936 research outputs found
Observation of cosmic ray positrons from 5 to 25 GeV
The positron data gathered in conjunction with electron data published elsewhere is reported. The basic recognition scheme was to look for low mass positive particles that cause a cascade in a 7 radiation length shower counter. The mass criteria is imposed by selecting particles that were accompanied by Cherenkov light but whose rigidity was below the proton Cherenkov threshold. Thus the proton Cherenkov threshold represents an upper limit to the range of the experiment
Absence of long-range chemical ordering in equimolar FeCoCrNi
Equimolar FeCoCrNi alloys have been the topic of recent research as "high-entropy alloys," where the name is derived from the high configurational entropy of mixing for a random solid solution. Despite their name, no systematic study of ordering in this alloy system has been performed to
date. Here, we present results from anomalous x-ray scattering and neutron scattering on quenched and annealed samples. An alloy of FeNi_3 was prepared in the same manner to act as a control. Evidence of long-range chemical ordering is clearly observed in the annealed FeNi_3 sample from both experimental techniques. The FeCoCrNi sample given the same heat treatment lacks long-range chemical order
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To be or not to be an auctioneer: Some thoughts on the legal nature of online eBay auctions and the protection of consumers
This paper discusses the legal classification of online “eBay” auctions. The discussion has key implications on the scope of consumer protection law as sale by auctions are, for example, excluded from the scope of the Consumer Protection (Distance Selling) Regulations 2000. The paper uncovers that online “eBay” auctions cannot always be considered as traditional auctions and that eBay, as an intermediary, is not to be considered as an auctioneer. This creates difficulties associated with a distributive application of consumer protection laws such as the Consumer Protection (Distance Selling) Regulations 2000. Another set of difficulties is associated with a lenient legal regime applicable to the liability of eBay under the Electronic Commerce (EC Directive) Regulations 2002 . The paper concludes that there is an urgent need to clarify the legal classification of online auctions and to rethink the liability of online auction sites to better protect consumers
Mass resolution optimization in a large isotopic composition experiment
A range-energy experiment was built to measure the isotopic composition of galactic cosmic rays. An enrichment of neutron rich isotopes, 22Ne and (25Mg + 26Mg) in particular, when compared to the solar composition is shown. A rich statistics measurement of these and other neutron-rich isotopes in the galactic flux yields information to the source of these particles. A computer simulation of the experiment was used to estimate the instrument resolution. The Cherenkov detector light collection efficiency, was calculated. Absorption of light in the radiator was considered to determine the optimum Cherenkov medium thickness. The experiment will determine the isotopic composition for the elements neon through argon in the energy range 300 to 800 MeV per nucleon
Magnetic susceptibility of EuTe/PbTe Heisenberg superlattices: experimental and theoretical studies
We report results on the temperature dependence of the susceptibilities of a
set of MBE-grown short-period EuTe/PbTe antiferromagnetic superlattices having
different EuTe layer thicknesses. In-plane and orthogonal susceptibilities have
been measured and display a strong anisotropy at low temperature, confirming
the occurrence of a magnetic phase transition in the thicker samples, as seen
also in neutron diffraction studies. We suggest that dipolar interactions
stabilize antiferromagnetic long-range order in an otherwise isotropic system
and we present numerical and analytical results for the low-temperature
orthogonal susceptibility.Comment: 30 pages, 8 ps figures, RevTe
Spin Glass Ordering in Diluted Magnetic Semiconductors: a Monte Carlo Study
We study the temperature-dilution phase diagram of a site-diluted Heisenberg
antiferromagnet on a fcc lattice, with and without the Dzyaloshinskii-Moriya
anisotropic term, fixed to realistic microscopic parameters for (IIB=Cd, Hg, Zn). We show that the dipolar Dzyaloshinskii-Moriya anisotropy
induces a finite-temperature phase transition to a spin glass phase, at
dilutions larger than 80%. The resulting probability distribution of the order
parameter P(q) is similar to the one found in the cubic lattice
Edwards-Anderson Ising model. The critical exponents undergo large finite size
corrections, but tend to values similar to the ones of the
Edwards-Anderson-Ising model.Comment: 4 pages plus 3 postscript figure
Measurement of the electric dipole moments for transitions to rubidium Rydberg states via Autler-Townes splitting
We present the direct measurements of electric-dipole moments for
transitions with for Rubidium atoms. The
measurements were performed in an ultracold sample via observation of the
Autler-Townes splitting in a three-level ladder scheme, commonly used for
2-photon excitation of Rydberg states. To the best of our knowledge, this is
the first systematic measurement of the electric dipole moments for transitions
from low excited states of rubidium to Rydberg states. Due to its simplicity
and versatility, this method can be easily extended to other transitions and
other atomic species with little constraints. Good agreement of the
experimental results with theory proves the reliability of the measurement
method.Comment: 12 pages, 6 figures; figure 6 replaced with correct versio
Reliability and Validity of a Self-paced Cardiopulmonary Exercise Test in Post-MI Patients
A self-paced peak oxygen uptake (V?O2peak) test (SPV) has been shown to produce higher V?O2peak values compared to standard cardiopulmonary exercise tests (sCPET), but has not been tested on any clinical population. This study aimed to assess the reliability of the SPV in a healthy population (study 1), and the validity and reliability of the SPV in post Myocardial Infarction (post-MI) patients (study 2). For study 1, twenty-five healthy participants completed three SPV’s. For study 2, twenty-eight post-MI patients completed one sCPET and two SPV’s. The SPV consisted of 5 x 2- min stages where participants were able to self-regulate their effort by using incremental ‘clamps’ in ratings of perceived exertion. The sCPET consisted of a 20 W/min ramp. Results demonstrated the SPV to have a coefficient of variation for V?O2peak of 4.7% for the healthy population, and 8.2% for the post-MI patients. Limits of agreement ranged between ± 4.22-5.86 ml·kg-1·min-1, with the intraclass correlation coefficient ranging between 0.89-0.95. In study 2, there was a significantly higher V?O2peak achieved in the SPV (23.07 ± 4.90 ml·kg-1·min-1) against the sCPET (21.29 ± 4.93 ml·kg-1·min-1). It is concluded that these results provide initial evidence that the SPV may be a safe, valid and reliable method for determining exercise capacity in post-MI patients
A Letter of Intent to Build a MiniBooNE Near Detector: BooNE
There is accumulating evidence for a difference between neutrino and
antineutrino oscillations at the eV scale. The MiniBooNE
experiment observes an unexplained excess of electron-like events at low
energies in neutrino mode, which may be due, for example, to either a neutral
current radiative interaction, sterile neutrino decay, or to neutrino
oscillations involving sterile neutrinos and which may be related to the LSND
signal. No excess of electron-like events (), however, is
observed so far at low energies in antineutrino mode. Furthermore, global 3+1
and 3+2 sterile neutrino fits to the world neutrino and antineutrino data
suggest a difference between neutrinos and antineutrinos with significant
() disappearance. In order to
test whether the low-energy excess is due to neutrino oscillations and whether
there is a difference between and disappearance, we
propose building a second MiniBooNE detector at (or moving the existing
MiniBooNE detector to) a distance of m from the Booster Neutrino
Beam (BNB) production target. With identical detectors at different distances,
most of the systematic errors will cancel when taking a ratio of events in the
two detectors, as the neutrino flux varies as to a calculable
approximation. This will allow sensitive tests of oscillations for both
and appearance and and disappearance.
Furthermore, a comparison between oscillations in neutrino mode and
antineutrino mode will allow a sensitive search for CP and CPT violation in the
lepton sector at short baseline ( eV).Comment: 43 pages, 40 figure
Epitaxial and layer-by-layer growth of EuO thin films on yttria-stabilized cubic zirconia (001) using MBE distillation
We have succeeded in growing epitaxial and highly stoichiometric films of EuO
on yttria-stabilized cubic zirconia (YSZ) (001). The use of the Eu-distillation
process during the molecular beam epitaxy assisted growth enables the
consistent achievement of stoichiometry. We have also succeeded in growing the
films in a layer-by-layer fashion by fine tuning the Eu vs. oxygen deposition
rates. The initial stages of growth involve the limited supply of oxygen from
the YSZ substrate, but the EuO stoichiometry can still be well maintained. The
films grown were sufficiently smooth so that the capping with a thin layer of
aluminum was leak tight and enabled ex situ experiments free from trivalent Eu
species. The findings were used to obtain recipes for better epitaxial growth
of EuO on MgO (001).Comment: 10 pages, 15 figure
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