Shape selection in Landsat time series: a tool for monitoring forest dynamics.

We present a new methodology for fitting nonparametric shape-restricted regression splines to time series of Landsat imagery for the purpose of modeling, mapping, and monitoring annual forest disturbance dynamics over nearly three decades. For each pixel and spectral band or index of choice in temporal Landsat data, our method delivers a smoothed rendition of the trajectory constrained to behave in an ecologically sensible manner, reflecting one of seven possible 'shapes'. It also provides parameters summarizing the patterns of each change including year of onset, duration, magnitude, and pre- and postchange rates of growth or recovery. Through a case study featuring fire, harvest, and bark beetle outbreak, we illustrate how resultant fitted values and parameters can be fed into empirical models to map disturbance causal agent and tree canopy cover changes coincident with disturbance events through time. We provide our code in the r package ShapeSelectForest on the Comprehensive R Archival Network and describe our computational approaches for running the method over large geographic areas. We also discuss how this methodology is currently being used for forest disturbance and attribute mapping across the conterminous United States.

A critical pathway for patients with acute chest pain and low risk for short-term adverse cardiac events: role of outpatient stress testing.

STUDY OBJECTIVE: We evaluate the safety and feasibility of a critical care pathway protocol in which patients with acute chest pain who are low risk for coronary artery disease and short-term adverse cardiac outcomes receive outpatient stress testing within 72 hours of an emergency department (ED) visit. METHODS: We performed an observational study of an ED-based chest pain critical pathway in an urban, community hospital in 979 consecutive patients. Patients enrolled in the protocol were observed in the ED before receiving 72-hour outpatient stress testing. The pathway was primarily analyzed for rates of death or myocardial infarction in the 6 months after ED discharge and outpatient stress testing. Secondary outcome measures included need for coronary intervention at initial stress testing and within 6 months after discharge, subsequent ED visits for chest pain, and subsequent hospitalization. RESULTS: Of 871 stress-tested patients aged 40 years or older, who had low risk for coronary artery disease and short-term adverse cardiac events, and had 6-month follow-up, 18 (2%) required coronary intervention, 1 (0.1%) had a myocardial infarction within 1 month, 2 (0.2%) had a myocardial infarction within 6 months, 6 (0.7%) had normal stress test results after discharge but required cardiac catheterization within 6 months, and 5 (0.6%) returned to the ED within 6 months for ongoing chest pain. Hospital admission rates decreased significantly from 31.2% to 26.1% after initiation of the protocol (P<.001). CONCLUSION: For patients with chest pain and low risk for short-term cardiac events, outpatient stress testing is feasible, safe, and associated with decreased hospital admission rates. With an evidence-based protocol, physicians efficiently identify patients at low risk for clinically significant coronary artery disease and short-term adverse cardiac outcomes.

Prevalence and degree of childhood and adolescent overweight in rural, urban, and suburban Georgia.

The prevalence and severity of child and adolescent overweight (OW) in the United States have been documented, but little is known regarding the prevalence of OW and "Extent of Overweight" (EOW) in individual states or specific regions within states. The aim of this study was to determine the prevalence of OW and EOW in school-aged youths from 4 regions of Georgia. A 2-stage cluster sampling procedure was performed in 2002, with participation of 4th-, 8th- and 11th-grade students (N = 3114). Measured height and weight were used to determine body mass index (BMI) for age percentiles and data were weighted to estimate population prevalence of OW. A logistic regression model determined predictors of OW. The overall estimate of OW prevalence was 20.2% and highest in males (22.0%), non-Hispanic blacks (21.8%), "other races" (32.4%), and students residing in rural growth (23.7%) and rural decline (23.0%) areas. Overweight prevalence was similar among grades. The overall estimated EOW was 4.3 and highest in males (4.7), other races (5.6), non-Hispanic blacks (5.2), and students from rural growth (5.4) and rural decline (5.0) areas. Sex, race, location, and economic tier were significant predictors (= 0.02) of OW. The prevalence and severity of OW was higher in youths residing in Georgia than nationally. School health professionals, community leaders, and parents should provide support for updated school policies aimed at providing BMI surveillance and a school environment that encourages physical activity and healthy nutrition practices.

Directed walk designs for dose-response problems with competing failure modes.

We examine adaptive allocation designs for the problem of determining the optimal therapeutic dose for subjects in early-phase clinical trials. A subject can fail due to lack of efficacy or due to a toxic reaction. Successful subjects will have both a positive response and no toxic side effects. Thus, we seek to maximize the product of the nontoxicity and efficacy dose-response curves. We are interested in sampling rules that perform well along several criteria, including the ethical criterion that, as often as possible, experimental subjects be treated at or close to the maximum in question. Statistically, we wish to identify the optimum dose with high probability at the close of the experiment. Here, we propose designs that combine new allocation policies, directed walks, with new smoothed shape-constrained curve-fitting techniques. These are compared with a variety of other curve-fitting techniques and with up-and-down and equal allocation rules.