bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Polymer Patterning Method based on Pattern Forming States of Liquid Crystals as Templates
Authors: Kang Shin-Woong , Sprunt Samuel , Chien Liang-Chy
Published: April 2011

We describe a new polymer patterning technique that produces controllable morphological and optical anisotropy in a polymer network. This technique is based on the use of pattern-forming states of nematic and cholesteric liquid crystals as templates for forming ordered polymer networks. One and two-dimensional optical patterns are induced by applying an electric field across a narrow gap of an electro-optical cell. These field-induced optical patterns are then stabilized by UV-induced polymerization of a typically 5 wt% reactive monomer in liquid crystal host. Depending on specific conditions (e.g., thickness to pitch ratio of a cholesteric, applied electric field, and wavelength of UV illumination), the polymer captures various degrees of the orientational order and spatial periodicity of the pattern-forming states of liquid crystals. The fidelity of the templating effect is explored using polarizing optical microscopy and SEM. We also describe the effect of UV wavelength on the network morphology and the morphological control over the”third” dimension (normal to the cell substrates).
Formation of Microporous Films via Pattern Photo-Polymerization Induced Phase Separation
Authors: Meng Scott , Nwabunma Domasius , Kyu Thein
Published: April 2011

We describe a method of fabricating microporous films through pattern photopolymerization induced phase separation in a mixture of solvent/monomer using multi-wave mixing, i.e., four-wave mixing through interference of two horizontal and two vertical waves. The simulation on the microporous forming process was undertaken in the framework of the time-dependent Ginzburg-Landau (TDGL) Model B equations coupled with the reaction kinetic equation of photopolymerization. In the total free energy description, Flory-Huggins free energy of mixing was combined with the elastic free energy of the network. The calculated results showed that the microporous size, shape, and spacing of the micropores depend on the angle of interference and the reaction rate controlled by the incident UV intensity.
Holographic Polymer Dispersed Liquid Crystals: Effect of Partial Matrix Fluorination on Electro-Optical and Morphological Properties
Authors: Schulte Michael D. , Clarson Stephen J. , Natarajan Lalgudi V. , Guymon C. Allan , Bunning Timothy J.
Published: April 2011

Holographic polymer dispersed liquid crystal (H-PDLC) films with partially fluorinated matrices were investigated. Electro-optical and morphological studies revealed that fluorinated composites were substantially different from non-fluorinated analogues. The addition of a fluorinated monofunctional acrylate monomer to a pentaacrylate-derived polymer matrix resulted in improved diffraction efficiency. These findings suggest that the partial fluorination of the host polymer decreases the compatibility between the matrix and liquid crystal phase. Morphological differences between fluorinated films and non-fluorinated control specimens were verified using low-voltage, high-resolution scanning electron microscopy (LVHRSEM).
Theory and Simulation of Fiber Texture Formation and Rheology of Carbonaceous Mesophase Fibers
Authors: Rey A. D.
Published: April 2011

Carbonaceous mesophases are discotic nematic liquid crystals that are spun into high performance carbon fibers using the melt spinning process. The spinning process produces a wide range of different fiber textures and cross-sectional shapes. Circular planar polar (PP), circular planar radial (PR) textures, ribbon planar radial (RPR), and ribbon planar line (RPL) textures are ubiquitous ones. This paper presents, solves, and validates a model of mesophase fiber texture formation based on the classical Landau-de Gennes theory of liquid crystals, adapted here to carbonaceous mesophases. The effects of fiber cross-sectional shape and elongational flow on texture formation are characterized. Emphasis is on qualitative model validation using existing experimental data [1, 2]. The results provide additional knowledge on how to optimize and control mesophase fiber textures.
Film Thickness Effects on Interfacial Fracture of Epoxy Bonds
Authors: Moody N. R. , Bahr D. F. , Kent M. S. , Emerson J. A. , Reedy E. D.
Published: April 2011

Nanoindentation test techniques were combined with deposition of highly stressed overlayers to study the interfacial fracture susceptibility of spin coated Epon 828/T403 on aluminized glass substrates as a function of film thickness. The test techniques required to induce fracture differed between samples. Nevertheless, the resulting interfacial fracture energies decreased monotonically with film thickness to a value near 0.5 J/m2. This value is higher than the ‘true work of adhesion' for uncured epoxy oliogomers on a methyl-terminated aluminum surface. However, it may indicate that we have irreversible specific interactions such as hydrogen bonding. Then 0.5 J/m2 may be near the fundamental value for such an interaction, or the ‘practical work of adhesion’.
Application of Self Assembled Monolayer Approach to Probe Fiber Matrix-Adhesion
Authors: Feresenbet E. , Raghavan D. , Holmes G. A.
Published: April 2011

Adhesion at the fiber-matrix interface of composites is often related to a combination of factors such as mechanical interlocking, physico-chemical interactions, and chemical bonding of the fiber-matrix interphase region. We demonstrate the use of self-assembled monolayer (SAMs) approach for depositing silane coupling agent on glass fiber and studying the impact of the individual interactions on the adhesion process. Through some unique chemistry, functionalized and non-functionalized C11 chlorosilanes were deposited on to E-glass fiber and modified. The adhesion of diglycidyl ether of bisphenol-A (DGEBA) cured with meta-phenylene diamine (m-PDA) to SAM layer on E-glass fibers was measured by performing single fiber fragmentation tests (SFFT). The extent of adhesion between the fiber and matrix was found to be dependent on carbon chain length of coupling agents, and the functional group at the end of the SAMs layer. Furthermore, the contributions to adhesion by physico-chemical interaction and covalent bonding has been individually assessed.
Surface and Interfacial Properties in Thin Poly(p-Phenylene Vinylene) Multilayers Prepared by Self-Assembly Method
Authors: Borges Célio A. M. , Marletta Alexandre , Faria Roberto M. , Guimarães Francisco E. G.
Published: April 2011

In this work we report on the influence of interfaces (metal/film, ITO/film) on the optical properties of ultrathin layers of poly(p-phenylene vinylene), PPV, adsorbed by self-assembly. PPV films were prepared exploiting the self-assembly method (SA) in addition to a low temperature conversion process for PPV. Using atomic force microscopy we show that 0.5 nm thick PPV layers can be homogeneously deposited on different metals (50% transmission Au, Cu, Pt, Ag, Cr films), glass and ITO surfaces. Absorption measurements reveal that the transitions involving φ-φ* conjugated states are blue shifted to different extents depending on the interface and on the film thickness. This indicates different extensions of interfacial disorder in the PPV layers. The ITO/PPV interface has the highest extension for disorder (∼16 nm) and highest surface roughness (RMS∼2.5 nm) while the lowest values (∼5 nm and 0.6 nm, respectively) were found for the quartz/PPV interface. The metal interface induces significant luminescence quenching and spectral shifts, which depend on the type of metal used. The effect from incorporation of carbonyl and from chemical modifications of the ITO/organic interface during PPV thermal conversion is discussed.
Emission Light from Prism/Silver/Molecular Ultrathin Films and Excitations of Multiple Surface Plasmons in ATR Kretschmann Configuration
Authors: Kaneko Futao , Nakano Takayuki , Sato Toshiharu , Shinbo Kazunari , Kato Keizo , Kawakami Takahiro , Wakamatsu Takashi
Published: April 2011

Emission light through the prism has been investigated from the Kretschmann configuration of the prism/ Ag thin film/ rhodamine-B (RB) LB film in the resonant excitation of the attenuated total reflection (ATR) measurement. The emission light and the spectra strongly depended upon the emission angles where the light was observed. The emission properties corresponded to the dispersion relation of the resonant excitations of surface plasmons (SPs) in the ATR configuration. It was concluded that the emission light was caused by multiple excitations of SPs in the ATR configuration. It is thought that the phenomenon will be used as a new sensing device.
Dielectric Properties of Multi-Layer High-K Polymer Composite Films
Authors: Sakai Wataru , Chiang C. K.
Published: April 2011

The electrical properties of thin polymer films are key parameters in the design of both smaller and faster circuit devices in the microelectronics industry. In this study, we made a three-layer film structure, ABA', to investigate the dielectric interaction between two high-K dielectric polymer thin films, A and A', as a function of the thickness of the middle B layer. The Cole-Cole plot showed clear changes with the thickness of the middle B layer. The total capacitances were evaluated with a simple serial three capacitances model. This ABA' structure is thought to be very useful for studying mechanical and thermal properties of thin polymer film system.
Modelling of the Thin Organic Film/Carbon Steel Interface
Authors: Popa Mihai V. , Drob Paula , Vasilescu Ecaterina , Anghel Maria , Rosca Iulia Mirza , Lopez Agustin Santana
Published: April 2011

The electrochemical impedance spectroscopy (EIS) has been used for the modelling of the alkyd organic film/carbon steel interface in 3% NaCl solution. Both the dielectric properties of the organic film and the corrosion processes of the metallic substrate were investigated with this method. Analysis of the impedance spectra (Nyquist and Bode plots) and the interpretation with the fitting software developed by Boukamp, established the presence of two time constants in the first 250 immersion hours. One time constant concerning the organic layer describes the electrical and barrier properties of film. The second time constant concerning the substrate represents the corrosion reactions at the film/metal interface. For long immersion periods, after the formation of the conductive pathways in the film and the development of the diffusion processes, are necessary another two time constants concerning these phenomenons. The error magnitude between the measured and calculated data with these electric equivalent circuits is satisfactory. The physical properties obtained from the principal elements of the equivalent electric circuits are in concordance with those obtained from others testing methods.
Nuclear Microprobe Analysis of Transmembrane Ion Flux in Rat Brain
Authors: Briski Karen P. , Hollerman William A. , Glass Gary A.
Published: April 2011

Maintenance of euglycemia is crucial because glucose is the sole nutrient that can be utilized by the brain, retina, and germinal epithelium in sufficient quantities to provide required levels of energy. Since carbohydrate reserves in neural tissue are limited, normal nerve cell function depends upon a continuous glucose supply. Neurons located in select brain sites, including the hindbrain nucleus tractus solitarius/area postrema complex (NTS/AP), exhibit unique electrophysiological and/or genomic responses to glucopenia, suggesting that regulatory signaling of this substrate fuel deficit originates within these select loci. Fundamental questions concerning the identification of monitored metabolic variables and the molecular mechanisms by which local sensor cells transduce energetic distributions into neural signals remain unresolved. The combination of microscopic particle induced x-ray emission (μPIXE) and scanning transmission ion microscopy (STIM) can permit quantitative multielemental mapping of the brain, at the single cell level, with part-per-million sensitivity while simultaneously providing structural information. Over the past year, the authors have investigated methods for utilization of μPIXE and STIM in conjunction with established neuroanatomical and pharmacological approaches in a novel strategy to characterize electrolytic indices of neuronal function. Micrometer-scale resolution of discrete brain sites is expected to yield critical information on intracellular levels of ions that regulate membrane potential and synaptic firing. This paper presents results on regional mapping for effects of metabolic manipulations deficits on the transmembrane flux of sodium, potassium, chlorine, and calcium ions. This research will significantly advance the current understanding of the cellular and molecular bases linking neuronal energetics with homeostatic regulation of metabolic substrate availability.
An Investigation of Nano-structured Polymers for Use as Bladder Tissue Replacement Constructs
Authors: Thapa Anil , Webster Thomas J. , Haberstroh Karen M.
Published: April 2011

Conventionally, studies investigating the design of synthetic bladder wall substitutes have involved polymers with micro-dimensional structures. Since the body is made up of nano-structured components (e.g., extracellular matrix proteins), our focus has been in the use of nano-structured polymers in order to design a three-dimensional synthetic bladder construct that mimics bladder tissue in vivo. In order to complete this task, we fabricated novel, nano-structured, biodegradable materials to serve as substrates for bladder tissue constructs and tested the cytocompatibility properties of these biomaterials in vitro. The results from our in vitro work to date have provided the first evidence that cellular responses (such as adhesion and proliferation) of bladder smooth muscle cells are enhanced as poly (lactic-co-glycolic acid) (PLGA) surface feature dimensions are reduced into the nanometer range.
In situ Mineralization of Hydroxyapatite for a Molecular Control of Mechanical Responses in Hydroxyapatite-Polymer Composites for Bone Replacement
Authors: Katti Kalpana , Gujjula Praveen , Ayyarsamy Arunprakash , Arens Timothy
Published: April 2011

In situ mineralization of hydroxyapatite (HAP) and the role of organics in initial nucleation and growth of HAP is critical for the resulting nano and microstructure of HAP. In situ mineralization of hydroxyapatite (HAP) in the presence of Ca binding polymers such as polyacrylic acid has shown some promise towards improvement of mechanical response of uniaxial compressed HAP/polymer composites to loading. This work represents fundamental studies on the nature of in situ HAP precipitation on resulting microstructure of the composite and bulk mechanical properties. Specifically, an experimental study, evaluating the role of initial stage mineralization of HAP on bulk mechanical responses is conducted. Fourier transform infrared (FT-IR) spectroscopic (with micro attenuated total reflectance) techniques are utilized to evaluate the association of polymer (polyacrylic acid) with HAP during mineralization of HAP. In situ HAP exhibits a faster mineralization as compared to the ex situ mineralization samples, This improved kinetics is responsible for altering the resulting micro and nanostructure of the HAP/polymer composite. Small spectral changes are detected in the absorbance spectra of in situ HAP as compared to ex situ samples. Changes in mechanical response to loading included improvement in strain-to-failure and resulting toughness characteristics of the in situ composite. The control and development of molecular-level associations of polymer with HAP is suggested to be critical for the resulting macro properties. Our results may have significant implications for design of nanocomposites for biomedical applications.
Small Diameter, High Surface Energy Carbon Nanofiber Formulations that Selectively Increase Osteoblast Function
Authors: Price Rachel L. , Elias Kathy L. , Haberstroh Karen M. , Webster Thomas J.
Published: April 2011

The objective of the present in vitro study was to investigate the potential of carbon nanofibers, which have nanometer dimensions similar to hydroxyapatite crystals in physiological bone, for orthopedic applications. Studies of alkaline phosphatase activity and calcium deposition by osteoblasts (the bone-synthesizing cells) were performed on both nanophase (less than 100 nm) and conventional (greater than 100 nm) diameter carbon nanofibers. Results provided the first evidence of a strong correlation between decreased carbon fiber diameter and both increased alkaline phosphatase activity and increased calcium deposition by osteoblasts at early time points (specifically, 7 days), but not at later time points (specifically, 14 and 21 days). Results of early calcium deposition by osteoblasts on carbon nanofibers are promising and consistent with the desired rapid formation of natural bone at the implant interface.
Synchrotron X-ray Observations of a Monolayer Template for Mineralization
Authors: DiMasi E. , Gower L. B.
Published: April 2011

Mineral nucleation at a Langmuir film interface has been studied by synchrotron x-ray scattering. Diluted calcium bicarbonate solutions were used as subphases for arachidic and stearic acid monolayers, compressed in a Langmuir trough. Self-assembly of the monolayer template is observed directly, and subsequent crystal growth monitored in-situ.
Electroactive Polymerized Vesicles as Stable Biomaterials for Charge Storage Systems and Electron Coupling Applications
Authors: Stanish Ivan , Singh Alok
Published: April 2011

Diacetylenic phospholipids with disulfide functionality were synthesized and incorporated at dopant levels with unmodified diacetylenic phosphatidylcholine lipids in polymerized vesicles. These polymerized vesicles were immobilized on Au films and structurally characterized in situ using AFM and ESEM and demonstrated surface stability of at least three days. Polymerized diacetylenic phospholipid vesicles displayed retention of entrapped ferricyanide with a half-life of 2.4 weeks at pH 7 and 25 oC. Membrane-bound benzoquinone mediated electron transport across polymerized vesicle membranes providing an initial current of 25 mA and a final charge capacity based on entrapped ferricyanide of 3.5 Ahr/kg. Electron transport across polymerized diacetylenic phospholipid vesicle membranes was described by a pseudosteady-state transport model and was found to be diffusion limited.
Bio-Inspired Nanocomposites: From Synthesis Toward Potential Applications
Authors: Asefa Tewodros , Coombs Neil , Grondey Hiltrud , Jaroniec Mietek , Kruk Michal , MacLachlan Mark J. , Ozin Geoffrey A.
Published: April 2011

In recent years, the extraordinary properties of bio-inspired nanocomposites have stimulated great interest in the development of bottom-up synthetic approaches to organic-inorganic hybrid materials in which molecular scale control is exerted over the interface between the organic and inorganic moieties. These developments have led to advanced materials with novel properties and potential use in catalysis, sensing, separations and environmental remediation. Periodic mesoporous organosilica (PMO) materials are an entirely new class of nanocomposites with molecularly integrated organic/inorganic networks, high surface areas and pore volumes, and well ordered and uniform size pores and channels. We recently have extended the approach to include novel PMO materials incorporating chiral and heteroatom-containing organic functional groups inside the inorganic framework that may be useful in asymmetric catalysis, enantiomeric separations and heavy metal remediation.
Fib/Tem Analysis of Paint Layers from Thomas Eakins' TheCrucifixion, 1880
Authors: Lins Andrew , Giannuzzi Lucille A. , Stevie Frederick A. , Price Beth , Tucker Mark , Gutman Nica
Published: April 2011

Many issues in the examination, treatment, and authentication of works of art depend on the accurate characterization of thin layers, which may challenge the resolution and detection limits of instrumentation routinely used for analyses, particularly SEM-EDS and EPMA. Such thin layers are the focus of recent conservation analysis in preparation for a major retrospective of Thomas Eakins' works. Interpretation of Eakins' paintings has often been complicated by mechanical and chemical cleaning procedures performed after the artist's death in 1916.

Recent advances in Focused Ion Beam (FIB) technology provide means for preparing specimens of thin layers that can be analyzed directly by transmission electron microscopy (TEM) yielding resolution in the nanometer range or better. This paper describes initial work undertaken to elucidate the inorganic components in the uppermost paint layers from Eakins' The Crucifixion, completed in 1880. Using TEM, we have observed a 250-500 nm Pb-rich nanocrystalline region, a pigment free zone less than 2 μm thick, and a lead white paint layer. An analysis of samples from two paintings that were subjected to mild cleaning operations did not show comparable Pb-rich nanocrystals. These results suggest that The Crucifixion may have been subjected to a more aggressive cleaning treatment which caused the entrainment of the Pbrich material–not resolvable by traditional analytical techniques – at the painting's surface. The use of FIB/TEM has enabled clear identification of the thin paint surface layers and offers enormous promise for understanding the processing and alteration of artists' materials, including issues of authentication.
The XthCent. Church in Drustar: Study of Wall Paintings by Spectroscopic Methods
Authors: Zorba T. , Paraskevopoulos K.M. , Siapkas D.I. , Pavlidou E. , Angelova S. , Kushev D.B.
Published: April 2011

The technique and painting used in the earlier wall paintings from the characteristic Christian church in Drustar - close to the river Danube - in Bulgaria, are studied. The fragments of wall paintings used in this study are examined mainly by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Analysis (EDS). It is concluded that the technique used was fresco and that the pigments used are common to those used in the Byzantine era.
Simulated Standards for the Characterization of Dolomitic Mortars
Authors: Montoya C. , Lanas J. , Arandigoyen M. , Navarro I. , Casado P.J. García , Alvarez J.I.
Published: April 2011

In order to clarify the structure underlying the appearance of several compounds in dolomitic mortars (specifically hydromagnesite, Mg5(CO3)4(OH)2.4H2O), as well as the suitability of the X-ray diffraction (XRD) and thermogravimetric and thermodifferential simultaneous analysis (TGA-DTA) in their determination, different patterns from phases that could be present in mortars of these characteristics have been prepared and studied by these techniques. The standards were prepared from: hydromagnesite (HY) with calcite in weight/weight proportions 1:1 to 1:5; HY with calcite and quartz in proportions 1:1:1 and 1:6:12; HY with quartz, 1:1 and 1:2; HY with portlandite (calcium hydroxide), 1:1 and 1:2; HY with portlandite and quartz, in 1:6:12, and HY with magnesium oxide in 1:1, 1:2 and 2:1.

The XRD results have shown that it is possible to detect HY and the other compounds (dolomite, calcite, magnesite, quartz, …), but when the HY is mixed, the intensity of its diffraction peaks is very weak, even not detectable in some cases. The poor crystallinity of the HY could be the reason of this drop in intensity. Therefore thermal studies were necessary to find HY phases in low weight percentages.

TGA-DTA led us to establish the experimental conditions most suitable for thermal studies. A high CO2 pressure around the sample was required for the occurrence of an exothermic peak at 500°C. This high pressure was guaranteed in the present work as follows: static air atmosphere, packed sample, high heating rate (20°C.min-1), and alumina crucibles with holed lids in order to establish a selfgenerated atmosphere. The thermal behavior of hydromagnesite phases has been clearly established in contradiction to some references of the literature; specifically, the exothermic peak at 500°C has been observed repeatedly. This result invalidates reports of the crystallization of magnesium carbonate from the amorphous phase.
Characterization of Ancient Dolomitic Binding Materials from Zamarce, in Navarre (Spain)
Authors: Montoya C. , Lanas J. , Arandigoyen M. , Navarro I. , García Casado P.J. , Alvarez J.I.
Published: April 2011

Ten ancient mortars of dolomitic origin, used in the construction of the church of Santa María de Zamarce in Navarre, Spain, have been studied in order to define their composition and to characterize the type of binder employed. A complete characterization has been carried out including: morphological examination (visually and using optical microscopy); mineralogical studies (X-ray diffraction, XRD); chemical analysis (main components and soluble salts); grain size distribution and thermal studies (thermogravimetric and thermodifferential simultaneous analysis, TGA-DTA). Dolomite and calcite, as binders, and quartz, as aggregate, have been found as the main phases. The important variability of the studied samples has confirmed that the choice of the raw materials and their preparation were not taken carefully. Thermal behavior of the samples has shown the endothermic peaks related to calcite and dolomite decarbonations. No hydromagnesite phases have been detected. Finally, the approximate indications of the original composition of the raw materials mixtures are presented.
Neutron-induced autoradiography in the study of oil paintings by Tintoretto, Marieschi and Bellotto
Authors: Pańczyk E. , Pytel K. , Kalicki A. , Rowińska L. , Sartowska B. , Waliś L.
Published: April 2011

A complex technological investigation of 14th-18th centuries Venetian paintings from the collection of the National Museum in Warsaw has been performed in connection with the “Serenissima- Light of Venice” exhibition. After analysis of the X-ray radiographs of the autoradiography to obtain indisputable information about over-painting (Tintoretto) or either confirmation or contradiction of their authenticity (Marieschi, Bellotto).

All the paintings under analysis were irradiated in a specially designed station at the research reactor MARIA in Swierk near Warsaw. Beta-rays emerging from the painting surface irradiated by thermal neutrons and recorded on a X-ray film displayed the distribution of elements in pigments used for creating individual layers of the painting. It allows for tracing the particular phases of the painting structure invisible to the naked eye.

The report presents results obtained for the following paintings: J. Tintoretto – Portrait of a Venetian Admiral, M. Marieschi – The palace of Doges in Venice, B. Bellotto called Canaletto – Fantasy architecture with self-portrait of the artist.
A New Method of Restoration and Conservation of Metallic Archeological Objects
Authors: Malkhasyan R. T. , Shakhverdyan R.
Published: April 2011

Our method of Quantum - Chemical Technology based on use of strongly non-equilibrium vibrationally highly excited, very active molecules of hydrogen, allows in conditions of low temperature and pressure to realize the direct restoration of the corroded archeological metal-containing objects, without change of their shape and sizes.
A Ghost Story: Remnant Structures in Corroded Ancient Iron Objects
Authors: Notis Michael R.
Published: April 2011

The applicability of a broad spectrum of laboratory analytical methods to the study of remnant structures still observable in the corrosion products of ancient iron objects is discussed. These methods range from examination by light optical microscopy and SEM to direct microanalysis using x-ray mapping in EPMA. Samples ranging from low carbon iron to steels to cast iron have been examined and it has been found possible to observe remnant structures and infer fabrication information from the large majority of objects studied. The author thanks the Nathan Rubin-Ida Ladd Foundation for its support.
Renaissance Enameled Jewelry and 19th century Renaissance Revival: Characterization of Enamel Compositions
Authors: Wypyski Mark T.
Published: April 2011

Enamels from European Renaissance enameled gold jewelry and other objects dating from the sixteenth and seventeenth centuries, and Renaissance style and other objects from the eighteenth and nineteenth centuries were quantitatively analyzed using energy dispersive X-ray spectrometry. Differences were observed in the overall compositions, as well as the colorants and opacifiers used, of the Renaissance period and most of the later enamels. Some enamels from as late as the early nineteenth century, however, appeared to be essentially the same as those used during the Renaissance. The differences found in the enamel compositions can provide a set of objective compositional criteria to help distinguish between authentic Renaissance period enameled objects and some later enamels done in the style of the Renaissance.
AMS radiocarbon dating of a Western Han period (3rd-1st century BC) lacquer-coated earthenware jar
Authors: Hodgins G. W. L , Farrell E. , Mowry R. D.
Published: April 2011

The chronometric dating of ceramic objects is normally achieved by thermoluminscence techniques (TL). Here we report both TL and a radiocarbon measurements on a Chinese earthenware hu jar (Harvard University Art Museums LTL1.2001.23 a,b). TL dates were obtained from earthenware core samples using established methods. The radiocarbon date was obtained from an organic coating present on the jar surface. The coating was preliminarily identified as urushi by a comparison of its FTIR absorption spectrum to absorption spectra obtained from modern and ancient lacquer standards. The material was found to be insoluble in a variety of solvents, mineral acids, and bases. Combustion and elemental analysis revealed that 64% of the coating mass was carbon. C measurement by AMS was carried out on a 3.9 mg sample of chemically cleaned lacquer. This measurement generated a date of 2191 ± 38 BP. Calibration of this measurement placed the age of the jar between 390BC and 160 BC at the 95% confidence interval. The calibrated radiocarbon date corroborated the TL measurement placing the jar at between 2400 and 1500 years old (400 BC to 500 AD). These findings also agreed with stylistic evidence that the jar was produced during the Western Han period (206 BC-AD 9). The literature on urushi composition, its pigment compatibility, its high carbon content, its apparent chemical stability, and the small sample required for C-accelerator mass spectrometry suggests that other lacquer-coated objects might be dated using a similar approach.
Investigating Ceramic Technology During Archaeological Field Seasons
Authors: Henrickson Robert C.
Published: April 2011

Investigation of many aspects of ancient ceramic production technologies is feasible during an archaeological field season, and requires little equipment. Descriptive variables such as color, inclusions ( temper ), variable textures within the paste, surface finish, hardness, and decorative techniques and style provide technological as well as stylistic or typological data. Residual surface traces, the surfaces of breaks themselves, and their overall patterning relative to both the vessel shape and size provide forming and finishing data. Subsequent laboratory analysis of samples complements the field data.
The Characterisation of a Bronze Age Weapon Hoard
Authors: Northover J.P. , Bridgford S.D.
Published: April 2011

The study described here is based on the proposition that all events in the life of a bronze artefact, from the moment it was cast to the time it became available for characterisation, have the potential to leave a trace that can be identified by one or more metallographic methods. The hoard presented here was found at Waterden, Norfolk, England by metal detecting and excavation after it was scattered by the plough. The find comprises 201 fragments from approximately 130 swords and spearheads. It is important for understanding the evolution of the Bronze Age sword in Britain, and also for understanding the destruction and deposition of weapons in weapon-only assemblages. Besides a consideration of the hoard from a typological perspective the project used five methods of examination: a) a surface study for manufacturing traces, combat damage, possible cremation, and damage in the ground or at recovery, b) radiography, c) compositional analysis by electron probe microanalysis, d) optical metallography, and e) microhardness testing. This is the first occasion in which these techniques have been combined in the investigation of a complete hoard. It has been possible to divide the results from each technique into simple categories so that clear correlations can be made, so it can be shown that sword blades had more elaborate finishing than others, that some workshops had better casting practice than others and that the great majority of swords had combat damage. The effects of destruction and fire are also discussed and a context for the deposition of the hoard reconstructed.
An Ethnoarchaeological Perspective on the Material and Chemical Residues of Communal Feasting at El Coyote, Northwest Honduras
Authors: Wells E. Christian , Urban Patricia A.
Published: April 2011

This paper examines artifact distributions and chemical analysis of anthropogenic sediments by ICP-AES spectroscopy from the main civic-ceremonial plaza at the Late Classic (ca. AD 700-900) site of El Coyote in northwestern Honduras. Based on ethnoarchaeological comparisons drawn from a phosphate study of plaza soils in the nearby modern-day town of Petoa, spatial aspects of the organization of communal feasting are inferred for El Coyote.
A Study on the Properties of Different IMP Ta, Ta(N) and Multi-Layer Ta/Ta(N) as Diffusion Barriers for Cu Metallization
Authors: He L. , Li C.Y. , Zeng Z.Q. , Wu J.J. , Qian Y. , Zhang Y. , Liu H.D. , Xie Joseph
Published: April 2011

We report a study on the properties of Ionized Metal Plasma (IMP) Ta, Ta(N) and multi-layer Ta/Ta(N) based on a comparative evaluation of their performance as diffusion barriers in Cu based metallization schemes. The film structures used in this study are: IMP Cu(2000Å)/IMP Ta(250Å)/Si; IMP Cu(2000Å)/IMP Ta(N)(250Å)/Si; and IMP Cu(2000Å)/IMP multi-layer Ta/Ta(N)(250Å)/Si. The samples were annealed in N2 ambient at 500 °C, 550°C, 600°C and 650°C, respectively, for 30 minutes. The failure behavior and film properties of different barriers were investigated using MetaPULSE, Film stress measurement (FSM), Four-point probe (FPP), X-ray diffractometry (XRD), Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM). It has been observed clearly from the sheet resistance measurements that failures of Ta(N) and Ta barriers occurred at 550°C and 600°C respectively, whereas the multi-layer Ta/Ta(N) could still survive from the annealing up to 650°C. Evidence showing the formation of Cu3Si in the failed film stacks was found from XRD spectra. Based on our studies, it can be concluded that microstructures of the barriers has the major effects on preventing Cu from diffusing through them to react with Si and this makes the multi-layer Ta/Ta(N), in overall, superior to the other two Ta and Ta(N) barriers.
Deposition and Characterization of PECVD SiOC Films by Using Bistrimethylsilylmethane (BTMSM) Precursor
Authors: Kim Yoon-Hae , Hwang Moo Sung , Lee Young , Kim Hyeong Joon
Published: April 2011

Carbon-containing silicon oxide (SiOC) is regarded as a potential low dielectric constant (low-κ) material for an interlayer dielectric (ILD) in next generation interconnection. In this study, we present the fundamental film properties and integration process compatibility of the low-κ SiOC film deposited by using bistrimethylsilylmethane (BTMSM) precursor. As more carbon was incorporated into film, both film density and dielectric constant decreased. The lowest κ-value, which we have obtained in this study, was 2.3 and the hardness of SiOC film was 1.1GPa as well as showing the thermal stability up to 500°C. In case of using conventional gases, organic components in SiOC film restricted etch rate. However, O2 addition could make it possible to obtaine a reasonable etch rate. The post-treatment of SiOC film in hydrogen plasma improved the resistance to O2 plasma in ashing process. The compatibility of SiOC film to the CMP process was also examined.
Chemical Vapor Deposition (CVD) of Tungsten Nitride for Copper Diffusion Barriers
Authors: Gordon Roy G. , Barton Jeffrey , Suh Seigi
Published: April 2011

A new process was developed for deposition of the tungsten nitride at moderate substrate temperatures (350-400 °C). The tungsten source bis (tert-butylamido)bis(tertbutylimido) tungsten, (tBuNH)2(tBuN)2W, reacts with ammonia in a low-pressure CVD reactor. Growth rates ranged from about 0.6 to 4.1 nm per minute. The stoichiometry of the films varied from WN1.2O1.7 to WN1.6o0.25, depending mainly on deposition temperature. The films are amorphous by X-ray diffraction, and smooth by scanning electron microscopy. Step coverage is nearly 100% in vias with an aspect ratio of 6:1 for films deposited at 400 °C or lower. Barriers 45 nm thick resist diffusion of copper up to temperatures of 600 °C. Adhesion is strong to all substrates tested, including silicon, silicon dioxide, soda-lime glass, glassy carbon, aluminum and stainless steel. This new halogen-free process avoids halogen contamination of films and corrosion of equipment. Uniformity of thickness and stoichiometry are readily achieved. This process is a promising method for forming copper diffusion barriers in future generations of microelectronics.
Defect Nucleation and Annihilation in Sheared Polymeric Liquid Crystals
Authors: Grecov Dana , Rey Alejandro D.
Published: April 2011

Shear–induced nucleation and annihilation of topological defects due to hydrodynamic instability in nematic liquid crystals is a phenomenon of both scientific interest and practical importance. We use a complete generalized non-linear second order tensor Landau-de Gennes model that takes into account short range order elasticity, long-range elasticity and viscous effects, to simulate the nucleation and annihilation of twist inversion walls in flow-aligning nematic polymers subjected to shear flow. Shearing a homogeneous nematic sample perpendicular to the director results in an linear instability that maybe symmetric at low shear rates, and antisymmetric at higher shear rates. At even higher shear rates the onset of nonlinearities results in the nucleation of a parallel array of twist inversion walls, such that asymmetry prevails. By increasing the shear rate the following director symmetry transition cascade is observed: symmetric → antisymmetric → asymmetric → symmetric. The nucleation of the parallel array of twist inversion walls in the asymmetric mode is due to the degeneracy in reorientation towards the shear plane. The annihilation of twist walls is mediated by twist waves along the velocity gradient direction. Twist walls annihilate by three mechanisms: wall-wall annihilations, wall-wall coalescence, and wall-bounding surface coalescence. The annihilation rate increases with increasing shear rate and at sufficiently high rates the layered structure is replaced by a homogeneously aligned system. The role of short range and long range elasticity on defect nucleation and annihilation is characterized in terms of the Deborah and Ericksen numbers. Close form solutions to approximated equations are used to explain the numerical results of the full Landau-de Gennes equations of nematodynamics.
Pulling Single Chains out of a Collapsed Polymer Monolayer in Bad-Solvent Conditions
Authors: Koutsos Vasileios , Haschke Heiko , Miles Mervyn J. , Madani Frédéric
Published: April 2011

It has been theoretically predicted that a polymer chain in poor solvent conditions undergoes a phase transition from a collapsed globule to a stretched coil. In this paper, we present force-distance curves, obtained by atomic force microscopy (AFM), showing the characteristic forceplateau associated with this transition. We show that the magnitude of the force depends on the environment (interfacial energy) that the stretched coil experiences when it is pulled-out as it is predicted by the theory.
Biomimetic Dextran Coatings On Silicon Wafers: Thin Film Properties And Wetting
Authors: Ombelli Michela , Eckmann David M. , Composto Russell J.
Published: April 2011

There has been much recent interest in polysaccharide coatings for biotechnology applications. We obtained highly wettable dextran coatings applied to flat silicon wafer surfaces through a two-step process: in the first step, the silicon is aminated by the deposition of a self-assembled monolayer of 3-aminopropyltriethoxysilane (APTES); in the second step, polydisperse and low dispersity dextrans with molecular weights ranging from 1 kDa to 100 kDa are covalently grafted along the backbone to the surface amino groups to achieve strong interfacial anchoring. The effect of dextran concentration on film thickness and contact angle is investigated. Atomic force microscopy (AFM) has been employed to characterize surface roughness and coverage of the dextrans as well as the APTES monolayers. The synthetic surfaces were also tested for gas bubble adhesion properties.
Hole injection and transport in a fluorene-containing copolymer
Authors: Khan Rizwan U. A. , Kreouzis Theo , Poplavskyy Dmytro , Bradley Donal D. C.
Published: April 2011

We have studied the electrical properties of a fluorene-containing copolymer which is currently being developed for state-of-the-art blue polymer LEDs. This copolymer is made up of three functional groups which are nominally the hole-conducting, electron conducting and emissive regions. Using a combination of current/voltage, time-of-flight and dark injection transient versus temperature measurements, the injection and transport properties of the material have been investigated. Hole injection from polystyrene sulphonate doped polyethylenedioxythiophene (PEDOT:PSS) into the polymer is found to be consistent with an ohmic contact. Hole transport within the fluorene copolymer is found to possess a mobility that is two orders of magnitude lower than that for previously studied polymers containing the copolymer constituents. Using the equations for trap-free space-charge limited current, predicted J/V characteristics have been obtained from the mobility values derived using the time-of-flight technique. We discuss both the reduced hole mobility of the copolymer, and the discrepancies between the measured and predicted J/V characteristics, in terms of variations in both the trap and transport site densities and their energetic and spatial distributions.
Charge Carrier Injection Into A Disordered Organic Dielectric
Authors: Arkhipov Vladimir I. , Bässler Heinz , Emelianova Evgenia V.
Published: April 2011

Based upon the concept of charge carrier hopping within a disordered organic solid a formalism for the temperature and field assisted charge injection from an electrode into an organic dielectric has been developed. Both back flow of charges towards the injecting electrode and the dependence of the injection efficiency upon the charge carrier mobility has implicitly been taken care of. Experimental results for electrode limited injection are in good agreement with the theory.
Modification of Conducting Polymer Thin Film Interfaces Using Self-Assembled Monolayers Containing Transition Metal Complexes
Authors: Sarno David M. , Prasad Sudhindra , Jones Wayne E. , Matienzo Luis J.
Published: April 2011

Thin films of polyaniline (PANi) have been in-situ deposited onto fused silica plates modified with ruthenium porphyrin and polypyridyl complexes coordinated to self-assembled monolayers of pyridyl-terminated alkylsilanes. Based on UV-vis and AFM studies, PANi exhibits a slower deposition rate and an earlier onset of secondary nucleation on the metal complex-modified interfaces. Electrical conductivity of the HCl-doped emeraldine salt form of PANi is increased to as high as 40 S/cm, relative to <1 S/cm on bare silica, measured under the same conditions and in the absence of any external modification to the polymer films. These changes are attributed to favorable π interactions between the aromatic surface species and the conjugated polymer that lead to a more expanded coil conformation for PANi.
Implant Surface Modification by Biological Multi-layer Systems
Authors: Willumeit Regine , Kamusewitz Helmut , Schossig Michael , Schröder Jens , Clemens Helmut
Published: April 2011

The current design of implants or implant materials is under the pressure of an increasing demand. In our society we find more and more active older people with an increasing life time. On the other hand it can be observed that also for younger people implants become more and more necessary due to sport or accidents. As a consequence the development of new surgery strategies as well as new materials systems is needed. In this work we present the idea of creating a metal implant surface which mimics a cell membrane or at least parts of it. Scanning electron and atomic force microscopy investigations show that a multilamellar closed lipid layer can be prepared and that this layer resembles the same contact angle observed for the membrane of an osteoblast.
Current-Induced Degradation in Polythiophene
Authors: Goldberg Velda , Kaplan Michael , Soltzberg Leonard , Genevich Joseph , Coombs Emily , Giacomozzi Erica , Kwasnik Valarie , Naeem Samia , Pham Eleana , Malliaras George
Published: April 2011

The three-year collaboration between Simmons College and the Cornell Center for Materials Research (CCMR) is focused on undergraduate student/faculty research in organic light emitting diodes (OLEDs). The physics of OLED devices is characterized by three major processes: charge injection, charge transfer, and light emission as a result of the electron-hole recombination. In the first year of the program our research has been related to the first two stages.

OLEDs based on small molecule as well as polymeric layers have been investigated. The devices were prepared using mostly aluminum (also nickel and iron) as electrodes and PC:TPD or polythiophene as the organic layer. Electrodes of about 20 nm were formed by vacuum evaporation, and organic layers of approximately 100–200 nm were spin-coated. The current-voltage characteristics, measured under forward and reverse bias up to 10 volts, demonstrate typical semiconductor S-shape behavior, and show variations dependent on aging, thickness of the polymer layer, and type and combination of electrodes.

The results presented here specifically track the degradation of devices using polythiophene sandwiched between aluminum electrodes. The I-V curves and successive current response as a function of time and under constant voltage drive are presented along with complementary mass spectra and UV-visible and infrared absorption spectra. These measurements along with preliminary computer modeling of HOMO and LUMO energies for a series of thiophene oligomers suggest a correlation between internal changes in the polymer and variations in the electrical characteristics of the devices.