823 research outputs found
Implementation of the LDA+U method using the full potential linearized augmented plane wave basis
We provide a straightforward and efficient procedure to combine LDA+U total
energy functional with the full potential linearized augmented plane wave
method. A detailed derivation of the LDA+U Kohn-Sham type equations is
presented for the augmented plane wave basis set, and a simple
``second-variation'' based procedure for self-consistent LDA+U calculations is
given. The method is applied to calculate electronic structure and magnetic
properties of NiO and Gd. The magnetic moments and band eigenvalues obtained
are in very good quantitative agreement with previous full potential LMTO
calculations. We point out that LDA+U reduces the total d charge on Ni by 0.1
in NiO
Effect of the GaAsP shell on optical properties of self-catalyzed GaAs nanowires grown on silicon
We realize growth of self-catalyzed core-shell GaAs/GaAsP nanowires (NWs) on
Si substrates using molecular-beam epitaxy. Transmission electron microscopy
(TEM) of single GaAs/GaAsP NWs confirms their high crystal quality and shows
domination of the zinc-blende phase. This is further confirmed in optics of
single NWs, studied using cw and time-resolved photoluminescence (PL). A
detailed comparison with uncapped GaAs NWs emphasizes the effect of the GaAsP
capping in suppressing the non-radiative surface states: significant PL
enhancement in the core-shell structures exceeding 2000 times at 10K is
observed; in uncapped NWs PL is quenched at 60K whereas single core-shell
GaAs/GaAsP NWs exhibit bright emission even at room temperature. From analysis
of the PL temperature dependence in both types of NW we are able to determine
the main carrier escape mechanisms leading to the PL quench
The psychological science accelerator’s COVID-19 rapid-response dataset
In response to the COVID-19 pandemic, the Psychological Science Accelerator coordinated three large-scale psychological studies to examine the effects of loss-gain framing, cognitive reappraisals, and autonomy framing manipulations on behavioral intentions and affective measures. The data collected (April to October 2020) included specific measures for each experimental study, a general questionnaire examining health prevention behaviors and COVID-19 experience, geographical and cultural context characterization, and demographic information for each participant. Each participant started the study with the same general questions and then was randomized to complete either one longer experiment or two shorter experiments. Data were provided by 73,223 participants with varying completion rates. Participants completed the survey from 111 geopolitical regions in 44 unique languages/dialects. The anonymized dataset described here is provided in both raw and processed formats to facilitate re-use and further analyses. The dataset offers secondary analytic opportunities to explore coping, framing, and self-determination across a diverse, global sample obtained at the onset of the COVID-19 pandemic, which can be merged with other time-sampled or geographic data.info:eu-repo/semantics/publishedVersio
Extremal dependence between temperature and ozone over the continental US
The co-occurrence of heat waves and pollution events and the resulting high
mortality rates emphasize the importance of the co-occurrence of pollution
and temperature extremes. Through the use of extreme value theory and other
statistical methods, tropospheric surface ozone and temperature extremes and
their joint occurrence are analyzed over the United States during the summer
months (JJA) using measurements and simulations of the present and future
climate and chemistry. Five simulations from the Chemistry-Climate Model
Initiative (CCMI) reference experiment using specified dynamics (REFC1SD)
were analyzed: the CESM1 CAM4-chem, CHASER, CMAM, MOCAGE and MRI-ESM1r1
simulations. In addition, a 25-year present-day simulation branched off the
CCMI REFC2 simulation in the year 2000 and a 25-year future simulation
branched off the CCMI REFC2 simulation in 2100 were analyzed using CESM1
CAM4-chem. The last two simulations differed in their concentration of carbon
dioxide (representative of the years 2000 and 2100) but were otherwise
identical. In general, regions with relatively high ozone extremes over the
US do not occur in regions of relatively high temperature extremes. A new
metric, the spectral density, is developed to measure the joint extremal
dependence of ozone and temperature by evaluating the spectral dependence of
their extremes. While in many areas of the country ozone and temperature are
highly correlated overall, the correlation is significantly reduced when
examined on the higher end of the distributions. Measures of spectral density
are less than about 0.35 everywhere, suggesting that at most only about a
third of the time do extreme temperatures coincide with extreme ozone. Two
regions of the US have the strongest measured extreme dependence of ozone and
temperature: the northeast and the southeast. The simulated future increase
in temperature and ozone is primarily due to a shift in their distributions,
not to an increase in their extremes. The locations where the right-hand side
of the temperature distribution does increase (by up to 30 %) are
consistent with locations where soil–moisture feedback may be expected.
Future changes in the right-hand side of the ozone distribution range
regionally between +20 % and −10 %. The location of future increases
in the high-end tail of the ozone distribution are weakly related to those of
temperature with a correlation of 0.3. However, the regions where the
temperature extremes increase are not located where the extremes in ozone are
large, suggesting a muted ozone response.</p
Transmembrane protein PERP is a component of tessellate junctions and of other junctional and non-junctional plasma membrane regions in diverse epithelial and epithelium-derived cells
Protein PERP (p53 apoptosis effector related to PMP-22) is a small (21.4 kDa) transmembrane polypeptide with an amino acid sequence indicative of a tetraspanin character. It is enriched in the plasma membrane and apparently contributes to cell-cell contacts. Hitherto, it has been reported to be exclusively a component of desmosomes of some stratified epithelia. However, by using a series of newly generated mono- and polyclonal antibodies, we show that protein PERP is not only present in all kinds of stratified epithelia but also occurs in simple, columnar, complex and transitional epithelia, in various types of squamous metaplasia and epithelium-derived tumors, in diverse epithelium-derived cell cultures and in myocardial tissue. Immunofluorescence and immunoelectron microscopy allow us to localize PERP predominantly in small intradesmosomal locations and in variously sized, junction-like peri- and interdesmosomal regions (“tessellate junctions”), mostly in mosaic or amalgamated combinations with other molecules believed, to date, to be exclusive components of tight and adherens junctions. In the heart, PERP is a major component of the composite junctions of the intercalated disks connecting cardiomyocytes. Finally, protein PERP is a cobblestone-like general component of special plasma membrane regions such as the bile canaliculi of liver and subapical-to-lateral zones of diverse columnar epithelia and upper urothelial cell layers. We discuss possible organizational and architectonic functions of protein PERP and its potential value as an immunohistochemical diagnostic marker
Promotion Determinants in Corporate Hierarchies: An Examination of Fast Tracks and Functional Area
This chapter estimates a dynamic reduced-form model of intra-firm promotions using an employer–employee panel of over 300 of the largest corporations in the United States in the period from 1981 to 1988. The estimation conditions on unobserved individual heterogeneity and allows for both an endogenous initial condition and sample attrition linked to individual heterogeneity in demonstrating the relative importance of variables that influence promotion. The role of the executive’s functional area in promotion is considered along with the existence and source of promotion fast tracks. We find that while the principal determinant of promotions is unobserved individual heterogeneity, functional area has a high explanatory power, resulting in promotion probabilities that differ by functional area for executives at the same reporting level and firm. No evidence is found that an executive’s recent speed of advancement in pay grade has a positive causal impact on in-sample promotions after conditioning on the executive’s career speed of advancement, except for the lowest level executives the data. Fast tracks appear to largely result from heterogeneity in persistent individual characteristics, not from an inherent benefit in recent advancement itself
Influence of timing on CSF tests value for Creutzfeldt-Jakob disease diagnosis
Background: The analysis of markers in the cerebrospinal fluid (CSF) is useful in the diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD). However, the time at which the study of these markers is most sensitive remains controversal. Objective: To assess the influence of time of sampling on the value of CSF tests in the diagnosis of sCJD. Method: In the framework of a multinational European study, we studied the results of 14-3-3, S100b, neurone specific enolase (NSE) and tau protein in 833 CSF samples from sCJD patients at different stages of disease and in 66 sequentially repeated lumbar punctures (LP). Results: 14-3-3 and tau protein tended to increase in sensitivity from onset (88%, 81%) to the advanced stage (91%, 90%). This was significant only in the methionine-valine (MV) heterozygous group of patients at codon 129. The absolute levels of S100b (p < 0.05), NSE and tau protein increased in the last stage of disease. High levels of tau protein, NSE and S100b were associated with shorter survival times (p < 0.01). Sixty-six sCJD patients underwent repeated LP. These sCJD patients were younger, had longer disease durations and were more frequently MV at codon 129 (p < 0.001) than the whole group. 14-3-3 sensitivity increased from 64% to 82% in the second LP (p = 0.025) and 88% sCJD patients had at least one positive result. Conclusions: Sensitivity and absolute levels of CJD markers increased with disease progression and were modulated by the codon 129 genotype. Early negative results should be inter-preted with caution, especially in young patients or those who are MV at codon 129
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