Doses under automatic exposure control (AEC) for direct digital radiographic (DDR) X-ray systems

Current guidelines quote tolerances for automatic exposure control (AEC) device performance for X-ray systems as 'Baseline ± X %'. However, in the situation where a baseline figure has not yet been achieved, as in the case of commissioning assessments, this tolerance is not relevant. The purpose of this work is to provide mean doses for direct digital radiography (DDR) X-ray system, operating in AEC, against which comparisons can be made. Dose measurements have been recorded under AEC operation on 29 DDR detectors from three different manufacturers. Two different testing protocols were examined: (1) water equivalent phantoms in front of the DDR detector and (2) aluminium block at the tube head. The average patient exit dose, using the aluminium block was 4.6 μGy with the antiscatter grid in place and 4.0 μGy with the grid removed. Using the water phantoms, the average dose was measured at 17.1 μGy with the antiscatter grid in place and 5.4 μGy with grid removed. Based on these results, it is clear that different testing configurations significantly impact on the measured dose.     

Microwave-assisted rapid discharge sintering of a bioactive glass�Cceramic

Bioactive glass-ceramics have been developed as successful bone graft materials. Although conventional sintering in an electrically-heated furnace is most commonly used, an alternative microwave plasma batch processing technique, known as rapid discharge sintering (RDS), is examined to crystallise the metastable base glass to form one or more ceramic phases. Apatite-mullite glass-ceramics (AMGC) were examined to elucidate the effects of RDS on the crystallization of a bioactive glass-ceramic. By increasing the fluorine content of the glass, the fluorapatite (FAp) and mullite crystallization onset temperatures can be reduced. Samples were sintered in a hydrogen and hydrogen/nitrogen discharge at temperatures of ≈800 and 1000 °C respectively with the higher sintering temperature required to form mullite. Results show that the material can be densified and crystallised using RDS in a considerably shorter time than conventional sintering due to heating and cooling rates of ≈400 °C/min.     

Self-regulation of motor vehicle advertising: is it working in Australia?

There is growing concern that certain content within motor vehicle advertising may have a negative influence on driving attitudes and behaviours of viewers, particularly young people, and hence a negative impact on road safety. In response, many developed countries have adopted a self-regulatory approach to motor vehicle advertising. However, it appears that many motor vehicle advertisements in Australia and elsewhere are not compliant with self-regulatory codes. Using standard commercial advertising methods, we exposed three motor vehicle ads that had been the subject of complaints to the Australian Advertising Standards Board (ASB) to, N = 463, 14–55 year olds to assess the extent to which their perceptions of the content of the ads communicated themes that were contrary to the Australian self-regulatory code. All three ads were found to communicate messages contrary to the code (such as the vehicle's speed and acceleration capabilities). However, the ASB had upheld complaints about only one of the ads. Where motor vehicle advertising regulatory frameworks exist to guide motor vehicle advertisers as to what is and what is not acceptable in their advertising, greater efforts are needed to ensure compliance with these codes. One way may be to make it mandatory for advertisers to report consumer pre-testing of their advertising to ensure that undesirable messages are not being communicated to viewers.     

Higher-level snake phylogeny inferred from mitochondrial DNA sequences of 12S rRNA and 16S rRNA genes

N-Nitrosomethylbenzylamine (NMBA) is a potent esophagus-specific carcinogen that has been utilized extensively in the study of esophageal carcinogenesis in rats. While many studies have focused on the pathogenesis of NMBA-induced esophageal tumors, the tumorigenicity of NMBA itself has not been thoroughly investigated in any single, systematic dose-response study. Therefore, in this study we evaluated NMBA tumorigenicity in rats following various short-term s.c. treatment regimens with the aim of developing an abbreviated treatment protocol which could be used in future studies. To assess the possible correlation of basal cell proliferation with NMBA tumorigenicity, we evaluated the expression of proliferating cell nuclear antigen (PCNA) in both control and NMBA-treated rats. In rats which received a cumulative NMBA dosage of 7.5 mg/kg over the course of 5 weeks, tumor incidence and multiplicity were as follows: 40% with 0.4 +/- 0.3 tumors/rat at week 10; 100% with 2.2 +/- 1.0 tumors/rat at week 20; and 100% with 2.3 +/- 1.0 tumors/rat at week 30. These rats exhibited marked increases in basal cell labeling, with indices that were 1.5- to 1.8-fold higher than controls. NMBA treatment regimens of shorter duration with equivalent or higher cumulative dosages were generally ineffective in producing esophageal tumors, even though significantly elevated levels of basal cell proliferation occurred. Together, these findings indicate that the duration of NMBA treatment is of critical importance in the tumorigenic potential of the carcinogen.     

Understanding Master-Planned Estates in Australian Cities: A Framework for Research

Master-planned estates (MPEs) are becoming increasingly important as a part of the urban residential fabric and have recently begun to attract significant research attention. Our purpose in this article is to engage critically with understandings of MPEs in the Australian context and to suggest the need for both empirical and theoretical expansion. We draw on research into MPEs in the greater metropolitan region of Sydney and demonstrate how their diverse form and character exceed the parameters of Blakely and Snyder's (Fortress America, Brookings Institution Press, Washington, DC, 1997) influential and widely cited typology of MPEs. In a move towards grounded theory, we build from our findings to suggest three key analytical dimensions needed to equip us with more complex and theory-driven understandings of the dynamic forms and outcomes of MPE development: (i) the nature of governance mechanisms that produce MPEs and govern life within them; (ii) the influence of housing market context on the unfolding of urban social processes; and (iii) the dynamic and lived nature of neighbourhood and community. These dimensions are aimed to capture the empirical multiplicity of the MPE phenomenon and to broaden the scope of the theoretical and analytical frameworks that have characterised their Australian analysis. It is our hope that analysis framed by these expanded dimensions can contribute to the project of enhancing theoretical recognition of urban difference under distinct and unique Australian conditions.     

Optimization of electrochemical infrared reflection absorption spectroscopy using Fresnel equations

To enhance the signal-to-noise ratio of electrochemical in situ IRRAS techniques, experimental conditions such as the angle of incidence and the thin cavity thickness should be optimized. Software which utilizes the Fresnel equations in matrix form was used to determine the experimental conditions at which the maximum in the mean square electric field strength (MSEFS) at the electrode surface is obtained. Calculations were done for Au in the mid infrared range from 4000 to 800 cm⁻¹ for six systems combined of three common IR windows (CaF₂, BaF₂ and ZnSe) and two electrolyte solvents (H₂O and D₂O). It was determined that the angle of incidence strongly depends on the refractive index of the electrolyte material, and that approximate values of the optimum angle of incidence can be found using a simple model and Snell's law. It was also shown that the thin cavity thickness affects the performance of the experimental setup via the phase shift of the radiation due to transmission through the solvent. The effect of the window materials and collimation on the experimental conditions is also discussed. The paper is designed to help researchers select the experimental conditions that optimize the performance of their spectroelectrochemical setup.     

Determination of foreign materials of plant origin in cotton linters

The present article describes a test procedure which can be used for determination of foreign materials of plant origin in raw cotton linters. Laboratories that perform the cellulose yield test require very little additional equipment to carry out this test. A portion of the dry cellulose sample, remaining after the completion of the AOCS Official Cellulose Yield Method Bb 3–47 is bleached, formed into a hand sheet and the total projected area of the visible dirts is determined on both sides of the hand sheet. The determination of the dirts is patterned according to principles used in Technical Association of Pulp and Paper Industries Standard Procedures T213 M-43 and T437 M-43. There are three main groups of foreign materials encountered: stalks, cockle burs and cotton seed hulls. The numbers and distribution of these particles vary with the general geographic locality and individual shipments of cotton linters. The test procedure described considers only those dirt particles which survive the major purification steps in the manufacturing of pulp from linters, and are undesirable from the quality point of view of the finished product. Prior to the development of the test only visual grading estimations have been used for this purpose. Presented at the AOCS Meeting, Minneapolis, 1963.