124 research outputs found
Strangeness in the baryon ground states
We compute the strangeness content of the baryon octet and decuplet states
based on an analysis of recent lattice simulations of the BMW, PACS, LHPC and
HSC groups for the pion-mass dependence of the baryon masses. Our results rely
on the relativistic chiral Lagrangian and large- sum rule estimates of the
counter terms relevant for the baryon masses at NLO. A partial summation is
implied by the use of physical baryon and meson masses in the one-loop
contributions to the baryon self energies. A simultaneous description of the
lattice results of the BMW, LHPC, PACS and HSC groups is achieved. From a
global fit we determine the axial coupling constants and in agreement with their values extracted from semi-leptonic
decays of the baryons. Moreover, various flavor symmetric limits of baron octet
and decuplet masses as obtained by the QCDSF-UKQCD group are recovered. We
predict the pion- and strangeness sigma terms and the pion-mass dependence of
the octet and decuplet ground states at different strange quark masses.Comment: 15 pages, 5 tables, 3 figures. There are two significant extensions
in the revised manuscript. First, a precise determination of the axial
coupling constants F and D from the lattice data on the baryon masses is
provided. Second, it is shown that the lattice data of the QCDSF-UKQCD group
on the baryon masses in the flavor symmetric limit are recovered. The 3rd
version is the published versio
Large-N_c operator analysis of 2-body meson-baryon counterterms in the chiral Lagrangian
The chiral SU(3) Lagrangian with the baryon octet and decuplet fields is
considered. The Q^2 counterterms involving the decuplet fields are constructed.
We derive the correlation of the chiral parameters implied by the 1/N_c
expansion at leading order in QCD.Comment: 20 pages, 3 figure
On the consistency of recent QCD lattice data of the baryon ground-state masses
In our recent analysis of lattice data of the BMW, LHPC and PACS-CS groups we
determined a parameter set of the chiral Lagrangian that allows a simultaneous
description of the baryon octet and decuplet masses as measured by those
lattice groups. The results on the baryon spectrum of the HSC group were
recovered accurately without their inclusion into our 6 parameter fit. We show
that the same parameter set provides an accurate reproduction of the recent
results of the QCDSF-UKQCD group probing the baryon masses at quite different
quark masses. This shows a remarkable consistency amongst the different lattice
simulations. With even more accurate lattice data in the near future it will
become feasible to determine all low-energy parameters relevant at NLO.Comment: 7 pages, 2 figure
Combined large- and heavy-quark operator analysis of 2-body meson-baryon counterterms in the chiral Lagrangian with charmed mesons
The chiral SU(3) Lagrangian with pseudoscalar and vector mesons and with
the octet and decuplet baryons is considered. The leading two-body counter
terms involving two baryon fields and two meson fields are constructed in
the open-charm sector. There are 26 terms. A combined expansion in the inverse
of the charm quark mass and in the inverse of the number of colors provides sum
rules that reduce the number of free parameter down to 5 only. Our result shows
the feasibility of a systematic computation of the open-charm baryon spectrum
based on coupled-channel dynamics.Comment: 19 page
TCP throughput guarantee in the DiffServ Assured Forwarding service: what about the results?
Since the proposition of Quality of Service architectures by the IETF, the
interaction between TCP and the QoS services has been intensively studied. This
paper proposes to look forward to the results obtained in terms of TCP
throughput guarantee in the DiffServ Assured Forwarding (DiffServ/AF) service
and to present an overview of the different proposals to solve the problem. It
has been demonstrated that the standardized IETF DiffServ conditioners such as
the token bucket color marker and the time sliding window color maker were not
good TCP traffic descriptors. Starting with this point, several propositions
have been made and most of them presents new marking schemes in order to
replace or improve the traditional token bucket color marker. The main problem
is that TCP congestion control is not designed to work with the AF service.
Indeed, both mechanisms are antagonists. TCP has the property to share in a
fair manner the bottleneck bandwidth between flows while DiffServ network
provides a level of service controllable and predictable. In this paper, we
build a classification of all the propositions made during these last years and
compare them. As a result, we will see that these conditioning schemes can be
separated in three sets of action level and that the conditioning at the
network edge level is the most accepted one. We conclude that the problem is
still unsolved and that TCP, conditioned or not conditioned, remains
inappropriate to the DiffServ/AF service
Family involvement for children with disruptive behaviors: The role of parenting stress and motivational beliefs
Children with disruptive behaviors are at risk for adverse outcomes. Family involvement is a significant predictor of positive child behavior outcomes; however, little research has investigated parent psychological variables that influence family involvement for children with disruptive behaviors. This study investigated the role of parental motivational beliefs (i.e., role construction and efficacy) as a potential mechanism by which parenting stress impacts family involvement for families of children with disruptive behaviors. Results indicated that parent role construction mediated the relation between parenting stress and all aspects of family involvement examined (i.e., home-based involvement, school-based involvement, and home–school communication). Parent efficacy mediated the relation between parenting stress and home-based involvement only. Parents of children with disruptive behaviors reporting stress may experience negative beliefs about their role and efficacy to support their child’s education, which may thereby negatively influence their actual involvement. Therefore, parent motivational beliefs may serve as an important point for intervention to support involvement of families of children with disruptive behavior
Glutamate Concentration in the Serum of Patients with Schizophrenia
Glutamate is the major neurotransmitter with multiple functions in the central nervous system. Glutamate-mediated excitotoxicity is involved in the pathophysiological processes in schizophrenia. The purpose of this study was to determine the concentration of glutamate in the serum of patients with paranoid schizophrenia compared with healthy individuals, and depending on the duration of the schizophrenic process and leading clinical symptoms. We investigated the level of glutamate in the serum of 158 patients with paranoid schizophrenia and 94 healthy persons. Higher concentrations of glutamate in schizophrenic patients compared with healthy persons have been found. The maximum concentrations of glutamate were detected in patients with disease duration of more than ten years. Glutamate level in the serum does not depend on the prevailing negative or positive clinical symptoms. The increased concentration of glutamate can hypothetically contribute to dopaminergic and glutamatergic imbalance, leading to the development of psychotic symptoms and cognitive dysfunction
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