124 résultats pour "develop"
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Parkinson Disease.
III SYMPTOMS Parkinson disease most notably affects motor control (muscle activity). The disease progresses differently for each individual—symptoms develop swiftly in some peopleand slowly in others. Some Parkinson patients may develop problems that affect their intellect or ability to reason, or they may suffer from depression or anxiety. A Motor Control Problems Doctors look for the presence of four principal symptoms in patients they suspect may have Parkinson disease. Tremor (the involun...
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Acquired Immunodeficiency Syndrome.
child transmission is particularly prevalent in Africa. D Misperceptions About HIV Transmission The routes of HIV transmission are well documented by scientists, but health officials continually grapple with people’s unfounded fears concerning the potential for HIVtransmission by other means. HIV differs from other infectious viruses in that it dies quickly if exposed to the environment. No evidence has linked HIV transmission tocasual contact with an infected person, such as a handshake, huggi...
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Alcoholism.
Although a consensus is growing among health professionals that alcohol dependence is a disease, society’s attitudes toward individuals with drinking problems remainambivalent and confused. Until the mid-20th century, the typical picture of the alcoholic was of someone without steady employment, unable to sustain familyrelationships and most likely in desperate financial straits. But this stereotype was largely dispelled when highly respected people publicly admitted their alcoholdependence and...
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Human Sexuality.
About six weeks after conception, if a Y chromosome is present in the embryo's cells (as it is in normal males), a gene on the chromosome directs the undifferentiatedgonads to become testes. If the Y chromosome is not present (as in normal females), the undifferentiated gonads will become ovaries. If the gonads become testes, they begin to produce androgens (male hormones, primarily testosterone) by about eight weeks after conception. These androgens stimulate development of the one set of the...
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Diabetes Mellitus.
Once diabetes is diagnosed, treatment consists of controlling the amount of glucose in the blood and preventing complications. Depending on the type of diabetes, thiscan be accomplished through regular physical exercise, a carefully controlled diet, and medication. Individuals with Type 1 diabetes must receive insulin, often two to four times a day, to provide the body with the hormone it does not produce. Insulin cannot be takenorally, because it is destroyed in the digestive system. Consequent...
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Fruit - biology.
from a flower with several pistils. The ovary may have a single compartment, or carpel, which houses the ovule or ovules. Or the ovary may consist of two or morecarpels, each of which may contain one or more ovules. A drupe develops from an ovary with a single carpel and is characterized by an edible exocarp and mesocarp and an inedible, hard endocarp, or pit that encloses asingle seed. Cherries, peaches, apricots, and plums are examples of drupes. Almonds also are classified as drupes, but in a...
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Flower - biology.
insects. The sepals unfurl as the flower opens and often resemble small green leaves at the flower’s base. In some flowers, the sepals are colorful and work with thepetals to attract pollinators. E Variations in Structure Like virtually all forms in nature, flowers display many variations in their structure. Most flowers have all four whorls—pistil, stamens, petals, and sepals. Botanists callthese complete flowers. But some flowers are incomplete, meaning they lack one or more whorls. Incomplet...
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Vitamin.
Vitamin B 1, or thiamine, promotes the metabolism of carbohydrates, enabling these nutrients to release their energy. Thiamine also plays a role in the functioning of the nervous system, muscles, and heart. The body does not store thiamine and people who are malnourished may develop thiamine deficiency. Mild thiamine deficiency cancause fatigue, muscle weakness, and loss of appetite. Severe thiamine deficiency causes beriberi, a disease characterized by muscle weakness, swelling of the heart,and...
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Heredity - biology.
allele from the mother and a mutated allele from the father. In both of these cases, the child will be a carrier. The child develops the disease only if he or she receives amutated allele from each parent. When both parents are carriers, there is a 25 percent chance that a child will be disease-free, a 25 percent chance that it will have thedisease, and a 50 percent chance that it will be a carrier. Examples of genetic diseases that follow the dominant-recessive pattern include sickle-cell anemi...
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Cloning - biology.
found that such embryo cells are totipotent (able to give rise to all the different cell types in the body). Exploiting this characteristic, scientists developed three techniques to clone embryo cells: blastomere separation, blastocyst division, and somatic cell nuclear transfer. A Blastomere Separation In blastomere separation, scientists fertilize an egg cell with a sperm cell in a laboratory dish. The resulting embryo is allowed to divide until it forms a mass of aboutfour cells. Scientist...
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Cancer (medicine).
unable to repair the DNA damage, p53 instructs the cell to undergo programmed cell death, or apoptosis , putting a stop to runaway cell division before it starts. Programmed cell death is a normal part of cell life and is tightly controlled by many genes, primarily p53. In a cancerous cell, one or more mutations prevent these genes from doing their jobs. When mutated, p53 allows a cell to continue to divide, even with damaged DNA.This can lead to additional mutations in proto-oncogenes or tumor...
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Child Development.
developmental scientists have studied how cultural values guide the skills and attitudes that children acquire as they mature, and how brain maturation influences thedevelopment of thinking and feeling. For a more detailed discussion of child development theories, see the Theories of Child Development section of this article. III BASIC QUESTIONS A Nature and Nurture Scholars have long debated the relative importance of nature (hereditary influences) and nurture (environmental influences) i...
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Soil.
I
INTRODUCTION
Soil, the loose material that covers the land surfaces of
an exchange between plants and the atmosphere, as oxygen diffuses into the soil and is used by roots for respiration. In turn, the resulting carbon dioxide diffusesthrough pore spaces and returns to the atmosphere. This exchange is most efficient in soils with a high degree of porosity. For farmers, gardeners, landscapers, andothers with a professional interest in soil health, the process of aeration—making holes in the soil surface to permit the exchange of air—is a crucial activity. Theburrowi...
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Library (institution).
rooms, special galleries for exhibitions, auditoriums for lectures or concerts, computer rooms, children’s rooms, photocopy rooms, and classrooms. A3 Lending Materials As part of their mission to provide information resources to the community, public libraries allow users to borrow items from their collections for limited amounts of time.To be eligible to borrow public library materials, a user must register her or his name, address, and other basic information with the local library’s circulat...
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Fungus - biology.
Many fungi can reproduce by the fragmentation of their hyphae. Each fragment develops into a new individual. Yeast, a small, single-celled fungus, reproduces bybudding, in which a bump forms on the yeast cell, eventually partitioning from the cell and growing into a new yeast cell. V CLASSIFICATION OF FUNGI Scientists have long disagreed about how to classify fungi, and the classification systems are still developing. The first description of fungi was published in 1729 byItalian botanist Pier...
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Mental Retardation.
For example, measles, chicken pox, and whooping cough may lead to encephalitis and meningitis, which can damage the brain. Physical trauma to the brain can also cause mental retardation. Brain damage may result from accidental blows to the head, near drowning, severe child abuse, andchildhood exposure to such toxins as lead and mercury. Experts believe that poverty and a lack of stimulation during infancy and early childhood can be factors inmental retardation. Children raised in poor environmen...
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Teeth.
treatments to reduce the risk of tooth decay; clear plastic coatings painted on the teeth, called dental sealants, and applications of the mineral fluoride, which fortifiestooth enamel, are two such treatments. Fluoride is also added to public water supplies in a process called fluoridation, which benefits more than 150 million Americans. Gum disease, or periodontal disease, is a progressive condition that worsens with age. Gum disease occurs when bacteria eat away at gum tissue, causing it to p...
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Endocrine System.
thermostat. When the heat in a house falls, the thermostat responds by switching the furnace on, and when the temperature is too warm, the thermostat switches thefurnace off. Usually, the change that a hormone produces also serves to regulate that hormone's secretion. For example, parathyroid hormone causes the body toincrease the level of calcium in the blood. As calcium levels rise, the secretion of parathyroid hormone then decreases. This feedback mechanism allows for tight controlover hormon...
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Leaf - biology.
The mesophyll, sandwiched between the upper and lower epidermis, consists of many thin-walled cells that are usually arranged in two layers. The palisade layer is next to the upper epidermis. It consists of cylindrical cells that are packed closely together. Next to the palisade layer and making up most of the thickness of the leaf bladeis the spongy layer. The spongy layer consists of roundish cells that are packed loosely together and have numerous air spaces between them. In most plants t...
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Genetic Engineering.
Pseudomonas fluorescens bacterium. The genetically altered Pseudomonas fluorescens bacterium produces light in proportion to the amount of its activity in breaking down the naphthalene, thus providing a way to monitor the efficiency of the process ( see Bioremediation). A3 Medicine In 1982 the United States Food and Drug Administration (FDA) approved for the first time the medical use of a recombinant DNA protein, the hormone insulin, whichhad been cloned in large quantities by inserting th...
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Honey Bee - biology.
B Reproduction and Development The queen controls the sex of her offspring. When an egg passes from her ovary to her oviduct, the queen determines whether the egg is fertilized with sperm from thespermatheca. A fertilized egg develops into a female honey bee, either worker or queen, and an unfertilized egg becomes a male honey bee, or drone. The queen lays the eggs that will develop into more queens in specially constructed downward-pointing, peanut-shaped cells, in which the egg adheres to the...
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Intelligence.
education. Teachers had no way of knowing which of the “slow” students had true learning problems and which simply had behavioral problems or poor prior education.In 1904 the French Ministry of Public Instruction asked Binet and others to develop a method to objectively identify children who would have difficulty with formaleducation. Objectivity was important so that conclusions about a child’s potential for learning would not be influenced by any biases of the examiner. The governmenthoped tha...
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Schizophrenia.
alcohol than other people. The use of alcohol and drugs often worsens the symptoms of schizophrenia, resulting in relapses and hospitalizations. IV CAUSES Schizophrenia appears to result not from a single cause, but from a variety of factors. Most scientists believe that schizophrenia is a biological disease caused by geneticfactors, an imbalance of chemicals in the brain, structural brain abnormalities, or abnormalities in the prenatal environment. In addition, stressful life events maycontri...
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Computer Science.
theoretical research is called algorithmic complexity. Computer scientists in this field seek to develop techniques for determining the inherent efficiency of algorithmswith respect to one another. Another area of theoretical research called computability theory seeks to identify the inherent limits of computation. Software engineers use programming languages to communicate algorithms to a computer. Natural languages such as English are ambiguous—meaning that theirgrammatical structure and vocab...
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Malaria.
last long and is unlikely to be fatal. Infants and children are especially vulnerable to malaria because they have not yet built up immunity to the parasite. Some peoplehave genetic traits that help them resist malaria. Sickle-cell anemia and thalassemia, for example, are inherited blood disorders linked to malaria resistance. Travelers who lack immunity to malaria should take precautionary measures when visiting areas where the disease is prevalent. Such measures include using insectrepellents,...
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Reproductive System.
in which the young develop, and a thinner channel, the vagina, which opens exteriorly. V GENITALS In animals that lay their eggs and discharge their sperm into water, the spermatozoa reach the eggs by chemical attraction; the eggs of individuals of a species attractonly the sperm of members of the same species. When eggs and sperm are deposited at great distances from each other, the number of eggs fertilized is small. Manyamphibians and aquatic vertebrates solve this problem by attaching thems...
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Autism.
may also repeat body movements, such as spinning, rocking, or flapping hands. When upset or excited, they may also harm themselves by skin-biting or head-banging. They may also show significant aggression toward other people or inanimateobjects, or may have episodes of extreme anger or frustration. D Associated Symptoms Some children with autism show other symptoms that do not contribute to the diagnosis of autism itself. Sensory sensitivity is quite common, especially to some textures, sounds,...
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Beetle - biology.
cut, or crush prey. Beetles that consume nectar from flowers use tubelike mouthparts to suck up nectar like a primitive straw. C Thorax The thorax, the body region behind the head, consists of three segments that provide attachments for the legs and wings. Each segment of the thorax carries a pair oflegs. The middle segment also bears the stiff wing sheaths called elytra, and the hind segment holds the membranous hind wings. D Legs Beetles have six jointed legs, each leg with five parts. The f...
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Puerto Rico - geography.
the length of the day remains fairly constant throughout the year. San Juan has a mean July temperature of 28°C (83°F) and a mean January temperature of 25°C (77°F). The average temperature of the seawater surrounding theisland is 27°C (81°F), with little variation during the course of the year. The entire island is cooled by the trade winds from the northeast. This air also contains much water vapor. As the air is forced to rise over the mountains, it becomescooler and the water vapor condenses...
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Stem Cell.
The medical profession used adult stem cells to treat diseases long before anyone isolated one. In 1968 scientists performed the first successful bone marrowtransplant, a procedure in which a patient receives an infusion of healthy bone marrow cells. The purpose of such transplants is to restore the blood-making capabilitiesof the patient’s diseased bone marrow after extremely strong chemotherapy has destroyed that bone marrow. From the beginning investigators suspected that stemcells in the inf...
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Drug Dependence.
these drugs develops rapidly, no withdrawal syndrome is apparent when they are discontinued. Phencyclidine, or PCP, known popularly by such names as “angel dust” and “rocket fuel,” has no medical purpose for humans but is occasionally used by veterinarians asan anesthetic and sedative for animals. It became a common drug of abuse in the late 1970s, and is considered a menace because it can easily be synthesized. Itseffects differ from those of other hallucinogens. LSD, for example, produces deta...
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Biodiversity.
a common molecule, ribonucleic acid (RNA), and most also have deoxyribonucleic acid (DNA). These molecules direct the production of proteins—molecules responsiblefor the structure and function of virtually all living cells. This is the evolutionary chain of life. All species are descended from a single common ancestor. From that ancient single-celled microbe, all inherited RNA. As time goesby, species diverge and develop their own peculiar attributes, thus making their own contribution to biodiv...
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Biodiversity - biology.
a common molecule, ribonucleic acid (RNA), and most also have deoxyribonucleic acid (DNA). These molecules direct the production of proteins—molecules responsiblefor the structure and function of virtually all living cells. This is the evolutionary chain of life. All species are descended from a single common ancestor. From that ancient single-celled microbe, all inherited RNA. As time goesby, species diverge and develop their own peculiar attributes, thus making their own contribution to biodiv...
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Primate - biology.
The primate order includes a handful of species that live entirely on meat (carnivores) and also a few that are strict vegetarians (herbivores), but it is composed chieflyof animals that have varied diets (omnivores). The carnivorous primates are the four species of tarsiers, which live in Southeast Asia. Using their long back legs, thesepocket-sized nocturnal hunters leap on their prey, pinning it down with their hands and then killing it with their needle-sharp teeth. Tarsiers primarily eat in...
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Virus (life science) - biology.
RNA into DNA earned them their name because this process is the reverse of the usual transfer of genetic information, from DNA to RNA.) The DNA form of theretrovirus genome is then integrated into the cellular DNA and is referred to as the provirus. The viral genome is replicated every time the host cell replicates its DNA and is thus passed on to daughter cells. Hepatitis B virus can also transcribe RNA to DNA, but this virus packages the DNA version of its genome into virus particles. Unlike...
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Shark - biology.
Sharks have two-chambered hearts that are relatively small compared to the rest of their bodies. Blood flows from the heart to the gills, where it collects oxygen fromwater and then distributes it to the other organs and tissues. The small heart produces weak blood pressure, and many sharks must swim continuously to create themuscular contractions needed to circulate blood throughout their bodies. Most sharks are cold-blooded—that is, they do not generate heat by digesting food. Instead, the bod...
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These poems explore encounters between the speaker or a character and a force that is greater than he is – How do the poets develop and contemplate this experience? Refer to the details of language and effect as you compare these poems.
There is a certain fluidity to the poem, as if it was a story-telling. While enjambments such as “how bright / their frail deeds” creates a sense of smooth motion to the poem, sporadic rhymes break the rhythm of the poem yet emphasize the feeling of rage. The poem is completed by a rhyming couplet, which is also the refrain. A sense of harmony is created as the most important message of the poem concludes it. Piano by D.H Lawrence however, concentrates on a happy past as the melancholic and n...
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Stroke.
IV DIAGNOSIS The symptoms typical of a stroke can also be caused by other conditions, including brain tumors, various infections, and overdoses of certain drugs. A patient that hasstrokelike symptoms may undergo a battery of imaging techniques to rule out other medical problems and confirm that a stroke has occurred. The key imagingtechnique used in diagnosing strokes is computed tomography (also known as CT or CAT scanning), which employs X rays to obtain images of the internal structures oft...
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Attention-Deficit Hyperactivity Disorder.
Although the drugs are prescribed most often to treat ADHD among children, increasingly adults are taking the drugs for ADHD. From 2002 to 2005 the number ofprescriptions written for adults reportedly increased by 90 percent. In the United States about 2.5 million children and about 1.5 million adults take ADHD drugs. Amember of the FDA advisory panel noted that adults are more likely to have a higher risk of heart problems. Most of the 25 sudden deaths, however, were amongchildren. The prelimin...
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Alzheimer's Disease.
compared residents of Ibadan, Nigeria, who eat a mostly low-fat vegetarian diet, with African Americans living in Indianapolis, Indiana, whose diet included a variety ofhigh-fat foods. The Nigerians were less likely to develop Alzheimer’s disease compared to their U.S. counterparts. Some researchers suspect that health problems suchas high blood pressure, atherosclerosis (arteries clogged by fatty deposits), high cholesterol levels, or other cardiovascular problems may play a role in the devel...
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Genetics - biology.
construct identical buildings. Just as each contractor would require a full copy of the blueprint to construct a complete building, each new cell needs a complete copy ofan organism’s genetic information to function properly. Organisms use two types of cell division to ensure that DNA is passed down from cell to cell during reproduction. Simple one-celled organisms and other organisms thatreproduce asexually—that is, without the joining of cells from two different organisms—reproduce by a proces...
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Influenza.
days and disappear in seven to ten days. However, coughing and fatigue may persist for two or more weeks. Death from influenza itself is rare. But influenza can aggravate underlying medical conditions, such as heart or lung disease. Invading influenza viruses produceinflammation in the lining of the respiratory tract, damage that increases the risk that secondary infections will develop. Common complications include bronchitis,sinusitis, and bacterial pneumonia, occurring most frequently in olde...
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Sigmund Freud.
reminiscences from the past and about her daydreams. Remarkably, as her narrative revisited memories from the past, which were associated with the onset of aparticular symptom, each symptom disappeared when accompanied by an emotional outburst. Breuer made use of this discovery to eliminate her symptoms one at atime. He called the treatment the cathartic technique (from the Greek katharsis meaning “purgation”). The treatment was time consuming and required considerable effort to reach dimly re...
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Psychotherapy.
Other managed-care companies pay therapists a set fee to meet with a client for up to a specified maximum number of sessions depending on the nature of theproblem, free of interference from case reviewers. For example, a managed-care firm may pay a therapist $200 to hold up to eight sessions with a person. If the clientuses all eight sessions, the therapist normally loses money. But if treatment stops after two or three sessions, the therapist makes a profit. This relatively new system iscontrov...
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Poliomyelitis.
Physical therapy helps patients with paralytic polio stretch and move affected muscles. This movement minimizes the atrophy, or shrinkage, of affected muscles andlimbs and builds strength. Exercises can also retrain working muscles to compensate for other muscles that have permanently lost the ability to move. Rehabilitativetherapy trains patients to use braces, crutches, and other devices that provide support and aid mobility. V PREVENTION OF POLIO Immunization with polio vaccine is the best w...
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Meteorology.
to find the corresponding relative humidity and dew-point temperature. III SPECIAL METEOROLOGICAL INSTRUMENTS Meteorologists have developed several sophisticated instruments that measure multiple physical characteristics of the air simultaneously and at more than one location.The most important of these special instruments are radiosondes, Doppler radar, and weather satellites. A Radiosonde A radiosonde measures air temperature, air pressure, and humidity from the earth’s surface up to an alt...
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Poverty.
economic and demographic trends, and (7) welfare incentives. A Overpopulation Overpopulation, the situation of having large numbers of people with too few resources and too little space, is closely associated with poverty. It can result from highpopulation density (the ratio of people to land area, usually expressed as numbers of persons per square kilometer or square mile) or from low amounts of resources, or from both. Excessively high population densities put stress on available resources....
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Coronary Heart Disease.
when a patient is at rest may indicate that the blood supply of the heart is not normal, and the ECG can often detect damage from a previous heart attack. In anexercise stress test, an ECG is recorded while a patient is performing physical activity such as walking on a treadmill or riding a stationary bicycle. As the intensity ofexercise increases, the doctor looks for specific changes in the ECG that indicate the heart is not getting enough oxygen. In cardiac catheterization, a long, thin, flex...
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Diseases of Animals.
infected animal. It may also spread in milk or in garbage that contains contaminated meat. Typical symptoms include blisters that appear on the mouth and feet;animals may become lame when their hooves degenerate. Canine distemper is a highly contagious disease caused by the paramyxovirus, which is transmitted in discharges from the nose and eyes. Symptoms begin with fever,malaise, and nasal and ocular discharges and may progress to convulsions and other nervous system disorders. Parvoviruses aff...
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Marketing.
Where advertising reaches a mass audience, personal or direct selling focuses on one customer at a time. That kind of individual attention makes direct sellingexpensive, but it also makes it effective. As the costs of personal selling have risen, the utilization of salespeople has changed. Simple transactions are completed byclerks. Salespeople are now used primarily where the products are complex and require detailed explanation, customized application, or careful negotiation over priceand paym...