High Polarization Levels Research Articles

Polarimetric Properties of the Crab Pulsar between 1.4 and 8.4 GHz

New polarimetric observations of the Crab pulsar at frequencies between 1.4 and 8.4 GHz are presented. Additional pulse components discovered in earlier observations are found to have high levels of linear polarization, even at 8.4 GHz. No abrupt sweeps in position angle are found within pulse components; however, the position angle and rotational phase of the interpulse do change dramatically between 1.4 and 4.9 GHz. The multifrequency profile morphology and polarization properties indicate a nonstandard origin of the emission. Several emission geometries are discussed, but the one favored locates sites of emission both near the pulsar surface and in the outer magnetosphere.

Morphological and biochemical characterization of primary culture of rabbit proximal kidney tubule cells grown on collagen-IV coated Millicell-CM.

The aim of this study was to better characterize rabbit proximal kidney tubule cells cultured on collagen IV-coated porous inserts, as compared to the same cells seeded in standard plastic wells. Total protein contents in confluent monolayers on permeable membranes were about twofold higher than those measured in confluent cultures in plastic wells. Microscopy examinations suggested that such a difference was probably due to a higher cell density and to an impressive development of the apical brush-border membrane. Moreover, measurement of unidirectional transport of p-aminohippuric acid and tetraethylammonium bromide confirmed the high polarization level of cultures on porous inserts. Results of methyl(alpha-D-[U-14C]glyco)pyranoside uptake suggested that cell phenotype was probably influenced by culture conditions. Analysis of different markers as a function of time in culture showed decreases of alkaline phosphatase (AP), gamma-glutamyltranspeptidase (GGT), and Na(+)-K(+)-ATPase activities as well as increases in LDH, ATP, and glutathione levels, similar to those formerly reported for cells cultured in standard plastic plates. However, comparative data from 6-d-old monolayers have shown that AP, GGT, Na(+)-K(+)-ATPase, glutathione reductase (GRED), and selenium-dependent glutathione peroxidase (Se-GPX) activities were 2.8-, 2.6-, 1.6-, 1.2-, and 2.1-fold, respectively, better preserved on precoated permeable membranes. On the other hand, this paper reports for the first time in the literature that GRED and SE-GPX, two phase II detoxification enzymes, were well maintained in cultures of rabbit proximal kidney tubule cells. Our results show that culturing rabbit proximal kidney tubule cells on collagen IV-coated porous membranes was accompanied by an improvement of both morphological and biochemical properties of the cells.

Polarization pattern of freshwater habitats recorded by video polarimetry in red, green and blue spectral ranges and its relevance for water detection by aquatic insects

The reflection-polarization patterns of small freshwater habitats under clear skies can be recorded by video polarimetry in the red, green and blue ranges of the spectrum. In this paper, the simple technique of rotating-analyzer video polarimetry is described and its advantages and disadvantages are discussed. It is shown that the polarization patterns of small water bodies are very variable in the different spectral ranges depending on the illumination conditions. Under clear skies and in the visible range of the spectrum, flat water surfaces reflecting light from the sky are most strongly polarized in the blue range. Under an overcast sky radiating diffuse white light, small freshwater habitats are characterized by a high level of horizontal polarization at or near the Brewster angle in all spectral ranges except that in which the contribution of subsurface reflection is large. In a given spectral range and at a given angle of view, the direction of polarization is horizontal if the light mirrored from the surface dominates and vertical if the light returning from the subsurface regions dominates. The greater the degree of dominance, the higher the net degree of polarization, the theoretical maximum value being 100 % at the Brewster angle for the horizontal E-vector component and approximately 30 % at flat viewing angles for the vertical E-vector component. We have made video polarimetric measurements of differently coloured fruits and vegetables to demonstrate that polarized light in nature follows this general rule. The consequences of the reflection-polarization patterns of small bodies of water for water detection by polarization-sensitive aquatic insects are discussed.

BVRI imaging polarimetric studies of the galaxy NGC 5128

Multi-colour imaging polarimetry of the galaxy NGC 5128 shows that polarization is present throughout the dust lane with patterns of orientation which are coherent on kpc scale-lengths. In the central regions of the dust lane, within ±0.7 kpc of the projected position of the galactic nucleus, the polarization is oriented parallel to the long axis of the lane and reaches levels up to 5 per cent. At the outer extremities of the the dust lane, higher levels of polarization are found with orientations perpendicular to the axis of the dust lane. In the intermediate regions, null points in the polarization are observed in addition to an unexpected reversal of polarization orientation across the dust lane. We are unable to account for all our observations — polarization maps and the wavelength dependence of polarization in the dust lane — without involving two competing polarizing mechanisms, namely, dichroic extinction and scattering by dust grains. The polarimetric properties of NGC 5128 are very similar to those found in galaxies such as M104, IC 4329A and NGC 2146, and it appears that azimuthal magnetic fields, confined to the equatorial planes of galaxies with prominent dust lanes, are a common occurrence. The nature and origins of these magnetic fields are considered.

Millimeter and Submillimeter Polarization Observations of Blazars

Millimeter and submillimeter polarization observations of blazars from the James Clerk Maxwell Telescope are presented. The data are interpreted in light of recent results from centimeter wavelength VLBI polarimetry studies. Observations of the superluminal quasar 3C 279 at 1.1 and 0.8 mm give a degree of polarization in excess of 10% and imply that the magnetic field is aligned orthogonal to the milliarcsecond (mas) jet to within 6?. This magnetic field orientation is consistent with that expected to arise in a transverse shock. The high level of polarization suggests that the centimeter VLBI core is depolarized by Faraday rotation rather than by increased magnetic field disorder at the base of the inhomogeneous relativistic jet. Three BL Lacertae objects were observed at 1.1 mm and were found to be between 3% and 17% polarized with position angles either closely parallel or closely perpendicular to the mas jet. Although further observations are needed, these data favor a picture in which the position angles in the cores of BL Lac objects display a bimodal distribution as found by centimeter VLBI studies. The close relationship between the millimeter polarization position angle and the mas jet is surprising given the results of millimeter VLBI studies which show evidence for significant jet bending.

The molecular environment of the HH 34 system

view Abstract Citations (30) References (77) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Molecular Environment of the HH 34 System Anglada, G. ; Estalella, R. ; Mauersberger, R. ; Torrelles, J. M. ; Rodriguez, L. F. ; Canto, J. ; Ho, P. T. P. ; D'Alessio, P. Abstract We present single-dish (angular resolution approximately 40 sec) and Very Large Array (VLA; angular resolution approximately 4 sec) ammonia observations toward the HH 34 region. Two main condensations are distinguished in both our single-dish and out VLA maps. The northern ammonia condensation is resolved by the VLA as an arclike structure that surrounds the east side of the star HH 34 IRS (the exciting source of the jet) and coincides in projection with Re 24, the reflection nebula associated with the infrared source IRS 5. We suggest that this ammonia structure is tracing the wall of a cavity around HH 34 IRS. Our results are in good agreement with the hypothesis that this cavity was created by the stellar wind from HH 34 IRS, indicating that along the life of the star two kinds of stellar wind might have been present: a low-collimation wind that created the cavity, and a highly collimated wind that is at the origin of the jet. A second VLA ammonia condensation coincides with Re 23, the brightest part of the arc of optical nebulosity previously proposed to be tracing the western wall of a cavity that contains the jet. The inner edges of these two ammonia condensations coincide with zones of a high level of polarization of the optical emission. With the angular resolution of our VLA observations, no ammonia (1, 1) emission is detected directly associated with the star HH 34 IRS, setting an upper limit of 0.1/(X(NH3)/10-8) solar masses for the mass of a possible circumstellar disk. From our single-dish observations, we find that there is extended emission (approximately 3 min) of high-density gas, not seen with the VLA. For this gas, we estimate a total mass of approximately 15 solar masses and a kinetic temperature of 15 K. Publication: The Astrophysical Journal Pub Date: April 1995 DOI: 10.1086/175560 Bibcode: 1995ApJ...443..682A Keywords: Ammonia; Herbig-Haro Objects; Interstellar Gas; Jet Flow; Molecules; Radio Astronomy; Radio Spectra; Stellar Evolution; Stellar Winds; Astronomical Maps; Cavities; Data Reduction; Optical Polarization; Radio Antennas; Very Large Array (Vla); Astrophysics; ISM: JETS AND OUTFLOWS; ISM: MOLECULES; RADIO LINES: ISM; STARS: INDIVIDUAL ALPHANUMERIC: HH 34; STARS: PRE--MAIN-SEQUENCE full text sources ADS | data products SIMBAD (20)

Near-infrared polarization in the bipolar outflow OH 0739-14

We present linear polarization observations of the bipolar outlfow source OH 0739-14 from 1.2 to 3.6 micrometers. The high levels of polarization (approximatly 47% in the bipolar lobes) and the angles of the vectors in the outflow lobes imply that the 1.2-3.6 micrometer polarization is due to single scattering by dust grains of light from the central source or from its immediate vicinity. Our polarization measurements, combined with phase-lag measurements of variability in the nebula by Kastner et al. (1992), tightly constrain the inclination angle i between the bipolar axis and the plane of the sky to be 35 deg less than or = i less than or = 37 deg. We observe the percentage polarization of the bipolar lobes to be constant with wavelength from 1.2 to 3.6 micrometers, which rules out any significant contribution by unpolarized emission, such as tiny grain emission, to the 3.6 micrometer emission. We propose to explain the K-L' color of the nebula as due to illumination by both the central star and by thermal emission from dust in a surrounding circumstellar shell with a dust temperature of 600-1000 K. Using this model, we find a relatively high minimum scattering optical depth at 3.75 micrometers of tau omega greater than 0.1. This is difficult to reconcile with Rayleigh scattering, which would then imply optically thick scattering at wavelengths of 1.2 and 1.65 micrometers, in constrast to the observations. We also find that the albedo of the grains at 3.75 micrometers and probably at 2.2 micrometers is higher than predicted for normal interstellar grains.

Evidence for the early onset of aspherical structure in the planetary nebula formation process: Spectropolarimetry of post-AGB stars

We present optical spectropolarimetry of 31 post-asymptotic giant branch (post-AGB) stars, objects that are believed to represent the first phases of the transition from the AGB to the planetary nebula stage. 24 of these objects are found to be intrinsically polarized. We group these objects into four classes based on their observed polarization properties, rho (lambda) and theta (lambda), and discuss possible explainations for the observed behaviors. Type 1 objects display high levels of polarization and large position angle rotations. Type 2 objects lack large position angle rotations, but have polarizations too large to be attributed to foreground interstellar material. Type 3 objects show position angle rotations and polarization changes across TiO absorption features; and finally, Type 4 are objects in which the observed polarization can be entirely attributed to interstellar effects. The currently popular paradigm of planetary nebula morphology of a dense torus plus bipolar lobes can explain the rho and theta behavior of the Type 1 and Type 2 objects. However, a large number of the objects exhibit time-variable rho and theta. This implies that their morphologies may not be stable, but rather evolving or transient structures. Regardless of any specific model for the morphology, our main result is that aspherical structure appears very early in the transition from the AGB to the planetary nebula stage. We compare the polarization properties of the post-AGB stars to the morphological characteristics of evolved planetary nebulae. Our results indicate that the nebular morphology may originate at an early evolutionary stage. We do not observe any correlation between chemistry (O-rich vs C-rich) and polarization class in the AGB stars. We examine the formation of aspherical planetary nebulae in the context of binary star evolution. If bipolar geometry is a consequence of binary star evolution, the number of highly polarized post-AGB stars in our sample requires a high binary star frequency.

A Threshold Model of Electoral Policy and Voter Turnout

Voter turnouts differ significantly across societies, and in some polities voting is compulsory. To explain differences in voter turnout it is necessary first to explain the variation in compulsion policies that exists across societies. A threshold model of collective action is used to provide an explanation for compulsion policies, which are treated as endogenous. Governments and parties are viewed as “demanding” turnout as a means to enhance political support. This theory suggests that voter turnout is high, and possibly government mandated, in societies that have high levels of political polarization and that use proportional representation. The predictions of the theory are tested using cross-country data.

Imaging polarimetry of the bipolar nebula Parsamyan 22

Par 22 shows high levels of polarization which confirm that it is a bipolar reflection nebula. We suggest that circumstellar material, which is very patchy and forms fingers which penetrate the central regions of the nebula, is the remnant of the circumstellar disc which is in the process of disintegration. We take this as an indication that the system is in the later stages of pre-main-sequence evolution. We discuss the origin of the sharp rim/diffuse boundary of each of the nebular lobes.

Polarization studies of comet Okazaki-Levy-Rudenko

Observations of comet Okazaki-Levy-Rudenko (1989r) during 1989 December show two unusual features. The first is a wedge-shaped coma which is seen to persist over several days. The results of a Haser model show that the shape can be explained by having an anisotropic source for the molecules making up the coma. The second notable feature is an antisolar jet seen on 1989 December 5. This shows up most clearly in the red polarization image, and the high level of polarization in this jet implies that it is made predominantly of dust particles

Detection of polarized ultraviolet emission from the high-redshift radio galaxy 3C 265

Significant polarization of the total emission of the high-redshift radio galaxy 3C 265 has been detected. The polarization position angle is roughly perpendicular to the axis of the radio emission and to the major axis of the UV emission of the galaxy in both B and R passbands. The observed high level of polarization and orientation of the polarization position angle suggest that a substantial fraction of the observed UV emission is scattered light. The data show no evidence of frequency dependence in the polarization between B and R. 23 refs.

The Argentine Paradox

The Argentine Paradox Carlos H. Waisman (bio) In July 1989 the new Argentine democracy passed a crucial test: Carlos Menem of the Peronist party succeeded to the office of president, replacing Raúl Alfonsín of the Radical party. This presidential transition, the first since the restoration of democracy in 1983, marked the first transfer of power since 1916 between elected presidents of different political parties. Moreover, it was the first time in Argentine history that both the incoming and outgoing president were elected on the basis of universal suffrage. But even as Argentina's fledgling democracy was recording this notable achievement, its economy was undergoing a deep crisis. Argentina is a land of paradoxes, not the least of which is this: even as its polity becomes more like that of an advanced capitalist nation, its economy and society increasingly resemble those of a typical underdeveloped country. The question is whether this new democracy, in a society where democratic traditions are weak, can be sustained amidst economic stagnation (or outright retrogression), triple-digit inflation (even higher for part of 1989), and massive foreign debt. I will argue that the effects of the economic crisis on democratic stability are complex: negative in the short term, for democracy will be strained by the discontent of those whose lot has worsened; but perhaps positive in the long term, for the crisis may break the stalemate that produced stagnation in Argentine society. Thus economic impoverishment may paradoxically end up facilitating the consolidation of democracy. [End Page 91] The wave of democratization sweeping most of Latin America and much of Eastern Europe provides students of democratic legitimation with a unique laboratory. High levels of both popular participation and competitive politics are being instituted in countries with widely different economic systems, social structures, ethnic compositions, and political cultures. Thus we can observe the conditions under which a new political regime becomes accepted "naturally, without questioning" (to use Jean Blondel's words) by the large majority of the population. Social scientists have been particularly concerned with the economic conditions of democratic legitimation. The proposition that capitalism has an elective affinity with liberal democracy—a proposition shared by liberal theorists and Marx alike—is based in part on the notion that a dynamic, capitalist economy can satisfy the demands of ail social groups, the lower classes included. And contemporary social scientists have argued that a regime's "efficacy" (an aspect of which is economic growth) is one of the determinants in its legitimation. Economic growth may not be a necessary condition for the legitimation of a new democracy, but it is clearly a powerful contributing factor in both the short and long terms. The explosion of group demands is characteristic of new democracies that succeed authoritarian regimes. This is usually a consequence of two factors: the forcible suppression of these demands (particularly those of labor and the lower classes) by the old regime, and the strong incentives and lowered costs for group organization and mobilization under democratic conditions. Economic growth allows for the satisfaction of at least some of these demands and thus prevents the development of zero-sum conflicts. In the long run, economic growth fuels legitimacy by permitting individual and collective upward mobility and by providing a safety net to contain downward mobility. Economic stagnation—or even retrogression—does not necessarily block legitimation, at least in the short run. It can be offset by favorable noneconomic factors such as strong democratic traditions, the formation of a democratic political culture, the commitment to democracy of economic or political elites, and strong political leadership. In the long run, however, the survival of democracy is doubtful under such conditions. Stagnation or retrogression is likely to lead to high levels of political polarization, especially in societies having large and mobilized working and middle classes. In the case of Argentina, democracy has been restored in a period of outright economic retrogression. For most of the past three decades, the economy has experienced sharp fluctuations but little or no net long-term growth. From 1970 to 1979, the gross domestic product (GDP) per capita grew by an average of 0.3 percent a year. From 1980 to 1988, however, the GDP declined...

Racial Bloc Voting and Political Mobilization in South Carolina

Over the last quarter century, major changes in Southern social structure have been accompanied by more positive white attitudes on racial issues. Has voting behavior reflected these changes? The question has important consequences. The degree of racial bloc voting and political mobilization often determines outcomes not only of elections but also of voting rights lawsuits. Data from 130 black/white elections in South Carolina were used to determine rates of racial polarization and mobilization. Bloc voting remained high. Other variables had little explanatory power. Some secondary factors helped explain variations in the generally high levels of polarization by race.

Spectral and statistical properties of strongly driven atoms coupled to frequency-dependent photon reservoirs.

Interesting new aspects of atomic behavior in the presence of strong driving fields appear when the driven atom resides not in free space, but in a region (such as an optical cavity) that displays a frequency-dependent photon-mode density. Under such conditions, it is found that a strong driving field can modify the spontaneous decay properties of an atom, and thereby give rise to interesting new features in the spectrum of strong-field resonance fluorescence. It is also found that a high level of dressed-state polarization can be maintained in a sample of resonantly or nonresonantly driven atoms by appropriate tuning of an enclosing cavity. Furthermore, for appropriate laser and cavity tunings, it is found that the atomic states become highly squeezed. In the course of analyzing these effects, a set of modified Bloch equations is derived that explicitly accounts for the finite response time associated with a frequency-dependent photon-mode density.

Denervation syndrome in the rat digastric muscle

Excitability parameters of m. digastricus muscle fibers were investigated in anesthetized (40 mg/kg of nembutal) rats 3-5 days after denervation. The number of fibers with high polarization level was increased as was the number of fibers with low and medium level in both bellies of m. digastricus. The differences in the level of polarization recorded in the muscle fibers of the abdominoposterior m. digastricus disappeared after denervation. It is suggested that denervation syndrome in m. digastricus deprived of spindle receptors was similar to that observed in other skeletal muscles.

Economic development and political transformation

Social structure and economic development largely influence the nature of social conflicts and political transformation. A combination of low political and economic integration and a high level of consolidation results in reformist conflicts. Low state intervention in the allocation and accumulation of capital reduces the probability that class conflict will be directed against the state. When state intervention is low, depoliticized, abstract market forces determine capital allocation and accumulation. In addition, low political and economic integration may give the state the appearance of serving societal interests rather than the interests of the upper class. This appearance of autonomy is reinforced by the institutions of formal democracy. As a consequence, class conflict is contained within civil society and deflected from the state. When consolidation is high, reformist conflicts against holders of capital may emerge. The United States experienced such movements in the 1930s. During the Great Depression, the state was drawn into some conflicts, but was not attacked by the working class. Today, the United States, like other advanced industrial societies, is less receptive to consolidation because of moderate levels of economic polarization, greater economic resilience, and high social differentiation. When state intervention and consolidation are low, organized groups with resources may gain economic benefits through segmented class conflict, whereas collectivities with weak solidarity and few resources remain inactive. Such is the case in the United States today. The combination of a high level of state intervention in capital allocation and accumulation with a high level of consolidation increases the likelihood of revolutionary conflict. High state intervention in capital allocation and accumulation has crucial social consequences. First, it politicizes other-wise abstract market relations. Second, it clearly reveals the state to be allied with a small circle of upper-class entrepreneurs, thereby discrediting the state's claim to serve societal interest. As a consequence, class conflict can readily assume a political character, expanding its target to include the state. A high level of consolidation enhances the capacity of challenging groups to act collectively to resist repression and seize power. Consolidation is more likely in societies with a high level of economic polarization, highly dependent economies, and low social differentiation. Russia in 1917 and Iran and Nicaragua in 1979 are revealing examples. The Russian and Nicaraguan revolutions were carried out primarily by workers and peasants, which helps explain the socialist orientation of the new leadership. In contrast, in Iran, the revolution was largely based on the conflicts and struggles of the traditional middle class, which eventually led to the formation of the theocratic state. A combination of high state intervention and low consolidation generates segmented conflict directed against the state. Many Third World societies are experiencing such a conflict today. To conclude, Marx's analysis focused primarily on social classes underemphasizing the significance of the state and its relation to society and economy. Skocpol's analysis, on the other hand, primarily focused on the state and the upper class, and failed to specify the proper, determining variables. If the analysis presented here is useful in specifying the conditions and forms of social conflicts, we must pay greater attention to social structural analysis, the nature of the relationship between the state, economy, social classes, and solidarity structures.

Commissioning the Polarized Beam in the AGS

After the successful operation of a high energy polarized proton beam at the Argonne Laboratory Zero Gradient Synchrotron (ZGS) was terminated, plans were made to commission such a beam at the Brookhaven National Laboratory Alternating Gradient Synchrotron (AGS). On February 23, 1984, 2 ..mu..A of polarized H/sup -/ was accelerated through the Linac to 200 MeV with a polarization of about 65%. 1 ..mu..A was injected into the AGS and acceleration attempts began. Several relatively short runs were then made during the next three months. Dedicated commissioning began in early June, and on June 26 the AGS polarized beam reached 13.8 GeV/c to exceed the previous ZGS peak momentum of 12.75 GeV/c. Commissioning continued to the point where 10/sup 10/ polarized protons were accelerated to 16.5 GeV/c with 40% polarization. Then, two experiments had a short polarized proton run. We plan to continue commissioning efforts in the fall of this year to reach higher energy, higher intensity, and higher polarization levels. We present a brief description of the facility and of the methods used for preserving the polarization of the accelerating beam.

Zenith polarization and color ratio during twilight

The excellent data of zenith polarization and color ratio (CR) during twilight obtained by Coulson at the Mauna Loa Observatory, Hawaii are subjected to a reinterpretation, especially with regard to the frequent deviations from the clear average. It is shown that a moderate lift of the earth's shadow by distant clouds (or by low level haze) will reduce the red/green CR, while greater lift shifts the CR peak to a smaller solar depression. The effect on zenith polarization at wavelengths >/=0.6 microm is seen to correspond to a slight reduction of overall polarization for a moderate lift, and for a large lift to a shift of the polarization minimum (depolarization by stratospheric aerosol) from 4 degrees solar depression angle to 2 degrees . A generally high level of polarization, but with a barely noticeable 4 degrees minimum, had also been observed earlier in Germany by Steinhorst when the stratospheric aerosol load was very small. The difference is explained by a higher and stronger aerosol layer in the tropics combined with a higher and cleaner troposphere.

Cathodic protection of steel in offshore concrete platforms : O. E. Gjorv and O. Vennesland. Mat. Perform. May 1980, 19(5), 49–52

To improve existing corrosion-control criteria for offshore concrete platforms, researchers studied the effects of various polarization levels on the reinforcement-bar bonding. Experimental investigations indicate that polarization of embedded steel down to -1350 mV (vs a saturated calomel electrode) has no harmful effect on bond strength and may even improve the bond strength of initially clean and smooth steel. For increasing polarization levels, fewer chloride ions from the seawater penetrate the concrete; a calcareous coating on the concrete surface may form at high polarization levels. The current necessary for cathodic protection of embedded steel is controlled primarily by the rate of oxygen diffusion through the concrete. Measurements indicate that the resistance to oxygen diffusion may be 10 times higher through the interface between the concrete and steel than through the concrete cover. The current density necessary for polarizing embedded steel in offshore concrete platforms may be as low as 0.014 mA/ft/sup 2/ (0.15 mA/m/sup 2/).