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A series of hybrid inorganic-organic composites were fabricated from a functionalized fluorinated polyimide and tetraethoxysilane (TEOS), tetramethoxysilane, methyltrimethoxysilane (MTMOS), and phenyltrimethoxy-silane (PTMOS) employing the sol-gel process. Polyimides were synthesized from 4,4'-hexafluoroisopropylidene dianiline (6FpDA) and 4,4'-hexafluoroisopropyl-idenediphthalic anhydride (6FDA) utilizing a solution imidization technique. The hybrid materials were synthesized by in-situ sol-gel processing of the aforementioned alkoxides and a fully imidized polyimide that was functionalized with 3-aminopropyltriethoxysilane. The gas permeability, diffusivity, and selectivity were evaluated for He, O2, N2, CH4, and CO2, while the physical properties of these hybrid materials were evaluated using several analytical techniques. The results from this study revealed that gas transport and physical properties were dependent on the type of alkoxide employed in the hybrid inorganic-organic material. Gas permeability was observed to increase with increasing gas penetrant size for MTMOS and PTMOS based hybrids, while TEOS based hybrids decreased gas permeability at all compositions. In general, MTMOS based hybrid materials had the largest increases in permeability, which was attributed to an increase in free volume. The TEOS based hybrid materials had the largest decreases in permeability, while PTMOS based hybrid materials had performance in between these alkoxides. Decreased permeability for the TEOS based hybrids was attributed to the formation of lower permeable material at a particle interface and coupled with increasing tortuosity. Results of PALS studies suggested that there was an increase in free volume and pore size for MTMOS based hybrids, while both TEOS and PTMOS based hybrids had decreases in both average pore size and free volume. The temperature dependence of permeation, diffusivity, and sorption were evaluated from 35oC to 125oC. These results suggested that there was a decrease in solubility for all hybrids employed in this study. Furthermore, increases in permeability for the MTMOS based hybrids were created by increased penetrant diffusion. Physical property studies revealed that the type of inorganic material incorporated into the hybrid influences the degree of swelling, bulk density, Tg, and thermal stability. Hybrid materials were also created employing 3,5-diaminobenzoic acid (DABA) in the synthesis of modified 6FDA-6FpDA polyimides in order to evaluate how improvements in inorganic and polymer compatibility influenced the gas transport properties. From this separate study, it was found that increases in both permeability and selectivity were possible. The mechanism attributed to this simultaneous increase in permeability and selectivity was the formation of a more permeable and selective interphase at the interface of an inorganic particle and the polymer matrix. In addition to these studies, 6FDA-6FpDA polyimide molecular weights were changed from 19.3K to 35.3K to probe its role on gas transport and physical properties. These studies revealed that permeability, diffusivity, and solubility increased with increasing molecular weight, while density decreased with increasing molecular weight. These results suggest that there is an increase in free volume with increasing 6FDA-6FpDA polyimide molecular weight. / Ph. D.

Cost-effective large-scale protein bioseparation will be the key issue for the biopharmaceutical industry in the coming years. Conventional protein purification techniques are severely limited in the sense that they give either good selectivity of separation at the cost of throughput or vice versa. Synthetic membrane based bioseparation techniques such as high-resolution ultrafiltration and membrane chromatography have the potential to combine high-throughput with high selectivity. This thesis focuses on approaches for obtaining both selectivity and throughput in membrane based protein bioseparation processes. Obtaining high selectivity is one of the main objectives in high-resolution ultrafiltration. This thesis reports a novel approach for flexibly manipulating the selectivity of protein separation using a dual-facilitating agent. In this study it has been shown for the first time that the selectivity of separation can be altered as desired, i.e. if required, the selectivity can be reversed and thereby smaller proteins can be retained and larger proteins can be made to permeate by using a dual-facilitating agent. The results are explained in terms of protein-protein electrostatic interactions and Donnan effect. This novel approach is expected to significantly increase the flexibility of carrying out high-resolution ultrafiltration. Membrane chromatography is based on the use of stacks of microporous synthetic membranes as chromatographic media. Due to lower binding capacities of commercial membranes in comparison to conventional beads for packed bed chromatography, the commercial success of membrane chromatography is largely limited to the flow-through applications. The study on membrane chromatography addresses the performances of new types of high-capacity macroporous gel-filled membranes for ion-exchange chromatography of proteins. This work demonstrates the suitability of using one of these novel membranes for fractionation of plasma proteins. Membrane fouling reduces product throughput and is considered a major problem in pressure driven membrane processes such as microfiltration and ultrafiltration. This thesis reports some significant contributions in the area of membrane fouling. A novel yet conceptually simple approach for modeling flux decline in constant pressure ultrafiltration, which takes into account the interplay between flux, concentration polarization and membrane fouling is discussed. Conventional fouling models account for the effects of concentration polarization and membrane fouling in a simple additive way. The basic hypothesis in the model discussed here is that flux decline in constant pressure ultrafiltration is self-attenuating in nature. This new approach is expected to be very useful in deciding the start-up conditions in membrane processes. Despite widespread use of in-line microfiltration for sterilization of therapeutic proteins prior to formulation, there has been no systematic study on fouling in such processes. Part of the fouling work in this thesis examines how resistance to filtration increases during in-line microfiltration of concentrated protein solution and the mechanism of protein fouling. It assesses the severity of fouling in terms of apparent reversible fouling and irreversible fouling. Traditional methods to measure the protein fouling resistances of membranes are time consuming and expensive. This thesis reports three protocols to compare the performance of microfiltration membranes for protein filtration. The first protocol, which is based on accelerated fouling in the dead end mode using pulsed injection technique is rapid, simple, and cost effective and gives valuable information about membrane performance. The remaining two protocols are based on the critical flux concept. / Thesis / Doctor of Philosophy (PhD)

A central issue in auditory research is how the auditory brain encodes complex stimuli. However, the process by which the auditory cortex interprets complex sounds during development and the extent to which cortical organization can be manipulated by complex stimulation is still undetermined. We have addressed this gap in the following three studies. First, we characterized the responses of cortical neurons in adult chinchillas to frequency-modulated (FM) stimulation. Next, we asked whether FM coding at the cortical level is innate or if its development is influenced by normal postnatal environmental experience. Finally, we investigated the effect of sustained neonatal FM sweep exposure on the development of cortical responses to tonal and FM stimuli. In our adult study, results indicated that >90% of sampled neurons were responsive to FM sweeps. The population preference was for upward FM sweeps and for medium to fast speeds ( 0.3 kHz/ms). Three types of temporal response patterns were observed: a single peak at sweep onset/offset (‘onset’) and a single peak (‘late’) or multiple peaks (‘burst’) during the sweep. ‘Late’ units expressed the highest direction and speed selectivity; ‘onset’ units were selective only for direction and ‘burst’ units were selective for neither direction nor speed. In our developmental study, our results showed a significant developmental increase in FM direction selectivity. However, FM speed selectivity appeared to be established early in development. In our developmental plasticity study, we hypothesized that constant FM exposure would increase the proportion of auditory neurons that are selectively responsive to the conditioning FM sweep. However, our results showed that while tonal response latencies increased after the exposure period, the conditioning stimulus had minimal effect on the FM direction preferences of cortical neurons and decreased overall neuronal FM speed selectivity. In conclusion, we suggest that chinchilla auditory cortical neurons are not uniquely activated by FM sounds but that FM responses are largely predictable based on how changing frequency stimuli interact with the receptive fields of these neurons. We also propose that the development of FM direction sensitivity is experience-independent and that perhaps normal acoustic experience is required to maintain FM speed tuning.

A central issue in auditory research is how the auditory brain encodes complex stimuli. However, the process by which the auditory cortex interprets complex sounds during development and the extent to which cortical organization can be manipulated by complex stimulation is still undetermined. We have addressed this gap in the following three studies. First, we characterized the responses of cortical neurons in adult chinchillas to frequency-modulated (FM) stimulation. Next, we asked whether FM coding at the cortical level is innate or if its development is influenced by normal postnatal environmental experience. Finally, we investigated the effect of sustained neonatal FM sweep exposure on the development of cortical responses to tonal and FM stimuli. In our adult study, results indicated that >90% of sampled neurons were responsive to FM sweeps. The population preference was for upward FM sweeps and for medium to fast speeds ( 0.3 kHz/ms). Three types of temporal response patterns were observed: a single peak at sweep onset/offset (‘onset’) and a single peak (‘late’) or multiple peaks (‘burst’) during the sweep. ‘Late’ units expressed the highest direction and speed selectivity; ‘onset’ units were selective only for direction and ‘burst’ units were selective for neither direction nor speed. In our developmental study, our results showed a significant developmental increase in FM direction selectivity. However, FM speed selectivity appeared to be established early in development. In our developmental plasticity study, we hypothesized that constant FM exposure would increase the proportion of auditory neurons that are selectively responsive to the conditioning FM sweep. However, our results showed that while tonal response latencies increased after the exposure period, the conditioning stimulus had minimal effect on the FM direction preferences of cortical neurons and decreased overall neuronal FM speed selectivity. In conclusion, we suggest that chinchilla auditory cortical neurons are not uniquely activated by FM sounds but that FM responses are largely predictable based on how changing frequency stimuli interact with the receptive fields of these neurons. We also propose that the development of FM direction sensitivity is experience-independent and that perhaps normal acoustic experience is required to maintain FM speed tuning.

The ecological impact of past extinction events is one of the central issues in paleobiology. In face of present environmental changes, a better understanding of past extinctions will enable us to identify the magnitude of biodiversity crises and their underlying processes. The Late Neogene was a time of extraordinary climatic reorganization, including Northern Hemisphere glaciation, the rise of the Central American Isthmus, and associated changes in environmental conditions. Therefore, the Late Neogene extinctions of marine molluscs of South Florida present an ideal platform to examine the interaction between environmental changes and biotic response. In the present study, three different aspects of the Late Neogene extinctions are examined: temporal diversity patterns, selectivity patterns, and the impacts of these extinction events on ecological interactions. In the first part of this study, the diversity pattern of marine bivalves of Florida during the Late Neogene. Using bulk samples enables to take account of varying sampling intensity and underlying relative abundance distributions in diversity estimation. Comparison of sample-standardized diversity analyses shows that both richness and evenness of marine bivalve community declined at the Tamiami - Caloosahatchee transition, which coincides with the proposed first phase of the Late Neogene extinctions at the end of the Pliocene. Although magnitude of biodiversity loss was severe during these late Neogene extinction events, extinction risk was non-randomly distributed across taxa. Selectivity analyses, a combination of both commonly used non-parametric tests and logistic regressions, suggest that abundance or local population size was positively related with survivorship during the late Neogene. As other biological or ecological traits can influence this observed relation between abundance and extinction vulnerability, multivariate approach is used to control for these traits. Even after effects of geographic range and feeding mode is considered, the positive relation between abundance and survivorship, which supports predictions from biological studies, is evident in case of these Late Neogene extinction events. While present analyses show that the increase in relative abundance of Chione is a major factor in driving changes in community compositions, interactions between Chione and its' drilling predators also varied during the Late Neogene. This study suggests that identification of predators is a critical part of evaluation of prey-predator interactions. When drill hole traces of two predatory gastropod groups, muricids and naticids, are differentiated based on a revised site selectivity criteria, temporal trend of prey size selectivity differs from previous reports. Both groups exhibit some changes in predatory behavior during phases of the Late Neogene extinctions, suggesting that previous hypothesis of prey turnover at the Caloosahatchee - Bermont transition cannot explain the observed temporal trends of prey size selectivity in the present study.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O experimento foi conduzido em condiÃÃes de sequeiro, no perÃodo de abril a setembro de 2010, na Fazenda Lavoura Seca, QuixadÃ, CE, no intuito de avaliar a eficiÃncia dos herbicidas diuron (diuron SC), pendimethalin (herbadox 500), e metolachlor (dual gold), em trÃs doses, no controle das plantas daninhas no consÃrcio mamona e feijÃo caupi e o efeito fitotÃxico desses herbicidas sobre a mamona e o feijÃo caupi. No consÃrcio utilizou-se a mamona, cv. BRS ENERGIA e o feijÃo caupi, cv. EPACE 10. As culturas foram plantadas em fileiras alternadas, com os arranjos seguintes: mamona em fileiras no espaÃamento 1,00 x 1,00 m, com uma fileira de feijÃo caupi entre duas fileiras de mamona. As fileiras de feijÃo caupi distaram 0,5 m das de mamona e as plantas dentro da fileira de 0,25 m. Os herbicidas e respectivas doses de ingrediente ativo avaliados foram: metolachor nas doses de (600 g ha-1, 1200 g ha-1 e 1800 g ha-1) diuron (1000 g ha-1, 2000 g ha-1 e 3000 g ha-1) e pendimenthalin (500 g ha-1, 1000 g ha-1 e 1500 g ha-1). Utilizou-se um delineamento experimental de blocos ao acaso, com arranjo fatorial e dois tratamentos adicionais (3x3+2) com 4 repetiÃÃes, exceto na anÃlise da matÃria seca das plantas daninhas onde utilizou-se um arranjo fatorial (3x3+1) com um tratamento adicional (testemunha sem capina). Os herbicidas diuron, pendimethalin e metolachlor foram nÃo seletivos a cultura da mamona causando atrasos na emergÃncia de plÃntulas, crescimento inicial, reduÃÃo dos estandes inicial e final, reduÃÃo da altura das plantas e decrÃscimos significativos na produtividade da cultura. No entanto, os mesmo herbicidas foram seletivos à cultura do feijÃo caupi, nÃo alterando a altura das plantas, nÃmero de vagens por planta e estande final. Quanto ao controle das plantas daninhas, avaliado atravÃs do peso da matÃria seca, os melhores resultados foram obtidos com o metolachor e diuron com destaque para a dose de 1800 g de i.a ha-1 do metolachlor, que reduziu de forma significativa o peso seco das plantas daninhas. / The experiment was conducted under rainfed conditions in the period April to September 2010, at Farm Lavoura Seca, QuixadÃ-CE, in order to evaluate the efficiency of diuron (Diuron SC), pendimethalin (herbadox 500), and metolachlor ( Dual Gold) in three doses on weed control in cowpea and castor bean intercropping and the phytotoxic effect of herbicides on the castor bean and cowpea. In the intercropping used the castor bean, cv. BRS ENERGY and the cowpea, cv. EPACE 10. The crops were planted in alternate rows, with the following arrangements: castor beans in rows with spacing 1.00 x 1.00 m, with a row of cowpea between two rows of castor oil. The rows of cowpea were far from castor 0.5 m and the plants within the row of 0.25 m. The herbicides and doses of active ingredient were: metolachor at doses (600 g ha-1, 1200 g ha-1 and 1800 g ha-1) diuron (1000 g ha-1, 2000 g ha-1 and 3000 g ha-1) and pendimenthalin (500 g ha-1, 1000 g ha-1 and 1500 g ha-1). We used a randomized block design, with factorial arrangement and two additional treatments (3x3 +2) with four replications, except in the analysis of dry matter of weeds where we used a factorial arrangement (3x3 +1) with a additional treatment (control without weeding). The herbicides diuron, metolachlor and pendimethalin were not selective castor bean crops causing delays in seedling emergence, early growth, reducing the initial and final stands, reduced plant height and significant decreases in yield. However, the same herbicides were harmless to the crop of cowpea, not changing the plant height, number of pods per plant and final stand. As for weed control as measured by the dry weight, the best results were obtained with diuron metolachor and especially a dose of 1800 g ai ha-1 of metolachlor, which significantly reduced the dry weight of weeds.

Polystyrene (PS) is one of the most important polymers in the plastic sector due to its inexpensive cost as well as many preferred properties. Its international market is expected to achieve $28.2 billion by 2019. Although PS has a high calorific value of 87 GJ tonne-1, there is no a practical method to manage its waste but landfill. As a result, the PS debris in the oceans has reached 70% of the total plastic debris. This issue is considered as the main economical and environmental drivers of converting polystyrene waste into renewable chemical feedstocks. The aim of this work is to develop a catalyst for converting PS into renewable chemicals under mild conditions. We introduce FeCu/Alumina with excellent catalytic activity to fully degrade polystyrene with 66% liquid yield at 250 °C. The GC/MS confirmed that the primary products are in the gasoline range. Next, we present the bimetallic FeCo/Alumina and successfully we have obtained 100% PS conversion and 90% liquid yield with maintaining the products selectivity. Later, the tri-metallic FeCuCo/Alumina was synthesized and showed 100% PS conversion and 91% liquid yield. Surprisingly, ethylbenzene was the major product in which 80 wt. % was achieved with excellent reproducibility. Furthermore, the real waste Styrofoam was thermally and catalytically degraded at 250 °C. Interestingly, a high styrene content of 78 wt. % was recovered after 30 minutes of the reaction under mild conditions. Keeping in mind that a good balance between acidity and basicity is required to convert PS into aromatic under mild reaction conditions catalytically. Finally, the performance of the catalysts was compared to literature reports and showed novel liquid yields. In conclusion, we have synthesized cheap, easy to scale up, and efficient catalysts to fully degrade PS into high liquid yields of aromatics with excellent selectivity.

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Call number: LD2668 .T4 1986 B42 / Master of Science / Psychological Sciences