Magneto-optical Kerr effect in Eu1−xCaxB6Eu_{1-x}Ca_{x}B_{6}

We have measured the magneto-optical Kerr rotation of ferromagnetic $Eu_{1-x}Ca_{x}B_{6}$ with x=0.2 and 0.4, as well as of $YbB_{6}$ serving as the non-magnetic reference material. As previously for $EuB_{6}$, we could identify a feature at 1 $eV$ in the Kerr response which is related with electronic transitions involving the localized 4f electron states. The absence of this feature in the data for $YbB_{6}$ confirms the relevance of the partially occupied 4f states in shaping the magneto-optical features of $Eu$-based hexaborides. Disorder by $Ca$-doping broadens the itinerant charge carrier contribution to the magneto-optical spectra

Estimating the Parameters of Sgr A*'s Accretion Flow Via Millimeter VLBI

Recent millimeter-VLBI observations of Sagittarius A* (Sgr A*) have, for the first time, directly probed distances comparable to the horizon scale of a black hole. This provides unprecedented access to the environment immediately around the horizon of an accreting black hole. We leverage both existing spectral and polarization measurements and our present understanding of accretion theory to produce a suite of generic radiatively inefficient accretion flow (RIAF) models of Sgr A*, which we then fit to these recent millimeter-VLBI observations. We find that if the accretion flow onto Sgr A* is well described by a RIAF model, the orientation and magnitude of the black hole's spin is constrained to a two-dimensional surface in the spin, inclination, position angle parameter space. For each of these we find the likeliest values and their 1-sigma & 2-sigma errors to be a=0(+0.4+0.7), inclination=50(+10+30)(-10-10) degrees, and position angle=-20(+31+107)(-16-29) degrees, when the resulting probability distribution is marginalized over the others. The most probable combination is a=0(+0.2+0.4), inclination=90(-40-50) degrees and position angle=-14(+7+11)(-7-11) degrees, though the uncertainties on these are very strongly correlated, and high probability configurations exist for a variety of inclination angles above 30 degrees and spins below 0.99. Nevertheless, this demonstrates the ability millimeter-VLBI observations, even with only a few stations, to significantly constrain the properties of Sgr A*.Comment: 10 pages, 7 figures, accepted by Ap

A system for early warning of bearing failure

System for detecting incipient failure in ball bearings is described. Ultrasonic equipment detects bearing system resonance and provides warning signal through electronic circuitry. Detector can be used to evaluate performance of newly installed bearings. Schematic diagram is provided to show components

The Effects of Resistance Deception on Muscular Strength, Muscular Endurance, and Perceived Exertion

Resistance deception during training is a lightly researched topic and is seen as a modification that can potentially act on central control during exercise. Studies that have observed effects of deception while training have yielded mixed results. The effects of deception on strength, muscular endurance, and perceived exertion and the mechanisms of action that may elicit changes are still unclear. Therefore, the purpose of this study is to determine the effects of resistance deception on muscular strength, muscular endurance, and perceived exertion in a trained population. Eight participants finished the study and underwent four trials, one of which was a baseline trial, that consisted of one-rep max and repetitions to failure testing, with 60% of one-rep max, on bench press. Ensuing three experimental trials consisted of the bench press tests but in deceived/masked conditions. One trial was a 5% increase in weight, one trial was a 5% decrease in weight, and the third trial consisted of a weight that was equivalent to that of baseline. Repetitions, bar speed, and perceived exertion were monitored during each trial. During the deceived equivalent weight trial, participants significantly increased the number of repetitions and mean bar speed during the repetitions to failure test and experienced significantly decreased perceived exertion during the one-rep max lift. These findings indicate deception during training can acutely enhance performance outcomes. Key words: Resistance deception, muscular strength, perceived exertion, muscular enduranc

Boundaries of governance: Social responsibility in mining in Western Australia

This research investigated the boundaries of governance of social responsibility in three multinational mining organisations based in Perth, Western Australia. The mining industry has economic, environmental and social impacts, both positive and negative. While most of the attention of the media and supporters in government seems to focus on the positive impacts, a growing concern regarding the social implications of mining is clearly evident in public discourse and the academic literature. In response to public concern, the mining industry has adopted terms such as ‘sustainability’, ‘sustainable development’, ‘social licence to operate’ and ‘social responsibility’. Such phrases are widely used in annual reports and public statements. It seems reasonable then to expect that organisations in the industry would be managing the social impacts of mining with the same diligence that is applied to economic and environmental impacts. However the governance of social impacts and the social responsibilities of mining organisations have historically been managed reactively, rather than proactively, or have not been addressed at all. This study used phenomenological research methods to examine the perceptions of the people who are at the forefront of decision making for social responsibility in the mining industry: the managers in mining companies. The findings detail different conceptions of social responsibility, and how these affected governance and boundaries. The term ‘boundaries’ is used here to express what participants perceived as the limits of their organisation’s social responsibility. The thesis explores whether boundary setting was formal or informal, how boundaries were defined and under what conditions they changed. The research confirmed that terms such as ‘sustainable development’ were used widely; however the meanings attributed to these often obscured the narrow conception of the terms. This interpretation aligned with an organisationally strategic approach to social responsibility that primarily aimed to benefit the organisation, while the provision of benefits to other parties was a secondary consideration. The research found that the perceived level of risk to the organisation was most influential in defining boundaries, and risk itself was in a constant state of flux based on changing economic and social circumstances and changing perceptions. The findings showed that the organisations governed social responsibility to reduce risk to the organisation, and construed their social responsibilities through narrow interpretations of sustainability and sustainable development that foregrounded the organisation, rather than as a way to effectively and systematically reduce the negative impacts of mining on society or to contribute to sustainability in a broader sense

Design and fabrication of prototype system for early warning of impending bearing failure

Ball bearing performance tests run on several identical ball bearings under a variety of load, speed, temperature, and lubrication conditions are reported. Bearing temperature, torque, vibration, noise, strain, cage speed, etc., were monitored to establish those measurements most suitable as indicators of ball bearing health. Tape records were made under steady-state conditions of a variety of speeds and loads. Sample sections were selected for narrowband spectral analysis with a real time analyzer. An artificial flow was created across the inner race surface of one bearing using an acid etch technique to produce the scratch. Tape records obtained before and after established a characteristic frequency response that identifies the presence of the flow. The signals found most useful as indicators of performance degradation were ultrasonic outputs