Discovery of Reflection Nebulosity Around Five Vega-like Stars

Coronagraphic optical observations of six Vega-like stars reveal reflection nebulosities, five of which were previously unknown. The nebulosities illuminated by HD 4881, HD 23362, HD 23680, HD 26676, and HD 49662 resemble that of the Pleiades, indicating an interstellar origin for dust grains. The reflection nebulosity around HD 123160 has a double-arm morphology, but no disk-like feature is seen as close as 2.5 arcsec from the star in K-band adaptive optics data. We demonstrate that uniform density dust clouds surrounding HD 23362, HD 23680 and HD 123160 can account for the observed 12-100 micron spectral energy distributions. For HD 4881, HD 26676, and HD 49662 an additional emission source, such as from a circumstellar disk or non-equilibrium grain heating, is required to fit the 12-25 micron data. These results indicate that in some cases, particularly for Vega-like stars located beyond the Local Bubble (>100 pc), the dust responsible for excess thermal emission may originate from the interstellar medium rather than from a planetary debris system.Comment: The Astrophysical Journal, in press for March, 2002 (32 pages, 13 figures

A Single Circumbinary Disk in the HD 98800 Quadruple System

We present sub-arcsecond thermal infrared imaging of HD 98800, a young quadruple system composed of a pair of low-mass spectroscopic binaries separated by 0.8'' (38 AU), each with a K-dwarf primary. Images at wavelengths ranging from 5 to 24.5 microns show unequivocally that the optically fainter binary, HD 98800B, is the sole source of a comparatively large infrared excess upon which a silicate emission feature is superposed. The excess is detected only at wavelengths of 7.9 microns and longer, peaks at 25 microns, and has a best-fit black-body temperature of 150 K, indicating that most of the dust lies at distances greater than the orbital separation of the spectroscopic binary. We estimate the radial extent of the dust with a disk model that approximates radiation from the spectroscopic binary as a single source of equivalent luminosity. Given the data, the most-likely values of disk properties in the ranges considered are R_in = 5.0 +/- 2.5 AU, DeltaR = 13+/-8 AU, lambda_0 = 2(+4/-1.5) microns, gamma = 0+/-2.5, and sigma_total = 16+/-3 AU^2, where R_in is the inner radius, DeltaR is the radial extent of the disk, lambda_0 is the effective grain size, gamma is the radial power-law exponent of the optical depth, tau, and sigma_total is the total cross-section of the grains. The range of implied disk masses is 0.001--0.1 times that of the moon. These results show that, for a wide range of possible disk properties, a circumbinary disk is far more likely than a narrow ring.Comment: 11 page Latex manuscript with 3 postscript figures. Accepted for publication in Astrophysical Journal Letters. Postscript version of complete paper also available at http://www.hep.upenn.edu/PORG/web/papers/koerner00a.p

Committee Reports

Contains reports from the following committees of the Washington State Bar Association: Administrative Law, Civil Rights, Code Commission, Cooperation with American Bar Association, Federal Legislation, Improvement of Probate Statutes, Law Examiners, Legal Education, Legal Ethics, Legal Institutes, Legislative, Obituary, Selection of Judges, and Unauthorized Practice of Law. Also includes the auditor\u27s report

Integrating Low- and High-Level Skills in Instructional Protocols for Writing Disabilities

Twenty-four children with writing problems were given instruction in handwriting automaticity, spelling strategies, and the composing process (plan, write, review, revise) in 14 one-hour individual tutorials during the summer between third and fourth grade. Half the children (8 boys, 4 girls) received extra practice in composing, while half the children (8 boys, 4 girls) received special training in orthographic and phonological coding. Hierarchical linear modeling of growth curves was used to compare the treatment groups to a non-contact control group (10 boys, 5 girls) on a standard battery at pretest, midtest, posttest, and the two treatment groups with each other on probe measures of handwriting, spelling, and composition in each tutorial session. The treatment groups improved at a faster rate than the control group on some measures of handwriting, spelling, and composition (fluency and quality) in the standard battery, but Verbal IQ did not predict rate of improvement. Differences were found between the two treatment groups in some probe measures of writing and a motivation variable (work avoidance). Repeated-measures ANOVA was used to compare treatment groups to a non-contact control group at pretest, midtest, posttest, and follow-up. Differences between the treatment and control groups favoring the treatment groups were maintained at 6- month follow-up on some handwriting, spelling, and composition (quality) measures. Individual differences were found in learner characteristics prior to treatment and in response to the same treatment. The importance of affect and motivation as well as cognitive variables is emphasized

Influence of gas flow rate on liquid distribution in trickle-beds using perforated plates as liquid distributors

Two wire mesh tomography devices and a liquid collector were used to study the influence of the gas flow rate on liquid distribution when fluids distribution on top of the reactor is ensured by a perforated plate. In opposition to most of the studies realized by other authors, conditions in which the gas has a negative impact in liquid distribution were evidenced. Indeed, the obtained results show that the influence of gas flow rate depends on the quality of the initial distribution, as the gas forces the liquid to "respect" the distribution imposed at the top of the reactor. Finally, a comparison between the two measuring techniques shows the limitations of the liquid collector and the improper conclusions to which its use could lead

A double-lined spectroscopic orbit for the young star HD 34700

We report high-resolution spectroscopic observations of the young star HD 34700, which confirm it to be a double-lined spectroscopic binary. We derive an accurate orbital solution with a period of 23.4877 +/- 0.0013 days and an eccentricity of e = 0.2501 +/- 0.0068. The stars are found to be of similar mass (M2/M1 = 0.987 +/- 0.014) and luminosity. We derive also the effective temperatures (5900 K and 5800 K) and projected rotational velocities (28 km/s and 22 km/s) of the components. These values of v sin i are much higher than expected for main-sequence stars of similar spectral type (G0), and are not due to tidal synchronization. We discuss also the indicators of youth available for the object. Although there is considerable evidence that the system is young --strong infrared excess, X-ray emission, Li I 6708 absorption (0.17 Angstroms equivalent width), H alpha emission (0.6 Angstroms), rapid rotation-- the precise age cannot yet be established because the distance is unknown.Comment: 17 pages, including 2 figures and 2 tables. Accepted for publication in AJ, to appear in February 200

A Keplerian Disk around the Herbig Ae star HD169142

We present Submillimeter Array observations of the Herbig Ae star HD169142 in 1.3 millimeter continuum emission and 12CO J=2-1 line emission at 1.5 arcsecond resolution that reveal a circumstellar disk. The continuum emission is centered on the star position and resolved, and provides a mass estimate of about 0.02 solar masses for the disk. The CO images show patterns in position and velocity that are well matched by a disk in Keplerian rotation with low inclination to the line-of-sight. We use radiative transfer calculations based on a flared, passive disk model to constrain the disk parameters by comparison to the spectral line emission. The derived disk radius is 235 AU, and the inclination is 13 degrees. The model also necessitates modest depletion of the CO molecules, similar to that found in Keplerian disks around T Tauri stars.Comment: 10 pages, 2 figures, accepted by A

The Effect of Work Rate on Oxygen Uptake Kinetics During Exhaustive Severe Intensity Cycling Exercise

The effect of work rate on oxygen uptake kinetics during exhaustive severe intensity cycling exercise Jennifer L. Sylvester, Samantha D. Burdette, Steven W. Cross, Nosa O. Idemudia, John, H. Curtis, Jakob L. Vingren, David W. Hill. Applied Physiology Laboratory, University of North Texas, Denton, TX During exhaustive severe intensity exercise, the oxygen uptake (VO2) increases exponentially, with a time constant of ~30 s. After ~1 to 2 min, a slow component emerges and drives the VO2 to its maximum. There are clear differences in the VO2 response profile across exercise intensity domains. These disparities might not be attributable to metabolic demand but, rather, to characteristics of the various intensity domains, such as the consequences of lactic acid production. PURPOSE: To investigate the role of exercise intensity on the VO2 response profile at intensities wholly within the severe domain. METHODS: Four women (mean ± SD: age 22 ± 2 years, height 167 ± 7 cm, mass 66 ± 5 kg) and eight men (age 23 ± 2 yr, height 179 ± 9 cm, mass 78 ± 10 kg) performed exhaustive constant-power cycle ergometer tests at two different severe intensity work rates (263 ± 78 W and 214 ± 64 W). Smoothed breath-by-breath VO2 data were fitted to a two-component (primary response and slow component) model using iterative regression. RESULTS: Times to exhaustion were 217 ± 27 s and 590 ± 82 s, respectively. The VO2max values were the same at the two different work rates (2973 ± 691 ml·min-1 and 3011 ± 728 ml·min-1). The amplitude of the primary response was greater (p \u3c 0.05) at the higher work rate (2095 ± 716 ml·min-1) than at the lower work rate (1857 ± 618 ml·min-1) and the amplitude of the slow component was smaller (367 ± 177 ml·min-1 vs 645 ± 347 ml·min-1). In addition, the time delay before the emergence of the slow component was shorter at the higher work rate (92 ± 22 s vs 116 ± 42 s). CONCLUSION: The results show that exercise intensity per se affects the VO2 response profile within the severe intensity domain and suggest that metabolic demand drives the primary response of VO2 kinetics within this domain. Category to be judged: Master\u27

Models of in vitro spermatogenesis

Understanding the mechanisms that lead to the differentiation of male germ cells from their spermatogonial stem cells through meiosis to give rise to mature haploid spermatozoa has been a major quest for many decades. Unlike most other cell types this differentiation process is more or less completely dependent upon the cells being located within the strongly structured niche provided by mature Sertoli cells within an intact seminiferous epithelium. While much new information is currently being obtained through the application and description of relevant gene mutations, there is still a considerable need for in vitro models with which to explore the mechanisms involved. Not only are systems of in vitro spermatogenesis important for understanding the basic science, they have marked pragmatic value in offering ex vivo systems for the artificial maturation of immature germ cells from male infertility patients, as well as providing opportunities for the transgenic manipulation of male germ cells. In this review, we have summarized literature relating to simplistic culturing of germ cells, co-cultures of germ cells with other cell types, especially with Sertoli cells, cultures of seminiferous tubule fragments, and briefly mention the opportunities of xenografting larger testicular pieces. The majority of methods are successful in allowing the differentiation of small steps in the progress of spermatogonia to spermatozoa; few tolerate the chromosomal reduction division through meiosis, and even fewer seem able to complete the complex morphogenesis which results in freely swimming spermatozoa. However, recent progress with complex culture environments, such as 3-d matrices, suggest that possibly success is now not too far away