bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigating Coherent Zone-Folded Acoustic Phonons in Si/SiGe Superlattices by Transient Thermoreflectance Technique
Authors: Michel Hélène , Pernot Gilles , Rampnoux Jean-Michel , Dilhaire Stefan , Grauby Stéphane , Ezzahri Younès , Shakouri Ali 
Published: August 2010

AbstractIn this paper, we present a systematic study of coherent phonons in Si/SiGe superlattices with two different periods. The superlattice periodicity affects the acoustic properties of the structure. Transient thermoreflectance (TTR) technique is used to perform picosecond ultrasonics experiments and then, investigate coherent zone-folded acoustic phonons in different Si/SiGe superlattice structures. Several classes of coherent phonons are produced in the superlattice, whose generation mechanisms are different: Brillouin oscillations, coherent longitudinal-acoustic phonon Bragg reflection and impulsive stimulated Raman scattering (ISRS).
Correlating Nanoparticle Dispersion to Surface Mechanical Properties of TiO2/Polymer Composites
Authors: Pang Yongyan , Watson Stephanie S. , Forster Aaron M. , Sung Lipiin 
Published: August 2010

AbstractThe objective of this study is to characterize the nanoparticle dispersion and to investigate its effect on the surface mechanical properties of nanoparticle-polymer systems. Two types of TiO2 nanoparticles were chosen to mix in two polymeric matrices: solvent-borne acrylic urethane (AU) and water-borne butyl-acrylic styrene latex (latex) coatings. Nanoparticle dispersion was characterized using laser scanning confocal microscopy. Overall, Particle A (PA, without surface treatment) dispersed better than Particle B (PB, organic treatment) in both systems. The AU-PA system exhibited the best dispersion of the four systems, however PB forms big clusters in both of the matrices. Surface mechanical properties, such as surface modulus at micron and sub-micron length scales were determined from depth sensing indentation equipped with a pyramidal tip or a conical tip. The surface mechanical properties were strongly affected by the dispersion of nanoparticle clusters, and a good correlation was found between dispersion of nanoparticle clusters near surface and the modulus-depth mapping using a pyramid tip.
Size Effect in the Shear-Coupled Migration of Grain Boundaries Pinned by Triple Junctions
Authors: Gil Sevillano Javier , Luque Aitor , Aldazabal Javier , Martinez-Esnaola José Manuel 
Published: August 2010

AbstractThis paper presents molecular dynamics simulations of shear-coupled migration of tilt boundaries pinned by triple junctions in a simple model structure of columnar grains of different sizes. Simulations are for copper at 300 K. The phenomenon is of interest as a possible explanation of the Hall-Petch relationship breakdown in nano-grained polycrystals deformed at high or moderate strain rate and low-temperature.
Mechanochemical Synthesis of Novel Sensor Materials
Authors: Sorescu Monica , Diamandescu Lucian , Tomescu Adelina 
Published: August 2010

AbstractThe xZnO-(1-x)alpha-Fe2O3 and xZrO2-(1-x)alpha-Fe2O3 nanoparticles systems have been obtained by mechanochemical activation for x=0.1, 0.3 and 0.5 and for ball milling times ranging from 2 to 24 hours. Structural and magnetic characteristics of the zinc and zirconium-doped hematite systems were investigated by X-ray diffraction (XRD), Mössbauer spectroscopy and conductivity measurements. Using the dual absorber method, the recoilless fraction was derived as function of ball milling time for each value of the molar concentration involved. As ZnO is not soluble in hematite in the bulk form, the present study clearly illustrates that the solubility limits of an immiscible system can be extended beyond the limits in the solid state by mechanochemical activation. Moreover, this synthetic route allowed us to reach nanometric particle dimensions, which makes these materials very important for gas sensing applications.
A Package for Fast FEM-based Simulation of X-ray Diffraction From Nano-structures
Authors: Wintersberger Eugen , Oswald Jay 
Published: August 2010

AbstractIn this work a novel package for the calculation of the diffracted intensity from nano-structures based on finite element simulations is presented. Besides a short introduction into the algorithm which we have developed two examples namely the diffraction from Si/SiGe systems with ripples and quantum dots with dislocations are shown.
Observation of Ultrafast Lattice Heating in thin Metal Films using Time-resolved Electron Diffraction
Authors: Ligges Manuel , Streubühr Carla , Brazda Thorsten , Posth Oliver , Hassel Christph , Dumpich Günter , Zhou Ping , von der Linde Dietrich 
Published: August 2010

AbstractWe show that time-resolved electron diffraction is capable of revealing the ultrafast lattice heating in thin metal films following excitation by a femtosecond laser pulse. The build-up of the lattice temperature leads to a reduction of the diffraction intensity of the various diffraction orders due to the Debye-Waller-effect. We also observed a reduction of the transmitted (000)-signal which exhibits the same temporal evolution as the diffraction signals.
Label-free Electrochemical Impedance Detection of Ovarian Cancer Markers CA-125 and CEA
Authors: Whited Allison M , Singh Kanwar V , Solanki Raj , Evans David R 
Published: August 2010

AbstractCA-125 and carcinoembryonic antigen (CEA) are two biomarkers present in blood that can indicate the presence of ovarian cancer. They can also be used, both in conjunction with each other and independently, to determine the effectiveness of the treatment being meted for the disease. A label-free multiplexed interdigitated electrode array (IDEA) immunosensor was developed to detect both CA-125 and CEA in buffer solution at levels typically seen in patients with ovarian cancer . Electrochemical impedance spectroscopy was used to measure the increase in impedance when a binding event occurred between the target antigen and its specific antibody that was anchored to the surface of an interdigitated electrode array. CA-125 was detected in concentrations as low as 10units/mL and as high as 80units/mL. CEA was detected in concentrations as low as 1pg/mL and as high as 10μg/mL.
A Microfluidic Chip for Analysis of Mechanical Forces Generated During Cell Migration
Authors: Zheng Xiaoyu , Frohlich Else , Collignon Sean , Zhang Xin 
Published: August 2010

AbstractVascular smooth muscle cell migration is a microscopic in vivo process where specific cells crawl in order to partake in crucial physiological functions relating to embryonic development, wound healing, and tissue development. Abnormalities of cell migration result in pathologies such as tumor metastasis, angiogenesis, chronic inflammation, and various immune response dysfunctions. The mechanism behind cellular migration and the role of intracellular proteins in the instigation of cell directionality remains poorly understood without effective biomedical device available. The development of microfluidic biochips technologies enable detection, sample preparation and treatment on one single chip. We are reporting the design and fabrication of a novel microfluidic trip for guiding and quantifying cell migrations. The chip featured micropillar arrays imbedded in a multichannel microfluidic chip, where cell migration can be guided by utilizing the characteristics of laminar flow. Non-blending layers of fluid injected through the multi-channel device simulated a wounded edge across a monolayer of cells by limiting flow of trypsin, a serine protease, to half of the main channel, promoting cell migration in a desired direction. Control over cell directionality allows for the measurement and analysis of mechanical forces generated during cell migration in relation to migratory responses from intracellular protein inhibition. The micro-fluidic chip template was designed and manufactured using photolithography techniques. Polydimethylsiloxane (PDMS) served as the bulk material of the two compromising chip layers (channels and pillars), which were subsequently aligned and adhered to form the device. It was confirmed through both computer simulation and experimentation that the through optimized arrangement of the chip design, this device can effectively hold laminar flows of trypsin and cell media. Thus, this microfluidic device allows the user to simultaneously acquire force data during cell migration and observe migratory patterns to ultimately gain a better understanding of the underlying mechanisms of cell migration and directionality.
Hybrid Nanomaterial Scaffolds for Specific Biomedical Applications
Authors: Gadre Mandar , Yang Jianing , Zenhausern Frederic 
Published: August 2010

AbstractHighly porous nanomaterials like aerogels, hybrid crosslinked aerogels (X-aerogels) and xerogels exhibit a broad range of tailorable properties such as the pore size, surface area, surface chemistry and mechanical strength. The versatile manufacturing route of sol-gel synthesis and various tunable properties makes aerogels and xerogels attractive candidates for biomedical applications including tissue engineering, sample collection applicators and engineered microenvironments for three-dimensional cell culture. The present study explores meso- and macroporous inorganic-organic hybrid aerogels prepared via sol-gel processing for two different applications, namely, as scaffolds for cell culture and as potential materials for sample collection applicators.
Magnetic properties characterization of functionalized iron oxide nanoparticles
Authors: Yuan Yuan , Borca-Tasciuc Diana-Andra 
Published: August 2010

AbstractThis paper uses complex magnetic susceptibility measurements to investigate the effects of different coatings on the susceptibility of iron oxide nanoparticles. The two coatings used in these measurements are aminosilane and carboxymethyl-dextran. Susceptibility measurements are carried out over a range of frequencies from 10 KHz to 1 MHz using a differential impedance method. The differential impedance measurement setup is validated by measuring the susceptibility of ferrofluids and comparing the results to values previously published in literature. The theoretical relaxation times based on Brownian and Neel mechanisms are used to predict the resonance frequency of imaginary part of complex susceptibility for iron oxide nanoparticles.
Adhesion Between Anti-EphA2 Antibody-Coated AFM Tips and Breast Cancer Cells
Authors: Paetzell Emily , Bogorad Andrew , Meng Juan , Soboyejo Winston oluwole 
Published: August 2010

AbstractThis paper presents the results of atomic force microscope (AFM) measurements of the adhesion force between MDA-MB-231 breast cancer cells and anti-EphA2 antibody-coated AFM tips. As a control, the adhesive interactions are measured between Hs578Bst normal breast cells and anti-EphA2 antibody-coated AFM tips. The measurements show conclusively that the adhesive forces to breast cancer cells are over five times greater than those to normal breast cells. The increase is attributed largely to the interactions between anti-EphA2 antibody and over-expressed EphA2 receptors that are revealed by the staining of receptor-ligand interactions. The implications of the results are discussed for the localized targeting and treatment of cancer with antibody-conjugated nanoparticles.
Role of Scaffold Architecture and Mechanical Properties of Electrospun Scaffolds in Cell Seeding
Authors: Wanasekara Nandula D. , Chen Ming , Chalivendra Vijaya B , Bhowmick Sankha 
Published: August 2010

AbstractSeeding a layer of cells at specific depths within scaffolds is an important optimization parameter for bi-layer skin models. The work presented investigated the effect of fiber diameter and its mechanical property on the depth of cell seeding for electro-spun fiber scaffold. Polycaprolactone (PCL) is used to generate scaffolds that are submicron (400nm) to micron (1100nm) using electro-spinning. 3T3 fibroblasts were seeded on the electro-spun fiber scaffold mat of 50-70 microns thickness in this study. In order to investigate the effect of fiber diameter on cell migration, first, the electrospun fiber scaffold was studied for variation of mechanical properties as a function of fiber diameters. Atomic force microscopy (AFM) was used to investigate the Young’s modulus (E) values as a function of fiber diameter. It was identified that as the fiber diameter increases, the Young’s modulus values decreases considerably from 1.1GPa to 200MPa. The variation in E is correlated with cell seeding depth as a function of vacuum pressure. A higher E value led to a lower depth of cell seeding (closer to the surface) indicating that nanofibrous scaffolds offer larger resistance to cell movement compared to microfibrous scaffolds.
Nanoclay-reinforced Polyacrylamide Composite: Synthesis, Structural and Mechanical Characterization
Authors: Sun Yong , Huang Zaiwang , Li Xiaodong 
Published: August 2010

AbstractA facile electrophoretic deposition method was successfully applied to achieve novel nanoclay-reinforced polyacrylamide nanocomposite thin films. A special curled architecture of the re-aggregated nanoclay-platelets was identified, providing a possible source for realizing the interlocking mechanism in the nanocomposites. The curled architecture could be the result from strain releasing when the thin films were peeled off from the substrates. Through micro-/nano-indentation and in situ observation of the deformation during tensile test with an atomic force microscope (AFM), the localized deformation mechanism of the synthesized materials was investigated in further details. The results implied that a localized crack diversion mechanism worked in the synthesized nanocomposite thin films, which resembled its nature counterpart-nacre. The deformation behavior and fracture mechanism were discussed with reference to lamellar structure, interfacial strength between the nanoclays and the polyacrylamide matrix, and nanoclay agglomeration.
Biomimetic Spinning of Recombinant Silk Proteins
Authors: Keerl David , Hardy John George , Scheibel Thomas 
Published: August 2010

AbstractIn the past, we have successfully designed and produced a variety of engineered spider silk-like proteins (eADF3 and eADF4) based upon the primary sequence of the natural dragline proteins ADF3 and ADF4 from the spider Araneus diadematus [1]. Genetically engineered spider silk proteins can be modified at the molecular level to optimize the biochemical and mechanical properties of the final product. Although engineered spider silk proteins can be processed into fibers using different spinning methods, our group is interested in the technical realization of a biomimetic approach.
Here, we present an overview over our biomimetic fiber production process.
Properties of Electrospinning Jets
Authors: Reneker Darrell H , Xin Yu , Lee Hyungjin , Lin Yinan , Liu Kaiyi , Zhong Zhenxin 
Published: August 2010

AbstractMeasurement of elongational stresses, stereographic images of jet paths, innovative collection of fluid jets, and utilization of elongational flow for assembly or disassembly of particulate structures, the electron microscopic views inside nanofibers, and the morphological and crystallographic changes that occur during heating of the metastable electrospun fibers illuminate the growing versatility of the electrospinning process.
Electrospun Polyacrylonitrile Nanocomposite Fibers Reinforced with Magnetic Nanoparticles
Authors: Zhang Di , Wei Suying , Guo Zhanhu 
Published: August 2010

AbstractThe manufacturing of magnetic PAN/Fe3O4 nanocomposite fibers is explored by an electrospinning process. The nanocomposite fibers were characterized by scanning electron microscopy (SEM). The magnetic properties of the nanoparticles in the polymer nanocomposite fibers are different from those of the dried as-received nanoparticles.
Functionalized Magnetic Nanoparticles for Selective Targeting of Cells
Authors: Tremel Wolfgang , Shukoor Mohammed Ibrahim , Natalio Filipe , Schladt Thomas , Barz Matthias , Tahir Muhammad Nawaz , Weber Stefan , Zentel Rudolf , Schreiber Laura Maria , Brieger Jürgen , Schröder Heinz Christoph , Müller Werner 
Published: August 2010

AbstractInitiation of pathways that lead to proliferation and chemoresistance by Toll-like receptors (TLRs) is an important factor in cancer progression. Here, we show the response of human cancer cells to TLR signaling inevitably linked to tumor biology. The approach is based on tailored multifunctional magnetic nanoparticles equipped with pathogen-derived ligands (CpG) functioning as TLR agonists (molecular component) to investigate the impact of transcription factor immune activation on human cancer cells. Magnetic nanoparticles (MnO and bifunctional Au-MnO) particles were covalently coated with a multifunctional polymer, displaying no cytotoxicity, to being able to enter cells while carrying foreign DNA (unmethylated CpG) to recognize intracellular TLR 9. Both, the particle and the nucleic acid are tagged with fluorescent markers for simultaneous visualization inside the cell. Apart from optical imaging, the magnetism of the particles also allows magnetic resonance imaging of organisms.
Protocrystalline Silicon for Micromorph Tandem Cells on Gen. 5 Size
Authors: van Elzakker Gijs , Sixtensson Daniel , Papathanasiou Niklas , Neubeck Klaus , Sillmann Roland 
Published: August 2010

AbstractInventux Technologies AG is a high volume producer of Micromorph (a-Si:H/μc-Si:H) tandem modules. The light-induced degradation of hydrogenated amorphous silicon (a-Si:H), called Staebler-Wronski effect (SWE), limits the stabilized efficiency of a-Si:H-based solar cells. Several laboratories have reported on the development of a-Si:H with increased resistance against light-soaking. This so-called ‘protocrystalline' silicon can be grown with plasma-enhanced chemical vapor deposition (PECVD) by diluting the silane source gas with hydrogen.The aim of the work presented in this paper was to scale-up the laboratory results on protocrystalline silicon to a size of 1.43 m2 (Gen. 5) using a process that is suitable for high volume production. We demonstrate that the strict boundary conditions regarding uniformity and growth rate, which are necessary for a production process, can be met. The reduced light-induced degradation of protocrystalline solar cells fabricated with the newly developed process is confirmed by a light-soaking experiment. As an outlook towards future work, we discuss issues related to the implementation of a protocrystalline top cell in the Micromorph tandem configuration. The challenge of choosing the right top-cell thickness is illustrated by experimental results on two tandem cells. The top cells of these tandems contain protocrystalline i-layers of different thicknesses.
High-efficiency Large-area Nanocrystalline Silicon Solar Cells Using MVHF Technology
Authors: Xu Xixiang , Su Tining , Ehlert Scott , Bobela David , Beglau Dave , Pietka Ginger , Li Yang , Zhang Jinyan , Yue Guozhen , Yan Baojie , DeMaggio Greg , Worrel Chris , Lord Ken , Banerjee Arindam , Yang Jeff , Guha Subhendu 
Published: August 2010

AbstractWe present the progress made in attaining high-efficiency large-area nc-Si:H based multi-junction solar cells using Modified Very High Frequency technology. We focused our effort on improving the spatial uniformity and homogeneity of nc-Si:H film growth and cell performance. We also conducted both indoor and outdoor light soaking studies and achieved 11.2% stabilized efficiency on large-area (≥400 cm2) encapsulated a-Si:H/nc-Si:H/nc-Si:H triple-junction cells.
Oxygenated Protocrystalline Silicon Thin Films for Wide Bandgap Solar Cells
Authors: Schropp Ruud E.I. , Schüttauf Jan Willem , van der Werf Karine 
Published: August 2010

AbstractProtocrystalline silicon, which is a material that has enhanced medium range order (MRO), can be prepared by using high hydrogen dilution in PECVD, or, alternatively, using high atomic H production from pure silane in HWCVD. We show that this material can accommodate percentage-level concentrations of oxygen without deleterious effects. The advantage of protocrystalline SiO:H for application in multijunction solar cells is not only that it has an increased band gap, providing a better match with the solar spectrum, but also that the solar cells incorporating this material have a reduced temperature coefficient. Further, protocrystalline materials have a reduced susceptibility to light-induced defect creation. We present the unique result in the PV field that these oxygenated protocrystalline silicon solar cells have an efficiency temperature coefficient (TCE) that is virtually zero (TCE is between -0.08%/°C and 0.0/°C). It is thus beneficial to make this cell the current limiting cell in multibandgap cells, which will lead to improved annual energy yield.
Plasmonic Light-trapping and Quantum Efficiency Measurements On Nanocrystalline Silicon Solar Cells and Silicon-On-Insulator Devices
Authors: Zhao Hui , Ozturk Birol , Schiff Eric A , Yan Baojie , Yang Jeff , Guha Subhendu 
Published: August 2010

AbstractQuantum efficiency measurements in (nc-Si:H) solar cells deposited onto textured substrates indicate that these cells are close to the “stochastic light-trapping limit“ proposed by Yablonovitch in the 1980s. An interesting alternative to texturing is “plasmonic“ light-trapping based on non-textured cells and using an overlayer of metallic nanoparticles to produce light-trapping. While this type of light-trapping has not yet been demonstrated for nc-Si:H solar cells, significant photocurrent enhancements have been reported on silicon-on-insulator devices with similar optical properties to nc-Si:H. Here we report our work on the measurerements of quantum efficiencies in nc-Si:H solar cells and normalized photoconductance spectra in SOI photdetectors with and without silver nanoparticle layers. As was done previously, the silver nanoparticles were created by thermal annealing of evaporated silver thin films. We observed enhancement in the normalized photoconductance spectra of SOI photodetectors at longer wavelengths with the silver nanoparticles. For nc-Si:H solar cells, we have not yet observed significant improvement of the quantum efficiency with the addition of annealed silver films.
High Quality, Low Bandgap a-Si Films and Devices Produced Using Chemical Annealing
Authors: Dalal Vikram , Shyam Ashutosh , Congreve Dan , Noack Max 
Published: August 2010

AbstractWe report on the growth and properties of novel amorphous Silicon (a-Si:H) p-i-n devices prepared using chemical annealing with argon gas. The i layer in the p-i-n devices was grown using a layer by layer approach, where the growth of a very thin a-Si:H layer (7-30 angstroms) grown using a silane:argon mixture was followed by chemical anneal by argon ions. Repeated cycling of such growth/anneal cycles was used to produce the desired total thickness of the i layer. The thickness of the a-Si layer, and duration of the anneal time, were varied systematically. Pressure and power of the plasma discharge were also systematically varied. It was found that a thin a-Si layer, <10 angstroms, and low pressures which led to relatively high ion flux on the surface, gave rise to a significantly smaller bandgap in the device, as indicated by a significant lateral shift in the quantum efficiency vs. photon energy curve to lower energies. The smallest Tauc gap observed was in the range of 1.62 eV. Corresponding to this smaller bandgap, the current in the solar cell increased, and the voltage decreased. The Urbach energies of the valence band tail were also measured in the device, using the quantum efficiency vs. energy curve, and found to be in the range of45 meV, indicating high quality devices. Too much ion bombardment led to an increase in Urbach energy, and an increase in defect density in the material. Raman spectra of the device i layer indicated an amorphous structure. When hydrogen was added to argon during the annealing cycle, some materials turned microcrystalline, as indicated by the Raman spectrum, and confirmed using x-ray diffraction.