466 research outputs found
THE EFFECTS OF THE NEUROTENSIN-1 RECEPTOR AGONIST PD149163 ON VISUAL SIGNAL DETECTION TASK PERFORMANCE IN RATS
A Two-Coordinate Nickel Imido Complex That Effects CāH Amination
An exceptionally low coordinate nickel imido complex, (IPr*)NiāN(dmp) (2) (dmp = 2,6-dimesitylphenyl), has been prepared by the elimination of N_2 from a bulky aryl azide in its reaction with (IPr*)Ni(Ī·^6-C_7H_8) (1). The solid-state structure of 2 features two-coordinate nickel with a linear CāNiāN core and a short NiāN distance, both indicative of multiple-bond character. Computational studies using density functional theory showed a NiāN bond dominated by Ni(dĻ)āN(pĻ) interactions, resulting in two nearly degenerate singly occupied molecular orbitals (SOMOs) that are NiāN Ļ* in character. Reaction of 2 with CO resulted in nitrene-group transfer to form (dmp)NCO and (IPr*)Ni(CO)_3 (3). Net CāH insertion was observed in the reaction of 2 with ethene, forming the vinylamine (dmp)NH(CHāCH_2) (5) via an azanickelacyclobutane intermediate, (IPr*)Ni{N,C:Īŗ^2-N(dmp)CH_2CH_2} (4)
Synthesis and Characterization of Three-Coordinate Ni(III)-Imide Complexes
A new family of low-coordinate nickel imides supported by 1,2-bis(di-tert-butylphosphino)ethane was synthesized. Oxidation of nickel(II) complexes led to the formation of both aryl- and alkyl-substituted nickel(III)-imides, and examples of both types have been isolated and fully characterized. The aryl substituent that proved most useful in stabilizing the Ni(III)-imide moiety was the bulky 2,6-dimesitylphenyl. The two Ni(III)-imide compounds showed different variable-temperature magnetic properties but analogous EPR spectra at low temperatures. To account for this discrepancy, a low-spin/high-spin equilibrium was proposed to take place for the alkyl-substituted Ni(III)-imide complex. This proposal was supported by DFT calculations. DFT calculations also indicated that the unpaired electron is mostly localized on the imide nitrogen for the Ni(III) complexes. The results of reactions carried out in the presence of hydrogen donors supported the findings from DFT calculations that the adamantyl substituent was a significantly more reactive hydrogen-atom abstractor. Interestingly, the steric properties of the 2,6-dimesitylphenyl substituent are important not only in protecting the NiāN core but also in favoring one rotamer of the resulting Ni(III)-imide, by locking the phenyl ring in a perpendicular orientation with respect to the NiPP plane
Sensitivity of exclusive proton knockout spin observables to different Lorentz invariant representations of the NN interaction
Within the framework of the relativistic plane wave impulse approximation, we
study the observable consequences of employing a complete Lorentz invariant
representation of the NN scattering matrix in terms of 44 independent
amplitudes, as opposed to the previously-employed, but ambiguous, five-term
Lorentz invariant parametrization of the NN scattering matrix, for the
prediction of complete sets of exclusive () polarization
transfer observables. Two kinematic conditions are considered, namely proton
knockout from the state of Pb at an incident energy of 202
MeV for coplanar scattering angles (), as well as
an incident energy of 392 MeV for the angle pair (). The results indicate that certain spin observables are ideal
for discriminating between the two representations.Comment: 19 pages, 5 figures, Revtex, To be published in Phys. Rev.
Nuclear medium modifications of the NN interaction via quasielastic () and () scattering
Within the relativistic PWIA, spin observables have been recalculated for
quasielastic () and () reactions on a Ca
target. The incident proton energy ranges from 135 to 300 MeV while the
transferred momentum is kept fixed at 1.97 fm^{-1}. In the present
calculations, new Horowitz-Love--Franey relativistic NN amplitudes have been
generated in order to yield improved and more quantitative spin observable
values than before. The sensitivities of the various spin observables to the NN
interaction parameters, such as (1) the presence of the surrounding nuclear
medium, (2) a pseudoscalar versus a pseudovector interaction term, and (3)
exchange effects, point to spin observables which should preferably be measured
at certain laboratory proton energies, in order to test current nuclear models.
This study also shows that nuclear medium effects become more important at
lower proton energies ( 200 MeV). A comparison to the limited available
data indicates that the relativistic parametrization of the NN scattering
amplitudes in terms of only the five Fermi invariants (the SVPAT form) is
questionable.Comment: 10 pages, 6 Postscript figures, uses psfig.sty and article.sty,
submitted to Phys. Rev.
Core Polarization and Tensor Coupling Effects on Magnetic Moments of Hypernuclei
The effects of core polarization and tensor coupling on the magnetic moments
in C, O, and Ca
-hypernuclei are studied in the Dirac equation with scalar, vector and
tensor potentials. It is found that the effect of core polarization on the
magnetic moments is suppressed by tensor coupling. The
tensor potential reduces the spin-orbit splitting of states
considerably. However, almost the same magnetic moments are obtained using the
hyperon wave function obtained via the Dirac equation either with or without
the tensor potential in the electromagnetic current vertex. The
deviations of magnetic moments for states from the Schmidt values
are found to increase with nuclear mass number.Comment: 10 pages, 2 figures, 2 table
Influences of wind and sandblasting on the endangered blowout penstemon
Blowout penstemon Penstemon haydenii is a federally endangered species growing only in areas with active wind erosion in sand dunes of the central United States. This early seral species declines as the blowout habitat stabilizes, allowing later seral species to increase. Blowout penstemon populations and plant size declined in the 1990s when precipitation was higher than normal, resulting in reduced sand movement. We conducted a greenhouse experiment to determine whether blowing sand influenced vigor and persistence of blowout penstemon seedlings. Treatments were wind, sandblasting, wind with sandblasting, and a control. The wind treatment was a constant 14 km hā1 from electric fans for 18 h daily. Sand was applied at 96 km hā1 weekly for 10 min to individual plants for the sandblasting treatment, and the wind with sandblasting treatment was a combination of both. Number of leaf pairs, height, and stem diameter were measured biweekly. Biomass was determined at the conclusion of each experiment. Both wind and sandblasting affected plant growth. The combination of wind with sandblasting increased plant height and stem diameter in Year 1, and stem diameter and shoot biomass in Year 2. This study supports field observations that blowout penstemon has a positive thigmomorphogenic response to wind and sandblasting. Less sand movement is associated with wet soils. Therefore, loss of mechanical stimuli could have been one of the reasons for population decline in the 1990s. Disturbance may be necessary to maintain the blowout habitat and provide an important stimulus to the blowout penstemon plants
Effects of Acute and Sustained Pain Manipulations on Performance in a VisualāSignal Detection Task of Attention in Rats
Preclinical ResearchPatients with pain often display cognitive impairment including deficits in attention. The visualāsignal detection task (VSDT) is a behavioral procedure for assessment of attention in rodents. Male Sprague Dawley rats were trained in a VSDT and tested with three different noxious stimuli: (i) intraperitoneal injection of lactic acid; (ii) intraplantar injection of formalin; and (iii) intraplantar injection of complete Freund's adjuvant (CFA). The muscarinic acetylcholine receptor antagonist, scopolamine was also tested as a positive control. Scopolamine (0.01ā1.0 mg/kg) dose dependently reduced accuracy and increased response latencies during completed trials with higher scopolamine doses increasing omissions. Lactic acid (0.56ā5.6% ip) also increased response latencies and omissions, although it failed to alter measures of response accuracy. Formalin produced a transient decrease in accuracy while also increasing both response latency and omissions. CFA failed to alter VSDT performance. Although VSDT effects were transient for formalin and absent for CFA, both treatments produced mechanical allodynia and paw edema for up to 7 days. These results support the potential for noxious stimuli to produce a painārelated disruption of attention in rats. However, relatively strong noxious stimulation appears necessary to disrupt performance in this version of the VSDT. Drug Dev Res 76 : 194ā203, 2015. Ā© 2015 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111955/1/ddr21255.pd
Effects of Nitrogen and Phosphorus Fertilizer and Topsoil Amendment on Native Plant Cover in Roadside Revegetation Projects
Establishing vegetation on roadsides following construction can be challenging, especially for relatively slow growing native species. Topsoil is generally removed during construction, and the surface soil following construction (ācut-slope soilsā) is often compacted and low in nutrients, providing poor growing conditions for vegetation. Nebraska Department of Transportation (NDOT) protocols have historically called for nitrogen (N) and phosphorus (P) fertilization when planting roadside vegetation following construction, but these recommendations were developed for cool-season grass plantings and most current plantings use slower-establishing, native warmseason grasses that may benefit less than expected from current planting protocols. We evaluated the effects of nitrogen and phosphorus fertilization, and also topsoil amendment, on the foliar cover of seeded and non-seeded species planted into two postconstruction roadside sites in eastern Nebraska. We also examined soil movement to determine how planting protocols and plant growth may affect erosion potential. Three years after planting, we found no consistent effects of N or P fertilization on foliar cover. Plots receiving topsoil amendment had 14% greater cover of warm-season grasses, 10% greater total foliar cover, and 4ā13% lower bare ground (depending on site) than plots without topsoil. None of the treatments consistently affected soil movement. We recommend that NDOT change their protocols to remove N and P fertilization and focus on stockpiling and spreading topsoil following construction
The quetiapine active metabolite N-Desalkylquetiapine and the neurotensin NTS1 receptor agonist PD149163 exhibit antidepressant-like effects on operant responding in male rats
Major depressive disorder (MDD) is the most common mood disorder in the United States and European Union; however, the limitations of clinically available antidepressant drugs have led researchers to pursue novel pharmacological treatments. Clinical studies have reported that monotherapy with the atypical antipsychotic drug quetiapine produces a rapid reduction in depressive symptoms that are apparent following one week of quetiapine treatment, and it is possible that the active metabolite N-Desalkylquetiapine, which structurally resembles an antidepressant drug, produces antidepressant effects. Neuropharmacological evaluations of the neurotensin NTS1 receptor agonist PD149163 are suggestive of antidepressant efficacy, but the effects of a NTS1 receptor agonist in an antidepressant animal model have yet to be reported. The present study examined the antidepressant-like effects of the N-Desalkylquetiapine, the neurotensin NTS1 receptor agonist PD14916, quetiapine, the tricylic antidepressant drug imipramine, the atypical antipsychotic drug risperidone, and the typical antipsychotic drug raclopride on responding in male Sprague-Dawley rats trained on a differential-reinforcement-of-low-rate (DRL) 72 s operant schedule, a procedure used for screening antidepressant drugs. Quetiapine, PD149163, risperidone, and imipramine exhibited antidepressant-like effects by increasing the number of reinforcers earned, decreasing the number of responses emitted, and shifting the interresponse time (IRT) distributions to the right. N-Desalkylquetiapine produced a partial antidepressant-like effect by decreasing the number of responses emitted and producing a rightward shift in the IRT distributions, but it did not significantly alter the number of reinforcers earned. The typical antipsychotic drug raclopride decreased both reinforcers and responses. These data suggest that N-Desalklyquetiapine likely contributes to quetiapineās antidepressant efficacy and identifies NTS1 receptor activation as a potential novel pharmacologic strategy for antidepressant drugs
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