283 research outputs found
Lattice quark masses: a non-perturbative measurement
We discuss the renormalization of different definitions of quark masses in
the Wilson and the tree-level improved SW-Clover fermionic action. For the
improved case we give the correct relationship between the quark mass and the
hopping parameter. Using perturbative and non-perturbative renormalization
constants, we extract quark masses in the \MSbar scheme from Lattice QCD in
the quenched approximation at , and for both
actions. We find: \bar{m}^{\MSbar}(2 GeV)=5.7 \pm 0.1 \pm 0.8 MeV,
m_s^{\MSbar}(2GeV)= 130 \pm 2 \pm 18 MeV and m_c^{\MSbar}(2 GeV) = 1662\pm
30\pm 230 MeV.Comment: 21 pages, 4 figures, typos corrected, no result change
Quark masses and the chiral condensate with a non-perturbative renormalization procedure
We determine the quark masses and the chiral condensate in the MSbar scheme
at NNLO from Lattice QCD in the quenched approximation at beta=6.0, beta=6.2
and beta=6.4 using both the Wilson and the tree-level improved SW-Clover
fermion action. We extract these quantities using the Vector and the Axial Ward
Identities and non-perturbative values of the renormalization constants. We
compare the results obtained with the two methods and we study the O(a)
dependence of the quark masses for both actions.Comment: LATTICE98(spectrum), 3 pages, 1 figure, Edinburgh 98/1
Causes of congenital corneal opacities and their management in a tertiary care center.
PURPOSE: To evaluate causes and management of congenital corneal opacities (CCO) diagnosed in a tertiary care eye center and to compare the data with a previous study at the same institution.
METHODS: Computerized medical records in all patients with congenital corneal opacities diagnosed in the Cornea Service at Wills Eye Hospital (Philadelphia, PA) between January 1, 2007, and December 31, 2015, were retrospectively reviewed. Children aged 12 years and younger at the first visit were included in the study. Patients\u27 demographics, ocular diagnosis, laterality, associated ocular abnormalities, other ocular surgery performed prior or subsequent to the first visit, and their treatment were extracted from the medical records.
RESULTS: A total of 77 eyes in 56 patients were examined. The mean age at presentation was 32.8 ± 44.2 months, with the mean follow-up period of 26.7 ± 30.1 months. The most frequent diagnosis was Peters anomaly (53.2%), followed by limbal dermoid (13.0%), aniridia with glaucoma and microphthalmos (6.5%), sclerocornea and congenital glaucoma (5.2%), idiopathic (3.9%), Axenfeld-Rieger anomaly and Hurler syndrome (2.6%), and microcornea (1.3%). Primary keratoplasty was performed in 26 eyes, with the outcome rate in the clear cornea of 76.0% during the follow-up.
CONCLUSION: Peters anomaly is the most common cause of congenital corneal opacities encountered at our institution. Penetrating keratoplasty is the most frequent choice of corneal surgery to treat congenital corneal opacities. Additional interventions during penetrating keratoplasty were moderately positively correlated with graft failure. This study also shows the rates of some etiologies of that changed over the recent decades in our tertiary care Cornea Service. Although Peters anomaly remains the most common presenting reason for congenital corneal opacities, its rate appears to be increasing over the recent decade. Congenital corneal opacities due to birth trauma, which is one of the preventable causes, were observed in a previous study in our clinic; however, no new cases were noted in this study
Decay Constants of Heavy-Light Mesons
The decay constants of the heavy-light pseudoscalar mesons are studied in a
high statistics run using the Wilson action at and , and
the clover action at . The systematics of discretisation
errors are discussed. Our best estimates of the decay constants are: =
218(9) MeV, = 1.11(1) and we obtain preliminary values for .Comment: at the Dallas Lattice Conference, October 1993. 3 pages in a single
postscript file, uuencoded form. Rome Preprint 93/98
Anterior Chamber Characteristics, Endothelial Parameters, and Corneal Densitometry After Descemet Stripping Automated Endothelial Keratoplasty in Patients With Fuchs Dystrophy
Purpose: To compare anterior segment parameters in patients with Fuchs endothelial dystrophy (FED) who underwent Descemet stripping automated endothelial keratoplasty (DSAEK) in one eye and no corneal surgery in the fellow eye.
Methods: This prospective study was conducted on 28 eyes of 14 patients with FED who underwent DSAEK in one eye at least one year prior (DSAEK group) and no corneal surgery in the fellow eye (control group). Each eye was analyzed with the anterior segment optical coherence tomography, specular microscopy, and Scheimpflug imaging systems. Data were compared between the two groups.
Results: The mean age of the patients was 76.9 ± 7.0 years. There were no statistically significant differences in the mean central corneal thickness (CCT), central anterior chamber depth, anterior chamber angle parameters, cylinder and keratometry values between two groups (all P-values > 0.05). The paracentral corneal thickness, corneal volume, endothelial cell density, and hexagonal cell ratio measurements were statistically significantly higher in the DSAEK group than the control (all P-values < 0.05), and anterior chamber volume in the DSAEK group was significantly less than the control (P = 0.046). While posterior and total corneal densitometry values in the DSAEK group were statistically significantly lower than the control (P < 0.001 and P = 0.011, respectively), there were no statistically significant differences in the anterior or middle corneal densities (P = 0.108 and P = 0.134, respectively).
Conclusion: We found that total corneal densitometry value decreased in DSAEK group. Although DSAEK surgery did not affect the anterior chamber angle parameters, it reduced the anterior chamber volume and increased the corneal volume and paracentral corneal thickness due to the addition of the DSAEK graft
RESULTS FOR THE B-MESON DECAY CONSTANT FROM THE APE COLLABORATION
The decay constant for the B-meson in the static limit is calculated using
the Wilson and clover actions at various lattice spacings. We show that both
the contamination of our results by excited states and the effects finite
lattice spacing are at most the order of the statistical uncertainties. A
comparison is made of our results and those obtained in other studies. Values
for and are also given.Comment: Contribution to Lattice'94, 3 pages PostScript, uuencoded compresse
Quenched -parameter with the Wilson and Clover actions at
We present results for the Kaon parameter from a sample of
configurations using the Wilson action and configurations using the
Clover action, on a lattice at . A slight
improvement of the chiral behaviour of is observed due to the Clover
action. We have also compared the results for obtained from two different
procedures for the boosting of the coupling constant . We observe a strong
dependence of on the prescription adopted for in the Wilson case,
contrary to the results of the Clover case which are almost unaffected by the
choice of . Combining some recently obtained non perturbative estimates for
the renormalisation constants with our Clover matrix element, we observe a
significant improvement in the chiral behaviour of .Comment: 3 pages, Latex, Postscript file with figures available at
ftp://hpteo.roma1.infn.it/pub/preprints/lat94/donini ; to appear in Lattice
'94, Nucl. Phys. (Proc.Suppl.
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