3,206 research outputs found
Integration of environmental and spectral data for sunflower stress determination
Stress in sunflowers was assessed in western and northwestern Minnesota. Weekly ground observations (acquired in 1980 and 1981) were analyzed in concert with large scale aerial photography and concurrent LANDSAT data. Using multidate supervised and unsupervised classification procedures, it was found that all crops grown in association with sunflowers in the study area are spectrally separable from one another. Under conditions of extreme drought, severely stressed plants were differentiable from those not severely stressed, but between-crop separation was not possible. Initial regression analyses to estimate sunflower seed yield showed a sensitivity to environmental stress during the flowering and seed development stages. One of the most important biological factors related to sunflower production in the Red River Valley area was found to be the extent and severity of insect infestations
Quiet engine program flight engine design study
The results are presented of a preliminary flight engine design study based on the Quiet Engine Program high-bypass, low-noise turbofan engines. Engine configurations, weight, noise characteristics, and performance over a range of flight conditions typical of a subsonic transport aircraft were considered. High and low tip speed engines in various acoustically treated nacelle configurations were included
The Bravyi-Kitaev transformation for quantum computation of electronic structure
Quantum simulation is an important application of future quantum computers
with applications in quantum chemistry, condensed matter, and beyond. Quantum
simulation of fermionic systems presents a specific challenge. The
Jordan-Wigner transformation allows for representation of a fermionic operator
by O(n) qubit operations. Here we develop an alternative method of simulating
fermions with qubits, first proposed by Bravyi and Kitaev [S. B. Bravyi, A.Yu.
Kitaev, Annals of Physics 298, 210-226 (2002)], that reduces the simulation
cost to O(log n) qubit operations for one fermionic operation. We apply this
new Bravyi-Kitaev transformation to the task of simulating quantum chemical
Hamiltonians, and give a detailed example for the simplest possible case of
molecular hydrogen in a minimal basis. We show that the quantum circuit for
simulating a single Trotter time-step of the Bravyi-Kitaev derived Hamiltonian
for H2 requires fewer gate applications than the equivalent circuit derived
from the Jordan-Wigner transformation. Since the scaling of the Bravyi-Kitaev
method is asymptotically better than the Jordan-Wigner method, this result for
molecular hydrogen in a minimal basis demonstrates the superior efficiency of
the Bravyi-Kitaev method for all quantum computations of electronic structure
Early Interferon-γ Production in Human Lymphocyte Subsets in Response to Nontyphoidal Salmonella Demonstrates Inherent Capacity in Innate Cells
Background
Nontyphoidal Salmonellae frequently cause life-threatening bacteremia in sub-Saharan Africa. Young children and HIV-infected adults are particularly susceptible. High case-fatality rates and increasing antibiotic resistance require new approaches to the management of this disease. Impaired cellular immunity caused by defects in the T helper 1 pathway lead to intracellular disease with Salmonella that can be countered by IFNγ administration. This report identifies the lymphocyte subsets that produce IFNγ early in Salmonella infection.
Methodology
Intracellular cytokine staining was used to identify IFNγ production in blood lymphocyte subsets of ten healthy adults with antibodies to Salmonella (as evidence of immunity to Salmonella), in response to stimulation with live and heat-killed preparations of the D23580 invasive African isolate of Salmonella Typhimurium. The absolute number of IFNγ-producing cells in innate, innate-like and adaptive lymphocyte subpopulations was determined.
Principal Findings
Early IFNγ production was found in the innate/innate-like lymphocyte subsets: γδ-T cells, NK cells and NK-like T cells. Significantly higher percentages of such cells produced IFNγ compared to adaptive αβ-T cells (Student's t test, P<0.001 and ≤0.02 for each innate subset compared, respectively, with CD4+- and CD8+-T cells). The absolute numbers of IFNγ-producing cells showed similar differences. The proportion of IFNγ-producing γδ-T cells, but not other lymphocytes, was significantly higher when stimulated with live compared with heat-killed bacteria (P<0.0001).
Conclusion/Significance
Our findings indicate an inherent capacity of innate/innate-like lymphocyte subsets to produce IFNγ early in the response to Salmonella infection. This may serve to control intracellular infection and reduce the threat of extracellular spread of disease with bacteremia which becomes life-threatening in the absence of protective antibody. These innate cells may also help mitigate against the effect on IFNγ production of depletion of Salmonella-specific CD4+-T lymphocytes in HIV infection
Lifshitz fermionic theories with z=2 anisotropic scaling
We construct fermionic Lagrangians with anisotropic scaling z=2, the natural
counterpart of the usual z=2 Lifshitz field theories for scalar fields. We
analyze the issue of chiral symmetry, construct the Noether axial currents and
discuss the chiral anomaly giving explicit results for two-dimensional case. We
also exploit the connection between detailed balance and the dynamics of
Lifshitz theories to find different z=2 fermionic Lagrangians and construct
their supersymmetric extensions.Comment: Typos corrected, comment adde
Honey bee foraging distance depends on month and forage type
To investigate the distances at which honey bee foragers collect nectar and pollen, we analysed 5,484 decoded waggle dances made to natural forage sites to determine monthly foraging distance for each forage type. Firstly, we found significantly fewer overall dances made for pollen (16.8 %) than for non-pollen, presumably nectar (83.2 %; P < 2.2 × 10−23). When we analysed distance against month and forage type, there was a significant interaction between the two factors, which demonstrates that in some months, one forage type is collected at farther distances, but this would reverse in other months. Overall, these data suggest that distance, as a proxy for forage availability, is not significantly and consistently driven by need for one type of forage over the other
Entropy, Dynamics and Instantaneous Normal Modes in a Random Energy Model
It is shown that the fraction f of imaginary frequency instantaneous normal
modes (INM) may be defined and calculated in a random energy model(REM) of
liquids. The configurational entropy S and the averaged hopping rate among the
states R are also obtained and related to f, with the results R~f and
S=a+b*ln(f). The proportionality between R and f is the basis of existing INM
theories of diffusion, so the REM further confirms their validity. A link to S
opens new avenues for introducing INM into dynamical theories. Liquid 'states'
are usually defined by assigning a configuration to the minimum to which it
will drain, but the REM naturally treats saddle-barriers on the same footing as
minima, which may be a better mapping of the continuum of configurations to
discrete states. Requirements of a detailed REM description of liquids are
discussed
Strong ellipticity and spectral properties of chiral bag boundary conditions
We prove strong ellipticity of chiral bag boundary conditions on even
dimensional manifolds. From a knowledge of the heat kernel in an infinite
cylinder, some basic properties of the zeta function are analyzed on
cylindrical product manifolds of arbitrary even dimension.Comment: 16 pages, LaTeX, References adde
Pole structure of the Hamiltonian -function for a singular potential
We study the pole structure of the -function associated to the
Hamiltonian of a quantum mechanical particle living in the half-line
, subject to the singular potential . We show that
admits nontrivial self-adjoint extensions (SAE) in a given range of values
of the parameter . The -functions of these operators present poles
which depend on and, in general, do not coincide with half an integer (they
can even be irrational). The corresponding residues depend on the SAE
considered.Comment: 12 pages, 1 figure, RevTeX. References added. Version to appear in
Jour. Phys. A: Math. Ge
Heat kernel of non-minimal gauge field kinetic operators on Moyal plane
We generalize the Endo formula originally developed for the computation of
the heat kernel asymptotic expansion for non-minimal operators in commutative
gauge theories to the noncommutative case. In this way, the first three
non-zero heat trace coefficients of the non-minimal U(N) gauge field kinetic
operator on the Moyal plane taken in an arbitrary background are calculated. We
show that the non-planar part of the heat trace asymptotics is determined by
U(1) sector of the gauge model. The non-planar or mixed heat kernel
coefficients are shown to be gauge-fixing dependent in any dimension of
space-time. In the case of the degenerate deformation parameter the lowest
mixed coefficients in the heat expansion produce non-local gauge-fixing
dependent singularities of the one-loop effective action that destroy the
renormalizability of the U(N) model at one-loop level. The twisted-gauge
transformation approach is discussed.Comment: 21 pages, misprints correcte
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