168 research outputs found
Measurement of direct photon production at Tevatron fixed target energies
Measurements of the production of high transverse momentum direct photons by
a 515 GeV/c piminus beam and 530 and 800 GeV/c proton beams in interactions
with beryllium and hydrogen targets are presented. The data span the kinematic
ranges of 3.5 < p_T < 12 GeV/c in transverse momentum and 1.5 units in
rapidity. The inclusive direct-photon cross sections are compared with
next-to-leading-order perturbative QCD calculations and expectations based on a
phenomenological parton-k_T model.Comment: RevTeX4, 23 pages, 32 figures, submitted to Phys. Rev.
Evidence for Parton kT Effects in High pT Particle Production
Inclusive pizero and direct-photon cross sections in the kinematic range 3.5
< pT < 12 GeV/c with central rapidities are presented for 530 and 800 GeV/c
proton beams and a 515 GeV/c pi- beam incident on beryllium targets. Current
Next-to-Leading-Order perturbative QCD calculations fail to adequately describe
the data for conventional choices of scales. Kinematic distributions from these
hard scattering events provide evidence that the interacting partons carry
significant initial-state parton transverse momentum (kT). Incorporating these
kT effects phenomenologically greatly improves the agreement between
calculations and the measured cross sections.Comment: 11 pages including 6 pages of figures with caption
Production of pizero and eta mesons at large transverse momenta in pi-p and pi-Be interactions at 515 GeV/c
We present results on the production of high transverse momentum pizero and
eta mesons in pi-p and pi-Be interactions at 515 GeV/c. The data span the
kinematic ranges 1 < p_T < 11 GeV/c in transverse momentum and -0.75 < y < 0.75
in rapidity. The inclusive pizero cross sections are compared with
next-to-leading order QCD calculations and to expectations based on a
phenomenological parton-k_T model.Comment: RevTeX4, 15 pages, 15 figures, to be submitted to Phys. Rev.
Carotid intima media thickness and blood biomarkers of atherosclerosis in patients after stroke or myocardial infarction
Aim To test if circulating levels of markers of inflammation,
endothelial function, and chronic infections, as well as association
between these markers and carotid intima media
thickness (CIMT), depend on the stage of atherosclerosis
expressed as a history of a major vascular event.
Methods The associations were analyzed separately in 75
healthy controls, 79 patients 3-6 months after the first-ever
non-cardioembolic ischemic stroke (IS), and 37 patients 3-6
months after the first-ever myocardial infarction (MI). Data
were collected prospectively in 2005. We measured high
sensitivity C-reactive protein (hs-CRP), procalcitonin, E-selectin,
intercellular adhesion molecule-1 (ICAM-1), serum
level of immune complexes (IC), and identified antibodies
against Herpes simplex virus type 1 (HSV), Cytomegalovirus,
Chlamydia pneumonia, and Helicobacter pylori. Correlations
with CIMT were determined using Pearson R and verified
after adjustment for age, sex, hypertension, diabetes,
and statin therapy.
Results Median ICAM-1 concentration was significantly
lower in controls than in post-IS patients (188 μg/L vs 215
μg/L), and significantly lower in post-IS patients than in
post-MI patients (215 μg/L vs 260 μg/L). Control patients
also had significantly lower IC level (0.03 U/L) and HSV antibody
index (6.0) compared to both post-IS (0.6 U/L, 9.6)
and post-MI (0.4 U/L, 9.2) patients. CIMT was correlated
with age (Pearson R = 0.38, P = 0.001) in the control group,
immune complexes (R = 0.26, P = 0.023) in the post-IS
group, and with hs-CRP (R = 0.40, P = 0.017) in the post-MI
group. These correlations were confirmed using multiple
regression analysis.
Conclusions Our study supports linear correlations between
CIMT and IC and hs-CRP levels. However, these associations
seem to depend on the type of vascular burden
Understanding the Origins of Bacterial Resistance to Aminoglycosides through Molecular Dynamics Mutational Study of the Ribosomal A-Site
Paromomycin is an aminoglycosidic antibiotic that targets the RNA of the bacterial small ribosomal subunit. It binds in the A-site, which is one of the three tRNA binding sites, and affects translational fidelity by stabilizing two adenines (A1492 and A1493) in the flipped-out state. Experiments have shown that various mutations in the A-site result in bacterial resistance to aminoglycosides. In this study, we performed multiple molecular dynamics simulations of the mutated A-site RNA fragment in explicit solvent to analyze changes in the physicochemical features of the A-site that were introduced by substitutions of specific bases. The simulations were conducted for free RNA and in complex with paromomycin. We found that the specific mutations affect the shape and dynamics of the binding cleft as well as significantly alter its electrostatic properties. The most pronounced changes were observed in the U1406C∶U1495A mutant, where important hydrogen bonds between the RNA and paromomycin were disrupted. The present study aims to clarify the underlying physicochemical mechanisms of bacterial resistance to aminoglycosides due to target mutations
Molecular dynamics of ribosomal elongation factors G and Tu
Translation on the ribosome is controlled by external factors. During polypeptide lengthening, elongation factors EF-Tu and EF-G consecutively interact with the bacterial ribosome. EF-Tu binds and delivers an aminoacyl-tRNA to the ribosomal A site and EF-G helps translocate the tRNAs between their binding sites after the peptide bond is formed. These processes occur at the expense of GTP. EF-Tu:tRNA and EF-G are of similar shape, share a common binding site, and undergo large conformational changes on interaction with the ribosome. To characterize the internal motion of these two elongation factors, we used 25 ns long all-atom molecular dynamics simulations. We observed enhanced mobility of EF-G domains III, IV, and V and of tRNA in the EF-Tu:tRNA complex. EF-Tu:GDP complex acquired a configuration different from that found in the crystal structure of EF-Tu with a GTP analogue, showing conformational changes in the switch I and II regions. The calculated electrostatic properties of elongation factors showed no global similarity even though matching electrostatic surface patches were found around the domain I that contacts the ribosome, and in the GDP/GTP binding region
Production of pizero and eta mesons at large transverse momenta in pp and pBe interactions at 530 and 800 GeV/c
We present results on the production of high transverse momentum pizero and
eta mesons in pp and pBe interactions at 530 and 800 GeV/c. The data span the
kinematic ranges: 1 < p_T < 10 GeV/c in transverse momentum and 1.5 units in
rapidity. The inclusive pizero cross sections are compared with next-to-leading
order QCD calculations and to expectations based on a phenomenological
parton-k_T model.Comment: RevTeX, 63 pages, 25 figures, to be submitted to Phys. Rev.
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