Astronomical CCD Imaging at UMR: An Interim Report

Progress towards the modernization and update of the UMR observatory through the implementation of astronomical CCD technology is detailed. Preliminary image data is presented, specifically: globular cluster M13 and the lunar surface. An evaluation of the Santa Barbara Instrument Group’s (SBIG) ST-6 CCD camera is presented; bias frames, dark frames, and flat-fields are all examined. A custom optical assembly for instrument focusing and housing BVRI photometry and RGB colorimetry filters is described. The ST60PS data acquisition program, provided by SBIG, is reviewed. Additional work towards the development of a custom image processing utility program is mentioned. Finally, optical telescope collimation and polar alignment issues are discussed

The Impact of Iterative Reconstruction on Computed Tomography Radiation Dosimetry: Evaluation in a Routine Clinical Setting

PURPOSE: To evaluate the effect of introduction of iterative reconstruction as a mandated software upgrade on radiation dosimetry in routine clinical practice over a range of computed tomography examinations. METHODS: Random samples of scanning data were extracted from a centralised Picture Archiving Communication System pertaining to 10 commonly performed computed tomography examination types undertaken at two hospitals in Western Australia, before and after the introduction of iterative reconstruction. Changes in the mean dose length product and effective dose were evaluated along with estimations of associated changes to annual cancer incidence. RESULTS: We observed statistically significant reductions in the effective radiation dose for head computed tomography (22-27%) consistent with those reported in the literature. In contrast the reductions observed for non-contrast chest (37-47%); chest pulmonary embolism study (28%), chest/abdominal/pelvic study (16%) and thoracic spine (39%) computed tomography. Statistically significant reductions in radiation dose were not identified in angiographic computed tomography. Dose reductions translated to substantial lowering of the lifetime attributable risk, especially for younger females, and estimated numbers of incident cancers. CONCLUSION: Reduction of CT dose is a priority Iterative reconstruction algorithms have the potential to significantly assist with dose reduction across a range of protocols. However, this reduction in dose is achieved via reductions in image noise. Fully realising the potential dose reduction of iterative reconstruction requires the adjustment of image factors and forgoing the noise reduction potential of the iterative algorithm. Our study has demonstrated a reduction in radiation dose for some scanning protocols, but not to the extent experimental studies had previously shown or in all protocols expected, raising questions about the extent to which iterative reconstruction achieves dose reduction in real world clinical practice

Eastern Poison Ivy (<em>Toxicodendron radicans</em> L.): A Bioindicator of Natural and Anthropogenic Stress in Fields and Forests

This chapter considers herbaceous and woody plants near the 1800s era hydrocarbon extraction areas (HEAs) in Wiikwemkoong Unceded Territory (WUT) on Manitoulin Island, Lake Huron, Ontario, Canada. Plant community assessment used patterns of diversity and distribution at five field and six forest sites to assess the response of the plants to HEAs. These sites receive brine episodically from HEAs and natural seeps over the Collingwood Oil Shale Formation. This brine contains high concentrations of chloride and sodium along with total dissolved solids that exceed 100,000 mg/L. Exposure to brine is identified as the causative factor shaping plant distribution, survival, size, leaf bleaching (i.e., chlorosis), and dead branches on woody stems. These sites demonstrate an ecotone of disturbance defined by transition from natural plant community to dominance by eastern poison ivy (EPI, Toxicodendron radicans L.). Disturbed sites within brine drainage areas are dominated by EPI, reflecting tolerance to elevated salinity due to rhizome growth strategy. Evaluation of the plant communities and EPI allowed for preparation of a framework that can be used to guide interpretation of response of plants to drainage of brine from HEAs and natural sources beyond WUT

Momentum Transfer Between Polydisperse Particles in Dense Granular Flow

We perform molecular dynamics (MD) simulations (based on the soft-sphere model) of a model dry granular system consisting of two types of spherical particles differing in size and/or density to characterize particle-particle momentum transfer (solid drag). The velocity difference between two types of particles is specified in the initial conditions, and the evolution of relative mean velocity and the velocity fluctuations in terms of granular temperature are quantified. The dependence of the momentum transfer is studied as a function of volume fraction, size and density ratio of the two types of particles, inelasticity, and friction coefficient. An existing continuum model of particle-particle momentum transfer is compared to the MD simulations. A modified continuum solid drag model is suggested for a limited range of parameters

Desired and Feared-Quo vadis or Quid agis?

The recent article by Meng (2009a) continues a long tradition of articles in this journal dealing with the future of statistics and statisticians. For over 25 years many of these accounts painted varying shades of the same grim picture-that our continued existence is under threat; the challenges are great; respect has been in short supply; and our future is bleak. In this article I suggest we spend less time scanning the cross-disciplinary borders for new intrusions and rather than shoring up the fortress, we open up the borders. I share Meng&apos;s upbeat enthusiasm for a bright future while recognizing much remains to be done to increase our relevance and effectiveness

bayesnec: An R Package for Concentration-Response Modeling and Estimation of Toxicity Metrics

The bayesnec package has been developed for R to fit concentration (dose)-response curves (CR) to toxicity data for the purpose of deriving no-effect-concentration (NEC), no-significant-effect-concentration (NSEC), and effect-concentration (of specified percentage "x", ECx) thresholds from non-linear models fitted using Bayesian Hamiltonian Monte Carlo (HMC) via R packages brms and rstan or cmdstanr. In bayesnec it is possible to fit a single model, custom model-set, specific model-set or all of the available models. When multiple models are specified, the bnec() function returns a model weighted average estimate of predicted posterior values. A range of support functions and methods is also included to work with the returned single, or multi-model objects that allow extraction of raw, or model averaged predicted, NEC, NSEC and ECx values and to interrogate the fitted model or model-set. By combining Bayesian methods with model averaging, bayesnec provides a single estimate of toxicity and associated uncertainty that can be directly integrated into risk assessment frameworks

Editorial: Nucleic Acids Research and Nucleic Acid Therapeutics

Nucleic Acids Research has recently commissioned the publication of a series of Survey and Summary articles that encapsulate the current ‘state of the art’ surrounding the creation, function, behavior and optimization of nucleic acid molecules that may be adopted for clinical applications

Synchronous dynamics of zooplankton competitors prevail in temperate lake ecosystems

Although competing species are expected to exhibit compensatory dynamics (negative temporal covariation), empirical work has demonstrated that competitive communities often exhibit synchronous dynamics (positive temporal covariation). This has led to the suggestion that environmental forcing dominates species dynamics; however, synchronous and compensatory dynamics may appear at different length scales and/or at different times, making it challenging to identify their relative importance. We compiled 58 long-term datasets of zooplankton abundance in north-temperate and sub-tropical lakes and used wavelet analysis to quantify general patterns in the times and scales at which synchronous/compensatory dynamics dominated zooplankton communities in different regions and across the entire dataset. Synchronous dynamics were far more prevalent at all scales and times and were ubiquitous at the annual scale. Although we found compensatory dynamics in approximately 14% of all combinations of time period/scale/lake, there were no consistent scales or time periods during which compensatory dynamics were apparent across different regions. Our results suggest that the processes driving compensatory dynamics may be local in their extent, while those generating synchronous dynamics operate at much larger scales. This highlights an important gap in our understanding of the interaction between environmental and biotic forces that structure communities

Gravitational Lensing by Galaxy Groups in the Hubble Deep Field

We investigate strong lensing of galaxies in the Hubble Deep Field by foreground groups and clusters of galaxies with masses from $10^{13}$ to 10^{15} \MSun. Over this mass range, groups with the profile of Navarro, Frenk, & White (1995) are less efficient than singular isothermal spheres at producing multiple images of galaxies, by factors of $5 \times 10^{- 2}$ to $10^{- 3}$. This difference highlights the sensitivity of the lensing cross section to the central density profile. Nonetheless, with either profile we find that the expected number of galaxies lensed by groups in the Hubble Deep Field is at most $\lesssim 1$, consistent with the lack of clearly identified group lens systems.Comment: 33 pages, 12 EPS figures, accepted by Ap