Software development for infrasound measurement system

A software package developed for detection and analysis of infrasounds produced by air turbulence is described

Design of infrasound-detection system via adaptive LMSTDE algorithm

A proposed solution to an aviation safety problem is based on passive detection of turbulent weather phenomena through their infrasonic emission. This thesis describes a system design that is adequate for detection and bearing evaluation of infrasounds. An array of four sensors, with the appropriate hardware, is used for the detection part. Bearing evaluation is based on estimates of time delays between sensor outputs. The generalized cross correlation (GCC), as the conventional time-delay estimation (TDE) method, is first reviewed. An adaptive TDE approach, using the least mean square (LMS) algorithm, is then discussed. A comparison between the two techniques is made and the advantages of the adaptive approach are listed. The behavior of the GCC, as a Roth processor, is examined for the anticipated signals. It is shown that the Roth processor has the desired effect of sharpening the peak of the correlation function. It is also shown that the LMSTDE technique is an equivalent implementation of the Roth processor in the time domain. A LMSTDE lead-lag model, with a variable stability coefficient and a convergence criterion, is designed

Hubble Space Telescope Imaging of Bright Lyman-break Galaxy Candidates from the Sloan Digital Sky Survey: Not LBGs After All

We present deep Hubble Space Telescope ACS and NICMOS images of six bright Lyman-break galaxy candidates that were previously discovered in the Sloan Digital Sky Survey. We find that five of the objects are consistent with unresolved point sources. Although somewhat atypical of the class, they are most likely LoBAL quasars, perhaps FeLoBALs. The sixth object, J1147, has a faint companion galaxy located ~0.8 arcsec to the southwest. The companion contributes ~8% of the flux in the observed-frame optical and infrared. It is unknown whether this companion is located at the same redshift as J1147.Comment: 16 pages, 8 figures, 3 tables; accepted for publication in A

Urine Orotic Acid-Orotidine Levels in Azaribine-Treated Patients with Psoriasis

Azaribine, as a pyrimidine analog, blocks the decarboxylase conversion of orotidylic acid to uridine monophosphate with a resultant excretion of accumulated orotic acid and orotidine in the urine. Patients treated with azaribine may develop transitory, severe central nervous system symptoms of depression, lethargy, and ataxia. These side effects are not predictable from oral dosage, and blood levels of the drug are very difficult to determine. All of our psoriatic patients treated with azaribine excreted large but variable amounts of orotic acid-orotidine in the urine. Spot urine ratios of orotic acid-orotidine:creatinine correlated very well with measured 24-hr urine output of orotic acid-orotidine. Patients with central nervous system symptoms were found to have very high urine levels of orotic acid orotidine. These symptoms can be prevented by monitoring the urinary orotic acid-orotidine:creatinine ratio levels and keeping them within a range which is still compatible with successful management of the psoriatic lesions

Longitudinal patterns in an Arkansas River Valley stream: an Application of the River Continuum Concept

The River Continuum Concept (RCC) provides the framework for studying how lotic ecosystems vary from headwater streams to large rivers. The RCC was developed in streams in eastern deciduous forests of North America, but watershed characteristics and land uses differ across ecoregions, presenting unique opportunities to study how predictions of the RCC may differ across regions. Additionally, RCC predictions may vary due to the influence of fishes, but few studies have used fish taxa as a metric for evaluating predictions of the RCC. Our goal was to determine if RCC predictions for stream orders 1 through 5 were supported by primary producer, macroinvertebrate, and fish communities in Cadron Creek of the Arkansas River Valley. We sampled chlorophyll a, macroinvertebrates, and fishes at five stream reaches across a gradient of watershed size. Contrary to RCC predictions, chlorophyll a did not increase in concentration with catchment size. As the RCC predicts, fish and macroinvertebrate diversity increased with catchment size. Shredding and collecting macroinvertebrate taxa supported RCC predictions, respectively decreasing and increasing in composition as catchment area increased. Herbivorous and predaceous fish did not follow RCC predictions; however, surface-water column feeding fish were abundant at all sites as predicted. We hypothesize some predictions of the RCC were not supported in headwater reaches of this system due to regional differences in watershed characteristics and altered resource availability due to land use surrounding sampling sites

A variable geometry truss manipulator for positioning large payloads

A major thrust within the Department of Energy`s (DOE) Decontamination and Dismantling (D&D) Robotics program is the development of a Selective Equipment Removal System (SERS). SERS will consist of a mobile vehicle, a Dual-Arm Work Module (DAWM), and a deployment manipulator capable of extending the DAWM up to 6.096m (20) from the vehicle. The DAWM, built by RedZone Robotics, includes two Schilling Titan II manipulators, a unique five degree-of-freedom (DOF) module for positioning/orienting the two Schilling arms, and a massive steel backplane to maintain structural rigidity. Together with its payload, the DAWM weighs about 975 kg (2150 pounds). In order to accurately position the DAWM, the Pacific Northwest Laboratory (PNL) together with the National Aeronautics and Space Administration`s Langley Research Center (NASA LARC) are developing a deployment manipulator, which includes two double-octahedral Variable Geometry Truss (VGT) modules connected with a static truss section. The entire SERS system (Figure 1) will include the mobile vehicle, a 2-DOF base actuation system (waist rotate and pitch) with an output link approximately 2.134m (7) in length, the VGT system and the DAWM. The VGT system (Figure 2) consists of a 1.067m (42) diameter ({approximately}1.346m (53) long) base VGT, which mounts to the end of the output link of the base actuation system, a 1.524m (60) long static truss section which tapers from 1.067m (42) diameter at its base to 0.8128m (32) diameter at the end, and a 0.8128m (32) diameter ({approximately}1.0922m (43) long) tip VGT to which the DAWM is mounted. The stiffness of the VGT system is such that with the base VGT mounted to a rigid base and the VGT system oriented horizontally (worst case), the static deflection of the DAWM together with full payload will be less than 0.0254m

M Dwarfs in SDSS Stripe 82: Photometric Light Curves and Flare Rate Analysis

We present a flare rate analysis of 50,130 M dwarf light curves in SDSS Stripe 82. We identified 271 flares using a customized variability index to search ~2.5 million photometric observations for flux increases in the u- and g-bands. Every image of a flaring observation was examined by eye and with a PSF-matching and image subtraction tool to guard against false positives. Flaring is found to be strongly correlated with the appearance of H-alpha in emission in the quiet spectrum. Of the 99 flare stars that have spectra, we classify 8 as relatively inactive. The flaring fraction is found to increase strongly in stars with redder colors during quiescence, which can be attributed to the increasing flare visibility and increasing active fraction for redder stars. The flaring fraction is strongly correlated with |Z| distance such that most stars that flare are within 300 pc of the Galactic plane. We derive flare u-band luminosities and find that the most luminous flares occur on the earlier-type M dwarfs. Our best estimate of the lower limit on the flaring rate (averaged over Stripe 82) for flares with \Delta u \ge 0.7 magnitudes on stars with u < 22 is 1.3 flares hour^-1 square degree^-1 but can vary significantly with the line-of-sight.Comment: 44 pages, 13 figure

Improved redshifts for SDSS quasar spectra

A systematic investigation of the relationship between different redshift estimation schemes for more than 91000 quasars in the Sloan Digital Sky Survey (SDSS) Data Release 6 (DR6) is presented. The publicly available SDSS quasar redshifts are shown to possess systematic biases of Dz/(1+z)>=0.002 (600km/s) over both small (dz~0.1) and large (dz~1) redshift intervals. Empirical relationships between redshifts based on i) CaII H & K host galaxy absorption, ii) quasar [OII] 3728, iii) [OIII] 4960,5008 emission, and iv) cross-correlation (with a master quasar template) that includes, at increasing quasar redshift, the prominent MgII 2799, CIII] 1908 and CIV 1549 emission lines, are established as a function of quasar redshift and luminosity. New redshifts in the resulting catalogue possess systematic biases a factor of ~20 lower compared to the SDSS redshift values; systematic effects are reduced to the level of Dz/(1+z)<10^-4 (30km/s) per unit redshift, or <2.5x10^-5 per unit absolute magnitude. Redshift errors, including components due both to internal reproducibility and the intrinsic quasar-to-quasar variation among the population, are available for all quasars in the catalogue. The improved redshifts and their associated errors have wide applicability in areas such as quasar absorption outflows, quasar clustering, quasar-galaxy clustering and proximity-effect determinations.Comment: Accepted to MNRAS. The QSO redshift catalogue and QSO template spectrum can be downloaded from ftp://ftp.ast.cam.ac.uk/pub/phewett/ until 1st May 201