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
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
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 , 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
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
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Synthesis and Coordination Compounds of A Bis(Imino)Acenaphthene (Bian)-Supported N-Heterocyclic Carbene
The bis(imino)acenaphthene-supported N-heterocyclic carbene IPr(BIAN) has been prepared by deprotonation of the precursor imidazolium chloride. Treatment of IPr(BIAN) imidazolium chloride with Ag(2)O afforded the silver complex [IPr(BIAN)]AgCl which can be converted into the corresponding gold complex [IPr(BIAN)]AuCl by reaction with (tht)AuCl (tht = tetrahydrothiophene). The iridium complex [IPr(BIAN)]Ir(COD)Cl was prepared by reaction of the imidazolium chloride with KO(t)Bu and [Ir(COD)Cl](2) and subsequently converted to the carbonyl complex [IPr(BIAN)]Ir(CO)(2)Cl by exposure to an atmosphere of CO. All new compounds were characterized by single-crystal X-ray diffraction, multinuclear NMR, MS and HRMS data.Robert A. Welch Foundation F-0003National Science Foundation 0741973Chemistr
Conditional preparation of states containing a definite number of photons
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
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
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
We present X-ray bolometric correction factors, (), 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,
, from literature infrared (IR) torus modeling and compile published
intrinsic 2--10 keV X-ray luminosities, , 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
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 of our sample in the range
erg/s is log
with an intrinsic scatter of dex, and that our derived
values are consistent with previously established relationships between
and and and Eddington ratio. We
investigate if is dependent on 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 values
for CT AGN identified in X-ray surveys as a function of their observed ,
where an estimate of their intrinsic 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
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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