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 $\delta F(R) \equiv \partial f/\partial R - 1$ is a decreasing function of R however. As a result, both Solar System constraints and stellar dynamics are perfectly consistent with $f(R) = R - \mu^4/R$.Comment: Published version, 6 pages, 1 figur

Detection of low energy single ion impacts in micron scale transistors at room temperature

We report the detection of single ion impacts through monitoring of changes in the source-drain currents of field effect transistors (FET) at room temperature. Implant apertures are formed in the interlayer dielectrics and gate electrodes of planar, micro-scale FETs by electron beam assisted etching. FET currents increase due to the generation of positively charged defects in gate oxides when ions (121Sb12+, 14+, Xe6+; 50 to 70 keV) impinge into channel regions. Implant damage is repaired by rapid thermal annealing, enabling iterative cycles of device doping and electrical characterization for development of single atom devices and studies of dopant fluctuation effects

Deglacial laminated facies on the NW European continental margin: The hydrographic significance of British-Irish Ice Sheet deglaciation and Fleuve Manche paleoriver discharges

[1] We have compiled results obtained from four high sedimentation rate hemipelagic sequences from the Celtic sector of the NW European margin ( NE Atlantic) to investigate the paleoceanographic and paleoclimatic evolution of the area over the last few climatic cycles. We focus on periods characteristic of deglacial transitions. We adopt a multiproxy sedimentological, geochemical, and micropaleontological approach, applying a sampling resolution down to ten microns for specific intervals. The investigation demonstrates the relationships between the Bay of Biscay hydrography and the glacial/deglacial history of both the proximal British-Irish Ice Sheet (BIIS) and the western European continent. We identify recurrent phases of laminae deposition concurrent with major BIIS deglacial episodes in all the studied cores. Evidence for abrupt freshwater discharges into the open ocean highlights the influence of such events at a regional scale. We discuss their impact at a global scale considering the present and past key location of the Bay of Biscay versus the Atlantic Meridional Overturning Circulation (AMOC)

High-Yield D-T Neutron Generator

A high-yield D-T neutron generator has been developed for neutron interrogation in homeland security applications such as cargo screening. The generator has been designed as a sealed tube with a performance goal of producing 5 {center_dot} 10{sup 11} n/s over a long lifetime. The key generator components developed are a radio-frequency (RF) driven ion source and a beam-loaded neutron production target that can handle a beam power of 10 kW. The ion source can provide a 100 mA D{sup +}/T{sup +} beam current with a high fraction of atomic species and can be pulsed up to frequencies of several kHz for pulsed neutron generator operation. Testing in D-D operation has been started

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

Endoplasmic reticulum stress inhibition protects against excitotoxic neuronal injury in the rat brain.

Elevated brain glutamate with activation of neuronal glutamate receptors accompanies neurological disorders, such as epilepsy and brain trauma. However, the mechanisms by which excitotoxicity triggers neuronal injury are not fully understood. We have studied the glutamate receptor agonist kainic acid (KA) inducing seizures and excitotoxic cell death. KA caused the disintegration of the endoplasmic reticulum (ER) membrane in hippocampal neurons and ER stress with the activation of the ER proteins Bip, Chop, and caspase-12. Salubrinal, inhibiting eIF2alpha (eukaryotic translation initiation factor 2 subunit alpha) dephosphorylation, significantly reduced KA-induced ER stress and neuronal death in vivo and in vitro. KA-induced rise in intracellular calcium was not affected by Salubrinal. The results show that ER responses are essential parts of excitotoxicity mediated by glutamate receptor activation and that Salubrinal decreases neuronal death in vivo. Inhibition of ER stress by small molecular compounds may be beneficial for treatment of various neuronal injuries and brain disorders

Equilibrium hydrostatic equation and Newtonian limit of the singular f(R) gravity

We derive the equilibrium hydrostatic equation of a spherical star for any gravitational Lagrangian density of the form $L=\sqrt{-g}f(R)$. The Palatini variational principle for the Helmholtz Lagrangian in the Einstein gauge is used to obtain the field equations in this gauge. The equilibrium hydrostatic equation is obtained and is used to study the Newtonian limit for $f(R)=R-\frac{a^{2}}{3R}$. The same procedure is carried out for the more generally case $f(R)=R-\frac{1}{n+2}\frac{a^{n+1}}{R^{n}}$ giving a good Newtonian limit.Comment: Revised version, to appear in Classical and Quantum Gravity

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 $f(R)=R-c /R^ b$ 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