237 research outputs found
Wilson versus Clover fermions: A case for improvement
We present evidence for improvement with tadpole improved clover fermions
based on an analysis of the chiral behavior of and the quark condensate.
Also presented are a comparison of the mass splittings in the baryon octet and
decuplet, a calculation of using standard 2-point correlation functions,
and the problem of zero modes of the Dirac operator.Comment: 3 pages. Makefile and sources included. Talk presented at LATTICE98
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pion scattering amplitude with Wilson fermions
We present an exploratory calculation of the scattering
amplitude at threshold using Wilson fermions in the quenched approximation,
including all the required contractions. We find good agreement with the
predictions of chiral perturbation theory even for pions of mass 560-700 MeV.
Within the 10\% errors, we do not see the onset of the bad chiral behavior
expected for Wilson fermions. We also derive rigorous inequalities that apply
to 2-particle correlators and as a consequence show that the interaction in the
antisymmetric state of two pions has to be attractive.Comment: This PS file includes 4 tables and figures 1-8 on 25 pages. Los
Alamos Preprint Number LAUR-92-364
Light meson decay constants beyond the quenched approximation
We calculate the effects of including dynamical fermion loops in the lattice
QCD estimates of meson decay constants, by extrapolating the results from
negative flavour numbers after a suitable matching of the pion and rho mass.
For moderately light quarks, the values of the decay constants not corrected
for the renormalization constants increase with respect to their quenched
values.Comment: 9 pages, uuencoded PS file, 2 figures include
The running coupling of 8 flavors and 3 colors
We compute the renormalized running coupling of SU(3) gauge theory coupled to
N_f = 8 flavors of massless fundamental Dirac fermions. The recently proposed
finite volume gradient flow scheme is used. The calculations are performed at
several lattice spacings allowing for a controlled continuum extrapolation. The
results for the discrete beta-function show that it is monotonic without any
sign of a fixed point in the range of couplings we cover. As a cross check the
continuum results are compared with the well-known perturbative continuum
beta-function for small values of the renormalized coupling and perfect
agreement is found.Comment: 15 pages, 17 figures, published versio
From Perturbation Theory to Confinement: How the String Tension is built up
We study the spatial volume dependence of electric flux energies for SU(2)
Yang-Mills fields on the torus with twisted boundary conditions. The results
approach smoothly the rotational invariant Confinement regime. The would-be
string tension is very close to the infinite volume result already for volumes
of . We speculate on the consequences of our result for
the Confinement mechanism.Comment: 6p, ps-file (uuencoded). Contribution to Lattice'93 Conference
(Dallas, 1993). Preprint INLO-PUB 18/93, FTUAM-93/4
Sortenvergleich von Lolium multiflorum unter Anbaubedingungen des ökologischen- und integrierten Landbaus
Forty-five varieties of Lolium multiflorum L. were examined in pure stands at three experimental sites over a three years period. One of these sites was on an organic farm, which was managed according to the “BIO SUISSE” guidelines. Due to the marked differences in management (weed control, N-fertilisation), the yield of the sown grass was clearly lower at the organic site. Nevertheless, there was an outstanding correspondence in terms of the yield of the different varieties among the experimental sites. The best varieties under integrated farming were also the best varieties in the organic system
Hyperuricemia during Pregnancy Leads to a Preeclampsia-Like Phenotype in Mice.
Hyperuricemia is a common feature in pregnancies compromised by pre-eclampsia, a pregnancy disease characterized by hypertension and proteinuria. The role of uric acid in the pathogenesis of pre-eclampsia remains largely unclear. The aim of this study was to investigate the effect of elevated uric acid serum levels during pregnancy on maternal blood pressure and neonatal outcome using two different murine knockout models. Non-pregnant liver-specific GLUT9 knockout (LG9KO) mice showed elevated uric acid serum concentrations but no hypertensive blood pressure levels. During pregnancy, however, blood pressure levels of these animals increased in the second and third trimester, and circadian blood pressure dipping was severely altered when compared to non-pregnant LG9KO mice. The impact of hyperuricemia on fetal development was investigated using a systemic GLUT9 knockout (G9KO) mouse model. Fetal hyperuricemia caused distinctive renal tissue injuries and, subsequently an impaired neonatal growth pattern. These findings provide strong evidence that hyperuricemia plays a major role in the pathogenesis of hypertensive pregnancy disorders such as pre-eclampsia. These novel insights may enable the development of preventive and therapeutic strategies for hyperuricemia-related diseases
Positive Mischungseffekte auf Ertrag und Stickstoffversorgung in Klee-Gras-Mischungen
High plant species richness has been shown to positively influence grassland biomass
production. In mixtures containing two forage grass and two forage legume species
we quantified the diversity-productivity effect and the nitrogen economy of the swards
across a broad range of species proportions. Positive diversity-productivity effects
resulted in higher yield (up to +35%) of the four-species grass-clover-mixtures than the
highest yielding monoculture (transgressive overyielding). The diversity-productivity
effect depended on the species proportion in the mixture and was maximal in well
balanced mixtures with a clover proportion of 40 – 60%. Transgressive overyielding
was significant over a fairly wide range of clover proportions. Well balanced grassclover-
mixtures allowed obtaining up to 320 kg N ha-1 yr-1 deriving from symbiotic N2
fixation and allowed an optimal transformation of fixed N into dry matter yield. These
mixtures allowed benefiting from maximal fixation activity of the legumes without
reducing the uptake of N from soil and fertiliser by the grasses in the sward
Recent Developments in Lattice QCD
I review the current status of lattice QCD results. I concentrate on new
analytical developments and on numerical results relevant to phenomenology.Comment: 35 pages, 4 figures (Figures are excerpted from others' work and are
not included) Uses harvmac.te
Glucose Transporter 9 (GLUT9) Plays an Important Role in the Placental Uric Acid Transport System.
BACKGROUND
Hyperuricemia is a common laboratory finding in pregnant women compromised by preeclampsia. A growing body of evidence suggests that uric acid is involved in the pathogenesis of preeclampsia. Glucose transporter 9 (GLUT9) is a high-capacity uric acid transporter. The aim of this study was to investigate the placental uric acid transport system, and to identify the (sub-) cellular localization of GLUT9.
METHODS
Specific antibodies against GLUT9a and GLUT9b isoforms were raised, and human villous (placental) tissue was immunohistochemically stained. A systemic GLUT9 knockout (G9KO) mouse model was used to assess the placental uric acid transport capacity by measurements of uric acid serum levels in the fetal and maternal circulation.
RESULTS
GLUT9a and GLUT9b co-localized with the villous (apical) membrane, but not with the basal membrane, of the syncytiotrophoblast. Fetal and maternal uric acid serum levels were closely correlated. G9KO fetuses showed substantially higher uric acid serum concentrations than their mothers.
CONCLUSIONS
These findings demonstrate that the placenta efficiently maintains uric acid homeostasis, and that GLUT9 plays a key role in the placental uric acid transport system, at least in this murine model. Further studies investigating the role of the placental uric acid transport system in preeclampsia are eagerly needed
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