bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface investigation of NiTi rotary endodontic instruments after magnetoelectropolishing
Authors: Hryniewicz Tadeusz , Rokosz Krzysztof , Rokicki Ryszard 
Published: April 2011

ABSTRACTThe purpose of the study was to reveal the effects of a new electropolishing process carried out under a constant magnetic field, termed as magnetoelectropolishing (MEP). In this work we investigated Nitinol rotary endodontic instruments by surface and morphology change after MEP. The MEP process greatly affects both surface also mechanical properties like the bending and fatigue resistance.The investigation covered surface interferometry measurements, X-ray Photoelectron Spectroscopy (XPS) studies, and Scanning Electron Microscopy (SEM) with EDAX studies referred to two groups of endodontic instruments: ready-to-use or as-received (AR) files, and magnetoelectropolished (MEP) instruments, in comparison with the instruments surface after a conventional electropolishing (EP). The treated surfaces of NiTi endodontic files were studied by interferometric method in view of getting multiple surface characteristics, together with digital data concerning the arithmetic mean height Sa and the maximum height of scale limited surface Sz.The investigation results obtained have indicated a considerable improvement of MEP surface in comparison with both AR and EP surfaces. Such a surface after MEP reveals several positive features, decreased roughness, elimination of metallic state (here Ni and Ti elements) in the surface film, much enriched with titanium oxides and diminished nickel oxides. The study results show that the contents of Ni compounds is higher after EP (18.3%) than after MEP (10.2%), whereas the contents of Ti compounds is higher after MEP (83.4%) than after EP (76.6%). The total Ti/Ni ratio indicates almost double surpass of titanium over nickel in the surface film after MEP in comparison with the total amount of that ratio after EP.The qualitative investigation of fatigue tests have indicated much better performance of NiTi endodontic file samples after MEP than those related to AR and/or after EP. We have proved that the magnetoelectropolishing process may further modify surface. The following studies are to be directed onto performance and specific mechanical properties of the endodontic files at work.
SiGe Nanowires Grown by LPCVD: Morphological and Structural Analysis
Authors: Rodríguez Andrés , Sangrador Jesús , Rodríguez Tomás , Ballesteros Carmen , Prieto Carmelo , Jimenez Juan 
Published: April 2011

AbstractSiGe nanowires were grown by the vapor-liquid-solid method using a low pressure chemical vapor deposition reactor and different flows of the GeH4 and Si2H6 gas precursors. The morphology of the nanowires was studied by field emission scanning electron microscopy, and the length, diameter and density of nanowires were determined. Their structure and crystallinity were analyzed by transmission electron microscopy and its related techniques. Energy dispersive X-ray emission of individual nanowires as well a Raman spectroscopy were used to determine their composition and to analyze its homogeneity.
Surface Molecular Vibrations as a Tool for Analyzing Surface Impurities in Copper Phthalocyanine Organic Nanocrystals
Authors: Nauka K. , Zhao Yan , Ng Hou-T , Hanson Eric G. 
Published: April 2011

AbstractComparison of the IR spectra of the Cu-phthalocyanine (CuPc) nanocrystals obtained using surface sensitive attenuated total reflectance (ATR) and bulk sensitive transmittance sample configurations revealed small but measurable changes of some vibrational frequencies of the molecules at the surface of nanocrystals with the outermost part of the surface CuPc molecules being the most affected. These changes are caused by electrostatic interactions between the polar components of the molecules on the surface of nanocrystals and external polar molecular species vicinal to the nanocrystals. The external polar species can be either chemically bonded to the CuPc nanocrystal's surface or they can reside in its vicinity without forming a chemical bond with the nanocrystal. Molecular modeling (DMOL3 - Materials Studio and Gaussian calculations) of the impact of selected external polar species vicinal to a CuPc molecule on the CuPc molecular vibrations confirmed experimentally observed changes in the vibrational frequencies of the selected CuPc molecular bonding configurations and provided detailed information on the forces involved in these interactions. The population of external polar species vicinal to the CuPc surface can be modified by washing the nanocrystals or by introducing polar molecular additives miscible with the CuPc nanocrystals. Reduction in the number of external polar additives was accomplished by either centrifuging the aqueous dispersion of the nanocrystals or by organic solvent-based Soxhlet extraction, while their number was increased by soaking (followed by drying) the nanocrystals in high and low pH aqueous solutions containing SO3- and OH- ions. These quantitative and qualitative modifications of the population of external polar species surrounding CuPc nanocrystals were reflected in the corresponding changes of the selected vibrational frequencies of the CuPc surface molecules providing an effective tool for not only recognizing the molecular species vicinal to a nanocrystal but also quantifying their concentration. Some of these modifications can also be observed with a naked eye in the form of noticeable color changes of the CuPc nancrystalline powder. This is due to the extremely high visible extinction coefficient of the CuPc nanocrystals causing that the impinging light is mostly absorbed/reflected within the surface region of the nanocrystals. Changes of the electronic structure within this region, caused by the interactions with the vicinal polar species, shift the vis absorption/reflection spectra changing the observed color of the nanocrystalline powder. Similar results were obtained for other molecular nanocrystals, including yellow chromophore molecules. Preliminary data indicate that the described analytical method of analyzing the molecular polar species vicinal to a molecular nanocrystal could find variety of applications ranging from molecular device fabrication to pharmaceutical materials.
Effect of Film Morphology on Charge Transport in C60-based Organic Field Effect Transistors
Authors: Ullah Mujeeb , Kadashchuk Andrey K. , Stadler Philipp , Kharchenko Alexander , Pivrikas Almantas , Simbrunner Clemens , Sariciftci Niyazi Serdar , Sitter Helmut 
Published: April 2011

AbstractThe critical factor that limits the efficiencies of organic electronic devices is the low charge carrier mobility which is attributed to disorder in organic films. In this work we study the effects of active film morphology on the charge transport in Organic Field Effect Transistors (OFETs). We fabricated the OFETs using different substrate temperature to grow different morphologies of C60 films by Hot Wall Epitaxy. Atomic Force Microscopy images and XRD results showed increasing grain size with increasing substrate temperature. An increase in field effect mobility was observed for different OFETs with increasing grain size in C60 films. The temperature dependence of charge carrier mobility in these devices followed the empirical relation named as Meyer-Neldel Rule and showed different activation energies for films with different degree of disorder. A shift in characteristic Meyer-Neldel energy was observed with changing C60 morphology which can be considered as an energetic disorder parameter.
Controlling the Physical Properties of Random Network Based Shape Memory Polymer Foams
Authors: Singhal Pooja , Wilson Thomas S , Maitland Duncan J 
Published: April 2011

AbstractShape memory polymers (SMPs) are increasingly being considered for use in minimally invasive medical devices. For safe deployment of implanted devices it is important to be able to precisely control the actuation temperature of the device. In this study we report the effect of varying monomer composition on the glass transitions/actuation temperatures (Tg) of novel low density shape memory foams. The foams were based on hexamethylenediisocyanate (HDI), triethanolamine (TEA) and tetrakis (2-hydroxyl propyl) ethylenediamine (HPED), and were produced via a combination of chemical and physical blowing process. The process for post-foaming cleaning was also varied. Foams were characterized by DSC, DMA, and for shape memory. No clear trends were observed for foam samples without cleaning, and this was attributed to process chemicals acting as plasticizers. In foams cleaned via washing and/or sonication, the Tg was observed to decrease for compositions that were higher in the TEA content. Also, no change in shape memory behavior was observed for varying compositions. This work demonstrates the ability to tailor actuation transition temperature while maintaining shape memory behavior for low density foams suitable for aneurysm treatment.
Synthesis of nanostructured metal (Fe, Al)-C60 composites
Authors: García I. I. Santana , Febles V. Garibay , Calderon H. A. 
Published: April 2011

AbstractComposites of M-2.5 mol. % Fullerene C60 composites (where M= Fe or Al) are prepared by mechanical milling and Spark Plasma Sintering (SPS). The SPS technique has been used to consolidate the resulting powders and preserve the massive nanostructure. Results of X-Ray Diffraction and Raman Spectroscopy show that larger milling balls (9.6 mm in diameter) produce transformation of the fullerene phase during mechanical milling. Alternatively smaller milling balls (4.9 mm in diameter) allow retention of the fullerene phase. SEM shows homogeneous powders with different particle sizes depending on milling times. Sintering produces nanostructured composite materials with different reinforcing phases including C60 fullerenes, diamonds and metal carbides. The presence of each phase depends characteristically on the energy input during milling. Transmission Electron Microscopy (TEM) and Raman Spectroscopy show evidence of the spatial distribution and nature of phases. Diamonds and carbides can be identified for the sintered Fe containing composites with a relatively high volume fraction.
Preparation and Mechanical Characterization of a Polymer-Matrix Composite Reinforced with PET
Authors: Elena Salazar–Nieto J. , Altamirano–Torres Alejandro , Sandoval–Pérez Francisco , Rocha–Rangel Enrique 
Published: April 2011

AbstractIn this study, polymer-matrix composites are fabricated by mixing liquid epoxy resin with 0, 15, 20 and 25 wt % of PET. PET is used as a reinforcement material since it can be recycled and this implies a beneficial environmental impact. After mixing, specimens are dried at room temperature during 24 h and then cured at 150°C during 0.5, 0.75 and 1 h. Then mechanical tests are performed. Experimental results obtained from the flexion test for 100 % epoxy resin and 15 % PET samples, without curing treatment show values of 30 and 21 MPa, respectively. Flexure strength values for the same samples but after curing treatment are: 56, 90, 32 MPa and 69, 64, 70 MPa, for 0.5, 0.75 and 1 h of treatment, respectively. These data show an important increase in the flexure strength for the sample reinforced with 15 % PET and curing time of 1h. This is most likely due to the behavior of PET's powders at this temperature and time. They can partially melt improving the adhesion to the polymeric matrix. For a curing time of 0.75h, this property decreases, due to the high porosity developed in the composite and the poor adhesion between polymeric matrix and reinforced material.
Microstructure Characterization of Textured Nickel Using Parameters of Extinction
Authors: Cadena Arenas A. , Kryshtab T. , Palacios Gómez J. , Gómez Gasga G. , de la Torre A. De Ita , Kryvko A. 
Published: April 2011

AbstractX ray diffraction (XRD) is the common technique for texture analysis by means of pole figure (PF) measurement. PF reflects the grains orientation distribution but contains no information about grain microstructure. The reflected intensity can be affected by the extinction phenomenon that reduces the pole density (PD). The parameters of extinction are related to the crystal microstructure. The parameter of the primary extinction is connected with domain size and parameter of the secondary extinction is related to the angle of domains disorientation that depends on dislocation density in domain boundary. An original XRD method is proposed for correction of PD, considering extinction phenomenon, and separation of the extinction parameters in the case of textured aluminum. The problem is solved under some assumptions. In the present work cold rolled nickel with and without annealing at 600 °C is investigated. The validity of the proposed assumptions for Ni is evaluated in terms of the extinction length. The corrected PD in the maximum of PF and the parameters of the primary and secondary extinction are calculated using the first order reflection for CuKα- and CoKα- radiations and the second order reflection for one of the used wavelengths. Both in cold rolled sample without annealing and in the annealed sample the primary and secondary extinctions are present simultaneously. According to the obtained parameters of extinction the microstructure of textured nickel is evaluated and their modification at the annealing process is demonstrated.
Alumina-Based Functional Materials Hardened with Al or Ti and Al-nitride or Ti-nitride Dispersions
Authors: Miranda-Hernández José G. , Refugio-Garcia Elizabeth , Garfias-García Elizabeth , Rocha-Rangel Enrique 
Published: April 2011

AbstractThe synthesis of Al2O3-based functional materials having 10 vol. % of fine aluminum or titanium and aluminum-disperse or titanium-dispersed nitride hardened-particles has been explored. Two experimental steps have been set for the synthesis; specifically, sintering of Al2O3-aluminum or Al2O3-titanium powders which were thoroughly mixed under high energy ball-milling, pressureless-sintered at 1400°C during 1 h in argon atmosphere and then for the second step it was induced formation of aluminum nitride or titanium nitride at 500°C during different times (24, 72 and 120 h) by a nitriding process via immersion in ammoniac salts. SEM analyses of the microstructures obtained in nitride bodies were performed in order to know the effect of the ammoniac salts used as nitrating on the microstructure of aluminum or titanium for each studied functional material. It was observed that an aluminum nitride or titanium nitride layer growth from the surface into the bulk and reaches different depth as the nitriding time of the functional material was increased. The use of aluminum or titanium significantly enhanced density level and hardness of the functional materials.
Elaboration and Evaluation of Membranes from Biopolymers as Delivery System of Plant Extracts
Authors: A Rodríguez-García , Galán-Wong L.J. Luis J. , K. Arévalo-Niño 
Published: April 2011

Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans are considered key pathogens in periodontitis that is the principal cause of tooth loss in adults. The treatment of periodontal disease consists on the use of chemicals which can alter oral microbiota and have undesirable side-effects such as vomiting, diarrhea and tooth stainingAt recent years, the use of natural sources like biomaterials such as biopolymers and plant extracts are enjoying great popularity. Chitosan and pullulan are polymers that have been proposed due to their favorable properties such as biocompatibility, biodegradability, adhesion ability and nontoxicityThe aim of this study was to develop films from chitosan and pullulan containing plant extracts as delivery system and determine the in vitro antibacterial activity against periodontopathogen microorganisms and their stability under different conditions of storage
Concrete Biodeterioration in the U.S.-Mexico Border Region
Authors: Rendon L. E. , Lara M. E. , Rendon S. K. , Rendon M. , Li X. 
Published: April 2011

AbstractConcrete biodeterioration is defined as the damage that the products of microorganism metabolism, in particular sulfuric acid, do to hardened concrete. In Canada and in the northern part of the United States, sewer failures from concrete biodeterioration are almost unknown. In the southern part of the United States and in Mexico, however, it is a serious and expensive problem in sewage collection systems, which rapidly deteriorate. Also, leaking sewage systems result in the loss of groundwater resources particularly important in this arid region. Almost every city in the Mexican-American border region, who's combined population is more than 15 million people, faces this problem. The U.S. cities have made some provision to face these infrastructure problems, but the Mexican cities have made less effort. We recommend here the Mexican norm (NMX-C-414-ONNCCE-2004) [1] to be reviewed, or at least that a warning be issued as a key measure to avoid concrete biodeterioration.
Cadmium(II) and Lead(II) removal by Chlorella sp. Immobilized and E. coli genetically engineered with mice Metallothionein I
Authors: Almaguer-Cantú V. , Morales-Ramos L. , Arevalo-Niño K. , Garza-González M.T. , Balderas-Rentería I. 
Published: April 2011

AbstractThe pollution caused by heavy metals is one of the major environmental problems that is imperative to be solved. New technologies, easy to implement and to adapt to any system, deserve special attention and are a focus of this work the ability of Chlorella sp. and E. coli genetically engineered with mice metallothionein I, both immobilized in alginate of calcium to remove Cd(II) and Pb(II) from aqueous solutions was investigated in batch assays for the treatment of diluted aqueous solutions. The kinetics, sorption capacities and sorption percentage were determined. The influence of metal concentration in solution is discussed in the terms of Langmuir isotherm and constants. Sorption capacities increased with increasing metal concentration in solution. For solution containing 300 mg/L of metal, the observed uptake capacities were 94.941±1.094 mgCd/gChlorella., 24.076±2.292 mgCd/gE.coli and 239.17±2.478 mgPb/gChlorella, 37.952±4.245 mgPb/gE.coli. The Langmuir constants to Chlorella sp. were qmax=285.72(mgPb/g), b=0.0276(l/mgPb), qmax=103.65(mgCd/g) and b=0.0005(l/mgCd) while to E. coli were qmax=28.141(mgPb/g), b=0.113(l/mgPb), qmax=24.272(mgCd/g) and b =0.019(1/mgCd). The biomass of the algae showed to have better capacity of metallic sorption that the biomass of the bacteria genetically engineering. The study proved that microorganisms biomass is a suitable material for the removal of the studied heavy metals ions from aqueous solutions, achieving removal efficiencies higher than 90%, and could be considered as a potential material for treating effluent polluted with Cd(II) and Pb(II) ions.
Synthesis and Thermoluminescence of New ZnO Phosphors
Authors: Cruz-Vázquez C. , Borbón-Nuñez H. A. , Orante-Barrón V. R. , Burruel-Ibarra S. E. , Castaño V. M. , Bernal R. 
Published: April 2011

AbstractIn this work, the synthesis and thermoluminescence properties of new ZnO phosphors obtained by a chemical method are reported. Some samples were exposed to beta particle irradiation for doses ranging from 10.0 up to 6,400 Gy, and it was found that the thermoluminescence response as a function of dose is linear for doses below 200 Gy, and sublinear with no saturation clouds for greater doses. A broad shape glow curve with maximum located above 230 °C, that shifts to lower temperatures as dose increases, indicating that second order kinetics thermoluminescence processes are involved. The lower detection limit was estimated to be 13 Gy. We conclude that the phosphors under study are promising to develop dosimeters for high dose radiation dosimetry.
Transformations of Supported Heteropoly Compounds in Oxidative Conversion of Alkanes
Authors: Tungatarova Svetlana A. 
Published: April 2011

AbstractDynamics of structural transformation of supported heteropoly compound was investigated by IR-spectroscopy, XRD, TPR, and TPO methods. The 15-30 wt.% H3PMo12O40and H3PV2Mo10O40, supported on SiO2catalysts were investigated in process under various conditions by interaction with O2(air) in the presence of water vapor, H2, alkane in TPR regime, O2in TPO regime (298-1273K) and H2O (298, 923K). The rank of reversible structural conversion of supported heteropoly compounds was established under influence of temperatureand medium. These new findings of reversible structural cycle explains the stability of the 12th series Mo heteropoly compounds supported on Si-containing carrier at high temperatures (873-1073K) which is close to the actual operation temperatures of the partial oxidation reactions and oxidative dehydrogenation of alkanes.
Study of the Formation of WOx Nanostructures Supported on Zirconia Prepared by Different Synthesis Routes
Authors: Hernández Martha L. , Montoya Ascención , angel Paz Del , Paredes Silvia P. , Flores Sergio O. 
Published: April 2011

AbstractDifferent synthesis procedures of Pt supported on tungstated zirconia catalysts (Pt/WOx-ZrO2) were investigated with the aim to elucidate the different WOx nanostructures developed on the zirconia surface depending on the preparation route. Pt/WOx-ZrO2 catalysts were synthesized by the coprecipitation and impregnation methods and pretreated by various procedures such as different calcinations temperatures or the use of reflux. The catalysts characterization was carried out by X-ray diffraction (XRD), Raman spectroscopy, transmission and scanning electron microscopy (TEM, SEM) and nitrogen physisorption, and the catalytic activity was evaluated in the n-hexane isomerization reaction. The results indicate that the development of active sites for isomerization of n-hexane is enhanced by the stabilization of the WOx nanostructures on the surface of zirconia, before the formation of the WO3 crystallites, and it largely depends on the synthesis method.
Thermal Diffusivity Measurement of Pure Te, (Hg1−x Cdx)1−yTey and (Hg1−xZnx)1−yTey
Authors: Maleki Hossein , Holland Lawrence R. 
Published: April 2011

AbstractThe thermal diffusivities of (Hg1−xCdx)1−yTey and (Hg1−xZnx)1−yTeywith 0.55 ≤ y ≤ 1.0 and 0.0125 ≤ x ≤ 0.05465 and of pure Te are measured over a wide temperature range by the laser flash technique. The diffusivity of near pseudobinary Hg1−xCdxTe solids decrease more rapidly with temperature approaching the melting point than pseudobinary solids previously reported. The solid diffusivity for x=0.02817 is 0.83 mm2/s at 371°C, decreasing to 0.22 mm2/s at 614°C. The diffusivity of Te rich (Hg1−xCdx)1−yTey melt increases with x and with temperature. The melt diffusivity for x=0.03934 is 0.91 mm2/s at 485°C, increasing to 4.93 mm2/s at 851°C. For Te rich (Hg1−xZnx)1−yTey melt with x=0.0125 and y=0.7944 there appears to be a minimum diffusivity of about 2.6 mm2/s near 700°C. The thermal diffusivity of pure Te solid is 0.97 mm2/s at 300°C and decreases to 0.64 mm2/s at 439°C. The melt diffusivity is 1.52 mm2/s at 486°C, increasing to 3.48 mm2/s at 584°C.