Detecting landscape changes in the interior of British Columbia from 1975 to 1992 using satellite imagery

To consider the regional scale effects of forest management requires complete and consistent data over large areas. We used Landsat Thematic Mapper and Multispectral Scanner (TM and MSS) imagery to map forest cover and detect major disturbances between 1975 and 1992 for a 4.2 x 106 ha area of interior British Columbia. Forested pixels were mapped into closed conifer, semiopen conifer, deciduous, and mixed forest classes, with further subdivision of the closed conifer type into three age-classes. The image-based estimate of harvested area was similar to an independent estimate from forest inventory data. Changes in landscape pattern from 1975 to 1992 were examined by calculating indices that describe overall landscape pattern and that of conifer and harvested patches in each biogeoclimatic zone. Harvesting affected 8.4% of the forest area outside provincial parks during the 17-year period. Harvested areas were consistently much smaller than conifer patches in all biogeoclimatic zones and had a lower percentage of interior area and perimeter/area ratio. Conifer patch-shape complexity varied between zones; harvested patches had simpler shapes and were similar in all zones. Results indicate that this landscape is only in the early stages of fragmentation, but a similar harvest pattern has been imposed on differing ecological zones.Keywords: land cover, forest harvesting, remote imagery, forest management, landscape pattern, patch complexit

Relativistic conservation laws and integral constraints for large cosmological perturbations

For every mapping of a perturbed spacetime onto a background and with any vector field $\xi$ we construct a conserved covariant vector density $I(\xi)$, which is the divergence of a covariant antisymmetric tensor density, a "superpotential". $I(\xi)$ is linear in the energy-momentum tensor perturbations of matter, which may be large; $I(\xi)$ does not contain the second order derivatives of the perturbed metric. The superpotential is identically zero when perturbations are absent. By integrating conserved vectors over a part \Si of a hypersurface $S$ of the background, which spans a two-surface \di\Si, we obtain integral relations between, on the one hand, initial data of the perturbed metric components and the energy-momentum perturbations on \Si and, on the other hand, the boundary values on \di\Si. We show that there are as many such integral relations as there are different mappings, $\xi$'s, \Si's and \di\Si's. For given boundary values on \di\Si, the integral relations may be interpreted as integral constraints (e.g., those of Traschen) on local initial data including the energy-momentum perturbations. Conservation laws expressed in terms of Killing fields \Bar\xi of the background become "physical" conservation laws. In cosmology, to each mapping of the time axis of a Robertson-Walker space on a de Sitter space with the same spatial topology there correspond ten conservation laws. The conformal mapping leads to a straightforward generalization of conservation laws in flat spacetimes. Other mappings are also considered. ...Comment: This paper, published 7 years ago, was found useful by some researchers but originally was not put on the gr-qc website. Now it has been retyped with very minor changes: few wordings have been modified and several misprints occurring in the printed version correcte

Evaluating the RELM Test Results

We consider implications of the Regional Earthquake Likelihood Models (RELM) test results with regard to earthquake forecasting. Prospective forecasts were solicited for M≥4.95 earthquakes in California during the period 2006–2010. During this period 31 earthquakes occurred in the test region with M≥4.95. We consider five forecasts that were submitted for the test. We compare the forecasts utilizing forecast verification methodology developed in the atmospheric sciences, specifically for tornadoes. We utilize a “skill score” based on the forecast scores λfi of occurrence of the test earthquakes. A perfect forecast would have λfi=1, and a random (no skill) forecast would have λfi=2.86×10-3. The best forecasts (largest value of λfi) for the 31 earthquakes had values of λfi=1.24×10-1 to λfi=5.49×10-3. The best mean forecast for all earthquakes was λ̅f=2.84×10-2. The best forecasts are about an order of magnitude better than random forecasts. We discuss the earthquakes, the forecasts, and alternative methods of evaluation of the performance of RELM forecasts. We also discuss the relative merits of alarm-based versus probability-based forecasts

Long-Term Impact of Malaria Chemoprophylaxis on Cognitive Abilities and Educational Attainment: Follow-Up of a Controlled Trial

OBJECTIVES: We investigated the long-term impact of early childhood malaria prophylaxis on cognitive and educational outcomes. DESIGN: This was a household-based cluster-controlled intervention trial. SETTING: The study was conducted in 15 villages situated between 32 km to the east and 22 km to the west of the town of Farafenni, the Gambia, on the north bank of the River Gambia. PARTICIPANTS: A total of 1,190 children aged 3–59 mo took part in the trial. We traced 579 trial participants (291 in the prophylaxis group and 288 in the placebo group) in 2001, when their median age was 17 y 1 mo (range 14 y 9 mo to 19 y 6 mo). INTERVENTIONS: Participants received malaria chemoprophylaxis (dapsone/pyrimethamine) or placebo for between one and three malaria transmission seasons from 1985 to 1987 during the controlled trial. At the end of the trial, prophylaxis was provided for all children under 5 y of age living in the study villages. OUTCOME MEASURES: The outcome measures were cognitive abilities, school enrolment, and educational attainment (highest grade reached at school). RESULTS: There was no significant overall intervention effect on cognitive abilities, but there was a significant interaction between intervention group and the duration of post-trial prophylaxis (p = 0.034), with cognitive ability somewhat higher in the intervention group among children who received no post-trial prophylaxis (treatment effect = 0.2 standard deviations [SD], 95% confidence interval [CI] −0.03 to 0.5) and among children who received less than 1 y of post-trial prophylaxis (treatment effect = 0.4 SD, 95% CI 0.1 to 0.8). The intervention group had higher educational attainment by 0.52 grades (95% CI = −0.041 to 1.089; p = 0.069). School enrolment was similar in the two groups. CONCLUSIONS: The results are suggestive of a long-term effect of malaria prophylaxis on cognitive function and educational attainment, but confirmatory studies are needed

Randomized Dose-Ranging Controlled Trial of AQ-13, a Candidate Antimalarial, and Chloroquine in Healthy Volunteers

OBJECTIVES: To determine: (1) the pharmacokinetics and safety of an investigational aminoquinoline active against multidrug–resistant malaria parasites (AQ-13), including its effects on the QT interval, and (2) whether it has pharmacokinetic and safety profiles similar to chloroquine (CQ) in humans. DESIGN: Phase I double-blind, randomized controlled trials to compare AQ-13 and CQ in healthy volunteers. Randomizations were performed at each step after completion of the previous dose. SETTING: Tulane–Louisiana State University–Charity Hospital General Clinical Research Center in New Orleans. PARTICIPANTS: 126 healthy adults 21–45 years of age. INTERVENTIONS: 10, 100, 300, 600, and 1,500 mg oral doses of CQ base in comparison with equivalent doses of AQ-13. OUTCOME MEASURES: Clinical and laboratory adverse events (AEs), pharmacokinetic parameters, and QT prolongation. RESULTS: No hematologic, hepatic, renal, or other organ toxicity was observed with AQ-13 or CQ at any dose tested. Headache, lightheadedness/dizziness, and gastrointestinal (GI) tract–related symptoms were the most common AEs. Although symptoms were more frequent with AQ-13, the numbers of volunteers who experienced symptoms with AQ-13 and CQ were similar (for AQ-13 and CQ, respectively: headache, 17/63 and 10/63, p = 0.2; lightheadedness/dizziness, 11/63 and 8/63, p = 0.6; GI symptoms, 14/63 and 13/63; p = 0.9). Both AQ-13 and CQ exhibited linear pharmacokinetics. However, AQ-13 was cleared more rapidly than CQ (respectively, median oral clearance 14.0–14.7 l/h versus 9.5–11.3 l/h; p ≤ 0.03). QTc prolongation was greater with CQ than AQ-13 (CQ: mean increase of 28 ms; 95% confidence interval [CI], 18 to 38 ms, versus AQ-13: mean increase of 10 ms; 95% CI, 2 to 17 ms; p = 0.01). There were no arrhythmias or other cardiac AEs with either AQ-13 or CQ. CONCLUSIONS: These studies revealed minimal differences in toxicity between AQ-13 and CQ, and similar linear pharmacokinetics

Economic Impact of Dengue Illness and the Cost-Effectiveness of Future Vaccination Programs in Singapore

Dengue illness is a tropical disease transmitted by mosquitoes that threatens more than one third of the worldwide population. Dengue has important economic consequences because of the burden to hospitals, work absenteeism and risk of death of symptomatic cases. Governments attempt to reduce the disease burden using costly mosquito control strategies such as habitat reduction and spraying insecticide. Despite such efforts, the number of cases remains high. Dengue vaccines are expected to be available in the near future and there is an urgent need to evaluate their cost-effectiveness, i.e. whether their cost will be justified by the reduction in disease burden they bring. For such an evaluation, we estimated the economic impacts of dengue in Singapore and the expected vaccine costs for different prices. In this way we estimated price thresholds for which vaccination is not cost-effective. This research provides useful estimates that will contribute to informed decisions regarding the adoption of dengue vaccination programs