Thursday, 28 May 2009
Pines have a pyramid shape with branches growing in layers....There is no pump inside a tree, but they do have tubes inside them. Inside these tubes, or pipelines, water drops become stacked on top of each other from the roots to the leaves. Special properties of water mean that it can rise hundreds of feet into the air. Water molecules stick to each other. When one molecule is pulled out of the leaf by evaporation, it pulls up the next water molecule in line and then the next one and so on. In this manner, water molecules are being pulled up through the tree.
If you’ve ever opened up a bottle of juice that’s been sitting in the sun, you probably noticed a rush of air coming out of the bottle as the pressure was released. In late winter, pressure in maple trees causes sap to flow out of any hole in the wood, or even to drip from a broken branch. When temperatures drop below freezing at night, the pressure changes to suction and the trees suck moisture from the ground. This moisture replenishes the sap. As the sun rises and warms the trees, pressure builds and sap flows again. This cycle of pressure and suction makes the tree act like a pump, drawing up moisture and then releasing it.
When an insect lands in tree resin, insects, plant debris and pollen can become encased in tree resin. The volatile components of the resin evaporate over thousands of years. First, it becomes a hard substance known as copal, and as all of the volatile compounds disappear, it turns into a hard, inert material called amber. These specimens are very useful, since they preserve the fossil's entire physical structure. Amber can also contain bubbles of water, air and gas.
The recent discovery of oxygen-rich bubbles that had apparently been preserved in amber since the time of the dinosaurs has drawn its first major challenge. Two researchers in California say that their amber samples show no oxygen at all.
Dr. Berner and his collaborator, Gary P. Landis of the United States Geological Survey, reported oxygen levels as high as 32 percent, compared with 21 percent now. They analyzed bubbles that they believe were trapped directly in amber - hardened yellow lumps of resin from pine trees.
Dr. Craig, however, believes the gases do not directly reflect the ancient atmosphere, but must first have been dissolved in fluid. Oxygen dissolves more readily than nitrogen, the major component of the atmosphere, so relatively high levels of oxygen might be expected, he said.
Although the Scripps team detected no oxygen in their samples, they did measure unusually high levels of argon, another gas that dissolves easily in water. Dr. Berner said that he, too, was seeing high levels of argon, which he acknowledged was ''puzzling.''
Argon is used to displace oxygen- and moisture-containing air in packaging material to extend the shelf-lives of the contents. Aerial oxidation, hydrolysis, and other chemical reactions which degrade the products are retarded or prevented entirely. Bottles of high-purity chemicals and certain pharmaceutical products are available in sealed bottles or ampules packed in argon. In winemaking, argon is used to top-off barrels to avoid the aerial oxidation of ethanol to acetic acid during the aging process.
Incandescent lights are filled with argon, to preserve the filaments at high temperature. It is used for the specific way it ionizes and emits light, such as in in plasma globes and calorimetry in experimental particle physics. Gas-discharge lamps filled with argon provide blue light. Argon is also used for the creation of blue laser light.
The third most abundant gas, making up one percent of the atmosphere. The quantity has increased since the Earth was formed because radioactive potassium turns into argon as it decays. Argon is a colourless, odourless gas that is totally inert to other substances, and for this reason it is ideal in light bulbs.
Tesla coil discharges inside a jar of argon welding gas.
Potassium-argon dating is a method for estimating the age of volcanic rocks by measuring the ratio of potassium-40 to argon-40 present.
The method is based on the fact that the potassium-40 isotope of potassium decays over time to form argon-40. The useful fact about these two substances is that at normal temperatures, potassium is a solid, but argon is a gas. Therefore, during volcanic eruptions, any argon that is present escapes from the rock. But after the rock solidifies, any potassium-40 that is present continues to decay, and the argon-40 that is produced cannot escape from the rock.
Thus, geologists use potassium-argon dating to measure the age of volcanic rocks. If the concentration of argon-40 is almost zero, then the rock was formed recently. If it is high relative to the amount of potassium-40 present, then the rock is old. Archaeologists and biologists are also sometimes able to use potassium-argon dating to measure the age of artifacts and fossils, when these have become trapped in or buried under volcanic rock.
Decomposition is most rapid when oxygen is present. If the supply of oxygen is restricted, as in the sediments of productive lakes or waterlogged soils, the decomposition process slows down. There are some micro-organisms (anaerobes) that are active in the absence of oxygen and, in the presence of organic matter, can contribute to the process of decomposition.
Denitrifying, sulphate-reducing, and methane-producing (methanogenic) bacteria utilize nitrate, sulphate, and carbon dioxide respectively to generate energy in much the same way as aerobic microbes use oxygen. Other anaerobes (fermenting bacteria) generate energy for metabolic processes by transforming organic compounds.