时间反转声响效应

换能器阵列能再现声音并将其发射回声源，就宛如时间被反转一般。此声学过程可用于粉碎肾结石、材料探伤及与潜艇通信。     

A semester-long project for teaching basic techniques in molecular biology such as restriction fragment length polymorphism analysis to undergraduate and graduate students

Several reports on science education suggest that students at all levels learn better if they are immersed in a project that is long term, yielding results that require analysis and interpretation. I describe a 12-wk laboratory project suitable for upper-level undergraduates and first-year graduate students, in which the students molecularly locate and map a gene from Drosophila melanogaster called dusky and one of dusky's mutant alleles. The mapping strategy uses restriction fragment length polymorphism analysis; hence, students perform most of the basic techniques of molecular biology (DNA isolation, restriction enzyme digestion and mapping, plasmid vector subcloning, agarose and polyacrylamide gel electrophoresis, DNA labeling, and Southern hybridization) toward the single goal of characterizing dusky and the mutant allele dusky(73). Students work as individuals, pairs, or in groups of up to four students. Some exercises require multitasking and collaboration between groups. Finally, results from everyone in the class are required for the final analysis. Results of pre- and postquizzes and surveys indicate that student knowledge of appropriate topics and skills increased significantly, students felt more confident in the laboratory, and students found the laboratory project interesting and challenging. Former students report that the lab was useful in their careers.     

Timing is everything: the demarcation of 'later' abortions in Scotland

Feminist STS analyses of contemporary reproductive medicine have illustrated the proliferation of practices that position fetuses as individual subjects, and have highlighted the major implications of such practices for pregnant women. In an attempt to challenge medicine's claims to 'know' the fetus, this body of literature has also demonstrated the renegotiable basis of pregnant/fetal subjectivity, using detailed empirical analyses of the practices through which particular pregnant and fetal subjects emerge in particular contexts. In this paper I contribute to this endeavour utilizing an empirical case study of an important, but neglected aspect of reproductive healthcare: the demarcation of temporal thresholds on abortion provision in the absence of diagnosed fetal abnormality. Drawing on semi-structured interviews with Scottish health professionals, I explore the discursive practices through which they demarcate 'later' abortion as a problematic decision. I argue that such practices are intimately dependent on particular co-constructions of temporality and pregnant/fetal subjectivity, and support this argument with reference to the counter-representations of the gestational timing of abortion that emerge from a minority of health professionals' accounts. I suggest that, collectively, this body of data illustrates the opportunities that (re)presenting temporality would afford those engaged in attempts to foster the construction of less oppressive pregnant/fetal subjectivities. My broader aim is to illustrate the insights that feminist theorizations of pregnant/fetal subjectivity gain from explicit engagement with another important theme of contemporary STS scholarship, namely, the constitutive role played by representations of temporality in technoscientific innovation and practice.     

Errors in the estimation of hydration status from changes in body mass

Hydration status is not easily measured, but acute changes in hydration status are often estimated from body mass change. Changes in body mass are also often used as a proxy measure for sweat losses. There are, however, several sources of error that may give rise to misleading results, and our aim in this paper is to quantify these potential errors. Respiratory water losses can be substantial during hard work in dry environments. Mass loss also results from substrate oxidation, but this generates water of oxidation which is added to the body water pool, thus dissociating changes in body mass and hydration status: fat oxidation actually results in a net gain in body mass as the mass of carbon dioxide generated is less than the mass of oxygen consumed. Water stored with muscle glycogen is presumed to be made available as endogenous carbohydrate stores are oxidized. Fluid ingestion and sweat loss complicate the picture by altering body water distribution. Loss of hypotonic sweat results in increased osmolality of body fluids. Urine and faecal losses can be measured easily, but changes in the water content of the bladder and the gastrointestinal tract cannot. Body mass change is not always a reliable measure of changes in hydration status and substantial loss of mass may occur without an effective net negative fluid balance.     

Leucine125Valine (Leu125Val) Gene Polymorphism of Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1) and Myocardial Infarction in Indian Population

Platelet-endothelial cell adhesion molecule-1 (PECAM-1) has role in atherosclerotic plaque development as well as in thrombosis leading to myocardial infarction (MI). Present study was aimed to analyse the association of PECAM-1 Leu125Val gene polymorphism with MI in Indian population. Subjects included healthy individuals as control (N = 116) and MI patients (N = 100) divided into two groups; MI patients at presentation of the acute event (MI-Group-1, N = 46) and patients with recent event of MI stabilized with treatment 4.5 days from their symptoms (MI-Group-2, N = 54). The difference in the distribution of Leu125Val genotype frequencies of controls and patients did not reach statistical significance. However Leu allele frequency (0.57) was more associated with MI patients as compared to control (0.504). sPECAM-1 levels were significantly elevated in patients at acute event of MI (MI-Group-1) by 44.1% (P = 0.009) as compared to controls and by 95.2% (P = 0.001) as compared to stabilized MI patients (MI-Group-2).     

Uniform yeast cell assembly via microfluidics

This paper reports the use of microfluidic approaches for the fabrication of yeastosomes (yeast-celloidosomes) based on self-assembly of yeast cells onto liquid-solid or liquid-gas interfaces. Precise control over fluidic flows in droplet- and bubble-forming microfluidic devices allows production of monodispersed, size-selected templates. The general strategy to organize and assemble living cells is to tune electrostatic attractions between the template (gel or gas core) and the cells via surface charging. Layer-by-Layer (LbL) polyelectrolyte deposition was employed to invert or enhance charges of solid surfaces. We demonstrated the ability to produce high-quality, monolayer-shelled yeastosome structures under proper conditions when sufficient electrostatic driving forces are present. The combination of microfluidic fabrication with cell self-assembly enables a versatile platform for designing synthetic hierarchy bio-structures.     

网络是无法管理的

现在，竭力改进域名系统的工作已进入第三个年头的重要阶段——交出域名系统将是美国政府从网络管理中脱身的计划的最后一步。看来还是在几年前就宣称因特网实际上无法管理的那些网络狂热者说得对。     

通灵的漂移

19世纪上半叶,进化论陷入了猜测的泥潭。这种情况一直持续到达尔文和华莱士整理出一个证据体系并提出自然选择这一进化驱动机制为止。