3,486 research outputs found
Precedence-effect thresholds for a population of untrained listeners as a function of stimulus intensity and interclick interval
Data are reported from 127 untrained individuals under lag-and single-click conditions in a precedence-effect task. In experiment I, each subject completed ten runs in a two-interval forced-choice design under a lag-click condition and three runs under a single-click condition. The cue to be discriminated was an interaural time difference ÍITDÍ. Stimuli were 125-s rectangular pulses and the interclick interval ÍICIÍ was 2 ms. Subjects were randomly assigned to three groups of approximately 30. Each group was tested at one stimulus intensity Í43, 58, or 73 dBÍ. Mean threshold within each group was greater than 500 s for lag-click ITD conditions, although substantial intersubject variability and a clear effect of stimulus intensity on lag-click ITD thresholds were observed, with lower thresholds for higher intensities. In experiment II, the ICI was varied from 0.3 to 10 ms, and thresholds were obtained from groups of approximately 20 untrained subjects. Data were also collected from three highly experienced observers as a function of ICI. The best naĂŻve subject produced mean thresholds near, but not as low as those obtained from experienced subjects. Analysis of adaptive-track patterns revealed abrupt irregularities in threshold tracking, consistent with either losing the cue or listening to the wrong cue in an ambiguous stimulus
Arachidonate Metabolism and the Signaling Pathway of Induction of Apoptosis by Oxidized LDL/Oxysterol
Owing at least in part to oxysterol components that can induce apoptosis, oxidized LDL (oxLDL) is cytotoxic to mammalian cells with receptors that can internalize it. Vascular cells possess such receptors, and it appears that the apoptotic response of vascular cells to the oxysterols borne by oxLDL is an important part of the atherogenic effects of oxLDL. Thus, an analysis of the signaling pathway of apoptotic induction by oxysterols is of value in understanding the development of atherosclerotic plaque. In a prior study, we demonstrated an induction of calcium ion flux into cells treated with 25-hydroxycholesterol (25-OHC) and showed that this response is essential for 25-OHC-induced apoptosis. One possible signal transduction pathway initiated by calcium ion fluxes is the activation of cytosolic phospholipase A2 (cPLA2). In the current study, we demonstrate that activation of cPLA2 does occur in both macrophages and fibroblasts treated with 25-OHC or oxLDL. Activation is evidenced by 25-OHC-induced relocalization of cPLA2 to the nuclear envelope and arachidonic acid release. Loss of cPLA2 activity, either through genetic knockout in mice, or by treatment with a cPLA2 inhibitor, results in an attenuation of arachidonic acid release as well as of the apoptotic response to oxLDL in peritoneal macrophages or to 25-OHC in cultured fibroblast and macrophage cell lines
The Erotic and the Vulgar: Visual Culture and Organized Labor's Critique of U.S. Hegemony in Occupied Japan
This essay engages the colonial legacy of postwar Japan by arguing that the political cartoons produced as part of the postwar Japanese labor movementâs critique of U.S. cultural hegemony illustrate how gendered discourses underpinned,
and sometimes undermined, the ideologies formally represented by visual artists and the organizations that funded them. A significant component of organized
laborâs propaganda rested on a corpus of visual media that depicted women as icons of Japanese national culture. Japanâs most militant labor unions were propagating anti-imperialist discourses that invoked an engendered/endangered nation that accentuated the importance of union roles for men by subordinating, then eliminating, union roles for women
Transiting Exoplanet Studies and Community Targets for JWST's Early Release Science Program
The James Webb Space Telescope will revolutionize transiting exoplanet
atmospheric science due to its capability for continuous, long-duration
observations and its larger collecting area, spectral coverage, and spectral
resolution compared to existing space-based facilities. However, it is unclear
precisely how well JWST will perform and which of its myriad instruments and
observing modes will be best suited for transiting exoplanet studies. In this
article, we describe a prefatory JWST Early Release Science (ERS) program that
focuses on testing specific observing modes to quickly give the community the
data and experience it needs to plan more efficient and successful future
transiting exoplanet characterization programs. We propose a multi-pronged
approach wherein one aspect of the program focuses on observing transits of a
single target with all of the recommended observing modes to identify and
understand potential systematics, compare transmission spectra at overlapping
and neighboring wavelength regions, confirm throughputs, and determine overall
performances. In our search for transiting exoplanets that are well suited to
achieving these goals, we identify 12 objects (dubbed "community targets") that
meet our defined criteria. Currently, the most favorable target is WASP-62b
because of its large predicted signal size, relatively bright host star, and
location in JWST's continuous viewing zone. Since most of the community targets
do not have well-characterized atmospheres, we recommend initiating preparatory
observing programs to determine the presence of obscuring clouds/hazes within
their atmospheres. Measurable spectroscopic features are needed to establish
the optimal resolution and wavelength regions for exoplanet characterization.
Other initiatives from our proposed ERS program include testing the instrument
brightness limits and performing phase-curve observations.(Abridged)Comment: This is a white paper that originated from an open discussion at the
Enabling Transiting Exoplanet Science with JWST workshop held November 16 -
18, 2015 at STScI (http://www.stsci.edu/jwst/science/exoplanets). Accepted
for publication in PAS
The Extreme Scattering Event Toward PKS 1741-038: VLBI Images
(Abridged) We report multi-epoch VLBI observations of the source PKS 1741-038
as it underwent an extreme scattering event. Observations at four epochs were
obtained, and images were produced at three of these. During the event the
source consisted of a dominant, compact component, essentially identical to the
structure seen outside the event. However, the source's diameter increased
slightly at 13 cm during the ESE. An increase in the source's diameter is
inconsistent with a simple refractive model. We also see no evidence for
ESE-induced substructure within the source or the formation of multiple images,
as would occur in a strongly refractive lens. However, a model in which the
decrease in flux density during the ESE occurs solely because of stochastic
broadening within the lens requires a larger broadening diameter during the ESE
than is observed. Thus, the ESE toward 1741-038 involved both stochastic
broadening and refractive defocussing within the lens. If the structure
responsible for the ESE has a size of order 1 AU, the level of scattering
within an ESE lens may be a factor of 10^7 larger than that in the ambient
medium. A filamentary structure could reduce the difference between the
strength of scattering in the lens and ambient medium, but we conclude that, if
ESEs arise from filamentary structures, they occur when the filamentary
structures are seen lengthwise. We predict the amount of pulse broadening that
would result from a comparable lens passing in front of a pulsar. The pulse
broadening would be no more than 1.1 microseconds, consistent with the lack of
pulse broadening detected during ESEs toward the pulsars PSR B1937+21 and PSR
J1643-1224.Comment: 19 pages, LaTeX2e with AASTeX-4.0, 1 LaTeX table and 5 figures in 9
PostScript files, to be published in the ApJ, minor change in Figures 2a, 3a,
and 4a to correct a labe
Prime movers : mechanochemistry of mitotic kinesins
Mitotic spindles are self-organizing protein machines that harness teams of multiple force generators to drive chromosome segregation. Kinesins are key members of these force-generating teams. Different kinesins walk directionally along dynamic microtubules, anchor, crosslink, align and sort microtubules into polarized bundles, and influence microtubule dynamics by interacting with microtubule tips. The mechanochemical mechanisms of these kinesins are specialized to enable each type to make a specific contribution to spindle self-organization and chromosome segregation
International criteria for electrocardiographic interpretation in athletes: Consensus statement.
Sudden cardiac death (SCD) is the leading cause of mortality in athletes during sport. A variety of mostly hereditary, structural or electrical cardiac disorders are associated with SCD in young athletes, the majority of which can be identified or suggested by abnormalities on a resting 12-lead electrocardiogram (ECG). Whether used for diagnostic or screening purposes, physicians responsible for the cardiovascular care of athletes should be knowledgeable and competent in ECG interpretation in athletes. However, in most countries a shortage of physician expertise limits wider application of the ECG in the care of the athlete. A critical need exists for physician education in modern ECG interpretation that distinguishes normal physiological adaptations in athletes from distinctly abnormal findings suggestive of underlying pathology. Since the original 2010 European Society of Cardiology recommendations for ECG interpretation in athletes, ECG standards have evolved quickly, advanced by a growing body of scientific data and investigations that both examine proposed criteria sets and establish new evidence to guide refinements. On 26-27 February 2015, an international group of experts in sports cardiology, inherited cardiac disease, and sports medicine convened in Seattle, Washington (USA), to update contemporary standards for ECG interpretation in athletes. The objective of the meeting was to define and revise ECG interpretation standards based on new and emerging research and to develop a clear guide to the proper evaluation of ECG abnormalities in athletes. This statement represents an international consensus for ECG interpretation in athletes and provides expert opinion-based recommendations linking specific ECG abnormalities and the secondary evaluation for conditions associated with SCD
Spatial and Temporal Dynamics of Attentional Guidance during Inefficient Visual Search
Spotting a prey or a predator is crucial in the natural environment and relies on the ability to extract quickly pertinent visual information. The experimental counterpart of this behavior is visual search (VS) where subjects have to identify a target amongst several distractors. In difficult VS tasks, it has been found that the reaction time (RT) is influenced by salience factors, such as the target-distractor similarity, and this finding is usually regarded as evidence for a guidance of attention by preattentive mechanisms. However, the use of RT measurements, a parameter which depends on multiple factors, allows only very indirect inferences about the underlying attentional mechanisms. The purpose of the present study was to determine the influence of salience factors on attentional guidance during VS, by measuring directly attentional allocation. We studied attention allocation by using a dual covert VS task in subjects who had 1) to detect a target amongst different items and 2) to report letters briefly flashed inside those items at different delays. As predicted, we showed that parallel processes guide attention towards the most relevant item by virtue of both goal-directed and stimulus-driven factors, and we demonstrated that this attentional selection is a prerequisite for target detection. In addition, we show that when the target is characterized by two features (conjunction VS), the goal-directed effects of both features are initially combined into a unique salience value, but at a later stage, grouping phenomena interact with the salience computation, and lead to the selection of a whole group of items. These results, in line with Guided Search Theory, show that efficient and rapid preattentive processes guide attention towards the most salient item, allowing to reduce the number of attentional shifts needed to find the target
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