2,876 research outputs found
Estimates of isospin breaking contributions to baryon masses
We estimate the isospin breaking contributions to the baryon masses which we
analyzed recently using a loop expansion in the heavy baryon approximation to
chiral effective field theory. To one loop, the isospin breaking corrections
come from the effects of the quark mass difference, the Coulomb and
magnetic moment interactions, and effective point interactions attributable to
color-magnetic effects. The addition of the first meson loop corrections
introduces new structure. We estimate the resulting low-energy, long-range
contributions to the mass splittings by regularizing the loop integrals using
connections to dynamical models for finite-size baryons. We find that the
resulting contributions to the isospin breaking corrections are of the right
general size, have the correct sign pattern, and agree with the experimental
values within the margin of error.Comment: 15 pages, 5 figures; changed title and conten
Smart Health for Autism in Northwest Ohio Survey Summary [Slides]
Slides from a presentation given by Louisa Ha, Lynne Hewitt and Linell Weinberg in 2011
Parents and Professionals\u27 Autism Information Environment Assessment, Information Needs and Use of Support Services Across the Life-Span of Individuals with Autism [Slides]
Slides from a presentation given by Louisa Ha, Lynne Hewitt, and Linell Weinberg in 2012
Extended Gauge Theories in Euclidean Space with Higher Spin Fields
The extended Yang-Mills gauge theory in Euclidean space is a renormalizable
(by power counting) gauge theory describing a local interacting theory of
scalar, vector, and tensor gauge fields (with maximum spin 2). In this article
we study the quantum aspects and various generalizations of this model in
Euclidean space. In particular the quantization of the pure gauge model in a
common class of covariant gauges is performed. We generalize the pure gauge
sector by including matter fermions in the adjoint representation of the gauge
group and analyze its N=1 and N=2 supersymmetric extensions. We show that the
maximum half-integer spin contained in these fermion fields in dimension 4 is
3/2. Moreover we develop an extension of this theory so as to include internal
gauge symmetries and the coupling to bosonic matter fields. The spontaneous
symmetry breaking of the extended gauge symmetry is also analyzed.Comment: LaTeX, 36 pages, section 4 expanded, new section 7 and new references
added, to appear in Annals of Physic
Effective field theory and the quark model
We analyze the connections between the quark model (QM) and the description
of hadrons in the low-momentum limit of heavy-baryon effective field theory in
QCD. By using a three-flavor-index representation for the effective baryon
fields, we show that the ``nonrelativistic'' constituent QM for baryon masses
and moments is completely equivalent through O(m_s) to a parametrization of the
relativistic field theory in a general spin--flavor basis. The flavor and spin
variables can be identified with those of effective valence quarks. Conversely,
the spin-flavor description clarifies the structure and dynamical
interpretation of the chiral expansion in effective field theory, and provides
a direct connection between the field theory and the semirelativistic models
for hadrons used in successful dynamical calculations. This allows dynamical
information to be incorporated directly into the chiral expansion. We find, for
example, that the striking success of the additive QM for baryon magnetic
moments is a consequence of the relative smallness of the non-additive
spin-dependent corrections.Comment: 25 pages, revtex, no figure
Enhanced roughness of lipid membranes caused by external electric fields
The behavior of lipid membranes in the presence of an external electric field
is studied and used to examine the influence of such fields on membrane
parameters such as roughness and show that for a micro sized membrane,
roughness grows as the field increases. The dependence of bending rigidity on
the electric field is also studied and an estimation of thickness of the
accumulated charges around lipid membranes in a free-salt solution is
presented.Comment: 9 pages, 6 figures, to appear in Computational Materials Scienc
Neutron Stars in Teleparallel Gravity
In this paper we deal with neutron stars, which are described by a perfect
fluid model, in the context of the teleparallel equivalent of general
relativity. We use numerical simulations to find the relationship between the
angular momentum of the field and the angular momentum of the source. Such a
relation was established for each stable star reached by the numerical
simulation once the code is fed with an equation of state, the central energy
density and the ratio between polar and equatorial radii. We also find a regime
where linear relation between gravitational angular momentum and moment of
inertia (as well as angular velocity of the fluid) is valid. We give the
spatial distribution of the gravitational energy and show that it has a linear
dependence with the squared angular velocity of the source.Comment: 19 pages, 14 figures. arXiv admin note: text overlap with
arXiv:1206.331
Baryon Washout, Electroweak Phase Transition, and Perturbation Theory
We analyze the conventional perturbative treatment of sphaleron-induced
baryon number washout relevant for electroweak baryogenesis and show that it is
not gauge-independent due to the failure of consistently implementing the
Nielsen identities order-by-order in perturbation theory. We provide a
gauge-independent criterion for baryon number preservation in place of the
conventional (gauge-dependent) criterion needed for successful electroweak
baryogenesis. We also review the arguments leading to the preservation
criterion and analyze several sources of theoretical uncertainties in obtaining
a numerical bound. In various beyond the standard model scenarios, a realistic
perturbative treatment will likely require knowledge of the complete two-loop
finite temperature effective potential and the one-loop sphaleron rate.Comment: 25 pages, 9 figures; v2 minor typos correcte
The `Friction' of Vacuum, and other Fluctuation-Induced Forces
The static Casimir effect describes an attractive force between two
conducting plates, due to quantum fluctuations of the electromagnetic (EM)
field in the intervening space. {\it Thermal fluctuations} of correlated fluids
(such as critical mixtures, super-fluids, liquid crystals, or electrolytes) are
also modified by the boundaries, resulting in finite-size corrections at
criticality, and additional forces that effect wetting and layering phenomena.
Modified fluctuations of the EM field can also account for the `van der Waals'
interaction between conducting spheres, and have analogs in the
fluctuation--induced interactions between inclusions on a membrane. We employ a
path integral formalism to study these phenomena for boundaries of arbitrary
shape. This allows us to examine the many unexpected phenomena of the dynamic
Casimir effect due to moving boundaries. With the inclusion of quantum
fluctuations, the EM vacuum behaves essentially as a complex fluid, and
modifies the motion of objects through it. In particular, from the mechanical
response function of the EM vacuum, we extract a plethora of interesting
results, the most notable being: (i) The effective mass of a plate depends on
its shape, and becomes anisotropic. (ii) There is dissipation and damping of
the motion, again dependent upon shape and direction of motion, due to emission
of photons. (iii) There is a continuous spectrum of resonant cavity modes that
can be excited by the motion of the (neutral) boundaries.Comment: RevTex, 2 ps figures included. The presentation is completely
revised, and new sections are adde
Rapid tests and urine sampling techniques for the diagnosis of urinary tract infection (UTI) in children under five years: a systematic review
Background: Urinary tract infection (UTI) is one of the most common sources of infection in children under five. Prompt diagnosis and treatment is important to reduce the risk of renal scarring. Rapid, cost-effective, methods of UTI diagnosis are required as an alternative to culture. Methods: We conducted a systematic review to determine the diagnostic accuracy of rapid tests for detecting UTI in children under five years of age. Results: The evidence supports the use of dipstick positive for both leukocyte esterase and nitrite (pooled LR+ = 28.2, 95% CI: 17.3, 46.0) or microscopy positive for both pyuria and bacteriuria (pooled LR+ = 37.0, 95% CI: 11.0, 125.9) to rule in UTI. Similarly dipstick negative for both LE and nitrite (Pooled LR- = 0.20, 95% CI: 0.16, 0.26) or microscopy negative for both pyuria and bacteriuria (Pooled LR- = 0.11, 95% CI: 0.05, 0.23) can be used to rule out UTI. A test for glucose showed promise in potty-trained children. However, all studies were over 30 years old. Further evaluation of this test may be useful. Conclusion: Dipstick negative for both LE and nitrite or microscopic analysis negative for both pyuria and bacteriuria of a clean voided urine, bag, or nappy/pad specimen may reasonably be used to rule out UTI. These patients can then reasonably be excluded from further investigation, without the need for confirmatory culture. Similarly, combinations of positive tests could be used to rule in UTI, and trigger further investigation
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