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Sample records for spectral induced polarization

  1. 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 provides the required accuracy for frequencies above 100 Hz.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Spectral Induced Polarization In Clean Water- Saturated Sand

    NASA Astrophysics Data System (ADS)

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

    A theoretical model of Spectral Induced Polarization (IP) of sand is proposed. In this model, contacts of sand grains and inter-grain solution-filled space are considered as electrical current passages of varying thickness, which differ in values of ion transport numbers. Ion-selective narrow passages are considered active zones, large passages - passive ones. The proposed model, called SShort Narrow PoreT(SNP) model, de- & cedil; scribes spectral IP characteristics for the medium where the length of passive zones is much greater than that of the active zones. Both time domain and frequency domain parameters were described. The SNP model predicts a growth of IP time constant with increase of length of the ion-selective zone. The parameters of Cole-Cole model cor- responding to the SNP model were found. The behaviour of the model parameters was compared with experimental data obtained on natural and sieved sands using the time domain technique. The spectra of natural sands correspond neither to the simple SNP model nor to the simple Cole-Cole model with single time constant. The constant phase angle model also cannot be applied. As long as the lengths of the ion-selective zones vary according to the grain size distribution, different values of time constant are produced, which explain the spectra behaviour. A comparison of the sieved sand spectra and the SNP model theoretical spectra reveals close correspondence between the experimental data and theoretical parameters. For four sieved sands, both the the- oretical and experimental data show that the time constant of IP is proportional to the square of the average grain size. This work was supported by INTAS, project No 32046.

  8. Spectral induced polarization (SIP) measurement of NAPL contaminated soils

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    The potential applicability of spectral induce polarization (SIP) as a tool to map NAPLs (non aqueous phase liquids) contaminants at the subsurface lead researchers to investigate the electric signature of those contaminant on the spectral response. However, and despite the cumulative efforts, the effect of NAPL on the electrical properties of soil, and the mechanisms that control this effect are largely unknown. In this work a novel experiment is designed to further examine the effect of NAPL on the electrical properties of partially saturated soil. The measurement system that used is the ZEL-SIP04 impedance meter developed at the Forschungszentrum Julich, Germany. The system accurately (nominal phase precision of 0.1 mrad below 1 kHz) measures the phase and the amplitude of a material possessing a very low polarization (such as soil). The sample holder has a dimension of 60 cm long and 4.6 cm in diameter. Current and potential electrodes were made of brass, and while the current electrodes were inserted in full into the soil, the contact between the potential electrode and the soil was made through an Agarose bridge. Two types of soils were used: clean quartz sand, and a mixture of sand with clean Bentonite. Each soil (sandy or clayey) was mixed with water to get saturation degree of 30%. Following the mixture with water, NAPL was added and the composite were mixed again. Packing was done by adding and compressing small portions of the soil to the column. A triplicate of each mixture was made with a good reproducible bulk density. Both for the sandy and clayey soils, the results indicate that additions of NAPL decrease the real part of the complex resistivity. Additionally, for the sandy soil this process is time depended, and that a further decrease in resistivity develops over time. The results are analyzed considering geometrical factors: while the NAPL is electrically insulator, addition of NAPL to the soil is expected to increase the connectivity of the water phase, and therefore a decrease in the real part of the complex resistivity occurs.

  9. 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 ...

  10. Time-Domain Spectral Induced Polarization Based on Pseudo-random Sequence

    NASA Astrophysics Data System (ADS)

    Li, Mei; Wei, Wenbo; Luo, Weibin; Xu, Qindong

    2013-12-01

    To reduce noise during electrical prospecting, we hereby propose a new method using correlation identification technology and conventional electrical exploration devices. A correlation operation can be carried out with the transmitted pseudo-random sequence and received time signal to suppress the random noise, and the time-domain impulse response and frequency response of the frequency domain of the underground media can be obtained. At the same time, using a dual Cole-Cole model to fit a complex resistivity spectrum, which is close to the frequency response, we can get a variety of induced polarization parameters and electromagnetic parameters of subsurface, which can provide more useful information for the exploration of mineral resources. This time domain prospecting method can effectively improve the efficiency of the spectral induced polarization method. In this article, we have carried out theoretical calculations and a simulation to prove the feasibility of such a method.

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

    PubMed

    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. PMID:26465485

  12. 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.

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

    SciTech Connect

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

    2007-10-01

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

  14. Relating the permeability of quartz sands to their grain size and spectral induced polarization characteristics

    NASA Astrophysics Data System (ADS)

    Koch, Kristof; Revil, André; Holliger, Klaus

    2012-07-01

    Recently, Revil & Florsch proposed a novel mechanistic model based on the polarization of the Stern layer relating the permeability of granular media to their spectral induced polarization (SIP) characteristics based on the formation of polarized cells around individual grains. To explore the practical validity of this model, we compare it to pertinent laboratory measurements on samples of quartz sands with a wide range of granulometric characteristics. In particular, we measure the hydraulic and SIP characteristics of all samples both in their loose, non-compacted and compacted states, which might allow for the detection of polarization processes that are independent of the grain size. We first verify the underlying grain size/permeability relationship upon which the model of Revil & Florsch is based and then proceed to compare the observed and predicted permeability values for our samples by substituting the grain size characteristics by corresponding SIP parameters, notably the so-called Cole-Cole time constant. In doing so, we also asses the quantitative impact of an observed shift in the Cole-Cole time constant related to textural variations in the samples and observe that changes related to the compaction of the samples are not relevant for the corresponding permeability predictions. We find that the proposed model does indeed provide an adequate prediction of the overall trend of the observed permeability values, but underestimates their actual values by approximately one order-of-magnitude. This discrepancy in turn points to the potential importance of phenomena, which are currently not accounted for in the model and which tend to reduce the characteristic size of the prevailing polarization cells compared to the considered model, such as, for example, membrane polarization, contacts of double-layers of neighbouring grains, and incorrect estimation of the size of the polarized cells because of the irregularity of natural sand grains.

  15. 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.

  16. 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.

  17. 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 ?S/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

  18. 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 (?) and decrease in the magnitudes of the real (?') and imaginary (?'') 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 ? and ?'' increased with increasing oil saturation, whereas ?' decreased. The magnitude of ?' and ?'' 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 ?' and ?'' 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 acids on the SIP response of porous media.

  19. 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.

  20. Resolving spectral information from time domain induced polarization data through 2-D inversion

    NASA Astrophysics Data System (ADS)

    Fiandaca, Gianluca; Ramm, James; Binley, Andrew; Gazoty, Aurélie; Christiansen, Anders Vest; Auken, Esben

    2013-02-01

    Field-based time domain (TD) induced polarization (IP) surveys are usually modelled by taking into account only the integral chargeability, thus disregarding spectral content. Furthermore, the effect of the transmitted waveform is commonly neglected, biasing inversion results. Given these limitations of conventional approaches, a new 2-D inversion algorithm has been developed using the full voltage decay of the IP response, together with an accurate description of the transmitter waveform and receiver transfer function. This allows reconstruction of the spectral information contained in the TD decay series. The inversion algorithm is based around a 2-D complex conductivity kernel that is computed over a range of frequencies and converted to the TD through a fast Hankel transform. Two key points in the implementation ensure that computation times are minimized. First, the speed of the Jacobian computation, time transformed from frequency domain through the same transformation adopted for the forward response is optimized. Secondly, the reduction of the number of frequencies where the forward response and Jacobian are calculated: cubic splines are used to interpolate the responses to the frequency sampling necessary in the fast Hankel transform. These features, together with parallel computation, ensure inversion times comparable with those of direct current algorithms. The algorithm has been developed in a laterally constrained inversion scheme, and handles both smooth and layered inversions; the latter being helpful in sedimentary environments, where quasi-layered models often represent the actual geology more accurately than smooth minimum-structure models. In the layered inversion approach, a general method to derive the thickness derivative from the complex conductivity Jacobian is also proposed. One synthetic example of layered inversion and one field example of smooth inversion show the capability of the algorithm and illustrates a complete uncertainty analysis of the model parameters. With this new algorithm, in situ TD IP measurements give access to the spectral content of the polarization processes, opening up new applications in environmental and hydrogeophysical investigations.

  1. Spectral induced polarization and the hydraulic properties of New Zealand sands

    NASA Astrophysics Data System (ADS)

    Joseph, S.; Ingham, M.

    2014-12-01

    Laboratory measurements of spectral induced polarization (SIP) and permeability have been made on unconsolidated samples representative of shallow coastal aquifers in New Zealand. The samples consisted of sands sieved into different fractions ranging from a mean grain size of 1.0 mm to 0.125 mm. Although the occurrence in New Zealand natural sands of titomagnetite means that the magnitude of the SIP phase response is significantly greater than is generally found for "clean" sands, the peak in SIP phase shows a clear dependence on grain size. The SIP spectra have been represented in terms of a Cole-Cole model and the relaxation times derived from this show a strong linear correlation with the measured values of permeability. The SIP and permeability measurements are then extended to mixtures of sieved sands, sand with varying amount of clay, samples with varying amount of magnetic minerals and also natural samples from various locations in New Zealand.

  2. Temporal and spectral induced polarization contribution to ore body detection and differenciation.

    NASA Astrophysics Data System (ADS)

    Schmutz, M.; Camerlynck, C.; Ghorbani, A.; Parisot, J.

    2007-12-01

    The aim of this paper is to show complementarity of temporal and spectral induced polarization, applied to ore body detection and differenciation. Study had been lead into well known geological background through borings, geochemical measurements, and also through some electrical resistivity tomographies. Temporal induced polarization (TIP) material and carry out: TIP had been carried out in a quite original way by employed device, and technique. Measurements had been done with SYSCAL PRO (Iris Instrument, Ltd.) transformed into ELREC PRO: this make it possible to differenciate transmitter device (with VIP generator manufactured by IRIS) from receiver one. The main interests are (i) to avoid internal coupling effects and between transmittor/receptor cables on soil, and (ii) to obtain higher electrical power (until 3000 watt) necessary to reach 30-40m depth. Voltage measurement is done through non-polarizable electrodes. Electrical chargeability and resistivity tomographies had been obtained by lateral device displacement. Pole-dipole device had been chosen because it is the best compromise between minimizing coupling effects, getting enough power to reach wanted depth, and necessary lateral resolution. Spectral induced polarization (SIP) material and carry out : SIP FUCHS II device (manufactured by Radic Research) had been used. As the device is not configurated into a multielectrode way, and as one sounding is very time consuming (about 7 hours), only 2 soundings had been done, located on major chargeability anomalies. First results: A a first analysis, a 3 lauer model can be observed: very resistivive level between 0 and 5m depth (up to 1000 ohm.m), more conductive between 5 and 20-25m depth (50 ohm.m), and finally an increasing resistivity. A finer analysis indicates some big conductive zone 50m wide (50 ohm.m) from surface until 30m depth. This could be exlplained by clay or ore body presence. Chargeability analysis indicate us values very high chargeabilities at resistivity anomaly zone (up to 80 mV/V), whereas everywhere else these values are less than 10mV/V. Such chargeability intensity may only be explained by ore body presence. At this stage we could think that there is only one kind of ore body (nevertheless geochemical analysis indicate 2 different types). Two SIP soundings had been done vertically to chargeability anomalies. There is no difference for resistivity values, but phase diagrams are very different (maximum phase is 3 Hz for one sounding and less than 0.1 Hz for the second). Some SIP modelling is now to be done to better characterize ore body nature. As a conclusion, the measurements of electrical resistivity, of chargeabilité and PPS are very complementary (fastness for the chargeability / strong capacity of differenciation for SIP).

  3. 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 of these electrodes were deployed at the SRS site in September of 2002. The project found that (1) currently available field instrumentation need to be faster by an order of magnitude for full SIP to be engaged for broadband characterization in the field, (2) some aspects of the capacitive coupling problem in borehole geometries can be solved by use of a high impedance receiver, (3) a careful investigation of ways to adequately compare inversion results to ground-truth data is warranted, (4) more laboratory studies should be directed to understand the influence of micro-organisms and long residence time of contaminants (aging) on spectral IP properties.

  4. Spectral induced polarization monitoring of CO2 injection in saturated sands: a laboratory experiment

    NASA Astrophysics Data System (ADS)

    Kremer, T.; Schmutz, M.; Agrinier, P.; Maineult, A. J.

    2013-12-01

    During the last decade, the interest of induced polarization methods for environmental studies has undoubtly grown. Here, we present a set of laboratory experiments aimed at assessing the ability of spectral induced polarisation (SIP) method to detect and monitor CO2 transfers in the subsurface. The objectives were the quantification of the influence of various parameters on the SIP response, such as the water conductivity, the chemical reactivity of the solid and of the gas phases, and the injection rate. SIP measurements in the frequency range 50 mHz - 20 kHz were thus performed during gas (N2 or CO2) injections in a metric-scaled, cylindrical tank filled with unconsolidated granular material (quartz or carbonate sands) and fully saturated with water. The system was most reactive to gas injection in the high frequency range (>1 kHz). In quartz sand, the presence of gas in the medium tends to decrease the measured values of the phase angle. This effect becomes more important when increasing the injection rate, and thus the amount of gas trapped in the medium. The magnitude of this effect decreases when the water conductivity increases. Dissolution processes (CO2 in water and also solid matrix in the case of carbonate sand) were evidenced from chemical measurements (pH, conductivity and anionic concentrations). The increased ionic strength resulted in a decrease of the bulk resistivity and in an increase of the phase values at high frequency. An interesting parameter is the ratio of the increase in phase to the decrease in resistivity. When dissolution processes are involved, this ratio increases strongly with the initial conductivity of the saturating fluid. Hence, in some cases the measured phase values still bring measurable information on the system evolution even if resistivity variations are very small.

  5. 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 the samples so that the users can adjust prior ranges and re-run the code. The application was tested with real data collected from two different field sites (Hanford, WA, and Rifle, CO) of the U.S. Department of Energy. This interface will be available at the poster session for testing. Users are requested to bring their datasets on a USB stick in advance with the following format: the first column of the dataset should be frequencies and the second and third columns of the dataset should be real and imaginary components of complex resistivity (or amplitude and phases) respectively.

  6. Monitoring of CO2-induced geochemical changes in a shallow aquifer by time domain spectral induced polarization

    NASA Astrophysics Data System (ADS)

    Doetsch, Joseph; Fiandaca, Gianluca; Auken, Esben; Christiansen, Anders V.; Cahill, Aaron G.; Jakobsen, Rasmus

    2014-05-01

    Contamination of potable groundwater by leaking CO2 is a potential risk of carbon sequestration. With the help of a field experiment, we investigate if surface monitoring of electrical resistivity and induced polarization can detect geochemical changes induced by CO2 in a shallow aquifer. For this purpose, we injected CO2 at a depth of 5 and 10 m and monitored its migration using 320 electrodes on a 126 m × 25 m surface grid. A fully automated acquisition system continuously collected direct current (DC) resistivity and full-decay induced polarization (IP) data and uploaded it into an online database. CO2 was injected for a period of 72 days and DC/IP monitoring started 20 days before and continued until 120 days after the beginning of the injection. The DC/IP data were supplemented by chemical analysis of water samples collected in 29 wells at time intervals of approximately 10 days. DC/IP data are inverted using a 2-D algorithm (AarhusInv) that incorporates the full voltage decay of the IP response to resolve DC resistivity, intrinsic chargeability and spectral IP content parameterized using the Cole-Cole model. Borehole information and a baseline inversion reveals the geology at the site consisting of aeolian sands near the surface, glacial sands between 5 and 10 m depth and marine sands below 10 m depth. Following the injection, we use a time-lapse inversion where differences in the DC/IP data are inverted for changes to the Cole-Cole parameters. Two different geochemical signatures that occur due to the injected CO2 are evident both in the geophysical inversions and the water samples. The first and clearest subsurface signal is a decrease in DC resistivity that moves advectively with the groundwater. The area of resistivity decrease expands with time in the direction of the groundwater flow and there is good correlation between geophysical and geochemical results. A chargeability decrease after the injection has been also observed, but in contrast to the decrease in DC resistivity, the chargeability anomaly remains localized around and slightly downstream of the injection wells throughout the experiment. This chargeability decrease correlates in space and time with a decrease in pH, which is observed in the water samples. Consequently, we attribute this change in chargeability to pH-induced changes to the grains surfaces. These results highlight the potential for monitoring of field scale geochemical changes by means of surface DC/IP measurements. Especially the different development of the DC resistivity and chargeability anomalies and the different associated geochemical processes, highlight the added value of induced polarization to resistivity monitoring.

  7. Unique Case of Highly Polarized Collision-Induced Light Scattering: The Very Far Spectral Wing by the Helium Pair

    NASA Astrophysics Data System (ADS)

    Rachet, Florent; Chrysos, Michael; Guillot-Noël, Christophe; Le Duff, Yves

    2000-03-01

    Contrary to what has been observed thus far collision-induced light scattering (CILS) can be completely polarized. This exceptional behavior characterizes the very far wing of the binary CILS spectrum by gaseous helium. This conclusion is drawn from an experimental study of the depolarization ratio of He 2 in a much extended, previously unexplored, spectral domain. Our analysis shows that this property, unique thus far, is mainly due to an almost perfect cancellation between polarization and exchange pair polarizability contributions to the depolarized spectrum, taking place at internuclear distances shorter than the atomic diameter.

  8. Application of a Spectral Induced Polarization Data Error Model for Field Scale Biogeophysical Monitoring

    NASA Astrophysics Data System (ADS)

    Flores-Orozco, A.; Williams, K. H.; Kemna, A.

    2008-12-01

    The aim of this study was to find an appropriate model for the description of measurement errors in field spectral induced polarization (SIP) data and to show that its implementation within an inversion scheme offers significant improvements in the resulting images for use in bioremediation monitoring. Accompanying a biostimulation experiment near Rifle, Colorado, SIP data collected over the 0.25 to 1000Hz frequency range were obtained along profiles oriented perpendicular to groundwater flow and located downgradient from a region of acetate amendment. Data errors were evaluated in terms of discrepancy between normal and reciprocal measurements. In agreement with previous studies, the normal-reciprocal resistance error increases linearly with resistance. For the phase error, we found an exponentially decreasing behavior with increasing resistance (i.e. with increasing signal strength). The proposed error model for the phase is given parameters, and R is the resistance measured. The implementation of the error model for the phase in a complex resistivity inversion algorithm provides images free of artifacts, exhibiting anomalies well correlated with spatiotemporal changes in geochemical conditions resulting from stimulated microbial activity. Using this approach, inversion of SIP data delineated two distinct biogeochemical processes in the subsurface. At frequencies <1Hz, anomalies exceeding 10mrad were correlated with the presence of reduced sulfur species (e.g. dissolved sulfide and FeS) accompanying stimulated sulfate reduction. At frequencies >4Hz, anomalies of 4-6mrad were correlated with elevated concentrations of dissolved iron resulting from the activity of iron reducing bacteria. Additionally, SIP data were collected using two different acquisition systems. Resistance and phase values recorded by both systems were consistent; however, the parameters obtained for the error model are not the same even when the final images obtained for resistivity and phase are very similar.

  9. The effect of organic acid on the spectral-induced polarization response of soil

    NASA Astrophysics Data System (ADS)

    Schwartz, N.; Shalem, T.; Furman, A.

    2014-04-01

    In spectral-induced polarization (SIP) studies of sites contaminated by organic hydrocarbons, it was shown that biodegradation by-products in general, and organic acids in particular, significantly alter the SIP signature of the subsurface. Still a systematic study that considers the effect of organic acid on the physicochemical and electrical (SIP) properties of the soil is missing. The goal of this work is to relate between the effect of organic acid on the physicochemical properties of the soil, and the soil electrical properties. To do so, we measured the temporal changes of the soil chemical (ion content) and electrical (low-frequency SIP) properties in response to influx of organic acid at different concentrations, gradually altering the soil pH. Our results show that organic acid reduces the soil pH, enhances mineral weathering and consequently reduces both the in-phase and quadrature conductivity. At the pH range where mineral weathering is most significant (pH 6-4.5) a negative linear relation between the soil pH and the soil formation factor was found, suggesting that mineral weathering changes the pore space geometry and hence affecting the in-phase electrical conductivity. In addition, we attribute the reduction in the quadrature conductivity to an exchange process between the natural cation adsorbed on the mineral surface and hydronium, and to changes in the width of the pore bottleneck that results from the mineral weathering. Overall, our results allow a better understanding of the SIP signature of soil undergoing acidification process in general and as biodegradation process in particular.

  10. Spectral Induced Polarization (SIP) measurements for monitoring toluene contamination in clayey soils

    NASA Astrophysics Data System (ADS)

    Ustra, A.; Slater, L. D.; Ntarlagiannis, D.

    2010-12-01

    The Spectral Induced Polarization (SIP) method has previously shown potential for detecting hydrocarbons in the subsurface when clay minerals are present. However, results from recent studies of soils containing hydrocarbon contaminants are inconclusive, and further research is needed. In an effort to better constrain the sensitivity of SIP to toluene contamination in clayey soils, samples consisting of mixtures of quartzitic sand and montmorillonite (5 and 10% by weight) were contaminated with varying amounts of toluene (5, 10 and 20% by weight) and saturated with sodium nitrate solution (0.003 mol/L). The SIP response of the various samples was monitored for a period of about 40 days. An important aspect of this experimental work was to minimize measurement errors related with the experimental set up and uncertainty in the interpretation of effects of hydrocarbon presence that will result from any variations in sample packing. Errors from the experimental setup (electrodes, sample holder and data acquisition device) varied from 0.02 mrad (at 0.01 Hz) to 9 mrad (at 1000 Hz), as determined from calibration measurements on water samples with known electrical properties. Variations associated with the packing effect (based on repeated sample packs) were from 0.1 mrad (at 0.01 Hz) to 11 mrad (at 1000 Hz). The real and imaginary conductivities at specified frequencies and the integral chargeability and time constant (obtained from a Debye decomposition fitting) were correlated to toluene and clay content. Repeated SIP measurements suggest that the toluene contaminated samples may take significant time to come into equilibrium. Low frequency SIP measurements are significantly related to toluene content only during early stages of contamination, when the dependence of SIP on clay concentration is apparently suppressed. At later time, progress towards a steady state SIP response (interpreted to indicate equilibrium surface chemistry) results in loss of a significant relation between SIP measurements and toluene content; instead the low frequency SIP measurements are then significantly correlated with clay concentration. The results show only subtle low frequency SIP signals observed in relation to toluene concentration, which initially decreases the interfacial polarization. Unlike earlier work, our results do not support the use of the SIP method as a tool for investigating toluene contamination in clay soils.

  11. 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 changes up to 3.5 mrads in the phase shift were recorded for both active columns, and for all electrode pairs. On the contrary, no change was observed in the control column for the duration of the experiment. These results may indicate that remote geophysical methods could successfully complement current MEOR monitoring schemes for promoting sustainable oil recovery.

  12. 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 clear distinction in the T2-distribution and D-T2 plots between live and dead cell pellets was also observed. These results will provide a basis for understanding the effect of microbes within geologic media on SIP and low-field NMR measurements. This research suggests that both SIP and NMR have the potential to monitor microbial growth and activities in the subsurface and could provide spatiotemporal variations in bacterial abundance in porous media.

  13. 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.

  14. 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.

  15. Markov chain Monte Carlo (McMC) estimation of spectral induced polarization (SIP) as a distribution of simple Debye relaxations

    NASA Astrophysics Data System (ADS)

    Keery, J. S.; Binley, A.; Slater, L. D.

    2010-12-01

    Proposed empirical relationships between frequency dependent complex electrical resistivity and key physical properties, such as grain or pore throat size, may allow hydraulic conductivity to be indirectly estimated from variable frequency electrical measurements, often referred to as spectral induced polarization (SIP). The SIP response may be described by several models, each providing one or more estimated values of relaxation time and chargeability, and a variety of additional parameters. Recent interest has been shown in modelling the SIP response as the coupling of a large number of simple Debye responses, each fully described by the two parameters of relaxation time and chargeability, and with no requirement for additional model parameters. This deterministic approach allows the SIP response to be matched with high accuracy, but since the mean, mode and median relaxation times of the total chargeability may differ widely, none of these statistics is sufficient to summarise the SIP response adequately. We introduce a parsimonious set of descriptors which efficiently summarises the distribution of Debye relaxations, with minimal loss of the information content in the electrical measurements. Our method applies a Markov chain Monte Carlo algorithm to provide a Bayesian estimation of the relaxation distribution parameters, and does not require an accurate prior estimation of DC resistivity. The distribution parameters may be combined with electrical-physical relationships identified in other studies, to give stochastic estimates of hydraulic conductivity. We apply our approach to electrical spectra measured in the laboratory and in field surveys, and we compare our results with those from deterministic methods.

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

    E-print Network

    Hubbard, Susan

    geophysical methods is iron sulfide (FeS) biomineralization induced by sulfate reducing bacteria [Williams et al., 2005; Ntarlagiannis et al., 2005]. The potential hence exists to monitor sulfide mineral formation processes in marine environments and wetlands, remediation of mine wastes using wetlands

  17. Influence of Surface Sorption Processes on Spectral Induced Polarization Evaluated Using in-Situ Monitoring of a Na-22 Tracer

    NASA Astrophysics Data System (ADS)

    Hao, N.; Moysey, S. M.; Powell, B. A.; Ntarlagiannis, D.

    2014-12-01

    Spectral Induced Polarization (SIP) has been used to monitor subsurface biogeochemical processes in a variety of lab and field studies. However, there are several competing mechanisms that have been proposed to explain the SIP effect. This work targets the influence of ion sorption to mineral surfaces as a controlling factor on SIP utilizing a pH dependent surface adsorption experiment. In this experiment we use silica gel as an idealized medium where the number of available sites for cation sorption, which in this case is limited to Na+ and H+ ions, is influenced by changes in pH via protonation/deprotonation of silanol groups. The experiment uses 22Na as an in situ tracer as the radioactive decay of this nuclide can be continuously and non-invasively monitored using sensors placed outside of a column. The experiment was conducted by continuously pumping a 0.01M NaCl solution spiked with of 1?Ci/L 22Na in to the column under three pH conditions (pH 5.0, 6.0 and 8.0). In the experiment, we observed an increasing number of gamma counts caused by the accumulation of sorbed 22Na in the column as we increased the pH from 5.0 to 6.5, and finally to 8.0. Simultaneously, we observed a linearly correlated (R2 = 0.99) rise in the imaginary conductivity response of the SIP measurements. Using the triple layer electrochemical polarization model for grain polarization to simulate our experimental SIP responses, we found that the estimated surface site density is within a factor of two of that estimated from the mass accumulation of sodium. Since the accumulation of sodium on the silica gel surface is responsible for both the increase in gamma radiation and the change in the electrical response, these observations support the theory that mobile ions in the Stern layer of mineral surfaces provide the primary control on SIP signals in silicate materials.

  18. The effect of pH and redox active ions on the spectral induced polarization signatures of magnetite

    NASA Astrophysics Data System (ADS)

    Hubbard, C. G.; West, L. J.; Rodriguez-Blanco, J. D.; Ntarlagiannis, D.; Slater, L. D.; Shaw, S.

    2011-12-01

    Spectral induced polarization (SIP) is a promising technique for monitoring biogeochemically induced changes in porous subsurface media, such as biomineral formation during the remediation of contaminated sites. A primary mechanism responsible for low-frequency SIP signatures is the frequency-dependent polarization of the electrical double layer (EDL) at the mineral-water interface. pH exerts a fundamental control on mineral-water interface properties, controlling the nature and number of charged surface functional groups. This in turn controls the surface complexation of ions sorbed to the mineral surface and, together with ionic strength, the thickness of the EDL and the distribution of ions in the diffuse and Stern layers of the EDL. Despite this, there are relatively few datasets on the effect of pH on SIP signatures. For electrically conductive minerals, such as magnetite, it has been further postulated that redox-active ions, such as Fe2+, enable charge-transfer from electrolytic to electronic conduction mechanisms. This process is often represented as a charge-transfer resistance and Warburg impedance and is thought to be an additional contribution to the SIP response. Here we report initial experimental results investigating the effect of pH and redox active ions on the SIP signature of magnetite grains (5 wt%) dispersed in Ottawa sand. Increasing the pH of a 2.5 mM FeCl2 solution from pH 4.5 to 8.0 made little difference to the resistivity or maximum phase angle magnitude of the magnetite-sand mixture but decreased the peak frequency from ~50 Hz to ~1 Hz. This has important implications for interpreting SIP data at contaminated sites where pH can vary across groundwater plumes and during/following remediation processes. We postulate that the shift in peak frequency reflects changes in the structure of the EDL as pH increases; this pH range overlaps with the published positions of both the point of zero charge (pzc) and the sorption edge of Fe2+ onto Fe-(oxyhydr)oxides. Ongoing experiments are being conducted to compare and contrast the observed pH dependent behaviour of Fe2+ with redox inactive ions and thereby help determine the importance of the charge-transfer mechanism for magnetite.

  19. 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 invert the time-lapse SIP data for chargeability and time constant using Cole-Cole models. By combining the limited borehole time series data with spatially distributed time-lapse geophysical data, we can obtain the spatial and temporal distribution of the bioremediation end-products (such as volume fraction of FeS and calcite) and their associated uncertainty information. Our study results show how time-lapse SIP datasets, when incorporated into a Bayesian hierarchical model, can be useful for quantifying the spatiotemporal distribution of remediation-induced end-products. The study also documents how the diagnostic geophysical signatures can be useful for identifying when and where critical, remediation-induced system transitions occur, such as those accompanying a rebound in aquifer redox status and the associated impact on immobilized contaminant stability.

  20. 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.

  1. 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.

  2. 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.

  3. 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. We measured a variation of less than 1 mS/m of the electrolyte conductivity during the time of measurement (~1h40) for a conductivity range 25-100 mS/m, showing no ionic contamination of the solution by the electrodes. An improvement to the cell design would be to control the internal temperature of the sample.

  4. Photonic Circuits for Generating Modal, Spectral, and Polarization Entanglement

    E-print Network

    Teich, Malvin C.

    Photonic Circuits for Generating Modal, Spectral, and Polarization Entanglement Volume 2, Number 5 Circuits for Generating Modal, Spectral, and Polarization Entanglement Mohammed F. Saleh,1 Giovanni Di@creol.ucf.edu). Abstract: We consider the design of photonic circuits that make use of Ti:LiNbO3 diffused channel

  5. Compressive spectral polarization imaging by a pixelized polarizer and colored patterned detector.

    PubMed

    Fu, Chen; Arguello, Henry; Sadler, Brian M; Arce, Gonzalo R

    2015-11-01

    A compressive spectral and polarization imager based on a pixelized polarizer and colored patterned detector is presented. The proposed imager captures several dispersed compressive projections with spectral and polarization coding. Stokes parameter images at several wavelengths are reconstructed directly from 2D projections. Employing a pixelized polarizer and colored patterned detector enables compressive sensing over spatial, spectral, and polarization domains, reducing the total number of measurements. Compressive sensing codes are specially designed to enhance the peak signal-to-noise ratio in the reconstructed images. Experiments validate the architecture and reconstruction algorithms. PMID:26560932

  6. 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.

  7. 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.

  8. Formation of polarized spectral lines in atmospheres with horizontal inhomogeneities

    NASA Astrophysics Data System (ADS)

    Tichý, A.; Št?pán, J.; Bueno, J. Trujillo; Kubát, J.

    2015-10-01

    We study the problem of the generation and transfer of spectral line intensity and polarization in models of stellar atmospheres with horizontal plasma inhomogeneities. We solve the non-LTE radiative transfer problem in full 3D geometry taking into account resonant scattering polarization and its modification by magnetic fields via the Hanle effect. We show that horizontal fluctuations of the thermodynamical conditions of stellar atmospheres can have a significant impact on the linear polarization of the emergent spectral line radiation and its center-to-limb variation.

  9. Comment on: Tarasov, A. & Titov, K., 2013, On the use of the Cole-Cole equations in spectral induced polarization, Geophys. J. Int., 195, 352-356

    NASA Astrophysics Data System (ADS)

    Macnae, James

    2015-07-01

    A recent paper by Tarasov and Titov suggested that the Cole-Cole conductivity models should be preferred to the Pelton resistivity model in fitting induced polarization responses. Each model has four parameters: resistivity ? (or its inverse conductivity ?), chargeability m, time parameter ? and frequency dependence c. Tarasov and Titov showed that in fitting experimental data, 3 of the parameters directly correspond across the two formulations, but that there is a difference between the Pelton and Cole-Cole model in that parameter ? is only the same at low frequency, but is an entangled function with m and c at high frequencies in the Pelton formulation. This claim of inconsistent ? was based on using the Pelton complex resistivity formulation and the Cole-Cole complex conductivity equation to analyse complex conductivity data as a function of frequency. However, if Pelton and Cole-Cole models are used to fit complex resistivity, rather than fitting conductivity, then it is the Cole-Cole model that has an entangled parameter at high chargeability m values. Simple testing shows that a Pelton model used to fit resistivity has all four model parameters directly corresponding with conductivity data fitted with a Cole-Cole model. The conclusion is that Cole-Cole and Pelton models in fact require identical independent parameters that can fit experimental or synthetic data, provided the Pelton resistivity formulation is restricted to fitting to resistivity data, and the Cole-Cole conductivity formulation is restricted to fitting conductivity results.

  10. 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 ? = 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.

  11. Study on backscattering spectral polarization characteristics of turbid medium

    NASA Astrophysics Data System (ADS)

    Wang, Xuezhen; Wang, Qinghua; Lai, Jiancheng; Li, Zhenhua

    2015-10-01

    Noninvasive monitoring of blood glucose is the current international academic research focus. Near-infrared (NIR) spectroscopy is the most prospective method of the present study, however, with the flaw of insufficient specificity to glucose. Tissue polarimetry has recently received considerable attention due to its specificity to glucose. Thus the glucose predicting accuracy would be improved by combining spectral intensity and polarization characteristics. However the backscattering spectral polarization characteristics of turbid media have not been reported within the wavelength range from visible to near-infrared light. In this paper, we simulated the backscattering spectral Mueller matrix of turbid medium by vector Monte Carlo. And the polarization characteristics, which are linear/circular degree of polarization (DOP) and linear/circular diattenuation, can be extracted from the simulated Mueller matrix by polar decomposition. Circular diattenuation is not discussed because it remains almost zero on the backscattering plane. While reduced scattering coefficient increases linearly with increasing wavelength, the spectral curves show distinct wavelength dependencies. Interestingly, the wavelength dependencies at center position are different from those at off-center position for linear/circular DOP and linear diattenuation. As expected, it is shown that both linear DOP and linear diattenuation increase with the increasing wavelength. However it is not the case for linear DOP in the central area around the incident point. In this area linear DOP decays approximately exponentially with increasing wavelength. As for circular DOP, it varies with wavelength non-monotonically. These results should be meaningful when spectral polarization characteristics are used to combine with spectral intensity to extract glucose concentration by chemometrics.

  12. Deep subsurface imaging in tissues using spectral and polarization filtering.

    PubMed

    Demos, S; Radousky, H; Alfano, R

    2000-07-01

    Deep subsurface imaging in tissues is demonstrated by employing both spectral and polarization discrimination of the backscattered photons. This technique provides enhancement in the visibility of subsurface structures via processing of the depolarized images obtained using polarized illumination at different wavelengths. The experimental results demonstrate detection and imaging of a high-scattering object located up to 1.5-cm beneath the surface of a host chicken tissue used as the model medium. PMID:19404365

  13. 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.

  14. Time domain para hydrogen induced polarization.

    PubMed

    Ratajczyk, Tomasz; Gutmann, Torsten; Dillenberger, Sonja; Abdulhussaein, Safaa; Frydel, Jaroslaw; Breitzke, Hergen; Bommerich, Ute; Trantzschel, Thomas; Bernarding, Johannes; Magusin, Pieter C M M; Buntkowsky, Gerd

    2012-01-01

    Para hydrogen induced polarization (PHIP) is a powerful hyperpolarization technique, which increases the NMR sensitivity by several orders of magnitude. However the hyperpolarized signal is created as an anti-phase signal, which necessitates high magnetic field homogeneity and spectral resolution in the conventional PHIP schemes. This hampers the application of PHIP enhancement in many fields, as for example in food science, materials science or MRI, where low B(0)-fields or low B(0)-homogeneity do decrease spectral resolution, leading to potential extinction if in-phase and anti-phase hyperpolarization signals cannot be resolved. Herein, we demonstrate that the echo sequence (45°-?-180°-?) enables the acquisition of low resolution PHIP enhanced liquid state NMR signals of phenylpropiolic acid derivatives and phenylacetylene at a low cost low-resolution 0.54 T spectrometer. As low field TD-spectrometers are commonly used in industry or biomedicine for the relaxometry of oil-water mixtures, food, nano-particles, or other systems, we compare two variants of para-hydrogen induced polarization with data-evaluation in the time domain (TD-PHIP). In both TD-ALTADENA and the TD-PASADENA strong spin echoes could be detected under conditions when usually no anti-phase signals can be measured due to the lack of resolution. The results suggest that the time-domain detection of PHIP-enhanced signals opens up new application areas for low-field PHIP-hyperpolarization, such as non-invasive compound detection or new contrast agents and biomarkers in low-field Magnetic Resonance Imaging (MRI). Finally, solid-state NMR calculations are presented, which show that the solid echo (90y-?-90x-?) version of the TD-ALTADENA experiment is able to convert up to 10% of the PHIP signal into visible magnetization. PMID:22365288

  15. Programmable polarization-independent spectral phase compensation and pulse shaping

    E-print Network

    Purdue University

    Programmable polarization-independent spectral phase compensation and pulse shaping R. D. Nelson, D optics communications; (320.5540) Pulse shaping; (070.2580) Fourier optics References and Links 1. A.M. Weiner, "Femtosecond Pulse Shaping Using Spatial Light Modulators," Rev. Sci. Instr. 71, 1929- 1960 (2000

  16. 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."

  17. 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.

  18. THE JOURNAL OF CHEMICAL PHYSICS 142, 184505 (2015) Observation and theory of reorientation-induced spectral diffusion

    E-print Network

    Fayer, Michael D.

    2015-01-01

    in the XXXX configuration. Polarization-selective 2D IR spectra of bulk water do not exhibit polarization-induced spectral diffusion in polarization-selective 2D IR spectroscopy Patrick L. Kramer,a) Jun Nishida,a) Chiara function (FFCF) observable under various polarization conditions is introduced, and model calculations

  19. 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.

  20. 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.

  1. 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 ?-rays can lead to about 15% polarization at viewing angles around ?/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.

  2. 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.

  3. 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.

  4. Photonic circuits for generating modal, spectral, and polarization entanglement

    E-print Network

    Mohammed F. Saleh; Giovanni Di Giuseppe; Bahaa E. A. Saleh; Malvin Carl Teich

    2010-09-22

    We consider the design of photonic circuits that make use of Ti:LiNbO$_{3}$ diffused channel waveguides for generating photons with various combinations of modal, spectral, and polarization entanglement. Down-converted photon pairs are generated via spontaneous optical parametric down-conversion (SPDC) in a two-mode waveguide. We study a class of photonic circuits comprising: 1) a nonlinear periodically poled two-mode waveguide structure, 2) a set of single-mode and two-mode waveguide-based couplers arranged in such a way that they suitably separate the three photons comprising the SPDC process, and, for some applications, 3) a holographic Bragg grating that acts as a dichroic reflector. The first circuit produces frequency-degenerate down-converted photons, each with even spatial parity, in two separate single-mode waveguides. Changing the parameters of the elements allows this same circuit to produce two nondegenerate down-converted photons that are entangled in frequency or simultaneously entangled in frequency and polarization. The second photonic circuit is designed to produce modal entanglement by distinguishing the photons on the basis of their frequencies. A modified version of this circuit can be used to generate photons that are doubly entangled in mode number and polarization. The third photonic circuit is designed to manage dispersion by converting modal, spectral, and polarization entanglement into path entanglement.

  5. Resonance-induced spectral tuning

    SciTech Connect

    Yang Shuangbo; Kellman, Michael E.

    2010-06-15

    A diabatic correlation diagram technique is extended to assign effective quantum numbers and classify sequences for extremely high excitations in a coupled two-mode model of an isomerizing system, with multiple wells separated by a potential barrier. At low values of the stretch quantum number n{sub s}, level spacings for sequences of bend excitations n{sub b}=0,... show a pattern of a smooth dip at the barrier, characteristic of the zero-order uncoupled system. In higher sequences n{sub s}=3-5, the spectral pattern is modified with the onset of a prominent nonlinear resonance. The level spacing 'tunes' to a flattened pattern similar to a harmonic oscillator, and the smooth dip at the barrier becomes almost vertical. This behavior is explained by the influence of periodic orbits of the resonance on the quantum spectrum and wave functions. In the n{sub s}=6 sequence the tuning reverts to a pattern more similar to zero order.

  6. 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 (?) 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%.

  7. A Fourier-Legendre spectral element method in polar coordinates

    NASA Astrophysics Data System (ADS)

    Qiu, Zhouhua; Zeng, Zhong; Mei, Huan; Li, Liang; Yao, Liping; Zhang, Liangqi

    2012-01-01

    In this paper, a new Fourier-Legendre spectral element method based on the Galerkin formulation is proposed to solve the Poisson-type equations in polar coordinates. The 1/ r singularity at r = 0 is avoided by using Gauss-Radau type quadrature points. In order to break the time-step restriction in the time-dependent problems, the clustering of collocation points near the pole is prevented through the technique of domain decomposition in the radial direction. A number of Poisson-type equations subject to the Dirichlet or Neumann boundary condition are computed and compared with the results in literature, which reveals a desirable result.

  8. Enhancement of spectral resolution and optical rejection ratio of Brillouin optical spectral analysis using polarization pulling.

    PubMed

    Preussler, Stefan; Zadok, Avi; Wiatrek, Andrzej; Tur, Moshe; Schneider, Thomas

    2012-06-18

    High-resolution, wide-bandwidth optical spectrum analysis is essential to the measuring and monitoring of advanced optical, millimeter-wave, and terahertz communication systems, sensing applications and device characterization. One category of high-resolution spectrum analyzers reconstructs the power spectral density of a signal under test by scanning a Brillouin gain line across its spectral extent. In this work, we enhance both the resolution and the optical rejection ratio of such Brillouin-based spectrometers using a combination of two techniques. First, two Brillouin loss lines are superimposed upon a central Brillouin gain to reduce its bandwidth. Second, the vector attributes of stimulated Brillouin scattering amplification in standard, weakly birefringent fibers are used to change the signal state of polarization, and a judiciously aligned output polarizer discriminates between amplified and un-amplified spectral contents. A frequency resolution of 3 MHz, or eight orders of magnitude below the central optical frequency, is experimentally demonstrated. In addition, a weak spectral component is resolved in the presence of a strong adjacent signal, which is 30 dB stronger and detuned by only 60 MHz. The measurement method involves low-bandwidth direct detection, and does not require heterodyne beating. The measurement range of the proposed method is scalable to cover the C + L bands, depending on the tunable pump source. The accuracy of the measurements requires that the pump frequencies are well calibrated. PMID:22714534

  9. Radiative interactions with micromachined surfaces: Spectral polarized emittance

    SciTech Connect

    Zemel, J.N.

    1991-01-01

    The spectral, angular, polarized emittance (SAPE) is a simple means for observing the allowed electromagnetic energy states associated with periodic structures whose dimensions are comparable to the wavelength of the observed light. Other methods for measuring absorption are far more time consuming when a broad survey is of interest. An extensive body of SAPE data was obtained on 350-- 400{degrees}C intrinsic silicon lamellar gratings. Current approximations to the vector wave equation such as guided wave, modal and Bloch wave methods provided insight into our experiments. A qualitative picture of the stationary electromagnetic states (SES) of lamellar gratings has been developed which agrees with experiment for a number of polarizations, and angular orientations of the emission k vector relative to the gratings. However, one type of emission does not fit any simple model we have examined and raises intriguing questions about emission from grating structures. A new, higher angular resolution emissometer (0.8{degrees} instead of 5{degrees}) has been completed. This system significantly increases the wavelength range from the current 3--14 {mu}m range to 2-25{mu}m, a doubling of the spectral regime. The system is currently in a shakedown'' mode. Preliminary data indicates that the new emissometer meets the design goals. 24 refs., 10 figs.

  10. Spectral properties of BADAN in solutions with different polarities

    NASA Astrophysics Data System (ADS)

    Fonin, A. V.; Kuznetsova, I. M.; Turoverov, K. K.

    2015-06-01

    Spectral characteristics (absorption spectra, excitation and emission spectra of solvatochromic dye 6-bromo-acetyl-2-dimethylamino-naphtalene (BADAN) were studied in solvents with different polarities. Comparison of BADAN fluorescence excitation spectra corrected for the primary inner filter effect and absorption spectra of this dye allowed to conclude that the long-wavelength absorption band of BADAN is determined by the superposition of two BADAN tautomeric forms having different conformation (planar and non-planar) and different distribution of electronic density. The analysis of BADAN excitation and emission spectra has shown that in non-polar solvents (hexane) fluoresces only one dye form which absorbs in more short-wave part of the spectrum than other conformer. In polar solvents (acetonitrile, mixture of acetonitrile/water) both forms fluoresce. It is concluded that the fluorescence of the dye in hexane and short-wavelength component of BADAN fluorescence at excitation in short-wavelength region of absorption spectrum are due to the locally excited state of the planar BADAN molecule. Fluorescence of BADAN in acetonitrile at excitation in long-wavelength part of long-wavelength absorption band and long-wavelength component of BADAN fluorescence spectrum in acetonitrile at excitation in short-wavelength region of absorption spectrum are due to non-planar BADAN conformers with internal charge transfer state.

  11. [Design of full-polarized and multi-spectral imaging system based on LCVR].

    PubMed

    Zhang, Ying; Zhao, Hui-jie; Cheng, Xuan; Xiong, Sheng-jun

    2011-05-01

    A new full-polarized multi-spectral imaging system is described, which uses electronically controlled LCVR (liquid crystal variable retarder) to modulate the full-polarized state of light in the visible to IR range. The system consisted of optical lenses, LCVRs, filters and CCD. Firstly, the system structure, working theory and optical design are introduced in the present paper. A polarization calibration method is provided and the calibration system was set up, which realized high-precision polarization calibration using a small polarized source. Then, a field experiment with the imaging system was carried out. Polarized spectral images with higher spectral and spatial resolution were collected. Finally, the data acquired were rough processed to get polarization degree image of the targets. It is concluded that the experiment has proved that the imaging system is effective in obtaining full-polarized and multi- spectral data. The image captured by the system can be applied to object identification and object classification. PMID:21800604

  12. 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.

  13. 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.

  14. Induced polarization of ?(1116) in kaon electroproduction

    E-print Network

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

    2014-06-16

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

  15. Induced Polarization methodology: application to a hydrocarbon contaminated site

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  16. SDP_mharwit_1: Demonstration of HIFI Linear Polarization Analysis of Spectral Features

    NASA Astrophysics Data System (ADS)

    Harwit, M.

    2010-03-01

    We propose to observe the polarization of the 621 GHz water vapor maser in VY Canis Majoris to demonstrate the capability of HIFI to make polarization observations of Far-Infrared/Submillimeter spectral lines. The proposed Demonstration Phase would: - Show that HIFI is capable of interesting linear polarization measurements of spectral lines; - Test out the highest spectral resolving power to sort out closely spaced Doppler components; - Determine whether the relative intensities predicted by Neufeld and Melnick are correct; - Record the degree and direction of linear polarization for the closely-Doppler shifted peaks.

  17. 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.

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

    E-print Network

    Shaw, Joseph A.

    Degree of linear polarization in spectral radiances from water-viewing infrared radiometers Joseph A. Shaw Infrared radiances from water become partially polarized at oblique viewing angles through of polarization for a water surface viewed at nadir angles of 0­75°. OCIS codes: 010.4450, 010.7340, 260.5430, 260

  19. Almost fully polarized collision-induced light scattering in helium

    NASA Astrophysics Data System (ADS)

    Chrysos, M.; Rachet, F.; Guillot-Noël, C.; Le Duff, Y.

    2001-04-01

    For the first time in collision-induced light scattering (CILS), a CCD camera has been implemented for the detection of the He2 far spectral wing. We have thus been able to detect signals as low as one photoelectron per pixel and per week, i.e. signals weaker than the electronic noise of our detection device. With our recorded experimental spectra, depolarized and isotropic ones, the frequency domain probed by the thus far available in the literature experimental spectra has greatly been extended up to ?=680 cm-1 and 1200 cm-1 respectively. The depolarization ratio has been found to attain values as low as 0.03 in the helium far wing, that is the signature of an almost fully polarized spectrum. This is a finding thus far unique in CILS by inert gases. Comparison with quantum mechanical computations (where use of up-to-date ab initio incremental polarizabilities has been made) has clearly shown that the origin of this striking property is an almost perfect, probably accidental, destructive interference between polarization and exchange spectral components in the depolarized intensities. In addition, what has been found is that the interference takes place in a very small interval of interatomic distances that are shorter than the diameter of the helium atom.

  20. 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.

  1. 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.

  2. 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 lower than both the rotational and the free-fall velocities for the corresponding range of radii. A combined net emission He II plus H{beta} low-velocity eclipse map reveals a twisted dipole emitting pattern near disk center. This is interpreted as being the projection of accretion curtains onto the orbital plane at two specific spin phases, as a consequence of the selection in velocity provided by the spectral eclipse mapping.

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

    E-print Network

    Greiner, Jochen

    High spectral and time resolution observations of the eclipsing polar RX J0719.2+6557 G. H Abstract. We present phase­resolved spectral and multicolor CCD­ photometric observations of the eclipsing. The light curves and eclipse profiles provide additional information about the system geometry. 1

  4. EFFICIENT SPECTRAL-GALERKIN METHODS III: POLAR AND ...

    E-print Network

    1999-10-21

    methods for second- and fourth-order equations in polar and cylindrical geometries. ... part [15], we presented efficient algorithms for solving elliptic equations in ... them to rectangular domains by using polar or cylindrical coordinates. ...... Chebyshev–Legendre–Galerkin method for the three-

  5. 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.

  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. The laboratory methods of induced polarization measurement of manganese sample

    NASA Astrophysics Data System (ADS)

    Adhiguna, D.; Handayani, G.

    2015-09-01

    Metallic minerals are polarizable. The polarizable property can be used as the basis for metallic minerals exploration process. By use of induced polarization method, we observed polarization phenomenon that occur in metallic material. In this study, physical events were observed that occur in rocks containing manganese minerals using induced polarization method. Induced polarization method is a geophysical method that is based on the principle of electrical charging and discharging of a capacitor which is applied to the rock. By using the method of induced polarization, chargeability values can be determined for the rock. Chargeability is one of the important properties of metal material. Measurement on this research will be done in two different ways to determine the induced events that occurred in both methods.

  8. THE IMPACT OF THE SPECTRAL RESPONSE OF AN ACHROMATIC HALF-WAVE PLATE ON THE MEASUREMENT OF THE COSMIC MICROWAVE BACKGROUND POLARIZATION

    SciTech Connect

    Bao, C.; Gold, B.; Hanany, S.; Baccigalupi, C.; Leach, S.; Didier, J.; Johnson, B. R.; Miller, A.; Jaffe, A.; O'Dea, D.; Matsumura, T.

    2012-03-10

    We study the impact of the spectral dependence of the linear polarization rotation induced by an achromatic half-wave plate on measurements of cosmic microwave background polarization in the presence of astrophysical foregrounds. We focus on the systematic effects induced on the measurement of inflationary gravitational waves by uncertainties in the polarization and spectral index of Galactic dust. We find that for the experimental configuration and noise levels of the balloon-borne EBEX experiment, which has three frequency bands centered at 150, 250, and 410 GHz, a crude dust subtraction process mitigates systematic effects to below detectable levels for 10% polarized dust and tensor-to-scalar ratio of as low as r = 0.01. We also study the impact of uncertainties in the spectral response of the instrument. With a top-hat model of the spectral response for each band, characterized by band center and bandwidth, and with the same crude dust subtraction process, we find that these parameters need to be determined to within 1 and 0.8 GHz at 150 GHz; 9 and 2.0 GHz at 250 GHz; and 20 and 14 GHz at 410 GHz, respectively. The approach presented in this paper is applicable to other optical elements that exhibit polarization rotation as a function of frequency.

  9. Spectral response of polarization properties of fiber Bragg grating under local pressure

    NASA Astrophysics Data System (ADS)

    Su, Yang; Zhu, Yong; Zhang, Baofu; Zhou, Hua; Li, Jianhua; Wang, Feng

    2015-10-01

    A study of the spectral characterization of polarization properties of locally pressed fiber Bragg grating (FBG) is presented. The evolutions of the first Stokes (s1) parameter of a FBG as function of the incident angle, the load magnitude, the loaded position and the loaded length of the grating are investigated. The numerical simulation based on the modified transfer matrix method is used to calculate the s1 response and the state of polarization (SOP) of the FBG. The theoretical analysis and numerical simulation demonstrate that the evolutions of polarization dependent parameters contain the information about the transverse load and have potential applications for distributed diametric load sensor.

  10. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D. (Los Alamos, NM)

    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.

  11. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D. (Los Alamos, NM)

    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.

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

    E-print Network

    Analysis of the spectral and angular response of the vegetated surface polarization for the purpose sensing from space in the solar spectrum remains in separating the aerosol contribution from that of the surface [4]. Over ocean, the surface is dark enough in the shortwave spectrum to not mask the atmospheric

  13. Spectral Study of Polarity Reversals in the Geomagnetic Field

    NASA Astrophysics Data System (ADS)

    Valbuena, C.; Gomez Perez, N.

    2013-05-01

    Self-consistent models of the dynamo process in the Earth's core have reached a state where they can be used to understand specific morphological and temporal properties of the geomagnetic field. In this work we study numerical dynamos in terms of the multipole components before, during and after polarity reversals. The numerical algorithm (MagIC 3.47) uses the Boussinesq approximation and was originally developed by G. Glatzmaier and most recently optimized by J. Wicht. Paleomagnetic studies provide limited information on the duration, intensity, geometry and orientation of the field during reversals and excursions. We will show how the magnitude of multipole components evolves in time. We will present how multipolar term magnitudes are correlated with the occurrence of geomagnetic reversals and excursions.

  14. 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.

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

    PubMed Central

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

    2010-01-01

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

  16. Spectral regularisation: induced gravity and the onset of inflation

    SciTech Connect

    Kurkov, Max A.; Sakellariadou, Mairi E-mail: mairi.sakellariadou@kcl.ac.uk

    2014-01-01

    Using spectral regularisation, we compute the Weyl anomaly and express the anomaly generating functional of the quantum effective action through a collective scalar degree of freedom of all quantum vacuum fluctuations. Such a formulation allows us to describe induced gravity on an equal footing with the anomaly-induced effective action, in a self-consistent way. We then show that requiring stability of the cosmological constant under loop quantum corrections, Sakharov's induced gravity and Starobinsky's anomaly-induced inflation are either both present or both absent, depending on the particle content of the theory.

  17. 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

  18. Ferroelectric domain wall motion induced by polarized light

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

  19. 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.

  20. 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.

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

    PubMed

    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, ? , is around 5 in lipid droplets and 25spectrally 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. PMID:26334975

  2. 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.

  3. 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).

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  5. 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.

  6. Local circular polarizations in nanostructures induced by linear polarization via optical near-fields

    E-print Network

    Naruse, Makoto; Inoue, Tetsuya; Yasuda, Hideki; Hori, Hirokazu; Naya, Masayuki

    2015-01-01

    We previously reported [Naruse, et al. Sci. Rep. 4, 6077, 2014] that the geometrical randomness of disk-shaped silver nanoparticles, which exhibit high reflection at near-infrared wavelengths, serves as the origin of a particle-dependent localization and hierarchical distribution of optical near-fields in the vicinity of the nanostructure. In this study, we show that the induced polarizations are circular, particularly at resonant wavelengths. We formulate optical near-field processes between nanostructures, accounting for their polarizations and geometries, and attribute circular polarization to the layout-dependent phase difference between the electrical susceptibilities associated with longitudinal and transverse-electric components. This study clarifies the fundamental optical properties of random nanostructured matter and offers generic theoretical concepts for implementing nanoscale polarizations of optical near-fields.

  7. Semiconducting and Piezoelectric Oxide Nanostructures Induced by Polar Surfaces**

    E-print Network

    Wang, Zhong L.

    . This article reviews our recent progress in the synthesis and characterization of polar-surface-induced ZnO transport along the nanobelt has been mea- sured.[14] Zinc oxide (ZnO) is the most typical and successful sensors and trans- ducers. Finally, ZnO is bio-safe and biocompatible, and it can be directly used

  8. 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.

  9. 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...

  10. Spectral features of electromagnetically induced absorption in 85Rb atoms

    NASA Astrophysics Data System (ADS)

    Rehman, Hafeez-ur; Adnan, Muhammad; Noh, Heung-Ryoul; Kim, Jin-Tae

    2015-06-01

    We present theoretical and experimental studies of electromagnetically induced absorption (EIA) for the {{F}g}=3\\to {{F}e}=4 transition of 85Rb-D2 line. From the results calculated by solving time-dependent density-matrix equations including the optical and Zeeman coherences connected via three-photon interactions, the EIA signals have ultra-narrow feature in low powers of coupling beam in both same- and orthogonal-polarization configurations for both stationary and thermal atoms. However, the ultra-narrow EIA signals from high powers of coupling laser beam still remained in the ultra-narrow state only in the same-polarization configuration for thermal atoms. The calculated results match well with experimental results except ultra-narrow EIA region considering linewidths of two separate coupling and probe lasers.

  11. A Spectral Analysis of Laser Induced Fluorescence of Iodine

    E-print Network

    Bayram, S B

    2015-01-01

    When optically excited, iodine absorbs in the 490- to 650-nm visible region of the spectrum and, after radiative relaxation, it displays an emission spectrum of discrete vibrational bands at moderate resolution. This makes laser-induced fuorescence spectrum of molecular iodine especially suitable to study the energy structure of homonuclear diatomic molecules at room temperature. In this spirit, we present a rather straightforward and inexpensive experimental setup and the associated spectral analysis which provides an excellent exercise of applied quantum mechanics fit for advanced laboratory courses. The students would be required to assign spectral lines, fill a Deslandres table, process the data to estimate the harmonic and anharmonic characteristics of the ground vibronic state involved in the radiative transitions, and thenceforth calculate a set of molecular constants and discuss a model of molecular vibrator.

  12. Induced polarization of Lambda(1116) in kaon electroproduction

    SciTech Connect

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

    2014-09-01

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

  13. 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

  14. Temporal and spectral studies of high-order harmonics generated by polarization-modulated infrared fields

    SciTech Connect

    Sola, I. J.; Zaier, A.; Cormier, E.; Mevel, E.; Constant, E.; Lopez-Martens, R.; Johnsson, P.; Varju, K.; Mauritsson, J.; L'Huillier, A.; Strelkov, V.

    2006-07-15

    The temporal confinement of high harmonic generation (HHG) via modulation of the polarization of the fundamental pulse is studied in both temporal and spectral domains. In the temporal domain, a collinear cross-correlation setup using a 40 fs IR pump for the HHG and a 9 fs IR pulse to probe the generated emission is used to measure the XUV pulse duration. The observed temporal confinement is found to be consistent with theoretical predictions. An increased confinement is observed when a 9 fs pulse is used to generate the harmonics. An important spectral broadening, including a continuum background, is also measured. Theoretical calculations show that with 10 fs driving pulses, either one or two main attosecond pulses are created depending on the value of the carrier envelope phase.

  15. Possible creation of net circular polarization and not only depolarization of spectral lines by isotropic collisions

    E-print Network

    Jiri Stepan; Sylvie Sahal-Brechot

    2008-11-27

    We will show that isotropic collisions of electrons and protons with neutral hydrogen can lead to creation of net orientation of the atomic levels in the presence of a magnetic field. Consequently, the emitted Stokes-V profile of the spectral lines can be almost symmetric in contrast to the typical antisymmetric signature of the Zeeman effect. Moreover, the amplitude of the symmetric lobe can be significantly higher than the amplitude of the antisymmetric components. This mechanism is caused by a $\\pm{M}$ symmetry breaking of the collisional transitions between different Zeeman sublevels. We will show an example of our first results for the H$\\alpha$ line. This new mechanism could perhaps explain the net circular polarization of spectral lines observed in some solar limb observations and which are currently not understood. However, our results are very preliminary and more developments are needed for going further on.

  16. Influence of temporal-spectral effects on ultrafast fiber coherent polarization beam combining system

    NASA Astrophysics Data System (ADS)

    Yu, H. L.; Ma, P. F.; Wang, X. L.; Su, R. T.; Zhou, P.; Chen, J. B.

    2015-10-01

    The active coherent polarization beam combining (CPBC) technique has been experimentally proved to be a promising approach for the energy and power scaling of ultrashort laser pulses, despite the tremendous challenge in temporal synchronization, dispersion management and nonlinearity control. In order to develop a comprehensive theoretical model to investigate the influence of temporal-spectral effects on ultrafast fiber active CPBC systems, a generalized nonlinear Schrödinger equation carrying spectral factors is used to depict the propagation of ultrashort pulses in fiber amplifier channels and ultrashort-pulsed Gaussian beams (PGBs) carrying temporal-spatial factors are utilized to picture the propagation of ultrashort pulses in the free space. To the best of our knowledge, the influence of different temporal-spectral effects has been segregated for the first time and corresponding analytical equations have been strictly derived to link the combining efficiency with specific factors. Based on our analysis, the optical path difference (OPD) has the most detrimental impact on the combining efficiency because of the high controlling accuracy and anti-interference requirements. For instance, the OPD must be controlled in ~??±14 ?m to achieve a combining efficiency of above 95% for combining ultrashort laser pulses with a 3 dB spectral bandwidth of 13?nm centered at 1064?nm. Besides, the analytical expression also demonstrates that the impact of self-phase modulation on the combining efficiency has no dependence on spectral bandwidth and only depends on the B integral difference if neglecting the direct influence of the peak power difference. Our analysis also indicates that the group velocity dispersion has relatively small influence on the combining efficiency. These formulas can be used to diagnose the influence of temporal-spectral effects and provide useful guidelines for the design or optimization of the active CPBC system of ultrafast fiber chirped-pulse amplifiers.

  17. 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

  18. Optical injection induced polarization mode switching and correlation analysis on a VCSEL

    E-print Network

    Damodarakurup, Sajeev; Vudayagiri, Ashok

    2015-01-01

    Vertical cavity Surface Emitting Laser (VCSEL) diodes emit light in two polarization modes. The amount of optical feedback is found to influence the intensities of the emitted modes. We investigate the effect of the amount of total output polarization feedback and polarization selective feedback on the intensities of the two emitted polarization modes. A 40 micro seconds resolution time series correlation analysis is done for different feedback conditions and investigate the power spectral continuity and onset of chaos on two polarization modes

  19. Induced Polarization Responses of the Specimen with Sulfide Ore Minerals

    NASA Astrophysics Data System (ADS)

    Park, S.; Sung, N. H.

    2012-04-01

    Basic data of the physical properties of the rocks is required to effectively interpret geologic structures and mineralized zones in study areas from the geophysical data in the field of subsurface investigations and mineral resources explorations. In this study, the spectral induced polarization (SIP) measurement system in the laboratory was constructed to obtain the IP characteristics of the specimen with sulfide ore minerals. The SIP measurement system consists of lab transmitter for electrical current transmission, and GDP-32 for current receiver. The SIP system employs 14 steps of frequencies from 0.123 to 1,024 Hz, and uses copper sulfate solution as an electrolyte. The SIP data for system verification was acquired using a measurement system of parallel circuit with fixed resistance and condenser. This measured data was in good agreement with Cole-Cole model data. First of all, the experiment on the SIP response was conducted in the laboratory with the mixture of glass beads and pyrite powders for ore grade assessment using characteristics of IP response of the rocks. The results show that the phase difference of IP response to the frequency is nearly proportional to the weight content of pyrite, and that the dominant frequency of the IP response varies with the size of the pyrite powder. Subsequently, the specimens used for SIP measurement are slate and limestone which were taken from drilling cores and outcrops of skarn ore deposits. All specimens are cylindrical in shape, with a diameter of 5 cm and a length of 10 cm. When measuring SIP of water-saturated specimens, the specimen surface is kept dry, tap water is put into the bottom of sample holder and a lid is closed. It is drawn that the SIP characteristics of the rocks show the phase difference depends on the amount of the sulfide minerals. The phase difference did not occur with frequencies applied in the absence of sulfide minerals in the rock specimens. On the contrary, the rock specimens containing sulfide minerals such as galena, sphalerite, pyrrhotite, chalcopyrite, pyrite show large phase differences with frequencies applied. In particular, the slate specimens with skarn Pb-Zn show high IP responses to the frequencies applied since the specimens contain high amount of the sulfide minerals. The specimens of other rocks in the skarn ore deposits, on the other hand, do not provide the detectable IP responses since the rocks consist mostly of silicate minerals. The phase difference derived from the frequency applied was converted to the data for ore grade since the phase of SIP response shows high relationship with the ore grade.

  20. 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.

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. 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 for a 15-m thick cloud of live BG located at a range of 400 m.

  6. 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.

  7. 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.

  8. 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 polarization data and vice- versa.

  9. Spectral and polarized light sensitivity of photoreceptors in the compound eye of the cricket (Gryllus bimaculatus).

    PubMed

    Zufall, F; Schmitt, M; Menzel, R

    1989-02-01

    Retinula cells in the compound eye of the cricket (Gryllus bimaculatus) were recorded intracellularly and stained with Lucifer yellow. Two different methods were used to determine the spectral sensitivity of these cells: a) the spectral scanning method, and b) the conventional flash method. Three spectral types, with S(lambda)-curves close to the rhodopsin-absorption functions, were found with lambda max at 332 nm (UV), 445 nm (blue) and 515 nm (green), respectively. Blue receptors were only recorded in the anatomically specialized dorsal rim area (DRA), and UV and green receptors in the dorsal region of the pigmented part of the eye, whereby green receptors were only found in the ventral eye. On the basis of these results, model calculations are presented for di- and trichromatic colour vision in the cricket. The fluorescence markings revealed green receptors whose axons project with short visual fibres to the lamina, and a UV receptor with a long visual fibre which projects through the lamina to the medulla. The blue receptors send their axons either to the lamina and medulla (long visual fibres) or only to the lamina (short visual fibres). The temporal dynamics of the three receptor types were examined. The blue receptors lack a phasic component of the receptor potential, and the time from stimulus on-set to peak potential is strongly increased compared to the UV and green receptors. Light adaptation reduces the latency to less than half of the dark adapted state. Spectral adaptation experiments revealed an 'unidirectional coupling' between UV and green receptors, and it was found that polarization sensitivity (PS) in blue cells was much higher (PS = 6.5 +/- 1.5) than that of UV (PS = 1.76 +/- 0.05) and green (2.26 +/- 0.57) receptors. The functional aspects of the three receptor types are discussed with respect to the presented physiological and morphological data. PMID:2709343

  10. 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.

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

    PubMed Central

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

    2014-01-01

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

  12. 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.

  13. 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.

  14. Absolute isotropic spectral intensities in collision-induced light scattering by helium pairs over a large frequency domain

    NASA Astrophysics Data System (ADS)

    Rachet, Florent; Le Duff, Yves; Guillot-Noël, Christophe; Chrysos, Michael

    2000-06-01

    We measured the polarized binary collision-induced light scattering spectrum from room-temperature gaseous helium over the greatly extended spectral domain ?=5-1200 cm-1, and then deduced the isotropic spectrum that we report in the interval ?=100-1200 cm-1. Our experimental results were calibrated on an absolute scale. These data were compared to those from quantum-mechanical computations, where use of advanced induced-polarizability incremental traces was made. This comparison enabled us to check several trace models and to show that for certain ab initio ones the computed spectra agree well with our measurements. As was borne out from our computations the main contributions to the spectral intensities come from the exchange component of the incremental trace and its negative mixing with the rest of the trace components.

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

    PubMed Central

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

    2012-01-01

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

  16. 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, ?. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to ?. PMID:26450679

  17. 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.

  18. 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, ?, 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 ?{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 ?{sup plane} = –2.98 ± 0.01 and ?{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, ?(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 ? = –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 ? = –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.

  19. 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 spherical grains versus the actual geometry associated with the nano-pores in the silica gel, though other polarization processes, e.g., proton hopping along the surface (Skold et al., 2013), may also be a contributing factor. As an alternative model-independent approach to confirming the link between surface sorption and SIP we initiated a study that will continue (unfunded) beyond the completion of this project to independently measure the accumulation of gamma emitting isotopes on the silica gel during the SIP monitoring experiments. Though our analyses of the project data are ongoing, our preliminary analyses are generally supportive of the grain (Stern layer) polarization theory of SIP. Experiments focused on evaluating the impact of physical modifications of the medium on polarization included etching and biotic and abiotic facilitated precipitation of carbonate and iron oxides to alter the roughness and electrical conductivity of the surfaces. These experiments were performed for both silica gel and glass beads, the latter of which lacked the interior porosity and high surface area of the silica gel. The results appear to be more nuanced that the chemical modifications of the system. In general, however, it was found that deposition of iron oxides and etching had relatively minimal or negative impacts on the polarization response of the medium, whereas carbonate coatings increased the polarization response. These results were generally consistent with changes in surface charge observed via AFM. Abiotic and biotic column flow through experiments demonstrated that precipitation of carbonate within the medium significantly impacted the real and imaginary conductivity over time in a manner generally consistent with the carbonate precipitation as observed from the batch grain coating experiments. Biotic effects were not observed to provide distinctly different signatures, but may have contributed to differences in the rate of changes observed with SIP. AFM was used in a variety of different ways to investigate the grain surfaces throughout the course of the proj

  20. 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 spherical grains versus the actual geometry associated with the nano?pores in the silica gel, though other polarization processes, e.g., proton hopping along the surface (Skold et al., 2013), may also be a contributing factor. As an alternative model?independent approach to confirming the link between surface sorption and SIP we initiated a study that will continue (unfunded) beyond the completion of this project to independently measure the accumulation of gamma emitting isotopes on the silica gel during the SIP monitoring experiments. Though our analyses of the project data are ongoing, our preliminary analyses are generally supportive of the grain (Stern layer) polarization theory of SIP. Experiments focused on evaluating the impact of physical modifications of the medium on polarization included etching and biotic and abiotic facilitated precipitation of carbonate and iron oxides to alter the roughness and electrical conductivity of the surfaces. These experiments were performed for both silica gel and glass beads, the latter of which lacked the interior porosity and high surface area of the silica gel. The results appear to be more nuanced that the chemical modifications of the system. In general, however, it was found that deposition of iron oxides and etching had relatively minimal or negative impacts on the polarization response of the medium, whereas carbonate coatings increased the polarization response. These results were generally consistent with changes in surface charge observed via AFM. Abiotic and biotic column flow through experiments demonstrated that precipitation of carbonate within the medium significantly impacted the real and imaginary conductivity over time in a manner generally consistent with the carbonate precipitation as observed from the batch grain coating experiments. Biotic effects were not observed to provide distinctly different signatures, but may have contributed to differences in the rate of changes observed with SIP. AFM was used in a variety of different ways to investigate the grain surfaces throughout the course

  1. Digital dispersion compensation for ultrabroad-bandwidth single-camera spectral-domain polarization-sensitive OCT

    E-print Network

    Oldenburg, Amy

    Downloaded from SPIE Digital Library on 08 Jun 2011 to 152.19.204.240. Terms of Use: httpDigital dispersion compensation for ultrabroad-bandwidth single-camera spectral-domain polarization-to-wavenumber nonlinearity requires either careful spectrometer alignment,[2] or digital compensation.[5] In fact

  2. 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 reactions that do not satisfy the time-scale separability inherent to nonadiabatic kinetic models.

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

    E-print Network

    Cattin, Rodolphe

    Spectral analysis of seismic noise induced by rivers: A new tool to monitor spatiotemporal changes. Bollinger, J. Vergne, R. Cattin, and J. L. Na´belek (2008), Spectral analysis of seismic noise induced March 2007; revised 19 September 2007; accepted 28 January 2008; published 2 May 2008. [1] Analysis

  4. Role of methyl-induced polarization in ion binding

    PubMed Central

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

    2013-01-01

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

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

    SciTech Connect

    Verma, Jai; Simon, John; Protasenko, Vladimir; Kosel, Thomas; Xing, Huili Grace; Jena, Debdeep

    2011-10-24

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

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

    E-print Network

    Ka Lok Ng; Kin-Wang Ng

    1994-06-30

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

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

    NASA Astrophysics Data System (ADS)

    Hultgren, Kristoffer; Gumbel, Jörg

    2014-12-01

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

  8. Self-consistent problem of induced polarization of electrokinetic origin

    NASA Astrophysics Data System (ADS)

    Svetov, B. S.; Ageev, V. V.; Karinskii, S. D.; Ageeva, O. A.

    2013-11-01

    In the first part of the paper, with some constraints, we find the analytical solution of the self-consistent problem of induced polarization (IP) for an electrokinetically polarized sphere. The stationary (on long time intervals) solution of the self-consistent problem is a set of the potential fields that are interconnected with each other: the exciting electric field, the extraneous hydrodynamical field (electroosmotic flow of a viscous incompressible fluid), and the resulting electromagnetic IP field. The extraneous field is the field of the osmotic flow of a charged liquid and the field of the charges that emerge due to the membrane effect in the narrowed segments of the pore channels. The calculations show that the IP fields derived by solving the self-consistent problem and by the Seigel-Komarov phenomenological approach are different. In the second part of the paper, by generalization of the obtained analytical solution, we formulate the self-consistent IP problem for isotropic ?-? media of arbitrary shape, which are bounded by a smooth surface. The problem can be solved by the numerical methods.

  9. Model-free methods to study membrane environmental probes: a comparison of the spectral phasor and generalized polarization approaches

    NASA Astrophysics Data System (ADS)

    Malacrida, Leonel; Gratton, Enrico; Jameson, David M.

    2015-12-01

    In this note, we present a discussion of the advantages and scope of model-free analysis methods applied to the popular solvatochromic probe LAURDAN, which is widely used as an environmental probe to study dynamics and structure in membranes. In particular, we compare and contrast the generalized polarization approach with the spectral phasor approach. To illustrate our points we utilize several model membrane systems containing pure lipid phases and, in some cases, cholesterol or surfactants. We demonstrate that the spectral phasor method offers definitive advantages in the case of complex systems.

  10. Optically induced rotation of Rayleigh particles by vortex beams with different states of polarization

    NASA Astrophysics Data System (ADS)

    Li, Manman; Yan, Shaohui; Yao, Baoli; Liang, Yansheng; Lei, Ming; Yang, Yanlong

    2016-01-01

    Optical vortex beams carry optical orbital angular momentum (OAM) and can induce an orbital motion of trapped particles in optical trapping. We show that the state of polarization (SOP) of vortex beams will affect the details of this optically induced orbital motion to some extent. Numerical results demonstrate that focusing the vortex beams with circular, radial or azimuthal polarizations can induce a uniform orbital motion on a trapped Rayleigh particle, while in the focal field of the vortex beam with linear polarization the particle experiences a non-uniform orbital motion. Among the formers, the vortex beam with circular polarization induces a maximum optical torque on the particle. Furthermore, by varying the topological charge of the vortex beams, the vortex beam with circular polarization gives rise to an optimum torque superior to those given by the other three vortex beams. These facts suggest that the circularly polarized vortex beam is more suitable for rotating particles.

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

    E-print Network

    Ion-induced nucleation in polar one-component fluids Hikaru Kitamuraa and Akira Onuki Department; published online 27 September 2005 We present a Ginzburg-Landau theory of ion-induced nucleation in a gas phase of polar one-component fluids, where a liquid droplet grows with an ion at its center

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

    E-print Network

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

    2004-05-11

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

  13. Polarized spectral properties and laser demonstration of Nd-doped Sr3Y2(BO3)4 crystal.

    PubMed

    Pan, Zhongben; Yu, Haohai; Cong, Hengjiang; Zhang, Huaijin; Wang, Jiyang; Wang, Qing; Wei, Zhiyi; Zhang, Zhiguo; Boughton, R I

    2012-10-20

    Detailed polarized spectral properties of a 0.685 at. % Nd(3+):Sr(3)Y(2)(BO(3))(4) crystal grown by the Czochralski method have been investigated, including the absorption cross section, the emission cross section, and the fluorescence lifetime. The anisotropy of the spectral properties in different polarized directions was discussed thoroughly. The absorption and emission spectra of Nd(3+) are found to be inhomogeneously broadened due to its internal disordered lattice. Additionally, the CW laser operation at 1.06 ?m was also demonstrated for the first time. The maximum output power of 905 mW was achieved, with corresponding optical conversion efficiency of 10.8% and slope efficiency of 12.8%. PMID:23089764

  14. Parahydrogen Induced Polarization by Pairwise Replacement on Pt and Ir Nanoparticles

    NASA Astrophysics Data System (ADS)

    Bowers, Clifford; Zhou, Ronghui; Zhao, Evan; Cheng, Wei; Neal, Luke; Weaver, Helena

    2015-03-01

    Parahydrogen Induced Polarization (PHIP) is a robust and scalable method for production of bulk quantities of hyperpolarized fluids. The symmetrization order inherent in parahydrogen is transformed via symmetry breaking hydrogenation reaction into NMR-observable hyperpolarization. Spin polarization of order unity can be obtained. A key requirement of PHIP is pairwise hydrogenation by addition of H atoms originating from the same H2 molecule. PHIP using supported metal catalysts is a promising recent development because it exploits the advantages over homogeneous and supported metal complexes. The present work demonstrates a new PHIP mechanism involving the pairwise replacement of parahydrogen into propene (the substrate) over TiO2 supported Ir and Pt nanoparticle catalysts. Analysis of the stereoselectivity of the pairwise replacement process is facilitated by density matrix spectral simulations. The cis and trans dispositions of the symmetrization order give strikingly different PHIP spectra. The observed stereoselectivity of the pairwise replacement step, together with control experiments, rule out an alternative mechanism involving dehydrogenation of free propane over the catalyst.

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

    NASA Astrophysics Data System (ADS)

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

    2002-07-01

    A theoretical model of spectral-induced polarization (IP) of sand is presented. In the proposed model, contacts of sand grains and intergrain solution-filled space are considered as electrical current passages of varying thickness, which differ in values of ion transport number. Ion-selective narrow passages are considered as active zones, large passages as passive. The proposed model describes spectral IP characteristics for the medium where the length of passive zones is much greater than the length of active ones. The model is called short narrow pores (SNP) model. The SNP model predicts a growth of IP time constant with increase of length of ion-selective zone. Both the time domain and frequency domain parameters are described. The parameters of Cole-Cole model corresponding to the SNP model were also found. The behaviour of model parameters is compared with experimental data obtained on natural and sieved sands using time domain technique. The natural sand spectra correspond neither to the simple SNP model nor simple Cole-Cole model with single time constant because the lengths of ion-selective zones vary, reflecting the grain-size distribution. The spectra of sieved sand compared with the theoretical SNP spectra reveal close correspondence between experimental data and theoretical parameters. For four sieved sands, both the theoretical and experimental data show that the time constant of the IP is proportional to the square of the average grain size.

  16. Current-induced spin polarization and spin-orbit torque in graphene

    NASA Astrophysics Data System (ADS)

    Dyrda?, A.; Barna?, J.

    2015-10-01

    Using the Green-function formalism, we calculate a current-induced spin polarization of weakly magnetized graphene with Rashba spin-orbit interaction. In a general case, all components of the current-induced spin polarization are nonzero, contrary to the nonmagnetic limit, where the only nonvanishing component of spin polarization is that in the graphene plane and normal to the electric field. When the induced spin polarization is exchange coupled to the magnetization, it exerts a spin-orbit torque on the latter. Using the Green-function method, we have derived some analytical formulas for the spin polarization and also determined the corresponding spin-orbit torque components. The analytical results are compared with those obtained numerically. Vertex corrections due to scattering on randomly distributed impurities are also calculated and shown to enhance the spin polarization calculated in the bare bubble approximation.

  17. Polarizers for a spectral range centered at 121.6 nm operating by reflectance or by transmittance

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    Polarimetry is a powerful tool to interpret how the coronal plasma is involved in the energy transfer processes from the Sun's inner parts to the outer space. Space polarimetry in the far ultraviolet (FUV) provides essential information of processes governed by the Doppler and Hanle resonant electron scattering effects. Among the key FUV spectral lines to observe these processes, H I Lyman ? (121.6 nm) is the most intense. Some developing or proposed solar physics missions, such as CLASP, SolmeX, and COMPASS, plan to perform polarimetry at 121.6 nm. Classical solutions, such as a parallel plate of a transparent material, either MgF2 or LiF, result in a modest efficiency of the passing polarization component. The development of more efficient linear polarizers at this wavelength will benefit future space instruments. A research has been conducted to develop polarizers based on (Al/MgF2)n multilayer coatings in a band containing 121.6 nm, to obtain a significant efficiency increase over plates. Coatings operating by reflectance resulted in a high efficiency after approximately one year of storage under nitrogen. In parallel, coating polarizers operating by transmittance have been prepared for the first time. Transmissive polarizers have the advantage that they involve no deviation of the beam. As a further benefit, the developed transmittance polarizers additionally incorporate filtering properties to help reject wavelengths both shortwards and longwards of a band containing 121.6 nm. Hence a polarizer combined with a filter is obtained with a single device. The combined polarizer-filter could enable a higher performance polarimeter for solar physics if the use of a separate filter to isolate Lyman ? turns unnecessary.

  18. 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.

  19. Magnetospheric Birefringence Induces Unique Polarization Signatures in Neutron-Star Spectra

    E-print Network

    R. M. Shannon; Jeremy S. Heyl

    2006-02-18

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

  20. 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.

  1. 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.

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

    DOEpatents

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

    2003-12-16

    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.

  3. Sudden Death of Entanglement induced by Polarization Mode Dispersion

    E-print Network

    Cristian Antonelli; Mark Shtaif; Misha Brodsky

    2011-01-27

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

  4. 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.

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

    PubMed Central

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

    2014-01-01

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

  6. 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 (? = 0.694?m, type OGM-20,? = 1.06?m with a home-made laser based on neodymium glass crystal, and ? = 10.6?m, similarly home-made) and pulse durations (Q-switched and free-running regimes). To follow the integral, dynamical and spectral characteristics of the luminous spot of microplasma we have used fast cameras (SFR-2M, IMACON-HADLAND), a high speed spectral camera (AGAT-2) and a spectrograph (STE-1). It has been shown that the microplasma consists of two parts: fast front (peak) with ??100 ns and slow front (tail) with ??1?s durations. The detonation front speed is of the order of ?10 5 cm s -1 and follows the temporal dependence of to t0.4. It depends on the composition of the surrounding gas and its pressure and could be connected with quick evaporation of the material investigated (peak) and optical breakdown of the ambient gaseous atmosphere (tail). From the delay in appearance of different characteristic spectral lines of the target material and its gaseous surrounding we have shown that the evolution of the microplasma involves evaporation and ionization of the atoms of the parent material followed by optical breakdown due to the incident and absorbed laser light, together with microplasma expansion.

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

    E-print Network

    Jones, Alan M.

    Dim-Red-Light-Induced Increase in Polar Auxin Transport in Cucumber Seedlings1 I. Development transport of [3 H]indole-3-acetic acid through hypocotyl seg- ments from etiolated cucumber (Cucumis sativus

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

    DOEpatents

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

    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.

  9. Behavior of tight-junction, adherens-junction and cell polarity proteins during HNF-4{alpha}-induced epithelial polarization

    SciTech Connect

    Satohisa, Seiro; Chiba, Hideki . E-mail: hidchiba@sapmed.ac.jp; Osanai, Makoto; Ohno, Shigeo; Kojima, Takashi; Saito, Tsuyoshi; Sawada, Norimasa

    2005-10-15

    We previously reported that expression of tight-junction molecules occludin, claudin-6 and claudin-7, as well as establishment of epithelial polarity, was triggered in mouse F9 cells expressing hepatocyte nuclear factor (HNF)-4{alpha} [H. Chiba, T. Gotoh, T. Kojima, S. Satohisa, K. Kikuchi, M. Osanai, N. Sawada. Hepatocyte nuclear factor (HNF)-4{alpha} triggers formation of functional tight junctions and establishment of polarized epithelial morphology in F9 embryonal carcinoma cells, Exp. Cell Res. 286 (2003) 288-297]. Using these cells, we examined in the present study behavior of tight-junction, adherens-junction and cell polarity proteins and elucidated the molecular mechanism behind HNF-4{alpha}-initiated junction formation and epithelial polarization. We herein show that not only ZO-1 and ZO-2, but also ZO-3, junctional adhesion molecule (JAM)-B, JAM-C and cell polarity proteins PAR-3, PAR-6 and atypical protein kinase C (aPKC) accumulate at primordial adherens junctions in undifferentiated F9 cells. In contrast, CRB3, Pals1 and PATJ appeared to exhibit distinct subcellular localization in immature cells. Induced expression of HNF-4{alpha} led to translocation of these tight-junction and cell polarity proteins to beltlike tight junctions, where occludin, claudin-6 and claudin-7 were assembled, in differentiated cells. Interestingly, PAR-6, aPKC, CRB3 and Pals1, but not PAR-3 or PATJ, were also concentrated on the apical membranes in differentiated cells. These findings indicate that HNF-4{alpha} provokes not only expression of tight-junction adhesion molecules, but also modulation of subcellular distribution of junction and cell polarity proteins, resulting in junction formation and epithelial polarization.

  10. Behavior of tight-junction, adherens-junction and cell polarity proteins during HNF-4alpha-induced epithelial polarization.

    PubMed

    Satohisa, Seiro; Chiba, Hideki; Osanai, Makoto; Ohno, Shigeo; Kojima, Takashi; Saito, Tsuyoshi; Sawada, Norimasa

    2005-10-15

    We previously reported that expression of tight-junction molecules occludin, claudin-6 and claudin-7, as well as establishment of epithelial polarity, was triggered in mouse F9 cells expressing hepatocyte nuclear factor (HNF)-4alpha [H. Chiba, T. Gotoh, T. Kojima, S. Satohisa, K. Kikuchi, M. Osanai, N. Sawada. Hepatocyte nuclear factor (HNF)-4alpha triggers formation of functional tight junctions and establishment of polarized epithelial morphology in F9 embryonal carcinoma cells, Exp. Cell Res. 286 (2003) 288-297]. Using these cells, we examined in the present study behavior of tight-junction, adherens-junction and cell polarity proteins and elucidated the molecular mechanism behind HNF-4alpha-initiated junction formation and epithelial polarization. We herein show that not only ZO-1 and ZO-2, but also ZO-3, junctional adhesion molecule (JAM)-B, JAM-C and cell polarity proteins PAR-3, PAR-6 and atypical protein kinase C (aPKC) accumulate at primordial adherens junctions in undifferentiated F9 cells. In contrast, CRB3, Pals1 and PATJ appeared to exhibit distinct subcellular localization in immature cells. Induced expression of HNF-4alpha led to translocation of these tight-junction and cell polarity proteins to beltlike tight junctions, where occludin, claudin-6 and claudin-7 were assembled, in differentiated cells. Interestingly, PAR-6, aPKC, CRB3 and Pals1, but not PAR-3 or PATJ, were also concentrated on the apical membranes in differentiated cells. These findings indicate that HNF-4alpha provokes not only expression of tight-junction adhesion molecules, but also modulation of subcellular distribution of junction and cell polarity proteins, resulting in junction formation and epithelial polarization. PMID:16098509

  11. Very-large-mode-area photonic bandgap Bragg fiber polarizing in a wide spectral range.

    PubMed

    Aleshkina, Svetlana S; Likhachev, Mikhail E; Pryamikov, Andrey D; Gaponov, Dmitry A; Denisov, Alexandr N; Bubnov, Mikhail M; Salganskii, Mikhail Yu; Laptev, Alexandr Yu; Guryanov, Aleksei N; Uspenskii, Yurii A; Popov, Nikolay L; Février, Sébastien

    2011-09-15

    A design of a polarizing all-glass Bragg fiber with a microstructure core has been proposed for the first time. This design provides suppression of high-order modes and of one of the polarization states of the fundamental mode. The polarizing fiber was fabricated by a new, simple method based on a combination of the modified chemical vapor deposition (MCVD) process and the rod-in-tube technique. The mode field area has been found to be about 870 ?m² near ?=1064 nm. The polarization extinction ratio better than 13 dB has been observed over a 33% wavelength range (from 1 to 1.4 ?m) after propagation in a 1.7 m fiber piece bent to a radius of 70 cm. PMID:21931392

  12. 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

    2016-01-01

    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.

  13. Current-Induced Spin Polarization in Anisotropic Spin-Orbit Fields

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    The magnitude and direction of current-induced spin polarization and spin-orbit splitting are measured in In0.04Ga0.96 As epilayers as a function of in-plane electric and magnetic fields. We show that, contrary to expectation, the magnitude of the current-induced spin polarization is smaller for crystal directions corresponding to larger spin-orbit fields. Furthermore, we find that the steady-state in-plane spin polarization does not align along the spin-orbit field, an effect due to anisotropy in the spin relaxation rate.

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

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

    In the quasi two-dimensional GaAs/AlGaAs system, we investigate the effect of rotating in situ the electric field of linearly polarized microwaves relative to the current, on the microwave-radiation-induced magnetoresistance oscillations. We find that the frequency and the phase of the photoexcited magnetoresistance oscillations are insensitive to the polarization. On the other hand, the amplitudes of the magneto resistance oscillations are remarkably responsive to the relative orientation between the microwave antenna and the current-axis in the specimen. The results suggest a striking linear-polarization-sensitivity in the radiation-induced magnetoresistance oscillations.

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

    PubMed

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

    2012-02-01

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

  16. Spin motive force induced in Fe3O4 thin films with negative spin polarization

    NASA Astrophysics Data System (ADS)

    Nagata, Masaki; Moriyama, Takahiro; Tanabe, Kenji; Tanaka, Kensho; Chiba, Daichi; Ohe, Jun-ichiro; Hisamatsu, Yuki; Niizeki, Tomohiko; Yanagihara, Hideto; Kita, Eiji; Ono, Teruo

    2015-12-01

    Spin motive force (SMF) is induced by a time and spatial derivative of magnetizations and is dependent on spin polarization. We compare the SMF in FeNi with positive spin polarization with that in a magnetite (Fe3O4) with negative spin polarization. We observe the SMF induced by a nonuniform ferromagnetic resonance in Fe3O4 and find that the SMF in Fe3O4 is opposite to that in FeNi. This result originates from the negative spin polarization of Fe3O4. Our clear observation of the SMF depending on the sign of the spin polarization agrees well with the framework of the SMF theory.

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

    SciTech Connect

    Gacesa, M.; Kharchenko, V.; Mueller, H.-R.; Cote, R.

    2011-05-10

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

  18. Polarization of the Charge-exchange X-rays Induced in the Heliosphere

    NASA Astrophysics Data System (ADS)

    Gacesa, M.; Müller, H.-R.; Côté, R.; Kharchenko, V.

    2011-05-01

    We report results of a theoretical investigation of polarization of the X-ray emissions induced in charge-exchange collisions of fully stripped solar wind (SW) ions C6 + and O8 + with the heliospheric hydrogen atoms. The polarization of X-ray emissions has been computed for line-of-sight observations within the ecliptic plane as a function of SW ion velocities, including a range of velocities corresponding to the slow and fast SW, and coronal mass ejections. To determine the variability of polarization of heliospheric X-ray emissions, the polarization has been computed for solar minimum conditions with self-consistent parameters of the SW plasma and heliospheric gas and compared with the polarization calculated for an averaged solar activity. We predict the polarization of charge-exchange X-rays to be between 3% and 8%, depending on the line-of-sight geometry, SW ion velocity, and the selected emission lines.

  19. 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.

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

    SciTech Connect

    Thomas, G.E. ); McPeters, R.D. ); Jensen, E.J. )

    1991-01-20

    Measurements from space of the Earth's ultraviolet albedo are affected by scattering of sunlight from polar mesospheric clouds (PMC). The authors have examined 8 years of solar backscattered ultraviolet (SBUV) albedo data and find evidence of an annual occurrence of PMC in the summertime polar cap regions of both hemispheres. The authors have devised a cloud selection algorithm based upon the expected spectral properties of PMC scattering and show that the albedo residuals selected by this algorithm, at least above some threshold brightness, possess the basic properties of PMC with regard to their brightness levels, their seasonal characteristics, and latitude variation. Because of the uniform sampling of the polar caps, particularly in the southern hemisphere, it is possible to examine year-to-year variations in PMC activity. The authors find that a significant trend is present in the PMC occurrence frequency values over the period 1978 to 1986. The increase (up to a factor of 10 at some brightness levels) in the occurrence frequency from solar maximum to solar minimum conditions indicates an anticorrelation with solar activity, an effect that also appears to be present in noctilucent cloud sightings over the past several decades. The authors have identified two kinds of hemispherical asymmetries: the first, that PMC in the northern hemisphere is significantly brighter than in the south is consistent with previous results derived from Solar Mesosphere Explorer data; and the second, that the solar cycle response in the south is more pronounced than in the north. The authors show that if PMC scattering is not taken into account in the SBUV ozone retrieval algorithm, systematic errors of order 10% can occur in derived ozone concentration in the 40-50 km region of the summer polar cap.

  1. 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.

  2. 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.

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

    E-print Network

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

    2015-03-30

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

  4. Interference of spin states in resonant photoemission induced by circularly polarized light from magnetized Gd

    SciTech Connect

    Mueller, N.; Khalil, T.; Pohl, M.; Uphues, T.; Heinzmann, U.; Polcik, M.; Rader, O.; Heigl, F.; Starke, K.; Fritzsche, S.; Kabachnik, N. M.

    2006-10-15

    We have observed the spin-state interference by measuring the photoelectron spin polarization in the resonant preedge 4d{yields}4f photoemission from magnetized Gd. The photoemission is induced by circularly polarized light which determines one preferential direction of electron spin orientation due to polarization transfer and spin-orbit interaction. Another direction perpendicular to the first one is determined by the target electron spin orientation connected with the target magnetization. We have measured the component of spin polarization perpendicular to those two directions which can only appear due to spin-state interference which implies coherence of the spin states produced by the two mechanisms of the photoelectron spin polarization.

  5. Textures in thin films of nematic liquid crystals induced by strongly focusing a circularly polarized laser

    NASA Astrophysics Data System (ADS)

    Miyakawa, K.; Yoshinaga, A.; Ariyoshi, D.

    2011-03-01

    We investigate the rearrangement of the director in thin films of nematic liquid crystals caused by tightly focusing circularly polarized laser beams. We find either target or spiral patterns, depending on the topology of the director configuration at the position of the beam focus. The induced rearrangements of the director are governed by the viscosity of the media, the handedness of circular polarization, and the irradiation power of the laser. Experimental observations are interpreted using a model derived from nematic continuum theory.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  8. 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

  9. 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.

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

    SciTech Connect

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

    2012-09-30

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

  11. 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.

  12. 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.

  13. Geometrically induced polarization and alignment of cells on nanopillar arrays

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  14. Modulated nematic structures induced by chirality and steric polarization

    E-print Network

    Lech Longa; Grzegorz Paj?k

    2015-11-20

    What kind of one-dimensional modulated nematic structures (ODMNS) can form nonchiral and chiral bent-core and dimeric materials? Here, using Landau-deGennes 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 have not been reported so far. These new structures are longitudinal ($N_{LP}$) and transverse ($N_{TP}$) periodic waves where the polarization field being periodic in one dimension stays parallel and perpendicular, respectively, to the wave vector. The other two phases have all characteristic features of the twist-bend nematic phase ($N_{TB}$) and the splay-bend nematic phase ($N_{SB}$), but their fine structure appears more complex than that considered so far. The presence of molecular chirality converts nonchiral $N_{TP}$ and $N_{SB}$ into new $N_{TB}$ phases. Interestingly, the nonchiral $N_{LP}$ phase can stay stable even in the presence of intrinsic molecular chirality. Exemplary phase diagrams provide further insights into the relative stability of these new modulated nematic structures.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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-1?, or tumor necrosis factor (TNF)-?. 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-?2 (TGF-?2) 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

  20. 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.

  1. Dynamics of microvortices induced by ion concentration polarization

    E-print Network

    de Valenca, Joeri; Lammertink, Rob G H; Tsai, Peichun Amy

    2015-01-01

    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 ($\\Delta V_{ohm}$), followed by a constant voltage jump ($\\Delta V_c$). Immediately after this voltage increase, micro-vortices 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 ...

  2. Induced spin polarization in V:FenVm superlattices and thin V films on Fe substrates

    NASA Astrophysics Data System (ADS)

    Izquierdo, J.; Vega, A.; Elmouhssine, O.; Dreyssé, H.; Demangeat, C.

    1999-06-01

    The spin polarization at the (100) and (110) Fe/V interfaces is investigated using the tight-binding linear muffin-tin orbital method. For both FenVm superlattices and thin Vm films on Fe substrates we consider epitaxial growth of V with in-plane interatomic distance equal to that of Fe and out-of-plane interatomic distance fitted to recover the volume of V bulk. We obtain a short-range induced spin polarization in V, as well as reduced Fe polarization at the Fe/V interface. In FenVm superlattices, V couples always antiferromagnetically with Fe. For thin V films grown on Fe(100) the V polarization presents oscillations (layered antiferromagnetic configuration). The magnetic moments of V and Fe depend on the crystallographic orientation of the sample. Our results are compared with the existing experimental observations.

  3. Investigation of the electronic transport in polarization-induced nanowires using conductive atomic force microscopy (AFM)

    NASA Astrophysics Data System (ADS)

    Selcu, Camelia; Carnevale, Santino C.; Kent, Thomas F.; Akyol, Fatih; Phillips, Patrick J.; Mills, Michael J.; Rajan, Siddharth; Pelz, Jonathan P.; Myers, Roberto C.

    2013-03-01

    In the search to improve short wavelength light emitting diodes (LED's), where the dislocations limit their performance and hole doping (Mg) is a fundamental challenge, the III-Nitride polarization-induced nanowire LED provides a promising system to address these problems. The new type of pn diode, polarization-induced nanowire LED (PINLED), was developed by linearly grading AlGaN composition of the nanowires (from GaN to AlN and back to GaN) from 0% to 100% and back to 0% Al (Carnevale et al, Nano Lett., 12, 915 (2012)). In III-Nitrides (Ga,Al/N), the effects of polarization are commonly observed at the surfaces and interfaces. Thus, in the case of the polarization-induced nanowire LEDs, taking advantage of the bound polarization charge, due to the grading of the AlGaN, the pn diodes are formed. The polarity of the nanowires determines the carrier type in each graded region, and therefore the diode orientation (n/p vs p/n). We used conductive AFM to investigate polarity of the PINLED's as well as hole conductivity in PINLED's made of AlGaN with and without acceptor doping. The results reveal that most of the wires are n-top/p-bottom (N-face), but some are p-top/n-bottom (Ga-face). Also, we found that the current density is 3 orders of magnitude larger in the case of the doped nanowires than the nanowires with no impurity doping.

  4. Modeling Robustness Tradeoffs in Yeast Cell Polarization Induced by Spatial Gradients

    E-print Network

    Nie, Qing

    Modeling Robustness Tradeoffs in Yeast Cell Polarization Induced by Spatial Gradients Ching such as spatial gradients. For example, yeast cells form a mating projection toward the source of mating pheromone over a broad range of ligand concentrations, and tracking of moving signal sources. In this work, we

  5. Polarization-resolved time-delay signatures of chaos induced by FBG-feedback in VCSEL

    E-print Network

    Chan, Sze-Chun

    Polarization-resolved time-delay signatures of chaos induced by FBG-feedback in VCSEL Zhu intensities from a vertical-cavity surface-emitting laser (VCSEL) subject to feedback from a fiber Bragg signatures. Finally, by comparing with a VCSEL subject to feedback from a mirror, the VCSEL subject

  6. 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.

  7. Water structure changes induced by hydrophobic and polar solutes revealed by simulations and infrared spectroscopy

    E-print Network

    Sharp, Kim

    Water structure changes induced by hydrophobic and polar solutes revealed by simulations on a water structure. The ionic solutes increase the mean water­ water H-bond angle in their first hydration shell concomitantly shifting the OH stretching mode to higher frequency, and shifting the HOH bending

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

    E-print Network

    Tong, Liang

    (3T3, HeLa, and CHO cells), we tested one prevailing hypothesis, namely, that electric fieldsElectric Field-Induced Polarization of Charged Cell Surface Proteins Does Not Determine of Biomedical Engineering, Columbia University, New York, New York 3 Department of Pathology and Cell Biology

  9. Measurements of submillimeter polarization induced by oblique reflection from aluminum alloy

    E-print Network

    Novak, Giles

    Measurements of submillimeter polarization induced by oblique reflection from aluminum alloy Tom of submillimeter radiation when it is obliquely reflected by a flat mirror made of aluminum alloy. For angles by oblique reflection from aluminum alloy at a wavelength of 1 cm agrees with the prediction of the ordinary

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

    E-print Network

    Boxer, Steven G.

    of Yeast tRNAPhe Elizabeth F. McCord, Kathleen M. Morden, Ignacio Tinoco, Jr., and Steven G. Boxer* ABSTRACT: Chemically induced dynamicnuclear polarization (CIDNP) has been observed from yeast t of yeast tRNAphein solution (see Figure 1 for the secondary structure of tRNAme). The results

  11. 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

    2015-01-01

    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.

  12. 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 (? Vohm ), followed by a constant voltage jump (? 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 ? Vohm+? Vc ) and sustain an approximately constant electrical conductivity, destroying the initial ICP with significantly low viscous dissipation.

  13. 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.

  14. 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.

  15. Immunization of WDM systems to nonlinearity-induced crosstalk using optical polarization-shift-keying

    NASA Astrophysics Data System (ADS)

    Song, Y. W.; Pan, Z.; Arieli, Y.; Motaghian, S. M. R.; Havstad, S. A.; Willner, A. E.

    2005-08-01

    We experimentally demonstrate the enhanced suppression of nonlinearity-induced crosstalk using polarization-shift-keying (PolSK) to guarantee constant optical power in a data stream. In a 40-km of LEAF link, PolSK has a 5 times lower nonlinearity-induced crosstalk level in a co-propagating channel with the channel spacing of 100 GHz than return-to-zero (RZ) modulation format. We reduce nonlinearity-induced power penalties by more than 4.6 dB compared with non-return-to-zero (NRZ), and 2.5 dB compared with RZ over the same fiber link at 10 Gbit/s.

  16. 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 ?-glycine, representing a broad class of non-centrosymmetric amino acids. We show that ?-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 ?-glycine are controlled by the charged domain walls which in turn can be manipulated by an external bias.

  17. Textures in thin films of nematic liquid crystals induced by strongly focusing a circularly polarized laser.

    PubMed

    Miyakawa, K; Yoshinaga, A; Ariyoshi, D

    2011-03-01

    We investigate the rearrangement of the director in thin films of nematic liquid crystals caused by tightly focusing circularly polarized laser beams. We find either target or spiral patterns, depending on the topology of the director configuration at the position of the beam focus. The induced rearrangements of the director are governed by the viscosity of the media, the handedness of circular polarization, and the irradiation power of the laser. Experimental observations are interpreted using a model derived from nematic continuum theory. PMID:21517515

  18. Charge-induced spin polarization in non-magnetic organic molecule Alq$_{3}$

    E-print Network

    Tarafder, Kartick; Oppeneer, Peter

    2010-01-01

    Electrical injection in organic semiconductors is a key prerequisite for the realization of organic spintronics. Using density-functional theory calculations we report the effect of electron transfer into the organic molecule Alq$_3$. Our first-principles simulations show that electron injection spontaneously spin-polarizes non-magnetic Alq$_3$ with a magnetic moment linearly increasing with induced charge. An asymmetry of the Al--N bond lengths leads to an asymmetric distribution of injected charge over the molecule. The spin-polarization arises from a filling of dominantly the nitrogen $p_z$ orbitals in the molecule's LUMO together with ferromagnetic coupling of the spins on the quinoline rings.

  19. Polarization induced instabilities in external four-mirror Fabry-Perot cavities

    E-print Network

    Zomer, F; Pavloff, N; Soskov, V; Variola, A

    2009-01-01

    Various four-mirror optical resonators are studied in the perspective of realizing passive stacking cavities. A comparative study of the mechanical stability is provided. The polarization properties of the cavity eigenmodes are described and it is shown that the effect of mirror misalignments (or motions) induces polarization and stacking power instabilities. These instabilities increase with the finesse of the Fabry-Perot cavity. A tetrahedral configuration of the four mirrors is found to minimize the consequences of the mirrors's motion and misalignment by reducing the instability parameter by at least two orders of magnitude

  20. Surface-induced heating of cold polar molecules

    E-print Network

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

    2009-12-14

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

  1. 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)

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

    NASA Astrophysics Data System (ADS)

    Huemmrich, K. F.; Corp, L.; Campbell, P. K.; Cook, B. D.; Middleton, E.; Cheng, Y.; Zhang, Q.; Russ, A.; Kustas, W. P.

    2013-12-01

    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 can 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. This 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.

  3. Spectral Enhancement of Laser-Induced Breakdown Spectroscopy in External Magnetic Field

    NASA Astrophysics Data System (ADS)

    Li, Cheng; Gao, Xun; Li, Qi; Song, Chao; Lin, Jingquan

    2015-11-01

    In this paper the spectral enhancement of laser-induced breakdown spectroscopy (LIBS) for copper plasma in the presence of a magnetic field is investigated and the temporal- and spatial-resolved plasma emission spectra are analyzed. Experimental results show that the copper plasma atomic and ion spectra have been enhanced in the presence of the external magnetic field. In addition, the Cu I 521.82 nm spectral intensity evolution with delay time appears to have a double peak around the delay time of 2 ?s, but that of Cu II 507.57 nm has a sharp decrease because of the electron-atom three body recombination process. The plasma temperature with magnetic confinement is lower than that of the case in the absence of magnetic fields. Finally, the spectral enhancement mechanisms of laser induced breakdown spectroscopy with magnetic confinement are analyzed. supported by National Natural Science Foundation of China (No. 61178022), the Natural Science Foundation of Jilin Province, China (No. 201215132) and the Doctoral Program of High Education of China (No. 20112216120006)

  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. 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.

  6. 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 ?-ray polarization, which are drastically different for the two types of models.

  7. 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.

  8. The role of crystal polarity in alpha-amino acid crystals for induced nucleation of ice.

    PubMed

    Gavish, M; Wang, J L; Eisenstein, M; Lahav, M; Leiserowitz, L

    1992-05-01

    The hydrophobic faces of single crystals of a series of pairs of racemic and chiral-resolved hydrophobic alpha-amino acids were used as a substrate, onto which water vapor has been cooled to freezing. The morphologies and molecular packing arrangements within each crystal pair are similar but only one of each pair exhibits a polar axis, parallel to the hydrophobic face exposed to water. Those crystals that have a polar axis induce a freezing point higher by 4 degrees to 5 degrees C than the corresponding crystals that do not have a polar axis. The results are interpreted in terms of an electric field mechanism that helps align the water molecules into ice-like clusters en route to crystallization. PMID:1589763

  9. 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-core cpus, it is not as fast as machine code. In the case of large datasets, someone should consider transferring parts of the code to C or Fortran through mex files. This code is available through EPA's website on the following link http://www.epa.gov/esd/cmb/GeophysicsWebsite/index.html Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

  10. Self-induced polarization tracking, tunneling effect and modal attraction in optical fiber

    E-print Network

    Guasoni, Massimiliano; Bony, Pierre-Yves; Wabnitz, Stefan; Fatome, Julien

    2015-01-01

    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 ro...

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

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoming; Tan, Xiaoli

    2015-08-01

    The ceramic Pb0.99Nb0.02[(Zr0.57Sn0.43)0.92Ti0.08]0.98O3 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 d33 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.

  12. 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.

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

    E-print Network

    R. Schiavilla

    2005-05-25

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

  14. Spin-polarized electronic current induced by sublattice engineering of graphene sheets with boron/nitrogen

    NASA Astrophysics Data System (ADS)

    Park, Hyoungki; Wadehra, Amita; Wilkins, John W.; Castro Neto, Antonio H.

    2013-02-01

    We show that spin-polarized electron transport can be achieved by the substitutional doping of only one sublattice of graphene by nitrogen or boron atoms. The bipartite character via two sublattices remains persistent in the electronic structures of graphene doped with low concentrations of nitrogens (borons). The delocalized spin-densities induced by the unpaired electrons at substitutional sites permeate only through the sublattice where the nitrogen (boron) atoms belong. For interacting nitrogen (boron) atoms located along the “zigzag” direction and in the same sublattice, the ferromagnetic spin-ordering is favorable, and substitution-induced localized impurity states selectively disturb the spin-polarized ? orbital of that same sublattice. The bipartite character of graphene lattice governs the unique properties of two-dimensional hybrid graphene-boron nitride nanostructures.

  15. 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.

  16. Chemically induced dynamic nuclear polarization studies of yeast tRNA/sup Phe/

    SciTech Connect

    McCord, E.F.; Morden, K.M.; Tinoco, I. Jr.; Boxer, S.G.

    1984-04-24

    Chemically induced dynamic nuclear polarization (CIDNP) has been observed from yeast tRNA/sup Phe/ following reaction with photoexcited riboflavin. At 20/sup 0/C, several resonances of tRNA in the native form show polarization; previous work predicts that only guanosine and its derivatives in single-stranded regions are likely to become polarized. The methyl protons of m/sub 2//sup 2/G-26 show strong negative spin polarization, indicating that this residue is accessible. The solvent accessibility of this residue has not been previously demonstrated. In addition, two positively polarized aromatic resonances are observed, which are likely due to two or more G(H8) protons, including those of G-20, m/sub 2//sup 2/G-26, and/or Gm-34. For temperatures below 50/sup 0/C, a negatively polarized signal in the aromatic region is shown to arise from cross relaxation with the methyl group protons of m/sub 2//sup 2/G-26. This indicates the proximity of an aromatic proton, probably H2 of A-44, to the methyl groups of m/sub 2//sup 2/G-26. At higher temperatures, the CIDNP spectra show polarization of several additional G resonances, including those of m/sup 2/G-10. These changes in the CIDNP spectra reflect melting of the tertiary and secondary structure of the tRNA. This work is the first use of CIDNP to study a large nucleic acid molecule and exemplifies the value of this technique in probing single-stranded and solvent-accessible regions of tRNA.

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

    PubMed

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

    2010-12-21

    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

  18. 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 (1?mol/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-?B activation and up-regulated peroxisome proliferator-activated receptors (PPAR?/?) 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-?B signaling pathway via PPAR?/? and HO-1 activation and its potential use in treatment of inflammatory diseases. PMID:25626689

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. The Enzymatic Activity of Lipases Correlates with Polarity-Induced Conformational Changes: A Trp-Induced Quenching Fluorescence Study.

    PubMed

    Skjold-Jørgensen, Jakob; Bhatia, Vikram K; Vind, Jesper; Svendsen, Allan; Bjerrum, Morten J; Farrens, David

    2015-07-14

    Triacylglycerol hydrolases (EC 3.1.1.3) are thought to become activated when they encounter the water-lipid interface causing a "lid" region to move and expose the catalytic site. Here, we tested this idea by looking for lid movements in Thermomyces lanuginosus lipase (TL lipase), and in variants with a mutated lid region of esterase (Esterase) and esterase/lipase (Hybrid) character. To measure lid movements, we employed the tryptophan-induced quenching (TrIQ) fluorescence method to measure how effectively a Trp residue on the lid of these mutants (at position 87 or 89) could quench a fluorescent probe (bimane) placed at nearby site 255 on the protein. To test if lid movement is induced when the enzyme detects a lower-polarity environment (such as at the water-lipid interface), we performed these studies in solvents with different dielectric constants (?). The results show that lid movement is highly dependent on the particular lid residue composition and solvent polarity. The data suggest that in aqueous solution (? = 80), the Esterase lid is in an "open" conformation, whereas for the TL lipase and Hybrid, the lid remains "closed". At lower solvent polarities (? < 46), the lid region for all of the mutants is more "open". Interestingly, these behaviors mirror the structural changes thought to take place upon activation of the enzyme at the water-lipid interface. Together, these results support the idea that lipases are more active in low-polarity solvents because the lid adopts an "open" conformation and indicate that relatively small conformational changes in the lid region play a key role in the activation mechanism of these enzymes. PMID:26087334

  5. 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.

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

    SciTech Connect

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

    2012-04-01

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

  7. 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.

  8. The Two-Body and Three-Body Breakup of Polarized HELIUM-3 Induced by the Quasielastic Scattering of Polarized Protons.

    NASA Astrophysics Data System (ADS)

    Miller, Michael Allen

    1995-01-01

    This dissertation presents the results of a study of the two-body and three-body breakup of polarized ^3{rm He} induced by quasi -elastic scattering of polarized protons. The analyzing powers, A_{n0} and A _{0n}, and the spin correlation parameter, A_{nn}, were measured for the quasi-elastic scattering reactions ^3vec{rm He}(vec{ rm p}, 2p), ^3vec {rm He}(vec{rm p}, pd) and ^3vec{rm He}(vec{rm p}, 2pd) at 197.3 MeV. The measurements were carried out using an internal metastability exchange optically pumped polarized ^3{rm He} target and the polarized proton beam of the Cooler storage ring at the Indiana University Cyclotron Facility. These were the first measurements made with an internal polarized target and a circulating polarized beam. The results are used to study the effective polarizations of protons and deuterons in ^3vec{rm He } and to explore the two-body and three-body breakup channels of the vec{rm p} + ^3vec{rm He} reaction.

  9. 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

  10. 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.

  11. 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.

  12. Synthetic approach for unsaturated precursors for parahydrogen induced polarization of choline and its analogs†

    PubMed Central

    Shchepin, Roman V.; Chekmenev, Eduard Y.

    2014-01-01

    Reported here are (i) a new synthetic approach for preparation of (ii) a new compound class, of –OH, for example, an –OH group is replaced with acetyl protecting group, protected 1,2-dehydrocholine analogs and (iii) a new synthetic route for betaine aldehyde. The C=C bond of 1,2-dehydrocholine moiety can be used for molecular addition of parahydrogen producing –OH protected hyperpolarized choline by parahydrogen-induced polarization (PHIP). The reported synthetic approach allows for incorporation of 15N and deuterium labels, which are necessary for preparation of highly polarized PHIP contrast agents. Isotope labeling with 15N and/or deuterium was conducted. Hyperpolarized 15N-choline enabled by the reported synthetic approach can be potentially used as an imaging biomarker of cancer similar to choline positron emission tomography tracers. PMID:25196027

  13. 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...

  14. 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...

  15. 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.

  16. 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; Research Institute of Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770

    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.

  17. Spectral Pattern Analysis of Propofol Induced Spindle Oscillations in the Presence of Auditory Stimulations

    PubMed Central

    Ozgoren, Murat; Bayazit, Onur; Gokmen, Necati; Oniz, Adile

    2010-01-01

    This study’s primary objective is to analyze human EEG spindle oscillations during propofol-induced anesthesia and to address possible activation sources. Such an analysis also has a secondary role of investigating the short- term spectral patterns and their functional role. Artifact-free epochs of spindle activations were selected from the electroencephalograms of patients undergoing propofol anesthesia. Power spectral analysis and source localization using standardized low-resolution-brain-electromagnetic-tomography (sLORETA) were performed. Additionally, spectrograms were obtained by means of using the Complex Morlet-based algorithm. In order to highlight the functional properties, auditory stimulations were conducted during the propofol administration. The loss of consciousness was reached at a level of 0.8-1.2 µg/mL, which also provided distinct spindle oscillations in the continuous EEG. The un-evoked (spontaneous) and evoked (auditory) conditions were examined across non-medicated and medicated conditions (propofol). The propofol administration resulted in appearance of 12-14 Hz spindle activity mostly localized in BA6, BA9, BA10, BA21, BA24 and BA37 areas. The presence of auditory stimulations slightly shifted these maximum activities to different locations. Between the medicated and non-medicated conditions, there was a significant reduction of spindle activity, which was pinpointed to BA7 (precuneus area). The findings indicate that spindle oscillations may have a dual nature. That is, spindle oscillations may be activity dependent and disruptive for large-scale information processing networks in the brain. Hence, the study of spindle oscillation may provide a basis for understanding the short-term spectral patterns of human EEG. PMID:21792383

  18. Spectrally-based quantification of plant heavy metal-induced stress

    NASA Astrophysics Data System (ADS)

    Kancheva, Rumiana; Georgiev, Georgi

    2012-09-01

    Recent developments in environmental studies are greatly related to worldwide ecological problems associated with anthropogenic impacts on the biosphere and first of all on vegetation. Modern remote sensing technologies are involved in numerous ecology-related investigations dealing with problems of global importance, such as ecosystems preservation and biodiversity conservation. Agricultural lands are subjected to enormous pressure and their monitoring and assessment have become an important ecological issue. In agriculture, remote sensing is widely used for assessing plant growth, health condition, and detection of stress situations. Heavy metals constitute a group of environmentally hazardous substances whose deposition in soils and uptake by species affect soil fertility, plant development and productivity. This paper is devoted to the study of the impact of heavy metal contamination on the performance of agricultural species. The ability of different spectral indicators to detect heavy metal-induced stress in plants is examined and illustrated. Empirical relationships have been established between the pollutant concentration and plant growth variables and spectral response. This allows not only detection but quantification of the stress impact on plant performance.

  19. 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

  20. 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

  1. Nonlinear dissipation of circularly polarized Alfven waves due to the beam-induced obliquely propagating waves

    SciTech Connect

    Nariyuki, Y.; Hada, T.; Tsubouchi, K.

    2012-08-15

    In the present study, the dissipation processes of circularly polarized Alfven waves in solar wind plasmas including beam components are numerically discussed by using a 2-D hybrid simulation code. Numerical results suggest that the parent Alfven waves are rapidly dissipated due to the presence of the beam-induced obliquely propagating waves, such as kinetic Alfven waves. The nonlinear wave-wave coupling is directly evaluated by using the induction equation for the parent wave. It is also observed both in the 1-D and 2-D simulations that the presence of large amplitude Alfven waves strongly suppresses the beam instabilities.

  2. Cytokine responses induced by diesel exhaust particles are suppressed by PAR-2 silencing and antioxidant treatment, and driven by polar and non-polar soluble constituents.

    PubMed

    Bach, Nicolai; Bølling, Anette Kocbach; Brinchmann, Bendik C; Totlandsdal, Annike I; Skuland, Tonje; Holme, Jørn A; Låg, Marit; Schwarze, Per E; Øvrevik, Johan

    2015-10-14

    Adsorbed soluble organics seem to be the main drivers of inflammatory responses induced by diesel exhaust particles (DEP). The specific compounds contributing to this process and the cellular mechanisms behind DEP-induced inflammation are not well known. We have assessed pro-inflammatory effects of DEP and various soluble DEP fractions, in human bronchial epithelial cells (BEAS-2B). DEP increased the expression of interleukin (IL)-6 and CXCL8. Silencing of the aryl hydrocarbon receptor (AhR) by siRNA or pretreatment with AhR-antagonists did not attenuate DEP-induced IL-6 and CXCL8 responses. However, the halogenated aromatic hydrocarbon (HAH)-selective AhR antagonist CH223191 caused a considerable reduction in DEP-induced CYP1A1 expression indicating that this response may be due to dioxin or dioxin-like constituents in DEP. Knock-down of protease activated receptor (PAR)-2 attenuated IL-6 responses without affecting CXCL8. Antioxidants did not affect IL-6 expression after 4h DEP-exposure and only partly reduced CXCL8 expression. However, after 24h exposure antioxidant treatment partly suppressed IL-6 protein release and completely blocked CXCL8 release. Furthermore, a heptane-soluble (non-polar) extract of DEP induced both IL-6 and CXCL8 release, whereas a PBS-soluble (highly polar) extract induced only IL-6. Thus, pro-inflammatory responses in DEP-exposed epithelial cells appear to be the result of both reactive oxygen species and receptor signaling, mediated through combinatorial effects between both non-polar and polar constituents adhered to the particle surface. PMID:26160521

  3. Pentameric Thiophene-Based Ligands that Spectrally Discriminate Amyloid-? and Tau Aggregates Display Distinct Solvatochromism and Viscosity-Induced Spectral Shifts

    PubMed Central

    Simon, Rozalyn A; Shirani, Hamid; Åslund, K O Andreas; Bäck, Marcus; Haroutunian, Vahram; Gandy, Sam; Nilsson, K Peter R

    2014-01-01

    A wide range of neurodegenerative diseases are characterized by the deposition of multiple protein aggregates. Ligands for molecular characterization and discrimination of these pathological hallmarks are thus important for understanding their potential role in pathogenesis as well as for clinical diagnosis of the disease. In this regard, luminescent conjugated oligothiophenes (LCOs) have proven useful for spectral discrimination of amyloid-beta (A?) and tau neurofibrillary tangles (NFTs), two of the pathological hallmarks associated with Alzheimer’s disease. Herein, the solvatochromism of a library of anionic pentameric thiophene-based ligands, as well as their ability to spectrally discriminate A? and tau aggregates, were investigated. Overall, the results from this study identified distinct solvatochromic and viscosity-dependent behavior of thiophene-based ligands that can be applied as indices to direct the chemical design of improved LCOs for spectral separation of A? and tau aggregates in brain tissue sections. The results also suggest that the observed spectral transitions of the ligands are due to their ability to conform by induced fit to specific microenvironments within the binding interface of each particular protein aggregate. We foresee that these findings might aid in the chemical design of thiophene-based ligands that are increasingly selective for distinct disease-associated protein aggregates. PMID:25111601

  4. Collision-induced emission of singlet oxygen in the visible spectral region at temperatures of 90-315 K

    NASA Astrophysics Data System (ADS)

    Zagidullin, M. V.; Svistun, M. I.; Khvatov, N. A.; Insapov, A. S.

    2014-04-01

    Collision-induced emission of singlet oxygen molecules is studied using spectrometers calibrated for absolute spectral sensitivity. The collision-induced emission-rate constants at wavelengths of 479, 514, 577, 634, and 703 nm are determined within the temperature range 90-315 K. It is found that the intensities of the emission bands increase with decreasing temperature below 100 K. The interrelation between the collision-induced emission-rate constants and the intensities of the collision-induced absorption bands is discussed. The Einstein coefficients for spontaneous emission of excited free O2: O2 complexes are estimated.

  5. Electric field-induced polarization rotation and ultrahigh piezoelectricity in PbTiO3

    NASA Astrophysics Data System (ADS)

    Ma, Wenhui; Hao, Aize

    2014-03-01

    Polarization rotation, phase changes, and piezoelectric property of PbTiO3 under high electric field have been investigated using a Landau-Ginzburg-Devonshire phenomenological approach. Electric field versus temperature phase diagram has been constructed. Tetragonal (T)-monoclinic (MA)-rhombohedral (R) phase transition occurs when electric field is applied along pseudo-cubic [111] axis, and piezoelectric coefficient d33 is remarkably enhanced near the critical electric field for MA-R transition. With electric field applied along pseudo-cubic [011] axis, the polarization rotation involves the other two monoclinic phases (MB and MC), and ultrahigh d33 over 8000 pC/N has been found at the monoclinic-orthorhombic (M-O) transition region. The critical field for M-O transition (˜1000 MV/m) can be greatly lowered under hydrostatic pressure. Based on the reported strain gradient induced polarization rotation in epitaxial film, flexoelectric coefficient ?12 of PbTiO3 is estimated to be ˜156-312 nC/m at room temperature.

  6. 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).

  7. 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.

  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. 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.

  10. 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.

  11. Self-Induced Polar Order of Active Brownian Particles in a Harmonic Trap

    NASA Astrophysics Data System (ADS)

    Hennes, Marc; Wolff, Katrin; Stark, Holger

    2014-06-01

    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 ?(p)˜exp(Apz) 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.

  12. 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)

  13. 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 ?m) was observed during maximum accommodation. In the 4 mm×4 mm macular area centered at the fovea, we did not find a significant quadrant-dependent difference in retinal volume change, which indicates that neither retinal stretching nor distortion was quadrant-dependent during accommodation. We speculate that the changes in RT with maximum accommodation resulted from accommodation-induced ciliary muscle contractions.

  14. 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.

  15. Chemically induced dynamic nuclear polarization studies of guanosine in nucleotides, dinucleotides, and oligonucleotides

    SciTech Connect

    McCord, E.F.; Morden, K.M.; Pardi, A.; Tinoco, I. Jr.; Boxer, S.G.

    1984-04-24

    The nuclear magnetic resonance (NMR) technique of chemically induced dynamic nuclear polarization (CIDNP) has been used to study the reactions between photoexcited flavins and a wide variety of nucleotides, dinucleotides, and oligonucleotides. The greatest emphasis is placed on the purine nucleosides adenosine (A), inosine (I), and guanosine (G), particularly guanosine. The presence of G suppresses the CIDNP effect for A, although A by itself shows very strong CIDNP. Very intense CIDNP signals are observed for the H8 proton in G-containing mononucleotides, but no nuclear polarization is detected for the sugar H1' proton. In contrast, both H8 and H1' protons exhibit CIDNP for G in a wide range of dinucleotides and higher oligonucleotides. Several possible mechanisms are analyzed to explain the H1' polarization, and it is concluded that the sugar H1' proton probably obtains spin density through interaction with guanine nitrogen 3. The proximity of the H1' proton to N3 depends explicity on the glycosidic torsion angle, chi. CIDNP studies of several model compounds in which chi is fixed are consistent with this suggestion. CIDNP for the self-complementary tetramer ApGpCpU was studied as a function of temperature. Strong CIDNP from G is only observed at temperatures above the double-strand melting temperature, suggesting that CIDNP is only detected in single-stranded regions, where the base is accessible to solvent. The use of brominated riboflavin as the photoreagent in place of riboflavin is shown to selectively invert the sign of A, I, and 1-methylguanosine polarization, providing a convenient method for distinguishing the NMR spectra of these residues in complex oligonucleotides.

  16. 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 two satellites would be adjusted to allow simultaneous observations of the overlapping zone viewed from the two parallel orbits of the twin satellites. Using twin satellites instead of a single satellite would allow measurements in a more complete range of scattering angles. A MAUVE/SWIPE satellite mission would improve significantly the accuracy of ocean color observations from space, and will extend the retrieval of ocean optical properties to the ultra-violet, where they become very sensitive to detritus material and dissolved organic matter. It would also provide a complete description of the scattering and absorption properties of aerosol particles, as well as their size distribution and vertical distribution. Over land, the retrieved bidirectional reflectance function would allow a better classification of terrestrial vegetation and discrimination of surface types. The twin satellite concept, by providing stereoscopic capability, would offer the possibility to analyze the three-dimensional structure and radiative properties of cloud fields.

  17. Reflection-induced spectral changes of the pulsed radiation emitted by a point source S. H. Wiersma,1

    E-print Network

    Visser, Taco D.

    Reflection-induced spectral changes of the pulsed radiation emitted by a point source S. H. Wiersma calculate the field emitted by a pulsed point source above a planar interface. It is found that the observed by a pulsed point source. Our analysis is carried out in the time domain, and yields analyti- cal expressions

  18. A Comparison of Propofol- and Dexmedetomidine-induced Electroencephalogram Dynamics Using Spectral and Coherence Analysis

    PubMed Central

    Akeju, Oluwaseun; Pavone, Kara J.; Westover, M. Brandon; Vazquez, Rafael; Prerau, Michael J.; Harrell, Priscilla G.; Hartnack, Katharine E.; Rhee, James; Sampson, Aaron L.; Habeeb, Kathleen; Lei, Gao; Pierce, Eric T.; Walsh, John L.; Brown, Emery N.; Purdon, Patrick L.

    2014-01-01

    Background Electroencephalogram patterns observed during sedation with dexmedetomidine appear similar to those observed during general anesthesia with propofol. This is evident with the occurrence of slow (0.1–1 Hz), delta (1–4 Hz), propofol-induced alpha (8–12 Hz), and dexmedetomidine-induced spindle (12–16 Hz) oscillations. However, these drugs have different molecular mechanisms and behavioral properties, and are likely accompanied by distinguishing neural circuit dynamics. Methods We measured 64-channel electroencephalogram under dexmedetomidine (n = 9) and propofol (n = 8) in healthy volunteers, 18–36 years of age. We administered dexmedetomidine with a 1mcg/kg loading bolus over 10 minutes, followed by a 0.7mcg/kg/hr infusion. For propofol, we used a computer controlled infusion to target the effect-site concentration gradually from and 0 µg/mL to 5 µg/mL. Volunteers listened to auditory stimuli and responded by button-press to determine unconsciousness. We analyzed the electroencephalogram using multitaper spectral and coherence analysis. Results Dexmedetomidine was characterized by spindles with maximum power and coherence at ~13 Hz, (mean±std; power, ?10.8dB±3.6; coherence, 0.8±0.08), while propofol was characterized with frontal alpha oscillations with peak frequency at ~11 Hz (power, 1.1dB±4.5; coherence, 0.9±0.05). Notably, slow oscillation power during a general anesthetic state under propofol (power, 13.2dB±2.4) was much larger than during sedative states under both propofol (power, ?2.5dB±3.5) and dexmedetomidine (power, ?0.4dB±3.1). Conclusion Our results indicate that dexmedetomidine and propofol place patients into different brain states, and suggests that propofol enables a deeper state of unconsciousness by inducing large amplitude slow oscillations that produce prolonged states of neuronal silence. PMID:25187999

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

    PubMed

    Ievlev, Anton V; Alikin, Denis O; Morozovska, Anna N; Varenyk, Olexander V; Eliseev, Eugene A; Kholkin, Andrei L; Shur, Vladimir Ya; Kalinin, Sergei V

    2015-01-27

    Polarization switching in ferroelectric materials is governed by a delicate interplay between bulk polarization dynamics and screening processes at surfaces and domain walls. Here we explore the mechanism of tip-induced polarization switching at nonpolar cuts of uniaxial ferroelectrics. In this case, the in-plane component of the polarization vector switches, allowing for detailed observations of the resultant domain morphologies. We observe a surprising variability of resultant domain morphologies stemming from a fundamental instability of the formed charged domain wall and associated electric frustration. In particular, we demonstrate that controlling the vertical tip position allows the polarity of the switching to be controlled. This represents a very unusual form of symmetry breaking where mechanical motion in the vertical direction controls the lateral domain growth. The implication of these studies for ferroelectric devices and domain wall electronics are discussed. PMID:25506745

  20. 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.

  1. 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 IFN?, 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

  2. 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.

  3. 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.

  4. 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

  5. Human B cells induce dendritic cell maturation and favour Th2 polarization by inducing OX-40 ligand.

    PubMed

    Maddur, Mohan S; Sharma, Meenu; Hegde, Pushpa; Stephen-Victor, Emmanuel; Pulendran, Bali; Kaveri, Srini V; Bayry, Jagadeesh

    2014-01-01

    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

  6. 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

  7. A simple inversion of induced-polarization data collected in the Haenam area of Korea

    NASA Astrophysics Data System (ADS)

    Jang, Hannuree; Park, Samgyu; Kim, Hee Joon

    2014-02-01

    We develop a two-stage method to invert induced polarization (IP) data. First, DC resistivity data are inverted to recover a background resistivity that is used to generate a sensitivity matrix for the IP inversion. The second stage accepts the background resistivity as the true resistivity of the medium and attempts to find a polarizability that satisfies the IP data. This is done by linearizing the equations for the background resistivity to produce a linear inverse problem that can be solved for the distribution of the subsurface polarizability. Smoothness and base-model constraints are used to stabilize the IP inversion process. These regularization methods are validated by inverting both synthetic and field data obtained in the Haenam epithermal mineralized area, Korea. As a result, the IP anomaly recovered from the base-model constraint indicates that fine-grained pyrite is disseminated in a shallow zone beneath the ridge of this site, which is confirmed by core samples.

  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. 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.

  10. 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.

  11. Orthogonal polarization mode coupling for pure twisted polarization maintaining fiber Bragg gratings.

    PubMed

    Yang, Fei; Fang, Zujie; Pan, Zhengqing; Ye, Qing; Cai, Haiwen; Qu, Ronghui

    2012-12-17

    Spectral characteristics of orthogonal polarization mode coupling for pure twisted polarization maintaining fiber Bragg gratings (PM-FBG) are proposed and analyzed experimentally and theoretically. Different from the polarization mode coupling in PM-FBG due to side pressure, a resonant peak at the middle of two orthogonal polarization modes is found when the PM-FBG is twisted purely which is attributed to the cross coupling of polarization modes. Its intensity increases with the twisting rate. A new coupled mode equation is built to describe the pure twist polarization mode coupling, in which both the normal strain induced by strain-applied parts and the tangential strain induced by twisting are taken into consideration and expressed in a unified coordinate. The novel phenomenon and its explanation are believed to be helpful for PM-FBG applications in fiber sensor and laser technologies. PMID:23263124

  12. 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 with depths of exploration ranging from 150 to 450 m. The sites included shallow geothermal sites near Reno Nevada, Pomarance Italy, and Volterra Italy; a mineral exploration site near Timmins Quebec; and a landslide investigation near Vajont Dam in northern Italy. These sites provided a series of challenges in survey design and deployment including some extremely difficult terrain and a broad range of background resistivity and induced values. Despite these challenges, comparison of multi-source results to resistivity and induced polarization data collection with more traditional methods support the thesis that the multi-source approach is capable of providing substantial improvements in both depth of penetration and resolution over conventional approaches.

  13. 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.

  14. 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.

  15. Self-screening of the quantum confined Stark effect by the polarization induced bulk charges in the quantum barriers

    E-print Network

    Demir, Hilmi Volkan

    Self-screening of the quantum confined Stark effect by the polarization induced bulk charges in the quantum barriers Zi-Hui Zhang, Wei Liu, Zhengang Ju, Swee Tiam Tan, Yun Ji, Zabu Kyaw, Xueliang Zhang); doi: 10.1063/1.4883894 View online: http://dx.doi.org/10.1063/1.4883894 View Table of Contents: http

  16. 3-D inversion of induced polarization data in wavelet domain and Yaoguo Li, Department of Geophysics, Colorado School of Mines

    E-print Network

    of Geophysics, Colorado School of Mines Summary We develop an algorithm of constrained inversion of IP data3-D inversion of induced polarization data in wavelet domain Yaping Zhu and Yaoguo Li, Department for recovering 3D chargeability in the wavelet do- main. The inversion is regularized directly by using a scale

  17. Electron transport through molecules: Gate-induced polarization and potential shift San-Huang Ke,1,2

    E-print Network

    Baranger, Harold U.

    the basis of a future molecular electronics technology.1,2 To control the transport and to realize singleElectron transport through molecules: Gate-induced polarization and potential shift San-Huang Ke,1 for electron transport. For a general view, we study several systems: 1 atomic chains of C or Al sandwiched

  18. Vapor-liquid Equilibria 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

    2015-01-01

    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 quantities from the actual GCP water model.

  19. Inducible Costimulator Protein (Icos) Controls T Helper Cell Subset Polarization after Virus and Parasite Infection

    PubMed Central

    Kopf, Manfred; Coyle, Anthony J.; Schmitz, Nicole; Barner, Marijke; Oxenius, Annette; Gallimore, Awen; Gutierrez-Ramos, Jose-Carlos; Bachmann, Martin F.

    2000-01-01

    It has been shown that certain pathogens can trigger efficient T cell responses in the absence of CD28, a key costimulatory receptor expressed on resting T cells. Inducible costimulator protein (ICOS) is an inducible costimulator structurally and functionally related to CD28. Here, we show that in the absence of CD28 both T helper cell type 1 (Th1) and Th2 responses were impaired but not abrogated after infection with lymphocytic choriomeningitis virus (LCMV), vesicular stomatitis virus (VSV), and the nematode Nippostrongylus brasiliensis. Inhibition of ICOS in CD28-deficient mice further reduced Th1/Th2 polarization. Blocking of ICOS alone had a limited but significant capacity to downregulate Th subset development. In contrast, cytotoxic T lymphocyte (CTL) responses, which are regulated to a minor and major extent by CD28 after LCMV and VSV infection, respectively, remained unaffected by blocking ICOS. Together, our results demonstrate that ICOS regulates both CD28-dependent and CD28-independent CD4+ subset (Th1 and Th2) responses but not CTL responses in vivo. PMID:10880526

  20. 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

  1. 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

  2. Effect of smoothing by spectral dispersion on flow induced laser beam deflection: The random phase modulation scheme

    SciTech Connect

    Rose, H.A.; Ghosal, S.

    1998-03-01

    Analytical results are presented for the effect of random phase modulated smoothing by spectral dispersion on flow induced laser beam deflection. It is shown that in the limit of a large number of color cycles, N{sub cc}, the effect is identical to that of the induced spatial incoherence method of temporal smoothing. For small N{sub cc}, the beam deflection rate may be significantly larger in the direction perpendicular to the dispersion, than in the parallel direction. {copyright} {ital 1998 American Institute of Physics.}

  3. 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 transport occurring under natural hydraulic conditions was monitored with resistivity imaging. IP improved characterization of the hydrogeologic framework but was of limited value in monitoring salt transport in these environments.

  4. 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 ?t (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.

  5. 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

  6. Dynamically induced hemispheric differences in the seasonal evolution of the summer polar mesopause

    NASA Astrophysics Data System (ADS)

    Becker, Erich; Luebken, Franz-Josef; Knoepfel, Rahel

    We analyze the seasonal cycle of the summer polar mesopause with regard to Interhemispheric and Intrahemispheric Coupling. Our basis is a long-term simulation with a new middle atmosphere GCM of intermediate complexity, including an explicit calculation of the radiation budget and the tropospheric moisture cycle. Hemispheric differences are solely induced by different tropospheric surface conditions (orography and land-sea contrasts). In particular, the prescribed stratospheric ozone and the solar insolation are assumed to be equivalent for both hemispheres. The same holds for the launch level parameters of non-orographic gravity waves. With this setup we find a pronounced hemispheric asymmetry in the seasonal evolution of the summer mesopause. This can be traced back to hemispheric differences in tropospheric planetary waves and its subsequent effects on temperature, zonal wind, and gravity-wave breaking in the middle atmosphere. The consequences are that, prior to solstice, the southern summer mesopause is higher than its northern hemispheric counterpart which is caused by Intrahemispheric Coupling. After solstice, the southern summer mesopause is warmer and at a lower altitude when compared to the corresponding situation in the northern hemisphere. This difference results from Interhemispheric Coupling. The simulated hemispheric differences correspond to recent ground-based temperature measurements at Antarctica in comparison to corresponding data from the northern hemisphere. Since complex climate models that resolve the MLT are not necessarily consistent with the observed hemispheric asymmetry, it is tempting to assume that different launch level parameters of extratropical non-orographic gravity waves need to be considered for the two hemispheres. One hint in this direction is obtained from the present model if we take the annual variation of the solar constant into account. Then the launch spectrum needs to be shifted to higher frequencies in the southern hemisphere in order to reproduce the hemispheric differences in the seasonal evolution of the summer polar mesopause.

  7. Dynamically induced hemispheric differences in the seasonal cycle of the summer polar mesopause

    NASA Astrophysics Data System (ADS)

    Becker, Erich; Knöpfel, Rahel; Lübken, Franz-Josef

    2015-07-01

    A mechanistic atmospheric general circulation model from the surface up to the mesopause region with explicit representations of radiation and the tropospheric moisture cycle is employed to study hemispheric differences during the summer season with focus on dynamical coupling processes in the middle atmosphere. Hemispheric differences are imposed in the model by the geographical distributions of surface parameters. Consistent with reanalyses, we find that prior to summer solstice, the polar troposphere and lower stratosphere are significantly colder in the southern hemisphere than in the northern hemisphere. This induces vertically altering wind and temperature differences between the two hemispheres that are consistent with the recently detected Intrahemispheric Coupling mechanism. In particular, in the southern hemisphere the model yields a high mesopause around solstice which propagates downward over the season. Such a behavior has recently been observed by lidar measurements in Antarctica and is different from the northern hemisphere where the polar mesopause stays at approximately the same altitude over the summer season. After summer solstice, the mesopause is significantly warmer in the southern hemisphere, which is in accordance with Interhemispheric Coupling, i.e., the hemispheric differences after summer solstice are influenced by the strong planetary Rossby-wave activity in the northern stratosphere during boreal winter. Also enhanced filtering of eastward GWs in the southern troposphere contributes to the behavior after solstice. Orbital eccentricity is found to enhance the importance of Intrahemispheric Coupling. A more quantitative description of the hemispheric differences in the stratosphere and lower mesosphere as seen in reanalyses is obtained by adding an additional westward gravity drag in the southern stratosphere. The vertical coupling mechanisms responsible for hemispheric differences apply also in this case.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. GAMMA-RAY POLARIZATION INDUCED BY COLD ELECTRONS VIA COMPTON PROCESSES

    SciTech Connect

    Chang Zhe; Jiang Yunguo; Lin Hainan E-mail: jiangyg@ihep.ac.cn

    2013-05-20

    The polarization measurement is an important tool to probe the prompt emission mechanism in gamma-ray bursts (GRBs). The synchrotron photons can be scattered by cold electrons in the outflow via Compton scattering (CS) processes. The observed polarization depends on both the photon energy and the viewing angle. With the typical bulk Lorentz factor {Gamma} {approx} 200, photons with energy E > 10 MeV tend to have smaller polarization than photons with energy E < 1 MeV. At the right viewing angle, i.e., {theta} {approx} {Gamma}{sup -1}, the polarization achieves its maximal value, and the polarization angle changes 90 Degree-Sign relative to the initial polarization direction. Thus, the synchrotron radiation plus CS model can naturally explain the 90 Degree-Sign change of the polarization angle in GRB 100826A.

  13. Excess-electron induced polarization and magnetoelectric effect in yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Kohara, Y.; Yamasaki, Y.; Onose, Y.; Tokura, Y.

    2010-09-01

    Magnetoelectric (ME) properties in yttrium iron garnet (YIG:Y3Fe5O12) , including both the first-order and second-order effects, have long been under dispute. In particular, the conflict between observations of the first-order ME effect and the centrosymmetric lattice structure has remained as a puzzling issue. As a key to solve the problem, we found that YIG shows quantum ME relaxation; the dielectric relaxation process is correlated closely with the magnetic one and has characteristic features of quantum tunneling. An application of magnetic field enhances the dielectric relaxation strength (by 300% at 10 K with 0.5 T), which gives rise to the large second-order ME (magnetocapacitance) effect critically dependent on the magnetization direction. The temperature and magnetic-field dependence of dielectric relaxation strength is well described by the noninteracting transverse-field Ising model for the excess-electron or Fe2+ center with the quantum tunneling and spin-orbit coupling effects. We could also spectroscopically identify such a ME Fe2+ center in terms of linear dichroism under a magnetic field along the specific direction. On this basis, the fictitious first-order ME effect—the magnetic-field induced electric polarization without the presence of external electric field—as observed for the electric-field cooled sample is ascribed to the combined effect of the above large second-order ME effect and the poling induced charge accumulation. The correlation between the ME effect and the thermally stimulated depolarization current indicates that hopping electrons freeze below around 125 K and the frozen-in dipoles generate an internal electric field (i.e., an electret-like effect). Investigation of electron-compensating doping effect on dielectric relaxation phenomena gives compelling evidences that excess electrons forming Fe2+ ions play a critical role in the charge accumulation as well as in the ME effect in YIG.

  14. 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 a greater propensity for elevated rates of microbial activity, with such regions (themselves often highly localized within a larger sedimentary matrix) exerting an outsized control on contaminant (e.g. U) fate and transport.

  15. LabVIEW-based control software for para-hydrogen induced polarization instrumentation.

    PubMed

    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 ((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 (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 (13)C based endogenous contrast agents used in molecular imaging. PMID:24784636

  16. LabVIEW-based control software for para-hydrogen induced polarization instrumentation

    SciTech Connect

    Agraz, Jose Grunfeld, Alexander; Li, Debiao; BIRI, Cedars Sinai Medical Center, West Hollywood, California 90048 ; 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.

  17. 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-? 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

  18. 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.

  19. 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.

  20. 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

  1. Effects of polarization azimuth in dynamics of electrically assisted light-induced gliding of nematic liquid-crystal easy axis

    NASA Astrophysics Data System (ADS)

    Dubtsov, A. V.; Shmeliova, D. V.; Pasechnik, S. V.; Kiselev, Alexei D.; Chigrinov, V. G.

    2012-04-01

    We experimentally study the reorientation dynamics of the nematic liquid crystal easy axis at photoaligned azo-dye films under the combined action of in-plane electric field and linearly polarized reorienting UV light at varying polarization azimuth, ?p. At non-zero values of the azimuth, ?p?0, as opposed to the case where the polarization vector of the light is parallel to the initial easy axis (?p=0), the easy axis reorientation was observed to be most pronounced outside the interelectrode gaps. In the regions between electrodes with non-vanishing electric field, it is found that the dynamics of reorientation slows down with ?p and the sense of easy axis rotation is independent of the sign of ?p. A generalized version of the phenomenological model that was previously developed to describe the electrically assisted light-induced gliding is applied to interpret the experimental data.

  2. CTLA-4Ig immunotherapy of obesity-induced insulin resistance by manipulation of macrophage polarization in adipose tissues

    SciTech Connect

    Fujii, Masakazu; Inoguchi, Toyoshi; Innovation Center for Medical Redox Navigation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 ; Batchuluun, Battsetseg; Sugiyama, Naonobu; Kobayashi, Kunihisa; Sonoda, Noriyuki; Innovation Center for Medical Redox Navigation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 ; 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 ?, peroxisome proliferator-activated receptor ?, 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.

  3. Telmisartan prevention of LPS-induced microglia activation involves M2 microglia polarization via CaMKK?-dependent AMPK activation.

    PubMed

    Xu, Yuan; Xu, Yazhou; Wang, Yurong; Wang, Yunjie; He, Ling; Jiang, Zhenzhou; Huang, Zhangjian; Liao, Hong; Li, Jia; Saavedra, Juan M; Zhang, Luyong; Pang, Tao

    2015-11-01

    Brain inflammation plays an important role in the pathophysiology of many psychiatric and neurological diseases. During brain inflammation, microglia cells are activated, producing neurotoxic molecules and neurotrophic factors depending on their pro-inflammatory M1 and anti-inflammatory M2 phenotypes. It has been demonstrated that Angiotensin II type 1 receptor blockers (ARBs) ameliorate brain inflammation and reduce M1 microglia activation. The ARB telmisartan suppresses glutamate-induced upregulation of inflammatory genes in cultured primary neurons. We wished to clarify whether telmisartan, in addition, prevents microglia activation through polarization to an anti-inflammatory M2 phenotype. We found that telmisartan promoted M2 polarization and reduced M1 polarization in LPS-stimulated BV2 and primary microglia cells, effects partially dependent on PPAR? activation. The promoting effects of telmisartan on M2 polarization, were attenuated by an AMP-activated protein kinase (AMPK) inhibitor or AMPK knockdown, indicating that AMPK activation participates on telmisartan effects. Moreover, in LPS-stimulated BV2 cells, telmisartan enhancement of M2 gene expression was prevented by the inhibitor STO-609 and siRNA of calmodulin-dependent protein kinase kinase ? (CaMKK?), an upstream kinase of AMPK. Furthermore, telmisartan enhanced brain AMPK activation and M2 gene expression in a mouse model of LPS-induced neuroinflammation. In addition, telmisartan reduced the LPS-induced sickness behavior in this in vivo model, and this effect was prevented by prior administration of an AMPK inhibitor. Our results indicate that telmisartan can be considered as a novel AMPK activator, suppressing microglia activation by promoting M2 polarization. Telmisartan may provide a novel, safe therapeutic approach to treat brain disorders associated with enhanced inflammation. PMID:26188187

  4. Tip-induced domain growth on the non-polar cuts of lithium niobate single-crystals

    NASA Astrophysics Data System (ADS)

    Alikin, D. O.; Ievlev, A. V.; Turygin, A. P.; Lobov, A. I.; Kalinin, S. V.; Shur, V. Ya.

    2015-05-01

    Currently, ferroelectric materials with designed domain structures are considered as a perspective material for new generation of photonic, data storage, and data processing devices. Application of external electric field is the most convenient way of the domain structure formation. Lots of papers are devoted to the investigation of domain kinetics on polar surface of crystals while the forward growth remains one of the most mysterious stages due to lack of experimental methods allowing to study it. Here, we performed tip-induced polarization reversal on X- and Y-non-polar cuts in single-crystal of congruent lithium niobate which allows us to study the forward growth with high spatial resolution. The revealed difference in the shape and length of domains induced on X- and Y-cuts is beyond previously developed theoretical approaches used for the theoretical consideration of the domains growth at non-polar ferroelectric surfaces. To explain experimental results, we used kinetic approach with anisotropy of screening efficiency along different crystallographic directions.

  5. Tip-induced domain growth on the non-polar cuts of lithium niobate single-crystals

    SciTech Connect

    Alikin, D. O.; Turygin, A. P.; Lobov, A. I.; Shur, V. Ya.; Ievlev, A. V.; Kalinin, S. V.

    2015-05-04

    Currently, ferroelectric materials with designed domain structures are considered as a perspective material for new generation of photonic, data storage, and data processing devices. Application of external electric field is the most convenient way of the domain structure formation. Lots of papers are devoted to the investigation of domain kinetics on polar surface of crystals while the forward growth remains one of the most mysterious stages due to lack of experimental methods allowing to study it. Here, we performed tip-induced polarization reversal on X- and Y-non-polar cuts in single-crystal of congruent lithium niobate which allows us to study the forward growth with high spatial resolution. The revealed difference in the shape and length of domains induced on X- and Y-cuts is beyond previously developed theoretical approaches used for the theoretical consideration of the domains growth at non-polar ferroelectric surfaces. To explain experimental results, we used kinetic approach with anisotropy of screening efficiency along different crystallographic directions.

  6. Interface-induced chiral domain walls, spin spirals and skyrmions revealed by spin-polarized scanning tunneling microscopy.

    PubMed

    von Bergmann, Kirsten; Kubetzka, André; Pietzsch, Oswald; Wiesendanger, Roland

    2014-10-01

    The spin textures of ultra-thin magnetic layers exhibit surprising variety. The loss of inversion symmetry at the interface of the magnetic layer and substrate gives rise to the so-called Dzyaloshinskii-Moriya interaction which favors non-collinear spin arrangements with unique rotational sense. Here we review the application of spin-polarized scanning tunneling microscopy to such systems, which has led to the discovery of interface-induced chiral domain walls and spin spirals. Recently, different interface-driven skyrmion lattices have been found, and the writing as well as the deleting of individual skyrmions based on local spin-polarized current injection has been demonstrated. These interface-induced non-collinear magnetic states offer new exciting possibilities to study fundamental magnetic interactions and to tailor material properties for spintronic applications. PMID:25214495

  7. Evolution of the linear-polarization-angle-dependence of the radiation-induced magnetoresistance-oscillations with microwave power

    SciTech Connect

    Ye, Tianyu; Mani, R. G.; Wegscheider, W.

    2014-11-10

    We examine the role of the microwave power in the linear polarization angle dependence of the microwave radiation induced magnetoresistance oscillations observed in the high mobility GaAs/AlGaAs two dimensional electron system. The diagonal resistance R{sub xx} was measured at the fixed magnetic fields of the photo-excited oscillatory extrema of R{sub xx} as a function of both the microwave power, P, and the linear polarization angle, ?. Color contour plots of such measurements demonstrate the evolution of the lineshape of R{sub xx} versus ? with increasing microwave power. We report that the non-linear power dependence of the amplitude of the radiation-induced magnetoresistance oscillations distorts the cosine-square relation between R{sub xx} and ? at high power.

  8. Interface-induced chiral domain walls, spin spirals and skyrmions revealed by spin-polarized scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    von Bergmann, Kirsten; Kubetzka, André; Pietzsch, Oswald; Wiesendanger, Roland

    2014-10-01

    The spin textures of ultra-thin magnetic layers exhibit surprising variety. The loss of inversion symmetry at the interface of the magnetic layer and substrate gives rise to the so-called Dzyaloshinskii-Moriya interaction which favors non-collinear spin arrangements with unique rotational sense. Here we review the application of spin-polarized scanning tunneling microscopy to such systems, which has led to the discovery of interface-induced chiral domain walls and spin spirals. Recently, different interface-driven skyrmion lattices have been found, and the writing as well as the deleting of individual skyrmions based on local spin-polarized current injection has been demonstrated. These interface-induced non-collinear magnetic states offer new exciting possibilities to study fundamental magnetic interactions and to tailor material properties for spintronic applications.

  9. 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 RH2A? 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 RH2A? 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

  10. Mycobacterium tuberculosis-Induced Polarization of Human Macrophage Orchestrates the Formation and Development of Tuberculous Granulomas In Vitro

    PubMed Central

    Guo, Yang; Chen, Jie; Xiong, Guoliang; Peng, Yiping; Ye, Jianqing; Li, Junming

    2015-01-01

    The tuberculous granuloma is an elaborately organized structure and one of the main histological hallmarks of tuberculosis. Macrophages, which are important immunologic effector and antigen-presenting cells, are the main cell type found in the tuberculous granuloma and have high plasticity. Macrophage polarization during bacterial infection has been elucidated in numerous recent studies; however, macrophage polarization during tuberculous granuloma formation and development has rarely been reported. It remains to be clarified whether differences in the activation status of macrophages affect granuloma formation. In this study, the variation in macrophage polarization during the formation and development of tuberculous granulomas was investigated in both sections of lung tissues from tuberculosis patients and an in vitro tuberculous granuloma model. The roles of macrophage polarization in this process were also investigated. Mycobacterium tuberculosis (M. tuberculosis) infection was found to induce monocyte-derived macrophage polarization. In the in vitro tuberculous granuloma model, macrophage transformation from M1 to M2 was observed over time following M. tuberculosis infection. M2 macrophages were found to predominate in both necrotic and non-necrotic granulomas from tuberculosis patients, while both M1 and M2 polarized macrophages were found in the non-granulomatous lung tissues. Furthermore, it was found that M1 macrophages promote granuloma formation and macrophage bactericidal activity in vitro, while M2 macrophages inhibit these effects. The findings of this study provide insights into the mechanism by which M. tuberculosis circumvents the host immune system as well as a theoretical foundation for the development of novel tuberculosis therapies based on reprogramming macrophage polarization. PMID:26091535

  11. In-plane electric field induced by polarization and lateral photovoltaic effect in a-plane GaN

    NASA Astrophysics Data System (ADS)

    Hu, Weiguo; Ma, Bei; Li, Dabing; Miyake, Hideto; Hiramatsu, Kazumasa

    2009-06-01

    A lateral photovoltaic effect was observed in a-plane GaN films grown on r-plane sapphire at room temperature. Under various light sources illuminations, contacts along the c-axis exhibited about ten times the photovoltage than those along the m-axis, which kept linear relationship with the illumination intensity. It was attributed to anisotropic in-plane electrical field induced by the intrinsic spontaneous/piezoelectric polarization, which spatially separated photogenerated carriers to produce the photovoltage.

  12. J. Non-Newtonian Fluid Mech. 134 (2006) 3343 Flow-induced anisotropy in polar ice and related

    E-print Network

    Gagliardini, Olivier

    2006-01-01

    . To construct ice-sheet flow models aimed at obtaining ac- curate information on the origin and the age of iceJ. Non-Newtonian Fluid Mech. 134 (2006) 33­43 Flow-induced anisotropy in polar ice and related ice of ice can be orientated by using only one single vector, i.e. its c-axis. Such a characteristic allows

  13. Large ferroelectric polarization in the new double perovskite NaLaMnWO$_{6}$ induced by non-polar instabilities

    E-print Network

    Fukushima, T; Picozzi, S; Perez-Mato, J M

    2011-01-01

    Based on density functional theory calculations and group theoretical analysis, we have studied NaLaMnWO$_{6}$ compound which has been recently synthesized [Phys. Rev. B 79, 224428 (2009)] and belongs to the $AA'BB'{\\rm O}_{6}$ family of double perovskites. At low temperature, the structure has monoclinic $P2_{1}$ symmetry, with layered ordering of the Na and La ions and rocksalt ordering of Mn and W ions. The Mn atoms show an antiferromagnetic (AFM) collinear spin ordering, and the compound has been reported as a potential multiferroic. By comparing the low symmetry structure with a parent phase of $P4/nmm$ symmetry, two distortion modes are found dominant. They correspond to MnO$_{6}$ and WO$_{6}$ octahedron \\textit{tilt} modes, often found in many simple perovskites. While in the latter these common tilting instabilities yield non-polar phases, in NaLaMnWO$_{6}$ the additional presence of the $A$-$A^{'}$ cation ordering is sufficient to make these rigid unit modes as a source of the ferroelectricity. Throu...

  14. Excitation mechanisms in 1 mJ picosecond laser induced low pressure He plasma and the resulting spectral quality enhancement

    NASA Astrophysics Data System (ADS)

    Idris, Nasrullah; Lahna, Kurnia; Abdulmadjid, Syahrun Nur; Ramli, Muliadi; Suyanto, Hery; Marpaung, Alion Mangasi; Pardede, Marincan; Jobiliong, Eric; Hedwig, Rinda; Suliyanti, Maria Margaretha; Lie, Zener Sukra; Lie, Tjung Jie; Kagawa, Kiichiro; Tjia, May On; Kurniawan, Koo Hendrik

    2015-06-01

    We report in this paper the results of an experimental study on the spectral and dynamical characteristics of plasma emission induced by 1 mJ picoseconds (ps) Nd-YAG laser using spatially resolved imaging and time resolved measurement of the emission intensities of copper sample. This study has provided the experimental evidence concerning the dynamical characteristics of the excitation mechanisms in various stages of the plasma formation, which largely consolidate the basic scenarios of excitation processes commonly accepted so far. However, it is also clearly shown that the duration of the shock wave excitation process induced by ps laser pulses is much shorter than those observed in laser induced breakdown spectroscopy employing nanosecond laser at higher output energy. This allows the detection of atomic emission due exclusively to He assisted excitation in low pressure He plasma by proper gating of the detection time. Furthermore, the triplet excited state associated with He I 587.6 nm is shown to be the one most likely involved in the process responsible for the excellent spectral quality as evidenced by its application to spectrochemical analysis of a number of samples. The use of very low energy laser pulses also leads to minimal destructive effect marked by the resulted craters of merely about 10 ?m diameter and only 10 nm deep. It is especially noteworthy that the excellent emission spectrum of deuterium detected from D-doped titanium sample is free of spectral interference from the undesirable ubiquitous water molecules without a precleaning procedure as applied previously and yielding an impressive detection limit of less than 10 ?g/g. Finally, the result of this study also shows a promising application to depth profiling of impurity distribution in the sample investigated.

  15. Excitation mechanisms in 1?mJ picosecond laser induced low pressure He plasma and the resulting spectral quality enhancement

    SciTech Connect

    Idris, Nasrullah; Lahna, Kurnia; Abdulmadjid, Syahrun Nur; Ramli, Muliadi; Suyanto, Hery; Marpaung, Alion Mangasi; Pardede, Marincan; Jobiliong, Eric; Hedwig, Rinda; Lie, Zener Sukra; Lie, Tjung Jie; Kurniawan, Koo Hendrik; Tjia, May On

    2015-06-14

    We report in this paper the results of an experimental study on the spectral and dynamical characteristics of plasma emission induced by 1 mJ picoseconds (ps) Nd-YAG laser using spatially resolved imaging and time resolved measurement of the emission intensities of copper sample. This study has provided the experimental evidence concerning the dynamical characteristics of the excitation mechanisms in various stages of the plasma formation, which largely consolidate the basic scenarios of excitation processes commonly accepted so far. However, it is also clearly shown that the duration of the shock wave excitation process induced by ps laser pulses is much shorter than those observed in laser induced breakdown spectroscopy employing nanosecond laser at higher output energy. This allows the detection of atomic emission due exclusively to He assisted excitation in low pressure He plasma by proper gating of the detection time. Furthermore, the triplet excited state associated with He I 587.6?nm is shown to be the one most likely involved in the process responsible for the excellent spectral quality as evidenced by its application to spectrochemical analysis of a number of samples. The use of very low energy laser pulses also leads to minimal destructive effect marked by the resulted craters of merely about 10??m diameter and only 10?nm deep. It is especially noteworthy that the excellent emission spectrum of deuterium detected from D-doped titanium sample is free of spectral interference from the undesirable ubiquitous water molecules without a precleaning procedure as applied previously and yielding an impressive detection limit of less than 10??g/g. Finally, the result of this study also shows a promising application to depth profiling of impurity distribution in the sample investigated.

  16. Temporal evolution of the spectral lines emission and temperatures in laser induced plasmas through characteristic parameters

    NASA Astrophysics Data System (ADS)

    Bredice, F.; Pacheco Martinez, P.; Sánchez-Aké, C.; Villagrán-Muniz, M.

    2015-05-01

    In this work, we propose an extended Boltzmann plot method to determine the usefulness of spectral lines for plasma parameter calculations. Based on the assumption that transient plasmas are under ideal conditions during an specific interval of time ?t, (i.e. thin, homogeneous and in local thermodynamic equilibrium (LTE)), the associated Boltzmann plots describe a surface in the space defined by the coordinates X = Energy, Y = Time and Z = ln (?jlIj/gjAjl), where Ij is the integrated intensity of the spectral line, gj is the statistical weight of the level j, ?jl is the wavelength of the considered line and Ajl is its transition rate. In order to express the Boltzmann plot surface in terms of a reduced set of constants Bi, and ?i, we developed as a power series of time, the logarithm of In(t)/In(t0), where In(t) is the integrated intensity of any spectral line at time t, and In(t0) at initial time. Moreover, the temporal evolution of the intensity of any spectral line and consequently the temperature of the plasma can be also expressed with these constants. The comparison of the temporal evolution of the line intensity calculated using these constants with their experimental values, can be used as a criterion for selecting useful lines in plasma analysis. Furthermore, this method can also be applied to determine self-absorption or enhancement of the spectral lines, to evaluate a possible departure of LTE, and to check or estimate the upper level energy value of any spectral line. An advantage of this method is that the value of these constants does not depend on the spectral response of the detection system, the uncertainty of the transition rates belonging to the analyzed spectral lines or any other time-independent parameters. In order to prove our method, we determined the constants Bi and ?i and therefore the Boltzmann plot surface from the temporal evolution of carbon lines obtained from a plasma generated by a Nd:YAG laser. The plasma was produced in vacuum and was observed at different distances from the target. A good agreement between the temperature calculated by the traditional Boltzmann plot and by this method was obtained.

  17. Field Test of Detection and Characterisation of Subsurface Ice using Broadband Spectral-Induced Polarisation

    E-print Network

    Stillman, David E.

    materials are dry or ice-rich, nor can it provide re- liable estimates of ice content. However containing unfrozen water. Unfortunately, both dry materials and totally frozen ice-rich materials have highField Test of Detection and Characterisation of Subsurface Ice using Broadband Spectral

  18. Airborne lidar observation of mountain-wave-induced polar stratospheric clouds during EASOE

    SciTech Connect

    Godin, S.; Megie, G.; David, C.; Haner, D. ); Flesia, C.; Emery, Y. )

    1994-06-22

    This article presents the results of airborne lidar measurements of aerosol and polar stratospheric clouds (PSC) above Kiruna. Polarization measurements allow the distinction between volcanic aerosols, and PSC. They observed PSC formations near Kiruna on December 11, 1991, extending over 100's of km west and east.

  19. Water polarization induced by thermal gradients: The extended simple point charge model (SPC/E)

    NASA Astrophysics Data System (ADS)

    Armstrong, J. A.; Bresme, F.

    2013-07-01

    We investigate the non-equilibrium response of extended simple point charge (SPC/E) water to thermal gradients. Using non-equilibrium molecular dynamics simulations, we show that SPC/E water features the thermo-polarization orientation effect, namely, water becomes polarized as a response to a thermal gradient. The polarization field increases linearly with the thermal gradient, in agreement with predictions of non-equilibrium thermodynamics theory. This observation confirms the generality of the thermo-polarization effect, first reported using the Modified Central Force Model (MCFM), and shows this physical effect is present irrespective of the water model details, in particular, dipole moment magnitude and model flexibility. The magnitude of the effect is the same for both models, although the sign of the electrostatic field is reversed in going from the MCFM to the SPC/E model. We further analyze the impact that the molecular geometry and mass distribution has on the magnitude of the polarization. Our results indicate that the thermo-polarization effect should be observed in a wide range of polar fluids, including fluids where hydrogen bonding is not present. Using various molecular models, we show that the polarization of these fluids under appropriate thermodynamic conditions can be of the same order or stronger than in water.

  20. Simultaneous electromagnetically induced transparency for two circularly polarized lasers coupled to the same linearly polarized laser in a four-level atomic system in the W scheme

    SciTech Connect

    Bahrim, Cristian; Nelson, Chris

    2011-03-15

    Electromagnetic induced transparency (EIT) can be produced in a four-level atomic system in the W scheme using a linearly polarized optical field for simultaneously slowing down two {sigma}{sup +} and {sigma}{sup -} circularly polarized optical fields. This four-level atomic system can be set up with a |{sup 1}S{sub 0}> ground state and three Zeeman levels of the |{sup 1}P{sub 1}> excited state of any alkali-metal atom placed in a weak magnetic field. We apply our W scheme to ultracold magnesium atoms for neglecting the collisional dephasing. Atomic coherences are reported after solving a density matrix master equation including radiative relaxations from Zeeman states of the |{sup 1}P{sub 1}> multiplet to the |{sup 1}S{sub 0}> ground state. The EIT feature is analyzed using the transit time between the normal dispersive region and the EIT region. The evolution of the EIT feature with the variation of the coupling field is discussed using an intuitive dressed-state representation. We analyze the sensitivity of an EIT feature to pressure broadening of the excited Zeeman states.

  1. 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 ?m) and M16 (11.8 ?m). 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

  2. Hyperoxia promotes polarization of the immune response in ovalbumin-induced airway inflammation, leading to a TH17 cell phenotype

    PubMed Central

    Nagato, Akinori C; Bezerra, Frank S; Talvani, André; Aarestrup, Beatriz J; Aarestrup, Fernando M

    2015-01-01

    Previous studies have demonstrated that hyperoxia-induced stress and oxidative damage to the lungs of mice lead to an increase in IL-6, TNF-?, and TGF-? expression. Together, IL-6 and TGF-? have been known to direct T cell differentiation toward the TH17 phenotype. In the current study, we tested the hypothesis that hyperoxia promotes the polarization of T cells to the TH17 cell phenotype in response to ovalbumin-induced acute airway inflammation. Airway inflammation was induced in female BALB/c mice by intraperitoneal sensitization and intranasal introduction of ovalbumin, followed by challenge methacholine. After the methacholine challenge, animals were exposed to hyperoxic conditions in an inhalation chamber for 24?h. The controls were subjected to normoxia or aluminum hydroxide dissolved in phosphate buffered saline. After 24?h of hyperoxia, the number of macrophages and lymphocytes decreased in animals with ovalbumin-induced airway inflammation, whereas the number of neutrophils increased after ovalbumin-induced airway inflammation. The results showed that expression of Nrf2, iNOS, T-bet and IL-17 increased after 24 of hyperoxia in both alveolar macrophages and in lung epithelial cells, compared with both animals that remained in room air, and animals with ovalbumin-induced airway inflammation. Hyperoxia alone without the induction of airway inflammation lead to increased levels of TNF-? and CCL5, whereas hyperoxia after inflammation lead to decreased CCL2 levels. Histological evidence of extravasation of inflammatory cells into the perivascular and peribronchial regions of the lungs was observed after pulmonary inflammation and hyperoxia. Hyperoxia promotes polarization of the immune response toward the TH17 phenotype, resulting in tissue damage associated with oxidative stress, and the migration of neutrophils to the lung and airways. Elucidating the effect of hyperoxia on ovalbumin-induced acute airway inflammation is relevant to preventing or treating asthmatic patients that require oxygen supplementation to reverse the hypoxemia. PMID:26417446

  3. Spectral Moments of Collision-Induced Absorption of CO2 Pairs: The Role of the Intermolecular Potential

    NASA Technical Reports Server (NTRS)

    Gruszka, Marcin; Borysow, Aleksandra

    1994-01-01

    In this paper we examine the role of the anisotropy of the intermolecular potential in the rototranslational collision-induced absorption of the CO2 pairs. Using newly developed formulas that include the effects of anisotropy of the potential to all orders, we calculate the two lowest spectral moments gamma(prime), and alpha(prime), for four different classes of C02 pair potentials and compare the results with the experimental values. We assumed only multipolar induction in the process of forming the induced dipole, with the second-order contributions included. Using a site-site LJ and a site-site semi-ab initio intermolecular potentials we were able to reproduce the experimental values of gamma(prime), and alpha(prime) moments over entire temperature range from 230 to 330 K. Also, the role of an electrostatic interaction between two C02 molecules and its impact on the spectral moments is thoroughly investigated. An isotropic core with a point quadrupole centered at each molecule is shown to be an inadequate representation of the C02-CO2 potential. Additionally, we show the results obtained with the first- and second-order perturbation theory to be more than twice too small.

  4. Three-body spectral moments for collision-induced light scattering by octahedral and tetrahedral molecules

    NASA Astrophysics Data System (ADS)

    El-Kader, M. S. A.; El-Sheikh, S. M.

    2001-04-01

    The zeroth and second moments of the three-body collision-induced light scattering spectra for SF6 and CF4 are computed at 295 k, using recent intermolecular-induced pair polarizability model. Comparisons were made with available experimental and calculated moments. The results show the very important role which is played by the choice of the potential and polarizability models.

  5. Tuning the polarization-induced free hole density in nanowires graded from GaN to AlN

    NASA Astrophysics Data System (ADS)

    Golam Sarwar, A. T. M.; Carnevale, Santino D.; Kent, Thomas F.; Yang, Fan; McComb, David W.; Myers, Roberto C.

    2015-01-01

    We report a systematic study of p-type polarization-induced doping in graded AlGaN nanowire light emitting diodes grown on silicon wafers by plasma-assisted molecular beam epitaxy. The composition gradient in the p-type base is varied in a set of samples from 0.7%Al/nm to 4.95%Al/nm corresponding to negative bound polarization charge densities of 2.2 × 1018 cm-3 to 1.6 × 1019 cm-3. Capacitance measurements and energy band modeling reveal that for gradients greater than or equal to 1.30%Al/nm, the deep donor concentration is negligible and free hole concentrations roughly equal to the bound polarization charge density are achieved up to 1.6 × 1019 cm-3 at a gradient of 4.95%Al/nm. Accurate grading lengths in the p- and n-side of the pn-junction are extracted from scanning transmission electron microscopy images and are used to support energy band calculation and capacitance modeling. These results demonstrate the robust nature of p-type polarization doping in nanowires and put an upper bound on the magnitude of deep donor compensation.

  6. Tunnel-injection quantum dot deep-ultraviolet light-emitting diodes with polarization-induced doping in III-nitride heterostructures

    SciTech Connect

    Verma, Jai Islam, S. M.; Protasenko, Vladimir; Kumar Kandaswamy, Prem; Xing, Huili; Jena, Debdeep

    2014-01-13

    Efficient semiconductor optical emitters in the deep-ultraviolet spectral window are encountering some of the most deep rooted problems of semiconductor physics. In III-Nitride heterostructures, obtaining short-wavelength photon emission requires the use of wide bandgap high Al composition AlGaN active regions. High conductivity electron (n-) and hole (p-) injection layers of even higher bandgaps are necessary for electrical carrier injection. This approach requires the activation of very deep dopants in very wide bandgap semiconductors, which is a difficult task. In this work, an approach is proposed and experimentally demonstrated to counter the challenges. The active region of the heterostructure light emitting diode uses ultrasmall epitaxially grown GaN quantum dots. Remarkably, the optical emission energy from GaN is pushed from 365?nm (3.4?eV, the bulk bandgap) to below 240?nm (>5.2?eV) because of extreme quantum confinement in the dots. This is possible because of the peculiar bandstructure and band alignments in the GaN/AlN system. This active region design crucially enables two further innovations for efficient carrier injection: Tunnel injection of carriers and polarization-induced p-type doping. The combination of these three advances results in major boosts in electroluminescence in deep-ultraviolet light emitting diodes and lays the groundwork for electrically pumped short-wavelength lasers.

  7. Interesting polarization-independent SERS detection performance induced by the rotation symmetry of multiparticle nanostructures.

    PubMed

    Feng, Chao; Zhao, Yan; Jiang, Yijian

    2016-01-29

    In this work, on the basis of finite difference time domain simulations and group theory, by employing regular nanosphere trimers as the main examples, we analyse and discuss the polarization-independent surface enhanced Raman scattering (SERS) phenomenon arising from the rotation symmetry of coined metallic nanomultimers. The results demonstrate why the rotationally symmetrical nanomultimers can show polarization-independent SERS performance. Because of the dramatically hybridized polarization-independent SERS performance over the whole 360° range, rotationally symmetrical coined metal nanomultimers, such as regular trimers, regular triangular tetramers and regular pentamers, are reliable and reproducible SERS substrates, which have the potential for convenient and flexible practical SERS detection without the need for optimally incident polarization outside the laboratory setting. PMID:26655083

  8. Microtubule-Induced Pins/Gai Cortical Polarity in Drosophila Neuroblasts

    E-print Network

    Doe, Chris

    cortical polarity in yeast, but few ex- amples are known in metazoans. We show that astral microtubules-size asymmetry, and distinct sibling fates. Khc-73 localizes to astral microtubule plus ends, and Dlg/Khc-73

  9. Enhanced carrier injection in InGaN/GaN multiple quantum wells LED with polarization-induced electron blocking barrier

    NASA Astrophysics Data System (ADS)

    Li, Chengguo; Liu, Hongfei; Chua, Soo Jin

    2016-03-01

    In this report, we designed a light emitting diode (LED) structure in which an N-polar p-GaN layer is grown on top of Ga-polar In0.1Ga0.9N/GaN quantum wells (QWs) on an n-GaN layer. Numerical simulation reveals that the large polarization field at the polarity inversion interface induces a potential barrier in the conduction band, which can block electron overflow out of the QWs. Compared with a conventional LED structure with an Al0.2Ga0.8N electron blocking layer (EBL), the proposed LED structure shows much lower electron current leakage, higher hole injection, and a significant improvement in the internal quantum efficiency (IQE). These results suggest that the polarization induced barrier (PIB) is more effective than the AlGaN EBL in suppressing electron overflow and improving hole transport in GaN-based LEDs.

  10. Route to polarization switching induced by optical injection in vertical-cavity surface-emitting lasers

    SciTech Connect

    Sciamanna, M.; Panajotov, K.

    2006-02-15

    We perform a theoretical investigation of the polarization dynamics in a vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection, i.e., the injected field has a linear polarization (LP) orthogonal to that of the free-running VCSEL. In agreement with previous experiments [Z. G. Pan et al., Appl. Phys. Lett. 63, 2999 (1993)], an increase of the injection strength may lead to a polarization switching accompanied by an injection locking. We find that this route to polarization switching is typically accompanied by a cascade of bifurcations to wave-mixing dynamics and time-periodic and possibly chaotic regimes. A detailed mapping of the polarization dynamics in the plane of the injection parameters (detuning, injection strength) unveils a large richness of dynamical scenarios. Of particular interest is the existence of another injection-locked solution for which the two LP modes both lock to the master laser frequency, i.e., an elliptically polarized injection-locked (EPIL) steady state. Modern continuation techniques allow us to unveil an unfolding mechanism of the EPIL solution as the detuning varies and also to link the existence of the EPIL solution to a resonance condition between the master laser frequency and the free-running frequency of the normally depressed LP mode in the slave laser. We furthermore report an additional case of bistability, in which the EPIL solution may coexist with the second injection-locked solution (the one being locked to the master polarization). This case of bistability is a result of the interaction between optical injection and the two-polarization-mode characteristics of VCSEL devices.

  11. Heat-induced darkening and spectral broadening in photodarkened ytterbium-doped fiber under thermal cycling.

    PubMed

    Söderlund, Mikko J; Montiel i Ponsoda, Joan J; Koplow, Jeffrey P; Honkanen, Seppo

    2009-06-01

    We study thermal bleaching of photodarkening-induced loss in a 20-microm core diameter, large-mode-area ytterbium-doped silica fiber. Pristine and photodarkened samples are subjected to thermal cycling pulses. Recovery of the photodarkened fiber absorption coefficient initiates at approximately 350 degrees C and complete recovery is reached at approximately 625 degrees C. However, prior to recovery, the photodarkened fiber exhibits further heat-induced increase of absorption loss. This increase of loss is attributed to both a permanent increase of loss-inducing color centers and a temperature-dependent broadening of the absorption spectrum. Post-irradiation heat-induced formation of color centers suggests the presence of an intermediate energy state in the near-infrared photochemical mechanism for photodarkening. PMID:19506644

  12. Current-induced giant polarization rotation using a ZnO single crystal doped with nitrogen ions

    PubMed Central

    Tate, Naoya; Kawazoe, Tadashi; Nomura, Wataru; Ohtsu, Motoichi

    2015-01-01

    Giant polarization rotation in a ZnO single crystal was experimentally demonstrated based on a novel phenomenon occurring at the nanometric scale. The ZnO crystal was doped with N+ and N2+ ions serving as p-type dopants. By applying an in-plane current using a unique arrangement of electrodes on the device, current-induced polarization rotation of the incident light was observed. From the results of experimental demonstrations and discussions, it was verified that this novel behavior originates from a specific distribution of dopants and the corresponding light–matter interactions in a nanometric space, which are allowed by the existence of such a dopant distribution. PMID:26246456

  13. Spectral anomalies of the light-induced drift effect caused by the velocity dependence of the collision broadening and shift of the absorption line

    SciTech Connect

    Parkhomenko, A I; Shalagin, Anatolii M

    2013-02-28

    We have theoretically investigated the spectral features of the light-induced drift (LID) effect, arising due to the dependence of the collision broadening {gamma} and shift {Delta} of the absorption line on the velocity of resonance particles, {nu}. It is shown that under certain conditions, account of this dependence can radically change the spectral shape of the LID signal, up to the appearance of additional zeros in the dependence of the drift velocity on the radiation frequency. (nonlinear optical phenomena)

  14. Experimental study of the spectral characteristics of laser-induced air plasma

    SciTech Connect

    Lin Zhaoxiang; Wu Jinquan; Sun Fenglou; Gong Shunsheng

    2010-05-01

    The characteristics of laser-induced air, N2, and O2 plasma spectra are investigated spectroscopically. The study concentrates mainly on the temporal behavior of laser-induced plasma after breakdown. We used delayed spectra and spectra evolution for this study. Except for the general one-beam laser-induced breakdown experiment, a second laser beam was added to further probe the behavior of plasma during its decay. We report the experimental results of spectra composition, spectra time evolution, and spectra affected by a second laser beam. We determined that all the laser-induced air plasma spectra are from a continuous spectrum and some line spectra superposed on the continuous spectrum. The stronger short wavelength continuous spectrum is caused by bremsstrahlung radiation of electrons in the plasma, and the weaker long wavelength continuous spectrum is caused by electron and ion recombination. Line spectra originate from excited molecules, atoms, and their first-order ions, but no line spectra form higher-order ions. The results show that the temporal behavior of some spectra is a decay-rise-redecay pattern. With the two laser beam experiment we found that all the spectra intensities are enhanced by the second laser beam, but the response of various spectra to the delay of the second laser beam is quite different, in particular, the intensity increments of some spectra increase with the delay of the second laser beam. Some microscopic processes of laser-induced plasma obtained from the experimental results are discussed. These results are useful for a better understanding of some laser-induced air plasma related applications, such as laser-guided lightning and laser-induced breakdown spectroscopy.

  15. Adsorption properties of polar/apolar inducers at a charged interface and their relevance to leukemia cell differentiation.

    PubMed Central

    Carlà, M; Cuomo, M; Arcangeli, A; Olivotto, M

    1995-01-01

    The interfacial adsorption properties of polar/apolar inducers of cell differentiation (PAIs) were studied on a mercury electrode. This study, on a clean and reproducible charged surface, unraveled the purely physical interactions among these compounds and the surface, apart from the complexity of the biological membrane. The interfacial behavior of two classical inducers, hexamethylenebisacetamide (HMBA) and dimethylsulfoxide, was compared with that of a typical apolar aliphatic compound, 1-octanol, that has a similar hydrophobic moiety as HMBA but a much smaller dipolar moment. Both HMBA and Octanol adsorb flat in contact with the surface because of hydrophobic forces, with a very similar free energy of adsorption. However, the ratio of polar to apolar moieties in PAIs turned out to be crucial to drive the adsorption maximum toward physiological values of surface charge density, where octanol is desorbed. The electrostatic effects in the interfacial region reflected the adsorption properties: the changes in the potential drop across the interfacial region as a function of the surface charge density, in the physiological range, were opposite in PAIs as compared with apolar aliphatic compounds, as exemplified by octanol. This peculiar electrostatic effect of PAIs has far-reaching relevance for the design of inducers with an adequate therapeutic index to be used in clinical trials. PMID:7647265

  16. ?? T Cells Are Required for M2 Macrophage Polarization and Resolution of Ozone-Induced Pulmonary Inflammation in Mice

    PubMed Central

    Mathews, Joel A.; Kasahara, David I.; Ribeiro, Luiza; Wurmbrand, Allison P.; Ninin, Fernanda M. C.; Shore, Stephanie A.

    2015-01-01

    We examined the role of ?? T cells in the induction of alternatively activated M2 macrophages and the resolution of inflammation after ozone exposure. Wildtype (WT) mice and mice deficient in ?? T cells (TCR?-/- mice) were exposed to air or to ozone (0.3 ppm for up to 72h) and euthanized immediately or 1, 3, or 5 days after cessation of exposure. In WT mice, M2 macrophages accumulated in the lungs over the course of ozone exposure. Pulmonary mRNA abundance of the M2 genes, Arg1, Retnla, and Clec10a, also increased after ozone. In contrast, no evidence of M2 polarization was observed in TCR?-/- mice. WT but not TCR?-/- mice expressed the M2c polarizing cytokine, IL-17A, after ozone exposure and WT mice treated with an IL-17A neutralizing antibody exhibited attenuated ozone-induced M2 gene expression. In WT mice, ozone-induced increases in bronchoalveolar lavage neutrophils and macrophages resolved quickly after cessation of ozone exposure returning to air exposed levels within 3 days. However, lack of M2 macrophages in TCR?-/- mice was associated with delayed clearance of inflammatory cells after cessation of ozone and increased accumulation of apoptotic macrophages in the lungs. Delayed restoration of normal lung architecture was also observed in TCR?-/- mice. In summary, our data indicate that ?? T cells are required for the resolution of ozone-induced inflammation, likely because ?? T cells, through their secretion of IL-17A, contribute to changes in macrophage polarization that promote clearance of apoptotic cells. PMID:26135595

  17. Spectral analysis of paramagnetic centers induced in human tooth enamel by x-rays and gamma radiation

    NASA Astrophysics Data System (ADS)

    Kirillov, V. A.; Kuchuro, I. I.

    2010-03-01

    Based on study of spectral and relaxation characteristics, we have established that paramagnetic centers induced in tooth enamel by x-rays and gamma radiation are identical in nature. We show that for the same exposure dose, the intensity of the electron paramagnetic resonance (EPR) signal induced by x-radiation with effective energy 34 keV is about an order of magnitude higher than the amplitude of the signal induced by gamma radiation. We have identified a three-fold attenuation of the EPR signal along the path of the x-radiation from the buccal to the lingual side of a tooth, which is evidence that the individual had undergone diagnostic x-ray examination of the dentition or skull. We have shown that the x-ray exposure doses reconstructed from the EPR spectra are an order of magnitude higher than the applied doses, while the dose loads due to gamma radiation are equal to the applied doses. The data obtained indicate that for adequate reconstruction of individual absorbed doses from EPR spectra of tooth enamel in the population subjected to the combined effect of x-radiation and accidental external gamma radiation as a result of the disaster at the Chernobyl nuclear power plant, we need to take into account the contribution to the dose load from diagnostic x-rays in examination of the teeth, jaw, or skull.

  18. 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.

  19. Probing the spin polarization of current by soft x-ray imaging of current-induced magnetic vortex dynamics

    SciTech Connect

    Kasai, Shinya; Fischer, Peter; Im, Mi-Young; Yamada, Keisuke; Nakatani, Yoshinobu; Kobayashi, Kensuke; Kohno, Hiroshi; Ono, Teruo

    2008-12-09

    Time-resolved soft X-ray transmission microscopy is applied to image the current-induced resonant dynamics of the magnetic vortex core realized in a micron-sized Permalloy disk. The high spatial resolution better than 25 nm enables us to observe the resonant motion of the vortex core. The result also provides the spin polarization of the current to be 0.67 {+-} 0.16 for Permalloy by fitting the experimental results with an analytical model in the framework of the spin-transfer torque.

  20. Dipole-dipole interaction-induced spin-orbit coupling of polar molecules in optical lattices

    NASA Astrophysics Data System (ADS)

    Wall, M. L.; Syzranov, S. V.; Rey, A. M.

    2014-05-01

    Long-range dipole-dipole interactions between polar molecules in an optical lattice enable rotational excitations to move through the lattice even when the molecules themselves cannot, as has been directly observed in recent experiments [Yan et al., Nature 501, 521-525 (2013)]. We study the dynamics of rotational excitations in a 2D lattice of (bosonic or fermionic) polar molecules in the presence of electric dipole-dipole interactions which exchange rotational ``spin'' angular momentum projection with orbital angular momentum, forming a cold molecule analog of the Einstein-de Haas effect. In particular, we present analytic results for the statics and dynamics of a dilute gas of rotational excitations in a unit-filed lattice. Prospects for observing such processes in near-term polar molecule experiments are discussed.

  1. Contact-induced spin polarization of monolayer hexagonal boron nitride on Ni(111)

    SciTech Connect

    Ohtomo, Manabu; Entani, Shiro; Matsumoto, Yoshihiro; Naramoto, Hiroshi; Sakai, Seiji; Yamauchi, Yasushi; Kuzubov, Alex A.; Eliseeva, Natalya S.; Avramov, Pavel V.

    2014-02-03

    Hexagonal boron nitride (h-BN) is a promising barrier material for graphene spintronics. In this Letter, spin-polarized metastable de-excitation spectroscopy (SPMDS) is employed to study the spin-dependent electronic structure of monolayer h-BN/Ni(111). The extreme surface sensitivity of SPMDS enables us to elucidate a partial filling of the in-gap states of h-BN without any superposition of Ni 3d signals. The in-gap states are shown to have a considerable spin polarization parallel to the majority spin of Ni. The positive spin polarization is attributed to the ?-d hybridization and the effective spin transfer to the nitrogen atoms at the h-BN/Ni(111) interface.

  2. Correlation between aging grade of T91 steel and spectral characteristics of the laser-induced plasma

    NASA Astrophysics Data System (ADS)

    Li, Jun; Lu, Jidong; Dai, Yuan; Dong, Meirong; Zhong, Wanli; Yao, Shunchun

    2015-08-01

    T91 steel with favorable mechanical performance has become the representative heat-resistant steel used as heat exchange surfaces in supercritical and ultra-supercritical boilers. The organizational structure and mechanical properties change during the service period, called material aging, which affects the service life and the equipment safety. To develop a fast and easy aging predictive technique of heat exchange metal surfaces, laser-induced breakdown spectroscopy (LIBS) was applied to investigate the plasma characteristics of T91 steel specimens with different aging grades. The metallographic structure, mechanical properties and spectral characteristics of the specimens were analyzed. Then, the correlations between the spectral characteristics and the aging grade were established. The analysis results show that the martensite substructure disappears, and the dimension of the carbide particles among the crystal lattices increases with aging. At the same time, the hardness of the samples gradually decreases. The peak intensities of both the matrix and the alloying element increases then decreases with aging, owing to the change of the metallography structure and mechanical properties. Furthermore, good unique value correlations between the intensity ratio of CrI/FeI, MoI/FeI and the aging grade are found. This demonstrates that LIBS is a possible new way to estimate the aging grade of metal materials.

  3. Endoscopic autofluorescence micro-spectroimaging of alveoli: comparative spectral analysis of amiodarone-induced pneumonitis patients and healthy smokers

    NASA Astrophysics Data System (ADS)

    Bourg-Heckly, G.; Vever-Bizet, C.; Blondel, W.; Salaün, M.; Thiberville, L.

    2011-03-01

    Fibered confocal fluorescence microscopy (FCFM) with spectroscopic analysis capability was used during bronchoscopy, at 488nm excitation, to record autofluorescence images and associated emission spectra of the alveoli of 5 healthy smoking volunteers and 7 non-smoking amiodarone-induced pneumonitis (AIP) patients. Alveolar fluorescent cellular infiltration was observed in both groups. Our objective was to assess the potential of spectroscopy in differentiating these two groups. Methods: We previously demonstrated that in healthy smokers alveolar elastin backbone and tobacco tar contained in macrophages contribute to the observed signal. Each normalized spectrum was modeled as a linear combination of 3 components: Sexp(?) = Ce.Se(?)+Ct.St(?)+CG.SG(?), Ce, Ct and CG are amplitude coefficients. Se(?) and St(?) are respectively the normalized elastin and tobacco tar emission spectra measured experimentally and SG(?) a gaussian spectrum with tunable width and central wavelength. Levenbergt-Marquardt algorithm determined the optimal set of coefficients. Results: AIP patient autofluorescence spectra can be uniquely modelized by the linear combination of the elastin spectrum (Ce = 0.61) and of a gaussian spectrum (center wavelength 550nm, width 40nm); the tobacco tar spectrum coefficient Ct is found to be zero. For healthy smoking volunteers, only two spectral components were considered: the tobacco tar component (Ct = 1,03) and the elastin component (Ce = 0). Conclusion: Spectral analysis is able to distinguish cellular infiltrated images from AIP patients and healthy smoking volunteers. It appears as a powerful complementary tool for FCFM.

  4. MASS SPECTRAL FRAGMENTATION PATHWAYS IN NITRAMINES. A COLLISION-INDUCED DISSOCIATION STUDY

    EPA Science Inventory

    A collision-induced dissociation (CID) study of five synthesized nitramines was carried out using a hybrid EBQQ mass spectrometer. ID spectra were obtained in two modes: /E linked-scan mode and MS/MS mode using the EB sector combination as the first mass spectrometer and the QQ a...

  5. Arsenic- and selenium-induced changes in spectral reflectance and morphology of soybean plants

    USGS Publications Warehouse

    Milton, N.M.; Ager, C.M.; Eiswerth, B.A.; Power, M.S.

    1989-01-01

    Soybean (Glycine max) plants were grown in hydroponic solutions treated with high concentrations of either arsenic or selenium. Spectral reflectance changes in arsenic-dosed plants included a shift to shorter wavelengths in the long-wavelength edge of the chlorophyll absorption band centered at 680 nm (the red edge) and higher reflectance in the 550-650 nm region. These results are consistent with vegetation reflectance anomalies observed in previous greenhouse experiments and in airborne radiometer studies. The selenium-dosed plants contrast, exhibited a shift to longer wavelengths of the red edge and lower reflectance between 550 nm and 650 wh when compared with control plants. Morphological effects of arsenic uptake included lower overall biomass, stunted and discolored roots, and smaller leaves oriented more vertically than leaves of control plants. Selenium-dosed plants also displayed morphological changes, but root and leaf biomass were less affected than were those of arsenic-dosed plants when compared to control plants. ?? 1989.

  6. Optical lattice polarization effects on magnetically induced optical atomic clock transitions

    SciTech Connect

    Taichenachev, A. V.; Yudin, V. I.; Oates, C. W.

    2007-08-15

    We derive the frequency shift for a forbidden optical transition J=0{yields}J{sup '}=0 caused by the simultaneous actions of an elliptically polarized lattice field and a static magnetic field. We find that a simple configuration of lattice and magnetic fields leads to a cancellation of this shift to first order in lattice intensity and magnetic field. In this geometry, the second-order lattice intensity shift can be minimized as well by use of optimal lattice polarization. Suppression of these shifts could considerably enhance the performance of the next generation of atomic clocks.

  7. Exine dehiscing induces rape microspore polarity, which results in different daughter cell fate and fixes the apical–basal axis of the embryo

    PubMed Central

    Tang, Xingchun; Liu, Yuan; Sun, Meng-xiang

    2013-01-01

    The roles of cell polarity and the first asymmetric cell division during early embryogenesis in apical–basal cell fate determination remain unclear. Previously, a novel Brassica napus microspore embryogenesis system was established, by which rape exine-dehisced microspores were induced by physical stress. Unlike traditional microspore culture, cell polarity and subsequent asymmetric division appeared in the exine-dehisced microspore, which finally developed into a typical embryo with a suspensor. Further studies indicated that polarity is critical for apical–basal cell fate determination and suspensor formation. However, the pattern of the first division was not only determined by cell polarity but was also regulated by the position of the ruptured exine. The first division could be equal or unequal, with its orientation essentially perpendicular to the polar axis. In both types of cell division, the two daughter cells could have different cell fates and give rise to an embryo with a suspensor, similar to zygotic apical–basal cell differentiation. The alignment of the two daughter cells is consistent with the orientation of the apical–basal axis of future embryonic development. Thus, the results revealed that exine dehiscing induces rape microspore polarization, and this polarity results in a different cell fate and fixes the apical–basal axis of embryogenesis, but is uncoupled from cell asymmetric division. The present study demonstrated the relationships among cell polarity, asymmetric cell division, and cell fate determination in early embryogenesis. PMID:23162119

  8. Exine dehiscing induces rape microspore polarity, which results in different daughter cell fate and fixes the apical-basal axis of the embryo.

    PubMed

    Tang, Xingchun; Liu, Yuan; He, Yuqing; Ma, Ligang; Sun, Meng-Xiang

    2013-01-01

    The roles of cell polarity and the first asymmetric cell division during early embryogenesis in apical-basal cell fate determination remain unclear. Previously, a novel Brassica napus microspore embryogenesis system was established, by which rape exine-dehisced microspores were induced by physical stress. Unlike traditional microspore culture, cell polarity and subsequent asymmetric division appeared in the exine-dehisced microspore, which finally developed into a typical embryo with a suspensor. Further studies indicated that polarity is critical for apical-basal cell fate determination and suspensor formation. However, the pattern of the first division was not only determined by cell polarity but was also regulated by the position of the ruptured exine. The first division could be equal or unequal, with its orientation essentially perpendicular to the polar axis. In both types of cell division, the two daughter cells could have different cell fates and give rise to an embryo with a suspensor, similar to zygotic apical-basal cell differentiation. The alignment of the two daughter cells is consistent with the orientation of the apical-basal axis of future embryonic development. Thus, the results revealed that exine dehiscing induces rape microspore polarization, and this polarity results in a different cell fate and fixes the apical-basal axis of embryogenesis, but is uncoupled from cell asymmetric division. The present study demonstrated the relationships among cell polarity, asymmetric cell division, and cell fate determination in early embryogenesis. PMID:23162119

  9. Polarizing cues.

    PubMed

    Nicholson, Stephen P

    2012-01-01

    People categorize themselves and others, creating ingroup and outgroup distinctions. In American politics, parties constitute the in- and outgroups, and party leaders hold sway in articulating party positions. A party leader's endorsement of a policy can be persuasive, inducing co-partisans to take the same position. In contrast, a party leader's endorsement may polarize opinion, inducing out-party identifiers to take a contrary position. Using survey experiments from the 2008 presidential election, I examine whether in- and out-party candidate cues—John McCain and Barack Obama—affected partisan opinion. The results indicate that in-party leader cues do not persuade but that out-party leader cues polarize. This finding holds in an experiment featuring President Bush in which his endorsement did not persuade Republicans but it polarized Democrats. Lastly, I compare the effect of party leader cues to party label cues. The results suggest that politicians, not parties, function as polarizing cues. PMID:22400143

  10. The effect of the external medium on the gravity-induced polarity of cytoplasmic streaming in Chara corallina (Characeae)

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    Gravity induces a polarity of cytoplasmic streaming in vertical internodal cells of Chara such that the downwardly directed stream moves faster than the upwardly directed stream. In order to determine whether the statolith theory (in which intracellular sedimenting particles are responsible for gravity sensing) or the gravitational pressure theory (in which the entire protoplast acts as the gravity sensor) best explain the gravity response in Chara internodal cells, we controlled the physical properties of the external medium, including density and osmolarity, with impermeant solutes and examined the effect on the polarity of cytoplasmic streaming. As the density of the external medium is increased, the polarity of cytoplasmic streaming decreases and finally disappears when the density of the external medium is equal to that of the cell (1015 kg/m3). A further increase in the density of the external medium causes a reversal of the gravity response. These results are consistent with the gravitational pressure theory of gravity sensing since the buoyancy of the protoplast is dependent on the difference between the density of the protoplast and the external medium, and are inconsistent with the statolith theory since the buoyancy of intracellular particles are unaffected by changes in the external medium.

  11. The effect of the external medium on the gravity-induced polarity of cytoplasmic streaming in Chara corallina (Characeae).

    PubMed

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

    1997-11-01

    Gravity induces a polarity of cytoplasmic streaming in vertical internodal cells of Chara such that the downwardly directed stream moves faster than the upwardly directed stream. In order to determine whether the statolith theory (in which intracellular sedimenting particles are responsible for gravity sensing) or the gravitational pressure theory (in which the entire protoplast acts as the gravity sensor) best explain the gravity response in Chara internodal cells, we controlled the physical properties of the external medium, including density and osmolarity, with impermeant solutes and examined the effect on the polarity of cytoplasmic streaming. As the density of the external medium is increased, the polarity of cytoplasmic streaming decreases and finally disappears when the density of the external medium is equal to that of the cell (1015 kg/m3). A further increase in the density of the external medium causes a reversal of the gravity response. These results are consistent with the gravitational pressure theory of gravity sensing since the buoyancy of the protoplast is dependent on the difference between the density of the protoplast and the external medium, and are inconsistent with the statolith theory since the buoyancy of intracellular particles are unaffected by changes in the external medium. PMID:11541058

  12. Simultaneous calorimetric and polarization microscopy investigations of light induced changes over phase transitions in a liquid crystal-napthopyran mixture.

    PubMed

    Paoloni, S; Mercuri, F; Marinelli, M; Pizzoferrato, R; Zammit, U; Kosa, T; Sukhomlinova, L; Taheri, B

    2015-10-01

    We have studied the specific heat and the thermal conductivity in a 4-(n-octyl)-4'-cyanobiphenyl liquid crystal (LC)-photochromic molecules mixture, before, during, and after the photo-activation of the dispersed photochromic molecules, over both the smectic A-nematic and the nematic-isotropic phase transitions. The evaluation of the specific heat has enabled the determination of the changes of the phase transition characteristics induced by the photochromic molecules photoisomerization, while that of the thermal conductivity could be used to monitor the modifications induced in the average LC molecular orientation. The polarization microscopy imaging of the sample texture constituted a valuable support for the interpretation of the obtained thermal conductivity results. PMID:26450328

  13. Simultaneous calorimetric and polarization microscopy investigations of light induced changes over phase transitions in a liquid crystal-napthopyran mixture

    NASA Astrophysics Data System (ADS)

    Paoloni, S.; Mercuri, F.; Marinelli, M.; Pizzoferrato, R.; Zammit, U.; Kosa, T.; Sukhomlinova, L.; Taheri, B.

    2015-10-01

    We have studied the specific heat and the thermal conductivity in a 4-(n-octyl)-4'-cyanobiphenyl liquid crystal (LC)-photochromic molecules mixture, before, during, and after the photo-activation of the dispersed photochromic molecules, over both the smectic A-nematic and the nematic-isotropic phase transitions. The evaluation of the specific heat has enabled the determination of the changes of the phase transition characteristics induced by the photochromic molecules photoisomerization, while that of the thermal conductivity could be used to monitor the modifications induced in the average LC molecular orientation. The polarization microscopy imaging of the sample texture constituted a valuable support for the interpretation of the obtained thermal conductivity results.

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

    E-print Network

    Stuttgart, Universität

    are modelled using a saw-tooth- shaped function for the time-history of ice sheets and spherical caps water masses and compare them with the result of the more simplistic models of spherical ice caps to model polar wander due to cur- rent and future melting of currently ice covered ar- eas. Furthermore, we

  15. Polarization-resolved time-delay signatures of chaos induced by FBG-feedback in VCSEL.

    PubMed

    Zhong, Zhu-Qiang; Li, Song-Sui; Chan, Sze-Chun; Xia, Guang-Qiong; Wu, Zheng-Mao

    2015-06-15

    Polarization-resolved chaotic emission intensities from a vertical-cavity surface-emitting laser (VCSEL) subject to feedback from a fiber Bragg grating (FBG) are numerically investigated. Time-delay (TD) signatures of the feedback are examined through various means including self-correlations of intensity time-series of individual polarizations, cross-correlation of intensities time-series between both polarizations, and permutation entropies calculated for the individual polarizations. The results show that the TD signatures can be clearly suppressed by selecting suitable operation parameters such as the feedback strength, FBG bandwidth, and Bragg frequency. Also, in the operational parameter space, numerical maps of TD signatures and effective bandwidths are obtained, which show regions of chaotic signals with both wide bandwidths and weak TD signatures. Finally, by comparing with a VCSEL subject to feedback from a mirror, the VCSEL subject to feedback from the FBG generally shows better concealment of the TD signatures with similar, or even wider, bandwidths. PMID:26193526

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

    E-print Network

    Zheludev, Nikolay

    Metamaterial with polarization and direction insensitive resonant transmission response mimicking February 2009; accepted 24 April 2009; published online 26 May 2009 We report on a planar metamaterial transparency phenomenon. © 2009 American Institute of Physics. DOI: 10.1063/1.3138868 Planar metamaterials

  17. Polar charges induced electric hysteresis of ZnO nano/microwire for fast data storage.

    PubMed

    Song, Jinhui; Zhang, Yan; Xu, Chen; Wu, Wenzuo; Wang, Zhong Lin

    2011-07-13

    We demonstrate an innovative memory device made of a single crystalline ZnO nanowire/microwire that works with a different mechanism from the p-n junction based memristor. A nonsymmetric, Schottky-Ohmic contacted ZnO nano/microwire can serve as a memristor if the channel length is short and the applied frequency is high. The observed phenomena could be explained based on a screening model of the polar charges at the two ends of the wire owing to the crystal structure of ZnO. The polar charges are usually fully screened by free electrons coming from the metal sides. But when the magnitude of the externally applied field exceeds a threshold value, the free electrons that screen the polar surfaces can be pulled away from the interface region, leading to a transient change in the effective height of the local Schottky barrier height owing to the electrical field formed by the polar surfaces of ZnO nanowires, which acts as a resistor with its magnitude depending on the total charges being transported. Such a phenomenon could be used for high density and fast writing/erasing data storage. PMID:21609005

  18. M2 polarized macrophages induced by CSE promote proliferation, migration, and invasion of alveolar basal epithelial cells.

    PubMed

    Fu, Xiao; Shi, Hengfei; Qi, Yue; Zhang, Weiyun; Dong, Ping

    2015-09-01

    Cigarette smoking plays an important role in the genesis of lung cancer, and tumor-associated macrophages (TAMs) are believed to accelerate the process. We therefore sought to clarify the relationship between cigarette smoking, TAMs and tumorigenesis. We treated macrophages (THP-1) with cigarette smoke extract (CSE) and found that the mRNA levels of IL-6, IL-10, IL-12 and TNF-? decreased, while TGF-? mRNA levels increased. CSE significantly inhibited the phagocytic ability of macrophages, as assessed by flow cytometric analysis of FITC-dextran internalization. JAK2/STAT3 was significantly activated by CSE, as determined by Western blot analysis. When the scavenger receptor CD163, a specific marker of M2 macrophages, was analyzed by flow cytometry, its expression was significantly increased. After inducing M2 polarization of THP-1 cells, we co-cultured macrophages and alveolar basal epithelial cells (A549). The proliferation of A549 cells was detected by the MTT assay and cell cycle analysis, while their migration and invasion were detected by scratch wound assay and transwell assay. The results showed that the proliferation, migration and invasion of A549 cells were significantly promoted by M2 macrophages but were slightly inhibited by CSE. In conclusion, we demonstrated that macrophage M2 polarization induced by CSE promotes proliferation, migration, and invasion of alveolar basal epithelial cells. PMID:26253658

  19. Helicobacter pylori-Induced Alteration of Epithelial Cell Signaling and Polarity: A Possible Mechanism of Gastric Carcinoma Etiology and Disparity

    PubMed Central

    Osman, Mahasin A.; Bloom, George S.; Tagoe, Emmanuel A.

    2013-01-01

    Gastric cancer, a disease of disparity associated with Helicobacter pylori (H. pylori) infection, is the world's second leading cause of cancer deaths. The pathogen H. pylori target the epithelial adhesion receptors, E-cadherin and ?1-integrin, to modulate the host cytoskeleton via disruption of the epithelial cell polarity necessary for maintaining the infection, but how this leads to the development of the carcinoma is widely unclear. While Rho family GTPases’ signaling to the cytoskeleton and these receptors is required for initiating and maintaining the infection, the responsible effectors, and how they might influence the etiology of the carcinomas are currently unknown. Here we discuss the potential role of the Cdc42-IQGAP1 axis, a negative regulator of the tumor suppressors E-cadherin and ?1-integrin, as a potential driver of H. pylori-induced gastric carcinoma and propose avenues for addressing its disparity. Chronic dysfunction of the IQGAP1-signaling pathway, resulting from H. pylori-induced disruption of cell polarity, can explain the pathogenesis of the carcinoma, at least, in subsets of infected population, and thus could provide a potential means for personalized medicine. PMID:23629919

  20. Polarization-Induced Interfacial Reactions between Nickel and Selenium in Ni/Zirconia SOFC Anodes and Comparison with Sulfur Poisoning

    SciTech Connect

    Marina, Olga A.; Pederson, Larry R.; Coyle, Christopher A.; Thomsen, Edwin C.; Edwards, Danny J.

    2011-01-10

    Three distinctly different characteristic responses of a nickel/yttria-stabilized zirconia (Ni/YSZ) cermet anode to the presence of hydrogen selenide in synthetic coal gas were observed, depending on temperature (650-800oC), H2Se concentration (0-40 ppm), and especially on the extent of anodic polarization (0 to ~0.5 V). The first level of response was characterized by a rapid but modest decrease in power density to a new steady state, with no further degradation observed in tests up to 700 hours in duration. Mostly observed at high temperatures, low H2Se concentrations, and low anodic polarizations, this response level was similar to effects caused by the presence of H2S, but with slower onset and lower reversibility. Higher anodic polarization at a constant current could trigger a second level of response characterized by oscillatory behavior involving cycles of rapid performance loss followed by rapid recovery. Oscillations at the constant current density were accompanied by the appearance and disappearance of a new feature in the electrochemical impedance spectrum with a summit frequency of ~100 Hz. Oscillatory behavior ceased when the current density was lowered. Such behavior was not observed for cells operated at a constant potential of similar magnitude, though. A third level of response, irreversible cell failure, could be induced by further increases in anodic polarization, additionally favored by low temperature and high H2Se concentration. Post-test analyses of failed cells by electron microscopy revealed the extensive microstructural changes including the appearance of nickel oxide and nickel selenide alteration phases, only at the anode/electrolyte interface. From bulk thermochemical considerations the formation of nickel selenides could not be expected. Local chemical conditions created at the anode/electrolyte interface appear to be of overriding importance with respect to the extent of Ni/YSZ anode interactions with H2Se in coal gas.

  1. Helicobacter pylori-Induced Disruption of Monolayer Permeability and Proinflammatory Cytokine Secretion in Polarized Human Gastric Epithelial Cells

    PubMed Central

    Fiorentino, Maria; Ding, Hua; Blanchard, Thomas G.; Czinn, Steven J.; Sztein, Marcelo B.

    2013-01-01

    Helicobacter pylori infection of the stomach is related to the development of diverse gastric pathologies. The ability of H. pylori to compromise epithelial junctional complexes and to induce proinflammatory cytokines is believed to contribute to pathogenesis. The purpose of this study was to use an in vitro human gastric epithelial model to investigate the ability of H. pylori to affect permeability and the extent and polarity of the host inflammatory response. NCI-N87 monolayers were cocultured with live or heat-killed H. pylori or culture supernatants. Epithelial barrier function was measured by transepithelial electric resistance (TEER) analysis, diffusion of fluorescein isothiocyanate (FITC)-labeled markers, and immunostaining for tight junction proteins. Supernatants from both apical and basolateral chambers were tested for cytokine production by multiplex analysis. H. pylori caused a significant decrease in TEER, an increased passage of markers through the infected monolayer, and severe disruption and mislocalization of ZO-1 and claudin-1 proteins. Cell viability was not altered by H. pylori, indicating that loss of barrier function could be attributed to a breakdown of tight junction integrity. Significantly high levels of cytokine secretion were induced by either viable or heat-killed H. pylori. H. pylori affects monolayer permeability of polarized human gastric epithelial cells. Proinflammatory cytokines were secreted in a polarized manner, mostly basolaterally. Live bacteria are required for disruption of tight junctions but not for the induction of cytokine secretion. The NCI-N87 cell line provides an excellent model for the in vitro study of H. pylori pathogenesis and the epithelial cell host response to infection. PMID:23297384

  2. Spectral anion sensing and ?-radiation induced magnetic modifications of polyphenol generated Ag-nanoparticles.

    PubMed

    Ansari, Zarina; Dhara, Susmita; Bandyopadhyay, Bilwadal; Saha, Abhijit; Sen, Kamalika

    2016-03-01

    A fast one step bio-synthesis for in situ preparation of silver nanoparticles is proposed. The method involves reduction of AgNO3 with an aqueous extract of peanut skin, which is a good source of polyphenols. The silver nanoparticles thus synthesized were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis absorption spectroscopy, Fourier Transform infrared (FTIR) spectroscopy and magnetic measurements. Effect of low dose ? irradiation during the synthesis was studied and their physico-chemical properties were compared with those produced without irradiation. On the contrary to the diamagnetic behavior of bulk silver, the silver nanoparticles thus prepared show a significant ferromagnetic moment component. Variable time exposure to ?-irradiation results in an exponential decay of ferromagnetic component. A freshly prepared solution of silver nanoparticles shows selective spectral changes towards iodide ions at trace concentration (below 50?M) among a series of 16 other competing anions. The prepared nanoparticles are therefore suitable for anion sensing application. PMID:26654966

  3. The acidic pH-induced structural changes in Pin1 as revealed by spectral methodologies

    NASA Astrophysics Data System (ADS)

    Wang, Jing-Zhang; Xi, Lei; Zhu, Guo-Fei; Han, Yong-Guang; Luo, Yue; Wang, Mei; Du, Lin-Fang

    2012-12-01

    Pin1 is closely associated with the pathogenesis of cancers and Alzheimer's disease (AD). Previously, we have shown the characteristics of the thermal denaturation of Pin1. Herein, the acid-induced denaturation of Pin1 was determined by means of fluorescence emission, synchronous fluorescence, far-UV CD, ANS fluorescence and RLS spectroscopies. The fluorescence emission spectra and the synchronous fluorescence spectra suggested the partially reversible unfolding (approximately from pH 7.0 to 4.0) and refolding (approximately from pH 4.0 to 1.0) of the structures around the chromophores in Pin1, apparently with an intermediate state at about pH 4.0-4.5. The far-UV CD spectra indicated that acidic pH (below pH 4.0) induced the structural transition from ?-helix and random coils to ?-sheet in Pin1. The ANS fluorescence and the RLS spectra further suggested the exposure of the hydrophobic side-chains of Pin1 and the aggregation of it especially below pH 2.3, and the aggregation possibly resulted in the formation of extra intermolecular ?-sheet. The present work primarily shows that acidic pH can induce kinds of irreversible structural changes in Pin1, such as the exposure of the hydrophobic side-chains, the transition from ?-helix to ?-sheet and the aggregation of Pin1, and also explains why Pin1 loses most of its activity below pH 5.0. The results emphasize the important role of decreased pH in the pathogenesis of some Pin1-related diseases, and support the therapeutic approach for them by targeting acidosis and modifying the intracellular pH gradients.

  4. Quantum pump effect induced by a linearly polarized microwave in a two-dimensional electron gas.

    PubMed

    Song, Juntao; Liu, Haiwen; Jiang, Hua

    2012-05-30

    A quantum pump effect is predicted in an ideal homogeneous two-dimensional electron gas (2DEG) that is normally irradiated by linearly polarized microwaves (MW). Without considering effects from spin-orbital coupling or the magnetic field, it is found that a polarized MW can continuously pump electrons from the longitudinal to the transverse direction, or from the transverse to the longitudinal direction, in the central irradiated region. The large pump current is obtained for both the low frequency limit and the high frequency case. Its magnitude depends on sample properties such as the size of the radiated region, the power and frequency of the MW, etc. Through the calculated results, the pump current should be attributed to the dominant photon-assisted tunneling processes as well as the asymmetry of the electron density of states with respect to the Fermi energy. PMID:22575800

  5. Spectral Response of the Pulsationally-Induced Shocks in the Atmosphere of BW Vulpeculae

    E-print Network

    Myron A. Smith; C. Simon Jeffery

    2002-10-08

    The star BW Vul excites an extremely strong radial pulsation that grows in its envelope and is responsible for visible shock features in the continuum flux and spectral line profiles emerging in the atmosphere At two phases separated by 0.8 cycles. Material propelled upwards in the atmosphere from the shock returns to the lower photosphere where it creates a second shock just before the start of the next cycle. We have obtained three nights of echelle data for this star over about 5 pulsation cycles (P = 0.201 days) in order to evaluate the effects of on a number of important lines in the spectrum, including the HeI 5875A and 6678A lines. These data were supplemented by archival high-dispersion IUE (UV) data from 1994. A comparison of profiles of the two HeI lines during the peak of the infall activity suggests that differences in the development of the blue wing at this time are due to heating and short-lived formations of an optically thin layer above the atmospheric region compressed by the infall. This discovery and the well-known decreases in equivalent widths of the CII 6578-83A doublet at the two shock phases, suggests that shock flattens the temperature gradient and produces heating in heating the upper atmosphere. Except for absorptions in the blue wings of the UV resonance lines, we find no evidence for sequential shock delays arriving at various regions of line formation of the photosphere (a "Van Hoof effect"). Phase lags cited by some former observers may be false indicators arising from varying degrees of desaturation of multiple lines, such as for the red HeI lines. In addition, an apparent lag in the equivalent width curve of lines arising from less excited atomic levels could instead be caused by post-shock cooling, followed by a rebound shock.

  6. Induced polarization of shaly sands - The effect of clay counterion type

    SciTech Connect

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

    1984-01-01

    The effects of clay counterion type on complex conductivities of shaly sands were studied for the Na/sup +/, Li/sup +/, K/sup +/, Ca/sup ++/ and (C/sub 2/H/sub 5/)/sub 4/N/sup +/ ions. The results are treated in terms of the Waxman-Smits in-phase conductivity equation and a new relation describing the quadrature conductivity. Topics considered include polarization, geochemistry, calculation methods, ionic conductivity, and reservoir rock.

  7. Sensing the Presence and Transport of Engineered Nanoparticles in Saturated PorousMedia using Spectral Induced Polarization (SIP) Method

    EPA Science Inventory

    Nano-materials are emerging into the global marketplace. Engineered Nano-particles, and other throwaway nanodevices may constitute a whole new class of non-biodegradable pollutants of which scientists have very little understanding. Therefore, the production of significant quanti...

  8. Strong induced polarity between Poly(vinylidene fluoride-co-chlorotrifluoroethylene) and ?-SiC and its influence on dielectric permittivity and loss of their composites

    NASA Astrophysics Data System (ADS)

    Feng, Yefeng; Gong, Honghong; Xie, Yunchuan; Wei, Xiaoyong; Yang, Lanjun; Zhang, Zhicheng

    2015-03-01

    Interface polarization and interface zone have been widely utilized to account for the abnormally improved dielectric properties of composites although their formation is rather vague and their influence has never been directly measured. In this work, micro ?-SiC was designed as the filler particles incorporated into poly(vinylidenefluoride-co-chlorotrifluoroethylene) with internal double bonds (P(VDF-CTFE-DB)) to construct polymer micro composites through solution casting method. The dielectric constant of the composites is found to be increasing linearly as SiC content increases at lower content and the highest value is obtained as 83 at 100 Hz, which is unusually higher than both pristine polymer (13@100 Hz) and SiC filler (17@100 Hz). By studying the dielectric properties of a bilayer model composite, the real dielectric permittivity of SiC sheet and P(VDF-CTFE-DB) layer has been directly measured to be significantly enhanced than their original value. The induced polarity between high polar PVDF units in polymer matrix and the electron-hole dipoles in ?-SiC is responsible for the elevated dielectric properties of both components, which could address the failure of binary series and parallel models in predicting the dielectric permittivity of 0-3 composites as well. The strong dependence of induced polarity on the volume content, thickness, and polar nature of both components strongly suggests establishing promising high induced polarity between polymer matrix and fillers may provide an alternative strategy for fabricating high-k composites.

  9. Weak measurement of photon polarization by back-action induced path interference

    E-print Network

    Masataka Iinuma; Yutaro Suzuki; Gen Taguchi; Yutaka Kadoya; Holger F. Hofmann

    2010-12-07

    The essential feature of weak measurements on quantum systems is the reduction of measurement back-action to negligible levels. To observe the non-classical features of weak measurements, it is therefore more important to avoid additional back-action errors than it is to avoid errors in the actual measurement outcome. In this paper, it is shown how an optical weak measurement of diagonal (PM) polarization can be realized by path interference between the horizontal (H) and vertical (V) polarization components of the input beam. The measurement strength can then be controlled by rotating the H and V polarizations towards each other. This well-controlled operation effectively generates the back-action without additional decoherence, while the visibility of the interference between the two beams only limits the measurement resolution. As the experimental results confirm, we can obtain extremely high weak values, even at rather low visibilities. Our method therefore provides a realization of weak measurements that is extremely robust against experimental imperfections.

  10. Porous implants modulate healing and induce shifts in local macrophage polarization in the foreign body reaction.

    PubMed

    Sussman, Eric M; Halpin, Michelle C; Muster, Jeanot; Moon, Randall T; Ratner, Buddy D

    2014-07-01

    The foreign body reaction (FBR) to implanted materials is of critical importance when medical devices require biological integration and vascularization to support their proper function (e.g., transcutaneous devices, implanted drug delivery systems, tissue replacements, and sensors). One class of materials that improves FBR outcomes is made by sphere-templating, resulting in porous structures with uniform, interconnected 34 ?m pores. With these materials we observe reduced fibrosis and increased vascularization. We hypothesized that improved healing is a result of a shift in macrophage polarization, often measured as the ratio of M1 pro-inflammatory cells to M2 pro-healing cells. In this study, macrophage polarity of 34 ?m porous implants was compared to non-porous and 160 ?m porous implants in subcutaneous mouse tissue. Immunohistochemistry revealed that macrophages in implant pores displayed a shift towards an M1 phenotype compared to externalized cells. Macrophages in 34 ?m porous implants had up to 63% greater expression of M1 markers and up to 85% reduction in M2 marker expression (p < 0.05). Macrophages immediately outside the porous structure, in contrast, showed a significant enrichment in M2 phenotypic cells. This study supports a role for macrophage polarization in driving the FBR to implanted materials. PMID:24248559

  11. CO2 induced climatic change and spectral variations in the outgoing terrestrial infrared radiation

    NASA Technical Reports Server (NTRS)

    Charlock, T. P.

    1984-01-01

    The published temperature changes produced in general circulation model simulations of CO2 induced climate modification are used to compute the top of the atmosphere, clear sky outgoing infrared radiance changes expected for doubled CO2. A significant wavenumber shift is produced, with less radiance emerging in the 500-800 per cm (20.0-12.5 micron) CO2 band and with more emerging in the 800-1200 per cm (12.5-8.3 micron) window. The effect varies greatly with latitude. The radiance shift in the 2300 per cm (4.3 micron) region is of the order of 10-30 percent for doubled CO2. It is suggested that the 2300 per cm region be carefully monitored as an aid in detecting the climatic effects of increasing CO2. The change in the wavenumber-integrated radiant exitance is at most a few percent.

  12. Does cosmic-ray-induced heterogeneous chemistry influence stratospheric polar ozone loss?

    PubMed

    Müller, Rolf; Grooss, Jens-Uwe

    2009-11-27

    Cosmic-ray (CR) -induced heterogeneous reactions of halogenated species have been suggested to play the dominant role in causing the Antarctic ozone hole. However, measurements of total ozone in Antarctica do not show a compact and significant correlation with CR activity. Further, a substantial CR-induced heterogeneous loss of chlorofluorocarbons is incompatible with multiyear satellite observations of N2O and CFC-12. Thus, CR-induced heterogeneous reactions cannot be considered as an alternative mechanism causing the Antarctic ozone hole. PMID:20366127

  13. Spectral Analysis of Rare Earth Elements using Laser-Induced Breakdown Spectroscopy

    SciTech Connect

    Madhavi Z. Martin; Robert V. Fox; Andrzej W. Miziolek; Frank C. DeLucia, Jr.; Nicolas Andre

    2001-05-01

    There is growing interest in rapid analysis of rare earth elements (REEs) both due to the need to find new natural sources to satisfy increased demand in their use in various electronic devices, as well as the fact that they are used to estimate actinide masses for nuclear safeguards and nonproliferation. Laser-Induced Breakdown Spectroscopy (LIBS) appears to be a particularly well-suited spectroscopy-based technology to rapidly and accurately analyze the REEs in various matrices at low concentration levels (parts-per-million). Although LIBS spectra of REEs have been reported for a number of years, further work is still necessary in order to be able to quantify the concentrations of various REEs in realworld complex samples. LIBS offers advantages over conventional solution-based radiochemistry in terms of cost, analytical turnaround, waste generation, personnel dose, and contamination risk. Rare earth elements of commercial interest are found in the following three matrix groups: 1) raw ores and unrefined materials, 2) as components in refined products such as magnets, lighting phosphors, consumer electronics (which are mostly magnets and phosphors), catalysts, batteries, etc., and 3) waste/recyclable materials (aka e-waste). LIBS spectra for REEs such as Gd, Nd, and Sm found in rare earth magnets are presented.

  14. Spectral analysis of rare earth elements using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Martin, Madhavi Z.; Fox, Robert V.; Miziolek, Andrzej W.; DeLucia, Frank C.; André, Nicolas

    2015-06-01

    There is growing interest in rapid analysis of rare earth elements (REEs) both due to the need to find new natural sources to satisfy increased demand in their use in various electronic devices, as well as the fact that they are used to estimate actinide masses for nuclear safeguards and nonproliferation. Laser-Induced Breakdown Spectroscopy (LIBS) appears to be a particularly well-suited spectroscopy-based technology to rapidly and accurately analyze the REEs in various matrices at low concentration levels (parts-per-million). Although LIBS spectra of REEs have been reported for a number of years, further work is still necessary in order to be able to quantify the concentrations of various REEs in realworld complex samples. LIBS offers advantages over conventional solution-based radiochemistry in terms of cost, analytical turnaround, waste generation, personnel dose, and contamination risk. Rare earth elements of commercial interest are found in the following three matrix groups: 1) raw ores and unrefined materials, 2) as components in refined products such as magnets, lighting phosphors, consumer electronics (which are mostly magnets and phosphors), catalysts, batteries, etc., and 3) waste/recyclable materials (aka e-waste). LIBS spectra for REEs such as Gd, Nd, and Sm found in rare earth magnets are presented.

  15. Laser-induced fluorescence of green plants. III - LIF spectral signatures of five major plant types

    NASA Technical Reports Server (NTRS)

    Chappelle, E. W.; Wood, F. M., Jr.; Newcomb, W. W.; Mcmurtrey, J. E., III

    1985-01-01

    A technique amenable to remote sensing use which utilizes laser-induced fluorescence (LIF) properties of plants has been successfully used in the laboratory to identify five major plant types. These included herbaceous dicots, herbaceous monocots, conifers, hardwoods, and algae. Each of these plant types exhibited a characteristic LIF spectra when excited by a pulsed N2 laser emitting at 337 nm. Although monocots and dicots possess common fluorescence maxima at 440, 685, and 740 nm, they could be differentiated from one another by using the ratio of the square of the fluorescence intensity at 440 nm to the nonsquared intensity at 685 nm, i.e., (440)-squared/685. In all cases, monocots yielded a significantly higher ratio. Conifers have fluorescence maxima at 440, 525, and 740 nm but none at 685 nm. Hardwoods exhibited fluorescence at 440, 525, 685, and 740 nm. Algae had very low fluorescence at 440 nm, no fluorescence at 525 nm, and fluorescence maxima at 685 and 740 nm. For algae, the ratio of the fluorescence intensity at 685 nm to that at 740 nm was much greater than that for monocots, dicots, and hardwoods. The potential use of the LIF technique for individual species identification is suggested.

  16. Radially and azimuthally polarized laser induced shape transformation of embedded metallic nanoparticles in glass.

    PubMed

    Tyrk, Mateusz A; Zolotovskaya, Svetlana A; Gillespie, W Allan; Abdolvand, Amin

    2015-09-01

    Radially and azimuthally polarized picosecond (~10 ps) pulsed laser irradiation at 532 nm wavelength led to the permanent reshaping of spherical silver nanoparticles (~30 - 40 nm in diameter) embedded in a thin layer of soda-lime glass. The observed peculiar shape modifications consist of a number of different orientations of nano-ellipsoids in the cross-section of each written line by laser. A Second Harmonic Generation cross-sectional scan method from silver nanoparticles in transmission geometry was adopted for characterization of the samples after laser modification. The presented approach may lead to sophisticated marking of information in metal-glass nanocomposites. PMID:26368440

  17. Faster motion of double 360° domain walls system induced by spin-polarized current

    SciTech Connect

    Zhang, S. F.; Zhu, Q. Y.; Mu, C. P.; Zheng, Q.; Liu, X. Y.; Liu, Q. F.; Wang, J. B.

    2014-05-07

    By micromagnetic simulation, we investigated a double 360° domain walls system in two parallel nanowires. Two domain walls are coupled to each other via magnetostatic interaction. When a spin-polarized current is applied to only one nanowire or both nanowires with the same direction, the two domain walls propagate along nanowires together. The critical velocity of such system is obviously higher than that of a single 360° domain wall. The interaction between the two domain walls can be modeled as two bodies that connected by a spring, and we analyzed the coupling characteritics of the double 360° domain walls at last.

  18. Radiometric calibration of a polarization-sensitive sensor

    SciTech Connect

    Ahmad, S.P.; Markham, B.L. NASA, Goddard Space Flight Center, Greenbelt, MD )

    1992-11-01

    The radiometric accuracy of a sensor is adversely affected by scene polarization if its optical system is sensitive to polarization. Tests performed on the reflective bands of the NS001 Thematic Mapper simulator, an aircraft multispectral scanner, show that it is very sensitive to the polarization state of the incoming radiations. For 100 percent linearly polarized light, errors in the measured intensity vary from -40 to +40 percent, depending on the scan angle and spectral band. To estimate polarization-induced errors in the intensity measured at aircraft level, the intensity and polarization of the atmospheric radiances were simulated using a realistic earth-atmosphere radiative transfer model. For the polarization of atmospheric radiances in the solar meridian plane over a vegetated target, intensity errors may range from -10 to + 10 percent. The polarization-induced errors are highest in the shortest NS001 spectral band (0.450-0.525 microns) because of large atmospheric polarizations contributed by Rayleigh particles and small diluting effects caused by the small contributions of weakly polarized radiations coming from aerosols and the surface. Depending on the illumination and view angles, the errors in derived surface reflectance due to the radiance errors can be very large. In particular, for large off-nadir view angles in the forward scattered direction when the sun is low, the relative errors in the derived surface reflectance can be as large as 4 to 5 times the relative error in the radiances. Polarization sensitivity errors cannot be neglected for the shorter wavelengths when the surface reflectance contribution to atmospheric radiances is very small. 40 refs.

  19. Nitrogen Limitation and Slow Drying Induce Desiccation Tolerance in Conjugating Green Algae (Zygnematophyceae, Streptophyta) from Polar Habitats

    PubMed Central

    Pichrtová, Martina; Kulichová, Jana; Holzinger, Andreas

    2014-01-01

    Background Filamentous Zygnematophyceae are typical components of algal mats in the polar hydro-terrestrial environment. Under field conditions, they form senescent vegetative cells, designated as pre-akinetes, which are tolerant to desiccation and osmotic stress. Key Findings Pre-akinete formation and desiccation tolerance was investigated experimentally under monitored laboratory conditions in four strains of Arctic and Antarctic isolates with vegetative Zygnema sp. morphology. Phylogenetic analyses of rbcL sequences revealed one Arctic strain as genus Zygnemopsis, phylogenetically distant from the closely related Zygnema strains. Algae were cultivated in liquid or on solidified medium (9 weeks), supplemented with or lacking nitrogen. Nitrogen-free cultures (liquid as well as solidified) consisted of well-developed pre-akinetes after this period. Desiccation experiments were performed at three different drying rates (rapid: 10% relative humidity, slow: 86% rh and very slow); viability, effective quantum yield of PS II, visual and ultrastructural changes were monitored. Recovery and viability of pre-akinetes were clearly dependent on the drying rate: slower desiccation led to higher levels of survival. Pre-akinetes survived rapid drying after acclimation by very slow desiccation. Conclusions The formation of pre-akinetes in polar Zygnema spp. and Zygnemopsis sp. is induced by nitrogen limitation. Pre-akinetes, modified vegetative cells, rather than specialized stages of the life cycle, can be hardened by mild desiccation stress to survive rapid drying. Naturally hardened pre-akinetes play a key role in stress tolerance and dispersal under the extreme conditions of polar regions, where sexual reproduction and production of dormant stages is largely suppressed. PMID:25398135

  20. Spectral State Dependence of the 0.4-2 MeV Polarized Emission in Cygnus X-1 Seen with INTEGRAL/IBIS, and Links with the AMI Radio Data

    NASA Astrophysics Data System (ADS)

    Rodriguez, Jérôme; Grinberg, Victoria; Laurent, Philippe; Cadolle Bel, Marion; Pottschmidt, Katja; Pooley, Guy; Bodaghee, Arash; Wilms, Jörn; Gouiffès, Christian

    2015-07-01

    Polarization of the ? 400 keV hard tail of the microquasar Cygnus X-1 has been independently reported by INTEGRAL/Imager on Board the INTEGRAL Satellite (IBIS), and INTEGRAL/SPectrometer on INTEGRAL and interpreted as emission from a compact jet. These conclusions were, however, based on the accumulation of all INTEGRAL data regardless of the spectral state. We utilize additional INTEGRAL exposure accumulated until 2012 December, and include the AMI/Ryle (15 GHz) radio data in our study. We separate the observations into hard, soft, and intermediate/transitional states and detect radio emission from a compact jet in hard and intermediate states (IS), but not in the soft. The 10-400 keV INTEGRAL (JEM-X and IBIS) state resolved spectra are well modeled with thermal Comptonization and reflection components. We detect a hard tail in the 0.4-2 MeV range for the hard state only. We extract the state dependent polarigrams of Cyg X-1, which are all compatible with no or an undetectable level of polarization except in the 400-2000 keV range in the hard state where the polarization fraction is 75% ± 32% and the polarization angle 40.°0 ± 14.°3. An upper limit on the 0.4-2 MeV soft state polarization fraction is 70%. Due to the short exposure, we obtain no meaningful constraint for the IS. The likely detection of a \\gt 400 keV polarized tail in the hard state, together with the simultaneous presence of a radio jet, reinforce the notion of a compact jet origin of the \\gt 400 keV emission.

  1. Built-in and Induced Polarization Across LaAlO3/SrTiO3 Heterojunctions

    SciTech Connect

    Guneeta, Singh-Bhalla

    2011-08-15

    Ionic crystals terminated at oppositely charged polar surfaces are inherently unstable and expected to undergo surface reconstructions to maintain electrostatic stability. Essentially, an electric field that arises between oppositely charged atomic planes gives rise to a built-in potential that diverges with thickness. Here we present evidence of such a built-in potential across polar LaAlO{sub 3} thin films grown on SrTiO{sub 3} substrates, a system well known for the electron gas that forms at the interface. By performing tunneling measurements between the electron gas and metallic electrodes on LaAlO{sub 3} we measure a built-in electric field across LaAlO{sub 3} of 80.1 meV/{angstrom}. Additionally, capacitance measurements reveal the presence of an induced dipole moment across the heterostructure. We forsee use of the ionic built-in potential as an additional tuning parameter in both existing and novel device architectures, especially as atomic control of oxide interfaces gains widespread momentum.

  2. T invariance and T-odd asymmetries for the cold-polarized-neutron-induced fission of nonoriented nuclei

    SciTech Connect

    Kadmensky, S. G.; Bunakov, V. E.; Titova, L. V.

    2014-12-15

    It is shown that the coefficients D{sup exp} for all T-odd asymmetries observed experimentally in the cross sections for the reactions of cold-polarized-neutron-induced fission of nonoriented target nuclei (which involves the emission of prescission and evaporated particles) comply in shape and scale with the coefficients D{sup theor} calculated for the analogous asymmetries on the basis of quantum-mechanical nuclear-fission theory for T-invariant Hamiltonians of fissile systems. It is also shown that the asymmetries in question arise upon taking into account the effect of (i) the interference between the fission amplitudes of s- and p-wave resonances of a polarized fissile compound nucleus formed in the aforementioned reactions; (ii) the collective rotation of the compound nucleus in question (this rotation entails a change in the angular distributions of fission fragments and third particles); and (iii) the wriggling vibrations of this compound nucleus in the vicinity of its scission point, which lead to the appearance of high aligned spins of fission fragments, with the result that the emission of neutrons and photons evaporated from these fragments becomes anisotropic. The possible contribution of T-noninvariant interactions to the formation of the T-odd asymmetries under analysis is estimated by using the results obtained in experimentally testing the detailed-balance principle, (P-A) theorem, and T invariance of cross sections for elastic proton-proton and proton-neutron scattering.

  3. Demonstration of Heterogeneous Parahydrogen Induced Polarization Using Hyperpolarized Agent Migration from Dissolved Rh(I) Complex to Gas Phase

    PubMed Central

    2015-01-01

    Parahydrogen-induced polarization (PHIP) was used to demonstrate the concept that highly polarized, catalyst-free fluids can be obtained in a catalysis-free regime using a chemical reaction with molecular addition of parahydrogen to a water-soluble Rh(I) complex carrying a payload of compound with unsaturated (C=C) bonds. Hydrogenation of norbornadiene leads to formation of norbornene, which is eliminated from the Rh(I) complex and, therefore, leaves the aqueous phase and becomes a gaseous hyperpolarized molecule. The Rh(I) metal complex resides in the original liquid phase, while the product of hydrogen addition is found exclusively in the gaseous phase based on the affinity. Hyperpolarized norbornene 1H NMR signals observed in situ were enhanced by a factor of approximately 10?000 at a static field of 47.5 mT. High-resolution 1H NMR at a field of 9.4 T was used for ex situ detection of hyperpolarized norbornene in the gaseous phase, where a signal enhancement factor of approximately 160 was observed. This concept of stoichiometric as opposed to purely catalytic use of PHIP-available complexes with an unsaturated payload precursor molecule can be extended to other contrast agents for both homogeneous and heterogeneous PHIP. The Rh(I) complex was employed in aqueous medium suitable for production of hyperpolarized contrast agents for biomedical use. Detection of PHIP hyperpolarized gas by low-field NMR is demonstrated here for the first time. PMID:24918975

  4. Generalized focusing of time-lapse changes with applications to direct current and time-domain induced polarization inversions

    NASA Astrophysics Data System (ADS)

    Fiandaca, Gianluca; Doetsch, Joseph; Vignoli, Giulio; Auken, Esben

    2015-11-01

    Often in geophysical monitoring experiments time-lapse inversion models vary too smoothly with time, owing to the strong imprint of regularization. Several methods have been proposed for focusing the spatiotemporal changes of the model parameters. In this study, we present two generalizations of the minimum support norm, which favour compact time-lapse changes and can be adapted to the specific problem requirements. Inversion results from synthetic direct current resistivity models that mimic developing plumes show that the focusing scheme significantly improves size, shape and magnitude estimates of the time-lapse changes. Inversions of the synthetic data also illustrate that the focused inversion gives robust results and that the focusing settings are easily chosen. Inversions of full-decay time-domain induced polarization (IP) field data from a CO2 monitoring injection experiment show that the focusing scheme performs well for field data and inversions for all four Cole-Cole polarization parameters. Our tests show that the generalized minimum support norms react in an intuitive and predictable way to the norm settings, implying that they can be used in time-lapse experiments for obtaining reliable and robust results.

  5. Polarization screening-induced magnetic phase gradients at complex oxide interfaces.

    PubMed

    Spurgeon, Steven R; Balachandran, Prasanna V; Kepaptsoglou, Despoina M; Damodaran, Anoop R; Karthik, J; Nejati, Siamak; Jones, Lewys; Ambaye, Haile; Lauter, Valeria; Ramasse, Quentin M; Lau, Kenneth K S; Martin, Lane W; Rondinelli, James M; Taheri, Mitra L

    2015-01-01

    Thin-film oxide heterostructures show great potential for use in spintronic memories, where electronic charge and spin are coupled to transport information. Here we use a La0.7Sr0.3MnO3 (LSMO)/PbZr0.2Ti0.8O3 (PZT) model system to explore how local variations in electronic and magnetic phases mediate this coupling. We present direct, local measurements of valence, ferroelectric polarization and magnetization, from which we map the phases at the LSMO/PZT interface. We combine these experimental results with electronic structure calculations to elucidate the microscopic interactions governing the interfacial response of this system. We observe a magnetic asymmetry at the LSMO/PZT interface that depends on the local PZT polarization and gives rise to gradients in local magnetic moments; this is associated with a metal-insulator transition at the interface, which results in significantly different charge-transfer screening lengths. This study establishes a framework to understand the fundamental asymmetries of magnetoelectric coupling in oxide heterostructures. PMID:25879160

  6. Polarization-induced transport in ferroelectric organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Laudari, A.; Guha, S.

    2015-03-01

    Ferroelectric dielectrics, permitting access to nearly an order of magnitude range of dielectric constants with temperature as the tuning parameter, offer a great platform to monitor the changes in interfacial transport in organic field-effect transistors (OFETs) as the polarization strength is tuned. Temperature-dependent transport studies have been carried out from pentacene-based OFETs using the ferroelectric copolymer poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) as a gate insulating layer. The thickness of the gate dielectric was varied from 20 nm to 500 nm. By fits to an Arrhenius-type dependence of the charge carrier mobility as a function of temperature, the activation energy in the ferroelectric phase is found to increase as the thickness of the PVDF-TrFE layer decreases. The weak temperature-dependence of the charge carrier mobility in the ferroelectric phase of PVDF-TrFE may be attributed to a polarization fluctuation driven transport, which results from a coupling of the charge carriers to the surface phonons of the dielectric. By comparing single layer PVDF-TrFE pentacene OFETs with stacked PVDF-TrFE/inorganic dielectric OFETs, the contribution from Fröhlich polarons is extracted. The temperature-dependent mobility of the polarons increases with the thickness of the PVDF-TrFE layer. Using a strongly coupled polaron model, the hopping lengths were determined to vary between 2 Å and 5 Å.

  7. Spectral anomalies of the effect of light-induced drift of caesium atoms caused by the velocity dependence of transport collision frequencies

    SciTech Connect

    Parkhomenko, A I; Shalagin, A M

    2014-10-31

    The spectral features of the light-induced drift (LID) velocity of caesium atoms in inert buffer gases are studied theoretically. A strong temperature dependence of the spectral LID line shape of Cs atoms in Ar or Kr atmosphere in the vicinity of T ? 1000 K is predicted. It is shown that the anomalous LID of Cs atoms in binary buffer mixtures of two different inert gases can be observed at virtually any (including ambient) temperature, depending on the content of the components in these mixtures. The results obtained make it possible to precisely test the interatomic interaction potentials in the experiments on the anomalous LID. (quantum optics)

  8. Laser-induced breakdown spectroscopy in gases using ungated detection in combination with polarization filtering and online background correction

    NASA Astrophysics Data System (ADS)

    Kiefer, J.; Tröger, J. W.; Seeger, T.; Leipertz, A.; Li, B.; Li, Z. S.; Aldén, M.

    2010-06-01

    Quantitative and fast analysis of gas mixtures is an important task in the field of chemical, security and environmental analysis. In this paper we present a diagnostic approach based on laser-induced breakdown spectroscopy (LIBS). A polarization filter in the signal collection system enables sufficient suppression of elastically scattered light which otherwise reduces the dynamic range of the measurement. Running the detector with a doubled repetition rate as compared to the laser online background correction is obtained. Quantitative measurements of molecular air components in synthetic, ambient and expiration air are performed and demonstrate the potential of the method. The detection limits for elemental oxygen and hydrogen are in the order of 15 ppm and 10 ppm, respectively.

  9. Soluble Extracts from Helicobacter pylori Induce Dome Formation in Polarized Intestinal Epithelial Monolayers in a Laminin-Dependent Manner

    PubMed Central

    Terrés, A. M.; Windle, H. J.; Ardini, E.; Kelleher, D. P.

    2003-01-01

    Helicobacter pylori colonizes the stomach at the interface between the mucus layer and the apical pole of gastric epithelial cells. A number of secreted and shed products from the bacteria, such as proteins and lipopolysaccharide, are likely to have a role in the pathogenesis at the epithelial level. To determine the physiological response of transporting polarized epithelia to released soluble factors from the bacterium, we used the T84 cell line. Monolayers of T84 cells were exposed to soluble extracts from H. pylori. The extracts induced rapid “dome” formation as well as an immediate decrease in transepithelial electrical resistance. Domes are fluid-filled blister-like structures unique to polarized epithelia. Their formation has been linked to sodium-transporting events as well as to diminished adherence of the cells to the substrate. H. pylori-induced dome formation in T84 monolayers was exacerbated by amiloride and inhibited by ouabain. Furthermore, it was associated with changes in the expression of the laminin binding ?6?4 integrin and the 67-kDa laminin receptor. Domes formed primarily on laminin-coated filters, rather than on fibronectin or collagen matrices, and their formation was inhibited by preincubating the bacterial extract with soluble laminin. This effect was specific to H. pylori and independent of the urease, vacA, cagA, and Lewis phenotype of the strains. These data indicate that released elements from H. pylori can alter the physiological balance and integrity of the epithelium in the absence of an underlying immune response. PMID:12819097

  10. Interface-induced phenomena in polarization response of ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Tagantsev, A. K.; Gerra, G.

    2006-09-01

    This article reviews the existing theoretical models describing the interface-induced phenomena which affect the switching characteristics and dielectric properties of ferroelectric thin films. Three groups of interface-induced effects are addressed—namely, "passive-layer-type" effects, ferroelectric-electrode contact potential effects, and the poling effect of the ferroelectric-electrode interface. The existing experimental data on dielectric and switching characteristics of ferroelectric thin film capacitors are discussed in the context of the reviewed theories. Special attention is paid to the case of internal bias field effects.

  11. 3-D SPECTRAL IP IMAGING: NON-INVASIVE CHARACTERIZATION OF CONTAMINANT PLUMES

    EPA Science Inventory

    The objective of this study is to develop a noninvasive tomographic imaging technique,based on the spectral induced-polarization method, to characterize the in-situ distribution of organic and inorganic groundwater contaminants. Recent advances in tomographic imaging, applied to ...

  12. Special Features of Polarization-Induced Relaxation in Structurally Disordered Finely Dispersed Systems

    NASA Astrophysics Data System (ADS)

    Shcherbachenko, L. A.; Tanaev, A. B.; Bezrukova, Ya. V.; Ezhova, L. I.; Baryshnikov, D. S.; Marchuk, S. D.; Berezovskii, P. P.

    2015-04-01

    Dielectric characteristics of finely dispersed hydrated natural coal from the Krasnoyarsk Strip Mine are measured in wide ranges of external measuring electric field frequencies, environmental temperatures, and humidities. The frequency, temperature, and concentration dispersions of the dielectric permittivity are revealed for the examined structures. An analysis of the results obtained demonstrates that a cluster layer of the polar aqueous matrix characterized by rigid fixing of water molecules is formed at the interphase boundaries of the examined system. It is demonstrated that this layer plays the role of the potential barrier that complicates transitions for both free water molecules and surface active dispersed coals oriented by the electric field. This layer can increase the electric strength of the examined disordered finely dispersed structures.

  13. Cosmic ray-induced stratospheric aerosols: A possible connection to polar ozone depletions

    NASA Astrophysics Data System (ADS)

    Kasatkina, E. A.; Shumilov, O. I.

    2005-03-01

    The model calculations of altitude distribution of CN (condensation nuclei), plausible centers of sulfate aerosol formation after the occurrence of GLE, are presented. Events with relativistic solar protons (i.e. protons with energies >450MeV) are observed at ground level by neutron monitors and called ground-level events (GLEs) (Shea and Smart, 2001). Analysis of experimental data and model calculations permits us to explain some distinctions observed in ozone total content (OTC) variations during several GLEs. For example, model simulations show a significant CN concentration enhancement during the May 1990 GLEs of relatively "moderate" magnitude, when polar ozone "mini-holes" (OTC depletions up to 20%) have been observed, while no OTC variations and considerable aerosol enhancements were seen during more powerful GLEs (4 August 1972, 2 May 1998, 14 July 2000) (Reagan et al., 1981; Shumilov et al., 1995, 2003). Our results demonstrate that "moderate" GLEs may increase aerosol content significantly and cause ozone "mini-hole" creation.

  14. Dynamic nuclear polarization in solid samples by electrical-discharge-induced radicals

    NASA Astrophysics Data System (ADS)

    Katz, Itai; Blank, Aharon

    2015-12-01

    Dynamic nuclear polarization (DNP) is a method for enhancing nuclear magnetic resonance (NMR) signals that has many potential applications in chemistry and medicine. Traditionally, DNP signal enhancement is achieved through the use of exogenous radicals mixed in a solution with the molecules of interest. Here we show that proton DNP signal enhancements can be obtained for solid samples without the use of solvent and exogenous radicals. Radicals are generated primarily on the surface of a solid sample using electrical discharges. These radicals are found suitable for DNP. They are stable under moderate vacuum conditions, yet readily annihilate upon compound dissolution or air exposure. This feature makes them attractive for use in medical applications, where the current variety of radicals used for DNP faces regulatory problems. In addition, this solvent-free method may be found useful for analytical NMR of solid samples which cannot tolerate solvents, such as certain pharmaceutical products.

  15. Circularly polarized luminescence of AIE-active chiral O-BODIPYs induced via intramolecular energy transfer.

    PubMed

    Zhang, Shuwei; Wang, Yuxiang; Meng, Fandian; Dai, Chunhui; Cheng, Yixiang; Zhu, Chengjian

    2015-05-28

    Two AIE-active chiral BINOL-based O-BODIPY enantiomers (R/S-5) were synthesized and showed mirror-image red-color CPL induced via intramolecular energy transfer. The chiroptical properties of the molecules indicate that the chirality of electronic ground and excited states is stable and independent of aggregation. PMID:25939571

  16. Collectively Induced Quantum-Confined Stark Effect in Monolayers of Molecules Consisting of Polar Repeating Units

    PubMed Central

    2011-01-01

    The electronic structure of terpyrimidinethiols is investigated by means of density-functional theory calculations for isolated molecules and monolayers. In the transition from molecule to self-assembled monolayer (SAM), we observe that the band gap is substantially reduced, frontier states increasingly localize on opposite sides of the SAM, and this polarization in several instances is in the direction opposite to the polarization of the overall charge density. This behavior can be analyzed by analogy to inorganic semiconductor quantum-wells, which, as the SAMs studied here, can be regarded as semiperiodic systems. There, similar observations are made under the influence of a, typically external, electric field and are known as the quantum-confined Stark effect. Without any external perturbation, in oligopyrimidine SAMs one encounters an energy gradient that is generated by the dipole moments of the pyrimidine repeat units. It is particularly strong, reaching values of about 1.6 eV/nm, which corresponds to a substantial electric field of 1.6 × 107 V/cm. Close-lying ?- and ?-states turn out to be a particular complication for a reliable description of the present systems, as their order is influenced not only by the docking groups and bonding to the metal, but also by the chosen computational approach. In the latter context we demonstrate that deliberately picking a hybrid functional allows avoiding pitfalls due to the infamous self-interaction error. Our results show that when aiming to build a monolayer with a specific electronic structure one can not only resort to the traditional technique of modifying the molecular structure of the constituents, but also try to exploit collective electronic effects. PMID:21955058

  17. Polarized cell motility induces hydrogen peroxide to inhibit cofilin via cysteine oxidation.

    PubMed

    Cameron, Jenifer M; Gabrielsen, Mads; Chim, Ya Hua; Munro, June; McGhee, Ewan J; Sumpton, David; Eaton, Philip; Anderson, Kurt I; Yin, Huabing; Olson, Michael F

    2015-06-01

    Mesenchymal cell motility is driven by polarized actin polymerization [1]. Signals at the leading edge recruit actin polymerization machinery to promote membrane protrusion, while matrix adhesion generates tractive force to propel forward movement. To work effectively, cell motility is regulated by a complex network of signaling events that affect protein activity and localization. H2O2 has an important role as a diffusible second messenger [2], and mediates its effects through oxidation of cysteine thiols. One cell activity influenced by H2O2 is motility [3]. However, a lack of sensitive and H2O2-specific probes for measurements in live cells has not allowed for direct observation of H2O2 accumulation in migrating cells or protrusions. In addition, the identities of proteins oxidized by H2O2 that contribute to actin dynamics and cell motility have not been characterized. We now show, as determined by fluorescence lifetime imaging microscopy, that motile cells generate H2O2 at membranes and cell protrusions and that H2O2 inhibits cofilin activity through oxidation of cysteines 139 (C139) and 147 (C147). Molecular modeling suggests that C139 oxidation would sterically hinder actin association, while the increased negative charge of oxidized C147 would lead to electrostatic repulsion of the opposite negatively charged surface. Expression of oxidation-resistant cofilin impairs cell spreading, adhesion, and directional migration. These findings indicate that H2O2 production contributes to polarized cell motility through localized cofilin inhibition and that there are additional proteins oxidized during cell migration that might have similar roles. PMID:25981793

  18. Polarized Cell Motility Induces Hydrogen Peroxide to Inhibit Cofilin via Cysteine Oxidation

    PubMed Central

    Cameron, Jenifer M.; Gabrielsen, Mads; Chim, Ya Hua; Munro, June; McGhee, Ewan J.; Sumpton, David; Eaton, Philip; Anderson, Kurt I.; Yin, Huabing; Olson, Michael F.

    2015-01-01

    Summary Mesenchymal cell motility is driven by polarized actin polymerization [1]. Signals at the leading edge recruit actin polymerization machinery to promote membrane protrusion, while matrix adhesion generates tractive force to propel forward movement. To work effectively, cell motility is regulated by a complex network of signaling events that affect protein activity and localization. H2O2 has an important role as a diffusible second messenger [2], and mediates its effects through oxidation of cysteine thiols. One cell activity influenced by H2O2 is motility [3]. However, a lack of sensitive and H2O2-specific probes for measurements in live cells has not allowed for direct observation of H2O2 accumulation in migrating cells or protrusions. In addition, the identities of proteins oxidized by H2O2 that contribute to actin dynamics and cell motility have not been characterized. We now show, as determined by fluorescence lifetime imaging microscopy, that motile cells generate H2O2 at membranes and cell protrusions and that H2O2 inhibits cofilin activity through oxidation of cysteines 139 (C139) and 147 (C147). Molecular modeling suggests that C139 oxidation would sterically hinder actin association, while the increased negative charge of oxidized C147 would lead to electrostatic repulsion of the opposite negatively charged surface. Expression of oxidation-resistant cofilin impairs cell spreading, adhesion, and directional migration. These findings indicate that H2O2 production contributes to polarized cell motility through localized cofilin inhibition and that there are additional proteins oxidized during cell migration that might have similar roles. PMID:25981793

  19. Induced formation of dominating polar phases of poly(vinylidene fluoride): positive ion-CF2 dipole or negative ion-CH2 dipole interaction.

    PubMed

    Liang, Cheng-Lu; Mai, Zhong-Hai; Xie, Qi; Bao, Rui-Ying; Yang, Wei; Xie, Bang-Hu; Yang, Ming-Bo

    2014-07-31

    The "ion-dipole" interaction has been the most widely accepted mechanism for the direct formation of polar phases (?, ?) of poly(vinylidene fluoride) (PVDF), which have been widely used as transducers, actuators, and sensors. However, the type of charged ions is still controversial. In order to throw light upon this issue, two types of charged small organic molecules that are in different physical states (melt or solid) during the crystallization of PVDF were melt-blended with PVDF resin. Results revealed that only the incorporation of positive charged molecules can lead to the formation of polar phases. Additionally, it is interesting to find that during the crystallization of PVDF, molten positively charged molecules resulted in ?-phase dominating, while solid positively charged molecules exclusively induced ?-phase. These results lead to the understanding that the induced formation of polar phases of PVDF is due to the "positive ion-CF2 dipole" interaction. PMID:25010928

  20. Multipolar polarizations of methane from isotropic and anisotropic collision-induced light scattering

    NASA Astrophysics Data System (ADS)

    Bancewicz, T.; Nowicka, K.; Godet, J.-L.; Le Duff, Y.

    2004-06-01

    The anisotropic and isotropic binary collision-induced spectra scattered by gaseous methane have been measured in absolute units up to 900 cm-1 from the Rayleigh line. Corresponding theoretical intensities taking into account multipolar polarizabilities have been calculated using a semiclassical procedure. From the analysis of, mainly, our isotropic scattering data, values of the dipole-quadrupole and dipole-octopole polarizabilities are deduced. They are found to be in good agreement with recent ab initio calculations.

  1. microRNA-223 Regulates Macrophage Polarization and Diet-induced Insulin Resistance 

    E-print Network

    Meng, Cong

    2013-05-01

    of epigenetic regulators including microRNAs in the pathogenesis of diabetes and this opened a new window for investigating mechanisms governing obesity induced inflammation and diabetes.9 MicroRNAs (miRs) are small noncoding RNAs of approximately 22... Transcription Polymerase Chain Reaction SiRNA Small interfering RNA SP3 Sp3 transcription factor T2DM Type 2 Diabetes Mellitus TGFBR3 Transforming Growth Factor, Beta Receptor III UTR Untranslated Region WT Wild...

  2. Femtosecond Raman-induced Kerr effect study of polar solvent dynamics: Amides

    SciTech Connect

    Chang, Yong Joon; Castner, E.W. Jr.

    1993-07-01

    We have measured the ultrafast pure solvent dynamics of highly power liquids, formamide (FA), N-methylformamide (NMF), N-methylacetamide (NMA), N-methylpropioamide (NMP) and N,N{prime}-dimethylformamide (DMF) using femtosecond optical-heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). The effects of deuteration and temperature-dependence were studied to characterize in detail both the inertial (or non-diffusive) and diffusive intermolecular motions in these liquids.

  3. Multipolar polarizations of methane from isotropic and anisotropic collision-induced light scattering

    SciTech Connect

    Bancewicz, T.; Nowicka, K.; Godet, J.-L.; Le Duff, Y.

    2004-06-01

    The anisotropic and isotropic binary collision-induced spectra scattered by gaseous methane have been measured in absolute units up to 900 cm{sup -1} from the Rayleigh line. Corresponding theoretical intensities taking into account multipolar polarizabilities have been calculated using a semiclassical procedure. From the analysis of, mainly, our isotropic scattering data, values of the dipole-quadrupole and dipole-octopole polarizabilities are deduced. They are found to be in good agreement with recent ab initio calculations.

  4. CCR2 Antagonism Alters Brain Macrophage Polarization and Ameliorates Cognitive Dysfunction Induced by Traumatic Brain Injury

    PubMed Central

    Jopson, Timothy D.; Liu, Sharon; Riparip, Lara-Kirstie; Guandique, Cristian K.; Gupta, Nalin; Ferguson, Adam R.

    2015-01-01

    Traumatic brain injury (TBI) is a major risk factor for the development of multiple neurodegenerative diseases. With respect to the increasing prevalence of TBI, new therapeutic strategies are urgently needed that will prevent secondary damage to primarily unaffected tissue. Consistently, neuroinflammation has been implicated as a key mediator of secondary damage following the initial mechanical insult. Following injury, there is uncertainty regarding the role that accumulating CCR2+ macrophages play in the injury-induced neuroinflammatory sequelae and cognitive dysfunction. Using CX3CR1GFP/+CCR2RFP/+ reporter mice, we show that TBI initiated a temporally restricted accumulation of peripherally derived CCR2+ macrophages, which were concentrated in the hippocampal formation, a region necessary for learning and memory. Multivariate analysis delineated CCR2+ macrophages' neuroinflammatory response while identifying a novel therapeutic treatment window. As a proof of concept, targeting CCR2+ macrophages with CCX872, a novel Phase I CCR2 selective antagonist, significantly reduced TBI-induced inflammatory macrophage accumulation. Concomitantly, there was a significant reduction in multiple proinflammatory and neurotoxic mediators with this treatment paradigm. Importantly, CCR2 antagonism resulted in a sparing of TBI-induced hippocampal-dependent cognitive dysfunction and reduced proinflammatory activation profile 1 month after injury. Thus, therapeutically targeting the CCR2+ subset of monocytes/macrophages may provide a new avenue of clinical intervention following TBI. PMID:25589768

  5. CCR2 antagonism alters brain macrophage polarization and ameliorates cognitive dysfunction induced by traumatic brain injury.

    PubMed

    Morganti, Josh M; Jopson, Timothy D; Liu, Sharon; Riparip, Lara-Kirstie; Guandique, Cristian K; Gupta, Nalin; Ferguson, Adam R; Rosi, Susanna

    2015-01-14

    Traumatic brain injury (TBI) is a major risk factor for the development of multiple neurodegenerative diseases. With respect to the increasing prevalence of TBI, new therapeutic strategies are urgently needed that will prevent secondary damage to primarily unaffected tissue. Consistently, neuroinflammation has been implicated as a key mediator of secondary damage following the initial mechanical insult. Following injury, there is uncertainty regarding the role that accumulating CCR2(+) macrophages play in the injury-induced neuroinflammatory sequelae and cognitive dysfunction. Using CX3CR1(GFP/+)CCR2(RFP/+) reporter mice, we show that TBI initiated a temporally restricted accumulation of peripherally derived CCR2(+) macrophages, which were concentrated in the hippocampal formation, a region necessary for learning and memory. Multivariate analysis delineated CCR2(+) macrophages' neuroinflammatory response while identifying a novel therapeutic treatment window. As a proof of concept, targeting CCR2(+) macrophages with CCX872, a novel Phase I CCR2 selective antagonist, significantly reduced TBI-induced inflammatory macrophage accumulation. Concomitantly, there was a significant reduction in multiple proinflammatory and neurotoxic mediators with this treatment paradigm. Importantly, CCR2 antagonism resulted in a sparing of TBI-induced hippocampal-dependent cognitive dysfunction and reduced proinflammatory activation profile 1 month after injury. Thus, therapeutically targeting the CCR2(+) subset of monocytes/macrophages may provide a new avenue of clinical intervention following TBI. PMID:25589768

  6. Pronounced polarization-induced energy level shifts at boundaries of organic semiconductor nanostructures

    PubMed Central

    Cochrane, K. A.; Schiffrin, A.; Roussy, T. S.; Capsoni, M.; Burke, S. A.

    2015-01-01

    Organic semiconductor devices rely on the movement of charge at and near interfaces, making an understanding of energy level alignment at these boundaries an essential element of optimizing materials for electronic and optoelectronic applications. Here we employ low temperature scanning tunneling microscopy and spectroscopy to investigate a model system: two-dimensional nanostructures of the prototypical organic semiconductor, PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) adsorbed on NaCl (2?ML)/Ag(111). Pixel-by-pixel scanning tunneling spectroscopy allows mapping of occupied and unoccupied electronic states across these nanoislands with sub-molecular spatial resolution, revealing strong electronic differences between molecules at the edges and those in the centre, with energy level shifts of up to 400?meV. We attribute this to the change in electrostatic environment at the boundaries of clusters, namely via polarization of neighbouring molecules. The observation of these strong shifts illustrates a crucial issue: interfacial energy level alignment can differ substantially from the bulk electronic structure in organic materials. PMID:26440933

  7. Sheath-induced distortions in particle distributions near enhanced polar outflow probe particle sensors

    SciTech Connect

    Hussain, S.; Marchand, R.

    2014-07-15

    We discuss sheath and kinetic effects on ion and electron distribution functions at the aperture of enhanced Polar Outflow Probe particle sensors. For this purpose, the interaction between the CASSIOPE spacecraft and space environment is simulated fully kinetically using the electrostatic Particle In Cell code PTetra. The simulations account for the geometry of the main features of the spacecraft body, the booms, and the sensors. In addition to the background plasma, the model also accounts for Earth magnetic field. The plasma parameters assumed in the simulations are obtained from the latest version of the International Reference Ionosphere (IRI) model and the value of magnetic field is obtained from the International Geophysical Reference Field model. Our analysis shows significant distortions in the ion distribution function in the plane of the sensor aperture, as well as in the direction along the boom holding the sensor. We argue that significant distortions and asymmetries should also occur at the aperture of the suprathermal electron imager when suprathermal electrons are detected, with energies of 5?eV or more.

  8. Pronounced polarization-induced energy level shifts at boundaries of organic semiconductor nanostructures.

    PubMed

    Cochrane, K A; Schiffrin, A; Roussy, T S; Capsoni, M; Burke, S A

    2015-01-01

    Organic semiconductor devices rely on the movement of charge at and near interfaces, making an understanding of energy level alignment at these boundaries an essential element of optimizing materials for electronic and optoelectronic applications. Here we employ low temperature scanning tunneling microscopy and spectroscopy to investigate a model system: two-dimensional nanostructures of the prototypical organic semiconductor, PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) adsorbed on NaCl (2?ML)/Ag(111). Pixel-by-pixel scanning tunneling spectroscopy allows mapping of occupied and unoccupied electronic states across these nanoislands with sub-molecular spatial resolution, revealing strong electronic differences between molecules at the edges and those in the centre, with energy level shifts of up to 400?meV. We attribute this to the change in electrostatic environment at the boundaries of clusters, namely via polarization of neighbouring molecules. The observation of these strong shifts illustrates a crucial issue: interfacial energy level alignment can differ substantially from the bulk electronic structure in organic materials. PMID:26440933

  9. Pronounced polarization-induced energy level shifts at boundaries of organic semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Cochrane, K. A.; Schiffrin, A.; Roussy, T. S.; Capsoni, M.; Burke, S. A.

    2015-10-01

    Organic semiconductor devices rely on the movement of charge at and near interfaces, making an understanding of energy level alignment at these boundaries an essential element of optimizing materials for electronic and optoelectronic applications. Here we employ low temperature scanning tunneling microscopy and spectroscopy to investigate a model system: two-dimensional nanostructures of the prototypical organic semiconductor, PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) adsorbed on NaCl (2 ML)/Ag(111). Pixel-by-pixel scanning tunneling spectroscopy allows mapping of occupied and unoccupied electronic states across these nanoislands with sub-molecular spatial resolution, revealing strong electronic differences between molecules at the edges and those in the centre, with energy level shifts of up to 400 meV. We attribute this to the change in electrostatic environment at the boundaries of clusters, namely via polarization of neighbouring molecules. The observation of these strong shifts illustrates a crucial issue: interfacial energy level alignment can differ substantially from the bulk electronic structure in organic materials.

  10. Hyperthermically induced changes in high spectral and spatial resolution MR images of tumor tissue – a pilot study

    PubMed Central

    Foxley, Sean; Fan, Xiaobing; River, Jonathan; Zamora, Marta; Markiewicz, Erica; Sokka, Shunmugavelu; Karczmar, Gregory S

    2012-01-01

    This pilot study investigated the feasibility of using MRI based on BOLD (blood oxygen level dependent) contrast to detect physiological effects of locally induced hyperthermia in a rodent tumor model. Nude mice bearing AT6.1 rodent prostate tumors inoculated in the hind leg were imaged at 9.4T scanner using a multi-gradient echo pulse sequence to acquire high spectral and spatial resolution (HiSS) data. Approximately 6 °C increases were produced locally in tumor tissue using fiber optic guided light from a 250 W halogen lamp. HiSS data were acquired over three slices through the tumor and leg both prior to and during heating. Water spectra were produced from these datasets for each voxel at each time point. Time dependent changes in water resonance peak width were measured during 15 minutes of localized tumor heating. The results demonstrated that hyperthermia produced both significant increases and decreases in water resonance peak width. Average decreases in peak width were significantly larger in the tumor rim than in normal muscle (p = 0.04). The effect of hyperthermia in tumor was spatially heterogeneous, i.e., the standard deviation of the change in peak width was significantly larger in the tumor rim than in normal muscle (p = 0.005). Therefore, mild hyperthermia produces spatially heterogeneous changes in water peak width in both tumor and muscle. This may reflect heterogeneous effects of hyperthermia on local oxygenation. The peak width changes in tumor and muscle were significantly different, perhaps due to abnormal tumor vasculature and metabolism. Response to hyperthermia measured by MRI may be useful for identifying and/or characterizing suspicious lesions as well as guiding development of new hyperthermia protocols. PMID:22504096

  11. Spectral Characteristics of Landslide Induced Seismicity: Experimental Validation Based on the Use of an Up-Scaled Sheer Box

    NASA Astrophysics Data System (ADS)

    Yfantis, G.; Carvajal, H. E. M.; Pytharouli, S.; Lunn, R. J.

    2014-12-01

    Microseismic monitoring has been used for the last 20 years as a tool to understand the landslide mechanisms and to help develop a methodology able to provide real time information regarding landslide behavior. These studies involve deployment of seismic sensors at active slopes, with data usually analyzed and interpreted along with data obtained using other monitoring methods, e.g. geodetic/geotechnical monitoring. The interpretation of the records is based on a number of assumptions regarding the nature of the recorded signals resulting in big uncertainties. In order to overcome this problem, we use an up-scaled sheer box to reproduce seismic signals as those emitted by the movement of a landslide. The experimental set up consists of a 65cm diameter and 50cm high concrete cylinder filled with unsaturated soil. The cylinder is pulled along a surficial corridor with the same type of soil under varying vertical loading conditions and the friction at the interface between the soil in cylinder and soil on corridor emits seismic signals. The signals are recorded by a network of 7 short period 3D seismic sensors at distances ranging from 4 to 15m from the cylinder. We analyse the recorded signals in the frequency and time-frequency domain. The obtained significant frequencies range up to 120Hz. Their amplitude changes depending on the source-to-sensor distance (attenuation effect) and the applied vertical load (simulating different depths of the failure plane). The spectral characteristics of the emitted signals when compared to those of signals emitted from a vertical face failure in very similar geological and loading conditions at a nearby site are consistent. Therefore, this experimental set-up is a good analogue for the study of landslide induced seismicity. The suggested methodology can be a powerful tool in studying the effects of the type of soil, the loading conditions on the failure plane, the degree of saturation and compaction of the soil on signals recorded during the microseismic monitoring of landslides. It allows for the study and understanding of landslide induced seismicity prior to any failure events allowing simulation of different failure scenarios and the creation of a database of signal characteristics that can be used for an accurate interpretation of the available microseismic records.

  12. Anomalous spectral dependence of optical polarization and its impact on spin detection in InGaAs/GaAs quantum dots

    SciTech Connect

    Puttisong, Y.; Huang, Y. Q.; Buyanova, I. A.; Chen, W. M.; Yang, X. J.; Subagyo, A.; Sueoka, K.; Murayama, A.

    2014-09-29

    We show that circularly polarized emission light from InGaAs/GaAs quantum dot (QD) ensembles under optical spin injection from an adjacent GaAs layer can switch its helicity depending on emission wavelengths and optical excitation density. We attribute this anomalous behavior to simultaneous contributions from both positive and negative trions and a lower number of photo-excited holes than electrons being injected into the QDs due to trapping of holes at ionized acceptors and a lower hole mobility. Our results call for caution in reading out electron spin polarization by optical polarization of the QD ensembles and also provide a guideline in improving efficiency of spin light emitting devices that utilize QDs.

  13. Using linear polarization to monitor nanoparticle purity

    NASA Astrophysics Data System (ADS)

    Barreda, Ángela I.; Sanz, Juan M.; Alcaraz de la Osa, Rodrigo; Saiz, José M.; Moreno, Fernando; González, Francisco; Videen, Gorden

    2015-09-01

    We study the effect of contaminants on the resonances of silicon nanoparticles (NPs) by considering the spectral evolution of the degree of linear polarization of light scattered at right angles to the incident beam, PL(90 °). From an optical point of view, a decrease in the purity of silicon nanoparticles due to the presence of contaminants impacts the NP effective refractive index. We analyze this effect for a silicon nanosphere (R=200 nm) suspended in different media. We focus on the spectral range where the quadrupolar magnetic, dipolar electric and dipolar magnetic resonances appear. The weakness of the resonances induced on the PL(90 °) spectrum by the lack of purity can be used to quantify the contamination of the material. In addition, it is shown that Kerker conditions also suffer from a spectral shift, that is quantified as a function of material purity.

  14. Observation of Gravitationally Induced Vertical Striation of Polarized Ultracold Neutrons by Spin-Echo Spectroscopy

    NASA Astrophysics Data System (ADS)

    Afach, S.; Ayres, N. J.; Ban, G.; Bison, G.; Bodek, K.; Chowdhuri, Z.; Daum, M.; Fertl, M.; Franke, B.; Griffith, W. C.; Gruji?, Z. D.; Harris, P. G.; Heil, W.; Hélaine, V.; Kasprzak, M.; Kermaidic, Y.; Kirch, K.; Knowles, P.; Koch, H.-C.; Komposch, S.; Kozela, A.; Krempel, J.; Lauss, B.; Lefort, T.; Lemière, Y.; Mtchedlishvili, A.; Musgrave, M.; Naviliat-Cuncic, O.; Pendlebury, J. M.; Piegsa, F. M.; Pignol, G.; Plonka-Spehr, C.; Prashanth, P. N.; Quéméner, G.; Rawlik, M.; Rebreyend, D.; Ries, D.; Roccia, S.; Rozpedzik, D.; Schmidt-Wellenburg, P.; Severijns, N.; Thorne, J. A.; Weis, A.; Wursten, E.; Wyszynski, G.; Zejma, J.; Zenner, J.; Zsigmond, G.

    2015-10-01

    We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a |B0|=1 ? T magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCNs of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of 1.1 pT /cm . This novel combination of a well-known nuclear resonance method and gravitationally induced vertical striation is unique in the realm of nuclear and particle physics and should prove to be invaluable for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron or the measurement of the neutron lifetime.

  15. Observation of gravitationally induced vertical striation of polarized ultracold neutrons by spin-echo spectroscopy

    E-print Network

    S. Afach; N. J. Ayres; G. Ban; G. Bison; K. Bodek; Z. Chowdhuri; M. Daum; M. Fertl; B. Franke; W. C. Griffith; Z. D. Gruji?; P. G. Harris; W. Heil; V. Hélaine; M. Kasprzak; Y. Kermaidic; K. Kirch; P. Knowles; H. -C. Koch; S. Komposch; A. Kozela; J. Krempel; B. Lauss; T. Lefort; Y. Lemière; A. Mtchedlishvili; M. Musgrave; O. Naviliat-Cuncic; J. M. Pendlebury; F. M. Piegsa; G. Pignol; C. Plonka-Spehr; P. N. Prashanth; G. Quéméner; M. Rawlik; D. Rebreyend; D. Ries; S. Roccia; D. Rozpedzik; P. Schmidt-Wellenburg; N. Severijns; J. A. Thorne; A. Weis; E. Wursten; G. Wyszynski; J. Zejma; J. Zenner; G. Zsigmond

    2015-09-08

    We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a $|B_0|=1~\\text{\\mu T}$ magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCN of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of $1.1~\\text{pT/cm}$. This novel combination of a well-known nuclear resonance method and gravitationally induced vertical striation is unique in the realm of nuclear and particle physics and should prove to be invaluable for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron or the measurement of the neutron lifetime.

  16. Observation of Gravitationally Induced Vertical Striation of Polarized Ultracold Neutrons by Spin-Echo Spectroscopy.

    PubMed

    Afach, S; Ayres, N J; Ban, G; Bison, G; Bodek, K; Chowdhuri, Z; Daum, M; Fertl, M; Franke, B; Griffith, W C; Gruji?, Z D; Harris, P G; Heil, W; Hélaine, V; Kasprzak, M; Kermaidic, Y; Kirch, K; Knowles, P; Koch, H-C; Komposch, S; Kozela, A; Krempel, J; Lauss, B; Lefort, T; Lemière, Y; Mtchedlishvili, A; Musgrave, M; Naviliat-Cuncic, O; Pendlebury, J M; Piegsa, F M; Pignol, G; Plonka-Spehr, C; Prashanth, P N; Quéméner, G; Rawlik, M; Rebreyend, D; Ries, D; Roccia, S; Rozpedzik, D; Schmidt-Wellenburg, P; Severijns, N; Thorne, J A; Weis, A; Wursten, E; Wyszynski, G; Zejma, J; Zenner, J; Zsigmond, G

    2015-10-16

    We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a |B_{0}|=1???T magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCNs of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of 1.1??pT/cm. This novel combination of a well-known nuclear resonance method and gravitationally induced vertical striation is unique in the realm of nuclear and particle physics and should prove to be invaluable for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron or the measurement of the neutron lifetime. PMID:26550870

  17. Investigation of the field-induced ferromagnetic phase transition in spin-polarized neutron matter: A lowest order constrained variational approach

    SciTech Connect

    Bordbar, G. H.; Rezaei, Z.; Montakhab, Afshin

    2011-04-15

    In this article, the lowest order constrained variational method is used to investigate the magnetic properties of spin-polarized neutron matter in the presence of strong magnetic field at zero temperature employing the AV{sub 18} potential. Our results indicate that a ferromagnetic phase transition is induced by a strong magnetic field with strength greater than 10{sup 18} G, leading to a partial spin polarization of the neutron matter. It is also shown that the equation of state of neutron matter in the presence of a magnetic field is stiffer than in the absence of a magnetic field.

  18. Direct current (DC) resistivity and induced polarization (IP) monitoring of active layer dynamics at high temporal resolution

    NASA Astrophysics Data System (ADS)

    Doetsch, Joseph; Ingeman-Nielsen, Thomas; Christiansen, Anders V.; Fiandaca, Gianluca; Auken, Esben; Adamson, Kathryn; Lane, Timothy; Elberling, Bo

    2014-05-01

    With climatic changes, permafrost thawing and changes in active layer dynamics influencing microbial activity and greenhouse gas feedbacks to the climate system, understanding of the interaction between biogeochemical and thermal processes in the ground is of increasing interest. Here we present results of from an on-going field experiment, where the active layer dynamics are monitored using direct current (DC) resistivity and induced polarization (IP) measurements at high temporal resolution. These DC/IP measurements are supplemented by pore water analysis, continuous ground temperature monitoring (0-150 cm depth) and structural information from ground penetrating radar (GPR). The study site (N69°15', W53°30', 30 m a.s.l.) is located at a Vaccinium/Empetrum heath tundra area near the Arctic Station on Qeqertarsuaq on the west coast of Greenland. Mean air temperatures of the warmest (July) and the coldest (February-March) months are 7.1 and -16.0°C, respectively. The DC/IP monitoring system was installed in July 2013 and has since been acquiring at least 6 data sets per day on a 42-electrode profile with 0.5 m electrode spacing. Recorded data include DC resistivity, stacked full-decay IP responses and full waveform data at 1 kHz sampling frequency. The monitoring system operates fully automatic and data are backed up locally and uploaded to a web server. Time-lapse DC resistivity inversions of data acquired during the freezing period of October - December 2013 clearly image the soil freezing as a strong increase in resistivity. While the freezing horizon generally moves deeper with time, some variations in the freezing depth are observed along the profile. Comparison with soil temperature measurements at different depths indicates a linear relationship between the logarithm of electrical resistivity and temperature. Preliminary time-lapse inversions of the full-decay induced polarization (IP) data indicate a decrease of chargeability with freezing of the ground. Once laboratory analysis of the pore water is available, we will assess if these changes in chargeability are caused by geochemical changes of the pore water.

  19. Polarized Human Embryonic Stem Cell-Derived Retinal Pigment Epithelial Cell Monolayers Have Higher Resistance to Oxidative Stress-Induced Cell Death Than Nonpolarized Cultures

    PubMed Central

    Hsiung, Jamie; Zhu, Danhong

    2015-01-01

    Oxidative stress-mediated injury to the retinal pigment epithelium (RPE) is a major factor involved in the pathogenesis of age-related macular degeneration (AMD), the leading cause of blindness in the elderly. Human embryonic stem cell (hESC)-derived RPE cells are currently being evaluated for their potential for cell therapy in AMD patients through subretinal injection of cells in suspension and subretinal placement as a polarized monolayer. To gain an understanding of how transplanted RPE cells will respond to the highly oxidatively stressed environment of an AMD patient eye, we compared the survival of polarized and nonpolarized RPE cultures following oxidative stress treatment. Polarized, nonpolarized/confluent, nonpolarized/subconfluent hESC-RPE cells were treated with H2O2. Terminal deoxynucleotidyl transferase dUTP nick end labeling stains revealed the highest amount of cell death in subconfluent hESC-RPE cells and little cell death in polarized hESC-RPE cells with H2O2 treatment. There were higher levels of proapoptotic factors (phosphorylated p38, phosphorylated c-Jun NH2-terminal kinase, Bax, and cleaved caspase 3 fragments) in treated nonpolarized RPE—particularly subconfluent cells—relative to polarized cells. On the other hand, polarized RPE cells had constitutively higher levels of cell survival and antiapoptotic signaling factors such as p-Akt and Bcl-2, as well as antioxidants superoxide dismutase 1 and catalase relative to nonpolarized cells, that possibly contributed to polarized cells’ higher tolerance to oxidative stress compared with nonpolarized RPE cells. Subconfluent cells were particularly sensitive to oxidative stress-induced apoptosis. These results suggest that implantation of polarized hESC-RPE monolayers for treating AMD patients with geographic atrophy should have better survival than injections of hESC-RPE cells in suspension. PMID:25411476

  20. The Physics of Polarization

    NASA Astrophysics Data System (ADS)

    Degl'Innocenti, Egidio Landi

    2015-10-01

    The introductory lecture that has been delivered at this Symposium is a condensed version of an extended course held by the author at the XII Canary Island Winter School from November 13 to November 21, 2000. The full series of lectures can be found in Landi Degl'Innocenti (2002). The original reference is organized in 20 Sections that are here itemized: 1. Introduction, 2. Description of polarized radiation, 3. Polarization and optical devices: Jones calculus and Muller matrices, 4. The Fresnel equations, 5. Dichroism and anomalous dispersion, 6. Polarization in everyday life, 7. Polarization due to radiating charges, 8. The linear antenna, 9. Thomson scattering, 10. Rayleigh scattering, 11. A digression on Mie scattering, 12. Bremsstrahlung radiation, 13. Cyclotron radiation, 14. Synchrotron radiation, 15. Polarization in spectral lines, 16. Density matrix and atomic polarization, 17. Radiative transfer and statistical equilibrium equations, 18. The amplification condition in polarized radiative transfer, and 19. Coupling radiative transfer and statistical equilibrium equations.

  1. L-shell polarization and alignment of heavy elements induced by 59.54keV photons.

    PubMed

    Ozdemir, Y; Durak, R; Kacal, M R; Kurudirek, M

    2011-07-01

    The polarization (%) of L-shell fluorescent X-rays (L?, L? and Ll) of Lu, Hf, Ta, W, Os, Pt, Au, Hg, Tl, Pb, Bi, Th and U excited by 59.54keV photons has been measured. These polarization degrees were then used to determine the alignment parameters A(2.) The Ll X-rays were found to be strongly polarized, whereas L? and L? X-rays showed less polarization. In this regard, the L?, L? and Ll groups show anisotropic spatial distributions. The results for polarization (%) as well as alignment parameters were compared with the ones available in literature. PMID:21489809

  2. Enhanced spin polarization in graphene with spin energy gap induced by spin-orbit coupling and strain

    SciTech Connect

    Liu, Zheng-Fang; Wu, Qing-Ping E-mail: aixichen@ecjtu.jx.cn; Chen, Ai-Xi E-mail: aixichen@ecjtu.jx.cn; Xiao, Xian-Bo; Liu, Nian-Hua

    2014-05-28

    We investigate the possibility of spin polarization in graphene. The result shows that a spin energy gap can be opened in the presence of both spin-orbit coupling and strain. We find that high spin polarization with large spin-polarized current is achieved in the spin energy gap. However, only one of the two modulations is present, no spin polarization can be generated. So the combination of the two modulations provides a way to design tunable spin polarization without need for a magnetic element or an external magnetic field.

  3. Surface plasmon induced polarization filter of the gold-coated photonic crystal fiber with a liquid core

    NASA Astrophysics Data System (ADS)

    Jiang, Linghong; Zheng, Yi; Hou, Lantian; Zheng, Kai; Peng, Jiying

    2015-06-01

    A new gold-coated photonic crystal fiber (PCF) which can achieve a specific wavelength filter has been proposed. The polarization filter characteristics of the PCF based on the finite element method are investigated. Numerical results show that moving the two gold-coated holes toward the central core in longitudinal direction and filling pure water in the central defected air-hole can effectively enhance polarization extinction ratio around the resonance wavelength. The resonance strength in y-polarized case is far stronger than that in x-polarized case, the peak loss of the PCF with different coating thickness in y polarization can reach 536.25 dB/cm and 412.91 dB/cm at the communication wavelength of 1.55 ?m and 1.31 ?m, respectively, while the losses are very low in x polarization. This is beneficial for the study and application in many polarization filter devices.

  4. Enhanced environmental stability induced by effective polarization of a polar dielectric layer in a trilayer dielectric system of organic field-effect transistors: a quantitative study.

    PubMed

    Subbarao, Nimmakayala V V; Gedda, Murali; Iyer, Parameswar K; Goswami, Dipak K

    2015-01-28

    We report a concept fabrication method that helps to improve the performance and stability of copper phthalocyanine (CuPc) based organic field-effect transistors (OFETs) in ambient. The devices were fabricated using a trilayer dielectric system that contains a bilayer polymer dielectrics consisting of a hydrophobic thin layer of poly(methyl methacrylate) (PMMA) on poly(vinyl alcohol) (PVA) or poly(4-vinylphenol) (PVP) or polystyrene (PS) with Al2O3 as a third layer. We have explored the peculiarities in the device performance (i.e., superior performance under ambient humidity), which are caused due to the polarization of dipoles residing in the polar dielectric material. The anomalous behavior of the bias-stress measured under vacuum has been explained successfully by a stretched exponential function modified by adding a time dependent dipole polarization term. The OFET with a dielectric layer of PVA or PVP containing hydroxyl groups has shown enhanced characteristics and remains highly stable without any degradation even after 300 days in ambient with three times enhancement in carrier mobility (0.015 cm(2)·V(-1)·s(-1)) compared to vacuum. This has been attributed to the enhanced polarization of hydroxyl groups in the presence of absorbed water molecules at the CuPc/PMMA interface. In addition, a model has been proposed based on the polarization of hydroxyl groups to explain the enhanced stability in these devices. We believe that this general method using a trilayer dielectric system can be extended to fabricate other OFETs with materials that are known to show high performances under vacuum but degrade under ambient conditions. PMID:25552195

  5. PPAR Activation Induces M1 Macrophage Polarization via cPLA2-COX-2 Inhibition, Activating ROS Production against Leishmania mexicana

    PubMed Central

    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?, 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-?, IL-1?, 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

  6. Switchable induced polarization in LaAlO3/SrTiO3 heterostructures.

    PubMed

    Bark, C W; Sharma, P; Wang, Y; Baek, S H; Lee, S; Ryu, S; Folkman, C M; Paudel, T R; Kumar, A; Kalinin, S V; Sokolov, A; Tsymbal, E Y; Rzchowski, M S; Gruverman, A; Eom, C B

    2012-04-11

    Demonstration of a tunable conductivity of the LaAlO(3)/SrTiO(3) interfaces drew significant attention to the development of oxide electronic structures where electronic confinement can be reduced to the nanometer range. While the mechanisms for the conductivity modulation are quite different and include metal-insulator phase transition and surface charge writing, generally it is implied that this effect is a result of electrical modification of the LaAlO(3) surface (either due to electrochemical dissociation of surface adsorbates or free charge deposition) leading to the change in the two-dimensional electron gas (2DEG) density at the LaAlO(3)/SrTiO(3) (LAO/STO) interface. In this paper, using piezoresponse force microscopy we demonstrate a switchable electromechanical response of the LAO overlayer, which we attribute to the motion of oxygen vacancies through the LAO layer thickness. These electrically induced reversible changes in bulk stoichiometry of the LAO layer are a signature of a possible additional mechanism for nanoscale oxide 2DEG control on LAO/STO interfaces. PMID:22400486

  7. Switchable Induced Polarization in LaAlO3/SrTiO3 Heterostructures

    SciTech Connect

    Bark, C; Sharma, P.; Wang, Y.; Baek, Seung Hyub; Lee, S.; Ryu, S.; Folkman, C H; Paudel, Tula R; Kumar, Amit; Kalinin, Sergei V; Sokolov, A.; Tsymbal, E Y; Rzchowski, M; Gruverman, Alexei; Eom, Professor Chang-Beom

    2012-01-01

    Demonstration of a tunable conductivity of the LaAlO3/SrTiO3 interfaces drew significant attention to the development of oxide electronic structures where electronic confinement can be reduced to the nanometer range. While the mechanisms for the conductivity modulation are quite different and include metal insulator phase transition and surface charge writing, generally it is implied that this effect is a result of electrical modification of the LaAlO3 surface (either due to electrochemical dissociation of surface adsorbates or free charge deposition) leading to the change in the twodimensional electron gas (2DEG) density at the LaAlO3/SrTiO3 (LAO/STO) interface. In this paper, using piezoresponse force microscopy we demonstrate a switchable electromechanical response of the LAO overlayer, which we attribute to the motion of oxygen vacancies through the LAO layer thickness. These electrically induced reversible changes in bulk stoichiometry of the LAO layer are a signature of a possible additional mechanism for nanoscale oxide 2DEG control on LAO/STO interfaces.

  8. SOLIS/VSM Polar Magnetic Field Data

    E-print Network

    Bertello, Luca

    2015-01-01

    The Vector Spectromagnetograph (VSM) instrument on the Synoptic Optical Long-term Investigations of the Sun (SOLIS) telescope is designed to obtain high-quality magnetic field observations in both the photosphere and chromosphere by measuring the Zeeman-induced polarization of spectral lines. With 1$^{\\prime \\prime}$ spatial resolution (1.14$^{\\prime \\prime}$ before 2010) and 0.05\\AA\\ spectral resolution, the VSM provides, among other products, chromospheric full-disk magnetograms using the CaII 854.2 nm spectral line and both photospheric full-disk vector and longitudinal magnetograms using the FeI 630.15 nm line. Here we describe the procedure used to compute daily weighted averages of the photospheric radial polar magnetic field at different latitude bands from SOLIS/VSM longitudinal full-disk observations. Time series of these measurements are publicly available from the SOLIS website at http://solis.nso.edu/0/vsm/vsm\\_plrfield.html. Future plans include the calculation of the mean polar field strength fr...

  9. Laser-induced fluorescence imaging of subsurface tissue structures with a volume holographic spatial-spectral imaging system.

    PubMed

    Luo, Yuan; Gelsinger-Austin, Paul J; Watson, Jonathan M; Barbastathis, George; Barton, Jennifer K; Kostuk, Raymond K

    2008-09-15

    A three-dimensional imaging system incorporating multiplexed holographic gratings to visualize fluorescence tissue structures is presented. Holographic gratings formed in volume recording materials such as a phenanthrenquinone poly(methyl methacrylate) photopolymer have narrowband angular and spectral transmittance filtering properties that enable obtaining spatial-spectral information within an object. We demonstrate this imaging system's ability to obtain multiple depth-resolved fluorescence images simultaneously. PMID:18794943

  10. Spectral sensitivity of light-induced hatching and expression of genes mediating photoreception in eggs of the Asian tadpole shrimp Triops granarius.

    PubMed

    Kashiyama, Kazuyuki; Ito, Chihiro; Numata, Hideharu; Goto, Shin G

    2010-08-01

    Embryonic development of the Asian tadpole shrimp Triops granarius is arrested at an early stage of organogenesis under darkness, whereas exposure to light resumes its development and promotes hatching. To better understand the photoreception systems involved in the light-induced hatching of T. granarius eggs, we examined the spectral sensitivity of hatching and the expression of genes involved in photoreception (opsins) and phototransduction (arrestin 2). Hatching of eggs is induced by light of broad wavelengths, from ultraviolet (UV) (395 nm) to red (660 nm), suggesting that visual pigments are involved in photoreception. Next, we focused on opsins which are protein moieties of visual pigments and arrestin 2 which is involved in a phototransduction cascade. Transcripts of several opsin genes and the arrestin 2 gene were detected in T. granarius eggs. Thus, we present a possibility that T. granarius eggs use visual pigments for light perception in light-induced hatching. PMID:20347048

  11. Growth, structure, defects and polarized absorption spectral properties of Er:Yb:YCa4O(BO3)3 crystals

    NASA Astrophysics Data System (ADS)

    Zhong, Degao; Teng, Bing; Kong, Weijin; Zhang, Shiming; Li, Yuyi; Li, Jianhong; Yang, Liting; Cao, Lifeng; Van Smaalen, Sander

    2016-01-01

    YCa4O(BO3)3 (YCOB) crystals co-doped with 3 at% Er3+ and 20 at% Yb3+ were successfully grown by the Czochralski method. X-ray powder diffraction (XRPD) results show that the as-grown Er:Yb:YCOB crystal belongs to the monoclinic system with space group Cm. And the lattice parameters are a=8.076(8) Å, b=16.023(7) Å, c=3.528(4) Å and ?=101.15(4)°. Crystal defects were revealed by chemical etching experiments. The density of etch pits, attributed to dislocations and observed on (010) planes, was found to be not uniform along the crystal diameter. The detailed polarized absorption spectra were measured. The polarized absorption cross sections at 977 nm are 1.01×10-20, 1.22×10-20 and 1.05×10-20 cm2 for E//X, E//Y and E//Z, respectively. And the polarized absorption cross sections at 1538 nm is about 1.86×10-20 cm2 for both E//X and E//Z, but for E//Y the result is 1.03×10-20 cm2, which is much smaller. The relationship between the crystal structure and absorption spectra was discussed.

  12. Electrical detection of current-induced spin polarization due to spin-momentum locking in the topological insulator Bi2Se3

    NASA Astrophysics Data System (ADS)

    Jonker, Berend

    2015-03-01

    Topological insulators (TIs) exhibit topologically protected metallic surface states populated by massless Dirac fermions with spin-momentum locking - the carrier spin lies in-plane, locked at right angle to the carrier momentum. An unpolarized charge current should thus create a net spin polarization whose amplitude and orientation are controlled by the charge current. Here we show direct electrical detection of this bias current induced spin polarization as a voltage measured on a ferromagnetic (FM) metal tunnel barrier surface contact. The magnetization of the contact determines the spin detection axis, and the voltage measured at this contact is proportional to the projection of the TI spin polarization onto this axis. When the charge current is orthogonal to the magnetization of the FM detector contact, the TI spin is parallel (or antiparallel) to the magnetization, and a spin-related signal is detected at the FM contact proportional to the magnitude of the charge current. The voltage measured scales inversely with Bi2Se3 film thickness, and its sign is that expected from spin-momentum locking and opposite that of a Rashba effect. Similar data are obtained for two different FM contact structures, Fe/Al2O3 and Co/MgO/graphene, underscoring the fact that these behaviors are due to bias current induced spin polarization in the TI surface states rather than the bulk, and are independent of the details of the contact. These results demonstrate simple and direct electrical access to the TI Dirac surface state spin system, provide clear evidence for the spin-momentum locking and bias current-induced spin polarization, and enable utilization of these remarkable properties for future technological applications. This work was supported by core programs at NRL and the Office of Naval Research.

  13. Indications of mineral zoning in a fossil hydrothermal system at the Meager Creek geothermal prospect, British Columbia, Canada, from induced polarization studies

    SciTech Connect

    Ward, S.H.; Zhao, J.X.; Groenwald, J.; Moore, J.N.

    1985-05-01

    By measuring the induced-polarization parameters m (chargeability) and tau (time-constant) we have found evidence that the center of a presumed fossil hydrothermal system at Meager Creek, British Columbia, lies south of the main manifestation of the present-day convective hydrothermal system. What implication this finding has for development of the present-day system is unknown. However, some of the fractures formed during the development of the fossil hydrothermal system may serve as conduits for fluids of the present-day system. The analysis is limited by the lack of availability of a good subsurface distribution of core samples. Nevertheless, a surface induced-polarization survey is expected to yield information about the geometry of the fossil system. Such knowledge would have implications not only for Meager Creek but for other hydrothermal systems of Cascades volcano type. 16 refs., 15 figs., 1 tab.

  14. Impact of optical feedback on current-induced polarization behavior of 1550 nm vertical-cavity surface-emitting lasers.

    PubMed

    Deng, Tao; Wu, Zheng-Mao; Xie, Yi-Yuan; Wu, Jia-Gui; Tang, Xi; Fan, Li; Panajotov, Krassimir; Xia, Guang-Qiong

    2013-06-01

    Polarization switching (PS) between two orthogonal linearly polarized fundamental modes is experimentally observed in commercial free-running 1550 nm vertical-cavity surface-emitting lasers (VCSELs) (Raycan). The characteristics of this PS are strongly modified after introducing a polarization-preserved (PP) or polarization-orthogonal (PO) optical feedback. Under the case that the external cavity is approximately 30 cm, the PP optical feedback results in the PS point shifting toward a lower injection current, and the region within which the two polarization modes coexist is enlarged with the increase of the PP feedback strength. Under too-strong PP feedback levels, the PS disappears. The impact of PO optical feedback on VCSEL polarization behavior is quite similar to that of PP optical feedback, but larger feedback strength is needed to obtain similar results. PMID:23736341

  15. Polarization in Optical Design

    NASA Astrophysics Data System (ADS)

    Reiley, Daniel J.

    The polarization effects of optical interfaces are important in certain types of optical systems. These systems include polarization microscopes, remote sensing platforms, optical computers, solar magnetographs, and barcode readers. These systems are characterized by their polarization aberration function, which maps a ray's amplitude, phase, and polarization state in the entrance pupil onto its amplitude, phase, and polarization state in the exit pupil. A unified discussion of the polarization aberration is presented and several useful special cases are explored. The most striking contributions presented in this dissertation relate to coating-induced wavefront aberrations; a theory is presented which shows that all-reflecting systems can suffer from chromatic aberration and that astigmatism can occur on-axis in radially symmetric systems. These aberrations arise because the phase shift introduced by coatings changes with angle of incidence and is different for s- and p-polarization states. An example analysis is given in which the simple coatings in a simple Cassegrain telescope introduce 0.76 waves of chromatic aberration and 0.30 waves of astigmatism. A particularly useful contribution contained in this dissertation is a new method for deriving an aberration expansion which describes the polarization effects which can occur in radially symmetric systems. This aberration expansion describes the polarization effects in simple functional forms and allows a designer to identify each surface's contribution to the overall polarization of the system. An example calculation is presented in which a polarization aberration expansion is used to find polarization -balancing coatings for a laser collimator. These polarization -balancing coatings reduce the instrumental polarization by a factor of 10 from a similar design without polarization balancing. A third contribution presented in this dissertation is the derivation of the average polarization in an image. Polarization aberration theory is extended to show that the average polarization of an image formed by a radially symmetric system is approximately equal to the polarization along the chief ray path.

  16. Improved hydrogeophysical characterization and monitoring through parallel modeling and inversion of time-domain resistivity and induced-polarization data

    SciTech Connect

    Timothy C. Johnson; Roeof J. Versteeg; Andy Ward; Frederick D. Day-Lewis; Andre Revil

    2010-09-01

    Electrical geophysical methods have found wide use in the growing discipline of hydrogeophysics, both for characterizing the electrical properties of the subsurface, and for monitoring subsurface processes in terms of the spatiotemporal changes in subsurface conductivity, chargeability, and source currents they govern. Current multichannel and multielectrode data collections systems are able to collect large amounts of data in relatively short periods of time. However, practitioners are often unable to fully utilize these large data sets and the information they contain due to the processing limitations of standard desktop computers. This limitation can be addressed by utilizing the storage and processing capabilities of high-performance parallel computing environments. We present a parallel distributed-memory forward and inverse modeling algorithm for analyzing resistivity and time-domain induced polarization data. The primary components of the parallel computations include distributed computation of the pole solutions in forward mode, distributed storage and computation of the Jacobian matrix in inverse mode, and parallel execution of the inverse equation solver. We demonstrate the corresponding parallel code for three efforts: (1) resistivity characterization of the Hanford 300 Area Integrated Field Research Challenge site in Hanford, WA; (2) resistivity characterization of a volcanic island in the southern Tyrrhenian Sea in Italy; and (3) resistivity and IP monitoring of biostimulation at a superfund site in Brandywine, MD. Inverse analysis of each of these data sets would be limited (or impossible) in a standard serial computing environment which underscores the need for high-performance computing to fully utilize the potential of electrical geophysical methods in hydrogeophysical applications.

  17. The Imaging Vector Magnetograph at Haleakal? IV: Stokes Polarization Spectra in the Sodium D1 589.6 nm Spectral Line

    NASA Astrophysics Data System (ADS)

    Leka, K. D.; Mickey, Donald L.; Uitenbroek, Han; Wagner, Eric L.; Metcalf, Thomas R.

    2012-06-01

    The Imaging Vector Magnetograph (IVM) at the Mees Solar Observatory, Haleakal?, Maui, Hawai'i, obtained many years of vector magnetic-field data in the photospheric Fe i 630.25 nm line. In the latter period of its operation, the IVM was modified to allow routine observations in the chromospheric Na i D1 line, as well as the Fe i line. We describe the sodium observational data in detail, including the data-reduction steps that differ from those employed for the Fe i 630.25 nm line, to obtain calibrated Stokes polarization spectra. We have performed a systematic comparison between the observational data and synthetic NLTE Na i D1 Stokes spectra derived for a variety of solar-appropriate atmospheric and magnetic configurations. While the Na i D1 Stokes polarization signals from the solar atmosphere are expected to be weak, they should generally be within the IVM capability. A comparison between synthetic spectra and observational data indicates that this is indeed the case.

  18. Spectral investigations of photoionized plasmas induced in atomic and molecular gases using nanosecond extreme ultraviolet (EUV) pulses

    SciTech Connect

    Bartnik, A.; Fiedorowicz, H.; Wachulak, P.

    2014-07-15

    In this paper, results of spectral investigations of low temperature photoionized plasmas, created by irradiation of gases with intense pulses of extreme ultraviolet (EUV) radiation from a laser-produced plasma (LPP) source, are presented. The LPP source was based on a double-stream KrXe/He gas-puff target irradiated with 4?ns/0.8?J/10?Hz Nd:YAG laser pulses. The most intense emission from the source spanned a relatively narrow spectral region ????10–12?nm; however, spectrally integrated intensity at longer wavelengths was also significant. The EUV beam was focused on a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Irradiation of gases resulted in formation of photoionized plasmas emitting radiation in the EUV range. Radiation spectra, measured for plasmas produced in various gases, are dominated by emission lines, originating from single charged ions. Significant differences in spectral intensities and distributions between plasmas created in neon and molecular gases were observed.

  19. Spectral shape of a signal in light-induced diffusive pulling (pushing) of particles into a light beam

    NASA Astrophysics Data System (ADS)

    Parkhomenko, A. I.; Shalagin, A. M.

    2015-02-01

    We study theoretically how the dependences of transport collision frequencies ?i, collision broadening ? and collision shift ? of the levels on the velocity v of resonant particles influence lightinduced diffusive pulling (pushing) (LDP) effects in the framework of a generalised model of strong collisions in the case of velocitydependent collision rates (so-called kangaroo model). It is found that allowance for the dependences ?i(v), ?(v) and ?(v) does not change the spectral shape of an LDP signal. In particular, in the case of low-intensity radiation, the spectral dependence of the LDP signal coincides with the absorption line shape. It is shown that the magnitude of the LDP effect is proportional to the difference between the diffusion coefficients of particles in the excited and ground states. It is found that the spectral anomalies previously predicted in the LDP effect [Gel'mukhanov F.Kh. JETP Lett., 55, 214 (1992)] for an idealised model of the Lorentz gas (the limiting case of heavy buffer particles), which arise due to the dependences ?i(v), ?(v) and ?(v), are typical only for this gas. At a realistic ratio of the masses of absorbing and buffer particles, spectral anomalies do not occur in the LDP effect.

  20. PI3K/Akt Signaling Pathway Modulates Influenza Virus Induced Mouse Alveolar Macrophage Polarization to M1/M2b

    PubMed Central

    Zhao, Xiangfeng; Dai, Jianping; Xiao, Xuejun; Wu, Liqi; Zeng, Jun; Sheng, Jiangtao; Su, Jinghua; Chen, Xiaoxuan; Wang, Gefei; Li, Kangsheng

    2014-01-01

    Macrophages polarized to M1 (pro-inflammation) or M2 (anti-inflammation) phenotypes in response to environmental signals. In this study, we examined the polarization of alveolar macrophage (AM), following induction by different influenza virus strains (ST169 (H1N1), ST602 (H3N2) and HKG9 (H9N2)). Macrophages from other tissues or cell line exert alternative responding pattern, and AM is necessary for investigating the respiratory system. AM polarized toward the M1 phenotype after 4 hours of infection by all three virus strains, and AM to presented M2b phenotype after 8 hours induction, and immunosuppressive phenotype after 24 hours of induction. Protein expression assay showed similar results as the gene expression analysis for phenotype verification. The ELISA assay showed that TNF-? secretion was up-regulated after 4 and 8 hours of infection by influenza viruses, and it returned to basal levels after 24 hours of infection. IL-10 expression was elevated after 8 and 24 hours of infection. Immunofluorescence showed that iNOS expression was up-regulated but not Arg1 expression. Influenza virus notably increased phospho-Akt but not phospho-Erk1/2 or phospho-p38, and the AM polarization pattern have been changed by LY294002 (PI3K inhibitor). In conclusion, our results demonstrate the dynamic polarization of AM induced by influenza viruses, and suggested that PI3K/Akt signaling pathway modulates AM polarization to M1/M2b. PMID:25105760

  1. Antidiabetic activity of medium-polar extract from the leaves of Stevia rebaudiana Bert. (Bertoni) on alloxan-induced diabetic rats

    PubMed Central

    Misra, Himanshu; Soni, Manish; Silawat, Narendra; Mehta, Darshana; Mehta, B. K.; Jain, D. C.

    2011-01-01

    Objective: To investigate the medicative effects of medium-polar (benzene:acetone, 1:1, v/v) extract of leaves from Stevia rebaudiana (family Asteraceae) on alloxan-induced diabetic rats. Materials and Methods: Diabetes was induced in adult albino Wistar rats by intraperitoneal (i.p.) injection of alloxan (180 mg/kg). Medium-polar extract was administered orally at daily dose of 200 and 400 mg/kg body wt. basis for 10 days. The control group received normal saline (0.9%) for the same duration. Glibenclamide was used as positive control reference drug against Stevia extract. Results: Medium-polar leaf extract of S. rebaudiana (200 and 400 mg/kg) produced a delayed but significant (P < 0.01) decrease in the blood glucose level, without producing condition of hypoglycemia after treatment, together with lesser loss in the body weight as compared with standard positive control drug glibenclamide. Conclusions: Treatment of diabetes with sulfonylurea drugs (glibenclamide) causes hypoglycemia followed by greater reduction in body weight, which are the most worrisome effects of these drugs. Stevia extract was found to antagonize the necrotic action of alloxan and thus had a re-vitalizing effect on ?-cells of pancreas. PMID:21687353

  2. Proposal for direct measurement of intense-field induced polarization in the continuum on the attosecond time scale using transient absorption

    NASA Astrophysics Data System (ADS)

    McCurdy, C. William; Haxton, Daniel; Li, Xuan

    2015-05-01

    A procedure is proposed for using transient absorption spectroscopy above the ionization threshold to measure the polarization of the continuum induced by an intense optical pulse. In this way transient absorption measurement can be used to probe sub-femtosecond intense field dynamics in atoms and molecules and extract the high frequency polarization that plays a central role in high harmonic generation. The method is based on a robust approximation to the dependence of these spectra on time-delay between an attosecond XUV probe pulse and an intense pump pulse that is verified over a wide range of intensities and time delays by all-electrons-active calculations using the Multiconfiguration Time-Dependent Hartree Fock method. To demonstrate the extraction of the field-induced polarization, we study the transient absorption spectrum of atomic Neon. Work at LBNL supported by USDOE, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, and work at UC Davis supported by USDOE grant No. DESC0007182.

  3. Absorption spectral change of peripheral-light harvesting complexes 2 induced by magnesium protoporphyrin IX monomethyl ester association.

    PubMed

    Yue, Huiying; Zhao, Chungui; Li, Kai; Yang, Suping

    2015-02-25

    Several spectrally different types of peripheral light harvesting complexes (LH) have been reported in anoxygenic phototrophic bacteria in response to environmental changes. In this study, two spectral forms of LH2 (T-LH2 and U-LH2) were isolated from Rhodobacter azotoformans. The absorption of T-LH2 was extremely similar to the LH2 isolated from Rhodobacter sphaeroides. U-LH2 showed an extra peak at ?423 nm in the carotenoid region. To explore the spectral origin of this absorption peak, the difference in pigment compositions of two LH2 was analyzed. Spheroidene and bacteriochlorophyll aP were both contained in the two LH2. And magnesium protoporphyrin IX monomethyl ester (MPE) was only contained in U-LH2. It is known that spheroidene and bacteriochlorophyll aP do not produce ?423 nm absorption peak either in vivo or in vitro. Whether MPE accumulation was mainly responsible for the formation of the ?423 nm peak? The interactions between MPE and different proteins were further studied. The results showed that the maximum absorption of MPE was red-shifted from ?415 nm to ?423 nm when it was mixed with T-LH2 and its apoproteins, nevertheless, the Qy transitions of the bound bacteriochlorophylls in LH2 were almost unaffected, which indicated that the formation of the ?423 nm peak was related to MPE-LH2 protein interaction. MPE did not bind to sites involved in the spectral tuning of BChls, but the conformation of integral LH2 was affected by MPE association, the alkaline stability of U-LH2 was lower than T-LH2, and the fluorescence intensity at 860 nm was decreased after MPE combination. PMID:25305606

  4. Absorption spectral change of peripheral-light harvesting complexes 2 induced by magnesium protoporphyrin IX monomethyl ester association

    NASA Astrophysics Data System (ADS)

    Yue, Huiying; Zhao, Chungui; Li, Kai; Yang, Suping

    2015-02-01

    Several spectrally different types of peripheral light harvesting complexes (LH) have been reported in anoxygenic phototrophic bacteria in response to environmental changes. In this study, two spectral forms of LH2 (T-LH2 and U-LH2) were isolated from Rhodobacter azotoformans. The absorption of T-LH2 was extremely similar to the LH2 isolated from Rhodobacter sphaeroides. U-LH2 showed an extra peak at ?423 nm in the carotenoid region. To explore the spectral origin of this absorption peak, the difference in pigment compositions of two LH2 was analyzed. Spheroidene and bacteriochlorophyll aP were both contained in the two LH2. And magnesium protoporphyrin IX monomethyl ester (MPE) was only contained in U-LH2. It is known that spheroidene and bacteriochlorophyll aP do not produce ?423 nm absorption peak either in vivo or in vitro. Whether MPE accumulation was mainly responsible for the formation of the ?423 nm peak? The interactions between MPE and different proteins were further studied. The results showed that the maximum absorption of MPE was red-shifted from ?415 nm to ?423 nm when it was mixed with T-LH2 and its apoproteins, nevertheless, the Qy transitions of the bound bacteriochlorophylls in LH2 were almost unaffected, which indicated that the formation of the ?423 nm peak was related to MPE-LH2 protein interaction. MPE did not bind to sites involved in the spectral tuning of BChls, but the conformation of integral LH2 was affected by MPE association, the alkaline stability of U-LH2 was lower than T-LH2, and the fluorescence intensity at 860 nm was decreased after MPE combination.

  5. Monitoring a CO2 plume using time-lapse 3D magnetotellurics, DC resistivity, and induced polarization

    NASA Astrophysics Data System (ADS)

    Bowles-martinez, E.; Schultz, A.; Vincent, P.

    2014-12-01

    When CO2 is injected into a deep saline aquifer, the combination of fluid displacement and chemical interaction with groundwater and minerals results in changes to the electrical properties of the storage formation. Geophysical methods that are sensitive to the electrical resistivity and chargeability of the rocks and fluids are used to monitor a modeled CO2 plume. The arrival of supercritical CO2 appears as a resistive pulse as the CO2 displaces water while rising buoyantly. Groundwater becomes carbonated and undergoes a rapid drop in pH. Formation conductivity increases as acidic fluid mobilizes ions in the surrounding rock. A surge of increased conductivity is seen at the plume front as easily-mobilized ions enter the fluid. As the injection proceeds and groundwater flows, this high-conductivity plume front migrates, leaving behind an aquifer largely depleted of highly-mobile ions, with only slightly elevated conductivity. Meanwhile, the dissolution of minerals reduces surface area along the fluid-mineral interface. This causes pore throat widening and reduction of sites where electric charge can build up, thereby reducing the polarizability in the parts of the formation that have encountered the plume. This study looks at monitoring methods that are sensitive to all of these changes in electrical properties at various depths within the earth. These methods include magnetotellurics (MT) and combined DC resistivity and induced polarization (IP). MT is useful for showing large-scale structure using an array that is moveable to cover an arbitrarily large area as the plume expands far beyond initial monitoring locations. MT also allows for phase tensor analysis to clearly show deep resistivity gradients and changes in dimensionality. The active-source nature of DC and IP makes them effective at clearly showing the plume's extent in the region within a few km of the injection well. All methods are modeled in 3D using the planned Kevin Dome carbon storage site in northern Montana as the geologic setting. This site's location on open prairie affords the use of a novel electrode array that simplifies the field logistics for efficient collection of 3D MT and DC/IP data.

  6. Proinflammatory-activated glioma cells induce a switch in microglial polarization and activation status, from a predominant M2b phenotype to a mixture of M1 and M2a/B polarized cells

    PubMed Central

    Lisi, Lucia; Stigliano, Egidio; Lauriola, Libero; Navarra, Pierluigi; Russo, Cinzia Dello

    2014-01-01

    Malignant gliomas are primary brain tumors characterized by morphological and genetic complexities, as well as diffuse infiltration into normal brain parenchyma. Within gliomas, microglia/macrophages represent the largest tumor-infiltrating cell population, contributing by at least one-third to the total tumor mass. Bi-directional interactions between glioma cells and microglia may therefore play an important role on tumor growth and biology. In the present study, we have characterized the influence of glioma-soluble factors on microglial function, comparing the effects of media harvested under basal conditions with those of media obtained after inducing a pro-inflammatory activation state in glioma cells. We found that microglial cells undergo a different pattern of activation depending on the stimulus; in the presence of activated glioma-derived factors, i.e. a condition mimicking the late stage of pathology, microglia presents as a mixture of polarization phenotypes (M1 and M2a/b), with up-regulation of iNOS (inducible nitric oxide synthase), ARG (arginase) and IL (interleukine)-10. At variance, microglia exposed to basal glioma-derived factors, i.e. a condition resembling the early stage of pathology, shows a more specific pattern of activation, with increased M2b polarization status and up-regulation of IL-10 only. As far as viability and cell proliferation are concerned, both LI-CM [LPS (lipopolysaccharide)–IFN? (interferon ?) conditioned media] and C-CM (control-conditioned media) induce similar effects on microglial morphology. Finally, in human glioma tissue obtained from surgical resection of patients with IV grade glioblastoma, we detected a significant amount of CD68 positive cells, which is a marker of macrophage/microglial phagocytic activity, suggesting that in vitro findings presented here might have a relevance in the human pathology as well. PMID:24689533

  7. Polarity inversion and coupling of laser beam induced current in As-doped long-wavelength HgCdTe infrared detector pixel arrays: Experiment and simulation

    NASA Astrophysics Data System (ADS)

    Hu, W. D.; Chen, X. S.; Ye, Z. H.; Chen, Y. G.; Yin, F.; Zhang, B.; Lu, W.

    2012-10-01

    In this paper, experimental results of polarity inversion and coupling of laser beam induced current for As-doped long-wavelength HgCdTe pixel arrays grown on CdZnTe are reported. Models for the p-n junction transformation are proposed and demonstrated using numerical simulations. Simulation results are shown to be in agreement with the experimental results. It is found that the deep traps induced by ion implantation are very sensitive to temperature, resulting in a decrease of the quasi Fermi level in the implantation region in comparison to that in the Hg interstitials diffusion and As-doped regions. The Hg interstitial diffusion, As-doping amphoteric behavior, ion implantation damage traps, and the mixed conduction, are key factors for inducing the polarity reversion, coupling, and junction broadening at different temperatures. The results provide the near room-temperature HgCdTe photovoltaic detector with a reliable reference on the junction reversion and broadening around implanted regions, as well as controlling the n-on-p junction for very long wavelength HgCdTe infrared detector pixels.

  8. Polarization-sensitive optical coherence tomography system tolerant to fiber disturbances using a line camera.

    PubMed

    Marques, Manuel J; Rivet, Sylvain; Bradu, Adrian; Podoleanu, Adrian

    2015-08-15

    This Letter presents a spectral-domain, polarization-sensitive optical coherence tomography (PS-OCT) system, where the light collection from the two arms of the interferometer is performed exclusively using single-mode fibers and couplers, and the two orthogonal polarization components are sequentially detected by a single line camera. Retardance measurements can be affected by polarimetric effects because of fiber birefringence and diattenuation in fiber couplers. This configuration bypasses such issues by performing polarization selection before the collection fiber through the combination of a polarization rotator and a linear polarizer. Retardance calibration is achieved with a Berek compensator. Similar net retardance maps of a birefringent phantom are obtained for two different settings of induced fiber birefringence, effectively demonstrating the tolerance of the configuration to fiber-based disturbances. PMID:26274678

  9. Power-induced polarization switching and bistability characteristics in 1550-nm VCSELs subjected to orthogonal optical injection

    NASA Astrophysics Data System (ADS)

    Chen, Jian-Jun; Xia, Guang-Qiong; Wu, Zheng-Mao

    2015-02-01

    The polarization switching (PS) and polarization bistability (PB) characteristics of a 1550-nm vertical-cavity surface-emitting laser (VCSEL) subjected to orthogonal optical injection are systematically investigated. The simulated results show that the PS and polarization-resolved nonlinear dynamical states of the VCSEL are critically dependent on the changing paths of the injected power. The polarization dynamics for different scanning directions of the injected power is presented to explain the polarization evolution during the formation of PS. In the case of forward scanning injected power, with the increase of frequency detuning level between the VCSEL and the injected light, the injected power required for PS gradually increases for negative frequency detuning but exhibits fluctuations for positive frequency detuning. In the case of reversely scanning injected power, the injected power required for PS displays fluctuant changes within the whole frequency detuning range. Specifically, PS may disappear under certain negative frequency detuning and large bias current. Furthermore, the hysteresis width as a function of the frequency detuning is calculated, and the regions for the appearance and disappearance of PB have been determined in the parameter space of the bias current and frequency detuning. Project supported by the National Natural Science Foundation of China (Grant Nos. 61178011, 61275116, and 61475127) and the Natural Science Foundation of Chongqing City, China (Grant No. 2012jjB40011).

  10. Polarization of Dielectrics by Acceleration

    E-print Network

    L. A. Melnikovsky

    2006-08-23

    We argue that acceleration induces electric polarization in usual dielectrics. Both accelerations in superfluid participate in the medium polarization. Excitations contribution to the polarization is calculated at low temperatures. Estimates of the effect show order of magnitude agreement with recent experimental results on electric effect of superflow.

  11. Nonlinear polarization response of a gaseous medium in the regime of atom stabilization in a strong radiation field

    SciTech Connect

    Volkova, E. A.; Popov, A. M. Tikhonova, O. V.

    2013-03-15

    The nonlinear polarization response of a quantum system modeling a silver atom in the field of high-intensity radiation in the IR and UV spectral ranges has been studied by direct numerical integration of a nonstationary Schroedinger equation. The domains of applicability of perturbation theory and polarization expansion in powers of the field intensity are determined. The contribution of excited atoms and electrons in a continuum to the atomic polarization response at the field frequency, which arises due to the radiation-induced excitation and photoionization processes, is analyzed. Features of the nonlinear response to an external field under conditions of atom stabilization are considered.

  12. Formation of laser-induced periodic surface structures on fused silica upon multiple cross-polarized double-femtosecond-laser-pulse irradiation sequences

    SciTech Connect

    Rohloff, M.; Das, S. K.; Hoehm, S.; Grunwald, R.; Rosenfeld, A.; Krueger, J.; Bonse, J.

    2011-07-01

    The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of fused silica with multiple irradiation sequences consisting of five Ti:sapphire femtosecond (fs) laser pulse pairs (150 fs, 800 nm) is studied experimentally. A Michelson interferometer is used to generate near-equal-energy double-pulse sequences with a temporal pulse delay from -20 to +20 ps between the cross-polarized individual fs-laser pulses ({approx}0.2 ps resolution). The results of multiple double-pulse irradiation sequences are characterized by means of Scanning Electron and Scanning Force Microscopy. Specifically in the sub-ps delay domain striking differences in the surface morphologies can be observed, indicating the importance of the laser-induced free-electron plasma in the conduction band of the solids for the formation of LIPSS.

  13. Diurnal and seasonal dynamics of canopy-level solar-induced chlorophyll fluorescence and spectral reflectance indices in a cornfield

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A collaborative field campaign was undertaken to examine the temporal dynamics of canopy-level solar-induced fluorescence (SIF) and the Photochemical Reflectance Index (PRI) in conjunction with photosynthetic light use efficiency (LUE) obtained from fluxes measured at an instrumented tower. We condu...

  14. PHYSICAL REVIEW B 91, 224426 (2015) Alternating spin-polarized current induces parametric resonance in spin valves

    E-print Network

    Gavilan, Marcel G. Clerc

    2015-01-01

    by the combination of alternating and direct spin-polarized electric currents. We show here that the alternating research in recent years [1­4]. In such devices, a perpendicular to plane electric current transfers spin in the radio-frequency domain. Furthermore, the addition of an alternating electric current, in the radio

  15. A computer program to calculate the resistivity and induced polarization response for a three-dimensional body in the presence of buried electrodes

    USGS Publications Warehouse

    Daniels, Jeffrey J.

    1977-01-01

    Three-dimensional induced polarization and resistivity modeling for buried electrode configurations can be achieved by adapting surface integral techniques for surface electrode configurations to buried electrodes. Modification of. the surface technique is accomplished by considering the additional mathematical terms required to express-the changes in the electrical potential and geometry caused by placing the source and receiver electrodes below the surface. This report presents a listing of a computer program to calculate the resistivity and induced polarization response from a three-dimensional body for buried electrode configurations. The program is designed to calculate the response for the following electrode configurations: (1) hole-to-surface array with a buried bipole source and a surface bipole receiver, (2) hole-to-surface array with a buried pole source and a surface bipole receiver, (3) hole-to-hole array with a buried, fixed pole source and a moving bipole receiver, (4) surface-to-hole array with a fixed pole source on the surface and a moving bipole receiver in the borehole, (5) hole-to-hole array with a buried, fixed bipole source and a buried, moving bipole receiver, (6) hole-to-hole array with a buried, moving bipole source and a buried, moving bipole receiver, and (7) single-hole, buried bipole-bipole array. Input and output examples are given for each of the arrays.

  16. Photon-induced neutron polarization from the {sup 2}H({gamma},n-vector){sup 1}H reaction within the NN-force model with an intermediate dibaryon

    SciTech Connect

    Kukulin, V. I.; Obukhovsky, I. T.; Pomerantsev, V. N.; Faessler, Amand; Grabmayr, Peter

    2008-04-15

    A model for the NN force, which is induced by the formation of an intermediate dibaryon dressed with {sigma}- and other meson fields, has been developed by the present authors in previous years. This model is applied to the deuteron photodisintegration processes with the main focus on the {gamma}-induced polarization P{sub y}{sup '} of the neutron at energies below E{sub {gamma}} < or approx. 30 MeV. The inclusion of the intermediate dibaryon leads to a model of the NN force completely different to the conventional NN potential models at short distances. Here the model is tested on the nucleonic level through comparison to rather similar predictions from the conventional NN potential model both for the total and differential cross sections and also for the spin polarization of the ejected neutrons. The predictions of the present model are at least of the same quality than those for the Nijmegen potential; the visible differences with experimental data for P{sub y}{sup '} still remain. However, in combination with the previous results a consistent description can be achieved simultaneously for many observables.

  17. Collisional Induced Absorption (CIA) bands of CO2 and H2 measured in the IR spectral range

    NASA Astrophysics Data System (ADS)

    Stefani, S.; Piccioni, G.; Snels, M.; Adriani, A.; Grassi, D.

    2015-10-01

    In this paper we present the results on the Collisional Induced Absorption (CIA) bands of CO2 and H2 measured employing two different experimental setup. Each of them allows us to reproduce typical planetary conditions, at a pressure and temperature from 1 up to 50 bar and from 298 up to 500 K respectively. A detailed study on the temperature dependence of the CO2 CIA absorption bands will be presented.

  18. Antiproliferative and Apoptosis Inducing Effects of Non-Polar Fractions from Lawsonia inermis L. in Cervical (HeLa) Cancer Cells.

    PubMed

    Kumar, Manish; Kaur, Paramjeet; Kumar, Subodh; Kaur, Satwinderjeet

    2015-04-01

    Two non-polar fractions viz. hexane (Hex-LI) and chloroform fraction (CHCl3-LI) of Lawsonia inermis were studied for their antiproliferative potential in various cancer cell lines viz. HeLa, MCF-7, A549 and C6 glioma cells. Both the fractions showed more than 60 % of growth inhibition in all the tested cell lines at highest tested concentration. In clonogenic assay, different concentrations of Hex-LI and CHCl3-LI decreased the number and size of colonies as compared to control in HeLa cells. The apoptotic effects as nuclear condensation, fragmentation were visualized with Hoechst-33342 staining of HeLa cells using confocal microscope. Both fractions induced apoptotic cell death in human cervical carcinoma (HeLa) cells as evident from flow cytometric analysis carried out using Annexin V-FITC and propidium iodide dyes. CHCl3-LI treated cells significantly induced apoptosis (25.43 %) in comparison to control. Results from Neutral Comet assay demonstrated that both fractions induced double stranded breaks (DSB's) in HeLa cells. Our data indicated that Hex-LI and CHCl3-LI treated cells showed significant increase of 32.2 and 18.56 % reactive oxygen species (ROS) levels in DCFH-DA assay respectively. Further, experimental studies to decipher exact pathway via which these fractions induce cell death are in progress. PMID:25931778

  19. Dynamic myocardial perfusion in a porcine balloon-induced ischemia model using a prototype spectral detector CT

    NASA Astrophysics Data System (ADS)

    Fahmi, Rachid; Eck, Brendan L.; Fares, Anas; Levi, Jacob; Wu, Hao; Vembar, Mani; Dhanantwari, Amar; Bezerra, Hiram G.; Wilson, David L.

    2015-03-01

    Myocardial CT perfusion (CTP) imaging is an application that should greatly benefit from spectral CT through the significant reduction of beam hardening (BH) artifacts using mono-energetic (monoE) image reconstructions. We used a prototype spectral detector CT (SDCT) scanner (Philips Healthcare) and developed advanced processing tools (registration, segmentation, and deconvolution-based flow estimation) for quantitative myocardial CTP in a porcine ischemia model with different degrees of coronary occlusion using a balloon catheter. The occlusion severity was adjusted with fractional flow reserve (FFR) measurements. The SDCT scanner is a single source, dual-layer detector system, which allows simultaneous acquisitions of low and high energy projections, hence enabling accurate projection-based material decomposition and effective reduction of BH-artifacts. In addition, the SDCT scanner eliminates partial scan artifacts with fast (0.27s), full gantry rotation acquisitions. We acquired CTP data under different hemodynamic conditions and reconstructed conventional 120kVp images and projection-based monoenergetic (monoE) images for energies ranging from 55keV-to-120keV. We computed and compared myocardial blood flow (MBF) between different reconstructions. With balloon completely deflated (FFR=1), we compared the mean attenuation in a myocardial region of interest before iodine arrival and at peak iodine enhancement in the left ventricle (LV), and we found that monoE images at 70keV effectively minimized the difference in attenuation, due to BH, to less than 1 HU compared to 14 HU with conventional 120kVp images. Flow maps under baseline condition (FFR=1) were more uniform throughout the myocardial wall at 70keV, whereas with 120kVp data about 12% reduction in blood flow was noticed on BH-hypoattenuated areas compared to other myocardial regions. We compared MBF maps at different keVs under an ischemic condition (FFR < 0.7), and we found that flow-contrast-to-noise-ratio (CNRf ) between LAD ischemic and remote healthy territories attains its maximum (2.87 +/- 0.7) at 70keV. As energies diverge from 70keV, we noticed a steady decrease in CNRf and an overestimation of mean-MBF. Flow overestimation was also noticed for conventional 120kVp images in different myocardial regions.

  20. Scattering Polarization in Solar Flares

    NASA Astrophysics Data System (ADS)

    Št?pán, Ji?í; Heinzel, Petr

    2013-11-01

    There is ongoing debate about the origin and even the very existence of a high degree of linear polarization of some chromospheric spectral lines observed in solar flares. The standard explanation of these measurements is in terms of the impact polarization caused by non-thermal proton and/or electron beams. In this work, we study the possible role of resonance line polarization due to radiation anisotropy in the inhomogeneous medium of the flare ribbons. We consider a simple two-dimensional model of the flaring chromosphere and we self-consistently solve the non-LTE problem taking into account the role of resonant scattering polarization and of the Hanle effect. Our calculations show that the horizontal plasma inhomogeneities at the boundary of the flare ribbons can lead to a significant radiation anisotropy in the line formation region and, consequently, to a fractional linear polarization of the emergent radiation of the order of several percent. Neglecting the effects of impact polarization, our model can provide a clue for resolving some of the common observational findings, namely: (1) why a high degree of polarization appears mainly at the edges of the flare ribbons; (2) why polarization can also be observed during the gradual phase of a flare; and (3) why polarization is mostly radial or tangential. We conclude that radiation transfer in realistic multi-dimensional models of solar flares needs to be considered as an essential ingredient for understanding the observed spectral line polarization.

  1. SCATTERING POLARIZATION IN SOLAR FLARES

    SciTech Connect

    Št?pán, Ji?í; Heinzel, Petr

    2013-11-20

    There is ongoing debate about the origin and even the very existence of a high degree of linear polarization of some chromospheric spectral lines observed in solar flares. The standard explanation of these measurements is in terms of the impact polarization caused by non-thermal proton and/or electron beams. In this work, we study the possible role of resonance line polarization due to radiation anisotropy in the inhomogeneous medium of the flare ribbons. We consider a simple two-dimensional model of the flaring chromosphere and we self-consistently solve the non-LTE problem taking into account the role of resonant scattering polarization and of the Hanle effect. Our calculations show that the horizontal plasma inhomogeneities at the boundary of the flare ribbons can lead to a significant radiation anisotropy in the line formation region and, consequently, to a fractional linear polarization of the emergent radiation of the order of several percent. Neglecting the effects of impact polarization, our model can provide a clue for resolving some of the common observational findings, namely: (1) why a high degree of polarization appears mainly at the edges of the flare ribbons; (2) why polarization can also be observed during the gradual phase of a flare; and (3) why polarization is mostly radial or tangential. We conclude that radiation transfer in realistic multi-dimensional models of solar flares needs to be considered as an essential ingredient for understanding the observed spectral line polarization.

  2. Spectral and Spread Spectral Teleportation

    SciTech Connect

    Humble, Travis S

    2010-01-01

    We report how quantum information encoded into the spectral degree of freedom of a single-photon state is teleported using a finite spectrally entangled biphoton state. We further demonstrate how the bandwidth of a teleported waveform can be controllably and coherently dilated using a spread spectral variant of teleportation. We present analytical fidelities for spectral and spread spectral teleportation when complex-valued Gaussian states are prepared using a proposed experimental approach, and we discuss the utility of these techniques for integrating broad-bandwidth photonic qubits with narrow-bandwidth receivers in quantum communication systems.

  3. Spin-orbit coupling induced FFLO-like superfluidity and skyrmion-like polarization textures in trapped Fermi gases

    NASA Astrophysics Data System (ADS)

    Iskin, Menderes

    2014-03-01

    We study the interplay between the Zeeman field and spin-orbit coupling (SOC) in harmonically trapped Fermi gases loaded into a two-dimensional single-band tight-binding optical lattice. Using the Bogoliubov-de Gennes theory, we find that the Zeeman field combined with a Rashba SOC gives rise to (i) Fulde-Ferrell-like superfluidity and (ii) skyrmion-like polarization textures near the edges of the system. The effects of interaction, temperature, SOC anisotropy and Zeeman field anisotropy on the superfluid ground state and polarization textures will also be discussed. This work is supported by the Marie Curie IRG Grant No. FP7-PEOPLE-IRG-2010-268239, TÜB I . TAK Career Grant No. 3501-110T839, and TÜBA-GEB I . P.

  4. Sensitivity of VIIRS Polarization Measurements

    NASA Technical Reports Server (NTRS)

    Waluschka, Eugene

    2010-01-01

    The design of an optical system typically involves a sensitivity analysis where the various lens parameters, such as lens spacing and curvatures, to name two parameters, are (slightly) varied to see what, if any, effect this has on the performance and to establish manufacturing tolerances. A sinular analysis was performed for the VIIRS instruments polarization measurements to see how real world departures from perfectly linearly polarized light entering VIIRS effects the polarization measurement. The methodology and a few of the results of this polarization sensitivity analysis are presented and applied to the construction of a single polarizer which will cover the VIIRS VIS/NIR spectral range. Keywords: VIIRS, polarization, ray, trace; polarizers, Bolder Vision, MOXTEK

  5. Polar Environmental Monitoring

    NASA Technical Reports Server (NTRS)

    Nagler, R. G.; Schulteis, A. C.

    1979-01-01

    The present and projected benefits of the polar regions were reviewed and then translated into information needs in order to support the array of polar activities anticipated. These needs included measurement sensitivities for polar environmental data (ice/snow, atmosphere, and ocean data for integrated support) and the processing and delivery requirements which determine the effectiveness of environmental services. An assessment was made of how well electromagnetic signals can be converted into polar environmental information. The array of sensor developments in process or proposed were also evaluated as to the spectral diversity, aperture sizes, and swathing capabilities available to provide these measurements from spacecraft, aircraft, or in situ platforms. Global coverage and local coverage densification options were studied in terms of alternative spacecraft trajectories and aircraft flight paths.

  6. Antilithic effects of extracts from different polarity fractions of Desmodium styracifolium on experimentally induced urolithiasis in rats.

    PubMed

    Xiang, Songtao; Zhou, Jianfu; Li, Jing; Wang, Qian; Zhang, Qiuhong; Zhao, Zhongxiang; Zhang, Lei; Chen, Zhiqiang; Wang, Shusheng

    2015-10-01

    Desmodium styracifolium (D. styracifolium) has been widely used in traditional Chinese medicine for the treatment of urolithiasis. This work was undertaken to investigate extracts from different polarity fractions of D. styracifolium for possible antilithic effects as well as antioxidant potential to explore the underlying phytochemically active constituents of this plant. The extracts of D. styracifolium were divided into four different polarity fractions by petroleum ether (Fr. PE), chloroform (Fr. CH), ethyl acetate (Fr. EA), and n-butyl alcohol (Fr. NB). The antilithic and antioxidant effects were evaluated and compared in vivo on an animal model of calcium oxalate (CaOx) urolithiasis, which was established by administration of 1 % ethylene glycol along with 2 % ammonium chloride in drinking water for 28 days. A total of 60 male Sprague-Dawley rats were randomly divided into six groups: normal control group, lithogenic group, and four different polarity fractions of D. styracifolium-treated groups. At the end of the study, urine, blood, and kidney tissue samples were all collected for evaluation. Among the four polarity fractions of D. styracifolium extracts, the Fr. PE and Fr. NB treatment significantly reduced the CaOx crystal deposition in kidneys, prevented the renal toxic changes like pH, Cr, and BUN. In addition, Fr. PE and Fr. NB treatment significantly decreased urinary excretion of oxalate along with a increase of citrate excretion. The increased amounts of malondialdehyde and decreased activities of superoxide dismutase, catalase, and glutathione peroxidase were detected in lithogenic group, D. styracifolium extracts treatment prevented the oxidative stress changes especially for the Fr. PE and Fr. NB extracts. In conclusion, our data suggest that the extracts from D. styracifolium possess the antiurolithic activity, possibly mediated through the inhibition of CaOx crystal aggregation as well as the alleviation of oxidative injury in the kidney, and the Fr. PE and Fr. NB extracts are the active fractions of D. styracifolium extract. PMID:26123751

  7. Multispectral polarized scene projector (MPSP)

    NASA Astrophysics Data System (ADS)

    Yu, Haiping; Wei, Hong; Guo, Lei; Wang, Shenggang; Li, Le; Lippert, Jack R.; Serati, Steve; Gupta, Neelam; Carlen, Frank R.

    2011-06-01

    This newly developed prototype Multispectral Polarized Scene Projector (MPSP), configured for the short wave infrared (SWIR) regime, can be used for the test & evaluation (T&E) of spectro-polarimetric imaging sensors. The MPSP system generates both static and video images (up to 200 Hz) with 512×512 spatial resolution with active spatial, spectral, and polarization modulation with controlled bandwidth. It projects input SWIR radiant intensity scenes from stored memory with user selectable wavelength (850-1650 nm) and bandwidth (12-100 nm), as well as polarization states (six different states) controllable on a pixel by pixel basis. The system consists of one spectrally tunable liquid crystal filter with variable bandpass, and multiple liquid crystal on silicon (LCoS) spatial light modulators (SLMs) for intensity control and polarization modulation. In addition to the spectro-polarimetric sensor test, the instrument also simulates polarized multispectral images of military scenes/targets for hardware-in-the loop (HIL) testing.

  8. Local Polarization Dynamics and Bias-Induced Phase Transitions in Ferroelectric Relaxors: Time-resolved Spectroscopy and Ergodic Gap Mapping

    NASA Astrophysics Data System (ADS)

    Kalinin, S. V.; Rodriguez, B.; Nikiforov, M. P.; Balke, N.; Jesse, S.; Ovchinnikov, O. S.; Bokov, A. A.; Ye, Z.-G.

    2009-03-01

    Mesoscopic domain structure and dynamics in PMN-PT solis solutions is studied using spatially resolved time- and voltage spectroscopic imaging modes. For compositions close to the MPB, we observe the formation of classical ferroelectric domains with rough self-affine boundaries. In the ergodic phase (PMN and PMN-10PT), the formation of non-classical labyrinthine domain patterns characterized by a single characteristic length scale is observed. The (a) persistence of these patterns well above Tc and (b) the fact that cannot be switched by tip bias suggest that they can be attributed to the frozen polarization component. Spatial variability of polarization relaxation dynamics in PMN-10PT is studied. Local relaxation attributed to the reorientation of polar nanoregions was found to follow stretched exponential dependence, with ? 0.4, much larger than the macroscopic value determined from dielectric spectra (? 0.09). The spatial inhomogeneity of relaxation time distribution with the presence of 100-200 nm ``fast'' and ``slow'' regions is observed. The results are analyzed to map the Vogel-Fulcher temperatures on the nanoscale. The applicability of this technique to map ``ergodic gap'' distribution on the surface is discussed. Research supported by the Division of Materials Science and Engineering, Basic Energy Sciences, U.S. Department of Energy at Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC.

  9. Polarized cell migration induces cancer type-specific CD133/integrin/Src/Akt/GSK3?/?-catenin signaling required for maintenance of cancer stem cell properties.

    PubMed

    Su, Ying-Jhen; Lin, Wei-Hsin; Chang, Yi-Wen; Wei, Kuo-Chen; Liang, Chi-Lung; Chen, Shin-Cheh; Lee, Jia-Lin

    2015-11-10

    CD133 is widely used as a surface marker to isolate cancer stem cells (CSCs). Here we show that in CSCs CD133 contributes to ?-catenin-mediated transcriptional activation and to the self-renewal capacity of sphere-forming and side-population (SP) cells in cell lines from brain, colon and lung cancers, but not gastric or breast cancers. In chromatin immunoprecipitation assays, ?-catenin binding to the proximal promoter regions of ITGA2-4 and ITGA10-11 in brain, colon and lung cancer cell lines could be triggered by CD133, and ?-catenin also bound to the proximal promoter regions of ITGB6 and ITGB8 in cell lines from gastric and breast cancers. CD133 thus induces ?-catenin binding and transcriptional activation of diverse targets that are cancer type-specific. Cell migration triggered by wounding CD133+ cells cultured on ECM-coated dishes can induce polarity and lipid raft coalescence, enhancing CD133/integrin signaling and asymmetric cell division. In response to directional cues, integrins, Src and the Par complex were enriched in lipid rafts, and the assembly and activation of an integrated CD133-integrin-Par signaling complex was followed by Src/Akt/GSK3? signaling. The subsequent increase and nuclear translocation of ?-catenin may be a regulatory switch to increase drug resistance and stemness properties. Collectively, these findings 1) indicate that a polarized cell migration-induced CD133/integrin/Src/Akt/GSK3?/?-catenin axis is required for maintenance of CSC properties, 2) establish a function for CD133 and 3) support the rationale for targeting CD133 in cancer treatment. PMID:26515729

  10. Emission spectral analysis of caspase-3 activation during artesunate (ART)-induced apoptosis of human lung adenocarcinoma cell

    NASA Astrophysics Data System (ADS)

    Pan, Wen-liang; Chen, Tong-sheng; Qu, Junle

    2009-02-01

    Artesunate (ART), a semi-synthetic derivative of the sesquiterpene artemisinin extracted from the Chinese herb Artemisia annua, exerts a broad spectrum of clinical activity against human cancers. Artemisinin-derivative combination chemotherapy is recommended by WHO since it acts rapidly and is well tolerated and particularly effective. In present investigation, we used CKK-8 assay to assess the inhibitory effects of ART on human lung adenocarcinoma (ASTC-a-1) cells. Apoptotic activity of ART in ASTC-a-1 cells was detected by means of nuclear staining with Hoechst33258. In order to monitor the activity of caspase-3 during ART-induced ASTC-a-1 cells apoptosis, the dynamical emission spectra of SCAT3, a FRET plasmid based on GFPs, were performed inside living cell expressed stably with SCAT3 after ART treatment. The results showed that (1) ART could inhibit ASTC-a-1 cells proliferation in a dose-dependent manner; (2) chromatin condensation was observed after ART treatment for 48 h; (3) the SCAT3 inside living cells were cleaved after ART treatment for 48 h, implying that caspase-3 was involved in the ART-induced apoptosis.

  11. A Study on the Characteristics of Carbon-Related Spectral Lines from a Laser-Induced Fly Ash Plasma

    NASA Astrophysics Data System (ADS)

    Pan, Gang; Lu, Jidong; Dong, Meirong; Yao, Shunchun; Xie, Zixin; Fan, Ju

    2015-08-01

    A 1064 nm Nd:YAG laser was used to ablate fly ash samples. The characteristics of the spectral lines measured from the laserablated fly ash plasmas are presented with special attention to atomic and molecular carbon emission. It is shown that the intensity of the atomic line C I 192.9 nm is weak and the shot-to-shot intensity is fluctuant. The carbon atomic line C I 247.7 nm is relatively intensive and stable, however it is seriously interfered with by Fe I 247.8 nm. The intensity of the CN molecular line is close to that of C I 247.7 nm and the CN line is stable and less interfered with. The comparison of molecular CN emission under different conditions (air, Ar and N2) shows that the CN lines detected from the plasmas formed in an atmospheric environment are correlated with the reaction of carbon atoms in the plasma with the nitrogen in air, which indicates that the CN line is also important in pulsed laser ablation fly ash plasmas and this information can be incorporated in the detection of unburned carbon content in fly ash. Finally, a calibration curve is established with a correlation coefficient R2 of 0.999, using C I 247.7 nm and the CN molecular line as associated variables. In addition, accuracy is improved to a certain extent. supported by National Natural Science Foundation of China (Nos. 51071069 and 51476061), Guangdong Province Key Laboratory of Efficient and Clean Energy Utilization, China (No. 2013A061401005) and Key Laboratory of Efficient and Clean Energy Utilization of Guangdong Higher Education Institutes of China (No. KLB10004)

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

    E-print Network

    Flatte, Michael E.

    2011-01-01

    and dipolar magnetic fields in semiconductor nanostructures Ionel T¸ifrea1,2 and Michael E. Flatt´e2 1 be measurable via optically induced nuclear magnetic resonance or time-resolved Faraday rotation experiments. We

  13. Quantum coherent ?-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

    NASA Astrophysics Data System (ADS)

    Mineo, Hirobumi; Fujimura, Yuichi

    2015-06-01

    We propose an ultrafast quantum switching method of ?-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent ?-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent ?-electron ring current, and discussed ring current transfer between two aromatic rings.

  14. On the possibility of contact-induced spin polarization in interfaces of armchair nanotubes with transition metal substrates

    NASA Astrophysics Data System (ADS)

    Kuzubov, Alexander A.; Kovaleva, Evgenia A.; Tomilin, Felix N.; Mikhaleva, Natalya S.; Kuklin, Artem V.

    2015-12-01

    The interaction between armchair carbon and boron nitride nanotubes (NT) with ferromagnetic transition metal (TM) surfaces, namely, Ni(111) and Co(0001), was studied by means of density functional theory. Different configurations of composite compartments mutual arrangement were considered. Partial densities of states and spin density spatial distribution of optimized structures were investigated. Influence of ferromagnetic substrate on nanotubes' electronic properties was discussed. The values of spin polarization magnitude at the Fermi level are also presented and confirm the patterns of spin density spatial distribution.

  15. Measuring the effect of ion-induced drift-gas polarization on the electrical mobilities of multiply-charged ionic liquid nanodrops in air.

    PubMed

    Fernández-García, Juan; Fernández de la Mora, Juan

    2013-12-01

    The electrical mobilities of multiply-charged nanodrops of the ionic liquid 1-ethyl, 3-methylimidazolium dicyanamide (EMI-N[CN]2) were accurately measured in air at 20 °C for mass-selected clusters of composition [EMI-N[CN]2] n [EMI(+)] z , with 2 ? n ? 369 and 1 ? z ? 10. We confirm prior reports that the mobility Z of a globular ion of mass m is given approximately by the modified Stokes-Millikan law for spheres, Z? = ?Z SM,mod (d m ? + ?d g ,?z,?m), where d m ? = ?(6m/??)(1/3) is the nanodrop mass-diameter based on the density ? of the liquid (corrected for the capillary compression and electrostatic deformation of the nanodrop), and d g is an effective air molecule diameter. There is however a measurable (up to 7%) and systematic z-dependent departure of Z from Z SM,mod . As theoretically expected at small ? (*) , this effect is accurately described by a simple correction factor of the form Z/Z SM,mod ? = ??(1? - ??? (*)), where kT? (*) is the potential energy due to the ion-induced dipole (polarization) attraction between a perfectly-conducting charged nanodrop and a polarized neutral gas-molecule at a distance (d m ? + ?d g )/2 from its center. An excellent fit of this model to hundreds of data points is found for d g ? 0.26 nm, ? ? 0.36, and ? ? 0.954. Accounting for the effect of polarization decreases d g considerably with respect to values inferred from earlier nanodrop measurements that ignored this effect. In addition, and in spite of ambiguities in the mobility calibration scale, the measured constant ? smaller than unity increases Millikan's drag enhancement factor from the accepted value ? m ? 1.36 to the new value ? ? ? m /? ? 1.42? ± 0.03. PMID:24048890

  16. Measuring the Effect of Ion-Induced Drift-Gas Polarization on the Electrical Mobilities of Multiply-Charged Ionic Liquid Nanodrops in Air

    NASA Astrophysics Data System (ADS)

    Fernández-García, Juan; Fernández de la Mora, Juan

    2013-12-01

    The electrical mobilities of multiply-charged nanodrops of the ionic liquid 1-ethyl, 3-methylimidazolium dicyanamide (EMI-N[CN]2) were accurately measured in air at 20 °C for mass-selected clusters of composition [EMI-N[CN]2] n [EMI+] z , with 2 ? n ? 369 and 1 ? z ? 10. We confirm prior reports that the mobility Z of a globular ion of mass m is given approximately by the modified Stokes-Millikan law for spheres, Z = Z SM, mod ( d m + d g , z, m), where d m = (6 m/ ??)1/3 is the nanodrop mass-diameter based on the density ? of the liquid (corrected for the capillary compression and electrostatic deformation of the nanodrop), and d g is an effective air molecule diameter. There is however a measurable (up to 7 %) and systematic z-dependent departure of Z from Z SM,mod . As theoretically expected at small ? * , this effect is accurately described by a simple correction factor of the form Z/ Z SM, mod = ?(1 - ?? *), where kT? * is the potential energy due to the ion-induced dipole ( polarization) attraction between a perfectly-conducting charged nanodrop and a polarized neutral gas-molecule at a distance ( d m + d g )/2 from its center. An excellent fit of this model to hundreds of data points is found for d g ? 0.26 nm, ? ? 0.36, and ? ? 0.954. Accounting for the effect of polarization decreases d g considerably with respect to values inferred from earlier nanodrop measurements that ignored this effect. In addition, and in spite of ambiguities in the mobility calibration scale, the measured constant ? smaller than unity increases Millikan's drag enhancement factor from the accepted value ? m ? 1.36 to the new value ? ? ? m / ? ? 1.42 ± 0.03.

  17. Spectropolarimetry and Infrared Photometry of Magnetic White Dwarfs: Vacuum Polarization Effect or Magnetic CIA?

    E-print Network

    Gnedin, Y N; Larionov, V M; Naidenov, I D; Natsvlishvili, T M; Piotrovich, M Y; Gnedin, Yu. N.

    2004-01-01

    We present brief review of two probable physical mechanisms that can explain the results of photometric and spectropolarimetric observations of magnetic white dwarfs: vacuum polarization effect into a strong magnetic field and, so-called, magnetic collision induced absorption (magnetic CIA). Both mechanisms provide observed rotation of polarization ellipse and suppression of spectral energy distributions. The results of spectropolarimetric observations of magnetic white dwarfs made at Russian BTA-6m and the results of the near infrared photometric observations with Russian-Italian AZT-24 telescope located at Campo Imperatore are also presented.

  18. Spectropolarimetry and Infrared Photometry of Magnetic White Dwarfs: Vacuum Polarization Effect or Magnetic CIA?

    E-print Network

    Yu. N. Gnedin; N. V. Borisov; V. M. Larionov; I. D. Naidenov; T. M. Natsvlishvili; M. Yu. Piotrovich

    2004-09-07

    We present brief review of two probable physical mechanisms that can explain the results of photometric and spectropolarimetric observations of magnetic white dwarfs: vacuum polarization effect into a strong magnetic field and, so-called, magnetic collision induced absorption (magnetic CIA). Both mechanisms provide observed rotation of polarization ellipse and suppression of spectral energy distributions. The results of spectropolarimetric observations of magnetic white dwarfs made at Russian BTA-6m and the results of the near infrared photometric observations with Russian-Italian AZT-24 telescope located at Campo Imperatore are also presented.

  19. Spectral line polarimetry with a channeled polarimeter.

    PubMed

    van Harten, Gerard; Snik, Frans; Rietjens, Jeroen H H; Martijn Smit, J; Keller, Christoph U

    2014-07-01

    Channeled spectropolarimetry or spectral polarization modulation is an accurate technique for measuring the continuum polarization in one shot with no moving parts. We show how a dual-beam implementation also enables spectral line polarimetry at the intrinsic resolution, as in a classic beam-splitting polarimeter. Recording redundant polarization information in the two spectrally modulated beams of a polarizing beam-splitter even provides the possibility to perform a postfacto differential transmission correction that improves the accuracy of the spectral line polarimetry. We perform an error analysis to compare the accuracy of spectral line polarimetry to continuum polarimetry, degraded by a residual dark signal and differential transmission, as well as to quantify the impact of the transmission correction. We demonstrate the new techniques with a blue sky polarization measurement around the oxygen A absorption band using the groundSPEX instrument, yielding a polarization in the deepest part of the band of 0.160±0.010, significantly different from the polarization in the continuum of 0.2284±0.0004. The presented methods are applicable to any dual-beam channeled polarimeter, including implementations for snapshot imaging polarimetry. PMID:25089978

  20. Planck 2015 polarization maps

    NASA Astrophysics Data System (ADS)

    Tristram, Matthieu

    2015-08-01

    On behalf of the Planck collaboration, I will present the maps from the last Planck release. I will focus on the difference with respect to the 2013 data and in particular describe the polarized maps.Planck uncertainties are dominated by residuals from systematics rather than statistical noise. To achieve this level of sensitivities, Planck is calibrated with an unprecedent precision. This is particularly important given the Planck scanning strategy which induce specific leakage from intensity to polarization.