Sunday, April 29, 2007


Nanotechnology is a pasture of applied science and technology covering a wide range of topics. The main unifying premise is the control of matter on a scale smaller than 1 micrometer, normally between 1-100 nanometers, as well as the manufacture of devices on this same length scale. It is a highly multidisciplinary field, drawing from fields such as colloidal science, device physics, and supramolecular chemistry. Much hypothesis exists as to what new science and technology might result from these lines of research. Some view nanotechnology as a marketing term that describes pre-existing lines of research applied to the sub-micron size scale.

In spite of the apparent ease of this definition, nanotechnology actually encompasses diverse lines of inquiry. Nanotechnology cuts across many disciplines, together with colloidal science, chemistry, applied physics, materials science, and even mechanical and electrical engineering. It could variously be seen as an extension of existing sciences into the nanoscale, or as a recasting of existing sciences using a newer, more recent term. Two major approaches are used in nanotechnology: one is a "bottom-up" approach where materials and devices are built from molecular components which gather themselves chemically using principles of molecular gratitude; the other being a "top-down" approach where nano-objects are constructed from larger entities without atomic-level control.

Monday, April 23, 2007


Water is a tasteless, odorless, and nearly colorless substance in its pure form that is essential to all known forms of life and is known also as the most worldwide solvent. Water is a plentiful essence on Earth. It exists in many places and forms: mostly in the oceans and polar ice caps, but also as clouds, rain water, rivers, freshwater aquifers, and
sea ice. On the planet, water is always moving through the cycle linking vanishing, rainfall, and runoff to the sea.
Water that humans consume is called potable water. This natural resource is becoming scarcer in certain places as human population in those places increases, and its availability is a major social and economic concern.

A surprising substance
Changing appearances
Drinking water for more details on this topic, see Category: Forms of water.
Water takes many different shapes on earth: water vapor and clouds in the sky, waves and icebergs in the sea, glaciers in the mountain, aquifers in the ground, to name but a few. Through evaporation, precipitation, and runoff, water is constantly flowing from one form to another, in what is called the water cycle.
Because of the value of precipitation to agriculture, and to mankind in general, we give different names to its various forms: while rain is common in most countries, other phenomena are quite surprising when seen for the first time: hail, snow, fog or dew for example. When properly lit, water drops in the air can refract sunlight to create rainbows.
Similarly, water runoffs have played main roles in human history: rivers and irrigation brought the water needed for agriculture. Rivers and the seas offered prospect for travel and commerce. Through erosion, runoffs played a major part in shaping our environment provided that river valleys and deltas which provide rich soil and level ground for the enterprise of population centers.
Water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs or more outstandingly in hot springs and geysers. Groundwater is also extracted unnaturally in wells.

Thursday, April 19, 2007

Transistor radio

The transistor radio is a small radio receiver.RCA demonstrated a prototype transistor radio in 1952. The first commercial transistor radio, the Regency TR-1, was announced on October 18, 1954 by the Regency Division of Industrial Development Engineering Associates of Indianapolis, Indiana and put on sale in November of 1954. It cost $49.95 (the equivalent of $361 in year-2005 dollars) and sold approximately 100,000 units.The use of transistors in its place of vacuum tubes as the amplifier elements meant that the device was much smaller and necessary far less power to operate than a tubed radio. The characteristic portable radio of the fifties was about the size and weight of a small laptop computer, and contained several heavy batteries: one or more A batteries to heat the tube filaments and a large 45 to 90 volt B battery for plate voltage. By comparison, the "transistor" was about the size and weight of today's cassette-playing Walkman and operated off a single compact 9 V battery. The now-familiar 9 V battery was introduced particularly for powering transistor radios.

Tuesday, April 10, 2007

Postal Marking

Less ordinary types include forwarding addresses, routing annotations, warnings, postage due notices and explanations, such as for damaged or delayed mail. A key part of postal history is the recognition of postal markings, their purpose, and period of use.

Service marks give information to the sender, recipient, or another post office. Advice marks notify about forwarding, misspending, and letters received in bad condition, letters received too late for delivery by a certain time, or the reason for a delay in mail delivery. Dead letter offices would use various markings to keep track of their progress in finding the addressee, such as a document that the letter had been advertised in the local newspaper. The tracking procedure for registered mail may entail multiple marks and notations.

Auxiliary marks are functional by an organization other than the postal administration. For instance, 19th century mail delivery often relied on a mix of private ships, steamboats, stagecoaches, railroads, and other transportation organizations to transfer mail. Many of these organizations applied their own markings to each item, occasionally saying simply "STEAMSHIP" or some such, while others had elaborate designs. Similar direction-finding notations were also used in the early days of airmail.

The traditional way to be valid a postal marking is with the use of a rubber or metal hand stamp; handwritten notations are sometimes seen for unusual situations or in very small post offices. In the United States, modern postal markings may appear in the form of yellow paste labels with the text printed on them. Many postal administrations now have the ability to print inkjet observations directly onto a cover, either as a barcode for reading by other equipment, or as text.

Friday, April 06, 2007


The Goshawk is an average large bird of quarry in the family Accipitridae which also includes many other diurnal raptors such as eagles, buzzards and harriers.

It is an extensive species all through the moderate parts of the northern hemisphere. In North America it is named as the Northern Goshawk. It is typically inhabitant, but birds from colder regions of north Asia and Canada journey south for the winter.

Goshawk in flight this species nests in trees, building a new nest each year. It hunts birds and mammals in woodland, relying on revelation as it flies from a perch or hedge-hops to catch its quarry ignorant. Animals as large as hares and Pheasant are taken. Its call is a ferocious screech. Many older goshawks reject to attack hares, if it was earlier seriously kicked by a hare which it tried to catch.

This bird is a raptor with short large wings and a long tail, both adaptations to maneuvering through trees. The male is blue-grey above and banned grey below, 49-56 cm long with a 93-105 cm wingspan. The much larger female is 58-64 cm long with a 108-127 cm wingspan, slate grey above grey below. The youthful is brown above and barred brown below. The flight is a characteristic "slow flap – slow flap – straight glide".
In Eurasia, the male is confusable with a female Sparrow hawk, but is superior, much bulkier and has moderately longer wings. In spring, he has an impressive roller-coaster display, and this is the best time to see this enigmatic forest bird

Monday, April 02, 2007


A lens is a device for either concentrating or diverging light, normally formed from a piece of shaped glass. Analogous devices used with other types of electromagnetic radiation are also called lenses: for instance, a microwave lens can be made from paraffin wax.The earliest records of lenses date to Ancient Greece, with Aristophanes' play The Clouds (424 BC) mentioning a burning-glass (a convex lens used to focus the sun's rays to produce fire). The writings of Pliny the Elder also show that burning-glasses were recognized to the Roman Empire, and mentions what is possibly the first use of a corrective lens: Nero was known to watch the gladiatorial games throughout a concave-shaped emerald (presumably to correct for myopia). Seneca the Younger (3 BC--65) described the magnifying effect of a glass globe filled with water.Widespread use of lenses did not happen until the invention of spectacles, probably in Italy in the 1280s.