Early silurian spore tetrads from new york: earliest new world evidence for vascular plants?

Several taxa of abundant cutinized trilete spores from earliest Silurian shale in New York predate by almost an entire period vascular land plant megafossils. Paleoecological evidence suggests that these spores may represent vascular land or semiaquatic plants but a bryophytic origin cannot be precluded on the basis of spore characters. An algal origin is considered unlikely.     

Mississippian fossils from southern appalachian metamorphic rocks and their implications for late paleozoic tectonic evolution

Fossils of Periastron reticulatum Unger emended. Beck recovered from the Erin Slate of the Talladega slate belt of Alabama establish that these rocks have a Mississippian (Kinderhookian-Tournaisian) age. The Talladega slate belt, the southwestern extension of the western Blue Ridge belt, was interpreted to have been affected by regional dynamothermal metamorphism and coeval deformation as a result of the Acadian orogeny. This fossil find indicates that metamorphism and deformation of the Talladega belt occurred after the Early Carboniferous (Alleghanian), requiring a reevaluation of tectonic interpretations of the southernmost Appalachians.     

Radioactive elements on Mercury's surface from MESSENGER: implications for the planet's formation and evolution

The MESSENGER Gamma-Ray Spectrometer measured the average surface abundances of the radioactive elements potassium (K, 1150 ± 220 parts per million), thorium (Th, 220 ± 60 parts per billion), and uranium (U, 90 ± 20 parts per billion) in Mercury's northern hemisphere. The abundance of the moderately volatile element K, relative to Th and U, is inconsistent with physical models for the formation of Mercury requiring extreme heating of the planet or its precursor materials, and supports formation from volatile-containing material comparable to chondritic meteorites. Abundances of K, Th, and U indicate that internal heat production has declined substantially since Mercury's formation, consistent with widespread volcanism shortly after the end of late heavy bombardment 3.8 billion years ago and limited, isolated volcanic activity since.     

The land as a social being: Ethical implications from societal expectations

The question to be answered is why do different cultures respond to the land differently? The question is born in the tension between Native American and the Anglo macroculture valuing of the land. Using the philosophy of George Herbert Mead, it is argued that the land is seen as a social being ,in the same way that an individual sees another person. Mead's philosophy of the development of the individual begins with the relation of the developing self and a social other. That relationship defines acts acceptable within the society, including the acts of observation and reflective thought. Thus, the very process of development becomes bound by the society. As the individual grows, according to Mead, the social other (and the relation between the other and the self) become generalized to include objects of the environment, such as the land. The acts toward others now become acts toward the land. As the acts toward others have value within the society, so the acts toward the land take on the same values. The individual mind is never an exact duplicate of the culture, but is limited by the culture, which results in specific tensions as two cultures come together. Again, using Mead, it is shown that the morality of our response to the land is dependent upon the growth of the individual, and that that growth can be provided by the very conflict of the acculturation.     

基于内部用地结构及其功能的农村居民点整理潜力辨析

选择东北典型农村,通过实地调研、农户访谈与遥感、地理信息系统相结合的方法,测算了农村居民点内部包括用于种植作物以及各种用途的土地面积的比例。结果表明,农村居民点内部有相当大比例的种植用地和养殖用地,这些土地具有农业生产功能,是农户生计不可或缺的组成部分。但是,土地利用现状调查中将农村院落内的种植农作物和养殖畜禽的土地都调绘为农村居民点即建设用地。因此,如果扣除这部分具有农畜产品生产功能的土地,农村居民点整治潜力并非很大。     

Convergence of Campylobacter species: implications for bacterial evolution

The nature of species boundaries in bacteria remains controversial. In particular, the mechanisms of bacterial speciation and maintenance in the face of frequent genetic exchange are poorly understood. Here, we report patterns of genetic exchange that show two closely related zoonotic pathogenic species, Campylobacter jejuni and Campylobacter coli, are converging as a consequence of recent changes in gene flow. Population expansion into a novel ecological niche generated by human activity is the most probable explanation for the increase in genetic exchange between these species. Bacterial speciation can therefore occur by mechanisms analogous to those seen in metazoans, where genetic diversification and incipient speciation caused by ecological factors have been reported in several genera.     

Chimpanzee bipedalism: cineradiographic analysis and implications for the evolution of gait

Bipedal chimpanzees reorient the pelvis to achieve an upright posture but retain the same pattern of femoral flexion and extension as in quadrupedal walking. Major differences from human gait are the abducted, relatively more flexed excursion of the femur and the timing of pelvic tilt, which raises during the swing phase. The femoral head morphology in the fossil hominid Australopithecus robustus is evidence of an approximately vertical excursion of the femur in contrast to the adducted pattern of modern man and the abducted pattern of chimpanzees.     

Buckytubes and derivatives: their growth and implications for buckyball formation

Transmission electron microscopy (TEM) observations of graphite tubules (buckytubes) and their derivatives have revealed not only the previously reported buckytube geometries but also additional shapes of the buckytube derivatives. Detailed cross-sectional TEM images reveal the cylindrical cross section of buckytubes and the growth pattern of buckytubes as well as their derivatives. These observations of frozen growth stages of buckytubes and derivatives suggest a helical growth mechanism analogous to that of crystal growth via screw dislocations. The helicacy of buckytubes is analyzed by electron diffraction whereas the anisotropy of electronic structure is revealed by momentum transfer resolved electron energy loss spectrometry. Based on the TEM observations, it is proposed that buckytubes act as precursors to closed-shell fullerene (buckyball) formation and the possible steps in buckyball formation are outlined. In arc evaporation experiments in which residue rods (containing various amounts of buckytubes) were used as the starting anode for fullerene production, the amount of buckytubes in the rod was correlated with fullerene yield.     

不产子实体蛹虫草单孢子分离株的获得及RAPD分析

对优势蛹虫草原始菌株WWM04进行单孢子分离,共获得9个单孢子分离株,采用米饭培养基培养确证并且获得6个完全不产子实体的单孢子分离株。利用随机扩增多态性DNA(RAPD)分子标记方法对菌落差异的4个菌落特征典型的不产子实体单孢子分离株(SSP2、SSP7、SSP19和SSP21)、原始菌株以及由原始菌株12次转接后退化的菌株进行遗传多样性分析。结果表明,引物S37、S61对6个菌株的扩增谱带具有非常明显的特异性,该结果为蛹虫草退化分子标记奠定基础,并且在一定程度上也印证了蛹虫草异核现象和准性生殖理论。     

A mechanism for surface attachment in spores of a plant pathogenic fungus

Rice blast disease is caused by a fungus that attacks all above-ground parts of the rice plant. In a study of the means by which the fungus attaches to the hydrophobic rice leaf surface, it was found that spores(conidia) of the rice blast fungus Magnaporthe grisea have a mechanism for immediate and persistent attachment to various surfaces, including Teflon. This attachment occurs at the spore apex and is blocked by the addition of the lectin concanavalin A. Microscopy of hydrated conidia shows that a spore tip mucilage that binds concanavalin A is expelled specifically from the conidial apex before germ tube emergence. Ultrastructural analysis of dry conidia shows a large periplasmic deposit, presumably spore tip mucilage, at the apex. The results indicate a novel mechanism for the attachment of phytopathogenic fungal spores to a plant surface.     

Head segmentation in early cambrian fuxianhuia: implications for arthropod evolution

The arthropod Fuxianhuia from the Chengjiang fauna displays primitive aspects of cephalic segmentation and trunk limb morphology that indicate a basal position within Euarthropoda. The cephalon consists of an eye-bearing sclerite that articulates with a head shield bearing antennules and subchelate appendages. Eye stalks, antennules, and subchelate appendages are proto-, deuto-, and tritocerebral limbs and organs, respectovely. The anterior position of the eye-bearing sclerite parallels the embryonic origin of arthropod eye lobes. The head of Fuxianhuia includes the acron and one somite and is regarded as a protocephalon. The definitive head of arthropods may have fused separate eye-bearing and appendage-bearing sclerites.     

An aptian plant with attached leaves and flowers: implications for angiosperm origin

Recent phylogenetic studies and fossil finds support a new view of the ancestral angiosperm. A diminutive fossil angiosperm from the Aptian of Australia has attached leaves, with intermediate pinnate-palmate, low-rank venation, and lateral axes bearing pistillate organs subtended by bracts and bracteoles that are the oldest direct evidence of flowers. A variety of data suggests a similar morphology for the ancestral angiosperm. This hypothesis explains similarities between rhizomatous to herbaceous Magnoliidae and basal monocots, scarcity of early agniosperm wood, and lack of recognition of earlier remains.     

Nucleotide sequence of yellow fever virus: implications for flavivirus gene expression and evolution

The sequence of the entire RNA genome of the type flavivirus, yellow fever virus, has been obtained. Inspection of this sequence reveals a single long open reading frame of 10,233 nucleotides, which could encode a polypeptide of 3411 amino acids. The structural proteins are found within the amino-terminal 780 residues of this polyprotein; the remainder of the open reading frame consists of nonstructural viral polypeptides. This genome organization implies that mature viral proteins are produced by posttranslational cleavage of a polyprotein precursor and has implications for flavivirus RNA replication and for the evolutionary relation of this virus family to other RNA viruses.     

Isotope fractionation and atmospheric oxygen: implications for phanerozoic O(2) evolution

Models describing the evolution of the partial pressure of atmospheric oxygen over Phanerozoic time are constrained by the mass balances required between the inputs and outputs of carbon and sulfur to the oceans. This constraint has limited the applicability of proposed negative feedback mechanisms for maintaining levels of atmospheric O(2) at biologically permissable levels. Here we describe a modeling approach that incorporates O(2)-dependent carbon and sulfur isotope fractionation using data obtained from laboratory experiments on carbon-13 discrimination by vascular land plants and marine plankton. The model allows us to calculate a Phanerozoic O(2) history that agrees with independent models and with biological and physical constraints and supports the hypothesis of a high atmospheric O(2) content during the Carboniferous (300 million years ago), a time when insect gigantism was widespread.     

乡村土地资源整合模式：土地流转与整治

受耕地细碎化、宅基地空置化、土地利用粗放化、耕地保护严峻化和新型四化同步推进的多维驱动影 响,乡村土地顺畅流转并带动城乡资源高效整合成为我国土地流转与土地整治互动机制创新的难点。为此,从土地 产权流转、农用地整治和建设用地整治三个层面,论述了乡村土地资源整合模式。研究表明院土地流转是土地使用权 转移和收益再分配,农用地整治是土地自然属性与利用方式的重构和调整,而居民点复垦、新村建设和建设用地增 减挂钩是城乡建设用地的布局优化和整体效用的提升。尽管从土地产权和工程改造层面,构建了特定区域或特定目 标的土地产权流转模式和田-水-路-林-村工程建设模式,但尚未形成“协调、互动、统筹”土地流转与资源整合模式 体系。因此,如何将土地流转与土地整治融为一体,通过政策引导与工程改造双向加力,搭建城乡资源高效整合和双 向流动的统筹链,成为土地流转与资源整合耦合模式创新的关键点。而该模式的创新发展,既应突破土地流转体制 障碍,又应突破新增耕地受路、沟、渠、林等占用多且乱的限制,农业产业化受土地细碎化、基础设施薄弱化的限制, 城乡建设用地受置换不对接的限制,还应吻合区域自然-社会-经济-生态-环境的现实发展态势。     

Historical nile floods and their implications for climatic change

Analysis of Nile flood stages from A.D. 640 to 1921 reveals major episodes of low Nile discharge during the years 930 to 1070 and 1180 to 1350 and major episodes of high Nile floods during 1070 to 1180 and 1350 to 1470. Examination of Nile flood maxima and minima and comparison with water levels in Lake Chad reveal a correlation between high Nile discharge and greater rainfall in equatorial East Africa. There is also apparently a correlation between low Nile discharge and cold climate in Europe.     

灵芝孢子粉总三萜的提取优化及其体外生物活性

对灵芝孢子粉总三萜的提取过程进行优化,以得率为指标,通过单因素试验、Plackett-Burman试验筛选出影响灵芝孢子粉总三萜得率的显著因素,利用响应面设计优化灵芝孢子粉总三萜的提取条件。对于提取出的灵芝孢子粉总三萜,评价其清除1,1-二苯基-2-三硝基苯肼(DPPH)自由基和ABTS⁺自由基的方法,并采用CCK-8比色法就其抗人肝癌细胞HepG-2增殖的活性进行研究。结果表明,最佳提取条件为乙醇体积分数80%,固液比1:23,超声功率540 W,提取温度40 ℃,提取时间60 min。此优化条件下提取的灵芝孢子粉总三萜具有较好的抗氧化能力,清除ABTS⁺的能力强于清除DPPH,对人肝癌细胞HepG-2亦具有一定的抑制作用。