bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Biodegradable Composite for Knee Cartilage Prosthesis Joint
Authors: Pérez-Reyes J.C. , Carbajal-De la Torre G. , Espinosa-Medina M. A. , Ibarra-Bracamontes L. A. , Villagómez-Galindo M. , Rubio-Rosas E. 
Published: November 2012

ABSTRACTOsteoarthritis is a very complex illness of the joints that affects cartilage and subcondral bone. At the last years, researching has been focused in the development and characterization of composite materials, evaluating their structural properties. Some o those composite materials are constituted by organic and inorganic compounds forming hybrids. These materials can improve their properties due to the interaction of reinforcement hard particles in the polymeric matrix. The interest on the composite biomaterials has been increased on the biomedical applications such as tissue regenerating based in synthetic polymers with biodegradable and biocompatible properties whose can be reinforced by calcium phosphates. In this sense, hydroxyapatite [Ca10(PO4)6(OH)2] is often used for biological implants due its mineral phase similitude with bone microstructure and tissue compatibility. Similarly, polylactic acid (PLA) is a used polymer for implant applications due physicochemical and biocompatibility properties, and short degradation time also. In order to obtain a composite that can be used as a regenerating material on the osteoarthritis problem, in this work a (90/10 wt.%) polylactic/hydroxyapatite hybrid composite was produced by chemical synthesis and characterized by X-ray diffraction, SEM, FT-IR and TGA/DSC techniques.
Fractal-based image texture analysis of trabecular bone architecture for assessment of bone health: bone aging in Mexican men
Authors: Navarrete M. , Cedillo E. , Solís L. , Villegas CH , Alvarado JA , Godínez FA 
Published: November 2012

ABSTRACTTwo methods based on fractal image analysis were used to extract the architectural features of the anisotropic structure of trabecular bone from scanning electron microscope (SEM) images of sliced bone samples in order to assess the bone’s medical condition. Two methods applied were Box-Counting (BC) and Fast Fourier Transform (FFT). Tests with synthetic images of known fractal dimension aided in the interpretation of the fractal dimension (FD) profiles. Samples from L3 vertebrae were removed from Mexican male donors at the time of necropsy and evaluated using computed axial tomography (CAT) scans. Three sliced samples in normal, osteopenic and osteoporotic conditions were identified in order to compare both methods across a range of samples. The three-dimensional projection of the FD profile reflected a multifractal behavior of the trabecular architecture and clearly showed the differences in texture between the three conditions studied: normal, osteopenic and osteoporotic. In addition, the results suggest that the FFT method provides an accurate and consistent estimated for characterizing trabecular bone than the BC method.
A look into the interaction of metal oxide thin films with biological media: Albumin and Fibrinogen adsorption
Authors: Silva-Bermudez P. , Muhl S. , Rivera M. , Rodil S. E. 
Published: November 2012

ABSTRACTIn the present work, the adsorption of albumin and fibrinogen on Ta, Nb, Ti and Zr oxidesthin films deposited on Si (100) wafers by magnetron sputtering was studied in order to get a better understanding of the correlation among the surface properties of these oxides and the protein adsorption phenomena on their surfaces. The surface energy, hydrophobicity, chemical composition, roughness and atomic order of the films were characterized. The films were immersedfor 45 minutes in single protein solutions; either albumin or fibrinogenand the adsorbed protein layer on the films was studied ex-situ in a dry ambient using bothX-ray photoelectron spectroscopy and atomic force microscopy.The adsorption of albumin and fibrinogen on the films modified the surface morphology and decreased the surface roughness for all the four different metal oxides. The XPS results confirmed the presence of the protein on the surface of the films and showed that the two proteins studied were adsorbed without undergoing a major chemical decomposition. A correlation between the surface roughness,the polar component of the surface energy of the films and the atomic percentage of nitrogen on the films after protein adsorption, an indirect signal of the amount of protein adsorbed, was found for albumin and fibrinogen adsorption on Ta, Nb and Ti oxides; the largest the roughness or the polar component the largest amount of adsorbed protein.
ZETA POTENTIAL STUDY OF BARIUM HEXAGONAL FERRITES (BaFe12O19) FOR DRUG RELEASE
Authors: Torres-Cadenas S. , Escudero-García R. , Espítia-Cabrera I. , Contreras-García M.E. 
Published: November 2012

ABSTRACTAdvances in nanotechnology observe new applications in many areas. Recently a great extent of research has been focused on the study of magnetic nanoparticles due to their potential application in areas such as bioscience and medicine. Magnetic nanoparticles are frequently used in biomedical and biotechnology applications since these particles associated to a given medicine are good candidates for drug release.In this work zeta potential measurements of both hexagonal barium ferrites (magnetic nanoparticles), and an antibiotic known as tetracycline were carried out. The knowledge of the measured values establishes the possibility of bringing the two particles together in order to adsorb the tetracycline on the magnetic nanoparticles, since the surface charge play an essential role in the adsorption of the pharmaceutical drug on nanomaterials (i.e., tetracycline on barium ferrites).Experimental results show the feasibility to adsorb tetracycline nanoparticles on barium hexaferrite solids at pH 7.0, based on the knowledge of the opposite electrical surface charge of the two solid species through the zeta potential measurement.
Synthesis and characterization of copolymeric micelles loaded with Taxol® as potential drug delivery systems for cancer treatment
Authors: Tapia L.V. , Castro J.S. , Martinez C.A. , Garcia P.E. , Rodriguez C.A. , Deymier P.A. 
Published: November 2012

ABSTRACTTaxol (Paclitaxel) is a very potent anticancer drug used in chemotherapy treatments. Due to its hydrophobic nature, toxic solubilizing agents are used to administer the drug via intravenously. However, this systemic administration is associated with toxic side effects and drug limited efficacy. An alternative to these problems are polymeric micelles. The effectiveness of this drug delivery system is related to its size, modification of pharmacokinetics, drug delivery control and toxicity reduction. In this study, micelles based on methoxy Poly(ethylene glycol)-block-Poly(ε-caprolactone) (mPEG-b-PCL) copolymer loaded with Taxol were synthesized thorough an uncommon method namely powder formulation, using tert-butanol as co-solvent, to our knowledge no reported previously for these micells. Taxol was conjugated to the hydrophobic block of mPEG-b-PCL copolymer. Characterization of this system was done by means of Fourier Transform Infrared Spectroscopy (FT-IR) and Field Emission Scanning Electron Microscopy (FESEM), observing good results as compared to previous reports.
Finite Element Stress Analysis of Cast Metal Inlays Restored Posterior Teeth
Authors: Sandu L. , Topală F. , Porojan S. , Babeş V. 
Published: November 2012

ABSTRACTCast metal inlays have overall characteristics unavailable in any other restorative procedure, including low restoration wear, low wear of opposing teeth, lack of breakage, burnishability, malleability, and proven long term service. They replace missing teeth structures, without doing anything to reinforce the remaining structures. Stress concentrations can manifest themselves in various forms of failures. The aim of the study was to investigate the effect of preparation design on stress distribution in molars with different class II preparations and restored with cast metal inlays.3D models of premolars and molars were created: intact teeth, unrestored teeth with class II preparations with different tapers (between 0 and 10 degree); the same teeth restored with metalic inlays. The geometries of the intact teeth were obtained by 3D scanning using a manufactured device. With Rhinoceros modeling program the preparations and the appropriately inlays were designed. These were exported in Ansys finite element analysis software for structural simulations. Stresses were registred around the occlusal contact areas. For the studied cases, the stress values were not significant influenced by the taper of the preparation. In the teeth restored with cast metal inlays, the von Mises equivalent stress values were similar to those in the intact tooth.From biomechanical point of view, it was demonstrated that class II cast metal inlays on posterior teeth restore the original strength of the teeth. Taking into account the other characteristics of these restorations, they remain the standard of care for long-term rehabilitations. A taper between 0 and 10 degree of the preparation is not decisive for the stress values.
Aging Effects of As-deposited and Passivated Cobalt Slanted Columnar Thin Films
Authors: Schmidt Daniel , Schubert Eva , Schubert Mathias 
Published: November 2012

ABSTRACTAging effects of as-deposited and passivated slanted columnar thin films from cobalt determined by generalized ellipsometry within the visible spectral region are reported. Slanted columnar thin films have been grown by glancing angle electron beam deposition and sub-sequently coated with Al2O3 by an atomic layer deposition process. An anisotropic Bruggeman effective medium approximation developed for highly ordered three dimensional metal nanostructures is employed to analyze spectroscopic Mueller matrix ellipsometry data. Our model approach allows for determination of biaxial optical and structural properties as well as fractions of multiple film constituents. While the optical properties of the uncoated film change over time, the alumina passivation layer prevents oxidation in air and therefore aging effects; however, it affects the intrinsic bulk-like Co optical properties.
Electron beam synthesis of 3D metal nanostructures from fluoride precursors
Authors: Ghatak Jay , Gnanavel T , Guan Wei , Möbus Günter 
Published: November 2012

ABSTRACTVarious metal fluoride crystals were subjected to electron beam irradiation at 200 and 300 kV using transmission electron microscopy in order to study in-situ fabrication of 3D metal nanostructures. Lithium fluoride, cobalt fluoride and aluminum fluoride salt fragments were chemically reduced and transformed by the electron beam to the corresponding metals. Using live video recording we observe that LiF crystals decompose in a unique way different to all other metal-halides. Li diffuses rapidly out of the salt crystal and covers its surface and the surrounding C-support film to many microns distance, where at random positions nucleation, growth and annihilation of Li nanorods and some nanospheres is observable. Decomposition of CoF2 also involves non-local synthesis of Co nanoparticles, mostly facetted, however, these are stable, without annihiliation, and their positioning seems to follow some degree of self-organisation. AlF3 transforms locally to Al grains inside the irradiated area only, and grain growth occurs to sizes proportional to the beam intensity. Findings are discussed in terms of displacement energy differences between the materials.
Morphological Evolution during Growth and Erosion on Vicinal Si(100) Surfaces: From Electronic Structure Analyses to Atomistic and Coarse-Grained Modeling
Authors: Liu Da-Jiang , Ackerman David M. , Guo Xiaofang , Albao Marvin A. , Roskop Luke , Gordon Mark S. , Evans James W. 
Published: November 2012

ABSTRACTStepped Si(100) surfaces exhibit alternating stiff SA and meandering SB steps, and thus constitute a so-called AB-vicinal surface. Both growth by Molecular Beam Epitaxy (MBE) or Chemical Vapor Deposition (CVD), and erosion by ion sputtering or chemical etching, induce step pairing, although different factors contribute. In addition, more complex pattern formation often occurs during step train motion. We synthesize recent developments in modeling of these processes ranging from ab-initio electronic structure approaches for key surface energetics, to atomistic lattice-gas modeling, to coarse-grained sharp-interface (front-tracking) and smeared-interface (phase-field) step dynamics approaches. We briefly describe development of new formalisms related to coarse-grained approaches, as well as selected results for step pairing.
Towards highly efficient solar cells based on merocyanine dyes
Authors: Steinmann Vera , Kronenberg Nils M. , Lenze Martin R. , Deppisch Manuela , Bürckstümmer Hannah , Würthner Frank , Meerholz Klaus 
Published: November 2012

ABSTRACTWe present the development of highly efficient merocyanine solar cells at the example of the dye MD376. Due to their unique processing flexibility, merocyanines have been applied in solution- as well as vacuum-processed organic photovoltaics. In fully vapor-deposited MD376 single cells, efficiencies up to 5.0% were achieved while maintaining a rather simple device setup with only four organic layers. Moreover, MD376 has been successfully introduced to vacuum-processed tandem cell structures, reporting a high open-circuit voltage of 2.1 V.
Directed Assembly of Model Block Copolymer-PCBM Blend System for Photovoltaic Applications
Authors: Singh G. , Kulkarni M. M. , Smilgies D. , Sides S. , Berry B. , Raghavan D. , Bucknall D.G. , Sumpter B , Karim A. 
Published: November 2012

ABSTRACTBlock copolymers are considered to be highly attractive materials with regards to future applications of nanomaterials and nanostructures owing to their self-assembling nature. Block copolymers, when supplied with sufficient energy, phase separate at the nanoscales to form periodically ordered structures in the nanometer-scale range. A diversity of architectures can be accessed via composition control of individual block components. An exciting area of application for block copolymer self assembly is organic photovoltaic devices (OPV‟s) where it is expected that the very high interfacial area of the blocks with ∼10-20 nm domain spacing would be highly advantageous for exciton diffusion and separation. For this purpose BCPs composed of amorphous (non-conjugated) polymers can also serve as a template for directed assembly of nanoparticles. Zone annealing is a well established method predominantly utilized for metallurgical and semi-conductor purification processes, where recrystallization and oriented grain growth occur on the planar front formed by the cooling-edge of the zone. We have previously applied this process to create highly ordered BCP cylinders that are parallel to the substrate with orientational control, long range order and faster ordering kinetics than conventional thermal annealing. In the present paper, we extend this idea to block copolymer - [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend system and report how the presence of PCBM nanoparticles influence the micro-phase separation behavior of cylinder forming poly(styrene-b-2-vinyl pyridine) under a dynamic thermal gradient field. A range of scattering techniques have been on the BCP:PCBM blend system, including grazing incidence small angle x-ray scattering (GISAXS) experiments to characterize in-plane and lateral ordering of BCP-PCBM blend system.
Naphthodithiophene-Diketopyrrolopyrrole Small Molecule Donors for Efficient Solution-Processed Solar Cells
Authors: Loser Stephen , Bruns Carson J. , Miyauchi Hiroyuki , Ortiz Rocío Ponce , Facchetti Antonio , Stupp Samuel I. , Marks Tobin J. 
Published: November 2012

ABSTRACTWe report the synthesis, characterization, and implementation of various naphtho[2,3- b:6,7-b’]dithiophene (NDT)-based donor molecules for organic photovoltaics (OPVs) When NDT(TDPP)2 (TDPP = thiophene-capped diketopyrrolopyrrole) contains all branched 2- ethylhexyl chains and is combined with the electron acceptor PC61BM, a power conversion efficiency (PCE) of 4.06±0.6% is achieved. This respectable PCE is attributed to the broad, high oscillator strength visible absorption, the ordered molecular packing, and a high hole mobility of 0.04 cm2·V-1·s-1. We find utilizing linear C-12 side chains on either the TDPP or NDT framework dramatically increases the d-spacing, which directly correlates with inferior OPV device performance. This leads to the conclusion that the selection of an appropriate side chain plays a key role in determining OPV device performance of a small molecule donor.
Stable Colloids of Paclitaxel Nanoparticles Coated with PEGylated Polyelectrolyte Shells
Authors: Shutava Tatsiana G. , Arapov Kirill A. , Pattekari Pravin P. , Lvov Yuri M. , Levchenko Tatyana S. , Sawant Rupa R. , Torchilin Vladimir P. 
Published: November 2012

ABSTRACTA novel nanoparticulated form of the poorly water-soluble anticancer drug paclitaxel (PTX) suitable for intravenous administration has been developed using sonication-assisted layer-by-layer (LbL) assembly. The nanoparticles contain up to 70 wt.% of the drug and consist of 150-180 nm solid crystal paclitaxel cores coated with 20-30 nm thick shells of alternative layers of PEGylated poly-L-lysine and heparin. Dispersions of PTX nanoparticles are stable in different biological solvents at concentrations up to 5 mg/ml. Intravenous administration of the LbL-coated nano-crystalline PTX to mice via tail injection provided the preliminary confirmation of their safety and tolerability.
Structure and Low Concentration Self Assembly of Food Grade Bacterial Cellulose Nano-Whiskers
Authors: Khandelwal Mudrika , Windle Alan H. 
Published: November 2012

ABSTRACTNata-de-coco (bacterial cellulose) forms nanowhiskers with a larger aspect ratio owing to higher crystalline, longer and thinner microfibrils than those formed by cellulose from other sources. Suspension of these nanowhiskers undergoes transition from isotropic to liquid crystalline phase at a very low concentration of about 0.05 wt% in water and through a broad biphasic region. Formation of nematic as well as cholesteric phase is presented in this work.
3-D Chiral Photonic Crystals Replicated from Butterfly Wing Scales
Authors: Mille Christian , Tyrode Eric C. , Corkery Robert W. 
Published: November 2012

ABSTRACTThree dimensional silica photonic crystals with the gyroid minimal surface structure have been synthesized using the butterfly Callophrys rubi as a template. The replicas are synthesized with a high degree of fidelity, which is confirmed by the spectral and morphological characterization. Further, the material is shown to be optically active.
Excitation of plasmon and guided-mode resonances in thin film silicon solar cells
Authors: Haug F.-J. , Söderström K. , Naqavi A. , Battaglia C. , Ballif C. 
Published: November 2012

ABSTRACTThin film silicon solar cells are an attractive option for the production of sustainable energy but their low response at long wavelengths requires additional measures for absorption enhancement. The most successful concepts are based on light scattering interface textures whose understanding is greatly facilitated by considering a superposition of periodic textures that diffract the light into oblique angles, ideally beyond the critical angle of total internal reflection. Because the thickness of the active layers is on the same scale as the wavelength, interference of diffracted waves gives rise to resonance phenomena. We discuss the absorption enhancement in terms of a perturbation approach using the modal structure of a corresponding device with flat interfaces.
Microstructural Modeling of Electrical Behavior in CNT Polymer Composites
Authors: Xu S. , Rezvanian O. , Peters K. , Zikry M.A. 
Published: November 2012

ABSTRACTA three-dimensional (3D) carbon nanotube (CNT) resistor network computational model was developed to investigate the electrical conductivity, and current and thermal flow in polymer composites with randomly dispersed CNTs. A search algorithm was developed to determine conductive paths for 3D CNT arrangements and to account for electron tunneling effects. By coupling Maxwell specialized finite-element (FE) formulation with Fermi-based tunneling resistance, specialized FE techniques were then used to obtain current density evolution for different CNT/polymer dispersions and tunneling distances. These computational approaches address the limitations of percolation theories that are used to estimate electrical conductivity of CNTs. The predictions indicate that tunneling distance significantly affects 3D electrical conductivity and thermal distributions.
Silver nanodiscs for light scattering in thin epitaxial silicon solar cells: influence of the disc radius
Authors: El Daif O. , Tong L. , Figeys B. , Jain S. , Miljkovic V. D. , Depauw V. , Vercruysse D. , Van Nieuwenhuysen K. , Dmitriev A. , Van Dorpe P. , Gordon I. , Dross F. 
Published: November 2012

ABSTRACTThe effect of silver nanoparticles showing localised plasmonic resonances on the efficiency of thin film silicon solar cells is studied. Silver (Ag) nanodiscs were deposited on the surface of silicon cells grown on highly doped silicon substrates, through hole-mask colloidal lithography, which is a low-cost and bottom-up technique. The cells have no back reflector in order to exclusively study the effect of the front surface on their properties. Cells with nanoparticles were compared with both bare silicon cells and cells with an antireflection coating. We optically observe a resonance showing an absorption increase controllable by the disc radius. We also see an increase in efficiency with respect to bare cells, but we see a decrease in efficiency with respect to cells with an antireflection coating due to losses at wavelengths below the plasmon resonance. As the material properties are not notably affected by the particles deposition, the loss mechanism is an important absorption in the nanoparticles. We confirm this by numerical simulations.
Light Trapping in Hydrogenated Amorphous and Nanocrystalline Silicon Based Thin-Film Solar Cells With Ag/ZnO Back Reflectors
Authors: Yan Baojie , Yue Guozhen , Sivec Laura , Owens-Mawson Jessica , Yang Jeffrey , Guha Subhendu 
Published: November 2012

ABSTRACTWe report on our systematic study of light trapping effects using Ag/ZnO BRs for nc-Si:H solar cells. The texture of Ag and ZnO was optimized to achieve enhancement in photocurrent. The light trapping effect on photocurrent enhancement in solar cells was carefully investigated. Comparing to single-junction solar cells deposited on flat stainless steel substrates, the gain in Jsc by using Ag/ZnO BRs is 57% for nc-Si:H solar cells. This gain in Jsc is much higher than what has been achieved by advanced light trapping approaches using photonic structures or plasmonic light trapping reported in the literature. We achieved a Jsc of 29-30 mA/cm2 in a nc-Si:H single-junction solar cell with an intrinsic layer thickness of ∼2.5 μm. We compared the quantum efficiency of single-junction cells to the classical limit of fully randomized scattering and found that there is a 6-7 mA/cm2 difference between the measured Jsc and the classical limit, in which 3-4 mA/cm2 is in the long wavelength region. However, by taking into consideration the losses from reflection of the top contact, absorption in the doped layers, and imperfect reflection in the BRs, the difference disappears. This implies we have reached the practical limit if the scattering from randomly textured substrates is the only mechanism of light trapping. Therefore, we believe future research for improving photocurrent should be directed toward reducing (i) reflection loss by the top contact, the absorption in ZnO and at the Ag/ZnO interface, and (ii) p layer absorption.