Experimentally-calibrated population of models predicts and explains inter-subject variability in cardiac cellular\ud electrophysiology

Cellular and ionic causes of variability in the electrophysiological activity of hearts from individuals of the same species are unknown. However, improved understanding of this variability is key to enable prediction of the response of specific hearts to disease and therapies. Limitations of current mathematical modeling and experimental techniques hamper our ability to provide insight into variability. Here we describe a methodology to unravel the ionic determinants of inter-subject variability exhibited in experimental recordings, based on the construction and calibration of populations of models. We illustrate the methodology through its application to rabbit Purkinje preparations, due to their importance in arrhythmias and safety pharmacology assessment. We consider a set of equations describing the biophysical processes underlying rabbit Purkinje electrophysiology and we construct a population of over 10,000 models by randomly assigning specific parameter values corresponding to ionic current conductances and kinetics. We calibrate the model population by closely comparing simulation output and experimental recordings at three pacing frequencies. We show that 213 of the 10,000 candidate models are fully consistent with the experimental dataset. Ionic properties in the 213 models cover a wide range of values, including differences up to ±100% in several conductances. Partial correlation analysis shows that particular combinations of ionic properties determine the precise shape, amplitude and rate dependence of specific action potentials. Finally, we demonstrate that the population of models calibrated using data obtained under physiological conditions quantitatively predicts the action potential duration prolongation caused by exposure to four concentrations of the potassium channel blocker dofetilide

Low loss Ge-on-Si waveguides operating in the 8–14 µm atmospheric transmission window

Germanium-on-silicon waveguides were modeled, fabricated and characterized at wavelengths ranging from 7.5 to 11 µm. Measured waveguide losses are below 5 dB/cm for both TE and TM polarization and reach values of ∼ 1 dB/cm for ≥ 10 µm wavelengths for the TE polarization. This work demonstrates experimentally for the first time that Ge-on-Si is a viable waveguide platform for sensing in the molecular fingerprint spectral region. Detailed modeling and analysis is presented to identify the various loss contributions, showing that with practical techniques losses below 1 dB/cm could be achieved across the full measurement range

Ohmic contacts to n-type germanium with low specific contact resistivity

A low temperature nickel process has been developed that produces Ohmic contacts to n-type germanium with specific contact resistivities down to (2.3 ± 1.8) x10<sup>-7</sup> Ω-cm<sup>2</sup> for anneal temperatures of 340 degC. The low contact resistivity is attributed to the low resistivity NiGe phase which was identified using electron diffraction in a transmission electron microscope. Electrical results indicate that the linear Ohmic behaviour of the contact is attributed to quantum mechanical tunnelling through the Schottky barrier formed between the NiGe alloy and the heavily doped n-Ge.<p></p&gt

Erasing Boundaries: Inter-School Collaboration and its Pedagogical Opportunities

(Excerpt) This article, based on a presentation that we gave at the AALS conference in New York in January of 2014, suggests that technology opens up new possibilities for law schools by allowing students from different schools to participate in complex inter-school simulations that can, if carefully prepared, teach important lessons about lawyering skills, behavior, and provide rich opportunities for the development of professional identity. It can, in short, deepen and enrich the experiential learning opportunities that law schools offer. The article does not propose that law school faculty should teach or grade students from another school, but that the faculty can collaborate on problems that are more elaborate and complex than could realistically be produced within one school, and that students from different schools can work together as co-counsel, or in opposition to each other, in a variety of projects, with students from other schools serving as judges or arbitrators, witnesses, and clients. In this way, faculty members teach and grade their own students but both faculty and students gain the advantages brought by collaborative learning environments across schools – enabled by technology. The article does not discuss a completed project, but rather describes and explores the possibilities presented by the rapidly-changing world of internet communication, and will suggest that this approach is something that can be undertaken now with minimal cost for the technology and by the faculty currently teaching in law schools. In other words, this approach suggests one way in which law schools can offer their students a richer and more engaging learning experience that will go at least some of the way to answering the questions about how they can offer realistic experiential learning opportunities and help students graduate practice ready lawyers without incurring significant, or even any, additional cost

Dimorphic fruit colour is associated with differences in germination of calligonum comosum

© 2019, Canadian Science Publishing. Calligonum comosum L’Hér is a perennial evergreen shrub that produces dimorphic fruits of distinctly yellow or red colour. The species is found on sand dunes of the Middle East, is valued as a highly palatable livestock feed that survives extreme drought, and is suitable for desert restoration of non-saline sandy soils. The association of fruit colour with germination was assessed in laboratory conditions under two temperature (15/20 and 20/30 °C) and two light (0 and 12 h per day) treatments. Additionally, the association of fruit colour with emergence and seedling growth up to 90 days from sowing was assessed in shade house conditions. Germination percentage in the laboratory was the only variable that exhibited significant variation by seed colour. Germination was highest for red seeds grown in the dark at the higher temperature but the influence of seed colour on germination was not repeated in the shade house study. The dimorphic fruit colour of C. comosum is thus associated with differing germination rates, but further study is needed to determine whether morphs employ differing recruitment strategies

Pepper-pot emittance measurement of laser-plasma wakefield accelerated electrons

The transverse emittance is an important parameter governing the brightness of an electron beam. Here we present the first pepper-pot measurement of the transverse emittance for a mono-energetic electron beam from a laser-plasma wakefield accelerator, carried out on the Advanced Laser-Plasma High Energy Accelerators towards X-Rays (ALPHA-X) beam line. Mono-energetic electrons are passed through an array of 52 mu m diameter holes in a tungsten mask. The pepper-pot results set an upper limit for the normalised emittance at 5.5 +/- 1 pi mm mrad for an 82 MeV beam