Adaptive phenotypic plasticity in response to climate change in a wild bird population     

Charmantier A  McCleery RH  Cole LR  Perrins C  Kruuk LE  Sheldon BC 《Science (New York, N.Y.)》2008,320(5877):800-803

Rapid climate change has been implicated as a cause of evolution in poorly adapted populations. However, phenotypic plasticity provides the potential for organisms to respond rapidly and effectively to environmental change. Using a 47-year population study of the great tit (Parus major) in the United Kingdom, we show that individual adjustment of behavior in response to the environment has enabled the population to track a rapidly changing environment very closely. Individuals were markedly invariant in their response to environmental variation, suggesting that the current response may be fixed in this population. Phenotypic plasticity can thus play a central role in tracking environmental change; understanding the limits of plasticity is an important goal for future research.  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   

Venus thermosphere and exosphere: first satellite drag measurements of an extraterrestrial atmosphere     

Keating GM  Tolson RH  Hinson EW 《Science (New York, N.Y.)》1979,203(4382):772-774

Atmospheric drag measurements obtained from the study of the orbital decay of Pioneer Venus 1 indicate that atomic oxygen predominates in the Venus atmosphere above 160 kilometers. Drag measurements give evidence that conditions characteristic of a planetary thermosphere disappear near sundown, with inferred exospheric temperatures sharply dropping from approximately 300 K to less than 150 K. Observed denisities are generally lower than given by theoretical models.  相似文献   

氮,磷,钾施用量对木薯产量的影响   总被引：6，自引：0，他引：6  

房伯平 Howe.  RH 《广东农业科学》1994,(1):28-30

氮，磷，钾定位施肥对木薯产量影响的研究表明，当磷，钾肥用量不变时，增施氮肥可以显著地提高木薯产量，品种及作对施氮的效应不大；氮，钾用量不变时，增施磷显著的产量效应，但品种及连作对磷的效应也有显著的影响，而氮，磷用量不变时，增施钾肥可以显著提高木薯产量，品种对施钾效应无影响，但年份间的变幅较大。  相似文献   

Empirical Explorations of SYNCHEM     

Gelernter HL  Sanders AF  Larsen DL  Agarwal KK  Boivie RH  Spritzer GA  Searleman JE 《Science (New York, N.Y.)》1977,197(4308):1041-1049

During the past several years, a substantial body of experience has accumulated in the use of SYNCHEM, a large-scale program which is able to discover synthesis routes for relatively complex organic structures without on-line guidance on the part of its chemist user. These results indicate that the approach to computer-directed organic synthesis route discovery embodied in the program has been valid and reasonable, and that SYNCHEM is likely to be fruitful from the point of view of its intended users as well as for our research objectives in artificial intelligence. The experiments have revealed a number of insufficiencies in the program as well. Most of these are rectified in SYNCHEM2, a revised version of the program which includes, among other improvements, a more highly developed synthesis search algorithm and the routine consideration of stereochemistry.  相似文献   

Triton's Global Heat Budget     

Brown RH  Johnson TV  Goguen JD  Schubert G  Ross MN 《Science (New York, N.Y.)》1991,251(5000):1465-1467

Internal heat flow from radioactive decay in Triton's interior along with absorbed thermal energy from Neptune total 5 to 20 percent of the insolation absorbed by Triton, thus comprising a significant fraction of Triton's surface energy balance. These additional energy inputs can raise Triton's surface temperature between approximately 0.5 and 1.5 K above that possible with absorbed sunlight alone, resulting in an increase of about a factor of approximately 1.5 to 2.5 in Triton's basal atmospheric pressure. If Triton's internal heat flow is concentrated in some areas, as is likely, local effects such as enhanced sublimation with subsequent modification of albedo could be quite large. Furthermore, indications of recent global albedo change on Triton suggest that Triton's surface temperature and pressure may not now be in steady state, further suggesting that atmospheric pressure on Triton was as much as ten times higher in the recent past.  相似文献   

Triton's Geyser-Like Plumes: Discovery and Basic Characterization     

Soderblom LA  Kieffer SW  Becker TL  Brown RH  Cook AF  Hansen CJ  Johnson TV  Kirk RL  Shoemaker EM 《Science (New York, N.Y.)》1990,250(4979):410-415

At least four active geyser-like eruptions were discovered in Voyager 2 images of Triton, Neptune's large satellite. The two best documented eruptions occur as columns of dark material rising to an altitude of about 8 kilometers where dark clouds of material are left suspended to drift downwind over 100 kilometers. The radii of the rising columns appear to be in the range of several tens of meters to a kilometer. One model for the mechanism to drive the plumes involves heating of nitrogen ice in a subsurface greenhouse environment; nitrogen gas pressurized by the solar heating explosively vents to the surface carrying clouds of ice and dark partides into the atmosphere. A temperature increase of less than 4 kelvins above the ambient surface value of 38 +/- 3 kelvins is more than adequate to drive the plumes to an 8-kilometer altitude. The mass flux in the trailing clouds is estimated to consist of up to 10 kilograms of fine dark particles per second or twice as much nitrogen ice and perhaps several hundred or more kilograms of nitrogen gas per second. Each eruption may last a year or more, during which on the order of a tenth of a cubic kilometer of ice is sublimed.  相似文献   

Comparison of calculated and measured ion densities on the dayside of venus     

Nagy AF  Cravens TE  Chen RH  Taylor HA  Brace LH  Brinton HC 《Science (New York, N.Y.)》1979,205(4401):107-109

Datafrom the Pioneer Venus ion mass spectrometers are compared with model calculations of the ion density distributions appropriate for daytime conditions. The model assumes diffusive equilibrium upper boundary conditions for the major ions (O(2)(+), O(+), CO(2)(+), He(+), and H(+)); the agreement between the calculated and measured gross behavior of these ions is reasonably good except for H(+), which may be influenced strongly by convective transport processes. The distributions of five minor ions (C(+), N(+), NO(+), CO(+), and N(2)(+)) are also calculated for the chemically controlled region ( less, similar 200 kilometers); the agreements are, in general, poor, an indication that our present understanding of the Venus minor ion chemistry is still incomplete.  相似文献   

Attenuation of low-frequency sound in freshwater     

Browning DG  Jones EN  Mellen RH  Thorp WH 《Science (New York, N.Y.)》1968,162(3858):1120-1121

Lake Superior was chosen as an experimental site to compare sound absorption of freshwater with the results of absorption measurements in seawater. The relaxation-like absorption at 1 kilohertz occurring in seawater is also present in freshwater. A relaxation related to the structural characteristics rather than to the salt content of water may be responsible for the anomalous absorption.  相似文献   

Psychological Brightness Reduction of Simulated Flashes from a Polyhedral Satellite     

Wilson RH 《Science (New York, N.Y.)》1958,128(3331):1086-1087

  相似文献