Dust Reddening in SDSS Quasars

We explore the form of extragalactic reddening toward quasars using a sample of 9566 quasars with redshifts 0<z<2.2, and accurate optical colors from the Sloan Digital Sky Survey (SDSS). We confirm that dust reddening is the primary explanation for the red ``tail'' of the color distribution of SDSS quasars. Our fitting to 5-band photometry normalized by the modal quasar color as a function of redshift shows that this ``tail'' is well described by SMC-like reddening but not by LMC-like, Galactic, or Gaskell et al. (2004) reddening. Extension to longer wavelengths using a subset of 1886 SDSS-2MASS matches confirms these results at high significance. We carry out Monte-Carlo simulations that match the observed distribution of quasar spectral energy distributions using a Lorentzian dust reddening distribution; 2% of quasars selected by the main SDSS targeting algorithm (i.e., which are not extincted out of the sample) have E_{B-V} > 0.1; less than 1% have E_{B-V} > 0.2, where the extinction is relative to quasars with modal colors. Reddening is uncorrelated with the presence of intervening narrow-line absorption systems, but reddened quasars are much more likely to show narrow absorption at the redshift of the quasar than are unreddened quasars. Thus the reddening towards quasars is dominated by SMC-like dust at the quasar redshift.Comment: 29 pages including 8 figures. AJ, September 2004 issu

A conceptual framework for evaluating cooking systems

PUBLISHED 7 March 2022Tami C Bond, Christian L, Orange, Paul R Medwell, George Sizoomu, Samer Abdelnour, Verena Brinkmann, Philip Lloyd and Crispin Pemberton-Pigot

A New Algorithm for Supernova Neutrino Transport and Some Applications

We have developed an implicit, multi-group, time-dependent, spherical neutrino transport code based on the Feautrier variables, the tangent-ray method, and accelerated ${\bf \Lambda}$ iteration. The code achieves high angular resolution, is good to O($v/c$), is equivalent to a Boltzmann solver (without gravitational redshifts), and solves the transport equation at all optical depths with precision. In this paper, we present our formulation of the relevant numerics and microphysics and explore protoneutron star atmospheres for snapshot post-bounce models. Our major focus is on spectra, neutrino-matter heating rates, Eddington factors, angular distributions, and phase-space occupancies. In addition, we investigate the influence on neutrino spectra and heating of final-state electron blocking, stimulated absorption, velocity terms in the transport equation, neutrino-nucleon scattering asymmetry, and weak magnetism and recoil effects. Furthermore, we compare the emergent spectra and heating rates obtained using full transport with those obtained using representative flux-limited transport formulations to gauge their accuracy and viability. Finally, we derive useful formulae for the neutrino source strength due to nucleon-nucleon bremsstrahlung and determine bremsstrahlung's influence on the emergent $\nu_{\mu}$ and $\nu_{\tau}$ neutrino spectra.Comment: 58 pages, single-spaced LaTeX, 23 figures, revised title, also available at http://jupiter.as.arizona.edu/~burrows/papers, accepted for publication in the Ap.

Real-Time Optical Coherence Tomography Controlled Microsecond Laser Retinal Microsurgery: First In-vivo Results

Reliable mild photocoagulation and selective retina therapy (SRT) selectively damaging the retinal pigment epithelium (RPE) while sparing the neuroretina, the photoreceptors as well as the choroid are highly demanded. However, due to the inter- and intraindividual variability of RPE and choroidal absorption, optical microsurgery requires reliable real-time laser dosing to prevent unwanted overexposure and extended damage of the neuroretina. In this experiment optical coherence tomography (OCT) was implemented to detect minimal damage, and a laser feedback control algorithm was used for real-time dosing. For the first time in-vivo experiments on rabbits were performed with microsecond laser pulses of varying duration. Pigment rabbit eyes (n=6) were exposed to laser pulses of 4, 8, 12, and 20 μs in duration (wavelength, 532 nm; ramp-mode, maximum 15 pulses; repetition rate, 100 Hz). Therefore, a system with a scanning laser ophthalmoscope and spectral-domain OCT (Heidelberg Engineering) extended with a prototype laser (Meridian Medical) was used. For each laser lesion, the increasing ramp’s end energy was individually controlled in real-time using OCT dosimetry (central wavelength, 870 nm; scan rate, 80 kHz). Within 1 hour after irradiation, retinal changes were assessed with fluorescein angiography (FA), indocyanine green angiography (ICGA), color fundus photography (CFP) and OCT. OCT dosimetry utilizing the control algorithm can interrupt the ramp-mode in real-time for each lesion individually. The preconditioned algorithm enabled treatment with a clearly visible breakdown of the blood-retinal barrier (BRB) according to FA and ICGA imaging and barely visible treatment lesions according to CFP. OCT B-scans through the treated areas provided a first indication of the morphological tissue impact. Preliminary evaluation shows that the algorithm stopped the laser at 4 μs at a ramp end energy of 53 μJ (corresponds to 13/15 pulses), at 8 μs at 68 μJ (5/15 pulses), at 12 μs at 74 μJ (7/15 pulses), and at 20 μs at 100 μJ (1/15 pulses). The novel system with OCT based laser dosing proved to induce minimal visible damage and BRB breakdown in a wide range of pulse durations. The new irradiation scheme and algorithm are being optimized and tested in multiple subjects to further limit unwanted damage and enable pure RPE selective laser microsurgery in real-time. This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually

Radiation-Driven Warping. II. Non-Isothermal Disks

Recent work by Pringle and by Maloney, Begelman & Pringle has shown that geometrically thin, optically thick, accretion disks are unstable to warping driven by radiation torque from the central source. In this paper we generalize the study of radiation-driven warping to include general power-law surface density distributions, $\Sigma\propto R^{-\delta}$. We consider the range $\delta=3/2$ (isothermal disks) to $\delta=-3/2$, which corresponds to a radiation-pressure-supported disk; this spans the range of surface density distributions likely to be found in real astrophysical disks. There is a critical minimum size for unstable disks. The critical radius and the steady-state precession rate depend only weakly on $\delta$. The case $\delta=1$ divides the solutions into two qualitatively different regimes. Nonlinear effects must be important if the warp extends to the disk inner edge for $\delta \ge 1$, but for $\delta < 1$ nonlinearity will be important only if the warp amplitude is large at the origin. The effects of shadowing of the central source by the warp will thus be very different in the two regimes of $\delta.$ In real accretion disks the outer boundary condition is likely to be different from the zero-crossing condition that we have assumed. In accretion disks around massive black holes in active galactic nuclei, the disk will probably become optically thin before the outer disk boundary is reached, while in X-ray binaries, there will be an outer disk region (outside the circularization radius) in which the inflow velocity is zero but angular momentum is still transported. We show that in both these cases the solutions are similar to the zero-crossing eigenfunctions.Comment: 43 pages, 16 figures, to appear in The Astrophysical Journa

Short-term follow up after Large-Area RPE Removal by Microsecond Laser followed by hiPS-RPE suspension transplantation in rabbits

Cell therapy is a promising treatment for retinal pigment epithelium (RPE)-associated eye diseases. Herein, microsecond laser irradiation targeting RPE cells was used for large-area RPE removal followed by subretinal injection of human induced pluripotent stem cell derived RPE (hiPS-RPE). 19 immunosuppressed pigmented rabbits (Chinchilla bastard hybrid) underwent a large area RPE removal using an infrared reflectance (IR) confocal scanning laser ophthalmoscope (cSLO) with spectral-domain optical coherence tomography (SD-OCT) system (Heidelberg Engineering ) extended with a prototype laser (modified Merilas 532 shortpulse ophthalmic laser photocoagulator, Meridian Medical) (wavelength, 532 nm; pulse duration, 8 µs), followed by a 25G vitrectomy. Subsequently, a suspension of hiPS-RPE (1000 cells/ µl) was grafted subretinally into the RPE laser lesion under real-time intraoperative OCT imaging (RESCAN 700, Zeiss) by manual injection via a 25/38G cannula connected to a 100µl Hamilton syringe. 5 rabbits served as a control with hiPS-RPE injected subretinally over healthy RPE. The rabbits were followed with in vivo multimodal retinal imaging at baseline after laser and then for 7 days including fluorescein (FA) and indocyanine angiography (ICGA), aw well as SD-OCT (Spectralis ®, Heidelberg Engineering). Baseline imaging of RPE laser wounds showed mild late phase FA/ICGA leakage, with normal outer retinal and choroidal reflectivity on OCT, without signs of coagulation. The size of the RPE wounds was typically 10-12mm2. Real time iOCT showed a directed spread of the bleb retinal detachment (bRD) within the lasered zone, in contrast to a circular spread in controls. Subretinal injection ranged from 5-20µl, with lesser volumes/ larger bRD areas over lasered regions. At 7 days, implanted regions showed FA/ICGA leakage, blockage due to hyperpigmentation was observed mostly at the edges of the lasered zone; OCT showed hyperreflectivity of the outer retina with RPE irregularities. Control implantation sites showed hyperreflectivity in all retinal layers and a variably thickened RPE band suggesting clumping. Microsecond laser irradiation to the RPE seems to accelerate the subretinal integration of hiPS-RPE, when compared to subretinal injection over intact RPE. Future work will address correlation of multimodal imaging and histology. This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually

Direct limits for scalar field dark matter from a gravitational-wave detector

The nature of dark matter remains unknown to date, although several candidate particles are being considered in a dynamically changing research landscape1. Scalar field dark matter is a prominent option that is being explored with precision instruments, such as atomic clocks and optical cavities2–8. Here we describe a direct search for scalar field dark matter using a gravitational-wave detector, which operates beyond the quantum shot-noise limit. We set new upper limits on the coupling constants of scalar field dark matter as a function of its mass, by excluding the presence of signals that would be produced through the direct coupling of this dark matter to the beam splitter of the GEO600 interferometer. These constraints improve on bounds from previous direct searches by more than six orders of magnitude and are, in some cases, more stringent than limits obtained in tests of the equivalence principle by up to four orders of magnitude. Our work demonstrates that scalar field dark matter can be investigated or constrained with direct searches using gravitational-wave detectors and highlights the potential of quantum-enhanced interferometry for dark matter detection. © 2021, The Author(s)