Spitzer observations of the Hyades: Circumstellar debris disks at 625 Myr of age

We use the Spitzer Space Telescope to search for infrared excess at 24, 70, and 160 micron due to debris disks around a sample of 45 FGK-type members of the Hyades cluster. We supplement our observations with archival 24 and 70 micron Spitzer data of an additional 22 FGK-type and 11 A-type Hyades members in order to provide robust statistics on the incidence of debris disks at 625 Myr of age an era corresponding to the late heavy bombardment in the Solar System. We find that none of the 67 FGK-type stars in our sample show evidence for a debris disk, while 2 out of the 11 A-type stars do so. This difference in debris disk detection rate is likely to be due to a sensitivity bias in favor of early-type stars. The fractional disk luminosity, L_dust/L*, of the disks around the two A-type stars is ~4.0E-5, a level that is below the sensitivity of our observations toward the FGK-type stars. However, our sensitivity limits for FGK-type stars are able to exclude, at the 2-sigma level, frequencies higher than 12% and 5% of disks with L_dust/L* > 1.0E-4 and L_dust/L* > 5.0E-4, respectively. We also use our sensitivity limits and debris disk models to constrain the maximum mass of dust, as a function of distance from the stars, that could remain undetected around our targets.Comment: 33 pages, 11 figures, accepted by Ap

Capsule-based ultrasound-mediated targeted gastrointestinal drug delivery

Diseases which are prevalent in the gastrointestinal (GI) tract, such as Crohn's disease, are a topic of increasing concern because diagnosis and specific treatment are difficult and may be ineffective. New techniques are therefore sought after and this paper describes a proof-of-concept tethered capsule for targeted drug delivery (TDD) in the GI tract. The capsule consists of a camera, illumination, a drug delivery channel and an ultrasound (US) transducer. The transducer is described in detail, including a comparison of different piezoceramic materials that has been carried out. It was found that PZ54 (Ferroperm Piezoceramics, Kvistgaard, Denmark) was the most suitable material for our application. When driven at 4 Vpp, the outer diameter 5 mm PZ54 transducer operates at a frequency f = 4.05 MHz providing an acoustic pressure, Pac = 125 kPa, with a beam diameter, BD = 0.75 mm at the focus. Pressures in the range 50 - 300 kPa have been previously reported as suitable for sonoporation, a process vital in many TDD applications, so this is a promising result. Basic functional testing of the capsule was performed by supplying glass microbubbles (MBs) through the drug delivery channel into the US focus, monitored via the onboard camera. It was found that the acoustic radiation forces have a clear influence on the MBs, significantly changing their direction at the US focus. This suggests that drugs may be targeted to specific tissue in the GI tract by the new capsule. The results translate into a capsule configuration with the potential to be clinically and biologically useful

Intensive Grazing Systems for Beef Cattle Production

The objective of this study was to compare grazing systems that used rotational and continuous stocking for beef cows-calves and stocker cattle grazing fescue (Festuca arundinacea) and clover (Trifolium repens). For each system seven cows/calves and seven stocker steers were used within each of two replicates. The cows and stockers grazed stockpiled forage and were fed hay in winter, and grazed growing forage during spring and summer. Cows in the rotational system gained at a faster rate (P\u3c . 05) from October to April than those in the continuous system. Daily gains of calves were higher (P\u3c . 05) for the continuous system. Rate of gain during the last 28 days was higher (P\u3c . 05) for the stockers in the rotational system. Average hay yields were not different for the two stocking systems, but more (P\u3c . 05) hay was fed to the cattle in the continuous system. The system that used continuous stocking was more easily managed and required less labor and facilities

The bends on a quantum waveguide and cross-products of Bessel functions

A detailed analysis of the wave-mode structure in a bend and its incorporation into a stable algorithm for calculation of the scattering matrix of the bend is presented. The calculations are based on the modal approach. The stability and precision of the algorithm is numerically and analytically analysed. The algorithm enables precise numerical calculations of scattering across the bend. The reflection is a purely quantum phenomenon and is discussed in more detail over a larger energy interval. The behaviour of the reflection is explained partially by a one-dimensional scattering model and heuristic calculations of the scattering matrix for narrow bends. In the same spirit we explain the numerical results for the Wigner-Smith delay time in the bend.Comment: 34 pages, 21 figure

White noise approach to parabolic stochastic partial differential equations

A certain dass of stochastic partial differential equations of parabolic type is studied within white noise analysis

A Planetary Companion to gamma Cephei A

We report on the detection of a planetary companion in orbit around the primary star of the binary system $\gamma$ Cephei. High precision radial velocity measurements using 4 independent data sets spanning the time interval 1981--2002 reveal long-lived residual radial velocity variations superimposed on the binary orbit that are coherent in phase and amplitude with a period or 2.48 years (906 days) and a semi-amplitude of 27.5 m s$^{-1}$. We performed a careful analysis of our Ca II H & K S-index measurements, spectral line bisectors, and {\it Hipparcos} photometry. We found no significant variations in these quantities with the 906-d period. We also re-analyzed the Ca II $\lambda$8662 {\AA} measurements of Walker et al. (1992) which showed possible periodic variations with the ``planet'' period when first published. This analysis shows that periodic Ca II equivalent width variations were only present during 1986.5 -- 1992 and absent during 1981--1986.5. Furthermore, a refined period for the Ca II $\lambda$8662 {\AA} variations is 2.14 yrs, significantly less than residual radial velocity period. The most likely explanation of the residual radial velocity variations is a planetary mass companion with $M$ sin $i$ = 1.7 $M_{Jupiter}$ and an orbital semi-major axis of $a_2$ $=$ 2.13 AU. This supports the planet hypothesis for the residual radial velocity variations for $\gamma$ Cep first suggested by Walker et al. (1992). With an estimated binary orbital period of 57 years $\gamma$ Cep is the shortest period binary system in which an extrasolar planet has been found. This system may provide insights into the relationship between planetary and binary star formation.Comment: 19 pages, 15 figures, accepted in Ap. J. Includes additional data and improved orbital solutio

First High Contrast Imaging Using a Gaussian Aperture Pupil Mask

Placing a pupil mask with a gaussian aperture into the optical train of current telescopes represents a way to attain high contrast imaging that potentially improves contrast by orders of magnitude compared to current techniques. We present here the first observations ever using a gaussian aperture pupil mask (GAPM) on the Penn State near-IR Imager and Spectrograph (PIRIS) at the Mt. Wilson 100$^{\prime\prime}$ telescope. Two nearby stars were observed, $\epsilon$ Eridani and $\mu$ Her A. A faint companion was detected around $\mu$ Her A, confirming it as a proper motion companion. Furthermore, the observed H and K magnitudes of the companion were used to constrain its nature. No companions or faint structure were observed for $\epsilon$ Eridani. We found that our observations with the GAPM achieved contrast levels similar to our coronographic images, without blocking light from the central star. The mask's performance also nearly reached sensitivities reported for other ground based adaptive optics coronographs and deep HST images, but did not reach theoretically predicted contrast levels. We outline ways that could improve the performance of the GAPM by an order of magnitude or more.Comment: 8 pages, 4 figures, accepted by ApJ letter

Planetary astronomy

The authors profile the field of astronomy, identify some of the key scientific questions that can be addressed during the decade of the 1990's, and recommend several facilities that are critically important for answering these questions. Scientific opportunities for the 1990' are discussed. Areas discussed include protoplanetary disks, an inventory of the solar system, primitive material in the solar system, the dynamics of planetary atmospheres, planetary rings and ring dynamics, the composition and structure of the atmospheres of giant planets, the volcanoes of IO, and the mineralogy of the Martian surface. Critical technology developments, proposed projects and facilities, and recommendations for research and facilities are discussed

Rigorous approach to the comparison between experiment and theory in Casimir force measurements

In most experiments on the Casimir force the comparison between measurement data and theory was done using the concept of the root-mean-square deviation, a procedure that has been criticized in literature. Here we propose a special statistical analysis which should be performed separately for the experimental data and for the results of the theoretical computations. In so doing, the random, systematic, and total experimental errors are found as functions of separation, taking into account the distribution laws for each error at 95% confidence. Independently, all theoretical errors are combined to obtain the total theoretical error at the same confidence. Finally, the confidence interval for the differences between theoretical and experimental values is obtained as a function of separation. This rigorous approach is applied to two recent experiments on the Casimir effect.Comment: 10 pages, iopart.cls is used, to appear in J. Phys. A (special issue: Proceedings of QFEXT05, Barcelona, Sept. 5-9, 2005