Estimating Column Density in Molecular Clouds with FIR and Sub-mm Emission Maps

We have used a numerical simulation of a turbulent cloud to synthesize maps of the thermal emission from dust at a variety of far-IR and sub-mm wavelengths. The average column density and external radiation field in the simulation is well matched to clouds such as Perseus and Ophiuchus. We use pairs of single-wavelength emission maps to derive the dust color temperature and column density, and we compare the derived column densities with the true column density. We demonstrate that longer wavelength emission maps yield less biased estimates of column density than maps made towards the peak of the dust emission spectrum. We compare the scatter in the derived column density with the observed scatter in Perseus and Ophiuchus. We find that while in Perseus all of the observed scatter in the emission-derived versus the extinction-derived column density can be attributed to the flawed assumption of isothermal dust along each line of sight, in Ophiuchus there is additional scatter above what can be explained by the isothermal assumption. Our results imply that variations in dust emission properties within a molecular cloud are not necessarily a major source of uncertainty in column density measurements.Comment: Accepted to ApJ Letter

The Propagation of Ly_ in Evolving Protoplanetary Disks

We study the role resonant scattering plays in the transport of Ly_ photons in accreting protoplanetary disk systems subject to varying degrees of dust settling. While the intrinsic stellar far-UV (FUV) spectrum of accreting T Tauri systems may already be dominated by a strong, broad Ly_ line (~80% of the FUV luminosity), we find that resonant scattering further enhances the Ly_ density in the deep molecular layers of the disk. Ly_ is scattered downward efficiently by the photodissociated atomic hydrogen layer that exists above the molecular disk. In contrast, FUV-continuum photons pass unimpeded through the photodissociation layer and (forward-)scatter inefficiently off dust grains. Using detailed, adaptive grid Monte Carlo radiative transfer simulations we show that the resulting Ly_/FUV-continuum photon density ratio is strongly stratified; FUV-continuum-dominated in the photodissociation layer and Ly_-dominated field in the molecular disk. The enhancement is greatest in the interior of the disk ( r ~ 1 AU) but is also observed in the outer disk ( r ~ 100 AU). The majority of the total disk mass is shown to be increasingly Ly_ dominated as dust settles toward the midplane.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90763/1/0004-637X_739_2_78.pd

Cognitive bias in a non-human primate: husbandry procedures influence cognitive indicators of psychological well-being in captive rhesus macaques

The measurement of 'cognitive bias' has recently emerged as a powerful tool for assessing animal welfare. Cognitive bias was initially, and widely, studied in humans, and describes the way in which particular emotions are associated with biases in information processing. People suffering from clinical levels of anxiety or depression, for example, interpret ambiguous events more negatively than do non-anxious or non-depressed people. Development of methods for use with non-human animals has revealed similar biases in several species of mammals and birds, and one invertebrate. However, cognitive bias has not been previously explored in any species of non-human primate, despite specific concerns raised about the welfare of these animals in captivity. Here, we describe a touchscreen-based cognitive-bias task developed for use with captive rhesus macaques (Macaca mulatta). Monkeys were initially trained on a 'Go/No-Go' operant task, in which they learned to touch one of two lines that differed in size in order to receive a reward (food), and to desist from touching the other line to avoid a mildly aversive stimulus (delay to the next trial and white noise). In testing sessions, the monkeys were presented with lines of intermediate size. We measured whether touchscreen responses to these ambiguous stimuli were affected by husbandry procedures (environmental enrichment, and a statutory health check involving restraint and ketamine hydrochloride injection) presumed to induce positive and negative shifts in affective state, respectively. Monkeys made fewer responses to ambiguous stimuli post health check compared to during the phase of enrichment suggesting greater expectation of negative outcomes following the health check compared to during enrichment. Shifts in affective state following standard husbandry procedures may therefore be associated with changes in information processing similar to those demonstrated in anxious and depressed humans, and in a number of other taxa

Emotion evaluation and response slowing in a non-human primate: New directions for cognitive bias measures of animal welfare

The cognitive bias model of animal welfare assessment is informed by studies with humans demonstrating that the interaction between emotion and cognition can be detected using laboratory tasks. A limitation of cognitive bias tasks is the amount of training required by animals prior to testing. A potential solution is to use biologically relevant stimuli that trigger innate emotional responses. Here; we develop a new method to assess emotion in rhesus macaques; informed byparadigms used with humans: emotional Stroop; visual cueing and; in particular; response slowing. In humans; performance on a simple cognitive task can become impaired when emotional distractor content is displayed. Importantly; responses become slower in anxious individuals in the presence of mild threat; a pattern not seen in non-anxious individuals; who are able to effectively process and disengage from the distractor. Here; we present a proof-of-concept study; demonstrating that rhesus macaques show slowing of responses in a simple touch-screen task when emotional content is introduced; but only when they had recently experienced a presumably stressful veterinary inspection. Our results indicate the presence of a subtle “cognitive freeze” response; the measurement of which may provide a means of identifying negative shifts in emotion in animals

A molecular genetic investigation of pivotal ABC-transporters involved in mycobacterial cell envelope biosynthesis

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is responsible for approximately 1.6 million deaths per annum. Mtb has a complex cell envelope that contains unique polysaccharide structures that include arabinogalactan, phosphatidyl-myo-inositol mannosides (PIMs), lipomannan and lipoarabinomannan. These glycoconjugates appear throughout Corynebacteria mycobacteria nocardia (CMN) group of bacterial organisms. However, the mechanism by which these key cell envelope components are translocated across the cytoplasmic membrane, remain to be elucidated. The ABC transporter superfamily of proteins are responsible for the movement of a wide variety of molecular species across membranes and require hydrolysis of ATP to provide energy to facilitate movement. Here I investigated two ABC transporter systems involved in galactan and PIM translocation in Corynebacteriaceae. Using phenotypic analysis of deletion mutants in C. glutamicum, I provide evidence to support that Rv1272c/Rv1273c are directly involved in PIM translocation as the deletion of the C. glutamicum orthologs results in a depletion of PIM species on the cell surface. Through characterising protein-ligand interactions between the M. smegmatis Rv3781 ortholog and immature galactan analogues, I present evidence to support the prediction that Rv3781/Rv3783 may be involved in galactan translocation. Finally, this study explores the effect of point mutations linked to Ethambutol (EMB) resistance in the key arabinosyltransferase (Emb) on the C. glutamicum cell envelope, through phenotypic characterisation of the effect on component cell envelope compounds