40,589 research outputs found
Scotch Pine Deterioration in Michigan Caused by Pine Root Weevil Complex
Pine root tip weevil, Hylobius rhizophagus, and pine root collar weevil, H. radicis, attack certain Scotch pine stands simultaneously causing more mortality than expected from either insect alone. Recommendations for curtailing this insect complex include favoring red pine, planting Scotch pine far from brood sources, and avoiding stump culture of Christmas trees
Constraints on Radial Migration in Spiral Galaxies - II. Angular momentum distribution and preferential migration
The orbital angular momentum of individual stars in galactic discs can be
permanently changed through torques from transient spiral patterns.
Interactions at the corotation resonance dominate these changes and have the
further property of conserving orbital circularity. We derived in an earlier
paper an analytic criterion that an unperturbed stellar orbit must satisfy in
order for such an interaction to occur i.e. for it to be in a trapped orbit
around corotation. We here use this criterion in an investigation of how the
efficiency of induced radial migration for a population of disc stars varies
with the angular momentum distribution of that population. We frame our results
in terms of the velocity dispersion of the population, this being an easier
observable than is the angular momentum distribution. Specifically, we
investigate how the fraction of stars in trapped orbits at corotation varies
with the velocity dispersion of the population, for a system with an assumed
flat rotation curve. Our analytic results agree with the finding from
simulations that radial migration is less effective in populations with
'hotter' kinematics. We further quantify the dependence of this trapped
fraction on the strength of the spiral pattern, finding a higher trapped
fraction for higher amplitude perturbations.Comment: 28 pages, 15 figure, accepted for publication in MNRA
Aspects of asymptotic safety for quantum gravity
We study fixed points of quantum gravity with renormalisation group methods,
and a procedure to remove convergence-limiting poles from the flow. The setup
is tested within the approximation for gravity by solving exact
recursive relations up to order in the Ricci scalar, combined with
resummations and numerical integration. Results include fixed points, scaling
exponents, gap in the eigenvalue spectrum, dimensionality of the UV critical
surface, fingerprints for weak coupling, and quantum equations of motion. Our
findings strengthen the view that ``most of quantum gravity'' is rather weakly
coupled. Another novelty are a pair of de Sitter solutions for quantum
cosmology, whose occurrence is traced back to the removal of poles. We also
address slight disparities of results in the literature, and give bounds on the
number of fundamentally free parameters of quantum gravity.Comment: 29 pages, 7 figures, v2: explanations added, to appear with PR
Michigan\u27s Cooperative Forest Pest Management Program, A Team Approach to Improving Forest Management
A forest management team was organized in the late 1970\u27s by cooperative efforts of Michigan\u27s universities. the Michigan Department of Natural Resources, and the USDA Forest Service.The goals were to devise new technologies, transfer available technology, and service and management alternatives to forest land managers in Michigan. The program throughout has emphasized forest management rather than pest management for prevention and control of pests. Dissemination of pest management information has been of importance and new research results have gone directly to land managers for immediate use. The team participates in forest compartmental reviews and helps prescribe management plans for land parcels, thus providing for preventative pest management. Services and management recommendations are provided mostly through forest pest specialists located in the field. They feed back results and problems to researchers and extension specialists of the team for further input. Preventive management information used by by local managers in recent years has nearly paid the cost of the program. Plans are to broaden the team effort by cooperating with organizations and in adjacent states through a computer network system and by other means
Atomic vapor-based high efficiency optical detectors with photon number resolution
We propose a novel approach to the important fundamental problem of detecting
weak optical fields at the few photon level. The ability to detect with high
efficiency (>99%), and to distinguish the number of photons in a given time
interval is a very challenging technical problem with enormous potential
pay-offs in quantum communications and information processing. Our proposal
diverges from standard solid-state photo-detector technology by employing an
atomic vapor as the active medium, prepared in a specific quantum state using
laser radiation. The absorption of a photon will be aided by a dressing laser,
and the presence or absence of an excited atom will be detected using the
``cycling transition'' approach perfected for ion traps. By first incorporating
an appropriate upconversion scheme, our method can be applied to a wide variety
of optical wavelengths.Comment: 4 pages, 2 figure
Changes in Pain Perception in Women During and Following an Exhaustive Incremental Cycling Exercise
Exercise has been found to alter pain sensitivity with a hypoalgesic response (i.e., diminished sensitivity to pain) typically reported during and/or following high intensity exercise. Most of this research, however, has involved the testing of men. Thus, the purpose of the following investigation was to examine changes in pain perception in women during and following exercise. Seventeen healthy female subjects (age 20.47±.87; VO2 peak 36.77± 4.95) volunteered to undergo pain assessment prior to, during, and after a graded exhaustive VO2 peak cycling challenge. Heart Rate (HR) and Oxygen Uptake (VO2) were monitored along with electro-diagnostic assessments of Pain Threshold (PT) and Pain Tolerance (PTOL) at: 1) baseline (B), 2) during exercise (i.e., 120 Watts), 3) at exhaustive intensity (VO2 peak), and 4) 10 minutes into recovery (R). Data were analyzed using repeated measures ANOVA to determine differences across trials. Significant differences in PT and PTOL were found across trials (PT, p = 0.0043; PTOL p = 0.0001). Post hoc analyses revealed that PT were significantly elevated at VO2 peak in comparison to B (p = 0.007), 120 Watts (p = 0.0178) and R (p = 0.0072). PTOL were found to be significantly elevated at 120 Watts (p = 0.0247), VO2 peak (p \u3c 0.001), and R (p = 0.0001) in comparison to B. In addition, PTOL were found to be significantly elevated at VO2 peak in comparison to 120 Watts (p = 0.0045). It is concluded that exercise-induced hypoalgesia occurs in women during and following exercise, with the hypoalgesic response being most pronounced following exhaustive exercise
Scale-Invariant Curvature Fluctuations from an Extended Semiclassical Gravity
We present an extension of the semiclassical Einstein equations which couples
n-point correlation functions of a stochastic Einstein tensor to the n-point
functions of the quantum stress-energy tensor. We apply this extension to
calculate the quantum fluctuations during an inflationary period, where we take
as a model a massive conformally coupled scalar field on a perturbed de Sitter
space and describe how a renormalization independent, almost-scale-invariant
power spectrum of the scalar metric perturbation is produced. Furthermore, we
discuss how this model yields a natural basis for the calculation of
non-Gaussianities of the considered metric fluctuations.Comment: 16 pages, 2 figures; final versio
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