Browsing by Subject "clay"
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Item Calcium Montmorillonite for the Mitigation of Aflatoxicosis and Gastrointestinal Inflammation(2014-08-06) Zychowski, Katherine EClays have been used for centuries as ?ancient medicine? for their therapeutic benefits. One particular clay, calcium montmorillonite, has historically been used as an anti-caking agent in animal feeds, but has also demonstrated the ability to bind toxins and alleviate infectious diarrhea. The full breadth of therapeutic applications and molecular mechanisms of montmorillonite is still unknown. Therefore, the purpose of this research was to explore novel therapeutic applications for NovaSil (NS), a calcium montmorillonite clay to reduce the risk of aflatoxicosis in farm-raised fish and alleviate gastrointestinal inflammation and dysbiosis in a mouse model of Crohn?s disease (CD). Aflatoxin B_(1) (AFB_(1)) is a fungal mycotoxin that commonly contaminates corn and peanut crops. It is produced by the fungi Aspergillus flavus and A. parasiticus during times of drought or due to improper post-harvest storage. Aflatoxin B_(1) is known to cause hepatocellular carcinoma, immunosuppression and growth stunting in several species. Recently, incorporation of plant-based alternatives into feed for farm-raised fish has become a trend, thereby increasing the risk for mycotoxin contamination. Inexpensive strategies to reduce AFB_(1) exposure are needed. Calcium montmorillonite clay, which is both inexpensive and abundant, has a dioctahedral structure that is known to sequester AFB_(1) in its negatively-charged interlayer, thereby reducing systemic bioavailability. There is also some evidence to suggest that calcium montmorillonite clays may possess gastrointestinal anti-inflammatory properties. NovaSil was used as a strategy to reduce the effects of AFB_(1) in Nile tilapia (Oreochromis niloticus) and red drum (Scieanops ocellatus). Juvenile tilapia and red drum were dosed with AFB_(1) and NS over the course of 10 and 7 weeks, respectively. Additionally, proinflammatory cytokine-clay binding was characterized using isothermal analysis, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Furthermore, a TNBS (2,4,6-Trinitrobenzenesulfonic acid)-colitis gastrointestinal mouse model was employed to study the anti-inflammatory properties of NS and its ability to protect the gut microbiome. Results suggest that NS can prevent aflatoxicosis in red drum at a 2% inclusion level over the course of 7 weeks. NovaSil also prevented some toxicity in Nile tilapia; however, these results were not significant. In vitro results also indicate that NS sorbs proinflammatory cytokines such as TNF? and IL-1? in its interlayers. Additionally, NS was found to reduce serum pro-inflammatory cytokine levels in TNBS-induced mice and reduce gut dysbiosis. These results could positively impact both human and animal populations with AFB_(1) exposure and/or chronic gastrointestinal inflammation.Item Characterization and Safety of Clays as Potential Dietary Supplements to Prevent Aflatoxicosis(2011-05-10) Marroquin-Cardona, Alicia 1979-Aflatoxins are toxic metabolites produced by Aspergillus flavus and A. parasiticus fungi. Aflatoxin B1 (AFB1) is the most toxic and is a potent carcinogen with antinutritional and immunosuppressive effects. Several natural outbreaks of poisoning have been reported in both animals and humans, with fatal consequences in some of the cases. Inclusion of clay minerals in the diet is a promising strategy to reduce the bioavailability of aflatoxins from contaminated foods. Several clay-based products are currently sold as ?mycotoxin binders? for addition in feeds, many of them lacking of detailed efficacy and safety data. Similarly, clays intended for human consumption in different countries also lack of safety studies, and for most of them the mineral composition is unknown. Earlier studies in our laboratory have shown that NovaSil clay (NS), a Ca-bentonite, is able to reduce the adverse effects associated with aflatoxin exposure in different animal species and recent human trials have confirmed its efficacy and safety. Most clays are derived from naturally-occurring deposits and batch-to-batch variations in composition, particle size, non-framework trace metal content and dioxin levels are expected. Therefore, objectives in this research were to determine the mineral composition, aflatoxin binding capacity and potential safety of ?mycotoxin binders? and edible clays for humans, and to investigate the mineral characteristics and safety of two potential aflatoxin adsorbents, a refined clay with more uniform particle size (UPSN) and a sodium bentonite (Na-BENT). Both clays have low dioxin/furans and heavy metals levels. According to mineralogical analysis, most of the ?binders? contained montmorillonite but the sorption capacities for AF varied. Most of the edible clays for humans contained kaolinite, mica and quartz, and they had low sorption capacities for aflatoxin. UPSN and Na-BENT had similar mineral characteristics and high sorption capacities for aflatoxin. After a 3-month rodent study using Sprague Dawley rats, no overall toxicity was observed for either clay. No changes were observed for most of the blood and serum biochemical parameters. Important findings included the increased serum Na, Ca, vitamin E and Na/K ratio and the reduction of serum K and Zn (in males) due to ingestion of the bentonites. Nonetheless, all parameters fell within the normal ranges reported for rats less than 6 months old and no trends of dose dependency were observed. We conclude that ingestion of low levels of bentonites does not present a health risk.Item Modeling of strain rate effects on clay in simple shear(Texas A&M University, 2006-08-16) Jung, Byoung ChanThe objective of this research is the development of a new constitutive model to describe the behavior of cohesive soils under time dependent loading. In the work presented here, the modified SIMPLE DSS model is expanded to account for the effects of strain rate on clays in simple shear conditions. The response of clay soils is highly dependent on the rate of strain for both effective stress path and stress-strain behavior. The undrained shear strength is strongly influenced by strain rate both in monotonic and cyclic simple shear tests. Nevertheless, the few available experimental results cover a very limited range of loading conditions and rates. The existing literature established that the soil response display a unique relationship between shear strength and log scale of strain rate. To include the effects of strain rate, the modified simple effective stress model starts with two assumptions: (1) a specific shear strength corresponds to a specific strain rate in a unique relation; and (2) the effect of strain rate does not change the failure envelope. The proposed model is developed from the original SIMPLE DSS model, based on an effective stress formulation in a reduced stress space, and utilizing concepts related to the framework of bounding surface plasticity. The proposed model evaluationwas carried out comparing model simulations with results of simple shear tests on Boston Blue Clay and San Francisco Young Bay Mud. The model capability is useful especially in strain rate dependent responses for both monotonic and cyclic behavior, including irregular loading and step-changed condition. It was found that undrained shear strength in simple shear is directly related to strain rate effects and the responses in cyclic test show the more rate dependent behavior than those in monotonic test. The proposed model is able to predict the increase in undrained shear strength for higher strain rate.Item Structure-property relationship in core-shell rubber toughened epoxy nanocomposites(Texas A&M University, 2004-09-30) Gam, Ki TakThe structure-property relationships of epoxy nanocomposites with inorganic layer-structure nanofillers have been studied to obtain the fundamental understanding of the role of nanofillers and the physics of polymer nanocomposites in this dissertation. Several polymer nanocomposite systems with modified montmorillonite (MMT) or ?-zirconium phosphate (ZrP) nanofillers were prepared with epoxy matrices of different ductility and properties. The successful nanofiller's exfoliations were confirmed with X-ray diffraction and transmision electronic microscopy (TEM). Dynamic mechanical analysis (DMA) on the prepared epoxy nanocomposites revealed the significant increase in rubbery plateau moduli of the epoxy nanocomposite systems above Tg, as high as 4.5 times, and tensile test results showed improved modulus by the nanofiller addition, while the fracture toughenss was not affected or slightly decreased by nanofillers. The brittle epoxy nanocomposite systems were toughened with core shell rubber (CSR) particles and showed remarkable increase in fracture toughness (KIC) value up to 270%. The CSR toughening is more effective at ductile matrices, and TEM observation indicates that major toughening mechanisms induced by the CSR addition involve a large scale CSR cavitation, followed by massive shear deformation of the matrix.Item The Effect of Physico-Chemical Factors on the Stability and Transport of Clay Particles(2012-07-16) Musharova, DaryaClays which exist in formations in the vicinity of injection and disposal wells is a worldwide problem in the petroleum industry. Clays can be categorized as two major groups: swelling clays, which include smectite group clays, and dispersing clays, which include the kaolinite groups of clays. Therefore, two basic damage mechanisms of clay minerals are swelling and dispersion. Both mechanisms cause pore plugging, and thus aggravate hydrocarbon ease of flow. In this thesis, the effect of temperature, injected water chemical composition, pH, and flowrate of the injected fluid were tested experimentally. Clay mineralogy, chemistry, and composition of the exchangeable cations were also examined. The existing theoretical models of evaluation of forces between clay particles and the rock matrix were used to quantify the interactions. Coreflood experiments were conducted to determine the effect of parameters such as variation of temperature, flowrate, pH, presence of various salts in working solution and their concentration. The results obtained from experimental and theoretical work show that clay minerals in sandstone formation are subject to fines migration and can cause a detrimental impact on the reservoir permeability. Every aforementioned factor has its influence on clays behavior and therefore, a degree of fines migration. The work accomplished summarizes and concludes what parameters sensitize clays migration. Moreover, recommendations for formation damage due to fines migration are given. The scope of work presented can be useful for petroleum engineers as well as geologists and clay mineralogists.