Flight of Winter Moths Near 0{degrees}C     

Heinrich B  Mommsen TP 《Science (New York, N.Y.)》1985,228(4696):177-179

Some noctuid winter moths fly at near 0 degrees C by maintaining an elevated(30 degrees to 35 degrees C) thoracic muscle temperature. Geometrid winter moths sustain themselves in free flight at subzero muscle temperatures. However, the temperature characteristics of citrate synthase and pyruvate kinase from both of these different kinds of moths and from a sphinx moth that flies with a muscles temperature of 40 degrees C are nearly identical. Furthermore, mass-specific rates of energy expenditure of both kinds of winter moths are also similar at given thoracic temperature (near 0 degrees C). The geometrids that are able to fly with a thoracic temperature near 0 degrees C do so largely because of unusually low wing-loading, which permits a low energetic cost of flight.  相似文献   

Materials science. Through thick and thin     

Brown E  Jaeger HM 《Science (New York, N.Y.)》2011,333(6047):1230-1231

  相似文献   

Molecule cascades     

Heinrich AJ  Lutz CP  Gupta JA  Eigler DM 《Science (New York, N.Y.)》2002,298(5597):1381-1387

Carbon monoxide molecules were arranged in atomically precise configurations, which we call "molecule cascades," where the motion of one molecule causes the subsequent motion of another, and so on in a cascade of motion similar to a row of toppling dominoes. Isotopically pure cascades were assembled on a copper (111) surface with a low-temperature scanning tunneling microscope. The hopping rate of carbon monoxide molecules in cascades was found to be independent of temperature below 6 kelvin and to exhibit a pronounced isotope effect, hallmarks of a quantum tunneling process. At higher temperatures, we observed a thermally activated hopping rate with an anomalously low Arrhenius prefactor that we interpret as tunneling from excited vibrational states. We present a cascade-based computation scheme that has all of the devices and interconnects required for the one-time computation of an arbitrary logic function. Logic gates and other devices were implemented by engineered arrangements of molecules at the intersections of cascades. We demonstrate a three-input sorter that uses several AND gates and OR gates, as well as the crossover and fan-out units needed to connect them.  相似文献   

The Selaginella genome identifies genetic changes associated with the evolution of vascular plants     

Banks JA  Nishiyama T  Hasebe M  Bowman JL  Gribskov M  dePamphilis C  Albert VA  Aono N  Aoyama T  Ambrose BA  Ashton NW  Axtell MJ  Barker E  Barker MS  Bennetzen JL  Bonawitz ND  Chapple C  Cheng C  Correa LG  Dacre M  DeBarry J  Dreyer I  Elias M  Engstrom EM  Estelle M  Feng L  Finet C  Floyd SK  Frommer WB  Fujita T  Gramzow L  Gutensohn M  Harholt J  Hattori M  Heyl A  Hirai T  Hiwatashi Y  Ishikawa M  Iwata M  Karol KG  Koehler B  Kolukisaoglu U  Kubo M  Kurata T  Lalonde S  Li K  Li Y  Litt A  Lyons E  Manning G  Maruyama T  Michael TP 《Science (New York, N.Y.)》2011,332(6032):960-963

  相似文献   

The force needed to move an atom on a surface     

Ternes M  Lutz CP  Hirjibehedin CF  Giessibl FJ  Heinrich AJ 《Science (New York, N.Y.)》2008,319(5866):1066-1069

Manipulation of individual atoms and molecules by scanning probe microscopy offers the ability of controlled assembly at the single-atom scale. However, the driving forces behind atomic manipulation have not yet been measured. We used an atomic force microscope to measure the vertical and lateral forces exerted on individual adsorbed atoms or molecules by the probe tip. We found that the force that it takes to move an atom depends strongly on the adsorbate and the surface. Our results indicate that for moving metal atoms on metal surfaces, the lateral force component plays the dominant role. Furthermore, measuring spatial maps of the forces during manipulation yielded the full potential energy landscape of the tip-sample interaction.  相似文献   

Application of stable carbon isotope analysis to the detection of testosterone administration to cattle     

Hebestreit M  Flenker U  Buisson C  Andre F  Le Bizec B  Fry H  Lang M  Weigert AP  Heinrich K  Hird S  Schänzer W 《Journal of agricultural and food chemistry》2006,54(8):2850-2858

The use of anabolic substances is prohibited in food-producing animals throughout the European Union. No method is available to reliably detect the misuse of natural hormones in cattle. A method was developed to detect the abuse of testosterone in cattle fattening. Synthesized testosterone is rather depleted in the (13)C/(12)C ratio. Hence, the method is based on gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analysis of urine. To select testosterone metabolites and endogenous reference compounds (ERC), the concentration of urinary steroids of cattle was investigated. Dehydroepiandrosterone and androst-5ene-3beta,17alpha-diol were chosen as ERCs to show endogenous (13)C/(12)C ratios. Etiocholanolone and 5alpha-androstane-3beta,17alpha-diol were chosen as the most important testosterone metabolites. Other metabolites known from literature like epitestosterone were less promising. In principle, GC/C/IRMS is a nonspecific method because finally carbon dioxide is analyzed. Therefore, a dedicated cleanup procedure for the selected steroids was developed. By means of proposed confidence intervals in the isotopic composition of ERCs and metabolites, the administration of testosterone to cattle could be detected reliably. Differences of up to 11 per thousand on the delta-scale between ERC and testosterone metabolites were found after testosterone administration, whereas endogenous differences did not exceed 2 per thousand.  相似文献   

The role of soil chemical properties,land use and plant diversity for microbial phosphorus in forest and grassland soils          下载免费PDF全文

Elisabeth Sorkau  Steffen Boch  Runa S. Boeddinghaus  Michael Bonkowski  Markus Fischer  Ellen Kandeler  Valentin H. Klaus  Till Kleinebecker  Sven Marhan  Jörg Müller  Daniel Prati  Ingo Schöning  Marion Schrumpf  Jan Weinert  Yvonne Oelmann 《植物养料与土壤学杂志》2018,181(2):185-197

Management intensity modifies soil properties, e.g., organic carbon (C_org) concentrations and soil pH with potential feedbacks on plant diversity. These changes might influence microbial P concentrations (P_mic) in soil representing an important component of the P cycle. Our objectives were to elucidate whether abiotic and biotic variables controlling P_mic concentrations in soil are the same for forests and grasslands, and to assess the effect of region and management on P_mic concentrations in forest and grassland soils as mediated by the controlling variables. In three regions of Germany, Schwäbische Alb, Hanich‐Dün, and Schorfheide‐Chorin, we studied forest and grassland plots (each n = 150) differing in plant diversity and land‐use intensity. In contrast to controls of microbial biomass carbon (C_mic), P_mic was strongly influenced by soil pH, which in turn affected phosphorus (P) availability and thus microbial P uptake in forest and grassland soils. Furthermore, P_mic concentrations in forest and grassland soils increased with increasing plant diversity. Using structural equation models, we could show that soil C_org is the profound driver of plant diversity effects on P_mic in grasslands. For both forest and grassland, we found regional differences in P_mic attributable to differing environmental conditions (pH, soil moisture). Forest management and tree species showed no effect on P_mic due to a lack of effects on controlling variables (e.g., C_org). We also did not find management effects in grassland soils which might be caused by either compensation of differently directed effects across sites or by legacy effects of former fertilization constraining the relevance of actual practices. We conclude that variables controlling P_mic or C_mic in soil differ in part and that regional differences in controlling variables are more important for P_mic in soil than those induced by management.  相似文献