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991.
Recent years have witnessed a strong trend towards analysis of single-cells. To access and handle single-cells, many new tools are needed and have partly been developed. Here, we present an improved version of a single-cell printer which is able to deliver individual single cells and beads encapsulated in free-flying picoliter droplets at a single-bead efficiency of 96% and with a throughput of more than 10 beads per minute. By integration of acoustophoretic focusing, the cells could be focused in x and y direction. This way, the cells were lined-up in front of a 40 μm nozzle, where they were analyzed individually by an optical system prior to printing. In agreement with acoustic simulations, the focusing of 10 μm beads and Raji cells has been achieved with an efficiency of 99% (beads) and 86% (Raji cells) to a 40 μm wide center region in the 1 mm wide microfluidic channel. This enabled improved optical analysis and reduced bead losses. The loss of beads that ended up in the waste (because printing them as single beads arrangements could not be ensured) was reduced from 52% ± 6% to 28% ± 1%. The piezoelectric transducer employed for cell focusing could be positioned on an outer part of the device, which proves the acoustophoretic focusing to be versatile and adaptable. 相似文献
992.
C. I. Jhala U. V. Shah T. K. Shah B. K. Naik J. D. Dafda 《Indian journal of clinical biochemistry : IJCB》1998,13(1):1-7
Fasting samples of 1329 apparently healthy vegetarian Gujarati population were tested for total cholesterol, triglycerides
and three major fractions of lipoproteins, i.e. high density lipoproteins, low density lipoproteins and very low density lipoproteins.
All the values showed marked increase with the age. Except for serum triglycerides, values differ in males and females in
the age group of above 45 years. Compared to Northern Indian population low density lipoprotein and high density lipoprotein
values were higher, but values of triglycerides and very low density lipoproteins were lower. There is no significant difference
in total cholesterol values. Compared to Southern Indian population low density lipoprotein and very low density lipoprotein
values were higher but values of triglycerides, total cholesterol and high density lipoprotein were lower. All serum lipid
values were significantly lower than the Westem population. The range of values for both the sexes is presented for different
age groups. 相似文献
993.
E.J. Malecki 《Research Policy》1980,9(1):2-22
R&D activities in the United States, as in other advanced economies, are geographically concentrated in certain types of locations. This study presents data on the location of four dimensions of R&D in the U.S.: industrial R&D laboratories, scientists and engineers engaged in R&D, scientists and engineers employed by the federal government, and research universities. Industrial R&D is much more concentrated in large urban areas than the other dimensions, and appears to locate more in response to the location of manufacturing activity than to the location of research universities and federal research facilities. The location of R&D employment, which includes government university, and industrial employees, is associated with facilities for all three types of R&D. Because of these factors, R&D in the U.S. is found on a significant per capita basis in 44 of 177 urban areas, most of them in the northeastern portion of the country. When two dimensions, industrial R&D laboratories and R&D employees, are combined as a measure of R&D concentration, the locational pattern is less clustered regionally. Ten urban areas in all regions of the U.S. are identified as important complexes of R&D. Since the location of R&D is a major indicator of comparative advantage for technological activities and the economic potential of urban regions, only a few areas of the U.S. are likely to remain important in the generation of innovations. 相似文献
994.
995.
Luciano Floridi argues that every existing entity is deserving of at least minimal moral respect in virtue of having intrinsic value qua information object. In this essay, I attempt a comprehensive assessment of this important view as well as the arguments Floridi offers in support of it. I conclude both that the arguments are insufficient and that the thesis itself is substantively implausible from the standpoint of ordinary intuitions. 相似文献
996.
In this paper, a detailed numerical and experimental investigation into the optimisation of hydrodynamic micro-trapping arrays for high-throughput capture of single polystyrene (PS) microparticles and three different types of live cells at trapping times of 30 min or less is described. Four different trap geometries (triangular, square, conical, and elliptical) were investigated within three different device generations, in which device architecture, channel geometry, inter-trap spacing, trap size, and trap density were varied. Numerical simulation confirmed that (1) the calculated device dimensions permitted partitioned flow between the main channel and the trap channel, and further, preferential flow through the trap channel in the absence of any obstruction; (2) different trap shapes, all having the same dimensional parameters in terms of depth, trapping channel lengths and widths, main channel lengths and widths, produce contrasting streamline plots and that the interaction of the fluid with the different geometries can produce areas of stagnated flow or distorted field lines; and (3) that once trapped, any motion of the trapped particle or cell or a shift in its configuration within the trap can result in significant increases in pressures on the cell surface and variations in the shear stress distribution across the cell’s surface. Numerical outcomes were then validated experimentally in terms of the impact of these variations in device design elements on the percent occupancy of the trapping array (with one or more particles or cells) within these targeted short timeframes. Limitations on obtaining high trap occupancies in the devices were shown to be primarily a result of particle aggregation, channel clogging and the trap aperture size. These limitations could be overcome somewhat by optimisation of these device design elements and other operational variables, such as the average carrier fluid velocity. For example, for the 20 μm polystyrene microparticles, the number of filled traps increased from 32% to 42% during 5–10 min experiments in devices with smaller apertures. Similarly, a 40%–60% reduction in trapping channel size resulted in an increase in the amount of filled traps, from 0% to almost 90% in 10 min, for the human bone marrow derived mesenchymal stem cells, and 15%–85% in 15 min for the human embryonic stem cells. Last, a reduction of the average carrier fluid velocity by 50% resulted in an increase from 80% to 92% occupancy of single algae cells in traps. Interestingly, changes in the physical properties of the species being trapped also had a substantial impact, as regardless of the trap shape, higher percent occupancies were observed with cells compared to single PS microparticles in the same device, even though they are of approximately the same size. This investigation showed that in microfluidic single cell capture arrays, the trap shape that maximizes cell viability is not necessarily the most efficient for high-speed single cell capture. However, high-speed trapping configurations for delicate mammalian cells are possible but must be optimised for each cell type and designed principally in accordance with the trap size to cell size ratio. 相似文献
997.
This is a historical study of organizational change projects based on documents as the primary data source. It covers a period of 15 years (1985–2000) at an offshore construction yard. The study shows that change agents created links between new and former projects when they prepared, introduced, and motivated employees for ‘yet another’ change project, a process coined as ‘institutional bridging.’ The bridges served both as legitimation of the new project and as a means to carry forward practices, values, and knowledge. For practicing managers and change agents, this finding implies that disruptive change may be avoided if one succeeds in building bridges between sequential change projects. Then planned change may serve both as carriers and as creators of organizational knowledge. Theoretically, the study contributes to the discussion of organizational carriers and how organizations continue and develop identity in contexts characterized by uncertainty and change. 相似文献
998.
Patrick J. Wolf 《Peabody Journal of Education》2013,88(4):690-702
Media reports are rife with claims that students in the United States are overtested and that they and their education are suffering as result. Here I argue the opposite—that students would benefit in numerous ways from more frequent assessment, especially of diagnostic testing. The regular assessment of students serves critical educational and life-learning functions. It focuses the efforts of educators and students on mastering important material. Testing provides educators with crucial intelligence about the needs and abilities of students and the performance of academic programs. Regular assessment provides students and parents with useful feedback regarding how well the student is building important skills and knowledge. It allows both parents and educators to identify motivational and learning problems with individual students at an early stage, when interventions have the greatest prospects for success. It is especially important in the areas of early reading acquisition and special education, supposedly “sensitive” areas where educators often eschew regular assessment. Finally, standardized testing provides students with an important skill—test-taking experience and facility—that will serve them well throughout their lives. A wealth of evidence confirms that testing alone boosts student achievement. 相似文献
999.
Checking both sides of an equation to make sure the units are right is something we tend to do as a matter of course (or should!). But as this article will try and illustrate, there is more to this routine procedure than meets the eye. 相似文献
1000.
A near‐peer (NP) teacher discussing structures of the head and neck region with first‐ and second‐year students in the anatomy laboratory at Brighton and Sussex Medical School. NP teachers are fourth‐year medical students who elect to teach in gross anatomy practical classes delivered to first‐ and second‐year medical students. Evans and Cuffe discuss design, implementation and outcomes of the NP teaching program in the current issue of ASE. 相似文献