Palaeoecology: a gigantic fossil arthropod trackway

A unique, complex trackway has been discovered in Scotland: it was made roughly 330 million years ago by a huge, six-legged water scorpion that was about 1.6 m long and a metre wide. To my knowledge, this is not only the largest terrestrial trackway of a walking arthropod to be found so far, but is also the first record of locomotion on land for a species of Hibbertopterus (Eurypterida). This evidence of lumbering movement indicates that these giant arthropods, now extinct, could survive out of water at a time when the earliest tetrapods were making their transition to the land.     

Isolation of an HTLV-III-related retrovirus from macaques with simian AIDS and its possible origin in asymptomatic mangabeys

Acquired immune deficiency syndrome (AIDS) has become a worldwide epidemic, so the development of vaccines and antiviral agents effective against the causative agent, human T-lymphotropic virus type III (HTLV-III), is vital. This work would be greatly simplified if a suitable animal model could be developed. Here we report the isolation of an HTLV-III-related retrovirus, STLV-III/Delta, from rhesus macaques (Macaca mulatta) with transmissible simian AIDS (SAIDS) and from asymptomatic sooty mangabeys (Cercocebus atys). SAIDS was initially diagnosed in several macaques previously inoculated with tissue homogenates of mangabey origin. Western blot analysis of both the mangabey and macaque sera demonstrated the presence of antibody cross-reactive primarily with the HTLV-III proteins p24 and p61. In a related experiment, analysis of these same sera revealed simian antibody to STLV-III/Delta proteins similar, but not identical, to those of HTLV-III with estimated relative molecular masses (Mrs) of 16,000 (16K), 26K, 35K, 45K, 60K and 110K. Infection of the mangabey, an African primate, with an HTLV-III-related virus may provide a clue to the origin of HTLV-III in humans. The apparent difference in susceptibility to SAIDS-like disease between infected macaques and mangabeys suggests that these species may respond differently to STLV-III infection.     

成功智力理论对高校应用型人才培养的启示

介绍了斯腾伯格成功智力理论,并结合我国高等教育的实际探讨该理论对高校应用型人才培养的启示。     

Massive infection and loss of memory CD4+ T cells in multiple tissues during acute SIV infection

It has recently been established that both acute human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections are accompanied by a dramatic and selective loss of memory CD4+ T cells predominantly from the mucosal surfaces. The mechanism underlying this depletion of memory CD4+ T cells (that is, T-helper cells specific to previously encountered pathogens) has not been defined. Using highly sensitive, quantitative polymerase chain reaction together with precise sorting of different subsets of CD4+ T cells in various tissues, we show that this loss is explained by a massive infection of memory CD4+ T cells by the virus. Specifically, 30-60% of CD4+ memory T cells throughout the body are infected by SIV at the peak of infection, and most of these infected cells disappear within four days. Furthermore, our data demonstrate that the depletion of memory CD4+ T cells occurs to a similar extent in all tissues. As a consequence, over one-half of all memory CD4+ T cells in SIV-infected macaques are destroyed directly by viral infection during the acute phase-an insult that certainly heralds subsequent immunodeficiency. Our findings point to the importance of reducing the cell-associated viral load during acute infection through therapeutic or vaccination strategies.     

计算交换代数2

计算交换代数将要成为这个世纪应用到现实世界的最为重要的数学工具之一，随着当今计算技术的飞速发展，采用符号计算的方法处理工业尺度的问题已经成为现实。本书的主要目的是继续为这种发展趋势提供理论基础，深入其中将可以发现与现世界相关的很多线索和暗示。虽然数值方法至今依然占据着统治地位，符号方法被视作数值方法的补充；虽然少数计算机代数系统（包括CoCoA）提供了进行混合计算的可能（例如混合了数值和符号方法），     

Questioning the evidence for Earth's oldest fossils

Structures resembling remarkably preserved bacterial and cyanobacterial microfossils from about 3,465-million-year-old Apex cherts of the Warrawoona Group in Western Australia currently provide the oldest morphological evidence for life on Earth and have been taken to support an early beginning for oxygen-producing photosynthesis. Eleven species of filamentous prokaryote, distinguished by shape and geometry, have been put forward as meeting the criteria required of authentic Archaean microfossils, and contrast with other microfossils dismissed as either unreliable or unreproducible. These structures are nearly a billion years older than putative cyanobacterial biomarkers, genomic arguments for cyanobacteria, an oxygenic atmosphere and any comparably diverse suite of microfossils. Here we report new research on the type and re-collected material, involving mapping, optical and electron microscopy, digital image analysis, micro-Raman spectroscopy and other geochemical techniques. We reinterpret the purported microfossil-like structure as secondary artefacts formed from amorphous graphite within multiple generations of metalliferous hydrothermal vein chert and volcanic glass. Although there is no support for primary biological morphology, a Fischer--Tropsch-type synthesis of carbon compounds and carbon isotopic fractionation is inferred for one of the oldest known hydrothermal systems on Earth.     

A belt of moonlets in Saturn's A ring

The origin and evolution of planetary rings is one of the prominent unsolved problems of planetary sciences, with direct implications for planet-forming processes in pre-planetary disks. The recent detection of four propeller-shaped features in Saturn's A ring proved the presence of large boulder-sized moonlets in the rings. Their existence favours ring creation in a catastrophic disruption of an icy satellite rather than a co-genetic origin with Saturn, because bodies of this size are unlikely to have accreted inside the rings. Here we report the detection of eight new propeller features in an image sequence that covers the complete A ring, indicating embedded moonlets with radii between 30 m and 70 m. We show that the moonlets found are concentrated in a narrow 3,000-km-wide annulus 130,000 km from Saturn. Compared to the main population of ring particles (radius s < 10 m), such embedded moonlets have a short lifetime with respect to meteoroid impacts. Therefore, they are probably the remnants of a shattered ring-moon of Pan size or larger, locally contributing new material to the older ring. This supports the theory of catastrophic ring creation in a collisional cascade.