Resolving the Gap and AU-scale Asymmetries in the Pre-transitional Disk of V1247 Orionis

archiveprefix: arXiv primaryclass: astro-ph.SR keywords: accretion, accretion disks, protoplanetary disks, stars: pre-main sequence, techniques: interferometric eid: 80 adsurl: http://adsabs.harvard.edu/abs/2013ApJ...768...80K adsnote: Provided by the SAO/NASA Astrophysics Data SystemarticlePre-transitional disks are protoplanetary disks with a gapped disk structure, potentially indicating the presence of young planets in these systems. In order to explore the structure of these objects and their gap-opening mechanism, we observed the pre-transitional disk V1247 Orionis using the Very Large Telescope Interferometer, the Keck Interferometer, Keck-II, Gemini South, and IRTF. This allows us to spatially resolve the AU-scale disk structure from near- to mid-infrared wavelengths (1.5-13 μm), tracing material at different temperatures and over a wide range of stellocentric radii. Our observations reveal a narrow, optically thick inner-disk component (located at 0.18 AU from the star) that is separated from the optically thick outer disk (radii gsim 46 AU), providing unambiguous evidence for the existence of a gap in this pre-transitional disk. Surprisingly, we find that the gap region is filled with significant amounts of optically thin material with a carbon-dominated dust mineralogy. The presence of this optically thin gap material cannot be deduced solely from the spectral energy distribution, yet it is the dominant contributor at mid-infrared wavelengths. Furthermore, using Keck/NIRC2 aperture masking observations in the H, K', and L' bands, we detect asymmetries in the brightness distribution on scales of ~15-40 AU, i.e., within the gap region. The detected asymmetries are highly significant, yet their amplitude and direction changes with wavelength, which is not consistent with a companion interpretation but indicates an inhomogeneous distribution of the gap material. We interpret this as strong evidence for the presence of complex density structures, possibly reflecting the dynamical interaction of the disk material with sub-stellar mass bodies that are responsible for the gap clearing.This work was done in part under contract with the California Institute of Technology (Caltech), funded by NASA through the Sagan Fellowship Program (S.K. and C.E. are Sagan Fellows). Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work was supported in part by the Aerospace Corporation's Independent Research and Development (IR&D) program. This work was supported by NASA ADP grant NNX09AC73G

Inherited pathogenic mitochondrial DNA mutations and gastrointestinal stem cell populations.

Inherited mitochondrial DNA (mtDNA) mutations cause mitochondrial disease, but mtDNA mutations also occur somatically and accumulate during ageing. Studies have shown that the mutation load of some inherited mtDNA mutations decreases over time in blood, suggesting selection against the mutation. However, it is unknown whether such selection occurs in other mitotic tissues, and where it occurs within the tissue. Gastrointestinal epithelium is a canonical mitotic tissue rapidly renewed by stem cells. Intestinal crypts (epithelium) undergo monoclonal conversion with a single stem cell taking over the niche and producing progeny. We show: (1) that there is a significantly lower mtDNA mutation load in the mitotic epithelium of the gastrointestinal tract when compared to the smooth muscle in the same tissue in patients with the pathogenic m.3243A>G and m.8344A>G mutations; (2) that there is considerable variation seen in individual crypts, suggesting changes in the stem cell population; (3) that this lower mutation load is reflected in the absence of a defect in oxidative phosphorylation in the epithelium. This suggests that there is selection against inherited mtDNA mutations in the gastrointestinal stem cells that is in marked contrast to the somatic mtDNA mutations that accumulate with age in epithelial stem cells leading to a biochemical defect. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.Wellcome Trust. Grant Number: G096919 MRC ESRC EPSRC BBSRC Newcastle University Centre for Ageing and Vitalit

Confronting Standard Models of Proto–Planetary Disks With New Mid–Infrared Sizes from the Keck Interferometer

This is the final version of the article. Available from American Astronomical Society via the DOI in this record.The accepted author manuscript is in ORE at http://hdl.handle.net/10871/21611We present near- and mid-infrared (MIR) interferometric observations made with the Keck Interferometer Nuller and near-contemporaneous spectro-photometry from the infrared telescope facilities (IRTFs) of 11 well-known young stellar objects, several of which were observed for the first time in these spectral and spatial resolution regimes. With au-level spatial resolution, we first establish characteristic sizes of the infrared emission using a simple geometrical model consisting of a hot inner rim and MIR disk emission. We find a high degree of correlation between the stellar luminosity and the MIR disk sizes after using near-infrared data to remove the contribution from the inner rim. We then use a semi-analytical physical model to also find that the very widely used "star + inner dust rim + flared disk" class of models strongly fails to reproduce the spectral energy distribution (SED) and spatially resolved MIR data simultaneously; specifically a more compact source of MIR emission is required than results from the standard flared disk model. We explore the viability of a modification to the model whereby a second dust rim containing smaller dust grains is added, and find that the 2-rim model leads to significantly improved fits in most cases. This complexity is largely missed when carrying out SED modeling alone, although detailed silicate feature fitting by McClure et al. recently came to a similar conclusion. As has been suggested recently by Menu et al., the difficulty in predicting MIR sizes from the SED alone might hint at "transition disk"-like gaps in the inner au; however, the relatively high correlation found in our MIR disk size versus stellar luminosity relation favors layered disk morphologies and points to missing disk model ingredients instead.M.S. was supported by NASA ADAP grant NNX09AC73G. R.W.R. was supported by the IR&D program of The Aerospace Corporation

Digital PCR methods improve detection sensitivity and measurement precision of low abundance mtDNA deletions

Mitochondrial DNA (mtDNA) mutations are a common cause of primary mitochondrial disorders, and have also been implicated in a broad collection of conditions, including aging, neurodegeneration, and cancer. Prevalent among these pathogenic variants are mtDNA deletions, which show a strong bias for the loss of sequence in the major arc between, but not including, the heavy and light strand origins of replication. Because individual mtDNA deletions can accumulate focally, occur with multiple mixed breakpoints, and in the presence of normal mtDNA sequences, methods that detect broad-spectrum mutations with enhanced sensitivity and limited costs have both research and clinical applications. In this study, we evaluated semi-quantitative and digital PCR-based methods of mtDNA deletion detection using double-stranded reference templates or biological samples. Our aim was to describe key experimental assay parameters that will enable the analysis of low levels or small differences in mtDNA deletion load during disease progression, with limited false-positive detection. We determined that the digital PCR method significantly improved mtDNA deletion detection sensitivity through absolute quantitation, improved precision and reduced assay standard error

Variability of disk emission in pre-main sequence and related stars. II. Variability in the gas and dust emission of the Herbig Fe star SAO 206462

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.We present 13 epochs of near-infrared (0.8-5 μm) spectroscopic observations of the pre-transitional, "gapped" disk system in SAO 206462 (=HD 135344B). In all, six gas emission lines (Brα, Brγ, Paβ, Paγ, Paδ, Paepsilon, and the 0.8446 μm line of O I) along with continuum measurements made near the standard J, H, K, and L photometric bands were measured. A mass accretion rate of approximately 2 × 10–8 M ☉ yr–1 was derived from the Brγ and Paβ lines. However, the fluxes of these lines varied by a factor of over two during the course of a few months. The continuum also varied, but by only ~30%, and even decreased at a time when the gas emission was increasing. The H I line at 1.083 μm was also found to vary in a manner inconsistent with that of either the hydrogen lines or the dust. Both the gas and dust variabilities indicate significant changes in the region of the inner gas and the inner dust belt that may be common to many young disk systems. If planets are responsible for defining the inner edge of the gap, they could interact with the material on timescales commensurate with what is observed for the variations in the dust, while other disk instabilities (thermal, magnetorotational) would operate there on longer timescales than we observe for the inner dust belt. For SAO 206462, the orbital period would likely be 1-3 years. If the changes are being induced in the disk material closer to the star than the gap, a variety of mechanisms (disk instabilities, interactions via planets) might be responsible for the changes seen. The He I feature is most likely due to a wind whose orientation changes with respect to the observer on timescales of a day or less. To further constrain the origin of the gas and dust emission will require multiple spectroscopic and interferometric observations on both shorter and longer timescales that have been sampled so far.This work was supported by NASA ADP grants NNH06CC28C and NNX09AC73G, Hubble Space Telescope grants HST-GO-10764 and HST-GO-10864, Chilean National TAC grants CNTAC-010A-064

Aquaglyceroporin-null trypanosomes display glycerol transport defects and respiratory-inhibitor sensitivity

Aquaglyceroporins (AQPs) transport water and glycerol and play important roles in drug-uptake in pathogenic trypanosomatids. For example, AQP2 in the human-infectious African trypanosome, Trypanosoma brucei gambiense, is responsible for melarsoprol and pentamidine-uptake, and melarsoprol treatment-failure has been found to be due to AQP2-defects in these parasites. To further probe the roles of these transporters, we assembled a T. b. brucei strain lacking all three AQP-genes. Triple-null aqp1-2-3 T. b. brucei displayed only a very moderate growth defect in vitro, established infections in mice and recovered effectively from hypotonic-shock. The aqp1-2-3 trypanosomes did, however, display glycerol uptake and efflux defects. They failed to accumulate glycerol or to utilise glycerol as a carbon-source and displayed increased sensitivity to salicylhydroxamic acid (SHAM), octyl gallate or propyl gallate; these inhibitors of trypanosome alternative oxidase (TAO) can increase intracellular glycerol to toxic levels. Notably, disruption of AQP2 alone generated cells with glycerol transport defects. Consistent with these findings, AQP2-defective, melarsoprol-resistant clinical isolates were sensitive to the TAO inhibitors, SHAM, propyl gallate and ascofuranone, relative to melarsoprol-sensitive reference strains. We conclude that African trypanosome AQPs are dispensable for viability and osmoregulation but they make important contributions to drug-uptake, glycerol-transport and respiratory-inhibitor sensitivity. We also discuss how the AQP-dependent inverse sensitivity to melarsoprol and respiratory inhibitors described here might be exploited

Integration of decision support systems to improve decision support performance

Decision support system (DSS) is a well-established research and development area. Traditional isolated, stand-alone DSS has been recently facing new challenges. In order to improve the performance of DSS to meet the challenges, research has been actively carried out to develop integrated decision support systems (IDSS). This paper reviews the current research efforts with regard to the development of IDSS. The focus of the paper is on the integration aspect for IDSS through multiple perspectives, and the technologies that support this integration. More than 100 papers and software systems are discussed. Current research efforts and the development status of IDSS are explained, compared and classified. In addition, future trends and challenges in integration are outlined. The paper concludes that by addressing integration, better support will be provided to decision makers, with the expectation of both better decisions and improved decision making processes

Task-Related Effects on the Temporal and Spatial Dynamics of Resting-State Functional Connectivity in the Default Network

Recent evidence points to two potentially fundamental aspects of the default network (DN), which have been relatively understudied. One is the temporal nature of the functional interactions among nodes of the network in the resting-state, usually assumed to be static. The second is possible influences of previous brain states on the spatial patterns (i.e., the brain regions involved) of functional connectivity (FC) in the DN at rest. The goal of the current study was to investigate modulations in both the spatial and temporal domains. We compared the resting-state FC of the DN in two runs that were separated by a 45 minute interval containing cognitive task execution. We used partial least squares (PLS), which allowed us to identify FC spatiotemporal patterns in the two runs and to determine differences between them. Our results revealed two primary modes of FC, assessed using a posterior cingulate seed – a robust correlation among DN regions that is stable both spatially and temporally, and a second pattern that is reduced in spatial extent and more variable temporally after cognitive tasks, showing switching between connectivity with certain DN regions and connectivity with other areas, including some task-related regions. Therefore, the DN seems to exhibit two simultaneous FC dynamics at rest. The first is spatially invariant and insensitive to previous brain states, suggesting that the DN maintains some temporally stable functional connections. The second dynamic is more variable and is seen more strongly when the resting-state follows a period of task execution, suggesting an after-effect of the cognitive activity engaged during task that carries over into resting-state periods

The Embodiment of Success and Failure as Forward versus Backward Movements

People often speak of success (e.g., “advance”) and failure (e.g., “setback”) as if they were forward versus backward movements through space. Two experiments sought to examine whether grounded associations of this type influence motor behavior. In Experiment 1, participants categorized success versus failure words by moving a joystick forward or backward. Failure categorizations were faster when moving backward, whereas success categorizations were faster when moving forward. Experiment 2 removed the requirement to categorize stimuli and used a word rehearsal task instead. Even without Experiment 1’s response procedures, a similar cross-over interaction was obtained (e.g., failure memorizations sped backward movements relative to forward ones). The findings are novel yet consistent with theories of embodied cognition and self-regulation