314 research outputs found
Intrinsic conduction through topological surface states of insulating BiTe epitaxial thin films
Topological insulators represent a novel state of matter with surface charge
carriers having a massless Dirac dispersion and locked helical spin
polarization. Many exciting experiments have been proposed by theory, yet,
their execution have been hampered by the extrinsic conductivity associated
with the unavoidable presence of defects in BiTe and BiSe bulk
single crystals as well as impurities on their surfaces. Here we present the
preparation of BiTe thin films that are insulating in the bulk and the
four-point probe measurement of the conductivity of the Dirac states on
surfaces that are intrinsically clean. The total amount of charge carriers in
the experiment is of order 10 cm only and mobilities up to 4,600
cm/Vs have been observed. These values are achieved by carrying out the
preparation, structural characterization, angle-resolved and x-ray
photoemission analysis, and the temperature dependent four-point probe
conductivity measurement all in-situ under ultra-high-vacuum conditions. This
experimental approach opens the way to prepare devices that can exploit the
intrinsic topological properties of the Dirac surface states.Comment: accepted for publication in Proceedings of the National Academy of
Sciences of the United States of America (PNAS
Online Learning: Exploring the Landscape
The Policy and Planning Council of the Metropolitan Educational Research Consortium (MERC) at Virginia Commonwealth University (VCU) rightfully identified online learning as an area ripe for study. This report summarizes findings from both phases of the research is the first report of the study that was ultimately commissioned. After a brief review of the literature, this report includes a description of the survey research portion of the study as well as findings from the statewide survey that was undertaken and then phase 2, which consisted of case studies of four Virginia school divisions. The report concludes with a brief summary of the findings and some policy and research recommendations
Detecting Opioid-Related Aberrant Behavior using Natural Language Processing
The United States is in the midst of a prescription opioid epidemic, with the number of yearly opioid-related overdose deaths increasing almost fourfold since 2000(1). To more effectively prevent unintentional opioid overdoses, the medical profession requires robust surveillance tools that can effectively identify at-risk patients. Drug-related aberrant behaviors observed in the clinical context may be important indicators of patients at risk for or actively abusing opioids. In this paper, we describe a natural language processing (NLP) method for automatic surveillance of aberrant behavior in medical notes relying only on the text of the notes. This allows for a robust and generalizable system that can be used for high volume analysis of electronic medical records for potential predictors of opioid abuse
Isolation and analysis of the genetic diversity of repertoires of VSG expression site containing telomeres from Trypanosoma brucei gambiense, T. b. brucei and T. equiperdum
Background African trypanosomes (including Trypanosoma brucei) are unicellular parasites which multiply in the mammalian bloodstream. T. brucei has about twenty telomeric bloodstream form Variant Surface Glycoprotein (VSG) expression sites (BESs), of which one is expressed at a time in a mutually exclusive fashion. BESs are polycistronic transcription units, containing a variety of families of expression site associated genes (ESAG s) in addition to the telomeric VSG. These polymorphic ESAG families are thought to play a role in parasite-host adaptation, and it has been proposed that ESAG diversity might be related to host range. Analysis of the genetic diversity of these telomeric gene families has been confounded by the underrepresentation of telomeric sequences in standard libraries. We have previously developed a method to selectively isolate sets of trypanosome BES containing telomeres using Transformation associated recombination (TAR) cloning in yeast. Results Here we describe the isolation of repertoires of BES containing telomeres from three trypanosome subspecies: Trypanosoma brucei gambiense DAL 972 (causative agent of West-African trypanosomiasis), T. b. brucei EATRO 2340 (a nonhuman infective strain) and T. equiperdum STIB 818 (which causes a sexually transmitted disease in equines). We have sequenced and analysed the genetic diversity at four BES loci (BES promoter region, ESAG6, ESAG5 and ESAG2) from these three trypanosome BES repertoires. Conclusion With the exception of ESAG2, the BES sequence repertoires derived from T. b. gambiense are both less diverse than and nearly reciprocally monophyletic relative to those from T. b. brucei and T. equiperdum. Furthermore, although we find evidence for adaptive evolution in all three ESAG repertoires in T. b. brucei and T. equiperdum, only ESAG2 appears to be under diversifying selection in T. b. gambiense. This low level of variation in the T. b. gambiense BES sequence repertoires is consistent both with the relatively narrow host range of this subspecies and its apparent long-term clonality. However, our data does not show a clear correlation between size of trypanosome host range and either number of BESs or extent of ESAG genetic diversity
Ultrafast Resonant Polarization Interferometry: Towards the First Direct Detection of Vacuum Polarization
Vacuum polarization, an effect predicted nearly 70 years ago, is still yet to
be directly detected despite significant experimental effort. Previous attempts
have made use of large liquid-helium cooled electromagnets which inadvertently
generate spurious signals that mask the desired signal. We present a novel
approach for the ultra-sensitive detection of optical birefringence that can be
usefully applied to a laboratory detection of vacuum polarization. The new
technique has a predicted birefringence measurement sensitivity of in a 1 second measurement. When combined with the extreme
polarizing fields achievable in this design we predict that a vacuum
polarization signal will be seen in a measurement of just a few days in
duration.Comment: 9 pages, 2 figures. submitted to PR
Detection of Vacuum Birefringence with Intense Laser Pulses
We propose a novel technique that promises hope of being the first to
directly detect a polarization in the quantum electrodynamic (QED) vacuum. The
technique is based upon the use of ultra-short pulses of light circulating in
low dispersion optical resonators. We show that the technique circumvents the
need for large scale liquid helium cooled magnets, and more importantly avoids
the experimental pitfalls that plague existing experiments that make use of
these magnets. Likely improvements in the performance of optics and lasers
would result in the ability to observe vacuum polarization in an experiment of
only a few hours duration.Comment: 4 pages, 1 figur
Targeted metabolomics reveals proline as a major osmolyte in the chemolithoautotroph Sulfurimonas denitrificans
© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in MicrobiologyOpen 7 (2018): e00586, doi:10.1002/mbo3.586.Chemoautotrophic bacteria belonging to the genus Sulfurimonas in the class
Campylobacteria are widespread in many marine environments characterized by redox
interfaces, yet little is known about their physiological adaptations to different environmental
conditions. Here, we used liquid chromatography coupled with tandem
mass spectrometry (LC-MS/
MS) in a targeted metabolomics approach to study the
adaptations of Sulfurimonas denitrificans to varying salt concentrations that are found
in its natural habitat of tidal mudflats. Proline was identified as one of the most abundant
internal metabolites and its concentration showed a strong positive correlation
with ionic strength, suggesting that it acts as an important osmolyte in S. denitrificans.
2,3-dihydroxypropane-
1-
sulfonate
was also positively correlated with ionic strength,
indicating it might play a previously unrecognized role in osmoregulation. Furthermore,
the detection of metabolites from the reductive tricarboxylic acid cycle at high internal
concentrations reinforces the importance of this pathway for carbon fixation in
Campylobacteria and as a hub for biosynthesis. As the first report of metabolomic data
for an campylobacterial chemolithoautotroph, this study provides data that will be
useful to understand the adaptations of Campylobacteria to their natural habitat at
redox interfaces.NSF, Grant/Award Number: OCE-
1136727 and OCE-1154320; Woods Hole
Oceanographic Institution; U.S. Geological
Surve
Lymphatic filariasis increases tissue compressibility and extracellular fluid in lower limbs of asymptomatic young people in Central Myanmar
When normal lymphatic function is hampered, imperceptible subcutaneous edema can develop and progress to overt lymphedema. Low-cost reliable devices for objective assessment of lymphedema are well accepted in clinical practice and research on breast-cancer related lymphedema but are untested in populations with lymphatic filariasis (LF). This is a cross-sectional analysis of baseline data in a longitudinal study on asymptomatic, LF antigen-positive and -negative young people in Myanmar. Rapid field screening was used to identify antigen-positive cases and a group of antigen-negative controls of similar age and gender were invited to continue in the study. Tissue compressibility was assessed with three tissue tonometers, and free fluids were assessed using bio-impedance spectroscopy (BIS). Infection status was confirmed by Og4C3 antigen assay. At baseline (n= 98), antigen-positive cases had clinically relevant increases in tissue compressibilityat the calf using a digital Indurometer (11.1%, p = 0.021), and in whole-leg free fluid using BIS (9.2%, p = 0.053). Regression analysis for moderating factors (age, gender, hydration) reinforced the between-infection group differences. Results demonstrate that sub-clinical changes associated with infection can be detected in asymptomatic cases. Further exploration of these low-cost devices in clinical and research settings on filariasis-related lymphedema are warranted
The effect of state and federal policies on biomass business investments in Wisconsin
2 pagesWood-based biomass energy plays a key role in Wisconsin’s wood products economy and in
the state’s commitment to renewable energy. The state has developed numerous policies and
programs to support biomass energy harvesting, transportation, and production, and the federal
government has implemented policies to support related business development. The research reported
here investigates what policies have been most important in fostering biomass business investments in
Wisconsin and in creating strategic opportunities along the biomass supply chain.This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2013-67009-20396 from the
USDA National Institute of Food and Agriculture
The effect of state and federal policies on biomass business investments in Minnesota
2 pagesWood-based biomass energy plays a key role in Minnesota’s wood products economy and in
the state’s commitment to renewable energy. The state has developed numerous policies and
programs to support biomass energy harvesting, transportation, and production, and the federal
government has implemented policies to support related business development. The research reported
here investigates what policies have been most important in fostering biomass business investments in
Minnesota and in creating strategic opportunities along the biomass supply chain.This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2013-67009-20396 from the
USDA National Institute of Food and Agriculture
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