Nanoscale multilayer coatings have high potential for numerous engineering applications because they can exhibit enhanced properties due to nanoscale effects and combine different properties from individual components. At present, scale effects on the mechanical behavior of multilayers are not well understood. Three multilayer nanocomposite systems, namely Al/Al2O3, Ti/TiN, and Cr/a-C, have been synthesized by using a dual-gun e-beam physical vapor deposition, to investigate the effect of layer thickness, the nature of components and their microstructures on the mechanical behavior. The deposited Al and Ti nanolayers were found to have polycrystalline fcc and hcp structure, respectively, the Cr and TiN layers had fine columnar bcc and fcc structure, respectively, and the Al2O3 and C layers were amorphous. Nanoscale effects were observed in all three systems with the metal layer thickness affecting significantly the mechanical behavior. The hardness response of the present systems can be described as a function of the metal layer thickness by a Hall-Petch relationship. A critical Al layer thickness of 40 nm, below which there was no further hardness enhancement, was found for the Al/Al2O3 multilayers. The critical Al layer thickness could be predicted by previous theoretical models. A hardness increase was observed down to a Ti layer thickness of 5 nm for the Ti/TiN system. The strengthening of the Ti/TiN multilayers was consistent with the macroyield maps based on a confined layer slip model. Hardness in the Cr/a-C system showed a continuous increase down to a Cr layer thickness of 20 nm. The fracture toughness of the monolithic ceramic phase was significantly improved by introducing a metal/ceramic multilayered structure. The wear behavior of the present multilayers was mainly controlled by the ceramic phase. The Cr/a-C multilayers achieved a low friction coefficient (~0.1) and low wear rate (~10-5 mm3/N m). The present research shows that properties can be tailored by appropriate selection of layer thickness and nature of individual components.

The availability of large amounts of genetic data from the mitochondrial DNA of species has created an unprecedented opportunity for the study of evolutionary processes. Being our closest relatives on the evolutionary tree the primates are a prime candidate for the study of evolutionary processes. The availability of large amounts of genetic data from the primates allows us to study and compare results from different phylogenetic reconstruction methods and to study and trace rudimentary evolutionary processes within the primate lineage. The evolutionary process studied here is the response of the nucleotide frequency ratios to single-strandedness of sites during mitochondrial DNA replication. This response curve is shown to be linear where the slope and intercept of the curve are related to the efficacy of the replication mechanisms and the binding capacity of the gamma-polymerase responsible for mitochondrial DNA replication. A Bayesian analysis of the response curves of the species is conducted and clustering schemes are developed to partition the species based on their response curves. These partitions are then mapped on the phylogenetic tree of the species to trace the evolution of the response curve within the primates.

Accurate hydrologic models are needed to aid engineers and researchers design, install and evaluate efficient and cost-effective agricultural water management systems to reduce risks associated with food production, and to reduce soil erosion and water pollution. One model used for the alluvial soils of Louisiana is DRAINMOD. This model does not accurately predict infiltration and runoff for the crusting-prone alluvial soils of Louisiana. The main goal of this study was to modify the current DRAINMOD model to incorporate the effects of rainfall intensity and deep chiseling to improve its estimation of infiltration and surface runoff. The second goal was to use information gained from the modified DRAINMOD model to assess how long farmers and environmentalists benefit from a particular deep chiseling operation and determine optimum deep chiseling frequency for given climatic conditions. A methodology for using a five-minute rainfall time increment subroutine within DRAINMOD was developed. Field experiments yielded an initial vertical saturated hydraulic conductivity of 2.0 cm/hr, a final vertical saturated hydraulic conductivity of 0.50 cm/hr and exponent of 0.03 cm-1 for model calibration. Deep chiseling modifications resulted in the DRAINMOD-STMAX, DRAINMOD-Ks and the combined DRAINMOD-Ks-STMAX models. DRAINMOD-STMAX, DRAINMOD-Ks and DRAINMOD-Ks-STMAX model improved surface runoff prediction by 57%, 73%, and 82% respectively in1995/96 season and by 27%, 45%, and 62% respectively in 1996/7 season. Using DRAINMOD-Ks-STMAX model, deep chiseling a Commerce silt loam soil increased infiltration by 9.4% and reduced runoff by 19.7% in 1995/96 season and by 5.7% and 19.2% respectively in 1996/97 season. All benefits resulting from deep chiseling were lost after 115 cm of rainfall since deep chiseling. Farmers should deep chisel once every year when annual rainfall is greater than 100 cm and once every two to three years when annual rainfall is less than 100 cm. Sixty percent or more of the maximum deep chiseling benefits had been lost by planting time; therefore, farmers need to deep chisel their fields just before planting. Further work is needed in the field to determine other factors affecting variation of Ks, to validate the DRAINMOD-STMAX, DRAINMOD-Ks and DRAINMOD-Ks-STMAX models, and to incorporate rainfall intensity subroutine.

Diamond-like carbon (DLC) films possess a combination of attractive properties and have been largely employed to modify the tribological behavior of materials. Nanocomposite, metal-containing DLC films are the new generation of these coatings providing tremendous potential to modify and tailor their properties expanding their applications in the field of nanotechnology. The present study investigates nanoscale effects on the tribological behavior of composite nanostructured DLC-based films and functional coatings. Three aspects were studied: (i) effect of Cr interlayer on a functionally gradient substrate; (ii) nanoparticulate Cr-containing DLC (Cr-DLC) films; and (iii) nanocomposite multilayered Cr/DLC coatings. Intensified plasma assisted nitriding produced a functionally graded interface and Cr layers exhibited best tribological behavior in their presence validating the theoretical concept. Nanocomposite Cr-DLC films were synthesized with Cr content in the range of about 0.1 at% to about 17 at%, on Si100 substrate. TEM studies showed defect free, dense and continuous film containing crystalline nanoclusters embedded in amorphous matrix. X-ray absorption spectroscopy showed that the chemical state and environment around Cr in films with ¡Ý1.5 at% Cr is similar to that in Cr-carbide. However, the environment around Cr in films with Cr ¡Ü0.4 at% is distinctly different with atomic clusters of Cr dissolved in the DLC matrix. Nanoindentation experiments showed that Cr-DLC films possess high hardness. Also, Cr-DLC films exhibit low friction (up to 12 at% Cr) and excellent wear resistance (up to ~5 at% Cr) with a low stable wear rate (10-7 mm3/N-m). In the multilayered nanocomposite films, DLC layers were found to be amorphous whereas Cr layers exhibit a nanocrystalline structure. Cr/DLC interfaces were found to be dense and continuous. Presence of DLC and a decrease of Cr layer thickness increases the hardness. This behavior was found to be consistent with the Hall-Petch formalism. Multilayered nanocomposite films with a significant volume fraction of DLC were found to possess low friction and low wear rate (10-7mm3/N-m). A common wear mechanism was found on both nanocomposite and multilayered systems. These nanocomposite and multilayered systems exhibited wear and friction properties comparable to those of DLC films, thereby expanding their scope in the field of nanotechnology.

Metal-containing, hydrogenated carbon films (Me-a-C:H) is a special class of nanocomposite films of particular interest since they can be multifunctional through the synergistic interaction of their individual components. Thus, nanocomposite thin films possess high potential in a wide field of engineering applications, especially in small scale devices. A series of multifunctional nanocomposite Co-a-C:H thin films have been synthesized by a hybrid chemical vapor deposition (CVD) and physical vapor deposition (PVD) process to uncover the relationship between synthesis, microstructure and properties. The effects of deposition parameters on the microstructural evolution and properties have been systematically studied. The results showed that the microstructure can be controlled through proper adjustment of the processing parameters, to produce Co in the shape of: nano particles, elongated particles, wormlike columns, self-assembled multilayers, self-assembled nano columns embedded in an amorphous a-C:H matrix. Self-assembly of Co nano columns in a-C:H is discovered. As-deposited Co-a-C:H thin films are composed of defect rich ε-Co encapsulated in a-C:H matrix. Regarding the properties, raising C content (reducing Co content) in the films improves their hardness and corrosion resistance and decreases friction and wear rate. All the Co-a-C:H films exhibit a low surface roughness. Nano columnar Co-a-C:H films show size-dependent magnetic behavior, such as superparamagnetic and perpendicular magnetism. Annealing studies reveal that the phase transitions of Co in Co-a-C:H film follow the sequence of Co-a-C:H film → (300 °C) ε-Co + δ ′Co2C → (343 °C) hcp-Co + δ ′Co2C → (407 °C) hcp-Co + graphite → (459 °C) fcc-Co + graphite. A mechanism and a zone diagram are presented to describe the microstructural evolution of Co-a-C:H films. Knowledge gained from this research allows the design and synthesis of nanocomposite Co-a-C:H films and other multifunctional systems of interest for new applications in the field of nanotechnology.

Cage molecules reversibly block the bioactivity of a target substrate molecule by a photolyzable covalent bond formed at a functional site of the target molecule. The attachment of cage molecules to DNA oligodeoxynucleotides (ODNs) to transiently block bioactivity, and site-specific restoration of bioactivity using targeted light exposure, would enable a new method of control for use in gene therapy, molecular/DNA computing, molecular biology, and drug delivery. The reaction of the cage molecule 1-(4,5-dimethoxy-2-nitrophenyl)diazoethane (DMNPE) with DNA ODNs in an batch reaction yields a mixture of products with varying degrees of caging. Purification and verification of the hypothesized site of DMNPE attachment are necessary for future applications of this technology to control DNA bioactivity with light. Size exclusion chromatography, high pressure liquid chromatography (HPLC), polyacrylamide gel electrophoresis (PAGE), and nuclear magnetic resonance (NMR) were performed on caged DNA samples. Alternatives to manganese dioxide (MnO2) as a DMNPE activator were investigated because MnO2 was found to interfere with NMR. Nickel peroxide (NiO2) was found to be an effective alternative. Increased caging was found to correspond with a broadening and small upfield shifts of 1-D ³¹P NMR resonances. 2-D heteronuclear multiple bond correlation (HMBC) NMR experiments successfully matched previous characterizations of the DMNPE site of attachment on caged ATP, and show crosspeaks between the ribose ring and phosphate moiety of ATP and DNA structures, but did not show a crosspeak between the DMNPE benzyl proton and DNA phosphate moiety. This may be due to bond angle or relaxation effects of the cage adduct. Because no phosphate attachment was discovered, base alkylation was evaluated by reaction of deoxynucleosides and DNA dimers with DMNPE. 2′-deoxynucleosides showed no caging under similar reaction conditions (pH 5.5). DNA dimers dTpT and dApA in those reaction conditions showed a caged product on thin layer chromatography plates, and dGpG and dCpC results also suggested some minimal product formation. Thus, the initial hypothesized site of DMNPE attachment at the phosphate backbone was retained. These results demonstrate useful techniques for future efforts in purification and characterization of caged nucleic acid species.

In the natural process of wet deposition, gas-water interfaces play an important role in the transport of chemical contaminants in the atmosphere via fog, rain and cloud drops. Evidences from several other works point out deviations in gas-liquid partitioning as predicted by Henrys law. Uptake and mass transfer of benzene, naphthalene, and phenanthrene was chosen to study in a falling droplet train apparatus. Higher droplet-to-vapor partition constant (KDV) was noted for diameters less than 200ìm and was attributed to surface adsorption and accumulation. Mass transfer of phenanthrene was dependent on gas-phase diffusion and mass accommodation at the interface, while the mass transfer of benzene was dependent on liquid phase diffusion and mass accommodation. Mass accommodation coefficients showed a negative dependence on temperature, resulting in lower partitioning at higher temperatures. In order to understand the influence of atmospheric oxidants such as ozone on mass transfer and uptake of organic vapors in water droplets, ozone was introduced into the modified droplet train apparatus. Ozone reacted with PAH vapor at the air-water interface, thereby decreasing the mass transfer resistance and increasing the rate of uptake of naphthalene into the droplet. A Langmuir-Hinshelwood reaction mechanism at the air-water interface satisfactorily described the surface reaction, where the surface reaction rate constant increased with decreasing droplet size. The presence of organic matter in the liquid phase resulted in a higher droplet-to-vapor partition constant due to both presence and absence of ozone in the reactor. Knowledge and observations from the laboratory scale setup were extended to field fogwater characterization. Various chemical properties and characteristics of fogwater were determined. Most of the chemical composition and make-up of fogwater was characterized due to near-surface local atmosphere. Concentration of certain pesticides and organic compounds were found in the fogwater far exceeding their aqueous solubility. The calculated KDV for the field samples were several orders of magnitude higher than bulk phase Henrys constant prediction. Higher organic compound concentrations were observed in smaller-sized fogwater than in larger-sized droplets. These conclusions support our laboratory observation of higher partitioning due to surface adsorption and due to presence of organic matter in the aqueous phase.

A methodology that combines high-resolution topographic mapping, field observations, subsurface evaluation, and geodetic data analysis has successfully located several fault-related geomorphic steps in an area of southwestern Louisiana once thought to be relatively devoid of such features. Comparison of height differences of benchmarks straddling these suspected fault-related steps shows that vertical displacement rates on faults in the study area ranged from about 2 mm/yr to as much as 6 mm/yr during the 1960s and 1970s. However, leveling data obtained as recently as January 2005 reveals that the majority of these faults are currently moving at rates of less than 1 mm/yr. This study identifies the presence of several previously mapped fault-related steps as well as some unidentified geomorphic features with the use of LIDAR (Light Detection and Ranging) digital elevation models and aerial photography. The majority of these topographic steps correlate well with upward projections of known subsurface faults, which suggests that they are of tectonic origin. Also, field observations have located offsets of roadways and damage to built structures due to the differential motion caused by active faulting. These lines of evidence, combined with the leveling data, suggest that the geomorphic features in the study area are the surface expressions of active faults that have moved during the past half-century. A possible cause for the accelerated fault slip rates computed for the 1960's and 1970's could be the substantial lowering of the piezometric surface that occurred due to increased subsurface fluid withdrawal. This suggests that in addition to the natural causes of faulting, anthropogenic activities may have also affected fault motion in this area of Louisiana.

Syntactic foams are light weight particulate composites that use hollow particles (microballoons) as reinforcement in a polymer resin matrix. High strength microballoons provide closed cell porosity which helps in reducing weight of the material. Due to their wide range of possible applications such as in aerospace and marine structures, it is desirable to modify the physical and mechanical properties of syntactic foams as per the requirements of an application. Various filler materials can be used to modify the foam microstructure to attain these desired properties. Compression tests have revealed that high density syntactic foams demonstrate poor damage tolerance and low fracture strain, when compared with low density syntactic foams, which exhibit higher damage tolerance and fracture strains. The present study deals with increasing the fracture strain and damage tolerance properties of high density syntactic foams. An approach of modifying the matrix resin with the incorporation of filler particles as a third phase is adopted, resulting in hybrid syntactic foam. Two types of high performance hybrid foam composites are developed using waste tire rubber particles and low cost nanoclay particle respectively. Such highly damage tolerant hybrid foams will be useful as sandwich core material in automobile, aerospace, and marine structures. An analytical study is performed in order to observe the behavior of microballoons in syntactic foams upon loading. All hybrid foams are characterized for compressive strength and flexural strength properties. Rubber hybrid foams are further characterized for hygrothermal properties. Mechanical properties of hybrid foams are compared with those of plain syntactic foams. Changes in properties are correlated with the change in structural composition due to incorporation of rubber and nanoclay particles respectively. High magnification Scanning Electron Microscopy (SEM) is used to study microstructure of all the specimens. Change in properties of rubber type hybrid foams due to change in the size of rubber particles is studied. The dispersion and intercalation of nanoclay particles in nanoclay hybrid foams is studied using Transmission Electron Microscopy and X-ray photoelectron spectroscopy. Deformation behavior of hybrid foams and pure syntactic foams are compared and correlated to the presence of different types of particles in them.

Rice bran oil was extracted using environmentally-friendly supercritical carbon dioxide at varying conditions. Experimental treatments included pressure (27.6, 41.4 and 55.2 MPa), temperature (40 and 60 oC) and flow rates (25, 45 and 65 g/min) of supercritical carbon dioxide. Extracts collected at different time intervals during 4-hour extraction runs in a 3-L extractor were analyzed for oil yield and antioxidants. Normal-phase HPLC was used for analyzing the extract for important antioxidant compounds of oryzanol, tocopherols, tocotrienols. Silica rich rice hull ash adsorbent was also incorporated in combined extraction-adsorption experiments under similar supercritical fluid conditions. Supercritical extraction yields of rice bran oil and antioxidants were compared with 6 -hour Soxhlet extraction using petroleum ether solvent. Total oil extract yields for SFE (17.26-18.52 %) and experiments conducted with ash (17.35-18.99 %) for the extraction conditions of higher pressure (55.2 MPa) and flow rates (65 g/min) were comparable to the ether extractable oil yield (17.88 %). Extract yield significantly increased (p<0.05) with an increase in pressure and flow rate. However, the temperature effect on extract yield was not significant. Antioxidant extraction significantly increased with increased pressure, but not with increased flow and temperature. These behaviors with pressure, flow and temperature were similar for oryzanol, tocopherols and tocotrienols. Rice hull ash adsorbent did not significantly affect oil yields, but did influence the antioxidants in the extract. A much greater ash adsorption effect for noted for oryzanol, which was different from the effect that was seen for of vitamin E components. A separate batch adsorption study carried out at different temperature (20, 30, 40 oC) for varied time intervals also showed similar adsorption behavior. Freundlich isotherms successfully described adsorption behavior of the antioxidant compounds in the batch study using rice bran oil-hexane miscella. Freundlich fitting parameters (k and 1/n) were used to plot Vanât Hoff- Arrhenius equations and calculate the change in enthalpy value (âH) due to adsorption of antioxidants. Goto et al. (1993) model was applied to extraction yield data and successfully characterized extraction behavior. Values of partition coefficient K and mass transfer coefficient Kp were calculated and reported.