7,941 research outputs found
Characterisation of the first authenticated organomercury hydroxide, 4-Me₂NC₆H₄HgOH
4-Me₂NC₆H₄HgOH was prepared from 4-Me₂NC₆H₄HgOAc. Full characterisation showed that it crystallises as discrete molecules, the first example of a true organomercury hydroxide in the solid state. The structures of 4-Me₂NC₆H₄HgOAc and (4-Me₂NC₆H₄)₂Hg are also discussed.
4-Me₂NC₆H₄HgOH has been characterised spectroscopically and crystallographically as a true organomercury hydroxide
Optimal pricing using online auction experiments: A P\'olya tree approach
We show how a retailer can estimate the optimal price of a new product using
observed transaction prices from online second-price auction experiments. For
this purpose we propose a Bayesian P\'olya tree approach which, given the
limited nature of the data, requires a specially tailored implementation.
Avoiding the need for a priori parametric assumptions, the P\'olya tree
approach allows for flexible inference of the valuation distribution, leading
to more robust estimation of optimal price than competing parametric
approaches. In collaboration with an online jewelry retailer, we illustrate how
our methodology can be combined with managerial prior knowledge to estimate the
profit maximizing price of a new jewelry product.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS503 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Wearable flexible lightweight modular RFID tag with integrated energy harvester
A novel wearable radio frequency identification (RFID) tag with sensing, processing, and decision-taking capability is presented for operation in the 2.45-GHz RFID superhigh frequency (SHF) band. The tag is powered by an integrated light harvester, with a flexible battery serving as an energy buffer. The proposed active tag features excellent wearability, very high read range, enhanced functionality, flexible interfacing with diverse low-power sensors, and extended system autonomy through an innovative holistic microwave system design paradigm that takes antenna design into consideration from the very early stages. Specifically, a dedicated textile shorted circular patch antenna with monopolar radiation pattern is designed and optimized for highly efficient and stable operation within the frequency band of operation. In this process, the textile antenna's functionality is augmented by reusing its surface as an integration platform for light-energy-harvesting, sensing, processing, and transceiver hardware, without sacrificing antenna performance or the wearer's comfort. The RFID tag is validated by measuring its stand-alone and on-body characteristics in free-space conditions. Moreover, measurements in a real-world scenario demonstrate an indoor read range up to 23 m in nonline-of-sight indoor propagation conditions, enabling interrogation by a reader situated in another room. In addition, the RFID platform only consumes 168.3 mu W, when sensing and processing are performed every 60 s
Validity of very short answer versus single best answer questions for undergraduate assessment
Background Single Best Answer (SBA) questions are widely used in undergraduate and postgraduate medical examinations. Selection of the correct answer in SBA questions may be subject to cueing and therefore might not test the student’s knowledge. In contrast to this artificial construct, doctors are ultimately required to perform in a real-life setting that does not offer a list of choices. This professional competence can be tested using Short Answer Questions (SAQs), where the student writes the correct answer without prompting from the question. However, SAQs cannot easily be machine marked and are therefore not feasible as an instrument for testing a representative sample of the curriculum for a large number of candidates. We hypothesised that a novel assessment instrument consisting of very short answer (VSA) questions is a superior test of knowledge than assessment by SBA. Methods We conducted a prospective pilot study on one cohort of 266 medical students sitting a formative examination. All students were assessed by both a novel assessment instrument consisting of VSAs and by SBA questions. Both instruments tested the same knowledge base. Using the filter function of Microsoft Excel, the range of answers provided for each VSA question was reviewed and correct answers accepted in less than two minutes. Examination results were compared between the two methods of assessment. Results Students scored more highly in all fifteen SBA questions than in the VSA question format, despite both examinations requiring the same knowledge base. Conclusions Valid assessment of undergraduate and postgraduate knowledge can be improved by the use of VSA questions. Such an approach will test nascent physician ability rather than ability to pass exams
Endotrivial complexes
Let be a finite group, a prime, and a field of characteristic
. We introduce the notion of an endotrivial complex of -permutation
-modules, and study the corresponding group of endotrivial complexes,
. Such complexes are shown to induce splendid Rickard
autoequivalences of . The elements of are determined
uniquely by integral invariants arising from the Brauer construction and a
degree 1 character . Using ideas from Bouc's theory of biset
functors, we provide a canonical decomposition of , and as an
application, determine complete descriptions of for abelian
groups and -groups of normal -rank 1. We investigate the image of
in the orthogonal unit group of the trivial source ring
induced via the Lefschetz invariant map, and using recent results of
Boltje and Carman, we determine a Frobenius stability condition an orthogonal
unit must satisfy to lift to an endotrivial complex.Comment: Minor changes for version 2: fixed numerous typos and revised some
proofs and statements for clarity and correctness. 36 pages, comments
welcome
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