Sensitivity of biphotonic systems to light intensity fluctuations: Experimental evidence in the thermoluminescence of fluoresceine in boric acid glass

1984 ◽  
Vol 81 (5) ◽  
pp. 2450-2457 ◽  
Author(s):  
J. C. Micheau ◽  
W. Horsthemke ◽  
R. Lefever
Keyword(s):  
Light Intensity ◽  
Boric Acid ◽  
Experimental Evidence ◽  
Intensity Fluctuations

scholarly journals Elaborate pupils in skates may help camouflage the eye

2018 ◽  
Author(s):  
Sean Youn ◽  
Corey Okinaka ◽  
Lydia M Mäthger
Keyword(s):  
Light Intensity ◽  
Spatial Frequency ◽  
Experimental Evidence ◽  
Pupillary Response ◽  
Pupil Dilation ◽  
Primary Factor ◽  
Natural Substrate ◽  
Spatial Frequencies ◽  
Pupillary Responses ◽  
Changing Light

AbstractThe little skate Leucoraja erinacea has elaborately shaped pupils, whose characteristics and functions have not been studied extensively. It has been suggested that such pupil shapes may camouflage the eye; yet, no experimental evidence has been presented to support this claim. Skates are bottom-dwellers that often bury into the substrate with their eyes protruding. If these pupils serve any camouflage function, we expect there to be a pupillary response related to the spatial frequency (“graininess”) of the background against which the eye is viewed. Here, we tested whether skate pupils dilate or constrict in response to background spatial frequency. We placed skates on background substrates with different spatial frequencies and recorded pupillary responses at three light intensities. In experiment 1, the skates’ pupillary response to three artificial checkerboards of different spatial frequencies was recorded. Skates responded to changing light intensity with pupil dilation/constriction; yet, their pupils did not change in response to spatial frequency. In experiment 2, in which skates could bury into three natural substrates with different spatial frequencies, such that their eyes protruded above the substrate, the pupils showed a subtle but statistically significant response to changes in substrate spatial frequency. Given the same light intensity, the smaller the spatial frequency of the natural substrate, the more constricted the pupil. While light intensity is the primary factor determining pupil dilation, these experiments are the first to show that pupils also change in response to background spatial frequency, which suggests that the pupil may aid in camouflaging the eye.

Light intensity fluctuations in backscatter from a turbulent medium

1984 ◽  
Vol 27 (10) ◽  
pp. 890-894 ◽  
Author(s):  
S. S. Kashkarov ◽  
T. N. Nesterova ◽  
A. S. Smirnov
Keyword(s):  
Light Intensity ◽  
Turbulent Medium ◽  
Intensity Fluctuations

ROOM TEMPERATURE STABILIZATION OF RADIATION-PRODUCED FREE RADICALS IN BARBITURIC ACIDS

1961 ◽  
Vol 39 (4) ◽  
pp. 514-533 ◽  
Author(s):  
J. A. R. Cloutier
Keyword(s):  
Free Radicals ◽  
Boric Acid ◽  
Experimental Evidence ◽  
Room Temperature ◽  
Barbituric Acid ◽  
Experimental Results ◽  
Temperature Stabilization ◽  
Barbituric Acid Derivatives

Experimental evidence has shown that a boric acid glass may be used to stabilize at room temperature organic free radicals produced by radiation in a number of barbituric acid derivatives. The method and the experimental results are discussed.

scholarly journals Scattered-light intensity fluctuations in diastolic rat cardiac muscle caused by spontaneous Ca++-dependent cellular mechanical oscillations.

1983 ◽  
Vol 82 (1) ◽  
pp. 119-153 ◽  
Author(s):  
M D Stern ◽  
A A Kort ◽  
G M Bhatnagar ◽  
E G Lakatta
Keyword(s):  
Light Intensity ◽  
Cardiac Muscle ◽  
Scattered Light ◽  
Photon Counting ◽  
Force Production ◽  
Intrinsic Property ◽  
Physiological Saline ◽  
Scattered Light Intensity ◽  
Mechanical Oscillations ◽  
Intensity Fluctuations

Laser light scattered by nonstimulated rat cardiac muscle bathed in physiological saline containing a [Ca++] of 0.4-2.5 mM displays scattered-light intensity fluctuations (SLIF); the frequencies of both SLIF and resting force are Ca++ dependent. Direct inspection of these muscles by phase-contrast microscopy under incoherent illumination revealed the presence of spontaneous asynchronous cellular motions that are also Ca++ dependent. The physical properties of the scattered light are compatible with the hypothesis that SLIF are due to the diastolic motion, except for the dependence on scattering angle, which may be perturbed because the muscles are optically thick. To determine whether diastolic SLIF and motion are an intrinsic property of activated myofilaments, photon-counting auto-correlation of the scattered light was performed both in rat right-ventricular papillary muscles skinned with the detergent Triton X-100 (1%) and in muscles with intact membranes under conditions that alter cellular Ca++ fluxes. In skinned muscles activated over a range of Ca++ from threshold to maximum force production, neither SLIF nor asynchronous motion was observed when Ca++ was buffered to constant values. In intact muscles the frequency of SLIF and the amplitude of diastolic motion were (a) markedly increased by substituting K+ or Li+ for Na+ in the bath; (b) not altered by verapamil (1 microM); and (c) reversibly abolished by caffeine (greater than or equal to 10 mM). These properties are exactly those of mechanical oscillations that have been observed in isolated cardiac cell fragments, which are the result Ca++ oscillations caused by Ca++ release from the sarcoplasmic reticulum (SR). We infer that mechanical oscillations caused by spontaneous Ca++-induced Ca++ release from the SR occur in intact nonstimulated cardiac muscle even in the absence of Ca++ overload and are the principle cause of SLIF, and that myoplasmic [Ca++] in "resting" muscle is not in a microscopic steady state.

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