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A method of measuring a library's capability for providing the documents its users need has been developed. The library is tested with a representative sample of such documents to determine how long would be required for users to obtain these documents. Test results are expressed in terms of a Capability Index, which has a maximal value of 100 only if all the sample documents are found "on shelf." Specific tests employing samples of 300 documents have been developed that are appropriate for academic and for "reservoir" biomedical libraries. Realistic field trials have demonstrated that these two tests are practical to administer and that test results are adequately reproducible. When strict comparability is not important, a library can test itself. In assessing a reservoir library, test results are supplemented by data on its typical processing time for interlibrary loan requests. Currently these tests are being used in a national survey. The general method is applicable to other types of libraries, provided appropriate test samples are established. If their limitations are clearly understood, these "Document Delivery Tests" can be valuable tools for planning and managing library services.  相似文献   
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A treatment group of three sections of a college art design class was given instruction that included the use of computers to complete design projects. The art design course covers the basic concepts of design and two-dimensional materials and the use of line, colour, illusion of space or mass, texture, value, shape, and size in composition. A control group of three sections completed the same assignments as the treatment group without computers. Both groups of students were then surveyed about their attitudes toward using computers in the course. Both the treatment group and the control group perceived the use of computers in a basic art design class as worthwhile. Both groups perceived the use of computers in a basic art design class as enhancing instruction. The treatment group had a more positive response to the computer as a design tool than did the control group. Survey responses by the treatment group documented that design projects used in the study needed improvement. Further studies should focus on best practices in the use of computers in art education.  相似文献   
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The mechanical behavior of cells offers insight into many aspects of their properties. We propose an approach to the mechanical analysis of cells that uses a combination of electromanipulation for stimulus and capacitance for sensing. To demonstrate this approach, polystyrene spheres and yeast cells flowing in a 25 μm×100 μm microfluidic channel were detected by a perpendicular pair of gold thin film electrodes in the channel, spaced 25 μm apart. The presence of cells was detected by capacitance changes between the gold electrodes. The capacitance sensor was a resonant coaxial radio frequency cavity (2.3 GHz) coupled to the electrodes. The presence of yeast cells (Saccharomyces cerevisiae) and polystyrene spheres resulted in capacitance changes of approximately 10 and 100 attoFarad (aF), respectively, with an achieved capacitance resolution of less than 2 aF in a 30 Hz bandwidth. The resolution is better than previously reported in the literature, and the capacitance changes are in agreement with values estimated by finite element simulations. Yeast cells were trapped using dielectrophoretic forces by applying a 3 V signal at 1 MHz between the electrodes. After trapping, the cells were displaced using amplitude and frequency modulated voltages to produce modulated dielectrophoretic forces. Repetitive displacement and relaxation of these cells was observed using both capacitance and video microscopy.  相似文献   
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