A Qualitative Dosimetric Comparison of Helical Tomotherapy, Coplanar Volumetric Modulated Arc Therapy, and Non-coplanar Volumetric Modulated Arc Therapy for Radiotherapy of Centrally Located Brain Tumors

Abstract Introduction The purpose of the work is to see if there is a dosimetric benefit to using one treatment modality over another when treating centrally located brain tumors. These modalities include helical tomotherapy, non-coplanar VMAT, and coplanar VMAT. Methods Thirty plans were created from ten previously treated patient’s datasets. All patients were planned using a simultaneously integrated boost with a PTV54 and PTV 60. The conformity index and homogeneity index were compared for targets. Dose maximums and means were compared for critical structures between the plans and modalities. Results A significant difference was found for the conformity index for 5400 cGy where helical tomotherapy was the furthest from 1 by more than 10%. For 95% of the higher prescription dose of 6000cGy (5700cGy), the mean conformity index was significantly closer to 1 for helical tomotherapy by more than 20% compared to the other two modalities. Helical Tomotherapy had a significantly higher dose to both lenses and both optic nerves as well as a higher mean dose for the brain stem and normal brain subtracting the PTVs. Helical tomotherapy met all dose constraints for all plans where coplanar VMAT and non-coplanar VMAT did not for two patients where the brainstem was within 3mm of the PTV60. Conclusion For centrally located brain tumors, helical tomotherapy was able to meet all constraints and had a higher CI for 95% of higher target volume. Non-coplanar and coplanar VMAT’s dose to normal structures were comparable and lower than helical tomotherapy but were unable to 3 meet brain stem dose constraints for 2 patients. While all modalities have proven acceptable and useful in treating centrally located brain tumors, the author recommends using HT

Eutrophication Effects on Prey Size and Food Available to Yellow Perch in Lake Erie

Before 1970, yellow perch Perca flavescens grew at similar rates in Lake Erie's western and central basins. At that time, high rates of nutrient loading were causing rapid eutrophication in both areas so that by the mid-1970s the central basin had become mildly eutrophic while the shallow western basin had reached hypereutrophy. From 1970 to 1983, growth rates of yellow perch in the western basin declined sharply while growth rates increased moderately in the central basin. Modeling of bioenergetics suggests that present differences in yellow perch growth rates are due to interbasin differences in food supply and not to temperature. Direct estimation of yellow perch feeding rates in each basin in 1983 supports this inference. Food limitation in the western basin appears related to a reduced size structure of benthic prey associated with advanced eutrophy. In the central basin, larger benthic prey are available and food consumption rates by yellow perch are high. Food limitation is more serious for larger than for smaller yellow perch in the western basin, and this has apparently caused stunting and population degradation. Further evidence from the literature suggests that changes in prey size structure which accompany eutrophication may be a primary cause of the succession of fish species that occurs as lakes age. Mechanistic understanding of this succession will enhance present capacity to predict fish community responses both to ongoing eutrophication and to the more recent oligotrophication of lakes.Funding for this project was provided by Federal Aid in Fish Restoration, Project F-35-R, Study 6, and Commercial Fisheries Research and Development, Project 3-379-R, Study 1, by contract from the Ohio Department of Natural Resources to the Ohio Cooperative Fish and Wildlife Research Unit

Largemouth Bass Predation on Stocked Tiger Muskellunge

To better understand why stocked esocids survive poorly, we estimated mortality rates of tiger muskellunge(F1 hybrid of female muskellunge Esox masquinongy * male northern pike E. lucius) that were placed into two Ohio reservoirs (mean fish total lengths, 171 and 179 mm; 62 fish per hectare). Because pond experiments showed that hybrids stocked at night experienced mortality rates as high as those released during the day, we stocked tiger muskellunge into lakes during the day. Mortality of stocked hybrids (estimated by catch per effort of electrofishing) exceeded 95% within 40 days in both lakes. Population estimates of largemouth bass Micropterus salmoides coupled with stomach-content data revealed that these predators accounted for 26% and 45% of the numbers stocked in the two lakes. In addition, some hybrids died from thermal stress. Improved survival of tiger muskellunge should result if they are stocked at lengths greater than 250 mm to reduce predation losses, and late in fall when thermal stress is reduced.This research was supported in part by funds from the Federal Aid in Fish Restoration Act under Dingell-Johnson Project F-57-R

Strong Semantic Systematicity from Unsupervised Connectionist Learning

A network exhibits strong semantic systematicity when, as a result of training, it can assign appropriate meaning rep?resentations to novel sentences (both simple and embedded) which contain words in syntactic positions they did not oc?cupy during training. Herein we describe a network which displays strong semcintic systematicity in response to unsu?pervised tiaimng. During tradning, two-thirds of all nouns are presented only in a single syntactic position (either as gram?matical subject or object). Yet, during testing, the network correctly interprets thousands of sentences containing those nouns in novel positions. In addition, the network generalizes to novel levek of embedding. Successful training requires a corpus of about 1000 sentences, and network training is quite rapid