stellar corona

text: In 2012, high resolution (<0.2″) soft X-ray imaging with the High Resolution Coronal Imager aboard a sounding rocket revealed tightly wound braids in the corona. It is hypothesized that the reconnection and unravelling of braids can act as primary sources of heating of the active solar corona to temperatures of up to 4 million kelvin. The main heat source in the quiescent corona (about 1.5 million kelvin) is assumed to originate from MHD waves.


title: Stellar corona

text: NASA's Parker Solar Probe is intended to approach the Sun to a distance of approximately 9.5 solar radii to investigate coronal heating and the origin of the solar wind. It was successfully launched on August 12, 2018 and has completed the first 13 by fall of 2022 of the more than 20 planned close approaches to the Sun.


title: Stellar corona

text: The wave heating theory, proposed in 1949 by Évry Schatzman, proposes that waves carry energy from the solar interior to the solar chromosphere and corona. The Sun is made of plasma rather than ordinary gas, so it supports several types of waves analogous to sound waves in air. The most important types of wave are magneto-acoustic waves and Alfvén waves. Magneto-acoustic waves are sound waves that have been modified by the presence of a magnetic field, and Alfvén waves are similar to ultra low frequency radio waves that have been modified by interaction with matter in the plasma. Both types of waves can be launched by the turbulence of granulation and super granulation at the solar photosphere, and both types of waves can carry energy for some distance through the solar atmosphere before turning into shock waves that dissipate their energy as heat.


title: Stellar corona

text: One problem with wave heating is delivery of the heat to the appropriate place. Magneto-acoustic waves cannot carry sufficient energy upward through the chromosphere to the corona, both because of the low pressure present in the chromosphere and because they tend to be reflected back to the photosphere. Alfvén waves can carry enough energy, but do not dissipate that energy rapidly enough once they enter the corona. Waves in plasmas are notoriously difficult to understand and describe analytically, but computer simulations, carried out by Thomas Bogdan and colleagues in 2003, seem to show that Alfvén waves can transmute into other wave modes at the base of the corona, providing a pathway that can carry large amounts of energy from the photosphere through the chromosphere and transition region and finally into the corona where it dissipates it as heat.


title: Stellar corona

text: Another problem with wave heating has been the complete absence, until the late 1990s, of any direct evidence of waves propagating through the solar corona. The first direct observation of waves propagating into and through the solar corona was made in 1997 with the Solar and Heliospheric Observatory space-borne solar observatory, the first platform capable of observing the Sun in the extreme ultraviolet (EUV) for long periods of time with stable photometry. Those were magneto-acoustic waves with a frequency of about 1 millihertz (mHz, corresponding to a wave period), that carry only about 10% of the energy required to heat the corona. Many observations exist of localized wave phenomena, such as Alfvén waves launched by solar flares, but those events are transient and cannot explain the uniform coronal heat.


title: Stellar corona

text: It is not yet known exactly how much wave energy is available to heat the corona. Results published in 2004 using data from the TRACE spacecraft seem to indicate that there are waves in the solar atmosphere at frequencies as high as (10 second period). Measurements of the temperature of different ions in the solar wind with the UVCS instrument aboard SOHO give strong indirect evidence that there are waves at frequencies as high as , well into the range of human hearing. These waves are very difficult to detect under normal circumstances, but evidence collected during solar eclipses by teams from Williams College suggest the presences of such waves in the 1– range.


title: Stellar corona

text: Recently, Alfvénic motions have been found in the lower solar atmosphere and also in the quiet Sun, in coronal holes and in active regions using observations with AIA on board the Solar Dynamics Observatory.


title: Stellar corona

text: These Alfvénic oscillations have significant power, and seem to be connected to the chromospheric Alfvénic oscillations previously reported with the Hinode spacecraft.


title: Stellar corona

text: Solar wind observations with the "Wind" spacecraft have recently shown evidence to support theories of Alfvén-cyclotron dissipation, leading to local ion heating.


title: Stellar corona

text: The magnetic reconnection theory relies on the solar magnetic field to induce electric currents in the solar corona. The currents then collapse suddenly, releasing energy as heat and wave energy in the corona. This process is called "reconnection" because of the peculiar way that magnetic fields behave in plasma (or any electrically conductive fluid such as mercury or seawater). In a plasma, magnetic field lines are normally tied to individual pieces of matter, so that the topology of the magnetic field remains the same: if a particular north and south magnetic pole are connected by a single field line, then even if the plasma is stirred or if the magnets are moved around, that field line will continue to connect those particular poles. The connection is maintained by electric currents that are induced in the plasma. Under certain conditions, the electric currents can collapse, allowing the magnetic field to "reconnect" to other magnetic poles and release heat and wave energy in the process.


title: Stellar corona

text: Magnetic reconnection is hypothesized to be the mechanism behind solar flares, the largest explosions in the Solar System. Furthermore, the surface of the Sun is covered with millions of small magnetized regions 50– across. These small magnetic poles are buffeted and churned by the constant granulation. The magnetic field in the solar corona must undergo nearly constant reconnection to match the motion of this "magnetic carpet", so the energy released by the reconnection is a natural candidate for the coronal heat, perhaps as a series of "microflares" that individually provide very little energy but together account for the required energy.


title: Stellar corona

text: The idea that nanoflares might heat the corona was proposed by Eugene Parker in the 1980s but is still controversial. In particular, ultraviolet telescopes such as TRACE and SOHO/EIT can observe individual micro-flares as small brightenings in extreme ultraviolet light, but there seem to be too few of these small events to account for the energy released into the corona. The additional energy not accounted for could be made up by wave energy, or by gradual magnetic reconnection that releases energy more smoothly than micro-flares and therefore doesn't appear well in the TRACE data. Variations on the micro-flare hypothesis use other mechanisms to stress the magnetic field or to release the energy, and are a subject of active research in 2005.


title: Stellar corona

text: For decades, researchers believed spicules could send heat into the corona. However, following observational research in the 1980s, it was found that spicule plasma did not reach coronal temperatures, and so the theory was discounted.


title: Stellar corona

text: As per studies performed in 2010 at the "National Center for Atmospheric Research" in Colorado, in collaboration with the "Lockheed Martin's Solar and Astrophysics Laboratory" (LMSAL) and the "Institute of Theoretical Astrophysics" of the University of Oslo, a new class of spicules (TYPE II) discovered in 2007, which travel faster (up to 100 km/s) and have shorter lifespans, can account for the problem. These jets insert heated plasma into the Sun's outer atmosphere.


title: Stellar corona

text: Thus, a much greater understanding of the corona and improvement in the knowledge of the Sun's subtle influence on the Earth's upper atmosphere can be expected henceforth. The Atmospheric Imaging Assembly on NASA's recently launched Solar Dynamics Observatory and NASA's Focal Plane Package for the Solar Optical Telescope on the Japanese Hinode satellite which was used to test this hypothesis. The high spatial and temporal resolutions of the newer instruments reveal this coronal mass supply.


title: Stellar corona

text: These observations reveal a one-to-one connection between plasma that is heated to millions of degrees and the spicules that insert this plasma into the corona.


title: National symbols of Pakistan

text: Pakistan has several official national symbols including a flag, an emblem, an anthem, a memorial tower as well as several national heroes. The symbols were adopted at various stages in the existence of Pakistan and there are various rules and regulations governing their definition or use. The oldest symbol is the Lahore Resolution, adopted by the All India Muslim League on 23 March 1940, and which presented the official demand for the creation of a separate country for the Muslims of India. The Minar-e-Pakistan memorial tower which was built in 1968 on the site where the Lahore Resolution was passed. The national flag was adopted just before independence was achieved on 14 August 1947. The national anthem and the state emblem were each adopted in 1954. There are also several other symbols including the national animal, bird, flower and tree.


title: National symbols of Pakistan

text: The Lahore Resolution ("Qarardad-e-Lahore") (), also known as the Pakistan Resolution, was a formal political statement adopted by the All India Muslim League at the occasion of its three-day general session on 22–24 March 1940 at Minto Park (now Iqbal Park), Lahore. The resolution called for greater Muslim autonomy in British India and has been largely interpreted as a demand for a separate Muslim state. The idea of separate state for Indian Muslims was first suggested by Muhammad Iqbal in 1930 and the name of Pakistan was proposed by Choudhary Rahmat Ali in his Pakistan Declaration pamphlet in 1933. Initially, Muhammad Ali Jinnah and other leaders were in favour of Hindu-Muslim unity, but the volatile political climate and religious hostilities of the 1930s made the idea more appealing.


title: National symbols of Pakistan

text: In his speech, Jinnah criticised the Indian National Congress and the nationalist Muslims, and espoused the Two-Nation Theory and the reasons for the demand for separate Muslim homelands. Sir Sikandar Hayat Khan, the Chief Minister of the Punjab, drafted the original resolution, but that was not fully acceptable to all the Working Committee, so extensive redrafting followed, by the Subject Committee of the Muslim League. The text is ambiguous in accepting the concept of various Muslim 'zones' within a "United India" due to communal concerns and it does not clearly recommend the creation of a separate, fully independent Muslim state. The resolution was moved in the general session by A.K. Fazlul Huq, Chief Minister of Bengal and was supported seconded by several leaders. The principle text of the Lahore Resolution was passed on 24 March 1940. In 1941 it became part of the Muslim League's constitution. By 1946, it formed the basis for the struggle of the Muslim League for a separate Muslim state. The statement declared:


title: National symbols of Pakistan

text: The Minar-e-Pakistan (Urdu: ; "Mīnār-ĕ Pākistān") which is the national tower of Pakistan also known as "Tower of Pakistan" is a 60 metre tall concrete minaret in Iqbal Park in Lahore. The Minar was built on the site where the Muslim League passed the Lahore Resolution, demanding the creation of Pakistan. Pakistan now celebrates this day as a national holiday each year under the name of Pakistan Day which is also the day in 1956 when the country became the first Islamic Republic in the world. It was designed by Muhammad Wali Ullah Khan and built by Mian Abdul Khaliq Company. The base of the tower is raised about 4 metres from the ground. The next 13 metres form a sculpted, flower-like base and from this point, the Minar tapers as it rises. The base platform is shaped like a five-pointed star and it encloses crescent-shaped pools. It is constructed of reinforced concrete, with the floors and walls rendered in stone and marble.


title: National symbols of Pakistan

text: The national flag was designed by Muhammad Ali Jinnah, the founder of Pakistan, and was based on the original flag of the Muslim League. It was adopted by the Constituent Assembly on 11 August 1947, just days before independence. The flag is referred to in the national anthem as "Parcham-e-Sitāra-o-Hilāl" in Urdu ("lit." Flag of the Crescent and Star). The flag comprises a dark green field, representing the Muslim majority of Pakistan, with a vertical white stripe in the hoist, representing religious minorities. In the centre is a white crescent moon, representing progress, and a white five-pointed star, representing light and knowledge. The flag symbolizes Pakistan's commitment to Islam, the Islamic world and the rights of religious minorities. The flag is flown on several important days of the year including Republic Day and Independence Day. The flag is also flown on the residences and motor vehicles of many public officials including the President and the Prime Minister.


title: National symbols of Pakistan

text: The national anthem of Pakistan or "Qaumī Tarāna" (Urdu: ), is played during any event involving the hoisting of the flag, for example Resolutions Day (23 March) and Independence Day (14 August). The Constituent Assembly had not adopted a national anthem by the time Pakistan became independent, so when the flag was hoisted at the independence ceremony it was accompanied by the song, ""Pakistan Zindabad, Azadi Paendabad"". Muhammad Ali Jinnah asked a Lahore-based Hindu writer, Jagan Nath Azad, to write a national anthem for Pakistan. Jinnah may have done this to promote a more secular idealism for Pakistan. The anthem written by Azad was quickly approved by Jinnah, and it was played on Radio Pakistan. Azad's work remained as Pakistan's national anthem for about eighteen months.


title: National symbols of Pakistan

text: A National Anthem Committee was formed in 1948, but it had difficulty finding suitable music and lyrics. The impending state visit of the Shah of Iran in 1950, resulted in the hasty adoption of a three stanza composition by Ahmed Ghulamali Chagla. Initially it was performed without lyrics for the Prime Minister Liaquat Ali Khan on 10 August 1950 and was approved for playing during the visit of the Shah. However, the anthem was not officially adopted until August 1954. The National Anthem Committee eventually approved lyrics written by Abu-Al-Asar Hafeez Jullandhuri and the new national anthem was first played properly on Radio Pakistan on 13 August 1954. Official approval was announced by the Ministry of Information and Broadcasting on 16 August 1954 followed by a performance of the national anthem in 1955 involving eleven major singers of Pakistan including Ahmad Rushdi.


title: National symbols of Pakistan

text: The State Emblem was adopted in 1954 and symbolizes Pakistan's ideological foundation, the basis of its economy, its cultural heritage and its guiding principles. The four components of the emblem are a crescent and star crest above a shield, which is surrounded by a wreath, below which is a scroll. The crest and the green colour of the emblem are traditional symbols of Islam. The quartered shield in the centre shows cotton, wheat, tea and jute, which were the major crops of Pakistan at independence and signify the agricultural base of the economy. The floral wreath, surrounding the shield, represents the floral designs used in traditional Mughal art and emphasizes the cultural heritage of Pakistan.


title: National symbols of Pakistan

text: The scroll supporting the shield contains Muhammad Ali Jinnah's motto in Urdu, which reads from right to left: () "Iman, Ittehad, Nazm o Zabt" translated as "Faith, Unity, Discipline" and are intended as the guiding principles for Pakistan.


title: Nathan Dales

text: Nathan Dales is a Canadian actor from Calgary, Alberta. He is most noted for his starring role as Daryl in "Letterkenny", for which he was a Canadian Screen Award nominee for Best Supporting Actor in a Comedy Series at the 5th Canadian Screen Awards in 2017.


title: Nathan Dales

text: A graduate of the American Academy of Dramatic Arts, he has also had roles in the television series "Tower Prep" and "The Indian Detective", and the films "", "" and "The Broken Hearts Gallery".


title: Jet Black

text: Brian John Duffy (26 August 1938 – 6 December 2022), professionally known as Jet Black, was an English drummer and founding member of punk rock/new wave band The Stranglers. He last performed with the band in 2015, and officially retired in 2018.


title: Jet Black

text: Black was born in Ilford, Essex. He was a successful businessman up until the mid-1970s, owning a fleet of ice cream vans, and an off-licence in Guildford, called 'The Jackpot'. This establishment was the base for the early Stranglers. He was also the owner of one of the earliest home brewing equipment companies, at a time when home brewing was in vogue.


title: Jet Black

text: He became a full-time professional musician in the mid-1970s and met Hugh Cornwell of the band "Johnny Sox" after reading an advertisement in the Melody Maker magazine. Cornwell joined Black in the Stranglers in 1974.


title: Jet Black

text: His style was usually simple and jazz-influenced, although "Duchess" and "Down in the Sewer" are examples of Stranglers songs that feature more frantic drumming. In the mid-1980s, Black elected to cease playing acoustic drums in the recording studio and used a Simmons kit triggered by pick-ups, most notably on the "Feline" and "Aural Sculpture" albums. Black performed with the Stranglers until 2015, with his retirement confirmed by 2018. His name is frequently chanted by the crowd at concerts.


title: Jet Black

text: Black said he was particularly fond of "The Raven" album because it was "the first time the Stranglers got major critical approval in the newspapers."


title: Jet Black

text: He wrote a short book, "Much Ado About Nothing", which detailed the riots in France which were blamed on The Stranglers' presence in 1981, and also wrote a book in 2010 titled "Seven Days in Nice" about the same subject.


title: Jet Black

text: During a long career in music, Black, like many other drummers, became aware of certain practical limitations inherent in the basic kit design and set about addressing the issue in the form of the now patented 'Jet Black Power Bass Drum Pedal'. which enables the bass drum to be placed anywhere and yet remain playable.


title: Jet Black

text: In March 2007, it was announced on the Stranglers' website that Black was suffering from atrial fibrillation and consequently refrained from appearing with the band until he had recovered. He returned to playing with the band in June, but it was at this time that he retired from performing outside of the United Kingdom due to health issues associated with lengthy travel. During Black's absences, his temporary replacement was his full-time drum technician Ian Barnard (born 1983).


title: Jet Black

text: In mid-2008, he was again absent from several Stranglers gigs. It was shortly thereafter announced that he was suffering from chest problems and was "not rushing back to work" on the advice of his doctor. In September 2008, he returned to full rehearsals and began touring with the band on 13 October.


title: Jet Black

text: During the Stranglers' 2010 and 2011 UK tours, Black performed at every gig. He played the full sets, which were approximately 90 minutes in length.


title: Jet Black

text: On 12 March 2012, Black was taken to hospital after "falling ill" shortly before a Stranglers concert at the O2 Academy Oxford. He was again replaced by Barnard during the gig. The Stranglers announced the following day that he had been taken to hospital via ambulance after feeling unwell shortly after the band's soundcheck. It was confirmed that the illness was a "severe chest infection" but that Black intended to rejoin the tour when he was "fit and able"; however, he did not rejoin the tour due to a slow recovery.


title: Jet Black

text: The Stranglers' annual tour began in March 2013, with Black playing the second half of the opening night set, drumming on 10 songs beginning with the distinctive Genetix drum intro. Drummer Jim Macaulay played the first half of the set on a separate, smaller drum kit. He had also by this time completely refrained from travelling outside of the UK with the band. Black did not feature at some subsequent gigs, but played half of the band's set at others where stage space would allow for the positioning of two drum kits. Jean-Jacques Burnel said ahead of the band's Leeds gig: "He's had a few health problems in recent years, but he’s really up for the tour, although he probably won’t be at every gig, or doing the full set."


title: Jet Black

text: His appearances during the 2014 Ruby Anniversary tour were sporadic. When present, his playing was restricted to the encore only. During the tour, he was quoted as saying: "I'll carry on until I'm incapable of doing it. I am going to have to stop one day, but I expect the band will carry on." However, bassist Jean-Jacques Burnel said during the same period: "When he can [no] longer contribute – and I don't think that's long – then there will be no more Stranglers." He remarked that Black was "on oxygen" even after drumming on slower numbers like "Golden Brown". In 2014, Black said of the Stranglers: "This is the best band in the world — and we'll carry on until we can't any more. Though we are not thinking about that." He was absent from the Stranglers' UK festival appearances and associated warm-up gigs in mid-2014.


title: Jet Black

text: In January 2015, Stranglers guitarist Baz Warne told the Louder Than War website: "Jet will do what he can when he can. He's a massive hard worker and he's never shirked away from anything but with the best will in the world you just can't cheat old age. He told Classic Rock Magazine that he has given us his blessing to carry on without him, he's sort of ready to hand over the baton to Jim, our new drummer who's been really welcomed by the fans. I know a lot of the old fans say it's not the same without Jet, and they're absolutely right but there comes a time when you have to ask yourself a simple question; do you want to see The Stranglers without Jet or just accept that you'll never see them again?"


title: Jet Black

text: In an interview with BBC Breakfast on 30 January, he said: "I've had a bit of trouble but I'm still playing gigs". During early dates on the tour, he relieved The Stranglers' touring drummer Jim Macaulay mid-set, playing approximately four songs including "Genetix". However, these appearances were limited to venues which had stages large enough for two drum kits. His appearances ceased regardless of venue size before the end of the tour, with his final appearance on stage with the Stranglers being at the Cambridge Corn Exchange on 20 March 2015.


title: Jet Black

text: Jean-Jacques Burnel confirmed, in a December 2015 interview, that Black would not take part in the band's 2016 tour. He said when questioned as to whether Black would be touring: "He can't. We tried that last year and I don't want him to become a freak show either. The most important thing for me is his health. If he can live a bit longer then that's a great thing. Physically he is in not a good place at all." Although he did not play with the band during their 2016 Black and White album tour, he continued to travel with the band, signing vinyl editions of the band's 1978 album, which were sold at gigs.


title: Jet Black

text: Shortly after his 78th birthday, Black said: "You find you just can't do some of the stuff you used to, and so the past seems so much more agreeable than the future ever could be. Something I guess we all get to know in time."


title: Jet Black

text: A promotional image released for the band's 2017 'Classics Collection' tour did not feature Black, and marked drummer Jim Macaulay's appearance in such an image for the first time. Black's departure from the band was officially confirmed in 2018 at the age of 79.


title: Jet Black

text: In 2008, an online petition on the British Government website campaigning for him to be included in the next list of honours attracted 477 signatures and was mentioned in the national press.


title: Jet Black

text: His second wife, Helena, left him following several arguments over the Stranglers rehearsing in their home during the early days of the band.


title: Jet Black

text: Black had no contact with former Stranglers singer Hugh Cornwell after he left the band in 1990. According to Cornwell's 2004 autobiography, when he telephoned Black to announce his resignation, the latter's response was simply "OK, fine." In 2014, he confirmed in a newspaper interview with the "Oxford Times" that he did not keep in touch with Cornwell. He most recently lived in Tetbury, Gloucestershire, where he reportedly designed and built wooden furniture.


title: Jet Black

text: Black died at his home in Wales on 6 December 2022, at the age of 84. Reacting to the news, Cornwell said: "We shared a special period of our lives when we strived to become professional musicians. We were immediately drawn to one another, he had a singular sense of purpose that I identified with. The Stranglers' success was founded on his determination and drive."


title: Jesus of Suburbia

text: "Jesus of Suburbia" is a song by American rock band Green Day. It was released as the fifth and final single from the group's seventh studio album, "American Idiot", and the second song on the album. With the song running for 9 minutes and 8 seconds, it is Green Day's second longest song (with the band's longest song being fellow "American Idiot" song "Homecoming", which runs for 9 minutes and 18 seconds) and the group's longest song to be released as a single. The studio version of the song was considered to be unfriendly for radio, so it was cut down to 6½ minutes for the radio edit. The long version was still played on many album rock and alternative rock radio stations. At most live shows on the first leg of the group's 21st Century Breakdown World Tour, the band would pick a member from the audience to play guitar for the song. The single has sold 205,000 copies as of July 2010. Despite its commercial success, the song is the only hit single from the "American Idiot" album not to be included on the band's greatest hits album "". The song has been described as a punk rock version of "Bohemian Rhapsody."


title: Jesus of Suburbia

text: "American Idiot" is a concept album that describes the story of a central character named Jesus of Suburbia, an anti-hero created by Billie Joe Armstrong. It is written from the perspective of a lower-middle-class suburban American teen, raised on a diet of "soda pop and Ritalin." Jesus hates his town and those close to him, so he leaves for The City.


title: Jesus of Suburbia

text: "Jesus of Suburbia" was the second multi-part song the group formed. Armstrong said it took "a long time" to write the song. Dirnt said that it came about from natural rehearsing between the trio. The song was an extension of Armstrong's desire to write the "Bohemian Rhapsody" of the future.


title: Jesus of Suburbia

text: Also, the opening bars of "Jesus of Suburbia," with their guitar-voice call and response structure, seem evocative of David Bowie's "Moonage Daydream."