Vertical structures induced by embedded moonlets in Saturn's rings: the gap region

We study the vertical extent of propeller structures in Saturn's rings. Our focus lies on the gap region of the propeller and on non-inclined propeller moonlets. In order to describe the vertical structure of propellers we extend the model of Spahn and Sremcevic (2000) to include the vertical direction. We find that the gravitational interaction of ring particles with the non-inclined moonlet does not induce considerable vertical excursions of ring particles, but causes a considerable thermal motion in the ring plane. We expect ring particle collisions to partly convert the lateral induced thermal motion into vertical excursions of ring particles. For the gap region of the propeller, we calculate gap averaged propeller heights on the order of 0.7 Hill radii, which is of the order of the moonlet radius. In our model the propeller height decreases exponentially until viscous heating and collisional cooling balance. We estimate Hill radii of 370m and 615m for the propellers Earhart and Bleriot. Our model predicts about 120km for the azimuthal extent of the Earhart propeller at Saturn's 2009 equinox, being consistent with values determined from Cassini images

Time-resolved Microwave Conductivity. Part 2.-Quantum-sized TiO_2 and the Effect of Adsorbates and Light Intensity on Charge-carrier Dynamics

Charge-carrier recombination dynamics after a pulsed laser excitation are investigated by time-resolved microwave conductivity (TRMC) for quantum-sized (Q-) TiO_2 and P25, a bulk-phase TiO_2. Adsorbed scavengers such as HNO_3, HC, HCIO_4, isopropyl alcohol, trans-decalin, tetranitromethane, and methyl viologen dichloride result in different charge-carrier recombination dynamics for Q-TiO_2 and P25. The differences include a current doubling with isopropyl alcohol for which electron injection into Q-TiO_2 is much slower than into P25 and relaxation of the selection rules of an indirect-bandgap semiconductor due to size quantization. However, the faster interfacial charge transfer predicted for Q-TiO_2 due to a 0. 2 eV gain in redox overpotentials is not observed. The effect of light intensity is also investigated. Above a critical injection level, fast recombination channels are opened, which may be a major factor resulting in the dependence of the steady-state photolysis quantum yields on l^(–1/2). The fast recombination channels are opened at lower injection levels for P25 than for Q-TiO_2, and a model incorporating the heterogeneity of surface-hole traps is presented

Confident metabolite structure annotation with COSMIC

Small molecules are key to biomarker discovery, drug development, toxicity screenings of ecosystems like rivers and lakes, and many more important research areas in multiple life sciences. Elucidating the exact structure of these metabolites is often crucial in determining their functionality, however, confident annotation of these structures remains a major challenge. To analyse samples of small molecules occurring in nature, mass spectrometry is the currently predominant technique. While mass spectrometry is used to measure the mass of a compound, tandem mass spectrometry can be used to additionally measure the mass of its fragments. The resulting spectral data however is highly non-trivial to interpret. This bottleneck accelerates the development of computational tools to annotate metabolite structures from mass spectrometry data, which enables rapid, large-scale structure annotation independent from spectral libraries. These tools return some proportion of incorrect annotations, which can vastly outnumber correct annotations. Scientists using these tools need to be able to differentiate correct from incorrect annotations. We develop an E-value computation that is based on proxy decoys drawn from the PubChem database and show that this E-value score outperforms the current CSI:FingerID hit score for the task of separating correct from incorrect annotations. To further improve on this, we develop a Percolator inspired machine learning approach, where we train linear support vector machines for this separation task. The confidence score outperforms the original CSI:FingerID hit score, the E-value score and all other tools that participated in the CASMI 2016 contest by a wide margin. Arguably, our confidence score enables confident structure annotation for a relevant portion of a dataset for the first time. We then show the power of this COSMIC workflow by annotating novel bile acid conjugate structures never reported before in a mouse fecal dataset

Time-resolved Microwave Conductivity. Part 1.—TiO_2 Photoreactivity and Size Quantization

Charge-carrier recombination dynamics after laser excitation are investigated by time-resolved microwave conductivity (TRMC) measurements of quantum-sized (Q-) TiO_2, Fe^(III)-doped Q-TiO_2, ZnO and CdS, and several commercial bulk-sized TiO2 samples. After pulsed laser excitation of charge carriers, holes that escape recombination react with sorbed trans-decalin within ns while the measured conductivity signal is due to conduction-band electrons remaining in the semiconductor lattice. The charge-carrier recombination lifetime and the interfacial electron-transfer rate constant that are derived from the TRMC measurements correlate with the CW photo-oxidation quantum efficiency obtained for aqueous chloroform in the presence of TiO_2. The quantum efficiencies are 0. 4 % for Q-TiO_2, 1. 6 % for Degussa P25, and 2. 0 % for Fe^(III)-doped Q-TiO_2. The lower quantum efficiencies for Q-TiO_2 are consistent with the relative interfacial electron-transfer rates observed by TRMC for Q-TiO_2 and Degussa P25. The increased quantum efficiencies of Fe^(III)-doped Q-TiO_2 and the observed TRMC decays are consistent with a mechanism involving fast trapping of valence-band holes as Fe^(IV) and inhibition of charge-order recombination

Using competencies in human resource management : case studies in Australian companies

This study investigated the use of competencies for human resource management in seven Australian companies. Despite advocacy for the use of competencies by Government Committees and Task Forces (For example Carmichael (1992), Mayer, (1992) and Karpin, 1995), and the existence of competency standards for eighty per cent of the Australian workforce, the competency approach has not been widely adopted. A review of the literature indicated that the term competency had several meanings with different implications for its use depending on the meaning. The study looked at how individuals have defined the term and applied the approach to human resource management practices. Interviews were conducted with Human Resource and Training managers, and operative staff in companies using competencies. How they defined the term, described the rationale for using competencies, and applied competencies to selection, training, performance appraisal and remuneration were determined. Case studies were written for each company to describe their particular application of competencies. Competencies were found to be defined in several ways by those interviewed. Some advantages of using competencies in human resource management applications were found. The amount of work involved in introducing the competency approach was described as a reason why competencies have not been more widely adopted

A Comparison of pattern classification techniques for orienting chest X-rays

The problem of orienting digital images of chest x-rays, which were captured at some multiple of 90 degrees from the true orientation, is a typical pattern classification problem. In this case, the solution to the problem must assign an instance of a digital image to one of four classes, where each class corresponds to one of the four possible orientations. A large number of techniques are available for developing a pattern classifier. Some of these techniques are characterized by independent variables whose values are difficult to relate back to the problem being solved. If a technique is highly sensitive to the values of these variables, the lack of a rigorous way of defining them can be a significant disadvantage to the inexperienced researcher. This thesis presents experiments by the author to solve the chest x-ray orientation problem using four different pattern classification techniques: genetic programming, an artificial neural network trained with back propagation, a probabilistic neural network, and a simple linear classifier. In addition, the author will demonstrate that an understanding of the design of a feature set may allow a programmer to develop a traditional program which does an adequate job of solving the classification problem. Comparisons of the different techniques will be based not only on their success at solving the problem, but also on the time required to find an acceptable solution and the degree to which each technique is sensitive to the values of the variables which characterize it. The thesis demonstrates that all of the techniques can be used to derive very accurate chest x-ray orientation classifiers. While it is dangerous to generalize the results of these experiments to pattern classification problems in general, the author will argue that the magnitude of the differences in performance between the different techniques minimizes this danger. In particular, the experiments suggest that the linear classifier is so computationally inexpensive that it is always worth trying, unless there is a priori knowledge that it will fail. The experiments also suggest that genetic programming is much more computationally expensive than are the linear classifier, artificial neural network, and probabilistic neural network techniques. Of the four conventional pattern classification techniques which were examined, it will be shown that the artificial neural network produced the most accurate classifiers for the x-ray orientation problem. In addition, the results of a number of trials suggest that the final accuracy of the classifier is relatively insensitive to the values of the parameters which characterize this technique, making it an appropriate choice for the inexperienced researcher. With respect to the ability of the resulting classifier to accurately orient sample x-rays which were not included in the training set, the artificial neural network performed well, when compared to the other techniques. Although the classifiers produced by the genetic programming technique were significantly more expensive to construct and were slightly less accurate than the best artificial neural networks, the results of genetic programming experiments can provide insights into the problem being studied, which would be difficult to discern from the classifiers produced by the other techniques. For example, one of the classifiers which was produced by genetic programming uses only eight of the twenty feature values extracted from the sample x-ray. Not only does this reduce the cost of extracting the feature values from an unknown sample, but the classifier itself would be much more efficient to evaluate than the classifiers produced by any of the other techniques

Impact of a smoking ban in hospitality venues on second hand smoke exposure : a comparison of exposure assessment methods

In May 2010, Switzerland introduced a heterogeneous smoking ban in the hospitality sector. While the law leaves room for exceptions in some cantons, it is comprehensive in others. This longitudinal study uses different measurement methods to examine airborne nicotine levels in hospitality venues and the level of personal exposure of non-smoking hospitality workers before and after implementation of the law.; Personal exposure to second hand smoke (SHS) was measured by three different methods. We compared a passive sampler called MoNIC (Monitor of NICotine) badge, to salivary cotinine and nicotine concentration as well as questionnaire data. Badges allowed the number of passively smoked cigarettes to be estimated. They were placed at the venues as well as distributed to the participants for personal measurements. To assess personal exposure at work, a time-weighted average of the workplace badge measurements was calculated.; Prior to the ban, smoke-exposed hospitality venues yielded a mean badge value of 4.48 (95%-CI: 3.7 to 5.25; n = 214) cigarette equivalents/day. At follow-up, measurements in venues that had implemented a smoking ban significantly declined to an average of 0.31 (0.17 to 0.45; n = 37) (p = 0.001). Personal badge measurements also significantly decreased from an average of 2.18 (1.31-3.05 n = 53) to 0.25 (0.13-0.36; n = 41) (p = 0.001). Spearman rank correlations between badge exposure measures and salivary measures were small to moderate (0.3 at maximum).; Nicotine levels significantly decreased in all types of hospitality venues after implementation of the smoking ban. In-depth analyses demonstrated that a time-weighted average of the workplace badge measurements represented typical personal SHS exposure at work more reliably than personal exposure measures such as salivary cotinine and nicotine

A quantum-dot heat engine operating close to the thermodynamic efficiency limits

Cyclical heat engines are a paradigm of classical thermodynamics, but are impractical for miniaturization because they rely on moving parts. A more recent concept is particle-exchange (PE) heat engines, which uses energy filtering to control a thermally driven particle flow between two heat reservoirs. As they do not require moving parts and can be realized in solid-state materials, they are suitable for low-power applications and miniaturization. It was predicted that PE engines could reach the same thermodynamically ideal efficiency limits as those accessible to cyclical engines, but this prediction has not been verified experimentally. Here, we demonstrate a PE heat engine based on a quantum dot (QD) embedded into a semiconductor nanowire. We directly measure the engine's steady-state electric power output and combine it with the calculated electronic heat flow to determine the electronic efficiency $\eta$. We find that at the maximum power conditions, $\eta$ is in agreement with the Curzon-Ahlborn efficiency and that the overall maximum $\eta$ is in excess of 70$\%$ of the Carnot efficiency while maintaining a finite power output. Our results demonstrate that thermoelectric power conversion can, in principle, be achieved close to the thermodynamic limits, with direct relevance for future hot-carrier photovoltaics, on-chip coolers or energy harvesters for quantum technologies