52,113 research outputs found
Estimates of isospin breaking contributions to baryon masses
We estimate the isospin breaking contributions to the baryon masses which we
analyzed recently using a loop expansion in the heavy baryon approximation to
chiral effective field theory. To one loop, the isospin breaking corrections
come from the effects of the quark mass difference, the Coulomb and
magnetic moment interactions, and effective point interactions attributable to
color-magnetic effects. The addition of the first meson loop corrections
introduces new structure. We estimate the resulting low-energy, long-range
contributions to the mass splittings by regularizing the loop integrals using
connections to dynamical models for finite-size baryons. We find that the
resulting contributions to the isospin breaking corrections are of the right
general size, have the correct sign pattern, and agree with the experimental
values within the margin of error.Comment: 15 pages, 5 figures; changed title and conten
Foreword
This work reports on the performances of ohmic contacts fabricated on highly p-type doped 4H-SiC epitaxial layer selectively grown by vapor-liquid-solid transport. Due to the very high doping level obtained, the contacts have an ohmic behavior even without any annealing process. Upon variation of annealing temperatures, it was shown that both 500 and 800 °C annealing temperature lead to a minimum value of the Specific Contact Resistance (SCR) down to 1.3×10−6 Ω⋅cm2. However, a large variation of the minimum SCR values has been observed (up to 4×10−4 Ω⋅cm2). Possible sources of this fluctuation have been also discussed in this paper
Green Function of the Sutherland Model with SU(2) internal symmetry
We obtain the hole propagator of the Sutherland model with SU(2) internal
symmetry for coupling parameter , which is the simplest nontrivial
case. One created hole with spin down breaks into two quasiholes with spin down
and one quasihole with spin up. While these elementary excitations are
energetically free, the form factor reflects their anyonic character. The
expression for arbitrary integer is conjectured.Comment: 13pages, Revtex, one ps figur
Sustainability performance measurement : a preliminary classification framework of models and indicators
In this position paper we focus on the diversity of sustainability measurements. Based on existing research on performance measurement, we propose a preliminary classification framework summarizing sustainability models and indicators. By describing illustrative examples, we claim that several models and indicators can be distinguished with their own peculiarities. Having such a framework is interesting for both academia and business to structure the range of models and indicators and to ultimately select the appropriate sustainability measurement approach. The proposed framework should be validated by further research
Spin-Charge Separation at Finite Temperature in the Supersymmetric t-J Model with Long-Range Interactions
Thermodynamics is derived rigorously for the 1D supersymmetric {\it t-J}
model and its SU() generalization with inverse-square exchange. The system
at low temperature is described in terms of spinons, antispinons, holons and
antiholons obeying fractional statistics. They are all free and make the spin
susceptibility independent of electron density, and the charge susceptibility
independent of magnetization. Thermal spin excitations responsible for the
entropy of the SU() model are ascribed to free para-fermions of order
.Comment: 10 pages, REVTE
Antonio Gramsci’s impact on critical pedagogy
This paper provides an account of Antonio Gramsci’s impact on the area of critical pedagogy. It indicates the Gramscian influence on the thinking of major exponents of the field. It foregrounds Gramsci's ideas and then indicates how they have been taken up by a selection of critical pedagogy exponents who were chosen on the strength of their identification and engagement with Gramsci's ideas, some of them even having written entire essays on Gramsci. The essay concludes with a discussion concerning an aspect of Gramsci's concerns, the question of powerful knowledge, which, in the present author's view, provides a formidable challenge to critical pedagogues.peer-reviewe
Sentinel surveillance of HIV-1 transmitted drug resistance, acute infection and recent infection.
BackgroundHIV-1 acute infection, recent infection and transmitted drug resistance screening was integrated into voluntary HIV counseling and testing (VCT) services to enhance the existing surveillance program in San Francisco. This study describes newly-diagnosed HIV cases and characterizes correlates associated with infection.Methodology/principal findingsA consecutive sample of persons presenting for HIV VCT at the municipal sexually transmitted infections (STI) clinic from 2004 to 2006 (N = 9,868) were evaluated by standard enzyme-linked immunoassays (EIA). HIV antibody-positive specimens were characterized as recent infections using a less-sensitive EIA. HIV-RNA pooled testing was performed on HIV antibody-negative specimens to identify acute infections. HIV antibody-positive and acute infection specimens were evaluated for drug resistance by sequence analysis. Multivariable logistic regression was performed to evaluate associations. The 380 newly-diagnosed HIV cases included 29 acute infections, 128 recent infections, and 47 drug-resistant cases, with no significant increases or decreases in prevalence over the three years studied. HIV-1 transmitted drug resistance prevalence was 11.0% in 2004, 13.4% in 2005 and 14.9% in 2006 (p = 0.36). Resistance to non-nucleoside reverse transcriptase inhibitors (NNRTI) was the most common pattern detected, present in 28 cases of resistance (59.6%). Among MSM, recent infection was associated with amphetamine use (AOR = 2.67; p<0.001), unprotected anal intercourse (AOR = 2.27; p<0.001), sex with a known HIV-infected partner (AOR = 1.64; p = 0.02), and history of gonorrhea (AOR = 1.62; p = 0.03).ConclusionsNew HIV diagnoses, recent infections, acute infections and transmitted drug resistance prevalence remained stable between 2004 and 2006. Resistance to NNRTI comprised more than half of the drug-resistant cases, a worrisome finding given its role as the backbone of first-line antiretroviral therapy in San Francisco as well as worldwide. The integration of HIV-1 drug resistance, recent infection, and acute infection testing should be considered for existing HIV/STI surveillance and prevention activities, particularly in an era of enhanced efforts for early diagnosis and treatment
Exact dynamical structure factor of the degenerate Haldane-Shastry model
The dynamical structure factor of the K-component (K = 2,3,4)
spin chain with the 1/r^2 exchange is derived exactly at zero temperature for
arbitrary size of the system. The result is interpreted in terms of a free
quasi-particle picture which is generalization of the spinon picture in the
SU(2) case; the excited states consist of K quasi-particles each of which is
characterized by a set of K-1 quantum numbers. Divergent singularities of
at the spectral edges are derived analytically. The analytic
result is checked numerically for finite systems.Comment: 4 pages, 1 figure, accepted for publication in Phys. Rev. Let
Spitzer Observations of Interstellar Object 1I/`Oumuamua
1I/`Oumuamua is the first confirmed interstellar body in our Solar System.
Here we report on observations of `Oumuamua made with the Spitzer Space
Telescope on 2017 November 21--22 (UT). We integrated for 30.2~hours at 4.5
micron (IRAC channel 2). We did not detect the object and place an upper limit
on the flux of 0.3 uJy (3sigma). This implies an effective spherical diameter
less than [98, 140, 440] meters and albedo greater than [0.2, 0.1, 0.01] under
the assumption of low, middle, or high thermal beaming parameter eta,
respectively. With an aspect ratio for `Oumuamua of 6:1, these results
correspond to dimensions of [240:40, 341:57, 1080:180] meters, respectively. We
place upper limits on the amount of dust, CO, and CO2 coming from this object
that are lower than previous results; we are unable to constrain the production
of other gas species. Both our size and outgassing limits are important because
`Oumuamua's trajectory shows non-gravitational accelerations that are sensitive
to size and mass and presumably caused by gas emission. We suggest that
`Oumuamua may have experienced low-level post-perihelion volatile emission that
produced a fresh, bright, icy mantle. This model is consistent with the
expected eta value and implied high albedo value for this solution, but, given
our strict limits on CO and CO2, requires another gas species --- probably H2O
--- to explain the observed non-gravitational acceleration. Our results extend
the mystery of `Oumuamua's origin and evolution
Elementary Excitations and Dynamical Correlation Functions of the Calogero-Sutherland Model with Internal Symmetry
We consider the physical properties of elementary excitations of the
Calogero-Sutherland (CS) model with SU(K) internal symmetry. From the results
on the thermodynamics of this model, we obtain the charge, spin, and statistics
of elementary excitations. Combining this knowledge and the known results on
the dynamics in the spinless CS model, we propose the expression for the
dynamical correlation functions of the SU(K) CS model. In the asymptotic
region, we confirm the consistency of our results with predictions from
conformal field theory.Comment: 22 pages, REVTe
- …