2,361 research outputs found
High-precision covariant one-boson-exchange potentials for np scattering below 350 MeV
All realistic potential models for the two-nucleon interaction are to some
extent based on boson exchange. However, in order to achieve an essentially
perfect fit to the scattering data, characterized by a chi2/Ndata ~ 1, previous
potentials have abandoned a pure one boson-exchange mechanism (OBE). Using a
covariant theory, we have found a OBE potential that fits the 2006 world np
data below 350 MeV with a chi2/Ndata = 1.06 for 3788 data. Our potential has
fewer adjustable parameters than previous high-precision potentials, and also
reproduces the experimental triton binding energy without introducing
additional irreducible three-nucleon forces.Comment: 4 pages; revised version with augmented data sets; agrees with
published versio
Sub-Planckian black holes and the Generalized Uncertainty Principle
The Black Hole Uncertainty Principle correspondence suggests that there could
exist black holes with mass beneath the Planck scale but radius of order the
Compton scale rather than Schwarzschild scale. We present a modified, self-dual
Schwarzschild-like metric that reproduces desirable aspects of a variety of
disparate models in the sub-Planckian limit, while remaining Schwarzschild in
the large mass limit. The self-dual nature of this solution under naturally implies a Generalized Uncertainty Principle
with the linear form . We also
demonstrate a natural dimensional reduction feature, in that the gravitational
radius and thermodynamics of sub-Planckian objects resemble that of -D
gravity. The temperature of sub-Planckian black holes scales as rather than
but the evaporation of those smaller than g is suppressed by
the cosmic background radiation. This suggests that relics of this mass could
provide the dark matter.Comment: 12 pages, 9 figures, version published in J. High En. Phy
Rotating black holes with equal-magnitude angular momenta in d=5 Einstein-Gauss-Bonnet theory
We construct rotating black hole solutions in Einstein-Gauss-Bonnet theory in
five spacetime dimensions. These black holes are asymptotically flat, and
possess a regular horizon of spherical topology and two equal-magnitude angular
momenta associated with two distinct planes of rotation. The action and global
charges of the solutions are obtained by using the quasilocal formalism with
boundary counterterms generalized for the case of Einstein-Gauss-Bonnet theory.
We discuss the general properties of these black holes and study their
dependence on the Gauss-Bonnet coupling constant . We argue that most
of the properties of the configurations are not affected by the higher
derivative terms. For fixed the set of black hole solutions terminates
at an extremal black hole with a regular horizon, where the Hawking temperature
vanishes and the angular momenta attain their extremal values. The domain of
existence of regular black hole solutions is studied. The near horizon geometry
of the extremal solutions is determined by employing the entropy function
formalism.Comment: 25 pages, 7 figure
Comparison of total ankle replacement and ankle arthrodesis in patients with haemophilia using gait analysis : two case reports
BACKGROUND: Severe hemophilia is an inherited, lifelong bleeding disorder characterized by spontaneous bleeding, which results in painful joint deformities. Currently two surgical treatments are available to treat haemophilia-related ankle joint destruction: ankle arthrodesis and total ankle replacement. The aim of the present study was to compare these two surgical procedures in haemophiliac subjects. CASE PRESENTATION: Kinematic and dynamic parameters were quantified using a three-dimensional gait-analysis system in two similar clinical cases. In Caucasian case 1, ankle arthrodesis was chosen because of a kinematic ankle flexion defect and lack of dynamic power regeneration. The defect in energy absorption was compensated for by the contralateral side. Total ankle replacement in Caucasian case 2 allowed sparing the ipsilateral knee (maximum 0.27 preoperatively vs. 0.71 W/kg postoperatively) and hip joints powers (maximum 0.43 preoperatively vs. 1.25 W/kg postoperatively) because of the small ankle dorsiflexion motion. CONCLUSIONS: Total ankle replacement is recommended for haemophiliac patients who present with a preserved ankle range of motion
Module-Based Analysis of Robustness Tradeoffs in the Heat Shock Response System
Biological systems have evolved complex regulatory mechanisms, even in situations where much simpler designs seem to be sufficient for generating nominal functionality. Using module-based analysis coupled with rigorous mathematical comparisons, we propose that in analogy to control engineering architectures, the complexity of cellular systems and the presence of hierarchical modular structures can be attributed to the necessity of achieving robustness. We employ the Escherichia coli heat shock response system, a strongly conserved cellular mechanism, as an example to explore the design principles of such modular architectures. In the heat shock response system, the sigma-factor σ(32) is a central regulator that integrates multiple feedforward and feedback modules. Each of these modules provides a different type of robustness with its inherent tradeoffs in terms of transient response and efficiency. We demonstrate how the overall architecture of the system balances such tradeoffs. An extensive mathematical exploration nevertheless points to the existence of an array of alternative strategies for the existing heat shock response that could exhibit similar behavior. We therefore deduce that the evolutionary constraints facing the system might have steered its architecture toward one of many robustly functional solutions
Cytogenetic and histological studies of the brook trout, Salvelinus fontinalis (Mitchill), and the Arctic char, S-alpinus (L.) hybrids
Although brook trout and the Arctic char hybrids are able to reproduce, individuals with decreased fertility or even fish that are unable to produce any gametes have been also described. Abnormal gonadal development and disturbances in the gamete production in the char hybrid offspring may be triggered by the odd chromosome number and disturbances in their pairing during meiosis. To verify this hypothesis, cytogenetic examination and the gonadal histology analysis of the brook trout x Arctic char hybrids were carried out. Diploid chromosome number in the studied char (F-1) hybrids varied from 82 to 84 (FN = 99-102). Among 28 hybrids, 12 males, three females, nine intersex individuals and two sterile specimens were described. In the case of two individuals, gonads were not found. Diploid chromosome numbers in the males and intersex individuals varied from 82 to 84. Chromosome numbers in the females were 82 and 83 chromosomes. Two sterile fish exhibited karyotypes composed of 82 and 84 chromosomes. Predominance of the ovarian component in the intersex gonads and gonadal sex ratio distortion towards the males suggested hybrid females had problems with gonadal differentiation. However, the lack of the clear relationship between chromosome number and gonadal development in the studied hybrids did not support our hypothesis that odd chromosome number may be responsible for such reproductive disturbances in the hybrid individuals. We have presumed that sterility and intersexual development of the gonads may be caused by interactions between brook trout and Arctic char genes on the sex chromosomes and autosomes rather than unpairing of the parental chromosomes.Polish National Science Center (NCN) [N N311 525240]info:eu-repo/semantics/publishedVersio
Influence of Prior Influenza Vaccination on Antibody and B-Cell Responses
Currently two vaccines, trivalent inactivated influenza vaccine (TIV) and live attenuated influenza vaccine (LAIV), are licensed in the USA. Despite previous studies on immune responses induced by these two vaccines, a comparative study of the influence of prior influenza vaccination on serum antibody and B-cell responses to new LAIV or TIV vaccination has not been reported. During the 2005/6 influenza season, we quantified the serum antibody and B-cell responses to LAIV or TIV in adults with differing influenza vaccination histories in the prior year: LAIV, TIV, or neither. Blood samples were collected on days 0, 7–9 and 21–35 after immunization and used for serum HAI assay and B-cell assays. Total and influenza-specific circulating IgG and IgA antibody secreting cells (ASC) in PBMC were detected by direct ELISPOT assay. Memory B cells were also tested by ELISPOT after polyclonal stimulation of PBMC in vitro. Serum antibody, effector, and memory B-cell responses were greater in TIV recipients than LAIV recipients. Prior year TIV recipients had significantly higher baseline HAI titers, but lower HAI response after vaccination with either TIV or LAIV, and lower IgA ASC response after vaccination with TIV than prior year LAIV or no vaccination recipients. Lower levels of baseline HAI titer were associated with a greater fold-increase of HAI titer and ASC number after vaccination, which also differed by type of vaccine. Our findings suggest that the type of vaccine received in the prior year affects the serum antibody and the B-cell responses to subsequent vaccination. In particular, prior year TIV vaccination is associated with sustained higher HAI titer one year later but lower antibody response to new LAIV or TIV vaccination, and a lower effector B-cell response to new TIV but not LAIV vaccination
Relativistic Hamiltonian Dynamics and Few-Nucleon Systems
We present a preliminary calculation of the electromagnetic form factors of
He and H, performed within the Light-Front Hamiltonian Dynamics.
Relativistic effects show their relevance even at the static limit, increasing
at higher values of momentum transfer, as expected.Comment: 6 pages, 4 figures. Proceedings of 20th European Conference on
Few-Body Problems in Physics; to be published in Few-Body System
IFNγ production in peripheral blood of early Lyme disease patients to hLFAα(L) (aa326-345)
BACKGROUND: It has been proposed that outer surface protein A (OspA) of Borrelia burgdorferi sensu stricto contains a T helper 1 (Th1) cell epitope that could play a role in an autoimmune response to hLFA1. METHODS: We used two peptides, hLFAα(L) (aa326-345) and Borrelia burgdorferi OspAB31 (aa164-183), as stimulating antigens to measure Th1 proinflammatory IFNγ cytokine production in peripheral blood of Lyme disease patients presenting with EM without history of arthritis, as well as in peripheral blood of healthy individuals. RESULTS: IFNγ responses to hLFA1 peptide were observed in 11 of 19 Lyme disease patients and in 3 of 15 healthy controls. In contrast, only 2 of 19 of the Lyme disease patients and none of the controls responded to the homologous OspAB31 peptide. CONCLUSIONS: IFNγ was produced in response to stimulation with peptide hLFAα(L) (aa326-345) in peripheral blood of 58% of patients with early Lyme disease without signs of arthritis, as well as in peripheral blood of 20% of healthy individuals, but not in response to stimulation with the homologous OspAB31 (aa164-183) peptide (p < 0.05). Our results suggest that reactivity to the hLFA1 peptide in peripheral blood may be the result of T cell degeneracy
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