Generalized Relativistic Meson Wave Function

We study the most general, relativistic, constituent $q{\overline q}$ meson wave function within a new covariant framework. We find that by including a tensor wave function component, a pure valence quark model is now capable of reproducing not only all static pion data ($f_\pi$, $\langle r_\pi^2 \rangle$) but also the distribution amplitude, form factor $(F_\pi(Q^2))$, and structure functions. Further, our generalized spin wave function provides a much better detailed description of meson properties than models using a simple relativistic extension of the $S=L=0$ nonrelativistic wave function.Comment: 17 pages, REXTeX 3.0 file, (uuencoded postscript files of 8 figures appended

Application of the density dependent hadron field theory to neutron star matter

The density dependent hadron field (DDRH) theory, previously applied to isospin nuclei and hypernuclei is used to describe $\beta$-stable matter and neutron stars under consideration of the complete baryon octet. The meson-hyperon vertices are derived from Dirac-Brueckner calculations of nuclear matter and extended to hyperons. We examine properties of density dependent interactions derived from the Bonn A and from the Groningen NN potential as well as phenomenological interactions. The consistent treatment of the density dependence introduces rearrangement terms in the expression for the baryon chemical potential. This leads to a more complex condition for the $\beta$-equilibrium compared to standard relativistic mean field (RMF) approaches. We find a strong dependence of the equation of state and the particle distribution on the choice of the vertex density dependence. Results for neutron star masses and radii are presented. We find a good agreement with other models for the maximum mass. Radii are smaller compared to RMF models and indicate a closer agreement with results of non-relativistic Brueckner calculations.Comment: 28 pages, 11 figure

Nuclear Sizes and the Isotope Shift

Darwin-Foldy nuclear-size corrections in electronic atoms and nuclear radii are discussed from the nuclear-physics perspective. Interpretation of precise isotope-shift measurements is formalism dependent, and care must be exercised in interpreting these results and those obtained from relativistic electron scattering from nuclei. We strongly advocate that the entire nuclear-charge operator be used in calculating nuclear-size corrections in atoms, rather than relegating portions of it to the non-radiative recoil corrections. A preliminary examination of the intrinsic deuteron radius obtained from isotope-shift measurements suggests the presence of small meson-exchange currents (exotic binding contributions of relativistic order) in the nuclear charge operator, which contribute approximately 1/2%.Comment: 17 pages, latex, 1 figure -- Submitted to Phys. Rev. A -- epsfig.sty require

Induction of chronic kidney failure in a long-term peritoneal exposure model in the rat: effects on functional and structural peritoneal alterations

A long-term peritoneal exposure model has been developed in Wistar rats. Chronic daily exposure to 3.86% glucose based, lactate buffered, conventional dialysis solutions is possible for up to 20 weeks and induces morphological abnormalities similar to those in long-term peritoneal dialysis (PD) patients. The possible effects of kidney failure in this model are unknown. The aim was to analyze the effects of chronic kidney failure on peritoneal function and morphology, alone and in combination with PD exposure, in a well-established, long term, peritoneal exposure model in the rat. ♢ 40 male Wistar rats were randomly assigned into four experimental groups: no nephrectomy, no peritoneal exposure (sham; n = 8); nephrectomy, no peritoneal exposure (Nx; n = 12); no nephrectomy, with peritoneal exposure (PD; n = 8); and nephrectomy, with peritoneal exposure (NxPD; n = 12). The nephrectomy consisted of a one-step 70% nephrectomy. The peritoneal exposure groups were infused once daily for 16 weeks with a 3.86% glucose-based dialysis solution. Development of chronic kidney disease was monitored during the experiment. Peritoneal function and morphological assessment of the peritoneal membrane were performed at the end of the experiment. ♢ During follow-up the nephrectomized groups developed uremia with remarkable renal tubular dilatation and glomerular sclerosis in the renal morphology. Functionally, uremia (Nx) and PD exposure (PD) alone showed faster small solute transport and a decreased ultrafiltration capacity, which were most pronounced in the combination group (NxPD). The presence of uremia resulted in histological alterations but the most severe fibrous depositions and highest vessel counts were present in the PD exposure groups (PD and NxPD). Significant relationships were found between the number of vessels and functional parameters of the peritoneal vascular surface area. ♢ It is possible to induce chronic kidney failure in our existing long-term peritoneal infusion model in the rat. The degree of impairment of kidney function after 16 weeks is comparable to chronic kidney disease stage IV. Uremia per se induces both functional and morphological alterations of the peritoneal membrane. An additive effect of these alterations is present with the addition of chronic kidney failure to the model. The latter makes the present long-term model important in better understanding the pathophysiology of the peritoneal membrane in P

Free water transport in children on peritoneal dialysis is higher with more biocompatible dialysis solutions, higher with older age and declines with time.

Item does not contain fulltextBACKGROUND: Water transport in peritoneal dialysis occurs through small pores and aquaporins. Free water transport (FWT) occurs through aquaporins only and gives a reflection of peritoneal aquaporin function. In this study, FWT in children was calculated for the first time in different settings. METHODS: A prospective cohort study was performed; 87 peritoneal equilibrium tests (PETs) were analysed in 65 patients. Three subgroups were analysed: patients with their first PET; patients in their second year on dialysis; patients in their third year on dialysis or thereafter. Patients using 3.86% glucose solution with low pH/high glucose degradation products (GDP) were compared to patients using 3.86% glucose solution with neutral pH/low GDP. Sixteen patients using neutral pH/low GDP solution were followed longitudinally. FWT was calculated using the dialysate/plasma ratio of sodium. RESULTS: The proportional contribution of FWT was significantly higher in patients using dialysis solution with neutral pH/low GDP solution compared to patients using solutions with low pH/high GDP (50 versus 40%). Transcapillary ultrafiltration (TCUF) showed the same trend but was not statistically significant. Total FWT was higher as well. Higher FWT was observed with older age. In the longitudinal group, TCUF and water transport through small pores declined, while FWT remained stable in the first 1.5 years. The contribution of FWT increased in this period (48-61%), then slowly declined again to baseline level during the third year. CONCLUSIONS: Total FWT and relative contribution of FWT were significantly higher with neutral pH/low GDP solution. This can reflect a better preservation of aquaporins. The decline in the contribution of FWT in long-term dialysis could hypothetically implicate aquaporin dysfunction or different trafficking of aquaporins.1 maart 201

Application of renormalized coupled-cluster methods to potential function of water

Abstract The goal of this paper is to examine the performance of the conventional and renormalized single-reference coupled-cluster (CC) methods in calculations of the potential energy surface of the water molecule. A comparison with the results of the internally contracted multi-reference configuration interaction calculations including the quasi-degenerate Davidson correction (MRCI(Q)) and the spectroscopically accurate potential energy surface of water resulting from the use of the energy switching (ES) approach indicates that the relatively inexpensive completely renormalized (CR) CC methods with singles (S), doubles (D), and a non-iterative treatment of triples (T) or triples and quadruples (TQ), such as CR-CCSD(T), CR-CCSD(TQ), and the recently developed rigorously size extensive extension of CR-CCSD(T), termed CR-CC(2,3), provide substantial improvements in the results of conventional CCSD(T) and CCSD(TQ) calculations at larger internuclear separations. It is shown that the CR-CC(2,3) results corrected for the effect of quadruply excited clusters through the CR-CC(2,3)+Q approach can compete with the highly accurate MRCI(Q) data. The excellent agreement between the CR-CC(2,3)+Q and MRCI(Q) results suggests ways of improving the global potential energy surface of water resulting from the use of the ES approach in the regions of intermediate bond stretches and intermediate energies connecting the region of the global minimum with the asymptotic regions

Spin Force Dependence Of Nucleon Structure Functions

Deep inelastic structure functions for the nucleon are obtained in a constituent quark model on the light cone. Parton model formulas are derived. The negative slope of $F_{2}^{n}/F_{2}^{p} requires attraction between scalar quark pairs. Color magnetism leads to a positive slope. 6 Figures are available from author. Typeset in REVTEX.Comment: 24 pages, Institute for Nuclear and Particle Physics, University of Virginia INPP-93-5 Phys. Rev.