Analysis of a laminar-flow diffusional mixer for directed self-assembly of liposomes     

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   

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  

Varley MC  Fairweather IH  Aughey RJ 《Journal of sports sciences》2012,30(2):121-127

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   

The effects of exercise in hypoxic and normoxic conditions on endothelin-1 and arterial compliance     

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   

Dopaminerge Modulation striataler Plastizität     

Frieder Beck  Klaus Blischke  Birgit Abler 《Sportwissenschaft》2012,42(4):271-279

This article attempts to outline the neuronal foundations of movement automatization. In particular, it is shown that an increase in automaticity corresponds to processes of synaptic plasticity in the corticostriatal and corticocortical system. This mechanism is supposed to induce changes in the neuronal representations of the respective skill. Furthermore, the role of phasic dopamine release will be discussed with respect to its modulating effect on processes of plasticity.  相似文献   

The 'mandarin-missionary' strategy: Robert Kennicott, Spencer Fullerton Baird and specimen collection in the Hudson's Bay Territory     

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   

Effects of schoolwide cluster grouping and within-class ability grouping on elementary school students’ academic achievement growth     

Michael S. Matthews  Jennifer A. Ritchotte  Matthew T. McBee 《High Ability Studies》2013,24(2):81-97

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   

The development of beginning mathematics teacher pedagogical content knowledge     

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   

Drunk and Alone in a K‐Mart Parking Lot: The Pedagogy of Simulations and Contemporary Attitudes Toward Drinking and Driving     

Matthew S. Crow  Richard M. Hough  Sr Jason Mosley  John Ortiz Smykla  Kimberly M. Tatum 《Journal of Criminal Justice Education》2013,24(3):417-431

This article introduces readers to the philosophy and design of team-based learning (TBL), a method developed by Dr. Larry Michaelsen that was influenced by literature in organizational psychology and pedagogy documenting what actually motivates adults to learn and how they master higher order learning skills. We describe how TBL was implemented in several criminal justice courses and illustrate how this method has drastically reduced student apathy, increased attendance, improved performance, and eliminated frustration for both instructors and students. Additionally, we reflect on how this method has reshaped our roles as educators.  相似文献   

Open Access to Criminal Justice Scholarship: A Matter of Social Justice     

Allan Scherlen  Matthew Robinson 《Journal of Criminal Justice Education》2013,24(1):54-74

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The Media and Criminologists: Interactions and Satisfaction     

Richard Tewksbury  Alexis Miller  Matthew T. DeMichele 《Journal of Criminal Justice Education》2013,24(2):227-243

Traditionally, academic criminologists have addressed two audiences—other academics and students—while largely ignoring other segments of society. Frequently neglected is attention to educating the public. This paper uses a random sample of American Society of Criminology (ASC) members to measure the level of interaction with and attitudes toward criminologists working with the media. Findings suggest that most criminologists have participated in an isolated incidence of working with the media, tend to be generally satisfied with this experience, and perceive working with the media as a worthwhile endeavor for criminologists.  相似文献