1,435 research outputs found
Hole mobility in organic single crystals measured by a "flip-crystal" field-effect technique
We report on single crystal high mobility organic field-effect transistors
(OFETs) prepared on prefabricated substrates using a "flip-crystal" approach.
This method minimizes crystal handling and avoids direct processing of the
crystal that may degrade the FET electrical characteristics. A chemical
treatment process for the substrate ensures a reproducible device quality. With
limited purification of the starting materials, hole mobilities of 10.7, 1.3,
and 1.4 cm^2/Vs have been measured on rubrene, tetracene, and pentacene single
crystals, respectively. Four-terminal measurements allow for the extraction of
the "intrinsic" transistor channel resistance and the parasitic series contact
resistances. The technique employed in this study shows potential as a general
method for studying charge transport in field-accumulated carrier channels near
the surface of organic single crystals.Comment: 26 pages, 7 figure
A Call to Standardize Teratoma Assays Used to Define Human Pluripotent Cell Lines
SummaryThe teratoma assay is the gold standard for documenting pluripotency of human stem cells. However, reports of new human ESC and iPSC lines vary widely in both methods and analysis of teratoma data. We call for consensus standards to be established to make this assay worthy of its âgoldenâ status
Electron mean free path from angle-dependent photoelectron spectroscopy of aerosol particles
We propose angle-resolved photoelectron spectroscopy of aerosol particles as
an alternative way to determine the electron mean free path of low energy
electrons in solid and liquid materials. The mean free path is obtained from
fits of simulated photoemission images to experimental ones over a broad range
of different aerosol particle sizes. The principal advantage of the aerosol
approach is twofold. Firstly, aerosol photoemission studies can be performed
for many different materials, including liquids. Secondly, the size-dependent
anisotropy of the photoelectrons can be exploited in addition to size-dependent
changes in their kinetic energy. These finite size effects depend in different
ways on the mean free path and thus provide more information on the mean free
path than corresponding liquid jet, thin film, or bulk data. The present
contribution is a proof of principle employing a simple model for the
photoemission of electrons and preliminary experimental data for potassium
chloride aerosol particles
Leaching of Cu, Zn, and Pb from sulfidic tailings under the use of sulfuric acid and chloride solutions
The imbalance between raw materials of high economic importance and their supply has increased the search for new approaches to obtain valuable elements from mining tailings. In this study, the extraction of copper, zinc, and lead from sulfidic tailing in sulfateâchloride media was investigated. A 3 3 BoxâBehnken design was applied to evaluate three variables over a 4-h testing period: sulfuric acid concentration (0.01â1.0 mol/L H 2 SO 4 ), sodium chloride (10â60 g/L NaCl), and temperature (20â70 °C). The design showed two optimum working regions: a combination of a high NaCl level, low H2SO4 level, and medium temperature level for lead leaching, while for copper and zinc, a combination of a mediumâhigh H 2 SO 4 level and a high temperature level. The concentration of NaCl had only a slight impact on their leaching. Based on these results, two-stage leaching was performed. The first stage was carried out under an experimental condition that favored the leaching of lead (60 g/L NaCl, 0.01 mol/L H 2 SO 4 , 45 °C, 1 h, 10:1 liquid-to-solid ratio), whereas the second stage maximized the leaching of copper and zinc (60 g/L NaCl, 0.5 mol/L H2SO4, 70 °C, 24 h, 10:1 liquid-to-solid ratio). The global leaching rate was 66.8 ± 3.0% copper, 84.1 ± 5.2% zinc, and 93.9 ± 3.2% lead. The iron and arsenic content were also leached by about 20 and 50% at the end of the second stage. The study demonstrated that the use of sulfateâchloride media in a two-stage leaching considerably improved the extraction of the desired metals and was, therefore, suitable for their recovery
Lifetime of d-holes at Cu surfaces: Theory and experiment
We have investigated the hole dynamics at copper surfaces by high-resolution
angle-resolved photoemission experiments and many-body quasiparticle GW
calculations. Large deviations from a free-electron-like picture are observed
both in the magnitude and the energy dependence of the lifetimes, with a clear
indication that holes exhibit longer lifetimes than electrons with the same
excitation energy. Our calculations show that the small overlap of d- and
sp-states below the Fermi level is responsible for the observed enhancement.
Although there is qualitative good agreement of our theoretical predictions and
the measured lifetimes, there still exist some discrepancies pointing to the
need of a better description of the actual band structure of the solid.Comment: 15 pages, 7 figures, 1 table, to appear in Phys. Rev.
Network analysis of synovial RNA sequencing identifies gene-gene interactions predictive of response in rheumatoid arthritis
Abstract Background To determine whether gene-gene interaction network analysis of RNA sequencing (RNA-Seq) of synovial biopsies in early rheumatoid arthritis (RA) can inform our understanding of RA pathogenesis and yield improved treatment response prediction models. Methods We utilized four well curated pathway repositories obtaining 10,537 experimentally evaluated gene-gene interactions. We extracted specific gene-gene interaction networks in synovial RNA-Seq to characterize histologically defined pathotypes in early RA and leverage these synovial specific gene-gene networks to predict response to methotrexate-based disease-modifying anti-rheumatic drug (DMARD) therapy in the Pathobiology of Early Arthritis Cohort (PEAC). Differential interactions identified within each network were statistically evaluated through robust linear regression models. Ability to predict response to DMARD treatment was evaluated by receiver operating characteristic (ROC) curve analysis. Results Analysis comparing different histological pathotypes showed a coherent molecular signature matching the histological changes and highlighting novel pathotype-specific gene interactions and mechanisms. Analysis of responders vs non-responders revealed higher expression of apoptosis regulating gene-gene interactions in patients with good response to conventional synthetic DMARD. Detailed analysis of interactions between pairs of network-linked genes identified the SOCS2/STAT2 ratio as predictive of treatment success, improving ROC area under curve (AUC) from 0.62 to 0.78. We identified a key role for angiogenesis, observing significant statistical interactions between NOS3 (eNOS) and both CAMK1 and eNOS activator AKT3 when comparing responders and non-responders. The ratio of CAMKD2/NOS3 enhanced a prediction model of response improving ROC AUC from 0.63 to 0.73. Conclusions We demonstrate a novel, powerful method which harnesses gene interaction networks for leveraging biologically relevant gene-gene interactions leading to improved models for predicting treatment response
Atomic correlations in itinerant ferromagnets: quasi-particle bands of nickel
We measure the band structure of nickel along various high-symmetry lines of
the bulk Brillouin zone with angle-resolved photoelectron spectroscopy. The
Gutzwiller theory for a nine-band Hubbard model whose tight-binding parameters
are obtained from non-magnetic density-functional theory resolves most of the
long-standing discrepancies between experiment and theory on nickel. Thereby we
support the view of itinerant ferromagnetism as induced by atomic correlations.Comment: 4 page REVTeX 4.0, one figure, one tabl
Glioma infiltration of the corpus callosum: early signs detected by DTI
The most frequent primary brain tumors, anaplastic astrocytomas (AA) and glioblastomas (GBM): tend to invasion of the surrounding brain. Histopathological studies found malignant cells in macroscopically unsuspicious brain parenchyma remote from the primary tumor, even affecting the contralateral hemisphere. In early stages, diffuse interneural infiltration with changes of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) is suspected. The purpose of this study was to investigate the value of DTI as a possible instrument of depicting evidence of tumor invasion into the corpus callosum (CC). Preoperatively, 31 patients with high-grade brain tumors (8 AA and 23 GBM) were examined by MRI at 3 T, applying a high-resolution diffusion tensor imaging (DTI) sequence. ADC- and FA-values were analyzed in the tumor-associated area of the CC as identified by fiber tracking, and were compared to matched healthy controls. In (MR-)morphologically normal appearing CC the ADC values were elevated in the tumor patients (n = 22; 0.978 Ă 10(â3) mmÂČ/s) compared to matched controls (0.917 Ă 10(â3) mmÂČ/s, p < 0.05), and the corresponding relative FA was reduced (rFA: 88 %, p < 0.01). The effect was pronounced in case of affection of the CC visible on MRI (n = 9; 0.978 Ă 10(â3) mmÂČ/s, p < 0.05; rFA: 72 %, p < 0.01). Changes in diffusivity and anisotropy in the CC can be interpreted as an indicator of tumor spread into the contralateral hemisphere not visible on conventional MRI
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