In-situ electrochemical fabrication of natural contacts on single nanowires

We report a template-based in-situ electrochemical method for fabricating natural electric contacts on single nanowires using a pair of cross-patterned electrodes. Such electric contacts are highly stable upon thermal cycling between room temperature and milli-Kelvin temperatures. Direct imaging of the single-nanowire contacts using scanning electron microscopy is also demonstrated.Comment: 13 pages, 4 figure

Identification and Characterization of microRNAs from Peanut (Arachis hypogaea L.) by High-Throughput Sequencing

BACKGROUND: MicroRNAs (miRNAs) are noncoding RNAs of approximately 21 nt that regulate gene expression in plants post-transcriptionally by endonucleolytic cleavage or translational inhibition. miRNAs play essential roles in numerous developmental and physiological processes and many of them are conserved across species. Extensive studies of miRNAs have been done in a few model plants; however, less is known about the diversity of these regulatory RNAs in peanut (Arachis hypogaea L.), one of the most important oilseed crops cultivated worldwide. RESULTS: A library of small RNA from peanut was constructed for deep sequencing. In addition to 126 known miRNAs from 33 families, 25 novel peanut miRNAs were identified. The miRNA* sequences of four novel miRNAs were discovered, providing additional evidence for the existence of miRNAs. Twenty of the novel miRNAs were considered to be species-specific because no homolog has been found for other plant species. qRT-PCR was used to analyze the expression of seven miRNAs in different tissues and in seed at different developmental stages and some showed tissue- and/or growth stage-specific expression. Furthermore, potential targets of these putative miRNAs were predicted on the basis of the sequence homology search. CONCLUSIONS: We have identified large numbers of miRNAs and their related target genes through deep sequencing of a small RNA library. This study of the identification and characterization of miRNAs in peanut can initiate further study on peanut miRNA regulation mechanisms, and help toward a greater understanding of the important roles of miRNAs in peanut

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Open-circuit photopotential characterization of photoelectrochemical activities of Au-modified TiO2 nanorods

The open circuit potential (OCP) of a semiconductor electrode can be used to quantify the transient photopotential (Ep), which represents wavelength-dependent charge accumulation and relaxation kinetics of a photoelectrode. Here OCP responses of a plasmonic Au@TiO2 nanorods (NRs) photoelectrode can be quantified without causing electrochemical corrosion of Au. The photogenerated charge accumulation kinetics data based on the wavelength-dependent growth rates of |Ep| can resolve the plasmonic effects on photoelectrochemistry (PEC) of Au@TiO2 NRs. Data fitting with Kohlrausch-Williams-Watts (KWW) stretched exponential kinetics model illustrates the complex charge relaxations at the Au/TiO2 Schottky contact, from which long relaxation lifetimes with broad lifetime distributions can be obtained. This is attributed to the abundant deep defects in the nanostructure TiO2, which has been strongly confirmed by reducing the oxygen vacancies using a post-thermal annealing treatment. Single-particle dark-field scattering (DFS) spectrum is measured with a tunable wavelength light source to support visible light activities of PEC characteristics of Au@TiO2 NRs. Light scattering spectra of >200 single Au@TiO2 NRs particles are collected to compare directly with PEC responses of OCP of the ensemble Au@TiO2 NRs

Investigating the jamming of particles in a three-dimensional fluid-driven flow via coupled CFD–DEM simulations

The clogging of a dense stream of particles when passing through an orifice occurs ubiquitously in both natural and industrial fields. Since most of the jamming phenomena lead to the negative effects, studying and preventing jamming is of great importance. There are two typical types of jamming due to different types of driving force: (a) gravity-driven jamming and (b) fluid-driven jamming. Among these two types of jamming, the fluid-driven jamming occurs in fluid-driven particle flows, and the initial solid concentration, the fluid velocity, and the orifice-particle size ratio has been demonstrated to have effects on the occurrence of this jamming. Although the individual influence of the initial solid concentration and orifice-particle size ratio on jamming has been studied, the coupled effects of these two factors on jamming are little known. In addition, the complex effects of the fluid velocity on jamming have not been fully discussed. To address these problems, this work performs a three-dimensional simulation of the fluid-driven jamming using the coupled Computational Fluid Dynamics–Discrete Element Method (CFD–DEM) model. At first, the jamming probability under different initial conditions is studied. The jamming probability is displayed on the solid concentration–orifice size ratio plane to illustrate the coupled effects of these two factors on jamming. The simulation results show that the critical solid concentration, at which the jamming probability increases to 1, increases with the orifice-particle size ratio. This is because an orifice with a larger orifice size ratio has a greater particle discharge capacity, which allows more particles to pass through without jamming. Then, we reveal the influence of fluid velocity over a wide range on the fluid-driven jamming type, jamming probability and shape of the jamming dome. To the author’s knowledge, this is the first time that the shape of the jamming dome has been related to the fluid velocity. The jamming dome formed in the higher-speed flow has a greater curvature due to the greater fluid drag acting on the particles

Design of a Piezoelectric Pump Driven by Inertial Force of Vibrator Supported by a Slotted Beam

This paper introduces the design, manufacture, dynamic analysis, and experimental results of a piezoelectric pump driven by the inertial force of a vibrator supported by a slotted beam. The piezoelectric vibrator is composed of a mass block, displacement amplifier, and slotted beam fixed with both ends. In the resonant mode, the displacement amplifier drives the slotted beam to work, and produces amplitude and inertial force. In this paper, the design of the slotted beam optimizes the output of the displacement amplifier. In addition, the slotted beam supports the displacement amplifier and increases the elastic output. The pump body adopts polydimethylsiloxane (PDMS) check valves and compressible spaces to improve the output performance. This research studies the influence of stiffness and mass on the output performance by qualitatively analyzing the inertial output force of the vibrator. Nine kinds of slotted beams with different stiffnesses and different mass blocks are designed for comparison. Thereafter, an optimal structure of the piezoelectric pump is selected. The experimental results show that under a driving voltage of 700 Vpp , the maximum flowrate is 441 mL&nbsp;min&minus;1 and the maximum back pressure is 25.3 kPa

Interfacial charge transfer events of BODIPY molecules: Single molecule spectroelectrochemistry and substrate effects

We present single molecule fluorescence and spectroelectrochemistry characteristics of 4,4′-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) bearing two carboxylic acid groups at its 2 and 6 positions. Our study shows a heterogeneous half redox potential distribution for the BODIPY molecules embedded in polystyrene film because of the heterogeneity in their charge transfer rates. Single molecules adsorbed onto a TiO2 surface with ordered nanostructures show surprising fluorescence blinking activity with the shortest ON duration time in comparison to bare glass and indium-tin oxide (ITO) surfaces. Single molecule stability tests show longer ON duration time and a stable fluorescence feature when dispersed in polystyrene thin film than molecules exposed to air. Shorter ON times are observed for molecules. In intimate contact with ITO in comparison to glass substrates. Such a decrease in their fluorescence stability or intensity is explained by charge transfer activities from the dye molecules to the metal oxide surface. Electron transfer and back transfer rates are calculated to illustrate the substrate effects by using a well-established model. © the Partner Organisations 2014