Monday, September 24, 2007

Transistor radio

The transistor radio is a small radio receiver.RCA established a prototype transistor radio in 1952. The first profitable 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.

Monday, September 17, 2007

The structure of pollen

Each pollen grain contain vegetative cells only one in the greater part flowering plant but several in other seed plants and a generative cell contain a tube nucleus that produces the pollen tube and a generative nucleus that divide to form the two sperm cells. The group of cells is surrounded by a cellulose cell wall and a thick, rough outer wall made of sporopollenin.

Pollen is created in the microsporangium contained in the anther of an angiosperm flower, male cone of a coniferous plant, or male cone of other seed plants. Pollen grains come in a broad multiplicity of shapes, sizes, and surface markings characteristic of the species see photomicrograph at right. Most, but surely not all, are spherical, Pollen grains of pines, firs, and spruces are wing. The minimum pollen grain that of the Forget-me-not plant (Myosotis sp.), is approximately 6 µm (0.006 mm) in diameter.

Pollen grains may have furrows, the course of which classify the pollen as colpate or sulcate. The number of furrows or pores helps categorize the flowering plants, with eudicots having three colpi (tricolpate), and other groups having one sulcus.

Monday, September 10, 2007

Earth's atmosphere

Earth's atmosphere is a layer of gases surrounding the planet Earth and retain by the Earth's gravity. It contains roughly (by molar content/volume) 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide; trace amounts of other gases, and a changeable amount (average around 1%) of water vapor. This mixture of gases is usually known as air. The atmosphere protects life on Earth by captivating ultraviolet solar radiation and reducing temperature extremes between day and night.

There is no exact border between the atmosphere and outer space, it slowly becomes thinner and fades into liberty. Three quarters of the atmosphere's mass is within 11 km of the terrestrial surface. In the United States, people who travel above a height of 80.5 km (50 statute miles) are selected astronauts. An altitude of 120 km (400,000 ft) marks the boundary where atmospheric property becomes obvious during re-entry. The Kármán line, at 100 km (328,000 ft), is also often regarded as the boundary between atmosphere and outer space.

Tuesday, September 04, 2007


A whaleboat is a type of open boat that is comparatively narrow and pointed at both ends, enabling it to move either forwards or backwards equally well. It was initially developed for whaling, and later became popular for work along beaches, as it does not need to be turned around for beaching or refloating.
Whaleboats are usually oar-powered, although in whaling use often had a dismountable mast and sails, too. After 1850 most were fitted with a centerboard for marine. When sailing, steering was with a rudder; when rowing, navigation was done with an oar held over the stern. Whaleboats used in whaling had a stout post mounted on the aft deck, approximately which the steersman would cinch the rope once the whale had been harpooned, and by which the whale would drag the boat awaiting it was killed.
The term "whaleboat" may be used casually of larger whalers, or of a boat used for whale watching.