六盘山自然保护区两栖动物栖息地的重要性评判

根据2011—2014年进行的宁夏六盘山国家级自然保护区生态监测得到的该地区两栖爬行动物种类和数量数据,运用综合模糊评判法对保护区内的5个监测点进行了两栖爬行动物栖息地的重要性评价.评判中隶属度的确定采用最佳因子值法,并分春夏两个最佳因子值进行评判.结果表明,夏季各监测点重要性比春季高,因此夏季是管理的重点;无论春季还是夏季,在种类的多样性和物种的濒危保护价值方面,小南川监测点相较于其他监测点其重要性(0.764和0.966)最高,应给予重点管理;老龙潭、二龙河的结果相近,重要程度次之,可持有较高程度的管理水平;冶家村春季物种数量和多样性均较高,应给予一般水平的管理,凉殿峡的夏季物种多样性较高,但也只需一般水平的管理.     

马克思的早期自然理论

关注和思考自然是马克思早期理论探讨的重要课题。在大学时期他通过对古代自然哲学的研究,就对自然概念作了创造性的探讨,肯定了人在自然面前的能动性。而在《1844年经济学哲学手稿》中,马克思在哲学与经济学相结合的基础上,从四个方面构建了一种新的辩证的自然理论雏形。     

马克思的早期自然理论

关注和思考自然是马克思早期理论探讨的重要课题。在大学时期他通过对古代自然哲学的研究，就对自然概念作了创造性的探讨，肯定了人在自然面前的能动性。而在《1844年经济学哲学手稿》中，马克思在哲学与经济学相结合的基础上，从四个方面构建了一种新的辩证的自然理雏形。     

Geochemistry: biosignatures and abiotic constraints on early life

Ueno et al. contend that methane found in fluid inclusions within hydrothermally precipitated quartz in the Dresser Formation of western Australia (which is roughly 3.5 Gyr old) provides evidence for microbial methanogenesis in the early Archaean era. The authors discount alternative origins for this methane, suggesting that the range of delta(13)C(CH(4)) values that they record (-56 to -36 per thousand) is attributable to mixing between a primary microbial end-member with a delta(13)C(CH(4)) value of less than -56 per thousand and a mature thermogenic gas enriched in (13)C (about -36 per thousand). However, abiotic methane produced experimentally and in other Precambrian greenstone settings has (13)C-depleted delta(13)C(CH(4)) values, as well as Delta(13)C(CO(2)-CH(4)) relationships that encompass the range measured for the inclusions by Ueno et al. - which suggests that an alternative, abiotic origin for the methane is equally plausible. The conclusions of Ueno et al. about the timing of the onset of microbial methanogenesis might not therefore be justified.     

The nature and origin of interstellar diamond

Microscopic diamond was recently discovered in oxidized acid residues from several carbonaceous chondrite meteorites (for example, the C delta component of the Allende meteorite). Some of the reported properties of C delta seem in conflict with those expected of diamond. Here we present high spatial resolution analytical data which may help to explain such results. The C delta diamond is an extremely fine-grained (0.5-10 nm) single-phase material, but surface and interfacial carbon atoms, which may comprise as much as 25% of the total, impart an 'amorphous' character to some spectral data. These data support the proposed high-pressure conversion of amorphous carbon and graphite into diamonds due to grain-grain collisions in the interstellar medium although a low-pressure mechanism of formation cannot be ruled out.     

极小项与极大项的运算性质

研究了极小项、极大项的运算性质，给出了一组运算公式，利用这些运算公式可以使求命题公式的主范式运算更简洁。     

多氯联苯的性质及其对环境的危害

多氯联苯（PCBs）是一类重要的环境持久性污染物。本文列出了37种多氯联苯化合物的辛醇-水分配系数及水溶解度的估算值与实验值,并对多氯联苯的理化性质及其对环境的危害做了初步的探讨。     

The nature of plant species

Many botanists doubt the existence of plant species, viewing them as arbitrary constructs of the human mind, as opposed to discrete, objective entities that represent reproductively independent lineages or 'units of evolution'. However, the discreteness of plant species and their correspondence with reproductive communities have not been tested quantitatively, allowing zoologists to argue that botanists have been overly influenced by a few 'botanical horror stories', such as dandelions, blackberries and oaks. Here we analyse phenetic and/or crossing relationships in over 400 genera of plants and animals. We show that although discrete phenotypic clusters exist in most genera (> 80%), the correspondence of taxonomic species to these clusters is poor (< 60%) and no different between plants and animals. Lack of congruence is caused by polyploidy, asexual reproduction and over-differentiation by taxonomists, but not by contemporary hybridization. Nonetheless, crossability data indicate that 70% of taxonomic species and 75% of phenotypic clusters in plants correspond to reproductively independent lineages (as measured by postmating isolation), and thus represent biologically real entities. Contrary to conventional wisdom, plant species are more likely than animal species to represent reproductively independent lineages.     

The nonlinear nature of friction

Tribology is the study of adhesion, friction, lubrication and wear of surfaces in relative motion. It remains as important today as it was in ancient times, arising in the fields of physics, chemistry, geology, biology and engineering. The more we learn about tribology the more complex it appears. Nevertheless, recent experiments coupled to theoretical modelling have made great advances in unifying apparently diverse phenomena and revealed many subtle and often non-intuitive aspects of matter in motion, which stem from the nonlinear nature of the problem.     

The nature of pulsar radiation

Pulsar radiation may be due to particles which gyrate while moving in bunches along curved orbits. If emitted by electrons, the pulses should come from near the speed of light circle; if emitted by protons, they should arise within a few stellar radii of the underlying star.     

Establishment of idiotypic helper T-cell repertoires early in life

Immunoglobulin variable-region (V) genes, it is now recognized, do not encode specific receptors for T lymphocytes. Classical observations on T-cell expression of immunoglobulin idiotypes had remained unexplained until recent experiments showed that immunoglobulin idiotypes expressed by T lymphocytes in normal mice are absent in cells of the same specificity isolated from donors whose B-cell system has been suppressed by administration of anti-mu antibodies from birth. This observation provided evidence for the 'learning' of T-cell idiotypes from the B-cell/antibody system and, therefore, for the importance of idiotypic network interactions in the selection of available lymphocyte repertoires before antigenic challenge. Previously described influences of B cells and/or antibodies on the T-helper (Th) cell compartment would appear to operate at the level of clonal repertoires by complementarities with defined immunoglobulin idiotypes. Other authors, however, had previously shown the striking stability of T-cell idiotype expression in chimaeric animals reconstituted with T and B cells originating from donors showing differential idiotype expression. We have now investigated this apparent discrepancy and present here results demonstrating that immunoglobulin-dependent selection of T-cell (idiotypic) repertoires only operates for the first 3 weeks of life.     

句法的符号性质

符号的本质是意义与形式的结合。对于符号的形式,我们要充分认识其复杂性和多样性;对于符号的意义,我们要认识到它不仅包括符号的实在意义,还包括符号的功能意义。从广义的符号定义看,句法可以被视为一种特殊的符号。     

The nature of human altruism

Some of the most fundamental questions concerning our evolutionary origins, our social relations, and the organization of society are centred around issues of altruism and selfishness. Experimental evidence indicates that human altruism is a powerful force and is unique in the animal world. However, there is much individual heterogeneity and the interaction between altruists and selfish individuals is vital to human cooperation. Depending on the environment, a minority of altruists can force a majority of selfish individuals to cooperate or, conversely, a few egoists can induce a large number of altruists to defect. Current gene-based evolutionary theories cannot explain important patterns of human altruism, pointing towards the importance of both theories of cultural evolution as well as gene-culture co-evolution.     

Antibiotics in early life alter the murine colonic microbiome and adiposity

Antibiotics administered in low doses have been widely used as growth promoters in the agricultural industry since the 1950s, yet the mechanisms for this effect are unclear. Because antimicrobial agents of different classes and varying activity are effective across several vertebrate species, we proposed that such subtherapeutic administration alters the population structure of the gut microbiome as well as its metabolic capabilities. We generated a model of adiposity by giving subtherapeutic antibiotic therapy to young mice and evaluated changes in the composition and capabilities of the gut microbiome. Administration of subtherapeutic antibiotic therapy increased adiposity in young mice and increased hormone levels related to metabolism. We observed substantial taxonomic changes in the microbiome, changes in copies of key genes involved in the metabolism of carbohydrates to short-chain fatty acids, increases in colonic short-chain fatty acid levels, and alterations in the regulation of hepatic metabolism of lipids and cholesterol. In this model, we demonstrate the alteration of early-life murine metabolic homeostasis through antibiotic manipulation.     

The deterministic nature of earthquake rupture

Understanding the earthquake rupture process is central to our understanding of fault systems and earthquake hazards. Multiple hypotheses concerning the nature of fault rupture have been proposed but no unifying theory has emerged. The conceptual hypothesis most commonly cited is the cascade model for fault rupture. In the cascade model, slip initiates on a small fault patch and continues to rupture further across a fault plane as long as the conditions are favourable. Two fundamental implications of this domino-like theory are that small earthquakes begin in the same manner as large earthquakes and that the rupture process is not deterministic--that is, the size of the earthquake cannot be determined until the cessation of rupture. Here we show that the frequency content of radiated seismic energy within the first few seconds of rupture scales with the final magnitude of the event. We infer that the magnitude of an earthquake can therefore be estimated before the rupture is complete. This finding implies that the rupture process is to some degree deterministic and has implications for the physics of the rupture process.     

环的反同态性质的研究

当两个环之间存在反同态映射时,利用已知环的代数结构和性质给出未知环的代数结构和性质,从而研究环的反同态所具有的传递性质。     

浅谈新闻真实性与写作的文学性

新闻写作是对客观事实的报道,必须具备真实性;同时,新闻写作又是人的主观能动性的体现,它又应该具备一定的文学性,这两方面是一个好的新闻作品应该兼具的要素。但文学性必须建立在新闻真实性的基础之上,两者之间必须要把握尺度。相互融通。