Support minimized limited view CT using a priori data

This paper reports progress in work on CT reconstruction of incomplete X-ray (Radon) projection sets in situations where explicit object geometry and composition information is available. Previous work on this problem, reported in [1,2,3], addressed two major issues: 1.) appropriate compensation for missing projection data regarding flaws for which no explicit a priori data is available, and 2.) the scaling and geometric registration of explicit a priori component data. The first of these issues is addressed by restricting interest to the reconstruction of flaws which have high-contrast (high S/N) discontinuous boundaries. This restriction focuses attention on problems such as the inspection of monolithic material struc- tural components for cracks, porosity, inclusions, or dimensional abnormalities. It tends to exclude applications such as the imaging of slight density variations, or the imaging of diffuse boundary structures, such as might be encountered in medical applications. It was noted in the first year of this project that when reconstructing projection data from a compact support discontinuous boundary object, removal of a number of projections invariably increased the “size” of the reconstruction (i.e. increased the number of pixels above noise). This suggested that rather than setting the missing projection values to zero (12 norm minimization), it might be desirable to interpolate the missing projections such that the reconstructed object has a minimum size, i.e.minimum support. In a majority cases studied, this approach yields quite reasonable reconstructions of the object geometry, even in extreme cases where half the projection data is missing. When discrepancies between the true object and the reconstruction are significant due to extremely limited data, it was observed that support minimized reconstructions tend to be more intelligible than those of other methods, due to the straight-forward visual interpretation of the support minimized reconstruction

Ultrasonic Modeling Using Finite Domain Cubic Phase Integrals

Models of ultrasonic phenomena based on integral representations involve evaluation of integrals of the form(1

Collaboration and competition: ethics in toxicology

From animal research through adverse events in clinical trials to health scares around food contamination, toxicology has frequently been a focus of scientific and societal concern. As these concerns shift with each new drug, new technology or public health scare, how can toxicology stay current, relevant and ethical? Two of the biggest ethical challenges in pharmaceutical toxicology are the use of animals in testing and the high safety-related attrition rates in new drug development. Both of these require progress in the discipline that will only be driven by research funding. Yet, very little is invested in these two fields compared with investment in new efficacy models, new disease targets and new technologies. How can this be addressed? Here, we explore current paradigms in toxicology that may have the potential for perceived or actual unethical ramifications. We discuss the underpinnings of such practices and make recommendations for change around peer review, resourcing, transparency and data sharing. These ideas build on the analysis presented in the 2004 Paton Prize lecture (Purchase, 2004) where issues around conflict of interest (COI), collaboration and competition in the context of ethical behaviours were highlighted. These areas are clearly relevant to many aspects of scientific research but here we focus on toxicology and specifically toxicology in the pharmaceutical industry

Laryngeal Nerve Activity During Pulse Emission in the CF-FM Bat, Rhinolophus ferrumequinum. I. Superior Laryngeal Nerve (External Motor Branch)

The activity of the external (motor) branch of the superior laryngeal nerve (SLN), innervating the cricothyroid muscle, was recorded in the greater horseshoe bat,Rhinolophus ferrumequinum. The bats were induced to change the frequency of the constant frequency (CF) component of their echolocation signals by presenting artificial signals for which they Doppler shift compensated. The data show that the SLN discharge rate and the frequency of the emitted CF are correlated in a linear manner

Ocean-bottom krill sex

For the first time the entire sequence of the mating behaviour of Antarctic krill (Euphausia superba) in the wild is captured on underwater video. This footage also provides evidence that mating can take place near the seafloor at depths of 400700 m. This observation challenges the generally accepted concept of the pelagic lifestyle of krill. The mating behaviour observed most closely resembles the mating behaviour reported for a decapod shrimp (Penaeus). The implications of the new observation are also discussed. © The Author 2011. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissionsoup.com2011This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. © © The Author 2011. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissionsoup.com

An XMM-Newton view of M101 - III. Diffuse X-ray emission

We present a study of the X-ray properties of the nearby face-on Scd spiral galaxy M101 based on recent XMM–Newton observations. In this third and final paper in the present series, we focus on the spatial and spectral properties of the residual emission, after excluding bright X-ray sources with LX > 1037 erg s−1. Within a central region of radius 10 arcmin (21 kpc), the X-ray emission broadly traces the pattern of the spiral arms, establishing a strong link with recent star formation, but it also exhibits a radial scalelength of ≈2.6 arcmin (5.4 kpc) consistent with optical data. We estimate the soft X-ray luminosity within the central 5 arcmin (10.5 kpc) region to be LX ≈ 2.1 × 1039 erg s−1 (0.5–2 keV), the bulk of which appears to originate as diffuse emission. We find a two-temperature thermal model best fits the spectral data with derived temperatures of keV which are very typical of the diffuse components seen in other normal and starburst galaxies. More detailed investigation of the X-ray morphology reveals a strong correlation with images recorded in the far-ultraviolet through to V band, with the best match being with the U band. We interpret these results in terms of a clumpy thin-disc component which traces the spiral arms of M101 plus an extended lower halo component with large filling factor

Analysis of Ultrasonic Backscatter for Porosity Characterization in Graphite-Epoxy Composites

This paper summarizes recent work on the use of ultrasonic back-scatter for the estimation of porosity levels in continuous-fiber-reinforced, layered graphite-epoxy composites. This work is a continuation of previous work described in Refs. 1–3, which addresses the effect of porosity on (1) azimuthal angle backscatter scans, and (2) the spectral characteristics of backscatter

Racial Microaggressions, Stress, and Depression in African Americans: Test of a Model

The purpose of this study was to examine the interrelationships between daily hassle stressors (i.e., racial microaggressions and college hassle stress), racial identity, perceived stress, and depression among Black/African American college students. It was hypothesized that perceived stress would partially mediate the relationships between daily hassle stressors and depression. Racial identity was hypothesized to moderate the relationship between racial microaggressions and perceived stress. Data were analyzed from a sample of 142 Black/African American college students from a medium sized university in the Midwest. Utilizing EQS, a path analysis was conducted to test the hypothesized model. Findings from the analysis revealed that perceived stress partially mediated the relationship between college hassle stress and depression. Findings also revealed that perceived stress fully mediated the relationship between racial microaggressions and depression. Interestingly, a significant negative relationship was found between racial microaggressions and perceived stress. Racial identity was not a significant moderator in this study. Findings are indicative that Black/African American college students experience race-related stress differently than general daily hassles. Implications for future research, clinical interventions, and social justice initiatives are discussed