Approved for public release; distribution is unlimited / The effects of radiation in GaAs solar cells has been extensively researched and the results of numerous investigation have yielded a considerable amount of information about the degradation in irradiated solar cells. This thesis establishes a novel method in which to use Silvaco's physically-based device simulator, ATLAS, to model the effects of radiation on solar cell output characteristics. A virtual model representing a single junction GaAs solar cell was created in ATLAS. The effects of radiation were modeled using carrier trapping statements representing the defects associated with various fluence levels of 1 MeV electron radiation which were characterized with Deep Level Transient Spectroscopy techniques. The resulting output characteristics of the virtual solar cell, illuminated with a simulated AM0 spectrum, were compared to published experimental measurements for GaAs solar cells of the same dimensions. The virtual solar cell demonstrated a good correlation between the measured and virtual solar cell output characteristics and accurate representation of the spectral response. Complete ATLAS and MATLAB codes are included in appendices. / Major, United States Marine Corps

CIVINS / The recent trend of using fine water mist systems to replace the legacy HALON-1301 fire suppression systems warrants further study into other applications of the water mist systems. Preliminary research and investigation indicates that fine mists (20-25 micro droplet size) may reduce peak overpressures of a shock wave traveling through a space. Such pressure reductions could be used to mitigate the destructive effects of a shock wave (initiated by an explosive device) traveling through a structure. Currently these blast mitigation effects have only been demonstrated in small-scale shock tube tests and computer simulations. Uncertainty exists as to the scalability of such a system. The intention of this research is to investigate the applicability of such a blast mitigation system for shipboard use. Study into the degree of mitigation necessary to make a system practical for shipboard installation was conducted. In addition, a theoretical study of the mechanisms of blast mitigation using water mists was completed. / CIVINS

Approved for public release, distribution unlimited / The flow around second-generation controlled diffusion blades in cascade at stall was examined experimentally through the use of a two-component laser-Doppler velocimeter (LDV). The experimental results were compared with computational fluid dynamics predictions in order to provide information that will allow for more exact design of advanced blades. Midspan blade surface pressure data were also collected over a range of Reynolds numbersbased on chord of 270,000 to 720,000. Pressure distribution plots verified that the blades were in the stalled condition. The LDV measurement surveys were taken at one inlet station, at three stations on the suction side of the blade, and at three stations in the wake.

Under the conditions of quasitransverse propagation of electromagnetic waves in a magnetoionic plasma, the effect analogous to Faraday rotation in the quasilongítudinal case (which we will call Faraday pulsation) can produce a large elliptical polarization of originally linearly polarized radiation. Therefore, the presence of elliptical polarization in the radiation cannot serve as a means for distinguishing between a synchrotron mechanism with high energy electrons and any other type of emission process in radio sources in which conditions suggesting quasi - transverse propagation (large magnetic fields) may take place. The Faraday pulsation has a wavelength dependence through which it can be identified.

PhD. (Chemistry) / This project assessed the toxicity of double-walled carbon nanotubes to three aquatic organisms belonging to different trophic levels, namely Pseudokirchneriella subcapitata (algae), Daphnia pulex (macro-invertebrate) and Poecilia reticulata (fish). Prior to the toxicity testing, the dry DWCNTs were characterised using scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. Dynamic light scattering was used to characterise DWCNT suspensions. Natural water parameters such as increased ionic strength (Ca2+ and Na+) and increased humic acid affected the agglomeration potential of DWCNTs in aquatic medium. Increased ionic strength increased the agglomeration of DWCNTs while humic acid decreased agglomeration. The study explored the lethal/effective concentrations and sublethal effects of DWCNTs on the three organisms. The LC50/EC50 of DWCNTs for the three organisms differed in order of magnitude with D. pulex being the most sensitive and P. reticulata being the least sensitive. The LC50 for D. pulex was 2.81 and 4.45 mg/L for pristine and oxidised DWCNTs, respectively. Pseudokirchneriella subcapitata had an average EC50 of 10.01 mg/L and 10.93 mg/L for pristine and oxidised DWCNTs, respectively. Poecilia reticulata had an LC50 of 113.64 mg/L and 214.0 mg/L for pristine and oxidised DWCNTs, respectively. Exploring the effects of natural water parameters such as humic acid and ionic strength revealed that the acute toxicity of DWCNTs to D. pulex and P. reticulata was increased with increasing humic acid concentrations in exposure media, but increased ionic strength decreased the toxicity of both pristine and oxidised DWCNTs. However, these water parameters all decreased the toxicity of DWCNTs to P. subcapitata. The acute toxicity of DWCNTs was found to be directly linked to their agglomeration state in aquatic systems. Humic acid decreased the hydrodynamic sizes of DWCNT agglomerates making the engineered nanomatrials (ENMs) more available to the organisms while the cations increased the hydrodynamic sizes of DWCNT agglomerates, thereby reducing the probability of interactions with organisms. Time-based survival plots revealed that for P. reticulata and P. subcapitata, there were steady mortality/growth inhibitions throughout the duration of the exposures. For D. pulex, however, the plots revealed that there was a high initial die-off, whereafter mortalities proceeded at different rates. An assessment of whether DWCNTs cause oxidative stress in the three organisms revealed that DWCNTs caused significantly high oxidative stress in D. pulex and P. reticulata but not in P. subcapitata. In D. pulex and P. reticulata, DWCNTs were found to also cause DNA damage. The sublethal toxicity of DWCNTs was affected differently by the humic acid and increased cation concentration in exposure experiments. The sublethal effects were linked to the mode of interaction between DWCNTs and organisms. In P. subcapitata, the interaction was mainly physical with DWCNTs entrapping the algal cells in agglomerates and depriving the algal cells of light for normal photosynthesis to take place. For the other two organisms, the interaction was through intestinal cells as the organisms ingested DWCNTs and through accumulation of nanotubes on the exterior or organisms. The intestinal cell/DWCNT interaction resulted in the excessive generation of reactive oxygen species (ROS) and led to the death of the organism. Humic acid induced the highest antioxidant responses in both D. pulex and P. reticulata and this led to increased DNA damage in both organisms. Increased ionic strengths induced increased antioxidant responses at some DWCNT concentrations but the DNA damage was not significantly increased. These results suggested that with humic acid, the ROS production was excessive and sustained and had an effect on the DNA. The ROS production in increased ionic strengths was not excessive and was not prolonged, reducing their impact on DNA. The use of three organisms to assess the toxicity of DWCNTs provided comprehensive information on the potential effects of these ENMs in the aquatic food chain. Moreover, a multi-tier approach provided information on the potential effect of DWCNTs on populations at sublethal concentrations.

The effect of ethanol on the stress response in rats was examined. Experimental animals were given 0.25 ml of 28 percent ethanol or 0.25 ml of water orally once a day, five days a week, for a period of twelve months and were then subjected to fifteen minute cold stress. Corticosterone levels in ethanol-treated males following stress were significantly lower (22 percent) than in the sham group. Adrenal weights in sham-treated females were significantly higher (15 percent) than in the ethanol group at the end of twelve months. Mortality in sham-treated males was significantly higher (60 percent) than in ethanol-treated males. The effects observed may be due to the sedative action of ethanol on cortical centers controlling the hypothalmus.

En este estudio se midió la microdureza Vickers del esmalte dental después de la exposición a tres bebidas industrializadas más consumidas en la ciudad de Lima y una bebida control, para evaluar el efecto erosivo de esta bebidas ácidas y su relación con la acidez titulable, el nivel de pH y el efecto buffer de las mismas. Se elaboraron 60 bloques de esmalte superficial de 2mm de espesor por 2-4mm de longitud; se colocaron en acrílico de curado rápido en moldes circunferenciales de 10mm de diámetro y 5mm de altura en diferentes colores (azul para la bebida carbonatada, anaranjado para la bebida refrescante, verde para la bebida isotónica y blanco para la bebida control; para poder diferenciarlos) los cuales se les dieron el paralelismo ente la superficie libre y la base del molde; luego se les dio un pulido tipo espejo para después ser llevados al microdurómetro Buehler donde se les midió la microdureza. Los datos obtenidos fueron analizados a través de la prueba estadística de TSTUDENT, ANALISIS DE VARIANZA ANOVA, TUKEY HSD, KRUSKAL WALLIS Y U DE MANN WHITNEY. Se concluyó que la microdureza superficial del esmalte disminuye significativamente luego de ser sometido a la acción de las bebidas ácidas estudiadas y que el efecto erosivo es inmediato y se incrementa con cada exposición. Se obtuvo como resultado que la bebida isotónica es más erosiva que las otras bebidas; y se concluyó que no hay una relación entre el efecto erosivo y los valores de pH, acidez titulable y efecto buffer las bebidas. / In this study we measured the Vickers microhardness of enamel after exposure to three industrialized beverages more consumed in the city of Lima, and a control beverage; we want to evaluate the erosive effect of the acidic beverages and their relation with the titratable acidity, the level of pH and buffer effect of this beverages. 60 blocks of surface enamel were made of 2mm thickness, and 2-4mm in length, were placed in fast curing acrylic circumferential mold of 10mm in diameter and 5mm in height, in different colors (blue for the carbonated drink, orange for the drink refreshing, green for the drink isotonic and white for the control beverage; to be differentiated); we gave them that the free surface being parallel with the base of the mold, then they were given a mirrorpolished for microhardness after that, they were being taken to Buehler where microhardness was measured. The data were analyzed by the statistical test T-STUDENT, ANALYSIS OF VARIANCE ANOVA, HSD TUKEY, YU WALLIS KRUSKAL WHITNEY MANN. It was concluded that the enamel surface microhardness decreases significantly after being subjected to the action of acidic drinks and the erosive effect is immediate and increases with each exposure. The result was that the isotonic beverage is more erosive than other drinks, and it was concluded that there is not a relationship between the erosive effect of pH values, titratable acidity and buffer effect of the beverages.

Superhydrophobicity refers to surfaces with extremely large water droplet contact angles (usually greater than 150°). This phenomenon requires a hydrophobic material with micro or nano-scale roughness. Superhydrophobic surfaces exist in nature (e.g. the lotus leaf) and can be produced synthetically. This project focuses on the development and characterization of superhydrophobic materials with tunable wettability (i.e. smart superhydrophobic materials). In this study, surfaces were prepared by electrospinning thin, aligned polystyrene fibers onto a piezoelectric unimorph substrate. Results showed electric field induced changes in substrate curvature, which produced corresponding changes in surface wettability. From experiments, an average change in water contact angle of 7.2° ± 1.2° with 90% confidence was observed in ~2μm diameter fiber coatings electrospun for 5 minutes with applied electric field. In addition, fiber coatings electrospun with equivalent deposition showed average electric field induced changes in WCA of 2.5° ± 0.92° for lower diameter fibers (~1μm) and 3.5° ± 1.37° for higher diameter fibers (~2μm) with 90% confidence.

The potential for human exposure to pesticides exists particularly for agricultural workers (i.e. migrant workers) and individuals within close proximity to pesticide-sprayed crops (i.e. those living on or near agricultural farms). Children, through biology and behavior, may be more susceptible and vulnerable to exposure to pesticides than adults. The purpose of this study was to examine young populations particularly at-risk for occupational or accidental exposure to pesticides and determine associated behavioral, emotional, and physical symptoms. A total of 444 students from two South Texas school districts completed questionnaires assessing level of risk of exposure to pesticides and were categorized into at-risk and low risk categories. Physical, emotional, and behavioral symptoms were obtained using the Youth Self-Report. Children who were at-risk demonstrated significantly higher scores on the Youth Self-Report (YSR) in the areas of anxious/depressed, attention problems, social problems, somatic complaints, thought problems, withdrawal, internalizing behaviors, and total problem behaviors than children who were at lower risk of pesticide exposure. Odds ratios were obtained and suggested that children in the at-risk category were more five times more likely to score in the clinically significant range on the Attention Problems subscale, and three times more likely to score in the clinically significant range on the Internalizing behavior composite. These findings suggest that children who may be at higher risk for pesticide exposure may also be at higher risk for physical, behavioral, and emotional problems compared to children who are at lower risk. This information is intended to benefit schools and health care professionals who work with rural or migrant populations involved in the agricultural trade. Future research will be needed to assess through biomarkers the degree of measurable pesticide exposure in comparison to parent reports, teacher reports, school achievement, neuropsychological testing, and medical records.

Microfluidic H-cells and surface enhanced Raman spectroscopy are capable of analysing the asphaltene content of petroleum. An H-cell is a microfluidic device that exploits the non-turbulent flow of fluids within a micrometre-dimensioned channel. Diffusive separation in an H-cell permits a liquid that is miscible with the sample matrix to be used as an extractant. It was demonstrated that n-hexane can be used as extractant to obtain an asphaltene-free fraction of oil. The difference between the UV-Vis adsorption spectra of the asphaltene-free oil and the oil sample can then be used to estimate its asphaltene content. This has been demonstrated for a range of oils with asphaltene content between 1-30% and API gravity values between 40-10°, thus liquid petroleum and bitumen can be rapidly assayed by an H-cell; similarly, asphaltene and carboxylic acid content of oil can be determined simultaneously when methanol is used as extractant. The results were shown to be comparable to assays achieved via the ASTM D4124 and ASTM D974 methods respectively. For the first time it was demonstrated that surface enhanced Raman spectroscopy, using a gold substrate and illumination at 514 nm, can detect extremely low concentrations of asphaltene. This was shown to be achievable for asphaltene and related materials at concentrations of 0.001 ppm. In addition, data also demonstrated that the core of the Raman-responsive units within asphaltene have crystallite sizes equivalent to the Raman-responsive units in kerogen (~3 nm). Both methods provide technological advances because they make it possible to detect asphaltene in small sample volumes, using smaller footprint instrumentation. The H-cell method would be extremely useful for appraising oilfield potential, record the attenuation of oil-spills and provide frequent geochemical data that can monitor these at point of need. Similarly, the SERS technique widens the field of application into areas previously inaccessible to current techniques such as the effect of low concentrations of asphaltene-like materials in ecological and living systems.