286 research outputs found
Review of Eustochus, a rarely collected genus of Mymaridae (Hymenoptera)
The four nominal species of Eustochus are reviewed. Four new species, E. confusus from Spain, E. pengellyi and E. yoshimotoi from North America, and E. nipponicus from Japan are described and a key to the eight species is given
Size and shape analysis of error-prone shape data
We consider the problem of comparing sizes and shapes of objects when landmark data are prone to measurement error. We show that naive implementation of ordinary Procrustes analysis that ignores measurement error can compromise inference. To account for measurement error, we propose the conditional score method for matching configurations, which guarantees consistent inference under mild model assumptions. The effects of measurement error on inference from naive Procrustes analysis and the performance of the proposed method are illustrated via simulation and application in three real data examples. Supplementary materials for this article are available online
Effects of site dilution on the magnetic properties of geometrically frustrated antiferromagnets
The effect of site dilution by non magnetic impurities on the susceptibility
of geometrically frustrated antiferromagnets (kagome and pyrochlore lattices)
is discussed in the framework of the Generalized Constant Coupling model, for
both classical and quantum Heisenberg spins. For the classical diluted
pyrochlore lattice, excellent agreement is found when compared with Monte Carlo
data. Results for the quantum case are also presented and discussed.Comment: 5 pages, 3 figure
The transient complex of cytochrome c and cytochrome c peroxidase: insights into the encounter complex from multifrequency EPR and NMR spectroscopy
Biological and Soft Matter Physic
The reaction in ion-ion collisions
We study the threshold -meson production in the process , which appears as a possible important mechanism in high energy
nuclei-nuclei collisions. The isotopic invariance of the strong interaction and
the selection rules due to P-parity and total angular momentum result in a
general and model independent parametrization of the spin structure of the
matrix element in terms of three partial amplitudes. In the framework of
one-pion exchange model these amplitudes can be derived in terms of the two
threshold partial amplitudes for the process . We predict the
ratio of cross sections for meson production in - and -collisions and the polarization properties of the -meson, in
, as a function of a single parameter, which
characterizes the relative role of transversal and longitudinal -meson
polarizations in the process .Comment: 10 pages 3 figure
Confusing non-standard neutrino interactions with oscillations at a neutrino factory
Most neutrino mass theories contain non-standard interactions (NSI) of
neutrinos which can be either non-universal (NU) or flavor-changing (FC). We
study the impact of such interactions on the determination of neutrino mixing
parameters at a neutrino factory using the so-called ``golden channels''
\pnu{e}\to\pnu{\mu} for the measurement of \theta_{13}. We show that a certain
combination of FC interactions in neutrino source and earth matter can give
exactly the same signal as oscillations arising due to \theta_{13}. This
implies that information about \theta_{13} can only be obtained if bounds on
NSI are available. Taking into account the existing bounds on FC interactions,
this leads to a drastic loss in sensitivity in \theta_{13}, at least two orders
of magnitude. A near detector at a neutrino factory offers the possibility to
obtain stringent bounds on some NSI parameters. Such near site detector
constitutes an essential ingredient of a neutrino factory and a necessary step
towards the determination of \theta_{13} and subsequent study of leptonic CP
violation.Comment: 23 pages, 5 figures, improved version, accepted for publication in
Phs. Rev. D, references adde
Finite Temperature Properties of Quantum Antiferromagnets in a Uniform Magnetic Field in One and Two Dimensions
Consider a -dimensional antiferromagnet with a quantum disordered ground
state and a gap to bosonic excitations with non-zero spin. In a finite external
magnetic field, this antiferromagnet will undergo a phase transition to a
ground state with non-zero magnetization, describable as the condensation of a
dilute gas of bosons. The finite temperature properties of the Bose gas in the
vicinity of this transition are argued to obey a hypothesis of ZERO
SCALE-FACTOR UNIVERSALITY for , with logarithmic violations in .
Scaling properties of various experimental observables are computed in an
expansion in , and exactly in .Comment: 27 pages, REVTEX 3.0, 8 Postscript figures appended, YCTP-xyz
Designing spin-spin interactions with one and two dimensional ion crystals in planar micro traps
We discuss the experimental feasibility of quantum simulation with trapped
ion crystals, using magnetic field gradients. We describe a micro structured
planar ion trap, which contains a central wire loop generating a strong
magnetic gradient of about 20 T/m in an ion crystal held about 160 \mu m above
the surface. On the theoretical side, we extend a proposal about spin-spin
interactions via magnetic gradient induced coupling (MAGIC) [Johanning, et al,
J. Phys. B: At. Mol. Opt. Phys. 42 (2009) 154009]. We describe aspects where
planar ion traps promise novel physics: Spin-spin coupling strengths of
transversal eigenmodes exhibit significant advantages over the coupling schemes
in longitudinal direction that have been previously investigated. With a chip
device and a magnetic field coil with small inductance, a resonant enhancement
of magnetic spin forces through the application of alternating magnetic field
gradients is proposed. Such resonantly enhanced spin-spin coupling may be used,
for instance, to create Schr\"odinger cat states. Finally we investigate
magnetic gradient interactions in two-dimensional ion crystals, and discuss
frustration effects in such two-dimensional arrangements.Comment: 20 pages, 13 figure
Clinical mastitis in cows treated with sometribove (recombinant bovine somatotropin) and its relationship to milk yield.
Effect of sometribove (methionyl bovine somatotropin) on mastitis in 15 full lactation trials (914 cows) in Europe and the US and 70 short-term studies (2697 cows) in eight countries was investigated. In full lactation studies, sometribove (500 mg/2 wk) was given for 252 d, commencing 60 d postpartum. Although herds varied considerably, incidence of clinical mastitis within a herd was similar for cows receiving control and sometribove treatments. Relative risk analyses indicated no treatment effect, and percentage of mastitis during treatment was similar for control and sometribove groups. A positive linear relationship existed between peak milk yield and mastitis incidence (percentage of cows contracting mastitis or cases per 100 cow days); sometribove treatment did not alter this relationship. Increases in mastitis related to milk yield increase from sometribove or related to genetic selection were similar. When expressed per unit of milk, mastitis incidence declined slightly as milk yield increased; this relationship was not altered by sometribove. No effect on clinical mastitis was observed in 70 commercial herds utilizing sometribove for 84 d. However, effects were significant for stage of lactation and milk yield. Overall, studies represented a wide range of research and commercial situations demonstrating that sometribove had no effect on incidence of clinical mastitis during the lactation of treatment. Furthermore, sometribove did not alter typical relationships between milk yield or herd factors and incidence of clinical mastitis
Theory of Two-Dimensional Quantum Heisenberg Antiferromagnets with a Nearly Critical Ground State
We present the general theory of clean, two-dimensional, quantum Heisenberg
antiferromagnets which are close to the zero-temperature quantum transition
between ground states with and without long-range N\'{e}el order. For
N\'{e}el-ordered states, `nearly-critical' means that the ground state
spin-stiffness, , satisfies , where is the
nearest-neighbor exchange constant, while `nearly-critical' quantum-disordered
ground states have a energy-gap, , towards excitations with spin-1,
which satisfies . Under these circumstances, we show that the
wavevector/frequency-dependent uniform and staggered spin susceptibilities, and
the specific heat, are completely universal functions of just three
thermodynamic parameters. Explicit results for the universal scaling functions
are obtained by a expansion on the quantum non-linear sigma model,
and by Monte Carlo simulations. These calculations lead to a variety of
testable predictions for neutron scattering, NMR, and magnetization
measurements. Our results are in good agreement with a number of numerical
simulations and experiments on undoped and lightly-doped .Comment: 81 pages, REVTEX 3.0, smaller updated version, YCTP-xxx
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