Estimating the spatial and temporal distribution of species richness within Sequoia and Kings Canyon National Parks.

Evidence for significant losses of species richness or biodiversity, even within protected natural areas, is mounting. Managers are increasingly being asked to monitor biodiversity, yet estimating biodiversity is often prohibitively expensive. As a cost-effective option, we estimated the spatial and temporal distribution of species richness for four taxonomic groups (birds, mammals, herpetofauna (reptiles and amphibians), and plants) within Sequoia and Kings Canyon National Parks using only existing biological studies undertaken within the Parks and the Parks' long-term wildlife observation database. We used a rarefaction approach to model species richness for the four taxonomic groups and analyzed those groups by habitat type, elevation zone, and time period. We then mapped the spatial distributions of species richness values for the four taxonomic groups, as well as total species richness, for the Parks. We also estimated changes in species richness for birds, mammals, and herpetofauna since 1980. The modeled patterns of species richness either peaked at mid elevations (mammals, plants, and total species richness) or declined consistently with increasing elevation (herpetofauna and birds). Plants reached maximum species richness values at much higher elevations than did vertebrate taxa, and non-flying mammals reached maximum species richness values at higher elevations than did birds. Alpine plant communities, including sagebrush, had higher species richness values than did subalpine plant communities located below them in elevation. These results are supported by other papers published in the scientific literature. Perhaps reflecting climate change: birds and herpetofauna displayed declines in species richness since 1980 at low and middle elevations and mammals displayed declines in species richness since 1980 at all elevations

Using Search Queries to Understand Health Information Needs in Africa

The lack of comprehensive, high-quality health data in developing nations creates a roadblock for combating the impacts of disease. One key challenge is understanding the health information needs of people in these nations. Without understanding people's everyday needs, concerns, and misconceptions, health organizations and policymakers lack the ability to effectively target education and programming efforts. In this paper, we propose a bottom-up approach that uses search data from individuals to uncover and gain insight into health information needs in Africa. We analyze Bing searches related to HIV/AIDS, malaria, and tuberculosis from all 54 African nations. For each disease, we automatically derive a set of common search themes or topics, revealing a wide-spread interest in various types of information, including disease symptoms, drugs, concerns about breastfeeding, as well as stigma, beliefs in natural cures, and other topics that may be hard to uncover through traditional surveys. We expose the different patterns that emerge in health information needs by demographic groups (age and sex) and country. We also uncover discrepancies in the quality of content returned by search engines to users by topic. Combined, our results suggest that search data can help illuminate health information needs in Africa and inform discussions on health policy and targeted education efforts both on- and offline.Comment: Extended version of an ICWSM 2019 pape

Predictive Biases in Natural Language Processing Models: A Conceptual Framework and Overview

An increasing number of works in natural language processing have addressed the effect of bias on the predicted outcomes, introducing mitigation techniques that act on different parts of the standard NLP pipeline (data and models). However, these works have been conducted in isolation, without a unifying framework to organize efforts within the field. This leads to repetitive approaches, and puts an undue focus on the effects of bias, rather than on their origins. Research focused on bias symptoms rather than the underlying origins could limit the development of effective countermeasures. In this paper, we propose a unifying conceptualization: the predictive bias framework for NLP. We summarize the NLP literature and propose a general mathematical definition of predictive bias in NLP along with a conceptual framework, differentiating four main origins of biases: label bias, selection bias, model overamplification, and semantic bias. We discuss how past work has countered each bias origin. Our framework serves to guide an introductory overview of predictive bias in NLP, integrating existing work into a single structure and opening avenues for future research.Comment: 9 pages excluding references, 1 figure, 3 pages for appendi

Effect of reverberation on the directional sensitivity of auditory neurons : peripheral factors

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis. Page 41 blank.Includes bibliographical references (p. 39-40).Reverberation poses a challenge for theories of sound localization due to the interaction between the direct sound and the various acoustic reflections. These reflections corrupt binaural cues available to the receiver, resulting in a degradation of directional information available in the acoustic stimulus. Despite this interaction, directionally-sensitive neural responses in the auditory midbrain have been shown to be more robust to reverberation than predicted by a binaural model based on the long- term cross-correlation of the two ear-input signals (Devore et al., 2009, Neuron 63(1), pp 123-134). To determine the extent to which this robustness is central or peripheral in origin, and to quantitatively investigate whether peripheral adaptation contributes to this robustness, we recorded auditory nerve (AN) responses to tokens of noise with varying levels of simulated reverberation. We found many qualitatively similar trends in AN responses as have been previously observed in the midbrain, suggesting a peripheral origin of robust directional coding. In particular, we found that degradation of directional coding in the AN due to reverberation is stronger at high frequencies, and that this degradation is limited near the stimulus onset. We also show that peripheral adaptation plays a positive role in increasing robustness of directional representation in the presence of reverberation. We also investigated the nature of the frequency dependence observed in the degradation of directional coding due to reverberation. Based on our experimental results and the results of an auditory model, we argue that in addition to being affected by AN fibers' synchrony to stimulus fine structure, the frequency dependence is also produced by temporal structure of the reverberant room response.by Andrew H. Schwartz.S.M

Effect of dynamic range compression on attending to sounds based on spatial location

Thesis (Ph. D. in Speech and Hearing Bioscience and Technology)--Harvard-MIT Program in Health Sciences and Technology, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 118-125).Many hearing aids introduce nonlinear compressive gain to accommodate the reduced dynamic range that often accompanies hearing loss. Unfortunately, when applied independently at either ear, this gain can introduce fluctuations in interaural level difference (ILD), which is an important cue for spatial perception and attending to sounds in an acoustic mixture. Moreover, natural sounds produce complicated interactions between different sounds in a mixture, as a compressor's gain is driven by whichever source dominates the mixture within a specified temporal window. While independent compression can interfere with spatial perception of sound, it does not always interfere with localization accuracy or speech identification. This thesis investigates the role of dynamic range compression on the ability to attend to target speech in the presence of interfering speech. First, the fundamental concepts behind dynamic range compression and its use are introduced, and used to develop a framework to understand some of the possible effects on ILD and spatial perception. This framework is applied toward the interpretation of the existing literature regarding dynamic range compression and spatial perception, bringing together a seemingly contradictory range of results. In particular, the framework presented here predicts that dynamic range compression will only affect performance in tasks for which relatively small spatial separations are tested, whereas many existing studies compare only large spatial separations to no spatial separation. We describe and analyze the results of an experiment designed to test this prediction by systematically varying the spatial separation between different speech sources that normal-hearing listeners attended to. We found a robust but modest detrimental effect of dynamic range compression on listeners' performance. Linking the left and right compressors so that ILD was unaltered restored performance. Lastly, we develop a model to describe the utility of ILD for such tasks. The results of this model provide insight into the reported behavioral results, and generate predictions for how hearing impairment may alter the observed pattern of results.by Andrew H. Schwartz.Ph.D.in Speech and Hearing Bioscience and Technolog

Bostonia: The Boston University Alumni Magazine. Volume 33

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs