The Cat Who Cried for Help: Attitudes, Emotions, and the Psychology of Cats—Nicholas Dodman. icon

The Cat Who Cried for Help: Attitudes, Emotions, and the Psychology of Cats—Nicholas Dodman.


Загрузка...
страницы:   1   2   3
скачать
Books


The Cat Who Cried for Help: Attitudes, Emotions, and the Psychology of Cats—Nicholas Dodman. Board-certified animal behaviorist Dodman addresses reasons for unwanted conduct by cats such as furniture clawing, inappropriate elimination, and hostility. Change in environment, adjustment of an owner’s attitude, and prescribing drugs are among his suggestions. Case studies of felines in distress help owners find a constructive solution to their cats’ problems. Originally published in hardcover in 1997. Bantam, 199, 235 p., paperback, $12.95.


The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory—Brian Greene. Many physicists and mathematicians believe that superstring theory (string theory for short) holds the key to the unified field theory that eluded Albert Einstein. String theorists assert that everything—from physical laws governing large objects to the quantum laws directing infinitely small objects—stems from the vibrations of microscopically tiny loops of energy that lie deep within the heart of matter. Greene strives to impart an understanding of this string theory to general readers and reveal its beneficial implications. These are feats he cleverly achieves as he traverses the history and complexity of modern physics. Norton, 1999, 448 p., illus., hardcover, $27.95.


The Fifth Miracle: The Search for the Origin and Meaning of Life—Paul Davies. Organisms lurking in geothermal vents and a Martian meteorite discovered in Antarctica insinuate that life is harbored beyond the confines of the “inhabitable” parts of Earth. Davies speculates that life may still linger below Mars’ crust in heated rocks and that superbugs living deep within the Earth are living fossils. If he is correct, then perhaps the universe teems with organisms. Many scientists suppose that life circumvents the second law of thermodynamics. Davies tackles this suspicion head-on and presents his theory that the key to comprehending biogenesis lies not in a molecular maelstrom but in the formation of primitive information-processing systems. S&S, 1999, 304 p., hardcover, $25.00.


That Gunk on Your Car: A Unique Guide to Insects of North America—by Mark Hostetler. For many, entomological curiosity does not extend beyond the grisly remains scraped from car windshields and grills. In an effort to indoctrinate such folks to the ancient world of bugs, Hostetler researched those most prone to highway mortality. However, this is not just a forensics guide to identifying splattered mosquitoes and moths. Classes of insects are profiled by virtue of their biological characteristics. Originally published in hardcover in 1997. Ten Speed Pr., 1998, 125 p., color plates, paperback, $9.95.

Go Figure: Using Math to Answer Everyday Imponderables—Clint Brookhart. It is almost cliché to say that “math is everywhere.” This book exemplifies that concept, however, by showing how mathematics can be used to compute the answers to common conundrums. Equations employed when figuring the weight of Earth or predicting a child’s height are highlighted in short chapters. Readers also discern how baseball violates the rules of arithmetic and how to figure out the wind-chill temperature and other fascinating sums. Contemporary Bks, 1998, 144 p., illus., hardcover, $22.95.


Mapping Time: The Calendar and its History—E.G. Richards. Remains of oracle bones recovered from the Shang Dynasty suggest that ancient Chinese divided time into sexagesimal periods—60 days. Such timekeeping systems permeated various cultures around the world for the next 1,000 years. Then, Mayan cultures in and around Oaxaca, Mexico, created the first recorded calendar, which charted 260 days as an important period. Richards details the components of calendars and their astronomical and mathematical foundations before plotting the course of dating systems over 2,500 years. The debate surrounding the appropriate date of Easter concludes the text. OUP, 1998, 438 p., b&w photos/illus., hardcover, $35.00.


The Official, Complete Home Reference Guide to Your Child’s Nutrition—William H. Dietz and Loraine Stern, eds. More than 25 physicians contributed to this guide from the American Academy of Pediatrics. Parents’ nutritional concerns for children from infancy through the teen years are addressed. With a strong emphasis on the psychological challenges of dealing with children and food, parents are guided toward accommodating preferences while maintaining a healthful diet. Beginning with the pros and cons of breast feeding, the book goes on to discuss picky eaters, eating disorders, allergies, and more. Villard, 1999, 234 p., illus., hardcover, $23.00.


Tsunami!—Walter C. Dudley and Min Lee. In its original publication 10 years ago, the focus of Tsunami! was on the devastation wrought by massive waves that struck Hawaii in 1946 and 1960. This expanded second edition is a global look at the phenomenon of tsunamis and an account of advances in predicting and understanding of them. Furious tsunamis in Japan, Chile, and California are detailed in depth with eyewitness accounts and the specifics of each tsunami’s arrival. An extensive chapter defines tsunamis and their relationship to earthquakes and volcanoes. U Hawaii Pr, 1998, 362 p., b&w photos/illus., paperback, $19.95.


Publisher’s Letter


The scientific community lost a towering figure on Feb. 25 with the death of Glenn T. Seaborg, who was chairman emeritus of the Board of Trustees of Science Service, publisher of ^ Science News.

Seaborg’s distinguished career began in the chemistry department of the University of California, Berkeley, where he later served as chancellor and associate director of the Lawrence Berkeley Laboratory.

Seaborg was awarded the 1951 Nobel Prize in Chemistry, which he shared with the late Edward McMillan, in recognition of his work with the transuranium elements, those beyond uranium on the periodic table. He discovered 10 atomic elements, including plutonium.

During World War II, under the aegis of the Manhattan Project, Seaborg assisted in the creation of the atomic bomb. He chaired the Atomic Energy Commission from 1961 to 1971. In that work, Seaborg channeled his ambivalence toward the atomic bomb into developing peaceful uses for nuclear energy.

A combination of intellect and warmth allowed him to move freely in the worlds of academia, research, and policy making. Seaborg was keenly aware of the need to make science accessible. From 1966 to 1995, he served as chairman of the Science Service Board of Trustees. He strongly supported Science News’ role in bringing timely research information to nonscientists.

Seaborg’s love of science was never more evident than in his interactions with young people. He figured large in the Science Talent Search, a scholarship program administered by Science Service. His enthusiasm and sense of adventure rubbed off on the high school seniors who participated in the final rounds of competition.

In his lectures to STS finalists, he played—with no small degree of pride—a tape of his appearance on a 1945 CBS radio program called “Adventures in Science,” hosted by Science Service Director Watson Davis. The broadcast showcased Seaborg’s talent for translating newly discovered knowledge into concepts easily digested by a general audience.

Seaborg was the living embodiment of Science Service’s mission: the public understanding of science. His life is a source of inspiration to us all. —Donald R. Harless


Antimatter-Matter Mirror Shows Warp

Amid the vast energies and ultrasmall dimensions of particle physics, a looking-glass world of antimatter shimmers into view. In 1964, surprised physicists discovered that this antimatter realm is not a perfect mirror image of the familiar matter-dominated surroundings. Now, for the first time since that revelation 35 years ago, scientists have detected another flaw in the mirror.

“What we have found is a new physical effect in nature,” says Bruce Winstein of the University of Chicago. The discovery may help illuminate how the universe went from nearly equal antimatter and matter at its birth to the overwhelming preponderance of matter seen today, the researchers say. It also dashes one theory offered to explain nature’s uneven way of dealing with matter and antimatter and bolsters the prevailing theory of particle physics known as the standard model.

Before 1964, physicists assumed that the outcomes of experiments would remain the same if two types of symmetrical particle characteristics were both changed. Under so-called charge, or C, symmetry, particles and antiparticles are interchanged; under parity, or P, symmetry, directions such as clockwise or right transform into their mirror images.

The landmark experiment by James W. Cronin of the University of Chicago and Val L. Fitch, now of Princeton University, and their colleagues revealed that nature—or at least particles called K mesons, or kaons—didn’t behave as expected. Cronin and Fitch later shared a Nobel prize for their demonstration that the combined symmetry could break down into a CP violation.

The new finding from Winstein and scores of his colleagues working on the “Kaons at the Tevatron,” or KTeV, experiment at Fermi National Accelerator Laboratory in Batavia, Ill., represents the first definitive evidence of another type of CP violation sought since 1964. Fermilab announced the finding on March 1.

“It’s a marvelous result,” Fitch says.

Researchers at the European Laboratory for Particle Physics (CERN) near Geneva published similar findings in 1988 and 1993, notes Konrad Kleinknecht of the University of Mainz in Germany. However, those results had too much uncertainty to be considered definitive, KTeV researchers say.

Scientists have also reported preliminary indications of a CP violation in experiments with a particle called a B meson (SN: 2/20/99, p. 118).

The new effect, like the 1964 finding, arises in kaons but from a different aspect of their behavior. These particles have an unusual property that enables matter and antimatter forms to intermingle by the rules of quantum mechanics to create blended particles called K-long (Kl) and K-short (Ks). The experimenters observe these particles rather than the pure matter and antimatter.

Theoretical arguments based on CP symmetry demand that Kl should always decay into three other particles, but Cronin and Fitch found that occasionally it would decay into only two particles in what physicists call an “indirect” CP violation.

The Fermilab experiment started with those signature decays of Kl to only two particles. The scientists examined which events produced offspring carrying electric charges and which produced neutral ones. The team then compared those outcomes to the decays of Ks particles. Analysis revealed that about one of every 300 of those Kl decays was a “direct” CP violation that resulted from a process other than the matter-antimatter mixing.

The finding challenges a theory of CP violation that postulates the existence of an extremely weak force of nature, known as superweak. “This throws that scheme out the window,” Fitch says.

While the standard model of particle physics predicts direct CP violation, theorists and experimenters have more work to do to determine whether the details of the model agree with the new findings, says Edward C. Blucher, also of the University of Chicago. —P. Weiss


Marrow transplant fights bone disease


Children born with a hereditary disease called osteogenesis imperfecta can face a lifetime of bone deformities, fractures, and short stature. These children produce faulty collagen—the white, fibrous protein that forms the framework for bone, tendons, and ligaments.

The skeletons of severely affected children are so weak that parents have been known to break a child’s leg accidentally while changing a diaper. There is no known cure for osteogenesis imperfecta. Treatment consists of inserting metal rods into the largest bones as reinforcements.

Now, initial findings in a study of three children with the disease who received bone marrow transplants from healthy siblings reveal sharp increases in the recipients’ bone mass, fewer fractures, and some height gain. The work, reported in the March Nature Medicine, raises the prospect of a treatment that attacks osteogenesis imperfecta at its core.

Three months after receiving the marrow transplants, only 1.5 to 2.0 percent of the patients’ osteoblasts—cells that make collagen—stemmed from donated marrow. Yet that small amount seems to have made a difference, says study coauthor Edwin M. Horwitz, a pediatric hematologist and oncologist at St. Jude Children’s Research Hospital in Memphis, Tenn.

Horwitz admits to being “a bit surprised” when analysis showed that the three children had added 21, 28, and 29 grams of bone in the 100 days after the transplant. Healthy children of these ages—two of the patients were 13 months old and the other 32 months old—showing the same modest weight gain would have been expected to add less than 4 g of bone, he says.

The children chosen for this study were shockingly fragile. One of the 13-month-old infants had already had at least 37 fractures. This baby had only 3 fractures during the 6 months following the marrow transplant. The other 13-month-old baby had had at least 20 fractures before treatment but only 2 during the follow-up period. The third child had had 3 fractures in the 6 months preceding transplant and none during the next 6 months.

During the 6-month follow-up period, the two younger children grew 8.0 and 6.5 centimeters, roughly on a par with healthy babies that age. The older child, who hadn’t grown at all during the 6 preceding months, grew 1.5 cm—38 percent of the normal rate.

One in 20,000 babies born in the United States has osteogenesis imperfecta. Those with severe cases—such as the children in the new study—usually don’t survive beyond their 20s, Horwitz says. Some with less severe disease live longer, but many need wheelchairs to get around.

Marrow transplants—most commonly used to fight blood cancers and certain genetic diseases—had never been tried against osteogenesis imperfecta for fear that the procedure would place too great a strain on the children. Better transplant techniques have made marrow donation safer, says Stanton L. Gerson, a hematology oncologist at Case Western Reserve University in Cleveland. The treatment seems to work, but until doctors give it to more children, it is “premature to talk about this as a clinical success,” he says. —N. Seppa


Birds in male harem just yell for a mate


Life in a harem of males, ruled by one female, cramps a guy’s style all right, but there’s a way to fight back. Just yell.

The first detailed study of the bird call that ornithologists have nicknamed the yell—repeated, loud, raucous cries—reveals a novel way for males to compete for female favor. “They’re yelling for sex,” says Stuart H.M. Butchart of the University of Cambridge in England.

The noisy males, bronze-winged jacanas, belong to the 0.2 percent of bird species in which females leave the parental care to males. These 20 or so species are mostly shorebirds, such as the painted snipe, plus 7 of the 8 tropical wetland species known as jacanas.

Bronze-winged jacanas live role reversal to the max, Butchart and his colleagues report in the March ^ Animal Behaviour. The flock he studied, about 50 birds, staked out territories on the lotus leaves and other vegetation bobbing on Vembanur, a lake in southern India.

Males fight each other as they carve their floating world into territories. “They’re quite violent,” Butchart recalls. Females spar with each other for exclusive rights to one to four male territories.

The reigning female visits all the males in her harem who are not preoccupied with a previous brood and then presents one of the males with eggs, which may have a variety of fathers. Even though the lucky fellow faces a significant chance of wasting effort on other males’ offspring, he assumes full parental responsibility. For the next 100 days, he does all the work—first incubating the clutch by snuggling it under his wing and then guarding the chicks.

When it comes to the standard male jockeying to assure paternity, the bronze-winged jacana doesn’t have a lot of options, Butchart notes. The bird can’t guard his mate since he can’t cross the border onto a fellow harem-member’s lily pads, and he can’t bully his mate since she outweighs him by 60 percent on average. So he yells.

Males make the yelling noise when their female strays far away or visits another member of the harem, Butchart reports. Once a male gets tied down by parental responsibilities, he doesn’t yell much at all. When the researchers broadcasted recordings of yells from a male’s territory, the presiding female rushed over more than 75 percent of the time.

Why does she cave in to such dramatics? Butchart notes that a yelling male also attracts outsider females willing to fight for additions to their harem. “Males are using this as blackmail,” Butchart speculates.

Peter H. Wrege of Cornell University puts a slightly different spin on the call. Among wattled jacanas in Panama, he and colleague Stephen Emlen heard similar yelling when males noticed a scary predator. Females rushed to the rescue. These males also called loudly when their female dallied in another sector, but Wrege speculates that in that case, “it’s a deceitful yell.” The male fakes an emergency to get the female away from another guy.

The wattled jacana system bears strong resemblances to Butchart’s birds, Wrege notes. He, too, has been intrigued by harem males competing for paternity. Others’ experiments with male-dominant species suggest that males slack off on parenting when they have evidence the chicks are not their own.

Male wattled jacanas can easily collect such evidence. The female makes the rounds of her harem before she settles down to egg laying. She averages some 65 matings during her tour of one to four males, Wrege and his colleagues report in the Dec. 22, 1998 Proceedings of the Royal Society of London B. Among harem males who are mating, each faces a 70 percent chance of raising a chick that is not his own. Yet the male wattled jacana, like the bronze-winged relative, tends his designated clutch.

If he doesn’t, Wrege notes, all offspring, including any he fathered, die because the female doesn’t step in to help. “The male is really in a bad situation,” Wrege notes, “and he can’t do anything about it.” Except yell. —S. Milius


A female bronze-winged jacana keeps one to four males in a harem and leaves all the chick care to them.


Learning may unify distant brain regions

In studies of many animal species, the brain shows signs of exerting less effort as individuals learn to perform simple tasks or to recognize relationships between repeatedly presented items. How this apparent neural efficiency arises, not to mention how it facilitates learning, remains unknown.

A new study provides clues to what underlies this efficiency. In laboratory trials, when people first try to discern the locations of various objects, separate brain areas that participate in identifying visible items or specifying their location display characteristic jolts of activity. As people learn an object’s location, however, these regions not only toil in a progressively more relaxed style but form a close working relationship that has gone largely unnoted, concludes a team of neuroscientists in the March 5 Science.

“These two visual pathways in the brain work as one big system in associative learning,” says Christian Büchel of the Institute of Neurology in London, lead author of the report. “Reciprocal relationships such as this may promote neural efficiency as organisms learn.”

Büchel’s team obtained functional magnetic resonance imaging (fMRI) scans of the brains of six adults as they learned the locations of 10 familiar objects displayed one at a time on a computer screen. Each volunteer correctly remembered the location of all 10 items by the end of eight learning trials.

The researchers took a total of 256 fMRI scans per trial for each participant. Scans showed blood-flow rates in the brain, an indirect measure of cells’ activity.

The researchers focused on sites located on two previously recognized anatomical pathways in the brain’s visual system. Both originate at the back of the brain in tissue that serves as the entry point for visual information. One pathway then runs along the top of the brain and handles object identities; the other takes a lower road and concentrates on object locations.

During the volunteers’ early learning trials, blood flow in the two pathways surged. At the same time, a mathematical analysis of fMRI data revealed only a weak relationship between changes in the blood-flow responses along the two routes.

Neural activity slackened in both pathways on later trials, as individuals demonstrated better knowledge of object locations. At the same time, blood-flow changes in the upper and lower pathways became closely aligned.

Büchel and his colleagues view the emergence of this strong link as a sign that the two pathways increasingly pool their efforts during learning trials. Studies of electrical responses in the brain also point to joint efforts among widely separated cell clusters during learning (SN: 2/20/99, p. 122).

The new investigation represents “exciting work,” but neural efficiency during learning remains poorly understood, comments neuroscientist Robert Desimone of the National Institute of Mental Health in Bethesda, Md.

Although most brain-scan studies examine one region at a time, attempts to establish functional relationships between neural regions will rapidly become more common, Desimone predicts. —B. Bower


Not so sunny weather: When currents go bad

On Aug. 4, 1972, a surge of electricity raced down a telephone cable in the midwestern United States, temporarily snarling long-distance phone service. Nearly 3 decades later, two Canadian scientists report that they have nabbed the culprit in that case and, in the process, have illuminated a dark side of the sun’s influence on Earth.

Space physicists have long suspected that solar disturbances played a role in the phone crisis, but they thought that the problem lay 30,000 kilometers above Earth’s surface, where the solar wind plows into Earth’s protective magnetic shield. The new study indicates the trouble resided much closer to the planet, only 100 km above northern Canada, in a region of the sky called the ionosphere.

As the sun gears up for a new round of turmoil over the next 2 years, the Canadian study can help scientists and engineers plan for emergencies. “This gives us a better understanding of the type of event that causes problems on the ground,” says David H. Boteler of the Geological Survey of Canada in Ottawa, Ontario. He and his colleague G. Jansen van Beek describe their work in the March 1 Geophysical Research Letters.

Every second, on average, the sun spits out 1 million tons of electrons, protons, and denser matter. As that solar wind approaches Earth, it gets deflected by the planet’s geomagnetic field and wraps around the backside of Earth, much like air streaming around a car. The boundary separating Earth’s magnetic sphere of influence from the solar wind is called the magnetopause.

During so-called solar storms, the sun jettisons blobs of matter and magnetic energy that are faster and denser than usual. When these crash into Earth’s magnetosphere, they push the magnetopause inward, sometimes quite dramatically (SN: 2/1/97, p. 68).

The 1972 phone-cable problem occurred at about the same time that a solar storm dented the magnetopause, leading investigators then to link the two events. Researchers concluded that electrical currents in the magnetopause induced harmful currents in the long-distance phone line.

Boteler and van Beek revisited that event after studying problems caused by solar storms in 1989, which caused power outages in Quebec and electrical malfunctions along the U.S. East Coast. They realized that some of the 1989 disturbances resulted when the storms caused a sudden intensification of electric currents that run eastward in Earth’s ionosphere. In the past, researchers have thought these currents incapable of building so abruptly.

To resolve what happened in 1972, Boteler and van Beek calculated the expected effects of currents in the magnetopause and the ionosphere. Magnetopause currents, because they are so high, should have caused disturbances across the entire Earth—a pattern that does not match the data, the researchers report. Currents in the ionosphere, however, should disrupt a smaller region, which matches the observations.

The new interpretation has won over Louis J. Lanzerotti of Lucent Technologies’ Bell Labs in Murray Hill, N.J., one of the authors of the original study implicating the magnetopause. “It says something about how much we’ve learned about Earth and space characteristics,” he says.

Solar storms are most frequent when the sun reaches the most active part of its 11-year-long cycle. Such a peak is expected next year. When they hit, these storms can damage satellites, hinder radio communications, and set up currents in power lines, telephone cables, and pipelines. Engineers are developing ways to lessen solar-storm damage.

“Trying to figure out what caused that particular outage in 1972 is important for making sure it doesn’t happen again,” says JoAnn C. Joselyn of the National Oceanic and Atmospheric Administration’s Space Environment Center in Boulder, Colo. —R. Monastersky


Simulations nab protein-folding mistakes


The human body manufactures thousands of different proteins, which act as enzymes, structural elements, or carriers. Each protein starts out as a long strand that must fold itself into the proper shape to perform its specific function.

To gain insights into the folding process, researchers have developed mathematical models that attempt to capture how a single strand rapidly collapses into its correct configuration (SN: 5/9/98, p. 296). New computer simulations now reveal how one protein strand can interfere with the folding of another.

“This is a step toward successful protein engineering,” says computer scientist Sorin Istrail of the Sandia National Laboratories in Albuquerque. “It provides our first clue in how to design sequences of laboratory proteins that can survive the essential but complicated folding process.”

The results could also help laboratory scientists understand the mechanisms underlying protein-folding mistakes, which are implicated in Alzheimer’s disease (SN: 7/4/98, p. 4) and other maladies.

Istrail and his collaborators, biologist Jonathan A. King and computer scientist Russell Schwartz of the Massachusetts Institute of Technology, report their findings in an upcoming Journal of Computational Biology.

Each protein is a string of amino acids spelling out a characteristic sequence. Scientists divide the 20 distinct amino acids into two groups according to whether they attract or repel water molecules, the main constituent of cells. Those interactions drive protein folding, creating globular structures in which water-repelling amino acids end up on the inside and water-attracting ones on the outside.

A simple model portrays a protein as a stiff but jointed structure, made of two types of beads, that can snap into a few positions at each joint. Because of the huge number of different folding possibilities for even a short strand, however, simulating the process on a computer has proved difficult.

Moreover, protein strands in cells have many jostling neighbors, King notes. Two partially folded protein molecules may end up sticking together.

To capture that additional complication, Istrail and his coworkers started with a well-studied, jointed-structure model originally developed by Ken Dill of the University of California, San Francisco. Taking advantage of Sandia’s powerful computers (SN: 7/5/97, p. 5), the researchers examined what happens when strands move about and bump into each other.

Although the specific amino acid sequence determines the protein’s function, the location of water-attracting components appears to be random. By tracking two highly simplified protein chains interacting on a grid, Istrail and his coworkers showed that this irregular arrangement plays an important role in preventing water-repelling units from binding to those of another strand.

A protein with an ordered distribution of water-attracting units tends to aggregate with other proteins to form an inert lump, Istrail says. Random positioning appears necessary to keep different strands apart, allowing the formation of the correct folds. —I. Peterson

In this computer simulation, two protein strands have linked (along dashed line) to create a misconfigured lump. The blue beads are water-attracting amino acids, and the red beads are water-repelling.


Pregnancy-hormone therapy blocks cancer


If pregnancies early in adulthood reduce a woman’s lifelong risk of developing breast cancer, could short-term hormonal treatments that simulate aspects of pregnancy do the same thing? A new study on rats suggests that the answer is yes.

This finding fuels hope that scientists can develop a means to reduce women’s risk of breast cancer. Among malignancies in women, it’s the second-leading cause of death.

Satyabrata Nandi of the University of California, Berkeley and his coworkers administered a potent carcinogen to 7-week-old female rats, a common procedure used to study cancer risk. Two weeks later, they treated each animal with one of several agents that cause a maturation, or differentiation, of breast structures known as terminal end buds.

The agents mimic changes during pregnancy when those end buds transform into milk-producing lobules. Untransformed buds are believed to be especially vulnerable to carcinogens (SN: 8/5/95, p. 92).

In one experiment, the researchers stimulated the lobule development with an injection of the drug perphenazine. In others, they implanted capsules that dispensed the hormones estrogen, progesterone, or both in a range of doses for 3 weeks—the gestation period of these animals. The implants increased blood hormone concentrations to those that occur in various phases of pregnancy.

In groups of rats getting no treatment, 90 to 100 percent of the carcinogen-exposed animals developed breast cancer within 9 months. The big surprise, Nandi’s group reports in the March 2




Download 105.13 Kb.
leave a comment
Page1/3
Date conversion01.09.2011
Size105.13 Kb.
TypeДокументы, Educational materials
Add document to your blog or website

страницы:   1   2   3
Be the first user to rate this..
Your rate:
Place this button on your site:
docs.exdat.com

The database is protected by copyright ©exdat 2000-2017
При копировании материала укажите ссылку
send message
Documents

upload
Documents

Рейтинг@Mail.ru
наверх