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1

Spectral induced polarization and electrodic potential monitoring of microbially mediated iron sulfide transformations  

E-print Network

Spectral induced polarization and electrodic potential monitoring of microbially mediated iron vulgaris. Two geoelectrical methods, (1) spectral induced polarization (SIP), and (2) electrodic potential. Ntarlagiannis, L. Slater, N. Yee, M. O'Brien, and S. Hubbard (2008), Spectral induced polarization

Hubbard, Susan

2

Pore-scale spectral induced polarization signatures associated with FeS biomineral transformations  

E-print Network

Pore-scale spectral induced polarization signatures associated with FeS biomineral transformations induced polarization (SIP) signatures in sand columns during (1) FeS biomineralization produced by sulfate), Pore-scale spectral induced polarization signatures associated with FeS biomineral transformations

Hubbard, Susan

3

Spectral induced polarization signatures of abiotic FeS precipitation  

SciTech Connect

In recent years, geophysical methods have been shown to be sensitive to microbial induced mineralization processes. The spectral induced polarization (SIP) method appears to be very promising for monitoring mineralization and microbial processes. With this work, we study the links of mineralization and SIP signals, in the absence of microbial activity. We recorded the SIP response during abiotic FeS precipitation. We show that the SIP signals are diagnostic of FeS mineralization and can be differentiated from SIP signals from bio-mineralization processes. More specifically the imaginary conductivity shows almost linear dependence on the amount of FeS precipitating out of solution, above the threshold value 0.006 gr under our experimental conditions. This research has direct implications for the use of the SIP method as a monitoring, and decision making, tool for sustainable remediation of metals in contaminated soils and groundwater.

Ntarlagiannis, D.; Doherty, R.; Williams, K. H.

2010-01-15

4

Spectral induced polarization (SIP) response of mine tailings.  

PubMed

Mine tailings impoundments are a source of leachates known as acid mine drainage (AMD) which can pose a contamination risk for surrounding surface and groundwater. Methodologies which can help management of this environmental issue are needed. We carried out a laboratory study of the spectral induced polarization (SIP) response of tailings from the Haveri Au-Cu mine, SW Finland. The primary objectives were, (1) to determine possible correlations between SIP parameters and textural properties associated with oxidative-weathering mechanisms, mineralogical composition and metallic content, and (2) to evaluate the effects of the pore water chemistry on SIP parameters associated with redox-inactive and redox-active electrolytes varying in molar concentration, conductivity and pH. The Haveri tailings exhibit well defined relaxation spectra between 100 and 10,000Hz. The relaxation magnitudes are governed by the in-situ oxidative-weathering conditions on sulphide mineral surfaces contained in the tailings, and decrease with the oxidation degree. The oxidation-driven textural variation in the tailings results in changes to the frequency peak of the phase angle, the imaginary conductivity and chargeability, when plotted versus the pore water conductivity. In contrast, the real and the formation electrical conductivity components show a single linear dependence on the pore water conductivity. The increase of the pore water conductivity (dominated by the increase of ions concentration in solution) along with a transition to acidic conditions shifts the polarization peak towards higher frequencies. These findings show the unique sensitivity of the SIP method to potentially discriminate AMD discharges from reactive oxidation zones in tailings, suggesting a significant advantage for monitoring threatened aquifers. PMID:25528133

Placencia-Gómez, Edmundo; Parviainen, Annika; Slater, Lee; Leveinen, Jussi

2015-02-01

5

Spectral induced polarization signatures of hydroxyl adsorption in porous media  

NASA Astrophysics Data System (ADS)

There is a growing interest in applying geophysical methods to monitor microbial enhanced mineral precipitation through urea hydrolysis. Sensing changes in mineral surface properties as well as changes in fluid chemistry could be used to track geochemical reactions fronts in subsurface environments. Frequency-dependent complex conductivity measured with the spectral induced polarization (SIP) technique is sensitive to both fluid chemistry and mineral surface properties. We had previously observed phase shifts (?) between current and voltage waveforms associated with hydroxyl concentration changes in a silica gel column during a urea hydrolysis experiment. In a study using less complex conditions we applied both SIP and geochemical measurements on a saturated column composed of sequential zones with Ottawa sand and silica gel in order to: 1) understand whether adsorption of hydroxyl contributes to the changes in complex conductivity, and 2) to determine whether changes in solution chemistry follow changes in surface chemistry in porous media (or vice versa). Silica gel is a highly porous form of silica (surface area is ~500 m2/g vs. <0.1 m2/g for Ottawa sand) and has a high sorption capacity for hydroxide ions. A column (48 cm) was packed with Ottawa sand at both the bottom and top sections, and with silica gel beads in the middle part of the column. The experiment started with a pH 7 sodium chloride solution (50 mM) flowing through the column at 10 ml/min, then sodium chloride solutions at higher pH (pH 8 and pH 10) replaced this solution and continued flow at the same rate for 49 hours. SIP measurements were made along the column as a function of time, and effluent samples along the column were taken for pH and conductivity measurements. The results show phase angle shifts (~4.5 mrad) in the silica gel, while no significant phase changes occurred in the Ottawa sands. Although changes in complex conductivity were only observed on synthetic high surface area material, the experiment opens the door to further investigate the correlation between complex conductivity and surface chemistry.

Zhang, C.; Johnson, T. C.; Slater, L. D.; Redden, G. D.

2010-12-01

6

Relationship between spectral induced polarization and hydraulic properties of saturated and unsaturated sandstone  

Microsoft Academic Search

There is growing interest in the use of geophysical methods for hydrological model parameterization. Empirical induced polarization (IP)-hydraulic conductivity (K) relationships have been developed, but these are only applicable to sediments in which the IP response shows limited variation with electrical current frequency. Here we examine the spectral IP response of samples taken from a UK sandstone aquifer and compare

Andrew Binley; Lee D. Slater; Melanie Fukes; Giorgio Cassiani

2005-01-01

7

Mapping Oil-Contaminated Sand and till with the Spectral Induced Polarization (sip) Method  

Microsoft Academic Search

The laboratory and field results from an environmental application of the spectral induced polarization (SIP) method are presented. The phase spectra of the resistivity of uncontaminated glacial till, silt, sand and gravel were measured in the laboratory. The effects of waste oil and motor oil on the phase and amplitude spectra of the resistivity were studied using artificially contaminated sand

Heikki Vanhala

1997-01-01

8

Pore-scale spectral induced polarization (SIP) signaturesassociated with FeS biomineral transformations  

SciTech Connect

The authors measured Spectral Induced Polarization (SIP) signatures in sand columns during (1) FeS biomineralization produced by sulfate reducing bacteria (D. vulgaris) under anaerboci conditions, and (2) subsequent biomineral dissolution upon return to an aerobic state. The low-frequency (0.1-10 Hz peak) relaxations produced during biomineralization can be modeled with a Cole-Cole formulation, from which the evolution of the polarization magnitude and relaxation length scale can be estimated. They find that the modeled time constant is consistent with the polarizable elements being biomineral encrused pores. Evolution of the model parameters is consistent with FeS surface area increases and pore-size reduction during biomineral growth, and subsequent biomineral dissolution (FeS surface area decreases and pore expansion) upon return to the aerobic state. They conclude that SIP signatures are diagnostic of pore-scale geometrical changes associated with FeS biomineralization by sulfate reducing bacteria.

Slater, Lee; Ntarlagiannis, Dimitrios; Personna, Yves R.; Hubbard, Susan

2007-10-01

9

Spectral induced polarization signatures of hydroxide adsorption and mineral precipitation in porous media  

SciTech Connect

The spectral induced polarization (SIP) technique is a promising approach for delineating subsurface physical and chemical property changes in a minimally invasive manner. We investigated spatiotemporal variations in complex conductivity during evolution of urea hydrolysis and calcite precipitation reaction fronts within a silica gel column. The real and imaginary parts of complex conductivity were shown to be sensitive to changes in both solution chemistry and calcium carbonate precipitation. Distinct changes in imaginary conductivity coincided with increased hydroxide ion concentration during urea hydrolysis. In a separate experiment focused on the effect of hydroxide concentration on interfacial polarization of silica gel and well-sorted sand, we found a strong dependence of the polarization response on pH changes of the solution. We propose a conceptual model describing hydroxide ion adsorption behavior in silica gel and its control on interfacial polarizability. Our results demonstrate the utility of SIP for non-invasive monitoring of reaction fronts, and indicate its potential for quantifying geochemical processes that control the polarization responses of porous media at larger spatial scales in the natural environment.

Chi Zhang; Lee Slater; George Redden; Yoshiko Fujita; Timothy Johnson; Don Fox

2012-04-01

10

Spectral Induced Polarization Signatures of Hydroxide Adsorption and Mineral Precipitation in Porous Media  

SciTech Connect

The spectral induced polarization (SIP) technique is a promising approach for delineating subsurface physical and chemical property changes in a minimally invasive manner. To facilitate the understanding of position and chemical properties of reaction fronts that involve mineral precipitation in porous media, we investigated spatiotemporal variations in complex conductivity during evolution of urea hydrolysis and calcite precipitation reaction fronts within a silica gel column. The real and imaginary parts of complex conductivity were shown to be sensitive to changes in both solution chemistry and calcium carbonate precipitation. Distinct changes in imaginary conductivity coincided with increased hydroxide ion concentration during urea hydrolysis. In a separate experiment focused on the effect of hydroxide concentration on interfacial polarization of silica gel and well-sorted sand, we found a significant dependence of the polarization response on pH changes of the solution. We propose a conceptual model describing hydroxide ion adsorption behavior in silica gel and its control on interfacial polarizability. Our results demonstrate the utility of SIP for noninvasive monitoring of reaction fronts, and indicate its potential for quantifying geochemical processes that control the polarization responses of porous media at larger spatial scales in the natural environment.

Zhang, Chi; Slater, Lee; Redden, George D.; Fujita, Yoshiko; Johnson, Timothy C.; Fox, Don

2012-04-17

11

Spectral induced polarization signatures from a crude-oil contaminated site undergoing biodegradation, Bemidji, MN  

NASA Astrophysics Data System (ADS)

The spectral induced polarization (SIP) technique is a promising biogeophysical technique for sensing microbially-induced changes in the petrophysical properties of porous media. Recent studies by Schmutz et al. for samples freshly contaminated with oil show a well defined relaxation peak in the 0.001-0.1 Hz frequency rangewith the magnitude of the phase and resistivity increasing with increase in the relative saturation of the oil. In this study, we extend work of Abdel Aal et al. by acquiring SIP measurements in the frequency range between 0.001 and 1000 Hz on sediment cores retrieved from a hydrocarbon contaminated site where intrinsic bioremediation is occurring. Our results show the following: (1) in general for both the saturated and unsaturated zone samples, the real and imaginary conductivity for samples from within the plume are higher than those for background samples; (2) the imaginary conductivity results show a well defined peak in the frequency range between 0.001 - 0.01 Hz for contaminated samples with the magnitude higher for samples from the smear zone (contaminated with residual-phase hydrocarbon), exceeding values obtained for samples contaminated with dissolved-phase hydrocarbons; (3) a secondary peak not observed in uncontaminated samples is also observed around 100 Hz for the contaminated samples. Our results are consistent with the Abel Aal et al. study suggesting that biodegradation increases the magnitude of the imaginary conductivity response. The peak at the lower frequency may be due to the polarization of the Stern layer as suggested by Schmutz et al. Our laboratory SIP measurements from core samples are consistent with downhole time domain induced polarization measurements that also how that the contaminated borehole is more chargeable than the background borehole.

Mewafy, F.; Atekwana, E. A.; Ntarlagiannis, D.; Slater, L. D.; Revil, A.; Skold, M.; Gorby, Y.; Werkema, D.

2010-12-01

12

Spectral induced polarization and electrodic potential monitoring of microbially mediated iron sulfide transformations  

SciTech Connect

Stimulated sulfate-reduction is a bioremediation technique utilized for the sequestration of heavy metals in the subsurface.We performed laboratory column experiments to investigate the geoelectrical response of iron sulfide transformations by Desulfo vibriovulgaris. Two geoelectrical methods, (1) spectral induced polarization (SIP), and (2) electrodic potential measurements, were investigated. Aqueous geochemistry (sulfate, lactate, sulfide, and acetate), observations of precipitates (identified from electron microscopy as iron sulfide), and electrodic potentials on bisulfide ion (HS) sensitive silver-silver chloride (Ag-AgCl) electrodes (630 mV) were diagnostic of induced transitions between an aerobic iron sulfide forming conditions and aerobic conditions promoting iron sulfide dissolution. The SIP data showed 10m rad anomalies during iron sulfide mineralization accompanying microbial activity under an anaerobic transition. These anomalies disappeared during iron sulfide dissolution under the subsequent aerobic transition. SIP model parameters based on a Cole-Cole relaxation model of the polarization at the mineral-fluid interface were converted to (1) estimated biomineral surface area to pore volume (Sp), and (2) an equivalent polarizable sphere diameter (d) controlling the relaxation time. The temporal variation in these model parameters is consistent with filling and emptying of pores by iron sulfide biofilms, as the system transitions between anaerobic (pore filling) and aerobic (pore emptying) conditions. The results suggest that combined SIP and electrodic potential measurements might be used to monitor spatiotemporal variability in microbial iron sulfide transformations in the field.

Hubbard, Susan; Personna, Y.R.; Ntarlagiannis, D.; Slater, L.; Yee, N.; O'Brien, M.; Hubbard, S.

2008-02-15

13

Delineation of subsurface hydrocarbon contamination at a former hydrogenation plant using spectral induced polarization imaging  

NASA Astrophysics Data System (ADS)

Broadband spectral induced polarization (SIP) measurements were conducted at a former hydrogenation plant in Zeitz (NE Germany) to investigate the potential of SIP imaging to delineate areas with different BTEX (benzene, toluene, ethylbenzene, and xylene) concentrations. Conductivity images reveal a poor correlation with the distribution of contaminants; whereas phase images exhibit two main anomalies: low phase shift values (< 5 mrad) for locations with high BTEX concentrations, including the occurrence of free-phase product (BTEX concentrations > 1.7 g/l), and higher phase values for lower BTEX concentrations. Moreover, the spectral response of the areas with high BTEX concentration and free-phase products reveals a flattened spectrum in the low frequencies (< 40 Hz), while areas with lower BTEX concentrations exhibit a response characterized by a frequency peak. The SIP response was modelled using a Debye decomposition to compute images of the median relaxation-time. Consistent with laboratory studies, we observed an increase in the relaxation-time associated with an increase in BTEX concentrations. Measurements were also collected in the time domain (TDIP), revealing imaging results consistent with those obtained for frequency domain (SIP) measurements. Results presented here demonstrate the potential of the SIP imaging method to discriminate source and plume of dissolved contaminants at BTEX contaminated sites.

Flores Orozco, Adrián; Kemna, Andreas; Oberdörster, Christoph; Zschornack, Ludwig; Leven, Carsten; Dietrich, Peter; Weiss, Holger

2012-08-01

14

Dependence of spectral-induced polarization response of sandstone on temperature and its relevance to permeability estimation  

Microsoft Academic Search

The possibility to estimate permeability from the electrical spectral induced polarization (SIP) response might be the most important benefit offered by SIP measurements. It can thus be deduced that, in the future, SIP measurements will be carried out more frequently at the field scale or in a well-logging context to estimate permeability. In the shallow subsurface, however, the temperature generally

N. Zisser; A. Kemna; G. Nover

2010-01-01

15

Delineation of subsurface hydrocarbon contamination at a former hydrogenation plant using spectral induced polarization imaging  

NASA Astrophysics Data System (ADS)

In the framework of the EU FP7 project ModelPROBE, broadband spectral induced polarization (SIP) measurements were conducted at a former hydrogenation plant in Zeitz for the characterization of a hydrocarbon contaminant plume. In the source area total concentrations of BTEX contaminants partly exceed 1.5 g/l. Previous studies at the laboratory scale have demonstrated the sensitivity of SIP measurements to different concentrations of organic minerals; however, only few studies have been conducted at the field scale. The aim of this study was to investigate the potential of SIP imaging to delineate areas with different BTEX concentrations. SIP measurements were performed in the frequency range from 60 mHz to 1 kHz along a 120 m profile across the area of the former hydrogenation plant. At a later stage, a trench was excavated along the location of the profile in order to remove pipes, foundations and different sources of anthropogenic noise associated with the hydrogenation plant. Thereafter, SIP measurements were repeated inside the trench to study the effect of anthropogenic noise on the SIP images. Computed images for the data collected before and after the excavation of the trench show similar results validating the proposed approach even in the presence of anthropogenic noise. SIP images, for frequencies below 100 Hz, exhibit two main anomalies: low phase shift values (~ 5 mrad) for locations with free phase product (BTEX concentrations > 1.7 g/l); whereas relatively high polarization values (> 10 mrad) were observed for lower BTEX concentrations (1 - 1.7 g/l). Moreover, the spectral response of the areas where free phase product was detected reveals a flattened spectrum; while the areas with lower concentrations exhibit a typical Cole-Cole response. Based on these results, SIP imaging appears to be a suitable tool to delineate source-zones at highly contaminated sites.

Flores Orozco, A.; Kemna, A.; Oberdoerster, C.; Zschornack, L.; Leven, C.; Dietrich, P.; Weiss, H.

2011-12-01

16

Induced Polarization with Electromagnetic Coupling: 3D Spectral Imaging Theory, EMSP Project No. 73836  

SciTech Connect

This project was designed as a broad foundational study of spectral induced polarization (SIP) for characterization of contaminated sites. It encompassed laboratory studies of the effects of chemistry on induced polarization, development of 3D forward modeling and inversion codes, and investigations of inductive and capacitive coupling problems. In the laboratory part of the project a physico-chemical model developed in this project was used to invert laboratory IP spectra for the grain size and the effective grain size distribution of the sedimentary rocks as well as the formation factor, porosity, specific surface area, and the apparent fractal dimension. Furthermore, it was established that the IP response changed with the solution chemistry, the concentration of a given solution chemistry, valence of the constituent ions, and ionic radius. In the field part of the project, a 3D complex forward and inverse model was developed. It was used to process data acquired at two frequencies (1/16 Hz and 1/ 4Hz) in a cross-borehole configuration at the A-14 outfall area of the Savannah River Site (SRS) during March 2003 and June 2004. The chosen SRS site was contaminated with Tetrachloroethylene (TCE) and Trichloroethylene (PCE) that were disposed in this area for several decades till the 1980s. The imaginary conductivity produced from the inverted 2003 data correlated very well with the log10 (PCE) concentration derived from point sampling at 1 ft spacing in five ground-truth boreholes drilled after the data acquisition. The equivalent result for the 2004 data revealed that there were significant contaminant movements during the period March 2003 and June 2004, probably related to ground-truth activities and nearby remediation activities. Therefore SIP was successfully used to develop conceptual models of volume distributions of PCE/TCE contamination. In addition, the project developed non-polarizing electrodes that can be deployed in boreholes for years. A total of 28 of these electrodes were deployed at the SRS site in September of 2002. The project found that (1) currently available field instrumentation need to be faster by an order of magnitude for full SIP to be engaged for broadband characterization in the field, (2) some aspects of the capacitive coupling problem in borehole geometries can be solved by use of a high impedance receiver, (3) a careful investigation of ways to adequately compare inversion results to ground-truth data is warranted, (4) more laboratory studies should be directed to understand the influence of micro-organisms and long residence time of contaminants (aging) on spectral IP properties.

Morgan, F. Dale; Sogade, John

2004-12-14

17

The effect of organic contaminants on the spectral induced polarization response of porous media - mechanistic approach  

NASA Astrophysics Data System (ADS)

In recent years, there is a growing interest in using geophysical methods in general and spectral induced polarization (SIP) in particular as a tool to detect and monitor organic contaminants within the subsurface. The general idea of the SIP method is to inject alternating current through a soil volume and to measure the resultant potential in order to obtain the relevant soil electrical properties (e.g. complex impedance, complex conductivity/resistivity). Currently, a complete mechanistic understanding of the effect of organic contaminants on the SIP response of soil is still absent. In this work, we combine laboratory experiments with modeling to reveal the main processes affecting the SIP signature of soil contaminated with organic pollutant. In a first set of experiments, we investigate the effect of non-aqueous phase liquids (NAPL) on the complex conductivity of unsaturated porous media. Our results show that addition of NAPL to the porous media increases the real component of the soil electrical conductivity and decreases the polarization of the soil (imaginary component of the complex conductivity). Furthermore, addition of NAPL to the soil resulted in an increase of the electrical conductivity of the soil solution. Based on these results, we suggest that adsorption of NAPL to the soil surface, and exchange process between polar organic compounds in the NAPL and inorganic ions in the soil are the main processes affecting the SIP signature of the contaminated soil. To further support our hypothesis, the temporal change of the SIP signature of a soil as function of a single organic cation concentration was measured. In addition to the measurements of the soil electrical properties, we also measured the effect of the organic cation on the chemical composition of both the bulk and the surface of the soil. The results of those experiments again showed that the electrical conductivity of the soil increased with increasing contaminant concentration. In addition, direct evidence showed that the organic cation was adsorbed on the soil surface and exchanged with inorganic ions that usually exist in soil. This experiment confirmed that adsorption to the soil surface and the associated release of inorganic ions is the main mechanism affecting the complex conductivity of the contaminated porous media. Furthermore, our results show that adsorption of organic ions to the soil surface resulted in a decrease of the soil polarization. Using a chemical complexation model of the soil surface and a model for the polarization of the Stern layer, we were able to show that the decrease in the polarization of the soil can be related to the decrease in the surface site density of inorganic ions, and that the contribution of the soil-organic complexes to the polarization of the soil is negligible. We attribute this to the strong interaction between polar organic compounds and soil which results in a significant decrease in the mobility of the organic compounds in the Stern layer. The results of this work are essential to better interpret SIP signatures of soil contaminated with organic contaminants.

Schwartz, N.; Huisman, J. A.; Furman, A.

2012-12-01

18

Preliminary results of spectral induced polarization measurements, Wadi Bidah District, Kingdom of Saudi Arabia  

USGS Publications Warehouse

Laboratory spectral induced polarization (SIP) measurements on 29 carbonaceous schist samples from the Wadi Bidah district show that most are associated with very long polarization decays or, equivalently, large time constants. In contrast, measurements on two massive sulfide samples indicate shorter polarization decays or smaller time constants. This difference in time constants for the polarization process results in two differences in the phase spectra in the frequency range of from 0.06 to 1Hz. First, phase values of carbonaceous rocks generally decrease as a function of increasing frequency. Second, phase values of massive sulfide-bearing rocks increase as a function of increasing frequency. These results from laboratory measurements agree well with those from other reported SIP measurements on graphites and massive sulfides from the Canadian Shield. Four SIP lines, measured by using a 50-m dipole-dipole array, were surveyed at the Rabathan 4 prospect to test how well the results of laboratory sample measurements can be applied to larger scale field measurements. Along one line, located entirely over carbonaceous schists, the phase values decreased as a function of increasing frequency. Along a second line, located over both massive sulfides and carbonaceous schists as defined by drilling, the phase values measured over carbonaceous schists decreased as a function of increasing frequency, whereas those measured over massive sulfides increased. In addition, parts of two lines were surveyed down the axes of the massive sulfide and carbonaceous units. The phase values along these lines showed similar differences between the carbonaceous schists and massive sulfides. To date, the SIP survey and the SIP laboratory measurements have produced the only geophysical data that indicate an electrical difference between the massive sulfide-bearing rocks and the surrounding carbonaceous rocks in the Wadi Bidah district. However, additional sample and field measurements in areas of known mineralization would fully evaluate the SIP method as applied to various geologic environments and styles of massive sulfide mineralization. Additionally, the efficiency of SIP surveys in delineating areas of sulfide mineralization might be improved by surveying lines down the axes of known electrical conductors. An evaluation of the applied research done on the SIP method to date suggests that this technique offers significant exploration applications to massive sulfide exploration in the Kingdom of Saudi Arabia.

Smith, Bruce D.; Tippens, C.L.; Flanigan, V.J.; Sadek, Hamdy

1983-01-01

19

A new model for the spectral induced polarization signature of bacterial growth in porous media  

NASA Astrophysics Data System (ADS)

The complex conductivity of porous materials and colloidal suspensions comprises two components: an in-phase conductivity associated with electromigration of the charge carriers and a quadrature conductivity associated with the reversible storage of the charges at some polarization length scales. We developed a quantitative model to investigate the frequency domain induced polarization response of suspensions of bacteria and bacteria growth in porous media. Induced polarization of bacteria (? polarization) is related to the properties of the electrical double layer of the bacteria. Surface conductivity and ? polarization are due to the Stern layer of counterions occurring in a brush of polymers coating the surface of the bacteria. These phenomena can be related to their cation exchange capacity. The mobility of the counterions in this Stern layer is found to be very small (4.7 × 10-10 m2 s-1 V-1 at 25°C). This implies a very low relaxation frequency for the ?polarization of the bacteria cells (typically around 0.1-5 Hz), in agreement with experimental observations. This new model can be coupled to reactive transport modeling codes in which the evolution of bacterial populations are usually described by Monod kinetics. We show that the growth rate and endogenous decay coefficients of bacteria in a porous sand can be inferred nonintrusively from time-lapse frequency domain induced polarization data.

Revil, A.; Atekwana, E.; Zhang, C.; Jardani, A.; Smith, S.

2012-09-01

20

Spectral Induced Polarization Response of Unconsolidated Saturated Sand and Surfactant Solutions  

NASA Astrophysics Data System (ADS)

Dense non-aqueous phase liquids (DNAPL), such as chlorinated solvents, are common groundwater contaminants. Traditional pump-and-treat methods are often not effective at removing residual DNAPL from the subsurface. Surfactant-enhanced aquifer remediation is a promising remediation method that utilizes subsurface surfactant floods to decrease the interfacial tension between the non-aqueous phase and groundwater and increase the contaminant solubility and mobility in water. This remediation method is not widely used because of unknown subsurface distribution and effectiveness. The ability to effectively monitor and perhaps map the spatial distribution of surfactant floods used in remediation could reduce monitoring uncertainty and increase their use. Previous work has shown that surfactants in aqueous solutions significantly alter the solution conductivity, but this work has not investigated the surfactant response in aquifer type materials. In this project, spectral induced polarization measurements of four surfactant aqueous solutions in a sand matrix were evaluated. The frequency range assessed was 0.732 Hz to 187.5 Hz. The surfactants, which are typically used in the remediation of tetrachloroethylene, were Aerosol MA-80-I, Dowfax 8390, and Steol CS-330. These surfactant solutions were injected into a closed system of 20-30 Ottawa silica sand. Resistivity and phase responses were measured. The surfactant treatments altered both phase and resistivity in varying degrees, with Aerosol MA-80-I showing a marked decrease in both, and the Steol CS- 330 exhibiting little change relative to the control column. These results suggest geoelectrical property changes may be an applicable property to map and monitor surfactant floods in the subsurface. Future work will continue to investigate this application.

Magill, M. T.; Werkema, D.; Kreamer, D. K.

2008-12-01

21

Laboratory technique for measurement of spectral induced polarization response of soil sampies1  

Microsoft Academic Search

Laboratory measurements of soil samples are necessary to assess the effect of mineralogy, grain size distribution, moisture content, and electrolyte composition the resistivity spectrum of soil material. Laboratory results are also required for the interpretation of field data. Induced polarization phenomena in glacial soils are poorly understood and so far no convenient laboratory techniques are available for measurement. Coarse grain

Heikki Vanhala; Heikki Soininen

1995-01-01

22

Pollutant monitoring in a sand-column with Spectral Induced Polarization, Time Domain Reflectometry, and geochemistry analysis: experimentation and modeling  

NASA Astrophysics Data System (ADS)

Geoelectrical methods have been proposed as non-invasive techniques to monitor the soil contamination. It is now well known that electrical properties of porous media depend on the composition of the electrolyte and its interaction with the surface of the minerals. So, understanding in the laboratory the influence of change in electrolyte composition on geolectrical measurements is critical to validate behaviour models. Following this path, we have been using two geolectrical methods, Time Domain Reflectometry and Spectral Induced Polarization measurements. We carried out column experiments to investigate the effect of mineralogy and electrolyte composition on the electrical signatures resulting from pollutant migration (CuSO4 and ZnSO4) in saturated flow conditions, and adsorption/desorption reaction between Cu, Zn and the surface of the minerals. Laboratory columns are filled with a 100 µm well sorted sand (nearly pure silica). These columns are saturated with different well known electrolytes (composition of the electrolyte is progressively modified during the course of the experiment). The evolution of the chemical composition in columns has been monitored to have a well understanding of transport and reaction processes. Spectral Induced Polarization measurements were performed in the frequency range 45 mHz - 12 kHz. Low-frequencies polarization characteristics in a such environment depend on two processes. There is the polarization of the mineral/electrolyte interface coating the surface of the grains (polarization of the Stern layer) and the Maxwell-Wagner polarization associated with accumulation of the electrical charges in the pore space of the medium. The model of low-frequency conductivity is connected to a double-layer model of electrochemical processes occurring at the surface of silica. Characteristics of this double-layer model (i.e., distribution of counterions between the diffuse layer and Stern layer) are computed with the code Phreeqc (USGS). Experimentation and modeling allows us to connect characteristics of the electrolyte and geoelectric responses.

Pierre, V.; Schmutz, M.; Franceschi, M.; Revil, A.

2009-12-01

23

Accounting for the effects of pore fluid chemistry on spectral induced polarization (SIP) measurements: the specific polarizability concept  

NASA Astrophysics Data System (ADS)

Recent spectral induced polarization (SIP) research has advanced our understanding of the controls of the physical and hydraulic properties of porous media on both the polarization magnitude and relaxation length scales in porous media. A critical current challenge is to improve our understanding of how pore fluid chemistry modifies the interfacial polarization measured with the SIP technique. We report results from two laboratory-scale experiments designed to advance this understanding. In the first experiment, we analyzed the influence of electrolyte concentration and valence on the interfacial polarization of three sandstones with differing porosity and permeability. A Debye decomposition (DD) approach was used to determine normalized chargeability and average relaxation time from spectral data. We find that SIP measurements of the polarization magnitude (single frequency imaginary conductivity and normalized chargeability derived from the DD) of sandstone samples can be described by the product of the pore space related internal surface and a quantity that represents the polarizability of the mineral-fluid interface and depends on electrolyte concentration and valence. We introduce a new parameter, the specific polarizability, describing this dependence. In the second experiment, we investigated the effect of pH and hydroxyl ion concentration on the interfacial polarization of both silica gel and well-sorted sand. We find a strong dependence of the polarization on pH in the silica gel. Evidence for the same dependence exists for the sand, although the signal is only just above the noise threshold (~0.1 mrad) of the instrument. We relate the weaker signal observed in the sands to the much smaller pore space related internal surface relative to silica gel, a unique substance with surface area in excess of 500 m2/g. These observations suggest that the specific polarizability is also a function of pH, although the pH dependence is likely to be weak in SIP measurements of porous media characterized by an internal surface typical of natural unconsolidated rocks and soils. Our findings provide a framework for quantifying structural characteristics of porous media from SIP data in the presence of variable fluid chemistry.

Slater, L. D.; Weller, A.; Zhang, C.; Breede, K.; Johnson, T. J.; Nordsiek, S.; Redden, G. D.; Fox, D. T.

2011-12-01

24

Induced Polarization with Electromagnetic Coupling: 3D Spectral Imaging Theory EMSP Project No. 73836  

Microsoft Academic Search

This report summarizes the research work completed on the project between December 2001 and September 2002. (1) A model of all Spectral IP capacitive couplings revealed that potential bearing electrodes should be carefully chosen to obviate some of the capacitive coupling problems. This need becomes more important for borehole sampling. Thus, work had been done to design a porous pot

F. Dale

2003-01-01

25

Estimating the spatiotemporal distribution of geochemical parameters associated with biostimulation using spectral induced polarization data and hierarchical Bayesian models  

NASA Astrophysics Data System (ADS)

We developed a hierarchical Bayesian model to estimate the spatiotemporal distribution of aqueous geochemical parameters associated with in-situ bioremediation using surface spectral induced polarization (SIP) data and borehole geochemical measurements collected during a bioremediation experiment at a uranium-contaminated site near Rifle, Colorado (USA). The SIP data were first inverted for Cole-Cole parameters, including chargeability, time constant, resistivity at the DC frequency, and dependence factor, at each pixel of two-dimensional grids using a previously developed stochastic method. Correlations between the inverted Cole-Cole parameters and the wellbore-based groundwater chemistry measurements indicative of key metabolic processes within the aquifer (e.g., ferrous iron, sulfate, uranium) were established and used as a basis for petrophysical model development. The developed Bayesian model consists of three levels of statistical submodels: (1) data model, providing links between geochemical and geophysical attributes, (2) process model, describing the spatial and temporal variability of geochemical properties in the subsurface system, and (3) parameter model, describing prior distributions of various parameters and initial conditions. The unknown parameters were estimated using Markov chain Monte Carlo methods. By combining the temporally distributed geochemical data with the spatially distributed geophysical data, we obtained the spatiotemporal distribution of ferrous iron, sulfate, and sulfide, and their associated uncertainty information. The obtained results can be used to assess the efficacy of the bioremediation treatment over space and time and to constrain reactive transport models.

Chen, Jinsong; Hubbard, Susan S.; Williams, Kenneth H.; Flores Orozco, AdriáN.; Kemna, Andreas

2012-05-01

26

INJECTION ELECTRODE POLARIZATION RESISTIVITY AND INDUCED POLARIZATION  

E-print Network

INJECTION ELECTRODE POLARIZATION IN RESISTIVITY AND INDUCED POLARIZATION J.B. Merriam University.merriam@usask.ca Abstract Polarization of injection electrodes in resistivity and induced polarization may reach several will only be a problem if the received signal is very much smaller than the polarization. In induced

Merriam, James

27

Time domain spectral induced polarization of disseminated electronic conductors: Laboratory data analysis through the Debye decomposition approach  

NASA Astrophysics Data System (ADS)

We measured Spectral Induced Polarization responses of 22 models of disseminated ore with a time domain (TD) technique. The models were mixtures of calibrated sand (0.2-0.3 mm) with calibrated ore grains (average radii: 0.045, 0.055, 0.13, 0.20, 0.38 and 0.55 mm). The grains represent a mixture of pyrrhotite (30%), pyrite (30%), magnetite (30%) and chalcopyrite (10%) coming from a natural ore. In the models, the grain concentration (by volume) varied between 0.6 and 30%. We obtained IP decays with a conventional field TD measuring technique and a lab low-current transmitter in the time range from 0.3 ms to 64 s. The IP decays measured with various current wavelength forms were inverted to relaxation time distributions (RTD) on the basis of the Debye decomposition approach. RTD parameters were found to be closely related to the ore volumetric content and the ore grain size. The total chargeability is independent of the grain size, but is determined by the grain volume fraction. In contrast, the mean IP relaxation time is related to the grain size. These facts make RTD attractive to use in ore prospecting and studying reactive permeable barriers. Moreover, for low salinity pore water used in this study, the relaxation times of disseminated ores are three to four decades smaller than that of the insulating grains of the same size typical of common soils and sediments. This allows recover the relaxation times on the basis of relatively fast IP measurements with short time pulses (in TD) or high frequency values in the frequency domain; however attention should be paid to inductive and capacitive couplings.

Gurin, Grigory; Tarasov, Andrey; Ilyin, Yuri; Titov, Konstantin

2013-11-01

28

Investigating the Effect of Saturation and Wettability on Spectral Induced Polarization of Biodegraded Oil in Porous Media  

NASA Astrophysics Data System (ADS)

Spectral induced polarization (SIP) has been suggested as the technique most sensitive to the presence of contaminants as well as accompanying bio-physicochemical processes associated with hydrocarbon biodegradation. Previous laboratory investigations have suggested that wettability is an important factor to consider when investigating the SIP response of oil bearing sands. The results to date provide experimental data for mostly fresh oil. However, these results differ significantly from field investigations where the oil is mostly in the degraded form. In this study we extend the work of Schmutz and others and Revil and others by investigating the SIP response of biodegraded oil in porous media. Laboratory experiments were conducted to investigate the effect of different oil saturation (0.2-0.8) and wettability (water wet and oil wet) on SIP of biodegraded and fresh oil in sand columns. The laboratory experiments were performed using a sand column filled with a mix of oil, artificial ground water (AGW) with a conductivity of 0.01 S/m and fine sands. Each experiment was conducted with clean sands mixed with oil (oil wet case) or AGW (water wet case). The proportions of oil and water were calculated to obtain the desired oil and water saturations, and using the same amount of sand. SIP measurements were made using a National Instruments NI 4551 dynamic signal analyzer and four electrodes technique. Phase shift between current stimulus-voltage signal and conductivity magnitude were measured between 0.1 and 1000 Hz and the real and imaginary components of the complex surface conductivity were calculated. The same experimental procedure was repeated using fresh oil as background and for comparison with biodegraded oil results. The results show that when water is the wetting phase, there is no significant difference in the IP parameters measured for both the fresh and degraded oil. Furthermore, both the fresh and biodegraded oil showed an increase in the magnitude of the phase and a decrease in the magnitudes of the real and imaginary conductivity components with increasing oil saturation. However, when oil is the wetting phase there is a noticeable difference in the magnitude of the IP parameters between the fresh and biodegraded oil. The magnitude of the phase and imaginary conductivity component increased with increasing oil saturation whereas real conductivity decreased. At the same time, the magnitude of the real and imaginary conductivity components for the biodegraded oil wet sands were relatively higher compared to fresh oil wet sand. Our results suggest that the biodegraded oil enhances the polarization only for the case where oil is the wetting phase. The enhancement in the polarization (imaginary conductivity) observed with the biodegraded oil wet sands may be attributed to the increase in polar components and nanoparticulate metals (magnetite, vanadium, nickel, etc.) content resulting from the biodegradation process.

Abdel Aal, G. Z.; Atekwana, E. A.

2012-12-01

29

Injection Electrode Polarization in Induced Polarization  

E-print Network

Injection Electrode Polarization in Induced Polarization J.B. Merriam Department of Geological-966-8593, E-mail: jim.merriam@usask.ca Polarization at the boundary between the current injection electrodes and the pore fluid occurs by a number of mechanisms. The polarization can be described as a variable contact

Merriam, James

30

Spectral and spectral-polarization characteristics of potato leaves  

NASA Astrophysics Data System (ADS)

The results of laboratory investigations of the spectral and spectral-polarization characteristics of radiation reflected from the leaves of potato (Solanum tuberosum) of different varieties are discussed. During the vegetation season of 1997, the angular dependence of the degree and azimuth of polarization of radiation reflected from potato leaves as well as the scattering indicatrices in the range 380 1080 nm were determined by a specially developed method with the use of a laboratory goniometric setup. The relationship between the spectral polarization characteristics of radiation and biological parameters of the potato has been obtained with the help of different methods of statistical analysis and explained on the basis of the known physical mechanisms.

Belyaev, B. I.; Belyaev, Yu. V.; Chumakov, A. V.; Nekrasov, V. P.; Shuplyak, V. I.

2000-07-01

31

Gaussian Induced Dipole Polarization Model  

PubMed Central

A new induced dipole polarization model based on interacting Gaussian charge densities is presented. In contrast to the original induced point dipole model, the Gaussian polarization model is capable of finite interactions at short distances. Aspects of convergence related to the Gaussian model will be explored. The Gaussian polarization model is compared with the damped Thole-induced dipole model and the point dipole model. It will be shown that the Gaussian polarization model performs slightly better than the Thole model in terms of fitting to molecular polarizability tensors. An advantage of the model based on Gaussian charge distribution is that it can be easily generalized to other multipole moments and provide effective damping for both permanent electrostatic and polarization models. Finally, a method of parameterizing polarizabilities is presented. This method is based on probing a molecule with point charges and fitting polarizabilities to electrostatic potential. In contrast to the generic atom type polarizabilities fit to molecular polarizability tensors, probed polarizabilities are significantly more accurate in terms of reproducing molecular polarizability tensors and electrostatic potential, while retaining conformational transferability. PMID:17299773

ELKING, DENNIS; DARDEN, TOM; WOODS, ROBERT J.

2007-01-01

32

THE EFFECT OF SYSTEMATICS ON POLARIZED SPECTRAL INDICES  

SciTech Connect

We study four particularly bright polarized compact objects (Tau A, Vir A, 3C 273, and For A) in the 7 year Wilkinson Microwave Anisotropy Probe (WMAP) sky maps, with the goal of understanding potential systematics involved in the estimation of foreground spectral indices. First, we estimate the spectral index, the polarization angle, the polarization fraction, and the apparent size and shape of these objects when smoothed to a nominal resolution of 1 Degree-Sign FWHM. Second, we compute the spectral index as a function of polarization orientation, {alpha}. Because these objects are approximately point sources with constant polarization angle, this function should be constant in the absence of systematics. However, for the K and Ka band WMAP data we find strong index variations for all four sources. For Tau A, we find a spectral index of {beta} = -2.59 {+-} 0.03 for {alpha} = 30 Degree-Sign , and {beta} = -2.03 {+-} 0.01 for {alpha} = 50 Degree-Sign . On the other hand, the spectral index between the Ka and Q bands is found to be stable. A simple elliptical Gaussian toy model with parameters matching those observed in Tau A reproduces the observed signal, and shows that the spectral index is particularly sensitive to the detector polarization angle. Based on these findings, we first conclude that estimation of spectral indices with the WMAP K band polarization data at 1 Degree-Sign scales is not robust. Second, we note that these issues may be of concern for ground-based and sub-orbital experiments that use the WMAP polarization measurements of Tau A for calibration of gain and polarization angles.

Wehus, I. K. [Oxford Astrophysics, University of Oxford, DWB, Keble Road, Oxford OX1 3RH (United Kingdom)] [Oxford Astrophysics, University of Oxford, DWB, Keble Road, Oxford OX1 3RH (United Kingdom); Fuskeland, U.; Eriksen, H. K., E-mail: i.k.wehus@fys.uio.no [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, N-0315 Oslo (Norway)

2013-02-15

33

Inversion of induced polarization data  

Microsoft Academic Search

The authors developed three methods to invert induced polarization (IP) data. The foundation for their algorithms is an assumption that the ultimate effect of chargeability is to alter the effective conductivity when current is applied. This assumption, which was first put forth by Siegel and has been routinely adopted in the literature, permits the IP responses to be numerically modeled

Douglas W. Oldenburg; Y. Li

1994-01-01

34

Polarized nuclear target based on parahydrogen induced polarization  

SciTech Connect

We discuss a novel concept of a polarized nuclear target for accelerator fixed-target scattering experiments, which is based on parahydrogen induced polarization (PHIP). One may be able to reach a 33% free-proton polarization in the ethane molecule. The potential advantages of such a target include operation at zero magnetic field, fast ({approx}100 HZ) polarization oscillation (akin to polarization reversal), and operation with large intensity of an electron beam.

D. Budker, M.P. Ledbetter, S. Appelt, L.S. Bouchard, B. Wojtsekhowski

2012-12-01

35

Spectral and Polarization Sensitivity of the Dipteran Visual System  

PubMed Central

Spectral and polarization sensitivity measurements were made at several levels (retina, first and third optic ganglion, cervical connective, behavior) of the dipteran visual nervous system. At all levels, it was possible to reveal contributions from the retinular cell subsystem cells 1 to 6 or the retinular cell subsystem cells 7 and 8 or both. Only retinular cells 1 to 6 were directly studied, and all possessed the same spectral sensitivity characterized by two approximately equal sensitivity peaks at 350 and 480 nm. All units of both the sustaining and on-off variety in the first optic ganglion exhibited the same spectral sensitivity as that of retinular cells 1 to 6. It was possible to demonstrate for motion detection and optomotor responses two different spectral sensitivities depending upon the spatial wavelength of the stimulus. For long spatial wavelengths, the spectral sensitivity agreed with retinular cells 1 to 6; however, the spectral sensitivity at short spatial wavelengths was characterized by a single peak at 465 nm reflecting contributions from the (7, 8) subsystem. Although the two subsystems exhibited different spectral sensitivities, the difference was small and no indication of color discrimination mechanisms was observed. Although all retinular cells 1 to 6 exhibited a preferred polarization plane, sustaining and on-off units did not. Likewise, motion detection and optomotor responses were insensitive to the polarization plane for long spatial wavelength stimuli; however, sensitivity to select polarization planes was observed for short spatial wavelengths. PMID:5027759

McCann, Gilbert D.; Arnett, David W.

1972-01-01

36

Spontaneous Polarization-Induced Nanohelixes, Nanosprings, and  

E-print Network

Spontaneous Polarization-Induced Nanohelixes, Nanosprings, and Nanorings of Piezoelectric Nanobelts polarization is induced across the nanobelt thickness. As a result, right-handed helical nanostructures-surface-dominated ZnO nanobelts are likely to be an ideal system for understanding piezoelectricity and polarization-induced

Wang, Zhong L.

37

Polarized nuclear target based on parahydrogen induced polarization  

E-print Network

We discuss a novel concept of a polarized nuclear target for accelerator fixed-target scattering experiments, which is based on parahydrogen induced polarization (PHIP). One may be able to reach a 33% free-proton polarization in the ethane molecule. The potential advantages of such a target include operation at zero magnetic field, fast ($\\sim$100 Hz) polarization reversal, and operation with large intensity of an electron beam.

D. Budker; M. P. Ledbetter; S. Appelt; L. S. Bouchard; B. Wojtsekhowski

2012-03-13

38

Propagation-induced polarization changes in partially coherent optical beams  

Microsoft Academic Search

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 polar- ization changes with propagation and also becomes nonuniform across the beam cross section. The extent of these

Govind P. Agrawal; Emil Wolf

2000-01-01

39

[Depth selectivity by using polarization-controlled spectral technique].  

PubMed

A continuous depth selectivity is examined by changing the state of polarization of the signal light, based on the orthogonal polarization spectral (OPS) microcirculation imaging system. Unlike the traditional OPS system, which could only rend a two dimensional image of a certain cross-section, the elliptically polarized light controlled by the polarizer unit and the analyzer unit could do the microscopy refocusing without mechanically scanning the sample, as a result, the tissue information at different depths could be obtained. Because the proposed system matches the emission spectrum of the light source with the absorption spectrum of the erythrocyte, it has relatively high signal-to-noise ratio, and could be used to detect microcirculation. Imaging of a pork fat with a target is acquired, and the quantitative relationship between image contrast and the state of polarization is illustrated. The results show that from linearly to circularly polarized illumination, the image contrast gradually increases, and the maximum visible depth also increases. Finally, the auricle vessel of a nude mouse was detected by this polarization-controlled spectral imaging system. Through the experiment the feasibility of depth selectivity was proved. The proposed method provides new insights to microscopy refocusing of microcirculation. PMID:24555345

Feng, Xu; Sun, Li-Qun; Zhang, En-Yao

2013-11-01

40

Spectral and polarization hole burning in neodymium glass lasers  

Microsoft Academic Search

Gain saturation in short-pulse glass laser amplifiers is treated including both spectral and polarization hole burning. A formalism is developed to calculate the performance of an amplifier based on media with a generalized cross section inhomogeneity. Predictions are made for the output fluence and the energy extraction efficiency, as well as the post-pulse gain of a weak probe of arbitrary

D. W. Hall; R. A. Haas; W. F. Krupke; M. J. Weber

1983-01-01

41

Spectral and Polarization Sensitivity of the Dipteran Visual System  

Microsoft Academic Search

Spectral and polarization sensitivity measurements were made at several levels (retina, first and third optic ganglion, cervical connective, be- havior) of the dipteran visual nervous system. At all levels, it was possible to reveal contributions from the retinular cell subsystem cells 1 to 6 or the retinular cell subsystem cells 7 and 8 or both. Only retinular cells I to

GILBERT D. McCANN; DAVID W. ARNETT

2009-01-01

42

Multilayer thin film design for far ultraviolet polarizers using an induced transmission and absorption technique  

NASA Technical Reports Server (NTRS)

An explanation of induced transmission for spectral regions excluding the far ultraviolet (FUV) is given to better understand how induced transmission and absorption can be used to design effective polarizers in the FUV spectral region. We achieve high s-polarization reflectance and a high degree of polarization (P equals (Rs-Rp)/(Rs+Rp)) by means of a MgF2/Al/MgF2 three layer structure on an opaque thick film of Al as the substrate. For example, our polarizer designed for the Lyman-alpha line (lambda equals 121.6 nm) has 87.95 percent reflectance for the s-polarization case and 0.43 percent for the p-polarization case, with a degree of polarization of 99.03 percent. If a double reflection polarizer is made with this design, it will have a degree of polarization of 99.99 percent and s-polarization throughput of 77.35 percent.

Kim, Jongmin; Zukic, Muamer; Torr, Douglas G.

1993-01-01

43

NON-ZEEMAN CIRCULAR POLARIZATION OF MOLECULAR ROTATIONAL SPECTRAL LINES  

SciTech Connect

We present measurements of circular polarization from rotational spectral lines of molecular species in Orion KL, most notably {sup 12}CO (J = 2 {yields} 1), obtained at the Caltech Submillimeter Observatory with the Four-Stokes-Parameter Spectral Line Polarimeter. We find levels of polarization of up to 1%-2% in general; for {sup 12}CO (J = 2 {yields} 1) this level is comparable to that of linear polarization also measured for that line. We present a physical model based on resonant scattering in an attempt to explain our observations. We discuss how slight differences in scattering amplitudes for radiation polarized parallel and perpendicular to the ambient magnetic field, responsible for the alignment of the scattering molecules, can lead to the observed circular polarization. We also show that the effect is proportional to the square of the magnitude of the plane of the sky component of the magnetic field and therefore opens up the possibility of measuring this parameter from circular polarization measurements of Zeeman insensitive molecules.

Houde, Martin; Jones, Scott; Rajabi, Fereshte [Department of Physics and Astronomy, The University of Western Ontario, London, ON, N6A 3K7 (Canada)] [Department of Physics and Astronomy, The University of Western Ontario, London, ON, N6A 3K7 (Canada); Hezareh, Talayeh [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)] [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)

2013-02-10

44

An Integrated Imaging Detector of Polarization and Spectral Content  

NASA Technical Reports Server (NTRS)

A new type of image detector has been designed to simultaneously analyze the polarization of light at all picture elements in a scene. The Integrated Dual Imaging Detector (IDID) consists of a polarizing beamsplitter bonded to a charge-coupled device (CCD), with signal-analysis circuitry and analog-to-digital converters, all integrated on a silicon chip. It should be capable of 1:10(exp 4) polarization discrimination. The IDID should simplify the design and operation of imaging polarimeters and spectroscopic imagers used, for example, in atmospheric and solar research. Innovations in the IDID include (1) two interleaved 512 x 1024-pixel imaging arrays (one for each polarization plane); (2) large dynamic range (well depth of 10(exp 6) electrons per pixel); (3) simultaneous readout of both images at 10 million pixels per second each; (4) on-chip analog signal processing to produce polarization maps in real time; (5) on-chip 10-bit A/D conversion. When used with a lithium-niobate Fabry-Perot etalon or other color filter that can encode spectral information as polarization, the IDID can collect and analyze simultaneous images at two wavelengths. Precise photometric analysis of molecular or atomic concentrations in the atmosphere is one suggested application. When used in a solar telescope, the IDID will charge the polarization, which can then be converted to maps of the vector magnetic fields on the solar surface.

Rust, D. M.; Thompson, K. E.

1993-01-01

45

Dynamic nuclear polarization from current-induced electron spin polarization  

NASA Astrophysics Data System (ADS)

Current-induced electron spin polarization is shown to produce nuclear hyperpolarization through dynamic nuclear polarization. Saturated fields of several millitesla are generated upon the application of an electric field over a time scale of 100 s in InGaAs epilayers and measured using optical Larmor magnetometry. We show that, in contrast to previous demonstrations of current-induced dynamic nuclear polarization, the direction of the current relative to the crystal axis and external magnetic field may be used to control the magnitude and direction of the saturation nuclear field.

Trowbridge, C. J.; Norman, B. M.; Kato, Y. K.; Awschalom, D. D.; Sih, V.

2014-08-01

46

Submillimeter Wave Frequency Selective Surface With Polarization Independent Spectral Responses  

Microsoft Academic Search

This paper reports the design, construction and electromagnetic performance of a new freestanding frequency selective surface (FSS) structure which generates coincident spectral responses for dual polarization excitation at oblique angles of incidence. The FSS is required to allow transmission of 316.5-325.5 GHz radiation with a loss les 0.6 dB and to achieve ges 30 dB rejection from 349.5-358.5 GHz. It

Raymond Dickie; Robert Cahill; Harold Gamble; Vincent Fusco; Manju Henry; Matthew Oldfield; Peter Huggard; Philip Howard; Norman Grant; Yvonne Munro; Peter de Maagt

2009-01-01

47

Cross borehole induced polarization to detect subsurface NAPL at the Savannah River Site, South Carolina  

E-print Network

Spectral induced polarization measurements were acquired in six cross-borehole panels within four boreholes at the Savannah River Site. The investigation was performed to delineate the presence of dense non-aqueous phase ...

Lambert, Michael B. (Michael Brian), 1980-

2003-01-01

48

Spectral signatures of polar stratospheric clouds and sulfate aerosol  

SciTech Connect

Multiwavelength observations of Antarctic and midlatitude aerosol by the Cryogenic Limb Array Etalon Spectrometer (CLAES) experiment on the Upper Atmosphere Research Satellite are used to demonstrate a technique that identifies the location of polar stratospheric clouds. The technique discussed uses the normalized area of the triangle formed by the aerosol extinctions at 925, 1257, and 1605 cm{sup {minus}1} (10.8, 8.0, and 6.2 {mu}m) to derive a spectral aerosol measure M of the aerosol spectrum. Mie calculations for spherical particles and T-matrix calculations for spheroidal particles are used to generate theoretical spectral extinction curves for sulfate and polar stratospheric cloud particles. The values of the spectral aerosol measure M for the sulfate and polar stratospheric cloud particles are shown to be different. Aerosol extinction data, corresponding to temperatures between 180 and 220 K at a pressure of 46 hPa (near 21-km altitude) for 18 August 1992, are used to demonstrate the technique. Thermodynamic calculations, based upon frost-point calculation and laboratory phase-equilibrium studies of nitric acid trihydrate, are used to predict the location of nitric acid trihydrate cloud particles. 47 refs., 22 figs., 3 tabs.

Massie, S.T.; Bailey, P.L.; Gille, J.C. [National Center for Atmospheric Research, Boulder, CO (United States)] [National Center for Atmospheric Research, Boulder, CO (United States); Lee, E.C. [Princeton Univ., NJ (United States)] [Princeton Univ., NJ (United States); Mergenthaler, J.L.; Roche, A.E.; Kumer, J.B. [Lockheed Palo Alto Research Lab., CA (United States)] [Lockheed Palo Alto Research Lab., CA (United States); Fishbein, E.F.; Waters, J.W. [California Institute of Technology, Pasadena, CA (United States)] [California Institute of Technology, Pasadena, CA (United States); Lahoz, W.A. [Univ. of Reading (United Kingdom)] [Univ. of Reading (United Kingdom)

1994-10-15

49

Current-induced pseudospin polarization in silicene  

NASA Astrophysics Data System (ADS)

The pseudospin polarization induced by an external electric field in silicene in the presence of weakly spin-independent impurities is considered theoretically in the linear response regime based on Green's function method. We study the effects of the interplay between the sublattice potential and the intrinsic spin orbit coupling on the pseudospin polarization. We show that the pseudospin polarization perpendicular to the electric field is independent of the impurity parameter, while the pseudospin polarization in the direction of the electric field is sensitive to the impurity parameter. The dependences of the pseudospin polarizations on the chemical potential are studied.

Wang, Lei; Zhu, Guo-Bao

2014-09-01

50

THE IMPACT OF QUANTUM INTERFERENCE BETWEEN DIFFERENT J-LEVELS ON SCATTERING POLARIZATION IN SPECTRAL LINES  

SciTech Connect

The spectral line polarization produced by optically pumped atoms contains a wealth of information on the thermal and magnetic structure of a variety of astrophysical plasmas, including that of the solar atmosphere. A correct decoding of such information from the observed Stokes profiles requires a clear understanding of the effects that radiatively induced quantum interference (or coherence) between pairs of magnetic sublevels produces on these observables, in the absence of and in the presence of magnetic fields of arbitrary strength. Here we present a detailed theoretical investigation of the role of coherence between pairs of sublevels pertaining to different fine-structure J-levels, clarifying when it can be neglected for facilitating the modeling of the linear polarization produced by scattering processes in spectral lines. To this end, we apply the quantum theory of spectral line polarization and calculate the linear polarization patterns of the radiation scattered at 90 Degree-Sign by a slab of stellar atmospheric plasma, both taking into account and neglecting the above-mentioned quantum interference. Particular attention is given to the {sup 2}S - {sup 2}P, {sup 5}S - {sup 5}P, and {sup 3}P - {sup 3}S multiplets. We point out the observational signatures of this kind of interference and analyze its sensitivity to the energy separation between the interfering levels, to the amount of emissivity in the background continuum radiation, to lower-level polarization, and to the presence of a magnetic field. Some interesting applications to the following spectral lines are also presented: Ca II H and K, Mg II h and k, Na I D{sub 1} and D{sub 2}, the Ba II 4554 #Angstrom# and 4934 #Angstrom# resonance lines, the Cr I triplet at 5207 #Angstrom#, the O I triplet at 7773 #Angstrom#, the Mg I b-lines, and the H{alpha} and Ly{alpha} lines of H I.

Belluzzi, Luca; Bueno, Javier Trujillo [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain)

2011-12-10

51

Degree of linear polarization in spectral radiances from water-viewing infrared radiometers  

E-print Network

Degree of linear polarization in spectral radiances from water-viewing infrared radiometers Joseph polarization should be expected for a water-viewing radiometer, how it varies with wavelength, and why. Water

Shaw, Joseph A.

52

Spectral sensitivity and absolute threshold of polarization vision in crickets: a behavioral study  

Microsoft Academic Search

1.Tethered crickets (Gryllus campestris) walking on an air-suspended ball exhibit a spontaneous response to thee-vector of polarized light presented from above. In this study we determined the spectral sensitivity of polarization vision by finding the threshold light intensities for eliciting thise-vector response at different wavelengths.2.The behaviorally determined spectral sensitivity was compared with the spectral sensitivity of the three spectral receptor

Dieter Herzmann; Thomas Labhart

1989-01-01

53

Ellipsoidal Universe Induces Large Scale CMB Polarization  

E-print Network

We calculate the large scale polarization of the cosmic microwave background induced by the anisotropy of the spatial geometry of our universe. Assuming an eccentricity at decoupling of about $0.64 10^{-2}$, we find $\\Delta T_{pol}/ T_0 \\simeq 0.53 10^{-6}$ quite close to the average level of polarization detected by the Wilkinson Microwave Anisotropy Probe.

Paolo Cea

2007-10-24

54

Non-Zeeman Circular Polarization of Molecular Maser Spectral Lines  

E-print Network

We apply the anisotropic resonant scattering model developed to explain the presence of non-Zeeman circular polarization signals recently detected in the $^{12}\\mathrm{CO}\\;\\left(J=2\\rightarrow1\\right)$ and $\\left(J=1\\rightarrow0\\right)$ transitions in molecular clouds to Stokes $V$ spectra of SiO $v=1$ and $v=2$, $\\left(J=1\\rightarrow0\\right)$ masers commonly observed in evolved stars. It is found that the observed antisymmetric "S" and symmetric "$\\cup$" or "$\\cap$" shaped spectral profiles naturally arise when the maser radiation scatters off populations of foreground molecules located outside the velocity range covered by the background maser radiation. Using typical values for the relevant physical parameters, it is estimated that magnetic field strengths on the order of a few times 15 mG are sufficient to explain the observational results found in the literature.

Houde, Martin

2014-01-01

55

Non-Zeeman Circular Polarization of Molecular Maser Spectral Lines  

NASA Astrophysics Data System (ADS)

We apply the anisotropic resonant scattering model developed to explain the presence of non-Zeeman circular polarization signals recently detected in the 12CO (J = 2 ? 1) and (J = 1 ? 0) transitions in molecular clouds to Stokes V spectra of SiO v = 1 and v = 2, (J = 1 ? 0) masers commonly observed in evolved stars. It is found that the observed antisymmetric "S"- and symmetric "?"- or "?"-shaped spectral profiles naturally arise when the maser radiation scatters off populations of foreground molecules located outside the velocity range covered by the background maser radiation. Using typical values for the relevant physical parameters, it is estimated that magnetic field strengths on the order of a few times 15 mG are sufficient to explain the observational results found in the literature.

Houde, Martin

2014-11-01

56

Optical Polarization and Spectral Variability in the M87 Jet  

NASA Astrophysics Data System (ADS)

During the last decade, M87's jet has been the site of an extraordinary variability event, with one knot (HST-1) increasing by over a factor 100 in brightness. Variability has also been seen on timescales of months in the nuclear flux. Here we discuss the optical-UV polarization and spectral variability of these components, which show vastly different behavior. HST-1 shows a highly significant correlation between flux and polarization, with P increasing from ~20% at minimum to >40% at maximum, while the orientation of its electric vector stayed constant. HST-1's optical-UV spectrum is very hard (?UV-O ~ 0.5, F ?vprop?-?), and displays "hard lags" during epochs 2004.9-2005.5, including the peak of the flare, with soft lags at later epochs. We interpret the behavior of HST-1 as enhanced particle acceleration in a shock, with cooling from both particle aging and the relaxation of the compression. We set 2? upper limits of 0.5? pc and 1.02c on the size and advance speed of the flaring region. The slight deviation of the electric vector orientation from the jet position angle (P.A.) makes it likely that on smaller scales the flaring region has either a double or twisted structure. By contrast, the nucleus displays much more rapid variability, with a highly variable electric vector orientation and "looping" in the (I, P) plane. The nucleus has a much steeper spectrum (?UV-O ~ 1.5) but does not show UV-optical spectral variability. Its behavior can be interpreted as either a helical distortion to a steady jet or a shock propagating through a helical jet.

Perlman, Eric S.; Adams, Steven C.; Cara, Mihai; Bourque, Matthew; Harris, D. E.; Madrid, Juan P.; Simons, Raymond C.; Clausen-Brown, Eric; Cheung, C. C.; Stawarz, Lukasz; Georganopoulos, Markos; Sparks, William B.; Biretta, John A.

2011-12-01

57

Optical Polarization and Spectral Variability in the M87 Jet  

NASA Technical Reports Server (NTRS)

During the last decade, M87's jet has been the site of an extraordinary variability event, with one knot (HST-1) increasing by over a factor 100 in brightness. Variability was also seen on timescales of months in the nuclear flux. Here we discuss the optical-UV polarization and spectral variability of these components, which show vastly different behavior. HST -1 shows a highly significant correlation between flux and polarization, with P increasing from approx 20% at minimum to > 40% at maximum, while the orientation of its electric vector stayed constant. HST-l's optical-UV spectrum is very hard (alpha(sub uv-0) approx. 0.5, F(sub v) varies as (v(exp -alpha)), and displays "hard lags" during epochs 2004.9-2005.5, including the peak of the flare, with soft lags at later epochs. We interpret the behavior of HST-1 as enhanced particle acceleration in a shock, with cooling from both particle aging and the relaxation of the compression. We set 2alpha upper limits of 0.5 delta parsecs and 1.02c on the size and advance speed of the flaring region. The slight deviation of the electric vector orientation from the jet PA, makes it likely that on smaller scales the flaring region has either a double or twisted structure. By contrast, the nucleus displays much more rapid variability, with a highly variable electric vector orientation and 'looping' in the (I, P) plane. The nucleus has a much steeper spectrum ((alpha(sub uv-0) approx. 1.5) but does not show UV-optical spectral variability. Its behavior can be interpreted as either a helical distortion to a steady jet or a shock propagating through a helical jet.

Perlman, Eric S.; Adams, Steven C.; Cara, Mihai; Bourque, Matthew; Harris, D. E.; Madrid, Juan P.; Simons, Raymond C.; Clausen-Brown, Eric; Cheung, C. C.; Stawarz, Lukasz; Georganopoulos, Markos; Sparks, William B.; Biretta, John A.

2011-01-01

58

Design of hyper-spectral and full-polarization imager based on AOTF and LCVR  

NASA Astrophysics Data System (ADS)

With the development of spectral imaging technology and polarization imaging technology, capturing the spectral profile and polarization signatures simultaneously will provide a wealth of evidence which helps to recognize the objects. Thus it has become a new trend in the area of remote sensing technology. In this paper, the existing polarization spectral imaging technologies are introduced and compared a new designing scheme to realize the miniaturized hyper-spectral and full-polarization imager are proposed, which is based on the combination of Acousto-Optic Tunable Filter (AOTF) and Liquid Crystal Variable Retarder (LCVR). The designing scheme is mainly composed of three modules: the spectral splitting module based on AOTF, the polarization control module based on LCVR and the image acquisition module based on Charge Coupled Device (CCD). The use of AOTF assists in achieving a hyper-spectral resolution higher than 5nm, as well as the abundant spectral information. While the LCVR enables us to gain multiple sets of polarization images of the target, after that, the polarization state of the target can be extracted according to Stokes vector and Mueller matrix. This designing scheme ensures a wide spectral range from 400nm to 2400nm by means of electronic tuning, and also achieves the hyper-spectral and full-polarization images of the target in rapid succession without mechanical moving parts. Besides, the development, testing, calibration and test scheme of the system are also introduced in the rest of the paper.

Li, Feifei; Xu, Yingyu; Ma, Yanhua

2014-11-01

59

Induced polarization of ?(1116) in kaon electroproduction  

E-print Network

We have measured the induced polarization of the ${\\Lambda}(1116)$ in the reaction $ep\\rightarrow e'K^+{\\Lambda}$, detecting the scattered $e'$ and $K^+$ in the final state along with the proton from the decay $\\Lambda\\rightarrow p\\pi^-$.The present study used the CEBAF Large Acceptance Spectrometer (CLAS), which allowed for a large kinematic acceptance in invariant energy $W$ ($1.6\\leq W \\leq 2.7$ GeV) and covered the full range of the kaon production angle at an average momentum transfer $Q^2=1.90$ GeV$^2$.In this experiment a 5.50 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. We have mapped out the $W$ and kaon production angle dependencies of the induced polarization and found striking differences from photoproduction data over most of the kinematic range studied. However, we also found that the induced polarization is essentially $Q^2$ independent in our kinematic domain, suggesting that somewhere below the $Q^2$ covered here there must be a strong $Q^2$ dependence. Along with previously published photo- and electroproduction cross sections and polarization observables, these data are needed for the development of models, such as effective field theories, and as input to coupled-channel analyses that can provide evidence of previously unobserved $s$-channel resonances.

M. Gabrielyan; B. A. Raue; D. S. Carman; K. Park; K. P. Adhikari; D. Adikaram; M. J. Amaryan; S. Anefalos Pereira; H. Avakian; J. Ball; N. A. Baltzell; M. Battaglieri; V. Baturin; I. Bedlinskiy; A. S. Biselli; J. Bono; S. Boiarinov; W. J. Briscoe; W. K. Brooks; V. D. Burkert; T. Cao; A. Celentano; S. Chandavar; G. Charles; P. L. Cole; M. Contalbrigo; O. Cortes; V. Crede; A. DAngelo; N. Dashyan; R. De Vita; E. De Sanctis; A. Deur; C. Djalali; D. Doughty; R. Dupre; L. El Fassi; P. Eugenio; G. Fedotov; S. Fegan; J. A. Fleming; T. A. Forest; B. Garillon; N. Gevorgyan; Y. Ghandilyan; G. P. Gilfoyle; K. L. Giovanetti; F. X. Girod; J. T. Goetz; E. Golovatch; R. W. Gothe; K. A. Griffioen; M. Guidal; L. Guo; K. Hafidi; H. Hakobyan; M. Hattawy; K. Hicks; D. Ho; M. Holtrop; S. M. Hughes; Y. Ilieva; D. G. Ireland; B. S. Ishkhanov; D. Jenkins; H. Jiang; H. S. Jo; K. Joo; D. Keller; M. Khandaker; W. Kim; F. J. Klein; S. Koirala; V. Kubarovsky; S. E. Kuhn; S. V. Kuleshov; P. Lenisa; W. I. Levine; K. Livingston; I. J. D. MacGregor; M. Mayer; B. McKinnon; C. A. Meyer; M. D. Mestayer; M. Mirazita; V. Mokeev; C. I. Moody; H. Moutarde; A Movsisyan; E. Munevar; C. Munoz Camacho; P. Nadel-Turonski; S. Niccolai; G. Niculescu; M. Osipenko; L. L. Pappalardo; R. Paremuzyan; E. Pasyuk; P. Peng; W. Phelps; J. J. Phillips; S. Pisano; O. Pogorelko; S. Pozdniakov; J. W. Price; S. Procureur; D. Protopopescu; D. Rimal; M. Ripani; A. Rizzo; F. Sabatie; C. Salgado; D. Schott; R. A. Schumacher; A. Simonyan; G. D. Smith; D. I. Sober; D. Sokhan; S. S. Stepanyan; S. Stepanyan; I. I. Strakovsky; S. Strauch; V. Sytnik; W. Tang; M. Ungaro; A. V. Vlassov; H. Voskanyan; E. Voutier; N. K. Walford; D. P. Watts; X. Wei; L. B. Weinstein; N. Zachariou; L. Zana; J. Zhang

2014-06-16

60

Induced polarization of ? (1116) in kaon electroproduction  

NASA Astrophysics Data System (ADS)

We have measured. the induced polarization of the ?(1116) in the reaction ep ?e'K+?, detecting the scattered e' and K+ in the final state along with the proton from the decay ? ?p?-. The present study used the CEBAF Large Acceptance Spectrometer (CLAS), which allowed for a large kinematic acceptance in invariant energy W (1.6?W?2.7 GeV) and covered the full range of the kaon production angle at an average momentum transfer Q2=1.90GeV2. In this experiment a 5.50-GeV electron beam was incident upon an unpolarized liquid-hydrogen target. We have mapped out the W and kaon production angle dependencies of the induced polarization and found striking differences from photoproduction data over most of the kinematic range studied. However, we also found that the induced polarization is essentially Q2 independent in our kinematic domain, suggesting that somewhere below the Q2 covered here there must be a strong Q2 dependence. Along with previously published photo- and electroproduction cross sections and polarization observables, these data are needed for the development of models, such as effective field theories, and as input to coupled-channel analyses that can provide evidence of previously unobserved s-channel resonances.

Gabrielyan, M.; Raue, B. A.; Carman, D. S.; Park, K.; Adhikari, K. P.; Adikaram, D.; Amaryan, M. J.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Baturin, V.; Bedlinskiy, I.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Cao, T.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Doughty, D.; Dupre, R.; El Fassi, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Fleming, J. A.; Forest, T. A.; Garillon, B.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hattawy, M.; Hicks, K.; Ho, D.; Holtrop, M.; Hughes, S. M.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Jenkins, D.; Jiang, H.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, W.; Klein, F. J.; Koirala, S.; Kubarovsky, V.; Kuhn, S. E.; Kuleshov, S. V.; Lenisa, P.; Levine, W. I.; Livingston, K.; MacGregor, I. J. D.; Mayer, M.; McKinnon, B.; Meyer, C. A.; Mestayer, M. D.; Mirazita, M.; Mokeev, V.; Moody, C. I.; Moutarde, H.; Movsisyan, A.; Munevar, E.; Munoz Camacho, C.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Pappalardo, L. L.; Paremuzyan, R.; Pasyuk, E.; Peng, P.; Phelps, W.; Phillips, J. J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Rimal, D.; Ripani, M.; Rizzo, A.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Simonyan, A.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S. S.; Stepanyan, S.; Strakovsky, I. I.; Strauch, S.; Sytnik, V.; Tang, W.; Ungaro, M.; Vlassov, A. V.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Wei, X.; Weinstein, L. B.; Zachariou, N.; Zana, L.; Zhang, J.; Zonta, I.; CLAS Collaboration

2014-09-01

61

Induced Polarization methodology: application to a hydrocarbon contaminated site  

NASA Astrophysics Data System (ADS)

Induced Polarization (IP) is a promising method for environmental studies (Vaudelet et al., 2011; Abdel Aal et al., 2006). This method has already been successful for the study of contaminations in the laboratory scale (Vanhala, 1997; Revil et al., 2011; Schmutz et al., 2012) but is still not trivial on the field. Temporal IP seems relatively common for field studies. When contamination implies a significative change of the polarization parameters, successful studies have been lead (Fiandaca et al. 2012; Dahlin et al., 2002 on landfills). Otherwise hydrocarbon contamination may induce small changes on IP parameters (Vaudelet et al., 2011). Spectral induced polarization has not been widely used for field application yet: this method is sensitive to coupling effects and time consuming. Moreover, all the phenomenon responsible of the signal is not completely understood yet (Kemna et al., 2012). The main aim of our presentation is about IP methodology, applied on site affected by a hydrocarbon contamination. In this case, precautions have to be taken to get explicit answers from the contamination. Field investigations have been made: chargeability measurements in order to delineate the free phase contamination extension and spectral induced polarization soundings in order to characterize more precisely the contamination. We would like to provide recommendations to improve induced polarization measurements especially on three aspects, (i) propose a different measurement sequence to make chargeability measurements and (ii) evaluate the influence of the current injection time on chargeability measurements (iii) give general precautions to achieve SIP measurements. A different new chargeability sequence is proposed integrating the use of separated injection and measure cables to avoid coupling phenomena in multicore cables. Indeed, this kind of coupling can significantly decrease the signal / noise ratio (Dahlin et al., 2012). Direct and reverse measurements have been made in order to evaluate if the data and data quality are comparable. Different times of injection have also been tested to evaluate their influence on chargeability measurements: long injection times (4 and 8 seconds) indicate the same high chargeability trend, to the contrary to small injection time (2 seconds). Long injection time generate (i) the polarization of more elements (ii) a stronger polarization of polarizable elements. For environmental purposes, long injection times are recommended. Spectral induced polarization soundings have been made using the SIP Fuchs device, with an amplifier in order to stabilize the injected current (Radic 2004). Unpolarizable measurement electrodes have been connected to the apparatus with optic fiber and metallic injection electrodes have been link with a specific cable arrangement, both to reduce coupling effect with the ground (Vaudelet et al., 2011; Ghorbani et al., 2007). These precautions give good quality result and allow the inversion of the data to obtain Cole Cole parameters (Ghorbani et al., 2007), useful for hydrogeological interpretations.

Blondel, Amelie; Schmutz, Myriam; Tichane, Frederic; Franceschi, Michel; Carles, Margaux

2013-04-01

62

Mask-induced polarization effects at high numerical aperture  

E-print Network

Mask-induced polarization effects at high numerical aperture Andrew Estroff Yongfa Fan Anatoly at higher numerical apertures NAs due to mask-induced polarization effects. We study how different photomask.21.240.32. Terms of Use: http://spiedl.org/terms #12;pass. The electric field of the TE polarized light induces

Zanibbi, Richard

63

Electric field induced spin-polarized current  

DOEpatents

A device and a method for generating an electric-field-induced spin current are disclosed. A highly spin-polarized electric current is generated using a semiconductor structure and an applied electric field across the semiconductor structure. The semiconductor structure can be a hole-doped semiconductor having finite or zero bandgap or an undoped semiconductor of zero bandgap. In one embodiment, a device for injecting spin-polarized current into a current output terminal includes a semiconductor structure including first and second electrodes, along a first axis, receiving an applied electric field and a third electrode, along a direction perpendicular to the first axis, providing the spin-polarized current. The semiconductor structure includes a semiconductor material whose spin orbit coupling energy is greater than room temperature (300 Kelvin) times the Boltzmann constant. In one embodiment, the semiconductor structure is a hole-doped semiconductor structure, such as a p-type GaAs semiconductor layer.

Murakami, Shuichi; Nagaosa, Naoto; Zhang, Shoucheng

2006-05-02

64

Spectral and polarization sensitivity of juvenile Atlantic salmon (Salmo salar): phylogenetic considerations.  

PubMed

We were interested in comparing the characteristics of polarization sensitivity in Atlantic salmon to those in Pacific salmon. Here we show that the common ancestor to the clade containing Salmo salar, Oncorhynchus mykiss, O. nerka, O. clarkii and Salvelinus fontinalis has the trait of ultraviolet polarization sensitivity. We examined spectral and polarization sensitivity of juvenile Atlantic salmon (Salmo salar) using both optic nerve compound action potential (CAP) and electroretinogram (ERG) recordings. Our experiments employed photic manipulation to adjust the sensitivity of the four cone mechanisms of Atlantic salmon. A spectrally broad background was used to ensure a contribution of all cone mechanisms to both spectral and polarization sensitivity. Chromatic adaptation was used to isolate the sensitivity of each of the four cone mechanisms for both spectral and polarization sensitivity. Under spectrally broad conditions, UV sensitive (UVS), mid wavelength sensitive (MWS) and long wavelength sensitive (LWS) cone mechanisms contributed to polarization sensitivity. CAP recordings produced the typical 'W' shaped polarization sensitivity curve reflecting two active polarization detectors with peaks at e-vector orientations of 0 deg, 90 deg and 180 deg, and troughs at 30 deg and 150 deg. ERG recordings produced a four-peaked polarization sensitivity curve reflecting two active polarization detectors and negative feedback activity, with peaks at e-vectors 0 deg, 45 deg, 90 deg, 135 deg and 180 deg, and troughs at 30 deg, 60 deg, 120 deg and 150 deg. Polarization-sensitivity measurements of isolated cone mechanisms revealed two orthogonal polarization detector mechanisms in Atlantic salmon, identical to that found in rainbow trout and other Pacific salmonid fishes. Moreover, under spectrally broad background conditions, CAP and ERG polarization sensitivity of Atlantic salmon did not differ significantly from that reported in Pacific salmonids. PMID:20802121

Hawryshyn, C W; Ramsden, S D; Betke, K M; Sabbah, S

2010-09-15

65

DC Resistivity and Induced Polarization Methods  

Microsoft Academic Search

Direct current (DC) resistivity (here referred to as resistivity) and induced polarization (IP) methods allow, respectively, the determination of the spatial distribution of the low-frequency\\u000a resistive and capacitive characteristics of soil. Since both properties are affected by lithology, pore fluid chemistry, and\\u000a water content (see Chapter 4 of this volume), these methods have significant potential for hydrogeophysical applications.\\u000a The methods

Andrew Binley; Andreas Kemna

66

Proton emission induced by polarized photons  

E-print Network

The proton emission induced by polarized photons is studied in the energy range above the giant resonance region and below the pion emission threshold. Results for the 12C, 16O and 40Ca nuclei are presented. The sensitivity of various observables to final state interaction, meson exchange currents and short range correlations is analyzed. We found relevant effects due to the virtual excitation of the $\\Delta$ resonance.

M. Anguiano; G. Co'; A. M. Lallena

2006-08-29

67

Theoretical and experimental study of time domain-induced polarization in water-saturated sands  

Microsoft Academic Search

A theoretical model of spectral-induced polarization (IP) of sand is presented. In the proposed model, contacts of sand grains and intergrain solution-filled space are considered as electrical current passages of varying thickness, which differ in values of ion transport number. Ion-selective narrow passages are considered as active zones, large passages as passive. The proposed model describes spectral IP characteristics for

K. Titov; V. Komarov; V. Tarasov; A. Levitski

2002-01-01

68

Variance of a generalized polarity-coincidence spectral-centroid estimator for Gaussian processes  

Microsoft Academic Search

The polarity coincidence estimator of the spectral centroid counts the net number of times the phasor of a stationary Gaussian process crosses a chosen phase-reference straight line through the origin during a time T. By following Pawula's (1968) approach, the covariance of two different simultaneous polarity-coincidence estimates having distinct phase reference lines is derived. This basic result is applied to

Alberto Laurenti; Gaetano Scarano

1994-01-01

69

Changes in the spectral degree of polarization of nonparaxial stochastic electromagnetic pulsed beams  

Microsoft Academic Search

By using the generalized vectorial Rayleigh-Sommerfeld diffraction integral, the analytical expression for the spectral degree of polarization (SDP) of stochastic spatially and spectrally partially coherent electromagnetic pulsed beams (SSSPCEPB) is derived, and used to study the changes in the SDP of SSSPCEPB in the nonparaxial regime. Similar to that of continuous beams, the f parameter and f?? parameter of pulsed

Chaoliang Ding; Liuzhan Pan; Zhao Zhiguo; Zhang Yongtao; Wang Haixia

2011-01-01

70

Ternary Fission Induced by Polarized Neutrons  

SciTech Connect

P-odd and T-odd asymmetries in the emission of fragments and light particles have been investigated in ternary fission induced by polarized neutrons. P-odd asymmetries unambiguously point to a violation of parity in the fission process. By contrast, T-odd asymmetries do not necessarily imply a violation of time reversal invariance. The asymmetries observed are rather due to a final state interaction between the light ternary particle and the nucleus from which they are ejected. New results with interesting information on the ternary fission process are presented.

Goennenwein, F.; Jesinger, P. [Physikalisches Institut, Universitaet Tuebingen, 72076 Tuebingen (Germany); Gagarski, A.; Petrov, G.; Bunakov, V. [Petersburg Nuclear Physics Institute, 188300 Gatchina (Russian Federation); Mutterer, M. [Institut fuer Kernphysik, Technische Universitaet, 64289 Darmstadt (Germany); Trzaska, W. [Department of Physics, Jyvaeskylae University, 40351 Jyvaeskylae (Finland); Nesvizhevsky, V.; Lelievre-Berna, E. [Institut Laue Langevin, 38042 Grenoble (France)

2005-05-24

71

Polarization studies of Zeeman affected spectral lines using the MSFC magnetograph  

NASA Technical Reports Server (NTRS)

The Marshall Space Flight Center (MSFC) vector magnetograph records polarization images of absorption lines that are sensitive to magnetic fields. A method is presented for analyzing the Stokes spectral-line profiles of a photospheric Fe I absorption line (5250.2 A) which is influenced by the Zeeman effect. Using nonlinear least-square optimization, the observed Stokes profiles are compared with those generated from the theoretical solution of the polarized radiative transfer equations. The optimization process accounts for the spectral convolution of the source and the MSFC vector magnetograph. The resulting physical properties of the active region producing the polarized light are discussed.

Balasubramaniam, K. S.; West, E. A.

1990-01-01

72

A Compact Imaging Detector of Polarization and Spectral Content  

NASA Technical Reports Server (NTRS)

A new type of image detector will simultaneously analyze the polarization of light at all picture elements in a scene. The integrated Dual Imaging Detector (IDID) consists of a polarizing beam splitter bonded to a charge-coupled device (CCD), with signal-analysis circuitry and analog-to-digital converters, all integrated on a silicon chip. The polarizing beam splitter can be either a Ronchi ruling, or an array of cylindrical lenslets, bonded to a birefringent wafer. The wafer, in turn, is bonded to the CCD so that light in the two orthogonal planes of polarization falls on adjacent pairs of pixels. The use of a high-index birefringent material, e.g., rutile, allows the IDID to operate at f-numbers as high as f/3.5. Other aspects of the detector are discussed.

Rust, D. M.; Kumar, A.; Thompson, K. E.

1993-01-01

73

Noninvasive Contaminant Site Characterization Using Geophysical Induced Polarization  

SciTech Connect

Results of aspects of a broad foundational study of time domain IP (TDIP) and spectral IP (SIP) for contaminant site characterization are presented. This ongoing study encompassed laboratory studies of coupled effects of rock/soil microgeometry and contaminant chemistry on induced polarization (IP), an investigation of electromagnetic coupling (EMC) noise and development of 3D modeling and inversion codes. SIP requires extensions to higher frequencies (above the typical 100Hz threshold) and EMC becomes the major limitation for field implementation, because conventional correction methods are inadequate at required higher frequencies. A proposed methodology is outlined, based on a model of all EMC components, that addresses the EMC problem by coupling IP and electromagnetic induction in modeling and inversion. Examples of application of IP and SIP to contaminant mapping and detection for TDIP and SIP will be presented for FS-12 plume at Massachusetts Military Reservation and a suspected DNAPL plume at Savannah River Site.

Morgan, F.D.; Sogade, J.; Lesmes, D.; Coles, D.; Vichabian, Y.; Scira-Scappuzzo, F.; Shi, W.; Vandiver, A.; Rodi, W.

2003-03-27

74

Magnetic-Field-Induced Electric Polarization in Multiferroic Nanostructures  

Microsoft Academic Search

Magnetic-field-induced electric polarization in nanostructured multiferroic composite films was studied by using the Green's function approach. The calculations showed that large magnetic-field-induced polarization could be produced in multiferroic nanostructures due to enhanced elastic coupling interaction. Especially, the 1-3 type films with ferromagnetic nanopillars embedded in a ferroelectric matrix exhibited large magnetic-field-induced polarization responses, while the 2-2 type films with ferroelectric

Ce-Wen Nan; Gang Liu; Yuanhua Lin; Haydn Chen

2005-01-01

75

[Polarization characteristic of LiF polarizer at UV-VUV spectral range].  

PubMed

A method of determinating the degree of polarization of grating, polarizer and analyzer at some wavelength is introduced. The degrees of polarization of LiF polarizers were determined with 1 m Seya-Namioka monochromator by this way. The source is hollow cathode source. The degrees of polarization of two, four and eight LiF plates were measured at 120, 149.2, 174.2, 214.2, 235.0, 300 and 340 nm. The theoretical and experimental reults were consistent within the error. The angular extinction dependence of the LiF polarizer and analyzer was measured at VUV wavelengths. The results showed the expected cosine square dependence, so a high degree of polarization was indeed produced. Also, the LiF polarizer was used to measure the polarization characters of the Al + MgF2 reflectance and the absolute grating efficiency at both parallel and perpendicular to their incident plane. PMID:12938362

Liu, Ying; Li, Fu-tian

2002-08-01

76

Scintillation-Induced Circular Polarization in Pulsars and Quasars  

E-print Network

We present a physical interpretation for the generation of circular polarization resulting from the propagation of radiation through a magnetized plasma in terms of a rotation measure gradient, or `Faraday wedges'. Criteria for the observability of scintillation-induced circular polarization are identified. Application of the theory to the circular polarization in pulsars and compact extragalactic sources is discussed.

J. -P. Macquart; D. B. Melrose

2000-07-28

77

Radiation induced polarization in CdTe detectors  

Microsoft Academic Search

Polarization induced by irradiation with intense gamma ray sources has been studied in chlorine-compensated CdTe detectors. The influence of several parameters, such as applied field strength, temperature and incident photon flux, on the polarization effect have been investigated. A relationship was found between the degree of polarization, detector efficiency and detector leakage current.

D. Vartsky; M. Goldberg; Y. Eisen; Y. Shamai; R. Dukhan; P. Siffert; J. M. Koebel; R. Regal; J. Gerber

1988-01-01

78

Induced polarization and self-potential geophysical signature of bacterial activity in porous media (Invited)  

NASA Astrophysics Data System (ADS)

The first part of the presentation will be dedicated to the spectral induced polarization signature of bacteria in porous media. We developed a quantitative model to investigate frequency-domain induced polarization response of suspensions of bacteria and bacteria growth in porous media. Induced polarization of bacteria (alpha-polarization) is related to the properties of the electrical double layer of the bacteria. Surface conductivity and alpha-polarization are due to the Stern layer of counterions occurring in a brush of polymers coating the surface of the bacteria. These phenomena can be related to the cation exchange capacity of the bacteria. The mobility of the counterions in this Stern layer is found to be very small (4.7×10-10 m2s-1 V-1 at 25°C). This implies a very low relaxation frequency for the alpha-polarization of the bacteria cells (typically around 0.1 to 5 Hertz) in agreement with experimental observations. This new model can be coupled to reactive transport modeling codes in which the evolution of bacterial populations are usually described by Monod kinetics. We show that the growth rate and endogenous decay coefficients of bacteria in a porous sand can be inferred non-intrusively from time lapse frequency-domain induced polarization data. The second part of the presentation will concern the biogeobattery mechanism showing new data, the concept of transient biogeobattery and the influence of the concentration of the electron acceptors in the process.

Revil, A.

2013-12-01

79

Spectral analyses of the dual polarization Doppler weather radar data  

Microsoft Academic Search

Echoes in clear air from biological scatterers mixed within the resolution volumes over a large region are presented. These echoes were observed with the polarimetric prototype of the forthcoming WSR-88D weather radar. The study case occurred in the evening of September 7, 2004, at the beginning of the bird migrating season. Novel polarimetric spectral analyses are used for distinguishing signatures

Svetlana Monakhova Bachmann

2007-01-01

80

Microtubule-induced cortical cell polarity  

Microsoft Academic Search

Most cells are polarized. Embryonic and stem cells can use their polarity to generate cell diversity by asymmet- ric cell division, whereas differentiated cells use their polarity to execute specific functions. For example, fi- broblasts form an actin-rich leading edge required for cell migration, neurons form distinctive axonal and dendritic compartments important for directional signaling, and epithelial cells have apical

Sarah E. Siegrist; Chris Q. Doe

2007-01-01

81

Biochemistry 1984, 23, 1935-1939 1935 Chemically Induced Dynamic Nuclear Polarization Studies of Yeast  

E-print Network

Biochemistry 1984, 23, 1935-1939 1935 Chemically Induced Dynamic Nuclear Polarization Studies* ABSTRACT: Chemically induced dynamicnuclear polarization (CIDNP) has been observed from yeast t). The NMR method chemically induced dynamic nuclear polarization (CIDNP) is well suited to probing

Boxer, Steven G.

82

Polarization conversions of linearly and circularly polarized lights through a plasmon-induced transparent metasurface  

NASA Astrophysics Data System (ADS)

Polarization control of the light can be realized by ultrathin plasmonic structures, which is generally based on the effect of extraordinary optical transmission. In this paper, we designed a U-shaped plasmon-induced transparent metasurface to investigate the polarization state conversions of resonantly transmitted light through reducing the structural symmetry by rotation. A significant optical polarization conversion capability is found for impinging light with linear as well as circular polarization. In particular, the different polarization conversions between the left-handed and right-handed circular lights manifest the characteristic of circular dichroism. The results are useful for the potential applications such as a broadband quarter-wave plate.

Shao, Jian; Li, Jie; Wang, Ying-Hua; Li, Jia-Qi; Chen, Qian; Dong, Zheng-Gao

2014-06-01

83

Reflective and transmissive broadband coating polarizers in a spectral range centered at 121.6 nm  

NASA Astrophysics Data System (ADS)

Polarimetry is a powerful tool for the interpretation of the role of the coronal plasma in the energy transfer processes from the inner parts of the Sun to the outer space. One of the key lines for observations is H I Lyman ? (121.6 nm) among few spectral lines in the far ultraviolet (FUV), and hence efficient linear polarizers at this line are demanded. New designs based on (Al/MgF2)n multilayer coatings have been developed to obtain the smallest possible reflectance in the parallel plane of polarization (Rpar) with a simultaneous high reflectance in the perpendicular plane of polarization (Rper). Samples stored in nitrogen for ˜8–17 months resulted in efficient polarizers at 121.6 nm, with Rpar ˜ 0.01–0.017 and Rper ˜ 0.69–0.725. The designs with a number n = 3–4 bilayers of Al/MgF2 result in a wider spectral range of efficient linear polarizers, compared to what can be obtained with n = 2. Coatings following various designs with good polarizing performance in a 7–8 nm wide FUV range were prepared. For the first time, a transmissive coating polarizer has been developed for this range, which has the benefit that it involves no deviation of the beam; it is based on another design of (Al/MgF2)3 multilayer coating. The transmissive polarizer has a good transmittance ratio between the two polarization components and, even though its figure of merit is not as high as that of the reflective polarizers, it incorporates filtering properties to reject wavelengths both below and above 121.6 nm; this property might enable a polarimeter for solar physics with an improved global figure of merit if a filter to isolate the H I Lyman ? line could be avoided.

Larruquert, Juan I.; Malvezzi, A. Marco; Giglia, Angelo; Aznárez, José A.; Rodríguez-de Marcos, Luis; Méndez, José A.; Miotti, Paolo; Frassetto, Fabio; Massone, Giuseppe; Nannarone, Stefano; Crescenzio, Giuseppe; Capobianco, Gerardo; Fineschi, Silvano

2014-12-01

84

High spectral and time resolution observations of the eclipsing polar RX J0719.2+6557  

E-print Network

Abstract. We present phase­resolved spectral and multicolor CCD­ photometric observations of the eclipsing a detailed study of the various components of this eclipsing polar. 1 #12; 2. Data acquisition and reduction and eclipse phase Based on the new photometric data combined with eclipse moments reported in (T97) we refined

Greiner, Jochen

85

High speed spectral domain polarization sensitive optical coherence tomography of the human retina.  

PubMed

We developed a high-speed polarization sensitive optical coherence tomography (PS-OCT) system for retinal imaging based on spectral domain OCT. The system uses two spectrometers, one for each polarization channel, that operate in parallel at 20000 A-lines/s each. It provides reflectivity, retardation, and cumulative optic axis orientation simultaneously. We present our instrument and discuss the requirements for the alignment of the two spectrometers specific for our setup. We show 2D spectral domain PS-OCT images and - to the best of our knowledge - the first 3D spectral domain PS-OCT data sets in form of fly-through movies and volume rendered data sets recorded in human retina in vivo. PMID:19503236

Götzinger, Erich; Pircher, Michael; Hitzenberger, Christoph K

2005-12-12

86

Scattering-induced optical polarization in thick accretion disks  

NASA Technical Reports Server (NTRS)

A general formalism for calculating the linear polarization induced by scattering within the central funnel of a thick accretion disk is presented, and it is shown that multiple photon reflections off the funnel walls can produce polarization values of up to about 10 percent, with the polarization position angle aligned parallel to the disk symmetry axis. It is suggested that this process is responsible for the observed optical polarization levels in X-ray-selected BL Lac objects (XBLs), which generally show linear polarization percentages P less than about 10 percent. According to this interpretation, XBLs with high optical polarization are viewed at an angle of less than about 60 deg to the funnel axis and their projected polarization vectors should be preferentially aligned with the associated radio jets. The possible relevance of this model to Seyfer 1 galaxies and quasars is also discussed.

Kartje, John F.; Konigl, Arieh

1991-01-01

87

CMB polarization induced by stochastic magnetic fields  

E-print Network

The complete calculation of the CMB polarization observables (i.e. E- and B-modes) is reported within the conventional $\\Lambda$CDM paradigm supplemented by a stochastic magnetic field. Intriguing perspectives for present and forthcoming CMB polarization experiments are outlined.

Massimo Giovannini; Kerstin E. Kunze

2008-04-14

88

Lambda Polarization in Lepton Induced Reactions  

E-print Network

Different phenomenological approaches for Lambda and Lambda-bar polarization in polarized semi-inclusive deep inelastic scattering and electron-positron annihilation at Z^0 pole are considered. Current and future experiments will soon provide accurate enough data to study spin phenomena in these reactions and distinguish between various models.

A. M. Kotzinian

1997-09-05

89

Spin transfer and polarization of antihyperons in lepton induced reactions  

E-print Network

We study the polarization of antihyperon in lepton induced reactions such as $e^+e^-\\to\\bar H+X$ and $l+p\\to l'+\\bar H+X$ with polarized beams using different models for spin transfer in high energy fragmentation processes. We compare the results with the available data and those for hyperons. We make predictions for future experiments.

Hui Dong; Jian Zhou; Zuo-tang Liang

2005-08-04

90

Poling-induced waveguide polarizers in electrooptic polymers  

Microsoft Academic Search

In order to demonstrate polymeric waveguide polarizers, photobleached polymer waveguides supporting both TE and TM modes are integrated with poling induced polymer waveguides that support either TE or TM modes. Fabrication parameters like UV exposures and poling voltages are controlled to reduce excess losses due to the mode profile mismatch between the connected waveguides. A TM-pass polarizer is realized by

Min-Cheol Oh; Sang-Yung Shin; Wol-Yon Hwang; Jang-Joo Kim

1996-01-01

91

Nuclear reactivity control using laser induced polarization  

DOEpatents

A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neutrons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

Bowman, Charles D. (Los Alamos, NM)

1991-01-01

92

Nuclear reactivity control using laser induced polarization  

DOEpatents

A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neturons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

Bowman, Charles D. (Los Alamos, NM)

1990-01-01

93

Stress-induced single-polarization single-mode fiber  

Microsoft Academic Search

The stress-induced birefringence in a single-mode optical fiber with an elliptical inner cladding or an elliptical core is calculated. The design of a fiber is proposed in which only one linearly polarized mode can propagate.

W. Eickhoff

1982-01-01

94

Tunnelling effects induced transparent polarization manipulation  

NASA Astrophysics Data System (ADS)

We proposed, designed and fabricated a three-layer metamaterial consisting of two layers of electrically spilt ring resonators (SRRs) and a layer of the subwavelength metal mesh symmetrically sandwiched between the two SRR layers. The numerical simulations and experimental measurements revealed that the linear-to-circular, linear-to-elliptical and linear-to-linear polarization controls can be accomplished by simply altering the polarization angle of incident waves. This transparent polarization conversion/rotator is related to the tunnelling effects of electromagnetic (EM) waves for both incident polarizations. The physical mechanism of tunnelling effect is also investigated both numerically and experimentally, and results have shown that the high-? SRR layer facilitates the EM waves to propagate through the metal mesh layer without attenuation. In addition, the magnetic field distribution in the structure is analysed to further illustrate this tunnelling phenomenon. The thickness of this polarization device is ultra-thin compared with the wavelength, which provides a new way for designing the miniaturized and light weight quarter wave plates or other polarization manipulation devices.

Dong, Liang; Zhu, Lei

2014-04-01

95

Subsurface imaging using the spectral polarization difference technique and NIR illumination  

SciTech Connect

A subsurface imaging system is utilized to test the ability of the spectral polarization difference imaging technique for deep subsurface imaging in tissues. The illumination of the system is derived from compact class III lasers in the red and NIR spectral region and, alternatively, from a white light source and selection of the appropriate illumination wavelength using band-pass optical filters. The experimental results demonstrate detection and imaging of a high-scattering object located up to 1.5 cm underneath the surface of a host chicken tissue.

Alfano, R R; Demos, S G; Radousky, H B

1999-01-26

96

Ferroelectric domain wall motion induced by polarized light  

NASA Astrophysics Data System (ADS)

Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO3 single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO3 at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light.

Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F.

2015-03-01

97

Ferroelectric domain wall motion induced by polarized light.  

PubMed

Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO3 single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO3 at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light. PMID:25779918

Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F

2015-01-01

98

Ferroelectric domain wall motion induced by polarized light  

PubMed Central

Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO3 single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO3 at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light. PMID:25779918

Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F.

2015-01-01

99

Polarization Raman Spectral Microscopy of Polymer Fibers Formed in Ferroelectric Liquid Crystal  

Microsoft Academic Search

This letter focuses on Raman spectral microscopy of polymer fiber networks, which are formed by the photopolymerization of liquid crystalline acrylate monomers in low-molecular-weight ferroelectric liquid crystal, using polarized infrared light to excite the polymer molecules. It was found that the tolane side-chain molecules of the polymer are significantly orientated with the liquid crystal alignment along the rubbing direction of

Hideo Fujikake; Takeshi Murashige; Hiroto Sato; Masahiro Kawakita; Hiroshi Kikuchi

2003-01-01

100

Vacuum polarization induced by a uniformly accelerated charge  

E-print Network

We consider a point charge fixed in the Rindler coordinates which describe a uniformly accelerated frame. We determine an integral expression of the induced charge density due to the vacuum polarization at the first order in the fine structure constant. In the case where the acceleration is weak, we give explicitly the induced electrostatic potential.

B. Linet

1995-03-30

101

Speckle noise reduction in high speed polarization sensitive spectral domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

We present a high speed polarization sensitive spectral domain optical coherence tomography system based on polarization maintaining fibers and two high speed CMOS line scan cameras capable of retinal imaging with up to 128 k A-lines/s. This high imaging speed strongly reduces motion artifacts and therefore averaging of several B-scans is possible, which strongly reduces speckle noise and improves image quality. We present several methods for averaging retardation and optic axis orientation, the best one providing a 5 fold noise reduction. Furthermore, a novel scheme of calculating images of degree of polarization uniformity is presented. We quantitatively compare the noise reduction depending on the number of averaged frames and discuss the limits of frame numbers that can usefully be averaged.

Götzinger, Erich; Pircher, Michael; Baumann, Bernhard; Schmoll, Tilman; Sattmann, Harald; Leitgeb, Rainer A.; Hitzenberger, Christoph K.

2011-07-01

102

Novel polarization interference filters for wide spectral tuning of an optical null  

NASA Astrophysics Data System (ADS)

Novel tunable polarization interference filters (PIF) employing active liquid crystal devices are presented, and the principles of operation are described. Filter designs are presented based on a requirement for tunable nulls in the visible and near infrared spectral regions, of high optical density, for protection from intense electromagnetic radiation outside of the spectral range of interest which can saturate an imaging or sensor system. Two types of PIFs are presented with their modeled results and device performances. Analog filters in a generalized Lyot-Ohmann geometry are presented which are capable of tuning an optical null through 260 nm, by employing a single active device per filter stage. Binary filters are also presented which can switch between two complimentary and non-overlapping spectral states. Both types of filter can operate in a "normally on" state with a broadband "white light" throughput.

Masterson, Hugh J.; Stockley, Jay E.

2004-05-01

103

Antiproton polarization induced by lepton interactions  

E-print Network

We present expressions for electromagnetic helicity amplitudes and spin observables for any elastic spin 1/2 - spin 1/2 scattering to first order in QED. In particular all electromagnetic helicity amplitudes and spin observables for elastic antiproton-electron and antiproton-proton scattering via single t-channel photon exchange are presented. Spin observables are required to describe the rate of increase of polarization in spin filtering. The PAX collaboration at GSI Darmstadt is interested in the buildup of polarization of an antiproton beam by repeated interaction with a hydrogen gas target in a storage ring. In order for the beam particles to remain in the ring after scattering it is important to consider small angle scattering, hence small momentum transfer t. In the low momentum transfer region electromagnetic effects dominate the hadronic effects. Of immediate importance is whether the polarization of an antiproton beam can be built up by spin filtering off polarized electrons either in a target or in a beam. We present the theoretical background for this discussion.

D. S. O'Brien; N. H. Buttimore

2006-09-22

104

Spectral decomposition of the stellar kinematics in the polar disk galaxy NGC 4650A  

NASA Astrophysics Data System (ADS)

Context. The prototype of polar ring galaxies NGC 4650A contains two main structural components, a central spheroid, which is the host galaxy, and an extended polar disk. Both photometric and kinematic studies revealed that these two components co-exist on two different planes within the central regions of the galaxy. Aims: The aim of this work is to study the spectroscopic and kinematic properties of the host galaxy and the polar disk in the central regions of NGC 4650A by disentangling their contributions to the observed galaxy spectrum. Methods: We applied the spectral decomposition technique introduced in previous works to long-slit spectroscopic observations in the CaII triplet region. We focused the analysis along the PA = 152° that corresponds to the photometric minor axis of the host galaxy, where the superimposition of the two components is more relevant and the spectral decomposition is necessary. We aim to disentangle the stars that move in the equatorial plane of the host galaxy from those that move in the meridan plane, which is along the polar disk. Results: We successfully disentangled the spectra of the two structural components of NGC 4650A and measured their line-of-sight velocity and velocity dispersion profiles, and the stellar content along PA = 152°. The host galaxy shows significant rotation along its photometric minor axis, indicating that the gravitational potential is not axisymmetric. The polar disk shows a kinematic decoupling: the inner regions counter-rotating with respect the outer-regions and the host spheroid. This suggests a complex formation history for the polar disk, characterised by mass accretion with decoupled angular momenta.

Coccato, L.; Iodice, E.; Arnaboldi, M.

2014-09-01

105

Water Ice Spectral Signatures and Grain Size Estimates in the Northern Polar Layered Deposits from MRO CRISM Measurements  

Microsoft Academic Search

The Compact Reconnaissance Infrared Spectrometer for Mars (CRISM) is carried onboard the NASA Mars Reconnaissance Orbiter (MRO). In this work, a portion of the northern polar region is examined with CRISM spectral measurements at full spatial resolution.

R. O. Green; S. L. Murchie

2008-01-01

106

Water Ice Spectral Signatures and Grain Size Estimates in the Northern Polar Layered Deposits from MRO CRISM Measurements  

NASA Astrophysics Data System (ADS)

The Compact Reconnaissance Infrared Spectrometer for Mars (CRISM) is carried onboard the NASA Mars Reconnaissance Orbiter (MRO). In this work, a portion of the northern polar region is examined with CRISM spectral measurements at full spatial resolution.

Green, R. O.; Murchie, S. L.; CRISM Team

2008-03-01

107

Mixed polarity in polarization-induced p-n junction nanowire light-emitting diodes.  

PubMed

Polarization-induced nanowire light emitting diodes (PINLEDs) are fabricated by grading the Al composition along the c-direction of AlGaN nanowires grown on Si substrates by plasma-assisted molecular beam epitaxy (PAMBE). Polarization-induced charge develops with a sign that depends on the direction of the Al composition gradient with respect to the [0001] direction. By grading from GaN to AlN then back to GaN, a polarization-induced p-n junction is formed. The orientation of the p-type and n-type sections depends on the material polarity of the nanowire (i.e., Ga-face or N-face). Ga-face material results in an n-type base and a p-type top, while N-face results in the opposite. The present work examines the polarity of catalyst-free nanowires using multiple methods: scanning transmission electron microscopy (STEM), selective etching, conductive atomic force microscopy (C-AFM), and electroluminescence (EL) spectroscopy. Selective etching and STEM measurements taken in annular bright field (ABF) mode demonstrate that the preferred orientation for catalyst-free nanowires grown by PAMBE is N-face, with roughly 10% showing Ga-face orientation. C-AFM and EL spectroscopy allow electrical and optical differentiation of the material polarity in PINLEDs since the forward bias direction depends on the p-n junction orientation and therefore on nanowire polarity. Specifically, C-AFM reveals that the direction of forward bias for individual nanowire LEDs changes with the polarity, as expected, due to reversal of the sign of the polarization-induced charge. Electroluminescence measurements of mixed polarity PINLEDs wired in parallel show ambipolar emission due to the mixture of p-n and n-p oriented PINLEDs. These results show that, if catalyst-free III-nitride nanowires are to be used to form polarization-doped heterostructures, then it is imperative to understand their mixed polarity and to design devices using these nanowires accordingly. PMID:23756087

Carnevale, Santino D; Kent, Thomas F; Phillips, Patrick J; Sarwar, A T M G; Selcu, Camelia; Klie, Robert F; Myers, Roberto C

2013-07-10

108

Polar Lipids of Burkholderia pseudomallei Induce Different Host Immune Responses  

PubMed Central

Melioidosis is a disease in tropical and subtropical regions of the world that is caused by Burkholderia pseudomallei. In endemic regions the disease occurs primarily in humans and goats. In the present study, we used the goat as a model to dissect the polar lipids of B. pseudomallei to identify lipid molecules that could be used for adjuvants/vaccines or as diagnostic tools. We showed that the lipidome of B. pseudomallei and its fractions contain several polar lipids with the capacity to elicit different immune responses in goats, namely rhamnolipids and ornithine lipids which induced IFN-?, whereas phospholipids and an undefined polar lipid induced strong IL-10 secretion in CD4+ T cells. Autologous T cells co-cultured with caprine dendritic cells (cDCs) and polar lipids of B. pseudomallei proliferated and up-regulated the expression of CD25 (IL-2 receptor) molecules. Furthermore, we demonstrated that polar lipids were able to up-regulate CD1w2 antigen expression in cDCs derived from peripheral blood monocytes. Interestingly, the same polar lipids had only little effect on the expression of MHC class II DR antigens in the same caprine dendritic cells. Finally, antibody blocking of the CD1w2 molecules on cDCs resulted in decreased expression for IFN-? by CD4+ T cells. Altogether, these results showed that polar lipids of B. pseudomallei are recognized by the caprine immune system and that their recognition is primarily mediated by the CD1 antigen cluster. PMID:24260378

Gonzalez-Juarrero, Mercedes; Mima, Naoko; Trunck, Lily A.; Schweizer, Herbert P.; Bowen, Richard A.; Dascher, Kyle; Mwangi, Waithaka; Eckstein, Torsten M.

2013-01-01

109

Spectral selective radio frequency emissions from laser induced breakdown of target materials  

SciTech Connect

The radio frequency emissions scanned over broad spectral range (30?MHz–1?GHz) from single shot nanosecond (7?ns) and picosecond (30 ps) laser induced breakdown (LIB) of different target materials (atmospheric air, aluminum, and copper) are presented. The dominant emissions from ns-LIB, compared to those from the ps-LIB, indicate the presence and importance of atomic and molecular clusters in the plasma. The dynamics of laser pulse-matter interaction and the properties of the target materials were found to play an important role in determining the plasma parameters which subsequently determine the emissions. Thus, with a particular laser and target material, the emissions were observed to be spectral selective. The radiation detection capability was observed to be relatively higher, when the polarization of the input laser and the antenna is same.

Vinoth Kumar, L.; Manikanta, E.; Leela, Ch.; Prem Kiran, P., E-mail: premkiranuoh@gmail.com [Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046 (India)

2014-08-11

110

Detection of a new spectral unit on the South Polar Region of Mars  

NASA Astrophysics Data System (ADS)

In this work we report on the detection of a new spectral unit on the Martian southern polar region. Data used in this study have been acquired by the OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) imaging spectrometer on board the ESA mission Mars Express (MEX). Spectrally, the unit is characterized by a 1 ?m band depth ~60% higher than the average value of surrounding terrain (LAT<-60°S), a distinctive shape of the reflectance peak at about 0.685 ?m and a steeper negative slope between ~0.8-1 ?m. The spectral parameters used to map the unit have been defined according to [1] and they show values similar to the one observed on the cratered Noachian terrain of the southern hemisphere (- 60 °S < LAT < 0°) characterized by a mineralogical composition rich in pyroxene. Morphologically, the considered area falls inside one of the flattest regions of Mars. In Figure 1 we show the spectral unit location and its typical spectrum (red curve), in comparison with other spectra. In Fig. 2 we show the spectral ratios between the spectra of the sites of Fig. 1. The spectrum 1 has bands near 1.05 and 2.3 ?m. The best match of this spectrum is the diopside, while the spectrum 2 has absorptions near 1.04 and 2.1 ?m consistent with a basalt, probably LCP.

Carrozzo, F. G.; Altieri, F.; Bellucci, G.; Poulet, F.; D'Aversa, E.; Bibring, J.-P.

2012-09-01

111

PHYSICAL REVIEW B 85, 094107 (2012) Interfacial polarization and pyroelectricity in antiferrodistortive structures induced  

E-print Network

coupling cannot induce polarization inside easy twins and antiphase boundaries; their polarization is the following: the biquadratic coupling induces bistable ferroelectric polarization inside hard antiphase, polarization, and magnetization, which can couple to induce new phenomena not present in the relevant bulk

Chen, Long-Qing

112

Spectral fluorescence and polarization characteristics of Z,Z-bilirubin IX?  

NASA Astrophysics Data System (ADS)

We have studied the spectral fluorescence and polarization characteristics of Z,Z-bilirubin IX?, at room temperature in chloroform and in aqueous buffer medium, within an equilibrium complex with human serum albumin (HSA), and also under low temperature conditions (T = -100°C) in isobutyl alcohol. We have observed a bathochromic shift of the fluorescence spectra, which is most pronounced for the bilirubin-albumin complex. The following are considered as possible reasons for the observed dependence of the position of the fluorescence (fluorescence excitation) spectra on the excitation (detection) wavelength: structural and spectral differences between the chromophores making up the bilirubin molecule; conformational heterogeneity of the pigment in solution; a contribution to the fluorescence from molecules which have not completed the vibrational relaxation process; inhomogeneous orientational broadening of the levels; heterogeneity of the microenvironment of the chromophores in the protein matrix. We show that polarized fluorescence of bilirubin occurs at room temperature, due to the anomalously short fluorescence lifetime ? (picosecond or subpicosecond ranges). Despite such a short ?, the absorption and emission polarization spectra suggest the presence of intramolecular nonradiative singlet-singlet energy transfer when bilirubin is excited to high vibrational sublevels of the S1 state (degree of polarization p = 0.11-0.12). When fluorescence is excited on the long-wavelength slope of the absorption band, no transfer occurs: the degree of polarization (p = 0.46-0.47) is close to the limiting value (p = 0.50). We discuss the question of the role played by exciton interactions between chromophores in the bilirubin molecule when it is excited.

Plavskii, V. Yu.; Mostovnikov, V. A.; Mostovnikova, G. R.; Tret'yakova, A. I.

2007-01-01

113

Three-dimensional induced polarization data inversion for complex resistivity  

SciTech Connect

The conductive and capacitive material properties of the subsurface can be quantified through the frequency-dependent complex resistivity. However, the routine three-dimensional (3D) interpretation of voluminous induced polarization (IP) data sets still poses a challenge due to large computational demands and solution nonuniqueness. We have developed a flexible methodology for 3D (spectral) IP data inversion. Our inversion algorithm is adapted from a frequency-domain electromagnetic (EM) inversion method primarily developed for large-scale hydrocarbon and geothermal energy exploration purposes. The method has proven to be efficient by implementing the nonlinear conjugate gradient method with hierarchical parallelism and by using an optimal finite-difference forward modeling mesh design scheme. The method allows for a large range of survey scales, providing a tool for both exploration and environmental applications. We experimented with an image focusing technique to improve the poor depth resolution of surface data sets with small survey spreads. The algorithm's underlying forward modeling operator properly accounts for EM coupling effects; thus, traditionally used EM coupling correction procedures are not needed. The methodology was applied to both synthetic and field data. We tested the benefit of directly inverting EM coupling contaminated data using a synthetic large-scale exploration data set. Afterward, we further tested the monitoring capability of our method by inverting time-lapse data from an environmental remediation experiment near Rifle, Colorado. Similar trends observed in both our solution and another 2D inversion were in accordance with previous findings about the IP effects due to subsurface microbial activity.

Commer, M.; Newman, G.A.; Williams, K.H.; Hubbard, S.S.

2011-03-15

114

Spectral Stokes singularities of partially coherent radially polarized beams focused by a high numerical aperture objective  

NASA Astrophysics Data System (ADS)

The dynamic behavior of spectral Stokes singularities of partially coherent radially polarized beams focused by a high numerical aperture (NA) objective is studied by using the vectorial Debye diffraction theory and complex spectral Stokes fields. It is shown that there exist s12, s23, and s31 singularities, as well as P (completely polarized) and U (unpolarized) singularities. The motion, pair creation and annihilation, and changes in the degree of polarization of s12, s23, and s31 singularities, and the handedness reversal of s12 singularities (C-points) may appear by varying a controlling parameter, such as the truncation parameter, NA, or spatial correlation length. The creation and annihilation occur for a pair of s12 singularities with opposite topological charge but the same handedness, and for a pair of oppositely charged s23 or s31 singularities. The critical value of the truncation parameter, at which the pair annihilation takes place, increases as the semi-angle of the aperture lens (or, equivalently, NA) or spatial correlation length increases. The collision of an s12 singularity with an L-line (s3 = 0 contour) leads to a V-point, which is located at the intersection of contours of s12 = 0 and s23 = 0 (or s31 = 0) and is unstable.

Luo, Yamei; Lü, Baida

2010-11-01

115

Spectral properties of identified polarized-light sensitive interneurons in the brain of the desert locust Schistocerca gregaria  

Microsoft Academic Search

Many migrating animals employ a celestial compass mechanism for spatial navigation. Behavioral experiments in bees and ants have shown that sun compass navigation may rely on the spectral gradient in the sky as well as on the pattern of sky polarization. While polarized-light sensitive interneurons (POL neurons) have been identified in the brain of several insect species, there are at

Michiyo Kinoshita; Keram Pfeiffer; Uwe Homberg

2007-01-01

116

Nonadiabatic molecular high-order harmonic generation from polar molecules: Spectral redshift  

SciTech Connect

Molecular high-order harmonic generation (MHOHG) from the polar diatomic molecule HeH{sup 2+} in short intense laser fields is studied numerically. Due to the nonadiabatic response of the molecular dipole to the rapid change of laser intensity, a spectral redshift is predicted in high-intensity and ultrashort laser pulses, contrary to the blueshift observed in the harmonics generated from atoms in long laser pulses. The MHOHG temporal structures are investigated by a wavelet time-frequency analysis, which shows that the enhanced excitation of localized long lifetime excited states shifts the harmonic generation spectrum in the falling part of short laser pulses, due to the presence of a permanent dipole moment, and thus is unique to polar molecules.

Bian Xuebin; Bandrauk, Andre D. [Departement de Chimie, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

2011-04-15

117

A power law power spectral density model of total electron content structure in the polar region  

NASA Astrophysics Data System (ADS)

Measurements by the early warning radar at Thule, Greenland, together with GPS measurements from the Air Force Research Laboratory (AFRL) Ionospheric Measurement System (IMS) receiver, have been analyzed to develop a model for the structure of the total electron content (TEC) of the polar ionosphere. For the model the TEC measurements are related to the Wide Band Model (WBMOD), a climatological model of small-scale ionization structure. The TEC data agree very well with the predictions of a simple extension of WBMOD to larger scales, where a slightly steeper spectral slope (p ? 3) is used for the TEC structure (compared to p = 2.7 for the small-scale structure of WBMOD's polar region model). The benefit of this approach is that the TEC model subsumes the climatology of WBMOD, which is built upon two solar cycles of ionospheric measurements.

Nickisch, L. J.

2004-02-01

118

High spectral and time resolution observations of the eclipsing polar RX J0719.2+6557  

E-print Network

We present phase-resolved spectral and multicolor CCD-photometric observations of the eclipsing polar RX J0719.2+6557 obtained with relatively high time (~600 sec/15 sec) and spectral (2.1 A) resolution when the system was in a high accretion state. The trailed spectrograms clearly reveal the presence of three different line components with different width and radial velocity variation. We were able to resolve all three components by line deblending, and by means of Doppler tomography were able to unambiguously identify the emission components with the secondary star, the ballistic part of the accretion stream and the magnetically funnelled part of the stream. The light curves and eclipse profiles provide additional information about the system geometry.

G. H. Tovmassian; P. Szkody; J. Greiner; S. Vrielmann; P. Kroll; S. Howell; R. Saxton; D. Ciardi; P. A. Mason; N. C. Hastings

1998-09-24

119

Calibration of a snapshot phase-resolved polarization-sensitive spectral reflectometer.  

PubMed

This Letter describes a universal calibration theory by which conventional interferometry can be extended to vibration robust snapshot polarization-sensitive spectral reflectometry without any complicated optical components or active devices. Experiments for verifying the proposed calibration theory have been conducted by using a Michelson-interferometer-based normal incidence spectroellipsometric system, and also some key system design considerations for object 3D pose tolerant measurement capability have been drawn. The proposed solution enables us to extract the spectroscopic ellipsometric parameter ?(k) of an anisotropic object within 10 ms with high accuracy. PMID:24322143

Kim, Daesuk; Jin, Moonseob; Chegal, Won; Lee, Jaejong; Magnusson, Robert

2013-11-15

120

Spectral Induced Polarization Measurements of Nanoparticles in Laboratory Column Experiments  

EPA Science Inventory

Nano sized materials are prevalent in consumer goods, manufacturing, industrial processes, and remediation technologies. The intentional and accidental introduction of nanoparticles (NP) into the subsurface pose a potential risk to the environment and public health. This resea...

121

Eustatic sea level fluctuations induced by polar wander  

Microsoft Academic Search

It is shown here that polar wander of a viscoelastic, stratified earth can induce global sea level fluctuations comparable to the short-term component in eustatic sea-level curves. The sign of these fluctuations, which are very sensitive to the rheological stratification, depends on the geographical location of the observation point; rises and falls in sea level can thus be coeval in

Roberto Sabadini; Carlo Doglioni; David A. Yuen

1990-01-01

122

General solutions for stress-induced polarization in optical fibers  

Microsoft Academic Search

General solutions of thermal stresses and material birefringence in polarization-maintaining optical fibers are presented. The solutions give the stresses and birefringence at every point in the cross section of various fibers. The fundamental solution of the stress field is constructed by using the complex variable method in elasticity. When the cores, inner claddings, or stress-inducing regions are ellipses, circles, or

Kun-Hsieh Tsai; Kyung-Suk Kim; T. F. Morse

1991-01-01

123

Effect of surface induced nucleation of ferroelastic domains on polarization switching in constrained ferroelectrics  

E-print Network

Effect of surface induced nucleation of ferroelastic domains on polarization switching polarization switching in constrained ferroelectrics is investigated using the time-dependent Ginzburg. A square-shaped finite sized constrained ferroelectric system with vanishing surface polarization

Cao, Wenwu

124

PHYSICAL REVIEW B 84, 155319 (2011) Nonequilibrium nuclear polarization and induced hyperfine and dipolar magnetic fields in  

E-print Network

PHYSICAL REVIEW B 84, 155319 (2011) Nonequilibrium nuclear polarization and induced hyperfine the induced nuclear spin polarization greatly exceeds the polarization of the electronic system that causes 2011) We investigate the dynamic nuclear polarization (DNP) caused by hyperfine coupling between

Flatte, Michael E.

125

Assessing Cd-induced stress from plant spectral response  

NASA Astrophysics Data System (ADS)

Remote sensing plays a significant role in local, regional and global monitoring of land covers. Ecological concerns worldwide determine the importance of remote sensing applications for the assessment of soil conditions, vegetation health and identification of stress-induced changes. The extensive industrial growth and intensive agricultural land-use arise the serious ecological problem of environmental pollution associated with the increasing anthropogenic pressure on the environment. Soil contamination is a reason for degradation processes and temporary or permanent decrease of the productive capacity of land. Heavy metals are among the most dangerous pollutants because of their toxicity, persistent nature, easy up-take by plants and long biological half-life. This paper takes as its focus the study of crop species spectral response to Cd pollution. Ground-based experiments were performed, using alfalfa, spring barley and pea grown in Cd contaminated soils and in different hydroponic systems under varying concentrations of the heavy metal. Cd toxicity manifested itself by inhibition of plant growth and synthesis of photosynthetic pigments. Multispectral reflectance, absorbance and transmittance, as well as red and far red fluorescence were measured and examined for their suitability to detect differences in plant condition. Statistical analysis was performed and empirical relationships were established between Cd concentration, plant growth variables and spectral response Various spectral properties proved to be indicators of plant performance and quantitative estimators of the degree of the Cd-induced stress.

Kancheva, Rumiana; Georgiev, Georgi

2014-10-01

126

A polarity-induced defect mechanism for conductivity and magnetism at polar–nonpolar oxide interfaces  

NASA Astrophysics Data System (ADS)

The discovery of conductivity and magnetism at the polar–nonpolar interfaces of insulating nonmagnetic oxides such as LaAlO3 and SrTiO3 has raised prospects for attaining interfacial functionalities absent in the component materials. Yet, the microscopic origin of such emergent phenomena remains unclear, posing obstacles to design of improved functionalities. Here we present first principles calculations of electronic and defect properties of LaAlO3/SrTiO3 interfaces and reveal a unifying mechanism for the origins of both conductivity and magnetism. We demonstrate that the polar discontinuity across the interface triggers thermodynamically the spontaneous formation of certain defects that in turn cancel the polar field induced by the polar discontinuity. The ionization of the spontaneously formed surface oxygen vacancy defects leads to interface conductivity, whereas the unionized Ti-on-Al antisite defects lead to interface magnetism. The proposed mechanism suggests practical design principles for inducing and controlling both conductivity and magnetism at general polar–nonpolar interfaces.

Yu, Liping; Zunger, Alex

2014-10-01

127

A polarity-induced defect mechanism for conductivity and magnetism at polar-nonpolar oxide interfaces.  

PubMed

The discovery of conductivity and magnetism at the polar-nonpolar interfaces of insulating nonmagnetic oxides such as LaAlO3 and SrTiO3 has raised prospects for attaining interfacial functionalities absent in the component materials. Yet, the microscopic origin of such emergent phenomena remains unclear, posing obstacles to design of improved functionalities. Here we present first principles calculations of electronic and defect properties of LaAlO3/SrTiO3 interfaces and reveal a unifying mechanism for the origins of both conductivity and magnetism. We demonstrate that the polar discontinuity across the interface triggers thermodynamically the spontaneous formation of certain defects that in turn cancel the polar field induced by the polar discontinuity. The ionization of the spontaneously formed surface oxygen vacancy defects leads to interface conductivity, whereas the unionized Ti-on-Al antisite defects lead to interface magnetism. The proposed mechanism suggests practical design principles for inducing and controlling both conductivity and magnetism at general polar-nonpolar interfaces. PMID:25307265

Yu, Liping; Zunger, Alex

2014-01-01

128

Spectrally-Polarized Features in Epsilon Aurigae In and Out of Eclipse  

NASA Astrophysics Data System (ADS)

The epsilon Aurigae system is a single-lined spectroscopic binary system that consists of a variable F0 supergiant star and an occulting disk surrounding an unseen object, probably a B star. The eclipse occurs once every 27 years and lasts for almost 2 years. We used spectropolarimetric techniques to probe both the primary star and the occulting disk before, during and after the most recent eclipse in order to better understand the origin and evolution of the disk in the system. We obtained 50+ epochs of high dispersion optical spectra from the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope (CFHT) during 2006-2013. These spectra included eclipse and out-of-eclipse observations rich with polarization features attributable to both the F0 star and the disk. We identified 4-sigma (or greater) linear polarization features in the spectra and matched them against absorption features also present in the spectra. Out-of-eclipse spectra revealed variable linear polarization features largely arising from Fe I and singly ionized species such as Ti II, Fe II, Sc II and others. Polarization features from these species demonstrated a preferred equatorial orientation. Hydrogen absorption features exhibited position angles that varied with orbital phase. Our CFHT observations revealed that polarization increased dramatically during eclipse. The increase in polarization across many species was consistent with spectral line behavior and may help constrain the density and temperature distribution of material in the outer layer of the disk. Out-of-eclipse linear polarization features attributed to the F star suggest that persistent anisotropies exist in mid- to upper layers of the stellar atmosphere, are consistent across those layers, and have a specific geometry in the stellar frame. Position angles calculated from eclipse spectra suggest that scattering processes likely arise from both the upper and lower outer layers of the disk, as well as leading and trailing edges of the disk and trailing material in the system. Position angles associated with hydrogen absorption polarization suggests that hydrogen absorption features likely consist of both stellar and extra-stellar components.

Geise, Kathleen M.; Stencel, R. E.

2013-07-01

129

Induced polarization of Lambda(1116) in kaon electroproduction  

SciTech Connect

We have measured the induced polarization of the ?(1116) in the reaction ep?e?K+?, detecting the scattered e? and K+ in the final state along with the proton from the decay ??p??.The present study used the CEBAF Large Acceptance Spectrometer (CLAS), which allowed for a large kinematic acceptance in invariant energy W (1.6?W?2.7 GeV) and covered the full range of the kaon production angle at an average momentum transfer Q2=1.90 GeV2.In this experiment a 5.50 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. We have mapped out the W and kaon production angle dependencies of the induced polarization and found striking differences from photoproduction data over most of the kinematic range studied. However, we also found that the induced polarization is essentially Q2 independent in our kinematic domain, suggesting that somewhere below the Q2 covered here there must be a strong Q2 dependence. Along with previously published photo- and electroproduction cross sections and polarization observables, these data are needed for the development of models, such as effective field theories, and as input to coupled-channel analyses that can provide evidence of previously unobserved s-channel resonances.

Gabrielyan, M.; Raue, B.A.; Carman, D.S.; Park, K.; Adhikari, K.P.; Adikaram, D.; Amaryan, M.J.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Baltzell, N.A.; Battaglieri, M.; Baturin, V.; Bedlinskiy, I.; Biselli, A.S.; Bono, J.; Boiarinov, S.; Briscoe, W.J.; Brooks, W.K.; Burkert, V.D.; Cao, T.; Celentano, A.; Chandavar, S.; Charles, G.; Cole, P.L.; Contalbrigo, M.; Cortes, O.; Crede, V.; D’Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Doughty, D.; Dupre, R.; ElFassi, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Fleming, J.A.; Forest, T.A.; Garillon, B.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G.P.; Giovanetti, K.L.; Girod, F.X.; Goetz, J.T.; Golovatch, E.; Gothe, R.W.; Griffioen, K.A.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hattawy, M.; Hicks, K.; Ho, D.; Holtrop, M.; Hughes, S.M.; Ilieva, Y.; Ireland, D.G.; Ishkhanov, B.S.; Jenkins, D.; Jiang, H.; Jo, H.S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, W.; Klein, F.J.; Koirala, S.; Kubarovsky, V.; Kuhn, S.E.; Kuleshov, S.V.; Lenisa, P.; Levine, W.I.; Livingston, K.; MacGregor, I.J.D.; Mayer, M.; McKinnon, B.; Meyer, C.A.; Mestayer, M.D.; Mirazita, M.; Mokeev, V.; Moody, C.I.; Moutarde, H.; Movsisyan, A; Munevar, E.; Munoz Camacho, C.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Pappalardo, L.L.; Paremuzyan, R.; Pasyuk, E.; Peng, P.; Phelps, W.; Phillips, J.J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J.W.; Procureur, S.; Protopopescu, D.; Rimal, D.; Ripani, M.; Rizzo, A.; Sabatie, F.; Salgado, C.; Schott, D.; Schumacher, R.A.; Simonyan, A.; Smith, G.D.; Sober, D.I.; Sokhan, D.; Stepanyan, S.S.; Stepanyan, S.; Strakovsky, I.I.; Strauch, S.; Sytnik, V.; Tang, W.; Ungaro, M.; Vlassov, A.V.; Voskanyan, H.; Voutier, E.; Walford, N.K.; Watts, D.P.; Wei, X.; Weinstein, L.B.; Zachariou, N.; Zana, L.; Zhang, J.

2014-09-01

130

Shapes of polarization-induced resonances in stimulated Bremsstrahlung spectra  

SciTech Connect

In the frame of fixed classical electron current approximation the cross-sections of the stimulated Bremsstrahlung (SBr) on highly charged ions (HCI) with the core are studied. The polarization of the HCI core in the laser field is taken into consideration as well as the interference between polarization and standard (static) SBr channels. Spectral and intensity (with respect to the laser field strength) analysis of the SBr cross-sections is made for the near-resonant transitions in the alkali-like HCI core with (i) {delta}n=0 and (ii) {delta}n=1. In the first case the influence of the fine-splitting of the near-resonant transition on the SBr line shape is investigated. In the second case the nondipole interaction between incident electron and HCI core is analyzed in Coulomb approximation for projectile trajectory.

Astapenko, V. A. [Moscow Institute for Physics and Technology, Dolgoprudnyi, Moscow region 141700 (Russian Federation)

1999-04-01

131

Spectral-to-temporal amplitude mapping polarization spectroscopy of rotational transients.  

PubMed

A new implementation of pump-probe polarization spectroscopy is presented where the revivals of an impulsively excited rotational wavepacket are mapped onto a broad-band, chirped continuum pulse to measure a long temporal window without the need for delay scanning. Experimental measurements and a theoretical framework for spectral-temporal amplitude mapping polarization spectroscopy (STAMPS) as applied to impulsive rotational motion are presented. In this technique, a femtosecond laser pulse is used to prepare a rotational wavepacket in a gas-phase sample at room temperature. The rotational revivals of the wavepacket are then mapped onto a chirped continuum (400-800 nm) pulse created by laser filamentation in argon. Nearly single-shot time-resolved rotational spectra are recorded over a 65 ps time window. The transient birefringence spectra are simulated by including terms for polarization rotation of the probe as well as cross-phase modulation. Measurements and simulations are presented for the cylindrically symmetric N2, O2, and CO2 molecules. The long time window of the method allows measurement of rotational spectra for asymmetric top molecules, and here we present measurements for ethylene and methanol. PMID:23651318

McCole, Erin T; Odhner, Johanan H; Romanov, Dmitri A; Levis, Robert J

2013-07-25

132

Microtubule-Induced Pins/Gai Cortical Polarity in Drosophila Neuroblasts  

E-print Network

Microtubule-Induced Pins/Gai Cortical Polarity in Drosophila Neuroblasts Sarah E. Siegrist1.09.043 SUMMARY Cortical polarity regulates cell division, mi- gration, and differentiation. Microtubules induce and Dlg/Pins co- immunoprecipitate, suggesting that micro- tubules induce Pins/Gai cortical polarity

Doe, Chris

133

Polarization-induced distortion in stimulated Brillouin scattering slow-light systems  

E-print Network

Polarization-induced distortion in stimulated Brillouin scattering slow-light systems Avi Zadok,1 show that SBS-related polarization-induced distor- tion is yet another mechanism responsible for pulse. Thus, it is shown below that this SBS- related polarization induced distortion is analogous

Zadok, Avinoam

134

Mask induced polarization effects at high NA Andrew Estroff, Yongfa Fan, Anatoly Bourov, Bruce Smith  

E-print Network

Mask induced polarization effects at high NA Andrew Estroff, Yongfa Fan, Anatoly Bourov, Bruce, material thickness, and illumination scheme all influence mask induced polarization effects. Keywords field of the TE polarized light induces a current in the length of the wires. Forward transmitted

Zanibbi, Richard

135

Measurements of submillimeter polarization induced by oblique reflection from aluminum alloy  

E-print Network

Measurements of submillimeter polarization induced by oblique reflection from aluminum alloy Tom Renbarger, Jessie L. Dotson, and Giles Novak We have measured the linear polarization induced in a beam of incidence in the range 15°­45°, we measured induced polarizations in the range 0.05%­0.25%. Our measurements

Novak, Giles

136

3DEMIII Workshop, February 2003, Adelaide. 1 3-D inversion of magnetic induced polarization data  

E-print Network

3DEMIII Workshop, February 2003, Adelaide. 1 3-D inversion of magnetic induced polarization data@geop.ubc.ca doug@geop.ubc.ca INTRODUCTION The magnetic induced polarization (MIP) is used as an alternative method to derive information relating to the induced polarization characteristics of the subsurface through

Oldenburg, Douglas W.

137

Enhancement of induced V polarization due to rough interfaces in polycrystalline V/Fe/V trilayers  

E-print Network

Enhancement of induced V polarization due to rough interfaces in polycrystalline V/Fe/V trilayers C July 2009 The effect of interface roughness on the induced polarization of V in polycrystalline V-mean-square interfacial roughness at the Fe/V interfaces. The induced polarization found in V was constrained to the Fe

Haskel, Daniel

138

3D induced-polarization data inversion for complex resistivity Michael Commer1  

E-print Network

3D induced-polarization data inversion for complex resistivity Michael Commer1 , Gregory A. Newman1, the routine three-dimensional (3D) interpretation of voluminous induced polarization (IP) data sets still findings about the IP effects due to subsurface microbial activity. INTRODUCTION The induced-polarization

Hubbard, Susan

139

Macroscopic rotation of photon polarization induced by a single spin  

NASA Astrophysics Data System (ADS)

Entangling a single spin to the polarization of a single incoming photon, generated by an external source, would open new paradigms in quantum optics such as delayed-photon entanglement, deterministic logic gates or fault-tolerant quantum computing. These perspectives rely on the possibility that a single spin induces a macroscopic rotation of a photon polarization. Such polarization rotations induced by single spins were recently observed, yet limited to a few 10?3 degrees due to poor spin–photon coupling. Here we report the enhancement by three orders of magnitude of the spin–photon interaction, using a cavity quantum electrodynamics device. A single hole spin in a semiconductor quantum dot is deterministically coupled to a micropillar cavity. The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by ±6° when the spin is optically initialized in the up or down state. These results open the way towards a spin-based quantum network.

Arnold, Christophe; Demory, Justin; Loo, Vivien; Lemaître, Aristide; Sagnes, Isabelle; Glazov, Mikhaïl; Krebs, Olivier; Voisin, Paul; Senellart, Pascale; Lanco, Loïc

2015-02-01

140

Macroscopic rotation of photon polarization induced by a single spin.  

PubMed

Entangling a single spin to the polarization of a single incoming photon, generated by an external source, would open new paradigms in quantum optics such as delayed-photon entanglement, deterministic logic gates or fault-tolerant quantum computing. These perspectives rely on the possibility that a single spin induces a macroscopic rotation of a photon polarization. Such polarization rotations induced by single spins were recently observed, yet limited to a few 10(-3) degrees due to poor spin-photon coupling. Here we report the enhancement by three orders of magnitude of the spin-photon interaction, using a cavity quantum electrodynamics device. A single hole spin in a semiconductor quantum dot is deterministically coupled to a micropillar cavity. The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by ±6° when the spin is optically initialized in the up or down state. These results open the way towards a spin-based quantum network. PMID:25687134

Arnold, Christophe; Demory, Justin; Loo, Vivien; Lemaître, Aristide; Sagnes, Isabelle; Glazov, Mikhaïl; Krebs, Olivier; Voisin, Paul; Senellart, Pascale; Lanco, Loïc

2015-01-01

141

Macroscopic rotation of photon polarization induced by a single spin  

PubMed Central

Entangling a single spin to the polarization of a single incoming photon, generated by an external source, would open new paradigms in quantum optics such as delayed-photon entanglement, deterministic logic gates or fault-tolerant quantum computing. These perspectives rely on the possibility that a single spin induces a macroscopic rotation of a photon polarization. Such polarization rotations induced by single spins were recently observed, yet limited to a few 10?3 degrees due to poor spin–photon coupling. Here we report the enhancement by three orders of magnitude of the spin–photon interaction, using a cavity quantum electrodynamics device. A single hole spin in a semiconductor quantum dot is deterministically coupled to a micropillar cavity. The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by ±6° when the spin is optically initialized in the up or down state. These results open the way towards a spin-based quantum network. PMID:25687134

Arnold, Christophe; Demory, Justin; Loo, Vivien; Lemaître, Aristide; Sagnes, Isabelle; Glazov, Mikhaïl; Krebs, Olivier; Voisin, Paul; Senellart, Pascale; Lanco, Loïc

2015-01-01

142

COSMIC MICROWAVE BACKGROUND INDUCED POLARIZATION FROM SINGLE SCATTERING BY CLUSTERS OF GALAXIES AND FILAMENTS  

SciTech Connect

We present light-cone-integrated simulations of the cosmic microwave background (CMB) polarization signal induced by a single scattering in the direction of clusters of galaxies and filaments. We characterize the statistical properties of the induced polarization signals from the presence of the CMB quadrupole component (pqiCMB) and as the result of the transverse motion of ionized gas clouds with respect to the CMB rest frame (p{beta}{sup 2}{sub t}SZ). From adiabatic N-body/hydrodynamic simulations, we generated 28 random sky patches integrated along the light cone, each with about 0.86 deg{sup 2} and angular resolution of 6''. Our simulation method involves a box-stacking scheme that allows to reconstruct the CMB quadrupole component and the gas physical properties along the line of sight. We find that the linear polarization degree in the logarithmic scale of both effects follows approximately a Gaussian distribution and the mean total signal is about 10{sup -8} and 10{sup -10} for the pqiCMB and p{beta}{sup 2}{sub t}SZ effects, respectively. The polarization angle is consistent with a flat distribution in both cases. From the mean distributions of the polarization degree with redshift, the highest peak is found at z {approx_equal} 1 for the induced CMB quadrupole and at z {approx_equal} 0.5 for the kinematic component. Our results suggest that most of the contribution for the total polarization signal arises from z {approx}< 4 for the pqiCMB and z {approx}< 3 for p{beta}{sup 2}{sub t}SZ. The spectral dependency of both integrated signals is strong, increasing with the frequency, especially in the case of the p{beta}{sup 2}{sub t}SZ signal, which increases by a factor of 100 from 30 GHz to 675 GHz. The maxima values found at the highest frequency are about 3 {mu}K and 13 {mu}K for the pqiCMB and p{beta}{sup 2}{sub t}SZ, respectively. The angular power spectra of these effects peak at large multipoles l > 10{sup 4}, being of the order of 10{sup -5} {mu}K{sup 2} for pqiCMB polarization and 10{sup -7} {mu}K{sup 2} for the p{beta}{sup 2}{sub t}SZ effect. Therefore, these effects will not be a relevant source of contamination for measurements of the primary polarization modes, and at larger multipoles of roughly l > 40, 000, pqiCMB may be the dominant component over the primary and lensing signals.

Ramos, Elsa P. R. G.; Da Silva, Antonio J. C. [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Liu, Guo-Chin, E-mail: eramos@astro.up.pt [Department of Physics, Tamkang University, Tamsui District, New Taipei City 251, Taiwan (China)

2012-09-20

143

Polarization-induced surface charges in hydroxyapatite ceramics  

NASA Astrophysics Data System (ADS)

Calcium hydroxyapatite (HAp; Ca10(PO4)6(OH)2) is a well-known biomaterial that is the main inorganic component of bones and teeth. Control over the surface charge on HAp would be a key advance in the development of the material for tissue engineering. We demonstrate here that surface charge can be induced by an electrical poling process using the Kelvin method. Positive and negative charges were induced on the HAp surface in response to the applied electric field in the poling process. The surface charging is attributed to dipole polarization that is homogeneously distributed in HAp. Additionally, the surface charging is considered to originate from the organization of OH- ions into a polar phase in the structure.

Horiuchi, N.; Nakaguki, S.; Wada, N.; Nozaki, K.; Nakamura, M.; Nagai, A.; Katayama, K.; Yamashita, K.

2014-07-01

144

Ion-induced nucleation in polar one-component fluids  

E-print Network

We present a Ginzburg-Landau theory of ion-induced nucleation in a gas phase of polar one-component fluids, where a liquid droplet grows with an ion at its center. By calculating the density profile around an ion, we show that the solvation free energy is larger in gas than in liquid at the same temperature on the coexistence curve. This difference much reduces the nucleation barrier in a metastable gas.

Hikaru Kitamura; Akira Onuki

2005-08-01

145

Topographic effects in resistivity and induced-polarization surveys  

Microsoft Academic Search

We have made a systematic study of dipole-dipole apparent resistivity anomalies due to topography and of the effect of irregular terrain on induced-polarization (IP) anomalies, using a two-dimensional (2-D), finite-element computer program. A valley produces a central apparent resistivity low in the resistivity pseudosection, flanked by zones of higher apparent resistivity. A ridge produces just the opposite anomaly pattern -

Richard C. Fox; G. W. Hohmann; T. J. Killpack; L. Rijo

1980-01-01

146

Polarization properties of self-induced transparency under Raman resonance  

NASA Astrophysics Data System (ADS)

Self-induced transparency under two-photon and Raman resonances is studied theoretically in the cases of small angular momentum of resonant transition and essentially different intensity of resonant waves. The last corresponds to the condition of experiment of Grabtchikov et al [Phys.Rev.Lett.81,5808 (1998)]. The problem with account to wave polarization was reduced to generalized Maxwell-Bloch equations which are exactly integrable by the inverse scattering transform method.

Basharov, Ashat M.

2001-11-01

147

Chemical Reaction-Induced Multi-molecular Polarization (CRIMP)  

PubMed Central

Here we present a novel hyperpolarization method, Chemical Reaction-Induced Multi-molecular Polarization (CRIMP), which could be applied to the study of several in vivo processes simultaneously including glycolysis, TCA cycle, fatty acid synthesis and pH mapping. Through the use of non-enzymatic decarboxylation, we generate four hyperpolarized imaging agents from hyperpolarized 1,2-13C pyruvic acid. PMID:25224323

Lee, Youngbok; Zacharias Millward, Niki M.; Piwnica-Worms, David

2015-01-01

148

Chemical reaction-induced multi-molecular polarization (CRIMP).  

PubMed

Here we present a novel hyperpolarization method, Chemical Reaction-Induced Multi-molecular Polarization (CRIMP), which could be applied to the study of several in vivo processes simultaneously including glycolysis, TCA cycle, fatty acid synthesis and pH mapping. Through the use of non-enzymatic decarboxylation, we generate four hyperpolarized imaging agents from hyperpolarized 1,2-(13)C pyruvic acid. PMID:25224323

Lee, Y; Zacharias, N M; Piwnica-Worms, D; Bhattacharya, P K

2014-11-01

149

Induced energy polarization of the vacuum and the resulting cosmology  

E-print Network

The theory of an induced energy polarized vacuum provides an alternative to the standard cosmological model. The theory has previously been shown to lead to the Baryonic Tully-Fisher Relationship [1], to agree with the observed rotation curve of the Galaxy [2], to readily produce the observed features in the rotational curves of other spiral galaxies [3], and to agree with observations of the Coma cluster [4]. All without the need for any free parameters. The theory of an induced energy polarized vacuum is now applied to superclusters. From a model of the distribution of superclusters, the overall density parameter of universe as given by the theory of an induced energy polarized vacuum is Omega = 0.94 plus/minus 0.23. This is consistent with a geometrically flat universe. In addition, by treating the superclusters as unbound systems, the theory leads to an accelerating expansion of the universe in line with observations and without requiring the need for dark energy.

Albert Raymond Penner

2014-04-10

150

Large-field high-speed polarization sensitive spectral domain OCT and its applications in ophthalmology  

PubMed Central

We present a novel spectral domain polarization sensitive OCT system (PS-OCT) that operates at an A-scan rate of 70 kHz and supports scan angles of up to 40° × 40°. The high-speed imaging allows the acquisition of up to 1024 × 250 A-scans per 3D scan, which, together with the large field of view, considerably increases the informative value of the images. To demonstrate the excellent performance of the new PS-OCT system, we imaged several healthy volunteers and patients with various diseases such as glaucoma, AMD, Stargardt’s disease, and albinism. The results are compared with clinically established methods such as scanning laser polarimetry and autofluorescence. PMID:23162711

Zotter, Stefan; Pircher, Michael; Torzicky, Teresa; Baumann, Bernhard; Yoshida, Hirofumi; Hirose, Futoshi; Roberts, Philipp; Ritter, Markus; Schütze, Christopher; Götzinger, Erich; Trasischker, Wolfgang; Vass, Clemens; Schmidt-Erfurth, Ursula; Hitzenberger, Christoph K.

2012-01-01

151

Extracting structural features of rat sciatic nerve using polarization-sensitive spectral domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

We present spectral domain polarization-sensitive optical coherence tomography (SD PS-OCT) imaging of peripheral nerves. Structural and polarization-sensitive OCT imaging of uninjured rat sciatic nerves was evaluated both qualitatively and quantitatively. OCT and its functional extension, PS-OCT, were used to image sciatic nerve structure with clear delineation of the nerve boundaries to muscle and adipose tissues. A long-known optical effect, bands of Fontana, was also observed. Postprocessing analysis of these images provided significant quantitative information, such as epineurium thickness, estimates of extinction coefficient and birefringence of nerve and muscle tissue, frequency of bands of Fontana at different stretch levels of nerve, and change in average birefringence of nerve under stretched condition. We demonstrate that PS-OCT combined with regular-intensity OCT (compared with OCT alone) allows for a clearer determination of the inner and outer boundaries of the epineurium and distinction of nerve and muscle based on their birefringence pattern. PS-OCT measurements on normal nerves show that the technique is promising for studies on peripheral nerve injury.

Islam, M. Shahidul; Oliveira, Michael C.; Wang, Yan; Henry, Francis P.; Randolph, Mark A.; Park, B. Hyle; de Boer, Johannes F.

2012-05-01

152

Extracting structural features of rat sciatic nerve using polarization-sensitive spectral domain optical coherence tomography  

PubMed Central

Abstract. We present spectral domain polarization-sensitive optical coherence tomography (SD PS-OCT) imaging of peripheral nerves. Structural and polarization-sensitive OCT imaging of uninjured rat sciatic nerves was evaluated both qualitatively and quantitatively. OCT and its functional extension, PS-OCT, were used to image sciatic nerve structure with clear delineation of the nerve boundaries to muscle and adipose tissues. A long-known optical effect, bands of Fontana, was also observed. Postprocessing analysis of these images provided significant quantitative information, such as epineurium thickness, estimates of extinction coefficient and birefringence of nerve and muscle tissue, frequency of bands of Fontana at different stretch levels of nerve, and change in average birefringence of nerve under stretched condition. We demonstrate that PS-OCT combined with regular-intensity OCT (compared with OCT alone) allows for a clearer determination of the inner and outer boundaries of the epineurium and distinction of nerve and muscle based on their birefringence pattern. PS-OCT measurements on normal nerves show that the technique is promising for studies on peripheral nerve injury. PMID:22612135

Islam, M. Shahidul; Oliveira, Michael C.; Wang, Yan; Henry, Francis P.; Randolph, Mark A.; Park, B. Hyle; de Boer, Johannes F.

2012-01-01

153

The spatial, spectral and polarization properties of solar flare X-ray sources  

NASA Astrophysics Data System (ADS)

X-rays are a valuable diagnostic tool for the study of high energy accelerated electrons. Bremsstrahlung X-rays produced by, and directly related to, high energy electrons accelerated during a flare, provide a powerful diagnostic tool for determining both the properties of the accelerated electron distribution, and of the flaring coronal and chromospheric plasmas. This thesis is specifically concerned with the study of spatial, spectral and polarization properties of solar flare X-ray sources via both modelling and X-ray observations using the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Firstly, a new model is presented, accounting for finite temperature, pitch angle scattering and initial pitch angle injection. This is developed to accurately infer the properties of the acceleration region from the observations of dense coronal X-ray sources. Moreover, examining how the spatial properties of dense coronal X-ray sources change in time, interesting trends in length, width, position, number density and thermal pressure are found and the possible causes for such changes are discussed. Further analysis of data in combination with the modelling of X-ray transport in the photosphere, allows changes in X-ray source positions and sizes due to the X-ray albedo effect to be deduced. Finally, it is shown, for the first time, how the presence of a photospheric X-ray albedo component produces a spatially resolvable polarization pattern across a hard X-ray (HXR) source. It is demonstrated how changes in the degree and direction of polarization across a single HXR source can be used to determine the anisotropy of the radiating electron distribution.

Jeffrey, Natasha L. S.

2014-12-01

154

Soft X-Ray Spectral Analysis of the North Polar Spur  

NASA Astrophysics Data System (ADS)

I present a soft X-ray spectral observation of the North Polar Spur (NPS), an enhanced feature in the Soft X-ray Background. The observation was made with a Charge Coupled Device (CCD) aboard a sounding rocket on May 2, 1997. CCD temperature during flight was -72°C, approximately 15° higher than optimal. A total of 330 seconds of data was collected. The spectrum, in the 0.22-10 keV energy range, was analyzed using the XSPEC data package. The data were fit by a three component model: an absorbed power law representing the extragalactic emission, a thermal plasma model representing the foreground emission from the Local Hot Bubble and a thermal plasma model representing emission from the North Polar Spur. The extragalactic component was fit with an absorbed power law, using a column density of 2 × 1020cm -2. The best fit gave a spectral index of 1.391 and a normalization of 11.11. The local component was fit with a Raymond and Smith thermal plasma model. The best fit resulted in a temperature of 1.5 × 106 K and an emission measure of 6.76 × 103cm-6 pc. The NPS component was fit with an absorbed Raymond and Smith thermal plasma model with a temperature of 3.5 × 106 K and an emission measures of 3.53 × 103cm-6 pc. The fit was significantly improved with the addition of Gaussians at energies of known astrophysical lines corresponding to N VII, Ne IX, Mg XI and Si Ly?. It was also significantly improved when the abundances of N, O, Ne, Ar, Fe, and Ni were allowed to vary using a variable Raymond and Smith thermal plasma model for the NPS component. Both fits are evidence of abundance variations in the North Polar Spur. An NEI (nonequilibrium ionization) model for the NPS component did not result in a significant improvement of the fit, suggesting that the NPS plasma is already in collisional ionization equilibrium.

Cawley, Laura Joan

155

Para-hydrogen induced polarization in heterogeneous hydrogenationreactions  

SciTech Connect

We demonstrate the creation and observation ofpara-hydrogen-induced polarization in heterogeneous hydrogenationreactions. Wilkinson's catalyst, RhCl(PPh3)3, supported on eithermodified silica gel or a polymer, is shown to hydrogenate styrene intoethylbenzene and to produce enhanced spin polarizations, observed throughNMR, when the reaction was performed with H2 gas enriched in the paraspinisomer. Furthermore, gaseous phase para-hydrogenation of propylene topropane with two catalysts, the Wilkinson's catalyst supported onmodified silica gel and Rh(cod)(sulfos) (cod = cycloocta-1,5-diene;sulfos) - O3S(C6H4)CH2C(CH2PPh2)3) supported on silica gel, demonstratesheterogeneous catalytic conversion resulting in large spin polarizations.These experiments serve as a direct verification of the mechanism ofheterogeneous hydrogenation reactions involving immobilized metalcomplexes and can be potentially developed into a practical tool forproducing catalyst-free fluids with highly polarized nuclear spins for abroad range of hyperpolarized NMR and MRI applications.

Koptyug, Igor V.; Kovtunov, Kirill; Burt, Scott R.; Anwar, M.Sabieh; Hilty, Christian; Han, Song-I; Pines, Alexander; Sagdeev, Renad Z.

2007-01-31

156

Electro-optic birefringence induced polarization anisotropy in vertical-cavity semiconductor optical amplifiers  

E-print Network

Electro-optic birefringence induced polarization anisotropy in vertical-cavity semiconductor-0407 pwen@ece.ucsd.edu Abstract: The polarization anisotropy including polarization dependent gain (PDG) and frequency splitting in VCSOAs are measured. Measurements of the output polarization state show

Esener, Sadik C.

157

L E T T E R S Microtubules induce self-organization of polarized PAR  

E-print Network

L E T T E R S Microtubules induce self-organization of polarized PAR domains in Caenorhabditis and Geraldine Seydoux1,2 A hallmark of polarized cells is the segregation of the PAR polarity regulators, atypical protein kinase C (aPKC) and PAR-1, have been implicated in polarity maintenance1

Seydoux, Geraldine

158

Polarization Changes in Optical Fibers induced by SelfPhase Modulation and CrossPhase  

E-print Network

Polarization Changes in Optical Fibers induced by Self­Phase Modulation and Cross­Phase Modulation in Conjunction with Birefrigence Lutz Rapp July 20, 2008 Abstract-- Polarization dependence of various fiber field of research activities. Polarization­ mode dispersion (PMD) and polarization­dependent loss (PDL

Paris-Sud XI, Université de

159

Current-induced spin polarization on metal surfaces probed by spin-polarized positron beam  

PubMed Central

Current-induced spin polarization (CISP) on the outermost surfaces of Au, Cu, Pt, Pd, Ta, and W nanoscaled films were studied using a spin-polarized positron beam. The Au and Cu surfaces showed no significant CISP. In contrast, the Pt, Pd, Ta, and W films exhibited large CISP (3~15% per input charge current of 105?A/cm2) and the CISP of Ta and W were opposite to those of Pt and Pd. The sign of the CISP obeys the same rule in spin Hall effect suggesting that the spin-orbit coupling is mainly responsible for the CISP. The magnitude of the CISP is explained by the Rashba-Edelstein mechanism rather than the diffusive spin Hall effect. This settles a controversy, that which of these two mechanisms dominates the large CISP on metal surfaces. PMID:24776781

Zhang, H. J.; Yamamoto, S.; Fukaya, Y.; Maekawa, M.; Li, H.; Kawasuso, A.; Seki, T.; Saitoh, E.; Takanashi, K.

2014-01-01

160

Modeling Robustness Tradeoffs in Yeast Cell Polarization Induced by Spatial Gradients  

E-print Network

Modeling Robustness Tradeoffs in Yeast Cell Polarization Induced by Spatial Gradients Ching-S, Nie Q, Yi T-M (2008) Modeling Robustness Tradeoffs in Yeast Cell Polarization Induced by Spatial Cells localize (polarize) internal components to specific locations in response to external signals

Nie, Qing

161

SHEAR FLOW INDUCED POLARIZATION IN FERROELECTRIC SMECTICS C P. PIERANSKI, E. GUYON and P. KELLER (*)  

E-print Network

1005 SHEAR FLOW INDUCED POLARIZATION IN FERROELECTRIC SMECTICS C P. PIERANSKI, E. GUYON and P to the plane of tilt (see Fig. 1). This, in turn, can induce a spontaneous polarization P in each layer smectic C phase has been established from polarization measurements in the presence of an electric field

Boyer, Edmond

162

Mask induced polarization Andrew Estroff, Yongfa Fan, Anatoly Bourov, Frank Cropanese,  

E-print Network

Mask induced polarization Andrew Estroff, Yongfa Fan, Anatoly Bourov, Frank Cropanese, Neal, Rochester, NY 14623 ABSTRACT The objective of this paper is to study the polarization induced by mask with mask features. RCWA allows the dependence of polarization effects of various wavelengths of radiation

Zanibbi, Richard

163

STRONG POLARIZATION OF THE RESIDUAL NUCLEUS IN A HEAVY-ION INDUCED TRANSFER REACTION  

E-print Network

STRONG POLARIZATION OF THE RESIDUAL NUCLEUS IN A HEAVY-ION INDUCED TRANSFER REACTION F. POUGHEON, P in a heavy-ion induced transfer. Polarization phenomena in heavy-ion reactions have already been studied de reproduire la polarisation correspondante. Abstract. 2014 A strong polarization of 20Ne levels has

Paris-Sud XI, Université de

164

Eustatic sea level fluctuations induced by polar wander  

NASA Technical Reports Server (NTRS)

It is shown here that polar wander of a viscoelastic, stratified earth can induce global sea level fluctuations comparable to the short-term component in eustatic sea-level curves. The sign of these fluctuations, which are very sensitive to the rheological stratification, depends on the geographical location of the observation point; rises and falls in sea level can thus be coeval in different parts of the world. This finding is a distinct contrast to the main assumption underlying the reconstruction of eustatic curves, namely that global sea-level events produce the same depositional sequence everywhere. It is proposed that polar wander should be added to the list of geophysical mechanisms that can control the third-order cycles in sea level.

Sabadini, Roberto; Doglioni, Carlo; Yuen, David A.

1990-01-01

165

How much information on permeability can we expect from induced polarization methods? (Invited)  

NASA Astrophysics Data System (ADS)

Recognizing the significance of permeability heterogeneity on solute transport in groundwater, the determination of qualitative and quantitative information on permeability has been a major focus in the field of hydrogeophysics for some time. This drive has been particularly encouraged due to the minimal invasive method of most geophysical techniques, and the ability to produce spatially dense datasets of geophysical properties. Whilst DC resistivity, as a method, has matured into an extremely robust and flexible technique, and despite its wide use for mapping lithologies, translation of DC resistivity, as a property, to permeability is extremely limited, principally because of the sensitivity to pore fluid states (e.g. salinity) and grain surface electrical conductivity. Induced polarization (IP), in contrast, is sensitive to properties related to the grain surface and/or pore throat geometry, and thus it is intuitive to assume that the permeability and induced polarization response may be closely linked. Spectral IP (SIP) potentially adds further valuable information, given the measure of distribution of polarization length scales. In fact, IP as a tool for hydrogeological studies has been recognized for over 50 years, although it is only over the past two decades that significant advances have been made in both methodology (e.g. instruments, data inversion, etc.) and hydrogeological interpretation. Attempts to link IP (including SIP) and permeability have been explored through laboratory, field and model studies. Mechanistic models have been proposed, along with several empirical relationships. Despite these efforts, the ability to link permeability to IP measurements remains challenging. Formation-specific relationships have been demonstrated, and yet a universal link continues to be elusive. Here, we discuss the principal constraints, illustrated using laboratory and field datasets from a number of studies. We highlight specific challenges, including: questionable treatment of one overarching mechanism of polarization (grain or pore-based) that is applicable to a wide range of porous media (e.g. from coarse unconsolidated to fine consolidated sediments); the weak signal sensitivity to significant variation in formation properties that influence permeability; limitations in field-based imaging due to unsaturated zone effects, the necessary treatment of salinity effects within polarization models; inverse model errors; particular limitations when dealing with highly permeable cobble dominated formations; the lack of well-constrained field investigations; practical difficulties in obtaining spectral IP information at the field scale. Despite these challenges, we assert that valuable information about permeability can be obtained from IP investigations, and offer suggestions for optimum strategies to achieve this.

Binley, A. M.; Slater, L. D.

2013-12-01

166

POLARIZED RAMAN SPECTROSCOPIC STUDY OF THE PRESSURE-INDUCED PHASE CHANGE FROM  

E-print Network

1747P POLARIZED RAMAN SPECTROSCOPIC STUDY OF THE PRESSURE-INDUCED PHASE CHANGE FROM C2/C TO P21/C will be reported. Polarized spectra of an oriented crystal will be presented demonstrating the ability to obtain

Downs, Robert T.

167

Quantifying microbe?mineral interactions leading to remotely detectable induced polarization signals  

SciTech Connect

The objective of this project was to investigate controls on induced polarization responses in porous media. The approach taken in the project was to compare electrical measurements made on mineral surfaces with atomic force microscopy (AFM) techniques to observations made at the column-scale using traditional spectral induced polarization measurements. In the project we evaluated a number of techniques for investigating the surface properties of materials, including the development of a new AFM measurement protocol that utilizes an external electric field to induce grain-scale polarizations that can be probed using a charged AFM tip. The experiments we performed focused on idealized systems (i.e., glass beads and silica gel) where we could obtain the high degree of control needed to understand how changes in the pore environment, which are determined by biogeochemical controls in the subsurface, affect mechanisms contributing to complex electrical conductivity, i.e., conduction and polarization, responses. The studies we performed can be classified into those affecting the chemical versus physical properties of the grain surface and pore space. Chemical alterations of the surface focused on evaluating how changes in pore fluid pH and ionic composition control surface conduction. These were performed as column flow through experiments where the pore fluid was exchanged in a column of silica gel. Given that silica gel has a high surface area due to internal grain porosity, high-quality data could be obtained where the chemical influences on the surface are clearly apparent and qualitatively consistent with theories of grain (i.e., Stern layer) polarization controlled by electrostatic surface sorption processes (i.e., triple layer theory). Quantitative fitting of the results by existing process-based polarization models (e.g., Leroy et al., 2008) has been less successful, however, due to what we have attributed to differences between existing models developed for spherical grains versus the actual geometry associated with the nano-pores in the silica gel, though other polarization processes, e.g., proton hopping along the surface (Skold et al., 2013), may also be a contributing factor. As an alternative model-independent approach to confirming the link between surface sorption and SIP we initiated a study that will continue (unfunded) beyond the completion of this project to independently measure the accumulation of gamma emitting isotopes on the silica gel during the SIP monitoring experiments. Though our analyses of the project data are ongoing, our preliminary analyses are generally supportive of the grain (Stern layer) polarization theory of SIP. Experiments focused on evaluating the impact of physical modifications of the medium on polarization included etching and biotic and abiotic facilitated precipitation of carbonate and iron oxides to alter the roughness and electrical conductivity of the surfaces. These experiments were performed for both silica gel and glass beads, the latter of which lacked the interior porosity and high surface area of the silica gel. The results appear to be more nuanced that the chemical modifications of the system. In general, however, it was found that deposition of iron oxides and etching had relatively minimal or negative impacts on the polarization response of the medium, whereas carbonate coatings increased the polarization response. These results were generally consistent with changes in surface charge observed via AFM. Abiotic and biotic column flow through experiments demonstrated that precipitation of carbonate within the medium significantly impacted the real and imaginary conductivity over time in a manner generally consistent with the carbonate precipitation as observed from the batch grain coating experiments. Biotic effects were not observed to provide distinctly different signatures, but may have contributed to differences in the rate of changes observed with SIP. AFM was used in a variety of different ways to investigate the grain surfaces throughout the course of the proj

Ntarlagiannis, Dimitrios; Moysey, Stephen; Dean, Delphine

2013-11-14

168

Quantifying Microbe-Mineral Interactions Leading to Remotely Detectable Induced Polarization Signals (Final Project Report)  

SciTech Connect

The objective of this project was to investigate controls on induced polarization responses in porous media. The approach taken in the project was to compare electrical measurements made on mineral surfaces with atomic force microscopy (AFM) techniques to observations made at the column?scale using traditional spectral induced polarization measurements. In the project we evaluated a number of techniques for investigating the surface properties of materials, including the development of a new AFM measurement protocol that utilizes an external electric field to induce grain?scale polarizations that can be probed using a charged AFM tip. The experiments we performed focused on idealized systems (i.e., glass beads and silica gel) where we could obtain the high degree of control needed to understand how changes in the pore environment, which are determined by biogeochemical controls in the subsurface, affect mechanisms contributing to complex electrical conductivity, i.e., conduction and polarization, responses. The studies we performed can be classified into those affecting the chemical versus physical properties of the grain surface and pore space. Chemical alterations of the surface focused on evaluating how changes in pore fluid pH and ionic composition control surface conduction. These were performed as column flow through experiments where the pore fluid was exchanged in a column of silica gel. Given that silica gel has a high surface area due to internal grain porosity, high?quality data could be obtained where the chemical influences on the surface are clearly apparent and qualitatively consistent with theories of grain (i.e., Stern layer) polarization controlled by electrostatic surface sorption processes (i.e., triple layer theory). Quantitative fitting of the results by existing process?based polarization models (e.g., Leroy et al., 2008) has been less successful, however, due to what we have attributed to differences between existing models developed for spherical grains versus the actual geometry associated with the nano?pores in the silica gel, though other polarization processes, e.g., proton hopping along the surface (Skold et al., 2013), may also be a contributing factor. As an alternative model?independent approach to confirming the link between surface sorption and SIP we initiated a study that will continue (unfunded) beyond the completion of this project to independently measure the accumulation of gamma emitting isotopes on the silica gel during the SIP monitoring experiments. Though our analyses of the project data are ongoing, our preliminary analyses are generally supportive of the grain (Stern layer) polarization theory of SIP. Experiments focused on evaluating the impact of physical modifications of the medium on polarization included etching and biotic and abiotic facilitated precipitation of carbonate and iron oxides to alter the roughness and electrical conductivity of the surfaces. These experiments were performed for both silica gel and glass beads, the latter of which lacked the interior porosity and high surface area of the silica gel. The results appear to be more nuanced that the chemical modifications of the system. In general, however, it was found that deposition of iron oxides and etching had relatively minimal or negative impacts on the polarization response of the medium, whereas carbonate coatings increased the polarization response. These results were generally consistent with changes in surface charge observed via AFM. Abiotic and biotic column flow through experiments demonstrated that precipitation of carbonate within the medium significantly impacted the real and imaginary conductivity over time in a manner generally consistent with the carbonate precipitation as observed from the batch grain coating experiments. Biotic effects were not observed to provide distinctly different signatures, but may have contributed to differences in the rate of changes observed with SIP. AFM was used in a variety of different ways to investigate the grain surfaces throughout the course

Moysey, Stephen [Clemson University] [Clemson University; Dean, Delphine [Clemson University] [Clemson University; Dimitrios, Ntarlagiannis [Rutgers University] [Rutgers University

2013-11-13

169

Reorientation-induced spectral diffusion in vibrational sum-frequency-generation spectroscopy.  

PubMed

There is a growing appreciation that dynamic processes play an important role in determining the line shape in surface-selective, nonlinear spectroscopies such as vibrational sum-frequency-generation (VSFG). Here we analyze the influence that reorientation can have on VSFG spectra when the vibrational transition frequency is a function of orientation. Under these circumstances, reorientation-induced spectral diffusion (RISD) causes the underlying spectral line shape to become time dependent. Unlike previously reported mechanisms through which reorientation can contribute to the VSFG signal, RISD influences the line shape regardless of the degree of polarization of the Raman transition that is probed. We assess the impact of RISD on VSFG spectra using a model system of liquid acetonitrile at a silica interface. Comparison of delay-time-dependent VSFG spectra with simulations that employ static line shapes suggests that RISD contributes substantially to the spectra, particularly at delay times that are comparable to or greater than the probe pulse duration. The observed behavior is in qualitative agreement with a two-state RISD model that uses orientational distributions determined from previous molecular dynamics simulations. PMID:24088038

Rivera, Christopher A; Souna, Amanda J; Bender, John S; Manfred, Katherine; Fourkas, John T

2013-12-12

170

Black hole stereotyping: Induced gravito-static polarization  

E-print Network

We discuss the black hole effective action and define its static subsector. We determine the induced gravito-static polarization constants (electric Love numbers) of static black holes (Schwarzschild) in an arbitrary dimension, namely the induced mass multipole as a result of an external gravitational field. We demonstrate that in 4d these constants vanish thereby settling a disagreement in the literature. Yet in higher dimensions these constants are non-vanishing, thereby disproving (at least in d>4) speculations that black holes have no effective couplings beyond the point particle action. In particular, when l/(d-3) is half integral these constants demonstrate a (classical) renormalization flow consistent with the divergences of the effective field theory. In some other cases the constants are negative indicating a novel non-spherical instability. The theory of hypergeometric functions plays a central role.

Barak Kol; Michael Smolkin

2011-10-17

171

Electromagnetic fields induced by a cuboidal inclusion with uniform spontaneous polarization and magnetization  

E-print Network

Electromagnetic fields induced by a cuboidal inclusion with uniform spontaneous polarization for the electromagnetic fields induced by a cuboidal inclusion with uniform spontaneous polarization and magnetization are employed to obtain the solution, with the results for the induced electric and magnetic potentials as well

Pan, Ernie

172

Ion-induced nucleation in polar one-component fluids Hikaru Kitamuraa  

E-print Network

Ion-induced nucleation in polar one-component fluids Hikaru Kitamuraa and Akira Onuki Department-Landau theory of ion-induced nucleation in polar one-component flu- ids in a gas phase. It will be based on our; published online 27 September 2005 We present a Ginzburg-Landau theory of ion-induced nucleation in a gas

173

Electric Field-Induced Polarization of Charged Cell Surface Proteins Does Not  

E-print Network

Electric Field-Induced Polarization of Charged Cell Surface Proteins Does Not Determine or speed of motility. Thus, our results demonstrate that electric field-induced polarization of charged, Columbia University, New York, New York Galvanotaxis, that is, migration induced by DC electric fields

Tong, Liang

174

Role of methyl-induced polarization in ion binding  

PubMed Central

The chemical property of methyl groups that renders them indispensable to biomolecules is their hydrophobicity. Quantum mechanical studies undertaken here to understand the effect of point substitutions on potassium (K-) channels illustrate quantitatively how methyl-induced polarization also contributes to biomolecular function. K- channels regulate transmembrane salt concentration gradients by transporting K+ ions selectively. One of the K+ binding sites in the channel’s selectivity filter, the S4 site, also binds Ba2+ ions, which blocks K+ transport. This inhibitory property of Ba2+ ions has been vital in understanding K-channel mechanism. In most K-channels, the S4 site is composed of four threonine amino acids. The K channels that carry serine instead of threonine are significantly less susceptible to Ba2+ block and have reduced stabilities. We find that these differences can be explained by the lower polarizability of serine compared with threonine, because serine carries one less branched methyl group than threonine. A T?S substitution in the S4 site reduces its polarizability, which, in turn, reduces ion binding by several kilocalories per mole. Although the loss in binding affinity is high for Ba2+, the loss in K+ binding affinity is also significant thermodynamically, which reduces channel stability. These results highlight, in general, how biomolecular function can rely on the polarization induced by methyl groups, especially those that are proximal to charged moieties, including ions, titratable amino acids, sulfates, phosphates, and nucleotides. PMID:23878238

Rossi, Mariana; Tkatchenko, Alexandre; Rempe, Susan B.; Varma, Sameer

2013-01-01

175

Spectral and photometric studies of the polar USNO-A2.0 0825-18396733  

NASA Astrophysics Data System (ADS)

Results of photometric and spectral studies of the new magnetic cataclysmic variable (polar) USNO-A2.0 0825-18396733 are presented. Photometric data in the B, V, and R c filters show that this object exhibits a red excess of R c - V = 1 m . A red continuum with superposed strong single-peaked Balmer emission lines and HeII ?4686 Å emission, weak lines of neutral helium, and lines of heavy elements are observed in the object's spectra. Doppler maps constructed using the hydrogen and ionized-helium lines indicate that these lines form near the inner Lagrangian point, and that their formation is associated with an accretion stream. The spectra and radial-velocity curves indicate the eclipse of the white dwarf in the system to be partial. Radial-velocity curves derived for emission lines are used to estimate the component masses. The mass of the white dwarf is estimated to be 0.71-0.78 M ?, and the mass of the red dwarf to be 0.18-0.20 M ?.

Gabdeev, M. M.; Borisov, N. V.; Shimansky, V. V.; Spiridonova, O. I.

2015-03-01

176

Tomographic and spectral views on the lifecycle of polar mesospheric clouds from Odin/OSIRIS  

NASA Astrophysics Data System (ADS)

Vertical and horizontal structures of Polar Mesospheric Clouds (PMC) have been recovered by tomographic retrieval from the OSIRIS instrument aboard the Odin satellite. The tomographic algorithm has been used to return local scattering coefficients at seven wavelengths in the ultraviolet. This spectral information is used to retrieve PMC particle sizes, number density, and ice mass density. While substantial horizontal variations are found, local vertical structures are overall consistent with the idea of a growth-sedimentation process leading to a visible cloud. Large numbers of small particles are present near the top of the observed cloud layer. Toward lower altitudes, particle sizes increase while particle number densities decrease. A close relationship is found between the distribution of local PMC scattering coefficient and ice mass density. The bottom of the cloud often features large particles with mode radii exceeding 70 nm that rain out of the cloud before sublimating. The number density of these large particles is small, and they do not contribute significantly to the overall cloud brightness. As a consequence, the presence of these large particles can be difficult to identify for remote sensing techniques that integrate over the entire cloud column. When it comes to deriving absolute values of particle mode radius and number density, there is a strong sensitivity to assumptions on the mathematical form of the particle size distribution. We see a continued strong need to resolve this issue by co-analysis of various remote sensing techniques and observation geometries.

Hultgren, Kristoffer; Gumbel, Jörg

2014-12-01

177

Disk instability and the spectral evolution of the 1992 outburst of the intermediate polar GK Persei  

NASA Technical Reports Server (NTRS)

The disk instability model can explain the previous history of dwarf-nova-like outbursts in the intermediate polar GK Per, which occur about once every three years. Disk models that reproduce the recurrence time and outburst light curves suggest that GK Per has a large effective inner disk radius (approx. 30-40 white dwarf radii) truncated by a strong magnetic field (10(exp 7) G). In this context, the effective radius is that of the portion of the disk that participates in the disk thermal instability. The radius derived is larger than the corotation radius, which must be an upper limit on the true dynamical inner radius of the disk. Disk instability models with this large effective inner radius predict that the ultraviolet continuum should be rather flat. Here we compare the predictions of the disk instability model to IUE observations of the 1981 outburst and to IUE and ROSAT observations of the recent 1992 outburst of GK Per. The model disk continuum spectral evolution is consistent with the observed UV and optical spectra, especially at maximum and in the early decay phase of the outburst. The consistency of the model with the observed UV spectra suggests that the effective inner radius of the disk is almost constant, independent of mass accretion rate, and that whatever structure lies between the effective inner radius and the corotation radius neither participates in the disk instability nor radiates substantially in the UV. The related physics of the inner disk region will be briefly discussed.

Kim, S.-W.; Wheeler, J. C.; Bruhweiler, F. C.; Fitzurka, M.; Beuermann, K.; Reinsch, K.; Mineshige, S.

1994-01-01

178

N-polar III-nitride quantum well light-emitting diodes with polarization-induced doping  

SciTech Connect

Nitrogen-polar III-nitride heterostructures present unexplored advantages over Ga(metal)-polar crystals for optoelectronic devices. This work reports N-polar III-nitride quantum-well ultraviolet light-emitting diodes grown by plasma-assisted molecular beam epitaxy that integrate polarization-induced p-type doping by compositional grading from GaN to AlGaN along N-face. The graded AlGaN layer simultaneously acts as an electron blocking layer while facilitating smooth injection of holes into the active region, while the built-in electric field in the barriers improves carrier injection into quantum wells. The enhanced doping, carrier injection, and light extraction indicate that N-polar structures have the potential to exceed the performance of metal-polar ultraviolet light-emitting diodes.

Verma, Jai; Simon, John; Protasenko, Vladimir; Kosel, Thomas; Xing, Huili Grace; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

2011-10-24

179

Gravitational Wave Induced Large-scale Polarization of \\\\Cosmic Microwave Background Radiation  

E-print Network

We discuss the contribution of gravitational wave to the cosmic microwave background radiation (CMBR) anisotropy and polarization. It is found that the large-scale polarization of CMBR is less than 1\\% for a standard recombination universe. The effect of matter reionization will enhance the CMBR polarization to a 10\\% level. We have computed the CMBR polarization for two extreme cases (not absolutely ruled out) and found that further enhancement of the ratio is possible. We conclude that measuring the polarization of CMBR on large-angular scales can probe the ionization history of the early universe, set constraints on baryon density and the spectral index of the gravitational waves.

Ka Lok Ng; Kin-Wang Ng

1994-06-30

180

Spectral binning for mitigation of polarization mode dispersion artifacts in catheter-based optical frequency domain imaging  

PubMed Central

Polarization mode dispersion (PMD) has been recognized as a significant barrier to sensitive and reproducible birefringence measurements with fiber-based, polarization-sensitive optical coherence tomography systems. Here, we present a signal processing strategy that reconstructs the local retardation robustly in the presence of system PMD. The algorithm uses a spectral binning approach to limit the detrimental impact of system PMD and benefits from the final averaging of the PMD-corrected retardation vectors of the spectral bins. The algorithm was validated with numerical simulations and experimental measurements of a rubber phantom. When applied to the imaging of human cadaveric coronary arteries, the algorithm was found to yield a substantial improvement in the reconstructed birefringence maps. PMID:23938487

Villiger, Martin; Zhang, Ellen Ziyi; Nadkarni, Seemantini K.; Oh, Wang-Yuhl; Vakoc, Benjamin J.; Bouma, Brett E.

2013-01-01

181

Cytoskeletal tension induces the polarized architecture of the nucleus.  

PubMed

The nuclear lamina is a thin filamentous meshwork that provides mechanical support to the nucleus and regulates essential cellular processes such as DNA replication, chromatin organization, cell division, and differentiation. Isolated horizontal imaging using fluorescence and electron microscopy has long suggested that the nuclear lamina is composed of structurally different A-type and B-type lamin proteins and nuclear lamin-associated membrane proteins that together form a thin layer that is spatially isotropic with no apparent difference in molecular content or density between the top and bottom of the nucleus. Chromosomes are condensed differently along the radial direction from the periphery of the nucleus to the nuclear center; therefore, chromatin accessibility for gene expression is different along the nuclear radius. However, 3D confocal reconstruction reveals instead that major lamin protein lamin A/C forms an apically polarized Frisbee-like dome structure in the nucleus of adherent cells. Here we show that both A-type lamins and transcriptionally active chromatins are vertically polarized by the tension exercised by the perinuclear actin cap (or actin cap) that is composed of highly contractile actomyosin fibers organized at the apical surface of the nucleus. Mechanical coupling between actin cap and lamina through LINC (linkers of nucleoskeleton and cytoskeleton) protein complexes induces an apical distribution of transcription-active subnucleolar compartments and epigenetic markers of transcription-active genes. This study reveals that intranuclear structures, such as nuclear lamina and chromosomal architecture, are apically polarized through the extranuclear perinuclear actin cap in a wide range of somatic adherent cells. PMID:25701041

Kim, Dong-Hwee; Wirtz, Denis

2015-04-01

182

Disorder-induced spin polarization in restricted geometries E. Eisenberg and R. Berkovits  

E-print Network

Disorder-induced spin polarization in restricted geometries E. Eisenberg and R. Berkovits disorder enhances the spin polarization of the system. The tendency of disorder to enhance magnetism in the ground state may be relevant to recent experimental observations of spin polarized ground states

Eisenberg, Eli

183

Sudden Death of Entanglement induced by Polarization Mode Dispersion Cristian Antonelli,1  

E-print Network

Sudden Death of Entanglement induced by Polarization Mode Dispersion Cristian Antonelli,1 Mark study the decoherence of polarization-entangled photon pairs subject to the effects of polariza- tion mode dispersion, the chief polarization decoherence mechanism in optical fibers. We show that fiber

Fisher, Kathleen

184

Imaging the anterior eye segment by polarization-sensitive spectral-domain and swept-source optical coherence tomography  

NASA Astrophysics Data System (ADS)

Polarization-sensitive optical coherence tomography (PS-OCT) has been developed to measure the birefringent properties of the human eye. In the retina, retinal nerve fiber layer and retinal pigment epitherial layer have the characteristic birefringent properties. 1.2 In addition to such normal tissue, abnormal fibrous tissue of the retina can be detected by PS-OCT. 3 In the anterior segment, the cornea is a birefringent tissue due to the multi-layered fibril structure. 4 The sclera and tendon also have the birefringence and the contrast of these structures can be enhanced by PS-OCT. 5 These studies have been used time-domain or spectral-domain PS-OCT. Recently, swept-source OCT (SS-OCT) has been applied for anterior eye segment imaging. 6 At the 1.3 um wavelength, SS-OCT is more promising than spectral-domain OCT, because the available camera for the spectrometer is limited. Three-dimensional imaging of the anterior segment is possible owing to the high penetration, high acquisition speed and high sensitivity. We have developed a new system of SS-OCT with polarization sensitivity. In this study, we measure the birefringent properties of anterior eye segment by polarization-sensitive spectral-domain OCT (PS-SD-OCT) at 840 nm and polarizationsensitive swept-source OCT (PS-SS-OCT) at 1.3 um, and evaluated the possibilities for clinical application.

Miura, Masahiro; Yamanari, Masahiro; Yatagai, Toyohiko; Yasuno, Yoshiaki

2008-02-01

185

Geometrically induced electric polarization in conical topological insulators  

E-print Network

We study the topological magnetoelectric effect on a conical topological insulator when a point charge $q$ is near the cone apex. The Hall current induced on the cone surface and the image charge configuration are determined. We also study a kind of gravitational Aharonov-Bohm effect in this geometry and realize a phase diference betwen the components of the wavefunctions (spinors) upon closed parallel transport around the (singular) cone tip. Concretely, a net current flowing towards cone apex (or botton) shows up, yielding electric polarization of the conical topological insulator. Such an effect may be detected, for instance, by means of the net accumulated Hall charge near the apex. Once it depends only on the geometry of the material (essetially, the cone apperture angle) this may be faced as a microscopic scale realization of (2+1)-dimensional Einstein gravity.

Jakson M. Fonseca; Winder A. Moura-Melo; Afranio R. Pereira

2011-11-29

186

A nanoparticle catalyst for heterogeneous phase para-hydrogen-induced polarization in water.  

PubMed

Para-hydrogen-induced polarization (PHIP) is a technique capable of producing spin polarization at a magnitude far greater than state-of-the-art magnets. A significant application of PHIP is to generate contrast agents for biomedical imaging. Clinically viable and effective contrast agents not only require high levels of polarization but heterogeneous catalysts that can be used in water to eliminate the toxicity impact. Herein, we demonstrate the use of Pt?nanoparticles capped with glutathione to induce heterogeneous PHIP in water. The ligand-inhibited surface diffusion on the nanoparticles resulted in a (1) H?polarization of P=0.25?% for hydroxyethyl propionate, a known contrast agent for magnetic resonance angiography. Transferring the (1) H?polarization to a (13) C?nucleus using a para-hydrogen polarizer yielded a polarization of 0.013?%. The nuclear-spin polarizations achieved in these experiments are the first reported to date involving heterogeneous reactions in water. PMID:25565403

Glöggler, Stefan; Grunfeld, Alexander M; Ertas, Yavuz N; McCormick, Jeffrey; Wagner, Shawn; Schleker, P Philipp M; Bouchard, Louis-S

2015-02-16

187

Optical feedback induces polarization mode hopping in vertical-cavity surface-emitting lasers  

Microsoft Academic Search

Vertical-cavity surface-emitting lasers subjected to weak polarization-insensitive optical feedback are studied experimentally and theoretically. We find that the feedback induces random anticorrelated hopping between the two orthogonal linearly polarized modes. This polarization mode hopping is accompanied by rapid anticorrelated oscillations in the linearly polarized intensities at the external-cavity frequency. The study of a simple stochastic delay differential equation suggests that

M. Sciamanna; K. Panajotov; H. Thienpont; I. Veretennicoff; P. Mégret; M. Blondel

2003-01-01

188

A Set of Analytical Formulae to Model Deglaciation-Induced Polar Wander  

E-print Network

A Set of Analytical Formulae to Model Deglaciation- Induced Polar Wander W. Keller Institute of Technology, Perth, Australia Abstract. Traditionally, deglaciation-induced po- lar wander changes the solution of convolution integrals. As being a central aspect of polar wander modelling we also revisit

Stuttgart, Universität

189

Ion induced electronic excitations in a spin-polarized electron gas  

E-print Network

Ion induced electronic excitations in a spin-polarized electron gas M. Alducin a R. D#19;#16;ez Mui the stopping power of a H atom and the number of electrons it excites, when it moves slowly in a spin-polarized electron gas. The potential induced by the projectile in which the medium electrons scatter o#11

Muiño, Ricardo Díez

190

ccsd00000796 Electric-eld induced capillary interaction of charged particles at a polar interface  

E-print Network

induced capillary interaction of charged particles at a polar interface. The algebraic tailsccsd­00000796 (version 1) : 28 Oct 2003 Electric-#12;eld induced capillary interaction of charged particles at a polar interface Lionel Foret and Alois Wurger CPMOH #3; , Universit#19;e Bordeaux 1, 351

191

Dim-Red-Light-Induced Increase in Polar Auxin Transport in Cucumber Seedlings1  

E-print Network

Dim-Red-Light-Induced Increase in Polar Auxin Transport in Cucumber Seedlings1 I. Development and characterized a system to analyze light effects on auxin transport independent of photosynthetic effects. Polar transport. This light- induced change probably manifests itself by alteration of function of the auxin

Jones, Alan M.

192

Induced Nucleon Polarization and Meson-Exchange Currents in (e,e'p) Reactions  

E-print Network

Nucleon recoil polarization observables in $(e,e'\\vec{p})$ reactions are investigated using a semi-relativistic distorted-wave model which includes one- and two-body currents with relativistic corrections. Results for the induced polarization asymmetry are shown for closed-shell nuclei and a comparison with available experimental data for $^{12}$C is provided. A careful analysis of meson exchange currents shows that they may affect significantly the induced polarization for high missing momentum.

F. Kazemi Tabatabaei; J. E. Amaro; J. A. Caballero

2004-05-11

193

Waveguide-induced inhomogeneous spectral broadening of stimulated Brillouin scattering in optical fiber  

Microsoft Academic Search

We provide direct experimental evidence of waveguide-induced inhomogeneous spectral broadening of stimulated Brillouin scattering (SBS) in optical fiber. It is shown that the SBS spectral width and gain depend on the numerical aperture for both single-mode and multimode fibers, the functional dependencies of which are in good agreement with our model description of the phenomenon.

Valeri I. Kovalev; Robert G. Harrison

2002-01-01

194

Light-induced scattering and energy transfer between orthogonally-polarized waves  

E-print Network

We present a detailed experimental investigation on polarization-isotropic and polarization-anisotropic holographic scattering in lithium niobate crystal doped with iron when recording parasitic gratings with an ordinary polarized pump beam. The kinetics of both types of scattering during the whole process of recording is studied. Holographic scattering is presented as a simple technique to monitor the energy transfer between beams of different polarization. Moreover, the spectral and the angular dependence of the transmitted intensity of the crystal during the reconstruction of the auto-generated parasitic gratings are measured.

M. A. Ellabban

2008-01-16

195

Comment on 'About an information theoretical spectral line shape proposed for the collision-induced spectroscopies'  

NASA Astrophysics Data System (ADS)

Information theory gives a good representation of collision-induced absorption spectral line shapes over the experimental frequency range. We answer criticisms put forward by Brown, Frommhold and Birnbaum [1].

Joslin, C. G.; Gray, C. G.; Sullivan, D. E.

196

Flow induced vibration of a cantilever column jet: a spectral analysis  

E-print Network

FLON INDUCED VIBRATION OF A CANTILEVER COLUMN JET ? A SPECTRAL ANALYSIS A Thesis by ROY BRYANT SHILLING III Submitted to the Graduate College of Texas A8M University ir, partial fulfillment of the requirement for the degree of MASTER... OF SCIENCE May 1978 Major Subject: Ocean Engineering FLOW INDUCED VIBRATION OF A CANTILEVER COLUMN JET - A SPECTRAL ANALYSIS A Thesis by ROY BRYANT SHILLING III Approved as to style and content by: (Chairman of Committee) (Head of Department) ember...

Shilling, Roy Bryant

1978-01-01

197

Induced Growth of Asymmetric Nanocantilever Arrays on Polar Surfaces Z. L. Wang,1,* X.Y. Kong,1  

E-print Network

Induced Growth of Asymmetric Nanocantilever Arrays on Polar Surfaces Z. L. Wang,1,* X.Y. Kong,1 show that the surface polarity can induce asymmetric growth on the two opposite surfaces. Zinc oxide-terminated ZnO (0001) polar surface is chemically active and the oxygen- terminated 0001 polar surface is inert

Wang, Zhong L.

198

Polarized Parton Distribution in Neutrino Induced Heavy Flavor Production  

E-print Network

In order to examine polarized strange quark distribution, semi-inclusive $D/\\Dbar$ production in neutrino deep inelastic scattering is studied including ${\\cal O}(\\alpha_s)$ corrections. Cross section and spin asymmetry are calculated by using various parametrizations of polarized parton distribution functions. It is found that $\\Dbar$ production is promising to directly extract the polarized strange sea.

Kazutaka Sudoh

2002-12-05

199

Metamaterial polarization spectral filter: Isolated transmission line at any prescribed wavelength  

E-print Network

the isoindex point, where birefringence is substantial, two orthogonally polarized waves, the "ordinary" wave with re- fractive index no and "extraordinary" wave with ne, are good eigenstates of the crystal crossed polarizers will transmit light. Torsional stress, magnetic field, or natural optical activ- ity

Zheludev, Nikolay

200

Effects of polarization on laser-induced electron-ion recombination  

SciTech Connect

The polarization dependence of laser-induced radiative recombination (LIR) to D{sup +} ions was investigated in the electron cooler of the CRYRING storage ring. The LIR gain as a function of wavelength into n = 3 principal quantum states of deuterium was measured at laser beam polarization angles of 0 deg. and 90 deg. with respect to the direction of the motional electric field in the interaction region. For the case of the polarization vector parallel to the external field, there is a double-peak structure in the gain curve that indicates a polarization effect in the LIR process. The two polarization directions also reveal a different width for the respective gain curves, giving additional evidence for the polarization effect, clearly seen by the behavior of a defined polarization parameter. The obtained polarization effect indicates a high sensitivity in recombination processes to external fields.

Mohamed, T.; Fogle, M.; Madzunkov, S.; Schuch, R. [Department of Physics, Atomic Physics, Stockholm University, S-106 91 Stockholm (Sweden); Andler, G. [Manne Siegbahn Laboratory, Stockholm University, S-10405 Stockholm (Sweden); Justiniano, E. [Department of Physics, East Carolina University, Greenville, North Carolina 27858 (United States)

2011-03-15

201

Magnetospheric Birefringence Induces Unique Polarization Signatures in Neutron-Star Spectra  

E-print Network

We study the propagation of polarization light through the magnetosphere of neutron stars. At intermediate frequencies (the optical through the infrared), both the birefringence induced by the plasma and by quantumelectrodynamics influence the observation polarization of radiation from the surface of the neutron star. Because these two processes compete in this regime, we find that polarization observations can constrain the properties of the neutron-star magnetosphere, specifically the total charge density. We calculate both the phase-resolved and the phase-averaged polarization signatures induced by magnetospheric birefringence.

R. M. Shannon; Jeremy S. Heyl

2006-02-18

202

Polarization manipulation based on electromagnetically induced transparency-like (EIT-like) effect.  

PubMed

We proposed, designed and fabricated a high transparency of metasurface-based polarization controller at microwave frequencies, which consists of orthogonal two pairs of cut wires. The high transmission and the strong dispersion properties governed by electromagnetically induced transparency-like (EIT-like) effects for both incident polarizations make our device efficiently manipulating the polarization of EM waves. In particular, the proposed polarization device is ultrathin (~0.017?), as opposed to bulky polarization devices. Microwave experiments are performed to successfully demonstrate our ideas, and measured results are in reasonable agreement with numerical simulations. PMID:24514804

Zhu, Lei; Meng, Fan-Yi; Dong, Liang; Fu, Jia-Hui; Zhang, Fang; Wu, Qun

2013-12-30

203

Basic program "IPFLTR" for induced polarization data reduction and filtering  

USGS Publications Warehouse

The recently developed induced polarization (IP) mapping technique can be successfully applied to IP dipole-dipole data and includes three types of filters that can be applied to IP pseudosections that have IP anomalies caused by different types of sources. The technique yields a single output value per station; this value reflects all levels of the pseudosection and is suitable for contouring in plan view. It also provides a quantitative picture of IP anomalies in their background or regional settings. In the 'IPFLTR' program, the application of the three types of IP filters to the IP pseudosection data was programmed in BASIC. The program allows the user to reduce IP field data and to produce IP pseudosections. It includes three filter subprograms, which calculate output data from each filter. The filtered data include a single reading for each station along the pseudosection. These data can be presented as individual IP profiles, or several profiles can be contoured together to produce an IP map. The program can optionally provide simple or complex plots either of the filtered data or of any selected level in the pseudosection.

Sadek, Hamdy S.

1983-01-01

204

Parahydrogen-induced polarization in heterogeneous catalytic processes.  

PubMed

Parahydrogen-induced polarization of nuclear spins provides enhancements of NMR signals for various nuclei of up to four to five orders of magnitude in magnetic fields of modern NMR spectrometers and even higher enhancements in low and ultra-low magnetic fields. It is based on the use of parahydrogen in catalytic hydrogenation reactions which, upon pairwise addition of the two H atoms of parahydrogen, can strongly enhance the NMR signals of reaction intermediates and products in solution. A recent advance in this field is the demonstration that PHIP can be observed not only in homogeneous hydrogenations but also in heterogeneous catalytic reactions. The use of heterogeneous catalysts for generating PHIP provides a number of significant advantages over the homogeneous processes, including the possibility to produce hyperpolarized gases, better control over the hydrogenation process, and the ease of separation of hyperpolarized fluids from the catalyst. The latter advantage is of paramount importance in light of the recent tendency toward utilization of hyperpolarized substances in in vivo spectroscopic and imaging applications of NMR. In addition, PHIP demonstrates the potential to become a useful tool for studying mechanisms of heterogeneous catalytic processes and for in situ studies of operating catalytic reactors. Here, the known examples of PHIP observations in heterogeneous reactions over immobilized transition metal complexes, supported metals, and some other types of heterogeneous catalysts are discussed and the applications of the technique for hypersensitive NMR imaging studies are presented. PMID:23097028

Kovtunov, Kirill V; Zhivonitko, Vladimir V; Skovpin, Ivan V; Barskiy, Danila A; Koptyug, Igor V

2013-01-01

205

General Theory for the Ferroelectric Polarization Induced by Spin-Spiral Order H. J. Xiang,1,* E. J. Kan,2  

E-print Network

General Theory for the Ferroelectric Polarization Induced by Spin-Spiral Order H. J. Xiang,1,* E. J polarization of triangular-lattice antiferromagnets induced by helical spin-spiral order is not explained a general theory for the ferroelectric polarization induced by spin-spiral order and then by evaluating

Gong, Xingao

206

PPARc Ligands Switched High Fat Diet-Induced Macrophage M2b Polarization toward M2a Thereby  

E-print Network

PPARc Ligands Switched High Fat Diet-Induced Macrophage M2b Polarization toward M2a Thereby the activation of alternative M2 macrophage polarization. Here, we evaluated the impact of high fat diet (HFD)-induced present a M2b polarization (TNF-ahigh , IL-10high , MR, Dectin-1). Interestingly, rosiglitazone induces

Boyer, Edmond

207

Method And Apparatus For Examining A Tissue Using The Spectral Wing Emission Therefrom Induced By Visible To Infrared Photoexcitation.  

DOEpatents

Method and an apparatus for examining a tissue using the spectral wing emission therefrom induced by visible to infrared photoexcitation. In one aspect, the method is used to characterize the condition of a tissue sample and comprises the steps of (a) photoexciting the tissue sample with substantially monochromatic light having a wavelength of at least 600 nm; and (b) using the resultant far red and near infrared spectral wing emission (SW) emitted from the tissue sample to characterize the condition of the tissue sample. In one embodiment, the substantially monochromatic photoexciting light is a continuous beam of light, and the resultant steady-state far red and near infrared SW emission from the tissue sample is used to characterize the condition of the tissue sample. In another embodiment, the substantially monochromatic photoexciting light is a light pulse, and the resultant time-resolved far red and near infrared SW emission emitted from the tissue sample is used to characterize the condition of the tissue sample. In still another embodiment, the substantially monochromatic photoexciting light is a polarized light pulse, and the parallel and perpendicular components of the resultant polarized time-resolved SW emission emitted from the tissue sample are used to characterize the condition of the tissue sample.

Alfano, Robert R. (3777 Independence Ave., Bronx, NY 10463); Demos, Stavros G. (3550 Pacific Ave., Apt. 304, Livermore, CA 94550); Zhang, Gang (3 Rieder Rd., Edison, NJ 08817)

2003-12-16

208

Acoustical phonon induced and polaron induced modulational amplification in polar semiconductors: a comparative study  

NASA Astrophysics Data System (ADS)

The paper aims to comparatively study the amplification and excitation characteristics of polaron induced and acoustical phonon induced modulators. Based on the hydrodynamic model, an analytical investigation of frequency modulational interaction is made. An explicit expression for the growth rate and threshold electric field for the onset of the acoustic phonon driven and polaron driven instability is presented and analyzed analytically. We have numerically investigated the dependence of the threshold electric field for different values of the external parameters of a typical polar semiconductor (InSb) and have given a numerical estimation of the growth rate. We also found that the amplification coefficient in polaron induced modulation enhances by a factor of 10 as compared to acoustical phonon induced modulation; though polaron induced modulational instability occurs at a lower threshold than acoustical phonon induced modulational instability. The cyclotron frequency can be used as a control parameter to reduce thresholds and improve growth rates. These results could be important for understanding and improving the performance of modulators. It is hoped that a low cost modulator using the n-InSb-CO2 system can be fabricated as the outcome of this work.

Agrawal, R.; Dubey, S.; Ghosh, S.

2013-10-01

209

Sudden Death of Entanglement induced by Polarization Mode Dispersion  

E-print Network

We study the decoherence of polarization-entangled photon pairs subject to the effects of polarization mode dispersion, the chief polarization decoherence mechanism in optical fibers. We show that fiber propagation reveals an intriguing interplay between the concepts of entanglement sudden death, decoherence-free sub-spaces and non-locality. We define the boundaries in which entanglement-based quantum communications protocols relying on fiber propagation can be applied.

Cristian Antonelli; Mark Shtaif; Misha Brodsky

2011-01-27

210

MAPPING THE LINEARLY POLARIZED SPECTRAL LINE EMISSION AROUND THE EVOLVED STAR IRC+10216  

SciTech Connect

We present spectro-polarimetric observations of several molecular lines obtained with the Submillimeter Array toward the carbon-rich asymptotic giant branch star IRC+10216. We have detected and mapped the linear polarization of the CO 3-2, SiS 19-18, and CS 7-6 lines. The polarization arises at a distance of {approx_equal} 450 AU from the star and is blueshifted with respect to the Stokes I. The SiS 19-18 polarization pattern appears to be consistent with a locally radial magnetic field configuration. However, the CO 3-2 and CS 7-6 line polarization suggests an overall complex magnetic field morphology within the envelope. This work demonstrates the feasibility of using spectro-polarimetric observations to carry out tomographic imaging of the magnetic field in circumstellar envelopes.

Girart, J. M. [Institut de Ciencies de l'Espai, (CSIC-IEEC), Campus UAB, Facultat de Ciencies, C5p 2, 08193 Bellaterra, Catalunya (Spain); Patel, N. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Vlemmings, W. H. T. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala (Sweden); Rao, Ramprasad, E-mail: girart@ice.cat [Submillimeter Array, Academia Sinica Institute of Astronomy and Astrophysics, 645 N. Aohoku Place, Hilo, HI 96720 (United States)

2012-05-20

211

Lambda and Lambda-bar Polarization in Lepton Induced Processes  

E-print Network

The study of the longitudinal polarization of Lambda and Lambda-bar hyperons produced in polarized deep inelastic scattering, neutrino scattering, and in Z0 decays allows to access the spin dynamics of the quark fragmentation process. Different phenomenological spin transfer mechanisms are considered and predictions for the Lambda and Lambda-bar longitudinal polarization in various processes using unpolarized and polarized targets are made. Current and future semi-inclusive deep inelastic scattering experiments will provide soon accurate enough data to study these phenomena and distinguish between various models for the spin transfer mechanisms.

A. Kotzinian; A. Bravar; D. von Harrach

1997-01-30

212

Spatial variability of oceanic phycoerythrin spectral types derived from airborne laser-induced fluorescence emissions.  

PubMed

We report spatial variability of oceanic phycoerythrin spectral types detected by means of a blue spectral shift in airborne laser-induced fluorescence emission. The blue shift of the phycoerythrobilin fluorescence is known from laboratory studies to be induced by phycourobilin chromophore substitution at phycoerythrobilin chromophore sites in some strains of phycoerythrin-containing marine cyanobacteria. The airborne 532-nm laser-induced phycoerythrin fluorescence of the upper oceanic volume showed distinct segregation of cyanobacterial chromophore types in a flight transect from coastal water to the Sargasso Sea in the western North Atlantic. High phycourobilin levels were restricted to the oceanic (oligotrophic) end of the flight transect, in agreement with historical ship findings. These remotely observed phycoerythrin spectral fluorescence shifts have the potential to permit rapid, wide-area studies of the spatial variability of spectrally distinct cyanobacteria, especially across interfacial regions of coastal and oceanic water masses. Airborne laser-induced phytoplankton spectral fluorescence observations also further the development of satellite algorithms for passive detection of phytoplankton pigments. Optical modifications to the NASA Airborne Oceanographic Lidar are briefly described that permitted observation of the fluorescence spectral shifts. PMID:18285931

Hoge, F E; Wright, C W; Kana, T M; Swift, R N; Yungel, J K

1998-07-20

213

Spatial variability of oceanic phycoerythrin spectral types derived from airborne laser-induced fluorescence emissions  

NASA Astrophysics Data System (ADS)

We report spatial variability of oceanic phycoerythrin spectral types detected by means of a blue spectral shift in airborne laser-induced fluorescence emission. The blue shift of the phycoerythrobilin fluorescence is known from laboratory studies to be induced by phycourobilin chromophore substitution at phycoerythrobilin chromophore sites in some strains of phycoerythrin-containing marine cyanobacteria. The airborne 532-nm laser-induced phycoerythrin fluorescence of the upper oceanic volume showed distinct segregation of cyanobacterial chromophore types in a flight transect from coastal water to the Sargasso Sea in the western North Atlantic. High phycourobilin levels were restricted to the oceanic (oligotrophic) end of the flight transect, in agreement with historical ship findings. These remotely observed phycoerythrin spectral fluorescence shifts have the potential to permit rapid, wide-area studies of the spatial variability of spectrally distinct cyanobacteria, especially across interfacial regions of coastal and oceanic water masses. Airborne laser-induced phytoplankton spectral fluorescence observations also further the development of satellite algorithms for passive detection of phytoplankton pigments. Optical modifications to the NASA Airborne Oceanographic Lidar are briefly described that permitted observation of the fluorescence spectral shifts.

Hoge, Frank E.; Wright, C. Wayne; Kana, Todd M.; Swift, Robert N.; Yungel, James K.

1998-07-01

214

Time-resolved spectral investigations of laser light induced microplasma  

NASA Astrophysics Data System (ADS)

The dynamical and spectral properties of an optical breakdown microplasma created by pulses of different lasers on surfaces of insulators (KCI), metals (Cu) and semiconductors (V 2O 5), have been investigated. Experiments were carried out in air and vacuum using different wavelengths (? = 0.694?m, type OGM-20,? = 1.06?m with a home-made laser based on neodymium glass crystal, and ? = 10.6?m, similarly home-made) and pulse durations (Q-switched and free-running regimes). To follow the integral, dynamical and spectral characteristics of the luminous spot of microplasma we have used fast cameras (SFR-2M, IMACON-HADLAND), a high speed spectral camera (AGAT-2) and a spectrograph (STE-1). It has been shown that the microplasma consists of two parts: fast front (peak) with ??100 ns and slow front (tail) with ??1?s durations. The detonation front speed is of the order of ?10 5 cm s -1 and follows the temporal dependence of to t0.4. It depends on the composition of the surrounding gas and its pressure and could be connected with quick evaporation of the material investigated (peak) and optical breakdown of the ambient gaseous atmosphere (tail). From the delay in appearance of different characteristic spectral lines of the target material and its gaseous surrounding we have shown that the evolution of the microplasma involves evaporation and ionization of the atoms of the parent material followed by optical breakdown due to the incident and absorbed laser light, together with microplasma expansion.

Nánai, L.; Hevesi, I.

1992-01-01

215

Polarization dependence of absorption and laser induced surface damage thresholds in wire grid polarizers  

Microsoft Academic Search

We report a theoretical and experimental study of the absorption of wire grid polarizers vs orientation and wavelength. Measurement of absorption and surface damage thresholds are in good agreement with the theory. In this paper we present a theoretical analysis of absorption of wire grid polarizers as a function of ori- entation and wavelength. We also report results of measurements

M. Mohebi; J. Q. Liang; M. J. Soileau

1989-01-01

216

A Signaling Network Induced by ?2 Integrin Controls the Polarization of Lytic Granulesin Cytotoxic Cells  

PubMed Central

Cytotoxic lymphocyte skill target cells by polarized release of the content of perforin-containing granules. In natural killer cells, the binding of ?2 integrin to its ligand ICAM-1 is sufficient to promote not only adhesion but also lytic granule polarization. This provided a unique opportunity to study polarization in the absence of degranulation, and ?2 integrin signaling independently of inside-out signals from other receptors. Using an unbiased proteomics approach we identified a signaling network centered on an integrin-linked kinase (ILK)–Pyk2–Paxillin core that was required for granule polarization. Downstream of ILK, the highly conserved Cdc42–Par6 signaling pathway that controls cell polarity was activated and required for granule polarization. These results delineate two connected signaling networks induced upon ?2 integrin engagement alone, which are integrated to control polarization of the microtubule organizing center and associated lytic granules toward the site of contact with target cells during cellular cytotoxicity. PMID:25292215

Zhang, Minggang; March, Michael E.; Lane, William S.; Long, Eric O.

2014-01-01

217

Charge trapping\\/detrapping induced lattice polarization\\/relaxation processes  

Microsoft Academic Search

The consequence of the coupling of a charged particle with a polarization field is the formation of a quasi particle called polaron. The degree of localization of the charge depends on the nature of this coupling. In this way, trapping at an atomic scale is described as resulting from the evolution of a coupling involving successively the electronic polarization field,

G. Blaise

1995-01-01

218

Metamaterial with polarization and direction insensitive resonant transmission response mimicking electromagnetically induced transparency  

E-print Network

Metamaterial with polarization and direction insensitive resonant transmission response mimicking electromagnetically induced transparency N. Papasimakis,1 Y. H. Fu,1,2 V. A. Fedotov,1,a S. L. Prosvirnin,3 D. P. Tsai, the resonant transmission frequency of which does not depend on the polarization and angle of incidence

Zheludev, Nikolay

219

Light-Induced Polar pH Changes in Leaves of Elodea canadensis1  

PubMed Central

The effect of an extracellular electron acceptor, ferricyanide, on the light-induced polar leaf pH changes of the submerged angiosperm Elodea canadensis in light and in darkness was determined. The rate of transmembrane ferricyanide reduction was stimulated by increased light intensity and was inhibited by inorganic carbon, indicating that changes in the redox state of the chloroplast were reflected at the plasma membrane. The addition of ferricyanide inhibited the light-induced polar leaf pH reaction. This effect could be balanced by increasing the light intensity. In the dark, the acidification induced by ferricyanide was not influenced by diethylstilbestrol at concentrations that completely inhibited the polar leaf pH changes. This indicates that the ferricyanide-induced H+ extrusion and the H+ transport during the polar reaction were mediated by different mechanisms. PMID:16667045

Elzenga, J. Theo M.; Prins, Hidde B. A.

1989-01-01

220

Multi-array borehole resistivity and induced polarization method with mathematical inversion of redundant data  

DOEpatents

Multiple arrays of electric or magnetic transmitters and receivers are used in a borehole geophysical procedure to obtain a multiplicity of redundant data suitable for processing into a resistivity or induced polarization model of a subsurface region of the earth.

Ward, Stanley H. (Salt Lake City, UT)

1989-01-01

221

Microtubule-Induced Pins\\/G?i Cortical Polarity in Drosophila Neuroblasts  

Microsoft Academic Search

SUMMARY Cortical polarity regulates cell division, mi- gration, and differentiation. Microtubules induce cortical polarity in yeast, but few ex- amples are known in metazoans. We show that astral microtubules, kinesin Khc-73, and Discs large (Dlg) induce cortical polari- zation of Pins\\/Ga ii nDrosophila neuro- blasts; this cortical domain is functional for generating spindle asymmetry, daughter- cell-size asymmetry, and distinct sibling

Sarah E. Siegrist; Chris Q. Doe

2005-01-01

222

Multiple-view spectrally resolved x-ray imaging observations of polar-direct-drive implosions on OMEGA  

NASA Astrophysics Data System (ADS)

We present spatially, temporally, and spectrally resolved narrow- and broad-band x-ray images of polar-direct-drive (PDD) implosions on OMEGA. These self-emission images were obtained during the deceleration phase and bang time using several multiple monochromatic x-ray imaging instruments fielded along two or three quasi-orthogonal lines-of-sight, including equatorial and polar views. The instruments recorded images based on K-shell lines from a titanium tracer located in the shell as well as continuum emission. These observations constitute the first such data obtained for PDD implosions. The image data show features attributed to laser imprinting and zero-order hydrodynamics. Equatorial-view images show a "double bun" structure that is consistent with synthetic images obtained from post-processing 2D and 3D radiation-hydrodynamic simulations of the experiment. Polar-view images show a pentagonal, petal pattern that correlates with the PDD laser illumination used on OMEGA, thus revealing a 3D aspect of PDD OMEGA implosions not previously observed. Differences are noted with respect to a PDD experiment performed at National Ignition Facility.

Mancini, R. C.; Johns, H. M.; Joshi, T.; Mayes, D.; Nagayama, T.; Hsu, S. C.; Baumgaertel, J. A.; Cobble, J.; Krasheninnikova, N. S.; Bradley, P. A.; Hakel, P.; Murphy, T. J.; Schmitt, M. J.; Shah, R. C.; Tregillis, I. L.; Wysocki, F. J.

2014-12-01

223

Polarization dependence of absorption and laser induced surface damage thresholds in wire grid polarizers.  

PubMed

We report a theoretical and experimental study of the absorption of wire grid polarizers vs orientation and wavelength. Measurement of absorption and surface damage thresholds are in good agreement with the theory. PMID:20555756

Mohebi, M; Liang, J Q; Soileau, M J

1989-09-01

224

Interaction induced deformation in momentum distribution of spin polarized nuclear matter  

E-print Network

Effects of spin polarization on the structure of symmetric nuclear matter and pure neutron matter are investigated. We show that the spin polarization induces a deformation of the Fermi spheres for nucleons with spin parallel and opposite to the polarization axes. This feature can be related to the structure of the one pion exchange contribution to a realistic nucleon-nucleon interaction. While the anisotropies in the momentum distribution lower the energy of the system by small amount, the associated variations of the single particle energies with the angle between the polarization axis and the particle momentum are significant.

T. Frick; H. Müther; A. Sedrakian

2002-03-19

225

Energy gap induced by the surface optical polaron in graphene on polar substrates  

NASA Astrophysics Data System (ADS)

The polaron effects are investigated in the presence of a magnetic field based on the carrier-surface optical phonon coupling induced by the polar substrates under the graphene. We find that the energy gap is opened in the zero-energy Landau level due to the polaron effect. The magnitude of energy gap is consistent with recent experimental measurements. Moreover, the gap can be tuned by choosing the polarization of substrates and controlling the distance between graphene and polar substrate. The results obtained provide a possible explanation for the origin of energy gap opening and highlight the bandgap engineering of graphene on polar substrates.

Wang, Zi-Wu; Liu, Lei; Li, Zhi-Qing

2015-03-01

226

Fly Photoreceptors. II. Spectral and Polarized Light Sensitivity in the Drone Fly Eristalis  

Microsoft Academic Search

Eristalis tenax, the honeybee mimic, has photoreceptors mainly with double peaks as in typical flies, but the peaks are near 350 and 450 nm. Other cell types with peaks at 350 or 450 or 520 nm were encountered but not commonly. Measurements of the polarization sensitivity lead to the conclusion, as in Calliphora, that where there are two visual pigments

G. A. Horridge; K. Mimura; Y. Tsukahara

1975-01-01

227

A power law power spectral density model of total electron content structure in the polar region  

Microsoft Academic Search

Measurements by the early warning radar at Thule, Greenland, together with GPS measurements from the Air Force Research Laboratory (AFRL) Ionospheric Measurement System (IMS) receiver, have been analyzed to develop a model for the structure of the total electron content (TEC) of the polar ionosphere. For the model the TEC measurements are related to the Wide Band Model (WBMOD), a

L. J. Nickisch

2004-01-01

228

Analysis of the spectral and angular response of the vegetated surface polarization for the purpose of  

E-print Network

. The surface polarization is well fitted by existing surface models which have two degrees of freedom Optical Society of America OCIS codes: 120.0280, 280.1100, 120.6660, 120.5410. 1. Introduction Aerosol Optical Society of America 1228 APPLIED OPTICS / Vol. 48, No. 6 / 20 February 2009 #12;2:2 m to evaluate

229

Polarization-induced Zener tunnel junctions in wide-band-gap heterostructures.  

PubMed

The large electronic polarization in III-V nitrides allows for novel physics not possible in other semiconductor families. In this work, interband Zener tunneling in wide-band-gap GaN heterojunctions is demonstrated by using polarization-induced electric fields. The resulting tunnel diodes are more conductive under reverse bias, which has applications for zero-bias rectification and mm-wave imaging. Since interband tunneling is traditionally prohibitive in wide-band-gap semiconductors, these polarization-induced structures and their variants can enable a number of devices such as multijunction solar cells that can operate under elevated temperatures and high fields. PMID:19659229

Simon, John; Zhang, Ze; Goodman, Kevin; Xing, Huili; Kosel, Thomas; Fay, Patrick; Jena, Debdeep

2009-07-10

230

Current-induced spin polarization in graphene due to Rashba spin-orbit interaction  

NASA Astrophysics Data System (ADS)

Spin polarization induced by an external electric field in graphene is considered theoretically in the linear-response regime. The graphene is assumed to be deposited on a substrate which leads to the spin-orbit interaction of Rashba type. The induced spin polarization is shown to be in the graphene plane and perpendicular to the electric field. However, orientation of the spin polarization becomes reversed when the Fermi level, the position of which can be controlled by an external gate voltage, crosses the Dirac points.

Dyrda?, A.; Barna?, J.; Dugaev, V. K.

2014-02-01

231

Polarization-induced pn diodes in wide-band-gap nanowires with ultraviolet electroluminescence.  

PubMed

Almost all electronic devices utilize a pn junction formed by random doping of donor and acceptor impurity atoms. We developed a fundamentally new type of pn junction not formed by impurity-doping, but rather by grading the composition of a semiconductor nanowire resulting in alternating p and n conducting regions due to polarization charge. By linearly grading AlGaN nanowires from 0% to 100% and back to 0% Al, we show the formation of a polarization-induced pn junction even in the absence of any impurity doping. Since electrons and holes are injected from AlN barriers into quantum disk active regions, graded nanowires allow deep ultraviolet LEDs across the AlGaN band-gap range with electroluminescence observed from 3.4 to 5 eV. Polarization-induced p-type conductivity in nanowires is shown to be possible even without supplemental acceptor doping, demonstrating the advantage of polarization engineering in nanowires compared with planar films and providing a strategy for improving conductivity in wide-band-gap semiconductors. As polarization charge is uniform within each unit cell, polarization-induced conductivity without impurity doping provides a solution to the problem of conductivity uniformity in nanowires and nanoelectronics and opens a new field of polarization engineering in nanostructures that may be applied to other polar semiconductors. PMID:22268600

Carnevale, Santino D; Kent, Thomas F; Phillips, Patrick J; Mills, Michael J; Rajan, Siddharth; Myers, Roberto C

2012-02-01

232

Circular Polarization Induced by Scintillation in a Magnetized Medium  

E-print Network

A new theory is presented for the development of circular polarization as radio waves propagate through the turbulent, birefringent interstellar medium. The fourth order moments of the wavefield are calculated and it is shown that unpolarized incident radiation develops a nonzero variance in circular polarization. A magnetized turbulent medium causes the Stokes parameters to scintillate in a non-identical manner. A specific model for this effect is developed for the case of density fluctuations in a uniform magnetic field.

J. -P. Macquart; D. B. Melrose

2000-06-30

233

Ultraviolet irradiation induced polarization restoration in electrically fatigued ferroelectric polymer films  

SciTech Connect

Polarization fatigue is a kind of phenomenon usually observed in most ferroelectric films, which severely degrades the electrical performance of ferroelectric devices. How to restore those degraded polarization as well as how to improve fatigue endurance has been attracting much attention. Here, we report the observation of ultraviolet (UV) irradiation induced polarization restoration in ferroelectric polymer films. Large numbers of experiments indicate that the simultaneous application of UV irradiation and DC bias voltage will result in polarization restoration, which is dependent on both electrical polarity of DC bias and the UV intensity. Repeated fatigue and restoration measurements are also conducted. Based on fatigue mechanism in ferroelectric polymer films, UV-induced restoration is discussed.

Fu Shaosong; Hu Jinghang; Zhu Guodong [Department of Materials Science, Fudan University, Shanghai 200433 (China); Yu Hao; Ding Shijin; Jiang Yulong [School of Microelectronics, Fudan University, Shanghai 200433 (China); Cheng Qian [Institute of Acoustics, Tongji University, Shanghai 200092 (China)

2013-03-21

234

Polar-surface dominated ZnO nanobelts and the electrostatic energy induced nanohelixes, nanosprings, and nanospirals  

E-print Network

#12;Polar-surface dominated ZnO nanobelts and the electrostatic energy induced nanohelixes for understanding piezoelectricity and polarization induced phenomena at nanoscale. © 2004 American Institute are dominated by the large polar surfaces. The nanobelts grow along the a axis, their large top/bottom surfaces

Wang, Zhong L.

235

Strain-Induced Polarization Rotation in Epitaxial (001) BiFeO3 Thin Films H. W. Jang,1  

E-print Network

Strain-Induced Polarization Rotation in Epitaxial (001) BiFeO3 Thin Films H. W. Jang,1 S. H. Baek,1 analysis reveals that a strain-induced polarization rotation mechanism is responsible for the large change measurement of the remanent polarization of high quality (001)-oriented epitaxial BiFeO3 thin films shows

Eom, Chang Beom

236

Reduction of polarization-induced artifacts in grating-based spectrometers.  

PubMed

An optical device that converts unpolarized light into a single polarization state is described. The device is based on a polarizing beam splitter that separates the two polarization directions. The beam splitter is combined with two pairs of equilateral prisms that are used to collimate the two beams in terms of both propagation and polarization directions. When it is used in combination with a blazed diffraction grating, this device is shown to effectively remove the polarization dependence of the first-order diffracted power. The device has an insertion loss of approximately 14% for purely s-polarized light. However, for unpolarized light incident upon the two gratings studied here, the increased throughput of the p-polarized component leads to an average relative gain in overall efficiency of 13%-19%, depending on the grating. In collimating the two polarization directions, the device may cause a reduction in spectral resolution for a rectangular entrance slit. As a result, the device is more likely to find use in spectrometers that have a circular aperture, such as that provided by an optical fiber. PMID:16237926

Kho, Kiang Wei; Stoddart, Paul R; Rosman, Gavan; Harris, Martin; Mazzolini, Alex

2005-10-10

237

POLARIZATION OF THE CHARGE-EXCHANGE X-RAYS INDUCED IN THE HELIOSPHERE  

SciTech Connect

We report results of a theoretical investigation of polarization of the X-ray emissions induced in charge-exchange collisions of fully stripped solar wind (SW) ions C{sup 6+} and O{sup 8+} with the heliospheric hydrogen atoms. The polarization of X-ray emissions has been computed for line-of-sight observations within the ecliptic plane as a function of SW ion velocities, including a range of velocities corresponding to the slow and fast SW, and coronal mass ejections. To determine the variability of polarization of heliospheric X-ray emissions, the polarization has been computed for solar minimum conditions with self-consistent parameters of the SW plasma and heliospheric gas and compared with the polarization calculated for an averaged solar activity. We predict the polarization of charge-exchange X-rays to be between 3% and 8%, depending on the line-of-sight geometry, SW ion velocity, and the selected emission lines.

Gacesa, M.; Kharchenko, V. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Mueller, H.-R. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Cote, R., E-mail: gacesa@phys.uconn.edu [Physics Department, University of Connecticut, 2152 Hillside Road, Storrs, CT 06269 (United States)

2011-05-10

238

Numerical analysis to four-wave mixing induced spectral broadening in high power fiber lasers  

NASA Astrophysics Data System (ADS)

For powers exceeding a threshold the spectral broadening in fiber amplifiers becomes a significant challenge for the development of high power narrow bandwidth fiber lasers. In this letter, we show that the spectral broadening can be partly caused by four-wave mixing(FWM) process in which the power of the central wavelength would transfer to the side ones. A practical FWM induced spectral broadening theory has been derived from the early works. A numerical model of fiber amplifier has been established and FWM process has been added to the model. During the simulation process, we find that when a 10 GHz, several watts narrow bandwidth laser is seeded into a few modes fiber laser amplifier, the FWM induced spectral broadening effect might continually increase the FWHM of the spectra of the continuum laser to 100 GHz within the amplification process to several hundred watts which has been convinced by our experiments. Some other results have also been analyzed in this paper to complete the four-wave mixing induced spectral broadening theory in fiber amplifiers.

Feng, Yujun; Wang, Xiaojun; Ke, Weiwei; Sun, Yinhong; Zhang, Kai; Ma, Yi; Li, Tenglong; Wang, Yanshan; Wu, Juan

2015-02-01

239

CMB-induced Cluster Polarization as a Cosmological Probe  

E-print Network

Scattering of the temperature anisotropy quadrupole by free electrons in galaxy clusters leads to a secondary polarization signal in the cosmic microwave background (CMB) fluctuations. At low redshifts, the temperature quadrupole contains a significant contribution from the integrated Sachs-Wolfe (ISW) effect associated with the growth of density fluctuations. Using polarization data from a sample of clusters over a wide range in redshift, one can statistically establish the presence of the ISW effect and determine its redshift evolution. Given the strong dependence of the ISW effect on the background cosmology, cluster polarization can eventually be used as a powerful probe of dark energy. As a further application, we also discuss how it might be used to understand the potential lack of power on large scales.

Daniel Baumann; Asantha Cooray

2003-04-23

240

Detection and calculation of reflected spectral shifts in fiber-Bragg gratings (FBG) in polarization maintaining optical fiber  

NASA Astrophysics Data System (ADS)

Fiber-Bragg Gratings (FBG) for Structural Health Monitoring (SHM) have been studied extensively as they offer electrically passive operation, EMI immunity, high sensitivity, and multiple multiplexing schemes, as compared to conventional electricity based strain sensors. FBG sensors written in Polarization Maintaining (PM) optical fiber offer an additional dimension of strain measurement simplifying sensor implementation within a structure. This simplification however, adds complexity to the detection of the sensor's optical response to its corresponding applied strain. We propose a method that calculates spectral shifts caused by axial and traversal strains for PM FBG sensors. The system isolates the orthogonal propagating optical waves incident to the optical interrogators. The post-processing algorithm determines the wavelength shifts, and compares to a predetermined baseline then correlates the shift magnitudes to a respective strain. This exercise validates the method of optical detection and shift calculation of multi-axis sensors as an automated, integrated system.

Quintana, Joel; Gonzalez, Virgilio

2014-04-01

241

Darkfield orthogonal polarized spectral imaging for studying endovascular laser-tissue interactions in vivo a preliminary study  

NASA Astrophysics Data System (ADS)

Due to the limited number of suitable intravital microscopy techniques, relatively little is known about the opto-thermal (endo)vascular responses to selective photothermolysis, used as a default treatment modality for superficial vascular anomalies such as port wine stains, telangiectasias, and hemangiomas. In this preliminary study we present a novel microscopy technique for studying (endo)vascular laser-tissue interactions in vivo, in which conventional orthogonal polarized spectral (OPS) imaging is combined with darkfield (DF) illumination. DFOPS imaging of rat mesenteric vasculature irradiated at increasing powers revealed the following (tissular) responses: formation of translucent aggregates, retrograde flow, gradual and immediate hemostasis, reinstatement of flow, vessel disappearance, and perivascular collagen damage. DFOPS imaging therefore constitutes a useful tool for examining (endo)vascular events following selective photothermolysis.

Heger, Michal; Beek, Johan F.; Stenback, Karin; Faber, Dirk J.; van Gemert, Martin J. C.; Ince, Can

2005-02-01

242

Effect of spin diffusion in the polarizer on current-induced magnetic switching  

NASA Astrophysics Data System (ADS)

Current-induced magnetic switching of a nanomagnet occurs due to the spin transfer torque exerted by current spin-polarized by another ferromagnet. Efficient switching is generally achieved by enhancing the polarizing properties of the latter. However, calculations show that switching is affected not only by the polarizing properties of the polarizer, but also by the electron diffusion in this layer [1,2]. To test the effects of spin diffusion in the polarizer on current-induced switching, we performed measurements of magnetic multilayer nanopillars with three different structures of the polarizing magnetic layer: a thick Co layer, a thin Co layer, and a bilayer consisting of a thin Co layer and a strongly spin-flipping FeMn alloy. In the pillars with a thick Co polarizer, the switching currents dramatically increase below 130 K, while the magnetoresistance exhibits a nonmonotonic dependence on temperature with a peak at 130 K. In contrast, the samples with a thin Co polarizer exhibit weak monotonic dependencies of switching and magnetoresistance on temperature. We discuss the implications of our results for our understanding of spin-dependent diffusion in magnetic multilayers. [1] A.A. Kovalev, A. Brataas, and G.E.W. Bauer, Phys. Rev. B 66, 224424 (2002). [2] Zhang, P.M. Levy, and A. Fert, Phys. Rev. Lett. 88, 236601 (2002).

Button, Scott; Urazhdin, Sergei

2009-03-01

243

Spectral analysis of seismic noise induced by rivers: A new tool to monitor spatiotemporal changes in  

E-print Network

Spectral analysis of seismic noise induced by rivers: A new tool to monitor spatiotemporal changes and deeply incised channel of the Trisuli River, a major trans-Himalayan river. The early summer increase the Trisuli River. Seasonal increase in ambient noise coincides with the strong monsoon rainfall and a period

Demouchy, Sylvie

244

MSX3 Switches Microglia Polarization and Protects from Inflammation-Induced Demyelination.  

PubMed

The major challenge for progressive multiple sclerosis therapy is the promotion of remyelination from inflammation-induced demyelination. A switch from an M1- to an M2-dominant polarization of microglia is critical in these repair processes. In this study, we identified the homeobox gene msh-like homeobox-3 (Msx3) as a new pivotal regulator for microglial polarization. MSX3 was induced during microglia M2 polarization and repressed in M1 cells. The expression of MSX3 in microglia was dynamically regulated during experimental autoimmune encephalomyelitis (EAE), which is an animal model of multiple sclerosis. The overexpression of MSX3 in microglia promoted M2 but impeded M1 polarization. Interrupting MSX3 expression in microglia accelerated inflammation-induced demyelination and neurodegeneration. The conditioned medium from MSX3-transduced microglia promoted oligodendrocyte progenitor survival, differentiation, and neurite outgrowth. The adoptive transfer of MSX3-transduced microglia suppressed EAE and facilitated remyelination within the murine CNS in EAE and the LPC model. Mechanically, chromatin immunoprecipitation assays also indicated that MSX3 directly regulated three key genes associated with microglia M2 polarization, including Pparg, Stat6, and Jak3. Importantly, we found that overexpression of MSX3 in human-derived microglia represents the M2 phenotype and ameliorated EAE after intraventricular injection. Our findings suggest a new homeobox protein-dependent mechanism for driving microglia M2 polarization and identify MSX3 as an attractive therapeutic approach for preventing inflammation-induced demyelination and promoting remyelination. PMID:25904788

Yu, Zhongwang; Sun, Dingya; Feng, Jifeng; Tan, Weixing; Fang, Xue; Zhao, Ming; Zhao, Xiaolin; Pu, Yingyan; Huang, Aijun; Xiang, Zhenghua; Cao, Li; He, Cheng

2015-04-22

245

A meteorological model for rain-induced cross polarization  

Microsoft Academic Search

After a brief summary of the existing theory on microwave attenuation and cross polarization by rain and of the supporting experimental evidence, the paper gives a physical explanation of raindrop canting. It is shown that vertical windgradients are a cause of canting. A model for the dependence of windspeed on height is then employed to calculate actual values of canting

GERT BRUSSAARD

1976-01-01

246

Continental lithospheric thickness and deglaciation induced true polar wander  

Microsoft Academic Search

Geophysical data are presented which strongly suggest a continental lithospheric thickness in excess of 250 km. The data are based on the polar motion record collected by the International Latitude Service since 1900. It is found that the dominant oscillatory signal produced by the 7 year beat between the 14 month Chandler wobble and the 12 month annual wobble is

W. R. Peltier; Patrick Wu

1983-01-01

247

Possible methane-induced polar warming in the early Eocene.  

PubMed

Reconstructions of early Eocene climate depict a world in which the polar environments support mammals and reptiles, deciduous forests, warm oceans and rare frost conditions. At the same time, tropical sea surface temperatures are interpreted to have been the same as or slightly cooler than present values. The question of how to warm polar regions of Earth without noticeably warming the tropics remains unresolved; increased amounts of greenhouse gases would be expected to warm all latitudes equally. Oceanic heat transport has been postulated as a mechanism for heating high latitudes, but it is difficult to explain the dynamics that would achieve this. Here we consider estimates of Eocene wetland areas and suggest that the flux of methane, an important greenhouse gas, may have been substantially greater during the Eocene than at present. Elevated methane concentrations would have enhanced early Eocene global warming, and also might specifically have prevented severe winter cooling of polar regions because of the potential of atmospheric methane to promote the formation of optically thick, polar stratospheric ice clouds. PMID:11536496

Sloan, L C; Walker, J C; Moore, T C; Rea, D K; Zachos, J C

1992-05-28

248

X-ray polarization fluctuations induced by cloud eclipses in active galactic nuclei  

NASA Astrophysics Data System (ADS)

Context. A fraction of active galactic nuclei (AGN) show dramatic X-ray spectral changes on the day-to-week time scales associated with variation in the line of sight of the cold absorber. Aims: We intend to model the polarization fluctuations arising from an obscuration event, thereby offering a method of determining whether flux variations are due to occultation or extreme intrinsic emission variability. Methods: Undertaking 1-100 keV polarimetric simulations with the Monte Carlo code Stokes, we simulated the journey of a variety of cold gas clouds in front of an extended primary source. We varied the hydrogen column density nH and size of the absorber, as well as the initial polarization state of the emitting source, to cover a wide range of scenarios. Results: Simulations indicate that different results are expected according to the initial polarization of the extended continuum source. For unpolarized primary fluxes, large (~50°) variations of the polarization position angle ? are expected before and after an occultation event, which is associated with very low residual polarization degrees (P ? 1%). In the case of an emitting disk with intrinsic, position-independent polarization, and for a given range of parameters, X-ray eclipses significantly alter the observed polarization spectra, with most of the variations seen in ?. Finally, non-uniformly polarized emitting regions produce very distinctive polarization variations due to the successive covering and uncovering of different portions of the disk. Plotted against time, variations in P and ? form detectable P Cygni type profiles that are distinctive signatures of non-axisymmetric emission. Conclusions: We find that X-ray polarimetry is particularly adapted to probing X-ray eclipses due to Compton-thin and Compton-thick gas clouds. Polarization measurements would distinguish between intrinsic intensity fluctuations and external eclipsing events, constrain the geometry of the covering medium, and test the hypothesis of non-uniformly emitting disks predicted by general relativity.

Marin, F.; Dov?iak, M.

2015-01-01

249

HIGH-FREQUENCY RADIO SPECTRAL ENERGY DISTRIBUTIONS AND POLARIZATION FRACTIONS OF SOURCES IN AN ATACAMA COSMOLOGY TELESCOPE SURVEY FIELD  

SciTech Connect

We present flux densities and polarization percentages of 159 radio galaxies based on nearly simultaneous Very Large Array observations at four frequencies, 4.86, 8.46, 22.46, and 43.34 GHz. This sample is selected from the high-frequency Australia Telescope 20 GHz (AT20G) survey and consists of all sources with flux density S{sub 20GHz} > 40 mJy in an equatorial field of the Atacama Cosmology Telescope (ACT) survey. For a subset of 25 of these sources, we used the Green Bank Telescope (GBT) to obtain 90 GHz data. The goals of this program are: (1) a characterization of the spectra, polarization, and variability of high-frequency-selected radio sources, (2) extrapolating from the few GHz regime to the {approx}150 GHz regime of the ACT survey, allowing for more accurate removal of the radio source signal in our particular field, and (3) providing a data set that will allow more accurate modeling of the high-frequency radio source contamination in current and future Sunyaev-Zeldovich and cosmic microwave background experiments. We find that, as expected, this sample consists of flatter spectrum and more compact or point-like sources than low-frequency-selected samples. In the K band, variability is typically {approx}<20%, although there are exceptions. The higher frequency data are well suited to the detection of extreme gigahertz peak spectrum sources. The inclusion of the 43 GHz data causes the relative fraction of inverted spectrum sources to go down and of peaked spectrum sources to go up when compared with the AT20G survey results. The trend largely continues with the inclusion of the 90 GHz data, although {approx}10% of the sources with GBT data show a spectral upturn from 43 GHz to 90 GHz. The measured polarization fractions are typically <5%, although in some cases they are measured to be up to {approx}20%. For sources with detected polarized flux in all four bands, about 40% of the sample, the polarization fractions typically increase with frequency. This trend is stronger for steeper spectrum sources as well as for the lower flux density sources.

Sajina, Anna [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Partridge, Bruce; Evans, Tyler; Vechik, Nicholas [Department of Physics and Astronomy, Haverford College, Haverford, PA 19041 (United States); Stefl, Shannon [Kent State University, Kent, OH 44242 (United States); Myers, Steve [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Dicker, Simon; Korngut, Phillip [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States)

2011-05-01

250

Experimental demonstrations of dual polarization CO-OFDM using mid-span spectral inversion for nonlinearity compensation.  

PubMed

We experimentally demonstrate fiber nonlinearity compensation in dual polarization coherent optical OFDM (DP CO-OFDM) systems using mid-span spectral inversion (MSSI). We use third-order nonlinearity between a pump and the signal in a highly nonlinear fiber (HNLF) for MSSI. Maximum launch powers at FEC threshold for two 10 × 80-km 16-QAM OFDM systems were increased by 6.4 dB at a 121-Gb/s data rate and 2.8 dB at 1.2 Tb/s. The experimental results are the first demonstration of using MSSI for nonlinearity compensation in any dual polarization coherent system. Simulations show that these increases could support a 22% increase in total transmission distance at 1.2-Tb/s system without increasing the number of inline amplifiers, by extending the fiber spans from 90 to 110 km. When spans of 80 km are used, simulations reveal that MSSI system performance shows less degradation with increasing transmission distance, and an overall transmission distance increase of more than 70% is expected using MSSI. PMID:24921747

Morshed, Monir; Du, Liang B; Foo, Benjamin; Pelusi, Mark D; Corcoran, Bill; Lowery, Arthur J

2014-05-01

251

A Program Library for Forward Modelling and Inversion of DC Resistivity and Induced Polarization Data over 3D Structures  

E-print Network

D DC RESISTIVITY AND INDUCED POLARIZATION DATA UBC-Geophysical Inversion Facility Department about DC resistivity and Induced Polarization field experiments, but who is not necessarily versedDCIP3D A Program Library for Forward Modelling and Inversion of DC Resistivity and Induced

Oldenburg, Douglas W.

252

Zeno and Anti-Zeno Polarization Control of Spin Ensembles by Induced Dephasing Gonzalo A. A lvarez,1,2  

E-print Network

Zeno and Anti-Zeno Polarization Control of Spin Ensembles by Induced Dephasing Gonzalo A. A´ lvarez (polarization) control of qubits entangled with multiple spins, using induced dephasing in nuclear magnetic the bath-induced upward and downward transition rates in the qubit. By contrast, less frequent measurements

Frydman, Lucio

253

Sperm Chromatin-Induced Ectopic Polar Body Extrusion in Mouse Eggs after ICSI and Delayed Egg Activation  

PubMed Central

Meiotic chromosomes in an oocyte are not only a maternal genome carrier but also provide a positional signal to induce cortical polarization and define asymmetric meiotic division of the oocyte, resulting in polar body extrusion and haploidization of the maternal genome. The meiotic chromosomes play dual function in determination of meiosis: 1) organizing a bipolar spindle formation and 2) inducing cortical polarization and assembly of a distinct cortical cytoskeleton structure in the overlying cortex for polar body extrusion. At fertilization, a sperm brings exogenous paternal chromatin into the egg, which induces ectopic cortical polarization at the sperm entry site and leads to a cone formation, known as fertilization cone. Here we show that the sperm chromatin-induced fertilization cone formation is an abortive polar body extrusion due to lack of spindle induction by the sperm chromatin during fertilization. If experimentally manipulating the fertilization process to allow sperm chromatin to induce both cortical polarization and spindle formation, the fertilization cone can be converted into polar body extrusion. This suggests that sperm chromatin is also able to induce polar body extrusion, like its maternal counterpart. The usually observed cone formation instead of ectopic polar body extrusion induced by sperm chromatin during fertilization is due to special sperm chromatin compaction which restrains it from rapid spindle induction and therefore provides a protective mechanism to prevent a possible paternal genome loss during ectopic polar body extrusion. PMID:19787051

Deng, Manqi; Li, Rong

2009-01-01

254

Nonlocal effects on the polarization state of a photon, induced by distant absorbers  

NASA Technical Reports Server (NTRS)

A variant of a Franson's two-photon correlation experiment is discussed, in which the linear polarization state of one of the photons depends on the path followed in the interferometer. It is shown that although the path difference is greater than the coherence length, the photon can be found in a polarization state represented by the superposition of the polarization states associated to the paths when there is coincident detection. Since the photons, produced via parametric down-conversion, are fairly well localized in space and time, the situation in which one of the photons is detected before the other can reach the interferometer raises an intriguing point: it seems that in some cases the second photon would have to be described by two wave packets simultaneously. Unlike previous experiments, in which nonlocal effects were induced by means of polarizers of phase shifters, in the proposed experiment nonlocal effects can be induced by means of variable absorbers.

Ryff, Luis Carlos B.

1994-01-01

255

Confinement Induced Quantum Phase Transition and Polarization Cooling in a Dipolar Crystal of Polar Molecules  

E-print Network

It is well-known that the liquid properties in a strongly confined system can be very different from their ordinary behaviors in an extended system, due to the competition between the thermal energy and the interaction energy. Here we show that, in a low-dimensional self-assembled dipolar crystal, the parabolic optical confinement potential can also strongly affect the quantum many-body properties in the low temperature regime. For example, by changing the confinement aspect ratio, the bulk of the system can undergo a quantum phase transition between a liquid state and a solid state via a nonmonotonic pattern formation of the domain wall. Furthermore, the entropy of a trapped dipolar crystal can be much larger than the liquid state in the weak dipole limit, indicating an intrinsic polarization cooling mechanism via increasing the external field. These highly correlated confinement effects are very important to the experimental preparation of a self-assembled dipolar crystal using ultracold polar molecules.

Yi-Ya Tian; Daw-Wei Wang

2008-09-16

256

Mesenchymal stem cells alleviate experimental asthma by inducing polarization of alveolar macrophages.  

PubMed

The reparative and immunoregulatory properties of mesenchymal stromal cells (MSCs) have made them attractive candidates for cellular therapy. However, the underlying mechanism of the effects of transplanted MSCs on allergic asthma remains elusive. Here, we show that administration of MSCs isolated from human bone marrow provoked a pronounced polarization in alveolar macrophages to M2 subtypes, rather than induced an increase in the total macrophage number, and efficiently inhibited hallmark features of asthma, including airway hyperresponsiveness and eosinophilic accumulation. Moreover, transforming growth factor beta (TGF-?) signaling pathway appeared to mediate the effects of MSCs on macrophage polarization and subsequently the inhibition of hallmark features of asthma. Inhibition of TGF-? signaling was sufficient to inhibit the macrophage polarization in response to MSCs and consequently reserved the inhibitory effects of macrophage polarization on hallmark features of asthma. Collectively, our data demonstrate that human MSCs have immunosuppressive activity on asthma, which is mediated by TGF-?-signaling-dependent alveolar macrophage polarization. PMID:24958014

Song, Xiaolian; Xie, Shuanshuan; Lu, Kun; Wang, Changhui

2015-04-01

257

Polarization Effects on Thermal-Induced Mode Instabilities in High Power Fiber Lasers  

E-print Network

We present detailed studies of the effect of polarization on thermal-induced mode instability (MI) in ytterbium-doped fiber amplifiers. Based on a steady-state theoretical model, which takes both electric fields along the two principal axes into consideration, the effect of polarization effects on the gain of Stokes wave was analyzed, which shows that the polarization characteristics of the fiber laser have no impact on the threshold of MI. Experimental validation of the theoretical analysis is presented with experimental results agreeing well with the theoretical results, in which polarization-maintained and non-polarization-maintained fiber lasers with core/inner cladding diameter of 30/250um and core NA of 0.07 were employed. The MI threshold power is measured to be about 367~386W.

Rumao Tao; Pengfei Ma; Xiaolin Wang; Pu Zhou; Zejin Liu

2015-03-30

258

Polarization Effects on Thermal-Induced Mode Instabilities in High Power Fiber Lasers  

E-print Network

We present detailed studies of the effect of polarization on thermal-induced mode instability (MI) in ytterbium-doped fiber amplifiers. Based on a steady-state theoretical model, which takes both electric fields along the two principal axes into consideration, the effect of polarization effects on the gain of Stokes wave was analyzed, which shows that the polarization characteristics of the fiber laser have no impact on the threshold of MI. Experimental validation of the theoretical analysis is presented with experimental results agreeing well with the theoretical results, in which polarization-maintained and non-polarization-maintained fiber lasers with core/inner cladding diameter of 30/250um and core NA of 0.07 were employed. The MI threshold power is measured to be about 367~386W.

Tao, Rumao; Wang, Xiaolin; Zhou, Pu; Liu, Zejin

2015-01-01

259

Passive polarization agile antenna based on the electromagnetically induced transparency-like effect  

NASA Astrophysics Data System (ADS)

We propose a design method for a passive polarization agile antenna based on the electromagnetically induced transparency-like (EIT-like) effect. Benefiting from strong dispersion properties governed by EIT-like effects, the proposed structure can endow electromagnetic waves transmitted through it with quite different polarization states at very close frequencies. The experimental measurement was conducted to demonstrate agile polarization controls by placing a designed EIT-like waveplate in front of a standard microwave horn antenna. Results show that the polarization state of radiated waves by the horn antenna with a waveplate can be easily transformed among linear, circular and elliptical polarizations through fine-tuning the operating frequency, which is extremely important for certain special applications, e.g. electronic countermeasures. Our scheme could also be utilized at higher operating frequencies by the simply scaling principle.

Zhu, Lei; Meng, Fan-Yi; Wu, Qun; Dong, Liang; Chen, Wan; Fu, Jia-Hui

2014-10-01

260

Comparative study of electroabsorption in InGaN/GaN quantum zigzag heterostructures with polarization-induced electric fields  

E-print Network

with polarization-induced electric fields Emre Sari,1,2,3 Tuncay Ozel,2,3,4 Asli Koc,2,3 Jin-Woo Ju,5 Haeng-Keun Ahn is externally applied to compensate for the polarization-induced electric field across the wells, and theoretical analysis of InGaN/GaN quantum zigzag structures with different levels of polarization-induced

Demir, Hilmi Volkan

261

Optical signal processing based on self-induced polarization rotation in a semiconductor optical amplifier  

Microsoft Academic Search

We demonstrate novel optical signal processing functions based on self-induced nonlinear polarization rotation in a semiconductor optical amplifier (SOA). Numerical and experimental results are presented, which demonstrate that a nonlinear polarization switch can be employed to achieve all-optical logic. We demonstrate an all-optical header processing system, an all-optical seed pulse generator for packet synchronization, and an all-optical arbiter that can

N. Calabretta; Y. Liu; F. M. Huijskens; M. T. Hill; H. de Waardt; G. D. Khoe; H. J. S. Dorren

2004-01-01

262

Magnetic-field-induced dielectric anomaly and electric polarization in Mn4Nb2O9  

NASA Astrophysics Data System (ADS)

Magnetic, dielectric, and magnetoelectric properties have been investigated in the polycrystalline Mn4Nb2O9. Under zero magnetic fields, no dielectric anomaly and electric polarization are observed in this compound. When the sample is exposed in magnetic field, finite dielectric peaks and electric polarization are induced, which increase with increasing magnetic field, showing magneto-dielectric and magnetoelectric effects. The origin of magnetoelectric coupling of this compound has been discussed.

Fang, Y.; Zhou, W. P.; Yan, S. M.; Bai, R.; Qian, Z. H.; Xu, Q. Y.; Wang, D. H.; Du, Y. W.

2015-05-01

263

Femtosecond Raman induced polarization spectroscopy studies of coherent rotational dynamics in molecular fluids  

SciTech Connect

We develop a polarization-sensitive femtosecond pump probe technique, Raman induced polarization spectroscopy (RIPS), to study coherent rotation in molecular fluids. By observing the collisional dephasing of the coherently prepared rotational states, we are able to extract information concerning the effects of molecular interactions on the rotational motion. The technique is quite sensitive because of the zero background detection method, and is also versatile due to its nonresonant nature.

Morgen, M.M. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National Lab., CA (United States)

1997-05-01

264

Spectral distribution of the polarized radiation from standard accretion disks in Active Galactic Nuclei: Observational analysis  

NASA Astrophysics Data System (ADS)

Spectropolarimetric observations of a number of Active Galactic Nuclei obtained using the SCORPIO-2 aperture focal reducer installed on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences are used to estimate physical parameters of these objects. The measured polarization and its wavelength dependence are consistent with the expectations of a standard accretion-disk model taking into account the effect of Faraday depolarization over the mean free path of the emitted photons. Estimates of the magnetic field in the accretion disk near the innermost stable orbit and the spin of the accreting central black hole are obtained. It is concluded that supermassive black holes with standard accretion disks and equal magnetic and radiative pressures are primarily Kerr black holes.

Afanas'ev, V. L.; Borisov, N. V.; Gnedin, Yu. N.; Buliga, S. D.; Natsvlishvili, T. M.; Piotrovich, M. Yu.

2014-10-01

265

Electron impact polarization of atomic spectral lines. I - A general theoretical scheme  

NASA Technical Reports Server (NTRS)

A suitable theoretical scheme able to describe, in a wide variety of astrophysical situations, the phenomenon of atomic line polarization by electron impact is developed. Starting from the general principles of quantum mechanics and assuming the Born approximation, the rate equations for the density matrix elements of a multilevel atomic system, interacting with a nonrelativistic electron beam having any kind of angular distribution, are derived in full generality. The resulting theory generalizes the previous ones by accounting for the collisional rates and the cross sections concerning both inelastic and superelastic collisions (in any geometrical situation), and, moreover, by taking into account the coherences among Zeeman sublevels split by a magnetic field. As an example of particular relevance, the general formulas derived in the first sections of the paper are subsequently particularized to the case of the electric dipole interaction.

Fineschi, Silvano; Degl'innocenti, Egidio L.

1992-01-01

266

Observation of linear-polarization-sensitivity in the microwave-radiation-induced magnetoresistance oscillations  

SciTech Connect

We examine the linear polarization sensitivity of the radiation- induced magneto-resistance oscillations by investigating the effect of rotating in-situ the electric field of linearly polarized microwaves relative to the current, in the GaAs/AlGaAs system. We find that the frequency and the phase of the photo-excited magneto-resistance oscillations are insensitive to the polarization. On the other hand, the amplitude of the resistance oscillations are strongly sensitive to the relative orientation between the microwave antenna and the current-axis in the specimen.

Mani, R. G.; Ramanayaka, A. N. [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States); Wegscheider, W. [Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich (Switzerland)

2013-12-04

267

Nanosize confinement induced enhancement of spontaneous polarization in a ferroelectric nanowire  

NASA Astrophysics Data System (ADS)

We theoretically showed that the spontaneous polarization in ferroelectric (FE) nanowires (NWs) can be considerably enhanced due to the nanosize confinement by the first-principles calculations. The spontaneous polarization along the wire direction in a fully relaxed PbTiO3 NW with 1.8 nm diameter is 1.26 times higher than that of bulk counterpart. The tension induced by NW surface curvature counteracts the near-surface depolarizing effect and meanwhile leads to the unusual enhancement of spontaneous polarization. These findings indicated that FE NWs can be promising in the applications of nanodevices.

Cai, M. Q.; Zheng, Y.; Wang, B.; Yang, G. W.

2009-12-01

268

Elemental analysis of laser induced breakdown spectroscopy aided by an empirical spectral database.  

PubMed

Laser induced breakdown spectroscopy (LIBS) is commonly used to identify elemental compositions of various samples. To facilitate this task, we propose the use of an elemental spectral library for single-pulsed, nanosecond LIBS in the spectral range 198-968 nm. This spectroscopic library is generated by measuring optical emissions from plasmas of 40 pure elements. To demonstrate the usefulness of the proposed database, we measure and analyze the LIBS spectra of pure iron and of ethanol and show that we identify these samples with a high degree of certainty. PMID:19122709

Rock, Steven; Marcano, Aristides; Markushin, Yuri; Sabanayagam, Chandran; Melikechi, Noureddine

2008-11-01

269

Direct experimental measurement of SRS-induced spectral tilt in multichannel multispan communication systems  

SciTech Connect

Nonlinear SRS-induced tilt of the spectrum of a multichannel DWDM signal is studied experimentally in standard singlemode fibreoptic communication lines. It is found that at a fixed spectral bandwidth and total power the nonlinear SRS tilt is independent of the number of channels, radiation source type, and the initial tilt (positive or negative). In a multispan line consisting of identical spans the total nonlinear tilt of the spectrum (in dB) is proportional to the number of spans, spectral width and total power. (optical fibres, lasers and amplifiers. properties and applications)

Kapin, Yu A; Nanii, Oleg E; Novikov, A G; Pavlov, V N; Plotskii, A Yu; Treshchikov, V N

2012-09-30

270

Light-induced polarization effects in atoms with partially resolved hyperfine structure and applications to absorption, fluorescence, and nonlinear magneto-optical rotation  

E-print Network

Light-induced polarization effects in atoms with partially resolved hyperfine structure polarization by atoms in a polarized state can be reduced electromagnetically induced transparency 3 or in involving magnetic-field-induced evolution of long-lived ground-state polarization--can be used to perform

Auzinsh, Marcis

271

Alignment and orientation of diatomic molecules induced by polarized electron impact This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Alignment and orientation of diatomic molecules induced by polarized electron impact This article induced by polarized electron impact J W Maseberg and T J Gay Behlen Laboratory of Physics, University induced by spin-polarized electron impact. Circular polarizations resulting from some Fulcher- transitions

Gay, Timothy J.

272

A holistic view of a black hole binary: bringing together spectral, timing, and polarization analysis of Cygnus X-1  

NASA Astrophysics Data System (ADS)

The microquasar Cygnus X-1 is a persistent high mass X-ray binary, consisting of an O-type supergiant and a stellar mass black hole, and therefore one of those systems which are often considered downscaled versions of AGN, an analogy supported in Cyg X-1 by observations of radio jets. The size and proximity of such systems allow us to observe phenomena on time-scales which are not accessible in their supermassive siblings. Cyg X-1 shows distinct X-ray states, characterized by X-ray spectral and timing properties. Radio behavior is strongly correlated with the X-ray states and a jet-break exists in the mid-IR range in the hard state. The source state is therefore essential for the interpretation of data at all wavelengths. For most observations lacking broadband X-ray coverage, however, the exact state determination proves challenging. In this work, I will present a recently developed novel approach that uses data from all sky monitors such as RXTE-ASM, MAXI, Swift-BAT, and Fermi-GBM to define states and state transitions on a timescales of a few hours over a period of more than 17 years. This approach can be used to investigate the context of high resolution observations of Cyg X-1 with Chandra and XMM, and to conduct state-resolved polarization analysis with INTEGRAL. I then combine spectral and model-independent X-ray timing analysis of over 1900 RXTE orbits over 14 years and investigate the evolution of Fourier-dependent timing parameters such as power spectra, coherence, and time lag at different photon energies over all spectral states. Results include a correlation between the shape of the power and time lag spectra in all hard and intermediate states, a photon-energy dependent increase of the fractional rms in the soft state, and a strong energy-dependency of the power spectra shapes during state transitions. The findings are crucial for constraining physical models for accretion and ejection in compact objects and for comparisons with other accreting objects, especially AGN, since timescales and energies in accreting black holes scale with mass so that observations at the same energies may probe different physical processes therefore show different spectral and timing behavior.

Grinberg, Victoria

2014-01-01

273

Light-Induced Polar pH Changes in Leaves of Elodea canadensis1  

PubMed Central

Leaves of the submerged aquatic Elodea canadensis Michx. exhibit a light induced polar pH reaction. In this study, the effects of light intensity and dissolved inorganic carbon concentration on this polar reaction were examined. At a light intensity of 100 watts per square meter the leaf showed a polar pH response when the dissolved inorganic carbon concentration was less than about 1 millimolar. The polar reaction was suppressed at a higher dissolved inorganic carbon concentration. This suppression was not due to the buffering capacity of bicarbonate. Because another weak acid, acetate, did not inhibit the polarity, but even had a small stimulatory effect, the effect of bicarbonate is also not due to acidification of the cytoplasm. The suppression of the polar reaction by CO2/HCO3? was relieved when the light intensity was increased. Apparently there is competition for product(s) of the photosynthetic light reactions between processes generating the polar reaction and the carbon fixation reactions. The possibility that the redox state of the cell regulates the generation of the polar reaction is discussed. PMID:16667044

Elzenga, J. Theo M.; Prins, Hidde B. A.

1989-01-01

274

Contact-induced spin polarization in BNNT(CNT)/TM (TM=Co, Ni) nanocomposites  

SciTech Connect

The interaction between carbon and BN nanotubes (NT) and transition metal Co and Ni supports was studied using electronic structure calculations. Several configurations of interfaces were considered, and the most stable ones were used for electronic structure analysis. All NT/Co interfaces were found to be more energetically favorable than NT/Ni, and conductive carbon nanotubes demonstrate slightly stronger bonding than semiconducting ones. The presence of contact-induced spin polarization was established for all nanocomposites. It was found that the contact-induced polarization of BNNT leads to the appearance of local conductivity in the vicinity of the interface while the rest of the nanotube lattice remains to be insulating.

Kuzubov, Alexander A. [Siberian Federal University, Krasnoyarsk 660041 (Russian Federation); L.V. Kirensky Institute of Physics SB RAS, Krasnoyarsk 660036 (Russian Federation); Siberian State Technological University, Krasnoyarsk 660049 (Russian Federation); Kovaleva, Evgenia A., E-mail: kovaleva.evgeniya1991@mail.ru; Avramov, Paul; Kuklin, Artem V.; Mikhaleva, Natalya S.; Tomilin, Felix N. [Siberian Federal University, Krasnoyarsk 660041 (Russian Federation); L.V. Kirensky Institute of Physics SB RAS, Krasnoyarsk 660036 (Russian Federation); Sakai, Seiji; Entani, Shiro; Matsumoto, Yoshihiro; Naramoto, Hiroshi [Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata Shirane, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan)

2014-08-28

275

CMB Induced Polarization from Single Scattering by Clusters of Galaxies and Filaments  

NASA Astrophysics Data System (ADS)

We present light-cone-integrated simulations of the cosmic microwave background (CMB) polarization signal induced by a single scattering in the direction of clusters of galaxies and filaments. We characterize the statistical properties of the induced polarization signals from the presence of the CMB quadrupole component (pqiCMB) and as the result of the transverse motion of ionized gas clouds with respect to the CMB rest frame (p?t2SZ). From adiabatic N-body/hydrodynamic simulations, we generated 28 random sky patches integrated along the light cone, each with about 0.86 deg2 at angular resolution of 6".

Liu, Guo-Chin; Ramos, Elsa P. R. G.; da Silva, António J. C.

2015-01-01

276

Contact-induced spin polarization in BNNT(CNT)/TM (TM=Co, Ni) nanocomposites  

NASA Astrophysics Data System (ADS)

The interaction between carbon and BN nanotubes (NT) and transition metal Co and Ni supports was studied using electronic structure calculations. Several configurations of interfaces were considered, and the most stable ones were used for electronic structure analysis. All NT/Co interfaces were found to be more energetically favorable than NT/Ni, and conductive carbon nanotubes demonstrate slightly stronger bonding than semiconducting ones. The presence of contact-induced spin polarization was established for all nanocomposites. It was found that the contact-induced polarization of BNNT leads to the appearance of local conductivity in the vicinity of the interface while the rest of the nanotube lattice remains to be insulating.

Kuzubov, Alexander A.; Kovaleva, Evgenia A.; Avramov, Paul; Kuklin, Artem V.; Mikhaleva, Natalya S.; Tomilin, Felix N.; Sakai, Seiji; Entani, Shiro; Matsumoto, Yoshihiro; Naramoto, Hiroshi

2014-08-01

277

Spectral albedo and emissivity of CO2 in Martian polar caps - Model results  

NASA Technical Reports Server (NTRS)

In this paper, a snow albedo model previously developed for terrestrial snow is extended to the case of CO2 snow on Mars. Pure CO2 snow is calculated to have high albedo at visible wavelengths but not as high as that of water snow. At any given wavelength, the primary variable controlling albedo and emissivity is the snow grain size, with albedo decreasing and emissivity increasing as grain size increases. Observations that red albedo is much higher than blue albedo in the Martian south polar cap indicates that the snow or the atmosphere is contaminated with red dust. The absorption coefficient of CO2 ice in the thermal infrared is two to three orders of magnitude smaller than that measured for H2O ice. CO2 snow emissivity is therefore much lower than H2O snow, varying substantially with wavelength and quite sensitive to grain size and emission angle. Factors tending to increase emissivity are large grain size, small emission angle, and large concentrations of dust or water.

Warren, Stephen G.; Wiscombe, Warren J.; Firestone, John F.

1990-01-01

278

Parameter-induced stochastic resonance based on spectral entropy and its application to weak signal detection.  

PubMed

The parameter-induced stochastic resonance based on spectral entropy (PSRSE) method is introduced for the detection of a very weak signal in the presence of strong noise. The effect of stochastic resonance on the detection is optimized using parameters obtained in spectral entropy analysis. Upon processing employing the PSRSE method, the amplitude of the weak signal is enhanced and the noise power is reduced, so that the frequency of the signal can be estimated with greater precision through spectral analysis. While the improvement in the signal-to-noise ratio is similar to that obtained using the Duffing oscillator algorithm, the computational cost reduces from O(N(2)) to O(N). The PSRSE approach is applied to the frequency measurement of a weak signal made by a vortex flow meter. The results are compared with those obtained applying the Duffing oscillator algorithm. PMID:25725879

Zhang, Jinjing; Zhang, Tao

2015-02-01

279

Spectral and polarization study of the double relics in Abell 3376 using the Giant Metrewave Radio Telescope and the Very Large Array  

NASA Astrophysics Data System (ADS)

Double radio relics in galaxy clusters are rare phenomena that trace shocks in the outskirts of merging galaxy clusters. We have carried out a spectral and polarization study of the spectacular double relics in the galaxy cluster A3376 using the Giant Metrewave Radio Telescope at 150 and 325 MHz and the Very Large Array at 1400 MHz. The polarization study at 1400 MHz reveals a high degree of polarization (˜30 per cent) and aligned magnetic field vectors (not corrected for Faraday rotation) in the eastern relic. A highly polarized (>60 per cent) filamentary radio source of size ˜300 kpc near the eastern relic and north of the bent-jet radio galaxy is detected for the first time. The western relic is less polarized and does not show aligned magnetic field vectors. The distribution of spectral indices between 325 and 1400 MHz over the radio relics shows steepening from the outer to the inner edges of the relics. The spectral indices of the eastern and the western relics imply Mach numbers in the range 2.2-3.3. Remarkable features such as the inward filament extending from the eastern relic, the highly polarized filament, the complex polarization properties of the western relic and the separation of the brightest cluster galaxy from the intracluster medium by a distance >900 kpc are noticed in the cluster. A comparison with simulated cluster mergers is required to understand the complex properties of the double relics in the context of the merger in A3376. An upper limit [log(P1.4 GHz W Hz-1) < 23.0] on the strength of a Mpc size radio halo in A3376 is estimated.

Kale, Ruta; Dwarakanath, K. S.; Bagchi, Joydeep; Paul, Surajit

2012-10-01

280

Geometrically induced polarization and alignment of cells on nanopillar arrays  

NASA Astrophysics Data System (ADS)

Topological features at the nano and microscale can trigger mammalian cell growth and differentiation. In this work, we describe geometrical tuning of ordered arrays of nanopillars and micropillars that elicit specialized morphologies in adherent cells. Systematic analysis of the effects of the pillar radius, height, and spacing reveals that stem cells assume either flattened, polarized, or stellate morphologies in direct response to interpillar spacing. Notably, on patterns of pitch near a critical spacing (dcrit = 2 ?m for C3H10T1/2 cells), cells exhibit rounding of the cell body, pronounced polarization, and extension of narrow axon-like cell projections aligned with the square or hexagonal lattice of the NP array. This morphology persists for various stem cell lines and primary mesenchymal stem cells. The neuron-like morphological characteristics suggest that NP arrays can be utilized in tissue engineering applications that require directed axon growth. The ability of nano and micropillars to support various morphogenetic trends will allow rational design of scaffolds that may be useful for stem cell lineage specification, formation of patterned neural networks, and enhancement of implant integration with adjoining tissue.

Vasquez, Yolanda; Bucaro, Michael; Hatton, Benjamin; Aizenberg, Joanna

2012-02-01

281

Measurement of the Induced Polarization of Lambda (1116) in Kaon Electroproduction with CLAS  

SciTech Connect

The CLAS Collaboration is using the p(e,e[prime]K+p)pi? reaction to measure the induced polarization of the electroproduced Lambda(1116). In this experiment a 5.499-GeV electron beam was incident upon an unpolarized liquid-hydrogen target. The CEBAF Large Acceptance Spectrometer (CLAS) was used to detect the scattered electron, the kaon, and the decay proton from the Lambda hyperon. CLAS allowed for a large kinematic acceptance in Q2(0.75<=Q2<=3.5 GeV2) and W(1.6<=W<=3.0 GeV), as well as the kaon center-of-mass scattering angle. The goal is to map out the kinematic dependencies for the induced polarization in order to provide new constraints on models of K-hyperon production. Along with previously published photo- and electroproduction cross sections and polarization observables from CLAS, LEPS, SAPHIR, and GRAAL, these new induced polarization data are needed in coupled-channel analyses to search for previously unobserved s-channel resonances. Preliminary polarization results are presented.

Marianna Gabrielyan, Brian Raue, Seema Dhamija, Daniel S. Carman

2010-08-01

282

Induced spin polarization effect in graphene by ferromagnetic nanocontact  

NASA Astrophysics Data System (ADS)

Chemically synthesized graphene contains large number of defects which act as localized spin moments at the defect sites. Cobalt nanosheets of variable thickness are grown on graphene surface to investigate spin/magnetotransport through graphene sheets containing large number of localized spins. Negative magnetoresistance (MR) is observed over the entire temperature range (5-300 K) for thin cobalt sheets, while a cross-over from negative to positive MR with increasing temperature is noticed for thicker cobalt sheets. The observed MR results are explained on the basis of recently reported spin polarization effect in graphene due to the presence of ferromagnetic atoms on the surface considering a spin valve like Co/graphene/Co nanostructures.

Mandal, Sumit; Saha, Shyamal K.

2015-03-01

283

Unfolding Spectral Patterns Induced by Artificial Weakly Relativistic Beam in the Ionosphere  

NASA Astrophysics Data System (ADS)

Very diverse set of HF spectra was induced by artificial electron beam injections from the APEX satellite. The spectra were registered in unplanned absence of Xe+ plasma jet, aimed to protect spacecraft against overcharging. Acceleration voltage of 10kV, current modulation frequency ranging from d.c. to 250kHz, low divergence of 4deg, slow variations of pitch angle and maximum instantaneous intensity of 0.15A characterize electron beam. In these time intervals a radiospectrometer operated in a survey mode providing one spectrum every 2s or 8s. The single spectrum was measured in 1s with an equally spaced mesh of 200 frequencies starting from 100kHz with a step of 50kHz. The receiver with a bandwidth of 15 kHz was connected to a tubular dipole antenna having half length of 7.5m. Total number of 400 spectra is not impressive but they are characterized by reproducibility of spectral patterns. From reproducibility or slow evolution of the spectra, it may be inferred that distinct interactions prevail for some ranges of ambient electron gyro (fc) and plasma (fn) frequencies, injection pitch angles and beam intensities. It appears that discrete emission can be identified at least on ambient plasma frequency or ambient upper hybrid frequency (fu). One class of arguments supporting such identifications is provided by interrelation between spectral signatures of local plasma density in passive mode and beam induced spectra. Another class of arguments is provided by interrelations between spectral structures induced by electron beam. For large angles of e-beam injection, electromagnetic character of gyroharmonics radiation from weakly relativistic beam and emissions at harmonics of upper hybrid frequency were reported. In this presentation we extend investigation to pitch angle dependence of electron beam induced spectra. Few examples of spectra induced by very weak beam and by strong beam draw attention to relevance of its intensity. We estimate relevance of propagation for spectral bandwidth with ray tracing of inferred emission modes. The diversity and reproducibility of spectral patterns support viability of simulation of astrophysical plasma in controlled electron beam-space plasma experiments. Narrow single mode emission induced in weak beam regime can be used for monitoring of ambient plasma density.

Kiraga, Arek

284

Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy.  

PubMed

Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180° polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results. PMID:24953042

Miao, Hongchen; Zhou, Xilong; Dong, Shuxiang; Luo, Haosu; Li, Faxin

2014-08-01

285

Microwave polarization in the direction of galaxy clusters induced by the CMB quadrupole anisotropy  

E-print Network

Electron scattering induces a polarization in the cosmic microwave background (CMB) signal measured in the direction of a galaxy cluster due to the presence of a quadrupole component in the CMB temperature distribution. Measuring the polarization towards distant clusters provides the unique opportunity to observe the evolution of the CMB quadrupole at moderate redshifts, z~0.5-3. We demonstrate that for the local cluster population the polarization degree will depend on the cluster celestial position. There are two extended regions in the sky, which are opposite to each other, where the polarization is maximal, 0.1(tau/0.02) microK in the Rayleigh-Jeans part of the CMB spectrum (tau being the Thomson optical depth across the cluster) exceeding the contribution from the cluster transverse peculiar motion if v_tpolarization components produced in clusters. These polarization effects, which are of the order of (v_t/c)^2 tau, (v_t/c) tau^2 and (kT_e/m_ec^2) tau^2, as well as the polarization due to the CMB quadrupole, were previously calculated by Sunyaev and Zel'dovich for the Rayleigh-Jeans region. We fully confirm their earlier results and present exact frequency dependencies for all these effects. The polarization is considerably higher in the Wien region of the CMB spectrum.

S. Y. Sazonov; R. A. Sunyaev

1999-03-18

286

Electric-field induced capillary interaction of charged particles at a polar interface  

E-print Network

We study the electric-field induced capillary interaction of charged particles at a polar interface. The algebraic tails of the electrostatic pressure of each charge results in a deformation of the interface $u\\sim \\rho ^{-4}$. The resulting capillary interaction is repulsive and varies as $\\rho ^{-6}$ with the particle distance. As a consequence, electric-field induced capillary forces cannot be at the origin of the secondary minimum observed recently for charged PMMA particles at on oil-water interface.

Lionel Foret; Alois Würger

2014-02-07

287

Induced circularly polarized luminescence arising from anion or protein binding to racemic emissive lanthanide complexes  

NASA Astrophysics Data System (ADS)

A circularly polarized luminescence (CPL) spectrometer has been built and used to study the binding interaction of lactate and four different proteins with racemic EuIII and TbIII complexes in aqueous solution. Lactate binding gives rise to strong induced CPL spectra, and the observed emission dissymmetry factors vary linearly with enantiomeric composition. Particularly strong induced TbIII CPL also characterizes the binding interaction of alpha-1-acid glycoprotein with a dissociation constant, Kd, of 2.5 ?M.

Carr, Rachel; Puckrin, Robert; McMahon, Brian K.; Pal, Robert; Parker, David; Pålsson, Lars-Olof

2014-06-01

288

The effects of tidally induced disc structure on white dwarf accretion in intermediate polars  

E-print Network

We investigate the effects of tidally induced asymmetric disc structure on accretion onto the white dwarf in intermediate polars. Using numerical simulation, we show that it is possible for tidally induced spiral waves to propagate sufficiently far into the disc of an intermediate polar that accretion onto the central white dwarf could be modulated as a result. We suggest that accretion from the resulting asymmetric inner disc may contribute to the observed X-ray and optical periodicities in the light curves of these systems. In contrast to the stream-fed accretion model for these periodicities, the tidal picture predicts that modulation can exist even for systems with weaker magnetic fields where the magnetospheric radius is smaller than the radius of periastron of the mass transfer stream. We also predict that additional periodic components should exist in the emission from low mass ratio intermediate polars displaying superhumps.

J. R. Murray; P. J. Armitage; L. Ferrario; D. T Wickramasinghe

1998-09-10

289

Left-handed electromagnetic waves in materials with induced polarization and magnetization  

NASA Astrophysics Data System (ADS)

We analyze the properties of electromagnetic waves inside materials with induced polarization and magnetization. We show that if the polarization and magnetization of the material are sufficiently large and appropriately phased, then the system supports the formation of left-handed waves. In some respects, such a system behaves similarly to materials with a negative index of refraction, yet there is one important advantage: Left-handed waves in materials with induced polarization and magnetization do not require as stringent material properties (such as the strength of resonances and the density of radiators). We numerically investigate the formation and propagation of such left-handed waves using finite-difference approximation to Maxwell's equations. We also discuss possible experimental observation of these ideas in a rare-earth-doped crystal.

Yavuz, D. D.; Brewer, N. R.

2014-12-01

290

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 12, JUNE 15, 2006 1365 Source-Induced Optical Noise in Polarization  

E-print Network

, polarization-mode dispersion (PMD), statistical optics. I. INTRODUCTION SOURCE-INDUCED optical noise may becomeIEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 12, JUNE 15, 2006 1365 Source-Induced Optical Noise in Polarization Measurements Avi Zadok and Avishay Eyal, Member, IEEE Abstract--Formalism is derived

Zadok, Avinoam

291

3-D inversion of induced polarization data in wavelet domain and Yaoguo Li, Department of Geophysics, Colorado School of Mines  

E-print Network

3-D inversion of induced polarization data in wavelet domain Yaping Zhu and Yaoguo Li, Department practical application to large field data sets. Introduction Inferring mineral deposits based on induced polarization (IP) data has evolved from qualitative interpretation of pseudosections to inversion of 2-D and 3

292

Polarization-Induced Charge Distribution at Homogeneous Zincblende/Wurtzite Heterostructural Junctions in ZnSe Nanobelts  

SciTech Connect

Homogeneous heterostructural wurtzite (WZ)/zincblende (ZB) junctions are successfully fabricated in ZnSe nanobelts. Polarity continuity across the ZB/WZ interface is demonstrated. The saw-tooth-like potential profile induced by spontaneous polarization across the WZ/ZB/WZ interfaces is identified directly at the nanoscale. The polarization-induced charge distribution across the homogeneous heterostructural interfaces is proposed as a viable alternative approach towards charge tailoring in semiconductor nanostructures.

Li, L.; Jin, L.; Wang, J.; Smith, D. J.; Yin, W. J.; Yan, Y.; Sang, H.; Choy, W. C. H.; McCartney, M. R.

2012-03-08

293

Resistivity and induced polarization monitoring of salt transport under natural hydraulic gradients  

Microsoft Academic Search

The authors demonstrate the use of resistivity\\/induced polarization (IP) monitoring of salt transport under natural hydraulic loads. Electrical monitoring of saline tracer transport during forced injection has been demonstrated previously. Detection of tracer transport under natural hydraulic loading is difficult because neither the hydraulic load nor the tracer resistivity can be controlled. In one study, the authors identify the electrical

Lee D. Slater; Stewart K. Sandberg

2000-01-01

294

Relativistic Calculations of Induced Polarization in $^{12}C$(e, e' \\vec{p})$ Reactions  

E-print Network

Relativistic calculations of the induced proton polarization in quasifree electron scattering on $^{12}C$ are presented. Good agreement with the experimental data of Woo et al. is obtained. The relativistic calculations yield a somewhat better description of the data than the non-relativistic ones. Differences between the two approaches are more pronounced at larger missing momenta suggesting further experimental work in this region.

J. I. Johansson; H. S. Sherif

1999-05-06

295

Tensor-Induced CMB Temperature-Polarization Correlation in Reionized Universes  

E-print Network

We reexamine the temperature-polarization correlation function of the cosmic microwave background induced by tensor mode with a scale-invariant spectrum in reionized standard cold dark matter models. It is found that the sign of the correlation function is positive on all angular scales even in a model with substantial reionization.

Kin-Wang Ng

1999-05-04

296

Inversion of two-dimensional resistivity and induced-polarization data  

Microsoft Academic Search

A fast ridge regression inversion technique was devised for the interpretation of simple two-dimensional resistivity and induced-polarization data. The program will determine the rectangular source under a single layer of overburden which best fits the observed data. Unfortunately, each ridge regression inversion requires a great many forward problem evaluations. One method to reduce the calculation time is to store in

W. H. Pelton; L. Rijo; C. M. Jr. Swift

1978-01-01

297

Multi-array borehole resistivity and induced polarization method with mathematical inversion of redundant data  

DOEpatents

Multiple arrays of electric or magnetic transmitters and receivers are used in a borehole geophysical procedure to obtain a multiplicity of redundant data suitable for processing into a resistivity or induced polarization model of a subsurface region of the earth. 30 figs.

Ward, S.H.

1989-10-17

298

A new strategy for in vivo spectral editing. Application to GABA editing using selective homonuclear polarization transfer spectroscopy  

NASA Astrophysics Data System (ADS)

A novel single-shot in vivo spectral editing method is proposed in which the signal to be detected, is regenerated anew from the thermal equilibrium magnetization of a source to which it is J-coupled. The thermal equilibrium magnetization of the signal to be detected together with those of overlapping signals are suppressed by single-shot gradient dephasing prior to the signal regeneration process. Application of this new strategy to in vivo GABA editing using selective homonuclear polarization transfer allows complete suppression of overlapping creatine and glutathione while detecting the GABA-4 methylene resonance at 3.02 ppm with an editing yield similar to that of conventional editing methods. The NAA methyl group at 2.02 ppm was simultaneously detected and can be used as an internal navigator echo for correcting the zero order phase and frequency shifts and as an internal reference for concentration. This new method has been demonstrated for robust in vivo GABA editing in the rat brain and for study of GABA synthesis after acute vigabatrin administration.

Shen, Jun; Yang, Jehoon; Choi, In-Young; Li, Shizhe Steve; Chen, Zhengguang

2004-10-01

299

Measured Stark Widths of Several Sn I and Sn II Spectral Lines in a Laser-induced Plasma  

Microsoft Academic Search

Data on Stark widths of spectral lines are of high interest for astrophysics and analytical techniques of stellar plasma diagnosis. Stark widths of 43 spectral lines of Sn I and 27 spectral lines of Sn II has been measured in a laser-induced plasma (LIP) at an electron temperature of 11,000 K and an electron density of 1.1×1016 cm-3. The LIP

A. Alonso-Medina; C. Colón

2008-01-01

300

STAT1-induced ASPP2 transcription identifies a link between neuroinflammation, cell polarity, and tumor suppression  

PubMed Central

Inflammation and loss of cell polarity play pivotal roles in neurodegeneration and cancer. A central question in both diseases is how the loss of cell polarity is sensed by cell death machinery. Here, we identify apoptosis-stimulating protein of p53 with signature sequences of ankyrin repeat-, SH3 domain-, and proline-rich region-containing protein 2 (ASPP2), a haploinsufficient tumor suppressor, activator of p53, and regulator of cell polarity, as a transcriptional target of signal transducer and activator of transcription 1 (STAT1). LPS induces ASPP2 expression in murine macrophage and microglial cell lines, a human monocyte cell line, and primary human astrocytes in vitro. LPS and IFNs induce ASPP2 transcription through an NF-?B RELA/p65-independent but STAT1-dependent pathway. In an LPS-induced maternal inflammation mouse model, LPS induces nuclear ASPP2 in vivo at the blood–cerebral spinal fluid barrier (the brain’s barrier to inflammation), and ASPP2 mediates LPS-induced apoptosis. Consistent with the role of ASPP2 as a gatekeeper to inflammation, ASPP2-deficient brains possess enhanced neuroinflammation. Elevated ASPP2 expression is also observed in mouse models and human neuroinflammatory disease tissue, where ASPP2 was detected in GFAP-expressing reactive astrocytes that coexpress STAT1. Because the ability of ASPP2 to maintain cellular polarity is vital to CNS development, our findings suggest that the identified STAT1/ASPP2 pathway may connect tumor suppression and cell polarity to neuroinflammation. PMID:24958857

Turnquist, Casmir; Wang, Yihua; Severson, David T.; Zhong, Shan; Sun, Bin; Ma, Jingyi; Constantinescu, Stefan N.; Ansorge, Olaf; Stolp, Helen B.; Molnár, Zoltán; Szele, Francis G.; Lu, Xin

2014-01-01

301

Field-induced polarization of Dirac valleys in bismuth  

NASA Astrophysics Data System (ADS)

The principal challenge in the field of ``valleytronics'' is to lift the valley degeneracy of electrons in a controlled way. In graphene, a number of methods to generate a valley-polarized flow of electrons have been proposed, which are yet to be experimentally realized. In bulk semi-metallic bismuth, the Fermi surface includes three cigar-shaped electron valleys lying almost perpendicular to the high-symmetry axis known as the trigonal axis. The in-plane mass anisotropy of each valley exceeds 200 as a consequence of Dirac dispersion, which drastically reduces the effective mass along two out of the three orientations. We present a study of angle-dependent magnetoresistance in bismuth which shows that a flow of Dirac electrons along the trigonal axis is extremely sensitive to the orientation of in-plane magnetic field. The effect is visible even at room temperature. Thus, a rotatable magnetic field can be used as a valley valve to tune the contribution of each valley to the total conductivity. At high temperature and low magnetic field, the three valleys are interchangeable and the three-fold symmetry of the underlying lattice is respected. As the temperature is decreased or the magnetic field increased, this symmetry is spontaneously lost. This loss may be an experimental manifestation of the recently proposed valley-nematic Fermi liquid state.

Behnia, Kamran; Zhu, Zengwei; Callaudin, Aurelie; Fauque, Benoit; Kang, Woun

2012-02-01

302

Modeling Yeast Cell Polarization Induced by Pheromone Gradients  

NASA Astrophysics Data System (ADS)

Yeast cells respond to spatial gradients of mating pheromones by polarizing and projecting up the gradient toward the source. It is thought that they employ a spatial sensing mechanism in which the cell compares the concentration of pheromone at different points on the cell surface and determines the maximum point, where the projection forms. Here we constructed the first spatial mathematical model of the yeast pheromone response that describes the dynamics of the heterotrimeric and Cdc42p G-protein cycles, which are linked in a cascade. Two key performance objectives of this system are (1) amplification—converting a shallow external gradient of ligand to a steep internal gradient of protein components and (2) tracking—following changes in gradient direction. We used simulations to investigate amplification mechanisms that allow tracking. We identified specific strategies for regulating the spatial dynamics of the protein components (i.e. their changing location in the cell) that would enable the cell to achieve both objectives.

Yi, Tau-Mu; Chen, Shanqin; Chou, Ching-Shan; Nie, Qing

2007-07-01

303

Identification of Genes Required for Normal Pheromone-Induced Cell Polarization in Saccharomyces Cerevisiae  

PubMed Central

In response to mating pheromones, cells of the yeast Saccharomyces cerevisiae adopt a polarized ``shmoo'' morphology, in which the cytoskeleton and proteins involved in mating are localized to a cell-surface projection. This polarization is presumed to reflect the oriented morphogenesis that occurs between mating partners to facilitate cell and nuclear fusion. To identify genes involved in pheromone-induced cell polarization, we have isolated mutants defective in mating to an enfeebled partner and studied a subset of these mutants. The 34 mutants of interest are proficient for pheromone production, arrest in response to pheromone, mate to wild-type strains, and exhibit normal cell polarity during vegetative growth. The mutants were divided into classes based on their morphological responses to mating pheromone. One class is unable to localize cell-surface growth in response to mating factor and instead enlarges in a uniform manner. These mutants harbor special alleles of genes required for cell polarization during vegetative growth, BEM1 and CDC24. Another class of mutants forms bilobed, peanut-like shapes when treated with pheromone and defines two genes, PEA1 and PEA2. PEA1 is identical to SPA2. A third class forms normally shaped but tiny shmoos and defines the gene TNY1. A final group of mutants exhibits apparently normal shmoo morphology. The nature of their mating defect is yet to be determined. We discuss the possible roles of these gene products in establishing cell polarity during mating. PMID:8013906

Chenevert, J.; Valtz, N.; Herskowitz, I.

1994-01-01

304

Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well solar cells  

NASA Astrophysics Data System (ADS)

Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well (MQW) solar cells are investigated. It is found that due to the reduction of piezoelectric polarization and the enhancement of tunneling transport of photo-generated carriers in MQWs, the external quantum efficiency (EQE) of the solar cells increases in a low energy spectral range (? > 370 nm) when the barrier thickness value decreases from 15 nm to 7.5 nm. But the EQE decreases abruptly when the barrier thickness value decreases down to 3.75 nm. The reasons for these experimental results are analyzed. We are aware that the reduction of depletion width in MQW region, caused by the high resistivity of the p-type GaN layer may be the main reason for the abnormally low EQE value at long wavelengths (? > 370 nm).

Yang, Jing; Zhao, De-Gang; Jiang, De-Sheng; Liu, Zong-Shun; Chen, Ping; Li, Liang; Wu, Liang-Liang; Le, Ling-Cong; Li, Xiao-Jing; He, Xiao-Guang; Wang, Hui; Zhu, Jian-Jun; Zhang, Shu-Ming; Zhang, Bao-Shun; Yang, Hui

2014-06-01

305

The spectral dependence for UVA-induced cumulative damage in human skin.  

PubMed

The wavelength dependence for UVA-induced cumulative damage was investigated in human skin. Epidermal changes (stratum corneum thickening, viable epidermal thickening sunburn cell production), as well as dermal alterations (lysozyme deposition, inflammation), were used as indices of cumulative photoperturbation. UVA wavelengths between 320 nm and 345 nm were more effective than longer wavelengths (360-400 nm) in inducing viable epidermal thickening. Similarly, the shorter wavelengths (320-345 nm) elicited more sunburn cells, although these differences did not reach statistical significance. All UVA bands were equally effective in inducing the dermal markers. At equal fluences, wavelengths > 400 nm produced no measurable cutaneous alterations. These findings suggest that (i) chronic epidermal and dermal damages have different spectral dependence and (ii) the action spectrum for dermal damage in the UVA is broad, extending up to 400 nm, and is different from the acute erythema spectrum in humans. PMID:8980280

Lavker, R; Kaidbey, K

1997-01-01

306

Polarized and unpolarized $?$-pair meson-induced Drell--Yan production and the pion distribution amplitude  

E-print Network

We present a detailed analysis of meson-induced massive lepton (muon) Drell--Yan production for the process $\\pi^{-}N\\to\\mu^{+}\\mu^{-}X$, considering both an unpolarized nucleon target and longitudinally polarized protons. Using a QCD framework, we focus on the angular distribution of $\\mu^+$, which is sensitive to the shape of the pion distribution amplitude, the goal being to test corresponding results against available experimental data. Predictions are made, employing various pion distribution amplitudes, for the azimuthal angle dependence of the $\\mu^{+}$ distribution in the polarized case, relevant for the planned COMPASS experiment. QCD evolution is given particular attention in both considered cases.

A. P. Bakulev; N. G. Stefanis; O. V. Teryaev

2007-09-06

307

Kondo-induced electric polarization modulated by magnetic flux through a triangular triple quantum dot  

NASA Astrophysics Data System (ADS)

The Kondo effect plays an important role in emergence of electric polarization in a triangular triple-quantum-dot system, where one of the three dots is point-contacted with a single lead, and a magnetic flux penetrates through the triangular loop. The Kondo-induced electric polarization exhibits an Aharonov-Bohm type oscillation as a function of the magnetic flux. Our theoretical study shows various oscillation patterns associated with the field-dependent mixing of twofold orbitally degenerate ground states and their sensitivity to the point contact.

Koga, M.; Matsumoto, M.; Kusunose, H.

2015-03-01

308

Induced Polarization of Glass Bead Packs With Varying Mean Grain Size, pH, and Salinities: a Review of Theoretical Models  

NASA Astrophysics Data System (ADS)

The spectral induced-polarization (IP) response of rocks and soils is described by a complex conductivity, which depends on pore solution chemistry, texture, and electrochemical properties of the mineral water interface. The complex conductivity response of porous media in the frequency range from the milliHertz to 10 kHertz reveals relaxations in the power spectrum. These relaxation effects are related mainly to surface polarization processes due to the existence of the electrical double or triple layer at the mineral water interface. A deeper knowledge of these physical mechanisms is important for the correct interpretation of field data. We have previously developed an electrical triple layer model to describe the electrochemical properties of clay minerals. The triple layer model comprises the Stern and the diffuse layer and their dependence on chemistry of the pore water. The low frequency dispersion is caused by the influence of field-induced electrolyte concentration variations on the local electric currents in the double layer. We use the Dukhin-Shilov theory combined with a triple layer model to predict the effect of the distribution of grain size (for a silica bead packs), pH, and water composition upon the induced polarization spectrum. Comparison with laboratory data is also provided.

Leroy, P.; Revil, A.

2006-12-01

309

Surface-induced heating of cold polar molecules  

E-print Network

We study the rotational and vibrational heating of diatomic molecules placed near a surface at finite temperature on the basis of macroscopic quantum electrodynamics. The internal molecular evolution is governed by transition rates that depend on both temperature and position. Analytical and numerical methods are used to investigate the heating of several relevant molecules near various surfaces. We determine the critical distances at which the surface itself becomes the dominant source of heating and we investigate the transition between the long-range and short-range behaviour of the heating rates. A simple formula is presented that can be used to estimate the surface-induced heating rates of other molecules of interest. We also consider how the heating depends on the thickness and composition of the surface.

Stefan Yoshi Buhmann; M. R. Tarbutt; Stefan Scheel; E. A. Hinds

2009-12-14

310

Spectral hole burning and holography. III. Electric field induced interference of holograms  

NASA Astrophysics Data System (ADS)

The electric field induced superposition of holograms recorded by spectral hole burning is investigated. Holograms have been burned at adjacent positions in a plane defined by wavelength and electric field. Application of an appropriate electric field to the sample causes the components of adjacent holograms to overlap as the spectral holes split due to Stark shifts of molecular transition frequencies. The diffraction efficiency of such superimposed holograms depends on their relative phase and has been studied theoretically and experimentally. It is shown that for zero phase difference, constructive interference leads to a strong diffraction efficiency whereas for a phase difference of ?, the gratings cancel leading to zero diffraction efficiency. Experiments have been performed with the dye cresyl violet in a polyvinylbutyral film at a temperature of 1.7 K and the data are compared with computer simulations.

Renn, Alois; Meixner, Alfred J.; Wild, Urs P.

1990-08-01

311

Study on quantitative analysis of slag based on spectral normalization of laser-induced plasma image  

NASA Astrophysics Data System (ADS)

To reduce the influence of laser-induced breakdown spectroscopy (LIBS) experimental parameter fluctuations to quantitative analysis of slag components, a normalization method using integral intensity of plasma image was proposed and a series of experiments with slag samples were performed. Mg II 279.55 nm, Ca II 396.85 and Ca I 422.67 nm were selected as analytical lines, and analytical curves of reference mass fractions versus spectral line intensities were established. With the increment of set threshold for edge extraction of plasma image, the determination coefficients and relative standard deviations of analytical curves were improved gradually and reached the optimum values when the threshold was equal to 10 000. Comparing with the results without normalization and normalized by whole spectrum area, the relativity between spectral line intensity and mass fraction can be enhanced efficiently after normalized by integral intensity of plasma image. The verification experiments with Ti alloy samples further confirmed the conclusions mentioned above.

Ni, Zhi-Bo; Chen, Xing-Long; Fu, Hong-Bo; Wang, Jing-Ge; Dong, Feng-Zhong

2014-08-01

312

X-ray polarization fluctuations induced by cloud eclipses in active galactic nuclei  

E-print Network

Context: A fraction of active galactic nuclei (AGN) show dramatic X-ray spectral changes on the day-to-week time scales associated with variation in the line of sight of the cold absorber. Aims: We intend to model the polarization fluctuations arising from an obscuration event, thereby offering a method of determining whether flux variations are due to occultation or extreme intrinsic emission variability. Methods: Undertaking 1 - 100 keV polarimetric simulations with the Monte Carlo code STOKES, we simulated the journey of a variety of cold gas clouds in front of an extended primary source. We varied the hydrogen column density nH and size of the absorber, as well as the initial polarization state of the emitting source, to cover a wide range of scenarios. Results: For unpolarized primary fluxes, large (about 50deg) variations of the polarization position angle psi are expected before and after an occultation event, which is associated with very low residual polarization degrees (P lower than 1 per cent). In...

Marin, F

2014-01-01

313

The evaluation of the photoaging of the human skin by three-dimensional polarization sensitive spectral domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

Noninvasive evaluation of dermal degeneration is important for a diagnosis of photoaging. Polarization sensitive optical coherence tomography (PS-OCT) can measure the distribution of phase retardation caused by birefringence property of collagen. The PS-OCT has been reported as the technology of in vivo investigation of collagen structure in the skin. PS-spectral domain (SD)-OCT provides a three-dimensional phase retardation volume, and it provides an en face distribution map of the slopes of cumulative phase retardation. In this research, we measured the lateral orbital area and forehead of 7 young (age = 24.7+/-1.1) and 6 elder (age = 72.5+/-1.4) volunteers by a custom-built 840 nm fiber based PS-SD-OCT. This system can measure the skin birefringence three-dimensionally (5.5 sec for a 3-D volume). There was a significant difference in mean of the distribution of phase retardation slopes of the lateral orbital area between young and old cohorts (young: 0.356+/-0.0255 degree/?m elder: 0.256+/-0.0118 degree/?m). However, there was no significant difference in forehead. On the other hand, the shapes of histogram was not normal distribution. Therefore, we calculated skewness and kurtosis of the distributions of slopes for the analysis. In the orbital area, there were also significant differences between young and old cohorts in skewness (y: 0.813+/-0.135 e: 1.51+/- 0.177) and kurtosis (y: 2.85+/-0.483 e: 5.23+/-0.862). In forehead, there was a significant difference between young and old cohorts in skewness (p=0.0289) in contrast with mean (p= 0.065).

Miyazawa, Arata; Sakai, Shingo; Matsumoto, Masayuki; Nakagawa, Noriaki; Yamanari, Masahiro; Yasuno, Yoshiaki

2008-02-01

314

Energy band engineering using polarization induced interface charges in MOCVD grown III-nitride heterojunction devices  

NASA Astrophysics Data System (ADS)

Characteristics of III-nitride based heterojunction devices are greatly influenced by the presence of high density of polarization induced interface charges. Research undertaken in the current doctoral thesis demonstrates the effect of presence of one, three and six sheets of polarization induced charges in three different III-nitride based devices, namely in a photocathode, a high electron mobility transistor (HEMT) and a hyperspectral detector structure. Through a systematic set of experiments and theoretical modeling an in-depth study of the interaction between multiple sheets of polarization induced charges and their impact on energy band profile was undertaken. Various device designs were studied and optimized using device simulations. Subsequently device structures were grown using metallorganic chemical vapor deposition (MOCVD). Growth conditions for III-nitride epilayers were optimized for pressure, temperature and V/III ratio. Devices were fabricated using photolithography and e-beam evaporation. Novel GaN and GaN/AlGaN photocathode structures were developed. First demonstration of effective negative electron affinity (ENEA) in a GaN photocathode without the use of Cs was made. Effect of polarization induced surface charges on photoemission characteristics was successfully explained using simulated energy band diagrams. AlGaN/GaN/AlGaN/SiO2 based back barrier HEMT structures were developed in which bandgap, thin film thicknesses and polarization induced charge density were engineered to demonstrate Normally OFF operation along with the ability to engineer turn ON voltage of the device. Further, AlGaN based tunable hyperspectral detector pixel with 6-heterojunctions, for application in wavelength spectrometry from UV to IR part of the spectrum, was developed. The novel device design used in the hyperspectral detector utilized voltage tunable internal photoemission (IPE) barriers to measure the energy of the incident photon. Detailed IPE measurements were performed on the device structures to distinguish between the hot electron and hot hole photoemission events, originating in both the semiconductor and the metal contact. Presence of high polarization induced electric fields was observed to result in counter intuitive device characteristics that were successfully explained by developing a systematic set of device structures and corresponding simulated energy band diagrams. Voltage controlled emission threshold variation from 3.9 eV to 4.5 eV was successfully demonstrated.

Tripathi, Neeraj

2011-12-01

315

Surface polar states and pyroelectricity in ferroelastics induced by flexo-A. N. Morozovska, E. A. Eliseev, S. V. Kalinin, Long Qing Chen, and Venkatraman Gopalan  

E-print Network

Surface polar states and pyroelectricity in ferroelastics induced by flexo- roto field A. N://apl.aip.org/about/rights_and_permissions #12;Surface polar states and pyroelectricity in ferroelastics induced by flexo-roto field A. N rotations, and thus, it can induce surface polar states and pyroelectricity in a large class of otherwise

Chen, Long-Qing

316

Giant Ferroelectric Polarization of CaMn7O12 Induced by a Combined Effect of Dzyaloshinskii-Moriya Interaction and Exchange Striction  

E-print Network

Giant Ferroelectric Polarization of CaMn7O12 Induced by a Combined Effect of Dzyaloshinskii induce a nonzero ferroelectric polarization. Recently, we presented a more general model [12] that explains the ferroelectric polarizations induced by a helical magnetic structure. These ferroelectric

Gong, Xingao

317

Polarization and collision-induced coherence in the beam-foil light source  

NASA Technical Reports Server (NTRS)

Monatomic systems were excited by the beam-foil method in order to re-examine the possibility that a particular magnetic substate was preferentially populated. O II, Ar II and He I levels were used. The results reveal that: (1) with a tilted foil substantial polarization (up to 15%) may be achieved, (2) the polarization is due to the foil, (3) the foil induces coherence among Zeeman substates with the appearance of quantum beats among these substates and that their coherence is due to the externally applied magnetic field perpendicular to the beam direction, and (4) the angular momentum of the emitted photon is perpendicular to the ion velocity. The possibility for detecting separate effects of alignment and polarization is noted.

Liu, C. H.; Bashkin, S.; Church, D. A.

1974-01-01

318

Surface polar states and pyroelectricity in ferroelastics induced by flexo-roto fields  

SciTech Connect

Theoretical analysis based on the Landau-Ginzburg-Devonshire theory is used to show that the joint action of flexoelectric effect and rotostriction leads to a large spontaneous in-plane polarization (1-5 lC/cm2) and pyroelectric coefficient (103 C/m2K) in the vicinity of surfaces of otherwise non-ferroelectric ferroelastics, such as SrTiO3, with static octahedral rotations. The origin of the improper polarization and pyroelectricity is an electric field we name flexo-roto field whose strength is proportional to the convolution of the flexoelectric and rotostriction tensors with octahedral tilts and their gradients. Flexo-roto field should exist at surfaces and interfaces in all structures with static octahedral rotations, and thus, it can induce surface polar states and pyroelectricity in a large class of otherwise nonpolar materials. VC 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3701152

Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine; Eliseev, E. A. [National Academy of Science of Ukraine, Kiev, Ukraine; Kalinin, Sergei V [ORNL; Chen, L. Q. [Pennsylvania State University; Gopalana, V. [Pennsylvania State University

2012-01-01

319

Fraunhofer-type absorption line splitting and polarization in confocal double-pulse laser induced plasma  

NASA Astrophysics Data System (ADS)

Strong line splitting and polarization are observed in Fraunhofer-type absorption lines in Pb, Sn, Si, Cd, In, and Zn in confocal double-pulse laser induced plasma (DP-LIP) experiments. This effect is detectable using medium laser power densities: (~ 1-2) × 1013 W/m2 for the first laser pulse and 1 × 1014 W/m2 for the second laser pulse. Polarization and splitting effects exist only during the second laser pulse (~ 7 ns). Absorption line polarization and splitting phenomena may be explained by a high overall magnetic field and motional Stark effect caused by the second laser pulse inside the laser plasma created by the first pulse.

Nagli, Lev; Gaft, Michael

2013-10-01

320

Modeling and inversion Matlab algorithms for resistivity, induced polarization and seismic data  

NASA Astrophysics Data System (ADS)

M. Karaoulis (1), D.D. Werkema (3), A. Revil (1,2), A., B. Minsley (4), (1) Colorado School of Mines, Dept. of Geophysics, Golden, CO, USA. (2) ISTerre, CNRS, UMR 5559, Université de Savoie, Equipe Volcan, Le Bourget du Lac, France. (3) U.S. EPA, ORD, NERL, ESD, CMB, Las Vegas, Nevada, USA . (4) USGS, Federal Center, Lakewood, 10, 80225-0046, CO. Abstract We propose 2D and 3D forward modeling and inversion package for DC resistivity, time domain induced polarization (IP), frequency-domain IP, and seismic refraction data. For the resistivity and IP case, discretization is based on rectangular cells, where each cell has as unknown resistivity in the case of DC modelling, resistivity and chargeability in the time domain IP modelling, and complex resistivity in the spectral IP modelling. The governing partial-differential equations are solved with the finite element method, which can be applied to both real and complex variables that are solved for. For the seismic case, forward modeling is based on solving the eikonal equation using a second-order fast marching method. The wavepaths are materialized by Fresnel volumes rather than by conventional rays. This approach accounts for complicated velocity models and is advantageous because it considers frequency effects on the velocity resolution. The inversion can accommodate data at a single time step, or as a time-lapse dataset if the geophysical data are gathered for monitoring purposes. The aim of time-lapse inversion is to find the change in the velocities or resistivities of each model cell as a function of time. Different time-lapse algorithms can be applied such as independent inversion, difference inversion, 4D inversion, and 4D active time constraint inversion. The forward algorithms are benchmarked against analytical solutions and inversion results are compared with existing ones. The algorithms are packaged as Matlab codes with a simple Graphical User Interface. Although the code is parallelized for multi-core cpus, it is not as fast as machine code. In the case of large datasets, someone should consider transferring parts of the code to C or Fortran through mex files. This code is available through EPA's website on the following link http://www.epa.gov/esd/cmb/GeophysicsWebsite/index.html Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

Karaoulis, M.; Revil, A.; Minsley, B. J.; Werkema, D. D.

2011-12-01

321

Spectral analysis of photo-induced delayed luminescence from human skin in vivo  

NASA Astrophysics Data System (ADS)

The UVA induced Delayed Luminescence (DL), has been measured in vivo in the forearm skin of some healthy volunteers of different sex and age during several periods of the year. An innovative instrument able to detect, in single photon counting mode, the spectrum and the time trend of the DL emission has been used. The measured differences in the time trends of the spectral components may be related to the sex and the age. The potential development of a new analysis technique based on this phenomenon is discussed.

Musumeci, Francesco; Lanzanò, Luca; Privitera, Simona; Tudisco, Salvatore; Scordino, Agata

2007-07-01

322

CPT transients induced by rapid changes in laser polarization: validation of a semi-empirical model  

NASA Astrophysics Data System (ADS)

In ultraminiature atomic physics (UAP), where the goal is to perform low-power, 'chip-scale' precision spectroscopy, stochastic-field/atom interactions can play a primary role in defining the limits of sensitivity. Unfortunately, the transient responses of a quantum system to random changes in the amplitude, phase or polarization of a resonant field are not well understood, forming the basis of what has come to be known as the stochastic-field/atom interaction problem. As the first step in understanding the more complicated stochastic problem, the present work considers the response of a coherent-population-trapping (CPT) signal to a sudden, step-function change in laser polarization. We find that the transient behaviour depends on both the redistribution of atomic population among the atom's Zeeman sublevels and the regeneration of atomic coherence between these sublevels. Despite the complicated nature of the dynamics, we develop and experimentally validate a semi-empirical, reasonably intuitive model of the CPT transient and demonstrate that in the 'typical' CPT signal the polarization-induced transients are dominated by redistribution of atomic population among the Zeeman sublevels. Further, the amplitudes of the polarization-induced transients are relatively large and could potentially 'swamp' the CPT signals of interest for UAP.

Huang, M.; Coffer, J. G.; Camparo, J. C.

2010-07-01

323

Polarization of L Dwarfs by Dust Scattering  

E-print Network

The degree of polarization in L dwarfs of spectral types L0 to L6 resulting from dust scattering in a rotation-induced oblate photosphere is calculated. Assuming that forsterite is the main condensate, the atmospheric dust distribution is derived for different spectral types based on a chemical equilibrium model. The degree of polarization at optical is then calculated using a single scattering model. The expected linear polarization at optical is found to peak at around spectral type L1. For a fixed rotational velocity, the degree of polarization decreases from hotter to cooler objects. However, with the increase in mean grain size, the degree of linear polarization reduces significantly. We fit the recently observed linear polarimetric data of L dwarfs and find that single dust scattering model coupled with the chemical equilibrium models of condensates is consistent with the observational results.

Sujan Sengupta; Sun Kwok

2005-02-16

324

Multilayer Thin Film Polarizer Design for Far Ultraviolet using Induced Transmission and Absorption Technique  

NASA Technical Reports Server (NTRS)

Good theoretical designs of far ultraviolet polarizers have been reported using a MgF2/Al/MgF2 three layer structure on a thick Al layer as a substrate. The thicknesses were determined to induce transmission and absorption of p-polarized light. In these designs Al optical constants were used from films produced in ultrahigh vacuum (UHV: 10(exp -10) torr). Reflectance values for polarizers fabricated in a conventional high vacuum (p approx. 10(exp -6 torr)) using the UHV design parameters differed dramatically from the design predictions. Al is a highly reactive material and is oxidized even in a high vacuum chamber. In order to solve the problem other metals have been studied. It is found that a larger reflectance difference is closely related to higher amplitude and larger phase difference of Fresnel reflection coefficients between two polarizations at the boundary of MgF2/metal. It is also found that for one material a larger angle of incidence from the surface normal brings larger amplitude and phase difference. Be and Mo are found good materials to replace Al. Polarizers designed for 121.6 nm with Be at 60 deg and with Mo at 70 deg are shown as examples.

Kim, Jongmin; Zukic, Muamer; Wilson, Michele M.; Park, Jung Ho; Torr, Douglas G.

1994-01-01

325

Induced Polarization in the $^2$H($?,\\vec n$)$^1$H Reaction at Low Energy  

E-print Network

The induced polarization, $P^\\prime_y$, of the neutron in the deuteron photo-disintegration from threshold up to 30 MeV is calculated using a variety of different, latest-generation potentials--Argonne $v_{18}$, Bonn 2000, and Nijmegen I-- and a realistic model for the nuclear electromagnetic current operator, including one- and two-body terms. The model dependence of the theoretical predictions is found to be very small. These predictions are systematically larger in magnitude than the measured $P^\\prime_y$ values, and corroborate the conclusions of an earlier, and much older, study. There is considerable scatter in the available experimental data. New and more accurate measurements of the induced polarization in the $^2$H($\\gamma,\\vec n$)$^1$H reaction are needed in order to establish unequivocally whether there is a discrepancy between theory and experiment.

R. Schiavilla

2005-05-25

326

B-mode polarization induced by gravitational waves from kinks on infinite cosmic strings  

E-print Network

We investigate the effect of the stochastic gravitational wave (GW) background produced by kinks on infinite cosmic strings, whose spectrum was derived in our previous work, on the B-mode power spectrum of the cosmic microwave background (CMB) anisotropy. We find that the B-mode polarization due to kinks is comparable to that induced by the motion of the string network and hence the contribution of GWs from kinks is important for estimating the B-mode power spectrum originating from cosmic strings. If the tension of cosmic strings \\mu is large enough i.e., G\\mu >~ 10^{-8}, B-mode polarization induced by cosmic strings can be detected by future CMB experiments.

Masahiro Kawasaki; Koichi Miyamoto; Kazunori Nakayama

2010-10-25

327

Light Induced Polarity of Redox Reactions in Leaves of Elodea canadensis Michx.  

PubMed

This paper reports that extracellular reductase activity in leaves of Elodea canadensis, hitherto never associated with polar processes thought to be involved in bicarbonate utilization, also shows a very marked polarity in light. The effect of ferricyanide, applied to the lower side of illuminated leaves, was a depolarization of the membrane electrical potential of up to 110 millivolts, while no depolarization was induced when ferricyanide was applied to the upper side. In the dark ferricyanide induced a depolarization when applied to either the upper or to the lower side of the leaf. Staining with tetrazolium salts, specific indicators for reductase activity, resulted in the formation of a precipitate on the lower side of the leaf when illuminated and on both sides in the dark. The precipitate was only located along the plasmalemma. PMID:16665663

Elzenga, J T; Prins, H B

1987-09-01

328

Eliminating polarization-induced fading in interferometric fiber optic arrays by modulation  

NASA Astrophysics Data System (ADS)

This paper puts forward a new method to overcome the polarization-induced fading (PIF) in conventional low- birefringence optical fiber constructed interferometric sensors arrays. By inducing high frequency modulation to the state of polarization at the output end of the array, the maximum PIF variation of each sensor's signal is 4.7dB or 6.3dB according to the selection of modulation signal. Combined with an electronic automatic gain control circuit or dividing each sensor's signal by its visibility, each sensor's signal fading is recovered at the expense of a relevant signal/noise degradation of 4.7dB or 6.3dB.

Zhou, Xiaodong; Zhou, Wen; Tang, Weizhong; Ye, Xianfeng

1998-08-01

329

Detection of gravity-induced polarity of cytoplasmic streaming in Chara  

Microsoft Academic Search

Summary Gravity induces a polarity of cytoplasmic streaming in vertically-oriented internodal cells of characean algae. The motive force that powers cytoplasmic streaming is generated at the ectoplasmic\\/endoplasmic interface. The velocity of streaming, which is about 100 µm\\/s at this interface, decreases with distance from the interface on either side of the cell to 0 µm\\/s near the middle. Therefore, when

M. P. Staves; R. Wayne; A. C. Leopold

1995-01-01

330

Spread of HTLV-I Between Lymphocytes by Virus-Induced Polarization of the Cytoskeleton  

Microsoft Academic Search

Cell contact is required for efficient transmission of human T cell leukemia virus- type 1 (HTLV-I) between cells and between individuals, because naturally infected lymphocytes produce virtually no cell-free infectious HTLV-I particles. However, the mechanism of cell-to-cell spread of HTLV-I is not understood. We show here that cell contact rapidly induces polarization of the cytoskeleton of the infected cell to

Tadahiko Igakura; Jane C. Stinchcombe; Peter K. C. Goon; Graham P. Taylor; Jonathan N. Weber; Gillian M. Griffiths; Yuetsu Tanaka; Mitsuhiro Osame; Charles R. M. Bangham

2003-01-01

331

Three-Dimensional Resistivity and Induced-Polarization Modeling Using Buried Electrodes  

Microsoft Academic Search

The three-dimensional induced-polarization and resistivity-modeling problem for buried source and receiver electrodes is solved by using a modified form of Barnett's surface-integral technique originally developed for surface-electrode configurations. Six different buried electrode configurations are considered in this study: three types of hole-to-hole configurations, hole-to-surface and surface-to-hole configurations, and the single hole (bipole-bipole) configuration. Results show there is no ''best'' method

Jeffrey J. Daniels

1977-01-01

332

A model-oriented approach to measure rain-induced cross-polarization  

Microsoft Academic Search

In this paper a new model oriented approach to measuring rain-induced cross-polarization is outlined: it aims at characterising\\u000a the physical properties of the depolarising medium rather than at directly measuring the channel depolarization, which is\\u000a the variable of direct interest for system design. This approach, which allows subsequent determination of depolarization\\u000a has the advantages of allowing a better understanding of

Carlo Capsoni; Aldo Paraboni; Francesco Fedi; Dario Maggiori

1981-01-01

333

Angular distribution of products of ternary nuclear fission induced by cold polarized neutrons  

Microsoft Academic Search

Within quantum fission theory, angular distributions of products originating from the ternary fission of nuclei that is induced\\u000a by polarized cold and thermal neutrons are investigated on the basis of a nonevaporative mechanism of third-particle emission\\u000a and a consistent description of fission-channel coupling. It is shown that the inclusion of Coriolis interaction both in the\\u000a region of the discrete and

V. E. Bunakov; S. G. Kadmensky; S. S. Kadmensky

2008-01-01

334

Measurement of Stark widths of Ni II spectral lines by laser induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

The Stark widths of 53 Ni II spectral lines have been measured by laser induced breakdown spectroscopy. The laser induced plasmas have been generated from Ni-Cu and Ni-Al alloys with a wide range of nickel concentrations. The electron density at the different instants of the plasma lifetime has been determined from the Stark broadening of the H? line and is in the range (1.6-6.8)×1017 cm-3. The plasma temperature, measured by the Boltzmann plot method, is in the range 13100-18000 K. Within the ranges of electron density and temperature in the experiment and the statistical errors, the Stark widths are found to be proportional to the electron density. A procedure, based on the curve-of-growth methodology and the use of samples with different nickel concentrations, has been applied to reduce self-absorption. The Stark widths obtained are compared to experimental and theoretical data available in the literature.

Aguilera, J. A.; Aragón, C.; Manrique, J.

2013-01-01

335

PORTA: A three-dimensional multilevel radiative transfer code for modeling the intensity and polarization of spectral lines with massively parallel computers  

NASA Astrophysics Data System (ADS)

The interpretation of the intensity and polarization of the spectral line radiation produced in the atmosphere of the Sun and of other stars requires solving a radiative transfer problem that can be very complex, especially when the main interest lies in modeling the spectral line polarization produced by scattering processes and the Hanle and Zeeman effects. One of the difficulties is that the plasma of a stellar atmosphere can be highly inhomogeneous and dynamic, which implies the need to solve the non-equilibrium problem of the generation and transfer of polarized radiation in realistic three-dimensional (3D) stellar atmospheric models. Here we present PORTA, an efficient multilevel radiative transfer code we have developed for the simulation of the spectral line polarization caused by scattering processes and the Hanle and Zeeman effects in 3D models of stellar atmospheres. The numerical method of solution is based on the non-linear multigrid iterative method and on a novel short-characteristics formal solver of the Stokes-vector transfer equation which uses monotonic Bézier interpolation. Therefore, with PORTA the computing time needed to obtain at each spatial grid point the self-consistent values of the atomic density matrix (which quantifies the excitation state of the atomic system) scales linearly with the total number of grid points. Another crucial feature of PORTA is its parallelization strategy, which allows us to speed up the numerical solution of complicated 3D problems by several orders of magnitude with respect to sequential radiative transfer approaches, given its excellent linear scaling with the number of available processors. The PORTA code can also be conveniently applied to solve the simpler 3D radiative transfer problem of unpolarized radiation in multilevel systems.

Št?pán, Ji?í; Trujillo Bueno, Javier

2013-09-01

336

Analysis and spectral assignments of mixed actinide oxide samples using laser-induced breakdown spectroscopy (LIBS).  

PubMed

In this paper, we report for the first time the identification and assignments of complex atomic emission spectra of mixed actinide oxides using laser-induced plasma spectroscopy or laser-induced breakdown spectroscopy (LIBS). Preliminary results of LIBS measurements on samples of uranium dioxide (UO2)/plutonium dioxide (PuO2) and UO2/PuO2/americium dioxide (AmO2)/neptunium dioxide (NpO2) simulated fuel pellets (or mixed actinide oxide samples) are reported and discussed. We have identified and assigned >800 atomic emission lines for a UO2/PuO2/AmO2/NpO2 fuel pellet thus far. The identification and assignments of spectral emission lines for U, Pu, and Am are consistent with wavelength data from the literature. However, only a few emission lines have been assigned with a high degree of confidence for Np compared with atomic emission data from the literature. We also indicate where atomic emission lines for Cm would most likely appear in the spectral regions shown. Finally, we demonstrate that a LIBS system with a resolving power of approximately 20,000 is adequate for analyzing complex mixtures of actinide elements within the same sample. PMID:23601543

Barefield, James E; Judge, Elizabeth J; Berg, John M; Willson, Stephen P; Le, Loan A; Lopez, Leon N

2013-04-01

337

Polar surface effects on the thermal conductivity of ZnO nanowires: a shell-like surface reconstruction-induced  

E-print Network

Polar surface effects on the thermal conductivity of ZnO nanowires: a shell-like surface reconstruction-induced preserving mechanism Jin-Wu Jiang,*ab Harold S. Park*c and Timon Rabczuk*bd We perform molecular dynamics (MD) simulations to investigate the effect of polar surfaces on the thermal transport

Lin, Xi

338

The effect of polar nanoregions on electromechanical properties of relaxor-PbTiO3 crystals: Extracting from electric-field-induced polarization and strain behaviors  

NASA Astrophysics Data System (ADS)

The electric-field-induced polarization and strain of Pb(Mg1/3Nb2/3)O3 (PMN) and Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 (PMN-0.27PT) crystals were investigated at temperatures above their respective maximum permittivity temperatures Tm, where the macro-polarizations vanish while polar nanoregions (PNRs) still persist. The local structure of PNRs was proved to be of rhombohedral phase in PMN, while the local phase was unstable for PMN-0.27PT, leading to the isotropic spontaneous polarization of PNRs and strong anisotropic electric-field-induced strain. The electrostrictive coefficient Q33 was determined as functions of temperature and E-field, with 50% increment over temperature range of 20 ˜120 °C for PMN, being attributed to the decrease of spontaneous polarization of PNRs with increasing temperature. The results presented in this paper indicate that the local structure and spontaneous polarization of PNRs play important roles on electromechanical properties of relaxor ferroelectrics.

Li, Fei; Xu, Zhuo; Zhang, Shujun

2014-09-01

339

Induced polarized state in intentionally grown oxygen deficient KTaO{sub 3} thin films  

SciTech Connect

Deliberately oxygen deficient potassium tantalate thin films were grown by RF magnetron sputtering on Si/SiO{sub 2}/Ti/Pt substrates. Once they were structurally characterized, the effect of oxygen vacancies on their electric properties was addressed by measuring leakage currents, dielectric constant, electric polarization, and thermally stimulated depolarization currents. By using K{sub 2}O rich KTaO{sub 3} targets and specific deposition conditions, KTaO{sub 3-{delta}} oxygen deficient thin films with a K/Ta = 1 ratio were obtained. Room temperature X-ray diffraction patterns show that KTaO{sub 3-{delta}} thin films are under a compressive strain of 2.3% relative to KTaO{sub 3} crystals. Leakage current results reveal the presence of a conductive mechanism, following the Poole-Frenkel formalism. Furthermore, dielectric, polarization, and depolarization current measurements yield the existence of a polarized state below T{sub pol} {approx} 367 Degree-Sign C. A Cole-Cole dipolar relaxation was also ascertained apparently due to oxygen vacancies induced dipoles. After thermal annealing the films in an oxygen atmosphere at a temperature above T{sub pol}, the aforementioned polarized state is suppressed, associated with a drastic oxygen vacancies reduction emerging from annealing process.

Mota, D. A.; Romaguera-Barcelay, Y.; Tkach, A.; Agostinho Moreira, J.; Almeida, A. [IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Department of Physics and Astronomy, Faculty of Science of University of Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Perez de la Cruz, J. [INESC TEC, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Vilarinho, P. M. [Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Tavares, P. B. [Centro de Quimica, Universidade de Tras-os-Montes e Alto Douro, Apartado 1013, 5001-801 Vila Real (Portugal)

2013-07-21

340

Measurement of the induced Lambda^0(1116) polarization in K^+ electroproduction at CLAS  

SciTech Connect

We are using the p(e,e'K{sup +}p){pi}{sup -} reaction to perform a measurement of the induced polarization of the electroproduced L(1116) using its p{pi}{sup -} parity-violating weak decay. This study uses the CEBAF Large Acceptance Spectrometer (CLAS) to detect the scattered electron, the kaon, and the decay proton over the kinematics 0.8 {le} Q{sup 2} {le} 3.5 GeV{sup 2}, 1.6 {le} W {le} 3.0 GeV, and the full kaon CM angle range. In this experiment a 5.5 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. The goal is to map out the kinematic dependencies for this polarization observable to provide new constraints for models of the electromagnetic production of K-hyperon final states. Along with previously published photo- and electroproduction cross sections and polarization observables from CLAS, SAPHIR, LEPS, and GRAAL, these data are needed in a coupled-channel analysis to identify previously unobserved s-channel resonances. Preliminary polarization results will be presented.

M. Gabrielyan, B. Raue, D. S. Carman, K. Park

2012-04-01

341

Polarization of macrophages induced by Toxoplasma gondii and its impact on abnormal pregnancy in rats.  

PubMed

Toxoplasma gondii infection is the leading cause of fetal intrauterine growth retardation among the five kinds of pathogens termed as TORCH, including Toxoplasma, Rubella virus, Cytomegalo virus, herpes virus and others during pregnancy. Pathogens infect the fetus through the placenta. T. gondii infection may result in congenital toxoplasmosis, miscarriage, stillbirth, and preemie, and increase pregnancy complications. Adaptive immune response induced by T. gondii infection stimulates T cells and macrophages to produce high levels of cytokines. Physiologically, the microenvironment of pregnancy was Th2-dominant. Here we set up a pregnant Sprague-Dawley rat model, and reported the polarization of macrophages induced by genotype Chinese 1 strain (Wh6) of Toxoplasma, and its adverse impact on pregnancy. The results showed that Wh6 infection pre- or in-gestation both led to abnormal pregnancy outcomes. Peritoneal macrophages in pre-gestation infection were polarized toward classically activated macrophages (M1), while in-gestation infection drove macrophages to polarize toward M2 activation. The Th2-dominant immune response in pregnant rat somewhat inhibits the excessive bias of the macrophages toward M1, and partially, toward M2. Infection of pre- and in-gestation may alter the physiological immune microenvironment in pregnant rats, giving rise to abnormal pregnancy outcomes. PMID:25496968

Kong, Lanting; Zhang, Qian; Chao, Jing; Wen, Huiqin; Zhang, Yihua; Chen, He; Pappoe, Faustina; Zhang, Aimei; Xu, Xiucai; Cai, Yihong; Li, Min; Luo, Qingli; Zhang, Linjie; Shen, Jilong

2015-03-01

342

Spectral Induced Polarization Response of Unconsolidated Saturated Sand and Surfactant Solutions  

EPA Science Inventory

Dense non-aqueous phase liquids (DNAPL), such as chlorinated solvents, are common groundwater contaminants. Traditional pump-and-treat methods are often not effective at removing residual DNAPL from the subsurface. Surfactant-enhanced aquifer remediation is a promising remediatio...

343

Influence of Oil Saturation Upon Spectral Induced Polarization of Oil Bearing Sands  

EPA Science Inventory

The presence of oil in an unconsolidated granular porous material such as sand changes both the resistivity of the material and the value of the phase shift between the low-frequency current and the voltage. The resistivity and the phase angle can be written as a complex-valued r...

344

Contact-Induced Mitochondrial Polarization Supports HIV-1 Virological Synapse Formation  

PubMed Central

ABSTRACT Rapid HIV-1 spread between CD4 T lymphocytes occurs at retrovirus-induced immune cell contacts called virological synapses (VS). VS are associated with striking T cell polarization and localized virus budding at the site of contact that facilitates cell-cell spread. In addition to this, spatial clustering of organelles, including mitochondria, to the contact zone has been previously shown. However, whether cell-cell contact specifically induces dynamic T cell remodeling during VS formation and what regulates this process remain unclear. Here, we report that contact between an HIV-1-infected T cell and an uninfected target T cell specifically triggers polarization of mitochondria concomitant with recruitment of the major HIV-1 structural protein Gag to the site of cell-cell contact. Using fixed and live-cell imaging, we show that mitochondrial and Gag polarization in HIV-1-infected T cells occurs within minutes of contact with target T cells, requires the formation of stable cell-cell contacts, and is an active, calcium-dependent process. We also find that perturbation of mitochondrial polarization impairs cell-cell spread of HIV-1 at the VS. Taken together, these data suggest that HIV-1-infected T cells are able to sense and respond to contact with susceptible target cells and undergo dynamic cytoplasmic remodeling to create a synaptic environment that supports efficient HIV-1 VS formation between CD4 T lymphocytes. IMPORTANCE HIV-1 remains one of the major global health challenges of modern times. The capacity of HIV-1 to cause disease depends on the virus's ability to spread between immune cells, most notably CD4 T lymphocytes. Cell-cell transmission is the most efficient way of HIV-1 spread and occurs at the virological synapse (VS). The VS forms at the site of contact between an infected cell and an uninfected cell and is characterized by polarized assembly and budding of virions and clustering of cellular organelles, including mitochondria. Here, we show that cell-cell contact induces rapid recruitment of mitochondria to the contact site and that this supports efficient VS formation and consequently cell-cell spread. Additionally, we observed that cell-cell contact induces a mitochondrion-dependent increase in intracellular calcium, indicative of cellular signaling. Taken together, our data suggest that VS formation is a regulated process and thus a potential target to block HIV-1 cell-cell spread. PMID:25320323

Groppelli, Elisabetta; Starling, Shimona

2014-01-01

345

Polarization dependent formation of femtosecond laser-induced periodic surface structures near stepped features  

SciTech Connect

Laser-induced periodic surface structures (LIPSS) are formed near 110?nm-tall Au microstructured edges on Si substrates after single-pulse femtosecond irradiation with a 150 fs pulse centered near a 780 nm wavelength. We investigate the contributions of Fresnel diffraction from step-edges and surface plasmon polariton (SPP) excitation to LIPSS formation on Au and Si surfaces. For certain laser polarization vector orientations, LIPSS formation is dominated by SPP excitation; however, when SPP excitation is minimized, Fresnel diffraction dominates. The LIPSS orientation and period distributions are shown to depend on which mechanism is activated. These results support previous observations of the laser polarization vector influencing LIPSS formation on bulk surfaces.

Murphy, Ryan D. [Applied Physics Program, University of Michigan, Ann Arbor, Michigan 48109 (United States); Torralva, Ben [Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States); Adams, David P. [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Yalisove, Steven M. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2014-06-09

346

ANALYSIS OF SEEING-INDUCED POLARIZATION CROSS-TALK AND MODULATION SCHEME PERFORMANCE  

SciTech Connect

We analyze the generation of polarization cross-talk in Stokes polarimeters by atmospheric seeing, and its effects on the noise statistics of spectropolarimetric measurements for both single-beam and dual-beam instruments. We investigate the time evolution of seeing-induced correlations between different states of one modulation cycle and compare the response to these correlations of two popular polarization modulation schemes in a dual-beam system. Extension of the formalism to encompass an arbitrary number of modulation cycles enables us to compare our results with earlier work. Even though we discuss examples pertinent to solar physics, the general treatment of the subject and its fundamental results might be useful to a wider community.

Casini, R.; De Wijn, A. G.; Judge, P. G. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States)

2012-09-20

347

A comparison of laser-induced-damage-threshold of two types of dielectric polarizing beam splitters  

NASA Astrophysics Data System (ADS)

Laser-induced-damage-threshold (LIDT) of polarizing Brewster-angle beam splitters based on two different layer system designs was measured using a laser apparatus working at 1060 nm wavelength with 10 ns pulse length and 1-on-1 test mode. Two sets of samples with different design of layer system using TiO2/SiO2 coating materials were examined. Both BK7 and fused silica substrate materials were used for manufacturing of samples. The measured damage thresholds in S- and P-polarization were compared with computed values of the internal electric field inside of the layer system and with computed values of absorption as a measure of integral interaction of laser beam throughout the layer system.

Å koda, Václav

2013-11-01

348

Nuclear-Charge Polarization at Scission in Proton-Induced Fission of Light Actinides  

NASA Astrophysics Data System (ADS)

Fragment mass yields and the average neutron multiplicity in the proton-induced fission of 232Th and 233U were measured by a double time-of-flight method. The most probable charges of secondary fragments were evaluated from the fragment mass yields measured and the fractional cumulative yields reported. The nuclear charge polarization of primary fragments at scission was obtained by correcting the most probable charge of secondary fragments for neutron evaporation. The results show that the nuclear-charge polarization at scission is associated with the liquid-drop properties of nuclei and the proton shell effect with Z = 50 of heavy fragments and that it is practically insensitive to mass and excitation energy of the fissioning nucleus in the region of light actinides.

Nishinaka, I.; Tanikawa, M.; Nagame, Y.; Nakahara, H.

2009-03-01

349

First principles calculation of polarization induced interfacial charges in GaN/AlN heterostructures  

E-print Network

We propose a new method to calculate polarization induced interfacial charges in semiconductor heterostructures using classical electrostatics applied to real-space band diagrams from first principles calculations and apply it to GaN/AlN heterostructures with ultrathin AlN layers (4-6 monolayers). We show that the calculated electric fields and interfacial charges are independent of the exchange-correlation functionals used (local-density approximation and hybrid functionals). We also find the calculated interfacial charge of (6.8 +/- 0.4) x 10^13 cm-2 to be in excellent agreement with experiments and the value of 6.58 x 10^13 cm-2 calculated from bulk polarization constants, validating the use of bulk constants even for very thin films.

Rohan Mishra; Oscar D. Restrepo; Siddharth Rajan; Wolfgang Windl

2011-05-17

350

Polarization dependent formation of femtosecond laser-induced periodic surface structures near stepped features  

NASA Astrophysics Data System (ADS)

Laser-induced periodic surface structures (LIPSS) are formed near 110 nm-tall Au microstructured edges on Si substrates after single-pulse femtosecond irradiation with a 150 fs pulse centered near a 780 nm wavelength. We investigate the contributions of Fresnel diffraction from step-edges and surface plasmon polariton (SPP) excitation to LIPSS formation on Au and Si surfaces. For certain laser polarization vector orientations, LIPSS formation is dominated by SPP excitation; however, when SPP excitation is minimized, Fresnel diffraction dominates. The LIPSS orientation and period distributions are shown to depend on which mechanism is activated. These results support previous observations of the laser polarization vector influencing LIPSS formation on bulk surfaces.

Murphy, Ryan D.; Torralva, Ben; Adams, David P.; Yalisove, Steven M.

2014-06-01

351

Four-wave mixing using polarization grating induced thermal grating in liquids exhibiting circular dichroism  

SciTech Connect

A novel four-wave mixing technique for the detection of circular dichroism in optically active liquid samples is demonstrated. When two cross-polarized laser beams are crossed at a small angle in a circular dichroic liquid a weak thermal grating is produced with a phase depending on the sign of the circular dichroism. The authors show that the polarization of one of the beams can be modified to allow coherent interference with an intensity-grating induced thermal grating. A probe beam scattering from the composite grating results in a signal that reveals the sign and magnitude of the circular dichroism. The use of this technique to optimize the signal-to-noise ratio in the presence of scattered light and laser intensity noise is discussed.

Nunes, J.A.; Tong, W.G. [San Diego State Univ., CA (United States). Dept. of Chemistry; Chandler, D.W.; Rahn, L.A. [Sandia National Lab., Livermore, CA (United States). Combustion Research Facility

1995-04-01

352

Vector magnetometry based on electromagnetically induced transparency in linearly polarized light  

NASA Astrophysics Data System (ADS)

We develop a generalized principle of electromagnetically induced transparency (EIT) vector magnetometry based on high-contrast EIT resonances and the symmetry of atom-light interaction in the linearly polarized bichromatic fields. Operation of such vector magnetometer on the D1 line of Rb87 has been demonstrated. The proposed compass-magnetometer has an increased immunity to shifts produced by quadratic Zeeman and ac-Stark effects, as well as by atom-buffer gas and atom-atom collisions. In our proof-of-principle experiment the detected angular sensitivity to magnetic field orientation is 10-3 deg/Hz1/2, which is limited by laser intensity fluctuations, light polarization quality, and magnitude of the magnetic field.

Yudin, V. I.; Taichenachev, A. V.; Dudin, Y. O.; Velichansky, V. L.; Zibrov, A. S.; Zibrov, S. A.

2010-09-01

353

Vector magnetometry based on electromagnetically induced transparency in linearly polarized light  

SciTech Connect

We develop a generalized principle of electromagnetically induced transparency (EIT) vector magnetometry based on high-contrast EIT resonances and the symmetry of atom-light interaction in the linearly polarized bichromatic fields. Operation of such vector magnetometer on the D{sub 1} line of {sup 87}Rb has been demonstrated. The proposed compass-magnetometer has an increased immunity to shifts produced by quadratic Zeeman and ac-Stark effects, as well as by atom-buffer gas and atom-atom collisions. In our proof-of-principle experiment the detected angular sensitivity to magnetic field orientation is 10{sup -3} deg/Hz{sup 1/2}, which is limited by laser intensity fluctuations, light polarization quality, and magnitude of the magnetic field.

Yudin, V. I. [Institute of Laser Physics, Siberian Branch of RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Novosibirsk State Technical University, Novosibirsk 630092 (Russian Federation); Taichenachev, A. V. [Institute of Laser Physics, Siberian Branch of RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Dudin, Y. O. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430 (United States); Velichansky, V. L. [Moscow State Engineering and Physics Institute, Moscow 115409 (Russian Federation); Lebedev Physical Institute, RAS, Moscow 117924 (Russian Federation); Zibrov, A. S. [Physics Department, Harvard University, Cambridge, Massachusetts 02138 (United States); Zibrov, S. A. [Lebedev Physical Institute, RAS, Moscow 117924 (Russian Federation)

2010-09-15

354

Strain-induced phase transition and electron spin-polarization in graphene spirals  

PubMed Central

Spin-polarized triangular graphene nanoflakes (t-GNFs) serve as ideal building blocks for the long-desired ferromagnetic graphene superlattices, but they are always assembled to planar structures which reduce its mechanical properties. Here, by joining t-GNFs in a spiral way, we propose one-dimensional graphene spirals (GSs) with superior mechanical properties and tunable electronic structures. We demonstrate theoretically the unique features of electron motion in the spiral lattice by means of first-principles calculations combined with a simple Hubbard model. Within a linear elastic deformation range, the GSs are nonmagnetic metals. When the axial tensile strain exceeds an ultimate strain, however, they convert to magnetic semiconductors with stable ferromagnetic ordering along the edges. Such strain-induced phase transition and tunable electron spin-polarization revealed in the GSs open a new avenue for spintronics devices. PMID:25027550

Zhang, Xiaoming; Zhao, Mingwen

2014-01-01

355

Hyper-NA imaging with solid-immersion optics and induced polarization imaging  

NASA Astrophysics Data System (ADS)

Solid immersion lens (SIL) is used in microscopic systems for hyper numerical aperture (NA) imaging. The NA of the SIL microscope can be larger than 2 by using the high refractive index SIL. In this paper, examples of hyper-NA (NA>1.4) imaging are illustrated, including a normal SIL microscope for imaging samples like CPU chips, photomasks which have no cover layer and a special SIL microscope for imaging samples like Blu-Ray optical discs which have cover layer to protect the pattern. In both cases, good contrast images can be achieved by minimizing the system aberration. At the end, characteristics of induced polarization imaging (imaging through crossed polarizers) and a twostep solid immersion lens using Gallium Phosphide (GaP) (NA~2) are discussed.

Zhang, Jun; Yang, Seung-Hune; Milster, Tom D.; Bletscher, Warren; Hansen, Delbert

2010-02-01

356

Polar Plasmodium falciparum lipids induce lipogenesis in rat adipocytes in vitro.  

PubMed

Previous studies have shown that 'toxic malarial antigens' released by Plasmodium yoelii can induce hypoglycaemia in mice and act synergistically with insulin in stimulating lipogenesis in rat adipocytes in vitro. In this study, it was shown that similar bioactivity could be detected in Plasmodium falciparum culture supernatant, and the molecular basis of this activity was further investigated. Boiled spent culture medium from P. falciparum cultures ('BS-Pf') (exclusively released into the culture supernatant when schizonts rupture) acts in synergy with insulin to increase lipogenesis in a rat adipocyte assay by more than 250% (P < 0.001). Control preparations prepared from non-parasitized erythrocytes grown under similar conditions had no effect (P < 0.001). While contamination with mycoplasma has previously been shown to interfere with the interpretation of data obtained with other molecules thought to be released from P. falciparum in culture, including those inducing TNF-alpha and NO production by macrophages, such contamination was unequivocally ruled out here. BS-Pf alone did not stimulate the lipogenesis in short-term assays (less than 4 h), while long-term exposure of rat adipocytes to BS-Pf alone (12-24 h) caused a stimulation of lipogenesis at a level comparable to that observed with insulin. Furthermore, lipogenesis-inducing activity was also detected in the serum of squirrel monkeys infected with different species of malaria parasites (P. vivax, P. falciparum and P. brasilianum). Preliminary biochemical characterization showed that the biological activity was found in the solvent-extracted polar lipid fraction of boiled supernatant of P. falciparum cultures. All the different polar lipid fractions, collected from silica gel column chromatography, showed a comparable lipogenesis-inducing activity. Enzymatic treatment by phospholipase C of the lipid fraction, which co-migrated with the phosphatidylcholine standard, showed that the activity of the fraction was associated with the 1,2-diacylglycerol (1,2-DAG) moieties released from polar lipids. When this exogenous 1,2-DAG was added to the adipocyte cultures (short- and long-term cultures), it induced stimulation of lipogenesis in rat adipocytes, while no lipogenic activity was obtained from bacterial polar lipids and 1,2-DAG isolated from unparasitized erythrocytes. The importance of these findings is discussed with reference to other toxic malarial antigens and also to the potential role of these molecules in the induction of hypoglycaemia in the severe forms of malaria. PMID:11165922

Zakeri, S; Taylor, K; Goad, J L; Hommel, M

2000-12-01

357

Plasma property effects on spectral line broadening in double-pulse laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Double-pulse Laser-Induced Breakdown Spectroscopy (LIBS) in an orthogonal configuration was used to investigate plasma temperature and electron density effects on Mg II emission spectral line broadening. The experiments were carried out with two Nd:YAG lasers, one operating at 355 nm for ablation and the other one at 1064 nm for plasma reheating in air at atmospheric pressure. Temporally resolved plasma temperature and electron density were measured at various delay times. Data in this study show prolonged emission of Mg II (280.27 nm) as well as enhancement of the signal intensity when using double-pulse excitation compared to the single-pulse case. An enhancement of ˜8× was attained with a delay between the laser pulses equal to 1 ?s. The enhancement was accompanied by higher plasma temperature and increased electron density. The double-pulse LIBS configuration provides energy to sustain the plasma emission at a period in time when the linewidth is minimum, thereby improving the analytical capabilities of low spectral resolution instrumentation typically used in LIBS system.

Choi, Inhee; Mao, Xianglei; Gonzalez, J. Jhanis; Russo, Richard E.

2013-03-01

358

Unexpected temporal evolution of atomic spectral lines of aluminum in a laser induced breakdown spectroscopy experiment  

NASA Astrophysics Data System (ADS)

The temporal evolution of the laser induced breakdown (LIBS) signal of a pure aluminum sample was studied under nitrogen and air atmospheres. In addition to the usual decrease of signal due to plasma cooling, unexpected temporal evolutions were observed for a spectral lines of aluminum, which revealed the existence of collisional energy transfer effects. Furthermore, molecular bands of AlN and AlO were observed in the LIBS spectra, indicating recombination of aluminum with the ambient gas. Within the experimental conditions reported in this study, both collisional energy transfer and recombination processes occurred around 1.5 ?s after the laser shot. This highlights the possible influence of collisional and chemical effects inside the plasma that can play a role on LIBS signals.

Saad, Rawad; L'Hermite, Daniel; Bousquet, Bruno

2014-11-01

359

Self-screening of the quantum confined Stark effect by the polarization induced bulk charges in the quantum barriers  

SciTech Connect

InGaN/GaN light-emitting diodes (LEDs) grown along the polar orientations significantly suffer from the quantum confined Stark effect (QCSE) caused by the strong polarization induced electric field in the quantum wells, which is a fundamental problem intrinsic to the III-nitrides. Here, we show that the QCSE is self-screened by the polarization induced bulk charges enabled by designing quantum barriers. The InN composition of the InGaN quantum barrier graded along the growth orientation opportunely generates the polarization induced bulk charges in the quantum barrier, which well compensate the polarization induced interface charges, thus avoiding the electric field in the quantum wells. Consequently, the optical output power and the external quantum efficiency are substantially improved for the LEDs. The ability to self-screen the QCSE using polarization induced bulk charges opens up new possibilities for device engineering of III-nitrides not only in LEDs but also in other optoelectronic devices.

Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Wei Sun, Xiao, E-mail: exwsun@ntu.edu.sg, E-mail: volkan@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Volkan Demir, Hilmi, E-mail: exwsun@ntu.edu.sg, E-mail: volkan@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Department of Electrical and Electronics, Department of Physics, and UNAM-Institute of Material Science and Nanotechnology, Bilkent University, TR-06800 Ankara (Turkey)

2014-06-16

360

Vacuum polarization induced by a cosmic string in anti-de Sitter spacetime  

E-print Network

In this paper we investigate the vacuum expectation values (VEVs) of the field squared and the energy-momentum tensor associated with a massive scalar quantum field induced by a generalized cosmic string in D-dimensional anti-de Sitter (AdS) spacetime. In order to develop this analysis we evaluate the corresponding Wightman function. As we shall observe, this function is expressed as the sum of two terms: the first one corresponds to the Wightman function in pure AdS bulk and the second one is induced by the presence of the string. The second contribution is finite at coincidence limit and is used to provide closed expressions for the parts in the VEVs of the field squared and the energy-momentum tensor induced by the presence of the string. Because the analysis of vacuum polarizations effects in pure AdS spacetime have been developed in the literature, here we are mainly interested in the investigation of string-induced effects. We show that the curvature of the background spacetime has an essential influence on the VEVs at distances larger than the curvature radius. In particular, at large distances the decay of the string-induced VEVs is power-law for both massless and massive fields. The string-induced parts vanish on the AdS boundary and they dominate the pure AdS part for points near the AdS horizon.

E. R. Bezerra de Mello; A. A. Saharian

2012-02-02

361

GSI promotes vincristine-induced apoptosis by enhancing multi-polar spindle formation  

PubMed Central

Gamma secretase inhibitors (GSI), cell-permeable small-molecule inhibitors of gamma secretase activity, had been originally developed for the treatment of Alzheimer disease. In recent years, it has been exploited in cancer research to inhibit Notch signaling that is aberrantly activated in various cancers. We previously found that GSI could synergize with anti-microtubule agent, vincristine (VCR) in a Notch-independent manner. Here, we delineate the underlying cell cycle-related mechanism using HeLa cells, which have strong mitotic checkpoints. GSI enhanced VCR-induced cell death, although GSI alone did not affect cell viability at all. GSI augmented VCR-induced mitotic arrest in a dose-dependent manner, which was preceded by apoptotic cell death, as shown by an increase in Annexin V-positive and caspase-positive cell population. Furthermore, GSI amplified multi-polar spindle formation triggered by VCR. Altogether, we show the evidence that GSI enhances VCR-induced apoptosis in HeLa cells via multi-polar mitotic spindle formation, independent of Notch signaling. These data suggest that one or more GS substrates, yet to be identified, in a post-GS processed form, may play a role in maintaining functional centrosomes/mitotic spindles. More significantly, the synergistic effect of GSI in combination with VCR could be exploited in clinical setting to improve the efficacy of VCR. PMID:24200971

Singh, Akannsha; Zapata, Mariana C; Choi, Yong Sung; Yoon, Sun-Ok

2014-01-01

362

Mycobacterium tuberculosislpdC, Rv0462, induces dendritic cell maturation and Th1 polarization  

SciTech Connect

Highlights: {yields} Treatment with Rv0462 induces the expression of surface molecules and the production of cytokines in DCs. {yields} Rv0462 induces the activation of MAPKs. {yields} Rv0462-treated DCs enhances the proliferation of CD4{sup +} T cells. -- Abstract: Mycobacterium tuberculosis, the etiological factor of pulmonary tuberculosis, causes significant morbidity and mortality worldwide. Activation of host immune responses for containment of mycobacterial infections involves participation of innate immune cells, such as dendritic cells (DCs). In this study, we demonstrated that the gene encoding lipoamide dehydrogenase C (lpdC) from M. tuberculosis, Rv0462, induce maturation and activation of DCs involved in the MAPKs signaling pathway. Moreover, Rv0462-treated DCs activated naive T cells, polarized CD4{sup +} and CD8{sup +} T cells to secrete IFN-{gamma} in syngeneic mixed lymphocyte reactions, which would be expected to contribute to Th1 polarization of the immune response. Our results suggest that Rv0462 can contribute to the innate and adaptive immune responses during tuberculosis infection, and thus modulate the clinical course of tuberculosis.

Heo, Deok Rim [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of)] [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Shin, Sung Jae; Kim, Woo Sik [Department of Microbiology, College of Medicine, Chungnam National University, Munwha-Dong, Jung-Ku, Daejeon 301-747 (Korea, Republic of)] [Department of Microbiology, College of Medicine, Chungnam National University, Munwha-Dong, Jung-Ku, Daejeon 301-747 (Korea, Republic of); Noh, Kyung Tae; Park, Jin Wook; Son, Kwang Hee [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of)] [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Park, Won Sun [Department of Physiology, Kangwon National University, School of Medicine, Chuncheon 200-701 (Korea, Republic of)] [Department of Physiology, Kangwon National University, School of Medicine, Chuncheon 200-701 (Korea, Republic of); Lee, Min-Goo [Department of Physiology, Korea University, College of Medicine, Anam-dong, Sungbuk-Gu, Seoul 136-705 (Korea, Republic of)] [Department of Physiology, Korea University, College of Medicine, Anam-dong, Sungbuk-Gu, Seoul 136-705 (Korea, Republic of); Kim, Daejin [Department of Anatomy, Chung-Ang University, College of Medicine, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756 (Korea, Republic of)] [Department of Anatomy, Chung-Ang University, College of Medicine, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756 (Korea, Republic of); Shin, Yong Kyoo [Department of Pharmacology, Chung-Ang University, College of Medicine, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756 (Korea, Republic of)] [Department of Pharmacology, Chung-Ang University, College of Medicine, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756 (Korea, Republic of); Jung, In Duk, E-mail: jungid@pusan.ac.kr [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Research Institute of Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Park, Yeong-Min, E-mail: immunpym@pusan.ac.kr [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of) [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Research Institute of Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of)

2011-08-05

363

Gravitational Wave Induced Rotation of the Plane of Polarization of Pulsar Signals  

E-print Network

We derive in this an expression for the rotation of plane of polarization, of an electromagnetic wave, induced by the field of a gravitational wave propagating along the same direction $\\approx \\f{G\\mu d^2\\Omega^4}{3\\o}$, $\\o$ and $\\Omega$ being their respective frequencies using the geometrical optics limit of the wave equation for fields. Estimating the effect for the case of pulses from binary pulsars, one finds it too small to be observable, there could be other sources like inspiralling binary or an asymmetric neutron star where the effect could be in the observable region.

A. R. Prasanna; S. Mohanty

2001-10-29

364

Shear wave induced resonance elastography of spherical masses with polarized torsional waves.  

PubMed

Shear Wave Induced Resonance (SWIR) is a technique for dynamic ultrasound elastography of confined mechanical inclusions. It was developed for breast tumor imaging and tissue characterization. This method relies on the polarization of torsional shear waves modeled with the Helmholtz equation in spherical coordinates. To validate modeling, an in vitro set-up was used to measure and image the first three eigenfrequencies and eigenmodes of a soft sphere. A preliminary in vivo SWIR measurement on a breast fibroadenoma is also reported. Results revealed the potential of SWIR elastography to detect and mechanically characterize breast lesions for early cancer detection. PMID:23687384

Henni, Anis Hadj; Schmitt, Cédric; Trop, Isabelle; Cloutier, Guy

2012-03-26

365

Altered Landscapes and Groundwater Sustainability — Exploring Impacts with Induced Polarization, DC Resistivity, and Thermal Tracing  

NASA Astrophysics Data System (ADS)

Anthropogenically impacted landscapes constitute rising proportions of the Earth’s surface that are characterized by generally elevated nutrient and sediment loadings concurrent with increased consumptive water withdrawals. In recent years a growing number of hydraulically engineered riparian habitat restoration projects have attempted to ameliorate negative impacts of land use on groundwater-surface water systems resulting, e.g., from agricultural practices and urban development. Often the nature of groundwater-surface water interactions in pre- and minimally altered systems is poorly known, making it difficult to assess the impacts of land use and restoration projects on groundwater sustainability. Traditional assessments of surface water parameters (flow, temperature, dissolved oxygen, biotic composition, etc.) can be complemented by hydraulic and thermal measurements to better understand the important role played by groundwater-surface water interactions. Hydraulic and thermal measurements are usually limited to point samples, however, making non-invasive and spatially extensive geophysical characterizations an attractive additional tool. Groundwater-surface water interactions along the Smith River, a tributary to the Missouri River in Montana, and Fish Creek and Flat Creek, tributaries to the Snake River in Wyoming, are being examined using a combination of hydraulic measurements, thermal tracing, and electrical-property imaging. Ninety-two direct-current (DC) resistivity and induced polarization cross sections were obtained at stream transects covering a wide variety of hydrogeologic settings ranging from shallow bedrock to thick alluvial sequences, nature of groundwater-surface water interactions (always gaining, always losing, or seasonally varying) and anthropogenic impacts (minimal low-intensity agriculture to major landscape engineering, including channel reconstruction). DC resistivity and induced polarization delineated mutually distinct features related to hydraulic architecture. For example, induced polarization imaging resolved channel-edge muck deposits that are presumed to be sites of low hydraulic conductivity, chemical reduction, and metal accumulation. DC resistivity delineated bedrock-alluvium contacts and showed potential for tracking changes in salinization. While electrical properties cannot substitute for hydraulic and thermal data, the addition of relatively rapidly acquired, spatially extensive resistivity and induced polarization imaging offers synergistic opportunities for interpretive hydrologic investigations.

Eddy-Miller, C.; Caldwell, R.; Wheeler, J.; McCarthy, P.; Binley, A. M.; Constantz, J. E.; Stonestrom, D. A.

2009-12-01

366

Assessment of system penalties induced by polarization mode dispersion in a 5 Gb\\/s optically amplified transoceanic link  

Microsoft Academic Search

The system penalties induced by polarization mode dispersion (PMD) in a 5 Gb\\/s optically amplified link are analyzed. A relation between differential group delays and system penalties is obtained from numerical simulations and used to derive analytic formulas for probability density functions of system penalties. Cumulated probabilities show that PMDs higher than 20 ps can induce significant fluctuations of the

F. Bruyere; O. Audouin

1994-01-01

367

THE JOURNAL OF CHEMICAL PHYSICS 135, 024201 (2011) Stark-induced adiabatic Raman passage for preparing polarized molecules  

E-print Network

THE JOURNAL OF CHEMICAL PHYSICS 135, 024201 (2011) Stark-induced adiabatic Raman passage for preparing polarized molecules Nandini Mukherjee and Richard N. Zarea) Department of Chemistry, Stanford online 8 July 2011) We propose a method based on Stark-induced adiabatic Raman passage (SARP

Zare, Richard N.

368

Performance analysis of 100 Gb/s polarization division multiplexed differential quadrature phase shift keying payload with spectral amplitude code labels  

NASA Astrophysics Data System (ADS)

We present the performance analysis of a spectral amplitude code labeled system with 100 Gb/s polarization division multiplexed (PDM) differential quadrature phase shift keying payload in simulation. Direct detection is chosen to demodulate the PDM payload by applying a polarization tracker, while 4-bits of the 156 Mb/s spectral amplitude code label is coherently detected with a scheme of frequency-swept coherent detection. We optimize the payload laser linewidth as well as the frequency spacing between the payload and label. For back-to-back system and 96 km transmission, label eye opening factors are 0.95 and 0.94, respectively, while payload optical signal-to-noise ratios are 20.6 dB and 22.0 dB, and the payload received optical powers are -15.0 dBm and -14.5 dBm for a bit error rate value of 10-9. The results show that both the payload and label have good transmission performances after long-haul transmission in a standard single mode fiber and dispersion compensating fiber, and the payload could be well demodulated after 288 km transmission.

Wang, Jin; Cao, Yongsheng; Chen, Fushen

2015-01-01

369

Laser-induced fluorescence and X-ray spectral analysis of carious process in hard dental tissues.  

PubMed

Morphological and spectral X-ray analysis of carious and noncarious extracted teeth showed the patterns of dentin ossification in caries of different degree. Parietal ectopic ossification of the canal and cavity lumens in stages III and IV dental caries is regarded as a specific structural marker of pathological regeneration. The X-ray spectral analysis showed that the progress of carious process is paralleled by loss of mineral components. Laser-induced fluorescent study of tissues in extracted teeth showed 4 spectral bands corresponding to mineral and protein components of the tooth. The progress of carious process was associated with reduction of the fluorescence intensities of the spectral bands characteristic of dental collagen and mineral components. PMID:21246104

Lidman, G Yu; Larionov, P M; Savchenko, S V; Lushnikova, E L; Orishich, A M; Rozhin, I A; Malov, A N; Maslov, N A; Titov, A T; Kositsyna, I G

2010-09-01

370

Magnetically-induced electric polarization in an organo-metallic magnet  

SciTech Connect

The coupling between magnetic order and ferroelectricity has been under intense investigation in a wide range of transition metal oxides. The strongest coupling is obtained in so-called magnetically induced multiferroics where ferroelectricity arises directly from magnetic order that breaks inversion symmetry. However, it has been difficult to find non-oxide based materials in which these effects occur. Here we present a study of copper dimethyl sulfoxide dichloride (CDC), an organometallic quantum magnet containing S =1/1 Cu spins, in which a switchable electric polarization arises from field-tuned magnetic order. Fast magnetic field pulses allow us to perform sensitive measurements of the electric polarization and demonstrate that the electric state is present only if the magnetic order is non-collinear. Furthermore, we show that the electric polarization can be switched in a stunning hysteretic fashion. Because the magnetic order in CDC is mediated by large organic molecules, our study shows that magnetoelectric interactions can exist in this important class of materials, opening the road to designing magnetoelectrics and multiferroics using large molecules as building blocks. Further, we demonstrate that CDC undergoes a magnetoelectric quantum phase transition -the first of its kind, where both ferroelectric and magnetic order emerge simultaneously as a function of magnetic field at very low temperatures.

Zapf, W S [Los Alamos National Laboratory; Fabris, F W [Los Alamos National Laboratory; Balakirev, F F [Los Alamos National Laboratory; Francoual, S M [Los Alamos National Laboratory; Kenzelmann, M [SWITZERLAND; Chen, Y [JOHNS HOPKINS UNIV

2009-01-01

371

Parahydrogen-induced polarization of carboxylic acids: a pilot study of valproic acid and related structures.  

PubMed

Parahydrogen-induced polarization (PHIP) is a promising new tool for medical applications of MR, including MRI. The PHIP technique can be used to transfer high non-Boltzmann polarization, derived from parahydrogen, to isotopes with a low natural abundance or low gyromagnetic ratio (e.g. (13)C), thus improving the signal-to-noise ratio by several orders of magnitude. A few molecules acting as metabolic sensors have already been hyperpolarized with PHIP, but the direct hyperpolarization of drugs used to treat neurological disorders has not been accomplished until now. Here, we report on the first successful hyperpolarization of valproate (valproic acid, VPA), an important and commonly used antiepileptic drug. Hyperpolarization was confirmed by detecting the corresponding signal patterns in the (1)H NMR spectrum. To identify the optimal experimental conditions for the conversion of an appropriate VPA precursor, structurally related molecules with different side chains were analyzed in different solvents using various catalytic systems. The presented results include hyperpolarized (13)C NMR spectra and proton images of related systems, confirming their applicability for MR studies. PHIP-based polarization enhancement may provide a new MR technique to monitor the spatial distribution of valproate in brain tissue and to analyze metabolic pathways after valproate administration. PMID:24812006

Lego, Denise; Plaumann, Markus; Trantzschel, Thomas; Bargon, Joachim; Scheich, Henning; Buntkowsky, Gerd; Gutmann, Torsten; Sauer, Grit; Bernarding, Johannes; Bommerich, Ute

2014-07-01

372

Detection of gravity-induced polarity of cytoplasmic streaming in Chara  

NASA Technical Reports Server (NTRS)

Gravity induces a polarity of cytoplasmic streaming in vertically-oriented internodal cells of characean algae. The motive force that powers cytoplasmic streaming is generated at the ectoplasmic/endoplasmic interface. The velocity of streaming, which is about 100 micrometers/s at this interface, decreases with distance from the interface on either side of the cell to 0 micrometers/s near the middle. Therefore, when discussing streaming velocity it is necessary to specify the tangential plane through the cell in which streaming is being measured. This is easily done with a moderate resolution light microscope (which has a lateral resolution of 0.6 micrometers and a depth of field of 1.4 micrometers), but is obscured when using any low resolution technique, such as low magnification light microscopy or laser Doppler spectroscopy. In addition, the effect of gravity on the polarity of cytoplasmic streaming declines with increasing physiological age of isolated cells. Using a classical mechanical analysis, we show that the effect of gravity on the polarity of cytoplasmic streaming cannot result from the effect of gravity acting directly on individual cytoplasmic particles. We suggest that gravity may best be perceived by the entire cell at the plasma membrane-extracellular matrix junction.

Staves, M. P.; Wayne, R.; Leopold, A. C.

1995-01-01

373

Self-induced polarization rotation of laser beam in fullerene (C70) solutions  

NASA Astrophysics Data System (ADS)

Nonlinear self-rotation of elliptically polarized laser pulses (? = 532 nm, ?FWHM ~ 12 ns) in toluene, benzene and binary mixture (toluene + ethanol) solutions of fullerene C70 has been investigated experimentally. Absolute values and signs of the nonlinear refractive indices (n2) and nonlinear optical susceptibilities ?(3)(?, - ?, ?) of C70 solutions in toluene and benzene at different values of polarization ellipse (? = 0.2 ÷ 0.8) have been determined. High-resolution transmission electron microscope studies of C70 solutions showed that in toluene + ethanol mixtures ball-shaped C70 clusters are formed with particle sizes in the range ~ 100 ÷ 500 nm. It has been demonstrated, that the clusters sizes depend on the C70 concentration and volume fraction of ethanol in toluene. Correlation between the processes of C70 clusters formation in solutions and the values of polarization self-rotation angle of transmitted laser beam has been demonstrated. Physical mechanisms of laser induced optical activity in fullerene solutions have been discussed.

Kokhkharov, A. M.; Bakhramov, S. A.; Makhmanov, U. K.; Kokhkharov, R. A.; Zakhidov, E. A.

2012-06-01

374

Accommodation-induced variations in retinal thickness measured by spectral domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

To research retinal stretching or distortion with accommodation, accommodation-induced changes in retinal thickness (RT) in the macular area were investigated in a population of young adults (n=23) by using a dual-channel spectral domain optical coherence tomography (SD-OCT) system manufactured in-house for this study. This dual-channel SD-OCT is capable of imaging the cornea and retina simultaneously with an imaging speed of 24 kHz A-line scan rate, which can provide the anatomical dimensions of the eye, including the RT and axial length. Thus, the modification of the RT with accommodation can be calculated. A significant decrease in the RT (13.50±1.25 ?m) was observed during maximum accommodation. In the 4 mm×4 mm macular area centered at the fovea, we did not find a significant quadrant-dependent difference in retinal volume change, which indicates that neither retinal stretching nor distortion was quadrant-dependent during accommodation. We speculate that the changes in RT with maximum accommodation resulted from accommodation-induced ciliary muscle contractions.

Fan, Shanhui; Sun, Yong; Dai, Cuixia; Zheng, Haihua; Ren, Qiushi; Jiao, Shuliang; Zhou, Chuanqing

2014-09-01

375

Nanoscale infrared spectroscopy: improving the spectral range of the photothermal induced resonance technique.  

PubMed

Photothermal induced resonance (PTIR) is a new technique which combines the chemical specificity of infrared (IR) spectroscopy with the lateral resolution of atomic force microscopy (AFM). PTIR requires a pulsed tunable laser for sample excitation and an AFM tip to measure the sample expansion induced by light absorption. The limited tunability of commonly available laser sources constrains the application of the PTIR technique to a portion of the IR spectrum. In this work, a broadly tunable pulsed laser relying on a difference frequency generation scheme in a GaSe crystal to emit light tunable from 1.55 ?m to 16 ?m (from 6450 cm(-1) to 625 cm(-1)) was interfaced with a commercial PTIR instrument. The result is a materials characterization platform capable of chemical imaging, in registry with atomic force images, with a spatial resolution that notably surpasses the light diffraction limit throughout the entire mid-IR spectral range. PTIR nanoscale spectra and images allow the identification of compositionally and optically similar yet distinct materials; organic, inorganic, and composite samples can be studied with this nanoscale analog of infrared spectroscopy, suggesting broad applicability. Additionally, we compare the results obtained with the two tunable lasers, which have different pulse lengths, to experimentally assess the recently developed theory of PTIR signal generation. PMID:23363013

Katzenmeyer, Aaron M; Aksyuk, Vladimir; Centrone, Andrea

2013-02-19

376

Humidity effects on tip-induced polarization switching in lithium niobate  

SciTech Connect

In the last several decades, ferroelectrics have attracted much attention as perspective materials for nonlinear optics and data storage devices. Scanning probe microscopy (SPM) has emerged as a powerful tool both for studies of domain structures with nanoscale spatial resolution and for writing the isolated nanodomains by local application of the electric field. Quantitative analysis of the observed behavior requires understanding the role of environmental factors on imaging and switching process. Here, we study the influence of the relative humidity in the SPM chamber on tip-induced polarization switching. The observed effects are attributed to existence of a water meniscus between the tip and the sample surface in humid atmosphere. These results are important for a deeper understanding of complex investigations of ferroelectric materials and their applications and suggest the necessity for fundamental studies of electrocapillary phenomena at the tip-surface junction and their interplay with bias-induced materials responses.

Ievlev, A. V. [The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37922 (United States); Ferroelectric Laboratory, Institute of Natural Sciences, Ural Federal University, 51 Lenin Ave., 620000 Ekaterinburg (Russian Federation); Morozovska, A. N. [Institute of Physics, National Academy of Sciences of Ukraine, 46 pr. Nauki, 03028 Kiev (Ukraine); Shur, V. Ya. [Ferroelectric Laboratory, Institute of Natural Sciences, Ural Federal University, 51 Lenin Ave., 620000 Ekaterinburg (Russian Federation); Kalinin, S. V. [The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37922 (United States)

2014-03-03

377

Self-induced polar order of active Brownian particles in a harmonic trap  

E-print Network

Hydrodynamically interacting active particles in an external harmonic potential form a self-assembled fluid pump at large enough P\\'eclet numbers. Here, we give a quantitative criterion for the formation of the pump and show that particle orientations align in the self-induced flow field in surprising analogy to ferromagnetic order where the active P\\'eclet number plays the role of inverse temperature. The particle orientations follow a Boltzmann distribution $\\Phi(\\mathbf{p}) \\sim \\exp(A p_z)$ where the ordering mean field $A$ scales with active P\\'eclet number and polar order parameter. The mean flow field in which the particles' swimming directions align corresponds to a regularized stokeslet with strength proportional to swimming speed. Analytic mean-field results are compared with results from Brownian dynamics simulations with hydrodynamic interactions included and are found to capture the self-induced alignment very well.

Marc Hennes; Katrin Wolff; Holger Stark

2014-02-06

378

Humidity effects on tip-induced polarization switching in lithium niobate  

NASA Astrophysics Data System (ADS)

In the last several decades, ferroelectrics have attracted much attention as perspective materials for nonlinear optics and data storage devices. Scanning probe microscopy (SPM) has emerged as a powerful tool both for studies of domain structures with nanoscale spatial resolution and for writing the isolated nanodomains by local application of the electric field. Quantitative analysis of the observed behavior requires understanding the role of environmental factors on imaging and switching process. Here, we study the influence of the relative humidity in the SPM chamber on tip-induced polarization switching. The observed effects are attributed to existence of a water meniscus between the tip and the sample surface in humid atmosphere. These results are important for a deeper understanding of complex investigations of ferroelectric materials and their applications and suggest the necessity for fundamental studies of electrocapillary phenomena at the tip-surface junction and their interplay with bias-induced materials responses.

Ievlev, A. V.; Morozovska, A. N.; Shur, V. Ya.; Kalinin, S. V.

2014-03-01

379

Humidity effects on tip-induced polarization switching in lithium niobate  

SciTech Connect

In the last several decades, ferroelectrics have attracted much attention as perspective materials for nonlinear optics and data storage devices. Scanning probe microscopy (SPM) has emerged as a powerful tool both for studies of domain structures with nanoscale spatial resolution and for writing the isolated nanodomains by local application of the electric field. Quantitative analysis of the observed behavior requires understanding the role of environmental factors on imaging and switching process. Here we study the influence of the relative humidity in the SPM chamber on tip-induced polarization switching. The observed effects are attributed to existence of a water meniscus between the tip and the sample surface in humid atmosphere. These results are important for a deeper understanding of complex investigations of ferroelectric materials and their applications, and suggest the necessity for fundamental studies of electrocapillary phenomena at the tip-surface junction and their interplay with bias-induced materials responses.

Ievlev, Anton [ORNL] [ORNL; Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine] [National Academy of Science of Ukraine, Kiev, Ukraine; Shur, Vladimir Ya. [Ural Federal University, Russia] [Ural Federal University, Russia; Kalinin, Sergei V [ORNL] [ORNL

2014-01-01

380

Modeling the impact of spectral sensor configurations on the FLD retrieval accuracy of sun-induced chlorophyll fluorescence  

Microsoft Academic Search

Chlorophyll fluorescence is related to photosynthesis and can serve as a remote sensing proxy for estimating photosynthetic energy conversion and carbon uptake. Recent advances in sensor technology allow remote measurements of the sun-induced chlorophyll fluorescence signal (Fs) at leaf and canopy scale. The commonly used Fraunhofer Line Depth (FLD) principle exploits spectrally narrow atmospheric oxygen absorption bands and relates Fs

Alexander Damm; André Erler; Walter Hillen; Michele Meroni; Michael E. Schaepman; Wout Verhoef; Uwe Rascher

2011-01-01

381

Magnetically induced electric polarization in an organometallic magnet V. S. Zapf,1 M. Kenzelmann,2 F. Wolff-Fabris,1,* F. Balakirev,1  

E-print Network

Magnetically induced electric polarization in an organometallic magnet V. S. Zapf,1 M. Kenzelmann,2 polarization in the presence of magnetic fields. Unlike many magnetically induced multiferroics, the mag- netic coupling is obtained in so-called magnetically induced multiferroics where ferroelectricity arises directly

McQuade, D. Tyler

382

Chemically induced dynamic nuclear polarization studies of guanosine in nucleotides, dinucleotides, and oligonucleotides  

SciTech Connect

The nuclear magnetic resonance (NMR) technique of chemically induced dynamic nuclear polarization (CIDNP) has been used to study the reactions between photoexcited flavins and a wide variety of nucleotides, dinucleotides, and oligonucleotides. The greatest emphasis is placed on the purine nucleosides adenosine (A), inosine (I), and guanosine (G), particularly guanosine. The presence of G suppresses the CIDNP effect for A, although A by itself shows very strong CIDNP. Very intense CIDNP signals are observed for the H8 proton in G-containing mononucleotides, but no nuclear polarization is detected for the sugar H1' proton. In contrast, both H8 and H1' protons exhibit CIDNP for G in a wide range of dinucleotides and higher oligonucleotides. Several possible mechanisms are analyzed to explain the H1' polarization, and it is concluded that the sugar H1' proton probably obtains spin density through interaction with guanine nitrogen 3. The proximity of the H1' proton to N3 depends explicity on the glycosidic torsion angle, chi. CIDNP studies of several model compounds in which chi is fixed are consistent with this suggestion. CIDNP for the self-complementary tetramer ApGpCpU was studied as a function of temperature. Strong CIDNP from G is only observed at temperatures above the double-strand melting temperature, suggesting that CIDNP is only detected in single-stranded regions, where the base is accessible to solvent. The use of brominated riboflavin as the photoreagent in place of riboflavin is shown to selectively invert the sign of A, I, and 1-methylguanosine polarization, providing a convenient method for distinguishing the NMR spectra of these residues in complex oligonucleotides.

McCord, E.F.; Morden, K.M.; Pardi, A.; Tinoco, I. Jr.; Boxer, S.G.

1984-04-24

383

Detection of global tropospheric clouds and polar stratospheric clouds over Antarctica using thermal infrared spectral data observed by TANSO-FTS/GOSAT  

NASA Astrophysics Data System (ADS)

Global tropospheric cloud distribution was derived from thermal infrared band data observed by Thermal And Near infrared Sensor for carbon Observation - Fourier Transform Spectrometer (TANSO-FTS) onboard Greenhouse gases Observation SATellite (GOSAT). It is expected that this band has ability to detect optically thin clouds compared with Cloud and Aerosol Imager (CAI) which is the other sensor on GOSAT. In addition, polar stratospheric clouds (PSCs) which can be harder to detect than the tropospheric clouds because of high reflectivity or low temperature of the surface and their low optical thickness were also detected. We have modified CO2 slicing method which was developed as one of the cirrus cloud detection techniques using thermal infrared band data to detect thin clouds more stably. The pseudo spectral channels were defined as sets of several actual spectral channels between 700cm-1 and 750cm-1 which have weighting function peak height in a same height range for each 0.5km. These pseudo channels were optimized with simulation studies using a multi-scattering radiative transfer code, Polarized radiance System for Transfer of Atmospheric Radiation (Pstar) 3 for several temperature profile patterns prepared based on latitudes and temperature at 500hPa. GOSAT data was analyzed with the combination of these pseudo channels determined for each of observation points from these simulations and the results were compared with the observational results from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) / Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The comparisons about global cloud are based on the coincident observations in 2010. Monthly occurrences of Antarctic PSCs were compared for each grid area from June to September in 2010. As a result, the correlation coefficients in each month are 0.76, 0.71, 0.75, and 0.61 relatively. Though that is low value in September, it can be explained by decrease of occurrences.

Someya, Yu; Imasu, Ryoichi; Ota, Yoshifumi; Saitoh, Naoko

2014-05-01

384

Infrared spectral signatures of CDCP1-induced effects in colon carcinoma cells.  

PubMed

Metastasis is the major cause of death by cancer. Indeed, metastatic colonies can reactivate and become life threatening, sometimes months or years after the initial diagnosis and surgery of the primary tumor. Therefore, there is a crucial need to develop methods for diagnosis of tumor cells that exhibit high metastatic potential. Here, we addressed the capability of vibrational spectroscopy for investigating the effects induced by CDCP1 expression in colon carcinoma cells. This transmembrane protein has been suggested to play a key role in metastasis by its pleiotropic function. We focused on a cellular model constituted by the cell lines SW480 and SW620 derived respectively from the primary tumor and a lymph node metastasis of the same patient. Induced CDCP1 expression in SW480 led to marked changes in cell morphology. Whereas SW480 form a cell layer, the SW480/CDCP1 cells exhibited reduced cell-to-cell contact. On collagen I, SW480 was more spread and filopodia were observed. In contrast, SW480/CDCP1 cells exhibited lower spreading with no formation of filopodia. Synchrotron Fourier transform infrared microspectroscopy experiments were performed on this cellular model. High quality spectroscopic information at sub-cellular resolution, provided by the use of the synchrotron source in infrared microspectroscopy, was recorded on numerous individual cells. Multivariate analysis of spectra recorded using principal component analysis indicated a highest intensity increase of the 970 and 1080 cm(-1) bands, and a modest intensity increase of the 1240 cm(-1) band in the SW480/CDCP1 cells. These bands were correlated with an increased content of phosphorylated proteins as confirmed by in situ labelling using a monoclonal antibody directed against phosphorylated tyrosines. Altogether, these results demonstrate that the vibrational technique used in this study exhibits the capability to characterize spectral signatures of CDCP1-induced effects in colon carcinoma cells. This study may open new avenues for rapid diagnosis of cells with a metastatic potential. PMID:22034616

Yousef, Ibraheem; Bréard, Jacqueline; SidAhmed-Adrar, Nazha; Maâmer-Azzabi, Aïda; Marchal, Céline; Dumas, Paul; Le Naour, François

2011-12-21

385

The use of the multiple-gradient array for geoelectrical resistivity and induced polarization imaging  

NASA Astrophysics Data System (ADS)

The use of most conventional electrode configurations in electrical resistivity survey is often time consuming and labour intensive, especially when using manual data acquisition systems. Often, data acquisition teams tend to reduce data density so as to speed up field operation thereby reducing the survey cost; but this could significantly degrade the quality and resolution of the inverse models. In the present work, the potential of using the multiple-gradient array, a non-conventional electrode configuration, for practical cost effective and rapid subsurface resistivity and induced polarization mapping was evaluated. The array was used to conduct 2D resistivity and time-domain induced polarization imaging along two traverses in a study site at Ota, southwestern Nigeria. The subsurface was characterised and the main aquifer delineated using the inverse resistivity and chargeability images obtained. The performance of the multiple-gradient array was evaluated by correlating the 2D resistivity and chargeability images with those of the conventional Wenner array as well as the result of some soundings conducted along the same traverses using Schlumberger array. The multiple-gradient array has been found to have the advantage of measurement logistics and improved image resolution over the Wenner array.

Aizebeokhai, Ahzegbobor P.; Oyeyemi, Kehinde D.

2014-12-01

386

Performance degradation induced by polarization-dependent loss in optical fiber transmission systems with and without polarization-mode dispersion  

Microsoft Academic Search

The performance degradation caused by polarization-dependent loss (PDL) in optical fiber transmission systems in both the absence and presence of polarization-mode dispersion (PMD) is studied. First a simple theory is given to show how PDL affects the system performance and then extensive simulation results are presented. We show that PDL causes a much larger fluctuation of optical-signal-to-orthogonal-noise ratio (OSNRort) than

Chongjin Xie; Linn F. Mollenauer

2003-01-01

387

Polar lipids from the marine macroalga Palmaria palmata inhibit lipopolysaccharide-induced nitric oxide production in RAW264.7 macrophage cells.  

PubMed

The EtOAc soluble fraction of a MeOH/CHCl3 extract of Palmaria palmata showed strong nitric oxide (NO) inhibitory activity against lipopolysaccharide (LPS)-induced NO production in murine RAW264.7 cells. NO inhibition-guided isolation led to identification of three new polar lipids including a sulfoquinovosyl diacylglycerol (SQDG) (2S)-1-O-eicosapentaenoyl-2-O-myristoyl-3-O-(6-sulfo-?-D-quinovopyranosyl)-glycerol (1) and two phosphatidylglycerols, 1-O-eicosapentaenoyl-2-O-trans-3-hexadecenoyl-3-phospho-(1'-glycerol)-glycerol (3) and 1-O-eicosapentaenoyl-2-O-palmitoyl-3-phospho-(1'-glycerol)-glycerol (4) from the EtOAc fraction. Seven known lipids were also isolated including a SQDG (2), a phospholipid (5) and five galactolipids (6-10). Structures of the isolated lipids were elucidated by spectral analyses. The isolated SQDGs, phosphatidylglycerols and phospholipid possessed strong and dose-dependent NO inhibitory activity compared to N(G)-methyl-L-arginine acetate salt (L-NMMA), a well-known NO inhibitor used as a positive control. Further study suggested that these polar lipids suppressed NO production through down-regulation of inducible nitric oxide synthase (iNOS). PMID:24569177

Banskota, Arjun H; Stefanova, Roumiana; Sperker, Sandra; Lall, Santosh P; Craigie, James S; Hafting, Jeff T; Critchley, Alan T

2014-05-01

388

Thermal and kinematic corrections to the microwave background polarization induced by galaxy clusters along the line of sight  

E-print Network

We derive analytic expressions for the leading-order corrections to the polarization induced in the cosmic microwave background (CMB) due to scattering off hot electrons in galaxy clusters along the line of sight. For a thermal distribution of electrons with a kinetic temperature of 10 keV and a bulk peculiar velocity of 1000 km/s, the dominant corrections to the polarization induced by the primordial CMB quadrupole and the cluster peculiar velocity arise from electron thermal motion and are at the level of 10 per cent in each case, near the peak of the polarization signal. When more sensitive measurements become feasible, these effects will be significant for the determination of transverse peculiar velocities, and the value of the CMB quadrupole at the cluster redshift, via the cluster polarization route.

Anthony Challinor; Matthew Ford; Anthony Lasenby

1999-09-30

389

The role of polarization fields in Auger-induced efficiency droop in nitride-based light-emitting diodes  

SciTech Connect

The rates of non-radiative Auger recombination (AR) and radiative recombination (RR) in polar GaN/AlN quantum wells (QWs) are calculated. It is shown that in these QWs the polarization field not only suppresses the RR but also strongly enhances the rate of AR. As a result, the polarization field triggers the Auger-induced efficiency droop, which, according to the calculations, does not exist in non-polar GaN/AlN QWs. We demonstrate that in polar QWs the droop can be overcome by suppression of AR using a gradual variation of the QW layer composition, which compensates the effect of the electric field acting on holes.

Vaxenburg, Roman; Lifshitz, Efrat [Technion - Israel Institute of Technology, Haifa 32000 (Israel)] [Technion - Israel Institute of Technology, Haifa 32000 (Israel); Rodina, Anna [Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation)] [Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Efros, Alexander L., E-mail: efros@nrl.navy.mil [Naval Research Laboratory, Washington, DC 20375 (United States)

2013-11-25

390

Symmetry breaking and electrical frustration during tip-induced polarization switching in the nonpolar cut of lithium niobate single crystals.  

PubMed

Polarization switching in ferroelectric materials is governed by a delicate interplay between bulk polarization dynamics and screening processes at surfaces and domain walls. Here we explore the mechanism of tip-induced polarization switching at nonpolar cuts of uniaxial ferroelectrics. In this case, the in-plane component of the polarization vector switches, allowing for detailed observations of the resultant domain morphologies. We observe a surprising variability of resultant domain morphologies stemming from a fundamental instability of the formed charged domain wall and associated electric frustration. In particular, we demonstrate that controlling the vertical tip position allows the polarity of the switching to be controlled. This represents a very unusual form of symmetry breaking where mechanical motion in the vertical direction controls the lateral domain growth. The implication of these studies for ferroelectric devices and domain wall electronics are discussed. PMID:25506745

Ievlev, Anton V; Alikin, Denis O; Morozovska, Anna N; Varenyk, Olexander V; Eliseev, Eugene A; Kholkin, Andrei L; Shur, Vladimir Ya; Kalinin, Sergei V

2015-01-27

391

Inhibition of cyclophosphamide-induced oxidative stress in rat brain by polar and non-polar extracts of Annatto (Bixa orellana) seeds.  

PubMed

Annatto (Bixa orellana) seeds are widely distributed throughout the Tropics and have been used to provide both colour and flavour to food. This study sought to assess the ability of dietary inclusion of polar (water) and non-polar (chloroform) extracts of Annatto (B. orellana) seeds on cyclophosphamide-induced oxidative stress in rat brain. The total phenol content and antioxidant activities of polar (water) and non-polar (chloroform) extracts of Annatto seeds were determined in vitro and in vivo. The results of the study showed that intraperitoneal administration of cyclophosphamide (75 mg/kg of body weight) caused a significant increase (P<0.05) in the malondialdehyde (MDA) content of the brain; however, dietary inclusion of Annatto seed extracts (0.1% and 0.2%) caused dose-dependent significant decrease (P<0.05) in the MDA content of the brain. Likewise, the extracts also caused dose-dependent inhibition of the elevated serum glutamate oxaloacetate transaminase (SGOT), glutamate pyruvate transaminase (SGPT), alkaline phosphatase and total bilirubin. However, the non-polar extract had significantly higher inhibitory effects on the elevated MDA production in brain and serum liver function markers. This higher protective effect of the non-polar extract could be attributed to its higher antioxidant properties as typified by its significantly higher (P<0.05) reducing power, free-radical scavenging and Fe (II) chelating ability. Therefore, dietary inclusion of Annato seed extracts as food colourant could prevent oxidative stress occasioned by cyclophosphamide administration, but the non-polar extract is a better protectant. PMID:20137904

Oboh, Ganiyu; Akomolafe, Toyin L; Adefegha, Stephen A; Adetuyi, Abayomi O

2011-03-01

392

Polarization-induced two-dimensional electron gas at Zn 1? x Mg x O\\/ZnO heterointerface  

Microsoft Academic Search

Spontaneous and piezoelectric polarizations, PSP and PPE, in the c-axis direction of Zn1?xMgxO\\/ZnO heterostructures are estimated by analyzing the density of the two-dimensional electron gas (2DEG) accumulated at the interface. The experimental data on 2DEGs indicated that positive sheet charges responsible for the 2DEG accumulation were induced at the interface by the polarization with a proportional increase to the x

Mitsuaki Yano; Kazuyuki Hashimoto; Kazuya Fujimoto; Kazuto Koike; Shigehiko Sasa; Masataka Inoue; Yasutomo Uetsuji; Tomoyuki Ohnishi; Katsuhiko Inaba

2007-01-01

393

Note: reducing polarization induced sidebands in Rayleigh backscattering spectra for accurate distributed strain measurement using optical frequency-domain reflectometry.  

PubMed

We describe a phenomenon called polarization-induced sidebands (PIS) in Rayleigh backscatter spectra (RBS) and discuss its deteriorating effects on the distributed strain measurement using an optical frequency-domain reflectometry. We propose using a special polarization diversity detection scheme to remove PIS and successfully demonstrate accurate distributed strain measurement in the range of 0.75 ??-225 ?? in a 50 m standard single mode fiber, with a good linearity between the strain and the spectra shift in RBS. PMID:23464263

Ding, Zhenyang; Yao, X Steve; Liu, Tiegen; Du, Yang; Liu, Kun; Han, Qun; Meng, Zhuo; Li, Dingjie

2013-02-01

394

Note: Reducing polarization induced sidebands in Rayleigh backscattering spectra for accurate distributed strain measurement using optical frequency-domain reflectometry  

NASA Astrophysics Data System (ADS)

We describe a phenomenon called polarization-induced sidebands (PIS) in Rayleigh backscatter spectra (RBS) and discuss its deteriorating effects on the distributed strain measurement using an optical frequency-domain reflectometry. We propose using a special polarization diversity detection scheme to remove PIS and successfully demonstrate accurate distributed strain measurement in the range of 0.75 ??-225 ?? in a 50 m standard single mode fiber, with a good linearity between the strain and the spectra shift in RBS.

Ding, Zhenyang; Steve Yao, X.; Liu, Tiegen; Du, Yang; Liu, Kun; Han, Qun; Meng, Zhuo; Li, Dingjie

2013-02-01

395

Study case - Induced Polarization response from a BTEX contaminated site in Brazil  

NASA Astrophysics Data System (ADS)

A hydrocarbon contaminated site in Brazil was investigated using DC-resistivity and Induced Polarization (IP) methods. The study area is a chemical industry facility that manufactures paint for automobiles. The industrial process involves the use of many hydrocarbon derivative products, including BTEX (benzene, toluene, ethyl benzene and xylene) and organic chlorides. The area was contaminated by some (not documented) accidental spills of BTEX throughout many years. Monitoring wells revealed concentrations from a few ppm to hundreds ppm of BTEX around the area, as well as other compounds. Two soil samples were collected from an area where some spills where known to have happened. Soil analyses of these samples found the presence of microbes, and therefore biodegradation is believed to be occurring at the site. The objective of this study is to relate the IP response distribution to the presence of contamination and/or microbial activity. The geophysical survey consisted in a rectangular mesh composed of 15 parallel lines with 60 meters of extension, using dipole-dipole array. Lines were spaced by 3 meters. Metallic electrodes were used for current injection, and non-polarizing electrodes (Cu/CuSO4) for potential measurement. Current was injected in cycles of 2 seconds. IP measurements were recorded after 160 milliseconds delay of current shut off, and integration time windows were 120, 220, 420, and 820 milliseconds. All data were concatenated into a single data set and submitted to 3D inversion routine. A conductive zone (resistivity less than 100 ohm.m and chargeability less than 2mV/V) was observed where microbes were found. This feature was interpreted as possibly due to natural biodegradation process, that increases total dissolved salts as a result of mineral weathering by organic acids produced in the degradation process. Normalized chargeability (chargeability divided by resistivity) showed an enhanced polarization zone where microbes were detected. This result was interpreted as possibly due to growth and attachment of microbes to grain surfaces, increasing grain surface area and therefore polarization. These results are in good agreement with published studies relating conductivity and polarization increase with microbial activity. However, further research is need on the effect of microbial activity on normalized chargeability, since this parameter is very sensitive to lithology and surface chemistry. The results from this work could assist the interpretation of IP surveys at hydrocarbon-contaminated sites undergoing natural degradation and at bioremediation sites.

Ustra, A.; Elis, V.; Minozzo, M.

2011-12-01

396

Orthogonal polarization mode coupling for pure twisted polarization maintaining fiber Bragg gratings.  

PubMed

Spectral characteristics of orthogonal polarization mode coupling for pure twisted polarization maintaining fiber Bragg gratings (PM-FBG) are proposed and analyzed experimentally and theoretically. Different from the polarization mode coupling in PM-FBG due to side pressure, a resonant peak at the middle of two orthogonal polarization modes is found when the PM-FBG is twisted purely which is attributed to the cross coupling of polarization modes. Its intensity increases with the twisting rate. A new coupled mode equation is built to describe the pure twist polarization mode coupling, in which both the normal strain induced by strain-applied parts and the tangential strain induced by twisting are taken into consideration and expressed in a unified coordinate. The novel phenomenon and its explanation are believed to be helpful for PM-FBG applications in fiber sensor and laser technologies. PMID:23263124

Yang, Fei; Fang, Zujie; Pan, Zhengqing; Ye, Qing; Cai, Haiwen; Qu, Ronghui

2012-12-17

397

A precise extraction of the induced polarization in the 4He(e,e'p)3H reaction  

SciTech Connect

We measured with unprecedented precision the induced polarization Py in 4He(e,e'p)3H at Q^2 = 0.8 (GeV/c)^2 and 1.3 (GeV/c)^2. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are over-estimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin independent charge-exchange term in the latter calculation.

S.P. Malace, M. Paolone, S. Strauch

2011-01-01

398

Precise extraction of the induced polarization in the {sup 4}He(e,e'p(pol){sup 3}H reaction.  

SciTech Connect

We measured with unprecedented precision the induced polarization P{sub y} in {sup 4}He(e,e'p(pol)){sup 3}H at Q{sup 2} = 0.8 and 1.3 (GeV/c){sup 2}. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are overestimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin-independent charge-exchange term in the latter calculation.

Malace, S. P.; Paolone, M.; Strauch, S.; Albayrak, I.; Arrington, J.; Solvignon, P.; The E03-104 Collaboration (Physics); (Univ. of South Carolina); (Hampton Univ.)

2011-01-31

399

Creation of High Mobility Two-Dimensional Electron Gases via Strain Induced Polarization at an Otherwise Nonpolar Complex Oxide Interface.  

PubMed

The discovery of two-dimensional electron gases (2DEGs) in SrTiO3-based heterostructures provides new opportunities for nanoelectronics. Herein, we create a new type of oxide 2DEG by the epitaxial-strain-induced polarization at an otherwise nonpolar perovskite-type interface of CaZrO3/SrTiO3. Remarkably, this heterointerface is atomically sharp and exhibits a high electron mobility exceeding 60?000 cm(2) V(-1) s(-1) at low temperatures. The 2DEG carrier density exhibits a critical dependence on the film thickness, in good agreement with the polarization induced 2DEG scheme. PMID:25692804

Chen, Yunzhong; Trier, Felix; Kasama, Takeshi; Christensen, Dennis V; Bovet, Nicolas; Balogh, Zoltan I; Li, Han; Thydén, Karl Tor Sune; Zhang, Wei; Yazdi, Sadegh; Norby, Poul; Pryds, Nini; Linderoth, Søren

2015-03-11

400

A precise extraction of the induced polarization in the 4He(e,e'p)3H reaction  

E-print Network

We measured with unprecedented precision the induced polarization Py in 4He(e,e'p)3H at Q^2 = 0.8 (GeV/c)^2 and 1.3 (GeV/c)^2. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are over-estimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin independent charge-exchange term in the latter calculation.

S. P. Malace; M. Paolone; S. Strauch

2011-01-13

401

Creation of High Mobility Two-Dimensional Electron Gases via Strain Induced Polarization at an Otherwise Nonpolar Complex Oxide Interface  

NASA Astrophysics Data System (ADS)

The discovery of two-dimensional electron gases (2DEGs) in SrTiO3-based heterostructures provides new opportunities for nanoelectronics. Herein, we create a new type of oxide 2DEG by the epitaxial-strain-induced polarization at an otherwise nonpolar perovskite-type interface of CaZrO3/SrTiO3. Remarkably, this heterointerface is atomically sharp, and exhibits a high electron mobility exceeding 60,000 cm2V-1s-1 at low temperatures. The 2DEG carrier density exhibits a critical dependence on the film thickness, in good agreement with the polarization induced 2DEG scheme.

Chen, Yunzhong; Trier, Felix; Kasama, Takeshi; Christensen, Dennis V.; Bovet, Nicolas; Balogh, Zoltan I.; Li, Han; Thydén, Karl Tor Sune; Zhang, Wei; Yazdi, Sadegh; Norby, Poul; Pryds, Nini; Linderoth, Søren

2015-03-01

402

Spectral lineshapes of collision-induced absorption (CIA) and collision-induced light scattering (CILS) for molecular nitrogen using isotropic intermolecular potential. New insights and perspectives  

NASA Astrophysics Data System (ADS)

The rototranslational collision-induced absorption (CIA) at different temperatures and collision-induced light scattering (CILS) at room temperature of nitrogen gas are analyzed in terms of new isotropic intermolecular potential, multipole-induced dipole functions and interaction-induced pair polarizability models, using quantum spectral lineshape computations. The irreducible spherical form for the induced operator of light scattering mechanisms was determined. The high frequency wings are discussed in terms of the collision-induced rotational Rayleigh effect and estimates for the dipole-octopole polarizability E4, is obtained and checked with the ab initio theoretical value. The quality of the present potential has been checked by comparing between calculated and experimental thermo-physical and transport properties over a wide temperature range, which are found to be in good agreement.

El-Kader, M. S. A.; Mostafa, S. I.; Bancewicz, T.; Maroulis, G.

2014-08-01

403

Spin-Exchange-Induced Circularly Polarized Molecular Fluorescence A. S. Green, G. A. Gallup, M. A. Rosenberry, and T. J. Gay  

E-print Network

Spin-Exchange-Induced Circularly Polarized Molecular Fluorescence A. S. Green, G. A. Gallup, M. A-0111, USA (Received 6 June 2003; published 1 March 2004) We have measured the circular polarization of light emitted from both atomic H and molecular H2 after bombarding H2 with longitudinally polarized electrons

Gay, Timothy J.

404

Th17 cells induce Th1-polarizing monocyte-derived dendritic cells.  

PubMed

In chronically inflamed tissues, such as those affected by autoimmune disease, activated Th cells often colocalize with monocytes. We investigate in this study how murine Th cells influence the phenotype and function of monocytes. The data demonstrate that Th1, Th2, and Th17 subsets promote the differentiation of autologous monocytes into MHC class II(+), CD11b(+), CD11c(+) DC that we call DCTh. Although all Th subsets induce the formation of DCTh, activated Th17 cells uniquely promote the formation of IL-12/IL-23-producing DCTh (DCTh17) that can polarize both naive and Th17 cells to a Th1 phenotype. In the inflamed CNS of mice with Th17-mediated experimental autoimmune encephalomyelitis, Th cells colocalize with DC, as well as monocytes, and the Th cells obtained from these lesions drive the formation of DCTh that are phenotypically indistinguishable from DCTh17 and polarize naive T cells toward a Th1 phenotype. These results suggest that DCTh17 are critical in the interplay of Th17- and Th1-mediated responses and may explain the previous finding that IL-17-secreting Th cells become IFN-?-secreting Th1 cells in experimental autoimmune encephalomyelitis and other autoimmune disorders. PMID:23794631

Davidson, Matthew G; Alonso, Michael N; Yuan, Robert; Axtell, Robert C; Kenkel, Justin A; Suhoski, Megan M; González, Joseph C; Steinman, Lawrence; Engleman, Edgar G

2013-08-01

405

Th17 Cells Induce Th1 Polarizing Monocyte-Derived Dendritic Cells  

PubMed Central

In chronically inflamed tissues, such as those affected by autoimmune disease, activated T helper (Th) cells often colocalize with monocytes. We investigate here how murine Th cells influence the phenotype and function of monocytes. The data demonstrate that Th1, Th2 and Th17 subsets promote the differentiation of autologous monocytes into MHC II+, CD11b+, CD11c+ DC that we call DCTh. While all Th subsets induce the formation of DCTh, activated Th17 cells uniquely promote the formation of IL-12/IL-23 producing DCTh (DCTh17) that can polarize both naïve and Th17 cells to a Th1 phenotype. In the inflamed CNS of mice with Th17-mediated experimental autoimmune encephalomyelitis (EAE), Th cells colocalize with DC, as well as monocytes, and the Th cells obtained from these lesions drive the formation of DCTh that are phenotypically indistinguishable from DCTh17 and polarize naive T-cells toward a Th1 phenotype. These results suggest that DCTh17 are critical in the interplay of Th17- and Th1-mediated responses and may explain the previous finding that IL-17 secreting Th cells become IFN? secreting Th1 cells in EAE and other autoimmune disorders. PMID:23794631

Davidson, Matthew G.; Alonso, Michael N.; Yuan, Robert; Axtell, Robert C.; Kenkel, Justin A.; Suhoski, Megan M.; González, Joseph C.; Steinman, Lawrence; Engleman, Edgar G.

2013-01-01

406

Dynamical heating of the polar summer mesopause induced by solar proton events  

NASA Astrophysics Data System (ADS)

The observed heating of the polar summer mesopause during and after a solar proton event (SPE) is interpreted as a large-scale dynamical response to the temporary diabatic cooling in the lower mesosphere above the summer pole that results from the temporary ozone depletion during an SPE. Our method is based on time slice sensitivity experiments performed with a mechanistic general circulation model. The model response shows that according to the gradient wind balance, the polar lower mesospheric cooling induces an anomalous eastward wind component. As a result, the drag exerted by eastward propagating gravity waves (GWs) shifts to lower altitudes in tandem with a balancing downward shift of the residual circulation. Around the extratropical summer mesopause, this is accompanied by an anomalous large-scale dynamic heating which qualitatively explains the positive temperature response in this region. A quantitative inspection of the zonal momentum and sensible heat budgets reveals that the GW drag response is partly compensated by a downshift of planetary Rossby waves and that about two thirds of the anomalous large-scale dynamic heating around the mesopause is balanced by changes of the direct thermal effects due to GWs, diffusion, and dissipation.

Becker, E.; von Savigny, C.

2010-05-01

407

COMPLEX RESISTIVITY OF FAULT GOUGE AND ITS SIGNIFICANCE FOR EARTHQUAKE LIGHTS AND INDUCED POLARIZATION.  

USGS Publications Warehouse

The authors measured complex resistivity of 2 water-saturated San Andreas fault gouges from 10** minus **3 to 10**6 Hz and confining pressures of 0. 2 to 200 MPa. Consistent with earlier observations of clays and common rocks, large low-frequency permittivities were observed in all cases. Comparisons were made to induced polarization (IP) measurements by inversion of the data into the time domain, where it was found that principal features of the IP response curves were due to these large low-frequency permittivities. The results also suggest that following large earthquakes, significant electrical charge could remain for many seconds and could result in a variety of reported electromagnetic effects. Refs.

Lockner, David A.; Byerlee, James D.

1985-01-01

408

Angular distribution of products of ternary nuclear fission induced by cold polarized neutrons  

NASA Astrophysics Data System (ADS)

Within quantum fission theory, angular distributions of products originating from the ternary fission of nuclei that is induced by polarized cold and thermal neutrons are investigated on the basis of a nonevaporative mechanism of third-particle emission and a consistent description of fission-channel coupling. It is shown that the inclusion of Coriolis interaction both in the region of the discrete and in the region of the continuous spectrum of states of the system undergoing fission leads to T-odd correlations in the aforementioned angular distributions. The properties of the TRI and ROT effects discovered recently, which are due to the interference between the fission amplitudes of neutron resonances, are explored. The results obtained here are compared with their counterparts from classic calculations based on the trajectory method.

Bunakov, V. E.; Kadmensky, S. G.; Kadmensky, S. S.

2008-11-01

409

Mapping polarization induced surface band bending on the Rashba semiconductor BiTeI  

PubMed Central

Surfaces of semiconductors with strong spin-orbit coupling are of great interest for use in spintronic devices exploiting the Rashba effect. BiTeI features large Rashba-type spin splitting in both valence and conduction bands. Either can be shifted towards the Fermi level by surface band bending induced by the two possible polar terminations, making Rashba spin-split electron or hole bands electronically accessible. Here we demonstrate the first real-space microscopic identification of each termination with a multi-technique experimental approach. Using spatially resolved tunnelling spectroscopy across the lateral boundary between the two terminations, a previously speculated on p-n junction-like discontinuity in electronic structure at the lateral boundary is confirmed experimentally. These findings realize an important step towards the exploitation of the unique behaviour of the Rashba semiconductor BiTeI for new device concepts in spintronics. PMID:24898943

Butler, Christopher John; Yang, Hung-Hsiang; Hong, Jhen-Yong; Hsu, Shih-Hao; Sankar, Raman; Lu, Chun-I; Lu, Hsin-Yu; Yang, Kui-Hon Ou; Shiu, Hung-Wei; Chen, Chia-Hao; Kaun, Chao-Cheng; Shu, Guo-Jiun; Chou, Fang-Cheng; Lin, Minn-Tsong

2014-01-01

410

Laser-induced damage in nonlinear crystals on irradiation direction and polarization  

NASA Astrophysics Data System (ADS)

Nonlinear-optical crystals are attractive materials for the high-power frequency converter with high damage threshold, phase matching characteristics, wide transparency range, and large effective nonlinear coefficients. Especially as to the power laser applications, its laser-induced damage threshold determines the limit of performance in the optical system. The threshold depends not only on the intrinsic material parameters but also on the laser beam parameters is use. We have investigated the bulk damage threshold of several crystals at a single-shot operation for frequency converter depending on the laser irradiation direction and its polarization. For KDP and CLBO crystals, the damage threshold in the direction of c-axis is about tow times higher than that in the a- or b-axis at 1.064 micrometers of wavelength. This result is consistent with the molecular bonding structure in different directions of the crystal. The relation between the bulk damage pattern and the crystal structure is also discussed.

Yoshida, Hidetsugu; Jitsuno, Takahisa; Fujita, Hisanori; Nakatsuka, Masahiro; Kamimura, Tomosumi; Yoshimura, Masashi; Sasaki, Takatomo; Miyamoto, Akio; Yoshida, Kunio

2000-03-01

411

Electric field induced spin and valley polarization within a magnetically confined silicene channel  

NASA Astrophysics Data System (ADS)

We study the electronic structure and transport properties of Dirac electrons along a channel created by an exchange field through the proximity of ferromagnets on a silicene sheet. The multiple total internal reflection induces localized states in the channel, which behaves like an electron waveguide. An effect of spin- and valley-filtering originating from the coupling between valley and spin degrees is predicted for such a structure. Interestingly, this feature can be tuned significantly by locally applying electric and exchange fields simultaneously. The parameter condition for observing fully spin- and valley-polarized current is obtained. These findings may be observable in todays' experimental technique and useful for spintronic and valleytronic applications based on silicene.

Liu, Yiman; Zhou, Xiaoying; Zhou, Ma; Long, Meng-Qiu; Zhou, Guanghui

2014-12-01

412

Field Trials of the Multi-Source Approach for Resistivity and Induced Polarization Data Acquisition  

NASA Astrophysics Data System (ADS)

Implementing systems of distributed receivers and transmitters for resistivity and induced polarization data is an almost inevitable result of the availability of wireless data communication modules and GPS modules offering precise timing and instrument locations. Such systems have a number of advantages; for example, they can be deployed around obstacles such as rivers, canyons, or mountains which would be difficult with traditional 'hard-wired' systems. However, deploying a system of identical, small, battery powered, transceivers, each capable of injecting a known current and measuring the induced potential has an additional and less obvious advantage in that multiple units can inject current simultaneously. The original purpose for using multiple simultaneous current sources (multi-source) was to increase signal levels. In traditional systems, to double the received signal you inject twice the current which requires you to apply twice the voltage and thus four times the power. Alternatively, one approach to increasing signal levels for large-scale surveys collected using small, battery powered transceivers is it to allow multiple units to transmit in parallel. In theory, using four 400 watt transmitters on separate, parallel dipoles yields roughly the same signal as a single 6400 watt transmitter. Furthermore, implementing the multi-source approach creates the opportunity to apply more complex current flow patterns than simple, parallel dipoles. For a perfect, noise-free system, multi-sources adds no new information to a data set that contains a comprehensive set of data collected using single sources. However, for realistic, noisy systems, it appears that multi-source data can substantially impact survey results. In preliminary model studies, the multi-source data produced such startling improvements in subsurface images that even the authors questioned their veracity. Between December of 2012 and July of 2013, we completed multi-source surveys at five sites with depths of exploration ranging from 150 to 450 m. The sites included shallow geothermal sites near Reno Nevada, Pomarance Italy, and Volterra Italy; a mineral exploration site near Timmins Quebec; and a landslide investigation near Vajont Dam in northern Italy. These sites provided a series of challenges in survey design and deployment including some extremely difficult terrain and a broad range of background resistivity and induced values. Despite these challenges, comparison of multi-source results to resistivity and induced polarization data collection with more traditional methods support the thesis that the multi-source approach is capable of providing substantial improvements in both depth of penetration and resolution over conventional approaches.

LaBrecque, D. J.; Morelli, G.; Fischanger, F.; Lamoureux, P.; Brigham, R.

2013-12-01

413

Multi-vortical flow inducing electrokinetic instability in ion concentration polarization layer  

NASA Astrophysics Data System (ADS)

In this work, we investigated multiple vortical flows inside the ion concentration polarization (ICP) layer that forms due to a coupling of applied electric fields and the semipermeable nanoporous junction between microchannels. While only a primary vortex near perm-selective membrane is traditionally known to lead to electrokinetic instability, multiple vortexes induced by the primary vortex were found to play a major role in the electrokinetic instability. The existence of multiple vortexes was directly confirmed by experiments using particle tracers and interdigitated electrodes were used to measure the local concentration profile inside the ICP layer. At larger applied electric fields, we observed aperiodic fluid motion due to electrokinetic instabilities which develop from a coupling of applied electric fields and electrical conductivity gradients induced by the ICP. The electrokinetic instability at micro-nanofluidic interfaces is important in the development of various electro-chemical-mechanical applications such as fuel cells, bio-analytical preconcentration methods, water purification/desalination and the fundamental study of ion electromigration through nanochannels and nonporous perm-selective membranes.In this work, we investigated multiple vortical flows inside the ion concentration polarization (ICP) layer that forms due to a coupling of applied electric fields and the semipermeable nanoporous junction between microchannels. While only a primary vortex near perm-selective membrane is traditionally known to lead to electrokinetic instability, multiple vortexes induced by the primary vortex were found to play a major role in the electrokinetic instability. The existence of multiple vortexes was directly confirmed by experiments using particle tracers and interdigitated electrodes were used to measure the local concentration profile inside the ICP layer. At larger applied electric fields, we observed aperiodic fluid motion due to electrokinetic instabilities which develop from a coupling of applied electric fields and electrical conductivity gradients induced by the ICP. The electrokinetic instability at micro-nanofluidic interfaces is important in the development of various electro-chemical-mechanical applications such as fuel cells, bio-analytical preconcentration methods, water purification/desalination and the fundamental study of ion electromigration through nanochannels and nonporous perm-selective membranes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32467a

Kim, Sung Jae; Ko, Sung Hee; Kwak, Rhokyun; Posner, Jonathan D.; Kang, Kwan Hyoung; Han, Jongyoon

2012-11-01

414

Observation of spectral composition and polarization of sub-terahertz emission from dense plasma during relativistic electron beam–plasma interaction  

SciTech Connect

The paper presents results of measurements of sub-terahertz electromagnetic emission from magnetized plasma during injection of a powerful relativistic electron beam of microsecond duration in plasma with the density of 3?×?10{sup 14?}cm{sup ?3}. It was found that the spectrum of the radiation concentrated in three distinct regions with high level of spectral power density. The first region is located near f{sub 1}?=?100?GHz; the second one is in the vicinity of 190?GHz, and the third region is in the frequency interval f{sub 3}?=?280–340?GHz. Polarization vectors of the emission in the first and third regions (f{sub 1} and f{sub 3}) are directed mainly perpendicular to the magnetic field in the plasma. At the same time, the polarization of the radiation in the vicinity of f{sub 2}?=?190?GHz is parallel to the magnetic field. The most likely mechanism of electromagnetic wave generation in the frequency regions f{sub 1} and f{sub 2} is the linear conversion of the plasma oscillations into the electromagnetic waves on strong gradients of the plasma density. The third region is situated in the vicinity of second harmonic of electron plasma frequency, and we explain this emission by the coalescence of the upper-hybrid oscillations at high level turbulence in plasma.

Arzhannikov, A. V.; Burmasov, V. S.; Ivanov, I. A.; Kuznetsov, S. A.; Postupaev, V. V.; Sinitsky, S. L.; Vyacheslavov, L. N. [Budker Institute of Nuclear Physics, 11 Lavrentiev Ave., Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090 (Russian Federation); Burdakov, A. V. [Budker Institute of Nuclear Physics, 11 Lavrentiev Ave., Novosibirsk 630090 (Russian Federation); Novosibirsk State Technical University, 20 Karl Marks Ave., Novosibirsk 630092 (Russian Federation); Gavrilenko, D. E.; Kasatov, A. A.; Mekler, K. I.; Rovenskikh, A. F. [Budker Institute of Nuclear Physics, 11 Lavrentiev Ave., Novosibirsk 630090 (Russian Federation); Polosatkin, S. V.; Sklyarov, V. F. [Budker Institute of Nuclear Physics, 11 Lavrentiev Ave., Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090 (Russian Federation); Novosibirsk State Technical University, 20 Karl Marks Ave., Novosibirsk 630092 (Russian Federation)

2014-08-15

415

Polarization phase-shifting interferometer by rotating azo-polymer film with photo-induced optical anisotropy  

NASA Astrophysics Data System (ADS)

A new type of phase-shifting interferometer was presented by rotating an azo-polymer film with photo-induced optical anisotropy in the light path of orthogonal polarization interferometry. By changing the angle of the optical axis of the azo-polymer film, four phase-shifted fringe patterns were obtained, from which phase difference between orthogonal polarized light could be calculated. The polarization states and the formation of the interferograms were analyzed theoretically using Jones matrix calculations and the experimental verification of the proposed method was also given. This method has a simple optical configuration which utilizes commercially available polarization devices and anisotropic azo-polymer film of low cost. The phase-shifting interferometer also demonstrates a new application of azo-polymer film.

Yan, Peizheng; Wang, Keyi; Gao, Jiangang

2015-01-01

416

Experimental determination of the Stark widths of Pb I spectral lines in a laser-induced plasma  

Microsoft Academic Search

Stark widths of 34 spectral lines of Pb I have been measured in a Laser-Induced-Plasma (LIP). The optical emission spectroscopy from a LIP generated by a 10640 Å radiation, with an irradiance of 1.4×1010 W cm?2 on a Sn–Pb target in an atmosphere of argon was analyzed between 1900 and 7000 Å. The Local Thermodynamic Equilibrium (LTE) conditions and plasma homogeneity have been

A. Alonsomedina

2008-01-01

417

Vapor-Liquid Equilibrium and Polarization Behavior of the GCP Water Model: Gaussian Charge-on-Spring versus Dipole Self-Consistent Field Approaches to Induced Polarization.  

PubMed

We developed the Gaussian charge-on-spring (GCOS) version of the original self-consistent field implementation of the Gaussian Charge Polarizable water model and test its accuracy to represent the polarization behavior of the original model involving smeared charges and induced dipole moments. For that purpose we adapted the recently proposed multiple-particle-move (MPM) within the Gibbs and isochoric-isothermal ensembles Monte Carlo methods for the efficient simulation of polarizable fluids. We assessed the accuracy of the GCOS representation by a direct comparison of the resulting vapor-liquid phase envelope, microstructure, and relevant microscopic descriptors of water polarization along the orthobaric curve against the corresponding quantities from the actual GCP water model. PMID:25803267

Chialvo, Ariel A; Moucka, Filip; Vlcek, Lukas; Nezbeda, Ivo

2015-04-16

418

Polarization-independent electromagnetically induced transparency-like effects in stacked metamaterials based on Fabry-Pérot resonance  

NASA Astrophysics Data System (ADS)

We propose a scheme for realizing plasmonic electromagnetically induced transparency (EIT)-like effects at optical frequencies in a stacked metamaterial that consists of two silver rings. The two silver rings are excited strongly by an incident wave. Based on Fabry-Pérot (FP) resonance coupling between the two resonators, polarization-independent EIT-like effects appear at optical frequencies.

Jin, Xing Ri; Qiao Zhang, Ying; Zhang, Shou; Lee, YoungPak; Rhee, Joo Yull

2013-12-01

419

Temperature dependence of carrier spin polarization determined from current-induced domain wall motion in a Co/Ni nanowire  

SciTech Connect

We have investigated the temperature dependence of the current-induced magnetic domain wall (DW) motion in a perpendicularly magnetized Co/Ni nanowire at various temperatures and with various applied currents. The carrier spin polarization was estimated from the measured domain wall velocity. We found that it decreased more with increasing temperature from 100 K to 530 K than the saturation magnetization did.

Ueda, K.; Koyama, T.; Hiramatsu, R.; Kobayashi, K.; Ono, T. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Chiba, D. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 322-0012 (Japan); Fukami, S. [Green Innovation Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501 (Japan); Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Tanigawa, H.; Suzuki, T. [RENESAS Electronics Corporation, Sagamihara, Kanagawa 252-5298 (Japan); Ohshima, N. [NEC Energy Device Ltd., 1120 Shimokuzawa, Chuo-ku, Sagamihara, Kanagawa 252-5298 (Japan); Ishiwata, N. [Green Innovation Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501 (Japan); Nakatani, Y. [University of Electro-communications, Chofu, Tokyo 182-8585 (Japan)

2012-05-14

420

Pressure-induced polar phases in multiferroic delafossite CuFeO2  

NASA Astrophysics Data System (ADS)

The pressure effect on the frustrated magnetic system CuFeO2 exhibiting multiferroic behavior has been studied by means of time-of-flight single crystal neutron diffraction combined with a hybrid-anvil-type pressure cell. The nonpolar collinear magnetic ground state (CM1 phase) with propagation vector k =(0,1/2,1/2) turns into a proper screw magnetic ordering with incommensurate modulation k =(0,q,1/2;q?0.4) and a polar 21' magnetic point group (ICM2 phase), between 3 and 4 GPa. This spin structure is similar to the ferroelectric phase induced by magnetic field or chemical doping under ambient pressure. Above, 4 GPa, a magnetic phase (ICM3) appears, with an incommensurate propagation vector that is unique for the CuFeO2 system, k =(qa,qb,qc;qa?0,qb?0.34,qc?0.43). This propagation vector at the general point results in triclinic magnetic symmetry which implies an admixture of both cycloidal and proper screw spin configurations. The ICM3 phase is stable in a narrow pressure range, and above 6 GPa, the spin-density collinear structure (ICM1 phase), similar to the first ordered state at ambient pressure, takes place. Comparing the degree of lattice distortions among the magnetic phases observed at ambient pressure, we discuss the origin of the pressure-induced magnetic phase transitions in CuFeO2.

Terada, Noriki; Khalyavin, Dmitry D.; Manuel, Pascal; Osakabe, Toyotaka; Radaelli, Paolo G.; Kitazawa, Hideaki

2014-06-01

421

Interferon Tau Alleviates Obesity-Induced Adipose Tissue Inflammation and Insulin Resistance by Regulating Macrophage Polarization  

PubMed Central

Chronic adipose tissue inflammation is a hallmark of obesity-induced insulin resistance and anti-inflammatory agents can benefit patients with obesity-associated syndromes. Currently available type I interferons for therapeutic immunomodulation are accompanied by high cytotoxicity and therefore in this study we have examined anti-inflammatory effects of interferon tau (IFNT), a member of the type I interferon family with low cellular toxicity even at high doses. Using a diet-induced obesity mouse model, we observed enhanced insulin sensitivity in obese mice administered IFNT compared to control mice, which was accompanied by a significant decrease in secretion of proinflammatory cytokines and elevated anti-inflammatory macrophages (M2) in adipose tissue. Further investigations revealed that IFNT is a potent regulator of macrophage activation that favors anti-inflammatory responses as evidenced by activation of associated surface antigens, production of anti-inflammatory cytokines, and activation of selective cell signaling pathways. Thus, our study demonstrates, for the first time, that IFNT can significantly mitigate obesity-associated systemic insulin resistance and tissue inflammation by controlling macrophage polarization, and thus IFNT can be a novel bio-therapeutic agent for treating obesity-associated syndromes and type 2 diabetes. PMID:24905566

Ying, Wei; Kanameni, Srikanth; Chang, Cheng-An; Nair, Vijayalekshmi; Safe, Stephen; Bazer, Fuller W.; Zhou, Beiyan

2014-01-01

422

Non-coherent Continuum Scattering as a Line Polarization Mechanism  

NASA Astrophysics Data System (ADS)

Line scattering polarization can be strongly affected by Rayleigh scattering at neutral hydrogen and Thomson scattering at free electrons. Often a depolarization of the continuum results, but the Doppler redistribution produced by the continuum scatterers, which are light (hence, fast), induces more complex interactions between the polarization in spectral lines and in the continuum. Here we formulate and solve the radiative transfer problem of scattering line polarization with non-coherent continuum scattering consistently. The problem is formulated within the spherical tensor representation of atomic and light polarization. The numerical method of solution is a generalization of the Accelerated Lambda Iteration that is applied to both the atomic system and the radiation field. We show that the redistribution of the spectral line radiation due to the non-coherence of the continuum scattering may modify the shape of the emergent fractional linear polarization patterns significantly, even yielding polarization signals above the continuum level in intrinsically unpolarizable lines.

del Pino Alemán, T.; Manso Sainz, R.; Trujillo Bueno, J.

2014-03-01

423

Macro- and microscopic spectral-polarization characteristics of the structure of normal and abnormally located chordae tendianeae of left ventricular  

NASA Astrophysics Data System (ADS)

The morphological peculiarities of TS mitral valve of the heart of man in normal and abnormal spaced strings of the left ventricle and the study of their structural features depending on the location was studied. There are given the results of comparative statistics, correlation and fractal study population Mueller-matrix images (MMI) of healthy and abnormal (early forms that are not diagnosed by histological methods) BT normal and abnormally located tendon strings left ventricle of the human heart. Abnormalities in the structure of the wings, tendon strings (TS), mastoid muscle (MM) in inconsistencies elements and harmonized operation of all valve complex shown in the features of the polarization manifestations of it laser images.

Malyk, Yu. Yu.; Prydij, O. G.; Zymnyakov, D. A.; Alonova, M. V.; Ushakova, O. V.

2013-12-01

424

Resistivity and induced polarization monitoring of salt transport under natural hydraulic gradients  

SciTech Connect

The authors demonstrate the use of resistivity/induced polarization (IP) monitoring of salt transport under natural hydraulic loads. Electrical monitoring of saline tracer transport during forced injection has been demonstrated previously. Detection of tracer transport under natural hydraulic loading is difficult because neither the hydraulic load nor the tracer resistivity can be controlled. In one study, the authors identify the electrical response to salt transport in a dynamic beach environment. Resistivity/IP imagine resolved the structure of the saltwater-freshwater interface and evidence for tide-induced groundwater transport. Resistivity increases in the near surface and at depth, upbeach of the high-tide mark, accompanied by tidal transgression. They attribute this to desaturation and decreasing salinity in the near surface and to decreasing salinity at depth, despite tidal transgression. Monitoring of groundwater levels indicates a phase lag between the tide level and groundwater level, supporting the electrical data. IP was insensitive to groundwater salinity variation. In a second study, the authors identify the electrical response to recharge-induced salt transport from a road-sale storage facility. Conductivity and IP models for monitoring lines, located on the basis of an EM31 survey, resolved the subsurface salt distribution, IP modeling resolved the sediment-bedrock interface. Modeling of monthly conductivity differences revealed conductivity increases and decreases at the locations of salt contamination, which correlate with the recharge pattern. They attribute near-surface conductivity increases after heavy rainfall to increasing saturation and ion dissolution. Corresponding conductivity decreases at depth are attributed to flushing of the bedrock with freshwater. Essentially, the opposite response was observed during a quiet monitoring period following heavy recharge. Near-surface IP changes are consistent with this interpretation. Salt transport occurring under natural hydraulic conditions was monitored with resistivity imaging. IP improved characterization of the hydrogeologic framework but was of limited value in monitoring salt transport in these environments.

Slater, L.D.; Sandberg, S.K.

2000-04-01

425

Graphene induced spectral tuning of metamaterial absorbers at mid-infrared frequencies  

NASA Astrophysics Data System (ADS)

In order to expand bandwidth of the resonant metamaterial absorbers, we investigate their spectral tuning at mid-infrared frequencies using graphene. We consider the absorbers with square metallic patches, cross-shaped resonators, and split ring resonators. Their resonances can be blue shifted by increasing graphene conductivity. Among these structures, split ring resonators produce the largest electric fields enabling huge spectral shifts, almost 30%. In addition, the tuning can be used for switching the mid-infrared waves at the absorber resonance. Here, the reflectance is zero, so even a small spectral shift of the resonance results in a huge increase of the reflectance.

Vasi?, Borislav; Gaji?, Radoš

2013-12-01

426

Modulated spin structure responsible for the magnetic-field-induced polarization switching in multiferroic TbMn2O5  

NASA Astrophysics Data System (ADS)

Orthorhombic TbMn2O5 (o -TMO ) is a well-known multiferroic manganite with the remarkable property of polarization switching at 3 K under a bias magnetic (H) field along the a axis of P b 21m . To theoretically account for this outstanding observation, we have proposed a modulated spin structure under the saturated bias H field by considering the relative strength of the three relevant exchange parameters in o -TMO . The proposed modulated structure based on density-functional theory (DFT) calculations is described in terms of the spin angle ? between the neighboring M n4 +-Mn3 + spin moments on the a-b plane. We have shown that the computed DFT polarization plotted as a function of ? satisfactorily accounts for the observed H -field-induced polarization switching. We have further theoretically shown that the square of the critical field strength (Hc) needed for the polarization switching is inversely proportional to the degree of the extrinsic magnetoelectric coupling. The computed partial charge density demonstrates that the H -field-induced polarization switching also accompanies with the switching in the sign of the excess valence-electron density.

Lee, Jung-Hoon; Jang, Hyun Myung

2015-01-01

427

Errors induced by the neglect of polarization in radiance calculations for Rayleigh-scattering atmospheres  

NASA Technical Reports Server (NTRS)

Although neglecting polarization and replacing the rigorous vector radiative transfer equation by its approximate scalar counterpart has no physical background, it is a widely used simplification when the incident light is unpolarized and only the intensity of the reflected light is to be computed. We employ accurate vector and scalar multiple-scattering calculations to perform a systematic study of the errors induced by the neglect of polarization in radiance calculations for a homogeneous, plane-parallel Rayleigh-scattering atmosphere (with and without depolarization) above a Lambertian surface. Specifically, we calculate percent errors in the reflected intensity for various directions of light incidence and reflection, optical thicknesses of the atmosphere, single-scattering albedos, depolarization factors, and surface albedos. The numerical data displayed can be used to decide whether or not the scalar approximation may be employed depending on the parameters of the problem. We show that the errors decrease with increasing depolarization factor and/or increasing surface albedo. For conservative or nearly conservative scattering and small surface albedos, the errors are maximum at optical thicknesses of about 1. The calculated errors may be too large for some practical applications, and, therefore, rigorous vector calculations should be employed whenever possible. However, if approximate scalar calculations are used, we recommend to avoid geometries involving phase angles equal or close to 0 deg and 90 deg, where the errors are especially significant. We propose a theoretical explanation of the large vector/scalar differences in the case of Rayleigh scattering. According to this explanation, the differences are caused by the particular structure of the Rayleigh scattering matrix and come from lower-order (except first-order) light scattering paths involving right scattering angles and right-angle rotations of the scattering plane.

Mishchenko, M. I.; Lacis, A. A.; Travis, L. D.

1994-01-01

428

Over-limiting currents and deionization "shocks" in current-induced polarization: local-equilibrium analysis.  

PubMed

The problem is considered theoretically of dynamics of current-induced concentration polarization of interfaces between ideally perm-selective and non-ideally perm-selective ("leaky") ion-exchange media in binary electrolyte solutions under galvanostatic conditions and at negligible volume flow. In contrast to the previous studies, the analysis is systematically carried out in terms of local thermodynamic equilibrium in the approximation of local electric neutrality in virtual solution. For macroscopically homogeneous media, this enables one to obtain model-independent results in quadratures for the stationary state as well as an approximate scaling-form solution for the transient response to the step-wise increase in electric-current density. These results are formulated in terms of such phenomenological properties of the "leaky" medium as ion transport numbers, diffusion permeability to salt and specific chemical capacity. An easy-to-solve numerically 1D PDE is also formulated in the same terms. A systematic parametric study is carried out within the scope of fine-pore model of "leaky" medium in terms of such properties as volumetric concentration of fixed electric charges and diffusivities of ions of symmetrical electrolyte. While previous studies paid principal attention to the shape and propagation rate of the so-called deionization "shocks", we also consider in detail the time evolution of voltage drop and interface salt concentration. Our analysis confirms the previously predicted pattern of propagating deionization "shocks" within the "leaky" medium but also reveals several novel features. In particular, we demonstrate that the deionization-shock pattern is really pronounced only at intermediate ratios of fixed-charge concentration to the initial salt concentration and at quite high steady-state voltages where the model used in this and previous studies is applicable only at relatively early stages of concentration-polarization process. PMID:22947188

Yaroshchuk, Andriy

2012-11-15

429

Application of time domain induced polarization to the mapping of lithotypes in a landfill site  

NASA Astrophysics Data System (ADS)

A direct current (DC) resistivity and time domain induced polarization (TDIP) survey was undertaken at a decommissioned landfill site situated in Hørløkke, Denmark, for the purpose of mapping the waste deposits and to discriminate important geological units that control the hydrology of the surrounding area. It is known that both waste deposits and clay have clear signatures in TDIP data, making it possible to enhance the resolution of geological structures compared to DC surveys alone. Four DC/TDIP profiles were carried out crossing the landfill, and another seven profiles in the surroundings provide a sufficiently dense coverage of the entire area. The whole dataset was inverted using a 1-D laterally constrained inversion scheme, recently implemented for TDIP data, in order to use the entire decay curves for reconstructing the electrical parameters of the soil in terms of the Cole-Cole polarization model. Results show that it is possible to resolve both the geometry of the buried waste body and key geological structures. In particular, it was possible to find a silt/clay lens at depth that correlates with the flow direction of the pollution plume spreading out from the landfill and to map a shallow sandy layer rich in clay that likely has a strong influence on the hydrology of the site. This interpretation of the geophysical findings was constrained by borehole data, in terms of geology and gamma ray logging. The results of this study are important for the impact of the resolved geological units on the hydrology of the area, making it possible to construct more realistic scenarios of the variation of the pollution plume as a function of the climate change.

Gazoty, A.; Fiandaca, G.; Pedersen, J.; Auken, E.; Christiansen, A. V.; Pedersen, J. K.

2012-06-01

430

Application of time domain induced polarization to the mapping of lithotypes in a landfill site  

NASA Astrophysics Data System (ADS)

A DC resistivity (DC) and Time Domain Induced Polarization (TDIP) survey was undertaken at a decommissioned landfill site situated in Hørløkke, Denmark, for the purpose of mapping the waste deposits and to discriminate important geological units that control the hydrology of the surrounding area. It is known that both waste deposits and clay have clear signatures in TDIP data, making possible to enhance the resolution of geological structures, when compared to DC surveys alone. Four DC/TDIP profiles were carried out crossing the landfill and another seven profiles in the surroundings, giving a dense coverage over the entire area. The whole dataset was inverted using a 1-D Laterally Constrained Inversion scheme, recently implemented for IP data, in order to use the entire decay curves for reconstructing the electrical parameters of the soil in terms of the Cole-Cole polarization model. Results show that it is possible to both resolve the geometry of the buried waste body and key geological structures. In particular, it was possible to find a silt/clay lens at depth, which correlates with the flow direction of the pollution plume spreading out from the landfill, and to map a shallow sandy layer rich in clay that likely has a strong influence on the hydrology of the site. This interpretation of the geophysical findings was constrained by boreholes data, in terms of geology and gamma ray logging. The results of this study are important for the impact that the resolved geological units have in the hydrology of the area, making it possible to construct more realistic scenarios of the variation of the pollution plume as a function of the climate change.

Gazoty, A.; Fiandaca, G.; Pedersen, J.; Auken, E.; Christiansen, A. V.; Pedersen, J. K.

2012-01-01

431

Gravitational Wave Induced Large-scale Polarization of \\\\\\\\Cosmic Microwave Background Radiation  

Microsoft Academic Search

We discuss the contribution of gravitational wave to the cosmic microwave\\u000abackground radiation (CMBR) anisotropy and polarization. It is found that the\\u000alarge-scale polarization of CMBR is less than 1\\\\% for a standard recombination\\u000auniverse. The effect of matter reionization will enhance the CMBR polarization\\u000ato a 10\\\\% level. We have computed the CMBR polarization for two extreme cases\\u000a(not

Ka Lok Ng; Kin-Wang Ng

1994-01-01

432

Identification of Genes Required for Normal Pheromone-Induced Cell ~ Polarization in Saccharomyces cerevisiae  

Microsoft Academic Search

ABSTRACT In response to mating pheromones, cells of the yeast Saccharomyces cerevisiae adopt a polarized “shmoo” morphology, in which the cytoskeleton and proteins involved in mating are localized to a cell- surface projection. This polarization , yet to be determined. We discuss the possible roles of these gene products in establishing cell polarity during mating. M ANY cell types generate

Janet Chenevert; Nicole Val; Ira Herskowitz

433

Chirality-induced polarization effects in the cuticle of scarab beetles: 100 years after Michelson  

Microsoft Academic Search

One hundred years ago Michelson discovered circular polarization in reflection from beetles. Today a novel Mueller-matrix ellipsometry setup allows unprecedented detailed characterization of the beetles' polarization properties. A formalism based on elliptical polarization for description of reflection from scarab beetles is here proposed and examples are given on four beetles of different character: Coptomia laevis – a simple dielectric mirror;

Hans Arwin; Roger Magnusson; Jan Landin; Kenneth Järrendahl

2012-01-01

434

Laser induced infrared spectral shift of the MgB2:Cr superconductor films.  

PubMed

During illumination of the MgB2:Cr2O3 films it was established substantial spectral shift of the infrared spectra in the vicinity of 20-50cm(-1). The excitations were performed by nanosecond Er:glass laser operating at 1.54?m and by microsecond 10.6?m CO2 laser. The spectral shifts of the IR maxima were in opposite spectral directions for the two types of lasers. This one observed difference correlates well with spectral shift of their critical temperatures. The possible explanation is given by performance of DFT calculations of the charge density redistribution and the time kinetics of the photovoltaic response. To understand the kinetics of the photoinduced processes the time kinetics of photoresponse was done for the particular laser wavelengths. PMID:25467659

AlZayed, N S; Kityk, I V; Soltan, S; El-Naggar, A M; Shahabuddin, M

2014-10-28