16,649 research outputs found
Design data collection with Skylab/EREP microwave instrument S-193
There are no author-identified significant results in this report
Epidemiology and potential preventative measures for viral infections in children with malignancy and those undergoing hematopoietic cell transplantation.
In pediatric patients with malignancy and those receiving hematopoietic stem cell transplants, bacterial and fungal infections have been the focus of fever and neutropenia episodes for decades. However, improved diagnostic capabilities have revealed viral pathogens as a significant cause of morbidity and mortality. Because of limited effective antiviral therapies, prevention of viral infections is paramount. Pre-exposure and post-exposure prophylaxis and antiviral suppressive therapeutic approaches are reviewed. Additionally, infection control practices specific to this patient population are discussed. A comprehensive approach utilizing each of these can be effective at reducing the negative impact of viral infections
U(1)' solution to the mu-problem and the proton decay problem in supersymmetry without R-parity
The Minimal Supersymmetric Standard Model (MSSM) is plagued by two major
fine-tuning problems: the mu-problem and the proton decay problem. We present a
simultaneous solution to both problems within the framework of a U(1)'-extended
MSSM (UMSSM), without requiring R-parity conservation. We identify several
classes of phenomenologically viable models and provide specific examples of
U(1)' charge assignments. Our models generically contain either lepton number
violating or baryon number violating renormalizable interactions, whose
coexistence is nevertheless automatically forbidden by the new U(1)' gauge
symmetry. The U(1)' symmetry also prohibits the potentially dangerous and often
ignored higher-dimensional proton decay operators such as QQQL and UUDE which
are still allowed by R-parity. Thus, under minimal assumptions, we show that
once the mu-problem is solved, the proton is sufficiently stable, even in the
presence of a minimum set of exotics fields, as required for anomaly
cancellation. Our models provide impetus for pursuing the collider
phenomenology of R-parity violation within the UMSSM framework.Comment: Version published in Phys. Rev.
Lanczos exact diagonalization study of field-induced phase transition for Ising and Heisenberg antiferromagnets
Using an exact diagonalization treatment of Ising and Heisenberg model
Hamiltonians, we study field-induced phase transition for two-dimensional
antiferromagnets. For the system of Ising antiferromagnet the predicted
field-induced phase transition is of first order, while for the system of
Heisenberg antiferromagnet it is the second-order transition. We find from the
exact diagonalization calculations that the second-order phase transition
(metamagnetism) occurs through a spin-flop process as an intermediate step.Comment: 4 pages, 4 figure
Coarse-graining the dynamics of coupled oscillators
We present an equation-free computational approach to the study of the
coarse-grained dynamics of {\it finite} assemblies of {\it non-identical}
coupled oscillators at and near full synchronization. We use coarse-grained
observables which account for the (rapidly developing) correlations between
phase angles and oscillator natural frequencies. Exploiting short bursts of
appropriately initialized detailed simulations, we circumvent the derivation of
closures for the long-term dynamics of the assembly statistics.Comment: accepted for publication in Phys. Rev. Let
Spectroscopic Evidence for Anisotropic S-Wave Pairing Symmetry in MgB2
Scanning tunneling spectroscopy of superconducting MgB ( K)
were studied on high-density pellets and c-axis oriented films. The sample
surfaces were chemically etched to remove surface carbonates and hydroxides,
and the data were compared with calculated spectra for all symmetry-allowed
pairing channels. The pairing potential () is best described by an
anisotropic s-wave pairing model, with , where is the angle relative to the
crystalline c-axis, meV, and meV.Comment: 4 pages and 3 figures. Submitted to Physical Review Letters.
Corresponding author: Nai-Chang Yeh (e-mail: [email protected]
Fragmented and Single Condensate Ground States of Spin-1 Bose Gas
We show that the ground state of a spin-1 Bose gas with an antiferro-
magnetic interaction is a fragmented condensate in uniform magnetic fields. The
number fluctuations in each spin component change rapidly from being enormous
(order ) to exceedingly small (order 1) as the magnetization of the system
increases. A fragmented condensate can be turned into a single condensate state
by magnetic field gradients. The conditions for existence and the method of
detecting fragmented states are presented.Comment: 4 pages, no figure
UBVI Surface Photometry of the Spiral Galaxy NGC 300 in the Sculptor Group
We present UBVI surface photometry for 20.'5 X 20.'5 area of a late-type
spiral galaxy NGC 300. In order to understand the morphological properties and
luminosity distribution characteristics of NGC 300, we have derived isophotal
maps, surface brightness profiles, ellipticity profiles, position angle
profiles, and color profiles. By merging the I-band data of our surface
brightness measurements with those of Boeker et al. (2002) based on Hubble
Space Telescope observations, we have made combined I-band surface brightness
profiles for the region of 0."02 < r < 500" and decomposed the profiles into
three components: a nucleus, a bulge, and an exponential disk.Comment: 16 pages(cjaa209.sty), Accepted by the Chinese J. Astron. Astrophys.,
Fig 2 and 8 are degraded to reduce spac
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