5,059 research outputs found
Modified bubble level senses pitch and roll angles over wide range
Bubble level sensor with fiber-optic field flattener is simple, rugged, small, and impervious to temperature and vibration effects. Pitch angles from -15 deg to +40 deg and roll angles of +30 deg are determined within 0.5 deg
Epitaxial Growth of an n-type Ferromagnetic Semiconductor CdCr2Se4 on GaAs(001) and GaP(001)
We report the epitaxial growth of CdCr2Se4, an n-type ferromagnetic
semiconductor, on both GaAs and GaP(001) substrates, and describe the
structural, magnetic and electronic properties. Magnetometry data confirm
ferromagnetic order with a Curie temperature of 130 K, as in the bulk material.
The magnetization exhibits hysteretic behavior with significant remanence, and
an in-plane easy axis with a coercive field of ~125 Oe. Temperature dependent
transport data show that the films are semiconducting in character and n-type
as grown, with room temperature carrier concentrations of n ~ 1 x 10^18 cm-3.Comment: 12 pages, 3 figure
Doubly heavy quark baryon spectroscopy and semileptonic decay
Working in the framework of a nonrelativistic quark model we evaluate the
spectra and semileptonic decay widths for the ground state of doubly heavy
and baryons. We solve the three-body problem using a variational
ansatz made possible by the constraints imposed by heavy quark spin symmetry.
In order to check the dependence of our resultson the inter-quark interaction
we have used five different quarkquark potentials which include Coulomb and
hyperfine terms coming fromone-gluon exchange, plus a confining term. Our
results for the spectra are in good agreement with a previous calculation done
using a Faddeev approach. For the semileptonic decay our results for the total
decay widths are in a good agreement with the ones obtained within a
relativistic quark model in the quark-diquark approximation.Comment: Talk given at the IVth International Conference on Quarks an Nuclear
Physics (QNP06), Madrid, June 5th-10th 200
SELEX RICH Performance and Physics Results
SELEX took data in the 1996/7 Fixed Target Run at Fermilab. The excellent
performance parameters of the SELEX RICH Detector had direct influence on the
quality of the obtained physics results.Comment: Contributed talk at the Fourth Workshop on RICH Detectors, June 5-10,
2002, Pylos, Greece. Accepted for publication in NIM
Off-Equilibrium Dynamics in Finite-Dimensional Spin Glass Models
The low temperature dynamics of the two- and three-dimensional Ising spin
glass model with Gaussian couplings is investigated via extensive Monte Carlo
simulations. We find an algebraic decay of the remanent magnetization. For the
autocorrelation function a typical
aging scenario with a scaling is established. Investigating spatial
correlations we find an algebraic growth law of
the average domain size. The spatial correlation function scales with . The sensitivity of the
correlations in the spin glass phase with respect to temperature changes is
examined by calculating a time dependent overlap length. In the two dimensional
model we examine domain growth with a new method: First we determine the exact
ground states of the various samples (of system sizes up to )
and then we calculate the correlations between this state and the states
generated during a Monte Carlo simulation.Comment: 38 pages, RevTeX, 14 postscript figure
Ozone Depletion from Nearby Supernovae
Estimates made in the 1970's indicated that a supernova occurring within tens
of parsecs of Earth could have significant effects on the ozone layer. Since
that time, improved tools for detailed modeling of atmospheric chemistry have
been developed to calculate ozone depletion, and advances have been made in
theoretical modeling of supernovae and of the resultant gamma-ray spectra. In
addition, one now has better knowledge of the occurrence rate of supernovae in
the galaxy, and of the spatial distribution of progenitors to core-collapse
supernovae. We report here the results of two-dimensional atmospheric model
calculations that take as input the spectral energy distribution of a
supernova, adopting various distances from Earth and various latitude impact
angles. In separate simulations we calculate the ozone depletion due to both
gamma-rays and cosmic rays. We find that for the combined ozone depletion
roughly to double the ``biologically active'' UV flux received at the surface
of the Earth, the supernova must occur at <8 pc. Based on the latest data, the
time-averaged galactic rate of core-collapse supernovae occurring within 8 pc
is ~1.5/Gyr. In comparing our calculated ozone depletions with those of
previous studies, we find them to be significantly less severe than found by
Ruderman (1974), and consistent with Whitten et al. (1976). In summary, given
the amplitude of the effect, the rate of nearby supernovae, and the ~Gyr time
scale for multicellular organisms on Earth, this particular pathway for mass
extinctions may be less important than previously thought.Comment: 24 pages, 4 Postscript figures, to appear in The Astrophysical
Journal, 2003 March 10, vol. 58
Aging and memory effects in beta-hydrochinone-clathrate
The out-of-equilibrium low-frequency complex susceptibility of the
orientational glass methanol(73%)-beta-hydrochinone-clathrate is studied using
temperature-stop protocols in aging experiments . Although the material does
not have a sharp glass transition aging effects including rejuvenation and
memory are found at low temperatures. However, they turn out to be much weaker,
however, than in conventional magnetic spin glasses.Comment: 5 pages RevTeX, 6 eps-figures include
Chiral Multiplets of Heavy-Light Mesons
The recent discovery of a narrow resonance in D_s+pi^0 by the BABAR
collaboration is consistent with the interpretation of a heavy J^P(0+,1+) spin
multiplet. This system is the parity partner of the groundstate (0-,1-)
multiplet, which we argue is required in the implementation of SU(3)_L x
SU(3)_R chiral symmetry in heavy-light meson systems. The (0+,1+)->(0-,1-)+pi
transition couplings satisfy a Goldberger-Treiman relation, g_pi =
Delta(M)/f_pi, where Delta(M) is the mass gap. The BABAR resonance fits the 0+
state, with a kinematically blocked principal decay mode to D+K. The allowed
D_s+pi, D_s+2pi and electromagnetic transitions are computed from the full
chiral theory and found to be suppressed, consistent with the narrowness of the
state. This state establishes the chiral mass difference for all such
heavy-quark chiral multiplets, and precise predictions exist for the analogous
B_s and strange doubly-heavy baryon states.Comment: 10 pages; minor editorial revisions; recomputed M1 transitio
Spin-dependent electrical transport in ion-beam sputter deposited Fe-Cr multilayers
The temperature dependence of the electrical resistivity and
magnetoresistance of Xe-ion beam sputtered Fe-Cr multilayers has been
investigated. The electrical resistivity between 5 and 300 K in the fully
ferromagnetic state, obtained by applying a field beyond the saturation field
(H_sat) necessary for the antiferromagnetic(AF)-ferromagnetic(FM) field-induced
transition, shows evidence of spin-disorder resistivity as in crystalline Fe
and an s-d scattering contribution (as in 3d metals and alloys). The sublattice
magnetization m(T) in these multilayers has been calculated in terms of the
planar and interlayer exchange energies. The additional spin-dependent
scattering \Delta \rho (T) = \rho(T,H=0)_AF - \rho(T,H=H_sat)_FM in the AF
state over a wide range of temperature is found to be proportional to the
sublattice magnetization, both \Delta \rho(T) and m(T) reducing along with the
antiferromagnetic fraction. At intermediate fields, the spin-dependent part of
the electrical resistivity (\rho_s (T)) fits well to the power law \rho_s (T) =
b - cT^\alpha where c is a constant and b and \alpha are functions of H. At low
fields \alpha \approx 2 and the intercept b decreases with H much the same way
as the decrease of \Delta \rho (T) with T. A phase diagram (T vs. H_sat) is
obtained for the field- induced AF to FM transition. Comparisons are made
between the present investigation and similar studies using dc magnetron
sputtered and molecular beam epitaxy (MBE) grown Fe-Cr multilayers.Comment: 8 pages, 10 figures, to appear in Phys. Rev.
Validating a generic cancer consumer quality index in eight European countries, patient reported experiences and the influence of cultural differences
BackgroundTaking patient centeredness into account is important in healthcare. The European Cancer Consumer Quality Index (ECCQI) is a validated tool for international benchmarking of patient experiences and satisfaction.This study aimed to further validate the ECCQI in larger and more uniform groups of high volume tumours such as breast and prostate cancer. A second objective was the verification of the influence of cultural factors of the country to determine its possible use in international benchmarking.MethodsData from two survey studies in eight European countries were combined. Socio-demographic correlations were analysed with Kruskall-Wallis and Mann-Whitney tests. Cronbach's alpha was calculated to validate internal consistency. Influences of masculinity (MAS), power distance (PD) and uncertainty avoidance (UA) were determined by linear regression analysis in a general model and subgroup models.ResultsA total of 1322 surveys were included in the analysis (1093 breast- and 348 prostate cancer patients). Cronbach's alpha was good (alpha >= 0.7) or acceptable (0.5Peer reviewe
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