bluuebunny/crossref_metadata_2025 huggingface dataset:
Takotsubo cardiomyopathy as a source of cardioembolic cerebral infarction
Authors: Kim Sun Moon , Aikat Shamik , Bailey Alison , White Matthew
Published: September 2012

Takotsubo cardiomyopathy is a stress-related cardiomyopathy that mimics acute myocardial infarction. However, it is frequently without obstructive coronary artery disease and is mainly seen in postmenopausal women after an emotional or physiological event. In rare cases, it favours the formation of intracardiac mural thrombus and subsequent cardioembolic events. We report a rare case where a patient developed a cerebral infarction as a cardioembolic sequela of takotsubo cardiomyopathy following the death of her beloved dog. The patient was successfully managed with anticoagulation where a repeat echocardiogram 4 months later showed resolution of the apical thrombus along with recovery of systolic function and left ventricle regional wall abnormalities. This case serves to increase awareness about the rare cardioembolic complications of takotsubo cardiomyopathy and emphasise the need for serial echocardiographic examinations and anticoagulation.
An uncommon presentation of ductal carcinoma in situ
Authors: Motindi Rodney , Mallon Peter , Dace Stephen
Published: September 2012

A 47-year-old woman presented with 6 weeks history of non-blood-stained nipple discharge. Two separate nipple cytology assessments revealed malignant cells despite normal clinical examination and radiological investigation (mammogram, ultrasound and MRI). The patient elected for a central segmentectomy which revealed a 1.8 cm area of high-grade comedo ductal carcinoma in situ in the subareolar region. The patient made a good postoperative recovery. 6 months follow-up revealed a 5 mm area of new calcification, core biopsy revealed atypical cells. After counselling, the patient elected for bilateral mastectomy which revealed fibrocystic tissue only.
Congenital pseudarthrosis of clavicle: illustrated operative technique and histological findings
Authors: Galanopoulos Ilias , Ashwood Neil , Garlapati Anand Kumar , Fogg Quentin
Published: September 2012

Congenital pseudarthrosis of the clavicle is a rare condition present at birth but often diagnosed later in childhood. Indications for surgical treatment include pain, deformity or neurovascular compromise. Reconstruction usually involves resection of the pseudarthrosis, placement of iliac crest bone graft or graft substitute and internal fixation. In this paper, we present a case of congenital pseudarthrosis of the clavicle in a 9-year-old boy who was treated with plate fixation and bone autograft. The majority of patients who undergo surgery because of cosmetic or functional problem heal well and proceed with a normal, unrestricted life. However, for those patients who are not bothered by the cosmetic appearance of the pseudarthrosis and are asymptomatic in that they are not functionally limited, non-surgical treatment is a viable option.
Parametric invariance and the Pioneer anomaly
Authors: Rañada Antonio F. , Tiemblo A.
Published: September 2012

It is usually assumed that the t parameter in the equations of dynamics can be identified with the indication of the pointer of a clock. Things are not so simple, however. In fact, because the equations of motion can be written in terms of t but also in terms of t′ = f(t), f being any well-behaved function, any one of those infinite parametric times t′ is as good as the newtonian one to study classical dynamics in hamiltonian form. Here we show that, as a consequence of parametric invariance, one of the foundations of classical dynamics, the relation between the mathematical parametric time t in the equations of dynamics and the physical dynamical time σ that is measured with a particular clock (which is itself a dynamical system) requires the characterization of the clock that is used to achieve a complete treatment of dynamical systems. These two kinds of time, therefore, must be carefully distinguished. Furthermore, we show that not all the dynamical clock-times are necessarily equivalent and that the observational fingerprint of this nonequivalence has, curiously, the same form as that of the Pioneer anomaly. This suggests, therefore, that an acceleration to one another of the astronomical and the atomic times, tastr and tatom, can contribute to the total amount of the anomaly.
Robust stabilization and H∞ control for discrete-time stochastic genetic regulatory networks with time delays
Authors: Mathiyalagan K. , Sakthivel R.
Published: September 2012

This paper presents some novel results on robust stabilization and H∞ control design for a class of uncertain discrete-time stochastic genetic regulatory networks (GRNs) with time-varying delays. The GRNs under consideration are subject to stochastic noise, time-varying, and norm bounded parameter uncertainties. By constructing a new Lyapunov–Krasovskii functional that contains some novel triple summation terms, we propose a state feedback gene controller to guarantee that the considered GRN is mean-square asymptotically stable about its equilibrium point for all admissible uncertainties. The other issue is to design a H∞ feedback gene controller so that the GRN is robustly stable with a prescribed H∞ disturbance attenuation level for all admissible uncertainties and for all delays to satisfy both the lower bound and upper bound of the interval time-varying delay. The obtained conditions are derived in terms of linear matrix inequalities (LMIs), which can be easily verified via the LMI toolbox. Finally, the control scheme has been implemented in a gene network model to illustrate the applicability and usefulness of the obtained results.
A treatment of the twin paradox based on the assumption of an instantaneous acceleration
Authors: Carvalho Marcelo
Published: September 2012

We investigate the twin paradox assuming the acceleration acts instantaneously on one of the twins and that its effect is just to revert the relative movement of the twins keeping the same relative speed. The relative motion of the twins is then split in two stages: one where they move away and another when they approach each other. Each stage is described by specific Lorentz transformations that obey certain boundary conditions related to the reversion of motion. We then show how the paradox arises from the particular form of the Lorentz transformation describing the approaching movement of the twins.
Investigation of spatial disorder in graphite by Raman lineshape analysis
Authors: Saxena Kapil , Kumar Vivek , Shukla A.K.
Published: September 2012

Disorder in graphite is studied as a function of phonon softening of Raman active modes. A comprehensive analysis of disorder is discussed here using the G and D modes of the graphite. Two-dimensional disorder is manifested in the correlation length of the sp2 hybridization in the graphitic plane. It is characterized here by lineshape analysis of Raman activated G and D modes. Phonon softening of the G mode is almost insensitive to disorder. It is more asymmetric on the lower energy side with increasing disorder. Phonon softening and line broadening of the D mode have high sensitivity to disorder in polycrystalline graphite. Electron–phonon coupling is responsible for phonon softening and line broadening of the D mode, which is double-resonant Raman scattering involving disorder, electron, and TO (tansverse optical) phonon. Increasing disorder allows TO phonons of higher wavevector and lower energy during double-resonant Raman scattering.
Growth of CuInSe2 thin films by a single-step electrodeposition technique using acetonitrile as complexing agent
Authors: Goswami Y.C. , Rajaram P
Published: September 2012

Thin films of CuInSe2 were grown on SnO2 coated glass microslides using a single-step electrodeposition technique. The bath was made up of a mixture of aqueous solutions of CuCl2, InCl3, and SeO2 with acetonitrile (CH3CN) acting as a complexing agent. Voltametric studies suggest that acetonitrile is a suitable complexing agent, which helps in bringing the deposition potentials of Cu, In, and Se close to each other. The films were characterized by EDAX, SIMS, X-ray diffraction, and optical studies, which show that the material is CuInSe2, with a direct band gap of about 1 eV. The films were annealed in a Se atmosphere to improve their crystalline properties. X-ray diffractograms show that the peaks of CuInSe2, which are broad and of low intensity for as-grown films, become sharp and intense after annealing in Se atmosphere. SIMS depth profiles show that the films have a fairly uniform composition along the depth of the films.
Artificially selected human sperm morphology after swim-up processing
Authors: Vladić Tomislav , Petersson Erik
Published: September 2012

The swim-up technique is a clinical practice used to select highly motile sperm cells from patient ejaculates to use in assisted fertilization. The aim of this study was to investigate whether the length of different sperm-cell components is related to gamete function. Thus, we explored whether swim-up technique selects for longer sperm cells than mean sperm cells from unprocessed ejaculates. Sperm midpiece, tail endpiece, and total length were measured before and after the swim-up selection by means of contrast-phase and electron microscopy. Correlations between sperm dimensions, sperm motility, and sperm concentration were also investigated. Swim-up selected cells with longer midpiece compared with the unprocessed fractions (5.8 μm (CI 5.52–6.16 μm) vs. 5.3 μm (CI 4.97–5.61 μm), p < 0.05) and shorter tail endpiece (7.8 μm (CI 7.11–8.44 μm) vs. 8.5 μm (CI 7.81–9.14 μm), p < 0.05 after meta-analysis), whereas no effect of swim-up selection was detected on the total sperm cell length. Individuals producing high sperm concentrations had longer sperm midpiece than had men producing lower sperm concentrations. It is concluded that short sperm flagellar tips with long midpieces may be used as biomarkers in infertility therapy.
Genetic and morphological differentiation of wolves (Canis lupus) and coyotes (Canis latrans) in northeastern Ontario
Authors: Wheeldon Tyler J. , Patterson Brent R.
Published: September 2012

Gray wolves ( Canis lupus L., 1758), eastern wolves ( Canis lycaon Schreber, 1775), and coyotes ( Canis latrans Say, 1823) are presently managed as a single biological population in primary wolf range in Ontario with the intent of minimizing incidental harvest of wolves. This management strategy is based on the assumption that wolves and coyotes cannot be reliably distinguished because of hybridization, and the resulting restrictions on coyote harvest are unpopular with hunters and farmers. We genetically and morphologically characterized a sample of sympatric wolves and coyotes harvested in the Lesser Clay Belt area of northeastern Ontario in 2006–2009 to test the hypothesis that these species cannot be reliably distinguished. We found that wolves and coyotes were genetically and morphologically distinct, with minimal hybridization between them. Our findings suggest that wolves and coyotes in the sampled area can be reliably distinguished, but further sampling is required to determine the full extent of areas in Ontario where wolves and coyotes are reliably distinguishable. We discuss unresolved issues regarding the feasibility of separate management for these species. We also discuss implications of our findings regarding wolf recovery in the northeastern United States.
Female Eastern Hog-nosed Snakes (Heterodon platirhinos) choose nest sites that produce offspring with phenotypes likely to improve fitness
Authors: Peet-Paré C.A. , Blouin-Demers G.
Published: September 2012

Nest-site selection is an important behaviour in oviparous reptiles because incubation conditions affect offspring phenotype, with favourable conditions leading to higher offspring fitness. We aimed to identify the habitat characteristics involved in nest-site selection in Eastern Hog-nosed Snakes ( Heterodon platirhinos Latreille, 1801) and to determine whether females select nest sites that result in offspring with phenotypes likely to improve fitness. We compared the habitat characteristics and temperature profiles of 21 nests with 21 randomly selected sites. Eastern Hog-nosed Snakes selected open, grassy sites with less herbs and shrubs than random sites, and nests were significantly warmer than random sites during the 2 years of the study. In the second year of the study, we incubated 215 eggs from eight nests in a split-clutch design at mean nest (24 °C) and random site (22 °C) temperatures approximating those of the first year of the study. Eggs incubated at 24 °C resulted in neonates that hatched earlier, had fewer scale anomalies, were larger, and swam faster than neonates from eggs incubated at 22 °C. Our results indicate that Eastern Hog-nosed Snakes select nest sites that lead to offspring with phenotypes likely to improve fitness.
Variation in catchment areas of Indiana bat (Myotis sodalis) hibernacula inferred from stable hydrogen (δ2H) isotope analysis
Authors: Britzke E.R. , Loeb S.C. , Romanek C.S. , Hobson K.A. , Vonhof M.J.
Published: September 2012

Understanding seasonal movements of bats is important for effective conservation efforts. Although female Indiana bats ( Myotis sodalis Miller and Allen, 1928) have been documented to migrate >500 km, knowledge of their migratory patterns is still extremely limited. We used the relationship between latitude and stable hydrogen isotope ratio in bat hair (δ2Hhair) to estimate the north–south extent of the summer range (catchment area) of bats hibernating in 14 Indiana bat hibernacula in eight states throughout its range. Range of δ2Hhair values varied substantially among hibernacula, suggesting large differences among sites in the north–south distance travelled by bats between summer and winter habitats. In particular, hibernacula in the southern portion of the range had greater catchment areas than those in the central and northern portions of the range. Variability in movement distances among sites was not associated with the number of hair samples analyzed or colony size. Significant year-to-year variation (2007–2008 to 2008–2009) in the distribution of δ2Hhair for two sites in Tennessee was observed. Currently, hibernacula considered important for species conservation are largely determined by population size, but our results suggest that migratory diversity should also be considered.
NUCLEON SPIN IN QCD: OLD CRISIS AND NEW RESOLUTION
Authors: CHO Y. M. , GE MO-LIN , ZHANG PENGMING
Published: September 2012

We clarify the on-going confusion on the long-standing gauge invariance problem of the nucleon spin decomposition to the spin and angular momentum of quarks and gluons. We provide two gauge-invariant decompositions of nucleon spin which have different physical meanings, using the gauge independent Abelian decomposition. The first one is based on the assumption that all (binding and valence) gluons contribute to the nucleon spin, but the second one is based on the assumption that only the binding gluons (and the quarks) contribute to it.
A WAY OF THE MINIMAL MODIFICATION TO TRIBIMAXIMAL MIXING
Authors: KITABAYASHI TERUYUKI
Published: September 2012

The tribimaximal mixing describes the observed solar and atmospheric neutrino mixings; however, it predicts vanishing reactor neutrino mixing angle, which is inconsistent with the observed data. We show a way of minimally modifying the tribimaximal mixing by including charged lepton contributions.
MORE M-BRANES ON PRODUCT OF RICCI-FLAT MANIFOLDS
Authors: IVASHCHUK V. D.
Published: September 2012

Partially supersymmetric intersecting (non-marginal) composite M-brane solutions defined on the product of Ricci-flat manifolds M0 × M1 × ⋯ × Mn in D = 11 supergravity are considered and formulae for fractional numbers of unbroken supersymmetries are derived for the following configurations of branes: M2 ∩ M2, M2 ∩ M5, M5 ∩ M5 and M2 ∩ M2 ∩ M2. Certain examples of partially supersymmetric configurations are presented.
Quantum Memory as a Perpetuum Mobile? Stability vs. Reversibility of Information Processing
Authors: Alicki Robert
Published: September 2012

It is argued using a Gedankenexperiment that a scalable quantum memory could be used as a perpetuum mobile of the second kind and hence cannot be realized in nature. The reasoning is based on the assumption that the Landauer's principle for measurements is a consequence of the second law of thermodynamics and not an independent postulate. This implies a modification of the Landauer's principle when applied for discrimination of equilibrium (metastable) states. While identification of the metastable state can be done at infinitesimally low cost, any change of such state involves dissipation of energy proportional to its stability factor.
Hausdorff Dimension and Nonlinear Relations Between Frequencies of Digits
Authors: Barreira Luis , Valls Claudia
Published: September 2012

For a class of sets defined in terms of frequencies of digits in some integer base m, we study their Hausdorff dimension. Our main aim is to consider nonlinear perturbations of the case when all frequencies are equal (and thus when the Hausdorff dimension is maximal). As a first step we consider the case when only one frequency is related to another, by the function x ↦ 1/m + εx + δx2, and for which the computations are already quite substantial. We show that the Hausdorff dimension is analytic in the parameters ε and δ, and we estimate the asymptotic behavior of the Taylor coefficients of the dimension in terms of m.
Born's Rule from Measurements of Classical Random Signals under the Assumption of Ergodicity at the Subquantum Time Scale
Authors: Khrennikov Andrei
Published: September 2012

The very old problem of the statistical content of quantum mechanics is studied in a novel framework. We show that quantum mechanics (QM) can be considered as a measurement model of prequantum classical statistical field theory (PCSFT): a pure field theory reproducing quantum correlations. We present a measurement scheme for classical signals which reproduces the basic rule of QM, the Born's rule. This is the scheme of threshold type detection. Calibration of detectors plays a crucial role. The size of the detection threshold is determined by the mean energy of a prequantum signal. QM is interpreted as theory of measurements of classical random signals with threshold type detectors which are calibrated in a proper way. The essence of this paper is the creation of a rigorous mathematical model of threshold detection of classical (ergodic) stochastic processes.
Large Deviation Strategy for Inverse Problem I
Authors: Ojima Izumi , Okamura Kazuya
Published: September 2012

Taken traditionally as a no-go theorem against the theoretical organization of inductive processes, Duhem-Quine thesis may interfere with the essence of statistical inference. This difficulty can be resolved by "Micro-Macro duality" [9, 10] which clarifies the importance of specifying the pertinent aspects and accuracy relevant to concrete contexts of scientific discussions and which ensures the matching between what is to be described and what to describe in the form of the validity of duality relations. This consolidates the foundations of the inverse problem, induction method, and statistical inference crucial for the sound relations between theory and experiments. To achieve the purpose, we propose here the large deviation strategy (LDS for short) on the basis of Micro-Macro duality, quadrality scheme, and large deviation principle. In reference to the quadrality scheme consisting of dynamics, algebra of observables together with its states and universal notion of classifying space, LDS will be seen to consist of the corresponding four levels; we discuss in detail its first and second levels, respectively, in this paper and the succeeding one, aiming at establishing statistical inference concerning observables.
GEOMETRIC PHASES, SQUEEZED QUANTUM STATES AND GAUSSIAN WAVE PACKET STATES OF RELIC GRAVITONS
Authors: BAKKE K. , PEDROSA I. A. , FURTADO C.
Published: September 2012

In this contribution, we discuss quantum effects on relic gravitons described by the Friedmann-Robertson-Walker (FRW) spacetime background by reducing the problem to that of a generalized time-dependent harmonic oscillator, and find the corresponding Schrödinger states with the help of the dynamical invariant method. Then, by considering a quadratic time-dependent invariant operator, we show that we can obtain the geometric phases and squeezed quantum states for this system. Furthermore, we also show that we can construct Gaussian wave packet states by considering a linear time-dependent invariant operator. In both cases, we also discuss the uncertainty product for each mode of the quantized field.
HIGH RESOLUTION SPECTROPOLARIMETRY OF THE SOLAR TWINS
Authors: DUARTE THARCISYO , DO NASCIMENTO J. D.
Published: September 2012

The study of solar twins offers a unique opportunity to investigating the solar magnetic field over longer timescales. Supported by the new generation of stellar spectropolarimeters (ESPaDOnS@CFHT, NARVAL@TBL), we are able to measure the large-scale magnetic field solar twins. Studying the behavior of solar magnetic field, we are able to learn about the mechanisms of magnetic field generation in the dynamo process. Besides convection, various physical parameters affect the dynamo operation, in particular the rotation and mass. We collected signature of the stellar large-scale magnetic field for solar twins and we present here a analysis of seven candidates.
RASTALL COSMOLOGY
Authors: FABRIS JÚLIO C. , PIATTELLA OLIVER F. , RODRIGUES DAVI C. , BATISTA CARLOS E. M. , DAOUDA MAHAMADOU H.
Published: September 2012

We review the difficulties of the generalized Chaplygin gas model to fit observational data, due to the tension between background and perturbative tests. We argue that such issues may be circumvented by means of a self-interacting scalar field representation of the model. However, this proposal seems to be successful only if the self-interacting scalar field has a non-canonical form. The latter can be implemented in Rastall's theory of gravity, which is based on a modification of the usual matter conservation law. We show that, besides its application to the generalized Chaplygin gas model, other cosmological models based on Rastall's theory have many interesting and unexpected new features.
SIMILARITIES OF SGRs WITH LOW MAGNETIC FIELD AND WHITE DWARF PULSARS
Authors: COELHO J. G. , MALHEIRO M.
Published: September 2012

Some of the most interesting types of astrophysical objects that have been intensively studied in the recent years are the Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) seen usually as neutron stars pulsars with super strong magnetic fields. However, in the last two years two SGRs with low magnetic fields have been detected. Moreover, fast and very magnetic white dwarf pulsars have also been observed in the last years. Based on these new pulsar discoveries, white dwarf pulsars have been proposed as an alternative explanation to the observational features of SGRs and AXPs. Here we present several properties of these SGRs/AXPs as WD pulsar, in particular the surface magnetic field and the magnetic dipole momentum.
LANDAU QUANTIZATION FOR A NEUTRAL PARTICLE IN THE PRESENCE OF TOPOLOGICAL DEFECTS
Authors: RIBEIRO L. R. , BAKKE K. , FURTADO C.
Published: September 2012

In this short communication, we study the Landau levels in the non-relativistic quantum dynamics of a neutral particle which possesses a permanent magnetic dipole moment interacting with an external electric field in curved spacetime background with the presence or absence of a torsion field. We show that the presence of the topological defect breaks the infinite degeneracy of the Landau levels.
WIGHTMAN FUNCTIONS IN DE SITTER AND ANTI-DE SITTER SPACETIMES IN THE PRESENCE OF COSMIC STRINGS
Authors: BEZERRA DE MELLO EUGÊNIO R.
Published: September 2012

In this paper we evaluate the Wightman functions associated with a massive quantum scalar field in de Sitter and anti-de Sitter spacetimes in the presence of a cosmic string. Having these functions we calculate the corresponding renormalized vacuum expectation values of the field squared and present the behavior of the contributions induced by the cosmic string as function of the proper distance to it for different values of the parameter which codify the presence of this linear topological defect.
A COMPARATIVE STUDY OF NON-GAUSSIANITY IN ILC–7YR CMB MAP
Authors: CARDONA WILMAR A. , BERNUI ARMANDO , REBOUÇAS MARCELO J.
Published: September 2012

A detection or non detection of primordial non–Gaussianity (NG) by using the cosmic microwave background radiation (CMB) is a possible way to break the degeneracy of early universe models. Since a single statistical estimator hardly can be sensitive to all possible forms of NG which may be present in the data, it is important to use different statistical estimators to study NG in CMB. Recently, two new large-angle NG indicators based on skewness and kurtosis of spherical caps or spherical cells of CMB sky have been proposed and used in both CMB data and simulated maps. Here, we make a comparative study of these two different procedures by examining the NG in the WMAP seven years ILC map. We show that the spherical cells procedure detects a higher level of NG than that obtained by the method with overlapping spherical caps.
QUANTUM EFFECTS IN HIGHER-DIMENSIONAL COSMOLOGICAL MODELS
Authors: SAHARIAN ARAM A.
Published: September 2012

Vacuum energy density and stresses are investigated for a scalar field in de Sitter spacetime with an arbitrary number of toroidally compactified spatial dimensions and in anti-de Sitter spacetime with two parallel branes. On the branes the field obeys the Robin boundary conditions. The behavior of the vacuum expectation values is discussed in various asymptotic regions of the parameters. Applications are given to Randall-Sundrum type braneworlds.
WHAT ROLE DOES CONVECTION PLAY IN THE SYNCHRONIZATION AND CIRCULARIZATION OF BINARIES WITH EVOLVED COMPONENTS?
Authors: SIMÕES F. , DO NASCIMENTO J. D.
Published: September 2012

Binary stars are important for understanding stellar structure and evolution. Binary systems with an evolved component give us an important constraint about the role played by convection on the characteristic time for tidal synchronization and circularization. On this study, we discuss about the role of convection in binary stars with evolved components. Base on a stellar sample composed by 260 binary stars with surface convective mass determined from evolutionary models computed with the Toulouse-Geneva Evolution Code (TGEC) as in do Nascimento et al. (2009). The stars with different convective deepening are represented in the Hertzsprung-Russell diagram (HR diagram). We are focused on the important question of how convection influence the evolution of the tidal synchronization and circularization of binary systems with an evolved component.
PRODUCTION OF THERMAL PHOTONS IN A SIMPLE CHIRAL-HYDRODYNAMIC MODEL
Authors: PERALTA-RAMOS J. , NAKWACKI M. S.
Published: September 2012

We use a self-consistent chiral-hydrodynamic formalism which combines the linear σ model with second-order hydrodynamics in 2 + 1 dimensions to compute the spectrum of thermal photons produced in Au+Au collisions at [Formula: see text]. The temperature-dependent shear viscosity of the model, η, is calculated from the linearized Boltzmann equation. We compare the results obtained in the chiral-hydrodynamic model to those obtained in the second-order theory with a Lattice QCD equation of state and a temperature-independent value of η/s. We find that the thermal photon production is significantly larger in the latter model due to a slower evolution and larger dissipative effects.
Film Thickness Dependence of Ferroelectric Properties of (111)-Oriented Epitaxial Bi(Mg1/2Ti1/2)O3 Films
Authors: Oikawa Takahiro , Yasui Shintaro , Watanabe Takayuki , Yabuta Hisato , Ehara Yoshitaka , Fukui Tetsuro , Funakubo Hiroshi
Published: September 2012

The origin of the ferroelectricity of Bi(Mg1/2Ti1/2)O3 films was investigated. Epitaxial Bi(Mg1/2Ti1/2)O3 films with film thicknesses of 50 to 800 nm were grown on (111)cSrRuO3/(111)SrTiO3 substrates by pulsed laser deposition. A Bi(Mg1/2Ti1/2)O3 film was not strongly clamped from the substrate and identified to have rhombohedral symmetry with a = 0.398 nm and α= 89.8°, which was independent of film thickness within 100 to 800 nm. The relative dielectric constant, remanent polarization, and coercive field of the Bi(Mg1/2Ti1/2)O3 films at room temperature were almost constant at about 250, 60 µC/cm2, and 240 kV/cm, respectively, for film thicknesses above 200 nm. These data suggest that Bi(Mg1/2Ti1/2)O3 films are ferroelectric.
Electric Properties and Interface Charge Trap Density of Ferroelectric Gate Thin Film Transistor Using (Bi,La)4Ti3O12/Pb(Zr,Ti)O3 Stacked Gate Insulator
Authors: Thanh Pham Van , Trinh Bui Nguyen Quoc , Miyasako Takaaki , Tue Phan Trong , Tokumitsu Eisuke , Shimoda Tatsuya
Published: September 2012

We successfully fabricated ferroelectric gate thin film transistors (FGTs) using solution-processed (Bi,La)4Ti3O12 (BLT)/Pb(Zr,Ti)O3 (PZT) stacked films and an indium–tin oxide (ITO) film as ferroelectric gate insulators and an oxide channel, respectively. The typical n-type channel transistors were obtained with the counterclockwise hysteresis loop due to the ferroelectric property of the BLT/PZT stacked gate insulators. These FGTs exhibited good device performance characteristics, such as a high ON/OFF ratio of 106, a large memory window of 1.7–3.1 V, and a large ON current of 0.5–2.5 mA. In order to investigate interface charge trapping for these devices, we applied the conductance method to MFS capacitors, i.e., Pt/ITO/BLT/PZT/Pt capacitors. As a result, the interface charge trap density (D
it) between the ITO and BLT/PZT stacked films was estimated to be in the range of 10-11–10-12 eV-1 cm-2. The small D
it value suggested that good interfaces were achieved.
The Orientation and Grain Texture Effect on Life Time Reliability of Sol–Gel Derived PbZr0.52Ti0.48O3 Films
Authors: Doi Toshihiro , Noguchi Takashi , Fuji Jun , Soyama Nobuyuki , Sakurai Hideaki
Published: September 2012

We fabricated Pb(Zr,Ti)O3 (PZT) films with different orientations and grain textures by the sol–gel method. The fabricated films were tested using the high accelerated lifetime testing system. As a result, films with coarse grain texture exhibited longer lifetimes and a higher acceleration factor than those with fine-grained texture. The film orientation did not affect the mean time to failure of the film. This suggests that breaking phenomena are strongly dependent on the number of grain boundaries.
Characterization of 57Fe-Enriched BiFeO3 Thin Films by Mössbauer Spectroscopy
Authors: Tanaka Kiyotaka , Tsukamoto Yoshinori , Hayakawa Kazuo , Yoshida Yutaka
Published: September 2012

57Fe-enriched BiFeO3 (BFO) thin films were fabricated on Pt/Ti/SiO2/Si substrates from a stoichiometric precursor solution by chemical solution deposition process. The Bi/Fe molar ratio of the BFO thin films was about 0.93. The crystallinity and surface morphology of the BFO thin films were improved by using a single-sintering technique. Mössbauer spectra of the BFO thin films were measured at room temperature, and the valence state of Fe ions was confirmed to be Fe3+ only. One of the BFO thin films fabricated by single-sintering at 550 °C showed a relatively saturated P–E hysteresis loop. The remanent polarization P
r and the coercive field E
c at 10 kHz were 59 µC/cm2 and 327 kV/cm, respectively, at room temperature.
Nanostructure Control of Barium Titanate–Potassium Niobate Nanocomplex Ceramics and Their Enhanced Ferroelectric Properties
Authors: Wada Satoshi , Yamashita Kenta , Fujii Ichiro , Nakashima Kouichi , Kumada Nobuhiro , Moriyoshi Chikako , Kuroiwa Yoshihiro , Fujikawa Yoshinori , Tanaka Daisuke , Furukawa Masahito
Published: September 2012

Barium titanate (BaTiO3,BT)–potassium niobate (KNbO3,KN) nanocomplex ceramics with various KN/BT molar ratios were prepared by a solvothermal method. From a transmission electron microscopy (TEM) observation, it was confirmed that the KN layer thickness on BT particles was controlled from 5 to 40 nm by controlling KN/BT molar ratios. Their dielectric constants were measured at room temperature and 1 MHz, and the maximum dielectric constant of 370 was measured for the BT–KN nanocomplex ceramics with a KN thickness of 22 nm. TEM observation revealed that at a KN thickness below 22 nm, the BT/KN heteroepitaxial interface was assigned as a strained interface, while at 40 nm, the interface was assigned as a relaxed one. These results suggested that the strained heteroepitaxial interface could be responsible for the enhanced dielectric properties.
Effect of Vanadium Addition on Reliability and Microstructure of BaTiO3-Based Multilayer Ceramic Capacitors
Authors: Natsui Hidesada , Shibahara Takeshi , Yonezawa Yu , Kido Osamu
Published: September 2012

The vanadium distribution in multilayer ceramic capacitors (MLCCs), sintered under a reducing atmosphere, was investigated using scanning transmission electron microscopy–electron energy loss spectroscopy (STEM–EELS), and insulation resistance degradation was analyzed using impedance spectroscopy in highly accelerated lifetime tests to clarify the effects of vanadium on both the electrical properties and microstructure of MLCCs. Vanadium mitigated insulation resistance degradation and increased the reliability of MLCCs. Moreover, vanadium content increased and insulation resistance at the ceramic/electrode interface decreased slowly. This change in dynamics directly resulted in an improved lifetime of MLCCs. The results of STEM–EELS analysis showed that vanadium distributed along the grain boundary and grain boundary junction, but substituted into BaTiO3 at the ceramic/electrode interface. Therefore, it is considered that vanadium substitution at the ceramic/electrode interface improves the reliability of MLCCs.
Elastic and Piezoelectric Properties of High-Quality Ferroelectric Bi4Ti3O12 Single Crystals
Authors: Kitanaka Yuuki , Noguchi Yuji , Miyayama Masaru , Kagawa Yutaka
Published: September 2012

Piezoelectric properties of ferroelectric Bi4Ti3O12 (BiT) single crystals have been investigated by a resonance–antiresonance method. Large and high-quality single crystals of BiT were obtained via top-seeded solution growth under a high oxygen pressure of 0.9 MPa. The elastic and piezoelectric constants in the (11), (12), (13), and (26) modes for BiT single crystals have been determined for the first time. It is shown that BiT has a large d
26 constant of 79 pC/N and a large k
26 factor of 40%, indicating that BiT is a promising ferroelectric material for application to shear-mode piezoelectric devices.
Polarization-Induced Photovoltaic Effects in Nd-Doped BiFeO3 Ferroelectric Thin Films
Authors: Ukai Yohei , Yamazaki Shuhei , Kawae Takeshi , Morimoto Akiharu
Published: September 2012

Nd-doped BiFeO3 (BNF) thin films were fabricated on SrRuO3 (SRO)-coated (100) Nb-doped SrTiO3 substrates by pulsed laser deposition, and nondoped BiFeO3 (BFO) thin films were also fabricated similarly for comparison. Then, Nd-doping effects on ferroelectric and photovoltaic properties were evaluated. Polarization-induced photovoltaic effects were observed in both the BFO and BNF solar cell structures with top and bottom electrodes under intense laser illumination. Using Au top electrodes, enhanced photovoltaic properties were observed in the BNF cell compared with the BFO cell. To improve the photovoltaic properties of the BNF cell, instead of the Au top electrodes, In–Sn–O (ITO) top electrodes were employed for the BNF cell. As a result, the photovoltaic properties were found to be markedly improved, resulting in an open circuit voltage of 0.81 V and a short circuit current density of 12.1 mA/cm2.
Microwave Dielectric Properties of LiF- and CaTiO3-Added MgO with Low Dielectric Loss and Near-Zero Temperature Coefficient of Resonant Frequency for Low-Temperature Cofired-Ceramic
Authors: Kan Akinori , Moriyama Tohru , Takahashi Susumu , Ogawa Hirotaka
Published: September 2012

The influences of LiF and CaTiO3 addition on the microwave dielectric properties of MgO ceramics were investigated in this study. The LiF was effective in reducing the sintering temperature of MgO without a detrimental effect on the quality factor (Q·f). The 0.05 mol LiF-added MgO ceramics were sintered at a temperature of 950 °C which resulted in dielectric constant (εr) and Q·f values of 9.6 and 215,000 GHz, respectively, though the temperature coefficient of resonant frequency (TCf) had a large negative value of -63.5 ppm/°C. In order to achieve near-zero TCf values, (0.95-x)MgO–xCaTiO3–0.05LiF ceramics were also investigated and the formation of a secondary phase in MgO–CaTiO3–LiF ceramics was not observed in the X-ray powder diffraction profiles. Although the Q·f values of the ceramics were lowered by CaTiO3 addition, a near-zero TCf was obtained at x = 0.05 (TCf= -3.2 ppm/°C). The εr and Q·f values of the 0.90MgO–0.05CaTiO3–0.05LiF (x = 0.05) ceramic were 12.7 and 93,500 GHz, respectively. From these results, it is considered that CaTiO3-added (0.95-x)MgO–xCaTiO3–0.05LiF ceramics are appropriate candidates as high-Q low-temperature cofired-ceramics (LTCCs).
Effectiveness of Iodine Termination for Ultrahigh Efficiency Solar Cells as a Means of Chemical Surface Passivation
Authors: Ju Minkyu , Lee Youn-jung , Lee Kyungsoo , Han Changsoon , Jo Youngmi , Yi Junsin
Published: September 2012

The use of iodine as a passivating agent for chemical modification of silicon surface is demonstrated. The measurement of carrier lifetime using microwave photoconductivity decay method shows an effective passivation with iodine treatment which is 5 times greater than hydrogen passivation. Unlike hydrogen termination, the negative charge created by the iodine termination enhances the solar cell performance. For n-type silicon, the charge effect results in electric passivation. For p-type silicon, the charge effect forms a barrier which acts as back surface field. For cells with the same area, open circuit voltage (V
OC), short circuit current density (J
SC), fill factor (FF), and efficiency (η) of iodine terminated one were 610 mV, 39.5 mA/cm2, 76.1%, and 18.3% while those of hydrogen passivated one were 600 mV, 33.4 mA/cm2, 73.1%, and 14.7%, respectively.
Effects of Substitution of Al and Bi for Ni on Structure and Hydrogen Storage Properties of LaNi4.7-xAl0.3Bix (x=0.1, 0.2, 0.3) Alloy
Authors: Yilmaz Fikret , Kilicaslan Muhammed Fatih , Atanur Osman Malik , Hong Soon-Jik , Uzun Orhan
Published: September 2012

In this research, the effects of Al and Bi substitution for Ni on the microstructure and hydrogen absorption/desorption properties of LaNi4.7-x
Al0.3Bi
x
(x=0.1, 0.2, 0.3) alloys were investigated. The results showed that substituting Ni with Al led to a desirable decrease in absorption/desorption plateau pressure as well as to hysteresis without a reduction in hydrogen capacity. However, Bi substitution reduced the hydrogen capacity and increased the absorption/desorption plateau pressure of the samples. The formation of the (Al,Ni) intermetallic and Bi phases at grain boundaries was found to be the main reason for the changes in hydrogen storage properties.
Thermal Stability Enhancement of Polyethylene Separators by Gamma-ray Irradiation for Lithium Ion Batteries
Authors: Kim Ki Jae , Park Min-Sik , Kim Hansu , Kim Young-Jun
Published: September 2012

The thermal stability of polyethylene (PE) separators irradiated by 50, 100, and 150 kGy dose gamma-rays is investigated when they are exposed to high-temperature environments. The gamma-ray irradiated separators have much lower Gurley numbers and higher ionic conductivity than a non-irradiated separator after storage at 100 and 120 °C. These results indicate that the thermal stability of PE separators can be drastically improved by gamma-ray irradiation. Even after storage at 120 °C for 1 h, the gamma-ray irradiated separator is maintaining its own structure. A cell assembled with a gamma-ray irradiated separator exhibits better rate-capability and cyclic performance than a pristine PE separator. The positive effects of gamma-ray irradiation are examined in detail with the purpose of improving battery performance.
AlGaN/GaN Schottky Barrier Diode on Si Substrate Employing NiOx/Ni/Au Contact
Authors: Kim Young Shil , Ha Min Woo , Kim Min Ki , Han Min Koo
Published: September 2012

We proposed and fabricated an AlGaN/GaN lateral Schottky barrier diode (SBD) employing nickel oxide (NiO
x
)-based double metal contacts, which showed a highly stable reverse blocking capability, by improving the reliability in the high-temperature reverse bias condition. The leakage current of the proposed device was decreased by three orders of magnitude. The measured leakage current of the diode, fabricated using a NiO
x
(oxidized at 500 °C)–Ni/Au contact as an anode was 236 pA at room temperature while that of the conventional diode was 2.6 µA. The barrier height of the proposed device measured at 200 °C was 0.84 eV while that of conventional one was 0.69 eV. We have also obtained a high breakdown voltage of 1200 V without any additional structure to mitigate the field concentrated at the anode. The highly rectifying contact of the proposed device was attributed to the increment in the barrier height owing to a stoichiometric change at the surface of the device.
Preisach Polarization–Electric Field Hysteresis Model with Iteration Method
Authors: Ikeda Hideyuki , Kadota Yoichi , Morita Takeshi
Published: September 2012

In this study, we introduce an iteration method for obtaining the distribution function of the Preisach polarization–electric field (P–E) hysteresis model for piezoelectric actuators. In a previously proposed method, numerous experimental hysteresis curves were indispensable for this function. On the other hand, by using the iteration method, only one major-loop experiment is sufficient. From this distribution function, any minor-loop hysteresis can be simulated by the Preisach distribution function F(i,j) with high resolution. First, we measured a hysteresis property of the polarization P versus input voltage V of the ferroelectric material. On the basis of this one hysteresis curve, the distribution function was obtained using the iteration method. Using this function, we could simulate the minor loops, and the simulation results showed good agreement with experimental data.
Comparison of Ferroelectric and Strain Properties between BaTiO3- and BaZrO3-Modified Bi1/2(Na0.82K0.18)1/2TiO3Ceramics
Authors: Tran Vu Diem Ngoc , Hussain Ali , Han Hyoung-Su , Dinh Thi Hinh , Lee Jae-Shin , Ahn Chang-Won , Kim Ill-Won
Published: September 2012

Effects of BaTiO3(BT) and BaZrO3(BZ) modification on the crystal structure and electromechanical properties of lead-free Bi1/2(Na0.82K0.18)1/2TiO3(BNKT) ceramics were compared within a doping range of 0–5 mol %. The differences between BT- and BZ-modification effects were clearly observed in polarization and electric field-induced strain hysteresis loops. BZ-modification induced a gradual transition from a ferroelectric to a nonpolar phase, resulting in an abnormal enhancement in the electric field-induced strain (EFIS) just after the transition. However, all BT-modified specimens showed strong ferroelectricity without abnormal enhancement in EFIS. The results suggest that Zr doping-induced B-site strains play a significant role in the ferroelectric-to-nonpolar phase transition in the Bi-perovskite.
Composition Design Rule for High Piezoelectric Voltage Coefficient in (K0.5Na0.5)NbO3Based Pb-Free Ceramics
Authors: Ahn Cheol-Woo , Han Guifang , Ryu Jungho , Yoon Woon-Ha , Choi Jong-Jin , Hahn Byung-Dong , Kim Jong-Woo , Choi Joon-Hwan , Park Dong-Soo
Published: September 2012

In this manuscript, the phase transition factor (Ft) was suggested as a design rule for high piezoelectric voltage coefficient in (K0.5Na0.5)NbO3(KNN) based ceramics. TheFtconsisted of the tolerance factor and electronegativity difference. High piezoelectric voltage coefficient was observed when the doping ratio for the starting point of phase transition (x*) was higher than 0.04 in KNN based ceramics. At the range ofFt< -0.01,x*was higher than 0.04 and highg33value (>30 mV·m/N) was observed in KNN based ceramics.
Study on the Ring Type Stator Design Technique for a Traveling Wave Rotary Type Ultrasonic Motor
Authors: Oh Jin-Heon , Yuk Hyung-Sang , Lim Kee-Joe
Published: September 2012

In this paper, the technique of design for the stator of traveling wave rotary type ultrasonic motor was proposed. To establish the design technique, the distribution of internal stresses of the stator was analyzed by applying the cylindrical bodies contact model of Hertz theory and the concept of “horn effect” was used to consider the influence of the projection structure. To verify the proposed technique, the prototype motor was fabricated on the authority of the projection shape dimension and the design specification. And its performance was evaluated. According to the estimate production of the experiment results using the extrapolation, we confirmed that the values obtained through the verification experiment were similar to those deduced by the proposed method properly.
Piezoelectrically Driven Dispensing Head for Encapsulation of Light Emitting Diode Chip
Authors: Ham Young-Bog , Jang Soo-Kwan , Oh Sung-Jin , Jeon Eun-Che , Park Jung-Ho , Yun So-Nam , Choi Sang-Gyu
Published: September 2012

This study is about an amplified piezoelectric actuator driving a noncontact dispensing head. This dispensing head is mostly used for dispensing silicone encapsulants in a light emitting diode (LED) packaging process. The dispensing head using the piezoelectric actuator is capable of precisely dispensing high-viscosity silicone encapsulants at a high speed. However, the multilayer piezoelectric actuator has a very tiny displacement as small as the order of 10 µm. Accordingly, a device for amplifying the displacement of multilayer piezoelectric actuators is needed. To this end, the authors designed and manufactured a displacement amplification device using a metal frame. The amplification device consists of two multilayer piezoelectric actuators and a metal frame for amplifying displacement. The amplification device has a 209 µm displacement at an input DC voltage of 150 V. The extension displacement and contraction displacement generate 9 and 10 N forces, respectively.
Design of 154 kV Extra-High-Voltage Prototype SF6 Bushing for Superconducting Electric Power Applications
Authors: Koo Ja-yoon , Seong Jae-gyu , Hwang Jae-sang , Lee Bang-wook , Lee Sang-hwa
Published: September 2012

One of the critical components to be developed for high-voltage superconducting devices, such as superconducting transformers, cables, and fault current limiters, is a high-voltage bushing to supply a high current to devices without insulation difficulties in cryogenic environments. Unfortunately, suitable bushings for high-temperature-superconductivity (HTS) equipment have not been fully developed to address cryogenic insulation issues. As a fundamental step towards developing the optimum design of the 154 kV prototype SF6 bushing of HTS devices, the puncture and creepage breakdown voltages of glass-fiber-reinforced-plastic (GFRP) were analyzed with a variety of configurations of electrodes and gap distances in the insulation material. And design factors of high-voltage cryogenic bushings were obtained from the result of tests. Finally, the withstand voltage tests of manufacturing a 154 kV extra-high-voltage (EHV) prototype bushing has been performed. Consequently, we verified the insulation level of the newly designed 154 kV EHV cryogenic prototype bushings for superconducting electric power applications.