218 research outputs found
The interior spacetimes of stars in Palatini f(R) gravity
We study the interior spacetimes of stars in the Palatini formalism of f(R)
gravity and derive a generalized Tolman-Oppenheimer-Volkoff and mass equation
for a static, spherically symmetric star. We show that matching the interior
solution with the exterior Schwarzschild-De Sitter solution in general gives a
relation between the gravitational mass and the density profile of a star,
which is different from the one in General Relativity. These modifications
become neglible in models for which is a decreasing function of R however. As a result, both Solar System
constraints and stellar dynamics are perfectly consistent with .Comment: Published version, 6 pages, 1 figur
Experiments with planar inductive ion source meant for creation ofH+ Beams
In this article the effect of different engineering parameters of an rf-driven ion sources with external spiral antenna and quartz disk rf-window are studied. Paper consists of three main topics: The effect of source geometry on the operation gas pressure, the effect of source materials and magnetic confinement on extracted current density and ion species and the effect of different antenna geometries on the extracted current density. The operation gas pressure as a function of the plasma chamber diameter, was studied. This was done with three cylindrical plasma chambers with different inner diameters. The chamber materials were studied using two materials, aluminum and alumina (AlO{sub 2}). The removable 14 magnet multicusp confinement arrangement enabled us to compare the effects of the two wall materials with and without the magnetic confinement. Highest proton fraction of {approx} 8% at 2000 W of rf-power and at pressure of 1.3 Pa was measured using AlO{sub 2} plasma chamber and no multicusp confinement. For all the compared ion sources at 1000W of rf-power, source with multicusp confinement and AlO2 plasma chamber yields highest current density of 82.7 mA/cm{sup 2} at operation pressure of 4 Pa. From the same source highest measured current density of 143 mA/cm{sup 2} at 1.3 Pa and 2200W of rf-power was achieved. Multicusp confinement increased the maximum extracted current up to factor of two. Plasma production with different antenna geometries was also studied. Antenna tests were performed using same source geometry as in source material study with AlO{sub 2} plasma chamber and multicusp confinement. The highest current density was achieved with 4.5 loop solenoid antenna with 6 cm diameter. Slightly lower current density with lower pressure was achieved using tightly wound 3 loop spiral antenna with 3.3 cm ID and 6 cm OD
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A D-D/D-T fusion reaction based neutron generator system for liver tumor BNCT
Boron-neutron capture therapy (BNCT) is an experimental radiation treatment modality used for highly malignant tumor treatments. Prior to irradiation with low energetic neutrons, a 10B compound is located selectively in the tumor cells. The effect of the treatment is based on the high LET radiation released in the {sup 10}B(n,{alpha}){sup 7}Li reaction with thermal neutrons. BNCT has been used experimentally for brain tumor and melanoma treatments. Lately applications of other severe tumor type treatments have been introduced. Results have shown that liver tumors can also be treated by BNCT. At Lawrence Berkeley National Laboratory, various compact neutron generators based on D-D or D-T fusion reactions are being developed. The earlier theoretical studies of the D-D or D-T fusion reaction based neutron generators have shown that the optimal moderator and reflector configuration for brain tumor BNCT can be created. In this work, the applicability of 2.5 MeV neutrons for liver tumor BNCT application was studied. The optimal neutron energy for external liver treatments is not known. Neutron beams of different energies (1eV < E < 100 keV) were simulated and the dose distribution in the liver was calculated with the MCNP simulation code. In order to obtain the optimal neutron energy spectrum with the D-D neutrons, various moderator designs were performed using MCNP simulations. In this article the neutron spectrum and the optimized beam shaping assembly for liver tumor treatments is presented
Histologically Verified Biliary Invasion was Associated with Impaired Liver Recurrence-Free Survival in Resected Colorectal Cancer Liver Metastases
Background and Aims: The impact of biliary invasion on recurrence and survival, after resection of colorectal cancer liver metastases, is not well known as publications are limited to small patient series. The aim was to investigate if biliary invasion in liver resected patients associated with liver relapses and recurrence-free survival. Secondary endpoints included association with other prognostic factors, disease-free survival and overall survival. Materials and Methods: All patients with histologically verified biliary invasion (n = 31, 9%) were identified among 344 patients with liver resection between January 2009 and March 2015. Controls (n = 78) were selected from the same time period and matched for, among others, size and number of colorectal cancer liver metastasis. Results: Median liver recurrence-free survival was significantly shorter in patients with biliary invasion than in controls (15.3 months versus not reached; p = 0.031) and more relapses were noted in the liver (61.3% versus 33.3%; p = 0.010), respectively. In univariate analyses for liver recurrence-free survival, biliary invasion was the only significant prognostic factor; p = 0.034. There were no statistical differences in disease-free and overall survival between the groups. Conclusion: Biliary invasion was associated with higher liver recurrence rates and shorter liver recurrence-free survival in patients with resected colorectal cancer liver metastasis.Peer reviewe
Cosmological perturbations in Palatini modified gravity
Two approaches to the study of cosmological density perturbations in modified
theories of Palatini gravity have recently been discussed. These utilise,
respectively, a generalisation of Birkhoff's theorem and a direct linearization
of the gravitational field equations. In this paper these approaches are
compared and contrasted. The general form of the gravitational lagrangian for
which the two frameworks yield identical results in the long-wavelength limit
is derived. This class of models includes the case where the lagrangian is a
power-law of the Ricci curvature scalar. The evolution of density perturbations
in theories of the type is investigated numerically. It is
found that the results obtained by the two methods are in good agreement on
sufficiently large scales when the values of the parameters (b,c) are
consistent with current observational constraints. However, this agreement
becomes progressively poorer for models that differ significantly from the
standard concordance model and as smaller scales are considered
Recurrence of Type 1 Diabetes After Simultaneous Pancreas-Kidney Transplantation, Despite Immunosuppression, Is Associated With Autoantibodies and Pathogenic Autoreactive CD4 T-Cells
ObjectiveTo investigate if recurrent autoimmunity explained hyperglycemia and C-peptide loss in three immunosuppressed simultaneous pancreas-kidney (SPK) transplant recipients.Research design and methodsWe monitored autoantibodies and autoreactive T-cells (using tetramers) and performed biopsy. The function of autoreactive T-cells was studied with in vitro and in vivo assays.ResultsAutoantibodies were present pretransplant and persisted on follow-up in one patient. They appeared years after transplantation but before the development of hyperglycemia in the remaining patients. Pancreas transplant biopsies were taken within approximately 1 year from hyperglycemia recurrence and revealed beta-cell loss and insulitis. We studied autoreactive T-cells from the time of biopsy and repeatedly demonstrated their presence on further follow-up, together with autoantibodies. Treatment with T-cell-directed therapies (thymoglobulin and daclizumab, all patients), alone or with the addition of B-cell-directed therapy (rituximab, two patients), nonspecifically depleted T-cells and was associated with C-peptide secretion for >1 year. Autoreactive T-cells with the same autoantigen specificity and conserved T-cell receptor later reappeared with further C-peptide loss over the next 2 years. Purified autoreactive CD4 T-cells from two patients were cotransplanted with HLA-mismatched human islets into immunodeficient mice. Grafts showed beta-cell loss in mice receiving autoreactive T-cells but not control T-cells.ConclusionsWe demonstrate the cardinal features of recurrent autoimmunity in three such patients, including the reappearance of CD4 T-cells capable of mediating beta-cell destruction. Markers of autoimmunity can help diagnose this underappreciated cause of graft loss. Immune monitoring during therapy showed that autoimmunity was not resolved by the immunosuppressive agents used
Curvature singularities, tidal forces and the viability of Palatini f(R) gravity
In a previous paper we showed that static spherically symmetric objects
which, in the vicinity of their surface, are well-described by a polytropic
equation of state with 3/2<Gamma<2 exhibit a curvature singularity in Palatini
f(R) gravity. We argued that this casts serious doubt on the validity of
Palatini f(R) gravity as a viable alternative to General Relativity. In the
present paper we further investigate this characteristic of Palatini f(R)
gravity in order to clarify its physical interpretation and consequences.Comment: 15 pages. CQG in press. Part of the material moved to an appendix,
discussion on the meV scale predictions of Palatini f(R) gravity adde
The Safety and Immunogenicity of GTU®MultiHIV DNA Vaccine Delivered by Transcutaneous and Intramuscular Injection With or Without Electroporation in HIV-1 Positive Subjects on Suppressive ART
International audiencePrevious studies have shown targeting different tissues via the transcutaneous (TC) and intramuscular injection (IM) with or without electroporation (EP) has the potential to trigger immune responses to DNA vaccination. The CUTHIVTHER 001 Phase I/II randomized controlled clinical trial was designed to determine whether the mode of DNA vaccination delivery (TC+IM or EP+IM) could influence the quality and function of induced cellular immune responses compared to placebo, in an HIV positive clade B cohort on antiretroviral therapy (ART). The GTU®MultiHIV B DNA vaccine DNA vaccine encoded a MultiHIV B clade fusion protein to target the cellular response. Overall the vaccine and regimens were safe and well-tolerated. There were robust pre-vaccination IFN-γ responses with no measurable change following vaccination compared to placebo. However, modest intracellular cytokine staining (ICS) responses were seen in the TC+IM group. A high proportion of individuals demonstrated potent viral inhibition at baseline that was not improved by vaccination. These results show that HIV positive subjects with nadir CD4+ counts ≥250 on suppressive ART display potent levels of cellular immunity and viral inhibition, and that DNA vaccination alone is insufficient to improve such responses. These data suggest that more potent prime-boost vaccination strategies are likely needed to improve pre-existing responses in similar HIV-1 cohorts (This study has been registered at http://ClinicalTrials.gov under registration no. NCT02457689)
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