Changes In Degree Of Polarization Research Articles

Cross-spectral density matrix of a random electromagnetic beam propagating through an apertured axially nonsymmetrical optical system

Using the fact that a hard-edged rectangular aperture function can be approximated by a two-dimensional multi-Gaussian series, analytic formulas for the elements of the cross-spectral density matrix of a random electromagnetic beam truncated by a rectangular aperture and passing through an axially nonsymmetrical optical system is derived. The analysis is illustrated by numerical examples relating to changes in the spectral degree of polarization of electromagnetic Gaussian Schell-model beams propagating through free space, focal system and dual-focus system. In particular, the effect of the size of the hard aperture on the spectral degree of polarization of the beam along its optical axis is discussed.

Changes in the polarization and coherence of a random electromagnetic beam propagating through a misaligned optical system

On the basis of the generalized diffraction integral formula for misaligned optical systems in the spatial domain, an analytical propagation expression for the elements of the cross-spectral density matrix of a random electromagnetic beam passing through a misaligned optical system is derived. Some analyses are illustrated by numerical examples relating to changes in the spectral degree of polarization and in the spectral degree of coherence of an electromagnetic Gaussian-Schell-model beam propagating through such an optical system. We find that the degree of polarization in the neighboring areas of the focal plane is oscillating, and the effect of misalignment on coherence is not so evident as that on polarization.

Quantification of scattering changes using polarization-sensitive optical coherence tomography

We demonstrate that changes in the degree of polarization (DOP) depend on changes in the scattering coefficient, and they can be quantified by using a polarization-sensitive optical coherence tomography (PS-OCT) system. We test our hypothesis using liquid and solid phantoms made from Intralipid suspensions and gelatin, respectively. We also quantify the DOP changes with depth caused by changes in the concentration of scatterers in the liquid and solid phantoms. It is clearly shown that the DOP change has a linear relationship with the scattering change. In our previous study, we showed that the axial slope of the DOP is different between normal and pathologic cervical tissues. Our results demonstrate that the quantification of the axial DOP slope can be used for the systematic diagnosis of certain tissue pathology.

Effect of Ni Nano-Powders Addition on the Dielectric Properties of Ba(Ti,Zr)O<sub>3</sub> Based Y5V Ceramics

In this paper, the influence of nickel (Ni) nano-powders addition on the microstructures and dielectric properties of Ba(Ti,Zr)O3 based Y5V non-reducing ceramics were investigated. The X-ray diffraction (XRD) analysis indicated that the primary phase was Ba(Ti,Zr)O3 and no Ni phase appeared until the amount of Ni exceeded 5mol%. Scanning electron microscope (SEM) observation showed that the Ni particles distributed homogenously throughout BTZ ceramic matrix. The incorporation of Ni altered the perovskite lattice parameters and thus led to the change of polarization degree under electric field and the improvement of the dielectric constant at Curie temperature.

Propagation-induced polarization changes in partially coherent optical beams.

Propagation of a partially coherent optical beam inside a linear, nondispersive, dielectric medium is studied, taking into account the vector nature of the electromagnetic field. Propagation-induced polarization changes are studied by using the Gaussian-Schell model for the cross-spectral-density tensor. The degree of polarization changes with propagation and also becomes nonuniform across the beam cross section. The extent of these changes depends on the coherence radius associated with the cross-correlation function. For optical beams with symmetric spectra, the bandwidth of the source spectra is found to play a relatively minor role.

The relationship of membrane fluidity to calcium flux in chick intestinal brush border membranes.

To evaluate whether membrane fluidity plays a role in regulating calcium flux across the intestinal brush border, we purified brush border membranes from different regions of the chick intestine and determined the relationship of their ability to transport calcium and their fluidity parameters, as determined by diphenylhexatriene fluorescence polarization. Raising the temperature from 4 to 37 C resulted in a 3-fold increase in calcium accumulation by duodenal brush border membrane vesicles (BBMV; 2.85 to 8.70 nmol/mg protein X 12 min). This rise in temperature was associated with a decrease in degree of polarization from 0.395 to 0.290. The methyl esters of cis- and trans-vaccenic acid markedly increased calcium uptake at all temperatures studied (4, 25, and 37 C); the trans isomer was more effective. Both cis- and trans-vaccenic acid lowered the degree of polarization of the BBMV from 0.340 to 0.311 and 0.293, respectively, at 25 C. cis- and trans-vaccenic acid were effective whether BBMV were prepared from vitamin D-deficient chicks or their hatchmates given 1,25-dihydroxyvitamin D [1,25-(OH)2D]. The ability to accumulate calcium correlated to the degree of polarization when calcium uptake by and degree of polarization of BBMV prepared from duodenum, jejunum, and ileum were compared at 25 C. The duodenal BBMV had the greatest calcium accumulation (9.4 nmol Ca/mg protein X 10 min) and the lowest degree of polarization (0.336); the ileal BBMV had the least calcium accumulation (3.5 nmol Ca/mg protein X 10 min) and the greatest degree of polarization (0.375); and the jejunal BBMV were intermediate (8.2 nmol Ca/mg protein X 10 min; 0.344). This rank order was the same whether the intestine was from vitamin D-deficient chicks or their hatchmates given 1,25-(OH)2D before they were killed. 1,25-(OH)2D stimulated calcium uptake by duodenal and jejunal BBMV, reaching a maximal effect at 4 h, but no changes in degree of polarization were observed during this period. A plot of the degree of polarization as a function of the reciprocal of absolute temperature showed an inflection point at approximately 25 C. Neither the slope of the plot nor the point of the inflection was altered by 1,25-(OH)2D. We conclude that chick intestinal BBMV membrane fluidity and calcium uptake correlate in relation to the effects of temperature, changes in membrane lipids, and regional differences in the intestine. However, 1,25-(OH)2D stimulates calcium uptake by BBMV without a detectable change in membrane fluidity.

Milliarcsecond structure of BL Lac during outburst

The well known object BL Lacerate is the prototype of a class of compact extragalactic sources which display rapid flux and polarization changes at radio and optical wavelengths and a nearly featureless optical spectrum1. After a period of relative quiescence, BL Lac has recently undergone a violent outburst at radio wavelengths, accompanied by rapid changes in degree of polarization and position angle (Fig. 1)2,3. For a better understanding of the physical mechanism responsible for the variable emission, we have mapped the radio structure at 5 and 10.6 GHz at three epochs during the large flux outburst of 1980 with an intercontinental VLBI array using telescopes in Bonn, West Germany; Green Bank, West Virginia; Westford, Massachusetts; Fort Davis, Texas; and Owens Valley, California. The synthesized beam had a resolution of about 1.0 m arc s at λ 6 cm and 0.5 m arc s at λ 2.8 cm, corresponding to linear sizes of 5.9 and 2.9 lyr (light year) at the source (using a redshift4 of 0.0695 and a Hubble constant of 55 km s−1 Mpc−1). We show here that comparison of the size and flux density of the core component with the flux history provides evidence for relativistic beaming effects, independent of detailed model considerations. The flux densities shown in Fig. 1 were obtained at the University of Michigan radio observatory.

Fast time structures superimposed to impulsive solar microwave bursts with slowly varying or stationary polarization degree

The ultimate definition of fast time structures superimposed on an impulsive solar microwave burst is limited by instrumental time resolution and sensitivity. We analysed 7 GHz bursts with a time constant of 100 ms. The fast time structures seem to be common to all events, although the resolution so far attained might still be smoothing out structures with finer scale. The polarization degree does not show corresponding fast changes. When the degree of circular polarization is referred to the burst's excess flux, it may show a slowly varying time development. When it is referred to the total active center contribution, the polarization degree might become nearly unchanged during the burst development. The polarization degree is set by the large scale magnetic field strength and morphology over the active center and the burst source. The present results suggest that the microwave fast component burst source might remain nearly stationary in relation to the polarizing medium, occupying the same position as the active center hot spot previous to the event. The absence of fast time structures in polarization degree indicate negligible fast changes in the large scale magnetic field which pervades the burst source. Slow changes in polarization degree are sometimes associated with the slow component of impulsive events, and might be representative of secondary accelerations interpreted in terms of trap models. We discuss qualitatively some energy conversion mechanisms based on turbulent processes which may account for the fast burst components.

The Relaxed Excited States of Paired Au- Ions in Potassium Chloride

The emission process and the relaxed excited states have been studied for the 520 nm emission band of the paired Au - ion center in KCl crystal. The emission band shows characteristic polarization correlation with the excitation band. The degree of polarization changes violently near 10 K in a complex way. The peak energy of the emission band also shifts at the same temperature showing a strong connection with the polarization change; the emission band shifts to higher energy with decreasing temperature above 10 K, but to lower energy below 10 K. The decay time of luminescence becomes longer with decreasing temperature and reaches to a constant value at about 8 K, implying the existence of a trapping state slightly below the emission state. The structure of the relaxed excited states connected with the 520 nm emission is discussed from these experimental results.

海面の偏光と視程(後篇)

Leaving the summit, where we had done observations before whose result we have already reported, we removed the observation tent to the top of a cliff very near to the seashore. The cliff is about 40 m. in height, and faces the Pacific Ocean to southern direction.(a) When we observe the sea surface from such a low level, it seems that the light which comes to the observer from the sea is consisted of sky light reflected by wavelets of the sea surface. Therefore, the condition of its polarization depends mainly upon the nature of the sky light which is reflected by the sea surface. And consequently, in this case, the polarization phenomena can not sufficiently be explained merely by the theory of Rayleigh's scattering as in the former case, and so we have proposed that it is necessary to take into account the Brewster's law of reflection too to explain the polarization.(b) In the case of clear skies, degrees and planes of polarization of light reflected by the sea surface varies parallel to those of the sky light from the zone at an altitude of about 10° in the same direction. In the case of overcast skies, the planes of polarization are always vertical for all directions.The range of variation in degrees of polarization is 0.1_??_0.4 for the light from the sea, and 0.0_??_0.7 for that from the sky.(c) As to the relation to bearings, such conspicuous correlation as seen in the preceding chapter can not be found, except in the case of clear and calm weather.(d) The degree of polarization changes abruptly at the sea horizon. Thus the contrast between the sky and sea surface can be increa_??_ed by using the polarized light in most cases, except in the direction at right angles to the vertical plane passing through the sun. This seems to be an important fact concerning the contribution of the Polaroid to the improvement of visibility at sea.