3,170 research outputs found

    Computation of Madelung Energies for Ionic Crystals of Variable Stoichiometries and Mixed Valencies and their application in Lithium-ion battery voltage modelling

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    Electrostatic energy (Madelung energy) is a major constituent of the cohesive energy of ionic crystals. Several physicochemical properties of these materials depend on the response of their electrostatic energy to a variety of applied thermal, electrical and mechanical stresses. In the present study, a method has been developed based on Ewalds technique, to compute the electrostatic energy arising from ion-ion interactions in ionic crystals like LixMn2O4 with variable stoichiometries and mixed valencies. An interesting application of this method in computing the voltages of lithium ion batteries employing spinel cathodes is presented for the first time. The advantages of the present method of computation over existing methods are also discussed.Comment: 15 page

    Glimmers: Resolving the Privacy/Trust Quagmire

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    Many successful services rely on trustworthy contributions from users. To establish that trust, such services often require access to privacy-sensitive information from users, thus creating a conflict between privacy and trust. Although it is likely impractical to expect both absolute privacy and trustworthiness at the same time, we argue that the current state of things, where individual privacy is usually sacrificed at the altar of trustworthy services, can be improved with a pragmatic GlimmerGlimmer ofof TrustTrust, which allows services to validate user contributions in a trustworthy way without forfeiting user privacy. We describe how trustworthy hardware such as Intel's SGX can be used client-side -- in contrast to much recent work exploring SGX in cloud services -- to realize the Glimmer architecture, and demonstrate how this realization is able to resolve the tension between privacy and trust in a variety of cases

    Separability of Hamilton-Jacobi and Klein-Gordon Equations in General Kerr-NUT-AdS Spacetimes

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    We demonstrate the separability of the Hamilton-Jacobi and scalar field equations in general higher dimensional Kerr-NUT-AdS spacetimes. No restriction on the parameters characterizing these metrics is imposed.Comment: 4 pages, no figure

    Conditional preparation of states containing a definite number of photons

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    A technique for conditionally creating single- or multimode photon-number states is analyzed using Bayesian theory. We consider the heralded N-photon states created from the photons produced by an unseeded optical parametric amplifier when the heralding detector is the time-multiplexed photon-number-resolving detector recently demonstrated by Fitch, et al. [Phys. Rev. A 68, 043814 (2003).] and simultaneously by Achilles, et al. [Opt. Lett. 28, 2387 (2003).]. We find that even with significant loss in the heralding detector, fields with sub-Poissonian photon-number distributions can be created. We also show that heralded multimode fields created using this technique are more robust against detector loss than are single-mode fields.Comment: 6 pages, 6 figures, reference added, typos corrected, content update

    Hidden Symmetry of Higher Dimensional Kerr-NUT-AdS Spacetimes

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    It is well known that 4-dimensional Kerr-NUT-AdS spacetime possesses the hidden symmetry associated with the Killing-Yano tensor. This tensor is "universal" in the sense that there exist coordinates where it does not depend on any of the free parameters of the metric. Recently the general higher dimensional Kerr-NUT-AdS solutions of the Einstein equations were obtained. We demonstrate that all these metrics with arbitrary rotation and NUT parameters admit a universal Killing-Yano tensor. We give an explicit presentation of the Killing-Yano and Killing tensors and briefly discuss their properties.Comment: 4 pages, some discussion and references are adde

    Efficacy of dormancy breaking methods in paddy genotypes

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    Paddy plays a pivotal role in Indian agriculture. It also possesses dormancy which needs to be studied thoroughly. Duration of dormancy usually ranges from 7 to 35 days. Environmental conditions that facilitate after-ripening in paddy is generally cool, moist substrate conditions referred to as stratification, chilling, or moist chilling, oxygen and other gases. 12 paddy genotypes were selected for the present investigation with various physical and chemical dormancy, breaking methods for freshly harvested seeds and the standard germination test was conducted thereafter. At 1% level of significance, heat treatment at 45°C for 72 h showed significantly highest mean germination (82.86%), seedling vigour index (2753), dehydrogenase activity (0.0449) and alpha amylase activity (12.14 mm) compared to other treatments and control.. The vigour index increased to 2753 (GA3 @ 50 ppm) from 985 in control. Significantly higher EC leachates was recorded in control (0.602) and lowest in heat treatment at 45°C for 72 hr (0.182) followed by HNO3 @ 1.5% (0.202) and GA3 @ 50 ppm (0.250) irrespective of the genotypes at 1% level of significance. Pre-heat treatment was followed by, HNO3 @ 1.5% and GA3 @ 50 ppm for germination (80.75%, 77.72%), dehydrogenase activity (0.0446,0.0443) and alpha amylase activity (12.10 cm,11.60 cm) respectively. The study is an exploration of cost effective treatment to alleviate seed dormancy in paddy with the background of biochemical observations for scientific explanation

    X-ray bolometric corrections for Compton-thick active galactic nuclei

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    We present X-ray bolometric correction factors, κBol\kappa_{Bol} (LBol/LX\equiv L_{Bol}/L_X), for Compton-thick (CT) active galactic nuclei (AGN) with the aim of testing AGN torus models, probing orientation effects, and estimating the bolometric output of the most obscured AGN. We adopt bolometric luminosities, LBolL_{Bol}, from literature infrared (IR) torus modeling and compile published intrinsic 2--10 keV X-ray luminosities, LXL_{X}, from X-ray torus modeling of NuSTAR data. Our sample consists of 10 local CT AGN where both of these estimates are available. We test for systematic differences in κBol\kappa_{Bol} values produced when using two widely used IR torus models and two widely used X-ray torus models, finding consistency within the uncertainties. We find that the mean κBol\kappa_{Bol} of our sample in the range LBol10421045L_{Bol}\approx10^{42}-10^{45} erg/s is log10κBol=1.44±0.12_{10}\kappa_{Bol}=1.44\pm0.12 with an intrinsic scatter of 0.2\sim0.2 dex, and that our derived κBol\kappa_{Bol} values are consistent with previously established relationships between κBol\kappa_{Bol} and LBolL_{Bol} and κBol\kappa_{Bol} and Eddington ratio. We investigate if κBol\kappa_{Bol} is dependent on NHN_H by comparing our results on CT AGN to published results on less-obscured AGN, finding no significant dependence. Since many of our sample are megamaser AGN, known to be viewed edge-on, and furthermore under the assumptions of AGN unification whereby unobscured AGN are viewed face-on, our result implies that the X-ray emitting corona is not strongly anisotropic. Finally, we present κBol\kappa_{Bol} values for CT AGN identified in X-ray surveys as a function of their observed LXL_X, where an estimate of their intrinsic LXL_{X} is not available, and redshift, useful for estimating the bolometric output of the most obscured AGN across cosmic time.Comment: Accepted for publication in Ap

    ‘It’s not what it looks like. I’m Santa’: connecting community through film

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    The lived experiences of young people are becoming increasingly marginalised within the narrowly defined curricula of neoliberal contexts. Many young people are also cast within the media according to deficit discourses of youth, which contributes to the fragmentation of communities and the limitation of interaction between generations. This article describes a film project in which young people living in an ex-mining community in the Midlands of England worked in and with their community to create a representation of where they live. As part of the process, the young filmmakers did more than connect to other people’s memories as repositories of information; both as process and as product, their film can be seen to connect shared narratives of people and place, across time and space. We argue that this project offers a timely opportunity to reflect upon the ways in which we understand learning in and out of English classrooms
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