195 research outputs found
Resummed Mass Distribution for Jets Initiated by Massive Quarks
We resum to all orders of perturbation theory the invariant mass distribution of jets initiated by massive quarks. We find that the inclusion of mass terms, in the N-moment space, results in the universal factor delta_N(Q^2;m^2), taking into account dead-cone effects in gluon emission, which multiplies the massless jet distribution function J_N(Q^2). The variable N is rescaled by the mass correction parameter r = m^2/Q^2 c l nu decay spectra or the inclusion of beauty mass effects in t --> b W decays, are briefly sketched
Photoemission kinks and phonons in cuprates
One of the possible mechanisms of high Tc superconductivity is Cooper pairing
with the help of bosons, which change the slope of the electronic dispersion as
observed by photoemission. Giustino et al. calculated that in the high
temperature superconductor La1.85Sr0.15CuO4 crystal lattice vibrations
(phonons) should have a negligible effect on photoemission spectra and
concluded that phonons do not play an important role. We show that the
calculations employed by Giustino et al. fail to reproduce huge influence of
electron-phonon coupling on important phonons observed in experiments. Thus one
would expect these calculations to similarly fail in explaining the role of
electron-phonon coupling for the electronic dispersion.Comment: To appear in Nature as a Brief Communiction Arisin
Physical fitness assessment in Goalball: A scoping review of the literature
Background: Goalball is a Paralympic sport for visually impaired athletes. Although it is widely practiced, a great variety of tests are adopted to evaluate athletes' physical fitness. Therefore, the objective was to identify the physical fitness tests adopted in this sport to find the common aspects between them and, eventually, to propose a standard operating procedure. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) guidelines were adopted. The studies were extracted from PubMed, Web of Science, and Scopus. A selection process by title, abstract, and full-text, according to the inclusion and exclusion criteria, was performed. The results were discussed with narrative synthesis. Results: A total of 7 papers and 222 participants were included. A wide variety of tests were adopted and the Brockport Physical Fitness Test (BPFT) was the only battery included to evaluate general athletes' well-being. Conclusions: Although few literature exists on Goalball, the BPFT could be the battery for evaluating Goalball athletes though the test battery should be standardized to the characteristics of this sport
First-Principles Study of Electron Linewidths in Graphene
We present first-principles calculations of the linewidths of low-energy
quasiparticles in n-doped graphene arising from both the electron-electron and
the electron-phonon interactions. The contribution to the electron linewidth
arising from the electron-electron interactions vary significantly with
wavevector at fixed energy; in contrast, the electron-phonon contribution is
virtually wavevector-independent. These two contributions are comparable in
magnitude at a binding energy of ~0.2 eV, corresponding to the optical phonon
energy. The calculated linewidths, with both electron-electron and
electron-phonon interactions included, explain to a large extent the linewidths
seen in recent photoemission experiments.Comment: 5 pages, 3 figure
EPW: A program for calculating the electron-phonon coupling using maximally localized Wannier functions
EPW (Electron-Phonon coupling using Wannier functions) is a program written
in FORTRAN90 for calculating the electron-phonon coupling in periodic systems
using density-functional perturbation theory and maximally-localized Wannier
functions. EPW can calculate electron-phonon interaction self-energies,
electron-phonon spectral functions, and total as well as mode-resolved
electron-phonon coupling strengths. The calculation of the electron-phonon
coupling requires a very accurate sampling of electron-phonon scattering
processes throughout the Brillouin zone, hence reliable calculations can be
prohibitively time-consuming. EPW combines the Kohn-Sham electronic eigenstates
and the vibrational eigenmodes provided by the Quantum-ESPRESSO package [1]
with the maximally localized Wannier functions provided by the wannier90
package [2] in order to generate electron-phonon matrix elements on arbitrarily
dense Brillouin zone grids using a generalized Fourier interpolation. This
feature of EPW leads to fast and accurate calculations of the electron-phonon
coupling, and enables the study of the electron-phonon coupling in large and
complex systems.Comment: 6 figure
Factors affecting the development of Bovine Respiratory Disease: a cross-sectional study in beef steers shipped from France to Italy
Bovine respiratory disease (BRD) is a complex, multifactorial syndrome and one of the major welfare and economical concerns for the cattle industry. This 1-year cross-sectional study was aimed at documenting the prevalence of BRD-related pathogens and clinical signs before and after a long journey and at identifying possible predisposition factors. Male Limousine beef steers (n = 169) traveling from France to Italy were health checked and sampled with Deep Nasopharyngeal Swabs (DNS) at loading (T0) and 4 days after arrival (T1). Real-time quantitative PCR was used to quantify the presence of bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine alphaherpesvirus 1 (BoHV-1), bovine coronavirus (BCoV), bovine adenovirus (BAdV), bovine parainfluenza virus 3 (BPIV-3), Histophilus somni, Mannheimia haemolytica, Mycoplasma bovis, and Pasteurella multocida. Weather conditions at departure and arrival were recorded, and the travel conditions were taken from the travel documentation. At T0, even if no animals displayed clinical signs, some of them were already positive for one or more pathogens. At T1, the number of animals displaying clinical signs and positive for BCoV, BAdV, BRSV, H. somni, M. haemolytica, M. bovis, and P. multocida increased dramatically (p < 0.001). Transport also significantly increased co-infection passing from 16.0% at T0 to 82.8% at T1 (p < 0.001). An extra stop during the journey seemed to favor BRSV, M. haemolytica, and P. multocida (p < 0.05). Weather conditions, in particular sudden climate changes from departure to arrival and daily temperature variance, were found to be predisposing factors for many of the pathogens. The farm of arrival also played a role for BRSV, BAdV, and H. somni (p < 0.05). BCoV increased dramatically, but no associations were found confirming that it spreads easily during transport phases. Our findings increased our understanding of factors increasing the likelihood of BRD-related pathogens shedding and can be useful to minimize the incidence of BRD and to implement animal transport regulations
Manual dexterity in school-age children measured by the Grooved Pegboard test: Evaluation of training effect and performance in dual-task
ackground: Manual dexterity is the ability to manipulate objects using the hands and fingers for a specific task. Although manual dexterity is widely investigated in the general and special popu- lation at all ages, numerous aspects still remain to be explored in children. The aim of this study was to assess the presence of the training effect of the execution of the Grooved Pegboard test (GPT) and to measure the performance of the GPT in dual-task (DT), i.e., during a motor task and a cognitive task.
Methods: In this observational, cross-sectional study manual dexterity was assessed in children aged between 6 and 8. The procedure consisted of two phases: (1) the execution of five consecutive trials of the GPT to evaluate the training effect; (2) the execution of one trial of the GPT associated with a motor task (finger tapping test, GPT-FTT), and one trial of the GPT asso- ciated with a cognitive task (counting test, GPT-CT) to evaluate the performance in DT.
Results: As for the training effect, a significant difference (p < 0.001) between the five trials of the GPT (i.e., GPT1, GPT2, GPT3, GPT4, GPT5) was detected. In particular, we found a significant difference between GPT1 and GPT3 (p < 0.05), GPT1 and GPT4 (p < 0.001), and GPT1 and GPT5 (p < 0.001), as well as between GPT2 and GPT4 (p < 0.001), and GPT2 and GPT5 (p < 0.001). As for the performance in DT, no differences between the best trial of the GPT (i.e., GPT5) and both the GPT-FTT and GPT-CT was found.
Conclusion: Our findings suggest that the execution of the GPT in children has a training effect up to the third consecutive trial. Furthermore, the administration of the GPT in DT does not affect GPT performance
Angle-resolved photoemission spectra of graphene from first-principles calculations
Angle-resolved photoemission spectroscopy (ARPES) is a powerful experimental
technique for directly probing electron dynamics in solids. The energy vs.
momentum dispersion relations and the associated spectral broadenings measured
by ARPES provide a wealth of information on quantum many-body interaction
effects. In particular, ARPES allows studies of the Coulomb interaction among
electrons (electron-electron interactions) and the interaction between
electrons and lattice vibrations (electron-phonon interactions). Here, we
report ab initio simulations of the ARPES spectra of graphene including both
electron-electron and electron-phonon interactions on the same footing. Our
calculations reproduce some of the key experimental observations related to
many-body effects, including the indication of a mismatch between the upper and
lower halves of the Dirac cone
Stevens-Johnson Syndrome From Combined Allopurinol and Angiotensin-Converting Enzyme Inhibitors: A Narrative Review
Stevens-Johnson syndrome (SJS) is a severe and potentially debilitating skin reaction frequently related to medication use. Allopurinol and angiotensin-converting enzyme (ACE) inhibitors are commonly prescribed medications for prevalent health conditions worldwide, and their interaction associated with SJS warrants further investigation. A comprehensive literature search was performed to investigate cases as studies related to SJS occurring in patients with concomitant use of allopurinol and ACE inhibitors. We identified case reports and studies detailing hypersensitivity reactions, including SJS, attributed to a combination of allopurinol and ACE inhibitors. Despite the drug-drug interactions or lack thereof seen in patient populations, there is no definitive evidence of a pharmacokinetic interaction between allopurinol and ACE inhibitors. We were only able to find one case report specifically detailing SJS in a patient on combined ACE inhibitors and allopurinol. While the exact mechanism of the interaction is unclear, those reported cases of severe hypersensitivity reactions suggest a previous history of impaired renal function as a predisposing factor in the development of SJS. The potential risk of SJS with coadministration of ACE inhibitors and allopurinol is a drug-drug interaction that physicians should be aware of. This topic requires additional attention to determine if this drug combination should be avoided entirely in certain patients
Crystallographic, Optical, and Electronic Properties of the Cs2AgBi1–xInxBr6 Double Perovskite: Understanding the Fundamental Photovoltaic Efficiency Challenges
We present a crystallographic and optoelectronic study of the double perovskite Cs2AgBi1–xInxBr6. From structural characterization we determine that the indium cation shrinks the lattice and shifts the cubic-to-tetragonal phase transition point to lower temperatures. The absorption onset is shifted to shorter wavelengths upon increasing the indium content, leading to wider band gaps, which we rationalize through first-principles band structure calculations. Despite the unfavorable band gap shift, we observe an enhancement in the steady-state photoluminescence intensity, and n-i-p photovoltaic devices present short-circuit current greater than that of neat Cs2AgBiBr6 devices. In order to evaluate the prospects of this material as a solar absorber, we combine accurate absorption measurements with thermodynamic modeling and identify the fundamental limitations of this system. Provided radiative efficiency can be increased and the choice of charge extraction layers are specifically improved, this material could prove to be a useful wide band gap solar absorber
- …