Spectral properties of microwave graphs with local absorption

The influence of absorption on the spectra of microwave graphs has been studied experimentally. The microwave networks were made up of coaxial cables and T junctions. First, absorption was introduced by attaching a 50 Ohm load to an additional vertex for graphs with and without time-reversal symmetry. The resulting level-spacing distributions were compared with a generalization of the Wigner surmise in the presence of open channels proposed recently by Poli et al. [Phys. Rev. Lett. 108, 174101 (2012)]. Good agreement was found using an effective coupling parameter. Second, absorption was introduced along one individual bond via a variable microwave attenuator, and the influence of absorption on the length spectrum was studied. The peak heights in the length spectra corresponding to orbits avoiding the absorber were found to be independent of the attenuation, whereas, the heights of the peaks belonging to orbits passing the absorber once or twice showed the expected decrease with increasing attenuation.Comment: 7 pages, 7 figure

The Mass Distributions of Starless and Protostellar Cores in Gould Belt Clouds

Using data from the SCUBA Legacy Catalogue (850 um) and Spitzer Space Telescope (3.6 - 70 um), we explore dense cores in the Ophiuchus, Taurus, Perseus, Serpens, and Orion molecular clouds. We develop a new method to discriminate submillimeter cores found by SCUBA as starless or protostellar, using point source photometry from Spitzer wide field surveys. First, we identify infrared sources with red colors associated with embedded young stellar objects (YSOs). Second, we compare the positions of these YSO-candidates to our submillimeter cores. With these identifications, we construct new, self-consistent starless and protostellar core mass functions (CMFs) for the five clouds. We find best fit slopes to the high-mass end of the CMFs of -1.26 +/- 0.20, -1.22 +/- 0.06, -0.95 +/- 0.20, and -1.67 +/- 0.72 for Ophiuchus, Taurus, Perseus, and Orion, respectively. Broadly, these slopes are each consistent with the -1.35 power-law slope of the Salpeter IMF at higher masses, but suggest some differences. We examine a variety of trends between these CMF shapes and their parent cloud properties, potentially finding a correlation between the high-mass slope and core temperature. We also find a trend between core mass and effective size, but we are very limited by sensitivity. We make similar comparisons between core mass and size with visual extinction (for A_V >= 3) and find no obvious trends. We also predict the numbers and mass distributions of cores that future surveys with SCUBA-2 may detect in each of these clouds.Comment: 56 pages, 18 figures, fixed typo in Eq 1, results in paper remain unchange

Liquid hydridosilane precursor prepared from cyclopentasilane via sonication at low temperatures without the action of light

AbstractWe report on a liquid hydridosilane precursor ink prepared via the ultrasonically induced ring-opening polymerisation of cyclopentasilane (Si5H10) without irradiation by ultraviolet light. The sonication is carried out in N2 atmosphere at temperatures between 20 and 75°C. We use size exclusion chromatography (SEC) to show polymer growth and estimate molecular mass with increasing sonication time. In combination with UV–vis transmission measurements, further SEC analysis is used to compare solutions subjected to either purely thermal or ultrasonic treatment at the same process temperature and for the same duration. Our findings provide strong evidence showing that the initiation of the polymerisation is sonocatalytic in nature and not thermic due to the macroscopic temperature of the solution. The liquid precursor is used to produce homogeneous hydrogenated amorphous silicon (a-Si:H) thin films via spin coating and pyrolytic conversion. The optoelectronic properties of the films are subsequently improved by hydrogen radical treatment. Fourier transform infrared spectroscopy (FTIR) is used to determine a compact film morphology and electrical conductivity measurements show that the layers attain a light-to-dark photosensitivity ratio of 2×103 making them suitable for application in optoelectronic devices

Microwave Realization of the Gaussian Symplectic Ensemble

This work was funded by the Deutsche Forschungsgemeinschaft via the individual Grants No. STO 157/16-1 and No. KU 1525/3-1. C. H. J. acknowledges the Leverhulme Trust (Grant No. ECF-2014-448) for financial support

Targeted Discovery of Glycoside Hydrolases from a Switchgrass-Adapted Compost Community

Development of cellulosic biofuels from non-food crops is currently an area of intense research interest. Tailoring depolymerizing enzymes to particular feedstocks and pretreatment conditions is one promising avenue of research in this area. Here we added a green-waste compost inoculum to switchgrass (Panicum virgatum) and simulated thermophilic composting in a bioreactor to select for a switchgrass-adapted community and to facilitate targeted discovery of glycoside hydrolases. Small-subunit (SSU) rRNA-based community profiles revealed that the microbial community changed dramatically between the initial and switchgrass-adapted compost (SAC) with some bacterial populations being enriched over 20-fold. We obtained 225 Mbp of 454-titanium pyrosequence data from the SAC community and conservatively identified 800 genes encoding glycoside hydrolase domains that were biased toward depolymerizing grass cell wall components. Of these, ∼10% were putative cellulases mostly belonging to families GH5 and GH9. We synthesized two SAC GH9 genes with codon optimization for heterologous expression in Escherichia coli and observed activity for one on carboxymethyl cellulose. The active GH9 enzyme has a temperature optimum of 50°C and pH range of 5.5 to 8 consistent with the composting conditions applied. We demonstrate that microbial communities adapt to switchgrass decomposition using simulated composting condition and that full-length genes can be identified from complex metagenomic sequence data, synthesized and expressed resulting in active enzyme

Different Sites of Alcohol Action in the NMDA Receptor GluN2A and GluN2B Subunits

The NMDA receptor is a major target of alcohol action in the CNS, and recent behavioral and cellular studies have pointed to the importance of the GluN2B subunit in alcohol action. We and others have previously characterized four amino acid positions in the third and fourth membrane-associated (M) domains of the NMDA receptor GluN2A subunit that influence both ion channel gating and alcohol sensitivity. In this study, we found that substitution mutations at two of the four corresponding positions in the GluN2B subunit, F637 and G826, influence ethanol sensitivity and ion channel gating. Because position 826 contains a glycine residue in the native protein, we focused our attention on GluN2B(F637). Substitution mutations at GluN2B(F637) significantly altered ethanol IC50 values, glutamate EC50 values for peak (Ip) and steady-state (Iss) current, and steady-state to peak current ratios (Iss:Ip). Changes in apparent glutamate affinity were not due to agonist trapping in desensitized states, as glutamate Iss EC50 values were not correlated with Iss:Ip values. Ethanol sensitivity was correlated with values of both Ip and Iss glutamate EC50, but not with Iss:Ip. Values of ethanol IC50, glutamate EC50, and Iss:Ip for mutants at GluN2B(F637) were highly correlated with the corresponding values for mutants at GluN2A(F636), consistent with similar functional roles of this position in both subunits. These results demonstrate that GluN2B(Phe637) regulates ethanol action and ion channel function of NMDA receptors. However, despite highly conserved M domain sequences, ethanol\u27s actions on GluN2A and GluN2B subunits differ

Shallow water marine sediment bacterial community shifts along a natural CO2 gradient in the Mediterranean Sea off Vulcano, Italy.

The effects of increasing atmospheric CO(2) on ocean ecosystems are a major environmental concern, as rapid shoaling of the carbonate saturation horizon is exposing vast areas of marine sediments to corrosive waters worldwide. Natural CO(2) gradients off Vulcano, Italy, have revealed profound ecosystem changes along rocky shore habitats as carbonate saturation levels decrease, but no investigations have yet been made of the sedimentary habitat. Here, we sampled the upper 2 cm of volcanic sand in three zones, ambient (median pCO(2) 419 μatm, minimum Ω(arag) 3.77), moderately CO(2)-enriched (median pCO(2) 592 μatm, minimum Ω(arag) 2.96), and highly CO(2)-enriched (median pCO(2) 1611 μatm, minimum Ω(arag) 0.35). We tested the hypothesis that increasing levels of seawater pCO(2) would cause significant shifts in sediment bacterial community composition, as shown recently in epilithic biofilms at the study site. In this study, 454 pyrosequencing of the V1 to V3 region of the 16S rRNA gene revealed a shift in community composition with increasing pCO(2). The relative abundances of most of the dominant genera were unaffected by the pCO(2) gradient, although there were significant differences for some 5 % of the genera present (viz. Georgenia, Lutibacter, Photobacterium, Acinetobacter, and Paenibacillus), and Shannon Diversity was greatest in sediments subject to long-term acidification (>100 years). Overall, this supports the view that globally increased ocean pCO(2) will be associated with changes in sediment bacterial community composition but that most of these organisms are resilient. However, further work is required to assess whether these results apply to other types of coastal sediments and whether the changes in relative abundance of bacterial taxa that we observed can significantly alter the biogeochemical functions of marine sediments