2,465 research outputs found
Heavy Quark Radiative Energy Loss - Applications to RHIC
Heavy quark energy loss in a hot QCD plasma is computed taking into account
the competing effects due to suppression of zeroth order gluon radiation bellow
the plasma frequency and the enhancement of gluon radiation due to transition
energy loss and medium induced Bremsstrahlung. Heavy quark medium induced
radiative energy loss is derived to all orders in opacity, .
Numerical evaluation of the energy loss suggest small suppression of high
charm quarks, and therefore provide a possible explanation for the
null effects observed by PHENIX in the prompt electron spectrum in as
and 200 AGeV.Comment: 4 pages, 4 figures, Contributed to 17th International Conference on
Ultra Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland,
California, 11-17 Jan 200
Heavy-to-light ratios as a test of medium-induced energy loss at RHIC and the LHC
The ratio of nuclear modification factors of high- heavy-flavored mesons
tolight-flavored hadrons (heavy-to-light ratio) is shown to be a sensitive tool
to test medium-induced energy loss at RHIC and LHC energies. Heavy-to-light
ratios of mesons at RHIC in the region GeV, and of and
mesons at the LHC in the region GeV, are proposed for such a test.
Finally, the different contributions to the nuclear modification factor for
electrons at RHIC are analyzed. Preliminary PHENIX and STAR data are compatible
with radiative energy loss provided the contribution of electrons from beauty
decays is small compared to that from charm.Comment: 5 pages, latex, 4 eps figs included using graphicx; to appear in the
proceedings of 18th International Conference on Ultrarelativistic
Nucleus-Nucleus Collisions: Quark Matter 2005 (QM 2005), Budapest, Hungary,
4-9 Aug 200
Magnetic and electric contributions to the energy loss in a dynamical QCD medium
The computation of radiative energy loss in a finite size QCD medium with
dynamical constituents is a key ingredient for obtaining reliable predictions
for jet quenching in ultra-relativistic heavy ion collisions. It was previously
shown that energy loss in dynamical QCD medium is significantly higher compared
to static QCD medium. To understand this difference, we here analyze magnetic
and electric contributions to energy loss in dynamical QCD medium. We find that
the significantly higher energy loss in the dynamical case is entirely due to
appearance of magnetic contribution in the dynamical medium. While for
asymptotically high energies, the energy loss in static and dynamical medium
approach the same value, we find that the physical origin of the energy loss in
these two cases is different.Comment: 6 pages, 4 figure
MicroRNA-Regulated Signaling Pathways: Potential Biomarkers for Pancreatic Ductal Adenocarcinoma
Pancreatic ductal adenocarcinoma (PDAC) is the most aggressive and invasive type of pancreatic cancer (PCa) and is expected to be the second most common cause of cancer-associated deaths. The high mortality rate is due to the asymptomatic progression of the clinical features until the advanced stages of the disease and the limited effectiveness of the current therapeutics. Aberrant expression of several microRNAs (miRs/miRNAs) has been related to PDAC progression and thus they could be potential early diagnostic, prognostic, and/or therapeutic predictors for PDAC. miRs are small (18 to 24 nucleotides long) non-coding RNAs, which regulate the expression of key genes by targeting their 3′-untranslated mRNA region. Increased evidence has also suggested that the chemoresistance of PDAC cells is associated with metabolic alterations. Metabolic stress and the dysfunctionality of systems to compensate for the altered metabolic status of PDAC cells is the foundation for cellular damage. Current data have implicated multiple systems as hallmarks of PDAC development, such as glutamine redox imbalance, oxidative stress, and mitochondrial dysfunction. Hence, both the aberrant expression of miRs and dysregulation in metabolism can have unfavorable effects in several biological processes, such as apoptosis, cell proliferation, growth, survival, stress response, angiogenesis, chemoresistance, invasion, and migration. Therefore, due to these dismal statistics, it is crucial to develop beneficial therapeutic strategies based on an improved understanding of the biology of both miRs and metabolic mediators. This review focuses on miR-mediated pathways and therapeutic resistance mechanisms in PDAC and evaluates the impact of metabolic alterations in the progression of PDAC
Jet suppression of pions and single electrons at Au+Au collisions at RHIC
Jet suppression is considered to be a powerful tool to study the properties
of a QCD medium created in ultra-relativistic heavy ion collisions. However,
theoretical predictions obtained by using jet energy loss in static QCD medium
show disagreement with experimental data, which is known as the heavy flavor
puzzle at RHIC. We calculate the suppression patterns of pions and single
electrons for Au+Au collisions at RHIC by including the energy loss in a finite
size dynamical QCD medium, with finite magnetic mass effects taken into
account. In contrast to the static case, we here report a good agreement with
the experimental results, where this agreement is robust with respect to
magnetic mass values. Therefore, the inclusion of dynamical QCD medium effects
provides a reasonable explanation of the heavy flavor puzzle at RHIC.Comment: 4 pages, 2 figure
Transition Radiation in QCD matter
In ultrarelativistic heavy ion collisions a finite size QCD medium is
created. In this paper we compute radiative energy loss to zeroth order in
opacity by taking into account finite size effects. Transition radiation occurs
on the boundary between the finite size medium and the vacuum, and we show that
it lowers the difference between medium and vacuum zeroth order radiative
energy loss relative to the infinite size medium case. Further, in all previous
computations of light parton radiation to zeroth order in opacity, there was a
divergence caused by the fact that the energy loss is infinite in the vacuum
and finite in the QCD medium. We show that this infinite discontinuity is
naturally regulated by including the transition radiation.Comment: 21 page, 22 figure
Chronic stress differentially affects antioxidant enzymes and modifies the acute stress response in liver of wistar rats.
Summary Clinical reports suggest close interactions between stressors, particularly those of long duration, and liver diseases, such as hepatic inflammation, that is proposed to occur via reactive oxygen species. In the present study we have used 21-day social isolation of male Wistar rats as a model of chronic stress to investigate protein expression/activity of liver antioxidant enzymes: superoxide dismutases (SODs), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GLR), and protein expression of their upstream regulators: glucocorticoid receptor (GR) and nuclear factor kappa B (NFkB). We have also characterized these parameters in either naive or chronically stressed animals that were challenged by 30-min acute immobilization. We found that chronic isolation caused decrease in serum corticosterone (CORT) and blood glucose (GLU), increase in NFkB signaling, and disproportion between CuZnSOD, peroxidases (CAT, GPx) and GLR, thus promoting H 2 O 2 accumulation and prooxidative state in liver. The overall results suggested that chronic stress exaggerated responsiveness to subsequent stressor at the level of CORT and GLU, and potentiated GLR response, but compromised the restoration of oxido-reductive balance due to irreversible alterations in MnSOD and GPx
Dietary fat intake as a risk factor for the development of diabetes. Multinational, multicenter study of the Mediterranean Group for the Study of Diabetes (MGDS)
In the context of the Multinational MGSD Nutrition Study, three groups of subjects were studied: 204 subjects with recently diagnosed diabetes(RDM),42subjectswithundiagnoseddiabetes(UDM)(AmericanDiabetesAssociation criteria—fasting plasma glucose [FPG] 126 mg/dl), and 55 subjects with impaired fasting glucose(IFG)(FPG 110and126mg/dl).Eachgroupwascomparedwithacontrolgroupof nondiabetic subjects, matched one by one for center, sex, age, and BMI. Nutritional habits were evaluated by a dietary history method, validated against the 3-day diet diary. In RDM, the questionnaire referred to the nutritional habits before the diagnosis of diabetes. Demographic data were collected, and anthropometrical and biochemical measurements were taken. RESULTS— Compared with control subjects, RDM more frequently had a family history of diabetes(49.0vs.14.2%;P0.001),exercisedless(exerciseindex53.5vs.64.4;P0.01),and more frequently had sedentary professions (47.5 vs. 27.4%; P 0.001). Carbohydrates contributed less to their energy intake (53.5 vs. 55.1%; P 0.05), whereas total fat (30.2 0.5 vs. 27.8 0.5%; P 0.001) and animal fat (12.2 0.3 vs. 10.8 0.3%; P 0.01) contributed moreandtheplant-to-animalfatratiowaslower(1.50.1vs.1.80.1;P0.01).UDMmore frequentlyhadafamilyhistoryofdiabetes(38.1vs.19.0%;P0.05)andsedentaryprofessions (58.5vs.34.1%;P0.05),carbohydratescontributedlesstotheirenergyintake(47.61.7vs. 52.81.4%;P0.05),totalfat(34.71.5vs.30.41.2%;P0.05)andanimalfat(14.2 0.9 vs. 10.6 0.7%; P 0.05) contributed more, and the plant-to-animal fat ratio was lower (1.6 0.2 vs. 2.3 0.4; P 0.05). IFG differed only in the prevalence of family history of diabetes (32.7 vs. 16.4%; P 0.05). CONCLUSIONS— Our data support the view that increased animal fat intake is associated with the presence of diabetes
Femoral or axillary artery as a cannulation site in the acute aortic dissection type A surgery: is there still a doubt?
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