1,411 research outputs found
Equation of state and critical behavior of polymer models: A quantitative comparison between Wertheim's thermodynamic perturbation theory and computer simulations
We present an application of Wertheim's Thermodynamic Perturbation Theory
(TPT1) to a simple coarse grained model made of flexibly bonded Lennard-Jones
monomers. We use both the Reference Hyper-Netted-Chain (RHNC) and Mean
Spherical approximation (MSA) integral equation theories to describe the
properties of the reference fluid. The equation of state, the density
dependence of the excess chemical potential, and the critical points of the
liquid--vapor transition are compared with simulation results and good
agreement is found. The RHNC version is somewhat more accurate, while the MSA
version has the advantage of being almost analytic. We analyze the scaling
behavior of the critical point of chain fluids according to TPT1 and find it to
reproduce the mean field exponents: The critical monomer density is predicted
to vanish as upon increasing the chain length while the critical
temperature is predicted to reach an asymptotic finite temperature that is
attained as . The predicted asymptotic finite critical temperature
obtained from the RHNC and MSA versions of TPT1 is found to be in good
agreement with the point of our polymer model as obtained from the
temperature dependence of the single chain conformations.Comment: to appear in J.Chem.Phy
Globular Clusters: DNA of Early-Type galaxies?
This paper explores if the mean properties of Early-Type Galaxies (ETG) can
be reconstructed from "genetic" information stored in their GCs (i.e., in their
chemical abundances, spatial distributions and ages). This approach implies
that the formation of each globular occurs in very massive stellar
environments, as suggested by some models that aim at explaining the presence
of multi-populations in these systems. The assumption that the relative number
of globular clusters to diffuse stellar mass depends exponentially on chemical
abundance, [Z/H], and the presence of two dominant GC sub-populations blue and
red, allows the mapping of low metallicity halos and of higher metallicity (and
more heterogeneous) bulges. In particular, the masses of the low-metallicity
halos seem to scale up with dark matter mass through a constant. We also find a
dependence of the globular cluster formation efficiency with the mean projected
stellar mass density of the galaxies within their effective radii. The analysis
is based on a selected sub-sample of galaxies observed within the ACS Virgo
Cluster Survey of the {\it Hubble Space Telescope}. These systems were grouped,
according to their absolute magnitudes, in order to define composite fiducial
galaxies and look for a quantitative connection with their (also composite)
globular clusters systems. The results strengthen the idea that globular
clusters are good quantitative tracers of both baryonic and dark matter in
ETGs.Comment: 20 pages, 28 figures and 5 table
Involvement of Gap Junction Proteins in Infectious Diseases Caused by Parasites
Parasitic diseases affect low-income nations with health consequences that affect the economy of these countries. Research aimed at understanding their biology and identification of potential targets for drug development is of the highest priority. Inhibitors of channels formed by proteins of the gap junction family such as suramin and probenecid are currently used for treatment of parasitic diseases caused by pathogenic protozoan. Gap junction proteins are present in both vertebrates and invertebrates permitting direct and indirect cellular communication. These cellular specializations are formed by two protein families corresponding to connexins (vertebrates) and innexins (invertebrates). In addition, a third protein family composed by proteins denominated pannexins is present in vertebrates and shows primary sequence homology to innexins. Channels formed by these proteins are essential in many biological processes. Recent evidences suggest that gap junction proteins play a critical role in bacterial and viral infections. Nonetheless, little is known about the role of these channels in parasitic infections. In this chapter, we summarized the current knowledge about the role of gap junction family proteins and channels in parasitic infections
Research Note : Persistent Salmonella problems in slaughterhouses related to clones linked to poultry companies
Salmonellosis remains one of the main foodborne zoonoses in Europe, with poultry products as the main source of human infections. The slaughterhouse has been identified as a potential source for Salmonella contamination of poultry meat. Despite the mandatory programme of the EU, there are companies with persistent Salmonella that are unable to remove the bacteria from their processing environment, compromising the entire production line. In this context, an intensive sampling study was conducted to investigate a slaughterhouse with persistent Salmonella problems, establishing the genetic relationship among Salmonella strains isolated during the slaughter process. A total of 36 broiler flocks were sampled during processing at the slaughterhouse. Salmonella was identified based on ISO 6579-1:2017 (Annex D), serotyped by Kauffman-White-Le-Minor technique, and the genetic relationship was assessed with ERIC-PCR followed by PFGE. The outcomes showed that 69.4% of the batches sampled carried Salmonella upon arrival at the slaughterhouse and that 46.3% of the different samples from carcasses were contaminated with Salmonella. The two serovars isolated at the different steps in the slaughterhouse were Enteritidis (98.2%) and Kentucky (1.8%). Pulsed-field gel electrophoresis analysis revealed a low genetic diversity, with all S. Enteritidis isolates showing a nearly identical pulsotype (similarity >85%) and S. Kentucky strains showed the same XbaI PFGE profile (95.0% genetic similarity). The results of this study showed a high genetic relationship among isolates recovered from carcasses and environmental samples in the slaughterhouse from both Salmonella -positive and Salmonella -free flocks. Salmonella strains re-circulated across to poultry flocks and re-entered the slaughterhouse to survive on the processing line. Thus, it is necessary to implement molecular diagnosis methods in time at the field level to determine the Salmonella epidemiology of the flock, to make rapid decisions for the control of Salmonella and prevent entry into the slaughterhouse environment
Research Note: Persistent Salmonella problems in slaughterhouses related to clones linked to poultry companies
Salmonellosis remains one of the main foodborne zoonoses in Europe, with poultry products as the main source of human infections. The slaughterhouse has been identified as a potential source for Salmonella contamination of poultry meat. Despite the mandatory programme of the EU, there are companies with persistent Salmonella that are unable to remove the bacteria from their processing environment, compromising the entire production line. In this context, an intensive sampling study was conducted to investigate a slaughterhouse with persistent Salmonella problems, establishing the genetic relationship among Salmonella strains isolated during the slaughter process. A total of 36 broiler flocks were sampled during processing at the slaughterhouse. Salmonella was identified based on ISO 6579-1:2017 (Annex D), serotyped by Kauffman-White-Le-Minor technique, and the genetic relationship was assessed with ERIC-PCR followed by PFGE. The outcomes showed that 69.4% of the batches sampled carried Salmonella upon arrival at the slaughterhouse and that 46.3% of the different samples from carcasses were contaminated with Salmonella. The two serovars isolated at the different steps in the slaughterhouse were Enteritidis (98.2%) and Kentucky (1.8%). Pulsed-field gel electrophoresis analysis revealed a low genetic diversity, with all S. Enteritidis isolates showing a nearly identical pulsotype (similarity >85%) and S. Kentucky strains showed the same XbaI PFGE profile (95.0% genetic similarity). The results of this study showed a high genetic relationship among isolates recovered from carcasses and environmental samples in the slaughterhouse from both Salmonella-positive and Salmonella-free flocks. Salmonella strains re-circulated across to poultry flocks and re-entered the slaughterhouse to survive on the processing line. Thus, it is necessary to implement molecular diagnosis methods in time at the field level to determine the Salmonella epidemiology of the flock, to make rapid decisions for the control of Salmonella and prevent entry into the slaughterhouse environment.info:eu-repo/semantics/publishedVersio
Circular strings, wormholes and minimum size
The quantization of circular strings in an anti-de Sitter background
spacetime is performed, obtaining a discrete spectrum for the string mass. A
comparison with a four-dimensional homogeneous and isotropic spacetime coupled
to a conformal scalar field shows that the string radius and the scale factor
have the same classical solutions and that the quantum theories of these two
models are formally equivalent. However, the physically relevant observables of
these two systems have different spectra, although they are related to each
other by a specific one-to-one transformation. We finally obtain a discrete
spectrum for the spacetime size of both systems, which presents a nonvanishing
lower bound.Comment: 11 pages, LaTeX2e, minor change
192 CELL DEATH IN CHONDROCYTES DURING THE PATHOGENESIS OF OSTEOARTHRITIS IS A COMBINATION OF APOPTOSIS AND AUTOPHAGY
Processing and mechanical properties of novel biodegradable poly-lactic acid/Zn 3D printed scaffolds for application in tissue regeneration
The feasibility to manufacture scaffolds of poly-lactic acid reinforced with
Zn particles by fused filament fabrication is demonstrated for the first time.
Filaments of 2.85 mm in diameter of PLA reinforced with different weight
fractions of m-sized Zn - 1 wt. \% Mg alloy particles (in the range 3.5 to
17.5 wt. \%) were manufactured by a double extrusion in method in which
standard extrusion is followed by a precision extrusion in a filament-maker
machine. Filaments with constant diameter, negligible porosity and a
homogeneous reinforcement distribution were obtained for Zn weight fractions of
up to 10.5\%. It was found that the presence of Zn particles led to limited
changes in the physico-chemical properties of the PLA that did not affect the
window temperature for 3D printing nor the melt flow index. Thus, porous
scaffolds could be manufactured by fused filament fabrication at 190\textdegree
C with poly-lactic acid/Zn composites containing 3.5 and 7 wt. \% of Zn and at
170\textdegree C when the Zn content was 10.5 wt. \% with excellent dimensional
accuracy and mechanical properties
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