Reducing dose for digital cranial radiography : The increased source to the image-receptor distance approach

This investigation proposes that an increased source to the image-receptor distance (SID) technique can be used to optimize occipital frontal and lateral cranial radiographs acquired with direct digital radiography. Although cranial radiography is not performed on a routine basis, it should nonetheless be optimized to keep the dose to the patient as low as reasonably achievable, particularly because it can form part of the facial bone and sinus series. Dose measurements were acquired at various SIDs, and image quality was assessed using visual grading analysis. Statistically significant reductions in the effective dose between 19.2% and 23.9% were obtained when the SID was increased from the standard 100 to 150 cm (P ≤.05), and visual grading analysis scores indicate that image quality remained diagnostically acceptable for both projections. This investigation concludes that increasing the SID effectively optimizes occipital frontal and lateral skull radiographs. Radiology departments must be advised of the benefits of this technique with the goal of introducing an updated reference SID of 150 cm into clinical practice.Peer reviewe

Breast screening attendance of Aboriginal and Torres Strait Islander women in the Northern Territory of Australia

Objective: To compare breast screening attendances of Indigenous and non-Indigenous women. Methods: A total of 4,093 BreastScreen cases were used including 857 self-identified Indigenous women. Chi-squared analysis compared data between Indigenous and non-Indigenous women. Logistic regression was used for groupings based on visits-to-screening frequency. Odds ratios and 95% confidence intervals were calculated for associations with low attendance. Results: Indigenous women were younger and had fewer visits to screening compared with non-Indigenous women. Non-English speaking was mainly associated with fewer visits for Indigenous women only (OR 1.9, 95%CI 1.3-2.9). Living remotely was associated with fewer visits for non-Indigenous women only (OR 1.3, 95%CI 1.1-1.5). Shared predictors were younger age (OR 12.3, 95%CI 8.1-18.8; and OR 11.5, 95%CI 9.6-13.7, respectively) and having no family history of breast cancer (OR 2.1, 95%CI 1.3-3.3; and OR 1.8, 95%CI 1.5-2.1, respectively). Conclusions: Factors associated with fewer visits to screening were similar for both groups of women, except for language which was significant only for Indigenous women, and remoteness which was significant only for non-Indigenous women. Implications for public health: Health communication in Indigenous languages may be key in encouraging participation and retaining Indigenous women in BreastScreen; improving access for remote-living non-Indigenous women should also be addressed

Cryptic multicolored lizards in the Polychrus marmoratus Group (Squamata: Sauria: Polychrotidae) and the status of Leiolepis auduboni Hallowell

The Neotropical genus Polychrus contains seven species of arboreal lizards. The type species for the genus is the widespread Polychrus marmoratus. We compared a few populations of P. marmoratus using 16S and COI mitochondrial gene sequences (1,035 bp total) and found several lineages existing under the name Polychrus marmoratus. Working backwards, using morphology we identify Polychrus marmoratus from the Guiana Shield and resurrect the name Leiolepis auduboni Hallowell for the species present in Trinidad, Tobago, and northern Venezuela. The number of species in the genus Polychrus is raised to eight. However, we also discuss evidence for the existence of other cryptic species withi

Why Do Only Some Galaxy Clusters Have Cool Cores?

Flux-limited X-ray samples indicate that about half of rich galaxy clusters have cool cores. Why do only some clusters have cool cores while others do not? In this paper, cosmological N-body + Eulerian hydrodynamic simulations, including radiative cooling and heating, are used to address this question as we examine the formation and evolution of cool core (CC) and non-cool core (NCC) clusters. These adaptive mesh refinement simulations produce both CC and NCC clusters in the same volume. They have a peak resolution of 15.6 h^{-1} kpc within a (256 h^{-1} Mpc)^3 box. Our simulations suggest that there are important evolutionary differences between CC clusters and their NCC counterparts. Many of the numerical CC clusters accreted mass more slowly over time and grew enhanced cool cores via hierarchical mergers; when late major mergers occurred, the CC's survived the collisions. By contrast, NCC clusters experienced major mergers early in their evolution that destroyed embryonic cool cores and produced conditions that prevented CC re-formation. As a result, our simulations predict observationally testable distinctions in the properties of CC and NCC beyond the core regions in clusters. In particular, we find differences between CC versus NCC clusters in the shapes of X-ray surface brightness profiles, between the temperatures and hardness ratios beyond the cores, between the distribution of masses, and between their supercluster environs. It also appears that CC clusters are no closer to hydrostatic equilibrium than NCC clusters, an issue important for precision cosmology measurements.Comment: 17 emulateapj pages, 17 figures, replaced with version accepted to Ap

Radar Altimetry as a Robust Tool for Monitoring the Active Lava Lake at Erebus Volcano, Antarctica

The level of lava within a volcanic conduit reflects the overpressure within a connected magma reservoir. Continuous monitoring of lava level can therefore provide critical insights into volcanic processes, and aid hazard assessment. However, accurate measurements of lava level are not easy to make, partly owing to the often dense fumes that hinder optical techniques. Here, we present the first radar instrument designed for the purpose of monitoring lava level, and report on its successful operation at Erebus volcano, Antarctica. We describe the hardware and data processing steps followed to extract a time series of lava lake level, demonstrating that we can readily resolve ~1 m cyclic variations in lake level that have previously been recognised at Erebus volcano. The performance of the radar (continuous, automated data collection in temperatures of around -30°C) indicates the suitability of this approach for sustained automated measurements at Erebus and other volcanoes with lava lakes

Dental service patterns among private and public adult patients in Australia

Background While the majority of dental care in Australia is provided in the private sector those patients who attend for public care remain a public health focus due to their socioeconomic disadvantage. The aims of this study were to compare dental service profiles provided to patients at private and public clinics, controlling for age, sex, reason for visit and income. Methods Data were collected in 2004–06, using a three-stage, stratified clustered sample of Australians aged 15+ years, involving a computer-assisted telephone interview (CATI), oral examination and mailed questionnaire. Analysis was restricted to those who responded to the CATI. Results A total of 14,123 adults responded to the CATI (49% response) of whom 5,505 (44% of those interviewed) agreed to undergo an oral epidemiological examination. Multivariate analysis controlling for age, sex, reason for visit and income showed that persons attending public clinics had higher odds [Odds ratio, 95%CI] of extraction (1.69, 1.26–2.28), but lower odds of receiving oral prophylaxis (0.50, 0.38–0.66) and crown/bridge services (0.34, 0.13–0.91) compared to the reference category of private clinics. Conclusion Socio-economically disadvantaged persons who face barriers to accessing dental care in the private sector suffer further oral health disadvantage from a pattern of services received at public clinics that has more emphasis on extraction of teeth and less emphasis on preventive and maintenance care.David S Brennan, Liana Luzzi and Kaye F Roberts-Thomso

Electrochemical characterization and regeneration of sulfur poisoned Pt catalysts in aqueous media

Understanding the poisoning and recovery of precious metal catalysts is greatly relevant for the chemical industry dealing with the synthesis of organic compounds. For example, hydrogenation reactions typically use platinum catalysts and sulfuric acid media, leading to poisoning by sulfur-containing species. In this work, we have applied electrochemical methods to understand the status and recovery of Pt catalysts by studying the electro-oxidation of a family of sulfur-containing species adsorbed at several types of Pt electrodes: (i) polycrystalline Pt foil; (ii) Pt single-crystal electrodes; and (iii) Pt nanoparticles supported on Vulcan carbon. The results obtained from polycrystalline Pt electrodes and Pt nanoparticles supported on Vulcan carbon demonstrate that all sulfur-containing species with different oxidation states (2-, 3+ and 4+) lead to the poisoning of Pt active sites. X-ray photoelectron spectroscopy (XPS) analysis was employed to elucidate the chemical state of sulfur species during the recovery process. The degree of poisoning decreased with increased sulfur oxidation state, while the rate of regeneration of the Pt surfaces generally increases with the oxidation state of the sulfur species. Finally, the use of Pt single-crystal electrodes reveals the surface-structure sensitivity of the oxidation of the sulfur species. This information could be useful in designing catalysts that are less susceptible to poisoning and/or more easily regenerated. These studies demonstrate voltammetry to be a powerful method for assessing the status of platinum surfaces and for recovering catalyst activity, such that electrochemical methods could find applications as sensors in catalysis and for catalyst recovery in-situ

Mammographic densities of Aboriginal and non-Aboriginal women living in Australia's Northern Territory

Objectives: To compare the mammographic densities and other characteristics of Aboriginal and non-Aboriginal women screened in Australia. Methods: Population screening programme data of Aboriginal (n = 857) and non-Aboriginal women (n = 3236) were used. Mann–Whitney U test compared ages at screening and Chi-square tests compared personal and clinical information. Logistic regression analysis was used for density groupings. OR and 95% CI were calculated for multivariate association for density. Results: Mammographic density was lower amongst Aboriginal women (P < 0.001). For non-Aboriginal women, higher density was associated with younger age (OR 2.4, 95% CI 2.1–2.8), recall to assessment (OR 2.2, 95% CI 1.6–3.0), family history of breast cancer (OR 1.4, 95% CI 1.2–1.6), English-speaking background (OR 1.4, 95% CI 1.2–1.6), and residence in remote areas (OR 1.2, 95% CI 1.1–1.4). For Aboriginal women, density was associated with younger age (OR 2.7, 95% CI 2.0–3.5; P < 0.001), and recall to assessment (OR 2.3, 95% CI 1.4–3.9; P < 0.05). Conclusions: Significant differences between Aboriginal and non-Aboriginal women were found. There were more significant associations for dense breasts for non-Aboriginal women than for Aboriginal women