bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Characterization of Nanostructured Particulate Catalytic Materials
Authors: Tong Baiyun , Siriwardane Upali , Naidu Seetala V. , Murty Akundi N. , Zhong Zhenchen 
Published: April 2011

AbstractLaser Induced Solution Deposition (LISD) is essentially a laser chemical processing with similar mechanism of the counterpart – laser chemical vapor deposition (LCVD). It is a novel method for synthesizing nanocsale particles or thin films with the combined advantages of laser chemical vapor deposition and electroless chemical deposition in solution (electrolyte). It is simple and efficient, and it can produce high quality nanoparticles or patterned uniform thin films. In this paper the nanostructured Co/CoOx particles have been fabricated by LISD technique. We have characterized the deposited materials by using scanning electron microscope (SEM), the high-resolution transmission electron microscope (HRTEM) and X-ray diffraction technique (XRD). We have found that the sizes of the deposited particles are smaller than 5 nm uniformly suspended in the solution used in the LISD deposition, and the sizes are smaller than 500 nm on the silicon substrates inserted in the deposited solution. The results by energy dispersive X-ray analysis (EDX) have indicated that there are Co peaks and O peaks, which meant there were oxygen contamination or the deposited products were cobalt oxide rather than pure cobalt nanoparticles. The X-ray diffraction has shown that we have obtained pure Co nanoparticles in some cases but we have obtained cobalt oxides in other cases, which mainly depended on the experimental conditions such as the selection of solvents and solutes as well as the selection of the lasers including the wavelength and the power of the laser beams. The studies of the magnetic properties, catalytic properties as well as their relationship of pure cobalt nanoparticles and cobalt oxide nanoparticles are in good progress and we will publish the useful results elsewhere.
Pressure Isotherms of Hydrogen Adsorption in Carbon Nanostructures
Authors: Chen Xiaohong , Dettlaff-Weglikowska Urszula , Haluska Miroslav , Hulman Martin , Roth Siegmar , Hirscher Michael , Becher Marion 
Published: April 2011

AbstractThe hydrogen adsorption capacity of various carbon nanostructures including single-wall carbon nanotubes, graphitic nanofibers, activated carbon, and graphite has been measured as a function of pressure and temperature. Our results show that at room temperature and a pressure of 80 bar the hydrogen storage capacity is less than 1 wt.% for all samples. Upon cooling, the capacity of hydrogen adsorption increases with decreasing temperature and the highest value was observed to be 2.9 wt. % at 50 bar and 77 K. The correlation between hydrogen storage capacity and specific surface area is discussed.
Reductive Photopatterning of Phenylene-Vinylene-Based Polymers
Authors: Kavc T. , Langer G. , Kern W. , Ruplitsch A. , Mahler K. , Stelzer F. , Hayn G. , Saf R. , List E.J.W. , Zojer E. , Ahmed M. T. , Pogantsch A. , Iskra K.F. , Neger T. , Hörhold H.-H. , Tillmann H. , Kranzelbinder G. , Toussaere E. , Jakopic G. 
Published: April 2011

ABSTRACTPhotochemical methods were developed to obtain a variation of the refractive index in aromatic polymer surfaces and a change in the photoluminescence characteristics of phenylene-vinylene-based polymers. Films of aromatic polymers, among them polystyrene (PS), poly(2-vinylnaphthalene) (PVN) and derivatives of poly(-phenylene-vinylene) (PPV) were UV irradiated in the presence of gaseous hydrazine (N2H4). The photoreaction led to a strongreduction of the refractive index of the polymers due to a hydrogenation of the aromatic units. In the case of PPV, we observed reductive photobleaching. This new technique was employed to produce photogenerated patterns in PPV. The results are compared to oxidative bleaching.
3D Periodic Arrays of Nanoparticles Inside Mesoporous Silica Films
Authors: Besson Sophie , Gacoin Thierry , Jacquiod Catherine , Ricolleau Christian , Boilot Jean-Pierre 
Published: April 2011

ABSTRACTCdS nanoparticles were grown inside a 3D hexagonal porous silica film. The film pore size and organization allowed the perfect control of particle repartition and size (3.5 nm), leading to a 3D nanocrystal array inside the silica matrix. The method was extended to another silica porous structure with larger pores, which allowed to obtain larger particles (5.8 nm). This process was then successfully generalized to other metal sulfides.
Flexible Plastic Liquid Crystal Displays
Authors: West John L. , Novotny Greg R. , Fisch Michael R. , Heineman David 
Published: April 2011

ABSTRACTFlexible plastic liquid crystal displays (LCDs) offer a number of advantages over traditional glass displays. Roll-to-roll manufacturing of such displays makes possible large size, inexpensive displays. While this type of manufacturing is still in the future, here we report solutions of some of the pressing problems needed to achieve this goal. We utilize liquid crystal effects that do not require polarizers and can therefore utilize commercially available, birefringent substrates such as polyesters and polyethylene terephthalate. We achieve excellent optical and mechanical performance of these flexible displays, even when bent, by creating polymer networks and polymer walls that adhere the front and back substrates and maintain uniform spacing between the substrates. Roll-to-roll processing of flexible plastic displays also requires that the photolithographic techniques used to pattern the electrodes on the current glass LCD’s be replaced by printing techniques and the development of techniques to rapidly etch unwanted electrode material. We must also develop and optimize techniques for rapidly forming polymer walls. Here we report methods of patterning ITO electrodes on flexible plastic substrates using conventional wax transfer printing techniques and rapid etching and cleaning techniques. We also report experiments that elucidate the basic science of rapidly forming polymer walls. We combine these new achievements and understanding and demonstrate their utility by fabricating a flexible plastic LCD using techniques compatible with roll-to-roll manufacturing. Finally, we discuss the critical issues that must be addressed if flexible plastic LCD’s are to reach their full potential.
Optical Rheology of New Liquid Crystalline Thermosets (LCTs): Influence of Shear on Disclination Texture
Authors: Qin Haihu , Mather Patrick T. 
Published: April 2011

ABSTRACTLiquid crystalline thermosets (LCTs) have been under intensive study because of their outstanding mechanical performance and low viscosity during processing. We have successfully synthesized four kinds of nematic bismaleimide thermosets that differ in the nature of a pendant group substitution and that feature a thermally stable nematic phase. Importantly, the pendant groups were found to be efficient in depressing the melting point to a level that allows for flow and cure at reasonably low temperatures. By blending two particular monomers with monofunctional maleimide that we synthesized, N-(4-hydroxyphenyl) maleimide (HPMI), the melting point is depressed and the curing process is postponed to higher temperatures. Such a blend has a processing window amenable to much-needed thermal and rheological characterization, particularly the evolution of disclination density during shear flow as cure progresses. Our previous work on disclination density measurements during shear flow has revealed particular scaling of dimensionless disclination density with dimensionless shear rate. The influence of shearing on the disclination density, flow patterns, and molecular orientation though gelation of thermosetting liquid crystals remains unexplored. In this presentation, we will follow a description of material synthesis with a report on the results of optical rheology experiments applied to the ternary blends containing HPMI and two bismaleimide monomers, detailing the influence of shear on disclination density though gelation.
Permeability of A Liquid Crystalline Epoxy
Authors: Feng Jianxun , Douglas Elliot P. 
Published: April 2011

ABSTRACTThis paper presents a comparison of moisture permeation in liquid crystalline and conventional epoxy systems. The permeability is obtained using a dynamic method. It is found that both epoxy systems exhibit Fickian behavior. The liquid crystalline epoxy network exhibits higher barrier properties for moisture transport than the conventional epoxy network. The efficient chain packing within the smectic mesophase of the liquid crystalline thermoset (LCT) is suggested as the main factor for this difference. The stoichiometry has a large effect on the moisture permeation. The diffusion coefficient decreases monotonically with increasing amine/epoxide functional ratio. The permeability (P) and solubility coefficient (S) reach a minimum at a functional ratio of one. The mechanism of the permeation is described in terms of the two-phase morphology present and hydrogen bonding between absorbed water and the network.
Nanocharacterization of Surface and Interface of Different Epoxy Networks
Authors: Gu X. , Raghavan D. , Ho D.L. , Sung L. , VanLandingham M.R. , Nguyen T. 
Published: April 2011

ABSTRACTThe effect of network changes on the surface and interface properties of amine-cured epoxy has been investigated. Samples of different crosslinked epoxies are prepared by mixing stoichiometrically pure diglycidyl ether of bisphenol A (n=0.03) with different ratios of 1,3-bis(aminomethyl)cyclohexane (terafunctional amine) and cyclohexylmethylamine (difunctional amine). All samples are cured in CO2-free air. Both the film surface in contact with air and that in contact with the silicon substrate (the interface) are analyzed using atomic force microscopy (AFM) and nanoindentation. Small angle neutron scattering (SANS), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, and contact angle measurements, are used to assist in the interpretation of AFM results. Substantial morphological and mechanical differences are observed between the surface and the interface for different crosslinked epoxies. The findings have strong implications on the wettablity, adhesion, and durability of amine-cured epoxies.
A Broad Perspective on the Dynamics of Highly Confined Polymer Films
Authors: Soles Christopher L. , Douglas Jack F. , Wu Wen-Li , Peng Huagen , Gidley David W. 
Published: April 2011

ABSTRACTThe manner in which the dynamics of a polymer are affected by thin film confinement is of technological significance, impacting thin film applications such as lubricants, adhesives, and chemically amplified photoresists. In this manuscript we use specular X-ray reflectivity (SXR), beam positron annihilation lifetime spectroscopy (PALS), and incoherent neutron scattering (INS) to study the influence of thin film confinement on the apparent glass transition temperature Tg and the thermal expansion coefficients of thin polycarbonate (PC) films. Both the SXR and PALS indicate a significant suppression of Tg when the film thickness becomes less than 200 Å. However, the INS measurements suggest an increase in the apparent Tg below this same length scale. These disparate estimates of the thin film Tg seem to indicate that each technique is sensitive to slightly different aspects of the glass formation process. However, all three agree that thin film confinement results in reduced thermal motion, regardless of the precise temperature that is ‘designated' as the thin film Tg.
Analysis of Radiation Damage in Lysozyme Crystals with High Resolution Triple Axis X-Ray Diffraction
Authors: Matyi Richard J. , Volz Heather M. 
Published: April 2011

ABSTRACTHigh resolution triple axis X-ray diffraction has been used to monitor the effects of X-ray radiation damage in hen egg white lysozyme crystals. At long irradiation the expected decrease in peak intensity and increase in the angular extent of the peak breadth was seen. In contrast, both the intesi-ties and peak breadths exhibited more complex behavior during the initial stages of irradiation. Possible reasons for these observations are discussed.
Deformation Mechanisms in Natural Polymer Fibers and Composites
Authors: Young Robert J. , Eichhorn Stephen J. , Sirichaisit J. , Brookes Victoria L. 
Published: April 2011

ABSTRACTThe molecular deformation of both silkworm (Bombyx mori) and spider dragline (Nephila edulis) silks has been studied using a combination of mechanical testing and Raman spectroscopy. It was found that both materials have well-defined Raman spectra and that some of the bands in the spectra shift to lower wavenumber under the action of tensile stress or strain. The band shift was linearly dependent upon stress for both types of silk fiber for the 1085/1095 cm-1 band. This observation provides a unique insight into the effect of tensile deformation upon molecular structure and the relationship between structure and mechanical properties. The measurement of micromechanical deformation within samples of wood, flax and hemp fibers using Raman spectroscopy is also reported. Upon tensile deformation of the samples it was found that the characteristic Raman peak for cellulose, located at 1095 cm-1, shifted towards a lower wavenumber, indicating that the polymer chains within the cellulose were also being deformed. The magnitude of the shift with strain was found to be similar for all samples. No shift occurred of the peak that is characteristic of the non-load-bearing lignin (1600 cm-1) in the wood samples due to its amorphous structure. The similarities between the Raman band shifts in silk and cellulose are discussed.
Near-Field Scanning Optical Images of Bacteria
Authors: Paula Ana M. de , Toledo Juliana A. , Silva Haroldo B. , Weber Gerald 
Published: April 2011

ABSTRACTNear field scanning optical microscopy (NSOM) and spectroscopy techniques were used to study the shape and the cell membrane details in bacteria. We present transmission and topo-graphic images for the bacteriaPseudomonas aeruginosausing the Aurora NSOM from ThermoMicroscopes. TheP. aeruginosahas been widely studied due to its clinical importance in many infectious diseases. The samples were stained by the Gram method and we measured the absorption of laser light at 488 nm by the dye (Safranin) fixed at the bacteria membrane. To obtain good images we had to improve the sample preparation in order to obtain isolated bacteria at the microscope slab. This was achieved using individual colonies, from a dry growth procedure, diluted in physiologic solution. Comparison of the topographic and transmission images give information on the shape and details of the absorption of the laser light by the cell membrane. The results show patterns that depend on the thickness and shape of the membrane, thus revealing details of the cell membrane with nanometer resolution. These results could be an important tool for instance in studies of the effects of antibiotics on the cell membrane.
Controlling Material Properties of Ionically Cross-Linked Alginate Hydrogels by Varying Molecular Weight Distribution
Authors: Kong Hyun-Joon , Mooney David J. 
Published: April 2011

ABSTRACTThe mechanical properties of alginate hydrogels are critical to their successful use in tissue engineering. We hypothesized that combining alginates of differing molecular weights would allow one to readily control and decouple the viscosity of the pre-gel solution from the post-gel stiffness. To test this, binary hydrogels were prepared by incorporating low molecular weight (MW) alginate (Mn ~ 3.3 x 104 g/mol) into 1 %(w/w) alginate solutions composed of high MW alginate (Mn ~ 2.2 x 105 g/mol). The addition of low MW alginate had minimal effects on the solution viscosity, allowing high solids loading in the solution while maintaining a workable solution. However, the increased mass loading resulted in much higher stiffness gels following ionic cross-linking with calcium. These data may be interpreted in relation to the microstructure of the solution versus hydrogel.
Low Temperature Deposition of Transparent Ultra Water-Repellent Thin Films by Microwave Plasma Enhanced Chemical Vapor Deposition
Authors: Wu Yunying , Inoue Yasushi , Sugimura Hiroyuki , Takai Osamu 
Published: April 2011

ABSTRACTOne of the most common methods for obtaining water repellent surfaces is spreading fluoropolymer or fluoroalkylsilane onto substrates. However, this method is not applicable to low heat-resistant substrates such as plastics, since after spreading, the method requires a heating process which is generally conducted at a temperature of about 600K. The objective of this study is the preparation of ultra water-repellent and optically transparent thin films at low temperatures below 373K. The films were deposited by means of microwave plasma enhanced plasma chemical vapor deposition (MPECVD) using organosilane, that is, trimethylmethoxysilane (TMMOS) as a source with adding Ar, CO2, N2, O2 or air as an excitation gas. Under optimized preparation conditions, films with water contact angles more than 150 degrees and optical transparencies more than 90% were successfully fabricated.
New Approaches to the Characterization of Obsidian from the Mediterranean Island Sources: Interpreting Chronological Change in Neolithic Sardinia and Corsica
Authors: Tykot Robert H. 
Published: April 2011

ABSTRACTGeochemical fingerprinting of obsidian sources was first applied in the Mediterranean region nearly four decades ago. Since then, a number of analytical methods (e.g. INAA, XRF, SEM/Microprobe, ICP-MS) have proven successful in distinguishing the Mediterranean island sources of Giali, Lipari, Melos, Palmarola, Pantelleria, and Sardinia. Moreover, recent geoarchaeological surveys of the central Mediterranean sources have resulted in the more precise location and documentation of each obsidian flow or outcrop, and multiple chemical groups have been identified on at least three of the islands. The ability to specifically attribute artifacts to one of at least five obsidian flows in the Monte Arci region of Sardinia, for example, has enabled the study of specific patterns of source exploitation and the trade mechanisms which resulted in the distribution of obsidian hundreds of kilometers away during the Neolithic period (ca. 6000-3000 BC).Results are presented here from the chemical analysis of 186 artifacts from several sites in Sardinia and Corsica as part of the largest and most comprehensive study of obsidian sources and trade in the Mediterranean. Analyses of large numbers of artifacts demonstrate the differential use of island subsources, which may be attributed to factors such as access (e.g. topography, distance from coast), size and frequency of nodules, and mechanical and visual properties. The patterns of source exploitation revealed by this study specifically support a down-the-line model of obsidian trade during the neolithic period. In addition, the spatial and chronological patterns of obsidian distribution may be used to address such issues as the colonization of the islands; the introduction of neolithic economies; and the increasing social complexity of neolithic and bronze age societies in the central Mediterranean.
Ancient Raw Copper from Primary Smelting Sites in Cyprus
Authors: Fasnacht W. , Northover J.P. 
Published: April 2011

ABSTRACTFinds of metallic copper from various primary smelting sites in the Sia valley in Cyprus have been analysed by ICP-OES for their composition and by optical and electron microscopy for metallography. Results show a characteristic pattern of impurities for each of the sites examined which allow an assignment to specific types of ore body and geological matrix. Different zones of the Cyprus Ophiolite Complex were exploited in different periods in antiquity, but these results show different types could be exploited contemporaneously within a specific period, especially during the first millennium BC. One location in this area, Agia Varvara-Almyras, an Iron Age copper smelting site with the only complete chain of operation recorded in ancient Cypriote metallurgy, is used to show how analytical work can guide future field surveys to find ancient furnaces, slag heaps and mines. The ultimate goal of the project is to extend it to reconstruct the complete history of copper production in a well-defined mining district over the last 4000 years.
Examination of Gilded Bronze Artifacts Using Nondestructive Eddy Current Techniques
Authors: Bernstein Johanna R. , McCarthy Blythe 
Published: April 2011

ABSTRACTIn the examination of gilded bronze objects, the analysis of the thickness of the gilding layer, the condition of the substrate and the gilding method is often difficult to manage without taking samples. Yet, the resulting information is vital to research on ancient metalworking and can answer questions of authenticity. The use of nondestructive eddy current techniques can overcome these sampling limitations. Eddy current methods are typically used in the automotive, power and aerospace industries for flaw inspection and alloy selection. In this method, the interaction of an electromagnetic field induced by a coil probe with the metal surface shifts the probe impedance which is measured and correlated to properties of the metal. Results are presented which show that eddy current testing can be used to characterize a gilding layer on a bronze substrate by variations in thickness or composition.
Organization of Flint Sickle Blade Production at an Early Bronze Age Workshop in Anatolia
Authors: Hartenberger Britt E. 
Published: April 2011

ABSTRACTA specialized workshop for the manufacture of flint sickle blades has recently been excavated at the site of Titris Hoyuk in southeastern Anatolia [1]. This paper will examine the sequence of production for the blades as well as the social context of this craft within the site. The workshop is the first example found containing evidence of the complete sequence of production for the ‘Canaanean blade,’ a type commonly used across the Near East in this period [2]. Since bronze was still new and relatively expensive, high-quality flint was used to manufacture sickle blades. Tabular flint was imported in the form of large slabs from several sources in the nearby hills. Specialists then prepared the blade cores, removed the blades, and then traded the final products to local farmers. A range of manufacturing debris has been found to illustrate the production sequence, including chunks of raw flint, core-shaping pieces, debitage pits, and stacks of exhausted and used cores. The large sample of over 1000 blade cores collected ensures a sizable data set for statistical analyses. Several types of raw flint were utilized for making the blades and production appears to vary slightly by these material types. The workshop is located within a household setting and is the only area within the excavated site containing debris from this craft. Spatial analyses of the types of flint used within the household workshop reveal its division into largely distinct areas for domestic versus specialist craft activities. The placement of the workshop in the suburbs far from the site's administrative center may indicate that its activities were independent of any elite. An estimate of the volume of blades produced combined with the location of the workshop at a major regional center suggest that it also supplied blades to other sites in the region.