38,111 research outputs found

    Microlensing of the Lensed Quasar SDSS0924+0219

    Full text link
    We analyze V, I and H band HST images and two seasons of R-band monitoring data for the gravitationally lensed quasar SDSS0924+0219. We clearly see that image D is a point-source image of the quasar at the center of its host galaxy. We can easily track the host galaxy of the quasar close to image D because microlensing has provided a natural coronograph that suppresses the flux of the quasar image by roughly an order of magnitude. We observe low amplitude, uncorrelated variability between the four quasar images due to microlensing, but no correlated variations that could be used to measure a time delay. Monte Carlo models of the microlensing variability provide estimates of the mean stellar mass in the lens galaxy (0.02 Msun < M < 1.0 Msun), the accretion disk size (the disk temperature is 5 x 10^4 K at 3.0 x 10^14 cm < rs < 1.4 x 10^15 cm), and the black hole mass (2.0 x 10^7 Msun < MBH \eta_{0.1}^{-1/2} (L/LE)^{1/2} < 3.3 x 10^8 Msun), all at 68% confidence. The black hole mass estimate based on microlensing is consistent with an estimate of MBH = 7.3 +- 2.4 x 10^7 Msun from the MgII emission line width. If we extrapolate the best-fitting light curve models into the future, we expect the the flux of images A and B to remain relatively stable and images C and D to brighten. In particular, we estimate that image D has a roughly 12% probability of brightening by a factor of two during the next year and a 45% probability of brightening by an order of magnitude over the next decade.Comment: v.2 incorporates referee's comments and corrects two errors in the original manuscript. 28 pages, 10 figures, published in Ap

    Investigating the Ecology of the Mound-Building Ant, \u3ci\u3eAcanthomyops Claviger\u3c/i\u3e (Hymenoptera: Formicidae), in Re-Created Prairie

    Get PDF
    Acanthomyops claviger (Roger) (Hymenoptera: Formicidae) forms conspicuous mounds within clumps of big bluestem, Andropogon gerardii, and prairie dropseed, Sporobolus heterolepsis, within a re-created tallgrass prairie in northeastern Illinois. This study explored the ecology of the nesting ant in the recreated prairie regarding the persistence of colonies, soil characteristics, the growth of grass clumps, and the species richness of the surrounding flora. Persistence of nests over one year was positively correlated to the diameters of mounds created by the colonies. Differences in soil moisture at 10 cm depth were significant over a growing season between grass clumps having nests of A. claviger and those not. Soil temperature at 10 cm depth over a growing season, organic fraction of the soil, and above-ground oven-dried biomass of grasses did not significantly vary based on nest presence. Floral richness was significantly higher in the vicinity of A. claviger nests than where nests were absent. Benefits of the ant-grass relationship are unknown, although a commensalistic relationship is at least suggested by the location of nests in grass clumps. The presence of A. claviger nests appears to have a positive effect on the richness of the surrounding flora, possibly through soil tunneling and seed distribution

    Radioisotope thermal photovoltaic application of the GaSb solar cell

    Get PDF
    An examination of a RTVP (radioisotopic thermophotovoltaic) conceptual design has shown a high potential for power densities well above those achievable with radioisotopic thermoelectric generator (RTG) systems. An efficiency of 14.4 percent and system specific power of 9.25 watts/kg were predicted for a system with sixteen GPHS (general purpose heat source) sources operating at 1100 C. The models also showed a 500 watt system power by the strontium-90 isotope at 1200 C at an efficiency of 17.0 percent and a system specific power of 11.8 watts/kg. The key to this level of performance is a high-quality photovoltaic cell with narrow bandgap and a reflective rear contact. Recent work at Boeing on GaSb cells and transparent back GaAs cells indicate that such a cell is well within reach

    Adeloye-Odeku Disease in Irrua, South-South Nigeria: The experience so far in a rural neurosurgical setting

    Get PDF
    First described in a publication by two Nigerian Neurosurgeons, Adeloye A and Odeku EL, in 1971, Adeloye-Odeku disease is a solitary congenital subgaleal inclusion dermoid cyst of the anterior fontanelle. This rare lesion, which makes up about 0.1-0.5% of all cranial tumours and 0.2% of all inclusion cysts, was initially thought to be found only in Africans. However, further reports have shown it to have a universal occurrence, as it has been reported in Caucasians, Chinese, Indians, and other part of the world. This lesion is also known as Congenital inclusion dermoid cyst (CIDS), is a benign slow-growing lesion, and if untreated, may persist to adult life. This article gives a highlight of the disease and its management and goes further to report 3 cases of this rare benign lesion seen in Irrua, South-South Nigeria, a rural, low-resource tertiary health institution. Incidentally and interestingly, all three cases presented within three consecutive months (January-March, 2019) at the neurosurgery outpatient clinic. Being uncomplicated cases, private and group counselling was done. The parents of the patients were much more reassured and relieved from their anxieties seeing others with similar problem. They were all worked up for surgery at different dates, had excision of the cysts with no complication and are currently being followed at the outpatient clinic.&nbsp

    Project for the analysis of technology transfer Quarterly evaluation report, 1 Jan. - 31 Mar. 1969

    Get PDF
    Technology transfer analysis project studying nonspace applications of NASA and AEC generated technolog

    Simultaneous Estimation of Time Delays and Quasar Structure

    Full text link
    We expand our Bayesian Monte Carlo method for analyzing the light curves of gravitationally lensed quasars to simultaneously estimate time delays and quasar structure including their mutual uncertainties. We apply the method to HE1104-1805 and QJ0158-4325, two doubly-imaged quasars with microlensing and intrinsic variability on comparable time scales. For HE1104-1805 the resulting time delay of (Delta t_AB) = t_A - t_B = 162.2 -5.9/+6.3 days and accretion disk size estimate of log(r_s/cm) = 15.7 -0.5/+0.4 at 0.2 micron in the rest frame are consistent with earlier estimates but suggest that existing methods for estimating time delays in the presence of microlensing underestimate the uncertainties. We are unable to measure a time delay for QJ0158-4325, but the accretion disk size is log(r_s/cm) = 14.9 +/- 0.3 at 0.3 micron in the rest frame.Comment: 21 pages, 6 figures, submitted to Ap

    Anchoring In Action: Manual Estimates Of Slant Are Powerfully Biased Toward Initial Hand Orientation And Are Correlated With Verbal Report

    Get PDF
    People verbally overestimate hill slant by approximately 15 degrees to 25 degrees, whereas manual estimates (e. g., palm board measures) are thought to be more accurate. The relative accuracy of palm boards has contributed to the widely cited theoretical claim that they tap into an accurate, but unconscious, motor representation of locomotor space. In the current work, 4 replications (total N = 204) carried out by 2 different laboratories tested an alternative anchoring hypothesis that manual action measures give low estimates because they are always initiated from horizontal. The results of all 4 replications indicate that the bias from response anchoring can entirely account for the difference between manual and verbal estimates. Moreover, consistent correlations between manual and verbal estimates given by the same observers support the conclusion that both measures are based on the same visual representation. Concepts from the study of judgment under uncertainty apply even to action measures in information rich environments

    Addressing student models of energy loss in quantum tunnelling

    Full text link
    We report on a multi-year, multi-institution study to investigate student reasoning about energy in the context of quantum tunnelling. We use ungraded surveys, graded examination questions, individual clinical interviews, and multiple-choice exams to build a picture of the types of responses that students typically give. We find that two descriptions of tunnelling through a square barrier are particularly common. Students often state that tunnelling particles lose energy while tunnelling. When sketching wave functions, students also show a shift in the axis of oscillation, as if the height of the axis of oscillation indicated the energy of the particle. We find inconsistencies between students' conceptual, mathematical, and graphical models of quantum tunnelling. As part of a curriculum in quantum physics, we have developed instructional materials to help students develop a more robust and less inconsistent picture of tunnelling, and present data suggesting that we have succeeded in doing so.Comment: Originally submitted to the European Journal of Physics on 2005 Feb 10. Pages: 14. References: 11. Figures: 9. Tables: 1. Resubmitted May 18 with revisions that include an appendix with the curriculum materials discussed in the paper (4 page small group UW-style tutorial

    Rapid toxicity detection in water quality control utilizing automated multispecies biomonitoring for permanent space stations

    Get PDF
    The objective of this study was to evaluate proposed design characteristics and applications of automated biomonitoring devices for real-time toxicity detection in water quality control on-board permanent space stations. Simulated tests in downlinking transmissions of automated biomonitoring data to Earth-receiving stations were simulated using satellite data transmissions from remote Earth-based stations
    corecore