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181.
182.
Piezoelectric materials have many applications at cryogenic temperatures. However, the piezoelectric response below 10 kelvin is diminished, making the use of these materials somewhat marginal. Results are presented on strontium titanate (SrTiO3), which exhibits a rapidly increasing piezoelectric response with decreasing temperature below 50 kelvin; the magnitude of its response around 1 kelvin is comparable to that of the best materials at room temperature. This "giant" piezoelectric response may open the way for a broad class of applications including use in ultralow-temperature scanning microscopies and in a magnetic field-insensitive thermometer. These observations, and the possible divergence of the mechanical response to electric fields at even lower temperatures, may arise from an apparent quantum critical point at absolute zero. 相似文献
183.
Eva DE LA PE
A Jos MARTÍN Isabel BARJA Raúl PREZ‐CABALLERO Isabel ACOSTA Juan CARRANZA 《Integrative zoology》2020,15(4):262-275
Testosterone secretion may regulate the reproductive effort and the development of sexual traits, but it may also involve costs at the immunological and metabolic levels. However, the evidence for this trade‐off in wild populations is scarce. Cortisol also plays an important role in mediating the reproductive and immune functions. In this study, we analyzed whether the endoparasite burden relates to hormonal levels (fecal testosterone and cortisol metabolites) and/or morphological sexual traits (size of the dark ventral patch, a trait that indicates reproductive effort in males) in male Iberian red deer. For this purpose, we sampled male red deer harvested during hunting actions in 2 types of populations in south western Spain that differed in structure, affecting the level of male–male competition for mates. We used coprological analyses to estimate the parasite burden mainly of gastrointestinal and bronchopulmonary nematodes and of protozoa, and assessed testosterone and cortisol metabolite levels from fecal pellets. We found a positive relationship of host parasitation with both testosterone levels and the size of the dark ventral patch, but these relationships depended on the intensity of male–male competition in the population, being only found under the high‐competition scenario. These results are discussed under the hypothesis of the testosterone immunocompetence handicap, suggesting a cost at the immunological level, and, therefore, higher susceptibility to parasite infection in males that make a greater reproductive effort. However, this effect seems to be modulated by the social environment (male–male competition) that might lead to different optima in testosterone production and sexual trait development. 相似文献
184.
Feline leukemia virus: occurrence of viral antigen in the tissues of cats with lymphosarcoma and other diseases 总被引:6,自引:0,他引:6
W D Hardy G Geering L J Old E DE Harven R S Brody S McDonough 《Science (New York, N.Y.)》1969,166(908):1019-1021
Felinie leutkemia viruts antigen is demonstrable by immunodiffusion with rabbit precipitating antiserum to purified felinie leukemia virus. The felinie leukemia virus antigen was found in the tissues of 25 of 33 cats with lymphosarcoma and of 5 of 13 cats with infectious peritonitis. Its presence was correlated with the occurrence of felinie leukemia virus demonstrable by electron microscopy. The one clinically normal cat giving a positive test for feline leukemia virus antigen belonged to a household in which two cats had developed lymphosarcoma. With the exception of a dog with lymphosarcoma induced by feline leukemia virus, the antigent was absent from lymphosarcoma and nonlymphomatous tumors of other species (man, dog, cow, goat, or pig). 相似文献
185.
The 3-0 rotation-vibration band of carbon monoxide in the near-infrared spectrum of Titan has been identified, and a reflecting layer model mixing ratio of carbon monoxide to molecular nitrogen of 6 x 10(-5) has been determined. This result supports the probable detection of carbon dioxide by Samuelson and his co-workers and strengthens possible analogies between the atmosphere of Titan and conditions on primitive Earth. 相似文献
186.
The discovery of an existing member of the Glypheidae, a family believed to have been extinct since the Eocene, may yield significant information on the evolution and classification of the decapod Crustacea. The single known specimen displays characters not apparent in fossil material, some of them perhaps representative of an ancestral decapod lineage, others reminiscent of the Astacidea and Thalassinidea. 相似文献
187.
DE ROBERTIS E SALGANICOFF L ZIEHER LM RODRIGUEZ DE LORES ARNAIZ G 《Science (New York, N.Y.)》1963,140(3564):300-301
Acetylcholine, cholinacetylase, and acetylcholinesterase were determined in three subfractions that resulted from the osmotic shock of the "mitochondrial" fraction of the rat brain. Acetylcholine and cholinacetylase were found concentrated in the subfraction that contained mainly synaptic vesicles and some membranes, whereas the larger proportion of the acetylcholinesterase was observed in the subfraction that contained torn nerve endings. These results support the idea that synaptic vesicles are the morphological units of acetylcholine within the synapse. 相似文献
188.
About 100 pure-bred samples of nine varieties of pulses raised in different state agricultural farms of India in 1957, when analyzed, indicated variations in the protein content of a single variety extending up to 60 percent in some cases, depending upon the strain and the locality where grown. 相似文献
189.
DE Vries H 《Science (New York, N.Y.)》1914,40(1020):77-84
190.
Parrish A DE Zafra RL Solomon PM Barrett JW Carlson ER 《Science (New York, N.Y.)》1981,211(4487):1158-1161
Stratospheric chlorine oxide, a significant intermediate product in the catalytic destruction of ozone by atomic chlorine, has been detected and measured by a ground-based 204-gigahertz, millimeter-wave receiver. Data taken at latitude 42 degrees N on 17 days between 10 January and 18 February 1980 yield an average chlorine oxide column density of approximately 1.05 x 10(14) per square centimeter or approximately 2/3 that of the average of eight in situ balloon flight measurements (excluding the anomalously high data of 14 July 1977) made over the past 4 years at 32 degrees N. We find less chlorine oxide below 35 kilometers and a larger vertical gradient than predicted by theoretical models of the stratospheric ozone layer. 相似文献