830 research outputs found

    Money in the twenty-first century.

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    What implications do 21st century monetary innovations bring for holdings of central bank money and standards of value? Emerging technologies such as cybercash, e-cash, and smart cards can be expected to reduce demand for central bank money, but the theoretical framework for monetary policy has not changed. The authors stress three points in this paper: 1) money innovations tend to reduce the demand for central bank money, but it remains to be seen whether the predictability of that demand, and thus the reliability of monetary policy, will decline in the coming century; 2) in principle, monetary authorities can continue to determine the price level as long as final settlement of tax and other obligations takes place using central bank liabilities; and 3) the viability of competing currencies and standards of value is gaining steam as a lively field of research.Money ; Payment systems ; Smart cards

    Separation of bacterial spores from flowing water in macro-scale cavities by ultrasonic standing waves

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    The separation of micron-sized bacterial spores (Bacillus cereus) from a steady flow of water through the use of ultrasonic standing waves is demonstrated. An ultrasonic resonator with cross-section of 0.0254 m x 0.0254 m has been designed with a flow inlet and outlet for a water stream that ensures laminar flow conditions into and out of the resonator section of the flow tube. A 0.01905-m diameter PZT-4, nominal 2-MHz transducer is used to generate ultrasonic standing waves in the resonator. The acoustic resonator is 0.0356 m from transducer face to the opposite reflector wall with the acoustic field in a direction orthogonal to the water flow direction. At fixed frequency excitation, spores are concentrated at the stable locations of the acoustic radiation force and trapped in the resonator region. The effect of the transducer voltage and frequency on the efficiency of spore capture in the resonator has been investigated. Successful separation of B. cereus spores from water with typical volume flow rates of 40-250 ml/min has been achieved with 15% efficiency in a single pass at 40 ml/min.Comment: 11 pages, 6 figure

    A Multiwavelength View at the Heart of the Superwind in NGC 253

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    Here we present new optical data from the Hubble Space Telescope of the NGC 253 central region, which reveal numerous discrete sources in a ring--like structure. This is combined with data at infrared, millimeter, radio and X-ray wavelengths to examine the nature of these discrete sources and the nucleus itself. We find that the majority of optical/IR/mm sources are young star clusters which trace out a ~50 pc ring, that defines the inner edge of a cold gas torus. This reservoir of cold gas has probably been created by gas inflow from a larger scale bar and deposited at the inner Lindblad resonance. The family of compact radio sources lie interior to the starburst ring, and in general do not have optical or IR counterparts. They are mostly SNRs. The radio nucleus, which is probably an AGN, lies near the centre of the ring. The X-ray emission from the nuclear source is extended in the ROSAT HRI detector indicating that not all of the X-ray emission can be associated with the AGN. The lack of X-ray variability and the flat radio spectrum of the nucleus, argues against an ultraluminous SN as the dominant energetic source at the galaxy core. The diffuse emission associated with the outflowing superwind is present in the central region on a size scale consistent with the idea of collimation by the gas torus.Comment: 26 pages, Latex, 6 figures, 4 tables, submitted to MNRA

    Hemodynamic effects of intravenous amiodarone

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    Amiodarone is a potent antiarrhythmic agent that is effective in controlling both atrial and ventricular arrhythmias. Recently, intravenous administration was demonstrated to be effective in the acute management of rhythm disorders and, in addition, appeared to shorten the loading period normally required for oral drug administration. This investigation examined the hemodynamic effects of amiodarone after both acute intravenous bolus and continuous intravenous administration. Patients with a left ventricular ejection fraction greater than 0.35 experienced improved cardiac performance due to both acute and chronic peripheral vasodilation. However, patients with a lower ejection fraction developed a 20% decrease in cardiac index and clinically significant elevation of right heart pressures after acute bolus administration; these changes were variably compensated for by peripheral vasodilation when the drug was administered intravenously over 3 to 5 days continuously. Therefore, intravenous amiodarone can result in significant impairment of left ventricular performance in patients with preexisting left ventricular dysfunction

    Comparing plasma and faecal measures of steroid hormones in Adelie penguins Pygoscelis adeliae

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    Physiological measurements of both stress and sex hormones are often used to estimate the consequences of natural or human-induced change in ecological studies of various animals. Different methods of hormone measurement exist, potentially explaining variation in results across studies; methods should be cross-validated to ensure that they correlate. We directly compared faecal and plasma hormone measurements for the first time in a wild free-living species, the Adelie penguin (Pygoscelis adeliae). Blood and faecal samples were simultaneously collected from individual penguins for comparison and assayed for testosterone and corticosterone (or their metabolites). Sex differences and variability within each measure, and correlation of values across measures were compared. For both hormones, plasma samples showed greater variation than faecal samples. Males had higher mean corticosterone concentrations than females, but the difference was only statistically significant in faecal samples. Plasma testosterone, but not faecal testosterone, was significantly higher in males than females. Correlation between sample types was poor overall, and weaker in females than in males, perhaps because measures from plasma represent hormones that are both free and bound to globulins, whereas measures from faeces represent only the free portion. Faecal samples also represent a cumulative measure of hormones over time, as opposed to a plasma ‘snapshot’ concentration. Our data indicate that faecal sampling appears more suitable for assessing baseline hormone concentrations, whilst plasma sampling may best define immediate responses to environmental events. Consequently, future studies should ensure that they select the most appropriate matrix and method of hormone measurement to answer their research questions

    An assessment of the correlation between robust CT-derived ventilation and pulmonary function test in a cohort with no respiratory symptoms

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    OBJECTIVE: To evaluate CT-ventilation imaging (CTVI) within a well-characterized, healthy cohort with no respiratory symptoms and examine the correlation between CTVI and concurrent pulmonary function test (PFT). METHODS: CT scans and PFTs from 77 Caucasian participants in the NORM dataset (clinicaltrials.gov NCT00848406) were analyzed. CTVI was generated using the robust Integrated Jacobian Formulation (IJF) method. IJF estimated total lung capacity (TLC) was computed from CTVI. Bias-adjusted Pearson’s correlation between PFT and IJF-based TLC was computed. RESULTS: IJF- and PFT-measured TLC showed a good correlation for both males and females [males: 0.657, 95% CI (0.438–0.797); females: 0.667, 95% CI (0.416–0.817)]. When adjusting for age, height, smoking, and abnormal CT scan, correlation moderated [males: 0.432, 95% CI (0.129–0.655); females: 0.540, 95% CI (0.207–0.753)]. Visual inspection of CTVI revealed participants who had functional defects, despite the fact that all participant had normal high-resolution CT scan. CONCLUSION: In this study, we demonstrate that IJF computed CTVI has good correlation with concurrent PFT in a well-validated patient cohort with no respiratory symptoms. ADVANCES IN KNOWLEDGE: IJF-computed CTVI’s overall numerical robustness and consistency with PFT support its potential as a method for providing spatiotemporal assessment of high and low function areas on volumetric non-contrast CT scan
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