10,433 research outputs found
Control of Aphids on Spring Oats and Winter Wheat With Slow Release Granular Systemic Insecticides
Aphid infestations (Homoptera: Aphididae) on spring oat (Avena sativa) cv. \u27Ogle\u27, and during the fall on winter wheat (Triticum aestivum) cv. \u27Clark\u27, composed mainly of Rhopalosiphum padi and Macrosiphum avenae, were reduced with applications at the 2-3 leaf stage of slow release granular formulations of acephate, carbofuran, and disulfoton, compared with carbofuran 15G and untreated controls, in field trials during 1990-1991 in northwestern Indiana. These field results corroborated those obtained by previous studies with the same formulations and dosages in the laboratory.
In oat, all insecticide treatments reduced aphid populations and percent- age aphid~infested plants, with a residual action of ca. 25 d. Barley yellow dwarf virus-like visual symptoms were reduced with disulfoton. In winter wheat, the residual action of all insecticide treatments in the fall lasted up to 19 d. The carbofuran treatment on winter wheat seedlings caused earthworms to move out of the soil, where they died; an effect requirining further study. Percentage of aphid-infested plants revealed relatively Wlder differences among tratments than total number of aphids in both test crops. Predation by Coleomegilla maculata (Coleoptera: Coccinellidae) contributed to the overall reduction of spring populations of cereal aphids in wheat and oat. Aphid mummies parasitized by micro-hymenopterans were common in oat plants
The role of expectations in an adaptive search model
The purpose of this paper is to find sufficient conditions under which the results of the simple search model are preserved when learning is allowed. It is shown that the properties of the simple search model are preserved with very simple assumptions. Intuitively, we need a non explosive agent. That is, expectations must be smooth.
Impact of Cosmic Variance on the Galaxy-Halo Connection for Lyman- Emitters
In this paper we study the impact of cosmic variance and observational
uncertainties in constraining the mass and occupation fraction, ,
of dark matter halos hosting Ly- Emitting Galaxies (LAEs) at high
redshift. To this end, we construct mock catalogs from an N-body simulation to
match the typical size of observed fields at (). In
our model a dark matter halo with mass in the range can only host one detectable LAE at most. We proceed to explore
the parameter space determined by , and
with a Markov Chain Monte-Carlo algorithm using the angular correlation
function (ACF) and the LAEs number density as observational constraints. We
find that the preferred minimum and maximum masses in our model span a wide
range , ; followed by a wide range in the
occupation fraction . As a consequence the
median mass, , of all the consistent models has a large uncertainty
. However,
we find that the same individual models have a relatively tight
scatter around the median mass dex.
We are also able to show that \focc\ is uniquely determined by ,
regardless of . We argue that upcoming large surveys covering at
least deg should be able to put tighter constraints on
and through the LAE number density distribution width constructed
over several fields of deg.Comment: 7 Pages, 5 figures. Accepted for publication in Ap
Non-equilibrium behavior at a liquid-gas critical point
Second-order phase transitions in a non-equilibrium liquid-gas model with
reversible mode couplings, i.e., model H for binary-fluid critical dynamics,
are studied using dynamic field theory and the renormalization group. The
system is driven out of equilibrium either by considering different values for
the noise strengths in the Langevin equations describing the evolution of the
dynamic variables (effectively placing these at different temperatures), or
more generally by allowing for anisotropic noise strengths, i.e., by
constraining the dynamics to be at different temperatures in d_par- and
d_perp-dimensional subspaces, respectively. In the first, case, we find one
infrared-stable and one unstable renormalization group fixed point. At the
stable fixed point, detailed balance is dynamically restored, with the two
noise strengths becoming asymptotically equal. The ensuing critical behavior is
that of the standard equilibrium model H. At the novel unstable fixed point,
the temperature ratio for the dynamic variables is renormalized to infinity,
resulting in an effective decoupling between the two modes. We compute the
critical exponents at this new fixed point to one-loop order. For model H with
spatially anisotropic noise, we observe a critical softening only in the
d_perp-dimensional sector in wave vector space with lower noise temperature.
The ensuing effective two-temperature model H does not have any stable fixed
point in any physical dimension, at least to one-loop order. We obtain formal
expressions for the novel critical exponents in a double expansion about the
upper critical dimension d_c = 4 - d_par and with respect to d_par, i.e., about
the equilibrium theory.Comment: 17 pages, revtex, one figure and EPJB style files include
Spokes cluster: The search for the quiescent gas
Context. Understanding the role of fragmentation is one of the most important
current questions of star formation. To better understand the process of star
and cluster formation, we need to study in detail the physical structure and
properties of the parental molecular cloud. The Spokes cluster, or NGC 2264 D,
is a rich protostellar cluster where previous N2H+(1-0) observations of its
dense cores presented linewidths consistent with supersonic turbulence.
However, the fragmentation of the most massive of these cores appears to have a
scale length consistent with that of the thermal Jeans length, suggesting that
turbulence was not dominant. Aims. These two results probe different density
regimes. Our aim is to determine if there is subsonic or less-turbulent gas
(than previously reported) in the Spokes cluster at higher densities. Methods.
We present APEX N2H+(3-2) and N2D+(3-2) observations of the NGC2264-D region to
measure the linewidths and the deuteration fraction of the higher density gas.
The critical densities of the selected transitions are more than an order of
magnitude higher than that of N2H+(1-0). Results. We find that the N2H+(3-2)
and N2D+(3-2) emission present significantly narrower linewidths than the
emission from N2H+(1-0) for most cores. In two of the spectra, the nonthermal
component is close (within 1-sigma) to the sound speed. In addition, we find
that the three spatially segregated cores, for which no protostar had been
confirmed show the highest levels of deuteration. Conclusions. These results
show that the higher density gas, probed with N2H+ and N2D+(3-2), reveals more
quiescent gas in the Spokes cluster than previously reported. More high-angular
resolution interferometric observations using high-density tracers are needed
to truly assess the kinematics and substructure within NGC2264-D. (Abridged)Comment: 8 pages, 4 figures. Accepted in A&
Resistance Stability of the Secondary Tiller of \u27Caldwell\u27 Wheat After the Primary Culm Was Infested With Virulent Hessian Fly (Diptera: Cecidomyiidae) Larvae
Secondary tiller resistance of \u27Caldwell\u27 wheat, Triticum aestivum, with the H6 gene for larval resistance to Hessian fly, Mayetiola destructor, was maintained, after the primary culm had been previously infested with virulent larvae. Earlier studies showed that a primary culm infested initially with a virulent larva allowed subsequent normally avirulent larvae to survive on that cultivar; however, in our study the resistance of secondary tillers was mainained even though the primary culm was infested earlier with virulent Hessian fly larvae. This gene stability for resistance is important for optimizing wheat yield of those cultivars that possess genes resistant to the Hessian fly that are tillering and infested with different biotypes
Grain Sorghum International Trade: U.S.-Mexico Simulation and Estimation Model
An econometric international supply/demand/trade simulation and forecast sorghum model in a partial equilibrium framework is built in this research paper to quantify the effects of key exogenous variables on the U.S.-Mexico sorghum trade. A forecast baseline is also established by using the validated model and values of exogenous variables provided by FAPRI to project the level of endogenous variables over the period of 2009 to 2017. Impacts of plausible alternative scenarios for key exogenous variables are simulated from 2009 to 2017.Sorghum, International Trade, Simulation, Estimation, International Relations/Trade,
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