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Sample records for spectral induced polarization

  1. Spectral induced polarization signature of contaminated soil

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    Spectral induced polarization (SIP) signatures of porous media contaminated with non aqueous phase liquids (NAPL) were measured using an accurate impedance meter. The samples were prepared by mixing air-dried sand with 15% by weight of bentonite clay, tap water and either diesel fuel or motor oil. Next, the soil was packed in a column and left for 24 hr before electrical measurements were performed. For all the samples, water saturation was constant (Sw = 0.47) and the NAPL saturation was 0 (control), 5, or 15 percent. Counter-intuitively, the results show that addition of NAPL to the porous media resulted in an increase of the real part of the complex conductivity. Evidently, for each type of contaminant, an increase in the contaminant saturation resulted in an increase in the real part of the conductivity. The imaginary part of the complex conductivity showed a reversed behavior: higher NAPL saturation resulted in a reduction of the imaginary part of the complex conductivity. For both the real and the imaginary part of the complex conductivity, the effect of NAPL on the complex electrical conductivity was more significant for motor oil than for diesel fuel. In addition to the electrical measurements, we also performed an extraction experiment to examine the effect of the presence of NAPL on the electrical conductivity (EC) of the pore water. The results from the extraction experiment showed that addition of NAPL to the porous media resulted in an increase of the pore water EC. We argue that this increase in the real part of the complex conductivity is related to adsorption of organic polar compounds from the NAPL onto the mineral surface and the associated release of inorganic ions from the mineral surface to the pore water. These exchange processes affect both the surface and the pore water conductivity. In addition, we suggest that the decrease in polarization (associated with the imaginary part of the complex conductivity) of the NAPL contaminated porous media

  2. Spectral Induced Polarization of Goethite Nanoparticles

    NASA Astrophysics Data System (ADS)

    Huisman, J. A.; Moradi, S.; Zimmermann, E.; Bosch, J.; Vereecken, H.

    2014-12-01

    Goethite nanoparticles are being considered as a tool to enhance in situ remediation of aquifers contaminated with aromatic hydrocarbons. Injection of goethite nanoparticles into the plume is expected to enhance microbial iron reduction and associated beneficial oxidation of hydrocarbons in a cost-effective manner. Amongst others, current challenges associated with this novel approach are the monitoring of nanoparticle delivery and the nanoparticle and contaminant concentration dynamics over time. Obviously, non-invasive monitoring of these properties would be highly useful. In this study, we aim to evaluate whether spectral induced polarization (SIP) measurements of the complex electrical conductivity are suitable for such non-invasive characterization. In principle, this is not unreasonable because the electrical double layers of the goethite nanoparticles are expected to affect electrical polarization and thus the imaginary part of the complex electrical conductivity. In a first set of measurements, we determined the complex electrical conductivity of goethite nanoparticle suspensions with different nanoparticle concentrations, pH, and ionic strength in the mHz to kHz frequency range. In a second set of measurements, mixtures of sand and different concentrations of goethite nanoparticles and variable pH and ionic strengths were analyzed. Finally, flow experiments were monitored with SIP in a 1-m long laboratory column to investigate dynamic effects associated with goethite nanoparticle injection and delivery. The results showed that the imaginary part of the electrical conductivity was only affected in the high frequency range (Hz - kHz), which is expected from the small size of the goethite nanoparticles. Overall, we found that the goethite nanoparticles are associated with a small increase in the imaginary electrical conductivity at 1 kHz that can be measured in situ using recently improved borehole electrical impedance tomography measurement equipment that

  3. Spectral induced polarization measurements on New Zealand sands

    NASA Astrophysics Data System (ADS)

    Jospeh, S.; Ingham, M.; Gouws, G.

    2012-12-01

    Because of the dependence of the ac electrical conductivity of granular materials on surface effects related to pore geometry, spectral induced polarization measurements (SIP) have the potential to provide a geophysical technique which can be used to estimate aquifer properties such as hydraulic conductivity. We present the results of laboratory SIP measurements on a variety of sand samples typical of aquifers in the coastal areas of New Zealand and relate these to the measured hydraulic conductivity.

  4. On the spectral induced polarization signature of soil organic matter

    NASA Astrophysics Data System (ADS)

    Schwartz, N.; Furman, A.

    2014-01-01

    Although often composing a non-negligible fraction of soil cation exchange capacity (CEC), the impact of soil organic matter (OM) on the electrical properties of soil has not been thoroughly investigated. In this research the impact of soil OM on the spectral induced polarization (SIP) signature of soil was investigated. Electrical and chemical measurements for two experiments using the same soil, one with calcium as the dominant cation and the other with sodium, with different concentration of OM were performed. Our results show that despite the high CEC of OM, a decrease in polarization and an increase in relaxation time with increasing concentration of OM is observed. For the soil with calcium as the dominant cation, the decreases in polarization and the increase in relaxation time were stronger. We explain these non-trivial results by accounting for the interactions between the OM and the soil minerals. We suggest that the formation of organo-mineral complexes reduce ionic mobility, explaining both the decrease in polarization and the increase in relaxation time. These results demonstrate the important role of OM on SIP response of soil, and call for a further research in order to establish a new polarization model that will include the impact of OM on soil polarization.

  5. Spectral Induced Polarization Signature of Soil Organic Matter

    NASA Astrophysics Data System (ADS)

    Schwartz, Nimrod; Furman, Alex

    2015-04-01

    Although often composing a non-negligible fraction of soil cation exchange capacity (CEC), the impact of soil organic matter (OM) on the electrical properties of soil has not been thoroughly investigated. In this research the impact of soil OM on the spectral induced polarization (SIP) signature of soil was investigated. Electrical and chemical measurements for two experiments using the same soil, one with calcium as the dominant cation and the other with sodium, with different concentration of OM were performed. Our results show that despite the high CEC of OM, a decrease in polarization and an increase in relaxation time with increasing concentration of OM is observed. For the soil with calcium as the dominant cation, the decreases in polarization and the increase in relaxation time were stronger. We explain these non-trivial results by accounting for the interactions between the OM and the soil minerals. We suggest that the formation of organo-mineral complexes reduce ionic mobility, explaining both the decrease in polarization and the increase in relaxation time. These results demonstrate the important role of OM on SIP response of soil, and call for a further research in order to establish a new polarization model that will include the impact of OM on soil polarization.

  6. Spectral induced polarization for monitoring electrokinetic remediation processes

    NASA Astrophysics Data System (ADS)

    Masi, Matteo; Losito, Gabriella

    2015-12-01

    Electrokinetic remediation is an emerging technology for extracting heavy metals from contaminated soils and sediments. This method uses a direct or alternating electric field to induce the transport of contaminants toward the electrodes. The electric field also produces pH variations, sorption/desorption and precipitation/dissolution of species in the porous medium during remediation. Since heavy metal mobility is pH-dependent, the accurate control of pH inside the material is required in order to enhance the removal efficiency. The common approach for monitoring the remediation process both in laboratory and in the field is the chemical analysis of samples collected from discrete locations. The purpose of this study is the evaluation of Spectral Induced Polarization as an alternative method for monitoring geochemical changes in the contaminated mass during remediation. The advantage of this technique applied to field-scale is to offer higher resolution mapping of the remediation site and lower cost compared to the conventional sampling procedure. We carried out laboratory-scale electrokinetic remediation experiments on fine-grained marine sediments contaminated by heavy metal and we made Spectral Induced Polarization measurements before and after each treatment. Measurements were done in the frequency range 10- 3-103 Hz. By the deconvolution of the spectra using the Debye Decomposition method we obtained the mean relaxation time and total chargeability. The main finding of this work is that a linear relationship exists between the local total chargeability and pH, with good agreement. The observed behaviour of chargeability is interpreted as a direct consequence of the alteration of the zeta potential of the sediment particles due to pH changes. Such relationship has a significant value for the interpretation of induced polarization data, allowing the use of this technique for monitoring electrokinetic remediation at field-scale.

  7. Spectral induced polarization signatures of abiotic FeS precipitation

    SciTech Connect

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

    2010-01-15

    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.

  8. Salinity dependence of spectral induced polarization in sands and sandstones

    NASA Astrophysics Data System (ADS)

    Revil, A.; Skold, M.

    2011-11-01

    In electrolyte-saturated sands, the reversible storage of electrical charges is responsible for a phase lag between the current (injected and retrieved by two current electrodes) and the electrical field recorded by two voltage electrodes. This phenomenon is called 'spectral induced polarization' in geophysics and can potentially be used to monitor salt tracer tests in shallow aquifers to infer their permeability and dispersivity tensors. We demonstrate analytically that the polarization of the inner part of the electrical triple layer coating the surface of the grains (named the Stern layer in electrochemistry) is consistent with available data. We also perform new experiments using silica sands saturated by NaCl and CaCl2 pore water solutions. The salinity dependence of quadrature conductivity can be modelled using an analytical solution of the triple layer model, which offers a simple way to interpret laboratory and field data. This analytical solution depends on the total site density of the mineral surface, the pH value and the sorption coefficient of the cation in the Stern layer. This model shows that both the specific surface conductivity of the Stern layer and the quadrature conductivity of the porous material depend on the conductivity of the pore water. The quadrature conductivity is becoming independent of the salinity above 1 S m-1. The parameters entering the analytical model are consistent with independent estimates from titration data and zeta potential measurements, which are two classical methods to characterize the electrical triple layer at the pore water mineral interface.

  9. Spectral induced polarization (SIP) response of mine tailings.

    PubMed

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

    2015-02-01

    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

  10. Spectral induced polarization (SIP) response of mine tailings

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    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 10,000 Hz. 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.

  11. Temperature dependence of spectral induced polarization data: experimental results and membrane polarization theory

    NASA Astrophysics Data System (ADS)

    Bairlein, Katharina; Bücker, Matthias; Hördt, Andreas; Hinze, Björn

    2016-04-01

    Spectral induced polarization measurements are affected by temperature variations due to a variety of temperature-dependent parameters that control the complex electrical conductivity. Most important is the influence of the ion mobility, which increases with increasing temperature. It is responsible for the increase of the conductivity of the fluid in the pores with temperature and influences the electrical double layer on the mineral surface. This work is based on laboratory measurements of 13 sandstone samples from different sources with different geological and petrophysical characteristics. We measured the complex impedance in a frequency range from 0.01 to 100 Hz and a temperature range from 0 to 40 °C. The main observation is a decrease of the characteristic time (defined by the inverse of the frequency, at which the phase shift is maximum) with increasing temperature. The strength of this decrease differs from one sample to another. The temperature dependence of the phase shift magnitude cannot easily be generalized, as it depends on the particular sample. The experimental findings suggest that neglecting the influence of temperature on complex conductivity may lead to significant errors when estimating hydraulic conductivity from relaxation time. We also simulate the temperature dependence with a theoretical model of membrane polarization and review some of the model properties, with an emphasis on the temperature dependence of the parameters. The model reproduces several features characterizing the measured data, including the temperature dependence of the characteristic times. Computed tomography and microscope images of the pore structure of three samples also allow us to associate differences in the geometrical parameters used in the modelling with pore scale parameters of the actual samples.

  12. Spectral Induced Polarization Signatures of Ethanol in Sand-Clay Medium

    EPA Science Inventory

    The spectral Induced Polarization (SIP) method has previously been investigated as a tool for detecting physicochemical changes occurring as result of clay-organic interactions in porous media. We performed SIP measurements with a dynamic signal analyzer (NI-4551) on laboratory ...

  13. Salinity effect on the spectral induced polarization porosimetry: theory and experiment

    NASA Astrophysics Data System (ADS)

    Niu, Q.; Revil, A.; Saidian, M.; Prasad, M.

    2015-12-01

    Spectral induced polarization (SIP) porosimetry is a new technique for characterizing the pore size distribution of a porous medium. The induced polarization of porous media under low frequencies is mainly attributed to the relaxation of the mineral/fluid interface, i.e., the electrical double layer (EDL, including both Stern and diffuse layers). Currently, the salinity effect is not considered while applying the SIP porosimetry although a number of experiments have shown the water salinity could affect the relaxation of EDL. In this study, we conducted SIP measurement of a Portland sandstone sample with a broad range of salinities. The relaxation time distributions of the sample at different salinities are obtained by inverting the measured SIP responses using the least-square method with optimized damping parameter. The modal relaxation time shows a non-negligible dependence on the salinity/fluid conductivity. The salinity dependence can be explained by considering the ions exchange between Stern and diffuse layers during polarization, i.e., diffuse layer polarization (DLP). It is also shown that the SIP porosimetry could underestimate the pore size if only Stern layer polarization is considered. It is therefore suggested to include DLP while interpreting the SIP porosimetry data in order to give consistent pore size information with other techniques such as nuclear magnetic resonance and mercury injection capillary porosimetry.

  14. Relaxation Time Distribution (RTD) of Spectral Induced Polarization (SIP) data from environmental studies

    NASA Astrophysics Data System (ADS)

    Ntarlagiannis, D.; Ustra, A.; Slater, L. D.; Zhang, C.; Mendonça, C. A.

    2015-12-01

    In this work we present an alternative formulation of the Debye Decomposition (DD) of complex conductivity spectra, with a new set of parameters that are directly related to the continuous Debye relaxation model. The procedure determines the relaxation time distribution (RTD) and two frequency-independent parameters that modulate the induced polarization spectra. The distribution of relaxation times quantifies the contribution of each distinct relaxation process, which can in turn be associated with specific polarization processes and characterized in terms of electrochemical and interfacial parameters as derived from mechanistic models. Synthetic tests show that the procedure can successfully fit spectral induced polarization (SIP) data and accurately recover the RTD. The procedure was applied to different data sets, focusing on environmental applications. We focus on data of sand-clay mixtures artificially contaminated with toluene, and crude oil-contaminated sands experiencing biodegradation. The results identify characteristic relaxation times that can be associated with distinct polarization processes resulting from either the contaminant itself or transformations associated with biodegradation. The inversion results provide information regarding the relative strength and dominant relaxation time of these polarization processes.

  15. Spectral and polarization structure of field-induced photonic bands in cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Palto, S. P.; Barnik, M. I.; Geivandov, A. R.; Kasyanova, I. V.; Palto, V. S.

    2015-09-01

    Transmission of planar layers of cholesteric liquid crystals is studied in pulsed electric fields perpendicular to the helix axis at normal incidence of both linearly polarized and unpolarized light. Spectral and light polarization properties of the primary photonic band and the field-induced bands up to fourth order of Bragg selective reflection are studied in detail. In our experiments we have achieved an electric field strength several times higher than the theoretical values corresponding to the critical field of full helix unwinding. However, the experiments show that despite the high strength of the electric field applied the helix does not unwind, but strongly deforms, keeping its initial spatial period. Strong helix deformation results in distinct spectral band splitting, as well as very high field-induced selective reflectance that can be applied in lasers and other optoelectronic devices. Peculiarities of inducing and splitting the bands are discussed in terms of the scattering coefficient approach. All observed effects are confirmed by numerical simulations. The simulations also show that liquid crystal surface anchoring is not the factor that prevents the helix unwinding. Thus, the currently acknowledged concept of continuous helix unwinding in the electric field should be reconsidered.

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

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    We measured spectral induced polarization (SIP) signatures in sand columns during (1) FeS biomineralization produced by sulfate reducing bacteria (Desulfovibrio vulgaris) under anaerobic 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. We find that the modeled time constant is consistent with the polarizable elements being biomineral encrusted 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. We conclude that SIP signatures are diagnostic of pore-scale geometrical changes associated with FeS biomineralization by sulfate reducing bacteria.

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

    SciTech Connect

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

    2012-04-01

    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.

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

    SciTech Connect

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

    2012-04-17

    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.

  19. Spectral induced polarization (SIP) response of biodegraded oil in porous media

    NASA Astrophysics Data System (ADS)

    Abdel Aal, Gamal Z.; Atekwana, Estella A.

    2014-02-01

    Laboratory experiments were conducted to investigate the effect of different oil saturation (0.2-0.8), wetting conditions (water-wet and oil-wet), and the addition of asphaltene on the spectral induced polarization (SIP) response of biodegraded and fresh crude oil in sand columns. In the water-wet case, no significant differences were observed for both the fresh and biodegraded oil and both displayed an increase in the magnitude of the phase (ϕ) and decrease in the magnitudes of the real (σ') and imaginary (σ'') conductivity components with increasing oil saturation. In this instance the SIP response is most likely controlled by the conduction and polarization of the electric double layer at the mineral-water interface. However, when oil is the wetting phase there were considerable differences in the magnitude of the SIP parameters between the fresh and biodegraded oil. The magnitude of ϕ and σ'' increased with increasing oil saturation, whereas σ' decreased. The magnitude of σ' and σ'' for the biodegraded oil-wetted sands were relatively higher compared to fresh oil-wetted sands. In experiments with fresh and biodegraded oil-wet sand, the addition of 1 per cent asphaltene increased σ' and σ'' with the biodegraded oil showing the highest magnitude. Asphaltenes are the most dipolar fraction of crude oil and increase in concentration with increasing biodegradation. Asphaltene creates a surface charge due to the ionization and complexation reactions of functional groups at interfaces. Therefore, the enhancement in the conduction and polarization observed with the biodegraded oil-wetted sands may be due to the increase in polar components (e.g. asphaltene) from the biodegradation process and the interactions of the polar components with the surfaces of water and mineral grains. Further studies are required to investigate the effect of other components in biodegraded oil such as resins, trace metals, biogenic metallic minerals (e.g. magnetite) and organic

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

    NASA Astrophysics Data System (ADS)

    Personna, Yves Robert; Ntarlagiannis, Dimitrios; Slater, Lee; Yee, Nathan; O'Brien, Michael; Hubbard, Susan

    2008-06-01

    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 Desulfovibrio vulgaris. 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 anaerobic iron sulfide forming conditions and aerobic conditions promoting iron sulfide dissolution. The SIP data showed ˜10 mrad 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.

  1. Two-dimensional inversion of spectral induced polarization data using MPI parallel algorithm in data space

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Yong; Tan, Han-Dong; Wang, Kun-Peng; Lin, Chang-Hong; Zhang, Bin; Xie, Mao-Bi

    2016-03-01

    Traditional two-dimensional (2D) complex resistivity forward modeling is based on Poisson's equation but spectral induced polarization (SIP) data are the coproducts of the induced polarization (IP) and the electromagnetic induction (EMI) effects. This is especially true under high frequencies, where the EMI effect can exceed the IP effect. 2D inversion that only considers the IP effect reduces the reliability of the inversion data. In this paper, we derive differential equations using Maxwell's equations. With the introduction of the Cole-Cole model, we use the finite-element method to conduct 2D SIP forward modeling that considers the EMI and IP effects simultaneously. The data-space Occam method, in which different constraints to the model smoothness and parametric boundaries are introduced, is then used to simultaneously obtain the four parameters of the Cole—Cole model using multi-array electric field data. This approach not only improves the stability of the inversion but also significantly reduces the solution ambiguity. To improve the computational efficiency, message passing interface programming was used to accelerate the 2D SIP forward modeling and inversion. Synthetic datasets were tested using both serial and parallel algorithms, and the tests suggest that the proposed parallel algorithm is robust and efficient.

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

    SciTech Connect

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

    2008-02-15

    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.

  3. Evaluation of Surface Sorption Processes Using Spectral Induced Polarization and a (22)Na Tracer.

    PubMed

    Hao, Na; Moysey, Stephen M J; Powell, Brian A; Ntarlagiannis, Dimitrios

    2015-08-18

    We investigate mechanisms controlling the complex electrical conductivity of a porous media using noninvasive spectral induced polarization (SIP) measurements of a silica gel during a pH dependent surface adsorption experiment. Sorption of sodium on silica gel surfaces was monitored as the pH of a column was equilibrated at 5.0 and then successively raised to 6.5 and 8.0, but the composition of the 0.01 M NaCl solution was otherwise unchanged. SIP measurements show an increase in the imaginary conductivity of the sample (17.82 ± 0.07 μS/cm) in response to the pH change, interpreted as deprotonation of silanol groups on the silica gel surface followed by sorption of sodium cations. Independent measurements of Na(+) accumulation on grain surfaces performed using a radioactive (22)Na tracer support the interpretation of pH-dependent sorption as a dominant process controlling the electrical properties of the silica gel (R(2) = 0.99) and confirms the importance of grain polarization (versus membrane polarization) in influencing SIP measurements of silicate minerals. The number of surface sorption sites estimated by fitting a mechanistic, triple-layer model for the complex conductivity to the SIP data (13.22 × 10(16) sites/m(2)) was 2.8 times larger than that estimated directly by a (22)Na mass balance (5.13 × 10(16) sites/m(2)), suggesting additional contributions to polarization exist. PMID:26191613

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

    SciTech Connect

    Morgan, F. Dale; Sogade, John

    2004-12-14

    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

  5. Integrated Geophysical Measurements for Bioremediation Monitoring: Combining Spectral Induced Polarization, Nuclear Magnetic Resonance and Magnetic Methods

    SciTech Connect

    Keating, Kristina; Slater, Lee; Ntarlagiannis, Dimitris; Williams, Kenneth H.

    2015-02-24

    This documents contains the final report for the project "Integrated Geophysical Measurements for Bioremediation Monitoring: Combining Spectral Induced Polarization, Nuclear Magnetic Resonance and Magnetic Methods" (DE-SC0007049) Executive Summary: Our research aimed to develop borehole measurement techniques capable of monitoring subsurface processes, such as changes in pore geometry and iron/sulfur geochemistry, associated with remediation of heavy metals and radionuclides. Previous work has demonstrated that geophysical method spectral induced polarization (SIP) can be used to assess subsurface contaminant remediation; however, SIP signals can be generated from multiple sources limiting their interpretation value. Integrating multiple geophysical methods, such as nuclear magnetic resonance (NMR) and magnetic susceptibility (MS), with SIP, could reduce the ambiguity of interpretation that might result from a single method. Our research efforts entails combining measurements from these methods, each sensitive to different mineral forms and/or mineral-fluid interfaces, providing better constraints on changes in subsurface biogeochemical processes and pore geometries significantly improving our understanding of processes impacting contaminant remediation. The Rifle Integrated Field Research Challenge (IFRC) site was used as a test location for our measurements. The Rifle IFRC site is located at a former uranium ore-processing facility in Rifle, Colorado. Leachate from spent mill tailings has resulted in residual uranium contamination of both groundwater and sediments within the local aquifer. Studies at the site include an ongoing acetate amendment strategy, native microbial populations are stimulated by introduction of carbon intended to alter redox conditions and immobilize uranium. To test the geophysical methods in the field, NMR and MS logging measurements were collected before, during, and after acetate amendment. Next, laboratory NMR, MS, and SIP measurements

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

    USGS Publications Warehouse

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

    1983-01-01

    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

  7. Spectral-induced polarization measurements on sieved sands and the relationship to permeability

    NASA Astrophysics Data System (ADS)

    Joseph, Sheen; Ingham, Malcolm; Gouws, Gideon

    2016-06-01

    Laboratory measurements of the permeability and spectral-induced polarization (SIP) response of samples consisting of unconsolidated sands typical of those found in New Zealand aquifers have been made. After correction of measured formation factors to allow for the fact that some were measured at only one fluid conductivity, predictions of permeability from the grain size (d) of the samples are found to agree well with measured values of permeability. The Cole-Cole time constant (derived from the SIP measurements) is found, as expected, to depend upon d2, but can be affected by the inclusion of smaller grains in the sample. Measurements made on samples comprising of mixtures of grain sizes show that inclusion in a sample of even 10% of smaller grains can significantly reduce both the Cole-Cole time constant (τCC) and the permeability, and support theoretical derivation of how the permeability of a mixture of grain sizes varies with the content of the mixture. Proposed relationships for using τCC as a predictor for permeability are tested and found to be crucially dependent on the assumed relationship between the dynamic pore radius and grain size. The inclusion of a multiplicative constant to take account of numerical approximations results in good predictions for the permeability of the samples in this study. It seems unlikely, however, that there is a single global expression for predicting permeability from SIP data for all samples.

  8. A Web Interface for Software of Stochastic Inversion of Spectral Induced Polarization Data

    NASA Astrophysics Data System (ADS)

    Chen, J.; Pullman, S.; Hubbard, S. S.; Peterson, J.

    2009-12-01

    The induced-polarization (IP) method has been used increasingly in environmental investigations because IP measurements are very sensitive to the low frequency capacitive properties of rocks and soils. The Cole-Cole model has been very useful for interpreting spectral IP data in terms of parameters, such as chargeability and time constant, which are used to estimate various subsurface properties. However, conventional methods for estimating Cole-Cole parameters use an iterative Gauss-Newton-based deterministic method, which has been shown that the obtained optimal solution depends on the choice of initial values and the estimated uncertainty information often is inaccurate or insufficient. Chen, Kemna, and Hubbard (2008) developed a Bayesian model for inverting spectral IP data for Cole-Cole parameters based on Markov chain Monte Carlo (MCMC) sampling methods. They have demonstrated that the MCMC-based inversion method provides extensive global information on unknown parameters, such as the marginal probability distribution functions, from which better estimates and tighter uncertainty bounds of the parameters can be obtained. Additionally, the results obtained with the MCMC method are almost independent of the choice of initial values. We have developed a web interface to the stochastic inversion software, which permits easy accessibility to the code. The web interface allows users to upload their own spectral IP data, specify prior ranges of unknown parameters, and remotely run the code in real time. After running the code (a few minutes), the interface provides a data file with all the statistics of each unknown parameter, including the median, mean, standard deviation, and 95% predictive intervals, and provides a data misfit file. The interface also allows users to visualize the histogram and posterior probability density of each unknown parameter as well as data misfits. For advanced users, the interface provides an option of producing time-series plots of all

  9. Application of high resolution 2D/3D spectral induced polarization (SIP) in metalliferous ore exploration

    NASA Astrophysics Data System (ADS)

    Chen, R.; Zhao, X.; Yao, H.; He, X.; Zeng, P.; Chang, F.; Yang, Y.; Zhang, X.; Xi, X.; He, L.

    2015-12-01

    Induced polarization (IP) is a powerful tool in metalliferous ore exploration. However, there are many sources, such as clay and graphite, which can generate IP anomaly. Spectral induced polarization (SIP) measures IP response on a wide frequency range. This method provides a way to discriminate IP response generated by metalliferous ore or other objects. The best way to explore metalliferous ore is 3D SIP exploration. However, if we consider the exploration cost and efficiency, we can use SIP profiling to find an anomaly, and then use 2D/3D SIP sounding to characterize the anomaly. Based on above idea, we used a large-scale distributed SIP measurement system which can realize 800 sounding sites in one direction at the same time. This system can be used for SIP profiling, 2D/3D SIP sounding with high efficiency, high resolution, and large depth of investigation (> 1000 m). Qiushuwan copper - molybdenum deposit is located in Nanyang city, Henan province, China. It is only a middle-size deposit although over 100 holes were drilled and over 40 years of exploration were spent because of very complex geological setting. We made SIP measurement over 100 rock and ore samples to discriminate IP responses of ore and rock containing graphite. Then we carried out 7 lines of 2D SIP exploration with the depth of investigation great than 1000 m. The minimum electode spacing for potential difference is only 20 m. And we increase the spacing of current electodes at linear scale. This acquisition setting ensures high density data acquired and high quality data acquisition. Modeling and inversion result proves that we can get underground information with high resolution by our method. Our result shows that there exists a strong SIP response related to ore body in depth > 300 m. Pseudo-3D inversion of five 2D SIP sounding lines shows the location and size of IP anomaly. The new drillings based our result found a big copper-molybdenum ore body in new position with depth > 300 m and

  10. Characterization of organic contaminants in porous media using nuclear magnetic resonance and spectral induced polarization measurements.

    NASA Astrophysics Data System (ADS)

    Rupert, Y. K.

    2015-12-01

    The remediation and monitoring of soils and groundwater contaminated with organic compounds is an important goal of many environmental restoration efforts. This laboratory research focuses on combining two innovative geophysical methods: nuclear magnetic resonance (NMR) and spectral induced polarization (SIP) to assess their suitability to characterize and quantify organic contaminants in porous media. Toluene, a light non-aqueous phase liquid (LNAPL), and ethoxy-nonafluorobutane, an engineered dense non-aqueous phase liquid (DNAPL), have been selected as representative organic contaminants. Low-field NMR relaxation time (T2) measurements and diffusion-relaxation (D-T2) correlation measurements, as well as low frequency SIP measurements (<10 kHz) are performed to quantify the amount of these two organic compounds in the presence of water in three types of porous media (sands, clay, and various sand-clay mixtures). The T2, D-T2, and SIP measurements are made on water, toluene, and the synthetic DNAPL in each porous media to understand the effect of different porous media on the NMR and SIP responses in each fluid. We then plan to make measurements on water-organic mixtures with varied concentrations of organic compounds in each porous medium to resolve the NMR and SIP response of the organic contaminants from that of water and to quantify the amount of organic contaminants. Building a relationship between SIP and NMR signatures from organic contaminants not only provides a fundamental yet important petrophysical relationship, but also builds a framework for continued investigation into how these two methods synergize. This will also provide spatially dense information about organic contaminated natural sediments at scales that will improve the quantitative characterization and remediation of contaminated sites.The remediation and monitoring of soils and groundwater contaminated with organic compounds is an important goal of many environmental restoration efforts

  11. Characterizing petrophysical properties of carbonate rocks using nuclear magnetic resonance and spectral induced polarization

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Zhang, Chi; Rankey, Eugene

    2016-04-01

    Unlike sandstones, with well-characterized correlations between porosity and permeability, carbonate rocks are well known for their highly complex petrophysical behaviors due to their intrinsically heterogeneous pore shape, pore size, and pore distributions and connectivity. The characterization of petrophysical properties of carbonate rocks, including rock properties and rock-fluid interactions, remains big challenges. This laboratory study focuses on integrating two geophysical methods: nuclear magnetic resonance (NMR) and spectral induced polarization (SIP) to determine porosity, pore size distribution, and permeability of carbonate rocks. NMR measures the relaxation of hydrogen nuclei at pore scale. Samples with different pore structures saturated by fluids have molecular relaxation responses to the external magnetic field which could generate various NMR signals. Permeability estimation from NMR in siliciclastic rocks is routine, however, is problematic in carbonates. SIP determines complex resistivity of a sample across a wide range of frequency and is sensitive to variations in the properties of solid-fluid and fluid-fluid interfaces in porous media. Previous studies investigated the relationships between permeability and parameters derived from SIP data, but are restricted to narrow lithology range. Our study used carbonate core samples from three depositional environments: tidal zone, shallow marine, and platform/reef margin of an atoll. Samples were fully saturated by water for T2 relaxation measurements and complex conductivity measurements at low frequencies. We compare the pore volume to surface area ratio measured from NMR and SIP and assess the applicability of established petrophysical models to estimate permeability from NMR and SIP data. We hope to build a relationship between NMR signals, SIP responses and petrophysical properties in carbonate rocks. The results could also provide new data and help further understand the unique and complex pore

  12. Spectral-induced polarization characteristics of rocks from Shinyemi deposit in Northeastern South Korea

    NASA Astrophysics Data System (ADS)

    Park, Samgyu; Shin, Seung Wook; Son, Jeong-Sul; Kim, Changryol

    2016-04-01

    Contact metasomatism between carbonate and igneous rocks leads to the formation of skarn deposits, and ore minerals are abundant. Geophysical methods that visualize the distributions of physical properties have been utilized to determine lithological boundaries in ore deposits. In particular, spectral-induced polarization (SIP) is the most effective of those methods for mineral exploration because it can obtain not only the boundaries but also the abundance and grain size of ore minerals. It is crucial to characterize the SIP responses of in situ rocks for a more realistic interpretation. Thus, typical rocks composed of igneous rock, skarn rock, skarn ore, and carbonate rock were sampled from drilling cores in the Shinyemi deposit, which is one of the well-known skarn deposits in Northeastern South Korea. The purpose of this study was to characterize the SIP responses of rocks by laboratory measurements. The characterization was performed by evaluating spectra and IP parameters. The IP properties were acquired from equivalent circuit analysis using a circuit model based on the electrochemical theory, and the analysis results of this circuit model were relatively well fit compared with those of the traditional Dias and Cole-Cole models. The frequency responses below 100 Hz in the spectra and the chargeability values of the skarn rocks and ores containing magnetite were relatively strong and high, respectively, compared with those of non-mineralized igneous and carbonate rocks. Therefore, it is considered that these characteristics are dependent on the abundance of magnetite. In case of the skarn ores with high magnetite content, the resistivity values were significantly low and the relaxation time values were influenced by the grain size of magnetite. On the other hand, it is considered that the DC resistivity and the relaxation time values of the igneous and carbonate rocks are slightly related to the porosity and the grade of hydrothermal alteration, respectively.

  13. Spectral Induced Polarization (SIP) monitoring during Microbial Enhanced Oil Recovery (MEOR)

    NASA Astrophysics Data System (ADS)

    Heenan, J. W.; Ntarlagiannis, D.; Slater, L. D.

    2010-12-01

    Jeffrey Heenan, Dimitrios Ntarlagiannis, Lee Slater Department of Earth and Environmental Sciences, Rutgers University, Newark NJ Microbial Enhanced Oil Recovery (MEOR) is an established, cost effective, method for enhancing tertiary oil recovery. Although not commonly used for shallow heavy oils, it could be a viable alternative since it can offer sustainable economic recovery and minimal environmental impact. A critical component of successful MEOR treatments is accurate, real time monitoring of the biodegradation processes resulting from the injection of microbial communities into the formation; results of recent biogeophysical research suggest that minimally-invasive geophysical methods could significantly contribute to such monitoring efforts. Here we present results of laboratory experiments, to assess the sensitivity of the spectral induced polarization method (SIP) to MEOR treatments. We used heavy oil, obtained from a shallow oilfield in SW Missouri, to saturate three sand columns. We then followed common industry procedures,and used a commercially available microbial consortia, to treat the oil columns. The active MEOR experiments were performed in duplicate while a control column maintained similar conditions, without promoting microbial activity and oil degradation. We monitored the SIP signatures, between 0.001 Hz and 1000 Hz, for a period of six months. To support the geophysical measurements we also monitored common geochemical parameters, including pH, Eh and fluid conductivity, and collected weekly fluid samples from the outflow and inflow for further analysis; fluid samples were analyzed to confirm that microbes actively degraded the heavy oils in the column while destructive analysis of the solid materials was performed upon termination of the experiment. Preliminary analysis of the results suggests that SIP is sensitive to MEOR processes. In both inoculated columns we recorded an increase in the low frequency polarization with time; measureable

  14. Pore fluid chemistry and spectral induced polarization signatures of calcium carbonate

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Hubbard, S. S.; Ajo Franklin, J. B.; Williams, K. H.

    2010-12-01

    Calcium carbonate (CaCO3) minerals are a key family of compounds that frequently precipitate during natural and engineered subsurface processes. They play important roles in elemental cycling within geosystems and can be utilized in the context of environmental remediation (such as metal sequestration through co-precipitation) and in geotechnical engineering (such as improving soil strength or decreasing rock permeability). Characterizing the spatial extent and temporal dynamics of carbonate mineral precipitation is critical for these studies. Our previous research has indicated the potential of geophysical methods, particularly spectral induced polarization (SIP) for tracking the onset and evolution of mineral precipitates, including calcite. Here, we experimentally document the significant role of pore fluid chemistry and surface charge structure on the SIP signature of calcium carbonates. Our column studies revealed that the SIP signature of calcium carbonate is dictated by surface charge structure that relies heavily on surface complexation properties, such as charge density and speciation. For calcium carbonate, the primary potential determining ions (PDIs) are calcium and carbonate ions and the SIP signatures of calcium carbonate are primarily controlled by the concentrations of these species. Our data show that calcium carbonates in thermodynamic equilibrium with pore fluid produce a negligible SIP response due to very small (if any) surface charges. In contrast, systems that are over saturated with respect to calcium carbonate (i.e., far from equilibrium) produce significant SIP responses, which is consistent with high surface charge densities shown by high zeta potential values in previous studies. Our studies reveal that a closed system that transitions from over-saturation to equilibrium conditions is accompanied by significant decrease of SIP signals (and vice-versa). The studies also show that the effect of pH on SIP signature of calcium carbonate is

  15. Monitoring microbial growth and activity using spectral induced polarization and low-field nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Keating, Kristina; Revil, Andre

    2015-04-01

    Microbes and microbial activities in the Earth's subsurface play a significant role in shaping subsurface environments and are involved in environmental applications such as remediation of contaminants in groundwater and oil fields biodegradation. Stimulated microbial growth in such applications could cause wide variety of changes of physical/chemical properties in the subsurface. It is critical to monitor and determine the fate and transportation of microorganisms in the subsurface during such applications. Recent geophysical studies demonstrate the potential of two innovative techniques, spectral induced polarization (SIP) and low-field nuclear magnetic resonance (NMR), for monitoring microbial growth and activities in porous media. The SIP measures complex dielectric properties of porous media at low frequencies of exciting electric field, and NMR studies the porous structure of geologic media and characterizes fluids subsurface. In this laboratory study, we examined both SIP and NMR responses from bacterial growth suspension as well as suspension mixed with silica sands. We focus on the direct contribution of microbes to the SIP and NMR signals in the absence of biofilm formation or biomineralization. We used Zymomonas mobilis and Shewanella oneidensis (MR-1) for SIP and NMR measurements, respectively. The SIP measurements were collected over the frequency range of 0.1 - 1 kHz on Z. mobilis growth suspension and suspension saturated sands at different cell densities. SIP data show two distinct peaks in imaginary conductivity spectra, and both imaginary and real conductivities increased as microbial density increased. NMR data were collected using both CPMG pulse sequence and D-T2 mapping to determine the T2-distribution and diffusion properties on S. oneidensis suspension, pellets (live and dead), and suspension mixed with silica sands. NMR data show a decrease in the T2-distribution in S. oneidensis suspension saturated sands as microbial density increase. A

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Recent biogeophysics studies demonstrated the sensitivity of complex conductivity to bacterial growth and microbial mediated mineral transformations in porous media. Frequency-domain induced polarization is a minimally invasive manner to measure the complex conductivity of a material over a broad range of frequencies. The real component of complex conductivity is associated with electromigration of the charge carriers, and the imaginary component represents reversible energy storage of charge carriers at polarization length scales. Quantitative relationship between frequency-domain induced polarization responses and bacterial growth and decay in porous media is analyzed in this study using a new developed model. We focus on the direct contribution of bacteria themselves to the complex conductivity in porous media in the absence of biomineralization. At low frequencies, the induced polarization of bacteria (α-polarization) is related to the properties of the electrical double layer surrounding the membrane surface of bacteria. Surface conductivity and α-polarization are due to the Stern layer of the counterions occurring in a brush of polymers coating the surface of the bacteria, and can be related to the cation exchange capacity of the bacteria. From the modeling results, at low frequencies (< 10 Hz), the mobility of the counterions (K+) in the Stern layer of bacteria is found to be extremely small (4.7×10-10 m2s-1 V-1 at 25°C), and is close to the mobility of the same counterions along the surface of clay minerals (Na+, 1.5×10-10 m2s-1 V-1 at 25°C). This result is in agreement with experimental observations and it indicates a very low relaxation frequency for the α-polarization of the bacteria cells (typically around 0.1 to 5 Hertz). By coupling this new model with reactive transport modeling in which the evolution of bacterial populations are usually described by Monod kinetics, we show that the changes in imaginary conductivity with time can be used to

  17. Influence of oil saturation upon spectral induced polarization of oil-bearing sands

    NASA Astrophysics Data System (ADS)

    Schmutz, M.; Revil, A.; Vaudelet, P.; Batzle, M.; Viñao, P. Femenía; Werkema, D. D.

    2010-10-01

    The induced polarization model developed recently by Revil and Florsch to understand the complex conductivity of fully saturated granular materials has been extended to partial saturation conditions. It is an improvement over previous models like the Vinegar and Waxman model, which do not account explicitly for the effect of frequency. The Vinegar and Waxman model can be considered as a limiting case of the Revil and Florsch model in the limit where the distribution of relaxation times is very broad. The extended model is applied to the case of unconsolidated sands partially saturated with oil and water. Laboratory experiments were performed to investigate the influence of oil saturation, frequency, grain size, and conductivity of the pore water upon the complex resistivity response of oil-bearing sands. The low-frequency polarization (below 100 Hz) is dominated by the polarization of the Stern layer (the inner part of the electrical double layer coating the surface of the grains in contact with water). The phase exhibits a well-defined relaxation peak with a peak frequency that is dependent on the mean grain diameter as predicted by the model. Both the resistivity and the magnitude of the phase increase with the relative saturation of the oil. The imaginary (quadrature) component of the complex conductivity is observed to decrease with the oil saturation. All these observations are reproduced by the new model.

  18. Investigating the effect of electro-active ion concentration on spectral induced polarization signatures arising from biomineralization pathways

    NASA Astrophysics Data System (ADS)

    Ntarlagiannis, D.; Slater, L. D.; Williams, K. H.; Hubbard, S. S.; Wu, Y.

    2010-12-01

    Spectral induced polarization (SIP) is a proven geophysical method for detecting biomineral formation with promising applications for monitoring biogeochemical products during microbial induced sequestration of heavy metals and radionuclides in soils. SIP has been used to monitor the evolution of bioremediation-induced end-products at the uranium-contaminated U.S. Department of Energy Rifle Integrated Field Research Challenge site in Colorado. Although a significant SIP response was detected, the quantitative interpretation is non-trivial as the polarization of metallic minerals depends both on the mineral surface properties and the electrolyte chemistry. In previous experiments SIP mechanisms were studied under complex environments and individual source mechanisms could not be evaluated. Here we examine the role of electrolyte chemistry by comparing the effect of redox active / inactive ions on metallic polarization. In these abiotic experiments magnetite was used as a proxy biomineral and dispersed within columns packed with sand. Parallel columns were saturated with solutions of different concentrations of active (Fe2+) and inactive (Ca2+) ions (0.01mM-10mM) and SIP measurements made (0.1-1000 Hz). Experimental results show small, but detectable, differences in the effect of active ion and inactive ion concentration on the SIP response. To better characterize the effect of electro-active ions on metallic minerals we used a Cole - Cole type relaxation model, to describe the SIP responses. In order to better resolve the relaxation model parameters, we followed a two-step approach whereby we started with a Bayesian based inversion to resolve for the initial parameter estimates, and subsequently used these estimates as a starting model for a deterministic solution. Our results suggest that changes in the active ion concentration, in the presence of magnetite, alone are unlikely to fully explain recent SIP monitoring data from the Rifle site.

  19. Observation and theory of reorientation-induced spectral diffusion in polarization-selective 2D IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kramer, Patrick L.; Nishida, Jun; Giammanco, Chiara H.; Tamimi, Amr; Fayer, Michael D.

    2015-05-01

    In nearly all applications of ultrafast multidimensional infrared spectroscopy, the spectral degrees of freedom (e.g., transition frequency) and the orientation of the transition dipole are assumed to be decoupled. We present experimental results which confirm that frequency fluctuations can be caused by rotational motion and observed under appropriate conditions. A theory of the frequency-frequency correlation function (FFCF) observable under various polarization conditions is introduced, and model calculations are found to reproduce the qualitative trends in FFCF rates. The FFCF determined with polarization-selective two-dimensional infrared (2D IR) spectroscopy is a direct reporter of the frequency-rotational coupling. For the solute methanol in a room temperature ionic liquid, the FFCF of the hydroxyl (O-D) stretch decays due to spectral diffusion with different rates depending on the polarization of the excitation pulses. The 2D IR vibrational echo pulse sequence consists of three excitation pulses that generate the vibrational echo, a fourth pulse. A faster FFCF decay is observed when the first two excitation pulses are polarized perpendicular to the third pulse and the echo, , than in the standard all parallel configuration, , in which all four pulses have the same polarization. The 2D IR experiment with polarizations ("polarization grating" configuration) gives a FFCF that decays even more slowly than in the configuration. Polarization-selective 2D IR spectra of bulk water do not exhibit polarization-dependent FFCF decays; spectral diffusion is effectively decoupled from reorientation in the water system.

  20. Observation and theory of reorientation-induced spectral diffusion in polarization-selective 2D IR spectroscopy.

    PubMed

    Kramer, Patrick L; Nishida, Jun; Giammanco, Chiara H; Tamimi, Amr; Fayer, Michael D

    2015-05-14

    In nearly all applications of ultrafast multidimensional infrared spectroscopy, the spectral degrees of freedom (e.g., transition frequency) and the orientation of the transition dipole are assumed to be decoupled. We present experimental results which confirm that frequency fluctuations can be caused by rotational motion and observed under appropriate conditions. A theory of the frequency-frequency correlation function (FFCF) observable under various polarization conditions is introduced, and model calculations are found to reproduce the qualitative trends in FFCF rates. The FFCF determined with polarization-selective two-dimensional infrared (2D IR) spectroscopy is a direct reporter of the frequency-rotational coupling. For the solute methanol in a room temperature ionic liquid, the FFCF of the hydroxyl (O-D) stretch decays due to spectral diffusion with different rates depending on the polarization of the excitation pulses. The 2D IR vibrational echo pulse sequence consists of three excitation pulses that generate the vibrational echo, a fourth pulse. A faster FFCF decay is observed when the first two excitation pulses are polarized perpendicular to the third pulse and the echo, 〈XXY Y〉, than in the standard all parallel configuration, 〈XXXX〉, in which all four pulses have the same polarization. The 2D IR experiment with polarizations 〈XY XY〉 ("polarization grating" configuration) gives a FFCF that decays even more slowly than in the 〈XXXX〉 configuration. Polarization-selective 2D IR spectra of bulk water do not exhibit polarization-dependent FFCF decays; spectral diffusion is effectively decoupled from reorientation in the water system. PMID:25978898

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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

  3. CR1Dinv: A Matlab program to invert 1D spectral induced polarization data for the Cole-Cole model including electromagnetic effects

    NASA Astrophysics Data System (ADS)

    Ghorbani, Ahmad; Camerlynck, Christian; Florsch, Nicolas

    2009-02-01

    An inversion code has been constructed using Matlab, to recover 1D parameters of the Cole-Cole model from spectral induced polarization data. In a spectral induced polarization survey, impedances are recorded at various frequencies. Both induced polarization and electromagnetic coupling effects occur simultaneously over the experimental frequency bandwidth, and these become progressively more dominant when the frequency increases. We used the CR1Dmod code published by Ingeman-Nielsen and Baumgartner [2006]. This code solves for electromagnetic responses, in the presence of complex resistivity effects in a 1D Earth. In this paper, a homotopy method has been designed by the authors to overcome the local convergence problem of normal iterative methods. In addition, in order to further condition the inverse problem, we incorporated standard Gauss-Newton (or quasi-Newton) methods. Graphical user interfaces enable straightforward entering of the data and the a priori model, as well as the cable configuration. Two synthetic examples are presented, showing that the spectral parameters can be recovered from multifrequency, complex resistivity data.

  4. A Hierarchical Bayesian Model for Estimating Remediation-induced Biogeochemical Transformations Using Spectral Induced Polarization Data: Development and Application to the Contaminated DOE Rifle (CO) Site

    NASA Astrophysics Data System (ADS)

    Chen, J.; Hubbard, S. S.; Williams, K. H.; Tuglus, C.; Flores-Orozco, A.; Kemna, A.

    2010-12-01

    Although in-situ bioremediation is often considered as a key approach for subsurface environmental remediation, monitoring induced biogeochemical processes, needed to evaluate the efficacy of the treatments, is challenging over field relevant scales. In this study, we develop a hierarchical Bayesian model that builds on our previous framework for estimating biogeochemical transformations using geochemical and geophysical data obtained from laboratory column experiments. The new Bayesian model treats the induced biogeochemical transformations as both spatial and temporal (rather than just temporal) processes and combines time-lapse borehole ‘point’ geochemical measurements with inverted surface- or crosshole-based spectral induced polarization (SIP) data. This model consists of three levels of statistical sub-models: (1) data model (or likelihood function), which provides links between the biogeochemical end-products and geophysical attributes, (2) process model, which describes the spatial and temporal variability of biogeochemical properties in the disturbed subsurface systems, and (3) parameter model, which describes the prior distributions of various parameters and initial conditions. The joint posterior probability distribution is explored using Markov Chain Monte Carlo sampling methods to obtain the spatial and temporal distribution of the hidden parameters. We apply the developed Bayesian model to the datasets collected from the uranium-contaminated DOE Rifle site for estimating the spatial and temporal distribution of remediation-induced end products. The datasets consist of time-lapse wellbore aqueous geochemical parameters (including Fe(II), sulfate, sulfide, acetate, uranium, chloride, and bromide concentrations) and surface SIP data collected over 13 frequencies (ranging from 0.065Hz to 256Hz). We first perform statistical analysis on the multivariate data to identify possible patterns (or ‘diagnostic signatures’) of bioremediation, and then we

  5. Spectral and spectral-polarization characteristics of potato leaves

    NASA Astrophysics Data System (ADS)

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

    2000-07-01

    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.

  6. Multiband stereometamaterial-based polarization spectral filter

    NASA Astrophysics Data System (ADS)

    Shi, J. H.; Ma, H. F.; Jiang, W. X.; Cui, T. J.

    2012-07-01

    We propose a kind of stereometamaterial composed of periodic structures with twisted asymmetrical split-ring (ASR) resonators. The proposed stereometamaterial has intrinsic chirality and can be used as a multiband polarization spectral filter. Full-wave simulation and experimental results demonstrate that the stereometamaterial with the twist angle of φ=90∘ exhibits three ripple-free cross-polarization transmission peaks at normal incidence of plane waves. The cross-polarization transmission bands are centered at the maxima of circular dichroism, accompanied by pairs of pure circular birefringence points. In physics, the near-field electric and magnetic coupling of orthogonal ASR molecules in parallel planes contributes to the conversion of two orthogonal linear polarizations. The transmission of the proposed multiband polarization spectral filter can be engineered via the mutual twist angle and asymmetry of the ASRs and the thickness of the dielectric spacer layer and also be tuned via the angle of incidence.

  7. Spectral degree of polarization uniformity for polarization-sensitive OCT

    PubMed Central

    Baumann, Bernhard; Zotter, Stefan; Pircher, Michael; Götzinger, Erich; Rauscher, Sabine; Glösmann, Martin; Lammer, Jan; Schmidt-Erfurth, Ursula; Gröger, Marion; Hitzenberger, Christoph K.

    2015-01-01

    Depolarization of light can be measured by polarization-sensitive optical coherence tomography (PS-OCT) and has been used to improve tissue discrimination as well as segmentation of pigmented structures. Most approaches to depolarization assessment for PS-OCT – such as the degree of polarization uniformity (DOPU) – rely on measuring the uniformity of polarization states using spatial evaluation kernels. In this article, we present a different approach which exploits the spectral dimension. We introduce the spectral DOPU for the pixelwise analysis of polarization state variations between sub-bands of the broadband light source spectrum. Alongside a comparison with conventional spatial and temporal DOPU algorithms, we demonstrate imaging in the healthy human retina, and apply the technique for contrasting hard exudates in diabetic retinopathy and investigating the pigment epithelium of the rat iris. PMID:26689829

  8. Spectral degree of polarization uniformity for polarization-sensitive OCT

    NASA Astrophysics Data System (ADS)

    Baumann, Bernhard; Zotter, Stefan; Pircher, Michael; Götzinger, Erich; Rauscher, Sabine; Glösmann, Martin; Lammer, Jan; Schmidt-Erfurth, Ursula; Gröger, Marion; Hitzenberger, Christoph K.

    2015-12-01

    Depolarization of light can be measured by polarization-sensitive optical coherence tomography (PS-OCT) and has been used to improve tissue discrimination as well as segmentation of pigmented structures. Most approaches to depolarization assessment for PS-OCT - such as the degree of polarization uniformity (DOPU) - rely on measuring the uniformity of polarization states using spatial evaluation kernels. In this article, we present a different approach which exploits the spectral dimension. We introduce the spectral DOPU for the pixelwise analysis of polarization state variations between sub-bands of the broadband light source spectrum. Alongside a comparison with conventional spatial and temporal DOPU algorithms, we demonstrate imaging in the healthy human retina, and apply the technique for contrasting hard exudates in diabetic retinopathy and investigating the pigment epithelium of the rat iris.

  9. A comparison between single- and multi-objective optimization to fit spectral induced polarization data from laboratory measurements on alluvial sediments

    NASA Astrophysics Data System (ADS)

    Inzoli, S.; Giudici, M.

    2015-11-01

    Spectral induced polarization measurements on unconsolidated and saturated alluvial samples, sand-clay mixtures and well sorted sandy samples, are modelled with the generalized Cole-Cole phenomenological model and two simplified models: the standard Cole-Cole and the Cole-Davidson model. The goodness of fit is evaluated, as a first step, through the root mean square error, weighted on the data errors of the real and the imaginary component. At a later stage a multi-objective optimization is proposed, based on two different indicators for the resistivity amplitude and phase misfit. The analysis of the misfits variations among all the tested parameters associations is conducted to identify the Pareto set of optimal solutions. Both procedures lead to model parameter estimates comparable with literature values. However, the multi-objective approach provides information about the uncertainty of the parameter estimates and highlights the presence of more than one characteristic value for the relaxation time and the frequency exponent in many samples, thus suggesting the possible occurrence of different polarization processes in the investigated frequency range.

  10. A comparison between Gauss-Newton and Markov chain Monte Carlo basedmethods for inverting spectral induced polarization data for Cole-Coleparameters

    SciTech Connect

    Chen, Jinsong; Kemna, Andreas; Hubbard, Susan S.

    2008-05-15

    We develop a Bayesian model to invert spectral induced polarization (SIP) data for Cole-Cole parameters using Markov chain Monte Carlo (MCMC) sampling methods. We compare the performance of the MCMC based stochastic method with an iterative Gauss-Newton based deterministic method for Cole-Cole parameter estimation through inversion of synthetic and laboratory SIP data. The Gauss-Newton based method can provide an optimal solution for given objective functions under constraints, but the obtained optimal solution generally depends on the choice of initial values and the estimated uncertainty information is often inaccurate or insufficient. In contrast, the MCMC based inversion method provides extensive global information on unknown parameters, such as the marginal probability distribution functions, from which we can obtain better estimates and tighter uncertainty bounds of the parameters than with the deterministic method. Additionally, the results obtained with the MCMC method are independent of the choice of initial values. Because the MCMC based method does not explicitly offer single optimal solution for given objective functions, the deterministic and stochastic methods can complement each other. For example, the stochastic method can first be used to obtain the means of the unknown parameters by starting from an arbitrary set of initial values and the deterministic method can then be initiated using the means as starting values to obtain the optimal estimates of the Cole-Cole parameters.

  11. Polarization induced doped transistor

    DOEpatents

    Xing, Huili; Jena, Debdeep; Nomoto, Kazuki; Song, Bo; Zhu, Mingda; Hu, Zongyang

    2016-06-07

    A nitride-based field effect transistor (FET) comprises a compositionally graded and polarization induced doped p-layer underlying at least one gate contact and a compositionally graded and doped n-channel underlying a source contact. The n-channel is converted from the p-layer to the n-channel by ion implantation, a buffer underlies the doped p-layer and the n-channel, and a drain underlies the buffer.

  12. Considerations on sample holder design and custom-made non-polarizable electrodes for Spectral Induced Polarization measurements on unsaturated soils

    NASA Astrophysics Data System (ADS)

    Kaouane, C.; Chouteau, M. C.; Fauchard, C.; Cote, P.

    2014-12-01

    Spectral Induced Polarization (SIP) is a geophysical method sensitive to water content, saturation and grain size distribution. It could be used as an alternative to nuclear probes to assess the compaction of soils in road works. To evaluate the potential of SIP as a practical tool, we designed an experiment for complex conductivity measurements on unsaturated soil samples.Literature presents a large variety of sample holders and designs, each depending on the context. Although we might find some precise description about the sample holder, exact replication is not always possible. Furthermore, the potential measurements are often done using custom-made Ag/AgCl electrodes and very few indications are given on their reliability with time and temperature. Our objective is to perform complex conductivity measurements on soil samples compacted in a PVC cylindrical mould (10 cm-long, 5 cm-diameter) according to geotechnical standards. To expect homogeneous current density, electrical current is transmitted through the sample via chambers filled with agar gel. Agar gel is a good non-polarizable conductor within the frequency range (1 mHz -20kHz). Its electrical properties are slightly known. We measured increasing of agar-agar electrical conductivity in time. We modelled the influence of this variation on the measurement. If the electrodes are located on the sample, it is minimized. Because of the dimensions at stake and the need for simple design, potential electrodes are located outside the sample, hence the gel contributes to the measurements. Since the gel is fairly conductive, we expect to overestimate the sample conductivity. Potential electrodes are non-polarizable Ag/AgCl electrodes. To avoid any leakage, the KCl solution in the electrodes is replaced by saturated KCl-agar gel. These electrodes are low cost and show a low, stable, self-potential (<1mV). In addition, the technique of making electrode can be easily reproduced and storage and maintenance are simple

  13. [Research on Spectral Polarization Imaging System Based on Static Modulation].

    PubMed

    Zhao, Hai-bo; Li, Huan; Lin, Xu-ling; Wang, Zheng

    2015-04-01

    The main disadvantages of traditional spectral polarization imaging system are: complex structure, with moving parts, low throughput. A novel method of spectral polarization imaging system is discussed, which is based on static polarization intensity modulation combined with Savart polariscope interference imaging. The imaging system can obtain real-time information of spectral and four Stokes polarization messages. Compared with the conventional methods, the advantages of the imaging system are compactness, low mass and no moving parts, no electrical control, no slit and big throughput. The system structure and the basic theory are introduced. The experimental system is established in the laboratory. The experimental system consists of reimaging optics, polarization intensity module, interference imaging module, and CCD data collecting and processing module. The spectral range is visible and near-infrared (480-950 nm). The white board and the plane toy are imaged by using the experimental system. The ability of obtaining spectral polarization imaging information is verified. The calibration system of static polarization modulation is set up. The statistical error of polarization degree detection is less than 5%. The validity and feasibility of the basic principle is proved by the experimental result. The spectral polarization data captured by the system can be applied to object identification, object classification and remote sensing detection. PMID:26197616

  14. BISIP I: A program for Bayesian inference of spectral induced polarization parameters, and application to mineral exploration at the Canadian Malartic gold deposit, Québec, CA

    NASA Astrophysics Data System (ADS)

    Lafrenière-Bérubé, Charles; Chouteau, Michel; Shamsipour, Pejman; Olivo, Gema R.

    2016-04-01

    Spectral induced polarization (SIP) parameters can be extracted from field or laboratory complex resistivity measurements, and even airborne or ground frequency domain electromagnetic data. With the growing interest in application of complex resistivity measurements to environmental and mineral exploration problems, there is a need for accurate and easy-to-use inversion tools to estimate SIP parameters. These parameters, which often include chargeability and relaxation time may then be studied and related to other rock attributes such as porosity or metallic grain content, in the case of mineral exploration. We present an open source program, available both as a standalone application or Python module, to estimate SIP parameters using Markov-chain Monte Carlo (MCMC) sampling. The Python language is a high level, open source language that is now widely used in scientific computing. Our program allows the user to choose between the more common Cole-Cole (Pelton), Dias, or Debye decomposition models. Simple circuits composed of resistances and constant phase elements may also be used to represent SIP data. Initial guesses are required when using more classic inversion techniques such as the least-squares formulation, and wrong estimates are often the cause of bad curve fitting. In stochastic optimization using MCMC, the effect of the starting values disappears as the simulation proceeds. Our program is then optimized to do batch inversion over large data sets with as little user-interaction as possible. Additionally, the Bayesian formulation allows the user to do quality control by fully propagating the measurement errors in the inversion process, providing an estimation of the SIP parameters uncertainty. This information is valuable when trying to relate chargeability or relaxation time to other physical properties. We test the inversion program on complex resistivity measurements of 12 core samples from the world-class gold deposit of Canadian Malartic. Results show

  15. [Research on New Type of Spectral Modulation Polarization Measurement Technology].

    PubMed

    Zhao, Jia; Zhou, Feng; Li, Huan; Zhao, Hai-bo

    2015-10-01

    Spectral Modulation Polarization Measurement technology (SMPM) is a new type of polarization modulation technology, with an achromatic /4 retarder, a multiple-order retarder and a polarizer the polarization information of incident light can be encoded into the spectral dimension, sinusoidal which amplitude scales with the degree of the linear polarization and phase scales with the angle of the linear polarization can be acquired directly. With a dedicated algorithm for the modulated spectrum, we can get degree and angle of the linear polarization, spectral information and radiation information of the target. This paper expounds the basic principle of SMPM and concrete implementation scheme is proposed. Demodulation algorithm is designed before experimental platform are set up. Experiment which verified the correctness on the SMPM has carried on. The experimental results show the correctness and feasibility of SMPM. Compared with traditional polarization modulate techniques no moving parts and electronic components are including in this scheme. It's also has the advantages of compact and low mass. We can get all the polarization information through one single measurement rather than get Stokes parameters for further calculations. This study provides a new kind of technological approaches for the development of new space polarization detecting sensor. PMID:26904842

  16. Spectral broadening of interacting pigments: polarized absorption by photosynthetic proteins.

    PubMed Central

    Somsen, O J; van Grondelle, R; van Amerongen, H

    1996-01-01

    Excitonic interaction between pigment molecules is largely responsible for the static and dynamic spectroscopic properties of photosynthetic pigment-proteins. This paper provides a new description of its effect on polarized absorption spectroscopy, in particular on circular dichroism (CD). We investigate excitonic spectra of finite width and use "spectral moments" to compare 1) inhomogeneously broadened excitonic spectra, 2) spectra that are (homogeneously broadened by vibrations or electron-phonon interaction, and 3) spectra that are simulated by applying convolution after the interaction has been evaluated. Two cases are distinguished. If the excitonic splitting is smaller than the width of the interacting absorption bands, the broadening of the excitonic spectrum can be approximated by a convolution approach, although a correction is necessary for CD spectra. If the excitonic splitting exceeds the bandwidth, the well-known exchange narrowing occurs. We demonstrate that this is accompanied by redistribution of dipole strength and spectral shifts. The magnitude of a CD spectrum is conveniently expressed by its first spectral moment. As will be shown, this is independent of spectral broadening as well as dispersive shifts induced by pigment-protein interactions. Consequently, it provides a simple tool to relate the experimental CD spectrum of a pigment complex to the excitonic interactions from which it originates. To illustrate the potential of the presented framework, the spectroscopy of the LH2 pigment-protein complex from purple bacteria is analyzed and compared for dimer-like and ring-like structures. Furthermore, it is demonstrated that the variability of the CD of chlorosomes from green bacteria can be explained by small changes in the structure of their cylindrical bacteriochlorophyll c subunits. Images FIGURE 3 FIGURE 4 PMID:8889168

  17. Polarization diversity scheme on spectral polarization coding optical code-division multiple-access network

    NASA Astrophysics Data System (ADS)

    Yen, Chih-Ta; Huang, Jen-Fa; Chang, Yao-Tang; Chen, Bo-Hau

    2010-12-01

    We present an experiment demonstrating the spectral-polarization coding optical code-division multiple-access system introduced with a nonideal state of polarization (SOP) matching conditions. In the proposed system, the encoding and double balanced-detection processes are implemented using a polarization-diversity scheme. Because of the quasiorthogonality of Hadamard codes combining with array waveguide grating routers and a polarization beam splitter, the proposed codec pair can encode-decode multiple code words of Hadamard code while retaining the ability for multiple-access interference cancellation. The experimental results demonstrate that when the system is maintained with an orthogonal SOP for each user, an effective reduction in the phase-induced intensity noise is obtained. The analytical SNR values are found to overstate the experimental results by around 2 dB when the received effective power is large. This is mainly limited by insertion losses of components and a nonflattened optical light source. Furthermore, the matching conditions can be improved by decreasing nonideal influences.

  18. Camouflaged target detection based on polarized spectral features

    NASA Astrophysics Data System (ADS)

    Tan, Jian; Zhang, Junping; Zou, Bin

    2016-05-01

    The polarized hyperspectral images (PHSI) include polarization, spectral, spatial and radiant features, which provide more information about objects and scenes than traditional intensity or spectrum ones. And polarization can suppress the background and highlight the object, leading to the high potential to improve camouflaged target detection. So polarized hyperspectral imaging technique has aroused extensive concern in the last few years. Nowadays, the detection methods are still not very mature, most of which are rooted in the detection of hyperspectral image. And before using these algorithms, Stokes vector is used to process the original four-dimensional polarized hyperspectral data firstly. However, when the data is large and complex, the amount of calculation and error will increase. In this paper, tensor is applied to reconstruct the original four-dimensional data into new three-dimensional data, then, the constraint energy minimization (CEM) is used to process the new data, which adds the polarization information to construct the polarized spectral filter operator and takes full advantages of spectral and polarized information. This way deals with the original data without extracting the Stokes vector, so as to reduce the computation and error greatly. The experimental results also show that the proposed method in this paper is more suitable for the target detection of the PHSI.

  19. Spectral distortions in the cosmic microwave background polarization

    SciTech Connect

    Renaux-Petel, Sébastien; Fidler, Christian; Pitrou, Cyril; Pettinari, Guido W. E-mail: christian.fidler@port.ac.uk E-mail: g.pettinari@sussex.ac.uk

    2014-03-01

    We compute the spectral distortions of the Cosmic Microwave Background (CMB) polarization induced by non-linear effects in the Compton interactions between CMB photons and the flow of intergalactic electrons. This signal is of the y-type and is dominated by contributions arising from the reionized era. We stress that it is not shadowed by the thermal SZ effect which has no equivalent for polarization. We decompose its angular dependence into E- and B-modes, and we calculate the corresponding power spectra, both exactly and using a suitable Limber approximation that allows a simpler numerical evaluation. We find that B-modes are of the same order of magnitude as E-modes. Both spectra are relatively flat, peaking around ℓ = 280, and their overall amplitude is directly related to the optical depth to reionization. Moreover, we find this effect to be one order of magnitude larger than the non-linear kinetic Sunyaev-Zel'dovich effect in galaxy clusters. Finally, we discuss how to improve the detectability of our signal by cross-correlating it with other quantities sourced by the flow of intergalactic electrons.

  20. Polarized nuclear target based on parahydrogen induced polarization

    SciTech Connect

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

    2012-12-01

    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.

  1. Polarized nuclear target based on parahydrogen induced polarization

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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 (˜100 Hz) polarization oscillation (akin to polarization reversal), and operation with large intensity of an electron beam.

  2. High dynamic, spectral, and polarized natural light environment acquisition

    NASA Astrophysics Data System (ADS)

    Porral, Philippe; Callet, Patrick; Fuchs, Philippe; Muller, Thomas; Sandré-Chardonnal, Etienne

    2015-03-01

    In the field of image synthesis, the simulation of material's appearance requires a rigorous resolution of the light transport equation. This implies taking into account all the elements that may have an influence on the spectral radiance, and that are perceived by the human eye. Obviously, the reflectance properties of the materials have a major impact in the calculations, but other significant properties of light such as spectral distribution and polarization must also be taken into account, in order to expect correct results. Unfortunately real maps of the polarized or spectral environment corresponding to a real sky do not exist. Therefore, it seemed necessary to focus our work on capturing such data, in order to have a system that qualifies all the properties of light and capable of powering simulations in a renderer software. As a consequence, in this work, we develop and characterize a device designed to capture the entire light environment, by taking into account both the dynamic range of the spectral distribution and the polarization states, in a measurement time of less than two minutes. We propose a data format inspired by polarimetric imaging and fitted for a spectral rendering engine, which exploits the "Stokes-Mueller formalism."

  3. NON-ZEEMAN CIRCULAR POLARIZATION OF MOLECULAR ROTATIONAL SPECTRAL LINES

    SciTech Connect

    Houde, Martin; Jones, Scott; Rajabi, Fereshte; Hezareh, Talayeh

    2013-02-10

    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.

  4. Method for induced polarization logging

    SciTech Connect

    Vinegar, H.J.; Waxman, M.H.

    1987-04-14

    A method is described for generating a log of the formation phase shift, resistivity and spontaneous potential of an earth formation from data obtained from the earth formation with a multi-electrode induced polarization logging tool. The method comprises obtaining data samples from the formation at measurement points equally spaced in time of the magnitude and phase of the induced voltage and the magnitude and phase of the current supplied by a circuit through a reference resistance R/sub 0/ to a survey current electrode associated with the tool.

  5. An Integrated Imaging Detector of Polarization and Spectral Content

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  6. Polarization of photons scattered by electrons in any spectral distribution

    SciTech Connect

    Chang, Zhe; Lin, Hai-Nan; Jiang, Yunguo

    2014-01-01

    On the basis of the quantum electrodynamics, we present a generic formalism of the polarization for beamed monochromatic photons scattered by electrons in any spectral distribution. The formulae reduce to the components of the Fano matrix when electrons are at rest. We mainly investigate the polarization in three scenarios, i.e., electrons at rest, isotropic electrons with a power-law spectrum, and thermal electrons. If the incident beam is polarized, the polarization is reduced significantly by isotropic electrons at large viewing angles; the degree of polarization caused by thermal electrons is about half of that caused by power-law electrons. If the incident bean is unpolarized, soft γ-rays can lead to about 15% polarization at viewing angles around π/4. For isotropic electrons, one remarkable feature is that the polarization as a function of the incident photon energy always peaks roughly at 1 MeV; this is valid for both the thermal and power-law cases. This feature can be used to distinguish the model of the inverse Compton scattering from that of the synchrotron radiation.

  7. Simultaneous Teleportation of the Spectral and Polarization States of a Photon

    SciTech Connect

    Humble, Travis S; Bennink, Ryan S; Grice, Warren P

    2008-01-01

    We describe how spectrally multimode, polarization-entangled photons simultaneously teleport quantum information encoded into the spectral and polarization degrees of freedom of a single photon using sum frequency generation to implement a Bell-state measurement.

  8. Spectral signatures of polar stratospheric clouds and sulfate aerosol

    SciTech Connect

    Massie, S.T.; Bailey, P.L.; Gille, J.C.; Lee, E.C.; Mergenthaler, J.L.; Roche, A.E.; Kumer, J.B.; Fishbein, E.F.; Waters, J.W.; Lahoz, W.A.

    1994-10-15

    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.

  9. Spectral signatures of polar stratospheric clouds and sulfate aerosol

    NASA Technical Reports Server (NTRS)

    Massie, S. T.; Bailey, P. L.; Gille, J. C.; Lee, E. C.; Mergenthaler, J. L.; Roche, A. E.; Kumer, J. B.; Fishbein, E. F.; Waters, J. W.; Lahoz, W. A.

    1994-01-01

    Multiwavelength observations of Antarctic and midlatitude aerosol by the Cryogenic Limb Array Etalon Spectrometer (CLAES) experiment on the Upper Atmosphere Research Satellite (UARS) 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 (10.8, 8.0, and 6.2 micrometers) to derive a spectral aerosol measure M of the aerosol spectrum. Mie calculations for spherical particles and T-matrix calculations for spheriodal 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 calculations and laboratory phase-equilibrium studies of nitric acid trihydrate, are used to predict the location of nitric acid trihydrate cloud particles.

  10. Wavelength encoded polarization measurements for simultaneous spectral and polarimetric characterization in near field

    NASA Astrophysics Data System (ADS)

    Patel, H. S.; Swami, M. K.; Kushwaha, P. K.; Uppal, A.; Gupta, P. K.

    2016-08-01

    We report a scheme for polarization sensitive near field imaging of nanostructured samples by making use of broadband polarized near field illumination and detection of polarization states of scattered light by a spectrally encoded analyzer. The analyzer comprising a combination of polarizer, a multi-order waveplate and a broadband quarter waveplate allows analysis of the spectrally encoded polarization states of scattered light for characterization of the polarization properties of nano structures from a single image scan. The scheme was validated by measuring the near field polarization parameters of silver nanowires. The approach allows simultaneous measurement of polarization characteristics as well as spectral features of the nano materials.

  11. Self-induced polarization anisoplanatism

    NASA Astrophysics Data System (ADS)

    Breckinridge, James B.

    2013-09-01

    This paper suggests that the astronomical science data recorded with low F# telescopes for applications requiring a known point spread function shape and those applications requiring instrument polarization calibration may be compromised unless the effects of vector wave propagation are properly modeled and compensated. Exoplanet coronagraphy requires "matched filter" masks and explicit designs for the real and imaginary parts for the mask transmittance. Three aberration sources dominate image quality in astronomical optical systems: amplitude, phase and polarization. Classical ray-trace aberration analysis used today by optical engineers is inadequate to model image formation in modern low F# highperformance astronomical telescopes. We show here that a complex (real and imaginary) vector wave model is required for high performance, large aperture, very wide-field, low F# systems. Self-induced polarization anisoplanatism (SIPA) reduces system image quality, decreases contrast and limits the ability of image processing techniques to restore images. This paper provides a unique analysis of the image formation process to identify measurements sensitive to SIPA. Both the real part and the imaginary part of the vector complex wave needs to be traced through the entire optical system, including each mirror surface, optical filter, and all masks. Only at the focal plane is the modulus squared taken to obtain an estimate of the measured intensity. This paper also discusses the concept of the polarization conjugate filter, suggested by the author to correct telescope/instrument corrupted phase and amplitude and thus mitigate6, in part the effects of phase and amplitude errors introduced by reflections of incoherent white-light from metal coatings.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  13. Spectral and polarization analysis of micropulsations observed at ATS-1

    NASA Technical Reports Server (NTRS)

    Morris, W.; Cummings, W. D.; Mcpherron, R. L.

    1972-01-01

    Results are reported for an analysis of low frequency oscillations in the earth's magnetic field as observed at the synchronous orbit by the magnetometer experiment on board ATS 1. Oscillations in the range .002 f .02 H3 for the period Dec. 1966 through Dec. 1967 were studied. The analysis combines a detailed, computer-processed, spectral analysis of selected events with a less detailed manual analysis of all events in the two year time interval from Dec. 1966 to Dec. 1968. The computer analysis revealed that a given event is often characterized by a dominat, narrow, spectral peak whose associated oscillations are almost entirely limited to a plane, together with several minor peaks. Dynamic spectral analyses revealed that minor spectral peaks appear as short isolated bursts. The sense of rotation of the perturbation vector tends to change from right-handed elliptical at the beginning of a burst to left-handed elliptical at the end. The major axis of the polarization ellipse is inclined by typically 30 deg east of radial.

  14. Polarized spectral complexes of optical functions of monovalent mercury iodide

    NASA Astrophysics Data System (ADS)

    Sobolev, V. V.; Sobolev, V. Val.; Anisimov, D. V.

    2015-12-01

    Spectral complexes of optical functions of monovalent mercury iodide Hg2I2 were determined for E ⊥ c and E || c polarizations in the range from 2 to 5.5 eV at 4.2 K. The permittivity and characteristic electron energy loss spectra were expanded in simple components with the determination of their main parameters, including the energy of the maximum and the oscillator strength. The calculations were performed based on known reflectance spectra. Computer programs based on Kramers-Kronig relations and the improved parameter-free method of Argand diagrams were used.

  15. Spectral and polarization properties of photospheric emission from stratified jets

    SciTech Connect

    Ito, Hirotaka; Nagataki, Shigehiro; Matsumoto, Jin; Lee, Shiu-Hang; Tolstov, Alexey; Mao, Jirong; Dainotti, Maria; Mizuta, Akira

    2014-07-10

    We explore the spectral and polarization properties of photospheric emissions from stratified jets in which multiple components, separated by sharp velocity shear regions, are distributed in lateral directions. Propagation of thermal photons injected at a high optical depth region are calculated until they escape from the photosphere. It is found that the presence of the lateral structure within the jet leads to the nonthermal feature of the spectra and significant polarization signal in the resulting emission. The deviation from thermal spectra, as well as the polarization degree, tends to be enhanced as the velocity gradient in the shear region increases. In particular, we show that emissions from multicomponent jet can reproduce the typical observed spectra of gamma-ray bursts irrespective of the position of the observer when a velocity shear region is closely spaced in various lateral (θ) positions. The degree of polarization associated with the emission is significant (>few percent) at a wide range of observer angles and can be higher than 30%.

  16. Correlation-induced spectral changes

    NASA Astrophysics Data System (ADS)

    Wolf, Emil; James, Daniel F. V.

    1996-06-01

    This paper presents a review of research, both theoretical and experimental, concerning the influence of coherence properties of fluctuating light sources and of correlation properties of scattering media on the spectra of radiated and scattered fields. Much of this research followed a discovery made in 1986, that the spectrum of light may change on propagation, even in free space. More than 100 papers on this topic have been published to date and many of them are reviewed, or at least mentioned, in this article. After an introduction and a summary of some of the main mathematical results relating to second-order coherence theory of statistically stationary optical fields, spectral changes that may take place on superposing fields produced by two partially correlated sources are discussed. Spectral effects in fields produced by two-dimensional secondary sources and by three-dimensional primary sources are then considered. The section which follows describes spectral changes that may arise when polychromatic light is scattered on media whose physical properties vary randomly either in space and/or in time. A review is also presented of recent research, which has revealed that under certain circumstances the changes in the spectrum of light scattered on random media may imitate the Doppler effect, even though the source, the medium and the observer are all at rest with respect to one another. In the final section a brief review is given of a new emerging technique sometimes called spatial-coherence spectroscopy. It is based on the discovery that it is possible, under certain circumstances, to determine field correlations from spectral measurements.

  17. The relationship between variable and polarized optical spectral components of luminous type 1 non-blazar quasars

    NASA Astrophysics Data System (ADS)

    Kokubo, Mitsuru

    2016-06-01

    Optical spectropolarimetry by Kishimoto et al. (2004, MNRAS, 354, 1065) has shown that several luminous type 1 quasars show a strong decrease of the polarized continuum flux in the rest-frame near-ultraviolet (UV) wavelengths of λ < 4000 Å. In the literature, this spectral feature is interpreted as evidence of the broadened hydrogen Balmer absorption edge imprinted on the accretion disk thermal emission due to the disk atmospheric opacity effect. On the other hand, quasar flux variability studies have shown that the variable continuum component in UV-optical spectra of quasars, which is considered to be a good indicator of the intrinsic spectral shape of the accretion disk emission, generally has a significantly flat spectral shape throughout the near-UV to optical spectral range. To examine whether the disk continuum spectral shapes revealed as the polarized flux and as the variable component spectra are consistent with each other, we carry out multi-band photometric monitoring observations for a sample of four polarization-decreasing quasars of Kishimoto et al.'s (4C 09.72, 3C 323.1, Ton 202, and B2 1208+32) to derive the variable component spectra and compare the spectral shape of them with that of the polarized flux spectra. Contrary to expectation, we confirm that the two spectral components of these quasars have totally different spectral shapes, in that the variable component spectra are significantly bluer compared to the polarized flux spectra. This discrepancy between two spectrals shape may imply either (1) the decrease of polarization degree in the rest-frame UV wavelengths is not indicating the Balmer absorption edge feature but is induced by some unknown (de)polarization mechanisms, or (2) the UV-optical flux variability is occurring preferentially at the hot inner radii of the accretion disk and thus the variable component spectra do not reflect the whole accretion disk emission.

  18. The relationship between variable and polarized optical spectral components of luminous type 1 non-blazar quasars

    NASA Astrophysics Data System (ADS)

    Kokubo, Mitsuru

    2016-08-01

    Optical spectropolarimetry by Kishimoto et al. (2004, MNRAS, 354, 1065) has shown that several luminous type 1 quasars show a strong decrease of the polarized continuum flux in the rest-frame near-ultraviolet (UV) wavelengths of λ < 4000 Å. In the literature, this spectral feature is interpreted as evidence of the broadened hydrogen Balmer absorption edge imprinted on the accretion disk thermal emission due to the disk atmospheric opacity effect. On the other hand, quasar flux variability studies have shown that the variable continuum component in UV-optical spectra of quasars, which is considered to be a good indicator of the intrinsic spectral shape of the accretion disk emission, generally has a significantly flat spectral shape throughout the near-UV to optical spectral range. To examine whether the disk continuum spectral shapes revealed as the polarized flux and as the variable component spectra are consistent with each other, we carry out multi-band photometric monitoring observations for a sample of four polarization-decreasing quasars of Kishimoto et al.'s (4C 09.72, 3C 323.1, Ton 202, and B2 1208+32) to derive the variable component spectra and compare the spectral shape of them with that of the polarized flux spectra. Contrary to expectation, we confirm that the two spectral components of these quasars have totally different spectral shapes, in that the variable component spectra are significantly bluer compared to the polarized flux spectra. This discrepancy between two spectral shapes may imply either (1) the decrease of polarization degree in the rest-frame UV wavelengths is not indicating the Balmer absorption edge feature but is induced by some unknown (de)polarization mechanisms, or (2) the UV-optical flux variability is occurring preferentially at the hot inner radii of the accretion disk and thus the variable component spectra do not reflect the whole accretion disk emission.

  19. Non-Zeeman circular polarization of molecular maser spectral lines

    SciTech Connect

    Houde, Martin

    2014-11-01

    We apply the anisotropic resonant scattering model developed to explain the presence of non-Zeeman circular polarization signals recently detected in the {sup 12}CO (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.

  20. Optical Polarization and Spectral Variability in the M87 Jet

    NASA Astrophysics Data System (ADS)

    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

    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 (αUV-O ~ 0.5, F νvpropν-α), 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 2σ upper limits of 0.5δ 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 (αUV-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.

  1. Optical Polarization and Spectral Variability in the M87 Jet

    NASA Technical Reports Server (NTRS)

    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

    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.

  2. Induced polarization response of microbial induced sulfideprecipitation

    SciTech Connect

    Ntarlagiannis, Dimitrios; Williams, Kenneth Hurst; Slater, Lee; Hubbard, Susan

    2004-06-04

    A laboratory scale experiment was conducted to examine the use of induced polarization and electrical conductivity to monitor microbial induced sulfide precipitation under anaerobic conditions in sand filled columns. Three columns were fabricated; one for electrical measurements, one for geochemical sampling and a third non-inoculated column was used as a control. A continual upward flow of nutrients and metals in solution was established in each column. Desulfovibrio vulgaris microbes were injected into the middle of the geochemical and electrical columns. Iron and zinc sulfides precipitated along a microbial action front as a result of sulfate reduction due by Desulfovibrio vulgaris. The precipitation front initially developed near the microbial injection location, and subsequently migrated towards the nutrient inlet, as a result of chemotaxis by Desulfovibrio vulgaris. Sampling during and subsequent to the experiment revealed spatiotemporal changes in the biogeochemical measurements associated with microbial sulfate reduction. Conductivity measurements were insensitive to all biogeochemical changes occurred within the column. Changes in the IP response (of up to 14 mrad)were observed to coincide in place and in time with the active microbe respiration/sulfide precipitation front as determined from geochemical sampling. The IP response is correlated with the lactate concentration gradient, an indirect measurement of microbial metabolism, suggesting the potential of IP as a method for monitoring microbial respiration/activity. Post experimental destructive sample analysis and SEM imaging verified the geochemical results and supported our hypothesis that microbe induced sulfide precipitation is directly detectable using electrical methods. Although the processes not fully understood, the IP response appears to be sensitive to this anaerobic microbial precipitation, suggesting a possible novel application for the IP method.

  3. Exploration of polar lipid accumulation profiles in Euglena gracilis using LipidBlast, an MS/MS spectral library constructed in silico.

    PubMed

    Ogawa, Takumi; Furuhashi, Takeshi; Okazawa, Atsushi; Nakai, Rai; Nakazawa, Masami; Kind, Tobias; Fiehn, Oliver; Kanaya, Shigehiko; Arita, Masanori; Ohta, Daisaku

    2014-01-01

    A rapid protocol for polar lipid profiling was applied to Euglena gracilis lipid metabolism by LipidBlast, an MS/MS spectral similarity search tool. The similarity search results suggested anoxia-induced polar lipid metabolism in Euglena characterized by the accumulation of differential lipid classes, carbon chain lengths, and unsaturated bond numbers. The informatics-supported MS spectral search provides an alternative option for global lipid profiling studies. PMID:25036478

  4. Two long-wave infrared spectral polarimeters for use in understanding polarization phenomenology

    NASA Astrophysics Data System (ADS)

    Sposato, Stephanie H.; Fetrow, Matthew P.; Bishop, Kenneth P.; Caudill, Thomas R.

    2002-05-01

    Spectrally varying long-wave infrared (LWIR) polarization measurements can be used to identify materials and to discriminate samples from a cluttered background. Two LWIR instruments have been built and fielded by the Air Force Research Laboratory: a multispectral LWIR imaging polarimeter (LIP) and a full-Stokes Fourier transform infrared (FTIR) spectral polarimeter (FSP), constructed for higher spectral resolution measurements of materials. These two instruments have been built to gain an understanding of the polarization signatures expected from different types of materials in a controlled laboratory and in varying field environments. We discuss the instruments, calibration methods, general operation, and measurements characterizing the emitted polarization properties of materials as a function of wavelength. The results show that we are able to make polarization measurements with a relative accuracy of 0.5% degree of polarization (DOP) between two different instruments that are calibrated with the same techniques, and that these measurements can improve the understanding of polarization phenomenology.

  5. SPECTRAL MAPPING OF THE INTERMEDIATE POLAR DQ HERCULIS

    SciTech Connect

    Saito, R. K.; Baptista, R.; Horne, K.; Martell, P.

    2010-06-15

    We report an eclipse-mapping study of the intermediate polar DQ Her based on time-resolved optical spectroscopy ({Delta}{lambda} {approx} 3800-5000 A) covering four eclipses. The spectra were sliced into 295 narrow passbands in the continuum and in the lines, and the corresponding light curves were analyzed to solve for a set of monochromatic maps of the disk brightness distribution and for the flux of an additional uneclipsed component in each band. Eclipse maps of the He II {lambda}4686 line indicate that an azimuthally and vertically extended bright spot at disk rim is an important source of the reprocessing of X-rays from the magnetic poles. The disk spectrum is flat with no Balmer or Helium lines in the inner regions, and shows double-peaked emission lines in the intermediate and outer disk regions, while the slope of the continuum becomes progressively redder with increasing radius. The inferred disk temperatures are in the range T {approx_equal} 13500-5000 K and can be reasonably well described by a steady-state disk with mass accretion rate of M-dot =(2.7{+-}1.0)x10{sup -9} M{sub sun} yr{sup -1}. A comparison of the radial intensity distribution for the Balmer lines reveals a linear correlation between the slope of the distribution and the transition energy. The spectrum of the uneclipsed light is dominated by Balmer and He I lines in emission (probably from the extended nova shell) with narrow absorption cores (likely from a collimated and optically thick wind from the accretion disk). The observed narrow and redshifted Ca II {lambda}3934 absorption line in the total light spectra plus the inverse P-Cygni profiles of the Balmer and He II {lambda}4686 emission lines in spectra of the asymmetric component indicate radial inflow of gas in the innermost disk regions and are best explained in terms of magnetically controlled accretion inside the white dwarf magnetosphere. We infer projected radial inflow velocities of {approx}200-500 km s{sup -1}, significantly

  6. A Compact Imaging Detector of Polarization and Spectral Content

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  7. A compact imaging detector of polarization and spectral content

    NASA Astrophysics Data System (ADS)

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

    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.

  8. Extracting the spectral index of the intergalactic magnetic field from radio polarizations

    NASA Astrophysics Data System (ADS)

    Tiwari, Prabhakar; Jain, Pankaj

    2016-08-01

    We explain the large-scale correlations in radio polarization in terms of the correlations of the galaxy supercluster magnetic field. Assuming that the polarization correlations closely follow the spatial correlations of the background magnetic field, we obtain the magnetic field spectral index as -2.74 ± 0.04. We discuss the possible physical scenarios in which the observed polarization alignment is plausible.

  9. Polarization studies of Zeeman affected spectral lines using the MSFC magnetograph

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  10. Electric field induced spin-polarized current

    DOEpatents

    Murakami, Shuichi; Nagaosa, Naoto; Zhang, Shoucheng

    2006-05-02

    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.

  11. New Methods for Studying Interstellar Continuum and Spectral Polarization

    NASA Astrophysics Data System (ADS)

    Messinger, David W.

    Polarization studies have been shown to provide information about the aligned component of interstellar dust particles. These particles are aligned with respect to the local magnetic field and as such, models of polarization observations provide morphological information in addition to the determination of grain characteristics. Continuum polarization in molecular clouds observed to have a change in the polarization position angle indicates a region with at least two distinct components in the line of sight. A slab model is developed using the Stokes parameters to separate the competing effects of these multiple components and investigate the properties of the ``clump'' within the larger cloud complex. This model is applied to two lines of sight in the Taurus Molecular Cloud toward HD 29647 and HD 283809. For this model, a third line of sight, toward HD 283812, is used to probe the ``standard'' properties of the larger cloud. It is shown that within these clumps, the average aligned grain size is larger than in the overall cloud complex. The degree of alignment toward HD 29647 is higher than toward HD 283809, but both ``clumps'' show a dramatic change in polarization position angle. It is hypothesized that this change in the local magnetic field direction is a remnant of, or reason for, the collapse of the material in the region of TMC-1. Spectropolarization provides further constraints on the aligned grain population in the line of sight compared when with spectroscopy studies. A model is developed to study these two datasets, absorption and polarization, simultaneously for the water-ice absorption feature at ~3.1 μm in particular. This model investigates the individual grain population properties through a multiple slab structure. The grain sizes, shapes, mantle thicknesses, compositions, and alignment characteristics are all parameters in the model. The water-ice mantle is modeled with a Lorentz oscillator model to simplify the process and remove any

  12. Inducing electric polarization in ultrathin insulating layers

    NASA Astrophysics Data System (ADS)

    Martinez-Castro, Jose; Piantek, Marten; Persson, Mats; Serrate, David; Hirjibehedin, Cyrus F.

    Studies of ultrathin polar oxide films have attracted the interest of researchers for a long time due to their different properties compared to bulk materials. However they present several challenges such as the difficulty in the stabilization of the polar surfaces and the limited success in tailoring their properties. Moreover, recently developed Van der Waals materials have shown that the stacking of 2D-layers trigger new collective states thanks to the interaction between layers. Similarly, interface phenomena emerge in polar oxides, like induced ferroelectricity. This represents a promising way for the creation of new materials with customized properties that differ from those of the isolated layers. Here we present a new approach for the fabrication and study of atomically thin insulating films. We show that the properties of insulating polar layers of sodium chloride (NaCl) can be engineered when they are placed on top of a charge modulated template of copper nitride (Cu2N). STM studies carried out in ultra-high vacuum and at low temperatures over NaCl/Cu2N/Cu(001) show that we are able to build up and stabilize interfaces of polar surface at the limit of one atomic layer showing new properties not present before at the atomic scale.

  13. Radio emission from RS CVn binaries. II - Polarization and spectral properties

    NASA Technical Reports Server (NTRS)

    Mutel, R. L.; Morris, D. H.; Doiron, D. J.; Lestrade, J. F.

    1987-01-01

    Multiepoch radio observations of circular polarization and spectral characteristics of several close, late-type stellar binaries are reported. The median luminosity of four well-studied systems ranged from 16.2 to 17.1 ergs/s/Hz. For individual systems, the fractional circular polarization decreases with increasing luminosity, particularly at frequencies above 5 GHz. Eclipsing binaries have significantly lower average circular polarization compared with noneclipsing systems. Helicity reversal is almost always observed between 1.4 and 4.9 GHz for systems with high orbital inclination. Comparison with ten years of previously published polarization observations for two RS CVn stellar systems show that the same helicity occurs at a given frequency for a given source, indicating a very stable, large-scale magnetic field geometry. These spectral and polarization characteristics strongly support a model of inhomogeneous gyrosynchrotron emission arising from electrons with power law energy spectra interacting with inhomogeneous magnetic fields.

  14. A peculiar spectral unit in the Southern Amazonian polar layered deposits

    NASA Astrophysics Data System (ADS)

    Carli, C.; Carrozzo, F. G.; Altieri, F.; Giacomini, L.

    South Polar regions were previously mapped by Tanaka and Scott (1987), revealing different geological units ranging from Noachian crater terrains to Amazonian polar layered and polar ice deposits (Apl and Api, respectively). In particular the Apl deposits are characterized by alternating dark and light lithologies in a smooth, medium albedo material with sparse craters (Milkovich et al., 2002). Recently, a spectral parameters analysis, around 1 mu m (see Carrozzo et al., 2012), highlighted how a portion of the Apl can be differentiated from a spectroscopical point of view respect to the rest. In particular this peculiar area seems different in composition from the surrounding Apl terrains, but spectrally similar to some craters dominated by dark dunes. This region was considered as a new spectral unit enriched in pyroxene content (Carrozzo et al., 2013). Here we have considered the spectral features from this region of interest and we have preliminary mapped it using the Spectral Angle Mapper (Kruse et al., 1993) supervised classifier to OMEGA mosaic of successive Solar longitude (Ls). The results evidence that this portion of the Apl area is the only region spectrally mapped, confirming that it is peculiar from a spectroscopical point of view compared to the rest of the South Polar regions. Here we will show morphological and spectroscopical characteristics of this region to better address the characteristic of this smooth region and understand its possible formation and evolution.

  15. Smoking Induced Hemolysis: Spectral and microscopic investigations.

    PubMed

    Masilamani, Vadivel; AlZahrani, Khalid; Devanesan, Sandhanasamy; AlQahtani, Hadi; AlSalhi, Mohamad Saleh

    2016-01-01

    Smoking is one of the major causes of lifestyle associated mortality and morbidity such as cancer of the oral cavity and lungs, and also cardiovascular diseases. In this study, we have provided evidences for the smoking-induced hemolysis using two methods: spectra of blood components and atomic force microscopic analysis of surface morphology. A total of 62 subjects (control = 31; smoker = 31: 21 male; 10 female in each set) were considered for the study. The findings indicate that smoking leads to potholes on the surface, swelling of shape, rupturing of erythrocytes, removal of hematoporphyrin and flushing into the plasma as metabolites of the erythrocyte. The overall morphology of the erythrocytes of the smoker group appears more like a Mexican hat. The mean surface roughness was 5.5 ± 3 nm for the smoker group, but 1.2 ± 0.2 nm for the control group. Such damages might help the toxins, (CO, peroxidants, aldehydes etc.,) to gain easy access and get strongly absorbed by the hemoglobin, leading to enhanced rates of hemolysis as shown by the spectral features of metabolites. This indicates that the average life span of the smoker's erythrocytes is significantly less than that of the control group. PMID:26891995

  16. Smoking Induced Hemolysis: Spectral and microscopic investigations

    PubMed Central

    Masilamani, Vadivel; AlZahrani, Khalid; Devanesan, Sandhanasamy; AlQahtani, Hadi; AlSalhi, Mohamad Saleh

    2016-01-01

    Smoking is one of the major causes of lifestyle associated mortality and morbidity such as cancer of the oral cavity and lungs, and also cardiovascular diseases. In this study, we have provided evidences for the smoking-induced hemolysis using two methods: spectra of blood components and atomic force microscopic analysis of surface morphology. A total of 62 subjects (control = 31; smoker = 31: 21 male; 10 female in each set) were considered for the study. The findings indicate that smoking leads to potholes on the surface, swelling of shape, rupturing of erythrocytes, removal of hematoporphyrin and flushing into the plasma as metabolites of the erythrocyte. The overall morphology of the erythrocytes of the smoker group appears more like a Mexican hat. The mean surface roughness was 5.5 ± 3 nm for the smoker group, but 1.2 ± 0.2 nm for the control group. Such damages might help the toxins, (CO, peroxidants, aldehydes etc.,) to gain easy access and get strongly absorbed by the hemoglobin, leading to enhanced rates of hemolysis as shown by the spectral features of metabolites. This indicates that the average life span of the smoker’s erythrocytes is significantly less than that of the control group. PMID:26891995

  17. Spectral-temporal-polarization encoding of photons for multi-user secure quantum communication

    NASA Astrophysics Data System (ADS)

    Donkor, Eric

    2014-05-01

    We describe a Quantum Key Distribution protocol that combines temporal-, spectraland polarization-encoding of photons for secure communication over an interconnected network of users. Temporal encoding is used to identify a user's location or address on the network. Polarization encoding is used to generate private cryptographic key. Polarization encoded information is locally and randomly generated by users and exchanged only over a dedicated secure channel. Spectral encoding allows for the detection of eavesdropping and tampering by a malicious agent. Temporal-spectral signals sent from the network administrator (Alice) to a user are bright light source. On the other hand spectral-temporal signal from a network user (Bob) to the administrator (Alice) are single photons. Signals are sent across the network as ordered light pairs. The ordering format is randomly chosen and are revealed only at the time of key selection between the parties so that a secure one-time cryptographic pad can be generated

  18. Birefringence imaging of biological tissue by spectral domain polarization sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Jing, Zhijun; Fan, Chuanmao; Jiang, Jingying; Gong, Qiang; Ma, Zhenhe; Zhang, Fan; Yao, Jianquan; Wang, R. K.

    2007-02-01

    A spectral domain Polarization sensitive optical coherence tomography (SDPS-OCT) system has been developed to acquire depth images of biological tissues such as porcine tendon, rabbit eye. The Stocks vectors (I, Q, U, and V) of the backscattered light from the biological tissues have been reconstructed. Further, the phase retardation and polarization degree between the two orthogonal polarizing states have been computed. Reconstructed images, i.e. birefringence images, from Stokes parameters, retardation and polarization degree of biological tissues show significant local variations in the polarization state. And the birefringence contrast of biological tissue possibly changes by some outside force. In addition, the local thickness of the birefringence layer determined with our system is significant. The results presented show SDPS-OCT is a potentially powerful technique to investigate tissue structural properties on the basis of the fact that any fibrous structure with biological tissues can influence the polarization state of light.

  19. IR spectral properties of dust and ice at the Mars south polar cap

    NASA Astrophysics Data System (ADS)

    Titus, T. N.; Kieffer, H. H.

    2001-11-01

    Removal of atmospheric dust effects is required to derive surface IR spectral emissivity. Commonly, the atmospheric-surface separation is based on radiative transfer (RT) spectral inversion methods using nadir-pointing observations. This methodology depends on a priori knowledge of the spectral shape of each atmospheric aerosol (e.g. dust or water ice) and a large thermal contrast between the surface and atmosphere. RT methods fail over the polar caps due to low thermal contrast between the atmosphere and the surface. We have used multi-angle Emission Phase Function (EPF) observations to estimate the opacity spectrum of dust over the springtime south polar cap and the underlying surface radiance, and thus, the surface emissivity. We include a few EPFs from Hellas Basin as a basis for comparisons between the spectral shape of polar and non-polar dust. Surface spectral emissivities over the seasonal cap are compared to CO2 models. Our results show that the spectral shape of the polar dust opacity is not constant, but is a two-parameter family that can be characterized by the 9 um and 20 um opacities. The 9 um opacity varies from 0.15 to 0.45 and characterizes the overall atmospheric conditions. The 9 um to 20 um opacity ratio varies from 2.0 to 5.1, suggesting changes in dust size distribution over the polar caps. Derived surface temperatures from the EPFs confirm that the slightly elevated temperatures (relative to CO2 frost temperature) observed in ``cryptic'' regions are a surface effect, not atmospheric. Comparison of broad-band reflectivity and surface emissivities to model spectra suggest the bright regions (e.g. perennial cap, Mountains of Mitchell) have higher albedos due to a thin surface layer of fine-grain CO2 (perhaps either frost or fractured ice) with an underlying layer of either coarse grain or slab CO2 ice.

  20. Radiative interactions with micromachined surfaces: Spectral polarized emittance. Final report

    SciTech Connect

    Zemel, J.N.

    1995-05-01

    This report covers work aimed at obtaining additional information on the electromagnetic emissions from heated, microstructured surface. Earlier work had established that thermal emission was a useful means for obtaining broad band information on the electromagnetic properties of these surfaces. Among the earlier results obtained was a demonstration that there was an increased amount of coherent radiation emitted from these structures. Also found was that the nature of the emission was dependent on the carrier concentration of the emitting material as well as the details of the geometry of surface structures. Described in this report is the normal polarized emissivity of undoped silicon gratings of different dimensions measured with a new emissometer. Deep grating fabrication, formation of a titanium silicide layer, and wafer cutting is described.

  1. Apparatus for focused electrode induced polarization logging

    SciTech Connect

    Vinegar, H.J.; Waxman, M.H.

    1986-04-15

    An induced polarization logging tool is described for measuring parameters of a formation surrounding a borehole. The logging tool consists of: a non-conductive logging sonde; a plurality of electrodes disposed on the sonde, the electrodes including at least a survey current electrode and guard electrodes disposed on opposite sides of the survey current electrode, a non-polarizing voltage measuring electrode, a non-polarizing voltage reference electrode and a current return electrode, both the voltage reference and current return electrodes being located a greater distance from the survey current electrode than the guard electrodes; means connected to the survey current electrode and the guard electrodes for generating a signal representative of the potential difference in the formation between the survey current electrode and the guard electrodes; first control means directly coupled to the survey current electrode, the first control means controlling the current flow to the survey current electrode in response to the potential difference signal; a second control means directly coupled to the guard electrodes to control the current flow to the guard electrodes in response to the potential difference signal; a source of alternating current located at the surface, one end of the source being coupled to the two control means and the other to the current return electrode, the source supplying alternating current at various discrete frequencies between substantially 0.01 and 100 Hz; measurement means directly coupled to the voltage measurement and survey current electrodes to measure the amplitude and phase of the voltage induced in the formation and the amplitude and phase of the current flow to the survey electrode; and transmission means for transmitting the measurements to the surface.

  2. Noninvasive Contaminant Site Characterization Using Geophysical Induced Polarization

    SciTech Connect

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

    2003-03-27

    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.

  3. Characterizing microstructural changes of skeletal muscle tissues using spectral transformed Mueller matrix polarization parameters

    NASA Astrophysics Data System (ADS)

    He, Chao; He, Honghui; Chang, Jintao; Ma, Hui

    2016-03-01

    Polarization imaging techniques are recognized as potentially powerful tools to detect the structural changes of biological tissues. Meanwhile, spectral features of the scattered light can also provide abundant microstructural information, therefore can be applied in biomedical studies. In this paper, we adopt the polarization reflectance spectral imaging to analyze the microstructural changes of hydrolyzing skeletal muscle tissues. We measure the Mueller matrix, which is a comprehensive description of the polarization properties, of the bovine skeletal muscle samples in different periods of time, and analyze its behavior using the multispectral Mueller matrix transformation (MMT) technique. The experimental results show that for bovine skeletal muscle tissues, the backscattered spectral MMT parameters have different values and variation features at different stages. We can also find the experimental results indicate that the stages of hydrolysis for bovine skeletal muscle samples can be judged by the spectral MMT parameters. The results presented in this work show that combining with the spectral technique, the MMT parameters have the potential to be used as tools for meat quality detection and monitoring.

  4. TEMPORAL SPECTRAL SHIFT AND POLARIZATION OF A BAND-SPLITTING SOLAR TYPE II RADIO BURST

    SciTech Connect

    Du, Guohui; Chen, Yao; Lv, Maoshui; Kong, Xiangliang; Feng, Shiwei; Guo, Fan; Li, Gang

    2014-10-01

    In many type II solar radio bursts, the fundamental and/or the harmonic branches of the bursts can split into two almost parallel bands with similar spectral shapes and frequency drifts. However, the mechanisms accounting for this intriguing phenomenon remain elusive. In this study, we report a special band-splitting type II event in which spectral features appear systematically earlier on the upper band (with higher frequencies) than on the lower band (with lower frequencies) by several seconds. Furthermore, the emissions carried by the splitting band are moderately polarized with the left-hand polarized signals stronger than the right-hand ones. The polarization degree varies in a range of –0.3 to –0.6. These novel observational findings provide important constraints on the underlying physical mechanisms of band-splitting of type II radio bursts.

  5. Spectrally efficient polarization multiplexed direct-detection OFDM system without frequency gap.

    PubMed

    Wei, Chia-Chien; Zeng, Wei-Siang; Lin, Chun-Ting

    2016-01-25

    We experimentally demonstrate a spectrally efficient direct-detection orthogonal frequency-division multiplexing (DD-OFDM) system. In addition to polarization-division multiplexing, removing the frequency gap further improves the spectral efficiency of the OFDM system. The frequency gap between a reference carrier and OFDM subcarriers avoids subcarrier-to-subcarrier beating interference (SSBI) in traditional DD-OFDM systems. Without dynamic polarization control, the resulting interference after square-law direct detection in the proposed gap-less system is polarization-dependent and composed of linear inter-carrier interference (ICI) and nonlinear SSBI. Thus, this work proposes an iterative multiple-input multiple-output detection scheme to remove the mixed polarization-dependent interference. Compared to the previous scheme, which only removes ICI, the proposed scheme can further eliminate SSBI to achieve the improvement of ∼ 7 dB in signal-to-noise ratio. Without the need for polarization control, we successfully utilize 7-GHz bandwidth to transmit a 39.5-Gbps polarization multiplexed OFDM signal over 100 km. PMID:26832560

  6. Ternary fission induced by polarized neutrons

    NASA Astrophysics Data System (ADS)

    Gönnenwein, Friedrich

    2013-12-01

    Ternary fission of (e,e) U- and Pu- isotopes induced by cold polarized neutrons discloses some new facets of the process. In the so-called ROT effect shifts in the angular distributions of ternary particles relative to the fission fragments show up. In the so-called TRI effect an asymmetry in the emission of ternary particles relative to a plane formed by the fragment momentum and the spin of the neutron appear. The two effects are shown to be linked to the components of angular momentum perpendicular and parallel to the fission axis at the saddle point of fission. Based on theoretical models the spectroscopic properties of the collective transitional states at the saddle point are inferred from experiment.

  7. Radiation induced polarization in CdTe detectors

    NASA Astrophysics Data System (ADS)

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

    1988-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Revil, A.

    2013-12-01

    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.

  9. Subsurface imaging using the spectral polarization difference technique and NIR illumination

    SciTech Connect

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

    1999-01-26

    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.

  10. Ultrasensitive time-resolved linear dichroism spectral measurements using near-crossed linear polarizers

    NASA Astrophysics Data System (ADS)

    Che, Diping; Shapiro, Daniel B.; Esquerra, Raymond M.; Kliger, David S.

    1994-07-01

    A simple and sensitive technique is introduced to measure time-resolved linear dichroism of spectral transitions. This technique uses the fact that a linear dichroic sample rotates the polarization plane of linearly polarized light. The theoretical basis of the technique is presented using Mueller calculus and a detailed signal analysis is given to account for the effects of various optical imperfections. The results of this analysis are confirmed with the application of the technique to the time-resolved linear dichroism of bacteriorhodopsin in membrane patches (purple membrane) during its photocycle. These experimental results demonstrate the sentivity of the technique.

  11. Nonlinear spectral cleaning of few-cycle pulses via cross-polarized wave (XPW) generation

    NASA Astrophysics Data System (ADS)

    Jullien, A.; Durfee, C. G.; Trisorio, A.; Canova, L.; Rousseau, J.-P.; Mercier, B.; Antonucci, L.; Chériaux, G.; Albert, O.; Lopez-Martens, R.

    2009-08-01

    The characterization of a temporal filter based on cross-polarized wave generation working in the few-optical-cycle regime is presented. We show that this device dramatically improves the spectral quality of the ultrashort seed pulses, opening the way to the production of sub-10 fs pulses with high incoherent and coherent contrast. The dispersion compensation conditions for an optimized behavior of the process are experimentally and theoretically discussed.

  12. Retrieval and analysis of a polarized high-spectral-resolution lidar for profiling aerosol optical properties.

    PubMed

    Liu, Dong; Yang, Yongying; Cheng, Zhongtao; Huang, Hanlu; Zhang, Bo; Ling, Tong; Shen, Yibing

    2013-06-01

    Taking advantage of the broad spectrum of the Cabannes-Brillouin scatter from atmospheric molecules, the high spectral resolution lidar (HSRL) technique employs a narrow spectral filter to separate the aerosol and molecular scattering components in the lidar return signals and therefore can obtain the aerosol optical properties as well as the lidar ratio (i.e., the extinction-to-backscatter ratio) which is normally selected or modeled in traditional backscatter lidars. A polarized HSRL instrument, which employs an interferometric spectral filter, is under development at the Zhejiang University (ZJU), China. In this paper, the theoretical basis to retrieve the aerosol lidar ratio, depolarization ratio and extinction and backscatter coefficients, is presented. Error analyses and sensitivity studies have been carried out on the spectral transmittance characteristics of the spectral filter. The result shows that a filter that has as small aerosol transmittance (i.e., large aerosol rejection rate) and large molecular transmittance as possible is desirable. To achieve accurate retrieval, the transmittance of the spectral filter for molecular and aerosol scattering signals should be well characterized. PMID:23736562

  13. Ir Spectral Mapping of the Martian South Polar Residual CAP Using Crism

    NASA Astrophysics Data System (ADS)

    Campbell, Jacqueline; Sidiropoulos, Panagiotis; Muller, Jan-Peter

    2016-06-01

    Polycyclic aromatic hydrocarbons (PAHs) are considered to be important in theories of abiogenesis (Allamandola, 2011) . There is evidence that PAHs have been detected on two icy Saturnian satellites using the Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft (Cruikshank et al., 2007). The hypothesised presence of PAHs in Mars south polar cap has not been systematically examined even though the Mars south polar cap may allow the preservation of organic molecules that are typically destroyed at the Martian surface by UV radiation (Dartnell et al. 2012). This hypothesis is supported by recent analyses of South Polar Residual Cap (SPRC) structural evolution (Thomas et al., 2009) that suggest the possibility that seasonal and long term sublimation may excavate dust particles from within the polar ice. Periodic sublimation is believed to be responsible for the formation of so-called "Swiss Cheese Terrain", a unique surface feature found only in the Martian south polar residual cap consisting of flat floored, circular depressions (Byrne, 2009). We show the first examples of work towards the detection of PAHs in Swiss Cheese Terrain, using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), on board NASA's Mars Reconnaissance Orbiter (MRO). CRISM is designed to search for mineralogical indications of past and present water, thus providing extensive coverage of the south polar cap. In this work, we discuss whether CRISM infrared spectra can be used to detect PAHs in Swiss Cheese Terrain and demonstrate a number of maps showing shifts in spectral profiles over the SPRC.

  14. Spectrally resolved fluorescence lifetime imaging of Nile red for measurements of intracellular polarity

    NASA Astrophysics Data System (ADS)

    Levitt, James A.; Chung, Pei-Hua; Suhling, Klaus

    2015-09-01

    Spectrally resolved confocal microscopy and fluorescence lifetime imaging have been used to measure the polarity of lipid-rich regions in living HeLa cells stained with Nile red. The emission peak from the solvatochromic dye in lipid droplets is at a shorter wavelength than other, more polar, stained internal membranes, and this is indicative of a low polarity environment. We estimate that the dielectric constant, ɛ, is around 5 in lipid droplets and 25<ɛ<40 in other lipid-rich regions. Our spectrally resolved fluorescence lifetime imaging microscopy (FLIM) data show that intracellular Nile red exhibits complex, multiexponential fluorescence decays due to emission from a short lifetime locally excited state and a longer lifetime intramolecular charge transfer state. We measure an increase in the average fluorescence lifetime of the dye with increasing emission wavelength, as shown using phasor plots of the FLIM data. We also show using these phasor plots that the shortest lifetime decay components arise from lipid droplets. Thus, fluorescence lifetime is a viable contrast parameter for distinguishing lipid droplets from other stained lipid-rich regions. Finally, we discuss the FLIM of Nile red as a method for simultaneously mapping both polarity and relative viscosity based on fluorescence lifetime measurements.

  15. Angle- and polarization-dependent spectral characteristics of circular grating filters.

    PubMed

    Wang, Wei; Zhu, Gangyi; Liu, Qifa; Li, Xin; Sa, Tongliang; Fang, Xiaojing; Zhu, Hongbo; Wang, Yongjin

    2016-05-16

    We design and implement one type of guided mode resonance (GMR) circular grating filters (CGFs) on an HfO2-on-silicon platform. Taking advantage of an angle-resolved micro-reflection measurement system, we achieve their incident angle- and polarization-dependent reflection spectra. For normal incident arbitrary linear polarization, a pair of reflection peaks is experimentally observed due to the coexistence of the azimuthal component Ea and the radial component Er of the incident wave electric field (E-field). For oblique incident s-polarization (E-field perpendicular to the incident plane), the peak excited by the Ea component splits into two sub-peaks due to the removal of degeneracy, while that excited by the Er component gradually fades away with the increase of the incident angle. For oblique incident p-polarization (E-field parallel to the incident plane), the spectrum appears to be reversed; that is, the peak corresponding to the Er component gets split while that corresponding to the Ea component gradually disappears when the incident angle increases. Moreover, we experimentally demonstrate the spectral relationships between CGFs and linear grating filters under not only normal incidence but also oblique incidence; these relationships greatly facilitate the spectral design and tailoring of the CGFs. PMID:27409926

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    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.

  17. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D.

    1991-01-01

    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.

  18. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D.

    1990-01-01

    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.

  19. GLOBAL SPECTRAL ENERGY DISTRIBUTION OF THE CRAB NEBULA IN THE PROSPECT OF THE PLANCK SATELLITE POLARIZATION CALIBRATION

    SciTech Connect

    MacIas-Perez, J. F.; Mayet, F.; Aumont, J.

    2010-03-01

    Within the framework of the Planck satellite polarization calibration, we present a study of the Crab Nebula spectral energy distribution (SED) over more than six decades in frequency ranging from 1 to 10{sup 6} GHz (from 299 to 2.99 x 10{sup -4} mm). The Planck satellite mission observes the sky from 30 to 857 GHz (from 9.99 to 0.3498 mm) and therefore we focus on the millimeter region. We use radio and submillimeter data from the WMAP satellite between 23 and 94 GHz (from 13 to 3.18 mm), from the Archeops balloon experiment between 143 (2.1 mm) and 545 GHz (0.55 mm), and a compendium of other Crab Nebula observations. The Crab SED is compared to models including three main components: synchrotron that is responsible for the emission at low and high frequencies, dust that explains the excess of flux observed by the IRAS satellite, and an extra component on the millimeter regime. From this analysis, we conclude that the unpolarized emission of the Crab Nebula at microwave and millimeter wavelengths is the same synchrotron emission as the one observed in the radio domain. Therefore, we expect the millimeter emission of the Crab Nebula to be polarized with the same degree of polarization and orientation as the radio emission. We set upper limits on the possible errors induced by any millimeter extra component on the reconstruction of the degree and angle of polarization at the percent level as a maximum. This result strongly supports the choice by the Planck collaboration of the Crab Nebula emission for performing polarization cross-checks in the range 30 (299 mm) to 353 GHz (0.849 mm).

  20. Polarization-based balanced detection for spectral-domain optical coherence tomography.

    PubMed

    Black, Adam J; Akkin, Taner

    2015-08-20

    We present a new design for spectral-domain optical coherence tomography that allows balanced detection using a single camera. The design uses polarization optics to encode the light in reference and sample arms. Two parallel and highly aligned spectra, which carry out-of-phase interference signals, in-phase common noise, and auto-interference terms, are focused on the camera, which performs the digital balanced detection for each wavelength. The optical system is characterized and tested for tissue imaging. Results demonstrate consistent signal gains in depth and suppression of DC and sample auto-interference. The design could be further amended for polarization-sensitive imaging and might demonstrate a market for manufacturing dual-line cameras with analog-balanced detection capability. PMID:26368760

  1. Decoupled polarization dynamics of incoherent waves and bimodal spectral incoherent solitons.

    PubMed

    Fusaro, A; Garnier, J; Michel, C; Xu, G; Fatome, J; Wright, L G; Wise, F W; Picozzi, A

    2016-09-01

    We consider the propagation of strongly incoherent waves in optical fibers in the framework of the vector nonlinear Schrödinger equation (VNLSE) accounting for the Raman effect. On the basis of the wave turbulence theory, we derive a kinetic equation that greatly simplifies the VNLSE and provides deep physical insight into incoherent wave dynamics. When applied to the study of polarization effects, the theory unexpectedly reveals that the linear polarization components of the incoherent wave evolve independently from each other, even in the presence of weak fiber birefringence. When applied to light propagation in bimodal fibers, the theory reveals that the incoherent modal components can be strongly coupled. After a complex transient, the modal components self-organize into a vector spectral incoherent soliton: The two solitons self-trap and propagate with a common velocity in frequency space. PMID:27607955

  2. Attometer resolution spectral analysis based on polarization pulling assisted Brillouin scattering merged with heterodyne detection.

    PubMed

    Preussler, Stefan; Schneider, Thomas

    2015-10-01

    Spectral analysis is essential for measuring and monitoring advanced optical communication systems and the characterization of active and passive devices like amplifiers, filters and especially frequency combs. Conventional devices have a limited resolution or tuning range. Therefore, the true spectral shape of the signal remains hidden. In this work, a small part of the signal under test is preselected with help of the polarization pulling effect of stimulated Brillouin scattering where all unwanted spectral components are suppressed. Subsequently, this part is analyzed more deeply through heterodyne detection. Thereby, the local oscillator is generated from a narrow linewidth fiber laser which acts also as pump wave for Brillouin scattering. By scanning the pump wave together with the local oscillator through the signal spectrum, the whole signal is measured. The method is tunable over a broad wavelength range, is not affected by unwanted mixing products and utilizes a conventional narrow bandwidth photo diode. First proof of concept experiments show the measurement of the power spectral density function with a resolution in the attometer or lower kilohertz range at 1550 nm. PMID:26480198

  3. Bright source of spectrally pure polarization-entangled photon with nearly single-mode emission

    SciTech Connect

    Evans, Philip G; Schaake, Jason; Bennink, Ryan S; Grice, Warren P; Humble, Travis S

    2010-12-01

    We present results of a bright entangled photon source operating at 1552 nm via type-II collinear degenerate spontaneous parametric down-conversion in periodically poled KTP crystal. We report a conservative inferred pair generation rate of 44,000/s/mW into collection modes. Minimization of spectral and spatial entanglement was achieved by group velocity matching the pump, signal and idler modes and through properly focusing the pump beam. By utilizing a pair of calcite beam displacers, we are able to overlap photons from adjacent collinear sources to obtain polarization-entanglement visibility of 94.7 +/- 1.1% with accidentals subtracted.

  4. High-power spectral beam combining of linearly polarized Tm:fiber lasers.

    PubMed

    Shah, Lawrence; Sims, R Andrew; Kadwani, Pankaj; Willis, Christina C C; Bradford, Joshua B; Sincore, Alex; Richardson, Martin

    2015-02-01

    To date, high-power scaling of Tm:fiber lasers has been accomplished by maximizing the power from a single fiber aperture. In this work, we investigate power scaling by spectral beam combination of three linearly polarized Tm:fiber MOPA lasers using dielectric mirrors with a steep transition from highly reflective to highly transmissive that enable a minimum wavelength separation of 6 nm between individual laser channels within the wavelength range from 2030 to 2050 nm. Maximum output power is 253 W with M(2)<2, ultimately limited by thermal lensing in the beam combining elements. PMID:25967785

  5. [Study on polarization spectral feature of suspended sediment in the water body].

    PubMed

    Zhu, Jin; Wang, Xian-Hua; Pan, Bang-Long

    2012-07-01

    Remote sensing of lake water based on water-leaving radiance is to retrieve the concentrations of suspended sediment, phytoplankton and yellow substance which have great impacts on spectrum to assess the water quality. Howerver, because of the complexity of the lake water compositons and the interference between the different components, it is of great difficulty to get accurate results with the reflectance spectrum method developed recently. In the present paper, the authors firstly discussed the reflectance and polarization spectral feature of suspended sediment water body, found out the relations of the reflectance and the degree of polarization of water-leaving radiance and the concentration of suspended sediment at the sensitive bands. The authors also compared the effectiveness of the retrieval approaches based on reflectance and polarization in laboratory water body and Chaohu water body respectively. The results show that in the lake water body where the constituents are very complex, the polarization information has greater capacity of anti-jamming, therefore it will have great potential applictions in lake water quality remote sensing. PMID:23016352

  6. Polarization-induced astigmatism caused by topographic masks

    NASA Astrophysics Data System (ADS)

    Ruoff, Johannes; Neumann, Jens Timo; Schmitt-Weaver, Emil; van Setten, Eelco; le Masson, Nicolas; Progler, Chris; Geh, Bernd

    2007-10-01

    With the continuous shrink of feature sizes the pitch of the mask comes closer to the wave length of light. It has been recognized that in this case polarization effects of the mask become much more pronounced and deviations in the diffraction efficiencies from the well-known Kirchhoff approach can no longer be neglected. It is not only the diffraction efficiencies that become polarization-dependent, also the phases of the diffracted orders tend to deviate from Kirchhoff theory when calculated rigorously. This also happens for large structures, where these phase deviations can mimic polarization dependent wave front aberrations, which in the case of polarized illumination can lead to non-negligible focus shifts that depend on the orientation and the features size themselves. This orientation dependence results in a polarization induced astigmatism offset, which can be of the same order of magnitude or even larger as polarization effects stemming from the lens itself. Hence, for correctly predicting polarization induced astigmatism offsets, one has to both consider lens and mask effects at the same time. In this paper we present a comprehensive study of polarized induced phase effects of topographic masks and develop a simple theoretical model that accurately describes the observed effects.

  7. Antiresonance induced spin-polarized current generation

    NASA Astrophysics Data System (ADS)

    Yin, Sun; Min, Wen-Jing; Gao, Kun; Xie, Shi-Jie; Liu, De-Sheng

    2011-12-01

    According to the one-dimensional antiresonance effect (Wang X R, Wang Y and Sun Z Z 2003 Phys. Rev. B 65 193402), we propose a possible spin-polarized current generation device. Our proposed model consists of one chain and an impurity coupling to the chain. The energy level of the impurity can be occupied by an electron with a specific spin, and the electron with such a spin is blocked because of the antiresonance effect. Based on this phenomenon our model can generate the spin-polarized current flowing through the chain due to different polarization rates. On the other hand, the device can also be used to measure the generated spin accumulation. Our model is feasible with today's technology.

  8. Surface spin polarization induced ferromagnetic Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Shih, Po-Hsun; Li, Wen-Hsien; Wu, Sheng Yun

    2016-05-01

    We report on the observation of ferromagnetic spin polarized moments in 4.5 nm Ag nanoparticles. Both ferromagnetic and diamagnetic responses to an applied magnetic field were detected. The spin polarized moments shown under non-linear thermoinduced magnetization appeared on the surface atoms, rather than on all the atoms in particles. The saturation magnetization departed substantially from the Bloch T3/2-law, showing the existence of magnetic anisotropy. The Heisenberg ferromagnetic spin wave model for Ha-aligned moments was then employed to identify the magnetic anisotropic energy gap of ~0.12 meV. Our results may be understood by assuming the surface magnetism model, in which the surface atoms give rise to polarized moments while the core atoms produce diamagnetic responses.

  9. Ferroelectric domain wall motion induced by polarized light.

    PubMed

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

    2015-01-01

    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

  10. Ferroelectric domain wall motion induced by polarized light

    PubMed Central

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

    2015-01-01

    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

  11. Suppressing Short-term Polarization Noise and Related Spectral Decoherence in All-normal Dispersion Fiber Supercontinuum Generation

    PubMed Central

    Liu, Yuan; Zhao, Youbo; Lyngsø, Jens; You, Sixian; Wilson, William L.; Tu, Haohua; Boppart, Stephen A.

    2015-01-01

    The supercontinuum generated exclusively in the normal dispersion regime of a nonlinear fiber is widely believed to possess low optical noise and high spectral coherence. The recent development of flattened all-normal dispersion fibers has been motivated by this belief to construct a general-purpose broadband coherent optical source. Somewhat surprisingly, we identify a large short-term polarization noise in this type of supercontinuum generation that has been masked by the total-intensity measurement in the past, but can be easily detected by filtering the supercontinuum with a linear polarizer. Fortunately, this hidden intrinsic noise and the accompanied spectral decoherence can be effectively suppressed by using a polarization-maintaining all-normal dispersion fiber. A polarization-maintaining coherent supercontinuum laser is thus built with a broad bandwidth (780–1300 nm) and high spectral power (~1 mW/nm). PMID:26166939

  12. White dwarf mass estimation with a new comprehensive X-ray spectral model of intermediate polars

    NASA Astrophysics Data System (ADS)

    Hayashi, Takayuki; Ishida, Manabu

    A white dwarf (WD) mass is important astrophysical quantity because the WD explodes as a type Ia supernova when its mass reaches the Chandrasekhar mass limit of 1.4 solar mass. Many WD masses in intermediate polars (IPs) were measured with their X-ray spectra emitted from plasma flows channeled by strong magnetic fields of the WDs. For the WD mass estimation, multi-temperature X-ray spectral models have been used which made by summing up X-ray spectra emitted from the top to the bottom of the plasma flow. However, in previous studies, distributions of physical quantities such as temperature and density etc., which are base of the X-ray spectral model, were calculated with assumptions of accretion rate per unit area (call "specific accretion rate") a = 1 g cm(-2) s(-1) and cylindrical geometry for the plasma flows. In fact, a part of the WD masses estimated with the X-ray spectral model is not consistent with that dynamically measured. Therefore, we calculated the physical quantity distributions with the dipolar geometry and the wide range of the specific accretion rate a = 0.0001 - 100 g cm(-2) s(-1) . The calculations showed that the geometrical difference changes the physical quantity distributions and the lower specific accretion rate leads softer X-ray spectrum under a critical specific accretion rate. These results clearly indicate that the previous assumptions are not good approximation for low accretion IPs. We made a new spectral model of the plasma flow with our physical quantity distributions and applied that to Suzaku observations of high and low accretion rate IPs V1223 Sagittarii and EX Hydrae. As a results, our WD masses are almost consistent with the those dynamically measured. We will present the summary of our theoretical calculation and X-ray spectral model, and application to the {¥it Suzaku} observations.

  13. Inclination-induced polarization of scattered millimetre radiation from protoplanetary discs: the case of HL Tau

    NASA Astrophysics Data System (ADS)

    Yang, Haifeng; Li, Zhi-Yun; Looney, Leslie; Stephens, Ian

    2016-03-01

    Spatially resolved polarized millimetre/submillimetre emission has been observed in the disc of HL Tau and two other young stellar objects. It is usually interpreted as coming from magnetically aligned grains, but can also be produced by dust scattering, as demonstrated explicitly by Kataoka et al. for face-on discs. We extend their work by including the polarization induced by disc inclination with respect to the line of sight. Using a physically motivated, semi-analytic model, we show that the polarization fraction of the scattered light increases with the inclination angle i, reaching 1/3 for edge-on discs. The inclination-induced polarization can easily dominate that intrinsic to the disc in the face-on view. It provides a natural explanation for the two main features of the polarization pattern observed in the tilted disc of HL Tau (i ˜ 45°): the polarized intensity concentrating in a region elongated more or less along the major axis, and polarization in this region roughly parallel to the minor axis. This broad agreement provides support to dust scattering as a viable mechanism for producing, at least in part, polarized millimetre radiation. In order to produce polarization at the observed level (˜1 per cent), the scattering grains must have grown to a maximum size of tens of microns. However, such grains may be too small to produce the opacity spectral index of β ≲ 1 observed in HL Tau and other sources; another population of larger, millimetre/centimetre-sized, grains may be needed to explain the bulk of the unpolarized continuum emission.

  14. 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...

  15. Josephson π state induced by valley polarization

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Yang, Y. H.; Chan, K. S.

    2014-02-01

    We theoretically explore possible π-state Josephson junctions made from graphene-like two-dimensional materials (G) with the honeycomb lattice structure. It is shown that the valley polarization in the G sheet could lead to a 0-π state transition of the Josephson junction because of the valley-singlet Cooper pairs acquiring a nonzero momentum. When the valley-mixing scattering exists in the interfaces of the junction due to lattice mismatch, an odd-frequency valley-triplet supercurrent flows in the system even though the G sheet is fully valley polarized, and the supercurrent is characterized by a rapid atomic-scale oscillation with a periodicity of three lattice constants.

  16. Spectral Cloud-Filtering of AIRS Data: Non-Polar Ocean

    NASA Technical Reports Server (NTRS)

    Aumann, Hartmut H.; Gregorich, David; Barron, Diana

    2004-01-01

    The Atmospheric Infrared Sounder (AIRS) is a grating array spectrometer which covers the thermal infrared spectral range between 640 and 1700/cm. In order to retain the maximum radiometric accuracy of the AIRS data, the effects of cloud contamination have to be minimized. We discuss cloud filtering which uses the high spectral resolution of AIRS to identify about 100,000 of 500,000 non-polar ocean spectra per day as relatively "cloud-free". Based on the comparison of surface channels with the NCEP provided global real time sst (rtg.sst), AIRS surface sensitive channels have a cold bias ranging from O.5K during the day to 0.8K during the night. Day and night spatial coherence tests show that the cold bias is due to cloud contamination. During the day the cloud contamination is due to a 2-3% broken cloud cover at the 1-2 km altitude, characteristic of low stratus clouds. The cloud-contamination effects surface sensitive channels only. Cloud contamination can be reduced to 0.2K by combining the spectral filter with a spatial coherence threshold, but the yield drops to 16,000 spectra per day. AIRS was launched in May 2002 on the Earth Observing System (EOS) Aqua satellite. Since September 2002 it has returned 4 million spectra of the globe each day.

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

    SciTech Connect

    Vinoth Kumar, L.; Manikanta, E.; Leela, Ch.; Prem Kiran, P.

    2014-08-11

    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.

  18. Influence of Solvent Polarity and DNA-Binding on Spectral Properties of Quaternary Benzo[c]phenanthridine Alkaloids

    PubMed Central

    Rájecký, Michal; Šebrlová, Kristýna; Mravec, Filip; Táborský, Petr

    2015-01-01

    Quaternary benzo[c]phenanthridine alkaloids are secondary metabolites of the plant families Papaveraceae, Rutaceae, and Ranunculaceae with anti-inflammatory, antifungal, antimicrobial and anticancer activities. Their spectral changes induced by the environment could be used to understand their interaction with biomolecules as well as for analytical purposes. Spectral shifts, quantum yield and changes in lifetime are presented for the free form of alkaloids in solvents of different polarity and for alkaloids bound to DNA. Quantum yields range from 0.098 to 0.345 for the alkanolamine form and are below 0.033 for the iminium form. Rise of fluorescence lifetimes (from 2–5 ns to 3–10 ns) and fluorescence intensity are observed after binding of the iminium form to the DNA for most studied alkaloids. The alkanolamine form does not bind to DNA. Acid-base equilibrium constant of macarpine is determined to be 8.2–8.3. Macarpine is found to have the highest increase of fluorescence upon DNA binding, even under unfavourable pH conditions. This is probably a result of its unique methoxy substitution at C12 a characteristic not shared with other studied alkaloids. Association constant for macarpine-DNA interaction is 700000 M-1. PMID:26091027

  19. Aharonov-Bohm effect induced by circularly polarized light

    NASA Astrophysics Data System (ADS)

    Sigurdsson, H.; Kibis, O. V.; Shelykh, I. A.

    2015-11-01

    We demonstrated theoretically that the strong electron interaction with circularly polarized photons in ring-like nanostructures changes the phase of electron wave. This optically-induced effect is caused by the breaking of time-reversal symmetry and is similar to the Aharonov-Bohm effect. As a consequence of this phenomenon, the conductance of mesoscopic rings irradiated by a circularly polarized electromagnetic wave behaves as an oscillating function of the intensity and frequency of the wave.

  20. Theory of Electric Polarization Induced by Inhomogeneity in Crystals

    NASA Astrophysics Data System (ADS)

    Xiao, Di; Shi, Junren; Clougherty, Dennis; Niu, Qian

    2008-03-01

    We develop a general theory of electric polarization induced by inhomogeneity in crystals. We show that contributions to polarization can be classified in powers of the gradient of the order parameter. The zeroth order contribution reduces to the well-known result obtained by King-Smith and Vanderbilt for uniform systems. The first order contribution, when expressed in a two- point formula, takes the Chern-Simons 3-form of the vector potentials derived from the Bloch wave functions. Using the relation between polarization and charge density, we demonstrate our formula by studying charge fractionalization in a two-dimensional dimer model recently proposed.

  1. Three-dimensional induced polarization data inversion for complex resistivity

    SciTech Connect

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

    2011-03-15

    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.

  2. Kinetic Sunyaev-Zeldovich effect in an anisotropic CMB model: Measuring low multipoles of the CMB at higher redshifts using intensity and polarization spectral distortions

    NASA Astrophysics Data System (ADS)

    Yasini, Siavash; Pierpaoli, Elena

    2016-07-01

    We present a novel mathematical formalism that allows us to easily compute the expected kinetic Sunyaev-Zeldovich (kSZ) signal in intensity and polarization due to an anisotropic primordial cosmic microwave background (CMB). We derive the expected intensity and polarization distortions in the direction of nonmoving galaxy clusters, and then we generalize our calculations for nonzero peculiar velocity. We show that, in the direction of moving clusters, low CMB multipoles impose intensity and polarization spectral distortions with different frequency dependences. The polarization signal primarily probes the quadrupole moment of the CMB, with a significant contribution from the primordial dipole and octupole moments. For a typical cluster velocity of 1000 km /s , corrections to the quadrupole-induced polarization of a nonmoving cluster are of the order of 2%-10% between 200-600 GHz, and depend on cluster's position on the sky, velocity magnitude, and direction of motion. We also find that the angular dependence of the signal varies with frequency of observation. The distinct frequency and angular dependences of the polarization induced by the primordial dipole and octupole can be exploited to measure them despite other physical effects and foregrounds. Contrary to polarization, intensity distortions are affected by all the CMB multipoles, so they cannot be readily used to probe the low multipoles at higher redshifts. However, correlations between intensity and polarization signals can be used to enhance the signal to noise ratio for the measurements of the primordial dipole, quadrupole, and octupole. The more general calculation of the aberration kernel presented in this work has applications reaching beyond the SZ cluster science addressed here. For example, it can be exploited to the deboost/deaberrate CMB multipoles as observed in our local frame.

  3. Assessing Cd-induced stress from plant spectral response

    NASA Astrophysics Data System (ADS)

    Kancheva, Rumiana; Georgiev, Georgi

    2014-10-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

  5. Spectral invariance hypothesis study of polarized reflectance with Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI)

    NASA Astrophysics Data System (ADS)

    Bradley, Christine L.; Kupinski, Meredith; Diner, David J.; Xu, Feng; Chipman, Russell A.

    2015-09-01

    Many models used to represent the boundary condition for the separation of atmospheric scattering from the surface reflectance in polarized remote sensing measurements assume that the polarized surface reflectance is spectrally neutral. The Spectral Invariance Hypothesis asserts that the magnitude and shape of the polarized bidirectional reflectance factor (pBRF) is equal for all wavelengths. In order to test this hypothesis, JPL's Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI) is used to measure polarization information of different outdoor surface types. GroundMSPI measures the linear polarization Stokes parameters (I, Q, U), at three wavelengths, 470 nm, 660 nm, and 865 nm. The camera is mounted on a two-axis gimbal to accurately select the view azimuth and elevation directions. On clear sky days we acquired day-long scans of scenes that contain various surface types such as grass, dirt, cement, brick, and asphalt and placed a Spectralon panel in the camera field of view to provide a reflectance reference. Over the course of each day, changing solar position in the sky provides a large range of scattering angles for this study. The polarized bidirectional reflectance factor (pBRF) is measured for the three wavelengths and the best fit slope of the spectral correlation is reported. This work reports the range of best fit slopes measured for five region types.

  6. Birefringence and polarization rotator induced by electromagnetically induced transparency in rare earth ion-doped crystals

    NASA Astrophysics Data System (ADS)

    Li, Zhixiang; Liu, Jianji; Yu, Ping; Zhang, Guoquan

    2016-05-01

    The birefringence induced by the electromagnetically induced transparency effect in a {Pr}^{3+}:{Y}_2 {SiO}_5 crystal was studied by using a balanced polarimeter technique. The results show that it is possible to control the polarization state of the output probe beam by adjusting the experimental conditions. Particularly, the coherently prepared {Pr}^{3+}:{Y}_2 {SiO}_5 crystal can serve as a polarization rotator for a linearly polarized input probe beam at the two-photon resonant condition. Such coherent control on the polarization of light should be useful for polarization-based classical and quantum information processing such as all-optical switching, polarization preserving light pulse memory and polarization qubits based on rare earth ion-doped solids.

  7. Slippage in stacking of graphene nanofragments induced by spin polarization

    NASA Astrophysics Data System (ADS)

    Lei, Yanyu; Jiang, Wanrun; Dai, Xing; Song, Ruixia; Wang, Bo; Gao, Yang; Wang, Zhigang

    2015-06-01

    Spin polarization and stacking are interesting effects in complex molecular systems and are both presented in graphene-based materials. Their possible combination may provide a new perspective in understanding the intermolecular force. The nanoscale graphene structures with zigzag edges could possess spin-polarized ground states. However, the mechanical effect of spin polarization in stacking of graphene nanofragments is not clear. Here we demonstrate the displacement between two stacked rhombic graphene nanofragments induced by spin polarization, using first-principles density-functional methods. We found that, in stacking of two rhombic graphene nanofragments, a spin-polarized stacked conformation with zero total spin is energetically more favorable than the closed-shell stacking. The spin-polarized conformation gives a further horizontal interlayer displacement within 1 angstrom compared with the closed-shell structure. This result highlights that, besides the well-known phenomenologically interpreted van der Waals forces, a specific mechanism dependent on the monomeric spin polarization may lead to obvious mechanical effects in some intermolecular interactions.

  8. Slippage in stacking of graphene nanofragments induced by spin polarization.

    PubMed

    Lei, Yanyu; Jiang, Wanrun; Dai, Xing; Song, Ruixia; Wang, Bo; Gao, Yang; Wang, Zhigang

    2015-01-01

    Spin polarization and stacking are interesting effects in complex molecular systems and are both presented in graphene-based materials. Their possible combination may provide a new perspective in understanding the intermolecular force. The nanoscale graphene structures with zigzag edges could possess spin-polarized ground states. However, the mechanical effect of spin polarization in stacking of graphene nanofragments is not clear. Here we demonstrate the displacement between two stacked rhombic graphene nanofragments induced by spin polarization, using first-principles density-functional methods. We found that, in stacking of two rhombic graphene nanofragments, a spin-polarized stacked conformation with zero total spin is energetically more favorable than the closed-shell stacking. The spin-polarized conformation gives a further horizontal interlayer displacement within 1 angstrom compared with the closed-shell structure. This result highlights that, besides the well-known phenomenologically interpreted van der Waals forces, a specific mechanism dependent on the monomeric spin polarization may lead to obvious mechanical effects in some intermolecular interactions. PMID:26078005

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

    PubMed

    Yu, Liping; Zunger, Alex

    2014-01-01

    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

  10. Polarization Induced Spin Wave Damping in Spin Polarized Liquid 3He 4He

    NASA Astrophysics Data System (ADS)

    Perisanu, Sorin; Vermeulen, Gerard

    2007-08-01

    We have measured the temperature and polarization dependence of Silin spin wave spectra in a saturated 3He 4He mixture with a concentration of 9.4% at a pressure of 8 bars. The mixture has been cooled and polarized by a Leiden dilution refrigerator to temperatures in the range 10 15 mK and polarizations as high as 9.2% corresponding to 3.4 times the equilibrium polarization of 2.7% in the external magnetic field of 11.36 T. The analysis takes into account the dipolar interactions and results in the relaxation time τ ⊥ and spin diffusion constant D ⊥ . We find that τ ⊥ and D ⊥ are proportional to 1/(T2+mathcal{A}2T_{a0}2) where T is the temperature, mathcal{A} is the polarization enhancement factor and T a0 is the anisotropy temperature for the mixture at equilibrium in the external field. Our result T a0=3.66±0.14 mK is 30% higher than the theoretical prediction for very dilute mixtures and is evidence for the existence of polarization induced relaxation of transverse spin currents.

  11. Spatial Variations in the Spectral Index of Polarized Synchrotron Emission in the 9 yr WMAP Sky Maps

    NASA Astrophysics Data System (ADS)

    Fuskeland, U.; Wehus, I. K.; Eriksen, H. K.; Næss, S. K.

    2014-08-01

    We estimate the spectral index, β, of polarized synchrotron emission as observed in the 9 yr Wilkinson Microwave Anisotropy Probe sky maps using two methods, linear regression ("T-T plot") and maximum likelihood. We partition the sky into 24 disjoint sky regions and evaluate the spectral index for all polarization angles between 0° and 85° in steps of 5°. Averaging over polarization angles, we derive a mean spectral index of βall-sky = -2.99 ± 0.01 in the frequency range of 23-33 GHz. We find that the synchrotron spectral index steepens by 0.14 from low to high Galactic latitudes, in agreement with previous studies, with mean spectral indices of βplane = -2.98 ± 0.01 and βhigh-lat = -3.12 ± 0.04. In addition, we find a significant longitudinal variation along the Galactic plane with a steeper spectral index toward the Galactic center and anticenter than toward the Galactic spiral arms. This can be well modeled by an offset sinusoidal, β(l) = -2.85 + 0.17sin (2l - 90°). Finally, we study synchrotron emission in the BICEP2 field, in an attempt to understand whether the claimed detection of large-scale B-mode polarization could be explained in terms of synchrotron contamination. Adopting a spectral index of β = -3.12, typical for high Galactic latitudes, we find that the most likely bias corresponds to about 2% of the reported signal (r = 0.003). The flattest index allowed by the data in this region is β = -2.5, and under the assumption of a straight power-law frequency spectrum, we find that synchrotron emission can account for at most 20% of the reported BICEP2 signal.

  12. Spatial variations in the spectral index of polarized synchrotron emission in the 9 yr WMAP sky maps

    SciTech Connect

    Fuskeland, U.; Eriksen, H. K.; Næss, S. K.; Wehus, I. K. E-mail: h.k.k.eriksen@astro.uio.no E-mail: i.k.wehus@fys.uio.no

    2014-08-01

    We estimate the spectral index, β, of polarized synchrotron emission as observed in the 9 yr Wilkinson Microwave Anisotropy Probe sky maps using two methods, linear regression ({sup T}-T plot{sup )} and maximum likelihood. We partition the sky into 24 disjoint sky regions and evaluate the spectral index for all polarization angles between 0° and 85° in steps of 5°. Averaging over polarization angles, we derive a mean spectral index of β{sup all-sky} = –2.99 ± 0.01 in the frequency range of 23-33 GHz. We find that the synchrotron spectral index steepens by 0.14 from low to high Galactic latitudes, in agreement with previous studies, with mean spectral indices of β{sup plane} = –2.98 ± 0.01 and β{sup high-lat} = –3.12 ± 0.04. In addition, we find a significant longitudinal variation along the Galactic plane with a steeper spectral index toward the Galactic center and anticenter than toward the Galactic spiral arms. This can be well modeled by an offset sinusoidal, β(l) = –2.85 + 0.17sin (2l – 90°). Finally, we study synchrotron emission in the BICEP2 field, in an attempt to understand whether the claimed detection of large-scale B-mode polarization could be explained in terms of synchrotron contamination. Adopting a spectral index of β = –3.12, typical for high Galactic latitudes, we find that the most likely bias corresponds to about 2% of the reported signal (r = 0.003). The flattest index allowed by the data in this region is β = –2.5, and under the assumption of a straight power-law frequency spectrum, we find that synchrotron emission can account for at most 20% of the reported BICEP2 signal.

  13. Debye decomposition of time-lapse spectral induced polarisation data

    NASA Astrophysics Data System (ADS)

    Weigand, M.; Kemna, A.

    2016-01-01

    Spectral induced polarisation (SIP) measurements capture the low-frequency electrical properties of soils and rocks and provide a non-invasive means to access lithological, hydrogeological, and geochemical properties of the subsurface. The Debye decomposition (DD) approach is now increasingly being used to analyse SIP signatures in terms of relaxation time distributions due to its flexibility regarding the shape of the spectra. Imaging and time-lapse (monitoring) SIP measurements, capturing SIP variations in space and time, respectively, are now more and more conducted and lead to a drastic increase in the number of spectra considered, which prompts the need for robust and reliable DD tools to extract quantitative parameters from such data. We here present an implementation of the DD method for the analysis of a series of SIP data sets which are expected to only smoothly change in terms of spectral behaviour, such as encountered in many time-lapse applications where measurement geometry does not change. The routine is based on a non-linear least-squares inversion scheme with smoothness constraints on the spectral variation and in addition from one spectrum of the series to the next to deal with the inherent ill-posedness and non-uniqueness of the problem. By means of synthetic examples with typical SIP characteristics we elucidate the influence of the number and range of considered relaxation times on the inversion results. The source code of the presented routines is provided under an open source licence as a basis for further applications and developments.

  14. Polarization and spectral characteristics of the two-photon luminescence from colloidal gold nanoparticles excited by tunable laser radiation

    SciTech Connect

    Yashunin, D. A. Korytin, A. I.; Stepanov, A. N.

    2015-12-15

    We have experimentally studied two-photon luminescence from a colloidal solution of spherical gold nanoparticles by tuning the wavelength of the exciting radiation. The measured polarization and spectral characteristics of the two-photon luminescence signal show that the observed nonlinear optical response is determined by the dimers present in the solution with a concentration of a few percent of total nanoparticle number.

  15. Spectral matrix analysis for detection of polarized wave arrivals and its application to seismic reflection studies using local earthquake data

    NASA Astrophysics Data System (ADS)

    Moriya, H.

    2009-12-01

    Local earthquakes observed at Sendai, Japan, were analyzed to confirm the validity of a method of polarization analysis using the spectral matrix of seismic wave and its application to seismic reflection studies of the crust using local earthquake data. Reflectors (Bright spots) are known below the Nagamachi-Rifu fault, which caused an M 5.0 class event in 1998. Polarization analysis was applied to earthquake data in and around the fault. Use of the Z-parameter, which is defined using the eigenvalues of the spectral matrix and a statistical value representing the confidence level for the detection of the arrival of polarized waves, allowed detection of linearly and elliptically polarized waves in coda waves. The Z-parameter was also used to image the reflectors by using a migration technique that assumes the P × P and S × S reflection waves travel through a multi-layered velocity structure. Distinct reflectors were detected at depths of around 10 km, 14 km, 17 km, 21-26 km, 35 km and 40 km, that is, from deeper than the fault and the Moho. This study demonstrated the feasibility of using the spectral matrix of three-component seismic signal to detect polarized waves and to image reflectors in the earth's crust and upper mantle.

  16. Spectrally resolved laser-induced fluorescence for bioaerosols standoff detection

    NASA Astrophysics Data System (ADS)

    Buteau, Sylvie; Stadnyk, Laurie; Rowsell, Susan; Simard, Jean-Robert; Ho, Jim; Déry, Bernard; McFee, John

    2007-09-01

    An efficient standoff biological warfare detection capability could become an important asset for both defence and security communities based on the increasing biological threat and the limits of the presently existing protection systems. Defence R&D Canada (DRDC) has developed, by the end of the 90s, a standoff bioaerosol sensor prototype based on intensified range-gated spectrometric detection of Laser Induced Fluorescence (LIF). This LIDAR system named SINBAHD monitors the spectrally resolved LIF originating from inelastic interactions with bioaerosols present in atmospheric cells customizable in size and in range. SINBAHD has demonstrated the capability of near real-time detection and classification of bioaerosolized threats at multi-kilometre ranges. In spring 2005, DRDC has initiated the BioSense demonstration project, which combines the SINBAHD technology with a geo-referenced Near InfraRed (NIR) LIDAR cloud mapper. SINBAHD is now being used to acquire more signatures to add in the spectral library and also to optimize and test the new BioSense algorithm strategy. In September 2006, SINBAHD has participated in a two-week trial held at DRDC-Suffield where different open-air wet releases of live and killed bioagent simulants, growth media and obscurants were performed. An autoclave killing procedure was performed on two biological materials (Bacillus subtilis var globigii or BG, and Bacillus thuringiensis or Bt) before being aerosolized, disseminated and spectrally characterized with SINBAHD. The obtained results showed no significant impact of this killing process on their normalised spectral signature in comparison with their live counterparts. Correlation between the detection signals from SINBAHD, an array of slit samplers and a FLuorescent Aerosol Particle Sensor (C-FLAPS) was obtained and SINBAHD's sensitivity could then be estimated. At the 2006 trial, a detection limit of a few tens of Agent Containing Particles per Liter of Air (ACPLA) was obtained

  17. Underwater light polarization and radiance fluctuations induced by surface waves.

    PubMed

    Sabbah, Shai; Shashar, Nadav

    2006-07-01

    The underwater light field is an ever-changing environment. Surface waves induce variability in the radiance and the light's polarization. We examined the dependence of the polarization fluctuations associated with diffuse light (not including contribution from direct skylight) on the viewing zenith angle (30 degrees, 70 degrees, and 90 degrees), solar zenith angle (23 degrees -72 degrees), depth of 0.5-3 m, and light wavelength (380-650 nm) while observing within the azimuthal plane in the wind-wave direction. Polarization and radiance fluctuated with time. Light variability (presented by the coefficient of variation calculated over a series of fluctuations in the radiance and percent polarization, and by the standard deviation calculated over a series of fluctuations in the e-vector orientation) was highest at a viewing zenith angle of 70 degrees , depended positively on the solar zenith angle, and decreased with depth at viewing zenith angles of 30 degrees and 70 degrees . Additionally, the variability of the percent polarization was significantly higher than that of the radiance. The temporal light fluctuations offer possibilities, such as enhancing the detection of transparent and reflecting objects; however, they set constraints on the optimal underwater polarization vision by both animals and by the use of instruments. PMID:16799688

  18. Polar Lipids of Burkholderia pseudomallei Induce Different Host Immune Responses

    PubMed Central

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

    2013-01-01

    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-γ, 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-γ 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

  19. Potential applications of near infrared auto-fluorescence spectral polarized imaging for assessment of food quality

    NASA Astrophysics Data System (ADS)

    Zhou, Kenneth J.; Chen, Jun

    2016-03-01

    The current growing of food industry for low production costs and high efficiency needs for maintenance of high-quality standards and assurance of food safety while avoiding liability issues. Quality and safety of food depend on physical (texture, color, tenderness etc.), chemical (fat content, moisture, protein content, pH, etc.), and biological (total bacterial count etc.) features. There is a need for a rapid (less than a few minutes) and accurate detection system in order to optimize quality and assure safety of food. However, the fluorescence ranges for known fluorophores are limited to ultraviolet emission bands, which are not in the tissue near infrared (NIR) "optical window". Biological tissues excited by far-red or NIR light would exhibit strong emission in spectral range of 650-1,100 nm although no characteristic peaks show the emission from which known fluorophores. The characteristics of the auto-fluorescence emission of different types of tissues were found to be different between different tissue components such as fat, high quality muscle food. In this paper, NIR auto-fluorescence emission from different types of muscle food and fat was measured. The differences of fluorescence intensities of the different types of muscle food and fat emissions were observed. These can be explained by the change of the microscopic structure of physical, chemical, and biological features in meat. The difference of emission intensities of fat and lean meat tissues was applied to monitor food quality and safety using spectral polarized imaging, which can be detect deep depth fat under the muscle food up to several centimeter.

  20. Analysis of input-polarization-induced phase noise in interferometric fiber-optic sensors and its reduction using polarization scrambling

    NASA Astrophysics Data System (ADS)

    Kersey, Alan D.; Marrone, Michael J.; Dandridge, Anthony

    1990-06-01

    The dependence of the phase shift of an interferometric fiber sensor on the input state of polarization is analyzed, and it is shown that fluctuations in the input polarization to a fiber interferometer can lead to the generation of excess phase noise. The relationship between this effect and the variation in visibility with input polarization is described and theoretically confirmed. The use of depolarized source light to eliminate input-polarization-induced excess phase noise is theoretically and experimentally demonstrated.

  1. Perceptual Spaces Induced by Cochlear Implant All-Polar Stimulation Mode.

    PubMed

    Marozeau, Jeremy; McKay, Colette M

    2016-01-01

    It has been argued that a main limitation of the cochlear implant is the spread of current induced by each electrode, which activates an inappropriately large range of sensory neurons. To reduce this spread, an alternative stimulation mode, the all-polar mode, was tested with five participants. It was designed to activate all the electrodes simultaneously with appropriate current levels and polarities to recruit narrower regions of auditory nerves at specific intracochlear electrode positions (denoted all-polar electrodes). In this study, the all-polar mode was compared with the current commercial stimulation mode: the monopolar mode. The participants were asked to judge the sound dissimilarity between pairs of two-electrode pulse-train stimuli that differed in the electrode positions and were presented in either monopolar or all-polar mode with pulses on the two electrodes presented either sequentially or simultaneously. The dissimilarity ratings were analyzed using a multidimensional scaling technique and three-dimensional stimulus perceptual spaces were produced. For all the conditions (mode and simultaneity), the first perceptual dimension was highly correlated with the position of the most apical activated electrode of the electrical stimulation and the second dimension with the position of the most basal electrode. In both sequential and simultaneous conditions, the monopolar and all-polar stimuli were significantly separated by a third dimension, which may indicate that all-polar stimuli have a perceptual quality that differs from monopolar stimuli. Overall, the results suggest that both modes might successfully represent spectral information in a sound processing strategy. PMID:27604784

  2. Polarized light-induced anisotropy of azo dyes studied by polarized FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Tawa, Keiko; Kamada, Kenji; Sakaguchi, Toru; Ohta, Koji

    1998-06-01

    The anisotropy induced in the poly(methyl methacrylate) (PMMA) films doped with Disperse Orange 3 (DO3, NO2-phenyl-N=N-phenyl-NH2) was investigated by polarized FTIR spectroscopy. Observed infrared absorption bands of DO3 in the polymers were assigned to symmetric (NO2s, 1341 cm-1) and antisymmetric (NO2as, 1523 cm-1) stretching modes of NO2, and the C-N stretching mode of C-NH2 (C-N, 1303 cm-1). By measuring the polarized IR spectra of DO3/PMMA, the infrared dichroism was observed in NO2s and C-N bands. From these results, the orientation factors, KZfn (f=x,y,z), for each isomer were determined. The factors indicate that it is difficult for NO2 group to move in the PMMA during trans-cis-trans isomerization and that phenyl group with NH2 mainly moves in PMMA on isomerization. This study clarified that the anisotropy of DO3 in PMMA is induced by photoselection with the irradiation of linearly polarized light and is not induced by reorientation of DO3 molecules, since the entire DO3 molecule cannot rotate in PMMA during a series of isomerization process.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  4. Macroscopic rotation of photon polarization induced by a single spin

    PubMed Central

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

    2015-01-01

    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

  5. Macroscopic rotation of photon polarization induced by a single spin.

    PubMed

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

    2015-01-01

    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

  6. Polarization-induced surface charges in hydroxyapatite ceramics

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

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

    SciTech Connect

    Ramos, Elsa P. R. G.; Da Silva, Antonio J. C.; Liu, Guo-Chin

    2012-09-20

    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

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

    PubMed

    Kinoshita, Michiyo; Pfeiffer, Keram; Homberg, Uwe

    2007-04-01

    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 present no data on the neural basis of coding the spectral gradient of the sky. In the present study we have analyzed the chromatic properties of two identified POL neurons in the brain of the desert locust. Both neurons, termed TuTu1 and LoTu1, arborize in the anterior optic tubercle and respond to unpolarized light as well as to polarized light. We show here that the polarized-light response of both types of neuron relies on blue-sensitive photoreceptors. Responses to unpolarized light depended on stimulus position and wavelength. Dorsal unpolarized blue light inhibited the neurons, while stimulation from the ipsilateral side resulted in opponent responses to UV light and green light. While LoTu1 was inhibited by UV light and was excited by green light, one subtype of TuTu1 was excited by UV and inhibited by green light. In LoTu1 the sensitivity to polarized light was at least 2 log units higher than the response to unpolarized light stimuli. Taken together, the spatial and chromatic properties of the neurons may be suited to signal azimuthal directions based on a combination of the spectral gradient and the polarization pattern of the sky. PMID:17401118

  9. Polarization induced two dimensional confinement of carriers in wedge shaped polar semiconductors

    PubMed Central

    Deb, S.; Bhasker, H. P.; Thakur, Varun; Shivaprasad, S. M.; Dhar, S.

    2016-01-01

    A novel route to achieve two dimensional (2D) carrier confinement in a wedge shaped wall structure made of a polar semiconductor has been demonstrated theoretically. Tapering of the wall along the direction of the spontaneous polarization leads to the development of charges of equal polarity on the two inclined facades of the wall. Polarization induced negative (positive) charges on the facades can push the electrons (holes) inward for a n-type (p-type) material which results in the formation of a 2D electron (hole) gas at the central plane and ionized donors (acceptors) at the outer edges of the wall. The theory shows that this unique mode of 2D carrier confinement can indeed lead to a significant enhancement of carrier mobility. It has been found that the reduced dimensionality is not the only cause for the enhancement of mobility in this case. Ionized impurity scattering, which is one of the major contributer to carrier scattering, is significantly suppressed as the carriers are naturally separated from the ionized centers. A recent experimental finding of very high electron mobility in wedge shaped GaN nanowall networks has been analyzed in the light of this theoretical reckoning. PMID:27210269

  10. Polarization induced two dimensional confinement of carriers in wedge shaped polar semiconductors.

    PubMed

    Deb, S; Bhasker, H P; Thakur, Varun; Shivaprasad, S M; Dhar, S

    2016-01-01

    A novel route to achieve two dimensional (2D) carrier confinement in a wedge shaped wall structure made of a polar semiconductor has been demonstrated theoretically. Tapering of the wall along the direction of the spontaneous polarization leads to the development of charges of equal polarity on the two inclined facades of the wall. Polarization induced negative (positive) charges on the facades can push the electrons (holes) inward for a n-type (p-type) material which results in the formation of a 2D electron (hole) gas at the central plane and ionized donors (acceptors) at the outer edges of the wall. The theory shows that this unique mode of 2D carrier confinement can indeed lead to a significant enhancement of carrier mobility. It has been found that the reduced dimensionality is not the only cause for the enhancement of mobility in this case. Ionized impurity scattering, which is one of the major contributer to carrier scattering, is significantly suppressed as the carriers are naturally separated from the ionized centers. A recent experimental finding of very high electron mobility in wedge shaped GaN nanowall networks has been analyzed in the light of this theoretical reckoning. PMID:27210269

  11. Polarization induced two dimensional confinement of carriers in wedge shaped polar semiconductors

    NASA Astrophysics Data System (ADS)

    Deb, S.; Bhasker, H. P.; Thakur, Varun; Shivaprasad, S. M.; Dhar, S.

    2016-05-01

    A novel route to achieve two dimensional (2D) carrier confinement in a wedge shaped wall structure made of a polar semiconductor has been demonstrated theoretically. Tapering of the wall along the direction of the spontaneous polarization leads to the development of charges of equal polarity on the two inclined facades of the wall. Polarization induced negative (positive) charges on the facades can push the electrons (holes) inward for a n-type (p-type) material which results in the formation of a 2D electron (hole) gas at the central plane and ionized donors (acceptors) at the outer edges of the wall. The theory shows that this unique mode of 2D carrier confinement can indeed lead to a significant enhancement of carrier mobility. It has been found that the reduced dimensionality is not the only cause for the enhancement of mobility in this case. Ionized impurity scattering, which is one of the major contributer to carrier scattering, is significantly suppressed as the carriers are naturally separated from the ionized centers. A recent experimental finding of very high electron mobility in wedge shaped GaN nanowall networks has been analyzed in the light of this theoretical reckoning.

  12. Measurement of energy contrast of amplified ultrashort pulses using cross-polarized wave generation and spectral interferometry.

    PubMed

    Iliev, Marin; Meier, Amanda K; Galloway, Benjamin; Adams, Daniel E; Squier, Jeff A; Durfee, Charles G

    2014-07-28

    We present a method using spectral interferometry (SI) to characterize a pulse in the presence of an incoherent background such as amplified spontaneous emission (ASE). The output of a regenerative amplifier is interfered with a copy of the pulse that has been converted using third-order cross-polarized wave generation (XPW). The ASE shows as a pedestal background in the interference pattern. The energy contrast between the short-pulse component and the ASE is retrieved. The spectra of the interacting beams are obtained through an improvement to the self-referenced spectral interferometry (SRSI) analysis. PMID:25089416

  13. EXSAA: Environmentally-Induced X-ray Spectral Analysis Automation

    NASA Astrophysics Data System (ADS)

    Fallon, F. W.; Clark, P. E.; Rilee, M. L.; Truszkowski, W.

    2005-05-01

    X-ray fluorescence (XRF) spectrometry is one of the principal means of compositional analysis in the lab and in the field: it will be a central tool in NASA's Exploration Initiative (EI) missions. No currently available XRF software has the generic functionality to provide the basis for XRF experiment design, instrument development, and data interpretation for the suite of prospective EI missions. In response to this need, we have developed EXSAA (Environmentally-induced X-ray Spectral Analysis Automation), a generic, fast, interactive spectral simulation tool which can be used in assessing broadband continuous spectra being generated and detected during reconnaissance missions and field campaigns involving planetary surfaces. The software produces model spectra of detectable environmentally-induced X-ray spectra from fundamental principles for target characteristics and conditions likely to be experienced in remote or in situ planetary missions. Fluorescence is modeled following Jenkins and DeVries (1967); coherent and Compton scattering following Hubbell (1969). The modeling provided is extensible, and a user interface provides for selection of source, detector characteristics, compositional components, and geometry for known targets. An immediate application of the tool is the prediction for mission planning purposes of X-ray flux to be expected for a range of targets and instrumentation. A longer-term application is the model basis for the recovery of surface composition from actual missions, where some parameters (e.g. source flux) will be known, and others obtained from a Bayesian analysis of the observations. Ultimately, EXSAA could function as part of the agent-based SAA Toolkit being developed by a group of physical scientists, systems engineers, and AI practitioners to automate portions of the spectral analysis process. EXSAA could be called on by human or machine agents to provide an understanding of XRF phenomena for tasks including specifically (1

  14. Ex vivo assessment of carbon tetrachloride (CCl(4))-induced chronic injury using polarized light spectroscopy.

    PubMed

    Ahmad, Manzoor; Ali, Safdar; Mehmood, Malik Sajjad; Ali, Hamid; Khurshid, Ahmat; Firdous, Shamaraz; Muhammad, Saleh; Ikram, Masroor

    2013-12-01

    The liver performs various functions, such as the production and detoxification of chemicals; therefore, it is susceptible to hepatotoxins such as carbon tetrachloride (CCl4), which causes chronic injury. Thus, assessment of injury and its status of severity are of prime importance. Current work reports an ex vivo study for probing the severance of hepatic injury induced by CCl4 with polarized light over the spectral range 400-800 nm. Different concentrations of CCl4 were used to induce varying severity of hepatic injury in a rat model. Linear retardance, depolarization rates, and diagonal Mueller matrix elements (m22, m33, and m44), were successfully used as the distinguishing criterion for normal and different liver injuries. Our results show that linear retardance for injured liver samples with lower doses of CCl4 tends to increase when compared with normal liver samples, while samples injured at higher doses of CCl4 offer almost no retardance. Total, linear, and circular depolarizations follow decreasing trends with increased liver injury severity over the entire investigated wavelength range. Linear polarization states were observed to be better maintained as compared to circular polarization states for all samples. Furthermore, numerical values of diagonal elements of the experimentally measured Mueller matrix also increase with increasing doses of CCl4. Liver fibroses, change in transport albedo, and the relative refractive index of the extracellular matrix caused by CCl4 are responsible for the observed differences. These results will provide a pathway to gauge the severity of injury caused by toxic chemicals. PMID:24359651

  15. Building Better Electrodes for Electrical Resistivity and Induced Polarization Data

    NASA Astrophysics Data System (ADS)

    Adkins, P. L.; La Brecque, D. J.

    2007-12-01

    In the third year of a project to understand and mitigate the systematic noise in resistivity and induced polarization measurements, we put a significant effort into understanding and developing better electrodes. The simple metal electrodes commonly used for both transmitting and receiving of electrical geophysical data are likely the Achilles" heal of the resistivity method. Even stainless steel, a commonly used electrode material because of its durability, showed only average results in laboratory tests for electrode noise. Better results have been found with non-polarizing metal-metal salt electrodes, which are widely used as surface electrodes and in IP surveys. But although they produce small measurement errors, they are not durable enough for in-situ borehole resistivity surveys, and often contain compounds that are toxic to the environment. They are also very seldom used as transmitters. In laboratory studies, we are exploring other materials and configurations for low-noise compound electrodes that will be nontoxic, inexpensive, and durable and can be used as both transmitters and receivers. Testing of the electrical noise levels of electrodes is an arduous task involving repeated measurements under varying conditions at field scales. Thus it is important to find methods of sorting out likely candidates from the mass of possible electrode configurations and construction methods. Testing of electrode impedance versus current density appears to provide simple criteria for predicting the suitability of electrodes. The best electrodes show relatively low overall contact impedance, relatively small changes in impedance with increased current density, and relatively small changes in impedance with time. Furthermore it can be shown that resistivity and induced polarization performance of electrodes is strongly correlated, so that methods of finding electrodes with low impedance and good direct current performance usually provide better quality induced

  16. Para-hydrogen induced polarization in heterogeneous hydrogenationreactions

    SciTech Connect

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

    2007-01-31

    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.

  17. Changes in the spectrum, in the spectral degree of polarization, and in the spectral degree of coherence of a partially coherent beam propagating through a gradient-index fiber.

    PubMed

    Roychowdhury, Hema; Agrawal, Govind P; Wolf, Emil

    2006-04-01

    Expressions are derived for the cross-spectral density matrix of an electromagnetic Gaussian Schell-model beam propagating through a paraxial ABCD system. Using the recently developed unified theory of coherence and polarization of electromagnetic beams and the ABCD matrix for gradient-index fibers, we study the changes of the spectral density, of the spectral degree of polarization, and of the spectral degree of coherence of such a beam as it travels through the fiber. Effects of material dispersion are also considered. PMID:16604779

  18. Polarization-induced resistive switching behaviors in complex oxide heterostructures

    NASA Astrophysics Data System (ADS)

    Wu, Lei; Zhang, Chao; Dong, Chunhui; Jia, Chenglong; Jiang, Changjun; Xue, Desheng

    2015-09-01

    Complex oxide heterostructures are fabricated by growing La0.67Ca0.33MnO3 films on ferroelectric 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (011) single-crystal substrates. The nonvolatile or pulsed resistive switching behaviors induced by an electric field are achieved simultaneously. Further analyses indicate that the different resistive switching behaviors are resulted from co-control of piezostrain and polarization current effects. With decreasing in-plane read current from 0.1 mA to 0.001 mA, the polarization current effect gradually begins to play a more important role than the piezostrain effect. Consequently, the nonvolatile resistive switching behavior is converted to pulse resistive switching behavior. The results further enhance the application of complex oxides in multifunctional memory devices.

  19. Eustatic sea level fluctuations induced by polar wander

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  20. Field-resolved measurement of reaction-induced spectral densities by polarizability response spectroscopy

    NASA Astrophysics Data System (ADS)

    Moran, Andrew M.; Nome, Rene A.; Scherer, Norbert F.

    2007-11-01

    The experimental design and theoretical description of a novel five-pulse laser spectroscopy is presented with an application to a pyridinium charge transfer complex in acetonitrile and methanol. In field-resolved polarizability response spectroscopy (PORS), an electronically resonant laser pulse first excites a solvated chromophore (reactant) and off-resonant Raman spectra of the resulting nuclear motions are measured as a function of the reaction time. The present apparatus differs from our earlier design by performing the Raman probe measurement (with fixed pulse delays) in the frequency domain. In addition, the full electric fields of the signals are measured by spectral interferometry to separate nonresonant and Raman responses. Our theoretical model shows how the PORS signal arises from nuclear motions that are displaced/driven by the photoinduced reaction. The field-resolved off-resonant (of the solute's electronic transitions) probing favors detection of solvent (as opposed to solute) dynamics coupled to the reaction. The sign of the signal represents the relative strengths of polarization responses associated with the ground and photoexcited solutions. Signatures of nonresonant and PORS signal contributions to the experimental results are analyzed with numerical calculations based on a theoretical model we have developed for reaction-induced PORS. Our model identifies two mechanisms of PORS signal generation: (i) structural relaxation induced resonance; (ii) dephasing induced resonance. In the charge transfer reaction investigated, the solvent-dependent and time-evolving (solvent) polarizability spectral density (PSD) is readily obtained. The general trend of an initial broadband inertial nuclear response followed by a decrease in the linewidth of the PSD establishes that the measured PSD is inconsistent with the approximation of a linear response. Furthermore, the explicit time evolution of the PSD is important for properly describing solvent control of

  1. Field-resolved measurement of reaction-induced spectral densities by polarizability response spectroscopy

    SciTech Connect

    Moran, Andrew M.; Nome, Rene A.; Scherer, Norbert F.

    2007-11-14

    The experimental design and theoretical description of a novel five-pulse laser spectroscopy is presented with an application to a pyridinium charge transfer complex in acetonitrile and methanol. In field-resolved polarizability response spectroscopy (PORS), an electronically resonant laser pulse first excites a solvated chromophore (reactant) and off-resonant Raman spectra of the resulting nuclear motions are measured as a function of the reaction time. The present apparatus differs from our earlier design by performing the Raman probe measurement (with fixed pulse delays) in the frequency domain. In addition, the full electric fields of the signals are measured by spectral interferometry to separate nonresonant and Raman responses. Our theoretical model shows how the PORS signal arises from nuclear motions that are displaced/driven by the photoinduced reaction. The field-resolved off-resonant (of the solute's electronic transitions) probing favors detection of solvent (as opposed to solute) dynamics coupled to the reaction. The sign of the signal represents the relative strengths of polarization responses associated with the ground and photoexcited solutions. Signatures of nonresonant and PORS signal contributions to the experimental results are analyzed with numerical calculations based on a theoretical model we have developed for reaction-induced PORS. Our model identifies two mechanisms of PORS signal generation: (i) structural relaxation induced resonance; (ii) dephasing induced resonance. In the charge transfer reaction investigated, the solvent-dependent and time-evolving (solvent) polarizability spectral density (PSD) is readily obtained. The general trend of an initial broadband inertial nuclear response followed by a decrease in the linewidth of the PSD establishes that the measured PSD is inconsistent with the approximation of a linear response. Furthermore, the explicit time evolution of the PSD is important for properly describing solvent control of

  2. Design and fabrication of thin-film polarizer at wavelength of 1540 nm and investigation of its laser-induced damage threshold

    NASA Astrophysics Data System (ADS)

    Sahraee, Masoume; Fallah, Hamid Reza; Moradi, Badri; Zabolian, Hosein; Mahmoodzade, Morteza Haji

    2014-12-01

    In this paper a thin-film polarizer at a wavelength of 1540 nm was designed and fabricated. These types of polarizer are usually used in laser systems to obtain linearly polarized light beams. Our design consists of a system of eighteen dielectric thin-film layers from repeated pairs of titanium dioxide and silicon dioxide layers that are deposited on a BK7 glass substrate. Design was carried out based on theoretical principles and computer calculations. Thin-film design software was used for designing the polarizer. The angle of incidence was supposed to be 56° that is the Browster angle for BK7 glass. Performance and laser-induced damage threshold of the polarizer were enhanced by a suitable selection of various parameters including thickness of each layer, their number and the electric field distribution of layers. After several designs, fabrications and refinement of parameters, the final polarizer was designed. Then the final sample of the polarizer was prepared using the electron beam evaporation (EBE) technique with Balzers BAK 760 coating machine. Spectral transmittance of the sample was measured by Shimadzu 3100 UV-VIS-NIR spectrophotometer. Investigation of spectral transmittance showed that at a wavelength of 1540nm, the transmission of P polarization is 87.82 and the transmission of S polarization is 0.43 which show a ratio ( T P / T S of 204. So, this ratio is an acceptable value for our desired polarizer.

  3. Polarization dependent, surface plasmon induced photoconductance in gold nanorod arrays

    NASA Astrophysics Data System (ADS)

    Diefenbach, S.; Erhard, N.; Schopka, J.; Martin, A.; Karnetzky, C.; Iacopino, D.; Holleitner, A. W.

    2014-03-01

    We report on the photoconductance in two-dimensional arrays of gold nanorods which is strongly enhanced at the frequency of the longitudinal surface plasmon of the nanorods. The arrays are formed by a combination of droplet deposition and stamping of gold nanorod solutions on SiO2 substrates. We find that the plasmon induced photoconductance is sensitive to the linear polarization of the exciting photons. We interpret the occurrence of the photoconductance as a bolometric enhancement of the arrays' conductance upon excitation of the longitudinal surface plasmon resonance of the nanorods.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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

  5. LINE-INTERLOCKING EFFECTS ON POLARIZATION IN SPECTRAL LINES BY RAYLEIGH AND RAMAN SCATTERING

    SciTech Connect

    Sampoorna, M.; Nagendra, K. N.; Stenflo, J. O. E-mail: knn@iiap.res.in

    2013-06-20

    The polarized spectrum of the Sun and stars is formed from the scattering of anisotropic radiation on atoms. Interpretation of this spectrum requires the solution of polarized line transfer in multilevel atomic systems. While sophisticated quantum theories of polarized line formation in multilevel atomic systems exist, they are limited by the approximation of complete frequency redistribution in scattering. The partial frequency redistribution (PRD) in line scattering is a necessary component in modeling the polarized spectra of strong lines. The polarized PRD line scattering theories developed so far confine themselves to a two-level or a two-term atom model. In this paper, we present a heuristic approach to the problem of polarized line formation in multilevel atoms taking into account the effects of PRD and a weak magnetic field. Starting from the unpolarized PRD multilevel atom approach of Hubeny et al., we incorporate the polarization state of the radiation field. However, the lower level polarization is neglected. Two iterative methods of solving the polarized PRD line transfer in multilevel atoms are also presented. Taking the example of a five-level Ca II atom model, we present illustrative results for an isothermal one-dimensional model atmosphere.

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

    SciTech Connect

    Moysey, Stephen; Dean, Delphine; Dimitrios, Ntarlagiannis

    2013-11-13

    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

  7. Quantifying microbe-mineral interactions leading to remotely detectable induced polarization signals

    SciTech Connect

    Ntarlagiannis, Dimitrios; Moysey, Stephen; Dean, Delphine

    2013-11-14

    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

  8. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    PubMed Central

    Ye, Tianyu; Liu, Han-Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

    2015-01-01

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ. PMID:26450679

  9. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation.

    PubMed

    Ye, Tianyu; Liu, Han-Chun; Wang, Zhuo; Wegscheider, W; Mani, Ramesh G

    2015-01-01

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ. PMID:26450679

  10. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    SciTech Connect

    Ye, Tianyu; Liu, Han -Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

    2015-10-09

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. As a result, for circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ.

  11. Recombination emissions and spectral blueshift of pump radiation from ultrafast laser induced plasma in a planar water microjet

    NASA Astrophysics Data System (ADS)

    Anija, M.; Philip, Reji

    2009-09-01

    We report spectroscopic investigations of an ultrafast laser induced plasma generated in a planar water microjet. Plasma recombination emissions along with the spectral blueshift and broadening of the pump laser pulse contribute to the total emission. The laser pulses are of 100 fs duration, and the incident intensity is around 10 15 W/cm 2. The dominant mechanisms leading to plasma formation are optical tunnel ionization and collisional ionization. Spectrally resolved polarization measurements show that the high frequency region of the emission is unpolarized whereas the low frequency region is polarized. Results indicate that at lower input intensities the emission arises mainly from plasma recombinations, which is accompanied by a weak blueshift of the incident laser pulse. At higher input intensities strong recombination emissions are seen, along with a broadening and asymmetric spectral blueshift of the pump laser pulse. From the nature of the blueshifted laser pulse it is possible to deduce whether the rate of change of free electron density is a constant or variable within the pulse lifetime. Two input laser intensity regimes, in which collisional and tunnel ionizations are dominant respectively, have been thus identified.

  12. Spectral-domain measurement of the strain sensitivity of phase modal birefringence of polarization-maintaining optical fibers

    NASA Astrophysics Data System (ADS)

    Kaczmarek, Cezary

    2016-09-01

    The paper presents a new and simple method of measuring the strain sensitivity of phase modal birefringence (dΔn/dε) of polarization maintaining fibers (PMFs). The method is based on measuring the spectral strain sensitivity of a strain sensor in the configuration of a Sagnac interferometer with a PMF. The measured spectral strain sensitivity of the sensor is used to determine the strain sensitivity of phase modal birefringence and the polarimetric strain sensitivity of the PMF. In addition, a new procedure for determining the sign of the strain sensitivity of phase and group modal birefringence of a PMF. Using this method, measurements of the strain sensitivity of modal birefringence of PMFs were performed: a PM-PCF and a Bow-Tie fiber, in the wavelength range 1460-1600 nm. A comparison of the results of these measurements with results obtained using other methods for the same types of fibers is presented.

  13. Visible and near-infrared spectral survey of Martian meteorites stored at the National Institute of Polar Research

    NASA Astrophysics Data System (ADS)

    Hiroi, Takahiro; Kaiden, Hiroshi; Misawa, Keiji; Niihara, Takafumi; Kojima, Hideyasu; Sasaki, Sho

    2011-09-01

    Martian meteorite chip samples stored at the National Institute of Polar Research (NIPR) have been studied by a visible and near-infrared (VNIR) spectrometer. Measured spots are about 3 × 2 mm in size, which are clearly marked on photographs of the meteorite chips. Rock types and approximate mineral compositions of studied meteorites have been identified or obtained through this spectral survey with no sample preparation required. This study demonstrates that this kind of spectral survey is effective in classifying and describing Marian meteorites, and that such a VNIR spectrometer on a Mars rover would be useful for identifying these kinds of unaltered Mars rocks. Further studies which utilize a smaller spot size are desired for improving the accuracy of identifying the clasts and mineral phases in the rocks.

  14. Satellite observations of polar mesospheric clouds by the solar backscattered ultraviolet spectral radiometer - Evidence of a solar cycle dependence

    NASA Technical Reports Server (NTRS)

    Thomas, Gary E.; Mcpeters, Richard D.; Jensen, Eric J.

    1991-01-01

    Results are presented on eight years of satellite observations of the polar mesospheric clouds (PMCs) by the SBUV spectral radiometer, showing that PMCs occur in the summertime polar cap regions of both hemispheres and that they exhibit year-to-year variability. It was also found that the increase in the PMC occurrence frequency was inversely correlated with solar activity. Two kinds of hemispherical asymmetries could be identified: (1) PMCs in the Northern Hemisphere were significantly brighter than in the Southern Hemisphere, in accordance with previous results derived from SME data; and (2) the solar cycle response in the south is more pronounced than in the north. The paper also describes the cloud detection algorithm.

  15. Spectral, kinetic and polarization characteristics of luminescence of acriflavine in polymeric matrix under pulsed excitation with different durations and intensities

    NASA Astrophysics Data System (ADS)

    Kaputskaya, I. A.; Ermilov, E. A.; Tannert, S.; Röder, B.; Gorbatsevich, S. K.

    2006-08-01

    Spectral, kinetic and polarization characteristics of fluorescence and thermally activated delayed fluorescence (TADF) of dye solid solutions have been investigated. It was shown that the increasing of the excitation pulse duration results in rise of TADF decay time, but an increasing of the long pulse excitation intensity results in a faster TADF decay. In the presence of Förster resonance energy transfer (FRET) the fluorescence spectrum is shifting non-monotonically with time when the intensity of the excitation pulse is high. At the time moment when the excitation is switched off the polarization degree of luminescence of the concentrated dye solutions strongly reduces. The energy transfer from the molecules in the S 1 state to the molecules in the T 1 state reduces the depolarization of luminescence caused by FRET. Numerical simulations were made by means of Monte-Carlo integrations and results were compared with experimental data obtained for acriflavine in polyvinyl alcohol films.

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

    SciTech Connect

    Girart, J. M.; Patel, N.; Vlemmings, W. H. T.; Rao, Ramprasad

    2012-05-20

    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.

  17. Single-Shot Measurement of Temporally-Dependent Polarization State of Femtosecond Pulses by Angle-Multiplexed Spectral-Spatial Interferometry

    PubMed Central

    Lin, Ming-Wei; Jovanovic, Igor

    2016-01-01

    We demonstrate that temporally-dependent polarization states of ultrashort laser pulses can be reconstructed in a single shot by use of an angle-multiplexed spatial-spectral interferometry. This is achieved by introducing two orthogonally polarized reference pulses and interfering them with an arbitrarily polarized ultrafast pulse under measurement. A unique calibration procedure is developed for this technique which facilitates the subsequent polarization state measurements. The accuracy of several reconstructed polarization states is verified by comparison with that obtained from an analytic model that predicts the polarization state on the basis of its method of production. Laser pulses with mJ-level energies were characterized via this technique, including a time-dependent polarization state that can be used for polarization-gating of high-harmonic generation for production of attosecond pulses. PMID:27596951

  18. Single-Shot Measurement of Temporally-Dependent Polarization State of Femtosecond Pulses by Angle-Multiplexed Spectral-Spatial Interferometry.

    PubMed

    Lin, Ming-Wei; Jovanovic, Igor

    2016-01-01

    We demonstrate that temporally-dependent polarization states of ultrashort laser pulses can be reconstructed in a single shot by use of an angle-multiplexed spatial-spectral interferometry. This is achieved by introducing two orthogonally polarized reference pulses and interfering them with an arbitrarily polarized ultrafast pulse under measurement. A unique calibration procedure is developed for this technique which facilitates the subsequent polarization state measurements. The accuracy of several reconstructed polarization states is verified by comparison with that obtained from an analytic model that predicts the polarization state on the basis of its method of production. Laser pulses with mJ-level energies were characterized via this technique, including a time-dependent polarization state that can be used for polarization-gating of high-harmonic generation for production of attosecond pulses. PMID:27596951

  19. Self-phase-modulation induced spectral broadening in silicon waveguides

    NASA Astrophysics Data System (ADS)

    Boyraz, Ozdal; Indukuri, Tejaswi; Jalali, Bahram

    2004-03-01

    The prospect for generating supercontinuum pulses on a silicon chip is studied. Using ~4ps optical pulses with 2.2GW/cm2 peak power, a 2 fold spectral broadening is obtained. Theoretical calculations, that include the effect of two-photon-absorption, indicate up to 5 times spectral broadening is achievable at 10x higher peak powers. Representing a nonlinear loss mechanism at high intensities, TPA limits the maximum optical bandwidth that can be generated.

  20. Spin-polarized semiconductor induced by magnetic impurities in graphene

    NASA Astrophysics Data System (ADS)

    Daghofer, Maria

    2011-03-01

    Magnetic impurities adsorbed on graphene sheets are coupled antiferromangetically via the itinerant electrons in the graphene. We study this interaction and its impact on the electrons' spectral density by use of unbiased Monte-Carlo simulations. The antiferromagnetic order breaks the symmetry between the sublattices, and a gap for the itinerant electrons opens. Our simulations show that the itinerant states below and above the gap are not dispersionless states trapped by the impurities, but are instead mobile states with a large dispersion. We compare various scenarios for the impurity distribution and find that random doping produces a standard semiconductor. If, on the other hand, all or most of the impurities are localized in the same sublattice, the spin degeneracy is lifted and the conduction band becomes spin-polarized. We also discuss the properties of edge states at edges or magnetic domain boundaries. M.~Daghofer, N.~Zheng, A.~Moreo; Phys.~Rev.~B 82, 121405(R) (2010) Supported by the DFG under the Emmy-Noether Program, and the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. DOE.

  1. Cytoskeletal tension induces the polarized architecture of the nucleus

    PubMed Central

    Kim, Dong-Hwee; Wirtz, Denis

    2016-01-01

    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

  2. Polar behaviour induced by lithium in potassium tantalate ceramics

    NASA Astrophysics Data System (ADS)

    Tkach, A.; Almeida, A.; Agostinho Moreira, J.; Chaves, M. R.; Espinha, A.; Vilarinho, P. M.

    2012-02-01

    Polar behaviour in K1-xLixTaO3 ceramics with x = 0.02, 0.05 and 0.10, processed by the conventional solid state method, is studied by Raman spectroscopy and thermally stimulated depolarization current (TSDC) techniques between 10 and 290 K. The TO1 mode of KTaO3 is revealed to harden in the whole temperature range and to split in the low-temperature range by Li doping. One splitting is observed for x = 0.02 and two consequent splittings are detected for x = 0.05 and 0.10. The temperatures, where TO1 mode splitting occurs, are found to correspond to those of the peaks of TSDC, and hence to the onset of the electric polarization. Such behaviour provides evidence for the order-disorder ferroelectric phase transition induced in KTaO3 by lithium doping, which emerges from deformations of the cubic phase developed on cooling either in one (for x = 0.02) or two steps (for x = 0.05 and 0.10).

  3. High-resolution ultraviolet spectral irradiance monitoring program in polar regions - nearly a decade of data available to polar researchers in ozone and ultraviolet-related studies

    SciTech Connect

    Booth, C.R.; Lucas, T.B.; Mestechkina, T.; Tusson, J. IV

    1994-12-31

    The Antarctic Ultraviolet Spectroradiometer Monitoring Network was established by the U.S. National Science Foundation (NSF) in 1988 in response to predictions of increased ultraviolet (UV) radiation in the polar regions. It is the first automated, high-resolution UV scanning spectroradiometer network installed in the world. The network consists of five automated, high-resolution spectroradiometers, placed in strategic locations in Antarctica and the Arctic, and one established in San Diego to collect data and serve as a training and testing facility. The network, which makes essential measurements of UV spectral irradiance, has been successfully operated in the harshest environments of Antarctica and the Arctic. It is currently returning data to researchers studying the effects of ozone depletion on terrestrial and marine biological systems, as well as being used to develop and verify models of atmospheric light transmission. 24 refs., 1 fig., 2 tabs.

  4. Self-induced spectral splits in supernova neutrino fluxes

    SciTech Connect

    Raffelt, Georg G.; Smirnov, Alexei Yu.

    2007-10-15

    In the dense-neutrino region above the neutrino sphere of a supernova (r < or approx. 400 km), neutrino-neutrino refraction causes collective flavor transformations. They can lead to 'spectral splits' where an energy E{sub split} splits the transformed spectrum sharply into parts of almost pure but different flavors. Unless there is an ordinary MSW resonance in the dense-neutrino region, E{sub split} is determined by flavor-lepton number conservation alone. Spectral splits are created by an adiabatic transition between regions of large and small neutrino density. We solve the equations of motion in the adiabatic limit explicitly and provide analytic expressions for a generic example.

  5. A fluctuation-induced plasma transport diagnostic based upon fast-Fourier transform spectral analysis

    NASA Technical Reports Server (NTRS)

    Powers, E. J.; Kim, Y. C.; Hong, J. Y.; Roth, J. R.; Krawczonek, W. M.

    1978-01-01

    A diagnostic, based on fast Fourier-transform spectral analysis techniques, that provides experimental insight into the relationship between the experimentally observable spectral characteristics of the fluctuations and the fluctuation-induced plasma transport is described. The model upon which the diagnostic technique is based and its experimental implementation is discussed. Some characteristic results obtained during the course of an experimental study of fluctuation-induced transport in the electric field dominated NASA Lewis bumpy torus plasma are presented.

  6. SPECTRAL POLARIZATION OF THE REDSHIFTED 21 cm ABSORPTION LINE TOWARD 3C 286

    SciTech Connect

    Wolfe, Arthur M.; Jorgenson, Regina A.; Robishaw, Timothy; Heiles, Carl; Xavier Prochaska, J. E-mail: raj@ast.cam.ac.uk E-mail: heiles@astro.berkeley.edu

    2011-05-20

    A reanalysis of the Stokes-parameter spectra obtained of the z = 0.692 21 cm absorption line toward 3C 286 shows that our original claimed detection of Zeeman splitting by a line-of-sight magnetic field, B{sub los} = 87 {mu}G, is incorrect. Because of an insidious software error, what we reported as Stokes V is actually Stokes U: the revised Stokes V spectrum indicates a 3{sigma} upper limit of B{sub los}< 17 {mu}G. The correct analysis reveals an absorption feature in fractional polarization that is offset in velocity from the Stokes I spectrum by -1.9 km s{sup -1}. The polarization position-angle spectrum shows a dip that is also significantly offset from the Stokes I feature, but at a velocity that differs slightly from the absorption feature in fractional polarization. We model the absorption feature with three velocity components against the core-jet structure of 3C 286. Our {chi}{sup 2} minimization fitting results in components with differing (1) ratios of H I column density to spin temperature, (2) velocity centroids, and (3) velocity dispersions. The change in polarization position angle with frequency implies incomplete coverage of the background jet source by the absorber. It also implies a spatial variation of the polarization position angle across the jet source, which is observed at frequencies higher than the 839.4 MHz absorption frequency. The multi-component structure of the gas is best understood in terms of components with spatial scales of {approx}100 pc comprised of hundreds of low-temperature (T {<=} 200 K) clouds with linear dimensions of <<100 pc. We conclude that previous attempts to model the foreground gas with a single uniform cloud are incorrect.

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

    SciTech Connect

    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.

    2014-12-15

    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.

  8. Optimized Spectral Editing of 13C MAS NMR Spectra of Rigid Solids Using Cross-Polarization Methods

    NASA Astrophysics Data System (ADS)

    Sangill, R.; Rastrupandersen, N.; Bildsoe, H.; Jakobsen, H. J.; Nielsen, N. C.

    Combinations of 13C magic-angle spinning (MAS) NMR experiments employing cross polarization (CP), cross polarization-depolarization (CPD), and cross polarization-depolarization-repolarization are analyzed quantitatively to derive simple and general procedures for optimized spectral editing of 13C CP/MAS NMR spectra of rigid solids by separation of the 13C resonances into CH n subspectra ( n = 0, 1, 2, and 3). Special attention is devoted to a differentiation by CPD/MAS of CH and CH 2 resonances since these groups behave quite similarly during spin lock under Hartmann-Hahn match and are therefore generally difficult to distinguish unambiguously. A general procedure for the design of subexperiments and linear combinations of their spectra to provide optimized signal-to-noise ratios for the edited subspectra is described. The technique is illustrated by a series of edited 13C CP/MAS spectra for a number of rigid solids ranging from simple organic compounds (sucrose and l-menthol) to complex pharmaceutical products (calcipotriol monohydrate and vitamin D 3) and polymers (polypropylene, polyvinyl alcohol, polyvinyl chloride, and polystyrene).

  9. Organizing and utilizing the imaging and spectral data from Polar BEAR

    NASA Astrophysics Data System (ADS)

    del Greco, F. P.; Huffman, R. E.; Larrabee, J. C.; Eastes, R. W.; Leblanc, F. J.

    1988-01-01

    The AIRS instrument (Auroral Ionospheric Remote Sensor) was launched into a 1000 km polar orbit aboard the Polar BEAR satellite on November 13, 1986. Optical data from AIRS are obtained at two vacuum ultraviolet wavelengths at the output of a grating monochromator and from two ultraviolet-visible wavelengths at the output of fixed filter photometers. Normally data are transmitted when the satellite is above 45 degrees North latitude; the primary receiving sites are permanent stations at Tromso, Norway and Sondrestrom, Greeland and a portable station often sited near Seattle, Washington, USA. During its first year of operation AIRS has provided imaging data at fixed wavelengths or nadir-looking spectrometer data from the vacuum ultraviolet and simultaneous imaging or photometric data from the fixed filters.

  10. Adaptation of the University of Wisconsin High Spectral Resolution Lidar for Polarization and Multiple Scattering Measurements

    NASA Technical Reports Server (NTRS)

    Eloranta, E. W.; Piironen, P. K.

    1992-01-01

    A new implementation of the High Spectral Resolution Lidar (HSRL) in an instrument van which allows measurements during field experiments is described. The instrument was modified to provide measurements of depolarization. In addition, both the signal amplitude and depolarization variations with receiver field of view are simultaneously measured. These modifications allow discrimination of ice clouds from water clouds and observation of multiple scattering contributions to the lidar return.

  11. Spectral-Content Readout Of Stress-Induced Birefringence

    NASA Technical Reports Server (NTRS)

    Redner, Alex S.; Voloshin, Arkady S.

    1992-01-01

    Spectrum of transmitted light indicates stress in sensor or specimen. Photoelastic apparatus demonstrates feasibility of analysis of spectrum of transmitted light to quantify birefringence in transparent specimen. By augmenting conventional photoelastic analysis with spectral sensors and automating it with computer control and processing of data, technique made more versatile and useful. Potential uses include measurement of stresses in optical fibers and transparent materials in general.

  12. Time-resolved spectral investigations of laser light induced microplasma

    NASA Astrophysics Data System (ADS)

    Nánai, L.; Hevesi, I.

    1992-01-01

    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 (λ = 0.694μm, type OGM-20,λ = 1.06μm with a home-made laser based on neodymium glass crystal, and λ = 10.6μm, 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 τ≈100 ns and slow front (tail) with τ≈1μs 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.

  13. Polarization induced electrospray ionization mass spectrometry for the analysis of liquid, viscous and solid samples.

    PubMed

    Meher, Anil Kumar; Chen, Yu-Chie

    2015-03-01

    In this study, a polarization-induced electrospray ionization mass spectrometry (ESI-MS) was developed. A micro-sized sample droplet was deposited on a naturally available dielectric substrate such as a fruit or a stone, and then placed close to (~2 mm) the orifice of a mass spectrometer applied with a high voltage. Taylor cone was observed from the sample droplet, and a spray emitted from the cone apex was generated. The analyte ion signals derived from the droplet were obtained by the mass spectrometer. The ionization process is similar to that in ESI although no direct electric contact was applied on the sample site. The sample droplet polarized by the high electric field provided by the mass spectrometer initiated the ionization process. The dielectric sample loading substrate facilitated further the polarization process, resulting in the formation of Taylor cone. The mass spectral profiles obtained via this approach resembled those obtained using ESI-MS. Multiply charged ions dominated the mass spectra of peptides and proteins, whereas singly charged ions dominated the mass spectra of small molecules such as amino acids and small organic molecules. In addition to liquid samples, this approach can be used for the analysis of solid and viscous samples. A small droplet containing suitable solvent (5-10 µl) was directly deposited on the surface of the solid (or viscous) sample, placed close the orifice of mass spectrometer applied with a high voltage. Taylor cone derived from the droplet was immediately formed followed by electrospray processes to generate gas-phase ions for MS analysis. Analyte ions derived from the main ingredients of pharmaceutical tablets and viscous ointment can be extracted into the solvent droplet in situ and observed using a mass spectrometer. PMID:25800179

  14. Influence of pore fluid chemistry on the complex conductivity and induced polarization responses of Berea sandstone

    NASA Astrophysics Data System (ADS)

    Lesmes, David P.; Frye, Kevin M.

    2001-01-01

    The spectral induced-polarization (IP) response of rocks and soils is a complex function of pore solution chemistry, sample microgeometry, and surface chemical properties. We measure the complex conductivity and the time domain IP responses of Berea sandstone as a function of pore fluid ionic strength and pH. Complex conductivity is measured over the frequency range 10-3 to 106 Hz, and chargeability is computed using a time window of 0.16 to 1.74 s. The field IP parameters: phase, percent frequency effect, and chargeability are functions of both the surface and bulk electrical properties of the sample and are observed to decrease with increasing solution conductivity. Dividing these parameters by the sample resistivity yields normalized IP parameters (quadrature conductivity, metal factor, normalized chargeability) that are proportional to the imaginary component of the complex surface conductivity. Normalized IP parameters increase with ionic strength up to concentrations of 10-1 M NaCl and show a reduced response at pH 3, the point of zero charge for quartz-dominated systems. For concentrations >10-1 M NaCl, the normalized parameters decrease with increasing concentration. This decrease in surface polarization may indicate a decrease in the effective mobility of polarizing charges at high solution concentration. Our data indicate that normalized IP parameters are directly related to the physiochemical parameters that control the surface conductivity responses of rocks and soils. Normalization of IP measurements in environmental investigations should increase the effectiveness of IP surveys, especially in high-conductivity environments.

  15. Spectral analysis of dike-induced earthquakes in Afar, Ethiopia

    NASA Astrophysics Data System (ADS)

    Tepp, Gabrielle; Ebinger, Cynthia J.; Yun, Sang-Ho

    2016-04-01

    Shallow dike intrusions may be accompanied by fault slip above the dikes, a superposition which complicates seismic and geodetic data analyses. The diverse volcano-tectonic and low-frequency local earthquakes accompanying the 2005-2010 large-volume dike intrusions in the Dabbahu-Manda Hararo rift (Afar), some with fault displacements of up to 3 m at the surface, provide an opportunity to examine the relations among the earthquakes, dike intrusions, and surface ruptures. We apply the frequency index (FI) method to characterize the spectra of swarm earthquakes from six of the dikes. These earthquakes often have broad spectra with multiple peaks, making the usual peak frequency classification method unreliable. Our results show a general bimodal character with high FI earthquakes associated with deeper dikes (top > 3 km subsurface) and low FI earthquakes associated with shallow dikes, indicating that shallow dikes result in earthquakes with more low-frequency content and larger-amplitude surface waves. Low FI earthquakes are more common during dike emplacement, suggesting that interactions between the dike and faults may lead to lower FI. Taken together, likely source processes for low FI earthquakes are shallow hypocenters (<3 km) possibly with surface rupture, slow rupture velocities, and interactions with dike fluids. Strong site effects also heavily influence the earthquake spectral content. Additionally, our results suggest a continuum of spectral responses, implying either that impulsive volcano-tectonic earthquakes and the unusual, emergent earthquakes have similar source processes or that simple spectral analyses, such as FI, cannot distinguish different source processes.

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

    DOEpatents

    Alfano, Robert R.; Demos, Stavros G.; Zhang, Gang

    2003-12-16

    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.

  17. Spectral hole-burning and stark effect: frequency dependence of the induced dipoe moment of a squaraine dye in polymers

    NASA Astrophysics Data System (ADS)

    Vauthey, Eric; Voss, Jochen; de Caro, Cosimo; Renn, Alois; Wild, Urs P.

    1994-06-01

    A study of the effect of an external electric field on spectral holes burnt at different frequencies in the inhomogeneous absorption band of a centrosymmetric squaraine dye, bis [4-(diethylamino)-2-hydroxyphenyl] squaraine (DEAH), in polymers of different polarity is presented. Average matrix induced dipole moment differences of about 1 D and 0.37 D were measured in the directions parallel and perpendicular to the long axis of DEAH. In all polymers investigated, the induced dipole moment difference decreased from the higher to the lower frequencies. Solvatochromic shift measurements were performed in order to elucidate the origin of this effect. The matrix field inducing the dipole moment is also partially responsible for the frequency shift of the absorption of DEAH. With increasing matrix field, the absorptiion frequency is shifted to the blue due to electrostatic interaction with the local dipoles of DEAH. The contribution of the electrostatic interactions to the frequency shift is smaller than the dispersion interactions by two orders of magnitude in polystyrene, but increases slightly in more polar polymers.

  18. Fluorescence in situ hybridization and spectral imaging analysisof human oocytes and first polar bodies

    SciTech Connect

    Weier, Heinz-Ulli G.; Weier, Jingly F.; Oter Renom, Maria; Zheng,Xuezhong; Colls, Pere; Nureddin, Aida; Pham, Chau D.; Chu, Lisa W.; Racowsky, Catherine; Munne, Santiago

    2004-10-06

    We investigated the frequencies of abnormalities involving either chromosome 1, 16, 18 or 21 in failed-fertilized human oocytes.While abnormalities involving chromosome 16 showed an age-dependant increase, results for the other chromosomes did not show statistically significant differences between the three age groups <35 yrs, 35-39 yrs, and >39 yrs. The scoring of four chromosomes is likely to underestimate the true rate of aneuploid cells. Thus, for a pilot study investigating a more comprehensive analysis of oocytes and their corresponding first polar bodies (1PBs), we developed a novel 8-probe chromosome enumeration scheme using FISH and SIm.

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

    NASA Astrophysics Data System (ADS)

    Quintana, Joel; Gonzalez, Virgilio

    2014-04-01

    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.

  20. Fluorescent Phosphorus Dendrimer as a Spectral Nanosensor for Macrophage Polarization and Fate Tracking in Spinal Cord Injury.

    PubMed

    Shakhbazau, Antos; Mishra, Manoj; Chu, Tak-Ho; Brideau, Craig; Cummins, Karen; Tsutsui, Shigeki; Shcharbin, Dzmitry; Majoral, Jean-Pierre; Mignani, Serge; Blanchard-Desce, Mireille; Bryszewska, Maria; Yong, V Wee; Stys, Peter K; van Minnen, Jan

    2015-11-01

    Dendrimers and dendriplexes, highly branched synthetic macromolecules, have gained popularity as new tools for a variety of nanomedicine strategies due to their unique structure and properties. We show that fluorescent phosphorus dendrimers are well retained by bone marrow-derived macrophages and exhibit robust spectral shift in its emission in response to polarization conditions. Fluorescence properties of this marker can also assist in identifying macrophage presence and phenotype status at different time points after spinal cord injury. Potential use of a single dendrimer compound as a drug/siRNA carrier and phenotype-specific cell tracer offers new avenues for enhanced cell therapies combined with monitoring of cell fate and function in spinal cord injury. PMID:26175127

  1. Voltage-induced conversion of helical to uniform nuclear spin polarization in a quantum wire

    NASA Astrophysics Data System (ADS)

    Kornich, Viktoriia; Stano, Peter; Zyuzin, Alexander A.; Loss, Daniel

    2015-05-01

    We study the effect of bias voltage on the nuclear spin polarization of a ballistic wire, which contains electrons and nuclei interacting via hyperfine interaction. In equilibrium, the localized nuclear spins are helically polarized due to the electron-mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Focusing here on nonequilibrium, we find that an applied bias voltage induces a uniform polarization, from both helically polarized and unpolarized spins available for spin flips. Once a macroscopic uniform polarization in the nuclei is established, the nuclear spin helix rotates with frequency proportional to the uniform polarization. The uniform nuclear spin polarization monotonically increases as a function of both voltage and temperature, reflecting a thermal activation behavior. Our predictions offer specific ways to test experimentally the presence of a nuclear spin helix polarization in semiconducting quantum wires.

  2. Spectral analysis of induced fluorescence in thyroid tissue

    NASA Astrophysics Data System (ADS)

    Giubileo, Gianfranco; Colao, Francesco; Rocchini, Paolo; Panzironi, Giuseppe

    2001-05-01

    In this paper thyroid samples have been analyzed by fluorescent technique and characterization of the spectral response has been performed by studying both emission and excitation fluorescence spectra. The measurements have been performed by using a double monochromator spectrofluorometer. The nature of the medium containing the tissue sample has resulted to be of great importance in eliminating spurious effects not related to the sample itself. Observations fulfilled on a number of samples will be reported and comparison between healthy tissue and tumor tissue will be discussed.

  3. Ocean color spectral variability studies using solar-induced chlorophyll fluorescence

    NASA Technical Reports Server (NTRS)

    Hoge, Frank E.; Swift, Robert N.

    1987-01-01

    It is suggested that chlorophyll-induced ocean color spectral variability can be studied using only a passive airborne spectroradiometer instrument, with solar-induced chlorophyll fluorescence used as the standard against which all correlations are performed. The intraspectral correlation (ISC) method is demonstrated with results obtained during an airborne mapping mission in the New York Bight. The curvature algorithm is applied to the solar-induced chlorophyll fluorescence at about 690 nm, and good agreement is found with results obtained using active-passive correlation spectroscopy. The ISC method has application to spectral variability and resulting chlorophyll concentration measurement in different environmental conditions and in different water types.

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

    NASA Astrophysics Data System (ADS)

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

    1998-07-01

    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.

  5. Reconstruction of CMB temperature anisotropies with primordial CMB induced polarization in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Liu, Guo-Chin; Ichiki, Kiyotomo; Tashiro, Hiroyuki; Sugiyama, Naoshi

    2016-07-01

    Scattering of cosmic microwave background (CMB) radiation in galaxy clusters induces polarization signals determined by the quadrupole anisotropy in the photon distribution at the location of clusters. This `remote quadrupole' derived from the measurements of the induced polarization in galaxy clusters provides an opportunity to reconstruct local CMB temperature anisotropies. In this Letter, we develop an algorithm of the reconstruction through the estimation of the underlying primordial gravitational potential, which is the origin of the CMB temperature and polarization fluctuations and CMB induced polarization in galaxy clusters. We found a nice reconstruction for the quadrupole and octopole components of the CMB temperature anisotropies with the assistance of the CMB induced polarization signals. The reconstruction can be an important consistency test on the puzzles of CMB anomalies, especially for the low-quadrupole and axis-of-evil problems reported in Wilkinson Microwave Anisotropy Probe and Planck data.

  6. Polarization force-induced changes in the dust sheath formation

    SciTech Connect

    Mayout, Saliha; Bentabet, Karima; Tribeche, Mouloud

    2015-09-15

    The modifications arising in the dusty plasma sheath structure due to the presence of polarization forces acting on the dust grains are investigated. The corresponding appropriate Bohm criterion for sheath formation is obtained. It is found that the critical Mach number, beyond which the dusty plasma electrostatic sheath sets in, decreases whenever the polarization effects become important. In addition, when the polarization force dominates over the electrical one, the dust plasma sheath cannot set in. This happens whenever the dust grain size exceeds a critical threshold. Moreover, the sheath electrostatic potential-gradient becomes abruptly steep, and the sheath thickness becomes broader as the polarization force effects strengthen.

  7. Polarization properties of fiber lasers with twist-induced circular birefringence

    SciTech Connect

    Kim, Ho Young; Lee, El Hang Kim, Byoung Yoon

    1997-09-01

    We have experimentally observed and theoretically analyzed the polarization properties of fiber lasers with twist-induced birefringence. Twisting a fiber induces the circular birefringence of a fiber laser cavity, and this birefringence reduces the effects of intrinsic linear birefringence on the polarization properties of fiber lasers. The frequencies of their polarization eigenmodes coincide with each other gradually as the twist rate increases, and the directions of polarization eigenmodes deviate from the birefringence axis at a much larger twist rate than the magnitude of intrinsic linear birefringence. We describe the successful experimental results for Nd and Er fiber lasers. {copyright} 1997 Optical Society of America

  8. Adaptation of the University of Wisconsin High Spectral Resolution Lidar for Polarization and Multiple Scattering Measurements

    NASA Technical Reports Server (NTRS)

    Eloranta, E. W.; Piironen, P. K.

    1996-01-01

    Quantitative lidar measurements of aerosol scattering are hampered by the need for calibrations and the problem of correcting observed backscatter profiles for the effects of attenuation. The University of Wisconsin High Spectral Resolution Lidar (HSRL) addresses these problems by separating molecular scattering contributions from the aerosol scattering; the molecular scattering is then used as a calibration target that is available at each point in the observed profiles. While the HSRl approach has intrinsic advantages over competing techniques, realization of these advantages requires implementation of a technically demanding system which is potentially very sensitive to changes in temperature and mechanical alignments. This paper describes a new implementation of the HSRL in an instrumented van which allows measurements during field experiments. The HSRL was modified to measure depolarization. In addition, both the signal amplitude and depolarization variations with receiver field of view are simultaneously measured. This allows for discrimination of ice clouds from water clouds and observation of multiple scattering contributions to the lidar return.

  9. Spectral changes induced by a phase modulator acting as a time lens

    SciTech Connect

    Plansinis, B. W.; Donaldson, W. R.; Agrawal, G. P.

    2015-07-06

    We show both numerically and experimentally that a phase modulator, acting as a time lens in the Fourier-lens configuration, can induce spectral broadening, narrowing, or shifts, depending on the phase of the modulator cycle. These spectral effects depend on the maximum phase shift that can be imposed by the modulator. In our numerical simulations, pulse spectrum could be compressed by a factor of 8 for a 30 rad phase shift. Experimentally, spectral shifts over a 1.35 nm range and spectral narrowing and broadening by a factor of 2 were demonstrated using a lithium niobate phase modulator with a maximum phase shift of 16 rad at a 10 GHz modulation frequency. All spectral changes were accomplished without employing optical nonlinear effects such as self- or cross-phase modulation.

  10. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    DOE PAGESBeta

    Ye, Tianyu; Liu, Han -Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

    2015-10-09

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. As a result, for circularly polarized radiation, the oscillatory magnetoresistive response ismore » hardly sensitive to θ.« less

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

    NASA Technical Reports Server (NTRS)

    Fineschi, Silvano; Degl'innocenti, Egidio L.

    1992-01-01

    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.

  12. Rebuilding cytoskeleton roads: Active-transport-induced polarization of cells

    NASA Astrophysics Data System (ADS)

    Hawkins, R. J.; Bénichou, O.; Piel, M.; Voituriez, R.

    2009-10-01

    Many cellular processes require a polarization axis which generally initially emerges as an inhomogeneous distribution of molecular markers in the cell. We present a simple analytical model of a general mechanism of cell polarization taking into account the positive feedback due to the coupled dynamics of molecular markers and cytoskeleton filaments. We find that the geometry of the organization of cytoskeleton filaments, nucleated on the membrane (e.g., cortical actin) or from a center in the cytoplasm (e.g., microtubule asters), dictates whether the system is capable of spontaneous polarization or polarizes only in response to external asymmetric signals. Our model also captures the main features of recent experiments of cell polarization in two considerably different biological systems, namely, mating budding yeast and neuron growth cones.

  13. SPEAR-induced field-aligned irregularities observed from bi-static HF radio scattering in the polar ionosphere

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Kornienko, V. A.; Kalishin, A. S.; Robinson, T. R.; Yeoman, T. K.; Wright, D. M.; Baddeley, L. J.

    2009-01-01

    Experimental results from SPEAR HF heating experiments in the polar ionosphere are examined. Bi-static scatter measurements of HF diagnostic signals were carried out on the Pori (Finland)-SPEAR-St. Petersburg path at operational frequencies of 11,755 and 15,400 kHz and the London-SPEAR-St. Petersburg path at frequencies of 12,095 and 17,700 kHz, using a Doppler spectral method. The SPEAR HF heating facility generates heater-induced artificial field-aligned small-scale irregularities (AFAIs), which can be detected by HF diagnostic bi-static radio scatter techniques at St. Petersburg at a distance of about 2000 km. In accordance with the Bragg condition, HF bi-static backscatters were sensitive to small-scale irregularities having spatial sizes of the order of 9-13 m across the geomagnetic field line. The properties and behaviour of AFAIs have been considered in the winter and summer seasons under quiet magnetic conditions and under various status of the polar ionosphere (the presence of "thick" and "thin" sporadic Es layers, different structures of the F2 layer). The experimental results obtained have shown that AFAIs can be excited in the F as well as in the E regions of the polar ionosphere. The excitation of a very intense wide-band spectral component with an abrupt increase in the spectral width up to 16-20 Hz has been found in the signals scattered from striations. Along with a wide-band component, a narrow-band spectral component can be also seen in the Doppler sonograms and in the average spectra of the signals scattered from the SPEAR-induced striations. AFAIs were excited even when the HF heater frequency was up to 0.5 MHz larger than the critical frequency. A simulation of the ray geometry for the diagnostic HF radio waves scattered from AFAIs in the polar ionosphere has been made for the geophysical conditions prevailing during experiments carried out in both the winter and summer seasons.

  14. Application of Laser Induced Breakdown Spectroscopy under Polar Conditions

    NASA Astrophysics Data System (ADS)

    Clausen, J. L.; Hark, R.; Bol'shakov, A.; Plumer, J.

    2015-12-01

    Over the past decade our research team has evaluated the use of commercial-off-the-shelf laser-induced breakdown spectroscopy (LIBS) for chemical analysis of snow and ice samples under polar conditions. One avenue of research explored LIBS suitability as a detector of paleo-climate proxy indicators (Ca, K, Mg, and Na) in ice as it relates to atmospheric circulation. LIBS results revealed detection of peaks for C and N, consistent with the presence of organic material, as well as major ions (Ca, K, Mg, and Na) and trace metals (Al, Cu, Fe, Mn, Ti). The detection of Ca, K, Mg, and Na confirmed that LIBS has sufficient sensitivity to be used as a tool for characterization of paleo-climate proxy indicators in ice-core samples. Techniques were developed for direct analysis of ice as well as indirect measurements of ice via melting and filtering. Pitfalls and issues of direct ice analysis using several cooling techniques to maintain ice integrity will be discussed. In addition, a new technique, laser ablation molecular isotopic spectroscopy (LAMIS) was applied to detection of hydrogen and oxygen isotopes in ice as isotopic analysis of ice is the main tool in paleoclimatology and glaciology studies. Our results demonstrated that spectra of hydroxyl isotopologues 16OH, 18OH, and 16OD can be recorded with a compact spectrograph to determine hydrogen and oxygen isotopes simultaneously. Quantitative isotopic calibration for ice analysis can be accomplished using multivariate chemometric regression as previously realized for water vapor. Analysis with LIBS and LAMIS required no special sample preparation and was about ten times faster than analysis using ICP-MS. Combination of the two techniques in one portable instrument for in-field analysis appears possible and would eliminate the logistical and cost issues associated with ice core management.

  15. Modulation of TNF-induced macrophage polarization by synovial fibroblasts.

    PubMed

    Donlin, Laura T; Jayatilleke, Arundathi; Giannopoulou, Eugenia G; Kalliolias, George D; Ivashkiv, Lionel B

    2014-09-01

    Mesenchymal stromal cells have emerged as powerful modulators of the immune system. In this study, we explored how the human macrophage response to TNF is regulated by human synovial fibroblasts, the representative stromal cell type in the synovial lining of joints that become activated during inflammatory arthritis. We found that synovial fibroblasts strongly suppressed TNF-mediated induction of an IFN-β autocrine loop and downstream expression of IFN-stimulated genes (ISGs), including chemokines CXCL9 and CXCL10 that are characteristic of classical macrophage activation. TNF induced the production of soluble synovial fibroblast factors that suppressed the macrophage production of IFN-β, and cooperated with TNF to limit the responsiveness of macrophages to IFN-β by suppressing activation of Jak-STAT signaling. Genome-wide transcriptome analysis showed that cocultured synovial fibroblasts modulate the expression of approximately one third of TNF-regulated genes in macrophages, including genes in pathways important for macrophage survival and polarization toward an alternatively activated phenotype. Pathway analysis revealed that gene expression programs regulated by synovial fibroblasts in our coculture system were also regulated in rheumatoid arthritis synovial macrophages, suggesting that these fibroblast-mediated changes may contribute to rheumatoid arthritis pathogenesis. This work furthers our understanding of the interplay between innate immune and stromal cells during an inflammatory response, one that is particularly relevant to inflammatory arthritis. Our findings also identify modulation of macrophage phenotype as a new function for synovial fibroblasts that may prove to be a contributing factor in arthritis pathogenesis. PMID:25057003

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  17. Hydroxamate-induced spectral perturbations of cobalt Aeromonas aminopeptidase.

    PubMed

    Wilkes, S H; Prescott, J M

    1987-06-25

    The absorption spectrum of cobalt(II)-substituted Aeromonas aminopeptidase is markedly perturbed by the presence of equimolar concentrations of D-amino acid hydroxamates and acyl hydroxamates that have previously been shown to be powerful inhibitors of this enzyme (Wilkes, S. H., and Prescott, J. M. (1983) J. Biol. Chem. 258, 13517-13521). D-Valine hydroxamate produces the most distinctive perturbation, splitting the characteristic 527 nm absorption peak of the cobalt enzyme to form peaks at 564, 520, and 487 nm with molar extinction values of 126, 98, and 67 M-1 cm-1, respectively. A qualitatively similar perturbation, albeit with lower extinction values, results from the addition of D-leucine hydroxamate, whereas D-alanine hydroxamate perturbs the spectrum, but does not evoke the peak at 564 nm. In contrast, hydroxamates of L-valine and L-leucine in concentrations equi-molar to that of the enzyme produce only faint indications of change in the spectrum, but the hydroxamates of several other L-amino acids perturb the spectrum essentially independently of the identity of the side chain and in a qualitatively different manner from that of D-valine hydroxamate and D-leucine hydroxamate. At the high enzyme:substrate ratios used in the spectral experiments, L-leucine hydroxamate and L-valine hydroxamate proved to be rapidly hydrolyzed, hence their inability to perturb the spectrum of the cobalt-substituted enzyme during the time course of a spectral experiment. Values of kcat for L-amino acid hydroxamates, all of which are good reversible inhibitors of the hydrolysis of L-leucine-p-nitroanilide by Aeromonas aminopeptidase, were found to range from 0.01 min-1 to 5.6 min-1 for the native enzyme and from 0.27 min-1 to 108 min-1 for the cobalt-substituted enzyme; their km values toward the cobalt aminopeptidase range from 1.2 X 10(-7) M to 1.9 X 10(-5) M. The mutual exclusivity of binding for hydroxamate inhibitors and 1-butaneboronic acid, previously shown by kinetics

  18. Polarization decay of pulses of electromagnetically induced transparency on J=0→J=1→J=2 degenerate quantum transitions

    NASA Astrophysics Data System (ADS)

    Parshkov, O. M.

    2016-02-01

    The evolution of radiation under conditions of electromagnetically induced transparency in the scheme of degenerate quantum transitions J = 0 → J = 1 → J = 2 in the pulsed interaction regime of the fields and with allowance for the Doppler broadening of spectral lines has been analyzed numerically. It has been shown that, if the input coupling radiation is linearly polarized, the circularly polarized input probe pulse splits in the medium into pulses with mutually perpendicular linear polarizations. The direction of polarization of one of these pulses coincides with the direction of polarization of the input coupling field. The distance that the probe pulse travels in the medium until it completely decays decreases with a decrease in both the duration of the input probe pulse and the intensity of the input coupling radiation. A change in the power of the input probe pulse hardly affects the distance required for the decay and the velocity of propagation of linearly polarized pulses in the medium. An increase in the Doppler broadening of spectral lines leads to a decrease in this distance and, simultaneously, to an increase in the energy losses of the probe radiation. Qualitative considerations that explain the physical reason for the investigated effects have been presented.

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

    DOEpatents

    Ward, Stanley H.

    1989-01-01

    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.

  20. The dependence of induced polarization on natural iron concentration in wetland soils

    NASA Astrophysics Data System (ADS)

    Slater, L. D.; Mansoor, N.

    2006-12-01

    Spectral Induced polarization (SIP) measurements in the frequency range 0.1-1000 Hz were conducted on clay and peat marsh soils, obtained from a contaminated freshwater weltand in New Jersey, that were subsequently analyzed for heavy metal concentrations, moisture content, organic matter, porosity, specific surface area, and pore fluid conductivity. A Cole-Cole relaxation model was fit to each of the samples and the model parameters analyzed in terms of the measured physiochemical properties. A linear relationship between the normalized chargeability (mn) and the estimated surface area to pore volume (Sp) is found when the iron content (ranging from 0.25 to 1.63 percent by volume between samples) is accounted for as a polarizable element of the soil. In fact, the dependence of mn on volumetric Fe concentration per unit volume of the bulk soil is described by a linear relationship with a correlation coefficient of 0.94. As the Fe concentration of soils is a critical biogeochemical parameter, these results suggest that SIP measurements may provide a hitherto unrecognized approach to probing soil geochemistry, iron cycling and anaerobic microbial activity. Furthermore, our results yield new insight into the physiochemical controls on SIP in natural, unconsolidated soils.

  1. Spectrally Consistent Scattering, Absorption, and Polarization Properties of Atmospheric Ice Crystals at Wavelengths from 0.2 to 100 um

    NASA Technical Reports Server (NTRS)

    Yang, Ping; Bi, Lei; Baum, Bryan A.; Liou, Kuo-Nan; Kattawar, George W.; Mishchenko, Michael I.; Cole, Benjamin

    2013-01-01

    A data library is developed containing the scattering, absorption, and polarization properties of ice particles in the spectral range from 0.2 to 100 microns. The properties are computed based on a combination of the Amsterdam discrete dipole approximation (ADDA), the T-matrix method, and the improved geometric optics method (IGOM). The electromagnetic edge effect is incorporated into the extinction and absorption efficiencies computed from the IGOM. A full set of single-scattering properties is provided by considering three-dimensional random orientations for 11 ice crystal habits: droxtals, prolate spheroids, oblate spheroids, solid and hollow columns, compact aggregates composed of eight solid columns, hexagonal plates, small spatial aggregates composed of 5 plates, large spatial aggregates composed of 10 plates, and solid and hollow bullet rosettes. The maximum dimension of each habit ranges from 2 to 10,000 microns in 189 discrete sizes. For each ice crystal habit, three surface roughness conditions (i.e., smooth, moderately roughened, and severely roughened) are considered to account for the surface texture of large particles in the IGOM applicable domain. The data library contains the extinction efficiency, single-scattering albedo, asymmetry parameter, six independent nonzero elements of the phase matrix (P11, P12, P22, P33, P43, and P44), particle projected area, and particle volume to provide the basic single-scattering properties for remote sensing applications and radiative transfer simulations involving ice clouds. Furthermore, a comparison of satellite observations and theoretical simulations for the polarization characteristics of ice clouds demonstrates that ice cloud optical models assuming severely roughened ice crystals significantly outperform their counterparts assuming smooth ice crystals.

  2. Reprint of : Spin polarization induced by an electric field in the presence of weak localization effects

    NASA Astrophysics Data System (ADS)

    Guerci, Daniele; Borge, Juan; Raimondi, Roberto

    2016-08-01

    We evaluate the spin polarization (Edelstein or inverse spin galvanic effect) and the spin Hall current induced by an applied electric field by including the weak localization corrections for a two-dimensional electron gas. We show that the weak localization effects yield logarithmic corrections to both the spin polarization conductivity relating the spin polarization and the electric field and to the spin Hall angle relating the spin and charge currents. The renormalization of both the spin polarization conductivity and the spin Hall angle combine to produce a zero correction to the total spin Hall conductivity as required by an exact identity. Suggestions for the experimental observation of the effect are given.

  3. Shock-induced polarized hydrogen emission lines in omicron Ceti

    NASA Astrophysics Data System (ADS)

    Fabas, N.; Lèbre, A.; Gillet, D.

    2012-05-01

    Hydrogen emission lines in Mira variable stars are a well-known phenomenon whose origin has been established as related to the propagation of radiative hypersonic shock waves throughout the stellar atmosphere. A polarimetric observation by McLean and Coyne [1] made on omicron Ceti (the prototype of Mira variable stars) has revealed the existence of linear polarization signatures associated with Balmer emission lines. However, the polarizing mechanism has never been properly explained so far. The study presented here is the first of its kind since it displays the results of a spectropolarimetric survey of omicron Ceti in the Balmer lines. The survey was made with the NARVAL spectropolarimeter (Telescope Bernard Lyot, France) in full Stokes mode. We did not just confirm the appearance of this polarization but we also and above all showed the temporal variation of the linear polarization in the lines. We conclude that the polarizing mechanism is definitely intrinsic to the shock wave propagation throughout the stellar atmosphere of Mira and give some leads about the nature of this mechanism.

  4. Neuronal polarity selection by topography-induced focal adhesion control.

    PubMed

    Ferrari, Aldo; Cecchini, Marco; Serresi, Michela; Faraci, Paolo; Pisignano, Dario; Beltram, Fabio

    2010-06-01

    Interaction between differentiating neurons and the extracellular environment guides the establishment of cell polarity during nervous system development. Developing neurons read the physical properties of the local substrate in a contact-dependent manner and retrieve essential guidance cues. In previous works we demonstrated that PC12 cell interaction with nanogratings (alternating lines of ridges and grooves of submicron size) promotes bipolarity and alignment to the substrate topography. Here, we investigate the role of focal adhesions, cell contractility, and actin dynamics in this process. Exploiting nanoimprint lithography techniques and a cyclic olefin copolymer, we engineered biocompatible nanostructured substrates designed for high-resolution live-cell microscopy. Our results reveal that neuronal polarization and contact guidance are based on a geometrical constraint of focal adhesions resulting in an angular modulation of their maturation and persistence. We report on ROCK1/2-myosin-II pathway activity and demonstrate that ROCK-mediated contractility contributes to polarity selection during neuronal differentiation. Importantly, the selection process confined the generation of actin-supported membrane protrusions and the initiation of new neurites at the poles. Maintenance of the established polarity was independent from NGF stimulation. Altogether our results imply that focal adhesions and cell contractility stably link the topographical configuration of the extracellular environment to a corresponding neuronal polarity state. PMID:20304485

  5. Proximity-Induced Spin Polarization of Graphene in Contact with Half-Metallic Manganite.

    PubMed

    Sakai, Seiji; Majumdar, Sayani; Popov, Zakhar I; Avramov, Pavel V; Entani, Shiro; Hasegawa, Yuri; Yamada, Yoichi; Huhtinen, Hannu; Naramoto, Hiroshi; Sorokin, Pavel B; Yamauchi, Yasushi

    2016-08-23

    The role of proximity contact with magnetic oxides is of particular interest from the expectations of the induced spin polarization and weak interactions at the graphene/magnetic oxide interfaces, which would allow us to achieve efficient spin-polarized injection in graphene-based spintronic devices. A combined approach of topmost-surface-sensitive spectroscopy utilizing spin-polarized metastable He atoms and ab initio calculations provides us direct evidence for the magnetic proximity effect in the junctions of single-layer graphene and half-metallic manganite La0.7Sr0.3MnO3 (LSMO). It is successfully demonstrated that in the graphene/LSMO junctions a sizable spin polarization is induced at the Fermi level of graphene in parallel to the spin polarization direction of LSMO without giving rise to a significant modification in the π band structure. PMID:27438899

  6. Ultraviolet irradiation induced polarization restoration in electrically fatigued ferroelectric polymer films

    SciTech Connect

    Fu Shaosong; Hu Jinghang; Zhu Guodong; Yu Hao; Ding Shijin; Jiang Yulong; Cheng Qian

    2013-03-21

    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.

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

    PubMed

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

    2009-07-10

    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

  8. Nonvolatile data storage using mechanical force-induced polarization switching in ferroelectric polymer

    SciTech Connect

    Chen, Xin; Tang, Xin; Chen, Xiang-Zhong; Chen, Yu-Lei; Shen, Qun-Dong; Guo, Xu; Ge, Hai-Xiong

    2015-01-26

    Ferroelectric polymers offer the promise of low-cost and flexible electronic products. They are attractive for information storage due to their spontaneous polarization which is usually switched by electric field. Here, we demonstrate that electrical signals can be readily written on ultra-thin ferroelectric polymer films by strain gradient-induced polarization switching (flexoelectric effect). A force with magnitude as small as 64nN is enough to induce highly localized (40 nm feature size) change in the polarization states. The methodology is capable of realizing nonvolatile memory devices with miniaturized cell size and storage density of tens to hundreds Gbit per square inch.

  9. Circularly polarized laser emission induced in isotropic and achiral dye systems.

    PubMed

    Cerdán, Luis; García-Moreno, Sara; Costela, Angel; García-Moreno, Inmaculada; de la Moya, Santiago

    2016-01-01

    The production of efficient, tunable, and switchable circularly polarized laser emission would have far reaching implications in optical communications or biophotonics. In this work, it is demonstrated the direct generation of circularly polarized (CP) laser emission in achiral and isotropic dye laser systems without the use of extracavity polarizing elements, and without resorting to chiral dyes, chiral liquid crystal matrices, or interferometric methods. The origin of this ellipticity arises from the dynamic birefringence induced by the strong and polarized laser pumping and the subsequent orientation anisotropy of the excited molecular dipoles. A complete polarimetric characterization of the polarization state of conventional dye laser oscillators as a function of different experimental parameters is performed and it is shown that the generated light always possesses a certain level of circularity that changes in a distinctive way with pump energy and polarization. These results demonstrate that it is possible to generate and modulate CP laser light from efficient and photostable conventional laser dyes. PMID:27350073

  10. Circularly polarized laser emission induced in isotropic and achiral dye systems

    NASA Astrophysics Data System (ADS)

    Cerdán, Luis; García-Moreno, Sara; Costela, Angel; García-Moreno, Inmaculada; de La Moya, Santiago

    2016-06-01

    The production of efficient, tunable, and switchable circularly polarized laser emission would have far reaching implications in optical communications or biophotonics. In this work, it is demonstrated the direct generation of circularly polarized (CP) laser emission in achiral and isotropic dye laser systems without the use of extracavity polarizing elements, and without resorting to chiral dyes, chiral liquid crystal matrices, or interferometric methods. The origin of this ellipticity arises from the dynamic birefringence induced by the strong and polarized laser pumping and the subsequent orientation anisotropy of the excited molecular dipoles. A complete polarimetric characterization of the polarization state of conventional dye laser oscillators as a function of different experimental parameters is performed and it is shown that the generated light always possesses a certain level of circularity that changes in a distinctive way with pump energy and polarization. These results demonstrate that it is possible to generate and modulate CP laser light from efficient and photostable conventional laser dyes.

  11. Circularly polarized laser emission induced in isotropic and achiral dye systems

    PubMed Central

    Cerdán, Luis; García-Moreno, Sara; Costela, Angel; García-Moreno, Inmaculada; de la Moya, Santiago

    2016-01-01

    The production of efficient, tunable, and switchable circularly polarized laser emission would have far reaching implications in optical communications or biophotonics. In this work, it is demonstrated the direct generation of circularly polarized (CP) laser emission in achiral and isotropic dye laser systems without the use of extracavity polarizing elements, and without resorting to chiral dyes, chiral liquid crystal matrices, or interferometric methods. The origin of this ellipticity arises from the dynamic birefringence induced by the strong and polarized laser pumping and the subsequent orientation anisotropy of the excited molecular dipoles. A complete polarimetric characterization of the polarization state of conventional dye laser oscillators as a function of different experimental parameters is performed and it is shown that the generated light always possesses a certain level of circularity that changes in a distinctive way with pump energy and polarization. These results demonstrate that it is possible to generate and modulate CP laser light from efficient and photostable conventional laser dyes. PMID:27350073

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

    NASA Astrophysics Data System (ADS)

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

    2004-10-01

    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.

  13. Leptonic and Hadronic Modeling of Fermi-Detected Blazars. Spectral Energy Distribution Modeling and High-Energy Polarization Predictions

    NASA Astrophysics Data System (ADS)

    Böttcher, Markus; Reimer, Anita; Zhang, Haocheng

    2013-12-01

    We describe new implementations of leptonic and hadronic models for the broadband emission from relativistic jets in AGN in a temporary steady state. The new model implementations are used to fit snap-shot spectral energy distributions of a representative set of Fermi-LAT detected blazars from the first LAT AGN catalogue. We find that the leptonic model is capable of producing acceptable fits to the SEDs of almost all blazars with reasonable parameters close to equipartition between the magnetic field and the relativistic electron population. If charge neutrality in leptonic models is provided by cold protons, our fits indicate that the kinetic energy carried by the jet should be dominated by protons. We also find satisfactory representations of the snapshot SEDs of most blazars in our sample with the hadronic model presented here. All of our hadronic model fits require powers in relativistic protons in the range 1047 - 1049 erg/s. As a potential way to distinguish between the leptonic and hadronic high-energy emission models considered here, we suggest diagnostics based on the predicted X-ray and γ-ray polarization, which are drastically different for the two types of models.

  14. Current-induced spin polarization in transition metals and Bi/Ag bilayers observed by spin-polarized positron beam

    NASA Astrophysics Data System (ADS)

    Zhang, Hongjun; Yamamoto, Shunya; Fukaya, Yuki; Maekawa, Masaki; Li, Hui; Kawasuso, Atsuo; Seki, Takeshi; Saitoh, Eiji; Takanashi, Koki; JAEA Team; Tohoku Team

    2015-03-01

    Current-induced spin polarization (CISP) on the outermost surfaces of Au, Cu, Pt, Pd, Ta, and W films were studied by spin-polarized positron beam (SPPB). The Au and Cu surfaces showed no significant CISP. In contrast, the Pt, Pd, Ta, and W films exhibited large CISP (3 ~ 15% per 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 outermost spin poalrization of Bi/Ag/Al2O3andAg/Bi/Al2O3 (charge currents directly connected to Ag layers) were probed by SPPB. The opposite outermost spin polarization of Bi/Ag/Al2O3andAg/Bi/Al2O3 clarified the charge-to-spin conversion in Bi/Ag bilayers. Nevertheless, the magnitudes of the outermost spin polarization of Bi(0.3 ~5)/Ag(25)/Al2O3 (numbers in parentheses denote thickness in nm) and Ag(25 ~500)/Bi(8)/Al2O3 decrease exponentially with increasing Bi thickness and Ag thickness, respectively. This provides probably the first direct evidence for spin diffusion mechanism. Financial support from JSPS Kakenhi Grant 24310072.

  15. Comparison of the threshold of thermal-induced mode instabilities in polarization-maintaining and non-polarization-maintaining active fibers

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    We present an investigation on the threshold of thermal-induced mode instability (MI) in ytterbium-doped polarization-maintaining and non-polarization-maintaining active fibers. By taking both electric fields along the two principal axes into consideration, we extend a previous steady-state theoretical model to analyze the polarization effect on MI. Based on the model, we analyzed whether maintaining the fiber’s polarization direction has an effect on the MI threshold, which showed that, for practical high power fiber laser systems, the MI threshold is nearly the same for polarization-maintaining and non-polarization-maintaining active fibers. Experimental validation of the theoretical analysis is presented with experimental results agreeing with the theoretical results, in which polarization-maintained and non-polarization-maintained fiber lasers with similar core/inner cladding diameters are employed.

  16. Twist phase-induced polarization changes in electromagnetic Gaussian Schell-model beams

    NASA Astrophysics Data System (ADS)

    Cai, Y.; Korotkova, O.

    2009-08-01

    Electromagnetic Gaussian Schell-model (EGSM) beam with twist phase (i.e., twisted EGSM beam) is introduced as an extension of its scalar version based on the unified theory of coherence and polarization. We show how analytical paraxial propagation formulae of isotropic and anisotropic EGSM beams passing through a general astigmatic ABCD optical system can be modified in the presence of the twist phase. Numerical examples demonstrate that the twist phase affects the spectral density, the state of coherence, and the degree of polarization of EGSM beams on propagation.

  17. Cyclooxygenase-2 inhibition attenuates hypoxic cancer cells induced m2-polarization of macrophages.

    PubMed

    Dubey, P; Shrivastava, R; Tripathi, C; Jain, N K; Tewari, B N; Lone, M-U-D; Baghel, K S; Kumar, V; Misra, S; Bhadauria, S; Bhatt, M L B

    2014-01-01

    Tumor-associated macrophages (TAMs), represent a major subpopulation of tumor infiltrating immune cells. These alternatively activated M2-polarized macrophages are well known for their pro-tumor functions. Owing to their established role in potentiating tumor-neovasculogenesis and metastasis, TAMs have emerged as promising target for anti-cancer immunotherapy. One of the key TAMs related phenomenon that is amenable to therapeutic intervention is their phenotype switching into alternatively activated M2-polarized macrophages. Hindering macrophage polarization towards a pro-tumor M2 phenotype, or better still reprogramming the M2 like TAMs towards M1 subtype is being considered a beneficial anti-cancer strategy. Hypoxic tumor milieu has been proposed as one of the most plausible factor governing M2-polarization of macrophages. We recently demonstrated that hypoxic tumor cells imparted a pro—angiogenic M2 skewed phenotype to macrophages. Furthermore, sizeable body of data indicates for participation of cyclooxygenase-2 (COX-2) in macrophage polarization. Concordantly, inhibition of COX-2 is associated with impaired macrophage polarization. Prompted by this in the current study we decided to explore if inhibition of COX-2 activity via chemical inhibitors may prevent hypoxic cancer cell induced M2-polarization of macrophages. We observed that treatment with Flunixin meglumine, an established preferential inhibitor of COX-2 activity markedly inhibited hypoxic cancer cell induced of M2-polarization of macrophages thereby indicating for usage of COX-2 inhibition as possible anti-cancer treatment modality. PMID:25210855

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

    SciTech Connect

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

    2008-11-01

    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.

  19. Enhancement of self-phase modulation induced spectral broadening in silicon suspended membrane waveguides

    NASA Astrophysics Data System (ADS)

    Zhang, Yaojing; Cheng, Zhenzhou; Liu, Linghai; Zhu, Bingqing; Wang, Jiaqi; Zhou, Wen; Wu, Xinru; Tsang, Hon Ki

    2016-05-01

    We experimentally observed a possibly enhanced self-phase modulation (SPM) in silicon suspended membrane waveguides (SMWs) by measuring the spectral broadening of optical pulses. The nonlinear coefficient n 2 and the two-photon absorption coefficient β 2 of silicon SMWs were measured to be (4.6 ± 0.9) × 10-18 m2 W-1 and 0.46 cm GW-1 at 1555 nm wavelength. We also proposed a method of using SPM-induced spectral broadening to obtain the coupling loss of a single grating coupler and experimentally compared the spectra of two grating couplers in silicon SMWs and in silicon-on-insulator waveguides.

  20. Protonation-induced red-coloured circularly polarized luminescence of [5]carbohelicene fused by benzimidazole.

    PubMed

    Sakai, Hayato; Kubota, Takako; Yuasa, Junpei; Araki, Yasuyuki; Sakanoue, Tomo; Takenobu, Taishi; Wada, Takehiko; Kawai, Tsuyoshi; Hasobe, Taku

    2016-07-12

    Benzimidazole-fused [5]carbohelicene ([5]HeliBI) was newly synthesized to examine the spectroscopic and chiroptical properties. The reversible protonation and deprotonation processes of [5]HeliBI were successfully investigated using (1)H NMR, absorption and fluorescence spectral measurements. We also confirmed the circularly polarized luminescence of protonated [5]HeliBI (H(+)-[5]HeliBI). This is the first observation of red-coloured CPL of a helicene derivative. PMID:27319321

  1. Evaluating the use of Spectral Induced Conductivity to Detect Biofilm Development within Porous Media

    NASA Astrophysics Data System (ADS)

    Rosier, C. L.; Atekwana, E. A.; Price, A.; Sharma, S.; Patrauchan, M.

    2015-12-01

    Microbial biomass accumulation in subsurface sediments dynamically alters porosity/permeability; factors critical to contaminant transport and management of bioremediation efforts. Current methodologies (i.e. plate counts, tracer/slug tests) offer some understanding of biofilm effect on subsurface hydrology, yet do not provide real-time information regarding biofilm development. Due to these limitations there is interest in assessing the near surface geophysical technique Spectral Induced Polarization (SIP), to measure biofilm formation. Our study assesses the influence of cell density and biofilm production on SIP response. Laboratory experiments monitored changes in SIP, measured colony forming units (CFU), and cellular protein levels on sand packed columns inoculated with either Pseudomonas aeruginosa PAO1 (non-mucoid strain) or Pseudomonas aeruginosa FRD1 (biofilm-overproducing mucoid strain) cells over one month. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were used to confirm the presence of biofilm. Our results indicate that phase and imaginary conductivity remained stable in PAO1 treatments as cell densities and cellular protein levels remained low (1.7x105 CFUml-1; 111 μg ml-1). However, we observed a significant decrease in both phase (0.5 to -0.20 mrad) and imaginary conductivity (0.0 to -3.0x10-5 S m-1) when both cell densities and cellular protein levels increased. In FRD1 treatments we observed an immediate decrease in phase (0.1 mrad) and imaginary conductivity (-2.0x10-6 S m-1) as cell densities were an order of magnitude greater then PAO1 treatments and cellular protein levels surpassed 500 μg ml-1. CLSM and SEM analysis confirmed the presence of biofilm and cells within both PAO1 and FRD1 treatments. Our findings suggest that the ratio of cells to cellular protein production is an important factor influencing both phase and imaginary conductivity response. However, our results are not in agreement with

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

    SciTech Connect

    Zhang, Jinjing; Zhang, Tao

    2015-02-15

    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{sup 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.

  3. Theoretical study of polarization insensitivity of carrier-induced refractive index change of multiple quantum well.

    PubMed

    Miao, Qingyuan; Zhou, Qunjie; Cui, Jun; He, Ping-An; Huang, Dexiu

    2014-12-29

    Characteristics of polarization insensitivity of carrier-induced refractive index change of 1.55 μm tensile-strained multiple quantum well (MQW) are theoretically investigated. A comprehensive MQW model is proposed to effectively extend the application range of previous models. The model considers the temperature variation as well as the nonuniform distribution of injected carrier in MQW. Tensile-strained MQW is expected to achieve polarization insensitivity of carrier-induced refractive index change over a wide wavelength range as temperature varies from 0°C to 40°C, while the magnitude of refractive index change keeps a large value (more than 3 × 10-3). And that the polarization insensitivity of refractive index change can maintain for a wide range of carrier concentration. Multiple quantum well with different material and structure parameters is anticipated to have the similar polarization insensitivity of refractive index change, which shows the design flexibility. PMID:25607157

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

    NASA Technical Reports Server (NTRS)

    Ryff, Luis Carlos B.

    1994-01-01

    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.

  5. Orthogonal polarization spectral imaging (OPS): a novel method to measure the microcirculation in term and preterm infants transcutaneously.

    PubMed

    Genzel-Boroviczény, Orsolya; Strötgen, Julia; Harris, Anthony G; Messmer, Konrad; Christ, Frank

    2002-03-01

    Little is known about the microvascular perfusion of the skin postnatally. Skin microvascular parameters can be assessed noninvasively with orthogonal polarization spectral imaging (OPS), a technique where, through the use of special optics, a virtual light source is created at a depth of 1 mm within the tissue. The light is absorbed by the Hb, yielding an image of the illuminated Hb-carrying structures in negative contrast. In nine term (weight 2100-4470 g) and 28 preterm infants (weight 550-2070 g; gestational age 24-33 wk) red blood cell velocity and vessel diameter and density were determined off-line with the Cap-Image program in vessels video-recorded by OPS near the axilla on d 1 and 5 of life. Blood pressure, heart rate, hematocrit, and body and incubator temperature were noted. Vessel diameter ranged from 6 to 24 microm, vessel density from 219 to 340 cm/cm(2) with no change between d 1 or 5 and no difference between term and preterm infants. Red blood cell velocity increased in preterm infants from d 1 [median 528 microm/s, 95% confidence interval (CI) 486-564 microm/s] to d 5 (median 570 microm/s; 95% CI 548-662 microm/s; p = 0.001) and correlated with the decrease in median hematocrit from 44% (CI 40%-60%) to 39% (CI 37%-43%) with r(2) = -0.37 with a 95% CI -0.59 to -0.11, p = 0.006. Hematocrit correlates with red blood cell velocity in the microvessels of the skin. The new technology can be used to assess quantitative changes in the microvessels and thus allows noninvasive assessment of tissue perfusion in term and preterm infants. PMID:11861946

  6. Mechanism of the chromosome-induced polar body extrusion in mouse eggs

    PubMed Central

    2011-01-01

    Background An oocyte undergoes two rounds of asymmetric division to generate a haploid gamete and two small polar bodies designed for apoptosis. Chromosomes play important roles in specifying the asymmetric meiotic divisions in the oocytes but the underlying mechanism is poorly understood. Results Chromosomes independently induce spindle formation and cortical actomyosin assembly into special cap and ring structures in the cortex of the oocyte. The spindle and the cortical cap/ring interact to generate mechanical forces, leading to polar body extrusion. Two distinct force-driven membrane changes were observed during 2nd polar body extrusion: a protrusion of the cortical cap and a membrane invagination induced by an anaphase spindle midzone. The cortical cap protrusion and invagination help rotate the spindle perpendicularly so that the spindle midzone can induce bilateral furrows at the shoulder of the protruding cap, leading to an abscission of the polar body. It is interesting to note that while the mitotic spindle midzone induces bilateral furrowing, leading to efficient symmetric division in the zygote, the meiotic spindle midzone induced cytokinetic furrowing only locally. Conclusions Distinct forces driving cortical cap protrusion and membrane invagination are involved in spindle rotation and polar body extrusion during meiosis II in mouse oocytes. PMID:21867530

  7. The application of induced polarization techniques to detect metal-bearing offshore anthropogenic waste and unexploded ordnance

    USGS Publications Warehouse

    Wynn, Jeff; Roberts, William

    2009-01-01

    Raw sewage and industrial waste have been dumped into sensitive estuaries, bays, and sounds for centuries. The full extents of the resulting sludge deposits are largely unknown, because they move in response to tidal and long‐shore currents, and because they are often buried by younger inert sediments. USGS field and laboratory measurements of toxic mine waste and organic effluent samples suggest that anthropogenic wastes typically contain finely‐divided metal and metal‐sulfide particles. The anoxic environment provided by anthropogenic wastes promotes the growth of anaerobic bacteria, creating a self‐reducing environment. We suggest that the finely‐divided metal and metal‐sulfide particles are the products of bacterial reduction and precipitation. The fine‐grained metallic precipitates are ideal targets for a surface‐effect electrochemical detection methodology called Induced Polarization (IP). A USGS‐patented (1998/2001) marine IP streamer technology has recently been commercialized and used to map “black smoker” sulfide deposits and their disseminated halos in the Bismarck Sea (2005), and titanium‐sand deposits offshore of South Africa (2007). The marine induced polarization system can do this mapping in three dimensions, more rapidly (it is towed at 3 knots), and with far higher resolution that land‐based measurements or vibracoring. Laboratory‐scale studies at the USGS suggest that anthropogenic wastes may display a specific multi‐frequency IP spectral signature that may be applicable to waste‐deposit mapping.

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

    SciTech Connect

    Morgen, M M

    1997-05-01

    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.

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

    PubMed Central

    Deng, Manqi; Li, Rong

    2009-01-01

    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

  10. Magnetic-Field-Induced Rotation of Polarized Light Emission from Monolayer WS2

    NASA Astrophysics Data System (ADS)

    Schmidt, Robert; Arora, Ashish; Plechinger, Gerd; Nagler, Philipp; Granados del Águila, Andrés; Ballottin, Mariana V.; Christianen, Peter C. M.; Michaelis de Vasconcellos, Steffen; Schüller, Christian; Korn, Tobias; Bratschitsch, Rudolf

    2016-08-01

    We control the linear polarization of emission from the coherently emitting K+ and K- valleys (valley coherence) in monolayer WS2 with an out-of-plane magnetic field of up to 25 T. The magnetic-field-induced valley Zeeman splitting causes a rotation of the emission polarization with respect to the excitation by up to 35° and reduces the polarization degree by up to 16%. We explain both of these phenomena with a model based on two noninteracting coherent two-level systems. We deduce that the coherent light emission from the valleys decays with a time constant of τc=260 fs .

  11. Polarization induced resistance switching effect in ferroelectric vinylidene-fluoride/trifluoroethylene copolymer ultrathin films

    SciTech Connect

    Usui, S. Nakajima, T.; Hashizume, Y.; Okamura, S.

    2014-10-20

    We observed a clear polarization reversal-induced resistance switching effect in ferroelectric Vinylidene-fluoride (VDF)/Trifluoroethylene (TrFE) copolymer thin films. Pt and Au were used as the bottom and top electrodes, respectively, and the thickness of the VDF/TrFE copolymer film was adjusted to be 10 nm. The conduction current was 100 times higher in the case of the spontaneous polarization of the VDF/TrFE film towards the Au electrode than that in the case of the opposite direction. This resistance switching was confirmed to be reproducible after 10 successive polarization reversals.

  12. In-Plane Electric Polarization of Bilayer Graphene Nanoribbons Induced by an Interlayer Bias Voltage.

    PubMed

    Okugawa, Ryo; Tanaka, Junya; Koretsune, Takashi; Saito, Susumu; Murakami, Shuichi

    2015-10-01

    We theoretically show that an interlayer bias voltage in the AB-stacked bilayer graphene nanoribbons with armchair edges induces an electric polarization along the ribbon. Both tight-binding and ab initio calculations consistently indicate that when the bias voltage is weak, the polarization shows opposite signs depending on the ribbon width modulo three. This nontrivial dependence is explained using a two-band effective model. A strong limit of the bias voltage in the tight-binding model shows either one-third or zero polarization, which agrees with the topological argument. PMID:26550741

  13. (2+1) laser-induced fluorescence of spin-polarized hydrogen atoms.

    PubMed

    Bougas, Lykourgos; Sofikitis, Dimitris; Everest, Michael A; Alexander, Andrew J; Rakitzis, T Peter

    2010-11-01

    We report the measurement of the spin polarization of hydrogen (SPH) atoms by (2+1) laser-induced fluorescence, produced via the photodissociation of thermal HBr molecules with circularly polarized 193 nm light. This scheme, which involves two-photon laser excitation at 205 nm and fluorescence at 656 nm, offers an experimentally simpler polarization-detection method than the previously reported vacuum ultraviolet detection scheme, allowing the detection of SPH atoms to be performed more straightforwardly, from the photodissociation of a wide range of molecules and from a variety of collision experiments. PMID:21054033

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

    SciTech Connect

    Mani, R. G.; Ramanayaka, A. N.; Wegscheider, W.

    2013-12-04

    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.

  15. Magnetic Flux Effect on a Kondo-Induced Electric Polarization in a Triangular Triple Quantum Dot

    NASA Astrophysics Data System (ADS)

    Koga, Mikito; Matsumoto, Masashige; Kusunose, Hiroaki

    2014-08-01

    A magnetic flux effect is studied theoretically on an electric polarization induced by the Kondo effect in a triangular triple-quantum-dot system, where one of the three dots is connected to a metallic lead. This electric polarization exhibits an Aharonov-Bohm oscillation as a function of the magnetic flux penetrating through the triangular loop. The numerical renormalization group analysis reveals how the oscillation pattern depends on the Kondo coupling of a local spin with lead electrons, which is sensitive to the point contact with the lead. It provides an experimental implication that the Kondo effect is the origin of the emergent electric polarization.

  16. Phase Angle-induced Photometric And Spectral Effects On Vesta: Implications For The Dawn Mission

    NASA Astrophysics Data System (ADS)

    Reddy, Vishnu; Nathues, A.; Archer, K. A.; Sanchez, J. A.; Gaffey, M. J.; Sierks, H.; Archer, R. A.

    2010-10-01

    4 Vesta is the largest basaltic asteroid that remains mostly intact today and can be considered as a model for the early stages of planetary differentiation. The NASA DAWN mission is currently on its way to Vesta and is expected to rendezvous in July 2011 for a one year orbital characterization mission. Phase angle-induced spectral effects impact the band depth of an absorption feature, the overall spectral slope and photometric calibration. Gaffey et al. (1981), Gradie and Veverka (1986), Reddy et al. (2005) and Nathues (2000 and 2010) have proven these spectral effects on laboratory and telescopic observations. We have obtained rotationally resolved near-IR (0.7-2.5 µm) spectra of Vesta in four different phase angle intervals (5-25°) using the SpeX instrument on NASA IRTF. Simultaneously, we obtained photometric lightcurves of Vesta through the DAWN FC filter set using a small telescope at Ironwood Remote Observatory over ten nights covering a phase angle range of 3.9-24.4°. Using these two data sets we intend to constrain phase angle induced spectral effects, and photometric phase coefficients that would be helpful in calibrating early DAWN FC and VIR data. Preliminary results from this effort will be presented at the meeting. VR's research was supported by NASA NEOO Program Grants NG04GI17G and NASA PGG Program grant NNX07AL29G. Portions of this work were supported by PAST grant NNG05GF90G.

  17. Modulated nematic structures induced by chirality and steric polarization

    NASA Astrophysics Data System (ADS)

    Longa, Lech; PajÄ k, Grzegorz

    2016-04-01

    What kind of one-dimensional modulated nematic structures (ODMNS) can form nonchiral and chiral bent-core and dimeric materials? Here, using the Landau-de Gennes theory of nematics, extended to account for molecular steric polarization, we study a possibility of formation of ODMNS, both in nonchiral and intrinsically chiral liquid crystalline materials. Besides nematic and cholesteric phases, we find four bulk ODMNS for nonchiral materials, two of which, to the best of our knowledge, have not been reported so far. These two structures are longitudinal (NLP) and transverse (NTP) periodic waves where the polarization field being periodic in one dimension stays parallel and perpendicular, respectively, to the wave vector. The other two phases are the twist-bend nematic phase (NTB) and the splay-bend nematic phase (NSB), but their fine structure appears more complex than that considered so far. The presence of molecular chirality converts nonchiral NTP and NSB into new NTB phases. Surprisingly, the nonchiral NLP phase can stay stable even in the presence of intrinsic chirality.

  18. Spectral properties of optical anisotropy induced by laser radiation in dye solutions

    SciTech Connect

    Pikulik, L G; Chernyavskii, V A; Grib, A F

    2000-06-30

    Spectral studies of induced quasi-crystal properties (which can be quantitatively characterised by the difference in the refractive indices of ordinary and extraordinary waves, {Delta}n=n{sub o}-n{sub e}) in Rhodamine 6G and Rhodamine 4C solutions in glycerine excited in the visible and UV ranges of the absorption spectrum are presented. It is demonstrated that the observed spectral dependences of {Delta}n of these dye solutions excited in the visible (long-wavelength) and UV (short-wavelength) ranges of the absorption spectrum can be interpreted in terms of an oscillator model of a molecule. The proposed method for the analysis of induced optical anisotropy in solutions of organic compounds allows the relative orientation of oscillators in a molecule and, thus, the relative orientation of electronic transitions in a molecule to be determined in a reliable way. (iv international conference on atom and molecular pulsed lasers (ampl'99))

  19. Discretely tunable thulium-doped fiber-based polarization-maintaining master oscillator power amplifier using fiber Bragg grating arrays as spectral filters

    NASA Astrophysics Data System (ADS)

    Tiess, Tobias; Junaid, Saher; Becker, Martin; Rothhardt, Manfred; Bartelt, Hartmut; Jäger, Matthias

    2016-06-01

    Thulium (Tm)-doped fiber lasers offer a broad emission bandwidth in the 2-μm region, providing the perfect basis to develop broadly tunable laser sources, e.g., for spectroscopic applications. Recently, a tuning principle for pulsed fiber lasers has been reported, which is based on a fiber Bragg grating (FBG) array as a discrete spectral filter. This concept uniquely combines an unrivaled spectral freedom for tailored tuning ranges with a monolithic layout preserving the inherent advantages of fiber-integrated systems. In this study, we investigate this discrete tuning method using a Tm-doped fiber laser in the spectral domain around 1950 nm. While the laser emits linearly polarized light based on a polarization-maintaining (PM) resonator, we also examine the possibility of using standard FBG arrays inscribed in non-PM fiber. In order to highlight the prospect for tunable high-power operation, the tunable seed laser is implemented in a master oscillator power amplifier configuration scaling the average power to ˜28 W. With a tuning range of up to 76 nm, the emission characteristics of the system are investigated showing pulse durations down to 11 ns and a very good spectral signal contrast with narrow linewidth.

  20. Spectrally resolved optical probing of laser induced magnetization dynamics in bismuth iron garnet

    NASA Astrophysics Data System (ADS)

    Koene, Benny; Deb, Marwan; Popova, Elena; Keller, Niels; Rasing, Theo; Kirilyuk, Andrei

    2016-07-01

    The spectrally resolved magnetization dynamics in bismuth iron garnet shows a fluence dependent light induced modification of the magneto-optical Faraday spectrum. It is demonstrated that the relative contributions from the tetrahedral and octahedral iron sites to the Faraday spectrum change due to the impact of the pump pulse. This change explains the observed deviation from a linear dependence of the amplitude of the oscillations on the fluence, as expected for the inverse Faraday effect.

  1. Spectrally resolved optical probing of laser induced magnetization dynamics in bismuth iron garnet.

    PubMed

    Koene, Benny; Deb, Marwan; Popova, Elena; Keller, Niels; Rasing, Theo; Kirilyuk, Andrei

    2016-07-13

    The spectrally resolved magnetization dynamics in bismuth iron garnet shows a fluence dependent light induced modification of the magneto-optical Faraday spectrum. It is demonstrated that the relative contributions from the tetrahedral and octahedral iron sites to the Faraday spectrum change due to the impact of the pump pulse. This change explains the observed deviation from a linear dependence of the amplitude of the oscillations on the fluence, as expected for the inverse Faraday effect. PMID:27213266

  2. Spectral broadening induced by intense ultra-short pulse in 4H–SiC crystals

    NASA Astrophysics Data System (ADS)

    Chun-hua, Xu; Teng-fei, Yan; Gang, Wang; Wen-jun, Wang; Jing-kui, Liang; Xiao-long, Chen

    2016-06-01

    We report the observation of spectral broadening induced by 200 femtosecond laser pulses with the repetition rate of 1 kHz at the wavelength of 532 nm in semi-insulating 4H–SiC single crystals. It is demonstrated that the full width at half maximum of output spectrum increases linearly with the light propagation length and the peak power density, reaching a maximum 870 cm‑1 on a crystal of 19 mm long under an incident laser with a peak power density of 60.1 GW/cm2. Such spectral broadening can be well explained by the self-phase modulation model which correlates time-dependent phase change of pulses to intensity-dependent refractive index. The nonlinear refractive index n 2 is estimated to be 1.88×10‑15 cm2/W. The intensity-dependent refractive index is probably due to both the nonlinear optical polarizability of the bound electrons and the increase of free electrons induced by the two-photon absorption process. Super continuum spectra could arise as crystals are long enough to induce the self-focusing effect. The results show that SiC crystals may find applications in spectral broadening of high power lasers. Project supported by the National High Technology Research and Development Program of China (Grant No. 2014AA041402) and the National Natural Science Foundation of China (Grant Nos. 51272276 and 51322211).

  3. Induced spin polarization effect in graphene by ferromagnetic nanocontact

    SciTech Connect

    Mandal, Sumit; Saha, Shyamal K.

    2015-03-07

    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.

  4. Spin Manipulation in Graphene by Chemically Induced Pseudospin Polarization

    NASA Astrophysics Data System (ADS)

    Van Tuan, Dinh; Roche, Stephan

    2016-03-01

    Spin manipulation is one of the most critical challenges to realize spin-based logic devices and spintronic circuits. Graphene has been heralded as an ideal material to achieve spin manipulation, but so far new paradigms and demonstrators are limited. Here we show that certain impurities such as fluorine adatoms, which locally break sublattice symmetry without the formation of strong magnetic moment, could result in a remarkable variability of spin transport characteristics. The impurity resonance level is found to be associated with a long-range sublattice pseudospin polarization, which by locally decoupling spin and pseudospin dynamics provokes a huge spin lifetime electron-hole asymmetry. In the dilute impurity limit, spin lifetimes could be tuned electrostatically from 100 ps to several nanoseconds, providing a protocol to chemically engineer an unprecedented spin device functionality.

  5. Spin Manipulation in Graphene by Chemically Induced Pseudospin Polarization.

    PubMed

    Van Tuan, Dinh; Roche, Stephan

    2016-03-11

    Spin manipulation is one of the most critical challenges to realize spin-based logic devices and spintronic circuits. Graphene has been heralded as an ideal material to achieve spin manipulation, but so far new paradigms and demonstrators are limited. Here we show that certain impurities such as fluorine adatoms, which locally break sublattice symmetry without the formation of strong magnetic moment, could result in a remarkable variability of spin transport characteristics. The impurity resonance level is found to be associated with a long-range sublattice pseudospin polarization, which by locally decoupling spin and pseudospin dynamics provokes a huge spin lifetime electron-hole asymmetry. In the dilute impurity limit, spin lifetimes could be tuned electrostatically from 100 ps to several nanoseconds, providing a protocol to chemically engineer an unprecedented spin device functionality. PMID:27015500

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

    SciTech Connect

    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

    2014-08-28

    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.

  7. Mechanism of covalency-induced electric polarization within the framework of maximally localized Wannier orbitals

    NASA Astrophysics Data System (ADS)

    Terakura, Kiyoyuki; Ishibashi, Shoji

    2015-05-01

    It has been well established that covalency significantly enhances the electric polarization produced by the ionic displacement for ferroelectric perovskite transition metal oxides (TMO). Furthermore, recent experimental and theoretical works on the organic ferroelectrics TTF-CA (tetrathiafulvalene-p -chloranil) have revealed that the covalency-induced polarization is one to two orders of magnitude larger than that of the ionic polarization and that the two contributions are in the opposite direction. Here we propose a formulation to analyze the detailed mechanism of the covalency-induced polarization within the framework of maximally localized Wannier orbitals and apply it to an organic exotic ferroelectrics TTF-CA and typical ferroelectric perovskite TMOs, BaTiO3, and PbTiO3. This formulation discriminates three components in the electronic contribution to the polarization. The first one corresponds to the point charge model, the second to the intra-atomic or molecular polarization, and the third comes from the electron transfer between unit cells. The framework of the present formulation is the same as the one proposed by Bhattacharjee and Waghmare [Phys. Chem. Chem. Phys. 12, 1564 (2010), 10.1039/b918890h], but we give a more explicit expression of each component and discuss fundamental aspects of the formulation.

  8. Donepezil Regulates 1-Methyl-4-phenylpyridinium-Induced Microglial Polarization in Parkinson's Disease.

    PubMed

    Chen, Teng; Hou, Ruihua; Xu, Shujun; Wu, Chengyuan

    2015-10-21

    1-Methyl-4-phenylpyridinium (MPP+) induces microglial activation and degeneration of dopaminergic (DAergic) neurons. Donepezil is a well-known acetylcholinesterase inhibitor used clinically to treat cognitive dysfunction in Alzheimer's disease (AD). In the present study, we tested the hypothesis that MPP+ promotes microglial M1 polarization and suppresses M2 polarization and that this can be restored by donepezil. Results indicate that MPP+ treatment in microglial BV2 cells promotes microglial polarization toward the M1 state. However, pretreatment with donepezil inhibited MPP+-induced M1 polarization in microglia by suppressing the release of interleukin (IL)-6, IL-1β, or tumor necrosis factor (TNF)-α. Importantly, we found that MPP+ inhibited microglial M2 polarization by suppressing expression of Arg-1, Fizz1, and Ym1, which was also rescued by pretreatment with donepezil. In addition, IL-4-mediated induction of anti-inflammatory marker genes IL-10, IL-13, and transforming growth factor-β2 (TGF-β2) were significantly attenuated by MPP+ in BV2 cells, which was restored by pretreatment with donepezil in a concentration-dependent manner. Mechanistically, we found that the addition of MPP+ reduced the intensity of phosphorylated signal transducer and activator of transcription 6 (STAT6) but not total STAT6 in IL-4-stimulated BV2 cells. Importantly, pretreatment of microglial BV2 cells with donepezil 3 h prior to administration of MPP+ rescued the reduction of STAT6 phosphorylation induced by MPP+. PMID:26114860

  9. Different temporal patterns of vector soliton bunching induced by polarization-dependent saturable absorber

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Cheng; Chen, Guo-Jie; Han, Ding-An; Li, Bin

    2014-06-01

    A fiber laser with either a polarization-independent semiconductor saturable absorption mirror (PID-SESAM) or a polarization-dependent SESAM (PD-SESAM) as a passive mode-locker is constructed for obtaining the vector soliton bunching. The temporal patterns of the soliton bunching generated from the fiber laser with a PD-SESAM are much more abundant than that in fiber laser with a PID-SESAM. Only the vibrating soliton bunching is generated from the fiber laser with a PID-SESAM. However, there are another three interesting temporal patterns of the soliton bunching generated from the fiber laser with a PD-SESAM except for the vibrating soliton bunching. They are variable length soliton bunching, breathing soliton bunching and stable soliton bunching along the slow axis induced by polarization instability. It is found that the polarization property of the saturable absorber plays a pivotal role for achieving different temporal patterns of the soliton bunching.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

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

    PubMed

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

    2014-08-01

    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

  12. Symmetry breaking and electrical frustration during tip-induced polarization switching in the non-polar cut of lithium niobate single crystals

    SciTech Connect

    Ievlev, Anton; Alikin, Denis O.; Morozovska, A. N.; Varenyk, O. V.; Eliseev, E. A.; Kholkin, Andrei; Shur, Vladimir Ya.; Kalinin, Sergei V.

    2014-12-15

    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 in the non-polar cuts of uniaxial ferroelectrics. In this case, in-plane component of polarization vector switches, allowing for detailed observations of resultant domain morphologies. We observe surprising variability of resultant domain morphologies stemming from fundamental instability of formed charged domain wall and associated electric frustration. In particular, we demonstrate that controlling vertical tip position allows the polarity of the switching to be controlled. This represents very unusual form of symmetry breaking where mechanical motion in vertical direction controls the lateral domain growth. The implication of these studies for ferroelectric devices and domain wall electronics are discussed.

  13. Symmetry breaking and electrical frustration during tip-induced polarization switching in the non-polar cut of lithium niobate single crystals

    DOE PAGESBeta

    Ievlev, Anton; Alikin, Denis O.; Morozovska, A. N.; Varenyk, O. V.; Eliseev, E. A.; Kholkin, Andrei; Shur, Vladimir Ya.; Kalinin, Sergei V.

    2014-12-15

    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 in the non-polar cuts of uniaxial ferroelectrics. In this case, in-plane component of polarization vector switches, allowing for detailed observations of resultant domain morphologies. We observe surprising variability of resultant domain morphologies stemming from fundamental instability of formed charged domain wall and associated electric frustration. In particular, we demonstrate that controlling vertical tip position allows the polarity of the switching to be controlled. This represents very unusual formmore » of symmetry breaking where mechanical motion in vertical direction controls the lateral domain growth. The implication of these studies for ferroelectric devices and domain wall electronics are discussed.« less

  14. [Laser induced breakdown spectra of coal sample and self-absorption of the spectral line].

    PubMed

    Zhang, Gui-yin; Ji, Hui; Jin, Yi-dong

    2014-12-01

    The LIBS of one kind of household fuel coal was obtained with the first harmonic output 532 nm of an Nd·YAG laser as radiation source. With the assignment of the spectral lines, it was found that besides the elements C, Si, Mg, Fe, Al, Ca, Ti, Na and K, which are reported to be contained in coal, the presented sample also contains trace elements, such as Cd, Co, Hf, Ir, Li, Mn, Ni, Rb, Sr, V, W, Zn, Zr etc, but the spectral lines corresponding to O and H elements did not appear in the spectra. This is owing to the facts that the transition probability of H and O atoms is small and the energy of the upper level for transition is higher. The results of measurement also show that the intensity of spectral line increases with the laser pulse energy and self-absorption of the spectral lines K766.493 nm and K769.921 nm will appear to some extent. Increasing laser energy further will make self-absorption more obvious. The presence of self-absorption can be attributed to two factors. One is the higher transition rate of K atoms, and the other is that the increase in laser intensity induces the enhancement of the particle number density in the plasma. PMID:25881446

  15. Selection of Spectral Data for Classification of Steels Using Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kong, Haiyang; Sun, Lanxiang; Hu, Jingtao; Xin, Yong; Cong, Zhibo

    2015-11-01

    Principal component analysis (PCA) combined with artificial neural networks was used to classify the spectra of 27 steel samples acquired using laser-induced breakdown spectroscopy. Three methods of spectral data selection, selecting all the peak lines of the spectra, selecting intensive spectral partitions and the whole spectra, were utilized to compare the influence of different inputs of PCA on the classification of steels. Three intensive partitions were selected based on experience and prior knowledge to compare the classification, as the partitions can obtain the best results compared to all peak lines and the whole spectra. We also used two test data sets, mean spectra after being averaged and raw spectra without any pretreatment, to verify the results of the classification. The results of this comprehensive comparison show that a back propagation network trained using the principal components of appropriate, carefully selected spectral partitions can obtain the best results. A perfect result with 100% classification accuracy can be achieved using the intensive spectral partitions ranging of 357-367 nm. supported by the National High Technology Research and Development Program of China (863 Program) (No. 2012AA040608), National Natural Science Foundation of China (Nos. 61473279, 61004131) and the Development of Scientific Research Equipment Program of Chinese Academy of Sciences (No. YZ201247)

  16. Field-induced polarization of Dirac valleys in bismuth

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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.

  17. Dynamics of microvortices induced by ion concentration polarization.

    PubMed

    de Valença, Joeri C; Wagterveld, R Martijn; Lammertink, Rob G H; Tsai, Peichun Amy

    2015-09-01

    We investigate the coupled dynamics of the local hydrodynamics and global electric response of an electrodialysis system, which consists of an electrolyte solution adjacent to a charge selective membrane under electric forcing. Under a dc electric current, counterions transport through the charged membrane while the passage of co-ions is restricted, thereby developing ion concentration polarization (ICP) or gradients. At sufficiently large currents, simultaneous measurements of voltage drop and flow field reveal several distinct dynamic regimes. Initially, the electrodialysis system displays a steady Ohmic voltage difference (ΔV_{ohm}), followed by a constant voltage jump (ΔV_{c}). Immediately after this voltage increase, microvortices set in and grow both in size and speed with time. After this growth, the resultant voltage levels off around a fixed value. The average vortex size and speed stabilize as well, while the individual vortices become unsteady and dynamic. These quantitative results reveal that microvortices set in with an excess voltage drop (above ΔV_{ohm}+ΔV_{c}) and sustain an approximately constant electrical conductivity, destroying the initial ICP with significantly low viscous dissipation. PMID:26465416

  18. Dynamics of microvortices induced by ion concentration polarization

    NASA Astrophysics Data System (ADS)

    de Valença, Joeri C.; Wagterveld, R. Martijn; Lammertink, Rob G. H.; Tsai, Peichun Amy

    2015-09-01

    We investigate the coupled dynamics of the local hydrodynamics and global electric response of an electrodialysis system, which consists of an electrolyte solution adjacent to a charge selective membrane under electric forcing. Under a dc electric current, counterions transport through the charged membrane while the passage of co-ions is restricted, thereby developing ion concentration polarization (ICP) or gradients. At sufficiently large currents, simultaneous measurements of voltage drop and flow field reveal several distinct dynamic regimes. Initially, the electrodialysis system displays a steady Ohmic voltage difference (Δ Vohm ), followed by a constant voltage jump (Δ Vc) . Immediately after this voltage increase, microvortices set in and grow both in size and speed with time. After this growth, the resultant voltage levels off around a fixed value. The average vortex size and speed stabilize as well, while the individual vortices become unsteady and dynamic. These quantitative results reveal that microvortices set in with an excess voltage drop (above Δ Vohm+Δ Vc ) and sustain an approximately constant electrical conductivity, destroying the initial ICP with significantly low viscous dissipation.

  19. Modeling Yeast Cell Polarization Induced by Pheromone Gradients

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

    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.

  20. Transepithelial pressure pulses induce nucleotide release in polarized MDCK cells.

    PubMed

    Praetorius, H A; Frøkiaer, J; Leipziger, J

    2005-01-01

    The release of nucleotides is involved in mechanosensation in various epithelial cells. Intriguingly, kidney epithelial cells are absolutely dependent on the primary cilium to sense changes in apical laminar flow. During fluid passage, the renal epithelial cells are subjected to various mechanical stimuli in addition to changes in the laminar flow rate. In the distal part of the collecting duct, the epithelial cells are exposed to pressure changes and possibly distension during papillary contractions. The aim of the present study was to determine whether nucleotide release contributes to mechanosensation in kidney epithelial cells, thereby establishing whether pressure changes are sufficient to produce nucleotide-mediated responses. Madin-Darby canine kidney (MDCK) cells grown on permeable supports were mounted in a closed double perfusion chamber on an inverted microscope. The intracellular Ca(2+) concentration ([Ca(2+)](i)) was monitored with the Ca(2+)-sensitive fluorescence probe fluo 4. Transepithelial pressure pulses of 30-80 mm Hg produced a transient increase in [Ca(2+)](i) of MDCK cells. This response is independent of the primary cilium, since it is readily observed in immature cells that do not yet express primary cilia. The amplitudes of the pressure-induced Ca(2+) transients varied with the applied chamber pressure in a quantity-dependent manner. The ATPase apyrase and the P2Y antagonist suramin significantly reduced the pressure-induced Ca(2+) transients. Applying apyrase or suramin to both sides of the preparation simultaneously nearly abolished the pressure-induced Ca(2+) response. In conclusion, these observations suggest that rapid pressure changes induce both apical and basolateral nucleotide release that contribute to mechanosensation in kidney epithelial cells. PMID:15367389

  1. [The Spectral Analysis of Laser-Induced Plasma in Laser Welding with Various Protecting Conditions].

    PubMed

    Du, Xiao; Yang, Li-jun; Liu, Tong; Jiao, Jiao; Wang, Hui-chao

    2016-01-01

    The shielding gas plays an important role in the laser welding process and the variation of the protecting conditions has an obvious effect on the welding quality. This paper studied the influence of the change of protecting conditions on the parameters of laser-induced plasma such as electron temperature and electron density during the laser welding process by designing some experiments of reducing the shielding gas flow rate step by step and simulating the adverse conditions possibly occurring in the actual Nd : YAG laser welding process. The laser-induced plasma was detected by a fiber spectrometer to get the spectral data. So the electron temperature of laser-induced plasma was calculated by using the method of relative spectral intensity and the electron density by the Stark Broadening. The results indicated that the variation of protecting conditions had an important effect on the electron temperature and the electron density in the laser welding. When the protecting conditions were changed, the average electron temperature and the average electron density of the laser-induced plasma would change, so did their fluctuation range. When the weld was in a good protecting condition, the electron temperature, the electron density and their fluctuation were all low. Otherwise, the values would be high. These characteristics would have contribution to monitoring the process of laser welding. PMID:27228732

  2. Determination of mask induced polarization effects on AltPSM mask structures

    NASA Astrophysics Data System (ADS)

    Hollein, Ingo; Teuber, Silvio; Bubke, Karsten

    2005-06-01

    In the process of discussion of possible mask-types for the 5x nm node (half-pitch) and below, the alternating phase-shifting mask (AltPSM) is a potential candidate to be screened. The current scenario suggests using 193 nm immersion lithography with NA values of up to 1.2 and above. New optical effects from oblique incident angles, mask-induced polarization of the transmitted light and birefringence from the substrate need to be taken into account when the optical performance of a mask is evaluated. This paper addresses mask induced polarization effects from dense lines-and-space structures on a real mask. Measurements of the polarization dependent diffraction efficiencies have been performed on AltPSM masks. Experimental results show good agreement with simulations. A comparison with Binary Masks is made.

  3. Polarization-induced Zener tunnel diodes in GaN/InGaN/GaN heterojunctions

    SciTech Connect

    Yan, Xiaodong; Li, Wenjun; Islam, S. M.; Pourang, Kasra; Fay, Patrick; Xing, Huili; Jena, Debdeep

    2015-10-19

    By the insertion of thin In{sub x}Ga{sub 1−x}N layers into Nitrogen-polar GaN p-n junctions, polarization-induced Zener tunnel junctions are studied. The reverse-bias interband Zener tunneling current is found to be weakly temperature dependent, as opposed to the strongly temperature-dependent forward bias current. This indicates tunneling as the primary reverse-bias current transport mechanism. The Indium composition in the InGaN layer is systematically varied to demonstrate the increase in the interband tunneling current. Comparing the experimentally measured tunneling currents to a model helps identify the specific challenges in potentially taking such junctions towards nitride-based polarization-induced tunneling field-effect transistors.

  4. Heuristic modeling of spectral plasma emission for laser-induced breakdown spectroscopy

    SciTech Connect

    Wester, Rolf; Noll, Reinhard

    2009-12-15

    A heuristic model was developed to describe the spectral emission of laser-induced plasmas generated for laser-induced breakdown spectroscopy under the assumption that the composition of the plasma and the plasma state is known. The plasma is described by a stationary spherical shell model surrounded by an ambient gas, which partially absorbs the emitted radiation. The radiation transport equation is used to calculate the spectrum emitted by the plasma. Simulations of a multiline iron spectrum and a self-reversed Al line are compared with experimental spectra. For the iron spectrum, the degree of congruence is moderate to good, which may be attributed to a lack of precise atomic and Stark broadening data as well as a simplified plasma model. The line profile of the Al resonance line with self reversal can be simulated with a high degree of agreement. Simulated spectra of a steel sample in the vacuum ultraviolet spectral range demonstrate the strong influence of the ambient atmosphere in the spectral range between 178 and 194 nm. The number of free parameters of the plasma model of 8 can be further reduced down to 3, taking into account the integral parameters of the plasma that are accessible experimentally.

  5. Anomalous photo-induced spectral changes in CdSe/ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Shcherbatyuk, G. V.; Inman, R. H.; Ghosh, S.

    2011-09-01

    We study photo-induced static and dynamic spectral changes in self-assembled CdSe/ZnS quantum dot (QD) thin films with varying QD concentrations under ambient conditions. Using spatially resolved scanning photoluminescence microscopy in conjunction with spectrally resolved time-correlated photon counting, we measure the variations in spectral intensity, emission wavelength, and recombination lifetimes as functions of photo-exposure time. We find that at low concentrations photo-darkening and photo-oxidation rates slow down with increasing QD density, but in the high concentration limit these rates are strongly enhanced. Our measurements lead us to conclude that the interplay of photo-induced surface trap discharging with preferential photo-oxidation of smaller QDs is further modulated by resonant energy transfer driven by strong inter-dot interactions in highly concentrated samples. Our results would imply that the efficiency and longevity of semiconducting nanoparticle based opto-electronic devices will be limited by the concentration of the active material

  6. On the global polarity reversal of the induced magnetosphere of Venus: a statistical study

    NASA Astrophysics Data System (ADS)

    Vech, Daniel; Stenberg, Gabriella; Nilsson, Hans; Edberg, Niklas; Opitz, Andrea; Szego, Karoly; Zhang, Tielong; Futaana, Yoshifumi

    2016-04-01

    In this study we present the first statistical analysis on the effects of Interplanetary Magnetic Field (IMF) sector boundary crossings on the induced magnetosphere of Venus. These events are of particular interest because they lead to the reconfiguration of the induced magnetosphere with opposite polarity. IMF sector boundary crossings can occur after Heliospheric Current Sheet (HCS) crossings and often after the passages of Interplanetary Coronal Mass Ejections (ICME) and Corotating Interaction Regions (CIR). The results show that the HCS crossings cause significant erosion of the dayside ionosphere and in this region the average heavy ion flux was reduced by a factor of 0.63 compared to the undisturbed cases. The heavy ion flux on the nightside changed by a factor of 0.81. On the nightside ion heating was observed and the average heavy ion temperature increased by the factor of 1.63 compared to the undisturbed cases. The ICME/CIR events were sorted into two groups depending on the polarity reversal of the induced magnetosphere. We found significant differences between them: the cases with polarity reversal showed significant ion heating and increased heavy ion flux upon arrival of the ICME/CIR event. We conclude that the observations are similar to the previous comet studies and the polarity reversal of the induced magnetosphere might be accompanied with dayside reconnection.

  7. Salmonella typhimurium-induced M1 macrophage polarization is dependent on the bacterial O antigen.

    PubMed

    Luo, Fengling; Sun, Xiaoming; Qu, Zhen; Zhang, Xiaolian

    2016-02-01

    Recently, macrophages were shown to be capable of differentiating toward two phenotypes after antigen stimulation: a classically activated (M1) or an alternatively activated phenotype (M2). To investigate the effect of Salmonella enteric serovar typhimurium (S. typhimurium) on macrophage differentiation, we compared macrophage phenotypes after infection of murine bone marrow-derived macrophages with wild-type S. typhimurium and its isogenic rfc mutant. S. typhimurium C5 induced M1 macrophage polarization and enhanced inducible nitric oxide synthase expression by macrophages; this induction was dependent on Toll-like receptor 4. In contrast, the Δrfc mutant (S. typhimurium C5 rfc::Km(r)) lost this function and induced an M2 response in the macrophages. Here, we propose that S. typhimurium C5 is capable of polarizing macrophages towards the M1 phenotype and that this polarization is dependent on the O antigen encoded by rfc. Our finding indicates that M1 macrophage polarization induced by S. typhimurium may be related to the ability of this intracellular bacterium to survive and replicate within macrophages, which is essential for systemic disease. PMID:26745982

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

    DOEpatents

    Ward, S.H.

    1989-10-17

    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.

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

    SciTech Connect

    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

    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.

  10. Magnon emission and radiation induced by spin-polarized current

    NASA Astrophysics Data System (ADS)

    Zholud, Andrei; Freeman, Ryan; Cao, Rongxing; Urazhdin, Sergei

    The spin-torque effect due to spin injection into ferromagnets can affect their effective dynamical damping, and modify the magnon populations. The latter leads to the onset of nonlinear damping that can prevent spontaneous current-induced magnetization oscillations. It has been argued that these nonlinear processes can be eliminate by the radiation of magnons excited by local spin injection in extended magnetic films. To test these effects, studied of the effects of spin injection on the magnon populations in nanoscale spin valves and magnetic point contacts. Measurements of the giant magnetoresistance show a significant resistance component that is antisymmetric in current, and linearly dependent on temperature T. This component is significantly larger for the nanopatterned ferromagnets than for point contacts. We interpret our observations in terms of stimulated generation of magnons by the spin current, and their radiation in point contacts. Supported by NSF ECCS-1305586, ECCS-1509794.

  11. Tip-induced domain structures and polarization switching in ferroelectric amino acid glycine

    SciTech Connect

    Seyedhosseini, E. Ivanov, M.; Bdikin, I.; Vasileva, D.; Kudryavtsev, A.; Rodriguez, B. J.; Kholkin, A. L.

    2015-08-21

    Bioorganic ferroelectrics and piezoelectrics are becoming increasingly important in view of their intrinsic compatibility with biological environment and biofunctionality combined with strong piezoelectric effect and a switchable polarization at room temperature. Here, we study tip-induced domain structures and polarization switching in the smallest amino acid β-glycine, representing a broad class of non-centrosymmetric amino acids. We show that β-glycine is indeed a room-temperature ferroelectric and polarization can be switched by applying a bias to non-polar cuts via a conducting tip of atomic force microscope (AFM). Dynamics of these in-plane domains is studied as a function of an applied voltage and pulse duration. The domain shape is dictated by polarization screening at the domain boundaries and mediated by growth defects. Thermodynamic theory is applied to explain the domain propagation induced by the AFM tip. Our findings suggest that the properties of β-glycine are controlled by the charged domain walls which in turn can be manipulated by an external bias.

  12. Tip-induced domain structures and polarization switching in ferroelectric amino acid glycine

    NASA Astrophysics Data System (ADS)

    Seyedhosseini, E.; Bdikin, I.; Ivanov, M.; Vasileva, D.; Kudryavtsev, A.; Rodriguez, B. J.; Kholkin, A. L.

    2015-08-01

    Bioorganic ferroelectrics and piezoelectrics are becoming increasingly important in view of their intrinsic compatibility with biological environment and biofunctionality combined with strong piezoelectric effect and a switchable polarization at room temperature. Here, we study tip-induced domain structures and polarization switching in the smallest amino acid β-glycine, representing a broad class of non-centrosymmetric amino acids. We show that β-glycine is indeed a room-temperature ferroelectric and polarization can be switched by applying a bias to non-polar cuts via a conducting tip of atomic force microscope (AFM). Dynamics of these in-plane domains is studied as a function of an applied voltage and pulse duration. The domain shape is dictated by polarization screening at the domain boundaries and mediated by growth defects. Thermodynamic theory is applied to explain the domain propagation induced by the AFM tip. Our findings suggest that the properties of β-glycine are controlled by the charged domain walls which in turn can be manipulated by an external bias.

  13. Polarized Exocytosis Induces Compensatory Endocytosis by Sec4p-Regulated Cortical Actin Polymerization.

    PubMed

    Johansen, Jesper; Alfaro, Gabriel; Beh, Christopher T

    2016-08-01

    Polarized growth is maintained by both polarized exocytosis, which transports membrane components to specific locations on the cell cortex, and endocytosis, which retrieves these components before they can diffuse away. Despite functional links between these two transport pathways, they are generally considered to be separate events. Using live cell imaging, in vivo and in vitro protein binding assays, and in vitro pyrene-actin polymerization assays, we show that the yeast Rab GTPase Sec4p couples polarized exocytosis with cortical actin polymerization, which induces endocytosis. After polarized exocytosis to the plasma membrane, Sec4p binds Las17/Bee1p (yeast Wiskott-Aldrich Syndrome protein [WASp]) in a complex with Sla1p and Sla2p during actin patch assembly. Mutations that inactivate Sec4p, or its guanine nucleotide exchange factor (GEF) Sec2p, inhibit actin patch formation, whereas the activating sec4-Q79L mutation accelerates patch assembly. In vitro assays of Arp2/3-dependent actin polymerization established that GTPγS-Sec4p overrides Sla1p inhibition of Las17p-dependent actin nucleation. These results support a model in which Sec4p relocates along the plasma membrane from polarized sites of exocytic vesicle fusion to nascent sites of endocytosis. Activated Sec4p then promotes actin polymerization and triggers compensatory endocytosis, which controls surface expansion and kinetically refines cell polarization. PMID:27526190

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

    PubMed Central

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

    1994-01-01

    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

  15. Polarized Exocytosis Induces Compensatory Endocytosis by Sec4p-Regulated Cortical Actin Polymerization

    PubMed Central

    Johansen, Jesper; Alfaro, Gabriel; Beh, Christopher T.

    2016-01-01

    Polarized growth is maintained by both polarized exocytosis, which transports membrane components to specific locations on the cell cortex, and endocytosis, which retrieves these components before they can diffuse away. Despite functional links between these two transport pathways, they are generally considered to be separate events. Using live cell imaging, in vivo and in vitro protein binding assays, and in vitro pyrene-actin polymerization assays, we show that the yeast Rab GTPase Sec4p couples polarized exocytosis with cortical actin polymerization, which induces endocytosis. After polarized exocytosis to the plasma membrane, Sec4p binds Las17/Bee1p (yeast Wiskott—Aldrich Syndrome protein [WASp]) in a complex with Sla1p and Sla2p during actin patch assembly. Mutations that inactivate Sec4p, or its guanine nucleotide exchange factor (GEF) Sec2p, inhibit actin patch formation, whereas the activating sec4-Q79L mutation accelerates patch assembly. In vitro assays of Arp2/3-dependent actin polymerization established that GTPγS-Sec4p overrides Sla1p inhibition of Las17p-dependent actin nucleation. These results support a model in which Sec4p relocates along the plasma membrane from polarized sites of exocytic vesicle fusion to nascent sites of endocytosis. Activated Sec4p then promotes actin polymerization and triggers compensatory endocytosis, which controls surface expansion and kinetically refines cell polarization. PMID:27526190

  16. A wound-induced Wnt expression program controls planarian regeneration polarity.

    PubMed

    Petersen, Christian P; Reddien, Peter W

    2009-10-01

    Regeneration requires specification of the identity of new tissues to be made. Whether this process relies only on intrinsic regulative properties of regenerating tissues or whether wound signaling provides input into tissue repatterning is not known. The head-versus-tail regeneration polarity decision in planarians, which requires Wnt signaling, provides a paradigm to study the process of tissue identity specification during regeneration. The Smed-wntP-1 gene is required for regeneration polarity and is expressed at the posterior pole of intact animals. Surprisingly, wntP-1 was expressed at both anterior- and posterior-facing wounds rapidly after wounding. wntP-1 expression was induced by all types of wounds examined, regardless of whether wounding prompted tail regeneration. Regeneration polarity was found to require new expression of wntP-1. Inhibition of the wntP-2 gene enhanced the polarity phenotype due to wntP-1 inhibition, with new expression of wntP-2 in regeneration occurring subsequent to expression of wntP-1 and localized only to posterior-facing wounds. New expression of wntP-2 required wound-induced wntP-1. Finally, wntP-1 and wntP-2 expression changes occurred even in the absence of neoblast stem cells, which are required for regeneration, suggesting that the role of these genes in polarity is independent of and instructive for tail formation. These data indicate that wound-induced input is involved in resetting the normal polarized features of the body axis during regeneration. PMID:19805089

  17. Polarization effects induced by a two-mirror laser beam scanner

    NASA Astrophysics Data System (ADS)

    Gimbal, Scott; Li, Qiaochu; Petrova-Mayor, Anna

    2012-10-01

    The polarization lidar technique requires that the transmitted laser beam in the atmosphere is linearly polarized so that a depolarization ratio from hydrometeors and aerosol particles can be detected. This is easily achieved in vertically pointing lidars used to study clouds. However, in scanning lidars, which are of interest for wind and pollution studies, stand-off detection and biodefense, the state of polarization of the laser beam is modified upon reflection by the mirrors of the scanner. We study experimentally the effect of a two-mirror scanner, or beam steering unit (BSU), on the polarization state of a linearly polarized beam at 1.54 micron wavelength. We built a miniature BSU in the lab and used a polarimeter to map the state of polarization (SOP) for all combinations of azimuth-elevation angles. We found that the linear polarization is preserved for a horizontal scan (elevation angle is 0°) but it rotates as a function of azimuth angle. There are a few more pointing directions in which the SOP is linear. Overall, the transmit beam is elliptically polarized for a non-zero elevation angle. The ellipticity and orientation of the ellipses is not constant. However, we found a period of repeatability of 180° in both azimuth and elevation angles. When comparing two different coatings, we note that the ellipticity is a function of the type of coating. We propose a method to eliminate the induced ellipticity by the BSU mirrors for all scan directions by means of altering the incident SOP on the BSU.

  18. Collision-induced Magnetic Reconnection and a Unified Interpretation of Polarization Properties of GRBs and Blazars

    NASA Astrophysics Data System (ADS)

    Deng, Wei; Zhang, Haocheng; Zhang, Bing; Li, Hui

    2016-04-01

    The jet composition and energy dissipation mechanism of gamma-ray bursts (GRBs) and blazars are fundamental questions that remain not fully understood. One plausible model is to interpret the γ-ray emission of GRBs and optical emission of blazars as synchrotron radiation of electrons accelerated from the collision-induced magnetic dissipation regions in Poynting-flux-dominated jets. The polarization observation is an important and independent information to test this model. Based on our recent 3D relativistic MHD simulations of collision-induced magnetic dissipation of magnetically dominated blobs, here we perform calculations of the polarization properties of the emission in the dissipation region and apply the results to model the polarization observational data of GRB prompt emission and blazar optical emission. We show that the same numerical model with different input parameters can reproduce well the observational data of both GRBs and blazars, especially the 90° polarization angle (PA) change in GRB 100826A and the 180° PA swing in blazar 3C279. This supports a unified model for GRB and blazar jets, suggesting that collision-induced magnetic reconnection is a common physical mechanism to power the relativistic jet emission from events with very different black hole masses.

  19. Online monitoring of chemical reactions by polarization-induced electrospray ionization.

    PubMed

    Meher, Anil Kumar; Chen, Yu-Chie

    2016-09-21

    Polarization-induced electrospray ionization (PI-ESI) is a simple technique for instant generation of gas-phase ions directly from a microliter-sized droplet for mass spectrometric analysis. A sample droplet was placed over a dielectric substrate and in proximity (2-3 mm) to the inlet of a mass spectrometer. Owing to the polarization effect induced by the high electric field provided by the mass spectrometer, the droplet was polarized and the electrospray was generated from the apex of the droplet. The polarization-induced electrospray could last for tens of seconds, which was sufficiently long to monitor fast reactions occurring within few seconds. Thus, we demonstrated the feasibility of using the droplet-based PI-ESI MS for the online monitoring of fast reactions by simply mixing two droplets (5-10 μL) containing reactants on a dielectric substrate placed in front of a mass spectrometer applied with a high voltage (-4500 V). Schiff base reactions and oxidation reactions that can generate intermediates/products within a few seconds were selected as the model reactions. The ionic reaction species generated from intermediates and products can be simultaneously monitored by PI-ESI MS in real time. We also used this approach to selectively detect acetone from a urine sample, in which acetone was derivatized in situ. In addition, the possibility of using this approach for quantitative analysis of acetone from urine samples was examined. PMID:27590551

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

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

  2. Beyond intensity: Spectral features effectively predict music-induced subjective arousal.

    PubMed

    Gingras, Bruno; Marin, Manuela M; Fitch, W Tecumseh

    2014-01-01

    Emotions in music are conveyed by a variety of acoustic cues. Notably, the positive association between sound intensity and arousal has particular biological relevance. However, although amplitude normalization is a common procedure used to control for intensity in music psychology research, direct comparisons between emotional ratings of original and amplitude-normalized musical excerpts are lacking. In this study, 30 nonmusicians retrospectively rated the subjective arousal and pleasantness induced by 84 six-second classical music excerpts, and an additional 30 nonmusicians rated the same excerpts normalized for amplitude. Following the cue-redundancy and Brunswik lens models of acoustic communication, we hypothesized that arousal and pleasantness ratings would be similar for both versions of the excerpts, and that arousal could be predicted effectively by other acoustic cues besides intensity. Although the difference in mean arousal and pleasantness ratings between original and amplitude-normalized excerpts correlated significantly with the amplitude adjustment, ratings for both sets of excerpts were highly correlated and shared a similar range of values, thus validating the use of amplitude normalization in music emotion research. Two acoustic parameters, spectral flux and spectral entropy, accounted for 65% of the variance in arousal ratings for both sets, indicating that spectral features can effectively predict arousal. Additionally, we confirmed that amplitude-normalized excerpts were adequately matched for loudness. Overall, the results corroborate our hypotheses and support the cue-redundancy and Brunswik lens models. PMID:24215647

  3. Anion-dye-induced spectral sensitization of holographic microsystems core-silver halide shell

    NASA Astrophysics Data System (ADS)

    Tyurin, A. V.; Zhukov, S. A.; Churashov, V. P.; Bekshaev, A. Y.

    2015-11-01

    We have studied spectral sensitization with anionic dyes of holographic microsystems "core - silver halide shell" (CSHS), cores of which can be either nonsilver or silver halide compounds. Conditions under which dye sensitizers, being adsorbed on cores, remain under silver halide shells after their growing are considered. Comparison of results of sensitometric and low-temperature (T = 77 K) luminescent measurements have shown that these conditions are determined by the charge state of cations of microsystem cores. If the shell contains the same univalent component in its composition as the core does, as in the case in which the core is a silver halide compound, the anionic dye is displaced to the outer surface of the shell. If the core contains a divalent cationic component, as in the case in which the core is a nonsilver compound, the dye remains under the silver halide shell; i.e., it is overgrown by the shell. We have shown that the charge state of core cations affects the character of the core interaction with anionic dyes, which ensures differences in the spectral sensitization of CSHS microsystems, as well as differences in the dye photoexcitation relaxation in them. We have found that supersensitization of AgBr microcrystals sensitized by infrachromatic dye affects the interaction between the dye aggregates and the surface silver ions, which induces modification of the holographic microsystems' spectral sensitivity range.

  4. MAUVE/SWIPE: an imaging instrument concept with multi-angular, -spectral, and -polarized capability for remote sensing of aerosols, ocean color, clouds, and vegetation from space

    NASA Astrophysics Data System (ADS)

    Frouin, Robert; Deschamps, Pierre-Yves; Rothschild, Richard; Stephan, Edward; Leblanc, Philippe; Duttweiler, Fred; Ghaemi, Tony; Riedi, Jérôme

    2006-12-01

    The Monitoring Aerosols in the Ultraviolet Experiment (MAUVE) and the Short-Wave Infrared Polarimeter Experiment (SWIPE) instruments have been designed to collect, from a typical sun-synchronous polar orbit at 800 km altitude, global observations of the spectral, polarized, and directional radiance reflected by the earth-atmosphere system for a wide range of applications. Based on the heritage of the POLDER radiometer, the MAUVE/SWIPE instrument concept combines the merits of TOMS for observing in the ultra-violet, MISR for wide field-of-view range, MODIS, for multi-spectral aspects in the visible and near infrared, and the POLDER instrument for polarization. The instruments are camera systems with 2-dimensional detector arrays, allowing a 120-degree field-of-view with adequate ground resolution (i.e., 0.4 or 0.8 km at nadir) from satellite altitude. Multi-angle viewing is achieved by the along-track migration at spacecraft velocity of the 2-dimensional field-of-view. Between the cameras' optical assembly and detector array are two filter wheels, one carrying spectral filters, the other polarizing filters, allowing measurements of the first three Stokes parameters, I. Q, and V, of the incident radiation in 16 spectral bands optimally placed in the interval 350-2200 nm. The spectral range is 350-1050 nm for the MAUVE instrument and 1050-2200 nm for the SWIPE instrument. The radiometric requirements are defined to fully exploit the multi-angular, multi-spectral, and multi-polarized capability of the instruments. These include a wide dynamic range, a signal-to-noise ratio above 500 in all channels at maximum radiance level, i.e., when viewing a surface target of albedo equal to 1, and a noise-equivalent-differential reflectance better than 0.0005 at low signal level for a sun at zenith. To achieve daily global coverage, a pair of MAUVE and SWIPE instruments would be carried by each of two mini-satellites placed on interlaced orbits. The equator crossing time of the

  5. 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...

  6. 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...

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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

  8. Optical Sensing of Ecosystem Carbon Fluxes Combining Spectral Reflectance Indices with Solar Induced Fluorescence

    NASA Astrophysics Data System (ADS)

    Huemmrich, K. F.; Middleton, E.; Corp, L. A.; Campbell, P. K.; Kustas, W. P.

    2014-12-01

    Optical sampling of spectral reflectance and solar induced fluorescence provide information on the physiological status of vegetation that can be used to infer stress responses and estimates of production. Multiple repeated observations are required to observe the effects of changing environmental conditions on vegetation. This study examines the use of optical signals to determine inputs to a light use efficiency (LUE) model describing productivity of a cornfield where repeated observations of carbon flux, spectral reflectance and fluorescence were collected. Data were collected at the Optimizing Production Inputs for Economic and Environmental Enhancement (OPE3) fields (39.03°N, 76.85°W) at USDA Beltsville Agricultural Research Center. Agricultural Research Service researchers measured CO2 fluxes using eddy covariance methods throughout the growing season. Optical measurements were made from the nearby tower supporting the NASA FUSION sensors. The sensor system consists of two dual channel, upward and downward looking, spectrometers used to simultaneously collect high spectral resolution measurements of reflected and fluoresced light from vegetation canopies. Estimates of chlorophyll fluorescence, combined with measures of vegetation pigment content and the Photosynthetic Reflectance Index (PRI) derived from the spectral reflectance are compared with CO2 fluxes over diurnal periods for multiple days. PRI detects changes in Xanthophyll cycle pigments using reflectance at 531 nm compared to a reference band at 570 nm. The relationships among the different optical measurements indicate that they are providing different types of information on the vegetation and that combinations of these measurements provide improved retrievals of CO2 fluxes than any index alone.

  9. Electric polarization induced by the inverse DM interactions in canted antiferromagnets

    NASA Astrophysics Data System (ADS)

    Furukawa, Nobuo; Miyahara, Shin

    We investigate electric polarizations induced by antisymmetric spin pairs Si ×Sj on distorted lattices through the inverse Dzyaloshinsky-Moriya (DM) interaction. From an extended Hubbard model, We microscopically derive a generic form of the electric polarization, p = d& circ; (Si ×Sj) , with a tensor d& circ;. This includes components of the electric polarization other than those given by the Katsura-Nagaosa-Balatsky formula p ~eij × (Si ×Sj) . Our results indicate that various magnetic structures, such as canted antiferromagnetic as well as proper screw spin structures, show multiferroic properties owing to these non-Katsura-Nagaosa-Balatsky components of the coupling. We also discuss possible novel multiferroic behaviours through these couplings in various compounds.

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    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.

  11. Polarization-maintaining, double-clad fiber amplifier employing externally applied stress-induced birefringence

    SciTech Connect

    Koplow, Jeffrey P.; Goldberg, Lew; Moeller, Robert P.; Kliner, Dahv A. V.

    2000-03-15

    We report a new approach to obtaining linear-polarization operation of a rare-earth-doped fiber amplifier in which the gain fiber is coiled under tension to induce birefringence. We demonstrated this method by constructing an Er/Yb-doped, double-clad, single-mode fiber amplifier with an output power of 530 mW and a polarization extinction ratio of >17 dB (when seeded with linearly polarized light) at a wavelength of {approx}1.5 {mu}m . The technique is achromatic, permits single- or multiple-pass operation of the amplifier, requires no additional components in the optical path, leaves the fiber ends unobstructed, and is inexpensive to implement. (c) 2000 Optical Society of America.

  12. Thickness and Temperature effect on tip induced polarization switching of Ni substituted PZT Thin Films

    NASA Astrophysics Data System (ADS)

    Kumari, Shalini; Pradhan, Dhiren; Vasudevan, Rama; Strelcove, Eveghni; Ortega, Nora; Kumar, Ashok; Kalinin, Sergei; Katiyar, Ram

    Piezoresponse force microscopy (PFM) is one of the most popular techniques used for the complex investigations of the ferroelectric materials, allowing visualization of the static ferroelectric domain structures. Substitution of Ni in B site of PZT has been chosen for the present study to reduce the optical band gap for phototovoltaic applications. Here we experimentally studied the effect of thickness and temperature on tip induced polarization reversal of Ni doped PZT thin films by band excitation PFM. The out of field and in field band excitation polarization spectroscopy along with poling experiment conclusively confirm the existence of ferroelectricity down to 5 nm. The decrease of piezoresponse is observed with increase of temperature. The ferroelectric phase transition is also probed by the temperature dependence of piezoresponse studies. Detailed studies on effect of thickness and temperature on coercive field, imprint, switchable polarization, nucleation bias of PZTNi30 will be discussed in the meeting.

  13. Magnetic-Field-Induced Rotation of Polarized Light Emission from Monolayer WS_{2}.

    PubMed

    Schmidt, Robert; Arora, Ashish; Plechinger, Gerd; Nagler, Philipp; Granados Del Águila, Andrés; Ballottin, Mariana V; Christianen, Peter C M; Michaelis de Vasconcellos, Steffen; Schüller, Christian; Korn, Tobias; Bratschitsch, Rudolf

    2016-08-12

    We control the linear polarization of emission from the coherently emitting K^{+} and K^{-} valleys (valley coherence) in monolayer WS_{2} with an out-of-plane magnetic field of up to 25 T. The magnetic-field-induced valley Zeeman splitting causes a rotation of the emission polarization with respect to the excitation by up to 35° and reduces the polarization degree by up to 16%. We explain both of these phenomena with a model based on two noninteracting coherent two-level systems. We deduce that the coherent light emission from the valleys decays with a time constant of τ_{c}=260  fs. PMID:27563997

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

    NASA Astrophysics Data System (ADS)

    Tripathi, Neeraj

    2011-12-01

    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

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

    PubMed

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

    2013-04-01

    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

  16. Connectivity changes underlying spectral EEG changes during propofol-induced loss of consciousness

    PubMed Central

    Boly, Mélanie; Moran, Rosalyn; Murphy, Michael; Boveroux, Pierre; Bruno, Marie-Aurélie; Noirhomme, Quentin; Ledoux, Didier; Bonhomme, Vincent; Brichant, Jean-François; Tononi, Giulio; Laureys, Steven; Friston, Karl

    2012-01-01

    The mechanisms underlying anesthesia-induced loss of consciousness remain a matter of debate. Recent electrophysiological reports suggest that while initial propofol infusion provokes an increase in fast rhythms (from beta to gamma range), slow activity (delta to alpha) rises selectively during loss of consciousness. Dynamic causal modeling was used to investigate the neural mechanisms mediating these changes in spectral power in humans. We analyzed source-reconstructed data from frontal and parietal cortices during normal wakefulness, propofol-induced mild sedation and loss of consciousness. Bayesian model selection revealed that the best model for explaining spectral changes across the three states involved changes in cortico-thalamic interactions. Compared to wakefulness, mild sedation was accounted for by an increase in thalamic excitability, which did not further increase during loss of consciousness. In contrast, loss of consciousness per se was accompanied by a decrease in backward cortico-cortical connectivity from frontal to parietal cortices, while thalamo-cortical connectivity remained unchanged. These results emphasize the importance of recurrent cortico-cortical communication in the maintenance of consciousness and suggest a direct effect of propofol on cortical dynamics. PMID:22593076

  17. Bastille Day Flare Multi-Spectral Characterization of Radio Emission Polarization from Milliseconds to Minutes Time Scale

    NASA Astrophysics Data System (ADS)

    Rodríguez Taboada, R. E.; Méndez Berhondo, A. L.

    2006-12-01

    In this work we pay attention to the characteristics of millisecond spikes in relation to the general activity in which they are included, processes with very different time scales. Observations were provided by the Trieste Astronomical Observatory (OAT) radio polarimeters in 237, 327, 408, 610, 1420 and 2695 MHz, with 100 Hz temporal resolution. Some complementary data were obtained from open sources in Internet (Goes X-R, SOHO images, etc.) The waiting time distribution between individual maxima (flux >10 sfu) was calculated searching for self-organized criticality. Left and right polarization components were analyzed separately. The analyzed temporal interval presents two activity periods. The first related to HXR and gamma emission with both polarization millisecond events, and the following activity period is dominated by the right polarized component events. This behavior is considered evidence of two different dominant generation mechanisms for millisecond events.

  18. Wavelength-tunable polarization converter utilizing the strain induced by proton exchange in lithium niobate

    NASA Astrophysics Data System (ADS)

    Wang, T.-J.; Chung, J.-S.

    2005-02-01

    A new wavelength-tunable polarization converter utilizing the strain induced by proton exchange is demonstrated in x-cut LiNbO3. The light polarization is converted by the strain-optic effect through the phase-matched coupling of two orthogonal polarizations. The stress-applying structure is designed to be composed of several proton-exchanged strip regions for maximization of the stress distribution. The principle of birefringent chain filters is utilized to design the device structure in order to avoid the requirement of large stress, which results in serious cracks on the substrate surface. The overlap integral between the optical field distribution and the stress distribution can be enhanced simply by prolonging the proton-exchange time. Besides, the stress distribution and its strength in the stress-applying structure can be fine tuned without affecting the waveguide characteristics such that the principle of the birefringent chain filters is completely satisfied. Therefore, the polarization-conversion efficiency can be optimized when utilizing this exclusive stress-tuning ability. By the thermal-optic effect, the wavelength of maximum conversion can be tuned at a rate of -0.115 nm/°C with a maximum conversion efficiency of 92.41%. The proposed polarization converter has the advantages of adequate stress distribution and strength, high parameter-tuning feasibility, low propagation loss, easy fabrication, and low fabrication cost.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  20. Gravity-induced PIN transcytosis for polarization of auxin fluxes in gravity-sensing root cells

    PubMed Central

    Kleine-Vehn, Jürgen; Ding, Zhaojun; Jones, Angharad R.; Tasaka, Masao; Morita, Miyo T.; Friml, Jiří

    2010-01-01

    Auxin is an essential plant-specific regulator of patterning processes that also controls directional growth of roots and shoots. In response to gravity stimulation, the PIN3 auxin transporter polarizes to the bottom side of gravity-sensing root cells, presumably redirecting the auxin flux toward the lower side of the root and triggering gravitropic bending. By combining live-cell imaging techniques with pharmacological and genetic approaches, we demonstrate that PIN3 polarization does not require secretion of de novo synthesized proteins or protein degradation, but instead involves rapid, transient stimulation of PIN endocytosis, presumably via a clathrin-dependent pathway. Moreover, gravity-induced PIN3 polarization requires the activity of the guanine nucleotide exchange factors for ARF GTPases (ARF-GEF) GNOM-dependent polar-targeting pathways and might involve endosome-based PIN3 translocation from one cell side to another. Our data suggest that gravity perception acts at several instances of PIN3 trafficking, ultimately leading to the polarization of PIN3, which presumably aligns auxin fluxes with gravity vector and mediates downstream root gravitropic response. PMID:21135243

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

    PubMed

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

    2015-04-01

    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-β) signaling pathway appeared to mediate the effects of MSCs on macrophage polarization and subsequently the inhibition of hallmark features of asthma. Inhibition of TGF-β 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-β-signaling-dependent alveolar macrophage polarization. PMID:24958014

  2. Horizontal polarization of ground motion in the Hayward fault zone at Fremont, California: dominant fault-high-angle polarization and fault-induced cracks

    NASA Astrophysics Data System (ADS)

    Pischiutta, M.; Salvini, F.; Fletcher, J.; Rovelli, A.; Ben-Zion, Y.

    2012-03-01

    We investigate shear wave polarization in the Hayward fault zone near Niles Canyon, Fremont, CA. Waveforms of 12 earthquakes recorded by a seven-accelerometer seismic array around the fault are analysed to clarify directional site effects in the fault damage zone. The analysis is performed in the frequency domain through H/V spectral ratios with horizontal components rotated from 0° to 180°, and in the time domain using the eigenvectors and eigenvalues of the covariance matrix method employing three component records. The near-fault ground motion tends to be polarized in the horizontal plane. At two on-fault stations where the local strike is N160°, ground motion polarization is oriented N88 ± 19° and N83 ± 32°, respectively. At a third on-fault station, the motion is more complex with horizontal polarization varying in different frequency bands. However, a polarization of N86 ± 7°, similar to the results at the other two on-fault stations, is found in the frequency band 6-8 Hz. The predominantly high-angle polarization from the fault strike at the Hayward Fault is consistent with similar results at the Parkfield section of the San Andreas Fault and the Val d'Agri area (a Quaternary extensional basin) in Italy. In all these cases, comparisons of the observed polarization directions with models of fracture orientation based on the fault movement indicate that the dominant horizontal polarization is near-orthogonal to the orientation of the expected predominant cracking direction. The results help to develop improved connections between fault mechanics and near-fault ground motion.

  3. Suppression of the antiferroelectric phase during polarization cycling of an induced ferroelectric phase

    SciTech Connect

    Liu, Xiaoming; Tan, Xiaoli

    2015-08-17

    The ceramic Pb{sub 0.99}Nb{sub 0.02}[(Zr{sub 0.57}Sn{sub 0.43}){sub 0.92}Ti{sub 0.08}]{sub 0.98}O{sub 3} can exist in either an antiferroelectric or a ferroelectric phase at room temperature, depending on the thermal and electrical history. The antiferroelectric phase can be partially recovered from the induced ferroelectric phase when the applied field reverses polarity. Therefore, polarization cycling of the ferroelectric phase in the ceramic under bipolar fields at room temperature is accompanied with repeated phase transitions. In this letter, the stability of the recovered antiferroelectric phase upon electrical cycling of the ceramic is investigated. Ex-situ X-ray diffraction reveals that bipolar cycling suppresses the antiferroelectric phase; this is indirectly supported by piezoelectric coefficient d{sub 33} measurements. It is speculated that the accumulated charged point defects during polarization cycling stabilize the polar ferroelectric phase. The findings presented are important to the fundamental studies of electric fatigue and field-induced phase transitions in ferroelectrics.

  4. [INVITED] Self-induced polarization tracking, tunneling effect and modal attraction in optical fiber

    NASA Astrophysics Data System (ADS)

    Guasoni, M.; Morin, P.; Bony, P.-Y.; Wabnitz, S.; Fatome, J.

    2016-06-01

    In this paper, we report the observation and exploitation of the capability of light to self-organize its state-of-polarization, upon propagation in optical fibers, by means of a device called Omnipolarizer. The principle of operation of this system consists in a counter-propagating four-wave mixing interaction between an incident signal and its backward replica generated at the fiber output thanks to a reflective fiber loop. We have exploited this self-induced polarization tracking phenomenon for all-optical data processing and successfully demonstrated the spontaneous repolarization of a 40-Gbit/s On-Off keying optical signal without noticeable impairments. Moreover, the strong local coupling between the two counter-propagating waves has also revealed a fascinating aspect of the Omnipolarizer called polarization-based tunneling effect. This intrinsic property enables us to instantaneously let "jump" a polarization information onto the reflected signal, long before the expected time-of-flight induced by the round-trip along the fiber span. Finally, we discuss how the concept of self-organization could be generalized to multimode fibers, which paves the way to new important applications in the framework of spatial-mode-multiplexing.

  5. 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)

    Wang, Jin; Cao, Yongsheng; Chen, Fushen

    2015-01-01

    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.

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

    SciTech Connect

    Kawasaki, Masahiro; Miyamoto, Koichi; Nakayama, Kazunori

    2010-11-15

    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} > or approx. 10{sup -8}, B-mode polarization induced by cosmic strings can be detected by future CMB experiments.

  7. Measurement of the Induced Proton Polarization Pn in the 12C(e, e', p) reaction

    SciTech Connect

    Woo, R J; Barkhuff, David; Bertozzi, William; Chen, Jian-ping; Dale, Dan; Dodson, G; Dow, K A; Epstein, Marty; Farkhondeh, Manouchehr; Finn, Mike; Gilad, Shalev; Jones, Mark K; Joo, Kyungseon; Kelly, James; Kowalski, Stanley; Lourie, Bob; Madey, Richard; Margaziotis, Dimitri; Markowitz, Pete; McIntyre, Justin; Mertz, Christoph; Milbrath, Brian; Mitchell, Joseph; Perdrisat, Charles F; Punjabi, Vina; Rutt, Paul; Sarty, Adam; Tieger, D; Tschalaer, C; Turchinetz, William; Ulmer, Paul E; Van Verst, S P; Vellidis, C; Warren, Glen; Weinstein, Lawrence

    1998-01-19

    The first measurements of the induced proton polarization Pn for the 12C(e,e',p) reaction are reported. The experiment was performed at quasifree kinematics for energy and momentum transfer (w,q) = (294 MeV, 765 MeV/c) and sampled a missing momentum range of 0-250 MeV/c. The induced polarization arises from final-state interactions and for these kinematics is dominated by the real part of the spin-orbit optical potential. The distorted-wave impulse approximation provides good agreement with data for the 1 p3/2 shell. The data for the continuum suggest that both the 1s1/2 shell and underlying l > 1 configurations contribute.

  8. Apparatus and Method for Elimination of Polarization-Induced Fading in Fiber-optic Sensor System

    NASA Technical Reports Server (NTRS)

    Chan, Hon Man (Inventor); Parker, Jr., Allen R. (Inventor)

    2015-01-01

    The invention is an apparatus and method of eliminating polarization-induced fading in interferometric fiber-optic sensor system having a wavelength-swept laser optical signal. The interferometric return signal from the sensor arms are combined and provided to a multi-optical path detector assembly and ultimately to a data acquisition and processing unit by way of a switch that is time synchronized with the laser scan sweep cycle.

  9. Epoxyeicosatrienoic Acids Regulate Macrophage Polarization and Prevent LPS-Induced Cardiac Dysfunction

    PubMed Central

    Dai, Meiyan; Wu, Lujin; He, Zuowen; Zhang, Shasha; Chen, Chen; Xu, Xizhen; Wang, Peihua; Gruzdev, Artiom; Zeldin, Darryl C.; Wang, Dao Wen

    2015-01-01

    Macrophages, owning tremendous phenotypic plasticity and diverse functions, were becoming the target cells in various inflammatory, metabolic and immune diseases. Cytochrome P450 epoxygenase 2J2 (CYP2J2) metabolizes arachidonic acid to form epoxyeicosatrienoic acids (EETs), which possess various beneficial effects on cardiovascular system. In the present study, we evaluated the effects of EETs treatment on macrophage polarization and recombinant adeno-associated virus (rAAV)-mediated CYP2J2 expression on lipopolysaccharide (LPS)-induced cardiac dysfunction, and sought to investigate the underlying mechanisms. In vitro studies showed that EETs (1μmol/L) significantly inhibited LPS-induced M1 macrophage polarization and diminished the proinflammatory cytokines at transcriptional and post-transcriptional level; meanwhile it preserved M2 macrophage related molecules expression and upregulated antiinflammatory cytokine IL-10. Furthermore, EETs down-regulated NF-κB activation and up-regulated peroxisome proliferator-activated receptors (PPARα/γ) and heme oxygenase 1 (HO-1) expression, which play important roles in regulating M1 and M2 polarization. In addition, LPS treatment in mice induced cardiac dysfunction, heart tissue damage and infiltration of M1 macrophages, as well as the increase of inflammatory cytokines in serum and heart tissue, but rAAV-mediated CYP2J2 expression increased EETs generation in heart and significantly attenuated the LPS-induced harmful effects, which mechanisms were similar as the in vitro study. Taken together, the results indicate that CYP2J2/EETs regulates macrophage polarization by attenuating NF-κB signaling pathway via PPARα/γ and HO-1 activation and its potential use in treatment of inflammatory diseases. PMID:25626689

  10. Interpreting current-induced spin polarization in topological insulator surface states

    NASA Astrophysics Data System (ADS)

    Li, Pengke; Appelbaum, Ian

    2016-06-01

    Several recent experiments on three-dimensional topological insulators claim to observe a large charge current-induced nonequilibrium ensemble spin polarization of electrons in the helical surface state. We present a comprehensive criticism of such claims, using both theory and experiment: First, we clarify the interpretation of quantities extracted from these measurements by deriving standard expressions from a Boltzmann transport equation approach in the relaxation-time approximation at zero and finite temperature to emphasize our assertion that, despite high in-plane spin projection, obtainable current-induced ensemble spin polarization is minuscule. Second, we use a simple experiment to demonstrate that magnetic field-dependent open-circuit voltage hysteresis (identical to those attributed to current-induced spin polarization in topological insulator surface states) can be generated in analogous devices where current is driven through thin films of a topologically trivial metal. This result ipso facto discredits the naive interpretation of previous experiments with TIs, which were used to claim observation of helicity, i.e., spin-momentum locking in the topologically protected surface state.

  11. Objective interpretation of induced polarization tomography using a quantitative approach for the investigation of periglacial environments

    NASA Astrophysics Data System (ADS)

    Banville, David Roy; Fortier, Richard; Dupuis, Christian

    2016-07-01

    The objective interpretation of induced polarization tomography for applications in periglacial environments is sometimes challenging using smoothness-regularized least square inversion because strong resistivity contrasts are often present. Ambiguities arise from the regularization process which smooths the contrast between layers and from artifacts created by the inversion. In periglacial environments, where frozen and thawed ground can coexist with large resistivity contrasts, such artefacts are often found in the models of electrical resistivity. To assess reliable cryohydrogeological models from the inversion of induced polarization tomography, quantitative interpretation criteria are needed. The present work describes a methodology based on forward-inverse modeling to build a cryohydrogeological model from induced polarization data and prior information using the resistivity and chargeability gradients to map transitions between adjacent layers. This methodology is tested on field-data acquired over a coarse grained aquifer within a glaciomarine deposit and ice-rich permafrost mounds within marine sediments. Delineation of the permafrost base is achieved despite the presence of an inversion artefact. The results of the interpretation are used to further constrain the inversion in order to map the ice-content based on the resistivity model and an empirical relationship. The proposed methodology provides a way to extract quantitative information even in difficult environmental settings.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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 μM.

  13. A low cost design to eliminate polarization induced phase shift for dual Mach-Zehnder fiber interferometer

    NASA Astrophysics Data System (ADS)

    Li, Rui; Liang, Sheng; Liu, Qianzhe; Xiao, Wen

    2015-08-01

    In dual Mach-Zehnder interferometer (DMZI) system, polarization induced phase shift (PIPS) leads to a big location error. Traditional approaches adopt polarization controller (PC) to eliminate PIPS by controlling polarization state (PS) of light source. Through establishing the influence model of input light PS and equivalent polarization parameters of sensing cable on interference signals, an approach using a simplified polarization controller (PC) to obtain high location accuracy is proposed. The simplified PC is composed of a polarizer and a fiber-fused half-wave plate and can provide a linearly polarized light with azimuth angle controlled. Simulation and experiment indicate that the proposed method and PC design not only has capability of eliminating PIPS, but also has the benefits of low cost and easy control.

  14. Polar/apolar compounds induce leukemia cell differentiation by modulating cell-surface potential.

    PubMed Central

    Arcangeli, A; Carlà, M; Del Bene, M R; Becchetti, A; Wanke, E; Olivotto, M

    1993-01-01

    The mechanism of action of polar/apolar inducers of cell differentiation, such as dimethyl sulfoxide and hexamethylene-bisacetamide, is still obscure. In this paper evidence is provided that their effects on murine erythroleukemia cells are modulated by various extracellular cations as a precise function of the cation effects on membrane surface potential. The interfacial effects of the inducers were directly measured on the charged electrode, showing that both dimethyl sulfoxide and hexamethylene-bisacetamide, at the effective concentrations for cell differentiation and within the physiological range of charge density, adsorb at the charged surface and produce a potential shift. A linear correlation was found between this shift and the inducer effects on cell differentiation. Besides offering a different interpretation of the mechanism of action of the inducers, these findings indicate that surface potential has a signaling function. They may also be relevant to cancer treatments based on tumor-cell commitment to terminal differentiation. Images Fig. 1 PMID:8516337

  15. Nonlinear temperature dependence of glue-induced birefringence in polarization maintaining FBG sensors

    NASA Astrophysics Data System (ADS)

    Hopf, Barbara; Koch, Alexander W.; Roths, Johannes

    2016-05-01

    Glue-induced stresses decrease the accuracy of surface-mounted fiber Bragg gratings (FBG). Significant temperature dependent glue-induced birefringence was verified when a thermally cured epoxy-based bonding technique had been used. Determining the peak separation of two azimuthally aligned FBGs in PM fibers combined with a polarization resolved measurement set-up in a temperature range between -30°C and 150°C revealed high glue-induced stresses at low temperatures. Peak separations of about 60 pm and a nonlinear temperature dependence of the glue-induced birefringence due to stress relaxation processes and a visco-elastic behavior of the used adhesive have been shown.

  16. Spectral observation of the soft X-ray background and of the North Polar Spur with solid state spectrometers

    NASA Technical Reports Server (NTRS)

    Rocchia, R.; Arnaud, M.; Blondel, C.; Cheron, C.; Christy, J. C.; Koch, L.; Rothenflug, R.; Schnopper, H. W.; Delvaille, J. P.

    1983-01-01

    Soft X-ray diffuse background observations in the 0.3-1.5 keV interval of two sky regions, near the north galactic pole and the North Polar Spur (NPS) are reported. Data were taken with a solid-state spectrometer carried by a rocket. The near-polar region exhibited O VII ion emissions at 530 eV. A second component was not identified but was attributed to the Galactic Halo. Fe XVIII, Ne IX, and O VIII contributions were detected in the NPS, along with an enhancement at 1.35 keV from Mg XI lines. A two-temperature contour was fit to the spectra and chi-square confidence levels of 90 and 68 percent were obtained.

  17. Spectral line polarization with angle-dependent partial frequency redistribution. I. A Stokes parameters decomposition for Rayleigh scattering

    NASA Astrophysics Data System (ADS)

    Frisch, H.

    2010-11-01

    Context. The linear polarization of a strong resonance lines observed near the solar limb is created by a multiple-scattering process. Partial frequency redistribution (PRD) effects must be accounted for to explain the polarization profiles. The redistribution matrix describing the scattering process is a sum of terms, each containing a PRD function multiplied by a Rayleigh type phase matrix. A standard approximation made in calculating the polarization is to average the PRD functions over all the scattering angles, because the numerical work needed to take the angle-dependence of the PRD functions into account is large and not always needed for reasonable evaluations of the polarization. Aims: This paper describes a Stokes parameters decomposition method, that is applicable in plane-parallel cylindrically symmetrical media, which aims at simplifying the numerical work needed to overcome the angle-average approximation. Methods: The decomposition method relies on an azimuthal Fourier expansion of the PRD functions associated to a decomposition of the phase matrices in terms of the Landi Degl'Innocenti irreducible spherical tensors for polarimetry T^K_Q(i, Ω) (i Stokes parameter index, Ω ray direction). The terms that depend on the azimuth of the scattering angle are retained in the phase matrices. Results: It is shown that the Stokes parameters I and Q, which have the same cylindrical symmetry as the medium, can be expressed in terms of four cylindrically symmetrical components I_Q^K (K = Q = 0, K = 2, Q = 0, 1, 2). The components with Q = 1, 2 are created by the angular dependence of the PRD functions. They go to zero at disk center, ensuring that Stokes Q also goes to zero. Each component I_Q^K is a solution to a standard radiative transfer equation. The source term S_Q^K are significantly simpler than the source terms corresponding to I and Q. They satisfy a set of integral equations that can be solved by an accelerated lambda iteration (ALI) method.

  18. The spectral-angular and polarization characteristics of radiation from an electron beam traversing an inhomogeneous electromagnetic wave

    SciTech Connect

    Koltsov, A.V.; Serov, A.V.

    1995-12-31

    The generation of frequency harmonics of a radiation when the electron beam traverse the inhomogeneous electromagnetic wave was investigated. The electromagnetic wave are linearly polarized. The plane beam of particles enters the wave at right angle with respect to the direction of propogation of the wave and the vector E of the wave. The spartial distribution of radiation from the higher harmonics and the power density contours are caculated.

  19. Electronic spill-out induced spectral broadening in quantum hydrodynamic nanoplasmonics.

    PubMed

    Li, Xiaoming; Fang, Hui; Weng, Xiaoyu; Zhang, Lichao; Dou, Xiujie; Yang, Aiping; Yuan, Xiaocong

    2015-11-16

    The hydrodynamic theory is a powerful tool to study the nonlocal effects in metallic nanostructures that are too small to obey classical electrodynamics while still too large to be handled with a full quantum-mechanical theory. The existing hydrodynamic model can give accurate quantitative predictions for the plasmonic resonance shifts in metallic nanoplasmonics, yet is not able to predict the spectral width which is usually taken as a pre-set value instead. By taking account the fact that due to electron density spill-out from a surface, the Coulomb interaction screening is less efficient close the surface thus leads to a higher electron-electron scattering rate in this paper, we study how the electron-density-related damping rate induced by such Coulomb interaction will affect the plasmonic spectral broadening. We perform the simulation on a Na nanowire, which shows that the absorption spectra width is wider when the size of the nanowire becomes smaller. This result is consistent well with the reported experiment. Therefore, our theoretical model extends the existing hydrodynamic model and can provide much more quantum insight about nonlocal effects in metallic nanostructures. PMID:26698456

  20. An open-source, massively parallel code for non-LTE synthesis and inversion of spectral lines and Zeeman-induced Stokes profiles

    NASA Astrophysics Data System (ADS)

    Socas-Navarro, H.; de la Cruz Rodríguez, J.; Asensio Ramos, A.; Trujillo Bueno, J.; Ruiz Cobo, B.

    2015-05-01

    With the advent of a new generation of solar telescopes and instrumentation, interpreting chromospheric observations (in particular, spectropolarimetry) requires new, suitable diagnostic tools. This paper describes a new code, NICOLE, that has been designed for Stokes non-LTE radiative transfer, for synthesis and inversion of spectral lines and Zeeman-induced polarization profiles, spanning a wide range of atmospheric heights from the photosphere to the chromosphere. The code features a number of unique features and capabilities and has been built from scratch with a powerful parallelization scheme that makes it suitable for application on massive datasets using large supercomputers. The source code is written entirely in Fortran 90/2003 and complies strictly with the ANSI standards to ensure maximum compatibility and portability. It is being publicly released, with the idea of facilitating future branching by other groups to augment its capabilities. The source code is currently hosted at the following repository: http://https://github.com/hsocasnavarro/NICOLE

  1. Performance Assessment of the C-Mod Multi-Spectral Line Polarization MSE (MSE-MSLP) Diagnostic

    NASA Astrophysics Data System (ADS)

    Scott, Steven; Mumgaard, Robert; Khoury, Matthew

    2015-11-01

    The accuracy of the Alcator C-Mod Motional Stark Effect (MSE) diagnostic is limited primarily by partially polarized background light that varies rapidly both in time (1 ms) and space - factor 10 variations are observed between adjacent spatial channels. ITER is likely to operate in a similar regime. Visible Bremsstrahlung, divertor molecular D2 emission, and glowing invessel structures generate unpolarized light that becomes partially polarized upon reflection. Because all three sources are broadband, the background light can be measured in real-time at wavelengths close to the MSE spectrum, thereby allowing the background to be interpolated in wavelength rather than in time. A 10-spatial-channel, 4-wavelength MSE-MSLP system has been developed using polarization polychromators that measure simultaneously the MSE pi- and sigma- lines as well as two nearby wavelengths that were chosen to avoid both the MSE spectrum and all known impurity lines on each sightline. Initial performance evaluation indicates that the background channel measurements faithfully track the background light in the pi- and sigma- lines. The improvement in accuracy of pitch-angle measurements and increased diagnostic flexibility over a wide range of plasma conditions will be reported. This work is supported by USDoE awards DE-FC02-99ER54512 and DE-AC02-09CH11466.

  2. Strain-Induced Spatial and Spectral Isolation of Quantum Emitters in Mono- and Bilayer WSe2.

    PubMed

    Kumar, S; Kaczmarczyk, A; Gerardot, B D

    2015-11-11

    Two-dimensional transition metal dichalcogenide semiconductors are intriguing hosts for quantum light sources due to their unique optoelectronic properties. Here, we report that strain gradients, either unintentionally induced or generated by substrate patterning, result in spatially and spectrally isolated quantum emitters in mono- and bilayer WSe2. By correlating localized excitons with localized strain variations, we show that the quantum emitter emission energy can be red-tuned up to a remarkable ∼170 meV. We probe the fine-structure, magneto-optics, and second-order coherence of a strained emitter. These results raise the prospect of strain-engineering quantum emitter properties and deterministically creating arrays of quantum emitters in two-dimensional semiconductors. PMID:26480237

  3. Strain-Induced Spatial and Spectral Isolation of Quantum Emitters in Mono- and Bilayer WSe2

    PubMed Central

    2015-01-01

    Two-dimensional transition metal dichalcogenide semiconductors are intriguing hosts for quantum light sources due to their unique optoelectronic properties. Here, we report that strain gradients, either unintentionally induced or generated by substrate patterning, result in spatially and spectrally isolated quantum emitters in mono- and bilayer WSe2. By correlating localized excitons with localized strain variations, we show that the quantum emitter emission energy can be red-tuned up to a remarkable ∼170 meV. We probe the fine-structure, magneto-optics, and second-order coherence of a strained emitter. These results raise the prospect of strain-engineering quantum emitter properties and deterministically creating arrays of quantum emitters in two-dimensional semiconductors. PMID:26480237

  4. Influence of non-aqueous phase liquid configuration on induced polarization parameters: Conceptual models applied to a time-domain field case study

    NASA Astrophysics Data System (ADS)

    Johansson, Sara; Fiandaca, Gianluca; Dahlin, Torleif

    2015-12-01

    Resistivity and induced polarization (IP) measurements on soil contaminated with non-aqueous phase liquids (NAPLs) show a great variety in results in previous research. Several laboratory studies have suggested that the presence of NAPLs in soil samples generally decrease the magnitude of the IP-effect, while others have indicated the opposite. A number of conceptual models have been proposed suggesting that NAPLs can alter the pore space in different ways, e.g. by coating the grain surfaces and thus inhibiting grain polarization, or by changing the pore throat size and thus affecting the membrane polarization mechanism. The main aim of this paper is to review previously published conceptual models and to introduce some new concepts of possible residual NAPL configurations in the pore space. Time domain induced polarization measurements were performed at a NAPL contaminated field site, and the data were inverted using the Constant Phase Angle (CPA) model and the Cole-Cole model respectively. No significant phase anomalies were observed in the source area of the contamination when the CPA inverted profiles were compared with soil sampling results of free-phase contaminant concentrations. However, relatively strong phase and normalized phase anomalies appeared next to the source area, where residual free-phase presence could be expected according to the chemical data. We conclude that depending on the NAPL configuration, different spectral IP responses can be expected. In previous research, the NAPL configurations in different samples or field sites are often unknown, and this may to some extent explain why different results have been achieved by different authors. In our field case, we believe that the NAPL forms a more or less continuous phase in the pore space of the source zone leading to an absence of IP anomalies. The increase in phase and normalized phase angle observed next to the source zone is interpreted as a degradation zone. The ongoing biodegradation

  5. Polarization induced effects in group-III-nitride heterostructures and devices

    NASA Astrophysics Data System (ADS)

    Ambacher, Oliver

    2001-03-01

    Two dimensional electron and hole gases in AlInGaN/GaN hetero- and quantum well structures suitable for high electron mobility transistors (HEMT´s) are induced by strong polarization effects. The sheet carrier concentration and the confinement of the two dimensional carrier gases located close to one of the AlInGaN/GaN interfaces are sensitive to a high number of different physical properties such as polarity, alloy composition, strain, thickness and doping of the barriers. We have investigated the structural quality, the carrier concentration profiles and electrical transport properties of undoped, silicon and magnesium doped structures by a combination of high resolution X-ray diffraction, atomic force microscopy, PL-spectroscopy, Hall effect, C-V profiling and Shubnikov-de Haas measurements. The investigated samples with N- and Ga-face polarity were grown by metalorganic vapor phase (MOCVD) or plasma induced molecular beam epitaxy (PIMBE) covering a broad range of alloy compositions, barrier and quantum well thicknesses. We have measured and calculated the polarization induced sheet charge based on different sets of piezoelectric constants available in the literature and the sheet carrier concentration for 2DEGS and 2DHGs self-consistently from a coupled Schrödinger and Poisson equation for different alloy compositions and degree of relaxation of the barrier. By comparison of theoretical and experimental results we demonstrate that the formation of two dimensional carrier gases in AlGaInN/GaN structures both rely on the difference of piezoelectric and spontaneous polarization between the AlGaInN and the GaN layer. In addition, the experimental evidence for accumulation of free carriers at interfaces of lattice matched AlInN/GaN heterostructures and pseudomorphic InGaN/GaN quatum well structures due to gradients in spontaneous or piezoelectric polarization will be presented. The influence and relevance of the resulting carrier distribution on the performance of

  6. A direct method for the correction of pressure-induced scrambling of polarized fluorescence intensities.

    PubMed

    Targowski, P; Davenport, L

    1999-10-15

    A simple and direct method for the simultaneous correction of steady-state polarized fluorescence intensities, depolarized (or scrambled) by the effects of applied hydrostatic pressure, is described. In the method discussed here, it is not necessary to first determine the scrambling factors from a separate experiment with a dye immobilized in a rigid medium. Rather correction for depolarizing effects of the high-pressure spectroscopy cell windows is achieved by direct recalculation of the measured polarized data obtained for the sample of interest at the time of data collection. This method of correction is tested for common fluorescent dyes 1, 6-diphenyl-1,3,5-hexatriene (DPH) and 9,10-diphenylanthracene in glycerol where their rotational behavior is well understood. In addition, the pressure-induced "melt" profile for the more complicated biologically relevant system of DPH imbedded within dipalmitoylphosphatidylcholine small unilamellar vesicles has been reexamined. While the method discussed here is used for the correction of steady-state polarized data, it may be easily adapted for use in time-resolved polarized fluorescence measurements. Advantages and limitations of the new correction method are discussed. PMID:10527523

  7. Spontaneous polarization induced electric field in zinc oxide nanowires and nanostars

    NASA Astrophysics Data System (ADS)

    Farid, S.; Choi, M.; Datta, D.; Stroscio, M. A.; Dutta, M.

    2016-04-01

    We report on the detection mechanism of spontaneous polarization using electrostatic force microscopy in zinc oxide nanowires and nanostars grown by vapor-liquid-solid technique. Optical and structural properties are investigated in detail to understand the complex ZnO nanostructures comprehensively. Calculations are carried out to estimate the electric field from the change in interleave amplitude induced by the electrostatic force due to the spontaneous polarization effects. Attraction of the probe between the tip and the sample varies for different structures with a stronger attraction for nanostars as compared to nanowires. Strength of electric field is dependent on the orientation of nanowires and nanostars c-axis with measured magnitude of electric field to be ˜107 V/m and 108 V/m respectively. This technique presents a unique detection mechanism of built-in spontaneous polarization and electric field from polar ZnO nanowires with applications in voltage gated ion channels, nano-bio interfaces, optoelectronic and photonic devices.

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

    SciTech Connect

    Mota, D. A.; Romaguera-Barcelay, Y.; Tkach, A.; Agostinho Moreira, J.; Almeida, A.; Perez de la Cruz, J.; Vilarinho, P. M.; Tavares, P. B.

    2013-07-21

    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.

  9. Heat-induced changes to lipid molecular structure in Vimy flaxseed: Spectral intensity and molecular clustering

    NASA Astrophysics Data System (ADS)

    Yu, Peiqiang; Damiran, Daalkhaijav

    2011-06-01

    Autoclaving was used to manipulate nutrient utilization and availability. The objectives of this study were to characterize any changes of the functional groups mainly associated with lipid structure in flaxseed ( Linum usitatissimum, cv. Vimy), that occurred on a molecular level during the treatment process using infrared Fourier transform molecular spectroscopy. The parameters included lipid CH 3 asymmetric (ca. 2959 cm -1), CH 2 asymmetric (ca. 2928 cm -1), CH 3 symmetric (ca. 2871 cm -1) and CH 2 symmetric (ca. 2954 cm -1) functional groups, lipid carbonyl C dbnd O ester group (ca. 1745 cm -1), lipid unsaturation group (CH attached to C dbnd C) (ca. 3010 cm -1) as well as their ratios. Hierarchical cluster analysis (CLA) and principal components analysis (PCA) were conducted to identify molecular spectral differences. Flaxseed samples were kept raw for the control or autoclaved in batches at 120 °C for 20, 40 or 60 min for treatments 1, 2 and 3, respectively. Molecular spectral analysis of lipid functional group ratios showed a significant decrease ( P < 0.05) in the CH 2 asymmetric to CH 3 asymmetric stretching band peak intensity ratios for the flaxseed. There were linear and quadratic effects ( P < 0.05) of the treatment time from 0, 20, 40 and 60 min on the ratios of the CH 2 asymmetric to CH 3 asymmetric stretching vibration intensity. Autoclaving had no significant effect ( P > 0.05) on lipid carbonyl C dbnd O ester group and lipid unsaturation group (CH attached to C dbnd C) (with average spectral peak area intensities of 138.3 and 68.8 IR intensity units, respectively). Multivariate molecular spectral analyses, CLA and PCA, were unable to make distinctions between the different treatment original spectra at the CH 3 and CH 2 asymmetric and symmetric region (ca. 2988-2790 cm -1). The results indicated that autoclaving had an impact to the mid-infrared molecular spectrum of flaxseed to identify heat-induced changes in lipid conformation. A future study

  10. Determination of mask induced polarization effects occurring in hyper NA immersion lithography

    NASA Astrophysics Data System (ADS)

    Teuber, Silvio; Bubke, Karsten; Hollein, Ingo; Ziebold, Ralf; Peters, Jan H.

    2005-05-01

    As the lithographic projection technology of the future will require higher numerical aperture (NA) values, new physical effects will have to be taken into consideration. Immersion lithography will result in NA values of up to 1.2 and above. New optical effects like 3D shadowing, effects from oblique incident angles, mask-induced polarization of the transmitted light and birefringence from the substrate should be considered when the masks optical performance is evaluated. This paper addresses mask induced polarization effects from dense lines-and-space structures of standard production masks. On a binary and on an attenuated phase-shifting mask, which were manufactured at the Advanced Mask Technology Center (AMTC) transmission experimental investigations were performed. Measurements of diffraction efficiencies for TE- and TM-polarized light using three different incident angles are presented for all considered mask types and compared to simulations. The structures under investigation include line-space-pattern with varying pitches as well as varying duty cycles. Experimental results show good agreement with simulations.

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

    PubMed

    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

    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

  12. Collisional Induced Absorption (CIA) bands measured in the IR spectral range .

    NASA Astrophysics Data System (ADS)

    Stefani, S.; Piccioni, G.; Snels, M.; Adriani, A.; Grassi, D.

    In this work we present two experimental setup able to characterize the optical properties of gases, in particular CO_2 and H_2, at typically planetary conditions. The apparatus consists of a Fourier Transform InfraRed (FT-IT) interferometer able to work in a wide spectral range, from 350 to 25000 cm-1 (0.4 to 29 mu m ) with a relatively high spectral resolution, from 10 to 0.07 cm-1. Two dedicated gas cells have been integrated with the FT-IR. The first, called High Pressure High Temperature (HP-HT), can support pressures up to 300 bar, temperatures up to 300oC and is characterized by an optical path of 2 cm. The second one, a Multi Pass (MP) absorption gas cell, is designed to have a variable optical path, from 2.5 to 30 m, can be heated up to 200o and operate at pressures up to 10 bar. In this paper, measurements of Collision-Induced Absorption (CIA) bands in carbon dioxide and hydrogen recorded in the InfraRed spectral range will be presented. In principle, linear symmetric molecules such as CO_2 and H_2 possess no dipole moment, but, even when the pressure is only a few bar, we have observed the Collisional Induced Absorption (CIA) bands. This absorption results from a short-time collisional interaction between molecules. The band integrated intensity shows a quadratic dependence versus density opposed to the absorption by isolated molecules, which follows Beer's law \\citep{Beer's}. This behaviour suggests an absorption by pairs rather than by individual molecules. The bands integrated intensities show a linear dependence vs square density according to \\citep {CIA Shape} and \\citep{CIA posi}. For what concerns the H_2 CIA bands, a preliminary comparison between simulated data obtained with the model described in \\citep{CIA H2}and measured, shows a good agreement. These processes are very relevant in the dense atmospheres of planets, such as those of Venus and Jupiter and also in extrasolar planets. A detailed knowledge of these contributions is very

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

    PubMed Central

    Groppelli, Elisabetta; Starling, Shimona

    2014-01-01

    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

  14. Method and apparatus for determining shaliness and oil saturations in earth formations using induced polarization in the frequency domain

    SciTech Connect

    Vinegar, H.J.; Waxman, M.H.

    1982-11-16

    An apparatus is disclosed for borehole measurements of the induced polarization of earth formations. The apparatus consists of an induced polarization logger capable of measuring both in-phase and quadrature conductivities in the frequency domain. A method is described which uses these measurements to determine cation exchange capacity per unit pore volume, Qv, brine conductivity, Cw, and oil and water saturations, So and Sw, in shaly sands.

  15. Microring resonator composed of vertical slot waveguides with minimum polarization mode dispersion over a wide spectral range.

    PubMed

    Fu, Po-Han; Chiang, Tsung-Yu; Cheng, Nai-Chia; Ma, Yao-Feng; Huang, Ding-Wei

    2016-05-01

    This paper proposes the design of a vertical slot waveguide-based optical ring resonator on a silicon photonic platform with minimized polarization mode dispersion (PMD) in the presence of waveguide dispersion over a wide band. Slot waveguides provide more degrees of freedom in the design, thereby achieving the minimum PMD over the communication wavelengths. The minimum PMD leads to nearly identical accumulated phase in the optical ring resonator for quasi-TE and TM modes, and thus the resonant wavelength mismatch between the quasi-TE and TM modes can be minimized from 1510 to 1590 nm. PMID:27140380

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

    NASA Astrophysics Data System (ADS)

    Å koda, Václav

    2013-11-01

    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.

  17. Vector magnetometry based on electromagnetically induced transparency in linearly polarized light

    SciTech Connect

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

    2010-09-15

    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.

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

    PubMed Central

    Zhang, Xiaoming; Zhao, Mingwen

    2014-01-01

    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

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

    SciTech Connect

    Casini, R.; De Wijn, A. G.; Judge, P. G.

    2012-09-20

    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.

  20. Current-induced spin polarization in InGaAs epilayers with varying doping densities

    NASA Astrophysics Data System (ADS)

    Luengo-Kovac, Marta; Huang, Simon; Del Gaudio, Davide; Occena, Jordan; Goldman, Rachel; Sih, Vanessa

    Current-induced spin polarization (CISP) is a phenomena in which an applied electric field produces a bulk spin polarization in the plane of the sample. As this is thought to arise from the spin-orbit coupling, it was originally predicted that the magnitude of CISP should be proportional to the spin-orbit (SO) splitting. However, crystal axis-dependent measurements of the CISP and SO fields showed a negative differential relationship between these two quantities. To develop a phenomenological understanding of the factors affecting the magnitude of CISP, we performed measurements on three In0.025Ga0.975As epilayers, Si-doped at 0.67, 9.6, and 14.1 x 1017 cm-3. We will discuss the effects of the doping density and electron mobility on the magnitudes of the SO fields and CISP.

  1. The rotation of scissioning nucleus considered trajectory calculations for ternary fission induced by cold polarized neutrons

    NASA Astrophysics Data System (ADS)

    Guseva, I.; Gusev, Yu.

    2009-10-01

    On the base of modified trajectory calculations the shift of angular distribution of α-particles accompanied the reaction 235U(n,f) induced by cold polarized neutrons is evaluated. It was supposed that angular distribution shift is caused by the rotation of nuclear system before scission. The orientation of a rotation motion is determined by the neutron spin polarization along and opposite to the beam direction. For the first time the estimation was done in the frame of trajectory calculations assuming the rotation motion of scissioning nucleus [1]. The result of the calculation is in a good agreement with experimental data of paper [2], where this new phenomenon was named as ROT-effect.

  2. Investigation of ultrafast nuclear spin polarization induced by short laser pulses.

    PubMed

    Nakajima, Takashi

    2007-07-13

    We theoretically investigate the dynamics of nuclear spin induced by short laser pulses and show that ultrafast nuclear spin polarization can take place. Combined use of the hyperfine interaction together with the static electric field is the key for that. Specifically we apply the idea to unstable isotopes, (27)Mg and (37)Ca, with nuclear spin of 1/2 and 3/2, respectively, and show that 88% and 62% of nuclear spin polarization can be achieved within a few to tens of ns, which is 2-3 orders of magnitude shorter than the time needed for any known optical methods. Because of its ultrafast nature, our scheme would be very effective not only for stable nuclei but also unstable nuclei with a lifetime as short as mus. PMID:17678226

  3. Semiclassical description of TRI asymmetry in ternary fission induced by cold polarized neutrons

    SciTech Connect

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

    2011-11-15

    The possibility of semiclassically describing T-even TRI-type asymmetry in ternary fission induced by polarized neutrons is considered on the basis of employing Coriolis interaction that takes into account the coupling of a light charged particle to the collective rotation of a polarized fissile nucleus. It is shown that allowance for this interaction makes it possible to explain qualitatively the magnitudes of two asymmetry effects observed in light-charge-particle emission both within the semiclassical and within the quantum-mechanical approach. The difference in the relative magnitudes and signs of the effects between different target nuclei is associated with the interference contributions to the cross section from neighboring neutron resonances and therefore cannot be explained within the semiclassical approach.

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

    SciTech Connect

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

    2014-06-09

    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.

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

    SciTech Connect

    Nunes, J.A.; Tong, W.G.; Chandler, D.W.; Rahn, L.A.

    1995-04-01

    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.

  6. Spectral domain polarization sensitive optical coherence tomography at 1.55 μm: novel developments and applications for dynamic studies in materials science

    NASA Astrophysics Data System (ADS)

    Stifter, David; Leiss-Holzinger, Elisabeth; Heise, Bettina; Bouchot, Jean-Luc; Major, Zoltan; Pircher, Michael; Götzinger, Erich; Baumann, Bernhard; Hitzenberger, Christoph K.

    2011-03-01

    In this paper it is demonstrated, how research in optical coherence tomography (OCT) for biomedical diagnostics successfully triggered new developments in the field of mechanical material testing. With the help of a specifically designed, compact and robust spectral domain polarization sensitive OCT (SD-PS-OCT) setup, which is operating at 1.55 μm, dynamic investigations of technical materials - like bulk polymers and composite samples - can be performed under various conditions. Already by evaluating the speckle pattern of the standard SD-OCT images with advanced image processing methods, valuable information on the deformation and flow characteristics of samples subjected to tensile tests can be obtained. By additionally taking the birefringence properties into account, complementary knowledge on the evolvement of the internal stress situation is obtained in a spatially resolved way.

  7. X-ray polarimetric signatures induced by spectral variability in the framework of the receding torus model

    NASA Astrophysics Data System (ADS)

    Marin, F.; Goosmann, R. W.; Petrucci, P.-O.

    2016-06-01

    Context. Obscuring circumnuclear dust is a well-established constituent of active galactic nuclei (AGN). Traditionally referred to as the receding dusty torus, its inner radius and angular extension should depend on the photo-ionizing luminosity of the central source. Aims: We quantify the expected time-dependent near-infrared (NIR), optical, ultraviolet (UV) and X-ray polarization of a receding dusty torus as a function of the variable X-ray flux level and spectral shape. Methods: Using a Monte Carlo approach, we simulate the radiative transfer between the multiple components of an AGN adopting model constraints from the bright Seyfert galaxy NGC 4151. We compare our model results to the observed NIR to UV polarization of the source and predict its X-ray polarization. Results: We find that the 2-8 keV polarization fraction of a standard AGN model varies from less then a few percent along polar viewing angles up to tens of percent at equatorial inclinations. At viewing angles around the type-1/type-2 transition, there is a different X-ray polarization variability in a static or a receding torus scenario. In the former case, the expected 2-8 keV polarization of NGC 4151 is found to be 1.21% ± 0.34% with a constant polarization position angle, while in the latter scenario it varies from 0.1% to 6% depending on the photon index of the primary radiation. Additionally, an orthogonal rotation of the polarization position angle with photon energy appears for very soft primary spectra. Conclusions: Future X-ray polarimetry missions will be able to test whether the receding model is valid for Seyfert galaxies seen at a viewing angle close to the torus horizon. The overall stability of the polarization position angle for photon indexes softer than Γ = 1.5 ensures that reliable measurements of X-ray polarization are possible. We derive a long-term observational strategy for NGC 4151 assuming observations with a small to medium-sized X-ray polarimetry satellite.

  8. Shock-induced polarized hydrogen emission lines in the Mira star o Ceti

    NASA Astrophysics Data System (ADS)

    Fabas, N.; Lèbre, A.; Gillet, D.

    2011-11-01

    induced by some giant convective cells located around the photosphere and a local one that implies a charge separation due to the passage of the shock wave, inducing an electrical current. Combined with the existing turbulence, this may generate a magnetic field, hence polarization. Based on spectropolarimetric observations obtained at the Télescope Bernard Lyot (TBL at Observatoire du Pic du Midi, CNRS and Université de Toulouse, France).

  9. The Spectral Emission Characteristics of Laser Induced Plasma on Tea Samples

    NASA Astrophysics Data System (ADS)

    Zheng, Peichao; Shi, Minjie; Wang, Jinmei; Liu, Hongdi

    2015-08-01

    Laser induced breakdown spectroscopy (LIBS) provides a useful technique for food security as well as determining nutrition contents. In this paper, optical emission studies of laser induced plasma on commercial tea samples were carried out. The spectral intensities of Mg, Mn, Ca, Al, C and CN vibration bands varying with laser energy and the detection delay time of an intensified charge coupled device were studied. In addition, the relative concentrations of six microelements, i.e., Mg, Mn, Ca, Al, Na and K, were analyzed semi-quantitatively as well as H, for four kinds of tea samples. Moreover, the plasma parameters were explored, including electron temperature and electron number density. The electron temperature and electron number density were around 11000 K and 1017 cm-3, respectively. The results show that it is reasonable to consider the LIBS technique as a new method for analyzing the compositions of tea leaf samples. supported by National Natural Science Foundation of China (No. 61205149), the Scientific and Technological Talents Training Project of Chongqing, China (No. CSTC2013kjrc-qnrc40002), the Scientific and Technological Project of Nan'an District (2011) and the Visiting Scholarship of State Key Laboratory of Power Transmission Equipment & System Security and New Technology at Chongqing University, China (No. 2007DA10512714409)

  10. Proteomic Analysis of Acetaminophen-Induced Changes in Mitochondrial Protein Expression Using Spectral Counting

    PubMed Central

    Stamper, Brendan D.; Mohar, Isaac; Kavanagh, Terrance J.; Nelson, Sidney D.

    2011-01-01

    Comparative proteomic analysis following treatment with acetaminophen (APAP) was performed on two different models of APAP-mediated hepatocellular injury in order to both identify common targets for adduct formation and track drug-induced changes in protein expression. Male C57BL/6 mice were used as a model for APAP-mediated liver injury in vivo and TAMH cells were used as a model for APAP-mediated cytotoxicity in vitro. SEQUEST was unable to identify the precise location of sites of adduction following treatment with APAP in either system. However, semiquantitative analysis of the proteomic datasets using spectral counting revealed a downregulation of P450 isoforms associated with APAP bioactivation, and an upregulation of proteins related to the electron transport chain by APAP compared to control. Both mechanisms are likely compensatory in nature as decreased P450 expression is likely to attenuate toxicity associated with N-acetyl-p-quinoneimine (NAPQI) formation, whereas APAP-induced electron transport chain component upregulation may be an attempt to promote cellular bioenergetics. PMID:21329376

  11. Accommodation-induced variations in retinal thickness measured by spectral domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Fan, Shanhui; Sun, Yong; Dai, Cuixia; Zheng, Haihua; Ren, Qiushi; Jiao, Shuliang; Zhou, Chuanqing

    2014-09-01

    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 μm) 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.

  12. Dysregulation of cell polarity proteins synergize with oncogenes or the microenvironment to induce invasive behavior in epithelial cells.

    PubMed

    Chatterjee, Samit; Seifried, Laurie; Feigin, Michael E; Gibbons, Don L; Scuoppo, Claudio; Lin, Wei; Rizvi, Zain H; Lind, Evan; Dissanayake, Dilan; Kurie, Jonathan; Ohashi, Pam; Muthuswamy, Senthil K

    2012-01-01

    Changes in expression and localization of proteins that regulate cell and tissue polarity are frequently observed in carcinoma. However, the mechanisms by which changes in cell polarity proteins regulate carcinoma progression are not well understood. Here, we report that loss of polarity protein expression in epithelial cells primes them for cooperation with oncogenes or changes in tissue microenvironment to promote invasive behavior. Activation of ErbB2 in cells lacking the polarity regulators Scribble, Dlg1 or AF-6, induced invasive properties. This cooperation required the ability of ErbB2 to regulate the Par6/aPKC polarity complex. Inhibition of the ErbB2-Par6 pathway was sufficient to block ErbB2-induced invasion suggesting that two polarity hits may be needed for ErbB2 to promote invasion. Interestingly, in the absence of ErbB2 activation, either a combined loss of two polarity proteins, or exposure of cells lacking one polarity protein to cytokines IL-6 or TNFα induced invasive behavior in epithelial cells. We observed the invasive behavior only when cells were plated on a stiff matrix (Matrigel/Collagen-1) and not when plated on a soft matrix (Matrigel alone). Cells lacking two polarity proteins upregulated expression of EGFR and activated Akt. Inhibition of Akt activity blocked the invasive behavior identifying a mechanism by which loss of polarity promotes invasion of epithelial cells. Thus, we demonstrate that loss of polarity proteins confers phenotypic plasticity to epithelial cells such that they display normal behavior under normal culture conditions but display aggressive behavior in response to activation of oncogenes or exposure to cytokines. PMID:22529912

  13. GSI promotes vincristine-induced apoptosis by enhancing multi-polar spindle formation.

    PubMed

    Singh, Akannsha; Zapata, Mariana C; Choi, Yong Sung; Yoon, Sun-Ok

    2014-01-01

    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

  14. Mycobacterium tuberculosislpdC, Rv0462, induces dendritic cell maturation and Th1 polarization

    SciTech Connect

    Heo, Deok Rim; Shin, Sung Jae; Kim, Woo Sik; Noh, Kyung Tae; Park, Jin Wook; Son, Kwang Hee; Park, Won Sun; Lee, Min-Goo; Kim, Daejin; Shin, Yong Kyoo; Jung, In Duk; Park, Yeong-Min

    2011-08-05

    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.

  15. Observation of spectral composition and polarization of sub-terahertz emission from dense plasma during relativistic electron beam–plasma interaction

    SciTech Connect

    Arzhannikov, A. V.; Burmasov, V. S.; Ivanov, I. A.; Kuznetsov, S. A.; Postupaev, V. V.; Sinitsky, S. L.; Vyacheslavov, L. N.; Burdakov, A. V.; Gavrilenko, D. E.; Kasatov, A. A.; Mekler, K. I.; Rovenskikh, A. F.; Polosatkin, S. V.; Sklyarov, V. F.

    2014-08-15

    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.

  16. Fourier transform infrared spectral detection of life in polar subsurface environments and its application to Mars exploration.

    PubMed

    Preston, Louisa J; Johnson, Diane; Cockell, Charles S; Grady, Monica M

    2015-09-01

    Cryptoendolithic lichen communities of the Dry Valleys, Antarctica, survive in an extremely inhospitable environment, finding refuge in microscopic niches where conditions suitable for life exist. Such "within-rock" communities may have evolved on Mars when conditions for life on the surface deteriorated to such an extent that they could no longer survive. Fourier transform infrared spectroscopy of unprepared whole-rock Antarctic Beacon sandstones was used to vertically profile molecular vibrations of fatty acids, proteins, and carboxylic acids created by endolithic communities. Spectral biosignatures were found localized to lichen-rich areas and were absent in crustal regions and the bulk rock substrate. These cryptoendolithic profiles will aid similar spectroscopic investigations of organic biosignatures during future Martian subsurface studies and will help in the identification of similar communities in other localities across the Earth. PMID:26414525

  17. Self-screening of the quantum confined Stark effect by the polarization induced bulk charges in the quantum barriers

    SciTech Connect

    Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Wei Sun, Xiao E-mail: volkan@stanfordalumni.org; Volkan Demir, Hilmi E-mail: volkan@stanfordalumni.org

    2014-06-16

    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.

  18. Self-screening of the quantum confined Stark effect by the polarization induced bulk charges in the quantum barriers

    NASA Astrophysics Data System (ADS)

    Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Wei Sun, Xiao; Volkan Demir, Hilmi

    2014-06-01

    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.

  19. Direct transverse load profile determination using the polarization-dependent loss spectral response of a chirped fiber Bragg grating.

    PubMed

    Descamps, Frédéric; Bette, Sébastien; Kinet, Damien; Caucheteur, Christophe

    2016-06-01

    The determination of stress profiles created by transverse loads was proved to be important in different domains, such as structural health monitoring and biomechanics, and, more specifically, in the prostheses domain. In this paper, we report an original method to estimate the transverse load profile from the polarization-dependent loss (PDL) spectrum of a chirped fiber Bragg grating (CFBG). This method makes use of the relationship between the integration of the PDL of a CFBG, and the force profile has the advantage of not requiring any iterative method to estimate the transverse load profile. The relationship linking the integration of the PDL and the force profile is demonstrated using an analytical approximation of the transmission spectrum of CFBGs. The validity of this method for the determination of non-uniform load profiles is then shown using a numerical analysis. An experimental demonstration is finally reported using a 48 mm-long CFBG subject to different step transverse load profiles. PMID:27411174

  20. Growth and polarized spectral properties of Sm3+ doped in Ca3La2(BO3)4 crystal

    NASA Astrophysics Data System (ADS)

    Wang, Yeqing; Chen, Aixi; Tu, Chaoyang

    2015-09-01

    A Sm3+-doped Ca3La2(BO3)4 single crystal was grown by the Czochralski method. Its polarized absorption, emission spectra and fluorescence lifetime measurements were carried out at room temperature. Based on the Judd-Ofelt theory, the spectroscopic parameters Ωt (t = 2, 4, 6), radiative transition probabilities, radiative lifetime and fluorescence branching ratios were obtained. The stimulated emission cross section, the fluorescence lifetime and the quantum efficiency of the promising laser transition were also calculated and compared with other reported crystals. The results showed that Sm3+:Ca3La2(BO3)4 is a promising candidate for the orange-yellow laser emission.

  1. Macro- and microscopic spectral-polarization characteristics of the structure of normal and abnormally located chordae tendianeae of left ventricular

    NASA Astrophysics Data System (ADS)

    Malyk, Yu. Yu.; Prydij, O. G.; Zymnyakov, D. A.; Alonova, M. V.; Ushakova, O. V.

    2013-12-01

    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.

  2. Alignment layer-free molecular ordering induced by masked photopolymerization with non-polarized light

    NASA Astrophysics Data System (ADS)

    Hisano, Kyohei; Kurata, Yosuke; Aizawa, Miho; Ishizu, Masaki; Sasaki, Takeo; Shishido, Atsushi

    2016-07-01

    Controlled and uniform molecular alignment can provide and enhance functionality in polymer films. We first report that masked photopolymerization with non-polarized light enables direct and precise control of molecular alignment without using a conventional molecular alignment layer. The photopolymerization of a mixture composed of an optically anisotropic acrylate monomer and an isotropic dimethacrylate crosslinker induces either unidirectional or complex molecular alignment, depending upon the shape of the photomask. Such molecular alignments are successfully achieved by shear stress arising from molecular diffusion, even when the photopolymerization is carried out at isotropic temperatures of both the monomer mixture and the obtained polymers.

  3. Field induced polarization and magnetization behaviour of Gd-doped lead magnesium niobate ceramics

    NASA Astrophysics Data System (ADS)

    Pandey, Adityanarayan; Gupta, Surya Mohan; Nigam, Arun Kumar

    2016-05-01

    Both superparaelectric and superparamagnetic behaviour has been observed in rare earth magnetic ion Gd3+ doped Lead Magnesium Niobate (Gd-PMN). Field induced polarization and magnetization studies reveal hystresis loss free P-E and M-H loop at 300K and 5K, respectively. Temperature dependence of inverse susceptibility plot shows deviation at a temperature "td" when fitted with the Curie-Weiss law. This deviation has been attributed to transition from paramagnetic to superparamagnetic behaviour as reported in amorphous Pd-Ni-Fe-P alloys.

  4. Confinement of plasma in a magnetic bottle induced by circularly polarized laser light

    SciTech Connect

    Eliezer, S.; Kolka, E.; Paiss, Y.

    1994-10-05

    A concept of plasma confinement using a combination of inertial and magnetic methods is suggested. A miniature magnetic bottle with the megagauss field can be induced by circularly polarized laser radiation inside a good conductor vessel containing a plasma. The laser pulses also heat the plasma to {similar_to}5 KeV during a few nanoseconds. The Lawson criteria for a DT plasma might be satisfied for densities of the order 5{center_dot}10{sup 21} cm{sup {minus}3} and confinement time about 20 nsec.(AIP) {copyright}{ital American} {ital Institute} {ital of} {ital Physics} 1994

  5. Frequency-dependent polarization-angle-phase-shift in the microwave-induced magnetoresistance oscillations

    SciTech Connect

    Liu, Han-Chun; Ye, Tianyu; Mani, R. G.; Wegscheider, W.

    2015-02-14

    Linear polarization angle, θ, dependent measurements of the microwave radiation-induced oscillatory magnetoresistance, R{sub xx}, in high mobility GaAs/AlGaAs 2D electron devices have shown a θ dependence in the oscillatory amplitude along with magnetic field, frequency, and extrema-dependent phase shifts, θ{sub 0}. Here, we suggest a microwave frequency dependence of θ{sub 0}(f) using an analysis that averages over other smaller contributions, when those contributions are smaller than estimates of the experimental uncertainty.

  6. Detection of gravity-induced polarity of cytoplasmic streaming in Chara

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  7. Phonon anomalies induced by polar nano-regions in a relaxor ferroelectric

    NASA Astrophysics Data System (ADS)

    Xu, Guangyong; Wen, Jinsheng; Stock, Chris; Gehring, Peter

    2007-03-01

    Inelastic neutron scattering was used to measure both acoustic and optic phonons polarized along (110) (T2 mode) in the relaxor ferroelectric compound PZN-4.5PT. In the low temperature rhombohedral phase, a single domain state was achieved by cooling the single crystal sample under an external electric field of 2 kV/cm along the [111] direction. Phonon measurements were performed near the (2,2,0) and (2,-2,0) Bragg peaks. We have found that the TA2 phonon couples closely to the diffuse scattering, which arises from polar nano-regions in the system. With the redistribution of diffuse scattering under the external field (see Ref. 1), a clear hardening of TA2 mode was observed near the (2,2,0) Bragg peak, while the TA2 mode near (2,-2,0) Bragg peak softens significantly and becomes over-damped. Our results indicate local inhomogeneities such as the PNR can have direct and significant effects on the lattice dynamics and stability of the whole system. Ref. 1: ``Electric-field-induced redistribution of polar nano-regions in a relaxor ferroelectric'', Guangyong Xu, Z. Zhong, Y. Bing, Z.-G. Ye, and G. Shirane, Nature Materials 5, 134, (2006).

  8. Integration of Induced Polarization Imaging, Ground Penetrating Radar and geochemical analysis to characterize hydrocarbon spills

    NASA Astrophysics Data System (ADS)

    Flores Orozco, Adrian; Kreutzer, Ingrid; Bücker, Matthias; Nguyen, Frederic; Hofmann, Thilo; Döberl, Gernot

    2015-04-01

    Because of their capability to provide spatially continuous data, Induced Polarization (IP) Imaging and Ground Penetrating Radar (GPR) have recently emerged as alternative non-invasive methods for the characterization of contaminated sites. In particular, the IP method has demonstrated to be sensitive to both, changes in the chemical composition of groundwater as a result of dissolved pollutants, and to the geometry of the pore space due to the occurrence of contaminants in non-aqueous phase liquids (NAPL). Although promising, an adequate interpretation of the IP imaging results requires geochemical information obtained from the analysis of soil and water samples. However, to date just rare studies have investigated the IP response at the field scale due to different contaminant concentrations. To demonstrate the advantages of an integrated geophysical and geochemical site investigation, we present studies from different hydrocarbon-contaminated sites. We observed a linear correlation between the polarization effect and the contaminant concentration for dissolved contaminants in the saturated zone. A negligible polarization effect was observed, however, in areas associated with the occurrence of contaminants in NAPL. Compared to the contaminant distribution obtained from the geochemical analysis only, the images obtained from time-domain IP measurements significantly improved the delineation of the contaminant plume. As a first step, GPR data collected along the same profiles provided complementary structural information and improved the interpretation of the IP images. The resolution of the electrical images was further improved using regularization constraints, based on the GPR and geochemical data, in the inversion of IP data.

  9. Magnetically-induced electric polarization in an organo-metallic magnet

    SciTech Connect

    Zapf, W S; Fabris, F W; Balakirev, F F; Francoual, S M; Kenzelmann, M; Chen, Y

    2009-01-01

    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.

  10. Mapping the chemical potential dependence of current-induced spin polarization in a topological insulator

    NASA Astrophysics Data System (ADS)

    Lee, Joon Sue; Richardella, Anthony; Hickey, Danielle Reifsnyder; Mkhoyan, K. Andre; Samarth, Nitin

    2015-10-01

    We report electrical measurements of the current-induced spin polarization of the surface current in topological insulator devices where contributions from bulk and surface conduction can be disentangled by electrical gating. The devices use a ferromagnetic tunnel junction (permalloy/Al 2O3 ) as a spin detector on a back-gated (Bi,Sb ) 2Te3 channel. We observe hysteretic voltage signals as the magnetization of the detector ferromagnet is switched parallel or antiparallel to the spin polarization of the surface current. The amplitude of the detected voltage change is linearly proportional to the applied dc bias current in the (Bi,Sb ) 2Te3 channel. As the chemical potential is tuned from the bulk bands into the surface state band, we observe an enhancement of the spin-dependent voltages up to 300% within the range of the electrostatic gating. Using a simple model, we extract the spin polarization near charge neutrality (i.e., the Dirac point).

  11. Parahydrogen-induced polarization of carboxylic acids: a pilot study of valproic acid and related structures.

    PubMed

    Lego, Denise; Plaumann, Markus; Trantzschel, Thomas; Bargon, Joachim; Scheich, Henning; Buntkowsky, Gerd; Gutmann, Torsten; Sauer, Grit; Bernarding, Johannes; Bommerich, Ute

    2014-07-01

    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

  12. Controlling pulse delay by light and low magnetic fields: slow light in emerald induced by transient spectral hole-burning.

    PubMed

    Rajan, Rajitha Papukutty; Riesen, Hans; Rebane, Aleksander

    2013-11-15

    Slow light based on transient spectral hole-burning is reported for emerald, Be(3)Al(2)Si(6)O(18):Cr(3+). Experiments were conducted in π polarization on the R(1)(± 3/2) line (E2 ← A(2)4) at 2.2 K in zero field and low magnetic fields B||c. The hole width was strongly dependent on B||c, and this allowed us to smoothly tune the pulse delay from 40 to 154 ns between zero field and B||c = 15.2 mT. The latter corresponds to a group velocity of 16 km/s. Slow light in conjunction with a linear filter theory can be used as a powerful and accurate technique in time-resolved spectroscopy, e.g., to determine spectral hole-widths as a function of time. PMID:24322070

  13. Wave trains induced by circularly polarized electric fields in cardiac tissues

    PubMed Central

    Feng, Xia; Gao, Xiang; Tang, Juan-Mei; Pan, Jun-Ting; Zhang, Hong

    2015-01-01

    Clinically, cardiac fibrillation caused by spiral and turbulent waves can be terminated by globally resetting electric activity in cardiac tissues with a single high-voltage electric shock, but it is usually associated with severe side effects. Presently, a promising alternative uses wave emission from heterogeneities induced by a sequence of low-voltage uniform electric field pulses. Nevertheless, this method can only emit waves locally near obstacles in turbulent waves and thereby requires multiple obstacles to globally synchronize myocardium and thus to terminate fibrillation. Here we propose a new approach using wave emission from heterogeneities induced by a low-voltage circularly polarized electric field (i.e., a rotating uniform electric field). We find that, this approach can generate circular wave trains near obstacles and they propagate outwardly. We study the characteristics of such circular wave trains and further find that, the higher-frequency circular wave trains can effectively suppress spiral turbulence. PMID:26302781

  14. Self-induced polar order of active Brownian particles in a harmonic trap.

    PubMed

    Hennes, Marc; Wolff, Katrin; Stark, Holger

    2014-06-13

    Hydrodynamically interacting active particles in an external harmonic potential form a self-assembled fluid pump at large enough Péclet 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 Péclet number plays the role of inverse temperature. The particle orientations follow a Boltzmann distribution Φ(p) ∼ exp(Ap(z)) where the ordering mean field A scales with the active Péclet 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. PMID:24972231

  15. Induced-charge electrokinetics, bipolar current, and concentration polarization in a microchannel-Nafion-membrane system.

    PubMed

    Park, Sinwook; Yossifon, Gilad

    2016-06-01

    The presence of a floating electrode array located within the depletion layer formed due to concentration polarization across a microchannel-membrane interface device may produce not only induced-charge electro-osmosis (ICEO) but also bipolar current resulting from the induced Faradaic reaction. It has been shown that there exists an optimal thickness of a thin dielectric coating that is sufficient to suppress bipolar currents but still enables ICEO vortices that stir the depletion layer, thereby affecting the system's current-voltage response. In addition, the use of alternating-current electro-osmosis by activating electrodes results in further enhancement of the fluid stirring and opens new routes for on-demand spatiotemporal control of the depletion layer length. PMID:27415327

  16. Induced-charge electrokinetics, bipolar current, and concentration polarization in a microchannel-Nafion-membrane system

    NASA Astrophysics Data System (ADS)

    Park, Sinwook; Yossifon, Gilad

    2016-06-01

    The presence of a floating electrode array located within the depletion layer formed due to concentration polarization across a microchannel-membrane interface device may produce not only induced-charge electro-osmosis (ICEO) but also bipolar current resulting from the induced Faradaic reaction. It has been shown that there exists an optimal thickness of a thin dielectric coating that is sufficient to suppress bipolar currents but still enables ICEO vortices that stir the depletion layer, thereby affecting the system's current-voltage response. In addition, the use of alternating-current electro-osmosis by activating electrodes results in further enhancement of the fluid stirring and opens new routes for on-demand spatiotemporal control of the depletion layer length.

  17. Humidity effects on tip-induced polarization switching in lithium niobate

    SciTech Connect

    Ievlev, A. V.; Morozovska, A. N.; Shur, V. Ya.; Kalinin, S. V.

    2014-03-03

    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.

  18. Humidity effects on tip-induced polarization switching in lithium niobate

    SciTech Connect

    Ievlev, Anton; Morozovska, A. N.; Shur, Vladimir Ya.; Kalinin, Sergei V

    2014-01-01

    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.

  19. Wave trains induced by circularly polarized electric fields in cardiac tissues.

    PubMed

    Feng, Xia; Gao, Xiang; Tang, Juan-Mei; Pan, Jun-Ting; Zhang, Hong

    2015-01-01

    Clinically, cardiac fibrillation caused by spiral and turbulent waves can be terminated by globally resetting electric activity in cardiac tissues with a single high-voltage electric shock, but it is usually associated with severe side effects. Presently, a promising alternative uses wave emission from heterogeneities induced by a sequence of low-voltage uniform electric field pulses. Nevertheless, this method can only emit waves locally near obstacles in turbulent waves and thereby requires multiple obstacles to globally synchronize myocardium and thus to terminate fibrillation. Here we propose a new approach using wave emission from heterogeneities induced by a low-voltage circularly polarized electric field (i.e., a rotating uniform electric field). We find that, this approach can generate circular wave trains near obstacles and they propagate outwardly. We study the characteristics of such circular wave trains and further find that, the higher-frequency circular wave trains can effectively suppress spiral turbulence. PMID:26302781

  20. Tight-binding model study of substrate induced pseudo-spin polarization and magnetism in mono-layer graphene

    NASA Astrophysics Data System (ADS)

    Sahu, Sivabrata; Rout, G. C.

    2016-06-01

    We present here a tight-binding model study of generation of magnetism and pseudo-spin polarization in monolayer graphene arising due to substrate, impurity and Coulomb correlation effects. The model Hamiltonian contains the first-, second- and third-nearest-neighbor hopping integrals for π electrons of graphene besides substrate induced gap, impurity interactions and Coulomb correlation of electrons. The Hubbard type Coulomb interactions present in both the sub-lattices A and B are treated within the mean-field approximation. The electronic Green's functions are calculated by using Zubarev's technique and hence the electron occupancies of both sub-lattices are calculated for up and down spins separately. These four temperature dependent occupancies are calculated numerically and self-consistently. Then we have calculated the temperature dependent pseudo-spin polarization, ferromagnetic and anti-ferromagnetic magnetizations. We observe that there exists pseudo-spin polarization for lower Coulomb energy, u < 2.2t1 and pseudo-spin polarization is enhanced with substrate induced gap and impurity effect. For larger Coulomb energy u > 2.5t1, there exists pseudo-spin polarization (p); while ferromagnetic (m) and antiferromagnetic (pm) magnetizations exhibit oscillatory behavior. With increase of the substrate induced gap, the ferromagnetic and antiferromagnetic transition temperatures are enhanced with increase of the substrate induced gap; while polarization (p) is enhanced in magnitude only.

  1. Anisotropic lattice response induced by a linearly-polarized femtosecond optical pulse excitation in interfacial phase change memory material

    PubMed Central

    Makino, Kotaro; Saito, Yuta; Fons, Paul; Kolobov, Alexander V.; Nakano, Takashi; Tominaga, Junji; Hase, Muneaki

    2016-01-01

    Optical excitation of matter with linearly-polarized femtosecond pulses creates a transient non-equilibrium lattice displacement along a certain direction. Here, the pump and probe pulse polarization dependence of the photo-induced ultrafast lattice dynamics in (GeTe)2/(Sb2Te3)4 interfacial phase change memory material is investigated under obliquely incident conditions. Drastic pump polarization dependence of the coherent phonon amplitude is observed when the probe polarization angle is parallel to the c–axis of the sample, while the pump polarization dependence is negligible when the probe polarization angle is perpendicular to the c–axis. The enhancement of phonon oscillation amplitude due to pump polarization rotation for a specific probe polarization angle is only found in the early time stage (≤2 ps). These results indicate that the origin of the pump and probe polarization dependence is dominantly attributable to the anisotropically-formed photo-excited carriers which cause the directional lattice dynamics. PMID:26805401

  2. Anisotropic lattice response induced by a linearly-polarized femtosecond optical pulse excitation in interfacial phase change memory material.

    PubMed

    Makino, Kotaro; Saito, Yuta; Fons, Paul; Kolobov, Alexander V; Nakano, Takashi; Tominaga, Junji; Hase, Muneaki

    2016-01-01

    Optical excitation of matter with linearly-polarized femtosecond pulses creates a transient non-equilibrium lattice displacement along a certain direction. Here, the pump and probe pulse polarization dependence of the photo-induced ultrafast lattice dynamics in (GeTe)2/(Sb2Te3)4 interfacial phase change memory material is investigated under obliquely incident conditions. Drastic pump polarization dependence of the coherent phonon amplitude is observed when the probe polarization angle is parallel to the c-axis of the sample, while the pump polarization dependence is negligible when the probe polarization angle is perpendicular to the c-axis. The enhancement of phonon oscillation amplitude due to pump polarization rotation for a specific probe polarization angle is only found in the early time stage (≤2 ps). These results indicate that the origin of the pump and probe polarization dependence is dominantly attributable to the anisotropically-formed photo-excited carriers which cause the directional lattice dynamics. PMID:26805401

  3. Anisotropic lattice response induced by a linearly-polarized femtosecond optical pulse excitation in interfacial phase change memory material

    NASA Astrophysics Data System (ADS)

    Makino, Kotaro; Saito, Yuta; Fons, Paul; Kolobov, Alexander V.; Nakano, Takashi; Tominaga, Junji; Hase, Muneaki

    2016-01-01

    Optical excitation of matter with linearly-polarized femtosecond pulses creates a transient non-equilibrium lattice displacement along a certain direction. Here, the pump and probe pulse polarization dependence of the photo-induced ultrafast lattice dynamics in (GeTe)2/(Sb2Te3)4 interfacial phase change memory material is investigated under obliquely incident conditions. Drastic pump polarization dependence of the coherent phonon amplitude is observed when the probe polarization angle is parallel to the c-axis of the sample, while the pump polarization dependence is negligible when the probe polarization angle is perpendicular to the c-axis. The enhancement of phonon oscillation amplitude due to pump polarization rotation for a specific probe polarization angle is only found in the early time stage (≤2 ps). These results indicate that the origin of the pump and probe polarization dependence is dominantly attributable to the anisotropically-formed photo-excited carriers which cause the directional lattice dynamics.

  4. Power and polarization dependences of ultra-narrow electromagnetically induced absorption (EIA) spectra of 85 Rb atoms in degenerate two-level system

    NASA Astrophysics Data System (ADS)

    Qureshi, Muhammad Mohsin; Rehman, Hafeez Ur; Noh, Heung-Ryoul; Kim, Jin-Tae

    2016-05-01

    We have investigated ultra-narrow EIA spectral features with respect to variations of polarizations and powers of pump laser beam in a degenerate two-level system of the transition of 85 Rb D2 transition line. Polarizations of the probe laser beam in two separate experiments were fixed at right circular and horizontal linear polarizations, respectively while the polarizations of the pump lasers were varied from initial polarizations same as the probe laser beams to orthogonal to probe polarizations. One homemade laser combined with AOMs was used to the pump and probe laser beams instead of two different lasers to overcome broad linewidths of the homemade lasers. Theoretically, probe absorption coefficients have been calculated from optical Bloch equations of the degenerate two level system prepared by a pump laser beam. In the case of the circular polarization, EIA signal was obtained as expected theoretically although both pump and probe beams have same polarization. The EIA signal become smaller as power increases and polarizations of the pump and probe beams were same. When the polarization of the pump beam was linear polarization, maximum EIA signal was obtained theoretically and experimentally. Experimental EIA spectral shapes with respect to variations of the pump beam polarization shows similar trends as the theoretical results.

  5. Paracoccin Induces M1 Polarization of Macrophages via Interaction with TLR4.

    PubMed

    Freitas, Mateus S; Oliveira, Aline F; da Silva, Thiago A; Fernandes, Fabrício F; Gonçales, Relber A; Almeida, Fausto; Roque-Barreira, Maria C

    2016-01-01

    The fungal human pathogen Paracoccidioides brasiliensis contains paracoccin (PCN), a multi-domain protein that has lectin and N-acetyl-glucosaminidase activities, which account for its effects on the growth and morphogenesis of the fungus and on the activation of host macrophages through its interaction with TLR N-glycans. With the purpose of detailing the knowledge on the effects of PCN on macrophages, we used recombinant PCN expressed in Pichia pastoris (p-rPCN) to stimulate isolated murine peritoneal macrophages. The activation of these cells manifested through the release of high levels of inflammatory mediators, such as nitric oxide, TNF-α, IL-12p40, and IL-6. Furthermore, peritoneal macrophages stimulated with p-rPCN increased the relative expression of STAT1, SOCS3, and iNOS2 mRNA (M1 polarization markers). However, the expression of Arginase-1, Ym-1, and FIZZ1 (M2 polarization markers) remained at basal levels. Interestingly, the observed M1 macrophages' polarization triggered by p-rPCN was abolished in cells obtained from knockout Toll-like receptor-4 mice. In this case, the p-rPCN-induced production of pro-inflammatory mediators was blocked too. These results demonstrate that the classical activation of macrophages induced by paracoccin depends on TLR4. Taken together, the results of our study indicate that paracoccin acts as a TLR agonist able to modulate immunity and exerts biological activities that favor its applicability as an immunotherapeutic agent to combat systemic fungal infections. PMID:27458431

  6. Hierarchical Bayesian method for mapping biogeochemical hot spots using induced polarization imaging

    NASA Astrophysics Data System (ADS)

    Wainwright, Haruko M.; Flores Orozco, Adrian; Bücker, Matthias; Dafflon, Baptiste; Chen, Jinsong; Hubbard, Susan S.; Williams, Kenneth H.

    2016-01-01

    In floodplain environments, a naturally reduced zone (NRZ) is considered to be a common biogeochemical hot spot, having distinct microbial and geochemical characteristics. Although important for understanding their role in mediating floodplain biogeochemical processes, mapping the subsurface distribution of NRZs over the dimensions of a floodplain is challenging, as conventional wellbore data are typically spatially limited and the distribution of NRZs is heterogeneous. In this study, we present an innovative methodology for the probabilistic mapping of NRZs within a three-dimensional (3-D) subsurface domain using induced polarization imaging, which is a noninvasive geophysical technique. Measurements consist of surface geophysical surveys and drilling-recovered sediments at the U.S. Department of Energy field site near Rifle, CO (USA). Inversion of surface time domain-induced polarization (TDIP) data yielded 3-D images of the complex electrical resistivity, in terms of magnitude and phase, which are associated with mineral precipitation and other lithological properties. By extracting the TDIP data values colocated with wellbore lithological logs, we found that the NRZs have a different distribution of resistivity and polarization from the other aquifer sediments. To estimate the spatial distribution of NRZs, we developed a Bayesian hierarchical model to integrate the geophysical and wellbore data. In addition, the resistivity images were used to estimate hydrostratigraphic interfaces under the floodplain. Validation results showed that the integration of electrical imaging and wellbore data using a Bayesian hierarchical model was capable of mapping spatially heterogeneous interfaces and NRZ distributions thereby providing a minimally invasive means to parameterize a hydrobiogeochemical model of the floodplain.

  7. Paracoccin Induces M1 Polarization of Macrophages via Interaction with TLR4

    PubMed Central

    Freitas, Mateus S.; Oliveira, Aline F.; da Silva, Thiago A.; Fernandes, Fabrício F.; Gonçales, Relber A.; Almeida, Fausto; Roque-Barreira, Maria C.

    2016-01-01

    The fungal human pathogen Paracoccidioides brasiliensis contains paracoccin (PCN), a multi-domain protein that has lectin and N-acetyl-glucosaminidase activities, which account for its effects on the growth and morphogenesis of the fungus and on the activation of host macrophages through its interaction with TLR N-glycans. With the purpose of detailing the knowledge on the effects of PCN on macrophages, we used recombinant PCN expressed in Pichia pastoris (p-rPCN) to stimulate isolated murine peritoneal macrophages. The activation of these cells manifested through the release of high levels of inflammatory mediators, such as nitric oxide, TNF-α, IL-12p40, and IL-6. Furthermore, peritoneal macrophages stimulated with p-rPCN increased the relative expression of STAT1, SOCS3, and iNOS2 mRNA (M1 polarization markers). However, the expression of Arginase-1, Ym-1, and FIZZ1 (M2 polarization markers) remained at basal levels. Interestingly, the observed M1 macrophages’ polarization triggered by p-rPCN was abolished in cells obtained from knockout Toll-like receptor-4 mice. In this case, the p-rPCN-induced production of pro-inflammatory mediators was blocked too. These results demonstrate that the classical activation of macrophages induced by paracoccin depends on TLR4. Taken together, the results of our study indicate that paracoccin acts as a TLR agonist able to modulate immunity and exerts biological activities that favor its applicability as an immunotherapeutic agent to combat systemic fungal infections. PMID:27458431

  8. Time lapse electrical resistivity and induced polarization monitoring of near-surface CO2 injection

    NASA Astrophysics Data System (ADS)

    Allègre, V.; Kremer, T.; Williard, E.; Schmutz, M.; Maineult, A. J.

    2013-12-01

    Field experiments were carried out to investigate the efficiency and the reliability of electrical geophysical methods to detect and monitor CO2 leakages at field scale. Each test consisted of injecting CO2 for approximately four hours at five meters depth, corresponding to a cumulative mass of gas of around six kilograms. Electrical resistivity tomography and temporal induced polarization were acquired at the surface before, during and after injections along profiles centered to the injection well. Time lapse measurements were compared to a reference acquisition performed before the injection. We observe that both methods are sensitive to variations in terms of gas saturation, the chargeability measurements being more sensitive to the presence of CO2 than electrical resistivity. During the injection, an increase of chargeability and a decrease of the measured resistivity are observed at depth in the vinicity of the injection well. Afterwards, the medium equilibrates and retrieves its original state, corresponding to the reference acquisition. The temporal variations of electrical resistivity and induced polarization responses are interpreted in terms of gas dissolution and water/gas saturation.

  9. The use of the multiple-gradient array for geoelectrical resistivity and induced polarization imaging

    NASA Astrophysics Data System (ADS)

    Aizebeokhai, Ahzegbobor P.; Oyeyemi, Kehinde D.

    2014-12-01

    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.

  10. Highly polarized Th17 cells induce EAE via a T-bet-independent mechanism

    PubMed Central

    Grifka-Walk, Heather M.; Lalor, Stephen J.; Segal, Benjamin M.

    2013-01-01

    Summary In the MOG35-55 induced EAE model, autoreactive Th17 cells that accumulate in the central nervous system (CNS) acquire Th1 characteristics via a T-bet dependent mechanism. It remains to be determined whether Th17 plasticity and encephalitogenicity are causally related to each other. Here we show that IL-23 polarized Tbet−/− Th17 cells are unimpaired in either activation or proliferation, and induce higher quantities of the chemokines RANTES and CXCL2 than wildtype (WT) Th17 cells. Unlike their WT counterparts, they retain an IL-17hiIFNγneg-lo cytokine profile following adoptive transfer into syngeneic hosts. This population of highly polarized Th17 effectors is capable of mediating EAE, albeit with a milder clinical course. It has previously been reported that the signature Th1 and Th17 effector cytokines, IFNγ and IL-17, are dispensable for the development of autoimmune demyelinating disease. The current study demonstrates that the “master regulator” transcription factor, T-bet, is also not universally required for encephalitogenicity. Our results contribute to a growing body of data showing heterogeneity of myelin-reactive T cells and the independent mechanisms they employ to inflict damage to CNS tissues, complicating the search for therapeutic targets relevant across the spectrum of individuals with multiple sclerosis. PMID:23878008

  11. The role of polarization fields in Auger-induced efficiency droop in nitride-based light-emitting diodes

    SciTech Connect

    Vaxenburg, Roman; Lifshitz, Efrat; Rodina, Anna; Efros, Alexander L.

    2013-11-25

    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.

  12. Stress-induced birefringence and fabrication of in-fiber polarization devices by controlled femtosecond laser irradiations.

    PubMed

    Yuan, Lei; Cheng, Baokai; Huang, Jie; Liu, Jie; Wang, Hanzheng; Lan, Xinwei; Xiao, Hai

    2016-01-25

    Optical birefringence was created in a single-mode fiber by introducing a series of symmetric cuboid stress rods on both sides of the fiber core along the fiber axis using a femtosecond laser. The stress-induced birefringence was estimated to be 2.4 × 10(-4) at the wavelength of 1550 nm. By adding the desired numbers of stressed rods, an in-fiber quarter waveplate was fabricated with a insertion loss of 0.19 dB. The stress-induced birefringence was further explored to fabricate in-fiber polarizers based on the polarization-dependent long-period fiber grating (LPFG) structure. A polarization extinction ratio of more than 20 dB was observed at the resonant wavelength of 1523.9 nm. The in-fiber polarization devices may be useful in optical communications and fiber optic sensing applications. PMID:26832490

  13. Statistical features of the global polarity reversal of the Venusian induced magnetosphere in response to the polarity change in interplanetary magnetic field

    NASA Astrophysics Data System (ADS)

    Vech, Daniel; Stenberg, Gabriella; Nilsson, Hans; Edberg, Niklas J. T.; Opitz, Andrea; Szegő, Károly; Zhang, Tielong; Futaana, Yoshifumi

    2016-05-01

    In this study we present the first statistical analysis on the effects of heliospheric current sheet crossings on the induced magnetosphere of Venus. These events are of particular interest because they lead to the reconfiguration of the induced magnetosphere with opposite polarity. We use a statistical approach based on 117 orbit pairs, and we study the spatial distribution of the heavy ion flux measurements in the plasma environment of Venus. The average and median heavy ion flux measurements are compared before and after the polarity reversal events. The results show that after the events the average and median heavy ion fluxes in the magnetotail are reduced by the factors of 0.75 ± 0.09 and 0.52, respectively. We find that even if a passage of a current sheet is a short time scale event lasting about 10 min, its effect on the near-Venus plasma environment lasts for a few hours. We conclude that the observations show similarities to the previous comet studies and the polarity reversal of the induced magnetosphere might be accompanied with dayside reconnection and magnetic disconnection of the plasma tail from the planetary ionosphere.

  14. Study case - Induced Polarization response from a BTEX contaminated site in Brazil

    NASA Astrophysics Data System (ADS)

    Ustra, A.; Elis, V.; Minozzo, M.

    2011-12-01

    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

  15. Macrophage Polarization in IL-10 Treatment of Particle-Induced Inflammation and Osteolysis.

    PubMed

    Jiang, Jianhao; Jia, Tanghong; Gong, Weiming; Ning, Bin; Wooley, Paul H; Yang, Shang-You

    2016-01-01

    This study investigated the therapeutic influence and potential mechanism of IL-10 in ameliorating orthopedic debris particle-induced inflammation and osteolysis. A murine air pouch with bone implantation and polyethylene particles was also used to evaluate the therapeutic effects of IL-10. The data suggested that the particle challenges significantly promoted macrophage activation and osteoclastogenesis, with dramatically increased macrophage infiltration into the pouch membranes and elevated tartrate-resistant acid phosphatase-positive cell deposition. Immunohistochemical stains revealed a significantly higher ratio of induced nitric oxide synthase-expressing cells in the particle-challenged group; treatment with IL-10 resulted in marked switching to CD163(+) cells. Also, IL-10 effectively reduced tartrate-resistant acid phosphatase-positive stained cells in the pouch membranes, and minimized the bone mineral density loss compared with untreated samples. Real-time PCR and Western blot examination indicated that IL-10 treatment significantly diminished the particle-induced IL-1β expression but promoted expression of CD163, transforming growth factor-β1, and CCR2. Furthermore, IL-10 significantly inhibited the ultra-high-molecular-weight polyethylene particle-elevated phospho-STAT1 and phospho-NF-κB p65 productions, and promoted phospho-STAT3 expression. Overall, the data indicate the pivotal effects of IL-10 on macrophage polarization. The effects of IL-10 in ameliorating local inflammation and osteolysis may be associated with macrophage polarization through the up-regulation of the Janus activating kinase/STAT3 signaling pathway, and the down-regulation of NF-κB and Janus activating kinase/STAT1 expression. PMID:26597885

  16. The X-ray spectrum and spectral energy distribution of FIRST J155633.8+351758: a LoBAL quasar with a probable polar outflow

    NASA Astrophysics Data System (ADS)

    Berrington, Robert C.; Brotherton, Michael S.; Gallagher, Sarah C.; Ganguly, Rajib; Shang, Zhaohui; DiPompeo, Michael; Chatterjee, Ritaban; Lacy, Mark; Gregg, Michael D.; Hall, Patrick B.; Laurent-Muehleisen, S. A.

    2013-12-01

    We report the results of a new 60 ks Chandra X-ray Observatory Advanced CCD Imaging Spectrometer S-array (ACIS-S) observation of the reddened, radio-selected, highly polarized `FeLoBAL' quasar FIRST J1556+3517. We investigated a number of models of varied sophistication to fit the 531-photon spectrum. These models ranged from simple power laws to power laws absorbed by hydrogen gas in differing ionization states and degrees of partial covering. Preferred fits indicate that the intrinsic X-ray flux is consistent with that expected for quasars of similarly high luminosity, i.e. an intrinsic, dereddened and unabsorbed optical to X-ray spectral index of -1.7. We cannot tightly constrain the intrinsic X-ray power-law slope, but find indications that it is flat (photon index Γ = 1.7 or flatter at a >99 per cent confidence for a neutral hydrogen absorber model). Absorption is present, with a column density a few times 1023 cm-2, with both partially ionized models and partially covering neutral hydrogen models providing good fits. We present several lines of argument that suggest the fraction of X-ray emissions associated with the radio jet is not large. We combine our Chandra data with observations from the literature to construct the spectral energy distribution of FIRST J1556+3517 from radio to X-ray energies. We make corrections for Doppler beaming for the pole-on radio jet, optical dust reddening and X-ray absorption, in order to recover a probable intrinsic spectrum. The quasar FIRST J1556+3517 seems to be an intrinsically normal radio-quiet quasar with a reddened optical/UV spectrum, a Doppler-boosted but intrinsically weak radio jet and an X-ray absorber not dissimilar from that of other broad absorption line quasars.

  17. NOS Inhibition Modulates Immune Polarization and Improves Radiation-Induced Tumor Growth Delay.

    PubMed

    Ridnour, Lisa A; Cheng, Robert Y S; Weiss, Jonathan M; Kaur, Sukhbir; Soto-Pantoja, David R; Basudhar, Debashree; Heinecke, Julie L; Stewart, C Andrew; DeGraff, William; Sowers, Anastasia L; Thetford, Angela; Kesarwala, Aparna H; Roberts, David D; Young, Howard A; Mitchell, James B; Trinchieri, Giorgio; Wiltrout, Robert H; Wink, David A

    2015-07-15

    Nitric oxide synthases (NOS) are important mediators of progrowth signaling in tumor cells, as they regulate angiogenesis, immune response, and immune-mediated wound healing. Ionizing radiation (IR) is also an immune modulator and inducer of wound response. We hypothesized that radiation therapeutic efficacy could be improved by targeting NOS following tumor irradiation. Herein, we show enhanced radiation-induced (10 Gy) tumor growth delay in a syngeneic model (C3H) but not immunosuppressed (Nu/Nu) squamous cell carcinoma tumor-bearing mice treated post-IR with the constitutive NOS inhibitor N(G)-nitro-l-arginine methyl ester (L-NAME). These results suggest a requirement of T cells for improved radiation tumor response. In support of this observation, tumor irradiation induced a rapid increase in the immunosuppressive Th2 cytokine IL10, which was abated by post-IR administration of L-NAME. In vivo suppression of IL10 using an antisense IL10 morpholino also extended the tumor growth delay induced by radiation in a manner similar to L-NAME. Further examination of this mechanism in cultured Jurkat T cells revealed L-NAME suppression of IR-induced IL10 expression, which reaccumulated in the presence of exogenous NO donor. In addition to L-NAME, the guanylyl cyclase inhibitors ODQ and thrombospondin-1 also abated IR-induced IL10 expression in Jurkat T cells and ANA-1 macrophages, which further suggests that the immunosuppressive effects involve eNOS. Moreover, cytotoxic Th1 cytokines, including IL2, IL12p40, and IFNγ, as well as activated CD8(+) T cells were elevated in tumors receiving post-IR L-NAME. Together, these results suggest that post-IR NOS inhibition improves radiation tumor response via Th1 immune polarization within the tumor microenvironment. PMID:25990221

  18. The MSHA strain of Pseudomonas aeruginosa (PA-MSHA) inhibits gastric carcinoma progression by inducing M1 macrophage polarization.

    PubMed

    Wang, Changming; Hu, Zunqi; Zhu, Zhenxin; Zhang, Xin; Wei, Ziran; Zhang, Yu; Hu, Dali; Cai, Qingping

    2016-05-01

    Macrophages play crucial roles in promoting tumor development and progression. In the present study, we found that the mannose-sensitive hemagglutination pilus strain of Pseudomonas aeruginosa (PA-MSHA) was efficient in inducing M1 macrophage polarization. PA-MSHA treatment increases expression of M1-related cytokines and promotes activation of murine peritoneal macrophages (MPM). Interestingly, PA-MSHA inhibits cell proliferation and migration and induces the apoptosis of gastric carcinoma cells. These effects of PA-MSHA on M1 polarization were associated with activation of NF-κB expression. Thus, inducing polarization of M1 by PA-MSHA may be one potential strategy for inhibiting gastric carcinoma progression in mice. PMID:26662800

  19. Induced polarization dependence on pore space geometry: Empirical observations and mechanistic predictions

    NASA Astrophysics Data System (ADS)

    Weller, A.; Slater, L. D.

    2015-12-01

    We use an extensive database to compare empirical observations and previously proposed empirical models against recently developed mechanistic formulations for the induced polarization (IP) response in porous media as a function of pore space geometry and interfacial chemistry. These comparisons support the argument that the pore-volume normalized internal surface (Spor) is the most important geometric parameter influencing the polarization. The specific polarizability derived from the empirical relationship between imaginary conductivity σ″ and Spor is independent of the porosity. By contrast, equivalent specific polarizability terms in recently proposed mechanistic models are found to be significantly correlated with porosity, and thus do not appear to represent an interfacial chemistry factor independent of the pore space geometry. Furthermore, the database shows no evidence for a significant decrease in the counterion mobility of clayey materials relative to clay-free materials, as postulated in recent studies. On the contrary, a single value of cp is consistent with no significant differences in ionic mobility given that all samples were saturated with a NaCl solution close to a common salinity of about 100 mS/m.

  20. Morphologies of laser-induced damage in hafnia-silica multilayer mirror and polarizer coatings

    SciTech Connect

    Genin, F.Y.; Stolz, C.J.

    1996-08-01

    Hafnium-silica multilayer mirrors and polarizers were deposited by e-beam evaporation onto BK7 glass substrates. The mirrors and polarizers were coated for operation at 1053 nm at 45{degree} and at Brewster`s angle (56{degree}), respectively. They were tested with a single 3-ns laser pulse. Morphology of the laser-induced damage was characterized by optical and scanning electron microscopy. Four distinct damage morphologies were found: pits, flatbottom pits, scalds, and delaminates. The pits and flat bottom pits (<30{mu}m dia) were detected at lower fluences (as low as 5 J/cm{sup 2}). The pits seemed to result from ejection of nodular defects by causing local enhancement of the electric field. Scalds and delaminates could be observed at higher fluences (above 13 J/cm{sup 2}) and seemed to result from the formation of plasmas on the surface. These damage types often originated at pits and were less than 300 {mu}m diameter; their size increased almost linearly with fluence. Finally, effects of the damage on the beam (reflectivity degradation and phase modulations) were measured.

  1. Influence of physical parameters to time domain induced polarization (TDIP) response

    NASA Astrophysics Data System (ADS)

    Yatini, Santoso, D.; Laesanpura, A.; Sulistijo, B.

    2016-03-01

    Induced Polarization (IP) method is one of geophysical method. This method is develop the resistivity method with additional measurement in ability of the ground to store electrical charge. Electrode polarization process is a major factor to the IP response in medium that contain metallic minerals. The relationship between the metallic mineral content and TDIP will be quantized. The TDIP response is influenced by porosity, grainsize, clay and metallic mineral content. Measurement is performed of artificial samples that made of iron ore mixed with quartz and cement. The samples are varied in iron ore content (0%-80%), grainsize (65-300) micron and clay content (0%-25%). If Fe-total content greather, then rise exponentially in chargeability M=1.53exp(0.029Fe). When the density becomes larger, chargeability rise exponentially M=0.347exp(0.852Dens). The presence of clay will enlarge the chargeability and minimize resistivity exponentially Rho=15.06exp(0.02C). Chargeability is lower and resistivity is higher for larger grainsize. Increasing water saturation will reduce the value of resistivity Rho=600,7exp(-0.028W) and Rho=191.4exp(- 0.025W) for Fe-total content of 28.3% and 21.2%, respectively.

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

    PubMed Central

    Shinkle, James R.; Kadakia, Rajan; Jones, Alan M.

    1998-01-01

    We have developed and characterized a system to analyze light effects on auxin transport independent of photosynthetic effects. Polar transport of [3H]indole-3-acetic acid through hypocotyl segments from etiolated cucumber (Cucumis sativus L.) seedlings was increased in seedlings grown in dim-red light (DRL) (0.5 μmol m−2 s−1) relative to seedlings grown in darkness. Both transport velocity and transport intensity (export rate) were increased by at least a factor of 2. Tissue formed in DRL completely acquired the higher transport capacity within 50 h, but tissue already differentiated in darkness acquired only a partial increase in transport capacity within 50 h of DRL, indicating a developmental window for light induction of commitment to changes in auxin transport. This light-induced change probably manifests itself by alteration of function of the auxin efflux carrier, as revealed using specific transport inhibitors. Relative to dark controls, DRL-grown seedlings were differentially less sensitive to two inhibitors of polar auxin transport, N-(naphth-1-yl) phthalamic acid and 2,3,5-triiodobenzoic acid. On the basis of these data, we propose that the auxin efflux carrier is a key target of light regulation during photomorphogenesis. PMID:9536069

  3. A precise extraction of the induced polarization in the 4He(e,e'p)3H reaction

    SciTech Connect

    S.P. Malace, M. Paolone, S. Strauch

    2011-01-01

    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.

  4. 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)

    El-Kader, M. S. A.; Mostafa, S. I.; Bancewicz, T.; Maroulis, G.

    2014-08-01

    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.

  5. Detector-level spectral characterization of the Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite long-wave infrared bands M15 and M16.

    PubMed

    Padula, Francis; Cao, Changyong

    2015-06-01

    The Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) sensor data record (SDR) product achieved validated maturity status in March 2014 after roughly two years of on-orbit characterization (S-NPP spacecraft launched on 28 October 2011). During post-launch analysis the VIIRS Sea Surface Temperature (SST) Environmental Data Record (EDR) team observed an anomalous striping pattern in the daytime SST data. Daytime SST retrievals use the two VIIRS long-wave infrared bands: M15 (10.7 μm) and M16 (11.8 μm). To assess possible root causes due to detector-level spectral response function (SRF) effects, a study was conducted to compare the radiometric response of the detector-level and operational-band averaged SRFs of VIIRS bands M15 and M16. The study used simulated hyperspectral blackbody radiance data and clear-sky ocean hyperspectral radiances under different atmospheric conditions. It was concluded that the SST product is likely impacted by small differences in detector-level SRFs and that if users require optimal radiometric performance, detector-level processing is recommended for both SDR and EDR products. Future work should investigate potential SDR product improvements through detector-level processing in support of the generation of Suomi NPP VIIRS climate quality SDRs. PMID:26192672

  6. Electric field induced spin and valley polarization within a magnetically confined silicene channel

    SciTech Connect

    Liu, Yiman; Zhou, Xiaoying; Zhou, Ma; Zhou, Guanghui; Long, Meng-Qiu

    2014-12-28

    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.

  7. Mapping polarization induced surface band bending on the Rashba semiconductor BiTeI

    PubMed Central

    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

    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

  8. COMPLEX RESISTIVITY OF FAULT GOUGE AND ITS SIGNIFICANCE FOR EARTHQUAKE LIGHTS AND INDUCED POLARIZATION.

    USGS Publications Warehouse

    Lockner, David A.; Byerlee, James D.

    1985-01-01

    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.

  9. Theoretical analysis on polarization-induced resistance switching effects of polymer thin films including dead layers

    NASA Astrophysics Data System (ADS)

    Honmi, Hitoshi; Hashizume, Yoichiro; Nakajima, Takashi; Okamura, Soichiro

    2015-10-01

    Polarization-induced resistance switching effects are analytically investigated. The electrostatic potential profile in metal is expressed by the Thomas-Fermi screening theory at the metal/ferroelectric interface. We estimate the current density using an assumed effective potential in metal/ferroelectric/metal junctions. Furthermore, we focus on the existence of a lower permittivity region such as a “dead layer” located at the boundary between the metal electrode and the ferroelectric material. In order to explain the ON/OFF ratio obtained in the experiment, we suggest that the dead layer near the smaller-work-function electrode side should be thicker by 2-3 Å than another electrode. Consequently, we propose a new hypothesis, that is, the thickness of the dead layer controls the ratio of resistance switching.

  10. Focusing Sources on Induced Polarization and Electrical Resistivity Method Applied to Soil Pollution Problems

    NASA Astrophysics Data System (ADS)

    Tejero, A.; Lopez, A.; Induced Polarization Team

    2013-05-01

    In recent years the problems of soil contamination have been increasing and geophysical methods, particularly electrical resistivity tomography (ERT) have struggled to find and monitor cases of contamination. Moreover, Induced Polarization (IP) has shown promise in mapping contaminant plumes, although both techniques (ERT and IP) have problems like noise, inductive coupling, effects of electrodes, etc. limiting the precision and accuracy of the data. To overcome these problems, this paper introduces a novel technique of focusing sources. This technique reduces the effects of adjacent vertical formations and contacts due to the flowing of current in a vertical way at the zone where the electrode potentials have been deployed. This fact allows obtaining cleaner data of ERT and IP. In order to introduce the proposed technique a vertical contact synthetic model is studied and after to a cultivar area in Hidalgo State, México which presents different types of

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

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

    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.

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

    SciTech Connect

    Bunakov, V. E. Kadmensky, S. G. Kadmensky, S. S.

    2008-11-15

    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 non-evaporative 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.

  13. Theory of magnetic-field-induced polarization flop in spin-spiral multiferroics

    NASA Astrophysics Data System (ADS)

    Mochizuki, Masahito

    2015-12-01

    The magnetic-field-induced 90∘ flop of ferroelectric polarization P in a spin-spiral multiferroic material TbMnO3 is theoretically studied based on a microscopic spin model. I find that the direction of the P flop or the choice of +Pa or -Pa after the flop is governed by magnetic torques produced by the applied magnetic field H acting on the Mn spins and thus is selected in a deterministic way, in contradistinction to the naively anticipated probabilistic flop. This mechanism resolves a puzzle of the previously reported memory effect in the P direction depending on the history of the magnetic-field sweep, and enables controlled switching of multiferroic domains by externally applied magnetic fields. My Monte-Carlo analysis also uncovers that the magnetic structure in the P ∥a phase under H ∥b is not a previously anticipated simple a b -plane spin cycloid but a conical spin structure.

  14. Enhancing Inhibition-Induced Plasticity in Tinnitus – Spectral Energy Contrasts in Tailor-Made Notched Music Matter

    PubMed Central

    Stein, Alwina; Engell, Alva; Lau, Pia; Wunderlich, Robert; Junghoefer, Markus; Wollbrink, Andreas; Bruchmann, Maximilian; Rudack, Claudia; Pantev, Christo

    2015-01-01

    Chronic tinnitus seems to be caused by reduced inhibition among frequency selective neurons in the auditory cortex. One possibility to reduce tinnitus perception is to induce inhibition onto over-activated neurons representing the tinnitus frequency via tailor-made notched music (TMNM). Since lateral inhibition is modifiable by spectral energy contrasts, the question arises if the effects of inhibition-induced plasticity can be enhanced by introducing increased spectral energy contrasts (ISEC) in TMNM. Eighteen participants suffering from chronic tonal tinnitus, pseudo randomly assigned to either a classical TMNM or an ISEC-TMNM group, listened to notched music for three hours on three consecutive days. The music was filtered for both groups by introducing a notch filter centered at the individual tinnitus frequency. For the ISEC-TMNM group a frequency bandwidth of 3/8 octaves on each side of the notch was amplified, additionally, by about 20 dB. Before and after each music exposure, participants rated their subjectively perceived tinnitus loudness on a visual analog scale. During the magnetoencephalographic recordings, participants were stimulated with either a reference tone of 500 Hz or a test tone with a carrier frequency representing the individual tinnitus pitch. Perceived tinnitus loudness was significantly reduced after TMNM exposure, though TMNM type did not influence the loudness ratings. Tinnitus related neural activity in the N1m time window and in the so called tinnitus network comprising temporal, parietal and frontal regions was reduced after TMNM exposure. The ISEC-TMNM group revealed even enhanced inhibition-induced plasticity in a temporal and a frontal cortical area. Overall, inhibition of tinnitus related neural activity could be strengthened in people affected with tinnitus by increasing spectral energy contrast in TMNM, confirming the concepts of inhibition-induced plasticity via TMNM and spectral energy contrasts. PMID:25951605

  15. Enhancing inhibition-induced plasticity in tinnitus--spectral energy contrasts in tailor-made notched music matter.

    PubMed

    Stein, Alwina; Engell, Alva; Lau, Pia; Wunderlich, Robert; Junghoefer, Markus; Wollbrink, Andreas; Bruchmann, Maximilian; Rudack, Claudia; Pantev, Christo

    2015-01-01

    Chronic tinnitus seems to be caused by reduced inhibition among frequency selective neurons in the auditory cortex. One possibility to reduce tinnitus perception is to induce inhibition onto over-activated neurons representing the tinnitus frequency via tailor-made notched music (TMNM). Since lateral inhibition is modifiable by spectral energy contrasts, the question arises if the effects of inhibition-induced plasticity can be enhanced by introducing increased spectral energy contrasts (ISEC) in TMNM. Eighteen participants suffering from chronic tonal tinnitus, pseudo randomly assigned to either a classical TMNM or an ISEC-TMNM group, listened to notched music for three hours on three consecutive days. The music was filtered for both groups by introducing a notch filter centered at the individual tinnitus frequency. For the ISEC-TMNM group a frequency bandwidth of 3/8 octaves on each side of the notch was amplified, additionally, by about 20 dB. Before and after each music exposure, participants rated their subjectively perceived tinnitus loudness on a visual analog scale. During the magnetoencephalographic recordings, participants were stimulated with either a reference tone of 500 Hz or a test tone with a carrier frequency representing the individual tinnitus pitch. Perceived tinnitus loudness was significantly reduced after TMNM exposure, though TMNM type did not influence the loudness ratings. Tinnitus related neural activity in the N1m time window and in the so called tinnitus network comprising temporal, parietal and frontal regions was reduced after TMNM exposure. The ISEC-TMNM group revealed even enhanced inhibition-induced plasticity in a temporal and a frontal cortical area. Overall, inhibition of tinnitus related neural activity could be strengthened in people affected with tinnitus by increasing spectral energy contrast in TMNM, confirming the concepts of inhibition-induced plasticity via TMNM and spectral energy contrasts. PMID:25951605

  16. Vapor–Liquid Equilibrium and Polarization Behavior of the GCP Water Model: Gaussian Charge-on-Spring versus Dipole Self-Consistent Field Approaches to Induced Polarization

    DOE PAGESBeta

    Chialvo, Ariel A.; Moucka, Filip; Vlcek, Lukas; Nezbeda, Ivo

    2015-03-24

    Here we implemented 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. Moreover, for that purpose we adapted the recently developed multiple-particle-move (MPM) within the Gibbs and isochoric-isothermal ensembles Monte Carlo methods for the efficient simulation of polarizable fluids. We also 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 againstmore » the corresponding quantities from the actual GCP water model.« less

  17. Vapor–Liquid Equilibrium and Polarization Behavior of the GCP Water Model: Gaussian Charge-on-Spring versus Dipole Self-Consistent Field Approaches to Induced Polarization

    SciTech Connect

    Chialvo, Ariel A.; Moucka, Filip; Vlcek, Lukas; Nezbeda, Ivo

    2015-03-24

    Here we implemented 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. Moreover, for that purpose we adapted the recently developed multiple-particle-move (MPM) within the Gibbs and isochoric-isothermal ensembles Monte Carlo methods for the efficient simulation of polarizable fluids. We also 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.

  18. 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

    Chialvo, Ariel A; Moucka, Filip; Vlcek, Lukas; Nezbeda, Ivo

    2015-04-16

    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

  19. Vapor-liquid Equilibria and Polarization Behavior of the GCP Water Model: Gaussian Charge-on-spring versus Dipole Self-consistent Field approaches to induced polarization

    DOE PAGESBeta

    Chialvo, Ariel A; Moucka, Filip; Vlcek, Lukas; Nezbeda, Ivo

    2015-01-01

    We implemented 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 developed 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 quantitiesmore » from the actual GCP water model.« less

  20. Field Trials of the Multi-Source Approach for Resistivity and Induced Polarization Data Acquisition

    NASA Astrophysics Data System (ADS)

    LaBrecque, D. J.; Morelli, G.; Fischanger, F.; Lamoureux, P.; Brigham, R.

    2013-12-01

    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

  1. Revisiting the time domain induced polarization technique, from linearization to inversion

    NASA Astrophysics Data System (ADS)

    Kang, S.; Oldenburg, D.

    2015-12-01

    The induced polarization (IP) technique has been successful in mineral exploration, particularly for finding disseminated sulphide or porphyry deposits, but also in helping solve geotechnical and environmental problems. Electrical induced polarization (EIP) surveys use grounded electrodes and take measurements of the electric field while the current is both "on" and "off". Currently, 2D and 3D inversions of EIP data are generally carried out by first finding a background conductivity from the asymptotic "on-time" measurements. The DC resistivity problem is then linearized about that conductivity to obtain a linear relationship between the off-time data and the "pseudo-chargeability". The distribution of pseudo-chargeability in the earth is then interpreted within the context of the initial geoscience problem pursued. Despite its success, the current EIP implementation does have challenges. A fundamental assumption, that there is no electromagnetic induction (EM) effect, breaks down when the background is conductive. This is especially problematic in regions having conductive overburden. EM induction complicates, and sometimes overwhelms, the IP signal. To ameliorate this effect, we estimate the inductive signal, subtract it from the "off-time" data and invert the resultant IP data using the linearized formulation. We carefully examine the conditions under which this works. We also investigate the potential alterations to the linearized sensitivity function that are needed to allow a linearized inversion to be carried out. Inversions of EIP data recover a "chargeability" but this is not a uniquely defined quantity. There are multiple definitions of this property because there are a diverse number of ways in which an IP datum is defined. In time domain IP surveys, the data might be mV/V or a time-integrated voltage with units of ms. In reality however, data from an EIP survey have many time channels and each one can be inverted separately to produce a chargeability

  2. Laser induced infrared spectral shift of the MgB2:Cr superconductor films

    NASA Astrophysics Data System (ADS)

    AlZayed, N. S.; Kityk, I. V.; Soltan, S.; El-Naggar, A. M.; Shahabuddin, M.

    2015-02-01

    During illumination of the MgB2:Cr2O3 films it was established substantial spectral shift of the infrared spectra in the vicinity of 20-50 cm-1. The excitations were performed by nanosecond Er:glass laser operating at 1.54 μm and by microsecond 10.6 μm 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.

  3. Human B cells induce dendritic cell maturation and favour Th2 polarization by inducing OX-40 ligand

    PubMed Central

    Maddur, Mohan S.; Sharma, Meenu; Hegde, Pushpa; Stephen-Victor, Emmanuel; Pulendran, Bali; Kaveri, Srini V.; Bayry, Jagadeesh

    2015-01-01

    Dendritic cells (DCs) play a critical role in immune homeostasis by regulating the functions of various immune cells, including T and B cells. Notably, DCs also undergo education on reciprocal signalling by these immune cells and environmental factors. Various reports demonstrated that B cells have profound regulatory functions, although only few reports have explored the regulation of human DCs by B cells. Here we demonstrate that activated but not resting B cells induce maturation of DCs with distinct features to polarize Th2 cells that secrete interleukin (IL)-5, IL-4 and IL-13. B-cell-induced maturation of DCs is contact dependent and implicates signalling of B-cell activation molecules CD69, B-cell-activating factor receptor, and transmembrane activator and calcium-modulating cyclophilin ligand interactor. Mechanistically, differentiation of Th2 cells by B-cell-matured DCs is dependent on OX-40 ligand. Collectively, our results suggest that B cells have the ability to control their own effector functions by enhancing the ability of human DCs to mediate Th2 differentiation. PMID:24910129

  4. Combined study of microwave-power-dependence and linear-polarization-dependence of the microwave-radiation-induced magnetoresistance oscillations

    NASA Astrophysics Data System (ADS)

    Ye, Tianyu; Liu, Han-Chun; Mani, Ramesh; Wegscheider, Werner; Georgia State University Collaboration; ETH Zurich Collaboration

    2014-03-01

    Microwave radiation induced magnetoresistance oscillations (MRIMOs) represent an interesting electrical property of the high mobility two dimensional electron gas (2DEG) at low temperatures in a perpendicular magnetic field and under microwave excitation. Some questions under discussion in this topic include: (a) whether MRIMOs' amplitudes grow linearly with the microwave power and (b) how the MRIMO amplitudes change with the rotation of the microwave polarization with respect to the sample. In this study, we utilize swept microwave power and continuously changed linear polarized microwave polarization angle as two variables in four-terminal low-frequency lock-in magnetoresistance measurements of the 2DEG samples. The results show that amplitude of MRIMOs varies non-linearly with the microwave power. Also, the microwave polarization dependence measurements show that MRIMOs depend sensitively on the polarization angle of the linearly polarized microwaves, while the oscillatory magnetoresistance follows a cosine square function of the polarization angle. We provide a simple model that conveys our understanding of our observations. Basic research at Georgia State University is supported by the DOE-BES, MSE Division under DE-SC0001762. Microwave work is supported by the ARO under W911NF-07-01-0158.

  5. Frequency-induced polarization bistability in vertical-cavity surface-emitting lasers with orthogonal optical injection

    SciTech Connect

    Gatare, I.; Panajotov, K.; Sciamanna, M.

    2007-02-15

    We report theoretically on a pure frequency-induced polarization bistability in a vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection, i.e., the master laser light polarization is orthogonal to that of the slave VCSEL. As the frequency detuning is scanned from negative to positive values and for a fixed injected power, the VCSEL exhibits two successive and possibly bistable polarization switchings. The first switching (from the slave laser polarization to the injected light polarization) exhibits a bistable region whose width is maximum for a given value of the injected power. Such a dependency of hysteresis width on the injected power is similar to that recently found experimentally by Hong et al.[Electron. Lett. 36, 2019 (2000)]. The bistability accompanying the second switching (from the injected light polarization back to the slave laser free-running polarization) exhibits, however, significantly different features related to the occurrence of optical chaos. Interestingly, the width of the bistable region can be tuned over a large range not only by modifying the injection parameters but also by modifying the device parameters, in particular the VCSEL linewidth enhancement factor.

  6. Spectral Integration Plasticity in Cat Auditory Cortex Induced by Perceptual Training

    PubMed Central

    Keeling, M. Diane; Calhoun, Barbara M.; Krüger, Katharina; Polley, Daniel B.; Schreiner, Christoph E.

    2008-01-01

    We investigated the ability of cats to discriminate differences between vowel-like spectra, assessed their discrimination ability over time, and compared spectral receptive fields in primary auditory cortex (AI) of trained and untrained cats. Animals were trained to discriminate changes in the spectral envelope of a broad-band harmonic complex in a 2-alternative forced choice procedure. The standard stimulus was an acoustic grating consisting of a harmonic complex with a sinusoidally modulated spectral envelope ('ripple spectrum'). The spacing of spectral peaks was conserved at 1, 2, or 2.66 peaks/octave. Animals were trained to detect differences in the frequency location of energy peaks, corresponding to changes in the spectral envelope phase. Average discrimination thresholds improved continuously during the course of the testing from phase-shifts of 96° at the beginning to 44° after 4–6 months of training. Responses of AI single units and small groups of neurons to pure tones and ripple spectra were modified during perceptual discrimination training with vowel-like ripple stimuli. The transfer function for spectral envelope frequencies narrowed and the tuning for pure tones sharpened significantly in discriminant versus naive animals. By contrast, control animals that used the ripple spectra only in a lateralization task showed broader ripple transfer functions and narrower pure-tone tuning than naïve animals. PMID:17896103

  7. Non-coherent continuum scattering as a line polarization mechanism

    SciTech Connect

    Del Pino Alemán, T.; Manso Sainz, R.; Trujillo Bueno, J. E-mail: rsainz@iac.es

    2014-03-20

    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.

  8. Angular correlations in emission of prescission neutrons from {sup 235}U fission induced by slow polarized neutrons

    SciTech Connect

    Danilyan, G. V.; Wilpert, T.; Granz, P.; Krakhotin, V. A.; Mezei, F.; Novitsky, V. V.; Pavlov, V. S.; Russina, M. V.; Shatalov, P. B.

    2008-12-15

    A new approach to searching for and studying scission neutrons, which is based on the analysis of specific angular correlations in nuclear fission induced by polarized neutrons, is described and used to evaluate the fraction of scission neutrons in the total number of prompt neutrons of {sup 235}U fission emitted perpendicularly to the fission axis.

  9. Temperature dependence of carrier spin polarization determined from current-induced domain wall motion in a Co/Ni nanowire

    SciTech Connect

    Ueda, K.; Koyama, T.; Hiramatsu, R.; Kobayashi, K.; Ono, T.; Chiba, D.; Fukami, S.; Tanigawa, H.; Suzuki, T.; Ohshima, N.; Ishiwata, N.; Nakatani, Y.

    2012-05-14

    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.

  10. Application of time domain induced polarization to the mapping of lithotypes in a landfill site

    NASA Astrophysics Data System (ADS)

    Gazoty, A.; Fiandaca, G.; Pedersen, J.; Auken, E.; Christiansen, A. V.; Pedersen, J. K.

    2012-06-01

    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.

  11. Application of time domain induced polarization to the mapping of lithotypes in a landfill site

    NASA Astrophysics Data System (ADS)

    Gazoty, A.; Fiandaca, G.; Pedersen, J.; Auken, E.; Christiansen, A. V.; Pedersen, J. K.

    2012-01-01

    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.

  12. Over-limiting currents and deionization "shocks" in current-induced polarization: local-equilibrium analysis.

    PubMed

    Yaroshchuk, Andriy

    2012-11-15

    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

  13. Errors induced by the neglect of polarization in radiance calculations for Rayleigh-scattering atmospheres

    NASA Technical Reports Server (NTRS)

    Mishchenko, M. I.; Lacis, A. A.; Travis, L. D.

    1994-01-01

    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.

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

    SciTech Connect

    Slater, L.D.; Sandberg, S.K.

    2000-04-01

    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

  15. Application of the new comprehensive X-ray spectral model to the two brightest intermediate polars EX Hydrae and V1223 Sagittarii

    NASA Astrophysics Data System (ADS)

    Hayashi, Takayuki; Ishida, Manabu

    2014-07-01

    We applied the new comprehensive X-ray spectral model for the post-shock accretion column (PSAC) of the intermediate polars (IPs) constructed by Hayashi and Ishida to the Suzaku data of the two brightest IPs EX Hydrae and V1223 Sagittarii. The white dwarf (WD) mass and the specific accretion rate of EX Hya are estimated to be M_WD= 0.63_{-0.14}^{+0.17} M⊙ and a=0.049_{-0.035}^{+0.66} g cm-2 s-1. Our WD mass of EX Hya is greater than that of previous X-ray estimations (˜0.4-0.5 M⊙), where higher specific accretion rate than ours is assumed, and marginally consistent with 0.790 ± 0.026 M⊙ measured by Beuermann and Reinsch using a binary motion. On the other hand, with the aid of the PSAC height of V1223 Sgr hV1223 < 0.07RWD, we estimated M_WD= 0.87_{-0.06}^{+0.10} M_{⊙} and a > 2.0 g cm-2 s-1 for V1223 Sgr. We evaluated the fractional accreting area of EX Hya and V1223 Sgr at 0.0033_{-0.0030}^{+0.0067} and <0.007, respectively. Calculation of the hydrodynamical equations with these best-fitting parameters show that the PSAC height of EX Hya is 0.33 RWD = 2.8 × 108 cm. The maximum temperature of the EX Hya and V1223 Sgr are calculated at 18.0 keV and 43.1 keV, respectively. In EX Hya, the temperature distribution is flatter and the density at the top of the PSAC is smaller than those of the previous PSAC models because of its low specific accretion rate.

  16. Switching of charge-current-induced spin polarization in the topological insulator BiSbTeSe2

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Ghatak, Subhamoy; Taskin, A. A.; Segawa, Kouji; Ando, Yuichiro; Shiraishi, Masashi; Kanai, Yasushi; Matsumoto, Kazuhiko; Rosch, Achim; Ando, Yoichi

    2016-08-01

    The charge-current-induced spin polarization is a key property of topological insulators for their applications in spintronics. However, topological surface states are expected to give rise to only one type of spin polarization for a given current direction, which has been a limiting factor for spin manipulations. Here, we report that in devices based on the bulk-insulating topological insulator BiSbTeSe2, an unexpected switching of spin polarization was observed upon changing the chemical potential. The spin polarization expected from the topological surface states was detected in a heavily electron-doped device, whereas the opposite polarization was reproducibly observed in devices with low carrier densities. We propose that the latter type of spin polarization stems from topologically trivial two-dimensional states with a large Rashba spin splitting, which are caused by a strong band bending at the surface of BiSbTeSe2 beneath the ferromagnetic electrode used as a spin detector. This finding paves the way for realizing the "spin transistor" operation in future topological spintronic devices.

  17. Variable light environments induce plastic spectral tuning by regional opsin coexpression in the African cichlid fish, Metriaclima zebra

    PubMed Central

    Dalton, Brian E.; Lu, Jessica; Leips, Jeff; Cronin, Thomas W.; Carleton, Karen L.

    2015-01-01

    Critical behaviors such as predation and mate choice often depend on vision. Visual systems are sensitive to the spectrum of light in their environment, which can vary extensively both within and among habitats. Evolutionary changes in spectral sensitivity contribute to divergence and speciation. Spectral sensitivity of the retina is primarily determined by visual pigments, which are opsin proteins bound to a chromophore. We recently discovered that photoreceptors in different regions of the retina, which view objects against distinct environmental backgrounds, coexpress different pairs of opsins in an African cichlid fish, Metriaclima zebra. This coexpression tunes the sensitivity of the retinal regions to the corresponding backgrounds and may aid detection of dark objects, such as predators. Although intraretinal regionalization of spectral sensitivity in many animals correlates with their light environments, it is unknown whether variation in the light environment induces developmentally plastic alterations of intraretinal sensitivity regions. Here, we demonstrate with fluorescent in situ hybridization and qPCR that the spectrum and angle of environmental light both influence the development of spectral sensitivity regions by altering the distribution and level of opsins across the retina. Normally M. zebra coexpresses LWS opsin with RH2Aα opsin in double cones of the ventral but not the dorsal retina. However, when illuminated from below throughout development, adult M. zebra coexpressed LWS and RH2Aα in double cones both dorsally and ventrally. Thus, environmental background spectra alter the spectral sensitivity pattern that develops across the retina, potentially influencing behaviors and related evolutionary processes such as courtship and speciation. PMID:26175094

  18. Variable light environments induce plastic spectral tuning by regional opsin coexpression in the African cichlid fish, Metriaclima zebra.

    PubMed

    Dalton, Brian E; Lu, Jessica; Leips, Jeff; Cronin, Thomas W; Carleton, Karen L

    2015-08-01

    Critical behaviours such as predation and mate choice often depend on vision. Visual systems are sensitive to the spectrum of light in their environment, which can vary extensively both within and among habitats. Evolutionary changes in spectral sensitivity contribute to divergence and speciation. Spectral sensitivity of the retina is primarily determined by visual pigments, which are opsin proteins bound to a chromophore. We recently discovered that photoreceptors in different regions of the retina, which view objects against distinct environmental backgrounds, coexpress different pairs of opsins in an African cichlid fish, Metriaclima zebra. This coexpression tunes the sensitivity of the retinal regions to the corresponding backgrounds and may aid in detection of dark objects, such as predators. Although intraretinal regionalization of spectral sensitivity in many animals correlates with their light environments, it is unknown whether variation in the light environment induces developmentally plastic alterations of intraretinal sensitivity regions. Here, we demonstrate with fluorescent in situ hybridization and qPCR that the spectrum and angle of environmental light both influence the development of spectral sensitivity regions by altering the distribution and level of opsins across the retina. Normally, M. zebra coexpresses LWS opsin with RH2Aα opsin in double cones of the ventral but not the dorsal retina. However, when illuminated from below throughout development, adult M. zebra coexpressed LWS and RH2Aα in double cones both dorsally and ventrally. Thus, environmental background spectra alter the spectral sensitivity pattern that develops across the retina, potentially influencing behaviours and related evolutionary processes such as courtship and speciation. PMID:26175094

  19. Magnetic-field-induced ferroelectric polarization reversal in the multiferroic Ge(1-x)Mn(x)Te semiconductor.

    PubMed

    Przybylińska, H; Springholz, G; Lechner, R T; Hassan, M; Wegscheider, M; Jantsch, W; Bauer, G

    2014-01-31

    Ge(1-x)Mn(x)Te is shown to be a multiferroic semiconductor, exhibiting both ferromagnetic and ferroelectric properties. By ferromagnetic resonance we demonstrate that both types of order are coupled to each other. As a result, magnetic-field-induced ferroelectric polarization reversal is achieved. Switching of the spontaneous electric dipole moment is monitored by changes in the magnetocrystalline anisotropy. This also reveals that the ferroelectric polarization reversal is accompanied by a reorientation of the hard and easy magnetization axes. By tuning the GeMnTe composition, the interplay between ferromagnetism and ferroelectricity can be controlled. PMID:24580486

  20. Gamma-ray burst polarization reduction induced by the Lorentz invariance violation

    NASA Astrophysics Data System (ADS)

    Lin, Hai-Nan; Li, Xin; Chang, Zhe

    2016-08-01

    It has been observed that photons in the prompt emission of some gamma-ray bursts (GRBs) are highly polarized. The high polarization is used by some authors to give a strict constraint on the Lorentz invariance violation (LIV). If the Lorentz invariance is broken, the polarization vector of a photon may rotate during its propagation. The rotation angle of polarization vector depends on both the photon energy and the distance of source. It is believed that if high polarization is observed, then the relative rotation angle (denoted by α) of polarization vector of the highest energy photon with respect to that of the lowest energy photon should be no more than π/2. Otherwise, the net polarization will be severely suppressed, thus couldn't be as high as what was actually observed. In this paper, we will give a detailed calculation on the evolution of GRB polarization arising from LIV effect duration the propagation. It is shown that the polarization degree rapidly decrease as α increases, and reaches a local minimum at α ≈ π, then increases until α ≈ 3π/2, after that decreases again until α ≈ 2π, etc. The polarization degree as a function of α oscillates with a quasi-period T ≈ π, while the oscillating amplitude gradually deceases to zero. Moreover, we find that a considerable amount (more than 60% of the initial polarization) of polarization degree can be conserved when α ≈ π/2. The polarization observation in a higher and wider energy band, a softer photon spectrum, and a higher redshift GRB is favorable in order to tightly constrain LIV effect.

  1. Laser-induced polarization of a quantum spin system in the steady-state regime

    NASA Astrophysics Data System (ADS)

    Zvyagin, A. A.

    2016-05-01

    The effect of the circularly polarized laser field on quantum spin systems in the steady-state regime, in which relaxation plays the central role, has been studied. The dynamical mean-field-like theory predicts several general results for the behavior of the time-average magnetization caused by the laser field. The induced magnetization oscillates with the frequency of the laser field (while Rabi-like oscillations, which modulate the latter in the dynamical regime, are damped by the relaxation in the steady-state regime). At high frequencies, that magnetization is determined by the value to which the relaxation process is directed. At low frequencies the slope of that magnetization as a function of the frequency is determined by the strength of the laser field. The anisotropy determines the resonance behavior of the time-averaged magnetization in both the ferromagnetic and antiferromagnetic cases with nonzero magnetic anisotropy. Nonlinear effects (in the magnitude of the laser field) have been considered. The effect of the laser field on quantum spin systems is maximal in resonance, where the time-averaged magnetization, caused by the laser field, is changed essentially. Out of resonance the changes in the magnetization are relatively small. The resonance effect is caused by the nonzero magnetic anisotropy. The resonance frequency is small (proportional to the anisotropy value) for spin systems with ferromagnetic interactions and enhanced by exchange interactions in the spin systems with antiferromagnetic couplings. We show that it is worthwhile to study the laser-field-induced magnetization of quantum spin systems caused by the high-frequency laser field in the steady-state regime in "easy-axis" antiferromagnetic spin systems (e.g., in Ising-like antiferromagnetic spin-chain materials). The effects of the Dzyaloshinskii-Moriya interaction and the spin-frustration couplings (in the case of the zigzag spin chain) have been analyzed.

  2. Characterization of Natural Attenuation in a uranium-contaminated site by means of Induced Polarization Imaging

    NASA Astrophysics Data System (ADS)

    Flores Orozco, Adrián; Bücker, Matthias; Williams, Kenneth

    2014-05-01

    Field experiments at the U.S. Department of Energy's (DOE) Integrated Field Research Challenge site (IFRC) in Rifle, Colorado (USA) have repeatedly demonstrated the ability of microorganisms to reductively immobilize uranium (U) in U tailings-contaminated groundwater accompanying organic carbon amendment. At the same time, geophysical monitoring during such amendment experiments has proven that Induced Polarization (IP) datasets can provide valuable information regarding geochemical changes induced by stimulated microbial activity, such as precipitation of metallic minerals (e.g. FeS) and accumulation of reactive, electroactive ions (Fe[II]). Based on these findings, we present a novel, modified application of the IP imaging method. Specifically, we utilized an IP characterization approach to delineate areas where fluvially deposited organic material, within aquifer sediments, naturally stimulates the activity of subsurface microflora, leading to both the natural immobilization of uranium and accumulation of reduced end-products (minerals and pore fluids) capable of generating anomalous IP signatures. These so-called 'naturally reduced zones' (NRZ's) are characterized by elevated rates of microbial activity relative to sediments having a lower concentration of organic matter. As noted and based on our previous experiments at the site, the accumulation of metallic minerals represents suitable targets for the exploration with IP tomographic methods. Here, we explore the application of the IP imaging method for the characterization of NRZ's at the scale of the floodplain. We present imaging results obtained through the inversion of 70 independent lines distributed along the floodplain (~600 m2). Imaging results are validated through comparisons with lithological data obtained from wells drilled at the site and laboratory analysis of sediment and groundwater samples. Our results show the applicability of the IP method for characterizing regions of the subsurface having

  3. Electric field induced critical points and polarization rotations in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Kutnjak, Zdravko; Blinc, Robert; Ishibashi, Y.

    2007-09-01

    The giant electromechanical response in ferroelectric relaxors such as Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) is of great importance for a number of ultrasonic and medical applications as well as in telecommunications. On the basis of the dielectric, heat capacity, and piezoelectric investigations on PMN-PT crystals of various PT compositions and bias fields, we have recently shown the existence of a line of critical points for the paraelectric to ferroelectric transformations in the composition-temperature-electric field (x-T-E) phase diagram. Here, we show the piezobehavior in more detail and present a theoretical evaluation of the Widom line and the critical line. This line effectively terminates a surface of first order transitions. Above this line, supercritical evolution has been observed. On approaching the critical point, both the enthalpy cost to induce the intermediate monoclinic states and thus the barrier for polarization rotations decrease significantly. The maximum of the piezoelectric response is not at E=0 , but at the critical field values. It is shown that the critical fluctuations in the proximity of the critical points are directly responsible for the observed enhancement of the electromechanical response in the PMN-PT system. In view of the large electric field dependence of the dielectric constant near the critical point, these systems may also be important as electric field tunable elements.

  4. Chiral Selective Chemistry Induced by Natural Selection of Spin-Polarized Electrons.

    PubMed

    Rosenberg, Richard A; Mishra, Debabrata; Naaman, Ron

    2015-06-15

    The search to understand the origin of homochirality in nature has been ongoing since the time of Pasteur. Previous work has shown that DNA can act as a spin filter for low-energy electrons and that spin-polarized secondary electrons produced by X-ray irradiation of a magnetic substrate can induce chiral selective chemistry. In the present work it is demonstrated that secondary electrons from a substrate that are transmitted through a chiral overlayer cause enantiomeric selective chemistry in an adsorbed adlayer. We determine the quantum yields (QYs) for dissociation of (R)- or (S)-epichlorohydrin adsorbed on a chiral self-assembled layer of DNA on gold and on bare gold (for control). The results show that there is a significant difference in the QYs between the two enantiomers when adsorbed on DNA, but none when they are adsorbed on bare Au. We propose that the effect results from natural spin filtering effects cause by the chiral monolayer. PMID:25950284

  5. The Formation of Ion Concentration Polarization Layer Induced by Bifurcated Current Path

    NASA Astrophysics Data System (ADS)

    Kim, Junsuk; Lee, Hyomin; Cho, Inhee; Kim, Ho-Young; Kim, Sung Jae; EES Team; MFM Team

    2015-11-01

    Ion Concentration Polarization (ICP) is a fundamental electrokinetic phenomenon that occurs near a perm-selective membrane and, thus, the characteristics can be significantly altered by the current path through the Nafion nanoporous membrane. In this work, a new ICP device that bifurcated the current path was fabricated using micro/micro-nano/nano/micro hybrid channel connection, while a conventional ICP device has employed micro/nano/micro channel connection. The propagation of ICP layer was initiated from the nano-channel at high concentration regime and from micro-nano connection at low concentration regime. Interestingly, the reverse propagation was observed at low concentration regime as well. These combined effects conveyed a competition between two distinguishable propagations at intermediate concentration regime, caused by singularity of the bifurcated current path. Experiments and an equivalent circuit analysis were conducted for this bifurcation. As a result, the conductance ratio of electrolyte to Nafion governed the bifurcation. Conclusively, the bifurcation-induced ICP layer formation was able to be characterized by analyzing current-time characteristic which have two distinct RC delay times. 2013R1A1A1008125, CISS- 2011-0031870 and 2012-0009563 by the Ministry of Science, ICT & Future Planning and HI13C1468, HI14C0559.

  6. LabVIEW-based control software for para-hydrogen induced polarization instrumentation

    SciTech Connect

    Agraz, Jose Grunfeld, Alexander; Li, Debiao; Cunningham, Karl; Willey, Cindy; Pozos, Robert; Wagner, Shawn

    2014-04-15

    The elucidation of cell metabolic mechanisms is the modern underpinning of the diagnosis, treatment, and in some cases the prevention of disease. Para-Hydrogen induced polarization (PHIP) enhances magnetic resonance imaging (MRI) signals over 10 000 fold, allowing for the MRI of cell metabolic mechanisms. This signal enhancement is the result of hyperpolarizing endogenous substances used as contrast agents during imaging. PHIP instrumentation hyperpolarizes Carbon-13 ({sup 13}C) based substances using a process requiring control of a number of factors: chemical reaction timing, gas flow, monitoring of a static magnetic field (B{sub o}), radio frequency (RF) irradiation timing, reaction temperature, and gas pressures. Current PHIP instruments manually control the hyperpolarization process resulting in the lack of the precise control of factors listed above, resulting in non-reproducible results. We discuss the design and implementation of a LabVIEW based computer program that automatically and precisely controls the delivery and manipulation of gases and samples, monitoring gas pressures, environmental temperature, and RF sample irradiation. We show that the automated control over the hyperpolarization process results in the hyperpolarization of hydroxyethylpropionate. The implementation of this software provides the fast prototyping of PHIP instrumentation for the evaluation of a myriad of {sup 13}C based endogenous contrast agents used in molecular imaging.

  7. LabVIEW-based control software for para-hydrogen induced polarization instrumentation

    NASA Astrophysics Data System (ADS)

    Agraz, Jose; Grunfeld, Alexander; Li, Debiao; Cunningham, Karl; Willey, Cindy; Pozos, Robert; Wagner, Shawn

    2014-04-01

    The elucidation of cell metabolic mechanisms is the modern underpinning of the diagnosis, treatment, and in some cases the prevention of disease. Para-Hydrogen induced polarization (PHIP) enhances magnetic resonance imaging (MRI) signals over 10 000 fold, allowing for the MRI of cell metabolic mechanisms. This signal enhancement is the result of hyperpolarizing endogenous substances used as contrast agents during imaging. PHIP instrumentation hyperpolarizes Carbon-13 (13C) based substances using a process requiring control of a number of factors: chemical reaction timing, gas flow, monitoring of a static magnetic field (Bo), radio frequency (RF) irradiation timing, reaction temperature, and gas pressures. Current PHIP instruments manually control the hyperpolarization process resulting in the lack of the precise control of factors listed above, resulting in non-reproducible results. We discuss the design and implementation of a LabVIEW based computer program that automatically and precisely controls the delivery and manipulation of gases and samples, monitoring gas pressures, environmental temperature, and RF sample irradiation. We show that the automated control over the hyperpolarization process results in the hyperpolarization of hydroxyethylpropionate. The implementation of this software provides the fast prototyping of PHIP instrumentation for the evaluation of a myriad of 13C based endogenous contrast agents used in molecular imaging.

  8. Subsidence-induced methane clouds in Titan's winter polar stratosphere and upper troposphere

    NASA Astrophysics Data System (ADS)

    Anderson, C. M.; Samuelson, R. E.; Achterberg, R. K.; Barnes, J. W.; Flasar, F. M.

    2014-11-01

    Titan's atmospheric methane most likely originates from lakes at the surface and subsurface reservoirs. Accordingly, it has been commonly assumed that Titan's tropopause region, where the vertical temperature profile is a minimum, acts as a cold trap for convecting methane, leading to the expectation that the formation of methane clouds in Titan's stratosphere would be rare. The additional assumption that Titan's tropopause temperatures are independent of latitude is also required. However, Cassini Composite InfraRed Spectrometer (CIRS) and Radio Science Subsystem (RSS) data sets reveal colder temperatures in Titan's tropopause region near the winter pole than those at low latitudes and in the summer hemisphere. This, combined with the presence of a cross-equatorial meridional circulation with winter polar subsidence, as suggested by current general circulation models, implies the inevitable formation of Subsidence-Induced Methane Clouds (SIMCs) over Titan's winter pole. We verified this by retrieving the stratospheric methane mole fraction at 70°N from the strength of the far infrared methane pure rotation lines observed by CIRS and by assuming the RSS-derived thermal profile at 74.1°N. Our retrieved methane mole fraction of 1.50 ± 0.15% allows for methane to condense and form SIMCs at altitudes between ∼48 and ∼20 km. Radiative transfer analyses of a color composite image obtained by the Cassini Visible and Infrared Mapping Spectrometer (VIMS) during northern winter appear to corroborate the existence of these clouds.

  9. Induced polarization of disseminated electronically conductive minerals: a semi-empirical model

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    We studied artificial ore models that contained galena, pyrite, magnetite, graphite and cryptomelane with the time domain induced polarization technique. The models were mixtures of sand and metallic-type, electronically conductive mineral particles. We varied the volumetric content of the particles, their mineral composition and average grain size, as well as the pore water salinity. Based on the Debye decomposition approach, we obtained relaxation time distributions, which contained peaks. From these distributions, we obtained the total chargeability and the peak relaxation time. We correlated these parameters with the particle mineral composition, grain size, particle content and the pore solution resistivity. We also compared the experimental data with the Wong model prediction, which was unable to explain the entire data set. The above-mentioned correlations, in conjunction with some previously published data, allowed us to formulate a new, semi-empirical model that links (1) the total chargeability with the volumetric content of the particles and the total chargeability of the host matrix and (2) the time constant with the particle mineralogy, the particle radius and the pore solution resistivity.

  10. Impacts of Polar Changes on the UV-induced Mineralization of Terrigenous Dissolved Organic Matter.

    PubMed

    Sulzberger, Barbara; Arey, J Samuel

    2016-07-01

    Local climates in the Northern and Southern Hemisphere are influenced by Arctic Amplification and by interactions of the Antarctic ozone hole with climate change, respectively. Polar changes may affect hydroclimatic conditions in temperate regions, for example, by increasing the length and intensity of precipitation events at Northern Hemisphere midlatitudes. Additionally, global warming has led to the thawing of ancient permafrost soils, particularly in Arctic regions, due to Arctic Amplification. Both heavy precipitation events and thawing of permafrost are increasing the net transfer of terrestrially derived dissolved organic matter (DOM) from land to surface waters. In aquatic ecosystems, UV-induced oxidation of terrigenous DOM (tDOM) produces atmospheric CO2 and this process is one of several mechanisms by which natural organic matter in aquatic and soil environments may play an important role in climate feedbacks. The Arctic is particularly affected by these processes: for example, melting of Arctic sea ice allows solar UV radiation to penetrate into the ice-free Arctic Ocean and to cause photochemical reactions that result in bleaching and mineralization of tDOM. Open questions, in addition to those shown in the Graphical Abstract, remain regarding the resulting contributions of tDOM photomineralization to CO2 production and global warming. PMID:27110903

  11. Parahydrogen induced polarization and the oxidative addition of hydrogen to iridium tribromostannyl carbonylate anions.

    PubMed

    Permin, Alexei; Eisenberg, Richard

    2002-05-01

    Activation of dihydrogen by a system composed of (Bu(4)N)[IrBr(2)(CO)(2)] (1) and tin dibromide in varying ratios was studied using parahydrogen induced polarization (PHIP) which allows the detection of transient dihydrides not observable in conventional (1)H NMR spectra. While the oxidative addition of dihydrogen to neutral and cationic Ir(I) species is common, there are only a few examples of H(2) addition to anionic complexes. Tin dibromide reacts with iridium(I) complex 1 in acetone forming equilibrium mixtures of cis- and trans-tribromostannyl derivatives [IrBr(n)()(SnBr(3))(2)(-)(n)()(CO)(2)](-), n = 0,1, the existence of which is inferred from the stereochemistries of the dihydrogen addition products determined using PHIP. The sigma-donating effect of the SnBr(3)(-) ligand facilitates the oxidative addition to the iridium center. The structures of the dihydrides formed upon addition of dihydrogen are assigned on the basis of hydride chemical shifts and values of (2)J((1)H-(117,119)Sn). The only dihydride observed in conventional (1)H NMR spectra is cis-trans-cis-[IrH(2)(SnBr(3))(2)(CO)(2)](-), the identity of which was confirmed using the (13)C labeled Ir(I) precursor. Both [IrBr(2)(CO)(2)](-) and its tribromostannyl derivatives catalyze cis-pairwise addition of dihydrogen to phenylacetylene. PMID:11978112

  12. Polarized linewidth-controllable double-trapping electromagnetically induced transparency spectra in a resonant plasmon nanocavity

    PubMed Central

    Wang, Luojia; Gu, Ying; Chen, Hongyi; Zhang, Jia-Yu; Cui, Yiping; Gerardot, Brian D.; Gong, Qihuang

    2013-01-01

    Surface plasmons with ultrasmall optical mode volume and strong near field enhancement can be used to realize nanoscale light-matter interaction. Combining surface plasmons with the quantum system provides the possibility of nanoscale realization of important quantum optical phenomena, including the electromagnetically induced transparency (EIT), which has many applications in nonlinear quantum optics and quantum information processing. Here, using a custom-designed resonant plasmon nanocavity, we demonstrate polarized position-dependent linewidth-controllable EIT spectra at the nanoscale. We analytically obtain the double coherent population trapping conditions in a double-Λ quantum system with crossing damping, which give two transparent points in the EIT spectra. The linewidths of the three peaks are extremely sensitive to the level spacing of the excited states, the Rabi frequencies and detunings of pump fields, and the Purcell factors. In particular the linewidth of the central peak is exceptionally narrow. The hybrid system may have potential applications in ultra-compact plasmon-quantum devices. PMID:24096943

  13. Disorder-induced reversal of spin polarization in the Heusler alloy Co{sub 2}FeSi

    SciTech Connect

    Bruski, P.; Ramsteiner, M.; Brandt, O.; Friedland, K.-J.; Farshchi, R.; Herfort, J.; Riechert, H.; Erwin, S. C.

    2011-04-01

    We study the spin polarization in the conduction band of Co{sub 2}FeSi layers with a different degree of structural order. The injected spin polarization in Co{sub 2}FeSi/(Al,Ga)As spin light-emitting diodes as well as the planar Hall effect measured for the Co{sub 2}FeSi injectors exhibit a sign reversal between injectors crystallized in the ordered L2{sub 1} phase and the Fe-Si disordered B2 phase. These results are explained by a disorder-induced change in the spin polarization at the Fermi energy of Co{sub 2}FeSi. Support for the occurrence of such a striking change in the electronic band structure is obtained by first principles calculations.

  14. Strain-induced coupling of electrical polarization and structural defects in SrMnO3 films.

    PubMed

    Becher, Carsten; Maurel, Laura; Aschauer, Ulrich; Lilienblum, Martin; Magén, César; Meier, Dennis; Langenberg, Eric; Trassin, Morgan; Blasco, Javier; Krug, Ingo P; Algarabel, Pedro A; Spaldin, Nicola A; Pardo, José A; Fiebig, Manfred

    2015-08-01

    Local perturbations in complex oxides, such as domain walls, strain and defects, are of interest because they can modify the conduction or the dielectric and magnetic response, and can even promote phase transitions. Here, we show that the interaction between different types of local perturbations in oxide thin films is an additional source of functionality. Taking SrMnO3 as a model system, we use nonlinear optics to verify the theoretical prediction that strain induces a polar phase, and apply density functional theory to show that strain simultaneously increases the concentration of oxygen vacancies. These vacancies couple to the polar domain walls, where they establish an electrostatic barrier to electron migration. The result is a state with locally structured room-temperature conductivity consisting of conducting nanosized polar domains encased by insulating domain boundaries, which we resolve using scanning probe microscopy. Our 'nanocapacitor' domains can be individually charged, suggesting stable capacitance nanobits with a potential for information storage technology. PMID:26030653

  15. Parahydrogen-induced polarization transfer to 19F in perfluorocarbons for 19F NMR spectroscopy and MRI.

    PubMed

    Plaumann, Markus; Bommerich, Ute; Trantzschel, Thomas; Lego, Denise; Dillenberger, Sonja; Sauer, Grit; Bargon, Joachim; Buntkowsky, Gerd; Bernarding, Johannes

    2013-05-10

    Fluorinated substances are important in chemistry, industry, and the life sciences. In a new approach, parahydrogen-induced polarization (PHIP) is applied to enhance (19)F MR signals of (perfluoro-n-hexyl)ethene and (perfluoro-n-hexyl)ethane. Unexpectedly, the end-standing CF3 group exhibits the highest amount of polarization despite the negligible coupling to the added protons. To clarify this non-intuitive distribution of polarization, signal enhancements in deuterated chloroform and acetone were compared and (19)F-(19)F NOESY spectra, as well as (19)F T1 values were measured by NMR spectroscopy. By using the well separated and enhanced signal of the CF3 group, first (19)F MR images of hyperpolarized linear semifluorinated alkenes were recorded. PMID:23526596

  16. PPAR activation induces M1 macrophage polarization via cPLA₂-COX-2 inhibition, activating ROS production against Leishmania mexicana.

    PubMed

    Díaz-Gandarilla, J A; Osorio-Trujillo, C; Hernández-Ramírez, V I; Talamás-Rohana, P

    2013-01-01

    Defence against Leishmania depends upon Th1 inflammatory response and, a major problem in susceptible models, is the turnoff of the leishmanicidal activity of macrophages with IL-10, IL-4, and COX-2 upregulation, as well as immunosuppressive PGE2, all together inhibiting the respiratory burst. Peroxisome proliferator-activated receptors (PPAR) activation is responsible for macrophages polarization on Leishmania susceptible models where microbicide functions are deactivated. In this paper, we demonstrated that, at least for L. mexicana, PPAR activation, mainly PPAR γ , induced macrophage activation through their polarization towards M1 profile with the increase of microbicide activity against intracellular pathogen L. mexicana. PPAR activation induced IL-10 downregulation, whereas the production of proinflammatory cytokines such as TNF- α , IL-1 β , and IL-6 remained high. Moreover, PPAR agonists treatment induced the deactivation of cPLA2-COX-2-prostaglandins pathway together with an increase in TLR4 expression, all of whose criteria meet the M1 macrophage profile. Finally, parasite burden, in treated macrophages, was lower than that in infected nontreated macrophages, most probably associated with the increase of respiratory burst in these treated cells. Based on the above data, we conclude that PPAR agonists used in this work induces M1 macrophages polarization via inhibition of cPLA2 and the increase of aggressive microbicidal activity via reactive oxygen species (ROS) production. PMID:23555077

  17. Dynamics of nuclear spin polarization induced and detected by coherently precessing electron spins in fluorine-doped ZnSe

    NASA Astrophysics Data System (ADS)

    Heisterkamp, F.; Kirstein, E.; Greilich, A.; Zhukov, E. A.; Kazimierczuk, T.; Yakovlev, D. R.; Pawlis, A.; Bayer, M.

    2016-02-01

    We study the dynamics of optically induced nuclear spin polarization in a fluorine-doped ZnSe epilayer via time-resolved Kerr rotation. The nuclear polarization in the vicinity of a fluorine donor is induced by interaction with coherently precessing electron spins in a magnetic field applied in the Voigt geometry. It is detected by nuclei-induced changes in the electron spin coherence signal. This all-optical technique allows us to measure the longitudinal spin relaxation time T1 of the 77Se isotope in a magnetic field range from 10 to 130 mT under illumination. We combine the optical technique with radio frequency methods to address the coherent spin dynamics of the nuclei and measure Rabi oscillations, Ramsey fringes, and the nuclear spin echo. The inhomogeneous spin dephasing time T2* and the spin coherence time T2 of the 77Se isotope are measured. While the T1 time is on the order of several milliseconds, the T2 time is several hundred microseconds. The experimentally determined condition T1≫T2 verifies the validity of the classical model of nuclear spin cooling for describing the optically induced nuclear spin polarization.

  18. CTLA-4Ig immunotherapy of obesity-induced insulin resistance by manipulation of macrophage polarization in adipose tissues

    SciTech Connect

    Fujii, Masakazu; Inoguchi, Toyoshi; Batchuluun, Battsetseg; Sugiyama, Naonobu; Kobayashi, Kunihisa; Sonoda, Noriyuki; Takayanagi, Ryoichi

    2013-08-16

    Highlights: •CTLA-4Ig completely alleviates HFD-induced insulin resistance. •CTLA-4Ig reduces epididymal and subcutaneous fat tissue weight and adipocyte size. •CTLA-4Ig alters ATM polarization from inflammatory M1 to anti-inflammatory M2. •CTLA-4Ig may lead to a novel anti-obesity/inflammation/insulin resistance agent. •We identified the mechanism of the novel favorable effects of CTLA-4lg. -- Abstract: It has been established that obesity alters the metabolic and endocrine function of adipose tissue and, together with accumulation of adipose tissue macrophages, contributes to insulin resistance. Although numerous studies have reported that shifting the polarization of macrophages from M1 to M2 can alleviate adipose tissue inflammation, manipulation of macrophage polarization has not been considered as a specific therapy. Here, we determined whether cytotoxic T-lymphocyte-associated antigen-4IgG1 (CTLA-4Ig) can ameliorate insulin resistance by induction of macrophages from proinflammatory M1 to anti-inflammatory M2 polarization in the adipose tissues of high fat diet-induced insulin-resistant mice. CTLA4-Ig treatment prevented insulin resistance by changing gene expression to M2 polarization, which increased the levels of arginase 1. Furthermore, flow cytometric analysis confirmed the alteration of polarization from CD11c (M1)- to CD206 (M2)-positive cells. Concomitantly, CTLA-4Ig treatment resulted in weight reductions of epididymal and subcutaneous adipose tissues, which may be closely related to overexpression of apoptosis inhibitors in macrophages. Moreover, proinflammatory cytokine and chemokine levels decreased significantly. In contrast, CCAAT enhancer binding protein α, peroxisome proliferator-activated receptor γ, and adiponectin expression increased significantly in subcutaneous adipose tissue. This novel mechanism of CTLA-4lg immunotherapy may lead to an ideal anti-obesity/inflammation/insulin resistance agent.

  19. Aluminum-induced changes in properties and fouling propensity of DOM solutions revealed by UV-vis absorbance spectral parameters.

    PubMed

    Zhou, Minghao; Meng, Fangang

    2016-04-15

    The integration of pre-coagulation with ultrafiltration (UF) is expected to not only reduce membrane fouling but also improve natural organic matter (NOM) removal. However, it is difficult to determine the proper coagulant dosage for different water qualities. The objective of this study was to probe the potential of UV-vis spectroscopic analysis to reveal the coagulant-induced changes in the fouling potentials of dissolved organic matter (DOM) and to determine the optimal coagulant dosage. The Zeta potentials (ZPs) and average particle size of the four DOM solutions (Aldrich humic acid (AHA), AHA-sodium alginate (SA), AHA-bovine serum albumin (BSA) and AHA-dextran (DEX)) coagulated with aluminum chloride (AlCl3) were measured. Results showed that increasing the aluminum coagulant dosage induced the aggregation of DOM. Meanwhile, the addition of aluminum coagulant resulted in an increase in DSlope(325-375) (the slope of the log-transformed absorbance spectra from 325 to 375 nm) and a decrease in S(275-295) (the slope of the log-transformed absorption coefficient from 275 to 295 nm) and SR (the ratio of Slope(275-295) and Slope(350-400)). The variations of these spectral parameters (i.e., DSlope(325-375), S(275-295) and SR) correlated well with the aluminum-caused changes in ZPs and average particle size. This implies that spectral parameters have the potential to indicate DOM aggregation. In addition, good correlations of spectral parameters and membrane fouling behaviors (i.e., unified membrane fouling index (UMFI)) suggest that the changes in DSlope(325-375), S(275-295) and SR were indicative of the aluminum-caused alterations of fouling potentials of all DOM solutions. Interestingly, the optimal dosage of aluminum (40 μM for AHA, AHA-BSA, and AHA-DEX) was obtained based on the relation between spectral parameters and fouling behaviors. Overall, the spectroscopic analysis, particularly for the utilization of spectral parameters, provided a convenient approach

  20. Ischemia induces partial loss of surface membrane polarity and accumulation of putative calcium ionophores.

    PubMed Central

    Molitoris, B A; Wilson, P D; Schrier, R W; Simon, F R

    1985-01-01

    To determine if ischemia induces alterations in renal proximal tubule surface membranes, brush border (BBM) and basolateral membranes (BLM) were isolated simultaneously from the same cortical homogenate after 50 min of renal pedicle clamping. Ischemia caused a selective decrease in the specific activity of BBM marker enzymes leucine aminopeptidase and alkaline phosphatase, but did not effect enrichment (15 times). Neither specific activity nor enrichment (10 times) of BLM NaK-ATPase was altered by ischemia. Contamination of BBM by intracellular organelles was also unchanged, but there was an increase in the specific activity (41.1 vs. 60.0, P less than 0.01) and enrichment (2.3 vs. 4.3, P less than 0.01) of NaK-ATPase in the ischemic BBM fraction. Ischemia increased BLM lysophosphatidylcholine (1.3 vs. 2.5%, P less than 0.05) and phosphatidic acid (0.4 vs. 1.3%, P less than 0.05). Ischemia also decreased BBM sphingomyelin (38.5 vs. 29.6%, P less than 0.01) and phosphatidylserine (16.1 vs. 11.4%, P less than 0.01), and increased phosphatidylcholine (17.2 vs. 29.7%, P less than 0.01), phosphatidylinositol (1.8 vs. 4.6%, P less than 0.01), and lysophosphatidylcholine (1.0 vs. 1.8%, P less than 0.05). The large changes in BBM phospholipids did not result from new phospholipid synthesis, since the specific activity (32P dpm/nmol Pi) of prelabeled individual and total phospholipids was unaltered by ischemia. We next evaluated if these changes were due to inability of ischemic cells to maintain surface membrane polarity. Cytochemical evaluation showed that while NaK-ATPase could be detected only in control BLM, specific deposits of reaction product were present in the BBM of ischemic kidneys. Furthermore, using continuous sucrose gradients, the enzymatic profile of ischemic BBM NaK-ATPase shifted away from ischemic BLM NaK-ATPase and toward the BBM enzymatic marker leucine aminopeptidase. Taken together, these data suggest that NaK-ATPase activity determined enzymatically