8,338 research outputs found
Impulse approximation in the n p --> d pi^0 reaction reexamined
The impulse approximation (one-body operator) in the n p --> d pi^0 reaction
is reexamined with emphasis on the issues of reducibility and recoil
corrections. An inconsistency when one pion exchange is included in the
production operator is demonstrated and then resolved via the introduction of
"wave function corrections" which nearly vanish for static nucleon propagators.
Inclusion of the recoil corrections to the nucleon propagators is found to
change the magnitude and sign of the impulse production amplitude, worsening
agreement with the experimental cross section by approximately 30%. A cutoff is
used to account for the phenomenological nature of the external wave functions,
and is found to have a significant impact up to approximately 2.5 GeV.Comment: Published versio
Genome Assembly Improvement and Mapping Convergently Evolved Skeletal Traits in Sticklebacks with Genotyping-by-Sequencing.
Marine populations of the threespine stickleback (Gasterosteus aculeatus) have repeatedly colonized and rapidly adapted to freshwater habitats, providing a powerful system to map the genetic architecture of evolved traits. Here, we developed and applied a binned genotyping-by-sequencing (GBS) method to build dense genome-wide linkage maps of sticklebacks using two large marine by freshwater F2 crosses of more than 350 fish each. The resulting linkage maps significantly improve the genome assembly by anchoring 78 new scaffolds to chromosomes, reorienting 40 scaffolds, and rearranging scaffolds in 4 locations. In the revised genome assembly, 94.6% of the assembly was anchored to a chromosome. To assess linkage map quality, we mapped quantitative trait loci (QTL) controlling lateral plate number, which mapped as expected to a 200-kb genomic region containing Ectodysplasin, as well as a chromosome 7 QTL overlapping a previously identified modifier QTL. Finally, we mapped eight QTL controlling convergently evolved reductions in gill raker length in the two crosses, which revealed that this classic adaptive trait has a surprisingly modular and nonparallel genetic basis
Distance measures in gravitational-wave astrophysics and cosmology
We present quantities which characterize the sensitivity of
gravitational-wave observatories to sources at cosmological distances. In
particular, we introduce and generalize the horizon, range, response, and reach
distances. These quantities incorporate a number of important effects,
including cosmologically well-defined distances and volumes, cosmological
redshift, cosmological time dilation, and rate density evolution. In addition,
these quantities incorporate unique aspects of gravitational wave detectors,
such as the variable sky sensitivity of the detectors and the scaling of the
sensitivity with inverse distance. An online calculator
(https://users.rcc.uchicago.edu/~dholz/gwc/) and python notebook
(https://github.com/hsinyuc/distancetool) to determine GW distances are
available. We provide answers to the question: "How far can gravitational-wave
detectors hear?
On Limitations to the achievable path following performance for linear multivariable plants
In this paper, we consider a problem termed “path
following”. This differs from the common problem of reference tracking, in that here we can adjust the speed at which we traverse the reference trajectory. We are interested in ascertaining the degree to which we can track a given trajectory, and in characterizing the class of paths for which we can generate an appropriate
temporal specification so that the path can be tracked arbitrarily well in an L2 sense.We give various bounds on the achievable performance, as well as tight results in special cases. In addition, we give a numerical procedure based on convex optimization for computing the achievable performance. The results demonstrate that there are situations where arbitrarily good L2 performance may
be achieved even though the origin is not in the convex hull of the positive limit set of the path to be followed
On Limitations to the achievable path following performance for linear multivariable plants
In this paper, we consider a problem termed “path
following”. This differs from the common problem of reference tracking, in that here we can adjust the speed at which we traverse the reference trajectory. We are interested in ascertaining the degree to which we can track a given trajectory, and in characterizing the class of paths for which we can generate an appropriate
temporal specification so that the path can be tracked arbitrarily well in an L2 sense.We give various bounds on the achievable performance, as well as tight results in special cases. In addition, we give a numerical procedure based on convex optimization for computing the achievable performance. The results demonstrate that there are situations where arbitrarily good L2 performance may
be achieved even though the origin is not in the convex hull of the positive limit set of the path to be followed
Thermodynamic Studies of [H_(2)Rh(diphosphine)_2]^+ and [HRh(diphosphine)_(2)(CH_(3)CN)]^(2+) Complexes in Acetonitrile
Thermodynamic studies of a series of [H_(2)Rh(PP)_2]^+ and [HRh(PP)_(2)(CH_(3)CN)]^(2+) complexes have been carried out in acetonitrile. Seven different diphosphine (PP) ligands were selected to allow variation of the electronic properties of the ligand substituents, the cone angles, and the natural bite angles (NBAs). Oxidative addition of H_2 to [Rh(PP)_2]^+ complexes is favored by diphosphine ligands with large NBAs, small cone angles, and electron donating substituents, with the NBA being the dominant factor. Large pK_a values for [HRh(PP)_(2)(CH_(3)CN)]^(2+) complexes are favored by small ligand cone angles, small NBAs, and electron donating substituents with the cone angles playing a major role. The hydride donor abilities of [H_(2)Rh(PP)_2]^+ complexes increase as the NBAs decrease, the cone angles decrease, and the electron donor abilities of the substituents increase. These results indicate that if solvent coordination is involved in hydride transfer or proton transfer reactions, the observed trends can be understood in terms of a combination of two different steric effects, NBAs and cone angles, and electron-donor effects of the ligand substituents
Control and tuning of a suspended Fabry-Perot cavity using digitally-enhanced heterodyne interferometry
We present the first demonstration of real-time closed-loop control and
deterministic tuning of an independently suspended Fabry-Perot optical cavity
using digitally-enhanced heterodyne interferometry, realising a peak
sensitivity of 10 pm over the 10-1000 Hz frequency
band. The methods presented are readily extensible to multiple coupled
cavities. As such, we anticipate that refinements of this technique may find
application in future interferometric gravitational-wave detectors
ECONOMIC IMPACT EVALUATION OF GLOBAL MARKETING SUPPORT SERVICES - AN EXPORTS ASSISTANCE PROGRAM ON THE ECONOMY OF ARKANSAS
This study determines the impact of Global Marketing Support Services (GMSS) - an exports assistance program in assisting 13 small and medium sized businesses to export. The total impact of exports (direct, indirect and induced effects) on added value, employment, labor income and tax impacts in Arkansas are estimated using Impact Analysis for Planning (IMPLAN).International Relations/Trade,
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