The ability to detect and use the polarization of light for orientation is widespread among invertebrates. Among terrestrial insects, the retinula cells that are responsible for polarization detection contain a single visual pigment, either ultraviolet or short (blue) wavelength sensitive. With the exception of a few aquatic insects, the visual ...

Polarization vision in vertebrates has been marked with significant controversy over recent decades. In the last decade, however, models from two laboratories have indicated that the spatial arrangement of photoreceptors provides the basis for polarization sensitivity Work in my laboratory, in collaboration with I. Novales Flamarique and F. I. Harosi, ...

A time-resolved Monte Carlo technique was used to simulate the propagation of polarized light in turbid media. Calculated quantities include the reflection Mueller matrices, the transmission Mueller matrices, and the degree of polarization (DOP). The effects of the polarization state of the incident light and of the size of scatterers ...

Subcutaneous injection of L-NAME inhibited afferent impulse activity in n. ischiadicus and n. saphenus and abolished the increase in this activity induced by stimulation of mechanoreceptors after skin irradiation with polarized light with various spectral characteristics. Subsequent subcutaneous injection of sodium nitroprusside restored the pattern of afferent impulse activity in ...

A synchronous polarimeter was set up for the measurement of small rotation angles of the polarization plane of light. The polarimeter is based on a polarizer-Faraday modulator-analyzer structure with a synchronous detection scheme, which produces a linear system response. The theoretical background is studied, and the system performance is investigated ...

The generation of polarity in the cells of eukaryotes in most cases requires an external asymmetrical input. This signal may originate from a random event such as the point of penetration of an egg by a sperm or from asymmetries present in the maternal environment as, for example, in megasporogenesis ...

We show how to two dimensionally encode the polarization state of an incident light beam using a parallel-aligned liquid-crystal spatial light modulator (LCSLM). Each pixel of the LCSLM acts as a voltage-controlled wave plate and can be programmed over a 2pi phase range at a wavelength of 514.5 nm. Techniques ...

Contrary to what has been observed thus far collision-induced light scattering (CILS) can be completely polarized. This exceptional behavior characterizes the very far wing of the binary CILS spectrum by gaseous helium. This conclusion is drawn from an experimental study of the depolarization ratio of He (2) in a much ...

Automatic threshold tracking (Autocapture) controls the amplitude of the pacing pulse and adjusts it to the actual pacing threshold. The algorithm is based on the proper detection of the evoked response (ER) amplitude after the pacing pulse. For this reason an intraoperative evaluation of ER and polarization is recommended. The ...

If light is diffracted by ultrasound in an isotropic medium with acoustically induced birefringence, the state of polarization is modified in each order of diffraction with respect to the initial state of polarization of the incident light wave. In the present paper, some polarization effects are discussed in the case ...

All known polarizers operate through a separation of orthogonal electric field components, one of which is subsequently discarded. As a result, 50% of the unpolarized incident light is wasted in the process of conversion to polarized light. We demonstrate a new method by which we use the optical power in ...

We reexamined the Late Cretaceous-early Tertiary apparent polar wander path for the Pacific plate using 27 paleomagnetic poles from seamounts dated by (40)Ar/(39)Ar geochronology. The path shows little motion from 120 to 90 million years ago (Ma), northward motion from 79 to 39 Ma, and two groups of poles separated ...

It has been shown that in the initial stages of motion processing, the ON and OFF pathways stay more or less separated. There is evidence that this distinction between motion signals from opposite contrast polarities remains at least partly intact in the integration stage of local motion information. At the ...

OBJECTIVE: Polarized light can be used to obtain images of superficial tissue layers such as skin, and some example images are presented. This study presents a study of the transition of linearly polarized light into randomly polarized light during light propagation through tissues. STUDY DESIGN/MATERIALS AND METHODS: The transition of ...

A dual-channel Mach-Zehnder interferometer using heterodyne detection allowed us to measure simultaneously parallel and perpendicular polarization components through various mammalian tissues at a wavelength of lambda = 633 nm. By contrast with liver tissue, squeletic muscles of a few millimeters thickness exhibit strong anisotropic properties that change the direction of ...

Cephalopods are sensitive to the linear polarization characteristics of light. To examine if this polarization sensitivity plays a role in the predatory behavior of cuttlefish, we examined the preference of Sepia officinalis when presented with fish whose polarization reflection was greatly reduced versus fish whose polarization reflection was not affected. ...

We describe two experiments that investigate the roles of polarity and symmetry in the perceptual grouping of contour fragments. Observers viewed, for one second on each presentation, arrays of oriented, spatial-frequency band-pass, elements, in which a subset of the elements was aligned along a twisting curve. In each of five ...

We present a method for selective detection of size-dependent scattering characteristics of epithelial cells in vivo based on polarized illumination and polarization sensitive detection of scattered light. We illustrate the method using phantoms designed to simulate squamous epithelial tissue and progressing to epithelial tissue in vitro and in vivo. Elastic ...

Jones matrices describe the polarization, or spin angular momentum, of a light beam as it passes through an optical system. We devise an equivalent of the Jones matrix formulation for light possessing orbital angular momentum. The matrices are then developed to account for light that has both spin and orbital ...

In this study, we show that negative polarity noise patterns appear to have a higher contrast than positive polarity noise patterns with identical expected Fourier amplitude spectra. This demonstrates a failure of contrast constancy over changes in pattern polarity. An examination of local contrast measures shows that negative polarity noise ...

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 ...

The ability of observers to extract depth from opposite luminance-contrast-polarity stimuli was investigated. The stimuli consisted of two dichoptic-pairs of Gaussians, with one of the Gaussians in each pair having a positive contrast-polarity and the other a negative contrast-polarity. Stimulus durations ranging from 0.2 to 4 s were used. This ...

The propagation of polarized light through the cornea is affected by the orientations of the corneal lamellae and by the refractive imbalance between the collagen fibrils and the ground substance. Thus, well-designed measurements and analyses of polarized light propagation through the cornea can be used to obtain information regarding the ...

We describe a novel method for the spectroscopic measurement of the state of polarization (SOP) of light. A pair of thick birefringent retarders is incorporated into the spectroscopic polarimeter, so the generated channeled spectrum is composed of three quasi-cosinusoidal components carrying the information about the SOP of the light that ...

PURPOSE: Techniques employing polarized light propagation and scattering are useful in examining the cornea's lamellar structure. Recent advances in theoretical methods have significantly increased the ability to relate features of lamellar arrangements to measurements of transmitted polarized light. The chick cornea, because of its hypothesized structure of a gradual helical ...

The author suggests that Freud was intrigued by those who explored the still unknown regions of the globe; in 1928 he received a letter from a colleague who knew he was interested in the psychology of polar explorers, asking him to comment on some strange visualizations that had haunted Roald ...

We fabricated polymer-dispersed liquid-crystal light valves (PDLCLV's) consisting of a 30-microm-thick hydrogenated amorphous-silicon film and a 10-microm-thick polymer-dispersed liquid-crystal (PDLC) film composed of nematic liquid-crystal (LC) microdroplets surrounded by polymer. The device can modulate high-power reading light, because the PDLC becomes transparent or opalescent independent of the polarization state of ...

We demonstrate significant differences in the propagation of polarized light through biological tissue compared with two common tissue phantoms. Depolarization of linearly and circularly polarized light was measured versus propagation distance by use of two independent measurement techniques. The measurements were performed on adipose and myocardial tissues and on tissue ...

A low threshold acoustic cavitation regime was observed for the excitation of hypersonic waves due to a stimulated Brillouin scattering (SBS) mechanism, when the optical pump lies within the uv frequency range. Cavitation occurs if the optical pump bandwidth Delta(+)>>Omega(0), where Omega(0) is the Stokes frequency shift (the hypersonic frequency). ...

We describe the use of degree of polarization to discriminate unscattered and weakly scattered light from multiply scattered light in an optically turbid material. We use spatially resolved measurements of the degree of polarization to compare how well linearly and circularly polarized light survives in a sample. Experiments were performed ...

We describe a method for increasing target contrast within a turbid medium by means of the polarization state of the scattered light. The backscattered Mueller matrices for various concentrations of 0.1-microm spherical scatterers were measured with and without a painted metal target. Simple discrimination based on detecting cross-polarized intensities is ...

The polarization state of a light beam is related to its spin angular momentum and can be represented on the Poincaré sphere. We propose a sphere for light beams in analogous orbital angular momentum states. Using the Poincaré-sphere equivalent, we interpret the rotational frequency shift for light beams with orbital ...

The responsivity at a constant detection area of non-steady-state photoinduced electromotive force (photo-emf) detectors is improved by a factor equal to the number of contact pairs contained in asymmetric interdigitated surface contacts. The polar nature of photo-emf current generation requires contact asymmetry in which one increases the total signal by ...

We review the main optical properties of bacteriorhodopsin that are relevant to its use as a spatial light modulator. A model is described for the transmittance of a film placed between crossed polarizers in which photoinduced birefringence occurs. We show when the transmittance is proportional to the write intensity. We ...

In the initial stages of visual processing in primates, more or less separated ON and OFF pathways have been shown to exist. There is ample evidence, that this separation includes the initial stages of motion processing. In the present study, experiments were conducted to investigate whether this ON versus OFF ...

Previously, Edwards, Pope & Schoor, Vision Research, 38, 705-717, demonstrated that transient disparity vergence appears to be mediated by a system that employs a single low-pass sensitive spatial channel whose performance is not reduced by dichoptic mixed contrasts (no contrast paradox) or dichoptic mixed spatial frequencies. This broadband tuning to ...

Despite its many advantages as an experimental system for the study of the epigenesis of polarity, it is obvious that the fucoid zygote also presents many problems. The development of polarity proceeds largely independently of direct gene action and thus may be considered a problem in cellular physiology. Ca2+ appears ...

The potentialities of polarization microscopy has been greatly increased by using specific stains for selective enhancement of the optical anisotropy of a macromolecular constituent of cells and tissues. Such stainings have proved to be especially useful in exploring the spatial orientation pattern of the extracellular matrix components. The retardation value, ...

Polarization sensitivity (PS) was examined in two classes of neurons, sustaining fibers and dimming fibers, in the medulla externa (second optic neuropile) of the crayfish, Pacifasticus leniusculus. Visual responses were recorded intracellularly and extracellularly. The influence of e-vector orientation (theta) was probed in steady-state responses, with brief flashes and with ...

A stereoscopic projector with polarized glasses is proposed that consists of spatial light modulators (SLM's) that control the retardation of projected light, a polarization beam splitter (PBS), and single-projection optics. This display's features include a three-dimensional (3-D) image display with a single projector and half the size and the power ...

The polarity of germinating single-celled spores of the fern Ceratopteris richardii Brogn. is influenced by gravity during a time period prior to the first cellular division designated a "polarity-determination window". After this window closes, control of polarity is seen in the downward (with respect to gravity) migration of the nucleus ...

Light-gradient photovoltage measurements were performed on EDTA-treated thylakoids and on osmotically swollen thylakoids (blebs), both of spherical symmetry but of different sizes. In the case of EDTA vesicles, a negative polarity (due to the normal light gradient) was observed in the blue range of the absorption spectrum, and a positive ...

INTRODUCTION: Even though the clinical advantage of biphasic defibrillation waveforms is well documented, the mechanisms that underlie this greater efficacy remain incompletely understood. It is established, though, that the response of relatively refractory cells to the shock is important in determining defibrillation success or failure. We used two computer models ...

Anisotropy in the polarization of the backscattered light from a polarized laser beam incident upon a scattering medium has been observed experimentally. When the beam is viewed through an oriented polarizer, characteristic patterns in the backscattered light are observed. We present here a simple explanation of these patterns, using the ...

Delivery of a strong electric shock to the heart remains the only effective therapy against ventricular fibrillation. Despite significant improvements in implantable cardioverter defibrillator (ICD) therapy, the fundamental mechanisms of defibrillation remain poorly understood. We have recently demonstrated that a monophasic defibrillation shock produces a highly nonuniform epicardial polarization pattern, ...

We recorded electrically evoked compound action potentials (EAPs) from guinea pigs and cats using monophasic current pulses delivered by a monopolar intracochlear electrode. By using simple stimuli, we sought results that could shed light on basic excitation properties of the auditory nerve. In these acute experiments, the recording electrode was ...

The light reflectors in the beetles Calloodes grayanus and Anoplognathus parvulus are examined. Contrasting multilayer reflectors are revealed. Calloodes grayanus appears a weak green colour, matching its background leaves, while A. parvulus is strongly metallic-gold coloured. The former reflection is diffuse, as the result of a structure causing scattering that ...

Large numbers of coccidian oocysts belonging to the genus Isospora were obtained from the intestinal contents of ten legless lizards Diplometopon zarudnyi collected from eastern region, Saudi Arabia. The oocysts are spherical to subspherical, 33.3 x 30.9 (28.6-35.2 x 26.8-32.7) microns with a bilayered wall 1.4 (1.3-1.6) microns thick. Micropyle, ...

Our recommendation is a 90-105 mm macro lens focusing from 1:1 to infinity and a minimum aperture of f/32. A reputable brand should be preferred: Nikon, Canon, Minolta, Sigma etc.... A 105 mm macro lens allows for adequate working distance (approx. 130 mm for a straight view at 1:1 magnification). ...

Using a Monte Carlo method, we simulate the appearance of light pillars produced by nearby light sources and compare their appearance with simulations of Sun pillars. Photographs of light pillars are also compared with the simulations. We expand the idea of light and Sun pillars by examining the reflected-light patterns ...