Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV

We report the results of a study of color coherence effects in ppbar collisions based on data collected by the D0 detector during the 1994-1995 run of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8 TeV. Initial-to-final state color interference effects are studied by examining particle distribution patterns in events with a W boson and at least one jet. The data are compared to Monte Carlo simulations with different color coherence implementations and to an analytic modified-leading-logarithm perturbative calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters

Search for electroweak production of single top quarks in ppˉp\bar{p} collisions.

We present a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector between 1992 and 1995. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb. (arXiv

Chemical Modification of a Nafion(R) Sulfonyl Fluoride Precursor Via In Situ Sol-Gel Reactions

The melt-processible sulfonyl fluoride precursor of a Nafion(R) ionomer was utilized as a sol-gel reaction medium for 3-aminopropyltriethoxysilane (APrTEOS). The diffusion-mediated reaction of APrTEOS with SO2F groups can be controlled with high degree of reaction. Fourier transform infra-red/attenuated total reflection studies show that sulfonamide linkages are formed and condensation reactions of SiOR groups provide covalent crosslinking of chains. Formic acid treatment plus high temperature plus long time resulted in a high degree of polymer crosslinking as seen in Si-29 solid state nuclear magnetic resonance spectra. Mechanical modulus and strength increase, and elongation-to-break decreases with increasing filler. Hybrids with \u3c18% uptake accumulate cracks with crosslinked outer layers, each event signalled by a drop in stress followed by stress recovery. While there are sharp visual material fronts inward from both surfaces, EDAX (energy dispersive analysis of X-rays) showed that there are no sharp Si composition boundaries. Differential scanning calorimetry (d.s.c.) revealed a broad, weak endothermic event peaking at 67 degrees C for the precursor and shifting to higher temperatures while broadening with increasing filler content, indicating progressively-restrictive glass-transition-temperature-related molecular motions within an increasingly nonhomogeneous environment. For the unreacted precursor, this d.s.c. transition occurs at a temperature just above a glass transition detected by dynamic mechanical means. (C) 1997 Elsevier Science Ltd

Bacterial overgrowth during treatment with omeprazole compared with cimetidine: a prospective randomised double blind study.

BACKGROUND: Gastric and duodenal bacterial overgrowth frequently occurs in conditions where diminished acid secretion is present. Omeprazole inhibits acid secretion more effectively than cimetidine and might therefore more frequently cause bacterial overgrowth. AIM: This controlled prospective study compared the incidence of gastric and duodenal bacterial overgrowth in patients treated with omeprazole or cimetidine. METHODS: 47 outpatients with peptic disease were randomly assigned to a four week treatment regimen with omeprazole 20 mg or cimetidine 800 mg daily. Gastric and duodenal juice were obtained during upper gastrointestinal endoscopy and plated for anaerobic and aerobic organisms. RESULTS: Bacterial overgrowth (> or = 10(5) cfu/ml) was present in 53% of the patients receiving omeprazole and in 17% receiving cimetidine (p < 0.05). The mean (SEM) number of gastric and duodenal bacterial counts was 6.0 (0.2) and 5.0 (0.2) respectively in the omeprazole group and 4.0 (0.2) and 4.0 (0.1) in the cimetidine group (p < 0.001 and < 0.01; respectively). Faecal type bacteria were found in 30% of the patients with bacterial overgrowth. Basal gastric pH was higher in patients treated with omeprazole compared with cimetidine (4.2 (0.5) versus 2.0 (0.2); p < 0.001) and in patients with bacterial overgrowth compared with those without bacterial overgrowth (5.1 (0.6) versus 2.0 (0.1); p < 0.0001). The nitrate, nitrite, and nitrosamine values in gastric juice did not increase after treatment with either cimetidine or omeprazole. Serum concentrations of vitamin B12, beta carotene, and albumin were similar before and after treatment with both drugs. CONCLUSIONS: These results show that the incidence of gastric and duodenal bacterial overgrowth is considerably higher in patients treated with omeprazole compared with cimetidine. This can be explained by more pronounced inhibition of gastric acid secretion. No patient developed signs of malabsorption or an increase of N-nitroso compounds. The clinical significance of these findings needs to be assessed in studies with long-term treatment with omeprazole, in particular in patients belonging to high risk groups such as HIV infected and intensive care units patients

The bb ¯ ¯ bb¯ production cross section and angular correlations in pp ¯ ¯ ¯ pp¯ collisions at s √ s = 1.8 TeV

We present measurements of the bb-bar Image production cross section and angular correlations using the DØ detector at the Fermilab Tevatron pp-bar Collider operating at ?s = 1.8 TeV. The b quark production cross section for |y^b| &lt; 1.0 and pT^b &gt; 6 GeV/c is extracted from single muon and dimuon data samples. The results agree in shape with the next-to-leading order QCD calculation of heavy flavor production but are greater than the central values of these predictions. The angular correlations between b and bbar quarks, measured from the azimuthal opening angle between their decay muons, also agree in shape with the next-to-leading order QCD prediction