Barack Obama

Barack Hussein Obama II ( born August 4, 1961) is the 44th and current President of the United States. He is the first African American to hold the office. Obama previously served as the junior United States Senator from Illinois, from January 2005 until he resigned after his election to the presidency in November 2008.

Originally from Hawaii, Obama is a graduate of Columbia University and Harvard Law School, where he was the president of the Harvard Law Review and where he received a doctorate in law. He was a community organizer in Chicago before earning his law degree. He worked as a civil rights attorney in Chicago and taught constitutional law at the University of Chicago Law School from 1992 to 2004.

Obama served three terms in the Illinois Senate from 1997 to 2004. Following an unsuccessful bid for a seat in the U.S. House of Representatives in 2000, he ran for United States Senate in 2004. Several events brought him to national attention during the campaign, including his victory in the March 2004 Democratic primary election for the United States Senator from Illinois and his prime-time televised keynote address at the Democratic National Convention in July 2004. He won election to the U.S. Senate in November 2004.

Obama's presidential campaign began in February 2007, and after a close campaign in the 2008 Democratic Party presidential primaries against Hillary Rodham Clinton, he won his party's nomination. In the 2008 general election, he defeated Republican nominee John McCain and was inaugurated as president on January 20, 2009. Obama is also the 2009 Nobel Peace Prize

Ancient Egypt

The culture of Ancient Egypt lived along the Nile river in Egypt from before the 5th millennium BC until the 4th Century AD. Ancient Egyptian society was based on farming the fertile Nile valley which flooded every year, enriching the soil with nutrients. The government of ancient Egypt, headed by the Pharaoh, was responsible for organizing farming efforts and collecting taxes for the state, which protected the country's borders and built grand monuments to the gods. The ancient Egyptian civilization effectively ended after the Roman domination, but the pyramids and colossal statues they left behind stand as testimony to the power of the pharaohs.


Ancient Egypt was an ancient civilization of eastern North Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. The civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh, and it developed over the next three millennia. Its history occurred in a series of stable Kingdoms, separated by periods of relative instability known as Intermediate Periods. Ancient Egypt reached its pinnacle during the New Kingdom, after which it entered a period of slow decline. Egypt was conquered by a succession of foreign powers in this late period, and the rule of the pharaohs officially ended in 31 BC when the early Roman Empire conquered Egypt and made it a province.

The success of ancient Egyptian civilization stemmed partly from its ability to adapt to the conditions of the Nile River Valley. The predictable flooding and controlled irrigation of the fertile valley produced surplus crops, which fueled social development and culture. With resources to spare, the administration sponsored mineral exploitation of the valley and surrounding desert regions, the early development of an independent writing system, the organization of collective construction and agricultural projects, trade with surrounding regions, and a military intended to defeat foreign enemies and assert Egyptian dominance. Motivating and organizing these activities was a bureaucracy of elite scribes, religious leaders, and administrators under the control of a pharaoh who ensured the cooperation and unity of the Egyptian people in the context of an elaborate system of religious beliefs.

The many achievements of the ancient Egyptians include the quarrying, surveying and construction techniques that facilitated the building of monumental pyramids, temples, and obelisks; a system of mathematics, a practical and effective system of medicine, irrigation systems and agricultural production techniques, the first known ships, Egyptian faience and glass technology, new forms of literature, and the earliest known peace treaty.Egypt left a lasting legacy. Its art and architecture were widely copied, and its antiquities carried off to far corners of the world. Its monumental ruins have inspired the imaginations of travellers and writers for centuries. A newfound respect for antiquities and excavations in the early modern period led to the scientific investigation of Egyptian civilization and a greater appreciation of its cultural legacy, for Egypt and the world.

Geography

New York covers 54,556 square miles (141,300 km2) and ranks as the 27th largest state by size. The Great Appalachian Valley dominates eastern New York, while Lake Champlain is the chief northern feature of the valley, which also includes the Hudson River flowing southward to the Atlantic Ocean. The rugged Adirondack Mountains, with vast tracts of wilderness, lie west of the valley. Most of the southern part of the state is on the Allegheny Plateau, which rises from the southeast to the Catskill Mountains. The western section of the state is drained by the Allegheny River and rivers of the Susquehanna and Delaware systems. The Delaware River Basin Compact, signed in 1961 by New York, New Jersey, Pennsylvania, Delaware, and the federal government, regulates the utilization of water of the Delaware system. The highest elevation in New York is Mount Marcy in the Adirondacks.

New York's borders touch (clockwise from the west) two Great Lakes (Erie and Ontario, which are connected by the Niagara River); the provinces of Ontario and Quebec in Canada; Lake Champlain; three New England states (Vermont, Massachusetts, and Connecticut); the Atlantic Ocean, and two Mid-Atlantic States, New Jersey and Pennsylvania. In addition, Rhode Island shares a water border with New York

Contrasting with New York City's urban atmosphere, the vast majority of the state is dominated by farms, forests, rivers, mountains, and lakes. New York's Adirondack Park is the largest state park in the United States. It is larger than the Yellowstone, Yosemite, Grand Canyon, Glacier and Olympic National Parks combined. New York established the first state park in the United States at Niagara Falls in 1885. Niagara Falls, on the Niagara River as it flows from Lake Erie to Lake Ontario, is a popular attraction. The Hudson River begins with Lake Tear of the Clouds and flows south through the eastern part of the state without draining Lakes George or Champlain. Lake George empties at its north end into Lake Champlain, whose northern end extends into Canada, where it drains into the Richelieu and then the St. Lawrence Rivers. Four of New York City's five boroughs are on the three islands at the mouth of the Hudson River: Manhattan Island, Staten Island, and Brooklyn and Queens on Long Island.

Upstate and downstate are often used informally to distinguish New York City or its greater metropolitan area from the rest of New York state. The placement of a boundary between the two is a matter of great contention. Unofficial and loosely defined regions of Upstate New York include the Southern Tier, which often includes the counties along the border with Pennsylvania. and the North Country, which can mean anything from the strip along the Canadian border to everything north of the Mohawk River.

From the 19th century, various types of fancy glass started to become significant branches of the decorative arts. Cameo glass was revived for the first time since the Romans, initially mostly used for pieces in a neo-classical style. The Art Nouveau movement in particular made great use of glass, with René Lalique, Émile Gallé, and Daum of Nancy important names in the first French wave of the movement, producing colored vases and similar pieces, often in cameo glass, and also using lustre techniques. Louis Comfort Tiffany in America specialized in secular stained glass, mostly of plant subjects, both in panels and his famous lamps. From the 20th century, some glass artists began to class themselves as in effect sculptors working in glass, and as part of the fine arts.

Several of the most common techniques for producing glass art include: blowing, kiln-casting, fusing, slumping, pate-de-verre, flame-working, hot-sculpting and cold-working. Cold work includes traditional stained glass work as well as other methods of shaping glass at room temperature. Glass can also be cut with a diamond saw, or copper wheels embedded with abrasives, and polished to give gleaming facets; the technique used in creating Waterford crystal.[38] Art is sometimes etched into glass via the use of acid, caustic, or abrasive substances. Traditionally this was done after the glass was blown or cast. In the 1920s a new mould-etch process was invented, in which art was etched directly into the mould, so that each cast piece emerged from the mould with the image already on the surface of the glass. This reduced manufacturing costs and, combined with a wider use of colored glass, led to cheap glassware in the 1930s, which later became known as Depression glass.[] As the types of acids used in this process are extremely hazardous, abrasive methods have gained popularity.

Objects made out of glass include not only traditional objects such as vessels (bowls, vases, bottles, and other containers), paperweights, marbles, beads, but an endless range of sculpture and installation art as well. Colored glass is often used, though sometimes the glass is painted, innumerable examples exist of the use of stained glass.
[edit] Museums

Apart from historical collections in general museums, modern works of art in glass can be seen in a variety of museums, including the Chrysler Museum, the Museum of Glass in Tacoma, the Metropolitan Museum of Art, the Toledo Museum of Art, and Corning Museum of Glass, in Corning, NY, which houses the world's largest collection of glass art and history, with more than 45,000 objects in its collection.

The Harvard Museum of Natural History has a collection of extremely detailed models of flowers made of painted glass. These were lampworked by Leopold Blaschka and his son Rudolph, who never revealed the method he used to make them. The Blaschka Glass Flowers are still an inspiration to glassblowers today.

हिस्टरी ऑफ़ glass

Naturally occurring glass, especially obsidian, has been used by many Stone Age societies across the globe for the production of sharp cutting tools and, due to its limited source areas, was extensively traded. But in general, archaeological evidence suggests that the first true glass was made in coastal north Syria, Mesopotamia or Old Kingdom Egypt.[ Due to Egypt's favorable environment for preservation, the majority of well-studied early glass is found in Egypt, although some of this is likely to have been imported. The earliest known glass objects, of the mid third millennium BC, were beads, perhaps initially created as accidental by-products of metal-working slags or during the production of faience, a pre-glass vitreous material made by a process similar to glazing.[

During the Late Bronze Age in Egypt and Western Asia there was a rapid growth in glass-making technology. Archaeological finds from this period include colored glass ingots, vessels (often colored and shaped in imitation of highly prized hardstone carvings in semi-precious stones) and the ubiquitous beads. The alkali of Syrian and Egyptian glass was soda ash, sodium carbonate, which can be extracted from the ashes of many plants, notably halophile seashore plants: (see saltwort). The earliest vessels were 'core-wound', produced by winding a ductile rope of glass round a shaped core of sand and clay over a metal rod, then fusing it with repeated reheatings. Threads of thin glass of different colors made with admixtures of oxides were subsequently wound around these to create patterns, which could be drawn into festoons by using metal raking tools. The vessel would then be rolled flat ('marvered') on a slab in order to press the decorative threads into its body. Handles and feet were applied separately. The rod was subsequently allowed to cool as the glass slowly annealed and was eventually removed from the center of the vessel, after which the core material was scraped out. Glass shapes for inlays were also often created in moulds. Much early glass production, however, relied on grinding techniques borrowed from stone working. This meant that the glass was ground and carved in a cold state.

By the 15th century BC extensive glass production was occurring in Western Asia, Crete and Egypt. It is thought the techniques and recipes required for the initial fusing of glass from raw materials was a closely guarded technological secret reserved for the large palace industries of powerful states. Glass workers in other areas therefore relied on imports of pre-formed glass, often in the form of cast ingots such as those found on the Ulu Burun shipwreck off the coast of Turkey.

Glass remained a luxury material, and the disasters that overtook Late Bronze Age civilisations seem to have brought glass-making to a halt. It picked up again in its former sites, in Syria and Cyprus, in the ninth century BC, when the techniques for making colorless glass were discovered. The first glassmaking "manual" dates back to ca. 650 BC. Instructions on how to make glass are contained in cuneiform tablets discovered in the library of the Assyrian king Ashurbanipal. In Egypt glass-making did not revive until it was reintroduced in Ptolemaic Alexandria. Core-formed vessels and beads were still widely produced, but other techniques came to the fore with experimentation and technological advancements. During the Hellenistic period many new techniques of glass production were introduced and glass began to be used to make larger pieces, notably table wares. Techniques developed during this period include 'slumping' viscous (but not fully molten) glass over a mould in order to form a dish and 'millefiori' (meaning 'thousand flowers') technique, where canes of multi-colored glass were sliced and the slices arranged together and fused in a mould to create a mosaic-like effect. It was also during this period that colorless or decolored glass began to be prized and methods for achieving this effect were investigated more fully.[

According to Pliny the Elder, Phoenician traders were the first to stumble upon glass manufacturing techniques at the site of the Belus River. Georgius Agricola, in De re metallica, reported a traditional serendipitous "discovery" tale of familiar type:

"The tradition is that a merchant ship laden with nitrum being moored at this place, the merchants were preparing their meal on the beach, and not having stones to prop up their pots, they used lumps of nitrum from the ship, which fused and mixed with the sands of the shore, and there flowed streams of a new translucent liquid, and thus was the origin of glass."[

This account is more a reflection of Roman experience of glass production, however, as white silica sand from this area was used in the production of Roman glass due to its low impurity levels.

During the first century BC glass blowing was discovered on the Syro-Palestinian coast, revolutionising the industry and laying the way for the growth of glass production that occurred throughout the Roman world. It was the Romans who began to use glass for architectural purposes, with the discovery of clear glass (through the introduction of manganese oxide), in Alexandria ca. AD 100. Cast glass windows, albeit with poor optical qualities, thus began to appear in the most important buildings in Rome and the most luxurious villas of Herculaneum and Pompeii. Over the next 1,000 years glass making and working continued and spread through southern Europe and beyond.

Physics of glass

The standard definition of a glass (or vitreous solid) is a solid formed by rapid melt quenching।[ If the cooling is sufficiently rapid (relative to the characteristic crystallization time) then crystallization is prevented and instead the disordered atomic configuration of the supercooled liquid is frozen into the solid state at the glass transition temperature Tg. Generally, the structure of a glass exists in a metastable state with respect to its crystalline form, although in certain circumstances, for example in atactic polymers, there is no crystalline analogue of the amorphous phase.[ As in other amorphous solids, the atomic structure of a glass lacks any long range translational periodicity. However, due to chemical bonding characteristics glasses do possess a high degree of short-range order with respect to local atomic polyhedra.[ It is deemed that the bonding structure of glasses, although disordered, has the same symmetry signature (Hausdorff-Besicovitch dimensionality) as for crystalline materials.[

Glass versus a supercooled लिकुइड

Glass is generally classed as an amorphous solid rather than a liquid.[ Glass displays all the mechanical properties of a solid. The notion that glass flows to an appreciable extent over extended periods of time is not supported by empirical research or theoretical analysis (see viscosity of amorphous materials). From a more commonsense point of view, glass should be considered a solid since it is rigid according to everyday experience.[

Some people consider glass to be a liquid due to its lack of a first-order phase transition[ where certain thermodynamic variables such as volume, entropy and enthalpy are discontinuous through the glass transition range. However, the glass transition may be described as analogous to a second-order phase transition where the intensive thermodynamic variables such as the thermal expansivity and heat capacity are continuous.[ . Despite this, the equilibrium theory of phase transformations in solids does not entirely hold for glass, and hence the glass transition cannot be classed as one of the classical equilibrium phase transformations in solids.[

Although the atomic structure of glass shares characteristics of the structure in a supercooled liquid, glass tends to behave as a solid below its glass transition temperature। A supercooled liquid behaves as a liquid, but it is below the freezing point of the material, and will crystallize almost instantly if a crystal is added as a core. The change in heat capacity at a glass transition and a melting transition of comparable materials are typically of the same order of magnitude, indicating that the change in active degrees of freedom is comparable as well. Both in a glass and in a crystal it is mostly only the vibrational degrees of freedom that remain active, whereas rotational and translational motion is arrested. This helps to explain why both crystalline and non-crystalline solids exhibit rigidity on most experimental time scales.

New chemical glass compositions or new treatment techniques can be initially investigated in small-scale laboratory experiments. The raw materials for laboratory-scale glass melts are often different from those used in mass production because the cost factor has a low priority. In the laboratory mostly pure chemicals are used. Care must be taken that the raw materials have not reacted with moisture or other chemicals in the environment (such as alkali oxides and hydroxides, alkaline earth oxides and hydroxides, or boron oxide), or that the impurities are quantified (loss on ignition).[10] Evaporation losses during glass melting should be considered during the selection of the raw materials, e.g., sodium selenite may be preferred over easily evaporating SeO2. Also, more readily reacting raw materials may be preferred over relatively inert ones, such as Al(OH)3 over Al2O3. Usually, the melts are carried out in platinum crucibles to reduce contamination from the crucible material. Glass homogeneity is achieved by homogenizing the raw materials mixture (glass batch), by stirring the melt, and by crushing and re-melting the first melt. The obtained glass is usually annealed to prevent breakage during processing.[10][11]

In order to make glass from materials with poor glass forming tendencies, novel techniques are used to increase cooling rate, or reduce crystal nucleation triggers. Examples of these techniques include aerodynamic levitation (the melt is cooled whilst floating in a gas stream), splat quenching, (the melt is pressed between two metal anvils) and roller quenching (the melt is poured through rollers).