H2O and OH gas in the terrestrial planet-forming zones of protoplanetary disks

We present detections of numerous 10-20 micron H2O emission lines from two protoplanetary disks around the T Tauri stars AS 205A and DR Tau, obtained using the InfraRed Spectrograph on the Spitzer Space Telescope. Follow-up 3-5 micron Keck-NIRSPEC data confirm the presence of abundant water and spectrally resolve the lines. We also detect the P4.5 (2.934 micron) and P9.5 (3.179 micron) doublets of OH and 12CO/13CO v=1-0 emission in both sources. Line shapes and LTE models suggest that the emission from all three molecules originates between ~0.5 and 5 AU, and so will provide a new window for understanding the chemical environment during terrestrial planet formation. LTE models also imply significant columns of H2O and OH in the inner disk atmospheres, suggesting physical transport of volatile ices either vertically or radially; while the significant radial extent of the emission stresses the importance of a more complete understanding of non-thermal excitation processes.Comment: 9 pages, 3 figures, 1 table, aastex, to appear in the Astrophysical Journa

Recessive osteogenesis imperfecta caused by LEPRE1 mutations: clinical documentation and identification of the splice form responsible for prolyl 3-hydroxylation

Abstract: Background: Recessive forms of osteogenesis imperfecta (OI) may be caused by mutations in LEPRE1, encoding prolyl 3-hydroxylase-1 (P3H1) or in CRTAP, encoding cartilage associated protein. These proteins constitute together with cyclophilin B (CyPB) the prolyl 3-hydroxylation complex that hydroxylates the Pro986 residue in both the type I and type II collagen alpha 1-chains. Methods: We screened LEPRE1, CRTAP and PPIB (encoding CyPB) in a European/Middle Eastern cohort of 20 lethal/severe OI patients without a type I collagen mutation. Results: Four novel homozygous and compound heterozygous mutations were identified in LEPRE1 in four probands. Two probands survived the neonatal period, including one patient who is the eldest reported patient (17(7/12) years) so far with P3H1 deficiency. At birth, clinical and radiologic features were hardly distinguishable from those in patients with autosomal dominant (AD) severe/lethal OI. Follow-up data reveal that the longer lived patients develop a severe osteochondrodysplasia that overlaps with, but has some distinctive features from, AD OI. A new splice site mutation was identified in two of the four probands, affecting only one of three LEPRE1 mRNA splice forms, detected in this study. The affected splice form encodes a 736 amino acid (AA) protein with a "KDEL'' endoplasmic reticulum retention signal. While western blotting and immunocytochemical analysis of fibroblast cultures revealed absence of this P3H1 protein, mass spectrometry and SDS-urea-PAGE data showed severe reduction of alpha 1(I) Pro986 3-hydroxylation and overmodification of type I (pro) collagen chains in skin fibroblasts of the patients. Conclusion: These findings suggest that the 3-hydroxylation function of P3H1 is restricted to the 736AA splice form

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

IRS Spectra of Solar-Type Stars: \break A Search for Asteroid Belt Analogs

We report the results of a spectroscopic search for debris disks surrounding 41 nearby solar type stars, including 8 planet-bearing stars, using the {\it Spitzer Space Telescope}. With accurate relative photometry using the Infrared Spectrometer (IRS) between 7-34 \micron we are able to look for excesses as small as $\sim$2% of photospheric levels with particular sensitivity to weak spectral features. For stars with no excess, the $3\sigma$ upper limit in a band at 30-34 $\mu$m corresponds to $\sim$ 75 times the brightness of our zodiacal dust cloud. Comparable limits at 8.5-13 $\mu$m correspond to $\sim$ 1,400 times the brightness of our zodiacal dust cloud. These limits correspond to material located within the $<$1 to $\sim$5 AU region that, in our solar system, originates from debris associated with the asteroid belt. We find excess emission longward of $\sim$25 $\mu$m from five stars of which four also show excess emission at 70 $\mu$m. This emitting dust must be located around 5-10 AU. One star has 70 micron emission but no IRS excess. In this case, the emitting region must begin outside 10 AU; this star has a known radial velocity planet. Only two stars of the five show emission shortward of 25 \micron where spectral features reveal the presence of a population of small, hot dust grains emitting in the 7-20 $\mu$m band. The data presented here strengthen the results of previous studies to show that excesses at 25 \micron and shorter are rare: only 1 star out of 40 stars older than 1 Gyr or $\sim 2.5$% shows an excess. Asteroid belts 10-30 times more massive than our own appear are rare among mature, solar-type stars

Dynamic Neuromuscular Control of the Lower Limbs in Response to Unexpected Single-Planar versus Multi-Planar Support Perturbations in Young, Active Adults.

PURPOSE: An anterior cruciate ligament (ACL) injury involves a multi-planar injury mechanism. Nevertheless, unexpected multi-planar perturbations have not been used to screen athletes in the context of ACL injury prevention yet could reveal those more at risk. The objective of this study was to compare neuromuscular responses to multi-planar (MPP) and single-planar perturbations (SPP) during a stepping-down task. These results might serve as a basis for future implementation of external perturbations in ACL injury screening programs. METHODS: Thirteen young adults performed a single leg stepping-down task in eight conditions (four MPP and four SPP with a specified amplitude and velocity). The amplitudes of vastus lateralis (VL), vastus medialis (VM), hamstrings lateralis (HL), hamstrings medialis (HM) EMG activity, medio-lateral and anterior-posterior centre of mass (COM) displacements, the peak knee flexion and abduction angles were compared between conditions using an one-way ANOVA. Number of stepping responses were monitored during all conditions. RESULTS: Significantly greater muscle activity levels were found in response to the more challenging MPP and SPP compared to the less challenging conditions (p < 0.05). No differences in neuromuscular activity were found between the MPP conditions and their equivalents in the SPP. Eighteen stepping responses were monitored in the SPP versus nine in the MPP indicating that the overall neuromuscular control was even more challenged during the SPP which was supported by greater COM displacements in the SPP. CONCLUSION: The more intense MPP and SPP evoked different neuromuscular responses resulting in greater muscle activity levels compared to small perturbations. Based on the results of COM displacements and based on the amount of stepping responses, dynamic neuromuscular control of the knee joint appeared less challenged during the MPP. Therefore, future work should investigate extensively if other neuromuscular differences (i.e. co-activation patterns and kinetics) exist between MPP and SPP. In addition, future work should examine the influence on the neuromuscular control of the magnitude of the perturbations and the magnitude of stepping height and stepping distance

The Circumstellar Disk of HD 141569 Imaged with NICMOS

Coronagraphic imaging with the Near Infrared Camera and Multi Object Spectrometer on the Hubble Space Telescope reveals a large, ~400 AU (4'') radius, circumstellar disk around the Herbig Ae/Be star HD 141569. A reflected light image at 1.1 micron shows the disk oriented at a position angle of 356 +/- 5 deg and inclined to our line of sight by 51 +/- 3 deg; the intrinsic scattering function of the dust in the disk makes the side inclined toward us, the eastern side, brighter. The disk flux density peaks 185 AU (1.''85) from the star and falls off to both larger and smaller radii. A region of depleted material, or a gap, in the disk is centered 250 AU from the star. The dynamical effect of one or more planets may be necessary to explain this morphology.Comment: 4 pages, LaTeX with emulateapj.sty and epsfig.sty, 4 postscript figures, Accepted to ApJ Letter