bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Distribution of Phosphorus in Romano-British Ironwork
Authors: Kaloyeros Alain E. , Ehrenreich Robert M. 
Published: March 2011

AbstractPhosphorus is found to be a common impurity in many of the iron tools and weapons produced during the pre-Roman and Roman Iron Ages of Britain (600 BC - 300 AD). The effects of this impurity on the properties and performance of antiquarian materials is not well understood, however. This paper presents the initial findings of an in-depth study of the distribution, chemistry, and effects of phosphorus in Romano-British ironwork. For this purpose, two Romano-British iron artifacts from the site of Ircheoter, Northamptonshire, were examined using powerful techniques for archeological materials analysis that include electron microprobe, secondary ion mass spectroscopy (SIMS), transmission electron microscopy (TEM) with energydispersive x-ray spectroscopy capabilities (EDXS), and Auger electron spectroscopy (AES). It was found that phosphorous was indeed present in the artifacts. The phosphorus atoms were predominantly segregated at grain boundaries and thus should have led to a lowering of grain boundary cohesion and a degradation in the performance of the tools.
Reconstructing Prehistoric Textile and Ceramic Technology from Impressions of Cloth in Figurines from Ecuador
Authors: Stothert Karen E. , Epstein Kathleen A. , Cummins Thomas R. , Freire Maritza 
Published: March 2011

AbstractA method is described for using vinyl polysiloxane dental impression material to make high definition casts from ceramic objects that bear negative imprints of textiles. Casts made from impressions found on prehistoric ceramic figurines from Ecuador were examined under magnification and features of the yarns and weaves were described. The data are used to reconstruct prehistoric spinning and weaving technology. The use of cloth in figurine manufacture and the reconstructed textile technology are interpreted in spatial, temporal and cultural perspectives.
The New Netherland/New York Ceramic Chemistry Archive: Compositional Analysis of Bricks by ICP
Authors: Gilbert Allan S. , Harbottle Garman 
Published: March 2011

AbstractHistorical archaeologists investigating early American production and trade must work with the written record as well as the evidence from controlled excavation. Both kinds of data have their place in the inquiry, yet the details they furnish are not necessarily congruent or applicable to the solution of all historical questions. To illustrate, artifacts were not always manufactured in the places where they are found, but in order to resolve this uncertainty accurately and directly, the origins of excavated materials must often be determined by means that are independent of historic documentation. If sources can be shown to be distant, then despite any similarity to items of known local manufacture or written evidence suggesting otherwise, long-range exchange structures must have been present. The interpretation of archaeological and historical data can then be guided by more informed judgment.
Thermal Analysis of Fresh and Mature Oil Paint Films: The Effect of Pigments as Driers and the Solvent Leaching of Mature Paint Films
Authors: McGlinchey Christopher W. 
Published: March 2011

AbstractThe effect of titanium white, zinc white and lead white on the drying properties of poppy, walnut and linseed oil are analyzed by differential scanning calorimetry (DSC). All of the fresh films undergo complex thermal transitions between -100 and O°C. For some of the dried films subambient transitions that resemble glass transitions occur at about -30 O°C. After exposure to certain solvents, these sub-ambient transitions disappear or are reduced significantly. It is suggested that samples with diminished sub-ambient transitions become more brittle as a result of the loss of materials that act as plasticizers.
A Mathematical Model for Microwave-Assisted Chemical Vapor Infiltration
Authors: Evans James W. , Gupta D. 
Published: March 2011

ABSTRACTA model for microwave heating of a ceramic preform is presented. Microwave power and external cooling are manipulated to obtain desired temperature profiles for effective chemical vapor infiltration (CVI) of the preform. A mass transport and chemical reaction model is developed to demonstrate preform densification. Conditions affecting matrix deposition are evaluated.
Generalized Pulse—Spectrum Technique for Solving Inverse Problems in Microwave Heating
Authors: Chen Y. M. , Wang Franklin F. Y. 
Published: March 2011

ABSTRACTThe Generalized Pulse—Spectrum Technique (GPST), a versatile, efficient and stable Newton-like iterative numerical inversion algorithm with Tikhonov regularization. GPSThas been been successfully applied to many practical inverse problems, including the inverse problems of equations of the diffusion type. Methodology in applying GPST for solving the inverse problems in microwave heating of ceramic samples is described.
Microwave Industrial, Scientific and Medical Applications in Brazil
Authors: Andrade Octavio M. 
Published: March 2011

ABSTRACTMicrowave ISM applications in Brazil are reviewed, with special emphasys on industrial. applications and measurement techniques of the dielectric properties of materials, where developments have been most sicgnificant.Special techniques for measuring the properties of typical Brazilian soils for radiometric applications in satellite remote sensing are discussed.High power microwave techniques are presented and analyzed.Industrial applications in ceramics, chemical products, food processing, sterilization, production of alcohol, and many others are explained. The design of special applicators for the above techniques, including continuous processing apparatus, detectors, special loads and waveguide configurations are reviewed.Various methods for obtaining the dielectric constant of solid and liquid substanlces are presented, and experimental techniques are analyzed.Biological and medical applications are in early stages of development, but present a great potential in the coming years at various well equipped medical institutions.In conclusion, the great potential of microwave non-communications applications in Brazil is explained, with promising achievements in the years ahead.
Estimates for Diffusion Barriers and Atomic Potentials in Mgo: Cndo/2 Calculations for the Study of Microwave Effects in Sintering
Authors: Skala L. , Kenkre V.M. , Weiser M.W. , Katz J.D. 
Published: March 2011

ABSTRACTAs part of a program of investigation of microwave sintering, self-consistent CNDO/2 calculations are presented for diffusion barriers and potentials for the motion of interstitial atoms and vacancies in MgO. Clusters of 30 atoms are used in the calculations. Activation energies, diffusion barriers, shape of the potentials and electron densities are obtained.
Processing of Silicon Wafers Followed by Microwave Photoconductivity Measurements
Authors: Sanders A. , Wetzel H. , Kunst M. 
Published: March 2011

ABSTRACTThe characterization of single crystalline silicon wafers for application in (opto)electronic devices by transient photoconductivity measurements is investigated. To this aim is the transient photoconductivity in Si wafers after different treatments determined by the Time Resolved Microwave Conductivity ( TRMC ) method. This technique is non-evasive and contactless and so in-situ measurements are possible. Application of TRMC measurements for process control and quality control of relevant process steps in the production of (opto)electronic devices is discussed in view of the experimental results presented.
An Amplitude-Only Measurement Technique for the Evaluation of the Complex Permittivity Of Composite Materials in the Microwave Range.
Authors: Bisceglia B. , Ciliberto A. , D'Ambrosio G. , Ferrara G. , Massa R. , Sabatino C. 
Published: March 2011

ABSTRACTThe basic transmission line and rectangular waveguide equations, with reference to different loading conditions, are firstly reviewed. Amplitude and phase, amplitudeonly, and phase-only permittivity measurement techniques are briefly discussed. Two very naive graphical and numerical calculation procedures are presented, together with the results of measurements on some composite materials.
Detoxification of Hazardous Waste Streams Using Microwave-Assisted Fluid-Bed Oxidation
Authors: Varma R. , Nandi S. P. , Katz J. D. 
Published: March 2011

ABSTRACTMicrowave-assisted oxidation of trichloroethane (TCE) performed at 500-580°C has been found to be significantly more efficient than conventional oxidation methods. Experiments were conducted using a 6 kW, 2.45 GHz power supply and a 6 inch bed of silicon carbide granules in a 1 inch diameter quartz reactor tube which in turn was placed in a microwave cavity. After heating the reactor to a given temperature a TCE-air stream was passed through the silicon carbide bed. TCE was almost completely detoxified (98-99%) in a single pass through the silicon carbide bed at 500-580°C. The oxidation products are HC1, CO2 and CO. By comparison the corresponding single-pass detoxification using conventional thermal methods results in only partial conversion. The principal products being dichloroethylene (C2H2C12) and HCl.
Acidic Biopolymers as Dispersants for Ceramic Processing
Authors: Pellerin N. , Staley J. T. , Ren T. , Graff G. L. , Treadwell D. R. , Aksay I. A. 
Published: March 2011

AbstractSome acidic biopolymers serve as dispersants for colloidal processing of ceramics. One biopolymer we tested was alginate, a heteropolysaccharide containing two carboxylic sugar acids, D-mannuronic and D-guluronic. Kelp alginate was a suitable dispersant, provided that its viscosity was reduced by partial acid hydrolysis. Low molecular weight polymers rich in guluronic acid proved to be better dispersants than those rich in mannuronic acid, perhaps due to their greater charge density caused by their buckled molecular configuration. In situ processing of ceramic materials was tested by growing the alginate-producing bacterium, Azotobacter vinelandii, in the presence of alumina particles. Growth occurred at 15 vol% alumina in medium. Alumina particles which were exposed to such treatment showed a high packing density comparable to that with purified polymer. We also tested polypeptide polymers of the dicarboxylic amino acids, glutamate and aspartate, which also served as excellent dispersants for small alumina particles.
Mimicking Photosynthetic Electron Transfer
Authors: Gust Devens , Moore Thomas A. , Moore Ana L. 
Published: March 2011

AbstractThe photosynthetic reaction centers of plants and bacteria are photovoltaic devices on the molecular scale which convert light energy into chemical potential energy in the form of long-lived, energetic charge separated states. It is now possible to prepare synthetic multicomponent molecules which mimic important aspects of this process. For example, one of the keys to reaction center function is a multistep electron transfer strategy. In this paper, two general types of multistep electron transfer, sequential and parallel, are described and illustrated with several synthetic triad and pentad molecules.
Parallel Fibres Control Fracture in Biological Systems
Authors: Vincent Julian F. V. 
Published: March 2011

AbstractGrass and horn keratin are presented as examples of biological materials which are notch-insensitive due to the presence of strong and stiff parallel fibres in a weaker more compliant matrix. A simple Voigt model is adequate to account for most of these properties. The biological significance of this morphology is explored: with grasses it affects the way animals graze, with horn keratin the behaviour of the horned animal maximises fracture control.
The Role of Ashed Bone in Hard Tissue Implants
Authors: Nash Alexis S. , Dahl Laura , Shepler Mark , Choo Hahn , Choi Sun W. , Nash Philip 
Published: March 2011

AbstractA novel composite consisting of Ultra-High Molecular Weight Polyethylene, UHMWPE, and ashed bone has been evaluated for human implant applications. The structure and mechanical properties of this composite have been studied using x-ray diffractometry (XRD), scanning electron microscopy (SEM) and dynamic torsion tests. Dynamic properties of the composite and its role in the enhancement of bone ingrowth and damping of vibrations at bone-implant interface are discussed. The new composite offers a novel technique that can provide the desired biological and mechanical fixation in a total hip surgery.
Structure, Morphology and Growth of Biogenic Greigite (Fe3S4)
Authors: Heywood B. R. , Manna S. , Frankelb R. B. 
Published: March 2011

AbstractSeveral species of aquatic bacteria are known to exploit the earth's geomagnetic field as a means of directing their motion towards suitable habitats. A feature common to these bacteria is the presence of discrete intracellular magnetic inclusions, magnetosomes, aligned in chains along the long axis of the organism. The size and orientation of the individual magnetic particles imparts a permanent magnetic dipole moment to the cell which is, in turn, responsible for the magnetotactic response. In all species examined to date the magnetic particles have been found to be well-ordered, single domain, membrane-bounded crystals with reproducible, species-specific morphologies. Until recently, however, only crystals of the mixed valence iron oxide, magnetite (Fe3O4), were identified in these magnetotactic bacteria. We have now identified three species of bacteria from sulphidic environments which contain crystals of the mixed valence ferrimagnetic iron sulphide, greigite (Fe3S4). High resolution electron microscopical studies of the biogenic greigite crystals showed that they also exhibit the narrow size range (50–90nm) and unique crystallographic habits (e.g. cubo-octahedral, rectangular prismatic) which characterized and distinguished the inclusions in other magnetotactic species. Thus, it would appear that the bio-precipitation of iron sulphides in magnetotactic bacteria is a highly regulated process which is directed and controlled at the molecular level. These findings are not only important to our understanding of biomineralization in unicellular organisms but may also be significant to studies of paleomagnetism. Furthermore, the controlled synthesis of greigite presents an interesting challenge to material scientists and solid state chemists.
Beam Assisted Atomic Layer Controlled Epitaxy and Etching of GaAs
Authors: Meguro T. , Aoyagi Y. 
Published: March 2011

ABSTRACTAtomic layer epitaxy (ALE) using laser irradiation and digital etching of GaAs are described herein.Epitaxy: We have succeeded in the laser-assisted ALE (laser-ALE) of GaAs using visible wavelength Art laser irradiation and an alkylgallium source. Visible wavelength photon irradiation induces surface decomposition but not volume decomposition of alkylmetal molecule source gases. ALE is realized by the enhancement of decomposition of alkylgallium molecules only on the As-terminated surface but not on the Ga-terminated surface. This site-selectivity of alkylgallium decomposition is induced by the optical absorption band broadening, which is due to the chemisorption of alkylgallium at the As-terminated surface.Etching: In ditigal etching, etchant gas pulses and an energetic beam sequentially impinge onto the substrate surface. In the Ar+/Cl2 system, the etch rate is found to be independent of both Cl2flux and Ar+ beam density, and the etch rate saturates at a level below one monolayer per cycle. By using Cl radicals as etchants instead of Cl2, the self-limited etching characteristics of digital etching are obtained within both the Ar+ incidence time and Cl feed time of the etching cycle.
Growth Rate Limiting and Carbon Reduction Processes for GaAs Grown by Alternate Gas Supply using H2 and N2 Carrier Gases
Authors: Shinohara M. , Yokoyama Y. , Inoue N. 
Published: March 2011

ABSTRACTProcesses limiting the growth of GaAs grown by an alternate gas supply are investigated by kinematical analysis. Based on these results, it is shown that the atomic layer epitaxial (ALE) window is expanded on the high temperature by the suppression of the decomposition of column III gas sources using a nitrogen carrier gas and on the low temperature side by the enhancement of their chemisorption to substrate surface atoms by a new method using a cracking tube. The latter enables us to achieve ALE of AlAs for the first time. Moreover, the carbon concentration is reduced by one order of magnitude by such a reaction control.
Atomic Level Control in Crystal Growth Utilizing Reconstruction of the Surface Superstructure
Authors: Fuyuki Takashi , Yoshinobu Tatsuo , Matsunami Hiroyuki 
Published: March 2011

ABSTRACTA novel mechanism of atomic level control in crystal growth utilizing reconstruction of surface superstructures is proposed. We have found a distinguished feature of surface reconstruction during crystal growth of 3C-SiC using an alternate gas molecular beam supply of Si2H6 and C2H2. When Si2H6 is supplied, S atoms generated by thermal decomposition adsorb on the surface constructing superstructures. A fixed number of Si atoms forming surface superstructures can react with C2H2 yielding single crystalline 3C-SiC growth in the subsequent period, which realizes atomic level control in epitaxy of 3C-SiC. The reconstruction sequence is analyzed based on RHEED observations, and the obtained crystal quality is discussed.
Cadmium Telluride Thin Films Grown By Atomic Layer Epitaxy
Authors: Kytökivi Arla , Koskinen Yrjö , Rautiainen Aimo , Skarp Jarmo 
Published: March 2011

ABSTRACTPolycrystalline CdTe films up to 2 μm thick were grown by Atomic Layer Epitaxy (ALE) at 350–450°C. The growth was carried out in a lateral flow reactor, using the elements as source materials and 25 cm2 glass/ITO and glass/ITO/SnO2 as substrates. A growth of CdS film by ALE preceded the growth of CdTe.Profilometry, X-ray diffraction analysis and scanning electron microscopy were used to characterize the films.The relatively high vapor pressure of CdTe determined the upper limit of the processing window, while the small vapor pressure of Te2 set a practical lower limit of 390–400°C.The CdTe films were smooth up to 100–500 nm depending on the temperature and the substrate surface. Development of surface roughness was detected as the growth process proceeded. At the same time there was an increase of the effective surface area of the film, observed as a significant increase in the macroscopic growth rate. The greater surface roughness was also evident in the reduced degree of (111) orientation.The CdS/CdTe structure was investigated for its potential in solar cell applications.
Surface Chemistry and Mechanism of Atomic Layer Growth of GaAs
Authors: Yu Ming L. , Buchan Nicholas I. , Souda Ryutaro , Kuech Thomas F. 
Published: March 2011

ABSTRACTThe success In attaining atomic layer epitaxy (ALE) of GaAs depends critically on the choice of the Ga precursor. Three systems were examined: trimethylgallium (TMGa) and diethylgallium chloride (DEGaCI) both of which give ALE, and triethylgallium (TEGa) which does not. We compared the surface reactions of these compounds on GaAs(100) and concluded that there was no evidence for reaction selectivity between Ga and As sites to cause ALE. Site blocking by the ligands on the Ga precursors alone also could not provide a self-limiting Ga deposition for ALE. We found evidence of a new mechanism by which self-limiting deposition of Ga resulted when the incoming Ga flux by the adsorption of Ga precursors was counter-balanced by an outgoing flux of Ga containing reaction product. For TMGa and DEGaCI with which ALE is successful, the products are CH3Ga and GaCl, respectively. For TEGa, the corresponding compound C2H5Ga was not formed.
Atomic Layer and Unit-Cell Layer Growth of (Ca,Sr)CuO2 and Bi2Sr2Can-1CunO2n+4 Thin Films by Laser Molecular Bean Epitaxy
Authors: Kanai Masaki , Kawai Tomoji , Matsumoto Takuya , Kawai Shichio 
Published: March 2011

ABSTRACTThin films of (Ca,Sr)CuO2 and Bi2Sr2Can-1CunO2n+4 are formed by laser molecular beam epitaxy with in-situ reflection high energy electron diffraction observation. The diffraction pattern shows that these materials are formed with layer-by-layer growth. The change of the diffraction intensity as well as the analysis of the total diffraction pattern makes It possible to control the grown of the atomic layer or the unit-cell layer.
Self Terminating Reaction of Dipivaloylmethanate Complexes with Hydroxyl Groups on Oxide Surface
Authors: Sekine Rika , Kawai Maki , Asakura Kiyotaka , Iwasawa Yasuhiro 
Published: March 2011

ABSTRACTWe have already reported that copper and calcium dipivaloylmethanates [Cu(DPM)2 and Ca(DPM)2 ] reacts selectively and stoichiometrically with surface hydroxyl groups (OH) on SiO2. In order to clarify the structure of the adsorbed species and the origin of the reaction between M(DPM)2 (M=Cu and Ca) and OH groups, the surface adsorbed species are studied by infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and the extended X-ray absorption fine structure (EXAFS). As a result, it was found that H from surface OH has moved into M(DPM)2 after the adsorption, where the four oxygen coordinated structure around Cu still exists in the adsorbed Cu(DPM)2. Introducing water vapor at 673 K to this surface results in the removal of ligand DPM from the adsorbed Cu(DPM)2. At 673 K, Cu atoms decomposed from the adsorbates aggregated on the surface. This fact supports that the interaction between the adsorbed Cu(DPM)2 and SiO2 surface is originated from that between the ligands and the surface.
Real-Time Analysis Of In-Situ Spectroscopic Ellipsometric Data During Mbe Growth Of III-V Semiconductors
Authors: Johs B. , Edwards J. L. , Shiralagi K. T. , Droopad R. , Choi K. Y. , Maracas G. N. , Meyer D. , Cooney G. T. , Woollam John A. 
Published: March 2011

ABSTRACTA modular spectroscopic ellipsometer, capable of both in-situ and ex-situ operation, has been used to measure important growth parameters of GaAs/AIGaAs structures. The ex-situ measurements provided layer thicknesses and compositions of the grown structures. In-situ ellipsometric measurements allowed the determination of growth rates, layer thicknesses, and high temperature optical constants. By performing a regression analysis of the in-situ data in real-time, the thickness and composition of an AIGaAs layer were extracted during the MBE growth of the structure.
High Carrier Concentration Improved N-Type SiGe/GaP Alloys
Authors: Scoville A. Nancy , Bajgar Clara , Vandersande Jan , Fleurial Jean-Pierre 
Published: March 2011

ABSTRACTSiGe alloys have been fabricated with the hiqghest carrier concentrations achieved to date. Values in excess of 4.0 × 1020 have been observed. The thermoelectric behavior of these samples has been characterized, both in the as-pressed state and as a function of 3anneal time and temperature. Figures-of-merit between 0.85 and 0.90 × 10−3 K−1 have been reproducibly achieved. Further improvements will be achieved by reducing the carrier concentration.
On The Thermoelectric Power in Degenerate Narrow Gap Semiconductors in the Presence of a Strong Magnetic Field
Authors: Ghatak Kamakhya Prasad , De Badal 
Published: March 2011

ABSTRACTIn this paper we have studied the thermoelectric power under strong magnetic field in degenerate semiconductors on the basis of fourth order in effective mass theory and taking into account the interactions of the conduction electrons, heavy-holes, light-holes and split-off holes respectively. The results obtained are then compared to those derived on the basis of the well-known three-band Kane model. It is found, taking n-Hg1-xCdxTe as an example, that the magneto-thermo power increases with decreasing electron concentration and increasing magnetic field respectively for both the models in an oscillatory way. The oscillations are due to SdH effects and the theoretical snelysis in accordance with fourth order in effective mass theory is in agreement with the experimental observation as reported elsewhere. In addition, the corresponding results for parabolic energy bands have also been obtained as special cases of our generalized foriulations.