bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Deformation Mechanisms at Mineral-Protein Composite Interface Using Steered Molecular Dynamics Simulations
Authors: Katti Dinesh R. , Ghosh Pijush , Katti Kalpana 
Published: April 2011

AbstractIn the area of clay-polymer nanocomposites, recently montmorillonite is extensively used because of its unique characteristics of swelling. In this work, steered molecular dynamics is used to evaluate the mechanical behavior of a new class of nanocomposites, using amino acids to intercalate clay interlayers. Two positively charged amino acids, lysine and arginine, are used here. Our simulation indicates that both the amino acids have preferred orientation inside the clay interlayer. Our simulations also indicate that the clay-amino acid interlayer is about three times stiffer under tension as compared to under compression. On the other hand, dry montmorillonite shows similar stiffness under tension and compression. The fundamental mechanism of deformation during tension and compression is intrinsically different in the amino acid-clay composite. The stress-strain behavior of this clay-amino acid interlayer is predominantly linear until a stress of 1.5 GPa. This study is a first step towards the potential use of biomacromolecules as modifiers in clay nanocomposites.
Elastic modulus of dental enamel: effect of enamel prism orientation and mineral content
Authors: Ferguson V.L. , Boyde Alan , Bushby Andrew J. 
Published: April 2011

AbstractNanomechanical properties of mineralized tissues are determined by microstructural tissue organization and relative composition of organic, mineral, and water phases. We combine nanoindentation and quantitative backscattered electron (qBSE) imaging to understand how these factors influence material properties at the ultrastructural and tissue level. Developmental stages of equine tooth enamel provide a good situation for studying the effects of enamel prism orientation and mineralization. Equine cheek teeth continue to form new enamel whilst mature tissue is being worn away. Hence we can study graded mineral content that increases with enamel maturity. Hunter-Schreger bands (HSBs) containing enamel prisms of contrasting orientations allow investigation of the effect of orientation on modulus. An equine second mandibular molar (2-year-old) was embedded in poly-methylmethacrylate, sectioned longitudinally, polished, carbon coated, imaged in qBSE, and subjected to nanoindentation testing. Elastic modulus increases significantly during maturation as enamel protein matrix degradation makes space for increased mineral content with closer proximity of enamel crystals, finally reaching values exceeding 80 GPa for little further increase in mineral content. Indentations spanning HSBs in immature, poorly mineralized enamel yielded modulus values that varied with prism orientation in a sinusoidal pattern where modulus varies by as much as a factor of three. Nanoindentation helps to elucidate how the composition and ultrastructural organization of enamel contribute to mechanical properties.
Uniaxial and Biaxial Mechanical Behavior of Human Amnion
Authors: Oyen Michelle L. , Stylianopoulos Triantafyllos , Barocas Victor H. , Calvin Steven E. , Cook Robert F. 
Published: April 2011

ABSTRACTChorioamnion, the membrane surrounding a fetus during gestation (the “amniotic sac”), is a structural soft tissue for which the mechanical behavior is poorly understood—despite its critical role in maintaining a successful pregnancy and delivery. Preterm rupture of the chorioamnion accounts for one third of all premature births. The structural component of chorioamnion is the amnion sublayer, which provides the membrane's mechanical integrity via a dense collagen network. Amnion uniaxial and planar equi-biaxial tension testing was performed using monotonic loading, cyclic loading and stress-relaxation. The prefailure material behavior was highly nonlinear, exhibiting an approximately quadratic response. Cyclic testing, both uniaxial and biaxial, exhibited dramatic energy dissipation in the first cycle followed by less hysteresis on subsequent cycles and an eventual stable hysteresis response with approximately 20% energy dissipation per cycle. Stress-relaxation testing, both uniaxial and biaxial, demonstrated a load dependent response and continued relaxation after long hold times. A nonlinear viscoelastic (separable) hereditary integral approach was used to model the amnion stress-strain-time response during relaxation. The mechanical results are discussed within the context of the in vivo clinical performance of amnion, and the potential for membrane repair.
Micro-Scale Physical and Chemical Heterogeneities in Biogenic Materials - A Combined Micro-Raman, Chemical Composition and Microhardness Investigation
Authors: Griesshaber E. , Job R. , Pettke T. , Schmahl W. W. 
Published: April 2011

ABSTRACTThe ultrastructure and chemical composition of calcitic shells of the modern brachiopod specimen Magellania flavescens (Linnaeus) – order: Terebratulida – was investigated with μ-Raman spectroscopy, Vickers microhardness indentation and laser-ablation-inductively-coupled-plasma-mass-spectrometry. The shells contain a thin outer, nanocrystalline primary layer, which is followed by an inner, much softer, secondary layer composed of inorganic/organic fibre composite material. We observed significant chemical and structural inhomogeneities within the shells. The calcite A1g Raman mode was slightly reduced from 1084 cm-1 at the hinge (lock) down to 1083.5 cm-1 towards the tip. This is accompanied by a variation of some chemical impurity concentrations (e.g. Mg, Sr). A strong decrease in microhardness and distinct changes in chemical composition from the primary or the outermost part of the secondary layer towards the innermost portion of the secondary shell layer can be observed. Thus, our measurements show that chemical and structural inhomogeneities occur in modern brachiopods and not only between the primary and the secondary shell layer, but also within the secondary layer of the shell.
A Model for the Increased Elastic Compliance in Human Cancer Cells
Authors: Mohrdieck Camilla , Arzt Eduard 
Published: April 2011

ABSTRACTHuman epithelial cancer cells are known to exhibit a reorganization of their keratin cytoskeleton and an attendant change in their elastic stiffness upon incubation with a natural lipid. The change in the keratin network was modeled and the model structures were computationally deformed using a Finite Element Method. The simulation results show a marked difference in the mechanical behavior of the cells for tensile and compressive loading conditions. In the former case, the elastic compliance increases in agreement with experimental findings. We interpret this increase by applying principles of structural engineering and suggest that cells may generally use these principles to regulate their cytoskeletal architecture.
A Novel Joint between Dissimilar Materials Inspired by the Mechanics of Trees
Authors: Roy Xu L. , Kuai Huacheng , Sengupta Sreeparna 
Published: April 2011

ABSTRACTAn integrated experimental and numerical investigation was conducted for removing the free-edge stress concentrations in dissimilar material joints. A convex interface/joint design, inspired by the shape and mechanics of trees, allows for least stress concentrations at bi-material corners for most engineering material combinations. In-situ photoelasticity experiments on convex polycarbonate-aluminum joints showed that the free-edge stress concentration was successfully removed. As a result, the new design not only improves the static load transfer capacity of dissimilar material joints, but also yields more reasonable interfacial tensile strength evaluation. For convex polycarbonate-aluminum and PMMA-aluminum joint specimens, the ultimate tensile load increased up to 81% while the total material volume reduced by at least 15% over that of traditional butt-joint specimens with severe free-edge stress concentrations.
Mechanical Behavior of Ceramic/SAM Bilayer Coatings
Authors: Yang Quan , Zhang Guangneng , Chitre Kaustubh , Cho Junghyun 
Published: April 2011

ABSTRACTCeramic/self-assembled monolayer (SAM) bilayer films can provide adequate protection and/or act as a multipurpose coating for microelectronics and MEMS applications, due to synergistic effects of the hybrid film structure. The organic SAM acts as a “template” for the growth of the ceramic film while the hard ceramic can provide protection from environmental and mechanical impact. To process the bilayer films, a low-temperature solution deposition technique (biomimetic process) is employed using phosphonate-based SAM and zirconium oxide precursors. A particulate zirconium oxide film is formed by enhanced hydrolysis of zirconium sulfate solutions in the presence of HCl at about 80°C, and its particle size and thickness effects are discussed. In addition, microstructure and micromechanics involved in the synthesis of both zirconia films and SAM are systematically assessed. Especially, mechanical properties such as Young's modulus and hardness are analyzed using a nanoindenter, as well as with the aid of theoretical models. Further, the substrate effects resulting from a large indentation depth relative to the film thickness are eliminated to obtain the “film-only” properties. This study also highlights the role of compliant SAM layer in forming a strain-tolerant bilayer film.
Surface Plasmon Excitations and Emission Light due to Molecular Luminescence on Metal Thin Film
Authors: Kaneko Futao , Toyoshima Susumu , Ohdaira Yasuo , Shinbo Kazunari , Kato Keizo 
Published: April 2011

ABSTRACTEmission light due to surface plasmon (SP) excitations has been investigated in Kretschmann configuration of prism/metal thin film/organic dye thin films by means of direct irradiation of a laser beam from air to the films. Emission light through the prism coincided with the resonant conditions of SP excitations in the configuration. It was thought that SPs on the metal surface were excited by luminescence of dye molecules close to the metal surface, and the SPs propagating along the metal surface were converted to the emission light according to the resonant conditions of SPs in the configuration. Intensities and spectra of the SP emission light through the prism strongly depended upon emission angles, nanostructures of dye films, the film thickness and mixture of two kinds of dyes.
Functionalized Guanidines for Electro-Optic Materials.
Authors: Buker Nicholas , Firestone Kimberly A. , Haller Marnie , Purvis Lafe , Lao David , Snoeberger Robert , Jen Alex K.-Y. , Dalton Larry R. 
Published: April 2011

ABSTRACTA family of nonlinear optical chromophores has been synthesized containing novel donor systems based on functionalized guanidines. Chromophores utilizing these donor systems display superior transparency and stability properties. The unusual and highly desirable characteristics of these chromophores make them very promising candidates for electro-optic applications. Systematic study of the molecular hyperpolarizabilities and bulk electro-optic properties of polymers containing these chromophores is being used to guide optimization of these systems.
New Light Emitting Polymers and High Energy Hosts for Triplet Emission
Authors: Mak Chris S. K. , Watkins Scott E. , Williams Charlotte K. , Evans Nicholas R. , Chan Khai Leok , Cho Sung Yong , Holmes Andrew B. , Boothby Clare E. , Friend Richard H. , Hayer Anna , Köhler Anna 
Published: April 2011

ABSTRACTThis paper describes two aspects of research aimed at harnessing the triplet energy generated in electron-hole recombination in polymer electroluminescent devices. The purpose is to design solution-processible phosphorescent organometallic triplet emitters and to design high triplet energy polymer hosts that can transfer triplet energy to the phosphorescent guests. The method employed Suzuki cross coupling reactions to incorporate either phosphorescent cores or high energy triplet monomers covalently into polymer hosts to evaluate their optoelectronic properties. The results showed (i) efficient energy transfer from polyfluorene hosts to red phosphorescent guests and (ii) that pyridine and carbazole monomers could raise triplet energies of hosts. It is concluded that these approaches offer promise in the design of solution processible electrophosphorescent materials for red and green light emitting devices.
Magnetotransport Properties of Compression Molded CrO2-Polyimide Composite
Authors: Mishra Sanjay R. , Ghosh Kartik , Losby Joe , Kehl Ted , Viano Ann 
Published: April 2011

ABSTRACTThe conductivity and magnetotransport properties of compression molded half-metallic CrO2/Polyimide composites over a range of different metallic concentrations have been studied. The conductivity measurements on these composites show negative slope of resistance versus temperature. The magnetoresistance measurement indicates obvious enhancement at low temperatures. The maximum in magnetoresistance (MR) is found to be temperature and metal volume fraction dependent. Significant differences in high and low temperature magnetoresistive behavior in the composite have been observed. The high field, 15 T MR measurements show 23% and 19% MR enhancement at 5K and 75 K, respectively. Thus, it is found that the polymer barrier can contribute to enhancing magnetoresistive properties of the composite.
Solution processable nanocomposites based on silsesquioxane cores for use in organic light emitting diodes (OLEDs)
Authors: Sellinger Alan , Tamaki Ryo , Laine Richard M. , Ueno Kazunori , Tanabe Hiroshi , Williams Evan , Jabbour Ghassan E. 
Published: April 2011

ABSTRACTA new family of materials that synergistically combine the attributes of both organic and inorganic properties for use in organic light emitting diodes (OLEDs) is presented. The hybrid materials are based on 3-D inorganic cores of octavinylsilsesquioxanes (OVS). The resultant materials have high Tg's (120–210°C), are formed from minimal step/high yield reactions and readily available starting reagents, are monodisperse (PDI<1.1), can be highly purified via common chroma-tographic techniques, and form defect-free amorphous films via spin-dip coating. For example TPD is known for its good hole injection/transport properties in OLED applications but suffers from a low Tg (65°C). TPD-OVS hybrid material has a Tg of 142°C while maintaining similar injection/transport properties to TPD. Photoluminescence analysis of the hybrid thin film reveals: 1) a 30 nm blue shift versus their dilute solution counterparts; and 2) 5 hour annealing cycles to within 10°C of their Tg show no indication of eximer formation (no red shift) that often causes reduced efficiencies in polymer LEDs.
Inorganic-Organic Hybrid Hierarchically Structured Methyl-modified Silica Monoliths
Authors: Brandhuber Doris , Hüsing Nicola , Peterlik Herwig 
Published: April 2011

ABSTRACTHighly porous inorganic-organic hybrid monoliths with mesopores in a macroporous network have been prepared from methyltris(2-hydroxyethoxy)silane (MeGMS) and tetrakis(2-hydroxyethoxy)silane (EGMS) in the presence of an amphiphilic block copolymer. The amount of methyltris(2-hydroxyethoxy)silane (MeGMS) in the gel has been varied from 0 to 100 %. These glycol-modified silanes have the advantage of being water-soluble and thus allowing for a direct templating of liquid-crystalline surfactant mesophases without the presence of a homogenizing organic solvent such as ethanol. The wet gels have been dried by supercritical extraction with carbon dioxide.In the present work, the sol-gel behaviour of these glycol-modified silanes is discussed especially with a focus on the formation of the meso- and macrostructure. In addition, the influences of the varying ratios of methyltris(2-hydroxyethoxy)silane on the structural features of the gels are investigated by various analytical techniques such as small angle X-ray scattering, nitrogen sorption, and scanning electron microscopy.
Formation and Reaction of Metal-containing Nanoparticles in Organic/Inorganic Hybrid Aerogels
Authors: Yao Chunhua , Risen William M. 
Published: April 2011

ABSTRACTSynthesis of hybrid aerogel materials that contain both selectively reactive nanoparticles and nanoparticles with appreciable magnetic susceptibilities will be reported. This has been achieved by a two stages process. First silica-bioderived polymer hybrid aerogels with incorporated metal ions were synthesized and then reduced by photolytically induced chemical reductions or decompositions. For example, silica-chitosan hybrid gels were prepared, Au(III) ions were coordinated to the chitosan, and, after forming the Au(III)-silica-chitosan aerogel by SCL extraction, UV photolysis afforded gold nanoparticles of controlled size in the aerogel. Second, an iron-containing organometallic compound, such as iron carbonyl itself, was absorbed into the aerogel, and then heating or photolysis afforded reduced metal decomposition products. Ferromagnetic organic/inorganic hybrid products containing Au(0) nanoparticles were obtained. Their size (TEM), crystallographic, optical and magnetic properties are discussed. Reactions of thiol compound with the metal nanoparticles in the aerogels were studied.
Inorganic-organic Hybrid materials from Layered Double Hydroxide structure and their subsequent carbonaceous repliqua
Authors: Leroux Fabrice , Moujahid El Mostafa , Roland-Swanson Claudia , Vieille Laetitia , Taviot-Guého Christine , Besse Jean-Pierre , Raymundo-Piñero Encarnacion , Béguin François 
Published: April 2011

ABSTRACTInterleaved monomers and polymers between the sheets of layered double hydroxide (LDH) (hydrotalcite-type) materials are considered as carbonaceous source. After a charring process constituted of a carbonisation and a subsequent demineralisation, carbonaceous materials of interesting textural properties were obtained. The initial preparation of the polymer LDH hybrid phase was found to strongly orientate the textural characteristics, microporous volume and creation of mesoporosity. Several methods to assess the microporosity, t-plot, αs and Dubinin-Astakhov, are compared. Specific surface area as high as 2300 m2/g measured by BET method and microporous volume of 1.07 mL/g were obtained. The carbonaceous materials tested as supercapacitor in acidic medium present capacitances in the range 60 - 120 F/g associated to a good behavior in cycling.
Constrainment Effects of Interleaved Organic Molecules into Layered Double Hydroxides
Authors: Dubois Marc , Moujahid El Mostafa , Besse Jean-Pierre , Leroux Fabrice 
Published: April 2011

ABSTRACTIncorporation and subsequent stabilization of organic molecules into layered double hydroxide are investigated. Through two types of hybrid materials, organic dyes and aniline-based monomers interleaved between LDH materials of cation composition Zn2Al and Cu2Cr respectively, it is shown that the effect of the constrainment is revealed by the interactions different according to the molecule size and stacking as exemplified by dye molecules, orange 6 and green 25 acids and two aniline-based monomers, m-amino-4-benzenesulfonic and 3-aniline-1-propanesulfonic acids.
Influence of TiO2 on the Pore Structure and Texture of SiO2-PDMS Hybrid Materials
Authors: Téllez Lucía , Rubio Juan , Valenzuela Miguel A. , Rubio Fausto , Morales Ernesto , Oteo José L. 
Published: April 2011

ABSTRACTPorous SiO2-PDMS-TiO2 hybrid materials have been prepared by the Sol-Gel method using tetraethoxysilane (TEOS), silanol terminated-Polydimethylsiloxane (PDMS) and tetrabuthylortotitanate (TBT) as precursors. These materials were characterized by means of nitrogen adsorption, mercury porosimetry and helium picnometry. It was found that the meso and microporosity are predominant in all samples. The influence of the TBT concentration in the final pore structure and texture of SiO2-PDMS-TiO2 hybrid materials was studied. Results showed that increasing the TBT concentration decreases the pore volume of micropores, mesopores and macropores. On the other hand the specific surface areas of meso and macropores decreases with increasing TBT content, but micropore areas increase with TBT. These results are assigned to the formation of ultramicropores when TBT is added. In addition, surface roughness is found to increase with TBT concentration which is attributed to the formation of hydrous titanium oxide based nanoparticles.
The Constrained Growth and Patterned Distribution of nc-Si from a-SiNx/a-Si:H/a-SiNx: Mechanism and Experiments
Authors: Chen K. J. , Chen K. , Wu L. C. , Ma Z. Y. , Han P. G. , Li W , Zhang L , Zhang Y. J. , Huang X. F. 
Published: April 2011

ABSTRACTWe get size-controlled nanocrystalline silicon (nc-Si) from a-SiNx/a-Si:H/a-SiNx sandwich structures by thermal annealing. Transmission electron microscope analyses show that the mean size and the grain size distribution (GSD) of the nc-Si are controlled by the annealing conditions and the a-Si sublayer thickness. We build a theoretical model of constrained crystallization which can well interpret the phenomena of the growth halt of nc-Si and higher crystallization temperature for the thinner a-Si sublayer. The experimental results indicate that constrained crystallization method is promising to achieve uniform and high density nc-Si array either by thermal annealing or by laser annealing. Based on this investigation we employ the method of laser interference crystallization (LIC) to fabricate nanocrystal Si with the two-dimensional (2D) patterned distribution within 10 nm thick a-Si:H single layer. Si nano-crystallites are selectively located in the discal regions within the initial a-Si:H layer. The present method is promising to fabricate various patterned nc-Si arrays for device applications simply by changing the geometry of the mask.
Nonlinear Stabilization Mechanisms in Amplitude Saturation During Sputter Ripple Formation on Silicon
Authors: Erlebacher Jonah , Brown Ari-David 
Published: April 2011

ABSTRACTSputter rippling refers to the formation of regular surface patterns during glancing incidence energetic ion beam etching of surfaces, usually as a result of a competition between etching (from the ion beam) and capillary action (driving smoothening via surface diffusion). Many different kinds of morphologies are often observed, including ripples oriented parallel and perpendicular to the projected ion beam direction and “quantum dots” arranged in hexagonal or rectangular arrays. Theoretical analyses of ripple evolution have concentrated on the initial stages of the surface instability leading to pattern formation, and the details associated with the nonlinear mechanisms leading to amplitude saturation and pattern stabilization remain a subject of active interest. The Si(111) surface is a single component surface with isotropic surface diffusion kinetics; for these reasons, this system provides a useful probe of surface evolution without complicating effects of compositional inhomogeneities and anisotropic terrace diffusion. Our examination of the Si(111) surface indicates that step-step interactions may play an important role in the evolution of sputter ripples in this system. To argue for this conclusion, a comparison with sputter ripple evolution on Si(001) is made.
Hexagonal-arranged ZnO Nanowire Arrays by Using Au Nanohole Membranes as Fabrication Template
Authors: Fan H. J. , Lee W. , Nielsch K. , Zacharias M. , Dadgar A. , Krost A. 
Published: April 2011

ABSTRACTA new template method for large-scale fabrication of hexagonally patterned and vertically aligned ZnO nanowires is demonstrated. The process involves a novel type of metal membrane, a gold catalyst template produced using the membrane as deposition mask, and the catalyst-guided growth of ZnO nanowires. The metal membranes, composed of hexagonal nanohole arrays, are electrochemically replicated from ordered porous alumina. The ZnO nanowires obtained have a uniform alignment perpendicular to the GaN surface and a distribution according to the pattern defined by the nanohole membrane. Such periodically arranged ZnO nanowires have potential applications as sensor arrays and piezoelectric transducers.