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251.
We present a simple technique for creating an on-chip magnetic particle conveyor based on exchange-biased permalloy microstripes. The particle transportation relies on an array of stripes with a spacing smaller than their width in conjunction with a periodic sequence of four different externally applied magnetic fields. We demonstrate the controlled transportation of a large population of particles over several millimeters of distance as well as the spatial separation of two populations of magnetic particles with different magnetophoretic mobilities. The technique can be used for the controlled selective manipulation and separation of magnetically labelled species.  相似文献   
252.
This study was undertaken to examine the acute effect of interferential current on mechanical pain threshold and isometric peak torque after delayed onset muscle soreness induction in human hamstrings. Forty-one physically active healthy male volunteers aged 18-33 years were randomly assigned to one of two experimental groups: interferential current group (n = 21) or placebo group (n = 20). Both groups performed a bout of 100 isokinetic eccentric maximal voluntary contractions (10 sets of 10 repetitions) at an angular velocity of 1.05 rad · s(-1) (60° · s(-1)) to induce muscle soreness. On the next day, volunteers received either an interferential current or a placebo application. Treatment was applied for 30 minutes (4 kHz frequency; 125 μs pulse duration; 80-150 Hz bursts). Mechanical pain threshold and isometric peak torque were measured at four different time intervals: prior to induction of muscle soreness, immediately following muscle soreness induction, on the next day after muscle soreness induction, and immediately after the interferential current and placebo application. Both groups showed a reduction in isometric torque (P < 0.001) and pain threshold (P < 0.001) after the eccentric exercise. After treatment, only the interferential current group showed a significant increase in pain threshold (P = 0.002) with no changes in isometric torque. The results indicate that interferential current was effective in increasing hamstrings mechanical pain threshold after eccentric exercise, with no effect on isometric peak torque after treatment.  相似文献   
253.
First, the theory of directed graphs (digraphs) was used to map the conceptual structure of the content, implicit in the instructional materials, in the area of electricity at college level. After this, the graphical representation of content structure, thus obtained, was compared with those obtained for the teacher's cognitive structure and the student's cognitive structure through a word association test and the multidimensional scaling technique. Research findings suggest mainly that the techniques used to assess content and cognitive structures might be useful tools for such a purpose.

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254.
Preface     
The International Federation for the Promotion of Mechanism and Machine Science (IFToMM) held the International Symposium on Robotics and Mechatronics (ISRM 2009) as the first in a series of conference events promoting robotics and mechantronics in the Asian IFToMM community. The first event was held in Hanoi University of Technology on Sept.  相似文献   
255.
The present study investigated whether the marked sex difference in the original mental rotation test (MRT) is simply a result of sex differences in response strategies. Thirty-four participants (17 males, 17 females) completed the revised Vandenberg and Kuse MRT [Peters, M., Laeng, B., Latham, K., Jackson, M., Zaiyouna, R., & Richardson, C. (1995). A redrawn Vandenberg & Kuse Mental Rotations Tests: Different versions and factors that affect performance. Brain and Cognition, 28, 39–58.] and a modified MRT. In the modified version, the number of matching figures varied from zero to four, so that participants had to match every single figure to the target, impeding leaps. Both men and women showed reduced performance in the modified version. However, men were clearly more affected than women. Although sex differences in the modified MRT were somewhat reduced, men still outperformed women (original MRT: d = .95, modified MRT: d = .76). The findings suggest that men rely more on a leaping response strategy than women, however, the robust sex differences in MRT was only marginally affected by sex differences in response strategies.  相似文献   
256.
How do intellectual propriety rights (IPRs) help firms profit from their innovation? Innovation literature frequently turns to patents to measure innovative IPR, but more recent work shifts focus to the other side of IPR, namely, trademarks. This article therefore discusses the effects of trademark strategies when companies decide to introduce their product portfolios in a new foreign market. Entrants might opt for a common trademark across different country markets (integration) or use several country-specific trademarks (responsiveness). This empirical study exploits the quasi-natural experiment created by the tariff shock that affected Spain when it joined the European Union in the 1990s. Data from the automotive industry reveal how non-European companies that already operated in other European countries sought to enter Spain rapidly, using various trademark strategies. The product portfolio characteristics are fixed at entry, so this study can specify how and when trademark responsiveness versus integration affects firm performance. The results reveal that trademark responsiveness increases firm performance if the firms suffer high liabilities of foreignness or newness.  相似文献   
257.
This article proposes a process to retrieve the URL of a document for which metadata records exist in a digital library catalog but a pointer to the full text of the document is not available. The process uses results from queries submitted to Web search engines for finding the URL of the corresponding full text or any related material. We present a comprehensive study of this process in different situations by investigating different query strategies applied to three general purpose search engines (Google, Yahoo!, MSN) and two specialized ones (Scholar and CiteSeer), considering five user scenarios. Specifically, we have conducted experiments with metadata records taken from the Brazilian Digital Library of Computing (BDBComp) and The DBLP Computer Science Bibliography (DBLP). We found that Scholar was the most effective search engine for this task in all considered scenarios and that simple strategies for combining and re-ranking results from Scholar and Google significantly improve the retrieval quality. Moreover, we study the influence of the number of query results on the effectiveness of finding missing information as well as the coverage of the proposed scenarios.  相似文献   
258.
Significant changes in state economic priorities are likely to have a formative and fateful effect on institutions of higher education. Yet economic accounts cannot themselves explain changes in the economic priorities of nationalist states, in part because of the ideological character of such states. The nationalist state's influence on institutions of higher education is often indirect, involving the interactions of social and political actors who are themselves influenced by prevailing social ideologies. Social ideologies contribute to shifts in state economic priorities, and these changes can indirectly but significantly influence the trajectory of institutions of higher education. A longitudinal case study of a Canadian distanceeducation university demonstrates the means by which nationalist sentiment encouraged a shift in state economic priorities, which in turn created a welcoming social climate for a new university's consumerist model of education.  相似文献   
259.
The use of a scanning electron microscope equipped with a microanalytical system is proposed for characterising ancient mortars. A calculation procedure is presented that allows a determination of the binder and aggregate compositions (including volatile components) from microprobe data collected on the binder, and chemical, mineralogical, petrographical and physical data collected on the mortar bulk sample. The proposed procedure is applied to 11 mortar samples from three historical monuments built in Pisa throughout the Middle Ages. The binder of the analysed samples consists of a carbonate crystalline fraction and an amorphous carbonate-free fraction that makes up from 20 to 60 % by weight of the binder. The aggregate composition, on average, is close to that of the Arno River sands.  相似文献   
260.
Students' opinions about the opportunities and the implications of VR in instruction were investigated by administering a questionnaire to humanities and engineering undergraduates. The questionnaire invited participants to rate a series of statements concerning motivation and emotion, skills, cognitive styles, benefits and learning outcomes associated with the use of VR in education. The representation which emerged was internally consistent and articulated into specific dimensions. It was not affected by gender, by the previous use of VR software, or by the knowledge of the main topics concerning the introduction of IT in instruction. Also the direct participation in a training session based on an immersive VR experience did not influence such a representation, which was partially modulated by the kind of course attended by students.  相似文献   
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