2,487 research outputs found
Application of (e,2e) Spectroscopy to the Electronic Structure of Valence Electrons in Crystalline and Amorphous Solids
Get PDFThis review presents theoretical and experimental aspects of (e,2e) spectroscopy specific to the study of crystalline and amorphous solids. The cross section for (e,2e) scattering is proportional to the spectral momentum density of the ejected electron under certain approximations. The theoretical framework for interpreting (e,2e) measurements is summarized here and general properties of the spectral momentum density of solids are discussed. Different designs of the (e,2e) spectrometer are described and sample preparation techniques are briefly reviewed. A summary of recent (e,2e) experiments on the electronic structure of valence electrons in graphite, ion sputtered and evaporated amorphous carbon, and aluminum-aluminum oxide films is given. The review concludes with a discussion of an ideal (e,2e) spectrometer for studying bulk properties of solids
HoxA9 binds and represses the Cebpa +8 kb enhancer
Get PDFC/EBPα plays a key role in specifying myeloid lineage development. HoxA9 is expressed in myeloid progenitors, with its level diminishing during myeloid maturation, and HOXA9 is over-expressed in a majority of acute myeloid leukemia cases, including those expressing NUP98-HOXD13. The objective of this study was to determine whether HoxA9 directly represses Cebpa gene expression. We find 4-fold increased HoxA9 and 5-fold reduced Cebpa in marrow common myeloid and LSK progenitors from Vav-NUP98-HOXD13 transgenic mice. Conversely, HoxA9 decreases 5-fold while Cebpa increases during granulocytic differentiation of 32Dcl3 myeloid cells. Activation of exogenous HoxA9-ER in 32Dcl3 cells reduces Cebpa mRNA even in the presence of cycloheximide, suggesting direct repression. Cebpa transcription in murine myeloid cells is regulated by a hematopoietic-specific +37 kb enhancer and by a more widely active +8 kb enhancer. ChIP-Seq analysis of primary myeloid progenitor cells expressing exogenous HoxA9 or HoxA9-ER demonstrates that HoxA9 localizes to both the +8 kb and +37 kb Cebpa enhancers. Gel shift analysis demonstrates HoxA9 binding to three consensus sites in the +8 kb enhancer, but no affinity for the single near-consensus site present in the +37 kb enhancer. Activity of a Cebpa +8 kb enhancer/promoter-luciferase reporter in 32Dcl3 or MOLM14 myeloid cells is increased ~2-fold by mutation of its three HOXA9-binding sites, suggesting that endogenous HoxA9 represses +8 kb Cebpa enhancer activity. In contrast, mutation of five C/EBPα-binding sites in the +8 kb enhancer reduces activity 3-fold. Finally, expression of a +37 kb enhancer/promoter-hCD4 transgene reporter is reduced ~2-fold in marrow common myeloid progenitors when the Vav-NUP98-HOXD13 transgene is introduced. Overall, these data support the conclusion that HoxA9 represses Cebpa expression, at least in part via inhibition of its +8 kb enhancer, potentially allowing normal myeloid progenitors to maintain immaturity and contributing to the pathogenesis of acute myeloid leukemia associated with increased HOXA9
The effect of anthelmintic treatment during pregnancy on HIV plasma viral load: results from a randomized, double-blind, placebo-controlled trial in Uganda.
Get PDFBACKGROUND: To investigate the effect of helminth infections and their treatment during pregnancy on HIV load, we conducted a 2 × 2 factorial randomized controlled trial of albendazole versus placebo and praziquantel versus placebo in pregnant women in Entebbe, Uganda. METHODS: Two hundred sixty-four HIV-infected pregnant women from the Entebbe Mother and Baby Study (ISRCTN 32849447) were included in this analysis. Women were tested for helminth infections at enrollment, and mean HIV load was compared between infected and uninfected groups. The effect of anthelmintic treatment on HIV load was evaluated at 6 weeks after treatment and at delivery using linear regression and adjusting for enrollment viral load. RESULTS: Hookworm and Trichuris infections were associated with higher mean viral load at enrollment [adjusted mean difference 0.24 log10 copies/mL, 95% confidence interval (CI): 0.01 to 0.47, P = 0.03, and 0.37 log(10) copies/mL, 95% CI: 0.00 to 0.74, P = 0.05, respectively]. There were no associations between viral load and other helminth species. There was some evidence that albendazole reduced viral load at 6 weeks after treatment (adjusted mean difference -0.17, 95% CI: -0.36 to 0.01, P = 0.07); however, this effect did not differ according to mother's hookworm infection status and had diminished at delivery (adjusted mean difference -0.11, 95% CI: -0.28 to 0.07, P = 0.23). There was no effect of praziquantel treatment on HIV load at any time point. CONCLUSIONS: Infection with some soil-transmitted helminth species is associated with increased HIV load in pregnancy. Treatment with albendazole causes a small decrease in HIV load; however, this may not represent a direct effect of worm removal
A visualisation tool to analyse usage of web-based interventions: The example of Positive Online Weight Reduction (POWeR)
Get PDFBackground: Attrition is a significant problem in web-based interventions. Consequently, research aims to identify the relation between web usage and benefit from such interventions. We have developed a visualisation tool that enables researchers to more easily examine large data sets on intervention usage that can be difficult to make sense of using traditional descriptive or statistical techniques alone. Objectives: This paper demonstrates how the visualisation tool was used to explore patterns in participants’ use of a web-based weight management intervention (POWeR: Positive Online Weight Reduction). We also demonstrate how the visualisation tool can be used to inform subsequent statistical analyses of the association between usage patterns, participant characteristics, and intervention outcome. Methods: The visualisation tool was used to analyse data from 132 participants who had accessed at least one session of the POWeR intervention. Results: There was a drop in usage of optional sessions after participants had accessed the initial, core POWeR sessions, but many users nevertheless continued to complete goal and weight review. POWeR tools relating to the food diary and steps diary were re-used most often. Differences in participant characteristics and usage of other intervention components were identified between participants who did and did not choose to access optional POWeR sessions (in addition to the initial core sessions) or re-use the food and steps diary. Re-use of the steps diary and the getting support tools was associated with greater weight loss. Conclusions: The visualisation tool provided a quick and efficient method for exploring patterns of web usage, which enabled further analyses of whether different usage patterns were associated with participant characteristics or differences in intervention outcome. Further usage of visualisation techniques is recommended in order to 1) make sense of large data sets more quickly and efficiently, 2) determine the likely active ingredients in web-based interventions, and thereby enhance the benefit they may provide and 3) inform (re-)design of future interventions to promote greater use and engagement by enabling users to easily access valued intervention content/tools
An Spectrometer for Investigating the Spectral Momentum Density of Thin Films
Get PDFAn (e, 2e) spectrometer has been constructed for detecting scattered and recoiling electrons from a thin solid film. The cross section for observing the two electrons in coincidence is proportional to the spectral momentum density of the target. In this spectrometer the energy of the incident electron beam is 25 keV and the beam current is approximately 40 μA. The energy resolution (FWHM) is ≤4 eV. The momentum resolution (FWHM) can be varied from 0.2 to 1.0 Å−1. Preliminary coincidence data from an amorphous carbon film are presented
The COMPLETE Nature of the Warm Dust Ring in Perseus
Full text linkThe Perseus molecular cloud complex is a ~30pc long chain of molecular clouds
most well-known for the two star-forming clusters NGC1333 and IC348 and the
well-studied outflow source in B5. However, when studied at mid- to
far-infrared wavelengths the region is dominated by a ~10pc diameter shell of
warm dust, likely generated by an HII region caused by the early B-star
HD278942. Using a revised calibration technique the COMPLETE team has produced
high-sensitivity temperature and column-density maps of the Perseus region from
IRAS Sky Survey Atlas (ISSA) 60 and 100um data. In this paper, we combine the
ISSA based dust-emission maps with other observations collected as part of the
COMPLETE Survey, along with archival H-alpha and MSX observations. Molecular
line observations from FCRAO and extinction maps constructed by applying the
NICER method to the 2MASS catalog provide independent estimates of the ``true''
column-density of the shell. H-alpha emission in the region of the shell
confirms that it is most likely an HII region located behind the cloud complex,
and 8um data from MSX indicates that the shell may be interacting with the
cloud. Finally, the two polarisation components previously seen towards
background stars in the region can be explained by the association of the
stronger component with the shell. If confirmed, this would be the first
observation of a parsec-scale swept-up magnetic field.Comment: Accepted by ApJ. Figures have been compressed - full resolution
version available at http://cfa-www.harvard.edu/COMPLETE/results.htm
Bacterial susceptibility and resistance to modelin-5.
Get PDFModelin-5 (M5-NH ) killed with a minimum lethal concentration (MLC) of 5.86 μM and strongly bound its cytoplasmic membrane (CM) with a of 23.5 μM. The peptide adopted high levels of amphiphilic α-helical structure (75.0%) and penetrated the CM hydrophobic core (8.0 mN m ). This insertion destabilised CM structure increased lipid packing and decreased fluidity (Δ 0) and promoted only low levels of lysis (24.3%). The insertion and lysis of the CM by M5-NH showed a strong negative correlation with its lysyl phosphatidylglycerol (Lys-PG) content ( > 0.98). In combination, these data suggested that Lys-PG mediated mechanisms inhibited the membranolytic action of M5-NH against , thereby rendering the organism resistant to the peptide. These results are discussed in relation to structure/function relationships of M5-NH and CM lipids that underpin bacterial susceptibility and resistance to the peptide
High Retention of Minority and International Faculty through a Formal Mentoring Program
Get PDFIn these economic times, retention of new faculty, particularly minority and international faculty, is a high priority. In this study, retention of new faculty from 2006 to 2013 was compared for participants and nonparticipants in a formal mentoring program. Retention was 92% for participating faculty and 58% for nonparticipating new faculty. For African American faculty, retention was 86% for participating and 56% for nonparticipating. Participating international faculty were retained at 100% and nonparticipating at 61%. The results indicate that mentoring programs including both individual and group mentoring provide a supportive community and self validation to new faculty, leading to high retention rates
Establishing a New Faculty Mentoring Program: Proposal Development
Get PDFMentoring programs for new faculty provide clear benefits to the participant. However, the availability of mentoring is typically uneven across many campuses. This article describes how faculty development centers can successfully propose a New Faculty Mentoring Program that both benefits and saves money for the larger university. Preparation for a proposal includes a review of the current literature on campus mentoring, an examination of the needs of potential stakeholders, a review of data collected on retention/tenure for new faculty, an analysis of current campus resources, a pilot program and plans for assessment of the program
Maximally Rotating Supermassive Stars at the Onset of Collapse: Effects of Gas Pressure
Full text linkThe "direct collapse" scenario has emerged as a promising evolutionary track
for the formation of supermassive black holes early in the Universe. In an
idealized version of such a scenario, a uniformly rotating supermassive star
spinning at the mass-shedding (Keplerian) limit collapses gravitationally after
it reaches a critical configuration. Under the assumption that the gas is
dominated by radiation pressure, this critical configuration is characterized
by unique values of the dimensionless parameters and , where
is the angular momentum, the polar radius, and the mass. Motivated by
a previous perturbative treatment we adopt a fully nonlinear approach to
evaluate the effects of gas pressure on these dimensionless parameters for a
large range of masses. We find that gas pressure has a significant effect on
the critical configuration even for stellar masses as large as . We also calibrate two approximate treatments of the gas pressure
perturbation in a comparison with the exact treatment, and find that one
commonly used approximation in particular results in increasing deviations from
the exact treatment as the mass decreases, and the effects of gas pressure
increase. The other approximation, however, proves to be quite robust for all
masses .Comment: 13 pages, 7 figures, version accepted for publication in MNRA
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