scholarly journals The impact of scaling rather than shaping attention: Changes in the scale of attention using global motion inducers influence both spatial and temporal acuity.

2020 ◽  
Vol 46 (3) ◽  
pp. 313-323 ◽  
Author(s):  
Rebecca K. Lawrence ◽  
Mark Edwards ◽  
Stephanie C. Goodhew
Keyword(s):  
Global Motion ◽  
Temporal Acuity ◽  
The Impact

scholarly journals The Effect of Stimulus Area on Global Motion Thresholds in Children and Adults

Vision ◽  
2019 ◽  
Vol 3 (1) ◽  
pp. 10
Author(s):  
Kimberly Meier ◽  
Deborah Giaschi
Keyword(s):  
Motion Perception ◽  
Spatial Integration ◽  
Global Motion ◽  
Motion Stimulus ◽  
Stimulus Area ◽  
Displacement Condition ◽  
Per Se ◽  
Spatial Displacements ◽  
Late Maturation ◽  
The Impact

Performance on random-dot global motion tasks may reach adult-like levels before 4 or as late as 16 years of age, depending on the specific parameters used to create the stimuli. Later maturation has been found for slower speeds, smaller spatial displacements, and sparser dot arrays. This protracted development on global motion tasks may depend on limitations specific to spatial aspects of a motion stimulus rather than to motion mechanisms per se. The current study investigated the impact of varying stimulus area (9, 36, and 81 deg2) on the global motion coherence thresholds of children 4–6 years old and adults for three signal dot displacements (∆x = 1, 5, and 30 arcmin). We aimed to determine whether children could achieve mature performance for the smallest displacements, a condition previously found to show late maturation, when a larger stimulus area was used. Coherence thresholds were higher in children compared to adults in the 1 and 5 arcmin displacement conditions, as reported previously, and this did not change as a function of stimulus area. However, both children and adults performed better with a larger stimulus area in the 30 arcmin displacement condition only. This suggests that immature spatial integration, as measured by stimulus area, cannot account for immaturities in global motion perception.

Numerical Investigation of the Effect due to Vessel Motion on Green Water Impact on Deck

2017 ◽  
Author(s):  
Ravindra Babu Kudupudi ◽  
Ranadev Datta
Keyword(s):  
Green Water ◽  
Global Motion ◽  
Cfd Model ◽  
Water Impact ◽  
Water Loading ◽  
Motion Effect ◽  
Heading Angle ◽  
Vessel Motion ◽  
Volume Method ◽  
The Impact

The present paper focuses on modeling of green water loading on an oscillating body using CFD. The vessel motion is calculated a priory using time domain panel method code, then green water impact is computed based on that pre-calculated motion. The finite volume method is used to capture the green water impact, however in order to represent the free surface, volume of fluid method is used. A sophisticated dynamic mesh is used to handle the motion of the vessel in fluid domain. Several examples and case studies are considered to validate the present CFD model as well as to check the effect of global motion on green water loading such as effect of steepness and heading angle on green water impact. Results show that due to the motion, the impact loading phenomena changes significantly and there is a significant change in pressure on the deck after considering the motion effect and it deviates considerably with the results obtained from fixed vessel cases.

Global Performance of the Perdido Spar in Waves, Wind and Current: Numerical Predictions and Comparison With Experiments

2010 ◽  
Author(s):  
Stergios Liapis ◽  
Shankar Bhat ◽  
Constantine Caracostis ◽  
Carl Webb ◽  
Curtis Lohr
Keyword(s):  
Gulf Of Mexico ◽  
Floating Body ◽  
Global Motion ◽  
Spar Platform ◽  
Mooring Lines ◽  
Numerical Predictions ◽  
Pumping Mode ◽  
Heave Plate ◽  
The Impact ◽  
Actual Geometry

In recent years, spars have become a preferred industry solution for certain offshore deepwater developments. Perdido is the first spar platform to be operated by Shell. The Perdido spar has been recently installed in the ultradeepwater Gulf of Mexico Alaminos Canyon and is scheduled for first oil in 2010. This Direct Vertical Access (DVA) spar will operate at a water depth of 7,825′ and will be the deepest spar production and drilling facility in the world. Numerical predictions of the spar global motions in waves, wind and current are presented in this paper. Motivation for this study comes from two facts: 1. Each spar platform design is unique in terms of its size, number and geometry of heave plates, riser system and mooring system. 2. Metocean design criteria have been increased in view of the recent hurricanes. Model tests of the Perdido spar were conducted at MARIN at a scale of 1:59.94. In these experiments, several Gulf of Mexico (GOM) wave, current and wind environments were considered. The six-degree-of-freedom motions, deck accelerations, air gap, as well as the loads on the heave plates, mooring lines and risers were measured. In this paper, global motion predictions of the Perdido spar are given using Shell’s in-house COSMOS/ WAMIT suite of programs. Extensive comparisons between the numerical predictions and the experimental results were undertaken. In all cases, the comparisons are very good. In order to include heave viscous loads and damping, special line members were included at the bottom of the hard tank, the bottom of the soft tank and each heave plate, in addition to standard line members used to describe the truss. These special members contribute heave viscous loads with drag coefficients selected from the Perdido experiments. Several heave plate configurations were considered to systematically study the impact of heave plates on the spar global motions. The influence of the heave plate geometry on the heave added mass and on the global motions was derived using WAMIT. The strakes’ actual geometry was also included in the WAMIT diffraction analysis. Most of the moonpool area at the bottom of the Perdido hard tank is closed. As a result, the pumping mode was not excited during the experiments. However, numerical simulations with WAMIT showed a sharp peak at the “pumping mode” resonant frequency. This peak was suppressed by introducing a second floating body that capped the moonpool at the water surface. Based on these learnings, recommendations for global motion modeling are presented in this paper.

Formation of Lunar Craters and Bright Rays as a Result of Meteorite Impacts

1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten
Keyword(s):  
Explosive Charge ◽  
The Moon ◽  
Meteorite Impacts ◽  
The Earth ◽  
Lunar Craters ◽  
The Impact

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.

The Geosciences Applied to Lunar Exploration

1962 ◽  
Vol 14 ◽  
pp. 169-257 ◽  
Author(s):  
J. Green
Keyword(s):  
Lunar Surface ◽  
Probable Mechanism ◽  
Point Of View ◽  
Lunar Exploration ◽  
Geological Model ◽  
Apply Geophysics ◽  
Surface Features ◽  
The Impact

The term geo-sciences has been used here to include the disciplines geology, geophysics and geochemistry. However, in order to apply geophysics and geochemistry effectively one must begin with a geological model. Therefore, the science of geology should be used as the basis for lunar exploration. From an astronomical point of view, a lunar terrain heavily impacted with meteors appears the more reasonable; although from a geological standpoint, volcanism seems the more probable mechanism. A surface liberally marked with volcanic features has been advocated by such geologists as Bülow, Dana, Suess, von Wolff, Shaler, Spurr, and Kuno. In this paper, both the impact and volcanic hypotheses are considered in the application of the geo-sciences to manned lunar exploration. However, more emphasis is placed on the volcanic, or more correctly the defluidization, hypothesis to account for lunar surface features.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

Organic Syntheses During the Impact of a Comet with a Gaseous Planet

1997 ◽  
Vol 161 ◽  
pp. 189-195
Author(s):  
Cesare Guaita ◽  
Roberto Crippa ◽  
Federico Manzini
Keyword(s):  
Polymeric Material ◽  
Molecular Form ◽  
Parent Compound ◽  
Blue Filter ◽  
Organic Syntheses ◽  
The Impact

AbstractA large amount of CO has been detected above many SL9/Jupiter impacts. This gas was never detected before the collision. So, in our opinion, CO was released from a parent compound during the collision. We identify this compound as POM (polyoxymethylene), a formaldehyde (HCHO) polymer that, when suddenly heated, reformes monomeric HCHO. At temperatures higher than 1200°K HCHO cannot exist in molecular form and the most probable result of its decomposition is the formation of CO. At lower temperatures, HCHO can react with NH3 and/or HCN to form high UV-absorbing polymeric material. In our opinion, this kind of material has also to be taken in to account to explain the complex evolution of some SL9 impacts that we observed in CCD images taken with a blue filter.

Hydrogen Cyanide Polymers from the Impact of Comet P/Shoemaker-Levy 9 on Jupiter

1997 ◽  
Vol 161 ◽  
pp. 179-187
Author(s):  
Clifford N. Matthews ◽  
Rose A. Pesce-Rodriguez ◽  
Shirley A. Liebman
Keyword(s):  
Amino Acids ◽  
Solar System ◽  
Hydrogen Cyanide ◽  
Nitrogen Heterocycles ◽  
Laboratory Studies ◽  
Heterogeneous Solids ◽  
The Many ◽  
Comet Halley ◽  
The Impact ◽  
By Products

AbstractHydrogen cyanide polymers – heterogeneous solids ranging in color from yellow to orange to brown to black – may be among the organic macromolecules most readily formed within the Solar System. The non-volatile black crust of comet Halley, for example, as well as the extensive orangebrown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia, the color observed depending on the concentration of HCN involved. Laboratory studies of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to α-amino acids. Black polymers and multimers with conjugated ladder structures derived from HCN could also be formed and might well be the source of the many nitrogen heterocycles, adenine included, observed after pyrolysis. The dark brown color arising from the impacts of comet P/Shoemaker-Levy 9 on Jupiter might therefore be mainly caused by the presence of HCN polymers, whether originally present, deposited by the impactor or synthesized directly from HCN. Spectroscopic detection of these predicted macromolecules and their hydrolytic and pyrolytic by-products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.

Unusual Microstructure in Shock-Compacted Graphite

1970 ◽  
Vol 28 ◽  
pp. 474-475
Author(s):  
Lucien F. Trueb
Keyword(s):  
Mechanical Characteristic ◽  
Compression Wave ◽  
Gray Zone ◽  
Flyer Plate ◽  
Compacted Graphite ◽  
The Impact

Crushed and statically compressed Madagascar graphite that was explosively shocked at 425 kb by means of a planar flyer-plate is characterized by a black zone extending for 2 to 3 nun below the impact plane of the driver. Beyond this point, the material assumes the normal gray color of graphite. The thickness of the black zone is identical with the distance taken by the relaxation wave to overtake the compression wave.The main mechanical characteristic of the black material is its great hardness; steel scalpels and razor blades are readily blunted during attempts to cut it. An average microhardness value of 95-3 DPHN was obtained with a 10 kg load. This figure is a minimum because the indentations were usually cracked; 14.8 DPHN was measured in the gray zone.

Drug Induced Changes in Cell Organelles

1968 ◽  
Vol 26 ◽  
pp. 110-111
Author(s):  
Sarah A. Luse
Keyword(s):  
Clinical Medicine ◽  
Cell Organelles ◽  
Riboflavin Deficiency ◽  
Drug Induced ◽  
New Era ◽  
Health And Disease ◽  
In The Beginning ◽  
Cellular Pathology ◽  
Induced Changes ◽  
The Impact

In the mid-nineteenth century Virchow revolutionized pathology by introduction of the concept of “cellular pathology”. Today, a century later, this term has increasing significance in health and disease. We now are in the beginning of a new era in pathology, one which might well be termed “organelle pathology” or “subcellular pathology”. The impact of lysosomal diseases on clinical medicine exemplifies this role of pathology of organelles in elucidation of disease today.Another aspect of cell organelles of prime importance is their pathologic alteration by drugs, toxins, hormones and malnutrition. The sensitivity of cell organelles to minute alterations in their environment offers an accurate evaluation of the site of action of drugs in the study of both function and toxicity. Examples of mitochondrial lesions include the effect of DDD on the adrenal cortex, riboflavin deficiency on liver cells, elevated blood ammonia on the neuron and some 8-aminoquinolines on myocardium.

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