bluuebunny/crossref_metadata_2025_split huggingface dataset:
Susceptibility of E. coli, P. aeruginosa, S. aureus and S. epidermidis to Different Bismuth Compounds.
Authors: Vega-Jiménez Alejandro L. , Berea-Montes Edgardo , Almaguer-Flores Argelia 
Published: November 2012

ABSTRACTBismuth has been used as an antimicrobial agent for treating gastrointestinal disorders, and has been used in the eradication of Helicobacter pylori. The aim of the present study was to analyze the antimicrobial activity of different Bi compounds against opportunistic pathogens. Ten bismuth compounds were tested with three different concentrations (60, 30 and 10%), against pure cultures of the following bacterial strains: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis. The results show that Bismuth subsalicylate, Bismuth trioxide and Bismuth subgallate had a good antibacterial activity however, Bismuth subsalicylate was the most effective in the inhibition of the four bacterial strains tested. In this study we confirm the antibacterial properties of Bi-based compounds for other bacteria than H. pylori.
Smart Additives for Self-Sealing and Self-Healing Concrete
Authors: De Belie Nele , Van Tittelboom Kim , Snoeck Didier , Wang Jianyun 
Published: November 2012

ABSTRACTLike broken bones are able to heal themselves, it would be desirable that damaged concrete may be repaired autonomously as high costs are related to the repair. Actually, concrete already has some self-healing properties; when cracks appear, water enters and reacts with unhydrated cement grains which results in crack healing. However, only small cracks can be healed in this way. Therefore, we want to improve the self-healing efficiency by adapting the concrete matrix. By introducing high amounts of fibers several small cracks appear instead of one large crack. Combination with superabsorbent polymers, also called hydrogels, provides immediate crack sealing. Another methodology is to embed encapsulated polymeric agents in the matrix. When cracks appear, the capsules break and the agent is released. Upon contact of both components, they react and the crack is healed. This technique is also combined with CaCO3precipitation of bacteria. In that case, not only polymers but also bacteria and nutrients are encapsulated and released upon cracking. First the polymer reacts, later the bacteria start to convert the nutrients into CaCO3crystals which make the polymer structure denser and thus seal the cracks completely. As crack healing by means of bacteria uses a repair material which is more compatible with concrete we also try to seal cracks by only using bacterial CaCO3. Therefore, bacteria are embedded inside aggregates. Upon cracking, bacteria are exposed to the air and when water enters the crack bacteria become active and fill the crack with CaCO3. From the first results it was noticed that due to autonomous crack healing, water permeability is reduced and regain in mechanical properties is obtained. This means that more durable concrete structures may be obtained by using the proposed self-healing techniques.
Cementitious Blends of Portland Cement with Calcium Sulphate, Fly Ash and Cupola Slag.
Authors: Rodríguez-Mendoza Yared E. , Fuentes Antonio F , Escalante-García J Iván 
Published: November 2012

ABSTRACTThis investigation is on alternative cementitious materials of low cost, energy and environmental emissions. Portland cement (PC) was replaced by different types of calcium sulphate (hemihydrate HH, or anhydrite AN), fly ash (PFA) and cupola slag (CS) from an iron foundry. Pastes of blends of (HH or AN) – CS – PC and (HH or AN) – PFA – PC were characterized. The compositions varied within the ranges of 0 – 35% PC, 15 – 80% HH or AN, 10 – 80% CS and 10 – 80% PFA. The water/solids ratio was kept at 0.45 for HH blends and 0.37 for those of AN. The pastes were cured in dry and for some time under water. Selected blends of CS were repeated with blast furnace slag (BFS) for comparison. CS showed better results over PFA and less than BFS, perhaps as derived from its chemical composition, phase configuration and physical characteristics. These and other results of microstructural characterization will be discussed. This work is part of a broader research on the development of alternative environment friendly hydraulic composite cements of Portland cement highly replaced by calcium sulphate and industrial byproducts.
Methods for Porosity Characterization of Cement Based Materials
Authors: Canut M.M. , Geiker M. R. 
Published: November 2012

ABSTRACTImportant pore structure parameters related to mechanical properties and durability of cement-based materials can be determined by techniques such as scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and low temperature calorimetry (LTC). The methods provide information on porosity characteristics as pore volume, pore thresholds and/or pore size distribution in different size ranges and do therefore to a large extent supplement each other. Pastes of w/b=0.4 with 0%, 40% or 70% slag by volume were cured saturated at 20ºC for up to two years. The porosity was characterized by LTC, MIP, and SEM. Higher volume of pores was obtained by MIP compared to results obtained using LTC and SEM. Measured porosity was correlated with predicted porosity using information on the density and degree of hydration of the cement and slag. Porosity estimation showed best agreement with the porosity data measured by MIP. The use of slag showed the same trend for all tests: a higher total volume of pores, but a lower threshold pore size when compared with Portland cement paste. The findings illustrate the importance of measuring not only pore volume but also threshold pore sizes when characterizing porosity of cement-based materials with different binder compositions.
Hydrogenated Nanocrystalline Silicon based Solar Cell with 13.6% Stable Efficiency
Authors: Yue Guozhen , Yan Baojie , Sivec Laura , Su Tining , Zhou Yan , Yang Jeff , Guha Subhendu 
Published: November 2012

ABSTRACTMulti-junction solar cells incorporating hydrogenated nanocrystalline silicon (nc-Si:H) exhibit a high current capability and low light-induced degradation. In this paper, we report our recent progress in developing nc-Si:H solar cells using a modified very-high-frequency glow discharge technique. We achieved a short-circuit current density >30 mA/cm2and 10.6% conversion efficiency from single-junction solar cells. Using the improved nc-Si:H cells in an a-Si:H/nc-Si:H/nc-Si:H triple-junction structure, we attained initial and stabilized efficiencies of 13.9% and 13.6%, respectively. Issues related to improving material properties and device structures are addressed. Besides using the conventional techniques, such as hydrogen dilution profiling, optimized Ag/ZnO back reflector, and buffer layers, we found that compensation from Boron and Oxygen micro-doping is also critical in obtaining the above achievements.
Influence of Ammoniating Temperatures on Microstructures, Morphologies and Optical Properties of GaN/Nb Nanostructures by RF Magnetron Sputtering Technique
Authors: Shi Feng , Xue Chengshan 
Published: November 2012

AbstractGaN nanowires and nanorods have been successfully synthesized on Si (111) substrates by magnetron sputtering through ammoniating Ga2O3/Nb thin films and the effects of ammoniation temperatures on growth of GaN nanowires and nanorods were analyzed in detail. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectra were carried out to characterize microstructures, morphologies, and optical properties of GaN samples. The results demonstrate that sample after ammoniation at 950 °C is single crystal GaN with hexagonal wurtzite structure and high crystalline quality, having the size of 30 - 80 nm in diameter. After ammoniation at 1000 °C, GaN nanorods appear with smooth and clean surface and more than 100 nm in diameter. The optical properties of GaN nanowires grown at 950 °C and nanorods grown at 1000 °C are best with strong emission intensities.
Growth of ZnO Nanostructures on Cellulosic Substrates
Authors: Athauda Thushara J. , Butt Umaiz , Harikumar Parameswar , Ozer Ruya R. 
Published: November 2012

ABSTRACTZnO nanostructures such as nanorods and nanoneedles were prepared on both cotton textiles and electrospun cellulosic nanofibers by a simple, two-step hydrothermal process at low temperature in aqueous solution. Commercially available cotton fabrics were used. Cellulosic nanofibers (average diameters of 100 nm) were obtained by electrospinning of cellulose acetate/polyvinyl acetate/polyethylene glycol mixture on glass slides to form non-woven mats.On cotton textiles, the systematic change of the seed-to-growth solution concentration ratio caused a noticeable variation on the morphology of the nanostructures. The loading ratio of ZnO nanorods and nanoneedles were 37.5% and 18.1 wt%, respectively. Durable superhydrophobicity was achieved with a static water contact angle of 160.7° upon fluorosilane treatment, even after prolonged exposure to UV and plasma irradiation. The surface wettability was found to slightly vary from nanorods (160.7°) to nanoneedles (159.8°). The ZnO nanostructures did not lose their superhydrophobicity after 1 h of agitation in DI water. Excellent UV blocking activities were observed for nanorods and nanoneedles in the wavelength region analyzed. On electrospun cellulosic nanofibers of approximately 100 nm diameter, the loading ratio of ZnO nanorods were found to be 33.3 wt% which are densely and uniformly distributed the entirety of the nanofibers. Although diameters of the nanofibers and cotton fibers are very different in size (around 100 nm and 15-20 micron, respectively) the ZnO loading on electrospun fibers are very close to that of cotton fabric due to the high surface area and coiled nature of electrospun fibers, resulting in high packing density. ZnO nanorods grown on electrospun nanofibers exhibited hydrophilic behavior.
Triiodide Photooxidation and Subsequent Regeneration in UVA Exposed Nano-Structured TiO2 Solar Cell Devices
Authors: Carnie Matthew , Watson Trystan , Worsley David 
Published: November 2012

ABSTRACTUV exposure of dye-sensitized solar cells (DSCs) results in a loss of triiodide from the electrolyte and this is as a result of direct band gap excitation of the TiO2 semiconductor. The UV stability of a typical electrolyte composition is explored further and the results show that the electrolyte is very stable to UV irradiation in the absence of TiO2 but experiences rapid triiodide loss in its presence. Furthermore, the effect of a periodic triiodide regeneration technique, applied to UV exposed DSCs, is investigated and whilst this treatment does not appear to be able to permanently reverse triiodide loss in UV exposed cells, devices that are periodically regenerated, maintain higher average photocurrents over the UV exposure period.
Intermediate Layers for Thin-Film Polycrystalline Silicon Solar Cells on Glass Formed by Diode Laser Crystallization
Authors: Dore Jonathon , Evans Rhett , Eggleston Bonne D. , Varlamov Sergey , Green Martin A. 
Published: November 2012

ABSTRACTIntermediate layers between silicon and borosilicate glass are investigated for compatibility with a diode laser crystallization technique for fabrication of thin-film polycrystalline silicon solar cells. SiCx, SiNx and SiOx layers or multilayer stacks of these materials have allowed silicon films of 10μm thickness to be successfully crystallized by diode laser irradiation without dewetting, with each option offering different advantages. SiCx allows the most robust crystallization process, while SiOx is the best barrier to contamination and the most stable layer. SiNx offers the best anti-reflection coating for superstrate configured solar cells. Presently, best device performance is achieved with a SiOxintermediate layer with cells achieving up to ∼540 mV open-circuit voltage.
Formation of Aluminum Oxide Films on Silicon Surface by Aluminum Evaporation in Oxygen Gas Atmosphere
Authors: Nagatomi Y. , Yoshidomi S. , Hasumi M. , Sameshima T. , Kohno A. 
Published: November 2012

ABSTRACTWe report formation of thin aluminum oxide AlOx films on the silicon surface by a simple method of Al metal evaporation in oxygen gas atmosphere. 520 μm thick 30-Ωcm p-type-silicon substrates with a top bare surface and a rear surface coated with 100 nm thick thermally grown SiO2 layers were prepared. AlOx films were formed on the top surfaces by Al metal evaporation up to 20 s in oxygen gas atmosphere at 0.8 Pa with a flow rate of 3 sccm. Samples were subsequently annealed with 9.0x105 Pa H2O vapor at 260°C for 3 h. Measurement of capacitance response to a modulation voltage at 500 kHz as a function of bias gate voltages C-V revealed that AlOx films had the effective oxide thickness ranging from 2.0 and 2.6 nm were formed. C-V measurements also revealed that negative fixed charges were accumulated with a density of 5x1012 cm-2 in AlOx films. Photo-induced carrier microwave absorption measurement resulted in a high minority carrier effective lifetime τeff of 3.6x10-4 s comparable to that of 4.1x10-4 s for thermally grown SiO2 passivation. Field effect passivation was probably caused by negative charges in AlOx so that the surface recombination velocity decreased to 70 cm/s. X-ray reflectivity analysis indicated that the interfacial layer like SiOx was formed between AlOx and Si substrate. High pressure H2O vapor heat annealing caused increase in the density and decrease in the thickness of AlOx layers, although it increased the density and thickness of the interfacial SiOx layer thickness. H2O vapor treatment is effective to improve the quality of nanometer thick AlOxlayer.
SiC multilayer photonic structures with self optical bias amplification
Authors: Vieira M. , Vieira M. A. , Louro P. , Fantoni A. , Silva V. , Barata M. 
Published: November 2012

ABSTRACTStacked layered pin a-SiC/a-Si devices based on a filter design are approached from a reconfigurable point of view. This paper shows that a double SiC/Si pin photodiode can be de-composed into two photonic active filters changeable in function. Reconfiguration is provided by optical control signals to the optoelectronic front and back pin building blocks. Depending on the wavelength and irradiation side of the external optical bias the device acts either as a short- and a long- pass band filter or as a band-stop filter, amplifying or rejecting a specific wavelength range. Particular attention is given to the amplification coefficient weights, which allow taking into account the wavelength background effects. We illustrate these effects in detail and discuss the filters transfer function characteristics. We present examples of filters and we propose a reconfigurable device for directed optical logic. An algorithm to decode the information is presented. An optoelectronic model supports the optoelectronic logic architecture.
Atomic Layer Deposition of TiO2 ultrathin films on 3D substrates for energy applications
Authors: Soum-Glaude Audrey , Tian Liang , Blanquet Elisabeth , Brizé Virginie , Cagnon Laurent , Giusti Gaël , Salhi Rached , Daniele Stéphane , Ternon Céline , Bellet Daniel 
Published: November 2012

ABSTRACTIn the present global environmental context, it becomes more and more critical to find efficient solutions to lower our energy consumption on one hand, and to produce energy from clean renewable sources on the other hand. Consequently, research efforts on materials for energy applications are intensifying.The present work aims at developing optoelectrical components usable for both energy saving (light emitting diodes) and renewable energy production (solar cells) by fabricating p-n heterojunctions based on a single semiconductor, titanium dioxide. TiO2 is indeed a very promising candidate: it is chemically and physically stable under irradiation, transparent to visible and near-infrared light (Eg= 3 – 3.5 eV), presents photocatalytic activity, is non-toxic and low cost, which permits to envisage its large scale use.In the present paper, the proposed architecture for both solar cells and LEDs is original as well as common for both applications: a three-dimensional architecture based on an anodic alumina nanoporous membrane which serves as nanomask for TiO2 growth in order to enlarge the effective surface of the components. TiO2is synthesized by Atomic Layer Deposition (ALD), a technique particularly well adapted to the deposition of ultrathin films (from one monolayer to few tens of nanometers) on 3D porous substrates patterned with high aspect ratio nanopores.In this work, the capacity of synthesizing 3D nanostructures is demonstrated. TiO2ultrathin films (10 to 100 nm) were grown by ALD on flat, micropatterned, microporous and nanoporous anodic alumina membranes (AAM) substrates. The films were highly conformal, as confirmed by SEM and TEM imaging. Both EDS and XPS analyses validated the dioxide film stoichiometry.
STUDY OF CO-ASSEMBLED CONDUCTING POLYMERS FOR ENHANCED ETHANOL ELECTRO-OXIDATION REACTION
Authors: Hoa Le Q. , Yoshikawa Hiroyuki , Saito Masato , Tamiya Eiichi 
Published: November 2012

ABSTRACTHerein, we investigated the effects of polyaniline (PANI) and polypyrrole (PPY) in their native and co-assembled forms as a thin layer on Pt nanoparticle-decorated multi-walled carbon nanotubes (Pt/MWCNTs) toward the ethanol oxidation reaction (EOR). The co-assembled conducting PANI-PPY deposited Pt/MWCNTs was successfully synthesized and demonstrated significant enhancement of the electro-catalytic activity and stability toward EOR as revealed by electrochemical characterizations. The presented results indicate that in the co-assembled form, PANI and PPY retained their own superior effects on the enhancement of stability and catalytic activity via intermediate species removal and ethanol adsorption, respectively. This preliminary result reveals a new strategy for the use of conducting polymers as potential catalyst supports due to its facile fabrication and functionalization, cost effectiveness and environmental friendliness in comparison to alloys and metal oxides, factors which are necessary for the practical application of direct ethanol fuel cells in the near future.
Shape-controlled Synthesis of Silver and Palladium Nanocrystals using β-Cyclodextrin
Authors: Berhault Gilles , Kochkar Hafedh , Ghorbel Abdelhamid 
Published: November 2012

ABSTRACTShape-controlled Ag and Pd nanocrystals were synthesized using seed-mediated techniques using β-cyclodextrin (β-CD) as structuring agent. First, seeds were obtained by reacting Na2PdCl4 or AgNO3 with a strong reducing agent, NaBH4 in the presence of sodium citrate dihydrate acting as stabilizing agent. These seeds were then injected into a growth solution containing the same metallic precursor, ascorbic acid (as a weak reducing agent) and β-CD as structuring agent. TEM results emphasize a strong influence of the relative concentration of β-CD on the final morphology. In the case of silver, well-facetted nanocrystals were obtained with a progressive shift from kinetically to thermodynamically-controlled nanoobjects when increasing the β-CD/Ag molar ratio. On palladium, β-CD leads to the formation of dendrites (urchin-like) or multipods through controlled aggregation of primary particles. The use of β-CD does not interfere negatively with the catalytic properties of the Pd nanocrystals in the hydrogenation of cinnamaldehyde.
Fabrication and Characterization of Organic Thin Films for Applications in Tissue Engineering: Emphasis on Cell-Surface Interactions
Authors: Wertheimer Michael R. , St-Georges-Robillard Amélie , Lerouge Sophie , Mwale Fackson , Elkin Bentsian , Oehr Christian , Wirges Werner , Gerhard Reimund 
Published: November 2012

ABSTRACTIn several recent communications from these laboratories, we have described observations that thin organic layers which are rich in primary amine (R-NH2) groups are very efficient surfaces for the adhesion of mammalian cells, even for controlling the differentiation of stem cells. We prepare such deposits by plasma polymerization at low pressure (thin films designated “L-PPE:N”, for “Low-pressure Plasma Polymerized Ethylene containing Nitrogen”), at atmospheric (“High”) pressure (“H-PPE:N”), or by vacuum-ultraviolet photo-polymerization (“UV-PE:N”). More recently, we have also investigated a commercially available material, Parylene diX AM.In the present communication we shall, first, briefly introduce literature relating to electrostatic interactions between cells, proteins, and charged surfaces. Next, we discuss the comparative results of physico-chemical characterizations of the various organic deposits mentioned above, which deliberately contain varying concentrations of nitrogen, [N], and amine groups, [NH2]. Finally, we present certain selected cell-response results that pertain to applications in orthopedic medicine; we discuss the influence of surface properties on the observed behaviors of various cell lines, with particular emphasis on possible electrostatic attractive forces due to positively charged R-NH3+ groups and negatively charged proteins and cells, respectively.
Porous Alumina Template based Versatile and Controllable Direct Synthesis of Silicon nanowires
Authors: Kim Ki-Hwan , Lefeveure Emmanuel , Châtelet Marc , Cojocaru Costel-Sorin 
Published: November 2012

ABSTRACTHighly densely packed, self-organized silicon nanowires with very narrow diameter distribution were synthesized within porous anodic alumina templates with electrodeposited catalytic metal nanoparticles. For successful catalytic metal nanoparticle deposition, electrochemical-, and chemical barrier layer thinning process was investigated following anodization process. Controlled pulsed electrodeposition process was carried out for a volume calibration of desired catalytic metal nanoparticle deposition inside nanopore arrays using different metal-ion containing electrolyte. Not only single metal nanoparticles, but also multi metal nanoparticles layers were filled inside PAA to enhance metal filling aspect, and to control the volume of nanoparticles more precisely. Using multilayered metal nanoparticles resulted on different SiNW’s growth behavior depending on the types of underlying metal nanoparticles.SiNWs were successfully synthesized using hot-filament assisted chemical vapor deposition system. Although silicon precursor gas can generally be dissociated at relatively low temperatures, the use of a hot filament activation help decreasing process temperature, and also, highly activated atomic hydrogen generation via the tungsten hot filament placed at gas inlet helps preventing parasitic amorphous silicon deposition on either the alumina membrane surface or the pore wall which hinders appropriate growth of SiNWs in PAA by nanopores clogging. Such densely packed, self-organized SiNWs are of high interest in many application fields like nanoelectronics, optoelectronics, and energy storage/conversion devices etc.
Probing the Viscoelasticity of Collagen Solutions via Optical-Tweezers-Based Microrheology
Authors: Shayegan Marjan , Forde Nancy R. 
Published: November 2012

ABSTRACTHow the molecular structure of proteins in solution correlates with the mechanical properties of the solution at different length scales is not known. Using optical-tweezers based microrheology, we investigate a key physical property, viscoelasticity, of collagen solutions. To do this, we measure short-range thermal fluctuations of probe particles to obtain elastic and viscous moduli of their surrounding medium, and validate our measurement and analysis techniques using the previously studied system of polyethylene oxide. Probing the concentration dependence of viscoelasticity, we find that collagen solutions exhibit elasticity of comparable strength to viscosity when the concentration reaches ∼5 mg/ml. We also find that the presence of telopeptides alters the viscoelasticity of collagen solutions, particularly at high frequencies