390 research outputs found
Intelligent component selection
Component-based software engineering (CBSE) provides solutions to the development of complex and evolving systems. As these systems are created and maintained, the task of selecting components is repeated. The context-driven component evaluation (CdCE) project is developing strategies and techniques for automating a repeatable process for assessing software components. This paper describes our work using artificial intelligence (AI) techniques to classify components based on an ideal component specification. Using AI we are able to represent dependencies between attributes, overcoming some of the limitations of existing aggregation-based approaches to component selection
Conformational dependence of the intrinsic acidity of the aspartic acid residue sidechain in N-acetyl-L-aspartic acid-N '-methylamide
The sidechain conformational potential energy hypersurfaces (PEHS) for
the gamma(L), beta(L), alpha(L), and alpha(D) backbone conformations of
N-acetyl-L-aspartate-M-methylamide were generated. Of the 81 possible
conformers initially expected for the aspartate residue, only seven
were found after geometric optimizations at the B3LYP/6-31G(d) level of
theory. No stable conformers could be located in the delta(L),
epsilon(L), gamma(D), delta(D), and epsilon(D) backbone conformations.
The 'adiabatic' deprotonation energies for the endo and exo forms of
N-acetyl-L-aspartic acid-N'-methylamide were calculated by comparing
their optimized relative energies against those found for the seven
stable conformers of N-acetyl-L-aspartate-N'-methylamide. Sideehain
conformational PEHSs were also generated for the estimation of
'vertical' deprotonation energies for both endo and exo forms of
N-acetyl-L-aspartic acid-N'-methylamide. All backbone-sidechain
(N-H...-O-C) and backbone-backbone (N-(HO)-O-...=C) hydrogen bond
interactions were analyzed. A total of two backbone-backbone and four
backbone-sidechain interactions were found for
N-acetyl-L-aspartate-N'-methylamide. The deprotonated sidechain of
N-acetyl-L-aspartate-N'-methylamide may allow the aspartyl residue to
form strong hydrogen bond interactions (since it is negatively charged)
which may be significant in such processes as protein-ligand
recognition and ligand binding. As a primary example, the molecular
geometry of the aspartyl residue may be important in peptide folding,
such as that. in the RGD tripeptide. (C) 2002 Elsevier science B.V. All
rights reserved
Recent upgrade of the klystron modulator at SLAC
The SLAC National Accelerator Laboratory employs 244 klystron modulators on its two-mile-long linear accelerator that has been operational since the early days of the SLAC establishment in the sixties. Each of these original modulators was designed to provide 250 kV, 262 A and 3.5 {mu}S at up to 360 pps using an inductance-capacitance resonant charging system, a modified type-E pulse-forming network (PFN), and a pulse transformer. The modulator internal control comprised of large step-start resistor-contactors, vacuum-tube amplifiers, and 120 Vac relays for logical signals. A major, power-component-only upgrade, which began in 1983 to accommodate the required beam energy of the SLAC Linear Collider (SLC) project, raised the modulator peak output capacity to 360 kV, 420 A and 5.0 {mu}S at a reduced pulse repetition rate of 120 pps. In an effort to improve safety, performance, reliability and maintainability of the modulator, this recent upgrade focuses on the remaining three-phase AC power input and modulator controls. The upgrade includes the utilization of primary SCR phase control rectifiers, integrated fault protection and voltage regulation circuitries, and programmable logic controllers (PLC) -- with an emphasis on component physical layouts for safety and maintainability concerns. In this paper, we will describe the design and implementation of each upgraded component in the modulator control system. We will also report the testing and present status of the modified modulators
Restoration of supersymmetric Slavnov-Taylor and Ward identities in presence of soft and spontaneous symmetry breaking
Supersymmetric Slavnov-Taylor and Ward identities are investigated in
presence of soft and spontaneous symmetry breaking. We consider an abelian
model where soft supersymmetry breaking yields a mass splitting between
electron and selectron and triggers spontaneous symmetry breaking, and we
derive corresponding identities that relate the electron and selectron masses
with the Yukawa coupling. We demonstrate that the identities are valid in
dimensional reduction and invalid in dimensional regularization and compute the
necessary symmetry-restoring counterterms.Comment: 35 pages, LaTeX, 9 postscript figure
A pleurocidin analogue with greater conformational flexibility, enhanced antimicrobial potency and in vivo therapeutic efficacy.
Antimicrobial peptides (AMPs) are a potential alternative to classical antibiotics that are yet to achieve a therapeutic breakthrough for treatment of systemic infections. The antibacterial potency of pleurocidin, an AMP from Winter Flounder, is linked to its ability to cross bacterial plasma membranes and seek intracellular targets while also causing membrane damage. Here we describe modification strategies that generate pleurocidin analogues with substantially improved, broad spectrum, antibacterial properties, which are effective in murine models of bacterial lung infection. Increasing peptide-lipid intermolecular hydrogen bonding capabilities enhances conformational flexibility, associated with membrane translocation, but also membrane damage and potency, most notably against Gram-positive bacteria. This negates their ability to metabolically adapt to the AMP threat. An analogue comprising D-amino acids was well tolerated at an intravenous dose of 15âmg/kg and similarly effective as vancomycin in reducing EMRSA-15 lung CFU. This highlights the therapeutic potential of systemically delivered, bactericidal AMPs
The BRS invariance of noncommutative U(N) Yang-Mills theory at the one-loop level
We show that U(N) Yang-Mills theory on noncommutative Minkowski space-time
can be renormalized, in a BRS invariant way, at the one-loop level, by
multiplicative dimensional renormalization of its coupling constant, its gauge
parameter and its fields. It is shown that the Slavnov-Taylor equation, the
gauge-fixing equation and the ghost equation hold, up to order , for the
MS renormalized noncommutative U(N) Yang-Mills theory. We give the value of the
pole part of every 1PI diagram which is UV divergent.Comment: Corrected typos. Version to appear in Nuclear Physics
Difference in distribution functions:A new diffusion weighted imaging metric for estimating white matter integrity
Diffusion weighted imaging (DWI) is a widely recognized neuroimaging technique to evaluate the microstructure of brain white matter. The objective of this study is to establish an improved automated DWI marker for estimating white matter integrity and investigating ageing related cognitive decline. The concept of Wasserstein distance was introduced to help establish a new measure: difference in distribution functions (DDF), which captures the difference of reshaping one's mean diffusivity (MD) distribution to a reference MD distribution. This new DWI measure was developed using a population-based cohort (n=19,369) from the UK Biobank. Validation was conducted using the data drawn from two independent cohorts: the Sydney Memory and Ageing Study, a community-dwelling sample (n=402), and the Renji Cerebral Small Vessel Disease Cohort Study (RCCS), which consisted of cerebral small vessel disease (CSVD) patients (n=171) and cognitively normal controls (NC) (n=43). DDF was associated with age across all three samples and better explained the variance of changes than other established DWI measures, such as fractional anisotropy, mean diffusivity and peak width of skeletonized mean diffusivity (PSMD). Significant correlations between DDF and cognition were found in the UK Biobank cohort and the MAS cohort. Binary logistic analysis and receiver operator characteristic curve analysis of RCCS demonstrated that DDF had higher sensitivity in distinguishing CSVD patients from NC than the other DWI measures. To demonstrate the flexibility of DDF, we calculated regional DDF which also showed significant correlation with age and cognition. DDF can be used as a marker for monitoring the white matter microstructural changes and ageing related cognitive decline in the elderly
Evaluation of FDG-PET/CT Use in Children with Suspected Infection or Inflammation
[
18F]-FDG-PET/CT ([18F]-fluoro-deoxyglucose (FDG) positron emission
tomography/computed tomography (PET/CT)) is increasingly used as a diagnostic tool in
suspected infectious or inflammatory conditions. Studies on the value of FDG-PET/CT in children are
scarce. This study assesses the role of FDG-PET/CT in suspected infection or inflammation in children.
In this multicenter cohort study, 64 scans in 59 children with suspected infection or inflammation
were selected from 452 pediatric FDG-PET/CT scans, performed in five hospitals between January
2016 and August 2017. Main outcomes were diagnostic information provided by FDG-PET/CT for
diagnostic scans and impact on clinical management for follow-up scans. Of these 64 scans, 50
were performed for primary diagnosis and 14 to monitor disease activity. Of the positive diagnostic
scans, 23/27 (85%) contributed to establishing a diagnosis. Of the negative diagnostic scans, 8/21
(38%) contributed to the final diagnosis by narrowing the differential or by providing information
on the disease manifestation. In all follow-up scans, FDG-PET/CT results guided managemen
Search for single top quarks in the tau+jets channel using 4.8 fb of collision data
We present the first direct search for single top quark production using tau
leptons. The search is based on 4.8 fb of integrated luminosity
collected in collisions at =1.96 TeV with the D0 detector
at the Fermilab Tevatron Collider. We select events with a final state
including an isolated tau lepton, missing transverse energy, two or three jets,
one or two of them tagged. We use a multivariate technique to discriminate
signal from background. The number of events observed in data in this final
state is consistent with the signal plus background expectation. We set in the
tau+jets channel an upper limit on the single top quark cross section of
\TauLimObs pb at the 95% C.L. This measurement allows a gain of 4% in expected
sensitivity for the observation of single top production when combining it with
electron+jets and muon+jets channels already published by the D0 collaboration
with 2.3 fb of data. We measure a combined cross section of
\SuperCombineXSall pb, which is the most precise measurement to date.Comment: 12 pages, 5 figure
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