Analytic expression for Taylor-Couette stability boundary

We analyze the mechanism that determines the boundary of stability in Taylor-Couette flow. By simple physical argument we derive an analytic expression to approximate the stability line for all radius ratios and all speed ratios, for co- and counterrotating cylinders. The expression includes viscosity and so generalizes Rayleigh's criterion. We achieve agreement with linear stability theory and with experiments in the whole parameter space. Explicit formulae are given for limiting cases.Comment: 6 pages (LaTeX with REVTEX) including 4 figures (Postscript) Revised, discussion of two additional references. See also http://staff-www.uni-marburg.de/~esse

Spatial scales of interactions among bacteria and between bacteria and the leaf surface.

Microbial life on plant leaves is characterized by a multitude of interactions between leaf colonizers and their environment. While the existence of many of these interactions has been confirmed, their spatial scale or reach often remained unknown. In this study, we applied spatial point pattern analysis to 244 distribution patterns of Pantoea agglomerans and Pseudomonas syringae on bean leaves. The results showed that bacterial colonizers of leaves interact with their environment at different spatial scales. Interactions among bacteria were often confined to small spatial scales up to 5-20 μm, compared to interactions between bacteria and leaf surface structures such as trichomes which could be observed in excess of 100 μm. Spatial point-pattern analyses prove a comprehensive tool to determine the different spatial scales of bacterial interactions on plant leaves and will help microbiologists to better understand the interplay between these interactions

To Flip or Not to Flip?: Individual Cognitive Differences and L2 Russian Acquisition of Verbal Morphology in a Flipped Classroom

The Elementary Russian curriculum at UVM is a flipped classroom, a relatively new approach to communicative language teaching, in which explicit grammar and vocabulary work is conducted at home and class time is reserved for communication between peers and the instructor. In this thesis, we measured the interactions between teaching methodology, learner cognitive capacity, and language proficiency in the acquisition of Russian as a second language (L2). As a means to investigate proficiency, we tested students’ knowledge of the complex Russian conjugation pattern for present tense. Participants completed cognitive tests measuring working memory (WM) capacity, attention, multi-tasking capacity, and fluid intelligence. These variables were correlated with the proficiency results, which revealed significant relationships between WM and attention capacity. In the present study, WM and attention predict a learner’s performance in the production of Russian verbal morphology

Topography, disturbance and climate: subalpine forest change 1972-2013, Rocky Mountain National Park, USA

2015 Spring.Includes bibliographical references.Many forest tree species are expected to migrate in order to track suitable habitat due to changing climate (Stohlgren et al. 2000, Holzinger et al. 2007, Bell et al. 2013). Changes in climate will likely alter important fine-scale ecological factors such as water balance or microsite conditions which are vital for vegetation (Dobrowski 2011). Species distribution models suggest that many species should have already begun to migrate to track apposite climate (Rehfeldt et al. 2006, Littell et al. 2010, Monahan et al. 2013). While these models are a good starting point, they do not incorporate many variables that are critical for understanding forest changes and migration such as fine-scale topography and disturbance (Pearson and Dawson 2003). I resampled 68 subalpine forest plots originally surveyed in 1972-73 in Rocky Mountain National Park (RMNP) to investigate changes in species composition and structure and assess species migration during the past 40 years. I specifically considered forest change and migration in the context of topography, disturbance and climate. Data indicate species composition has remained relatively stable, with new species arriving in only 13% of plots. Forest structure has changed, shifting toward greater abundance of large-diameter trees with a reduction in small-diameter trees. Total stem densities decreased on south-facing slopes, increased on north-facing slopes, and remained stable at low elevations and increased at higher elevations. Species migration has been predominantly upslope on south-facing slopes while species elevations remained stable across north-facing slopes. These findings suggest that climate change has impacted forests of RMNP during the past 40 years. Impacts to vegetation have been mediated by topographic position and disturbance, demonstrating the importance of these factors in altering climate change impacts at the microsite scale. Northern aspects appear to be more buffered from the impacts of warming temperatures than southern aspects and these areas may become potential refugia in the future. Further understanding of the interactions among topography, disturbance and climate is vital for anticipating how forests could change and this information will lead to better ecosystem management and preservation of biodiversity in the future

The South African King IV Report on corporate governance: is the crown shiny enough?

No abstract available

Characterisation and calibration of a scintillating fibre detector with > 4000 multi-anode photomultiplier channels

In the Kaos spectrometer at the Mainz Microtron a high-resolution coordinate detector for high-energy particles is operated. It consists of scintillating fibres with diameters of 4000 multi-anode photomultiplier channels. It is one of the most modern focal-plane detectors for magnetic spectrometers world-wide. To correct variations in the detection efficiency, caused by the different gains and the different optical transmittances, a fully automated off-line calibration procedure has been developed. The process includes the positioning of a radioisotope source alongside the detector plane and the automated acquisition and analysis of the detector signals. It was possible to characterise and calibrate each individual fibre channel with a low degree of human interaction.Comment: Nucl. Instrum. Meth. A (2012

Excitonic - vibronic coupled dimers: A dynamic approach

The dynamical properties of exciton transfer coupled to polarization vibrations in a two site system are investigated in detail. A fixed point analysis of the full system of Bloch - oscillator equations representing the coupled excitonic - vibronic flow is performed. For overcritical polarization a bifurcation converting the stable bonding ground state to a hyperbolic unstable state which is basic to the dynamical properties of the model is obtained. The phase space of the system is generally of a mixed type: Above bifurcation chaos develops starting from the region of the hyperbolic state and spreading with increasing energy over the Bloch sphere leaving only islands of regular dynamics. The behaviour of the polarization oscillator accordingly changes from regular to chaotic.Comment: uuencoded compressed Postscript file containing text and figures. In case of questions, please, write to [email protected]

Transcriptome analysis of Listeria monocytogenes exposed to biocide stress reveals a multi-system response involving cell wall synthesis, sugar uptake, and motility

peer-reviewedListeria monocytogenes is a virulent food-borne pathogen most often associated with the consumption of “ready-to-eat” foods. The organism is a common contaminant of food processing plants where it may persist for extended periods of time. A commonly used approach for the control of Listeria monocytogenes in the processing environment is the application of biocides such as quaternary ammonium compounds. In this study, the transcriptomic response of a persistent strain of L. monocytogenes (strain 6179) on exposure to a sub-lethal concentration of the quaternary ammonium compound benzethonium chloride (BZT) was assessed. Using RNA-Seq, gene expression levels were quantified by sequencing the transcriptome of L. monocytogenes 6179 in the presence (4 ppm) and absence of BZT, and mapping each data set to the sequenced genome of strain 6179. Hundreds of differentially expressed genes were identified, and subsequent analysis suggested that many biological processes such as peptidoglycan biosynthesis, bacterial chemotaxis and motility, and carbohydrate uptake, were involved in the response of L. monocyotogenes to the presence of BZT. The information generated in this study further contributes to our understanding of the response of bacteria to environmental stress. In addition, this study demonstrates the importance of using the bacterium's own genome as a reference when analysing RNA-Seq data.This work was supported by the E.U.7th framework projects PROMISE (project number 265877)and FOODSEG(project number 266061).Aidan Casey was supported by the Teagasc Walsh Fellowship programme