bluuebunny/crossref_metadata_2025 huggingface dataset:
Antioxidant Capacities of Phenolic Compounds and Tocopherols from Tunisian Pomegranate (Punica granatum) Fruits
Authors: Elfalleh Walid , Tlili Nizar , Nasri Nizar , Yahia Yassine , Hannachi Hédia , Chaira Nizar , Ying Ma , Ferchichi Ali
Published: April 2011

Abstract:  This article aims to determine the phenolic, tocopherol contents, and antioxidant capacities from fruits (juices, peels, and seed oils) of 6 Tunisian pomegranate ecotypes. Total anthocyanins were determined by a differential pH method. Hydrolyzable tannins were determined with potassium iodate. The tocopherol (α‐tocopherol, γ‐tocopherol, and δ‐tocopherol) contents were, respectively, 165.77, 107.38, and 27.29 mg/100 g from dry seed. Four phenolic compounds were identified and quantified in pomegranate peel and pulp using the high‐performance liquid chromatography/ultraviolet method: 2 hydroxybenzoic acids (gallic and ellagic acids) and 2 hydroxycinnamic acids (caffeic and p‐coumaric acids). Juice, peel, and seed oil antioxidants were confirmed by ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) methods. The highest values were recorded in peels with 25.63 mmol trolox equivalent/100 g and 22.08 mmol TE/100 g for FRAP and ORAC assay, respectively. Results showed that the antioxidant potency of pomegranate extracts was correlated with their phenolic compound content. In particular, the highest correlation was reported in peels. High correlations were also found between peel hydroxybenzoic acids and FRAP ORAC antioxidant capacities. Identified tocopherols seem to contribute in major part to the antioxidant activity of seed oil. The results implied that bioactive compounds from the peel might be potential resources for the development of antioxidant function dietary food.
Inhibition of synaptic transmission and G protein modulation by synthetic CaV2.2 Ca2+ channel peptides
Authors: Bucci Giovanna , Mochida Sumiko , Stephens Gary J.
Published: April 2011

Non‐technical summary  Nerve cells (neurones) in the body communicate with each other by releasing chemicals (neurotransmitters) which act on proteins called receptors. An important group of receptors (called G protein coupled receptors, GPCRs) regulate the release of neurotransmitters by an action on the ion channels that let calcium into the cell. Here, we show for the first time that small peptides based on specific regions of calcium ion channels involved in GPCR signalling can themselves inhibit nerve cell communication. We show that these peptides act directly on calcium channels to make them more difficult to open and thus reduce calcium influx into native neurones. These peptides also reduce GPCR‐mediated signalling. This work is important in increasing our knowledge about modulation of the calcium ion channel protein; such knowledge may help in the development of drugs to prevent signalling in pathways such as those involved in pain perception.
SK2 channel expression and function in cerebellar Purkinje cells
Authors: Hosy Eric , Piochon Claire , Teuling Eva , Rinaldo Lorenzo , Hansel Christian
Published: April 2011

Abstract  Small‐conductance calcium‐activated K+ channels (SK channels) regulate the excitability of neurons and their responsiveness to synaptic input patterns. SK channels contribute to the afterhyperpolarization (AHP) following action potential bursts, and curtail excitatory postsynaptic potentials (EPSPs) in neuronal dendrites. Here we review evidence that SK2 channels are expressed in rat cerebellar Purkinje cells during development and throughout adulthood, and play a key role in diverse cellular processes such as the regulation of the spike firing frequency and the modulation of calcium transients in dendritic spines. In Purkinje cells as well as in other types of neurons, SK2 channel plasticity seems to provide an important mechanism allowing these cells to adjust their intrinsic excitability and to alter the probabilities for the induction of synaptic learning correlates, such as long‐term potentiation (LTP).
The fusimotor and reafferent origin of the sense of force and weight
Authors: Luu Billy L. , Day Brian L. , Cole Jonathan D. , Fitzpatrick Richard C.
Published: April 2011

Non‐technical summary  Signals generated by the brain are thought to create the sensation of heaviness when we lift an object. We show here that signals arising from the body underlie this sensation. We fatigued the thumb muscles to half strength and had subjects lift a weight. Two subjects without sensation from the body said it felt twice as heavy, as expected by the central‐signal theory. However, normal subjects felt that the weight was lighter, inconsistent with the central‐signal theory. When we paralysed the muscles with curare and let them recover to half‐strength, the weights felt lighter despite the greater central signal. This is explained by smaller signals returning from muscle spindles because they have also been paralysed by the curare. Thus, peripheral signals with a major contribution from muscle spindles normally create the sense of heaviness. It also shows that muscle spindles provide more than information about limb position and movement.
The Tip Leakage Flow of an Unshrouded High Pressure Turbine Blade With Tip Cooling
Authors: Zhou Chao , Hodson Howard
Published: April 2011

Experimental, analytical, and numerical methods have been employed to study the aerodynamic performance of four different cooled tips with coolant mass ratios between 0% and 1.2% at three tip gaps of 1%, 1.6%, and 2.2% of the chord. The four cooled tips are two flat tips with different coolant holes, a cooled suction side squealer tip and a cooled cavity tip. Each tip has ten coolant holes with the same diameter. The uncooled cavity tip produces the smallest loss among all uncooled tips. On the cooled flat tip, the coolant is injected normally into the tip gap and mixes directly with flow inside the tip gap. The momentum exchange between the coolant and the flow that enters the tip gap creates significant blockage. As the coolant mass flow ratio increases, the tip leakage loss of the cooled flat tip first decreases and then increases. For the cooled cavity tip, the blockage effect of the coolant is not as big as that on the cooled flat tip. This is because after the coolant exits the coolant holes, it mixes with flow in the cavity first and then mixes with tip flow in the tip gap. The tip leakage loss of the cooled cavity tip increases as the coolant mass flow ratio increase. As a result, at a tip gap of 1.6% of the chord, the cooled cavity tip gives the lowest loss. At the smallest tip gap of 1% of the chord, the cooled flat tip produces less loss than the cooled cavity tip when the coolant mass flow ratios larger than 0.23%. This is because with the same coolant mass flow ratio, a proportionally larger blockage is created at the smallest tip gap. At the largest tip gap of 2.2% of the chord, the cavity tip achieves the best aerodynamic performance. This is because the effect of the coolant is reduced and the benefits of the cavity tip geometry dominate. At a coolant mass flow ratio of 0.55%, the cooled flat tips produce a lower loss than the cavity tip at tip gaps less than 1.3% of the chord. The cooled cavity tip produces the least loss for tip gaps larger than 1.3% of the chord. The cooled suction side squealer has the worst aerodynamic performance for all tip gaps studied.
Transonic Turbine Blade Tip Aerothermal Performance With Different Tip Gaps—Part I: Tip Heat Transfer
Authors: Zhang Q. , O’Dowd D. O. , He L. , Oldfield M. L. G. , Ligrani P. M.
Published: April 2011

A closely combined experimental and computational fluid dynamics (CFD) study on a transonic blade tip aerothermal performance at engine representative Mach and Reynolds numbers (Mexit=1,Reexit=1.27×106) is presented here and its companion paper (Part II). The present paper considers surface heat-transfer distributions on tip surfaces and on suction and pressure-side surfaces (near-tip region). Spatially resolved surface heat-transfer data are measured using infrared thermography and transient techniques within the Oxford University high speed linear cascade research facility. The Rolls-Royce PLC HYDRA suite is employed for numerical predictions for the same tip configuration and flow conditions. The CFD results are generally in good agreement with experimental data and show that the flow over a large portion of the blade tip is supersonic for all three tip gaps investigated. Mach numbers within the tip gap become lower as the tip gap decreases. For the flow regions near the leading edge of the tip gap, surface Nusselt numbers decrease as the tip gap decreases. Opposite trends are observed for the trailing edge region. Several “hot spot” features on blade tip surfaces are attributed to enhanced turbulence thermal diffusion in local regions. Other surface heat-transfer variations are attributed to flow variations induced by shock waves. Flow structure and surface heat-transfer variations are also investigated numerically when a moving casing is present. The inclusion of moving casing leads to notable changes to flow structural characteristics and associated surface heat-transfer variations. However, significant portions of the tip leakage flow remain transonic with clearly identifiable shock wave structures.
How to fragment a polypeptide? An ab initio computational study of pair interactions between amino acids and ligand-amino acids in proteins
Authors: Klusák Vojtěch , Dobeš Petr , Černý Jiří , Vondrášek Jiří
Published: April 2011

To determine reasonably which amino acid side chain contributes significantly to the stability of a protein or to the stability of a protein–ligand complex is not a straightforward task. We suggest a partial but systematic solution of the problem by a specific fragmentation of a protein chain into blocks of single amino acid side chains with their corresponding backbone part. For such systems of building blocks, we have calculated the stabilisation/interaction energies by means of correlated ab initio calculations. We have shown that a reasonable way to treat an amino-acid residue composing the protein is to break the homonuclear C–C bond between the Cα atom and the C(O) carboxyl carbon. The reference data obtained by the RI-MP2 method with the cc-pVDZ basis set were compared with RIDFT, RIDFT augmented by the dispersion term, SCC-DFTB-D and Hartree–Fock calculations. The results clearly show the failure of those methods lacking an appropriate treatment of the correlation energy. The DFT methods augmented by the empirical dispersion term on the other hand describe the interaction in good agreement with the reference method.
FLUID STRUCTURE INTERACTION AND ADMITTANCE BOUNDARY CONDITIONS: SETUP OF AN ANALYTICAL EXAMPLE
Authors: MARBURG STEFFEN , ANDERSSOHN ROBERT
Published: April 2011

Often, acoustic simulation techniques suffer from errors of the computational model and its parameters. Quantification of the boundary condition is a crucial point for simulations. In particular, the boundary admittance is often unknown and hard to quantify. This article demonstrates how to reduce a fluid-structure interaction model to a pure fluid model with local or nonlocal admittance boundary conditions. Starting point is a BEM formulation for the fluid and a FEM formulation for the structure. An admittance matrix is derived from this formulation. Then, the multidimensional BEM–FEM formulation is adjusted to a one-dimensional example, a duct with structural elements at both ends. Two configurations are investigated, one with local admittance boundary conditions and one with nonlocal admittance boundary conditions which result in a diagonal and in a fully populated admittance matrix, respectively.
COMPUTATIONAL ACOUSTICS IN MULTI-FIELD PROBLEMS
Authors: KALTENBACHER MANFRED
Published: April 2011

We present physical/mathematical models base on partial differential equations (PDEs) and efficient numerical simulation schemes based on the Finite Element (FE) method for multi-field problems, where the acoustic field is the field of main interest. Acoustics, the theory of sound, is an emerging scientific field including disciplines from physics over engineering to medical science. We concentrate on the following three topics: vibro-acoustics, aero-acoustics and high intensity focused ultrasound. For each topic, we discuss the physical/mathematical modeling, efficient numerical schemes and provide practical applications.
INVERSE DYNAMICS OF THE LOWER EXTREMITIES: NOVEL APPROACH CONSIDERING TALOCRURAL AND SUBTALAR JOINT AXIS
Authors: RUPP TILLE KAROLINE , SCHMITT SYN
Published: April 2011

A recent survey of epidemiological studies lists ankle injuries as one common sport injury. However, the details of the injury mechanisms of ankle sprains — the majority of ankle injuries — remain not well understood.

The purpose of the presented study is twofold. The first aim is to introduce a new, widely applicable method to calculate ankle joint torques during movement using inverse dynamics. The subtalar and talocrural joint are modeled as anatomically based revolute joints. The kinematics of the lower extremities and ground reaction force are used as input data. Second, a comparison of two calculation approaches (dynamic versus static) is reported, aimed at verifying and simplifying the introduced method to have a more convenient tool at hand for applications in the field. For one first movement measurement (hopping), the calculated joint torques show a good match for the two calculation approaches.

After further application, the evaluation of the resulting joint torques will provide further insights into the joint mechanics and can contribute to a better understanding of the respective injury mechanisms.

Hence, this approach is interesting for researchers to be used in order to understand ankle injuries and to determine the influence of landing grounds and shoes on ankle joint torques.
NANOSCALE FINFET SENSOR FOR DETERMINING THE BREAST CANCER TISSUES USING WAVELET COEFFICIENTS
Authors: RAMESH R. , MADHESWARAN M. , KANNAN K.
Published: April 2011

A noninvasive optical method for determining the optical properties of normal and cancerous breast tissues by interpolating wavelet approach using the characteristics of nanoscale FinFET sensor has been theoretically developed and presented in this paper. This novel approach classifies the normal and cancerous tissues of human breast by calculating the surface potential variations of nanoscale FinFET illuminated by laser source of different wavelengths. Using these surface potential variations, the optical properties of the tissues are determined. By using this method, the point-to-point variations in tissue composition and structural variations in healthy and diseased tissues could be identified. The results obtained are used to examine the performance of the device for its suitable use as a nanoscale sensor.
THE EFFECTS OF CHANGES IN STEP WIDTH ON PLANTAR FOOT PRESSURE PATTERNS OF YOUNG FEMALE SUBJECTS DURING WALKING
Authors: LEE SU-YA , CHOU CHEN-YU , HOU YI-YOU , WANG YU-LIN , YANG CHICH-HAUNG , GUO LAN-YUEN
Published: April 2011

The aim of this study was to investigate the foot plantar pressure distribution and the effect of different step width during walking. Methods: Nineteen female volunteers who aged 18~30 years old and with no history of lower extremity injury were considered. Subjects walked at a pre-determined set speed with varied step width (5 cm, 10 cm, and 20 cm) for three trials at each step width. This study used an in-sole plantar pressure measurement system to collect the peak pressure, maximum ground reaction force, pressure–time integral, and force–time integral data of eight different foot regions. Results: The data revealed that the peak plantar foot pressure on the medial arch increased with wider step width (p < 0.05). In contrast, maximum ground reaction force, peak plantar pressure, pressure–time integral, and force–time integral on the lateral arch and lateral side of the metatarsals decreased with wider step width (p < 0.05). Conclusion: The results of this study revealed that smaller step width during walking result in decreasing the pressure on the medial arch of the foot. It may have the relieving effect for clients with pes planus and it can be a reference for rehabilitation clinicians while treating the above-mentioned subjects.
Normal faulting on Sifnos and the South Cycladic Detachment System, Aegean Sea, Greece
Authors: Ring Uwe , Glodny Johannes , Will Thomas M. , Thomson Stuart
Published: April 2011

We constrain the timing and kinematics of normal faulting on Sifnos, Cyclades, Greece. Penetrative top-to-the-NE kinematic indicators associated with a shallow dipping foliation occur in the deepest tectonic unit (Greenschist Unit). Combined
P
–
T
analysis and Rb–Sr dating indicates that this deformation was under way by 29.4 ± 3.4 Ma at
P
–
T
conditions of
c
. 16 kbar and
c
. 550 °C, and continued to operate at least until 22.8 ± 0.2 Ma at
P
–
T
conditions of
c
. 8 kbar and
c
. 400 °C. The later top-to-the-south directed Sifnos Detachment developed at the top of the Greenschist Unit and cuts the top-to-the-NE structures. Zircon fission-track ages suggest that deformation on the Sifnos Detachment was largely terminated by about 13–10 Ma. Subsequent extension was accommodated by high-angle normal faults. Regionally the top-to-the-south detachment phase on Sifnos correlates with top-to-the-south extensional faulting on nearby Serifos, which started there at
c
. 15–13 Ma. Top-to-the-south extensional shearing on Ios to the SE commenced earlier at
c
. 19–18 Ma, suggesting that top-to-the-south extension propagated westward from Ios to Sifnos and Serifos, or that extension was partitioned into different top-to-the-south detachment systems that operated at different times. Collectively these top-to-the-south detachments are named here the South Cycladic Detachment System, which played a key role in the opening of the Cretan Sea forearc basin.
(Research Award of the Energy and Technology Division) (Photo)Electrochemistry in the Service of Solar Energy Conversion
Authors: Lévy-Clément Claude
Published: April 2011

The paper is a short summary of the lecture delivered for the 2011 Research Award of the Energy Technology Division. The main expertise field of my group is materials science and (photo)electrochemistry for energy conversion and storage. The motivations that oriented my research are described, spanning from photoelectrochemistry of single crystal semiconductors, p-n photoelectroelectrochemical cells for solar hydrogen generation, to the photoetching of semiconductors, electrochemical processing of silicon surface including porous silicon, electrodeposition of polycrystalline semiconductor thin films and monocrystalline nanowires and development of Eta (extremely thin absorber) solar cells.
(European Section Heinz Gerischer Award Presentation) Some Major Electrochemical Challenges Towards a Sustainable Energy Future
Authors: Tributsch Helmut
Published: April 2011

Most precise and challenging standards towards a sustainable energy future have been given by nature`s own energy system, which has shaped our climate and enabled higher life. It converts light into electrochemical energy, uses this energy to split water, and attaches hydrogen to carbon carrying molecules (carbon dioxide) for energy and chemicals. This contribution will analyse what we know about the basic mechanisms involved and what we still have to learn when following the energy strategy of evolution on a high technical level. Nature achieves photovoltaic energy conversion kinetically by simply allowing electron transfer only into one direction. Its function can be derived from the principle of least action. Binding of water to a catalyst is critical for water splitting and requires a coordination chemical mechanisms as well as feedback controlled self-organized electron transfer. Since efficient direct carbon dioxide reduction essentially failed a biomimetic electrochemical carbon dioxide fixation strategy is discussed.
Porous InP as Piezoelectric Component in Magneto-Electric Composite Sensors
Authors: Gerngross Mark-Daniel , Sprincean Veaceslav , Leisner Malte , Carstensen Jürgen , Föll Helmut , Tiginyanu Ion
Published: April 2011

We report on the fabrication of cheap piezoelectric porous InP templates by electrochemical etching and additional purely chemical post-etching and on the galvanic filling of the resulting nanopore array with Ni-Fe using a highly viscous electrolyte. The d14 component of porous InP is found to be around a stunning |60| pm/V. The deposited Ni-Fe shows a very narrow hysteresis loop with low coercive field strength (170 G) and very low remanence (0.005 emu).
(Invited) Functionalization and Behavior in Aqueous Media of Silicon Surfaces for Improved Biochemical Sensing
Authors: Chazalviel Jean-Noel , Allongue Philippe , Gouget-Laemmel Anne Chantal , Henry de Villeneuve Catherine , Moraillon Anne , Ozanam François
Published: April 2011

The silicon surface may be functionalized with organic groups through direct Si-C bonding, which provides the obtained surfaces with improved chemical stability and allows for the immobilization of probe molecules for the elaboration of sensors. We here review recent work done in our group, using carboxyl-terminated alkyl monolayers on model Si(111) surfaces as a benchmark to study in details further surface functionalization, then extending the processes to amorphous hydrogenated silicon and amorphous hydrogenated silicon/carbon alloys, which can be deposited in thin-film form on any substrate. By designing appropriate structures, fluorescence biochips were then obtained, with strongly improved performance in terms of sensitivity, stability and reliability.
(Invited) Recent Advances in Electrodeposition of Interfacial Buffer Layers in Chalcopyrite-Based Solar Cells
Authors: Chassaing Elisabeth , Naghavi Negar , Rocha Gabriel , Bockelee Valérie , Leite Enrique , Bouttemy Muriel , Vigneron Jacki , Etcheberry Arnaud , Lincot Daniel
Published: April 2011

Soft chemical processes such as screen printing, sol-gel, electrochemical or chemical bath-deposition, enable low cost and easily scalable processes for thin layer solar cells. For the CIGSe based solar cells, with the standard Mo/Cu(In,Ga)Se2/CdS/i-ZnO/n+-ZnO structure, all layers of the p-n heterojunction and the transparent conductive oxide window can be grown by aqueous solution processes. Based on our previous work and the literature it was shown that cells with electrodeposited Cu(In,Ga)(S,Se)2-based absorbers can present conversion efficiencies up to 13.8 %. When ZnO:Cl window layer is deposited by electrodeposition with a coevaporated CIGS-based absorber, efficiency above 15% can be reached. In this work we will mainly focus on the application of this soft deposition technique for the preparation of the buffer layer. Electrochemical investigation of In-S layers is carried out. XPS analysis show the presence of both S and O. Conversion efficiencies of complete devices up to 9.5 % are obtained.
Electrochemical and Chemical Behavior of InSb Surfaces
Authors: Aureau Damien , Chaghi Radhouane , Etcheberry Arnaud
Published: April 2011

This manuscript presents the issues associated with the surface chemistry of a low band gap III-V semiconductor, the indium antimony InSb. The composition and the quantity of surface oxide obtained by electrochemical or electroless processes are especially discussed. XPS data suggest that mixed oxide of various morphology are obtained when the etching is driven by di-halogen etchants compared to the Sb-rich oxides obtained by anodic oxidation in acidic media.
Electromigration Characteristics for Electron Down-Flow in Copper Interconnects
Authors: Cheng Yi-Lung , Chang Wei-Yuan , Wang Ying-Lang
Published: April 2011

In this study, electron down-flow electromigration (EM) behavior of Copper (Cu) interconnects was characterized in terms of the line width and the via number. For a single-via structure, slit-like voiding underneath the via and line-depletion modes were observed. The slit-like voiding mode is a fatal EM failure for the narrow and wide Cu lines with a single-via structure due to a relatively short lifetime. This failure mode can be eliminated by optimizing via clean process or increasing redundant via. The line-depletion can be further distinguished two kinds of failure modes in terms of the voiding location and shows the different line width dependence EM behaviors. For line-depletion failure mode with voiding location away from via, the EM failure time increases with increasing the metal width. On the other hand, the failure times are similar in the wide and narrow metal lines for line-depletion mode with voiding location originating from the edge of the via.
3D MOSCAP Vehicle for Electrical Characterization of Sidewall Dielectrics for 3D Monolithic Integration
Authors: Wood Bingxi , McDougall Brendan , Chan Osbert , Dent Alan , Ni Chi-Nung , Hung Raymond , Chen Hao , Xu Ping , Nguyen Phong , Okazaki Motoya , Mao Daxin , Xu Xumou , Ramiraz Ricardo , Cai Man-Ping , Jin Miao , Lee Won , Noori Atif , Shek Meiyee , Chang Chorng-Ping
Published: April 2011

We have developed 3D MOSCAP to characterize sidewall dielectric electrical performance to help gauge quality and reliability of non-planar devices, such as FinFETs. The 3D MOSCAP can be used for process and materials development for high K metal gate, spacer, and liner applications for 3D monolithic integration for future generation devices. In comparison, traditional 2D (planar) MOSCAP is for characterization of dielectrics in the horizontal plane only. This study used different oxides as examples to compare sidewall dielectric quality and electrical performance, and compare with that of oxide on horizontal surface. Data analysis methodology is developed and demonstrated to extract sidewall dielectric properties from measured electrical results.
High Rate Copper Isotropic Wet Chemical Etching
Authors: Mayer Steven T.
Published: April 2011

A high-rate copper isotropic wet-etching process has been developed. The process is found to be surface-kinetic controlled, so the etching rate within the isolated feature does not increase upon removal of all metal from the field, as well as remains flat and uniform across individual feature and across an array of features, independent of feature size. Also discussed are some of the issues and means of implementing this low cost but inherently-unstable peroxide/alkaline etching solution, as well as some general chemical-variant behavior trends of the amine based etching chemistry. Combining a straightforward, robust 300 mm spin-spray reactor design with optimized chemical formulations and process conditions enabled a tunable removal-profile that can be tailored to match the copper plating profile. Copper removal rates of >1.5 um/min, WIW removal-rate variability <1.5% (full range, 2 mm edge exclusion), post-etch mirror like-surfaces, reflectivity rates of change of < 2% per 5 um of removal, and a wafer to wafer rate and uniformity variability of less than 2% have been implemented.
(Invited) Band-Edge Effective Work Functions by Controlling HfO2/TiN Interfacial Composition for Gate-Last CMOS
Authors: Hinkle Christopher , Galatage Rohit , Chapman Richard , Vogel Eric , Alshareef H. N. , Freeman Clive , Wimmer Erich , Niimi Hiro , Li-Fatou Andrei , Chambers James , Shaw Judy
Published: April 2011

Effective work function (EWF) changes of TiN/HfO2 annealed at low temperatures in different ambient environments are correlated to the atomic concentration of oxygen, nitrogen, and aluminum at the metal/dielectric interface. Low EWFs (4.0 eV) are obtained by allowing aluminum to migrate to the TiN/HfO2 interface during a forming gas anneal. High EWFs (5.1 eV) are achieved with anneals that incorporate oxygen throughout the TiN with [O] = 2.8x1021 cm-3 near the TiN/HfO2 interface. First-principles calculations indicate the exchange of O and N atoms near the TiN/HfO2 interface cause the formation of dipoles that increase the EWF.
Formation of Ordered Silicon Nano-Textures Suitable for Field Emission Applications
Authors: Malekpour Hoda , Mehran Mahdieh , Mohajerzadeh Shamsoddin
Published: April 2011

We report on the use of silicon nano-grass and nano-textured structures for the field emission applications. A triode device, which can be used as a field emission transistor with gate, emitter (cathode) and a collector (anode), has been realized. Anode in this structure is a silicon substrate placed opposite to the silicon grass tips acting as the emitter. The silicon nano grass formation is based on the hydrogen assisted reactive ion etching process where a mixture of O2/H2 and SF6 gases are used in a sequential manner. The results of electrical measurements for this investigation show a sharp rise in the emission current.
The Physics of Nanonet Fabrics and Its Applications in Electronic, Opto-electronic, Biosensing, Energy Storage, and MEMS Devices and Systems
Authors: Alam Muhammad Ashraful
Published: April 2011

Flexible electronics provides new opportunities to broaden the range of applications of electronic components in addressing the grand challenges of energy, health care, sensing, and display technologies. While there have been considerable progress in this area based on advances of conducting polymers, newer approaches based on nanonet fabrics, transfer-printed thin films, and flexible interconnects may potentially offer higher performance and more reliable alternatives. In this article, we discuss the electrical, optical, biosensing, and energy storage potential of nanonet fabrics. Our analysis shows that an entirely new conceptual framework that combines classical techniques with nonlinear percolation model, fractal geometry of surfaces, and stochastic transport models is necessary to design and optimize systems based on nanonet technology. The key ideas turn out to elegantly simple generalization of standard textbook approaches and once these techniques are understood, the design of nanonet components becomes no more difficult than those based on classical bulk devices.
Nano-Scale Strain-Induced Giant Pseudo-Magnetic Fields and Charging Effects in CVD-Grown Graphene on Copper
Authors: Yeh Nai-Chang , Teague Marcus L. , Wu Renee T. , Yeom Sinchul , Standley Brian , Boyd David , Bockrath Marc W.
Published: April 2011

Scanning tunneling microscopic and spectroscopic (STM/STS) studies of graphene grown by chemical vapor deposition (CVD) on copper reveal that the monolayer carbon structures remaining on copper are strongly strained and rippled, with different regions exhibiting different lattice structures and local electronic density of states (LDOS). The large and non-uniform strain induces pseudo-magnetic field up to ∼ 50 Tesla, as manifested by the integer and fractional pseudo-magnetic field quantum Hall effects (IQHE and FQHE) in the LDOS of graphene. Additionally, ridges appear along the boundaries of different lattice structures, which exhibit excess charging effects. For graphene transferred from copper to SiO2 substrates after the CVD growth, the average strain and the corresponding charging effects and pseudo-magnetic fields become much reduced. These findings suggest the feasibility of strain-engineering of graphene-based nano-electronics.
An Investigation of the Geometrical Effects on the Thermal Conductivity of Graphene Antidot Lattices
Authors: Karamitaheri Hossein , Pourfath Mahdi , Faez Rahim , Kosina Hans
Published: April 2011

In this work we investigate the thermal conductivity of graphene-based antidot lattices. A third nearest-neighbor tight-binding model and a forth nearest-neighbor force constant model are employed to study the electronic and phononic band structures of graphene-based antidot lattices. Ballistic transport models are used to evaluate the electronic and the thermal conductivities. Methods to reduce the thermal conductivity and to increase the thermoelectric figure of merit of such structures are studied. Our results indicate that triangular antidot lattices have the smallest thermal conductivity due to longer boundaries and the smallest distance between the neighboring dots.
Large-Area Synthesis of Graphene by Chemical Vapor Deposition and Transfer-Free Fabrication of Field-Effect Transistors
Authors: Sato Shintaro , Yagi Katsunori , Kondo Daiyu , Hayashi Kenjiro , Yamada Ayaka , Harada Naoki , Yokoyama Naoki
Published: April 2011

Graphene was synthesized on SiO2/Si wafers as large as 200 mm in diameter by thermal chemical vapor deposition (CVD) using Fe or Cu films as catalyst, and top-gated field-effect transistors (FETs) were fabricated directly on the wafer using a graphene-transfer-free process. For transistor fabrication, graphene was synthesized on patterned Fe films. The iron was subsequently etched after both ends of the graphene were fixed by source and drain electrodes (Au/Ti), resulting in the graphene channels bridging the electrodes all over the wafer. Top-gated FETs were then formed after covering the channels with HfO2 by the atomic layer deposition (ALD) method. The fabricated transistors exhibit ambipolar behavior and can sustain a high-density current. Dependence of graphene growth on catalyst types and various growth parameters was also investigated.
Capacitance-Voltage and Interface State Density Characteristics of GaAs and In0.53Ga0.47As MOS Capacitors Incorporating a PECVD Si3N4 Dielectric
Authors: O'Connor Eamon , Djara Vladimir , Monaghan Scott , Hurley Paul , Cherkaoui Karim
Published: April 2011

Si3N4 films were simultaneously deposited on GaAs and In0.53Ga0.47As in a PECVD reactor to explore NH3 plasma exposure of both substrates without any subsequent ambient exposure prior to dielectric formation. For both GaAs and In0.53Ga0.47As MOS devices the interface defect density near midgap was significantly reduced due to NH3 plasma and post-metallisation forming gas annealing (FGA). A 10 second NH3 plasma combined with FGA resulted in a 50% reduction in the peak Dit for the near-midgap defect on GaAs, and a 66% reduction in Dit for the midgap defect on In0.53Ga0.47As. This comparable defect-response behaviour suggests that the defect observed at midgap for In0.53Ga0.47As is very similar in nature to the near-midgap defect in GaAs, and is potentially the same defect. This would indicate that the influence of Ga or As-related defect states are predominant compared to In-related defect states for the midgap defect response typically observed for In0.53Ga0.47As devices
Atomic Layer Deposition of Al-Doped ZrO2 Thin Films for Advanced Gate Stack on III-V Substrates
Authors: Lamagna Luca , Molle Alessandro , Wiemer Claudia , Spiga Sabina , Grazianetti Carlo , Fanciulli Marco
Published: April 2011

We have investigated the atomic layer deposition (ALD) on III-V substrates (i.e., GaAs and In0.53Ga0.47As) of Al-doped ZrO2 (Al-ZrO2) films. The aim is to benefit from TMA-based chemistry as adopted in the ALD of Al2O3 and to boost the dielectric constant of the stack. An in situ monitoring of the process with spectroscopic ellipsometry was carried out in order to address the formation of the first few monolayers of the films. The correlation with the structural and chemical characterization provides insights about the interface composition upon ALD. The electrical performances of capacitors fabricated on In0.53Ga0.47As including Al-ZrO2 as gate dielectric exhibits encouraging properties compared to those acquired for Al2O3.
Recent Progress in Development and Manufacturing of SOFC at Topsoe Fuel Cell A/S and Riso̸ DTU
Authors: Christiansen Niels , Holm-Larsen Helge , Primdahl So̸ren , Wandel Marie , Ramousse Severine , Hagen Anke
Published: April 2011

The SOFC development at Topsoe Fuel Cell A/S (TOFC) and Riso̸ DTU is based on a R&D consortium which includes material development and manufacturing of materials, cells and stacks with metallic interconnects focussing on high electrochemical performance, durability and robustness. A significant effort is directed towards improvement of current generations as well as development of the next generation SOFC technology. The innovative concept of the next generation, aiming at improved reliability and robustness, is based on metal-supported cells and nano-structured electrodes with perspectives of several potential advantages over conventional Ni-YSZ anode supported cells. Recently, record-breaking results have been obtained on cell level as well as on stack level. The collaboration has the objective to effectively transfer scientific results to industrial technology up-scaling and application. TOFC is engaged in development and demonstration of stack assemblies, multi-stack modules and PowerCore units that integrate stack modules with hot fuel processing units.
Metal Supported Solid Oxide Fuel Cells and Stacks for Auxilary Power Units - Progress, Challenges and Lessons Learned
Authors: Ansar Asif , Szabo Patric , Arnold Johannes , Ilhan Zeynep , Soysal Dennis , Costa Rémi , Zagst Armin , Gindrat Malko , Franco Thomas
Published: April 2011

The current paper reports the details of challenges and progress in the joint project on development of metal supported solid oxide fuel cells and stacks by the teams of German Aerospace Center (DLR), ElringKlinger, Sulzer Metco and Plansee. An account of the materials is given followed by the advances in the processing techniques which include alternative plasma spraying and colloidal spraying. Improvement in the cell and stack design is then discussed followed by challenges faced during stack building and operations and solution implemented.
Universal SOFC Module for Rapid Start-Ups
Authors: Bossel Ulf
Published: April 2011

The compact SOFC module characterized by its rapid start-up capability has been further improved. An optimized afterburner with catalytic ignition has been added, as well as innovative heat exchangers for fuel-exhaust-to-fuel and air-exhaust-to-air. The current module can be run on hydrogen, as well as on reformate from hydrocarbon fuels or alcohols. The stack temperature can be raised to 700°C in less than five minutes by electric heaters placed in all bipolar plates. The heating power may be drawn from a battery which can be later recharged at times of low power demand. Only about 4 Wh of energy are needed per installed cell. As the nominal cell output is 10 Watts, start-up energy is recovered in about 24 minutes of operation. The complete and functional modules are packaged in sealed metal containers. The current 200 Watt demonstration module has a diameter of 100 mm (4 in) and is 100 mm (4 in) tall. The suspended stack of 20 planar cells of 60 mm x 60 mm size can deliver up to 200 Watts of DC power at around 800°C. However, the design of the module can be expanded to power levels of 1 kW or more.
Long-Term Operation of Planar Type SOFC Stacks
Authors: De Haart L.G.J. , Vinke I.C.
Published: April 2011

The feasibility of long-term operation of SOFC is demonstrated with a short-stack with 2 anode supported cells at 700 °C at constant current density of 0.5 A/cm² over 30,000 hours resulting in a degradation rate in the order of 8 mV/kh on average. Reduction of the degradation rate to about 4 mV/kh is shown to be possible by selecting alternative manufacturing methods as for instance atmospheric plasma spraying for the protective coating on interconnect steel.
Post-Test Characterization of an SOFC Short-Stack after 17,000 Hours of Steady Operation
Authors: Menzler N.H. , Batfalsky Peter , Groß Sonja , Shemet Vladimir , Tietz Frank
Published: April 2011

The characterization of operated SOFC stacks is one important possibility to i) develop novel materials, ii) to optimize cell microstructures, iii) to understand interactions during start-up, operation and shut-down, iv) to analyse unwanted interruptions or stack failure, v) to control manufacturing quality and vi) to characterize stack structural integrity with respect to the engineering drawings, manufacturing admeasurements and tolerances. In the past 10 years approximately 150 stacks were, after operation, carefully dissected, photographed, characterized and follow-up examinations from all stack components performed. This chapter deals with the description of the course of action and highlights various analyses, including the analytical methods, concerning different stack parts. Finally some conclusions based on the post-test characterization for ongoing R&D were presented.
Durability Tests of Flatten Tubular Segmented-in-Series Type SOFC Stacks for Intermediate Temperature Operation
Authors: Horiuchi Kenji , Nakamura Kazuo , Matsuzaki Yoshio , Yamashita Satoshi , Horita Teruhisa , Kishimoto Haruo , Yamaji Katsuhiko , Yokokawa Harumi
Published: April 2011

Durability tests of flatten tubular segmented-in-series type SOFC stacks for intermediate temperature operation have been carried out since FY 2008 in the NEDO project, "Development of system and elemental technology on SOFCs". A short bundle composed of four cell stacks fabricated in FY 2009 showed a degradation rate of 0.31 % during the last 1000 hour of a 4000 hour continuous test at rated current density of 0.24 A/cm2 in an electric furnace, while another deteriorated by about 0.01 %/cycle in 100 thermal cycles. Secondary ion mass spectroscopy, scanning electron microscope and Raman spectroscopy analyses of tested cell stacks indicated that fuel leakage reduction at the cell stack surface, Cr poisoning reduction in cathode and uniform and dense formation of cathode interlayer were important for their durability improvement. FY 2010 durability tests are now in progress.
Recent Development of Electrolyte Supported Cells with High Power Density
Authors: Trofimenko Nikolai , Kusnezoff Mihails , Michaelis Alexander
Published: April 2011

Development and progress in manufacturing of high power density electrolyte supported cell is presented. The maximum power density increased from 529 mW/cm2 for commercial cell (Fa. Kerafol) up to 973 mW/cm2 for novel IKTS cell at 0.7V@860°C and is comparable with the performance of anode-supported SOFC cells. The changes in polarization resistance of tested cells under different conditions are discussed on basis of analysis of impedance spectra.
Evaluation of ScSZ-Based Microtubular SOFCs under 3% Humidified CH4 Fuel Flow at Intermediate Temperature
Authors: Yamaguchi Toshiaki , Sammes Nigel
Published: April 2011

This report summarizes the feasibility studies on the fabrication and evaluation of a Sc2O3-doped zirconia (ScSZ)-based microtubular SOFC under 3 % humidified CH4 fuel flow at intermediate temperature, in addition to those under 3 % humidified H2 fuel flow. The cell was fabricated through co-sintering of a ScSZ electrolyte layer and a NiO-ScSZ anode support, and then a La0.6Sr0.4Co0.2Fe0.8O3-x-Ce0.9Gd0.1O1.95 cathode layer was coated on the electrolyte layer. Evaluation was conducted using a potentio/galvanostat and impedance analyzer under the humidified H2 and CH4 flows. The maximum power densities at 650 and 700 °C were 41.6 and 58.5 mW/cm2, respectively, under the CH4 gas flow. And the cell showed a good stability during one hour current loading test under 3 % humidified CH4 flow.
Imaging of Oxide Ionic Flows at Practical SOFC Cells by Isotope Labeling Technique
Authors: Horita Teruhisa , Shimonosono Taro , Kishimoto Haruo , Yamaji Katsuhiko , Brito Manuel E. , Yokokawa Harumi
Published: April 2011

Oxygen ionization and diffusion were visualized at the practical flatten tube SOFC stack/cells. Stable isotope oxygen (18O) was applied to label the motion of oxygen/oxide ions with secondary ion mass spectrometry (SIMS) analysis. Surface reactivity and diffusivity of oxygen (oxide ions) were compared between the fuel cell operating condition and non-current flow conditions. A peak of 18O-concentration was observed under fuel cell operating condition at the interlayer between cathode and electrolyte. This suggested that the active sites for 18O ionization and diffusion were at the interlayer. Also, a slow 18O diffusion layer can be formed at the interlayer/electrolyte interface because of the discontinuous 18O distribution profiles.
The Influence of Porous Support Morphology on the Electrochemical Performance of Solid Oxide Fuel Cells
Authors: Torabi Alireza , Hanifi Amir R. , Etsell Thomas H. , Sarkar Partha
Published: April 2011

The impact of porous support morphology on the electrochemical performance of symmetrical cathode cells was investigated. Controlling YSZ particle size, pore former content and sintering temperature, the total volume fraction of open porosity was identically kept in the range of 50-55% for all the cells. The influence of size, connectivity and distribution of the pores as well as the configuration of YSZ particles on the ohmic and polarization resistance of the cathode were studied using ac impedance spectroscopy. It was found that a calcined YSZ-based structure had the most uniform morphology. Low temperature sintered cells with an as received YSZ-based structure, however, exhibited the lowest polarization resistance. The significance of using calcined YSZ-based structures in practical development of porous YSZ supports is discussed.
Progress Toward Inkjet Deposition of Segmented-in-Series Solid-Oxide Fuel Cell Architectures
Authors: Faino Nicolaus , Rosensteel Wade , Gorman Brian , Sullivan Neal
Published: April 2011

This paper presents our progress in applying inkjet-printing technology in fabrication of solid-oxide fuel cells (SOFCs) in the segmented-in-series architecture. Cell materials include a nickel anode, yttria-stabilized zirconia electrolyte, strontium-doped lanthanum manganate cathode, and lanthanum-doped strontium titanate interconnect. Inks are formulated from commercially sourced powders, and printed onto porous, chemically inert, partially stabilized zirconia supports. Accurate registration of SOFC materials is observed at a feature size of approximately 100 μm. After high-temperature sintering, good adhesion between SOFC materials and the support is also evident.
Power Generating Property of Tubular SOFC Using DME as Fuel: Focus on Portable Device
Authors: Sato Katsutoshi , Tanaka Yohei , Momma Akihiko , Kato Ken , Negishi Akira , Kato Tohru
Published: April 2011

In this study, we investigated the possibility of constructing a portable SOFC system using DME as a fuel. It was clarified that DME have some suitable properties as a fuel for the portable device. Tubular SOFC was fabricated and measurements of cell performance with different condition were carried out. The fabricated cell obtained successfully 0.122 Wcm-2 as the maximum power density at 750ºC. The impedance spectra showed that the resistances for electrochemical reactions were dominant factor of voltage drops. Thus it was clarified that decreasing these activation overvoltages is most promising approach to improve power generation property of our fabricated cell.
Combined Theoretical and Experimental Studies of H2 and CO Oxidation over YSZ Surface
Authors: Gorski Alexandr , Yurkiv Vitaliy , Bessler Wolfgang G. , Volpp Hans-Robert
Published: April 2011

The mechanism of H2 and CO adsorption and oxidation on yttria-stabilized zirconia, frequently used as electrolyte in solid oxide fuel cell composite anodes, was investigated employing temperature-programmed spectroscopy (TPS) and density functional theory (DFT). In agreement with theory, the experimental results show that interaction of gaseous H2O with YSZ results in dissociative adsorption leading to strongly bound OH surface species. In the interaction of gaseous H2 with an oxygen-enriched YSZ surface (YSZ+O), similar OH surface species are formed as reaction intermediates in the H2 oxidation. In contrast, the interaction of CO with an oxygen-enriched YSZ leads to direct formation of gaseous CO2 via an Eley-Rideal type reaction that was also confirmed by TPS measurements.