A “twisted” microfluidic mixer suitable for a wide range of flow rate applications     

Shilpa Sivashankar  Sumeyra Agambayev  Yousof Mashraei  Er Qiang Li  Sigurdur T. Thoroddsen  Khaled Nabil Salama 《Biomicrofluidics》2016,10(3)

This paper proposes a new “twisted” 3D microfluidic mixer fabricated by a laser writing/microfabrication technique. Effective and efficient mixing using the twisted micromixers can be obtained by combining two general chaotic mixing mechanisms: splitting/recombining and chaotic advection. The lamination of mixer units provides the splitting and recombination mechanism when the quadrant of circles is arranged in a two-layered serial arrangement of mixing units. The overall 3D path of the microchannel introduces the advection. An experimental investigation using chemical solutions revealed that these novel 3D passive microfluidic mixers were stable and could be operated at a wide range of flow rates. This micromixer finds application in the manipulation of tiny volumes of liquids that are crucial in diagnostics. The mixing performance was evaluated by dye visualization, and using a pH test that determined the chemical reaction of the solutions. A comparison of the tornado-mixer with this twisted micromixer was made to evaluate the efficiency of mixing. The efficiency of mixing was calculated within the channel by acquiring intensities using ImageJ software. Results suggested that efficient mixing can be obtained when more than 3 units were consecutively placed. The geometry of the device, which has a length of 30 mm, enables the device to be integrated with micro total analysis systems and other lab-on-chip devices.  相似文献   

Predictors of psychological distress and positive resources among Palestinian adolescents: trauma, child, and mothering characteristics   总被引：1，自引：0，他引：1  

Qouta S  Punamäki RL  Montgomery E  El Sarraj E 《Child abuse & neglect》2007,31(7):699-717

OBJECTIVE: The aim was to examine how traumatic and stressful events, responses to violence, child characteristics, and mothering quality, as measured in middle childhood predict psychological distress and positive resources in adolescence. METHOD: The participants were 65 Palestinian adolescents (17+/-.85 years; 52% girls), who had been studied during the First Intifada (T1), during the Palestinian Authority rule (T2) and before the Second Al Aqsa Intifada (T3) in Gaza. Psychological distress was indicated by PTSD, and depressive symptoms and positive resources by resilient attitudes and satisfaction with quality of life, all measured at T3. The predictors that were measured at T1 were exposure to military violence, active coping with violence and children's intelligence, cognitive capacity, and neuroticism. Mothering quality and stressful life-events were measured at T2, the former reported by both the mother and the child, and the latter by the mother. RESULTS: Adolescents' PTSD symptoms were most likely if they had been exposed to high levels of traumatic and stressful experiences and had poor cognitive capacity and high neuroticism in middle childhood. Only high levels of childhood military violence and stressful life-events predicted high depressive symptoms and low satisfaction with quality of life in adolescence. CONCLUSIONS: Military violence in childhood forms risks for both increased psychological distress and decreased positive resources. However, child characteristics such as cognitive capacity and personality are important determinants of psychological vulnerability in military trauma.  相似文献   

Shared Sense-making in Curriculum Reform: Orchestrating the Local Curriculum Work     

Janne Pietarinen  Kirsi Pyhältö  Tiina Soini 《Scandinavian Journal of Educational Research》2019,63(4):491-505

This study aims to gain a better understanding of the Finnish national curriculum reform by examining how the educational practitioners, at the district level, orchestrate the shared sense-making concerning the reform work in their school districts. Qualitative focus group data was collected from 12 groups, throughout Finland, that were responsible for orchestrating curriculum reform work at the district level. Results showed that curriculum reform steering groups recognized the importance of orchestrating shared sense-making. They strived to develop functional, context sensitive, and shared strategies for reform implementation across their districts. They employed a range of strategies for managing, navigating, and regulating the shared sense-making of the local curriculum work.  相似文献   

Is teacher attrition a poor estimate of the value of teacher education? A Swedish case     

Rickard Carlsson  Ulla Karin Nordänger 《欧洲师范教育杂志》2019,42(2):243-257

Far from all who complete teacher education end up working as teachers throughout their entire career. At first sight the value of teacher education, in terms of efficiency, seems to be a failure. In the present article we argue that teacher attrition, when defined as whether one is working as teacher or not, is a too blunt measure to gauge whether teacher education has been valuable. With a unique dataset, where we have detailed information on 87 Swedish teacher graduates’ working life across 23 years, we can consider whether activities and/or experiences point to an apparent use of teacher education. In conclusion, we find that in order to get informative estimates of its value it is important to consider it from different perspectives and to consider attrition related to the total working time spent in educational settings across a career rather than percentage leaving teaching after a set of years  相似文献   

Improving Group Work Practices in Teaching Life Sciences: Trialogical Learning     

Tammeorg  Priit  Mykkänen  Anna  Rantamäki  Tomi  Lakkala  Minna  Muukkonen  Hanni 《Research in Science Education》2019,49(3):809-828

Research in Science Education - Trialogical learning, a collaborative and iterative knowledge creation process using real-life artefacts or problems, familiarizes students with working life...  相似文献   

Frequent sit-to-stand transitions and several short standing periods measured by hip-worn accelerometer are associated with smaller waist circumference among adults     

Pauliina Husu  Jaana Suni  Kari Tokola  Henri Vähä-Ypyä  Heli Valkeinen  Tomi Mäki-Opas 《Journal of sports sciences》2019,37(16):1840-1848

This cross-sectional study analysed the association of sedentary behaviour (SB) and standing with waist circumference. Finnish adults aged 30-75 years from a sub-sample of population-based Health 2011 Study used a hip-worn tri-axial accelerometer (Hookie AM20, Traxmeet, Ltd, Espoo, Finland) for seven days. Those 1405 participants (57% women) who used accelerometer at least four days, minimum of 10 hours/day, were included. SB and standing were analysed in 6s epochs using validated algorithm. Daily total time, daily number and accumulated time from bouts (30s–5min,30s–10min,30s–15min,30s 30min,>5min,>10min,>15min, >30min) as well as daily number of sit-to-stand transitions were determined. Waist circumference (cm) was measured in standardized way. Participants’ mean age was 52 years (SD 12.2). Mean waist circumference was 97cm (SD 12.3) in men and 87cm (SD 12.7) in women. According to multivariable stepwise linear regression analysis, sit-to-stand transitions [standardised regression coefficient (β)= -0.14, 95%CI -0.20 to -0.09], standing bouts of 30s–5min (β= -0.21, 95%CI -0.26 to -0.15) and number of 30s-30min SB bouts (β=0.12, 95%CI 0.06 to 0.17) were most strongly associated with waist circumference. Besides assessing total SB time, future studies should assess also different bout lengths of SB and sit-to-stand transitions and standing times should be assessed separately.  相似文献   

我国海洋体育旅游安全管理体系研究 ——基于12395平台的模型构建          下载免费PDF全文

仝二宝 《河北体育学院学报》2016,30(2):7-14

近年来中国海洋体育旅游发展迅速,但是其客观存在的风险因素和安全管理的结构性缺陷直接影响到整个产业的良性发展.从管理学角度出发,通过对影响安全的各种因素进行分析,对现有的行政管理体制和社会资源进行梳理整合,提出在12395的平台上构建海洋体育旅游安全管理体系的构想,并对其运营管理路径进行设计,以促进海洋体育旅游产业安全有序发展.  相似文献   

Two games in town: a comparison of dealer and auction prices in contemporary visual arts markets     

Michael Hutter  Christian Knebel  Gunnar Pietzner  Maren Schäfer 《Journal of Cultural Economics》2007,31(4):247-261

The article tests a couple of hypotheses relating to markets where demand is not taken as a given, but subject to sophisticated and encompassing price-building strategies. The study uses a data set that provides quoted dealer prices for medium-sized works of 100 leading visual artists from 1970 to 2004. These data are compared with auction price results for works by the same artists. The study reports significant discrepancies with respect to the relationship between the age of artists and prices paid for their works in the two markets, and with respect to general price developments in the two markets as measured by indices.

Michael HutterEmail:

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Examining coaches’ perceptions of how their stress influences the coach–athlete relationship     

Richard C. Thelwell  Christopher R. D. Wagstaff  Michael T. Chapman  Göran Kenttä 《Journal of sports sciences》2017,35(19):1928-1939

This study extends recent coach stress research by evaluating how coaches perceive their stress experiences to affect athletes, and the broader coach–athlete relationship. A total of 12 coaches working across a range of team sports at the elite level took part in semi-structured interviews to investigate the 3 study aims: how they perceive athletes to detect signals of coach stress; how they perceive their stress experiences to affect athletes; and, how effective they perceive themselves to be when experiencing stress. Following content analysis, data suggested that coaches perceived athletes able to detect when they were experiencing stress typically via communication, behavioural, and stylistic cues. Although coaches perceived their stress to have some positive effects on athletes, the overwhelming effects were negative and affected “performance and development”, “psychological and emotional”, and “behavioural and interaction” factors. Coaches also perceived themselves to be less effective when stressed, and this was reflected in their perceptions of competence, self-awareness, and coaching quality. An impactful finding is that coaches are aware of how a range of stress responses are expressed by themselves, and to how they affect athletes, and their coaching quality. Altogether, findings support the emerging view that coach stress affects their own, and athlete performance.  相似文献   

Sport disciplines,types of sports,and waist circumference in young adulthood – a population-based twin study     

Mirva Rottensteiner  Sara Mäkelä  Leonie H. Bogl  Timo Törmäkangas  Jaakko Kaprio  Urho M. Kujala 《European Journal of Sport Science》2017,17(9):1184-1193

Purpose: The benefits of physical activity (PA) in preventing abdominal obesity are well recognized, but the role of different sport disciplines remains open. We aimed, therefore, to investigate how participation in different sport disciplines, and the number and types of sports engaged in are associated with waist circumference (WC) in young adulthood. Methods: This population-based cohort study comprised 4027 Finnish twin individuals (1874 men), with a mean age of 34 y (32–37), who answered a survey, including self-measured WC. We extracted the number and identified the types (aerobic, power, and mixed) of the different sport disciplines respondents reported participating in. Results: The number of sport disciplines participated in was inversely associated with WC, the linear decrease averaging 1.38?cm (95% CI 1.10–1.65) per each additional sport discipline. The result persisted after adjustment for the main covariates, such as volume of PA and diet quality. Among dizygotic twin pairs discordant for sports participation (0–2 vs. 5 or more disciplines), the mean within-pair difference in WC was 4.8?cm (95% CI 0.4–9.1) for men and 11.2?cm (95% CI 4.4–18.0) for women; among discordant monozygotic pairs, no differences were observed. In men, all three types of sports were individually associated with smaller WC, while in women, only mixed and power sports showed this association. Conclusions: Participation in several sport disciplines and sport types was associated with smaller WC among young adults in their mid-30s. Shared genetic background may explain some of the associations.  相似文献