scholarly journals THEORY AND MEASUREMENT OF VISUAL MECHANISMS

1943 ◽  
Vol 27 (2) ◽  
pp. 119-138 ◽  
Author(s):  
W. J. Crozier ◽  
Ernst Wolf
Keyword(s):  
White Light ◽  
Wave Length ◽  
Visual Performance ◽  
Mean Intensity ◽  
Flicker Response ◽  
Intensity Threshold ◽  
Neural Integration ◽  
Full Participation ◽  
Image Area ◽  
The Mean

Flicker response contours (F vs. log Im) for a square image subtending 0.602° on a side, located in the fovea, are simplex probability integrals for a "white" and for four (five) spectral regions filtered from this white, and with different light-time fractions in the flash cycle. The subjective phenomena (the appearance of the field, the intensity threshold for color, and others) at the fusion points along these contours parallel in a variety of ways those obtained on duplex flicker contours resulting from the use of larger or eccentrically placed flickered images. These phenomena therefore cannot be held to indicate involvements of "rod" excitation. The scatter of the index of variation of I1 is such as to demonstrate the full participation of all the potentially excitable neural units at all levels of flash frequency, for each kind of light. The magnitude of this scatter, a measure of neural integration in visual performance, is a function of the number of these units (with Fmax. nearly constant); the two quantities vary together when wave-length composition of light is altered. The properties of the contours for a white light and for the spectral regions filtered from it show that, for the image within the fovea, different numbers of units are excitable in flicker recognition according to the wave-length band used, and different mean frequencies of elements of effect under fixed conditions. The changes in the mean intensity for activation of these units as a function of the light-time fraction in the flash cycle are correlated with the numbers of these units; when this is corrected for, it is pointed out that despite the differences in shape of F vs. log I it cannot be concluded that the mechanism of excitation differs for different wave-lengths. It is indicated that "white" must be regarded as a synthesis, not a mere summation, of effects due to different spectral regions. Certain differences are pointed to as between foveal and more peripheral regions tested, and as between observers differing in the degree of the "yellow spot effect," with regard to the relative effects of wave-length and of image area. A general consequence is the outlining of conditions required for the precise comparison of excitabilities as a function of wave-length in the multivariate visual system.

scholarly journals THEORY AND MEASUREMENT OF VISUAL MECHANISMS

1941 ◽  
Vol 25 (2) ◽  
pp. 293-308 ◽  
Author(s):  
W. J. Crozier ◽  
Ernst Wolf
Keyword(s):  
Wave Length ◽  
Theoretical Interpretation ◽  
Rational Relation ◽  
Flicker Response ◽  
Foveal Region ◽  
Two Factors ◽  
Image Area ◽  
Real Test

The several parameters of the flicker response contour (F – log I) are considered as a function of wave-length composition (white, blue, and red) and light-time fraction, for an extra-foveal region (monocular, temporal retina). These data are compared with those secured for the same image area centrally fixated at the fovea. The systematic changes in the parameters are shown to be in rational relation to other relevant excitability data. Since for two retinal regions the primary contours are quite different, the systematic nature of the behavior of the parameters in the two cases is a real test of the power of the analysis proposed. Theoretical interpretation is required to deal with the properties of sets of performance contours under systematically varied conditions, and cannot rely simply on the comparison of (for example) two contours under the same arbitrary conditions at two retinal locations. In particular it is emphasized that a qualitative separation must be made of the two factors of (a) number of units and (b) the frequencies of their actions, before the wave-length problem can be dealt with effectively.

scholarly journals The refraction and dispersion of argon, and redeterminations of the dispersion of helium, neon, krypton, and xenon

1910 ◽  
Vol 84 (567) ◽  
pp. 13-15 ◽  
Keyword(s):  
Refractive Index ◽  
White Light ◽  
Wave Length ◽  
Great Accuracy ◽  
The Other ◽  
Dispersion Effect ◽  
The Mean ◽  
Helium Neon

So far as we are aware only four determinations of the refractivity of argon have been published. These are as follows:— The first two determinations only deal with the refraction of white light, while the value of Ahrberg’s results is limited by the fact that he was only able to count 12 bands in the red and 50 bands at the other points selected; so that his whole dispersion effect must have been about one band in the violet, a number which is insufficient to ensure great accuracy. Another determination may not, therefore, be considered superfluous. The specimen of argon used by us was kindly lent by Sir William Ramsay, by whom it was purified. The spectrum showed a trace of hydrogen, but none of other gases. The mean of seven experiments gave a refractive index of 1.00028230 for the wave-length 5461. These determinations varied between 1.00028258 and 1.00028183. The dispersion was measured for the seven wave-lengths 6438.5 (Cd), 5790.5 (Hg), 5769.5 (Hg), 5460.7 (Hg), 5209.1 (Ag), 5085.8 (Cd), 4799.9 (Cd).

scholarly journals Gastrointestinal nematode infections in sheep raised in Botucatu, state of São Paulo, Brazil

2014 ◽  
Vol 23 (3) ◽  
pp. 348-354 ◽  
Author(s):  
Maurício Orlando Wilmsen ◽  
Bruna Fernanda Silva ◽  
César Cristiano Bassetto ◽  
Alessandro Francisco Talamini do Amarante
Keyword(s):  
Haemonchus Contortus ◽  
Natural Infection ◽  
Gastrointestinal Nematode ◽  
Gastrointestinal Nematodes ◽  
Sao Paulo ◽  
São Paulo ◽  
Mean Intensity ◽  
Oesophagostomum Columbianum ◽  
The Mean ◽  
In Parenthesis

Gastrointestinal nematode infections were evaluated in sheep raised in Botucatu, state of São Paulo, Brazil between April 2008 and March 2011. Every month, two tracer lambs grazing with a flock of sheep were exposed to natural infection with gastrointestinal nematodes for 28 consecutive days. At the end of this period, the lambs were sacrificed for worm counts. Haemonchus contortus presented 100% of prevalence. The seasons exerted no significant influence on the mean intensity of H. contortus, which ranged from 315 worms in November 2010 to 2,5205 worms in January 2011. The prevalence of Trichostrongylus colubriformis was also 100%, with the lowest mean intensity (15 worms) recorded in February 2011 and the highest (9,760 worms) in October 2009. In the case of T. colubriformis, a significant correlation coefficient was found between worm counts vs. rainfall (r = −0.32; P <0.05). Three other nematodes species were found in tracer lambs, albeit in small numbers. Their prevalence and mean intensity (in parenthesis) were as follows: Oesophagostomum columbianum 28% (25.2), Cooperia curticei 7% (4.5) and Trichuris spp. 2% (1). In conclusion, the environmental conditions of the area proved to be highly favorable for the year-round transmission of H. contortus and T. colubriformis.

scholarly journals Digenetic Trematode Parasites in Two Fresh Water Fishes Ophiocephalus Punctatus and Xenentodon Cancila From North West Himalayas

2021 ◽  
Author(s):  
Sukanya Rajput ◽  
Seema Langer
Keyword(s):  
Fresh Water ◽  
Digenetic Trematode ◽  
Host Fish ◽  
Mean Intensity ◽  
North West ◽  
Trematode Infection ◽  
Xenentodon Cancila ◽  
The Mean ◽  
Union Territory ◽  
Trematode Parasites

Abstract The study was conducted during September 2018-August 2019 to study the digenetic trematode infection in fresh water fishes of some of the water bodies viz. Gho-manhasan, Chakrali and Chadwal of Jammu region of J&K union territory A total of 220 fishes comprising Ophiocephalus punctatus and Xenentodon cancila belonging to families Channidae and Belonidae respectively were examined. A total of 4 digenetic trematode parasites belonging to 4 different families i.e., Euclinostomum heterostomum (Clinostomidae Luhe, 1901); Phyllodistomum tripathi (Gorgoderidae Looss, 1901); Genarchopsis piscicola (Hemiuridae, Luhe, 1901), and Bucephalopsis karvei (Bucephalidae Poche, 1907) were detected. The overall prevalence of digenetic trematode infection was 65.90% and the mean intensity was 3.58. Among these Genarchopsis piscicola showed the highest prevalence (40.38%) with mean intensity 2.95 in the host fish Xenentodon cancila, while in other species the prevalence ranged between 26.23% and 34.62%. Present study authenticates the presence of several species of digenetic trematode parasites in the fishes inhabiting freshwater of J&K union territory.

Effect of Chlorophyllin on Urinary Odor in Incontinent Geriatric Patients

1983 ◽  
Vol 17 (10) ◽  
pp. 732-734 ◽  
Author(s):  
Milap C. Nahata ◽  
Carole A. Slencsak ◽  
Judith Kamp
Keyword(s):  
Visual Analog Scale ◽  
Washout Period ◽  
Geriatric Patients ◽  
Odor Intensity ◽  
Controlled Study ◽  
Analog Scale ◽  
Double Blind ◽  
Mean Intensity ◽  
The Mean ◽  
Percent Decrease

This randomized, double-blind, crossover, placebo-controlled study involved 20 incontinent geriatric patients; all had indwelling Foley catheters. Each patient received chlorophyllin 100 mg/d for two weeks and placebo daily for two weeks, separated by a washout period of one week. For each subject, the intensity of urinary odor was measured ten times during both the treatment and placebo regimen and three times during the washout period, using a visual analog scale. A decrease in urinary odor was associated with chlorophyllin in 12 patients and with placebo in 6 patients at the end of two weeks on each regimen. Chlorophyllin treatment was associated with about a 21-percent decrease in mean urinary odor intensity, whereas placebo increased the odor by about 9 percent. The mean intensity of urinary odor was lowest during the second week of chlorophyllin treatment. Despite the decrease in urinary odor in many patients receiving chlorophyllin, its effect was not significantly greater than that of placebo. Our data suggest that chlorophyllin 100 mg/d for two weeks may not be effective in incontinent geriatric patients with mild to moderate urinary odor.

THE REACTIONS OF THE HOUSEFLY, MUSCA DOMESTICA LINN., TO LIGHT OF DIFFERENT WAVE-LENGTHS

1938 ◽  
Vol 16d (11) ◽  
pp. 307-342 ◽  
Author(s):  
J. W. MacBain Cameron
Keyword(s):  
White Light ◽  
Copper Sulphate ◽  
Wave Length ◽  
Short Wave ◽  
Quantitative Relation ◽  
Copper Sulphate Solution ◽  
Quartz Mercury ◽  
Intensity Changes ◽  
Constant Quality ◽  
Colored Lights

Houseflies were reared on an artificial medium and tested with different wave-lengths of spectral light obtained from a quartz-mercury arc. The spectrum tested extended from λ3022 Å to λ5780 Å, and the lines were made of approximately equal intensity throughout. In addition, λ5461 Å and λ4078 Å were tested at several other intensities. The comparison standard in all cases was white light, obtained from a tungsten-filament, inside-frosted bulb, and filtered through copper sulphate solution. It was of constant quality, and the intensity was varied by changing the size of the bulb and by varying the distance from the bulb to the copper sulphate filter. The lighted areas to which the flies reacted were 5 by 10 mm. On one of these fell a total intensity of colored light of approximately 10.3 microwatts, on the other a range of intensity of white light of from 0.34 to 36.1 μw.Flies to be tested were removed from the breeding cage ten hours before tests began and were kept in darkness until used. Each fly whose record was used in compiling the final results was caused to make ten trips towards the two test lights, and a record was kept of the choice on each trip.A description and discussion of the four different methods found in the literature for conducting experiments of this type, and for analyzing the results, are included. In the first method, the intensity of the test light of a given wave-length is kept constant, while that of the standard light, usually white, is varied until both are equally attractive.The second method involves testing the colored light against a fixed intensity of white and finding the ratio of insects attracted to color. The intensity of white that will give the same ratio of attractiveness when tested against the standard is then determined.In the third method, the two test lights are made equal in intensity, and their relative efficiency is considered to be directly proportional to the number of insects attracted to each.In the last method, the standard is kept fixed in both quality and intensity, and the intensity of the test color is varied until the two are equal in attractiveness.Application of the first three methods to the same data shows that they give results that vary greatly as the intensity changes. Some show that efficiency increases as the intensity increases, while others show a decrease in efficiency with increasing intensity.If the intensities of all colored lights are equal, the three methods give practically the same qualitative results when applied to the same data. That is, a curve of efficiency is found which has its peak at the same wave-length, whatever method is used. Quantitatively, the results given by the three methods differ, so that no definite ratio of attractiveness can be determined between colors.The data obtained were not amenable to analysis by the fourth method, but published results indicate that this is perhaps the best method for determining the quantitative relation between the stimulative efficiencies of light of different colors.The housefly, M. domestica, is much more strongly stimulated by ultraviolet light of wave-length 3656 Å than by any other part of the spectrum examined. The effect decreases, at first rapidly and then more slowly, as the longer wave-lengths are reached; it also decreases on the short-wave side of the peak. The spectrum available extended only as far as λ3022 Å in the ultraviolet, at which point there was still an appreciable attractiveness, apparently greater than that of either yellow or green.Several problems are suggested that require further investigation.

VARIATIONS IN THE KARA SEA LEVEL, THEIR STERIC FACTORS, AND SOLAR RADIATION DURING 1993-2018

2021 ◽  
pp. 38-52
Author(s):  
A.V. KHOLOPTSEV ◽  
◽  
S.A. PODPORIN ◽  
V.A. SAFONOV ◽  
◽  
...  
Keyword(s):  
Solar Radiation ◽  
Sea Level ◽  
Water Layer ◽  
Kara Sea ◽  
Mean Values ◽  
Mean Intensity ◽  
Steric Factors ◽  
The Mean ◽  
Long Term Variations

The GLORYS12v.1 and ERA5 reanalyses for different months are used to study a relationship between long-term variations in the monthly mean values of sea level in different areas of the Kara Sea and their steric factors during 1993-2018. The areas of the sea were identified where the relationships between these changes and variations in the mean temperature and salinity of the upper quasihomogeneous water layer, as well as the variations in the monthly mean intensity of their insolation, are statistically significant.

scholarly journals Occurrence and Spatial Distribution of Dibothriocephalus Latus (Cestoda: Diphyllobothriidea) in Lake Iseo (Northern Italy): An Update

2020 ◽  
Vol 17 (14) ◽  
pp. 5070
Author(s):  
Vasco Menconi ◽  
Paolo Pastorino ◽  
Ivana Momo ◽  
Davide Mugetti ◽  
Maria Cristina Bona ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Perca Fluviatilis ◽  
Northern Italy ◽  
Commercial Fishing ◽  
European Perch ◽  
Chi Square ◽  
Mean Intensity ◽  
Southern Area ◽  
Total Prevalence ◽  
The Mean

Dibothriocephalus latus (Linnaeus, 1758) (Cestoda: Diphyllobothriidea; syn. Diphyllobothrium latum), is a fish-borne zoonotic parasite responsible for diphyllobothriasis in humans. Although D. latus has long been studied, many aspects of its epidemiology and distribution remain unknown. The aim of this study was to investigate the prevalence, mean intensity of infestation, and mean abundance of plerocercoid larvae of D. latus in European perch (Perca fluviatilis) and its spatial distribution in three commercial fishing areas in Lake Iseo (Northern Italy). A total of 598 specimens of P. fluviatilis were caught in 2019. The total prevalence of D. latus was 6.5%. However, there were significant differences between areas (10.2% North; 7.3% Center; 1.5% South) (Chi-square test, p = 0.0018). The mean intensity of infestation ranged from 1 larva in southern area to 1.2 larvae in both the central and northern (Pisogne) areas. In addition, the mean abundance ranged from 0.02 in the southern area to 0.26 in the northern area (Pisogne). The total number of larvae (anterior dorsal—AD = 21; anterior ventral—AV = 1; posterior dorsal—PD = 15; posterior ventral—PV = 5) differed significantly between the four anatomical quadrants (Kruskal–Wallis test; p = 0.0001). The prevalence of D. latus plerocercoid larvae in European perch from Lake Iseo has long been investigated, but without an appropriate sampling design. With the present study, a broader analysis in spatial distribution has been added to the existing literature, revealing new information about D. latus distribution and occurrence in Lake Iseo, with new data that will be useful for health authorities and future studies.

scholarly journals Preliminary evaluation of the VIsion PERformance (VIPER) simulator

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Denise S. Ryan ◽  
Rose K. Sia ◽  
Jennifer B. Eaddy ◽  
Lorie A. Logan ◽  
Jide O. Familoni ◽  
...  
Keyword(s):  
Visual Assessment ◽  
Identification Accuracy ◽  
Visual Performance ◽  
Preliminary Evaluation ◽  
Detection Distance ◽  
Sensitivity Testing ◽  
Road Signs ◽  
The Mean ◽  
Improvised Explosive ◽  
Explosive Devices

Abstract Background This study evaluated the VIsion PERformance (VIPER) simulator’s ability to assess the functional visual performance in warfighters conducting civilian and military tasks. Methods Thirty service members, aged 25–35 years old with a best corrected distance visual acuity (VA) better than or equal to 20/20 or logarithm of the minimum angle of resolution (logMAR) 0.00, were randomized to locate and identify road signs and mock improvised explosive devices (IEDs) under either daytime conditions or with infrared imagery, with (cc) and without (sc) wearing their habitual correction. Participants also underwent binocular uncorrected (UDVA) and corrected (CDVA) visual assessment, refraction, contrast sensitivity testing and wavefront aberrometry. Results The mean age was 28.47 years. The manifest spherical equivalent was − 3.16 ± 1.75 diopters (D), the UDVA in both eyes (OU) was logMAR 0.83 ± 0.47, and the CDVA OU was − 0.11 ± 0.06. For VIPER, the mean difference in the detection distance (DD) for road signs ccDD vs. scDD was 76.7 ± 52.8 m (P < 0.001). The average difference in identification distance (ID) ccID vs. scID was 13.9 ± 6.3 m (P < 0.001). The mean accuracies were 83.5 and 27.9% for cc and sc, respectively (P < 0.001). The regression analysis indicated that a 1.6 m change in the distance accounts for a 1% change in the accuracy (P = 0.002). Without correction, a 4.1 m change accounts for a 1% change in the accuracy (P < 0.001). The average IED ccDD was 29.9 ± 8.2 m, and that for scDD was 13.2 ± 13.6 m (P < 0.001). The average IED ccID was 32.2 ± 6.2 m and that for the scID was 7.4 ± 10.3 m (P < 0.001). The mean IED identification accuracy was 46.7 and 11.4% for cc and sc, respectively (P < 0.001). Conclusions The preliminary results reflect VIPER’s ability to assess functional visual performance when detecting and identifying signs and IEDs. Furthermore, VIPER is able to detect performance changes with and without correction.

The Effects on Visually Impaired Children of Viewing Fluorescent Stimuli under Black-Light Conditions

1998 ◽  
Vol 92 (5) ◽  
pp. 313-321 ◽  
Author(s):  
S.J. LaGrow ◽  
J-P Leung ◽  
S. Leung ◽  
P. Yeung
Keyword(s):  
Visual Acuity ◽  
White Light ◽  
Visually Impaired ◽  
Low Vision ◽  
Visual Performance ◽  
Light Conditions ◽  
Black Light ◽  
High Acuity ◽  
Impaired Children ◽  
Visually Impaired Children

In this study, 30 children with low vision (divided into a high and a low visual acuity group) were presented with stimuli under four conditions (white stimuli-white light, orange stimuli-white light, white stimuli-black light, and orange stimuli-black light) and were asked to rank their preferences for the four conditions. The goal was to determine the effects of the various combinations of stimuli and lighting on the children's visual performance. The orange stimuli viewed under black light resulted in the best performance overall, benefited the low-acuity group more than the high-acuity group, and was the most-preferred condition for both groups.

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