Gray Filter Research Articles

Color discrimination in horses

Four Arabian horses and one Thoroughbred were presented with a series of two-choice color vs. gray discrimination problems. Testing was done in a stall containing a wall with two translucent panels that were illuminated from behind by light projected through color or gray filters to provide the discriminative stimuli. Horses first learned to push one of the panels in order to receive the food reward behind the positive stimulus in an achromatic light–dark discrimination task, and were then tested on their ability to discriminate between gray and four individual colors: red (617 nm), yellow (581 nm), green (538 nm), and blue (470 nm). The criterion for learning was set at 85% correct responses, and final testing for all color vs. gray discriminations involved grays of varying intensities, making brightness an irrelevant cue. Three subjects were tested with all four colors. Two of those subjects successfully reached the criterion for learning on all four color vs. gray discriminations, while the third reached criterion with red and blue, but performed at chance levels for yellow and green. A fourth horse was only tested with green and yellow, and a fifth only with blue, and both of those horses successfully reached criterion on the discriminations they attempted. With the exception of the one subject's poor performance with yellow and green, there was no significant difference between horses on any of the discrimination tasks, and no significant difference in their performance with different colors. The results suggest that horses have color vision that is at least dichromatic, although partial color-blindness may occur in some individuals.

A modified confocal laser scanning microscope allows fast ultraviolet ratio imaging of intracellular Ca2+ activity using Fura-2.

A confocal, ultraviolet laser scanning microscope (LSM) for reliable ratio measurements of localized intracellular Ca2+ gradients using the Ca2+-sensitive dye Fura-2 was developed. In a commercial LSM, the filter wheels for the excitation band-pass filters and the grey filters were replaced by acousto-optic tunable filters (AOTF) for rapid switching (</=1.5 micros) of the ultraviolet (351 and 364 nm) and the visible (457, 476, 488, 514 nm) excitation light. This enabled dual wavelength excitation of Fura-2, or 2'7'-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF) for pH measurements. Changing to a transmitted-light detector of high sensitivity allowed for simultaneous recording of differential interference contrast images of the preparation with the excitation light. The AOTF fine control of the intensity of the excitation light and improvements in the emission detector sensitivity enabled the acquisition of up to 120 ratio pairs of high-quality images from a single cell. The optical capabilities and limitations of the instrument were evaluated with fluorescent beads and dye-loaded cultured cells. Agonist-induced intracellular Ca2+ transients in HT29 cells were recorded to test for the instrument's ability to measure changes in [Ca2+]i. Ratio z-sections from Fura-2-loaded cells showed an inhomogeneity of the Fura-2 loading with an accumulation of the dye mostly in the mitochondria. We show, as an example of the microscope's achievable resolution, the spatial and temporal heterogeneity of [Ca2+]i signals in mitochondria and the cytosol in response to agonist-evoked stimulation of HT29 cells. In addition, we show that the lipophilic, membrane-bound Fura-2 derivative Fura-C18, for measurements of near-membrane Ca2+ changes, can be used with this confocal microscope. This new LSM is expected to deepen our understanding of localized [Ca2+]i signals; for example, the nuclear Ca2+ signalling or the [Ca2+]i changes that occur during stimulation of ion secretion in polarized epithelial cells.

Learning optimization of morphological filters with gray scale structuring elements

Mathematical morphology with gray scale structuring elements has attracted much attention, since combinations of the operations in this class can realize almost all noise-removing filters. However, the optimization method for the combination is still uncertain. In this paper, an optimization method for a mathematical morphological filter with gray scale structuring elements is proposed. This method is based on the concept of a neural network with morphological operations and on learning using simulated annealing. The method is also applied to gray scale bipolar morphological filters for image differentiation.

A quantitative method to measure alkaline phosphatase activities in individual leukocytes by image analysis.

Leucocyte alkaline phosphatase (L-ALP) is well known as leukemia marker, but recent results suggest its usefulness for the diagnosis of several diseases. The aim of this study was to develop a quantitative method to measure alkaline phosphatase activities in individual leukocytes by image analysis. We studied the reaction rate of L-ALP in human polymorphonuclear leucocytes by a microscope attached to a TV camera and a computerized image analyzer. The optical density (OD) measured was standardized by grey filters with known absorbance. We measured IOD for individual cells after a set incubation time by end-point measurements. Studies of kinetic parameters of L-ALP were performed by single-point measurements in the linear phase of the reaction and at increasing substrate concentrations. Cellular IOD increased proportionally with incubation time up to 10 min. The mean KM(mM) and Vmax(delta IOD/min) values were 0.70 +/- 0.11 and 1.76 +/- 0.2 (mean +/- SE, n = 5) respectively. Our findings are comparable to previous results using a polyvynil alcohol method in microphotometry analysis. The image analysis of cellular L-ALP activity appears a valuable tool for quantitative studies.

Fe i density measurements by laser induced fluorescence spectroscopy

The density of Fe atoms produced by bombardment of a stainless steel target by Ar+ ions was measured by laser induced fluorescence (LIF) using a tunable dye laser. The excitation transition involved was a 5D4→y 5D04 (λ=302.064 nm); measurements of the fluorescence signal, from the y 5D04→a 5F5 decay (λ=382.043 nm), were made by varying the laser power incident on Fe atoms by means of grey filters. An absolute calibration of the detection system allowed the determination of the number of the emitting atoms, versus the incident power. So the experimental curve of the fraction of total pumped atoms versus the saturation parameter was obtained. On the other hand, that fraction can be calculated by using standard rate equations for LIF process involving three level atoms. The result is strongly dependent on the model for the pumping laser pulse, particularly (as expected) at low incident power level. Assuming a realistic Gaussian temporal dependence for the radiation field energy flux at frequency v, i.e., U (vt) ∼ Uv0te−t2 and calculating the fraction of atoms pumped by the incident pulse, an agreement better than assuming a square time dependence for U(v,t) was found. The measurement sensitivity limit is 109 atoms/cm3 when LIF diagnostic on FTU is considered including plasma emission background.

Image-analysis and cartography of sand hill massifs on high resolution images: application to the Great Western Erg (NW of Algerian Sahara)

Abstract The northeastern part of the Great Western Erg (Algerian Sahara) is an area with a continuous cover of coarse sands organized in alignments of large domes separated by corridors where deflation prevails. The domes are covered by small sharp dunes of fine sand (akles). The homogeneity of the substratum does not favour a spectral approach. The cartography of the domes and deflation areas is performed by using the methods of Mathematical Morphology. Panchromatic SPOT images are preferred, because the 10m pixel resolution is the only unclassified satellite image data that enables differentiation of the landforms. The initial image is processed with grey tone filters in order to homogenize the akles areas. It is next thresholded and the contours of the resulting sets are then regularized. The validation is obtained by comparison with aerial photo-interpretation. At a smaller scale, the orientations of the domes are measured on images from their medial axes.

Binary representation of nonlinear correlators

We describe binary encoding of both gray scale nonlinear joint transform correlators and gray scale nonlinear matched filters. For the nonlinear joint transform correlator, the joint power spectrum transformed by various degrees of nonlinearity is represented in a binary format using a multiple level threshold function. For the nonlinear matched filter, the matched filter function transformed by a general type of nonlinearity, is represented in a binary format using a variable threshold function.

Synthesis of arbitrary digital transfer functions using allpass-based structures derived via LBR two-pair extraction procedure

The implementation of a digital filter transfer function with all transmission zeros on the unit circle is developed via the synthesis of an appropriate allpass function. The synthesis procedure is based on the “LBR-extraction” approach. The resulting structure is in the form of a doubly terminated cascade of lossless (LBR) two-pairs, with each two-pair realizing a single real or a pair of complex transmission zeros. The Concepts of complete and partial “1” removals, and “1” shifting are introduced and utilized during the synthesis process. The resulting structures have several properties in common with the Gray and Markel lattice filters, but do not require tap coefficients for numerator realization. The building blocks used in this paper are similar to those in certain wave-digital filters and orthogonal filters.

Free static threshold perimetry with the Goldmann perimeter

Areas of defects in the visual field can be investigated with the Goldmann perimeter in greater detail by means of free static threshold perimetry. The areas to be investigated are fixed according to the problem in question, either during or after standard perimetry, and are then checked at the threshold. As a basis the grid of supraliminal pattern perimetry on the Goldmann perimeter is taken, so that checks monitoring changes in defects can be made at the same test points. The combination of the neutral gray filter sets in the Goldmann perimeter allows threshold investigation at stimuli intervals of 1 dB. Examples of findings are used to show how free static threshold perimetry can be employed to check for defects, and particularly for the early stages of glaucoma.

A "high-performance" 2D gel scanner.

We describe the design principles of a photometric flatbed scanner with a scan area of 250 X 250 mm2, a dynamic range of 4000 gray levels, a signal/noise ratio of 2000/1, a step size of 0.1 mm, and a step frequency of 2000 steps per second. It is controlled by a microcomputer and used to acquire data for quantitative evaluation of gels or chromatograms. The performance of the instrument is demonstrated by the data obtained by scanning gratings, gray step filters, and high-resolution electropherograms.

Effect of irradiation on the optical, electrophysical, and surface properties of GaAlAs heterostructures

The effect of irradiation with 3.5-MeV electrons on the properties of GaAlAs-based light-emitting structures is investigated. It is shown that the considerable reduction in the intensity of light emitted as a result of electron irradiation is not accompanied by changes in the recombination and electrical properties of the structures mentioned. Electron microscope and Auger spectral measurements have established that electron irradiation leads to the appearance on the external surface of the n layer of the structure regions of free aluminum accumulation, the number and size of which depend on the electron dose. The assumption is advanced that the regions mentioned may play the role of a gray filter for the light emitted by the structure.

Spatial frequency coloring and feature coloring

Presents a method that uses as components a dispersive element (prism or grating) and a gray spatial filter. The dispersive element produces a multitude of laterally shifted spatial frequency spectra in the Fourier domain. A suitable gray transparency in the Fourier plane assigns to every spatial frequency a typical wavelength. Hence, the texture of the object can be color encoded in the image. In a second experiment the filter is computed such that one out of two different patterns appear red and the other green. This experiment is an extension of Wiener filtering.

Research on the Radiation Character near the Plant (1)

A spectroradiometer covering the wavelength range of 340mμ-820mμ was devised to measure the light intensity in plant canopies.The spectroradiometer consists of a small radiation receiving head which is able to move freely in all directions and to be put in the direct neiborhood of the plant, a light tube, an amplifier, an electric power, a meter, and a standard tungsten lamp. The incoming radiation is scattered by the receiving head made of scattering frosted quartz plate, and the scattered light is conducted in the light tube about 1.6 meter long to neutral gray filters, a chopper drived by a synchronons motor, and a detector (photomultiplier). Wavelength scanning was carried out by exchanging filters mounted on a disc, and the calibration of the meter was made by measuring the radiation energy from the standard tungsten lamp.

Discussion on the resolution of optical images

When working with bacteria, bacteriophages and viruses, the limits, first of resolution and then of visibility, were approached. Examples showed how resolution was increased by increasing the numerical aperture (N.A.) and the refractive index. Internal structures, involution granules and spores in dried not-fixed bacteria, bacteriophages from B. coli and staphylococci can be resolved in this way. A method of azimuthal illumination was shown to give similar results with active cells. Further, a method was described in which resolution was obtained by reduction of intensity; the reduction was effected by crossing polaroid discs or by interposing neutral grey filters. This method of increased resolution by decreased intensity was illustrated by a number of photographs showing the separation of otherwise inseparable holes in a screen, the resolution of the shape of otherwise unresolved holes and the application of this method to viruses. In this way the slit between diplococci could be resolved after highest N.A. and n had not rendered it resolvable. The elementary bodies of certain viruses were separated and their shapes resolved. This method has been applied successfully to the measurement of the sizes of virus bodies. The measurements were checked and confirmed with a microphotometer built on the artificial star principle. Most of the results were recorded photographically as well as observed visually, showing that the effect of increased resolution by reduced intensity can be produced if the eye is the perceptive instrument or if the photographic emulsion is employed for the purpose. The medium of reception, whether retina or emulsion grain, imposes its modifications on the effect, which was realized with a number of different optical systems by various makers. To sum up, it appeared in the course of the experiments described that all ways of increasing resolution must lead to the same effect, that is the reduction of the diameter of the Airy disc or diffraction fringe. Whether this is done by increasing the N.A. or n, or decreasing the wave-length or the intensity, the result must be in the same direction. The factors N.A., n and λ are represented in the formula for resolution, and it was suggested that intensity should be included.

CARBON DIOXIDE REDUCTION WITH MOLECULAR HYDROGEN IN GREEN ALGAE

CARBON DIOXIDE REDUCTION WITH MOLECULAR HYDROGEN IN GREEN ALGAE

PRELIMINARY STUDY OF THE NUTRITION OF THE CULTIVATED MUSHROOM

Mushrooms are commercially grown uponl composts of horse manure. As the available supply of manure is becoming less, it is important to explain the wide difference between average and maximum yields. This requires a better knowledge of the nutrition of the cultivated mushroom than we now have. The first attempts to culture Agaricus campestris L. in media of known composition were made by Duggar (2), who made a series of cultures on gray filter paper to which were added various carbonaceous and nitrogenous cornpounds, along with a mineral nutrient solution. His successful cultures included those containing calcium hippurate, peptone, and casein; while the unsuccessful ones were upon the common sugars, starch, mannite, tartrates, lactates, urea, asparagine, ammonium salts, and nitrates. He concluded that the fungus could not utilize carbon in the form of sugars and organic acid salts, nor nitrogen in inorganic form. This conclusion is surprising in view of the general use of these compounds in culture media for fungi. Even the higher fungi have been grown upon such media, Lutz (6) having used a solution of xylose, maltose, ammonium salts, and minerals for hymenomycetes of several types. It is possible that Duggar's negative results were due in part to some adverse condition not easily observed rather than to the inability of the myceliun to develop upon simple nutrients. This possibility was considered in planning the present investigation. Hebert and Heim (4) asserted that calcium and potassium should be added to manures used in the commercial culture of mnushrooms, but supported the assertion only with analyses of mushrooms showing high contents of these elements. Later Hebert and Heim (5) reported that the composting of manure for mushroom culture was marked by losses in ammonia, organic acids, gums, cellulose, and xylan, and by increases in vasculose ( the black materials of the compost) and complex nitrogenous materials. They suggested that the nutrition of the mushroom was dependent upon a supply of the latter groups rather than of the former. Boyer (i), in a study of Agaricuts campestris, transferred his cultures from the original into manure, but said, Almost all organic materials and many inorganic substrata are good. He did not obtain growth upon blotting paper or cellulose; however, it was not stated what medium was used with these materials. Boyer did not mention the inorganic materials used, except to state that potassium nitrate did not improve the growth in

The Selectiveness of the Eye's Response to Wave-Length and its Change with Change of Intensity.

The present study was undertaken in the attempt to deal quantitatively with the selectiveness of the eye's response. More particularly it sought to determine the chromatic RL at seven points on the spectrum and the number of j. n. d. between the lower and upper chromatic thresholds of the four primary colors. The apparatus was designed to present to O two colored stimuli in a visual field subtending an angle of 1° 55.8' with the surrounding field either dark or equated to the brightness of the stimuli. The variations in energy of physical light required for determinations of chromatic j. n. d. from zero to maximum were effected by means of neutral grey gelatine filters and sector disks devised especially for liminal work. The method of limits was the procedure employed for arriving at the j. n. d. With the dark surrounding field it was found that liminal chromatic sensitivity increased in the following order: O, R, Y, BG, B, YG, and G. With the light surrounding field the order was: O, Y, R, YG, B, G, and BG. At the upper threshold, with the dark field, decreasing sensitivity followed the order of YG, G, O, B, BG, R, and Y; with the light field, YG, G, O, BG, B, R, and Y. In the work on chromatic discrimination with the four primary colors it was found that with the dark field Y, G, R, and B reached their maximum points of saturation at the 20th, 32nd, 40th, and 55th j. n. d. respectively; with the light field Y, G, B, and R reached their maxima at the 46th, 70th, 72nd, and 81st j. n. d. From Psych Bulletin 20:05:00336. (PsycINFO Database Record (c) 2012 APA, all rights reserved)