2,076 research outputs found
How Voltage Drops are Manifested by Lithium Ion Configurations at Interfaces and in Thin Films on Battery Electrodes
Battery electrode surfaces are generally coated with electronically
insulating solid films of thickness 1-50 nm. Both electrons and Li+ can move at
the electrode-surface film interface in response to the voltage, which adds
complexity to the "electric double layer" (EDL). We apply Density Functional
Theory (DFT) to investigate how the applied voltage is manifested as changes in
the EDL at atomic lengthscales, including charge separation and interfacial
dipole moments. Illustrating examples include Li(3)PO(4), Li(2)CO(3), and
Li(x)Mn(2)O(4) thin-films on Au(111) surfaces under ultrahigh vacuum
conditions. Adsorbed organic solvent molecules can strongly reduce voltages
predicted in vacuum. We propose that manipulating surface dipoles, seldom
discussed in battery studies, may be a viable strategy to improve electrode
passivation. We also distinguish the computed potential governing electrons,
which is the actual or instantaneous voltage, and the "lithium cohesive energy"
based voltage governing Li content widely reported in DFT calculations, which
is a slower-responding self-consistency criterion at interfaces. This
distinction is critical for a comprehensive description of electrochemical
activities on electrode surfaces, including Li+ insertion dynamics, parasitic
electrolyte decomposition, and electrodeposition at overpotentials.Comment: 35 pages. 10 figure
Giving New Zealand: Philanthropic Funding 2006
This report provides measurement of New Zealanders' philanthropic funding for the 2005/2006 year and what these funds supported
Reversible simulation of bipartite product Hamiltonians
Consider two quantum systems A and B interacting according to a product
Hamiltonian H = H_A x H_B. We show that any two such Hamiltonians can be used
to simulate each other reversibly (i.e., without efficiency losses) with the
help of local unitary operations and local ancillas. Accordingly, all non-local
features of a product Hamiltonian -- including the rate at which it can be used
to produce entanglement, transmit classical or quantum information, or simulate
other Hamiltonians -- depend only upon a single parameter. We identify this
parameter and use it to obtain an explicit expression for the entanglement
capacity of all product Hamiltonians. Finally, we show how the notion of
simulation leads to a natural formulation of measures of the strength of a
nonlocal Hamiltonian.Comment: 10 page
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Building the Emirati Arabic FrameNet
The Emirati Arabic FrameNet (EAFN) project aims to initiate a FrameNet for Emirati Arabic, utilizing the Emirati Arabic Corpus. The goal is to create a resource comparable to the initial stages of the Berkeley FrameNet. The project is divided into manual and automatic tracks, based on the predominant techniques being used to collect frames in each track. Work on the EAFN is progressing, and we here report on initial results for annotations and evaluation. The EAFN project aims to provide a general semantic resource for the Arabic language, sure to be of interest to researchers from general linguistics to natural language processing. As we report here, the EAFN is well on target for the first release of data in the coming year
Prevalence of age-related macular degeneration in Nakuru, Kenya: a cross-sectional population-based study.
BACKGROUND: Diseases of the posterior segment of the eye, including age-related macular degeneration (AMD), have recently been recognised as the leading or second leading cause of blindness in several African countries. However, prevalence of AMD alone has not been assessed. We hypothesized that AMD is an important cause of visual impairment among elderly people in Nakuru, Kenya, and therefore sought to assess the prevalence and predictors of AMD in a diverse adult Kenyan population. METHODS AND FINDINGS: In a population-based cross-sectional survey in the Nakuru District of Kenya, 100 clusters of 50 people 50 y of age or older were selected by probability-proportional-to-size sampling between 26 January 2007 and 11 November 2008. Households within clusters were selected through compact segment sampling. All participants underwent a standardised interview and comprehensive eye examination, including dilated slit lamp examination by an ophthalmologist and digital retinal photography. Images were graded for the presence and severity of AMD lesions following a modified version of the International Classification and Grading System for Age-Related Maculopathy. Comparison was made between slit lamp biomicroscopy (SLB) and photographic grading. Of 4,381 participants, fundus photographs were gradable for 3,304 persons (75.4%), and SLB was completed for 4,312 (98%). Early and late AMD prevalence were 11.2% and 1.2%, respectively, among participants graded on images. Prevalence of AMD by SLB was 6.7% and 0.7% for early and late AMD, respectively. SLB underdiagnosed AMD relative to photographic grading by a factor of 1.7. After controlling for age, women had a higher prevalence of early AMD than men (odds ratio 1.5; 95% CI, 1.2-1.9). Overall prevalence rose significantly with each decade of age. We estimate that, in Kenya, 283,900 to 362,800 people 50 y and older have early AMD and 25,200 to 50,500 have late AMD, based on population estimates in 2007. CONCLUSIONS: AMD is an important cause of visual impairment and blindness in Kenya. Greater availability of low vision services and ophthalmologist training in diagnosis and treatment of AMD would be appropriate next steps. Please see later in the article for the Editors' Summary
Defining Classical Tenor Saxophone: performer identity, performance practice and contemporary repertoire
The tenor saxophone has gained prominence as a classical instrument for composers and performers during the last four decades. Interest in the instrument has inspired the creation of innovative works and tenor saxophonists are charged with preparing these works for performance. Performing new repertoire has impacted the way in which the classical tenor saxophonists explore the musical potential of their instrument and their role in a larger sense. The aim of this study is to identify important works in the contemporary classical tenor saxophone repertoire, establish how performers approach these works, and discover their perceptions of the instrument. Twenty-two professional saxophonists from Australia, Europe, the United Kingdom and the United States of America completed a questionnaire in which they identified significant contemporary classical tenor saxophone works and explained why the works were important to the instrument’s modern repertoire. Twelve saxophonists then participated in an interview in which they explored their perceptions of classical tenor saxophone performance, and gave insights into their experiences studying, performing and teaching the most significant repertoire. Three key works written between 1986 and 2011 were identified, all of which utilised the tenor saxophone’s extensive musical and technical capabilities. These works were all written in a contemporary style and featured strong influences from jazz/pop music. Saxophonists regarded the tenor saxophone as a versatile instrument remarkably suited to the classical idiom and unique in the saxophone family. These professionals employed novel technical and musical approaches in their performance of the contemporary tenor saxophone repertoire to create successful and authentic interpretations. They explained their common perceptions of the instrument and shared a collective musical identity as classical tenor saxophonists
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