Perle

Les perles sont de petites billes blanches créées par certains mollusques, principalement les huîtres. Quand un objet irritant passe à l'intérieur de la coquille, l'animal réagit en entourant l'objet d'une couche de carbonate de calcium CaCO3 sous la forme d'aragonite ou de calcite. Ce mélange est appelé nacre.

Autrefois uniquement obtenues par le hasard, les perles font aujourd'hui l'objet d'une culture (perliculture). Elle a été mise au point par les Japonais du début du XXe siècle aux années 1970. Depuis, le secret de leur technique s'est répandu dans tout les archipels de l'océan Pacifique, et la Polynésie française est le principal producteur.

Joaillerie
Les perles sont utilisées pour confectionner des bijoux depuis l'Antiquité ; elles étaient appelées les larmes d'Aphrodite. Les familles romaines qui en avaient les moyens achetaient à leur filles une ou deux perles chaque année, afin qu'elles aient un collier complet à leur majorité.

Elles doivent leur brillance iridescente (proche de l'arc-en-ciel) à la réflexion et à la réfraction des couches superficielles translucides de nacre. La brillance est d'autant plus fine que les couches sont plus fines et nombreuses.

Les perles sont souvent blanches, parfois avec une teinte crème ou rose, mais peuvent être teintées en jaune, vert, bleu, marron ou noir. Les perles noires sont très chères car très rares ; leur production augmente toutefois sensiblement, notamment en provenance de Polynésie.

La valeur des perles est déterminée par leur brillance, leur couleur, leur taille, et leur symétrie. La brillance est le plus important des critères pour juger de la qualité d'une perle, surtout pour les joailliers, mais plus la perle est grosse, plus elle se vend cher. Les grosses perles parfaitement rondes sont très rares, et très recherchées pour des colliers à plusieurs rangs.

Les perles sont divisées en huit formes de base : rondes, semi-rondes, bouton, larme, poire, ovale, baroque (irrégulière), et baguée. Les perles parfaitement rondes sont les plus rares et les plus chères, et montées sur des colliers, ou de simples rangs de perles. Les perles en forme de larmes sont plus utilisées en pendants (d'oreilles ou de cou) ; les perles irrégulières sont le plus souvent utilisées dans des colliers ou des pièces de joaillerie où la forme irrégulière peut être cachée, et laisser croire à une perle parfaitement ronde. Les perles bouton sont légèrement aplaties autour de la perle, et peuvent être utilisées pour des colliers, ou pour des pendants ou des boucles d'oreille, où la partie arrière de la boucle est cachée, ce qui permet de laisser croire à une perle plus grosse et ronde. Les perles en larme et en poire sont utilisées dans les boucles d'oreille, ou comme perle centrale du collier. Les perles baroques, totalement irrégulières, ont parfois une forme intéressante qui permet de les monter en collier. Les perles baguées sont caractérisées par les arêtes concentriques autour du corps de la perle.

Les perles sont pesées en grains ; un grain de joaillier vaut 0,05 grammes (avant la Révolution française, 0,053 grammes). Il y a 75 grains dans un momme (3,75 grammes).

Culture des perles
Les premiers essais de culture des perles sont anciens : les Chinois introduisaient des statuettes de Bouddha dans les huîtres en guise de nucleus. Le Suédois Carl von Linné et un Français font des essais, mais ce sont les Japonais To Kichi Nishikawa, Tatsuhei Mise et surtout Kokichi Mikimoto (1858-1954) qui réussissent à mettre la technique au point, et en font une industrie.


Beaucoup d'huîtres meurent après la greffe : environ dix pour cent immédiatement, et dix pour cent dans les deux ans. Un tiers des huîtres rejettent le nucléus et la nacre sécrétée par le greffon forme alors un keshi (graine de pavot en japonais), une sorte de perle manquée. Un cinquième des huîtres greffées produisent une perle inutilisable. Sur les trente pour cent de greffons donnant une perle utilisable, seul un pour cent font des perles parfaites.

Dans certaines variétés d'huîtres, on pose un noyau contre la coquille : c'est le mabé, une demi-perle enchassée dans de la nacre. C'est Coco Chanel qui rendit ces mabés « populaires », montés en boucles d'oreille.

À Rome

Saturnales
Dans la Rome antique, les citoyens fêtaient les Saturnales : d'abord du 17 au 21 décembre, puis plus tard du 17 au 24 décembre, les hommes et les femmes portaient des guirlandes autour du cou et s'offraient toutes sortes de cadeaux. Les gens sacrifiaient aussi symboliquement un mannequin représentant un jeune homme, pensant ainsi transmettre la vitalité du personnage à la nouvelle année.
La fête des sigillaires, « ancêtre » de la Saint Sylvestre, concluait les festivités à la fin du mois de décembre. Pendant ce temps de bascule vers l'an neuf, les gens s'offraient des menus cadeaux de terre cuite, les esclaves devenaient les maîtres et inversement.

Sol Invictus
À partir du règne d'Aurélien (270-275), les Romains fêtent officiellement le Sol Invictus (Soleil invaincu) au moment du solstice d'hiver qui commençait la nouvelle année, annoncée par le rallongement des jours. Ce culte reprend des aspects de la mythologie d'Apollon et du culte de Mithra venu de Perse, s'est répandu au IVe et IIIe siècles av. J.-C. et se concluait par le sacrifice d'un taureau, le Sol Invictus correspondant à la naissance du jeune dieu solaire, qui était censé surgir d'un rocher ou d'une grotte sous la forme d'un enfant nouveau-né.

Winnie-the-Pooh

Winnie-the-Pooh, commonly shortened to Pooh and once referred to as Edward Bear, is a bear created by A. A. Milne. The character first appeared in the children's books Winnie-the-Pooh (1926) and The House at Pooh Corner (1928). Milne also included several poems about Winnie-the-Pooh in the children’s poetry books When We Were Very Young and Now We Are Six. All four volumes were illustrated by E. H. Shepard.
The hyphens in the character's name were later dropped when The Walt Disney Company adapted the Pooh stories into a series of Winnie the Pooh featurettes that became one of the company's most successful franchises worldwide.
The Pooh stories have been translated into many languages, notably including Alexander Lenard's Latin translation, Winnie ille Pu, which was first published in 1958, and, in 1960, became the first foreign-language book to be featured on the New York Times Bestseller List, and is the only book in Latin ever to have been featured therein.

Fuel and propulsion technologies

See also: Alternative fuel vehicle
Most automobiles in use today are propelled by gasoline (also known as petrol) or diesel internal combustion engines, which are known to cause air pollution and are also blamed for contributing to climate change and global warming.[18] Increasing costs of oil-based fuels and tightening environmental law and restrictions on greenhouse gas emissions are propelling work on alternative power systems for automobiles. Efforts to improve or replace these technologies include hybrid vehicles, electric vehicles and hydrogen vehicles.

Diesel
Diesel engined cars have long been popular in Europe with the first models being introduced in the 1930s by Mercedes Benz and Citroen. The main benefit of Diesels are a 50% fuel burn efficiency compared with 27%[19] in the best gasoline engines. A down side of the diesel is the presence in the exhaust gases of fine soot particulates and manufacturers are now starting to fit filters to remove these. Many diesel powered cars can also run with little or no modifications on 100% biodiesel.

Gasoline
Gasoline engines have the advantage over diesel in being lighter and able to work at higher rotational speeds and they are the usual choice for fitting in high performance sports cars. Continuous development of gasoline engines for over a hundred years has produced improvements in efficiency and reduced pollution. The carburetor was used on nearly all road car engines until the 1980s but it was long realised better control of the fuel/air mixture could be achieved with fuel injection. Indirect fuel injection was first used in aircraft engines from 1909, in racing car engines from the 1930s, and road cars from the late 1950s.[19] Gasoline Direct Injection (GDI) is now starting to appear in production vehicles such as the 2007 BMW MINI. Exhaust gases are also cleaned up by fitting a catalytic converter into the exhaust system. Clean air legislation in many of the car industries most important markets has made both catalysts and fuel injection virtually universal fittings. Most modern gasoline engines are also capable of running with up to 15% ethanol mixed into the gasoline - older vehicles may have seals and hoses that can be harmed by ethanol. With a small amount of redesign, gasoline-powered vehicles can run on ethanol concentrations as high as 85%. 100% ethanol is used in some parts of the world (such as Brazil), but vehicles must be started on pure gasoline and switched over to ethanol once the engine is running. Most gasoline engined cars can also run on LPG with the addition of an LPG tank for fuel storage and carburetion modifications to add an LPG mixer. LPG produces fewer toxic emissions and is a popular fuel for fork lift trucks that have to operate inside buildings.

Ethanol
Ethanol and other alcohol fuels have widespread use an automotive fuel. Most alcohols have less energy per liter than gasoline and are usually blended with gasoline. Alcohols are used for a variety of reasons - to increase octane, to improve emissions and as an alternative to petroleum based fuel, since they can be made from agricultural crops. Brazil's ethanol program provides about 20% of the nations automotive fuel needs, including several million cars that operate on pure ethanol.

Electric
Main articles: Battery electric vehicle, Hybrid vehicle, and Plug-in hybrid

The Henney Kilowatt, the first modern (transistor-controlled) electric car.

2007 Tesla electric powered Roadster
The first electric cars were built around 1832 well before internal combustion powered cars appeared.[20] For a period of time electrics were considered superior due to the silent nature of electric motors compared to the very loud noise of the gasoline engine. This advantage was removed with Hiram Percy Maxim's invention of the muffler in 1897. Thereafter internal combustion powered cars had two critical advantages: 1) long range and 2) high specific energy (far lower weight of petrol fuel versus weight of batteries). The building of battery electric vehicles that could rival internal combustion models had to wait for the introduction of modern semiconductor controls and improved batteries. Because they can deliver a high torque at low revolutions electric cars do not require such a complex drive train and transmission as internal combustion powered cars. Some post-2000 electric car designs such as the Venturi Fétish are able to accelerate from 0-60 mph (96 km/h) in 4.0 seconds with a top speed around 130 mph (210 km/h). Others have a range of 250 miles (400 km) on the EPA highway cycle requiring 3-1/2 hours to completely charge[21]. Equivalent fuel efficiency to internal combustion is not well defined but some press reports give it at around 135 mpg(1.74 l/100 km).

Steam
Main article: steam car
Steam power, usually using an oil or gas heated boiler, was also in use until the 1930s but had the major disadvantage of being unable to power the car until boiler pressure was available. It has the advantage of being able to produce very low emissions as the combustion process can be carefully controlled. Its disadvantages include poor heat efficiency and extensive requirements for electric auxiliaries.[22]

Gas turbine
In the 1950s there was a brief interest in using gas turbine (jet) engines and several makers including Rover and Chrysler produced prototypes. In spite of the power units being very compact, high fuel consumption, severe delay in throttle response, and lack of engine braking meant no cars reached production.

Rotary (Wankel) engines
Rotary Wankel engines were introduced into road cars by NSU with the Ro 80 and later were seen in several Mazda models. In spite of their impressive smoothness, poor reliability and fuel economy led to them largely disappearing. Mazda, beginning with the RX-2, has continued research on these engines, overcoming most of the earlier problems with the RX-7 and RX-8.

Rocket and jet cars
A rocket car holds the record in drag racing. However, the very fastest cars are used for the Land Speed Record, and are propelled by propulsive jets emitted from rocket, turbojet, or more recently and most successfully turbofan engines. The ThrustSSC car using two Rolls-Royce Spey turbofans with reheat was able to exceed the speed of sound at ground level.

Star

This article is about the astronomical object. For other uses, see Star (disambiguation).

The Pleiades, an open cluster of stars in the constellation of Taurus. NASA photo

Look up Star inWiktionary, the free dictionary.
A star is a massive, luminous ball of plasma. Stars group together to form galaxies, and they dominate the visible universe. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth, including daylight. Other stars are visible in the night sky, when they are not outshone by the Sun. A star shines because nuclear fusion in its core releases energy which traverses the star's interior and then radiates into outer space. Almost all elements heavier than hydrogen and helium were created inside the cores of stars.
Astronomers can determine the mass, age, chemical composition and many other properties of a star by observing its spectrum, luminosity and motion through space. The total mass of a star is the principal determinant in its evolution and eventual fate. Other characteristics of a star that are determined by its evolutionary history include the diameter, rotation, movement and temperature. A plot of the temperature of many stars against their luminosities, known as a Hertzsprung-Russell diagram (H-R diagram), allows the current age and evolutionary state of a particular star to be determined.
A star begins as a collapsing cloud of material that is composed primarily of hydrogen along with some helium and heavier trace elements. Once the stellar core is sufficiently dense, some of the hydrogen is steadily converted into helium through the process of nuclear fusion. The remainder of the star's interior carries energy away from the core through a combination of radiative and convective processes. These processes keep the star from collapsing upon itself and the energy generates a stellar wind at the surface and radiation into outer space.[1]
Once the hydrogen fuel at the core is exhausted, those stars having at least 0.4 times the mass of the Sun[2] expand to become a red giant, fusing heavier elements at the core, or in shells around the core. The star then evolves into a degenerate form, recycling a portion of the matter into the interstellar environment, where it will form a new generation of stars with a higher proportion of heavy elements.[3]
Binary and multi-star systems consist of two or more stars that are gravitationally bound, and generally move around each other in stable orbits. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution.

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H i s t o r y B a r b i e

Ruth Handler watched her daughter Barbara at play with paper dolls, and noticed that she often enjoyed giving them adult roles. At the time, most children's toy dolls were representations of infants. Realizing that there could be a gap in the market, Handler suggested the idea of an adult-bodied doll to her husband Elliot, a co-founder of the Mattel toy company. He was unenthusiastic about the idea, as were Mattel's directors.
During a trip to Europe in 1956 with her children Barbara and Kenneth, Ruth Handler came across a German toy doll called Bild Lilli.[1] The adult-figured Lilli doll was exactly what Handler had in mind, so she purchased three of them. She gave one to her daughter and took the others back to Mattel. The Lilli doll was based on a popular character appearing in a comic strip drawn by Reinhard Beuthin for the newspaper Die Bild-Zeitung. Lilli was a working girl who knew what she wanted and was not above using men to get it. The Lilli doll was first sold in Germany in 1955, and although it was initially sold to adults, it became popular with children who enjoyed dressing her up in outfits that were available separately.
Upon her return to the United States, Handler reworked the design of the doll (with help from engineer Jack Ryan) and the doll was given a new name, Barbie, after Handler's daughter Barbara. The doll made its debut at the American International Toy Fair in New York on March 9, 1959. This date is also used as Barbie's official birthday. Mattel acquired the rights to the Bild Lilli doll in 1964 and production of Lilli was stopped. The first Barbie doll wore a black and white zebra striped swimsuit and signature topknot ponytail, and was available as either a blonde or brunette. The doll was marketed as a "Teen-age Fashion Model," with her clothes created by Mattel fashion designer Charlotte Johnson. The first Barbie dolls were manufactured in Japan, with their clothes hand-stitched by Japanese homeworkers. Around 350,000 Barbie dolls were sold during the first year of production.
Ruth Handler believed that it was important for Barbie to have an adult appearance, and early market research showed that some parents were unhappy about the doll's chest, which had distinct breasts. Barbie's appearance has been changed many times, most notably in 1971 when the doll's eyes were adjusted to look forwards rather than having the demure sideways glance of the original model.
Barbie was one of the first toys to have a marketing strategy based extensively on television advertising, which has been copied widely by other toys. It is estimated that over a billion Barbie dolls have been sold worldwide in over 150 countries, with Mattel claiming that three Barbie dolls are sold every second.[2]
The standard range of Barbie dolls and related accessories are manufactured to approximately 1/6th scale, which is also known as playscale.[3] Barbie products include not only the range of dolls with their clothes and accessories, but also a huge range of Barbie branded goods such as books, fashion items and video games. Barbie has appeared in a series of animated films and makes a brief guest appearance in the 1999 film Toy Story 2.
Almost uniquely for a toy fashion doll, Barbie has become a cultural icon and has been given honors that are rare in the toy world. In 1974 a section of Times Square in New York City was renamed Barbie Boulevard for a week, while in 1985 the artist Andy Warhol created a painting of Barbie.[4][5]