scholarly journals Skylight Polarization patterns and Animal Orientation

1982 ◽  
Vol 96 (1) ◽  
pp. 69-91 ◽  
Author(s):  
MICHAEL L. BRINES ◽  
JAMES L. GOULD
Keyword(s):  
Rayleigh Scattering ◽  
Polarized Light ◽  
Processing System ◽  
Light Polarization ◽  
Degree Of Polarization ◽  
Atmospheric Conditions ◽  
Apparent Paradox ◽  
Skylight Polarization ◽  
Visible Wavelengths ◽  
Vector Orientation

1. Although many invertebrate animals orient by means of ultraviolet sky-light polarization patterns, existing measurements of these patterns are inadequate for full analysis of the biologically relevant information available from the sky. To fill this gap we have used a precision scanning polarimeter to measure simultaneously the intensity, degree, and direction of vibration (E-vector orientation) of polarized light at 5° intervals over the sky. The resulting sky maps were constructed for u.v. (350 nm) and visible wavelengths (500 and 650 nm) under a variety of atmospheric conditions. 2. Our measurements confirmed that the patterns of radiance and degree of polarization of skylight are highly variable and hence unreliable as orientation cues; but patterns of E-vector orientation are relatively stable and predictable over most of the sky under all but very hazy or overcast conditions. 3. The observed E-vector patterns correspond more closely to predictions based on first order (Rayleigh) scattering at 650 and 500 nm than at 350 nm. This is true both in terms of absolute accuracy and the proportion of the sky with relatively ‘correct’ information. Yet most insects respond to polarization patterns only at u.v. wavelengths. This apparent paradox can perhaps be resolved by assuming that there is no great selective advantage for any particular wavelength when large areas of blue sky are visible, but that under special and difficult conditions ultraviolet has advantages over longer wavelengths. Measurements under partially cloud-covered sky, for instance, or under extensive vegetation, show that both spuriously polarized and unpolarized light resulting from reflexions present more troublesome interference at longer wavelengths than in the u.v. 4. The accuracy of orientation achieved by dancing honey bees appears to be greater than can readily be accounted for by assuming that they use a strictly geometrical or analytical processing system for their orientation to polarized light.

scholarly journals Polarized Skylight Navigation in Insects: Model and Electrophysiology of e-Vector Coding by Neurons in the Central Complex

2008 ◽  
Vol 99 (2) ◽  
pp. 667-682 ◽  
Author(s):  
Midori Sakura ◽  
Dimitrios Lambrinos ◽  
Thomas Labhart
Keyword(s):  
Vision System ◽  
Gain Control ◽  
Central Complex ◽  
Degree Of Polarization ◽  
Insect Brain ◽  
Atmospheric Conditions ◽  
Compass Orientation ◽  
Vector Coding ◽  
Skylight Polarization ◽  
Vector Orientation

Many insects exploit skylight polarization for visual compass orientation or course control. As found in crickets, the peripheral visual system (optic lobe) contains three types of polarization-sensitive neurons (POL neurons), which are tuned to different (∼60° diverging) e-vector orientations. Thus each e-vector orientation elicits a specific combination of activities among the POL neurons coding any e-vector orientation by just three neural signals. In this study, we hypothesize that in the presumed orientation center of the brain (central complex) e-vector orientation is population-coded by a set of “compass neurons.” Using computer modeling, we present a neural network model transforming the signal triplet provided by the POL neurons to compass neuron activities coding e-vector orientation by a population code. Using intracellular electrophysiology and cell marking, we present evidence that neurons with the response profile of the presumed compass neurons do indeed exist in the insect brain: each of these compass neuron-like (CNL) cells is activated by a specific e-vector orientation only and otherwise remains silent. Morphologically, CNL cells are tangential neurons extending from the lateral accessory lobe to the lower division of the central body. Surpassing the modeled compass neurons in performance, CNL cells are insensitive to the degree of polarization of the stimulus between 99% and at least down to 18% polarization and thus largely disregard variations of skylight polarization due to changing solar elevations or atmospheric conditions. This suggests that the polarization vision system includes a gain control circuit keeping the output activity at a constant level.

scholarly journals OPTICAL POLARIZED EFFECTS FOR QUANTITATIVE REMOTE SENSING

2020 ◽  
Vol XLIII-B1-2020 ◽  
pp. 593-598
Author(s):  
L. Yan ◽  
Y. Li ◽  
H. Mortimer ◽  
R. Zhang ◽  
J. Peltoniemi ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Linear Polarization ◽  
Rayleigh Scattering ◽  
Weather Conditions ◽  
Degree Of Polarization ◽  
Gradual Change ◽  
Distribution Law ◽  
Solar Altitude ◽  
Quantitative Remote Sensing ◽  
Skylight Polarization

Abstract. Polarization is one of the four basic physical properties of solar radiation. After the solar radiation reaches the surface of these media, it reflects, scatters or refracts, and exhibits different degrees of polarization. We use Rayleigh scattering model to get the simulation results of the sky polarization field. We use polarized fisheye camera to collect the sky polarization image, and calculate the distribution pattern of DOLP (degree of linear polarization) and AOLP (azimuth of linear polarization) of the skylight. The stability and gradual change of the degree of polarization in the zenith direction are verified, and the distribution law and daily change law of the degree of polarization in the sky are obtained. With the increase of the solar altitude angle, the degree of polarization will decrease. We also observed the skylight polarization in different weather conditions.

Daphnia pulex swims towards the most strongly polarized light - a response that leads to ‘shore flight’

1999 ◽  
Vol 202 (24) ◽  
pp. 3631-3635 ◽  
Author(s):  
R. Schwind
Keyword(s):  
Visual Field ◽  
Rayleigh Scattering ◽  
Daphnia Pulex ◽  
Polarized Light ◽  
Open Water ◽  
The Other ◽  
Lower Degree ◽  
Degree Of Polarization ◽  
Large Area ◽  
Linearly Polarized

When Daphnia pulex are presented on one side of their visual field with diffuse, large-area linearly polarized light with a horizontal e-vector and on the other side of their visual field with large-area polarized light with a lower degree of polarization, they swim towards the place with the higher degree of polarization. The response is intensity-invariant: Daphnia pulex swim towards the place of maximal polarization regardless of which side of their visual field has the higher intensity of light. As a result of Rayleigh scattering in a pond, the light surrounding the Daphnia is polarized and has a horizontal e-vector. Near the shore, polarization is not homogeneous. The light seen in the direction of the open water has a higher degree of polarization than that seen in the direction towards the shore. Therefore, in a pond, swimming towards the place with the highest degree of polarization leads the Daphnia away from the shore. For Daphnia, this response explains a mechanism that underlies the well-known phenomenon of ‘shore flight’, the active departure of small pelagic crustaceans from shore zones.

scholarly journals How polarization-sensitive interneurones of crickets perform at low degrees of polarization

1996 ◽  
Vol 199 (7) ◽  
pp. 1467-1475 ◽  
Author(s):  
T Labhart
Keyword(s):  
Compound Eye ◽  
Polarized Light ◽  
Degree Of Polarization ◽  
Modulation Amplitude ◽  
Optimal Conditions ◽  
Vector Information ◽  
Vector Orientation ◽  
D Values ◽  
Low Degrees ◽  
Sinusoidal Function

In crickets, polarized-light information from the blue sky is processed by polarization-opponent interneurones (POL-neurones). These neurones receive input from the polarization-sensitive blue receptors found in the specialized dorsal rim area of the compound eye. Even under optimal conditions, the degree of polarization d does not exceed 0.75 in the blue region of the spectrum and it is normally much lower. The aim of this study is to assess how POL-neurones perform at low, physiologically relevant degrees of polarization. The spiking activity of POL-neurones is a sinusoidal function of e-vector orientation with a 180 ° period. The modulation amplitude of this function decreases strongly as the degree of polarization decreases. However, our data indicate that POL-neurones can signal e-vector information at d-values as low as 0.05, which would allow the polarization-sensitive system of crickets to exploit polarized light from the sky for orientation even under unfavourable meteorological conditions.

Skylight Polarization Patterns and the Orientation of Migratory Birds

1989 ◽  
Vol 141 (1) ◽  
pp. 241-256
Author(s):  
KENNETH P. ABLE
Keyword(s):  
Migratory Birds ◽  
Polarized Light ◽  
Degree Of Polarization ◽  
Zonotrichia Albicollis ◽  
Directional Information ◽  
Clear Sky ◽  
Migratory Orientation ◽  
Skylight Polarization ◽  
Colour Patterns ◽  
Artificial Nature

Patterns of polarized light present in the clear dusk sky provide directional information relevant to the orientation behaviour of migratory birds. Experiments performed with white-throated sparrows (Zonotrichia albicollis) and American tree sparrows (Spizella arborea), North American night migrants, examined migratory orientation between the time of sunset and the first appearance of stars under several manipulations of skylight polarization patterns. Under clear skies, birds tested in Emlen funnel orientation cages oriented their hopping basically parallel to the E-vector of polarized light, with a bias towards the brightest part of the sky (sunset direction). Under solid, thick overcast conditions (no polarized light from the natural sky), birds showed axially bimodal hopping orientation parallel to an imposed E-vector. When birds were tested in cages covered with depolarizing material under a clear sky, their hopping orientation was seasonally appropriate and indistinguishable from controls viewing an unaltered clear sky. Skylight polarization patterns are not necessary for the occurrence of migratory orientation, but birds respond strongly to manipulations of the E-vector direction. The results reported here support the hypothesis that the relevant stimulus is the E-vector orientation rather than other parameters of skylight, e.g. intensity or colour patterns, degree of polarization. It appears that these night migrants are using skylight polarization at dusk as one of a set of multiple compass capabilities. Because of the necessarily artificial nature of the polarized light stimuli used in the experimental manipulations, it has not been possible to establish the relationship between this orientation cue and other known mechanisms (magnetic, sun and star compasses).

scholarly journals THE ORIENTATION OF THE E-VECTOR OF LINEARLY POLARIZED LIGHT DOES NOT AFFECT THE BEHAVIOUR OF THE PIGEON COLUMBA LIVIA

1994 ◽  
Vol 191 (1) ◽  
pp. 107-123 ◽  
Author(s):  
M Coemans ◽  
J Hzn ◽  
J Nuboer
Keyword(s):  
Polarized Light ◽  
Columba Livia ◽  
Light Polarization ◽  
Homing Pigeon ◽  
Qualitative Studies ◽  
Polarization Sensitivity ◽  
Directional Response ◽  
Linearly Polarized ◽  
Vector Orientation ◽  
Indirect Reference

Orientation with reference to the time-compensated sun-azimuth compass has been established for the homing pigeon Columba livia. Previous qualitative studies claim that pigeons are sensitive to the orientation of a polarizer and it has been suggested that these animals are able to use sky-light polarization as an indirect reference to the sun's position when the latter is shielded from view. We report experiments which were undertaken to quantify the sensitivity of the homing pigeon to the orientation of linearly polarized light. The results of our initial experiments suggested that the animals responded to secondary cues. Further experiments were carried out to avoid such artefacts. Under circumstances where secondary cues were rigorously avoided, we were, however, not able to demonstrate any directional response that was caused by the E-vector orientation of the illumination. These results throw doubt on the suggested polarization-sensitivity of birds in general.

High-resolution measurement of birefringent fine structure in living cells using a new polarized light microscope

1995 ◽  
Vol 53 ◽  
pp. 54-55
Author(s):  
Rudolf Oldenbourg
Keyword(s):  
Light Microscope ◽  
Fluorescent Dyes ◽  
Polarized Light ◽  
Processing System ◽  
Video Camera ◽  
Molecular Organization ◽  
Computer Assisted ◽  
Image Recording ◽  
Birefringent Crystal ◽  
Technological Advances

The recent renaissance of the light microsope is fueled in part by technological advances in components on the periphery of the microscope, such as the laser as illumination source, electronic image recording (video), computer assisted image analysis and the biochemistry of fluorescent dyes for labeling specimens. After great progress in these peripheral parts, it seems timely to examine the optics itself and ask how progress in the periphery facilitates the use of new optical components and of new optical designs inside the microscope. Some results of this fruitful reflection are presented in this symposium.We have considered the polarized light microscope, and developed a design that replaces the traditional compensator, typically a birefringent crystal plate, with a precision universal compensator made of two liquid crystal variable retarders. A video camera and digital image processing system provide fast measurements of specimen anisotropy (retardance magnitude and azimuth) at ALL POINTS of the image forming the field of view. The images document fine structural and molecular organization within a thin optical section of the specimen.

scholarly journals Magneto-optical design of anomalous Nernst thermopile

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jian Wang ◽  
Asuka Miura ◽  
Rajkumar Modak ◽  
Yukiko K. Takahashi ◽  
Ken-ichi Uchida
Keyword(s):  
Optical Design ◽  
Polarized Light ◽  
Ferromagnetic Material ◽  
Light Polarization ◽  
Optical Recording ◽  
Induced Voltage ◽  
Large Area ◽  
Circularly Polarized Light ◽  
Out Of Plane ◽  
Order Of Magnitude

AbstractThe introduction of spin caloritronics into thermoelectric conversion has paved a new path for versatile energy harvesting and heat sensing technologies. In particular, thermoelectric generation based on the anomalous Nernst effect (ANE) is an appealing approach as it shows considerable potential to realize efficient, large-area, and flexible use of heat energy. To make ANE applications viable, not only the improvement of thermoelectric performance but also the simplification of device structures is essential. Here, we demonstrate the construction of an anomalous Nernst thermopile with a substantially enhanced thermoelectric output and simple structure comprising a single ferromagnetic material. These improvements are achieved by combining the ANE with the magneto-optical recording technique called all-optical helicity-dependent switching of magnetization. Our thermopile consists only of Co/Pt multilayer wires arranged in a zigzag configuration, which simplifies microfabrication processes. When the out-of-plane magnetization of the neighboring wires is reversed alternately by local illumination with circularly polarized light, the ANE-induced voltage in the thermopile shows an order of magnitude enhancement, confirming the concept of a magneto-optically designed anomalous Nernst thermopile. The sign of the enhanced ANE-induced voltage can be controlled reversibly by changing the light polarization. The engineering concept demonstrated here promotes effective utilization of the characteristics of the ANE and will contribute to realizing its thermoelectric applications.

ROTATIONAL PROPERTIES OF MICRO-SLABS DRIVEN BY LINEARLY-POLARIZED LIGHT

2005 ◽  
Vol 14 (03) ◽  
pp. 375-382 ◽  
Author(s):  
CHIH-LANG LIN ◽  
IRÈNE WANG ◽  
MARC PIERRE ◽  
ISABELLE COLOMBIER ◽  
CHANTAL ANDRAUD ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Polarized Light ◽  
Polarization Plane ◽  
Light Polarization ◽  
Good Prediction ◽  
Polarization Anisotropy ◽  
Two Photon ◽  
Flat Slabs ◽  
Linearly Polarized ◽  
Optical Torque

We study the rotational motion of objects trapped in a focused laser beam (optical tweezers). Micrometer-sized flat slabs are fabricated using two-photon photopolymerization. These objects, trapped by linearly-polarized light, tend to align parallel to the polarization plane. This alignment effect is attributed to the polarization anisotropy resulting from the object shape and we present a simple electromagnetic approach to estimate the resulting optical torque. Micro-rotors of different sizes are studied experimentally. We characterize the behavior of micro-objects when the light polarization is rotated at constant speed. Our theoretical approach gives a good prediction of how the size of micro-objects affects their rotation efficiency.

The Nature of Infill Material on the Discontinuities of the Muntele Mare Granite (Beliş-Fantânele, Romania)

2021 ◽  
Author(s):  
Nicolae Har ◽  
Robert Gheorghiu
Keyword(s):  
Slope Stability ◽  
Atmospheric Oxygen ◽  
Polarized Light ◽  
Rock Slope Stability ◽  
Rock Properties ◽  
Iron Hydroxides ◽  
Atmospheric Conditions ◽  
Secondary Phases ◽  
Alteration Processes ◽  
Infill Material

Abstract The stability of rock massifs is strongly influenced by natural degradation processes. In combination with hydrothermal activity or atmospheric exposure, rock alteration processes can lead to the formation of secondary phases that ultimately control the rock quality and slope stability, which are particularly important for engineering works (e.g., road cuts, open pits, quarries, tunnels). The Bozgai open quarry in the Muntele Mare granite massif in the northern Apuseni Mountains (Romania) offers an excellent opportunity to investigate the influence of alteration processes on rock properties, especially owing to the extensive exposure of granite and specific mineral assemblages of hydrothermal genesis to atmospheric conditions. The alteration processes generated secondary phases located on the primary minerals of the affected rocks or deposited as infill material along the granite discontinuities. Natural and oriented samples of the Bozgai quarry infill material were investigated using polarized light, X-ray diffraction, and scanning electron microscopy to obtain images and identify their mineralogical composition. The hydrothermal vein material consists of kaolinite, illite, pyrite, marcasite, quartz, iron hydroxides, albite, and microcline. These samples were exposed to atmospheric oxygen and meteoric water and secondary sulphates (jarosite and gypsum) formed in an acidic environment generated by the oxidization of pyrite and marcasite. The sheeted structure of kaolinite and geochemical behavior of the sulphates in the presence of water play a particularly important role in the reduced rock slope stability in the Bozgai quarry.

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