Seeing Star Formation Regions with Gravitational Microlensing

We qualitatively study the effects of gravitational microlensing on our view of unresolved extragalactic star formation regions. Using a general gravitational microlensing configuration, we perform a number of simulations that reveal that specific imprints of the star forming region are imprinted, both photometrically and spectroscopically, upon observations. Such observations have the potential to reveal the nature and size of these star forming regions, through the degree of variability observed in a monitoring campaign, and hence resolve the star formation regions in distant galaxies which are too small to be probed via more standard techniques.Comment: 7 pages, 8 figures, ApJ accepte

Quasar Microlensing: when compact masses mimic smooth matter

The magnification induced by gravitational microlensing is sensitive to the size of a source relative to the Einstein radius, the natural microlensing scale length. This paper investigates the effect of source size in the case where the microlensing masses are distributed with a bimodal mass function, with solar mass stars representing the normal stellar masses, and smaller masses (down to $8.5\times 10^{-5}$M$_\odot$) representing a dark matter component. It is found that there exists a critical regime where the dark matter is initially seen as individual compact masses, but with an increasing source size the compact dark matter acts as a smooth mass component. This study reveals that interpretation of microlensing light curves, especially claims of small mass dark matter lenses embedded in an overall stellar population, must consider the important influence of the size of the source.Comment: 6 pages, to appear in ApJ. As ever, quality of figures reduce

Corrections for gravitational lensing of supernovae: better than average?

We investigate the possibility of correcting for the magnification due to gravitational lensing of standard candle sources, such as Type Ia supernovae. Our method uses the observed properties of the foreground galaxies along the lines-of-sight to each source and the accuracy of the lensing correction depends on the quality and depth of these observations as well as the uncertainties in translating the observed luminosities to the matter distribution in the lensing galaxies. The current work is limited to cases where the matter density is dominated by the individual galaxy halos. However, it is straightforward to generalize the method to include also gravitational lensing from cluster scale halos. We show that the dispersion due to lensing for a standard candle source at z=1.5 can be reduced from about 7% to ~< 3%, i.e. the magnification correction is useful in reducing the scatter in the Type Ia Hubble diagram, especially at high redshifts where the required long exposure times makes it hard to reach large statistics and the dispersion due to lensing becomes comparable to the intrinsic Type Ia scatter.Comment: Matches accepted version, includes clarifications and additional issues. 28 pages, 7 figures, accepted for publication in Ap

Thermophysical properties. Quarterly report, 1 July 1992--30 September 1992

Numerous fluids have been identified as promising alternative refrigerants, but much of the information needed to predict their behavior as pure fluids and as components in mixtures does not exist. In particular, reliable thermophysical properties data and models are needed to predict the performance of the new refrigerants in heating and cooling equipment, and to design and optimize equipment to be reliable and energy efficient. Objective of this project is to provide highly accurate, selected thermophysical properties data for Refrigerants 32, 123, 124, and 125, and to use these data to fit simple and complex equations of state and detailed transport property models. The new data will fill gaps in the existing data sets and resolve the problems and uncertainties that exist in and between the data sets. This report describes the progress made during the third quarter of this fifteen-month project, which was initiated in late January, 1992

Gravitational lensing as folds in the sky

We revisit the gravitational lensing phenomenon using a new visualization technique. It consists in projecting the observers sky into the source plane, what gives rise to a folded and stretched surface. This provides a clear graphical tool to visualize some interesting well-known effects, such as the development of multiple images of a source, the structure of the caustic curves, the parity of the images and their magnification as a function of the source position.Comment: 11 pages, 8 figure

Discovery of a Galaxy Cluster in the Foreground of the Wide-Separation Quasar Pair UM425

We report the discovery of a cluster of galaxies in the field of UM425, a pair of quasars separated by 6.5arcsec. Based on this finding, we revisit the long-standing question of whether this quasar pair is a binary quasar or a wide-separation lens. Previous work has shown that both quasars are at z=1.465 and show broad absorption lines. No evidence for a lensing galaxy has been found between the quasars, but there were two hints of a foreground cluster: diffuse X-ray emission observed with Chandra, and an excess of faint galaxies observed with the Hubble Space Telescope. Here we show, via VLT spectroscopy, that there is a spike in the redshift histogram of galaxies at z=0.77. We estimate the chance of finding a random velocity structure of such significance to be about 5%, and thereby interpret the diffuse X-ray emission as originating from z=0.77, rather than the quasar redshift. The mass of the cluster, as estimated from either the velocity dispersion of the z=0.77 galaxies or the X-ray luminosity of the diffuse emission, would be consistent with the theoretical mass required for gravitational lensing. The positional offset between the X-ray centroid and the expected location of the mass centroid is about 40kpc, which is not too different from offsets observed in lower redshift clusters. However, UM425 would be an unusual gravitational lens, by virtue of the absence of a bright primary lensing galaxy. Unless the mass-to-light ratio of the galaxy is at least 80 times larger than usual, the lensing hypothesis requires that the galaxy group or cluster plays a uniquely important role in producing the observed deflections. Based on observations performed with the Very Large Telescope at the European Southern Observatory, Paranal, Chile.Comment: 12 pages, accepted by ApJ 2005, May 1

Diffusion with critically correlated traps and the slow relaxation of the longest wavelength mode

We study diffusion on a substrate with permanent traps distributed with critical positional correlation, modeled by their placement on the perimeters of a critical percolation cluster. We perform a numerical analysis of the vibrational density of states and the largest eigenvalue of the equivalent scalar elasticity problem using the method of Arnoldi and Saad. We show that the critical trap correlation increases the exponent appearing in the stretched exponential behavior of the low frequency density of states by approximately a factor of two as compared to the case of no correlations. A finite size scaling hypothesis of the largest eigenvalue is proposed and its relation to the density of states is given. The numerical analysis of this scaling postulate leads to the estimation of the stretch exponent in good agreement with the density of states result.Comment: 15 pages, LaTeX (RevTeX

Lens or Binary? Chandra Observations of the Wide Separation Broad Absorption Line Quasar Pair UM425

We have obtained a 110 ksec Chandra ACIS-S exposure of UM425, a pair of QSOs at z=1.47 separated by 6.5 arcsec, which show remarkably similar emission and broad absorption line (BAL) profiles in the optical/UV. Our 5000 count X-ray spectrum of UM425A (the brighter component) is well-fit with a power law (photon spectral index Gamma=2.0) partially covered by a hydrogen column of 3.8x10^22 cm^-2. The underlying power-law slope for this object and for other recent samples of BALQSOs is typical of radio-quiet quasars, lending credence to the hypothesis that BALs exist in every quasar. Assuming the same Gamma for the much fainter image of UM425B, we detect an obscuring column 5 times larger. We search for evidence of an appropriately large lensing mass in our Chandra image and find weak diffuse emission near the quasar pair, with an X-ray flux typical of a group of galaxies at redshift z ~ 0.6. From our analysis of archival HST WFPC2 and NICMOS images, we find no evidence for a luminous lensing galaxy, but note a 3-sigma excess of galaxies in the UM425 field with plausible magnitudes for a z=0.6 galaxy group. However, the associated X-ray emission does not imply sufficient mass to produce the observed image splitting. The lens scenario thus requires a dark (high M/L ratio) lens, or a fortuitous configuration of masses along the line of sight. UM425 may instead be a close binary pair of BALQSOs, which would boost arguments that interactions and mergers increase nuclear activity and outflows.Comment: 13 pages, 9 figures, Accepted for publication in the Astrophysical Journa

Prognostic significance of endogenous adhesion/growth-regulatory lectins in lung cancer

Objective: To determine the expression of endogenous adhesion/growth-regulatory lectins and their binding sites using labeled tissue lectins as well as the binding profile of hyaluronic acid as an approach to define new prognostic markers. Methods: Sections of paraffin-embedded histological material of 481 lungs from lung tumor patients following radical lung excision processed by a routine immunohistochemical method (avidin-biotin labeling, DAB chromogen). Specific antibodies against galectins-1 and - 3 and the heparin-binding lectin were tested. Staining by labeled galectins and hyaluronic acid was similarly visualized by a routine protocol. After semiquantitative assessment of staining, the results were compared with the pT and pN stages and the histological type. Survival was calculated by univariate and multivariate methods. Results: Binding of galectin-1 and its expression tended to increase, whereas the parameters for galectin-3 decreased in advanced pT and pN stages at a statistically significant level. The number of positive cases was considerably smaller among the cases with small cell lung cancer than in the group with non-small-cell lung cancer, among which adenocarcinomas figured prominently with the exception of galectin-1 expression. Kaplan-Meier computations revealed that the survival rate of patients with galectin-3-binding or galectin-1-expressing tumors was significantly poorer than that of the negative cases. In the multivariate calculations of survival lymph node metastases ( p < 0.0001), histological type ( p = 0.003), galectin-3-binding capacity ( p = 0.01), galectin-3 expression ( p = 0.03) and pT status ( p = 0.003) proved to be independent prognostic factors, not correlated with the pN stage. Conclusion: The expression and the capacity to bind the adhesion/growth regulatory galectin-3 is defined as an unfavorable prognostic factor not correlated with the pTN stage. Copyright (C) 2005 S. Karger AG, Basel

Neutrino oscillations from the splitting of Fermi points

As was shown previously, oscillations of massless neutrinos may be due to the splitting of multiply degenerate Fermi points. In this Letter, we give the details and propose a three-flavor model of Fermi point splittings and neutrino mixings with only two free parameters. The model may explain recent experimental results from the K2K and KamLAND collaborations. There is also rough agreement with the data on atmospheric neutrinos (SuperK) and solar neutrinos (SNO), but further analysis is required. Most importantly, the Ansatz allows for relatively strong T-violating (CP-nonconserving) effects in the neutrino sector.Comment: 6 pages with jetplFRK.cls, v4: published versio