4,849 research outputs found
R-values in Low Energy e^+e^- Annihilation
This presentation briefly summarizes the recent measurements of R-values in
low energy e^+e^- annihilation. The new experiments aimed at reducing the
uncertainties in R-values and performed with the upgraded Beijing Spectrometer
(BESII) at Beijing Electron Positron Collider (BEPC) in Beijing and with CMD-2
and SND at VEEP-2M in Novosibirsk are reviewed and discussed.Comment: 17 pages, 10 figures, invited presentation at the XIX International
Symposium on Lepton and Photon Interactions at High Energy, Stanford
University, August 199
Berry's phase for large spins in external fields
It is shown that even for large spins the fundamental difference between
integer and half-integer spins persists. In a quasi-classical description this
difference enters via Berry's connection. This general phenomenon is derived
and illustrated for large spins confined to a plane by crystalline electric
fields. Physical realizations are rare-earth Nickel Borocarbides. Magnetic
moments for half-integer spin
(Dy, ) and magnetic susceptibilities for integer spin
(Ho, ) are calculated. Experiments are proposed to furnish evidence
for the predicted fundamental difference.Comment: 4 pages RevTe
Bias-Dependent Generation and Quenching of Defects in Pentacene
We describe a defect in pentacene single crystals that is created by bias
stress and persists at room temperature for an hour in the dark but only
seconds with 420nm illumination. The defect gives rise to a hole trap at Ev +
0.38eV and causes metastable transport effects at room temperature. Creation
and decay rates of the hole trap have a 0.67eV activation energy with a small
(108 s-1) prefactor, suggesting that atomic motion plays a key role in the
generation and quenching process.Comment: 10 pages, 3 figure
Wear Testing of a Mechanized Percussion Well Drilling System for Water Access in West Africa
The Mechanized Percussion Well Drilling (MPWD) Collaboratory project is assisting in the development of a mechanized well drilling system for drilling shallow water wells in West Africa. Our client, Mr. Joseph Longenecker with Open Door Development (ODD), desires to make water wells accessible to all in this region, but has experienced difficulty drilling through hard soil layers. To overcome this problem, the MPWD team has worked closely with Mr. Joseph Longenecker to develop a mechanized percussion well drilling rig using a rubber friction wheel drive system that is capable of drilling through these harder layers.
Currently, the MPWD team is working to provide recommendations to improve the useful service life of our client’s new, mechanized rig design. The MPWD team’s most recent work includes the design and fabrication of a testing rig to simulate the operation of our client’s full-size rig. The testing rig will allow our team to conduct fatigue testing on a model of the driveline system to analyze the wear patterns on the rubber friction wheel and to estimate its expected service life. The team has also performed a series of finite element analyses on the mast design of our client\u27s rig to evaluate working stresses under static loading and buckling, along with fatigue analysis, to confirm safe operation of the rig and to identify any elements that might require upgrades.
Funding for this work provided by The Collaboratory for Strategic Partnerships and Applied Research.https://mosaic.messiah.edu/engr2022/1010/thumbnail.jp
Magnetic Field and Pressure Phase Diagrams of Uranium Heavy-Fermion Compound UZn
We have performed magnetization measurements at high magnetic fields of up to
53 T on single crystals of a uranium heavy-fermion compound UZn
grown by the Bridgman method. In the antiferromagnetic state below the N\'{e}el
temperature = 9.7 K, a metamagnetic transition is found at
32 T for the field along the [110] direction (-axis). The
magnetic phase diagram for the field along the [110] direction is
given. The magnetization curve shows a nonlinear increase at 35
T in the paramagnetic state above up to a characteristic
temperature where the magnetic susceptibility or
electrical resistivity shows a maximum value. This metamagnetic behavior of the
magnetization at is discussed in comparison with the metamagnetic
magnetism of the heavy-fermion superconductors UPt, URuSi, and
UPdAl. We have also carried out high-pressure resistivity measurement
on UZn using a diamond anvil cell up to 8.7 GPa. Noble gas argon was
used as a pressure-transmitting medium to ensure a good hydrostatic
environment. The N\'{e}el temperature is almost
pressure-independent up to 4.7 GPa and starts to increase in the
higher-pressure region. The pressure dependences of the coefficient of the
term in the electrical resistivity , the antiferromagnetic gap
, and the characteristic temperature are
discussed. It is found that the effect of pressure on the electronic states in
UZn is weak compared with those in the other heavy fermion
compounds
Determinants of antibody persistence across doses and continents after single-dose rVSV-ZEBOV vaccination for Ebola virus disease: an observational cohort study.
BACKGROUND: The recombinant vesicular stomatitis virus (rVSV) vaccine expressing the Zaire Ebola virus (ZEBOV) glycoprotein is efficacious in the weeks following single-dose injection, but duration of immunity is unknown. We aimed to assess antibody persistence at 1 and 2 years in volunteers who received single-dose rVSV-ZEBOV in three previous trials. METHODS: In this observational cohort study, we prospectively followed-up participants from the African and European phase 1 rVSV-ZEBOV trials, who were vaccinated once in 2014-15 with 300 000 (low dose) or 10-50 million (high dose) plaque-forming units (pfu) of rVSV-ZEBOV vaccine to assess ZEBOV glycoprotein (IgG) antibody persistence. The primary outcome was ZEBOV glycoprotein-specific IgG geometric mean concentrations (GMCs) measured yearly by ELISA compared with 1 month (ie, 28 days) after immunisation. We report GMCs up to 2 years (Geneva, Switzerland, including neutralising antibodies up to 6 months) and 1 year (Lambaréné, Gabon; Kilifi, Kenya) after vaccination and factors associated with higher antibody persistence beyond 6 months, according to multivariable analyses. Trials and the observational study were registered at ClinicalTrials.gov (Geneva: NCT02287480 and NCT02933931; Kilifi: NCT02296983) and the Pan-African Clinical Trials Registry (Lambaréné PACTR201411000919191). FINDINGS: Of 217 vaccinees from the original studies (102 from the Geneva study, 75 from the Lambaréné study, and 40 from the Kilifi study), 197 returned and provided samples at 1 year (95 from the Geneva study, 63 from the Lambaréné, and 39 from the Kilifi study) and 90 at 2 years (all from the Geneva study). In the Geneva group, 44 (100%) of 44 participants who had been given a high dose (ie, 10-50 million pfu) of vaccine and who were seropositive at day 28 remained seropositive at 2 years, whereas 33 (89%) of 37 who had been given the low dose (ie, 300 000 pfu) remained seropositive for 2 years (p=0·042). In participants who had received a high dose, ZEBOV glycoprotein IgG GMCs decreased significantly between their peak (at 1-3 months) and month 6 after vaccination in Geneva (p0·05). Neutralising antibodies seem to be less durable, with seropositivity dropping from 64-71% at 28 days to 27-31% at 6 months in participants from the Geneva study. INTERPRETATION: Antibody responses to single-dose rVSV-ZEBOV vaccination are sustained across dose ranges and settings, a key criterion in countries where booster vaccinations would be impractical. FUNDING: The Wellcome Trust and Innovative Medicines Initiative 2 Joint Undertaking
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