bluuebunny/crossref_metadata_2025 huggingface dataset:
Pitch ranking, electrode discrimination, and physiological spread of excitation using current steering in cochlear implants
Authors: Goehring Jenny L. , Neff Donna L. , Baudhuin Jacquelyn L. , Hughes Michelle L.
Published: December 2014

The first objective of this study was to determine whether adaptive pitch-ranking and electrode-discrimination tasks with cochlear-implant (CI) recipients produce similar results for perceiving intermediate “virtual-channel” pitch percepts using current steering. Previous studies have not examined both behavioral tasks in the same subjects with current steering. A second objective was to determine whether a physiological metric of spatial separation using the electrically evoked compound action potential spread-of-excitation (ECAP SOE) function could predict performance in the behavioral tasks. The metric was the separation index (Σ), defined as the difference in normalized amplitudes between two adjacent ECAP SOE functions, summed across all masker electrodes. Eleven CII or 90 K Advanced Bionics (Valencia, CA) recipients were tested using pairs of electrodes from the basal, middle, and apical portions of the electrode array. The behavioral results, expressed as d′, showed no significant differences across tasks. There was also no significant effect of electrode region for either task. ECAP Σ was not significantly correlated with pitch ranking or electrode discrimination for any of the electrode regions. Therefore, the ECAP separation index is not sensitive enough to predict perceptual resolution of virtual channels.
Temporal weighting functions for interaural time and level differences. IV. Effects of carrier frequency
Authors: Stecker G. Christopher
Published: December 2014

Temporal variation in listeners' sensitivity to interaural time and level differences (ITD and ILD, respectively) was measured for sounds of different carrier frequency using the temporal weighting function (TWF) paradigm [Stecker and Hafter (2002) J. Acoust. Soc. Am. 112,1046–1057]. Listeners made lateralization judgments following brief trains of filtered impulses (Gabor clicks) presented over headphones with overall ITD and/or ILD ranging from ±500 μs ITD and/or ±5 dB ILD across trials. Individual clicks within each train varied by an additional ±100 μs ITD or ±2 dB ILD to allow TWF calculation by multiple regression. In separate conditions, TWFs were measured for carrier frequencies of 1, 2, 4, and 8 kHz. Consistent with past studies, TWFs demonstrated high weight on the first click for stimuli with short interclick interval (ICI = 2 ms), but flatter weighting for longer ICI (5–10 ms). Some conditions additionally demonstrated greater weight for clicks near the offset than near the middle of the train. Results support a primary role of the auditory periphery in emphasizing onset and offset cues in rapidly modulated low-frequency sounds. For slower modulations, sensitivity to ongoing high-frequency ILD and low-frequency ITD cues appears subject to recency effects consistent with the effects of leaky temporal integration of binaural information.
Evidence for signature whistles in Guiana dolphins (Sotalia guianensis) in Ilhéus, northeastern Brazil
Authors: Lima Alice , Le Pendu Yvonnick
Published: December 2014

Signature whistles have been widely studied in bottlenose dolphins (Tursiops truncatus). A recent study suggested the occurrence of signature whistles in Guiana dolphins (Sotalia guianensis) but could not identify the whistlers. The objective of this study is to describe the whistle characteristics in the population of S. guianensis from Ilhéus and investigate the occurrence of signature whistles. Dolphins from 55 groups were photographed and sound emissions from 21 groups were recorded. The frequency parameters and duration of the 847 recorded whistles were similar to those recorded in 12 other populations, on an intermediate position of a latitudinal gradient. The visual classification method was applied to the spectrograms of 68 stereotyped potential signature whistles. Five out of 6 human judges agreed on the formation of 13 groups. The presence of the same individuals in different recording occasions of stereotyped whistles suggests that some whistle types are produced by specific individuals. The study is the first to use the photo-identification technique to identify Guiana dolphins emitting whistles and the results reinforce the hypothesis of signature whistles in this species.
Accounting for binaural detection as a function of masker interaural correlation: Effects of center frequency and bandwidth
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: December 2014

Binaural detection was measured as a function of the center frequency, bandwidth, and interaural correlation of masking noise. Thresholds were obtained for 500-Hz or 125-Hz Sπ tonal signals and for the latter stimuli (noise or signal-plus-noise) transposed to 4 kHz. A primary goal was assessment of the generality of van der Heijden and Trahiotis' [J. Acoust. Soc. Am. 101, 1019–1022 (1997)] hypothesis that thresholds could be accounted for by the “additive” masking effects of the underlying No and Nπ components of a masker having an interaural correlation of ρ. Results indicated that (1) the overall patterning of the data depended neither upon center frequency nor whether information was conveyed via the waveform or by its envelope; (2) thresholds for transposed stimuli improved relative to their low-frequency counterparts as bandwidth of the masker was increased; (3) the additivity approach accounted well for the data across stimulus conditions but consistently overestimated MLDs, especially for narrowband maskers; (4) a quantitative approach explicitly taking into account the distributions of time-varying ITD-based lateral positions produced by masker-alone and signal-plus-masker waveforms proved more successful, albeit while employing a larger set of assumptions, parameters, and computational complexity.
On the method of lumens
Authors: Shera Christopher A.
Published: December 2014

Parent and Allen [(2007). J. Acoust. Soc. Am. 122, 918–931] introduced the “method of lumens” to compute the plane-wave reflectance in a duct terminated with a nonuniform impedance. The method involves splitting the duct into multiple, fictitious subducts (lumens), solving for the reflectance in each subduct, and then combining the results. The method of lumens has considerable intuitive appeal and is easily implemented in the time domain. Previously applied only in a complex acoustical setting where proper evaluation is difficult (i.e., in a model of the ear canal and tympanic membrane), the method is tested here by using it to compute the reflectance from an area constriction in an infinite lossless duct considered in the long-wavelength limit. Neither the original formulation of the method—shown here to violate energy conservation except when the termination impedance is uniform—nor a reformulation consistent with basic physical constraints yields the correct solution to this textbook problem in acoustics. The results are generalized and the nature of the errors illuminated.
Computational speech segregation based on an auditory-inspired modulation analysis
Authors: May Tobias , Dau Torsten
Published: December 2014

A monaural speech segregation system is presented that estimates the ideal binary mask from noisy speech based on the supervised learning of amplitude modulation spectrogram (AMS) features. Instead of using linearly scaled modulation filters with constant absolute bandwidth, an auditory-inspired modulation filterbank with logarithmically scaled filters is employed. To reduce the dependency of the AMS features on the overall background noise level, a feature normalization stage is applied. In addition, a spectro-temporal integration stage is incorporated in order to exploit the context information about speech activity present in neighboring time-frequency units. In order to evaluate the generalization performance of the system to unseen acoustic conditions, the speech segregation system is trained with a limited set of low signal-to-noise ratio (SNR) conditions, but tested over a wide range of SNRs up to 20 dB. A systematic evaluation of the system demonstrates that auditory-inspired modulation processing can substantially improve the mask estimation accuracy in the presence of stationary and fluctuating interferers.
Multidecadal warming of Antarctic waters
Authors: Schmidtko Sunke , Heywood Karen J. , Thompson Andrew F. , Aoki Shigeru
Published: December 2014

Decadal trends in the properties of seawater adjacent to Antarctica are poorly known, and the mechanisms responsible for such changes are uncertain. Antarctic ice sheet mass loss is largely driven by ice shelf basal melt, which is influenced by ocean-ice interactions and has been correlated with Antarctic Continental Shelf Bottom Water (ASBW) temperature. We document the spatial distribution of long-term large-scale trends in temperature, salinity, and core depth over the Antarctic continental shelf and slope. Warming at the seabed in the Bellingshausen and Amundsen seas is linked to increased heat content and to a shoaling of the mid-depth temperature maximum over the continental slope, allowing warmer, saltier water greater access to the shelf in recent years. Regions of ASBW warming are those exhibiting increased ice shelf melt.
Roadmap to the epitranscriptome
Authors: Dominissini Dan
Published: December 2014

N
6
-methyl-adenosine signals the way and YTH proteins respond
Size does matter
Authors: Bar-Peled Liron
Published: December 2014

Lysosome-based signaling machine regulates cell growth
Environmental change and the ecology of infectious disease
Authors: Wood Chelsea L.
Published: December 2014

When and where do human impacts increase disease risk for people and wildlife?
Host Genetic and Viral Determinants of HIV-1 RNA Set Point among HIV-1 Seroconverters from Sub-Saharan Africa
Authors: Mackelprang Romel D. , Carrington Mary , Thomas Katherine K. , Hughes James P. , Baeten Jared M. , Wald Anna , Farquhar Carey , Fife Kenneth , Campbell Mary S. , Kapiga Saida , Gao Xiaojiang , Mullins James I. , Lingappa Jairam R.
Published: December 2014

We quantified the collective impact of source partner HIV-1 RNA levels, human leukocyte antigen (HLA) alleles, and innate responses through Toll-like receptor (TLR) alleles on the HIV-1 set point. Data came from HIV-1 seroconverters in African HIV-1 serodiscordant couple cohorts. Linear regression was used to determine associations with set point andR2to estimate variation explained by covariates. The strongest predictors of set point were HLA alleles (B*53:01, B*14:01, and B*27:03) and plasma HIV-1 levels of the transmitting partner, which explained 13% and 10% of variation in set point, respectively. HLA-A concordance between partners and TLR polymorphisms (TLR2rs3804100 andTLR7rs179012) also were associated with set point, explaining 6% and 5% of the variation, respectively. Overall, these factors and genital factors of the transmitter (i.e., male circumcision, bacterial vaginosis, and use of acyclovir) explained 46% of variation in set point. We found that both innate and adaptive immune responses, together with plasma HIV-1 levels of the transmitting partner, explain almost half of the variation in viral load set point.

IMPORTANCEAfter HIV-1 infection, uncontrolled virus replication leads to a rapid increase in HIV-1 concentrations. Once host immune responses develop, however, HIV-1 levels reach a peak and subsequently decline until they reach a stable level that may persist for years. This stable HIV-1 set point represents an equilibrium between the virus and host responses and is predictive of later disease progression and transmission potential. Understanding how host and virus factors interact to determine HIV-1 set point may elucidate novel mechanisms or biological pathways for treating HIV-1 infection. We identified host and virus factors that predict HIV-1 set point in people who recently acquired HIV-1, finding that both innate and adaptive immune responses, along with factors that likely influence HIV-1 virulence and inoculum, explain ∼46% of the variation in HIV-1 set point.
Structural Flexibility of a Conserved Antigenic Region in Hepatitis C Virus Glycoprotein E2 Recognized by Broadly Neutralizing Antibodies
Authors: Meola Annalisa , Tarr Alexander W. , England Patrick , Meredith Luke W. , McClure C. Patrick , Foung Steven K. H. , McKeating Jane A. , Ball Jonathan K. , Rey Felix A. , Krey Thomas
Published: December 2014

Neutralizing antibodies (NAbs) targeting glycoprotein E2 are important for the control of hepatitis C virus (HCV) infection. One conserved antigenic site (amino acids 412 to 423) is disordered in the reported E2 structure, but a synthetic peptide mimicking this site forms a β-hairpin in complex with three independent NAbs. Our structure of the same peptide in complex with NAb 3/11 demonstrates a strikingly different extended conformation. We also show that residues 412 to 423 are essential for virus entry but not for E2 folding. Together with the neutralizing capacity of the 3/11 Fab fragment, this indicates an unexpected structural flexibility within this epitope. NAbs 3/11 and AP33 (recognizing the extended and β-hairpin conformations, respectively) display similar neutralizing activities despite converse binding kinetics. Our results suggest that HCV utilizes conformational flexibility as an immune evasion strategy, contributing to the limited immunogenicity of this epitope in patients, similar to the conformational flexibility described for other enveloped and nonenveloped viruses.

IMPORTANCEApproximately 180 million people worldwide are infected with hepatitis C virus (HCV), and neutralizing antibodies play an important role in controlling the replication of this major human pathogen. We show here that one of the most conserved antigenic sites within the major glycoprotein E2 (amino acids 412 to 423), which is disordered in the recently reported crystal structure of an E2 core fragment, can adopt different conformations in the context of the infectious virus particle. Recombinant Fab fragments recognizing different conformations of this antigenic site have similar neutralization activities in spite of converse kinetic binding parameters. Of note, an antibody response targeting this antigenic region is less frequent than those targeting other more immunogenic regions in E2. Our results suggest that the observed conformational flexibility in this conserved antigenic region contributes to the evasion of the humoral host immune response, facilitating chronicity and the viral spread of HCV within an infected individual.
Structure-Function Analysis of Vaccinia Virus H7 Protein Reveals a Novel Phosphoinositide Binding Fold Essential for Poxvirus Replication
Authors: Kolli Swapna , Meng Xiangzhi , Wu Xiang , Shengjuler Djoshkun , Cameron Craig E. , Xiang Yan , Deng Junpeng
Published: December 2014

Phosphoinositides and phosphoinositide binding proteins play a critical role in membrane and protein trafficking in eukaryotes. Their critical role in replication of cytoplasmic viruses has just begun to be understood. Poxviruses, a family of large cytoplasmic DNA viruses, rely on the intracellular membranes to develop their envelope, and poxvirus morphogenesis requires enzymes from the cellular phosphoinositide metabolic pathway. However, the role of phosphoinositides in poxvirus replication remains unclear, and no poxvirus proteins show any homology to eukaryotic phosphoinositide binding domains. Recently, a group of poxvirus proteins, termed viral membrane assembly proteins (VMAPs), were identified as essential for poxvirus membrane biogenesis. A key component of VMAPs is the H7 protein. Here we report the crystal structure of the H7 protein from vaccinia virus. The H7 structure displays a novel fold comprised of seven α-helices and a highly curved three-stranded antiparallel β-sheet. We identified a phosphoinositide binding site in H7, comprised of basic residues on a surface patch and the flexible C-terminal tail. These residues were found to be essential for viral replication and for binding of H7 to phosphatidylinositol-3-phosphate (PI3P) and phosphatidylinositol-4-phosphate (PI4P). Our studies suggest that phosphoinositide binding by H7 plays an essential role in poxvirus membrane biogenesis.

IMPORTANCE
Poxvirus viral membrane assembly proteins (VMAPs) were recently shown to be essential for poxvirus membrane biogenesis. One of the key components of VMAPs is the H7 protein. However, no known structural motifs could be identified from its sequence, and there are no homologs of H7 outside the poxvirus family to suggest a biochemical function. We have determined the crystal structure of the vaccinia virus (VACV) H7 protein. The structure displays a novel fold with a distinct and positively charged surface. Our data demonstrate that H7 binds phosphatidylinositol-3-phosphate and phosphatidylinositol-4-phosphate and that the basic surface patch is indeed required for phosphoinositide binding. In addition, mutation of positively charged residues required for lipid binding disrupted VACV replication. Phosphoinositides and phosphoinositide binding proteins play critical roles in membrane and protein trafficking in eukaryotes. Our study demonstrates that VACV H7 displays a novel fold for phosphoinositide binding, which is essential for poxvirus replication.
Bilateral acute angle closure glaucoma associated with hydrochlorothiazide-induced hyponatraemia
Authors: Chen Sylvia H , Karanjia Rustum , Chevrier Robert L , Marshall David H
Published: December 2014

We report a case of a 67-year-old woman presenting with bilateral acute angle closure. On investigation, she was found to have bilateral ciliary effusions and profound hyponatraemia. Her effusions resolved with the cessation of hydrochlorothiazide and normalisation of her blood sodium levels by fluid restriction. This case displays a novel association of hyponatraemia as a possible mechanism for the development of bilateral acute angle closure.
Successful recanalization for acute ischemic stroke via the transbrachial approach
Authors: Okawa Masakazu , Tateshima Satoshi , Liebeskind David , Ali Latisha K , Thompson Michael L , Saver Jeffrey , Duckwiler Gary R
Published: December 2014

The recent development of revascularization devices, including stent retrievers, has enabled increasingly higher revascularization rates for arterial occlusions in acute ischemic stroke. Patient-specific factors such as anatomy, however, may occasionally limit endovascular deployment of these new devices via the conventional transfemoral approach. We report three cases of acute ischemic stroke where a transbrachial endovascular approach to revascularization was used, resulting in successful recanalization. These examples suggest that a transbrachial approach may be considered as an alternative in the endovascular treatment of acute ischemic stroke.
Level Sets and NonGaussian Integrals of Positively Homogeneous Functions
Authors: Lasserre Jean B.
Published: December 2014

We investigate various properties of the sublevel set G = {x : g(x) ≤ 1} and the integration of h on this sublevel set when g and h are positively homogeneous functions (and in particular homogeneous polynomials). For instance, the latter integral reduces to integrating h exp (-g) on the whole space ℝn (a nonGaussian integral) and when g is a polynomial, then the volume of G is a convex function of the coefficients of g. We also provide a numerical approximation scheme to compute the volume of G or integrate h on G (or, equivalently to approximate the associated nonGaussian integral). We also show that finding the sublevel set {x : g(x) ≤ 1} of minimum volume that contains some given subset K is a (hard) convex optimization problem for which we also propose two convergent numerical schemes. Finally, we provide a Gaussian-like property of nonGaussian integrals for homogeneous polynomials that are sums of squares and critical points of a specific function.
Effects of Pre-Existing Defects on Nanoimprint Process Investigated by Molecular Dynamics Simulation
Authors: Yuan Ying , Zhang Junjie , Sun Tao , Liu Cong
Published: December 2014

In current study molecular dynamics (MD) simulations are performed to reveal effects of pre-existing defects on nanoimprint of single crystal aluminum ( Al ) thin films. Simulation results suggest that critical force required for plastic deformation initiation decreases with the increase of vacancy volume fraction, but increases with the interstitial volume fraction. It is found that adsorption phenomenon is affected by pre-existing defects, as adsorption phenomenon weakens with the increasing interstitial volume fraction. Pre-existing defects have significant influence on the deformation mechanisms and imprint forces during the nanoimprint processes. Simulation results also show that surface deformation is strongly affected by pre-existing defects.
Tectonic and magmatic evolution of the mantle lithosphere during the rifting stages of a fossil slow–ultraslow spreading basin: insights from the Erro–Tobbio peridotite (Voltri Massif, NW Italy)
Authors: Padovano Matteo , Piccardo Giovanni B. , Vissers Reinoud L. M.
Published: December 2014

We investigate the structural, petrological and compositional features recorded by strongly deformed and melt-percolated Erro–Tobbio peridotites (Voltri Massif, Ligurian Alps, NW Italy), in order to demonstrate that the processes of shear-zone formation and melt percolation are intimately linked by a positive feedback. We focus on spinel and plagioclase peridotites, and extensional shear zones that underwent infiltration by upwelling asthenospheric melts. Shear and porosity bands, which developed during extension prior to melt infiltration, represent important structural and rheological pathways to facilitate and enhance melt infiltration into the extending lithosphere and the ascent of such melts to shallower levels.

Our results lend strong support to numerical models addressing the physical processes underlying extensional systems. These show that, in the case of slow–ultraslow continental extension and the subsequent formation of slow–ultraslow spreading oceans, porosity and shear-localization bands may develop in a previously unstructured lithosphere, prior to melt infiltration. Our studies on the Erro–Tobbio peridotites allow a model for the inception of continental extension and rifting to drifting of slow–ultraslow spreading oceans to be proposed. We suggest that integrated studies of on-land peridotites, coupled with geophysical–structural results from modern oceans, may provide clues to the geodynamic processes governing continental extension and passive rifting.
(Invited) Electron Tunneling Based SEI Formation Model
Authors: Li Dongjiang , Danilov Dmitry , Zhang Zhongru , Chen Huixin , Yang Yong , Notten Peter H.L.
Published: December 2014

A new model, describing the capacity loss of C6/LiFePO4 batteries under open-circuit storage conditions has been developed. De-gradation is attributed to the formation of a Solid Electrolyte Interface (SEI) at the surface of the graphite particles in the negative electrode. The model takes into account that the Solid Electrolyte Interface consists of an inner and outer SEI layer. The rate determining step of the SEI formation process is proposed to be electron tunneling through the inner SEI layer. The simulation results demonstrate that the capacity loss is dependent on the State-of-Charge (SoC), the electrode potential and storage time. The inner SEI layer was found to grow much slower than the outer SEI layer.
Synthesis and Electrochemical Properties of Nano WO3/C Composite for Lithium-Ion Batteries
Authors: Gao Hong , Yang Shuijin , Feng Chuanqi , Wang Jiazhao , Guo Zaiping
Published: December 2014

WO3/C nanorods were prepared by a combination of hydrothermal synthesis method and the solid phase reaction method, using (NH4)10H2(W2O7)6, H2C2O4·2H2O and glucose(carbon source) as raw materials. The effects of different proportions of glucose on the morphologies and electrochemical properties of the final products were systematically investigated. The results showed that the WO3/C nanorods prepared with the 10 wt.% glucose as carbon source exhibited the highest reversible specific capacity (807 mAh g−1) at current density of 50 mA g−1 and the best cycle performances among all samples. Besides, it behaved good rate performance. It indicated that WO3/C nanorods could be promising electrode materials for lithium ion battery application.
Porous Silicon as Nanostructured Anode Material for Lithium Ion Batteries
Authors: Miele Ermanno , Goriparti Subrahmanyam , Messina Gabriele Carmine , Prato Mirko , Ansaldo Alberto , Barone Alberto , DeAngelis Francesco , Zaccaria Remo Proietti , Capiglia Claudio
Published: December 2014

Future research and manufacturing developments of energy storage materials necessitate the investigation of novel and scalable lithium ion batteries anodes as well as strategies to improve their performances. Among others, silicon-based anodes are particularly promising because of the high theoretical capacity, material abundance and processability. Some major issues still limit the effective employment of silicon, in particular its large volume expansion in cyclation and low coulombic efficiency. In this manuscript bulk crystalline silicon is nanostructured to form porous silicon (PSi) by controlled HF etching and carbon coated via CVD. Mechanical behavior in respect of porosity has been studied by nanoindentation. Pristine and carbon coated silicon have been characterized in their morphological and chemical properties by SEM, XRD and XPS. Finally, the improvements in electrochemical behavior provided by carbon coating have been proved by cyclic voltammetry and galvanostatic charging/discharging measurements.
Crystal Structure and Electrochemistry of Na2-XLixFePO4F (0≤x≤1) New Cathode Materials for Na- and Li-Ion Batteries
Authors: Kosova Nina V. , Podugolnikov Vladislav R. , Bobrikov Ivan A. , Balagurov Anatoly M.
Published: December 2014

A series of the mixed sodium-lithium iron fluorophosphates Na2-xLixFePO4F with 0≤x≤1 has been synthesized by mechanochemically assisted solid-state route. Their crystal and local structure, and electrochemical properties were investigated by X-ray and neutron powder diffraction, 57Fe Mössbauer spectroscopy and electrochemical measurements with GITT. Three single-phase compounds Na2FePO4F, Na1.5Li0.5FePO4F and NaLiFePO4F were obtained. The former crystallize with space group Pbcn, while the latter - with Pnma, differing by Na+/Li+ distribution. All as-prepared Na2-xLixFePO4F samples are electrochemically active in Li cell pointing to the occurrence of a gradual Na+/Li+ ion exchange. Ex situ XRD and EDX study indicates that it results in the formation of lithium rich phases: NaLiFePO4F (S.G. Pbcn) for Na2FePO4F and Na0.3Li1.7FePO4F (S.G. Pnma) for Na1.5Li0.5FePO4F. Charge-discharge curves exhibit sloping profiles with an average potential of 3.3-3.4 V vs. Li/Li+. The average value of DLi determined by GITT is 10-15 and 10-16 cm2 s-1 for NaLiFePO4F and Na0.3Li1.7FePO4F, respectively.
Mesoporous Silicon Nanostructures by Pulsed Laser Deposition as Li-Ion Battery Anodes
Authors: Biserni Erika , Garino Nadia , Li Bassi Andrea , Bruno Paola , Gerbaldi Claudio
Published: December 2014

Silicon is very attractive as active material for Li-ion battery anodes due to its high theoretical capacity, but proper nanostructuring is needed to accommodate the large volume expansion/shrinkage upon reversible cycling. This would overcome the destructuration induced by the lithiation/delithiation processes, often resulting in poor long-term performance. Hereby, novel mesoporous silicon nanostructures are grown at room temperature by Pulsed Laser Deposition (PLD) directly on top of the Cu current collector surface, and their promising electrochemical behaviour demonstrated in lab-scale lithium cells. Depending on the porosity, easily tunable by PLD, initial specific capacities approaching 300 µAh cm-
2 are obtained with a quasi-stable reversible cycling. Engineering voids at the nanoscale, by direct introduction of specific porosity during growth, opens up the route for the effective use of silicon as lithium battery anode without the need for any binder or conductive additive which would lower the overall energy density.
Changing the Electrochemical Properties of LiCoO2 Depending on the Time Elapsed from the Synthesis
Authors: Kazda Tomáš , Vondrák Jiří , Sedlaříková Marie , Visintin Arnaldo , Čudek Pavel
Published: December 2014

Lithium-ion batteries occupy every year more and more dominant position on the market with batteries. One of the most commonly used materials for the commercial production of lithium-ion battery is the cathode material LiCoO2. It can be interesting to see how long the cathode material can be stored under normal conditions without significantly affecting its electrochemical properties for the production of lithium-ion batteries. This article deals with the changes in the electrochemical properties of the cathode material LiCoO2 synthesized according to the time elapsed since its synthesis. The materials were stored under normal conditions and after a certain period of time their capacity during cycling and stability at higher loads were monitored. The synthesized material was further studied by SEM and EDX. Measurements showed that with increasing time elapsed since the synthesis there appears deterioration of the electrochemical properties up to the complete degradation of the material.
Multicell Stack of Nonaqueous Lithium–Air Batteries
Authors: Kubo Yoshimi , Ito Kimihiko
Published: December 2014

The lithium–air rechargeable battery has been considerably improved through the use of ether-based electrolytes. However, to realize high energy density in practical applications, a large number of lithium–air cells must be stacked, similar to the configuration of conventional lithium-ion batteries. This configuration requires a novel design of the cell stack such that air can be supplied to the cathode. We have recently developed an “air-breathing” passive system for lithium–air batteries comprising multicell stacks, where air is breathed in and out through porous current collectors sandwiched between cathodes. A ten-cell stack was assembled and subjected to more than ten discharge–charge cycles.
Multi-Methodology Modeling and Design of Lithium-Air Cells with Aqueous Electrolyte
Authors: Grübl Daniel , Danner Timo , Schulz Volker P , Latz Arnulf , Bessler Wolfgang G.
Published: December 2014

Metal-air batteries are being investigated as alternative to state-of-the-art lithium-ion batteries for mobile and stationary applications due to their higher specific energy and potentially lower cost. Modeling and simulation techniques allow a better understanding and improvement of the complex mechanisms and properties of metal-air batteries. We present simulation results of a lithium-air (Li/O2) battery with aqueous alkaline (LiOH) electrolyte using three different methodologies, (i) Lattice-Boltzmann modeling on the porous electrode scale, (ii) multi-physics continuum modeling on the single-cell scale and (iii) system simulation of a Li/O2-battery-powered electric vehicle. Different cell designs (porous separator, stirred separator, and redox-flow design) are investigated in order to quantitatively assess their performance. Virtual aqueous lithium-air batteries yielded high specific energy (up to 755 Wh/kg), but considerably uncompetitive specific power, which prohibit the use in battery electric vehicles at the present stage of development.
Solid State Electrolytes for Ambient and Middle Temperature Next Generation Electrochemical Storage Systems
Authors: Ahlbrecht Katharina , Holzapfel Michael , Tübke Jens , Hoffmann Michael J
Published: December 2014

Solid state electrolytes are typically known for their utilization in high-temperature or stationary electrochemical energy storage systems. For practical applications as well as for next generation systems like sulfur or air cells, the solid state electrolyte (SSE) has to be stable, dense and flexible. The thickness therefore needs to be reduced to obtain an acceptable passive weight. The aim of this study is the demonstration of an innovative, flexible solid state electrolyte for future systems, and to calculate the impact of its thickness on the energy densities of various storage systems.
A Micro-/Macroscopic Safety Mechanism Study for Li Ion Battery
Authors: Chung Jaesik
Published: December 2014

In order to understand the battery safety mechanisms including cell degradations on abuse conditions and field safety incidents, we used micro-/macroscopic tool to analyze the Li-ion battery design and manufacturing status which have strong direct relationship with the failure. The micro-/macroscopic analysis tool was applied to both gap measurements for the DPA (Destructive Physical Analysis) and the non-destructive failure/structure analysis of computerized tomography for the damaged samples after abuse testing. Through the combination analysis of the gap measurement by micro-/macroscopic tool and the non-destructive failure/structure analysis by X-Ray with the result of cell abuse verification tests, we can identify the latent root causes of field incident, study the battery safety mechanism and classify the safety risk level of each cell model. It can be suggested that a micro-/macroscopic analysis tool is a good method to study lithium ion battery safety mechanism and the root cause analysis of the failure.
Lithium Redox in Imidazolium Ionic Liquids Composed of Five-Membered Cyclic Amide
Authors: Matsumoto Hajime , Tsuzuki Seiji , Kubota Keigo
Published: December 2014

A Lithium metal deposition and stripping peak could be observed in 1-ethyl-3-methylimidazolium (=[C1C2im]+) ionic liquids containing five-membered cyclic amide (4,4,5,5-tetrafluoro-[1,3,2]dithiazolidin-2-ide 1,1,3,3-tetraoxide). The theoretically estimated interaction energy between a Li+ and an anion and the adsorption energy of [C1C2im]+-based IL on Li(100) and the results of EQCM measurements were carried out to compare among the cyclic amide and the other typical amide anions, such as bis(trifluoromethylsulfonyl)amide and bis(fluorosulfonyl)amide.
Solvent Free Lithium Molten Salt as Electrolyte of Lithium Secondary Battery
Authors: Kubota Keigo , Matsumoto Hajime
Published: December 2014

Low-melting alkali metal salts containing a (fluorosulfonyl)(trifluoromethylsulfonyl)amide have possibility to be molten salt electrolytes for lithium secondary batteries. A composite graphite negative electrode can be combined with this molten salt along with the LiCoO2 and LiFePO4 positive electrode. The charge-discharge of a graphite || Li cell was successful without any organic solvent due to formation of a solid electrolyte interface derived by decomposition of the anion. Its discharge capacity is near the ideal value.
Characterisation of LTO // NMC Batteries Containing Ionic Liquids or Carbonates after Cycling and Overcharge
Authors: Chancelier Léa , Benayad Anass , Gutel Thibaut , Mailley Sophie , Santini Catherine C.
Published: December 2014

Electrochemical performances in cycling and overcharge of Li4Ti5O12 (LTO) // LiNi1/3Mn1/3Co1/3O2 (NMC) batteries with two ionic liquid-based electrolytes and a commercial carbonate were investigated at 60 °C. These experiments were performed in coin and pouch cells allowing the full characterization of decomposition products and electrodes surface by SEM, XRD and XPS techniques, after cycling and overcharge.
Lithium Distribution in Monocrystalline Silicon-Based Lithium-Ion Batteries
Authors: Janski Rafael , Fugger Michael , Sternad Michael , Wilkening Martin
Published: December 2014

The ability of nitrides and alloys of refractory metals to act as solid-state diffusion barrier for Li migration in Si was evaluated by mass spectrometry techniques. Magnetron sputtered barrier films on silicon, assembled in a Swagelok® half-cell, were used as working electrodes to determine whether several barrier layers are able to prevent the formation of Li-Si alloys. In addition, lithium ion diffusion was studied in monocrystalline silicon. To determine the depth profiles in the silicon substrate and in the barrier layer, respectively, two complementary techniques, being based on mass spectrometry, were applied: (i) ToF-SIMS was used as imaging technique for depth profiling the first microns and (ii) laser ablation ICP-MS was carried out to study depth profiles of up to hundreds of microns. Titanium nitride as well as tantalum nitride barriers turned out to prevent or inhibit the reaction between lithium and silicon. Regarding Li diffusion in silicon preliminary tests were performed to investigate both diffusion coefficients and the activation energies in (100) monocrystalline silicon.
Ion Conduction and Electrochemical Performance of Poly(oxetane)-Based Electrolytes with Tri(cyanoethoxymethyl) Moiety As a Side Chain
Authors: Nakano Yohei , Tsutsumi Hiromori
Published: December 2014

We have prepared solid polymer electrolyte films based on poly(oxetane) with tri(cyanoethoxymethyl) moiety as a side chain. The oxetane monomer (COA) was synthesized by coupling reaction between oxetane with carboxylic acid moiety and branched amine with tri(cyanoethoxymethyl) groups. COA was polymerized through ring opening reaction of oxetane by using cationic initiator, BF3(Et)2O. The solid polymer electrolyte films were prepared from the poly(oxetane), poly(vinylidenedifluoride-co-hexafluoropropylene), and LiTFSA. The highest ionic conductivity for the polymer electrolyte films is 0.74 mS cm-1 at 343 K and 0.098 mS cm-1 at 293 K. Electrochemical stability of the electrolyte films and plating and stripping of lithium in them were investigated by linear sweep and cyclic voltammetric techniques.
New Insights into SEI Formation in Lithium Ion Batteries: Inhomogeneous Distribution of Irreversible Charge Losses Across Graphite Electrodes
Authors: Klink Stefan , Weide Philipp , Muhler Martin , Schuhmann Wolfgang , La Mantia Fabio
Published: December 2014

A vertical split electrode (VSE) with three layers was developed to investigate the formation of the solid electrolyte interphase (SEI) during first charge of graphite electrodes in lithium ion batteries. Ex-situ X-ray photoelectron spectroscopy (XPS) on each layer revealed that the first layer showed distinctively different signal patterns in the O 1s and C 1s regions. It was concluded that the SEI formed in the first layer closest to the counter electrode is thicker as well as different in chemical nature as compared to the SEI in the electrode bulk.
Compositions of Co-doped LiMn2O4 Spinel with MCNT in Lithium Prototype Accumulator
Authors: Apostolova Raisa , Peskov Roman , Shembel Elena
Published: December 2014

In order to obtain Co-doped LiMn2O4, high-temperature synthesis was used. Co-doping increases the conductivity of spinel, being in form of extruded pellet, at the temperature of 293 and 323 K. The advantage of compositions of Co-doped LiMn2O4 spinel with MCNT over pure LiMn2O4 lies in the increase of cycling efficiency and the rate of intercalation/deintercalation processes of lithium ions in thin-layer electrodes. At the discharge rate of 30-40 C the discharge capacity of (Co)LiMn2O4 in composition with MCNT is 80% of those obtained at the rate of 1 C. The reasons of the decrease in discharge capacity of composition of Co-doped LiMn2O4 spinel with MCNT in redox reaction with lithium at continuous galvanostatic cycling and reduced temperature were shown. On the basis of the analyses of system impedance spectrum, the composition of Co-doped LiMn2O4 spinel with MCNT/(EC, DMC, 1 M LiClO4)-electrolyte, the key role of charge-transfer resistance through composition/electrolyte surface was defined as well as degradation factors of particular stages of redox reaction of lithium with spinel composition.
Highly Reversible Silicon/Carbon Nanofiber/Carbon Nanotube Nanocomposite Anodes for Lithium Ion Batteries
Authors: Cetinkaya Tugrul , Uysal Mehmet , Akbulut Hatem
Published: December 2014

Silicon/Carbon Nanofiber (Si/CNF) and Silicon/Carbon Nanofiber/ Carbon Nanotube (Si/CNF/CNT) nanocomposite anode materials were produced by mechanical alloying and subsequently then heat treatment methods. Produced nanocomposite structures were characterized by scanning electron microscopy (SEM), X-ray diffraction patterns (XRD) and Raman Spectroscopy. Electrochemical performance of the produced electrodes were tested between 0.05V and 1.5V at a constant current density of 200 mAg-1. As a result, the produced Si/CNF/CNT nanocomposite electrodes containing 50 wt.% CNT showed 1127 mAhg-1 discharge capacity even after 100 cycles.
Conducting Polymers as Binder Additives for Cathodes in Li Ion Battery
Authors: Das Pratik Ranjan , Gräfenstein Alexander , Ledwoch Daniela , Osters Oliver , Komsiyska Lidiya , Wittstock Gunther
Published: December 2014

Commercial applications of Li-ion batteries for the electro mobility and stationary storage require high energy density, high rate capability and long cycle life of the battery. In this paper we have shown the improvement in energy density and rate capability of LiFePO4 composite cathodes by partially replacing conventional binders with poly-o-methoxyaniline (POMA) and tosylate doped poly(3,4-ethylenedioxythiophene) (PEDOT:p-Tos). Due to different redox properties of the used conducting polymers, POMA specifically improves the capacity to 14% as compared to conventional polyvinylidene difluoride (PVDF) and in case of PEDOT:p-Tos 83% capacity is retained at 5 C charging rate.
Gel Polymer Electrolyte
Authors: Dvořák Petr , Chladil Ladislav , Sedlaříková M , Vondrák J
Published: December 2014

Gel polymer electrolyte containing immobilized different types of salts (LiPF6, LiBF4, TEABF4) in aprotic solvents (PC, EC:DEC, EC DMC) were prepared by UV polymerization. Electrolytes were optimized to achieve suitable ionic conductivity (up to 7.5 mS/cm) and good mechanical stability. The electrochemical stability up to 4 V was determined on stainless steel electrode by voltammetrical measurements.
Characteristics of FeS2 in Electrolytes Based on DMC-LiAn Mixtures During Galvanostatic Cycling
Authors: Globa Nataliy , Sirosh Vitalii , Prisyazhnyi V. D.
Published: December 2014

The specific capacity of natural pyrite (FeS2) was investigated by galvanostatic cycling method. Investigation was carried out in electrolytes consisting of dimethyl carbonate (DMC) and a lithium salt (LiBF4, LiClO4, LiN(CF3SO2)2). It was shown that the specific capacity of FeS2 and its stability during cycling depend on the concentration and nature anion lithium salt. The best characteristics of the FeS2 during cycling are attained in DMC – LiClO4 and DMC – LiN(CF3SO2)2 electrolytes at salt concentration in the range of 0.1 – 0.2 mole fraction (m.f.).
Study of the Electrochemical Behavior of Lithium Iron Phosphate Doped by Chromium and Nickel
Authors: Chekannikov Andrey , Kapaev R , Novikova S , Kulova Tatiana , Skundin A , Yaroslavtsev A
Published: December 2014

Lithium iron phosphate samples doped with chromium and nickel were successfully synthesized by sol-gel method. Their electrochemical behavior has been investigated with the use of charge/discharge tests. These studies showed that doped lithium iron phosphate has lower discharge capacity compared with undoped sample. However, the dependence of discharge capacity versus current density for all of the doped samples is less pronounced.
Compatibility of Aprotic Electrolytes with Negative Electrode Materials in Lithium-Ion Batteries
Authors: Libich Jiri , Máca Josef , Sedlaříková Marie , Vondrák Jiří , Visintin Arnaldo
Published: December 2014

This short research presents an introduction to the fire safety of Lithium-ion batteries. Nowadays, as the most weak part of aprotic battery is its aprotic electrolyte. The aprotic electrolyte (commonly the mixture of aprotic solvents) that is used in Lithium-ion batteries have got low flash point with poor thermal stability. This paper describes using sulfolane as an aprotic solvent in Lithium-ion battery. Measurements were focused on performance, cyclability and stability of aprotic electrolyte with relation of graphite material as a negative electrode. Like a possible substitution of graphite, the LTO material was used and tested. Lithium Titanate Oxide (LTO) seems to be promising negative electrode material for Lithium-ion batteries.
Computational Modeling of Lithium Ion Battery
Authors: Vyroubal Petr , Maxa Jiří , Kazda Tomáš , Vondrák Jiří
Published: December 2014

Computer simulation is a very popular engineering tool for describing and modelling phenomena occurring in real life and allows us to quickly obtain the basic characteristics of the studied system. In this work, we studied the possibilities of numerical simulations of lithium ion batteries. We focus on the use of secondary power sources. The lithium-ion battery is an ideal candidate for a wide variety of applications due to its high energy/power density and operating voltage. The article presents the mathematical formulation of physics-based lithium ion battery and structure of the governing equations in Comsol Multiphysics and Matlab Simulink programs. The real lithium ion battery is compared with simulation results and with real measurements. For numerical study in Comsol Multiphysics, which works with finite element method, 2D geometry model was used.
Hydrogen Technologies in the Project SUSEN at Research Center Rez
Authors: Tkáč Martin , Stehlík Karin , Kryková Markéta
Published: December 2014

The Research Center Rez CVR, close to Prague, is well known in the field of material research for nuclear applications. Within the European infrastructure programme SUSEN a laboratory for testing and manufacturing of high-temperature electrolysis cells will be built up until 2015. The first objective is hydrogen production using coupling to a high-temperature process, e.g. generation IV gas-cooled nuclear reactor. The research Center Rez is a member of HYTEP, Czech Hydrogen Technical Platform, which brings together all stakeholders interested in hydrogen technologies in the Czech Republic. HYTEP also represents Czech Republic in other European hydrogen associations.
Electrochemical Properties of CeVO4 and FeVO4 at High Temperatures
Authors: Behofsits Timea , Pani Georg , Gross Markus , Fafilek Günter , Malys Marcin
Published: December 2014

High temperature corrosion of steel is dramatically accelerated by ashes and scales containing compounds of iron, vanadium, oxygen and sulfur. High temperature electrochemical impedance spectroscopy (HT-EIS) and cyclic voltammetry (HT-CV) on ash samples from a heavy crude oil furnace, showed high conductivity of at least one of the several existing phases and also some redox activity, which could be related to redox processes of vanadium containing compounds. On the one hand, it is unfavorable for the corrosion stability of construction materials; on the other hand it might be an effective material for several applications, like high temperature fuel cells electrodes, intercalation materials in ion-batteries or as catalyst. FeVO4 was identified as one of the few potentially highly conductive phases in the ash. Pure FeVO4 was synthesized and investigated by HT-EIS and HT-CV on micro-samples. For comparison CeVO4 was included in this investigation.
Electrochemistry in the Electrochemical Cells: There is More than Just the Working Electrode
Authors: Vanýsek Petr , Tavassol Hadi , Pilson Kate-Leigh
Published: December 2014

The tacit assumption in an electrochemical experiment is that a properly set up electrochemical cell, working electrode, counter electrode, reference electrode and a potentiostat, will perform an experiment by "applying potential on the working electrode" without any need to consider the properties of the reference electrodes, the effect of electrochemistry on the counter electrode and the real properties of the potentiostat. While this is in first approximation a valid assumption, in the extremes it is also necessary to consider the other parts of the system. In this work we visit two interesting cases that may lead to experimental artifacts. The first is the effect of electrochemical solution changes during impedance measurement. The second is effect of the time constant of a reference electrode on an impedance measurement in an electrochemical cell.