Simulation of electrophoretic stretching of DNA in a microcontraction using an obstacle array for conformational preconditioning

Recently our group has reported experiments using an obstacle array to precondition the conformations of DNA molecules to facilitate their stretch in a microcontraction. Based upon previous successes simulating electrophoretic stretching in microcontractions without obstacles, we use our simulation model to study the deformation of DNA chains in a microcontraction preceded by an array of cylindrical obstacles. We compare our data to the experimental results and find good qualitative, and even quantitative, agreement concerning the behavior of the chains in the array; however, the simulations overpredict the mean stretch of the chains as they leave the contraction. We examine the amount of stretch gained between leaving the array and reaching the end of the contraction and speculate that the differences seen are caused by nonlinear electrokinetic effects that become important in the contraction due to a combination of field gradients and high field strengths.     

Implementation of Ethical Higher Education Marketing

Tertiary Education and Management - With consumerism changing students to customers and teachers to service providers, ever more vulnerable and naïve students enrol and, instead of...     

Men who were sexually abused in childhood: Coping strategies and comparisons in psychological functioning

ObjectiveCoping strategies of men who were sexually abused in childhood were examined to ascertain their relationship to clinical diagnoses. Time elapsed since the abuse occurred was examined for its relationship to psychological functioning. Clinical psychopathology of this primary sample of sexually abused men was compared to a community sample of men.MethodsA primary sample of 147 Australian men was recruited from agencies and self-help groups who support adults who were sexually abused in childhood. For comparative purposes a secondary data set that consisted of 1,231 men recruited randomly in an Australian community survey was utilized. Both samples were administered the 28-item General Health Questionnaire (GHQ28). The primary sample was administered the 60-item coping style inventory instrument (COPE).ResultsCoping strategies influenced the possibility of being classified as clinical or nonclinical. The most important strategies associated with better functioning were positive reinterpretation and growth and seeking instrumental social support. Whereas strategies that were more associated with a clinical outcome were themed around internalization, acceptance and disengagement. The sample of men who were sexually abused in childhood was up to 10 times more likely to be classified as “clinical” then the sample of community men. Time elapsed since the abuse occurred did not have a moderating effect on men's psychological functioning.ConclusionsMen who have been sexually abused in childhood are more likely to have clinical diagnoses but coping strategies may play an important part in this outcome. Seeking active assistance appears to be important coping strategy in reframing the experience, however, the timing of this help seeking is not critical.Practice implicationsThe findings reinforce the importance of professionals being aware that men's psychiatric symptoms might be the sequel to past child sexual abuse. Coping strategies that focus on internalization or disengagement are potentially damaging to the men's long-term psychological functioning. Importantly there are coping strategies that appear to have a moderating effect on clinical diagnoses. Focus needs to be given to support services to male victims that provide practical strategies and allow for cognitive reframing to assist men to see their strength and positive growth arising from survival.     

Preface to Special Topic: Papers from the 82nd American Chemical Society Colloid and Surface Science Symposium, Raleigh, North Carolina, 2008

This Special Topic section of Biomicrofluidics contains original contributions that were presented at the 82nd Colloid and Surface Science Symposium, which took place on 15–18 June 2008 at North Carolina State University. The Symposium covered a wide range of topics that are relevant to the fundamentals of fluidics and their application to biological systems.The recent interest in microfluidics and nanofluidics is constantly increasing due to the numerous applications that these techniques have to offer. They have been used for chemical and biomolecular sensing, separation of charged analytes, and single DNA molecule manipulation. These applications were facilitated by the significant increase in the range of advanced microfabrication and nanofabrication techniques. Improving and extending the range of applicability of micro- and nanofluidic techniques also requires better fundamental understanding of the physics of the transport at small length scales. The transport of fluids and solutes in microchannels and nanochannels usually occurs at very small Reynolds regime. The typical length scale and the surface forces (electrostatic, van der Waals, hydrophobic, hydration, etc.) may be comparable to the size of the channels. All these features often require the development of new experimental techniques and approaches for theoretical analysis.The importance and the substantial recent interest in micro- and nanofluidics prompted the organization of a special session on Electrokinetic Phenomena and Microfluidics as part of the program at the 82nd Colloid and Surface Science Symposium at North Carolina State University in June 2008. The collected papers in this issue of Biomicrofluidics cover some of the very important fundamental and engineering aspects of electrokinetic phenomena in micro- and nanofluidic channels. These include molecular dynamics simulation of biomolecules in confined spaces, analysis of the electric double layer effects on the fluid flow in nanochannels, hydrodynamic resistance to droplet motion in microchannels, electrophoresis in nanocomposite gels, and microfluidics for nanoparticle fabrication. The paper by Srivastava et al.¹ explores the possibility of using microfluidics for fabrication of Janus nanofibers. Chang² presented a theoretical analysis of the electro-osmosis on a salt-free microchannel by simultaneously solving the nonlinear Poisson–Boltzmann equation for the electrostatic potential distribution and the Navier–Stokes equations for the fluid flow. Trahan and Doyle³ reported theoretical analysis of DNA molecule interaction with obstacles in a microchannel. Finally, Labrot et al.⁴ presented studies on the droplet hydrodynamic resistance in a microfluidic channel.We hope that the reader will find the papers useful and informative.     

Research and practice in undergraduate education: And never the twain shall meet?

This paper identifies some of the most significant -- and counterproductive -- gaps between what research reveals about how college students learn and how to maximize student learning, on the one hand, and, on the other, current academic, pedagogical, and administrative practices and policies. Drawing on research evidence from the cognitive and neural sciences, anthropology, sociology, psychology, education, and other sources, the paper first summarizes what is known about how students learn and what instructional practices and structures appear to be most effective in promoting student learning. The paper then contrasts this research-based evidence with current pedagogical, curricular, structural, and administrative practices and policies, and discusses the implications for instructional and organizational practices and policies. The paper concludes with a discussion of five explanations of why the gap exists and what might be done to close it.     

Variations of stroking parameters associated with 200 m competitive performance improvement in top-standard front crawl swimmers

The aim of this study was to analyse the variations of stroking parameters (speed, stroke length, stroke rate, and stroke index) associated with the 200 m front crawl competitive performance improvement. Two races completed by 17 top swimmers were analysed in the 200 m freestyle final of French or European championships, each final being separated by two years. All the swimmers' performances were bettered in the second race (mean +/- SD: 113.44 +/- 2.50 vs 111.78 +/- 2.71 s; p < 0.01) and were associated with a significant increase of stroke rate without variation of average stroke length and stroke index values (p > 0.05). Swimmers emphasized the first part of the race, with higher speed in the first three lengths, higher stroke rate in the first two lengths and lower stroke length in the first one. Stroke length and stroke rate variations were highly correlated (r = 0.98; p < 0.05). In 11 of the 17 swimmers, the improvement was concomitant with a decrease in stroke length and an increase in stroke rate. Only one swimmer's improvement was associated with a substantial increase in stroke length. These results highlighted that stroke length and stroke index cannot be considered as the only parameters linked to improvement in a 200 m crawl in adult swimmers competing at high standard. Moreover, an increase in stroke rate associated with a slight decrease in stroke length should not be considered as ineffective, especially at top standard.