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R Gilman

Publications and source records attributed to R Gilman.

At least 37 records · Page 2Linked to original sources
PubMed2001

Measurement of the high energy two-body deuteron photodisintegration differential cross section.

The first measurements of the d(gamma,p)n differential cross section at forward angles and photon energies above 4 GeV were performed at the Thomas Jefferson National Accelerator Facility (JLab). The results indicate evidence of an angular dependent scaling threshold. Results at straight theta(cm) = 37 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 4 GeV, while those at 70 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 1.5 GeV.

Journal Article↗
PubMed2001

Dynamics of the 16O(e, e'p) reaction at high missing energies.

We measured the cross section and response functions for the quasielastic 16O(e,e'p) reaction for missing energies 25< or =E(m)< or =120 MeV at missing momenta P(m)< or =340 MeV/c. For 25<E(m)<50 MeV and P(m) approximately 60 MeV/c, the reaction is dominated by a single 1s(1/2) proton knockout. At larger P(m), the single-particle aspects are increasingly masked by more complicated processes. Calculations which include pion exchange currents, isobar currents, and short-range correlations account for the shape and the transversity, but for only half of the magnitude of the measured cross section.

Journal Article↗
PubMed2001

Polarization measurements in high-energy deuteron photodisintegration.

We present measurements of the recoil proton polarization for the d(gamma-->,p-->)n reaction at straight theta(c.m.) = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization p(y) vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(gamma,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.

Journal Article↗
PubMed2001

Measurement of the charged pion electromagnetic form factor.

Separated longitudinal and transverse structure functions for the reaction 1H(e,e(')pi(+))n were measured in the momentum transfer region Q2 = 0.6--1.6 (GeV/c)(2) at a value of the invariant mass W = 1.95 GeV. New values for the pion charge form factor were extracted from the longitudinal cross section by using a recently developed Regge model. The results indicate that the pion form factor in this region is larger than previously assumed and is consistent with a monopole parametrization fitted to very low Q2 elastic data.

Journal Article↗
PubMed2001

A multilocus genotypic analysis of Cryptosporidium meleagridis.

Cryptosporidium meleagridis is a common cause of cryptosporidiosis in birds. In addition, recent reports have described the parasite as an etiologic agent of cryptosporidiosis in both immunocompetent and immunocompromised humans. Therefore, it is important to genetically characterize isolates of C. meleagridis from different hosts and geographic areas, and to develop molecular tools to differentiate isolates from various hosts or areas. In this study, a total of 11 isolates of Cryptosporidium meleagridis from both human and avian hosts were examined at three genetic loci: the small-subunit rRNA, 60-kDa glycoprotein precursor, and 70-kDa heat shock protein genes. Two genotypes of C. meleagridis were seen at the small-subunit rRNA locus. These differed from each other by the presence or lack of a heterogeneous copy of the gene and an ATT repeat. The 60-kDa glycoprotein precursor gene divided these eleven isolates of C. meleagridis into six genotypes with high sequence diversity between groups. The highest genetic heterogeneity, however, was seen at the 70-kDa heat shock protein locus, and was primarily present at the 3' end of the gene. This heterogeneity separated eight isolates of C. meleagridis into six genotypes. These data could be useful in the development of molecular tools to promote understanding of the transmission of C. meleagridis in humans.

AIDS-Related Opportunistic Infections↗
PubMed2000

Measurement of tensor polarization in elastic electron-deuteron scattering at large momentum transfer

Tensor polarization observables ( t(20), t(21), and t(22)) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)(2). The experiment was performed at the Jefferson Laboratory in Hall C using the electron High Momentum Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q2 the deuteron charge form factors G(C) and G(Q). They are in good agreement with relativistic calculations and disagree with perturbative QCD predictions.

Journal Article↗
PubMed2000

Two-year study of the protective efficacy of the oral whole cell plus recombinant B subunit cholera vaccine in Peru.

The protective efficacy of an oral inactivated whole cell Vibrio cholerae plus recombinant B subunit cholera vaccine was determined against El Tor cholera among Peruvian children and adults (2-65 years old) in a randomized, double-blind manner. Study subjects received 2 doses of vaccine or placebo 2 weeks apart, followed by a booster dose 10 months later. Surveillance for cholera was performed actively, with 2 visits per week to each household, and passively, at a local hospital. Stool samples were collected during diarrhea episodes and were cultured for V. cholerae. A total of 17,799 persons received 2 doses of vaccine or placebo, and 14,997 of these persons received the booster dose. After 2 doses (first surveillance period), V. cholerae biotype O1 was isolated from 17 vaccinees and 16 placebo recipients, demonstrating vaccine efficacy (VE) of -4%. After 3 doses (second surveillance period), V. cholerae O1 was isolated from 13 vaccinees and 32 placebo recipients, demonstrating VE of 61% (95% confidence interval ¿CI, 28%-79%). In the second surveillance period, the VE for illness requiring hospitalization was 82% (95% CI, 27%-96%). VE was also higher for persons >15 years old (VE, 72%; 95% CI, 28%-89%).

Administration, Oral↗
PubMed2000

Lactulose-mannitol intestinal permeability test in children with diarrhea caused by rotavirus and cryptosporidium. Diarrhea Working Group, Peru.

BACKGROUND: The relationship between intestinal permeability and acute secretory diarrheal syndromes caused by rotavirus and Cryptosporidium parvum in infants less than 36 months of age was studied using the lactulose-mannitol excretion assay. METHODS: An oral solution containing 0.4 g/kg lactulose and 0.1 g/kg mannitol was administered to 15 infants with rotavirus, 7 with Cryptosporidium infection and a control group of 7 with secretory diarrhea admitted to the Oral Rehydration Unit of the National Children's Hospital in Lima, Peru. Urinary sugar excretion was measured using an enzymatic spectrophotometric method. The ratio of urinary excretion of lactulose to mannitol was used to measure intestinal mucosal permeability, with higher ratios indicative of increased intestinal permeability. Infants in all three groups were retested 20 days after the initial test. RESULTS: The (mean +/- SE) lactulose:mannitol (L:M) excretion ratios during the acute phase (day 1) of diarrhea in infants with rotavirus or Cryptosporidium and control infants were 0.67 +/- 0.1, 0.76 +/- 0.16, and 0.26 +/- 0.04, respectively. In the convalescent phase (day 20) the ratios were 0.19 +/- 0.02, 0.28 +/- 0.05, and 0.29 +/- 0.07, respectively. Significant reductions in L:M ratios were noted in rotavirus patients between days 1 and 20 (paired t-test; P < 0.01), Cryptosporidium patients between days 1 and 20 (paired t-test; P < 0.05), and between control subjects on day 1 and rotavirus patients on day 1 and Cryptosporidium patients on day 1 (unpaired t-tests; P < 0.05 for both). There were no significant differences in control subjects between days 1 and 20, control subjects and rotavirus patients on day 20, or control subjects and Cryptosporidium patients on day 20. CONCLUSIONS: The results indicate that increased intestinal permeability caused by rotavirus or cryptosporidium infections in Peruvian infants less than 36 months of age is a significant but reversible phenomenon. The temporal relationship observed in the current study and the contribution of such alterations in intestinal mucosal integrity to the burden of diarrheal disease and the development of malnutrition in developing countries is discussed.

Animals↗
PubMed2000

Attempts to establish experimental Cyclospora cayetanensis infection in laboratory animals.

Attempts were made to develop an animal model for Cyclospora cayetanensis to identify a practical laboratory host for studying human cyclosporiasis. Oocysts collected from stool of infected humans in the United States, Haiti, Guatemala, Peru, and Nepal were held in potassium dichromate solution to allow development of sporozoites. The following animal types were inoculated: 9 strains of mice, including adult and neonatal immunocompetent and immune-deficient inbred and outbred strains, rats, sandrats, chickens, ducks, rabbits, jirds, hamsters, ferrets, pigs, dogs, owl monkeys, rhesus monkeys, and cynomolgus monkeys. Most animals were inoculated by gavage, although some of the primates were fed oocysts on food items. The animals were examined for signs of infection, particularly diarrhea, and stool samples were examined for 4-6 wk after inoculation. None of the animals developed patent infections or signs of infection. We conclude that none of the animals tested is susceptible to infection with C. cayetanensis.

Animals↗
PubMed2000

Benefiting from VDV.

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Computer Communication Networks↗
PubMed1997

Characterization of pncA mutations in pyrazinamide-resistant Mycobacterium tuberculosis.

Pyrazinamide (PZA) is a first-line drug for short-course tuberculosis therapy. Resistance to PZA is usually accompanied by loss of pyrazinamidase (PZase) activity in Mycobacterium tuberculosis. PZase converts PZA to bactericidal pyrazinoic acid, and the loss of PZase activity is associated with PZA resistance. The gene (pncA) encoding the M. tuberculosis PZase has recently been sequenced, and mutations in pncA were previously found in a small number of PZA-resistant M. tuberculosis strains. To further understand the genetic basis of PZA resistance and determine the frequency of PZA-resistant strains having pncA mutations, we analyzed a panel of PZA-resistant clinical isolates and mutants made in vitro. Thirty-three of 38 PZA-resistant clinical isolates had pncA mutations. Among the five strains that did not contain pncA mutations, four were found to be falsely resistant and one was found to be borderline resistant to PZA. The 33 PZA-resistant clinical isolates and 8 mutants made in vitro contained various mutations, including nucleotide substitutions, insertions, or deletions in the pncA gene. The identified mutations were dispersed along the pncA gene, but some degree of clustering of mutations was found at the following regions: Gly132-Thr142, Pro69-Leu85, and Ile5-Asp12. PCR-single-strand conformation polymorphism (SSCP) analysis was shown to be useful for the rapid detection of pncA mutations in the PZA-resistant strains. We conclude that a mutation in the pncA gene is a major mechanism of PZA resistance and that direct sequencing by PCR or SSCP analysis should help to rapidly identify PZA-resistant M. tuberculosis strains.

Amidohydrolases↗
PubMed1996

Production of monoclonal antibodies for the identification of the eggs of Taenia solium.

Two antibodies, one monoclonal and one polyclonal, were produced and used to identify Taenia solium eggs, using the enzyme-linked immuno-electrotransfer blot technique (EITB). Different life-stages of Taenia solium and T. saginata, including eggs from gravid proglottids recovered, post-treatment, from patients infected with the tapeworms, and eggs of Diphyllobothrium pacificum and Hymenolepis nana from other patients were tested with these antibodies. The monoclonal antibody only recognized the eggs and immature proglottids of T. solium. The polyclonal antibody, however, not only reacted with the eggs, cysticerci and immature proglottids of T. solium but also with the eggs and immature proglottids of T. saginata. The sensitivity and specificity of the EITB were both 100% using the monoclonal antibody but only 78% and 60%, respectively, using the polyclonal antibody. Diagnostic bands for T. solium eggs corresponded to proteins of 22.5 kDa using the polyclonal antibody and 22.5-37 kDa using the monoclonal antibody. Species-specific fluorescence was obtained with an anti-T. solium monoclonal antibody which bound to egg-derived oncospheres of T. solium but not to those of T. saginata.

Animals↗