Joint bidding, information pooling, and the performance of petroleum lease auctions / BEBR No.889

Includes bibliographical references (p. 22)

The Effects of the Hemlock Woolly Adelgid on Abundance and Nymphal Infection Prevalence of Black-Legged Ticks in Maine

The black-legged tick (Ixodes scapularis) has recently made a tremendous impact in Maine due to its role as a vector for the bacterial pathogen Borrelia burgdorferi, the causative agent of Lyme disease. A lesser known, but equally concerning, invasive insect is the hemlock woolly adelgid (HWA; Adelges tsugae), a sap-sucking scale that is primarily responsible for the ongoing widespread decline of eastern hemlock in the northeast. Maine is currently experiencing a co-invasion of these species, and this study tests the hypothesis that the phenomenon of hemlock loss may facilitate the invasion of the black-legged tick by a combination of indirect effects. By killing eastern hemlock trees, the HWA alters forest structure (e.g., letting more light through the canopy) and changes the species composition of plant and wildlife communities, including important hosts of the black-legged tick. My study simulates the consequences of HWA infestation by comparing tick abundance and nymphal infection prevalence (NIP) in hemlock and hardwood stands in southern Maine and the Bangor area. I hypothesized that the HWA is indirectly increasing both tick abundance and Lyme disease risk in Maine by creating ecological conditions that alter abundance of deer and provide a more suitable microhabitat for the tick. I also predicted that NIP would differ between the two treatments, with ticks collected in deciduous stands having higher infection prevalence. My results showed no significant difference in either tick abundance or NIP between the two treatments. Additionally, I tested one mechanism that could explain these patterns by conducting deer scat surveys using standardized transects. There was no significant difference in deer scat counts between the treatments. Conclusions from this work could inform park managers and Maine citizens about the likelihood of Lyme infection or tick bites in certain areas of forests or parks

Stability of conversational language samples from children in kindergarten: the effects of time, sample length, and topic

The purpose of this study was to examine the reliability of measures from conversational language samples in the school-aged population. Two 10-minute conversational language samples were collected from 20 at-risk kindergarten children to determine their reliability and feasibility as an assessment and progress monitoring tool. All samples were collected and transcribed by one examiner using an outlined elicitation protocol in which the children were asked open ended questions about school and home activities in various time segments. Test-retest reliability was determined across eleven language measures for each child. Significant reliability correlation coefficients were observed for each language sample measure. The amount of variance due to sample length and topic were analyzed utilizing generalizability theory, which observes various facets accounting for measurement error. Variance was calculated for each language measure. Conversational language samples were found to have strong test-retest reliability across all language measures. The greatest amount of variance in measures was attributed to the child in most language measures with the interaction between the child, session, and length/topic accounting for the second largest amount of variance in most   measures. Length and topic accounted for negligible amounts of variance in language measures. These findings demonstrated that shorter conversational language samples are reliable across time and that the length and topic of the sample do not have a substantial impact on the reliability of language measures.  M.S