313 research outputs found
Fatigue Life Prediction under Random Loading Conditions in 7475-T7351 Aluminum Alloy using the RMS Model
One-and-a-half quantum de Finetti theorems
We prove a new kind of quantum de Finetti theorem for representations of the
unitary group U(d). Consider a pure state that lies in the irreducible
representation U_{mu+nu} for Young diagrams mu and nu. U_{mu+nu} is contained
in the tensor product of U_mu and U_nu; let xi be the state obtained by tracing
out U_nu. We show that xi is close to a convex combination of states Uv, where
U is in U(d) and v is the highest weight vector in U_mu. When U_{mu+nu} is the
symmetric representation, this yields the conventional quantum de Finetti
theorem for symmetric states, and our method of proof gives near-optimal bounds
for the approximation of xi by a convex combination of product states. For the
class of symmetric Werner states, we give a second de Finetti-style theorem
(our 'half' theorem); the de Finetti-approximation in this case takes a
particularly simple form, involving only product states with a fixed spectrum.
Our proof uses purely group theoretic methods, and makes a link with the
shifted Schur functions. It also provides some useful examples, and gives some
insight into the structure of the set of convex combinations of product states.Comment: 14 pages, 3 figures, v4: minor additions (including figures),
published versio
Large-scale collective motion of RFGC galaxies
We processed the data about radial velocities and HI linewidths for 1678 flat
edge-on spirals from the Revised Flat Galaxy Catalogue. We obtained the
parameters of the multipole components of large-scale velocity field of
collective non-Hubble galaxy motion as well as the parameters of the
generalized Tully-Fisher relationship in the "HI line width - linear diameter"
version. All the calculations were performed independently in the framework of
three models, where the multipole decomposition of the galaxy velocity field
was limited to a dipole, quadrupole and octopole terms respectively. We showed
that both the quadrupole and the octopole components are statistically
significant.
On the basis of the compiled list of peculiar velocities of 1623 galaxies we
obtained the estimations of cosmological parameters Omega_m and sigma_8. This
estimation is obtained in both graphical form and as a constraint of the value
S_8=sigma_8(Omega_m/0.3)^0.35 = 0.91 +/- 0.05.Comment: Accepted for publication in Astrophysics and Space Scienc
The incidence and risk factors for shipping fever in horses transported by air to Hong Kong: Results from a 2-year prospective study
Evaluating Providers’ Prescription Opioid Instructions to Pediatric Patients
Receiving an opioid prescription during childhood increases the risk of hazardous prescription opioid (PO) use during emerging adulthood. Instruction on how to safely use POs plays an essential role in pediatric patients’ capacity to utilize as well as to discontinue POs appropriately. This study aimed to evaluate pediatric PO label instructions provided to a large sample of pediatric outpatients. Data were extracted from the electronic healthcare records system identifying pediatric patients who received a PO between 2016 and 2019 from pediatric outpatient medical clinics were affiliated with a northwestern United States medical center and children’s hospital. Pediatric patients (n = 12,613) between 0–17 years old who received a PO during outpatient care were included. Patients with chronic health conditions (e.g., cancer) or who received their PO from an inpatient medical setting were excluded. Patient demographics, medication instructions, associated diagnoses, and other prescription information (e.g., name of medication, dose, and quantity dispensed) were examined using automated text classification. Many label instructions did not include any indication/reason for use (20.8%). Virtually none of the POs (\u3e99%) included instructions for how to reduce/wean off POs, contact information for questions about the POs, and/or instructions around how to dispose of the POs. Efforts are needed to ensure that pediatric PO instructions contain essential elements to improve comprehension of when and how to use POs for pediatric patients
Pastoral production is associated with increased peste des petits ruminants seroprevalence in northern Tanzania across sheep, goats and cattle
Peste des petits ruminants virus (PPRV) causes a contagious disease of high morbidity and mortality in small ruminant populations globally. Using cross-sectional serosurvey data collected in 2016, our study investigated PPRV seroprevalence and risk factors among sheep, goats and cattle in 20 agropastoral (AP) and pastoral (P) villages in northern Tanzania. Overall observed seroprevalence was 21.1% (95% exact confidence interval (CI) 20.1–22.0) with 5.8% seroprevalence among agropastoral (95% CI 5.0–6.7) and 30.7% among pastoral villages (95% CI 29.3–32.0). Seropositivity varied significantly by management (production) system. Our study applied the catalytic framework to estimate the force of infection. The associated reproductive numbers (R0) were estimated at 1.36 (95% CI 1.32–1.39), 1.40 (95% CI 1.37–1.44) and 1.13 (95% CI 1.11–1.14) for sheep, goats and cattle, respectively. For sheep and goats, these R0 values are likely underestimates due to infection-associated mortality. Spatial heterogeneity in risk among pairs of species across 20 villages was significantly positively correlated (R2: 0.59–0.69), suggesting either cross-species transmission or common, external risk factors affecting all species. The non-negligible seroconversion in cattle may represent spillover or cattle-to-cattle transmission and must be investigated further to understand the role of cattle in PPRV transmission ahead of upcoming eradication efforts
Svestka's Research: Then and Now
Zdenek Svestka's research work influenced many fields of solar physics,
especially in the area of flare research. In this article I take five of the
areas that particularly interested him and assess them in a "then and now"
style. His insights in each case were quite sound, although of course in the
modern era we have learned things that he could not readily have envisioned.
His own views about his research life have been published recently in this
journal, to which he contributed so much, and his memoir contains much
additional scientific and personal information (Svestka, 2010).Comment: Invited review for "Solar and Stellar Flares," a conference in honour
of Prof. Zden\v{e}k \v{S}vestka, Prague, June 23-27, 2014. This is a
contribution to a Topical Issue in Solar Physics, based on the presentations
at this meeting (Editors Lyndsay Fletcher and Petr Heinzel
Sensitivity optimization in quantum parameter estimation
We present a general framework for sensitivity optimization in quantum
parameter estimation schemes based on continuous (indirect) observation of a
dynamical system. As an illustrative example, we analyze the canonical scenario
of monitoring the position of a free mass or harmonic oscillator to detect weak
classical forces. We show that our framework allows the consideration of
sensitivity scheduling as well as estimation strategies for non-stationary
signals, leading us to propose corresponding generalizations of the Standard
Quantum Limit for force detection.Comment: 15 pages, RevTe
Exo-hydrogenated Single Wall Carbon Nanotubes
An extensive first-principles study of fully exo-hydrogenated zigzag (n,0)
and armchair (n,n) single wall carbon nanotubes (CH), polyhedral
molecules including cubane, dodecahedrane, and CH points to
crucial differences in the electronic and atomic structures relevant to
hydrogen storage and device applications. CH's are estimated to be
stable up to the radius of a (8,8) nanotube, with binding energies proportional
to 1/R. Attaching a single hydrogen to any nanotube is always exothermic.
Hydrogenation of zigzag nanotubes is found to be more likely than armchair
nanotubes with similar radius. Our findings may have important implications for
selective functionalization and finding a way of separating similar radius
nanotubes from each other.Comment: 5 pages, 4 postscript figures, Revtex file, To be appear in Physical
Review
Interplay of quantum magnetic and potential scattering around Zn or Ni impurity ions in superconducting cuprates
To describe the scattering of superconducting quasiparticles from
non-magnetic (Zn) or magnetic (Ni) impurities in optimally doped high T
cuprates, we propose an effective Anderson model Hamiltonian of a localized
electron hybridizing with -wave BCS type superconducting
quasiparticles with an attractive scalar potential at the impurity site. Due to
the strong local antiferromagnetic couplings between the original Cu ions and
their nearest neighbors, the localized electron in the Ni-doped materials is
assumed to be on the impurity sites, while in the Zn-doped materials the
localized electron is distributed over the four nearest neighbor sites of the
impurities with a dominant symmetric form of the wave function.
With Ni impurities, two resonant states are formed above the Fermi level in the
local density of states at the impurity site, while for Zn impurities a sharp
resonant peak below the Fermi level dominates in the local density of states at
the Zn site, accompanied by a small and broad resonant state above the Fermi
level mainly induced by the potential scattering. In both cases, there are no
Kondo screening effects. The local density of states and their spatial
distribution at the dominant resonant energy around the substituted impurities
are calculated for both cases, and they are in good agreement with the
experimental results of scanning tunneling microscopy in
BiSrCaCuO with Zn or Ni impurities, respectively.Comment: 24 pages, Revtex, 8 figures, submitted to Physical Review B for
publication. Sub-ject Class: Superconductivity; Strongly Correlated Electron
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