162 research outputs found
Test of the Conserved Vector Current Hypothesis by beta-ray Angular Distribution Measurement in the Mass-8 System
The beta-ray angular correlations for the spin alignments of 8Li and 8B have
been observed in order to test the conserved vector current (CVC) hypothesis.
The alignment correlation terms were combined with the known beta-alpha-angular
correlation terms to determine all the matrix elements contributing to the
correlation terms. The weak magnetism term, 7.5\pm0.2, deduced from the
beta-ray correlation terms was consistent with the CVC prediction 7.3\pm0.2,
deduced from the analog-gamma-decay measurement based on the CVC hypothesis.
However, there was no consistent CVC prediction for the second-forbidden term
associated with the weak vector current. The experimental value for the
second-forbidden term was 1.0 \pm 0.3, while the CVC prediction was 0.1 \pm 0.4
or 2.1 \pm 0.5.Comment: 31 pages, 12 figures, Accepted for publication in Phys. Rev.
Quantum Monte Carlo calculations of nuclei
We report on quantum Monte Carlo calculations of the ground and low-lying
excited states of nuclei using realistic Hamiltonians containing the
Argonne two-nucleon potential alone or with one of several
three-nucleon potentials, including Urbana IX and three of the new Illinois
models. The calculations begin with correlated many-body wave functions that
have an -like core and multiple p-shell nucleons, -coupled to the
appropriate quantum numbers for the state of interest. After
optimization, these variational trial functions are used as input to a Green's
function Monte Carlo calculation of the energy, using a constrained path
algorithm. We find that the Hamiltonians that include Illinois three-nucleon
potentials reproduce ten states in Li, Be, Be, and B with
an rms deviation as little as 900 keV. In particular, we obtain the correct
3 ground state for B, whereas the Argonne alone or with
Urbana IX predicts a 1 ground state. In addition, we calculate isovector
and isotensor energy differences, electromagnetic moments, and one- and
two-body density distributions.Comment: 28 pages, 12 tables, 7 figure
Suzaku observation of the giant radio galaxy 3C 326
A Suzaku observation of a giant radio galaxy, 3C 326, which has a physical
size of about 2 Mpc, was conducted on 2008 January 19 -- 21. In addition to
several X-ray sources, diffuse emission was significantly detected associated
with its west lobe, but the east lobe was contaminated by an unidentified X-ray
source WARP J1552.4+2007. After careful evaluation of the X-ray and Non X-ray
background, the 0.4 -- 7 keV X-ray spectrum of the west lobe is described by a
power-law model. The photon index and 1 keV flux density was derived as
and nJy,
respectively, where the first and second errors represent the statistical and
systematic ones. The diffuse X-rays were attributed to be inverse Compton
radiation by the synchrotron radio electrons scattering off the cosmic
microwave background photons. This radio galaxy is the largest among those with
lobes detected through inverse Compton X-ray emission. A comparison of the
radio to X-ray fluxes yields the energy densities of electron and magnetic
field as ergs/cm3 and ergs/cm3, respectively. The galaxy
is suggested to host a low luminosity nucleus with an absorption-corrected 2 --
10 keV luminosity of ergs/s, together with a relatively
weak radio core. The energetics in the west lobe of 3C 326 were compared with
those of moderate radio galaxies with a size of kpc. The west lobe
of 3C 326 is confirmed to agree with the correlations for the moderate radio
galaxies, and , where
is their total physical size. This implies that the lobes of 3C 326 are
still being energized by the jet, despite the current weakness of the nucleus.Comment: 11 pages, 10 figures, 6 tables, Accepted for ApJ (v706 issue
Neurophysiological modeling of bladder afferent activity in the rat overactive bladder model
The overactive bladder (OAB) is a syndrome-based urinary dysfunction characterized by “urgency, with or without urge incontinence, usually with frequency and nocturia”. Earlier we developed a mathematical model of bladder nerve activity during voiding in anesthetized rats and found that the nerve activity in the relaxation phase of voiding contractions was all afferent. In the present study, we applied this mathematical model to an acetic acid (AA) rat model of bladder overactivity to study the sensitivity of afferent fibers in intact nerves to bladder pressure and volume changes. The afferent activity in the filling phase and the slope, i.e., the sensitivity of the afferent fibers to pressure changes in the post-void relaxation phase, were found to be significantly higher in AA than in saline measurements, while the offset (nerve activity at pressure ~0) and maximum pressure were comparable. We have thus shown, for the first time, that the sensitivity of afferent fibers in the OAB can be studied without cutting nerves or preparation of single fibers. We conclude that bladder overactivity induced by AA in rats is neurogenic in origin and is caused by increased sensitivity of afferent sensors in the bladder wall
Precision measurement of the electric quadrupole moment of 31Al and determination of the effective proton charge in the sd-shell
he electric quadrupole coupling constant of the 31Al ground state is measured
to be nu_Q = |eQV_{zz}/h| = 2196(21)kHz using two different beta-NMR (Nuclear
Magnetic Resonance) techniques. For the first time, a direct comparison is made
between the continuous rf technique and the adiabatic fast passage method. The
obtained coupling constants of both methods are in excellent agreement with
each other and a precise value for the quadrupole moment of 31Al has been
deduced: |Q(31Al)| = 134.0(16) mb. Comparison of this value with large-scale
shell-model calculations in the sd and sdpf valence spaces suggests that the
31Al ground state is dominated by normal sd-shell configurations with a
possible small contribution of intruder states. The obtained value for
|Q(31Al)| and a compilation of measured quadrupole moments of odd-Z even-N
isotopes in comparison with shell-model calculations shows that the proton
effective charge e_p=1.1 e provides a much better description of the nuclear
properties in the sd-shell than the adopted value e_p=1.3 e
Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).
Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)
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