A Photometric Survey for Variables and Transits in the Field of Praesepe with KELT

The Kilodegree Extremely Little Telescope (KELT) project is a small aperture, wide-angle search for planetary transits of solar-type stars. In this paper, we present the results of a commissioning campaign with the KELT telescope to observe the open cluster Praesepe for 34 nights in early 2005. Lightcurves were obtained for 69,337 stars, out of which we identify 58 long period variables and 152 periodic variables. Sixteen of these are previously known as variable, yielding 194 newly discovered variable stars for which we provide properties and lightcurves. We also searched for planetary-like transits, finding four transit candidates. Follow-up observations indicate that two of the candidates are astrophysical false positives, with two candidates remaining as potential planetary transits.Comment: 45 pages, 16 figures. Submitted to AJ. PDF version with full resolution figures located at http://www.astronomy.ohio-state.edu/~pepper/kelt.pd

The Viking seismometry

Efforts were made to determine the seismicity of Mars as well as define its internal structure by detecting vibrations generated by marsquakes and meteoroid impacts. The lack of marsquakes recognized in the Viking data made it impossible to make any direct inferences about the interior of Mars and only allowed the setting of upper bounds on the seismic activity of the planet. After obtaining more than 2100 hours worth of data during the quite periods at rates of one sample per second or higher, the Viking 2 seismometer was turned off as a consequence of a landing system failure. During the periods when adequate data were obtained, one event of possible seismic or meteoroid impact origin was recognized; however, there is a significant probability that this event was generated by a wind gust

Improved spatial separation of neutral molecules

We have developed and experimentally demonstrated an improved electrostatic deflector for the spatial separation of molecules according to their dipole-moment-to-mass ratio. The device features a very open structure that allows for significantly stronger electric fields as well as for stronger deflection without molecules crashing into the device itself. We have demonstrated its performance using the prototypical OCS molecule and we discuss opportunities regarding improved quantum-state-selectivity for complex molecules and the deflection of unpolar molecules.Comment: 6 figure

Speckle Interferometry of Metal-Poor Stars in the Solar Neighborhood. I

We report the results of speckle-interferometric observations of 109 high proper-motion metal-poor stars made with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We resolve eight objects -- G102-20, G191-55, BD+19$^\circ$~1185A, G89-14, G87-45, G87-47, G111-38, and G114-25 -- into individual components and we are the first to astrometrically resolve seven of these stars. New resolved systems included two triple (G111-38, G87-47) and one quadruple (G89-14) star. The ratio of single-to-binary-to-triple-to-quadruple systems among the stars of our sample is equal to 71:28:6:1.Comment: 8 pages, 4 figures, accepted to Astrophysical Bulleti

The effects of UV radiation and electron bombardment on the flashover characteristics of alumina based high voltage insulators in vacuum

The effects of UV and electron bombardment on the flashover characteristics of highly stressed alumina insulators in vacuum were investigated as part of a project to improve the performance of high voltage insulators in large particle accelerators at CERN. An experimental system has been developed which allowed photon and electron bombardment of stressed insulator samples under vacuum, in order to investigate the causes and characteristics of insulator flashover, and to identify sample preparations which could improve insulator performance

The Interannual variability of hurricane activity in the Atlantic and east pacific regions

The investigation of the interannual and interdecadal variations in hurricane activity has been an important topic of study lately, especially with regard to their implications for climate change issues. On the interannual time-scale, the El Niño and Southern Oscillation (ENSO) phase has been correlated with hurricane activity in the Atlantic and Eastern Pacific Ocean Basins. For example, various atmospheric and oceanic parameters that influence hurricane development become significantly altered during an El Niño event, leading to suppressed easterly wave development and growth in the Atlantic, but more activity in the Eastern Pacific Ocean Basin. This study examined the interannual variability of hurricane intensity (measured as wind speed and interpreted through the Saffir-Simpson Scale) from 1938 through 2007 in the Atlantic and 1970 through 2007 in the Pacific basins, respectively. These data were then compared with the occurrence of El Niño/La Niña events as defined using the Japan Meteorological Association (JMA) index. El Niño/La Niña variability superimposed on variability associated with the Pacific Decadal Oscillation (PDO) was also examined here. Not surprisingly, during an El Niño year the intensity of Atlantic hurricanes was found to be weaker than during a neutral year or a La Niña year, but these conclusions were opposite in the Eastern Pacific Ocean Basin. There were also significant differences found in hurricane intensity between El Niño and La Niña years when the PDO was in phase 1 (warm phase), rather than when the PDO was in phase 2 (cool phase). This study also examined the interannual variation in hurricane intensity by genesis region (i.e. Atlantic: the eastern and western Atlantic Ocean Basins, the Caribbean, and the Gulf of Mexico; Eastern Pacific: divided into quadrants using 20o N and 125o W as the quadrant intersection point). Finally, the utility of this information in a long-range forecast application is demonstrated

A comparative study of different integrate-and-fire neurons: spontaneous activity, dynamical response, and stimulus-induced correlation

Stochastic integrate-and-fire (IF) neuron models have found widespread applications in computational neuroscience. Here we present results on the white-noise-driven perfect, leaky, and quadratic IF models, focusing on the spectral statistics (power spectra, cross spectra, and coherence functions) in different dynamical regimes (noise-induced and tonic firing regimes with low or moderate noise). We make the models comparable by tuning parameters such that the mean value and the coefficient of variation of the interspike interval match for all of them. We find that, under these conditions, the power spectrum under white-noise stimulation is often very similar while the response characteristics, described by the cross spectrum between a fraction of the input noise and the output spike train, can differ drastically. We also investigate how the spike trains of two neurons of the same kind (e.g. two leaky IF neurons) correlate if they share a common noise input. We show that, depending on the dynamical regime, either two quadratic IF models or two leaky IFs are more strongly correlated. Our results suggest that, when choosing among simple IF models for network simulations, the details of the model have a strong effect on correlation and regularity of the output.Comment: 12 page

Integrating CRISPR/Cas systems with programmable DNA nanostructures for delivery and beyond

Precise genome editing with CRISPR/Cas paves the way for many biochemical, biotechnological, and medical applications, and consequently, it may enable treatment of already known and still-to-be-found genetic diseases. Meanwhile, another rapidly emerging field—structural DNA nanotechnology—provides a customizable and modular platform for accurate positioning of nanoscopic materials, for e.g., biomedical uses. This addressability has just recently been applied in conjunction with the newly developed gene engineering tools to enable impactful, programmable nanotechnological applications. As of yet, self-assembled DNA nanostructures have been mainly employed to enhance and direct the delivery of CRISPR/Cas, but lately the groundwork has also been laid out for other intriguing and complex functions. These recent advances will be described in this perspective

Asteroseismology of solar-type stars with K2

We present the first detections by the NASA K2 Mission of oscillations in solar-type stars, using short-cadence data collected during K2 Campaign\,1 (C1). We understand the asteroseismic detection thresholds for C1-like levels of photometric performance, and we can detect oscillations in subgiants having dominant oscillation frequencies around $1000\,\rm \mu Hz$. Changes to the operation of the fine-guidance sensors are expected to give significant improvements in the high-frequency performance from C3 onwards. A reduction in the excess high-frequency noise by a factor of two-and-a-half in amplitude would bring main-sequence stars with dominant oscillation frequencies as high as ${\simeq 2500}\,\rm \mu Hz$ into play as potential asteroseismic targets for K2.Comment: Accepted for publication in PASP; 16 pages, 2 figure