External loading determines specific ECM genes regulation

Bio artificial matrices embedded with cells are simulated in bioreactors to facilitate ECM production. As cells attach, they develop forces, which are dependent on cell type and matrix stiffness. External forces (i.e strain), however, are critical for tissue homeostasis and elicit specific cellular responses, such as gene expression and protein production. Collagen Type I is a widely used scaffold in Tissue engineering. The aim of this study was to study the mechanical and molecular responses, of different cell types to increasing collagen substrate stiffness

Non-response biases in surveys of school children: the case of the English PISA samples

We analyse response patterns to an important survey of school children, exploiting rich auxiliary information on respondents’ and non-respondents’ cognitive ability that is correlated both with response and the learning achievement that the survey aims to measure. The survey is the Programme for International Student Assessment (PISA), which sets response thresholds in an attempt to control data quality. We analyse the case of England for 2000 when response rates were deemed high enough by the PISA organisers to publish the results, and 2003, when response rates were a little lower and deemed of sufficient concern for the results not to be published. We construct weights that account for the pattern of non-response using two methods, propensity scores and the GREG estimator. There is clear evidence of biases, but there is no indication that the slightly higher response rates in 2000 were associated with higher quality data. This underlines the danger of using response rate thresholds as a guide to data quality.Non-response, bias, school survey, data linkage, PISA

Spatially inhomogeneous electron state deep in the extreme quantum limit of strontium titanate

When an electronic system is subjected to a sufficiently strong magnetic field that the cyclotron energy is much larger than the Fermi energy, the system enters the "extreme quantum limit" (EQL) and becomes susceptible to a number of instabilities. Bringing a three-dimensional electronic system deeply into the EQL can be difficult, however, since it requires a small Fermi energy, large magnetic field, and low disorder. Here we present an experimental study of the EQL in lightly-doped single crystals of strontium titanate, which remain good bulk conductors down to very low temperatures and high magnetic fields. Our experiments probe deeply into the regime where theory has long predicted electron-electron interactions to drive the system into a charge density wave or Wigner crystal state. A number of interesting features arise in the transport in this regime, including a striking re-entrant nonlinearity in the current-voltage characteristics and a saturation of the quantum-limiting field at low carrier density. We discuss these features in the context of possible correlated electron states, and present an alternative picture based on magnetic-field induced puddling of electrons.Comment: 8 pages, 5 figures, 7 pages of supplementary information; to appear in Nature Communication

Single-cell Motility Analysis of Tethered Human Spermatozoa.

Vigorous sperm flagellar motility is essential for fertilization, and so the quantitative measurement of motility is a useful tool to assess the intrinsic fertility potential of sperm cells and explore how various factors can alter sperm's ability to reach the egg and penetrate its protective layers. Human sperm beat their flagella many times each second, and so recording and accurately quantifying this movement requires a high-speed camera. The aim of this protocol is to provide a detailed description of the tools required for quantitative beat frequency measurement of tethered human sperm at the single-cell level and to describe methods for investigating the effects of intracellular or extracellular factors on flagellar motion. This assay complements bulk measurements of sperm parameters using commercially-available systems for computer-assisted sperm analysis (CASA)

HIDDEN IN PLAIN SIGHT: A DESCRIPTIVE CASE STUDY ANALYSIS EXPLORING THE LIVED EXPERIENCES OF POST-TRADITIONAL REMEDIAL LEARNERS AND THEIR DETERMINANTS OF STUDENT SUCCESS

The Post-Traditional Remedial Learner in higher education is a student constituency that has historically been Hidden in Plain Sight and strikingly absent from substantive discussions that foreground their lived experiences, relevance, and success in post-secondary education. Though physically present on campus and numerically significant within the academy, they are not recognized as an influential and consequential student demographic. The juxtaposition of their presence, specifically within the community college setting, and absence in the literature calls our attention to one of higher education’s most perplexing omissions. This study\u27s purpose is to explore the lived experiences of Post-Traditional Remedial Learners (PTLs) in a specific developmental education program within a community college setting and discover which factors promote and impact their success. Also critical to this study is exploring the situational, dispositional, and institutional barriers PTRLs face as they attempt to complete developmental education milestones. This study employs a triangulated approach to qualitative investigation, centering the voices and lived experiences of 12 Post-Traditional Remedial Learners between the ages of 25 and 75, nine community college academic personnel, and document analysis through the review of documentary evidence that serves to supplement and corroborate the interview and focus group data. This multi-perspective approach was utilized to gain a deeper understanding and to be provided with thick descriptions that would help to explicate the phenomenon further and increase the credibility and validity of the findings. Ultimately, the study serves as both a resource and infrastructure upon which further work may be developed with opportunities to provoke a profound interest in this student populous and heightened levels of understanding, integration, and support for their collegial success

Unbiased bases (Hadamards) for 6-level systems: Four ways from Fourier

In quantum mechanics some properties are maximally incompatible, such as the position and momentum of a particle or the vertical and horizontal projections of a 2-level spin. Given any definite state of one property the other property is completely random, or unbiased. For N-level systems, the 6-level ones are the smallest for which a tomographically efficient set of N+1 mutually unbiased bases (MUBs) has not been found. To facilitate the search, we numerically extend the classification of unbiased bases, or Hadamards, by incrementally adjusting relative phases in a standard basis. We consider the non-unitarity caused by small adjustments with a second order Taylor expansion, and choose incremental steps within the 4-dimensional nullspace of the curvature. In this way we prescribe a numerical integration of a 4-parameter set of Hadamards of order 6.Comment: 5 pages, 2 figure

Ionic conductivity on a wetting surface

Recent experiments measuring the electrical conductivity of DNA molecules highlight the need for a theoretical model of ion transport along a charged surface. Here we present a simple theory based on the idea of unbinding of ion pairs. The strong humidity dependence of conductivity is explained by the decrease in the electrostatic self-energy of a separated pair when a layer of water (with high dielectric constant) is adsorbed to the surface. We compare our prediction for conductivity to experiment, and discuss the limits of its applicability.Comment: 5 pages, 3 figures; one section and two illustrations added; figures updated and discussion added; typo fixe