Dynamic Amodal Completion Through the Magic Wand Illusion

In the Magic Wand effect, an overlying figure of the same color as its background is revealed by the motion of a wand behind it. The occluding figure is inferred by integration of the occluding edge information over time. The overlying figure is perceived by modal completion, while the wand and the background underneath are perceived by amodal completion. This illusion is compared with its predecessor from nearly two centuries ago, the Plateau Anorthoscopic Illusion, in which an object is recognizable when moved behind a slit

Unmanned extravehicular environments operation qualification test of the Gemini extravehicular support package and extended umbilical Test plan

Gemini extravehicular support package tests for unmanned part of extravehicular environments operation qualification test progra

The effect of injector design on thrust- chamber erosion

Relation between injector design and erosion of ablative and pyrolytic graphite thrust chamber throa

Torque control system

System stabilizes aximuth of gondolas which are carried by high-altitude balloons as platforms for tracking telescopes. When telescopes must be constantly aimed at specific targets, control system stabilizes gondola to within 5 arc-seconds

Carfentrazone-ethyl Pond Dissipation and Efficacy on Floating Plants

Carfentrazone-ethyl (CE) is a reduced risk herbicide that is currently being evaluated for the control of aquatic weeds. Greenhouse trials were conducted to determine efficacy of CE on water hyacinth ( Eichhornia crassipes (Mart.) Solms- Laub.), water lettuce ( Pistia stratiotes L.), salvinia ( Salvinia minima Baker) and landoltia (Landoltia punctata (G. Mey.) Les & D. J. Crawford ) . CE controlled water lettuce, water hyacinth and salvinia at rates less than the maximum proposed use rate of 224 g ha -1 . Water lettuce was the most susceptible to CE with an EC 90 of 26.9 and 33.0 g ha -1 in two separate trials. Water hyacinth EC 90 values were calculated to be 86.2 to 116.3 g ha -1 , and salvinia had a similar susceptibility to water hyacinth with an EC 90 of 79.1 g ha -1 . Landoltia was not adequately controlled at the rates evaluated. In addition, CE was applied to one-half of a 0.08 ha pond located in North Central, Florida to determine dissipation rates in water and hydrosoil when applied at an equivalent rate of 224 g ha -1 . The half-life of CE plus the primary metabolite, CE-chloropropionic acid, was calculated to be 83.0 h from the whole pond, and no residues were detected in water above the limit of quantification (5 μg L -1 ) 168 h after treatment. CE dissipated rapidly from the water column, did not occur in the sediment above the levels of quantification, and in greenhouse studies effectively controlled three species of aquatic weeds at relatively low rates.(PDF contains 6 pages.

Length summation in noise

To investigate the effect of background noise on visual summation, we measured the contrast detection thresholds for targets with or without a white noise mask in luminance contrast. The targets were Gabor patterns placed at 3° eccentricity to either the left or right of the fixation and elongated along an arc of the same radius to ensure equidistance from fixation for every point along the long axis. The task was a spatial two-alternative forced-choice (2AFC) paradigm in which the observer had to indicate whether the target was on the left or the right of the fixation. The threshold was measured at 75% accuracy with a staircase procedure. The detection threshold decreased with target length with slope −1/2 on log-log coordinates for target lengths between 30′ and 300′ half-height full-width (HHFW), defining a range of ideal matched-filter summation extending up to about 200′ (or about 16× the center width of the Gabor targets). The summation curves for different noise contrasts were shifted copies of each other. For the threshold versus mask contrast (TvN) functions, the target threshold was constant for noise levels up to about −22 dB, then increased with noise contrast to a linear asymptote on log-log coordinates. Since the “elbow” of the target threshold versus noise function is an index of the level of the equivalent noise experienced by the visual system during target detection, our results suggest that the signal-to-noise ratio was invariant with target length. We further show that a linear-nonlinear-linear gain-control model can fully account for these results with far fewer parameters than a matched-filter model

How did Leonardo perceive himself? Metric iconography of da Vinci's self-portraits

Some eighteen portraits are now recognized of Leonardo in old age, consolidating the impression from his bestestablished self-portrait of an old man with long white hair and beard. However, his appearance when younger is generally regarded as unknown, although he was described as very beautiful as a youth. Application of the principles of metric iconography, the study of the quantitative analysis of the painted images, provides an avenue for the identification of other portraits that may be proposed as valid portraits of Leonardo during various stages of his life, by himself and by his contemporaries. Overall, this approach identifies portraits of Leonardo by Verrocchio, Raphael, Botticelli, and others. Beyond this physiognomic analysis, Leonardo's first known drawing provides further insight into his core motivations. Topographic considerations make clear that the drawing is of the hills behind Vinci with a view overlooking the rocky promontory of the town and the plain stretching out before it. The outcroppings in the foreground bear a striking resemblance to those of his unique composition, 'The Virgin of the Rocks', suggesting a deep childhood appreciation of this wild terrain. and an identification with that religious man of the mountains, John the Baptist, who was also the topic of Leonardo's last known painting. Following this trail leads to a line of possible selfportraits continuing the age-regression concept back to a self view at about two years of age