Capturing patterns of spatial and temporal autocorrelation in ordered response data : a case study of land use and air quality changes in Austin, Texas

textMany databases involve ordered discrete responses in a temporal and spatial context, including, for example, land development intensity levels, vehicle ownership, and pavement conditions. An appreciation of such behaviors requires rigorous statistical methods, recognizing spatial effects and dynamic processes. This dissertation develops a dynamic spatial ordered probit (DSOP) model in order to capture patterns of spatial and temporal autocorrelation in ordered categorical response data. This model is estimated in a Bayesian framework using Gibbs sampling and data augmentation, in order to generate all autocorrelated latent variables. The specifications, methodologies, and applications undertaken here advance the field of spatial econometrics while enhancing our understanding of land use and air quality changes. The proposed DSOP model incorporates spatial effects in an ordered probit model by allowing for inter-regional spatial interactions and heteroskedasticity, along with random effects across regions (where "region" describes any cluster of observational units). The model assumes an autoregressive, AR(1), process across latent response values, thereby recognizing time-series dynamics in panel data sets. The model code and estimation approach is first tested on simulated data sets, in order to reproduce known parameter values and provide insights into estimation performance. Root mean squared errors (RMSE) are used to evaluate the accuracy of estimates, and the deviance information criterion (DIC) is used for model comparisons. It is found that the DSOP model yields much more accurate estimates than standard, non-spatial techniques. As for model selection, even considering the penalty for using more parameters, the DSOP model is clearly preferred to standard OP, dynamic OP and spatial OP models. The model and methods are then used to analyze both land use and air quality (ozone) dynamics in Austin, Texas. In analyzing Austin's land use intensity patterns over a 4-point panel, the observational units are 300 m × 300 m grid cells derived from satellite images (at 30 m resolution). The sample contains 2,771 such grid cells, spread among 57 clusters (zip code regions), covering about 10% of the overall study area. In this analysis, temporal and spatial autocorrelation effects are found to be significantly positive. In addition, increases in travel times to the region's central business district (CBD) are estimated to substantially reduce land development intensity. The observational units for the ozone variation analysis are 4 km × 4 km grid cells, and all 132 observations falling in the study area are used. While variations in ozone concentration levels are found to exhibit strong patterns of temporal autocorrelation, they appear strikingly random in a spatial context (after controlling for local land cover, transportation, and temperature conditions). While transportation and land cover conditions appear to influence ozone levels, their effects are not as instantaneous, nor as practically significant as the impact of temperature. The proposed and tested DSOP model is felt to be a significant contribution to the field of spatial econometrics, where binary applications (for discrete response data) have been seen as the cutting edge. The Bayesian framework and Gibbs sampling techniques used here permit such complexity, in world of two-dimensional autocorrelation.Civil, Architectural, and Environmental Engineerin

Colorimetric determination of copper ions based on the catalytic leaching of silver from the shell of silver-coated gold nanorods

We have developed a method for the colorimetric determination of copper ions (Cu2+) that is based on the use of silver-coated gold nanorods (Au@Ag NRs). Its outstanding selectivity and sensitivity result from the catalytic leaching process that occurs between Cu2+, thiosulfate (S2O3 (2-)), and the surface of the Au@Ag NRs. The intrinsic color of the Au@Ag NRs changes from bright red to bluish green with decreasing thickness of the silver coating. The addition of Cu2+ accelerates the leaching of silver from the shell caused in the presence of S2O3 (2-). This result in a decrease in the thickness of the silver shell which is accompanied a change in color and absorption spectra of the colloidal solution. The shifts in the absorption maxima are linearly related to the concentrations of Cu2+ over the 3-1,000 nM concentration range (R = 0.996). The method is cost effective and was applied to the determination of Cu2+ in real water samples.We have developed a method for the colorimetric determination of copper ions (Cu2+) that is based on the use of silver-coated gold nanorods (Au@Ag NRs). Its outstanding selectivity and sensitivity result from the catalytic leaching process that occurs between Cu2+, thiosulfate (S2O3 (2-)), and the surface of the Au@Ag NRs. The intrinsic color of the Au@Ag NRs changes from bright red to bluish green with decreasing thickness of the silver coating. The addition of Cu2+ accelerates the leaching of silver from the shell caused in the presence of S2O3 (2-). This result in a decrease in the thickness of the silver shell which is accompanied a change in color and absorption spectra of the colloidal solution. The shifts in the absorption maxima are linearly related to the concentrations of Cu2+ over the 3-1,000 nM concentration range (R = 0.996). The method is cost effective and was applied to the determination of Cu2+ in real water samples

TNF-α mediates choroidal neovascularization by upregulating VEGF expression in RPE through ROS-dependent β-catenin activation

Inflammation, oxidative stress, and angiogenesis have been proposed to interact in age-related macular degeneration. It has been postulated that external stimuli that cause oxidative stress can increase production of vascular endothelial growth factor (VEGF) in retinal pigment epithelial (RPE) cells. In this study, we tested the hypothesis that the inflammatory cytokine, tumor necrosis factor alpha (TNF-α), contributed to choroidal neovascularization (CNV) by upregulating VEGF in RPE through intracellular reactive oxygen species (ROS)-dependent signaling and sought to understand the mechanisms involved

Occupant injury severity using a heteroscedastic ordered logit model: Distinguishing the effects of vehicle weight and type

This paper uses a heteroscedastic ordered logit model to study the effects of various vehicle, environmental, roadway and occupant characteristics on the severity of injuries sustained by vehicle occupants, conditional on the crash occurrence. As expected, the models find that heavier vehicles increase both a vehicle’s crashworthiness and its aggressiveness towards others. The models also find that if all passenger vehicles were to become 1000 lbs heavier, crash injury outcomes would not change dramatically. However, if all passenger cars were to become light duty trucks (i.e., minivans, pickups and sport utility vehicles) of the same weight, incapacitating injuries and the fatalities are predicted to rise by 26 and 64 percent, respectively. Beyond weight and vehicle type, many other factors were controlled for all well. For example, older occupants and female occupants are more likely to experience injury and death, particularly when navigating curved roadway sections with higher speed limits

Fabrication of electrospun fibrous meshes and 3D porous titanium scaffolds for tissue engineering

Tissue engineering is a multidisciplinary field that is rapidly emerging as a promising approach for tissue repair and regeneration. In this approach, scaffolds which allow cells to invade the construct and guide the cells grow into specific tissue play a pivotal role. Electrospinning has gained popularity recently as a simple and versatile method to produce fibrous structures with nano- to microscale dimensions. These electrospun fibers have been extensively applied to create nanofiber scaffolds for tissue engineering applications. Specifically for bone and cartilage tissue engineering, polymeric materials have some attractive properties such as the biodegradability. Ceramic scaffolds and implant coatings, such as hydroxyapatite and silica-based bioglass have also been considered as bone graft substitutes for bone repair because of their bioactivity and, in some cases, tunable resorbability. Besides tissue engineering scaffolds, for clinical application, especially for load-bearing artificial implants, metallic materials such as titanium are the most commonly used material. Osseointegration between bone and implants is very essential for implant success. To achieve better osseointegration between bone and the implant surface, three dimensional porous structures can provide enhanced fixation with bone by allowing tissue to grow into the pores. In this study, pre-3D electrospun polymer and ceramic scaffolds with peptide conjugation and 3D titanium scaffolds with different surface morphology were fabricated to testify the osteoblast and mensechymal stem cell attachment and differentiation. The overall goal of this thesis is to determine if the peptide functionalization of polymeric scaffolds and physical parameters of ceramic and metallic scaffold can promote osteoblast maturation and mesenchymal stem cell differentiation in vitro to achieve an optimal scaffold design for greater osseointegration. The results of the studies showed with functionalization of MSC- specific peptide, polymer scaffolds behaved with higher biocompatibility and MSC affinity. For the ceramic and metallic scaffolds, microstructures and nanostructures can synergistically promote osteoblast maturation and 3D micro-environment with micro-roughness is a promising design for osteoblast maturation and MSC differentiation in vitro compared to 2D surfaces.Ph.D

Latent split of aggregate counts: revealing home deliveries per commodity types and potential freight trip implications

This paper suggests a joint econometric model that allows estimating latent marginal counts when only total counts and types of commodities purchased are available. The basis for this model is the Negative binomial hurdle model, which is expanded by incorporating different features for the latent classes, allowing eventual null latent counts for one or more classes. A validation procedure for the proposed splitting is discussed. The methodology was used to estimate and validate a model for the propensity to shop online and the corresponding number of shipments per commodity group. The results confirm existing research on online shopping behaviour: elderly is less likely to buy online, while high income, education and having kids motivate online shopping. The average online shopper receives 2.4 shipments/month (0.077 shipments/day), with variations in shipments and commodities depending on the consumer profile. Correlation between commodity groups reveals that consolidation can reduce shipments of up to 30%.publishedVersio

Highly Sensitive Surface-Enhanced Raman Scattering Sensing of Heparin Based on Antiaggregation of Functionalized Silver Nanoparticles

We report a simple and sensitive surface-enhanced Raman scattering (SERS) platform for the detection of heparin, based on antiaggregation of 4-mercaptopyridine (4-MPY) functionalized silver nanoparticles (Ag NPs). Here, protamine was employed as a medium for inducing the aggregation of negatively charged 4-MPY functionalized Ag NPs through surface electrostatic interaction, which resulted in significantly enhanced Raman signal of the Raman reporter. However, in the presence of heparin, the interaction between heparin and protamine decreased the concentration of free protamine, which dissipated the aggregated 4-MPY functionalized Ag NPs and thus decreased Raman enhancement effect. The degree of aggregation and Raman enhancement effect was proportional to the concentration of added heparin. Under optimized assay conditions, good linear relationship was obtained over the range of 0.5-150 ng/mL (R-2 = 0.998) with a minimum detectable concentration of 0.5 ng/mL in standard aqueous solution. Furthermore, the developed method was also successfully applied for detecting heparin in fetal bovine serum samples with a linear range of 1-400 ng/mL.We report a simple and sensitive surface-enhanced Raman scattering (SERS) platform for the detection of heparin, based on antiaggregation of 4-mercaptopyridine (4-MPY) functionalized silver nanoparticles (Ag NPs). Here, protamine was employed as a medium for inducing the aggregation of negatively charged 4-MPY functionalized Ag NPs through surface electrostatic interaction, which resulted in significantly enhanced Raman signal of the Raman reporter. However, in the presence of heparin, the interaction between heparin and protamine decreased the concentration of free protamine, which dissipated the aggregated 4-MPY functionalized Ag NPs and thus decreased Raman enhancement effect. The degree of aggregation and Raman enhancement effect was proportional to the concentration of added heparin. Under optimized assay conditions, good linear relationship was obtained over the range of 0.5-150 ng/mL (R-2 = 0.998) with a minimum detectable concentration of 0.5 ng/mL in standard aqueous solution. Furthermore, the developed method was also successfully applied for detecting heparin in fetal bovine serum samples with a linear range of 1-400 ng/mL

Establishment and verification of solar radiation calculation model of glass daylighting roof in hot summer and warm winter zone in China

In this paper, solar heat gain through glass daylighting roof is deeply studied by theoretical calculation method, taking Guangzhou in the Hot Summer and Warm Winter (HSWW) zone as an example. The direct solar radiation is calculated by Bouguer formula whereas the diffuse solar radiation is calculated by Berlage formula, representing the basis for the calculation method of the solar radiation intensity through the glass daylighting roof. Through the establishment of solar radiation calculation model, the solar heat gain of the commonly used glass types has been calculated and analyzed, especially comparatively analyzing of Low-E cored-glass with double-coated silver and 6+12A+6 insulating glass. Then, comparison between solar heat gain as calculated and measured by field measurement tested the indoor solar radiation heat gain distribution by using adjacent rooms with different glass types in a hot summer area, with the aim of demonstrating the effectiveness of the model. The research in this paper is expected to further improve the calculation accuracy of both thermal load and indoor temperature