Animal disease outbreaks either through deliberate terroristic act or accidental introductions present a serious economic problem. This work concentrates on the economics of choosing strategies to mitigate possible agricultural terrorism and accidental introduction events largely in the animal disease management setting. General economic issues and the economic literature related to agricultural terrorism broadly and animal disease concerns specifically are reviewed. Basic economic aspects, such as the economic consequences of outbreaks, costs and benefits of various mitigation strategies, and stochastic characteristics of the problem are discussed. A conceptual economic model is formulated to depict the animal disease outbreak related decision making process. The key element of this framework is the choice between ex ante versus ex post mitigation strategies. The decision of investing in preventative and/or responsive strategies prior to the occurrence of an event versus relying on response and recovery actions after an outbreak event needs careful consideration. Comparative statics investigations reveal that factors that affect this decision are event probability, and severity, as well as costs, benefits, and effectiveness of various mitigation strategies. A relatively simplified empirical case study is done analyzing the economic tradeoffs between and optimum levels of ex ante detection, as a form of prevention, and ex post slaughter, as a form of response. The setting chosen involves Foot and Mouth Disease management. Empirical investigation is done on the conditions under which it is economically more advantageous to invest in ex ante detection as opposed to relying just on ex post response. Results show that investment in ex ante activities becomes more advantageous as the probability and severity of an agricultural terrorism event increases, response effectiveness decreases, and costs of surveillance decrease. Also spread rate is found to play a key role in determining optimal combination of ex ante and ex post strategies with more done ex ante the faster the disease spread. Finally, an economic framework is posed for future work given availability of a more detailed epidemiologic model. Access to such a model will allow for incorporation of wider spectrum of strategies including numerous possibilities for prevention, detection, response and market recovery facilitation. The framework allows more localized options, multiple possible events and incorporation of risk aversion among other features.
The 1690 expedition led by Alonso de LeÃ³n into present day Texas proved to be a pivotal journey that had lasting effects on the development of Spains land north of the Rio Grande. This expedition established the first Catholic mission in the area. Also, La Salles abandoned settlement was burned, and several Frenchmen living among the Indians were captured and returned with the expedition party to Mexico. The bartering for the release of some of these Frenchmen resulted in a skirmish in which four native Indians were killed. In addition, De LeÃ³n chronicled a great amount of information about the land through which he traveled, leaving a lasting diary recording his experiences as well as offering a glimpse into the then unsettled lands in present day eastern Texas. The 1690 expedition diary exists in the form of six manuscripts, and their analysis is the focus of this thesis. No scholar has ever taken into consideration all six manuscripts when conducting research regarding this expedition, and therefore research conducted thus far is not thorough. A comparative analysis of these six manuscripts is undertaken in this thesis, and the manuscripts are classified as revised or unrevised. Foster (1997) was the first scholar to classify manuscripts of the 1690 expedition as unrevised and revised. He classified only the Beinecke manuscript as revised, but this thesis also incorporates two other revised manuscripts unknown to Foster, the Gilcrease 67.1 and Gilcrease 67.2. The unrevised manuscripts included in this study are the AGI, AGN, and BNMex manuscripts. Three semi-paleographic transcriptions of manuscripts of Alonso de LeÃ³ns 1690 expedition diary are also presented. The AGI and Beinecke manuscripts are transcribed and an in-depth comparative analysis of the unrevised and revised manuscripts is completed. This analysis presents the numerous discrepancies that exist between the two families of manuscripts. Also, a transcription of the Gilcrease 67.1 manuscript is included to present a document previously unknown to scholars. The findings of this thesis should be of interest to scholars in many different fields of study who have interest in this time period and this region of the U.S. Southwest.
Anahtar Kelimeler :
Alonso de LeÃ³n, Expedition Diaries, Texas, Semi-Paleographic Transcriptions, 1690
Recent research has demonstrated the use of electrical signature analysis (ESA), that is, the use of induction motor currents and voltages, for early detection of motor faults in the form of embedded algorithms. In the event of multiple motors energized by a common voltage bus, the cost of installing and maintaining fault monitoring and detection devices on each motor may be avoided, by using bus level aggregate electrical measurements to assess the health of the entire population of motors. In this research an approach for detecting commonly encountered induction motor mechanical faults from bus level aggregate electrical measurements is investigated. A mechanical fault indicator is computed processing the raw electrical measurements through a series of signal processing algorithms. Inference of an incipient fault is made by the percentage relative change of the fault indicator from the ÂhealthyÂ baseline, thus defining a Fault Indicator Change (FIC). To investigate the posed research problem, healthy and faulty motors with broken rotor bar faults are simulated using a detailed transient motor model. The FIC based on aggregate electrical measurements is studied through simulations of different motor banks containing the same faulty motor. The degradation in the FIC when using aggregate measurements, as compared to using individual motor measurements, is investigated. For a given motor bank configuration, the variation in FIC with increasing number of faulty motors is also studied. In addition to simulation studies experimental results from a two-motor setup are analyzed. The FIC and degradation in the FIC in the case of load eccentricity fault, and a combination of shaft looseness and bearing damage is studied through staged fault experiments in the laboratory setup. In this research, the viability of using bus level aggregate electrical measurements for detecting incipient faults in motors energized by a common voltage bus is demonstrated. The proposed approach is limited in that as the power rating fraction of faulty motors to healthy motors in a given configuration decreases, it becomes far more difficult to detect the presence of incipient faults at very early stages.
In this thesis analysis and design of a wide input range DC-DC converter is proposed along with a robust power control scheme. The proposed converter and its control is designed to be compatible to a fuel cell power source, which exhibits 2:1 voltage variation as well as a slow transient response. The proposed approach consists of two stages: a primary three-level boost converter stage cascaded with a high frequency, isolated boost converter topology, which provides a higher voltage gain and isolation from the input source. The function of the first boost converter stage is to maintain a constant voltage at the input of the cascaded DC-DC converter to ensure optimal performance characteristics with high efficiency. At the output of the first boost converter a battery or ultracapacitor energy storage is connected to take care of the fuel cell slow transient response (200 watts/min). The robust features of the proposed control system ensure a constant output DC voltage for a variety of load fluctuations, thus limiting the power being delivered by the fuel cell during a load transient. Moreover, the proposed configuration simplifies the power control management and can interact with the fuel cell controller. The simulation results and the experimental results confirm the feasibility of the proposed system.
Anahtar Kelimeler :
fuel cell, conditioner, DC-DC converter, digital control
A new technique, called the polymerization algorithm, is described for the hierarchical segmentation of polymerized volume data sets (PVDS) using the Lblock data structure. The Lblock data structure is defined as a 3dimensional isorectangular block of enhanced vertex information. Segmentation of the PVDS is attained by intersecting and merging Lblock coverings of the enhanced volumetric data. The data structure allows for easy compression, storage, segmentation, and reconstruction of volumetric data obtained from scanning a mammalian brain at submicron resolution, using threedimensional light microscopy (knifeedge scanning microscopy (KESM), confocal microscopy (CFM), and multiphoton microscopy (MPM)). A hybrid technique using the polymerization algorithm and an existing vectorbased tracing algorithm is developed. Both the polymerized and the hybrid algorithm have been tested and their analyzed results are presented.
Interference for adjacent wells may be beneficial to Coalbed-Methane production. The effect is the acceleration of de-watering which should lead to earlier and higher gas rate peaks. It is inherent that permeability anisotropy exists in the coalbed methane formation. It means that the placement of wells (wells configuration) has an effect on the development of coalbed methane field. The effect of Palmer-Mansoori Theory is increasing effective permeability at lower pressures due to matrix shrinkage during desorption. This effect should increase the gas recovery of coalbed methane production. Palmer and Mansoori model should be considered and included to coalbed methane reservoir simulation. These effects and phenomena can be modeled with the CMG simulator. A systematic sensitivity study of various reservoir and operating parameters will result in generalized guidelines for operating these reservoirs more effectively.
Anahtar Kelimeler :
Well Spacing, Permeability Anisotropy, and Palmer and Mansoori Model
The permeability of hot mix asphalt (HMA) is of special interest to engineers and researchers due to the effects that water has on asphalt pavement performance. Significant research has been done to study HMA permeability. However, most of the studies primarily focused on relating permeability to the average percent air voids in the mix. Such relationships cannot predict permeability accurately due to the different distributions of air void structures at a given average percent of air voids. Air void distribution is a function of many factors such as mix design, compaction method, and aggregate properties. Recent advances in X-ray computed tomography and image analysis techniques offer a unique opportunity to better quantify the air void structure and, consequently, predict HMA permeability. This study is focused on portraying permeability as a function of air void size distribution by using a probabilistic approach that was previously developed by Garcia Bengochea for soils. This approach expresses permeability as a function of the probability density function (pdf) of the air void size distribution. Equations are derived in this thesis to describe this relationship for laboratory specimens compacted using the linear kneading compactor (LKC) and Superave^TM gyratory compactor (SGC) as well as for field cores (labeled as MS). A good correlation exists between permeability and the pdf of the air voids that formed the flow paths (i.e. connected voids). The relationship between moisture damage, air void structure, and cohesive and adhesive bond energy is also investigated in this study. Moisture damage is evaluated by monitoring changes in mechanical properties due to moisture conditioning. The influence of air void structure on pore pressure is studied using a recently developed program at Texas A&M University that simulates fluid flow and pore pressure in a porous medium. The surface free energy of the aggregates and asphalt are calculated from laboratory measurements using the Universal Sorption Device (USD) and the Wilhelmy Plate method, respectively, in order to test the compatibility of the aggregates with the asphalt in the presence of water.
Anahtar Kelimeler :
hot mix asphalt, x-ray computed tomography, permeability
A new optical imaging modality has been developed for small animal in vivo imaging of near-infrared fluorescence resulting from fluorescent contrast agents specifically targeted to molecular markers of cancer. The imaging system is comprised of an intensified charge-coupled device (ICCD) for the detection of ultra-low levels of re-emitted fluorescence following the delivery of an expanded beam of excitation light. The design of the ICCD detection system allows for both continuous wave (CW) and frequency-domain modes of operation. Since the accurate acquisition of frequency-domain photon migration (FDPM) data is important for tomographic imaging, the imaging system was also validated using experimentally obtained FDPM measurements of homogenous turbid media and diffusion theory to obtain estimates of the optical properties characteristic of the media. The experiments demonstrated that the absorption and reduced scattering coefficients are determined least accurately when relative rel measurements of average light intensity IDC are employed either alone or in a rel combination with relative modulation amplitude data IAC and/or relative phase shift data rel . However, when FDPM measurements of are employed either alone or in rel combination with IAC data, the absorption and reduced scattering coefficients may be found accurate to within 15% and 11%, respectively, of the values obtained from standard single-pixel measurements; a result that suggests that FDPM data obtained from an ICCD detection system may in fact be useful in tomographic imaging. Furthermore, intensified-detection allows for sub-second exposure times, permitting the acquisition of dynamic fluorescence images immediately following administration of the contrast agent. Experimental results demonstrate that when coupled with a suitable pharmacokinetic model describing targeted dye distribution throughout the body, dynamic fluorescence imaging may be used to discriminate spontaneous canine adenocarcinoma from normal mammary tissue. A separate experiment demonstrates that pharmacokinetic analysis of dynamic fluorescence images enables one to estimate the rate constant governing Kaposis sarcoma tumor uptake of an integrin-targeted dye and integrin receptor turnover rate. The rate constant for uptake was calculated to be 0.16-sec-1 while the turnover rate of the integrin receptor was estimated to occur within 24-hours.
In the present study, we propose a computational model for the linear and nonlinear analysis of shell structures. We consider a tensor-based finite element formulation which describes the mathematical shell model in a natural and simple way by using curvilinear coordinates. To avoid membrane and shear locking we develop a family of high-order elements with Lagrangian interpolations. The approach is first applied to linear deformations based on a novel and consistent third-order shear deformation shell theory for bending of composite shells. No simplification other than the assumption of linear elastic material is made in the computation of stress resultants and material stiffness coefficients. They are integrated numerically without any approximation in the shifter. Therefore, the formulation is valid for thin and thick shells. A conforming high-order element was derived with 0 C continuity across the element boundaries. Next, we extend the formulation for the geometrically nonlinear analysis of multilayered composites and functionally graded shells. Again, Lagrangian elements with high-order interpolation polynomials are employed. The flexibility of these elements mitigates any locking problems. A first-order shell theory with seven parameters is derived with exact nonlinear deformations and under the framework of the Lagrangian description. This approach takes into account thickness changes and, therefore, 3D constitutive equations are utilized. Finally, extensive numerical simulations and comparisons of the present results with those found in the literature for typical benchmark problems involving isotropic and laminated composites, as well as functionally graded shells, are found to be excellent and show the validity of the developed finite element model. Moreover, the simplicity of this approach makes it attractive for future applications in different topics of research, such as contact mechanics, damage propagation and viscoelastic behavior of shells.
Dihydroorotase (DHO) is a zinc metallo-enzyme that functions in the pathway for the biosynthesis of pyrimidine nucleotides by catalyzing the reversible interconversion of carbamoyl aspartate and dihydroorotate. The X-ray crystal structure of the enzyme was obtained at a resolution of 1.7 Ã . The pH-rate profiles for the hydrolysis of dihydroorotate or thio-dihydroorotate demonstrated that a single group of DHO must be unprotonated for maximal catalytic activity. The pH-rate profiles for the condensation of carbamoyl aspartate to dihydroorotate showed that a single group from the enzyme must be protonated for maximal catalytic activity. The native zinc ions within the active site of DHO were substituted with cobalt or CADmium by reconstitution of the apo-enzyme with divalent cations. The ionizations observed in the pH-rate profiles were dependent on the specific metal ion bound to the active site. Mutation of Asp-250 resulted in the loss of catalytic activity. These results are consistent with the formation of a hydroxide bridge between the two divalent cations that functions as the nucleophile during the hydrolysis of dihydroorotate. In addition, Asp250 is postulated to shuttle the proton from the bridging hydroxide to the leaving group amide during dihydroorotate hydrolysis. The X-ray crystal structure of DHO showed that the side-chain carboxylate of dihydroorotate is electrostatically interacting with Arg20, Asn-44 and His-254. Mutation of these residues resulted in the loss of catalytic activity, indicating that these residues are critical for substrate recognition. The thioanalog of dihydroorotate, (TDO) was found to be a substrate of DHO. A comprehensive chemical mechanism for DHO was proposed based on the experimental data presented in this dissertation. Armed with this understanding of the structure-function relationship of DHO, a rational approach was used to alter the substrate specificity of the enzyme. The R20/N44/H254 mutant of DHO was obtained and found to have increased activity on dihydrouracil compared to the wild-type enzyme. The sequence of the gene PA5541 from Pseudomonas aeruginosa has a glutamine at a position where most active DHO proteins have a histidine residue. Results from the characterization of PA5541 indicate that it is a functional DHO.
Many intervention methods theoretically have the potential to eliminate microorganisms. However, they do not perform efficiently once applied to fruits and vegetables. In this study Salmonella Typhimurium LT2 and hydrogen peroxide (H2O2) were used as model systems on 6 different types of produce to determine the effect of produce surface characteristics on sanitizer effectiveness. Microbial attachment on produce surfaces was induced after 3 h of drying at 24Â°C and high relative humidity (RH). Afterwards, produce was stored for 3 subsequent days and washed with sterilized tap water for 5, 10 and 15 minutes to separate weakly from strongly attached microorganisms from the produce surface. The strongly attached microorganisms were then treated with 3% H2O2 for 1, 3, and 5 minutes. These results were compared to the log reduction curves obtained with a pure liquid culture and 3% H2O2. Additionally, contact angle of water and diiodomethane on each type of surface were measured and used as indicator of wettability, and for calculating surface tension characteristics of the produce surfaces. Then these surface characteristics were related to the bacterial attachment and population reduction values obtained after applying the treatments. In general, the geometric mean equation was the most useful in predicting the surface tension values of produce surface and the polar and non-polar components of produce surface tension. Our results suggest that surface properties, such as roughness and surface tension of fruits and vegetables are important factors limiting decontamination. These surface properties allow the formation of micro-air pockets within the rough surface, thus contributing to create a protective environment for microorganisms and reducing the effectiveness of the chemical aqueous based intervention methods applied. Wettable surfaces (water contact angle < 90Â°) allowed more bacteria to attach after the washing and H2O2 chemical treatments. Roughness and surface polarity are intrinsic characteristics of produce surfaces which affect wettability and the spreading and penetration of the sanitizer treatment on the produce surface. Rough surface and porosity, considered an extreme case of roughness, enhance a deeper cell internalization and a protective environment for bacteria.
Anahtar Kelimeler :
Chemical methods, microorganism elimination, produce surfaces
Conditioning geologic models to production data and assessment of uncertainty is generally done in a Bayesian framework. The current Bayesian approach suffers from three major limitations that make it impractical for field-scale applications. These are: first, the CPU time scaling behavior of the Bayesian inverse problem using the modified Gauss-Newton algorithm with full covariance as regularization behaves quadratically with increasing model size; second, the sensitivity calculation using finite difference as the forward model depends upon the number of model parameters or the number of data points; and third, the high CPU time and memory required for covariance matrix calculation. Different attempts were used to alleviate the third limitation by using analytically-derived stencil, but these are limited to the exponential models only. We propose a fast and robust adaptation of the Bayesian formulation for inverse modeling that overcomes many of the current limitations. First, we use a commercial finite difference simulator, ECLIPSE, as a forward model, which is general and can account for complex physical behavior that dominates most field applications. Second, the production data misfit is represented by a single generalized travel time misfit per well, thus effectively reducing the number of data points into one per well and ensuring the matching of the entire production history. Third, we use both the adjoint method and streamline-based sensitivity method for sensitivity calculations. The adjoint method depends on the number of wells integrated, and generally is of an order of magnitude less than the number of data points or the model parameters. The streamline method is more efficient and faster as it requires only one simulation run per iteration regardless of the number of model parameters or the data points. Fourth, for solving the inverse problem, we utilize an iterative sparse matrix solver, LSQR, along with an approximation of the square root of the inverse of the covariance calculated using a numerically-derived stencil, which is broadly applicable to a wide class of covariance models. Our proposed approach is computationally efficient and, more importantly, the CPU time scales linearly with respect to model size. This makes automatic history matching and uncertainty assessment using a Bayesian framework more feasible for large-scale applications. We demonstrate the power and utility of our approach using synthetic cases and a field example. The field example is from Goldsmith San Andres Unit in West Texas, where we matched 20 years of production history and generated multiple realizations using the Randomized Maximum Likelihood method for uncertainty assessment. Both the adjoint method and the streamline-based sensitivity method are used to illustrate the broad applicability of our approach.
One of the most toxic environmentally mobile compounds found in water is arsenic. It has been used as a pesticide to control insects, fungi, weeds and rodents since the early part of this century because of its high toxicity. Sorption of toxic metals onto a metal oxy-hydroxide is the most popular and practical arsenic removal method from contaminated water. Water treatment with oxy-hydroxides creates arsenic containing residuals, which are usually disposed of in landfills. To prevent leaching, stabilization of the solid residuals is required. It has been reported that calcium may inhibit arsenic desorption and/or benefit arsenic sorption. The objective of this investigation is to assess arsenic leaching in the presence of calcium and phosphate ions at extreme pH. Two hypotheses have been identified to explain the decrease in soluble arsenic in the presence of calcium. One explanation is that arsenic reacts with calcium to form calcium arsenic solids. The second hypothesis is that calcium affects the surface properties of the oxy-hydroxide solid in solution. Results show that calcium enhances the removal by iron oxides and prevents the leaching of arsenic from the residuals. Isotherm experiments show that arsenic adsorption can be described as occurring on nonporous powders or powders with pore diameters larger than micro-pores. Physically, with increase in adsorbate concentration, second and more layers are completed until saturation when the numbers of adsorbed layers becomes infinite. Further, experimental data were fitted to a Brunauer, Emmett and Teller isotherm (BET) model which assumes the initial layer can act as substrate for further adsorption. Finally, calcium-arsenic and calcium-phosphate solids were predicted to be formed by Visual MINTEQ modeling program. Nevertheless, from the x-ray diffraction output calcium-arsenic or calcium-phosphate solids were not identified. Because no calcium arsenate solids were found it was concluded that calcium affects the surface properties of the oxy-hydroxide solids in solution. Increasing the pH produces negative surface charge, which in turn increases repulsion between the negatively charged hydrated arsenate ions and the Fe(OH)3 surface. CalciumÂs positive charge might neutralize this effect enhancing the sorption of arsenic onto the oxy-hydroxide. Also, it was concluded that the competition between arsenic and phosphate was reduced by the same mechanisms.
Anahtar Kelimeler :
arsenic leaching, water treatment, arsenic waste, iron oxide absorption, drinking water
There are two main portions to this study. In the first portion (Chapters I-III) we identify policies, procedures, programs, and pedagogical practices in public school districts in Texas that increase levels of college preparation among black and Hispanic students across a range of educational settings (rural, suburban, and urban). We identify these practices by interviewing school administrators at twenty-two school districts throughout the state. The school districts were selected by using education production function models to identify the highest and lowest performing school districts on a variety of college preparation measures. The first portion of the study is largely descriptive and qualitative in orientation. In the second portion of the study we identify high college preparation levels among minority students as a positive externality. Because college attendance benefits students as individuals, regardless of the beneficial aspects of college attendance for society at large, students, parents, and others will request that school districts increase college preparation levels to some degree. However, given the nature of positive externalities, we explore the possibility that the reason why some school districts have higher college preparation levels among minority students than others is that they are led by an official policy-maker (the superintendent) who is committed to acting in the long-term interests of society (in other words, whose representational style is to act as a trustee). The second portion attempts to extend the causal chain back one link by exploring the possibility that superintendent representational style affects the types of policies, procedures, programs and pedagogical practices adopted and the districtÂs commitment to implementing them, which in turn affects college preparation levels among minority students. The relationship between superintendent representational style and minority student preparation for college is tested using two data sources: a survey of public school superintendents throughout Texas gathered by the Texas Educational Excellence Project and college preparation measures gathered by the Texas Education Agency for all public schools in Texas.
Anahtar Kelimeler :
Hispanic student college preparation, Black student college preparation, superintendent representational style
This work presents a novel slack management technique, the Service Rate Based Slack Distribution Technique, for dynamic real-time distributed embedded systems targeting the reduction and management of energy consumption. Energy minimization is critical for devices such as laptop computers, PCS telephones, PDAs and other mobile and embedded computing systems simply because it leads to extended battery lifetime. Such systems being power hungry rely greatly upon the system design and algorithms for processing, slack and power management. This work presents an effcient dynamic slack management scheme for an energy aware design of such systems. The proposed Service Rate Based Slack Distribution Technique has been considered with two static(FCFS, WRR) and two dynamic(EDF, RBS) scheduling schemes used most commonly in distributed systems. A fault tolerance mechanism has also been incorporated into the proposed technique inorder to use the available dynamic slack to maintain checkpoints and provide for rollbacks on faults. Results show that in comparion to contemporary techniques, the proposed Service Rate Based Slack Distribution Technique provides for about 29% more perfor-mance/overhead savings when validated with real world and random benchmarks.
Anahtar Kelimeler :
real-time, peak power, slack, periodic service rate
This paper uncovers the relationship between stock markets and exchange rates in seven countries by employing stable aggregate currency (SAC) for the period of 1973- 2004. Ordinary Least Squares (OLS) regression, time series methods, and directed acyclic graphs are applied to the daily data on stock market indices and exchange rates. The findings based on regression analysis show that exchange rate exposure of stock markets is statistically significant when stock indexes in SAC are used. Using an innovation accounting technique, we confirm that stock markets and exchange rates are correlated. Moreover, in most cases stock markets are more exogenous than foreign currency markets, which explains the relatively high percentage of uncertainty in the foreign currency market. Overall, SAC-based models give relatively more accurate and robust results than those which employ stock indices in local currencies, because it is more accurate to convert both variables into the same denominator.
Anahtar Kelimeler :
Stock Markets, Exchange Rates, Time Series Analysis, Directed Graphs
The objective of my research is to identify and analyze the techniques of exaggeration, simplification, and abstraction used by caricature and cartoon artists. I apply these techniques to an expressive 3D modelling process which is used to create building caricatures. This process minimizes the number of unimportant details and increases the recognizability of the buildings. Additionally, the building caricature process decreases the time spent modelling the buildings and reduces their overall file sizes. The building caricature process has been used to create other building caricatures, as well as interactive visualizations and 3D maps of the Texas A&M University campus.
The endocrine system, specifically relating to sex hormones, and genetic material can be targets of environmental contaminants. Environmental contaminants in the Rio Grande region may originate from industrial or agricultural processes and growing populations lacking proper water and sewage infrastructure. Cliff (Petrochelidon pyrrhonota) and cave (P. fulva) swallows breeding near the Rio Grande were selected to monitor aromatase activity alterations and DNA damage. Swallows were sampled at six sites along the Rio Grande from Brownsville to Laredo, and a reference site (Somerville) 350 miles north of the Rio Grande. DNA damage, based on nuclear DNA content, was determined by flow cytometry. A significantly larger mean half peak coefficient of variation (HPCV) of DNA content in contaminated sites compared to a reference site reflects possible chromosomal damage. No detectable HPCV differences were observed in cave swallows among locations, notwithstanding the presence of mutagenic contaminants. Selenium may provide a protective role against genetic damage. However, cliff swallows from Laredo had significantly higher HPCV values than those from Somerville. DNA damage could be attributed to metals and polycyclic aromatic hydrocarbons released near Laredo. Brains and gonads, two estrogen-dependent organs, were tested for aromatase activity with a tritiated water method. Brain aromatase activity was higher, though not always statistically, for male cave and male and female cliff swallows. Dichlorodiphenyldichloroethylene (DDE) may play a role in the increased activity. Female cave swallows in Llano Grande appeared to have a greatly depressed brain aromatase activity, possibly attributed to past human use of toxaphene. Testicular and ovarian aromatase activity in cliff and cave swallows from Rio Grande was higher than in those from Somerville, though not always significantly. DDE, atrazine, sewage treatment plant contaminants (phthalates, alkylphenols, ethynylestradiol), metals, or other pollutants could play a role in the increased gonadal activity. Increased aromatase activity, in association with contaminants, may be easier to detect in testes of male birds which normally exhibit low levels of estrogen. Siterelated contaminants may be playing a role in DNA damage and aromatase alterations. This is the first known study which uses aromatase activity as an endocrine disruptor indicator in wild birds.
The A-cluster of acetyl-CoA synthase (ACS) catalyzes the formation of acetyl- CoA from CO, coenzyme-A, and a methyl group donated by a corrinoid iron-sulfur protein. Recent crystal structures have exhibited three different metals, Zn, Cu, and Ni, in the proximal site, which bridges a square-planar nickel site and a [Fe4S4] cubane. Contradicting reports supported both the nickel and copper containing forms as representing active enzyme. The results presented here indicate that copper is not necessary or sufficient for catalysis and that copper addition to ACS is deleterious. Several proposed mechanisms exist for the synthesis of acetyl-CoA, the two most prominent are the ÂparamagneticÂ and ÂdiamagneticÂ mechanisms. The ÂdiamagneticÂ mechanism proposes a two electron activation that precedes methylation to produce an EPR silent Ni2+-CH3 species. This then reacts with CO and coenzyme-A to form acetyl- CoA and regenerate the starting species. The ÂparamagneticÂ mechanism assumes a one electron activation prior to the methylation of the paramagnetic Ni1+-CO state to form an unstable Ni3+-acetyl species. This is immediately reduced by an electron shuttle. Results are presented here that no shuttle or external redox mediator is necessary for catalysis. This supports the ÂdiamagneticÂ mechanism, specifically that a two-electron reductive activation is necessary and that the Ni1+-CO species is not an intermediate. The two-electron reductive activation required by the ÂdiamagneticÂ mechanism results in an unknown electronic state. Two proposals have been made to describe this form of the A-cluster. The first hypothesis from Brunold et al involves a one-electron reduction of the [Fe4S4]2+ cube and a one-electron reduction of the Nip 2+. This should result in a spin-coupled state that is S = integer. The Ni0 hypothesis requires both electrons to localize on the Nip 2+ forming a zero-valent proximal nickel. MÃ¶ssbauer spectroscopy has been used to probe the oxidation state and spin state of the [Fe4S4] cube in the reduced active form. No integer spin system is found and this is interpreted as supporting the Ni0 hypothesis. Additionally, spectra are presented that indicate the heterogeneous nature of the A-cluster is not caused by the occupancy of the proximal site.
This dissertation counters the visual bias, and the simplistic approach to the senses, in architectural thought, by investigating the connections among different sense modalities (sight, sound, smell, taste and touch). Literature from the cognitive sciences shows that sensory modalities are connected perceptually; what we see affects what we hear, what we smell affects what we taste, and so on. This has a direct impact on the perceptual choices we make in our day-to-day lives. A case study conducted in an urban plaza investigates the perceptual choices people make (or what they attend to) as they explore their physical environment. Results show that people construct subjective and embodied mental maps of their environments where sensory impressions are integrated with cognitive concepts such as emotions or object recognition. Furthermore, when one sense is muted (such as closing the eyes) other senses are prioritized. A theoretical framework termed as the Sensthetic Model is developed illustrating the interdependence of sensory, kinesthetic and cognitive factors, and the hierarchical and lateral relationship between sense-modalities. The latter is the focus of studies with architecture students in abstract thinking exercises: a) Hierarchical: Students perceive a hierarchy of senses (sensory order) when they think about different places. Vision is primary, but not always. Touch, classically relegated to the bottom of the hierarchy, is often higher in the hierarchy and coupled with sound. b) Lateral: Students associate colors with different sounds, smells, textures, temperatures, emotions and objects and cross over modalities conceptually, with a degree of consistency. There are more associations with emotions and objects (which are not constrained to a single sense-modality), than with purely sensory images. Finally, the theoretical model is further developed as a tool to think across modalities (crossmodally) based on the identification of sensory orders and sensory correspondences. By focusing on the sensory modalities (nodes) and the relationships among them (connections), the model serves as a conceptual tool for professionals to create sensory environments. This dissertation is an initial step beyond the aesthetics of appearance, towards the Sensthetics of experience.
Squeeze film dampers (SFDs) with low levels of external pressurization and poor end sealing are prone to air entrapment, thus reducing the damping capability. Furthermore, existing predictive models are too restrictive. Single frequency, unidirectional load and centered circular orbit experiments were conducted on a revamped SFD test rig. The damper journal is 1 in length and 5 in diameter, with nominal clearance of 5 mils (0.127 mm). The SFD feed end is flooded with oil, while the discharge end contains a recirculation groove and four orifice discharge ports to prevent air ingestion. The discharge end is fully sealed with a wave-spring that pushes a seal ring into contact with the SFD journal. The measurements conducted without and with lubricant in the squeeze film lands, along with a frequency domain identification procedure, render the mechanical seal dry-friction force and viscous damping force coefficients as functions of frequency and motion amplitude. The end seal arrangement is quite effective in eliminating side leakage and preventing air entrainment into the film lands. Importantly enough, the dry friction force, arising from the contact forces in relative motion, increases significantly the test element equivalent viscous damping coefficients. The identified system damping coefficients are thus frequency and amplitude of motion dependent, albeit decreasing rapidly as the motion parameters increase. Identified force coefficients, damping and added mass, for the squeeze film damper alone agree very well with predictions based on the full film, short length SFD model.
Agricultural cooperatives are a unique form of business whose performance is tied closely to the financial health of their farmer members. The changing business environment in Texas and other parts of the Midwest has put strain on farm and ranch owners as well as the cooperatives that serve them. As margins diminish and customer base grows smaller, cooperatives must become more financially efficient to remain economically viable. This study was aimed at identifying those operational decisions and company characteristics that separate successful, growing cooperative agribusinesses from stagnant ones through empirical analysis. In addition, through the use of directed acyclic graphs and econometric techniques, the study sought to explain the connection of manager practices and perceptions to organizational performance. The analysis was based on a survey of managers in the state of Texas operating a diverse group of agricultural cooperatives. It did not include financial or utilities cooperatives. The results indicated that successful cooperatives were larger in size, had a smaller number of close competitors, and perceived loyalty to be a large issue for the cooperative. Strategic planning was utilized equally by successful and stagnant cooperatives. Successful cooperatives were more apt to have a formal equity redemption plan, but this did not appear to have a significant impact on financial performance. The directed graphs showed a strong impact of manager perceptions in the area of member loyalty and performance. Further econometric analysis brought us to the conclusion that performance group and perceptions have some measurable impact in the areas of competition and loyalty. This is evidenced by the coefficients of the slope and intercept shifters for performance group being different from zero. An understanding of the factors that have the greatest impact on performance, such as competition and loyalty, can assist cooperative management teams in making operational decisions to mitigate their greatest risks and weaknesses, leading to a stronger financial position.
Correct localization of lipidated cytosolic proteins to the plasma membrane (PM) is mediated by interactions between lipid anchors of proteins and cell membranes. Previously, dietary fish oil and its major n-3 polyunsaturated fatty acid (PUFA), docosahexaenoic acid (DHA), have been shown to decrease Ras membrane association, concomitantly reducing rat colon tumor incidence and Ras signaling, compared with corn oil and linoleic acid (LA), a highly prevalent vegetable fat and dietary PUFA in the U.S. diet. In order to explore the potential regulatory role of the cellular lipid environment in PM targeting of lipidated proteins, young adult mouse colon (YAMC) cells were treated with 50 ÂµM DHA, LA, or oleic acid (OA) 24 h prior to and 36-48 h after transfection with green fluorescent protein (GFP) fusion constructs of various lipidated cytosolic proteins. Relative expression of each GFP fusion protein at the PM and the Golgi in living cells was quantified using z-serial confocal microscopy and digital image processing. DHA differentially altered the subcellular localization of Ras isoforms and Src-related tyrosine kinases in a reversible manner. DHA significantly decreased the PM localization and increased the endomembrane association of H-Ras, N-Ras, and Lck, which are targeted to the PM via the exocytic pathway, regardless of their functional state. In contrast, the subcellular distribution of K-Ras and Fyn, of which transport is independent of the vesicular transport pathway, was unaffected by DHA. Moreover, DHA selectively inhibited lipidated cytosolic protein targeting since the PM delivery of transmembrane protein cargo was unaffected, indicating that DHA does not alter the bulk flow of secretory vesicular traffic. Overall, the present study presents compelling evidence that select dietary constituents with membrane lipid-modifying properties can differentially modulate subcellular localization of important lipidated signaling proteins depending on their intracellular trafficking route to the PM.