AKTIVITAS REPELLENT FORMULASI SEDIAAN SPRAY KOMBINASI MINYAK ATSIRI SERAI (Cymbopogon winterianus), DAUN KEMANGI (Ocimum basilicum) DAN NILAM (Pogostemon Cablin) BESERTA UJI PREFERENSINYA

Plants that are played as mosquito repellents, one of which is plants that contain essential oils, such as lemongrass, basil and patchouli. As an effort to make it easier to use, this research will make a spray repellent preparation with a combination of active ingredients from essential oils of lemongrass, basil and patchouli. The research methods included making a spray repellent using essential oils of lemongrass, basil, patchouli every 0.1 ml (5 concentrations %), 0.2 ml (10% concentration), 0.3 ml (15% concentration) and the additives 1ml Propylene glycol and 5 ml 96% Ethanol which functions as a solvent. The experiment used five treatments, namely: Negative control (Kn), Formula A (0.1ml), Formula B (0.2ml), Formula C (0.3ml), and Positive Control (Kp). The parameters tested included pH test, patch test, organoleptic, specific gravity, emulsion stability, preference and percentage of protective power. The protective power test was carried out 10 times from each treatment for 6 hours of observation (0-1 hours, 1-2 hours, 2-3 hours, 3-4 hours, 4-5 hours and 5-6 hours). The results showed that the best spray expulsion treatment was formula B with a concentration of 10% (0.2 ml)

The White Effect

The White effect is an illusion in which gray test patches of identical luminance placed on the black and white bars of a square-wave grating appear different in brightness/lightness. The effect has received much attention because the direction of the brightness change does not correlate with the amount of black or white border in contact with the gray test patch or its general vicinity. The test patch on the black bar appears lighter than the test patch on the white bar despite changes in test patch height or inducing grating spatial frequency. In addition, although the test patch shows a smooth change in brightness/lightness as its spatial position is varied relative to the inducing grating, spatial inhomogeneities in brightness/lightness within the test patch are also visible. A large number of “higher-level” explanations have been offered for the White effect; only the oriented-difference-of-Gaussians model can account for all of these properties.

The Munker–White Effect and Chromatic Induction Share Similar Nonlinear Response Properties

The brightness or color appearance of a region may be altered by the presence of a pattern surrounding it in the visual field. The Munker–White effect (grating surround) and brightness or color induction from concentric annuli ('bull's-eye' surround) are two examples. We examined whether these two phenomena share similar properties. In the asymmetric matching experiment, the task of an observer was to adjust the appearance of a matching patch to match the appearance of a test patch embedded in one of the two types (square wave grating or concentric annuli) of inducing surrounds (inducers). The inducer modulated in one of three color directions (isochromatic: ±(L + M + S) and isoluminance: ±(L – M) or ±S). Each inducer type and color direction had two opposing phases and four contrast levels. The results show that the induced appearance shift increases as a power function of the inducer contrast, regardless of the spatial configuration of the inducer. Further analysis showed that a sensitivity modulation model of lateral interaction could explain both induction effects.

Surface gloss and color perception of 3D objects

Two experiments explore the color perception of objects in complex scenes. The first experiment examines the color perception of objects across variation in surface gloss. Observers adjusted the color appearance of a matte sphere to match that of a test sphere. Across conditions we varied the body color and glossiness of the test sphere. The data indicate that observers do not simply match the average light reflected from the test. Indeed, the visual system compensates for the physical effect of varying the gloss, so that appearance is stabilized relative to what is predicted by the spatial average. The second experiment examines how people perceive color across locations on an object. We replaced the test sphere with a soccer ball that had one of its hexagonal faces colored. Observers were asked to adjust the match sphere have the same color appearance as this test patch. The test patch could be located at either an upper or lower location on the soccer ball. In addition, we varied the surface gloss of the entire soccer ball (including the test patch). The data show that there is an effect of test patch location on observers' color matching, but this effect is small compared to the physical change in the average light reflected from the test patch across the two locations. In addition, the effect of glossy highlights on the color appearance of the test patch was consistent with the results from Experiment 1.

Lightness Constancy: A Direct Test of the Illumination-Estimation Hypothesis

Many models of color constancy assume that the visual system estimates the scene illuminant and uses this estimate to determine an object's color appearance. A version of this illumination-estimation hypothesis, in which the illuminant estimate is associated with the explicitly perceived illuminant, was tested. Observers made appearance matches between two experimental chambers. Observers adjusted the illumination in one chamber to match that in the other and then adjusted a test patch in one chamber to match the surface lightness of a patch in the other. The illumination-estimation hypothesis, as formulated here, predicted that after both matches the luminances of the light reflected from the test patches would be identical. The data contradict this prediction. A second experiment showed that manipulating the immediate surround of a test patch can affect perceived lightness without affecting perceived illumination. This finding also falsifies the illumination-estimation hypothesis.