线虫动物门、腹毛动物门及轮虫动物门间的系统学研究

用支序分析方法对线虫动物门、腹毛动物门和轮虫动物门三者之间的系统学进行了分析，结论是三者为一单系群，其中腹毛动物门和轮虫动物门为一对姐妹群，线虫动物门则是三者的共同祖先较早地分出的另一支。由此我们认为，应将这三者合并为一新门合胞体动物门（Syncytia)，原来各门分别降为线虫纲、腹毛纲和轮虫纲；原腔动物门这一分类阶元应予废弃。     

Real-space imaging of an orbital Kondo resonance on the Cr(001) surface

The Kondo effect is usually connected with the interaction between a localized spin moment and itinerant electrons. This interaction leads to the formation of a narrow resonance at the Fermi level, which is called the Abrikosov-Suhl or Kondo resonance. Scanning tunnelling microscopy is an ideal technique for real-space investigations of complicated electronic structures and many-body phenomena, such as the formation of the Kondo resonance or d-wave pairing in high-T(c) superconductors. Theory has predicted that similar, Kondo-like many-electron resonances are possible for scattering centres with orbital instead of spin degrees of freedom--the quadruple momenta in uranium-based compounds or two-level systems in metallic glasses are examples of such 'pseudo-Kondo' scattering centres. Here we present evidence for the orbital Kondo resonance on a transition-metal surface. Investigations of an atomically clean Cr(001) surface at low temperature using scanning tunnelling microscopy reveal a very narrow resonance at 26 meV above the Fermi level, and enable us to visualize the orbital character of the corresponding state. The experimental data, together with many-body calculations, demonstrate that the observed resonance is an orbital Kondo resonance formed by two degenerate d(xz), d(yz) surface states.     

多层膜样品的背散射/沟道、溅射剥层/背散射和二次离子质谱分析

用背散射／沟道、溅射剥层／背散射和二次离子质谱方法分析了分子束外延生长的Si/GexSi1-x多层膜。由2MeV^4He^ 离子背散射／沟道分析，确定了外延生长薄膜的厚度、组分和晶格结构的完美性；用低能Ar^ 离子溅射剥层，减薄样品外延层厚度后，再做背散射分析，可获得有关较深层薄膜与基体界面和溅射剥层的信息；二次离子质谱分析清晰地显示出溅射剥层前后样品的交替层周期性结构。     

RNA interference screen for human genes associated with West Nile virus infection

West Nile virus (WNV), and related flaviviruses such as tick-borne encephalitis, Japanese encephalitis, yellow fever and dengue viruses, constitute a significant global human health problem. However, our understanding of the molecular interaction of such flaviviruses with mammalian host cells is limited. WNV encodes only 10 proteins, implying that it may use many cellular proteins for infection. WNV enters the cytoplasm through pH-dependent endocytosis, undergoes cycles of translation and replication, assembles progeny virions in association with endoplasmic reticulum, and exits along the secretory pathway. RNA interference (RNAi) presents a powerful forward genetics approach to dissect virus-host cell interactions. Here we report the identification of 305 host proteins that affect WNV infection, using a human-genome-wide RNAi screen. Functional clustering of the genes revealed a complex dependence of this virus on host cell physiology, requiring a wide variety of molecules and cellular pathways for successful infection. We further demonstrate a requirement for the ubiquitin ligase CBLL1 in WNV internalization, a post-entry role for the endoplasmic-reticulum-associated degradation pathway in viral infection, and the monocarboxylic acid transporter MCT4 as a viral replication resistance factor. By extending this study to dengue virus, we show that flaviviruses have both overlapping and unique interaction strategies with host cells. This study provides a comprehensive molecular portrait of WNV-human cell interactions that forms a model for understanding single plus-stranded RNA virus infection, and reveals potential antiviral targets.     

Conformity to cultural norms of tool use in chimpanzees

Rich circumstantial evidence suggests that the extensive behavioural diversity recorded in wild great apes reflects a complexity of cultural variation unmatched by species other than our own. However, the capacity for cultural transmission assumed by this interpretation has remained difficult to test rigorously in the field, where the scope for controlled experimentation is limited. Here we show that experimentally introduced technologies will spread within different ape communities. Unobserved by group mates, we first trained a high-ranking female from each of two groups of captive chimpanzees to adopt one of two different tool-use techniques for obtaining food from the same 'Pan-pipe' apparatus, then re-introduced each female to her respective group. All but two of 32 chimpanzees mastered the new technique under the influence of their local expert, whereas none did so in a third population lacking an expert. Most chimpanzees adopted the method seeded in their group, and these traditions continued to diverge over time. A subset of chimpanzees that discovered the alternative method nevertheless went on to match the predominant approach of their companions, showing a conformity bias that is regarded as a hallmark of human culture.     

Stable sea surface temperatures in the western Pacific warm pool over the past 1.75 million years

About 850,000 years ago, the period of the glacial cycles changed from 41,000 to 100,000 years. This mid-Pleistocene climate transition has been attributed to global cooling, possibly caused by a decrease in atmospheric carbon dioxide concentrations. However, evidence for such cooling is currently restricted to the cool upwelling regions in the eastern equatorial oceans, although the tropical warm pools on the western side of the ocean basins are particularly sensitive to changes in radiative forcing. Here we present high-resolution records of sea surface temperatures spanning the past 1.75 million years, obtained from oxygen isotopes and Mg/Ca ratios in planktonic foraminifera from the western Pacific warm pool. In contrast with the eastern equatorial regions, sea surface temperatures in the western Pacific warm pool are relatively stable throughout the Pleistocene epoch, implying little long-term change in the tropical net radiation budget. Our results challenge the hypothesis of a gradual decrease in atmospheric carbon dioxide concentrations as a dominant trigger of the longer glacial cycles since 850,000 years ago. Instead, we infer that the temperature contrast across the equatorial Pacific Ocean increased, which might have had a significant influence on the mid-Pleistocene climate transition.     

一种新的植物枝条弯曲生成算法

枝条弯曲模拟对于形象地绘制模特图形很重要。从计算机图形学的角度出发,提出了一种计算枝条弯曲形状的简易力学模型,实现了基于“双尺度自动机模型”的枝条弯曲算法。该算法虽然所需参数少,但能有效地生成自然逼真的枝条弯曲形状,并且能反映植物在生长中枝条的动态弯曲过程。文中通过几个枝条弯曲的例子验证了算法的有效性。     

不同结构和形态的天然镁硅酸盐:与K反应制备生物柴油的K2MgSiO4催化剂

In this work, different magnesium silicate mineral samples based on antigorite, lizardite, chrysotile (which have the same general formula Mg₃Si₂O₅(OH)₄), and talc (Mg₃Si₄O₁₀(OH)₂) were reacted with KOH to prepare catalysts for biodiesel production. Simple impregnation with 20wt% K and treatment at 700–900°C led to a solid-state reaction to mainly form the K₂MgSiO₄ phase in all samples. These results indicate that the K ion can diffuse into the different Mg silicate structures and textures, likely through intercalation in the interlayer space of the different mineral samples followed by dehydroxylation and K₂MgSiO₄ formation. All the materials showed catalytic activity for the transesterification of soybean oil (1:6 of oil : methanol molar ratio, 5wt% of catalyst, 60°C). However, the best results were obtained for the antigorite and chrysotile precursors, which are discussed in terms of mineral structure and the more efficient formation of the active phase K₂MgSiO₄.     

Minimal ProtoHox cluster inferred from bilaterian and cnidarian Hox complements

Bilaterian animals have a Hox gene cluster essential for patterning the main body axis, and a ParaHox gene cluster. Comparison of Hox and ParaHox genes has led workers to postulate that both clusters originated from the duplication of an ancient cluster named ProtoHox, which contained up to four genes with at least the precursors of anterior and posterior Hox/ParaHox genes. However, the way in which genes diversified within the ProtoHox, Hox and ParaHox clusters remains unclear because no systematic study of non-bilaterian animals exists. Here we characterize the full Hox/ParaHox gene complements and genomic organization in two cnidarian species (Nematostella vectensis and Hydra magnipapillata), and suggest a ProtoHox cluster simpler than originally thought on the basis of three arguments. First, both species possess bilaterian-like anterior Hox genes, but their non-anterior genes do not appear as counterparts of either bilaterian central or posterior genes; second, two clustered ParaHox genes, Gsx and a gene related to Xlox and Cdx, are found in Nematostella vectensis; and third, we do not find clear phylogenetic support for a common origin of bilaterian Cdx and posterior genes, which might therefore have appeared after the ProtoHox cluster duplication. Consequently, the ProtoHox cluster might have consisted of only two anterior genes. Non-anterior genes could have appeared independently in the Hox and ParaHox clusters, possibly after the separation of bilaterians and cnidarians.