Survival of P. fluorescens 10586s FAC510 was studied in liquid culture and soil microcosms in the presence of the ciliate C. steinii and the flagellate Cercomonas sp. Both protozoa caused a reduction in bacterial viable cell concentration, however the ciliate caused a greater decrease in abundance. Starvation of the bacterial prey caused a reduction in grazing rates of both the ciliate and flagellate, indicating the lower nutrional quality of starved as opposed to non-starved cells. Manipulation of the physiological state of prey cells, by starvation, had much the same effect as observed when bacterial prey resources are reduced. Luminescence provided a valuable marker for monitoring P. fluorescens 10586s FAC510 in liquid culture and soil, since detection by luminometry provided a sensitive, rapid, and non-extractive technique for measurement of microbial activity. In the presence of C. steinii, bacterial activity increased, whilst predation by Cercomonas sp. caused a reduction. The different responses of the bacterial inoculum may reflect the divergent balance between bacterial turnover, leading to nutrient regeneration, and grazing strategies, which are selective of the two protozoa. The distribution of bacterial cells in the soil pore network was manipulated by adjustment of the antecedant matric potential prior to inoculation. The ability to predominantly place bacterial and protozan cells in specific pore size classes was confirmed by partial chloroform fumigation and resin impregnated sections of soil.

Thesis advisor: Larry W. McLaughlin / Thesis advisor: Mary F. Roberts / Nucleic acids are essential biological molecules for life. For example, deoxyribonucleic acid (DNA) is the main genetic information carrier; ribonucleic acid (RNA) plays a critical role in translation and transcription. These characteristics place nucleic acids as the fundamental genetic materials of a living system. Since over a century ago, intensive attempts have been made by researchers to study the nucleic acid properties. For chemists, it is particularly interesting and important to understand the relationship between structures and properties of nucleic acids. For instance chemical modifications can alter stability of nucleic acids, and consequently influence their biochemical behaviors. In this work, we began by investigation of a 5',6-cyclo-modified nucleic acid resembling the product of DNA oxidation, and then developed a library of cyclomodifications. Our research on their structures and properties indicated that by installing cyclo-modifications we might be able to add some properties, that were not observed in nature to nucleic acids. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Fatigue cracking is one of the fundamental distresses that occur in the life of a Hot Mix Asphalt Concrete (HMAC) pavement. This load induced distress leads to structural collapse of the entire pavement ultimately and can only be remedied by rehabilitation. There is the need, therefore, for a total understanding of the phenomenon to be able to counter its occurrence. The fatigue resistance of hot mix asphalt concrete (HMAC) has been estimated using approaches ranging from empirical methods to mechanistic-empirical methods to purely mechanistic methods. A continuum mechanics based approach called the Calibrated Mechanistic with Surface Energy (CMSE) measurements was developed at Texas A&M University and recommended after comparison with other approaches in predicting fatigue lives of two Texas HMAC mixtures. The CMSE approach which includes fundamental material properties such as fracture, aging, healing, and anisotropy has been shown to effectively model the parameters that affect the performance of HMAC pavements exposed to repetitive traffic loads. Polymer modified asphalt (PMA) improves pavement performance by providing additional resistance to the primary distresses in flexible pavements, including permanent deformation or rutting, thermal cracking, and fatigue cracking. In this research, the CMSE approach was utilized to estimate the fatigue resistance of HMAC fabricated with asphalts modified with Styrene-butadiene-Styrene (SBS) co-block polymer. These HMAC mixtures were fabricated from materials used on three different road sections in Texas and one test pavement in Minnesota. The CMSE approach was validated as an effective approach for estimating the fatigue resistance of HMAC mixtures with PMA. The effect of oxidative aging on the fatigue resistance of the HMAC mixtures was also verified. Oxidative aging of the mixtures resulted in a corresponding decrease in mixture fatigue resistance. In addition, for two HMAC mixtures with the same binder content and aggregate gradation, the mixture with the softer of the two Performance Grade (PG) binders exhibited greater fatigue resistance. The use of the Utility Theory revealed the possible effects of aggregate geometric properties on the HMAC mixture properties and consequently on their fatigue resistance.

In recent years an increased use of polymers has occurred to modify asphalt binders, mainly to decrease pavement rutting but also to improve binder failure strain in direct tension. Whereas all of these effects positively impact the durability of polymermodified pavements, a need exists to quantify these improvements and the duration in the presence of oxidative aging. This research evaluated the durability of polymer modified asphalt (PMA) through a number of determinations that included the characterization of the original binder property and pavement-aged binder for modified and unmodified binders. Changes in styrene-butadiene-styrene (SBS) polymer modified binder properties from oxidation were analyzed using dynamic shear rheometry, ductility, and force ductility. Previous literature reports using size exclusion chromatography showed that degradation of the molecular weight profile of SBS accompanied the loss of PMA ductility. Yet base binder embrittlement also occurred, as evidenced by ductility and force ductility. Testing aged PMA binders at higher temperatures to soften the base binder restored the polymer modulus to the force ductility measurements as did blending with a softer deasphalted oil. These measurements indicate that the more significant cause of PMA degradation with aging is base binder embrittlement rather than polymer degradation. Sixteen pavements in 11 Texas Districts, plus four MnRoad pavements were evaluated in order to obtain a more detailed profile of binder oxidation in pavements. Slices of each core provided detail on binder oxidation and air voids. The data confirm that binders can oxidize at least several inches into the pavement. However, oxidation also can be significantly slowed, apparently by very low accessible air voids. Interestingly, the data indicate that the air voids that are relevant to the binder at a specific depth of the pavement are those in the immediate vicinity of the binder; low air voids above or below the binder do not seem to significantly affect the binder oxidation rate. Furthermore, that binders oxidize inches below the surface shows that temperature conducts well into the pavement, consistent with a heat conduction model that is used to calculate ground temperatures as a function of depth.

ABSTRACT The purpose of this research was to investigate the modified photocatalyst(TiO2) from the heterogeneous photocatalysis of perchloroethylene(PCE) products distribution by different operating conditions using near UV/TiO2 hope that could enhance the PCE¡¦s conversion and mineralization rate and explore the reaction pathways.The modified photocatalyst of this research was completed with Ag/TiO2¡BAu/TiO2¡BPt/TiO2¡BWO3/TiO2 and AC/TiO2. The added species except activied carbon was 10 % weight of photocatalyst(TiO2) others the noble metal (sillver¡Bgold and platinum) and tungsten oxide(WO3) were 0.5 % weight of TiO2. Then the experiments were conducted by varying relative humidity(R.H.=0~60 %), oxygen concentration(0~21 %), and retention time(0.38~0.89 sec). Glass beds coated with modified Degussa P-25 anatase TiO2 were filled in a Pyrex glass reactor. TiO2 was illuminated by four 10 watts ultraviolet(UV) lamps. Results from QA/QC experiments indicated that PCE could not be photodegradated by near UV of wavelength 365 nm. However, It can be decomposed quickly through heterogeneous photocatalysis. And it also find that no modified photocatalyst would be envenomed in photoactivied continuance test. The best PCE conversion and mineralization rate of modified photocatalyst were WO3/TiO2 and AC/TiO2. The modified photocatalyst Ag/TiO2 were the same as TiO2 but Au/TiO2 and Pt/TiO2 were worse to TiO2. The highest converstion rate of PCE could top to 99.5 %¡F The experiment showed that PCE was decomposed as oxygen concentration and retention time increased. But a higher concentration of oxygen was not efficient on the increase of PCE conversion. The conversion ratio of PCE could be inhibited at higher relative humidities. The end products observed from UV/TiO2 heterogeneous photocatalytic reactions included CHCl3, CCl4, C2HCl5, C2Cl6, COCl2, CCl3CClO, Cl2, HCl, CO, and CO2. The major chlorinated compound was Cl2 when the photocatalytic reactions proceed at higher oxygen concentration and less humid conditions. As water vapor existed, the major chlorinated compound became HCl. The major product was CO2 during the entire experimental process of heterogeneous photocatalytic reactions.

Fatigue cracking is one of the fundamental distresses that occur in the life of a Hot Mix Asphalt Concrete (HMAC) pavement. This load induced distress leads to structural collapse of the entire pavement ultimately and can only be remedied by rehabilitation. There is the need, therefore, for a total understanding of the phenomenon to be able to counter its occurrence. The fatigue resistance of hot mix asphalt concrete (HMAC) has been estimated using approaches ranging from empirical methods to mechanistic-empirical methods to purely mechanistic methods. A continuum mechanics based approach called the Calibrated Mechanistic with Surface Energy (CMSE) measurements was developed at Texas A&M University and recommended after comparison with other approaches in predicting fatigue lives of two Texas HMAC mixtures. The CMSE approach which includes fundamental material properties such as fracture, aging, healing, and anisotropy has been shown to effectively model the parameters that affect the performance of HMAC pavements exposed to repetitive traffic loads. Polymer modified asphalt (PMA) improves pavement performance by providing additional resistance to the primary distresses in flexible pavements, including permanent deformation or rutting, thermal cracking, and fatigue cracking. In this research, the CMSE approach was utilized to estimate the fatigue resistance of HMAC fabricated with asphalts modified with Styrene-butadiene-Styrene (SBS) co-block polymer. These HMAC mixtures were fabricated from materials used on three different road sections in Texas and one test pavement in Minnesota. The CMSE approach was validated as an effective approach for estimating the fatigue resistance of HMAC mixtures with PMA. The effect of oxidative aging on the fatigue resistance of the HMAC mixtures was also verified. Oxidative aging of the mixtures resulted in a corresponding decrease in mixture fatigue resistance. In addition, for two HMAC mixtures with the same binder content and aggregate gradation, the mixture with the softer of the two Performance Grade (PG) binders exhibited greater fatigue resistance. The use of the Utility Theory revealed the possible effects of aggregate geometric properties on the HMAC mixture properties and consequently on their fatigue resistance.

Introduction: The Genetically Modified (GM) food, which is one of the fruit of the modern biotechnology, is closely related to people's lives. GM food, specifically, GM crops, also known as biotech food, are produced from genetically modified organisms (GMO), which use genetic engineering techniques to introduce, recombine and modify DNA. The safety of GM food still do not have final conclusion at present. Although GM food has been introduced into China for over 15 years, many of the surveys show that Chinese consumers‘ knowledge of GM food is relatively low comparing with other countries. In 2002, China‘s Ministry of Agriculture promulgated three regulations to manage the GMOs in China. The attitudes and acceptance of market for GM food have direct impact on the development of genetic engineering technique and government‘s policy making. This review aims to investigate cognition and attitudes of GM food among Chinese consumers; to investigate how the consumers react to the GM food labeling policy; to find out how factors such as knowledge about transgenic information, price of GM food would affect the consumption of GM food. Methods: Relevant studies published between January 2002 and May 2013 were searched and identified through NCBI, CNKI, and Google Scholar with a combination of keywords, such as “GM”, “China”, “attitude”, “knowledge”, and “willingness” both in English and Chinese. Studies regarding the average knowledge level, acceptance and willingness-to-pay (WTP) for GM food among Chinese consumers, and factors affecting the WTP were included. Results: Of 1032 papers identified, 9 articles fulfilling the selection criteria were included in this systematic review. Among the 9 articles, 7 were written in English, 2 in Chinese. Awareness and knowledge of GM food among Chinese consumers were still not satisfying. Given the potential risks, the public tended to hold divergent attitudes to GM food, which had significantly influenced the WTP. Socio-economic factors such as the number of children, and external factors such as information and price also affected the WTP. Among all the factors, positive attitudes (including willingness-to-accept WTA), and positive information about GM food have significant positive influence on the WTP of GM food, while consumer‘s number of children, price of GM food and negative information about GM food would reduce the purchase intention. Discussion: Positive attitudes (including willingness-to-accept WTA), and positive information have significant positive influence on the WTP of GM food, while increasing number of children and price of GM food and negative information would reduce the purchase intention. It is necessary to strengthen the comprehensive and objective propaganda of GM food and transgenic technology; enhance the management of GM food; plan and develop GM food industry with focus on low-income consumers for they are more willing to buy GM food. / published_or_final_version / Public Health / Master / Master of Public Health