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1.
A fourth specimen of Archaeopteryx (cf. lithographica), the oldest known fossil bird, was recently found in the collections of the Teyler Museum in the Netherlands. Unique preservation of the horny sheaths of the manus claws provides new evidence that may be relevant to the question of the origins of avian flight. Tentative interpretation suggests a cursorial rather than arboreal origin.  相似文献   

2.
Jeletzkya douglassae Johnson and Richardson is described as the oldest known representative of an extant squid group. The species is known from a single specimen from the Middle Pennsylvanian of Illinois. This very unusual fossil consists of the complete tentacular crown and a fragile shell. The arms bear hooks in double rows.  相似文献   

3.
The discovery of an existing member of the Glypheidae, a family believed to have been extinct since the Eocene, may yield significant information on the evolution and classification of the decapod Crustacea. The single known specimen displays characters not apparent in fossil material, some of them perhaps representative of an ancestral decapod lineage, others reminiscent of the Astacidea and Thalassinidea.  相似文献   

4.
The International Workshop on Trichoderma and Gliocladiurn has been a regularly organized meeting since 1984, and promotes presentation of research as well as discussion of new ideas among scientists working on various aspects of these two genera of fungi.  相似文献   

5.
Koenig R 《Science (New York, N.Y.)》2000,288(5472):1719-1721
Germany's premier basic research organization, the Max Planck Society, released a long-awaited blueprint for change during its annual meeting this week, recommending that the society's nearly 3000 scientists embrace more interdisciplinary and international projects in a range of new research priorities. The report, called Max Planck 2000-Plus, is the product of an 18-month-long internal review. Its recommendations were formulated by some two dozen Max Planck researchers and administrators, who sought input from every institute.  相似文献   

6.
Service RF 《Science (New York, N.Y.)》1994,266(5192):1807-1808
Physicists, chemists, and other scientists gathered in Boston from 28 November to 2 December for the fall meeting of the Materials Research Society (MRS) to explore everything from the behavior of single atoms to bulk structures. Among the more than 4000 papers and posters presented, attendees learned about novel devices that convert light directly to sound, new techniques for studying minuscule structures called quantum dots, and organic-inorganic hybrid materials.  相似文献   

7.
Vogel G 《Science (New York, N.Y.)》2000,288(5474):2119-2120
BOULDER, COLORADO--Nearly 600 scientists gathered at the base of the Flatirons to discuss the growth and patterning of organisms including plants, worms, fruit flies, fish, and mice at the 59th annual meeting of the Society for Developmental Biology. Among the highlights were clues about how blind cave fish lost their eyes and how a gene that influences cell movement might help cancer spread.  相似文献   

8.
Brush SG 《Science (New York, N.Y.)》1989,246(4934):1124-1129
Is a theory that makes successful predictions of new facts better than one that does not? Does a fact provide better evidence for a theory if it was not known before being deduced from the theory? These questions can be answered by analyzing historical cases. Einstein's successful prediction of gravitational light bending from his general theory of relativity has been presented as an important example of how "real" science works (in contrast to alleged pseudosciences like psychoanalysis). But, while this success gained favorable publicity for the theory, most scientists did not give it any more weight than the deduction of the advance of Mercury's perihelion (a phenomenon known for several decades). The fact that scientists often use the word "prediction" to describe the deduction of such previously known facts suggests that novelty may be of little importance in evaluating theories. It may even detract from the evidential value of a fact, until it is clear that competing theories cannot account for the new fact.  相似文献   

9.
SAN FRANCISCO-Engineers, physicists, and other scientists interested in material behavior came together at the 1994 spring meeting of the Materials Research Society from 4 to 8 April. Among the 2200 papers given, researchers heard presentations on a variety of functional substances: a semiconductor suitable for a laser that gives off blue light, an improved magnetic refrigerator, and a method of keeping pollutants from forming in engine exhaust.  相似文献   

10.
农业的发展离不开科技的进步,但石油农业的发展和人口的增长给农业带来了前所未有的严峻挑战,农业要走出这种困境就必须进行一次新的技术革命。现代生物技术及其它高新技术正日益应用于农业生产的各个领域,并取得了重大成果,为农业技术的改造、更新和农业新技术革命提供了可能。为了迎接农业新技术革命的到来,作者认为,必须加强人才的培养、加强物种的保护和种质资源的研究。  相似文献   

11.
Cohen J 《Science (New York, N.Y.)》2000,289(5486):1850-1851
At center stage at a meeting on the origin of the AIDS epidemic, held here this week at the Royal Society, was a controversial theory that a contaminated polio vaccine tested in Africa more than 40 years ago sparked the epidemic. The theory took a hit when researchers revealed that tests of old samples of the vaccine provided no supporting evidence, and the main proponent of the theory, British writer Edward Hooper, endured a verbal battering himself from several prominent scientists. But Hooper, unbowed, got in plenty of jabs of his own.  相似文献   

12.
Recent discoveries of fossil vertebrates from the Late Cretaceous of Madagascar include several specimens of a large theropod dinosaur. One specimen includes a nearly complete and exquisitely preserved skull with thickened pneumatic nasals, a median frontal horn, and a dorsal projection on the parietals. The new materials are assigned to the enigmatic theropod group Abelisauridae on the basis of a number of unique features. Fossil remains attributable to abelisaurids are restricted to three Gondwanan landmasses: South America, Madagascar, and the Indian subcontinent. This distribution is consistent with a revised paleogeographic reconstruction that posits prolonged links between these landmasses (via Antarctica), perhaps until late in the Late Cretaceous.  相似文献   

13.
Here at the "Body Farm," a research plot where human corpses are studied as they decompose, the corpses are teaching scientists much about how to reconstruct the manner and circumstances of unexplained deaths. In fact, new techniques developed at the site, officially known as the University of Tennessee, Knoxville's, Anthropological Research Facility, are already beginning to land criminals behind bars.  相似文献   

14.
The fossil evidence for the early evolution of vertebrates consists of the remains of agnathans, jawless vertebrates, from the Ordovician of Australia, North America, and Bolivia. Because of the fragmentary nature of the material, it has not been possible to reconstruct these animals sufficiently well to understand their relation to each other and to later vertebrates. Though two genera have been known from the Harding Sandstone of North America since 1892, there are still only three articulated specimens known, two of Astraspis desiderata and one of Eriptychius americanus. The most recently found specimen of Astraspis was reexamined and found to show the orbit, a series of eight branchial openings and a complete tail, structures hitherto undescribed in any Ordovician vertebrate. A reconstruction ofAstraspis shows, on the basis of the series of branchial openings, that it is a primitive craniate and not a heterostracan as previously thought.  相似文献   

15.
The maximum length of 36.5 feet (11.1 meters) attributed to the white shark (Carcharodon carcharias) by Günther and others is a mistake. Examination of the jaws and teeth of the specimen referred to by Günther and comparison with the jaws of white sharks of known length revealed a length of about 17 feet ( approximately 5 meters). The largest white shark reliably measured was a 21-foot (6.4-meter) individual from Cuba. Bites on whale carcasses found off southern Australia suggest that white sharks as long as 25 or 26 feet (7 (1/2) or 8 meters) exist today. The size of extinct Carcharodon has also been grossly exaggerated. Based on a projection of a curve of tooth size of Recent Carcharodon carcharias, the largest fossil Carcharodon were about 43 feet ( approximately 13 meters) long.  相似文献   

16.
A 95-million-year-old fossil snake from the Middle East documents the most extreme hindlimb development of any known member of that group, as it preserves the tibia, fibula, tarsals, metatarsals, and phalanges. It is more complete than Pachyrhachis, a second fossil snake with hindlimbs that was recently portrayed to be basal to all other snakes. Phylogenetic analysis of the relationships of the new taxon, as well as reanalysis of Pachyrhachis, shows both to be related to macrostomatans, a group that includes relatively advanced snakes such as pythons, boas, and colubroids to the exclusion of more primitive snakes such as blindsnakes and pipesnakes.  相似文献   

17.
Luo ZX  Ji Q  Wible JR  Yuan CX 《Science (New York, N.Y.)》2003,302(5652):1934-1940
Derived features of a new boreosphenidan mammal from the Lower Cretaceous Yixian Formation of China suggest that it has a closer relationship to metatherians (including extant marsupials) than to eutherians (including extant placentals). This fossil dates to 125 million years ago and extends the record of marsupial relatives with skeletal remains by 50 million years. It also has many foot structures known only from climbing and tree-living extant mammals, suggesting that early crown therians exploited diverse niches. New data from this fossil support the view that Asia was likely the center for the diversification of the earliest metatherians and eutherians during the Early Cretaceous.  相似文献   

18.
Service RF 《Science (New York, N.Y.)》2000,288(5473):1955-1957
After decades of incremental advances, a spurt of findings suggests that fuel cells that run on good old fossil fuels are almost ready for prime time. Although conventional ceramic cells, known as solid oxide fuel cells, require expensive heat-resistant materials, a new generation of SOFCs, including one featured on page 2031, converts hydrocarbons directly into electricity at lower temperatures. And a recent demonstration of a system of standard SOFCs large enough to light up more than 200 homes showed that it is the most efficient large-scale electrical generator ever designed.  相似文献   

19.
The UNISOR cooperative project, envisioned more than 3 years ago, is now successfully working. Research problems that involve a full range of experiments on nuclei far from beta stability are being investigated jointly by groups of scientists from several institutions. Some of the first work reported (16) included the identification, half-lives, and decay schemes of three new isotopes, (186)T1, (188)T1, and (116)I; the first or new decay schemes of (189)T1, (190)T1, (117)Xe, and (117)I; and the results of the perturbed gamma-gamma directional correlation work in (126)Xe. UNISOR is already stimulating international interest. A report (1) on the new research being planned with an isotope separator on-line to ORIC was presented at a Soviet Academy of Sciences meeting on nuclear structure in 1971. At an international nuclear physics conference in Munich in August 1973, Academician G. N. Flerov, director of the heavy-ion laboratory in Dubna, said the UNISOR project had inspired his laboratory to secure funds for a new, much improved isotope separator which is now installed on-line to their heavy-ion cyclotron to be used for detailed studies of nuclei far from stability. The UNISOR model for research has inspired a second such project, the Atomic Physics Consortium at Oak Ridge (APCOR). After an exploratory conference at Oak Ridge, scientists from ten institutions met in November 1973 to form an organizing committee for APCOR. As with UNISOR, the universities and the AEC will each provide a significant portion of the capital and operating costs. Heavy ions have opened up much new research in atomic physics, but such accelerator-based research represents a real "shift from traditional approaches concerning how, where, and on what time scale atomic physics experiments should be done" (17).  相似文献   

20.
Amato I 《Science (New York, N.Y.)》1993,261(5127):1388-1389
Two times each year, legions of chemists gather in North America for a massive meeting to discuss the state of the art in their science. The second of this year's get-togethers occurred 2 weeks ago, when the 206th national meeting of the American Chemical Society (ACS) drew about 13,000 chemists, scientists, and onlookers to Chicago. Researchers shared 4800 or so papers and posters on everything from making waste plastic into fuel oil to the chemical basis for the stench of ginkgo fruit to modeling the first instants of photosynthesis.  相似文献   

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