Improving the photometric precision of IRAC Channel 1

Planning is underway for a possible post-cryogenic mission with the Spitzer Space Telescope. Only Channels 1 and 2 (3.6 and 4.5 μm) of the Infrared Array Camera (IRAC) will be operational; they will have unmatched sensitivity from 3 to 5 microns until the James Webb Space Telescope is launched. At SPIE Orlando, Mighell described his NASA-funded MATPHOT algorithm for precision stellar photometry and astrometry and presented MATPHOT-based simulations that suggested Channel 1 stellar photometry may be significantly improved by modeling the nonuniform RQE within each pixel, which, when not taken into account in aperture photometry, causes the derived flux to vary according to where the centroid falls within a single pixel (the pixel-phase effect). We analyze archival observations of calibration stars and compare the precision of stellar aperture photometry, with the recommended 1-dimensional and a new 2-dimensional pixel-phase aperture-flux correction, and MATPHOT-based PSF-fitting photometry which accounts for the observed loss of stellar flux due to the nonuniform intrapixel quantum efficiency. We show how the precision of aperture photometry of bright isolated stars corrected with the new 2-dimensional aperture-flux correction function can yield photometry that is almost as precise as that produced by PSF-fitting procedures. This timely research effort is intended to enhance the science return not only of observations already in Spitzer data archive but also those that would be made during the Spitzer Warm Mission

Socioecology of Marmots: Female Reproductive Strategies

This is the publisher's version, also available electronically from http://www.jstor.org/stable/info/1936439The relationship between female reproductive success and both spring food and hibernacula resources was examined in a high-altitude population of yellow-bellied marmots (Marmota flaviventris). The number of offspring a female weaned was significantly associated with the estimated number she could potentially produce, based on food resources. The production of young by these females is probably food limited to varying degrees. Hibernacula may be a restricted resource; young reared in an area without a hibernaculum were not recaptured as yearlings. Delaying pregnancy until forage is available fails as a strategy because young have insufficient time to accumulate fat for hibernation. Adult females deposit fat at a single maximum rate regardless of reproductive history; few females gain weight prior to weaning their young. In areas with short growing seasons, measured as the period during which nonreproductive adults gain weight, females may occasionally or regularly fail to reproduce in consecutive years. The short period of time following weaning may not permit the accumulation of fat sufficient to provide energy for hibernation, postmergence activity, and reproduction. The growth rate (g/day) of young marmots is greater at high than at intermediate elevations. This increase in growth rate warrants further examination of the hypothesis that increased sociality among marmots living in areas with short growing seasons is a response to decreased growth rates of young animals

Parallel biocomputing

<p>Abstract</p> <p>Background</p> <p>With the advent of high throughput genomics and high-resolution imaging techniques, there is a growing necessity in biology and medicine for parallel computing, and with the low cost of computing, it is now cost-effective for even small labs or individuals to build their own personal computation cluster.</p> <p>Methods</p> <p>Here we briefly describe how to use commodity hardware to build a low-cost, high-performance compute cluster, and provide an in-depth example and sample code for parallel execution of R jobs using MOSIX, a mature extension of the Linux kernel for parallel computing. A similar process can be used with other cluster platform software.</p> <p>Results</p> <p>As a statistical genetics example, we use our cluster to run a simulated eQTL experiment. Because eQTL is computationally intensive, and is conceptually easy to parallelize, like many statistics/genetics applications, parallel execution with MOSIX gives a linear speedup in analysis time with little additional effort.</p> <p>Conclusions</p> <p>We have used MOSIX to run a wide variety of software programs in parallel with good results. The limitations and benefits of using MOSIX are discussed and compared to other platforms.</p

Project PARAS: Phased array radio astronomy from space

An orbiting radio telescope is proposed which, when operated in a very long baseline interferometry (VLBI) scheme, would allow higher than currently available angular resolution and dynamic range in the maps and the ability to observe rapidly changing astronomical sources. Using passive phased array technology, the proposed design consists of 656 hexagonal modules forming a 150-m diameter antenna dish. Each observatory module is largely autonomous, having its own photovoltaic power supply and low-noise receiver and processor for phase shifting. The signals received by the modules are channeled via fiber optics to the central control computer in the central bus module. After processing and multiplexing, the data are transmitted to telemetry stations on the ground. The truss frame supporting each observatory panel is a novel hybrid structure consisting of a bottom graphite/epoxy tubular triangle and rigidized inflatable Kevlar tubes connecting the top observatory panel and the bottom triangle. Attitude control and station keeping functions will be performed by a system of momentum wheels in the bus and four propulsion modules located at the compass points on the periphery of the observatory dish. Each propulsion module has four monopropellant thrusters and four hydrazine arcjets, the latter supported by either a photovoltaic array or a radioisotope thermoelectric generator. The total mass of the spacecraft is about 20,500 kg

Dynamic simulation and modeling of gripper for applications in autonomous drone catcher

With advancing technology allowing for drones to become more efficient and evasive in their flight paths, researchers are looking for ways to solve the question of how can these drone be caught midair? Drawing inspiration from nature, the Biomimetics and Dexterous Manipulation Laboratory has developed a method of catching drone’s midair with an in-house designed and manufactured drone utilizing mechanisms from natures design. In implementing this drone design, simulations were needed to gain a better understanding of how the drone catcher would work as well as what data could be collected from a simulated collision. The 3D modeling software Solidworks was utilized to run a realistic simulation on the movement and motion of the main drone catching gripper. In running the simulations on the gripper collisions, it was found that this software was not capable of running high speed collisions at such a high rate of speed. In order for accurate simulations to be run, numerous calculations were needed to be evaluated in the span of a few thousandths of a second. This processing power could not be run on relatively powerful computers and the simulation was run at a slower, micro-gravity emulating, rate of speed. The resulting simulation gave a better understanding of how the drone catching device could capture objects midair, as well as how the mechanism worked within an instance of a collision.Oklahoma Louis Stokes Alliance for Minority Participation ProgramStanford University. Summer Undergraduate Research FellowshipSkydioMechanical Engineerin

Performance management i en krisetid

This article critically examines perfor- mance management. Performance management is an overall trend in manage- ment that focuses on Key Performance Indicators, generating and utilizing knowledge about the performance of employees in or- der to generate constant organizational performance and improvement. In the article we examine whether performance management is an effective management discipline in our contemporary times. We argue that our contemporary times after the financial crisis are more complex and filled with ambiguities than ever. In order to practice effective organizational leadership, this means that leaders must be able to navigate in and handle increasingly complex realities. Based on a theoretical discussion, exemplified by empirical materials, we argue that the performance management objectives of control, management and learning must be well-balanced and skillfully implemented in organizational practices for this discipline to actually support individual and organizational high-performance in times of complexity and ambiguity.Denne artikel undersøger, om 'performance management'-eller på dansk præstationsledelse— er et effektivt svar på de udfordringer, som organisationer står overfor i krisetider. I tiden efter finanskrisen i september 2008 er det blevet endnu mere relevant for ledere at kunne navigere i en brydningsfyldt krisetid, hvor fast grund under fødderne er svær at finde. I artiklen argumenteres for, at ledelse i en sådan krisetid godt kan drage inspiration fra præstationsledelsesparadigmet og dets fokus på styring, kontrol og læring, men kun hvis lederne formår at integrere og balancere netop styring, kontrol og læring

Improving the photometric precision of IRAC Channel 1

Planning is underway for a possible post-cryogenic mission with the Spitzer Space Telescope. Only Channels 1 and 2 (3.6 and 4.5 μm) of the Infrared Array Camera (IRAC) will be operational; they will have unmatched sensitivity from 3 to 5 microns until the James Webb Space Telescope is launched. At SPIE Orlando, Mighell described his NASA-funded MATPHOT algorithm for precision stellar photometry and astrometry and presented MATPHOT-based simulations that suggested Channel 1 stellar photometry may be significantly improved by modeling the nonuniform RQE within each pixel, which, when not taken into account in aperture photometry, causes the derived flux to vary according to where the centroid falls within a single pixel (the pixel-phase effect). We analyze archival observations of calibration stars and compare the precision of stellar aperture photometry, with the recommended 1-dimensional and a new 2-dimensional pixel-phase aperture-flux correction, and MATPHOT-based PSF-fitting photometry which accounts for the observed loss of stellar flux due to the nonuniform intrapixel quantum efficiency. We show how the precision of aperture photometry of bright isolated stars corrected with the new 2-dimensional aperture-flux correction function can yield photometry that is almost as precise as that produced by PSF-fitting procedures. This timely research effort is intended to enhance the science return not only of observations already in Spitzer data archive but also those that would be made during the Spitzer Warm Mission

Molecular Phylogenetics of Phyllanthaceae: Evidence from Plastid MatK and Nuclear PHYC Sequences

Plastid matK and a fragment of the low-copy nuclear gene PHYC were sequenced for 30 genera of Phyllanthaceae to evaluate tribal and generic delimitation. Resolution and bootstrap percentages obtained with matK are higher than that of PHYC but both regions show nearly identical phylogenetic patterns. Phylogenetic relationships inferred from the independent and combined data are congruent and differ from previous, morphology-based classifications but are highly concordant with those of the plastid gene rbcL previously published. Phyllanthaceae is monophyletic and gives rise to two well-resolved clades (T and F) that could be recognized as subfamilies. DNA sequence data for Keayodendron and Zimmermanniopsis are presented for the first time. Keayodendron is misplaced in tribe Phyllantheae and belongs to the Bridelia alliance. Zimmermanniopsis is sister to Zimmermannia. Phyllanthus and Cleistanthus are paraphyletic. Savia and Phyllanthus subgenus Kirganelia are not monophyletic.Organismic and Evolutionary Biolog