Benjamin Franklin and Timothy Folger's First Printed Chart of the Gulf Stream     

Richardson PL 《Science (New York, N.Y.)》1980,207(4431):643-645

A print of the Benjamin Franklin and Timothy Folger 1769-1770 chart of the Gulf Stream, all copies of which have been "lost" for nearly 200 years, was found in the Bibliothèque Nationale in Paris. This is the first chart of the Gulf Stream and continues today to be a good summary of its strength, course, and breadth.  相似文献   

Larvae retention: genes or oceanography?     

Colin PL 《Science (New York, N.Y.)》2003,300(5626):1657-9; author reply 1657-9

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Positional syntenic cloning and functional characterization of the mammalian circadian mutation tau     

Lowrey PL  Shimomura K  Antoch MP  Yamazaki S  Zemenides PD  Ralph MR  Menaker M  Takahashi JS 《Science (New York, N.Y.)》2000,288(5465):483-492

The tau mutation is a semidominant autosomal allele that dramatically shortens period length of circadian rhythms in Syrian hamsters. We report the molecular identification of the tau locus using genetically directed representational difference analysis to define a region of conserved synteny in hamsters with both the mouse and human genomes. The tau locus is encoded by casein kinase I epsilon (CKIepsilon), a homolog of the Drosophila circadian gene double-time. In vitro expression and functional studies of wild-type and tau mutant CKIepsilon enzyme reveal that the mutant enzyme has a markedly reduced maximal velocity and autophosphorylation state. In addition, in vitro CKIepsilon can interact with mammalian PERIOD proteins, and the mutant enzyme is deficient in its ability to phosphorylate PERIOD. We conclude that tau is an allele of hamster CKIepsilon and propose a mechanism by which the mutation leads to the observed aberrant circadian phenotype in mutant animals.  相似文献   

FURTHER STUDIES ON THE RELATIONSHIP BETWEEN XANTHOPTERIN,FOLIC ACID AND VITAMIN M     

Totter JR  Mims V  Day PL 《Science (New York, N.Y.)》1944,100(2593):223-225

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HST and VLT investigations of the fragments of comet C/1999 S4 (LINEAR)     

Weaver HA  Sekanina Z  Toth I  Delahodde CE  Hainaut OR  Lamy PL  Bauer JM  A'Hearn MF  Arpigny C  Combi MR  Davies JK  Feldman PD  Festou MC  Hook R  Jorda L  Keesey MS  Lisse CM  Marsden BG  Meech KJ  Tozzi GP  West R 《Science (New York, N.Y.)》2001,292(5520):1329-1333

At least 16 fragments were detected in images of comet C/1999 S4 (LINEAR) taken on 5 August 2000 with the Hubble Space Telescope (HST) and on 6 August with the Very Large Telescope (VLT). Photometric analysis of the fragments indicates that the largest ones have effective spherical diameters of about 100 meters, which implies that the total mass in the observed fragments was about 2 x 10(9) kilograms. The comet's dust tail, which was the most prominent optical feature in August, was produced during a major fragmentation event, whose activity peaked on UT 22.8 +/- 0.2 July 2000. The mass of small particles (diameters less than about 230 micrometers) in the tail was about 4 x 10(8) kilograms, which is comparable to the mass contained in a large fragment and to the total mass lost from water sublimation after 21 July 2000 (about 3 x 10(8) kilograms). HST spectroscopic observations during 5 and 6 July 2000 demonstrate that the nucleus contained little carbon monoxide ice (ratio of carbon monoxide to water is less than or equal to 0.4%), which suggests that this volatile species did not play a role in the fragmentation of C/1999 S4 (LINEAR).  相似文献   

The structure of ferrihydrite, a nanocrystalline material   总被引：2，自引：0，他引：2  

Michel FM  Ehm L  Antao SM  Lee PL  Chupas PJ  Liu G  Strongin DR  Schoonen MA  Phillips BL  Parise JB 《Science (New York, N.Y.)》2007,316(5832):1726-1729

Despite the ubiquity of ferrihydrite in natural sediments and its importance as an industrial sorbent, the nanocrystallinity of this iron oxyhydroxide has hampered accurate structure determination by traditional methods that rely on long-range order. We uncovered the atomic arrangement by real-space modeling of the pair distribution function (PDF) derived from direct Fourier transformation of the total x-ray scattering. The PDF for ferrihydrite synthesized with the use of different routes is consistent with a single phase (hexagonal space group P6(3)mc; a = approximately 5.95 angstroms, c = approximately 9.06 angstroms). In its ideal form, this structure contains 20% tetrahedrally and 80% octahedrally coordinated iron and has a basic structural motif closely related to the Baker-Figgis delta-Keggin cluster. Real-space fitting indicates structural relaxation with decreasing particle size and also suggests that second-order effects such as internal strain, stacking faults, and particle shape contribute to the PDFs.  相似文献   

The Lunar Laser Ranging Experiment: Accurate ranges have given a large improvement in the lunar orbit and new selenophysical information     

Bender PL  Currie DG  Poultney SK  Alley CO  Dicke RH  Wilkinson DT  Eckhardt DH  Faller JE  Kaula WM  Mulholland JD  Plotkin HH  Silverberg EC  Williams JG 《Science (New York, N.Y.)》1973,182(4109):229-238

The lunar ranging measurements now being made at the McDonald Observatory have an accuracy of 1 nsec in round-trip travel time. This corresponds to 15 cm in the one-way distance. The use of lasers with pulse-lengths of less than 1 nsec is expected to give an accuracy of 2 to 3 cm in the next few years. A new station is under construction in Hawaii, and additional stations in other countries are either in operation or under development. It is hoped that these stations will form the basis for a worldwide network to determine polar motion and earth rotation on a regular basis, and will assist in providing information about movement of the tectonic plates making up the earth's surface. Several mobile lunar ranging stations with telescopes having diameters of 1.0 m or less could, in the future, greatly extend the information obtainable about motions within and between the tectonic plates. The data obtained so far by the McDonald Observatory have been used to generate a new lunar ephemeris based on direct numerical integration of the equations of motion for the moon and planets. With this ephemeris, the range to the three Apollo retro-reflectors can be fit to an accuracy of 5 m by adjusting the differences in moments of inertia of the moon about its principal axes, the selenocentric coordinates of the reflectors, and the McDonald longitude. The accuracy of fitting the results is limited currently by errors of the order of an arc second in the angular orientation of the moon, as derived from the best available theory of how the moon rotates in response to the torques acting on it. Both a new calculation of the moon's orientation as a function of time based on direct numerical integration of the torque equations and a new analytic theory of the moon's orientation are expected to be available soon, and to improve considerably the accuracy of fitting the data. The accuracy already achieved routinely in lunar laser ranging represents a hundredfold improvement over any previously available knowledge of the distance to points on the lunar surface. Already, extremely complex structure has been observed in the lunar rotation and significant improvement has been achieved in our knowledge of lunar orbit. The selenocentric coordinates of the retroreflectors give improved reference points for use in lunar mapping, and new information on the lunar mass distribution has been obtained. Beyond the applications discussed in this article, however, the history of science shows many cases of previously unknown, phenomena discovered as a consequence of major improvements in the accuracy of measurements. It will be interesting to see whether this once again proves the case as we acquire an extended series of lunar distance observations with decimetric and then centimetric accuracy.  相似文献   

Sounding the stratosphere and mesosphere by infrared limb scanning from space   总被引：1，自引：0，他引：1  

Gille JC  Bailey PL  Craig RA  House FB  Anderson GP 《Science (New York, N.Y.)》1980,208(4442):397-399

Inversion of the measurements obtained by the infrared limb scanner on the Nimbus 6 satellite has demonstrated that the stratospheric and mesospheric temperatures and ozone concentrations may be obtained remotely from space with accuracy and precision comparable to in situ methods. Such global data have many applications in middle atmospheric research and operational temperature sounding.  相似文献   

TELANG LIVER AND VITAMIN A TOXICITY     

Herbst EJ  Pavcek PL  Elvehjem CA 《Science (New York, N.Y.)》1944,100(2598):338-339

(1) About 20 per cent. of fresh telang livers were toxic to weanling rats receiving the calcium supplemented livers as their sole dietary. (2) The symptoms observed in rats were growth failure and multiple spontaneous fractures of the bones of the extremities. (3) The toxicity of certain telang livers was due to their abnormally high stores of vitamin A. When these livers, supplemented only with calcium carbonate, were fed to weanling rats, the daily intake of vitamin A was in excess of the toxic dosage of 15,000 I.U. per day. (4) Identical symptoms of toxicity were observed in weanling rats fed 20,000 I.U. of crystalline vitamin A per day in conjunction with a standard stock ration.  相似文献   

Temperatures, winds, and composition in the saturnian system     

Flasar FM  Achterberg RK  Conrath BJ  Pearl JC  Bjoraker GL  Jennings DE  Romani PN  Simon-Miller AA  Kunde VG  Nixon CA  Bézard B  Orton GS  Spilker LJ  Spencer JR  Irwin PG  Teanby NA  Owen TC  Brasunas J  Segura ME  Carlson RC  Mamoutkine A  Gierasch PJ  Schinder PJ  Showalter MR  Ferrari C  Barucci A  Courtin R  Coustenis A  Fouchet T  Gautier D  Lellouch E  Marten A  Prangé R  Strobel DF  Calcutt SB  Read PL  Taylor FW  Bowles N  Samuelson RE  Abbas MM  Raulin F  Ade P  Edgington S  Pilorz S  Wallis B  Wishnow EH 《Science (New York, N.Y.)》2005,307(5713):1247-1251

Stratospheric temperatures on Saturn imply a strong decay of the equatorial winds with altitude. If the decrease in winds reported from recent Hubble Space Telescope images is not a temporal change, then the features tracked must have been at least 130 kilometers higher than in earlier studies. Saturn's south polar stratosphere is warmer than predicted from simple radiative models. The C/H ratio on Saturn is seven times solar, twice Jupiter's. Saturn's ring temperatures have radial variations down to the smallest scale resolved (100 kilometers). Diurnal surface temperature variations on Phoebe suggest a more porous regolith than on the jovian satellites.  相似文献