1,426 research outputs found

    Analytic Examples, Measurement Models and Classical Limit of Quantum Backflow

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    We investigate the backflow effect in elementary quantum mechanics - the phenomenon in which a state consisting entirely of positive momenta may have negative current and the probability flows in the opposite direction to the momentum. We compute the current and flux for states consisting of superpositions of gaussian wave packets. These are experimentally realizable but the amount of backflow is small. Inspired by the numerical results of Penz et al (M.Penz, G.Gr\"ubl, S.Kreidl and P.Wagner, J.Phys. A39, 423 (2006)), we find two non-trivial wave functions whose current at any time may be computed analytically and which have periods of significant backflow, in one case with a backwards flux equal to about 70 percent of the maximum possible backflow, a dimensionless number cbm0.04c_{bm} \approx 0.04 , discovered by Bracken and Melloy (A.J.Bracken and G.F.Melloy, J.Phys. A27, 2197 (1994)). This number has the unusual property of being independent of \hbar (and also of all other parameters of the model), despite corresponding to an obviously quantum-mechanical effect, and we shed some light on this surprising property by considering the classical limit of backflow. We discuss some specific measurement models in which backflow may be identified in certain measurable probabilities.Comment: 33 pages, 14 figures. Minor revisions. Published versio

    Diamondoids are not forever: microbial biotransformation of diamondoid carboxylic acids

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    Oil sands process‐affected waters (OSPW) contain persistent, toxic naphthenic acids (NAs), including the abundant yet little‐studied diamondoid carboxylic acids. Therefore, we investigated the aerobic microbial biotransformation of two of the most abundant, chronically toxic and environmentally relevant diamondoid carboxylic acids: adamantane‐1‐carboxylic acid (A1CA) and 3‐ethyl adamantane carboxylic acid (3EA). We inoculated into minimal salts media with diamondoid carboxylic acids as sole carbon and energy source two samples: (i) a surface water sample (designated TPW) collected from a test pit from the Mildred Lake Settling Basin and (ii) a water sample (designated 2 m) collected at a water depth of 2 m from a tailings pond. By day 33, in TPW enrichments, 71% of A1CA and 50% of 3EA was transformed, with 50% reduction in EC20 toxicity. Similar results were found for 2 m enrichments. Biotransformation of A1CA and 3EA resulted in the production of two metabolites, tentatively identified as 2‐hydroxyadamantane‐1‐carboxylic acid and 3‐ethyladamantane‐2‐ol respectively. Accumulation of both metabolites was less than the loss of the parent compound, indicating that they would have continued to be transformed beyond 33 days and not accumulate as dead‐end metabolites. There were shifts in bacterial community composition during biotransformation, with Pseudomonas species, especially P. stutzeri, dominating enrichments irrespective of the diamondoid carboxylic acid. In conclusion, we demonstrated the microbial biotransformation of two diamondoid carboxylic acids, which has potential application for their removal and detoxification from vast OSPW that are a major environmental threat

    Do specific delirium aetiologies have different associations with death? A longitudinal cohort of hospitalised patients

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    PURPOSE: To describe aetiology-specific associations with mortality among older hospital patients with delirium. METHODS: Over 21 months, a cohort of 1702 patients with 2471 acute hospital admissions (median age 85, IQR 80-90, 56% women) were assessed for delirium, categorised with inflammatory and metabolic aetiologies based on available laboratory results, and followed up for all-cause mortality. Interactions between aetiology and delirium were tested. RESULTS: The total mortality for the cohort was 35.2%. While inflammation, metabolic disturbance, and delirium at time of admission all demonstrated independent associations with mortality, there was no evidence for any interactions between delirium and these laboratory-measured aetiologies. CONCLUSIONS: Delirium remains an important predictor of death in older hospital patients, irrespective of underlying aetiology

    Interfacial Properties of Colloidal Silica Dispersions in Contact with Solutions of Fatty Amines in Hexane

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    Many natural phenomena and technologies are concerned with the interactions between micro- or nano-metre sized particles and surfactant molecules at liquid interfaces. Highly stable emulsions are produced by using surfactants to modify the surfaces of nanoparticles. Particle attachment to bubbles is controlled by surfactant adsorption in flotation technologies. So far, however, few experimental studies have explored the properties of these complex interfacial layers

    High purity nanoparticles exceed stoichiometry limits in rebox chemistry: the nano way to cleaner water

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    A potentially cheaper and more effective way of cleaning wastewater has been discovered by scientists at Nazarbayev University and the University of Brighton researching nanotechnology [1]. It is well established that when particles are reduced to the nanoscale unexpected effects occur. Silver, for example, interacts with mercury ions in a fixed ratio of atoms (stoichiometry), typically 2:1, which presents a limit that has never been exceeded. In this project we used an alternative chemical procedure based on modified quartz sand to immobilise silver nanoparticles (NPs) with control over their size. We found that when the size of the silver NPs decreased below 35 nm the amount of mercury ions reacting with silver increased beyond the long-held limit and rose to a maximum of 1:1.2 for 10 nm sized silver

    Network Connections in REIT Markets

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    Relationships play a central role across the spectrum of real estate transactions. Whether negotiating prices, securing funding, or acquiring permits, knowing the right people provides multiple channels to facilitate deal making. To better understand the role of relationships in real estate markets, we examine how the connectedness of REIT directors is associated with deal making, growth, and profitability. We find strong evidence that REIT connections are positively associated with both deal making and accounting based measures of profitability, however, those relations do not translate into better market returns or higher valuations. One explanation of these somewhat contradictory results is that connections also increase firm risk. Preliminary support for this conjecture is found through our examination of each firm’s implied cost of equity capital. Specifically, we find increasing connectedness is associated with a higher cost of equity capital. Thus, connections appear to offer both advantages and disadvantages to REIT managers and shareholders

    High purity nanoparticles exceed stoichiometry limits in rebox chemistry: the nano way to cleaner water

    Get PDF
    A potentially cheaper and more effective way of cleaning wastewater has been discovered by scientists at Nazarbayev University and the University of Brighton researching nanotechnology [1]. It is well established that when particles are reduced to the nanoscale unexpected effects occur. Silver, for example, interacts with mercury ions in a fixed ratio of atoms (stoichiometry), typically 2:1, which presents a limit that has never been exceeded. In this project we used an alternative chemical procedure based on modified quartz sand to immobilise silver nanoparticles (NPs) with control over their size. We found that when the size of the silver NPs decreased below 35 nm the amount of mercury ions reacting with silver increased beyond the long-held limit and rose to a maximum of 1:1.2 for 10 nm sized silver
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