bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of Intersubband Transitions in Arrays of Bi Nanowire Samples Using Optical Transmission
Authors: Black M.R. , Maskaly K. R. , Rabin O. , Lin Y. M. , Cronin S. B. , Padi M. , Find Y. , Dresselhaus M.S. 
Published: April 2011

ABSTRACTThis paper reports the fabrication of large diameter pores (> 150nm) in anodic alumina that can be used to create wire arrays with significant surface effects, but without significant quantum confinement. These wires, therefore, allow us to distinguish between optical absorption spectra features originationg from quantum effects and those from surface effects. The paper presents techniques towards fabrication these bismuth wire arrays, and presents optical absorption data from two bismuth namowire arrays in the semimetal-semiconductor transition diameter regime. The results from previous publications are summarized and future directions are outlined.
Electric Field Induced Patterning of Polymer Films.
Authors: Bucknall David G. , Briggs G. Andrew D. 
Published: April 2011

ABSTRACTBy confining a polymer film between two electrodes one of which is solid but thin enough to be flexible, a characteristic lateral morphology is produced when a strong electric field is applied across the film. A simple model to describe the observed behaviour is presented which accounts for the length scales of the observed morphology. This model demonstrates that feature sizes ranging from microns to nanometers can be obtained through selective choice of key parameters.
Charge Transport in Mesoscopic Carbon Network Structures
Authors: Ksenevich V. , Galibert J. , Samuilov V. , Seo Y.-S. , Sokolov J. , Rafailovich M. 
Published: April 2011

ABSTRACTThe charge transport and quantum interference effects in low-dimensional mesoscopic carbon networks prepared using self-assembling were investigated.The mechanism of conduction in low-dimensional carbon networks was found to depend on the annealing temperature of the nitrocellulose precursor. The charge transport mechanism for carbon networks obtained at Tann=750°C was found to be the hopping conductivity in the entire investigated temperature range. The Coulomb gap near the Fermi level in the density of states was observed in the investigated carbon networks. The width of the Coulomb gap was found to be decreased with the annealing temperature of the carbon structures. The crossover from the strong localization to the weak localization regime of the charge transport in the carbon structures, obtained at Tann=950°C and Tann=1150°C, was observed in the temperature range T>100 K and T>20 K, respectively.
Characterization of Self-Assembled SnO2 Nanoparticles for Fabrication of a High Sensitivity and High Selectivity Micro-Gas Sensor
Authors: Ghan R.C. , Lvov Y. , Besser R.S. 
Published: April 2011

ABSTRACTIn order to refine further the material technology for tin-oxide based gas sensing we are exploring the use of precision nanoparticle deposition for the sensing layer. Layers of SnO2 nanoparticles were grown on Quartz Crystal Microbalance (QCM) resonators using the layer-by-layer self-assembly technique. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Electron Diffraction Pattern (EDP) analyses were performed on the self-assembled layers of SnO2 nanoparticles. The results showed that SnO2 nanoparticle films are deposited uniformly across the substrate. The size of the nanoparticles is estimated to be about 3-5 nm. Electrical characterization was done using standard current-voltage measurement technique, which revealed that SnO2 nanoparticle films exhibit ohmic behavior. Calcination experiments have also been carried out by baking the substrate (with self-assembled nanoparticles) in air at 350°C. Results show that 50%-70% of the polymer layers (which are deposited as precursor layers and also alternately in-between SnO2 nanoparticle monolayers) are eliminated during the process.
Nanostructuring of Multilayers by a Thermally Driven Self Assembling Process
Authors: Herweg C. , Dreyer S. , Troche P. , Hoffmann J. , Sievers S. , Lang C. , Freyhardt H. C. 
Published: April 2011

ABSTRACTMultilayers consisting of two immiscible components (e.g. Fe/Ag Fe/Au or Ni/NiO) could by transformed by an annealing process into a nanostructured system of non statistically distributed nearly spherical particles in a surrounding matrix of the complementary component. The non statistical arrangement of the particles and the dynamics of the disintegration process strongly depend on the initial interface energy, i.e. the local interface curvature and the local interfacial stress. Detailed microstructure investigations of the different systems are used to interpret the measured transport properties.
Nonlinear Optical Absorption and Related Phenomena in Liquid Crystals
Authors: Tabiryan N.V. , Hrozhyk U.A. , Margaryan H.L. , Mora M.J. , Nersisyan S.R. , Serak S.V. 
Published: April 2011

SUMMARYThus, in the present paper, we reported about several processes of nonlinear absorption and transmission in dye-doped NLC: nonlinear absorption due to light induced reorientation of NLC doped by highly dichroic dyes; nonlinear transmission due to nonlinear birefringence, and self-extinguishing of the beam due to”critical opalescence,” critically enhanced light scattering at the pre-transition region of nematic-isotropic phase transition. All these processes have large application potential for laser beam control and characterization techniques.
Theory and Simulation of Texture Transformations in Chiral Systems: Applications to Biological Fibrous Composites
Authors: Luca Gino De , Rey Alejandro D. 
Published: April 2011

ABSTRACTNumerous studies [1-3] have shown that chiral biological structures share common properties with liquids crystals, in particular a tendency to assemble in three-dimensional lattices very similar to that of chiral nematics. Biological fibrous composites are usually found in planar (film) and cylindrical (fibber) twist geometries. In this work, the formation process of the planar twist architecture is numerically investigated using a mesoscopic model based on the Landau-de Gennes theory of chiral nematic liquid crystals. The simulations and visualizations of the computed textures provide new information on some of the principles that govern the formation of chiral biological structures. It is found that a defect-free planar twist architecture arises from a chiral front propagation process with a fully relaxed wake.
Synthesis of Triphenylene-Based Discotic Liquid Crystal Monomer Containing Azobenzene Moieties
Authors: Silong Sidik , Rahman Lutfor , Yunus WMZ Wan , Rahman M Zaki , Ahmad Mansor , Haron Jelas 
Published: April 2011

ABSTRACTThe synthesis of a novel discotic liquid crystal monomer was carried out based on vinyl monomer whose molecular architecture consists of a triphenylene as central core and the peripheral cores were linked to the central core through an alkyl chain spacer. Consequently, a disk-like poymerizable monomer 2, 3, 6, 7, 10, 11-hexakis-[11-(4-{4-(acryloxy)phenylazo}phenoxy)undecanoxy]triphenylene was prepared by using a ferric chloride oxidation method. Polarizing optical microscopy and DSC analysis shows that the monomer exhibited a wide columnar mesophase. UV-vis spectra of the azobenzene mesogens showed that a significant tailing, which would allow the use of laser in the visible range to photoinduce isomerization and reorientation of the azo groups.
Photoactive Cholesteric Polymeric Material With Dual Photochromism
Authors: Bobrovsky Alexey , Boiko Natalia , Shibaev Valery 
Published: April 2011

ABSTRACTNew cholesteric polymeric material containing a liquid crystalline (LC) copolymer with side phenylbenzoate nematogenic and photochromic spiropyran groups and 5 mol % chiral photochromic dopant based on cinnamic acid and isosorbide was prepared. It was shown that UV irradiation and subsequent annealing of planarly-oriented mixture films lead to untwisting of the cholesteric helix and cause an irreversible shift of selective light reflection to the long-wavelength region. This process is explained by the E-Z isomerization of chiral photochromic groups of the dopant relative to a C=C bond accompanied by a decrease in their twisting ability. Upon UV irradiation of films at room temperature, a thermally reversible transformation of spiropyran groups into a merocyanine form takes place, which is followed by the appearance of an intense absorption maximum in the visible spectral region. It was shown, that the use of the material prepared in this work provides an opportunity to record two images at a time: one image is due to a change in the helical pitch and another image (above) is due to the photochromism of spiropyran groups. It is pertinent to note that using the approach developed in this work allows one to widely vary the range of materials exhibiting dual photochromism. It was demonstrated that the mixture under examination shows promise as new photosensitive material for optics, optoelectronics, and data recording.
Cavity Morphology of Polymer Dispersed System Utilizing Atomic Force Microscopy
Authors: Fontecchio Adam K. , Crawford Gregory P. , Content David 
Published: April 2011

ABSTRACTHolographically-formed Polymer Dispersed Liquid Crystal have been imaged using atomic force microscopy (AFM) tapping techniques to study the droplet cavity morphology. Reflection-mode Bragg gratings were created using a 532 nm beam expanded laser to holographically form a grating structure within the liquid crystal / polymer film. The films were removed from their glass substrates prior to imaging by an atomic force microscope, and the digital files were analyzed. The surface structure is not smooth, as anticipated, but contains cavities with a dimpled morphology. We report our investigations and analysis including AFM images, image analysis, and liquid crystal / polymer alignment considerations.
Computational Modelling of Mesophase Pitches’ Shear Rheology
Authors: Grecov Dana , Rey Alejandro D. 
Published: April 2011

ABSTRACTFlow modelling of mesophase pitches is performed using a previously formulated mesoscopic viscoelastic rheological theory [1] that takes into account flow-induced texture transformations. A complete extra stress tensor equation is developed from first principles for liquid crystal materials under non-homogeneous arbitrary flow. Predictions for a given simple shear flow, under non-homogeneous conditions, for the apparent shear viscosity and first normal stress differences are presented. The rheological functions are explained using macroscopic orientation effects, which predominate at low shear rates. The predicted normal stress differences and apparent shear viscosity are in agreement with experimental measurements.
Studies of Silane Adhesion Promoters on Silica Filler Particles for use in Microelectronic Packaging
Authors: Jenkins Maura , DeVries Gretchen , Dauskardt Reinhold H. , Bravman John C. 
Published: April 2011

ABSTRACTTo avoid delamination which often occurs in microelectronic packaging as a result of widely varying thermal expansion coefficients, epoxy underfill is often loaded with particulate silica filler. This filler typically complicates the fracture behavior of the epoxy and surrounding layers. However, delamination of interfaces within the composite may contribute to toughening if the fracture path is adhesive between the epoxy and surrounding layers or otherwise removed from filler-epoxy delamination regions. In this work, the interface between silica filler and epoxy is altered with the use of silane coupling agents to elucidate the fracture and toughening mechanisms of filled epoxies. Two model epoxies are investigated, and coupling agents were chosen to encourage chemical reaction with each system. For the aliphatic epoxy system, coupling agents were identified which both augment and degrade the interface between filler and epoxy. In composite structures, it was observed that those coupling agents which degrade the filler-epoxy interface act as toughening agents. SEM indicates that most deformation is not at the filler-epoxy interface, but rather through the epoxy, very close to the filler particle surfaces. In contrast, no coupling agents were identified which act as toughening agents in the bisphenol-f system. Further, no variation in fracture toughness of composite structures was observed with the use of coupling agents, indicating that filler-epoxy delamination does not occur in this system. With few exceptions, SEM supports this interpretation.
Polypropylene-Functionalized Probes for Scanning Force Microscopy
Authors: González-Ronda L. , Kaberline S. L. , Durieux E. L. 
Published: April 2011

ABSTRACTSFM probe tips have been functionalized with polypropylene (PP) layers by immersion into dilute solution. The immersion process was carefully controlled and monitored using a programmable dynamic contact angle analyzer (DCA) equipped with a microbalance and a motor capable of speeds ranging from 2-24 μm/s. Probes were submitted to treatment with ozone prior to coating to eliminate surface contamination, particularly silicone oils, resulting from commercial packaging methods. The chemical composition of the tip surface after the cleaning, coating, and scanning processes was analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). The three-dimensional tip shape and dimensions before and after coating were evaluated by blind reconstruction from images of a columnar titanium thin film using Digital Instruments' Tip Evaluation algorithm. Coating thicknesses of up to 20 nm were calculated, with the thicker coatings showing a larger degree of non-uniformity.
Substituent Effects on a Photo-Induced Alternation of the Lower Critical Solution Temperatures of Poly(N-isopropylacrylamide) with Azobenzene Units
Authors: Akiyama Haruhisa , Tamaoki Nobuyuki 
Published: April 2011

ABSTRACTWe synthesized copolymers of N-isopropylacrylamide (NIPAM) and azobenzene-containing acrylates or acrylamides by free radical polymerization, and investigated the water solubility of these polymers upon irradiation with ultra-violet and visible light. The solubility depended on concentration and structure of photoreactive azobenzene unit in the polymers. The soluble polymers showed the lower critical solution temperature, which was varied along with light irradiation. Photo-induced large wettability alteration was observed in the film.
Organic-Inorganic Network Assembles of Nanoparticles as Chemically Sensitive Interfacial Materials
Authors: Han Li , Kneller Jason M. , Daniel David R. , Kowaleski Scott R. , Kirk F. Louis , Luo Jin , Zhong Chuan-Jian 
Published: April 2011

ABSTRACTThis paper reports the result of a study of organic-inorganic network assembles as chemically sensitive interfacial materials. Core-shell gold nanoparticles of a 5 nm size and organic linkers such as 1,9-nonanedithiol and 1,5-pentadithiol are utilized as building blocks for constructing network assembles on planar substrates. To explore the responsive properties of such materials to volatile organic compounds, we utilized interdigitated microelectrodes as transducer. The responses at these nanostructured interfaces are demonstrated to be dependent on the chain length of the linking molecules. The difference of molecular interactions at the nanostructured interface has a significant impact to the response profile and sensitivity. The implications of the findings to the delineation of design parameters for constructing organic-inorganic network assemblies as chemically-sensitive interfacial materials are also discussed.
Preparation and Characterization of C60-Perdeuterated Styrene Copolymer Nanofilms
Authors: Lin Zhang , Kai Du , Houqiong Zhang , Yongheng Fan , Haiyan Tu , Xuan Luo 
Published: April 2011

ABSTRACTC60-Perdeuterated Styrene Copolymer (C60-DPS) was synthesized by the free radical polymerization. Thin films of C60-DPS were prepared by the Langmuir-Boldgett (LB) technique. The surface morphology and friction performance were characterized by atomic force microscopy (AFM). Results exhibit the presence of spherical granules in the compact LB films, which result from self-polymerization of C60 and showed friction of the LB films increased basically as C60 content of C60-DPS decreased.
Viscoelastic Effects on the Scratch Resistance of Polymers: Relationship Between Mechanical Properties and Scratch Properties at Various Temperatures
Authors: Morel Pierre , Jardret Vincent 
Published: April 2011

ABSTRACTScratch resistance of polymers has been the subject of numerous studies, which have lead to specific definitions for plastic characteristic and fracture phenomena during scratch behavior. Viscoelastic and viscoplastic behavior during a scratch process has been related to dynamic mechanical properties that can be measured via dynamic nano-indentation testing. Yet, the understanding of the origin of the fracture process of a polymer during scratch remains approximate. Parameters like tip geometry and size, scratch velocity and loading rate, applied strain and strain rates, have been considered critical parameters for the fracture process, but no correlation has been clearly established.The goal of this work was to analyze the scratch resistance and indentation properties of PMMA as a function of temperature. Compression and tensile properties from literature have also been compared to the scratch results for more complete understanding of the material's behavior.The analysis of the evolution of the properties of PMMA at various temperatures, along with the evolution of the fracture toughness during scratch with temperature and scratch velocity has helped in identifying a correlation between the tensile stress-strain behavior and scratch fracture toughness for PMMA. This correlation brings a new understanding of the origin of the fracture mechanisms during a scratch process, and the strain effect on the fracture strength of PMMA.
Monte Carlo Simulations of Copolymer Adsorption from Copolymer / Homopolymer Melts at Planar Chemically Patterned Surfaces
Authors: Semler James J. , Genzer Jan 
Published: April 2011

ABSTRACTWe investigate the adsorption of copolymers from copolymer / homopolymer mixtures at planar chemically patterned surfaces. The Monte Carlo bond fluctuation model is used in conjunction with configurational biased Monte Carlo moves to study the effect of: i) the copolymer microstructure, ii) the size and spatial distribution of chemical heterogeneities on the substrate, and iii) the polymer/substrate interactions on the ability of the copolymer to recognize the substrate chemical pattern. Our results confirm that the surface pattern recognition occurs whenever the characteristic size of the copolymer distribution sequence matches that of the surface heterogeneity domain. Moreover, the copolymer sequence distribution plays a crucial role in determining the extent of the surface pattern transfer into the bulk material. Our results reveal that more pronounced surface pattern transfer into the bulk occurs for small attractions of the adsorbing species to particular surface domains relative to the large attractions.
Bio-active Calcium Phosphate Thin Films on Implant Grade Titanium Alloy Using a Silica Barrier Layer
Authors: Reid J. , Sayer M. , Smith T.J.N. 
Published: April 2011

ABSTRACTResorbable calcium phosphate (CaP) thin films previously prepared only on quartz substrates were fabricated on Ti-6Al-4V implant grade titanium alloy. In order to maintain the characteristic phase composition and surface morphology of the CaP thin film, an intermediate silica barrier layer was deposited on the titanium alloy via chemical vapour deposition (CVD) using a metal organic precursor. CaP thin films were subsequently deposited on the intermediate SiO2 layer using the dip coating method, and sintered at 1000°C. The final sintered films have a multiphase composition consisting of calcium hydroxyapatite (HA) and a silicon stabilized form of alpha tri-calcium phosphate, or Si-TCP. The thickness of the silica barrier layers were evaluated in terms of the main CVD processing parameters using variable wavelength fixed angle ellipsometry and these parameters were optimized to best reproduce the characteristic CaP thin film. The phase composition and surface morphology of the CaP thin films were characterized using glancing angle X-ray diffraction and scanning electron microscopy.
Biocompatibility Comparison of Stainless Steel, Gold-Coated, and Heat-Treated Gold-Coated Endovascular Stents
Authors: Morss Alisa S. , Seifert Philip , Groothius Adam , Bornstein Danielle , Rogers Campbell , Edelman Elazer R. 
Published: April 2011

ABSTRACTEndovascular stents can be altered to improve radioopacity by applying a gold coating. We examined the vascular response in porcine coronary arteries to implantation of 9 mm NIR® stents that were either left intact, gold-coated, or heat-treated following gold coating. Our results show that while gold coating exacerbates neointimal hyperplasia and the inflammatory response, heat treatment removes this negative effect. Heat treatment was shown to increase the diffusion at the gold-steel interface and reduce the surface roughness.
Microstructure And Mechanical Properties Of Skeletal Bone In Gene-Mutated Stöpseldtl28d And Wild-Type Zebrafish (Danio Rerio)
Authors: Zhang Yang , Cui Fu-Zhai , Wang Xiu-Mei , Cai Qang , Feng Qing-Ling 
Published: April 2011

ABSTRACTZebrafish (Danio rerio), the only vertebrate organism now amenable to large scale of “saturation genetic screens”, provides a single opportunity to investigate the complex gene mechanisms for normally vertebrate-specific processes. Studies of bone formation and bone diseases utilizing zebrafish system are therefore of interest. In the present study, microstructure and mechanical properties of skeletal bone in gene-mutated Stöpsel dtl28d (stp/stp) and wild-type zebrafish were investigated using transmission electron microscopy (TEM) and an atomic force microscopy (AFM)-based nanoindenter. Abnormal collagen matrix and minerals were observed in stp/stp bone comparing to the wild-type control. Nanoindentation measurement disclosed that there was a significant increase of elastic modulus in stp/stp bone compared to that of the control. AFM examinations of the residual indenter impressions indicate that the bone of zebrafish becomes more brittle after stp gene-mutation. This observation of the alteration of bone collagen, minerals and mechanical behavior by gene-mutation in zebrafish system is of scientific and clinical importance in many fields, such as bone fracture and brittleness in human heritable disorders and materials fabrication of bone tissue engineering via gene control.