Dynamic Thermal Structure of Imported Fire Ant Mounds

A study was undertaken to characterize surface temperatures of mounds of imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae) and S. richteri Forel, and their hybrid, as it relates to sun position and shape of the mounds, to better understand factors that affect absorption of solar radiation by the nest mound and to test feasibility of using thermal infrared imagery to remotely sense mounds. Mean mound surface temperature peaked shortly after solar noon and exceeded mean surface temperature of the surrounding surface. Temperature range for mounds and their surroundings peaked near solar noon, and the temperature range of the mound surface exceeded that of the surrounding area. The temperature difference between mounds and their surroundings peaked around solar noon and ranged from about 2 to 10°C. Quadratic trends relating temperature measurements to time of day (expressed as percentage of daylight hours from apparent sunrise to apparent sunset) explained 77 to 88% of the variation in the data. Mounds were asymmetrical, with the apex offset on average 81.5 ± 1.2 mm to the north of the average center. South facing aspects were about 20% larger than north facing aspects. Mound surface aspect and slope affected surface temperature; this affect was greatly influenced by time of day. Thermal infrared imagery was used to illustrate the effect of mound shape on surface temperature. These results indicate that the temperature differences between mounds and their surroundings are sufficient for detection using thermal infrared remote sensing, and predictable temporal changes in surface temperature may be useful for classifying mounds in images

Assessing mode effects in online and telephone victimization surveys

Victimization surveys not only represent a vital data source for estimating the amount of crime within a social entity but also provide victimological researchers with valuable information, e.g. about the social distribution and consequences of victimization experiences. To assure adequate interpretation of victimization survey data, knowledge about the data-generating process in general and the measurement of victimization experiences in particular is essential. In 2010, a new round of the International Crime and Victim Survey (ICVS-2) was conducted to explore the different effects of telephone and online victimization surveys. To understand the processes behind these, this study follows a theory-driven approach. Based on a four-step cognitive model of survey response, hypotheses about expected mode effects on the response behavior were developed. For hypothesis testing, a hierarchical modeling strategy based on logistic regressions was applied to the ICVS-2 data. As hypothesized, no effects of survey mode on the response process could be identified for most victimization items. After controlling for sampling frame and unit non-response, the effects of survey administration mode on the propensity of reporting victimization vanished. The sensitive sexual victimization item represented the only exception. In this case, the remaining mode effect could be fully accounted for by systematically differing item non-response rates between modes