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101.
Matthew J. Kennedy Harold D. Ladouceur Tiffany Moeller Dickson Kirui Carl A. Batt 《Biomicrofluidics》2012,6(4)
The present work describes the operation and simulation of a microfluidic laminar-flow mixer. Diffusive mixing takes place between a core solution containing lipids in ethanol and a sheath solution containing aqueous buffer, leading to self assembly of liposomes. Present device architecture hydrodynamically focuses the lipid solution into a cylindrical core positioned at the center of a microfluidic channel of 125 × 125-μm2 cross-section. Use of the device produces liposomes in the size range of 100–300 nm, with larger liposomes forming at greater ionic strength in the sheath solution and at lower lipid concentration in the core solution. Finite element simulations compute the concentration distributions of solutes at axial distances of greater than 100 channel widths. These simulations reduce computation time and enable computation at long axial distances by utilizing long hexahedral elements in the axial flow region and fine tetrahedral elements in the hydrodynamic focusing region. Present meshing technique is generally useful for simulation of long microfluidic channels and is fully implementable using comsol Multiphysics. Confocal microscopy provides experimental validation of the simulations using fluorescent solutions containing fluorescein or enhanced green fluorescent protein. 相似文献
102.
Validity and reliability of GPS for measuring instantaneous velocity during acceleration, deceleration, and constant motion 总被引:2,自引:2,他引:0
In this study, we assessed the validity and reliability of 5 and 10 Hz global positioning systems (GPS) for measuring instantaneous velocity during acceleration, deceleration, and constant velocity while straight-line running. Three participants performed 80 running trials while wearing two GPS units each (5 Hz, V2.0 and 10 Hz, V4.0; MinimaxX, Catapult Innovations, Scoresby, VIC, Australia). The criterion measure used to assess GPS validity was instantaneous velocity recorded using a tripod-mounted laser. Validity was established using the standard error of the estimate (± 90% confidence limits). Reliability was determined using typical error (± 90% confidence limits, expressed as coefficient of variation) and Pearson's correlation. The 10 Hz GPS devices were two to three times more accurate than the 5 Hz devices when compared with a criterion value for instantaneous velocity during tasks completed at a range of velocities (coefficient of variation 3.1-11.3%). Similarly, the 10 Hz GPS units were up to six-fold more reliable for measuring instantaneous velocity than the 5 Hz units (coefficient of variation 1.9-6.0%). Newer GPS may provide an acceptable tool for the measurement of constant velocity, acceleration, and deceleration during straight-line running and have sufficient sensitivity for detecting changes in performance in team sport. However, researchers must account for the inherent match-to-match variation reported when using these devices. 相似文献
103.
Giles LV Warburton DE Esch BT Fedoruk MN Rupert JL Taunton JE 《Journal of sports sciences》2012,30(3):261-267
The purpose of this study was to determine the effects of short-term normoxic and hypoxic exercise on plasma endothelin-1 and nitric oxide levels, and the relationship of arterial compliance and pulmonary artery pressure to endothelin-1. Seven endurance-trained males completed two incremental and two steady-state exercise tests performed at ventilatory threshold in normoxia and hypoxia (fraction of inspired oxygen = 0.14). Plasma endothelin-1was measured throughout steady-state tests. Arterial compliance using applanation tonometry, plasma nitric oxide and pulmonary artery pressure using Doppler echocardiography were measured before and after exercise. Small arterial compliance and pulmonary artery pressure significantly increased following exercise. There were no main effects of condition or time for plasma endothelin-1and nitric oxide levels. There were no significant relationships between plasma endothelin-1 and arterial compliance or pulmonary artery pressure. In conclusion, mechanisms other than the endothelial system may play a role in the exercise-induced changes in small artery compliance in this study population. Moderate hypoxia and a 30-minute steady-state exercise have limited effects on plasma endothelin-1 in endurance-trained males. 相似文献
104.
M Martín-Matillas FB Ortega JR Ruiz D Martínez-Gómez G Vicente-Rodríguez A Marcos L Béghin A Kafatos M González-Gross M Zaccaria D Molnár S De Henauw M Sjöström LA Moreno MJ Castillo On Behalf Of The Helena Study 《Journal of sports sciences》2012,30(13):1329-1335
Abstract High physical fitness in childhood and adolescence is positively associated with favourable health-related outcomes. Our aim was to examine the relationship between relatives' (father, mother, brother, sister, and best friend) physical activity engagement and encouragement on adolescents' physical fitness. Adolescents were part of the HELENA study, a multi-centre study conducted in 10 cities from nine European countries in 2006-2008. Participants were 3288 adolescents (48% boys, 52% girls) aged 12.5-17.5 years with valid data on at least one of the three fitness variables studied: muscular strength (standing long jump), speed/agility (4×10 m shuttle run), and cardiorespiratory fitness (20 m shuttle run). The adolescents reported their relatives' physical activity engagement and encouragement. Analysis of covariance showed that relatives' physical activity engagement (father, mother, brother, and best friend) was positively related to cardiorespiratory fitness (P?0.05); and mother's and sisters' physical activity engagement were positively associated with higher muscular strength in adolescents (P?0.05). Furthermore, father's physical activity encouragement was positively linked to physical fitness (all fitness components) in adolescents (P?0.05). Interventions aimed at improving physical fitness in young people might be more successful when family members, particularly mothers and fathers, are encouraged to engage in physical activity and support adolescents' physical activity. 相似文献
105.
Laubacher M 《Endeavour》2012,36(2):46-54
In 1859, Robert Kennicott, one of the most promising specimen collectors and young naturalists in the United States, was dispatched to Hudson's Bay Territory by Spencer Fullerton Baird, the Assistant Secretary of the Smithsonian. Kennicott was chosen because of previous experience in Canada, the familiarity with biota of the American Midwest, and because he had a boundless, infectious, enthusiasm for natural history that was typical among Baird's closest protégées. Kennicott was a natural scientific envoy--or missionary--to the officers of the Hudson's Bay Company, and many officers were enthusiastically 'converted' to the cause of collecting and/or overseeing the collection of natural history specimens. Due to this collaboration between Baird, Kennicott and the officers of the Hudson's Bay Company, the Smithsonian became a leading center of Canadian natural history in the Western hemisphere. 相似文献
106.
Juan-Gabriel Cegarra-Navarro José Rodrigo Córdoba Pachón José Luis Moreno Cegarra 《International Journal of Information Management》2012
As a mixture of new technologies, processes and services oriented to the citizen, e-government has become one of the most important keywords for the public sector reform with proponents claiming that it guarantees transparency, accountability and better communication between local and national administrations and their public. Few if any studies have investigated the factors that might contribute to the establishment of trusting relationship between city councils and citizens. This paper examines the relative importance and significance of three types of information communication technologies (ICTs) towards the use of e-government and the development of civic engagement. We conduct an empirical investigation of 179 Spanish official town websites (web sites in the municipalities). The research findings suggest that implementing ICT not only involves a step towards an increase in the use of e-government services by people, but also provides numerous opportunities for their civic engagement. The main conclusion of this study is that although ICT can leverage the adoption of e-government, it cannot create alone engagement with traditional activities of the local government. What is missing from this relationship is a mediating variable (adoption of e-government by government officers), which in turn can greatly help to better understand how ICT impacts relationships between governments and their citizens. 相似文献
107.
Nine children with severe-profound prelingual hearing loss and single-word reading scores not more than 10 months behind chronological age (Good Readers) were matched with 9 children whose reading lag was at least 15 months (Poor Readers). Good Readers had significantly higher spelling and reading comprehension scores. They produced significantly more phonetic errors (indicating the use of phonological coding) and more often correctly represented the number of syllables in spelling than Poor Readers. They also scored more highly on orthographic awareness and were better at speech reading. Speech intelligibility was the same in the two groups. Cluster analysis revealed that only three Good Readers showed strong evidence of phonetic coding in spelling although seven had good representation of syllables; only four had high orthographic awareness scores. However, all 9 children were good speech readers, suggesting that a phonological code derived through speech reading may underpin reading success for deaf children. 相似文献
108.
We evaluated the effects of one year of schoolwide cluster grouping on the academic achievement growth of gifted and non-identified elementary students using a piecewise multilevel growth model. Scores from 186 non-identified and 68 gifted students’ Measures of Academic Progress Reading and Math scores were examined over three school years. In 2008–2009 within-class ability grouping was used. In 2009–2010 schoolwide cluster grouping was implemented. In 2010–2011 students once again were grouped only within classrooms by ability and students identified as gifted were spread across all classrooms at each grade level. Results suggest that schoolwide cluster grouping influenced student performance in the year following its implementation, but only for mathematics and not the area of reading. 相似文献
109.
Over the past several decades, the Latino population throughout the USA has demonstrated significant growth and exceeded that of other ethnic minority groups. This influx is particularly evident in the student enrollment of US schools as the number of Latino students has increased by approximately 10 million within the past 10 years. With this dramatic increase, there are a number of critical issues that present significant barriers to a high-quality educational experience for Latino students, specifically overrepresentation of Latinos receiving disciplinary actions and the high number of referrals to special education evaluation for emotional and behavioral disorders. This paper will discuss the impact of the Latino population in US schools, the concern of overrepresentation and biased referrals, and the use of a culturally attuned functional behavioral assessment as a pragmatic solution to better serve this growing population. 相似文献
110.
John K. Lannin Matthew Webb Kathryn Chval Fran Arbaugh Sarah Hicks Cynthia Taylor Rebecca Bruton 《Journal of Mathematics Teacher Education》2013,16(6):403-426
Recent research efforts (Schmidt et al. in The preparation gap: teacher education for middle school mathematics in six countries, MSU Center for Research in Mathematics and Science Education, 2007) demonstrate that teacher development programs in high-performing countries offer experiences that are designed to develop both mathematical knowledge and pedagogical knowledge. However, identifying the nature of the mathematical knowledge and the pedagogical content knowledge (PCK) required for effective teaching remains elusive (Ball et al. in J Teacher Educ 59:389–407, 2008). Building on the initial conceptual framework of Magnusson et al. (Examining pedagogical content knowledge, Kluwer, Dordrecht, pp 95–132, 1999), we examined the PCK development for two beginning middle and secondary mathematics teachers in an alternative certification program. The PCK development of these two individuals varied due to their focus on developing particular aspects of their PCK, with one individual focusing on assessment and student understanding, and the other individual focusing on curricular knowledge. Our findings indicate that these individuals privileged particular aspects of their knowledge, leading to differences in their PCK development. This study provides insight into the specific aspects of PCK that developed through the course of actual instructional practice, providing a lens for future research in this area. 相似文献