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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
191

Crystalline frameworks self-assembled from amphiphilic DNA nanostructures

Brady, Ryan January 2019 (has links)
Many emerging technologies would greatly benefit from reliable methods for the production of functional materials with well-defined 3D nanoscale structure. Conceptually, approaches to produce such architectures are divided into two broad classes; top down and bottom up manufacture. In the top down approach, nanoscale structure is created through the controlled removal of material from a bulk starting object. Top down methods have a proven record of reliability in the fabrication of extended two dimensional arrays with fine control over nanoscale features. However, such approaches become increasingly cumbersome when attempting to define structure in three dimensions rather than two. Bottom up methods promise a more reliable route to the formation of such materials. Here, molecular scale building units self-assemble to form a desired structure, driven by pre-defined interactions between individual motifs. Due to the highly specific molecular recognition properties of nucleic acids, along with their relatively simple synthesis and wide range of potential chemical modifications, DNA nanotechnology is now regarded as a prime route for the bottom up fabrication of nanostructured materials. However, current approaches to the formation of designed 3D DNA crystals are complicated by the difficulties in designing sub-units able to assemble in a predictable fashion over length-scales orders of magnitude larger than themselves. Amphiphiles are able to self-assemble into a variety of 3D crystalline phases driven by the frustrated micro-phase separation of hydrophobic and hydrophilic domains, with the structural properties reliant primarily on overall topology of the molecules rather than their exact chemical and geometrical features. Although the mechanism underlying amphiphile self-assembly is robust, it inherently limits control over the fine-scale structural details. This thesis reports on a new class of self-assembling DNA motifs; amphiphilic cholesterol-functionalised DNA nanostars, \emph {C-stars}. C-stars combine key advantages of all-DNA motifs and conventional amphiphilic molecules -- allowing for the preparation of expanded crystalline frameworks with tunable properties and embedded functionality.
192

Hierarchical Modeling and Design of Corona Driven DNA-Mediated Self-Assembly

Vo, Thi D. January 2017 (has links)
Nanoscale colloids and nanoparticles (NPs), have recently emerged as a new class of materials that possess photonic, plasmonic, and/or catalytic emergent properties. However, methods for their rational fabrication into materials with designed structural organization remain to be established. Self-assembly -- the idea that NPs can find each other and spontaneously form a targeted macroscale structure with prescribed microscale organization -- is attractive in this context, particularly because it potentially lends itself to facile, large-scale manufacturing. Such a process, however, relies on a combination of interactions and shape effects for the formation of ordered long-range morphologies and a detailed molecular understanding of the governing physics for these systems remains an open question. In an attempt to reduce the complexity of such systems, a major thrust has been to use two NP sub-populations grafted with complementary single stranded DNA (DNA-NPs). The base pairing of these strands drives their spontaneous organization into crystalline arrays. DNA-mediated self-assembly provides a powerful tool to experimentally realize three dimensional crystalline ordering of NP networks; however, the majority of works within this field have focused on an isotropic, purely attractive interaction motif. While successful in controlling NP ordering, the usage of such symmetric designs severely restricts the range of accessible morphologies. This thesis systematically addresses the various limitations imposed by such a design strategy through both theoretical modeling of DNA-NPs interactions and inverse design of optimized self-assembly building blocks. We first relax the assumption that enthalpy completely dominates self-assembly by directly accounting for the effects of chain-chain repulsion as well as entropic frustrations that results from varying the mixing stoichiometry. We then build in the effect of utilizing anisotropy as a structural motif through the development of a scaling theory that captures the interplay between the chain dynamics and local curvature that results in the formation of non-trivial anisotropic coronas. The effects of anisotropy on both the local morphology and long-range crystalline ordering can then be model through the usage of mean-field and perturbation theories. The resulting composite model enables us to directly study how nano-scale phenomena drive micron-scale self-assembly. Lastly, theoretical developments are combined with a genetic algorithm optimization process into an inverse design framework that allows for an a priori design of molecular building blocks such that they spontaneously pack into any desired lattice morphologies. This strategy serves to address the long-standing challenge of nanomaterials design where one can take arbitrary nano-scale objects and arrange them into desired three-dimensional lattices that posses interesting, emergent properties.
193

Investigating how the Spindle Assembly Checkpoint inhibits the onset of anaphase

Lara González, Pablo January 2013 (has links)
The Spindle Assembly Checkpoint (SAC) delays the onset of anaphase in response to unattached kinetochores. The mechanism by which the SAC works is by inhibiting the activity of the Anaphase-promoting complex/cyclosome (APC/C), a large E3 ubiquitin ligase that targets several anaphase inhibitors for proteasome-mediated degradation, including securin and cyclin B. When the SAC is satisfied, the APC/C becomes active and this allows progression through the cell cycle. Work from the last decade identified the mitotic checkpoint complex (MCC) as the main transducer of the SAC. The MCC is composed of BubR1, Bub3, Mad2 and Cdc20 and it is a very potent inhibitor of the APC/C. When the SAC is active, the MCC binds the APC/C and it inhibits its activity. Once the SAC is satisfied, the MCC becomes disassembled, which allows APC/C activation and mitotic progression. However, the mechanisms that dictate MCC assembly and how it inhibits the APC/C remain to be understood. Here, I used a combination of cell biology and in vitro biochemistry to investigate the mechanism by which the MCC component BubR1 participates in the SAC. My data shows that through its interaction with Bub3, BubR1 localises to kinetochores and this event greatly facilitates its assembly onto the MCC and its SAC function. On the other hand, MCC formation and APC/C binding were only dependent on BubR1's N-terminus, therefore questioning the existence of a second Cdc20 binding site. Within this region, TPR domains and an N-terminal motif known as the KEN box (KEN1) mediates these interactions. By contrast, BubR1's second KEN box (KEN2) does not participate in MCC assembly or APC/C binding. However, both in cells and in vitro, the KEN2 box is required for APC/C inhibition. Indeed, I show that this second KEN box promotes SAC function by blocking the interaction of the APC/C with its substrates. Thus, both KEN boxes in BubR1 participate differentially in the SAC, the first to promote MCC assembly and the second one to block substrate recruitment to the APC/C.In addition, I investigated the mechanisms that mediate MCC inactivation, following SAC silencing. I observed that p31comet and APC/C activity cooperate to promote MCC turnover. The implication of these observations in our understanding of the SAC is discussed.
194

Self-assembly assisted polypolymerization (SAAP): a novel approach for the preparation of multiblock copolymers. / CUHK electronic theses & dissertations collection

January 2007 (has links)
In Chapter 1-3, properties and applications of block copolymers, synthetic methods especially living anionic polymerization as well as the development of the SAAP concept with some of previous successful examples are reviewed. Experimental methods, including the design and establishment of a special high-vacuum system, size exclusion chromatography and laser light scattering, are explained. / In Chapter 4, living anionic polymerization of alpha,o-di bromobutyl end-capped PI-b-PS-b-PI triblock copolymers and the end-capping reaction with 1,4-dibromobutane at the end of polymerization are described, including a in-depth analysis of the reaction mechanism that involves the dimerization of two living oligomer chain during the reaction of living polymeric anions with haloalkanes, i.e., the Wurtz-type coupling reaction. The self assembly and coupling reaction of 1,4-dilithio-1,1,4,4-tetraphenylbutane (DD2-) in n-hexane to form long (PI- b-PS-b-PI)10 multiblock chains are discussed. The coupling efficiencies with and without the self assembly are compared to demonstrate the principle of SAAP. However, the coupling reaction with dianion linker is troublesome because a trace amount of impurities in the solvent can remove its activity. / In Chapter 5, a method of improving the coupling efficiency is described. In this method, PI-b-PS-b-PI triblock copolymers is end-capped with avo-dicarboxylic acid groups via a reaction between living anions and carbon dioxide. Such prepared HOOC-ISI-COOH chains can be coupled with 1,6-hexamethylenediamine (HDA) in the presence of 1,3-dicyclohexylcarbodiimide (DCC) after the self assembly. The size exclusion chromatography (SEC) analysis shows that the SAAP method mainly leads to the formation of triblock copolymer chain dimers and the coupling efficiency is close to 50%. There is no coupling in THF without the self assembly. Further, a much better method of using alpha,o-diacyl chloride end-capped PI-b-PS-b-PI triblock copolymer chains in SAAP to prepare long multiblock copolymer chains is described. Using this recently developed method, we are able to prepared long ∼90-block copolymer chains (PI-b-PS-b-PI)30 which clearly shows the advantage of using SAAP to prepare long multiblock copolymers with a controllable sequence and different block lengths. / In this thesis, we have proposed and developed a novel method: The Self-Assembly Assisted Polypolymerization (SAAP). Namely, using the self-assembly of A-B-A triblock copolymers with two active end groups in a selective solvent for the A-block to concentrate and expose the active end groups on the periphery of the resultant core-shell polymeric micelles, we can effectively couple each two active ends on different chains together to form a long multiblock copolymer chain with its sequence and block length well controlled by the initial triblock copolymer. To accomplish this project, we first built a high-vacuum system for living anionic polymerization and then synthesized and characterized narrowly distributed polyisoprene-b-polystyrene- b-polyisoprene (PI-b-PS-b-PI) triblock copolymer chains with their both ends capped respectively with bromobutyl and carboxylic acid active groups. The self assembly of such prepared triblock copolymers in n-hexane, a selective solvent for PI, was studied by a combination of static and dynamic laser light scattering (LLS). Finally, the self-assembled end-functionalized PI-b-PS-b-PI chains were coupled together by difunctional small molecules (linkers) to form long multiblock copolymers with a controlled structure. / Hong, Liangzhi. / "Aug 2007." / Adviser: Chi Wu. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1036. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.
195

Regulatory mechanisms and biological implications of protein complex assembly

Wells, Jonathan Nicholas January 2018 (has links)
Every living organism possesses a genome that contains within it a unique set of genes, a substantial number of which encode proteins. Over the last 20 years, it has become apparent that organismal complexity arises not from the specific complement of genes per se, but rather from interactions between the gene products - in particular, interactions between proteins. As an inevitable consequence of the crowded cellular interior, most protein-protein interactions are fleeting. However, many are significantly more long-lived and result in stable protein complexes, in which the constituent subunits are obligately dependent on their binding partners. Despite the abundance of protein complexes and their critical importance to the cell, we currently have an incomplete understanding of the mechanisms by which the cell ensures their correct assembly. In the chapters that follow, I have attempted to improve our understanding of the regulatory systems underlying assembly of protein complexes, and the way in which assembly as a whole affects the behaviour of the cell. The thesis opens with an extended literature review covering the currently available methods for characterising protein complexes. After this introduction, chapters 2-4 are concerned with regulatory mechanisms and biological implications common to the assembly of all protein complexes. Chapter 5 diverges from this work, and describes a family of evolutionarily related proteins that regulate the behaviour of condensins and cohesins. Bacterial and archaeal genomes contain far less non-coding DNA than eukaryotes, and coding genes are often packaged into discrete units known as operons. The proteins encoded within operons are usually functionally related, either through participation in metabolic pathways or as subunits of heteromeric protein complexes. Since protein complexes assemble via ordered pathways, we reasoned that there might be a signature of assembly order present in operons, the genes of which are translated in sequential order. By comparing computationally predicted assembly pathways with gene order in operons, we demonstrated this to be the case for the large majority of operon-encoded complexes. Within operons, gene order follows assembly order, and adjacent genes are substantially more likely to share a physical interface than those further apart. This work demonstrates that efficient assembly of complexes is of sufficient importance as to have placed major constraints on the evolution of operon gene order. Following this study of bacterial operons, I present results from research investigating how patterns of protein degradation in eukaryotes are influenced by the formation of protein complexes. This showed that, whilst most proteins display exponential degradation kinetics, a sizeable minority deviate considerably from this pattern, instead being more consistent with a two-step degradation process. These proteins are predominantly members of heteromeric complexes, and their two-step decay profiles can be explained using a model under which bound and unbound subunits are degraded at different rates. Within individual complexes, we find that non-exponentially decaying proteins tend to form larger interfaces, assemble earlier, and show a higher degree of coexpression, consistent with the idea that bound subunits are degraded at a slower rate than unbound or peripheral subunits. This model also explains the behaviour of proteins in aneuploid cells where one or more chromosomes have been duplicated. In general, protein abundance scales with gene copy number, so that the immediate effect of duplicating a chromosome is to double the abundance of the proteins encoded on it. However, previous analyses of mass spectrometry data, as well as my own, have shown that the abundance of many proteins on duplicated chromosomes is significantly attenuated compared to what one would expect. These proteins, like those with non-exponential degradation patterns, are very often members of larger complexes. Since the overall concentration of a protein complex is constrained by that of its least abundant members, duplicating a single subunit will predominantly increase the unbound, unstable fraction of that subunit. The results from this work strongly suggest that the apparent attenuation of many proteins observed in aneuploid cells is indeed a consequence of the failure of these proteins to assemble into complexes. Finally, I present a study concerning an important, universally conserved family of protein complexes, namely the SMC-kleisins. Two members of this family, condensin and cohesin, are responsible for two hallmarks of eukaryotic chromatin organisation: the formation of condensed, linear chromosomes, and sister chromatid cohesion during cell division. Unlike other SMC-kleisins, condensin and cohesin possess a number of regulators containing HEAT repeats. By developing a computational pipeline for searching and clustering paralogous repeat proteins, I was able to demonstrate that these regulators form a distinct sub-family within the larger class of HEAT repeat proteins. Furthermore, these regulators arose very early in eukaryotic history, hinting at a possible role in the origin of modern condensins and cohesins.
196

Multisystem functional characterisation of motile ciliopathy genes HEATR2 and ZMYND10

Mali, Girish Ram January 2015 (has links)
Cilia are polarized extensions of the cells microtubule-based cytoskeleton dedicated to sensory, signaling and motility-related functions. In mammals, there are two main types of cilia, immotile and motile, where motile cilia generate/modulate fluid flow at the embryonic node, in respiratory airways, cerebral ventricles and the oviduct in addition to sperm propulsion via the flagellum. Defects in cilia motility cause a rare genetic disorder called Primary Ciliary Dyskinesia (PCD). In this thesis, I present functional and molecular characterisation of two PCD causing genes HEATR2 and ZMYND10. Core cilia genes are transcriptionally activated by members of the winged-helix transcription factors of the RFX family. The forkhead transcription factor FOXJ1, additionally activates motility genes such as the ones encoding components of axonemal dynein motors which transfer the chemical energy released from ATP hydrolysis to kinetic motion necessary for ciliary motility. I present data in this thesis which show that Heatr2 and Zmynd10 are both targets of the RFX3-FOXJ1 transcriptional module which co-operatively switches on genes required to make motile cilia Mutations in both HEATR2 and ZMYND10 cause the same subtype of PCD (loss of inner and outer arm dyneins in cilia). I characterise a human PCD causing mutation in HEATR2 in this thesis. Additionally, using genetic null mouse models generated using the CRISPR technology, I describe the phenotypic effects of complete loss of Zmynd10 in mice. Zmynd10 mutant mice display characteristic PCD-like features. Adding to my functional studies, I present proteomic data to propose mechanisms by which HEATR2 and ZMYND10 proteins control cilia motility. Mass spectrometry and protein interaction studies support distinct roles for HEATR2 and ZMYND10 in intracellular transport and pre-assembly of axonemal dynein motors. The multisystem approaches described in this thesis to characterise the roles of HEATR2 and ZMYND10 highlight the molecular complexity underlying the assembly and delivery of axonemal dyneins to motile cilia and provide novel functional and molecular insights into the pathophysiology of PCD.
197

Study of hydrodynamic coupling and interfacial property in emulsion system

Zhou, Liangyu 01 January 2006 (has links)
No description available.
198

Zwitterionic Sulfobetaine-based Copolymers and their Biomedical Applications / Synthèse de copolymères zwitterioniques dérivés du sulfobétaïne et leurs applications biomédicales

Shih, Yu-Ju 06 December 2012 (has links)
Les polymères biomimétiques incorporant des groupes zwitterioniques mimant la phosphatidylcholine, comme par exemple la phosphobétaïne, la sulfobétaïne ou encore la carboxybétaïne, ont reçu une attention grandissante pour une utilisation dans la prochaine génération de matériaux en contact avec le sang, grâce à leur excellentes propriétés anti-bioadhésives. Le poly(methacrylate de sulfobétaïne) (polySBMA), avec un squelette methacrylate et un analogue de la taurine bétaïne (CH2CH2N+(CH3)2CH2CH2CH2SO3-) comme groupe pendant, est de loin le polymère le plus étudié en raison de sa relative facilité de préparation. Il est maintenant admis que les brosses polymères recouvrant une surface de groupes zwitterioniques permettent l'obtention d'une surface résistance à l'adsorption de biocomposants, permettant d'envisager une application potentielle pour des matériaux mis en contact du sang, comme les implants par exemple. Dans cette thèse, la nouvelle fonctionnalisation de copolymères dérivés du sulfobétaïne et leurs potentielles applications sont développées et étudiées.Dans une première partie, des copolymères diblocs « schizophréniques » contenant des blocs nonioniques et zwittérioniques ont été préparés pour différentes masses molaires via la polymérisation radicalaire contrôlée (ATRP : atom-transfer radical polymerization). Dans ce travail nous présentons une étude systématique de la relation entre la conformation des chaînes copolymères en solution et leur impact sur l'hémocompatibilité dans une solution de sang humain. Le comportement « schizophrénique » de copolymères PNIPAAm-b-PSBMA a été observé par RMN 1H, diffusion dynamique de la lumière et turbidité, démontrant ainsi une double transition morphologique avec à la fois une LCST (lower critical solution temperature) et une UCST (upper critical solution temperature) en solution aqueuse. En dessous de l'UCST du bloc PSBMA, des micelles sont obtenues avec un cœur insoluble de PSBMA entouré d'une écorce soluble de PNIPAAm alors que la structure inverse est observée au-dessus de la LCST du bloc PNIPAAm. Entre l'UCST et la LCST, des unimères parfaitement solubles ont été détectés. La taille hydrodynamique des copolymères et des homopolymères correspondants a également permise de corréler directement la morphologie micellaire avec la compatibilité avec du sang humain. L'adsorption isolée de fibrinogènes humains sur le copolymère à bloc a été étudiée par DLS pour déterminer la stabilité de la résistance à la bio-adhésion d'une suspension de copolymères. Le PNIPAAm-b-PSBMA a démontré une activité anti-coagulante et anti-hémolytique extrêmement élevées sur une large gamme de température allant de 4 à 40°C. La non-dépendance de la biocompatibilité à la température, associée au comportement schizophrénique en solution aqueuse, nous a amené à réfléchir à d'éventuelles applications.Dans la seconde partie de ce manuscrit, des copolymères diblocs « intelligents » contenant des blocs ioniques et zwittérioniques ont été préparés par polymérisation radicalaire contrôlée de type RAFT (reversible the addition-fragmentation chain transfer). Dans ce travail, nous présentons une étude systématique sur la formation d'un nouveau vecteur d'ADN à partir d'un coeur polyplexe ADN/ poly(dimethylaminoethyl methacrylate) (PDMAEMA), recouvert, via des interactions électrostatiques, de copolymères poly(acide acrylique)-block-poly(méthacrylate de sulfobétaïne) (PAA-b-PSBMA). Son impact sur l'hémocompatibilité ainsi que sur l'efficacité de la transfection de gènes ont été vérifiés, en prenant comme référence des polyplexes formés à partir de polyethyleneimine (Pei). La capacité d'interaction des plasmides ADN avec le Pei, PDMAEMA, et PAA-b-PSBMA a été évaluée par « ethidium bromide displacement assays » et « agarose gel retardation assays » en fixant le rapport en atomes d'azote de polymère par atomes de phosphore des nucléotides (rapport N/P) ainsi que le pH de la solution. La mesure du temps de coagulati / Biomimetic polymers containing zwitterionic structures poly(sulfobetaine methacrylate) (polySBMA) has become the most widely studied zwitterionic polymer due to its easy of synthetic preparation. It is now recognized that grafted dense polymer brushes, composed of zwitterionic polySBMA, formed an effective and stable nonfouling surface, potentially enabling the practical use in human blood-contacting devices and implants. In this dissertation, the new functionalization of zwitterionic sulfobetaine-based copolymers and their potential biomedical applications was developed and investigated. In the first part of the dissertation, “schizophrenic” diblock copolymers containing nonionic and zwitterionic blocks were prepared with well-controlled molecular weights via the atom-transfer radical polymerization (ATRP). In this work, we demonstrate a systematic study of how morphological changes of poly(N-isopropylacrylamide)-block-poly(sulfobetaine methacrylate) (PNIPAAm-b- PSBMA) copolymers affect hemocompatibility in the human blood solution. The “schizophrenic” behavior of PNIPAAm-b-PSBMA was observed by 1H nuclear magnetic resonance (1H NMR), dynamic light scattering (DLS), and turbidity measurement with double morphological transition, exhibiting both lower critical solution temperature (LCST) and upper critical solution temperature (UCST) in aqueous solution. Human fibrinogen adsorption onto the PNIPAAm-b-PSBMA copolymers from single-protein solutions was measured by DLS to determine the nonfouling stability of copolymer suspension. The new nonfouling nature of PNIPAAm-b-PSBMA copolymers was demonstrated to show an extremely high anticoagulant activity and antihemolytic activity in human blood over a wide range of explored temperatures from 4 ºC to 40 ºC and suggests their potential in blood-contacting applications.In the second part of the dissertation, “intelligent” diblock copolymers containing ionic and zwitterionic blocks were prepared with well-controlled molecular weights via reversible the addition-fragmentation chain transfer (RAFT) polymerization. In this work, we demonstrate a systematic study of how zwitterionic shielding on a new self-assembled cargo of plasmid DNA/poly(dimethylaminoethyl methacrylate) (PDMAEMA) polyplexes conjugated with poly(acrylic acid)-block-poly(sulfobetaine methacrylate) (PAA-b-PSBMA) copolymers affect hemocompatibility in human blood solution and gene transfection onto target cells. The carrier stability, cell toxicity, hemocompatibility, and gene transfection efficiency of DNA/ PDMAEMA/PAA-b-PSBMA polyplexes was investigated as compared with DNA/polyethyleneimine (PEI)/PAA-b-PSBMA. Hemocompatibility of the prepared polyplexes was evaluated by the anticoagulant activity of the blood coagulant determined by testing the plasma-clotting time and the antihemolytic activity in human blood by measuring red blood-cell hemolysis. The pH-dependent gene transfection of DNA/ PDMAEMA/PAA-b-PSBMA polyplexes, along with their stimuli-responsive behavior, suggests their potential in blood-contacting gene delivery applications.In the final part of the dissertation, ionic/zwitterionic PAA-b-PSBMA diblock copolymer was extended to prepare anti-fouling poly(ether imide) membranes with well-controlled nano-pore structures and water flux via layer-by-layer self-assembled coating process. The surface charge property of the prepared membrane can be regulated by PEI/PAA ratios. Low protein-fouling membrane surfaces from BSA and fibrinogen solution with respect to uncoated membrane surfaces are achieved with optimized block ratio of PAA and PSBMA. Thus, positively charged membranes, coated with zwitterionic copolymers containing anionic groups via charge-driven, are ideal for highly resisting protein adsorption if the membrane surface density of the zwitterionic groups is controlled to a high-level densities.
199

Molecular dynamics simulations of structure and friction in lubricants

Bradley-Shaw, Joshua Louis January 2016 (has links)
Glycerol monooleate (GMO) is a common engine oil lubricant additive used to reduce friction and wear in engines. The aim of this thesis is to investigate the properties of GMO in bulk and under confined conditions with shear using molecular dynamics simulations. The self-assembly of GMO into reverse micelles (RMs) in toluene and n-heptane solvents is studied at a range of concentrations and subsequently with several common engine impurities over simulation timescales of 5-30 ns. The dimensional properties of the RMs are found to correspond well with experimentally studied SANS/SAXS measurements. Secondly, the properties of GMO confined between mica surfaces are studied under quiescent and shear conditions. Under shear, the performance of GMO as a friction modifier is studied and the structural and frictional properties are examined. In particular, the mass density and velocity profiles of the fluid are used to gain insights into the structure and dynamics of the confined GMO fluid films, under a variety of shear rates and surface separation. The data is found to fit excellently to the universal friction curve. Following this the effect of hydrolysing the GMO to oleic acid is studied in bulk and under shear, it is found that increasing oleic acid concentration typically reduces the propensity to self-assemble and under confinement increases the friction coefficient. And finally, a study on a range of other similar surfactants is conducted to investigate the effect of unsaturation, head group and chain length on the calculated friction coefficient and the structure of the surfactant films.
200

Metoda za projektovanje i optimizaciju sistema za montažu zasnovanih na lean konceptu / Method for optimisation and design of assembly systems based on leanconcept

Dragičević Dragan 11 April 2018 (has links)
<p>Istraživanja u okviru doktorske disertacije usmerena su ka razvoju<br />metode za projektovanje i optimizaciju sistema za montažu zasnovanih<br />na lean konceptu. Analizirani su postojeći instrumenti lean-a i posebno<br />je istražen njihov uticaj na razvoj sistema za montažu i analizu<br />ključnih parametara sistema. Na osnovu prethodnog istraživanja,<br />izvršena je selekcija instrumenata lean koncepta koji su<br />implementirani u metodu za projektovanje i optimizaciju sistema za<br />montažu. Verifikacija predložene metode realizovana je na studiji<br />slučaja optimizacije postojećeg sistema za montažu cirkulacionih<br />pumpi. Osim navedenog, izvršeno je i projektovanje potpuno novog<br />sistema za montažu cirkulacionih pumpi.</p> / <p>Research in this PhD thesis is focused on development of method for<br />optimization and design of assembly systems based on lean concept. Existing<br />instruments of lean are analysed especially their impact on development of<br />assembly system and key parameters analysis. Based on previous research a<br />selection of lean instruments was made and they were implemented in method<br />for optimization and design of assembly sustems. Verification of proposed<br />method was realized on case study where existing assembly system was<br />optimized. In adition to the above completely new assembly system was<br />designed using proposed method.</p>

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