2,733 research outputs found
Children and youth with diabetes are not at increased risk for hospitalization due to COVID-19
The severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2), responsible for the coronavirus disease COVID-19, was first identified in Wuhan, China in December 2019. Diabetes, as well as other cardiovascular comorbidities, has been recognized as a major risk factor for outcomes and mortality in adults with COVID-19, particularly in the elderly with type 2 diabetes. Based on these conclusions, COVID-19 data on adults have been generalized to youth with diabetes. Nevertheless, experience from pediatric diabetes practices in China (Wuhan), Italy, Spain (Catalonia), and the United States (San Francisco Bay Area) consistently report only a single severe case of COVID-19 in a 20-year-old female youth with type 1 diabetes (T1D) that was hospitalized for bilateral pneumonia and was subsequently discharged without complications. In Italy, information on COVID-19 in all children with diabetes is collected on a weekly basis and those with positive swab test or infection-related symptoms reported to a dedicated national registry. Of a total of 15 500 children tested, 11 subjects with T1D (age 8-17y) tested positive for COVID-19; 6/11 were asymptomatic and the rest presented with mild symptoms. In the rest of locations, youths with T1D diagnosed with COVID-19 were based on clinical suspicion and a confirmatory PCR test (Wuhan:0; Catalonia-HSJD:3; California-Stanford:2). All of them were asymptomatic or had a mild course. We suggest that COVID-19 data from adults should not be generalized to children, adolescents, and youth with diabetes as their outcomes and prognosis seem to be similar to their non-diabetic-peers and consistently milder than adults with diabetes
Density of states of a layered S/N d-wave superconductor
We calculate the density of states of a layered superconductor in which there
are two layers per unit cell. One of the layers contains a d-wave pairing
interaction while the other is a normal metal. The goal of this article is to
understand how the d-wave behaviour of the system is modified by the coupling
between the layer-types. This coupling takes the form of coherent, single
particle tunneling along the c-axis. We find that there are two physically
different limits of behaviour, which depend on the relative locations of the
Fermi surfaces of the two layer-types. We also discuss the interference between
the interlayer coupling and pairing interaction and we find that this
interference leads to features in the density of states.Comment: 33 pages and 11 PostScript figure
Lattice Dynamics and Specific Heat of - GeTe: a theoretical and experimental study
We extend recent \textit{ab initio} calculations of the electronic band
structure and the phonon dispersion relations of rhombohedral GeTe to
calculations of the density of phonon states and the temperature dependent
specific heat. The results are compared with measurements of the specific heat.
It is discovered that the specific heat depends on hole concentration, not only
in the very low temperature region (Sommerfeld term) but also at the maximum of
(around 16 K). To explain this phenomenon, we have performed
\textit{ab initio} lattice dynamical calculations for GeTe rendered metallic
through the presence of a heavy hole concentration ( 2
10 cm). They account for the increase observed in the maximum of
.Comment: 8 pages, 7 figures, ref. 19 correcte
Optical Absorption of an Interacting Many-Polaron Gas
The optical absorption of a many (continuum) polaron gas is derived in the
framework of a variational approach at zero temperature and weak or
intermediate electron-phonon coupling strength. We derive a compact formula for
the optical conductivity of the many-polaron system taking into account
many-body effects in the electron or hole system. Within the method presented
here, these effects are contained completely in the dynamical structure factor
of the electron or hole system. This allows to build on well-established
studies of the interacting electron gas. Based on this approach a novel feature
in the absorption spectrum of the many-polaron gas, related to the emission of
a plasmon together with a phonon, is identified. As an application and
illustration of the technique, we compare the theoretical many-polaron optical
absorption spectrum as derived in the present work with the `d-band' absorption
feature in NdCuO. Similarities are shown between the theoretically
and the experimentally derived first frequency moment of the optical absorption
of a family of differently doped NdCeCuO materials.Comment: 24 pages, 5 figures; revised and expanded versio
Positivity Constraints on Anomalies in Supersymmetric Gauge Theories
The relation between the trace and R-current anomalies in supersymmetric
theories implies that the U, U and U anomalies which
are matched in studies of N=1 Seiberg duality satisfy positivity constraints.
Some constraints are rigorous and others conjectured as four-dimensional
generalizations of the Zamolodchikov -theorem. These constraints are tested
in a large number of N=1 supersymmetric gauge theories in the non-Abelian
Coulomb phase, and they are satisfied in all renormalizable models with unique
anomaly-free R-current, including those with accidental symmetry. Most striking
is the fact that the flow of the Euler anomaly coefficient, , is
always positive, as conjectured by Cardy.Comment: latex, 36 page
Triplet Exciton Generation in Bulk-Heterojunction Solar Cells based on Endohedral Fullerenes
Organic bulk-heterojunctions (BHJ) and solar cells containing the trimetallic
nitride endohedral fullerene 1-[3-(2-ethyl)hexoxy
carbonyl]propyl-1-phenyl-Lu3N@C80 (Lu3N@C80-PCBEH) show an open circuit voltage
(VOC) 0.3 V higher than similar devices with [6,6]-phenyl-C[61]-butyric acid
methyl ester (PC61BM). To fully exploit the potential of this acceptor molecule
with respect to the power conversion efficiency (PCE) of solar cells, the short
circuit current (JSC) should be improved to become competitive with the state
of the art solar cells. Here, we address factors influencing the JSC in blends
containing the high voltage absorber Lu3N@C80-PCBEH in view of both
photogeneration but also transport and extraction of charge carriers. We apply
optical, charge carrier extraction, morphology, and spin-sensitive techniques.
In blends containing Lu3N@C80-PCBEH, we found 2 times weaker photoluminescence
quenching, remainders of interchain excitons, and, most remarkably, triplet
excitons formed on the polymer chain, which were absent in the reference
P3HT:PC61BM blends. We show that electron back transfer to the triplet state
along with the lower exciton dissociation yield due to intramolecular charge
transfer in Lu3N@C80-PCBEH are responsible for the reduced photocurrent
Observation of an Excited Bc+ State
Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date
Measurement of the CKM angle γ from a combination of B±→Dh± analyses
A combination of three LHCb measurements of the CKM angle γ is presented. The decays B±→D K± and
B±→Dπ± are used, where D denotes an admixture of D0 and D0 mesons, decaying into K+K−, π+π−, K±π∓, K±π∓π±π∓, K0Sπ+π−, or K0S K+K− final states. All measurements use a dataset corresponding to 1.0 fb−1 of integrated luminosity. Combining results from B±→D K± decays alone a best-fit value of
γ =72.0◦ is found, and confidence intervals are set
γ ∈ [56.4,86.7]◦ at 68% CL,
γ ∈ [42.6,99.6]◦ at 95% CL.
The best-fit value of γ found from a combination of results from B±→Dπ± decays alone, is γ =18.9◦,
and the confidence intervals
γ ∈ [7.4,99.2]◦ ∪ [167.9,176.4]◦ at 68% CL
are set, without constraint at 95% CL. The combination of results from B± → D K± and B± → Dπ±
decays gives a best-fit value of γ =72.6◦ and the confidence intervals
γ ∈ [55.4,82.3]◦ at 68% CL,
γ ∈ [40.2,92.7]◦ at 95% CL
are set. All values are expressed modulo 180◦, and are obtained taking into account the effect of D0–D0
mixing
Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at √s=7 TeV
Bose-Einstein correlations of same-sign charged pions, produced in protonproton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected
by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the
form of an enhancement of pairs of like-sign charged pions with small four-momentum
difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source
is investigated, determining both the correlation radius and the chaoticity parameter. The
measured correlation radius is found to increase as a function of increasing charged-particle
multiplicity, while the chaoticity parameter is seen to decreas
Measurement of the inelastic pp cross-section at a centre-of-mass energy of 13TeV
The cross-section for inelastic proton-proton collisions at a centre-of-mass energy of 13TeV is measured with the LHCb detector. The fiducial cross-section for inelastic interactions producing at least one prompt long-lived charged particle with momentum p > 2 GeV/c in the pseudorapidity range 2 < η < 5 is determined to be ϭ acc = 62:2 ± 0:2 ± 2:5mb. The first uncertainty is the intrinsic systematic uncertainty of the measurement, the second is due to the uncertainty on the integrated luminosity. The statistical uncertainty is negligible. Extrapolation to full phase space yields the total inelastic proton-proton cross-section ϭ inel = 75:4 ± 3:0 ± 4:5mb, where the first uncertainty is experimental and the second due to the extrapolation. An updated value of the inelastic cross-section at a centre-of-mass energy of 7TeV is also reported
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