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Search Results: 1 - 10 of 203002 matches for " Timothy N. Welsh "
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Negative Priming in a Joint Selection Task
Timothy N. Welsh, Laura M. McDougall
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0042963
Abstract: Recent studies have suggested that the observation of another individual executing a movement activates representations of the observed movement in the observer. These representations are thought to be used by other systems to facilitate a variety of social cognitive processes, such as social searches. Previous research on social searches has primarily involved contexts where targets were presented in isolation. Typical environments, however, contain targets and non-targets and one must select the correct information for task completion. To gain insight into the processes underlying social searches, participants completed negative priming tasks alone and in pairs. Results indicated that there were no differences in the negative priming effects resulting from the participants observed or performed the preceding selection task. Further, the correlations between individual and joint negative priming suggest that similar processes were activated on these tasks. The findings support the co-representation hypothesis and provide insight into the processes underlying selection in individual and social settings.
Distractor Interference during a Choice Limb Reaching Task
Matthew Ray, Daniel Weeks, Timothy N. Welsh
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0085961
Abstract: According to action-centered models of attention, the patterns of distractor interference that emerge in selective reaching tasks are related to the time and effort required to resolve a race for activation between competing target and non-target response producing processes. Previous studies have only used unimanual aiming tasks and, as such, only examined the effects of competition that occurs within a limb. The results of studies using unimanual aiming movements often reveal an “ipsilateral effect” - distractors on the same side of space as the effector cause greater interference than distractors on the opposite side of space. The cost of the competition when response selection is between the limbs has yet to be addressed. Participants in the present study executed reaching movements to 1 of 4 (2 left, 2 right) possible target locations with and without a distractor. Participants made ipsilateral reaches (left hand to left targets, right hand to right targets). In contrast to studies using unimanual aiming movements, a “contralateral effect” was observed; distractors affording responses for the other hand (in contralateral space) caused more interference than distractors affording responses for the same hand. The findings from the present research demonstrate that when certain portions of response planning must be resolved prior to response initiation, distractors that code for that dimension cause the greatest interference.
The Response Activation Model and Cross-Modal Facilitation and Inhibition of Return: A Trajectory Analysis
Lawrence E.M. Grierson, Timothy N. Welsh, Steve Hansen, Nicola J. Hodges, Spencer Hayes, James LyonsDigby Elliott
The Open Psychology Journal , 2008, DOI: 10.2174/1874350100801010035]
Abstract: Non-informative spatial cues presented prior to a goal-directed movement influence not only movement initiation time but also the spatial characteristics of the movement trajectories. These trajectory effects are thought to stem from an integration of competing motor responses. In the present experiments, trajectories of rapid aiming movements were examined under the constraints of a cue-target inhibition of return (IOR) paradigm. Aiming movements were made to targets that were preceded by a cue stimulus in the same or different location. Four experiments were conducted in which the modality of the cue and target stimulus was manipulated across vision and audition. Although facilitation effects were present under the cross modality protocols, IOR effects were observed only for same cue-target pairings. At short stimulus onset asynchronies, limb trajectories deviated toward the target that had just been cued, particularly when the cue occurred in left space. These trajectory effects are consistent with response activation models of selective attention and movement preparation.
In Vitro Cultured Rat Islets Express Genes That both Prevent and Promote Angiogenesis
Tillmar L,Welsh N
JOP Journal of the Pancreas , 2004,
Abstract: CONTEXT: Endogenous pancreatic islets are supported by a dense sinusoidal capillary system which is disrupted following isolation and culture in vitro. A rapid and accurate revascularization is therefore crucial for the survival and functioning of the transplanted islet. Although a blood flow is established in islet grafts within 1-2 weeks, these islets show poor development of intra-islet capillaries. To improve the revascularization process and the arrangement of the new blood vessels, islet production of the factors governing these processes needs to be further characterized. OBJECTIVE: To study the expression of factors which regulate angiogenesis in cultured rat islets. DESIGN AND MAIN OUTCOME MEASURES: Rat islets were isolated and cultured for one week. After 6 hours of exposure to normoxic (21% O2) or hypoxic (1% O2) conditions, mRNA expression was evaluated by the GEArray Angiogenesis 1 and 2 systems. The expression of the vascular endothelial growth factor (VEGF), the tyrosine kinase with immunoglobulin and epidermal growth factor homology domains 1 (Tie1) and acidic fibroblast growth factor (aFGF), was further evaluated by semi-quantitative RT-PCR. RESULTS: We found the expression of 19 genes that code for factors either promoting or preventing angiogenesis. Only VEGF and Tie1 were upregulated in response to hypoxia. CONCLUSION: Hypoxia-induced islet vascularization may involve VEGF and Tie-induced signaling events. The results also show that cultured islets express genes which prevent angiogenesis concurrently with genes coding for factors stimulating angiogenesis. The balance between these factors is probably of vital importance for the revascularization process in transplanted islets. Thus, pharmacologic or genetic attenuation of islet-derived angiostatic factors may prove beneficial in promoting islet revascularization in future transplantation trials.
Kepler Observations of Transiting Hot Compact Objects
Jason F. Rowe,William J. Borucki,David Koch,Steve B. Howell,Gibor Basri,Natalie Batalha,Timothy M. Brown,Douglas Caldwell,William D. Cochran,Edward Dunham,Andrea K. Dupree,Jonathan J. Fortney,Thomas N. Gautier III,Ronald L. Gilliland,Jon Jenkins,David W. Latham,Jack . J. Lissauer,Geoff Marcy,David G. Monet,Dimitar Sasselov,William F. Welsh
Physics , 2010, DOI: 10.1088/2041-8205/713/2/L150
Abstract: Kepler photometry has revealed two unusual transiting companions orbiting an early A-star and a late B-star. In both cases the occultation of the companion is deeper than the transit. The occultation and transit with follow-up optical spectroscopy reveal a 9400 K early A-star, KOI-74 (KIC 6889235), with a companion in a 5.2 day orbit with a radius of 0.08 Rsun and a 10000 K late B-star KOI-81 (KIC 8823868) that has a companion in a 24 day orbit with a radius of 0.2 Rsun. We infer a temperature of 12250 K for KOI-74b and 13500 K for KOI-81b. We present 43 days of high duty cycle, 30 minute cadence photometry, with models demonstrating the intriguing properties of these object, and speculate on their nature.
KOI-54: The Kepler Discovery of Tidally-Excited Pulsations and Brightenings in a Highly Eccentric Binary
William F. Welsh,Jerome A. Orosz,Conny Aerts,Timothy M. Brown,Erik Brugamyer,William D. Cochran,Ronald L. Gilliland,Joyce Ann Guzik,D. W. Kurtz,David W. Latham,Geoffrey W. Marcy,Samuel N. Quinn,Wolfgang Zima,Christopher Allen,Natalie M. Batalha,Steve Bryson,Lars A. Buchhave,Douglas A. Caldwell,Thomas N. Gautier III,Steve B. Howell,K. Kinemuchi,Khadeejah A. Ibrahim,Howard Isaacson,Jon M. Jenkins,Andrej Prsa,Martin Still,Rachel Street,Bill Wohler,David G. Koch,William J. Borucki
Physics , 2011, DOI: 10.1088/0067-0049/197/1/4
Abstract: Kepler observations of the star HD 187091 (KID 8112039, hereafter KOI-54) revealed a remarkable light curve exhibiting sharp periodic brightening events every 41.8 days with a superimposed set of oscillations forming a beating pattern in phase with the brightenings. Spectroscopic observations revealed that this is a binary star with a highly eccentric orbit, e=0.83. We are able to match the Kepler light curve and radial velocities with a nearly face-on (i=5.5 degree) binary star model in which the brightening events are caused by tidal distortion and irradiation of nearly identical A stars during their close periastron passage. The two dominant oscillations in the light curve, responsible for the beating pattern, have frequencies that are the 91st and 90th harmonic of the orbital frequency. The power spectrum of the light curve, after removing the binary star brightening component, reveals a large number of pulsations, 30 of which have a signal-to-noise ratio > 7. Nearly all of these pulsations have frequencies that are either integer multiples of the orbital frequency or are tidally-split multiples of the orbital frequency. This pattern of frequencies unambiguously establishes the pulsations as resonances between the dynamic tides at periastron and the free oscillation modes of one of the stars. KOI-54 is only the 4th star to show such a phenomenon, and is by far the richest in terms of excited modes.
Modeling Kepler transit light curves as false positives: Rejection of blend scenarios for Kepler-9, and validation of Kepler-9d, a super-Earth-size planet in a multiple system
Guillermo Torres,Fran?ois Fressin,Natalie M. Batalha,William J. Borucki,Timothy M. Brown,Stephen T. Bryson,Lars A. Buchhave,David Charbonneau,David R. Ciardi,Edward W. Dunham,Daniel C. Fabrycky,Eric B. Ford,Thomas N. Gautier III,Ronald L. Gilliland,Matthew J. Holman,Steve B. Howell,Howard Isaacson,Jon M. Jenkins,David G. Koch,David W. Latham,Jack J. Lissauer,Geoffrey W. Marcy,David G. Monet,Andrej Prsa,Darin Ragozzine,Jason F. Rowe,Dimitar D. Sasselov,Jason H. Steffen,William F. Welsh
Physics , 2010, DOI: 10.1088/0004-637X/727/1/24
Abstract: Light curves from the Kepler Mission contain valuable information on the nature of the phenomena producing the transit-like signals. To assist in exploring the possibility that they are due to an astrophysical false positive, we describe a procedure (BLENDER) to model the photometry in terms of a "blend" rather than a planet orbiting a star. A blend may consist of a background or foreground eclipsing binary (or star-planet pair) whose eclipses are attenuated by the light of the candidate and possibly other stars within the photometric aperture. We apply BLENDER to the case of Kepler-9, a target harboring two previously confirmed Saturn-size planets (Kepler-9b and Kepler-9c) showing transit timing variations, and an additional shallower signal with a 1.59-day period suggesting the presence of a super-Earth-size planet. Using BLENDER together with constraints from other follow-up observations we are able to rule out all blends for the two deeper signals, and provide independent validation of their planetary nature. For the shallower signal we rule out a large fraction of the false positives that might mimic the transits. The false alarm rate for remaining blends depends in part (and inversely) on the unknown frequency of small-size planets. Based on several realistic estimates of this frequency we conclude with very high confidence that this small signal is due to a super-Earth-size planet (Kepler-9d) in a multiple system, rather than a false positive. The radius is determined to be 1.64 (+0.19/-0.14) R(Earth), and current spectroscopic observations are as yet insufficient to establish its mass.
La herencia semiótica europea y su expresion en la retorica: México colonial y poscolonial
Gimate,Adrián; Welsh,; Sankey García,María Rayo;
Cuadernos de la Facultad de Humanidades y Ciencias Sociales. Universidad Nacional de Jujuy , 2001,
Abstract: el tema de la herencia semiotica en el ámbito mexicano lo podemos ver desde un acercamiento historico o bien disciplinario. en este breve ensayo, hemos rastreado la influencia semiotica europea según se manifiesta en la poética y la retorica, sobre todo esta última. para ello hemos examinado la circulacion de obras de retorica de los diversos autores a fin de averiguar qué autores han tenido una mayor presencia, pero también hemos querido ver qué países de europa y qué ciudades han tenido mayor influencia en la colonia mexicana, incluyendo los inicios del méxico independiente. para llevar a cabo este estudio nos dimos a la tarea de investigar los fondos reservados de la biblioteca palafoxiana en puebla y de la universidad autonoma de puebla.
Designing Organizations for Exploration and Exploitation
Timothy N. Carroll
Journal of Organization Design , 2012, DOI: 10.7146/jod.1.2.6344
Abstract: All organizations face the core challenge of deciding on investments in two very different types of activities: exploration and exploitation. Exploration activities are future-oriented, such as developing new capabilities, experimenting with new technologies, and pursuing new customers and markets. Exploitation activities, in contrast, focus on the refinement of existing competencies, processes, and products. Because an organization’s design should reflect its goals, it is difficult to accommodate exploration and exploitation activities within a single organization. This article discusses four major approaches used to tackle this problem, and notes the strengths and limitations of each approach.
A First Comparison of Kepler Planet Candidates in Single and Multiple Systems
David W. Latham,Jason F. Rowe,Samuel N. Quinn,Natalie M. Batalha,William J. Borucki,Timothy M. Brown,Stephen T. Bryson,Lars A. Buchhave,Douglas A. Caldwell,Joshua A. Carter,Jesse L. Christiansen,David R. Ciardi,William D. Cochran,Edward W. Dunham,Daniel C. Fabrycky,Eric B. Ford,Thomas N. Gautier III,Ronald L. Gilliland,Matthew J. Holman,Steve B. Howell,Khadeejah A. Ibrahim,Howard Isaacson,Gibor Basri,Gabor Furesz,John C. Geary,Jon M. Jenkins,David G. Koch,Jack J. Lissauer,Geoffrey W. Marcy,Elisa V. Quintana,Darin Ragozzine,Dimitar D. Sasselov,Avi Shporer,Jason H. Steffen,William F. Welsh,Bill Wohler
Physics , 2011, DOI: 10.1088/2041-8205/732/2/L24
Abstract: In this letter we present an overview of the rich population of systems with multiple candidate transiting planets found in the first four months of Kepler data. The census of multiples includes 115 targets that show 2 candidate planets, 45 with 3, 8 with 4, and 1 each with 5 and 6, for a total of 170 systems with 408 candidates. When compared to the 827 systems with only one candidate, the multiples account for 17 percent of the total number of systems, and a third of all the planet candidates. We compare the characteristics of candidates found in multiples with those found in singles. False positives due to eclipsing binaries are much less common for the multiples, as expected. Singles and multiples are both dominated by planets smaller than Neptune; 69 +2/-3 percent for singles and 86 +2/-5 percent for multiples. This result, that systems with multiple transiting planets are less likely to include a transiting giant planet, suggests that close-in giant planets tend to disrupt the orbital inclinations of small planets in flat systems, or maybe even to prevent the formation of such systems in the first place.
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