Sample records for spectral induced polarization

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

    NASA Astrophysics Data System (ADS)

    Revil, A.; Skold, M.

    2011-11-01

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

  2. 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.

  3. 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

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

    Microsoft Academic Search

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

    2007-01-01

    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

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

    Microsoft Academic Search

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

    2005-01-01

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

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

    Microsoft Academic Search

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

    2008-01-01

    Stimulated sulfate-reduction is a bioremediation technique utilized for the sequestration of heavy metals in the subsurface. We performed laboratory column experiments to investigate the geoelectrical response of iron sulfide transformations by Desulfovibrio vulgaris. Two geoelectrical methods, (1) spectral induced polarization (SIP), and (2) electrodic potential measurements, were investigated. Aqueous geochemistry (sulfate, lactate, sulfide, and acetate), observations of precipitates (identified from

  7. 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).

  8. INDUCED POLARIZATION WITH ELECTROMAGNETIC COUPLING: 3D SPECTRAL IMAGING THEORY: EMSP PROJECT NO. 73836

    SciTech Connect

    Morgan, F. Dale; Lesmes, David

    2004-12-31

    The principal objective of the project was to develop a non-invasive imaging technique, based on spectral induced polarization (SIP), to characterize in-situ distribution of organic and inorganic contaminants. This was to be an advance over a similar technique offered by the DC resistivity method. The motivation for the choice of IP over resistivity is rooted in the fact that resistivity response is governed by volume distributions of electrical parameters and therefore is relatively insensitive to small changes contributed by the presence of contaminants. IP response on the other hand is governed by the electrochemical properties of the rock-grain pore-fluid interface, which can be significantly altered by the incoming contaminant (ions) over long residence times. Small concentrations of contaminants are the rule rather than the exception thus, the detection threshold for IP, which is more sensitive to small concentrations, is much lower than for resistivity (IP field threshold for PCE/TCE is about 1mg/g). Additionally, the observation that IP depends on the chemistry of the contaminants provided the motivation that a spectral IP response could lead to a database of identifying signatures by which contaminants can be discriminated.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  12. 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.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  15. Spectral induced polarization of shaly sands: Influence of the electrical double layer

    NASA Astrophysics Data System (ADS)

    Revil, A.

    2012-02-01

    I developed a new model named POLARIS describing the complex conductivity of (pyrite-free) shaly poorly sorted sands. This model is based on the solution given by the effective medium theory for grains coated by an electrical double layer and immersed in a background electrolyte. The electrical double layer comprises the Stern layer and the diffuse layer. Both layers play very distinct roles in the in-phase and quadrature conductivities. The polarization of the shaly sands is mainly controlled by the polarization of the Stern layer (except at very high salinities) with a very small mobility of the counterions contained in this layer. The in-phase component of the conductivity is controlled by the conductivity of the pore water with a contribution associated with the diffuse layer (the contribution of the Stern layer seems negligible). The fraction of counterions in the Stern layer is computed from a simple sorption isotherm and is used to infer the quadrature conductivity. The quadrature conductivity is assumed to be frequency independent, which is a reasonable approximation in clayey sands and sandstones, in agreement with observations. The polarization model is also based on the assumption that the Stern layer is discontinuous between grains, an assumption that is consistent with recent models of ionic transport in clayey sands. POLARIS explains the dependence of the quadrature conductivity on the salinity, cation exchange capacity, specific surface area (or specific surface per unit pore volume), and temperature. It can be used to predict the saturation and the permeability (inside 1 order of magnitude).

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  18. INJECTION ELECTRODE POLARIZATION RESISTIVITY AND INDUCED POLARIZATION

    E-print Network

    Merriam, James

    INJECTION ELECTRODE POLARIZATION IN RESISTIVITY AND INDUCED POLARIZATION J.B. Merriam University.merriam@usask.ca Abstract Polarization of injection electrodes in resistivity and induced polarization may reach several elsewhere that this may present a problem for programmable switching resistivity meters because

  19. Electromagnetically induced polarization conversion

    NASA Astrophysics Data System (ADS)

    Khanikaev, Alexander B.; Mousavi, S. Hossein; Wu, Chihhui; Dabidian, Nima; Alici, Kamil B.; Shvets, Gennady

    2012-07-01

    Electromagnetically induced transparency and polarization conversion due to interference between two polarization-selective plasmonic resonances coexisting in the same planar metamaterial are studied. The metasurface represents a periodic array of two topologically distinct metamolecules combined on the same substrate: i) monopole antennas connected to wires and supporting a high-Q resonance radiatively coupled to x-polarization, and ii) dipolar antennas supporting a low-Q resonance coupled to y-polarization. We demonstrate that due to the interaction between these modes through a capacitive coupling between the metamolecules, one can observe a circularly-polarized Electromagnetically Induced Transparency (EIT) and thereby achieve an efficient ultra-thin quarter-wave plate.

  20. Bright, saturated, red-to-yellow organic light-emitting devices based on polarization-induced spectral shifts

    Microsoft Academic Search

    V Bulovi?; A Shoustikov; M. A Baldo; E Bose; V. G Kozlov; M. E Thompson; S. R Forrest

    1998-01-01

    We demonstrate red, orange, and yellow organic light-emitting devices (OLED) with the electroluminescent layer consisting of aluminum tris(8-hydroxyquinoline) (Alq3) doped with laser dye DCM2, with the emission color dependent on the concentration of DCM2. A peak emission wavelength shift of up to 50 nm is found to be due to strong polarization effects. For red and yellow–orange OLEDs, a maximum

  1. 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.

  2. Polarization-based microscopy using a fiber optic spectral polarimeter

    Microsoft Academic Search

    Eunha Kim; Digant P. Dave; Thomas E. Milner

    2002-01-01

    We present a fiber optic spectral polarimeter, an instrument that allows measurement of the spectrally resolved Stokes parameters. The instrument consists of a pair of polarization maintaining (PM) fibers spliced at 45 degree(s) with respect to each other in line with a polarizer module whose transmission axis is aligned to the fast axis of the first PM fiber. The generated

  3. Polarization based Microscopy using a Fiber Optic Spectral Polarimeter

    Microsoft Academic Search

    Eunha Kim; Digant P Dave; Thomas E. Milner

    ABSTRCT We present a fiber optic spectral polarimeter, an instrument that allows measurement of the spectrally resolved Stokes parameters. The instrument consists of a pair of polarization maintaining (PM) fibers spliced at 45 ° with respect to each other in line with a polarizer module whose transmission axis is aligned to the fast axis of the first PM fiber. The

  4. Chemically induced unfolding of bovine serum albumin by urea and sodium dodecyl sulfate: a spectral study with the polarity-sensitive charge-transfer fluorescent probe (E)-3-(4-methylaminophenyl)acrylic acid methyl ester.

    PubMed

    Ghosh, Shalini; Guchhait, Nikhil

    2009-07-13

    Sensitivity of the charge-transfer (CT) band of the fluorescence probe (E)-3-(4-methylaminophenyl)acrylic acid methyl ester (MAPAME) towards the polarity of its immediate environment is employed to investigate the binding interaction of the probe with bovine serum albumin (BSA) and uncoiling of BSA by the denaturants urea and sodium dodecyl sulfate micelles. Binding of the probe with BSA produces a blue shift and enhanced intensity of the CT emission band which clearly point toward a decrease in polarity of the immediate environment of MAPAME. This is expected, since binding with BSA moves the probe from a polar water environment to a much less polar, hydrophobic protein interior, where the CT band is expected to be blue-shifted. Higher intensity arises due to fewer non-radiative decay paths available to the probe in the hydrophobic protein environment. Chemically induced unfolding of BSA by urea and sodium dodecyl sulfate is tracked by monitoring the induced spectral changes of the protein-bound probe MAPAME. Red-edge excitation shift or REES, fluorescence resonance energy transfer (FRET) and anisotropy measurements are used to investigate and monitor these binding and unfolding processes. PMID:19466702

  5. Polarization-based microscopy using a fiber optic spectral polarimeter

    NASA Astrophysics Data System (ADS)

    Kim, Eunha; Dave, Digant P.; Milner, Thomas E.

    2002-06-01

    We present a fiber optic spectral polarimeter, an instrument that allows measurement of the spectrally resolved Stokes parameters. The instrument consists of a pair of polarization maintaining (PM) fibers spliced at 45 degree(s) with respect to each other in line with a polarizer module whose transmission axis is aligned to the fast axis of the first PM fiber. The generated spectrum is composed of three quasi- cosinusoidal components, which carry information required to reconstruct the spectrally resolved Stokes parameters of incident light. Fourier transform of the measured spectrum provides the significant parameters for determination of the spectrally resolved Stokes parameters of light. The performance of the fiber optic spectral polarimeter is demonstrated by the computer simulation and experiments with input light of known polarization states. A unique characteristic of this instrument is that the spectrally resolved polarization state of incident light can be determined from one spectral measurement without any mechanical movement. Moreover, the instrument can be incorporated into a tomographic imaging system such as a conventional microscopy system. Polarization based microscopy combined with a fiber optic spectral polarimeter will provide measurements that allow better understanding of depolarization process of light passing through biological materials for diagnostic imaging.

  6. Accurate spectral characterization of polarization-dependent loss

    Microsoft Academic Search

    R. M. Craig

    2003-01-01

    Building on previous work, a rapid automated nonmechanical measurement system for spectral characterization of polarization-dependent loss (PDL) has been developed. A deterministic fixed-states Mueller-Stokes method in conjunction with realtime calibrated spectral information is used to derive wavelength-dependent Mueller matrix elements. Voltage-modulated liquid-crystal variable retarders set the input polarization states. A narrow voltage-tuned filter provides a wavelength sweep following a broadband

  7. Spectral and Polarization Sensitivity of the Dipteran Visual System

    PubMed Central

    McCann, Gilbert D.; Arnett, David W.

    1972-01-01

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

  8. Integrated spectral-polarization imaging sensor with aluminum nanowire polarization filters.

    PubMed

    Kulkarni, Meenal; Gruev, Viktor

    2012-10-01

    Current division-of-focal-plane polarization imaging sensors can perceive intensity and polarization in real time with high spatial resolution, but are oblivious to spectral information. We present the design of such a sensor, which is also spectrally selective in the visible regime. We describe its extensive spectral and polarimetric characterization. The sensor has a pixel pitch of 5 µm and an imaging array of 168 by 256 elements. Each element comprises spectrally sensitive vertically stacked photodetectors integrated with a 140 nm pitch nanowire linear polarizer. The sensor has a maximum measured SNR of 45 dB, extinction ratio of ~3.5, QE of 12%, and linearity error of 1% in the green channel. We present sample spectral-polarization images. PMID:23188263

  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. Modulation in the spectral degrees of polarization and cross polarization of a stochastic electromagnetic beam through a one-dimensional compound photonic crystal.

    PubMed

    Zhuang, Fei; Du, Xinyue; Zhao, Daomu

    2011-03-15

    We design a one-dimensional compound photonic crystal constituted of a periodic arrangement of electromagnetic-induced transparency atomic vapor. It is shown that, when a stochastic electromagnetic beam propagates through the compound photonic crystal, the spectral degrees of polarization and cross polarization of the beam can be modulated by changing the parameters of the supercells of the compound photonic crystal. PMID:21403735

  11. Spectral polarization analysis of the interplanetary magnetic field fluctuations

    NASA Technical Reports Server (NTRS)

    Polygiannakis, J. M.; Moussas, X.; Quenby, J. J.; Smith, E. J.

    1994-01-01

    A new computational method and algorithm, based on complex Fourier analysis, is used to derive the spectral density of plane and circularly polarized fluctuation components of the interplanetary magnetic field. Applications of the method have been made using HEOS 2 (1 AU), Pioneer 10 (5 AU), Pioneer 11 (20 AU), and International Cometary Explorer (ICE) (Giocabini-Zinner's comet) data sets. The results show the existence of circularly polarized magnetohydrodynamic (MHD) waves in all cases.

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

    E-print Network

    Purdue University

    . Backus, and G. Vdovin, "Adaptive pulse compression for transform-limited 15-fs high-energy pulse Fourier transform pulse shapers [1] are an important tool for controlling the waveforms of ultrafastProgrammable polarization-independent spectral phase compensation and pulse shaping R. D. Nelson, D

  13. 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@creol.ucf.edu). Abstract: We consider the design of photonic circuits that make use of Ti:LiNbO3 diffused channel-mode waveguide (TMW). We study a class of photonic circuits comprising: 1) a nonlinear periodically poled TMW

  14. 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."

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

    SciTech Connect

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

    2013-02-10

    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.

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

    SciTech Connect

    Chang, Zhe; Lin, Hai-Nan [Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing (China); Jiang, Yunguo, E-mail: jiangyg@ihep.ac.cn [School of Space Science and Physics, Shandong University at Weihai, 264209 Weihai (China)

    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.

  17. 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.

  18. Quantitative polarized light microscopy using spectral multiplexing interferometry.

    PubMed

    Li, Chengshuai; Zhu, Yizheng

    2015-06-01

    We propose an interferometric spectral multiplexing method for measuring birefringent specimens with simple configuration and high sensitivity. The retardation and orientation of sample birefringence are simultaneously encoded onto two spectral carrier waves, generated interferometrically by a birefringent crystal through polarization mixing. A single interference spectrum hence contains sufficient information for birefringence determination, eliminating the need for mechanical rotation or electrical modulation. The technique is analyzed theoretically and validated experimentally on cellulose film. System simplicity permits the possibility of mitigating system birefringence background. Further analysis demonstrates the technique's exquisite sensitivity as high as ?20??pm for retardation measurement. PMID:26030573

  19. Spectral Signatures of Polar Stratospheric Clouds and Sulfate Aerosol.

    NASA Astrophysics Data System (ADS)

    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.

    1994-10-01

    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 cm1 (10.8, 8.0, and 6.2 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 calculations and laboratory phase-equilibrium studies of nitric acid trihydrate, are used to predict the location of nitric acid trihydrate cloud particles.

  20. 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.

  1. 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.

  2. Polarization maintaining fiber based ultra-high resolution spectral domain polarization sensitive optical coherence tomography.

    PubMed

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

    2009-12-01

    We present a new ultra high resolution spectral domain polarization sensitive optical coherence tomography (PS-OCT) system based on polarization maintaining (PM) fibers. The method transfers the principles of our previous bulk optic PS-OCT systems to a fiberized setup. The phase shift between the orthogonal polarization states travelling in the two orthogonal modes of the PM fiber is compensated by software in post processing. Thereby, the main advantage of our bulk optics setups, i.e. the use of only a single input polarization state to simultaneously acquire reflectivity, retardation, optic axis orientation, and Stokes vector, is maintained. The use of a broadband light source of 110 nm bandwidth provides improved depth resolution and smaller speckle size. The latter is important for improved resolution of depolarization imaging. We demonstrate our instrument for high-resolution PS-OCT imaging of the healthy human retina. PMID:20052196

  3. 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.

  4. Production of highly polarized 3 He using spectrally narrowed diode laser

    E-print Network

    Walker, Thad G.

    Production of highly polarized 3 He using spectrally narrowed diode laser array bars B. Chann, E obtained with either a spectrally narrowed laser or one type of broadband laser. Based on tests of several is typically three times lower for the spectrally narrowed laser. This last result indicates that spectrally

  5. Demonstration of spectral correlation control in a source of polarization entangled photon pairs at telecom wavelength

    E-print Network

    Lutz, Thomas; Jennewein, Thomas

    2013-01-01

    Spectrally correlated photon pairs can be used to improve performance of long range fiber based quantum communication protocols. We present a source based on spontaneous parametric down-conversion producing polarization entangled photons without spectral filtering. In addition, the spectral correlation within the photon pair can be controlled by changing the pump pulse duration or coupled spatial modes characteristics. The spectral and polarization correlations were characterized. The generated photon pairs feature both positive spectral correlations, no correlations, or negative correlations and polarization entanglement with the fidelity as high as 0.97 (no background subtraction) with the expected Bell state.

  6. Non-Zeeman Circular Polarization of Molecular Maser Spectral Lines

    E-print Network

    Houde, Martin

    2014-01-01

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

  7. Modal, spectral, and polarization entanglement in guided-wave parametric down-conversion Mohammed F. Saleh*

    E-print Network

    Teich, Malvin C.

    Modal, spectral, and polarization entanglement in guided-wave parametric down-conversion Mohammed F, spectral, and polarization entanglement properties of photon pairs generated in a nonlinear periodically spontaneous parametric down-conversion. Any of the possible degrees of freedom--mode num- ber, frequency

  8. 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.

  9. Effects of spectral entanglement in polarization-entanglement swapping and type-I fusion gates

    SciTech Connect

    Humble, Travis S [ORNL; Grice, Warren P [ORNL

    2008-01-01

    We examine how spectral entanglement in polarization-entangled photon states generated from bulk-crystal, spontaneous parametric down-conversion affects the success of entanglement swapping and type-I fusion gates. We quantify the success of the entanglement swapping and fusion gates by calculating the bipartite concurrence and residual tangle, respectively, in terms of the joint spectral probability amplitudes of the initial broad-bandwidth polarization-entangled states. We find that both polarization-entanglement measures depend strongly on the initial spectral entanglement, as well as on the configuration of the independent sources. Specifically, when spectral differences correlate with polarization, the optimal source configuration is different for the two protocols. We conclude that this distinction is founded in how the underlying Bell-state measurement and quantum-erasure techniques respond differently to distinguishing spectral information.

  10. Electromagnetically induced transparency over spectral hole-burning

    E-print Network

    Shahriar, Selim

    Electromagnetically induced transparency over spectral hole-burning temperature in a rare the spectral hole-burning temperature. The transmission of the probe laser beam is increased by a factor of exp over the spectral hole-burning temperature in a rare-earth­doped solid represents important progress

  11. Relationships between induced polarization relaxation time and hydraulic properties of sandstone

    Microsoft Academic Search

    Konstantin Titov; Andrey Tarasov; Yuri Ilyin; Nikita Seleznev; Austin Boyd

    2010-01-01

    We investigated electrical and physical-chemical properties of six sandstone samples with contrasting mineralogical characteristics and with hydraulic conductivity varying in a wide range. The electrical data were obtained from time domain spectral induced polarization (IP) measurements. We inverted the IP decays to relaxation time distributions, and then compared the modal relaxation times with the dominant pore throat diameters obtained from

  12. Spectrally Resolved Quantum Tomography of Polarization Entangled States

    E-print Network

    Dmitry A. Kalashnikov; Leonid A. Krivitsky

    2010-09-25

    We study broadband polarization entangled states generated within the line width of type-II Spontaneous Parametric Down Conversion (SPDC). Applying a complete quantum polarization tomography protocol at arbitrary combination of frequency and angular sideband modes we reveal a complex structure of non-degenerate non-collinear polarization entangled states generated within the SPDC line width. It is demonstrated that simultaneous compensation of longitudinal and transverse walk off leads to homogenizing the structure of polarization entanglement.

  13. 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.

  14. SPECTRAL MAPPING OF THE INTERMEDIATE POLAR DQ HERCULIS

    SciTech Connect

    Saito, R. K. [Departamento de AstronomIa y Astrofisica, Pontificia Universidad Catolica de Chile, Vicuna Mackenna 4860, Casilla 306, Santiago 22 (Chile); Baptista, R. [Departamento de Fisica, Universidade Federal de Santa Catarina, Trindade, 88040-900 Florianopolis, SC (Brazil); Horne, K. [School of Physics and Astronomy, University of St. Andrews, KY16 9SS, Scotland (United Kingdom); Martell, P., E-mail: rsaito@astro.puc.c [University of Wisconsin Center-Marinette, 750 W. Bay Shore Street, Marinette, WI 54143 (United States)

    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.

  15. Wavelength-switchable erbium-doped fiber ring laser using spectral polarization-dependent loss element

    Microsoft Academic Search

    Yong Wook Lee; Byoungho Lee

    2003-01-01

    We propose a wavelength-switchable erbium-doped fiber ring laser that uses a spectral polarization-dependent loss element. The element was fabricated by inscribing a long-period grating on a polarization-maintaining fiber. Dual-wavelength switching operation was accomplished by rotating the polarization plane of the fiber laser cavity. The amplitude variation of both laser lines was measured to be less than 1 dB and the

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Revil, A.

    2013-12-01

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

  18. Modal, spectral, and polarization entanglement in guided-wave parametric down-conversion

    SciTech Connect

    Saleh, Mohammed F.; Saleh, Bahaa E. A.; Teich, Malvin Carl [Department of Electrical and Computer Engineering, Quantum Photonics Laboratory, Boston University, Boston, Massachusetts 02215 (United States); Department of Electrical and Computer Engineering, Quantum Photonics Laboratory, Boston University, Boston, Massachusetts 02215, USA and Quantum Photonics Laboratory, College of Optics and Photonics (CREOL), University of Central Florida, Orlando, Florida 32816 (United States); Department of Electrical and Computer Engineering, Quantum Photonics Laboratory, Boston University, Boston, Massachusetts 02215 (United States) and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States)

    2009-05-15

    We examine the modal, spectral, and polarization entanglement properties of photon pairs generated in a nonlinear periodically poled two-mode waveguide (one-dimensional planar or two-dimensional circular) via nondegenerate spontaneous parametric down-conversion. Any of the possible degrees of freedom - mode number, frequency, or polarization - can be used to distinguish the down-converted photons while the others serve as attributes of entanglement. Distinguishing the down-converted photons based on their mode numbers enables us to efficiently generate spectral or polarization entanglement that is either narrowband or broadband. On the other hand, when the generated photons are distinguished by their frequencies in a type-0 process, modal entanglement turns out to be an efficient alternative to polarization entanglement. Moreover, modal entanglement in type-II down-conversion may be used to generate a doubly entangled state in frequency and polarization.

  19. Modal, Spectral, and Polarization Entanglement in Guided-Wave Parametric Down-Conversion

    E-print Network

    Mohammed F. Saleh; Bahaa E. A. Saleh; Malvin Carl Teich

    2010-07-19

    We examine the modal, spectral, and polarization entanglement properties of photon pairs generated in a nonlinear, periodically poled, two-mode waveguide (1-D planar or 2-D circular) via nondegenerate spontaneous parametric down-conversion. Any of the possible degrees of freedom -- mode number, frequency, or polarization -- can be used to distinguish the down-converted photons while the others serve as attributes of entanglement. Distinguishing the down-converted photons based on their mode numbers enables us to efficiently generate spectral or polarization entanglement that is either narrowband or broadband. On the other hand, when the generated photons are distinguished by their frequencies in a Type-0 process, modal entanglement turns out to be an efficient alternative to polarization entanglement. Moreover, modal entanglement in Type-II down-conversion may be used to generate a doubly entangled state in frequency and polarization.

  20. Recognition of camouflage targets with hyper-spectral polarization imaging system

    NASA Astrophysics Data System (ADS)

    Wang, Qi-chao; Wang, Jia-chun; Zhao, Da-peng; Ma, Li-fang; Chen, Zong-sheng; Li, Zhi-gang

    2013-08-01

    On the basis of the principle of polarization detection, a hyper-spectral polarization imaging system, which is based on linear polarizer and acousto-optic tunable filter (AOTF), was designed to detect and recognize camouflage target intelligently and rapidly in this paper. Our design has neither moving parts nor modulation, and has fast and electronically tuning property, so a quick scan of spectrum at 400 nm~1000 nm can be realized electronically. At the same time, it not only could obtain the intensity image, hyper-spectral information, but also could acquire polarization signatures of the scene. Then the spectral polarization experiment about aluminous plane which covered with the bottle green, shallow green and khaki camouflage pigments within meadow were conducted at specifically wavelength by the instrument. Finally, the polarization information of the man-made targets and natural background in the scene, and the fusion image based on HIS color space were deduced through processing the experiment data. The experimental result demonstrates that the polarization characteristics of camouflage pigments were different from that of natural background. As the contrast of target and background could be enhanced by polarization information, the camouflage target could be identified effectively from the image according to polarization information. On the other hand, the camouflage target is more obvious in the fused image. Therefore, the proposed method and the system in this paper are reasonable and effective. Consequently, the hyper-spectral polarization detection technique which relative to the classical intensity detection is of significance to improve the accuracy of recognition of camouflage targets in mixed background under proper detection condition.

  1. 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. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Baccigalupi, C.; Leach, S. [SISSA, Astrophysics Sector, Via Bonomea 265, Trieste 34136 (Italy); Didier, J.; Johnson, B. R.; Miller, A. [Department of Physics, Columbia University, New York, NY 10027 (United States); Jaffe, A.; O'Dea, D. [Department of Physics, Imperial College, London SW72AZ (United Kingdom); Matsumura, T. [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    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.

  2. Spectral analyses of the dual polarization Doppler weather radar data

    Microsoft Academic Search

    Svetlana Monakhova Bachmann

    2007-01-01

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

  3. Signatures of Pulsar Polar-Cap Emission at the High-Energy Spectral Cut-off

    E-print Network

    J. Dyks; B. Rudak

    2003-04-18

    We address four unique signatures in pulsar gamma-ray radiation as predicted by polar-cap models. These signatures are expected to be present nearby the spectral high-energy cutoff at around several GeV. Their magnitude and, therefore, their observability depends strongly on the orientational factors, the rotation, as well as on the details of the polar cap structure. These strong predictions are likely to be verified by the NASA's future gamma-ray mission GLAST.

  4. Spectral Interferometric Implementation with Passive Polarization Optics of Coherent Anti-Stokes Raman Scattering

    NASA Astrophysics Data System (ADS)

    Littleton, Brad; Kavanagh, Thomas; Festy, Frederic; Richards, David

    2013-09-01

    We have developed an interferometric implementation of coherent anti-Stokes Raman scattering which enables broadband coherent Raman spectroscopy free from the nonresonant background, with a signal strength proportional to concentration. Spectra encode mode symmetry information into the amplitude response, which can be directly compared to polarized spontaneous Raman spectra. The method requires only passive polarization optics and is suitable for a wide range of laser linewidths and pulse durations. The method’s application to Raman spectral imaging is demonstrated.

  5. Polarized spectral properties of Er3+ ions in NaGd(WO4)2 crystal

    Microsoft Academic Search

    J. H. Huang; X. H. Gong; Y. J. Chen; Y. F. Lin; J. S. Liao; X. Y. Chen; Z. D. Luo; Y. D. Huang

    2007-01-01

    Polarized spectral properties of Er3+:NaGd(WO4)2 single crystal are reported. The crystal was grown by the Czochralski method. The Judd Ofelt theory was applied to analyze the polarized absorption spectra and then calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios. Fluorescence decay curves of the 4 I 13\\/2, 4 I 11\\/2, and 4 S 3\\/2 multiplets for the Er3+

  6. Line shapes of photon-gated persistent spectral hole burning in polarization spectroscopy

    Microsoft Academic Search

    Yong Qin; Lizeng Zhao; Zhenzhong Lu; Xiaomei Zhang; Yuxin Nie; Duoyuan Wang; Minxue Hu

    1997-01-01

    We introduce a method of polarization spectroscopy into photon-gated persistent spectral hole burning, which results in considerable improvement in the signal-to-background ratio. Fifty multiple spectral holes burnt into meso-phenyl-tetrabenzoporphyrinato-zinc aromatic cyanide poly(methyl methacrylate) were clearly detected by this measurement technique. We developed a simplified model to account for the hole shapes. Background birefringence combined with refractive dispersion is thought to

  7. Polarization spectral synthesis for Type Ia supernova explosion models

    NASA Astrophysics Data System (ADS)

    Bulla, M.; Sim, S. A.; Kromer, M.

    2015-06-01

    We present a Monte Carlo radiative transfer technique for calculating synthetic spectropolarimetry for multidimensional supernova explosion models. The approach utilizes `virtual-packets' that are generated during the propagation of the Monte Carlo quanta and used to compute synthetic observables for specific observer orientations. Compared to extracting synthetic observables by direct binning of emergent Monte Carlo quanta, this virtual-packet approach leads to a substantial reduction in the Monte Carlo noise. This is not only vital for calculating synthetic spectropolarimetry (since the degree of polarization is typically very small) but also useful for calculations of light curves and spectra. We first validate our approach via application of an idealized test code to simple geometries. We then describe its implementation in the Monte Carlo radiative transfer code ARTIS and present test calculations for simple models for Type Ia supernovae. Specifically, we use the well-known one-dimensional W7 model to verify that our scheme can accurately recover zero polarization from a spherical model, and to demonstrate the reduction in Monte Carlo noise compared to a simple packet-binning approach. To investigate the impact of aspherical ejecta on the polarization spectra, we then use ARTIS to calculate synthetic observables for prolate and oblate ellipsoidal models with Type Ia supernova compositions.

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

    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; Nannarone, Stefano; Crescenzio, Giuseppe; Capobianco, Gerardo; Fineschi, Silvano

    2014-12-01

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

  9. Programmable polarization-independent spectral phase compensation and pulse shaping by use of a

    E-print Network

    Purdue University

    codes: 060.2330, 320.5540, 070.2580. 1. Introduction Fourier transform pulse shapers1 are widely applied in the patent lit- erature10 but prior to this work was not tested exper- imentally. Fourier-transform pulseProgrammable polarization-independent spectral phase compensation and pulse shaping by use

  10. Spectral signal processing in intrinsic interferometric sensors based on birefringent polarization-maintaining optical fibers

    Microsoft Academic Search

    Sergey A. Egorov; Anatoly N. Mamaev; Alexander S. Polyantsev

    1995-01-01

    The straightforward spectral signal processing technique is applied in intrinsic strain, temperature and distributed linear position interferometric fiber optic sensors based on birefringent polarization maintaining fibers. The method provides nonincremental absolute measurements of external physical parameter affecting the sensing fiber. Simultaneous interrogation of sensors in a network is demonstrated

  11. 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 [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai 264209 (China); Guo, Fan [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Li, Gang, E-mail: yaochen@sdu.edu.cn [Department of Space Science and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

    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.

  12. Hydrated electrons as a probe of local anisotropy: Simulations of ultrafast polarization-dependent spectral hole burning

    NASA Astrophysics Data System (ADS)

    Schwartz, Benjamin J.; Rossky, Peter J.

    1994-05-01

    Polarized transient hole-burning spectra of the hydrated electron are calculated via quantum nonadiabatic molecular dynamics simulation. They underlying isotropic and anisotropic solvent fluctuations are found to relax on different time scales, leading to polarized spectral holes which are significantly more persistent than unpolarized holes. This separation of time scales leads to a clear spectral signature: transient bleaching in one set of polarizations and transient absorption in the other. This prediction can be directly tested experimentally.

  13. Ferroelectric domain wall motion induced by polarized light.

    PubMed

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

    2015-01-01

    Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO? 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 BaTiO? 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

  14. 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

  15. 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.

  16. Speckle noise reduction by averaging in polarization sensitive spectral domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    We demonstrate an ultra high speed fiber based polarization sensitive spectral domain optical coherence tomography system, using two ultra high speed CMOS line scan cameras. With this system an A-scan rate of up to 128 kHz was achieved. The system is based on polarization maintaining fibers and retrieves the backscattered intensity, retardation and optic axis orientation with only one A-scan per measurement location. This high speed data acquisition enables averaging of several acquired B-scans of intensity, retardation, optic axis orientation, and Stokes vectors, which strongly reduces speckle noise. We discuss different averaging techniques and compare the results in healthy human retinas.

  17. Polarized spectral properties of Er 3+ ions in NaGd(WO 4 ) 2 crystal

    Microsoft Academic Search

    J. H. Huang; X. H. Gong; Y. J. Chen; Y. F. Lin; J. S. Liao; X. Y. Chen; Z. D. Luo; Y. D. Huang

    2007-01-01

    Polarized spectral properties of Er3+:NaGd(WO4)2 single crystal are reported. The crystal was grown by the Czochralski method. The Judd–Ofelt theory was applied to analyze\\u000a the polarized absorption spectra and then calculate the spontaneous emission probabilities, radiative lifetimes, and branching\\u000a ratios. Fluorescence decay curves of the 4\\u000a I\\u000a 13\\/2, 4\\u000a I\\u000a 11\\/2, and 4\\u000a S\\u000a 3\\/2 multiplets for the Er3+ ions

  18. Glass polarization induced drift in microelectromechanical capacitor

    NASA Astrophysics Data System (ADS)

    Haarahiltunen, A.; Varpula, A.; Leinvuo, J.; Siren, E.; Rytkönen, V.-P.; Savin, H.

    2012-05-01

    We present a quantitative physical model for glass substrate polarization and study the glass polarization by measuring the capacitance drift from microelectromechanical capacitor test structure. The model consists of mobile and immobile charge species, which are related to alkali metals and non-bridging oxygen in glass. The model explains consistently our results and the previously observed non-homogeneous charging effect in a radio-frequency switch fabricated on a glass substrate. The results indicate that the bulk properties of the glass layer itself can be a significant source of drift. The modeling allows estimation of the drift behavior of the several kinds of device structures.

  19. 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.

  20. Schistosoma japonicum infection induces macrophage polarization

    PubMed Central

    Xu, Jingwei; Zhang, Hao; Chen, Lin; Zhang, Donghui; Ji, Minjun; Wu, Haiwei; Wu, Guanling

    2014-01-01

    Abstract The role of macrophages (M?) as the first line of host defense is well accepted. These cells play a central role in orchestrating crucial functions during schistosomal infection. Thus, understanding the functional diversity of these cells in the process of infection as well as the mechanisms underlying these events is crucial for developing disease control strategies. In this study, we adopted a M? polarization recognition system. M1 macrophage was characterized by expressing CD16/32, IL-12 and iNOS. M2 macrophage was characterized by expressing CD206, IL-10 and arg-1. In vivo (mouse peritoneal macrophages of different infection stages were obtained) and in vitro (different S. japonicum antigens were used to stimulate RAW264.7) were characterized by using the above mentioned system. NCA and ACA stimulated RAW264.7 express significantly higher levels of IL-12 while significantly higher levels of IL-10 were detected after soluble egg antigen (SEA) stimulation. The results showed that dramatic changes of antigen in the microenvironment before and after egg production led to macrophage polarization. Furthermore, through TLR blocking experiments, the TLR4 signaling pathway was found to play a role in the process of macrophage polarization toward M1. Our data suggest that macrophage polarization during S. japonicum infection had significant effects on host immune responses to S. japonicum. PMID:25050114

  1. Wavelength and polarization dependence of spectral hole-burning efficiency in highly oriented J-aggregates

    Microsoft Academic Search

    Kazuhiko Misawa; Shinjiro Machida; Kazuyuki Horie; Takayoshi Kobayashi

    1995-01-01

    From the concentration dependence of the dichroic spectrum of highly oriented J-aggregates as well as the strong dependences of the spectral hole-burning efficiency on the burning wavelength and polarization, a system of cyanine dye aggregates was concluded to have a hierarchic structure of mesoscopic and macroscopic aggregates. The observed low efficiency, by a factor of 10?3, on the higher-energy side

  2. Polarization-induced ?-holes and hydrogen bonding.

    PubMed

    Hennemann, Matthias; Murray, Jane S; Politzer, Peter; Riley, Kevin E; Clark, Timothy

    2012-06-01

    The strong collinear polarizability of the A-H bond in A-H···B hydrogen bonds is shown to lead to an enhanced ?-hole on the donor hydrogen atom and hence to stronger hydrogen bonding. This effect helps to explain the directionality of hydrogen bonds, the well known cooperative effect in hydrogen bonding, and the occurrence of blue-shifting. The latter results when significant additional electron density is shifted into the A-H bonding region by the polarization effect. The shift in the A-H stretching frequency is shown to depend essentially linearly on the calculated atomic charge on the donor hydrogen for all donors in which A belongs to the same row of the periodic table. A further result of the polarization effect, which is also expected for other ?-hole bonds, is that the strength of the non-covalent interaction depends strongly on external electric fields. PMID:22015592

  3. Polarization-induced trapped charge in ferroelectrics

    SciTech Connect

    Warren, W.L.; Pike, G.E.; Tuttle, B.A.; Dimos, D. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1349 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87185-1349 (United States)

    1997-04-01

    We have examined the nature of the defects in BaTiO{sub 3} capacitors that have been subjected to an electric field at elevated temperatures (an accelerated aging process) using thermally stimulated current (TSC) and electron paramagnetic resonance measurements. The accelerated aging stress causes the ferroelectric capacitor to exhibit a reduction in its insulating resistance and a voltage offset in its polarization-voltage hysteresis loop. Following the accelerated aging treatment, the trapped charge estimates obtained from the TSC and the hysteresis measurements (as ascertained from the voltage offset) differ significantly and are attributed to either local charge compensation or uniform charge trapping within the dielectric. We also show that some of the trapped charge in ferroelectric materials is directly associated with the net polarization. {copyright} {ital 1997 American Institute of Physics.}

  4. Spectral broadening using a polarization-maintaining photonic crystal fiber by an optical parametric amplifier

    NASA Astrophysics Data System (ADS)

    Yu, Yongqin; Ruan, Shuangchen; Du, Chenlin; Zhao, Jihong; Zeng, Jianchun

    2006-01-01

    Supercontinuum was generated in a polarization-maintaining (PM) PCF. The main advantage with the PM-PCF is the preservation of the state of polarization of the field propagating. For several applications, it is essential that the output has a well-defined polarization. In addition, the preserved polarization enhances the nonlinear interactions so that less power is required to generate the SC. The field patterns, birefringence and nonlinearity in the PM-PCF were simulated using a full-vector finite element method. Spectral broadening was achieved pumped by the optical parameter amplifier system (OPA). It was concluded that the SC generation was depended on the pump wavelength, and the difference group velocities in the two sides of the zero dispersive wavelength of the PCF and the OH absorption at about 1.4?m in the PCF affected the flatness of the generated supercontinuum. When the pump wavelength lied further away from the zero dispersive wavelength, the flatness was reduced, even in the visible region the blue-shift peaks were separated and didn't come into being supercontinuum. Supercontinuum with a broad bandwidth of 300 nm to 1350 nm was generated when the pump wavelength of 1200 nm, and the generated spectral bandwidth was beyond two octaves.

  5. Temperature sensing using the spectral interference of polarization modes in a highly birefringent fiber

    NASA Astrophysics Data System (ADS)

    Hlubina, P.; Kadulova, M.; Ciprian, D.; Mergo, P.

    2015-07-01

    The spectral interference of polarization modes in a highly birefringent (HB) fiber to measure temperature is analyzed theoretically and experimentally. A tandem configuration of a birefringent delay line and a sensing HB fiber is considered and the spectral interferograms are modelled for the known birefringence dispersion of the HB fiber under test. As the delay line, a birefringent quartz crystal of a suitable thickness is employed to resolve a channeled spectrum. The channeled spectra are recorded for different temperatures and the polarimetric sensitivity to temperature, determined in the spectral range from 500 to 850 nm, is decreasing with wavelength. It is demonstrated that the temperature sensing is possible using the wavelength interrogation, i.e., the position of a given interference maximum is temperature dependent. The temperature sensitivity of the HB fiber under test is -0.25 nm/K and the resolution is better than 0.5 K.

  6. 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.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

  11. Spectral, spatial, and polarization characteristics of harmonics generated at interaction of intense laser radiation with aluminum foils

    Microsoft Academic Search

    Rashid A. Ganeev; J. A. Chakera; M. Raghuramaiah; A. K. Sharma; P. A. Naik; Parshotam D. Gupta

    2001-01-01

    Investigations on harmonic generation in laser-matter interaction of Nd:glass laser radiation with solid surfaces have been performed. Detailed measurements were made on the intensity of second, third and fourth harmonics, their polarization properties and spectral distribution, as well as dependencies of these characteristics on intensity and polarization of the incident laser radiation. Intensity dependence of second, third and fourth harmonics

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

    NASA Astrophysics Data System (ADS)

    Yu, Liping; Zunger, Alex

    2014-10-01

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

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

    PubMed

    Yu, Liping; Zunger, Alex

    2014-01-01

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

  14. 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.

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

    SciTech Connect

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

    2011-04-15

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

  16. 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.

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

    SciTech Connect

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

    2010-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  19. Polarization effects in 3D vectorial-induced current reconstructions.

    PubMed

    Eyraud, Christelle; Vaillon, Rodolphe; Litman, Amélie; Geffrin, Jean-Michel; Merchiers, Olivier

    2013-10-01

    In tomography algorithms, the complex amplitude scattering matrix corresponds to the input parameter. When considering 3D targets, the scattering matrix now contains vectorial information. Thus, this scattering matrix might be calculated with various polarization projections. Moreover, when dealing with experimental data, we are almost every time faced with truncated data. We focus here on the impact of selecting parts of the amplitude scattering matrix elements versus others and in particular on the influence of the polarization choices on the imaging results. In order to better apprehend the physical content associated to each polarization term, the study is conducted with a simple vectorial-induced current reconstruction algorithm allowing reconstruction of qualitative maps of the scene. This algorithm is applied on scaled models of aggregates combined with experimental scattered fields acquired in the microwave frequency range. PMID:24322851

  20. Field-induced percolation of polar nanoregions in relaxor ferroelectrics.

    PubMed

    Prosandeev, S; Wang, Dawei; Akbarzadeh, A R; Dkhil, B; Bellaiche, L

    2013-05-17

    A first-principles-based effective Hamiltonian is used to investigate low-temperature properties of Ba(Zr,Ti)O(3) relaxor ferroelectrics under an increasing dc electric field. This system progressively develops an electric polarization that is highly nonlinear with the dc field. This development leads to a maximum of the static dielectric response at a critical field, E(th), and involves four different field regimes. Each of these regimes is associated with its own behavior of polar nanoregions, such as shrinking, flipping, and elongation of dipoles or change in morphology. The clusters propagating inside the whole sample, with dipoles being parallel to the field direction, begin to form at precisely the E(th) critical field. Such a result, and further analysis we perform, therefore, reveal that field-induced percolation of polar nanoregions is the driving mechanism for the transition from the relaxor to ferroelectric state. PMID:25167451

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    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.

  3. 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

  4. Dependence of spectral width of polar cap HF echoes upon electric field

    NASA Astrophysics Data System (ADS)

    Koustov, A. V.; Shalimov, S.; Kozlovsky, A.

    2010-12-01

    The EISCAT Svalbard Radar (ESR) monitors plasma parameters in the ionospheric region that is frequently located near the polar cap boundary. The SuperDARN radar at Hankasalmi, Finland detects coherent echoes from this region and these echoes typically show increased spectral width. We consider data of joint ESR and SuperDARN observations to show that the spectral width of HF echoes tends to increase with the electric field. This relationship is explained in terms of non-linear evolution of the ExB gradient drift instability with energy cascade from hundred of meters wavelengths to meter wavelengths. We assume that non-linearly generated, relatively strong decameter waves (seen by the Hankasalmi radar) decay through three-wave interaction with shorter wavelengths and estimate that the decameter waves/irregularities decay time is determined by the parameters of the shorter wavelength structures. We associate the decameter wave decay time with the correlation time, and thus the spectral width, of HF echoes.

  5. Estimation of soil moisture and components by measuring the degree of spectral polarization with a remote sensing simulator.

    PubMed

    Genda, H; Okayama, H

    1978-11-01

    The components of an object and the moisture in it can be estimated by measuring the degree of spectral polarization of scattered light from that object. In this paper the degree of spectral polarization of scattered light from CuSO(4), CuCl(2), Fe(2)O(3), SiC, S, NiCl(2), and CoCl(2) as models of soil was measured and compared with that of volcanic ash and natural soil. From these results it is estimated that Fe appears in natural soil and Si appears in volcanic ash. The field capacity point of soil was obtained from measurements of the degree of spectral polarization, and it was detected more clearly in a shorter wavelength region (about 400 nm). PMID:20203998

  6. 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.

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

    PubMed

    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

    2012-11-01

    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

  8. 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.

  9. Investigations on spatio-spectrally resolved Stokes polarization parameters of oxide-confined vertical-cavity surface-emitting lasers.

    PubMed

    Molitor, Andreas; Hartmann, Sébastien; Elsäßer, Wolfgang

    2015-07-01

    Recently, we have shown [Opt. Lett.37, 4799 (2012)OPLEDP0146-959210.1364/OL.37.004799] that the amount of unpolarized light, quantified by the degree of polarization (DOP), is strongly enhanced by increasing the oxide aperture of vertical-cavity surface-emitting lasers (VCSELs). Here, we reveal the physical mechanism of the DOP reduction when investigating spatio-spectrally resolved Stokes polarization parameters of transverse multi-mode VCSELs. These results uncover a complementary polarization behavior of each particular transverse mode contributing to the total emission, resulting in the observed unpolarized state of light. PMID:26125382

  10. Unified model for spin order induced polarization in multiferroics

    NASA Astrophysics Data System (ADS)

    Xiang, Hongjun

    2014-03-01

    The microscopic origins of ferroelectricity in different multiferroic systems were theoretically investigated. We proposed a unified model which includes purely electronic and ion-displacement contribution simultaneously to describe spin-order induced ferroelectricity. An efficient method was developed to compute the model parameters from first-principles. On the basis of the unified model and density functional calculations, we explained the ferroelectricity induced by the proper-screw spin spiral, discovered a novel magnetoelectric coupling mechanism in which the magnitude of the polarization is governed by the exchange striction with the direction by the spin chirality, proposed that the ferroelectricity in the chiral-lattice magnet Cu2OSeO3 is due to the unusual single-spin site term, unraveled that the magnetoelectric effect observed in BiFeO3 originates from the exchange striction.

  11. Dynamics of field-induced polarization reversal in thin strained perovskite ferroelectric films with c -oriented polarization

    NASA Astrophysics Data System (ADS)

    Baudry, Laurent; Luk'yanchuk, Igor A.; Razumnaya, Anna

    2015-04-01

    The field-induced polarization reversal in the c -oriented ferroelectric phase of strained perovskite film has been studied. We show that in addition to the conventional longitudinal switching mechanism, when the c -oriented polarization vector changes its modulus, the longitudinal-transversal and transversal mechanisms when the perpendicular component of polarization is dynamically admixed are possible. The latter process can occur either via the straight-abrupt or initially continues polarization turnover scenario. We specified the obtained results for the case of PbTiO3 and BaTiO3 ferroelectrics and propose the experimental methods for their investigation.

  12. Relationships between induced polarization relaxation time and hydraulic properties of sandstone

    NASA Astrophysics Data System (ADS)

    Titov, Konstantin; Tarasov, Andrey; Ilyin, Yuri; Seleznev, Nikita; Boyd, Austin

    2010-03-01

    We investigated electrical and physical-chemical properties of six sandstone samples with contrasting mineralogical characteristics and with hydraulic conductivity varying in a wide range. The electrical data were obtained from time domain spectral induced polarization (IP) measurements. We inverted the IP decays to relaxation time distributions, and then compared the modal relaxation times with the dominant pore throat diameters obtained from the Mercury Injection Capillary Pressure (MICP) data. We found a positive logarithmic relationship between the relaxation time and the pore throat diameter. Also, we found the normalized chargeability (an integral IP parameter) to be positively correlated with the clay content. These two results suggest that the polarization of our sandstones is controlled by the pore throat distribution, and by the clay content. The logarithmic relationship contradicts previous theories, and is not universal. Adopting an approach of Kruschwitz and her co-workers, we calculated the effective diffusivity from IP and MICP data, and we found the effective diffusivity values ranging from 2.9 × 10-13 to 1.6 × 10-10 m2s-1. High diffusivity values, typical of surface diffusion, were obtained for clean sandstones. Low diffusivity values were obtained for clayey sandstones, and they were one to two orders of magnitude lower than those characteristic of the surface diffusion. We proposed two mechanisms to explain the `slow' diffusion: (1) the effect of surface tortuosity of pore throats filled with clay minerals and (2) the effect of pore geometry. These two effects represent an obstacle in assessing the pore throat diameter and hydraulic conductivity of sandstones with large specific surface and clay content on the basis of spectral IP measurements. However, we believe that the sandstones featuring `slow' diffusion can be discriminated based on the integral polarization parameters, and that the relaxation time remains a valuable parameter for assessing hydraulic properties of clean sandstones.

  13. 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 [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

    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.

  14. Spectral and polarization characteristics of the nonspherically decaying radiation generated by polarization currents with superluminally rotating distribution patterns

    Microsoft Academic Search

    Houshang Ardavan; Arzhang Ardavan; John Singleton

    2004-01-01

    We present a theoretical study of the emission from a superluminal polarization current whose distribution pattern rotates (with an angular frequency omega) and oscillates (with a frequency Omega) at the same time and that comprises both poloidal and toroidal components. This type of polarization current is found in recent practical machines designed to investigate superluminal emission. We find that the

  15. Imaging ambipolar two-dimensional carriers induced by the spontaneous electric polarization of a polar semiconductor BiTeI

    NASA Astrophysics Data System (ADS)

    Kohsaka, Y.; Kanou, M.; Takagi, H.; Hanaguri, T.; Sasagawa, T.

    2015-06-01

    Two-dimensional (2D) mobile carriers are a wellspring of quantum phenomena. Among various 2D-carrier systems, such as field effect transistors and heterostructures, polar materials hold a unique potential; the spontaneous electric polarization in the bulk could generate positive and negative 2D carriers at the surface. Although several experiments have shown ambipolar carriers at the surface of a polar semiconductor BiTeI, their origin is yet to be specified. Here we provide compelling experimental evidences that the ambipolar 2D carriers at the surface of BiTeI are induced by the spontaneous electric polarization. By imaging electron standing waves with spectroscopic imaging scanning tunneling microscopy, we find that positive or negative carriers with Rashba-type spin splitting emerge at the surface corresponding to the polar directions in the bulk. The electron densities at the surface are constant independently of those in the bulk, corroborating that the 2D carriers are induced by the spontaneous electric polarization. We also successfully image that lateral p -n junctions are formed along the boundaries of submicron-scale domains with opposite polar directions. Our study presents a means to endow nonvolatile, spin-polarized, and ambipolar 2D carriers as well as, without elaborate fabrication, lateral p -n junctions of those carriers at atomically sharp interfaces.

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

    PubMed

    Kinoshita, Michiyo; Pfeiffer, Keram; Homberg, Uwe

    2007-04-01

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

  17. Spectral Broadening in a Polarization-Maintaining Photonic Crystal Fibre by Femtosecond Pulses from an Optical Parametric Amplifier

    NASA Astrophysics Data System (ADS)

    Yu, Yong-Qin; Ruan, Shuang-Chen; Cheng, Chao; Du, Chen-Lin; Liu, Cheng-Xiang; Lin, Hao-Jia

    2005-02-01

    The spectral broadening with the bandwidth of 83 nm (1.2486-1.3318 ?m) in the 1.3 ?m region is achieved in a 0.2-m-long, polarization-maintaining photonic crystal fibre (PCF) with an average core radius of 1.8 ?m, pumped by optical pulses at the wavelength 1.269 ?m, with the duration 250 fs and the repetition rate 250 kHz from an optical parametric amplifier. The polarization characteristics of the output spectra are also investigated.

  18. Polar behaviour induced by lithium in potassium tantalate ceramics.

    PubMed

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

    2012-02-01

    Polar behaviour in K(1-x)Li(x)TaO(3) ceramics with x = 0:02, 0.05 and 0.10, processed by the conventional solid state method, is studied by Raman spectroscopy and thermally stimulated depolarization current (TSDC) techniques between 10 and 290 K. The TO1 mode of KTaO(3) is revealed to harden in the whole temperature range and to split in the low-temperature range by Li doping. One splitting is observed for x = 0:02 and two consequent splittings are detected for x = 0:05 and 0.10. The temperatures, where TO1 mode splitting occurs, are found to correspond to those of the peaks of TSDC, and hence to the onset of the electric polarization. Such behaviour provides evidence for the order-disorder ferroelectric phase transition induced in KTaO(3) by lithium doping, which emerges from deformations of the cubic phase developed on cooling either in one (for x = 0:02) or two steps (for x = 0:05 and 0.10). PMID:22223586

  19. Induced spectral broadening of a weak picosecond pulse in glass produced by an intense picosecond pulse

    SciTech Connect

    Alfano, R.R.; Li, Q.X.; Jimbo, T.; Manassah, J.T.; Ho, P.P.

    1986-10-01

    Spectral broadening of a weak 80-..mu..J picosecond 530-nm laser pulse in a BK-7 glass has been enhanced over the entire spectral band by the presence of an intense millijoule picosecond 1060-nm laser pulse. The spectral distributions of the self-phase modulation and the induced-phase modulation signals are similar. The dominant enhancement mechanism for the induced supercontinuum was determined to be caused by an induced-phase modulation process, not by stimulated four-photon scattering.

  20. Strain-induced Polarization Rotation in Epitaxial (001) BiFeO3 Thin Films

    SciTech Connect

    Jang, J H [Univeristy of Wisconsson; Baek, S H [University of Wisconsin; Ortiz, D [University of Wisconsin; Das, R [University of Wisconsin; Folkman, C H [University of Wisconsin; Chu, Y H [University of Wisconsin; Shafer, Paul [University of Wisconsin; Zhang, J X [University of Wisconsin; S, Choudhury [Pennsylvania State University; Vaithyanathan, V [Pennsylvania State University; Chen, Y B [University of Michigan; Felker, D A [University of Wisconsin; Biegalski, Michael D [ORNL; Rzchowski, M [University of Wisconsin; Pan, X Q [University of Michigan; Chen, Long-Qing [Pennsylvania State University; Schlom, Darrell [Pennsylvania State University; Ramesh, R. [University of California, Berkeley; Eom, Chang-Beom [ORNL

    2008-01-01

    Direct measurement of the remanent polarization of high quality (001)-oriented epitaxial BiFeO3 thin films shows a strong strain-dependence, even larger than conventional (001)-oriented PbTiO3 films. Thermodynamic analysis reveals that a strain-induced polarization rotation mechanism is responsible for the large change in the out-of-plane polarization of (001) BiFeO3 with biaxial strain while the spontaneous polarization itself remains almost constant.

  1. Strain-Induced Polarization Rotation in Epitaxial (001) BiFeO3 Thin Films

    Microsoft Academic Search

    H. W. Jang; S. H. Baek; D. Ortiz; C. M. Folkman; R. R. Das; Y. H. Chu; Paul Shafer; J. X. Zhang; S. Choudhury; V. Vaithyanathan; Y. B. Chen; D. A. Felker; Michael D Biegalski; M. S. Rzchowski; X. Q. Pan; D. G. Schlom; L. Q. Chen; R. Ramesh; Chang-Beom Eom

    2008-01-01

    Direct measurement of the remanent polarization of high quality (001)-oriented epitaxial BiFeO3 thin films shows a strong strain dependence, even larger than conventional (001)-oriented PbTiO3 films. Thermodynamic analysis reveals that a strain-induced polarization rotation mechanism is responsible for the large change in the out-of-plane polarization of (001) BiFeO3 with biaxial strain while the spontaneous polarization itself remains almost constant.

  2. Strain-induced polarization rotation in epitaxial (001) BiFeO3 thin films.

    PubMed

    Jang, H W; Baek, S H; Ortiz, D; Folkman, C M; Das, R R; Chu, Y H; Shafer, P; Zhang, J X; Choudhury, S; Vaithyanathan, V; Chen, Y B; Felker, D A; Biegalski, M D; Rzchowski, M S; Pan, X Q; Schlom, D G; Chen, L Q; Ramesh, R; Eom, C B

    2008-09-01

    Direct measurement of the remanent polarization of high quality (001)-oriented epitaxial BiFeO3 thin films shows a strong strain dependence, even larger than conventional (001)-oriented PbTiO3 films. Thermodynamic analysis reveals that a strain-induced polarization rotation mechanism is responsible for the large change in the out-of-plane polarization of (001) BiFeO3 with biaxial strain while the spontaneous polarization itself remains almost constant. PMID:18851256

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

    PubMed Central

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

    2013-01-01

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

  4. Spectral Broadening in a Polarization-Maintaining Photonic Crystal Fibre by Femtosecond Pulses from an Optical Parametric Amplifier

    Microsoft Academic Search

    Yong-Qin Yu; Shuang-Chen Ruan; Chao Cheng; Chen-Lin Du; Cheng-Xiang Liu; Hao-Jia Lin

    2005-01-01

    The spectral broadening with the bandwidth of 83 nm (1.2486-1.3318 mum) in the 1.3 mum region is achieved in a 0.2-m-long, polarization-maintaining photonic crystal fibre (PCF) with an average core radius of 1.8 mum, pumped by optical pulses at the wavelength 1.269 mum, with the duration 250 fs and the repetition rate 250 kHz from an optical parametric amplifier. The

  5. Spectral-mismatch-induced resolution limit of interferometric fiber Fabry–Perot sensor system

    Microsoft Academic Search

    Siliang Niu; Lina Ma; Shuidong Xiong; Yongming Hu

    2011-01-01

    The mismatch of fiber Bragg gratings (FBGs) in spectral profiles can lead to a severe degraded resolution of the constructed fiber Fabry–Perot (FFP) sensor system through its effect on the fringe visibility. The variation of visibility induced by spectral mismatch and the corresponding phase resolution limit are analyzed theoretically and experimentally. Theoretical analyses are based on the approximation of Gaussian

  6. HYBRID ANALYTICAL-SPECTRAL METHOD FOR THE MODELING OF PIEZOELECTRICALLY INDUCED WAVES IN PLATES

    E-print Network

    Paris-Sud XI, Université de

    HYBRID ANALYTICAL-SPECTRAL METHOD FOR THE MODELING OF PIEZOELECTRICALLY INDUCED WAVES IN PLATES of big memory storage capacity. On the other hand, analytical and semi-analytical methods, which offer the use of an hybrid of analytical and spectral methods to model the propagation of elastic guided waves

  7. Spectral broadening using a polarization-maintaining photonic crystal fiber by an optical parametric amplifier

    Microsoft Academic Search

    Yongqin Yu; Shuangchen Ruan; Chenlin Du; Jihong Zhao; Jianchun Zeng

    2006-01-01

    Supercontinuum was generated in a polarization-maintaining (PM) PCF. The main advantage with the PM-PCF is the preservation of the state of polarization of the field propagating. For several applications, it is essential that the output has a well-defined polarization. In addition, the preserved polarization enhances the nonlinear interactions so that less power is required to generate the SC. The field

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

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    PubMed

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

    2013-12-30

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

  11. Parahydrogen-induced polarization in heterogeneous catalytic processes.

    PubMed

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

    2013-01-01

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

  12. Proton magnetic resonance imaging with para-hydrogen induced polarization.

    PubMed

    Dechent, Jan F; Buljubasich, Lisandro; Schreiber, Laura M; Spiess, Hans W; Münnemann, Kerstin

    2012-02-21

    A major challenge in imaging is the detection of small amounts of molecules of interest. In the case of magnetic resonance imaging (MRI) their signals are typically concealed by the large background signal of e.g. the body. This problem can be tackled by hyperpolarization which increases the NMR signals up to several orders of magnitude. However, this strategy is limited for (1)H, the most widely used nucleus in NMR and MRI, because the enormous number of protons in the body screens the small amount of hyperpolarized ones. Here, we describe a method giving rise to high (1)H MRI contrast for hyperpolarized molecules against a large background signal. The contrast is based on the J-coupling induced rephasing of the NMR signal of molecules hyperpolarized via PHIP and it can easily be implemented in common pulse sequences. We discuss several scenarios with different or equal dephasing times T(2)* for the hyperpolarized and thermally polarized compounds and verify our approach by experiments. This method may open up unprecedented opportunities to use the standard MRI nucleus (1)H for e.g. metabolic imaging in the future. PMID:22240943

  13. Production of highly polarized 3He using spectrally narrowed diode laser array bars

    Microsoft Academic Search

    B. Chann; E. Babcock; L. W. Anderson; T. G. Walker; W. C. Chen; T. B. Smith; A. K. Thompson; T. R. Gentile

    2003-01-01

    We have produced 70%–75% 3He polarization by spin-exchange optical pumping in cells ≈100 cm3 in volume. The polarization achieved is consistent with known spin-exchange and spin-relaxation rates, but only when the recently discovered temperature dependence of 3He relaxation is included. Absolute 3He polarization measurements were performed using two different methods in two different laboratories. The results were obtained with either

  14. Production of highly polarized 3He using spectrally narrowed diode laser array bars

    Microsoft Academic Search

    B. Chann; E. Babcock; L. W. Anderson; T. G. Walker; W. C. Chen; T. B. Smith; A. K. Thompson; T. R. Gentile

    2003-01-01

    We have produced 70%-75% 3He polarization by spin-exchange optical pumping in cells ~100 cm3 in volume. The polarization achieved is consistent with known spin-exchange and spin-relaxation rates, but only when the recently discovered temperature dependence of 3He relaxation is included. Absolute 3He polarization measurements were performed using two different methods in two different laboratories. The results were obtained with either

  15. 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.

  16. FROST-INDUCED CHANGES IN SPECTRAL CHARACTERISTICS OF GRAIN SORGHUM.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Visible and near-infrared spectral properties of grain sorghum (Sorghum bicolor) were observed using wideband and hyperspectral radiometers in Arizona. Field measurements that were taken before and after the later-planted, 1998 crop was damaged by frost, displayed temporal dynamics that were correl...

  17. Polarized distribution of inducible nitric oxide synthase regulates activity in intestinal epithelial cells

    E-print Network

    Paris-Sud XI, Université de

    1 Polarized distribution of inducible nitric oxide synthase regulates activity in intestinal deoxycholate; iNOS, inducible nitric oxide synthase; IFN-, interferon-; IL-1 interleukin-1, IL-6, interleukin-6; NO, nitric oxide; TLR5, Toll-like receptor 5; TX-100, Triton X-100 Key words: Inducible nitric oxide

  18. Spacerless circular-polarization spectral-hole filters using chiral sculptured thin films: theory and experiment

    Microsoft Academic Search

    Ian J. Hodgkinson; Qi Hong Wu; Karen E. Thorn; Akhlesh Lakhtakia; Martin W. McCall

    2000-01-01

    In the Bragg wavelength regime, a sculptured thin film with chiral micromorphology permits light of a particular circular polarization state to pass virtually unhindered, but light of the other polarization state is reflected almost completely. On cascading two such films, but with one film twisted with respect to the other by an angle of 90°, a hole appears in the

  19. A universal compensator for polarization changes induced by birefringence on a retracing beam

    Microsoft Academic Search

    Mario Martinelli

    1989-01-01

    We report a new optical scheme that eliminates birefringence effects on the polarization state of a beam which retraces its path. The operation is based on the symmetry properties induced by a Faraday rotator followed by a mirror on the Poincaré sphere rotations. The entrance and exit polarizations states turn out to be always orthogonal points on the Poincaré sphere.

  20. Effects of Buflomedil and Pentoxifylline on Hamster Skin-Flap Microcirculation: Prediction of Flap Viability Using Orthogonal Polarization Spectral Imaging

    PubMed Central

    Coelho da Mota, Denise Salles; Furtado, Eliane; Bottino, Daniel Alexandre; Bouskela, Eliete

    2009-01-01

    OBJECTIVE This study investigated the effects of buflomedil and pentoxifylline, both of which are used in reconstructive surgery of hamster skin flap microcirculation, and evaluated the skin flap survival rate by orthogonal polarization spectral imaging. METHOD Twenty-four adult male Syrian golden hamsters were divided into three groups: a control (C, 0.1 ml 0.9% saline), buflomedil (B, 3 mg/kg/day), and pentoxifylline group (P, 14.5 mg/kg/day). Treatments administered intraperitoneally were initiated 1 hour before skin flap preparation and continued for 7 days post-operatively at 12-hour intervals. Preparations (skin flaps) were divided into 12 fields, which were organized into six bands. Functional capillary density (FCD, in mm/mm2), distance from the skin flap base to blood flow cessation (Distwith flow, in cm), percentage of viable skin (VA, in%), and qualitative analysis of blood flow by orthogonal polarization spectral imaging were performed at 1 and 24 hours and on the seventh post-operative day. RESULT Bands IV, V, and VI presented no flow independent of time. The functional capillary density group B was higher than that of groups C and P, primarily after 24 hours. All groups showed an increase in D with time but reached similar final distances (C = 2.73, B = 2.78 and P = 2.70 cm). Moreover, the percentage of viable areas remained at approximately 50%. The orthogonal polarization spectral imaging was useful to assess viability by counting fields with and without blood flow. CONCLUSIONS Functional capillary density values were higher in the buflomedil group compared to the control and pentoxifylline groups in this model. Functional capillary density did not influence D or the percentage of VA, and the technique showed favorable potential to assess/predict the viability of skin flaps within 1 h after surgery. PMID:19690666

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  2. CMB-induced cluster polarization as a cosmological probe

    Microsoft Academic Search

    Daniel Baumann; Asantha Cooray

    2003-01-01

    Scattering of the temperature anisotropy quadrupole by free electrons in galaxy clusters leads to a secondary polarization signal in the cosmic microwave background (CMB) fluctuations. At low redshifts, the temperature quadrupole contains a significant contribution from the integrated Sachs–Wolfe (ISW) effect associated with the growth of density fluctuations. Using polarization data from a sample of clusters over a wide range

  3. Spectral-Content Readout Of Stress-Induced Birefringence

    NASA Technical Reports Server (NTRS)

    Redner, Alex S.; Voloshin, Arkady S.

    1992-01-01

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

  4. 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.

  5. Development of a field-widened Michelson spectroscopic filter for a polarized near-infrared high spectral resolution lidar

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    Standard backscatter lidars encounter problems when solving the two unknowns (aerosol backscatter coefficient and extinction coefficient) from the only one recorded lidar equation. With the help of the high-spectral-resolution filter, high spectral resolution lidars (HSRLs) can provide unambiguous retrieval without critical assumptions. Spectral discrimination between scattering from molecules and aerosols or cloud particles is the basis of the HSRL technique, and several lidar approaches have been developed to obtain this discrimination. Iodine cell filter, which is a kind of atomic/molecular absorption filter, is robust, stable, and can achieve very good separation of aerosol Mie scattering from atmosphere molecular Cabannes scattering. However, absorption filters are lossy and gaseous absorption lines do not exist at many convenient laser wavelengths. Fabry-Perot interferometers are simple and can be tuned to any wavelength, but are limited by acceptance angle. Field-widened Michelson interferometer (FWMI) is considered to have the ability to overcome the deficiencies of the aforementioned filters as it can perform well at relatively large off-axis angles, is nearly lossless, and can be built to any wavelength. In this paper, the development process of an FWMI that is introduced to be the spectroscopic filter for a polarized near-infrared HSRL instrument will be present. The retrieval process of the aerosol optical properties, the design requirements with special focus on the selection of the free spectral range (FSR) of the FWMI, as well as the design result will be described in detail.

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

    SciTech Connect

    Satohisa, Seiro [Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556, (Japan); Department of Obstetrics and Gynecology, Sapporo Medical University School of Medicine, Sapporo 060-8556, (Japan); Chiba, Hideki [Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556 (Japan)]. E-mail: hidchiba@sapmed.ac.jp; Osanai, Makoto [Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556, (Japan); Ohno, Shigeo [Department of Molecular Biology, Yokohama City University School of Medicine, Yokohama 236-0004 (Japan); Kojima, Takashi [Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556, (Japan); Saito, Tsuyoshi [Department of Obstetrics and Gynecology, Sapporo Medical University School of Medicine, Sapporo 060-8556 (Japan); Sawada, Norimasa [Department of Pathology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556 (Japan)

    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.

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

    Microsoft Academic Search

    L G Pikulik; V A Chernyavskii; A F Grib

    2000-01-01

    Spectral studies of induced quasi-crystal properties (which can be quantitatively characterised by the difference in the refractive indices of ordinary and extraordinary waves, n=n{sub o}-n{sub e}) in Rhodamine 6G and Rhodamine 4C solutions in glycerine excited in the visible and UV ranges of the absorption spectrum are presented. It is demonstrated that the observed spectral dependences of n of these

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  9. Periodic microbending-induced core-to-cladding mode coupling in polarization-maintaining fibers.

    PubMed

    Lin, Chien-Hung; Li, Qun; Lee, Henry P

    2003-06-15

    We investigate codirectional mode coupling induced by periodic microbending in polarization-maintaining (PM) fibers by using both an acoustic flexural wave and a pair of corrugated fixtures. The measured filtering spectra are found to be strongly polarization dependent. In addition, the coupling strength depends on the angle between the birefringence axes and the bending direction. These characteristics can be utilized for a variety of applications, such as fiber polarizers, polarization-dependent-loss compensators, and on-line alignment of birefringence axes for the manufacture of PM fiber couplers. PMID:12836758

  10. Large ferroelectric polarization in the new double perovskite NaLaMnWO6 induced by non-polar instabilities.

    PubMed

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

    2011-07-14

    Based on density functional theory calculations and group theoretical analysis, we have studied NaLaMnWO(6) compound which has been recently synthesized [G. King, A. Wills and P. M. Woodward, Phys. Rev. B: Condens. Matter, 2009, 79, 224428] and belongs to the AA'BB'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 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 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 a source of the ferroelectricity. Through a trilinear coupling with the two unstable tilting modes, a polar distortion is induced, although the system has no intrinsic polar instability. The calculated electric polarization resulting from this polar distortion is as large as ?16 ?C cm(-2). Despite its secondary character, this polarization is coupled with the dominant tilting modes and its switching is bound to produce the switching of one of two tilts, enhancing in this way a possible interaction with the magnetic ordering. The transformation of common non-polar purely steric instabilities into sources of ferroelectricity through a controlled modification of the parent structure, as done here by the cation ordering, is a phenomenon to be further explored. PMID:21647478

  11. Observations of self-induced ultraslow light in a persistent spectral hole burning medium.

    PubMed

    Hahn, J; Ham, B S

    2008-10-13

    We present observations of self induced ultraslow light in a persistent spectral hole-burning rare-earth doped crystal. The observed group delay (velocity) is as long as 40 micros (75 m/s), which is comparable to that obtained using electromagnetically induced transparency or coherent population oscillations. We analyze the observed ultraslow light as a function of frequency detuning, light intensity, and atom population (oscillator strength). The present observation of ultraslow light in a persistent spectral hole-burning medium gives potentials to all-optical information processing such as on-demand all-optical buffer memories. PMID:18852781

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    Microsoft Academic Search

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

    1975-01-01

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

  15. Spectral features of SKR observed by Cassini\\/RPWS: Frequency bandwidth, flux density and polarization

    Microsoft Academic Search

    Patrick H. M. Galopeau; Mohammed Y. Boudjada; Alain Lecacheux

    2007-01-01

    We report on an analysis about the spectral shape of the Saturnian kilometric radiation (SKR) recorded by the RPWS\\/HFR experiment onboard the Cassini spacecraft. The SKR envelope is found to be very variable in timescales covering a large range, from hours to days. Despite this change, we proceed to a classification of the shape in the frequency range from 3.5

  16. Spectral analysis of induced color change on periodically nanopatterned silk films

    E-print Network

    Spectral analysis of induced color change on periodically nanopatterned silk films Jason J. Amsden1 on periodic nanopatterned 2D lattices in pure protein films of silk fibroin. We show here periodic lattices in silk fibroin films with feature sizes of hundreds of nanometers that exhibit different colors

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

    E-print Network

    Demouchy, Sylvie

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

  18. Characterization of EOS induced defects on submicron devices using 2D spectral imaging

    Microsoft Academic Search

    M. F. Bailon; P. F. Salinas; J. S. Arboleda; J. C. Miranda

    2005-01-01

    Localization, identification and characterization of EOS-induced defects found in submicron devices were demonstrated using a new FA procedure. IR photon emission and circuit analysis were used for defect localization while spectral profile of photon emission was utilized for defect finger-printing analysis. Finally, frontside and backside FA methods were done to confirm the actual failure mechanism in the device under analysis

  19. Observations of a distinctive infra-red spectral feature in the atmospheric spectra of polar stratospheric clouds measured by the CRISTA instrument

    Microsoft Academic Search

    Reinhold Spang; John J. Remedios

    2003-01-01

    Polar stratospheric cloud particles (PSCs) are known to strongly influence the infra-red emission spectrum of the lower stratosphere in cold polar winters. The characteristics of these infra-red features have been examined using limb sounding spectra recorded by the CRISTA experiment in August 1997 when many Antarctic PSCs were observed. A distinctive spectral feature centered at 820 cm-1 has been identified

  20. Observations of a distinctive infra-red spectral feature in the atmospheric spectra of polar stratospheric clouds measured by the CRISTA instrument

    Microsoft Academic Search

    Reinhold Spang; John J. Remedios

    2003-01-01

    Polar stratospheric cloud particles (PSCs) are known to strongly influence the infra-red emission spectrum of the lower stratosphere in cold polar winters. The characteristics of these infra-red features have been examined using limb sounding spectra recorded by the CRISTA experiment in August 1997 when many Antarctic PSCs were observed. A distinctive spectral feature centered at 820 cm?1 has been identified

  1. Gaussian-Beam S-wave Polarization-based Location Method for Hydraulic Fracturing Induced Seismicity

    Microsoft Academic Search

    X. Zhao; D. Collins; P. Young

    2008-01-01

    We propose a new method to locate hydraulic fracturing induced seismicity using three-component waveforms based on the Gaussian-beam S-wave polarization modified from Rentsch et al. (Geophysics, 2007) who used P-wave polarization. As a highly automated method, the method only requires a window around the S-wave peak amplitude and does not depend on arrival-time picking as used in standard location routines.

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

    SciTech Connect

    Morgen, M M [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    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.

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

    PubMed

    Heger, Michal; Beek, Johan; Stenback, Karin; Faber, Dirk; van Gemert, Martin; Ince, Can

    2005-02-01

    Due to the limited number of suitable intravital microscopy techniques, relatively little is known about the opto-thermal (endo)vascular responses to selective photothermolysis, used as a default treatment modality for superficial vascular anomalies such as port wine stains, telangiectasias, and hemangiomas. In this preliminary study we present a novel microscopy technique for studying (endo)vascular laser-tissue interactions in vivo, in which conventional orthogonal polarized spectral (OPS) imaging is combined with darkfield (DF) illumination. DFOPS imaging of rat mesenteric vasculature irradiated at increasing powers revealed the following (tissular) responses: formation of translucent aggregates, retrograde flow, gradual and immediate hemostasis, reinstatement of flow, vessel disappearance, and perivascular collagen damage. DFOPS imaging therefore constitutes a useful tool for examining (endo)vascular events following selective photothermolysis. PMID:19494931

  4. 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.

  5. Polarization relaxation induced by a depolarization field in ultrathin ferroelectric capacitors.

    PubMed

    Kim, D J; Jo, J Y; Kim, Y S; Chang, Y J; Lee, J S; Yoon, Jong-Gul; Song, T K; Noh, T W

    2005-12-01

    Time-dependent polarization relaxation behavior induced by a depolarization field E(d) was investigated on high-quality ultrathin SrRuO3/BaTiO3/SrRuO3 capacitors. The E(d) values were determined experimentally from an applied external field to stop the net polarization relaxation. These values agree with those from the electrostatic calculations, demonstrating that a large E(d) inside the ultrathin ferroelectric layer could cause severe polarization relaxation. For numerous ferroelectric devices of capacitor configuration, this effect will set a stricter size limit than the critical thickness issue. PMID:16384347

  6. CMB-induced Cluster Polarization as a Cosmological Probe

    Microsoft Academic Search

    Daniel Baumann; Asantha Cooray

    2003-01-01

    Scattering of the temperature anisotropy quadrupole by free electrons in\\u000agalaxy clusters leads to a secondary polarization signal in the cosmic\\u000amicrowave background (CMB) fluctuations. At low redshifts, the temperature\\u000aquadrupole contains a significant contribution from the integrated Sachs-Wolfe\\u000a(ISW) effect associated with the growth of density fluctuations. Using\\u000apolarization data from a sample of clusters over a wide range

  7. Oxidized LDL/CD36 interaction induces loss of cell polarity and inhibits macrophage locomotion.

    PubMed

    Park, Young Mi; Drazba, Judith A; Vasanji, Amit; Egelhoff, Thomas; Febbraio, Maria; Silverstein, Roy L

    2012-08-01

    Cell polarization is essential for migration and the exploratory function of leukocytes. However, the mechanism by which cells maintain polarity or how cells revert to the immobilized state by gaining cellular symmetry is not clear. Previously we showed that interaction between oxidized low-density lipoprotein (oxLDL) and CD36 inhibits macrophage migration; in the current study we tested the hypothesis that oxLDL/CD36-induced inhibition of migration is the result of intracellular signals that regulate cell polarity. Live cell imaging of macrophages showed that oxLDL actuated retraction of macrophage front end lamellipodia and induced loss of cell polarity. Cd36 null and macrophages null for Vav, a guanine nucleotide exchange factor (GEF), did not show this effect. These findings were caused by Rac-mediated inhibition of nonmuscle myosin II, a cell polarity determinant. OxLDL induced dephosphorylation of myosin regulatory light chain (MRLC) by increasing the activity of Rac. Six-thioguanine triphosphate (6-thio-GTP), which inhibits Vav-mediated activation of Rac, abrogated the effect of oxLDL. Activation of the Vav-Rac-myosin II pathway by oxidant stress may induce trapping of macrophages at sites of chronic inflammation such as atherosclerotic plaque. PMID:22718904

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

    SciTech Connect

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

    2011-05-01

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

  9. Polarization of the radiation induced by electron impact on He and Hg

    Microsoft Academic Search

    H. G. M. Heideman; C. Smit; J. A. Smit

    1969-01-01

    The polarization of a number of He and Hg spectral lines, excited by a beam of electrons, has been measured as a function of the electron energy. The transitions studied are: for helium 41D ? 21P, 51D ? 21P, 43S ? 23P, 33D ? 23P 43D ? 23P, for mercury 61D2 ? 61P1, 63D2 ? 61P1, 73S1 ? 63P1, and

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

    SciTech Connect

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

    2008-11-01

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

  11. Magnetic field induced nutation of exciton-polariton polarization in (Cd,Zn)Te crystals

    NASA Astrophysics Data System (ADS)

    Godde, T.; Glazov, M. M.; Akimov, I. A.; Yakovlev, D. R.; Mariette, H.; Bayer, M.

    2013-10-01

    We study the polarization dynamics of exciton-polaritons propagating in sub-mm-thick (Cd,Zn)Te bulk crystals using polarimetric time-of-flight techniques. The application of a magnetic field in Faraday geometry leads to synchronous temporal oscillations of all Stokes parameters of an initially linearly or circularly polarized, spectrally broad optical pulse of 150-fs duration propagating through the crystal. Strong dispersion for photon energies close to the exciton resonance leads to stretching of the optical pulse to a duration of 200-300 ps and enhancement of magneto-optical effects such as the Faraday rotation and the nonreciprocal birefringence. The oscillation frequency of the exciton-polariton polarization increases with magnetic field B, reaching 10 GHz at B˜5 T. Surprisingly, the relative contributions of Faraday rotation and nonreciprocal birefringence undergo strong changes with photon energy, which is attributed to a nontrivial spectral dependence of Faraday rotation in the vicinity of the exciton resonance. This leads to polarization nutation of the transmitted optical pulse in the time domain. The results are well explained by a model that accounts for Faraday rotation and magnetospatial dispersion in zinc-blende crystals. We evaluate the exciton g factor |gexc|=0.2 and the magnetospatial constant |V|=5×10-12 eV cm T-1.

  12. Polarization conversion in ring resonator phase shifters

    Microsoft Academic Search

    Andrea Melloni; Francesco Morichetti; Mario Martinelli

    2004-01-01

    The effect of the polarization rotation induced by curved waveguides on the spectral behavior of phase shifter ring resonators is investigated both theoretically and experimentally. At resonance the polarization rotation that takes place in curved waveguides is strongly enhanced. The effect can be detrimental, or it can be exploited for new devices. The ring vectorial transfer function is derived, together

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

    NASA Astrophysics Data System (ADS)

    Zhang, Jinjing; Zhang, Tao

    2015-02-01

    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(N2) 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.

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

    PubMed

    Zhang, Jinjing; Zhang, Tao

    2015-02-01

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

  15. Spectral Modifications and Polarization Dependent Coupling in Tailored Assemblies of Quantum Dots and Plasmonic Nanowires

    PubMed Central

    2013-01-01

    The coupling of optical emitters with a nanostructured environment is at the heart of nano- and quantum optics. We control this coupling by the lithographic positioning of a few (1–3) quantum dots (QDs) along plasmonic silver nanowires with nanoscale resolution. The fluorescence emission from the QD-nanowire systems is probed spectroscopically, by microscopic imaging and decay time measurements. We find that the plasmonic modes can strongly modulate the fluorescence emission. For a given QD position, the local plasmon field dictates the coupling efficiency, and thus the relative weight of free space radiation and emission into plasmon modes. Simulations performed with a generic few-level model give very good agreement with experiment. Our data imply that the 2D degenerate emission dipole orientation of the QD can be forced to predominantly emit to one polarization component dictated by the nanowire modes. PMID:23968490

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

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

    PubMed

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

    2014-08-01

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

  1. Magnetization and phase transition induced by circularly polarized laser in quantum magnets

    NASA Astrophysics Data System (ADS)

    Takayoshi, Shintaro; Aoki, Hideo; Oka, Takashi

    2014-08-01

    We theoretically predict a nonequilibrium phase transition in quantum spin systems induced by a laser, which provides a purely quantum-mechanical way of coherently controlling magnetization. Namely, when a circularly polarized laser is applied to a spin system, the magnetic component of a laser is shown to induce a magnetization normal to the plane of polarization, leading to an ultrafast phase transition. We first demonstrate this phenomenon numerically for an S =1 antiferromagnetic Heisenberg spin chain, where a new state emerges with magnetization perpendicular to the polarization plane of the laser in place of the topologically ordered Haldane state. We then elucidate its physical mechanism by mapping the system to an effective static model. The theory also indicates that the phenomenon should occur in general quantum spin systems with a magnetic anisotropy. The required laser frequency is in the terahertz range, with the required intensity being within a prospective experimental feasibility.

  2. Laser-induced thermodiffusion of semiconductor inhomogeneities in the spectral transparency region

    Microsoft Academic Search

    N. N. Grigor'ev; T. A. Kudykina; S. V. Plyatsko; F. F. Sizov

    1988-01-01

    Analysis of the thermal diffusion contribution to laser-irradiation-induced dissolving in semiconductors of inhomogeneities enriched in metallic components has been carried out for the laser spectral region h(cross) omega

  3. Cross sections of collision induced rotational transitions of polar molecules perturbed by isotropic projectiles

    Microsoft Academic Search

    Masatoshi Kajita; Hitoshi Odashima; Tadao Shimizu

    1991-01-01

    A semiempirical formula for the cross section of collision induced rotational relaxation is presented, which allows one to estimate fairly accurate values of cross sections for any pairs of polar molecules and isotropic perturbers. The cross section does not critically depend on the quantum states, but is described simply by the parameters of colliding atoms and molecules, such as van

  4. Spin polarized electric currents in semiconductor heterostructures induced by microwave radiation

    E-print Network

    Ganichev, Sergey

    Spin polarized electric currents in semiconductor heterostructures induced by microwave radiation C oscillations in the resistivity of a two-dimensional electron gas 2DEG at- tracted growing attention and a split-coil superconducting magnet yielding a field By 110 with a strength up t

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

    SciTech Connect

    Ievlev, Anton [ORNL; Alikin, Denis O [Ural Federal University, Russia; Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine; Varenyk, O. V. [Kiev University, Ukraine; Eliseev, E. A. [National Academy of Science of Ukraine, Kiev, Ukraine; Kholkin, Andrei [University of Aveiro, Portugal; Shur, Vladimir Ya. [Ural Federal University, Russia; Kalinin, Sergei V [ORNL

    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.

  6. Hole-burning-induced spectral-spatial gratings in neutron-colored sapphire

    NASA Astrophysics Data System (ADS)

    Aizengendler, Mark; Dolindo, Ivan; Sildos, Ilmo

    1990-07-01

    Due to the birefringence of sapphire the 36O 450 rim phototransformation of the absorption spectrum of a neutron-coloured u-A12O3 leads to the persistent spatial modulation of defects concentration in both absorption bands. Spectral-spatial structures were detected by means of the luminescence of the photoproduct and by a direct observation the Bragg diffraction of light. After neutron irradiation and the subsequent thermal annealing of sappire one can find a number of polarized bands in its absorption spectrum. The aim of the present report is to study a persistent spectralspatial modulation in an optically anisotropic crystal neutronirradiated a-Al203 created by the 360* 450 nm laser phototransformation. Sapphire is a negative uniaxial crystal A fragment of the crystal structure and a model of anisotropic defects are shown in Fig. la. For photobleaching in the 360 nm absorption band a linearly polarized light with E''[OOOl] propagating in the direction k II [1210] was used. Due to birefringepce of sapphire this beam changes its polarization state periodically. The concentration of the defects in the 360 nm absorption band decreases due to the phototransformation of the defects and forms a periodical spatial structure. 0 100 200 r Fig. l. (a) A fragment of the a-A12O3 structure where d mdicates the arrangement of the anisotropic defect. On the left the direction of the laser beam for bleaching (or for exciting luminescence) is shown. In the upper part condition

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

    PubMed

    Zomer, Fabian; Fedala, Yasmina; Pavloff, Nicolas; Soskov, Viktor; Variola, Alessandro

    2009-12-10

    Various four-mirror optical resonators are studied from 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' motion and misalignment by reducing the instability parameter by at least 2 orders of magnitude. PMID:20011005

  8. Alternating spin-polarized current induces parametric resonance in spin valves

    NASA Astrophysics Data System (ADS)

    Clerc, Marcel G.; Coulibaly, Saliya; Laroze, David; León, Alejandro O.; Núñez, Álvaro S.

    2015-06-01

    Ferromagnetic systems under the influence of spin-polarized currents exhibit rich spatiotemporal dynamics at nanoscales. We study spin-transfer nano-oscillators driven by the combination of alternating and direct spin-polarized electric currents. We show here that the alternating current induces parametric instabilities on spin valves, that is, the magnetization responses at half the forcing frequency. A spatial self-organization emerges as a result of the oscillatory current, which includes dissipative solitons and Faraday-type waves. The parametric regime is described analytically by means of the Landau-Lifshitz-Gilbert-Slonczewski equation, in good agreement with micromagnetic simulations including the full dipolar field.

  9. Demonstration of a folded Sagnac sensor array immune to polarization-induced signal fading

    NASA Astrophysics Data System (ADS)

    Vakoc, Benjamin J.; Digonnet, Michel J. F.; Kino, Gordon S.

    2003-12-01

    We demonstrate a new folded Sagnac sensor array design that combines a Faraday rotator mirror and a polarization beam splitter to eliminate the optical noise pulses otherwise generated in a folded Sagnac sensor array. A depolarization scheme compatible with this configuration is also proposed and demonstrated experimentally. It is shown that this new configuration passively eliminates polarization-induced signal fading on every sensor in the array. The minimum detectable phase was measured to be approximately 1.1 ?rad/?Hz, in agreement with theory.

  10. Polarization-induced noise in a fiber-optic Michelson interferometer with Faraday rotator mirror elements

    NASA Astrophysics Data System (ADS)

    Ferreira, L. A.; Santos, J. L.; Farahi, F.

    1995-10-01

    Faraday rotator mirror elements have been used in a number of applications as compensators for induced birefringence in retracing paths. In interferometric systems, such as the fiber-optic Michelson interferometer, this approach proved to be useful in providing maximum fringe visibility and insensitivity to the polarization state of light injected into the interferometer. However, it is found that, when the characteristics of the fiber coupler depend on the polarization state of the input beam, the efficiency of the Faraday mirror elements is limited. Theoretical analysis and experimental results in support of this statement are presented.

  11. Dynamic polarization potential induced by the Coulomb excitation of deformed heavy ions: Geometric scattering approach

    SciTech Connect

    Takigawa, N. (Department of Physics, Tohoku University, 980 Sendai, Japan (JP)); Michel, F. (Faculte des Sciences, Universite de Mons-Hainaut, B-7000 Mons, (Belgium)); Balantekin, A.B. (Physics Department, University of Wisconsin, Madison, Wisconsin 53706 (USA)); Reidemeister, G. (Faculte des Sciences, Universite Libre de Bruxelles, B-1050 Bruxelles, (Belgium))

    1991-07-01

    The geometric scattering theory and the Wentzel-Kramers-Brillouin (WKB) approximation are used to derive explicit expressions for the dynamic polarization potential induced by Coulomb excitation in heavy-ion collisions involving strongly deformed targets. We build two phase-equivalent potentials with very different radial and angular-momentum behaviors, which are discussed in the context of polarization potentials obtained previously within different frameworks. This correspondence provides a recipe for approximately correcting the deficiencies of the geometric scattering approach, which tends to overemphasize the effects of Coulomb coupling.

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

    NASA Astrophysics Data System (ADS)

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

    2004-10-01

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

  13. Palmitoleate Reverses High Fat-induced Proinflammatory Macrophage Polarization via AMP-activated Protein Kinase (AMPK).

    PubMed

    Chan, Kenny L; Pillon, Nicolas J; Sivaloganathan, Darshan M; Costford, Sheila R; Liu, Zhi; Théret, Marine; Chazaud, Benedicte; Klip, Amira

    2015-07-01

    A rise in tissue-embedded macrophages displaying "M1-like" proinflammatory polarization is a hallmark of metabolic inflammation during a high fat diet or obesity. Here we show that bone marrow-derived macrophages (BMDM) from high fat-fed mice retain a memory of their dietary environment in vivo (displaying the elevated proinflammatory genes Cxcl1, Il6, Tnf, Nos2) despite 7-day differentiation and proliferation ex vivo. Notably, 6-h incubation with palmitoleate (PO) reversed the proinflammatory gene expression and cytokine secretion seen in BMDM from high fat-fed mice. BMDM from low fat-fed mice exposed to palmitate (PA) for 18 h ex vivo also showed elevated expression of proinflammatory genes (Cxcl1, Il6, Tnf, Nos2, and Il12b) associated with M1 polarization. Conversely, PO treatment increased anti-inflammatory genes (Mrc1, Tgfb1, Il10, Mgl2) and oxidative metabolism, characteristic of M2 macrophages. Therefore, saturated and unsaturated fatty acids bring about opposite macrophage polarization states. Coincubation of BMDM with both fatty acids counteracted the PA-induced Nos2 expression in a PO dose-dependent fashion. PO also prevented PA-induced I?B? degradation, RelA nuclear translocation, NO production, and cytokine secretion. Mechanistically, PO exerted its anti-inflammatory function through AMP-activated protein kinase as AMP kinase knockout or inhibition by Compound C offset the PO-dependent prevention of PA-induced inflammation. These results demonstrate a nutritional memory of BMDM ex vivo, highlight the plasticity of BMDM polarization in response to saturated and unsaturated fatty acids, and identify the potential to reverse diet- and saturated fat-induced M1-like polarization by administering palmitoleate. These findings could have applicability to reverse obesity-linked inflammation in metabolically relevant tissues. PMID:25987561

  14. 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.

  15. Spectral changes in layered f -electron systems induced by Kondo hole substitution in the boundary layer

    NASA Astrophysics Data System (ADS)

    Sen, Sudeshna; Moreno, J.; Jarrell, M.; Vidhyadhiraja, N. S.

    2015-04-01

    We investigate the effect of disorder on the dynamical spectrum of layered f -electron systems. With random dilution of f sites in a single Kondo insulating layer, we explore the range and extent to which Kondo hole incoherence can penetrate into adjacent layers. We consider three cases of neighboring layers: band insulator, Kondo insulator, and simple metal. The disorder-induced spectral weight transfer, used here for quantification of the proximity effect, decays algebraically with distance from the boundary layer. Further, we show that the spectral weight transfer is highly dependent on the frequency range considered as well as the presence of interactions in the clean adjacent layers. The changes in the low-frequency spectrum are very similar when the adjacent layers are either metallic or Kondo insulating, and hence are independent of interactions. In stark contrast, a distinct picture emerges for the spectral weight transfers across large energy scales. The spectral weight transfer over all energy scales is much higher when the adjacent layers are noninteracting as compared to when they are strongly interacting Kondo insulators. Thus, over all scales, interactions screen the disorder effects significantly. We discuss the possibility of a crossover from non-Fermi-liquid to Fermi-liquid behavior upon increasing the ratio of clean to disordered layers in particle-hole asymmetric systems.

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

    NASA Astrophysics Data System (ADS)

    Tripathi, Neeraj

    2011-12-01

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

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

    SciTech Connect

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

    2012-01-01

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

  18. Relationship between Hydrological Parameters and Induced Polarization Spectra of Soil Samples

    NASA Astrophysics Data System (ADS)

    Nordsiek, S.; Durner, W.; Hoerdt, A.; Diamantopoulos, E.

    2011-12-01

    Problems concerning groundwater renewal, surface runoff, and agricultural questions are examples where soil hydraulic properties are relevant. Soil hydraulic properties describe the relationships between the state properties water content, capillary pressure, and hydraulic conductivity in partially water saturated soils. To obtain these properties for an area by soil hydrologic measurement techniques is time-consuming. Furthermore, the information gained is valid only for the vicinity of the investigated location. Geophysical methods offer a relatively quick way to get areal information. Geoelectrical measurements are most suitable for this purpose due to the correlation between electrical resistivity and properties like pore fluid conductivity and water saturation. Measuring complex resistivity instead of direct current resistivity yields the additional information of the quadrature component of resistivity, which is expected to correlate with properties of the interface between the pore fluid and the solid matrix. The spectral induced polarization (SIP) is a common geoelectrical method to investigate complex resistivity for a defined frequency range. The amplitude of the complex resistivity and the phase angle between real and imaginary part of resistivity are recorded for frequencies from 0.01 Hz to 100 Hz. The understanding of the correlation between complex electrical and hydraulic properties is essential for a successful application of the SIP method to hydrological problems. Therefore, laboratory SIP measurements and hydrologic Multi-Step-Outflow (MSO) experiments were performed on different soil samples. The investigated material include sand with a narrow grain size distribution as well as real soil samples from different locations in the vicinity of Braunschweig. The SIP measurements were performed at first on samples fully saturated with a sodium-chloride solution. The fluid conductivity is approximately 20 mS/m. Later, additional SIP spectra were recorded at different desaturation states. From the measured SIP spectra the mean relaxation time and the total chargeability were derived by application of the Deybe decomposition approach. After finishing all SIP measurements, the samples were re-saturated completely to perform the MSO experiments to obtain the retention curves and hydraulic conductivity functions. The parameters of the functions were then compared with the mean relaxation time and the total chargeability, respectively, to find correlations between the electrical and hydrological properties.

  19. 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.

  20. Sensitivity of force-detected NMR spectroscopy with resonator-induced polarization

    NASA Astrophysics Data System (ADS)

    Butler, Mark C.; Weitekamp, Daniel P.

    2013-02-01

    In the low-temperature regime where the thermal polarization P is of order unity and spin-lattice relaxation is “frozen out,” resonator-induced relaxation can be used to polarize a nuclear-spin sample for optimal detection sensitivity. We characterize the potential of resonator-induced polarization for enhancing the sensitivity of nuclear-magnetic-resonance spectroscopy. The sensitivities of two detection schemes are compared, one involving detection of a polarized sample dipole and the other involving detection of spin-noise correlations in an unpolarized sample. In the case where the dominant noise source is instrument noise associated with resonator fluctuations and with detection of the mechanical motion, a simple criterion can be used to compare the two schemes. Polarizing the sample improves sensitivity when P is larger than the signal-to-noise ratio for detection of a fully-polarized spin during a single transient. Even if the instrument noise is decreased to a level near the quantum-mechanical limit, it is larger than spin noise for unpolarized samples containing up to a few tens of nuclei. Under these conditions, spin polarization of order unity would enhance spectroscopic detection sensitivity by an order of magnitude or more. In the limiting case where signal decay is due to resonator-induced dissipation during ideal spin locking, and where resonator fluctuations are the noise source, the only parameter of the spin-resonator system that affects the sensitivity per spin is the ratio of frequency to temperature. A balance between the coupling strength, the noise power, and the signal lifetime causes the cancellation of other parameters from the sensitivity formula. Partial cancellation of parameters, associated with a balance between the same three quantities, occurs more generally when the resonator is both the dominant noise source and the dominant source of signal decay. An intrinsic sensitivity limit exists for resonant detection of coherent spin evolution, due to the fact that the detector causes signal decay by enhancing the spins' spontaneous emission. For a single-spin sample, the quantum-limited signal-to-noise ratio for resonant detection is 1/3. In contrast to the sensitivity, the time required for sample polarization between transients depends strongly on resonator parameters. We discuss resonator design and show that for a torsional resonator, the coupling is optimal when the resonator's magnetization remains aligned with the applied field during the mechanical oscillations.

  1. Polarized spectral properties of Yb3+ : Li2Gd4(MoO4)7 crystal: a candidate for tunable and ultrashort pulse lasers

    Microsoft Academic Search

    Haomiao Zhu; Yujin Chen; Yanfu Lin; Xinghong Gong; Jinsheng Liao; Xueyuan Chen; Zundu Luo; Yidong Huang

    2007-01-01

    Detailed polarized spectral properties of a 3.2 at.% Yb3+ : Li2Gd4(MoO4)7 crystal, including absorption cross-section, emission cross-section, up-conversion spectrum and intrinsic fluorescence lifetime, were investigated. The laser potentiality was also evaluated and the results show that this crystal is a good candidate for tunable and ultrashort pulse lasers.

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

    SciTech Connect

    Kawasaki, Masahiro [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa, Chiba 277-8568 (Japan); Miyamoto, Koichi [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Nakayama, Kazunori [KEK Theory Center, Institute of Particle and Nuclear Studies, KEK, Tsukuba, Ibaraki 305-0801 (Japan)

    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.

  3. Epoxyeicosatrienoic acids regulate macrophage polarization and prevent LPS-induced cardiac dysfunction.

    PubMed

    Dai, Meiyan; Wu, Lujin; He, Zuowen; Zhang, Shasha; Chen, Chen; Xu, Xizhen; Wang, Peihua; Gruzdev, Artiom; Zeldin, Darryl C; Wang, Dao Wen

    2015-09-01

    Macrophages, owning tremendous phenotypic plasticity and diverse functions, were becoming the target cells in various inflammatory, metabolic and immune diseases. Cytochrome P450 epoxygenase 2J2 (CYP2J2) metabolizes arachidonic acid to form epoxyeicosatrienoic acids (EETs), which possess various beneficial effects on cardiovascular system. In the present study, we evaluated the effects of EETs treatment on macrophage polarization and recombinant adeno-associated virus (rAAV)-mediated CYP2J2 expression on lipopolysaccharide (LPS)-induced cardiac dysfunction, and sought to investigate the underlying mechanisms. In vitro studies showed that EETs (1µmol/L) significantly inhibited LPS-induced M1 macrophage polarization and diminished the proinflammatory cytokines at transcriptional and post-transcriptional level; meanwhile it preserved M2 macrophage related molecules expression and upregulated anti-inflammatory 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. J. Cell. Physiol. 230: 2108-2119, 2015. © 2015 Wiley Periodicals, Inc. PMID:25626689

  4. Frequency-dependent polarization-angle-phase-shift in the microwave-induced magnetoresistance oscillations

    NASA Astrophysics Data System (ADS)

    Liu, Han-Chun; Ye, Tianyu; Wegscheider, W.; Mani, R. G.

    2015-02-01

    Linear polarization angle, ?, dependent measurements of the microwave radiation-induced oscillatory magnetoresistance, Rxx, in high mobility GaAs/AlGaAs 2D electron devices have shown a ? dependence in the oscillatory amplitude along with magnetic field, frequency, and extrema-dependent phase shifts, ?0. Here, we suggest a microwave frequency dependence of ?0(f) using an analysis that averages over other smaller contributions, when those contributions are smaller than estimates of the experimental uncertainty.

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

    Microsoft Academic Search

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

    2009-01-01

    Fragment mass yields and the average neutron multiplicity in the proton-induced fission of 232Th and 233U were measured by a double time-of-flight method. The most probable charges of secondary fragments were evaluated from the fragment mass yields measured and the fractional cumulative yields reported. The nuclear charge polarization of primary fragments at scission was obtained by correcting the most probable

  6. 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.

  7. Eliminating spectral distinguishability in ultrafast spontaneous parametric down-conversion

    SciTech Connect

    Poh, Hou Shun; Lim, Jiaqing; Lamas-Linares, Antia; Kurtsiefer, Christian [Centre for Quantum Technologies and Department of Physics, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore); Marcikic, Ivan [Temasek Laboratories, National University of Singapore, Singapore 117508 (Singapore)

    2009-10-15

    Generation of polarization-entangled photon pairs with a precise timing through down-conversion of femtosecond pulses is often faced with a degraded polarization entanglement quality. In a previous experiment, we have shown that this degradation is induced by spectral distinguishability between the two decay paths, in accordance with theoretical predictions. Here, we present an experimental study of the spectral compensation scheme proposed and first implemented by Kim and Grice [J. Mod. Opt. 49, 2309 (2002)]. By measuring the joint spectral properties of the polarization correlations of the photon pairs, we show that the spectral distinguishability between the down-converted components is eliminated. This scheme results in a polarization visibility of 97.9{+-}0.5% without any spectral filtering.

  8. Polar/apolar compounds induce leukemia cell differentiation by modulating cell-surface potential.

    PubMed Central

    Arcangeli, A; Carlà, M; Del Bene, M R; Becchetti, A; Wanke, E; Olivotto, M

    1993-01-01

    The mechanism of action of polar/apolar inducers of cell differentiation, such as dimethyl sulfoxide and hexamethylene-bisacetamide, is still obscure. In this paper evidence is provided that their effects on murine erythroleukemia cells are modulated by various extracellular cations as a precise function of the cation effects on membrane surface potential. The interfacial effects of the inducers were directly measured on the charged electrode, showing that both dimethyl sulfoxide and hexamethylene-bisacetamide, at the effective concentrations for cell differentiation and within the physiological range of charge density, adsorb at the charged surface and produce a potential shift. A linear correlation was found between this shift and the inducer effects on cell differentiation. Besides offering a different interpretation of the mechanism of action of the inducers, these findings indicate that surface potential has a signaling function. They may also be relevant to cancer treatments based on tumor-cell commitment to terminal differentiation. Images Fig. 1 PMID:8516337

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  10. 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

  11. Transverse Mode Selection and Bistability in Vertical-Cavity Surface-Emitting Lasers Induced by Parallel Polarized Optical Injection

    Microsoft Academic Search

    Matias Fernando Salvide; Maria Susana Torre; Angel Valle; Luis Pesquera

    2011-01-01

    Modal selection induced by parallel polarized opti- cal injection in a vertical-cavity surface-emitting laser (VCSEL) emitting in two transverse modes is analyzed from a theoretical point of view. We show that the selection of the fundamental transverse mode can be achieved when the two transverse modes have parallel polarizations. This selection is accompanied by locking of the fundamental mode to

  12. Retrieval of solar-induced fluorescence spectral shape of oil slicks from the infilling of solar Fraunhofer lines

    NASA Astrophysics Data System (ADS)

    Raimondi, Valentina; Palombi, Lorenzo; Guzzi, Donatella; Lognoli, David; Nardino, Vanni; Petroni, Francesco; Pippi, Ivan

    2013-10-01

    In this paper we present the spectral behavior of the Solar Induced Fluorescence (SIF) of a crude oil, retrieved from its radiance spectrum acquired in eight selected spectral windows of the visible spectrum from about 389 nm to 659 nm. Each spectral window was chosen to cover one or more solar Fraunhofer Lines (FL) so as to retrieve the in-filling due to the oil fluorescence contribution induced by the solar irradiance. The selected Fraunhofer lines were chosen within the solar lines rather than the telluric ones since the former ones offer several advantages for the application from air- or space-borne platform. Solar FL, compared with telluric ones, require a simpler atmospheric model to evaluate ground solar irradiance. Besides, the signal measured at the sensor is not affected by re-absorption effects. For each spectral window, oil fluorescence contribution and reflectance were evaluated by comparing the measured total radiance of the oil with the incident sun irradiance spectrum measured in the same conditions. Fluorescence and reflectance spectral shapes were evaluated within each measured spectral window by applying a spectral fitting method (SFM) and polynomial modeling. Solar-induced fluorescence data were then used to evaluate the fluorescence spectrum of the oil. The SIF spectrum of the same oil was also simulated by using emission-excitation fluorescence data and a simulated solar irradiance. The measured and simulated spectra were then compared.

  13. Reduction of polarization-induced performance degradation in WDM PON utilizing MQW-SLD-based broadband source.

    PubMed

    Park, Paul K J; Jun, S B; Kim, Hoon; Jung, D K; Lee, W R; Chung, Y C

    2007-10-17

    We report on the reduction of polarization-induced performance degradation in WDM PON utilizing MQW-SLD-based ASE source for injection locking to FPLD. The results show that, to suppress the polarization-induced Q penalty sufficiently less than 0.5 dB, the MQW-SLD output should be depolarized within the locking range of the wavelength-locked FPLD. PMID:19550697

  14. The Origin of the Ultra-Violet Spectral Components in the Polar-Like Intermediate Polar, RE075 Cycle 4 High

    Microsoft Academic Search

    Simon Rosen

    1994-01-01

    RE0751+14, is arguably the most important magnetic cataclysmic variable (CV) to be discovered for many years. Although it is undoubtedly an intermediate polar, it also exhibits highly unusual properties (e.g. a strong EUV component, modulated optical\\/IR polarization, X-ray, optical and IR dips in its rotational light curve and a very red rotational pulsation) which strongly suggest that its white dwarf

  15. Induced polarized state in intentionally grown oxygen deficient KTaO3 thin films

    NASA Astrophysics Data System (ADS)

    Mota, D. A.; Romaguera-Barcelay, Y.; Tkach, A.; Pérez de la Cruz, J.; Vilarinho, P. M.; Tavares, P. B.; Agostinho Moreira, J.; Almeida, A.

    2013-07-01

    Deliberately oxygen deficient potassium tantalate thin films were grown by RF magnetron sputtering on Si/SiO2/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 K2O rich KTaO3 targets and specific deposition conditions, KTaO3-? oxygen deficient thin films with a K/Ta = 1 ratio were obtained. Room temperature X-ray diffraction patterns show that KTaO3-? thin films are under a compressive strain of 2.3% relative to KTaO3 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 Tpol ˜ 367 °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 Tpol, the aforementioned polarized state is suppressed, associated with a drastic oxygen vacancies reduction emerging from annealing process.

  16. Frustrated optical instability - Self-induced periodic and chaotic spatial distribution of polarization in nonlinear optical media

    NASA Astrophysics Data System (ADS)

    Yumoto, J.; Otsuka, K.

    1985-04-01

    The universal nature of self-induced polarization rotation in nonlinear optical media having a third-order nonlinearity is depicted in terms of phase-space trajectories characterized by separatrix orbits. The existence of nonlinear eigenpolarization, and of periodic synchronized spatial as well as chaotic spatial distributions of the polarization of light, are found in the mutual interaction of counterpropagating laser beams (collinear degenerate four-wave mixing geometry). Such spatial polarization turbulences cause a frustrated optical instability in input-versus-output intensity characteristics, when a fixed output polarization is selected.

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

    PubMed Central

    Groppelli, Elisabetta; Starling, Shimona

    2014-01-01

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

  18. 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

  19. Vector magnetometry based on electromagnetically induced transparency in linearly polarized light

    SciTech Connect

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

    2010-09-15

    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.

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

    SciTech Connect

    Nishinaka, I.; Nagame, Y. [Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Tanikawa, M. [School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0032 (Japan); Nakahara, H. [Department of Chemistry, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 (Japan)

    2009-03-04

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

  1. GSI promotes vincristine-induced apoptosis by enhancing multi-polar spindle formation

    PubMed Central

    Singh, Akannsha; Zapata, Mariana C; Choi, Yong Sung; Yoon, Sun-Ok

    2014-01-01

    Gamma secretase inhibitors (GSI), cell-permeable small-molecule inhibitors of gamma secretase activity, had been originally developed for the treatment of Alzheimer disease. In recent years, it has been exploited in cancer research to inhibit Notch signaling that is aberrantly activated in various cancers. We previously found that GSI could synergize with anti-microtubule agent, vincristine (VCR) in a Notch-independent manner. Here, we delineate the underlying cell cycle-related mechanism using HeLa cells, which have strong mitotic checkpoints. GSI enhanced VCR-induced cell death, although GSI alone did not affect cell viability at all. GSI augmented VCR-induced mitotic arrest in a dose-dependent manner, which was preceded by apoptotic cell death, as shown by an increase in Annexin V-positive and caspase-positive cell population. Furthermore, GSI amplified multi-polar spindle formation triggered by VCR. Altogether, we show the evidence that GSI enhances VCR-induced apoptosis in HeLa cells via multi-polar mitotic spindle formation, independent of Notch signaling. These data suggest that one or more GS substrates, yet to be identified, in a post-GS processed form, may play a role in maintaining functional centrosomes/mitotic spindles. More significantly, the synergistic effect of GSI in combination with VCR could be exploited in clinical setting to improve the efficacy of VCR. PMID:24200971

  2. GSI promotes vincristine-induced apoptosis by enhancing multi-polar spindle formation.

    PubMed

    Singh, Akannsha; Zapata, Mariana C; Choi, Yong Sung; Yoon, Sun-Ok

    2014-01-01

    Gamma secretase inhibitors (GSI), cell-permeable small-molecule inhibitors of gamma secretase activity, had been originally developed for the treatment of Alzheimer disease. In recent years, it has been exploited in cancer research to inhibit Notch signaling that is aberrantly activated in various cancers. We previously found that GSI could synergize with anti-microtubule agent, vincristine (VCR) in a Notch-independent manner. Here, we delineate the underlying cell cycle-related mechanism using HeLa cells, which have strong mitotic checkpoints. GSI enhanced VCR-induced cell death, although GSI alone did not affect cell viability at all. GSI augmented VCR-induced mitotic arrest in a dose-dependent manner, which was preceded by apoptotic cell death, as shown by an increase in Annexin V-positive and caspase-positive cell population. Furthermore, GSI amplified multi-polar spindle formation triggered by VCR. Altogether, we show the evidence that GSI enhances VCR-induced apoptosis in HeLa cells via multi-polar mitotic spindle formation, independent of Notch signaling. These data suggest that one or more GS substrates, yet to be identified, in a post-GS processed form, may play a role in maintaining functional centrosomes/mitotic spindles. More significantly, the synergistic effect of GSI in combination with VCR could be exploited in clinical setting to improve the efficacy of VCR. PMID:24200971

  3. Polyunsaturated fatty acids induce polarized submembranous F-actin aggregates and kill Entamoeba histolytica.

    PubMed

    Manna, Dipak; Grewal, Jaspreet Singh; Sarkar, Bidyut; Maiti, Sudipta; Lohia, Anuradha

    2013-05-01

    We have recently identified a novel galacto-glycerolipid (GGL) from the plant Oxalis corniculata that killed the human pathogen Entamoeba histolytica. In this study, we show that the anti-amoebic activity of GGL was due to the polyunsaturated fatty acid ?-linolenic acid (C18:3 ) side chain. Treatment of ?-linolenic acid to E. histolytica trophozoites disrupted the cytoskeletal network and led to polarization of F-actin at one end of the cells with prominent filopodial extensions. In addition, clustering of surface receptors and signaling molecules was also observed adjacent to the polarized actin similar to concanavalin-A-(Con-A) induced capping. But, in contrast to Con-A-induced capping, ?-linolenic acid induced caps were not shed and showed accumulation of long and numerous filopodia at the cap site. We found that ?-linolenic acid disrupts the actin cytoskeletal network, which led to the detachment of plasma membrane from the underlying cytoskeleton. A similar effect was observed with other dietary fatty acids such as linoleic acid (C18:2 ), arachidonic acid (C20:4 ), eicosapentaenoic acid (C20:5 ), and docosahexaenoic acid (C22:6 ). Our findings showed that dietary polyunsaturated fatty acids are powerful anti-amoebic agents that lead to disruption of the actin cytoskeleton. PMID:23568815

  4. Macrophage polarization induced by neuropeptide methionine enkephalin (MENK) promotes tumoricidal responses.

    PubMed

    Chen, Wenna; Liu, Jinling; Meng, Jingjuan; Lu, Changlong; Li, Ximing; Wang, Enhua; Shan, Fengping

    2012-10-01

    The aim of this study is to investigate macrophages polarization induced by methionine enkephalin (MENK) that promotes tumoricidal responses in vivo and in vitro. Both phenotypic and functional activities of macrophages were assessed by the quantitative analysis of key surface molecules on macrophages with flow cytometry, immunofluorescent staining, and the production of cytokines with enzyme-linked immunosorbent assay and reverse transcriptase-polymerase chain reaction. Our results showed that MENK could down-regulate the expression of CD206 and the production of arginase-1 (the markers of alternatively activated (M2) macrophage) in tumor-associated macrophages in vivo, meanwhile it could significantly up-regulate the expression of CD64, MHC-II, and the production of induced nitric oxide synthase (the markers of classically activated (M1) macrophages). Furthermore, the studies on bone marrow-derived macrophages treated with MENK (10(-12) M) in vitro had demonstrated that MENK could markedly increase tumoricidal activity. MENK could also enhance the release of reactive oxidant species and the production of interleukin-12p40, tumor necrosis factor-?, while decrease the production of interleukin-10. In conclusion, MENK could effectively induce M2 macrophages polarizing to M1 macrophages, sequentially to modulate the Th1 responses of the host immune system. Our results suggest that MENK might have great potential as a new therapeutic agent for cancer. PMID:22419372

  5. Mycobacterium tuberculosislpdC, Rv0462, induces dendritic cell maturation and Th1 polarization

    SciTech Connect

    Heo, Deok Rim [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of)] [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Shin, Sung Jae; Kim, Woo Sik [Department of Microbiology, College of Medicine, Chungnam National University, Munwha-Dong, Jung-Ku, Daejeon 301-747 (Korea, Republic of)] [Department of Microbiology, College of Medicine, Chungnam National University, Munwha-Dong, Jung-Ku, Daejeon 301-747 (Korea, Republic of); Noh, Kyung Tae; Park, Jin Wook; Son, Kwang Hee [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of)] [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Park, Won Sun [Department of Physiology, Kangwon National University, School of Medicine, Chuncheon 200-701 (Korea, Republic of)] [Department of Physiology, Kangwon National University, School of Medicine, Chuncheon 200-701 (Korea, Republic of); Lee, Min-Goo [Department of Physiology, Korea University, College of Medicine, Anam-dong, Sungbuk-Gu, Seoul 136-705 (Korea, Republic of)] [Department of Physiology, Korea University, College of Medicine, Anam-dong, Sungbuk-Gu, Seoul 136-705 (Korea, Republic of); Kim, Daejin [Department of Anatomy, Chung-Ang University, College of Medicine, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756 (Korea, Republic of)] [Department of Anatomy, Chung-Ang University, College of Medicine, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756 (Korea, Republic of); Shin, Yong Kyoo [Department of Pharmacology, Chung-Ang University, College of Medicine, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756 (Korea, Republic of)] [Department of Pharmacology, Chung-Ang University, College of Medicine, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756 (Korea, Republic of); Jung, In Duk, E-mail: jungid@pusan.ac.kr [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Research Institute of Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Park, Yeong-Min, E-mail: immunpym@pusan.ac.kr [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of) [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Research Institute of Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of)

    2011-08-05

    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.

  6. Spectral features in isolated neutron stars induced by inhomogeneous surface temperatures

    NASA Astrophysics Data System (ADS)

    Viganò, Daniele; Perna, Rosalba; Rea, Nanda; Pons, José A.

    2014-09-01

    The thermal X-ray spectra of several isolated neutron stars display deviations from a pure blackbody. The accurate physical interpretation of these spectral features bears profound implications for our understanding of the atmospheric composition, magnetic field strength and topology, and equation of state of dense matter. With specific details varying from source to source, common explanations for the features have ranged from atomic transitions in the magnetized atmospheres or condensed surface, to cyclotron lines generated in a hot ionized layer near the surface. Here, we quantitatively evaluate the X-ray spectral distortions induced by inhomogeneous temperature distributions of the neutron star surface. To this aim, we explore several surface temperature distributions, we simulate their corresponding general relativistic X-ray spectra (assuming an isotropic, blackbody emission), and fit the latter with a single blackbody model. We find that, in some cases, the presence of a spurious `spectral line' is required at a high significance level in order to obtain statistically acceptable fits, with central energy and equivalent width similar to the values typically observed. We also perform a fit to a specific object, RX J0806.4-4123, finding several surface temperature distributions able to model the observed spectrum. The explored effect is unlikely to work in all sources with detected lines, but in some cases it can indeed be responsible for the appearance of such lines. Our results enforce the idea that surface temperature anisotropy can be an important factor that should be considered and explored also in combination with more sophisticated emission models like atmospheres.

  7. Spectral line polarization with angle-dependent partial frequency redistribution. I. A Stokes parameters decomposition for Rayleigh scattering

    Microsoft Academic Search

    Hélène Frisch

    2010-01-01

    Context. The linear polarization of a strong resonance lines observed near the solar limb is created by a multiple-scattering process. Partial frequency redistribution (PRD) effects must be accounted for to explain the polarization profiles. The redistribution matrix describing the scattering process is a sum of terms, each containing a PRD function multiplied by a Rayleigh type phase matrix. A standard

  8. 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.

  9. Induced spin polarization in ferromagnetic Gd62.4Y37.6

    NASA Astrophysics Data System (ADS)

    Duffy, J. A.; Dugdale, S. B.; McCarthy, J. E.; Alam, M. A.; Cooper, M. J.; Palmer, S. B.; Jarlborg, T.

    2000-06-01

    Evidence of a spin moment, induced through a Ruderman-Kittel-Kasuya-Yosida-type interaction in Gd62.4Y37.6, is presented. The additional moment, of 0.16+/-0.03?B, arises from polarization of Y-like electrons in the alloy. The moment was detected in a Compton scattering experiment via the measurement of the one-dimensional projection of the momentum space electron-spin density in Gd and in the alloy. The result is consistent with theoretical predictions calculated using the linear muffin-tin orbital method within the local spin-density approximation.

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

    SciTech Connect

    Nariyuki, Y. [Faculty of Human Development, University of Toyama, 3190, Toyama City, Toyama 930-8555 (Japan); Hada, T. [Department of Earth System Science and Technology, Kyushu University, 6-1, Kasuga City, Fukuoka 816-8580 (Japan); Tsubouchi, K. [Department of Earth and Planetary Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan)

    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.

  11. Shear wave induced resonance elastography of spherical masses with polarized torsional waves.

    PubMed

    Henni, Anis Hadj; Schmitt, Cédric; Trop, Isabelle; Cloutier, Guy

    2012-03-26

    Shear Wave Induced Resonance (SWIR) is a technique for dynamic ultrasound elastography of confined mechanical inclusions. It was developed for breast tumor imaging and tissue characterization. This method relies on the polarization of torsional shear waves modeled with the Helmholtz equation in spherical coordinates. To validate modeling, an in vitro set-up was used to measure and image the first three eigenfrequencies and eigenmodes of a soft sphere. A preliminary in vivo SWIR measurement on a breast fibroadenoma is also reported. Results revealed the potential of SWIR elastography to detect and mechanically characterize breast lesions for early cancer detection. PMID:23687384

  12. 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

  13. Heat-induced changes to lipid molecular structure in Vimy flaxseed: Spectral intensity and molecular clustering

    NASA Astrophysics Data System (ADS)

    Yu, Peiqiang; Damiran, Daalkhaijav

    2011-06-01

    Autoclaving was used to manipulate nutrient utilization and availability. The objectives of this study were to characterize any changes of the functional groups mainly associated with lipid structure in flaxseed ( Linum usitatissimum, cv. Vimy), that occurred on a molecular level during the treatment process using infrared Fourier transform molecular spectroscopy. The parameters included lipid CH 3 asymmetric (ca. 2959 cm -1), CH 2 asymmetric (ca. 2928 cm -1), CH 3 symmetric (ca. 2871 cm -1) and CH 2 symmetric (ca. 2954 cm -1) functional groups, lipid carbonyl C dbnd O ester group (ca. 1745 cm -1), lipid unsaturation group (CH attached to C dbnd C) (ca. 3010 cm -1) as well as their ratios. Hierarchical cluster analysis (CLA) and principal components analysis (PCA) were conducted to identify molecular spectral differences. Flaxseed samples were kept raw for the control or autoclaved in batches at 120 °C for 20, 40 or 60 min for treatments 1, 2 and 3, respectively. Molecular spectral analysis of lipid functional group ratios showed a significant decrease ( P < 0.05) in the CH 2 asymmetric to CH 3 asymmetric stretching band peak intensity ratios for the flaxseed. There were linear and quadratic effects ( P < 0.05) of the treatment time from 0, 20, 40 and 60 min on the ratios of the CH 2 asymmetric to CH 3 asymmetric stretching vibration intensity. Autoclaving had no significant effect ( P > 0.05) on lipid carbonyl C dbnd O ester group and lipid unsaturation group (CH attached to C dbnd C) (with average spectral peak area intensities of 138.3 and 68.8 IR intensity units, respectively). Multivariate molecular spectral analyses, CLA and PCA, were unable to make distinctions between the different treatment original spectra at the CH 3 and CH 2 asymmetric and symmetric region (ca. 2988-2790 cm -1). The results indicated that autoclaving had an impact to the mid-infrared molecular spectrum of flaxseed to identify heat-induced changes in lipid conformation. A future study is needed to quantify the relationship between lipid molecular structure changes and functionality/availability.

  14. 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.

  15. Edge proximity-induced magnetoresistance and spin polarization in ferromagnetic gated bilayer graphene nanoribbon

    NASA Astrophysics Data System (ADS)

    Derakhshan, Vahid; Cheraghchi, Hosein

    2014-05-01

    Coherent spin-dependent transport through a junction containing normal/ferromagnetic/normal bilayer graphene nanoribbon with zigzag edges is investigated by using Landauer formalism. In a more realistic set-up, the exchange field is induced by two ferromagnetic insulator strips deposited on the ribbon edges while a perpendicular electric field is applied by the top gated electrodes. Our results show that, for antiparallel configuration, a band gap is opened giving rise to a semiconducting behavior, while for parallel configuration, the band structure has no band gap. As a result, a giant magnetoresistance is achievable by changing the alignment of induced magnetization. Application of a perpendicular electric field on the parallel configuration results in a spin field-effect transistor where a fully spin polarization occurs around the Dirac point. To compare our results with the one for monolayer graphene, we demonstrate that the reflection symmetry and so the parity conservation fail in bilayer graphene nanoribbons with the zigzag edges.

  16. Accommodation-induced variations in retinal thickness measured by spectral domain optical coherence tomography.

    PubMed

    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. PMID:25233144

  17. 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.

  18. Wnt signaling gradients establish planar cell polarity by inducing Vangl2 phosphorylation through Ror2

    PubMed Central

    Gao, Bo; Song, Hai; Bishop, Kevin; Elliot, Gene; Garrett, Lisa; English, Milton; Andre, Philipp; Robinson, James; Sood, Raman; Minami, Yasuhiro; Economides, Aris N.; Yang, Yingzi

    2011-01-01

    It is fundamentally important that signaling gradients provide positional information to govern morphogenesis of multicellular organisms. Morphogen gradients can generate different cell types in specific spatial order at distinct threshold concentrations. However, it is largely unknown whether and how signaling gradients also control cell polarities by acting as global cues. Here we show that Wnt signaling gradient provides directional information to a field of cells. Vangl2, a core component in planar cell polarity, forms Wnt-induced receptor complex with Ror2 to sense Wnt dosages. Wnts dose-dependently induce Vangl2 phosphorylation of Serine/Threonine residues and Vangl2 activities depend on its levels of phosphorylation. In the limb bud, Wnt5a signaling gradient controls limb elongation by establishing PCP in chondrocytes along the proximal-distal axis through regulating Vangl2 phosphorylation. Our studies have provided new insight to Robinow Syndrome, Brachydactyly Type B1 and spinal bifida which are caused by mutations in human ROR2, WNT5A or VANGL. PMID:21316585

  19. Highly polarized Th17 cells induce EAE via a T-bet independent mechanism.

    PubMed

    Grifka-Walk, Heather M; Lalor, Stephen J; Segal, Benjamin M

    2013-11-01

    In the MOG35-55 induced EAE model, autoreactive Th17 cells that accumulate in the central nervous system acquire Th1 characteristics via a T-bet dependent mechanism. It remains to be determined whether Th17 plasticity and encephalitogenicity are causally related to each other. Here, we show that IL-23 polarized T-bet(-/-) Th17 cells are unimpaired in either activation or proliferation, and induce higher quantities of the chemokines RANTES and CXCL2 than WT Th17 cells. Unlike their WT counterparts, T-bet(-/-) Th17 cells retain an IL-17(hi) IFN-?(neg-lo) cytokine profile following adoptive transfer into syngeneic hosts. This population of highly polarized Th17 effectors is capable of mediating EAE, albeit with a milder clinical course. It has previously been reported that the signature Th1 and Th17 effector cytokines, IFN-? and IL-17, are dispensable for the development of autoimmune demyelinating disease. The current study demonstrates that the "master regulator" transcription factor, T-bet, is also not universally required for encephalitogenicity. Our results contribute to a growing body of data showing heterogeneity of myelin-reactive T cells and the independent mechanisms they employ to inflict damage to central nervous system tissues, complicating the search for therapeutic targets relevant across the spectrum of individuals with multiple sclerosis. PMID:23878008

  20. Interferon regulatory factor 4 regulates obesity-induced inflammation through regulation of adipose tissue macrophage polarization.

    PubMed

    Eguchi, Jun; Kong, Xingxing; Tenta, Masafumi; Wang, Xun; Kang, Sona; Rosen, Evan D

    2013-10-01

    Interferon regulatory factors (IRFs) play functionally diverse roles in the transcriptional regulation of the immune system. We have previously shown that several IRFs are regulators of adipogenesis and that IRF4 is a critical transcriptional regulator of adipocyte lipid handling. However, the functional role of IRF4 in adipose tissue macrophages (ATMs) remains unclear, despite high expression there. Here we show that IRF4 expression is regulated in primary macrophages and in ATMs of high-fat diet-induced obese mice. Irf4(-/-) macrophages produce higher levels of proinflammatory cytokines, including interleukin-1? and tumor necrosis factor-?, in response to fatty acids. In coculture experiments, IRF4 deletion in macrophages leads to reduced insulin signaling and glucose uptake in 3T3-L1 adipocytes. To determine the macrophage-specific function of IRF4 in the context of obesity, we generated myeloid cell-specific IRF4 knockout mice, which develop significant insulin resistance on a high-fat diet, despite no difference in adiposity. This phenotype is associated with increased expression of inflammatory genes and decreased insulin signaling in adipose tissue, skeletal muscle, and liver. Furthermore, Irf4(-/-) ATMs express markers suggestive of enhanced M1 polarization. These findings indicate that IRF4 is a negative regulator of inflammation in diet-induced obesity, in part through regulation of macrophage polarization. PMID:23835343

  1. Full-range polarization-sensitive swept-source optical coherence tomography by simultaneous transversal and spectral modulation.

    PubMed

    Yamanari, Masahiro; Makita, Shuichi; Lim, Yiheng; Yasuno, Yoshiaki

    2010-06-21

    Polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) is used to measure three-dimensional phase-retardation images of birefringent biological tissue in vivo. PS-SS-OCT with continuous source polarization modulation is used to multiplex the incident states of polarization in the signal frequency of each A-scan. Although it offers the advantage of measurement speed that is as high as that of standard SS-OCT, its disadvantage is low axial measurement range. To overcome this drawback, we employed the B-M-mode scan (BM-scan) method, which removes complex conjugate ambiguity by applying phase modulation along the transversal scanning direction. Since polarization modulation and BM-scan are applied in different scanning directions, these methods can be combined to make the optimum use of both full range and polarization-sensitive imaging. Phase fluctuations that cause measurement failure were numerically canceled before demodulating the B-scan oriented modulation. After removing complex conjugate artifacts, the axial measurement range was 5.35 mm, and the signal-to-conjugate ratio was 40.5 dB. We demonstrated retinal imaging using the PS-SS-OCT system with a frequency-swept laser at a center wavelength of 1064 nm and an axial resolution of 11.4 microm in tissue. Full-range polarization-sensitive retinal images showed characteristic birefringence of fibrous tissues such as retinal nerve fiber, sclera, and lamina cribrosa. PMID:20588529

  2. Study case - Induced Polarization response from a BTEX contaminated site in Brazil

    NASA Astrophysics Data System (ADS)

    Ustra, A.; Elis, V.; Minozzo, M.

    2011-12-01

    A hydrocarbon contaminated site in Brazil was investigated using DC-resistivity and Induced Polarization (IP) methods. The study area is a chemical industry facility that manufactures paint for automobiles. The industrial process involves the use of many hydrocarbon derivative products, including BTEX (benzene, toluene, ethyl benzene and xylene) and organic chlorides. The area was contaminated by some (not documented) accidental spills of BTEX throughout many years. Monitoring wells revealed concentrations from a few ppm to hundreds ppm of BTEX around the area, as well as other compounds. Two soil samples were collected from an area where some spills where known to have happened. Soil analyses of these samples found the presence of microbes, and therefore biodegradation is believed to be occurring at the site. The objective of this study is to relate the IP response distribution to the presence of contamination and/or microbial activity. The geophysical survey consisted in a rectangular mesh composed of 15 parallel lines with 60 meters of extension, using dipole-dipole array. Lines were spaced by 3 meters. Metallic electrodes were used for current injection, and non-polarizing electrodes (Cu/CuSO4) for potential measurement. Current was injected in cycles of 2 seconds. IP measurements were recorded after 160 milliseconds delay of current shut off, and integration time windows were 120, 220, 420, and 820 milliseconds. All data were concatenated into a single data set and submitted to 3D inversion routine. A conductive zone (resistivity less than 100 ohm.m and chargeability less than 2mV/V) was observed where microbes were found. This feature was interpreted as possibly due to natural biodegradation process, that increases total dissolved salts as a result of mineral weathering by organic acids produced in the degradation process. Normalized chargeability (chargeability divided by resistivity) showed an enhanced polarization zone where microbes were detected. This result was interpreted as possibly due to growth and attachment of microbes to grain surfaces, increasing grain surface area and therefore polarization. These results are in good agreement with published studies relating conductivity and polarization increase with microbial activity. However, further research is need on the effect of microbial activity on normalized chargeability, since this parameter is very sensitive to lithology and surface chemistry. The results from this work could assist the interpretation of IP surveys at hydrocarbon-contaminated sites undergoing natural degradation and at bioremediation sites.

  3. A precise extraction of the induced polarization in the 4He(e,e'p)3H reaction

    E-print Network

    Malace, S P; Strauch, S

    2010-01-01

    We measured with unprecedented precision the induced polarization Py in 4He(e,e'p)3H at Q^2 = 0.8 (GeV/c)^2 and 1.3 (GeV/c)^2. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are over-estimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin independent charge-exchange term in the latter calculation.

  4. Precise Extraction of the Induced Polarization in the He4(e,e'p?)H3 Reaction

    NASA Astrophysics Data System (ADS)

    Malace, S. P.; Paolone, M.; Strauch, S.; Albayrak, I.; Arrington, J.; Berman, B. L.; Brash, E. J.; Briscoe, B.; Camsonne, A.; Chen, J.-P.; Christy, M. E.; Chudakov, E.; Cisbani, E.; Craver, B.; Cusanno, F.; Ent, R.; Garibaldi, F.; Gilman, R.; Glamazdin, O.; Glister, J.; Higinbotham, D. W.; Hyde-Wright, C. E.; Ilieva, Y.; de Jager, C. W.; Jiang, X.; Jones, M. K.; Keppel, C. E.; Khrosinkova, E.; Kuchina, E.; Kumbartzki, G.; Lee, B.; Lindgren, R.; Margaziotis, D. J.; Meekins, D.; Michaels, R.; Park, K.; Pentchev, L.; Perdrisat, C. F.; Piasetzky, E.; Punjabi, V. A.; Puckett, A. J. R.; Qian, X.; Qiang, Y.; Ransome, R. D.; Saha, A.; Sarty, A. J.; Schulte, E.; Solvignon, P.; Subedi, R. R.; Tang, L.; Tedeschi, D.; Tvaskis, V.; Udias, J. M.; Ulmer, P. E.; Vignote, J. R.; Wesselmann, F. R.; Wojtsekhowski, B.; Zhan, X.

    2011-02-01

    We measured with unprecedented precision the induced polarization Py in He4(e,e'p?)H3 at Q2=0.8 and 1.3(GeV/c)2. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are overestimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin-independent charge-exchange term in the latter calculation.

  5. Precise Extraction of the Induced Polarization in the He4(e,e'p-->)H3 Reaction

    Microsoft Academic Search

    S. P. Malace; M. Paolone; S. Strauch; I. Albayrak; J. Arrington; B. L. Berman; E. J. Brash; B. Briscoe; A. Camsonne; J.-P. Chen; M. E. Christy; E. Chudakov; E. Cisbani; B. Craver; F. Cusanno; R. Ent; F. Garibaldi; R. Gilman; O. Glamazdin; J. Glister; D. W. Higinbotham; C. E. Hyde-Wright; Y. Ilieva; C. W. de Jager; X. Jiang; M. K. Jones; C. E. Keppel; E. Khrosinkova; E. Kuchina; G. Kumbartzki; B. Lee; R. Lindgren; D. J. Margaziotis; D. Meekins; R. Michaels; L. Pentchev; C. F. Perdrisat; E. Piasetzky; V. A. Punjabi; A. J. R. Puckett; X. Qian; Y. Qiang; R. D. Ransome; A. Saha; A. J. Sarty; E. Schulte; P. Solvignon; R. R. Subedi; L. Tang; D. Tedeschi; V. Tvaskis; J. M. Udias; P. E. Ulmer; J. R. Vignote; F. R. Wesselmann; B. Wojtsekhowski; X. Zhan

    2011-01-01

    We measured with unprecedented precision the induced polarization Py in He4(e,e'p-->)H3 at Q2=0.8 and 1.3(GeV\\/c)2. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are overestimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin-independent

  6. A precise extraction of the induced polarization in the 4He(e,e'p)3H reaction

    Microsoft Academic Search

    S. P. Malace; M. Paolone; S. Strauch

    2011-01-01

    We measured with unprecedented precision the induced polarization Py in 4He(e,e'p)3H at Q^2 = 0.8 (GeV\\/c)^2 and 1.3 (GeV\\/c)^2. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are over-estimated by a calculation with strong charge-exchange effects. Our data are used to constrain the

  7. Creation of high mobility two-dimensional electron gases via strain induced polarization at an otherwise nonpolar complex oxide interface.

    PubMed

    Chen, Yunzhong; Trier, Felix; Kasama, Takeshi; Christensen, Dennis V; Bovet, Nicolas; Balogh, Zoltan I; Li, Han; Thydén, Karl Tor Sune; Zhang, Wei; Yazdi, Sadegh; Norby, Poul; Pryds, Nini; Linderoth, Søren

    2015-03-11

    The discovery of two-dimensional electron gases (2DEGs) in SrTiO3-based heterostructures provides new opportunities for nanoelectronics. Herein, we create a new type of oxide 2DEG by the epitaxial-strain-induced polarization at an otherwise nonpolar perovskite-type interface of CaZrO3/SrTiO3. Remarkably, this heterointerface is atomically sharp and exhibits a high electron mobility exceeding 60,000 cm(2) V(-1) s(-1) at low temperatures. The 2DEG carrier density exhibits a critical dependence on the film thickness, in good agreement with the polarization induced 2DEG scheme. PMID:25692804

  8. Polarized spectral analysis of Er 3+ ions in biaxial Bi 2 (MoO 4 ) 3 crystal

    Microsoft Academic Search

    X. H. Gong; Y. F. Lin; Y. J. Chen; J. S. Liao; X. Y. Chen; Z. D. Luo; Y. D. Huang

    2008-01-01

    An Er3+:Bi2(MoO4)3 single crystal has been grown by the Czochralski technique. The Stark sublevels of the 4I15\\/2 and 4I13\\/2 multiplets of Er3+ ions in the crystal were determined. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay\\u000a curve of the crystal were measured at room temperature and the relevant spectroscopic parameters, including the Judd–Ofelt\\u000a intensity parameters, spontaneous emission probability,

  9. Compact polar moieties induce lipid-water systems to form discontinuous reverse micellar phase.

    PubMed

    Kumar, Manoj; Patil, Naganath G; Choudhury, Chandan Kumar; Roy, Sudip; Ambade, Ashootosh V; Kumaraswamy, Guruswamy

    2015-07-01

    The role of molecular interactions in governing lipid mesophase organization is of fundamental interest and has technological implications. Herein, we describe an unusual pathway for monoolein/water reorganization from a bicontinuous mesophase to a discontinuous reverse micellar assembly, directed by the inclusion of polar macromolecules. This pathway is very different from those reported earlier, wherein the Fd3m phase formed only upon addition of apolar oils. Experiments and molecular dynamics simulations indicate that hydrophilic ternary additives capable of inducing discontinuous phase formation must (i) interact strongly with the monoolein head group and (ii) have a compact molecular architecture. We present a detailed investigation that contrasts a monoolein-water system containing polyamidoamine (PAMAM) dendrons with one containing their linear analogs. The Fd3m phase forms only on the addition of PAMAM dendrons but not their linear analogs. Thus, the dendritic architecture of PAMAM plays an important role in determining lipid mesophase behavior. Both dendrons and their linear analogs interact strongly with monoolein through their amine groups. However, while linear polymers adsorb and spread on monoolein, dendrons form aggregates that interact with the lipid. Dendrons induce formation of an intermediate reverse hexagonal phase, which subsequently restructures into the Fd3m phase. Finally, we demonstrate that other additives with compact structures that are known to interact with monoolein, such as branched polyethylenimine and polyhedral silsesquioxane cages, also induce the formation of the Fd3m phase. PMID:26023767

  10. Ligand Induced Circular Dichroism and Circularly Polarized Luminescence in CdSe Quantum Dots

    PubMed Central

    Tohgha, Urice; Deol, Kirandeep K.; Porter, Ashlin G.; Bartko, Samuel G.; Choi, Jung Kyu; Leonard, Brian M.; Varga, Krisztina; Kubelka, Jan; Muller, Gilles; Balaz, Milan

    2014-01-01

    Chiral thiol capping ligands L- and D-cysteines induced modular chiroptical properties in achiral cadmium selenide quantum dots (CdSe QDs). Cys-CdSe prepared from achiral oleic acid capped CdSe by post-synthetic ligand exchange displayed size-dependent electronic circular dichroism (CD) and circularly polarized luminescence (CPL). Opposite CPL signals were measured for the CdSe QDs capped with D- and L-cysteine. The CD profile and CD anisotropy varied with size of CdSe nanocrystals with largest anisotropy observed for CdSe nanoparticles of 4.4 nm. Magic angle spinning solid state NMR (MAS ssNMR) experiments suggested bidentate interaction between cysteine and the surface of CdSe. Density functional theory (DFT) calculations verified that attachment of L- and D-cysteine to the surface of model (CdSe)13 nanoclusters induces measurable opposite CD signals for the exitonic band of the nanocluster. The chirality was induced by the hybridization of highest occupied CdSe molecular orbitals with those of the chiral ligand. PMID:24200288

  11. Controlling pulse delay by light and low magnetic fields: slow light in emerald induced by transient spectral hole-burning.

    PubMed

    Rajan, Rajitha Papukutty; Riesen, Hans; Rebane, Aleksander

    2013-11-15

    Slow light based on transient spectral hole-burning is reported for emerald, Be(3)Al(2)Si(6)O(18):Cr(3+). Experiments were conducted in ? polarization on the R(1)(± 3/2) line (E2 ? A(2)4) at 2.2 K in zero field and low magnetic fields B||c. The hole width was strongly dependent on B||c, and this allowed us to smoothly tune the pulse delay from 40 to 154 ns between zero field and B||c = 15.2 mT. The latter corresponds to a group velocity of 16 km/s. Slow light in conjunction with a linear filter theory can be used as a powerful and accurate technique in time-resolved spectroscopy, e.g., to determine spectral hole-widths as a function of time. PMID:24322070

  12. 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

  13. 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

  14. Focusing Sources on Induced Polarization and Electrical Resistivity Method Applied to Soil Pollution Problems

    NASA Astrophysics Data System (ADS)

    Tejero, A.; Lopez, A.; Induced Polarization Team

    2013-05-01

    In recent years the problems of soil contamination have been increasing and geophysical methods, particularly electrical resistivity tomography (ERT) have struggled to find and monitor cases of contamination. Moreover, Induced Polarization (IP) has shown promise in mapping contaminant plumes, although both techniques (ERT and IP) have problems like noise, inductive coupling, effects of electrodes, etc. limiting the precision and accuracy of the data. To overcome these problems, this paper introduces a novel technique of focusing sources. This technique reduces the effects of adjacent vertical formations and contacts due to the flowing of current in a vertical way at the zone where the electrode potentials have been deployed. This fact allows obtaining cleaner data of ERT and IP. In order to introduce the proposed technique a vertical contact synthetic model is studied and after to a cultivar area in Hidalgo State, México which presents different types of

  15. Ferroelectric polarization induces electric double layer bistability in electrolyte-gated field-effect transistors.

    PubMed

    Fabiano, Simone; Crispin, Xavier; Berggren, Magnus

    2014-01-01

    The dense surface charges expressed by a ferroelectric polymeric thin film induce ion displacement within a polyelectrolyte layer and vice versa. This is because the density of dipoles along the surface of the ferroelectric thin film and its polarization switching time matches that of the (Helmholtz) electric double layers formed at the ferroelectric/polyelectrolyte and polyelectrolyte/semiconductor interfaces. This combination of materials allows for introducing hysteresis effects in the capacitance of an electric double layer capacitor. The latter is advantageously used to control the charge accumulation in the semiconductor channel of an organic field-effect transistor. The resulting memory transistors can be written at a gate voltage of around 7 V and read out at a drain voltage as low as 50 mV. The technological implication of this large difference between write and read-out voltages lies in the non-destructive reading of this ferroelectric memory. PMID:24251907

  16. Electric field-induced coherent control in GaAs: polarization dependence and electrical measurement [Invited].

    PubMed

    Wahlstrand, J K; Zhang, H; Choi, S B; Sipe, J E; Cundiff, S T

    2011-11-01

    A static electric field enables coherent control of the photoexcited carrier density in a semiconductor through the interference of one- and two-photon absorption. An experiment using optical detection is described. The polarization dependence of the signal is consistent with a calculation using a 14-band k · p model for GaAs. We also describe an electrical measurement. A strong enhancement of the phase-dependent photocurrent through a metal-semiconductor-metal structure is observed when a bias of a few volts is applied. The dependence of the signal on bias and laser spot position is studied. The field-induced enhancement of the signal could increase the sensitivity of semiconductor-based carrier-envelope phase detectors, useful in stabilizing mode-locked lasers for use in frequency combs. PMID:22109135

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

    SciTech Connect

    Bunakov, V. E., E-mail: bunakov@vb13190.spbu.edu; Kadmensky, S. G., E-mail: kadmensky@phys.vsu.ru; Kadmensky, S. S. [Voronezh State University (Russian Federation)

    2008-11-15

    Within quantum fission theory, angular distributions of products originating from the ternary fission of nuclei that is induced by polarized cold and thermal neutrons are investigated on the basis of a non-evaporative mechanism of third-particle emission and a consistent description of fission-channel coupling. It is shown that the inclusion of Coriolis interaction both in the region of the discrete and in the region of the continuous spectrum of states of the system undergoing fission leads to T-odd correlations in the aforementioned angular distributions. The properties of the TRI and ROT effects discovered recently, which are due to the interference between the fission amplitudes of neutron resonances, are explored. The results obtained here are compared with their counterparts from classic calculations based on the trajectory method.

  18. 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

  19. Multi-vortical flow inducing electrokinetic instability in ion concentration polarization layer

    NASA Astrophysics Data System (ADS)

    Kim, Sung Jae; Ko, Sung Hee; Kwak, Rhokyun; Posner, Jonathan D.; Kang, Kwan Hyoung; Han, Jongyoon

    2012-11-01

    In this work, we investigated multiple vortical flows inside the ion concentration polarization (ICP) layer that forms due to a coupling of applied electric fields and the semipermeable nanoporous junction between microchannels. While only a primary vortex near perm-selective membrane is traditionally known to lead to electrokinetic instability, multiple vortexes induced by the primary vortex were found to play a major role in the electrokinetic instability. The existence of multiple vortexes was directly confirmed by experiments using particle tracers and interdigitated electrodes were used to measure the local concentration profile inside the ICP layer. At larger applied electric fields, we observed aperiodic fluid motion due to electrokinetic instabilities which develop from a coupling of applied electric fields and electrical conductivity gradients induced by the ICP. The electrokinetic instability at micro-nanofluidic interfaces is important in the development of various electro-chemical-mechanical applications such as fuel cells, bio-analytical preconcentration methods, water purification/desalination and the fundamental study of ion electromigration through nanochannels and nonporous perm-selective membranes.In this work, we investigated multiple vortical flows inside the ion concentration polarization (ICP) layer that forms due to a coupling of applied electric fields and the semipermeable nanoporous junction between microchannels. While only a primary vortex near perm-selective membrane is traditionally known to lead to electrokinetic instability, multiple vortexes induced by the primary vortex were found to play a major role in the electrokinetic instability. The existence of multiple vortexes was directly confirmed by experiments using particle tracers and interdigitated electrodes were used to measure the local concentration profile inside the ICP layer. At larger applied electric fields, we observed aperiodic fluid motion due to electrokinetic instabilities which develop from a coupling of applied electric fields and electrical conductivity gradients induced by the ICP. The electrokinetic instability at micro-nanofluidic interfaces is important in the development of various electro-chemical-mechanical applications such as fuel cells, bio-analytical preconcentration methods, water purification/desalination and the fundamental study of ion electromigration through nanochannels and nonporous perm-selective membranes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32467a

  20. Frequency-induced polarization bistability in vertical-cavity surface-emitting lasers with orthogonal optical injection

    SciTech Connect

    Gatare, I. [Supelec, LMOPS CNRS UMR-7132, Unite de Recherche Commune Supelec et Universite de Metz, Rue Edouard Belin 2, F-57070 Metz (France); Department of Applied Physics and Photonics, (TW-TONA), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels (Belgium); Panajotov, K. [Department of Applied Physics and Photonics, (TW-TONA), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels (Belgium); Sciamanna, M. [Supelec, LMOPS CNRS UMR-7132, Unite de Recherche Commune Supelec et Universite de Metz, Rue Edouard Belin 2, F-57070 Metz (France)

    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.

  1. PHYSICAL REVIEW B 86, 085310 (2012) Spin-polarized electric currents in diluted magnetic semiconductor heterostructures induced

    E-print Network

    Ganichev, Sergey

    2012-01-01

    semiconductor heterostructures induced by terahertz and microwave radiation P. Olbrich,1 C. Zoth,1 P. Lutz,1 C structures based on II-VI and III-V semiconductors as well as for hybrid II-VI/III-V heterostructures. We on the study of spin-polarized electric currents in diluted magnetic semiconductor (DMS) quantum wells

  2. 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. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Chiba, D. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 322-0012 (Japan); Fukami, S. [Green Innovation Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501 (Japan); Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Tanigawa, H.; Suzuki, T. [RENESAS Electronics Corporation, Sagamihara, Kanagawa 252-5298 (Japan); Ohshima, N. [NEC Energy Device Ltd., 1120 Shimokuzawa, Chuo-ku, Sagamihara, Kanagawa 252-5298 (Japan); Ishiwata, N. [Green Innovation Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501 (Japan); Nakatani, Y. [University of Electro-communications, Chofu, Tokyo 182-8585 (Japan)

    2012-05-14

    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.

  3. 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

    PHYSICAL REVIEW B 84, 155319 (2011) Nonequilibrium nuclear polarization and induced hyperfine Department of Physics and Astronomy, California State University, Fullerton, California 92835, USA 2 Department of Physics and Astronomy and Optical Science and Technology Center, University of Iowa, Iowa City

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

    E-print Network

    Gagliardini, Olivier

    2006-01-01

    ice crystallizes in the hexagonal system (ice Ih). The viscoplastic deformation of the ice Ih single to the hexagonal symmetry axis, called the c-axis [1]. As a consequence, ice Ih is one of the most anisotropicJ. Non-Newtonian Fluid Mech. 134 (2006) 33­43 Flow-induced anisotropy in polar ice and related ice

  5. Algorithm to Retrieve Aerosol Optical Properties From High-Spectral-Resolution Lidar and Polarization Mie-Scattering Lidar Measurements

    Microsoft Academic Search

    Tomoaki Nishizawa; Nobuo Sugimoto; Ichiro Matsui; Atsushi Shimizu; Boyan Tatarov; Hajime Okamoto

    2008-01-01

    We developed an algorithm to estimate the vertical profiles of extinction coefficients at 532 nm for three aerosol types that are water-soluble, soot, and dust particles, using the extinction and backscattering coefficients at 532 nm for total aerosols derived from high-spectral-resolution lidar (HSRL) measurements and the receiving signal at 1064 nm and total depolarization ratio at 532 nm measured with

  6. Solar-blind AlxGa1-xN/AlN/SiC photodiodes with a polarization-induced electron filter

    NASA Astrophysics Data System (ADS)

    Rodak, L. E.; Sampath, A. V.; Gallinat, C. S.; Chen, Y.; Zhou, Q.; Campbell, J. C.; Shen, H.; Wraback, M.

    2013-08-01

    Heterogeneous n-III-nitride/i-p silicon carbide (SiC) photodetectors have been demonstrated that enable the tailoring of the spectral response in the solar blind region below 280 nm. The negative polarization induced charge at the aluminum gallium nitride (AlxGa1-xN)/aluminum nitride (AlN) interface in conjunction with the positive polarization charge at the AlN/SiC interface creates a large barrier to carrier transport across the interface that results in the selective collection of electrons photoexcited to the ? and L valleys of SiC while blocking the transport of electrons generated in the M valley. In addition, the AlxGa1-xN alloys act as transparent windows that enhance the collection of carriers generated by high energy photons in the fully depleted SiC absorption regions. These two factors combine to create a peak external quantum efficiency of 76% at 242 nm, along with a strong suppression of the long-wavelength response from 260 nm to 380 nm.

  7. 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 [ORNL; Moucka, Filip [Jan Evangelista Purkyn? University in Ústí nad Labem, Czech Republic; Vlcek, Lukas [ORNL; Nezbeda, Ivo [Jan Evangelista Purkyn? University in Ústí nad Labem, Czech Republic

    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.

  8. Pressure-induced polar phases in multiferroic delafossite CuFeO2

    NASA Astrophysics Data System (ADS)

    Terada, Noriki; Khalyavin, Dmitry D.; Manuel, Pascal; Osakabe, Toyotaka; Radaelli, Paolo G.; Kitazawa, Hideaki

    2014-06-01

    The pressure effect on the frustrated magnetic system CuFeO2 exhibiting multiferroic behavior has been studied by means of time-of-flight single crystal neutron diffraction combined with a hybrid-anvil-type pressure cell. The nonpolar collinear magnetic ground state (CM1 phase) with propagation vector k =(0,1/2,1/2) turns into a proper screw magnetic ordering with incommensurate modulation k =(0,q,1/2;q?0.4) and a polar 21' magnetic point group (ICM2 phase), between 3 and 4 GPa. This spin structure is similar to the ferroelectric phase induced by magnetic field or chemical doping under ambient pressure. Above, 4 GPa, a magnetic phase (ICM3) appears, with an incommensurate propagation vector that is unique for the CuFeO2 system, k =(qa,qb,qc;qa?0,qb?0.34,qc?0.43). This propagation vector at the general point results in triclinic magnetic symmetry which implies an admixture of both cycloidal and proper screw spin configurations. The ICM3 phase is stable in a narrow pressure range, and above 6 GPa, the spin-density collinear structure (ICM1 phase), similar to the first ordered state at ambient pressure, takes place. Comparing the degree of lattice distortions among the magnetic phases observed at ambient pressure, we discuss the origin of the pressure-induced magnetic phase transitions in CuFeO2.

  9. Multi-vortical flow inducing electrokinetic instability in ion concentration polarization layer.

    PubMed

    Kim, Sung Jae; Ko, Sung Hee; Kwak, Rhokyun; Posner, Jonathan D; Kang, Kwan Hyoung; Han, Jongyoon

    2012-12-01

    In this work, we investigated multiple vortical flows inside the ion concentration polarization (ICP) layer that forms due to a coupling of applied electric fields and the semipermeable nanoporous junction between microchannels. While only a primary vortex near perm-selective membrane is traditionally known to lead to electrokinetic instability, multiple vortexes induced by the primary vortex were found to play a major role in the electrokinetic instability. The existence of multiple vortexes was directly confirmed by experiments using particle tracers and interdigitated electrodes were used to measure the local concentration profile inside the ICP layer. At larger applied electric fields, we observed aperiodic fluid motion due to electrokinetic instabilities which develop from a coupling of applied electric fields and electrical conductivity gradients induced by the ICP. The electrokinetic instability at micro-nanofluidic interfaces is important in the development of various electro-chemical-mechanical applications such as fuel cells, bio-analytical preconcentration methods, water purification/desalination and the fundamental study of ion electromigration through nanochannels and nonporous perm-selective membranes. PMID:23085964

  10. 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

  11. Non-coherent continuum scattering as a line polarization mechanism

    SciTech Connect

    Del Pino Alemán, T.; Manso Sainz, R.; Trujillo Bueno, J., E-mail: tanausu@iac.es, E-mail: rsainz@iac.es, E-mail: jtb@iac.es [Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain)

    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.

  12. 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.

  13. Optically thin composite resonant absorber at the near-infrared band: a polarization independent and spectrally broadband configuration

    NASA Astrophysics Data System (ADS)

    Boratay Alici, Kamil; Burak Turhan, Adil; Soukoulis, Costas M.; Ozbay, Ekmel

    2011-07-01

    We designed, fabricated, and experimentally characterized thin absorbers utilizing both electrical and magnetic impedance matching at the near-infrared regime. The absorbers consist of four main layers: a metal back plate, dielectric spacer, and two artificial layers. One of the artificial layers provides electrical resonance and the other one provides magnetic resonance yielding a polarization independent broadband perfect absorption. The structure response remains similar for the wide angle of incidence due to the sub-wavelength unit cell size of the constituting artificial layers. The design is useful for applications such as thermal photovoltaics, sensors, and camouflage.

  14. Modulated spin structure responsible for the magnetic-field-induced polarization switching in multiferroic TbMn2O5

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Hoon; Jang, Hyun Myung

    2015-01-01

    Orthorhombic TbMn2O5 (o -TMO ) is a well-known multiferroic manganite with the remarkable property of polarization switching at 3 K under a bias magnetic (H) field along the a axis of P b 21m . To theoretically account for this outstanding observation, we have proposed a modulated spin structure under the saturated bias H field by considering the relative strength of the three relevant exchange parameters in o -TMO . The proposed modulated structure based on density-functional theory (DFT) calculations is described in terms of the spin angle ? between the neighboring M n4 +-Mn3 + spin moments on the a-b plane. We have shown that the computed DFT polarization plotted as a function of ? satisfactorily accounts for the observed H -field-induced polarization switching. We have further theoretically shown that the square of the critical field strength (Hc) needed for the polarization switching is inversely proportional to the degree of the extrinsic magnetoelectric coupling. The computed partial charge density demonstrates that the H -field-induced polarization switching also accompanies with the switching in the sign of the excess valence-electron density.

  15. 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

  16. 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.

  17. Polarization selective computer-generated holograms created by femtosecond pulse induced birefringence

    Microsoft Academic Search

    Wenjian Cai; Ariel Libertun; Rafael Piestun

    2006-01-01

    We demonstrate polarization selective birefringent computer-generated holograms fabricated in glass with femtosecond lasers. We present a coding technique adapted to the writing process. The experimental reconstruction shows excellent polarization selectivity at the design wavelength.

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

    Microsoft Academic Search

    Ka Lok Ng; Kin-Wang Ng

    1994-01-01

    We discuss the contribution of gravitational wave to the cosmic microwave\\u000abackground radiation (CMBR) anisotropy and polarization. It is found that the\\u000alarge-scale polarization of CMBR is less than 1\\\\% for a standard recombination\\u000auniverse. The effect of matter reionization will enhance the CMBR polarization\\u000ato a 10\\\\% level. We have computed the CMBR polarization for two extreme cases\\u000a(not

  19. Magnetic-field-induced ferroelectric polarization reversal in the multiferroic Ge(1-x)Mn(x)Te semiconductor.

    PubMed

    Przybyli?ska, H; Springholz, G; Lechner, R T; Hassan, M; Wegscheider, M; Jantsch, W; Bauer, G

    2014-01-31

    Ge(1-x)Mn(x)Te is shown to be a multiferroic semiconductor, exhibiting both ferromagnetic and ferroelectric properties. By ferromagnetic resonance we demonstrate that both types of order are coupled to each other. As a result, magnetic-field-induced ferroelectric polarization reversal is achieved. Switching of the spontaneous electric dipole moment is monitored by changes in the magnetocrystalline anisotropy. This also reveals that the ferroelectric polarization reversal is accompanied by a reorientation of the hard and easy magnetization axes. By tuning the GeMnTe composition, the interplay between ferromagnetism and ferroelectricity can be controlled. PMID:24580486

  20. The spectral maps of dynamic speckle patterns: A new perspective to look at the motion-induced spatiotemporal cross-correlation

    NASA Astrophysics Data System (ADS)

    Wang, Dake; Ranger, James

    2015-06-01

    We introduce the spectral map method as a means to visualize the spatiotemporal correlation in dynamic speckles. Dynamic speckle patterns of moving diffuse objects are Fourier transformed to construct spectral maps in spatial domain (r-space) and spatial-frequency domain (k-space). The periodic patterns in r-space spectral maps demonstrate the spatiotemporal cross-correlation induced by the directional motions. To resolve the spectral bands in k-space spectral maps, and to observe the concomitant appearance of the periodic pattern in r-space spectral maps, the frequency must exceed the minimum values given by the speckle size and the speed. A bigger speckle size helps to reveal fast dynamics, and to ease the requirement on the minimum frequency. The transition from ordered translational speckles to chaotic boiling speckles at different speeds and speckle sizes is elucidated in connection with the change observed in spectral maps.

  1. Vector photochromism in polarization-sensitive materials.

    PubMed

    Chaganava, Irakli; Kakauridze, George; Kilosanidze, Barbara; Mshvenieradze, Yuri

    2014-07-01

    The phenomenon of vector photochromism was observed in some high-efficient polarization-sensitive materials depending on the radiant exposure of the inducing linearly polarized actinic light. The phenomenon has the purely vector nature because the absorption of the irradiated and unirradiated areas of the material is practically identical when we use unpolarized probing light. However, an essential change in the absorption spectrum was observed under probing the sample by linearly polarized nonactinic light when it passes through an analyzer, and this change depends on the value of radiant exposure. The kinetics of the photoanisotropy induced by linearly polarized actinic light at 457 nm was studied in case of wavelengths of 532 and 635 nm of the probing beam. The noticeable difference in absorbance was observed with increase in radiant exposure from 60??J/cm² up to 250??J/cm² for the used wavelengths of the probing beam. The experimental results obtained in polarization-sensitive material based on the ammonium salt of the azodye Mordant pure yellow in a gelatin matrix are presented. The dependence of the effective anisotropy on the material thickness has been investigated. The mechanism of the phenomenon is discussed. The observed effect can be used for creating dynamic polarization spectral filters controlled by light and the spectrally selective dynamic polarization holographic gratings. PMID:24978751

  2. Asymmetrical, agonist-induced fluctuations in local extracellular [Ca2+] in intact polarized epithelia

    PubMed Central

    Caroppo, Rosa; Gerbino, Andrea; Debellis, Lucantonio; Kifor, Olga; Soybel, David I.; Brown, Edward M.; Hofer, Aldebaran M.; Curci, Silvana

    2001-01-01

    We recently proposed that extracellular Ca2+ ions participate in a novel form of intercellular communication involving the extracellular Ca2+-sensing receptor (CaR). Here, using Ca2+-selective microelectrodes, we directly measured the profile of agonist-induced [Ca2+]ext changes in restricted domains near the basolateral or luminal membranes of polarized gastric acid-secreting cells. The Ca2+-mobilizing agonist carbachol elicited a transient, La3+-sensitive decrease in basolateral [Ca2+] (average ?250 µM, but as large as 530 µM). Conversely, carbachol evoked an HgCl2-sensitive increase in [Ca2+] (average ?400 µM, but as large as 520 µM) in the lumen of single gastric glands. Both responses were significantly reduced by pre-treatment with sarco-endoplasmic reticulum Ca2+ ATPase (SERCA) pump inhibitors or with the intracellular Ca2+ chelator BAPTA-AM. Immunofluores cence experiments demonstrated an asymmetric localization of plasma membrane Ca2+ ATPase (PMCA), which appeared to be partially co-localized with CaR and the gastric H+/K+-ATPase in the apical membrane of the acid-secreting cells. Our data indicate that agonist stimulation results in local fluctuations in [Ca2+]ext that would be sufficient to modulate the activity of the CaR on neighboring cells. PMID:11707403

  3. 2.5D induced polarization forward modeling using the adaptive finite-element method

    NASA Astrophysics Data System (ADS)

    Ye, Yi-Xin; Li, Yu-Guo; Deng, Ju-Zhi; Li, Ze-Lin

    2014-12-01

    The conventional finite-element (FE) method often uses a structured mesh, which is designed according to the user's experience, and it is not sufficiently accurate and flexible to accommodate complex structures such as dipping interfaces and rough topography. We present an adaptive FE method for 2.5D forward modeling of induced polarization (IP). In the presented method, an unstructured triangulation mesh that allows for local mesh refinement and flexible description of arbitrary model geometries is used. Furthermore, the mesh refinement process is guided by dual error estimate weighting to bias the refinement towards elements that affect the solution at the receiver locations. After the final mesh is generated, the Jacobian matrix is used to obtain the IP response on 2D structure models. We validate the adaptive FE algorithm using a vertical contact model. The validation shows that the elements near the receivers are highly refined and the average relative error of the potentials converges to 0.4 % and 1.2 % for the IP response. This suggests that the numerical solution of the adaptive FE algorithm converges to an accurate solution with the refined mesh. Finally, the accuracy and flexibility of the adaptive FE procedure are also validated using more complex models.

  4. Concentration polarization effects in nanochannel induced-charge electro-osmosis

    NASA Astrophysics Data System (ADS)

    Andersen, Mathias; Bruus, Henrik

    2009-11-01

    Concentration polarization (CP) has been observed in a variety of configurations: nanochannels, nanopores, ion-permselective membranes, and embedded conductors. It is believed, but not conclusively proven, that electric double-layer (EDL) overlap plays a significant role in CP. Consequently, further studies of fundamental electrokinetic effects related to CP are needed. We present theoretical and numerical studies of CP effects near an un-biased conductor placed in a straight nanoslit. In our model we combine the full Poisson-Nernst-Planck equations with Helmholtz-Smoluchowski slip, whereby we can construct large computational domains and at the same time resolve the EDL in the vicinity of the conductor. Based on our results we try to identify the basic physical mechanisms that lead to the CP. We show that when subjected to an external bias the axial symmetry is broken by the electro-osmotic flow. This leads to nonlinear interactions between flow, electric potential, and charged chemical species in the induced EDL on the conductor.

  5. In situ NMR observation of mono- and binuclear rhodium dihydride complexes using parahydrogen-induced polarization.

    PubMed

    Koch, A; Bargon, J

    2001-01-29

    Starting from the binuclear complex [RhCl(NBD)]2 (NBD = 2,5-norbornadiene) in the presence of the phosphines L = PMe3, PMe2Ph, PMePh2, PEt3, PEt2Ph, PEtPh2, or P(n-butyl)3, various mononuclear dihydrides of the type Rh(H)2CIL3, i.e., those of the homogeneous hydrogenation catalysts RhCIL3, have been obtained upon addition of parahydrogen, and their 1H NMR spectra have been investigated using parahydrogen-induced polarization (PHIP). Furthermore, the two binuclear complexes (H)(Cl)Rh(PMe3)2(mu-Cl)(mu-H)Rh(PMe3) and (H)(Cl)Rh(PMe2Ph)2(mu-Cl)(mu-H)Rh(PMe2Ph) have been detected and characterized by means of this in situ NMR method. Analogous complexes with trifluoroacetate instead of chloride, i.e., Rh(H)2(CF3COO)L3, have been generated in situ starting from Rh(NBD)(acac) in the presence of trifluoroacetic acid in combination with the phosphines L = PPh3, PEt2Ph, PEt3, and P(n-butyl)3, and their 1H NMR parameters have been determined. PMID:11209612

  6. Chiral Selective Chemistry Induced by Natural Selection of Spin-Polarized Electrons.

    PubMed

    Rosenberg, Richard A; Mishra, Debabrata; Naaman, Ron

    2015-06-15

    The search to understand the origin of homochirality in nature has been ongoing since the time of Pasteur. Previous work has shown that DNA can act as a spin filter for low-energy electrons and that spin-polarized secondary electrons produced by X-ray irradiation of a magnetic substrate can induce chiral selective chemistry. In the present work it is demonstrated that secondary electrons from a substrate that are transmitted through a chiral overlayer cause enantiomeric selective chemistry in an adsorbed adlayer. We determine the quantum yields (QYs) for dissociation of (R)- or (S)-epichlorohydrin adsorbed on a chiral self-assembled layer of DNA on gold and on bare gold (for control). The results show that there is a significant difference in the QYs between the two enantiomers when adsorbed on DNA, but none when they are adsorbed on bare Au. We propose that the effect results from natural spin filtering effects cause by the chiral monolayer. PMID:25950284

  7. Chloroplasts do not have a polarity for light-induced accumulation movement.

    PubMed

    Tsuboi, Hidenori; Yamashita, Hiroko; Wada, Masamitsu

    2009-01-01

    Chloroplast photorelocation movement in green plants is generally mediated by blue light. However, in cryptogam plants, including ferns, mosses, and algae, both red light and blue light are effective. Although the photoreceptors required for this phenomenon have been identified, the mechanisms underlying this movement response are not yet known. In order to analyze this response in more detail, chloroplast movement was induced in dark-adapted Adiantum capillus-veneris gametophyte cells by partial cell irradiation with a microbeam of red and/or blue light. In each case, chloroplasts were found to move toward the microbeam-irradiated area. A second microbeam was also applied to the cell at a separate location before the chloroplasts had reached the destination of the first microbeam. Under these conditions, chloroplasts were found to change their direction of movement without turning and move toward the second microbeam-irradiated area after a lag time of a few minutes. These findings indicate that chloroplasts can move in any direction and do not exhibit a polarity for chloroplast accumulation movement. This phenomenon was analyzed in detail in Adiantum and subsequently confirmed in Arabidopsis thaliana palisade cells. Interestingly, the lag time for direction change toward the second microbeam in Adiantum was longer in the red light than in the blue light. However, the reason for this discrepancy is not yet understood. PMID:19037581

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

    NASA Astrophysics Data System (ADS)

    Sharp, Kim A.; Madan, Bhupinder; Manas, Eric; Vanderkooi, Jane M.

    2001-01-01

    A combination of simulations and Fourier transform infrared spectroscopy was used to examine the effect of three ionic solutes (KCl, NaCl, and KSCN), the polar solute urea, and the osmolyte trimethylamine-N-oxide (TMAO) 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 mode to lower frequency. TMAO decreases the mean water-water H-bond angle in its first hydration shell, shifts the OH stretching mode frequency down, and shifting the HOH bending mode frequency up. Urea has no effect on the mean H-bond angle, OH stretch, and HOH bend frequencies. These results can be explained in terms of changes in the relative proportions of two H-bond angle populations: Ionic solutes increase the population of more distorted (larger angle) H bonds relative to the less distorted population, TMAO has the reverse effect, while urea does not affect the H-bond angle probability distribution. The negligible effect of urea on water structure supports the direct binding model for urea-induced protein denaturation.

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

    SciTech Connect

    Fujii, Masakazu, E-mail: masakazu731079@yahoo.co.jp [Department of Internal Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan)] [Department of Internal Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan); Inoguchi, Toyoshi, E-mail: toyoshi@intmed3.med.kyushu-u.ac.jp [Department of Internal Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan) [Department of Internal Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan); Innovation Center for Medical Redox Navigation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan); Batchuluun, Battsetseg, E-mail: battsetseg.batchuluun@gmail.com [Department of Internal Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan)] [Department of Internal Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan); Sugiyama, Naonobu, E-mail: nao1@intmed1.med.kyushu-u.ac.jp [Department of Medicine and Biosystemic Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan)] [Department of Medicine and Biosystemic Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan); Kobayashi, Kunihisa, E-mail: nihisak@fukuoka-u.ac.jp [Department of Endocrinology and Diabetes Mellitus, Fukuoka University Chikushi Hospital, 1-1-1 Zokumyoin, Chikushino, Fukuoka 818-8502 (Japan)] [Department of Endocrinology and Diabetes Mellitus, Fukuoka University Chikushi Hospital, 1-1-1 Zokumyoin, Chikushino, Fukuoka 818-8502 (Japan); Sonoda, Noriyuki, E-mail: noriyuki@intmed3.med.kyushu-u.ac.jp [Department of Internal Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan) [Department of Internal Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan); Innovation Center for Medical Redox Navigation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan); Takayanagi, Ryoichi, E-mail: takayana@intmed3.med.kyushu-u.ac.jp [Department of Internal Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan)] [Department of Internal Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582 (Japan)

    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.

  10. Extracellular DC electric fields induce nonuniform membrane polarization in rat hippocampal CA1 pyramidal neurons.

    PubMed

    Akiyama, Hiroki; Shimizu, Yuki; Miyakawa, Hiroyoshi; Inoue, Masashi

    2011-04-01

    Non-synaptic interactions among neurons via extracellular electric fields may play functional roles in the CNS. Previously in a study using voltage-sensitive dye imaging, we reported characteristic membrane polarization profiles in the CA1 region of hippocampal slices during exposure to extracellular DC fields: slow monophasic polarization in somatic region and biphasic polarization (fast polarization and following slow repolarization) in mid-dendritic region. Here, using optical imaging and patch-clamp recordings, we showed that CA1 pyramidal neurons indeed show the characteristic polarization in response to DC fields, and investigated the mechanism underlying the profiles. Both the monophasic and biphasic polarization could be fitted with a double exponential function. The ?s (ms) were 12.6±2.5 and 56.0±4.7 for the monophasic polarization, and 14.2±1.2 and 42.2±2.8 for the biphasic polarization. Based on our previous theoretical studies, we hypothesized that lower resistivity in the distal apical dendrites is responsible for generating the characteristic polarization profiles. We tested this hypothesis by removing the distal apical dendrites or by blocking ion channel-mediated conductance. Removal of distal dendrites caused drastic changes in the polarization profiles, e.g. biphasic polarization was damped. However, none of the blockers tested had a marked effect on the biphasic polarization. Our results demonstrate the importance of the apical dendrite for generating the characteristic polarization profiles, and suggest that voltage-activated conductance, including HCN channel-mediated conductance, had only minor contributions to these profiles. These findings provide a better understanding of how neurons in the CNS respond to extracellular electric fields. PMID:21295559

  11. 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.

  12. 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

  13. On the determination of polarization observables in proton-induced reactions using large-acceptance magnetic spectrometers

    NASA Astrophysics Data System (ADS)

    Hannen, V. M.; Bassini, R.; van den Berg, A. M.; Blasi, N.; De Frenne, D.; De Leo, R.; Ellinghaus, F.; Frekers, D.; Hagemann, M.; Harakeh, M. N.; Henderson, R.; Heyse, J.; de Huu, M. A.; Jacobs, E.; Krüsemann, B. A. M.; Rakers, S.; Schmidt, R.; Sohlbach, H.; Wörtche, H. J.

    2003-03-01

    For proton-induced reactions, a formalism is presented to determine polarization observables using a focal-plane polarimeter in combination with a large-acceptance spectrometer, where also the effect of the scattering in the non-dispersive plane of the spectrometer is taken into account. The inclusive proton-carbon analyzing power needed for the determination of spin observables was studied over a wide angular range and a new parameterization for this quantity was deduced.

  14. Mass dependence of fragment angular distributions in the fission of 232Th and 236U induced by polarized photons

    Microsoft Academic Search

    F. Steiper; Th. Frommhold; W. Henkel; A. Jung; U. Kneissl; R. Stock

    1993-01-01

    Near-barrier fission of 232Th and 236U induced by linearly polarized photons has been investigated. The experiments have been carried out at the ``off-axis'' bremsstrahlung facility of the Giessen 65 MeV electron linac. Fragment angular, mass and energy distributions have been measured simultaneously allowing the investigation of correlations between these fragment characteristics. A consistent assignment of the quantum numbers Jpi and

  15. Generation of elliptically polarized terahertz waves from laser-induced plasma with double helix electrodes.

    PubMed

    Lu, Xiaofei; Zhang, X-C

    2012-03-23

    By applying a helical electric field along a plasma region, a revolving electron current is formed along the plasma and an elliptically polarized far-field terahertz wave pattern is observed. The observed terahertz wave polarization reveals the remarkable role of velocity retardation between optical pulses and generated terahertz pulses in the generation process. Extensive simulations, including longitudinal propagation effects, are performed to clarify the mechanisms responsible for polarization control of air-plasma-based terahertz sources. PMID:22540584

  16. 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.

  17. 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...

  18. Mode-locking of fiber lasers induced by residual polarization dependent loss of cavity components

    Microsoft Academic Search

    X. Wu; D. Y. Tang; L. M. Zhao; H. Zhang

    2010-01-01

    We found experimentally that under strong pumping, mode locking could self-start in a fiber laser even without inserting a polarizer or a mode locker in the cavity. It was identified that the mode locking was caused by the large residual polarization dependent loss (PDL) of a cavity component. We have experimentally determined the strength of PDL in our fiber lasers.

  19. Experimental and theoretical investigation of a self-absorbed spectral line emitted from laser-induced plasmas

    SciTech Connect

    Ben Ahmed, Jalloul; Cowpe, John

    2010-06-20

    Using well-known expressions describing radiative transfer, we have established an expression predicting the spectral profile of a self-absorbed Ca{sup ++}393.4 nm emission line as emitted by a transient laser-induced plasma. In this approach, the plasma was approximated as comprising five distinct layers, each of thickness 0.5 mm, and each characterized by a unique uniform electron density, electron temperature, and optical depth. The validity of the theoretical model was confirmed by successful comparison with experimental data. Inhomogeneous laser-induced plasmas were produced on the surface of an aqueous CaCl2 (0.01 mol/l) solution using a frequency-doubled Nd:YAG laser. Optical emission spectra were collected in such a way as to allow for temporal and spatial diagnostics of the plasma plumes.

  20. The X-ray Spectrum and Spectral Energy Distribution of FIRST J155633.8+351758: a LoBAL Quasar with a Probable Polar Outflow

    E-print Network

    Berrington, Robert C; Gallagher, Sarah C; Ganguly, Rajib; Shang, Zhaohui; DiPompeo, Michael; Chatterjee, Ritaban; Lacy, Mark; Gregg, Michael D; Hall, Patrick B; Laurent-Muehleisen, S A

    2013-01-01

    We report the results of a new 60 ks Chandra X-ray Observatory Advanced CCD Imaging Spectrometer S-array (ACIS-S) observation of the reddened, radio-selected, highly polarized `FeLoBAL' quasar FIRST J1556+3517. We investigated a number of models of varied sophistication to fit the 531-photon spectrum. These models ranged from simple power laws to power laws absorbed by hydrogen gas in differing ionization states and degrees of partial covering. Preferred fits indicate that the intrinsic X-ray flux is consistent with that expected for quasars of similarly high luminosity, i.e., an intrinsic, dereddened and unabsorbed optical to X-ray spectral index of -1.7. We cannot tightly constrain the intrinsic X-ray power-law slope, but find indications that it is flat (photon index Gamma = 1.7 or flatter at a >99% confidence for a neutral hydrogen absorber model). Absorption is present, with a column density a few times 10^23 cm^-2, with both partially ionized models and partially covering neutral hydrogen models providi...

  1. 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 [Department of Physics, Lamar University, P.O. Box 10046, Beaumont, Texas 77710 (United States)

    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.

  2. Chlorine detection in cement with laser-induced breakdown spectroscopy in the infrared and ultraviolet spectral range

    NASA Astrophysics Data System (ADS)

    Gehlen, Christoph Dominic; Wiens, Eugen; Noll, Reinhard; Wilsch, Gerd; Reichling, Kenji

    2009-10-01

    A significant parameter to monitor the status of concrete buildings like bridges or parking garages is the determination of the depth profile of the chlorine concentration below the exposed concrete surface. This information is required to define the needed volume of restoration for a construction. Conventional methods like wet chemical analysis are time- and cost-intensive so an alternative method is developed using laser-induced breakdown spectroscopy (LIBS). The idea is to deploy LIBS to analyze drill cores by scanning the sample surface with laser pulses. Chlorine spectral lines in the infrared (IR) and ultraviolet (UV)-range were studied for chlorine detection in hydrated cement samples. The excitation energies of these spectral lines are above 9.2 eV. Hence high plasma temperatures and pulse energies in the range of some hundred millijoules are needed to induce sufficient line intensity levels at the required working distance. To further increase the line intensity and to lower the detection limit (LOD) of chlorine a measuring chamber is used where different ambient pressures and gases can be chosen for the measurements. The influences on the line intensity for pressures between 5 mbar and 400 mbar using helium as process gas and the influence of different laser burst modi like single and collinear double pulses are investigated. For the first time a LOD according to DIN 32 645 of 0.1 mass% was achieved for chlorine in hydrated cement using the UV line 134.72 nm.

  3. Exercise-induced enhancement of insulin sensitivity is associated with accumulation of M2-polarized macrophages in mouse skeletal muscle.

    PubMed

    Ikeda, Shin-ichi; Tamura, Yoshifumi; Kakehi, Saori; Takeno, Kageumi; Kawaguchi, Minako; Watanabe, Takahiro; Sato, Fumihiko; Ogihara, Takeshi; Kanazawa, Akio; Fujitani, Yoshio; Kawamori, Ryuzo; Watada, Hirotaka

    2013-11-01

    Exercise enhances insulin sensitivity in skeletal muscle, but the underlying mechanism remains obscure. Recent data suggest that alternatively activated M2 macrophages enhance insulin sensitivity in insulin target organs such as adipose tissue and liver. Therefore, the aim of this study was to determine the role of anti-inflammatory M2 macrophages in exercise-induced enhancement of insulin sensitivity in skeletal muscle. C57BL6J mice underwent a single bout of treadmill running (20 m/min, 90 min). Twenty-four hours later, ex vivo insulin-stimulated 2-deoxy glucose uptake was found to be increased in plantaris muscle. This change was associated with increased number of CD163-expressing macrophages (i.e. M2-polarized macrophages) in skeletal muscle. Systemic depletion of macrophages by pretreatment of mice with clodronate-containing liposome abrogated both CD163-positive macrophage accumulation in skeletal muscle as well as the enhancement of insulin sensitivity after exercise, without affecting insulin-induced phosphorylation of Akt and AS160 or exercise-induced GLUT4 expression. These results suggest that accumulation of M2-polarized macrophages is involved in exercise-induced enhancement of insulin sensitivity in mouse skeletal muscle, independently of the phosphorylation of Akt and AS160 and expression of GLUT4. PMID:24120496

  4. The Spectral Dependence for UVA-Induced Cumulative Damage in Human Skin

    Microsoft Academic Search

    Robert Lavker; Kays Kaidbey

    1997-01-01

    The wavelength dependence for UVA-induced cumulative damage was investigated in human skin. Epidermal changes (stratum corneum thickening, viable epidermal thickening sunburn cell production), as well as dermal alterations (lysozyme deposition, inflammation), were used as indices of cumulative photoperturbation. UVA wavelengths between 320 lint and 345 nm were more effective than longer wavelengths (360-400 nm) in inducing viable epidermal thickening. Similarly,

  5. Growth-induced polarity formation in solid solutions of organic molecules: Markov mean-field model and Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Wüst, Thomas; Hulliger, Jürg

    2005-02-01

    A layer-by-layer growth model is presented for the theoretical investigation of growth-induced polarity formation in solid solutions H1-XGX of polar (H) and nonpolar (G) molecules (X: molar fraction of G molecules in the solid, 0polarity results from a combined effect of orientational selectivity by H and G molecules with respect to the alignment of the dipoles of H molecules and miscibility between the two components. Even though both native structures (H,G) may be centrosymmetric, polarity can arise just from the admixture of G molecules in the H crystal upon growth. An overview of possible phenomena is given by random selection of molecular interaction energies within an assumed but realistic energy range. The analytical approach describes sufficiently basic phenomena and is in good agreement with simulations. High probabilities for significant vectorial alignment of H molecules are found for low (X?0.2) and high (X?0.8) fractions of G molecules, respectively, as well as for ordered HG compounds (X=0.5).

  6. Spectral hole burning and fluorescence in femtosecond laser induced Sm 2+-doped glasses

    Microsoft Academic Search

    Gil Jae Park; Tomokatsu Hayakawa; Masayuki Nogami

    2004-01-01

    The femtosecond laser was used to irradiate sol–gel derived Sm3+-doped Al2O3–SiO2 glasses, in which the Sm3+ was reduced into Sm2+ ions. The fluorescence line narrowing was applied to investigate the coordination sphere of the Sm2+ ion. The spectral hole burning was performed on 7F0?5D0 transition of the Sm2+. The depth and width of the burnt holes were ?27% and ?4cm?1

  7. Coherent Polarization Control of Terahertz Waves Generated from Two-Color Laser-Induced Gas Plasma

    SciTech Connect

    Dai Jianming; Karpowicz, Nicholas; Zhang, X.-C. [Center for Terahertz Research, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2009-07-10

    Electrons ionized from an atom or molecule by circularly or elliptically polarized femtosecond omega and 2omega pulses exhibit different trajectory orientations as the relative phase between the two pulses changes. Macroscopically, the polarization of the terahertz wave emitted during the ionization process was found to be coherently controllable through the optical phase. This new finding can be completely reproduced by numerical simulation and may enable fast terahertz wave modulation and coherent control of nonlinear responses excited by intense terahertz waves with controllable polarization.

  8. Pressure-induced polar phases in relaxor multiferroic PbFe0.5Nb0.5O3

    NASA Astrophysics Data System (ADS)

    Kozlenko, D. P.; Kichanov, S. E.; Lukin, E. V.; Dang, N. T.; Dubrovinsky, L. S.; Liermann, H.-P.; Morgenroth, W.; Kamynin, A. A.; Gridnev, S. A.; Savenko, B. N.

    2014-05-01

    The structural, magnetic, and vibrational properties of PbFe0.5Nb0.5O3 relaxor multiferroic have been studied by means of x-ray, neutron powder diffraction, and Raman spectroscopy at pressures up to 30 GPa. Two successive structural phase transitions from the initial R3m polar phase to Cm and Pm monoclinic polar phases were observed at P = 5.5 and 8.5 GPa. Both transitions are associated with anomalies in pressure behavior of several stretching and bending modes of oxygen octahedra as well as Fe/Nb localized vibrational modes. The G-type antiferromagnetic order remains stable upon compression up to 6.4 GPa, assuming possible multiferroic properties of pressure-induced phases. The Néel temperature increases with a pressure coefficient (1/TN)dTN/dP=0.012 GPa-1. The observed pressure-induced phenomena in PbFe0.5Nb0.5O3 are in drastic contrast with conventional multiferroics, exhibiting a general tendency towards a suppression of polar phases and/or magnetoelectric coupling under pressure.

  9. Defect-induced Nonpolar-to-polar Transition at the Surface of Chalcopyrite Semiconductors

    SciTech Connect

    Jaffe, John E.; Zunger, Alex

    2001-12-15

    In contrast to zinc-blende semiconductors, where the nonpolar (110) surface has the lowest energy, our first-principles calculations on the chalcopyrite semiconductor CuInSe2 reveal that facets terminated by the (112)-cation and (-1-1-2)-Se polar surfaces are lower in energy than the unfaceted (110) plane, despite the resulting increased surface area. This explains the hitherto puzzling existence of polar microfacets on nominally nonpolar (110) chalcopyrite surfaces. The extraordinary stability of these polar facets originates from the effective neutralization of surface charge by low-energy ordered CuIn antisite or Cu vacancy surface defects, while the relaxed but defect-free (112) surface is metallic and much higher in energy. We explain the low carrier density of the observed faceted surface in terms of autocompensation between opposite-polarity facets.

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

    E-print Network

    Meng, Cong

    2013-05-01

    -mediated regulation of adipose tissue inflammation and insulin resistance were then confirmed by transplantation analysis. Moreover, using bone marrow-derived macrophages, we demonstrated that miR-223 is a novel regulator of macrophage polarization, which suppresses...

  11. Interface-induced modulation of charge and polarization in thin film Fe(3)O(4).

    PubMed

    Tian, He; Verbeeck, Jo; Brück, Sebastian; Paul, Markus; Kufer, Dominik; Sing, Michael; Claessen, Ralph; Tendeloo, Gustaaf Van

    2014-01-22

    Charge and polarization modulations in Fe3 O4 are controlled by taking advantage of interfacial strain effects. The feasibility of oxidation state control by strain modification is demonstrated and it is shown that this approach offers a stable configuration at room temperature. Direct evidence of how a local strain field changes the atomic coordination and introduces atomic displacements leading to polarization of Fe ions is presented. PMID:24167041

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

    SciTech Connect

    Sciamanna, M. [Supelec, Laboratoire Materiaux Optiques, Photonique et Systemes (LMOPS), CNRS UMR-7132, Unite de Recherche Commune Supelec et Universite de Metz, 2 Rue Edouard Belin, F-57070 Metz (France); Panajotov, K. [Department of Applied Physics and Photonics (TW-TONA), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels (Belgium)

    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.

  13. Patterns of and mechanisms for shock-induced polarization in the heart: a bidomain analysis

    Microsoft Academic Search

    Emilia Entcheva; N. A. Trayanov; Fritz J. Claydon

    1999-01-01

    This paper examines the combined action of cardiac fiber curvature and transmural fiber rotation in polarizing the myocardium under the conditions of a strong electrical shock. The study utilizes a three-dimensional finite element model and the continuous bidomain representation of cardiac tissue to model steady-state polarization resulting from a defibrillation-strength uniform applied field. Fiber architecture is incorporated in the model

  14. Beam-Induced Nuclear Depolarization in a Gaseous Polarized-Hydrogen Target

    Microsoft Academic Search

    K. Ackerstaff; A. Airapetian; N. Akopov; M. Amarian; E. C. Aschenauer; H. Avakian; R. Avakian; A. Avetissian; B. Bains; C. Baumgarten; M. Beckmann; J. E. Belz; Th. Benisch; S. Bernreuther; N. Bianchi; J. Blouw; H. Böttcher; A. Borissov; J. Brack; S. Brauksiepe; B. Braun; B. Bray; St. Brons; W. Brückner; A. Brüll; E. E. Bruins; H. J. Bulten; R. V. Cadman; G. P. Capitani; P. Carter; P. Chumney; E. Cisbani; G. R. Court; P. F. Dalpiaz; E. de Sanctis; D. de Schepper; E. Devitsin; P. K. de Witt Huberts; P. di Nezza; M. Düren; A. Dvoredsky; G. Elbakian; A. Fantoni; A. Fechtchenko; M. Ferstl; D. Fick; K. Fiedler; B. W. Filippone; H. Fischer; B. Fox; J. Franz; S. Frabetti; S. Frullani; M.-A. Funk; N. D. Gagunashvili; H. Gao; Y. Gärber; F. Garibaldi; G. Gavrilov; P. Geiger; V. Gharibyan; V. Giordjian; A. Golendukhin; G. Graw; O. Grebeniouk; P. W. Green; L. G. Greeniaus; C. Grosshauser; A. Gute; W. Haeberli; J.-O. Hansen; D. Hasch; O. Häusser; R. Henderson; Th. Henkes; M. Henoch; R. Hertenberger; Y. Holler; R. J. Holt; W. Hoprich; H. Ihssen; M. Iodice; A. Izotov; H. E. Jackson; A. Jgoun; R. Kaiser; E. Kinney; A. Kisselev; P. Kitching; H. Kobayashi; N. Koch; K. Königsmann; M. Kolstein; H. Kolster; V. Korotkov; W. Korsch; V. Kozlov; L. H. Kramer; V. G. Krivokhijine; G. Kyle; W. Lachnit; W. Lorenzon; N. C. Makins; S. I. Manaenkov; F. K. Martens; J. W. Martin; F. Masoli; A. Mateos; M. McAndrew; K. McIlhany; R. D. McKeown; F. Meissner; A. Metz; N. Meyners; O. Mikloukho; C. A. Miller; M. A. Miller; R. Milner; V. Mitsyn; A. Most; R. Mozzetti; V. Muccifora; A. Nagaitsev; Y. Naryshkin; A. M. Nathan; F. Neunreither; M. Niczyporuk; W.-D. Nowak; M. Nupieri; H. Ogami; T. G. O'Neill; B. R. Owen; V. Papavassiliou; S. F. Pate; M. Pitt; S. Potashov; D. H. Potterveld; G. Rakness; A. Reali; R. Redwine; A. R. Reolon; R. Ristinen; K. Rith; H. Roloff; P. Rossi; S. Rudnitsky; M. Ruh; D. Ryckbosch; Y. Sakemi; I. Savin; F. Schmidt; H. Schmitt; G. Schnell; K. P. Schüler; A. Schwind; T.-A. Shibata; T. Shin; V. Shutov; C. Simani; A. Simon; K. Sinram; P. Slavich; J. Sowinski; M. Spengos; E. Steffens; J. Stenger; J. Stewart; F. Stock; U. Stoesslein; M. Sutter; H. Tallini; S. Taroian; A. Terkulov; B. Tipton; M. Tytgat; G. M. Urciuoli; J. J. van Hunen; R. van de Vyver; J. F. van den Brand; G. van der Steenhoven; M. C. Vetterli; M. Vincter; E. Volk; W. Wander; S. E. Williamson; T. Wise; K. Woller; S. Yoneyama; K. Zapfe-Düren; H. Zohrabian

    1999-01-01

    Spin-polarized atomic hydrogen is used as a gaseous polarized-proton target in high-energy and nuclear-physics experiments operating with internal beams in storage rings. When such beams are intense and bunched, this type of target can be depolarized by a resonant interaction with the transient magnetic field generated by the beam bunches. This effect has been studied with the HERA positron beam

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

    NASA Astrophysics Data System (ADS)

    Sciamanna, M.; Panajotov, K.

    2006-02-01

    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 , 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.

  16. Mode-locking of fiber lasers induced by residual polarization dependent loss of cavity components

    Microsoft Academic Search

    X. Wu; D. Y. Tang; L. M. Zhao; H. Zhang

    2010-01-01

    We found experimentally that under strong pumping, mode locking could self-start in a fiber laser even without inserting a\\u000a polarizer or a mode locker in the cavity. It was identified that the mode locking was caused by the large residual polarization\\u000a dependent loss (PDL) of a cavity component. We have experimentally determined the strength of PDL in our fiber lasers.

  17. N-single-helix photonic-metamaterial based broadband optical range circular polarizer by induced phase lags between helices.

    PubMed

    Behera, Saraswati; Joseph, Joby

    2015-02-10

    In this work, we have designed a photonic-metamaterial based broadband circular polarizer using N=4 phase-lagged aluminum single helices arranged in a square array as a unit cell. The effect of phase differences between the helices in an array on the optical performance of the structure is studied, and a comparative study is done with that of multi-intertwined helices. It is observed that the proposed metamaterial structure shows circular polarization sensitivity over a broad optical wavelength range (?450-900??nm), with improved optical performance in average extinction ratio and broad positive circular dichroism in comparison to multiple intertwined helices. The induced phase lag between the helices in a square-array based unit cell reduces the linear birefringence and leads to the recovery of circular space symmetry in the structure. PMID:25968042

  18. 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 [Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

    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)

  19. Ovarian cancer stem cells induce the M2 polarization of macrophages through the PPAR? and NF-?B pathways.

    PubMed

    Deng, Xinchao; Zhang, Ping; Liang, Tingting; Deng, Suye; Chen, Xiaojie; Zhu, Lin

    2015-08-01

    Increasing evidence suggests an association between cancer stem cells and the tumor microenvironment. Ovarian cancer stem cell (OCSC) factors can influence the tumor microenvironment and prognosis. However, the effects of OCSCs on macrophage M1/M2 polarization are not yet completely understood. In the present study, we evaluated the effects of OCSCs on macrophage M1/M2 polarization. In addition, we investigated whether the activation of the peroxisome proliferator-activated receptor ? (PPAR?)/nuclear factor-?B (NF-?B) pathway is involved in these effects, thus modulating the M1/M2 differentiation of monocytes into macrophages. The expression levels of markers of the M1 state, such as tumor necrosis factor (TNF)-?, inducible nitric oxide synthase (iNOS) and CD86, as well as those of markers of M2 activation, such as mannose receptor (MR), interleukin (IL)-10 and arginase-1 (Arg-1), were measured by RT-qPCR. We found that the OCSCs promoted the M2 polarization of Raw264.7 macrophages by upregulating the expression of MR, IL-10 and Arg-1, while the expression levels of M1 macrophages markers, including TNF-?, iNOS and CD86 were suppressed. In addition, treatment with OCSCs activated PPAR? and suppressed NF-?B in the Raw264.7 cells. Furthermore, the PPAR?, antagonist GW9662, attenuated the promoting effects of OCSCs on the M2 polarization of macrophages. To the best of our knowledge, the findings of the present study, provide the first evidence that OCSCs promote the M2 polarization of macrophages through the PPAR?/NF-?B pathway. PMID:26035689

  20. Preferential macrophage recruitment and polarization in LPS-induced animal model for COPD: noninvasive tracking using MRI.

    PubMed

    Al Faraj, Achraf; Sultana Shaik, Asma; Pureza, Mary Angeline; Alnafea, Mohammad; Halwani, Rabih

    2014-01-01

    Noninvasive imaging of macrophages activity has raised increasing interest for diagnosis of chronic obstructive respiratory diseases (COPD), which make them attractive vehicles to deliver contrast agents for diagnostic or drugs for therapeutic purposes. This study was designed to monitor and evaluate the migration of differently polarized M1 and M2 iron labeled macrophage subsets to the lung of a LPS-induced COPD animal model and to assess their polarization state once they have reached the inflammatory sites in the lung after intravenous injection. Ex vivo polarized bone marrow derived M1 or M2 macrophages were first efficiently and safely labeled with amine-modified PEGylated dextran-coated SPIO nanoparticles and without altering their polarization profile. Their biodistribution in abdominal organs and their homing to the site of inflammation in the lung was tracked for the first time using a free-breathing non-invasive MR imaging protocol on a 4.7T magnet after their intravenous administration. This imaging protocol was optimized to allow both detection of iron labeled macrophages and visualization of inflammation in the lung. M1 and M2 macrophages were successfully detected in the lung starting from 2 hours post injection with no variation in their migration profile. Quantification of cytokines release, analysis of surface membrane expression using flow cytometry and immunohistochemistry investigations confirmed the successful recruitment of injected iron labeled macrophages in the lung of COPD mice and revealed that even with a continuum switch in the polarization profile of M1 and M2 macrophages during the time course of inflammation a balanced number of macrophage subsets predominate. PMID:24598763

  1. Preferential Macrophage Recruitment and Polarization in LPS-Induced Animal Model for COPD: Noninvasive Tracking Using MRI

    PubMed Central

    Al Faraj, Achraf; Sultana Shaik, Asma; Pureza, Mary Angeline; Alnafea, Mohammad; Halwani, Rabih

    2014-01-01

    Noninvasive imaging of macrophages activity has raised increasing interest for diagnosis of chronic obstructive respiratory diseases (COPD), which make them attractive vehicles to deliver contrast agents for diagnostic or drugs for therapeutic purposes. This study was designed to monitor and evaluate the migration of differently polarized M1 and M2 iron labeled macrophage subsets to the lung of a LPS-induced COPD animal model and to assess their polarization state once they have reached the inflammatory sites in the lung after intravenous injection. Ex vivo polarized bone marrow derived M1 or M2 macrophages were first efficiently and safely labeled with amine-modified PEGylated dextran-coated SPIO nanoparticles and without altering their polarization profile. Their biodistribution in abdominal organs and their homing to the site of inflammation in the lung was tracked for the first time using a free-breathing non-invasive MR imaging protocol on a 4.7T magnet after their intravenous administration. This imaging protocol was optimized to allow both detection of iron labeled macrophages and visualization of inflammation in the lung. M1 and M2 macrophages were successfully detected in the lung starting from 2 hours post injection with no variation in their migration profile. Quantification of cytokines release, analysis of surface membrane expression using flow cytometry and immunohistochemistry investigations confirmed the successful recruitment of injected iron labeled macrophages in the lung of COPD mice and revealed that even with a continuum switch in the polarization profile of M1 and M2 macrophages during the time course of inflammation a balanced number of macrophage subsets predominate. PMID:24598763

  2. 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

  3. 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.

  4. Porphyromonas gingivalis Lipopolysaccharide Weakly Activates M1 and M2 Polarized Mouse Macrophages but Induces Inflammatory Cytokines

    PubMed Central

    Holden, James A.; Attard, Troy J.; Laughton, Katrina M.; Mansell, Ashley; O'Brien-Simpson, Neil M.

    2014-01-01

    Porphyromonas gingivalis is associated with chronic periodontitis, an inflammatory disease of the tooth's supporting tissues. Macrophages are important in chronic inflammatory conditions, infiltrating tissue and becoming polarized to an M1 or M2 phenotype. As responses to stimuli differ between these phenotypes, we investigated the effect of P. gingivalis lipopolysaccharide (LPS) on M1 and M2 macrophages. M1 and M2 polarized macrophages were produced from murine bone marrow macrophages (BMM?) primed with gamma interferon (IFN-?) or interleukin-4 (IL-4), respectively, and incubated with a low or high dose of P. gingivalis LPS or control TLR2 and TLR4 ligands. In M1-M?, the high dose of P. gingivalis LPS (10 ?g/ml) significantly increased the expression of CD40, CD86, inducible nitric oxide synthase, and nitric oxide secretion. The low dose of P. gingivalis LPS (10 ng/ml) did not induce costimulatory or antibacterial molecules but did increase the secretion of IL-1?, IL-6, IL-12p40, IL-12p70, and tumor necrosis factor alpha (TNF-?). P. gingivalis LPS marginally increased the expression of CD206 and YM-1, but it did enhance arginase expression by M2-M?. Furthermore, the secretion of the chemokines KC, RANTES, eotaxin, and MCP-1 from M1, M2, and nonpolarized M? was enhanced by P. gingivalis LPS. TLR2/4 knockout macrophages combined with the TLR activation assays indicated that TLR2 is the main activating receptor for P. gingivalis LPS and whole cells. In conclusion, although P. gingivalis LPS weakly activated M1-M? or M2-M? compared to control TLR ligands, it induced the secretion of inflammatory cytokines, particularly TNF-? from M1-M? and IL-10 from M2-M?, as well as chemotactic chemokines from polarized macrophages. PMID:25047849

  5. ?? 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

  6. Scaling depth-induced wave-breaking in two-dimensional spectral wave models

    NASA Astrophysics Data System (ADS)

    Salmon, J. E.; Holthuijsen, L. H.; Zijlema, M.; van Vledder, G. Ph.; Pietrzak, J. D.

    2015-03-01

    Wave breaking in shallow water is still poorly understood and needs to be better parameterized in 2D spectral wave models. Significant wave heights over horizontal bathymetries are typically under-predicted in locally generated wave conditions and over-predicted in non-locally generated conditions. A joint scaling dependent on both local bottom slope and normalized wave number is presented and is shown to resolve these issues. Compared to the 12 wave breaking parameterizations considered in this study, this joint scaling demonstrates significant improvements, up to ?50% error reduction, over 1D horizontal bathymetries for both locally and non-locally generated waves. In order to account for the inherent differences between uni-directional (1D) and directionally spread (2D) wave conditions, an extension of the wave breaking dissipation models is presented. By including the effects of wave directionality, rms-errors for the significant wave height are reduced for the best performing parameterizations in conditions with strong directional spreading. With this extension, our joint scaling improves modeling skill for significant wave heights over a verification data set of 11 different 1D laboratory bathymetries, 3 shallow lakes and 4 coastal sites. The corresponding averaged normalized rms-error for significant wave height in the 2D cases varied between 8% and 27%. In comparison, using the default setting with a constant scaling, as used in most presently operating 2D spectral wave models, gave equivalent errors between 15% and 38%.

  7. 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.

  8. Measurements and polarization analysis of radio pulses from cosmic-ray-induced air showers at the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Fraenkel, Daniël; Pierre Auger Collaboration

    2013-02-01

    The Auger Engineering Radio Array (AERA) is designed to study the radio emissions from extensive air showers at the Pierre Auger Observatory. The array currently consists of a grid of 23 autonomous radio detector stations that measure the radio emissions from cosmic-ray-induced air showers since April 2011. The array is still under construction and is planned to be extended to 160 stations. The new detection technique provides an augmentation of the existing detectors, improves the sensitivity of the observatory and sheds new light on the shower physics. An analysis of the emission processes based on the polarization of the radio pulses is presented.

  9. Transition probabilities of Ni II spectral lines measured by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    Experimental transition probabilities for 48 lines of the transition array 3d84s-3d84p of Ni II have been obtained by laser induced breakdown spectroscopy. A procedure based on the measurement and fitting of curves of growth that avoids the systematic error due to self-absorption has been used. The laser induced plasmas are generated using a Nd:YAG laser from a set of Ni-Cu alloys with different Ni concentrations. A comparison is made of our results with the available experimental and theoretical values.

  10. Use of the vacuum ultraviolet spectral region for laser-induced breakdown spectroscopy-based Martian geology and exploration

    NASA Astrophysics Data System (ADS)

    Radziemski, Leon; Cremers, David A.; Benelli, Katharine; Khoo, Cynthia; Harris, Ronny D.

    2005-02-01

    Several elements important to planetary geology (e.g. Br, C, Cl, P, S) and the human exploration of Mars (e.g. toxic elements such as As) have strong emission lines in the purge and vacuum ultraviolet (VUV) spectral region (100 200 nm). This spectral region has not been extensively studied for space applications using geological samples. We studied emissions from the laser-induced breakdown spectroscopy (LIBS) plasma in this region using a sample chamber filled with 7 torr (930 Pa) of CO2 to simulate the Martian atmosphere. Pressures down to 0.02 torr were also used to evaluate the effect of the residual CO2 on the spectra and to begin investigating the use of VUV-LIBS for airless bodies such as asteroids and the Moon. Spectra were recorded using a 0.3-m vacuum spectrometer with an intensified CCD (ICCD) camera. The effects of time delay and laser energy on LIBS detection at reduced pressure were examined. The effect of ambient CO2 on the detection of C in soil was also evaluated. Lines useful for the spectrochemical analysis of As, Br, C, Cl, P, and S were determined and calibration curves were prepared for these elements. Although LIBS is being developed for stand-off analysis at many meters distance, the experiments reported here were aimed at in-situ (close-up) analysis.

  11. 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.

  12. 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.

  13. Mechanisms of CDC-42 activation during contact-induced cell polarization

    PubMed Central

    Chan, Emily; Nance, Jeremy

    2013-01-01

    Summary Polarization of early embryos provides a foundation to execute essential patterning and morphogenetic events. In Caenorhabditis elegans, cell contacts polarize early embryos along their radial axis by excluding the cortical polarity protein PAR-6 from sites of cell contact, thereby restricting PAR-6 to contact-free cell surfaces. Radial polarization requires the cortically enriched Rho GTPase CDC-42, which in its active form recruits PAR-6 through direct binding. The Rho GTPase activating protein (RhoGAP) PAC-1, which localizes specifically to cell contacts, triggers radial polarization by inactivating CDC-42 at these sites. The mechanisms responsible for activating CDC-42 at contact-free surfaces are unknown. Here, in an overexpression screen of Rho guanine nucleotide exchange factors (RhoGEFs), which can activate Rho GTPases, we identify CGEF-1 and ECT-2 as RhoGEFs that act through CDC-42 to recruit PAR-6 to the cortex. We show that ECT-2 and CGEF-1 localize to the cell surface and that removing their activity causes a reduction in levels of cortical PAR-6. Through a structure–function analysis, we show that the tandem DH-PH domains of CGEF-1 and ECT-2 are sufficient for GEF activity, but that regions outside of these domains target each protein to the cell surface. Finally, we provide evidence suggesting that the N-terminal region of ECT-2 may direct its in vivo preference for CDC-42 over another known target, the Rho GTPase RHO-1. We propose that radial polarization results from a competition between RhoGEFs, which activate CDC-42 throughout the cortex, and the RhoGAP PAC-1, which inactivates CDC-42 at cell contacts. PMID:23424200

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

    SciTech Connect

    Taichenachev, A. V.; Yudin, V. I.; Oates, C. W. [Institute of Laser Physics SB RAS, Novosibirsk 630090 (Russian Federation) and Novosibirsk State University, Novosibirsk 630090 (Russian Federation); National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)

    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.

  15. Coupling of Pressure-Induced Structural Shifts to Spectral Changes in a Yellow Fluorescent Protein

    E-print Network

    Gruner, Sol M.

    -ray diffraction analysis of pressure-induced structural changes in the Aequorea yellow fluorescent protein Citrine of the Citrine chromophore. This study describes the structural linkages in Citrine that are responsible for the local reorientation of the chromophore. The deformation of the Citrine chromophore is actuated

  16. 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.

  17. 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.

  18. Magnetically-induced circular-polarization-dependent loss of magneto-optic fiber Bragg gratings with linear birefringence

    NASA Astrophysics Data System (ADS)

    Wu, Baojian; Wen, Feng; Qiu, Kun; Han, Rui; Lu, Xin

    2013-06-01

    The concept of magnetically-induced circular-polarization-dependent loss (MCDL) for magneto-optic fiber Bragg gratings (MFBGs) is introduced. The magnetic field dependency of MCDL for linearly birefringent MFBGs is simulated by use of the equivalent theoretical model given in the paper. This model is mainly composed of an elliptical polarization extractor and a couple of isotropic fiber Bragg gratings (FBGs) with different effective refractive indices. It is shown by simulation that, (1) when the magnetooptic-to-grating coupling coefficient ratio is less than 0.1, the peak MCDL is proportional to applied magnetic induction; (2) the MCDL method is more suitable for the magnetic field measurement than the conventional polarization dependent loss (PDL) for the linearly birefringent MFBGs. As an example, the MCDL of an erbium-doped MFBG (Er-MFBG) is measured and the experimental data are in agreement with the theoretical results. The effective Verdet constant for the Er-MFBG is about -11 rad/(T·m) and the peak MCDL is up to 1 dB at 1.15 T.

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

    NASA Astrophysics Data System (ADS)

    Ye, Tianyu; Mani, Ramesh; Wegscheider, Werner

    2015-03-01

    Microwave radiation-induced magnetoresistance oscillations (MRIMRO) are huge photo-excited oscillations in the resistance in a transverse magnetic field, which are sensitive to different aspects of the microwave radiation such as the microwave frequency, microwave power, and linear polarization angle. As a consequence, MRIMROs are potentially interesting for sensing applications. In order to better understand the role of the microwave power and the linear polarization angle in MRIMROs, the role of these variables have been more carefully examined in this experimental study. Thus, the diagonal resistance Rxx was measured as a function of both the microwave power (P) and the linear polarization angle (?) at the MRIMRO extrema. Color contour plots reveal that Rxx vs ? follows a cosine square function at relatively low microwave power with systematic lineshape distortions occurring with increasing microwave power. Here, we demonstrate that the non-linearity of Rxxvs P relation is the main factor that influences the lineshape distortion from the sinusoidal Rxx vs ? relation observed at low P. Magnetotransport measurements by Ye at GSU were supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Material Sciences and Engineering Division under DE-SC0001762. Additional support was provided by the ARO under W911NF-07-01-015.

  20. Mechanically induced long-period gratings in polarization maintaining photonic crystal fiber with a supercontinuum generation source

    NASA Astrophysics Data System (ADS)

    Huerta-Mascotte, E.; Mata-Chávez, R. I.; Estudillo-Ayala, J. M.; Guzman-Chavez, A. D.; Cano-Contreras, M.; Trejo-Durán, M.; Rojas-Laguna, R.; Vargas-Rodriguez, E.; Guryev, I. V.

    2014-09-01

    We present the results from the fabrication and characterization of mechanically induced long period fiber gratings in polarization maintaining photonic crystal fiber (PM-PCF). A supercontinuum source in the range of 600nm - 1700nm is used. This source is generated using a micro-chip laser at 1064nm and a single mode fiber. A long-period grating is induced over 40mm long unjacketed PCF using a V-grooved aluminum plate. External pressure is gradually applied with a metal screw and a torque meter and a loss dip with resonance wavelength is observed. Low insertion losses are depicted from (1-3) dBm with a bandwidth of about 30nm and a loss dip around 15dBm. Sensitivity for this preliminary work is found at 27 dB/Lb. Several applications are potentially possible with the optimization of the transmission spectrum controlled by applied pressure.

  1. Application of parahydrogen induced polarization techniques in NMR spectroscopy and imaging.

    PubMed

    Duckett, Simon B; Mewis, Ryan E

    2012-08-21

    Magnetic resonance provides a versatile platform that allows scientists to examine many different types of phenomena. However, the sensitivity of both NMR spectroscopy and MRI is low because the detected signal strength depends on the population difference that exists between the probed nuclear spin states in a magnetic field. This population difference increases with the strength of the interacting magnetic field and decreases with measurement temperature. In contrast, hyperpolarization methods that chemically introduce parahydrogen (a spin isomer of hydrogen with antiparallel spins that form a singlet) based on the traditional parahydrogen induced polarization (PHIP) approach tackle this sensitivity problem with dramatic results. In recent years, the potential of this method for MRI has been recognized, and its impact on medical diagnosis is starting to be realized. In this Account, we describe the use of parahydrogen to hyperpolarize a suitable substrate. This process normally involves the introduction of a molecule of parahydrogen into a target to create large population differences between nuclear spin states. The reaction of parahydrogen breaks the original magnetic symmetry and overcomes the selection rules that prevent both NMR observation and parahydrogen/orthohydrogen interconversion, yielding access to the normally invisible hyperpolarization associated with parahydrogen. Therefore the NMR or MRI measurement delivers a marked increase in the detected signal strength over the normal Boltzmann-population derived result. Consequently, measurements can be made which would otherwise be impossible. This approach was pioneered by Weitekamp, Bargon, and Eisenberg, in the late 1980s. Since 1993, we have used this technique in York to study reaction mechanisms and to characterize normally invisible inorganic species. We also describe signal amplification by reversible exchange (SABRE), an alternative route to sensitize molecules without directly incorporating a molecule of parahydrogen. This approach widens the applicability of PHIP methods and the range of materials that can be hyperpolarized. In this Account we describe our parahydrogen studies in York over the last 20 years and place them in a wider context. We describe the characterization of organometallic reaction intermediates including those involved in catalytic reactions, either with or without hydride ligands. The collection of spectroscopic and kinetic data with rapid inverse detection methods has proved to be particularly informative. We can see enhanced signals for the organic products of catalytic reactions that are linked directly to the catalytic intermediates that form them. This method can therefore prove unequivocally that a specific metal complex is involved in a catalytic cycle, thus pinpointing the true route to catalysis. Studies where a pure nuclear spin state is detected show that it is possible to detect all of the analyte molecules present in a sample using NMR. In addition, we describe methods that achieve the selective detection of these enhanced signals, when set against a strong NMR background such as that of water. PMID:22452702

  2. Dopamine induces growth inhibition and vascular normalization through reprogramming M2-polarized macrophages in rat C6 glioma.

    PubMed

    Qin, Tian; Wang, Chenlong; Chen, Xuewei; Duan, Chenfan; Zhang, Xiaoyan; Zhang, Jing; Chai, Hongyan; Tang, Tian; Chen, Honglei; Yue, Jiang; Li, Ying; Yang, Jing

    2015-07-15

    Dopamine (DA), a monoamine catecholamine neurotransmitter with antiangiogenic activity, stabilizes tumor vessels in colon, prostate and ovarian cancers, thus increases chemotherapeutic efficacy. Here, in the rat C6 glioma models, we investigated the vascular normalization effects of DA and its mechanisms of action. DA (25, 50mg/kg) inhibited tumor growth, while a precursor of DA (levodopa) prolonged the survival time of rats bearing orthotopic C6 glioma. DA improved tumor perfusion, with significant effects from day 3, and a higher level at days 5 to 7. In addition, DA decreased microvessel density and hypoxia-inducible factor-1? expression in tumor tissues, while increasing the coverage of pericyte. Conversely, an antagonist of dopamine receptor 2 (DR2) (eticlopride) but not DR1 (butaclamol) abrogated DA-induced tumor regression and vascular normalization. Furthermore, DA improved the delivery and efficacy of temozolomide therapy. Importantly, DA increased representative M1 markers (iNOS, CXCL9, etc.), while decreasing M2 markers (CD206, arginase-1, etc.). Depletion of macrophages by clodronate or zoledronic acid attenuated the effects of DA. Notably, DA treatment induced M2-to-M1 polarization in RAW264.7 cells and mouse peritoneal macrophages, and enhanced the migration of pericyte-like cells (10T1/2), which was reversed by eticlopride or DR2-siRNA. Such changes were accompanied by the downregulation of VEGF/VEGFR2 signaling. In summary, DA induces growth inhibition and vascular normalization through reprogramming M2-polarized macrophages. Thus, targeting the tumor microvasculature by DA represents a promising strategy for human glioma therapy. PMID:25818600

  3. Dynamical heating of the polar summer mesopause induced by solar proton events

    Microsoft Academic Search

    E. Becker; C. von Savigny

    2010-01-01

    The observed heating of the polar summer mesopause during and after a solar proton event (SPE) is interpreted as a large-scale dynamical response to the temporary diabatic cooling in the lower mesosphere above the summer pole that results from the temporary ozone depletion during an SPE. Our method is based on time slice sensitivity experiments performed with a mechanistic general

  4. Simulation of streamers propagating along helium jets in ambient air: Polarity-induced effects

    SciTech Connect

    Naidis, G. V. [Joint Institute for High Temperatures, RAS, 125412 Moscow (Russian Federation)

    2011-04-04

    Results of modeling of streamer propagation along helium jets for both positive and negative polarities of applied voltage are presented. Obtained patterns of streamer dynamics and structure in these two cases are similar to those observed in experiments with plasma jets.

  5. Polarization selective computer-generated holograms realized in glass by femtosecond laser induced nanogratings

    Microsoft Academic Search

    Wenjian Cai; Ariel R. Libertun; Rafael Piestun

    2006-01-01

    We demonstrate polarization selective computer-generated holograms (PSCGH) for visible light operation fabricated in glass by a femtosecond laser. For this purpose we create arrays of tailored microwaveplates by controlling the laser formation of nanogratings embedded in fused silica. A birefringent cell-oriented encoding method adapted to the characteristics of the physical writing process is proposed and implemented. According to this method,

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

    E-print Network

    Sharp, Kim

    ionic solutes KCl, NaCl, and KSCN , the polar solute urea, and the osmolyte trimethylamine-N-oxide TMAO mode to lower frequency. TMAO decreases the mean water­water H-bond angle in its first hydration shell the population of more distorted larger angle H bonds relative to the less distorted population, TMAO has

  7. 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.

  8. Assessment of laser photobiomodulation and polarized light on the healing of cutaneous wounds on euthyroid and hypothyroid induced rats

    NASA Astrophysics Data System (ADS)

    Ramalho, Luciana Maria Pedreira; Weyll, Barbara Mayoral Pedroso; da Costa Lino, Maíra Dória M.; Ramalho, Maria Jose Pedreira; Barbosa Pinheiro, Antonio Luis

    2010-02-01

    The aim of this study was to assess the influence of low-level laser therapy (LLLT) or polarized light (PL) in cutaneous wound healing of hypothyroid rats at dosages of 20 or 40J/cm2. Bioestimulatory effects of Laser radiation and Polarized light are recognized alternative therapies to improve healing on systemic disease patients, but their usefulness in the improvement of hypothyroidism healing impairment is uncertain till date. Forty Wistar rats were used in this study. Hypothyroidism was propylthiouracil- induced. Standard excisional cutaneous wounds were created without suturing and LLLT (?660nm, 30mW, ? 3mm) or PL (? 400-2000nm, 40mW, ? 10mm) was applied every 48 hours up to seven days on experimental groups. The rats were killed on the eighth day when wound contraction was assessed. The healing features were evaluated by light microscopy (H/E and Sirius Red). The cutaneous wounds of hypothyroid rats showed delayed healing process characterized by reduced thickness of epithelial layers, incipient formation of disorganized collagen fibers and wound contraction to a lesser extent (FISHER, p=0.0276), when compared to the euthyroid group. The use of both the Laser and Polarized Light on hypothyroid rats increased the amount of fibroblasts and the thickness of collagen fibers, especially on the L 20J/cm2 group. Euthyroid rats have still demonstrated more regular collagen fibers pattern than hypothyroid rats. It was therefore concluded that hypothyroidism delays wound healing and both Laser photobiomodulation and Polarized Light at 20j/cm2 dosages had improved the healing process in hypothyroid rats.

  9. IP4DI: A software for time-lapse 2D/3D DC-resistivity and induced polarization tomography

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    We propose a 2D/3D forward modelling and inversion package to invert direct current (DC)-resistivity, time-domain induced polarization (TDIP), and frequency-domain induced polarization (FDIP) data. Each cell used for the discretization of the 2D/3D problems is characterized by a DC-resistivity value and a chargeability or complex conductivity for TDIP/FDIP problems, respectively. The governing elliptic partial differential equations are solved with the finite element method, which can be applied for both real and complex numbers. The inversion can be performed either for a single snapshot of data or for a sequence of snapshots in order to monitor a dynamic process such as a salt tracer test. For the time-lapse inversion, we have developed an active time constrained (ATC) approach that is very efficient in filtering out noise in the data that is not correlated over time. The forward algorithm is benchmarked with simple analytical solutions. The inversion package IP4DI is benchmarked with three tests, two including simple geometries. The last one corresponds to a time-lapse resistivity problem for cross-well tomography during enhanced oil recovery. The algorithms are based on MATLAB® code package and a graphical user interface (GUI).

  10. Using multi-spectral imagery to detect and map stress induced by Russian wheat aphid

    NASA Astrophysics Data System (ADS)

    Backoulou, Georges Ferdinand

    Scope and Method of Study. The rationale of this study was to assess the stress in wheat field induced by the Russian wheat aphid using multispectral imagery. The study was conducted to (a) determine the relationship between RWA and edaphic and topographic factors; (b) identify and quantify the spatial pattern of RWA infestation within wheat fields; (c) differentiate the stress induced by RWA from other stress causing factors. Data used for the analysis included RWA population density from the wheat field in, Texas, Colorado, Wyoming, and Nebraska, Digital Elevation Model from the Unites States Geological Survey (USGS), soil data from the Soil Survey Geographic database (SSURGO), and multispectral imagery acquired in the panhandle of Oklahoma. Findings and Conclusions. The study revealed that the population density of the Russian wheat aphid was related to topographic and edaphic factors. Slope and sand were predictor variables that were positively related to the density of RWA at the field level. The study has also demonstrated that stress induced by the RWA has a specific spatial pattern that can be distinguished from other stress causing factors using a combination of landscape metrics and topographic and edaphic characteristics of wheat fields. Further field-based studies using multispectral imagery and spatial pattern analysis are suggested. The suggestions require acquiring biweekly multispectral imagery and collecting RWA, topographic and edaphic data at the sampling points during the phonological growth development of wheat plants. This is an approach that may pretend to have great potential for site specific technique for the integrated pest management.

  11. 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

  12. Paradoxical resistance to high-fat diet-induced obesity and altered macrophage polarization in mineralocorticoid receptor-overexpressing mice.

    PubMed

    Kuhn, Emmanuelle; Bourgeois, Christine; Keo, Vixra; Viengchareun, Say; Muscat, Adeline; Meduri, Geri; Le Menuet, Damien; Fève, Bruno; Lombès, Marc

    2014-01-01

    The mineralocorticoid receptor (MR) exerts proadipogenic and antithermogenic effects in vitro, yet its in vivo metabolic impact remains elusive. Wild type (WT) and transgenic (Tg) mice overexpressing human MR were subjected to standard chow (SC) or high-fat diet (HFD) for 16 wk. Tg mice had a lower body weight gain than WT animals and exhibited a relative resistance to HFD-induced obesity. This was associated with a decrease in fat mass, an increased population of smaller adipocytes, and an improved glucose tolerance compared with WT animals. Quantitative RT-PCR studies revealed decreased expression of PPAR?2, a master adipogenic gene, and of glucocorticoid receptor and 11?-hydroxysteroid dehydrogenase type 1, consistent with an impaired local glucocorticoid signaling in adipose tissues (AT). This paradoxical resistance to HFD-induced obesity was not related to an adipogenesis defect since differentiation capacity of Tg preadipocytes isolated from stroma-vascular fractions was unaltered, suggesting that other nonadipocyte factors might compromise AT development. Although AT macrophage infiltration was not different between genotypes, Tg mice exhibited a distinct macrophage polarization, as revealed by FACS analysis and CD11c/CD206 expression studies. We further demonstrated that Tg macrophage-conditioned medium partially impaired preadipocyte differentiation. Therefore, we propose that modification of M1/M2 polarization of hMR-overexpressing macrophages could account in part for the metabolic phenotype of Tg mice. Collectively, our results provide evidence that MR exerts a pivotal immunometabolic role by controlling adipocyte differentiation processes directly but also indirectly through macrophage polarization regulation. Our findings should be taken into account for the pharmacological treatment of metabolic disorders. PMID:24222670

  13. Two dimensional electron gases induced by spontaneous and piezoelectric polarization in undoped and doped AlGaN\\/GaN heterostructures

    Microsoft Academic Search

    O. Ambacher; B. Foutz; J. Smart; J. R. Shealy; N. G. Weimann; K. Chu; M. Murphy; A. J. Sierakowski; W. J. Schaff; L. F. Eastman; R. Dimitrov; A. Mitchell; M. Stutzmann

    2000-01-01

    Two dimensional electron gases in AlxGa1-xN\\/GaN based heterostructures, suitable for high electron mobility transistors, are induced by strong polarization effects. The sheet carrier concentration and the confinement of the two dimensional electron gases located close to the AlGaN\\/GaN interface are sensitive to a large number of different physical properties such as polarity, alloy composition, strain, thickness, and doping of the

  14. Trapping, corralling and spectral bonding of optical resonances through optically induced potentials

    NASA Astrophysics Data System (ADS)

    Rakich, Peter T.; Popovi?, Miloš A.; Solja?i?, Marin; Ippen, Erich P.

    2007-11-01

    Optical forces resulting from interacting modes and cavities can scale to remarkably large values as the optical modes shrink to nanometre dimensions. Such forces can be harnessed in fundamentally new ways when optical elements can freely adapt to them. Here, we propose the use of optomechanically coupled resonators as a general means of tailoring optomechanical potentials through the action of optical forces. We show that significant attractive and repulsive forces arising from optomechanically coupled cavity resonances can give rise to strong and highly localized optomechanical potential wells whose widths can approach picometre scales. These potentials enable unique all-optical self-adaptive behaviours, such as the trapping and corralling (or dynamic capture) of microcavity resonances with light. It is shown, for example, that a resonator can be designed to dynamically self-align (or spectrally bond) its resonance to an incident laser line. Although these concepts are illustrated through dual-microring cavity designs, broad extension to other photonic topologies can be made.

  15. 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.

  16. Beam-Induced Nuclear Depolarization in a Gaseous Polarized-Hydrogen Target

    SciTech Connect

    Green, P.W.; Greeniaus, L.G.; Kitching, P.; Martens, F.K.; Miller, C.A. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2N2 (CANADA); Gao, H.; Hansen, J.; Jackson, H.E.; Makins, N.C.; ONeill, T.G.; Potterveld, D.H. [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Bray, B.; Carter, P.; Dvoredsky, A.; Filippone, B.W.; Korsch, W.; McIlhany, K.; McKeown, R.D.; Pitt, M. [W. K. Kellog Radiation Lab, California Institute of Technology, Pasadena, California 91125 (United States); Brack, J.; Fox, B.; Kinney, E.; Rakness, G.; Ristinen, R. [Nuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446 (United States); Ackerstaff, K.; Funk, M.; Holler, Y.; Ihssen, H.; Meyners, N.; Schueler, K.P.; Sinram, K.; Spengos, M.; Woller, K.; Zapfe-Dueren, K. [DESY, Deutsches Elektronen Synchrotron, 22603 Hamburg (Germany); Boettcher, H.; Borissov, A.; Brons, S.; Gaerber, Y.; Hasch, D.; Korotkov, V.; Meissner, F.; Nowak, W.; Roloff, H.; Schwind, A.; Stoesslein, U. [DESY, 15738 Zeuthen (Germany); Fechtchenko, A.; Gagunashvili, N.D.; Krivokhijine, V.G.; Mitsyn, V.; Nagaitsev, A.; Savin, I.; Shutov, V. [Joint Institute for Nuclear Research, 141980 Dubna (Russia); Benisch, T.; Bernreuther, S.; Braun, B.; Dueren, M.; Ferstl, M.; Fiedler, K.; Grosshauser, C.; Gute, A.; Henoch, M.; Lachnit, W.; Neunreither, F.; Rith, K.; Schmidt, F.; Steffens, E.; Stenger, J.; Stock, F.; Wander, W. [Physikalisches Institut, Universitaet Erlangen-Nuernberg, 91058 Erlangen (Germany); Dalpiaz, P.F.; Frabetti, S.; Masoli, F.; Reali, A.; Simani, C.; Slavich, P. [Dipartimento di Fisica, Universita di Ferrara, 44100 Ferrara (Italy); Avakian, H.; Bianchi, N.; Capitani, G.P.; De Sanctis, E.; Di Nezza, P.; Fantoni, A.; Giordjian, V.; Mozzetti, R.; Muccifora, V.; Nupieri, M.; Reolon, A.R.; Rossi, P.; Slavich, P. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati (Italy); Kramer, L.; and others

    1999-02-01

    Spin-polarized atomic hydrogen is used as a gaseous polarized-proton target in high-energy and nuclear-physics experiments operating with internal beams in storage rings. When such beams are intense and bunched, this type of target can be depolarized by a resonant interaction with the transient magnetic field generated by the beam bunches. This effect has been studied with the HERA positron beam in the HERMES experiment at DESY. Resonances have been observed and a simple analytic model has been used to explain their shape and position. Operating conditions for the experiment have been found where there is no significant target depolarization due to this effect. {copyright} {ital 1999} {ital The American Physical Society }

  17. Electric polarization reversal and memory in a multiferroic material induced by magnetic fields.

    PubMed

    Hur, N; Park, S; Sharma, P A; Ahn, J S; Guha, S; Cheong, S-W

    2004-05-27

    Ferroelectric and magnetic materials are a time-honoured subject of study and have led to some of the most important technological advances to date. Magnetism and ferroelectricity are involved with local spins and off-centre structural distortions, respectively. These two seemingly unrelated phenomena can coexist in certain unusual materials, termed multiferroics. Despite the possible coexistence of ferroelectricity and magnetism, a pronounced interplay between these properties has rarely been observed. This has prevented the realization of multiferroic devices offering such functionality. Here, we report a striking interplay between ferroelectricity and magnetism in the multiferroic TbMn2O5, demonstrated by a highly reproducible electric polarization reversal and permanent polarization imprint that are both actuated by an applied magnetic field. Our results point to new device applications such as magnetically recorded ferroelectric memory. PMID:15164057

  18. Loss of polarity protein AF6 promotes pancreatic cancer metastasis by inducing Snail expression.

    PubMed

    Xu, Yi; Chang, Renxu; Peng, Zhiyong; Wang, Yanmei; Ji, Weiwei; Guo, Jingyu; Song, Lele; Dai, Cheng; Wei, Wei; Wu, Yanjun; Wan, Xinjian; Shao, Chenghao; Zhan, Lixing

    2015-01-01

    Pancreatic cancer (PC) is a particularly lethal form of cancer with high potential for metastasis to distant organs. Disruption of cell polarity is a hallmark of advanced epithelial tumours. Here we show that the polarity protein AF6 (afadin and MLLT4) is expressed at low levels in PC. We demonstrate that depletion of AF6 markedly promotes proliferation and metastasis of PC cells through upregulation of the expression of Snail protein, and this requires the nuclear localization of AF6. Furthermore, AF6 deficiency in PC cells leads to increased formation of a Dishevelled 2 (Dvl2)-FOXE1 complex on the promoter region of Snail gene, and activation of Snail expression. Altogether, our data established AF6 as a potential inhibitor of metastasis in PC cells. Targeting the Dvl2-FOXE1-Snail signalling axis may thus represent a promising therapeutic strategy. PMID:26013125

  19. Polarization control of ultrabroadband supercontinuum generation from midinfrared laser-induced harmonic emission

    NASA Astrophysics Data System (ADS)

    Jiao, Zhi-Hong; Wang, Guo-Li; Li, Peng-Cheng; Zhou, Xiao-Xin

    2014-08-01

    We present an efficient scheme for generation of an isolated attosecond (as) pulse based on the combination of two well-known methods: polarization gating method plus a method based on using two colors (? +?/2). The first uses a pulse whose ellipticity is small within a very short time interval (called a polarization gating). By adding a second pulse whose frequency is a half-frequency (midinfrared) of the first pulse, we extend significantly the cutoff frequency, as well as the width of the supercontinuum harmonic spectrum. The high-order harmonic generation is calculated using the strong-field approximation theory. As a result, an isolated 42-as pulse is generated directly by superposing the hundreds of harmonics. To explain the mechanism of the ultrashort attosecond generation, we perform the semiclassical three-step model simulation and wavelet time-frequency transform of the harmonic spectra.

  20. Interaction-induced ferroelectricity in the rotational states of polar molecules

    SciTech Connect

    Lin, C.-H.; Hsu, Y.-T.; Lee Hao [Physics Department, National Tsing-Hua University, Hsinchu 300, Taiwan (China); Wang, D.-W. [Physics Department, National Tsing-Hua University, Hsinchu 300, Taiwan (China); Physics Division, National Center for Theoretical Sciences, Hsinchu 300, Taiwan (China)

    2010-03-15

    We show that a ferroelectric quantum phase transition can be driven by the dipolar interaction of polar molecules in the presence a microwave field. The obtained ferroelectricity crucially depends on the harmonic confinement potential, and the macroscopic dipole moment persists even when the external field is turned off adiabatically. The transition is shown to be second order for fermions and for bosons of a smaller permanent dipole moment, but is first order for bosons of a larger moment. Our results suggest the possibility of manipulating the microscopic rotational state of polar molecules by tuning the trap's aspect ratio (and other mesoscopic parameters), even though the later's energy scale is smaller than the former's by six orders of magnitude.

  1. In vivo near-infrared spectral detection of pressure-induced changes in breast tissue

    NASA Astrophysics Data System (ADS)

    Jiang, Shudong; Pogue, Brian W.; Paulsen, Keith D.; Kogel, Christine; Poplack, Steven P.

    2003-07-01

    A diffuse near-infrared tomography system was used to measure dynamic changes in the absolute optical properties of the human breast that were induced through pressure applied to the tissue surface. Results from five subjects show that absorption and scattering coefficients changed measurably when pressure was increased and that these relative changes correlated with the subjects' body-mass index, indicating that the effect depends on tissue composition. Fitting the absolute absorption and scattering coefficients at six wavelengths to the molar absorption spectra of the three predominant chromophores revealed that both the average total hemoglobin and oxygen saturation increased by 10%, while water concentration decreased by more than 12%. These changes indicate that the pressure-induced variation is likely due to water displacement and vascular volume increase in the region being imaged, for mild application of pressure to the breast. These results suggest that the pressure applied during optical measurements of tissue may alter the tissue physiology, and care should be taken to factor this effect into the design of optical medical instrumentation. In addition, the technique provides a unique approach to measuring tissue elastic changes in vivo in the female breast and may offer a new method for dynamic contrast imaging based on elasto-optical measurements.

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

    Microsoft Academic Search

    Y. Cai; O. Korotkova

    2009-01-01

    Electromagnetic Gaussian Schell-model (EGSM) beam with twist phase (i.e., twisted EGSM beam) is introduced as an extension\\u000a of its scalar version based on the unified theory of coherence and polarization. We show how analytical paraxial propagation\\u000a formulae of isotropic and anisotropic EGSM beams passing through a general astigmatic ABCD optical system can be modified\\u000a in the presence of the twist

  3. Spin-polarized current induced magnetization switch: Is the modulus of the magnetic layer conserved? (invited)

    Microsoft Academic Search

    J.-E. Wegrowe; X. Hoffer; Ph. Guittienne; A. Fábián; L. Gravier; T. Wade; J.-Ph. Ansermet

    2002-01-01

    The direct effect of spin-polarized current on magnetization states is studied on various electrodeposited single contacted nanowires (diameter about 60 nm). Three kinds of samples have been studied: (1) Homogeneous Ni nanowires, (2) nanowires composed of both a homogeneous Ni part and a multilayered Co(10 nm)\\/Cu(10 nm) part, (3) pseudospin-valve pillars Co(30 nm)\\/Cu(10 nm)\\/Co(10) electrodeposited in Cu wires. The magnetization

  4. Elliptically polarized light-induced second harmonic generation in SiN x O y

    Microsoft Academic Search

    K. Plucinski; I. V. Kityk; A. Mefleh

    2000-01-01

    Elliptically polarized photoinduced second harmonic generation (PISHG) in SiNxOy films was studied for specimens with different nitrogen to oxygen (N\\/O) ratios. As a source for the photoinducing light, we used a nitrogen Q-switched pulse laser at a wavelength of 337 nm. YAG:Nd pulse laser (?=1.06 ?m; W=30 MW; ?=10–50 ps) was used to measure the PISHG. All measurements were made

  5. Nuclear Lamin A\\/C Deficiency Induces Defects in Cell Mechanics, Polarization, and Migration

    Microsoft Academic Search

    Jerry S. H. Lee; Christopher M. Hale; Porntula Panorchan; Shyam B. Khatau; Jerry P. George; Yiider Tseng; Colin L. Stewart; Didier Hodzic; Denis Wirtz

    2007-01-01

    Lamin A\\/C is a major constituent of the nuclear lamina, a thin filamentous protein layer that lies beneath the nuclear envelope. Here we show that lamin A\\/C deficiency in mouse embryonic fibroblasts (Lmna?\\/? MEFs) diminishes the ability of these cells to polarize at the edge of a wound and significantly reduces cell migration speed into the wound. Moreover, lamin A\\/C

  6. 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.

  7. Changes in induced polarization associated with the sorption of sodium, lead, and zinc on silica sands.

    PubMed

    Vaudelet, P; Revil, A; Schmutz, M; Franceschi, M; Bégassat, P

    2011-08-15

    Low-frequency dielectric spectroscopy can be measured in terms of a conductance and a phase lag between the electrical current and the electrical field. This conductance and phase lag can be written as into a complex conductivity with both an in-phase and quadrature components that are frequency dependent. In sands, the low-frequency (10 mHz-40 kHz) spectra of the complex conductivity are dominated by the polarization of the electrical double layer (especially the internal part of the electrical double layer called the Stern layer) and the Maxwell-Wagner polarization (typically above 100 Hz). We present a polarization that is able to explain the complex conductivity spectra including the grain size distribution, the porosity, and the complexation of the mineral surface with the ions of the pore water. To test this model, we investigate the sorption of various cations (Na, Pb, Zn) characterized by different affinities with the surface of silica. Sand column experiments were carried out to see the change in the complex conductivity during the advective/dispersive transport of a lead nitrate solution and a zinc sulfate solution, replacing a sodium chloride solution in the pore space of the sand. The complex conductivity model is able to explain the change of the phase over time. PMID:21570082

  8. Multi-beam sounding ionograms in the polar cap region: Absorption induced by proton precipitations

    NASA Astrophysics Data System (ADS)

    Moskaleva, E. V.; Zaalov, N. Y.

    2014-11-01

    The simulation of the multi-beam ionograms in the polar cap region, assessing absorption effect is performed. It is reasonable to distinguish among four different mechanisms responsible for absorption: regular absorption due to solar UV illumination, absorption associated with energetic particles precipitation, absorption connected with X-rays flare and additional absorption in Auroral oval area. In this paper the absorption attributed to proton precipitations is envisaged. The computational model of the high-latitude ionosphere with irregularities oriented to application for the high frequency wave propagation problem was elaborated (Zaalov et al., 2005). A number of the quasi-vertical ionograms in the polar cap region were simulated on the basis of this model. A well-known algorithm (Sauer and Wilkinson, 2008) is applied for the absorption effects calculation. The simulated high-latitude ionograms with the absorption effect and the measured ionograms exhibit quite a good resemblance. This paper illustrates the importance of the understanding and taking into account the absorption effect in the presence of the various structural features in the polar ionosphere (in particular, patches of enhanced electron density) in interpreting ionosonde data.

  9. Using elaborative interrogation to induce characteristics of polar and nonpolar solvents from animations of their molecular structures

    NASA Astrophysics Data System (ADS)

    Ems-Wilson, Janice

    This study concerned (a) how general chemistry students learn to classify solvent polarity from animated molecules, (b) whether peer interaction increases the number of correct classifications, and (c) whether language, academic ability, logical thinking ability, or prior knowledge interact with rate of learning or posttest performance. Two types of interaction were compared, group discussion and elaborative interrogation. The study rested on three assumptions: (a) animated molecules are appropriate for learning the concept of solvent polarity, (b) question stems and a guided interrogation enhance learning of a visual concept, (c) general chemistry students can induce the concept of solvent polarity from animated molecules when no guiding cues, either visual or verbal, are given. After a review of molecular geometry and bonding theories, students were presented with four trials of ten animated molecular structures. Ten three-to-five minute discussions were distributed among the four trials. Prior to the trials the experimental group received a 45-minute training session on elaborative interrogation; the topic was what happens on the molecular level when a carbonated beverage is opened. The control group received a 45-minute expository lecture on the same carbonated beverage topic. Participants were given a four-part posttest immediately following the trials. Results of the study suggest that most students tend to classify the solvent polarity of animated molecules based on certain structural features using a prototype or feature-frequency categorization strategy. Elaborative interrogation did not show a significant effect on the rate of learning or on the performance of learners on posttest measures of recall and comprehension. The experimental group noted a significantly greater number and range of types of features, and offered higher quality generalizations and explanations of their polarity classification procedure. Finally, the results implied that learning from animations depends more on prior knowledge of relevant concepts than on academic ability, logical thinking ability, or preferred language. Although some benefits may arise from accompanying computer animation with an interactive discussion, additional visual and verbal, cueing may be necessary for optimal outcomes.

  10. Effect of the spectral width of optical sources upon the output of an optical current sensor

    Microsoft Academic Search

    Zheng Ping Wang; Xiaozhong Wang; Xiaoyu Liu; Chunmei Ouyang; Qiao Tan

    2005-01-01

    In bulk glass optical current sensing systems with polarization-preserving total reflection layers and wide spectral optical sources, the Verdet constant of the material of the sensing head, the linear birefringence inside the sensing element and the reflection-induced-retardance are all a function of the wavelength. Therefore, there will be error accumulation due to spectral width variation shown in the output of

  11. Loop-induced photon spectral lines from neutralino annihilation in the NMSSM

    NASA Astrophysics Data System (ADS)

    Chalons, G.; Semenov, A.

    2011-12-01

    We have computed the loop-induced processes of neutralino annihilation into two photons and, for the first time, into a photon and a Z 0 boson in the framework of the NMSSM. The photons produced from these radiative modes are monochromatic and possess a clear "smoking gun" experimental signature. This numerical analysis has been done with the help of the SloopS code, initially developed for automatic one-loop calculation in the MSSM. We have computed the rates for different benchmark points coming from SUGRA and GMSB soft SUSY breaking scenarios and compared them with the MSSM. We comment on how this signal can be enhanced, with respect to the MSSM, especially in the low mass region of the neutralino. We also discuss the possibility of this observable to constrain the NMSSM parameter space, taking into account the latest limits from the FERMI collaboration on these two modes.

  12. Precise Extraction of the Induced Polarization in the {sup 4}He(e,e{sup '}p-vector){sup 3}H Reaction

    SciTech Connect

    Malace, S. P.; Paolone, M.; Strauch, S.; Ilieva, Y.; Tedeschi, D. [University of South Carolina, Columbia, South Carolina 29208 (United States); Albayrak, I.; Christy, M. E.; Keppel, C. E.; Tang, L.; Tvaskis, V. [Hampton University, Hampton, Virginia 23668 (United States); Arrington, J.; Solvignon, P. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Berman, B. L.; Briscoe, B. [George Washington University, Washington, D.C. 20052 (United States); Brash, E. J. [Christopher Newport University, Newport News, Virginia 23606 (United States); Camsonne, A.; Chen, J.-P.; Chudakov, E.; Ent, R.; Higinbotham, D. W. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

    2011-02-04

    We measured with unprecedented precision the induced polarization P{sub y} in {sup 4}He(e,e{sup '}p-vector){sup 3}H at Q{sup 2}=0.8 and 1.3 (GeV/c){sup 2}. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are overestimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin-independent charge-exchange term in the latter calculation.

  13. A new coupled spectral element and modal solution method for global seismology: A first application to the scattering induced

    E-print Network

    A new coupled spectral element and modal solution method for global seismology: A first application simulation method based on the coupling of the Spectral Element Method (SEM) with a modal solution method and based upon the coupling between a Spectral Element Method (SEM) and a modal solution, is shown

  14. 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.

  15. Electric field-induced translocation of single-stranded DNA through a polarized carbon nanotube membrane.

    PubMed

    Xie, Yinghong; Kong, Yong; Soh, A K; Gao, Huajian

    2007-12-14

    Molecular dynamics simulations based on a novel polarizable nanotube model were performed to study the dynamics in translocation of a single-stranded deoxyribonucleic acid oligonucleotide through a polarized carbon nanotube membrane by an applied electric field. The study revealed a nonlinear dependence of translocation velocity and an inverse quadratic dependence of translocation time on the electric field strength, as well as a threshold electric field below which the translocation process becomes impossible. The translocation rate was found to be pore-size dependent. The polarizable nanotube model developed for this study provides a useful platform for investigating the dynamics of a range of bionanosystems. PMID:18081421

  16. 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 ...

  17. 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

  18. Spin-orbit-induced spin-polarized surface states in one-atomic-layer Pb films on Si(111)

    NASA Astrophysics Data System (ADS)

    Lee, Hyungjun; Choi, Hyoung Joon

    2013-03-01

    As a route to spintronics without magnetism, spin-orbit coupling (SOC) generates and manipulates the spin-polarized carriers, thereby providing key ingredients for spin field-effect transistors. Along this line, we investigated the spin-orbit induced effects in Pb monolayers on Si(111) substrates, modeled by ?{ 3} ×?{ 3} phase with Pb coverage of 4/3 ML, based on first-principles calculations with the inclusion of SOC. We focus on the electronic structures of surface states with characteristic Rashba-type spin splitting and spin texture as well as the charge flow pattern by calculating the current density distribution for the spin-polarized surface states. We also discuss our results on the difference from the spin splitting in the Shockley surface states on Au(111) surface. This work was supported by the NRF of Korea (Grant No. 2011-0018306), and computational resources have been provided by KISTI Supercomputing Center (Project No. KSC-2012-C2-14).

  19. 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.

  20. Magnetic-induced polarization in charge-ordered CaMn7O12 system

    NASA Astrophysics Data System (ADS)

    Saldana-Greco, Diomedes; Lim, Jin Soo; Rappe, Andrew M.

    2015-03-01

    The electronic properties of CaMn7O12 yield interesting physical phenomena including charge-ordering, non-collinear magnetism, and improper ferroelectricity. The charge-ordered CaMn7O12 is a complex quadruple perovskite whose chemical formula is (CaMn33+)(Mn33+ Mn4+)O12 where three Mn3+ are on the A-site (Mn1), three Mn3+ on the B-site (Mn2), and one Mn4+ on the B-site (Mn3). Three parallel c-chains with alternating Mn1 and Mn2 form a Kagome lattice with either Mn3 or Ca at the center of the hexagonal rings. The non-collinear magnetic state consists of spin moments lying on the ab -plane, forming a helical pattern along the c-axis. Our DFT+ U+ J study shows that the Mn3 spins adopt a (90°,30°) spin configuration with respect to the surrounding (Mn1,Mn2) spins, breaking the inversion symmetry and generating a Berry-phase computed ferroelectric polarization of 2975 ?C/m2 along the c-axis. We demonstrated that when the magnetic helicity of the system is reversed, the ferroelectric polarization flips. This study aims to explore how the electronic and magnetic properties are intertwined to give rise to a multiferroic, charge-ordered state.

  1. Plasmonic planar antenna for wideband and efficient linear polarization conversion

    NASA Astrophysics Data System (ADS)

    Lévesque, Quentin; Makhsiyan, Mathilde; Bouchon, Patrick; Pardo, Fabrice; Jaeck, Julien; Bardou, Nathalie; Dupuis, Christophe; Haïdar, Riad; Pelouard, Jean-Luc

    2014-05-01

    The design of metasurfaces able to efficiently control the polarization state of an electromagnetic wave is of importance for various applications. We demonstrate both theoretically and experimentally that plasmonic planar L-shaped antennas can induce a 90°-rotation of the linear polarization of light with a nearly total efficiency in the infrared (3-5 µm). The nanoantenna geometry is engineered so that the polarization conversion occurs over a 1 ?m-wide spectral band ([3.25-4.25] µm ) with a mean polarization conversion efficiency of 95 %. In order to validate a theoretical model describing the antenna behaviour, we investigate the polarization conversion effect as function of the incident and azimuthal angles.

  2. Inversion of polarization by light-induced stabilization in NO2 revisited

    NASA Astrophysics Data System (ADS)

    Weber, H. G.

    2015-07-01

    We show that light-induced coherence between a state | a > of the electronic ground state X2A1 and a state | b > of the excited electronic state A2B2 of a laser-induced transition in NO2 affects the evolution of the molecule in the excited state. The optical coherence couples | b > strongly with | a >. This optical coupling works against a radiationless process, which is driving the molecule away from the metastable state | b > to a final state | c >. The optical field stabilizes the molecule in the state | b > by the coupling to the ground state | a >. This causes the inversion effect in NO2.

  3. Combined study of microwave-power/linear-polarization dependence of the microwave-radiation-induced magnetoresistance oscillations in GaAs/AlGaAs devices

    NASA Astrophysics Data System (ADS)

    Ye, Tianyu; Liu, Han-Chun; Wegscheider, W.; Mani, R. G.

    2014-04-01

    We report the results of a combined microwave polarization-dependence and power-dependence study of the microwave-radiation-induced magnetoresistance oscillations in high mobility GaAs/AlGaAs heterostructure devices at liquid helium temperatures. The diagonal resistance was measured with the magnetic field fixed at the extrema of the radiation-induced magnetoresistance oscillations, as the microwave power was varied at a number of microwave polarization angles. The results indicate a nonlinear relation between the oscillatory peak or valley magnetoresistance and the microwave power, as well as a cosine square relation between the oscillatory peak or valley magnetoresistance and the microwave polarization angle. The main features are briefly compared with the predictions of existing models.

  4. Salinomycin induces activation of autophagy, mitophagy and affects mitochondrial polarity: differences between primary and cancer cells.

    PubMed

    Jangamreddy, Jaganmohan Reddy; Ghavami, Saeid; Grabarek, Jerzy; Kratz, Gunnar; Wiechec, Emilia; Fredriksson, Bengt-Arne; Rao Pariti, Rama Krishna; Cie?lar-Pobuda, Artur; Panigrahi, Soumya; ?os, Marek J

    2013-09-01

    The molecular mechanism of Salinomycin's toxicity is not fully understood. Various studies reported that Ca(2+), cytochrome c, and caspase activation play a role in Salinomycin-induced cytotoxicity. Furthermore, Salinomycin may target Wnt/?-catenin signaling pathway to promote differentiation and thus elimination of cancer stem cells. In this study, we show a massive autophagic response to Salinomycin (substantially stronger than to commonly used autophagic inducer Rapamycin) in prostrate-, breast cancer cells, and to lesser degree in human normal dermal fibroblasts. Interestingly, autophagy induced by Salinomycin is a cell protective mechanism in all tested cancer cell lines. Furthermore, Salinomycin induces mitophagy, mitoptosis and increased mitochondrial membrane potential (??) in a subpopulation of cells. Salinomycin strongly, and in time-dependent manner decreases cellular ATP level. Contrastingly, human normal dermal fibroblasts treated with Salinomycin show some initial decrease in mitochondrial mass, however they are largely resistant to Salinomycin-triggered ATP-depletion. Our data provide new insight into the molecular mechanism of preferential toxicity of Salinomycin towards cancer cells, and suggest possible clinical application of Salinomycin in combination with autophagy inhibitors (i.e. clinically-used Chloroquine). Furthermore, we discuss preferential Salinomycins toxicity in the context of Warburg effect. PMID:23639289

  5. 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

  6. Time-resolved polarization-sensitive measurements of the electric field in a sliding discharge by means of dc-field-induced coherent Raman scattering

    Microsoft Academic Search

    S. N. Tskhai; S. V. Mitko; V. N. Ochkin; A. Yu. Serdyuchenko; D. A. Akimov; D. A. Sidorov-Biryukov; D. V. Sinyaev; A. M. Zheltikov

    2001-01-01

    Summary form only given. The analysis of the general polarization properties of dc-field-induced coherent Raman scattering allows us to suggest this process as a convenient method for nonintrusive local measurements of dc and quasi-static electric fields. We experimentally studied the properties of the IR signal generated through coherent Raman scattering involving the Q(1) transition (?= 0, J = 1? ?=1,

  7. Effect of polarization and geometric factors on quantitative laser-induced fluorescence- to-Raman intensity ratios of water samples and a new calibration technique

    Microsoft Academic Search

    Vasanthi Sivaprakasam; Dennis K. Killinger

    2003-01-01

    A 266-nm laser-induced fluorescence system was used to study the effect of polarization of the excitation source and geometry of the collection optics on the ratio of the signal from a fluorescence standard, quinine sulfate, and the Raman scatter from water. Although the ratio is sometimes considered to be a constant and is used for intersystem comparisons, our studies showed

  8. Micromagnetic simulations of magnetization dynamics in a nanowire induced by a spin-polarized current injected via a point contact

    NASA Astrophysics Data System (ADS)

    Berkov, D. V.; Boone, C. T.; Krivorotov, I. N.

    2011-02-01

    We present a detailed numerical analysis of the magnetization auto-oscillations induced in a thin NiFe nanowire by a direct spin-polarized current injected via a square-shaped CoFe nanomagnet [a system experimentally studied in Boone Phys. Rev. BPLRBAQ1098-012110.1103/PhysRevB.79.140404 79, 140404 (2009).]. We demonstrate that all auto-oscillation modes in the nanowire are localized under the nanocontact for magnetic field applied in the plane of the nanowire. This mode localization is induced by a strong, stray magnetic field acting on the NiFe nanowire from the CoFe current injector. We find that the auto-oscillation frequency, power, and the frequency shift with the current strongly depend on the exchange constant of NiFe. We also find that the auto-oscillation power depends nonmonotonically on the CoFe saturation magnetization, and we demonstrate that this effect has its origin in resonant excitation of the CoFe eigenmodes by magnetization oscillations in the NiFe nanowire. The calculated dependence of the oscillation frequency on current is in good agreement with the experiment. However, the agreement between theory and experiment for the oscillation power is unsatisfactory. Finally, we have shown that an auto-oscillatory mode propagating along the nanowire in the system under study is possible when a sufficiently strong out-of-plane field is applied.

  9. Organ-specific cytokine polarization induced by adoptive transfer of transgenic T cells.

    PubMed

    Zhang, Lei; Lizzio, Elaine F; Gubina, Elena; Chen, Trina; Mostowski, Howard; Kozlowski, Steven

    2002-11-15

    There are two distinct phenotypes of T cell cytokine responses that lead to different effector functions and different outcomes in disease processes. Although evidence suggests a possible role of the local microenvironment in the differentiation or localization of T cells with these phenotypes, there are no examples of divergent T cell cytokine phenotypes with the same Ag specificity concurrently existing in different tissue compartments. Using a CD8(+) T cell adoptive transfer model for graft-vs-host disease, we demonstrate that a potent type 2 cytokine response develops in the spleen while a potent type 1 cytokine response simultaneously develops in the testis. These experiments demonstrate for the first time that cytokine production can be oppositely polarized in different organs of the same individual. This may have important implications for organ-specific pathology in infection or autoimmunity: infections or autoimmune diseases that affect multiple organs may have heterogeneity in tissue cytokine responses that is not revealed in systemic lymphocyte cytokine responses. Therefore, attempts to modulate the immune response phenotype may ameliorate pathology in one organ while exacerbating pathology in another. PMID:12421927

  10. 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. [Department of Physics, Chemistry and Biology, Linköping University, S-581 83 Linköping (Sweden); Yang, X. J.; Subagyo, A.; Sueoka, K.; Murayama, A. [Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814 (Japan)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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 using a 9.4 T scanner using a multi-gradient echo pulse sequence to acquire high spectral and spatial resolution (HiSS) data. Temperature increases of approximately 6 °C were produced 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 min 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 the development of new hyperthermia protocols.

  12. 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.

  13. Effect of electric field distribution on the morphologies of laser-induced damage in hafnia-silica multilayer polarizers

    SciTech Connect

    Genin, F.Y.; Stolz, C.J.; Reitter, T.; Kozlowski, M.R. [Lawrence Livermore National Lab., CA (United States); Bevis, R.P.; vonGunten, M.K. [Spectra-Physics Lasers, Inc., Mountain View, CA (United States)

    1997-01-01

    Hafnia-silica multilayer polarizers were deposited by e-beam evaporation onto BK7 glass substrates. The polarizers were designed to operate at 1064 nm at Brewster`s angle (56{degree}). They were tested with a 3-ns laser pulse at 45, 56, and 65{degree} incidence angle in order to vary the electric field distribution in the multilayer, study their effects on damage morphology, and investigate possible advantages of off-use angle laser conditioning. Morphology of the laser-induced damage was characterized by optical and scanning electron microscopy. Four distinct damage morphologies (pit, flat bottom pit, scald, outer layer delamination) were observed; they depend strongly on incident angle of the laser beam. Massive delamination observed at 45 and 56{degree} incidence, did not occur at 65{degree}; instead, large and deep pits were found at 65{degree}. Electric field distribution, temperature rise, and change in stress in the multilayer were calculated to attempt to better understand the relation between damage morphology, electric field peak locations, and maximum thermal stress gradients. The calculations showed a twofold increase in stress change in the hafnia top layers depending on incident angle. Stress gradient in the first hafnia-silica interface was found to be highest for 45, 56, and 65{degree}, respectively. Finally, the maximum stress was deeper in the multilayer at 65{degree}. Although the limitations of such simple thermal mechanical model are obvious, the results can explain that outer layer delamination is more likely at 45 and 56{degree} than 65{degree} and that damage sites are expected to be deeper at 65{degree}.

  14. Flagellin-induced tolerance of the Toll-like receptor 5 signaling pathway in polarized intestinal epithelial cells.

    PubMed

    Sun, Jun; Fegan, Pamela E; Desai, Anjali S; Madara, James L; Hobert, Michael E

    2007-03-01

    Salmonella typhimurium is a gram-negative enteric pathogen that invades the mucosal epithelium and is associated with diarrheal illness in humans. Flagellin from S. typhimurium and other gram-negative bacteria has been shown to be the predominant proinflammatory mediator through activation of the basolateral Toll-like receptor 5 (TLR5). Recent evidence has shown that prior exposure can render immune cells tolerant to subsequent challenges by TLR ligands. Accordingly, we examined whether prior exposure to purified flagellin would render human intestinal epithelial cells insensitive to future contact. We found that flagellin-induced tolerance is common to polarized epithelial cells and prevents further activation of proinflammatory signaling cascades by both purified flagellin and Salmonella bacteria but does not affect TNF-alpha stimulation of the same pathways. Flagellin tolerance is a rapid process that does not require protein synthesis, and that occurs within 1 to 2 h of flagellin exposure. Prolonged flagellin exposure blocks activation of the NF-kappaB, MAPK, and phosphoinositol 3-kinase signaling pathways and results in the internalization of a fraction of the basolateral TLR5 without affecting the polarity or total expression of TLR5. After removal of flagellin, cells require more than 24 h to fully recover their ability to mount a normal proinflammatory response. We have found that activation of phosphoinositol 3-kinase and Akt by flagellin has a small damping effect in the early stages of flagellin signaling but is not responsible for tolerance. Our study indicates that inhibition of TLR5-associated IL-1 receptor-associated kinase-4 activity occurs during the development of flagellin tolerance and is likely to be the cause of tolerance. PMID:17138965

  15. Scattering polarization of hydrogen lines from electric-induced atomic alignment

    E-print Network

    R. Casini; R. Manso Sainz

    2008-03-11

    We consider a gas of hydrogen atoms illuminated by a broadband, unpolarized radiation with zero anisotropy. In the absence of external fields, the atomic J-levels are thus isotropically populated. While this condition persists in the presence of a magnetic field, we show instead that electric fields can induce the alignment of those levels. We also show that this electric alignment cannot occur in a two-term model of hydrogen (e.g., if only the Ly-alpha transition is excited), or if the level populations are distributed according to Boltzmann's law.

  16. Cooperative molecular field effect and induced orientational ordering effect in polar liquid crystalline films on metals.

    PubMed

    Taguchi, Dai; Kajimoto, Norifumi; Manaka, Takaaki; Iwamoto, Mitsumasa

    2007-07-28

    Using the in situ measurements of the surface potential built across the evaporated liquid crystalline 4-n-pentyl-4'-cyanobiphenyl (5CB) films on metal electrodes with different work functions, we studied the cooperative molecular field effect (CMFE) that assists carrier injection from electrodes and the induced orientational reordering in evaporated liquid crystalline molecules on metals. The surface potential increased, and then became constant after the 5CB monomolecular layer was formed. It was shown that the CMFE accompanying orientational reordering accounts for the metal work function dependence of the surface potential. Finally, the orientational reordering is discussed in terms of the anchoring energy. PMID:17672713

  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. [Department of Physics, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha, P.O. Box 55134-441, Maragha 55177-36698 (Iran, Islamic Republic of); Rezaei, Z.; Montakhab, Afshin [Department of Physics, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)

    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. Chemerin aggravates DSS-induced colitis by suppressing M2 macrophage polarization

    PubMed Central

    Lin, Yuli; Yang, Xuguang; Yue, Wenjie; Xu, Xiaofei; Li, Bingji; Zou, Linlin; He, Rui

    2014-01-01

    Chemerin is present in various inflammatory sites and is closely involved in tissue inflammation. Recent studies have demonstrated that chemerin treatment can cause either anti-inflammatory or pro-inflammatory effects according to the disease model being investigated. Elevated circulating chemerin was recently found in patients with inflammatory bowel disease (IBD); however, the role of chemerin in intestinal inflammation remains unknown. In this study, we demonstrated that the administration of exogenous chemerin (aa17–156) aggravated the severity of dextran sulfate sodium (DSS)-induced colitis, which was characterized by higher clinical scores, extensive mucosal damage and significantly increased local and systemic production of pro-inflammatory cytokines, including IL-6, TNF-? and interferon (IFN-?). Interestingly, chemerin did not appear to influence the magnitudes of inflammatory infiltrates in the colons, but did result in significantly decreased colonic expression of M2 macrophage-associated genes, including Arginase 1 (Arg-1), Ym1, FIZZ1 and IL-10, following DSS exposure, suggesting an impaired M2 macrophage skewing in vivo. Furthermore, an in vitro experiment showed that the addition of chemerin directly suppressed M2 macrophage-associated gene expression and STAT6 phosphorylation in IL-4-stimulated macrophages. Significantly elevated chemerin levels were found in colons from DSS-exposed mice and from ulcerative colitis (UC) patients and appeared to positively correlate with disease severity. Moreover, the in vivo administration of neutralizing anti-chemerin antibody significantly improved intestinal inflammation following DSS exposure. Taken together, our findings reveal a pro-inflammatory role for chemerin in DSS-induced colitis and the ability of chemerin to suppress the anti-inflammatory M2 macrophage response. Our study also suggests that upregulated chemerin in inflamed colons may contribute to the pathogenesis of IBD. PMID:24727542

  19. Toward a theory of the general-anesthetic-induced phase transition of the cerebral cortex. II. Numerical simulations, spectral entropy, and correlation times.

    PubMed

    Steyn-Ross, D A; Steyn-Ross, M L; Wilcocks, L C; Sleigh, J W

    2001-07-01

    In our two recent papers [M.L. Steyn-Ross et al., Phys. Rev. E 60, 7299 (1999); 64, 011917 (2001)] we presented clinical evidence for a general anesthetic-induced phase change in the cerebral cortex, and showed how the significant features of the cortical phase change (biphasic power surge, spectral energy redistribution, "heat capacity" divergence), could be explained using a stochastic single-macrocolumn model of the cortex. The model predictions were based on rather strong "adiabatic" assumptions which assert that the mean-field excitatory and inhibitory macrocolumn voltages are "slow" variables whose equilibration times are much longer than those of the input "currents" that drive the macrocolumn. In the present paper we test the adiabatic assumption by running numerical simulations of the stochastic differential equations. These simulations confirm the number and nature of the steady-state solutions, the growth of fluctuation power at transition, and the redistribution of spectral energy towards lower frequencies. We use spectral entropy to quantify these changes in the power spectral density, and to show that the spectral entropy should decrease markedly at the point of transition. This prediction agrees with recent clinical findings by Viertiö-Oja and colleagues [J. Clinical Monitoring Computing 16, 60 (2000)]. Our modeling work shows that there is an inverse relationship between spectral entropy H and correlation time T of the soma-voltage fluctuations: H inversely proportional to (ln T). In a theoretical analysis we prove that this proportionality becomes exact for an ideal Lorentzian process. These findings suggest that by monitoring the changes in EEG correlation time, it should be possible to track changes in the state of patient consciousness. PMID:11461299

  20. 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.

  1. Parahydrogen Induced Polarization of 1-13C-Phospholactate-d2 for Biomedical Imaging with >30,000,000-fold NMR Signal Enhancement in Water

    PubMed Central

    2015-01-01

    The synthetic protocol for preparation of 1-13C-phosphoenolpyruvate-d2, precursor for parahydrogen-induced polarization (PHIP) of 1-13C-phospholactate-d2, is reported. 13C nuclear spin polarization of 1-13C-phospholactate-d2 was increased by >30,000,000-fold (5.75 mT) in water. The reported 13C polarization level approaching unity (>15.6%), long lifetime of 13C hyperpolarized 1-13C-phospholactate-d2 (58 ± 4 s versus 36 ± 2 s for nondeuterated form at 47.5 mT), and large production quantities (52 ?moles in 3 mL) in aqueous medium make this compound useful as a potential contrast agent for the molecular imaging of metabolism and other applications. PMID:24738968

  2. Quantitation of a spin polarization-induced nuclear Overhauser effect (SPINOE) between a hyperpolarized (13) C-labeled cell metabolite and water protons.

    PubMed

    Marco-Rius, Irene; Bohndiek, Sarah E; Kettunen, Mikko I; Larkin, Timothy J; Basharat, Meer; Seeley, Colm; Brindle, Kevin M

    2014-01-01

    The spin polarization-induced nuclear Overhauser effect (SPINOE) describes the enhancement of spin polarization of solvent nuclei by the hyperpolarized spins of a solute. In this communication we demonstrate that SPINOEs can be observed between [1,4-(13) C2 ]fumarate, hyperpolarized using the dissolution dynamic nuclear polarization technique, and solvent water protons. We derive a theoretical expression for the expected enhancement and demonstrate that this fits well with experimental measurements. Although the magnitude of the effect is relatively small (around 2% measured here), the SPINOE increases at lower field strengths, so that at clinically relevant magnetic fields (1.5-3?T) it may be possible to track the passage through the circulation of a bolus containing a hyperpolarized (13) C-labeled substrate through the increase in solvent water (1) H signal. PMID:24523064

  3. Influence of potential's electrode selection on physical modeling of time domain induced polarization (TDIP), case studies of homogeneous isotropic medium

    NASA Astrophysics Data System (ADS)

    Yatini, Laesanpura, A.

    2013-09-01

    The relationship between metal mineral content and induced polarization response is not well known. Mathematical and physical modeling in laboratory scale was applied to find out those relationship. Their relationship was obtained by curve mathching. The physical modeling data quality was very importand in obtaining the relationship, therefore accurate and precise measurements are needed. Physical modeling data quality depend on the type of electrode, measurement techniques and equipment. Therefore, it is important to know the characteristics of the utilized potential electrode materials. The results show that porouspot is the most excellent potential electrodes used for TDIP physical modeling. The obtained resistivity and chargeability of the TDIP response of the porouspot electrodes and copper electrodes are 16.11 Ohm-m and 0.015 mSec, and 16 Ohm-m and 0.36 mSec, respectively. It is concluded that the groundwater can be used in homogeneous isotropic medium approach and also it is a good method for host medium in physical modeling.

  4. Characterization of data error in time-domain induced polarization tomography based on the analysis of decay curves

    NASA Astrophysics Data System (ADS)

    Gallistl, Jakob; Flores-Orozco, Adrián; Bücker, Matthias; Williams, Kenneth H.

    2015-04-01

    Time-domain induced polarization (TDIP) measurements are based on the recording of remnant voltages after current switch off and thus typically suffer from low signal-to-noise ratios. The analysis of the discrepancy between normal and reciprocal measurements has demonstrated to be a suitable method to quantify the data error in TDIP data sets, permitting to compute images with enhanced resolution. However, due to time constraints, it is not always possible to collect reciprocal measurements. Hence, we propose an alternative methodology to quantify data error in TDIP, which is based on fitting model curves to the measured IP decay. Based on the goodness of the fit, we can identify outliers and derive error parameters for the inversion of the tomographic TDIP data. In order to assess the practicability of our approach, we present a comparison of imaging results obtained based on the fitting of decay curves with those obtained based on the analysis of repeated measurements and normal-reciprocal measurements. Inversion results presented here were computed for extensive field data sets collected at the Rifle (CO) and Shiprock (NM) test sites. These data sets include TDIP data collected with different devices and using different IP windows.

  5. Reduction of phase-induced intensity noise in a fiber-based coherent Doppler lidar using polarization control.

    PubMed

    Rodrigo, Peter John; Pedersen, Christian

    2010-03-01

    Optimization of signal-to-noise ratio is an important aspect in the design of optical heterodyne detection systems such as a coherent Doppler lidar (CDL). In a CDL, optimal performance is achieved when the noise in the detector signal is dominated by local oscillator shot-noise. Most modern CDL systems are built using rugged and cost-efficient fiber optic components. Unfortunately, leakage signals such as residual reflections inherent within fiber components (e.g. circulator) can introduce phase-induced intensity noise (PIIN) to the Doppler spectrum in a CDL. Such excess noise may be a few orders of magnitude above the shot-noise level within the relevant CDL frequency bandwidth--corrupting the measurement of typically weak backscattered signals. In this study, observation of PIIN in a fiber-based CDL with a master-oscillator power-amplifier tapered semiconductor laser source is reported. Furthermore, we experimentally demonstrate what we believe is a newly proposed method using a simple polarization scheme to reduce PIIN by more than an order of magnitude. PMID:20389545

  6. A microbial fuel cell in contaminated ground delineated by electrical self-potential and normalized induced polarization data

    NASA Astrophysics Data System (ADS)

    Doherty, R.; Kulessa, B.; Ferguson, A. S.; Larkin, M. J.; Kulakov, L. A.; Kalin, R. M.

    2010-09-01

    There is a growing interest in the use of geophysical methods to aid investigation and monitoring of complex biogeochemical environments, for example delineation of contaminants and microbial activity related to land contamination. We combined geophysical monitoring with chemical and microbiological analysis to create a conceptual biogeochemical model of processes around a contaminant plume within a manufactured gas plant site. Self-potential, induced polarization and electrical resistivity techniques were used to monitor the plume. We propose that an exceptionally strong (>800 mV peak to peak) dipolar SP anomaly represents a microbial fuel cell operating in the subsurface. The electromagnetic and electrical geophysical data delineated a shallow aerobic perched water body containing conductive gasworks waste which acts as the abiotic cathode of microbial fuel cell. This is separated from the plume below by a thin clay layer across the site. Microbiological evidence suggests that degradation of organic contaminants in the plume is dominated by the presence of ammonium and its subsequent degradation. We propose that the degradation of contaminants by microbial communities at the edge of the plume provides a source of electrons and acts as the anode of the fuel cell. We hypothesize that ions and electrons are transferred through the clay layer that was punctured during the trial pitting phase of the investigation. This is inferred to act as an electronic conductor connecting the biologically mediated anode to the abiotic cathode. Integrated electrical geophysical techniques appear well suited to act as rapid, low cost sustainable tools to monitor biodegradation.

  7. 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.

  8. 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.

  9. Atmosphere Models of Magnetized Neutron Stars: QED Effects, Radiation Spectra, and Polarization Signals

    E-print Network

    Matthew van Adelsberg; Dong Lai

    2006-09-22

    Theoretical modeling of surface emission from magnetized neutron stars (NSs) requires proper treatment of QED effects, in particular the effect of photon mode conversion due to the ``vacuum resonance'' between plasma and vacuum polarization. Previous NS atmosphere models incorporated this effect approximately, using transfer equations for the photon modes which are inadequate near the vacuum resonance, particularly for field strengths around $B_l\\simeq 7\\times 10^{13}$ G, where the vacuum resonance occurs near the photosphere. In this paper, we provide an accurate treatment of the QED-induced mode conversion effect in NS atmosphere models, employing both the modal radiative transfer equations, coupled with an accurate mode conversion probability at the resonance, and the full evolution equations for the photon Stokes parameters. In doing so, we are able to quantitatively calculate the effects of vacuum polarization on the atmosphere emission spectra, beam patterns, and polarizations for the entire range of field strengths, $B=10^{12}-10^{15}$ G. We find that for NSs with $B\\ga 2 B_l$, vacuum polarization reduces the widths of spectral features, and softens the hard spectral tail typical of magnetized atmosphere models. For $B\\la B_l/2$, vacuum polarization does not change the emission spectra, but can significantly affect the polarization signals. We show that vacuum polarization induces a unique energy-dependent linear polarization signature, and that circular polarization can be generated in the magnetospheres of rapidly rotating NSs. We discuss the implications of our results for recent observations of thermally emitting isolated NSs and magnetars, as well as the prospects for future spectral and polarization observations.

  10. Large angle out of plane steady precession induced by spin-transfer with perpendicular to plane polarizer

    NASA Astrophysics Data System (ADS)

    Houssameddine, Dimitri

    2008-03-01

    The dynamics of a ferromagnetic system is characterized by a conservative precession torque, as well as a non-conservative damping torque. The damping torque is responsible for the realignment of the magnetisation with the equilibrium direction after excitation. Recently it has been shown that the damping torque can be compensated by a spin transfer torque that is due to the interaction between a spin polarized current and the local magnetization. This additional spin transfer torque can lead to auto-oscillations of the magnetization close to constant energy trajectories. The potential exploitation of such large angle auto-oscillations for tuneable microwave devices is currently driving many research efforts. For an in-plane magnetized thin film with uniaxial anisotropy, two types of constant energy trajectories exist which are commonly called in-plane precession (IPP), where the magnetization oscillates around the in-plane energy minimum, and out of plane precession (OPP) where the magnetization oscillates around the out of plane energy maximum [1]. IPP and OPP oscillations differ substantially in their dependence of frequency and amplitude as a function of current and/or applied bias field. In many experiments so far, IPP precessions have been obtained at the threshold current using in-plane magnetized spin valve structures. However, from an applications point of view it will be of interest to excite OPP oscillations since they will lead to a larger output signal than IPP oscillations. Here, we will present experimental evidence of large angle OPP oscillations using a spin torque oscillator that contains a perpendicularly magnetized polarizing layer and an in-plane magnetized analyzing layer in addition to a planar free layer [2]. We will show that OPP oscillations are induced at the threshold current for moderate current densities of 9x10^6 A/cm^2. The experimental current-field state diagram as well as the dependence of the frequency vs. current and applied bias field is in good qualitative agreement with macrospin and micromagnetic simulations. Furthermore, due to the planar analyzer, there exist IPP oscillations which allow a direct comparison of the OPP and IPP precession amplitudes. [1] A. N. Slavin, V. S. Tyberkevich Phys. Rev. B 72, 94428 (2005) [2] Houssameddine et al, Nature Materials 6, 441 (2007)

  11. The Adsorption of L Tryptophan to the H 2 O–CCl 4 Interface, Monitored by Red-Edge Two Photon-Induced Polarized Fluorescence

    Microsoft Academic Search

    D. T. Cramb; S. C. Wallace

    1998-01-01

    The adsorption of L-tryptophan to the H2O–CCl4 interface has been studied using the novel method of two photon-induced fluorescence polarization. The process of two-photon absorption allows excitation of a very small volume of molecules near an interface. In the instance where molecules maintain a preferential orientation at the interface, interface-specific phenomena are observed as a dependence of the absorption and

  12. Advanced search for the origin of life's homochirality: asymmetric photon induced processes on chiral compounds with far UV circularly polarized synchrotron radiation

    Microsoft Academic Search

    Laurent Nahon; Gustavo Garcia; Ivan Powis; Uwe Meierhenrich; André Brack

    2007-01-01

    Assuming an extra-terrestrial formation of life's molecular building blocks such as amino-acids, a possible abiotic explanation for the selection of the L enantiomers could be the exposure to an asymmetric bias such as far UV Circularly Polarized Light (CPL), during their journey towards Earth, inducing some enantiomeric excess (e.e) that could then be amplified on Earth via suitable autocatalytic mechanisms.

  13. Afm Study of the Evolution of Double Layer on SiO2 Surface and Self-Assembly Monolayer Induced by the Polarization with DC Voltages

    Microsoft Academic Search

    Tian Tian; Yong Zhang; Haitao Wang; Ningping Huang; Zhongdang Xiao

    2009-01-01

    AFM was used to study the evolution of double layer on SiO2 surface and self-assembly monolayer induced by the polarization with DC voltages. Approach force curves were recorded when external DC voltages were applied between solution and SiO2 or aminopropyltriethoxysilane (APTES) modified SiO2 surfaces in electrolyte solution. The results showed that the reversing of tip-surface interaction forces between attraction and

  14. Novel helical assembly of a Pt(ii) phenylbipyridine complex directed by metal-metal interaction and aggregation-induced circularly polarized emission.

    PubMed

    Ikeda, Toshiaki; Takayama, Midori; Kumar, Jatish; Kawai, Tsuyoshi; Haino, Takeharu

    2015-07-14

    Pt(ii) phenylbipyridine complexes possessing bis(phenylisoxazolyl)phenylacetylene ligands self-assembled to form stacked aggregates via Pt-Pt, ?-? stacking, and dipole-dipole interactions. The assembled structures were influenced by the solvent properties. Non-helical assemblies found in chloroform displayed metal-metal-to-ligand charge transfer absorption and emission, whereas helical assemblies formed in toluene showed aggregation-induced enhancement of emission and aggregation-induced circularly polarized luminescence. The rates of the association and dissociation of the assemblies were significantly reduced in toluene, and the non-helical structures formed in chloroform were surprisingly memorized. PMID:26108199

  15. Spectral effects in quantum teleportation

    SciTech Connect

    Humble, Travis S.; Grice, Warren P. [Center for Engineering Science Advanced Research, Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6016 (United States)

    2007-02-15

    We use a multimode description of polarization-encoded qubits to analyze the quantum teleportation protocol. Specifically, we investigate how the teleportation fidelity depends on the spectral correlations inherent to polarization-entangled photons generated by type-II spontaneous parametric down conversion. We find that the maximal obtainable fidelity depends on the spectral entanglement carried by the joint probability amplitude, a result which we quantify for the case of a joint spectrum approximated by a correlated Gaussian function. We contrast these results with a similar analysis of the visibility obtained in a polarization-correlation experiment.

  16. Dietary n-3 polyunsaturated fatty acids promote activation-induced cell death in Th1-polarized murine CD4+ T-cells

    PubMed Central

    Switzer, Kirsten C.; Fan, Yang-Yi; Wang, Naisyin; McMurray, David N.; Chapkin, Robert S.

    2015-01-01

    Dietary n-3 PUFAs have been shown to attenuate T-cell-mediated inflammation. To investigate whether dietary n-3 PUFAs promote activation-induced cell death (AICD) in CD4+ T-cells induced in vitro to a polarized T-helper1 (Th1) phenotype, C57BL/6 mice were fed diets containing either 5% corn oil (CO; n-6 PUFA control) or 4% fish oil (FO) plus 1% CO (n-3 PUFA) for 2 weeks. Splenic CD4+ T-cells were cultured with ?-interleukin-4 (?IL-4), IL-12, and IL-2 for 2 days and then with recombinant (r) IL-12 and rIL-2 for 3 days in the presence of diet-matched homologous mouse serum (HMS) to prevent loss of cell membrane fatty acids, or with fetal bovine serum. After polarization, Th1 cells were reactivated and analyzed for interferon-? and IL-4 by intracellular cytokine staining and for apoptosis by Annexin V/propidium iodide. Dietary FO enhanced Th1 polarization by 49% (P = 0.0001) and AICD by 24% (P = 0.0001) only in cells cultured in the presence of HMS. FO enhancement of Th1 polarization and AICD after culture was associated with the maintenance of eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) in plasma membrane lipid rafts. In conclusion, n-3 PUFAs enhance the polarization and deletion of proinflammatory Th1 cells, possibly as a result of alterations in membrane micro-domain fatty acid composition. PMID:15145980

  17. 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

  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. [Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland)

    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. Highly polarization-dependent periodic coupling in mechanically induced long period grating over air-silica fibers

    NASA Astrophysics Data System (ADS)

    Lee, D.; Jung, Y.; Jeong, Y. S.; Oh, K.; Kobelke, J.; Schuster, K.; Kirchhof, J.

    2006-02-01

    A very flexible and versatile tunable mechanical grating platform is introduced, with which highly polarization-dependent mode coupling is observed for three types of air-silica microstructured fibers: hollow core fiber, hexagonal-boundary holey fiber (HHF), and circular-boundary holey fiber. The resonances of gratings showed highly polarization-dependent broadband coupling compared with conventional single-mode fibers due to their unique beat-length dispersions between the core and the cladding modes, which could find applications in wideband polarization-dependent loss compensation. We further present significance of the spatial symmetry of HHF in distinct mode coupling for different rotation angles around the fiber axis.

  1. CCL2 and interleukin-6 promote survival of human CD11b+ peripheral blood mononuclear cells and induce M2-type macrophage polarization.

    PubMed

    Roca, Hernan; Varsos, Zachary S; Sud, Sudha; Craig, Matthew J; Ying, Chi; Pienta, Kenneth J

    2009-12-01

    CCL2 and interleukin (IL)-6 are among the most prevalent cytokines in the tumor microenvironment, with expression generally correlating with tumor progression and metastasis. CCL2 and IL-6 induced expression of each other in CD11b(+) cells isolated from human peripheral blood. It was demonstrated that both cytokines induce up-regulation of the antiapoptotic proteins cFLIP(L) (cellular caspase-8 (FLICE)-like inhibitory protein), Bcl-2, and Bcl-X(L) and inhibit the cleavage of caspase-8 and subsequent activation of the caspase-cascade, thus protecting cells from apoptosis under serum deprivation stress. Furthermore, both cytokines induced hyperactivation of autophagy in these cells. Upon CCL2 or IL-6 stimulation, CD11b(+) cells demonstrated a significant increase in the mannose receptor (CD206) and the CD14(+)/CD206(+) double-positive cells, suggesting a polarization of macrophages toward the CD206(+) M2-type phenotype. Caspase-8 inhibitors mimicked the cytokine-induced up-regulation of autophagy and M2 polarization. Furthermore, E64D and leupeptin, which are able to function as inhibitors of autophagic degradation, reversed the effect of caspase-8 inhibitors in the M2-macrophage polarization, indicating a role of autophagy in this mechanism. Additionally, in patients with advanced castrate-resistant prostate cancer, metastatic lesions exhibited an increased CD14(+)/CD206(+) double-positive cell population compared with normal tissues. Altogether, these findings suggest a role for CCL2 and IL-6 in the survival of myeloid monocytes recruited to the tumor microenvironment and their differentiation toward tumor-promoting M2-type macrophages via inhibition of caspase-8 cleavage and enhanced autophagy. PMID:19833726

  2. Defect-induced Nonpolar-to-polar Transition at the Surface of CuInSe2

    SciTech Connect

    Jaffe, John E.; Zunger, Alex

    2003-09-10

    In contrast to zinc-blende semiconductors, where the nonpolar (110) surface has the lowest energy, our first-principles calculations on the chalcopyrite semiconductor CuInSe2 reveal that facets terminated by the (112)-cation and -Se polar surfaces are lower in energy than the unfaceted (110) plane, despite the resulting increased surface area. This explains the hitherto puzzling existence of polar microfacets on nominally nonpolar (110) chalcopyrite surfaces. The extraordinary stability of these polar facets originates from the effective neutralization of surface charge by low-energy ordered CuIn antisite or Cu vacancy surface defects, while the relaxed but defect-free (112) surface is metallic and much higher in energy. We explain the low carrier density of the observed faceted surface in terms of autocompensation between opposite-polarity facets.

  3. Exchange-striction induced giant ferroelectric polarization in copper-based multiferroic material ? -Cu2V2O7

    NASA Astrophysics Data System (ADS)

    Sannigrahi, J.; Bhowal, S.; Giri, S.; Majumdar, S.; Dasgupta, I.

    2015-06-01

    We report ? -Cu2V2O7 to be an improper multiferroic with the simultaneous development of electric polarization and magnetization below TC=35 K . The observed spontaneous polarization of 0.55 ? C cm-2 magnitude is highest among copper-based improper multiferroic materials. Our study demonstrates a sizable amount of magnetoelectric coupling below TC, even with a low magnetic field. The theoretical calculations based on density functional theory indicate magnetism in ? -Cu2V2O7 is a consequence of ferro-orbital ordering driven by a polar lattice distortion due to the unique pyramidal (CuO5) environment of Cu. Spin-orbit coupling further stabilizes orbital ordering and is crucial for magnetism. The calculations indicate that the origin of the giant ferroelectric polarization is primarily due to the symmetric exchange-striction mechanism and is corroborated by temperature-dependent x-ray studies.

  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. Spatial light modulator based color polarization imaging.

    PubMed

    Tsai, Tsung-Han; Yuan, Xin; Brady, David J

    2015-05-01

    We describe a compressive snapshot color polarization imager that encodes spatial, spectral, and polarization information using a liquid crystal modulator. We experimentally show that polarization imaging is compressible by multiplexing polarization states and present the reconstruction results. This compressive camera captures the spatial distribution of four polarizations and three color channels. It achieves <0.027° spatial resolution, 103 average extinction ratio, and >30 PSNR. PMID:25969281

  6. Interplay between group-delay-dispersion-induced polarization gating and ionization to generate isolated attosecond pulses from multicycle lasers.

    PubMed

    Altucci, Carlo; Velotta, Raffaele; Tosa, Valer; Villoresi, Paolo; Frassetto, Fabio; Poletto, Luca; Vozzi, Caterina; Calegari, Francesca; Negro, Matteo; De Silvestri, Sandro; Stagira, Salvatore

    2010-08-15

    We implemented a new experimental scheme for the generation of single-shot extreme-UV continua that exploits a combination of transform-limited 15 fs, 800 nm pulses and chirped 35 fs, 800 nm pulses with orthogonal polarizations. Continua are interpreted as the formation of a single attosecond pulse and attributed to the interplay between polarization, ionization gating, and trajectory selection operated by suitable phase-matching conditions. PMID:20717461

  7. Depth-selective measurements of induced magnetic polarization in the Cu layer of Gd/Cu multilayers by [superscript 119] Sn Mössbauer Spectroscopy

    SciTech Connect

    Ohkochi, T.; Hosoito, N.; Mibu, K. (Kyoto); (Nara Institute)

    2010-07-20

    We performed {sup 119}Sn Moessbauer spectroscopic measurements on Gd/Cu multilayers with {sup 119}Sn probing atoms. The Cu layers are delta-doped with Sn probes at a certain depth. Hyperfine fields are observed in the Moessbauer spectra at low temperatures below the Curie temperature of the Gd layers. From the temperature-dependent measurements, the hyperfine field is found to be proportional to the spontaneous magnetization of the Gd layer. The result indicates that the Gd magnetization induces magnetic polarization in the Cu layers. The hyperfine field per Gd magnetization is found to be {approx}40 kOe/{mu}{sub B(Gd)}, regardless of the position of the {sup 119}Sn atoms and the Cu thickness (20-40 {angstrom}), suggesting that the magnetic polarization in the Cu layer is uniform at any depth from the Gd/Cu interface.

  8. Performance evaluation for on-orbit modulation transfer function of FengYun-3C medium resolution spectral imager (MERSI) using polar ice and snow

    NASA Astrophysics Data System (ADS)

    Min, Min; Hu, Xiuqing; Bai, Yu

    2014-11-01

    Modulation transfer function (MTF) can be used to evaluate spatial quality of an satellite imaging sensor using a sharp edge, a pulse target, or bar pattern target. This investigation evaluates on-orbit MTF performance of FengYun (FY)-3C MERSI with 20 Bands with 1 km and 250 m spatial resolutions using polar ice and snow as a sharp edge, which was launched on September 23 of 2013. The MTF is calculated by using a Fourier transformation on the line spread function (LSF) though a simple differentiation of the edge spread function (ESF). The final MTF Nyqusit frequencies of the most of MERSI Bands along FY-3C flight direction are higher than 0.30, which are satisfy the original design requirements of 0.25 (250 m) and 0.27 (1km). But the Nyquist frequencies of all Bands along FY-3C scanning direction are around 0.13 that are clearly lower than 0.25/0.27. This relatively worse spatial quality of image along FY-3C scanning direction is primarily attributed to the 27% overlapped scan mode of MERSI sensor for every pixel. The objective of design defect in FY-3C MERSI instrument system is to enhance the signal-to-noise ratio (SNR) of scanning image. To overcome the drawback, in future, we will develop some deblurring methods to restore FY-3C/MERSI image along scanning direction.

  9. Polarization spectroscopy of tokamak plasmas

    SciTech Connect

    Wroblewski, D.

    1991-09-01

    Measurements of polarization of spectral lines emitted by tokamak plasmas provide information about the plasma internal magnetic field and the current density profile. The methods of polarization spectroscopy, as applied to the tokamak diagnostic, are reviewed with emphasis on the polarimetry of motional Stark effect in hydrogenic neutral beam emissions. 25 refs., 7 figs.

  10. 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.

  11. A polarization model overcoming the geometric restrictions of the laplace solution for spheroidal cells: obtaining new equations for field-induced forces and transmembrane potential.

    PubMed

    Gimsa, J; Wachner, D

    1999-09-01

    We present a new model for a variety of electric polarization effects on oblate and prolate homogeneous and single-shell spheroids. For homogeneous spheroids the model is identical to the Laplace model. For single-shell spheres of cell-like geometry the calculated difference of the induced dipole moments is in the thousandths range. To solve Laplace's equation for nonspherical single-shell objects it is necessary to assume a confocal shell, which results in different cell membrane properties in the pole and equator regions, respectively. Our alternative model addresses this drawback. It assumes that the disturbance of the external field due to polarization may project into the medium to a characteristic distance, the influential radius. This parameter is related to the axis ratio of the spheroid over the depolarizing factors and allows us to determine the geometry for a finite resistor-capacitor model. From this model the potential at the spheroid's surface is obtained and, consequently, the local field inside a homogeneous spheroid is determined. In the single-shell case, this is the effective local field of an equivalent homogeneous spheroid. Finally, integration over the volume yields the frequency-dependent induced dipole moment. The resistor-capacitor approach allowed us to find simple equations for the critical and characteristic frequencies, force plateaus and peak heights of deformation, dielectrophoresis and electrorotation for homogeneous and single-shell spheroids, and a more generalized equation for the induced transmembrane potential of spheroidal cells. PMID:10465744

  12. A polarization model overcoming the geometric restrictions of the laplace solution for spheroidal cells: obtaining new equations for field-induced forces and transmembrane potential.

    PubMed Central

    Gimsa, J; Wachner, D

    1999-01-01

    We present a new model for a variety of electric polarization effects on oblate and prolate homogeneous and single-shell spheroids. For homogeneous spheroids the model is identical to the Laplace model. For single-shell spheres of cell-like geometry the calculated difference of the induced dipole moments is in the thousandths range. To solve Laplace's equation for nonspherical single-shell objects it is necessary to assume a confocal shell, which results in different cell membrane properties in the pole and equator regions, respectively. Our alternative model addresses this drawback. It assumes that the disturbance of the external field due to polarization may project into the medium to a characteristic distance, the influential radius. This parameter is related to the axis ratio of the spheroid over the depolarizing factors and allows us to determine the geometry for a finite resistor-capacitor model. From this model the potential at the spheroid's surface is obtained and, consequently, the local field inside a homogeneous spheroid is determined. In the single-shell case, this is the effective local field of an equivalent homogeneous spheroid. Finally, integration over the volume yields the frequency-dependent induced dipole moment. The resistor-capacitor approach allowed us to find simple equations for the critical and characteristic frequencies, force plateaus and peak heights of deformation, dielectrophoresis and electrorotation for homogeneous and single-shell spheroids, and a more generalized equation for the induced transmembrane potential of spheroidal cells. PMID:10465744

  13. Unidirectional spectral singularities.

    PubMed

    Ramezani, Hamidreza; Li, Hao-Kun; Wang, Yuan; Zhang, Xiang

    2014-12-31

    We propose a class of spectral singularities emerging from the coincidence of two independent singularities with highly directional responses. These spectral singularities result from resonance trapping induced by the interplay between parity-time symmetry and Fano resonances. At these singularities, while the system is reciprocal in terms of a finite transmission, a simultaneous infinite reflection from one side and zero reflection from the opposite side can be realized. PMID:25615339

  14. Escherichia coli Maltose-Binding Protein Induces M1 Polarity of RAW264.7 Macrophage Cells via a TLR2- and TLR4-Dependent Manner

    PubMed Central

    Wang, Wan; Yuan, Hong-Yan; Liu, Guo-Mu; Ni, Wei-Hua; Wang, Fang; Tai, Gui-Xiang

    2015-01-01

    Maltose-binding protein (MBP) is a critical player of the maltose/maltodextrin transport system in Escherichia coli. Our previous studies have revealed that MBP nonspecifically induces T helper type 1 (Th1) cell activation and activates peritoneal macrophages obtained from mouse. In the present study, we reported a direct stimulatory effect of MBP on RAW264.7 cells, a murine macrophage cell line. When stimulated with MBP, the production of nitric oxide (NO), IL-1?, IL-6 and IL-12p70, and the expressions of CD80, MHC class II and inducible nitric oxide synthase (iNOS) were all increased in RAW264.7 cells, indicating the activation and polarization of RAW264.7 cells into M1 macrophages induced by MBP. Further study showed that MBP stimulation upregulated the expression of TLR2 and TLR4 on RAW264.7 cells, which was accompanied by subsequent phosphorylation of I?B-? and p38 MAPK. Pretreatment with anti-TLR2 or anti-TLR4 antibodies largely inhibited the phosphorylation of I?B-? and p38 MAPK, and greatly reduced MBP-induced NO and IL-12p70 production, suggesting that the MBP-induced macrophage activation and polarization were mediated by TLR2 and TLR4 signaling pathways. The observed results were independent of lipopolysaccharide contamination. Our study provides a new insight into a mechanism by which MBP enhances immune responses and warrants the potential application of MBP as an immune adjuvant in immune therapies. PMID:25941931

  15. Non-conventional imaging systems for 3D digitization of transparent objects: Shape from polarization in the IR and shape from visible fluorescence induced UV

    NASA Astrophysics Data System (ADS)

    Meriaudeau, F.; Rantoson, R.; Adal, K. M.; Fofi, D.; Stolz, C.

    2013-05-01

    This paper presents a comparison between recent advances made in the field of non-conventional imaging techniques for 3D digitization of transparent object. After a survey, this paper focuses on two recent techniques later called: shape from Visible Fluorescence UV-induced and shape from polarization in the IR which recently emerged. Results obtained with the technique of Scanning from Heating which, originally developed in 2008 for the digitization of transparent objects, has successfully been modified and applied to the digitization of specular objects.

  16. Oxygen-vacancy-induced polar behavior in (LaFeO3)2/(SrFeO3) superlattices

    NASA Astrophysics Data System (ADS)

    Mishra, Rohan; Pantelides, Sokrates; Kim, Young-Min; Salafranca, Juan; Pennycook, Stephen; Borisevich, Albina; Kim, Seong Keun; Chang, Seohyoung; Bhattacharya, Anand; Eastman, Jeffrey; Fong, Dillon

    2014-03-01

    Complex oxides displaying ferroelectric and/or multiferroic behavior are of high fundamental and applied interest. In this work, for the first time, we show that it is possible to achieve polar order in a superlattice made up of two non-polar oxides by means of oxygen vacancy ordering. Using scanning transmission electron microscopy imaging, we show polar displacement of magnetic Fe ions in a superlattice of (LaFeO3)2/(SrFeO3) grown on a SrTiO3 substrate. Using density functional theory calculations, we systematically study the effect of epitaxial strain. octahedral rotations and surface terminations in the superlattice and find them to have negligible effect on the antiferroelectric displacements of the Fe ions lying in between SrO and LaO layers of the superlattice. Introduction of oxygen vacancies, on the other hand, triggers a polar displacement of the Fe ions. We confirm this important result using electron energy loss spectroscopy, which shows oxygen vacancy ordering in the region where polar displacements are observed and an absence of vacancy ordering outside of that area. Overall our results open up a new pathway to design new ferroelectrics and multiferroics.

  17. Polar Bears

    NSDL National Science Digital Library

    Mr. Thomas

    2010-09-27

    Use the following websites to answer questions about the rapid disappearance of polar bears in the Arctic region. Polar Bear picture Polar Bear Tracker 1: What region in the world has the fewest polar bears? 2: Using the internet as a resource, provide some reasons as to why this region is suffering from the most polar bear differences? Polar Bears Change Diet 1: Why are polar bears having to change their diets? 2: List some other factors (besides diet) in the ...

  18. 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.

  19. Thermally induced cooperative molecular reorientation and nanoscale polarization switching behaviors of ultrathin poly(vinylidene fluoride-trifluoroethylene) films.

    PubMed

    Guo, Dong; Stolichnov, Igor; Setter, Nava

    2011-11-24

    Ultrathin films of the ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] have recently attracted intensive research interest due to their potential applications in emerging organic devices. As special geometry confinement systems, many aspects about their processing, microstructure, and performance are far from being well understood. Here, the cooperative molecular orientation, macroscopic ferroelectric properties, and nanoscale polarization switching behaviors of thermally crystallized ultrathin P(VDF-TrFE) films were investigated. With increasing annealing temperature, the films showed a distinct granule toward layered needle-network (LNN) morphology transition with deteriorated ferroelectricity at a critical point (T(cr)) around 140 °C. Accompanying this is that the polymer backbone first lay more parallel relative to the substrate, and then exactly at T(cr) it showed an abrupt standing-up reorientation. Interestingly, the polarization axis simultaneously showed just opposite orientation and reorientation. Nanoscale polarization switching characterization by using piezoresponse force microscopy and local ferroelectric hysteresis loops revealed a varied molecular orientation in the same needle grain and a polarization reversal constraint effect by the inhomogeneous LNN structure. On the basis of these observations, a tilted-chain lamellae structural model was proposed for the LNN film. The lying down of the polarization axis and the polarization reversal constrain effect well explain the inferior performance of the LNN film despite its higher crystallinity than that of the granular film. The results may shed some light on the understanding of the intercorrelation among the thermal crystallization, microstructure, and macroscopic performance of ultrathin polymer films. PMID:22004404

  20. Cationic vacancies and anomalous spectral-weight transfer in Ti1-xTaxO2 thin films studied via polarization-dependent near-edge x-ray absorption fine structure spectroscopy

    NASA Astrophysics Data System (ADS)

    Qi, Dong-Chen; Barman, Arkajit Roy; Debbichi, Lamjed; Dhar, S.; Santoso, Iman; Asmara, Teguh Citra; Omer, Humair; Yang, Kesong; Krüger, Peter; Wee, Andrew T. S.; Venkatesan, T.; Rusydi, Andrivo

    2013-06-01

    We report the electronic structures of Ta-doped anatase TiO2 thin films grown by pulsed laser deposition (PLD) with varying magnetization using a combination of first-principles calculations and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. The roles of Ta doping and Ti vacancies are clarified, and the observed room-temperature ferromagnetism is attributed to the localized magnetic moments at Ti vacancy sites ferromagnetically ordered by electron charge carriers. O K-edge spectra exhibit significant polarization dependence which is discussed and supported by first-principles calculations in relation to both the crystal symmetry and the formation of defects. In particular, anomalous spectral-weight transfer across the entire O K edge for the ferromagnetic thin film is associated exclusively with the occurrence of Ti vacancies and strong correlation effects, which result in the enhancement of the direct interaction between oxygen sites and of the anisotropy of the eg-p? hybridizations in the out-of-plane component. Our results show that O K-edge NEXAFS spectra can provide reliable experimental probes capable of revealing cationic defects that are intimately related to the ferromagnetism in transition metal oxides.

  1. 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...

  2. Spectral and Spread Spectral Teleportation

    SciTech Connect

    Humble, Travis S [ORNL

    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. Polarization and polar climate

    NASA Astrophysics Data System (ADS)

    Overland, James; Schweitzer, Peter

    2012-10-01

    International Polar Year 2012 Conference: From Knowledge to Action;Montreal, Quebec, Canada, 22-27 April 2012 As a follow- up to the 2007-2008 International Polar Year (IPY), more than 3000 international participants came together in April 2012 at a conference entitled “From Knowledge to Action.” The conference addressed a broad scope of topics beyond academic science to include challenges of globalization, climate change, and social and economic issues. Participants included researchers and others with expertise in multiple fields: policy and decision making, law, industry, nongovernmental organizations, circumpolar communities, and indigenous peoples. The challenge of translating academic and other forms of knowledge into societal benefits dominated the event.

  4. 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.

  5. Abnormal dependence of strong-field-ionization-induced nitrogen lasing on polarization ellipticity of the driving field

    NASA Astrophysics Data System (ADS)

    Zhang, Haisu; Jing, Chenrui; Li, Guihua; Xie, Hongqiang; Yao, Jinping; Zeng, Bin; Chu, Wei; Ni, Jielei; Xu, Huailiang; Cheng, Ya

    2013-12-01

    We experimentally investigate lasing behaviors of population-inverted N2+ ions for the transitions between the vibrational level (v' = 0) of excited electronic B 2?u+ state and the two lowest vibrational levels (v = 0, 1) of the ground X 2?g+ state in an elliptically polarized laser field. It is found that, as the polarization of the pump laser evolves from linear to circular, the lasing signal for the 0 ? 0 transition at 391 nm first increases with a maximum enhancement of ˜40% at the ellipticity of 0.3 and then decreases, whereas for the 0 ? 1 transition at 428 nm, the lasing signal decreases monotonically. This difference between the 391- and 428-nm lasing signals is ascribed to the high sensitivity of the strong-field response of the molecular ion to molecular vibrations, which indicates the possibility to control the vibrational state distribution of molecules by tuning the ellipticity of the laser pulse.

  6. The spectral factor in noise-induced hearing loss: A case for retaining the A-weighting

    NASA Astrophysics Data System (ADS)

    Robinson, D. W.

    1983-09-01

    For the measurement of industrial noise in hearing conservation, majority usage including international standard practice favours the A-weighting. Any change would have important practical consequences and wide administrative repercussions, but direct validation of this frequency weighting through comparisons of persistent threshold shift (PTS) is lacking. Data from the study of hearing and noise in industry by Burns and Robinson are re-examined, paying particular attention to the age and noise exposure equivalence of groups of subjects classified by spectrum slope and shape. The results for 101 subjects exposed to 47 different noises fail to reveal significant advantage of the A-weighting over other standardized frequency weightings, a conclusion which may be read as a justification for continued use of the former. The real lesson to be learnt from this analysis is that the possibility of clear-cut determination of an optimum frequency weighting is remote. It would be attainable only through a more extensive bank of data of high reliability covering a wider spectral range, and this does not appear to exist at present.

  7. Tidally induced variations of polar mesospheric cloud altitudes and ice water content using a data assimilation system

    Microsoft Academic Search

    Michael H. Stevens; David E. Siskind; Stephen D. Eckermann; Lawrence Coy; John P. McCormack; Christoph R. Englert; Karl W. Hoppel; Kim Nielsen; Andrew J. Kochenash; Mark E. Hervig; Cora E. Randall; Jerry Lumpe; Scott M. Bailey; Markus Rapp; Peter Hoffmann

    2010-01-01

    A variety of spaceborne experiments have observed polar mesospheric clouds (PMC) since the late 20th century. Many of these experiments are on satellites in Sun-synchronous orbits and therefore allow observations only at fixed local times (LT). Temperature oscillations over the diurnal cycle are an important source of PMC variability. In order to quantify long-term natural or anthropogenic changes in PMCs,

  8. Electrical detection of charge-current-induced spin polarization due to spin-momentum locking in Bi2Se3.

    PubMed

    Li, C H; van 't Erve, O M J; Robinson, J T; Liu, Y; Li, L; Jonker, B T

    2014-03-01

    Topological insulators exhibit metallic surface states populated by massless Dirac fermions with spin-momentum locking, where the carrier spin lies in-plane, locked at right angles to the carrier momentum. Here, we show that a charge current produces a net spin polarization via spin-momentum locking in Bi2Se3 films, and this polarization is directly manifested as a voltage on a ferromagnetic contact. This voltage is proportional to the projection of the spin polarization onto the contact magnetization, is determined by the direction and magnitude of the charge current, scales inversely with Bi2Se3 film thickness, and its sign is that expected from spin-momentum locking rather than Rashba effects. Similar data are obtained for two different ferromagnetic contacts, demonstrating that these behaviours are independent of the details of the ferromagnetic contact. These results demonstrate direct electrical access to the topological insulators' surface-state spin system and enable utilization of its remarkable properties for future technological applications. PMID:24561354

  9. Polar Bear Polar Bear

    NSDL National Science Digital Library

    Kelly Burgess

    2012-09-11

    In this lesson, students will listen for key details in a nonfiction text about polar bears. They will work at completing a graphic organizer with the teacher to help organize their thinking and understanding of key details about a text. They will also complete an independent assignment where they will draw or write two things that they learned about the topic.

  10. Stark broadening of Mg I and Mg II spectral lines and Debye shielding effect in laser induced plasma

    NASA Astrophysics Data System (ADS)

    Cveji?, M.; Gavrilovi?, M. R.; Jovi?evi?, S.; Konjevi?, N.

    2013-07-01

    We report Stark broadening parameters for three Mg I lines and one Mg II line in the electron number density range (0.67-1.09) · 1017 cm- 3 and electron temperature interval (6200-6500) K. The electron density is determined from the half width of hydrogen impurity line, the H?, while the electron temperature is measured from relative intensities of Mg I or Al II lines using Boltzmann plot technique. The plasma source was induced by Nd:YAG laser radiation at 1.06 ?m having pulse width 15 ns and pulse energy 50 mJ. Laser induced plasma is generated in front of a solid state surface. High speed photography is used to determine time of plasma decay with good homogeneity and then applied line self-absorption test and Abel inversion procedure. The details of data acquisition and data processing are described and illustrated with typical examples. The experimental results are compared with two sets of semiclassical calculations and the results of this comparison for Mg I lines are not unambiguous while for Mg II 448.1 nm line, the results of Dimitrijevi? and Sahal-Bréchot calculations agree well with our and other experimental results in the temperature range (5000-12,000) K and these theoretical results are recommended for plasma diagnostic purposes. The study of line shapes within Mg I 383.53 nm multiplet shows that the use of Debye shielding correction improves the agreement between theoretical and experimental Stark broadening parameters.

  11. The role of auditory beats induced by frequency modulation and polyperiodicity in the perception of spectrally embedded complex target sounds.

    PubMed

    Marin, C M; McAdams, S

    1996-09-01

    The contribution of auditory beats to the perception of target sounds differing from an interfering background by their frequency modulation (FM) pattern or by a difference in fundamental frequency (F0) was investigated. On each trial, test sounds composed of a single, second-order formant were embedded in harmonic backgrounds and presented in successive intervals. The center frequencies of these "normal" formants differed across intervals. Subjects were to decide which interval contained the test formant with a center frequency matching that of an isolated target formant presented before each test stimulus. Matching thresholds were measured in terms of the width of modulation for FM stimuli or the mistuning of the F0's of unmodulated test formants relative to that of the background. Beats may have allowed the identification of the spectral region of the target in both experiments. To reduce interactions between test and background components, matching thresholds were measured for "flat" formants composed of two or three equal-amplitude components embedded in a harmonic background in which components corresponding to those of test formants were absent. These measures were repeated with the addition of a pink noise floor. Matching was still possible in all cases, though at higher thresholds than for normal formants. Computer simulations suggested that the modulation depth of envelope fluctuations within auditory channels played a significant role in the matching of target sounds when their components were mixed in the same frequency region with those of an interfering sound, but not when the target and background components were separated by as much as 250 Hz, the F0 of the stimulus. PMID:8817900

  12. Spatial and Continuous Observations of Stream Hydrodynamics and Bedload Transport From Spectral Analysis of River Induced Seismic Noise

    NASA Astrophysics Data System (ADS)

    Burtin, A.; Bollinger, L.; Vergne, J.; Cattin, R.; Náb?lek, J. L.

    2007-12-01

    Analysis of continuous seismic data recorded by a passive seismological network (Hi-CLIMB) installed across the Himalayas reveals strong spatial and temporal variations in the ambient seismic energy produced at high frequencies (> 1 Hz). During the summer 2003, an increase of high-frequency seismic noise is observed for all the stations located along a steep narrow and deeply-incised channel of the Trisuli River, a major trans- Himalayan river. The summer growth in high-frequency energy is modulated by a 24-hour periodicity with minimum amplitude around noon and maximum late in the evening. The comparison of seismic noise amplitude with both regional meteorological and hydrological data along the river reveals clear correlations. Seasonal increase in ambient noise coincides with the strong Monsoon rainfall and a period of rapid melting of snow and ice in the high elevations. The observed 24-hour cyclicity is consistent with the daily fluctuation of the precipitation and river-discharge in the region. The observed river seismic noise is partly generated by stream turbulence but this mechanism fails to explain the noticed clockwise hysteresis of seismic noise amplitude versus water level. This pattern is better explained if a significant part of the observed seismic noise is caused by ground vibrations generated by bedload transport. Monitoring river bedload is essential to understand erosion processes and the evolution of bedload transport are valuable data difficult to acquire, especially during periods of flood crisis. Spectral analysis of background seismic noise could offer a great potential to safely quantify in continuous river bedload and monitor its spatial variations.

  13. L-shaped metallic antenna for linear polarization conversion in reflection

    NASA Astrophysics Data System (ADS)

    Bouchon, Patrick; Lévesque, Quentin; Makhsiyan, Mathilde; Pardo, Fabrice; Jaeck, Julien; Haïdar, Riad; Pelouard, Jean-Luc

    2015-02-01

    The design of metasurfaces able to efficiently control the polarization state of an electromagnetic wave is of importance for various applications. We demonstrate both theoretically and experimentally that plasmonic planar L-shaped antennas can induce a 90° -rotation of the linear polarization of light with a nearly total efficiency in the infrared (3-5 µm). The influence of the in-plane geometry of the nanoantenna is investigated, and it is shown that it can be engineered so that the polarization conversion occurs over a 1 µm-wide spectral band ([3.25-4.25] µm) with a mean polarization conversion efficiency of 95%. These results are experimentally confirmed on two samples with distinctive geometries.

  14. Electrochemical Polarization-Induced Changes in the Growth of Individual Cells and Biofilms of Pseudomonas fluorescens (ATCC 17552)

    PubMed Central

    Busalmen, Juan Pablo; de Sánchez, Susana R.

    2005-01-01

    The effect of surface electrochemical polarization on the growth of cells of Pseudomonas fluorescens (ATCC 17552) on gold electrodes has been examined. Potentials positive or negative to the potential of zero charge (PZC) of gold were applied, and these resulted in changes in cell morphology, size at cell division, time to division, and biofilm structure. At ?0.2 V (Ag/AgCl-3 M NaCl), cells elongated at a rate of up to 0.19 ?m min?1, rendering daughter cells that reached up to 3.8 ?m immediately after division. The doubling time for the entire population, estimated from the increment in the fraction of surface covered by bacteria, was 82 ± 7 min. Eight-hour-old biofilms at ?0.2 V were composed of large cells distributed in expanded mushroom-like microcolonies that protruded several micrometers in the solution. A different behavior was observed under positive polarization. At an applied potential of 0.5 V, the doubling time of the population was 103 ± 8 min, cells elongated at a lower rate (up to 0.08 ?m min?1), rendering shorter daughters (2.5 ± 0.5 ?m) after division, although the duplication times were virtually the same at all potentials. Biofilms grown under this positive potential were composed of short cells distributed in a large number of compact microcolonies. These were flatter than those grown at ?0.2 V or at the PZC and were pyramidal in shape. Polarization effects on cell growth and biofilm structure resembled those previously reported as produced by changes in the nutritional level of the culture medium. PMID:16204543

  15. 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.

  16. 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

  17. 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.

  18. Improving the delineation of hydrocarbon-impacted soils and water through induced polarization (IP) tomographies: a field study at an industrial waste land.

    PubMed

    Deceuster, John; Kaufmann, Olivier

    2012-08-01

    Without a good estimation of samples representativeness, the delineation of the contaminated plume extent and the evaluation of volumes of hydrocarbon-impacted soils may remain difficult. To contribute to this question, a time domain induced polarization (IP) field experiment was conducted on an industrial waste land. Boreholes were drilled to specify the local geological context. Cross-hole seismic tomographies were performed to extend borehole logs and to draw an interpreted geological cross-section. Soil samples taken during drillings were analysed in laboratory. A preliminary survey was conducted to locate the IP profile. The polarization signatures linked to the presence of clayey sediments were filtered out from the data set. Chargeability and resistivity depth soundings were computed and compared to mean concentrations of total organic products to overcome the data support issue between the geophysical models and the spot samples of soils. A logarithmic relation between chargeabilities and smoothed hydrocarbon concentrations in soils was found. Taking into account contaminant's concentration thresholds defined in local codes and regulations allows defining chargeability classes to delineate hotspots on this site. This showed that IP tomography can be an accurate screening methodology. A statistical methodology is proposed to assess the efficiency of the investigation strategy. PMID:22659399

  19. Epidermal growth factor receptor activation induces nuclear targeting of cyclooxygenase-2, basolateral release of prostaglandins, and mitogenesis in polarizing colon?cancer?cells

    PubMed Central

    Coffey, Robert?J.; Hawkey, Chris?J.; Damstrup, Lars; Graves-Deal, Ramona; Daniel, Vincent?C.; Dempsey, Peter?J.; Chinery, Rebecca; Kirkland, Susan?C.; DuBois, Raymond?N.; Jetton, Thomas?L.; Morrow, Jason?D.

    1997-01-01

    Nonsteroidal antiinflammatory drugs reduce the risk of colon cancer, possibly via cyclooxygenase (COX) inhibition. The growth factor-inducible COX-2, which is overexpressed in neoplastic colonic tissue, is an attractive target to mediate this effect. Herein we have exploited the ability of a human colon cancer cell line, HCA-7 Colony 29, to polarize when cultured on Transwell (Costar) filters to study COX-2 production and the vectorial release of prostaglandins (PGs). Administration of type ? transforming growth factor to the basolateral compartment, in which the epidermal growth factor receptor (EGFR) resides, results in a marked induction of COX-2 immunoreactivity at the base of the cells and the unexpected appearance of COX-2 in the nucleus. The increase in COX-2 protein is associated with a dose- and time-dependent increase in PG levels in the basolateral, but not apical, medium. Amphiregulin is the most abundantly expressed EGFR ligand in these cells, and the protein is present at the basolateral surface. EGFR blockade reduces baseline COX-2 immunoreactivity, PG levels, and mitogenesis in a concentration-dependent manner. Two specific COX-2 inhibitors, SC-58125 and NS 398, also, in a dose-dependent manner, attenuate baseline and type ? transforming growth factor-stimulated mitogenesis, although PG levels are decreased >90% at all concentrations of inhibitor tested. These findings show that activation of the EGFR stimulates COX-2 production and its translocation to the nucleus, vectorial release of PGs, and mitogenesis in polarized HCA-7 Colony 29 cells. PMID:9012840

  20. The Dynamic Polar Magnetic Field Before Its Polarity Reversal

    NASA Astrophysics Data System (ADS)

    Sun, X.; Hoeksema, J. T.; Liu, Y.; Sainz Dalda, A.; Norton, A.; Hayashi, K.

    2012-12-01

    We characterize the magnetic field in the Sun's polar region using the spectropolarimetric measurement from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). With HMI's high cadence, continuous time coverage, and moderate spectral and spatial resolution, we are able to estimate the polar magnetic flux, its latitudinal distribution, and its temporal variation over three years (2010-2012) during Cycle 24's rising phase. A comparison with higher spectral resolution observations from Hinode SOT/SP provides constraints on the flux estimates. The tracking of individual magnetic element movements yields new insight on the polar field's dynamic behavior leading up to the polarity reversal. We compare the result with that from the HMI line-of-sight data, as well as MDI data for Cycle 23. All observations indicate an earlier reversal of the northern hemisphere owing to more solar activity in the rising phase, which resulted in a significant hemispheric asymmetry.

  1. Inducing polarity in [VO{sub 3}]{sub n}{sup n-} chain compounds using asymmetric hydrogen-bonding networks

    SciTech Connect

    Smith, Matthew D.; Blau, Samuel M.; Chang, Kelvin B. [Department of Chemistry, Haverford College, Haverford PA 19041 (United States)] [Department of Chemistry, Haverford College, Haverford PA 19041 (United States); Tran, Thanh Thao [Department of Chemistry, University of Houston, Houston, TX 77204 (United States)] [Department of Chemistry, University of Houston, Houston, TX 77204 (United States); Zeller, Matthias [Department of Chemistry, Youngstown State University, Youngstown OH 44555 (United States)] [Department of Chemistry, Youngstown State University, Youngstown OH 44555 (United States); Halasyamani, P. Shiv [Department of Chemistry, University of Houston, Houston, TX 77204 (United States)] [Department of Chemistry, University of Houston, Houston, TX 77204 (United States); Schrier, Joshua [Department of Chemistry, Haverford College, Haverford PA 19041 (United States)] [Department of Chemistry, Haverford College, Haverford PA 19041 (United States); Norquist, Alexander J., E-mail: anorquis@haverford.edu [Department of Chemistry, Haverford College, Haverford PA 19041 (United States)

    2012-11-15

    1,4-Bis(3-aminopropyl)piperazine, (R)-3-aminopiperidine and (S)-3-aminopiperidine were used in the syntheses of [C{sub 10}H{sub 26}N{sub 4}][VO{sub 3}]{sub 2}{center_dot}2H{sub 2}O, [(R)-C{sub 5}H{sub 14}N{sub 2}][VO{sub 3}]{sub 2} and [(S)-C{sub 5}H{sub 14}N{sub 2}][VO{sub 3}]{sub 2}, which all contain similar [VO{sub 3}]{sub n}{sup n-} chains. Inversion symmetry within the 1,4-bis(3-aminopropyl)piperazine allows for crystallization of [C{sub 10}H{sub 26}N{sub 4}][VO{sub 3}]{sub 2}{center_dot}2H{sub 2}O in a centrosymmetric space group, while the use of enantiomerically pure sources of either (R)-3-aminopiperidine or (S)-3-aminopiperidine forces crystallographic noncentrosymmetry. Moreover, asymmetry in the hydrogen-bonding networks between the metavanadate chains and either [(R)-3-aminopiperidineH{sub 2}]{sup 2+} or [(S)-3-aminopiperidineH{sub 2}]{sup 2+} cations directs alignment of the chains and crystallization in a polar space group (C2, no. 5). Component and net dipole moments were calculated using iterative-Hirshfeld partial atomic charges. [(R)-C{sub 5}H{sub 14}N{sub 2}][VO{sub 3}]{sub 2} and [(S)-C{sub 5}H{sub 14}N{sub 2}][VO{sub 3}]{sub 2} both display type 1 phase-matching capabilities and exhibit second harmonic generation activities of {approx}140 Multiplication-Sign {alpha}-SiO{sub 2}. - Graphical abstract: One centrosymmetric and a pair of polar noncentrosymmetric templated metavanadates were synthesized under mild hydrothermal conditions. Asymmetry in the hydrogen-bonding between either [(R)-C{sub 5}H{sub 14}N{sub 2}]{sup 2+} or [(S)-C{sub 5}H{sub 14}N{sub 2}]{sup 2+} and [VO{sub 3}]{sub n}{sup n-} chains results in polar structures that exhibit type 1 phase-matching capabilities. Hirshfeld surfaces were used to probe the hydrogen-bonding networks and component and net dipole moments were calculated from atomic positions and iterative-Hirshfeld partial charges. Highlights: Black-Right-Pointing-Pointer One centrosymmetric and a pair of polar templated metavanadate chain compounds are reported. Black-Right-Pointing-Pointer Asymmetry in the hydrogen-bonding networks drives the compound polarities. Black-Right-Pointing-Pointer Iterative-Hirshfeld partitioning was used to calculate partial atomic charges. Black-Right-Pointing-Pointer Net and component dipole moments are calculated for each compound. Black-Right-Pointing-Pointer Type 1 phase-matching behavior and SHG activities of {approx}140 Multiplication-Sign {alpha}-SiO{sub 2} are found.

  2. Low-Frequency Oscillations and Transport Processes Induced by Multiscale Transverse Structures in the Polar Wind Outflow: A Three-Dimensional Simulation

    NASA Technical Reports Server (NTRS)

    Ganguli, Supriya B.; Gavrishchaka, Valeriy V.

    1999-01-01

    Multiscale transverse structures in the magnetic-field-aligned flows have been frequently observed in the auroral region by FAST and Freja satellites. A number of multiscale processes, such as broadband low-frequency oscillations and various cross-field transport effects are well correlated with these structures. To study these effects, we have used our three-dimensional multifluid model with multiscale transverse inhomogeneities in the initial velocity profile. Self-consistent-frequency mode driven by local transverse gradients in the generation of the low field-aligned ion flow and associated transport processes were simulated. Effects of particle interaction with the self-consistent time-dependent three-dimensional wave potential have been modeled using a distribution of test particles. For typical polar wind conditions it has been found that even large-scale (approximately 50 - 100 km) transverse inhomogeneities in the flow can generate low-frequency oscillations that lead to significant flow modifications, cross-field particle diffusion, and other transport effects. It has also been shown that even small-amplitude (approximately 10 - 20%) short-scale (approximately 10 km) modulations of the original large-scale flow profile significantly increases low-frequency mode generation and associated cross-field transport, not only at the local spatial scales imposed by the modulations but also on global scales. Note that this wave-induced cross-field transport is not included in any of the global numerical models of the ionosphere, ionosphere-thermosphere, or ionosphere-polar wind. The simulation results indicate that the wave-induced cross-field transport not only affects the ion outflow rates but also leads to a significant broadening of particle phase-space distribution and transverse particle diffusion.

  3. Detecting a new source for photochemically induced dynamic nuclear polarization in the LOV2 domain of phototropin by magnetic-field dependent (13)C NMR spectroscopy.

    PubMed

    Kothe, Gerd; Lukaschek, Michail; Link, Gerhard; Kacprzak, Sylwia; Illarionov, Boris; Fischer, Markus; Eisenreich, Wolfgang; Bacher, Adelbert; Weber, Stefan

    2014-10-01

    Phototropin is a flavin mononucleotide (FMN) containing blue-light receptor, which regulates, governed by its two LOV domains, the phototropic response of higher plants. Upon photoexcitation, the FMN cofactor triplet state, (3)F, reacts with a nearby cysteine to form a covalent adduct. Cysteine-to-alanine mutants of LOV domains instead generate a flavin radical upon illumination. Here, we explore the formation of photochemically induced dynamic nuclear polarization (CIDNP) in LOV2-C450A of Avena sativa phototropin and demonstrate that photo-CIDNP observed in solution (13)C NMR spectra can reliably be interpreted in terms of solid-state mechanisms including a novel triplet mechanism. To minimize cross-polarization, which transfers light-induced magnetization to adjacent (13)C nuclei, our experiments were performed on proteins reconstituted with specifically (13)C-labeled flavins. Two potential sources for photo-CIDNP can be identified: The photogenerated triplet state, (3)F, and the triplet radical pair (3)(F(-•)W(+•)), formed by electron abstraction of (3)F from tryptophan W491. To separate the two contributions, photo-CIDNP studies were performed at four different magnetic fields ranging from 4.7 to 11.8 T. Analysis revealed that, at fields <9 T, both (3)(F(-•)W(+•)) and (3)F contribute to photo-CIDNP, whereas at high magnetic fields, the calculated enhancement factors of (3)F agree favorably with their experimental counterparts. Thus, we have for the first time detected that a triplet state is the major source for photo-CIDNP in a photoactive protein. Since triplet states are frequently encountered upon photoexcitation of flavoproteins, the novel triplet mechanism opens up new means of studying electronic structures of the active cofactors in these proteins at atomic resolution. PMID:25207844

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

    NASA Astrophysics Data System (ADS)

    Burtin, A.; Bollinger, L.; Vergne, J.; Cattin, R.; NáB?Lek, J. L.

    2008-05-01

    Analysis of continuous seismic data recorded by a dense passive seismological network (Hi-CLIMB) installed across the Himalayas reveals strong spatial and temporal variations in the ambient seismic energy produced at high frequencies (>1 Hz). From June to September 2003, the high-frequency seismic noise is observed to increase up to 20 dB (relative to (m/s)2/Hz) for all the stations located along a steep 30-km-long narrow and deeply incised channel of the Trisuli River, a major trans-Himalayan river. The early summer increase in high-frequency energy is modulated by a 24-h periodicity where the minimum of seismic noise level is reached around noon and the maximum is reached late in the evening. A detailed study of seismic noise amplitude reveals a clear correlation with both regional meteorological and hydrological data along the Trisuli River. Seasonal increase in ambient noise coincides with the strong monsoon rainfall and a period of rapid melting of snow and ice in the high elevations. The observed 24-h cyclicity is consistent with the daily fluctuation of the precipitation and river discharge in the region. River-induced seismic noise is partly generated by stream turbulence, but this mechanism fails to explain the observed clockwise hysteresis of seismic noise amplitude versus water level. This pattern is better explained if a significant part of the observed seismic noise is caused by ground vibrations generated by bed load transport. This points out the potential of using background seismic noise to quantify in continuous river bed load and monitor its spatial variations, which remain difficult with classical approaches.

  5. Vacuum polarization and Casimir energy of a Dirac field induced by a scalar potential in one spatial dimension

    NASA Astrophysics Data System (ADS)

    Gousheh, S. S.; Mousavi, S. S.; Shahkarami, L.

    2014-08-01

    We investigate the vacuum polarization and Casimir energy of a Dirac field coupled to a scalar potential in one spatial dimension. Both of these effects have a common cause, which is the distortion of the spectrum of the Dirac field due to its coupling with the background field. Choosing the potential to be a symmetrical square well renders the problem exactly solvable, and we can obtain the whole spectrum of the system analytically. We show that the total number of states and the total density remain unchanged as compared with the free case, as one expects. Furthermore, since there is a reflection symmetry between positive- and negative-energy eigenstates of the fermion, the total density and the total number of negative and positive states remain unchanged, separately. This, along with the fact that there is no zero mode, mandate that the vacuum polarization in this model is zero for any choice of the parameters of the potential. It is important to note that although the vacuum polarization is zero due to the symmetries of the model, the Casimir energy of the system is not zero in general. In the graph of the Casimir energy as a function of the depth of the well, there is a maximum approximately when the bound energy levels change direction and move back towards their continuum of origin. The Casimir energy for a fixed value of the depth is an almost linear increasing function of the width. Moreover, the Casimir energy density (the energy density of all the negative-energy states) and the energy density of all the positive-energy states are exactly the mirror images of each other. Finally, we compute the total energy of a valence fermion present in the lowest positive-energy fermionic bound state. We find that taking into account the Casimir energy does not result in the appearance of any local minima in the graphs of the total energy as a function of the parameters of the model, and this is in sharp contrast to the cases where there are levels crossing the line E=0.

  6. Induced spin-polarization of EuS at room temperature in Ni/EuS multilayers

    SciTech Connect

    Poulopoulos, P., E-mail: poulop@upatras.gr [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Materials Science Department, University of Patras, 26504 Patras (Greece); Goschew, A.; Straub, A.; Fumagalli, P. [Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin-Dahlem (Germany); Kapaklis, V.; Wolff, M. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden); Delimitis, A. [Chemical Process and Energy Resources Institute (CPERI), Centre for Research and Technology Hellas (CERTH), 57001 Thermi, Thessaloniki (Greece); Wilhelm, F.; Rogalev, A. [European Synchrotron Radiation Facility (ESRF), B.P.220, 38043 Grenoble (France); Pappas, S. D. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden)

    2014-03-17

    Ni/EuS multilayers with excellent multilayer sequencing are deposited via e-beam evaporation on the native oxide of Si(100) wafers at 4?×?10{sup ?9} millibars. The samples have very small surface and interface roughness and show sharp interfaces. Ni layers are nanocrystalline 4–8?nm thick and EuS layers are 2–4?nm thick and are either amorphous or nanocrystalline. Unlike for Co/EuS multilayers, all Eu ions are in divalent (ferromagnetic) state. We show a direct antiferromagnetic coupling between EuS and Ni layers. At room temperature, the EuS layers are spin-polarized due to the proximity of Ni. Therefore, Ni/EuS is a candidate for room-temperature spintronics applications.

  7. Inducing self-rotation of cells with natural and artificial melanin in a linearly polarized alternating current electric field

    PubMed Central

    Ouyang, Mengxing; Ki Cheung, Wing; Liang, Wenfeng; Mai, John D.; Keung Liu, Wing; Jung Li, Wen

    2013-01-01

    The phenomenon of self-rotation observed in naturally and artificially pigmented cells under an applied linearly polarized alternating current (non-rotating) electrical field has been investigated. The repeatable and controllable rotation speeds of the cells were quantified and their dependence on dielectrophoretic parameters such as frequency, voltage, and waveform was studied. Moreover, the rotation behavior of the pigmented cells with different melanin content was compared to quantify the correlation between self-rotation and the presence of melanin. Most importantly, macrophages, which did not originally rotate in the applied non-rotating electric field, began to exhibit self-rotation that was very similar to that of the pigmented cells, after ingesting foreign particles (e.g., synthetic melanin or latex beads). We envision the discovery presented in this paper will enable the development of a rapid, non-intrusive, and automated process to obtain the electrical conductivities and permittivities of cellular membrane and cytoplasm in the near future. PMID:24404075

  8. Synthesis of polymer-derived ceramic Si(B)CN-carbon nanotube composite by microwave-induced interfacial polarization.

    PubMed

    Bhandavat, R; Kuhn, W; Mansfield, E; Lehman, J; Singh, G

    2012-01-01

    We demonstrate synthesis of a polymer-derived ceramic (PDC)-multiwall carbon nanotube (MWCNT) composite using microwave irradiation at 2.45 GHz. The process takes about 10 min of microwave irradiation for the polymer-to-ceramic conversion. The successful conversion of polymer coated carbon nanotubes to ceramic composite is chemically ascertained by Fourier transform-infrared and X-ray photoelectron spectroscopy and physically by thermogravimetric analysis and transmission electron microscopy characterization. Frequency dependent dielectric measurements in the S-Band (300 MHz to 3 GHz) were studied to quantify the extent of microwave-CNT interaction and the degree of selective heating available at the MWCNT-polymer interface. Experimentally obtained return loss of the incident microwaves in the specimen explains the reason for heat generation. The temperature-dependent permittivity of polar molecules further strengthens the argument of internal heat generation. PMID:22141448

  9. Laser excitation-induced structure distortion and persistent spectral hole burning of Eu{sup 3+} in BaFC1.

    SciTech Connect

    Liu, G. K.; Li, S. T.; Beitz, J. V.; Chemistry

    1999-11-01

    Persistent spectral hole burning (PSHB) has been demonstrated in the inhomogeneously broadened {sup 7}F{sub 0}{yields}{sup 5}D{sub 0} transition of Eu{sup 3+} ions in crystals of BaFCl at temperatures below 77 K. It was shown that the observed PSHB effect was due to laser excitation-induced site conversion. In the lattice of BaFCl, multiple Eu{sup 3+} sites formed due to charge imbalance and the presence of defects. Eu{sup 3+} population at one site could be depleted and converted to another site. This process was not optically reversible and holes were erased only when temperature was increased to 150 K. Persistent holes burned at 3 K had an average width of 500 MHz while hyperfine transient holes burned at the same temperature were only 25 MHz wide. Although cycling of sample temperature did not affect the shape of the persistent hole, hole width and peak position were quadratic functions of temperature.

  10. Spectral Switching Control of Ultrafast Pulses in Dual Core Photonic Crystal Fibre

    NASA Astrophysics Data System (ADS)

    Koys, M.; Bugar, I.; Hrebikova, I.; Mesaros, V.; Buczynski, R.; Uherek, F.

    2013-07-01

    The work presented in this paper is a study of an all-optical narrow-band switch in extended spectral area by dual core photonic crystal fibre expressing nonlinear coupler performance. The investigation is focused on the nonlinear propagation of femtosecond pulses in the near infrared spectral region at up to 50 kW peak power which induces spectral broadening through almost two octaves. The mutual effect of nonlinear spectral transformation and field redistribution between the two fibre cores is analyzed by both theoretical and experimental approaches. The simulation of the nonlinear propagation is based on coupled generalized nonlinear Schrödinger equations. A modified numerical model utilizing split-step Fourier method was adapted for dual core fibres. The complex experimental study was accomplished for various input settings such as polarization, intensity and selective coupling into each core and the selective detection of spectra from each core. The presented work e! ncompasses promising results obtained regarding a spectral intensity switch between the two output channels by input intensity or polarization change in the S-band of optical communication systems.

  11. Polarized Sunglasses

    NSDL National Science Digital Library

    2011-12-05

    In this activity, learners explore how polarizing sunglasses can help diminish road glare. By rotating a pair of polarizing sunglass lenses or other polarizing materials, learners will discover that some angles are better at reducing glare than others. Learners observe light from the sky, reflected from a mirror, or reflected from the surface of a pond. Use this activity to introduce learners to principles of light and polarization.

  12. Polarized Electrons for Polarized Positrons

    NASA Astrophysics Data System (ADS)

    Fanchini, Erica

    2012-03-01

    Recently, the nuclear and high-energy physics communities have shown a growing interest in the availability of high current, highly spin-polarized positron beams. The Polarized Electrons for Polarized Positrons (PEPPo) experiment at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) aims to measure the transfer of polarization from a low energy 10 MeV highly spin polarized electron beam to positrons. A sufficiently energetic polarized photon or lepton may generate, via bremsstrahlung and pair creation processes within a target foil, electron-positron pairs that will carry a fraction of the initial polarization. This approach has been successfully tested using polarized photons created with a multi-GeV unpolarized electron beam, resulting in positrons with polarization of 80%. Although pair creation yield is reduced at lower energy, recent advances in high current milliampere spin-polarized electron sources at Jefferson Lab offer the perspective of creating polarized positrons using a low energy electron beam. A successful demonstration of this technique would provide an alternative scheme to produce low energy polarized positrons, as well as useful information to optimize the design of a polarized positron source using sub-GeV electron beam. An overview and status of the PEPPo experiment will be presented, along with some of the motivations in the context of the Jefferson Lab nuclear physics program.

  13. Advanced search for the origin of life's homochirality: asymmetric photon induced processes on chiral compounds with far UV circularly polarized synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Nahon, Laurent; Garcia, Gustavo; Powis, Ivan; Meierhenrich, Uwe; Brack, André

    2007-09-01

    Assuming an extra-terrestrial formation of life's molecular building blocks such as amino-acids, a possible abiotic explanation for the selection of the L enantiomers could be the exposure to an asymmetric bias such as far UV Circularly Polarized Light (CPL), during their journey towards Earth, inducing some enantiomeric excess (e.e) that could then be amplified on Earth via suitable autocatalytic mechanisms. Synchrotron Radiation (SR), with its intense flux and broad tunability, is a unique tool which mimics such an interstellar far UV CPL. We have recently employed it to study : (1) The irradiation of solid films of the amino acid D,L-leucine, i.e. under relevant astrophysical conditions. Starting from racemic D,L-leucine irradiated with CPL SR beam at 6.8 eV (182 nm), we have been able to induce by enantioselective photolysis an e.e. of 2.6 %, as measured by chiral-sensitive CG-MS analysis, in accordance with the CD spectrum recorded on the same type of sample. (2) CPL-induced gas phase photoionization of chiral molecules. By measuring the angular distribution of photoelectrons ejected from pure enantiomers, we observed a strong anisotropy (up to 16 %) in the forward/backward direction with respect to the light propagation axis. Because of momentum conservation, such an effect is accompanied by an asymmetric recoil of the corresponding ions that could lead to a high e.e. Future prospects on the new VUV SR beamline DESIRS at SOLEIL are presented.

  14. Loss of AQP4 polarized localization with loss of ?-dystroglycan immunoreactivity may induce brain edema following intracerebral hemorrhage.

    PubMed

    Qiu, Guo-Ping; Xu, Jin; Zhuo, Fei; Sun, Shan-Quan; Liu, Hui; Yang, Mei; Huang, Juan; Lu, Wei-Tian; Huang, Si-Qin

    2015-02-19

    The aquaporin-4 (AQP4) water channel contributes to brain water homeostasis in perivascular and subpial membrane domains of astrocytes where it is concentrated. These membranes form the interface between the neuropil and the extracellular liquid spaces. The brain-selective deletion of the dystroglycan (DG) gene causes a disorganization of AQP4 on the astroglial endfeet. First, we analyzed the expression of AQP4, ?-DG in the brain following intracerebral hemorrhage (ICH) and correlated AQP4 expression with the expression pattern of the ?-DG, which is a component of dystrophin-dystroglycan complex (DDC). Besides, the vessels ultrastructure and brain water content were investigated at different time points post-ICH (day 1, day 3, day 7). We found that AQP4 polarity was disturbed in parallel with the loss of ?-DG in the perihematomal area post-ICH. At day 1 post-ICH, brain edema was obvious and the damage of vascular ultrastructure was the most severe. These results suggest a role for ?-DG in targeting and stabilizing AQP4 channel in astrocytic cells, which may be critical for water homeostasis in brain. PMID:25545558

  15. Magnetization switching of a metallic nanomagnet via current-induced surface spin-polarization of an underlying topological insulator

    NASA Astrophysics Data System (ADS)

    Roy, Urmimala; Dey, Rik; Pramanik, Tanmoy; Ghosh, Bahniman; Register, Leonard F.; Banerjee, Sanjay K.

    2015-04-01

    We consider a thermally stable, metallic nanoscale ferromagnet (FM) subject to spin-polarized current injection and exchange coupling from the spin-helically locked surface states of a topological insulator (TI) to evaluate possible non-volatile memory applications. We consider parallel transport in the TI and the metallic FM, and focus on the efficiency of magnetization switching as a function of transport between the TI and the FM. Transport is modeled as diffusive in the TI beneath the FM, consistent with the mobility in the TI at room temperature, and in the FM, which essentially serves as a constant potential region albeit spin-dependent except in the low conductivity, diffusive limit. Thus, it can be captured by drift-diffusion simulation, which allows for ready interpretation of the results. We calculate switching time and energy consumed per write operation using self-consistent transport, spin-transfer-torque (STT), and magnetization dynamics calculations. Calculated switching energies and times compare favorably to conventional spin-torque memory schemes for substantial interlayer conductivity. Nevertheless, we find that shunting of current from the TI to a metallic nanomagnet can substantially limit efficiency. Exacerbating the problem, STT from the TI effectively increases the TI resistivity. We show that for optimum performance, the sheet resistivity of the FM layer should be comparable to or larger than that of the TI surface layer. Thus, the effective conductivity of the FM layer becomes a critical design consideration for TI-based non-volatile memory.

  16. Escherichia coli maltose-binding protein activates mouse peritoneal macrophages and induces M1 polarization via TLR2/4 in vivo and in vitro.

    PubMed

    Ni, Weihua; Zhang, Qingyong; Liu, Guomu; Wang, Fang; Yuan, Hongyan; Guo, Yingying; Zhang, Xu; Xie, Fei; Li, Qiongshu; Tai, Guixiang

    2014-07-01

    Maltose-binding protein (MBP) is a component of the maltose transport system of Escherichia coli. Our previous study found that MBP combined with Bacillus Calmette-Guerin (BCG) increases the percentage of activated macrophages in the spleen and the pinocytic activity of peritoneal macrophages in vivo. However, the effect of MBP alone on macrophages remains unclear. In the present study, the results showed that MBP enhanced LPS-stimulated macrophage activity in vivo. Subsequently, we investigated the regulatory effect of MBP on mouse peritoneal macrophages in vitro and the possible underlying mechanism. The results showed that MBP directly promoted macrophage phagocytic activity and increased the production of NO, IL-1? and IL-6. Notably, macrophage phenotypic analysis showed that MBP significantly increased iNOS, IL-12p70 and CD16/32. In contrast, MBP decreased the secretion of IL-10 and slightly decreased Arg-1 mRNA and CD206 protein expression. These results suggested that MBP activated macrophages and polarized them into M1 macrophages. Further study found that MBP directly bound to macrophages and upregulated TLR2 mRNA expression. This process was accompanied by a clear increase in MyD88 expression and phosphorylation of p38 MAPK and I?B-?, but these effects were largely abrogated by pretreatment with anti-TLR2 or anti-TLR4 antibodies. The effects of MBP on macrophage NO production were also partially inhibited by anti-TLR2 and/or anti-TLR4 antibodies. Furthermore, the effect of MBP on IL-12 and IL-10 secretion was largely influenced by the NF-?B inhibitor PDTC and the p38 MAPK inhibitor SB203580. These results suggest that MBP directly activates macrophages and induces M1 polarization through a process that may involve TLR2 and TLR4. PMID:24825603

  17. Tidally induced variations of polar mesospheric cloud altitudes and ice water content using a data assimilation system

    NASA Astrophysics Data System (ADS)

    Stevens, Michael H.; Siskind, David E.; Eckermann, Stephen D.; Coy, Lawrence; McCormack, John P.; Englert, Christoph R.; Hoppel, Karl W.; Nielsen, Kim; Kochenash, Andrew J.; Hervig, Mark E.; Randall, Cora E.; Lumpe, Jerry; Bailey, Scott M.; Rapp, Markus; Hoffmann, Peter

    2010-09-01

    A variety of spaceborne experiments have observed polar mesospheric clouds (PMC) since the late 20th century. Many of these experiments are on satellites in Sun-synchronous orbits and therefore allow observations only at fixed local times (LT). Temperature oscillations over the diurnal cycle are an important source of PMC variability. In order to quantify long-term natural or anthropogenic changes in PMCs, it is therefore essential to understand their variation over the diurnal cycle. To this end, we employ a prototype global numerical weather prediction system that assimilates satellite temperature and water vapor observations from the ground to ˜90 km altitude. We assemble the resulting 6 hourly high-altitude meteorological assimilation fields from June 2007 in both LT and latitude and use them to drive a one-dimensional PMC formation model with cosmic smoke serving as nucleation sites. We find that there is a migrating diurnal temperature tide at 69°N with a variation of ±4 K at 83 km, which controls the variation of PMC total ice water content (IWC) over the diurnal cycle. The calculated IWC is normalized to observations at 2300 LT by the Solar Occultation for Ice Experiment and allowed to vary with temperature over the diurnal cycle. We find that the IWC at 69°N has a single maximum between 0700 and 0800 LT and a minimum between 1900 and 2200 LT and varies by at least a factor of 5. The calculated variation of IWC with LT is substantially larger at 57°N, with a single prominent peak near 0500 LT.

  18. Coherent ?-electron dynamics of (P)-2,2'-biphenol induced by ultrashort linearly polarized UV pulses: Angular momentum and ring current

    NASA Astrophysics Data System (ADS)

    Mineo, H.; Lin, S. H.; Fujimura, Y.

    2013-02-01

    The results of a theoretical investigation of coherent ?-electron dynamics for nonplanar (P)-2,2'-biphenol induced by ultrashort linearly polarized UV pulses are presented. Expressions for the time-dependent coherent angular momentum and ring current are derived by using the density matrix method. The time dependence of these coherences is determined by the off-diagonal density matrix element, which can be obtained by solving the coupled equations of motion of the electronic-state density matrix. Dephasing effects on coherent angular momentum and ring current are taken into account within the Markov approximation. The magnitudes of the electronic angular momentum and current are expressed as the sum of expectation values of the corresponding operators in the two phenol rings (L and R rings). Here, L (R) denotes the phenol ring in the left (right)-hand side of (P)-2,2'-biphenol. We define the bond current between the nearest neighbor carbon atoms Ci and Cj as an electric current through a half plane perpendicular to the Ci-Cj bond. The bond current can be expressed in terms of the inter-atomic bond current. The inter-atomic bond current (bond current) depends on the position of the half plane on the bond and has the maximum value at the center. The coherent ring current in each ring is defined by averaging over the bond currents. Since (P)-2,2'-biphenol is nonplanar, the resultant angular momentum is not one-dimensional. Simulations of the time-dependent coherent angular momentum and ring current of (P)-2,2'-biphenol excited by ultrashort linearly polarized UV pulses are carried out using the molecular parameters obtained by the time-dependent density functional theory (TD-DFT) method. Oscillatory behaviors in the time-dependent angular momentum (ring current), which can be called angular momentum (ring current) quantum beats, are classified by the symmetry of the coherent state, symmetric or antisymmetric. The bond current of the bridge bond linking the L and R rings is zero for the symmetric coherent state, while it is nonzero for the antisymmetric coherent state. The magnitudes of ring current and ring current-induced magnetic field are also evaluated, and their possibility as a control parameter in ultrafast switching devices is discussed. The present results give a detailed description of the theoretical treatment reported in our previous paper [H. Mineo, M. Yamaki, Y. Teranish, M. Hayashi, S. H. Lin, and Y. Fujimura, J. Am. Chem. Soc. 134, 14279 (2012), 10.1021/ja3047848].

  19. Macroscopic polarization entanglement in type II OPO

    Microsoft Academic Search

    R. Zambrini; A. Gatti; L. Lugiato; M. San Miguel

    2003-01-01

    The paper reports on the investigation on to which extent the microscopic polarization properties survive at a macroscopic level, in presence of a continuous flux of photons, in a transverse spatially extended system. A prototype device to generate polarization entangled beams is a quadratic crystal in the type II phase matching configuration. The spectral brightness can be increased by means

  20. Vibrationally induced inversion of photoelectron forward-backward asymmetry in chiral molecule photoionization by circularly polarized light

    PubMed Central

    Garcia, Gustavo A.; Nahon, Laurent; Daly, Steven; Powis, Ivan

    2013-01-01

    Electron–nuclei coupling accompanying excitation and relaxation processes is a fascinating phenomenon in molecular dynamics. A striking and unexpected example of such coupling is presented here in the context of photoelectron circular dichroism measurements on randomly oriented, chiral methyloxirane molecules, unaffected by any continuum resonance. Here, we report that the forward-backward asymmetry in the electron angular distribution, with respect to the photon axis, which is associated with photoelectron circular dichroism can surprisingly reverse direction according to the ion vibrational mode excited. This vibrational dependence represents a clear breakdown of the usual Franck–Condon assumption, ascribed to the enhanced sensitivity of photoelectron circular dichroism (compared with other observables like cross-sections or the conventional anisotropy parameter-?) to the scattering phase off the chiral molecular potential, inducing a dependence on the nuclear geometry sampled in the photoionization process. Important consequences for the interpretation of such dichroism measurements within analytical contexts are discussed. PMID:23828557

  1. Polarization-sensitive cathodoluminescence Fourier

    E-print Network

    Polman, Albert

    and B. Hecht, Principles of Nano-Optics (Cambridge University Press, New York, 2006), 251­362. 3. N. J@amolf.nl Abstract: Determining the emission polarization properties of sub- wavelength structures like optical with the sensitivity to the local density of optical states, broad spectral range and high excitation resolution, can

  2. Nonlinear polarization conversion using microring resonators

    Microsoft Academic Search

    Chris Fietz; Gennady Shvets

    2007-01-01

    We present a design of a polarization converter between linear, circular, and elliptic accomplished with an on-chip high-Q dielectric microring resonator. Nonlinear polarization switching can be accomplished at modest input intensities because of the high-intensity compression in the ring. We predict an optical bistability effect making the polarization of the transmitted light dependent on its spectral or intensity history.

  3. Spectral unmixing

    Microsoft Academic Search

    Carmen Quintano; Alfonso Fernández-Manso; Yosio E. Shimabukuro; Gabriel Pereira

    2012-01-01

    Satellite imagery is formed by finite digital numbers representing a specific location of ground surface in which each matrix element is denominated as a picture element or pixel. The pixels represent the sensor measurements of spectral radiance. The radiance recorded in the satellite images is then an integrated sum of the radiances of all targets within the instantaneous field of

  4. Spectral classification

    Microsoft Academic Search

    C. Jaschek

    1982-01-01

    Taxonomic classification of astronomically observed stellar objects is described in terms of spectral properties. Stars receive a classification containing a letter, number, and a Roman numeral, which relates the star to other stars of higher or lower Roman numerals. The citation indicates the stellar chromatic emission in relation to the wavelengths of other stars. Standards are chosen from the available

  5. Enantiomeric excesses induced in amino acids by ultraviolet circularly polarized light irradiation of extraterrestrial ice analogs: A possible source of asymmetry for prebiotic chemistry

    SciTech Connect

    Modica, Paola; De Marcellus, Pierre; D'Hendecourt, Louis Le Sergeant [Univ. Paris-Sud, Institut d'Astrophysique Spatiale, UMR 8617, F-91405 Orsay (France); Meinert, Cornelia; Meierhenrich, Uwe J. [Univ. Nice Sophia Antipolis, Institut de Chimie de Nice, UMR 7272 CNRS, F-06108 Nice (France); Nahon, Laurent, E-mail: laurent.nahon@synchrotron-soleil.fr, E-mail: ldh@ias.u-psud.fr [Synchrotron SOLEIL, F-91192 Gif-sur-Yvette (France)

    2014-06-10

    The discovery of meteoritic amino acids with enantiomeric excesses of the L-form (ee {sub L}) has suggested that extraterrestrial organic materials may have contributed to prebiotic chemistry and directed the initial occurrence of the ee {sub L} that further led to homochirality of amino acids on Earth. A proposed mechanism for the origin of ee {sub L} in meteorites involves an asymmetric photochemistry of extraterrestrial ices by UV circularly polarized light (CPL). We have performed the asymmetric synthesis of amino acids on achiral extraterrestrial ice analogs by VUV CPL, investigating the chiral asymmetry transfer at two different evolutionary stages at which the analogs were irradiated (regular ices and/or organic residues) and at two different photon energies (6.6 and 10.2 eV). We identify 16 distinct amino acids and precisely measure the L-enantiomeric excesses using the enantioselective GC × GC-TOFMS technique in five of them: ?-alanine, 2,3-diaminopropionic acid, 2-aminobutyric acid, valine, and norvaline, with values ranging from ee {sub L} = –0.20% ± 0.14% to ee {sub L} = –2.54% ± 0.28%. The sign of the induced ee {sub L} depends on the helicity and the energy of CPL, but not on the evolutionary stage of the samples, and is the same for all five considered amino acids. Our results support an astrophysical scenario in which the solar system was formed in a high-mass star-forming region where icy grains were irradiated during the protoplanetary phase by an external source of CPL of a given helicity and a dominant energy, inducing a stereo-specific photochemistry.

  6. Polarization developments

    SciTech Connect

    Prescott, C.Y.

    1993-07-01

    Recent developments in laser-driven photoemission sources of polarized electrons have made prospects for highly polarized electron beams in a future linear collider very promising. This talk discusses the experiences with the SLC polarized electron source, the recent progress with research into gallium arsenide and strained gallium arsenide as a photocathode material, and the suitability of these cathode materials for a future linear collider based on the parameters of the several linear collider designs that exist.

  7. Electric Field and Structural Phase Transition Induced Magnetization Effects in BaTiO3 -FeRh Heterostructures Probed using Polarized Neutron Reflectometry

    NASA Astrophysics Data System (ADS)

    Bennett, Steven; Ward, Thomas; Biegalski, Michael; Wong, Tony; Liu, Zhiqi; Ambaye, Haile; Glavic, Artur

    2015-03-01

    The ability to change the magnetic state of a material with an electric field opens up a plethora of possible devices in spintronics and memory applications. A strong candidate material for such a control is FeRh, whose magneto-structural phase transition from antiferromagnetic (AFM) to ferromagnetic (FM) at T ~350K, has shown to be controllably changed by an electric field when grown on ferroelectric BaTiO3 (BTO). It has been suggested that this shift is largely due to the -0.47% in plane compressive strain induced by the piezoelectric BTO. Here we show a sharp repeatable change in magnetization as the system is heated/cooled through the tetragonal to orthorhombic (280-290K) and orthorhombic to rhombohedral (180-205K) crystalline phase transitions of BTO. To further characterize the effect polarized neutron reflectometry (PNR) was used to evolve the depth profile of magnetization in FeRh within the temperature vicinity of these transitions with and without the application of electric field. This work was carried out at the Center for Nanophase Materials Sciences (CNMS) and the Spallation Neutron Source (SNS) supported by the Scientific User Facilities Divisions, Office of Basic Energy Sciences, DOE.

  8. Magnetization oscillations induced by a spin-polarized current in a point-contact geometry: Mode hopping and nonlinear damping effects

    NASA Astrophysics Data System (ADS)

    Berkov, D. V.; Gorn, N. L.

    2007-10-01

    In this paper, we study magnetization excitations induced in a thin extended film by a spin-polarized dc current injected through a point contact in the current-perpendicular-to-plane geometry. Using full-scale micromagnetic simulations, we demonstrate that in addition to the oscillations of the propagating wave type, there exist also two localized oscillation modes. The first localized mode has a relatively homogeneous magnetization structure of its core and corresponds to the so-called “bullet” predicted analytically by Slavin and Tiberkevich [Phys. Rev. Lett. 95, 237201 (2005)]. Magnetization pattern of the second localized mode core is highly inhomogeneous, leading to a much lower power of magnetoresistance oscillations caused by this mode. We have also studied the influence of a nonlinear damping for this system and have found the following main qualitative effects: (i) the appearance of frequency jumps within the existence region of the propagating wave mode and (ii) the narrowing of the current region where the bullet mode exists, until this mode completely disappears for a sufficiently strong nonlinear damping.

  9. CONTROL OF LASER RADIATION PARAMETERS: Spectral nonreciprocity induced by a magnetic field in nonstationary lasing regimes of a solid-state ring laser

    NASA Astrophysics Data System (ADS)

    Kravtsov, Nikolai V.; Lariontsev, E. G.; Pashinin, Pavel P.; Sidorov, S. S.; Chekina, S. N.

    2004-04-01

    It is found experimentally that the application of a magnetic field to the active element of a monolithic ring Nd:YAG chip laser in nonstationary lasing regimes can result in nonidentical spectral parameters of counterpropagating radiation waves (spectral nonreciprocity) in quasi-periodic and chaotic lasing regimes. The value of the spectral nonreciprocity depends on the coupling coefficient of counterpropagating waves, the excess over the pump threshold, and the optical nonreciprocity of the ring cavity. The obtained results are in good agreement with the results of numerical simulation.

  10. Neuronal polarization.

    PubMed

    Takano, Tetsuya; Xu, Chundi; Funahashi, Yasuhiro; Namba, Takashi; Kaibuchi, Kozo

    2015-06-15

    Neurons are highly polarized cells with structurally and functionally distinct processes called axons and dendrites. This polarization underlies the directional flow of information in the central nervous system, so the establishment and maintenance of neuronal polarization is crucial for correct development and function. Great progress in our understanding of how neurons establish their polarity has been made through the use of cultured hippocampal neurons, while recent technological advances have enabled in vivo analysis of axon specification and elongation. This short review and accompanying poster highlight recent advances in this fascinating field, with an emphasis on the signaling mechanisms underlying axon and dendrite specification in vitro and in vivo. PMID:26081570

  11. Invariance of spectrum and polarization of electromagnetic Gaussian Schell-model beams propagating in free space

    Microsoft Academic Search

    Jixiong Pu

    2006-01-01

    The propagation of polychromatic electromagnetic Gaussian Schell-model (EGSM) beams in free space is investigated. It is shown that the spectral degree of polarization, spectral degree of coherence, and normalized spectrum change generally on propagation. The conditions of keeping the spectral invariance and keeping polarization invariance for the polychromatic EGSM beams are derived respectively. The results indicate that the constraints on

  12. Spectral classification

    NASA Astrophysics Data System (ADS)

    Jaschek, C.

    Taxonomic classification of astronomically observed stellar objects is described in terms of spectral properties. Stars receive a classification containing a letter, number, and a Roman numeral, which relates the star to other stars of higher or lower Roman numerals. The citation indicates the stellar chromatic emission in relation to the wavelengths of other stars. Standards are chosen from the available objects detected. Various classification schemes such as the MK, HD, and the Barbier-Chalonge-Divan systems are defined, including examples of indexing differences. Details delineating the separations between classifications are discussed with reference to the information content in spectral and in photometric classification schemes. The parameters usually used for classification include the temperature, luminosity, reddening, binarity, rotation, magnetic field, and elemental abundance or composition. The inclusion of recently discovered extended wavelength characteristics in nominal classifications is outlined, together with techniques involved in automated classification.

  13. Polar Bear

    USGS Publications Warehouse

    Amstrup, S.D.; DeMaster

    1988-01-01

    Polar bears are long-lived, late-maturing carnivores that have relatively low rates of reproduction and natural mortality. Their populations are susceptible to disturbance from human activities, such as the exploration and development of mineral resources or hunting. Polar bear populations have been an important renewable resource available to coastal communities throughout the Arctic for thousands of years.

  14. Muons for spintronics: Photo-induced conduction electron polarization in n-type GaAs observed by the muonium method

    NASA Astrophysics Data System (ADS)

    Yokoyama, K.; Nagamine, K.; Shimomura, K.; Tom, H. W. K.; Kawakami, R.; Bakule, P.; Matsuda, Y.; Pratt, F. L.; Torikai, E.

    2009-04-01

    The spin-dependent exchange scattering between the muonium (Mu) electron and polarized conduction electrons excited by circularly polarized 831 nm laser light was observed in n-type GaAs with 3.6×10 16 cm -3 Si doping at low temperature by measuring a change in the polarization of Mu against the conduction electron polarization (CEP) direction. Correct signal response was confirmed with respect to the laser power. These results are encouraging for the Mu technique to be applied to probe CEP in various spintronics material systems.

  15. An interpretation of induced-polarization data collected in the Haenam area, southern part of Korea Peninsula, based on effective nonlinear inversion

    NASA Astrophysics Data System (ADS)

    Kim, Bitnarae; Jang, Hannuree; Nam, Myung Jin; Kim, Hee Joon; Son, Jeong-Sul

    2015-04-01

    The Haenam area in the southern tip of Korean Peninsula, which experienced broad hydrothermal transition during the Late Cretaceous and Early Tertiary times and whose geology is composed of granitic rocks, quartz porphyry, andesite, rhyolite, tuff and sedimentary rocks, is known to have many clay-alunite and gold-silver deposits. For the investigation of new gold deposits near an existing gold mine, both electrical-resistivity and induced polarization (IP) surveys have been conducted based on dipole-dipole array with 10 m-electrode spacing. The survey line is set to be 200 m and nearly normal to the geological strike. Together with the surveys, an investigation borehole was drilled about 130 m away from the survey line, and coring has been conducted during the drilling. For the interpretation of IP data, linear inversion of IP data based on approximate linearization has been conducted after making 3D inversion of electrical-resistivity data. The inversion result shows that area of high intrinsic chargeability complies with area of high-salinity, which is interpreted from the borehole data. However, the linear inversion has high chance to contain unwanted error during the inversion process since the inversion is based on the linearization approximation of a non-linear problem by assuming the value of intrinsic chargeability is very small. In this study, we first develop an efficient non-linear inversion algorithm to invert the IP data based on finite element method using tetrahedral elements. Then, we apply the developed algorithm to synthetic IP data and compare its results with those from existing IP inversion algorithms. Finally, we make non-linear inversion of the Haenam field data not only to interpret the data more precisely but also to compare its results with existing-interpretation results from linear-IP inversion. The analysis confirms that the non-linear time domain IP inversion reflects the geological characteristics in the survey area, complying with the logging data.

  16. Low-energy spectral features of supernova (anti)neutrinos in inverted hierarchy

    NASA Astrophysics Data System (ADS)

    Fogli, G. L.; Lisi, E.; Marrone, A.; Mirizzi, A.; Tamborra, I.

    2008-11-01

    In the dense supernova core, self-interactions may align the flavor polarization vectors of ? and ?¯ and induce collective flavor transformations. Different alignment Ansätze are known to describe approximately the phenomena of synchronized or bipolar oscillations and the split of ? energy spectra. We discuss another phenomenon observed in some numerical experiments in inverted hierarchy, showing features akin to a low-energy split of ?¯ spectra. The phenomenon appears to be approximately described by another alignment Ansatz which, in the considered scenario, reduces the (nonadiabatic) dynamics of all energy modes to only two ? plus two ?¯ modes. The associated spectral features, however, appear to be fragile when passing from single to multiangle simulations.

  17. Recent Advances in Polarized He-3 Targets

    SciTech Connect

    Singh, Jaideep; Dolph, Peter; Mooney, Karen; Nelyubin, Vladimir; Tobias, Al; Cates, Gordon [Physics Department, University of Virginia, P.O.Box 400714, Charlottesville, VA 22904-4714 (United States); Kelleher, Aidan; Averett, Todd [Dept. of Physics, College of William and Mary, P.O. Box 8795, Williamsburg, VA 23187-8795 (United States)

    2009-08-04

    Recently there have been many important advances made in spin-exchange optical-pumping (SEOP) polarized He-3 targets. Use of hybrid K-Rb SEOP achieved He-3 polarizations near 50% in-beam during the recent JLab G{sub E}{sup n} experiment (E02013). Combining well-optimized alkali-hybrid SEOP with high-power spectrally-narrowed laser diode arrays increases He-3 polarizations to 70%. We describe how these technologies work and why they improve target polarization.

  18. Molecule Polarity

    NSDL National Science Digital Library

    The PhET project at the University of Colorado creates "fun, interactive, research-based simulations of physical phenomena." This particular one deals with molecular polarity. When is a molecule polar? Change the electronegativity of atoms in a molecule to see how it affects polarity. This simulation will allow visitors to see how molecules behave in an electric field, and change the bond angle to see how shape affects polarity for real molecules in 3D. The simulation is also paired with teaching tips and user-contirubed Teaching Ideas, lessons using the simulation in context, that can be found near the bottom of the page. The simulation is also available in multiple languages.

  19. Generation of Polarization-Entangled Photons in a Standard Polarization-Maintaining Fiber

    NASA Astrophysics Data System (ADS)

    Lorenz, V. O.; Fang, Bin; Cohen, Offir

    2013-02-01

    We demonstrate the capability of standard, commercially available polarization-maintaining fibers (PMFs) to generate polarization-entangled photon-pairs by inserting a PMF source into a Sagnac interferometer. We perform a quantum state tomography to reconstruct the density matrix, yielding, without background subtraction or spectral filtering, a polarization-entangled photon-pair state with 92.37 ± 0.14% fidelity to the maximally entangled Bell state. With its high coupling efficiency into SMFs and ability to produce spectrally uncorrelated photons, we expect this source to be useful for free-space and fiber-based quantum information protocols.

  20. Polarization ellipse and Stokes parameters of a stochastic electromagnetic Gaussian Schell-model beam propagating through a polarization grating

    Microsoft Academic Search

    G. Wu; Y. Cai

    An analytical propagation formula for the cross-spectral density matrix of a stochastic electromagnetic Gaussian Schell-model\\u000a (EGSM) beam after propagating through a polarization grating is derived with the help of a tensor method. The statistics properties,\\u000a particularly the degree of polarization, polarization ellipse and Stokes parameters, of the EGSM beam on propagation after\\u000a passing through a polarization grating are studied numerically.