Lensing Properties of Cored Galaxy Models

A method is developed to evaluate the magnifications of the images of galaxies with lensing potentials stratified on similar concentric ellipses. A simple contour integral is provided which enables the sums of the magnifications of even parity or odd parity or the central image to be easily calculated. The sums for pairs of images vary considerably with source position, while the signed sums can be remarkably uniform inside the tangential caustic in the absence of naked cusps. For a family of models in which the potential is a power-law of the elliptic radius, the number of visible images is found as a function of flattening, external shear and core radius. The magnification of the central image depends on the core radius and the slope of the potential. For typical source and lens redshifts, the missing central image leads to strong constraints; the mass distribution in the lensing galaxy must be nearly cusped, and the cusp must be isothermal or stronger. This is in accord with the cuspy cores seen in high resolution photometry of nearby, massive, early-type galaxies, which typically have the surface density falling like distance^{-1.3} outside a break radius of a few hundred parsecs. Cuspy cores by themselves can provide an explanation of the missing central images. Dark matter at large radii may alter the slope of the projected density; provided the slope remains isothermal or steeper and the break radius remains small, then the central image remains unobservable. The sensitivity of the radio maps must be increased fifty-fold to find the central images in abundance.Comment: 42 pages, 11 figures, ApJ in pres

Kinetics and Mechanisms of Atrazine Adsorption and Desorption in Soils Under No-Till and Conventional Management

Both soils (Maury silt loam and Sadler) exhibited three apparent mechanisms of atrazine adsorption. The first two mechanisms were very rapid (10 minutes) and were assigned to soil-clay surface adsorption reactions via hydrogen bonding. The quantity of atrazine involved in these two reactions for the 0.5 mg/1 solution atrazine varied, depending on the soil, from 67 μg/100 g clay to 219 μg/100 g clay. The reason there were two possible atrazine sinks in this range of atrazine adsorption was believed to be the presence of two types of reactive surfaces, the clay inorganic phase and the organic carbon phase. The latter phase exhibited more influence on the Maury silt loam soil than on the Sadler soil, where the Maury silt loam soil contained more organic carbon than the Sadler soil. The third mechanism involved an atrazine condensation mechanism. It was a relatively slow reaction and it appeared to persist for at least 2 hours. This mechanism accounted for about three fourths of the total atrazine adsorbed. After 75 minutes of solution flow the total atrazine adsorbed by the soil clay samples varied from 333 μg/100 g to 710 μg/100 g. Reversibility of the adsorption process was shown to be limited. Approximately one-third of the adsorbed atrazine was desorbed after a 2 hour leaching with l mmol L-1 CaCl2 solution. The desorption process was shown to be controlled by two types of reactions. A short rapid one and a long extremely slow one (diffusion controlled). The above findings suggest that the amount of atrazine leaching into surface water or groundwater would depend on the amount of time atrazine had to react with the soil. If it rained immediately following atrazine application then most of the atrazine would be carried in the runoff, making water the main mechanism of atrazine movement. If, on the other hand, a significant amount of time passed after atrazine was applied then a much smaller proportion of the applied atrazine would be leached, making soil erosion the main mechanism of atrazine movement. Equations for all these processes have been developed to aid in modeling the movement of atrazine during rain fall events

The Energy-Momentum Tensor in Fulling-Rindler Vacuum

The energy density in Fulling-Rindler vacuum, which is known to be negative "everywhere" is shown to be positive and singular on the horizons in such a fashion as to guarantee the positivity of the total energy. The mechanism of compensation is displayed in detail.Comment: 9 pages, ULB-TH-15/9

Polymerase chain reactions with alphoid-repeat primers in combination with Alu or LINEs primers, generate chromosome-specific DNA fragments

Y alphoid primers in combination with Alu and LINEs primers generated new DNA fragments in polymerase chain reactions (PCR) on DNA from a Y-only somatic cell hybrid but not from X-only, 3-only, or 21-only hybrids. X alphoid primers used in a similar manner generated new DNA fragments from the X-only hybrid, and 1 of the primers (X 2 ) also generated new DNA fragments on 3-only and 21-only hybrids when used in conjunction with Alu or LINEs primers. In all but one case, consensus alphoid primers generated new chromosome-specific fragments in PCR reactions with the Alu or LINEs primers. A search for cryptic Alu- or alphoid-alone PCR products as the source for one Alu -alphoid band (chosen at random) was negative. Partial sequencing of products demonstrated that alphoid and Alu sequences were indeed contiguous in some newly synthesized DNA fragments. While Alu or LINEs primers generate smears of DNA fragments on total human DNA, the alphoid-nonalphoid repeat combinations generated electrophoretically distinguishable bands of DNA when the template was total DNA. While these were distinguishable with different chromosome-specific alphoid primers, the DNA fragments were not of the same sizes as those generated with the chromosome-only hybrids.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66359/1/j.1469-1809.1991.tb00414.x.pd

Some Heuristic Semiclassical Derivations of the Planck Length, the Hawking Effect and the Unruh Effect

The formulae for Planck length, Hawking temperature and Unruh-Davies temperature are derived by using only laws of classical physics together with the Heisenberg principle. Besides, it is shown how the Hawking relation can be deduced from the Unruh relation by means of the principle of equivalence; the deep link between Hawking effect and Unruh effect is in this way clarified.Comment: LaTex file, 6 pages, no figure

The Ammount of Interstellar Carbon Locked in Solid Hydrogenated Amorphous Carbon

We review the literature and present new experimental data to determine the amount of carbon likely to be locked in form of solid hydrogenated amorphous carbon (HAC) grains. We conclude on the basis of a thorough analysis of the intrinsic strength of the C-H stretching band at 3.4 micron that between 10 and 80 ppM H of carbon is in the form of HAC grains. We show that it is necessary to know the level of hydrogenation (H/C) of the interstellar HAC to determine more precisely the amount of carbon it ties up. We present optical constants, photoluminescence spectroscopy, and IR absorption spectroscopy for a particular HAC sample that is shown to have a 3.4 micron absorption feature that is quantatively consistent with that observed in the diffuse interstellar medium.Comment: This paper is 14 pages long with 5 figures and will appear in the 1 December 1999 issue of Ap

Dust in the Local Interstellar Wind

The gas-to-dust mass ratios found for interstellar dust within the Solar System, versus values determined astronomically for the cloud around the Solar System, suggest that large and small interstellar grains have separate histories, and that large interstellar grains preferentially detected by spacecraft are not formed exclusively by mass exchange with nearby interstellar gas. Observations by the Ulysses and Galileo satellites of the mass spectrum and flux rate of interstellar dust within the heliosphere are combined with information about the density, composition, and relative flow speed and direction of interstellar gas in the cloud surrounding the solar system to derive an in situ value for the gas-to-dust mass ratio, $R_{g/d} = 94^{+46}_{-38}$. Hubble observations of the cloud surrounding the solar system yield a gas-to-dust mass ratio of Rg/d=551+61-251 when B-star reference abundances are assumed. The exclusion of small dust grains from the heliosheath and heliosphere regions are modeled, increasing the discrepancy between interstellar and in situ observations. The shock destruction of interstellar grains is considered, and comparisons are made with interplanetary and presolar dust grains.Comment: 87 pages, 9 figures, 6 tables, accepted for publication in Astrophysical Journal. Uses AASTe

The Photophysics of the Carrier of Extended Red Emission

Interstellar dust contains a component which reveals its presence by emitting a broad, unstructured band of light in the 540 to 950 nm wavelength range, referred to as Extended Red Emission (ERE). The presence of interstellar dust and ultraviolet photons are two necessary conditions for ERE to occur. This is the basis for suggestions which attribute ERE to an interstellar dust component capable of photoluminescence. In this study, we have collected all published ERE observations with absolute-calibrated spectra for interstellar environments, where the density of ultraviolet photons can be estimated reliably. In each case, we determined the band-integrated ERE intensity, the wavelength of peak emission in the ERE band, and the efficiency with which absorbed ultraviolet photons are contributing to the ERE. The data show that radiation is not only driving the ERE, as expected for a photoluminescence process, but is modifying the ERE carrier as manifested by a systematic increase in the ERE band's peak wavelength and a general decrease in the photon conversion efficiency with increasing densities of the prevailing exciting radiation. The overall spectral characteristics of the ERE and the observed high quantum efficiency of the ERE process are currently best matched by the recently proposed silicon nanoparticle (SNP) model. Using the experimentally established fact that ionization of semiconductor nanoparticles quenches their photoluminescence, we proceeded to test the SNP model by developing a quantitative model for the excitation and ionization equilibrium of SNPs under interstellar conditions for a wide range of radiation field densities.Comment: 42 p., incl. 8 fig. Accepted for publication by Ap

Exotic Spaces in Quantum Gravity I: Euclidean Quantum Gravity in Seven Dimensions

It is well known that in four or more dimensions, there exist exotic manifolds; manifolds that are homeomorphic but not diffeomorphic to each other. More precisely, exotic manifolds are the same topological manifold but have inequivalent differentiable structures. This situation is in contrast to the uniqueness of the differentiable structure on topological manifolds in one, two and three dimensions. As exotic manifolds are not diffeomorphic, one can argue that quantum amplitudes for gravity formulated as functional integrals should include a sum over not only physically distinct geometries and topologies but also inequivalent differentiable structures. But can the inclusion of exotic manifolds in such sums make a significant contribution to these quantum amplitudes? This paper will demonstrate that it will. Simply connected exotic Einstein manifolds with positive curvature exist in seven dimensions. Their metrics are found numerically; they are shown to have volumes of the same order of magnitude. Their contribution to the semiclassical evaluation of the partition function for Euclidean quantum gravity in seven dimensions is evaluated and found to be nontrivial. Consequently, inequivalent differentiable structures should be included in the formulation of sums over histories for quantum gravity.Comment: AmsTex, 23 pages 5 eps figures; replaced figures with ones which are hopefully viewable in pdf forma

Semiclassical thermodynamics of scalar fields

We present a systematic semiclassical procedure to compute the partition function for scalar field theories at finite temperature. The central objects in our scheme are the solutions of the classical equations of motion in imaginary time, with spatially independent boundary conditions. Field fluctuations -- both field deviations around these classical solutions, and fluctuations of the boundary value of the fields -- are resummed in a Gaussian approximation. In our final expression for the partition function, this resummation is reduced to solving certain ordinary differential equations. Moreover, we show that it is renormalizable with the usual 1-loop counterterms.Comment: 24 pages, 5 postscript figure