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P. D. Anoop 《Resonance》2011,16(1):29-37
This article deals with the timekeepers of the past, the sundials. Apart from discussing the structure of a few common sundials,
we point out the reasons for the variation between sundial time and the time shown by mechanical timekeepers. 相似文献
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Giraud G Pethig R Schulze H Henihan G Terry JG Menachery A Ciani I Corrigan D Campbell CJ Mount AR Ghazal P Walton AJ Crain J Bachmann TT 《Biomicrofluidics》2011,5(2):24116
The manipulation of ribosomal RNA (rRNA) extracted from E. coli cells by dielectrophoresis (DEP) has been demonstrated over the range of 3 kHz-50 MHz using interdigitated microelectrodes. Quantitative measurement using total internal reflection fluorescence microscopy of the time dependent collection indicated a positive DEP response characterized by a plateau between 3 kHz and 1 MHz followed by a decrease in response at higher frequencies. Negative DEP was observed above 9 MHz. The positive DEP response below 1 MHz is described by the Clausius-Mossotti model and corresponds to an induced dipole moment of 3300 D with a polarizability of 7.8×10(-32) F m(2). The negative DEP response above 9 MHz indicates that the rRNA molecules exhibit a net moment of -250 D, to give an effective permittivity value of 78.5 ε(0), close to that of the aqueous suspending medium, and a relatively small surface conductance value of ～0.1 nS. This suggests that our rRNA samples have a fairly open structure accessible to the surrounding water molecules, with counterions strongly bound to the charged phosphate groups in the rRNA backbone. These results are the first demonstration of DEP for fast capture and release of rRNA units, opening new opportunities for rRNA-based biosensing devices. 相似文献
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This paper studies collective formations of multi-agent systems, modeled with unicycle dynamics, while admitting heterogeneity in both controller gains and speeds of the agents along with saturation on the controller outputs. This addresses a practical scenario where the speeds are usually nonidentical and the controller gains may vary due to imperfect implementation. The paper analyzes the effect of both heterogeneous controller gains and speeds simultaneously on the collective formations obtained by optimizing the average linear momentum of the group of agents. A detailed analysis of the two-agent system is given in the paper and some results on the locus of the collective centroid with varying controller gains are obtained. Effect of saturation is also studied for two cases when the controller gains are bounded and when the control efforts are bounded. Simulation examples are given to illustrate the theoretical findings. 相似文献
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Adding to the literature on the recognition and spread of ideas, and alongside the bias against novelty view documented in prior research, we introduce the perspective that articles compete for the attention of researchers who might build upon them. We investigate this effect by analyzing more than 5.3 million research publications from 1970 to 1999 in the life sciences. In support of our competition for attention perspective, we show that articles covering rarely addressed topics tend to receive more citations and have a higher chance of being breakthrough papers as compared to articles on more popular topics. We also explore conditions under which these effects might vary by using decade subsamples, home- versus foreign-field forward citations, as well as short-, medium- and long-term time windows. Finally, we also find evidence consistent with the previously documented bias against novelty and show that both mechanisms can work simultaneously. 相似文献
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Bruce Carrington Alastair Bonnett Anoop Nayak Christine Skelton Fay Smith Richard Tomlin 《International Studies in Sociology of Education》2013,23(1):3-22
This article reports on part of a larger, ongoing two-year investigation supported by the Teacher Training Agency into the recruitment of new teachers from minority ethnic backgrounds via Postgraduate Certificate in Education (PGCE) courses in England. The authors focus here on interviews with admissions tutors, course directors and other senior staff at teacher training institutions. The interviews revealed differences between institutions in the measures taken to attract minority ethnic students. The research indicates a need for much clearer guidelines for admissions tutors on the issues surrounding the question of 'positive action' on the recruitment of new teachers from minority ethnic groups. 相似文献
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ABSTRACT This article will focus upon the role of humour in the cultures of young men in school. We adopt an ethnographic approach to illustrate the variety of these interactions which can include forms of game-play, mythic storytelling and ritual insults. Our analysis suggests that humorous exchanges are constitutive of heterosexual masculine identities. We argue that humour is a technique utilised for the regulation of masculinities and the negotiation of gender-sexual hierarchies within pupil cultures. Bodily practices were prevalent in the interchanges, playing a part in the contestation and production of differentiated heterosexualities. Humour was an organising principle, deployed to position pupils within differing dominant and subordinate peer group sexual cultures. The paper focuses on conformist aspects of humour and recognises the oppressive dynamics articulated in these exchanges. Finally, we consider the implications of these practices for contemporary working-class masculinity. 相似文献
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