bluuebunny/crossref_metadata_2025 huggingface dataset:
Linear Growth Rate Estimation From Dynamics and Statistics of Acoustic Signal Envelope in Turbulent Combustors
Authors: Noiray Nicolas
Published: September 2016

Considerable research and development efforts are required to meet the targets of future gas turbine technologies in terms of performance, emissions and operational flexibility. One of the recurring problem is the constructive coupling between flames and combustor’s acoustics. These thermoacoustic interactions can cause high amplitude dynamic pressure limit cycles, which reduce the lifetime of the hot-gas-path parts or in the worst case scenario destroy these mechanical components as a result of a sudden catastrophic event. It is shown in this paper that the dynamics and the statistics of the acoustic signal envelope can be used to identify the linear growth rates hidden behind the observed pulsations, and the results are validated against numerical simulations. This is a major step forward and it will contribute to the development of future gas turbine combustors, because the knowledge of these linear growth rates is essential to develop robust active and passive systems to control these combustion instabilities.
Differences in acoustic impedance of fresh and embedded human trabecular bone samples—Scanning acoustic microscopy and numerical evaluation
Authors: Ojanen Xiaowei , Töyräs Juha , Inkinen Satu I. , Malo Markus K. H. , Isaksson Hanna , Jurvelin Jukka S.
Published: September 2016

Trabecular bone samples are traditionally embedded and polished for scanning acoustic microscopy (SAM). The effect of sample processing, including dehydration, on the acoustic impedance of bone is unknown. In this study, acoustic impedance of human trabecular bone samples (n = 8) was experimentally assessed before (fresh) and after embedding using SAM and two-dimensional (2-D) finite-difference time domain simulations. Fresh samples were polished with sandpapers of different grit (P1000, P2500, and P4000). Experimental results indicated that acoustic impedance of samples increased significantly after embedding [mean values 3.7 MRayl (fresh), 6.1 MRayl (embedded), p < 0.001]. After polishing with different papers, no significant changes in acoustic impedance were found, even though higher mean values were detected after polishing with finer (P2500 and P4000) papers. A linear correlation (r = 0.854, p < 0.05) was found between the acoustic impedance values of embedded and fresh bone samples polished using P2500 SiC paper. In numerical simulations dehydration increased the acoustic impedance of trabecular bone (38%), whereas changes in surface roughness of bone had a minor effect on the acoustic impedance (−1.56%/0.1 μm). Thereby, the numerical simulations corroborated the experimental findings. In conclusion, acoustic impedance measurement of fresh trabecular bone is possible and may provide realistic material values similar to those of living bone.
A local representation of the head-related transfer function
Authors: Hu Shichao , Trevino Jorge , Salvador Cesar , Sakamoto Shuichi , Li Junfeng , Suzuki Yôiti
Published: September 2016

Spatial descriptions of the head-related transfer function (HRTF) using spherical harmonics, which is commonly used for the purpose, consider all directions simultaneously. However, in perceptual studies, it is necessary to model HRTFs with different angular resolutions at different directions. To this end, an alternative spatial representation of the HRTF, based on local analysis functions, is introduced. The proposal is shown to have the potential to describe the local features of the HRTF. This is verified by comparing the reconstruction error achieved by the proposal to that of the spherical harmonic decomposition when reconstructing the HRTF inside a spherical cap.
Tall timber
Authors: Cornwall Warren
Published: September 2016

High-tech wood is taking the place of steel in a new wave of green high-rises.
Solving Australia's language puzzle
Authors: Erard Michael
Published: September 2016

Methods borrowed from evolutionary biology show how people spread across the continent, giving birth to new languages.
Webinar | Combating the "garbage-in-garbage-out" paradigm:The importance of library prep in next-gen sequencing workflows
Authors: Costello Maura , Quail Michael A.
Published: September 2016

In the context of next-generation sequencing, the old saying "garbage in, garbage out" translates to "poor sample preparation results in poor data"—sometimes even unusable data. As those poor results often become apparent only after expensive, time-consuming sequencing, it behooves researchers to pay extra attention to the preparation of their DNA samples at every step, from isolation through library preparation to loading the samples onto their sequencer of choice. This webinar will focus particularly on best practices for library preparation, including whole-genome library prep and shearing methods for PCR-free vs. PCR-plus prep, which can substantially impact bias and coverage, among other variables. Attendees will also hear about best practices for quality control of the library preparation process, as well as the impact of library quality on downstream data quality.

View the Webinar
A Multilaboratory, Multicountry Study To Determine MIC Quality Control Ranges for Phenotypic Drug Susceptibility Testing of Selected First-Line Antituberculosis Drugs, Second-Line Injectables, Fluoroquinolones, Clofazimine, and Linezolid
Authors: Kaniga Koné , Cirillo Daniela M. , Hoffner Sven , Ismail Nazir A. , Kaur Devinder , Lounis Nacer , Metchock Beverly , Pfyffer Gaby E. , Venter Amour
Published: September 2016

Our objective was to establish reference MIC quality control (QC) ranges for drug susceptibility testing of antimycobacterials, including first-line agents, second-line injectables, fluoroquinolones, and World Health Organization category 5 drugs for multidrug-resistant tuberculosis using a 7H9 broth microdilution MIC method. A tier-2 reproducibility study was conducted in eight participating laboratories using Clinical Laboratory and Standards Institute (CLSI) guidelines. Three lots of custom-made frozen 96-well polystyrene microtiter plates were used and prepared with 2× prediluted drugs in 7H9 broth-oleic acid albumin dextrose catalase. The QC reference strain was
Mycobacterium tuberculosis
H37Rv. MIC frequency, mode, and geometric mean were calculated for each drug. QC ranges were derived based on predefined, strict CLSI criteria. Any data lying outside CLSI criteria resulted in exclusion of the entire laboratory data set. Data from one laboratory were excluded due to higher MIC values than other laboratories. QC ranges were established for 11 drugs: isoniazid (0.03 to 0.12 μg/ml), rifampin (0.03 to 0.25 μg/ml), ethambutol (0.25 to 2 μg/ml), levofloxacin (0.12 to 1 μg/ml), moxifloxacin (0.06 to 0.5 μg/ml), ofloxacin (0.25 to 2 μg/ml), amikacin (0.25 to 2 μg/ml), kanamycin (0.25 to 2 μg/ml), capreomycin (0.5 to 4 μg/ml), linezolid (0.25 to 2 μg/ml), and clofazimine (0.03 to 0.25 μg/ml). QC ranges could not be established for nicotinamide (pyrazinamide surrogate), prothionamide, or ethionamide, which were assay nonperformers. Using strict CLSI criteria, QC ranges against the
M. tuberculosis
H37Rv reference strain were established for the majority of commonly used antituberculosis drugs, with a convenient 7H9 broth microdilution MIC method suitable for use in resource-limited settings.
Multiple Antibody Lineages in One Donor Target the Glycan-V3 Supersite of the HIV-1 Envelope Glycoprotein and Display a Preference for Quaternary Binding
Authors: Longo Nancy S. , Sutton Matthew S. , Shiakolas Andrea R. , Guenaga Javier , Jarosinski Marissa C. , Georgiev Ivelin S. , McKee Krisha , Bailer Robert T. , Louder Mark K. , O'Dell Sijy , Connors Mark , Wyatt Richard T. , Mascola John R. , Doria-Rose Nicole A.
Published: September 2016

One of the goals of HIV-1 vaccine development is the elicitation of neutralizing antibodies against vulnerable regions on the envelope glycoprotein (Env) viral spike. Broadly neutralizing antibodies targeting the Env glycan-V3 region (also called the N332 glycan supersite) have been described previously, with several single lineages each derived from different individual donors. We used a high-throughput B-cell culture method to isolate neutralizing antibodies from an HIV-1-infected donor with high serum neutralization breadth. Clonal relatives from three distinct antibody lineages were isolated. Each of these antibody lineages displayed modest breadth and potency but shared several characteristics with the well-characterized glycan-V3 antibodies, including dependence on glycans N332 and N301, VH4 family gene utilization, a heavy chain complementarity-determining region 2 (CDRH2) insertion, and a longer-than-average CDRH3. In contrast to previously described glycan-V3 antibodies, these antibodies preferentially recognized the native Env trimer compared to monomeric gp120. These data indicate the diversity of antibody specificities that target the glycan-V3 site. The quaternary binding preference of these antibodies suggests that that their elicitation likely requires the presentation of a native-like trimeric Env immunogen.

IMPORTANCE
Broadly neutralizing antibodies targeting the HIV-1 glycan-V3 region with single lineages from individual donors have been described previously. Here we describe three lineages from a single donor, each of which targets glycan-V3. Unlike previously described glycan-V3 antibodies, these mature antibodies bind preferentially to the native Env trimer and weakly to the gp120 monomer. These data extend our knowledge of the immune response recognition of the N332 supersite region and suggest that the mode of epitope recognition is more complex than previously anticipated.
Severe liver involvement in two patients with long-term history of fever: remember familial Mediterranean fever
Authors: Gatselis Nikolaos K , Skendros Panagiotis , Ritis Konstantinos , Dalekos George N
Published: September 2016

Familial Mediterranean fever (FMF) is characterised by recurrent, self-limited fever attacks and serositis. Severe liver involvement has rarely been reported. We present two FMF cases of a 55-year-old man and a 20-year-old woman in whom the prevailing manifestations were recurrent unexplained episodes of anicteric hepatitis (man) and recurrent severe jaundice (woman). A long-term history of recurrent self-limited episodes of fever was also claimed in both. After exclusion of infectious, malignant, autoimmune, and liver and biliary diseases, a diagnosis of FMF as confirmed by molecular analysis was established. The patients started colchicine 1 mg/day with immediate resolution of symptoms. During follow-up, no new episodes of fever and exacerbation of liver biochemical parameters have been recorded for 5 and 1 years. Physicians must keep FMF in mind in patients with recurrent episodes of unexplained severe liver impairment and fever and especially in regions like Mediterranean basin where hereditary periodic fever syndromes are common.
Ex vivo study of human visceral nociceptors
Authors: McGuire Cian , Boundouki George , Hockley James R F , Reed David , Cibert-Goton Vincent , Peiris Madusha , Kung Victor , Broad John , Aziz Qasim , Chan Christopher , Ahmed Shafi , Thaha Mohamed A , Sanger Gareth J , Blackshaw L Ashley , Knowles Charles H , Bulmer David C
Published: September 2016

Objective

The development of effective visceral analgesics free of deleterious gut-specific side effects is a priority. We aimed to develop a reproducible methodology to study visceral nociception in human tissue that could aid future target identification and drug evaluation.

Design

Electrophysiological (single unit) responses of visceral afferents to mechanical (von Frey hair (VFH) and stretch) and chemical (bradykinin and ATP) stimuli were examined. Thus, serosal afferents (putative nociceptors) were used to investigate the effect of tegaserod, and transient receptor potential channel, vanilloid 4 (TRPV4) modulation on mechanical responses.

Results

Two distinct afferent fibre populations, serosal (n=23) and muscular (n=21), were distinguished based on their differences in sensitivity to VFH probing and tissue stretch. Serosal units displayed sensitivity to key algesic mediators, bradykinin (6/14 units tested) and ATP (4/10), consistent with a role as polymodal nociceptors, while muscular afferents are largely insensitive to bradykinin (0/11) and ATP (1/10). Serosal nociceptor mechanosensitivity was attenuated by tegaserod (−20.8±6.9%, n=6, p<0.05), a treatment for IBS, or application of HC067047 (−34.9±10.0%, n=7, p<0.05), a TRPV4 antagonist, highlighting the utility of the preparation to examine the mechanistic action of existing drugs or novel analgesics. Repeated application of bradykinin or ATP produced consistent afferent responses following desensitisation to the first application, demonstrating their utility as test stimuli to evaluate analgesic activity.

Conclusions

Functionally distinct subpopulations of human visceral afferents can be demonstrated and could provide a platform technology to further study nociception in human tissue.
AGE–GENDER DIFFERENCE IN THE BIOMECHANICAL FEATURES OF SIT-TO-STAND MOVEMENT
Authors: KWON YURI , HEO JAE-HOON , JEON HYEONG-MIN , MIN SE DONG , JUN JAE-HOON , TACK GYE-RAE , PARK BYUNG KYU , KIM JI-WON , EOM GWANG-MOON
Published: September 2016

The purpose of this study was to investigate the effects of age and gender on the biomechanical features of sit-to-stand (STS) movement. Twenty young subjects and 20 elderly subjects participated in this study. Nine events during STS movement were defined where joint angles and joint moments were extracted for further analyses. Two-way repeated measures ANOVA was performed for joint angles and joint moments with age and gender as independent factors. Major gender differences were shown in joint angles. Women used a sliding forward strategy more than men (more flexion of ankle and knee joint) during mid-phases of STS movement ([Formula: see text]) and men used an exaggerated trunk flexion strategy more than women (more hip flexion) in later phases of STS movement ([Formula: see text]). Age differences were shown in joint moments. Elderly subjects showed smaller knee extension moment (normalized by body weight) but greater ankle plantar flexion moment than young subjects in mid-to-late phases of STS movement ([Formula: see text]). More anterior positioning of center of mass (COM) in the elderly might be the reason for the strategy difference. That is, the shorter distance of COM from the knee joint would require less knee extension moment, and likewise, the more forward displacement of COM with respect to the ankle joint would need more plantar flexion moment. More anterior positioning of COM in the elderly, compared to the young was reflected on center of pressure (COP), and the forward displacement of COP was correlated well with the higher body mass index (BMI) and shorter thigh length ([Formula: see text]).
MEASUREMENT OF UPPER LIMB MUSCLE FATIGUE USING DEEP BELIEF NETWORKS
Authors: SU YI , SUN SHILEI , OZTURK YUSUF , TIAN MAO
Published: September 2016

In recent years, a robust increasing interest has been observed in wearable devices featuring smart health, smart fitness, and human–machine interaction applications. While we gained some advances on use of surface electromyography (sEMG) signals recorded from upper extremities for controlling external devices, only limited attempt has been made to track the status of targeted muscles and forecast muscle fatigue onset. In this study, we address use of sEMG signals acquired from upper extremities to predict onset of muscle fatigue using deep belief networks (DBNs) as a learning mechanism. We demonstrate that a deep architecture can learn from raw data and provide comparable performance to feature-based approaches. Experimental results show that the DBNs model investigated in this study achieves an average classification accuracy of 85.3% without any subject-oriented calibration and achieves a best case accuracy of 97.60%. A transient-to-fatigue state is introduced before the fatigue onsets as an early warning state. The aim of this paper is to evaluate the performance of the popular deep models in real fatigue detection applications. The model provides a promising result compared with state-of-art works without any feature selection process, which could potentially generate better features while reducing the requirement for expertise in data.
Property control by elastic strain engineering: Application to graphene
Authors: Baimova Julia A.
Published: September 2016

Various carbon nanostructures, including graphene, are of great interest nowadays for many applications. It has been shown that graphene has unique physical and mechanical properties and its properties can be controlled by the applied strain. The objective of the present paper is to describe several physical properties of graphene that can be controlled by means of elastic strain engineering. The space of in-plane elastic strain components is divided into regions with different structural configurations and physical properties of graphene. It is shown that a gap in the phonon density of states is observed when graphene is strained close to the appearance of ripples. Sound velocities of unstrained graphene do not depend on the propagation direction but application of strain, apart hydrostatic tension, makes graphene elastically anisotropic. The orientation, amplitude and wavelength of unidirectional ripples in graphene can be controlled by a change in the components of the applied strain.
QoS for Long-Range Wireless Sensors Under Duty-Cycle Regulations with Shared Activity Time Usage
Authors: Pham Congduc
Published: September 2016

Long-range radio can connect sensors/IoT devices without complex and costly deployment of relay nodes. However, this flexibility comes with stricter legal regulations such as maximum radio activity time per 1-hour period. Under such constraints it is difficult to provide service guarantees, which is quite paradoxical when devices are deployed for surveillance systems. The approach we propose allows devices to go “exceptionally” beyond the activity time limitation by borrowing time from other devices. The mechanism is not intended to be used on a regular basis, where a device is commissioned to always report data at a rate that makes it consuming more than the allowed duty-cycle limitation, but to offer a “last chance” solution for providing better surveillance service guarantees while globally satisfying duty-cycle regulations. The proposition has been implemented on our long-range image sensor platform, and preliminary experiments show that it can maintain the system’s consistency and keep the number of control messages small while being capable of handling sleep-wakeup behavior and dynamic insertion of new devices. Although initially targeted for image sensors, the proposition can also be deployed to increase the quality of service of traditional sensors by guaranteeing that important messages can be sent despite the duty-cycle regulation limit.
Performance Modelling and Analysis of Software-Defined Networking under Bursty Multimedia Traffic
Authors: Miao Wang , Min Geyong , Wu Yulei , Wang Haozhe , Hu Jia
Published: September 2016

Software-Defined Networking (SDN) is an emerging architecture for the next-generation Internet, providing unprecedented network programmability to handle the explosive growth of big data driven by the popularisation of smart mobile devices and the pervasiveness of content-rich multimedia applications. In order to quantitatively investigate the performance characteristics of SDN networks, several research efforts from both simulation experiments and analytical modelling have been reported in the current literature. Among those studies, analytical modelling has demonstrated its superiority in terms of cost-effectiveness in the evaluation of large-scale networks. However, for analytical tractability and simplification, existing analytical models are derived based on the unrealistic assumptions that the network traffic follows the Poisson process, which is suitable to model nonbursty text data, and the data plane of SDN is modelled by one simplified Single-Server Single-Queue (SSSQ) system. Recent measurement studies have shown that, due to the features of heavy volume and high velocity, the multimedia big data generated by real-world multimedia applications reveals the bursty and correlated nature in the network transmission. With the aim of capturing such features of realistic traffic patterns and obtaining a comprehensive and deeper understanding of the performance behaviour of SDN networks, this article presents a new analytical model to investigate the performance of SDN in the presence of the bursty and correlated arrivals modelled by the Markov Modulated Poisson Process (MMPP). The Quality-of-Service performance metrics in terms of the average latency and average network throughput of the SDN networks are derived based on the developed analytical model. To consider a realistic multiqueue system of forwarding elements, a Priority-Queue (PQ) system is adopted to model the SDN data plane. To address the challenging problem of obtaining the key performance metrics, for example, queue-length distribution of a PQ system with a given service capacity, a versatile methodology extending the Empty Buffer Approximation (EBA) method is proposed to facilitate the decomposition of such a PQ system to two SSSQ systems. The validity of the proposed model is demonstrated through extensive simulation experiments. To illustrate its application, the developed model is then utilised to study the strategy of the network configuration and resource allocation in SDN networks.
Preparations of Turpentine Based Carbon Nanospheres as Anode Materials for Lithium Ion Batteries
Authors: Arie Arenst Andreas , Devina Konstantia Inez , Halim Martin , Lee Joong-Kee
Published: September 2016

Nanocarbon materials such as carbon nanotubes (CNTs) and carbon nanospheres (CNSs) have excellent electrical properties so that they can be used to substitute graphite as anode material for lithium-ion battery. The use of nanocarbon as anode material provides a short path for the ion and electron movement in electrodes. Therefore, the energy density of the battery can be improved. In this work, the synthesis of nano carbons was carried out through nebulized spray nebulization method at different reaction temperature for 15 minutes in the presence of ferrocene as catalyst with the concentration of 0.02 g/ml. Turpentine oil, an environmentally friendly precursor, was used as carbon source. The materials obtained were physically characterized by SEM, TEM, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Meanwhile, the electrochemical properties will be analyzed by plotting charge-discharge capacity vs cycle number and electrochemical impedance spectroscopy.
Impact of Hydrogen on Carrier Mobility and Concentration in Graphene Decorated with Pd Nanoparticle
Authors: Goto Akihito , Takeuchi Go , Yamachi Ryosuke , Tanaka Takahisa , Takahashi Tsunaki , Uchida Ken
Published: September 2016

As a candidate of highly-sensitive hydrogen sensors, Palladium (Pd)-decorated graphene sensors have been investigated. Thanks to high reactivity of Pd nanoparticles to hydrogen and high surface-to-volume ratio of two-dimensionally layered graphene, graphene decorated with Pd nanoparticles can be used as a highly sensitive hydrogen sensor. Although the conductivity of Pd-graphene sensor is known to be greatly changed in hydrogen atmosphere, the mechanisms of conductivity change have not been fully understood. In this work, both carrier concentration and mobility in hydrogen are investigated using Hall effect measurement. It is shown that relative change of carrier concentration is greater when carrier concentration is lower. On the other hand, mobility is not systematically changed as a function of carrier concentration. This mobility behavior is attributed to the competition between greater effective mass and shorter screening length at higher carrier concentration. Based on these observations, we develop strategy for achieving high sensitivity in Pd graphene hydrogen sensor.
Carbon Nitride (C3N4) Photocatalysts Synthesized from Different Methods for Photocatalytic Reaction Under Visible Light Irradiation
Authors: Hu Che-Chia , Wang Mao-Sheng , Guo Zheng-Wei
Published: September 2016

C3N4 have generally been synthesized with a solid-state(SS) method, which formed a graphitic feature with tri-s-triazine(C6N7) units. This study reports a solvothermal(ST) synthesis, in which the powders were obtained as low as 150-220°C. X-ray diffraction analyses showed that the crystalline structure of ST changed from pseudocubic- to beta-C3N4 with increasing the solvothermal temperature, and C3N4 obtained from SS method displayed a graphitic structure with diffraction angles at 13.1° and 27.5°. The diffraction angles represented (100) plane of tri-s-triazine units and (002) plane of stacking of the conjugated-aromatic system, respectively. UV-Vis absorbance spectra showed that the band gap of SS was 2.6 eV, and that of ST samples were 1.9-2.45 eV. To evaluate the visible-light responded photocatalytic activity of the samples, degradation of methylene orange dyes was conducted. ST revealed a higher photo-activity, which result from its larger light absorbance in the visible regime compared to that of SS ones.
(Invited) Nanostructures Growth by Oxidation of Metallic Alloy Thin Films with Atmospheric Pressure Remote Plasma
Authors: Imam Abdallah , Gries Thomas , Hussein Khaled , Amati Mateo , Belmonte Thierry
Published: September 2016

In this work, we report on a process based on an atmospheric pressure micro-afterglow to synthesize oxide nanostructures of copper-iron alloy thin films deposited by magnetron sputtering. In plasma afterglow processes, active species like oxygen atoms or metastable states of oxygen are available. Oxidation of metals in these conditions promotes the growth of oxide nanostructures. The morphology, shape and size distribution can be controlled by varying the experimental parameters: the amount of oxygen injected in the plasma, the microwave power, the treatment time or the alloy composition. Different kinds of nanostructures are obtained with good reproducibility in a single-step process: nanowires, nanowalls or nanoblades. We show that both oxides (CuO and Fe2O3) can be formed in the same area. By controlling the composition of the alloy, ultrathin CuO nanowires (diameters ~ 5 nm) can be grown. Finally, a localization of the growth of nanowires is observed by using bilayer configurations.
Perfect Separation of Hybrid Orientation Structure of CeO2(100) and (110) Regions Grown on Silicon on Insulator Substrates with Lithographically Formed Trenches
Authors: Inoue Tomoyasu , Shida Shigenari
Published: September 2016

The hybrid orientation structure (HOS) of the CeO2(100) and (110) regions on Si(100) substrates is studied using electron beam induced orientation selective epitaxial growth by reactive magnetron sputtering. Two separate areas of growth are seen, with CeO2(100) layers found to grow in areas irradiated by electrons during the growth process, and the CeO2(110) layers growing in the areas not irradiated by the beam. The lateral orientation mapping obtained by X-ray diffraction measurements reveals the existence of transition regions between these two ori-entation areas. The width of the transition region is found to decrease with the underlying Si substrate resistivity as low as approximately the size of the electron beam diameter. The HOS growth experiments using silicon on insulator substrates with lithographically formed trenches show that perfect separation of the two areas becomes possible by optimizing the cross-sectional geometry of the trenches, especially using dry etching.
Electrophoretic Deposition of Nanoparticles into Three-Dimensional Felt as an Electrocatalyst for the Solar Sulfur Ammonia Thermochemical Cycle
Authors: Pacheco Nicole S , Talbot J. B.
Published: September 2016

The penetration and coating of nanoparticles by electrophoretic deposition (EPD) into three-dimensional substrates was studied. Specifically, EPD of cobalt ferrite nanoparticles was investigated as a possible electrocatalyst to improve the kinetically slow anodic reaction of the oxidation of ammonium sulfite to ammonium sulfate in the hydrogen production sub-cycle of the proposed solar sulfur-ammonia thermochemical water-splitting process. The primary goals were to uniformly penetrate and coat nanoparticles into 3D substrates by electrophoretic deposition and then to test their electrocatalytic activity by linear sweep voltammetry in 2 M ammonium sulfite.
Electropolishing of an Fe-Ni-Co Alloy in Acetic Acid-Perchloric Acid Mixture
Authors: Aksu Yasemin , Erdogan Metehan , Demirci Gökhan , Karakaya Ishak
Published: September 2016

Among Fe-Ni-Co alloys, Kovar (53%Fe-29%Ni-17%Co) designated as ASTM F-15 (1), is a well-known glass-sealing alloy. It is also classified as low–expansion alloy (2). Low expansion is required to avoid internal stresses in applications that involve strong ceramic to metal joining such as in vacuum systems (3-6). Electropolishing is applied to obtain smooth metallic surfaces to gain low outgassing rates from the chamber walls in vacuum applications (7-9). The effects of current density, perchloric acid concentration and bath temperature on surface roughness and thickness change were investigated in acetic acid-perchloric acid electrolyte. It was found that current density, perchloric acid concentration and temperature of the bath had a decreasing influence on surface roughness in the given order. On the other hand, thickness change was found to have a direct correlation with the current density and was independent of bath concentration and temperature.
Nickel and Gold Coatings of Germanium and Kovar Substrates
Authors: Cetin Yasin , Erdogan Metehan , Demirci Gökhan , Karakaya Ishak
Published: September 2016

The integration of germanium to other materials such as Kovar® (registered trademark of Carpenter Technology Corporation), an Fe-Ni-Co alloy, by soldering requires a surface preparation due to poor wetting characteristics of germanium. Coating (metallization) by successive electroplating of 3 mm wide nickel and gold frames well adhered to the outer edge of a circular germanium window and kovar body was applied to attain successful joining of germanium to kovar. Surface cleaning of parts to be joined or plated plays an important role in the quality of the depositions. HF and HCl solutions were used for germanium surface cleaning and the results showed that HF solution was more effective than HCl in terms of removing oxide capability. The desired small grain sized solderable nickel layer was achieved by pulse plating from Watts solution. Likewise, non-porous very thin gold was deposited by pulse plating again and it prevented the diffusion of oxygen to nickel and diffusion of nickel to the free surface. Characterization of the coatings were performed in terms of microstructure, roughness and elemental analysis by scanning electron microscopy (SEM), white light interferometry and x-ray photoelectron spectroscopy (XPS), respectively.
Electrochemical Analysis of Synthetized Iridium Nanoparticles for Oxygen Evolution Reaction in Acid Medium
Authors: Lettenmeier Philipp , Majchel Jan , Wang Li , Gago Aldo Saul , Friedrich K. Andreas
Published: September 2016

The anode side catalyst is one of the key parts for sustainable hydrogen production via proton exchange membrane (PEM) electrolysis. An optimized synthesis of the oxygen evolution reaction (OER) catalysts may lead to a cost efficient production, promoting the commercialization of new catalyst materials. This work compares the electrochemical characteristics of Ir nanoparticles synthetized in different purities of ethanol and deionized (DI) water as solvents. The use of cetyltrimethyl ammonium bromide (CTAB) as a surfactant is discussed as well. In general, the absence of the surfactant and use of either low ethanol purity or water is detrimental for electrocatalytic properties of the materials. Changes in the Tafel slope are observed, while the analysis of the specific exchange current can be misleading. The active sites from the IrIII/IrIV oxidation peak do not correlate exactly with the OER activities, while the capacitive current provides more meaningful information.
Proton Exchange Membrane Electrolyzer Systems Operating Dynamically at High Current Densities
Authors: Lettenmeier Philipp , Wang Rainey , Abouatallah Rami , Burggraf Fabian , Gago Aldo Saul , Friedrich K. Andreas
Published: September 2016

The fluctuating behavior of renewable energy sources hinders the widespread integration of those in a reliable electricity grid. Presumably, the wide operation range and rapid response of proton exchange membrane (PEM) electrolyzers can stabilize the grid, yet the degradation effects are not fully understood. The results presented here show no negative effect of dynamic operation at current 0.8, 1.6, 2.5 and 3.3 A cm-2, on commercial membrane electrode assemblies (MEA) with two different catalyst loadings. Conversely, the reduction of the loading of precious metal in the MEA leads to a cell voltage increase by 100 mV at 3.3 A cm-2. In addition, stack temperature correction of industrial facilities is necessary for proper comparison of cell potential and analysis of degradation mechanisms.
Simultaneously Coupled Mechanical-Electrochemical-Thermal Simulation of Lithium-Ion Cells
Authors: Zhang Chao , Santhanagopalan Shriram , Sprague Michael A. , Pesaran Ahmad
Published: September 2016

Understanding the combined electrochemical-thermal and mechanical response of a system has a variety of applications, for example, structural failure from electrochemical fatigue and the potential induced changes of material properties. For lithium-ion batteries, there is an added concern over the safety of the system in the event of mechanical failure of the cell components. In this work, we present a generic multi-scale simultaneously coupled mechanical-electrochemical-thermal model to examine the interaction between mechanical failure and electrochemical-thermal responses. We treat the battery cell as a homogeneous material while locally we explicitly solve for the mechanical response of individual components using a homogenization model and the electrochemical-thermal responses using an electrochemical model for the battery. A benchmark problem is established to demonstrate the proposed modeling framework. The model shows the capability to capture the gradual evolution of cell electrochemical-thermal responses, and predicts the variation of those responses under different short-circuit conditions.
Mathematical Modeling of Direct Ethanol Fuel Cells Using a Multi-Step Chemical Kinetic Mechanism
Authors: Sanchez-Monreal Juan , García-Salaberri Pablo A. , Vera Marcos
Published: September 2016

A 1D across-the-channel model is proposed for the anode of a Direct Ethanol Fuel Cell. The complex kinetics of the multi-step ethanol oxidation reaction is described using the reaction mechanism proposed by Meyer et al. [Electrochim. Acta, 56, 4299 (2011)], which considers free and adsorbed intermediate species on a Pt-based binary catalyst. The adsorbed species are modeled using coverage factors to account for the blockage of the active reaction sites on the catalyst surface. The reactions rates are described by Butler-Volmer equations, including the effect of ethanol and acetaldehyde crossover. A genetic algorithm is employed for determining the reaction constants for several catalyst types using polarization curves obtained from literature sources. By adjusting the reaction constants, different catalyst layers can be modeled and their selectivities can be partially reproduced. The discrepancies between the experimental and numerical results at low current densities suggest that Meyer’s mechanism could be improved by adding acetaldehyde to the adsorbed intermediates.
Nickel-Rare Earth (RE = Ce, Sm, Dy) Electrodes for H2O2 Reduction in Fuel Cells
Authors: Santos Diogo M.F. , Cardoso David , Sljukic Biljana , Sequeira Cesar A.C. , Macciò Daniele , Saccone Adriana
Published: September 2016

The use of hydrogen peroxide (H2O2) as an oxidant is considered a good alternative to oxygen for the cathodic process in liquid fuel cells. Herein, we studied the reduction of H2O2 at nickel and at nickel-rare earth (RE = Ce, Sm, Dy) alloys containing 5 and 10 at.% of RE metal. The alloys were prepared by arc melting, starting from the stoichiometric amounts of the two parent metals, and analyzed by X-ray diffraction and scanning electron microscopy coupled with energy-dispersive spectroscopy. The electrochemical characterization was carried out by voltammetry and chronoamperometry measurements in alkaline media. Ni0.95Ce0.05 alloy exhibited the highest catalytic activity for H2O2 reduction reaction, with a number of exchanged electrons of 1.7. Additionally, activation energies were estimated according to Arrhenius equation.
(Invited) The Influence of the Carbon Support and Platinum Particles Size on Degradation of Cathode for Low Platinum-Loading Catalyst Layer
Authors: Yu Haoran , Baricci Andrea , Casalegno Andrea , Guetaz Laure , Maric Radenka
Published: September 2016

We demonstrated the ability to control the platinum particle size in the synthesis of carbon supported Pt (Pt/C) electrocatalyst with reactive spray deposition technology (RSDT). The degradation of Pt cathode with loading of 0.1 mg/cm2 in membrane electrode assembly (MEA) under simulated drive cycles (30000 triangular wave cycles between 0.6 and 1.0 VRHE) showed similar electrochemical surface area (ECSA) at the end of life (EOL), regardless of the initial Pt particle size or carbon support type. However, it is possible to reduce the loss of ECSA using a gradient catalyst layer consisting of a 6 mm layer with Pt particles of 5 nm toward the membrane and another 6 mm layer with Pt particles of 2 nm toward the GDL. Microscopy studies suggested that the gradient catalyst layer have less Pt loss% into the electrolyte, thereby maintained higher ECSA at EOL.
PtNi-Decorated Metal Oxide Electrodes for Borohydride Fuel Cells
Authors: Martins Marta , Sljukic Biljana , Sequeira Cesar A.C. , Soylu Gülin S.P. , Bayrakçeken Yurtcan Ayse , Bozkurt Gamze , Sener Tansel , Santos Diogo M.F.
Published: September 2016

PtNi nanoparticles are grafted onto three different metal oxide supports, namely MnO2, MnO2+TiO2 and MnO2+NiO. Subsequently, their activity for oxygen reduction reaction (ORR) and borohydride oxidation reaction (BOR) in alkaline media was studied using voltammetric techniques. The dependence of electrocatalysts behavior on reaction conditions, such as electrolyte temperature, was also evaluated. ORR and BOR kinetic parameters, namely Tafel slopes, kinetic current densities, and activation energies, were determined from the obtained data in order to compare the performance of the three electrocatalysts prepared. These results show that PtNi anchored on metal oxide supports possess electrocatalytic activity for ORR and BOR in alkaline media, which suggests potential application of these materials in direct borohydride fuel cells.
Gold-Cobalt Deposited on Titania Nanotubes as Anode Catalyst for Direct Borohydride Fuel Cells
Authors: Santos Diogo M.F. , Balciunaite Aldona , Tamasauskaite-Tamasiunaite Loreta , Zabielaite A. , Jagminiene A. , Stankeviciene Ina , Norkus E.
Published: September 2016

In the present work gold-cobalt catalysts deposited on titania nanotubes surface (denoted as AuCo/TiO2-NTs) are studied as possible anode materials for direct borohydride/hydrogen peroxide fuel cells. The fuel cell measurements are performed in the 25 - 55 ºC temperature range on a lab-scale direct alkaline NaBH4-H2O2 single fuel cell. Polarization curves are recorded to evaluate the fuel cell performance using each prepared anode catalyst. It has been determined that the peak power density values are in the range from 87 to 102 mWcm–2 on the Co/TiO2-NTs catalyst and from 163 to 283 mWcm–2 on the AuCo/TiO2-NTs catalysts with Au loadings ranging from 10 to 60 µgAu cm–2.
Investigations of the Electrochemical Behavior of Hydrocarbons in Adiponitrile
Authors: Cheek Graham T.
Published: September 2016

The very wide 8-volt potential range of adiponitrile/0.20 M tetraethylammonium tetrafluoroborate has been exploited for the investigation of hydrocarbon electrochemistry. Naphthalene undergoes reversible one-electron reduction in this solvent system at glassy carbon; however, naphthalene oxidation is irreversible. The reduction of benzene is not observed, but its oxidation is also irreversible. The electrochemical oxidation of cyclohexene can also be observed in this system, but addition of cyclohexane caused only a slight (+0.1 V) shift in the positive potential limit. A comparison with results in other solvent systems is presented.
Scanning Probe-Based In Situ High Temperature Electrical and Electrochemical Measurements in Atmospheric Pressure
Authors: Ng Chee Seng , Baek Jong Dae , Zade Vishal , Villegas Adrian , Lee Tsung-Han , Su Pei-Chen , Martini Ashlie , Lee Min Hwan
Published: September 2016

Atomic force microscopy (AFM)-based study of electrical and electrochemical properties of a material/system at an elevated temperature in atmospheric pressure has been limited to ~250°C in conventional AFM setups. In this report, we have demonstrated the viability of a new approach for high temperature electrical and electrochemical studies (up to 700°C) in a conventional AFM setup by employing a combination of a micron-scale heater stage (MHS) and custom-made all-metal tips. We present the design, fabrication process and characterization of the MHS and all-metal tips. A temperature dependent impedance measurement on an MHS-integrated half-cell was then successfully demonstrated with a custom-made Pt-Ir tip. Issues and possible room to improve regarding the new approach were also discussed.
Activity and Long-Term Stability Study of Pt-Y/C Electrocatalysts for Oxygen Reduction Reaction
Authors: Silva Gabriel Christiano da , Santos Nathalia Abe , Perez Joelma
Published: September 2016

Pt-Y/C catalysts were prepared by a modified formic acid method and their activities for oxygen reduction reaction (ORR) were evaluated. X-ray diffraction analysis showed that no alloy was formed between the metals, while x-ray photoelectron spectroscopy revealed that yttrium is present as Y2O3, Y(OH)3, and Y-O-Pt. The Pt-Y/C 7:3 material had the highest specific activity (94 µA cmPt
-2) for ORR, and was superior to other Pt-Y/C materials. Following repetitive potential cycling, ORR activity of the Pt-Y/C 7:3 catalyst decreased in a similar proportion to that of Pt/C. X-ray photoelectron spectroscopy results of the aged ultrathin catalyst layer were in agreement with energy-dispersive x-ray spectroscopy data. These studies revealed that the intensities of the Y 3d peaks were suppressed due to voltammetric cycling and that while Y2O3 and Y(OH)3 dissolved, Y-O-Pt remained in the catalyst.
Iron-Based Electrocatalysts Supported on Nanostructured Carbon to Enhance Oxygen Reduction in Microbial Fuel Cells
Authors: Mecheri Barbara , Iannaci Alessandro , D'Epifanio Alessandra , Nieto-Monge Maria Jesus , Lázaro Maria Jesus , Licoccia Silvia
Published: September 2016

Microbial fuel cells (MFCs) are bioelectrochemical systems ideally suited to address two sustainability problems at once: energy generation and wastewater treatment. However, one of the major barriers to the widespread diffusion of this technology is the high cost of materials, in particular platinum used at cathode side. To overcome this drawback, we developed catalysts based on iron phthalocyanine (FePc) supported on nanostructured carbon materials with physical and morphological differences, such as nanofibers and xerogels. To facilitate catalyst dispersion and obtain effective ORR active sites, the supports were modified by a two - step treatment with nitric acid and ammonia gas. The obtained catalysts were used to prepare cathodes which were assembled in single chamber MFCs. The body of results indicated that FePc based catalysts can be used as cathode materials for MFC applications.
Micromolding of Ni-P for the Realization of a 3D Electrostatic Energy Harvesting MEMS
Authors: Risquez Sarah , Woytasik Marion , Cai Huijuan , Philippe Hadrien , Bayle Fabien , Lefeuvre Elie , Moulin Johan
Published: September 2016

This paper presents the development of nickel phosphorous (Ni-P) micromolding for the manufacturing of a 3D electrostatic energy harvesting microsystem. Ni-P alloy exhibits weak ferromagnetic properties beyond 10-12 wt% P content. Deposits were prepared at different current densities (-10 to -150 mA/cm²) and concentration of phosphorous acid in the electrolyte (0 -20g/l). The rate decreases when phosphorous content increases in the deposit. The final process leaded to choose a H3PO3 concentration of 5 g/l which give a 0.1 µm/min deposition rate for P content higher than 13 wt%. Mechanical, electrical and magnetic properties of the Ni-P films were investigated on 1mm² and 1cm² deposits and confirmed the suitability of that material for the target MEMS. Comb patterns of Ni-P micromolding have been realized on 2 inch wafer, leading to a 10 µm thick deposit containing 13.5 wt% in P, which is, at our knowledge, the first Ni-P micromolding involving electrodeposition growth.
Effect of n
+ Layer Deposition Power on Light Sensing of Amorphous Silicon pin Diodes
Authors: Henry Kai , Kuo Yue
Published: September 2016

The effect of the plasma-enhanced chemical vapor deposition power of the phosphorus-doped n
+ layer on the performance of the hydrogenated amorphous silicon pin diode for the light sensing, i.e., under solar, red, green, and blue light exposures, has been investigated. With all other deposition parameters fixed, the plasma power influenced the n
+ film deposition rate, resistivity, and defects, which are critical to the light sensing characteristics. The optimized n
+ layer deposition power for the light sensing, i.e., based on the external quantum efficiency, has been identified and discussed.
Temperature-Responsive PNIPAM-g-alginate Gel Wrapped with LbL Assembled Chitosan/DNA Membranes for Development of Controlled Drug Release System
Authors: Zhang Yuanyuan , Arugula Mary A , Zhou Lang , Simonian Aleksandr
Published: September 2016

While considerable consumers experience more-than-recommended-dose usage of commercially available scar cream for scar therapy treatment, we report here a novel and smart thermally controlled drug delivery gel patch system for scar therapy purpose. The gel patch contains a core of amine-terminated-poly(N-isopropylacrylamide) (NH2-PNIPAM) grafted alginate wrapped with outer membranes consisting of layer-by-layer (LbL) assembled chitosan and DNA thin films. The outer membrane via LbL assembly controls the rate and profile of model dye rhodamine B. A dramatically reduced burst effect in the delivery process and a diffusion controlled behavior was observed for the proposed system. NH2-PNIPAM cross-linked onto side chain of alginate exhibits contraction and expansion above and below its lower critical solution temperature (LCST: 36℃) and therefore serves as a switch turning “on and off” the release of drug entrapped in the core. The difference in the release of Texas-red conjugated epidermal growth factor (EGF-TR) at 36℃ and 22℃ were monitored with fluorescence microscopy and the system showed higher release of EGF-TR at 36℃ than at 22 ◦C. Below LCST (at 22℃), the expanded NH2-PNIPAM resembles stretched arms that close the release of EGF-TR, while above LCST (at 36℃), the NH2-PNIPAM arms coil and allow the release of EGF, showing great potential for application in controlled drug release system.