2,961 research outputs found
Photoabsorption spectra of the diamagnetic hydrogen atom in the transition regime to chaos: Closed orbit theory with bifurcating orbits
With increasing energy the diamagnetic hydrogen atom undergoes a transition
from regular to chaotic classical dynamics, and the closed orbits pass through
various cascades of bifurcations. Closed orbit theory allows for the
semiclassical calculation of photoabsorption spectra of the diamagnetic
hydrogen atom. However, at the bifurcations the closed orbit contributions
diverge. The singularities can be removed with the help of uniform
semiclassical approximations which are constructed over a wide energy range for
different types of codimension one and two catastrophes. Using the uniform
approximations and applying the high-resolution harmonic inversion method we
calculate fully resolved semiclassical photoabsorption spectra, i.e.,
individual eigenenergies and transition matrix elements at laboratory magnetic
field strengths, and compare them with the results of exact quantum
calculations.Comment: 26 pages, 9 figures, submitted to J. Phys.
Semiclassical quantization of the hydrogen atom in crossed electric and magnetic fields
The S-matrix theory formulation of closed-orbit theory recently proposed by
Granger and Greene is extended to atoms in crossed electric and magnetic
fields. We then present a semiclassical quantization of the hydrogen atom in
crossed fields, which succeeds in resolving individual lines in the spectrum,
but is restricted to the strongest lines of each n-manifold. By means of a
detailed semiclassical analysis of the quantum spectrum, we demonstrate that it
is the abundance of bifurcations of closed orbits that precludes the resolution
of finer details. They necessitate the inclusion of uniform semiclassical
approximations into the quantization process. Uniform approximations for the
generic types of closed-orbit bifurcation are derived, and a general method for
including them in a high-resolution semiclassical quantization is devised
The hydrogen atom in an electric field: Closed-orbit theory with bifurcating orbits
Closed-orbit theory provides a general approach to the semiclassical
description of photo-absorption spectra of arbitrary atoms in external fields,
the simplest of which is the hydrogen atom in an electric field. Yet, despite
its apparent simplicity, a semiclassical quantization of this system by means
of closed-orbit theory has not been achieved so far. It is the aim of this
paper to close that gap. We first present a detailed analytic study of the
closed classical orbits and their bifurcations. We then derive a simple form of
the uniform semiclassical approximation for the bifurcations that is suitable
for an inclusion into a closed-orbit summation. By means of a generalized
version of the semiclassical quantization by harmonic inversion, we succeed in
calculating high-quality semiclassical spectra for the hydrogen atom in an
electric field
Kentucky Anabaptists' Knowledge of Newborn Screening
The Plain Anabaptist population in Kentucky is growing, with the Amish population alone expected to double about every 20 years. Anabaptists in Kentucky are largely composed of Amish (both Old Order and New Order) and Old Order and Conservative Mennonites. All Anabaptists experience an increased incidence of recessive genetic disorders. Newborn screening (NBS) is a state-regulated program that identifies inherited and congenital disorders and conditions. The purpose of this study is to determine the knowledge of Kentucky Amish and Mennonite communities regarding NBS. A researcher-adapted questionnaire was mailed to Kentucky Amish and Mennonite households, and 292 respondents returned the questionnaire. The majority (85.2%) reported at least "a little" knowledge of NBS; however, only 6.8% reported "a lot" of knowledge. Respondents identified the midwife as the most common source of information related to NBS; however, 18% reported NBS was not offered by any provider. There was a statistically significant relationship between knowledge of NBS and children receiving NBS, indicating that knowledge of NBS increased participation in NBS. As the midwife is the most common source of NBS knowledge, an educational program for midwives as well as the Anabaptist communities throughout Kentucky is planned
Exploring disorganized attachment style among Malay mothers in Malaysia: a study using the Attachment Style Interview
This article explores emerging themes involving disorganized attachment style among Malay Muslim mothers using the Attachment Style Interview (ASI). Analysis of the 18 mothers with disorganized attachment style (those with combined anxious and avoidant styles) utilized themes deemed important from the attachment research literature and selected based on a careful reading of the narrative cases. These include more extreme negative interpersonal experiences than found in other insecure attachment style descriptors, and included partner violence and related isolation/social exclusion. It also indicated more complex cognitive-affective disturbance including mixed or contradictory dependency patterns and both angry and fearful attitudes to others. We discuss the concept of disorganized attachment style in relation to abuse, social exclusion, and its implication for psychopathology, intervention, and treatment
Revertant fibres and dystrophin traces in Duchenne muscular dystrophy: Implication for clinical trials
Duchenne muscular dystrophy (DMD) is characterised by the absence of dystrophin in muscle biopsies, although residual dystrophin can be present, either as dystrophin-positive (revertant) fibres or traces. As restoration of dystrophin expression is the end point of clinical trials, such residual dystrophin is a key factor in recruitment of patients and may also confound the analysis of dystrophin restoration in treated patients, if, as previously observed in the mdx mouse, revertant fibres increase with age. In 62% of the diagnostic biopsies reports of 65 DMD patients studied, traces or revertants were recorded with no correlation between traces or revertants, the patients' performance, or corticosteroids response. In nine of these patients, there was no increase in traces or revertants in biopsies taken a mean of 8.23 years (5.8-10.4 years) after the original diagnostic biopsy. This information should help in the design and execution of clinical trials focused on dystrophin restoration strategies. (C) 2010 Elsevier B.V. All rights reserved
XTE J1739-302: An Unusual New X-ray Transient
A new x-ray transient, designated XTE J1739-302, was discovered with the
Proportional Counter Array (PCA) on the Rossi X-ray Timing Explorer (RXTE) in
data from 12 August 1997. Although it was the brightest source in the Galactic
Center region while active (about 3.0 x 10^-9 ergs/cm2/s from 2 to 25 keV), it
was only observed on that one day; it was not detectable nine days earlier or
two days later. There is no known counterpart at other wavelengths, and its
proximity to the Galactic Center will make such an identification difficult due
to source confusion and extinction. The x-ray spectrum and intensity suggest a
giant outburst of a Be/neutron star binary, although no pulsations were
observed and the outburst was shorter than is usual from these systems.Comment: 11 pages incorporating 6 figures, AAStex; accepted for The
Astrophysical Journal, Part 2 (Letters
1H MR Spectroscopy in Gliomatosis: Is there a Sensitivity Issue?
Objective. 1H MR spectroscopy (MRS) is widely performed for assessment of brain tumours and is considered a highly sensitive technique capable of differentiating benign from malignant conditions and tumour grading. Method. We present a case of a 69 year old woman who was suspected to have gliomatosis on MRI. Results. MRS performed using single voxel and chemical shift/multivoxel techniques was within normal limits. A repeat scan 6 months later showed progressive disease, and biopsy was performed that proved the diagnosis of glioblastoma. Conclusion. Normal MRS in a patient with suspicion of gliomatosis on MRI should not reassure clinicians into assuming a benign aetiology or a good prognosis in short term
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