No description available.

No description available.

No description available.

No description available.

This dissertation presents the development of a new form of biomolecular material system which features interface lipid bilayers capable of hosting a wide variety of natural and engineered proteins. This research builds on the droplet interface bilayer (DIB) platform which first demonstrated that, through self-assembly, lipid-encased water droplets submersed in oil can be physically connected to form a liquid-supported lipid bilayer at the droplet interface. Key advantages of the DIB method over previous bilayer formation techniques include the lack of a supporting substrate which simplifies bilayer formation and the ability to connect many droplets to form `cell-inspired' networks which can provide a collective utility based on the compositions and arrangement of the droplets. The research present herein specifically seeks to overcome three limitations of the original droplet interface bilayer: limited portability due to lack of droplet support, the use of externally supported electrodes to electrically probe the network, and the requirement that in order to form DIB networks, aqueous volumes must be individually dispensed and arranged. The approach presented in this document is to provide increased interactions between the contained liquid phases and a supporting substrate in order to achieve both increased usability through refined methods of packaging and in situ interface formation which eliminates the need to create individual droplets. Physical encapsulation is defined as the the use of a solid substrate to contain both liquid phases such that the aqueous volumes are physically supported on one length scale (10-1000µm) while not inhibiting the self-assembly of phospholipids at the oil/water interface occurring on a much smaller length scale (1-10nm). Physically-encapsulated droplet interface bilayers are achieved by connecting lipid-encased droplets within a substrate that tightly confines the positions of neighboring droplets. A term called the packing factor is introduced to quantify the ratio of the aqueous volumes per the total compartment volume. Physically-encapsulated droplet interface bilayers formed in high packing factor substrate (30%) that also features integrated electrodes demonstrate all of the properties that unencapsulated DIBs exhibit (electrical resistances greater than 1GΩ, failure potentials between |200-300|mV, and the ability to host transmembrane proteins) but these confined assemblies can be moved, shaken, and even completely inverted. Additionally, a structured experiment to quantify the durability of interface bilayers shows that encapsulated and unencapsulated droplet interface bilayers can both survive 3-7g of lateral acceleration prior to bilayer failure, but have different modes of failure. Encapsulated DIBs tend to rupture, while unencapsulated DIBs completely separate. Physical encapsulation is also shown to permit the in situ formation of durable interface bilayers when the substrate is made from a flexible material. The importance of this approach stems from the fact that, by using the substrate to locally partition a single aqueous volume into multiple volumes, there is no need to arrange individual droplets. This method of bilayer formation is termed the regulated attachment method (RAM), since the separation and subsequent reattachment of the aqueous volumes is regulated by the opening and closing of an aperture within the flexible substrate. In this dissertation, a mechanical force is used to directly modulate the aperture dimension for controlling both the initial formation and final size of the interface. With the demonstrated advantages of portability and controlled attachment offered by physical encapsulation, encapsulated lipid bilayers are formed within a completely sealed flexible substrate. A key aspect of this final work is to demonstrate that both the organic and aqueous phases can be stabilized internally, creating a complete material system that features tailorable interface bilayers. / Ph. D.

Hop (Humulus lupulus L.) is an indispensable raw material in beer brewing because it can provide unique aroma and bitterness to beer products. With growing consumer interests in locally-sourced ingredients and increasing number of microbreweries, hop production is emerging in many non-traditional U.S. growing regions like Virginia (VA). However, the lack of understanding on aroma chemistry of regional hops limited their prosperity. Moreover, suitable postharvest drying and packaging practices for VA hop producers are not available. This dissertation aims to address above issues by investigating the aroma chemistry of VA hops by varieties (Cascade, Chinook), growing locations (Meadowview/Petersburg/Blacksburg, VA), smaller-scale drying practices (oven drying, dehydrator drying, freeze drying) and packaging materials (PA/PE, OPP/Foil/PE, EVOH). Our efforts also extended to the novel application of hop-derived ingredients in non-beer drinks to promote value-added products. Solid phase microextraction and solvent-assisted flavor evaporation were applied for aroma extraction. Gas chromatography-mass spectrometry-olfactometry was used with stable isotope dilution analysis and standard addition method for accurate quantitation of aroma-active compounds. A total of 33 and 36 aroma-active compounds were identified in all fresh and dried hops, respectively. Geraniol, β-myrcene, linalool, methyl octanoate and trans-α-bergamotene were found to be the predominant compounds. Aroma profiles varied significantly with growing locations for both varieties. Individual aroma contents and total essential oil were the highest in dehydrator-dried hops, indicating the advantage of dehydrator-drying being a suitable practice to retain aroma power in hops for most smaller-scale producers in VA. Most volatile compounds in different packaged dried hops showed decreased concentrations over 8-month storage, but the variation was not statistically significant. Hop essential oil (HEO) microcapsules, manufactured by spray drying using modified starch CAPSUL® as the wall material, showed high flavor retention and controlled aroma release. The addition of HEO microcapsules significantly improved the aroma recovery and stability in hop tea. Our findings enhance the understanding of the aroma chemistry in regional hops as affected by multiple pre- and postharvest factors. The novel non-beer application of HEO was also successfully demonstrated. / Doctor of Philosophy / Hop (Humulus lupulus L.) is an essential raw material in beer brewing because it can provide beer products with unique flavor. With the growing "buy local" trend among consumers in recent years, hop production is moving to many non-traditional growing regions in the U.S. including Virginia. This resulted in an increasing number of local craft breweries operating on a smaller scale across the state. However, the aroma characteristics of Virginia-grown hops are unclear. Specific suggestions related to hop postharvest processing and storage are also unavailable for regional smaller-scale hop producers. Therefore, this study aims to study the aroma characteristics of Virginia-grown hops by varieties, growing locations, smaller-scale drying practices and packaging strategies. The novel non-alcoholic application of hop essential oil (HEO, mixture of many hop aroma compounds) was also demonstrated in hop tea. The results showed that both fresh and dried Virginia hops had a complicated profile of aroma compounds that primarily exhibited typical citrus, woody and fruity attributes. Both Cascade and Chinook varieties harvested from Meadowview showed significantly higher aroma contents than hops harvested from the other two locations in Virginia. Most aroma compounds in hops were better preserved by dehydrator drying than freeze an oven drying. No significant change was observed in aroma compositions from hops packaged in three different materials after storage. Finally, HEO particles with enhanced stability were prepared by engineering approaches, which were finally added to hop tea bags for the evaluation of aroma-intensifying effects and storage stability. The results indicated an overall desirable characteristic for the obtained HEO particles. The addition of HEO particles could significantly enhance the aroma stability of hop tea products during storage. Overall, the findings from this study enable a better understanding of flavor chemistry of regional hops from various origins and demonstrated a successful application of HEO particles as a flavoring agent in non-beer products.

This dissertation works towards the larger objective of identifying and assessing the key features of molecular structure that lead to desired polymer processing performance with an ultimate goal of being able to tailor-make specific macromolecules that yield the desired processing response. A series of eight well-characterized, high-density polyethylene (HDPE) resins, with varying degrees of sparse long chain branching (LCB) content, is used to study the effect of both LCB content and distribution on the rheological and commercial processing response using the Pom-pom constitutive relationship. A flow instability known as ductile failure in extensional flow required the development a novel technique known as encapsulation in order to carry out shear-free rheological characterization. Ductile failure prevents the rheological measurement of transient stress growth at higher strains for certain strain-hardening materials. This reduces the accuracy of nonlinear parameters for constitutive equations fit from transient stress growth data, as well as their effectiveness in modeling extensionally driven processes such as film casting. An experimental technique to overcome ductile failure called encapsulation in which the material that undergoes ductile failure is surrounded by a resin that readily deforms homogeneously at higher strains is introduced. A simple parallel model is shown to calculate the viscosity of the core material. The effect of sparse long chain branching, LCB, on the film-casting process is analyzed at various drawdown ratios. A full rheological characterization in both shear and shear-free flows is also presented. At low drawdown ratios, the low-density polyethylenes, LDPE, exhibited the least degree of necking at distances less than the HDPE frostline. The sparsely-branched HDPE resins films had similar final film-widths that were larger than those of the linear HDPE. As the drawdown ratio was increased, film width profiles separated based on branching level. Small amounts of LCB were found to reduce the amount of necking at intermediate drawdown ratios. At higher drawdown ratios, the sparsely-branched HDPE resins of lower LCB had content film-widths that mimicked that of the linear HDPE, while the sparsely-branched HDPE resins of higher LCB content retained a larger film width. Molecular structural analysis via the Pom-pom constitutive model suggested that branching that was distributed across a larger range of backbone lengths serve to improve resistance to necking. As the drawdown ratio increased, the length of the backbones dominating the response decreased, so that the linear chains were controlling the necking behavior of the sparsely-branched resins of lower LCB content while remaining in branched regime for higher LCB content HDPEs. Other processing variables such as shear viscosity magnitude, extrudate swell, and non-isothermal processing conditions were eliminated as contributing factors to the differences in the film width profile. The effect of sparse long chain branching, LCB, on the shear step-strain relaxation modulus is analyzed using a series of eight well-characterized, high-density polyethylene (HDPE) resins. The motivation for this work is in assessing the ability of step-strain flows to provide specific information about a material's branching architecture. Fundamental to this goal is proving the validity of relaxation moduli data at times shorter than the onset of time-strain separability. Strains of 1% to 1250% are imposed on materials with LCB content ranging from zero to 3.33 LCB per 10,000 carbon atoms. All materials are observed to obey time-strain separation beyond some characteristic time, Ï k. The presence of LCB is observed to increase the value of Ï k relative to the linear resin. Furthermore, the amount of LCB content is seen to correlate positively with increasing Ï k. The behavior of the relaxation modulus at times shorter than Ï k is investigated by an analysis of the enhancement seen in the linear relaxation modulus, G0(t), as a function of strain and LCB content. This enhancement is seen to 1) increase with increasing strain in all resins, 2) be significantly larger in the sparsely-branched HDPE resins relative to the linear HDPE resin, and 3) increase in magnitude with increasing LCB content. The shape and smoothness of the damping function is investigated to rule out the presence of wall-slip and material rupture during testing. The finite rise time to impose the desired strain is carefully monitored and compared to the Rouse relaxation time of the linear HDPE resins studied. Sparse LCB is found to increase the magnitude of the relaxation modulus at short times relative to the linear resin. It is shown that these differences are due to variations in the material architecture, specifically LCB content, and not because of mechanical anomalies. / Ph. D.

Yes / Herein the potential of a relatively new water soluble fiber, resistant maltodextrin (RMD) to encapsulate grapefruit polyphenol, naringin, using spray drying was evaluated. Full factorial Design Of Experiments (DOE) for spray drying with two levels of fiber–naringin ratio and spray dryer inlet temperature was executed. Resulting powders were characterized with respect to particle size and morphology, crystallinity, thermal properties, moisture sorption and naringin aqueous solubility increase. A 60–80% encapsulation was achieved. Thermal and moisture sorption behaviors of these dispersions were found to be dominated by RMD. By varying fiber–naringin ratio and spray drying temperatures, naringin was able to disperse in amorphous form in RMD matrix, which led to 20–55% increase in aqueous solubility. Solubility enhancement was found to correlate positively with increasing fiber: naringin ratio and spray drying temperature due to multiple factors discussed in this study. In conclusion, fiber–polyphenol bicomponent nutraceutical was successfully developed based on a well-established encapsulation technology i.e. spray-drying.

Yes / Ultrasmall SnO2 nanocrystals as anode materials for lithium-ion batteries (LIBs) have been synthesized by bubbling an oxidizing gas into hot surfactant solutions containing Sn-oleate complexes. Annealing of the particles in N2 carbonifies the densely packed surface capping ligands resulting in carbon encapsulated SnO2 nanoparticles (SnO2/C). Carbon encapsulation can effectively buffer the volume changes during the lithiation/delithiation process. The assembled SnO2/C thus deliver extraordinarily high reversible capacity of 908 mA.h.g(-1) at 0.5 C as well as excellent cycling performance in the LIBs. This method demonstrates the great potential of SnO2/C nanoparticles for the design of high power LIBs. / National Natural Science Foundation of China (21103039), Anhui Province Natural Funds for Distinguished Young Scientists, https://bradscholars.brad.ac.uk/browse?order=ASC&rpp=20&sort_by=-1&etal=-1&offset=6150&type=authorResearch Fund for the Doctoral Program of Higher Education of China (20110111120008), Beijing National Laboratory for Molecular Sciences (BNLMS), and Deutsche Forschungsgemeinschaft Grant (DFG): H1113/3-5. C.Y. acknowledges the support from the “Thousand Talents Program” and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

Le développement de technologies plus propres et économes en énergie amène aujourd’hui l’industrie du raffinage à modifier ses stratégies de préparation de catalyseurs et à se tourner vers l'utilisation plus massive de catalyseurs hétérogènes plus actifs, sélectifs, stables et régénérables.Récemment une méthode originale a été développée par Dufaud et al. (J. Mater. Chem., 2009, 19, 1142-1150) pour encapsuler des polyoxométallates (POMs) dans les murs des silices mésoporeuses. Le projet de thèse a visé l’élaboration de nouveaux catalyseurs basés sur cette nouvelle méthodologie qui devrait conduire à des systèmes à haute teneur en métal actif Mo/W bien dispersé, avec une meilleure proximité spatiale entre le Mo/W et son promoteur. Afin de mettre en évidence cette proximité, différentes voies ont été envisagées :i) synthèse en deux étapes comportant l'encapsulation des POMs dans les murs de SBA-15, suivie d’une imprégnation à sec des promoteurs (Ni(NO3)2 ou Co(NO3)2)ii) synthèse en une seule étape comportant l'imprégnation à sec de POMs substitués Co3PCoMo11O40H, Ni3PNiMo11O40H, Co3/2PMo12O40 ou Ni3/2PMo12O40 iii) préparation traditionnelle par co-Imprégnation à sec d’une silice SBA-15 par une solution de POMs et Ni(NO3)2 ou Co(NO3)2, afin de mettre en évidence non seulement l'intérêt de la nouvelle méthode de préparation mais aussi le gain lié à l'utilisation de supports de type SBA-15 (par rapport aux supports aluminiques conventionnels) ayant des caractéristiques texturales aussi remarquables. L’effet du traitement de sulfuration sur ces solides a été étudié et l’évaluation des propriétés catalytiques de ces matériaux a été réalisée sur des molécules modèles en hydrogénation du toluène, hydrodésulfuration du thiophène et du 4,6-DMDBT. A partir des résultats obtenus, une des stratégies de synthèse a été optimisée, en vue de l'élaboration de matériaux encore plus actifs. / Economic growth in the developing countries over the past decade has increased the global demand for crude oil. It is projected that the global crude slate will become sourer, with a sulfur content above 1.3 wt%. An overall aim of policymakers is thus to ensure that transportation fuels do not surpass a sulfur content of 10 ppm. Several solutions are possible to achieve the nowadays goals, that affect either the process or the catalyst. The latter solution, which does not involve significant additional costs for refiners, is therefore the most studied. One way to improve the nowadays catalysts would be to increase the content of active metal (eg cobalt and molybdenum in the case of CoMo systems). Nevertheless, at higher metal loadings, the formation of refractory species such as CoMoO4 or Co3O4 by sintering during calcination and/or sulfidation steps has been reported for alumina-Supported catalysts. This PhD project is based on the development of new hydrotreating catalysts, through a 2-Step one-Pot method : synthesis of polyoxometalates-Containing mesoporous SBA-15 materials, followed by incipient wetness impregnation of active phase promoter. The encapsulation of these species within the silica matrix would prevent the agglomeration of large particles during sulfidation reactions and could thus lead to systems with high content of active metal well dispersed over the support. One aim of this study was to evaluate the potential of these catalysts in the hydrotreating of several feedstocks, such as diesel oil, gasoline or vegetal oil. A second objective was the understanding of the nature of the different interactions between the active phase precursors and the support, according to each preparation technique.The non-Promoted hybrid catalyst showed a better dispersion of the metallic phase in the oxide state, compared to the catalysts prepared by incipient wetness impregnation, which can be correlated with stronger interactions between encapsulated POM and silica functionalities, such as siloxanes and silanols, as evidenced by Raman spectroscopy. However, the wide-Angle XRD showed the presence of MoO3 crystallites. HRTEM analyzes of the sulfided catalysts showed different species on this catalyst: small MoS2 slabs and metal particles (∼ 1 nm) mainly in the walls but also on the surface of pores; curved MoS2 slabs at mesopores surface leaving the entrance of the pore free; MoS2 hanks blocking the pores.This catalyst showed a relatively low sulfidation rate (determined by XPS), which could be associated with the presence of refractory species already present before activation. Thus, the toluene conversion represented per MoS2 clearly showed the interest of the catalyst prepared by this innovative method, presenting an intrinsic activity two-Fold higher than that of the catalyst prepared by dry impregnation.The subsequent impregnation of the active phase promoter of the hybrid catalyst (Pr(NO3)2, Pr = Ni or Co; 4 <pH <6), resulted in a very heterogeneous distribution of species, which could be attributed to a POM destruction by the impregnation solution, that afterward led to the sintering of large clusters. However, the hybrid catalysts promoted showed improved catalytic performances when compared to the traditional alumina-Based catalysts, when nickel is used as a promoter. However, the sulfidation and promotion rates of these catalysts must be improved: the catalyst with the highest Ni content showed (i) a high Ni/Mo atomic ratio of 0.4, which would lead to a loss of active sites by excessive decoration, and (ii) the formation of species such as NixOwSy or NixSy, which could lead to the loss of active sites, dispersion and access to the active phase.Perspectives towards an enhanced HDT catalyst based on the findings of this project are:Milder synthesis calcination conditionsSulfidationPost-Synthetic treatment in order to introduce Ni and Mo in proximal vicinityRegeneration of HDT hybrid catalysts