Creating Raster Omnimax Images from Multiple Perspective Views Using the Elliptical Weighted Average Filter

Creation of Omnimax animation by computer opens up fantastic new visual possibilities. Unfortunately, the fish-eye distortion of Omnimax film images complicates synthesis by computer, since most image-synthesis programs can create only perspective views. As an alternative to modifying existing image-synthesis programs to produce Omnimax projections directly, we present a method for creating them from multiple perspective views. Four perspective views of the environment are created, each a projection onto a face of a cube centered at the camera, and then a mapping program creates an Omnimax projection from them. To minimize aliasing during resampling, the mapping program uses the elliptical weighted average filter, a space-variant filter we developed for this application that computes a weighted average over an arbitrarily oriented elliptical area. This filter can also be used for texture mapping 3D surfaces.     

Survey of Texture Mapping

Texture mapping is one of the most successful new techniques in high-quality image synthesis. It can enchance the visual richness of raster-scan images immensely while entailing only a relatively smann increase in computation. The technique has been applied to a number of surface attributes: surface color, surface normal, specularity, transparency, illumination, and surface displacement?to name a few. Although the list is potentially endless, the techniques of texture mapping are essentially the same in all cases. This article surveys the fundamentals of texture mapping, which can be spilt into two topics: the geometric mapping that warps a texture onto a surface, and the filtering necessary to avoid aliasing. An extensive bibliography is included.     

Simulating impacts of water trading in an institutional perspective

Water availability in outback Australia is defined by the occurrence of large rainfall events, and changes often from a situation of scarcity to temporary abundance. Informal institutions are often able to translate such dynamics into sustainable water-use rules. Policy interventions are mainly focused on changing access rules to avoid over-use or inefficiencies. Such formal institutional changes can lead to unexpected unsustainable outcomes; outcomes that are often captured in the ‘story’ behind informal arrangements.This paper analyses one case study on water access in outback Australia and translates field work results into an agent-based model. The agent-based model is calibrated based on data from experiments conducted with actual farmers from the case study region. In order to project unintended outcomes of institutional changes, interventions in water access is explored in an applied context. The core focus of the modelling exercise is the treatment of newcomers on a newly created trading scheme for water access rights. Simulation results show that total water extraction is significantly lower if the burden of water restrictions is limited to newcomers while the regional economic performance is not statistically different from a case in which the burden is carried by all irrigators. Interview data documents that currently extraction levels are regulated by informal processes as community members communicate observations on river health to irrigators who adjust accordingly, which indicates perceived personal responsibility. Overall, the environmental and economic performance of a water trading scheme that will replace this informal self-regulating system depends on how water restrictions are implemented and how valid the overall cap of 20% outtake is, which is not widely accepted throughout the community.     

Temporal patterns of antihypertensive medication use among older adults, 1989 through 1992. An effect of the major clinical trials on clinical practice?

OBJECTIVE: To describe the changing patterns of antihypertensive medication use in the years immediately before and after the publication of the results of three major clinical trials of the treatment of hypertension in older adults. DESIGN: In this cohort study, adults 65 years or older were examined annually on four occasions between June 1989 and May 1992, and the use of antihypertensive medications was assessed by inventory at each visit. The four visits defined the boundaries of three study periods. For each study period, participants receiving antihypertensive therapy were either continuous users (n = 1667, 1643, and 1605, respectively) or starters (n = 157, 142, 120) of hypertensive therapy. The large clinical trials that convincingly proved the efficacy and safety of low-dose diuretic therapy in older adults were published during the latter parts of period 2 and the early parts of period 3. RESULTS: Among starters, the proportion initiating therapy on diuretics increased from 35.9% in period 2 to 47.5% in period 3, significantly so among women (P = .04). The proportions initiating other drugs displayed no significant trends. Among continuous users, the use of diuretics, beta-blockers, and vasodilators generally decreased over the 3-year period, while the use of calcium channel blockers and angiotensin-converting enzyme inhibitors increased significantly in each of the three periods (P < .05). The decline of 2.7% in the prevalence of diuretic use in period 1 abated during period 2 (1.8% decline), and it slowed significantly (P = .03) to almost a complete halt during period 3 (0.2% decline). The rate of increase in the use of calcium channel blockers slowed significantly (P = .01) between period 1 (+6.7%) and period 3 (+2.8%). CONCLUSIONS: Although other factors such as cost may have been important, the temporal trends in antihypertensive drug therapy coincided in time with and may have reflected in part the influence of the major clinical trials on the patterns of clinical practice.     

Temporal patterns in the medical treatment of congestive heart failure with angiotensin-converting enzyme inhibitors in older adults, 1989 through 1995

BACKGROUND: Evidence from clinical trials in the past decade has consistently shown that angiotensin-converting enzyme (ACE) inhibitors reduce morbidity and mortality in patients with congestive heart failure (CHF). The extent to which clinical practice has adopted ACE inhibitor therapy is unknown. METHODS: The Cardiovascular Health Study is a prospective observational study of 5201 community-dwelling adults aged 65 years and older. Prevalent CHF cases were identified on study entry (from June 10, 1989, through May 31, 1990) and incident CHF cases were identified throughout 5 years of follow-up. Medication data were collected from annual medication inventories. The percentage of patients with CHF using ACE inhibitors was calculated at each annual examination. Temporal trends in CHF treatment with ACE inhibitors between June 10, 1989, through May 31, 1990, and June 1, 1994, through May 31, 1995, were analyzed. RESULTS: Use of ACE inhibitors to treat CHF increased slightly over time among prevalent cases at each annual examination: 26% of prevalent CHF cases were treated in 1989-1990 compared with 36% of prevalent cases in 1994-1995. This 10% increase was statistically significant (P<.01). Participants with low ejection fractions were 2 times more likely to be treated with ACE inhibitors than were those with normal ejection fraction and this tendency did not change over time. Among cases newly diagnosed in the year before the 1990-1991 examination, 42% were using ACE inhibitors; among those newly diagnosed in the year before 1994-1995, 40% were using ACE inhibitors. This 2% decrease was not statistically significant (P=.68). CONCLUSION: These findings suggest that, while the medical management of CHF with ACE inhibitors has increased modestly over time in prevalent cases, these drugs may still be underused, especially among incident cases.     

Hostility, aggression and the risk of nonfatal myocardial infarction in postmenopausal women

Integration of human papillomavirus type 16 DNA sequences into host DNA is a frequent event in cervical carcinogenesis. However, recent studies showing that HPV16 is present exclusively in an episomal form in many primary cervical cancers suggest that HPV16 can transform target cells by mechanisms that do not require viral integration. We have established a cervical carcinoma cell line that harbors episomal copies of HPV16 DNA of approximately 10 kb. Restriction enzyme and two-dimensional gel analysis confirmed that HPV16 DNA was extrachromosomal with both monomeric and multimeric forms present. HPV16 was maintained as episomes with passage both in culture and after subcutaneous growth in nude mice. The 10 kb viral genome, consisting of a full-length copy of HPV16 and a partial duplication of the long control region and the L1 open reading frame, exhibited transforming activity comparable to prototype HPV16. This cell line should provide a useful model system for studying the biological significance of the physical state of the HPV16 genome in cervical carcinoma cells.     

Assessment of trans-fatty acid intake with a food frequency questionnaire and validation with adipose tissue levels of trans-fatty acids

Past studies of the association of trans-fatty acid intake with coronary heart disease have been hindered by the lack of a database on the trans-fatty acid content of various foods. The authors used new data from the US Department of Agriculture to estimate trans-fatty acid intake using a self-administered food frequency questionnaire (FFQ), and they assessed the validity of the FFQ by comparing the dietary estimates with trans-fatty acid concentrations in adipose tissue. The 1996 study included 27 women and 24 men aged 51-78 years. The mean consumption of total trans-fatty acids estimated from the FFQ was 2.24 g per day and 5% of total dietary fat. The mean concentration of total trans-fatty acids in buttock adipose tissue was 4.7% of total fatty acids. Pearson correlations between total dietary intake of trans-fatty acids and total trans-fatty acid levels in adipose tissue were 0.67 (95% confidence interval (CI) 0.36-0.84) among men and 0.58 (95% CI 0.26-0.79) among women. After adjustment for energy intake, age, and body mass index, the correlation coefficients were 0.76 (95% CI 0.51-0.89) among men and 0.52 (95% CI 0.17-0.75) among women. The FFQ validated in this study is an important new tool for assessing usual intake of trans-fatty acids.