bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Characterization of Cadmium Telluride Doped Heterostructured Opaline Photonic Crystal
Authors: Solovyev V. G. , Romanov S.G. , Sotomayor Torres C.M. , Gaponik N. , Eychmüller A. , Rogach A. L.
Published: April 2011

A double-layer photonic crystal (PhC) possessing incomplete photonic band gap (PBG) has been prepared by successive formation of one opaline film on top of another and subsequent impregnation with CdTe colloidal nanocrystals as the light source. Transmission, reflection and photoluminescence (PL) spectra of this nanocomposite have been measured from 1.8 to 2.5 eV at different angles of the light incidence and detection. The suppression of emission intensity has been found at both stop bands of the PhC heterostructure. Depending on the excitation power, either suppression or enhancement of the emission rate at the stop band has been observed.
The Role of the Interfaces in the Optical Effects of Large-Sized SiCxO1-xN Nanocrystallites
Authors: Plucinski K.J. , Kaddouri H. , Kityk I.V.
Published: April 2011

The band energy structure of large-sized (10-25) nm nanocrystallites (NC) of SiCxO1-xN (0.961.06) was investigated using different band energy approaches, as well as modified Car Parinello molecular dynamics simulations of interfaces. A thin carbon sheet (of about 1e nm) appears, covering the crystallites. This sheet leads to substantial reconstruction of the near-the-interface SiCxO1-xN crystalline layers. Numerical modeling shows that these NC may be treated as quantum dot-like SiCxO1-xN reconstructed crystalline surfaces, covering the appropriate crystallites. All band energy calculation approaches (semi-empirical pseudopotential, fully augmented plane waves and norm-conserving self-consistent pseudopotential approaches) predicted the experimental spectroscopic data. In particular, it was shown that the near-the-surface carbon sheet plays a dominant role in the behavior of the reconstructed band energy structure. Independent evidence for the important role of the dot-like crystalline layers are the excitonic-like states, which are not dependent on the particular structure of the SiC, but are sensitive to the thickness of the carbon layer.
Surfactant Templated Assembly of Hexagonal Mesostructured Semiconductors Based on [Ge4Q10]4- (Q=S, Se) and Pd2+ and Pt2+ ions.
Authors: Trikalitis Pantelis N. , Rangan Krishnaswamy K. , Kanatzidis Mercouri G.
Published: April 2011

4-Mesostructured semiconducting non-oxidic materials were prepared by linking [Ge4Q10]4- (Q=S, Se) clusters with the square planar noble metal cations of Pd2+ and Pt2+ in the presence of cetylpyridinium surfactant molecules. The use of Pt2+ afforded materials with exceptionally high hexagonal pore order similar to those of high quality silica MCM-41. These materials are semiconductors with energy band gap in the range 1.8<Eg<2.5 eV.
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

This 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

By 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

The 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

In 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.
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

Thus, 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

Numerous 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

The 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

New 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

Holographically-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

Flow 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

To 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

SFM 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

We 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

This 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

C60-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

Scratch 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

We 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

Resorbable 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

Endovascular 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

Zebrafish (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.
UV Laser Induced Amino Group Substitution on Pet Ligament to Promote Inhibition of Collagen
Authors: Omuro H. , Hamada K. , Nakajima T. , Sinpuku E. , Nakagawa M. , Fukuda H. , Murahara M.
Published: April 2011

An amino functional group was substituted on a PET film surface for the purpose of making the implantation of collagen readily. The PET has been widely used for medical materials such as an artificial ligament because of its strength and antibacterial action. However, when transplanted in human bodies, its compatibility is not good enough to adapt to the collagen which grows from living body tissues. To avoid this reaction medicine has been used clinically which makes the PET fiber into a mesh state and after the transplantation into a human body, makes the tissue intrude in the PET fiber. However, this method has not shown satisfactory enough results to promote rehabilitation. If the living body compatibility of materials is improved the initial adapting power with the tissue can be enhanced.

Then we substituted NH2, which has a high affinity for collagen, on the PET surface by ArF laser. PET is highly hydrophobic and does not dissolve well in aqueous solutions. To avoid this reaction we make a thin ammonium fluoride solution layer on the PET surface with capillary phenomenon. Then an ArF laser beam was irradiated vertically onto the sample. The result of this treatment shows that an untreated sample having the contact angle of 80° with water and the bonding strength of only 1.0 kg/cm2 with collagen was improved to have the contact angle of 22° and the bonding strength to be 12 kg/cm2.

When the treated sample had been implanted into the subcutaneous tissue of a rabbit's regiones dorsales, existence of leukocyte colonies that are indicators of human histocompatibility was confirmed on the hydrophilic parts of the sample.
Engineering Micrometer and Nanometer Scale Features in Polydimethylsiloxane Elastomers for Controlled Cell Function
Authors: Feinberg Adam W. , Seegert Charles A. , Gibson Amy L. , Brennan Anthony B.
Published: April 2011

Cell movement, differentiation and metabolic function must be controlled in precise ways to produce both regenerated tissues such as bone and functional tissue equivalents such as immuno-isolated islet cells. Close examination of extracellular matrix (ECM) reveals structures on the micron and nanometer scale that are shown to influence these factors and therefore we hypothesize that cells will move based on topographical cues in the scaffold. We have engineered siloxane elastomer surfaces that mimic the ECM by combining micron and nanometer scale topographic features. Micron scale pillars and ridges ranging in height from 1.5 to 5 microns and separated by 5, 10 and 20 microns were fabricated in a silicon wafer using micro- processing techniques and replicated in polydimethylsiloxane (PDMS) elastomer. Nanometer scale pillars, ridges and more complex shapes ranging in height from 12 to 300 nanometers were superimposed on the micron scale features using nanolithography. This was achieved by using a tapping mode tip in the atomic force microscope (AFM) to plastically deform the substrate surface. The AFM enabled nano-features to be placed on sloped surfaces and added directly to the PDMS elastomer surface. Surface topography was examined using scanning electron microscopy, atomic force microscopy and white light interference profilometry to verify surface modifications and fidelity of the replication process. Results indicate that it is possible to create spatially engineered surface textures from 10-5 m to 10-8 m in size, in specified patterns, by using a combination of microprocessing and nanolithography techniques. As better understanding of ECM function and design is gained, the processing methods outlined here will assist in fabricating tissue engineering scaffolds optimized at the nanometer and micron scale.
Bioerodible Polypyrrole
Authors: Zelikin Alexander , Shastri Venkatram , Lynn David , Farhadi Jian , Martin Ivan , Langer Robert
Published: April 2011

Conductive polymers such as polypyrrole (Ppy) are potentially useful as an active interface for altering cellular processes and function. Their utilization in medically related applications however have been substantially held back by their non-degradable nature. Herein we report a novel approach to creation of bioerodible polypyrroles via modification of pyrrole beta-carbon with an ionizable moiety. It has been shown that the erosion rate of acid-bearing derivative of polypyrrole increases with pH, which is consistent with the pH dependent ionization of carboxylic acid group. The novel paradigm proposed for the creation of bioerodible polypyrroles allows for simple and efficient control over the erosion rate of the substrate independent of the polymer chain length, via the choice of the terminal ionizable group and its concentration along the polymer backbone.
Imaging of Subsurface Defects in Bivalve Shells by Photothermal Techniques
Authors: Gómez-Martínez O. , Zambrano-Arjona M. , Alvarado-Gil J.J.
Published: April 2011

The potential of photothermal radiometry for subsurface defect imaging in shells of Crassostrea virginica is explored. It is shown that using this technique in the modality of modulated frequency, it is possible to obtain photothermal images in the case of small thermal diffusion lengths. By controlling the modulation frequency, it is shown that the technique can be useful in the study of buried defects in the shell. The application of this technique in monitoring living organisms is discussed.
Treatment and Analysis of a Paint Chip from “Water Lilies” a Fire Damaged Monet
Authors: Miller Sharon K.R. , Banks Bruce A. , Tollis Greg
Published: April 2011

A museum fire in 1958 severely damaged a Monet “Water Lilies” (1916-1926) painting that was on display. The surface of the painting is very dark with areas of blistering and charring. Over the years, traditional techniques have been found to be ineffective at removal of the soot and char from the surface. The painting, which is now in the care of the New York University (NYU) Conservation Center of the Institute of Fine Arts, was the subject of a study to determine if atomic oxygen treatment could remove the soot and char without damaging the fragile painting underneath. For test purposes, a small chip of paint was removed from the edge of the painting by a conservator at NYU and supplied to NASA Glenn Research Center for atomic oxygen treatment and analysis. The diffuse spectral reflectance, at three locations on the paint chip, was monitored at intervals during the atomic oxygen treatment process. Photo documentation of the chip during treatment was also performed. The color contrast was calculated from the spectral reflectance data as a function of treatment duration. Results of the testing indicated that the contrast improved as a result of the treatment, and the differentiation of colors on the surface was significantly improved. Soot and char could be removed without visibly affecting the gross surface features such as impasto areas. These results indicate the feasibility for the treatment of the “Water Lilies” painting.
The Condition and Cleaning of Acrylic Emulsion Paintings
Authors: Murray Alison , Berenfeld Celina Contreras de , Chang S.Y. Sue , Jablonski Elizabeth , Klein Tracey , Riggs Marion C. , Robertson Elizabeth C. , Tse W.M. Anthony
Published: April 2011

Cleaning acrylic emulsion paintings is challenging because of the material properties of the paint films, including their solubility. The goal of this work was to learn more about the effect of aqueous treatments on acrylic paints. Paint manufacturers were asked for their recommendations for cleaning these paintings and conservators were asked to comment on the damage observed in them and on the treatments applied. Responses showed that aqueous cleaning treatments are used, despite the associated risks, and that more technical information is needed about the effects of cleaning. The experimental section of this paper evaluated the changes in physical and mechanical properties of aged cobalt blue paint as a result of exposure to aqueous cleaning solutions. The results indicated that short immersions in these solutions caused a drop in most mechanical properties, but longer immersions did not; the drop after the short immersions was mostly due to the great increase in dimensional thickness of the paint films. Longer conservation treatment times are not being advocated.
Practical Bloomery Smelting
Authors: Sauder W. H. Lee , Williams Henry G.
Published: April 2011

The art and technique of bloomery smelting, man's original method for winning metalliciron from its ore, has been largely lost in recent centuries. Many reconstructions of this technique have been attempted by archaeologists in the last 30 years. These experimental smelts have tended to be rather disappointing in terms of the production of usable iron; nonetheless, many conclusions have been drawn from this work.

The main goal of our work with bloomery smelting is the production of iron for the creation of forged sculpture. Our focus on producing a usable product has led us to a somewhat different view of the technology from what has been published in the archaeological literature.

In this paper, we will briefly summarize our work through the spring of 2000, which has been published elsewhere. We'll then report our recent findings from the 2000-2001 smelting season, describing a typical smelt of the most efficient smelting regimen we have yet discovered. We will pay particular attention to methods that differ from those of other experimenters, especially in regards to blowing rate, slag management, and the recycling of furnace products. Finally, we'll point toward areas of upcoming research.
Achieving High Spatial Resolution in Elemental Mapping of Metal Samples from Archaeological Contexts
Authors: Lea Scott , Baer Don , Paparazzo Ernesto , Northover Peter , Salter Chris
Published: April 2011

Improving the characterisation of archaeological artifacts brings a need to understand better the relationships between composition, structure and properties. With archaeological material there is also a requirement to consider the effects of ageing and environmental interactions in altering the original structure and composition, both in the bulk and at the surface. However, curatorial constraints and, frequently, the condition of the objects preclude the sampling methods required for the most powerful means of structural analysis of materials, the high resolution transmission electron microscope. The samples normally available are small bulk samples and we must find other means of maximising spatial resolution in microchemical and microstructural analysis of both bulk and surface regions of the samples. This paper describes ways in which this is being achieved using the scanning proton microprobe (SPM) with both particle induced X-ray emission (PIXE) and Rutherford back scattered proton (RBS) spectra at resolutions down to ca. 1:m, electron probe microanalysis (EPMA) at 250-300nm, and scanning Auger microscopy (SAM) at resolutions of 10-20nm, but only from the surface layers of atoms in a sample. Examples will be given which demonstrate the contribution that each instrument can make, and that new and useful information is obtained each time resolution is increased. They will also show that structural features can be identified which are invisible to other microscopies. It will also be shown how modern PC-based software has greatly enhanced the mapping capability of all instruments.
A Materials Investigation into the Metal Composition and Coating Structures of Four Ming Dynasty Cast Iron Statues, with Subsequent Discussion and Development of a Treatment Protocol
Authors: Moffatt Elizabeth A. , Shugar Aaron N. , Sirois P. Jane , Stock Susan
Published: April 2011

Four iron statues dated by inscription to the Ming Dynasty, China, (1491 A.D.) were investigated for their metal composition and coating structures. The investigation was initiated with the intent of ascertaining whether any prior treatment had been done and to determine the present condition of the objects. During visual examination and simple surface cleaning, it became apparent that the objects had some form of surface decoration and polychrome. On closer examination, gilding, lacquer, and traces of pigment around the hat, eyes, and garments were visible. A sample of the metal was taken for metallography and chemical compositional analysis. Samples were taken from the surface of the four objects to identify the composition of the observed decoration and corrosion. The results revealed that the statues are white cast iron and were fully decorated with multiple colours and gilding as well as being sequentially lacquered. Recommendations for the cleaning and conservation of these and similar objects are given.
A 16,000 Year-Old Ceramic Human-Figurine from Maina, Russia
Authors: Vandiver Pamela B. , Vasil'ev Sergey A.
Published: April 2011

The ceramic technology used to construct and fire an image of a human figurine excavated from a 16,000 year old layer at the archaeological site of Maina on the Yenesei River in southern Siberia is reconstructed using x-radiography, x-ray diffraction, optical and scanning electron microscopy with simultaneous energy dispersive x-ray analysis, and electron beam microprobe analysis. Evidence is provided from the archaeological excavation as well as radiocarbon dating. Comparative studies of the clayey soils at the site add contextual and environmental evidence to establish this remarkable technology as having been carried out at the site using a local clay-loam resource.
Pixe, Electron Microprobe Data, and Experimental Archaeology: Tell el-Ajjul and Pilot Studies of Gold Granulation Joining Practices in the Mediterranean Bronze Age
Authors: Politis Thea
Published: April 2011

This paper discusses the results of a pilot study using Proton Induced X-ray Emission (PIXE) analysis of gold granulated objects from the Bronze Age site of Tell el-Ajjul in Southern Palestine obtained with the Oxford University proton microprobe. Using modern granulated samples with known smithing processes as points of comparison, it is demonstrated how information on ancient joining practices may be accurately gauged. The importance of characterizing objects of known provenance is emphasized in a discussion of archaeological context. It is argued that the building of a large Mediterranean-wide database of granulation analyses can add new depths to our understanding of temporal, social, cultural and technological relationships in the past.
Microstructural Analysis of A Steel Tool Rescued from Historical Site in Rio De Janeiro State
Authors: Campos Guadalupe do Nascimento , Solórzano Guillermo
Published: April 2011

The present work has as its objective a metallographic analysis of a metallic archaeological artifact using methods of optical microscopy (OM) and scanning electron microscopy (SEM). The object of study is a scythe from the Brazilian colonial period, dated beginning of XVII century, removed from an archaeological site, Sítio Cruzeiro, in excavations conducted by researchers of the Brazilian Archaeological Institute. Sample preparation required a meticulous procedure in view of the fragility of the object. The scythe has been suffering the action of oxidation-corrosion for over 300 years, allowing the impregnation of mineral sediments. A detailed metallographic analysis coupled with spectroscopic SEM measurements concluded that of the object was made of steel with a carbon content of the order of 0.4%. The equi-axed microstructure together with the alignment of inclusions strongly suggest a metal working procedure followed by heat treatment and a slow cooling rate as the method used for fabricating the artifact.
Investigation of N2 Plasma Effects on the Density Profile of Hydrogen Silsesquioxane Thin Films
Authors: Lee H. J. , Lin E. K. , Wu W. L. , Fanconi B. M. , Lan J. K. , Cheng Y. L. , Liou H. C. , Wang Y. L. , Feng M. S. , Chao C. G.
Published: April 2011

The density depth profile and chemical bond structure of hydrogen silsesquioxane (HSQ) thin films treated with an N2 plasma with varying power and exposure time were measured using specular x-ray reflectivity (SXR) and Fourier transform infrared (FTIR) spectroscopy. The SXR data indicate that the density profile of an untreated HSQ film is not uniform and four layers with different electron densities were required to fit the SXR data. For HSQ films treated with either increasing plasma power or plasma exposure time, the film roughness increased and a densified layer was observed at the film/air interface. The thickness of the densified layer increased with both plasma power and plasma exposure time. As a result, up to seven distinct layers were used to model the experimental SXR data from plasma treated films. The FTIR data show that the plasma transforms the Si-H bonds in the HSQ film into Si-O bonds leaving more oxygen atoms around a Si atom. These data are also consistent with the densification observed in the SXR measurements. In general, the HSQ film is more sensitive to increasing plasma power than to increasing plasma exposure time.
Correlations Between Structural Characteristics and Process Conditions of HSQ Based Porous Low-k Thin Films
Authors: Lee Hae-Jeong , Lin Eric K. , Wang Howard , Wu Wen-Li , Chen Wei , Deis Thomas A.
Published: April 2011

A novel methodology using a combination of ion scattering, x-ray reflectivity (SXR), and small angle neutron scattering was used to characterize the structure and properties of a hydrogen silsesquioxane (HSQ) based porous low-k dielectric films after varying process conditions. The dielectric constant and the remaining Si-H fraction (degree of cure) of the samples were varied from 1.5 to 2.2 and from 30 % to 52 %, respectively, by controlling the mass ratio of the solvent and the HSQ resin in the initial solutions and the wet ammonia treatment time. We determined the density depth profile, average mass density, wall density, porosity, average pore size, average wall thickness, pore connectivity and atomic composition. The chemical bond structures were also measured using Fourier transform infrared (FTIR) spectroscopy. The density profile of each porous low-k film was uniform and only two layers were required to fit the experimental SXR data. Higher dielectric constant films show significantly higher wall densities and lower porosities and pore sizes. The measured increases in the wall density with lower Si-H fractions are consistent with the FTIR results.
Low Dielectric Constant Functionalized Silica Gels
Authors: Gorman Brian P. , Orozco-Teran Rosa A. , Roepsch Jodi A. , Mueller Dennis W. , Reidy Richard F.
Published: April 2011

Scaling requirements of the semiconductor industry demand interlayer dielectric materials with low dielectric constants, chemical compatibility with Cu, thermal and mechanical stability, and the capability of integration into planned device structures. We have developed a novel low-k silica gel processing technique capable of both bulk and spin-on film architectures. Derived from fluorinated silica, this gel exhibits very low dielectric constants (1.18 in bulk and 2.1 in thin film measured using AC impedance methods). Structural determination from FTIR illustrates a fluorinated silica structure with shortened Si-O bonds, however, the fluorine is lost after annealing at elevated temperatures. Microstructural analysis by TEM indicate a highly unusual morphology with highly linked features and pore sizes in the 30nm range, coinciding with nitrogen adsorption results. Mechanical properties of the thin films, as studied by nanoindentation methods, shows that the films have extraordinarily high elastic moduli (12GPa) and hardness (1GPa).
Comparative Analysis of the Nucleation and Growth of Copper on Different Low-k Polymers
Authors: Zaporojtchenko V. , Erichsen J. , Strunskus T. , Behnke K. , Faupel F. , Baklanov M. , Maex K.
Published: April 2011

In this work we present investigations of the nucleation and growth of evaporated copper on several low-k polymers. The evolving interfaces were characterized using transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results were compared between the PMDA/ODA polyimide, Teflon AF 1601 and Silk®. A diffusion coefficient for copper atoms in Silk® determined by low energy ion-beam depth profiling in conjunction with XPS is reported.
Highly (111) Oriented Al Thin Films by Ion-Plating Method Using Discharge Plasma
Authors: Masui Shin , Kinoshita Kimio , Sakuragi Susumu , Kudo Toshio , Takayama Shinji
Published: April 2011

Application to aluminum deposition using ion-plating method is described. This method has several superior features for generating highly (111) orientation. The origin of this orientation and surface roughness are discussed in connection with a kinetic energy of the ions. The film properties thus made were compared with those of a conventional sputtered film. The higher (111) oriented film showed high resistance against hillock formation even after annealing at high temperatures. An effect of a plasma cleaning of substrate surface was confirmed to be quite helpful for promotion of (111) preferred orientation.
Bridging Properties of Multiblock Copolymers
Authors: Rasmussen K.Ø. , Kober E. M. , Lookman T. , Saxena A.
Published: April 2011

Using self-consistent field theory, we attempt to elucidate the links between microscopically determined properties, such as the bridging fraction of chains, and mechanical properties of multiblock copolymer materials. We determine morphological aspects such as period and interfacial width and calculate the bridging fractions, and compare with experimental data.
Patterned Deposition from Compressed Carbon Dioxide
Authors: Luscombe C. K. , Huck W. T. S. , Holmes A. B. , Lu T. , Leeke G. A. , Santos R. C. D. , Al-Duri B. , Seville J. P. K.
Published: April 2011

Compressed CO2 is employed as the solvent for the deposition of polymers onto patterned surfaces created by a lithographic technique. This deposition technique should have wide applicability in the deposition of organic and polymeric materials for optoelectronic devices. The advantage of controlled deposition confers a further benefit in the control of the patterned surface. In a specific example a perfluorinated polymer was dissolved in liquid carbon dioxide. The polymer solution was deposited by use of a nozzle onto a pre-patterned surface. The resulting polymer film showed a clear image of the original pattern as measured by optical microscopy.
Analysis on the Characteristics of Low-k Benzo-Cyclo-Butene Passivation
Authors: Sul W. S. , Han H. J. , Lee H. S. , Lee B. H. , Kim S. D. , Rhee J. K.
Published: April 2011

Surface passivation for the devices is very important for ensuring the DC and RF performances as well as the reliability in pseudomorphic high electron mobility transistors (PHEMT's). We performed the comparative study on the DC, RF and noise characteristics of the 0.1 μm gate length PHEMT's passivated by low dielectric constant benzo-cyclo-butene (BCB) layers with those passivated by the conventional Si3N4 or the. The noise performance of the BCB passivation for the PHEMT's was much superior to that of the Si3N4, whereas the DC and other RF properties were not significantly affected by the passivation materials.