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

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

Comparative activity of the penem antibiotic Sch 34343 against Gram-negative and Gram-positive bacteria with special reference to multiresistant strains

A new penem antibiotic, Sch 34343, was shown to be active against a large number of Gram-positive bacteria. The drug inhibited penicillinase-positive and -negative staphylococci equally well, being five times more active than cefamandole and ten times more active than methiallin. Most methicillin-rcsistant staphylococci were inhibited by concentrations between 0.25 and 4 mg/1, but a small group of highly resistant strains were observed. Sch 34343 was eight times less active than ampicillin and penicillin G, but as active as piperacilhn against enterococci. The drug showed excellent activity against various streptococci. Sch 34343 was as bactericidal as flucloxacillin, ampicillin and penicillin G against staphylococci, enterococci and streptococci, respectively, in killing kinetic tests Enterobacteriaceae susceptible to third-generation cephalosporins were approximately five times less susceptible to Sch 34343, but MICs were far below the susceptibility breakpoint Sch 34343 was equally active against Citrobacter and Enterobacter strains that were highly resistant to third-generation cephalosporins and to aztreonam. Together with thienamycin, this drug seems to be a good alternative for the treatment of infections caused by bacteria resistant to third-generation cephalosporins and to aztreona

Bounds on gamma from CP violation measurements in B -> pi+ pi- and B -> psi K_S

We study the determination of gamma from CP-violating observables in B -> pi+ pi- and B -> psi K_S. This determination requires theoretical input to one combination of hadronic parameters. We show that a mild assumption about this quantity may allow bounds to be placed on gamma, but we stress the pernicious effects that an eightfold discrete ambiguity has on such an analysis. The bounds are discussed as a function of the direct (C) and interference (S) CP-violating observables obtained from time-dependent B -> pi+ pi- decays, and their behavior in the presence of new physics effects in B-Bbar mixing is studied. (V2: Misprints corrected. Slightly improved discussion.)Comment: 11 pages, RevTex 4, 5 eps figures include

Interactive and automated application of virtual microscopy

Virtual microscopy can be applied in an interactive and an automated manner. Interactive application is performed in close association to conventional microscopy. It includes image standardization suitable to the performance of an individual pathologist such as image colorization, white color balance, or individual adjusted brightness. The steering commands have to include selection of wanted magnification, easy navigation, notification, and simple measurements (distances, areas). The display of the histological image should be adjusted to the physical limits of the human eye, which are determined by a view angle of approximately 35 seconds. A more sophisticated performance should include acoustic commands that replace the corresponding visual commands. Automated virtual microscopy includes so-called microscopy assistants which can be defined similar to the developed assistants in computer based editing systems (Microsoft Word, etc.). These include an automated image standardization and correction algorithms that excludes images of poor quality (for example uni-colored or out-of-focus images), an automated selection of the most appropriate field of view, an automated selection of the best magnification, and finally proposals of the most probable diagnosis. A quality control of the final diagnosis, and feedback to the laboratory determine the proposed system. The already developed tools of such a system are described in detail, as well as the results of first trials. In order to enhance the speed of such a system, and to allow further user-independent development a distributed implementation probably based upon Grid technology seems to be appropriate. The advantages of such a system as well as the present pathology environment and its expectations will be discussed in detail

Probing the Atmospheres of Planets Orbiting Microlensed Stars via Polarization Variability

We present a new method to identify and probe planetary companions of stars in the Galactic Bulge and Magellanic Clouds using gravitational microlensing. While spectroscopic studies of these planets is well beyond current observational techniques, monitoring polarization fluctuations during high magnification events induced by binary microlensing events will probe the composition of the planetary atmospheres, an observation which otherwise is currently unattainable even for nearby planetary systems.Comment: 7 pages, 2 figures. To appear in Astrophysical Journal Letter

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

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

Extended Source Diffraction Effects Near Gravitational Lens Fold Caustics

Calculations are presented detailing the gravitational lens diffraction due to the steep brightness gradient of the limb of a stellar source. The lensing case studied is the fold caustic crossing. The limb diffraction signal greatly exceeds that due to the disk as a whole and should be detectable for white dwarf sources in our Galaxy and it's satellites with existing telescopes. Detection of this diffraction signal would provide an additional mathematical constraint, reducing the degeneracy among models of the lensing geometry. The diffraction pattern provides pico-arcsecond resolution of the limb profile.Comment: 19 pages including 17 figures, Accepted for publication in ApJ, Minor conceptual change from previous versio

Movement-Related Cortical Potential Amplitude Reduction after Cycling Exercise Relates to the Extent of Neuromuscular Fatigue.

Exercise-induced fatigue affects the motor control and the ability to generate a given force or power. Surface electroencephalography allows researchers to investigate movement-related cortical potentials (MRCP), which reflect preparatory brain activity 1.5 s before movement onset. Although the MRCP amplitude appears to increase after repetitive single-joint contractions, the effects of large-muscle group dynamic exercise on such pre-motor potential remain to be described. Sixteen volunteers exercised 30 min at 60% of the maximal aerobic power on a cycle ergometer, followed by a 10-km all-out time trial. Before and after each of these tasks, knee extensor neuromuscular function was investigated using maximal voluntary contractions (MVC) combined with electrical stimulations of the femoral nerve. MRCP was recorded during 60 knee extensions after each neuromuscular sequence. The exercise resulted in a significant decrease in the knee extensor MVC force after the 30-min exercise (-10 ± 8%) and the time trial (-21 ± 9%). The voluntary activation level (VAL; -6 ± 8 and -12 ± 10%), peak twitch (Pt; -21 ± 16 and -32 ± 17%), and paired stimuli (P100 Hz; -7 ± 11 and -12 ± 13%) were also significantly reduced after the 30-min exercise and the time trial. The first exercise was followed by a decrease in the MRCP, mainly above the mean activity measured at electrodes FC1-FC2, whereas the reduction observed after the time trial was related to the FC1-FC2 and C2 electrodes. After both exercises, the reduction in the late MRCP component above FC1-FC2 was significantly correlated with the reduction in P100 Hz (r = 0.61), and the reduction in the same component above C2 was significantly correlated with the reduction in VAL (r = 0.64). In conclusion, large-muscle group exercise induced a reduction in pre-motor potential, which was related to muscle alterations and resulted in the inability to produce a maximal voluntary contraction