611 research outputs found
Instanton Effects in Hadron Spectroscopy Revisited
We use an optimised clover action to study spectroscopy on an instanton
ensemble reconstructed from smoothed Monte Carlo configurations. Due to the
better chirality of the clover action, the artificial configurations show a
marked difference from the free field behaviour obtained with the Wilson
action. They however still fail to reproduce the physics observed on the
smoothed configurations. The presence of freely propagating quark modes is
found to be responsible for this.Comment: 3 pages, LaTeX with 4 eps figures, LATTICE99(topology
Comments on the Instanton Size Distribution
By studying the non-linear effects of overlapping instanton pairs we address
difficulties in the identification of instanton distributions when the average
instanton size is comparable to the average distance. For the exact charge two
solution, we study how its parametrisation relates to a description in terms of
individual instantons. There exist two dual sets of parameters describing the
same charge two instanton solution. This duality implies the existence of a
minimal separation between two instantons. Conventionally used lattice
instanton finder algorithms based on the assumption of diluteness tend to
underestimate instanton sizes. Finally we numerically confirm this for
realistic parameters of the instanton liquid. The effect is enhanced by
parallel orientation in group space.Comment: LaTeX, 15 pages, 3 figure
webchem: An R Package to Retrieve Chemical Information from the Web
A wide range of chemical information is freely available online, including identifiers, experimental and predicted chemical properties. However, these data are scattered over various data sources and not easily accessible to researchers. Manual searching and downloading of such data is time-consuming and error-prone. We developed the open-source R package webchem that allows users to automatically query chemical data from currently 14 web sources. These cover a broad spectrum of information. The data are automatically imported into an R object and can directly be used in subsequent analyses. webchem enables easy, structured and reproducible data retrieval and usage from publicly available web sources. In addition, it facilitates data cleaning, identification and reporting of substances. Consequently, it reduces the time researchers need to spend on chemical data compilation
Investigating and Optimizing the Chiral Properties of Lattice Fermion Actions
We study exceptional modes of both the Wilson and the clover action in order
to understand why quenched clover spectroscopy suffers so severely from
exceptional configurations. We show that, in contrast to the case of the Wilson
action, a large clover coefficient can make the exceptional modes extremely
localized and thus very sensitive to short distance fluctuations. We describe a
way to optimize the chiral behavior of Wilson-type lattice fermion actions by
studying their low energy real eigenmodes. We find a candidate action, the
clover action with fat links with a tuned clover term. We present a calculation
of spectroscopy and matrix elements at Wilson gauge coupling beta=5.7. When
compared to simulations with the standard (nonperturbatively improved) clover
action at small lattice spacing, the action shows good scaling behavior, with
an apparent great reduction in the number of exceptional configurations.Comment: 29 pages, LaTeX with 24 eps figures; Due to the suggestion of a
referee, the previous version of this paper has been merged with
hep-lat/9807002. Otherwise no major change in the contents of either pape
Instantons and Chiral Symmetry on the Lattice
I address the question of how much of QCD in the chiral limit is reproduced
by instantons. After reconstructing the instanton content of smoothed Monte
Carlo lattice configurations, I compare hadron spectroscopy on this instanton
ensemble to the spectroscopy on the original ``physical'' smoothed
configurations using a chirally optimised clover fermion action. By studying
the zero mode zone in simple instances I find that the optimised action gives a
satisfactory description of it. Through the Banks-Casher formula, instantons by
themselves are shown to break chiral symmetry but hadron correlators on the
instanton backgrounds are strongly influenced by free quark propagation. This
results in unnaturally light hadrons and a small splitting between the vector
and the pseudoscalar meson channels. Superimposing a perturbative ensemble of
zero momentum gauge field fluctuations (torons) on the instantons is found to
be enough to eliminate the free quarks and restore the physical hadron
correlators. I argue that the torons that are present only in finite volumes,
are probably needed to compensate the unnaturally large finite size effects due
to the lack of confinement in the instanton ensemble.Comment: 32 pages, LaTeX with 14 eps figure
Oxidative damage control in a human (mini-) organ: Nrf2 activation protects against oxidative stress-induced hair growth inhibition
The in situ control of redox insult in human organs is of major clinical relevance, yet remains incompletely understood. Activation of Nrf2, the “master regulator” of genes controlling cellular redox homeostasis, is advocated as a therapeutic strategy for diseases with severely impaired redox balance. It remains to be shown whether this strategy is effective in human organs, rather than isolated human cell types. We have therefore explored the role of Nrf2 in a uniquely accessible human (mini-) organ, human scalp hair follicles (HFs). Microarray and qPCR analysis of human HFs following Nrf2 activation using sulforaphane identified the modulation of phase II metabolism, ROS clearance, the pentose phosphate pathway and glutathione homeostasis. Nrf2 knockdown (siRNA) in cultured human HFs confirmed the regulation of key Nrf2 target genes (i.e. HO-1, NQO1, GSR, GCLC, ABCC1, PRDX1). Importantly, Nrf2 activation significantly reduced ROS levels and associated lipid peroxidation. Nrf2 pre-activation reduced oxidative stress-stimulated (H2O2 or menadione) premature
catagen and hair growth inhibition, significantly ameliorated the H2O2-dependent increase in matrix keratinocyte apoptosis and reversed the ROS-induced reduction in proliferation. This study thus provides direct evidence for the crucial role of Nrf2 in protecting human organ function (i.e. scalp HFs) against redox insult
Heveny gastrointestinalis vérzések ellátása = Management of acute gastrointestinal bleeding
Gastrointestinal bleeding has a profound impact on public health due to its high prevalence and severity. With the elderly population taking more anticoagulants/antiaggregants/non-steroid anti-inflammatory drugs, the digestive bleeding will certainly raise more and more challenges in quantity as well as in severity for the public healthcare system. The emergency medicine specialists and gastroenterologists have a central role in the management of patients presenting with gastrointestinal bleeding. In certain cases, radiologists, invasive radiologists, intensive care specialists and surgeons should also be involved in the decision making process and management of patients. Therefore, Hungarian experts felt the need to elaborate a comprehensive, multidisciplinary, practical local guideline reflecting the frequently arisen aspects based on current international guidelines. This guideline proposal covers topics of basic requirements, initial assessment of patients, risk evaluation, laboratory tests, hemodynamic resuscitation in the case of gastrointestinal bleeding followed by its consecutive steps of diagnosis and therapy sorted by location of the source of the hemorrhage. The authors give practical instructions for unsuccessful hemostasis or rebleeding. Finally, the role of surgery is also summarized in the management of gastrointestinal bleeding. Orv Hetil. 2020; 161(30): 1231-1242
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