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‣ Biomechanical effects of environmental and engineered particles on human airway smooth muscle cells

BERNTSEN, P.; PARK, C. Y.; ROTHEN-RUTISHAUSER, B.; TSUDA, A.; SAGER, T. M.; MOLINA, R. M.; DONAGHEY, T. C.; Alencar, Adriano Mesquita; KASAHARA, D. I.; ERICSSON, T.; MILLET, E. J.; SWENSON, J.; TSCHUMPERLIN, D. J.; BUTLER, J. P.; BRAIN, J. D.; FREDBERG, J
Fonte: ROYAL SOC Publicador: ROYAL SOC
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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The past decade has seen significant increases in combustion-generated ambient particles, which contain a nanosized fraction (less than 100 nm), and even greater increases have occurred in engineered nanoparticles (NPs) propelled by the booming nanotechnology industry. Although inhalation of these particulates has become a public health concern, human health effects and mechanisms of action for NPs are not well understood. Focusing on the human airway smooth muscle cell, here we show that the cellular mechanical function is altered by particulate exposure in a manner that is dependent upon particle material, size and dose. We used Alamar Blue assay to measure cell viability and optical magnetic twisting cytometry to measure cell stiffness and agonist-induced contractility. The eight particle species fell into four categories, based on their respective effect on cell viability and on mechanical function. Cell viability was impaired and cell contractility was decreased by (i) zinc oxide (40-100 nm and less than 44 mu m) and copper(II) oxide (less than 50 nm); cell contractility was decreased by (ii) fluorescent polystyrene spheres (40 nm), increased by (iii) welding fumes and unchanged by (iv) diesel exhaust particles, titanium dioxide (25 nm) and copper(II) oxide (less than 5 mu m)...

‣ Conformação mecânica: efeito da topografia na tansferência de material e no atrito.; Metal forming: the effect of topography on the metal transfer and friction.

Leite, Mario Vitor
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 30/06/2010 Português
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37.224336%
Com a evolução dos processos de fabricação, aumenta o emprego de topografias engenheiradas com o objetivo de aumentar o desempenho dessas superfícies sob vários aspectos. Apesar do bom desempenho comprovado em algumas aplicações, existem outras em que o desempenho é questionável, como, em condições não lubrificadas e com elevadas pressões de contato. Neste cenário de dúvidas sobre a utilização de superfícies engenheiradas, o presente trabalho objetiva contribuir com as discussões por meio de um estudo do efeito de topografias anisotrópicas na transferência de material e resistência ao movimento em condições de deslizamento a seco com deformação plástica micro e macroscópica. O método utilizado contempla ensaios tribológicos que consistem, basicamente, em deslizar um material sobre superfícies engenheiradas de outro material com maior dureza, em duas condições de deformação plástica: i/ localizada no pico das asperezas em contato (ensaio pino-sobre-disco) e ii/ volumétrica (ensaio de compressão do anel). Os resultados permitiram concluir que os mecanismos de desgaste podem ser reproduzidos nos dois ensaios. Com deformação plástica microscópica (pino-sobre-disco) constatou-se que: i/ os vales e cavidades da topografia atuam de forma a evitar o contato das partículas de desgaste com o corpo em deslizamento; e ii/ os maiores valores do coeficiente de atrito foram obtidos com a superfície com maior quantidade de cavidades...

‣ A estamparia têxtil contemporânea: produção, produtos e subjetividades; The contemporary textile printing: production, products and subjectivities.

Vieira, Liliana Bellio
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 24/06/2014 Português
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27.39544%
A contemporaneidade vem sendo marcada por mudanças em vários aspectos, em especial para o design. As últimas décadas inauguraram tecnologias digitais em que os recursos para captura, tratamento e reprodução de imagens alteram modos de desenvolvimento, produção e percepção estética. Este estudo refere-se ao design de superfície, especialidade do design, especificamente à estamparia têxtil digital. Tem como propósito investigar os recursos digitais voltados à estamparia têxtil como produtores de elementos visuais causadores de sentido e significado tendo em vista a relação: produção criativa, produto (aspectos subjetivos da estampa) e diferenciação. A pesquisa parte da abordagem qualitativa de caráter exploratório, por meio de referências bibliográficas, observação em estamparia digital selecionada na cidade de São Paulo e entrevistas a designers de superfície atuantes. Este estudo também propõe uma reflexão sobre alguns aspectos diferenciais e de subjetividade que as estampas permitem em produtos de moda em vestuário e decoração. Ao identificar e discutir possibilidades, potencialidades e limitações da estamparia digital nas áreas mencionadas, sugere-se contribuições para o design de superfície na criação de estamparia com fotografia a partir da demanda por diferenciação...

‣ Sol-Gel SiO2-CaO-P2O5 biofilm with surface engineered for medical application

Federman,Sonia Regina; Costa,Vilma Conceição; Vasconcelos,Daniela Cordeiro Leite; Vasconcelos,Wander Luiz
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2007 Português
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36.710962%
Sol-gel film in the SiO2-CaO-P2O5 system was prepared from TEOS, TEP, alcohol and hydrated calcium nitrate in an acidic medium. The coatings were deposited on stainless steel using the dip-coating technique. After deposition, the composite was submitted to heat treatment, at different temperatures and exposure times to investigate the influence of such parameters on the surface morphology of the composite. The coated surfaces were characterized by AFM, SEM and FTIR. The present study showed that the formation of different textures (an important parameter in implant fixation) could be controlled by temperature and time of heat treatment.

‣ Pancreatic Islets Engineered with SA-FasL Protein Establish Robust Localized Tolerance by Inducing T Regulatory Cells in Mice

Yolcu, Esma S; Zhao, Hong; Bandura-Morgan, Laura; Lacelle, Chantale; Woodward, Kyle B; Askenasy, Nadir; Shirwan, Haval
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
27.4065%
Allogeneic islet transplantation is an important therapeutic approach for the treatment of T1D. Clinical application of this approach, however, is severely curtailed by allograft rejection primarily initiated by pathogenic T effector cells regardless of chronic use of immunosuppression. Given the role of Fas-mediated signaling in regulating T effector cell responses, we tested if pancreatic islets can be engineered ex vivo to display on their surface an apoptotic form of FasL protein chimeric with streptavidin (SA-FasL), and whether such engineered islets induce tolerance in allogeneic hosts. Islets were modified with biotin following efficient engineering with SA-FasL protein that persisted on the surface of islets for over a week in vitro. SA-FasL-engineered islet grafts established euglycemia in chemically diabetic syngeneic mice indefinitely, demonstrating functionality and lack of acute toxicity. Most importantly, the transplantation of SA-FasL-engineered BALB/c islet grafts in conjunction with a short course of rapamycin treatment resulted in robust localized tolerance in 100% C57BL/6 recipients. Tolerance was initiated and maintained by CD4+CD25+FoxP3+ T regulatory (Treg) cells as their depletion early during tolerance induction or late after established tolerance resulted in prompt graft rejection. Furthermore...

‣ Improving the Magnetic Resonance Imaging Contrast and Detection Methods with Engineered Magnetic Nanoparticles

Huang, Jing; Zhong, Xiaodong; Wang, Liya; Yang, Lily; Mao, Hui
Fonte: Ivyspring International Publisher Publicador: Ivyspring International Publisher
Tipo: Artigo de Revista Científica
Publicado em 10/01/2012 Português
Relevância na Pesquisa
27.459631%
Engineering and functionalizing magnetic nanoparticles have been an area of the extensive research and development in the biomedical and nanomedicine fields. Because their biocompatibility and toxicity are well investigated and better understood, magnetic nanoparticles, especially iron oxide nanoparticles, are better suited materials as contrast agents for magnetic resonance imaging (MRI) and for image-directed delivery of therapeutics. Given tunable magnetic properties and various surface chemistries from the coating materials, most applications of engineered magnetic nanoparticles take advantages of their superb MRI contrast enhancing capability as well as surface functionalities. It has been found that MRI contrast enhancement by magnetic nanoparticles is highly dependent on the composition, size and surface properties as well as the degree of aggregation of the nanoparticles. Therefore, understanding the relationships between these intrinsic parameters and the relaxivities that contribute to MRI contrast can lead to establishing essential guidance that may direct the design of engineered magnetic nanoparticles for theranostics applications. On the other hand, new contrast mechanism and imaging strategy can be developed based on the novel properties of engineered magnetic nanoparticles. This review will focus on discussing the recent findings on some chemical and physical properties of engineered magnetic nanoparticles affecting the relaxivities as well as the impact on MRI contrast. Furthermore...

‣ Early Fixation of Cobalt-Chromium Based Alloy Surgical Implants to Bone Using a Tissue-engineering Approach

Ogawa, Munehiro; Tohma, Yasuaki; Ohgushi, Hajime; Takakura, Yoshinori; Tanaka, Yasuhito
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 09/05/2012 Português
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27.39544%
To establish the methods of demonstrating early fixation of metal implants to bone, one side of a Cobalt-Chromium (CoCr) based alloy implant surface was seeded with rabbit marrow mesenchymal cells and the other side was left unseeded. The mesenchymal cells were further cultured in the presence of ascorbic acid, β-glycerophosphate and dexamethasone, resulting in the appearance of osteoblasts and bone matrix on the implant surface. Thus, we succeeded in generating tissue-engineered bone on one side of the CoCr implant. The CoCr implants were then implanted in rabbit bone defects. Three weeks after the implantation, evaluations of mechanical test, undecalcified histological section and electron microscope analysis were performed. Histological and electron microscope images of the tissue engineered surface exhibited abundant new bone formation. However, newly formed bone tissue was difficult to detect on the side without cell seeding. In the mechanical test, the mean values of pull-out forces were 77.15 N and 44.94 N for the tissue-engineered and non-cell-seeded surfaces, respectively. These findings indicate early bone fixation of the tissue-engineered CoCr surface just three weeks after implantation.

‣ A Synthetic, Xeno-Free Peptide Surface for Expansion and Directed Differentiation of Human Induced Pluripotent Stem Cells

Jin, Sha; Yao, Huantong; Weber, Jennifer L.; Melkoumian, Zara K.; Ye, Kaiming
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 30/11/2012 Português
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Human induced pluripotent stem cells have the potential to become an unlimited cell source for cell replacement therapy. The realization of this potential, however, depends on the availability of culture methods that are robust, scalable, and use chemically defined materials. Despite significant advances in hiPSC technologies, the expansion of hiPSCs relies upon the use of animal-derived extracellular matrix extracts, such as Matrigel, which raises safety concerns over the use of these products. In this work, we investigated the feasibility of expanding and differentiating hiPSCs on a chemically defined, xeno-free synthetic peptide substrate, i.e. Corning Synthemax® Surface. We demonstrated that the Synthemax Surface supports the attachment, spreading, and proliferation of hiPSCs, as well as hiPSCs’ lineage-specific differentiation. hiPSCs colonies grown on Synthemax Surfaces exhibit less spread and more compact morphology compared to cells grown on Matrigel™. The cytoskeleton characterization of hiPSCs grown on the Synthemax Surface revealed formation of denser actin filaments in the cell-cell interface. The down-regulation of vinculin and up-regulation of zyxin expression were also observed in hiPSCs grown on the Synthemax Surface. Further examination of cell-ECM interaction revealed that hiPSCs grown on the Synthemax Surface primarily utilize αvβ5 integrins to mediate attachment to the substrate...

‣ Microtopography of the eye surface of the crab Carcinus maenas: an atomic force microscope study suggesting a possible antifouling potential

Greco, G.; Lanero, T. Svaldo; Torrassa, S.; Young, R.; Vassalli, M.; Cavaliere, A.; Rolandi, R.; Pelucchi, E.; Faimali, M.; Davenport, J.
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Publicado em 06/07/2013 Português
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Marine biofouling causes problems for technologies based on the sea, including ships, power plants and marine sensors. Several antifouling techniques have been applied to marine sensors, but most of these methodologies are environmentally unfriendly or ineffective. Bioinspiration, seeking guidance from natural solutions, is a promising approach to antifouling. Here, the eye of the green crab Carcinus maenas was regarded as a marine sensor model and its surface characterized by means of atomic force microscopy. Engineered surface micro- and nanotopography is a new mechanism found to limit biofouling, promising an effective solution with much reduced environmental impact. Besides giving a new insight into the morphology of C. maenas eye and its characterization, our study indicates that the eye surface probably has antifouling/fouling-release potential. Furthermore, the topographical features of the surface may influence the wettability properties of the structure and its interaction with organic molecules. Results indicate that the eye surface micro- and nanotopography may lead to bioinspired solutions to antifouling protection.

‣ Nanoporous Anodic Alumina Platforms: Engineered Surface Chemistry and Structure for Optical Sensing Applications

Kumeria, Tushar; Santos, Abel; Losic, Dusan
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 07/07/2014 Português
Relevância na Pesquisa
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Electrochemical anodization of pure aluminum enables the growth of highly ordered nanoporous anodic alumina (NAA) structures. This has made NAA one of the most popular nanomaterials with applications including molecular separation, catalysis, photonics, optoelectronics, sensing, drug delivery, and template synthesis. Over the past decades, the ability to engineer the structure and surface chemistry of NAA and its optical properties has led to the establishment of distinctive photonic structures that can be explored for developing low-cost, portable, rapid-response and highly sensitive sensing devices in combination with surface plasmon resonance (SPR) and reflective interference spectroscopy (RIfS) techniques. This review article highlights the recent advances on fabrication, surface modification and structural engineering of NAA and its application and performance as a platform for SPR- and RIfS-based sensing and biosensing devices.

‣ Penetration of engineered antibody fragments into the eye

Thiel, M.; Coster, D.; Standfield, S.; Brereton, H.; Mavrangelos, C.; Zola, H.; Taylor, S.; Yusim, A.; Williams, K.
Fonte: Blackwell Science Ltd Publicador: Blackwell Science Ltd
Tipo: Artigo de Revista Científica
Publicado em //2002 Português
Relevância na Pesquisa
37.037458%
Antibodies are powerful immunotherapeutic agents but their use for treating ocular disorders is limited by their poor penetration into the eye. We hypothesized that antibody fragments of relatively small size might penetrate the cornea more readily. Monovalent single chain variable region (scFv) antibody fragments and divalent miniantibodies were engineered from existing monoclonal antibodies, expressed in a bacterial expression system, and purified by metal ion affinity chromatography. Corneoscleral preparations from normal pig and cat eyes were mounted in a corneal perfusion chamber. Intact antibodies and antibody fragments were applied topically to the anterior corneal surface over 12-h periods, and samples were collected from the artificial anterior chamber. Similar experiments were performed with whole enucleated pig and human eyes. Penetration of antibodies and fragments was quantified by highsensitivity flow cytometry on appropriate target cells. Both monovalent scFv and divalent miniantibody fragments (but not whole immunoglobulin molecules) passed through de-epithelialized and intact corneas after topical administration, and could be detected by antigen binding. Addition of 0•5% sodium caprate facilitated penetration through intact corneas. Topically-applied scFv was found to penetrate into the anterior chamber fluid of rabbit eyes in vivo. The engineered fragments were stable and resistant to ocular proteases. Monovalent and divalent antibody constructs of molecular weight 28kD and 67kD...

‣ Enzyme detection by surface plasmon resonance using specially engineered spacers and plasmonic labelling

François, A.; Heng, S.; Monro, T.; Kostecki, R.
Fonte: SPIE; United States Publicador: SPIE; United States
Tipo: Conference paper
Publicado em //2011 Português
Relevância na Pesquisa
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Surface Plasmon Resonance (SPR) is a powerful label free optical biosensing technology that relies on the measurement of the refractive index or change of mass in close vicinity of the sensor surface. Therefore, there is an experimental limitation in the molecular weight of the molecule that can be detected and consequently small molecules are intrinsically more difficult to detect using SPR. One approach to overcoming this limitation is to first adsorb smaller molecules onto the sensor surface, and to follow this by using their higher molecular weight antibodies counterparts which ensure the specificity (and are easier to detect via SPR due to their higher weight). Although this has been demonstrated with some success, it is not applicable in every case and some biomolecules such as enzyme are still difficult to detect due to their specific reactivity (enzymatic reaction). In this paper, we present a powerful new method that utilises specifically engineered spacers attached on one end to the sensor surface and on the other end to a nanoparticle that behaves as a plasmonic label. These spacers are design to specifically react with the biomolecule to be detected and release the (relatively large) plasmonic label, which in turn results in a measurable SPR shift (which is much larger than the shift that would have been associated with the binding of the relatively small biomolecule). As a proof of concept...

‣ Tuning drug loading and release properties of diatom silica microparticles by surface modifications

Bariana, M.; Aw, M.; Kurkuri, M.; Losic, D.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
Relevância na Pesquisa
46.869507%
Diatomaceous earth (DE), or diatomite silica microparticles originated from fossilized diatoms are a potential substitute for its silica-based synthetic counterparts to address limitations in conventional drug delivery. This study presents the impact of engineered surface chemistry of DE microparticles on their drug loading and release properties. Surface modifications with four silanes, including 3-aminopropyltriethoxy silane (APTES), methoxy-poly-(ethylene-glycol)-silane (mPEG-silane), 7-octadecyltrichlorosilane (OTS), 3-(glycidyloxypropyl)trimethoxysilane (GPTMS) and two phosphonic acids, namely 2-carboxyethyl-phosphonic acid (2 CEPA) and 16-phosphono-hexadecanoic acid (16 PHA) were explored in order to tune drug loading and release characteristics of water insoluble (indomethacin) and water soluble drugs (gentamicin). Successful grafting of these functional groups with different interfacial properties was confirmed using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Thermogravimetric analysis (TGA) was applied to determine the amount of loaded drugs and UV-spectrophotometry to analyse in vitro drug release from modified DE microparticles. Differences in drug release time (13–26 days) and loading capacity (14–24%) were observed depending on functional groups on the surface of DE microparticles. It was found that hydrophilic surfaces...

‣ Nanoporous anodic alumina platforms: engineered surface chemistry and structure for optical sensing applications

Kumeria, T.; Santos, A.; Losic, D.
Fonte: MDPI AG Publicador: MDPI AG
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Relevância na Pesquisa
46.815806%
Electrochemical anodization of pure aluminum enables the growth of highly ordered nanoporous anodic alumina (NAA) structures. This has made NAA one of the most popular nanomaterials with applications including molecular separation, catalysis, photonics, optoelectronics, sensing, drug delivery, and template synthesis. Over the past decades, the ability to engineer the structure and surface chemistry of NAA and its optical properties has led to the establishment of distinctive photonic structures that can be explored for developing low-cost, portable, rapid-response and highly sensitive sensing devices in combination with surface plasmon resonance (SPR) and reflective interference spectroscopy (RIfS) techniques. This review article highlights the recent advances on fabrication, surface modification and structural engineering of NAA and its application and performance as a platform for SPR- and RIfS-based sensing and biosensing devices.; Tushar Kumeria, Abel Santos and Dusan Losic

‣ Modeling flow and sediment transport dynamics in the lowermost Mississippi River, Louisiana, USA, with an upstream alluvial-bedrock transition and a downstream bedrock-alluvial transition: Implications for land building using engineered diversions

Viparelli, Enrica; Nittrouer, Jeffrey A.; Parker, Gary
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.110366%
The lowermost Mississippi River, defined herein as the river segment downstream of the Old River Control Structure and hydrodynamically influenced by the Gulf of Mexico, extends for approximately 500?km. This segment includes a bedrock (or more precisely, mixed bedrock-alluvial) reach that is bounded by an upstream alluvial-bedrock transition and a downstream bedrock-alluvial transition. Here we present a one-dimensional mathematical formulation for the long-term evolution of lowland rivers that is able to reproduce the morphodynamics of both the alluvial-bedrock and the bedrock-alluvial transitions. Model results show that the magnitude of the alluvial equilibrium bed slope relative to the bedrock surface slope and the depth of bedrock surface relative to the water surface base level strongly influence the mobile bed equilibrium of low-sloping river channels. Using data from the lowermost Mississippi River, the model is zeroed and validated at field scale by comparing the numerical results with field measurements. The model is then applied to predict the influence on the stability of channel bed elevation in response to delta restoration projects. In particular, the response of the river bed to the implementation of two examples of land-building diversions to extract water and sediment from the main channel is studied. In this regard...

‣ Simulation of Engineered Nanostructured Thin Films

Cheung, JASON
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 7599462 bytes; application/pdf
Português
Relevância na Pesquisa
36.710962%
The invention of the Glancing Angle Deposition (GLAD) technique a decade ago enabled the fabrication of nanostructured thin films with highly tailorable structural, electrical, optical, and magnetic properties. Here a three-dimensional atomic-scale growth simulator has been developed to model the growth of thin film materials fabricated with the GLAD technique, utilizing the Monte Carlo (MC) and Kinetic Monte Carlo (KMC) methods; the simulator is capable of predicting film structure under a wide range of deposition conditions with a high degree of accuracy as compared to experiment. The stochastic evaporation and transport of atoms from the vapor source to the substrate is modeled as random ballistic deposition, incorporating the dynamic variation in substrate orientation that is central to the GLAD technique, and surface adatom diffusion is modeled as either an activated random walk (MC), or as energy dependent complete system transitions with rates calculated based on site-specific bond counting (KMC). The Sculptured Nanostructured Film Simulator (SNS) provides a three-dimensional physical prediction of film structure given a set of deposition conditions, enabling the calculation of film properties including porosity, roughness, and fractal dimension. Simulations were performed under various growth conditions in order to gain an understanding of the effects of incident angle...

‣ First-principles Calculations of Engineered Surface Spin Structures

Lin, Chiung-Yuan; Jones, B. A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/03/2010 Português
Relevância na Pesquisa
37.110366%
The engineered spin structures recently built and measured in scanning tunneling microscope experiments are calculated using density functional theory. By determining the precise local structure around the surface impurities, we find the Mn atoms can form molecular structures with the binding surface, behaving like surface molecular magnets. The spin structures are confirmed to be antiferromagnetic, and the exchange couplings are calculated within 8% of the experimental values simply by collinear-spin GGA+U calculations. We can also explain why the exchange couplings significantly change with different impurity binding sites from the determined local structure. The bond polarity is studied by calculating the atomic charges with and without the Mn adatoms.

‣ Effect of processing methods on the mechanical properties of engineered bamboo

Sharma, Bhavna; Gat?o, Ana; Ramage, Michael H.
Fonte: Elsevier Publicador: Elsevier
Tipo: Article; published version
Português
Relevância na Pesquisa
37.111025%
This is the final published version. It first appeared at http://www.sciencedirect.com/science/article/pii/S0950061815001956.; Engineered bamboo is increasingly explored as a material with significant potential for structural applications. The material is comprised of raw bamboo processed into a laminated composite. Commercial methods vary due to the current primary use as an architectural surface material, with processing used to achieve different colours in the material. The present work investigates the effect of two types of processing methods, bleaching and caramelisation, to determine the effect on the mechanical properties. A comparison to other engineered bamboo and timber products is also presented. The results of the study indicate that processing does affect the mechanical properties of engineered bamboo products. Areas in need of further research are also identified for thermally treated bamboo to be used in structural applications.; The presented work is supported by EPRSC Grant EP/K023403/1, and forms part of a collaboration between the University of Cambridge, Massachusetts Institute of Technology (MIT) and University of British Columbia (UBC).

‣ Geometric Modeling of Engineered Abrasive Processes*

Carrano, Andres
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.491482%
One of the common issues that arises in abrasive machining is the inconsistency of the surface roughness within the same batch and under identical machining conditions. Recent advances in engineered abrasives have allowed replacement of the random arrangement of minerals on conventional belts with precisely shaped structures uniformly cast directly onto a backing material. This allows for abrasive belts that are more deterministic in shape, size, distribution, orientation, and composition. A computer model based on known tooling geometry was developed to approximate the asymptotic surface profile that was achievable under specific loading conditions. Outputs included the theoretical surface parameters, R^sub q^, R^sub a^, R^sub v^, R^sub p^, R^sub t^, and R^sub sk^. Experimental validation was performed with a custom-made abrader apparatus and using engineered abrasives on highly polished aluminum samples. Interferometric microscopy was used in assessing the surface roughness. Results include the individual effects of pyramid base width, pyramid height, attack angle, and indentation depth on the surface descriptors.

‣ Parametric modeling of tooling: Workpiece interaction with engineered abrasives

Kataria, Hitesh
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
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Abrasive processes are some of the most important operations employed in manufacturing to remove unwanted material and introduce desired geometry and surface finish. However, some of the difficulties encountered when trying to model abrasive process are related to a multi-point of contact tooling composed of extremely hard and brittle particles which geometry, shape and distribution are unknown. With the introduction of engineered abrasives to the market over the past few years, the opportunity to drastically improve the quality and consistency of abrasive machining now exists. One of the main benefits of engineered abrasives is the ability to control the abrasive grit properties i.e. size, shape, distribution and composition. The objective of this study was to develop a parametric model of the engineered abrasives that allows for studying the interaction of this particular tooling with various surfaces. This would also allow for prediction of surface roughness from a given tool-workpiece pair. The development of this model, the analysis of the tool-workpiece interaction, and the algorithms for surface generation are carried out using a computer model developed for each specific purpose. Additionally, experimental validation of this model is presented. It was found that the machined surface improves as the depth of indentation increases...