Comparison of forest attributes derived from two terrestrial lidar systems.

Abstract Terrestrial lidar (TLS) is an emerging technology for deriving forest attributes, including conventional inventory and canopy characterizations. However, little is known about the influence of scanner specifications on derived forest parameters. We compared two TLS systems at two sites in British Columbia. Common scanning benchmarks and identical algorithms were used to obtain estimates of tree diameter, position, and canopy characteristics. Visualization of range images and point clouds showed clear differences, even though both scanners were relatively high-resolution instruments. These translated into quantifiable differences in impulse penetration, characterization of stems and crowns far from the scan location, and gap fraction. Differences between scanners in estimates of effective plant area index were greater than differences between sites. Both scanners provided a detailed digital model of forest structure, and gross structural characterizations (including crown dimensions and position) were relatively robust; but comparison of canopy density metrics may require consideration of scanner attributes

Comparison of results from different imputation techniques for missing data from an anti-obesity drug trial

BackgroundIn randomised trials of medical interventions, the most reliable analysis follows the intention-to-treat (ITT) principle. However, the ITT analysis requires that missing outcome data have to be imputed. Different imputation techniques may give different results and some may lead to bias. In anti-obesity drug trials, many data are usually missing, and the most used imputation method is last observation carried forward (LOCF). LOCF is generally considered conservative, but there are more reliable methods such as multiple imputation (MI).ObjectivesTo compare four different methods of handling missing data in a 60-week placebo controlled anti-obesity drug trial on topiramate.MethodsWe compared an analysis of complete cases with datasets where missing body weight measurements had been replaced using three different imputation methods: LOCF, baseline carried forward (BOCF) and MI.Results561 participants were randomised. Compared to placebo, there was a significantly greater weight loss with topiramate in all analyses: 9.5 kg (SE 1.17) in the complete case analysis (N = 86), 6.8 kg (SE 0.66) using LOCF (N = 561), 6.4 kg (SE 0.90) using MI (N = 561) and 1.5 kg (SE 0.28) using BOCF (N = 561).ConclusionsThe different imputation methods gave very different results. Contrary to widely stated claims, LOCF did not produce a conservative (i.e., lower) efficacy estimate compared to MI. Also, LOCF had a lower SE than MI

Sustainable and personalized nutrition: From earth health to public health

Sustainable nutrition, equaling earth health, involves a personalized approach designed in terms of precision and avoidance of still cogent but unjustified dogmas, equaling public health. For instance, current dietary recommendations continue to dwell on the need to limit as much as possible the intake of saturated fatty acids (SFA), notwithstanding the mounting evidence that the effects of food on health cannot be predicted from the content of single nutrients without considering the overall macronutrient composition and the role of the food matrix. The traditional recommendation to restrict SFA ignores that their effects on health depend on the interaction between naturally occurring food components and those introduced by food processing. It is warranted to modify the still widely promoted dietary guidelines based upon such single nutrients as SFA and instead personalize dietary habits on the basis of the whole pattern of the food matrix. Accordingly, the double edge of malnutrition, that involves deficiency as well as excess and materializes in many individuals throughout their life course, might be tackled by implementing sustainability, with the additional effect of overcoming global inequalities. Within this context SFA may regain their position of tasty and cheap sources of energy to be adapted to each individual lifestyle

Excitations in antiferromagnetic cores of superconducting vortices

We study excitations of the predicted antiferromagnetically ordered vortex cores in the superconducting phase of the newly proposed SO(5) model of strongly correlated electrons. Using experimental data from the literature we show that the susceptibilities in the spin sector and the charge sector are nearly equal, and likewise for the stiffnesses. In the case of strict equality SO(5) symmetry is possible, and we find that if present the vortices give rise to an enhanced neutron scattering cross section near the so called pi resonance at 41 meV. In the case of broken SO(5) symmetry two effects are predicted. Bound excitations can exist in the vortex cores with ``high'' excitation energies slightly below 41 meV, and the massless Goldstone modes corresponding to the antiferromagnetic ordering of the core can acquire a mass and show up as core excitation with ``low'' excitation energies around 2 meV.Comment: 9 pages, RevTeX, including 3 postscript figures, submitted to Phys. Rev. B, July 10, 199