Strategic success for hydropower in Laos     

Guerrier G  Paul R  Sananikhom P  Kaul S  Luthi R  Katz JP  Robino M  Khammanithong P  Brey PT 《Science (New York, N.Y.)》2011,334(6052):38

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The rise of oxygen over the past 205 million years and the evolution of large placental mammals   总被引：2，自引：0，他引：2  

Falkowski PG  Katz ME  Milligan AJ  Fennel K  Cramer BS  Aubry MP  Berner RA  Novacek MJ  Zapol WM 《Science (New York, N.Y.)》2005,309(5744):2202-2204

On the basis of a carbon isotopic record of both marine carbonates and organic matter from the Triassic-Jurassic boundary to the present, we modeled oxygen concentrations over the past 205 million years. Our analysis indicates that atmospheric oxygen approximately doubled over this period, with relatively rapid increases in the early Jurassic and the Eocene. We suggest that the overall increase in oxygen, mediated by the formation of passive continental margins along the Atlantic Ocean during the opening phase of the current Wilson cycle, was a critical factor in the evolution, radiation, and subsequent increase in average size of placental mammals.  相似文献   

Broadband modulation of light by using an electro-optic polymer     

Lee M  Katz HE  Erben C  Gill DM  Gopalan P  Heber JD  McGee DJ 《Science (New York, N.Y.)》2002,298(5597):1401-1403

A major challenge to increasing bandwidth in optical telecommunications is to encode electronic signals onto a lightwave carrier by modulating the light up to very fast rates. Polymer electro-optic materials have the necessary properties to function in photonic devices beyond the 40-GHz bandwidth currently available. An appropriate choice of polymers is shown to effectively eliminate the factors contributing to an optical modulator's decay in the high-frequency response. The resulting device modulates light with a bandwidth of 150 to 200 GHz and produces detectable modulation signal at 1.6 THz. These rates are faster than anticipated bandwidth requirements for the foreseeable future.  相似文献   

Clear-air turbulence: simultaneous observations by radar and aircraft     

Hicks JJ  Katz I  Landry CR  Hardy KR 《Science (New York, N.Y.)》1967,157(3790):808-809

Ultrasensitive radars and uninstrumented jet aircraft in concert have probed regions of the clear atmosphere in search of clear-air turbulence. All sources of clear-air radar echoes above 6 kilometers that were probed simultaneously by the aircraft were found to be turbulent.  相似文献   

Photoinduced nucleation of water vapor     

Wen FC  McLaughlin T  Katz JL 《Science (New York, N.Y.)》1978,200(4343):769-771

Strong photoinduced nucleation of pure water vapor was found to occur in a wavelength range where no ultraviolet absorption of water vapor has been reported. Systematic studies were made of the dependence of the nucleation rate and the delay time for the initiation of nucleation on light intensity. The results obtained were accurately fitted by a phenomenological mechanism whereby the nucleation is initiated by clusters accumulating an appropriate number of photoexcited water molecules.  相似文献   

Characterization of the reconstructed 1918 Spanish influenza pandemic virus     

Tumpey TM  Basler CF  Aguilar PV  Zeng H  Solórzano A  Swayne DE  Cox NJ  Katz JM  Taubenberger JK  Palese P  García-Sastre A 《Science (New York, N.Y.)》2005,310(5745):77-80

The pandemic influenza virus of 1918-1919 killed an estimated 20 to 50 million people worldwide. With the recent availability of the complete 1918 influenza virus coding sequence, we used reverse genetics to generate an influenza virus bearing all eight gene segments of the pandemic virus to study the properties associated with its extraordinary virulence. In stark contrast to contemporary human influenza H1N1 viruses, the 1918 pandemic virus had the ability to replicate in the absence of trypsin, caused death in mice and embryonated chicken eggs, and displayed a high-growth phenotype in human bronchial epithelial cells. Moreover, the coordinated expression of the 1918 virus genes most certainly confers the unique high-virulence phenotype observed with this pandemic virus.  相似文献   

Comparison of Single and Sequential Extraction Procedures for Assessing Metal Leaching from Dredged Coastal Sediments     

Agnes šÖmen Joksič  Sidney A. Katz  Milena Horvat  Radmila Milačič 《Water, air, and soil pollution》2005,162(1-4):265-283

Potential uses of dredged sediments have raised questions about leaching of contaminants from such material once transported to other locations and exposed to other environments. In order to estimate leachable, i.e. available fractions of chemical elements in such materials, a number of analytical protocols were proposed, of which none is internationally accepted as a standard procedure. As a consequence, comparability of the results obtained by different protocols in various laboratories is difficult to demonstrate. In the present study some commonly used protocols including a leaching test with (i) seawater, following the modified German Standard Method (DIN), (ii) a single extraction with 25% acetic acid, following the method proposed by the United Nations Environment Programme (UNEP), and (iii) a three-step sequential extraction, following both the original and the modified protocols of the Standards, Measurements and Testing Programme (formerly Community Bureau of Reference – BCR), were performed for assessing the availability of lead, zinc, nickel and copper leachable from dredged marine sediments. A comparison of the results obtained by the different protocols indicated that the single extraction with acetic acid is a reliable simplified technique and allows more rapid evaluations of dredged areas of coastal lagoons in the Northern Adriatic. This procedure provides information on the potentially bioavailable portion of metals.  相似文献   

A cost comparison of more and less nutritious food choices in US supermarkets     

Katz DL  Doughty K  Njike V  Treu JA  Reynolds J  Walker J  Smith E  Katz C 《Public health nutrition》2011,14(9):1693-1699

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In vivo and in vitro genetic recombination between conventional and gene-deleted vaccine strains of pseudorabies virus   总被引：7，自引：0，他引：7  

L M Henderson  J B Katz  G A Erickson  J E Mayfield 《American journal of veterinary research》1990,51(10):1656-1662

Pseudorabies virus (PRV), an alpha-herpesvirus, causes substantial economic losses in the swine industry and is currently the focus of eradication and control programs. Some of these programs rely on the ability of veterinarians to differentiate animals exposed to virulent strains of PRV from animals exposed to avirulent vaccine strains of PRV on the basis of a serologic response to nonessential glycoproteins that are deleted in some vaccine strains of PRV. Genetic recombination resulting in the creation of virulent strains of PRV with the same negative immunologic markers as vaccine strains could disrupt these programs. Two strains of PRV were coinoculated either into tissue culture or into sheep to facilitate recombination. Progeny viruses were selected to detect a specific recombinant phenotype. We were able to detect genetic recombination between vaccine strains of PRV following in vitro or in vivo coinoculation of 2 strains of PRV. The selected recombinants had marker-deleted phenotypes in strains with restored virulence genes. Increased virulence was observed in sheep after coinoculation of 2 avirulent vaccine strains of PRV.  相似文献   

Endocrine systems and behavior     

L S Katz 《Veterinary Clinics of North America: Food Animal Practice》1987,3(2):393-404

Estradiol, either directly from the ovary of females or as a metabolite of testosterone from the testes of males, seems to be the necessary and probably sufficient endocrine signal for sexual differentiation and adult sexual expression. Progesterone, in females, may play an important priming or facilitative role prior to estrus, especially following pregnancy, when blood estrogen levels are high for a prolonged period. At high doses, progesterone clearly inhibits the expression of sexual behavior.  相似文献