3,220 research outputs found
LiBeB, Cosmic Rays and Gamma-Ray Line Astronomy
This article is a summary of a recently held conference on the light
elements, Li, Be and B, and their relationship to cosmic-ray origin and
gamma-ray astronomy. The proceedings will be published by the PASP.Comment: latex 6 pages, uses aasms4.sty To appear in the Publications of the
Astronomical Society of the Pacific (PASP
A Simple Way of Calculating Cosmological Relic Density
A simple procedure is presented which leads to a dramatic simplification in
the calculation of the relic density of stable particles in the Universe.Comment: 7 pages in LaTex, no figures; University of Michigan preprint
UM-TH-94-02 (February 1994). Changes: a coefficient in (Eq. 16)
corrected; added Acknowledgements and revised Note Added; plain LaTex only
(no need to use RevTex
Screening effect in Spin-Hall Devices
The stationary state of the spin-Hall bar is studied in the framework of a
variational approach that includes non-equilibrium screening effects. The
minimization of the power dissipated in the system is performed with taking
into account the spin-flip relaxation and the global constrains due to the
electric generator and global charge conservation. The calculation is performed
in both approximations of negligible spin-flip scattering and strong spin-flip
scattering. In both cases, the expressions of the spin-accumulation and the
longitudinal and transverse pure spin-currents are derived analytically. Due to
the small value of the Debye-Fermi screening length, the spin-accumulation is
shown to be linear in (across the device), linear in the electric field
imposed by the generator, and inversely proportional to the temperature for
non-degenerate conductors
Comparative US-MRI evaluation of the Insall–Salvati index
Purpose: To investigate whether the universally accepted range of normal patellar height ratio derived from MRI for the Insall–Salvati (IS) method could be similarly applied to ultrasound (US). Materials and methods: This study included 52 patients (age range 11–75 years) who underwent a bi-modality (US and MRI) examination, with a total of 60 knees evaluated. IS index (ratio of the patella tendon length to length of the patella) was acquired with both methods. Two operators, with different experiences of musculoskeletal imaging and blinded to the results of other investigators, separately performed the MRI and US measurements. Results: For the two operators, MRI reported a mean value of patellar height ratio of 1.10 ± 0.16 (mean ± standard deviation SD), while US a mean value of 1.17 ± 0.16 (mean ± SD). For comparable results, the small addition of 0.16 is needed for the measurements on US compared with MRI. Inter-observer agreements using intra-class correlation coefficient (ICC) was, respectively, 0.97 for MRI and 0.98 for US. The difference of mean values in patellar height ratios between MRI and US was not statistically significant (p = 0.15). The ICC between the two modalities was 0.94. Conclusion: According to our experience, IS index can be appropriately evaluated on US images, reducing the need of other imaging techniques
Update on the Direct Detection of Supersymmetric Dark Matter
We compare updated predictions for the elastic scattering of supersymmetric
neutralino dark matter with the improved experimental upper limit recently
published by CDMS II. We take into account the possibility that the \pi-nucleon
\Sigma term may be somewhat larger than was previously considered plausible, as
may be supported by the masses of exotic baryons reported recently. We also
incorporate the new central value of m_t, which affects indirectly constraints
on the supersymmetric parameter space, for example via calculations of the
relic density. Even if a large value of \Sigma is assumed, the CDMS II data
currently exclude only small parts of the parameter space in the constrained
MSSM (CMSSM) with universal soft supersymmetry-breaking Higgs, squark and
slepton masses. None of the previously-proposed CMSSM benchmark scenarios is
excluded for any value of \Sigma, and the CDMS II data do not impinge on the
domains of the CMSSM parameter space favoured at the 90 % confidence level in a
recent likelihood analysis. However, some models with non-universal Higgs,
squark and slepton masses and neutralino masses \lappeq 700 GeV are excluded by
the CDMS II data.Comment: 25 pages, 28 eps figure
Numerical simulations on the 4d Heisenberg spin glass
We study the 4d Heisenberg spin glass model with Gaussian nearest-neighbor
interactions. We use finite size scaling to analyze the data. We find a
behavior consistent with a finite temperature spin glass transition. Our
estimates for the critical exponents agree with the results from
epsilon-expansion.Comment: 11 pages, LaTeX, preprint ROMA1 n. 105
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