bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence of Magnetoelectric Coupling in Pb(Fe0.5Nb0.5)O3 Ceramics Through Impedance Spectroscopy and Electromechanical Resonance Measurements
Authors: Raymond Oscar , Font Reinaldo , Almodovar Nelson S. , Portelles Jorge J. , Siqueiros Jesús M 
Published: August 2009

AbstractMultifunctional materials such as the single phase compound Pb(Fe0.5Nb0.5)O3 (PFN), where ferroelectric and antiferromagnetic order coexist, are very promising and have great interest from the academic and technological points of view. In this work, coupling of the ferroelectric and magnetic ordering has been observed. For this study, a combination of the small signal response using the impedance spectroscopy technique and the electromechanical resonance method with the large signal response through standard ferroelectric measurement, has been used with and without an applied magnetic field. The measurements to determine the electrical properties of the ceramic were performed as functions of the bias and poling electric fields. A simultaneous analysis of the complex dielectric constant , impedance , electric modulus , and the electromechanical coupling factors is presented. The results are correlated with a previous study of structural, morphological, small signal dielectric frequency-temperature response, and the ferroelectric hysteretic, magnetic and magnetodielectric behaviors. The observed shifts of the resonance and antiresonance frequency values can be associated with change of the domain size favored by the readjustment of the oxygen octahedron when the magnetic field is applied.From P-E hysteresis loops obtained without and with an external applied magnetic field a maximum value of dc magnetoelectric coefficient αME = 4 kV/cm T (400 mV/cm Oe) was obtained.
Flexible Ceramic-Polymer Composite Substrates with Spatially Variable Dielectrics for Miniaturized RF Applications
Authors: Tasdemir Zuhal , Kiziltas Gullu 
Published: August 2009

AbstractThe goal of this research is to develop a process suitable for producing monolithic conformal substrates with a spatial arrangement of material cells according to a particular design creating novel material systems, useful for many multi- functional electronic and Radio Frequency devices. In this study, MCT ceramics (Mg-Ca-Ti-O systems) and organic binders (polymer solution) are mixed and fabricated as films through a process called tape casting to compromise between high dielectric constant and flexibility. Prior to optimizing the process, several characterization studies are carried out: Commercial spray dried MCT powders (Transtech Inc.) with dielectric constant k=70 and k=20 were analyzed as pressed and produced into tape cast films. Dielectric properties are then measured by an Agilent 16451B material analysis kit and their microscopic behavior is examined by scanning electron microscopy. Results show that flexible composite films show a maximum dielectric constant of ε∼22 unlike their powder pressed form with ε ∼16 but their loss behavior deteriorates when compared with their sintered form and a loss tangent factor of 0.001. The difference is attributed to the air content vs. polymer presence of the material in powder pressed form. Also, these substrates naturally are no longer flexible; hence studies are focused on their tape cast form. The potential of these dielectric shades to serve as candidate constituents for producing monolithic textured polymer-ceramic-composites with controllable loss is studied further. Four properties are of prime importance: tunability of dielectric constants to achieve miniaturization, flexibility via low temperature processing of polymers and loss controllability.
Characterisation of Secondary Phases in Cu Poor CuInSe2: Surface and in-depth resolved Raman scattering analysis of polycrystalline layers
Authors: Izquierdo-Roca Victor , Fontané Xavier , Calvo-Barrio Lorenzo , Álvarez-García Jacobo , Pérez-Rodríguez Alejandro , Morante Joan Ramón , Witte Wolfram , Klenk Reiner 
Published: August 2009

AbstractThis work reports the surface and in-depth resolved Raman scattering analysis of polycrystalline CuInSe2 layers grown with different chemical composition, as function of the Cu to In content ratio (0.48 ≤ × ≤ 1.14). Measurements performed at the surface of the Cu-poor layers corroborate the formation of both Cu-poor Ordered Vacancy Compound (OVC) and CuAu ordered CuInSe2 phases for compositions corresponding to x ≤ 0.82 (OCV) and x ≤ 0.66 (CuAu), respectively. In-depth resolved measurements performed on the layers with lower Cu content have allowed observing a strong decrease with the depth of the intensity of the Raman peak from the chalcopyrite ordered CuInSe2 phase. This suggests a preferential formation of both OVC and CuAu ordered phases at the region close to the interface with the back Mo layer. On the other hand, the comparison between the spectra directly measured on the front and back surfaces of the layers -after removal of the layers from the Mo coated glass substrates- suggests also a worsening of the crystalline quality at the back region of the layers in the whole range of compositions.
Crystalline Perfection of Epitaxial Structure: Correlations with Composition, Thickness, and Elastic Strain of Epitaxial Layers
Authors: Jampana Balakrishnam R , Faleev Nikolai N , Ferguson Ian T , Opila Robert L , Honsberg Christiana B 
Published: August 2009

AbstractCrystalline perfection of InGaN epi-layers is the missing design parameter for InGaN solar cells. Structural deterioration of InGaN epi-layers depends on the thickness, composition and growth conditions as well. Increasing the InGaN epi-layer thickness beyond a critical point introduces extended crystalline defects that hinder the optical absorption and electrical properties. Increasing the InGaN composition further reduces this critical layer thickness. The optical absorption band edge is sharp for III-nitride direct band gap materials. The band edge profile is deteriorated by creation of extended crystalline defects in the InGaN epitaxial material. The design of InGaN solar cells requires the growth of epi-layers where a trade off between crystalline perfection and optical absorption properties is reached.
Electron Microscopy Characterization of Low-Temperature Growth Zn-doped TiO2 Nanowires
Authors: Eastman Micah , Li Haiyan , Jiao Jun 
Published: August 2009

AbstractWe report the synthesis of Zn-doped TiO2 nanowires by a solution-based process. The synthesis takes place at 200°C in an alkali solution and results in both nanowire and nanoparticle precipitates. Several transmission electron microscopy techniques were used to characterize the resulting precipitates: diffraction patterns and high resolution phase contrast images provided identification of the crystalline phase of the material as well as insights into the resulting lattice parameters, energy dispersive x-ray spectroscopy allowed identification of constituent elements, and electron energy loss spectroscopy permitted quantification of relative concentrations of hydroxyl and lattice-type oxygen bonding. In addition, scanning electron microscope images provide overall perspective of the growth uniformity and morphology.
ZnO nano-pillar Resonators with Coaxial Bragg-Reflectors
Authors: Schmidt-Grund Rudiger , Hinkel Annekatrin , Hilmer Helena , Zúñiga-Pérez Jesus , Sturm Chris , Rheinländer Bernd , Grundmann Marius 
Published: August 2009

AbstractWe demonstrate the growth of lateral concentric BR on ZnO nano-pillars. It opens the opportunity to be used for (i) the enhancement of the lateral confinement in classical pillar-resonators in order to increase the emission rates in the regime of weak exciton-photon coupling (Purcell-effect), (ii) to enhance the exciton-polariton coupling strength in the strong-coupling regime, and (iii) to be used for two-dimensional confinement in free-standing photonic wire resonators. Spatially resolved PL experiments in dependence on the pillar diameter and on the temperature provide strong hints for the ZnO nano-pillar resonator being in the strong-coupling regime. The coupling strength can be estimated to be V = 80 meV.
Laser Micro-machining of Three-Dimensional Microstructures in Optical Materials
Authors: Wang Xianghua , Lai Pui To , Choi Anthony H.W. 
Published: August 2009

AbstractWe demostrate an advanced precision cutting tool using a 349 nm nanosecond-pulsed UV laser micromachining setup. After expansion and collimation, the laser beam is directed vertically and focused with a high performance triplet lens. With an Al mirror inserted in the path of the convergent beam, the beam can be focused on a horizontal machining plane at any desired tilting angles. Microstructures of a wide range of geometries on hard materials can be formed using this custom machining method. Conventional linear and rotary machining on sapphire materials have been demonstrated.
Fidelity of Holographic Lithography for Fabrication of 3D SU-8 Photonic Structures and How to Minimize Distortion by Optical Design
Authors: Zhu Xuelian , Xu Yongan , Cheng Shih-Chieh , Yang Shu 
Published: August 2009

AbstractTheoretical analysis can impart great benefits on the rationale design of 3D photonic structures by revealing the underlying mechanisms of structural distortion during each processing step. In this report, we quantitatively study the distortion of a three-term diamond-like structure fabricated in SU-8 polymer by four-beam interference lithography, which can be attributed to refraction at the air-film interface, and resist film shrinkage during lithographic process. In study of photonic bandgap (PBG) properties of Si photonic crystals templated by the SU-8 structures, we find that the distortion has degraded the quality of PBGs. Furthermore, we theoretically design new optical setups to fabricate three-term diamond-like structure with minimal deformation. Instead of single exposure of four beams, we use triple exposure of two beams, one from the central beam and the other from the side beam each time. A set of new linear polarization vectors is suggested to enhance the contrast between the minimal and maximal intensities of interference pattern.
Geometrical Critical Thickness Theory for the Size Effect at the Initiation of Plasticity
Authors: Zhu Ting , Ehrler Bruno , Bushby Andy , Dunstan Dave 
Published: August 2009

AbstractRecently, size effects in the initiation of plasticity have been clearly observed and reported in different geometries; e.g., bending (Ehrler et al. Phil. Mag. 2008), twisting (Ehrler et al., MRS, Spring Meeting 2009) and indentation (Zhu et al. J. Mech. Phys. Sol. 56, 1170, 2008). Strain gradient plasticity theory is the principal approach for explaining size effects during plastic deformation in these geometries. However, it fails to account for any size effect at the initial yield. Geometrical critical thickness theory was proposed to explain the yield size effect in bending and torsion (Dunstan and Bushby, Proc. Roy. Soc. A460, 2781, 2004). The theory shows that the initial yield strength is scaled with the inverse square root of the characteristic length scale without requiring any free fitting parameters. Here, we extend the theory to describe the yield size effect in indentation. The theory agrees fairly well with experimental observations in micro-torsion (Ehrler et al., MRS, Spring Meeting 2009) and nanoindentation (Zhu et al., J. Mech. Phys. Solid, 2008).
Peptide-Mediated Deposition of Nanostructured TiO2 into the Periodic Structure of Diatom Biosilica and its Integration into the Fabrication of a Dye-Sensitized Solar Cell Device
Authors: Li Haiyan , Jeffryes Clayton , Gutu Timothy , Jiao Jun , Rorrer Gregory L. 
Published: August 2009

AbstractBiological fabrication approaches were used to enhance the performance of a dye-sensitized solar cell (DSSC) device stack for the conversion of light to electricity. Diatoms are single-celled algae that make silica shells called frustules that possess periodic structures ordered at the micro- and nanoscale. Nanostructured TiO2 was deposited onto the frustule biosilica of the diatom Pinnularia sp. Poly-L-lysine (PLL) conformally adsorbed onto surface of the frustule biosilica. The hydrolysis and condensation of soluble Ti-BALDH to TiO2 by PLL-adsorbed diatom biosilica deposited 0.77 ± 0.05 g TiO2/g SiO2 onto the diatom biosilica. The periodic pore array of the diatom frustule served as a template for the deposition of ˜20 nm TiO2 nanoparticles, which completely filled the 200 nm frustule pores and also coated the frustule outer surface. This material was then integrated into the DSSC device stack. Specifically, a single layer of diatom-TiO2 frustules was deposited to surface coverage 100μg/cm2 on top of the 25 nm anatase TiO2 nanocrystal layer (2.5 mg/cm2) that was doctor-bladed onto conductive FTO glass. The composite structure was thermally annealed in air at 400 °C, followed by addition of N719 dye, I3-/3I- liquid electrolyte, and semi-transparent Pt back electrode sputter coated on FTO glass. The solar cell efficiency increased from 0.20% to 0.70% when the diatom-TiO2 layer was added to anatase TiO2 base layer of the semi-transparent device. The increase in efficiency cannot be attributed solely to the added TiO2, because the amount of TiO2 in the diatom-TiO2 layer contributed to only 3% of the total TiO2 in the device. Instead, it is proposed that the diatom-TiO2 layer may have helped to improve photon capture within the DSSC because of its periodic structure and high dielectric contrast.
A Thermoviscoelastic Approach for Modeling Shape Memory Polymers
Authors: Nguyen Thao D 
Published: August 2009

AbstractThis paper presents a thermoviscoelastic model for shape memory polymers (SMPs). The model has been developed base on the hypothesis that structural and stress relaxation are the primary shape memory mechanisms of crosslinked, glassy SMP, and that consideration of these mechanisms is essential for predicting the time-dependence of the shape memory response. Comparisons with experiments show that the model can reproduce the rate-dependent strain-temperature and stress-strain response of a crossslinked, glassy SMP. The model also captures many important features of the temperature and time dependence of the free strain recovery and constrained stress recovery response.
Dome-like PVDF Actuators: Preparation, Phase Transformation and Piezoelectric Properties
Authors: Wegener Michael , Schwerdtner Robert , Schueller Martin , Morschhauser Andreas 
Published: August 2009

AbstractIn this work, dome structures in PVDF films were prepared as ultrasonic transducer. The domes are realized by a deep-drawing process. The dome-forming process leads to a phase transformation from the non-polar α into the polar β phase within dome wall and roof of the PVDF films. A ferroelectric polarization is obtained in these dome areas after suitable electrical poling which yields a piezoelectric activity. Because of the piezoelectric activity within the film plane, a dome-roof up-and-down actuation is observed with resonance frequencies in the range between 65 and 93 kHz.
In vitro study of mouse fibroblast tumor cells with TNF coated and Alexa488 marked silica nanoparticles with an endoscopic device for real time cancer visualization
Authors: Herz Marion , Rank Andreas , Tovar Güenter E. M. , Hirth Thomas , Kaltenbacher Dominik , Stallkamp Jan , Weber Achim 
Published: August 2009

AbstractTumor resection done by minimally invasive procedure owns the challenge of a fast and reliable differentiation between healthy and tumorous tissue. We aim at investigating and developing a method for an intraoperative visualization of tumor cells with functionalized nanoparticles. The goal is to use this technique for the intraoperative use. Our so-called biohybrid systems consist of nanoparticles that are produced by Stöber synthesis and coupled with bio active proteins. Such biomimetic nanostructures are capable of imitating the effects of membrane-bound cytokines, which bind to tumor cells for labeling them. A flexible and modular test environment has been developed to evaluate the spraying properties of the particles and to study tissue probes. It enables a fast investigation of different particle configurations and spraying parameters like pressure, spray volume, nozzle geometry, etc.
Tests of the Affinity Assumption in Phantomlike Elastomer Networks
Authors: Davies Misty , Lew Adrian 
Published: August 2009

AbstractPhantomlike elastomer simulations do not always deform globally affinely in the way that classical theory predicts. Assuming that each crosslink will deform affinely with its topological neighbors gives much better results, and creates a way to isolate crosslinks with unpredictable deformation properties. The correlation of non-affinities and network properties depends on the constitutive model and boundary condition used. We always find a correlation between local density of crosslinks and degree of non-affinity.
Use of Ester as a Precursor to Clean Formate Drill-In Fluid Damage in Horizontal Wells
Authors: Alotaibi M. B. , Nasr-El-Din H. A. , Hill A. D. 
Published: August 2009

Summary
Long horizontal and multilateral oil and gas wells provide an attractive option for maximizing reservoir contact. Formate-based brines have been used in drilling and completion operations for more than 10 years. Advantages of these fluids include high density, solid-free brines, better compatibility with XC polymer, starches, and less potential for formation damage. These advantages were reported in several previous publications.
Filter cakes that are generated by drilling fluids can act as a barrier to the fluid flow in both cased and openhole wells. Calcium carbonate particles are frequently used as weighting material to maintain the pressure that is required for well control and minimizing leakoff rate. These solid particles become consolidated and trapped in a polymeric material, and this makes the filter cake a very effective permeability barrier.
The conventional method for cleaning filter cake is by using solids-free formate brines, either by soaking or circulating for many hours at high flow rates. This mechanical technique removes only external filter cake. Chemical means like acids, oxidizers, chelating agents, enzymes, or combinations of these chemicals are usually used as an alternative method for dissolving both the external and internal filter cake. Most of these fluids cannot give a full coverage to the wellbore because of the formation heterogeneity.
A new precursor (ester of an organic acid) can generate an acid downhole at a low release rate, which results in uniform fluid distribution through the wellbore. Compatibility and thermal stability tests between the precursor solution and formation brine were studied in detail. Return permeability experiments were conducted by using high-pressure/high-temperature (HP/HT) dynamic fluid loss cells. The ester solution was effective in cleaning the filter cake in comparison to the formate brines.
A field application, where formate brine was used to drill and complete a gas producer in a sandstone reservoir, is included in this paper. The gas well was drilled in a weakly consolidated reservoir and was completed with expandable sand screens (ESSs). The bottomhole temperature was 285°F. The produced gas contained 2–3 vol% carbon dioxide and no hydrogen sulfide. Full analysis of flowback samples indicated that most of the returned solids were calcium carbonate. Laboratory tests indicated that the ester solution can be used to restore well productivity by removing damage induced by the drilling mud filter cake.
The Political Economy of Agricultural Market Reforms in Developing Countries
Authors: Giuliano Paola , Scalise Diego 
Published: August 2009

Abstract
We study the determinants of agricultural market reforms in developing countries. What prompted the governments in these countries to abruptly begin deregulating their agricultural markets in the late 1980's? We answer this question by constructing a completely new dataset based on agricultural market regulations in 88 developing countries from 1960 to 2003. Our results suggest that the sudden and strong decline in the international price of agricultural commodities played a crucial role in destabilizing the financial equilibrium of marketing boards. In addition, changes in the rural representation in the political arena and government ideology also played significant roles in breaking up the status quo.
Cancer Preventing Properties of Cruciferous Vegetables
Authors: Czapski Janusz 
Published: August 2009

Cancer Preventing Properties of Cruciferous Vegetables
Health-promoting phytonutrients in cruciferous vegetables have been gaining attention for their powerful effects in combating cancer. This review concerns anticancer properties of cruciferous green vegetables of "Brassica" genus such as broccoli, kale, Brussels sprouts, watercress. The role and mechanisms of action of cruciferous active compounds such as sulforaphane, indole-3-carbinol, diindolylmethane and phenethyl isothiocyanate in protection against cancer and cancer-fighting are discussed. Losses of nutrients and active compounds during cooking, microwaving, and blanching of vegetables which may be more substantial than commonly perceived are also reviewed.
Relationship between Technological Characters in Capsicum SPP. Soft-Flesh Forms
Authors: Nowaczyk Lubosława , Nowaczyk Paweł , Banach-Szott Magdalena 
Published: August 2009

Relationship between Technological Characters in Capsicum SPP. Soft-Flesh Forms
The present research involved the evaluation of relationships between technological characters of soft-flesh fruit in the lines derived from the hybrid Capsicum frutescens L. × C. annuum L. The evaluation was performed in groups of genotypes which differed in their fruit weight and pericarp thickness. The material researched was made up of the pericarp from which placenta with seeds was removed and the puree obtained as a result of whole fruit crushing. The analysis of the content of capsaicinoids was made using the HPLC method. The content of capsaicin was in each case higher than that of dihydrocapsaicin. There were observed highly significantly positive correlations between the average fruit weight and the wall thickness in the genotypes of a higher level of these characters, namely in the groups over 20 g (fruit weight) and over 3 mm (wall thickness). In these groups the content of capsaicinoids was negatively correlated with the average fruit weight. The significance of this relationship was confirmed in the genotypes of a higher fruit weight as compared with the content of capsaicin and dihydrocapsaicine in the puee. The relationships between the capsaicinoids researched were more stable in the genotypes of a higher fruit weight and demonstrating a higher pericarp wall thickness.
Canopy Architecture and Yielding of Different Tomato Morphotypes Under Glasshouse Conditions
Authors: Abukhovich Aliaksandr , Pietkiewicz Stefan , Karwowska Romualda , Kobryń Jolanta , Kalaji Hazem 
Published: August 2009

Canopy Architecture and Yielding of Different Tomato Morphotypes Under Glasshouse Conditions
Two tomato morphotypes (cvs. Favorita, Organza and Azarro) of different fruit size were grown during 2005-2006 on a rockwool substrate under greenhouse conditions. Leaf area index (LAI), solar radiation absorption coefficient (TAO) and leaf area duration (LAD) were determined. Tested tomato cultivars proved different yielding strategies expressed by dissimilar values of the measured and calculated physiological indices (LAI, LAD, TAO and the canopy yielding efficiency). Cv. Organza showed the highest canopy yielding efficiency, cv. Azarro showed a negative dependence between LAD and yield, while cv. Favorita canopy architecture allowed to achieve better penetration of light energy to lower canopy layers and showed better tolerance of this cultivar to thermal stress.