765 research outputs found
Towards a direct transition energy measurement of the lowest nuclear excitation in 229Th
The isomeric first excited state of the isotope 229Th exhibits the lowest
nuclear excitation energy in the whole landscape of known atomic nuclei. For a
long time this energy was reported in the literature as 3.5(5) eV, however, a
new experiment corrected this energy to 7.6(5) eV, corresponding to a UV
transition wavelength of 163(11) nm. The expected isomeric lifetime is
3-5 hours, leading to an extremely sharp relative linewidth of Delta E/E ~
10^-20, 5-6 orders of magnitude smaller than typical atomic relative
linewidths. For an adequately chosen electronic state the frequency of the
nuclear ground-state transition will be independent from influences of external
fields in the framework of the linear Zeeman and quadratic Stark effect,
rendering 229mTh a candidate for a reference of an optical clock with very high
accuracy. Moreover, in the literature speculations about a potentially enhanced
sensitivity of the ground-state transition of Th for eventual
time-dependent variations of fundamental constants (e.g. fine structure
constant alpha) can be found. We report on our experimental activities that aim
at a direct identification of the UV fluorescence of the ground-state
transition energy of 229mTh. A further goal is to improve the accuracy of the
ground-state transition energy as a prerequisite for a laser-based optical
control of this nuclear excited state, allowing to build a bridge between
atomic and nuclear physics and open new perspectives for metrological as well
as fundamental studies
Dynamics of single polymers under extreme confinement
We study the dynamics of a single chain polymer confined to a two dimensional
cell. We introduce a kinetically constrained lattice gas model that preserves
the connectivity of the chain, and we use this kinetically constrained model to
study the dynamics of the polymer at varying densities through Monte Carlo
simulations. Even at densities close to the fully-packed configuration, we find
that the monomers comprising the chain manage to diffuse around the box with a
root mean square displacement of the order of the box dimensions over time
scales for which the overall geometry of the polymer is, nevertheless, largely
preserved. To capture this shape persistence, we define the local tangent field
and study the two-time tangent-tangent correlation function, which exhibits a
glass-like behavior. In both closed and open chains, we observe reptational
motion and reshaping through local fingering events which entail global monomer
displacement.Comment: 22 pages, 18 figures, slightly extended version to appear in JSTA
Geometric Laws of Vortex Quantum Tunneling
In the semiclassical domain the exponent of vortex quantum tunneling is
dominated by a volume which is associated with the path the vortex line traces
out during its escape from the metastable well. We explicitly show the
influence of geometrical quantities on this volume by describing point vortex
motion in the presence of an ellipse. It is argued that for the semiclassical
description to hold the introduction of an additional geometric constraint, the
distance of closest approach, is required. This constraint implies that the
semiclassical description of vortex nucleation by tunneling at a boundary is in
general not possible. Geometry dependence of the tunneling volume provides a
means to verify experimental observation of vortex quantum tunneling in the
superfluid Helium II.Comment: 4 pages, 2 figures, revised version to appear in Phys. Rev.
Caregiver perspectives on the continued impact of the COVID-19 pandemic on children with intellectual/developmental disabilities
The COVID-19 pandemic has significantly impacted caregivers, especially those raising a child with an intellectual/developmental disability (IDD). While research has shown substantial disruption to the family, school, and occupational lives of the IDD community, little is known about the long-term impacts of COVID-19. To address this question, 249 caregivers were surveyed via an online questionnaire, between April and August of 2022 (more than 2 years into the pandemic) about potential impacts of the COVID-19 pandemic on their child\u27s access to health- and school-based therapeutic services, caregiver mental health, and family life. The majority of caregivers reported disruptions in access to and quality of school-based therapeutic services for their child as well as a reduction in educational accommodations in the 2021-2022 academic year. Nearly half of caregivers reported feeling anxious and almost a quarter reported feeling depressed for the majority of their days. More than half of respondents reported decreased social support, and one-fifth reported employment disruptions and decreased access to food. These findings suggest that families of children with IDD are still experiencing ongoing negative impacts of the pandemic, emphasizing the critical need for continued support in the wake of the initial and more obvious disruptions caused by the COVID-19 outbreak
The Dual Formulation of Cosmic Strings and Vortices
We study four dimensional systems of global, axionic and local strings. By
using the path integral formalism, we derive the dual formulation of these
systems, where Goldstone bosons, axions and missive vector bosons are described
by antisymmetric tensor fields, and strings appear as a source for these tensor
fields. We show also how magnetic monopoles attached to local strings are
described in the dual formulation. We conclude with some remarks.Comment: 18 pages, CU-TP-588 and CERN-TH.6780/9
Analysis of Race and Sex Bias in the Autism Diagnostic Observation Schedule (ADOS-2)
Importance: There are long-standing disparities in the prevalence of autism spectrum disorder (ASD) across race and sex. Surprisingly, few studies have examined whether these disparities arise partially out of systematic biases in the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2), the reference standard measure of ASD.
Objective: To examine differential item functioning (DIF) of ADOS-2 items across sex and race.
Design, Setting, and Participants: This is a cross-sectional study of children who were evaluated for ASD between 2014 and 2020 at a specialty outpatient clinic located in the Mid-Atlantic region of the US. Data were analyzed from July 2021 to February 2022.
Exposures: Child race (Black/African American vs White) and sex (female vs male).
Main Outcomes and Measures: Item-level biases across ADOS-2 harmonized algorithm items, including social affect (SA; 10 items) and repetitive/restricted behaviors (RRBs; 4 items), were evaluated across 3 modules. Measurement bias was identified by examining DIF and differential test functioning (DTF), within a graded response, item response theory framework. Statistical significance was determined by a likelihood ratio χ2 test, and a series of metrics was used to examine the magnitude of DIF and DTF.
Results: A total of 6269 children (mean [SD] age, 6.77 [3.27] years; 1619 Black/African American [25.9%], 3151 White [50.3%], and 4970 male [79.4%]), were included in this study. Overall, 16 of 140 ADOS-2 diagnostic items (11%) had a significant DIF. For race, 8 items had a significant DIF, 6 of which involved SA. No single item showed DIF consistently across all modules. Most items with DIF had greater difficulty and poorer discrimination in Black/African American children compared with White children. For sex, 5 items showed significant DIF. DIF was split across SA and RRB. However, hand mannerisms evidenced DIF across all 5 algorithms, with generally greater difficulty. The magnitude of DIF was only moderate to large for 2 items: hand mannerisms (among female children) and repetitive interests (among Black/African American children). The overall estimated effect of DIF on total DTF was not large.
Conclusions and Relevance: These findings suggest that the ADOS-2 does not have widespread systematic measurement bias across race or sex. However, the findings raise some concerns around underdetection that warrant further research
Extraction of BoNT/A, /B, /E, and /F with a Single, High Affinity Monoclonal Antibody for Detection of Botulinum Neurotoxin by Endopep-MS
Botulinum neurotoxins (BoNTs) are extremely potent toxins that are capable of causing respiratory failure leading to long-term intensive care or death. The best treatment for botulism includes serotype-specific antitoxins, which are most effective when administered early in the course of the intoxication. Early confirmation of human exposure to any serotype of BoNT is an important public health goal. In previous work, we focused on developing Endopep-MS, a mass spectrometry-based endopeptidase method for detecting and differentiating the seven serotypes (BoNT/A-G) in buffer and BoNT/A, /B, /E, and /F (the four serotypes that commonly affect humans) in clinical samples. We have previously reported the success of antibody-capture to purify and concentrate BoNTs from complex matrices, such as clinical samples. However, to check for any one of the four serotypes of BoNT/A, /B, /E, or /F, each sample is split into 4 aliquots, and tested for the specific serotypes separately. The discovery of a unique monoclonal antibody that recognizes all four serotypes of BoNT/A, /B, /E and /F allows us to perform simultaneous detection of all of them. When applied in conjunction with the Endopep-MS assay, the detection limit for each serotype of BoNT with this multi-specific monoclonal antibody is similar to that obtained when using other serotype-specific antibodies
Fractional Statistics in Three Dimensions: Compact Maxwell-Higgs System
We show that a (3+1)-dimensional system composed of an open magnetic vortex
and an electrical point charge exhibits the phenomenon of Fermi-Bose
transmutation. In order to provide the physical realization of this system we
focus on the lattice compact scalar electrodynamics whose topological
excitations are open Nielsen-Olesen strings with magnetic monopoles attached at
their ends.Comment: 8 page
Effects of a torsion field on Big Bang nucleosynthesis
In this paper it is investigated whether torsion, which arises naturally in
most theories of quantum gravity, has observable implications for the Big Bang
nucleosynthesis. Torsion can lead to spin flips amongst neutrinos thus turning
them into sterile neutrinos. In the early Universe they can alter the helium
abundance which is tightly constrained by observations. Here I calculate to
what extent torsion of the string theory type leads to a disagreement with the
Big Bang nucleosynthesis predictions.Comment: accepted by General Relativity and Gravitatio
Characteristic cohomology of -form gauge theories
The characteristic cohomology for an arbitrary set of free
-form gauge fields is explicitly worked out in all form degrees ,
where is the spacetime dimension. It is shown that this cohomology is
finite-dimensional and completely generated by the forms dual to the field
strengths. The gauge invariant characteristic cohomology is also computed. The
results are extended to interacting -form gauge theories with gauge
invariant interactions. Implications for the BRST cohomology are mentioned.Comment: Latex file, no figures, 44 page
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