The solution rheological and electrospinning behavior of a series of charge-containing polymers, surface-active agents, and carbon nanotube composites was studied to investigate the effect of intermolecular interactions, including electrostatic interactions, hydrogen bonding, surface activity, and surface functionalization of carbon nanotubes. The synthesis of novel polyelectrolytes with varied topologies, charge content, and counterions tailored the charged macromolecules to elucidate structure-rheology and structure-processing relationships. In addition, the use of additives for electrospinning, including surfactants and nanofillers, allows us to tailor the functionality of electrospun nanofibers for high-performance applications. Novel polyelectrolytes based on poly(2-(N,N-dimethyl)aminoethyl methacrylate) (DMAEMA) were synthesized with the counteranions Cl-, NO3-, (CN)2N-, BF4-, PF6-, triflate (TfO-), and bis(trifluoromethanesulfonyl)imide (Tf2N-). The counteranion selection controlled the thermal transitions and degradation; the larger and more charge-delocalized anions typically resulted in lower Tg and higher decomposition temperature. The polyelectrolyte behavior in solution was nearly independent of anion choice, though solution conductivity depended on the electrophoretic mobility of the counterion. Charge containing copolymers of DMAEMA and di(ethylene glycol) methyl ether methacrylate (MEO2MA) were synthesized and demonstrated that polyelectrolyte behavior in solution was also nearly independent of charge content. Low ionic contents resulted in extended solution conformations and high conductivities. Controlled atom-transfer radical polymerization allowed the synthesis of star-shaped polyelectrolytes with varying arm numbers and lengths. The solution behavior of the stars deviated slightly from the linear polyelectrolytes due to significant counterion condensation within the star core and constrained polymer conformations. The linear and star-shaped polyelectrolytes were electrospun to understand the interplay between polyelectrolyte structure and electrospinnability. Similar to other strong polyelectrolytes described in the literature, PDMAEMA-based polyelectrolytes with polar anions (e.g. Cl-) experienced significant instabilities during electrospinning, requiring high concentrations and viscosities to stabilize the electrospinning jet. The use of large, more hydrophobic anions (BF4-, TfO-) led to increased electrospinnability. Unlike neutral branched polymers, which electrospin nearly identically to linear polymers of similar molecular weight, the star-shaped PDMAEMA-based polyelectrolytes required even higher viscosities than linear polyelectrolytes for stable electrospinning. The correlations between electrospinnability and solution rheological analysis are detailed. The use of surfactants facilitates the electrospinning of neutral polymers at lower concentrations. However, we have demonstrated that specific cylindrical aggregates of surfactants (wormlike micelles) can be electrospun into microfibers under the proper conditions. Ammonium and phospholipids surfactants as well as organogelators were studied using solution rheology and DLS to determine the effects of micellar structure and solution viscosity on the electrospinnability of low molar mass surfactants. In addition, the effects of charged and uncharged surfactants on the electrospinning behavior of poly(methyl methacrylate) were determined. Added surfactant facilitated uniform fiber formation at lower PMMA concentrations. XPS analysis demonstrated the formation of core-shell fibrous structures resulting from the self-migration of surfactants to the fiber surface. Hydrogen bonding also influences fiber formation through electrospinning. Star-shaped poly(D,L-lactide)s (PDLLAs) were end-functionalized with adenine (A) or thymine (T) units. The complementary hydrogen bonding between the adenine and thymine lead to thermoresponsive rheological behavior for mixtures of PDLLA-A and PDLLA-T. The mixtures could be electrospun above the hydrogen bond dissociation temperature and resulted in thicker fibers compared to unfunctionalized PDLLA stars. The hydrogen bonding allows the preparation of polymers with a combination desirable solid-state properties and very low processing viscosities. The effects of carbon nanotube incorporation on electrospinning behavior and fiber morphology were also investigated. Nonfuntionalized and carboxylic-acid functionalized carbon nanotubes were electrospun into polyurethane nanofibers. The nonfunctionalized nanotubes required high-shear melt mixing to disperse within the polyurethane, but remained well dispersed through electrospinning. The surface functionalization with acid groups produced nanotubes which dispersed more readily into the polyurethane solutions. TEM analysis revealed that nanotube dispersion and alignment within the nanofibers was similar for both nonfunctionalized and acid-functionalized nanotubes. / Ph. D.

Polyacrylonitrile (PAN) fiber is one of the most important synthetic fibers in the world because it is a precursor to carbon fiber. Compared to the traditional solution spinning process, the melting spinning process of PAN is less costly and can further reduce the price of PAN fiber. This dissertation is concerned with the objective of establishment of conditions (temperature, plasticizer type, and plasticizer composition) that a PAN copolymer is able to be stable melt spun with water based plasticizers. More specifically, PAN/water/acetonitrile (70/15/15) mixture is considered as reference sample in this study because it was proposed in a BASF patent in which it was claimed it could be stably melt spun. We are looking for a more benign plasticizer so that the use of acetonitrile can be avoided and PAN can still be stably melt spun. To achieve this objective, the first step is to measure the melting point (Tm) of PAN copolymer with various plasticizers and compositions by using differential scanning calorimetry (DSC). The results indicate the Tm of PAN copolymer can be reduced to around 160 oC with water only as a plasticizer, which is lower than the degradation temperature of PAN (180 oC). Moreover, using a water/ethanol mixture and water/acetonitrile as plasticizers can further reduce the melting point of PAN to 150 oC and 135 oC, respectively. The second step is conducting rheological measurements on the PAN/plasticizers mixture. A pressure chamber was designed and attached to the capillary rheometer in order to prevent the foaming and evaporation of plasticizers during the viscosity experiments. Both steady-shear and time-dependent viscosity measurements were conducted. The rheological measurement results indicate that PAN can keep stable for more than 120 minutes with all plasticizers under 170 oC, and it starts to degrade in 60 minutes at 180 oC, except samples plasticized with 30 wt% of water (which keep stable for 120 minutes as well). The steady-shear viscosity results indicate the shear-thinning behavior is observed for the PAN/plasticizer mixtures at a temperature ranging from 170 oC to 190 oC and provide the fundamental viscosity data which can be applied to the extrusion process. In conclusion, the rheological measurements show PAN/Water (70/30 wt%) at 180 oC and PAN/EtOH/Water (70/15/15) at 170 oC are two potential systems for carrying out the PAN melt spinning process. Scanning electron microscopy (SEM) images were taken for the reference state and potential conditions. These images show that the copolymer strands have more and larger voids when plasticized with water only compared to those plasticized with water/acetonitrile and water/ethanol mixture. In this case, PAN/EtOH/Water (70/15/15) at 170 oC is considered to be the most benign system for that PAN melt spinning. / Doctor of Philosophy / The melt spinning process of polyacrylonitrile (PAN) has been studied in the past few decades. Compared to the traditional solution spinning process, it does not require toxic organic solvents. The major problem of the PAN melt spinning process is the melting point (Tm) of PAN is much higher than its degradation temperature. However, by adding plasticizers the Tm of PAN can be significantly reduced, which makes PAN melt spinning feasible. In this work we discuss the feasibility of the melt spinning process of polyacrylonitrile (PAN) copolymer plasticized with water based plasticizers by using differential scanning calorimetry (DSC) and rheological methods. The objective is to use water only as a plasticizer to melt spin PAN under specific conditions (composition, temperature etc). The melting point and rheological measurements have been conducted by DSC and a modified capillary rheometer, respectively, for this plasticized system. The DSC results show that the melting point of the PAN copolymer can be reduced below the degradation temperature of PAN, and the rheological results show that the PAN copolymer can be extruded with a reasonable viscosity at 15-20 o v above its melting point, and also the stability and viscosity are strongly dependent on temperature and the plasticizer type and content. Furthermore, the Scanning electron microscopy (SEM) images show the copolymer strands extruded from PAN/H2O mixture have many more and larger voids than PAN/H2O/EtOH mixture. In conclusion, the results indicate that the most appropriate condition for PAN melt spinning is PAN/H2O/EtOH mixture of 70/15/15 wt% ratio at a temperature of 170 oC

This dissertation is aimed at understanding the microstructure evolution in styrene — diene block copolymer — based pressure-sensitive adhesive compositions in melt. The work also focuses on determining the microphase separation mechanism in adhesive melts containing various amounts of low molecular weight resin (tackifiers) blended with styrene — diene block copolymers. To understand the correlation between adhesive morphology and their dynamic mechanical behavior, small angle X-ray scattering (SAXS) and rheological analysis were performed on blends with different compositions. A modified Percus — Yevick model combined with Gaussian functions was used fit the liquid like disordered and bcc — ordered peaks of the SAXS intensity profiles. The morphological parameters derived from SAXS analysis corresponded to features such as the size and extent of ordering of the microphase separated polystyrene domains. The variation in these parameters with respect to temperature and adhesive composition correlated reasonably well with the trends observed in the shear modulus measured using rheological analysis. It was found that the ordering of polystyrene domains was influenced by the tackifier content in the adhesive blends. Polymer chain mobility was determined to be the dominant factor governing ordering kinetics, which depended on both the quench temperature and tackifier content in the blends. The addition of increasing amounts of tackifier eventually leads to a shift from a nucleation and growth type mechanism to a spinodal decomposition mechanism for phase separation and ordering. The compatibility of the tackifier with the polystyrene chains had a significant impact on the morphological transitions and microphase separation in adhesive blends. The blends containing a styrene — incompatible tackifier showed ordering over a broader range of temperatures compared to the blends containing a polystyrene — compatible tackifier. / Ph. D.

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Alkali-soluble rheology modifiers are commercially synthesised via conventional freeradical polymerisation processes. This results in the end product having certain limitations; there is poor control over the molar mass, molar mass distribution and chain architecture of the polymer chains. These limitations can be overcome by using a controlled/living free radical polymerisation process, for example the RAFT process. This alternate method of synthesis was used here to prepare model alkali-soluble rheology modifiers. The structure/property relationships of model alkali-soluble rheology modifiers synthesised via the RAFT process were studied. Model alkali-soluble rheology modifiers of different molar masses and chain architectures (block, co- and ter-polymers) were successfully synthesised by the RAFT polymerisation of methyl methacrylate, methacrylic acid and various hydrophobic macromonomers. The different types of alkali-soluble rheology modifiers were synthesised in solution and in miniemulsion. Each of the two systems had certain advantages and disadvantages. The conversion limit of reactions in solution was about 60 % and reaction times were much slower than those of the miniemulsion reactions. Higher final conversions were recorded for miniemulsion reactions, reactions were faster and no solvent removal was required. Unfortunately it was not possible to synthesise all the different types of associative rheology modifiers investigated here in a miniemulsion system. The latex solutions thickened with conventional rheology modifiers (co-polymers) show very contrasting behaviour (rheology profile and dynamic properties) to that of the latex solutions thickened with the associative rheology modifiers (ter-polymers). The AB block copolymers gave the latex solutions rheology results between those obtained with conventional rheology modifiers and those with the associative rheology modifiers. Varying the number of ethylene oxide spacer units in the hydrophobic macromonomers of the associative rheology modifiers had a significant influence on the rheology properties of the latex and alkali solutions. As the number of ethylene oxide spacer units was increased from 20 to 100 there was a significant increase in the zero-shear viscosity of the latex solutions thickened with the associative rheology modifiers. Contrasting results were obtained for the polymer solutions (no latex present), where the use of the associative rheology modifiers containing the highest number (EO = 100) of ethylene oxide spacer units resulted in solutions with the lowest viscosity, but the rheology modifiers containing the 50 ethylene oxide spacer units gave the highest steady shear viscosity. / AFRIKAANSE OPSOMMING: Alkali-oplosbare reologie-modifiseerders word kommersieël gesintetiseer d.m.v. konvensionele vrye-radikaal polimerisasieprosesse. Hierdie prosesse lewer gewoonlik 'n eindproduk met sekere tekortkominge, a.g.v. swak beheer oor molekulêre massa, molekulêre massa-verspreiding, en polimeerkettingstruktuur (Eng. chain architecture). Hierdie tekortkominge kan oorbrug word deur gebruik te maak van 'n beheerde/lewende vrye-radikaal polimerisasieproses, soos byvoorbeeld die RAFT-proses (Eng. RAFT: reversible addition-fragmentation chain transfer polymerisation). Hierdie alternatiewe metode is in die studie gebruik om model alkali-oplosbare reologiemodifiseerders te sintetiseer. Die struktuur-eienskapverhoudings van die model alkali-oplosbare reologie modifiseerders wat d.m.v. die RAFT-proses gesintetiseer is, is bestudeer. Model alkali-oplosbare reologiemodifiseerders van verskillende molekulêre massas en kettingstrukture (blok, ko- en ter-polimere) is suksesvol gesintetiseer d.m.v. RAFT-polimerisasie van metielakrilaat, metakrielsuur en hidrofobiese makromonomere. Die verskillende alkali-oplosbare reologiemodifiseerders is in organiese oplosmiddel sowel as in mini-emulsie gesintetiseer. Elkeen van die sisteme het sekere voordele en nadele getoon. In die reaksies wat in organiese oplosmiddels gedoen is, is slegs 60 % van die monomere ingebou in die polimeerkettings en die tydsduur van hierdie reaksie was heelwat langer as by die wat uitgevoer is in mini-emulsie. Meer as 60 % van die monomere is omgeskakel na polimeer tydens die reaksies wat in mini-emulsie uitgevoer is, die reaksietempo was vinniger en dit was nie nodig om die organiese oplosmiddel te verwyder nie. Ongelukkig was dit nie moontlik om al die verskillende tipes assosiatiewe-reologiemodifiseerders (Eng: associative rheology modifiers) in miniemulsie te sintetiseer nie. Die lateks wat met konvensionele reologiemodifiseerders (ko-polimere) verdik is, het kontrasterende eienskappe (reologie-profiel en dinamiese eienskappe) getoon teenoor die van die lateks-oplossings wat met assosiatiewe-reologiemodifiseerders (ter-polimere) verdik is. Die AB-tipe blok ko-polimere gee reologieresultate vir die lateks-oplossings wat lê tussen die wat bepaal is vir konvensionele reologieodifiseerders en assosiatiewe reologiemodifiseerders. Variasie in die aantal etileenoksiedeenhede in die hidrofobiese makromonomere van die assosiatiewe reologiemodifiseerders het 'n betekenisvolle invloed op die reologie-eienskappe van die lateks, sowel as die alkali-oplossings gehad. Namate die aantal etileenoksiedeenhede van 20 tot 100 vermeerder is, het 'n betekenisvolle verhoging in die "zero-shear " viskositeit van die lateks oplossings wat met die assosiatiewe reologiemodifiseerders verdik is voorgekom. Teenstrydige resultate is verkry vir die polimeeroplossings met geen lateks teenwoordig nie: die assosiatiewe reologiemodifiseerders met die hoogste aantal etieleenoksiedeenhede (EO = 100) het die laagste viskositeitsresultate opgelewer en die reologiemodifiseerders met slegs 50 etieleenoksiedeenhede het die hoogste viskositeitsresultate gelewer.

在這篇論文中，我們提出了在醫學模擬應用的血管或傷口上作相互作用的粒子血流變模型框架。通過平滑粒子流體動力學（SPH）制定的非牛頓流體，進行了血液流變學的模擬。通過建模血管壁結構虛擬粒子，流體 - 結構相互作用（FSI）是一個純粹的拉格朗日(Lagrange)顆粒模型進行建模的血管或血液的交互。我們的建議的方法基於純粹的非網格方法，可用於常見的動脈瘤和血管狹窄等病症的建立上。如需模擬開放性傷口在手術部位中發生較大的變形情況時，我們則採用質量 - 彈簧系統進行血顆粒的交互，此交互框架可應用到幾個開放性手術模擬，如骨科或胃鏡檢查為基礎的手術。無論是常見的醫療圖像：如CT血管造影（CTA）、磁共振血管造影（MRA）或基於網格的數據也可以 作為系統輸入的數據。血栓形成與溶解模型也被集成到這個流固耦合框架中。實驗結果證明採用我們建議的粒子互相作用框架在模擬血管中的凝血過程是可行的。受益於簡潔的拉格朗日粒子交互作用模擬，我們的系統可以保持在互動幀速率中。 / 首先，我們在這篇論文中建議把無網格流變模擬框架應用於血管手術的建模中。於非牛頓粘性流動的假設下，我們建立了血液結構的一般模型方程：以平滑粒子流體動力學實現多血粘度模型與低彈性血管壁模型。血流動力學和軟組織都可以於相同的拉格朗日粒子為基礎下模擬。在這個意義上說，通過延伸平滑粒子流體動力學的密度和動量求和不管顆粒的性質下，本論文提出了一個有效的流體 - 固體交互作用模型。該模型是特別有利於整合多種類型的介質（包括固體或液體）的。在這方面，我們進一步提出了一個與流體相關的血塊凝集溶解模型，可以適用於許多不同種類的醫學模擬：例如血栓栓塞。 / 其次，本論文亦提出了如何基於粒子的血液建模框架的前提下，擴展到大變形的軟組織互動。我們是以耦合雙向階段性質量 - 彈簧系統與固體顆粒，去代替無網格粒子固體的建模，用以維持真正人體組織的高保真度，此方法可以實現類似軟組織的皮膚或真皮的交互式模擬。而耦合血顆粒與平滑粒子方面，則由一個聰明的碰撞模塊處理，使得利用模擬皮膚表面之上，可以模擬出真實的表皮出血現象。該模型的動態計算進一步以物理學處理單元加速；而渲染的模型則是通過一個強大的圖形處理單元為基礎的立方體運行（marching cubes）的方法來實現。該模型已應用於全身血液管理培訓中。 / In this thesis, we propose particle-based rheological modeling frameworks for blood-vessel and blood-wound interaction in medical simulation applications. The effect of blood rheology has been simulated through a smoothed particle hydrodynamics (SPH) formulation of non-Newtonian flow. By modeling the vessel wall structure as virtual particles, a pure Lagrange particle formulation for fluid-structure interaction (FSI) is proposed for modeling the blood-vessel or blood-device interaction. Our proposed framework synthesizes common vascular complication sites such as stenosis and aneurysm based on purely mesh-less approach. For larger deformation situations happened in surgical sites such as open wound, we adopt a mass-spring system to interact with the blood particles; the blood-wound interaction framework can be applied to several open surgery simulations such as orthopedics or endoscopy-based interventions. Input of the data can be obtained from either common medical modalities like computed tomographic angiography (CTA), magnetic resonance angiography (MRA) or processing mesh-based data. A thrombus (clot) formation-dissolution model is also integrated into this fluid-solid interaction framework. Results have demonstrated the feasibility of employing our proposed particle framework in simulating blood-vessel interaction in the clotting process which is essential to vascular procedure simulations. Having benefited from the elegant formulation of Lagrangian particle interaction; the simulation can be maintained at interactive frame-rates. / In this thesis, first, a meshless rheological modeling framework for medical simulation of vascular procedures is proposed. Instead of assuming a Newtonian non-viscous flow, we have built our model based on the general constitutive equation of blood. The multi-regime of viscosity in blood model with a hypoelastic model of vessel wall has been realized under a SPH formulation. The hemodynamic and the soft tissue can all be simulated under the same Lagrangian particle-based formulation. In this sense, an efficient formulation of fluid-solid interaction is proposed through extending SPH summations of density and momentum regardless the nature of particles. This model is particularly beneficial to the integration of multiple types of media (including solids or fluids). With this regards, we further propose a flow related clot aggregation-dissolution model which can be applicable to many different kinds of medical simulation e.g. thrombo-embolization. / Second, the proposed particle-based blood modeling framework has been extended to interact with large deformation of soft tissue. Instead of modeling the solid as meshless particles, a bi-phasic mass-spring system is coupled with solid particles so that an interactive simulation of skin or dermis like soft tissue can be realized with high fidelity to real human tissue. To couple with the SPH formulation of blood particles, a smart collision handling module is exploited so that a realistic bleeding simulation on top of the skin surface can be created. The dynamic computation of this model is further accelerated by the physics processing unit; while the rendering of the model is realized through a robust graphics processing unit based marching cube approach. The proposed model has been applied to provide general blood management training. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chui, Yim Pan. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 98-113). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Abstract --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Related works on physically based fluid-structure models --- p.7 / Chapter 2.1 --- Eulerian grid-based methods --- p.8 / Chapter 2.2 --- Lagrangian grid-based methods --- p.9 / Chapter 2.3 --- Lagrangian meshfree methods --- p.11 / Chapter 2.4 --- Fluid-structure interaction (FSI) --- p.12 / Chapter 2.5 --- Endovascular simulation --- p.14 / Chapter 2.6 --- Overview of Our Model --- p.15 / Chapter 3 --- Meshless blood-clot interaction --- p.16 / Chapter 3.1 --- Basic equations of fluid dynamics --- p.17 / Chapter 3.2 --- SPH basics --- p.18 / Chapter 3.3 --- SPH Rheological hemodynamics of blood --- p.20 / Chapter 3.4 --- SPH modeling of the hypoelastic vessel --- p.26 / Chapter 3.5 --- Fluid-solid interaction model --- p.28 / Chapter 3.6 --- Flow-related clot aggregation-dissolution model --- p.33 / Chapter 3.7 --- Time integration --- p.36 / Chapter 3.8 --- Hardware-friendly formulation --- p.37 / Chapter 3.9 --- Results --- p.39 / Chapter 3.9.1 --- Classical Dam-break problem --- p.41 / Chapter 3.9.2 --- Poiseuille flow --- p.43 / Chapter 3.9.3 --- Couette flow --- p.45 / Chapter 3.9.4 --- Mechanical model with material strength --- p.47 / Chapter 3.9.5 --- Hemoelastic feedback system --- p.49 / Chapter 3.9.6 --- Clotting in a stenosed vessel --- p.52 / Chapter 3.9.7 --- Timing results --- p.53 / Chapter 4 --- Meshless modeling of thrombo-embolization --- p.55 / Chapter 4.1 --- Modeling framework for thrombus formation within blood vessel . --- p.60 / Chapter 4.2 --- Geometric Modeling and Flow Simulation --- p.61 / Chapter 4.2.1 --- Data processing on vascular data --- p.61 / Chapter 4.2.2 --- Blood-Vessel particle distribution --- p.62 / Chapter 4.2.3 --- Blood-structure Interaction --- p.65 / Chapter 4.3 --- Visualization and Thrombosis Simulation --- p.66 / Chapter 4.3.1 --- Flow Visualization --- p.66 / Chapter 4.3.2 --- Thromb-Embolization Simulation --- p.68 / Chapter 4.4 --- Conclusion and discussion --- p.72 / Chapter 5 --- Lagrangian modeling framework for bleeding simulation --- p.76 / Chapter 5.1 --- SPH-based bleeding model --- p.78 / Chapter 5.2 --- Biphasic Soft-tissue deformation --- p.79 / Chapter 5.3 --- Interaction between blood and soft tissue --- p.83 / Chapter 5.4 --- Integrated training for blood management --- p.87 / Chapter 6 --- Discussion and Conclusion --- p.93 / Bibliography --- p.98

Conducting polymer coating is the new developing area in the field of advanced textiles. In this project the rheological behaviour of paste containing conducting polymer was studied during formulation to coating application. The literature study is done by keeping all the contents of project in mind and a wide area of conductive polymer, coating methods, binder system and rheology modifier is covered. The rheological behaviour of different fluid containing newtanion and non-newtanion behaviour is discussed for better understanding of the project working. Polyester fabric was coated by knife coating method. In paste formulation, the chemicals used were polyurethane binder with two HEUR based rheology modifiers. A lot of experiments were performed to determine the right amount of rheology modifier alone or in combination for paste formulation and coating application and interesting findings were observed during the experimental work which had been justified in results and analysis. After application, the coated fabric was checked for resistivity. / Program: Magisterutbildning i textilteknologi

Airborne infectious diseases remain a major global health threat. The primary vector for their transmission is coarse and fine droplets, known as bioaerosols, exhaled from infected individuals during natural respiratory maneuvers, such as breathing, coughing and sneezing. Unfortunately, our current knowledge of the mechanisms by which these exhaled bioaerosols are formed in the lungs is in its infancy. In particular, progress in this field has been hindered by the complex structure of the respiratory fluid and the resulting lack of understanding of the biophysical properties of the fluid. In this thesis, a series of in vitro mimetics of conducting airway mucus were developed to enable in depth studies of mucus properties and bioaerosol formation from mucus-like surfaces. These mucus mimetics overcome major limitations of currently available models by matching the primary chemical composition and key physical properties of the mimetic to that of native tracheal mucus. Three mimetics were chosen to facilitate the study of highly viscoelastic (diseased) mucus and non-diseased mucus under low shear conditions, such as breathing, or high shear conditions, such as cough. To study bioaerosol formation in vitro, an enhanced simulated cough machine (SCM) was developed to generate bioaerosols from mucus mimetic surfaces during cough. By controlling the temperature and relative humidity within the SCM, the detectability of bioaerosols generated from the mimetic surfaces was improved due to limited aerosol drying. The size distribution of the bioaerosols was multimodal, with four to five modes being observed for all surfaces probed. While varying the composition of surfactant at the air-mucus interface had a significant impact on surface viscoelastic properties, the size distribution of bioaerosols generated from these surfaces did not differ significantly. However, the ability to generate bioaerosols from different surfaces was highly dependent on surface properties of the mimetic, with highly viscoelastic surfaces generating bioaerosols in only half the experiments. This research will enhance our knowledge of bioaerosol formation in the respiratory tract and ultimately guide the development of alternative strategies to suppress bioaerosol formation.

The rheological properties of cement based grouts change with water/cement ratio and time, during the course of hydration. For this reason, it is desirable to be able to measure this change continuously, in-line, with a robust instrument during the entire grouting operation in the field. The rheological properties of commonly used cement grouts were determined using the Ultrasound Velocity Profiling combined with the Pressure Difference (UVP+PD) method. A non-model approach was used that directly provides the properties, and the results were compared with the properties obtained using the Bingham and Herschel-Bulkley rheological models. The results show that it is possible to determine the rheological properties, as well as variations with concentration and time, with this method. The UVP+PD method has been found to be an effective measuring device for velocity profile visualization, volumetric flow determination and the characteristics of the grout pump used. / <p>QS 2013</p>

La formation du caillot de fibrine, processus clé de la coagulation sanguine, implique la polymérisation des monomères de fibrine en un réseau de fibres. Ce réseau contrôle les propriétés mécaniques du caillot et constitue le squelette sur lequel se base la cicatrisation. Si l’influence des conditions de réaction (pH, concentration, …) est bien connue, le rôle de la composition du fibrinogène sur la structure de la fibrine est inexploré. Cet aspect pourrait être important pour les pathologies cardiovasculaires qui présentent toutes une structure de fibrine anormale.Nous avons étudié la relation entre la composition de plusieurs fibrinogènes et les propriétés structurelles nano- et micro-métriques ainsi que la mécanique des caillots de fibrine. La composition en protéines co-purifiées de ces fibrinogènes a peu d’influence, alors que le profil de polydispersité contrôle la structure multi-échelle de la fibrine. Des mesures de diffusion des rayons x, de spectrophotométrie multi-longueur d’ondes et de microscopie confocale ont mis en évidence que les fibres provenant des fibrinogènes monodisperses sont quasi-cristallines, droites et rigides. Les fibres provenant de fibrinogènes polydisperses sont, elles, beaucoup moins organisées, courbées, avec un module de rigidité faible. Enfin, les propriétés mécaniques de la fibrine ont montré que la réponse des caillots aux déformations, aussi que les scenarios de rupture, sont directement liés à sa structure et donc significativement dépendants du profil de polydispersité des fibrinogènes. Ces résultats ouvrent de nouvelles perspectives dans plusieurs domaines, que ce soit pour l’utilisation optimale des fibrinogènes pour les dysfibrinogénémies et hémorragies, mais également pour la reconstruction tissulaire, ainsi que la compréhension du lien entre la structure anormale des caillots et les maladies cardiovasculaires. / Fibrin clot formation is one of the major processes leading to blood clotting. It involves the polymerization of fibrin monomers into a network of fibrin fibres. This network controls the mechanical properties of the clot and serves as a skeleton for wound healing. Environmental factors (pH, concentration, …) have been proved to influence polymerization, however the role of fibrinogen composition on the structure of fibrin remains unexplored. This aspect might be important for the case of cardiovascular pathologies, which present abnormal fibrin structures.We have determined the relation between different sources of fibrinogen with the nano- and micro-metric structural and mechanical properties of fibrin clots. The composition in co-purified proteins of the fibrinogens has no significant importance, however the polydispersity profile controls the multiscale properties of fibrin. Indeed, x-ray scattering, multi-wavelength spectrophotometry and confocal microscopy measurements have proved that fibres from monodisperse fibrinogens are quasi-crystalline, straight and rigid. Fibres from polydisperse fibrinogens are less organised, curbed and less rigid. Finally, the mechanical properties of fibrin showed that the response of clots to deformation, as well as the scenarios of rupture are closely related to the structure, and consequently related to the profiles of polydispersity. This opens outstanding perspectives in many fields such the optimisation of fibrinogen’s use on dysfibrinogenemias or haemorrhages, tissue regeneration or the understanding between the abnormal structure of clots and cardiovascular diseases.

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