bluuebunny/crossref_metadata_2025 huggingface dataset:
Water oxidation catalysed by iron complex of N,N′-dimethyl-2,11-diaza[3,3](2,6)pyridinophane. Spectroscopy of iron–oxo intermediates and density functional theory calculations
Authors: To Wai-Pong , Wai-Shan Chow Toby , Tse Chun-Wai , Guan Xiangguo , Huang Jie-Sheng , Che Chi-Ming
Published: July 2015

FeIV=O and/or FeV=O intermediates are suggested to be involved in water oxidation with [NH4]2[CeIV(NO3)6], NaIO4, or Oxone catalyzed by [FeIII(L1)Cl2]+ (1) on the basis of spectroscopic measurements and DFT calculations.
One-pot synthesis of MWW zeolite nanosheets using a rationally designed organic structure-directing agent
Authors: Luo Helen Y. , Michaelis Vladimir K. , Hodges Sydney , Griffin Robert G. , Román-Leshkov Yuriy
Published: July 2015

A new material MIT-1 comprised of delaminated MWW zeolite nanosheets is synthesized in one-pot using a rationally designed organic structure-directing agent.
Cooperative benzylic–oxyallylic stabilized cations: regioselective construction of α-quaternary centers in ketone-derived compounds
Authors: Dange Nitin S. , Stepherson Jacob R. , Ayala Caitlan E. , Fronczek Frank R. , Kartika Rendy
Published: July 2015

Herein we describe a direct capture of benzylic–oxyallylic stabilized carbocations with high value nucleophiles towards regioselective construction of α-quaternary centers.
MOF derived Co3O4nanoparticles embedded in N-doped mesoporous carbon layer/MWCNT hybrids: extraordinary bi-functional electrocatalysts for OER and ORR
Authors: Li Xinzhe , Fang Yiyun , Lin Xiaoqing , Tian Min , An Xingcai , Fu Yan , Li Rong , Jin Jun , Ma Jiantai
Published: July 2015

Highly efficient and non-precious metal electrocatalysts for oxygen evolution reactions (OERs) and oxygen reduction reactions (ORRs) are at the heart of key renewable-energy technologies.
Hybrids of Mo2C nanoparticles anchored on graphene sheets as anode materials for high performance lithium-ion batteries
Authors: Wang Beibei , Wang Gang , Wang Hui
Published: July 2015

We propose a novel strategy to fabricate Mo2C/GR hybrids through a simple and environmentally friendly carburization process. The as-prepared Mo2C/GR hybrids display significantly improved electrochemical performance compared to bulk Mo2C and pure GR.
A triple-layered, hierarchical 1D core–shell nanostructure with a plasmonic Ag octahedral core for use in solid-state dye-sensitized solar cells
Authors: Kim Dong Jun , Ahn Sung Hoon , Lee Chang Soo , Kim Jong Hak
Published: July 2015

A triple-layered, core–shell hetero-nanostructure was prepared with Ag octahedra, a SnO2nanotube (SNT), and a TiO2nanosheet (TNS)viaa combined process of electrospinning and solvothermal reaction.
Modular composite hydrogels from cholesterol-functionalized polycarbonates for antimicrobial applications
Authors: Lee Ashlynn L. Z. , Venkataraman Shrinivas , Fox Courtney H. , Coady Daniel J. , Frank Curtis W. , Hedrick James L. , Yang Yi Yan
Published: July 2015

A modular and versatile approach of mixing pre-optimized functional components with ABA-triblock gelators to access drug-loaded or antimicrobial gel is presented.
In vitro and in vivo drug release behavior and osteogenic potential of a composite scaffold based on poly(ε-caprolactone)-block-poly(lactic-co-glycolic acid) and β-tricalcium phosphate
Authors: Zhao Pei , Li Dawei , Yang Fei , Ma Yuanzheng , Wang Tiantian , Duan Shun , Shen Hong , Cai Qing , Wu Decheng , Yang Xiaoping , Wang Shenguo
Published: July 2015

To cure serious bone tuberculosis, a novel long-term drug delivery system was designed and prepared to satisfy the needs of both bone regeneration and antituberculous drug therapy.
Silica-coated Gd(DOTA)-loaded protein nanoparticles enable magnetic resonance imaging of macrophages
Authors: Bruckman Michael A. , Randolph Lauren N. , Gulati Neetu M. , Stewart Phoebe L. , Steinmetz Nicole F.
Published: July 2015

Shaping contrast agents for macrophage imaging.
Facile preparation of porous magnetic polydopamine microspheres through an inverse replication strategy for efficient enzyme immobilization
Authors: Han Pingping , Jiang Zhongyi , Wang Xiaoli , Wang Xueyan , Zhang Shaohua , Shi Jiafu , Wu Hong
Published: July 2015

Porous microspheres composed of biocompatible dopamine and magnetic Fe3O4 nanoparticles were fabricated by inverse replication of CaCO3 templates.
The synthesis of CdTe/ZnS core/shell quantum dots using molecular single-source precursors
Authors: Taniguchi Shohei , Green Mark
Published: July 2015

In this paper, we report the synthesis of CdTe/ZnS quantum dots using molecular single source precursors, and we explore the tuning of the optical properties.
Photochromic sensors: a versatile approach for recognition and discrimination
Authors: Qin Meng , Huang Yu , Li Fengyu , Song Yanlin
Published: July 2015

This review summarizes the applications of photochromic sensors in the areas of specific recognition and multi-analyte discrimination.
A unique serpin P1′ glutamate and a conserved β-sheet C arginine are key residues for activity, protease recognition and stability of serpinA12 (vaspin)
Authors: Ulbricht David , Pippel Jan , Schultz Stephan , Meier René , Sträter Norbert , Heiker John T.
Published: July 2015

SerpinA12 (vaspin) is thought to be mainly expressed in adipose tissue and has multiple beneficial effects on metabolic, inflammatory and atherogenic processes related to obesity. KLK7 (kallikrein 7) is the only known protease target of vaspin to date and is inhibited with a moderate inhibition rate. In the crystal structure, the cleavage site (P1-P1′) of the vaspin reactive centre loop is fairly rigid compared with the flexible residues before P2, possibly supported by an ionic interaction of P1′ glutamate (Glu379) with an arginine residue (Arg302) of the β-sheet C. A P1′ glutamate seems highly unusual and unfavourable for the protease KLK7. We characterized vaspin mutants to investigate the roles of these two residues in protease inhibition and recognition by vaspin. Reactive centre loop mutations changing the P1′ residue or altering the reactive centre loop conformation significantly increased inhibition parameters, whereas removal of the positive charge within β-sheet C impeded the serpin–protease interaction. Arg302 is a crucial contact to enable vaspin recognition by KLK7 and it supports moderate inhibition of the serpin despite the presence of the detrimental P1′ Glu379, which clearly represents a major limiting factor for vaspin-inhibitory activity. We also show that the vaspin-inhibition rate for KLK7 can be modestly increased by heparin and demonstrate that vaspin is a heparin-binding serpin. Noteworthily, we observed vaspin as a remarkably thermostable serpin and found that Glu379 and Arg302 influence heat-induced polymerization. These structural and functional results reveal the mechanistic basis of how reactive centre loop sequence and exosite interaction in vaspin enable KLK7 recognition and regulate protease inhibition as well as stability of this adipose tissue-derived serpin.
An E-Platform for Rehabilitation of Persons With Hearing Problems
Authors: Vlaescu George , Carlbring Per , Lunner Thomas , Andersson Gerhard
Published: July 2015

Purpose

The aim of this research forum article was to describe a feasible web-based solution for improving the quality of life of persons with hearing problems, such as hearing loss or tinnitus. The online platform was developed at the Department of Behavioural Sciences and Learning at Linköping University, Sweden, and has been running for a number of years and used in numerous studies and treatments.

Method

The security aspects of the platform as well as the process flow for running a study or treatment are described, focusing primarily on the technical and practical considerations. Also presented are the design characteristics and the main features and functions available in the platform.

Results

We point out the many advantages of running Internet-assisted intervention treatments, the challenges that we have faced, and some intended developments. Many of our research colleagues, both from Sweden and other countries, have already implemented or intend to implement their own studies on this platform.

Conclusions

Audiological rehabilitation can be delivered via the Internet using a stable online platform. Security and usability are important factors to have in mind for the design as well as adaptability to the patients. A next development step is to implement and test blended treatments using video conferencing inside the platform.
Readability of Internet Information on Hearing: Systematic Literature Review
Authors: Laplante-Lévesque Ariane , Thorén Elisabet Sundewall
Published: July 2015

Purpose

This systematic literature review asks the following question: “What is the readability of Internet information on hearing that people with hearing impairment and their significant others can access in the context of their hearing care?”

Method

Searches were completed in three databases: CINAHL, PubMed, and Scopus. Seventy-eight records were identified and systematically screened for eligibility: 8 records were included that contained data on the readability of Internet information on hearing that people with hearing impairment and their significant others can access in the context of their hearing care.

Results

Records reported mean readability levels from 9 to over 14. In other words, people with hearing impairment and their significant others need 9 to 14 years of education to read and understand Internet information on hearing that they access in the context of their hearing care.

Conclusion

The poor readability of Internet information on hearing has been well documented; it is time to focus on valid and sustainable initiatives that address this problem.
Apps for Hearing Science and Care
Authors: Paglialonga Alessia , Tognola Gabriella , Pinciroli Francesco
Published: July 2015

Purpose

Our research aims at the identification and assessment of applications (referred to as
apps
) in the hearing health care domain. This research forum article presents an overview of the current availability, affordability, and variety of hearing-related apps.

Method

The available apps were reviewed by searching on the leading platforms (iOS, Android, Windows Phone stores) using the keywords
hearing, audiology, audio, auditory, speech, language, tinnitus, hearing loss, hearing aid, hearing system, cochlear implant, implantable device, auditory training, hearing rehabilitation,
and
assistive technology/tool/device.
On the basis of the offered services, apps were classified into 4 application domains: (a) screening and assessment, (b) intervention and rehabilitation, (c) education and information, and (d) assistive tools.

Conclusions

A large variety of apps are available in the hearing health care domain. These cover a wide range of services for people with hearing or communication problems as well as for hearing professionals, families, or informal caregivers. This evolution can potentially bring along considerable advantages and improved outcomes in the field of hearing health care. Nevertheless, potential risks and threats (e.g., safety, quality, effectiveness, privacy, and regulation) should not be overlooked. Significant research—particularly in terms of assessment and guidance—is still needed for the informed, aware, and safe adoption of hearing-related apps by patients and professionals.
Internet Interventions for Hearing Loss
Authors: Thorén Elisabet Sundewall , Öberg Marie , Andersson Gerhard , Lunner Thomas
Published: July 2015

Purpose

The purpose of the two studies presented in this research forum article was to develop audiological rehabilitation programs for experienced hearing aid users and evaluate them in online versions. In this research forum article, the differences between the two studies are discussed.

Method

Two randomized controlled trials (RCTs) were performed evaluating the efficacy of online rehabilitation, including professional guidance by an audiologist. In each RCT, the effects of the online programs were compared with the effects measured in a control group.

Results

The results from the first RCT showed a significant increase in activity and participation for both groups with participants in the intervention group improving more than those in the control group. At the 6-month follow-up, after the study, the significant increase was maintained; however, amounts of increase in the two groups were no longer significantly different. The results from the second RCT showed significant increase in activity and participation for the intervention group, although the control group did not improve.

Conclusions

The results from the RCTs provide evidence that the Internet can be used to deliver rehabilitation to hearing-aid users and that their problems are reduced by the intervention; however, the content of the online rehabilitation program requires further investigation.
Language Ability Groups in Bilingual Children: A Latent Profile Analysis
Authors: Kapantzoglou Maria , Restrepo M. Adelaida , Gray Shelley , Thompson Marilyn S.
Published: July 2015

Purpose

Classifying children into two language ability groups, with and without language impairment, may underestimate the number of groups with distinct language ability patterns, or, alternatively, there may be only a single group characterized by a continuum of language performance. The purpose of the current study was to identify the number and characteristics of latent (unobservable) language ability groups in an unclassified sample of predominantly Spanish-speaking children.

Method

An unclassified sample of 431 predominantly Spanish-speaking 5- to 7-year-olds learning English participated in the study. The groups were identified on the basis of (a) language sample analyses (semantic, grammatical, and sentence-length measures); (b) language processing tasks (phonological working memory and processing speed measures); and (c) nonverbal cognitive abilities assessed using a standardized measure. All tasks were administered in Spanish. Latent profile analysis was used to examine the number and nature of distinct language ability groups in the unclassified sample.

Results

Results indicated that a three-group model best represented the data, characterized by low grammaticality in one group, low phonological working memory in another group, and average skills in a third group.

Conclusion

Classifying children into two groups, those with and without language impairment, may lead to misidentification of language impairment.
Look to LSHSS for Cutting-Edge Research
Authors: Nippold Marilyn A.
Published: July 2015

Purpose

In this article, the Editor of
Language, Speech, and Hearing Services in Schools
emphasizes that cutting-edge research should be a major force guiding daily clinical decisions regarding children with known or suspected communication disorders. She affirms that this issue contains such cutting-edge research. The latest research reported in this issue can serve to inform school-based SLPs in their decision-making regarding assessment and intervention for children with communication disorders, in their role as consultants to other professionals and to parents who ask critical questions, and in their capacity as leaders who seek to make positive changes that move the profession forward.
Maximising energy efficiency in antenna selection MIMO wireless systems subject to QoS constraints
Authors: Le N.P. , Safaei F. , Tran L.C.
Published: July 2015

Energy‐efficiency (EE) in antenna selection multi‐input–multi‐output (MIMO) systems over Nakagami‐m fading channels is investigated. An EE metric is defined as the number of successfully received bits per unit of energy consumption, which takes into account several important system parameters such as channel coding and modulation. An optimisation problem that maximises the EE metric subject to an error‐performance constraint is formulated. On the basis of an analysis of this problem, the optimal value of the average energy per transmitted data symbol is obtained, such that the EE in the system is maximised. Simulation results are provided to validate the analysis.
Adaptive on‐time control with adjustable virtual ripple and offset cancellation for buck converter
Authors: Li Chia‐Hsing , Chiu Huang‐Jen , Lo Yu‐Kang , Wang Chao‐Chun
Published: July 2015

Ripple‐based adaptive on‐time (RBAOT) control with virtual ripple is a conceptually simple, fast dynamic transient response at lower duty cycle application and lower component count. This control scheme solves the instability issue of subharmonic oscillation when ceramic capacitors are used. These characteristics make the regulators particularly well‐suited for power management applications in portable electronic devices and computers. However, this control scheme has some drawbacks of poor dynamic transient response at a specified duty cycle range and inherent output voltage offset problem. This study discussed the aforementioned shortcomings. A new method called RBAOT control with adjustable virtual ripple was proposed to improve dynamic transient response. A new output voltage offset cancellation was also proposed in this study. Simulation and experimental results show that the proposed concept achieved fast dynamic transient response without output voltage offset.
Design, implementation issues and performance of an inductive power transfer system for electric vehicle chargers with series–series compensation
Authors: García Xavier del Toro , Vázquez Javier , Roncero‐Sánchez Pedro
Published: July 2015

The design, construction and evaluation of a contactless battery charger for electric vehicles (EVs) based on inductive power transfer (IPT) is presented in this study. The design of such systems entails a high degree of complexity because of the large number of design parameters involved and, consequently, trade‐offs in selecting the key design parameters have to be established. The design process and selection of the IPT system parameters is detailed in this study, considering the most common specifications of EV chargers and the practical issues of the implementation. Regarding the compensation scheme, which is one of the main issues in the design, series compensation in both the primary and secondary has been adopted because of the advantages identified after a comprehensive analysis. A laboratory prototype has been built and tested, providing extensive results of the system performance in terms of efficiency and power transfer capability, considering load power variations, as well as changes in the air gap between coils. A detailed analysis of the efficiency of each stage in the IPT system and their contribution to the overall efficiency is also provided.
Inter‐module state‐of‐charge balancing and fault‐tolerant operation of cascaded H‐bridge converter using multi‐dimensional modulation for electric vehicle application
Authors: Kandasamy Karthik , Vilathgamuwa Mahinda , Tseng King Jet
Published: July 2015

This study presents a method for module‐level state‐of‐charge (SOC) balancing and fault‐tolerant operation of the cascaded H‐bridge (CHB) converter‐based battery energy storage system for electric vehicle (EV) application. The proposed methods are based on the multi‐dimensional pulse‐width modulation (MD‐PWM) strategy. It is shown that the proposed methods are conveniently integrated with the PWM generation algorithm. A conceptual design of modular battery pack (or micro‐pack) system using lithium‐ion cells for the CHB converter is described to show its feasibility for EV application. A brief review on the MD‐PWM strategy and a detailed explanation on the method to integrate the inter‐module SOC balancing and fault‐tolerant control with the PWM generation are presented. Experimental results from the laboratory setup of a five‐level CHB converter driving an induction motor with a battery system consisting of six 52.8 V 60 Ah (16 lithium‐ion cells in series) modules are presented to verify the system operation for fault‐tolerant control and the proposed SOC balancing method. The results demonstrate the need of SOC balancing, and efficacy of the proposed methods in achieving fault‐tolerant as well as SOC‐balanced operation to prolong the system operation.
Häufigkeit und psychiatrische Komorbiditäten von selbstberichtetem diagnostiziertem Burnout-Syndrom
Authors: Maske Ulrike , Riedel-Heller Steffi , Seiffert Ingeburg , Jacobi Frank , Hapke Ulfert
Published: July 2015

Korrigierte Zusammenfassung

Ziel: Darstellung der Häufigkeit von selbstberichtetem diagnostiziertem Burnout-Syndrom und psychiatrische Komorbiditäten.

Methode: Bundesweite Studie, n = 7987. Burnout-Syndrom: selbstberichtete ärztl./psychother. Diagnose. Psychische Störungen: diagnostisches Interview, n = 4483.

Ergebnisse: Prävalenz: Lebenszeit 4,2 %, 12 Monate 1,5 %. Irgendeine psychische Störung: 70,9 % derer mit Burnout-Diagnose. Assoziierte Störungen: somatoforme, affektive, Angststörungen.

Schlussfolgerung: Burnout-Diagnosen werden seltener berichtet als erwartet. Betroffene haben häufig eine manifeste psychische Störung.
Outcome Prediction of Treatment of Graves’ Hyperthyroidism with Antithyroid Drugs
Authors: Piantanida E. , Lai A. , Sassi L. , Gallo D. , Spreafico E. , Tanda M. L. , Bartalena L.
Published: July 2015

Graves’ disease is the most common cause of hyperthyroidism in iodine-replete areas and is ultimately due to antibodies interacting with the TSH receptor on thyroid follicular cells [TSH-receptor antibody (TRAb)]. Antithyroid drugs (ATDs) belonging to the family of thionamides are the first-line treatment in Europe. ATD treatment is commonly continued for 18–24 months. Its major limitation is the high rate of relapses after drug withdrawal. Factors particularly bound to subsequent relapses are the large thyroid volume, smoking habit, persistence of TRAb in the circulation at the end of treatment, and the post-partum period. Under these conditions, consideration should be given to a definitive therapy for hyperthyroidism (radioiodine treatment, thyroidectomy), particularly if the patient is at risk of cardiovascular complications that might be exacerbated by persistence or recurrence of hyperthyroidism.
High order numerical simulations of the Richtmyer– Meshkov instability in a relativistic fluid
Authors: Zanotti O. , Dumbser M.
Published: July 2015

We study the Richtmyer–Meshkov (RM) instability of a relativistic perfect fluid by means of high order numerical simulations with adaptive mesh refinement (AMR). The numerical scheme combines a finite volume reconstruction in space, a local space-time discontinuous Galerkin predictor method, a high order one-step time update scheme, and a “cell-by-cell” space-time AMR strategy with time-accurate local time stepping. In this way, third order accurate (both in space and in time) numerical simulations of the RM instability are performed, spanning a wide parameter space. We present results both for the case in which a light fluid penetrates into a higher density one (Atwood number A > 0) and for the case in which a heavy fluid penetrates into a lower density one (Atwood number A < 0). We find that for large Lorentz factors γs of the incident shock wave, the relativistic RM instability is substantially weakened and ultimately suppressed. More specifically, the growth rate of the RM instability in the linear phase has a local maximum which occurs at a critical value of γs ≈ [1.2, 2]. Moreover, we have also revealed a genuinely relativistic effect, absent in Newtonian hydrodynamics, which arises in three dimensional configurations with a non-zero velocity component tangent to the incident shock front. In particular, in A > 0 models, the tangential velocity has a net magnification effect, while in A < 0 models, the tangential velocity has a net suppression effect.
Wafer-scale synthesis of multi-layer graphene by high-temperature carbon ion implantation
Authors: Kim Janghyuk , Lee Geonyeop , Kim Jihyun
Published: July 2015

We report on the synthesis of wafer-scale (4 in. in diameter) high-quality multi-layer graphene using high-temperature carbon ion implantation on thin Ni films on a substrate of SiO2/Si. Carbon ions were bombarded at 20 keV and a dose of 1 × 1015 cm−2 onto the surface of the Ni/SiO2/Si substrate at a temperature of 500 °C. This was followed by high-temperature activation annealing (600–900 °C) to form a sp2-bonded honeycomb structure. The effects of post-implantation activation annealing conditions were systematically investigated by micro-Raman spectroscopy and transmission electron microscopy. Carbon ion implantation at elevated temperatures allowed a lower activation annealing temperature for fabricating large-area graphene. Our results indicate that carbon-ion implantation provides a facile and direct route for integrating graphene with Si microelectronics.
In situ and fast detection of single-walled carbon nanotubes by using DNA mediated aggregation method and quartz crystal microbalance
Authors: Jang Kuewhan , Park Jinsung , Lee Sangmyung , You Juneseok , Park Chanho , Lee Jaeryung , Park Woonghwi , Yun Jinsu , Ahn Sanghyun , Na Sungsoo
Published: July 2015

Carbon nanotubes (CNTs) have attracted great interest from scientific interest to industrial areas. Due to the toxicity effect of CNTs, assessment methods for CNTs are one of the noticeable issues. In this work, we report the in situ and fast detection of single-walled carbon nanotubes (SWCNTs) by using a quartz crystal microbalance. The detection is based on DNA hybridization between the DNA on a quartz electrode and the DNA of aggregated SWCNTs. It is shown that our detection tool is capable of the in situ and fast detection of 5 min with the limit of detection (LOD) of 10 ng ml−1 in distilled water. Furthermore, our detection tool is able to detect SWCNTs in a real practical sample of tap water with the LOD of 100 ng ml−1. Our work sheds light on a direct monitoring tool that could detect and assess the toxicity of SWCNTs in a real environment.
Selective deposition of a crystalline Si film by a chemical sputtering process in a high pressure hydrogen plasma
Authors: Ohmi Hiromasa , Kakiuchi Hiroaki , Yasutake Kiyoshi
Published: July 2015

The selective deposition of Si films was demonstrated using a chemical sputtering process induced by a high pressure hydrogen plasma at 52.6 kPa (400 Torr). In this chemical sputtering process, the initial deposition rate (Rd) is dependent upon the substrate type. At the initial stage of Si film formation, Rd on glass substrates increased with elapsed time and reached to a constant value. In contrast, Rd on Si substrates remained constant during the deposition. The selective deposition of Si films can be achieved by adjusting the substrate temperature (Tsub) and hydrogen concentration (CH2) in the process atmosphere. For any given deposition time, it was found that an optimum CH2 exists for a given Tsub to realize the selective deposition of a Si film, and the optimum Tsub value tends to increase with decreasing CH2. According to electron diffraction patterns obtained from the samples, the selectively prepared Si films showed epitaxial-like growth, although the Si films contained many defects. It was revealed by Raman scattering spectroscopy that some of the defects in the Si films were platelet defects induced by excess hydrogen incorporated during Si film formation. Raman spectrum also suggested that Si related radicals (SiH2, SiH, Si) with high reactivity contribute to the Si film formation. Simple model was derived as the guideline for achieving the selective growth.
Reliable measurement of the Seebeck coefficient of organic and inorganic materials between 260 K and 460 K
Authors: Beretta D. , Bruno P. , Lanzani G. , Caironi M.
Published: July 2015

A new experimental setup for reliable measurement of the in-plane Seebeck coefficient of organic and inorganic thin films and bulk materials is reported. The system is based on the “Quasi-Static” approach and can measure the thermopower in the range of temperature between 260 K and 460 K. The system has been tested on a pure nickel bulk sample and on a thin film of commercially available PEDOT:PSS deposited by spin coating on glass. Repeatability within 1.5% for the nickel sample is demonstrated, while accuracy in the measurement of both organic and inorganic samples is guaranteed by time interpolation of data and by operating with a temperature difference over the sample of less than 1 K.
New developments in high pressure x-ray spectroscopy beamline at High Pressure Collaborative Access Team
Authors: Xiao Y. M. , Chow P. , Boman G. , Bai L. G. , Rod E. , Bommannavar A. , Kenney-Benson C. , Sinogeikin S. , Shen G. Y.
Published: July 2015

The 16 ID-D (Insertion Device - D station) beamline of the High Pressure Collaborative Access Team at the Advanced Photon Source is dedicated to high pressure research using X-ray spectroscopy techniques typically integrated with diamond anvil cells. The beamline provides X-rays of 4.5-37 keV, and current available techniques include X-ray emission spectroscopy, inelastic X-ray scattering, and nuclear resonant scattering. The recent developments include a canted undulator upgrade, 17-element analyzer array for inelastic X-ray scattering, and an emission spectrometer using a polycapillary half-lens. Recent development projects and future prospects are also discussed.
Onset of convection in a two–phase binary mixture with the Soret effect in weightlessness
Authors: Ryzhkov Ilya I. , Tsarev Sergey P.
Published: July 2015

The linear stability of mechanical equilibrium in a two–layer system formed by different phases of the same binary mixture is investigated. The temperature difference is applied to the layers by heating and cooling the opposite rigid boundaries. In the state of mechanical equilibrium, the applied temperature gradient induces concentration gradients due to the Soret effect. The conservation of mass for the mixture components leads to the dependence of layer thicknesses on the applied temperature difference. In weightlessness, the main mechanisms of instability in the considered system are related to phase change and Marangoni effect. The calculations are performed for cyclohexane–methanol binary mixture, which has a liquid–liquid miscibility gap. The analytical solution of amplitude equations for monotonic perturbations is found and expression for the critical temperature difference is derived. It is shown that the phase change instability is long–wave and favoured when the difference between interfacial concentrations in the basic state decreases. When the Marangoni effect is taken into account, additional monotonic and oscillatory modes appear. They result from the interplay between thermocapillarity and phase change with latent heat release/absorption. The most unstable monotonic and oscillatory modes are identified depending on the heating regime and relative thickness of the layers.
Solute location in a nanoconfined liquid depends on charge distribution
Authors: Harvey Jacob A. , Thompson Ward H.
Published: July 2015

Nanostructured materials that can confine liquids have attracted increasing attention for their diverse properties and potential applications. Yet, significant gaps remain in our fundamental understanding of such nanoconfined liquids. Using replica exchange molecular dynamics simulations of a nanoscale, hydroxyl-terminated silica pore system, we determine how the locations explored by a coumarin 153 (C153) solute in ethanol depend on its charge distribution, which can be changed through a charge transfer electronic excitation. The solute position change is driven by the internal energy, which favors C153 at the pore surface compared to the pore interior, but less so for the more polar, excited-state molecule. This is attributed to more favorable non-specific solvation of the large dipole moment excited-state C153 by ethanol at the expense of hydrogen-bonding with the pore. It is shown that a change in molecule location resulting from shifts in the charge distribution is a general result, though how the solute position changes will depend upon the specific system. This has important implications for interpreting measurements and designing applications of mesoporous materials.
A computer simulation approach to quantify the true area and true area compressibility modulus of biological membranes
Authors: Chacón Enrique , Tarazona Pedro , Bresme Fernando
Published: July 2015

We present a new computational approach to quantify the area per lipid and the area compressibility modulus of biological membranes. Our method relies on the analysis of the membrane fluctuations using our recently introduced coupled undulatory (CU) mode [Tarazona et al., J. Chem. Phys. 139, 094902 (2013)], which provides excellent estimates of the bending modulus of model membranes. Unlike the projected area, widely used in computer simulations of membranes, the CU area is thermodynamically consistent. This new area definition makes it possible to accurately estimate the area of the undulating bilayer, and the area per lipid, by excluding any contributions related to the phospholipid protrusions. We find that the area per phospholipid and the area compressibility modulus features a negligible dependence with system size, making possible their computation using truly small bilayers, involving a few hundred lipids. The area compressibility modulus obtained from the analysis of the CU area fluctuations is fully consistent with the Hooke’s law route. Unlike existing methods, our approach relies on a single simulation, and no a priori knowledge of the bending modulus is required. We illustrate our method by analyzing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers using the coarse grained MARTINI force-field. The area per lipid and area compressibility modulus obtained with our method and the MARTINI forcefield are consistent with previous studies of these bilayers.
Continuous Stockwell transform: Coherent states and localization operators
Authors: Hutníková Mária , Mišková Anna
Published: July 2015

There are several methods of interest in signal analysis and image processing. The most widely used are the wavelet transform, the short-time Fourier transform, the shearlet transform, and the Stockwell transform. Putting a filter in the corresponding reproducing formula, one gets the well-known Calderón-Toeplitz and Gabor-Toeplitz localization operators widely studied in the context of time scale, time-frequency as well as shearlet analysis. Using Vasilevski’s technique of Hilbert-space decomposition (applied for the space of continuous Stockwell transforms of L2(ℝ)-functions), we get the structural results of the transform space and we study Toeplitz operators in this context with many desirable properties of localization operators. We find their unitary equivalent images for the case of separable generating symbols and show that the Wick symbols for these operators are associated with a well-defined calculus. Also, certain algebras generated by these operators are described in detail. Thus, the results complete the full picture about properties and behavior of Toeplitz localization operators related to four most commonly used signal transforms.
Silicon detectors for monitoring neutron beams in n-TOF beamlines
Authors: Cosentino L. , Musumarra A. , Barbagallo M. , Colonna N. , Damone L. , Pappalardo A. , Piscopo M. , Finocchiaro P.
Published: July 2015

During 2014, the second experimental area (EAR2) was completed at the n-TOF neutron beam facility at CERN (n-TOF indicates neutron beam measurements by means of time of flight technique). The neutrons are produced via spallation, by means of a high-intensity 20 GeV pulsed proton beam impinging on a thick target. The resulting neutron beam covers the energy range from thermal to several GeV. In this paper, we describe two beam diagnostic devices, both exploiting silicon detectors coupled with neutron converter foils containing 6Li. The first one is based on four silicon pads and allows monitoring of the neutron beam flux as a function of the neutron energy. The second one, in beam and based on position sensitive silicon detectors, is intended for the reconstruction of the beam profile, again as a function of the neutron energy. Several electronic setups have been explored in order to overcome the issues related to the gamma flash, namely, a huge pulse present at the start of each neutron bunch which may blind the detectors for some time. The two devices were characterized with radioactive sources and also tested at the n-TOF facility at CERN. The wide energy and intensity range they proved capable of sustaining made them attractive and suitable to be used in both EAR1 and EAR2 n-TOF experimental areas, where they became immediately operational.
Exact calculations of first-passage properties on the pseudofractal scale-free web
Authors: Peng Junhao , Agliari Elena , Zhang Zhongzhi
Published: July 2015

In this paper, we consider discrete time random walks on the pseudofractal scale-free web (PSFW) and we study analytically the related first passage properties. First, we classify the nodes of the PSFW into different levels and propose a method to derive the generation function of the first passage probability from an arbitrary starting node to the absorbing domain, which is located at one or more nodes of low-level (i.e., nodes with large degree). Then, we calculate exactly the first passage probability, the survival probability, the mean, and the variance of first passage time by using the generating functions as a tool. Finally, for some illustrative examples corresponding to given choices of starting node and absorbing domain, we derive exact and explicit results for such first passage properties. The method we propose can as well address the cases where the absorbing domain is located at one or more nodes of high-level on the PSFW, and it can also be used to calculate the first passage properties on other networks with self-similar structure, such as (u, v) flowers and recursive scale-free trees.
Copper ESEEM and HYSCORE through ultra-wideband chirp EPR spectroscopy
Authors: Segawa Takuya F. , Doll Andrin , Pribitzer Stephan , Jeschke Gunnar
Published: July 2015

The main limitation of pulse electron paramagnetic resonance (EPR) spectroscopy is its narrow excitation bandwidth. Ultra-wideband (UWB) excitation with frequency-swept chirp pulses over several hundreds of megahertz overcomes this drawback. This allows to excite electron spin echo envelope modulation (ESEEM) from paramagnetic copper centers in crystals, whereas up to now, only ESEEM of ligand nuclei like protons or nitrogens at lower frequencies could be detected. ESEEM spectra are recorded as two-dimensional correlation experiments, since the full digitization of the electron spin echo provides an additional Fourier transform EPR dimension. Thus, UWB hyperfine-sublevel correlation experiments generate a novel three-dimensional EPR-correlated nuclear modulation spectrum.
Transport and capture properties of Auger-generated high-energy carriers in (AlInGa)N quantum well structures
Authors: Nirschl A. , Binder M. , Schmid M. , Karow M. M. , Pietzonka I. , Lugauer H.-J. , Zeisel R. , Sabathil M. , Bougeard D. , Galler B.
Published: July 2015

Recent photoluminescence experiments presented by M. Binder et al. [Appl. Phys. Lett. 103, 071108 (2013)] demonstrated the visualization of high-energy carriers generated by Auger recombination in (AlInGa)N multi quantum wells. Two fundamental limitations were deduced which reduce the detection efficiency of Auger processes contributing to the reduction in internal quantum efficiency: the transfer probability of these hot electrons and holes in a detection well and the asymmetry in type of Auger recombination. We investigate the transport and capture properties of these high-energy carriers regarding polarization fields, the transfer distance to the generating well, and the number of detection wells. All three factors are shown to have a noticeable impact on the detection of these hot particles. Furthermore, the investigations support the finding that electron-electron-hole exceeds electron-hole-hole Auger recombination if the densities of both carrier types are similar. Overall, the results add to the evidence that Auger processes play an important role in the reduction of efficiency in (AlInGa)N based LEDs.
Self-consistent simulation of CdTe solar cells with active defects
Authors: Brinkman Daniel , Guo Da , Akis Richard , Ringhofer Christian , Sankin Igor , Fang Tian , Vasileska Dragica
Published: July 2015

We demonstrate a self-consistent numerical scheme for simulating an electronic device which contains active defects. As a specific case, we consider copper defects in cadmium telluride solar cells. The presence of copper has been shown experimentally to play a crucial role in predicting device performance. The primary source of this copper is migration away from the back contact during annealing, which likely occurs predominantly along grain boundaries. We introduce a mathematical scheme for simulating this effect in 2D and explain the numerical implementation of the system. Finally, we will give numerical results comparing our results to known 1D simulations to demonstrate the accuracy of the solver and then show results unique to the 2D case.
Non-universal behavior of leaky surface waves in a one dimensional asymmetric plasmonic grating
Authors: Vempati Sesha , Iqbal Tahir , Afsheen Sumera
Published: July 2015

We report on a non-universal behavior of leaky surface plasmon waves on asymmetric (Si/Au/analyte of different height) 1D grating through numerical modelling. The occurrence of the leaky surface wave was maximized (suppressing the Fabry–Perot cavity mode), which can be identified in a reflection spectrum through characteristic minimum. Beyond a specific analyte height (h), new sets of surface waves emerge, each bearing a unique reflection minimum. Furthermore, all of these minima depicted a red-shift before saturating at higher h values. This saturation is found to be non-universal despite the close association with their origin (being leaky surface waves). This behavior is attributed to the fundamental nature and the origin of the each set. Additionally, all of the surface wave modes co-exit at relatively higher h values.
Highly reliable photosensitive organic-inorganic hybrid passivation layers for a-InGaZnO thin-film transistors
Authors: Bermundo Juan Paolo , Ishikawa Yasuaki , Yamazaki Haruka , Nonaka Toshiaki , Fujii Mami N. , Uraoka Yukiharu
Published: July 2015

We report the fabrication of a photosensitive hybrid passivation material on amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) that greatly enhance its stability and improve its electrical characteristics. The hybrid passivation based on polysilsesquioxane is transparent and fabricated using a simple solution process. Because the passivation is photosensitive, dry etching was never performed during TFT fabrication. TFTs passivated with this material had a small threshold voltage shift of 0.5 V during positive bias stress, 0.5 V during negative bias stress, and −2.5 V during negative bias illumination stress. Furthermore, TFTs passivated by this layer were stable after being subjected to high relative humidity stress — confirming the superb barrier ability of the passivation. Analysis of secondary ion mass spectrometry showed that a large amount of hydrogen, carbon, and fluorine can be found in the channel region. We show that both hydrogen and fluorine reduced oxygen vacancies and that fluorine stabilized weak oxygen and hydroxide bonds. These results demonstrate the large potential of photosensitive hybrid passivation layers as effective passivation materials.
Interfacial Ga-As suboxide: Structural and electronic properties
Authors: Colleoni Davide , Pasquarello Alfredo
Published: July 2015

The structural and electronic properties of Ga-As suboxide representative of the transition region at the GaAs/oxide interface are studied through density functional calculations. Two amorphous models generated by quenches from the melt are taken under consideration. The absence of As–O bonds indicates that the structure is a mixture of GaAs and Ga-oxide, in accordance with photoemission experiments. The band edges of the models are found to be closely aligned to those of GaAs. The simulation of charging and discharging processes leads to the identification of an As-related defect with an energy level at ∼0.7 eV above the GaAs valence band maximum, in good agreement with the experimental density of interface states.
Optical loss by surface transfer doping in silicon waveguides
Authors: Alloatti L. , Koos C. , Leuthold J.
Published: July 2015

We show that undoped silicon waveguides may suffer of up to 1.8 dB/cm free-carrier absorption caused by improper surface passivation. To verify the effects of free-carriers, we apply a gate field to the waveguides. Smallest losses correspond to higher electrical sheet resistances and are generally obtained with non-zero gate fields. The presence of free carriers for zero gate field is attributed to surface transfer doping. These results open new perspectives for minimizing propagation losses in silicon waveguides and for obtaining low-loss and highly conductive silicon films without applying a gate voltage.
Artefacts at the liquid interface and their impact in miniaturized biochemical assay
Authors: Litten Brett , Blackett Carolyn , Wigglesworth Mark , Goddard Nicholas , Fielden Peter
Published: July 2015

Droplet microfluidic technology has the potential to significantly reduce reagent use, and therefore, lower costs of assays employed in drug discovery campaigns. In addition to the reduction in costs, this technology can also reduce evaporation and contamination which are often problems seen in miniaturized microtitre plate formats. Despite these advantages, we currently advise caution in the use of these microfluidic approaches as there remains a lack of understanding of the artefacts of the systems such as reagent partitioning from droplet to carrier oil and interaction of the biological reagents with the water-oil interface. Both types of artefact can lead to inaccurate and misleading data. In this paper, we present a study of the partitioning of a number of drug-like molecules in a range of oils and evidence of protein binding at the water-oil interface which results in reduced activity of a cytochrome P450 enzyme. Data presented show that the drug-like molecules partitioned the least into fluorocarbon oils and the interaction of the 1A2 cytochrome at the water-oil interface resulted in a lower or complete absence of enzyme activity. This loss of activity of cytochrome 1A2 could be restored by the use of secondary blocking proteins although changes in the pharmacology of known 1A2 inhibitors were observed. The artefacts described here due to reagents partitioning into the carrier oil or protein binding at the water-oil interface significantly impact the potential use of these microfluidic systems as a means to carry out miniaturized biological assays, and further work is needed to understand the impact and reduction of these phenomena.
Abnormal bipolar resistive switching behavior in a Pt/GaO1.3/Pt structure
Authors: Guo D. Y. , Wu Z. P. , Zhang L. J. , Yang T. , Hu Q. R. , Lei M. , Li P. G. , Li L. H. , Tang W. H.
Published: July 2015

A stable and repeatable abnormal bipolar resistive switching behavior was observed in a Pt/GaO1.3/Pt sandwich structure without an electroforming process. The low resistance state (LRS) and the high resistance state (HRS) of the device can be distinguished clearly and be switched reversibly under a train of the voltage pulses. The LRS exhibits a conduction of electron tunneling, while the HRS shows a conduction of Schottky-type. The observed phenomena are considered to be related to the migration of oxygen vacancies which changes the space charge region width of the metal/semiconductor interface and results in a different electron transport mechanism.