Dichlorodiphenyl trichloroethane (DDT) is a nonsystemic contact insecticide. The compound has been employed against a variety of pests. Although DDT can be used to combat insect-transmitted disease, it's most common application is in agriculture. The chemical was widely utilized across the globe from World War II up until 1972. In that year, concern over the potential threat of environmental damage eventually caused the United States to restrict its use.
An organochlorine, DDT's chemical formula is C14H9Cl5. The compound can be variously described. In addition to dichlorodiphenyl trichloroethane, it is also known as the following: (1) p,p'-DDT; (2) 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane; and (3) 4,4'DDT. There are actually three ..."
Abstract A discussion between family members that gives a lesson in biology and defines several aspects of biology such as vegetarianism, protein, vitamin B12, cladistics, tetrapods, and antisense technology. Because this colloquial paper is written in the style of a story being told to the lay person, the reader is able to easily understand the bioligical concepts.
From the Paper ""I'm being more efficient," Sadie said. "The 10% rule of ecology says that only 10% of the available energy stored in a food can be used by the next level of the ecosystem. So plants can use only 10% of the energy sent by the sun, and we can use only 10% of the energy stored by plants when we eat them, or 1% of what comes from the sun. Eating meat cuts the percentage to one-tenth of 1%. Too inefficient. That's why I eat only plants" ("Vegetarianism"). Sadie nodded her head wisely.
"She's right, you know." David was a graduate student in molecular biology. He knew that sort of stuff backward and forward. Uncle Eldridge looked a little startled.
"I learned that in class, too," I added.
"But what about protein? How do you get enough protein?" Aunt Sally looked worried.
"There are a lot of sources of protein besides meat. The need for protein is based on getting both essential and non-essential amino acids from your food," Sadie explained. "It can be from complete protein foods, like meat or fish or chicken, that include all the amino acids. But non-complete protein foods are just called that because they don't include every amino acid. So you just have to combine them to get all the amino acids you need."
"Will you be able to get all your amino acids today without the turkey?" Mom asked.
"Probably," Sadie said. "The beans, the potatoes, the walnuts, and the corn in the cornbread probably include all the essential amino acids between them." ("Protein")."
Abstract Radioactive dating is the process of determining the age of rocks and other specimens from the decay of their radioactive elements. By applying this information, geologists are able to decipher the 4.6-billion-year history of the earth. The paper introduces the history of this type of dating in chronological order. It discusses other issues related to radioactive dating such as Carbon-14 dating, fission track dating, Potassium Argon Dating, the Rubidium-Strontium method, lead-alpha age and debated ideas of radioactive dating.
From the Paper "Cosmic rays from the sun strike nitrogen 14 atoms in the earth's atmosphere and cause nitrogen atoms to lose a proton making it a carbon isotope this then turns into radioactive carbon 14, which combines with oxygen to form radioactive carbon dioxide. All living things are in equilibrium with the atmosphere, and the radioactive carbon dioxide is absorbed from the air and used by green plants. Then the radioactive carbon dioxide gets passed on through the plants into the food chain and the carbon cycle. All living things contain a constant ratio of Carbon 14 to Carbon 12 of about 1 in a trillion. The amount of carbon 14 lost in a species is continually replenished as long as it still takes in food and oxygen. At death, the exchange of carbon 14 ceases and any that is left in the tissues of the organism begins to decay to Nitrogen 14, this is not replenished by any new C-14. The change in the Carbon 14 to Carbon 12 ratio is the basis for dating this dating technique. The half-life is so short (5730 years) that this method can only be used on materials less than 70,000 years old. A lot of archaeological dating uses this method. It is also very useful in attempting to date remnants of the ice ages (Pleistocene epoch.)"
Tags: Marie, Pierre, Curie, Clair, Patterson, U, 235, atom
Abstract A thorough discussion of the main variants of hemoglobin, their structures, effects and biochemical signifigance. The discussion of the hemoglobin mutants also involves the diseases associated with them, as well as the symptoms and treatments of these disease.
From the Paper "Hemoglobin is an extremely important molecule to the life processes of animals. Hemoglobin functions to transfer oxygen from the lunge to the individual cells of the body, allowing respiration to occur, and providing the oxygen necessary for life functions. Hemoglobin comes in many different forms and each change in structure effects the overall function of hemoglobin. How each type of change specifically changes the function of hemoglobin is important to understand how hemoglobin works as well as for treatment in diseases caused by hemoglobin mutants."
This paper looks at a study conducted on mice which shows that the suppression of p53, done in conjunction with cancer therapy, may give patients some relief from unpleasant side-effects.
Abstract The paper suggests that while the chemical inhibitor of p53 is suppressed, at the same time this treatment can allow for appropriate treatment to destroy p53-deficient cancer cells in a patient. The paper gives the chemical explanation for how the results were found in mice. The writer concludes with a discussion of the importance of this research for the future of cancer patients undergoing the intense treatment to fight the spread of the disease.
From the Paper "The p53 inhibitor had almost no protective effect if it was added up to 18 hours prior to, and removed immediately before, irradiation. A short, 3-hour treatment with PFT-alpha after irradiation had a pronounced protective effect on the cells, and a 24-hour incubation gave maximal protection. If PFT-alpha was added 3 hours after irradiation, it was not able to rescue the cells from radiation-induced damage. This suggests that ultraviolet radiation-induced apoptosis is significantly reduced within several hours, and completely eradicated within 24 hours of irradiation by PFT-alpha."
Abstract This paper provides an insight into brass, a useful alloy of two metals, copper and zinc which has been used for cultural uses and ornamentation since the 13th century BC. It examines how the porosity, or the ratio of the volume of interstices of a material to the volume of its mass, can be reduced in order for brasses of all compositions to be worked or hardened to form wires, fittings or ornaments with the most utilitarian strength, elasticity or ductility features.
Outline
Introduction
Brass
A Thousand Years of Brass-Making
Phase Diagram for All Brasses
Density of Brass Varieties
Porosity in Brass
Metal Porosity--in its Place
Manufacturing Methods to Reduce Porosity
Post-Manufacturing Methods that May Reduce Porosity
Unavoidable Internal Change Mechanisms Possibly Affecting Porosity
Summary and Conclusions
From the Paper "As with many metals and alloys, brass is often worked after its formation, not merely for shaping into the desired form, but also to alter for improvement one or more of its physical properties: Strength or hardness, ductility or elasticity, as examples. The methods are generally lumped as a number of "hardening" types, although their purposes rarely include the reduction of porosity, per se. Some are carried out at room temperature (called "cold work"); others are performed at a variety of elevated temperatures, each having its own intended effect (called "hot working")(14:7-9)."
Abstract This paper examines how magic and religion have always seemed to be at odds with the scientific community and how ironically enough they were major contributors to the motivation and means behind the Scientific Revolution. It looks at how many of the leaders of discovery in that time were heavily influenced by religious matters and how men like Descartes, Newton and Galileo saw their work as evidence of God's infinite wisdom. It examines the specific circumstances surrounding scientific discovery in the 1600s and the natural philosophers themselves and evaluates the influence of these factors on methodology and motivation.
From the Paper "Magic was redefined as well. The new interest that began the Scientific Revolution was due in part to a desire for more practical convenience. Mechanism and alchemy came directly from magic and the occult, but according to our present definition of magic, this fact is blurred. We tend to view the mystical, demonic, or spiritual side of magic as the whole, but in truth, scientists took the physical, known use of magic and renamed it SCIENCE. At one time, using an herb or a mineral solution to cure a physical ailment was considered natural magic. To use one thing in nature to affect another, to study their interaction closely, and to derive conclusions from this intimate knowledge of the natural power of things, was an early form of the Scientific Method. This method was taken directly from natural magicians."
Abstract This report explains in detail the function, structure and assembly of flagella in E.coli and Salmonella, using plain language and a number of diagrams. Movement (chemotaxis) is the primary function of flagella but its design also incorporates efficient repair capability and antigenic variation. In Salmonella and E.coli the flagellar filament is a homopolymer of flagellin monomers, although other species (such as Helicobacter) build their flagella from mixtures of two types of subunit. All the properties of the functioning filament are reflected in the structure of the flagellin monomer, which has conserved and variable regions, regions targeted by chaperones and coiling enzymes and regions evolved specifically for interaction between monomers. Chemotaxis is driven by a proton motive force (as in oxidative phosphorylation) and the basal complex that converts this energy into rapid rotation of the flagellum is highly complex.
From the Paper "Many bacteria are motile and exhibit chemotaxis ? migration through the extracellular medium towards attractants (e.g. carbon sources), and away from repellents (e.g. antibiotics). The majority move using flagella ?protein structures variable in number and position (Box 1) that generate thrust by rotating like propellers. Flagella are 15nm in diameter and can be observed under light microscopy after thick metal staining or using advanced microscopy techniques such as electron microscopy. Because of the competitive advantages of chemotaxis, there has been strong selection for efficient chemotactic apparatus and flagellar efficiency. The flagellum is based in the bacterial surface layers where a complex array of proteins forms the flagellar motor. Resembling the electric rotary motor and the membrane-bound F1F0-ATPase, and powered by a proton influx across the inner membrane, this highly efficient machine is merely 30nm in diameter. Its mechanism is the subject of ongoing research."
Abstract This paper explains that nature acts as a pharmacy, offering us products, from the forest pharmacy and the pharmacy below water, with which we can heal ourselves: For example, aspirin, quinine, cyclosporins, and penicillin. This paper details the techniques that are available to researchers, to collect samples of natural products from the wild in a systematic manner, to extract compounds from these samples, to isolate the biologically-active compounds within these extracts, to characterize the biologically-active compounds chemically in terms of their structure, to evaluate the biologically-active compounds biologically, to determine potentially useful therapeutic effects and finally the methodology necessary to take these compounds to clinical trial. The author stresses the importance of finding new and more effective drugs to fight against bacterial infections and cancer. Outline.
Table of Contents
Introduction
Nature's Pharmacopeia.
The Isolation of Biologically-Active Compounds and their Extraction Identification: Techniques
Introduction
Chemical Extraction
Biological Evaluation
Chemical Analysis
Chromatography
Solid Phase Extraction
Paper Chromatography
Thin Layer Chromatography
Flash Chromatography
High Performance Liquid Chromatography
Central Counter Current Chromatography
Determining the Chemical Structure of Compounds Isolated by Chromatography
Nuclear Magnetic Resonance
Mass Spectrometry
Drug Development
Examples of the Isolation and Identification
An Example of Extraction, Isolation and Chemical Characterization of Biologically-Active Compounds from Larch Wood
Biologically-active Compounds from Marine Organisms
What Compounds Have Been Isolated From Marine Organisms?
Biologically-Active Anti-Cancer Compounds ? Testing for Human Safety
Conclusion
From the Paper "Chromatography is the process whereby two or more compounds or ions are separated through the distribution of the compound or ion between two phases, one that is mobile and the other which is stationary. These two phases can be of any combination: liquid-liquid, solid-solid, solid-liquid or gas-liquid, gas-gas, or gas-solid. There are many specific techniques for chromatography, some of which will be described below, and all follow the same basic principles. All forms of chromatography involve a rapid and dynamic equilibrium of molecules between the two phases, either free ? mobile - or absorbed ? stationary. Molecules will constantly move back and forth between the free and absorbed states, with millions of molecules absorbing and desorbing every second. The equilibrium between these states depends on three factors: the polarity and size of the molecule, the polarity of the stationary phase, and the polarity of the solvent. Thus, three different variables can be changed in chromatography, which can change the equilibrium between the stationary and mobile phases: this allows one to choose mobile and stationary phases that will separate just about any combination of compounds."
Abstract This paper discusses the differences between organic and inorganic chemistry and provides a brief insight into organic chemistry and the family of the hydrocarbons. It looks at how the salient point to remember in the formation of compounds (everything else flows from there) that drives chemical processes is the need to complete the valence or the atomic shell of each element's inherent instability. It shows how inorganic and organic chemistry are the results of variable approaches to solving the instability and how this then results in the formation of the stable compounds that the world we live in and the universe at large need to survive.
From the Paper "The arrangement of the four electrons around the carbon lend it a tetrahedral (equal on four sides in three dimensions) geometry. The simplest organic compound is methane (inflammable gas found in sewers and coal mines) where a single carbon atom is covalently linked to four hydrogen atoms. In this way, each hydrogen atom can claim two electrons needed to complete its shell (its own and one from carbon). The four carbon electrons and one each from the four hydrogen atoms complete its shell of eight. If one considers a chain of carbon atoms linked together carbon to carbon (C-C) with associated carbon to hydrogen (C-H) bonds, an organic molecule is formed. These compounds are straight chains, rings, or chains with cross- links and branches."
Abstract This paper provides a detailed analysis of several gases and chemicals which are present in the air we breathe and how these are causing adverse effects on our health. It explains that air pollution created by humans is the most dangerous and discusses possible ways to reduce this phenomena.
Outdoor Air Pollution
Ozone
Nitrogen Dioxide
Sulphur Dioxide
Acid Aerosols
Particulates
Air Toxics
Carbon Monoxide
Lead
Asbestos
Asbestos: Health and Exposure
Potential Effects of Outdoor Air Pollution on Health
War: Detrimental Consequences and Air Pollution
War Gases
Classification of War Gases
Asphyxiants (Irrespirable Gases)
Sewer Gas
Emphysema
From the Paper "The air that surrounds us is a mixture of 78 percent nitrogen; 21 percent oxygen; less than 1 percent of carbon dioxide, argon, and other gases; and varying amounts of water vapor. Any other particles, gases or unoriginal constituents hanging in the air which are not part of its original composition are called "Pollutants" and this kind of air is called
Polluted Air. Even inhaling small amounts of such air pollutants can have serious effects on one's health and leads to environmental problems. We can see some air pollutants such as the reddish-brown haze in smog; however, other air pollutants, including some of the most dangerous, are invisible.
Air pollution can be natural or human-made. Air pollution occurs naturally during volcano eruptions, forest fires, or dust storms. This has been an occasional problem for humans. However, during the past hundred years, air pollution created by humans has become a major, persistent problem."
Abstract This paper discusses the importance and value of the preservation of library materials. It then discusses how this is done, including the technological process. The writer further examines how this process has evolved and advanced over time.
From the Paper "Since the beginnings of the library system in the United States, many methods have been devised for the preservation of library materials, such as books, manuscripts, autographs and related ephemera, prints, maps, paintings, photographs, movie film, sound recordings and videotape/DVD's. Some of these specialized techniques have been highly successful, while others have often failed to preserve certain items in their original, pristine conditions. As Caroline Horton points out, items of special value held in library collections "require the skills of trained conservators, for the vast majority of materials deteriorate rapidly" (167), not to mention the skills and talents required to preserve common items that are usually part of the circulating system of any public or academic library."
Abstract This paper relates that scientists have deciphered every last one of the 3 billion DNA "letters" in the human body. The author points out that the completed DNA sequence is now expected to give scientists understandings about the workings of the human body that have never been made before. The paper stresses that this development will revolutionize medicine and biology.
Abstract This paper examines and analyzes the use of water as a fire-extinguishing agent. The characteristics of water that make it a good extinguishing agent are discussed, the detrimental features of water when used for fire extinguishment are listed, and the means of overcoming some of these handicaps in the use of water are evaluated.
