4,949 research outputs found
Total energy differences between SiC polytypes revisited
The total energy differences between various SiC polytypes (3C, 6H, 4H, 2H,
15R and 9R) were calculated using the full-potential linear muffin-tin orbital
method using the Perdew-Wang-(91) generalized gradient approximation to the
exchange-correlation functional in the density functional method. Numerical
convergence versus k-point sampling and basis set completeness are demonstrated
to be better than 1 meV/atom. The parameters of several generalized anisotropic
next-nearest-neighbor Ising models are extracted and their significance and
consequences for epitaxial growth are discussed.Comment: 8 pages, 3 figures, Latex, uses epsfig and revte
Clinical and kidney structural characteristics of living kidney donors with nephrolithiasis and their long-term outcomes
Background: Nephrolithiasis in living kidney donors is concerning due to the potential impact on long-term postdonation kidney function.
Methods: We performed a cohort study of living kidney donors from 2 centers with a baseline computed tomography scan and implantation renal biopsy. Donors (\u3e5 y since donation) completed a follow-up survey or underwent chart review to assess eGFR and incident hypertension. Stone formers were classified as symptomatic if they had a past symptomatic episode or asymptomatic if only incidental radiographic kidney stones were identified during donor evaluation. We compared baseline clinical, imaging, and biopsy characteristics by stone former status including review of metabolic evaluations in stone formers. Long-term risks of renal complications (low eGFR and hypertension) by stone former status were evaluated.
Results: There were 12 symptomatic and 76 asymptomatic stone formers among 866 donors. Overall, baseline clinical characteristics and implantation biopsy findings were similar between stone formers and non-stone formers. After a median follow-up of 10 y, stone former status was not associated with eGFR \u3c60 mL/min/1.73 m2, eGFR \u3c45 mL/min/1.73 m
Conclusions: Both asymptomatic and symptomatic SF have favorable histology findings at baseline. Long-term kidney outcomes were favorable in select stone formers with no evident increased long-term risk for decreased kidney function or hypertension after donation
Detailed Inspection of Metal Implants
Detailed visual inspection of metal hips is the first step in retrieval analysis. In this study a systematic visual inspection protocol was developed to quantify bearing surface changes and their associations with material loss was investigated. Simple and multiple linear regression models found that moderate surface scratching, discolouration, haziness and the size of visible wear scars were all significantly associated with material loss (R2 = 5% - 73%, p<0.05). Visual inspection is not a substitute for measurement of material loss but an understanding of bearing surface changes may offer unique clues as to the mechanisms of failure of retrieved hips
The public view of immigrant integration:multidimensional and consensual. Evidence from survey experiments in the UK and the Netherlands
The future of patient safety: Surgical trainees accept virtual reality as a new training tool
BACKGROUND: The use of virtual reality (VR) has gained increasing interest to acquire laparoscopic skills outside the operating theatre and thus increasing patients' safety. The aim of this study was to evaluate trainees' acceptance of VR for assessment and training during a skills course and at their institution.
METHODS: All 735 surgical trainees of the International Gastrointestinal Surgery Workshop 2006-2008, held in Davos, Switzerland, were given a minimum of 45 minutes for VR training during the course. Participants' opinion on VR was analyzed with a standardized questionnaire.
RESULTS: Fivehundred-twenty-seven participants (72%) from 28 countries attended the VR sessions and answered the questionnaires. The possibility of using VR at the course was estimated as excellent or good in 68%, useful in 21%, reasonable in 9% and unsuitable or useless in 2%. If such VR simulators were available at their institution, most course participants would train at least one hour per week (46%), two or more hours (42%) and only 12% wouldn't use VR. Similarly, 63% of the participants would accept to operate on patients only after VR training and 55% to have VR as part of their assessment.
CONCLUSION: Residents accept and appreciate VR simulation for surgical assessment and training. The majority of the trainees are motivated to regularly spend time for VR training if accessible
A Survey of Air-to-Ground Propagation Channel Modeling for Unmanned Aerial Vehicles
In recent years, there has been a dramatic increase in the use of unmanned
aerial vehicles (UAVs), particularly for small UAVs, due to their affordable
prices, ease of availability, and ease of operability. Existing and future
applications of UAVs include remote surveillance and monitoring, relief
operations, package delivery, and communication backhaul infrastructure.
Additionally, UAVs are envisioned as an important component of 5G wireless
technology and beyond. The unique application scenarios for UAVs necessitate
accurate air-to-ground (AG) propagation channel models for designing and
evaluating UAV communication links for control/non-payload as well as payload
data transmissions. These AG propagation models have not been investigated in
detail when compared to terrestrial propagation models. In this paper, a
comprehensive survey is provided on available AG channel measurement campaigns,
large and small scale fading channel models, their limitations, and future
research directions for UAV communication scenarios
Search for Electron Neutrino Appearance in a 250 km Long-baseline Experiment
We present a search for electron neutrino appearance from accelerator
produced muon neutrinos in the K2K long baseline neutrino experiment. One
candidate event is found in the data corresponding to an exposure of 4.8*10^19
protons on target. The expected background in the absence of neutrino
oscillations is estimated to be 2.4+-0.6 events and is dominated by
mis-identification of events from neutral current pi^0 production. We exclude
the \nu_\mu to \nu_e oscillations at 90% C.L. for the effective mixing angle in
2-flavor approximation of sin^2(2theta_\mu_e) (~= 1/2 sin^2 2 th_13) > 0.15 at
Delta m^2_\mu_e = 2.8*10^{-3} eV^2, the best fit value of the \nu_\mu
disappearance analysis in K2K. The most stringent limit of sin^2(2theta_\mu_e)
< 0.09 is obtained at Delta m^2_\mu_e = 6*10^{-3} eV^2.Comment: 5 pages with 2 figures embeded in two column revtex4 style. Accepted
to be published in Phys. Rev. Let
The HY5-PIF regulatory module coordinates light and temperature control of photosynthetic gene transcription
The ability to interpret daily and seasonal alterations in light and temperature signals is essential for plant survival. This is particularly important during seedling establishment when the phytochrome photoreceptors activate photosynthetic pigment production for photoautotrophic growth. Phytochromes accomplish this partly through the suppression of phytochrome interacting factors (PIFs), negative regulators of chlorophyll and carotenoid biosynthesis. While the bZIP transcription factor long hypocotyl 5 (HY5), a potent PIF antagonist, promotes photosynthetic pigment accumulation in response to light. Here we demonstrate that by directly targeting a common promoter cis-element (G-box), HY5 and PIFs form a dynamic activation-suppression transcriptional module responsive to light and temperature cues. This antagonistic regulatory module provides a simple, direct mechanism through which environmental change can redirect transcriptional control of genes required for photosynthesis and photoprotection. In the regulation of photopigment biosynthesis genes, HY5 and PIFs do not operate alone, but with the circadian clock. However, sudden changes in light or temperature conditions can trigger changes in HY5 and PIFs abundance that adjust the expression of common target genes to optimise photosynthetic performance and growth
AFe2As2 (A = Ca, Sr, Ba, Eu) and SrFe_(2-x)TM_(x)As2 (TM = Mn, Co, Ni): crystal structure, charge doping, magnetism and superconductivity
The electronic structure and physical properties of the pnictide compound
families OFeAs ( = La, Ce, Pr, Nd, Sm), FeAs ( = Ca,
Sr, Ba, Eu), LiFeAs and FeSe are quite similar. Here, we focus on the members
of the FeAs family whose sample composition, quality and single
crystal growth are better controllable compared to the other systems. Using
first principles band structure calculations we focus on understanding the
relationship between the crystal structure, charge doping and magnetism in
FeAs systems. We will elaborate on the tetragonal to
orthorhombic structural distortion along with the associated magnetic order and
anisotropy, influence of doping on the site as well as on the Fe site, and
the changes in the electronic structure as a function of pressure.
Experimentally, we investigate the substitution of Fe in
SrFeAs by other 3 transition metals, = Mn, Co, Ni.
In contrast to a partial substitution of Fe by Co or Ni (electron doping) a
corresponding Mn partial substitution does not lead to the supression of the
antiferromagnetic order or the appearance of superconductivity. Most calculated
properties agree well with the measured properties, but several of them are
sensitive to the As position. For a microscopic understanding of the
electronic structure of this new family of superconductors this structural
feature related to the Fe-As interplay is crucial, but its correct ab initio
treatment still remains an open question.Comment: 27 pages, single colum
- …