1,441 research outputs found
Orbit design for future SpaceChip swarm missions in a planetary atmosphere
No full textThe effect of solar radiation pressure and atmospheric drag on the orbital dynamics of satellites-on-a-chip (SpaceChips) is exploited to design equatorial long-lived orbits about the oblate Earth. The orbit energy gain due to asymmetric solar radiation pressure, considering the Earth's shadow, is used to balance the energy loss due to atmospheric drag. Future missions for a swarm of SpaceChips are proposed, where a number of small devices are released from a conventional spacecraft to perform spatially distributed measurements of the conditions in the ionosphere and exosphere. It is shown that the orbit lifetime can be extended and indeed selected through solar radiation pressure and the end-of-life re-entry of the swarm can be ensured, by exploiting atmospheric drag
The Neural Basis of Successful Word Reading in Aphasia
No full textObjective: Understanding the neural basis of recovery from stroke is a major research goal. Many functional neuroimaging studies have identified changes in brain activity in people with aphasia, but it is unclear whether these changes truly support successful performance or merely reflect increased task difficulty. We addressed this problem by examining differences in brain activity associated with correct and incorrect responses on an overt reading task. On the basis of previous proposals that semantic retrieval can assist pronunciation of written words, we hypothesized that recruitment of semantic areas would be greater on successful trials. Methods: Participants were 21 patients with left-hemisphere stroke with phonologic retrieval deficits. They read words aloud during an event-related fMRI paradigm. BOLD signals obtained during correct and incorrect trials were contrasted to highlight brain activity specific to successful trials. Results: Successful word reading was associated with higher BOLD signal in the left angular gyrus. In contrast, BOLD signal in bilateral posterior inferior frontal cortex, SMA, and anterior cingulate cortex was greater on incorrect trials. Interpretation: These data show for the first time the brain regions where neural activity is correlated specifically with successful performance in people with aphasia. The angular gyrus is a key node in the semantic network, consistent with the hypothesis that additional recruitment of the semantic system contributes to successful word production when phonologic retrieval is impaired. Higher activity in other brain regions during incorrect trials likely reflects secondary engagement of attention, working memory, and error monitoring processes when phonologic retrieval is unsuccessful.Peer reviewe
Surface Errors Without Semantic Impairment in Acquired Dyslexia: A Voxel-Based Lesion-Symptom Mapping Study
No full textPatients with surface dyslexia have disproportionate difficulty pronouncing irregularly spelled words (e.g., pint), suggesting impaired use of lexical-semantic information to mediate phonological retrieval. Patients with this deficit also make characteristic "regularization" errors, in which an irregularly spelled word is mispronounced by incorrect application of regular spelling-sound correspondences (e.g., reading plaid as "played"), indicating over-reliance on sublexical grapheme-phoneme correspondences. We examined the neuroanatomical correlates of this specific error type in 45 left hemisphere chronic stroke patients. Voxel-based lesion-symptom mapping (VLSM) showed a strong positive relationship between the rate of regularization errors and damage to the posterior half of the left middle temporal gyrus. Semantic deficits on tests of single-word comprehension were generally mild, and these deficits were not correlated with the rate of regularization errors. Furthermore, the deep occipital-temporal white matter locus associated with these mild semantic deficits was distinct from the lesion site associated with regularization errors. Thus, in contrast to patients with surface dyslexia and semantic impairment from anterior temporal lobe degeneration, surface errors in our patients were not related to a semantic deficit. We propose that these patients have an inability to link intact semantic representations with phonological representations. The data provide novel evidence for a post-semantic mechanism mediating the production of surface errors, and suggest that the posterior middle temporal gyrus may compute an intermediate representation linking semantics with phonology.Peer reviewe
The productivity effects of decentralized reforms - an analysis of the Chinese industrial reforms
Get PDFThe empirical literature on the effects of ownership has not distinguished between the effects of ownership and the effects of control. It has also generally ignored the dynamic effects of various ownership and control rights. Using a rich set of panel data about changes in China's state-owned enterprises, the author examines the static and dynamic effects of decentralizing ownership and control rights. He finds that productivity and growth rates improved significantly when reform improved the incentives for managers and employees to learn and to work hard - for example by decentralizing the rights to control wages, make production decisions, and appoint new managers. Increasing profit-retention rates and adopting performance contracts - conventionally viewed as the most important reforms for China's state enterprises - did not improve productivity much. Overall, decentralization accounted for a least 42 percent of productivity growth in Chinese state enterprises in the 1980s. Much of that gain came from improvements in the growth rate of productivity rather than in improved levels of productivity.Labor Policies,Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Public Health Promotion,Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Health Monitoring&Evaluation,Municipal Financial Management
Biocatalytic Activation of Sulfur Heteroaromatics Facilitates Dearomatizing Cross-couplings to Set Stereogenic Centres or Axes
No full textThe enantioselective manipulation of abundant flat (hetero)aromatic building blocks through either dearomatization, to establish new stereocenters, or cross-coupling, to construct a stereogenic axis, is an attractive means to generate three-dimensional molecular architectures. By merging the selectivity of engineered biocatalysts with the versatility of chemical synthesis, we establish a new platform for the metal-free enantioselective manipulation of sulfur-containing heteroaromatics, allowing either point or axial chirality to be set. The key to this approach is our ability to leverage the prochirality of sulfur heteroarenes; biocatalytic oxidation of benzothiophenes “switches on” reactivity and establishes a sulfur stereocenter that directs the stereochemical course of subsequent cross-couplings with non-prefunctionalized partners. Exploiting a previously unexplored mechanism, either point-to-point or point-to-axial chirality transfer from sulfur selectively delivers two different sets of chiral molecules. Enzyme evolution is used to convert a wild-type oxygenase into an efficient and selective engineered S-oxygenase capable of furnishing enantiopure benzothiophene S-oxides─little-known sulfoxides whose configurational stability we map out. Our integrated chemoenzymatic approach provides a blueprint for unlocking the potential of sulfur chirality, lying dormant in important heterocycles, to direct transformations that deliver diverse enantioenriched products
Interview with author John Irving about his new book, In One Person , in which
No full textInterview with author John Irving about his new book, In One Person , in which he also responds to questions about his previous books and describes his novels as predetermined collision courses; the reader always anticipates what\u27s coming - you just don\u27t know the how and the when, and the small details
Joseph E. Lowery With Others at an Event, circa 1997
No full textJoseph E. Lowery is shown standing with others including Evander Holyfield, Colin Powell, and Jimmy Carter (second thru fourth from left, respectively, after Lowery) at an event related to the election observation team for the Jamaican elections.The Atlanta University Center Robert W. Woodruff Library acknowledges the generous support of the Joseph & Evelyn Lowery Institute for Justice and Human Rights, the Joseph Echols Lowery Irrevocable Trust, and other donors in supporting the processing and digitization of Morehouse College's Joseph Echols and Evelyn Gibson Lowery Collection
Music for classical guitar by South African composers : a historical survey, notes on selected works and a general catalogue
No full textIncludes abstract.Includes bibliographical references (leaves 296-309).This is the first comprehensive investigation of music for, or including, the classical guitar by South African composers. The focus of this research has been, firstly, to uncover as much of the repertoire as possible, and, secondly, to collate, study, catalogue and report on the information. A brief historical survey of the guitar in South Africa provides the context within which this study was conducted. The primary sources of quantitative data collection were through the archival catalogues of the South African Music Rights Organisation and through personal contact with guitarists, composers and guitar teachers. Other sources consulted were publishers, broadcasting corporations, recording companies, libraries and the internet. The body of the dissertation comprises biographical sketches, background notes, analyses and technical notes on 17 selected solo and chamber works dating from 1947 to 2007 by some of South Africa's most prominent composers and guitaristcomposers. The repertoire ranges in style from the traditional and ethnically inspired to the experimental and abstract. As this is an empirical survey, each selected entry includes details on instrumentation, duration, level of difficulty, number of pages, scordatura, commissions or requests, sources or publishers, premières and recordings. A biography of each composer is provided as well as background notes which offer an overview of the selected work. The notes discuss historical, cultural, musical and extra-musical influences, and frequently include references to interview material. The commentaries on the selected works, with musical examples, include an analytical component describing structure, form, stylistic and compositional elements, while the technical observations include performance suggestions and a grading for each work
Of bludgeons and ballots: Political violence, municipal enfranchisement, and local governance in mid-nineteenth-century Montreal
No full textThe chapter, "Of bludgeons and ballots: political violence, municipal enfranchisement, and local governance in mid-nineteenth-century Montreal" was written by Colin Grittner (Douglas College Faculty). "This edited collection offers a broad reinterpretation of the origins of Canada. Drawing on cutting-edge research in a number of fields, Violence, Order, and Unrest explores the development of British North America from the mid-eighteenth century through the aftermath of Confederation. The chapters cover an ambitious range of topics, from Indigenous culture to municipal politics, public executions to runaway slave advertisements. Cumulatively, this book examines the diversity of Indigenous and colonial experiences across northern North America and provides fresh perspectives on the crucial roles of violence and unrest in attempts to establish British authority in Indigenous territories. Drawing on specific case studies of law and state formation in English and French Canada, Violence, Order, and Unrest brings together innovative research in different fields to reconsider the ideology, governance, and political culture that underpinned British North America. The contributors offer a unique take on Canadian culture and history, demonstrating that we cannot understand Canada today without considering its origins as a colonial project." --From publisher description.book chapterPublished
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