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J Mayers

Publications and source records attributed to J Mayers.

17 recordsLinked to original sources
PubMed2006

On the origin of the redshift of the OH stretch in Ice Ih: evidence from the momentum distribution of the protons and the infrared spectral density.

Recent measurements of the momentum distribution in water and ice have shown that the proton is in a considerably softer potential in ice Ih than in water or the free monomer. This is broadly consistent with the large red shift observed in the vibrational spectrum. We show that existing water models, which treat the intramolecular potential as unchanged by the hydrogen bonding are unable to reproduce the momentum distribution. In addition, even if they can substantially explain the red shift they are unable to explain the large increase in intensity observed in the infrared spectrum in going from the monomer to ice Ih. We show that the inclusion of a bond dipole derivative term is essential to explain the observed intensities in the infrared spectrum. Though this term is partially responsible for the softening of the effective potential of the proton we show that best agreement with the observed momentum distribution requires a further softening of the harmonic component of the intramolecular potential. We introduce an efficient normal-mode molecular dynamics algorithm for calculating the momentum distribution with path-integrals.

Journal Article↗
PubMed2004

Bose-Einstein condensation, phase coherence, and two-fluid behavior in 4He.

It is shown that the assumption that the many particle wave functions describing superfluid 4He have some phase coherence properties of correlated basis functions provides a new explanation of the link between Bose-Einstein condensation and two fluid behavior. This assumption also implies that the condensate fraction is proportional to the superfluid fraction, in agreement with experiment, and provides a simple quantitative explanation of the anomalous reduction in spatial order and liquid density, observed as the temperature is lowered in superfluid 4He.

Journal Article↗
PubMed2002

Direct observation of tunneling in KDP using Neutron Compton scattering.

Neutron Compton scattering measurements presented here of the momentum distribution of hydrogen in KH2PO4 just above and well below the ferroelectric transition temperature are sufficiently sensitive to show clearly that the proton is coherent over both sites in the high temperature phase, a result that invalidates the commonly accepted order-disorder picture of the transition. The Born-Oppenheimer potential for the hydrogen, extracted directly from data for the first time, is consistent with neutron dif-fraction data, and the vibrational spectrum is in substantial agreement with infrared absorption measurements. The measurements are sensitive enough to detect the effect of surrounding ligands on the hydrogen bond, and can be used to study the systematic effect of the variation of these ligands in other hydrogen bonded systems.

Journal Article↗
PubMed2000

Hepatitis A vaccine administration: comparison between jet-injector and needle injection.

INTRODUCTION: Type A hepatitis virus (HAV) is a serious health problem throughout the world and can be spread via fecal-oral contact. Both immune globulin and an HAV vaccine provide protection, but the vaccine gives complete protection. Efficacy of methods of vaccination in relation to the formation of anti-HAV antibodies is unclear; thus, this study seeks to determine if significant differences exist between the syringe as compared to the jet injection technique. The purpose of this study was to compare in a randomized trial Biojet jet-injection system to a needle-syringe method. To determine if a significant difference between these two methods in seroconversion rates or geometric mean titers of anti HAV antibody occurs at day 15, 30, and 210 days after vaccination. METHOD: Anti-HAV IgG(-) adult hospital employees were randomized to receive 1440 EL.U of hepatitis a vaccine (HAVRIX(R)) in 2 doses by either needle or jet-injector (Biojector(R)) system at month 0 and 6. HAV seroconversion titer results were measured by the Boehringer-Mannheim method. RESULTS/DISCUSSION: A higher proportion of persons who received HAV vaccine via the Biojector(R) seroconverted with anti-HAV level >/=20 mIU at day 15, 30, and month 7 when compared with a needle injection.Side-effect profiles reported by participants in both methods were below those identified in current published and insert information, but the Biojector(R) had greater local reactivity in all categories when compared to the needle method.

Adult↗
PubMed2000

Bose-einstein condensation and spatial correlations in 4He

A new Monte Carlo method for calculating ground-state properties of liquid 4He is described. It is shown that Bose-Einstein condensation (BEC) implies delocalization of the wave function. It is shown that there is no general connection between the static structure factor and BEC. It is suggested that the observed connection in liquid 4He is due to the creation of spaces in the liquid structure, which are required so that the wave function can delocalize, in the presence of the hard-core interactions. It is shown that this suggestion is quantitatively consistent with observations on liquid 4He.

Journal Article↗
PubMed1997

The safety and pharmacokinetics of single-agent and combination therapy with megestrol acetate and dronabinol for the treatment of HIV wasting syndrome. The DATRI 004 Study Group. Division of AIDS Treatment Research Initiative.

This randomized, open-labeled, multicenter study was designed to assess safety and pharmacokinetics of dronabinol (Marinol) tablets and megestrol acetate (Megace) micronized tablets, alone and in combination, for treatment of HIV wasting syndrome. Weight and quality of life data were also collected. Fifty-two patients (mean CD4+ count, 59 cells/microliter) were randomized to one of four treatment arms: dronabinol 2.5 mg twice/day (D); megestrol acetate 750 mg/day (M750); megestrol acetate 750 mg/day+dronabinol 2.5 mg twice/day (M750+D); or megestrol acetate 250 mg/day+dronabinol 2.5 mg twice/day (M250+D). After therapy initiation, 47 patients returned for at least one visit, and 39 completed the planned 12 weeks of study visits. Occurrence of adverse events, drug discontinuation, new AIDS-defining conditions, or CD4+ T lymphocyte changes were not statistically significantly different among arms. Serious adverse events assessed as related to dronabinol included CNS events (e.g., confusion, anxiety, emotional lability, euphoria, hallucinations) and those assessed as related to megestrol acetate included dyspnea, liver enzyme changes, and hyperglycemia. The mean weight change +/- SE over 12 weeks was as follows: D, -2.0 +/- 1.3 kg; M750, +6.5 +/- 1.1 kg; M750+D, +6.0 +/- 1.0 kg; and M250+D, -0.3 +/- 1.0 kg (difference among treatment arms, p = 0.0001). Pharmacokinetic parameters measured after 2 weeks of therapy for M750 were Cmax = 985 ng/ml and AUC = 22,487 ng x hr/ml, and for dronabinol and its active metabolite (HO-THC), respectively, were Cmax = 2.01; 4.61 ng/ml and AUC = 5.3; 23.7 ng x hr/ml. For megestrol acetate, but not dronabinol, there was a positive correlation at week 2 between both Cmax and AUC with each of the following: (1) weight change, (2) breakfast visual analog scale for hunger (VASH) score, and (3) dinner VASH score.

Adolescent↗
PubMed1994

Dismal rehabilitation in geriatric inner-city hemodialysis patients.

OBJECTIVE: To assess the extent of functional and vocational rehabilitation achieved by elderly inner-city patients sustained on maintenance hemodialysis. DESIGN: Inception cohort study of elderly patients who have end-stage renal disease using a modified Karnofsky rating system. The need for a wheelchair, participation in household activities, and effect of comorbid conditions were noted. Current status was compared with patient's recollection of functional activity level 2 years before commencing maintenance hemodialysis. SETTING: Seven outpatient, hospital-affiliated and private hemodialysis units in Brooklyn, NY. PATIENTS: One hundred four patients aged 65 years or older who were receiving maintenance hemodialysis for at least 6 months. MAIN OUTCOME MEASURES: A score of 76 or greater on a modified Karnofsky scale indicated independent function at a level that permitted participation in activities beyond those mandated by the hemodialysis regimen. A comorbidity score 6 or greater on a newly constructed index correlated with severe debility. Employment status was also recorded. RESULTS: Present functional activity had deteriorated to a modified Karnofsky score of 66 +/- 12.3 (+/- SD) compared with patients' recollection of a mean score of 84 +/- 14.3 (P < .001) 2 years before initiation of hemodialysis. Diabetic patients had a lower score than nondiabetic patients. The mean comorbidity index of the entire study group was 7.8 +/- 2.9 (mean +/- SD). Within the diabetic subset, severe debility constrained 71 patients (68%) to limit all activity to their residence with the exception of travel to and from their dialysis facility. By contrast, 2 years prior to commencing dialytic therapy, 81 diabetic patients (78%) had interests and activities that took them outside their homes (P < .001). Generalized weakness was the most common explanation given for the lack of outside activity by nine patients (9%) who were wheelchair bound. Erythropoietin, though regularly administered to 87 patients (84%) in the study group, was unsuccessful in raising mean hematocrit reading above 0.28 +/- 0.05 (mean +/- SD). CONCLUSIONS: Maintenance hemodialysis does not return inner-city elderly patients to their predialysis level of functioning. Few elderly, diabetic hemodialysis patients conduct any substantive portion of their lives outside their homes. For nondiabetic patients, the modified Karnofsky score of whites (70.4 +/- 11.9) and blacks (66.5 +/- 15.3), though low, was equivalent (P < .4).

Activities of Daily Living↗