bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein expression pattern of PAWP in bull spermatozoa is associated with sperm quality and fertility following artificial insemination
Authors: Kennedy Chelsey E. , Krieger Kari Beth , Sutovsky Miriam , Xu Wei , Vargovič Peter , Didion Bradley A. , Ellersieck Mark R. , Hennessy Madison E. , Verstegen John , Oko Richard , Sutovsky Peter
Published: February 2014

Post‐acrosomal WW‐domain binding protein (PAWP) is a signaling molecule located in the post‐acrosomal sheath (PAS) of mammalian spermatozoa. We hypothesized that the proper integration of PAWP in the sperm PAS is reflective of bull‐sperm quality and fertility. Cryopreserved semen samples from 298 sires of acceptable, but varied, fertility used in artificial insemination services were analyzed using immunofluorescence microscopy and flow cytometry for PAWP protein. In normal spermatozoa, PAWP fluorescence formed a regular band around the proximal PAS. Anomalies of PAWP labeling in defective spermatozoa were reflected in flow cytometry by varied intensities of PAWP‐induced fluorescence. Distinct sperm phenotypes were also identified, including morphologically normal and some defective spermatozoa with moderate levels of PAWP; grossly defective spermatozoa with low/no PAWP; and defective spermatozoa with high PAWP. Analysis by ImageStream flow cytometry confirmed the prevalence of abnormal sperm phenotypes in the spermatozoa with abnormal PAWP content. Live/dead staining and video recording showed that some abnormal spermatozoa are viable and capable of progressive motility. Conventional flow‐cytometric measurements of PAWP correlated significantly with semen quality and fertility parameters that reflect the sires' artificial insemination fertility, including secondary sperm morphology, conception rate, non‐return rate, and residual value. A multiplex, flow‐cytometric test detecting PAWP, aggresomes (ubiquitinated protein aggregates), and acrosomal integrity (peanut‐agglutinin‐lectin labeling) had a predictive value for conception rate, as demonstrated by step‐wise regression analysis. We conclude that PAWP correlates with semen/fertility parameters used in the cattle artificial insemination industry, making PAWP a potential biomarker of bull fertility. Mol. Reprod. Dev. 81: ???–???, 2014. © 2014 Wiley Periodicals, Inc.
Changes in motor unit properties in SOD1 (G93A) rats
Authors: Kryściak Katarzyna , Grieb paweł , Celichowski Jan
Published: February 2014

Introduction: In amyotrophic lateral sclerosis (ALS), progressive death of motor neurons results in denervation and reinnervation of muscles. It is not clear how ALS affects the properties of motor units (MUs). Methods: Properties of single MUs in the medial gastrocnemius (MG) muscle of rats bearing the human mutated superoxide dismutase gene type 1 (SOD1) were determined at 3 stages: asymptomatic (ALS I); early symptomatic (ALS II); and terminal (ALS III). Results: In ALS II, higher proportions of FF (fast fatigable) and S (slow) MUs were observed, whereas in ALS III higher percentages of S and lower percentages of FF MUs were noted compared with controls. S motor neurons reinnervated fast muscle fibers, and those MUs gained some properties of fast MUs, including lower fatigue resistance, greater force generation, and higher action potential amplitudes. Conclusion: Changes in MU properties of SOD1 rats have progressive and multidirectional character and speed depending on the MU type. Muscle Nerve 50: 577–586, 2014
Late adult‐onset of X‐linked myopathy with excessive autophagy
Authors: Crockett Cameron D. , Ruggieri Alessandra , Gujrati Meena , Zallek Christopher M. , Ramachandran Nivetha , Minassian Berge A. , Moore Steven A.
Published: February 2014

Introduction: X‐linked myopathy with excessive autophagy (XMEA) is characterized by autophagic vacuoles with sarcolemmal features. Mutations in VMA21 result in insufficient lysosome acidification, causing progressive proximal weakness with onset before age 20 years and loss of ambulation by middle age. Methods: We describe a patient with onset of slowly progressive proximal weakness of the lower limbs after age 50, who maintains ambulation with the assistance of a cane at age 71. Results: Muscle biopsy at age 66 showed complex muscle fiber splitting, internalized capillaries, and vacuolar changes characteristic of autophagic vacuolar myopathy. Vacuoles stained positive for sarcolemmal proteins, LAMP2, and complement C5b‐9. Ultrastructural evaluation further revealed basal lamina reduplication and extensive autophagosome extrusion. Sanger sequencing identified a known pathologic splice site mutation in VMA21 (c.164–7T>G). Conclusions: This case expands the clinical phenotype of XMEA and suggests VMA21 sequencing be considered in evaluating men with LAMP2‐positive autophagic vacuolar myopathy. Muscle Nerve 50: 138–144, 2014
Genetic heterogeneity of amyotrophic lateral sclerosis: Implications for clinical practice and research
Authors: Su Xiaowei W. , Broach James R. , Connor James R. , Gerhard Glenn S. , Simmons Zachary
Published: February 2014

Genetic insights into the pathophysiology of amyotrophic lateral sclerosis (ALS) are untangling the clinical heterogeneity that may contribute to poor clinical trial outcomes and thus to a lack of effective treatments. Mutations in a large number of genes, including SOD1, C9ORF72, TARDBP, FUS, VAPB, VCP, UBQLN2, ALS2, SETX, OPTN, ANG, and SPG11, are thought to cause ALS, whereas others, including ATAXN2, GRN, HFE, NEFH, UNC13A, and VEGF, appear to be disease‐modifying genes. Epigenetic influences may also play important roles. An improved understanding of ALS genetics should lead to better trial designs, insights into common molecular pathways, and better characterization of preclinical models. New genetic sequencing techniques, which use high‐throughput methods to assess variants across the genome or exome, may facilitate rational patient stratification for clinical trials and permit more individualized prognostic information and treatment decisions in clinical care. Muscle Nerve 49: 786–803, 2014
Improvement of interfacial properties of carbon fiber‐reinforced poly(phthalazinone ether ketone) composites by introducing carbon nanotube to the interphase
Authors: Zhang Shu , Liu Wenbo , Wang Jian , Li Bichen , Hao Lifeng , Wang Rongguo
Published: February 2014

This article aims to improve interfacial properties of carbon fiber‐reinforced poly(phthalazinone ether ketone) (PPEK) composites by means of preparing carbon nanotube (CNT)/carbon fiber hybrid fiber. XPS was used to characterize the chemical structure of unsized carbon fiber and SEM was used to observe the surface topography of carbon fibers. Specific area measurement, dynamic contact angle, and interfacial shear strength (IFSS) testing were performed to examine the effect of CNT on the interfacial properties of carbon fiber/PPEK composites. By the introduction of CNT to the interphase of carbon fiber‐reinforced PPEK composites, an enhancement of IFSS by 55.52% was achieved. Meanwhile, the interfacial fracture topography was also observed and the reinforcing mechanism was discussed. POLYM. COMPOS., 36:26–33, 2015. © 2014 Society of Plastics Engineers
Catalytically synergistic effects of novel LaMnO3 composite metal oxide in intumescent flame‐retardant polypropylene system
Authors: Sheng Yan , Chen Yinghong , Bai Yuanzhang
Published: February 2014

The newly prepared LaMnO3 was introduced as a novel perovskite composite metal oxide catalyst for the first time to improve the flame retardancy of flame‐retarded (FR) polypropylene with intumescent flame‐retardant (IFR) system consisting of ammonium polyphosphate (APP), pentaerythritol (PER), and melamine (MA). The synergistic effects of LaMnO3 catalyst on the performance of IFR PP composites as well as the corresponding catalytically synergistic FR mechanism were investigated. The experimental results show that the incorporated LaMnO3 catalyst plays an excellently catalytic and synergistic part in improvement of the flame retardancy of FR PP system. Compared with FR system without LaMnO3, the incorporation of only 0.5 wt% LaMnO3 into PP FR system could obviously improve the UL‐94 level from failure to V‐0 rating and decrease the micro‐scale calorimetry parameters peak heat release rate and heat release capacity. The remarkable improvement in flammability can be ascribed to the catalytic carbonization effect of LaMnO3 on the intumescent flame retardant PP system. The incorporation of appropriate amount of LaMnO3, on one hand, could improve the thermal stability of FR PP material, and on the other hand, could also act as nuclei to induce formation of the continuous, compact and smooth condensed phase intumescent charred layer with radialized spherulite‐like structure. As a result, the char yield and also the quality of the formed condensed phase charred layers are correspondingly enhanced remarkably, which is beneficial to improvement of the FR properties. POLYM. COMPOS., 35:2390–2400, 2014. © 2014 Society of Plastics Engineers
Preparation and characterization of porous PDMS beads for oil and organic solvent sorption
Authors: Li Ning , Li Tao , Lei Xiaomei , Fu Bo , Liao Weixi , Qiu Jian
Published: February 2014

In this article, poly (dimethyl siloxane) (PDMS) porous beads were prepared by suspension polymerization method using n‐octane and carbon tetrachloride (CCl4) as diluents and pore formation agents. The apparent density, porosity and other characteristics were characterized. The absorption experiments showed that the porous PDMS beads exhibited more absorption capacity and faster absorption rate toward oils than the nonporous or oligoporous PDMS beads did, moreover they are of remarkable stability and recyclability, which could provide a path to absorb the oils floating on water. POLYM. ENG. SCI., 54:2965–2969, 2014. © 2014 Society of Plastics Engineers
Exploring the human tear fluid: Discovery of new biomarkers in multiple sclerosis
Authors: Salvisberg Cindy , Tajouri Nadja , Hainard Alexandre , Burkhard Pierre R. , Lalive Patrice H. , Turck Natacha
Published: February 2014

Purpose

Multiple sclerosis is the first cause of progressive neurological disability among young adults living in Western countries. Its diagnosis is mostly based on clinical evaluation, neuroimaging, and in some cases cerebrospinal fluid (CSF) analysis, but no definitive diagnostic test exists. We proposed here that the exploration of tears from multiple sclerosis patients could lead to the discovery of new biomarkers.

Experimental design

Thirty multiple sclerosis patients (20% men) recruited to the Geneva University Hospitals were included in our study (mean age ± SD [years]: 42.4 ± 15.9). Twenty‐five control patients (32% men) were also enrolled (mean age ± SD [years]: 42.7±15.1). Tears, CSF or blood was collected for each patient. Three independent quantitative (tandem mass tag) experiments were carried out between tears from multiple sclerosis and control patients. Protein verification was performed by Western blot on tears and CSF and by ELISA on serum samples.

Results

Combined proteomics analyses provided 185 identified tear proteins. Among the differential proteins, alpha‐1 antichymotrypsin was the only one to be significantly increased in the three experiments with similar ratios (ratios 1.6 to 2.5, p < 0.05). Its tear, CSF and serum elevation were further confirmed by Western blot and ELISA, respectively.

Conclusions and clinical relevance

This study supports the concept that modifications of the tear proteome can reflect biological abnormalities associated with multiple sclerosis and perhaps other inflammatory conditions affecting the CNS. In addition, alpha‐1 antichymotrypsin elevation in tear fluid emerges as a promising biomarker for the diagnosis of multiple sclerosis.
A decade of crystallization drops: Crystallization of the cbb3 cytochrome c oxidase from Pseudomonas stutzeri
Authors: Buschmann Sabine , Richers Sebastian , Ermler Ulrich , Michel Hartmut
Published: February 2014

The cbb3 cytochrome c oxidases are distant members of the superfamily of heme copper oxidases. These terminal oxidases couple O2 reduction with proton transport across the plasma membrane and, as a part of the respiratory chain, contribute to the generation of an electrochemical proton gradient. Compared with other structurally characterized members of the heme copper oxidases, the recently determined cbb3 oxidase structure at 3.2 Å resolution revealed significant differences in the electron supply system, the proton conducting pathways and the coupling of O2 reduction to proton translocation. In this paper, we present a detailed report on the key steps for structure determination. Improvement of the protein quality was achieved by optimization of the number of lipids attached to the protein as well as the separation of two cbb3 oxidase isoenzymes. The exchange of n‐dodecyl‐β‐d‐maltoside for a precisely defined mixture of two α‐maltosides and decanoylsucrose as well as the choice of the crystallization method had a most profound impact on crystal quality. This report highlights problems frequently encountered in membrane protein crystallization and offers meaningful approaches to improve crystal quality.
Regeneration of reptilian scales after wounding: neogenesis, regional difference, and molecular modules
Authors: Wu Ping , Alibardi Lorenzo , Chuong Cheng‐Ming
Published: February 2014

Lizard skin can produce scales during embryonic development, tail regeneration, and wound healing; however, underlying molecular signaling and extracellular matrix protein expression remains unknown. We mapped cell proliferation, signaling and extracellular matrix proteins in regenerating and developing lizard scales in different body regions with different wound severity. Following lizard tail autotomy (self‐amputation), de novo scales regenerate from regenerating tail blastema. Despite topological differences between embryonic and adult scale formation, asymmetric cell proliferation produces the newly formed outer scale surface. Regionally different responses to wounding were observed; open wounds induced better scale regeneration from tail skin than trunk skin. Molecular studies suggest that neural cell adhesion molecule enriched dermal regions exhibit higher cell proliferation associated with scale growth. β‐catenin may be involved in epidermal scale differentiation. Dynamic tenascin‐C expression suggests its involvement in regeneration. We conclude that different skin regions exhibit different competence for de novo scale formation. While cellular and morphogenetic paths differ during development and regeneration of lizard scale formation, they share general proliferation patterns, epithelial−mesenchymal interactions and similar molecular modules composed of adhesion and extracellular matrix molecules.
Accuracy of radiographs in assessment of displacement in lateral humeral condyle fractures
Authors: Knutsen Ashleen , Avoian Tigran , Borkowski Sean L. , Ebramzadeh Edward , Zionts Lewis E. , Sangiorgio Sophia N.
Published: February 2014

Purpose

Determining the magnitude of displacement in pediatric lateral humeral condyle fractures can be difficult. The purpose of this study was to (1) assess the effect of forearm rotation on true fracture displacement using a cadaver model and to (2) determine the accuracy of radiographic measurements of the fracture gap.

Methods

A non-displaced fracture was created in three human cadaveric arms. The specimens were mounted on a custom apparatus allowing forearm rotation with the humerus fixed. First, the effect of pure rotation on fracture displacement was simulated by rotating the forearm from supination to pronation about the central axis of the forearm, to isolate the effects of muscle pull. Then, the clinical condition of obtaining a lateral oblique radiograph was simulated by rotating the forearm about the medial aspect of the forearm. Fracture displacements were measured using a motion-capture system (true-displacement) and clinical radiographs (apparent-displacement).

Results

During pure rotation of the forearm, there were no significant differences in fracture displacement between supination and pronation, with changes in displacement of <1.0 mm. During rotation about the medial aspect of the forearm, there was a significant difference in true displacements between supination and pronation at the posterior edge ( p < 0.05).

Conclusion

Overall, true fracture displacement measurements were larger than apparent radiographic displacement measurements, with differences from 1.6 to 6.0 mm, suggesting that the current clinical methods may not be sensitive enough to detect a displacement of 2.0 mm, especially when positioning the upper extremity for an internal oblique lateral radiograph.
New layer-by-layer Nb2O5–TiO2 film as an effective underlayer in dye-sensitised solar cells
Authors: Paula L. F. , Amaral R. C. , Murakami Iha N. Y. , Paniago R. M. , Machado A. E. H. , Patrocinio A. O. T.
Published: February 2014

All-inorganic layer-by-layer TiO2–Nb2O5 films were applied as underlayers in DSCs, leading to an expressive improvement on the conversion efficiency.
Operation and development status of the J-PARC ion source
Authors: Yamazaki S. , Ikegami K. , Ohkoshi K. , Ueno A. , Koizumi I. , Takagi A. , Oguri H.
Published: February 2014

A cesium-free H− ion source driven with a LaB6 filament is being operated at the Japan Proton Accelerator Research Complex (J-PARC) without any serious trouble since the restoration from the March 2011 earthquake. The H− ion current from the ion source is routinely restricted approximately 19 mA for the lifetime of the filament. In order to increase the beam power at the linac beam operation (January to February 2013), the beam current from the ion source was increased to 22 mA. At this operation, the lifetime of the filament was estimated by the reduction in the filament current. According to the steep reduction in the filament current, the break of the filament was predicted. Although the filament has broken after approximately 10 h from the steep current reduction, the beam operation was restarted approximately 8 h later by the preparation for the exchange of new filament. At the study time for the 3 GeV rapid cycling synchrotron (April 2013), the ion source was operated at approximately 30 mA for 8 days. As a part of the beam current upgrade plan for the J-PARC, the front end test stand consisting of the ion source and the radio frequency quadrupole is under preparation. The RF-driven H− ion source developed for the J-PARC 2nd stage requirements will be tested at this test stand.
Synthesis and spectroscopy of cyanotriacetylene (HC7N) in solid argon
Authors: Couturier-Tamburelli I. , Piétri N. , Crépin C. , Turowski M. , Guillemin J.-C. , Kołos R.
Published: February 2014

UV laser irradiations of cryogenic solid argon matrices doped with a mixture of acetylene and cyanodiacetylene (HC5N) resulted in the formation of a longer carbon–nitrogen chain, cyanotriacetylene (HC7N). The identification of this species was accomplished based on IR vibrational spectroscopy (including the study of isotopically labeled compounds), on electronic luminescence spectroscopy, and on theoretical predictions. Additionally, IR absorption bands recognized as due to HC7N were detected in photolysed Ar matrices doped with a cyanoacetylene/diacetylene mixture; this assignment was confirmed with the mass spectrometry of gases released upon the warm-up of the sample.
Reduction of the thermal conductivity in free-standing silicon nano-membranes investigated by non-invasive Raman thermometry
Authors: Chávez-Ángel E. , Reparaz J. S. , Gomis-Bresco J. , Wagner M. R. , Cuffe J. , Graczykowski B. , Shchepetov A. , Jiang H. , Prunnila M. , Ahopelto J. , Alzina F. , Sotomayor Torres C. M.
Published: February 2014

We report on the reduction of the thermal conductivity in ultra-thin suspended Si membranes with high crystalline quality. A series of membranes with thicknesses ranging from 9 nm to 1.5 μm was investigated using Raman thermometry, a novel contactless technique for thermal conductivity determination. A systematic decrease in the thermal conductivity was observed as reducing the thickness, which is explained using the Fuchs-Sondheimer model through the influence of phonon boundary scattering at the surfaces. The thermal conductivity of the thinnest membrane with d = 9 nm resulted in (9 ± 2) W/mK, thus approaching the amorphous limit but still maintaining a high crystalline quality.
Research Update: Strategies for efficient photoelectrochemical water splitting using metal oxide photoanodes
Authors: Cho Seungho , Jang Ji-Wook , Lee Kun-Hong , Lee Jae Sung
Published: February 2014

Photoelectrochemical (PEC) water splitting to hydrogen is an attractive method for capturing and storing the solar energy in the form of chemical energy. Metal oxides are promising photoanode materials due to their low-cost synthetic routes and higher stability than other semiconductors. In this paper, we provide an overview of recent efforts to improve PEC efficiencies via applying a variety of fabrication strategies to metal oxide photoanodes including (i) size and morphology-control, (ii) metal oxide heterostructuring, (iii) dopant incorporation, (iv) attachments of quantum dots as sensitizer, (v) attachments of plasmonic metal nanoparticles, and (vi) co-catalyst coupling. Each strategy highlights the underlying principles and mechanisms for the performance enhancements.
Millimeter wave ferromagnetic resonance in gallium-substituted ε-iron oxide
Authors: Chao Liu , Afsar Mohammed N. , Ohkoshi Shin-ichi
Published: February 2014

In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe12O19) and strontium ferrite (SrFe12O19), which have natural ferromagnetic resonant frequency range from 40 GHz to 60 GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A new series of gallium-substituted ε-iron oxides (ε-GaxFe2−xO3) are synthesized which have ferromagnetic resonant frequencies appearing over the frequency range 30 GHz–150 GHz. The ε-GaxFe2−xO3 is synthesized by the combination of reverse micelle and sol-gel techniques or the sol-gel method only. The particle sizes are observed to be smaller than 100 nm. In this paper, the free space magneto-optical approach has been employed to study these newly developed ε-GaxFe2−xO3 particles in millimeter waves. This technique enables to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the millimeter wave frequency range from a single set of direct measurements. The transmittance and absorbance spectra of ε-GaxFe2−xO3 are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.
Monte Carlo simulation of nitrogen dissociation based on state-resolved cross sections
Authors: Kim Jae Gang , Boyd Iain D.
Published: February 2014

State-resolved analyses of N + N2 are performed using the direct simulation Monte Carlo (DSMC) method. In describing the elastic collisions by a state-resolved method, a state-specific total cross section is proposed. The state-resolved method is constructed from the state-specific total cross section and the rovibrational state-to-state transition cross sections for bound-bound and bound-free transitions taken from a NASA database. This approach makes it possible to analyze the rotational-to-translational, vibrational-to-translational, and rotational-to-vibrational energy transfers and the chemical reactions without relying on macroscopic properties and phenomenological models. In nonequilibrium heat bath calculations, the results of present state-resolved DSMC calculations are validated with those of the master equation calculations and the existing shock-tube experimental data for bound-bound and bound-free transitions. In various equilibrium and nonequilibrium heat bath conditions and 2D cylindrical flows, the DSMC calculations by the state-resolved method are compared with those obtained with previous phenomenological DSMC models. In these previous DSMC models, the variable soft sphere, phenomenological Larsen-Borgnakke, quantum kinetic, and total collision energy models are considered. From these studies, it is concluded that the state-resolved method can accurately describe the rotational-to-translational, vibrational-to-translational, and rotational-to-vibrational transfers and quasi-steady state of rotational and vibrational energies in nonequilibrium chemical reactions by state-to-state kinetics.
Effect of internal noise on the oscillation of N2O decomposition over Cu-ZSM-5 zeolites using a stochastic description
Authors: Liu Fuliang , Li Yaping , Sun Xiaoming
Published: February 2014

When considering stochastic oscillations of heterogeneous catalyst systems, most researches have focused on the surface of a metal or its oxide catalysts, but there have been few studies on porous catalysts. In this work, the effects of internal noise on oscillations of N2O decomposition over Cu-ZSM-5 zeolites are investigated, using the chemical Langevin equation and a mesoscopic stochastic model. Considering that Cu-ZSM-5 particles are finely divided particles, the number of Cu ions (Ns) is proportional to the particle size at a certain Cu/Al, and the internal noise is inversely proportional to Ns. Stochastic oscillations can be observed outside the deterministic oscillatory region. Furthermore, the performance of the oscillation characterized by the signal-to-noise ratio has a maximum within the optimal size range of 4–8 nm. This suggests that a nanometer-sized zeolite may be best for oscillations.
Tuning spin transport properties and molecular magnetoresistance through contact geometry
Authors: Ulman Kanchan , Narasimhan Shobhana , Delin Anna
Published: February 2014

Molecular spintronics seeks to unite the advantages of using organic molecules as nanoelectronic components, with the benefits of using spin as an additional degree of freedom. For technological applications, an important quantity is the molecular magnetoresistance. In this work, we show that this parameter is very sensitive to the contact geometry. To demonstrate this, we perform ab initio calculations, combining the non-equilibrium Green's function method with density functional theory, on a dithienylethene molecule placed between spin-polarized nickel leads of varying geometries. We find that, in general, the magnetoresistance is significantly higher when the contact is made to sharp tips than to flat surfaces. Interestingly, this holds true for both resonant and tunneling conduction regimes, i.e., when the molecule is in its “closed” and “open” conformations, respectively. We find that changing the lead geometry can increase the magnetoresistance by up to a factor of ∼5. We also introduce a simple model that, despite requiring minimal computational time, can recapture our ab initio results for the behavior of magnetoresistance as a function of bias voltage. This model requires as its input only the density of states on the anchoring atoms, at zero bias voltage. We also find that the non-resonant conductance in the open conformation of the molecule is significantly impacted by the lead geometry. As a result, the ratio of the current in the closed and open conformations can also be tuned by varying the geometry of the leads, and increased by ∼400%.
Multi-scale simulation of lithium diffusion in the presence of a 30° partial dislocation and stacking fault in Si
Authors: Wang Chao-Ying , Yang Li-Jun , Zhao Wei , Meng Qing-Yuan , Li Chen-liang , Wu Guo-Xun , Wang Bao-Lai
Published: February 2014

The multi-scale simulation method is employed to investigate how defects affect the performances of Li-ion batteries (LIBs). The stable positions, binding energies and dynamics properties of Li impurity in Si with a 30° partial dislocation and stacking fault (SF) have been studied in comparison with the ideal crystal. It is found that the most table position is the tetrahedral (Td) site and the diffusion barrier is 0.63 eV in bulk Si. In the 30° partial dislocation core and SF region, the most stable positions are at the centers of the octagons (Oct-A and Oct-B) and pentahedron (site S), respectively. In addition, Li dopant may tend to congregate in these defects. The motion of Li along the dislocation core are carried out by the transport among the Oct-A (Oct-B) sites with the barrier of 1.93 eV (1.12 eV). In the SF region, the diffusion barrier of Li is 0.91 eV. These two types of defects may retard the fast migration of Li dopant that is finally trapped by them. Thus, the presence of the 30° partial dislocation and SF may deactivate the Li impurity and lead to low rate capability of LIB.
Vacuum ultraviolet photoionization of carbohydrates and nucleotides
Authors: Shin Joong-Won , Bernstein Elliot R.
Published: February 2014

Carbohydrates (2-deoxyribose, ribose, and xylose) and nucleotides (adenosine-, cytidine-, guanosine-, and uridine-5′-monophosphate) are generated in the gas phase, and ionized with vacuum ultraviolet photons (VUV, 118.2 nm). The observed time of flight mass spectra of the carbohydrate fragmentation are similar to those observed [J.-W. Shin, F. Dong, M. Grisham, J. J. Rocca, and E. R. Bernstein, Chem. Phys. Lett. 506, 161 (2011)] for 46.9 nm photon ionization, but with more intensity in higher mass fragment ions. The tendency of carbohydrate ions to fragment extensively following ionization seemingly suggests that nucleic acids might undergo radiation damage as a result of carbohydrate, rather than nucleobase fragmentation. VUV photoionization of nucleotides (monophosphate-carbohydrate-nucleobase), however, shows that the carbohydrate-nucleobase bond is the primary fragmentation site for these species. Density functional theory (DFT) calculations indicate that the removed carbohydrate electrons by the 118.2 nm photons are associated with endocyclic C–C and C–O ring centered orbitals: loss of electron density in the ring bonds of the nascent ion can thus account for the observed fragmentation patterns following carbohydrate ionization. DFT calculations also indicate that electrons removed from nucleotides under these same conditions are associated with orbitals involved with the nucleobase-saccharide linkage electron density. The calculations give a general mechanism and explanation of the experimental results.
Low-lying excited states and nonradiative processes of 9-methyl-2-aminopurine
Authors: Trachsel Maria A. , Lobsiger Simon , Schär Tobias , Leutwyler Samuel
Published: February 2014

The UV spectrum of the adenine analogue 9-methyl-2-aminopurine (9M-2AP) is investigated with one- and two-color resonant two-photon ionization spectroscopy at 0.3 and 0.05 cm−1 resolution in a supersonic jet. The electronic origin at 32 252 cm−1 exhibits methyl torsional subbands that originate from the $0A_{1}^{{\prime \prime }}$0A1′′ (l = 0) and 1E″ (l = ±1) torsional levels. These and further torsional bands that appear up to $0_0^0+230$000+230 cm−1 allow to fit the threefold (V3) barriers of the torsional potentials as $|V^{\prime \prime }_3|\break = 50$|V3′′|=50 cm−1 in the S0 and $|V^{\prime }_3 |=126$|V3′|=126 cm−1 in the S1 state. Using the B3LYP density functional and correlated approximate second-order coupled cluster CC2 methods, the methyl orientation is calculated to be symmetric relative to the 2AP plane in both states, with barriers of $V^{\prime \prime }_3=20$V3′′=20 cm−1 and $V^{\prime }_3\break =115$V3′=115 cm−1. The $0_0^0$000 rotational band contour is 75% in-plane (a/b) polarized, characteristic for a dominantly long-axis 1ππ* excitation. The residual 25% c-axis polarization may indicate coupling of the 1ππ* to the close-lying 1nπ* state, calculated at 4.00 and 4.01 eV with the CC2 method. However, the CC2 calculated 1nπ oscillator strength is only 6% of that of the 1ππ* transition. The 1ππ* vibronic spectrum is very complex, showing about 40 bands within the lowest 500 cm−1. The methyl torsion and the low-frequency out-of-plane $\nu ^{\prime }_1$ν1′ and $\nu ^{\prime }_2$ν2′ vibrations are strongly coupled in the 1ππ* state. This gives rise to many torsion-vibration combination bands built on out-of-plane fundamentals, which are without precedence in the 1ππ* spectrum of 9H-2-aminopurine [S. Lobsiger, R. K. Sinha, M. Trachsel, and S. Leutwyler, J. Chem. Phys. 134, 114307 (2011)]. From the Lorentzian broadening needed to fit the $0_0^0$000 contour of 9M-2AP, the 1ππ* lifetime is τ ⩾ 120 ps, reflecting a rapid nonradiative transition.
Morphology and magnetic properties of SmCo3/α-Fe nanocomposite magnets prepared via severe plastic deformation
Authors: Poudyal Narayan , Xia Weixing , Yue Ming , Ping Liu J.
Published: February 2014

We report bulk SmCo3/α-Fe nanocomposite magnets prepared via high energy ball milling and warm compaction. The evolution of structure and magnetic properties with soft phase fraction have been systematically studied. Microstructural studies revealed that grain size of the nanocomposite magnets can be controlled below 20 nm with a homogeneous distribution of α-Fe phase in the matrix of hard magnetic SmCo3 phase after severe plastic deformation. The refinement of the hard and soft phases morphology in nanoscale leads to effective inter-phase exchange coupling that gives rise to single-phase-like demagnetization behavior with enhanced remanence and maximum energy product (BH)max. The (BH)max up to 13.5 MGOe in the isotropic SmCo3/α-Fe nanocomposites with 25 wt. % of the soft phase has been obtained. Magnetic characterization at elevated temperatures shows that the nanocomposite SmCo3/α-Fe magnets have improved energy product compared to the single-phase SmCo3 magnets.
Effect of capping material on interfacial ferromagnetism in FeRh thin films
Authors: Baldasseroni C. , Pálsson G. K. , Bordel C. , Valencia S. , Unal A. A. , Kronast F. , Nemsak S. , Fadley C. S. , Borchers J. A. , Maranville B. B. , Hellman F.
Published: February 2014

The role of the capping material in stabilizing a thin ferromagnetic layer at the interface between a FeRh film and cap in the nominally antiferromagnetic phase at room temperature was studied by x-ray magnetic circular dichroism in photoemission electron microscopy and polarized neutron reflectivity. These techniques were used to determine the presence or absence of interfacial ferromagnetism (FM) in films capped with different oxides and metals. Chemically stable oxide caps do not generate any interfacial FM while the effect of metallic caps depends on the element, showing that interfacial FM is due to metallic interdiffusion and the formation of a ternary alloy with a modified antiferromagnetic to ferromagnetic transition temperature.
Structural changes of water in poly(vinyl alcohol) hydrogel during dehydration
Authors: Kudo Kushi , Ishida Junichi , Syuu Gika , Sekine Yurina , Ikeda-Fukazawa Tomoko
Published: February 2014

To investigate the mechanism of structural changes of water and polymer networks with drying and swelling, we measured the Raman spectra of a physically cross-linked poly(vinyl alcohol) (PVA) hydrogel synthesized using the freezing–thawing method. The results show that the vibrational frequencies of the O–H and C–H stretching modes decrease with dehydration. The frequency shifts observed are attributed to reduction of free water inside the polymer network. The C–H bonds elongate as the water density decreases, and the average length of the O–H bonds increases with increasing proportion of bound water to the total amount of water. On the basis of the dependence of the frequency shifts on the PVA concentration of the original solution, it was found that the structure of the polymer network in the reswollen hydrogel becomes inhomogeneous due to shrinkage of the polymer network with drying. Furthermore, to investigate the effects of the cross-linking structure on the drying process, these results were compared with those of a chemically cross-linked PVA hydrogel synthesized using glutaraldehyde as a cross-linker. The result shows that the vibrational frequency of the O–H stretching mode for the chemically cross-linked hydrogel increases with dehydration, whereas that of the C–H stretching mode decreases. The opposite trend observed in the O–H stretching mode between the physically and chemically cross-linked hydrogels is due to the difference in the shrinkage rate of the polymer network. Because the rate of shrinking is slow compared with that of dehydration in the chemically cross-linked hydrogel, water density in the polymer network decreases. For the physically cross-linked hydrogel, the polymer network structure can be easily shrunken, and the average strength of hydrogen bonds increases with dehydration. The results show that the structures of the polymer network and water change with the gel preparation process, cross-linking method, and drying and reswelling processes. The structure of the polymer network and the behavior of water accommodated in the network are important factors governing the chemical and physical properties of gel materials.
Rotational defects in cyclotrimethylene trinitramine (RDX) crystals
Authors: Pal A. , Picu R. C.
Published: February 2014

Cyclotrimethylene trinitramine (RDX) crystalizes in the orthorhombic α-phase at the ambient pressure and temperature. In principle, the point defects commonly found in monatomic crystals, such as vacancies and interstitials, may exist in RDX as well. However, in molecular crystals one encounters additional point defects associated with the distortion of the molecules. A set of rotational defects are described in this article. These are molecules which are located in the proper positions in the crystal but are rotated relative to the molecules in the perfect crystal, and their ring is slightly puckered. The energetic barriers for defect formation and for their annealing back to the perfect crystal configuration are computed using an atomistic model. It is shown that the formation energy of rotational defects is smaller than the vacancy formation energy. Such defects are identified in the cores of dislocations in RDX and hence their concentration in the crystal is expected to increase during plastic deformation. The importance of such point defects is related to their role in phonon scattering and in dislocation-mediated plastic deformation.
Online tuning of impedance matching circuit for long pulse inductively coupled plasma source operation—An alternate approach
Authors: Sudhir Dass , Bandyopadhyay M. , Kraus W. , Gahlaut A. , Bansal G. , Chakraborty A.
Published: February 2014

Impedance matching circuit between radio frequency (RF) generator and the plasma load, placed between them, determines the RF power transfer from RF generator to the plasma load. The impedance of plasma load depends on the plasma parameters through skin depth and plasma conductivity or resistivity. Therefore, for long pulse operation of inductively coupled plasmas, particularly for high power (∼100 kW or more) where plasma load condition may vary due to different reasons (e.g., pressure, power, and thermal), online tuning of impedance matching circuit is necessary through feedback. In fusion grade ion source operation, such online methodology through feedback is not present but offline remote tuning by adjusting the matching circuit capacitors and tuning the driving frequency of the RF generator between the ion source operation pulses is envisaged. The present model is an approach for remote impedance tuning methodology for long pulse operation and corresponding online impedance matching algorithm based on RF coil antenna current measurement or coil antenna calorimetric measurement may be useful in this regard.
Density fitting for three-electron integrals in explicitly correlated electronic structure theory
Authors: Womack James C. , Manby Frederick R.
Published: February 2014

The principal challenge in using explicitly correlated wavefunctions for molecules is the evaluation of nonfactorizable integrals over the coordinates of three or more electrons. Immense progress was made in tackling this problem through the introduction of a single-particle resolution of the identity. Decompositions of sufficient accuracy can be achieved, but only with large auxiliary basis sets. Density fitting is an alternative integral approximation scheme, which has proven to be very reliable for two-electron integrals. Here, we extend density fitting to the treatment of all three-electron integrals that appear at the MP2-F12/3*A level of theory. We demonstrate that the convergence of energies with respect to auxiliary basis size is much more rapid with density fitting than with the traditional resolution-of-the-identity approach.
Quantum and quasi-classical dynamics of the OH + CO → H + CO2 reaction on a new permutationally invariant neural network potential energy surface
Authors: Li Jun , Chen Jun , Zhang Dong H. , Guo Hua
Published: February 2014

A permutationally invariant global potential energy surface for the HOCO system is reported by fitting a larger number of high-level ab initio points using the newly proposed permutation invariant polynomial-neural network method. The small fitting error (∼5 meV) indicates a faithful representation of the potential energy surface over a large configuration space. Full-dimensional quantum and quasi-classical trajectory studies of the title reaction were performed on this potential energy surface. While the results suggest that the differences between this and an earlier neural network fits are small, discrepancies with state-to-state experimental data remain significant.
Flows and torques in Brownian ferrofluids subjected to rotating uniform magnetic fields in a cylindrical and annular geometry
Authors: Torres-Diaz I. , Cortes A. , Cedeño-Mattei Y. , Perales-Perez O. , Rinaldi C.
Published: February 2014

Ferrofluid flow in cylindrical and annular geometries under the influence of a uniform rotating magnetic field was studied experimentally using aqueous ferrofluids consisting of low concentrations (<0.01 v/v) of cobalt ferrite nanoparticles with Brownian relaxation to test the ferrohydrodynamic equations, elucidate the existence of couple stresses, and determine the value of the spin viscosity in these fluids. An ultrasound technique was used to measure bulk velocity profiles in the spin-up (cylindrical) and annular geometries, varying the intensity and frequency of the rotating magnetic field generated by a two pole stator winding. Additionally, torque measurements in the cylindrical geometry were made. Results show rigid-body like velocity profiles in the bulk, and no dependence on the axial direction. Experimental velocity profiles were in quantitative agreement with the predictions of the spin diffusion theory, with a value of the spin viscosity of ∼10−8 kg m/s, two orders of magnitude larger than the value estimated earlier for iron oxide based ferrofluids, and 12 orders of magnitude larger than estimated using dimensional arguments valid in the infinite dilution limit. These results provide further evidence of the existence of couple stresses in ferrofluids and their role in driving the spin-up flow phenomenon.
Sub-additive ionic transport across arrays of solid-state nanopores
Authors: Gadaleta A. , Sempere C. , Gravelle S. , Siria A. , Fulcrand R. , Ybert C. , Bocquet L.
Published: February 2014

Nanopores, either biological, solid-state, or ultrathin pierced graphene, are powerful tools which are central to many applications, from sensing of biological molecules to desalination and fabrication of ion selective membranes. However, the interpretation of transport through low aspect-ratio nanopores becomes particularly complex as 3D access effects outside the pores are expected to play a dominant role. Here, we report both experiments and theory showing that, in contrast to naïve expectations, long-range mutual interaction across an array of nanopores leads to a non-extensive, sub-linear scaling of the global conductance on the number of pores N. A scaling analysis demonstrates that the N-dependence of the conductance depends on the topology of the network. It scales like G ∼ N/log N for a 1D line of pores, and like $G\sim \sqrt{N}$G∼N for a 2D array, in agreement with experimental measurements. Our results can be extended to alternative transport phenomena obeying Laplace equations, such as diffusive, thermal, or hydrodynamic transport. Consequences of this counter-intuitive behavior are discussed in the context of transport across thin membranes, with applications in energy harvesting.
Exact exchange plane-wave-pseudopotential calculations for slabs
Authors: Engel Eberhard
Published: February 2014

The exact exchange of density functional theory is applied to both free-standing graphene and a Si(111) slab, using the plane-wave pseudopotential (PWPP) approach and a periodic repetition of the supercell containing the slab. It is shown that (i) PWPP calculations with exact exchange for slabs in supercell geometry are basically feasible, (ii) the width of the vacuum required for a decoupling of the slabs is only moderately larger than in the case of the local-density approximation, and (iii) the resulting exchange potential vx shows an extended region, both far outside the surface of the slab and far from the middle of the vacuum region between the slabs, in which vx behaves as −e2/z, provided the width of the vacuum is chosen sufficiently large. This last result is corroborated by an analytical analysis of periodically repeated jellium slabs. The intermediate −e2/z behavior of vx can be used for an absolute normalization of vx and the total Kohn-Sham potential, which, in turn, allows the determination of the work function.
Compact portable biosensor for arsenic detection in aqueous samples with Escherichia coli bioreporter cells
Authors: Truffer Frederic , Buffi Nina , Merulla Davide , Beggah Siham , van Lintel Harald , Renaud Philippe , van der Meer Jan Roelof , Geiser Martial
Published: February 2014

We present a compact portable biosensor to measure arsenic As(III) concentrations in water using Escherichia coli bioreporter cells. Escherichia coli expresses green fluorescent protein in a linearly dependent manner as a function of the arsenic concentration (between 0 and 100 μg/L). The device accommodates a small polydimethylsiloxane microfluidic chip that holds the agarose-encapsulated bacteria, and a complete optical illumination/collection/detection system for automated quantitative fluorescence measurements. The device is capable of sampling water autonomously, controlling the whole measurement, storing and transmitting data over GSM networks. We demonstrate highly reproducible measurements of arsenic in drinking water at 10 and 50 μg/L within 100 and 80 min, respectively.
Fermi level pinning and the charge transfer contribution to the energy of adsorption at semiconducting surfaces
Authors: Krukowski Stanisław , Kempisty Paweł , Strak Paweł , Sakowski Konrad
Published: February 2014

It is shown that charge transfer, the process analogous to formation of semiconductor p-n junction, contributes significantly to adsorption energy at semiconductor surfaces. For the processes without the charge transfer, such as molecular adsorption of closed shell systems, the adsorption energy is determined by the bonding only. In the case involving charge transfer, such as open shell systems like metal atoms or the dissociating molecules, the energy attains different value for the Fermi level differently pinned. The Density Functional Theory (DFT) simulation of species adsorption at different surfaces, such as SiC(0001) or GaN(0001) confirms these predictions: the molecular adsorption is independent on the coverage, while the dissociative process adsorption energy varies by several electronvolts.