459 research outputs found
Parasites and ecosystem energy flow:
No full textIt has been difficult to incorporate parasites into ecological studies at the community and ecosystem levels. The small size of parasites makes them easily overlooked, and the effects of parasites can often be subtle, indirect and difficult to measure. In this thesis I argue that the best way to include parasites into ecological studies is to measure the direct costs of parasites at the individual, population, and community levels. Furthermore, I propose that the best measure of cost is direct energy loss because this metric will scale from the individual to the ecosystem level. Thus, the objectives of this dissertation were to determine the direct and indirect energetic costs of parasitism within individuals, populations, and communities of hosts. To determine the energetic effects of parasites, field surveys, bomb calorimetry, and respirometry were used to create energy budgets for all species collected from streams of the New Jersey Pinelands, including the parasites. The most common parasite was Acanthocephalus tehlequahensis, and at the individual and population level, this parasite significantly alters the energy allocation patterns in its isopod intermediate host. Infection increased ingestion and respiration, decreased survival and reproduction, and caused significantly more production energy to be allocated to growth. This parasite extracted 6.7% of the production energy from the isopod population (infected and uninfected hosts). On the other hand, in the definitive hosts, the parasite had little effect on energy allocation, and there were no significant differences in the energy budgets between infected and uninfected pirate perch hosts infected with A. tehlequahensis and the trematode Phyllodsitomum sp. Although, parasite infection double to the proportion of production energy allocated to reproduction from 7% to 14%, and parasites within the fish population (infected and uninfected hosts) received 1.3% of the host’s production energy. At the ecosystem level, energy budgets were created within two pineland streams, one with a high-level of parasitism and one with a low level of parasitism. Parasites extracted a small amount of energy from both streams (<1%), but proportionally less energy went to parasitism in the stream with low levels of parasitism. Parasite establishment within this stream may be constrained by energy flow through the food web because little energy makes it up the food web to trophic levels that parasites infect. A stable isotope analysis (δ13C andδ15N) was used to determine energy flow and trophic relationships of adult and juvenile parasites and their hosts. There were significant differences in δ15N values of juvenile and adult parasites, and different parasite species within the same hosts. These data suggest that juvenile parasites can feed at a higher trophic level than their adult counter-parts, and when co-occurring within the same fish host different parasite species may acquire energy from different trophic positions. The results of this dissertation suggest that parasites require a small amount of energy from their hosts at all levels of ecological organization. However, parasites are intimately tied to the energy flow of a system because they alter energy allocation patterns of their hosts, they derive their energy from many trophic levels within a food web, and energy dynamics may regulate parasite establishment and maintenance at the ecosystem level. Therefore, energy can be a useful metric in determining the ecological costs of parasitism.Ph.D.Includes bibliographical references (p. 148-163)by Stacey E. Lettin
Code canonicalization and clustering applied to grading
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.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.Includes bibliographical references (page 51).Teachers of MOOCs need to analyze large quantities of student submissions. There are a few systems designed to provide feedback at scale. Adapting these systems for residential courses would provide a substantial benefit for instructors, as a large residential course might still have several hundred students. OverCode, one such system, clusters and canonicalizes student submissions that have been marked correct by an autograder. We present GroverCode, an expanded version of OverCode that canonicalizes incorrect student submissions as well, and includes interface features for assigning grades to submissions. GroverCode was deployed in 6.0001, an introductory Python programming course, to assist teaching staff in grading exams. Overall reactions to the system were very positive.by Stacey Terman.M. Eng
A multi-stage genome-wide association study of bladder cancer identifies multiple susceptibility loci.
No full textWe conducted a multi-stage, genome-wide association study of bladder cancer with a primary scan of 591,637 SNPs in 3,532 affected individuals (cases) and 5,120 controls of European descent from five studies followed by a replication strategy, which included 8,382 cases and 48,275 controls from 16 studies. In a combined analysis, we identified three new regions associated with bladder cancer on chromosomes 22q13.1, 19q12 and 2q37.1: rs1014971, (P = 8 × 10⁻¹²) maps to a non-genic region of chromosome 22q13.1, rs8102137 (P = 2 × 10⁻¹¹) on 19q12 maps to CCNE1 and rs11892031 (P = 1 × 10⁻⁷) maps to the UGT1A cluster on 2q37.1. We confirmed four previously identified genome-wide associations on chromosomes 3q28, 4p16.3, 8q24.21 and 8q24.3, validated previous candidate associations for the GSTM1 deletion (P = 4 × 10⁻¹¹) and a tag SNP for NAT2 acetylation status (P = 4 × 10⁻¹¹), and found interactions with smoking in both regions. Our findings on common variants associated with bladder cancer risk should provide new insights into the mechanisms of carcinogenesis
Neurophysiological Correlates of Sensory-Based Subtypes in Autism
No full textAbstract
Date Presented 3/30/2017
Substantial heterogeneity within the population of children with autism suggests possible sensory subtypes that may help to explain behavioral differences. This study considers objective neurophysiological measurements in response to sensory exposure as a means to better characterize such subtypes.
Primary Author and Speaker: Kelle DeBoth
Contributing Authors: Stacey Reynolds, Shelly J. Lane, Henry Carretta, Alison E. Lane, Roseann C. Schaaf</jats:p
Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits
No full text© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hage, S., Galy, V. V., Cartigny, M. J. B., Acikalin, S., Clare, M. A., Grocke, D. R., Hilton, R. G., Hunt, J. E., Lintern, D. G., McGhee, C. A., Parsons, D. R., Stacey, C. D., Sumner, E. J., & Talling, P. J. Efficient preservation of young terrestrial organic carbon in sandy turbidity-current deposits. Geology, 48(9), (2020): 882-887, doi:10.1130/G47320.1.Burial of terrestrial biospheric particulate organic carbon in marine sediments removes CO2 from the atmosphere, regulating climate over geologic time scales. Rivers deliver terrestrial organic carbon to the sea, while turbidity currents transport river sediment further offshore. Previous studies have suggested that most organic carbon resides in muddy marine sediment. However, turbidity currents can carry a significant component of coarser sediment, which is commonly assumed to be organic carbon poor. Here, using data from a Canadian fjord, we show that young woody debris can be rapidly buried in sandy layers of turbidity current deposits (turbidites). These layers have organic carbon contents 10× higher than the overlying mud layer, and overall, woody debris makes up >70% of the organic carbon preserved in the deposits. Burial of woody debris in sands overlain by mud caps reduces their exposure to oxygen, increasing organic carbon burial efficiency. Sandy turbidity current channels are common in fjords and the deep sea; hence we suggest that previous global organic carbon burial budgets may have been underestimated.We thank C. Johnson, M. Lardie, A. Gagnon, A. McNichol, and the NOSAMS (National Ocean Sciences Accelerator Mass Spectrometry) team (Woods Hole Oceanographic Institution [WHOI], Massachusetts, USA) for their help with ramped oxidation system and isotopes. We thank the captain and crew of CCGS Vector. Support was provided by UK Natural Environment Research Council (NERC) grants NE/M007138/1 (to Cartigny) and NE/L013142/1 (to Talling), NE/P005780/1 and NE/P009190/1 (to Clare); a Royal Society Research Fellowship (to Cartigny); an International Association of Sedimentologists Postgraduate Grant and National Oceanography Centre Southampton–WHOI exchange program funds (to Hage); an independent study award from WHOI (to Galy); the Climate Linked Atlantic Sector Science (CLASS) program (NERC grant NE/R015953/1); and the European Research Council under the European Union’s Horizon 2020 research and innovation program (Grant 725955, to Parsons). We thank François Baudin, Xingqian Cui, editor James Schmitt, and three anonymous reviewers
Embedding Employability: Insights and Outcomes
No full textSpeakers: Dr Sayjda Talib (lead author), Teaching Fellow, Lancaster University with Dr Stacey Noble Senior Teaching Associate, Lancaster University Talib and Noble (2018) Abstract - “This paper details the experiences of embedding bespoke employability modules within the accounting and finance curriculum at Lancaster Unviersity and also provides a take on the role of the Academic Employability Champion, a new departmental ‘curriculum facing’ post for academic staff. The paper begins by outlining the pedagogical gaps faced by the department with increasing anecdotal employer feedback that graduates were not ‘desk ready’. The paper then outlines the consultation process with the faculty/central careers team and the initial provision of AcF.150 and AcF.350, the employability modules. Changes to the module in the five years which it has been operational include greater involvement with employers, intensive student conferences and workshops, integration of cutting edge technology (e.g. video interview simulations and business games).The paper ends with a discussion on the feedback from students, staff and employers and the potential applicability of the bespoke modules in other Higher Education (HE) institutions
Gender and the politics of the gaze in Bronte's Wuthering Heights
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Letras/Inglês e Literatura Correspondente, Florianópolis, 2009.O objetivo deste estudo é apresentar uma análise de como a imagem de Catherine é moldada pelo olhar masculino, como ela enfrenta os três tipos de olhar - o olhar dos personagens, o olhar do leitor, e o olhar do autor - e finalmente, se o olhar masculino é interrompido. O parâmetro teórico desta análise, o conceito do olhar masculino, é teorizado por Laura Mulvey no artigo "Prazer Visual e Cinema Narrativo" (1975) o qual critica a relação entre o olhar masculino e a imagem feminina do prazer visual moldado pela sociedade patriarcal. Através da crítica de Mulvey do prazer visual generizado em filmes, que pertence ao contexto do cinema clássico de Hollywood, articulo sua teoria em relação ao romance Wuthering Heights de Emily Brontë para examinar a dinâmica do olhar masculino em relação à personagem feminina Catherine. Este estudo teve também por objetivo analisar o quanto o paradigma teórico de Mulvey produzido para cinema poderia ser aplicado especificamente em um texto literário escrito no século XIX.The objective of this thesis is to present an analysis of whether Catherine's image has been shaped by the male gaze, how she contends with the three looks of the male gaze - the look of the characters, the look of the reader, and the look of the author - and finally, how the male gaze is broken. The theoretical parameter of this analysis, the concept of the male gaze, is theorized by Laura Mulvey in the article "Visual Pleasure and Narrative Cinema" (1975) which critiques the relation between the male gaze and the female image within the patriarchal molding of visual pleasure. Borrowing Mulvey's critique of the gendering of visual pleasure in films, which pertains to the context of classical Hollywood cinema, I have articulated her theory in relation to Emily Brontë's Wuthering Heights, to examine the dynamics of the male gaze regarding the female character, Catherine. This study also aimed at examing the extent to which Mulvey's theoretical paradigm produced for cinema could be articulated specifically in relation to a literary text written in the nineteenth century
Asymmetric Information and Receiving Investor Outcomes in the Block Market for Corporate Bonds
No full textWe study block trades in the corporate bond market, where dealers buy or sell blocks from initiating customers and offset their positions with receiving investors. Our findings indicate that while receivers benefit from trading cost savings, they primarily bear adverse selection costs and experience worse outcomes when informed trading is prevalent. Mandatory trade reporting improves receiver outcomes by revealing dealers’ private information, but the benefits are reduced when reporting is delayed. Our results emphasize the importance of transparency regime design and suggest potential market fragility: if information asymmetry becomes severe, receivers may withdraw from the block market
Can Deal Failure Be Predicted?
No full textUsing an ex-post realized measure of deal failure, the write-down of acquisition goodwill, we find in a sample of 1,400 completed acquisition deals, that, on average, goodwill exceeds 50% of the purchase price, is impaired for 24% of acquirers, and over
The Death of the Deal: Are Withdrawn Acquisition Deals Informative of CEO Quality?
No full textTo examine the market response to positive revelations of chief executive officer (CEO) quality, this study focuses on CEOs who withdraw acquisition bids when the price becomes increasingly expensive. Firms that withdrawal for price-related reasons earn higher withdrawal returns than firms that withdraw for other reasons. This relation is stronger when CEO uncertainty and discretion is high. CEOs unwilling to increase the offer price are less likely to be replaced and more likely to advance to a larger firm than a control group of CEOs. The finding that the market attaches value to CEO-specific information suggests that unobservable manager characteristics can meaningfully impact firm outcomes.
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