Resolving Exceptional Configurations

In lattice QCD with Wilson fermions, exceptional configurations arise in the quenched approximation at small quark mass. The origin of these large previously uncontrolled lattice artifacts is identified. A simple well-defined procedure (MQA) is presented which removes the artifacts while preserving the correct continuum limit.Comment: Talk presented by E. Eichten at Lattice 97, Edinburgh(UK), July97. 6 pages, LaTeX, 1 table, 5 figure

30S Beam Development and X-ray Bursts

Over the past three years, we have worked on developing a well-characterized 30S radioactive beam to be used in a future experiment aiming to directly measure the 30S(alpha,p) stellar reaction rate within the Gamow window of Type I X-ray bursts. The importance of the 30S(alpha,p) reaction to X-ray bursts is discussed. Given the astrophysical motivation, the successful results of and challenges involved in the production of a low-energy 30S beam are detailed. Finally, an overview of our future plans regarding this on-going project are presented.Comment: 7 pages, 2 figures, 5th European Summer School on Experimental Nuclear Astrophysics, Santa Tecla, Sicily, September 200

Quenched QCD with domain-wall fermions on coarse lattices

We investigate the existence of chiral zero modes at a^{-1} \simeq 1 GeV in quenched domain-wall QCD. Simulations are carried out for the plaquette and an RG-improved gauge actions on a 12^3x24xN_s lattice with N_s=10-50. We find that the pion mass in the chiral limit remains non-vanishing as N_s\to\infty for both gauge actions. Possible origins of this non-vanishing pion mass are discussed.Comment: LATTICE99(chiral fermions), 3 pages, 6 ps figures, LaTex, espcrc2.st

Quenched Chiral Artifacts for Wilson-Dirac Fermions

We examine artifacts associated with the chiral symmetry breaking induced through the use of Wilson-Dirac fermions in lattice Monte Carlo computations. For light quark masses, the conventional quenched theory can not be defined using direct Monte Carlo methods due to the existence of nonintegrable poles in physical quantities. These poles are associated with the real eigenvalue spectrum of the Wilson-Dirac operator. We show how this singularity structure can be observed in the analysis of both QED in two dimensions and QCD in four dimensions.Comment: 32 pages (Latex) including 13 figures (EPS

On the low fermionic eigenmode dominance in QCD on the lattice

We demonstrate the utility of a spectral approximation to fermion loop operators using low-lying eigenmodes of the hermitian Dirac-Wilson matrix, Q. The investigation is based on a total of 400 full QCD vacuum configurations, with two degenerate flavors of dynamical Wilson fermions at beta =5.6, at two different sea quark masses. The spectral approach is highly competitive for accessing both topological charge and disconnected diagrams, on large lattices and small quark masses. We propose suitable partial summation techniques that provide sufficient saturation for estimating Tr Q^{-1}, which is related to the topological charge. In the effective mass plot of the eta' meson we achieved a consistent early plateau formation, by ground state projecting the connected piece of its propagator.Comment: 15 pages, 25 figures, citations adde

Effect of Mono and Di-rhamnolipids on Biofilms Pre-formed by Bacillus subtilis BBK006.

Different microbial inhibition strategies based on the planktonic bacterial physiology have been known to have limited efficacy on the growth of biofilms communities. This problem can be exacerbated by the emergence of increasingly resistant clinical strains. Biosurfactants have merited renewed interest in both clinical and hygienic sectors due to their potential to disperse microbial biofilms. In this work, we explore the aspects of Bacillus subtilis BBK006 biofilms and examine the contribution of biologically derived surface-active agents (rhamnolipids) to the disruption or inhibition of microbial biofilms produced by Bacillus subtilis BBK006. The ability of mono-rhamnolipids (Rha-C10-C10) produced by Pseudomonas aeruginosa ATCC 9027 and the di-rhamnolipids (Rha-Rha-C14-C14) produced by Burkholderia thailandensis E264, and phosphate-buffered saline to disrupt biofilm of Bacillus subtilis BBK006 was evaluated. The biofilm produced by Bacillus subtilis BBK006 was more sensitive to the di-rhamnolipids (0.4 g/L) produced by Burkholderia thailandensis than the mono-rhamnolipids (0.4 g/L) produced by Pseudomonas aeruginosa ATCC 9027. Rhamnolipids are biologically produced compounds safe for human use. This makes them ideal candidates for use in new generations of bacterial dispersal agents and useful for use as adjuvants for existing microbial suppression or eradication strategies

An efficient trio-based mini-haplotyping method for genetic diagnosis of phenylketonuria

Objective: The phenylalanine hydroxylase (PAH) locus has high linkage disequilibrium. Haplotypes related to this locus may thus be considered sufficiently informative for genetic diagnosis and carrier screening using multi-allelic markers. In this study, we present an efficient method for haplotype analysis of PAH locus using multiplexing dyes. In addition, we explain how to resolve the dye shift challenge in multiplex short tandem repeat (STR) genotyping. Materials and Methods: One hundred family trios were included in this descriptive study. The forward primer of a tetra-nucleotide STR and the reverse primer of a variable number tandem repeat (VNTR) were labeled with three different non-overlapping dyes 5-carboxyfluorescein (FAM), 6-carboxy-N,N,N�,N�-tetramethylrhodamine (HEX) and 6-carboxy-N,N,N�,N�-tetramethylrhodamine (TAMRA). The polymerase chain reaction (PCR) products from each family trio were multiplexed for capillary electrophoresis and results were analyzed using Peak Scanner software. Results: Multiplexing trio products decreased the cost significantly. The TAMRA labeled products had a significant predictable shift (migrated at a slower electrophoretic rate) relative to the HEX and FAM labeled products. Through our methodology we achieve, the less inter-dye shift than intra-dye shift variance. Correcting the dye shift in the labeled products, according to the reference allele size, significantly decreased the inter-dye variability (P<0.001). Conclusion: Multiplexing trio products helps to detect and resolve the dye shift accurately in each family, which otherwise would result in diagnostic error. The dye system of FAM, HEX and TAMRA is more feasible and cheaper than other dye systems

Discriminative Features in Three Autosomal Recessive Cutis Laxa Syndromes: Cutis Laxa IIA, Cutis Laxa IIB, and Geroderma Osteoplastica.

Contains fulltext : 175115.pdf (publisher's version ) (Open Access)Cutis laxa is a heterogeneous condition characterized by redundant, sagging, inelastic, and wrinkled skin. The inherited forms of this disease are rare and can have autosomal dominant, autosomal recessive, or X-linked inheritance. Three of the autosomal recessive cutis laxa syndromes, namely cutis laxa IIA (ARCL2A), cutis laxa IIB (ARCL2B), and geroderma osteodysplastica (GO), have very similar clinical features, complicating accurate diagnosis. Individuals with these conditions often present with cutis laxa, progeroid features, and hyperextensible joints. These conditions also share additional features, such as short stature, hypotonia, and congenital hip dislocation, but the severity and frequency of these findings are variable in each of these cutis laxa syndromes. The characteristic features for ARCL2A are abnormal isoelectric focusing and facial features, including downslanting palpebral fissures and a long philtrum. Rather, the clinical phenotype of ARCL2B includes severe wrinkling of the dorsum of the hands and feet, wormian bones, athetoid movements, lipodystrophy, cataract and corneal clouding, a thin triangular face, and a pinched nose. Normal cognition and osteopenia leading to pathological fractures, maxillary hypoplasia, and oblique furrowing from the outer canthus to the lateral border of the supraorbital ridge are discriminative features for GO. Here we present 10 Iranian patients who were initially diagnosed clinically using the respective features of each cutis laxa syndrome. Each patient's clinical diagnosis was then confirmed with molecular investigation of the responsible gene. Review of the clinical features from the cases reported from the literature also supports our conclusions