38,625 research outputs found
Aphidophagous Coccinellids in Alfalfa, Small Grains, and Maize in Eastern South Dakota
In a 13-year study of aphidophagous coccinellids associated with alfalfa (Medicago sativa), maize (Zea mays), and small grain crops in eastern South Dakota, the following species were consistently associated with the crops: Hippodamia convergens, H. tredecimpunctata tibialis, H. parenthesis, Coleomegilla maculata lengi, Coccinella transversoguttata richardsoni, Cycloneda munda, and Adalia bipunctata. All species except A. bipunctata were associated with each of the three crops, while A. bipunctata occurred only in maize. Relative abundances of each species varied among crops and among years. Although only seven species were associated with the crops, additional species were captured on sticky traps stationed adjacent to sampled fields. The species diversity of immature coccinellids did not differ among crops but did differ among years. The diversity of adults differed among crops and years. The site from which samples were taken had no influence on the diversity of immatures or adults. Species relative abundances in alfalfa and small grains were more similar to each other than they were to relative abundances in maize
Prospective cognitions in anxiety and depression: Replication and methodological extension
The present study presents a replication and methodological extension of MacLeod, Tata, Kentish, and Jacobsen (1997) with a nonclinical sample, using future-directed imagery to assess prospective cognitions. Results showed that only anxiety (but not depression) was related to enhanced imagery for future negative events. Both anxiety and depression showed significant zero-order correlations with reduced imagery for future positive events. However, when the overlap between anxiety and depression was controlled for, only depression (but not anxiety) showed a unique association with reduced imagery for positive events. Implications of these findings for cognitive models of anxiety and depression are discussed
A Descriptive Study of the Population Dynamics of Adult \u3ci\u3eDiabrotica Virgifera Virgifera\u3c/i\u3e (Coleoptera: Chrysomelidae) in Artificially Infested Corn Fields
The influence of corn plant phenology on the dynamics of adult western corn rootworm, Diabrotica virgifera virgifera, populations was studied during 1988 and 1989 in com fields artificially infested with eggs. Fifty percent of adult emergence from the soil occurred by day 194 in 1988 and day 203 in 1989. In both years, adult emergence was synchronized with corn flowering, eggs were recovered in soil samples approximately four days after reproductive females were first observed in the population, and oviposition was essentially complete about 25 days after it began. The number of reproductive female beetle-days accumulating per m2 was similar in both years. Approximately two times as many eggs were laid in 1988 (1239 eggs 1m2) as in 1989 (590 eggs 1m2). The difference in egg density may have been caused by differences among years in the temporal synchrony of reproductive beetles with flowering corn. Daily survival rates of adults were high while corn was flowering; exhibited a gradual decline during grain filling; and decreased rapidly during the grain drying stage
Superstatistics, thermodynamics, and fluctuations
A thermodynamic-like formalism is developed for superstatistical systems
based on conditional entropies. This theory takes into account large-scale
variations of intensive variables of systems in nonequilibrium stationary
states. Ordinary thermodynamics is recovered as a special case of the present
theory, and corrections to it can be systematically evaluated. A generalization
of Einstein's relation for fluctuations is presented using a maximum entropy
condition.Comment: 16 pages, no figures. The title changed, some explanations and
references added. Accepted for publication in Phys. Rev.
Models and Strategies for Variants of the Job Shop Scheduling Problem
Recently, a variety of constraint programming and Boolean satisfiability
approaches to scheduling problems have been introduced. They have in common the
use of relatively simple propagation mechanisms and an adaptive way to focus on
the most constrained part of the problem. In some cases, these methods compare
favorably to more classical constraint programming methods relying on
propagation algorithms for global unary or cumulative resource constraints and
dedicated search heuristics. In particular, we described an approach that
combines restarting, with a generic adaptive heuristic and solution guided
branching on a simple model based on a decomposition of disjunctive
constraints. In this paper, we introduce an adaptation of this technique for an
important subclass of job shop scheduling problems (JSPs), where the objective
function involves minimization of earliness/tardiness costs. We further show
that our technique can be improved by adding domain specific information for
one variant of the JSP (involving time lag constraints). In particular we
introduce a dedicated greedy heuristic, and an improved model for the case
where the maximal time lag is 0 (also referred to as no-wait JSPs).Comment: Principles and Practice of Constraint Programming - CP 2011, Perugia
: Italy (2011
Coulomb Charging Effects for Finite Channel Number
We consider quantum fluctuations of the charge on a small metallic grain
caused by virtual electron tunneling to a nearby electrode. The average
electron number and the effective charging energy are determined by means of
perturbation theory in the tunneling Hamiltonian. In particular we discuss the
dependence of charging effects on the number N of tunneling channels. Earlier
results for N>>1 are found to be approached rather rapidly with increasing N.Comment: 6 pages, 5 figure
The population of deformed bands in Cr by emission of Be from the S + Mg reaction
Using particle- coincidences we have studied the population of final
states after the emission of 2 -particles and of Be in nuclei
formed in S+Mg reactions at an energy of . The data were obtained in a setup
consisting of the GASP -ray detection array and the multidetector array
ISIS. Particle identification is obtained from the E and E signals of
the ISIS silicon detector telescopes, the Be being identified by the
instantaneous pile up of the E and E pulses. -ray decays of the
Cr nucleus are identified with coincidences set on 2 -particles
and on Be. Some transitions of the side-band with show
stronger population for Be emission relative to that of 2
-particles (by a factor ). This observation is interpreted as
due to an enhanced emission of Be into a more deformed nucleus.
Calculations based on the extended Hauser-Feshbach compound decay formalism
confirm this observation quantitatively.Comment: 17 pages, 9 figures accepted for publication in J. Phys.
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