Wednesday, May 30, 2007


A transformer is a tool that transfer electrical power from one route to another by magnetic mixture without require relative action between its parts. It regularly comprises two or more joined windings, and, in most cases, a center to focus magnetic instability.

An irregular voltage applied to one twisting creates a time-varying attractive flux in the center, which induce a electrical energy in the other windings. Varying the relation numeral of turns between major and derived windings determine the ratio of the contribution and production voltages, thus transform the voltage by step it up or down among circuits.

Wednesday, May 16, 2007


A codex is composed of many books; a book is of one scroll. It is called codex by way of metaphor from the trunks (codex) of trees or vines, as if it were a wooden stock, because it contains in itself a multitude of books, as it were of branches. In schools, in accounting and for taking notes wax tablets was the normal writing material. Wax tablets had the advantage of being reusable: the wax could be melted and a new text carved into the wax. The custom of binding several wax tablets together is a possible precursor for modern books .Also the etymology of the word codex suggests that it may have developed from wooden wax tablets.

Tuesday, May 08, 2007

The Colossus of Rhodes

From its building to its destruction lies a time span of merely 56 years. Yet the colossus earned a place in the famous list of Wonders.But even lying on the ground, it is a marvel, said Pliny the Elder. The Colossus of Rhodes was not only a gigantic statue. It was rather a symbol of unity of the people who inhabited that beautiful Mediterranean island Rhodes.

Let us first clear a misconception about the appearance of the Colossus. It has long been believed that the Colossus stood in front of the Mandraki harbor, one of many in the city of Rhodes, straddling its entrance. Given the height of the statue and the width of the harbor mouth, this picture is rather impossible than improbable. Moreover, the fallen Colossus would have blocked the harbor entrance. Recent studies suggest that it was erected either on the eastern promontory of the Mandraki harbor, or even further inland. Anyway, it did never straddle the harbor entrance.

Sunday, May 06, 2007

Water pollution

Water pollution is a large set of unfavorable belongings upon water bodies such as lakes, rivers, oceans, and groundwater caused by human activities. Although natural phenomena such as volcanoes, algae blooms, storms, and earthquakes also cause main changes in water quality and the environmental status of water, these are not deemed to be pollution. Water pollution has many causes and characteristics. Increases in nutrient loading may lead to eutrophication. Organic wastes such as sewage inflict high oxygen demands on the getting water leading to oxygen depletion with potentially severe impacts on the whole eco-system. Industries discharge a variety of pollutants in their wastewater including grave metals, organic toxins, oils, nutrients, and solids. Discharges can also have thermal effects, especially those from power stations, and these too reduce the available oxygen. Silt-bearing runoff from many activities together with construction sites, deforestation and agriculture can reduce the penetration of sunlight through the water column, restricting photosynthesis and causing blanketing of the lake or river bed, in turn damaging ecological systems.

Pollutants in water consist of a wide spectrum of chemicals, pathogens, and physical chemistry or sensory changes.A lot of the chemical substances are toxic. Pathogens can apparently produce waterborne diseases in either human or animal hosts. Alteration of water's physical chemistry include acidity, conductivity, temperature, and eutrophication. Eutrophication is the fertilisation of surface water by nutrients that were previously scarce. Even many of the municipal water supplies in developed countries can present health risks.