4,260 research outputs found
Transition Density and Pressure at the Inner Edge of Neutron Star Crusts
Using the nuclear symmetry energy that has been recently constrained by the
isospin diffusion data in intermediate-energy heavy ion collisions, we have
studied the transition density and pressure at the inner edge of neutron star
crusts, and they are found to be 0.040 fm
fm and 0.01 MeV/fm MeV/fm,
respectively, in both the dynamical and thermodynamical approaches. We have
also found that the widely used parabolic approximation to the equation of
state of asymmetric nuclear matter gives significantly higher values of
core-crust transition density and pressure, especially for stiff symmetry
energies. With these newly determined transition density and pressure, we have
obtained an improved relation between the mass and radius of neutron stars.Comment: 7 pages, 3 figures, proceeding of "The International Workshop on
Nuclear Dynamics in Heavy-Ion Reactions and the Symmetry Energy (IWND2009)
Purely electronic transport and localization in the Bose glass
We discuss transport and localization properties on the insulating side of
the disorder dominated superconductor-insulator transition, described in terms
of the dirty boson model. Analyzing the spectral properties of the interacting
bosons in the absence of phonons, we argue that the Bose glass phase admits
three distinct regimes. For strongest disorder the boson system is a fully
localized, perfect insulator at any temperature. At smaller disorder, only the
low temperature phase exhibits perfect insulation while delocalization takes
place above a finite temperature. We argue that a third phase must intervene
between these perfect insulators and the superconductor. This conducting Bose
glass phase is characterized by a mobility edge in the many body spectrum,
located at finite energy above the ground state. In this insulating regime
purely electronically activated transport occurs, with a conductivity following
an Arrhenius law at asymptotically low temperatures, while a tendency to
superactivation is predicted at higher T. These predictions are in good
agreement with recent transport experiments in highly disordered films of
superconducting materials.Comment: Discussion about 2d case added. Proceddings of TIDS 13, to be
published in Annals of Physic
Catastrophic rearrangement of a compact star due to the quark core formation
We study properties of compact stars with the deconfinement phase transition
in their interiors. The equation of state of cold baryon-rich matter is
constructed by combining a relativistic mean-field model for the hadronic phase
and the MIT Bag model for the deconfined phase. In a narrow parameter range two
sequences of compact stars (twin stars), which differ by the size of the quark
core, have been found. We demonstrate the possibility of a rapid transition
between the twin stars with the energy release of about ergs. This
transition should be accompanied by the prompt neutrino burst and the delayed
gamma-ray burst.Comment: Latex, 14 pages including five postscript figure
Refinement of IntelliCage protocols for complex cognitive tasks through replacement of drinking restrictions by incentive-disincentive paradigms
The IntelliCage allows automated testing of cognitive abilities of mice in a social home cage environment without handling by human experimenters. Restricted water access in combination with protocols in which only correct responses give access to water is a reliable learning motivator for hippocampus-dependent tasks assessing spatial memory and executive function. However, water restriction may negatively impact on animal welfare, especially in poor learners. To better comply with the 3R principles, we previously tested protocols in which water was freely available but additional access to sweetened water could be obtained by learning a task rule. While this purely appetitive motivation worked for simple tasks, too many mice lost interest in the sweet reward during more difficult hippocampus-dependent tasks. In the present study, we tested a battery of increasingly difficult spatial tasks in which water was still available without learning the task rule, but rendered less attractive either by adding bitter tasting quinine or by increasing the amount of work to obtain it. As in previous protocols, learning of the task rule provided access to water sweetened with saccharin. The two approaches of dual motivation were tested in two cohorts of female C57BL/6âN mice. Compared to purely appetitive motivation, both novel protocols strongly improved task engagement and increased task performance. Importantly, neither of the added disincentives had an adverse impact on liquid consumption, health status or body weight of the animals. Our results show that it is possible to refine test protocols in the IntelliCage so that they challenge cognitive functions without restricting access to water
Exact Groundstates for Antiferromagnetic Spin-One Chains with Nearest and Next-Nearest Neighbour Interactions
We have found the exact ground state for a large class of antiferromagnetic
spin-one chains with nearest and next-nearest neighbour interactions. The
ground state is characterized as a matrix product of local site states and has
the properties characteristic of the Haldane scenario.Comment: 8 pages, to appear in Z. Phys. B, preprint Cologne-94-474
Structural insights into Legionella RidL-Vps29 retromer subunit interaction reveal displacement of the regulator TBC1D5
Legionella pneumophila can cause Legionnairesâ disease and replicates intracellularly in a distinct Legionella-containing vacuole (LCV). LCV formation is a complex process that involves a plethora of type IV-secreted effector proteins. The effector RidL binds the Vps29 retromer subunit, blocks retrograde vesicle trafficking, and promotes intracellular bacterial replication. Here, we reveal that the 29-kDa N-terminal domain of RidL (RidL2â281) adopts a âfoot-likeâ fold comprising a protruding ÎČ-hairpin at its âheelâ. The deletion of the ÎČ-hairpin, the exchange to Glu of Ile170 in the ÎČ-hairpin, or Leu152 in Vps29 abolishes the interaction in eukaryotic cells and in vitro. RidL2â281 or RidL displace the Rab7 GTPase-activating protein (GAP) TBC1D5 from the retromer and LCVs, respectively, and TBC1D5 promotes the intracellular growth of L. pneumophila. Thus, the hydrophobic ÎČ-hairpin of RidL is critical for binding of the L. pneumophila effector to the Vps29 retromer subunit and displacement of the regulator TBC1D5
Computer-Aided Histopathological Characterisation of Endometriosis Lesions.
Endometriosis is a common gynaecological condition characterised by the growth of endometrial tissue outside the uterus and is associated with pain and infertility. Currently, the gold standard for endometriosis diagnosis is laparoscopic excision and histological identification of endometrial epithelial and stromal cells. There is, however, currently no known association between the histological appearance, size, morphology, or subtype of endometriosis and disease prognosis. In this study, we used histopathological software to identify and quantify the number of endometrial epithelial and stromal cells within excised endometriotic lesions and assess the relationship between the cell contents and lesion subtypes. Prior to surgery for suspected endometriosis, patients provided menstrual and abdominal pain and dyspareunia scores. Endometriotic lesions removed during laparoscopic surgery were collected and prepared for immunohistochemistry from 26 patients. Endometrial epithelial and stromal cells were identified with Cytokeratin and CD10 antibodies, respectively. Whole slide sections were digitised and the QuPath software was trained to automatically detect and count epithelial and stromal cells across the whole section. Using this classifier, we identified a significantly larger number of strongly labelled CD10 stromal cells (p = 0.0477) in deeply infiltrating lesions (99,970 ± 2962) compared to superficial lesions (2456 ± 859). We found the ratio of epithelial to stromal cells was inverted in deeply infiltrating endometriosis lesions compared to superficial peritoneal and endometrioma lesions and we subsequently identified a correlation between total endometrial cells and abdominal pain (p = 0.0005) when counted via the automated software. Incorporating histological software into current standard diagnostic pipelines may improve endometriosis diagnosis and provide prognostic information in regards to severity and symptoms and eventually provide the potential to personalise adjuvant treatment decisions
Immune response to pneumococcal polysaccharides 4 and 14 in elderly and young adults. I Antibody concentrations, avidity and functional activity
Streptococcus pneumoniae is a serious worldwide pathogen and the focus of numerous vaccine development projects. Currently the most widely accepted surrogate marker for evaluating the efficacy of a given vaccine is to utilize ELISA. Measurement of antibody concentration by ELISA without reduction in cross-reactive antibodies causes an overestimation of antibody concentration and therefore protection, this is most notable in the aged, an at risk group for this infection. We compared the immune response to the pneumococcal polysaccharides (PPS) 4 and 14 of 20 young to 20 elderly adults. Pre-and post-vaccination IgG antibody concentrations and antibody avidity against PPS4 and PPS14 were measured using two different enzyme-linked immunosorbant assay (ELISA) absorption protocols. All sera were pre-absorbed with either cell-wall polysaccharide (CPS), or CPS and serotype 22F polysaccharide. Pre- and post-vaccination IgG antibody concentrations for serotype 4, but not 14, were significantly lowered with the additional absorption with serotype 22F polysaccharide in both age groups. Young and elderly demonstrated a significant increase from pre- to post-immunization antibody concentration, using either absorption method; and opsonophagocytic antibody titers in response to both PPS4 and PPS14. The correlation coefficients between ELISA and opsonophagocytic assays were improved by additional absorption with serotype 22F in response to serotype 4, but not serotype 14 in all age groups. Opsonophagocytic antibody titers in a sub-group of elderly (>77 years of age) were significantly lower than the opsonophagocytic antibody concentrations in young adults. These results suggest the importance of eliminating cross-reactive antibodies from ELISA measurements by absorption of serum and an age-related impairment in the antibody response to pneumococcal polysaccharides
Accreting Black Holes
This chapter provides a general overview of the theory and observations of
black holes in the Universe and on their interpretation. We briefly review the
black hole classes, accretion disk models, spectral state classification, the
AGN classification, and the leading techniques for measuring black hole spins.
We also introduce quasi-periodic oscillations, the shadow of black holes, and
the observations and the theoretical models of jets.Comment: 41 pages, 18 figures. To appear in "Tutorial Guide to X-ray and
Gamma-ray Astronomy: Data Reduction and Analysis" (Ed. C. Bambi, Springer
Singapore, 2020). v3: fixed some typos and updated some parts. arXiv admin
note: substantial text overlap with arXiv:1711.1025
Forging Fluorine-Containing Quaternary Stereocenters by a Light-Driven Organocatalytic Aldol Desymmetrization Process
Reported herein is a light-triggered organocatalytic strategy for the desymmetrization of achiral 2-fluoro-substi- tuted cyclopentane-1,3-diketones. The chemistry is based on an intermolecular aldol reaction of photochemically generated hydroxy-o-quinodimethanes and simultaneously forges two adjacent fully substituted carbon stereocenters, with one bearing a stereogenic carbonâfluorine unit. The method uses readily available substrates, a simple chiral organocatalyst, and mild reaction conditions to afford an array of highly function- alized chiral 2-fluoro-3-hydroxycyclopentanones
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