Disrupting the wall accumulation of human sperm cells by artificial corrugation     

H. A. Guidobaldi  Y. Jeyaram  C. A. Condat  M. Oviedo  I. Berdakin  V. V. Moshchalkov  L. C. Giojalas  A. V. Silhanek  V. I. Marconi 《Biomicrofluidics》2015,9(2)

Many self-propelled microorganisms are attracted to surfaces. This makes their dynamics in restricted geometries very different from that observed in the bulk. Swimming along walls is beneficial for directing and sorting cells, but may be detrimental if homogeneous populations are desired, such as in counting microchambers. In this work, we characterize the motion of human sperm cells ∼60 μm long, strongly confined to ∼25 μm shallow chambers. We investigate the nature of the cell trajectories between the confining surfaces and their accumulation near the borders. Observed cell trajectories are composed of a succession of quasi-circular and quasi-linear segments. This suggests that the cells follow a path of intermittent trappings near the top and bottom surfaces separated by stretches of quasi-free motion in between the two surfaces, as confirmed by depth resolved confocal microscopy studies. We show that the introduction of artificial petal-shaped corrugation in the lateral boundaries removes the tendency of cells to accumulate near the borders, an effect which we hypothesize may be valuable for microfluidic applications in biomedicine.  相似文献   

Physical activity patterns of ethnic children from low socio-economic environments within the UK     

Emma Lisa Jane Eyre  Michael Joseph Duncan  Samantha Louise Birch  Valerie Cox  Matthew Blackett 《Journal of sports sciences》2015,33(3):232-242

Many children fail to meet physical activity (PA) guidelines for health benefits. PA behaviours are complex and depend on numerous interrelated factors. The study aims to develop current understanding of how children from low Socio-economic environments within the UK use their surrounding built environments for PA by using advanced technology. The environment was assessed in 96 school children (7–9 years) using global positioning system (GPS) monitoring (Garmin Forerunner, 305). In a subsample of 46 children, the environment and PA were assessed using an integrated GPS and heart rate monitor. The percentage of time spent indoor, outdoor, in green and non-green environments along with time spent in moderate-to-vigorous PA (MVPA) in indoor and outdoor environments were assessed. A 2-by-2 repeated measures analysis of covariance, controlling for body mass index, BF%, assessed the environmental differences. The findings show that 42% of children from deprived wards of Coventry fail to meet PA guidelines, of which 43% was accumulated during school. Children engaged in more MVPA outdoor than indoor environments (P < 0.01) and a greater amount of time was spent in non-green environments (P < 0.01). Increased time outdoors was negatively associated with BF%. In conclusion, outdoor environments are important for health-enhancing PA and reducing fatness in deprived and ethnic children.  相似文献   

Reliability and validity of a talent identification test battery for seated and standing Paralympic throws     

Jemima Grace Spathis  Mark James Connick  Emma Maree Beckman  Peter Anthony Newcombe  Sean Michael Tweedy 《Journal of sports sciences》2015,33(8):863-871

Paralympic throwing events for athletes with physical impairments comprise seated and standing javelin, shot put, discus and seated club throwing. Identification of talented throwers would enable prediction of future success and promote participation; however, a valid and reliable talent identification battery for Paralympic throwing has not been reported. This study evaluates the reliability and validity of a talent identification battery for Paralympic throws. Participants were non-disabled so that impairment would not confound analyses, and results would provide an indication of normative performance. Twenty-eight non-disabled participants (13 M; 15 F) aged 23.6 years (±5.44) performed five kinematically distinct criterion throws (three seated, two standing) and nine talent identification tests (three anthropometric, six motor); 23 were tested a second time to evaluate test–retest reliability. Talent identification test–retest reliability was evaluated using Intra-class Correlation Coefficient (ICC) and Bland–Altman plots (Limits of Agreement). Spearman’s correlation assessed strength of association between criterion throws and talent identification tests. Reliability was generally acceptable (mean ICC = 0.89), but two seated talent identification tests require more extensive familiarisation. Correlation strength (mean r_s = 0.76) indicated that the talent identification tests can be used to validly identify individuals with competitively advantageous attributes for each of the five kinematically distinct throwing activities. Results facilitate further research in this understudied area.  相似文献   

Increasing plantarflexion angle during landing reduces vertical ground reaction forces,loading rates and the hip’s contribution to support moment within participants     

K. Michael Rowley  James G. Richards 《Journal of sports sciences》2015,33(18):1922-1931

The ankle joint’s role in shock absorption during landing has been researched in many studies, which have found that landing with higher amounts of plantarflexion (PF) results in lower peak vertical ground reaction forces and loading rates. However, there has not yet been a study that compares drop landings within participants along a quantitative continuum of PF angles. Using a custom-written real-time feedback program, participants adjusted their ankles to an instructed PF angle and dropped onto two force platforms. For increasing PF, peak ground reaction force and peak loading rate during weight acceptance decreased significantly. The hip’s contribution to peak support moment decreased as PF at initial contact increased up to 30°. The ankle and knee contributions increased over this same continuum of PF angles. There appears to be no optimal PF angle based on peak ground reaction force and loading rate measurements, but there may be an optimum where joint contributions to peak support moment converge and the hip moment’s contribution is minimised.  相似文献   

Filling the Information Gap: Radio Free Europe–Radio Liberty and the Politics of Accreditation at the 1984 Los Angeles Olympic Games     

Toby C. Rider 《国际体育史杂志》2015,32(1):37-52

Due to the decision of the Soviet Union and nearly all of its East European satellites to withdraw from the 1984 Los Angeles Summer Games, the communist media provided audiences in the Soviet bloc with few reports on the sporting events in the Olympic city. When Radio Free Europe and Radio Liberty, broadcasters funded by the US government, attempted to fill this ‘information gap’ by beaming coverage of the Los Angeles Games behind the Iron Curtain, the Soviet Union protested to the International Olympic Committee. They claimed, with a mixture of fact and fiction, that the Radios were tools of the American intelligence establishment and accused them of broadcasting ‘subversive’ propaganda to Eastern Europe and the USSR. Stirred into action by this Soviet manoeuvre, leading spokesmen for the Radios were joined by government officials, private citizens, US Olympic Committee members and the American media in a concerted attempt not only to defend the work of the broadcasters, but also to secure their press accreditation for Los Angeles.  相似文献   

Core-shell hydrogel beads with extracellular matrix for tumor spheroid formation     

L. Yu  S. M. Grist  S. S. Nasseri  E. Cheng  Y.-C. E. Hwang  C. Ni  K. C. Cheung 《Biomicrofluidics》2015,9(2)

Creating multicellular tumor spheroids is critical for characterizing anticancer treatments since they may provide a better model of the tumor than conventional monolayer culture. Moreover, tumor cell interaction with the extracellular matrix can determine cell organization and behavior. In this work, a microfluidic system was used to form cell-laden core-shell beads which incorporate elements of the extracellular matrix and support the formation of multicellular spheroids. The bead core (comprising a mixture of alginate, collagen, and reconstituted basement membrane, with gelation by temperature control) and shell (comprising alginate hydrogel, with gelation by ionic crosslinking) were simultaneously formed through flow focusing using a cooled flow path into the microfluidic chip. During droplet gelation, the alginate acts as a fast-gelling shell which aids in preventing droplet coalescence and in maintaining spherical droplet geometry during the slower gelation of the collagen and reconstituted basement membrane components as the beads warm up. After droplet gelation, the encapsulated MCF-7 cells proliferated to form uniform spheroids when the beads contained all three components: alginate, collagen, and reconstituted basement membrane. The dose-dependent response of the MCF-7 cell tumor spheroids to two anticancer drugs, docetaxel and tamoxifen, was compared to conventional monolayer culture.  相似文献   

Multiscale modeling of droplet interface bilayer membrane networks     

Eric C. Freeman  Amir B. Farimani  Narayana R. Aluru  Michael K. Philen 《Biomicrofluidics》2015,9(6)

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题目：一种支持产品平台设计的多准则模块划分方法   总被引：2，自引：0，他引：2  

Wei WEI  Ang LIU  Stephen C.Y.LU  Thorsten WUEST 《浙江大学学报(A卷英文版)》2015,(1):1-10

目的：研究多准则约束下的产品模块划分方法,为企业建立稳健的模块化产品平台奠定基础。方法：采用改进的多目标进化算法对建立的多准则模块划分数学模型求解,并采用模糊集合评价机制进行最优解的寻取,得到基于多准则模块划分方法的产品模块划分结果。结论：通过改进的多目标进化算法求解多准则模块划分模型,能够得到有效支持产品平台设计的产品模块划分方案。通过与已有优化方法的比较验证了本文提出的多准则模块划分方法的优越性。  相似文献   

A Strategy for the Management,Preservation, and Reutilization of Geographical Information Based on the Lifecycle of Geospatial Data: An Assessment and a Proposal Based on Experiences from Spain and Europe     

Maria C. Porcal-Gonzalo 《Journal of Map & Geography Libraries》2015,11(3):289-329

In recent years, there has been a growing recognition of the fact that the proper management of information has to include concern for its preservation and future re-use. This ambition is particularly significant for geospatial data. The primary aim of this article is to define the European and Spanish frameworks for the preservation and reutilization of geographical information, with the ultimate goal of proposing an articulated, lifecycle-based data management model. With this, the intent is to shed some light on a complex, difficult and ever-evolving subject.

The article is divided into two main parts. The first part begins with a conceptual justification for geospatial data management and continues by synthesizing the current normative and technological framework for the preservation and reutilization of geographical information. Within this context, the implementation of Spatial Data Infrastructures (SDI) in Spain is evaluated. The second part begins with a case study from Spain that aims to identify different agents and flows that influence the lifecycle of geographical data, as well as the strengths and weaknesses found in each stage of the process under examination. Finally, the foregoing ideas are used in order to propose a SDI-related system for the management of geographical information.  相似文献   

Harnessing health information to foster disadvantaged teens' community engagement,leadership skills,and career plans: a qualitative evaluation of the Teen Health Leadership Program     

Alla Keselman  Einas A. Ahmed  Deborah C. Williamson  Janice E. Kelly  Gale A. Dutcher 《Journal of the Medical Library Association》2015,103(2):82-86

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