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191.
Tsukuba Science City is Japan's new municipal complex of research laboratories and educational facilities. About 30 percent of the nation's government research laboratories and more than 40 percent of its government research manpower are concentrated in the community. A brief history of the monumental project is presented and problems confronting the city are discussed. 相似文献
192.
S E Bloom 《Science (New York, N.Y.)》1970,170(956):457-458
The first known cases of trisomy-3, trisomy-4, and triploidy (3A-ZZZW) in chickens are reported. The trisomic embryos were near death at 4 days of incubation; the triploid embryo appeared normal and probably could have developed further. Although the triploid (3A-ZZZW) was found after sampling more than 2000 embryos, the trisomic-3 and trisomic-4 embryos were discovered in the first sampling of a line of chickens selected for low egg production. These studies suggest that the sex chromosomes (Z and W), as well as the autosomes, can undergo nondisjunction in meiosis of chickens. 相似文献
193.
Bloom JS Giannios D Metzger BD Cenko SB Perley DA Butler NR Tanvir NR Levan AJ O'Brien PT Strubbe LE De Colle F Ramirez-Ruiz E Lee WH Nayakshin S Quataert E King AR Cucchiara A Guillochon J Bower GC Fruchter AS Morgan AN van der Horst AJ 《Science (New York, N.Y.)》2011,333(6039):203-206
Gas accretion onto some massive black holes (MBHs) at the centers of galaxies actively powers luminous emission, but most MBHs are considered dormant. Occasionally, a star passing too near an MBH is torn apart by gravitational forces, leading to a bright tidal disruption flare (TDF). Although the high-energy transient Sw 1644+57 initially displayed none of the theoretically anticipated (nor previously observed) TDF characteristics, we show that observations suggest a sudden accretion event onto a central MBH of mass about 10(6) to 10(7) solar masses. There is evidence for a mildly relativistic outflow, jet collimation, and a spectrum characterized by synchrotron and inverse Compton processes; this leads to a natural analogy of Sw 1644+57 to a temporary smaller-scale blazar. 相似文献
194.
Cyclic adenosine monophosphate: possible mediator for norepinephrine effects on cerebellar Purkinje cells 总被引:8,自引:0,他引:8
Microelectrophoretic application of norepinephrine or cyclic adenosine monophosphate reduces the discharge frequency of Purkinje cells in the rat cerebellum. In contrast, other nucleotides accelerate the discharge rate of most units. Parenterally administered theophylline, which inhibits the hydrolysis of cyclic adenosine monophosphate enhances the effects of norepinephrine and cyclic adenosine monophosphate. Therefore, norepinephrine may be able to regulate Purkinje cells functionally by metabolic stimulation of cyclic adenosine monophosphate synthesis. 相似文献
195.
Lesions of central norepinephrine terminals with 6-OH-dopamine: biochemistry and fine structure 总被引:8,自引:0,他引:8
Intracisternal injections of 6-hydroxydopamine produce rapid and long-lasting depletion of brain catecholamines without effects on serotonin concentrations. Depletion of norepinephrine is greatest in areas containing only nerve terminals and axons and least in areas containing monoamine cell bodies. The norepinephrine loss is accompanied by electron microscopic evidence of nerve terminal degeneration and decreased turnover. Dopamine loss is less marked and is not accompanied by degeneration or alteration of turnover rate. 相似文献
196.
Abdo AA Ackermann M Ajello M Allafort A Baldini L Ballet J Barbiellini G Bastieri D Bechtol K Bellazzini R Berenji B Blandford RD Bloom ED Bonamente E Borgland AW Bouvier A Brandt TJ Bregeon J Brez A Brigida M Bruel P Buehler R Buson S Caliandro GA Cameron RA Cannon A Caraveo PA Casandjian JM Çelik Ö Charles E Chekhtman A Cheung CC Chiang J Ciprini S Claus R Cohen-Tanugi J Costamante L Cutini S D'Ammando F Dermer CD de Angelis A de Luca A de Palma F Digel SW do Couto e Silva E Drell PS 《Science (New York, N.Y.)》2011,331(6018):739-742
A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10(15) electron volts) electrons in a region smaller than 1.4 × 10(-2) parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory. 相似文献
197.
A preliminary investigation comparing pre-operative morphine and buprenorphine for postoperative analgesia and sedation in cats 总被引:1,自引:1,他引:1
GW Stanway BVSC Cert VA PM Taylor MA Vet MB PhD DVA Dip ECVA & DC Brodbelt† MA Vet MB DVA Dip ECVA MRCVS 《Veterinary anaesthesia and analgesia》2002,29(1):29-35
Objective To compare the postoperative analgesic and sedative properties of buprenorphine and morphine in cats. Study Design Prospective, randomized, blinded study. Animals Thirty‐two domestic cats undergoing surgery. Methods Cats received pre‐anaesthetic medication with acepromazine (0.05 mg kg?1) given intramuscularly and were randomly allocated to group M and given morphine (0.1 mg kg?1) intramuscularly (IM) or to group B and given buprenorphine (0.01 mg kg?1) IM. Anaesthesia was induced with propofol and maintained with halothane in oxygen and nitrous oxide. Pain and sedation scores using visual analogue scales, and heart and respiratory rates, were measured immediately before, and 30, 60, 120, 180, 300 and 420 minutes after anaesthesia. Results Pain scores were significantly lower at 60, 120 and 180 minutes after anaesthesia in group B. Group B also had higher heart rates at 30 minutes. There were no other statistically significant differences between the groups. Clinical relevance Buprenorphine (0.01 mg kg?1) appeared to provide better postoperative analgesia than morphine (0.1 mg kg?1) and may also have a longer duration of action. 相似文献