Induction of cellular senescence in immortalized cells by human chromosome 1

The control of cellular senescence by specific human chromosomes was examined in interspecies cell hybrids between diploid human fibroblasts and an immortal, Syrian hamster cell line. Most such hybrids exhibited a limited life span comparable to that of the human fibroblasts, indicating that cellular senescence is dominant in these hybrids. Karyotypic analyses of the hybrid clones that did not senesce revealed that all these clones had lost both copies of human chromosome 1, whereas all other human chromosomes were observed in at least some of the immortal hybrids. The application of selective pressure for retention of human chromosome 1 to the cell hybrids resulted in an increased percentage of hybrids that senesced. Further, the introduction of a single copy of human chromosome 1 to the hamster cells by microcell fusion caused typical signs of cellular senescence. Transfer of chromosome 11 had no effect on the growth of the cells. These findings indicate that human chromosome 1 may participate in the control of cellular senescence and further support a genetic basis for cellular senescence.     

Atomic and molecular manipulation with the scanning tunneling microscope

The prospect of manipulating matter on the atomic scale has fascinated scientists for decades. This fascination may be motivated by scientific and technological opportunities, or from a curiosity about the consequences of being able to place atoms in a particular location. Advances in scanning tunneling microscopy have made this prospect a reality; single atoms can be placed at selected positions and structures can be built to a particular design atom-by-atom. Atoms and molecules may be manipulated in a variety of ways by using the interactions present in the tunnel junction of a scanning tunneling microscope. Some of these recent developments and some of the possible uses of atomic and molecular manipulation as a tool for science are discussed.     

饲粮中主要谷物与谷物颗粒大小对早期罗曼褐壳蛋鸡生产性能和蛋品质的影响

试验旨在研究饲粮中主要谷物和谷物的几何平均粒径（GMD）对20～48周龄罗曼褐壳蛋鸡生产性能与蛋品质的影响。试验选择960只罗曼褐壳蛋鸡,采用完全随机设计为6×2×3,共分6个处理组．谷物饲粮分别为玉米和小麦,谷物粉碎粒度分别为6、8、10mm。每个处理设8个重复,每个重复20只。所有的饲粮配方设计中包含50％的玉米或小麦。每4周记录生产性能结果,第48周龄时测量蛋品质。试验结果表明,GMD为10mm时鸡采食量显著高于GMD为6和8mm时（P〈0.05）,说明粗糙的谷物粉碎粒度一定程度上有助于提高蛋鸡的采食量,而对蛋品质参数均没有显著影响。可以得出结论,谷物类型与谷物GMD除了影响早期罗曼褐壳蛋鸡采食量随谷物粉碎粒度的增加而增加外,其生产性能和蛋品质指标变化均不显著。     

Dissemination of precision farming in Germany: acceptance, adoption, obstacles, knowledge transfer and training activities

The adoption of precision farming (PF) was studied on the basis of personal interviews conducted at several agricultural exhibitions in Germany. Between 6.65% and 11% of the interviewed farmers used PF. The majority used data collection techniques such as GPS-based area measurement and soil sampling rather than variable rate application techniques such as site-specific sowing and fertilising. Roughly half the farmers interviewed knew about PF. About 7–10% of them intended to start using PF in the future. The results indicated that a large number of farmers did not even know what PF meant. In order to get more insight into this situation, several interviews were conducted with farmers already using PF techniques. A further study in 2005 of PF education in Germany indicated that, especially at vocational and technical schools, the subject was only covered to a small extent although the aim was to give a better coverage in future. At higher education levels, such as at universities and technical colleges, the teaching of PF was clearly better established. In order to promote awareness of PF among farmers, information and teaching materials adapted to the relevant educational levels were developed and tried out at training events. The main topics addressed were parallel tracking systems, site-specific nitrogen fertilising, yield mapping in grain production and the use of PDAs in crop farming. Finally, preliminary survey results are presented showing how knowledge about PF can best lead to its adoption and transfer into daily practice.     

Radar images of Mars

Full disk images of Mars have been obtained with the use of the Very Large Array (VLA) to map the radar reflected flux density. The transmitter system was the 70-m antenna of the Deep Space Network at Goldstone, California. The surface of Mars was illuminated with continuous wave radiation at a wavelength of 3,5 cm. The reflected energy was mapped in individual 12-minute snapshots with the VLA in its largest configuration; fringe spacings as small as 67 km were obtained. The images reveal near-surface features including a region in the Tharsis volcano area, over 2000 km in east-west extent, that displayed no echo to the very low level of the radar system noise. The feature, called Stealth, is interpreted as a deposit of dust or ash with a density less than about 0.5 gram per cubic centimeter and free of rocks larger than 1 cm across. The deposit must be several meters thick and may be much deeper. The strongest reflecting geological feature was the south polar ice cap, which was reduced in size to the residual south polar ice cap at the season of observation. The cap image is interpreted as arising from nearly pure CO(2) or H(2)O ice with a small amount of martian dust (less than 2 percent by volume) and a depth greater than 2 to 5 m. Only one anomalous reflecting feature was identified outside of the Tharsis region, although the Elysium region was poorly sampled in this experiment and the north pole was not visible from Earth.     

The future of terrace farming in Yemen: A development dilemma

The country of Yemen, on the southwestern corner of the Arabian Peninsula, is one of the most extensively terraced areas in the world. There is a well-documented tradition of both dryland and irrigated farming over the past three millennia and much of the indigenous agricultural knowledge survives. Development efforts over the past two decades in the north of Yemen have focused on expansion of tubewell irrigation at the expense of the major land use on dryland terraces and traditional subsistence crops. Despite millions of dollars in aid, Yemen is far from agriculturally self-sufficient and its scarce water resource is rapidly being depleted. This articles explores the relevance of indigenous Yemeni knowledge of agriculture and the environment for the future of terrace farming in the country. It is argued that farmer knowledge can contribute to sustainable production and can be grafted on to modern methods and technology. Within Yemen the existing community support networks and pride in national heritage would assist in a reinvestment effort for the existing resource of the terraces.     

Interwoven metal-organic framework on a periodic minimal surface with extra-large pores

Interpenetration (catenation) has long been considered a major impediment in the achievement of stable and porous crystalline structures. A strategy for the design of highly porous and structurally stable networks makes use of metal-organic building blocks that can be assembled on a triply periodic P-minimal geometric surface to produce structures that are interpenetrating-more accurately considered as interwoven. We used 4,4',4"-benzene-1,3,5-triyl-tribenzoic acid (H(3)BTB), copper(II) nitrate, and N,N'-dimethylformamide (DMF) to prepare Cu(3)(BTB)(2)(H(2)O)(3).(DMF)(9)(H(2)O)(2) (MOF-14), whose structure reveals a pair of interwoven metal-organic frameworks that are mutually reinforced. The structure contains remarkably large pores, 16.4 angstroms in diameter, in which voluminous amounts of gases and organic solvents can be reversibly sorbed.     

A cortical area selective for visual processing of the human body

Despite extensive evidence for regions of human visual cortex that respond selectively to faces, few studies have considered the cortical representation of the appearance of the rest of the human body. We present a series of functional magnetic resonance imaging (fMRI) studies revealing substantial evidence for a distinct cortical region in humans that responds selectively to images of the human body, as compared with a wide range of control stimuli. This region was found in the lateral occipitotemporal cortex in all subjects tested and apparently reflects a specialized neural system for the visual perception of the human body.