On Estimating the QSO Transmission Power Spectrum

We present new methods to minimize the systematic and random errors for measuring the transmission power spectrum from the Lyman-alpha forest. Sources of systematic errors explored include metal line contamination and continuum-fitting. We advocate the technique of trend-removal in place of traditional continuum-fitting -- here, a spectrum is normalized by its (smoothly varying) mean rather than its continuum -- this method is easily automated and removes biases introduced by continuum-fitting. Trend- removal can be easily applied to spectra where continuum-fitting is difficult, such as when the resolution or signal-to-noise is low, or for spectra at high redshifts. Furthermore, a measurement of the continuum power spectrum using trend-removal, from either low redshift quasar spectra or the red-side of Lyman-alpha, allows in principle the removal of spurious power introduced by the continuum and thereby expanding scales probed to larger ones. We also derive expressions for the shot-noise bias and variance of the power spectrum estimate, taking into account the non-Poissonian nature of the shot-noise and the non-Gaussianity of the cosmic fluctuations. An appropriate minimum variance weighting of the data is given. Finally, we give practical suggestions on observing strategy: the desired resolution and S/N for different purposes, and how to distribute one's finite observing time among quasar targets. Also discussed is the quasar spectroscopic study of the Sloan Digital Sky Survey, which has the potential to measure the power spectrum at z ~ 2-4 accurate to better than 1 % per mode -- the techniques presented here will be useful for tackling the anticipated issues of shot-noise and continuum contamination.Comment: 35 pages, 14 figures, submitted to Ap

Mounting structure

A mounting platform for heat producing instruments operated in a narrow equilibrium temperature range comprises a grid-like structure with relatively large openings therein. The instruments are secured to and thermally coupled with the grid surface facing the instruments. Excess heat from the instruments is selectively radiated to the ambient through openings in the grid, the grid surfaces at these openings exhibiting low thermal emissivity and adsorptivity. The remainder of the grid is maintained at the equilibrium temperature and is covered with a thermal insulating blanket. Thus, the entire system including the platform and instruments is maintained substantially isothermal, whereby the instruments remain in fixed physical relationship to one another

Artemin Is a Vascular-Derived Neurotropic Factor for Developing Sympathetic Neurons

AbstractArtemin (ARTN) is a member of the GDNF family of ligands and signals through the Ret/GFRα3 receptor complex. Characterization of ARTN- and GFRα3-deficient mice revealed similar abnormalities in the migration and axonal projection pattern of the entire sympathetic nervous system. This resulted in abnormal innervation of target tissues and consequent cell death due to deficiencies of target-derived neurotrophic support. ARTN is expressed along blood vessels and in cells nearby to sympathetic axonal projections. In the developing vasculature, ARTN is expressed in smooth muscle cells of the vessels, and it acts as a guidance factor that encourages sympathetic fibers to follow blood vessels as they project toward their final target tissues. The chemoattractive properties of ARTN were confirmed by the demonstration that sympathetic neuroblasts migrate and project axons toward ARTN-soaked beads implanted into mouse embryos

Pyroelectric detectors

The multi-agency, long-term Global Change programs, and specifically NASA's Earth Observing system, will require some new and advanced photon detector technology which must be specifically tailored for long-term stability, broad spectral range, cooling constraints, and other parameters. Whereas MCT and GaAs alloy based photovoltaic detectors and detector arrays reach most impressive results to wavelengths as long as 12 microns when cooled to below 70 K, other materials, such as ferroelectrics and pyroelectrics, appear to offer special opportunities beyond 12 microns and above 70 K. These materials have found very broad use in a wide variety of room temperature applications. Little is known about these classes of materials at sub-room temperatures and no photon detector results have been reported. From the limited information available, researchers conclude that the room temperature values of D asterisk greater than or equal to 10(exp 9) cm Hz(exp 1/2)/W may be improved by one to two orders of magnitude upon cooling to temperatures around 70 K. Improvements of up to one order of magnitude appear feasible for temperatures achievable by passive cooling. The flat detector response over a wavelength range reaching from the visible to beyond 50 microns, which is an intrinsic advantage of bolometric devices, makes for easy calibration. The fact that these materials have been developed for reduced temperature applications makes ferro- and pyroelectric materials most attractive candidates for serious exploration

Structural studies of the PARP-1 BRCT domain

<p>Abstract</p> <p>Background</p> <p>Poly(ADP-ribose) polymerase-1 (PARP-1) is one of the first proteins localized to foci of DNA damage. Upon activation by encountering nicked DNA, the PARP-1 mediated trans-poly(ADP-ribosyl)ation of DNA binding proteins occurs, facilitating access and accumulation of DNA repair factors. PARP-1 also auto-(ADP-ribosyl)ates its central BRCT-containing domain forming part of an interaction site for the DNA repair scaffolding protein X-ray cross complementing group 1 protein (XRCC1). The co-localization of XRCC1, as well as bound DNA repair factors, to sites of DNA damage is important for cell survival and genomic integrity.</p> <p>Results</p> <p>Here we present the solution structure and biophysical characterization of the BRCT domain of rat PARP-1. The PARP-1 BRCT domain has the globular α/β fold characteristic of BRCT domains and has a thermal melting transition of 43.0°C. In contrast to a previous characterization of this domain, we demonstrate that it is monomeric in solution using both gel-filtration chromatography and small-angle X-ray scattering. Additionally, we report that the first BRCT domain of XRCC1 does not interact significantly with the PARP-1 BRCT domain in the absence of ADP-ribosylation. Moreover, none of the interactions with other longer PARP-1 constructs which previously had been demonstrated in a pull-down assay of mammalian cell extracts were detected.</p> <p>Conclusions</p> <p>The PARP-1 BRCT domain has the conserved BRCT fold that is known to be an important protein:protein interaction module in DNA repair and cell signalling pathways. Data indicating no significant protein:protein interactions between PARP-1 and XRCC1 likely results from the absence of poly(ADP-ribose) in one or both binding partners, and further implicates a poly(ADP-ribose)-dependent mechanism for localization of XRCC1 to sites of DNA damage.</p

Nutrient Enrichment Drives Gulf of Mexico Hypoxia

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95312/1/eost16763.pd

Bostonia: The Boston University Alumni Magazine. Volume 32

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Stability of Satellite Planes in M31 II: Effects of the Dark Subhalo Population

The planar arrangement of nearly half the satellite galaxies of M31 has been a source of mystery and speculation since it was discovered. With a growing number of other host galaxies showing these satellite galaxy planes, their stability and longevity have become central to the debate on whether the presence of satellite planes are a natural consequence of prevailing cosmological models, or represent a challenge. Given the dependence of their stability on host halo shape, we look into how a galaxy plane's dark matter environment influences its longevity. An increased number of dark matter subhalos results in increased interactions that hasten the deterioration of an already-formed plane of satellite galaxies in spherical dark halos. The role of total dark matter mass fraction held in subhalos in dispersing a plane of galaxies present non trivial effects on plane longevity as well. But any misalignments of plane inclines to major axes of flattened dark matter halos lead to their lifetimes being reduced to < 3 Gyrs. Distributing > 40% of total dark mass in subhalos in the overall dark matter distribution results in a plane of satellite galaxies that is prone to change through the 5 Gyr integration time period.Comment: 11 pages, 9 figures, accepted to MNRAS September 22 201

Minimally Invasive Mitral Valve Surgery III: Training and Robotic-Assisted Approaches.

Minimally invasive mitral valve operations are increasingly common in the United States, but robotic-assisted approaches have not been widely adopted for a variety of reasons. This expert opinion reviews the state of the art and defines best practices, training, and techniques for developing a successful robotics program