9,445 research outputs found
Cosmological Density Perturbations with a Scale-Dependent Newton's G
We explore possible cosmological consequences of a running Newton's constant
, as suggested by the non-trivial ultraviolet fixed point
scenario in the quantum field-theoretic treatment of Einstein gravity with a
cosmological constant term. In particular we focus here on what possible
effects the scale-dependent coupling might have on large scale cosmological
density perturbations. Starting from a set of manifestly covariant effective
field equations derived earlier, we systematically develop the linear theory of
density perturbations for a non-relativistic, pressure-less fluid. The result
is a modified equation for the matter density contrast, which can be solved and
thus provides an estimate for the growth index parameter in the
presence of a running . We complete our analysis by comparing the fully
relativistic treatment with the corresponding results for the non-relativistic
(Newtonian) case, the latter also with a weakly scale dependent .Comment: 54 pages, 4 figure
Relativistic Effects in Nuclear Matter and Nuclei
The status of relativistic nuclear many-body calculations of nuclear systems
to be built up in terms of protons and neutrons is reviewed. In detail,
relativistic effects on several aspects of nuclear matter such as the effective
mass, saturation mechanism, and the symmetry energy are considered. This review
will especially focus on isospin asymmetric issues, since these aspects are of
high interest in astrophysical and nuclear structure studies. Furthermore, from
the experimental side these aspects are experiencing an additional boost from a
new generation of radioactive beam facilities, e.g. the future GSI facility
FAIR in Germany or SPIRAL2 at GANIL/France. Finally, the prospects of studying
finite nuclei in microscopic calculations which are based on realistic
interactions by including relativistic effects in calculations of low momentum
interactions are discussed.Comment: 57 pages, 16 figure
Use of ERTS-1 data in identification, classification, and mapping of salt-affected soils in California
There are no author-identified significant results in this report
Amount and Distribution of Isozyme Variation in Ponderosa pine from Eastern Montana
Pinus ponderosa seeds from 50 trees in each of six small isolated stands located within a nine kilometer radius of Colstrip, Montana, were examined at 23 isozyme loci. Megagametophyte and embryo tissue from each seed were screened separately. Measures of genetic diversity showed no significant differences between male and female components within or between stands. The average proportion of heterozygous loci per embryo (He) was not significantly different between stands. For all stands combined, He was 0.012. Genotype proportions did not deviate from expected Hardy-Weinberg proportions.
Nearly 99 % of the genetic diversity resided within individual stands, with a significant 1.5 % due to differences between stands. Genetic distance between stands is not correlated with geographic distance. Considering the natural fire history of the stands, it is suggested that there is a great deal of gene flow into a stand during its early stage of development
Monotonic properties of the shift and penetration factors
We study derivatives of the shift and penetration factors of collision theory
with respect to energy, angular momentum, and charge. Definitive results for
the signs of these derivatives are found for the repulsive Coulomb case. In
particular, we find that the derivative of the shift factor with respect to
energy is positive for the repulsive Coulomb case, a long anticipated but
heretofore unproven result. These results are closely connected to the
properties of the sum of squares of the regular and irregular Coulomb
functions; we also present investigations of this quantity.Comment: 13 pages, 1 figur
Tetranuclear Group 7/8 Mixed-Metal and Open Trinuclear Group 7 Metal Carbonyl Clusters Bearing Bridging 2-mercapto-1-methylimidazole Ligands
The reactivity of group 7 metal dinuclear carbonyl complexes [M2(CO)6(μ-SN2C4H5)2] (1, M = Re; 2, M = Mn) toward group 8 metal trinuclear carbonyl clusters were examined. Reactions of 1 and 2 with [Os3(CO)10(NCMe)2] in refluxing benzene furnished the tetranuclear mixed-metal clusters [Os3Re(CO)13(μ3-SN2C4H5)] (3) and [Os3Mn(CO)13(μ3-SN2C4H5)] (4), respectively. Similar treatment of 1 and 2 with Ru3(CO)12 yielded the ruthenium analogs [Ru3Re(CO)13(μ3-SN2C4H5)] (5), and [Ru3Mn(CO)13(μ3-SN2C4H5)] (6), but in the case of 2 a secondary product [Mn3(CO)10(μ-Cl)(μ3-SN2C4H5)2] (7) was also formed. Compounds 3–6 have a butterfly core of four metal atoms with the M (Mn or Re) at a wingtip of the butterfly and containing a noncrystallographic mirror plane of symmetry. This result provides a potential method for the synthesis of a series of new group 7/8 mixed metal complexes containing a bifunctional heterocyclic ligand. Compound 7 is a unique example of a 54-electron trimanganese complex having bridging 2-mercapto-1-methylimidazolate and chloride ligands. Interestingly, the reaction of 1 with Fe3(CO)12 at 70–75 °C furnished the tri- and dirhenium complexes [Re3(CO)10(μ-H)(μ3-SN2C4H5)2] (8) and [Re2(CO)6(N2C4H5)(μ-SN2C4H5)2] (9), respectively instead of the expected formation of the mixed-metal clusters. The former is an interesting example of a 52-electron trirhenium-hydridic complex containing bridging 2-mercapto-1-methylimidazolate ligand, while the latter can be viewed as a 1-methylimidazole adduct of 1. No mixed Fe–Re complexes were produced in this reaction. The molecular structures of the new compounds 3–5 and 7–9 were established by single-crystal X-ray diffraction analyses and the DFT studies of compounds 5, 7 and 8 are reported
Archaeological Testing for a Proposed Landfill Expansion (Phase II) City of Del Rio, Val Verde County, Texas
During September 1989, a pedestrian survey was conducted within a I~S-acre tract acquired by the City of Del Rio, Val Verde County, for a landfill expansion project. The surface reconnaissance recorded one prehistoric site, 41 VV 1251. As a result, recommendation was made for Phase II subsurface testing.
The Phase II subsurface testing, which included a geomorphic study, was accomplished during February 1990. Cultural resources were recovered indicating presence at site 41 VV 1251 from the Late Paleo-Indian period to the Late Archaic period. However, the site was determined to be almost totally deflated. The geomorphological tests verified this assessment and indicated no deeply buried deposits. Site 41 VV 1251 is not deemed potentially eligible for nomination to the National Register of Historic Places or for designation as a State Archeological Landmark
Kinetic Limit for Wave Propagation in a Random Medium
We study crystal dynamics in the harmonic approximation. The atomic masses
are weakly disordered, in the sense that their deviation from uniformity is of
order epsilon^(1/2). The dispersion relation is assumed to be a Morse function
and to suppress crossed recollisions. We then prove that in the limit epsilon
to 0 the disorder averaged Wigner function on the kinetic scale, time and space
of order epsilon^(-1), is governed by a linear Boltzmann equation.Comment: 71 pages, 3 figure
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