Do you know what is ozone?

Ozone is a form of oxygen that is present in the earth's athmosphere in small amounts.Ozone in the upper athmosphere is a major factor in making life on the earth posible.But it contrributes to air pollution in the lower athmoshere.Ozone is used commercially in water purification processes and as bleaching agent.
Ordinary oxygen molecules have two oxygent atoms.Ozone molecules have tree.Ozone is produced naturally through photochemical and electric discharges,including lightning and spark from motors,also convert ordinary oxygen to ozone.Ozone is produced comercially by electric discharges in a machine.
Ozone has the chemical formula O3 and a molecular weight of 47.998.
Pure ozone is paleblue gas that has a sharp,irritating odor.The word ozone comes from a greek word meaning to smell.The german chemist Christian friedrich schonbein discovered ozone in 1840.
Ozone in the upper atmosphere.Most ozone is found in the upper athmosphere.The highest concentration of ozone is reached,depending on the latitude,between 9 and 18 miles (15 and 30 kilometers) above the earth's surface.This concentration is 10 parts per million by volume that is ,10 parts ozone per 1 million part air.This ozone layer in the upper athsmophere shields the earth from 95-99 percent of the sun's ultraviolet rays.Overexposure to these rays is cause of skin cancer.
In the mid-1970's,some scientists exspressed concern that chemical compounds called chlorofluorocarbons (CFC's) were breaking down the protective ozone layer.At the time,CFC's werw widely use as propellants in aerosol spray cans.Chlorofluorocarbons do not occur in nature,they are industrially produced chemicals.CFC's do not readily undergo chemical reactions.After CFC's are released in to the athmosphere,they rise slowly.When they reach the upper athmosphere,the suns ultraviolet radiation breaks them apart.Some of the resulting molecular fragment react with ozone, thecreasing the amount of it.
In 1978,the United States goverment banned the use of CFC's in aerosol cans.However,the ban did not affect the use of CFC's as refrigerants or in isulations. By the mid-1990's, the United States and most other industrialized countrie that produced CFC's had ended production.
Ozone hole. Since the late 1970's,scientists have observed a seasonal depletion (thinning) of ozone over antarctica.The amount of ozone decreases by up to 50 percent for two months,creating an ozone hole.Scientist belived the winter weather in antarctica promotes the prodution of the chemicals that can destroy ozone.In the winter -from june to september-Antarctica is extremely cold,and its dark for long periods.Swirling winds above Antarctica stop normal patterns of air circulations.In the spring,an increase in sunlight triggers chemical reactions that destroy ozone.As a result,the ozone hole forms.By the end of november,the reaction that deplete ozone stop.Air from non polar region flows into the polar area,raising the amount of ozone to normal levels.
Scientist have also discovered that a much less severe ozone hole occurse over the Arctic in late winter.Scientist measure ozone in the upper athmosphere with instruments on air aircraft,balloons,and satellites.

Ozone in the lower atmosphere.Ozone in the lower atmosphere is an air pollutant.It is formed by chemical reactions between sunlight and pollutants already in the athmosphere.Ozone produced in this way is component of photochemical smog.Such ozone can damage rubber,plastic,and plant and animal tissue.Exposure to certain concentration causes headaches,burning eyes, and irritation of respiratory tract in many individuals. (reff: W.B 2001)

OXYGEN (O2)

History. Oxygen was discovered by two chemist working independently. They were Carl Scheele of Sweden and Joseph Priestly of England. Scheele's laboratory notes show that the prepared oxygen in the early 1770's by heating various compounds,including saltpeter and mercuric oxide. But Scheele's experiments were not published untill 1777. He described how he prepared oxygen in 1774 by heating mercuric oxide.

Scheele called oxygen fire air. Priestley called it dephologisticated air.In 1779,the franch chemist Antoine Lavoisier named the gas oxygen. The word means acid producer. Lavoiser and others had found that oxygen is a part of several acid. Lavoiser incorrectly reasoned that oxygen is needed to make all acids. He combined the greek words oxys (meaning sharp or acids) and gignomai (meaning produce) to form the franch words oxygene.This word is oxygen in english.

Oxygen is a life supporting gas and chemical element. Nearly all living things need oxygen to stay alive. Oxygen combines with other chemical in plant and animal cells to produce energy needed for live processes.Oxygen is also needed to make most fuels burn. During the burning process,oxygen combines with the fuels in a chemical reaction. Heat is released during the burning process.

Oxygen is one of the most plentiful chemical elements on the earth. Its makes up about a fifth of the volume of air.Nitrogen makes up most of the other four-fifth. Oxygen is also found in the earth's crust and in water.This oxygen is not pure, but is combined with others elements.On average, 100 pounds of the earth's crust contains about 47 pounds of oxygen.Nearly half of the weight of most rocks and minerals is oxygen.Every 100 pounds of water contains about 89 pounds of oxygen. Hydrogen makes up the other 11 pounds of water.



Chemical properties.Oxygen has an atomic number of 8 and atomic weight of 15.9994. Its chemical symbols is O. Ordinary oxygen molecules,such as those that make up about 20 percent of the atmosphere, have two oxygen atoms bonded together. This ordinary oxygen, O2,is coloress,odorless and tasteless. Oxygen molecules that have three oxygen atoms make up a gass called Ozone (O3). Oxygen combines with many elements,forming compounds called oxides .

Ordinary oxygen changes to a pale blue liquid when cooled to its boiling point, -182.962 C at athmospheric pressure. Oxygen liquiefies at higher temperature when the pressure is increased. At a pressure of 730 pounds per square inch.oxygen liquefies at -118.8 C. These values of temperature and pressure. Its imposible to liquefy oxygen at a higher temperature and pressure.

How oxygen supports life. Only a few kinds of living things,include certain germs, can live wuthout free (chemical uncombined) oxygen,O2. Human being and the other land animals get oxygen from the air. Fish and most others water animals get dissolved oxygen from water.
Free oxygen enters a person's bloodstreams through the lungs. It enters a fish's bloodstreams through the gills. The blood carries oxygen to the cell of the body. In the food. Energy produced during this process makes it possible for each cell to perform its function in the body.Carbon dioxide is produced in the cells as waste product.

Some people believed that breathing pure oxygen will leads to an early death.They think the body's cell will use oxygen too fast, causing a person to die of exhaustion. But in certain situations,breathing pure oxygen may be necesarry. For example, pilots who fly at high altitudes,where the air is too thin too supply enough oxygen,breath from tanks of pure oxygen.

Plant cells use oxygen in much the same way that animal cells do. Plant cells also make oxygen in the process of Photosynthesis . During this process,the cells use the energy of sunlight to make sugar from carbon dioxide and water. Oxygen is produced as a by-product,and is reeased into the atmosphere. Scientists believe that all of the air's oxygen has been formed from water by this process over billions of years.

Other uses of oxygen. Oxygen has many uses in industry and medical services.In industry , some steel is manufactured by the basic oxygen process.In this process,a stream of high pressure oxygen blasts down on melted pig iron and burn out impurities.Welders mix oxygen with fuel in their torches to produce an extremely hot flame wit temperature about 6000 F degrees (3300 C). Liquid oxygen,called LOX, is used in rockets propelled by liquid fuels. LOX combines with varius fuels,including kerosene and liquid hydrogen, to produce the rocket's thrust (pushing force). LOX is also mixed with other fuel's to make explosives for blasting.

Making oxygen. Most commercial oxygen is distilled from liquid air. During the distillation process,the nitrogen boils before the oxygen does,because nitrogen has a lower boiling point. As the nitrogent boils a way,the liquid air is left with greater concentration of oxygen. Comercial oxygen is stored in steel tanks at a pressure of about,2000 pounds per square inc (140 kilograms per square centimeter), more than hundred times the pressure of the atmosphere.
Small amounts of oxygen can be made by heating potassium chlorate. A little manganese dioxide added to the potasium chlorate speeds up the formation of oxygen.

AIDS

History of AIDS

AIDS was first identified as a "new" disease by phsysician in Los Angeles in New York City in 1980 and 1981,the doctor recognized the condition as some something new because all the patients were previously healthy,young homosexual men suffering from otherwise rare forms of cancer and pneumonia.The name AIDS was adopted in 1982. Scientist soon determined thats AIDS occurred when the immune system become damaged, and that the agent that caused the damage was spread trough sexual contact,shared drug needles,and infecred blood transfusions.

After HIV(human immunodeffiency virus) was isolated as the cause of AIDS in 1983 and 1984,researchers developed test to detect HIV virus infection.These tests have also been used to analyze stored tissues from several people who died from the late 1950"s through the 1970"s. Scientist have concluded that some of these people died from AIDS

Cases of HIV infection reported worldwide rose dramatically during the 1980"s and 1990"s.an estimated 33 million people throughout the world had HIV infection or AIDS, and an estimated 16,000 people were infected with HIV each day.

How AIDS affects the body.
Cause. AIDS is caused by two viruses that belong to a group called retrovirus. HIV infects certain white blood cells,including T-helper cell and macrophage, that play key roles in the immune system.The virus attaches to CD4 receptor molecules on the surface of these cells,which are often called CD4 cells.HIV enters CD4 cells and inserts its own genes into the cell's reproductive system. The cell than produces more HIV, which spreads to other CD4 cells .Eventually,infected cell die.The immune produces millions of CD4 cells every day,but HIV destroys them as fast as they produced.



Symptoms. People infected with HIV eventually develop symptoms that also may be caused by others,less serious conditions.With HIV infections ,however these symptoms are prolonged and often more severe.They include enlarged lymp glands,tiredness,fever,loss of appetite and weight,diarrhea,yeast infections of the mouth and vagina and night sweats.

HIV commonly causes a severe "wasting sydrome" resulting in substantial weight loss, a general decline in health and some cases,death. The virus often infects the brain and nervous system. There HIV may cause dementia,a condition characterized by sensory,thingking or memory disorders.HIV infection of the brain also may cause movement or coordination problems.

How HIV is transmitted.

Researchers have identified three ways in which HIV is transmitted: (1) sexual intercourse,(2) direct contact with infected blood,and (3)tranmission from an infected woman to her fetus or baby. The most common way of becoming infected is through sexual intercourse with an HIV infected person.In the united States, sexual transmission of HIV has occured mainly among homosexual and bisexual men,but it is becoming more frequent among heterosexual men and women.HIV is transmitted through all forms of sexual intercourse,including genital,anal and oral sex.

People who inject drugs into their bodies can be expossed to infected blood by sharing needles,syringes or equipment used to prepare drug for injection.In the past,tranfusion and transplant recipients and people with hemphilia,contracted the virus from the blood,blood components,tissues, or organs of infected donors.But screening and testing of donated blood and potential organ donors have virtually eliminated this hazard. Health care workers can become infected with HIV by coming into direct contact with infected blood. This infection may occur through injury with a needle or other sharp instrument used in treating an HIV infected patient. A few patints become infected while receiving treatment from HIV infected American dentist and from france surgeon.

An infected pregnant woman can transmit the AIDS virus to her fetus even if she has no symptoms.Transmision may also occur from an HIV infected mother to her baby through breast-feeding. Studies indicate that HIV is not transmitted through air,food,water or by insect. No known cases of AIDS have resulted from sharing eating utensils,bathrooms,locker,living space or classrooms.
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Stages of HIV infection.
People infected with HIV go through three stages are: (1) Acute retroviral sydrome and symptomatic period,(2)symptomatic HIV infection and (3) AIDS.The lengt of time any person stay in each stage varies greatly and depends on many factors including medical treatment. HIV can be transmitted during all stages of infection,even no symptoms occur.
Acute retroviral syndroms and asymptomatic period.
Most people get a flulike or mononucleosis like illness within 12 weeks after becoming infected by HIV. This illness ,known as acute retroviral syndrom usually goes away without treatment. from this point on,the infected persons blood test positive for HIV antibodies even through symptoms usually do not develop for 2 to 15 years or more.
Symptomatic HIV infection.
In this stage,a wide variety of mild or severe symptoms may appear. Common symptoms include tiredness,enlarge lymph glands,yeast infection,skin rashes, and dental disease. This stage of the infection may last from a few month to many years.
AIDS.is characterized by severe damage of the immune system and such opporunistic infections as pneumocystic carinii pneumonia and kaposi'ssarcoma. The progressive breakdown of the immune system eventually leads to death,usually wuthin a few years.
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Treatments
Treatment have been developed,but no cure for HIV infection or AIDS has yet been found. Ever since AIDS identified. In 1996, several studies showed that certain combinations of anti viral drugs could decrease HIV in the blood to undetectable levels. Although HIV appears to perist inside CD4 cells.the studies raised hope that combination theraphy can control reproduction of the virus.
Physician also prevent and treat opportunistic infection in AIDS patient. PCP can be prevented with spesific antibiotics. Physician use biological subtances called interferons to treat kaposi'ssarcoma.Researchers believe any eventual cure for AIDS must stop the growth of the virus,prevent opportunistic illness and restore normal fanction to thr immune sytems.

Prevention.To prevent transmission of HIV,sexual contact with anyone who is or might be infected with the virus must be avoided. The most effective preventive strategies are to refrain from all sexual intimacy or restrict sexual intimacy to one uninfected person. Drug users should seek help to stop taking drugs and should never share hypodermic needless,syrings or other injection equipment.
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Additional resources: AIDS images of epidemic world health organization,1994,greift,judith and golden,B.A.AIDS care at home.Wiley,1994.landau-stanton,judith and clements,C.d AIDS,heallth and mental health.Brunnner-mazel,1993.Schoub,barry D.AIDS and prespectiv.cambridge.
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Nutrition (part II )

Kinds of nutrients.

The foods we eat contain thousands of different chemicals. However, only few dozen of these chemicals are absolutly essential to keep us healthy. These few dozen are the nutrients-the subtances we must obtain from the food we consume.

Nutritionists classify nutrients into six main group: (1) water,(2) carbohydrates,(3) fats, (4) proteins,(5) minerals and (6) vitamins. The first four group are called "macronutrients". The last two group ,which are required in small quantities are known as " micronutrients".

Water is needed in great amounts because the body concists largely of water.Usually between 50 and 75 percent of a person's body weight is made up of water.

The body requires large quantities of carbohydrates,fats, and protein because these nutrients provide energy. Food energy is measured in units called kilocalories. A kilocalorie is equal to 1,000 calories. A calorie is the energy required to rise the temperature of one gram of water one celsius degree. However, kilocalories are often referred to as simply "calories".The calories mentioned in this article are actually kilocalories.

Although minerals and vitamins are needed in only small amounts, they are as vital to health as any other nutrients. Minerals and vitamins are needed for growth and to maintain tissues and regulate body fanctions.

Water is, perhaps,the most critical nutrients. We can live without other nutrients for several weeks, but we can go without water for only about one week. The body needs water to carry out all of its life processes. Watery solutions help dissolve other nutrients and carry them to all the tissues. The chemical reactions that run food into energy or tissue building materials can take place only in watery solutions.The body also need water to carry away waste product and to cool itself. Adult should consume about 2 1/2 quarts (2.4 liters) of water a day in the form of beverages or water in food.

Carbohydrates include all sugars and starches. They serve as the main source of energy for living things. Each gram (0.035 ounce) of carbohydrate provides about 4 calories.

There are two kinds of carbohydrates-simple and complex. Simple carbohydrates, all of wich are sugars, have a simple molecular structure. Complex carbohydrates,which include starches, have a larger and more complicated molecular structure that concist of many simple carbohydrates linked together.

Most foods contain carbohydrates. The main sugar in food is sucrose,ordinary white or brown sugar.Another important sugar,lactose,is found in milk.Fructose,an extremly sweet sugar,comes from most fruits and many vegetables. Foods containing starches include beans,breads,cereal,corn,pasta (macaroni,spaghetti and similar foods made of flour),peas and potatoes.

Fats are a highly concentrated source of energy. Each gram of fat provides about 9 calories.All fat are composed of an alcohol called glycerol and subtances called fatty acids . A fatty acid concists of a long chain of carbon atoms, to which hydrogens atoms are attached .
Most saturated fatty acids occur in food derived from animals,such as butter,lard,dairy product and fatty red meat. But some come fro vegetable sources, such as coconut oil or palm oil. Polyunsaturated fatty acids are found in the oils of such plants as corn and soybeans and such fish as salmon and mackerel.

Proteins provide energy-4calories per gram,as carbohydrates do, but more importanly, protein serve as one of the main building materials of the body,muscle,skin,cartilage and hair, for example are made up largely of protein.The best sources of proteins are cheese,egg,fish,lean meat, and milk.Protein in these foods are called complate protein because they contain adequate amounts of all essentials amino acid.

Minerals are needed for the growth and maintenance of body structures.They are also needed to maintain the composition of digestive juice and the fluid that are found in and around cells.People need only small amounts of minerals each day.
unlike vitamins,carbohydrates,fats and proteins,minerals are inorganic compounds -that is, they are not created by living things.Plants obtain minerals from the water soil, and animals by eating plants or pant-eating animals. unlike other nutrients,minerals are not broken down by the body.

Reqired minerals include
calcium,chlorine,magnesium,phosphorus,potasium,sodium, and sulfur. Calcium,magnesium and phosphorus are essentials for healt bone and teeth. Calcium also necessary for blood clotting. Milk and milk products are the richest sources of calcium. Cereal and meats provide phosphorus. Whole grain, cereals,nuts,legumens,and grean leafy vegetables are good sources of magnesium.



Vitamins are essentialsa for good health because they regulate chemical reaction in which the body converts food into energy and tissues. There are 13 vitamins: vitaminA, the vitamin B complex,which is group of 8 vitamins, and vitamins C,D,E and K.

Vitamin A is necessary for healthy skin and development of strong bones. Sources of this vitamin include liver,green and yellow vegetables and milk.
Vitamin B1 also called thiamine, is necessary for changing starches and sugars ino energy. Its found in meat and whole grain cereals.
Vitamin B2 also known as riboflavin,is essentials for complicated chemical reactions that take place during the body use of foods. Milk cheese,fish,liver,and green vegetables supply vitamin B2.
Vitamin B6 also called pyridoxyn, its play role in chemical reactions essentials for growth. Liver,yeast contain these vitamins.
Vitamin B12 and folic acid also called folate, are both needed for forming red blood cells and for a healthy nervous system, Vitamin B12 is found in animal products especially liver. Folic acid is present in green leafy vegetables. Doctors recommend that all women who are capable of becoming pregnant consume small amounts of folic acid each day to reduce the risk of spina bifida, a serius birth defect.

Niacin also part of the B complex. Cells need niacin to release energy from carbohydrates. liver,yeast,lean meat,fish,nuts and legument contain niacin.

Vitamin C also called ascorbic acid,is needed for the maintenance of ligaments, tendons, and other supportive tissue. It found in fruits and potatoes.

Vitamin D is necessary for body use calcium. its present in fish,liver oil, and vitamin D-fortified milk, vitamin D also forms when skin is exposed to sunlight.

Vitamin E , also known as tocopherol, helps maintain cell membrans. Vegetable oils,whole-grain cereals are especially rich in this vitamin.

Vitamin K is necessary for proper clotting of blood. Green leafy vegetables contain vitamin K. It is also manufactured by bacteria in the intestine.( Ref.WB.2001)
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Additional resources:Van cleave,janice.Food and nutrition for every kid.Wiley,1999.Features kitchen experiments.Anderson,jean and deskins,barbara.The nutrition bible.Morow,1995. Dietz,william H, and stern,lorain,eds. American academy of pediatrics guide to your child's nutrition.
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Nutrition (part 1)

Nutrition is the science that deals with food and how the body uses it.People,like all living things,need food to live.Food supplies the energy for every action we perform,from reading to running.Food also provides subtances that the body needs to build and repair its tissues and to regulate its organs and systems.

What we eat directly affects our health.A proper diet helps prevent certain illnesses and aids in recovery from others.An improper or inadequate diet increases the risk of various diseases.Eating a balanced diet is the best way to ensure that the body receives all the food subtances it need.Nutrition experts recommend that the daily diet include a certain number of servings from each of the five major food groups: (1) breads,cereals,rice,and pasta (2)vegetables (3) fruits (4) milk,yogurt and cheese,and (5) meat,poultry,fish,dried beans and peas,eggs and nuts. Fats are also essential,but like sweets,should be eaten in small quantities.Workers in the field of nutrition oversee school food services,plan menus for hospitalized patients,and provide nutrition counseling for individuals.They administer international food frograms and investigatethe relationship between diet and health.They seek improved ways of processing,packaging and distributing foods,and they create new foods.

How the body uses food?
Food provides certain chemical subtances needed for good health.The subtances called nutrients perform one or more of three functions: (1) They provide materials for building,repairing, or maintaining body tissues(2) They help regulate body processes and (3)They serve as fuel to provide energy.The body needs energy to maintain all its functions.


FOOD PYRAMID

The body breaks food down into its nutrients through the process of digestion.Digestion begins in the mouth. As food is being chewed,saliva moistens the particles.The saliva begins break down such starchy foods as breads,cereals. After the food is swallowed, it passes trough the esophagus, a tube that leads into the stomach.In the stomach,digestive juices speed up the break down of such foods as meat,eggs and milk.

The partly digested food,called chyme (pronounced kym), passes from the stomach into the small intestine.In the small intestine,others juices break down the food into molecules that pass through the walls of the intestine and into the blood.

Blood distributes nutrients troughout the body.In the body's cells and tissues,the nutrients are broken down to produce energy,or are used to rebuild tissue or to regulatechemical processes. some nutrient are stored in the body, and others are used over and over again. But most of nutrients undergo chemical changes as they are used.These chemical changes produce waste product, which go to into bloodstream.

Some of these wastes are carried to the kidneys.which filter them from the blood. The body expels these wastes in the urine. The liver also filters out some wastes and concentrates them into a liquid called bile.in addition to concentrating certain wastes,bile helps digest fats.

Bile is stored in the gall bladder until it is needed to aid in digestion.Then the gall bladder empties bile into the small intestine.Bile then passes in to the large intestine along with parts of the food not digested in the small intestine.The large intestine absorbs water and small amounts of minerals from this waste material.This material along with bacterial present in the large intestine,become the finalsolid waste product,the feces and it is eleminated from the body.

How influenza spreads?

I Influenza is an infectious diseas caused by the influenza virus.The disease is commonly called flu or grippe.The word "influenza" is some time used to refer generally to either influenza or smiliar illness.

The symptoms of influenza include fever,headache,aches,chills and weakness.The symptoms usually disappear in about a week.The patient's resistance may be lowered,so that secondary infections,such as bacterial pneumonia,follow the influenza.

How influnza spreads. Influenza is mainly is respiratory disease.The virus is inhaled and comes in contact with cell of the upper air passage.It penetrates the cell that line these passages and reproduces.In time ,new viruses are released from the infected cell and infect other cells along the respiratory tract.Influenza may spread deep within the lungs.The viruse may also be carried away in exhaled air and infect other people.
People develop immunity or resistance to influenza when the body produces subtances called antibodies, which can attach themselves to influenza viruses and prevent them from infectingcells.But the virus may change its chemical composition so that the antibodies no longer works.New kind of of antibodies must be produced by the cells of the body .The body also can make cells called cytotoxic T cells. also called killer T cells ,that recognize and kill cells infected by influenza virus.

Prevention and treatment. Health authorities try to prevent the spread of influenza by means of vaccination.Most influenza vaccine concist of killed influenza viruses.These vaccines offer some protection but are not as effective as scientists would like them to be.During the mid-1970's,vaccines made with live viruses were developed and become available in some parts of the world.Scientists believe
such vaccines may offer better protection than killed virus vaccines do.Also genetic engineering techniques are being used to produce better vaccine.In addition to vaccines,antiviral drugs,such as amantadine and rimantadine can be used to treat or prevent certain types of influenza.

Treatment of patients Treatment of patient may include combatting secondary infections,wich cause most of the deaths associated with influenza.Phsyicians control these infections with antibotics and other drugs.

Flu epidemics . Influenza tends to occur in epidemics each out break is caused by a virus slightly different from the earlier ones. Scientists often name the defferent strains(type) of the virus after the place were the strain was first identified, for example asian flu was first identified in asia and later spread throughout the world.

Cold weather does not directly cause influenza, as many people believe .However ,influenza outbreaks do occurs most frequently in winter in temperate zones.These outbreaks maybe related to the crowding of people indoors in cold weather.In such crowded situations ,the virus has greater chance than usual to spread.

One of the worst global epidemics of influenza occured in 1918-1919.About 20 million people,including more than 500,000 americans,died in this epidemic. In 1957-1958,asian flu caused a worldwide epidemic, as did hongkong flu in 1968-1969.far fewer death resulthed from these epidemics.due largely to the control of secondary infections with antibiotics.

There are Three main type of influenza viruses: Type A,type B and C . Type B and C appear to infect only human beings. Type A can infect people and certain animals . The animals may then carry and tansmit the infection. (ref:w.b 2004)