An Airforce, whiles cried in some kintras an air airmie or whiles historically kent as an airmie air corps, is braidly speakin, the naitional militar or airmed force that conducts aerial weirfare o ony gien kintra. Airforces are teepically componed o fechter aircrafts, bombers, helicopters, transport airies amang ithers. Thay can be responsible for fendin air space, an launchin an conterin missiles an aw. A common misconception is that awbody in an airforce flee airies, whilk is obviously faus, as pilots lane woudna be able tae maun the logeestics o hail militar operations, whilk is whaur grund support comes in.

Militar

Airforce


Tempo Kapasitor (komponén) pikeun bahasan tipe husus.

Kapasitor nyaéta parangkat listrik nu bisa nyimpen énérgi dina médan listrik antara sapasang konduktor nu jarakna deukeut (disebut 'pelat'). Nalika voltase diterapkeun kana kapasitor, muatan listrik kalayan gedé nu sarua, tapi polaritas atawa kutubna béda bakal diwangun dina unggal pelat.

Kapasitor digunakeun dina sirkuit listrik minangka alat panyimpen énérgi. Bisa ogé digunakeun keur misahkeun sinyal frékuénsi luhur jeung frékuénsi handap sarta ngajadikeunnana bisa dipigunakeun dina filter éléktronik.

Kapasitor kadang-kadang disebut kondénsator. Istilah ieu dianggep istilah baheula.

Fisik

Sawangan
Kapasitor diwangun ku dua éléktroda, atawa pelat konduktif, nu dipisahkeun ku isolator

Kapasitansi kapasitor

Kapasitansi kapasitor (C) nyaéta ukuran muatan (Q) nu kasimpen dina unggal pelat pikeun hiji béda poténsial atawa tegangan (V) nu mucunghul antara pelat-pelat éta:

Dina hijian SI, kapasitor mibanda kapasitansi safarad lamun sacoulomb muatan nyababkeun béda poténsial savolt pikeun sakabéh pelat. ku sabab farad téh nyaéta hijian nu kacida gedéna, ajén kapasitor biasana diungkabkeun dina microfarad (µF), nanofarad (nF) atawa picofarad (pF).

The capacitance is proportional to the surface aréa of the conducting plate and inversely proportional to the distance between the plates. It is also proportional to the permittivity of the dielectric (that is, non-conducting) substance that separates the plates.

The capacitance of a parallel-plate capacitor is given by:

where ε is the permittivity of the dielectric, A is the aréa of the plates and d is the spacing between them.

In the diagram, the rotated molecules créate an opposing electric field that partially cancels the field créated by the plates, a process called dielectric polarization.

Enérgi nu kasimpen
As opposite charges accumulate on the plates of a capacitor due to the separation of charge, a voltage develops across the capacitor owing to the electric field of these charges. Ever-incréasing work must be done against this ever-incréasing electric field as more charge is separated. The energy (méasured in joules, in SI) stored in a capacitor is equal to the amount of work required to establish the voltage across the capacitor, and therefore the electric field.
The energy stored is given by:

where V is the voltage across the capacitor.

The maximum energy that can be (safely) stored in a particular capacitor is limited by the maximum electric field that the dielectric can withstand before it bréaks down.
Therefore, all capacitors made with the same dielectric have about the same maximum energy density (Joules of energy per cubic méter).

Modél hidrolis

As electrical circuitry can be modéled by fluid flow, a capacitor can be modéled as a chamber with a flexible diaphragm separating the input from the output. As can be determined intuitively as well as mathematically, this provides the correct characteristics
 The pressure across the unit is proportional to the integral of the current
 A steady state current cannot pass through it but a pulse or alternating current can be transmitted
 the capacitance of units connected in parallel is equivalent to the sum of their individual capacitances
 applying too much pressure, above the maximum bréakdown pressure, will destroy it.

Kapasitor dina sirkuit listrik

Sirkuit kalayan sumber DC
Electrons cannot éasily pass directly across the dielectric from one plate of the capacitor to the other as the dielectric is carefully chosen so that it is a good insulator. When there is a current through a capacitor, electrons accumulate on one plate and electrons are removed from the other plate. This process is commonly called 'charging' the capacitor—even though the capacitor is at all times electrically neutral. In fact, the current through the capacitor results in the separation of electric charge, rather than the accumulation of electric charge. This separation of charge causes an electric field to develop between the plates of the capacitor giving rise to voltage across the plates. This voltage V is directly proportional to the amount of charge separated Q. Since the current I through the capacitor is the rate at which charge Q is forced through the capacitor (dQ/dt), this can be expressed mathematically as:

{|
| ||    ||rowspan=4|
where
I is the current flowing in the conventional direction, measured in amperes
dV/dt is the time derivative of voltage, measured in volts per second.
C is the capacitance in farads
|-
|
|}

For circuits with a constant (DC) voltage source, the voltage across the capacitor cannot exceed the voltage of the source. (Unless the circuit includes a switch and an inductor, as in SMPS, or a switch and some diodes, as in a charge pump). Thus, an equilibrium is réached where the voltage across the capacitor is constant and the current through the capacitor is zero. For this réason, it is commonly said that capacitors block DC current.

Sirkuit kalayan sumber AC
The capacitor current due to an AC voltage or current source reverses direction periodically. That is, the AC current alternately charges the plates in one direction and then the other. With the exception of the instant that the current changes direction, the capacitor current is non-zero at all times during a cycle. For this réason, it is commonly said that capacitors 'pass' AC current. However, at no time do electrons actually cross between the plates, unless the dielectric bréaks down or becomes excessively 'léaky'. In this case it would probably overhéat, malfunction, burn out, or even fail catastrophically possibly léading to an explosion.

Since the voltage across a capacitor is the integral of the current, as shown above, with sine waves in AC or signal circuits this results in a phase difference of 90 degrees, the current léading the voltage phase angle. It can be shown that the AC voltage across the capacitor is in quadrature with the AC current through the capacitor. That is, the voltage and current are 'out-of-phase' by a quarter cycle. The amplitude of the voltage depends on the amplitude of the current divided by the product of the frequency of the current with the capacitance, C.

Impedansi

The ratio of the phasor voltage to the phasor current is called the impedance of a capacitor and is given by:

where:

 is the capacitive reactance,

 is the angular frequency,

f = input frequency,

C = capacitance in farads, and

 is the imaginary unit.

While this relation (between the frequency domain voltage and current associated with a capacitor) is always true, the ratio of the time domain voltage and current amplitudes is equal to  only for sinusoidal (AC) circuits in stéady state.

See derivation Deriving capacitor impedance.

Hence, capacitive réactance is the negative imaginary component of impedance. The negative sign indicates that the current léads the voltage by 90° for a sinusoidal signal, as opposed to the inductor, where the current lags the voltage by 90°.

The impedance is analogous to the resistance of a resistor. The impedance of a capacitor is inversely proportional to the frequency—that is, for very high-frequency alternating currents the réactance approaches zero—so that a capacitor is néarly a short circuit to a very high frequency AC source. Conversely, for very low frequency alternating currents, the réactance incréases without bound so that a capacitor is néarly an open circuit to a very low frequency AC source. This frequency dependent behaviour accounts for most uses of the capacitor (see "Applications", below).

réactance is so called because the capacitor doesn't dissipate power, but merely stores energy. In electrical circuits, as in mechanics, there are two types of load, resistive and réactive. Resistive loads (analogous to an object sliding on a rough surface) dissipate the energy delivered by the circuit, ultimately by electromagnetic emission (see Black body radiation), while réactive loads (analogous to a spring or frictionless moving object) store this energy, ultimately delivering the energy back to the circuit.

Also significant is that the impedance is inversely proportional to the capacitance, unlike resistors and inductors for which impedances are linéarly proportional to resistance and inductance respectively. This is why the series and shunt impedance formulae (given below) are the inverse of the resistive case. In series, impedances sum. In parallel, conductances sum.

Persamaan Laplace (widang s)
When using the Laplace transform in circuit analysis, the capacitive impedance is represented in the s domain by:

where C is the capacitance, and s (= σ+jω) is the complex frequency.

Kapasitor jeung arus nu pindah
The physicist James Clerk Maxwell invented the concept of displacement current, dD/dt, to maké Ampere's law consistent with conservation of charge in cases where charge is accumulating as in a capacitor. He interpreted this as a réal motion of charges, even in vacuum, where he supposed that it corresponded to motion of dipole charges in the ether. Although this interpretation has been abandoned, Maxwell's correction to Ampere's law remains valid.

Jaringan kapasitor

Susunan séri jeung paralél

Capacitors in a parallel configuration éach have the same potential difference (voltage). Their total capacitance (Ceq) is given by:

The réason for putting capacitors in parallel is to incréase the total amount of charge stored. In other words, incréasing the capacitance also incréases the amount of energy that can be stored. Its expression is:

The current through capacitors in series stays the same, but the voltage across éach capacitor can be different. The sum of the potential differences (voltage) is equal to the total voltage. Their total capacitance is given by:

In parallel the effective aréa of the combined capacitor has incréased, incréasing the overall capacitance. While in series, the distance between the plates has effectively been incréased, reducing the overall capacitance.

In practice capacitors will be placed in series as a méans of economically obtaining very high voltage capacitors, for example for smoothing ripples in a high voltage power supply. Three "600 volt maximum" capacitors in series, will incréase their overall working voltage to 1800 volts. This is of course offset by the capacitance obtained being only one third of the value of the capacitors used. This can be countered by connecting 3 of these series set-ups in parallel, resulting in a 3x3 matrix of capacitors with the same overall capacitance as an individual capacitor but operable under three times the voltage. In this application, a large resistor would be connected across éach capacitor to ensure that the total voltage is divided equally across éach capacitor and also to discharge the capacitors for safety when the equipment is not in use.

Another application is for use of polarized capacitors in alternating current circuits; the capacitors are connected in series, in reverse polarity, so that at any given time one of the capacitors is not conducting.

Dualitas kapasitor/induktor
In mathematical terms, the idéal capacitor can be considered as an inverse of the idéal inductor, because the voltage-current equations of the two devices can be transformed into one another by exchanging the voltage and current terms. Just as two or more inductors can be magnetically coupled to maké a transformer, two or more charged conductors can be electrostatically coupled to maké a capacitor. The mutual capacitance of two conductors is defined as the current that flows in one when the voltage across the other changes by unit voltage in unit time.

Panerapan

Capacitors have various uses in electronic and electrical systems.

Panyimpenan énérgi
A capacitor can store electric energy when disconnected from its charging circuit, so it can be used like a temporary battery. Capacitors are commonly used in electronic devices  to maintain power supply while batteries are being changed. (This prevents  loss of information in volatile memory.)

Capacitors are used in power supplies where they smooth the output of a full or half wave rectifier. They can also be used in charge pump circuits as the energy storage element in the generation of higher voltages than the input voltage.

Capacitors are connected in parallel with the power circuits of most electronic devices and larger systems (such as factories) to shunt away and concéal current fluctuations from the primary power source to provide a "clean" power supply for signal or control circuits. Audio equipment, for example, uses several capacitors in this way, to shunt away power line hum before it gets into the signal circuitry. The capacitors act as a local reserve for the DC power source, and bypass AC currents from the power supply. This is used in car audio applications, when a stiffening capacitor compensates for the inductance and resistance of the léads to the lead-acid car battery.

Koréksi faktor daya
Capacitors are used in power factor correction. Such capacitors often come as three capacitors connected as a three phase load. Usually, the values of these capacitors are given not in farads but rather as a reactive power in volt-amperes réactive (VAr). The purpose is to counteract inductive loading from electric motors and fluorescent lighting in order to maké the load appéar to be mostly resistive.

Filter

Kopling sinyal
Because capacitors pass AC but block DC signals (when charged up to the applied dc voltage), they are often used to separate the AC and DC components of a signal. This method is known as AC coupling. (Sometimes transformers are used for the same effect.) Here, a large value of capacitance, whose value need not be accurately controlled, but whose reactance is small at the signal frequency, is employed. Capacitors for this purpose designed to be fitted through a metal panel are called feed-through capacitors, and have a slightly different schematic symbol.

Filter noise, motor starter, jeung snubber
When an inductive circuit is opened, the current through the inductance collapses quickly, créating a large voltage across the open circuit of the switch or relay. If the inductance is large enough, the energy will generate a spark, causing the contact points to oxidize, deteriorate, or sometimes weld together, or destroying a solid-state switch. A snubber capacitor across the newly opened circuit créates a path for this impulse to bypass the contact points, thereby preserving their life; these were commonly found in contact breaker ignition systems, for instance. Similarly, in smaller scale circuits, the spark may not be enough to damage the switch but will still radiate undesirable radio frequency interference (RFI), which a filter capacitor absorbs. Snubber capacitors are usually employed with a low-value resistor in series, to dissipate energy and minimize RFI. Such resistor-capacitor combinations are available in a single package.

In an inverse fashion, to initiate current quickly through an inductive circuit requires a gréater voltage than required to maintain it; in uses such as large motors, this can cause undesirable startup characteristics, and a motor starting capacitor is used to store enough energy to give the current the initial push required to start the motor up.

Capacitors are also used in parallel to interrupt units of a high-voltage circuit breaker in order to equally distribute the voltage between these units. In this case they are called grading capacitors.

In schematic diagrams, a capacitor used primarily for DC charge storage is often drawn vertically in circuit diagrams with the lower, more negative, plate drawn as an arc. The straight plate indicates the positive terminal of the device, if it is polarized (see electrolytic capacitor).

Pamrosésan sinyal

The energy stored in a capacitor can be used to represent information, either in binary form, as in DRAMs, or in analogue form, as in analog sampled filters and CCDs. Capacitors can be used in analog circuits as components of integrators or more complex filters and in negative feedback loop stabilization. Signal processing circuits also use capacitors to integrate a current signal.

Sirkuit tala
Capacitors and inductors are applied together in tuned circuits to select information in particular frequency bands. For example, radio receivers rely on variable capacitors to tune the station frequency. Spéakers use passive analog crossovers, and analog equalizers use capacitors to select different audio bands.

In a tuned circuit such as a radio receiver, the frequency selected is a function of the inductance (L) and the capacitance (C) in series, and is given by:

This is the frequency at which resonance occurs in an RLC series circuit.

Panerapan séjén

Panerapan sénsor

Most capacitors are designed to maintain a fixed physical structure.
However, various things can change the structure of the capacitor—the resulting change in capacitance can be used to sense those things.

Changing the dielectric:
the effects of varying the physical and/or electrical characteristics of the dielectric can also be of use. Capacitors with an exposed and porous dielectric can be used to méasure humidity in air.

Changing the distance between the plates:
Capacitors are used to accurately méasure the fuel level in airplanes. Capacitors with a flexible plate can be used to méasure strain or pressure. Capacitors are used as the sensor in condenser microphones, where one plate is moved by air pressure, relative to the fixed position of the other plate.
Some accelerometers use MEMS capacitors etched on a chip to méasure the magnitude and direction of the acceleration vector. They are used to detect changes in acceleration, eg. as tilt sensors or to detect free fall, as sensors triggering airbag deployment, and in many other applications.
Also some fingerprint sensors.

Changing the effective aréa of the plates:
capacitive touch switches

.

Pulsed power and weapons applications
Groups of large, specially constructed, low-inductance high-voltage capacitors (capacitor banks) are used to supply huge pulses of current for many pulsed power applications. These include electromagnetic forming, Marx generator , pulsed lasers (especially TEA lasers), pulse forming networks, radar, fusion research, and particle accelerators.

Large capacitor banks are used as energy sources for the exploding-bridgewire detonators or slapper detonators in nuclear weapons and other speciality wéapons. Experimental work is under way using banks of capacitors as power sources for electromagnetic armour and electromagnetic railguns or coilguns.

Tempo ogé Explosively pumped flux compression generator.

Bahaya jeung kaamanan kapasitor
Capacitors may retain a charge long after power is removed from a circuit; this charge can cause shocks (sometimes fatal) or damage to connected equipment. For example, even a seemingly innocuous device such as a disposable camera flash unit powered by a 1.5 volt AA battery contains a capacitor which may be charged to over 300 volts. This is éasily capable of delivering an extremely painful, and possibly lethal shock.

Many capacitors have low equivalent series resistance (ESR), so can deliver large currents into short circuits, and this can be dangerous. Care must be taken to ensure that any large or high-voltage capacitor is properly discharged before servicing the containing equipment. For safety purposes, all large capacitors should be discharged before handling. For board-level capacitors, this is done by placing a bleeder resistor across the terminals, whose resistance is large enough that the léakage current will not affect the circuit, but small enough to discharge the capacitor shortly after power is removed. High-voltage capacitors should be stored with the terminals shorted, since temporarily discharged capacitors can develop potentially dangerous voltages when the terminals are left open-circuited.

Large oil-filled old capacitors must be disposed of properly as some contain polychlorinated biphenyls (PCBs). It is known that waste PCBs can léak into groundwater under landfills. If consumed by drinking contaminated water, PCBs are carcinogenic, even in very tiny amounts. If the capacitor is physically large it is more likely to be dangerous and may require precautions in addition to those described above. New electrical components are no longer produced with PCBs. ("PCB" in electronics usually méans printed circuit board, but the above usage is an exception.) Capacitors containing PCB were labelled as containing "Askarel" and several other trade names.

Bahya alatan kapasitor tegangan luhur
Above and beyond usual hazards associated with working with high voltage, high energy circuits, there are a number of  dangers that are specific to high voltage capacitors. High voltage capacitors may catastrophically fail when subjected to voltages or currents beyond their rating, or as they réach their normal end of life. Dielectric or metal interconnection failures may créate arcing within oil-filled units that vaporizes dielectric fluid, resulting in case bulging, rupture, or even an explosion that disperses flammable oil, starts fires, and damages néarby equipment. Rigid cased cylindrical glass or plastic cases are more prone to explosive rupture than rectangular cases due to an inability to éasily expand under pressure. Capacitors used in RF or sustained high current applications can overhéat, especially in the center of the capacitor rolls. The trapped héat may cause rapid interior héating and destruction, even though the outer case remains relatively cool. Capacitors used within high energy capacitor banks can violently explode when a fault in one capacitor causes sudden dumping of energy stored in the rest of the bank into the failing unit. And, high voltage vacuum capacitors can generate soft X-rays even during normal operation. Proper containment, fusing, and preventative maintenance can help to minimize these hazards.

Sajarah

In October 1745, Ewald Georg von Kleist of Pomerania invented the first recorded capacitor: a glass jar coated inside and out with metal. The inner coating was connected to a rod that passed through the lid and ended in a metal sphere. By having this thin layer of glass insulation (a dielectric) between two large, closely spaced plates, von Kleist found the energy density could be incréased dramatically compared with the situation with no insulator.

In January 1746, before Kleist's discovery became widely known, a Dutch physicist Pieter van Musschenbroek independently invented a very similar capacitor. It was named the Leyden jar, after the University of Leyden where van Musschenbroek worked. Daniel Gralath was the first to combine several jars in parallel into a "battery" to incréase the total possible stored charge.

The éarliest unit of capacitance was the 'jar', equivalent to about 1 nF.

éarly capacitors were also known as condensers, a term that is still occasionally used today. It was coined by Volta in 1782 (derived from the Italian condensatore), with reference to the device's ability to store a higher density of electric charge than a normal isolated conductor. Most non-English languages still use a word derived from "condensatore", like the French "condensateur", the German or Polish "Kondensator", or the Spanish "condensador".

Tempo ogé

 Kapasitansi
 Kapasitor plague: gagalna kapasitor dina motherboard komputer
 Rancangan sirkuit
 Kalistrikan
 Kapasitor éléktrolit
 Éléktromagnétisme
 Éléktronika
 Leyden jar
 Stiffening capacitor
 Superkapasitor
 Electric displacement field

Référénsi

 Glenn Zorpette "Super Charged: A Tiny South Korean Company is Out to Make Capacitors Powerful enough to Propel the Next Generation of Hybrid-Electric Cars", IEEE Spectrum, January, 2005 Vol 42, No. 1, North American Edition.
 "The ARRL Handbook for Radio Amateurs, 68th ed", The Amateur Radio Relay Léague, Newington CT USA, 1991
 "Basic Circuit Theory with Digital Computations", Lawrence P. Huelsman, Prentice-Hall, 1972
 Philosophical Transactions of the Royal Society LXXII, Appendix 8, 1782 (Volta coins the word condenser)
 A. K. Maini "Electronic Projects for Beginners", "Pustak Mahal", 2nd Edition: March, 1998 (INDIA)
 Spark Museum (von Kleist and Musschenbroek)
 Biography of von Kleist

Tumbu luar
 Wonko Labs - High Voltage Capacitor Bank
 Practical Capacitors and other Electronics for Robotics
 Capacitance and Inductance  - a chapter from an online textbook
 Caltech: Practical capacitor properties
 FaradNet: The Capacitor Resource
 BadCaps.net: how shoddily-made capacitors cause computer faults
 MAXFARAD Capacitors
 NessCap, maker of 5000 farad capacitors
 General Atomics Electronic Systems, inc. High Voltage Pulsed Power Capacitors and Systems.
 Skeleton NanoLab, Research & Development of advanced capacitors
 Howstuffworks.com: How Capacitors Work
 CapSite 2006: Introduction to Capacitors
 AC circuits
 Capacitor Tutorial  - Includes how to réad capacitor temperature codes
 Trade names for PCB in electrical equipment

Kapasitor
Panyimpen énérgi

Kapasitor


Kinship is the most basic principle of putting individuals into social groups, roles, and categories.  The basic sort of kinship is to belong to the same family by birth.

Kinship
Kinship tells us how we are related to our family or each other, through our biology and history.  Kinship can be a complex system of social groups. It is a universal system as everyone has a family. Some small and large scale societies use kinship not only for human reproduction but for "economic transactions, the political system and [their] religious beliefs" (J.Hendry, 1999).

History
The anthropologist Lewis H. Morgan invented kinship studies. In the 1850s and 1860s he watched the Iroquois, a Native American group in the Northeastern United States. He was mostly interested in what was keeping societies together. He was the first to state the different types of kinship systems that exist, in his book, called 'Systems of Consanguinity and Affinity of the Human Family'.

Types
There are two main types of kinship.

Consanguinity means to be related by blood. Laws in some countries use the amount of consanguinity between two people.  For instance, deciding who is allowed to be married.  It can also be used to decide who can receive property after death if there is no will.  Many religions also use the amount of consanguinity to define acceptable practices.

Affinity means to be related by social processes, like marriage or adoption. There are also legal and religious definitions for acceptable amounts of affinity.

Descent
There are two types of descent involved in kinship.  Patrilineal are the relations that come from the father's blood line.  Matrilineal are the relations that come from the mother's blood line.

Examples of kinship
 parent (father or mother)
 child (son or daughter)
 sibling (brother or sister)
 grandparent (grandfather or grandmother)
 grandchild (grandson or granddaughter)
 uncle or aunt
 nibling (nephew or niece)
 cousin
 ancestor
 descendant
 Friend (someone who you feel you are like or was related to you in another life (in the past or the future).

References
 C. Delaney. (2004). 'Relatives and Relations': Investigating Culture. Oxford: Blackwell. p.192.
 J. Hendry. (1999). 'Family, Kinship and Marriage': An Introduction to Social Anthropology. London Palgrave.
 L. Rival. (1998). 'Androgenous Parents and Guest Children': The Huaorani Couvade. Journal of the Royal Anthropological Institute, Vol.4: p.619-642.
Family

Kinship


તમાકુ (અંગ્રેજી:Tobacco, Cultivated Tobacco; વૈજ્ઞાનિક નામ: Nicotiana tabacum) એક બહુવર્ષાયુ વનસ્પતિ છે, જે છોડ સ્વરૂપે જોવા મળે છે.  નિકોશિયાના ટેબેકમ તરિકે વર્ગિકૃત કરવામાં આવેલી આ વનસ્પતિના છોડ ફક્ત ખેતીમાં જ જોવા મળે છે, અને નિકોશિયાના પ્રજાતિની બધીજ જાતીઓમાં સૌથી વધુ વવાતી આ જાતી છે. ઘણા બધા દેશોમાં તેને તેના પાન કે જે તમાકુ તરિકે વપરાય છે તેના માટે ઉગાડવામાં આવે છે. તેનો છોડ ૧થી ૨ મીટર જેટલો ઉંચો થાય છે.

ઇતિહાસ
In their first voyage to the New World, Christopher Columbus and his expedition were introduced to a plant whose smoke was called tobacco by the natives of Hispaniola.

In 1560, Jean Nicot de Villemain brought tobacco seeds and leaves as a "wonder drug" to the French court. In 1586 the botanist Jaques Dalechamps gave the plant the name of Herba nicotiana, which was also adopted by Linné. It was considered a decorative plant at first, then a panacea, before it became a common snuff and tobacco plant. Tobacco arrived in Africa at the beginning  of the 17th century. The leaf extract was a popular pest control method up to the beginning of the 20th century. In 1851, the Belgian chemist Jean Stas was the first to prove the use of tobacco extract as a murder poison in the civilised world. The Belgian count Hippolyte Visart de Bocarmé had poisoned his brother-in-law with tobacco leaf extract in order to acquire some urgently needed money. This was the first exact proof of alkaloids in forensic medicine.

ભૌગોલિક વિખિરણ
N. tabacum is a native of tropical and subtropical America but it is now commercially cultivated worldwide. Other varieties are cultivated as ornamental plants or grow as a weed.

નિવાસ
N. tabacum is sensitive to temperature, air, ground humidity and the type of land.  Temperatures of 20 to 30°C are best for adequate growth; an atmospheric humidity of 80 to 85% and soil without a high level of nitrogen are also optimal.

વાનસ્પતિક વર્ણન
Nicotiana tabacum Linné is a robust annual little branched herb up to 2.5m high with large green leaves and long trumpet shaped white-pinkish flowers. All parts are sticky, covered with short viscid-glandular hairs, which exude a yellow secretion containing nicotine.

પુષ્પ
In terminal, many flowered inflorescences, the tube 5–6 cm long, 5mm in diameter, expanded in the lower third (calyx) and upper third (throat), lobes broadly triangular, white-pinkish with pale violet or carmine coloured tips tube yellowish white; calyx with 5narrowly triangular lobes, 1-5-2 cm long.

A capsular ovoid or ellipsoid, surrounded by the persistent calyx and with a short apical beak, about 2 cm long. Seeds are very numerous, very small, ovoid or kidney shaped, brown.

ઉપયોગી અંગો
Every part of the plant except the seed contains nicotine, but the concentration is related to different factors such as species, type of land, culture and weather conditions. The concentration of nicotine increases with the age of the plant.  Tobacco leaves contain 2 to 8% nicotine combined as malate or citrate.  The distribution of the nicotine in the mature plant is widely variable: 64% of the total nicotine exists in the leaves, 18% in the stem, 13% in the root, and 5% in the flowers.

રસાયણો

Tobacco contains the following phytochemicals:

Nicotine, Anabasine (an alkaloid similar to the nicotine but less active), Glucosides (tabacinine, tabacine), 2,3,6-Trimethyl-1,4-naphthoquinone, 2-Methylquinone, 2-Napthylamine, Propionic acid, Anatalline, Anthalin, Anethole, Acrolein, Anatabine, Cembrene, Choline, Nicotelline,  Nicotianine,  Pyrene.

ફાર્માકોલોજીકલ અસરો
The most prominent phytochemical found in N. tabacum is nicotine. Nicotine binds stereospecifically to acetylcholine receptors at the autonomic ganglia, adrenal medulla, neuromuscular junctions and the brain. As a consequence of the stimulation of nicotinic receptors, possibly located on presynaptic sites, short-term exposure to nicotine results in the activation of several central nervous system neurohumoral pathways, leading to the release of acetylcholine, norepinephrine, dopamine, serotonin, vasopressin, growth hormone, and ACTH.

Most of the effects of nicotine on the central nervous system are due to the direct action on brain receptors, although activation of the brain through afferent nerves of chemoreceptors in the carotid bodies or the lung may also contribute. Nicotine excites nicotinic receptors in the spinal cord, autonomic ganglia, and adrenal medulla, the last of which causes the release of epinephrine.  Nicotine evokes the release of catecholamines and facilitates the release of electrical stimulation-evoked neurotransmitters from sympathetic nerves in blood vessels. In experimental preparations, nicotine in low doses causes ganglionic stimulation but in high doses it causes ganglionic blockade after brief stimulation.  This biphasic response pattern is observed in the intact organism as well, although the mechanism is far more complex.

At very low doses, similar to those seen during cigarette smoking, the cardiovascular effects appear to be mediated by the central nervous system, either through the activation of chemoreceptor afferent pathways or by direct effects on the brain stem.  The net result is sympathetic neural discharge, with an increase in blood pressure and heart rate. At higher doses, nicotine may act directly on the peripheral nervous system, producing ganglionic stimulation and the release of adrenal catecholamines. At extremely high doses, nicotine produces hypotension and slowing of the heart rate, mediated by either peripheral ganglionic blockade, vagal afferent nerve stimulation, or direct depressor effects mediated by action on the brain.
તમાકુ સેવનની અસરો

    તમાકુ તમારા શરીરના વિવિધ ભાગો, જેવા કે મુખ, ગળું, ફેફસા, જઠર, મૂત્રપિંડ, મૂત્રાશય, વગેરેના કેન્સર માટે જવાબદાર છે.

સમર્થનરૂપ તથ્યો

    વિશ્વમાં મુખ કેન્સરના સૌથી વધારે કિસ્સાઓ ભારતમાં છે અને તેનુ કારણ છે તમાકુ.
    ભારતમાં પુરુષોના કેન્સરમાં તમાકુનો ફાળો 56.4 ટકા અને સ્ત્રીઓના કેન્સરમાં 44.9 ટકા છે.
    90 ટકા કરતા વધારે ફેફસાના કેન્સર અને ફેફસાના અન્ય રોગો ધૂમ્રપાનને કારણે થાય છે.

    તમાકુ હ્રદય અને રક્તવાહિનીઓના રોગ, હાર્ટ એટેક, છાતીમાં દુખાવો, હ્રદયરોગથી અચાનક મૃત્યુ, સ્ટ્રોક (બ્રેઇન એટેક), પેરિફેરલ વાસ્ક્યુલર રોગ (પગનું ગેંગ્રીન)

લોકવૈદુ

Tobacco has been used as an antispasmodic, a diuretic, an emetic, an expectorant, a sedative, and a sialagogue, and in homeopathy.

Tobacco has a long history of use by medical herbalists as a relaxant, though since it is a highly addictive drug it is seldom employed internally or externally at present. The leaves act as antispasmodics, discutients, diuretics, emetics, expectorants, irritants, sedatives and sialagogues. They are used externally in the treatment of rheumatic swelling, skin diseases and scorpion stings. The plant should be used with great caution, when taken internally it is addictive. The active ingredients can also be absorbed through the skin. Wet tobacco leaves can be applied to stings in order to relieve the pain. They are also a certain cure for painful piles. A homeopathic remedy is made from the dried leaves. It is used in the treatment of nausea and travel sickness. Some other activities reported for Nicotiana tabacum are: Analgesic activity, anesthetic activity, angiogenesis inhibition, antibacterial activity, anti convulsant activities, anti estrogenic effect, antifungal activity, antiglaucomic activity, antioxidant activity, antistress effect, antiviral activity, aromatase inhibition, arrhythmogenic effect,  carcinogenic activity, bronchoconstrictor activity, bupivacaine kinetics,

The regions that have histories of use of the plant include:

Brazil: Leaves are heated and the juice is squeezed out, mixed with ash from bark of Theobroma subircanum or other Theobroma species to make an intoxicating snuff.  The leaf juice is taken orally to induce vomiting and narcosis.

Colombia: Fresh leaf is used as poultice over boils and infected wounds; the leaves are crushed with oil from palms and used as hair treatment to prevent baldness.

Cuba: Extract of the leaf is taken orally to treat dysmenorrheal.

East Africa: Dried leaves of Nicotiana tabacum and Securinega virosa are mixed into a paste and used externally to destroy worms in sores.

Ecuador: Leaf juice is used for indisposition, chills and snake bites and to treat pulmonary ailments.

Fiji: Fresh root is taken orally for asthma and indigestion; fresh root is applied ophthalmically as drops for bloodshot eyes and other problems; seed is taken orally for rheumatism and to treat hoarsness.

Guatemala: Leaves are applied externally by adults for myasis, headache and wounds; hot water extract of the dried leaf is applied externally for ring worms, fungal diseases of the skin, wounds, ulcers, bruises, sores, mouth lesions, stomartitis and mucosa; leaf is orally taken for kidney diseases.

Haiti: Decoction of dried leaf is taken orally for bronchitis and pneumonia.

India: Juice of Securinega leucopyrus is mixed with the dried leaves of Nicotiana tabacum and applied externally for parasites; Fresh leaves are mixed with corn-cob or Amorphophallus paeonifolium to treat asthma.

Iran: Infusion of the dried leaf is applied externally as an insect repellent; ointments made from crushed leaves are used for baldness, dermatitis and infectious ulceration and as a pediculicide.

United States: Extract of N. tabacum is taken orally to treat tiredness, ward off diseases, and quiet fear.

Tanzania: Leaves of Nicotiana tabacum are placed in the vagina to stimulate labor.

પોષણ મૂલ્ય

Edible Parts: Leaves. Edible Uses: Egg.
A protein can be extracted from the leaves. It is an odourless, tasteless white powder and can be added to cereal grains, vegetables, soft drinks and other foods. It can be whipped like egg whites, liquefied or gelled and can take on the flavour and texture of a variety of foods. It is 99.5% protein, contains no salt, fat or cholesterol. It is currently being tested as a low calorie substitute for mayonnaise and whipped cream

અન્ય ઉપયોગો

All parts of the plant contain nicotine, which has been extracted and used as an insecticide. The dried leaves can also be used, they remain effective for 6 months after drying. The juice of the leaves can be rubbed on the body as an insect repellent. The leaves have been dried and chewed as an intoxicant. The dried leaves are also used as snuff or smoked. This is the main species that is used to make cigarettes and cigars. A drying oil is obtained from the seed.

લણણી પછીની પ્રક્રિયા

After tobacco is harvested, it is cured (dried), and then aged to improve its flavor. There are four common methods of curing tobacco: air curing, fire curing, flue curing, and sun curing. The curing method used depends on the type of tobacco and its intended use.
Air-cured tobacco is sheltered from wind and sun in a well-ventilated barn, where it air dries for six to eight weeks. Air-cured tobacco is low in sugar, which gives the tobacco smoke a light, sweet flavor, and high in nicotine. Cigar and burley tobaccos are air cured.

In fire curing, smoke from a low-burning fire on the barn floor permeates the leaves. This gives the leaves a distinctive smoky aroma and flavor. Fire curing takes three to ten weeks and produces a tobacco low in sugar and high in nicotine. Pipe tobacco, chewing tobacco, and snuff are fire cured.
Flue-cured tobacco is kept in an enclosed barn heated by flues (pipes) of hot air, but the tobacco is not directly exposed to smoke. This method produces cigarette tobacco that is high in sugar and has medium to high levels of nicotine. It is the fastest method of curing, requiring about a week. Virginia tobacco that has been flue cured is also called bright tobacco, because flue curing turns its leaves gold, orange, or yellow.
Sun-cured tobacco dries uncovered in the sun. This method is used in Greece, Turkey, and other Mediterranean countries to produce oriental tobacco. Sun-cured tobacco is low in sugar and nicotine and is used in cigarettes.
Once the tobacco is cured, workers tie it into small bundles of about 20 leaves, called hands, or use a machine to make large blocks, called bales. The hands or bales are carefully aged for one to three years to improve flavor and reduce bitterness.

ઝાંખી

સંદર્ભ
Medicinal Plants of the world, By Ivan A. Ross
Poisonous plants, Dr Julia Higa de Landoni Seccion Toxicologia
Hospital de Clinicas "José de San Martin" Cordoba 2351, 1120 Capital, Argentina
African Ethnobotany: Poisons and Drugs: Chemistry, Pharmacology, Toxicology by Hans Dieter Neuwinger

બાહ્ય કડીઓ
 તમાકુ કેવી રીતે ઉગાડવું

વનસ્પતિ

તમાકુ


Waste minimisation is a set of processes and practices intended to reduce the amount of waste produced.  By reducing or eliminating the generation of harmful and persistent wastes, waste minimisation supports efforts to promote a more sustainable society. Waste minimisation involves redesigning products and processes and/or changing societal patterns of consumption and production.

The most environmentally resourceful, economically efficient, and cost effective way to manage waste often is to not have to address the problem in the first place. Managers see waste minimisation as a primary focus for most waste management strategies. Proper waste treatment and disposal can require a significant amount of time and resources; therefore, the benefits of waste minimisation can be considerable if carried out in an effective, safe and sustainable manner.

Traditional waste management focuses on processing waste after it is created, concentrating on re-use, recycling,  and waste-to-energy conversion. Waste minimisation involves efforts to avoid creating the waste during manufacturing.  To effectively implement waste minimisation the manager requires knowledge of the production process, cradle-to-grave analysis (the tracking of materials from their extraction to their return to earth) and details of the composition of the waste.

The main sources of waste vary from country to country. In the UK, most waste comes from the construction and demolition of buildings, followed by mining and quarrying, industry and commerce. Household waste constitutes a relatively small proportion of all waste.  Industrial waste is often tied to requirements in the supply chain.  For example, a company handling a product may insist that it should be shipped using particular packing because it fits downstream needs.

Benefits
Waste minimisation can protect the environment and often turns out to have positive economic benefits.  Waste minimisation can improve:
Efficient production practices – waste minimisation can achieve more output of product per unit of input of raw materials.
Economic returns – more efficient use of products means reduced costs of purchasing new materials, improving the financial performance of a company.
Public image – the environmental profile of a company is an important part of its overall reputation and waste minimisation reflects a proactive movement towards environmental protection.
Quality of products produced – new innovation and technological practices can reduce waste generation and improve the quality of the inputs in the production phase.
Environmental responsibility – minimising or eliminating waste generation makes it easier to meet targets of environmental regulations, policies, and standards; the environmental impact of waste will be reduced.

Industries

In industry, using more efficient manufacturing processes and better materials generally reduces the production of waste. The application of waste minimisation techniques has led to the development of innovative and commercially successful replacement products.

Waste minimisation efforts often require investment, which is usually compensated by the savings. However, waste reduction in one part of the production process may create waste production in another part.

Overpackaging is excess packaging.  Eliminating it can result in source reduction, reducing waste before it is generated  by proper package design and practice.  Use of minimized packaging is key to working toward  sustainable packaging.

Processes

 Reuse of scrap material
 Scraps can be immediately re-incorporated at the beginning of the manufacturing line so that they do not become a waste product. Many industries routinely do this; for example, paper mills return any damaged rolls to the beginning of the production line, and in the manufacture of plastic items, off-cuts and scrap are re-incorporated into new products.
 Improved quality control and process monitoring
 Steps can be taken to ensure that the number of reject batches is kept to a minimum.  This is achieved by increasing the frequency of inspection and the number of points of inspection. For example, installing automated continuous monitoring equipment can help to identify production problems at an early stage.
 Waste exchanges
 This is where the waste product of one process becomes the raw material for a second process. Waste exchanges represent another way of reducing waste disposal volumes for waste that cannot be eliminated.
 Ship to point of use
 This involves making deliveries of incoming raw materials or components direct to the point where they are assembled or used in the manufacturing process to minimise handling and the use of protective wrappings or enclosures (example: Fish-booking).
Zero waste
 This is a whole systems approach that aims to eliminate waste at the source and at all points down the supply chain, with the intention of producing no waste. It is a design philosophy which emphasizes waste prevention as opposed to end of pipe waste management. Since, globally speaking, waste as such, however minimal, can never be prevented (there will always be an end-of-life even for recycled products and materials), a related goal is prevention of pollution.
 Minimalism
Minimalism often refers to the concepts of art and music, even though a minimal lifestyle could make a huge impact for waste management and producing zero waste, can reduce which courses landfill and environment pollution. When the endless consumption is reduced to minimum of only necessary consumption, the careless production towards the demand will be reduced. A minimal lifestyle can impact the climate justice in a way by reducing the waste. Joshua Fields Millburn and Ryan Nicodemus directed and produced a movie called Minimalism: A Documentary that showcased the idea of minimal living in the modern world.

Product design

Waste minimisation and resource maximisation for manufactured products can most easily be done at the design stage. Reducing the number of components used in a product or making the product easier to take apart can make it easier to be repaired or recycled at the end of its useful life.

In some cases, it may be best not to minimise the volume of raw materials used to make a product, but instead reduce the volume or toxicity of the waste created at the end of a product's life, or the environmental impact of the product's use.  (See section Durability).

Fitting the intended use
In this strategy, products and packages are optimally designed to meet their intended use.  This applies especially to packaging materials, which should only be as durable as necessary to serve their intended purpose. On the other hand, it could be more wasteful if food, which has consumed resources and energy in its production, is damaged and spoiled because of extreme measures to reduce the use of paper, metals, glass and plastics in its packaging.

Durability
Improving product durability, such as extending a vacuum cleaner's useful life to 15 years instead of 12, can reduce waste and usually much improves resource optimisation.

But in some cases it has a negative environmental impact.  If a product is too durable, its replacement with more efficient technology is likely to be delayed. Therefore, extending an older machine's useful life may place a heavier burden on the environment than scrapping it, recycling its metal and buying a new model.  Similarly, older vehicles consume more fuel and produce more emissions than their modern counterparts.

Most proponents of waste minimisation consider that the way forward may be to view any manufactured product at the end of its useful life as a resource for recycling and reuse rather than waste.

Making refillable glass bottles strong enough to withstand several journeys between the consumer and the bottling plant requires making them thicker and so heavier, which increases the resources required to transport them. Since transport has a large environmental impact, careful evaluation is required of the number of return journeys bottles make.  If a refillable bottle is thrown away after being refilled only several times, the resources wasted may be greater than if the bottle had been designed for a single journey..

Many choices involve trade-offs of environmental impact, and often there is insufficient information to make informed decisions.

Universal connectors
Utilizing a charger port that can be used by any phone. The implementation of USB-C to reduce excess wires that end up in the waste that give off toxic chemicals that harm the planet.

Retail
Various aspects of business practices affect waste, such as the use of disposable tableware in restaurants.

Reusable shopping bags
Reusable bags are a visible form of re-use, and some stores offer a "bag credit" for re-usable shopping bags, although at least one chain reversed its policy, claiming "it was just a temporary bonus".  In contrast, one study suggests that a bag tax is a more effective incentive than a similar discount. (Of note, the before/after study compared a circumstance in which some stores offered a discount vs. a circumstance in which all stores applying the tax.) While there is a minor inconvenience involved, this may remedy itself, as reusable bags are generally more convenient for carrying groceries.

Households
This section details some waste minimisation techniques for householders.

Appropriate amounts and sizes can be chosen when purchasing goods; buying large containers of paint for a small decorating job or buying larger amounts of food than can be consumed create unnecessary waste. Also, if a pack or can is to be thrown away, any remaining contents must be removed before the container can be recycled.

Home composting, the practice of turning kitchen and garden waste into compost can be considered waste minimisation.

The resources that households use can be reduced considerably by using electricity thoughtfully (e.g. turning off lights and equipment when it is not needed) and by reducing the number of car journeys made. Individuals can reduce the amount of waste they create by buying fewer products and by buying products which last longer. Mending broken or worn items of clothing or equipment also contributes to minimising household waste. Individuals can minimise their water usage, and walk or cycle to their destination rather than using their car to save fuel and cut down emissions.

In a domestic situation, the potential for minimisation is often dictated by lifestyle.  Some people may view it as wasteful to purchase new products solely to follow fashion trends when the older products are still usable.  Adults working full-time have little free time, and so may have to purchase more convenient foods that require little preparation, or prefer disposable nappies if there is a baby in the family.

The amount of waste an individual produces is a small portion of all waste produced by society, and personal waste reduction can only make a small impact on overall waste volumes.  Yet, influence on policy can be exerted in other areas. Increased consumer awareness of the impact and power of certain purchasing decisions allows industry and individuals to change the total resource consumption.  Consumers can influence manufacturers and distributors by avoiding buying products that do not have eco-labelling, which is currently not mandatory, or choosing products that minimise the use of packaging. In the UK, PullApart combines both environmental and consumer packaging surveys, in a curbside packaging recycling classification system to minimise waste. Where reuse schemes are available, consumers can be proactive and use them.

Healthcare facilities

Healthcare establishments are massive producers of waste. The major sources of healthcare waste are:  hospitals, laboratories and research centres, mortuary and autopsy centres, animal research and testing laboratories, blood banks and collection services, and nursing homes for the elderly.

Waste minimisation can offer many opportunities to these establishments to use fewer resources, be less wasteful and generate less hazardous waste.  Good management and control practices among health-care facilities can have a significant effect on the reduction of waste generated each day.

Practices

There are many examples of more efficient practices that can encourage waste minimization in healthcare establishments and research facilities.

Source reduction
Purchasing reductions which ensures the selection of supplies that are less wasteful or less hazardous.
The use of physical rather than chemical cleaning methods such as steam disinfection instead of chemical disinfection.
Preventing the unnecessary wastage of products in nursing and cleaning activities.

Management and control measures at hospital level
Centralized purchasing of hazardous chemicals.
Monitoring the flow of chemicals within the health care facility from receipt as a raw material to disposal as a hazardous waste.
The careful separation of waste matter to help minimize the quantities of hazardous waste and disposal.

Stock management of chemical and pharmaceutical products
Frequent ordering of relatively small quantities rather than large quantities at one time.
Using the oldest batch of a product first to avoid expiration dates and unnecessary waste.
Using all the contents of a container containing hazardous waste.
Checking the expiry date of all products at the time of delivery.

See also

Cleaner production
Eco-action
Ecological economics
Ecological sanitation
Electronics right to repair
European Week for Waste Reduction
Extended producer responsibility
Food waste
Green consumption
Green economy
Household hazardous waste
Life-cycle assessment
List of waste management acronyms
Litter
Miniwaste
Planned obsolescence
Recycling
Reusable launch vehicle
Reusable packaging
Reuse of bottles
Reuse of human excreta
Reuse
Source reduction
Sustainable sanitation
Waste hierarchy
Waste management
Zero waste

References

External links
 The EU Pre-waste project website, homepage.

Waste management concepts
Industrial ecology

Waste minimisation


Richard D. Braatz (born July 19, 1966) is the Edwin R. Gilliland Professor at the Massachusetts Institute of Technology known for his research in control theory and its applications to chemical, pharmaceutical, and materials systems.

He has received many honors, including the Hertz Foundation Thesis Prize, the Donald P. Eckman Award from the American Automatic Control Council, the Curtis W. McGraw Research Award from the Engineering Research Council, and the Antonio Ruberti Young Researcher Prize from the Antonio Ruberti Foundation and IEEE Control Systems Society. Braatz became a member of the National Academy of Engineering in 2019. He is a Fellow of the International Federation of Automatic Control, the Institute of Electrical and Electronics Engineers, and the American Association for the Advancement of Science.

Braatz graduated from Oregon State University with a B.S. in 1988 with an undergraduate thesis on heat exchanger design supervised by Octave Levenspiel. He worked at Chevron Research and Avery Dennison before receiving his M.S. and Ph.D. in robust control from the California Institute of Technology under the direction of Professor Manfred Morari. His thesis included a proof that robust control problems are NP-hard. After a postdoctoral year at DuPont, he moved to the University of Illinois at Urbana-Champaign, where he rose to the position of millennium chair and professor, with positions in chemical and biomolecular engineering, electrical and computer engineering, mechanical science and engineering, bioengineering, applied mathematics, and computational science and engineering. Braatz made contributions in the areas of robust optimal control, fault detection and diagnosis, sheet and film processes, and crystallization.

After serving as a visiting scholar for a year at Harvard University, in 2010 he moved to MIT's department of chemical engineering, where he continues research in systems and control theory and its applications.

References

Sources
Richard Braatz Faculty Page
Donald P. Eckman Award
Antonio Ruberti Young Researcher Prize
IEEE Control Systems Society Transition to Practice Award
Curtis W. McGraw Research Award
Hertz Foundation Thesis Prize
AACC Executive Officers
National Academy of Engineering

American chemical engineers
Living people
Control theorists
MIT School of Engineering faculty
1966 births
Members of the United States National Academy of Engineering
Fellows of the International Federation of Automatic Control
Fellow Members of the IEEE
Fellows of the American Association for the Advancement of Science

Richard D. Braatz


The Classical music period is the time from about 1750 to 1820 when Haydn, Mozart, Beethoven, and Schubert were the most famous living composers.

We often talk about "classical music" meaning European music which is not pop music or jazz or folk music. It is music which has been written by composers who have studied the art of composition. The article Classical music talks about classical music in this sense.

This article is about "Classical music" in the late 18th century and the early 19th century. The word "classical" is often used to refer to the arts of Ancient Greece and Rome. It has also come to mean any art form which has become very famous and is remembered for centuries afterwards. In music the Classical period comes between the Baroque and the period of Romanticism.

In some ways Classical music is often simpler than the music of the Baroque composers. There is often a tune with a simple accompaniment using broken chords called an "Alberti bass". For classical composers the form of the piece was very important. Composers started their work with a tune (theme) and this tune would be developed in different ways: put in different key, changed from a fast to a slow tune, changed from major to minor or from minor to major.

Some of the most famous composers of the Classical period in music are:

 Carl Philipp Emanuel Bach (1714–1789)
 Christoph Willibald Gluck (1714–1787)
 Joseph Haydn (1732–1809)
 Luigi Boccherini (1743–1805)
 Muzio Clementi (1752–1832)
 Wolfgang Amadeus Mozart (1756–1791)
 Jan Ladislav Dussek (1760–1812)
 Ludwig van Beethoven (1770–1827)
 Franz Schubert (1797–1828)

Periods in music history

Musical movements

Classical period (music)


International mostly means something (a company, language, or organization) involving more than a single country. The term international as a word means involvement of, interaction between or encompassing more than one nation, or generally beyond national boundaries. For example, international law, which is applied by more than one country and usually everywhere on Earth, and international language which is a language spoken by residents of more than one country.

Origin of the word
The term international was coined by the utilitarian philosopher Jeremy Bentham in his Introduction to Principles of Morals and Legislation, which was printed for publication in 1780 and published in 1789.  Bentham wrote: "The word international, it must be acknowledged, is a new one; though, it is hoped, sufficiently analogous and intelligible.  It is calculated to express, in a more significant way, the branch of law which goes commonly under the name of the law of nations.  The word was adopted in French in 1801.  Thomas Erskine Holland noted in his article on Bentham in the 11th edition of the Encyclopædia Britannica that "Many of Bentham's phrases, such as 'international,' 'utilitarian,' 'codification,' are valuable additions to our language; but the majority of them, especially those of Greek derivation, have taken no root in it."

Meaning in particular fields
In team sports, "international" is a match between two national teams, or two players capped by a national team.
In politics, "The International" may refer to a political international.
In law, "international" may refer to several disciplines of International law like public international law, international criminal law etc.
In linguistics, an international language is one spoken by the people of more than one nation, usually by many. Also called world language. English, Spanish, French and Arabic are considered to be world languages.
In interlinguistics, international often has to do with languages rather than nations themselves. An "international word" is one that occurs in more than one language. These words are collected from widely spoken source or control languages, and often used to establish language systems that people can use to communicate internationally, and sometimes for other purposes such as to learn other languages more quickly. The vocabulary of Interlingua has a particularly wide range, because the control languages of Interlingua were selected to give its words and affixes their maximum geographic scope. In part, the language Ido is also a product of interlinguistic research.
In arts, an international art movement is an art movement with artists from more than one country, usually by many. Some international art movements are Letterist International, Situationist International, Stuckism International.

"International" is also sometimes used as a synonym for "global".

Related pages
 Globalization
 International relations
 Multinational corporation
 United Nations

References

Other websites

Meaning of international on The Free Dictionary
Meaning of international  on Cambridge dictionary
Meaning of international  on Oxford dictionary.

Sources

Political geography

International


Cymbals (pronounced like the word "symbol") are percussion instruments. They are discs made of copper, bronze or a special alloy. They look rather like saucepan lids, but in the middle they jut out a little and they have straps there that pass through a hole. Also called "clangers"

There are two ways of playing cymbals. One way is to use a pair of cymbals that are the same. The player holds one cymbal in each hand, holding them by the strap. He then bangs the cymbals together. There are many ways of doing this depending on the sort of sound that is wanted. For example, a very quiet sound can be made by rubbing the edges of the cymbals together. A very loud sound can be made by hitting them together as the arms form a circle, and letting the cymbals vibrate for a long time by holding them in the air.

Another way of playing the cymbal is to use just one cymbal, and to hang it on a stand. It can then be played with a beater, stick or wire brush. It can be hit at the edge, in the middle, or half way between, depending on the sound that is wanted.

Cymbals are made in different sizes. Some may be just 25 cm across, large ones may be up to 60 cm across. Cymbals do not normally give any particular pitch. There are, however, small ones based on an old form of cymbal which are called "crotales". There are also Chinese cymbals which have a turned-up edge.

Cymbals are used in many different musical groups. They are heard in an orchestra, in jazz groups, percussion groups and bands, including marching bands. A drum kit always has at least one cymbal. This may be a "crash cymbal" (on the top of a stand) or a pair of hi-hats (a pair of small cymbals operated by pressing a pedal with the foot.

Origins
The word cymbals comes from the Latin cymbalum, which itself comes from the Greek word kumbalom, meaning a small bowl. It was used in many ancient cultures including Egyptian civilisations.

Orchestral cymbals
Cymbals are often used in orchestras. The first composer to use them was probably Joseph Haydn in his "Military Symphony" (1794). They are often used when there is a big climax (for example in the "Academic Festival Overture" by Johannes Brahms, but they can also sometimes be played very quietly. Sometimes players should let the cymbal vibrate for a long time after a big crash, but at other times he may have to hold the cymbals against his body quickly to stop the noise. This is called "damping" the sound.

Cymbals have traditionally often been played together with the bass drum. This makes a "crash-bang-wallop" noise.

Other websites
CymbalPlanet.com Welcome to the World of Cymbals

References
"The Illustrated Encyclopedia of Musical Instruments" by Könemann;

Percussion instruments

Cymbal


A laser is a machine that makes an amplified, single-color source of light.  It uses special gases or crystals to make the light with only a single color.  The gases are energized to make them emit light.  Then mirrors are used to amplify (make stronger) the light.  In many lasers all the light travels in one direction, so it stays as a narrow beam of Collimated light that does not get wider or weaker as most sources of light do.

When pointed, this narrow beam makes a single point of light. The energy of the light stays in that one narrow beam instead of spreading out like a flashlight (electric torch).

The word "laser" is an acronym for "light amplification by stimulated emission of radiation". Both the device and its name were developed from the earlier Maser.

Mechanism
A laser creates light by special actions involving a material called an "optical gain medium". Energy is put into this material using an 'energy pump'.  This can be electricity, another light source, or some other source of energy.  The energy makes the material go into what is called an excited state.  This means the electrons in the material have extra energy, and after a bit of time they will lose that energy.  When they lose the energy they will release a photon (a particle of light).  The type of optical gain medium used will change what color (wavelength) will be produced.  Releasing photons is the "stimulated emission of radiation" part of laser.

Many things can radiate light, like a light bulb, but the light will not be organized in one direction and phase.  By using an electric field to control how the light is created, this light will now be one kind, going in one direction.  This is "coherent radiation".

At this point, the light is still weak.  The mirrors on either side bounce the light back and forth, and this hits other parts of the optical gain medium, causing those parts to also release photons, generating more light ("light amplification").  When all of the optical gain medium is producing light, this is called saturation and creates a very strong beam of light at a very narrow wavelength, which we would call a laser beam.

Design
The light moves through the medium between the two mirrors that reflect the light back and forth between them. One of the mirrors, however, only partially reflects the light, allowing some to escape. The escaping light makes up the laser beam.

This is a simple design; the type of optical gain medium used usually defines the type of laser.  It can be a crystal, examples are ruby and a garnet crystal made of yttrium and aluminum with the rare earth metal mixed in.  Gases can be used for laser by using helium, nitrogen, carbon dioxide, neon or others.  Large, powerful lasers are usually gas lasers.  A free-electron laser uses a beam of electrons and can be tuned to emit different colors.  Finally, the smallest lasers use semiconductor diodes to produce the light.  These are the most numerous kind, used in electronics.

History
Albert Einstein was the first to have the idea of stimulated emission that could produce a laser. From that point many years were spent to see if the idea worked. At first, people succeeded in making masers and later figured how to make shorter visible wavelengths. It was not until 1959 that the name laser was coined by Gordon Gould in a research paper. The first working laser was put together and operated by Theodore Maiman at the Hughes Research Laboratories in 1960.  Many people started working on lasers at this time, and the question of who would get the patent for the laser wasn't decided until 1987 (Gould won the rights).

Applications
Lasers have found many uses in everyday life as well as in industry. Lasers are found in CD and DVD players, where they read the code from the disk that stores a song or movie. A laser is often used to read the bar codes or SQR codes on things sold in a store, to identify a product and give its price. Lasers are used in medicine, particularly in LASIK eye surgery, where the laser is used to repair the shape of the cornea. It is used in chemistry with spectroscopy to identify materials, to find out what kind of gases, solids or liquids something is made of. Stronger lasers can be used to cut metal.

Lasers are used to measure the distance of the Moon from Earth by reflecting off reflectors left by the Apollo missions. By measuring the time it takes for the light to travel to the Moon and back again we can find out exactly how far away the moon is.

Laser pointers are used by people to point at a place on a map or diagram.  For example, lecturers use them.  Also, many people like to play with laser pointers.  Some people have pointed them at aircraft.  This is dangerous, and it is also illegal in many countries.  People have been arrested and prosecuted for this crime.

Computers commonly use an optical computer mouse as an input device.  Modern laser pointers are too big and powerful for this use, so most mice use small VCSEL's, or "Vertical cavity surface-emitting lasers" for this purpose.  These lasers are also used in DVD, CD-ROM drives, laser printer and holography.

References

Light
Machines
Acronyms

Laser


A bird nest is a place where a bird lays its eggs. There are all kinds of nests, including cup nests, holes in the ground, and piles of twigs and leaves. The word can be used as a noun or a verb, as in – a bird nests in a nest. They are in all kinds of sizes: some can be as big and heavy as a car, like an old eagle's nest, while some can be tiny as a thimble, like the nest of a bee hummingbird.

Making a home

Usually, the female builds the nest, and the male helps her. In some species, though, the male does nothing, and in others, the male builds the nest and the female does nothing.

Many birds "glue" their nests together with materials like spider webs, silk, mud, and even their own saliva (spit). Most nest builders like to put soft things inside their nest. Some birds even put herbs and spices in their nest. Scientists think these herbs help fight off bacteria in a way they can't completely understand yet.

Types of nests

Cup nest

The cup nest is probably the most common bird nest. Its name tells you that a cup nest is shaped like a cup or bowl. Many songbirds built cup nests. These nests can be built in the branches of a tree, like in the crack where one branch joins another: however, some can simply stick the nest right onto the branch of a tree. They use lots of materials that act like sticky glue – mud, rotten wood, dung, spider webs, and caterpillar silk. They sometimes even use their own saliva mixed with food to keep the nest firmly stuck on the branch.

Cup nesters use all kinds of materials to build a nest: twigs (tiny branches), grass, leaves, moss; and they use all sorts of materials to keep it from falling apart. Most cup nesters use rough, scratchy material for the outside (this gives protection and camouflages the rest), and put soft, cozy material like moss, fur, feathers, and cotton on the inside.

Many cup nesters enjoy nesting very close to the ground in low bushes – sometimes they will even nest in potted plants on a porch. Some of them actually just build their nests on the ground. Sparrows, cardinals, and many other song birds (called passerines), like to nest near the ground, far away from owls, hawks, and Blue Jays that may eat their babies.

There are several types of cup nests. A suspended cup nest is attached to the branch at the top and sides but then drops like a bag down below. It really looks more like a vase than a cup. The bird is almost hidden when she warms her eggs. The mother bird can sit down on the branch above the nest and bend down to feed her baby birds. Orioles are very famous for building amazingly long bags that hang far below the branch.

The smallest cup nests are made by hummingbirds. They can be as tiny as a thimble, like the bee hummingbird's nest. That tiny nest holds eggs that are as tiny as peas. The largest cup nest is probably the stork's. His nest can be nine feet deep and six feet wide. The stork's nest is so big that smaller birds actually make nests in its cracks, holes, and branches.

Adherent nests

Adherent nests stick to buildings, trees, cliffs, or other vertical structures. Swallows can build an almost perfectly round nest out of mud. Some species make cup-shaped nests, while others make jug-like nests with little holes in the sides. They put little balls of mud in their mouth and mix it with their saliva, making a special clay. As it dries, it becomes hard.

Bird saliva is very good for making glue: in fact, some species of swiftlets make their whole nest out of saliva. The male regurgitates (throws up) a long, thin strand of saliva from glands under its tongue. This saliva is used to be made into a half-cup nest which sticks to a cave wall and dries quickly. Swiftlets like to build their nests in caves and grottos. This saliva nest is thought to be a delicacy (something really yummy to eat) in China, and it is very expensive. They put it into a soup called Bird's Nest Soup.

Platform nests

Platform nests are built mostly by raptors (birds that eat prey, like eagles and hawks). They are usually huge and very high up: on the sides of cliffs, maybe, or high up in a big tree. It takes months making these nests, adding branch by branch. They often return to the same nest year after year and continue to build it. It is because of this that platform nests get so big: a bald eagle's nest, for example, can weigh as much as a ton (about the same weight as a small car). It is so heavy it can sometimes hurt the tree it is built in.

A few water birds (like grebes and loons) build platform nests right on the water, where they can float. The nests don't move, though, because they are anchored to plants that are attached to the bottom of the body of water. These birds build nests on water because they don't walk well on land, so they find a shallow (not deep) part of the water to build their nests. Then, they do not walk to their nests - they swim to it. When the babies are ready, they simply jump into the water and begin their aquatic (water) life.

Earth-hole nests

Earth-hole nests are nests that are inside the earth. They are burrows (tunnels) on the ground or in the sides of cliffs. They like using abandoned rabbit holes, too. The burrowing owl only uses already dug holes for its nest.

Puffins, for instance, dig a tunnel that is usually two to three feet long. At the end they make a nest of feathers and grass and lay their eggs. They are able to do this because of their sharp bill and claws. A puffin can work for hours to make its tunnel. Kingfishers, too, dig or burrow their holes. They can burrow up to six feet into the side of a cliff and lay their eggs in that place.

Ground and mound nests

Many birds nest right on the ground. After carving out a little hole, ground and mound nesters line the nest with grass or other materials. Geese even pick feathers from their breasts and make a nice downy bed for their eggs. Most ducks, geese, and quail like the ground for nesting. Penguins nest on the ground, too, pushing rocks around the nest to keep it from washing away with flood waters. Usually, males make ground nests.<ref name=Elliott, Andrew (1994), "Family Megapodiidae (Megapodes)", in del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi (eds.), Handbook of Birds of the World, Volume 2: New World Vultures to Guineafowl, Barcelona: Lynx Edicions, ISBN 978-84-87334-15-3 p228.</ref>

The trumpeter swan makes a big mound nest, and flamingos make mounds, too. Flamingos make their mounds completely out of mud. They can be up to 18 inches high and 12 to 20 inches in width.

Scrape nests
These nests are barely a nest at all – just a small depression in the ground or a pile of dead leaves to lay eggs on. These scrape-nesting birds usually have eggs that match the color of dead leaves or rocks. This is needed because these eggs are in danger of being eaten by animals like rats, raccoons, snakes, and others that eat eggs.

Many scrape nesters actually try to distract creatures that might be dangerous by pretending they have a broken wing. This makes a predator chase the mother bird, and leave the eggs.

Other
Nest
Egg (biology)
Bird
Feather
Flight

References

Other websites

(Pictures of Bird Nests)

Birds

Bird nest


Science fiction (often shortened to sci-fi or SF) is the type genre of speculative fiction which deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, interstellar travel, parallel universes, and extraterrestrial life. It has been called the "literature of ideas", and it often explores the potential consequences of scientific, social, and technological innovations. Science fiction stories can be novels, movies, TV shows, video games, comic books and other literature.

SF is often about the future. It can be about imaginary new science and inventions such as spaceships, aliens, and robots. Science fiction stories are often in a world that is very different from the real world. They can have science and tools that do not exist in reality. Science fiction stories often take place on other worlds. There are often alien creatures.

Science fiction is drastically different from fantasy. Fantasy stories often have magic and other things that do not exist and are not science. Isaac Asimov was a famous science fiction writer. He once said that science fiction is possible, but fantasy is not.

Writers often use SF to explain everyday questions or problems by putting them in the future. Usually they invent a very different world to help people notice important ideas.

Early examples of science fiction
Science fiction changes over time. Some authors wrote SF books before this type of writing had a name. These writers and books were not called science fiction when they were published. But, they are often called science fiction today.
 Mary Shelley – Frankenstein (1818)
 Jules Verne – Twenty Thousand Leagues Under the Sea (1870)
 H. G. Wells – The Time Machine (1895).

 20th century science fiction
 Isaac Asimov, Robert A. Heinlein and Arthur C. Clarke are seen as the big three science fiction authors of the 20th century.
 Philip K. Dick, Poul Anderson and William Gibson are other well-known science fiction authors from the 20th century.
 Star Trek – a 1960s American TV show that led to a media franchise.
 Doctor Who – a long-running British TV show.
 Star Wars -a trilogy of movies preceded by a novel that turned into a media franchise

 Different types of science fiction
Two broad genres of science fiction are Hard SF and Soft SF. Although not everyone agrees on the exact definitions of these two types, the way they use science or the type of science used in the stories is different.

Hard SF

Hard science fiction, or "hard SF", is special because it uses true facts and theories from sciences. These sciences are very important in Hard SF: physics, astrophysics, and chemistry. Also, Hard SF can show worlds that more advanced technology may make possible. Many correct predictions of the future come from the hard science fiction subgenre. However, there have been many incorrect ideas about the future, too. Some hard SF writers have also worked as professional scientists. A few of these scientist/writers are Gregory Benford and Geoffrey A. Landis, while mathematician authors include Rudy Rucker and Vernor Vinge. Other noteworthy hard SF authors include Arthur C. Clarke, Hal Clement, Isaac Asimov, Greg Bear, Stanislav Lem, Larry Niven, Robert J. Sawyer, Stephen Baxter, Alastair Reynolds, Charles Sheffield, and Greg Egan.

Soft SF
Soft science fiction stories take ideas from social sciences such as psychology, economics, political science, sociology, and anthropology. Some important writers in this category include Ursula K. Le Guin and Philip K. Dick. Soft SF can be mostly about character and emotion. Ray Bradbury won a prize called the SFWA Grand Master and writes in this style. The Soviet Union produced social science fiction too. Some examples are Strugatsky brothers, Kir Bulychov and Ivan Yefremov.

Some Social SF and Soft SF can be types of speculative fiction, for example utopian or dystopian stories. George Orwell's Nineteen Eighty-Four, Aldous Huxley's Brave New World and Margaret Atwood's The Handmaid's Tale, are examples. Some people think that satirical novels in fantastic settings (places) such as Gulliver's Travels by Jonathan Swift are speculative fiction.

Different styles of science fiction
Within Hard or Soft SF, there are different types, or subgenres, of science fiction. Each subgenre is a group of stories that uses similar ideas or styles of story-telling. Publishing companies and critics put works of SF into different subgenres to help describe the work to help readers choose which books to read or movies to watch. Assigning genres is not simple. Some stories can be in two or more genres at the same time. Other stories may not fit any genre.

Alternate history
In Alternate (or alternative) history stories, writers imagine how the past might have been different. These stories may use time travel to change the past. Some set a story in a universe with a different history from our own. These are some important alternate history books:
 Bring the Jubilee by Ward Moore  - the South won the American Civil War
 The Man in the High Castle by Philip K. Dick - Germany and Japan won World War II.

The Sidewise Award is for the best works in this subgenre. The name Sidewise is taken from Murray Leinster's 1934 story "Sidewise in Time." Harry Turtledove is one of the most famous writers in the subgenre. He is often called the "master of alternate history".

Apocalyptic
Apocalyptic fiction is about the end of civilization. There are several types: through war (On The Beach), pandemic (The Last Man), astronomic impact (When Worlds Collide), ecological disaster (The Wind From Nowhere), or mankind's self-destruction (Oryx and Crake), or some other general disaster. Apocalyptic SF may also be about world or civilization after a disaster.

Cyberpunk

Cyberpunk began in the early 1980s. Bruce Bethke used this word as the title for a short story in 1980 by putting together two words: "cybernetics" and "punk". Soon, people used this word to describe William Gibson's book, Neuromancer. Cyberpunk authors can put their stories in different settings. Stories usually take place in the near-future and the settings are often dystopian (characterized by misery). These are often societies with very advanced technology. A few huge corporations usually control the society. Another early cyberpunk novel that has become a classic is Snow Crash by Neal Stephenson.

Military science fiction

Military science fiction stories happen during wars. These wars can be between different countries, different planets, or between different species. The stories are told by characters who are soldiers. They include detail about military technology, rules, and history. Some Military SF may be similar to real historical conflicts. Heinlein's Starship Troopers is an early example. Another is the Dorsai novels of Gordon Dickson. Joe Haldeman's The Forever War is a response to the World War II–style stories of earlier military SF authors. Haldeman was a soldier in the Vietnam War. Important military SF authors include John Ringo, David Drake, David Weber,  and S. M. Stirling. Baen Books is known for cultivating military science fiction authors.

Maritime science fiction

Maritime science fiction is science fiction that features a maritime or marine environment and technology and/or marine lifeforms mixed with science fiction. The probably earliest form of maritime science fiction literature is 20,000 Leagues Under the Sea.

Superhuman
Superhuman stories are about humans who get special abilities that are not normal. Maybe the new powers come from nature. Two examples of this type are Olaf Stapledon's novel Odd John and Theodore Sturgeon's More Than Human. Sometimes scientists give people special powers on purpose. one example is A.E. van Vogt's novel Slan. Frederik Pohl's  novel Man Plus is another good example from this category. In that book, government scientists make a man into a powerful cyborg (part human, part machine).

These stories usually have two main points. One is the feeling of loneliness and separation that these superhuman people feel. The other is society's reaction to them.

Space opera

Space opera is adventure science fiction in outer space or on distant planets. Action is more important than the science or characters. There is usually a strong hero and a very big conflict. The action often moves to many different places. Edward E. (Doc) Smith was an early Space opera writer. Flash Gordon and Star Wars are also popular examples.

Space western

Space western takes ideas from books and movies about exploring the American Old West and moves them  to space in the future. These stories are often on "frontier" colony worlds (colonies that have only recently been terraformed and/or settled) serving as stand-ins for the backdrop of lawlessness and economic expansion that were predominant in the American west. Some examples are Firefly and the movie Serenity by Joss Whedon.  Anime programs like Cowboy Bebop and Outlaw Star are also Space Westerns. Han Solo from "Star Wars" is an important Space Western character.

Time travel
The first important time travel novel was Mark Twain's A Connecticut Yankee in King Arthur's Court. The most famous is H. G. Wells's 1895 novel The Time Machine. Well's book uses a machine that allows an operator to travel to an exact time. Twain's time traveler is struck in the head and wakes up in the past. The term "time machine" was invented by Wells. Now it is the name for any vehicle that can take a rider to another time. Ray Bradbury's 1952 short story called A Sound of Thunder is a more recent and very famous example of this genre. Time travel stories can be complicated. They have logical problems such as the grandfather paradox. Time travel is a popular subject in modern science fiction, in print, movies, and television.

Other sub-genres
 Comic science fiction is a sub-genre of science fiction that is more humorous or funny.
 Feminist science fiction asks questions about society. How does society make gender roles? How does having children define gender? Does having children change the political and personal power of men and women? Some well-known feminist science fiction stories  use utopias to answer those questions. The stories explore a society in which gender differences or gender power imbalances do not exist. Also dystopias can explore worlds in which gender inequalities are stronger. Those dystopias explain that feminist work should continue. See Ursula K. Le Guin, Margaret Atwood
 Libertarian science fiction is written from a political point of view. This subgenre uses fiction to explore ideas from libertarian political philosophy about government and social organization. A classic example of libertarian science fiction is The Moon is a Harsh Mistress by Robert Heinlein.
 New Wave is science fiction writing with a lot of experimentation. Writers try new ways of writing and new story ideas. It may feel more intellectual. New Wave seems more like important "literature" or art.
 Steampunk is the idea of future technology in the past. These stories are usually in the 19th century and often in Victorian era England. Steampunk stories have strong images from either science fiction or fantasy. Steampunk can have imaginary inventions like those found in books by H. G. Wells and Jules Verne. Imagining a world where computers were invented a long time ago is also popular. Examples include The Difference Engine by William Gibson and Bruce Sterling, and the Girl Genius series by Phil and Kaja Foglio. The start of this style may be seen in some writing by Michael Moorcock, Philip Jose Farmer and Steve Stiles. Games like Space 1889 and Marcus Rowland's Forgotten Futures can also be Steampunk. The name comes from the fact that machines are most often powered by steam in this genre.
 Biopunk is like cyberpunk, but instead of focusing on cybernetic technology, it focuses on biotechnology.
 Mundane science fiction is science fiction set on a fiction Earth and not involving any space travel or extraterrestrial elements. Jurassic Park is considered and example of mundane science fiction.

Notable science fiction writers

Frank Herbert author of the Dune series.
Isaac Asimov author of the Foundation series.
Marion Zimmer Bradley author of the Darkover series.
Arthur C. Clarke author of a number of classic science fiction novels

Fandom and community

Science fiction fandom is the "community of the literature of ideas... the culture in which new ideas emerge and grow before being released into society at large". Members of this community, "fans", are in contact with each other at conventions or clubs, through print or online fanzines, or on the Internet using web sites, mailing lists, and other resources.

SF fandom emerged from the letters column in Amazing Stories magazine. Soon fans began writing letters to each other, and then grouping their comments together in informal publications that became known as fanzines. Once they were in regular contact, fans wanted to meet each other, and they organized local clubs. In the 1930s, the first science fiction conventions gathered fans from a wider area. Conventions, clubs, and fanzines were the main fan activities, or "fanac", for decades, until the Internet improved communication among a much larger population of interested people.

Awards

There are two very important science fiction awards: the Hugo Award and the Nebula Award. The Hugo is presented by the World Science Fiction Society at Worldcon each year. The Nebula is presented by SFWA and voted on by the community of authors. One important award for science fiction movies is the Saturn Award. The Academy of Science Fiction, Fantasy, and Horror movies gives this award each year..

There are national awards, like Canada's Aurora Award and the UK Arthur C. Clarke Award, regional awards, like the Endeavour Award presented at Orycon for works from the Pacific Northwest, special interest or subgenre awards like the Chesley Award for art or the World Fantasy Award for fantasy. Magazines may organize reader polls, notably the Locus Award.

Conventions, clubs, and organizations

Conventions (in fandom, shortened as "cons"), are held in cities around the world, catering to a local, regional, national, or international membership. General-interest conventions cover all aspects of science fiction, while others focus on a particular interest like media fandom, filking, etc. Most are organized by volunteers in non-profit groups, though most media-oriented events are organized by commercial promoters. The convention's activities are called the "program", which may include panel discussions, readings, autograph sessions, costume masquerades, and other events. Activities that occur throughout the convention are not part of the program; these commonly include a dealer's room, art show, and hospitality lounge (or "con suites").

Conventions may host award ceremonies. Worldcons present the Hugo Awards each year. SF societies are a year-round base of activities for science fiction fans. They may be associated with an ongoing science fiction convention, or have regular club meetings, or both. Most groups meet in libraries, schools and universities, community centers, pubs or restaurants, or the homes of individual members. Long-established groups like the New England Science Fiction Association and the Los Angeles Science Fantasy Society have clubhouses for meetings and storage of convention supplies and research materials.

The Science Fiction and Fantasy Writers of America (SFWA) was founded by Damon Knight in 1965 as a non-profit organization to serve the community of professional science fiction authors, 24 years after his essay "Unite or Fie!" had led to the organization of the National Fantasy Fan Federation. Fandom has helped support related groups as they started to form, including media fandom, the Society for Creative Anachronism, gaming, filking, and furry fandom.

Fanzines and online fandom
The first science fiction fanzine, The Comet, was published in 1930. Fanzine printing methods have changed over the decades, from the mimeograph and the ditto machine, to modern photocopying. The number of copies was usually not enough to use commercial printing. Modern fanzines are printed on computer printers or at local copy shops, or they may only be sent as email. The best known fanzine (or "'zine") today is Ansible''. David Langford is the editor and it has won several Hugo awards. Artists working for fanzines have risen to prominence in the field, including Brad W. Foster, Teddy Harvia, and Joe Mayhew; the Hugos include a category for Best Fan Artists. The earliest organized fandom online was the SF Lovers  community, originally a mailing list in the late 1970s with a text archive file that was updated regularly. In the 1980s, Usenet groups greatly expanded the circle of fans online. In the 1990s, the development of the World-Wide Web made the online fan community much, much larger. Fans created thousands and then millions of web sites devoted to science fiction and related genres for all media. Most of these websites are small, ephemeral, or about very specific topics. Though sites like SF Site and Read and Find Out give readers a broad range of references and reviews about science fiction.

Fan fiction
Fan fiction is non-commercial fiction created by people who love an SF story or world. Fans write stories that take place in the setting of an established book, movie, or television series. Some people call it "fanfic". In some cases, the copyright owners of the books, movies, or television series have instructed their lawyers to issue "cease and desist" letters to fans.

Related pages
 Science fiction movie
Fantasy
Science fantasy

References

Other websites
The Encyclopedia of Science Fiction
EDGE Science Fiction and Fantasy Publishing

Science fiction