A Fire Simulation Model for Heterogeneous Environments Using the Level Set Method

Wildfire hazard and its destructive consequences have become a growing issue around the world especially in the context of global warming. An effective and efficient fire simulation model will make it possible to predict the fire spread and assist firefighters in the process of controlling the damage and containing the fire area. Simulating wildfire spread remains challenging due to the complexity of fire behaviors. The raster-based method and the vector-based method are two major approaches that allow one to perform computerized fire spread simulation. In this thesis, we present a scheme we have developed that utilizes a level set method to build a fire spread simulation model. The scheme applies the strengths and overcomes some of the shortcomings of the two major types of simulation method. We store fire data and local rules at cells. Instead of calculating which are the next ignition points cell by cell, we apply Huygens\u27 principle and elliptical spread assumption to calculate the direction and distance of the expanding fire by the level set method. The advantage to storing data at cells is that it makes our simulation model more suitable for heterogeneous fuel and complex topographic environment. Using a level set method for our simulation model makes it possible to overcome the crossover problem. Another strength of the level set method is its continuous data processing. Applying the level set method in the simulation models, we need fewer vector points than raster cells to produce a more realistic fire shape. We demonstrate this fire simulation model through two implementations using narrow band level set method and fast marching method. The simulated results are compared to the real fire image data generated from Troy and Colina fires. The simulation data are then studied and compared. The ultimate goal is to apply this simulation model to the broader picture to better predict different types of fires such as crown fire, spotting fires, etc

Prospective evaluation of low-dose ketoconazole plus hydrocortisone in docetaxel pre-treated castration-resistant prostate cancer patients.

BackgroundKetoconazole is a well-known CYP17-targeted systemic treatment for castration-resistant prostate cancer (CRPC). However, most of the published data has been in the pre-chemotherapy setting; its efficacy in the post-chemotherapy setting has not been as widely described. Chemotherapy-naïve patients treated with attenuated doses of ketoconazole (200-300 mg three times daily) had PSA response rate (>50% decline) of 21-62%. We hypothesized that low-dose ketoconazole would likewise possess efficacy and tolerability in the CRPC post-chemotherapy state.MethodsMen with CRPC and performance status 0-3, adequate organ function and who had received prior docetaxel were treated with low-dose ketoconazole (200 mg orally three times daily) and hydrocortisone (20 mg PO qAM and 10 mg PO qPM) until disease progression. Primary endpoint was PSA response rate (>50% reduction from baseline) where a rate of 25% was to be considered promising for further study (versus a null rate of <5%); 25 patients were required. Secondary endpoints included PSA response >30% from baseline, progression-free survival (PFS), duration of stable disease and evaluation of adverse events (AEs).ResultsThirty patients were accrued with median age of 72 years (range 55-86) and median pre-treatment PSA of 73 ng ml(-1) (range 7-11,420). Twenty-nine patients were evaluable for response and toxicity. PSA response (>50% reduction) was seen in 48% of patients; PSA response (>30% reduction) was seen in 59%. Median PFS was 138 days; median duration of stable disease was 123 days. Twelve patients experienced grade 3 or 4 AEs. Of the 17 grade 3 AEs, only 3 were attributed to treatment. None of the two grade 4 AEs were considered related to treatment.ConclusionsIn docetaxel pre-treated CRPC patients, low-dose ketoconazole and hydrocortisone is a well-tolerated, relatively inexpensive and clinically active treatment option. PSA response to low-dose ketoconazole appears historically comparable to that of abiraterone in this patient context. A prospective, randomized study of available post-chemotherapy options is warranted to assess comparative efficacy

The role of initial geometry in experimental models of wound closing

Wound healing assays are commonly used to study how populations of cells, initialised on a two-dimensional surface, act to close an artificial wound space. While real wounds have different shapes, standard wound healing assays often deal with just one simple wound shape, and it is unclear whether varying the wound shape might impact how we interpret results from these experiments. In this work, we describe a new kind of wound healing assay, called a sticker assay, that allows us to examine the role of wound shape in a series of wound healing assays performed with fibroblast cells. In particular, we show how to use the sticker assay to examine wound healing with square, circular and triangular shaped wounds. We take a standard approach and report measurements of the size of the wound as a function of time. This shows that the rate of wound closure depends on the initial wound shape. This result is interesting because the only aspect of the assay that we change is the initial wound shape, and the reason for the different rate of wound closure is unclear. To provide more insight into the experimental observations we describe our results quantitatively by calibrating a mathematical model, describing the relevant transport phenomena, to match our experimental data. Overall, our results suggest that the rates of cell motility and cell proliferation from different initial wound shapes are approximately the same, implying that the differences we observe in the wound closure rate are consistent with a fairly typical mathematical model of wound healing. Our results imply that parameter estimates obtained from an experiment performed with one particular wound shape could be used to describe an experiment performed with a different shape. This fundamental result is important because this assumption is often invoked, but never tested

Influence of Socioeconomic Factors, Gender and Indigenous Status on Smoking in Taiwan.

The indigenous Austronesian minority of Taiwan is heavily affected by health disparities which may include suffering from a greater burden of the tobacco epidemic. While a lack of representative data has historically precluded an investigation of the differences in smoking between Taiwanese ethnicities, these data have recently become available through an annual population-based telephone survey conducted by the Health Promotion Administration, Ministry of Health and Welfare (previously known as the Bureau of Health Promotion (BHP), Department of Health). We used the BHP monitoring data to observe the prevalence of smoking and environmental tobacco smoke exposure among indigenous and non-indigenous Taiwanese surrounding a tobacco welfare tax increase in 2006, investigate ethnic differences in smoking prevalence and environmental tobacco smoke exposure each year between 2005 and 2008, and perform multiple logistic regression to estimate measures of association between potential risk factors and smoking status. Despite significant ethnic and gender differences in smoking prevalence, smoking status was not found to be significantly associated with ethnicity after controlling for socioeconomic and demographic factors