A vital stain for the Golgi apparatus

The Golgi complex, a membranous organelle with important functions in membrane traffic and macromolecular synthesis, has been stained in living cells with a fluorescent sphingolipid. Cells were first incubated with liposomes containing N-[7-(4-nitrobenzo-2-oxa-1,3-diazole)]-6-aminocaproyl sphingosine (C6-NBD-ceramide), or with a bovine serum albumin complex of the fluorescent lipid, and then examined by fluorescence microscopy. An intensely fluorescent perinuclear structure was identified as the Golgi apparatus by its colocalization with known Golgi markers in fixed cells. C6-NBD-ceramide was used to observe the morphology of the Golgi apparatus in living cells in the presence or absence of monensin or Colcemid, and during mitosis. In all cases, C6-NBD-ceramide revealed a Golgi apparatus in the living cell that was identical to that obtained with conventional procedures that require fixation.     

Defects in semiconductors: some fatal, some vital

REVIEW The role of defects as essential entities in semiconductor materials is reviewed. Early experiments with semiconductors were hampered by the extreme sensitivity of the electronic properties to minute concentrations of impurities. Semiconductors were viewed as a family of solids with irreproducible properties. Scientific efforts overcame this idiosyncrasy and turned the art of impurity doping into today's exceedingly useful and reproducible technology that is used to control precisely electrical conductivity, composition, and minority-carrier lifetimes over wide ranges. Native defects such as vacancies and self-interstitials control basic processes, foremost self- and dopant diffusion. The structural properties of dislocations and higher dimensional defects have been studied with atomic resolution, but a thorough theoretical understanding of their electronic properties is incomplete. Reactions between defects within the host lattices are increasingly better understood and are used for gettering and electrical passivation of unwanted impurities. Metastable defects such as DX centers and the EL2-related arsenic antisite are briefly discussed. The recent development of isotopically controlled semiconductors has created new research opportunities in this field.     

Silenced voices,vital arguments: smallholder farmers in the Mexican GM maize controversy

Smallholder producers are the collective most likely to be affected by the introduction of GMOs globally, yet the least included in public debates and consultation about the development, implementation or regulation of this agricultural biotechnology. Why are the voices and arguments of smallholder farmers being excluded from national and international GM debates and regulation? In this article, we identify barriers which prevent smallholder farmers in Mexico from having a voice in public political, economic, scientific and social fori regarding the GM maize controversy. Through the analysis of empirical data from a case study in Mexico, we identify political, institutional, economic and ontological reasons that lie behind that exclusion. We conclude with an appraisal of smallholder farmers’ perspectives on GM maize and their visions of Mexico’s rural future, within which they demand a meaningful and rightful space.     

鱼类生物能量学及鳗鲡相关研究进展

鱼类生物能量学是研究能量在鱼体内转换的学科。介绍了鱼类能量收支的基本理论、主要方法、能量收支模型以及各种生态因子对鱼类能量收支的影响,并对鳗鲡生物能量学的研究现状进行了概述,分析了当前鳗鲡养殖业的现状,对鱼类生物能量学在鳗鲡养殖方面的应用作出了展望。     

温度和体重对养殖大黄鱼能量收支的影响

主要分4个温度级、5个体重级研究了温度和体重对养殖大黄鱼能量收支的影响。结果表明,大黄鱼的代谢能（R）及排泄能（U）与温度成指数关系,关系式分别为R=107e^0.0288T,U=38.6e^0.0171（T15℃≤T≤30℃）;大黄鱼代谢能和排泄能与体重呈负相关的幂指数关系,关系式分别为R=228W^-0.150,U=61.5W^-0.199,均符合Y=aW^b模式。温度和体重对代谢能（R）和排粪能（F）所占摄食能（C）比例均有显著差异（P〈0.05）,生长能（G）所占比例随着温度上升和体重增加而有所下降。     

DNA: a programmable force sensor

Direct quantification of biomolecular interaction by single-molecule force spectroscopy has evolved into a powerful tool for materials and life sciences. We introduce an approach in which the unbinding forces required to break intermolecular bonds are measured in a differential format by comparison with a known reference bond (here, a short DNA duplex). In addition to a marked increase in sensitivity and force resolution, which enabled us to resolve single-base pair mismatches, this concept allows for highly specific parallel assays. This option was exploited to overcome cross-reactions of antibodies in a protein biochip application.     

Molecular origins of friction: the force on adsorbed layers

Simulations and perturbation theory are used to study the molecular origins of friction in an ideal model system, a layer of adsorbed molecules sliding over a substrate. These calculations reproduce several surprising features of experimental results. In most cases, the frictional force on a solid monolayer has a different form from that observed between macroscopic solids. No threshold force or static friction is needed to initiate sliding; instead, the velocity is proportional to the force. As in experiments, incommensurate solid layers actually slide more readily than fluid layers. A comparison of experiment, simulation, and analytic results shows that dissipation arises from anharmonic coupling between phonon modes and substrate-induced deformations in the adsorbate.