First optical images of circumstellar dust surrounding the debris disk candidate HD 32297

Near-infrared imaging with the Hubble Space Telescope recently revealed a circumstellar dust disk around the A star HD 32297. Dust scattered light is detected as far as 400 AU radius and the linear morphology is consistent with a disk ~10 degrees away from an edge-on orientation. Here we present the first optical images that show the dust scattered light morphology from 560 to 1680 AU radius. The position angle of the putative disk midplane diverges by 31 degrees and the color of dust scattering is most likely blue. We associate HD 32297 with a wall of interstellar gas and the enigmatic region south of the Taurus molecular cloud. We propose that the extreme asymmetries and blue disk color originate from a collision with a clump of interstellar material as HD 32297 moves southward, and discuss evidence consistent with an age of 30 Myr or younger.Comment: 5 pages; Accepted for publication in ApJ Letter

Calculation of Infrared-Divergent Feynman Diagrams with Zero Mass Threshold

Two-loop vertex Feynman diagrams with infrared and collinear divergences are investigated by two independent methods. On the one hand, a method of calculating Feynman diagrams from their small momentum expansion extended to diagrams with zero mass thresholds is applied. On the other hand, a numerical method based on a two-fold integral representation is used. The application of the latter method is possible by using lightcone coordinates in the parallel space. The numerical data obtained with the two methods are in impressive agreement.Comment: 20 pages, Latex with epsf-figures, References updated, to appear in Z.Phys.

System Identification Applied to Dynamic CFD Simulation and Wind Tunnel Data

Demanding aerodynamic modeling requirements for military and civilian aircraft have provided impetus for researchers to improve computational and experimental techniques. Model validation is a key component for these research endeavors so this study is an initial effort to extend conventional time history comparisons by comparing model parameter estimates and their standard errors using system identification methods. An aerodynamic model of an aircraft performing one-degree-of-freedom roll oscillatory motion about its body axes is developed. The model includes linear aerodynamics and deficiency function parameters characterizing an unsteady effect. For estimation of unknown parameters two techniques, harmonic analysis and two-step linear regression, were applied to roll-oscillatory wind tunnel data and to computational fluid dynamics (CFD) simulated data. The model used for this study is a highly swept wing unmanned aerial combat vehicle. Differences in response prediction, parameters estimates, and standard errors are compared and discusse

Closing the achievement gap : the implementation of direct instruction in Whiteville City schools

In Whiteville City Schools, beginning third grade students have a reading achievement gap as evidenced by students who score Level 3 or 4 on the Third Grade Pre-Test. Historically, the largest gap has been between African American males and White females. The achievement gap also extends to a gap in mathematics proficiency. In addition to having achievement gaps by race and gender, overall third grade students in Whiteville City Schools have proficiency levels that are lower that the state average and lower than those of comparable local schools. This thesis reports on an effort to close and eventually eliminate the achievement gap and raise proficiency overall; specifically, at the primary school, Direct Instruction was implemented as the reading program. Direct Instruction has proven successful as an effective method of instructing all children, particularly African American, in reading. The research has shown that success in reading is effective in closing achievement gaps. Findings show that, after adopting Direct Instruction at this one school, student achievement and proficiency increased and the achievement gap closed

Planets around active stars

We present the results of radial velocity measurements of two samples of active stars. The first sample contains field G and K giants across the Red Giant Branch, whereas the second sample consists of nearby young stars (d < 150 pc) with ages between 10 - 300 Myrs. The radial velocity monitoring program has been carried out with FEROS at 1.52 m ESO telescope (1999 - 2002) and continued since 2003 at 2.2 m MPG/ESO telescope. We observed stellar radial velocity variations which originate either from the stellar activity or the presence of stellar/substellar companions. By means of a bisector technique we are able to distinguish the sources of the radial velocity variation. Among them we found few candidates of planetary companions, both of young stars and G-K giants sample.Comment: 4 pages, 5 figures, to appear in the Proceedings of the ESO Workshop "Precision Spectroscopy in Astrophysics", eds. L. Pasquini, M. Romaniello, N.C. Santos, A. Correi

The Bearing Capacity of Simulated Lunar Surfaces in Vacuum

The static bearing capacity of a granular material consisting of dry, crushed olivine basalt was determined in air and in a 10^(-6) mm Hg vacuum by means of cylindrical probes with a range of diameters. Samples with various particle size distributions (all below 35 mesh) were used for these tests. It was found that the packing density of these granular materials was the factor which had the greatest effect on the bearing capacity. The minimum bearing capacity of a loosely packed sample with a density of 1.25 g/cm^3 was about 0.1 kg/cm^2. The maximum bearing capacity of a densely packed sample with density of 2.1 g/cm^3 was about 7 kg/cm^2. The effects of vacuum were insignificant compared with the effect of packing density. Direct shear tests indicated the cohesion in a few densely packed samples to be 1-2 X 10^4 dynes/cm^2. For the small probes used, the cohesion was estimated to contribute 85 to 95% of the observed bearing capacity for the densely packed samples, but much less for the loosely packed samples

Building a Practical Natural Laminar Flow Design Capability

A preliminary natural laminar flow (NLF) design method that has been developed and applied to supersonic and transonic wings with moderate-to-high leading-edge sweeps at flight Reynolds numbers is further extended and evaluated in this paper. The modular design approach uses a knowledge-based design module linked with different flow solvers and boundary layer stability analysis methods to provide a multifidelity capability for NLF analysis and design. An assessment of the effects of different options for stability analysis is included using pressures and geometry from an NLF wing designed for the Common Research Model (CRM). Several extensions to the design module are described, including multiple new approaches to design for controlling attachment line contamination and transition. Finally, a modification to the NLF design algorithm that allows independent control of Tollmien-Schlichting (TS) and cross flow (CF) modes is proposed. A preliminary evaluation of the TS-only option applied to the design of an NLF nacelle for the CRM is performed that includes the use of a low-fidelity stability analysis directly in the design module

Precise radial velocities of giant stars: I. Stable stars

Context: Future astrometric missions such as SIM PlanetQuest need very stable reference stars. K giants have large luminosities, which place them at large distances and thus the jitter of their photocenters by companions is relatively small. Therefore K giants would be best suited as references. To confirm this observationally a radial velocity survey is performed to quantify the level of intrinsic variability in K giants. Aims: From this radial velocity survey we present 34 K giants with an observed standard deviation of the radial velocity of less than 20 m/s. These stars are considered ``stable'' and can be used as radial velocity standards. Methods: The radial velocity survey contains 179 K giants. All K giants have a declination between -30 and +65 degrees and visual magnitude of 3-6 mag. The Coude Auxiliary Telescope (CAT) at UCO/Lick Observatory is used to obtain radial velocities with an accuracy of 5-8 m/s. The number of epochs for the 34 stable stars ranges from 11 to 28 with a total timespan of the observations between 1800 and a little over 2200 days. Results: The observational results of the 34 ``stable'' stars are shown together with a discussion about their position in the M_{V} vs. B-V diagram and some conclusions concerning the radial velocity variability of K giants. These results are in agreement with the theoretical predictions. K giants in a certain range of the M_{V} vs. B-V diagram are suitable reference stars.Comment: 8 pages, 4 figures, 2 tables, accepted for publication in A&

Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties

Since 1999, we have been conducting a radial velocity survey of 179 K giants using the CAT at UCO/Lick observatory. At present ~20-100 measurements have been collected per star with a precision of 5 to 8 m/s. Of the stars monitored, 145 (80%) show radial velocity (RV) variations at a level >20 m/s, of which 43 exhibit significant periodicities. Our aim is to investigate possible mechanism(s) that cause these observed RV variations. We intend to test whether these variations are intrinsic in nature, or possibly induced by companions, or both. In addition, we aim to characterise the parameters of these companions. A relation between log g and the amplitude of the RV variations is investigated for all stars in the sample. Furthermore, the hypothesis that all periodic RV variations are caused by companions is investigated by comparing their inferred orbital statistics with the statistics of companions around main sequence stars. A strong relation is found between the amplitude of the RV variations and log g in K giant stars, as suggested earlier by Hatzes & Cochran (1998). However, most of the stars exhibiting periodic variations are located above this relation. These RV variations can be split in a periodic component which is not correlated with log g and a random residual part which does correlate with log g. Compared to main-sequence stars, K giants frequently exhibit periodic RV variations. Interpreting these RV variations as being caused by companions, the orbital param eters are different from the companions orbiting dwarfs. Intrinsic mechanisms play an important role in producing RV variations in K giants stars, as suggested by their dependence on log g. However, it appears that periodic RV variations are additional to these intrinsic variations, consistent with them being caused by companions.Comment: 10 pages, accepted by A&