Widespread magma oceans on asteroidal bodies in the early Solar System

Immediately following the formation of the Solar System, small planetary bodies accreted, some of which melted to produce igneous rocks. Over a longer timescale (15-33 Myr), the inner planets grew by incorporation of these smaller objects through collisions. Processes operating on such asteroids strongly influenced the final composition of these planets, including Earth. Currently there is little agreement about the nature of asteroidal igneous activity: proposals range from small-scale melting, to near total fusion and the formation of deep magma oceans. Here we report a study of oxygen isotopes in two basaltic meteorite suites, the HEDs (howardites, eucrites and diogenites, which are thought to sample the asteroid 4 Vesta) and the angrites (from an unidentified asteroidal source). Our results demonstrate that these meteorite suites formed during early, global-scale melting (> or = 50 per cent) events. We show that magma oceans were present on all the differentiated Solar System bodies so far sampled. Magma oceans produced compositionally layered planetesimals; the modification of such bodies before incorporation into larger objects can explain some anomalous planetary features, such as Earth's high Mg/Si ratio.     

Chemical communication: chirality in elephant pheromones

Musth in male elephants is an annual period of heightened sexual activity and aggression that is linked to physical, sexual and social maturation. It is mediated by the release of chemical signals such as the pheromone frontalin, which exists in two chiral forms (molecular mirror images, or enantiomers). Here we show that enantiomers of frontalin are released by Asian elephants in a specific ratio that depends on the animal's age and stage of musth, and that different responses are elicited in male and female conspecifics when the ratio alters. This precise control of communication by molecular chirality offers insight into societal interactions in elephants, and may be useful in implementing new conservation protocols.     

Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch

The warmest global climates of the past 65 million years occurred during the early Eocene epoch (about 55 to 48 million years ago), when the Equator-to-pole temperature gradients were much smaller than today and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume. Recently the early Eocene has received considerable interest because it may provide insight into the response of Earth's climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future as a consequence of unabated anthropogenic carbon emissions. Climatic conditions of the early Eocene 'greenhouse world', however, are poorly constrained in critical regions, particularly Antarctica. Here we present a well-dated record of early Eocene climate on Antarctica from an ocean sediment core recovered off the Wilkes Land coast of East Antarctica. The information from biotic climate proxies (pollen and spores) and independent organic geochemical climate proxies (indices based on branched tetraether lipids) yields quantitative, seasonal temperature reconstructions for the early Eocene greenhouse world on Antarctica. We show that the climate in lowland settings along the Wilkes Land coast (at a palaeolatitude of about 70° south) supported the growth of highly diverse, near-tropical forests characterized by mesothermal to megathermal floral elements including palms and Bombacoideae. Notably, winters were extremely mild (warmer than 10?°C) and essentially frost-free despite polar darkness, which provides a critical new constraint for the validation of climate models and for understanding the response of high-latitude terrestrial ecosystems to increased carbon dioxide forcing.     

A new species of Phrynobatrachus (Amphibia: Anura: Phrynobatrachidae) from the Northern Mountains of Tanzania

ABSTRACT

Using integrative approaches, a new large-bodied species of Phrynobatrachus is described from a series of 48 specimens from the montane forests of the West Usambara and North Pare Mountains of Tanzania. The most distinguishing morphological feature separating Phrynobatrachus ambanguluensis sp. nov from similar species is the markedly overhanging and pointed upper jaw and snout. Mitochondrial 16S rRNA indicates that the new species differs from all other species with published sequence data by a minimum distance of 4.75% and is sister to P. krefftii, with which it has been confused in the past. The new species is known from two forest reserves and is of high conservation concern given these areas are highly impacted by anthropogenic change.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:E0C82A87-47A5-426B-978D-96D27FA7A3B7     

高级动力学

高级动力学可以对动力学的分析工具作宽广且详尽的描写，可以讨论不同的强度和弱点，特别强调怎样才能彻底解决问题的技能。本书开始详尽评述矢量动力学，继而瞄准拉格朗日和哈密尔顿两方程以及诸如冲激响应、微分形式和可积性等不熟悉课题，还描述计算效能上超过传统经典法，特别当用于复杂的动力系统时效果更显著的重大改进。数值分析处理包括讨论数值稳定性和约束稳定两方面。本教科书每章附有不少工作例子和课后的思考问题。     

Genome-wide association scan identifies a colorectal cancer susceptibility locus on chromosome 8q24

Using a multistage genetic association approach comprising 7,480 affected individuals and 7,779 controls, we identified markers in chromosomal region 8q24 associated with colorectal cancer. In stage 1, we genotyped 99,632 SNPs in 1,257 affected individuals and 1,336 controls from Ontario. In stages 2-4, we performed serial replication studies using 4,024 affected individuals and 4,042 controls from Seattle, Newfoundland and Scotland. We identified one locus on chromosome 8q24 and another on 9p24 having combined odds ratios (OR) for stages 1-4 of 1.18 (trend; P = 1.41 x 10(-8)) and 1.14 (trend; P = 1.32 x 10(-5)), respectively. Additional analyses in 2,199 affected individuals and 2,401 controls from France and Europe supported the association at the 8q24 locus (OR = 1.16, trend; 95% confidence interval (c.i.): 1.07-1.26; P = 5.05 x 10(-4)). A summary across all seven studies at the 8q24 locus was highly significant (OR = 1.17, c.i.: 1.12-1.23; P = 3.16 x 10(-11)). This locus has also been implicated in prostate cancer.     

Malaria in 2002

The burden of malaria is increasing, especially in sub-Saharan Africa, because of drug and insecticide resistance and social and environmental changes. Thus, there is an urgent need for vaccines, new drugs and insecticides. Parasite, mosquito and human genome projects are helping in the search for new control tools and international donors are developing new funding mechanisms that could make them available to poor countries. But these new tools will achieve their maximum impact only if additional resources are deployed to strengthen malaria research and control communities in countries where the new tools will be used.