Abstract
The vortex lattice (VL) in MgB
2
is characterized by the presence of long-lived metastable states (MSs), which arise from cooling or heating across the equilibrium phase boundaries. A return ...to the equilibrium configuration can be achieved by inducing vortex motion. Here we report on small-angle neutron scattering studies of MgB
2
, focusing on the structural properties of the VL as it is gradually driven from metastable to equilibrium states (ESs) by an AC magnetic field. Measurements were performed using initial MSs obtained either by cooling or heating across the equilibrium phase transition. In all cases, the longitudinal correlation length remains constant and comparable to the sample thickness. Correspondingly, the VL may be considered as a system of straight rods, where the formation and growth of ES domains only occurs in the two-dimensional plane perpendicular to the applied field direction. Spatially resolved raster scans of the sample were performed with apertures as small as 80
μ
m, corresponding to only 1.2 × 10
6
vortices for an applied field of 0.5 T. These revealed spatial variations in the metastable and equilibrium VL populations, but individual domains were not directly resolved. A statistical analysis of the data indicates an upper limit on the average domain size of approximately 50
μ
m.
Raloxifene, a selective estrogen receptor modulator approved for the prevention and treatment of postmenopausal osteoporosis, has shown a significant reduction in breast cancer incidence after 3 ...years in this placebo-controlled, randomized clinical trial in postmenopausal women with osteoporosis. This article includes results from an additional annual mammogram at 4 years and represents 3,004 additional patient-years of follow-up in this trial. Breast cancers were ascertained through annual screening mammograms and adjudicated by an independent oncology review board. A total of 7,705 women were enrolled in the 4-year trial; 2,576 received placebo, 2,557 raloxifene 60 mg/day, and 2,572 raloxifene 120 mg/day. Women were a mean of 66.5-years old at trial entry, 19 years postmenopause, and osteoporotic (low bone mineral density and/or prevalent vertebral fractures). As of 1 November 1999, 61 invasive breast cancers had been reported and were confirmed by the adjudication board, resulting in a 72% risk reduction with raloxifene (relative risk (RR) 0.28, 95% confidence interval (CI) 0.17, 0.46). These data indicate that 93 osteoporotic women would need to be treated with raloxifene for 4 years to prevent one case of invasive breast cancer. Raloxifene reduced the risk of estrogen receptor-positive invasive breast cancer by 84% (RR 0.16, 95% CI 0.09, 0.30). Raloxifene was generally safe and well-tolerated, however, thromboembolic disease occurred more frequently with raloxifene compared with placebo (p=0.003). We conclude that raloxifene continues to reduce the risk of breast cancer in women with osteoporosis after 4 years of treatment, through prevention of new cancers or suppression of subclinical tumors, or both. Additional randomized clinical trials continue to evaluate this effect in postmenopausal women with osteoporosis, at risk for cardiovascular disease, and at high risk for breast cancer.
Monitoring the atmospheric concentrations of the greenhouse gases (GHG) carbon dioxide (CO.sub.2) and methane (CH.sub.4) is a key ingredient for fostering our understanding of the mechanisms behind ...the sources and sinks of these gases and for verifying and quantitatively attributing their anthropogenic emissions. Here, we present the instrumental setup and performance evaluation of an open-path GHG observatory in the city of Heidelberg, Germany. The observatory measures path-averaged concentrations of CO.sub.2 and CH.sub.4 along a 1.55 km path in the urban boundary layer above the city. We combine these open-path data with local in situ measurements to evaluate the representativeness of these observation types on the kilometer scale. This representativeness is necessary to accurately quantify emissions, since atmospheric models tasked with this job typically operate on kilometer-scale horizontal grids.
A new gas-filled ionization chamber for high count rate particle identification has been constructed and commissioned at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National ...Laboratory (ORNL). To enhance the response time of the ionization chamber, a design utilizing a tilted entrance window and tilted electrodes was adopted, which is modified from an original design by Kimura et al. 1. A maximum counting rate of ~700,000~700,000 particles per second has been achieved. The detector has been used for several radioactive beam measurements performed at the HRIBF.
The majority of airborne aerosol measurements employ forward-facing inlets with near-isokinetic sampling; these inlets have known artifacts when sampling in clouds such that data taken in cloud must ...typically be discarded. Here we report first results from a perpendicular inlet for sampling interstitial submicron black-carbon (BC) containing aerosol. The inlet, consisting of a flat plate to stabilize flow prior to perpendicular sampling, was evaluated using a single particle soot photometer (SP2) aboard the NASA WB-57F aircraft during the Midlatitude Airborne Cirrus Properties Experiment (MACPEX) of 2011. The new inlet rejects large particles and is free of aerosol artifacts when sampling in ice clouds while allowing sampling of submicron BC-containing aerosol with the same unit efficiency as a validated isokinetic inlet, thus allowing for airborne sampling of interstitial BC aerosol.
Copyright 2013 American Association for Aerosol Research
We report the direct measurement of the topological skyrmion energy barrier through a hysteresis of the skyrmion lattice in the chiral magnet MnSi. Measurements were made using small-angle neutron ...scattering with a custom-built resistive coil to allow for high-precision minor hysteresis loops. The experimental data were analyzed using an adapted Preisach model to quantify the energy barrier for skyrmion formation and corroborated by the minimum-energy path analysis based on atomistic spin simulations. We reveal that the skyrmion lattice in MnSi forms from the conical phase progressively in small domains, each of which consisting of hundreds of skyrmions, and with an activation barrier of several eV.
CDF Central Outer Tracker Affolder, T; Allspach, D; Ambrose, D ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2004, Letnik:
526, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The Central Outer Tracker is a large cylindrical drift chamber constructed to replace Collider Detector at Fermilab's original central drift chamber for the higher luminosity expected for Run 2 at ...the Fermilab Tevatron. The chamber's drift properties are described in the context of meeting the operating requirements for Run 2. The design and construction of the chamber, the front-end readout electronics, and the high-voltage system are described in detail. Wire aging considerations are also discussed.
To take full advantage of advanced exotic beam facilities, target technology must also be advanced. Particularly important to the study of astrophysical reaction rates is the creation of localized ...and dense targets of hydrogen and helium. The Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas-jet target has been constructed for this purpose. JENSA was constructed at Oak Ridge National Laboratory (ORNL) where it was tested and characterized, and has now moved to the ReA3 reaccelerated beam hall at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University for use with radioactive beams.
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