2,431 research outputs found
Medium dependence of the bag constant in the quark-meson coupling model
Possible variations of the quark-meson coupling (QMC) model are examined in
which the bag constant decreases in the nuclear medium. The reduction is
supposed to depend on either the mean scalar field or the effective mass of the
nucleon. It is shown that the electric and magnetic radii of the bound nucleon
are almost linearly correlated with the bag constant. Using the fact that the
size of the bound nucleon inside a nucleus is strongly constrained by
-scaling data in quasielastic, electron-nucleus scattering, we set a limit
for the reduction allowed in the bag constant for these two models. The present
study implies that the bag constant can decrease up to 10--17 % at average
nuclear density, depending on the details of the model.Comment: 31 pages including 4 ps figures, to appear in Nucl.Phys.
The Role of Color Neutrality in Nuclear Physics--Modifications of Nucleonic Wave Functions
The influence of the nuclear medium upon the internal structure of a
composite nucleon is examined. The interaction with the medium is assumed to
depend on the relative distances between the quarks in the nucleon consistent
with the notion of color neutrality, and to be proportional to the nucleon
density. In the resulting description the nucleon in matter is a superposition
of the ground state (free nucleon) and radial excitations. The effects of the
nuclear medium on the electromagnetic and weak nucleon form factors, and the
nucleon structure function are computed using a light-front constituent quark
model. Further experimental consequences are examined by considering the
electromagnetic nuclear response functions. The effects of color neutrality
supply small but significant corrections to predictions of observables.Comment: 37 pages, postscript figures available on request to
[email protected]
The challenges of implementing packaged hospital electronic prescribing and medicine administration systems in UK hospitals: premature purchase of immature solutions?
The UK National Health Service is making major efforts to implement Hospital Electronic Prescribing and Medicine Administration (HEPMA) to improve patient safety and quality of care. Substantial public investments have attracted a wide range of UK and overseas suppliers offering Commercial-Off –The-Shelf (COTS) solutions. A lack of (UK) implementation experience and weak supplier-user relationships are reflected in systems with limited configurability, poorly matched to the needs and practices of English hospitals. This situation echoes the history of comparable corporate information infrastructures - Enterprise Resource Planning systems - in the 1980s/1990s. UK government intervention prompted a similar swarming of immature, often unfinished, products into the market. This resulted, in both cases, in protracted and difficult implementation processes as vendors and adopters struggled to get the systems to work and match the circumstances of the adopting organisations. An analysis of the influence of the Installed Base on Information Infrastructures should explore how the evolution of COTS solutions is conditioned by the structure of adopter and vendor ‘communities’
The ratio of proton's electric to magnetic form factors measured by polarization transfer
The ratio of the proton's elastic electromagnetic form factors was obtained
by measuring the transverse and longitudinal polarizations of recoiling protons
from the elastic scattering of polarized electrons with unpolarized protons.
The ratio of the electric to magnetic form factor is proportional to the ratio
of the transverse to longitudinal recoil polarizations. The ratio was measured
over a range of four-momentum transfer squared between 0.5 and 3.5 GeV-squared.
Simultaneous measurement of transverse and longitudinal polarizations in a
polarimeter provides good control of the systematic uncertainty. The results
for the ratio of the proton's electric to magnetic form factors show a
systematic decrease with increasing four momentum squared, indicating for the
first time a marked difference in the spatial distribution of charge and
magnetization currents in the proton.Comment: 5 pages, 2 figures, version of paper after corrections due to
referees comments and shortened by removing one figure for Physical Review
Letter
Nucleon and hadron structure changes in the nuclear medium and impact on observables
We review the effect of hadron structure changes in a nuclear medium using
the quark-meson coupling (QMC) model, which is based on a mean field
description of non-overlapping nucleon (or baryon) bags bound by the
self-consistent exchange of scalar and vector mesons. This approach leads to
simple scaling relations for the changes of hadron masses in a nuclear medium.
It can also be extended to describe finite nuclei, as well as the properties of
hypernuclei and meson-nucleus deeply bound states. It is of great interest that
the model predicts a variation of the nucleon form factors in nuclear matter.
We also study the empirically observed, Bloom-Gilman (quark-hadron) duality.
Other applications of the model include subthreshold kaon production in heavy
ion collisions, D and D-bar meson production in antiproton-nucleus collisions,
and J/Psi suppression. In particular, the modification of the D and D-bar meson
properties in nuclear medium can lead to a large J/Psi absorption cross
section, which explains the observed J/Psi suppression in relativistic heavy
ion collisions.Comment: 143 pages, 77 figures, references added, a review article accepted in
Prog. Part. Nucl. Phy
Neutral and Charged Polymers at Interfaces
Chain-like macromolecules (polymers) show characteristic adsorption
properties due to their flexibility and internal degrees of freedom, when
attracted to surfaces and interfaces. In this review we discuss concepts and
features that are relevant to the adsorption of neutral and charged polymers at
equilibrium, including the type of polymer/surface interaction, the solvent
quality, the characteristics of the surface, and the polymer structure. We pay
special attention to the case of charged polymers (polyelectrolytes) that have
a special importance due to their water solubility. We present a summary of
recent progress in this rapidly evolving field. Because many experimental
studies are performed with rather stiff biopolymers, we discuss in detail the
case of semi-flexible polymers in addition to flexible ones. We first review
the behavior of neutral and charged chains in solution. Then, the adsorption of
a single polymer chain is considered. Next, the adsorption and depletion
processes in the many-chain case are reviewed. Profiles, changes in the surface
tension and polymer surface excess are presented. Mean-field and corrections
due to fluctuations and lateral correlations are discussed. The force of
interaction between two adsorbed layers, which is important in understanding
colloidal stability, is characterized. The behavior of grafted polymers is also
reviewed, both for neutral and charged polymer brushes.Comment: a review: 130 pages, 30 ps figures; final form, added reference
Plastisol Foaming Process. Decomposition of the Foaming Agent, Polymer Behavior in the Corresponding Temperature Range and Resulting Foam Properties
The decomposition of azodicarbonamide, used as foaming agent in PVC - plasticizer (1/1) plastisols was studied by DSC. Nineteen different plasticizers, all belonging to the ester family, two being polymeric (polyadipates), were compared. The temperature of maximum decomposition rate (in anisothermal regime at 5 K min-1 scanning rate), ranges between 434 and 452 K. The heat of decomposition ranges between 8.7 and 12.5 J g -1. Some trends of variation of these parameters appear significant and are discussed in terms of solvent (matrix) and viscosity effects on the decomposition reactions. The shear modulus at 1 Hz frequency was determined at the temperature of maximum rate of foaming agent decomposition, and differs significantly from a sample to another. The foam density was determined at ambient temperature and the volume fraction of bubbles was used as criterion to judge the efficiency of the foaming process. The results reveal the existence of an optimal shear modulus of the order of 2 kPa that corresponds roughly to plasticizer molar masses of the order of 450 ± 50 g mol-1. Heavier plasticizers, especially polymeric ones are too difficult to deform. Lighter plasticizers such as diethyl phthalate (DEP) deform too easily and presumably facilitate bubble collapse
Proteinuria Is Associated with Quality of Life and Depression in Adults with Primary Glomerulopathy and Preserved Renal Function
BACKGROUND: There is no information about HRQoL, depression and associated factors in adult with nephrotic syndrome-associated glomerulopathy. METHODOLOGY/PRINCIPAL FINDINGS: Patients with primary glomerulopathy where compared with age and sex-matched hemodialysis patients and healthy subjects. Laboratory data, medical history, comorbid conditions were collected to evaluate factors associated with HRQoL (SF-36) and Depression (Hamilton Depression Rating Scale-HAMD). Glomerulopathy patients had low HRQoL in all eight SF-36 domains and two composite scores (physical and mental) in comparison with healthy subjects. HAMD score also was elevated and there was high depression prevalence. Overall, these data were comparable between glomerulopathy and hemodialysis patients. Using multiple regression analysis, factors associated with low HRQoL physical composite score were: last 24 h-urine protein excretion (-0.183, 95%CI -0.223 to -0.710 for each gram of proteinuria, p = 0.01) and cyclosporine use (-15.315, 95%CI -25.913 to -2.717, p = 0.03). Low HRQoL mental composite score was associated with last 24 h-urine protein excretion (-0.157, 95%CI -0.278 to -0.310 for each gram of proteinuria, p = 0.03) and HMAD score was independently associated with age (0.155, 95%CI 0.318 to 0.988 for each year, p = 0.04), female sex (4.788, 95%CI 1.005 to 8.620, 0 = 0.03), disease duration (0.074, 95%CI 0.021 to 0.128 for each month, p = 0.01) and last 24 h-urine protein excretion (0.050, 95%CI 0.018 to 0.085 for each gram of proteinuria, p = 0.02). CONCLUSIONS/SIGNIFICANCE: Nephrotic-syndrome associated glomerulopathy patients have low HRQoL and high prevalence of depression symptoms, comparable with those of hemodialysis patients. Last 24 h-protein excretion rate is independently associated with physical and mental HRQoL domains in addition to depression
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