809 research outputs found
Degenerate limit thermodynamics beyond leading order for models of dense matter
Analytical formulas for next-to-leading order temperature corrections to the
thermal state variables of interacting nucleons in bulk matter are derived in
the degenerate limit. The formalism developed is applicable to a wide class of
non-relativistic and relativistic models of hot and dense matter currently used
in nuclear physics and astrophysics (supernovae, proto-neutron stars and
neutron star mergers) as well as in condensed matter physics. We consider the
general case of arbitrary dimensionality of momentum space and an arbitrary
degree of relativity (for relativistic mean-field theoretical models). For
non-relativistic zero-range interactions, knowledge of the Landau effective
mass suffices to compute next-to-leading order effects, but in the case of
finite-range interactions, momentum derivatives of the Landau effective mass
function up to second order are required. Numerical computations are performed
to compare results from our analytical formulas with the exact results for
zero- and finite-range potential and relativistic mean-field theoretical
models. In all cases, inclusion of next-to-leading order temperature effects
substantially extends the ranges of partial degeneracy for which the analytical
treatment remains valid.Comment: 28 pages, 8 figure
Thermal properties of hot and dense matter with finite range interactions
We explore the thermal properties of hot and dense matter using a model that
reproduces the empirical properties of isospin symmetric and asymmetric bulk
nuclear matter, optical model fits to nucleon-nucleus scattering data,
heavy-ion flow data in the energy range 0.5-2 GeV/A, and the largest
well-measured neutron star mass of 2 . Results of this model
which incorporates finite range interactions through Yukawa type forces are
contrasted with those of a zero-range Skyrme model that yields nearly identical
zero-temperature properties at all densities for symmetric and asymmetric
nucleonic matter and the maximum neutron star mass, but fails to account for
heavy-ion flow data due to the lack of an appropriate momentum dependence in
its mean field. Similarities and differences in the thermal state variables and
the specific heats between the two models are highlighted. Checks of our exact
numerical calculations are performed from formulas derived in the strongly
degenerate and non-degenerate limits. Our studies of the thermal and adiabatic
indices, and the speed of sound in hot and dense matter for conditions of
relevance to core-collapse supernovae, the thermal evolution of neutron stars
from their birth and mergers of compact binary stars reveal that substantial
variations begin to occur at sub-saturation densities before asymptotic values
are reached at supra-nuclear densities.Comment: 47 pages, 40 figure
The APR equation of state for simulations of supernovae, neutron stars and binary mergers
Differences in the equation of state (EOS) of dense matter translate into
differences in astrophysical simulations and their multi-messenger signatures.
Thus, extending the number of EOSs for astrophysical simulations allows us to
probe the effect of different aspects of the EOS in astrophysical phenomena. In
this work, we construct the EOS of hot and dense matter based on the Akmal,
Pandharipande, and Ravenhall (APR) model and thereby extend the open-source
SROEOS code which computes EOSs of hot dense matter for Skyrme-type
parametrizations of the nuclear forces. Unlike Skrme-type models, in which
parameters of the interaction are fit to reproduce the energy density of
nuclear matter and/or properties of heavy nuclei, the EOS of APR is obtained
from potentials resulting from fits to nucleon-nucleon scattering and
properties of light nuclei. In addition, this EOS features a phase transition
to a neutral pion condensate at supra-nuclear densities. We show that
differences in the effective masses between EOSs have consequences for the
properties of nuclei in the sub-nuclear inhomogeneous phase of matter. We also
test the new EOS of APR in spherically symmetric core-collapse of massive stars
with and , respectively. We find that the phase
transition in the EOS of APR speeds up the collapse of the star. However, this
phase transition does not generate a second shock wave or another neutrino
burst as reported for the hadron-to-quark phase transition. The reason for this
difference is that the onset of the phase transition in the EOS of APR occurs
at larger densities than for the quark-to-hadron transition employed earlier
which results in a significantly smaller softening of the high density EOS.Comment: 35 pages, 17 figures, 5 table
Increasing Antiproliferative Properties of Endocannabinoids in N1E-115 Neuroblastoma Cells through Inhibition of Their Metabolism
The antitumoral properties of endocannabinoids received a particular attention these last few years. Indeed, these endogenous molecules have been reported to exert cytostatic, apoptotic and antiangiogenic effects in different tumor cell lines and tumor xenografts. Therefore, we investigated the cytotoxicity of three N-acylethanolamines – N-arachidonoylethanolamine (anandamide, AEA), N-palmitoylethanolamine (PEA) and N-oleoylethanolamine (OEA) - which were all able to time- and dose-dependently reduce the viability of murine N1E-115 neuroblastoma cells. Moreover, several inhibitors of FAAH and NAAA, whose presence was confirmed by RT-PCR in the cell line, induced cell cytotoxicity and favored the decrease in cell viability caused by N-acylethanolamines. The most cytotoxic treatment was achieved by the co-incubation of AEA with the selective FAAH inhibitor URB597, which drastically reduced cell viability partly by inhibiting AEA hydrolysis and consequently increasing AEA levels. This combination of molecules synergistically decreased cell proliferation without inducing cell apoptosis or necrosis. We found that these effects are independent of cannabinoid, TRPV1, PPARα, PPARγ or GPR55 receptors activation but seem to occur through a lipid raft-dependent mechanism. These findings further highlight the interest of targeting the endocannabinoid system to treat cancer. More particularly, this emphasizes the great potential benefit of designing novel anti-cancerous therapies based on the association of endocannabinoids and inhibitors of their hydrolysis
A computer simulation protocol to assess the accuracy of a Radio Stereometric Analysis (RSA) image processor according to the ISO-5725
Radio-Stereometric-Analysis and x-ray fluoroscopy are radiological techniques
that require dedicated software to process data. The accurate calibration of
these software is therefore critical. The aim of this work is to produce a
protocol for evaluating the softwares' accuracy according to the ISO-5725. A
series of computer simulations of the radiological setup and images were
employed. The noise level of the images was also changed to evaluate the
accuracy with different image qualities. The protocol was tested on a custom
software developed by the authors. Radiological scene reconstruction accuracy
was of (0.092 +- 0.14) mm for tube position, and (0.38 +- 0.31) mm / (2.09 +-
1.39) deg for detectors oriented in a direction other than the source-detector
direction. In the source-detector direction the accuracy was of (2.68 +- 3.08)
mm for tube position, and of (0.16 +- 0.27) mm / (0.075 +- 1.16) deg for the
detectors. These disparate results are widely discussed in the literature.
Model positioning and orientation was also highly accurate: (0.22 +- 0.46) mm /
(0.26 +- 0.22) deg. Accuracy was not affected by the noise level. The protocol
was able to assess the accuracy of the RSA system. It was also useful to detect
and fix hidden bugs. It was also useful to detect and resolve hidden bugs in
the software, and in optimizing the algorithms
Custom-made implants for massive acetabular bone loss: accuracy with CT assessment
Background: Custom-made implants are a valid option in revision total hip arthroplasty to address massive acetabular bone loss. The aim of this study was to assess the accuracy of custom-made acetabular implants between preoperative planning and postoperative positioning using CT scans. Methods: In a retrospective analysis, three patients who underwent an acetabular custom-made prosthesis were identified. The custom-made designs were planned through 3D CT analysis considering surgical points of attention. The accuracy of intended implants positioning was assessed by comparing pre- and postoperative CT analyzing the center of rotation (CoR), anteversion, inclination, screws, and implant surface in contact with the bone. Results: The three cases presented satisfactory accuracy in positioning. A malpositioning in the third case was observed due to the posterization of the CoR of the implant of more than 10 mm. The other CoR vectors considered in the third patient and all vectors in the other two cases fall within 10 mm. All the cases were positioned with a difference of less than 10° of anteversion and inclination with respect to the planning. Conclusions: The current case series revealed promising accuracy in the positioning of custom-made acetabular prosthesis comparing the planned implant in preoperative CT with postoperative CT
The endocannabinoid system links gut microbiota to adipogenesis
We investigated several models of gut microbiota modulation: selective (prebiotics, probiotics, high-fat), drastic (antibiotics, germ-free mice) and mice bearing specific mutations of a key gene involved in the toll-like receptors (TLR) bacteria-host interaction (Myd88−/−). Here we report that gut microbiota modulates the intestinal endocannabinoid (eCB) system-tone, which in turn regulates gut permeability and plasma lipopolysaccharide (LPS) levels.The activation of the intestinal endocannabinoid system increases gut permeability which in turn enhances plasma LPS levels and inflammation in physiological and pathological conditions such as obesity and type 2 diabetes.The investigation of adipocyte differentiation and lipogenesis (both markers of adipogenesis) indicate that gut microbiota controls adipose tissue physiology through LPS-eCB system regulatory loops and may play a critical role in the adipose tissue plasticity during obesity.In vivo, ex vivo and in vitro studies indicate that LPS acts as a master switch on adipose tissue metabolism, by blocking the cannabinoid-driven adipogenesis
Expression of cortistatin and MrgX2, a specific cortistatin receptor, in human neuroendocrine tissues and related tumours
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