Note: This page contains sample records for the topic spectral induced polarization from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

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

National Technical Information Service (NTIS)

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 mod...

F. D. Morgan

2004-01-01

2

Spectral induced polarization signatures of hydroxyl adsorption in porous media  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

3

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

Microsoft Academic Search

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

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

2005-01-01

4

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

Microsoft Academic Search

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

Heikki Vanhala

1997-01-01

5

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

Microsoft Academic Search

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

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

2008-01-01

6

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

7

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

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

8

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

SciTech Connect

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

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

2007-10-01

9

Spectral induced polarization of partially saturated clay-rocks: a mechanistic approach  

NASA Astrophysics Data System (ADS)

We have developed a mechanistic model to interpret spectral induced polarization data of partially saturated clay-rocks. This model accounts for the polarization of the grains through an electrical double layer model with a polarization model of the inner part of the electrical double layer called the Stern layer. The polarization model accounts also for the Maxwell-Wagner polarization at frequencies higher than 100 Hz. The Maxwell-Wagner polarization is modelled by using a conductivity model modified to account for the presence of a non-wetting immiscible phase like air in the pore space. The resulting model is consistent with the first and second Archie's laws in the case where surface conductivity can be neglected. The volumetric charge density of the diffuse layer at saturation is divided by the saturation of the water phase to account for the partial water saturation of the porous material. The model comprises seven fundamental parameters: the formation factor, the second Archie's exponent, a critical water saturation level, the mean electrical potential of the pore space at saturation, the density of the counterions in the Stern layer, and at least two parameters describing the grain size distribution. Most of these parameters can be derived independently using alternative measurements and electrochemical models. Measurements were performed in the frequency range 10 mHz-45 kHz using five samples from the Callovo-Oxfordian formation in the eastern part of the Paris Basin, France. The model agrees fairly well with the experimental data at saturation and for partially saturated clay-rocks down to 1 Hz. Most of the seven physical parameters entering the model were independently evaluated.

Jougnot, D.; Ghorbani, A.; Revil, A.; Leroy, P.; Cosenza, P.

2010-01-01

10

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

NASA Astrophysics Data System (ADS)

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

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

2008-06-01

11

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

SciTech Connect

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

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

2008-02-15

12

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

NASA Astrophysics Data System (ADS)

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).

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

2007-12-01

13

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

SciTech Connect

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.

Morgan, F. Dale; Lesmes, David

2004-12-31

14

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

SciTech Connect

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

Morgan, F. Dale; Sogade, John

2004-12-14

15

Pore-scale Spectral Induced Polarization (SIP) signatures associated with FeS biomineral transformations  

NASA Astrophysics Data System (ADS)

We measured Spectral Induced Polarization (SIP) signatures in sand columns during (1) FeS biomineralization produced by sulfate reducing bacteria (D. vulgaris) under anaerobic conditions, and (2) subsequent biomineral dissolution upon return to an aerobic state. The low-frequency (0.1-10 Hz peak) relaxations produced during biomineralization can be modeled with a Cole-Cole formulation, from which the evolution of the polarization magnitude and relaxation length scale can be estimated. We convert the polarization magnitude to an equivalent FeS surface area per unit pore volume using a previously published empirical relation. The modeled time constant is converted to an equivalent polarizable sphere diameter using a theoretical relation and an assumed value of the surface diffusion coefficient. We find that the modeled time constant is consistent with the polarizable elements being biomineral encrusted pores rather than the biominerals themselves. The temporal SIP signatures suggest FeS surface area increases and pore-size reduction during biomineral growth, with subsequent FeS surface area decreases and pore expansion upon FeS dissolution that occurs during the return of the system to an aerobic state. The geoelectrical interpretation is consistent with changes in aqueous chemistry during the experiment, and solid phase analysis conducted at the termination of the experiment. We conclude that SIP signatures are diagnostic of pore-scale geometrical changes associated with FeS biomineralization by sulfate reducing bacteria. The study highlights the potential for using geoelectrical methods to monitor microbial driven changes in hydraulic conductivity resulting from biomineralization.

Slater, L.; Ntarlagiannis, D.; Personna, Y.; Hubbard, S.

2007-12-01

16

Spectral induced polarization measurements for environmental purposes and predicting the hydraulic conductivity in sandy aquifers  

NASA Astrophysics Data System (ADS)

Low-frequency field and laboratory induced polarization measurements are carried out to characterize the hydrogeological conditions at Schillerslage test site in Germany. The laboratory spectral induced polarization (SIP) data are analyzed to derive an empirical relationship for predicting the hydraulic conductivity (K) in the field scale. On the other hand, the results from SIP sounding and profiling field data indicate that the method identifies the lithological layers with sufficient resolution to achieve our objectives. Two main Quaternary groundwater aquifers separated by a till layer can be well differentiated. Furthermore, the phase images are also capable of monitoring thin peat layers within the sandy groundwater aquifer. However, the field results show limitations of decreasing resolution with depth and/or low data coverage. Similarly, the SIP laboratory results show a certain shift in SIP response due to different compaction and sorting of the samples. The overall results obtained show that the integration of field and laboratory SIP measurements is an efficient tool to avoid a hydrogeological misinterpretation. In particular, two significant but weak correlations between individual real resistivities (?') and relaxation times (?), based on a Debye decomposition (DD) model, with measured K are found for the upper groundwater aquifer. While the maximum relaxation time (?max) and logarithmically weighted average relaxation time (?lw) show a better relation with K values than the median value ?50, however, the single relationships are weak. A combined power law relation between individual ?' and/or ? with K is developed with an expression of A · (?')B · (?lw)C, where A, B and C are determined using a least-squares fit between the measured and predicted K. The suggested approach with the calculated coefficients of the first aquifer is applied for the second one. The results indicate a good correlation with the measured K and prove to be superior to single phase angle models as the Börner or Slater models.

Attwa, M.; Günther, T.

2013-04-01

17

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

USGS Publications Warehouse

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

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

1983-01-01

18

Spectral induced polarization response to nanoparticles in a saturated sand matrix  

NASA Astrophysics Data System (ADS)

Nanoparticles have grown in importance over the last decade with significant consumer and industrial applications. Yet, the behavior (fate and transport) of nanoparticles in the environment is virtually unknown. Research is needed to identify, characterize, and monitor nanomaterials in the subsurface. Here, we investigate the spectral induced polarization (SIP) response of nanometallic powders (nZVI, nAg, nTiO 2, nZnO, and nCeO 2) in porous geologic media. Our main objective is to determine the sensitivity of the SIP response (0.1-10,000 Hz) to the presence of nanoparticles (metals and metal oxides) in porous media. The SIP response was tested under various conditions: increasing particle concentration under constant solution chemistry; varying solution molarity (0.0 M-1.0 M), and varying solution valence (+ 1, + 2, + 3 valence) under constant particle volume. We examine the results in terms of phase shift and resistance magnitude. Our data suggest that the oxide nanoparticles do not show SIP responses to increasing particle concentration, solution valence, and molarity, while the metallic particles show a clear response to increasing particle concentration, and frequency. Silver was the only material to show any significant response to increasing solution molarity, valence, and frequency. Because of the high propensity of the nanoparticles to form aggregates, they essentially behave as colloidal and clay particles allowing us to apply conventional SIP theory to our interpretation. We suggest that the oxidation state of the metals diminishes their SIP response consistent with more recent studies that have documented that polarization decreases with oxidation of metallic particles. We infer from our results that nanoparticle crystalline composition and aggregation effects control the SIP response of nanoparticles in porous media.

Joyce, Ryan A.; Glaser, Danney R.; Werkema, D. Dale; Atekwana, Estella A.

2012-02-01

19

Spectral induced polarization measurements for predicting the hydraulic conductivity in sandy aquifers  

NASA Astrophysics Data System (ADS)

Field and laboratory spectral induced polarization (SIP) measurements are integrated to characterize the hydrogeological conditions at the Schillerslage test site in Germany. The phase images are capable of monitoring thin peat layers within the sandy aquifers. However, the field results show limitations of decreasing resolution with depth. In comparison with the field inversion results, the SIP laboratory measurements show a certain shift in SIP response due to different compaction and sorting of the samples. The SIP data are analyzed to derive an empirical relationship for predicting the hydraulic conductivity (K). In particular, two significant but weak correlations between individual real resistivities (?') and relaxation times (?), based on a Debye decomposition (DD) model, with measured K are found for the upper groundwater aquifer. The maximum relaxation time (?max) and logarithmically weighted average relaxation time (?lw) show a better relation with K values than the median value ?50. A combined power law relation between individual ?' and ? with K is developed with an expression of A · (?')B · (?lw)C, where A, B and C are determined using a least-squares fit between the measured and predicted K. The suggested approach with the calculated coefficients of the first aquifer is applied for the second. Results show good correlation with the measured K indicating that the derived relationship is superior to single phase angle models as Börner or Slater models.

Attwa, M.; Günther, T.

2013-10-01

20

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

NASA Astrophysics Data System (ADS)

The induced-polarization (IP) method has been used increasingly in environmental investigations because IP measurements are very sensitive to the low frequency capacitive properties of rocks and soils. The Cole-Cole model has been very useful for interpreting spectral IP data in terms of parameters, such as chargeability and time constant, which are used to estimate various subsurface properties. However, conventional methods for estimating Cole-Cole parameters use an iterative Gauss-Newton-based deterministic method, which has been shown that the obtained optimal solution depends on the choice of initial values and the estimated uncertainty information often is inaccurate or insufficient. Chen, Kemna, and Hubbard (2008) developed a Bayesian model for inverting spectral IP data for Cole-Cole parameters based on Markov chain Monte Carlo (MCMC) sampling methods. They have demonstrated that the MCMC-based inversion method provides extensive global information on unknown parameters, such as the marginal probability distribution functions, from which better estimates and tighter uncertainty bounds of the parameters can be obtained. Additionally, the results obtained with the MCMC method are almost independent of the choice of initial values. We have developed a web interface to the stochastic inversion software, which permits easy accessibility to the code. The web interface allows users to upload their own spectral IP data, specify prior ranges of unknown parameters, and remotely run the code in real time. After running the code (a few minutes), the interface provides a data file with all the statistics of each unknown parameter, including the median, mean, standard deviation, and 95% predictive intervals, and provides a data misfit file. The interface also allows users to visualize the histogram and posterior probability density of each unknown parameter as well as data misfits. For advanced users, the interface provides an option of producing time-series plots of all the samples so that the users can adjust prior ranges and re-run the code. The application was tested with real data collected from two different field sites (Hanford, WA, and Rifle, CO) of the U.S. Department of Energy. This interface will be available at the poster session for testing. Users are requested to bring their datasets on a USB stick in advance with the following format: the first column of the dataset should be frequencies and the second and third columns of the dataset should be real and imaginary components of complex resistivity (or amplitude and phases) respectively.

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

2009-12-01

21

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

22

Spectral Induced Polarization Response of Unconsolidated Saturated Sand and Surfactant Solutions  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

23

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

NASA Astrophysics Data System (ADS)

Jeffrey Heenan, Dimitrios Ntarlagiannis, Lee Slater Department of Earth and Environmental Sciences, Rutgers University, Newark NJ Microbial Enhanced Oil Recovery (MEOR) is an established, cost effective, method for enhancing tertiary oil recovery. Although not commonly used for shallow heavy oils, it could be a viable alternative since it can offer sustainable economic recovery and minimal environmental impact. A critical component of successful MEOR treatments is accurate, real time monitoring of the biodegradation processes resulting from the injection of microbial communities into the formation; results of recent biogeophysical research suggest that minimally-invasive geophysical methods could significantly contribute to such monitoring efforts. Here we present results of laboratory experiments, to assess the sensitivity of the spectral induced polarization method (SIP) to MEOR treatments. We used heavy oil, obtained from a shallow oilfield in SW Missouri, to saturate three sand columns. We then followed common industry procedures,and used a commercially available microbial consortia, to treat the oil columns. The active MEOR experiments were performed in duplicate while a control column maintained similar conditions, without promoting microbial activity and oil degradation. We monitored the SIP signatures, between 0.001 Hz and 1000 Hz, for a period of six months. To support the geophysical measurements we also monitored common geochemical parameters, including pH, Eh and fluid conductivity, and collected weekly fluid samples from the outflow and inflow for further analysis; fluid samples were analyzed to confirm that microbes actively degraded the heavy oils in the column while destructive analysis of the solid materials was performed upon termination of the experiment. Preliminary analysis of the results suggests that SIP is sensitive to MEOR processes. In both inoculated columns we recorded an increase in the low frequency polarization with time; measureable changes up to 3.5 mrads in the phase shift were recorded for both active columns, and for all electrode pairs. On the contrary, no change was observed in the control column for the duration of the experiment. These results may indicate that remote geophysical methods could successfully complement current MEOR monitoring schemes for promoting sustainable oil recovery.

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

2010-12-01

24

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

25

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

Microsoft Academic Search

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

Heikki Vanhala; Heikki Soininen

1995-01-01

26

Pore fluid chemistry and spectral induced polarization signatures of calcium carbonate  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

27

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

28

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

29

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

30

A mechanistic model for the spectral induced polarization of clay materials  

Microsoft Academic Search

Water-saturated clay-rich media exhibit low-frequency (1 Hz to 1 MHz) effective conductivity and effective permittivity dispersions that are the consequence of both the polarization of the mineral\\/water interface coating the surface of the grains and the Maxwell-Wagner polarization. These low-frequency properties are modeled by combining (1) a complexation model of the surface properties of clay minerals (kaolinite, illite, and smectite),

P. Leroy; A. Revil

2009-01-01

31

A mechanistic model for the spectral induced polarization of clay materials  

NASA Astrophysics Data System (ADS)

Water-saturated clay-rich media exhibit low-frequency (1 Hz to 1 MHz) effective conductivity and effective permittivity dispersions that are the consequence of both the polarization of the mineral/water interface coating the surface of the grains and the Maxwell-Wagner polarization. These low-frequency properties are modeled by combining (1) a complexation model of the surface properties of clay minerals (kaolinite, illite, and smectite), (2) a polarization model of the Stern layer (the inner portion of the electrical double layer coating the surface of the minerals), and (3) a macroscopic model comprising the electrochemical polarization of the grains and the contribution of the Maxwell-Wagner effect. The macroscopic model is based on the differential effective medium theory. It includes a convolution product with the grain size distribution. For kaolinite, the diffuse layer occupies a small fraction of the pore space and is considered as part of the surface of the grains. This is due to the low specific surface area of kaolinite. In the case of illite and smectite, the situation is different. Because of the high specific surface areas of these minerals, the diffuse layer occupies a large fraction of the pore space and is considered as part of the pore space and is described using a Donnan equilibrium model. We obtain excellent comparisons between various experimental data reported in the literature and our model. Then, we considered low-porosity (compacted or cemented) clay rocks and shales. Here too, we obtained a good agreement between the data and the predictions of a model based on a volume-averaging approach. We also note that at very low frequencies (<1 Hz), another polarization mechanism exists that is not reproduced by our model. We believe that this polarization corresponds to a nonlinear membrane polarization contribution.

Leroy, P.; Revil, A.

2009-10-01

32

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

33

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

34

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

35

Multiband stereometamaterial-based polarization spectral filter  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

36

Coded aperture snapshot spectral polarization imaging.  

PubMed

We describe a single-shot polarization spectral imager that combines two birefringent crystals with a binary coded aperture to encode the spatial, spectral and polarization data cube for compressive sampling on a two-dimensional (2D) detector array. We use a total variation prior to reconstruct the four-dimensional (4D) data cube from the single 2D measurement. The 4D data cube includes 1500×1240 pixels in the spatial domain, 19 wavelength channels between 400 and 680 nm and two Stokes parameters. PMID:23545971

Tsai, Tsung-Han; Brady, David J

2013-04-01

37

The effect of free-phase NAPL on the spectral induced polarization signature of variably saturated soil  

NASA Astrophysics Data System (ADS)

In this study, the influence of a free phase nonaqueous phase liquid (NAPL), decane, on the soil's SIP signature was experimentally investigated. The complex electrical conductivity was determined using the SIP measurement system and compared between two main treatment types: clean and decane contaminated. Complementary chemical and temporal measurements were conducted. The results show a clear decrease in the imaginary part of the complex conductivity for the decane contaminated soil. Moreover, a shift of the relaxation frequency was observed for the contaminated soil. Our chemical analysis suggests that there was no change in the chemical composition of the Stern layer, and clearly, the grain size distribution did not change as well. Therefore, these results are attributed to membrane polarization. The decane addition to the unsaturated porous media changes the pore-scale liquid phase distribution, thus affecting membrane polarization. Further, the electrical signature is a time-related process associated with liquid phase arrangement time. The findings of this study can enable a better understanding of the SIP response for soils contaminated with free-phase organic compounds.

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

2013-10-01

38

3-D Spectral Induced Polarization (IP) Imaging: Non-Invasive Characterization of Contaminant Plumes. Annual Progress Report for Period September 15, 1996-September 14, 1997.  

National Technical Information Service (NTIS)

The objective of this project is to develop the scientific basis for characterizing contaminant plumes in the earths subsurface using field measurements of induced polarization (IP) effects. Our first-year accomplishments are (1) laboratory experiments on...

F. D. Morgan D. P. Lesmes W. Rodi W. Shi K. M. Frye J. Sturrock

1997-01-01

39

EIT measurement system with high phase accuracy for the imaging of spectral induced polarization properties of soils and sediments  

NASA Astrophysics Data System (ADS)

A powerful method for the non-invasive structural characterization of material is electrical impedance tomography (EIT) combined with the capabilities of impedance spectroscopy. This method determines the complex resistivity magnitude and phase images at a set of different measurement frequencies. We are particularly interested in the application of such an advanced approach for the improved characterization of soils and sediments, which only show a weak polarizability. Here, typical phase values lie between 1 and 20 mrad only, requiring instrumentation with relatively high phase resolution and accuracy. In this paper, we present a new spectral EIT data acquisition system for laboratory applications, which operates in the frequency range from 1 mHz to 45 kHz and which was developed to meet these requirements. In this context, we also present a new measurement method based on current injection swapping, which leads to significantly improved phase images, particularly for higher measurement frequencies. The system and the new measurement method are tested on a water-filled tank and column containing different 2D and 3D targets (metallic and biological objects). The tests prove a phase accuracy of 1 mrad for frequencies of up to 1 kHz and higher, resulting in a clear discrimination of the objects on the basis of the reconstructed phase images.

Zimmermann, E.; Kemna, A.; Berwix, J.; Glaas, W.; Vereecken, H.

2008-09-01

40

Angle-multiplexed spatial-spectral interferometry for simultaneous measurement of spectral phase and polarization state.  

PubMed

A novel method to simultaneously extract the polarization state and relative spectral phase of an ultrashort laser pulse from an angle-multiplexed spatial-spectral interferometric measurement is proposed and experimentally demonstrated. Spectral interference is produced between an arbitrary polarized signal pulse and two orthogonal linearly polarized reference pulses. The accuracy of this technique has been verified by reconstructing the known relative spectral phase arising from material dispersion and the known elliptical polarization state. Measurement of the relative spectral phase and the spatially variable polarization state of a radially polarized pulse is also demonstrated. An additional independent measurement of the spectral phase of reference pulses provides absolute spectral and temporal characteristics of the signal pulse. PMID:24216911

Rakhman, Abdurahim; Lin, Ming-wei; Jovanovic, Igor

2013-11-01

41

Cross-spectral density matrices of polarized light beams.  

PubMed

We show that there is no unique form of the cross-spectral density matrix of completely polarized light beams. We present three kinds of such matrices, each of which represents a beam that is completely polarized at every point. Some of the beams do not imitate monochromatic beams, in contrast to the usual assumption made in polarization optics. PMID:19252550

Lahiri, Mayukh; Wolf, Emil

2009-03-01

42

THE EFFECT OF SYSTEMATICS ON POLARIZED SPECTRAL INDICES  

SciTech Connect

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

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

2013-02-15

43

Mechanisms Resulting in Induced Polarization  

Microsoft Academic Search

Induced polarization (IP) has received considerable attention in the last decade. The technique provides more information about the subsurface than DC resistivity and has potential for detecting various contaminants in the subsurface including non-polar organic compounds and heavy metals. IP may also be applied to determine the hydraulic conductivity of geologic materials and to the study of biogeophysics. In this

M. Skold; A. Revil; P. Vaudelet; F. Martinez

2010-01-01

44

Ground Vehicle Spectral and Polarization Imaging Sensor.  

National Technical Information Service (NTIS)

This paper summarizes the design of an Imaging Spectropolarimeter that operates in the visible wavelength region. The sensor uses computed tomographic imaging techniques to instantaneously form an object cube (spectral and spatial image) during each frame...

C. Vandervlugt R. Karlsen R. Sampson

2007-01-01

45

A comparison between non-linear optimization methods of Bayesian inversion and genetic algorithm for inverting spectral induced polarization data for Cole-Cole parameters  

NASA Astrophysics Data System (ADS)

The induced polarization (IP) method has been used in mining prospecting and increasingly in environmental investigations because IP measurements are very sensitive to the low frequency capacitive properties of rocks and soils. Cole-Cole model parameters widely use to interpret both of time and frequency domain induced polarization data. Among many studies in which Cole-Cole parameters are estimated from SIP measurements on soils and rocks, the majority use least squares methods. In this work, we developed a Bayesian method with simulated annealing sampling algorithm to invert for double Cole-Cole parameters from SIP data. We also reproduced the genetic algorithm developed by Cao et al. and compared performance of simulated annealing method with genetic algorithm method through inversion of synthetic data. Both of two methods are provides a global approach for inverting SIP data for Cole-Cole parameters; the obtained estimates are independent of initial values. Our results show that for the SIP synthetic data with random noises up to 10%, the inversed parameters obtained from simulated annealing method in comparison with genetic algorithm method are more close to the real parameters.

Ghorbani, Ahmad; Okay, Gonca; Cosenza, Philippe

2010-05-01

46

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

PubMed

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

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

1996-10-01

47

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

PubMed Central

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

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

1996-01-01

48

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

49

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

PubMed

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

Kulkarni, Meenal; Gruev, Viktor

2012-10-01

50

Mechanisms Resulting in Induced Polarization  

NASA Astrophysics Data System (ADS)

Induced polarization (IP) has received considerable attention in the last decade. The technique provides more information about the subsurface than DC resistivity and has potential for detecting various contaminants in the subsurface including non-polar organic compounds and heavy metals. IP may also be applied to determine the hydraulic conductivity of geologic materials and to the study of biogeophysics. In this technique, an alternating electrical current is injected in two electrodes and the resulting voltage response is measured in separate electrodes. In the frequency domain both a phase lag and the absolute resistance is recorded. As with most geophysical techniques, field investigations can be performed with minimal intrusion. One challenge, however, stems from the fact that the geological property of interest is not measured but the collected data need to be interpreted to provide practical value. Also, despite the recent successes, the underlying polarization mechanisms are not well understood. A better understanding of polarization mechanism would increase the usefulness of IP. It is clear that polarization at solid-water interfaces plays a key role, but several competing mechanisms make it challenging to determine their relative importance. Polarization of the two parts of the electrical double layer, the Stern and the diffuse layers, along with membrane and Maxwell-Wagner polarizations have been suggested to be responsible for the observed IP response. We use a mechanistic and numerical model to explain the response of induced polarization in silica sand in the presence of sodium chloride at various pH. The model is based on surface complexation and on the migration of counterions within the Stern and diffuse layers. In our experimental results, the imaginary part of the complex conductivity reaches a minimum near the isoelectric point consistent with counterions polarizing the sand grains. The model is capable of explaining experimentally observed IP response and data presented in the literature. The results indicate that polarization of the Stern layer is more significant than diffuse layer and membrane polarization.

Skold, M.; Revil, A.; Vaudelet, P.; Martinez, F.

2010-12-01

51

Spectral and polarization selective fiber-optic elements  

Microsoft Academic Search

A pair of coupled step-index waveguides is analyzed. Characteristic equations are obtained and used to evaluate the cutoff frequencies and coupling constants. Mode transformation at tapers is analyzed. The spectral properties of fused couplers and tapered filters for which cutoff frequencies of higher modes were observed are studied. A fiber polarization splitter is realized. A semiconductor laser with an external

A. G. Bulushev; Y. V. Gurov; E. M. Dianov; O. G. Kuznetsov; O. G. Okhotnikov; V. M. Paramonov

1988-01-01

52

Inversion of induced polarization data  

Microsoft Academic Search

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

Douglas W. Oldenburg; Y. Li

1994-01-01

53

Polarized nuclear target based on parahydrogen induced polarization  

SciTech Connect

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

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

2012-12-01

54

An Integrated Imaging Detector of Polarization and Spectral Content  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

55

Submillimeter Wave Frequency Selective Surface With Polarization Independent Spectral Responses  

Microsoft Academic Search

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

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

2009-01-01

56

Propagation-induced polarization changes in partially coherent optical beams  

Microsoft Academic Search

Propagation of a partially coherent optical beam inside a linear, nondispersive, dielectric medium is studied, taking into account the vector nature of the electromagnetic field. Propagation-induced polarization changes are studied by using the Gaussian-Schell model for the cross-spectral-density tensor. The degree of polar- ization changes with propagation and also becomes nonuniform across the beam cross section. The extent of these

Govind P. Agrawal; Emil Wolf

2000-01-01

57

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

58

Spectral and Polarization Properties of Photospheric Emission from Stratified Jets  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

59

Complex variation of spectral line widths observed in polar corona  

NASA Astrophysics Data System (ADS)

Spectroscopic observations of the solar corona, using high spatial and spectral resolution 25cm coronagraph, at Norikura observatory, were made on large number of days during 2004 at the mid latitude and polar coronal regions. We have analyzed several raster scans that cover mid and high latitude regions on the off-limb corona in four bright emission lines of iron, namely, [Fe X] 6374 Å, [Fe XI]~7892~Å, [Fe XIII] 10747~Å, and [Fe XIV]~5303~Å. We find that the FWHM of red line increases with height and that of green line decreases with height as observed earlier, at equatorial regions. The comparison of line widths and their gradients with the results from equatorial regions indicate that these are higher for polar regions for the observed emission lines except for the green line. FWHM values show an increase towards poles in all the lines except for the green line which shows little or no change. Higher values of FWHM at polar regions may imply higher non-thermal velocities which could be linked to the solar wind, but the behavior of green emission line with almost same values of FWHM at equatorial and polar regions is surprising. This may also give some indications on the existence of preferential heating.

Prasad Samayamanthula, Krishna; Banerjee, Dipankar; Singh, Jagdev

2012-07-01

60

Radiative interactions with micromachined surfaces: Spectral polarized emittance  

SciTech Connect

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.

Zemel, J.N.

1991-01-01

61

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

SciTech Connect

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

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

2011-12-10

62

Polarized spectral combs probe optical fiber surface plasmons.  

PubMed

The high-order cladding modes of conventional single mode fiber come in semi-degenerate pairs corresponding to mostly radially or mostly azimuthally polarized light. Using tilted fiber Bragg gratings to excite these mode families separately, we show how plasmonic coupling to a thin gold coating on the surface of the fiber modifies the effective indices of the modes differently according to polarization and to mode order. In particular, we show the existence of a single "apolarized" grating resonance, with equal effective index for all input polarization states. This special resonance provides direct evidence of the excitation of a surface plasmon on the metal surface but also an absolute wavelength reference that allows for the precise localization of the most sensitive resonances in refractometric and biochemical sensing applications. Two plasmon interrogation methods are proposed, based on wavelength and amplitude measurements. Finally, we use a biotin-streptavidin biomolecular recognition experiment to demonstrate that differential spectral transmission measurements of a fine comb of cladding mode resonances in the vicinity of the apolarized resonance provide the most accurate method to extract information from plasmon-assisted Tilted fiber Bragg gratings, down to pM concentrations and at least 10(-5) refractive index changes. PMID:23481763

Caucheteur, Christophe; Voisin, Valérie; Albert, Jacques

2013-02-11

63

Optical Polarization and Spectral Variability in the M87 Jet  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

64

Electric field effects on persistent spectral holes: Perylene in the polar polymer polyvinylbutyral  

NASA Astrophysics Data System (ADS)

We investigated the effects of an electric field on a spectral hole burned in the inhomogeneously broadened S 0 S 1 transition of perylene in different samples of the polar polymer polyvinylbutyral (PVB) and in cellulose nitrate. The spectral hole is broadened and reduced in depth by the electric field. It was checked experimentally for perylene in PVB that the hole area remains constant when an electric field is applied. We determined the effective matrix-induced electric dipole moment differences ??* for perylene in different PVB samples and in cellulose nitrate. Within experimental accuracy the value of ??* is approximately independent of the composition of PVB and its water content. For perylene in cellulose nitrate the value of ??* is larger by a factor of 1.5 than in PVB. The results are discussed on the basis of a simple model for the electric field effect.

Kanaan, Y.; Attenberger, T.; Bogner, U.; Maier, M.

1990-11-01

65

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

PubMed

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

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

2010-09-15

66

Methods in arthropod retinography for evaluation of spectral polarization sensitivity  

NASA Astrophysics Data System (ADS)

We describe apparatus and methods to measure the sensitivity of arthropod eyes to wavelength and polarization. While these general methods are well-known in the retinography community, they are less familiar to the general optics community. Measurement of polarization sensitivity is particularly uncommon even among retinographers, and our research plan and example results are detailed.

Wehling, Martin F.; Goldstein, Dennis H.

2010-04-01

67

Characterization of the polarization state of weak ultrashort coherent signals by dual-channel spectral interferometry.  

PubMed

We demonstrate that dual-channel spectral interferometry in conjunction with a well-characterized reference pulse can be used to time resolve the polarization state of extremely weak ultrashort coherent signals from linear-and nonlinear-optical experiments by measuring the intensity and the phase of two orthogonal polarization components. In this way the signal is completely characterized. PMID:18183109

Walecki, W J; Fittinghoff, D N; Smirl, A L; Trebino, R

1997-01-15

68

A compact imaging detector of polarization and spectral content  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

69

Induced Polarization methodology: application to a hydrocarbon contaminated site  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

70

Tunable thin film polarizer for the vacuum ultraviolet and soft x-ray spectral regions  

NASA Astrophysics Data System (ADS)

A low pass polarizer that suppresses higher-order diffraction light from vacuum ultraviolet and soft x-ray monochromators is presented in this paper. This vacuum ultraviolet and soft x-ray polarizer is based on a concept of sandwiched metal-dielectric-metal triple reflection configuration. By appropriate optimization of material and angle of incidence, the proposed Au-SiC-Au polarizer demonstrates the capability of matching to desired cutoff edge of photon energy. Furthermore, the optimized soft x-ray polarizer shows the possibility to tune cutoff photon energy in a broadband spectral region ranging from 80 down to down to 20 eV.

Yang, Minghong; Cobet, Christoph; Esser, Norbert

2007-03-01

71

DC Resistivity and Induced Polarization Methods  

Microsoft Academic Search

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

Andrew Binley; Andreas Kemna

72

Constraints on Inflation from Polarization and CMB Spectral Distortions  

NASA Astrophysics Data System (ADS)

This talk will summarize some things we can do with future CMB experiments to study the early Universe. An obvious first is to map the polarization from density perturbations to the cosmic-variance limit to improve upon the types of things (cosmological-parameter determination, lensing, etc.) that have been done so far with the temperature. Another direction, which already has considerable momentum, is the pursuit of the characteristic polarization signature of inflationary gravitational waves. But there is also a strong case, which I will review, now being assembled for a space mission to seek the tiny but nonzero departures from a blackbody spectrum that are expected in the standard cosmological model and that may arise from several interesting exotic mechanisms.

Kamionkowski, Marc

2014-01-01

73

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

Microsoft Academic Search

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

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

2002-01-01

74

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

SciTech Connect

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.

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

75

Noninvasive Contaminant Site Characterization Using Geophysical Induced Polarization  

SciTech Connect

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

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

2003-03-27

76

Magnetic-Field-Induced Electric Polarization in Multiferroic Nanostructures  

Microsoft Academic Search

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

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

2005-01-01

77

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

PubMed

Spectrally correlated photon pairs can be used to improve the performance of long-range fiber-based quantum communication protocols. We present a source based on spontaneous parametric downconversion, which allows one to control spectral correlations within the entangled photon pair without spectral filtering by changing the pump-pulse duration or the characteristics of the coupled spatial modes. The spectral correlations and polarization entanglement are characterized. We find that the generated photon pairs can feature both positive spectral correlations, decorrelation, or negative correlations at the same time as polarization entanglement with a high fidelity of 0.97 (no background subtraction) with the expected Bell state. PMID:24690818

Lutz, Thomas; Kolenderski, Piotr; Jennewein, Thomas

2014-03-15

78

Ternary fission induced by polarized neutrons  

NASA Astrophysics Data System (ADS)

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

Gönnenwein, Friedrich

2013-12-01

79

Radiation induced polarization in CdTe detectors  

Microsoft Academic Search

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

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

1988-01-01

80

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

NASA Astrophysics Data System (ADS)

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

Revil, A.

2013-12-01

81

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

NASA Astrophysics Data System (ADS)

By using the generalized vectorial Rayleigh-Sommerfeld diffraction integral, the analytical expression for the spectral degree of polarization (SDP) of stochastic spatially and spectrally partially coherent electromagnetic pulsed beams (SSSPCEPB) is derived, and used to study the changes in the SDP of SSSPCEPB in the nonparaxial regime. Similar to that of continuous beams, the f parameter and f?? parameter of pulsed beams also play an important role in determining the nonparaxiality of SSSPCEPB. However, the pulse duration and temporal coherence length of the pulse can change the nonparaxiality of SSSPCEPB. The dependence of SDP on the f parameter, pulse duration and temporal coherence length is emphasized and illustrated numerically.

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

2011-10-01

82

Chromosome identification in human oocytes and polar bodies by spectral karyotyping  

Microsoft Academic Search

Sixty unfertilized human oocytes and two fresh polar bodies were karyotyped by spectral karyotyping (SKY). The oocytes were provided by 29 women ranging from 30 to 42 yr of age. The mean hybridization efficiency for oocytes was 95.2% (60\\/63). Nondisjunction of bivalent chromosomes (13.3%) and predivision of sister chromatids at meiosis I (3.3%) were unequivocally determined by analysis first with

C. Márquez; J. Cohen; S. Munné

1998-01-01

83

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

Microsoft Academic Search

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

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

2003-01-01

84

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

Microsoft Academic Search

We have studied the spectral fluorescence and polarization characteristics of Z,Z-bilirubin IX?, at room temperature in chloroform\\u000a and in aqueous buffer medium, within an equilibrium complex with human serum albumin (HSA), and also under low temperature\\u000a conditions (T = ?100°C) in isobutyl alcohol. We have observed a bathochromic shift of the fluorescence spectra, which is most\\u000a pronounced for the bilirubin-albumin

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

2007-01-01

85

Spectral fluorescence and polarization characteristics of Z,Z-bilirubin IXalpha  

Microsoft Academic Search

We have studied the spectral fluorescence and polarization characteristics of Z,Z-bilirubin IXalpha, at room temperature in chloroform and in aqueous buffer medium, within an equilibrium complex with human serum albumin (HSA), and also under low temperature conditions (T = -100°C) in isobutyl alcohol. We have observed a bathochromic shift of the fluorescence spectra, which is most pronounced for the bilirubin-albumin

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

2007-01-01

86

Microtubule-induced cortical cell polarity  

Microsoft Academic Search

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

Sarah E. Siegrist; Chris Q. Doe

2007-01-01

87

Theoretical and experimental studies of the spectral changes of a polychromatic partially coherent radially polarized beam.  

PubMed

In a recent publication (Appl. Phys. Lett. 100 (2012) 051108), a monochromatic partially coherent radially polarized (RP) beam was generated experimentally. In this paper, we analyze the spectral changes of a polychromatic partially coherent RP beam focused by a thin lens for the first time, and compare with that of a focused scalar polychromatic GSM beam. Furthermore, we report experimental generation of a polychromatic partially coherent RP beam and carry out experimental measurement of the spectral changes of such beam focused by a thin lens. Our results show that the behavior of the spectral changes of a focused polychromatic partially coherent RP beam is different from that of a focused scalar polychromatic GSM beam. Our experimental results are consistent with the theoretical predictions. PMID:24514286

Zhu, Shijun; Zhu, Xianglong; Liu, Lin; Wang, Fei; Cai, Yangjian

2013-11-18

88

Induced and Form Birefringence in High-Frequency Polarization Gratings  

NASA Astrophysics Data System (ADS)

High-frequency phase polarization gratings are fabricated holographically in dichromated gelatin dyed with malachite green. It is observed that the intensity of the -1 diffracted beam is a sinusoidal function of the incident polarization angle. In addition, we analyze the dependence of the diffracted order polarization on grating frequency. It is evident from our results that form birefringence becomes significant when the grating period is smaller than the illumination wavelength, thus modifying the optically induced birefringence. Then, in polarization hologram reconstruction, it is not possible to obtain the polarization distribution at the recording step for high-frequency objects.

Martinez-Ponce, Geminiano; Solano, Cristina

2001-08-01

89

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

NASA Astrophysics Data System (ADS)

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

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

2007-01-01

90

Nuclear reactivity control using laser induced polarization.  

National Technical Information Service (NTIS)

A control element for reactivity control of a fission source provides an atomic density of (sup 3)He in a control volume which is effective to control criticality as the (sup 3)He is spin-polarized. Spin-polarization of the (sup 3)He affects the cross sec...

C. D. Bowman

1989-01-01

91

Scattering-induced optical polarization in thick accretion disks  

NASA Technical Reports Server (NTRS)

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

Kartje, John F.; Konigl, Arieh

1991-01-01

92

Electrostatic Gate Control of Optically-Induced Nuclear Polarization  

Microsoft Academic Search

We report initial experiments on optically-induced nuclear spin polarization in gated GaAs 2D electron gas structures, detected via transport. We investigate how polarization depends on gate-controlled depletion, with the ultimate goal of creating submicron regions of polarized nuclei. These regions are expected to yield strong local effective magnetic fields through hyperfine coupling, and may provide a means of manipulating electron

A. A. Houck; J. A. Folk; C. M. Marcus; M. Shayegan

2001-01-01

93

Analysis of random induced cross polarization  

NASA Astrophysics Data System (ADS)

Streamlined radomes will always introduce depolarization because of the fact that any material surface viewed at an oblique angle has different transmission coefficients for fields polarized parallel and perpendicular to the plane of incidence, a phenomenon known as divorce. The cross polarized fields are similar in nature to those responsible for Condon lobes of parabolic reflectors, and which are known to make those antennas susceptible to cross polarization jamming. The relative strength of those lobes is directly related to the amount of divorce, and is quite sensitive to the phase difference of parallel and perpendicular transmission coefficients. A mere 20 deg of phase divorce has a comparable effect to 3 dB of amplitude divorce. This paper presents a detailed analysis for general radome shapes, based on geometrical optics (ray tracing). Example results are presented for conical and tangent ogive radome geometries used in conjunction with a circular-aperture antenna that is mechanically scanned. The results show that when the antenna is scanned off axis, the cross polarized pattern changes from a Condon lobe structure to a difference pattern in the direction orthogonal to the axis of scan, e.g.: under azimuth scanning the cross polarized sum pattern resembles an elevation difference pattern, while the cross polarized elevation difference resembles a sum beam. Hence, interference in the cross polarization will introduce a tracking error in the direction orthogonal to the scan plane.

McGrath, Daniel T.

1992-03-01

94

Poling-induced waveguide polarizers in electrooptic polymers  

Microsoft Academic Search

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

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

1996-01-01

95

Three-Dimensional Induced Polarization Data Inversion for Complex Resistivity.  

National Technical Information Service (NTIS)

The conductive and capacitive material properties of the subsurface can be quantified through the frequency-dependent complex resistivity. However, the routine three-dimensional interpretation of voluminous induced polarization (IP) data sets still poses ...

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

2011-01-01

96

Shock-Induced Polarization of Plexiglas and Polystyrene.  

National Technical Information Service (NTIS)

The theory describing the electric polarization produced in certain dielectrics by the passage of a shock front has been generalized to take account of relaxationeffects. The shock-induced displacement current is described in terms of three parameters: P ...

F. E. Allison G. E. Hauver

1964-01-01

97

Stress-induced single-polarization single-mode fiber  

Microsoft Academic Search

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

W. Eickhoff

1982-01-01

98

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

SciTech Connect

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.

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

2010-01-01

99

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

PubMed

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

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

2013-11-15

100

Charge-induced spin polarization in thiophene oligomers  

NASA Astrophysics Data System (ADS)

Charge-induced spin polarization in small organic molecules is a key factor for spin transport and magnetic effects in related organic devices. In this work, we study spin polarization in charged thiophene oligomer molecules by calculating the magnetic moment with density functional theory. It is found that the emergence and variation of the net magnetic moment is related to both the amount of charge injected and the polymerization of the oligomer. In combination with model analysis, we conclude that the strong electron-electron interaction and electron-lattice interaction in organic materials are responsible for charge-induced spin polarization.

Hou, Dong; Qiu, Junjie; Xie, Shijie; Saxena, Avadh

2013-07-01

101

Schistosoma japonicum infection induces macrophage polarization  

PubMed Central

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.

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

2014-01-01

102

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

103

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

104

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

PubMed

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

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

2013-07-10

105

Polarization and fluence dependence of the polarized emission in nanosecond laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Several studies have appeared in the past two years reporting that the continuum emission produced by the laser ablation of solid materials is strongly polarized. In a paper that appears to conflict with these findings, Asgill et al. report that they did not observe a significant amount of polarization produced by nanosecond laser excitation of nitrogen gas and laser ablation of copper and steel ( M.E. Asgill, H.Y. Moon, N. Omenetto, D.W. Hahn, Investigation of polarization effects for nanosecond laser-induced breakdown spectroscopy, Spectrochim. Acta Part B (2010) xxx-xxx [7]). Here we show that the apparent discrepancy is resolved when laser fluence and polarization are taken into account. Using a 532 nm Nd:YAG laser to ablate Al samples in air, we find that the degree of polarization, P, of the continuum is greater for s- vs. p-polarized excitation and that P decreases with increasing fluence. We show that P would be < 10% under the conditions of Asgill et al., whereas P > 60% is obtained at low fluences with s-polarized excitation. We also confirm that at high fluence the polarization of the discrete emission is much smaller than that of the continuum.

Penczak, John S.; Liu, Yaoming; Gordon, Robert J.

2011-02-01

106

Polar Lipids of Burkholderia pseudomallei Induce Different Host Immune Responses  

PubMed Central

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

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

2013-01-01

107

Three-dimensional induced polarization data inversion for complex resistivity  

SciTech Connect

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

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

2011-03-15

108

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

PubMed Central

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

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

2012-01-01

109

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

PubMed

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

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

2012-11-01

110

Coherent control of absorption and polarization decay in a GaAs quantum well: time and spectral domain studies  

PubMed

Two phase-locked pulses are used to coherently excite excitonic polarizations. It is shown that the second pulse can either be strongly amplified by taking up energy gained from the destruction of the exciton polarization or can be decreased drastically by giving up all its energy to excitons. Both the temporal and the spectral signatures of the transmitted pulse shapes agree well with model calculations. PMID:11019118

Yee; Yee; Hohng; Kim; Meier; Koch

2000-04-10

111

Nitrogen-induced local spin polarization in graphene on cobalt  

NASA Astrophysics Data System (ADS)

Using first principles calculations, we demonstrate an effective method to tailor the local spin configuration of graphene on Co(0 0 0 1) surface through nitrogen doping. Two different site occupancies of the N impurities are discussed with the focus on structural, electronic and magnetic properties. N induces opposite local spin polarization at the two sites through ?-d Zener exchange-type hybridization with Co substrate. In addition, the induced spin polarization is energy dependent and controllable by electric field. Consequently, this structure can be applied as a spin injection source in graphene based spintronics.

Chen, Zhongping; Miao, Ling; Miao, Xiangshui

2013-09-01

112

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

113

Induced interaction in a spin-polarized Fermi gas  

SciTech Connect

We study the effect of the induced interaction on the superfluid transition temperature of a spin-polarized Fermi gas. In the BCS limit, the polarization is very small in the superfluid state, and the effect of the induced interaction is almost the same as in the spin-balanced case. The temperature T{sub t} and the polarization P{sub t} of the tricritical point are both reduced from mean-field results by a factor about 2.22. This reduction is also significant beyond the BCS limit. In the unitary limit, we find (P{sub t},T{sub t}/T{sub F})=(0.42,0.16), in comparison with mean-field and experimental results.

Yu Zengqiang; Yin Lan [School of Physics, Peking University, Beijing 100871 (China)

2010-07-15

114

Spectral and Polarization Characteristics of Selected Targets and Backgrounds: Instrumentation and Measured Results (3.3-14.0 micrometers).  

National Technical Information Service (NTIS)

Spectral, polarization, and view-angle dependent characteristics of 3.3-14.0 micrometers radiance have been measured for a number of target and background materials. Emittances have been measured in the laboratory and radiances measured in the field. Sign...

D. Faulkner R. Horvath J. P. Ulrich E. Work

1971-01-01

115

Eustatic sea level fluctuations induced by polar wander  

Microsoft Academic Search

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

Roberto Sabadini; Carlo Doglioni; David A. Yuen

1990-01-01

116

Building Better Electrodes for Electrical Resistivity and Induced Polarization Data  

Microsoft Academic Search

In the third year of a project to understand and mitigate the systematic noise in resistivity and induced polarization measurements, we put a significant effort into understanding and developing better electrodes. The simple metal electrodes commonly used for both transmitting and receiving of electrical geophysical data are likely the Achilles\\

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

2007-01-01

117

General solutions for stress-induced polarization in optical fibers  

Microsoft Academic Search

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

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

1991-01-01

118

Magnetically Induced Spectral Line Redshifts Full Disk Measurements  

NASA Technical Reports Server (NTRS)

A method which allows the calibration of the magnetically induced velocities and permits an improvement of the information from various planned solar oscillation experiments is presented. Based on the differential sensitivity to the magnetic effects of various spectral lines, a correction function giving the Doppler shift in each line as a function of the difference between shifts of the lines is derived. For 5250 A, the correction to be added to the observed velocity is -0.9 + or - 0.1 (V = 5237 to 5250).

Ulrich, Roger K.; Boyden, John E.; Webster, Larry; Shieber, Tom

1988-01-01

119

Spectrally resolved laser-induced fluorescence for bioaerosols standoff detection  

NASA Astrophysics Data System (ADS)

An efficient standoff biological warfare detection capability could become an important asset for both defence and security communities based on the increasing biological threat and the limits of the presently existing protection systems. Defence R&D Canada (DRDC) has developed, by the end of the 90s, a standoff bioaerosol sensor prototype based on intensified range-gated spectrometric detection of Laser Induced Fluorescence (LIF). This LIDAR system named SINBAHD monitors the spectrally resolved LIF originating from inelastic interactions with bioaerosols present in atmospheric cells customizable in size and in range. SINBAHD has demonstrated the capability of near real-time detection and classification of bioaerosolized threats at multi-kilometre ranges. In spring 2005, DRDC has initiated the BioSense demonstration project, which combines the SINBAHD technology with a geo-referenced Near InfraRed (NIR) LIDAR cloud mapper. SINBAHD is now being used to acquire more signatures to add in the spectral library and also to optimize and test the new BioSense algorithm strategy. In September 2006, SINBAHD has participated in a two-week trial held at DRDC-Suffield where different open-air wet releases of live and killed bioagent simulants, growth media and obscurants were performed. An autoclave killing procedure was performed on two biological materials (Bacillus subtilis var globigii or BG, and Bacillus thuringiensis or Bt) before being aerosolized, disseminated and spectrally characterized with SINBAHD. The obtained results showed no significant impact of this killing process on their normalised spectral signature in comparison with their live counterparts. Correlation between the detection signals from SINBAHD, an array of slit samplers and a FLuorescent Aerosol Particle Sensor (C-FLAPS) was obtained and SINBAHD's sensitivity could then be estimated. At the 2006 trial, a detection limit of a few tens of Agent Containing Particles per Liter of Air (ACPLA) was obtained for a 15-m thick cloud of live BG located at a range of 400 m.

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

2007-10-01

120

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

NASA Astrophysics Data System (ADS)

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

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

1990-06-01

121

Nanosecond polarization-resolved laser-induced breakdown spectroscopy.  

PubMed

It is shown that the continuum emission produced in the ablation of an Al target with nanosecond laser pulses is much more strongly polarized than the discrete line emission. This effect may be utilized to improve the resolution of the laser-induced breakdown spectroscopy spectrum by using a polarizer to filter out the continuum background. The effects of laser fluence and focal position are also reported. It is further shown that the lifetime of the emission closely tracks the intensity spectrum. PMID:20081938

Liu, Yaoming; Penczak, John S; Gordon, Robert J

2010-01-15

122

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

Microsoft Academic Search

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

Houshang Ardavan; Arzhang Ardavan; John Singleton

2004-01-01

123

Spectral Methods in Polar Coordinates with AN Application to the Stability of a Trailing Vortex.  

NASA Astrophysics Data System (ADS)

In cylindrical and spherical coordinates the coordinate singularity can decrease the accuracy or computational efficiency of the spectral method. The problem arises due to the increased resolution near the coordinate singularity. For time dependent advection problems it becomes a stiffness problem which forces one to choose an unusually small time step compared to other spectral methods which do not have coordinate singularities. In this dissertation we present two sets of basis functions which inherently do not suffer from any stiffness problem. The first set of basis functions consists of the eigenfunctions of a singular Sturm-Liouville equation and is suited for a spectral method on the unit disk in polar coordinates. The basis functions are polynomials. The second set of basis functions is algebraically mapped associated Legendre functions whose domain extends from the origin to infinity in the radial direction of a cylindrical coordinates. The basis functions are rational functions. These basis sets satisfy simple recurrence relations for important operations such as the multiplication of some elementary functions, differentiation, and the application of the Laplacian and Helmholtz operators. The forward and backward application of these recurrence relations can be made very efficient. We illustrate these new methods by some examples. The examples include the treatment of a vector field by its toroidal and poloidal components. As an application of practical importance, we apply the rational basis function method to simulate the nonlinear development of linearly unstable modes of an airplane trailing vortex with axial flow. It is found that the nonlinear development of the linearly unstable modes depends strongly on the swirl parameter q which is the ratio of the magnitude of swirling motion to that of the axial flow of the vortex. For q = 0.2 and q = 0.6, the vortex core breaks up significantly and the mean core radius becomes a few times larger than the unperturbed core radius. If q = 1.0, the mean core radius does not become larger than the unperturbed case even though instability develops initially.

Matsushima, Tatsuhito

124

Induced Polarization Surveying for Acid Rock Screening in Highway Design  

NASA Astrophysics Data System (ADS)

Highway and pipeline construction agencies have become increasingly vigilant in their efforts to avoid cutting through sulphide-bearing bedrock that has potential to produce acid rock drainage. Blasting and fragmentation of such rock increases the surface area available for sulphide oxidation and hence increases the risk of acid rock drainage unless the rock contains enough natural buffering capacity to neutralize the pH. In December, 2001, the New Brunswick Department of Transportation (NBOT) sponsored a field trial of geophysical surveying in order to assess its suitability as a screening tool for locating near-surface sulphides along proposed highway alignments. The goal was to develop a protocol that would allow existing programs of drilling and geochemical testing to be targeted more effectively, and provide design engineers with the information needed to reduce rock cuts where necessary and dispose of blasted material in a responsible fashion. Induced polarization (IP) was chosen as the primary geophysical method given its ability to detect low-grade disseminated mineralization. The survey was conducted in dipole-dipole mode using an exploration-style time domain IP system, dipoles 8 to 25 m in length, and six potential dipoles for each current dipole location (i.e. n = 1 - 6). Supplementary information was provided by resistivity and VLF-EM surveys sensitive to lateral changes in electrical conductivity, and by magnetic field surveying chosen for its sensitivity to the magnetic susceptibility of pyrrhotite. Geological and geochemical analyses of samples taken from several IP anomalies located along 4.3 line-km of proposed highway confirmed the effectiveness of the screening technique. IP pseudosections from a region of metamorphosed shales and volcaniclastic rocks identified discrete, well-defined mineralized zones. Stronger, overlapping, and more laterally extensive IP anomalies were observed over a section of graphitic and sulphide-bearing metasedimentary rocks. Attempts to use spectral IP characteristics to determine relative abundances of sulphides and graphite were not conclusive. The overall effectiveness of the screening technique however encouraged NBDOT to apply it to an additional 50 km of planned rock cuts along the corridor selected for the new Trans-Canada Highway.

Butler, K. E.; Al, T.; Bishop, T.

2004-05-01

125

Polarization effects in 3D vectorial-induced current reconstructions.  

PubMed

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

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

2013-10-01

126

Field-Induced Percolation of Polar Nanoregions in Relaxor Ferroelectrics  

NASA Astrophysics Data System (ADS)

A first-principles-based effective Hamiltonian is used to investigate low-temperature properties of Ba(Zr,Ti)O3 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, Eth, 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 Eth 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.

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

2013-05-01

127

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

SciTech Connect

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

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

2012-09-20

128

Spectral inhomogeneity induced by vacancies and thermal phonons and associated observables in time- and frequency-domain nonlinear spectroscopy: I2 isolated in matrix argon  

NASA Astrophysics Data System (ADS)

The vibrational self-consistent field method is used to analyze the inhomogeneous spectral distribution of transitions caused by vacancies and thermally populated phonons, specializing to molecular iodine isolated in an Ar matrix. At experimentally relevant temperatures, for a vacancy concentration of 1.4%, both defect-induced and phonon-induced spectral shifts contribute to the spectral distribution. Both contributions scale linearly with vibrational overtone number. The predicted widths are consistent with reported resonant Raman spectra. In time-resolved coherent anti-Stokes Raman scattering (TRCARS) measurements, spectral indistinguishability implies that all members of the inhomogeneous ensemble contribute coherently to the detectable homodyne signal. The connection between spectral distribution and the observable in TRCARS is derived. The predicted polarization beats and free induction decay due to the inhomogeneous ensemble are in qualitative agreement with experiments.

Bihary, Z.; Karavitis, M.; Gerber, R. B.; Apkarian, V. A.

2001-11-01

129

Topographic effects in resistivity and induced-polarization surveys  

Microsoft Academic Search

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

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

1980-01-01

130

Intensity-Induced Changes in Optical Polarizations in Glasses  

Microsoft Academic Search

Using a single-mode ruby laser we have made the first measurements of intensity-induced changes of the optical polarization (ellipse rotation) in solids, viz., fused quartz and Schott BK-7 and SF-7 glasses for which we have obtained the nonlinear susceptibility values c1221(-omega, omega, omega, - omega)=1.5, 2.3, and 9.9×10-15 esu, respectively. These values are accurate to within 10% relative to the

Adelbert Owyoung; R. W. Hellwarth; Nicholas George

1972-01-01

131

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

PubMed Central

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

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

2013-01-01

132

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

PubMed

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

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

2013-07-15

133

Spectrally Efficient Long-Haul Optical Networking Using 112Gb\\/s Polarization-Multiplexed 16-QAM  

Microsoft Academic Search

We discuss the generation, wavelength-division-multiplexed (WDM) long-haul transmission, and coherent detection of 112-Gb\\/s polarization-division-multiplexed (PDM) 16-ary quadrature amplitude modulation (16-QAM) at a line rate of 14 Gbaud and spectral efficiencies beyond 4 b\\/s\\/Hz. We describe the (off-line) digital signal processing and blind filter adaptation algorithms used in our intradyne receiver and characterize its performance using both simulated and measured 16-QAM

P. J. Winzer; A. H. Gnauck; C. R. Doerr; M. Magarini; L. L. Buhl

2010-01-01

134

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

PubMed Central

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

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

2014-01-01

135

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

PubMed

Current-induced spin polarization (CISP) on the outermost surfaces of Au, Cu, Pt, Pd, Ta, and W nanoscaled films were studied using a spin-polarized positron beam. The Au and Cu surfaces showed no significant CISP. In contrast, the Pt, Pd, Ta, and W films exhibited large CISP (3~15% per input charge current of 10(5)?A/cm(2)) and the CISP of Ta and W were opposite to those of Pt and Pd. The sign of the CISP obeys the same rule in spin Hall effect suggesting that the spin-orbit coupling is mainly responsible for the CISP. The magnitude of the CISP is explained by the Rashba-Edelstein mechanism rather than the diffusive spin Hall effect. This settles a controversy, that which of these two mechanisms dominates the large CISP on metal surfaces. PMID:24776781

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

2014-01-01

136

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

137

Design and performance of a tunable polarizer for VUV and soft x-ray spectral regions  

NASA Astrophysics Data System (ADS)

A low pass polarizer is presented for suppressing higher order diffraction light from vacuum ultraviolet and soft x-ray monochromators. By optimization of materials combination and angle of incidence, the polarizer demonstrates the capability to match to the desired photon energy cut-off. With the proposed hybrid polarizer, a higher order suppression unit, such as a thin film filter, gas filter or double reflecting mirror, is no longer required. The filtering effect of higher harmonics is integrated within the proposed polarizer.

Yang, Minghong

2007-10-01

138

Building Better Electrodes for Electrical Resistivity and Induced Polarization Data  

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

139

Induced polarization of ?(1116) in kaon electroproduction with CLAS  

NASA Astrophysics Data System (ADS)

The CLAS Collaboration is using the p(e,e'K+p)?- reaction to perform a measurement of the induced polarization of the electroproduced ?(1116). The parity-violating weak decay of the ? into p&pgr- (64%) allows extraction of the recoil polarization of the ?. This study uses the CEBAF Large Acceptance Spectrometer (CLAS) to detect the scattered electron, the kaon, and the decay proton. CLAS allows for a large kinematic acceptance with 0.8 <= Q2 <= 3.5 GeV2, 1.6 <= W <= 3.0 GeV, as well as the kaon scattering angle. In this experiment a 5.5 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. The goal is to map out the kinematic dependencies for this polarization observable to provide new constraints for theoretical models of the electromagnetic production of kaon-hyperon final states. Along with previously published photo- and electro-production cross sections and polarization observables from CLAS, SAPHIR, and GRAAL, these data are needed in a coupled-channel analysis to identify previously unobserved s-channel resonances.

Gabrielyan, Marianna; Raue, Brian; Carman, Daniel S.; Park, Kijun

2013-10-01

140

[The multi-angle polarization spectral character of water and its applications in water color remote sensing].  

PubMed

The reflectance of pure water is very low at visible and near infrared bands. Its spectral characteristics are not obvious. Water always shows dark hue in optical remote sensing images. This dark hue causes the difficulties in water remote sensing identification. There is an interesting phenomenon when the authors research the water polarization spectroscopy. The authors measured water's polarization spectra and reflectance spectra at different view zenith angles using the ASD spectrometer. When the view zenith angle was zero (measured vertically), as the spectrum people commonly measure, there was no polarization phenomenon at the water surface, and the reflectance was low at each band. Along with the increase in view zenith angle, the DOP spectra curves increased evidently, while the reflectance curves only changed a little. When the view zenith angle was over 30 degree, the values of DOP spectrum were much larger than the reflectance spectrum values at the entire visible and near infrared bands. At some bands, the DOP value was several dozen times than its reflectance value. This phenomenon shows that the water's brightness in DOP image is much higher than its brightness in intensity image under the same condition. This rule was verified by the PARASOL multiangle polarization satellite data. Comparing the average brightness of DOP images with the average brightness of intensity images at 490, 670 and 865 nm band, the former is higher than the latter apparently. The brighter DOP images are better for water remote sensing identification It is the first time that the authors found this special multiangle polarization spectral character of water. It revealed the advantage of water detection using the multiangle polarization remote sensing data. This method solved the low reflectivity problem of water color remote sensing. It will greatly improve the capability of water remote sensing identification and the retrieval accuracy of water quality parameters. PMID:20384143

Wu, Tai-Xia; Yan, Lei; Xiang, Yun; Zhao, Yun-Sheng; Chen, Wei

2010-02-01

141

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

PubMed

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

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

2013-12-12

142

Soliton-induced spectrally uniform ion line power enhancements at the ionospheric F region peak  

NASA Astrophysics Data System (ADS)

We present European Incoherent Scatter (EISCAT) observations of spectrally uniform ion line power enhancements (SUIPE), where the up- and downshifted shoulder and the spectral valley between them are enhanced simultaneously and equally. We have identified 48 cases of this type of ion line enhancement in data from the EISCAT Svalbard radar taken during the International Polar Year (extending from March 2007 to the end of February 2008). The SUIPEs are observed at altitudes between 210 km and 280 km with a standard deviation of 9% of the average occurrence height 230 km. The power enhancements are one order of magnitude above the thermal level. The SUIPEs occur at the ionospheric F region density peak with 85% of the cases located within 10 km of the peak. These characteristics are in good agreement with the predictions of a recently published model for soliton-induced ion-line enhancements at the F region peak. The SUIPE occurrence shows a clear preference for magnetically disturbed conditions, with the likelihood of occurrence increasing with increasing K index. A majority of the events occur in the magnetic evening to pre-midnight sector.

Ekeberg, J.; Wannberg, G.; Eliasson, L.; Häggström, I.

2012-07-01

143

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

NASA Astrophysics Data System (ADS)

The experimental design and theoretical description of a novel five-pulse laser spectroscopy is presented with an application to a pyridinium charge transfer complex in acetonitrile and methanol. In field-resolved polarizability response spectroscopy (PORS), an electronically resonant laser pulse first excites a solvated chromophore (reactant) and off-resonant Raman spectra of the resulting nuclear motions are measured as a function of the reaction time. The present apparatus differs from our earlier design by performing the Raman probe measurement (with fixed pulse delays) in the frequency domain. In addition, the full electric fields of the signals are measured by spectral interferometry to separate nonresonant and Raman responses. Our theoretical model shows how the PORS signal arises from nuclear motions that are displaced/driven by the photoinduced reaction. The field-resolved off-resonant (of the solute's electronic transitions) probing favors detection of solvent (as opposed to solute) dynamics coupled to the reaction. The sign of the signal represents the relative strengths of polarization responses associated with the ground and photoexcited solutions. Signatures of nonresonant and PORS signal contributions to the experimental results are analyzed with numerical calculations based on a theoretical model we have developed for reaction-induced PORS. Our model identifies two mechanisms of PORS signal generation: (i) structural relaxation induced resonance; (ii) dephasing induced resonance. In the charge transfer reaction investigated, the solvent-dependent and time-evolving (solvent) polarizability spectral density (PSD) is readily obtained. The general trend of an initial broadband inertial nuclear response followed by a decrease in the linewidth of the PSD establishes that the measured PSD is inconsistent with the approximation of a linear response. Furthermore, the explicit time evolution of the PSD is important for properly describing solvent control of reactions that do not satisfy the time-scale separability inherent to nonadiabatic kinetic models.

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

2007-11-01

144

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

145

Line-interlocking Effects on Polarization in Spectral Lines by Rayleigh and Raman Scattering  

NASA Astrophysics Data System (ADS)

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

Sampoorna, M.; Nagendra, K. N.; Stenflo, J. O.

2013-06-01

146

Polarization and incidence insensitive dielectric electromagnetically induced transparency metamaterial.  

PubMed

In this manuscript, we demonstrate numerically classical analogy of electromagnetically induced transparency (EIT) with a windmill type metamaterial consisting of two dumbbell dielectric resonator. With proper external excitation, dielectric resonators serve as EIT bright and dark elements via electric and magnetic Mie resonances, respectively. Rigorous numerical analyses reveal that dielectric metamaterial exhibits sharp transparency peak characterized by large group index due to the destructive interference between EIT bright and dark resonators. Furthermore, such EIT transmission behavior keeps stable property with respect to polarization and incidence angles. PMID:24105514

Zhang, Fuli; Zhao, Qian; Zhou, Ji; Wang, Shengxiang

2013-08-26

147

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

SciTech Connect

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

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

2013-11-13

148

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

SciTech Connect

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

Ntarlagiannis, Dimitrios; Moysey, Stephen; Dean, Delphine

2013-11-14

149

Imaging the human retina in vivo with combined spectral-domain polarization-sensitive optical coherence tomography and scanning laser ophthalmoscopy  

Microsoft Academic Search

Polarization-sensitive (PS) optical coherence tomography (OCT) allows for depth-resolved measurement of light polarizing properties of different layers in the human retina. Since their inherent polarizing properties are different, the retinal structures can be identified using PS-OCT. We present an improved PS-OCT instrument for in vivo imaging of healthy and diseased human retinas. The system is based on spectral-domain (SD) PS-OCT

Bernhard Baumann; Michael Pircher; Erich Götzinger; Harald Sattmann; Martin Wurm; David Stifter; Christopher Schütze; Christian Ahlers; Wolfgang Geitzenauer; Ursula Schmidt-Erfurth; Christoph K. Hitzenberger

2009-01-01

150

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

PubMed Central

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.

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

2009-01-01

151

Retrieval of aerosol optical properties over a vegetation surface using multi-angular, multi-spectral, and polarized data  

NASA Astrophysics Data System (ADS)

An algorithm to retrieve aerosol optical properties using multi-angular, multi-spectral, and polarized data without a priori knowledge of the land surface was developed. In the algorithm, the surface polarized reflectance was estimated by eliminating the atmospheric scattering from measured polarized reflectance at 1640 nm. A lookup table (LUT) and an iterative method were adopted in the algorithm to retrieve the aerosol optical thickness (AOT, at 665 nm) and the Ångström exponent (computed between the AOTs at 665 and 865 nm). Experiments were performed in Tianjin to verify the algorithm. Data were provided by a newly developed airborne instrument, the Advanced Atmosphere Multi-angle Polarization Radiometer (AMPR). The AMPR measurements over the target field agreed well with the nearby ground-based sun photometer. An algorithm based on Research Scanning Polarimeter (RSP) measurements was introduced to validate the observational measurements along a flight path over Tianjin. The retrievals were consistent between the two algorithms. The AMPR algorithm shows potential in retrieving aerosol optical properties over a vegetation surface.

Wang, Han; Sun, Xiaobing; Sun, Bin; Liang, Tianquan; Li, Cuili; Hong, Jin

2014-07-01

152

Self-phase-modulation induced spectral broadening in silicon waveguides  

NASA Astrophysics Data System (ADS)

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

Boyraz, Ozdal; Indukuri, Tejaswi; Jalali, Bahram

2004-03-01

153

Magnetically induced electric polarization in an organometallic magnet  

NASA Astrophysics Data System (ADS)

The coupling between magnetic order and ferroelectricity has been under intense investigation in a wide range of transition-metal oxides. The most direct coupling is obtained in so-called magnetically induced multiferroics where ferroelectricity arises directly from magnetic order that breaks spatial inversion symmetry. However, it has been difficult to find nonoxide-based materials in which these effects occur. Here we present a study of copper dimethyl sulfoxide dichloride (CDC), an organometallic quantum magnet containing S=1/2 Cu spins, in which electric polarization arises from noncollinear magnetic order. We show that the electric polarization can be switched in a stunning hysteretic fashion. Because the magnetic order in CDC is mediated by large organic molecules, our study shows that magnetoelectric interactions can exist in this important class of materials, opening the road to designing magnetoelectrics and multiferroics using large molecules as building blocks. Further, we demonstrate that CDC undergoes a magnetoelectric quantum phase transition where both ferroelectric and magnetic order emerge simultaneously as a function of magnetic field at very low temperatures.

Zapf, V. S.; Kenzelmann, M.; Wolff-Fabris, F.; Balakirev, F.; Chen, Y.

2010-08-01

154

Self-consistent problem of induced polarization of electrokinetic origin  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

155

Electromagnetic Land Surface Classification by Integrated Multi-Spectral and Polarized Radar Remote Sensing Data  

NASA Astrophysics Data System (ADS)

We present a new hierarchical electromagnetic (EM) land surface classification scheme by the integration of high-resolution multi-spectral optical and polarimetric SAR images. In addition to spectral characteristics of the reflected surface conventionally extracted from multispectral images, backscattered amplitude of radar image is used to classify land surface in terms of EM parameters such as permittivity, conductivity, permeability, surface roughness, correlation length, and specific attenuation parameters. A hybrid classification algorithm is developed, in which direct field and lab EM measurements data as well as data from literatures are used. The new classification scheme gives us new insight on the wave propagation modeling for a mobile communication and electrical hazard estimation.

Baek, J.; Kim, J.; Wang, X.; Lim, G.; Jeon, J.

2009-05-01

156

Polarization-dependent spectral redshifts at {nu}=1 and {nu}=2 in a GaAs quantum well in high magnetic fields up to 60 T  

SciTech Connect

Polarized magnetophotoluminescence measurements performed on a wide parabolic GaAs/Al{sub 0.2}Ga{sub 0.8}As quantum well reveal the presence of spectral redshifts in the energy at filling factors {nu}=1 and 2. The magnitude of these redshifts depends on the polarization and filling factor. While the values for the case of the {sigma}{sup -} polarization agree with existing theories, the results for the {sigma}{sup +} polarizations are less understood. (c) 2000 The American Physical Society.

Munteanu, F. M. [National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States) [National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Kim, Yongmin [National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Perry, C. H. [National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States) [National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Heiman, D. [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States)] [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Rickel, D. G. [National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Sundaram, M. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)] [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Gossard, A. C. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)] [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

2000-08-15

157

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

Microsoft Academic Search

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

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

1975-01-01

158

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

NASA Astrophysics Data System (ADS)

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

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

159

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

Microsoft Academic Search

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

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

2003-01-01

160

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

Microsoft Academic Search

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.

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

161

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

SciTech Connect

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.

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

162

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

SciTech Connect

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

Wolfe, Arthur M. [Department of Physics, and Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0424 (United States); Jorgenson, Regina A. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom); Robishaw, Timothy [Sydney Institute for Astronomy, University of Sydney, NSW 2006 (Australia); Heiles, Carl [Department of Astronomy, University of California, Berkeley, CA 95064 (United States); Xavier Prochaska, J., E-mail: awolfe@ucsd.edu, E-mail: raj@ast.cam.ac.uk, E-mail: tim.robishaw@sydney.edu.au, E-mail: heiles@astro.berkeley.edu, E-mail: xavier@ucolick.org [Department of Astronomy and Astrophysics, UCO/Lick Observatory, 1156 High Street, University of California, Santa Cruz, CA 95064 (United States)

2011-05-20

163

Fluorescence polarization of atomic, dissociated atomic, and molecular transitions induced by spin-polarized electron impact  

NASA Astrophysics Data System (ADS)

Excitation of atoms by spin-polarized electron impact yields fluorescence that can generally exhibit both linear and circular polarization. For experiments where the scattered electrons are not detected, symmetry requires that the electron beam be spinpolarized in order for non-zero circular polarization to be observed. Extensive theoretical and experimental investigations have been performed regarding fluorescence polarizations (Stokes parameters) resulting from spin-polarized electron impact excitation of atoms. Measurement of fluorescence polarization provides insight into the angular momentum coupling that exists in the atomic state of interest. It also enables the measurement of electron spin polarization and experimental benchmarking of theoretical atomic structure calculations. In an extension of previous atomic investigations, fluorescence polarization from polarized electron impact dissociation and excitation of simple diatomic molecules is considered. Stokes parameters are presented for dissociated atomic transitions in H, D, and N. Rotationally resolved molecular Fulcher band transitions in H2 and D2, as well as partially resolved transitions in N2, are also presented. Non-zero circular polarizations are observed for both the dissociation and molecular excitation processes. For the rotationally resolved molecular transitions, lower circular polarizations are observed for higher values of rotational states.

Maseberg, Jack William

164

Broadening, shift and polarization of spectral line emitted from hollow cathode discharge  

Microsoft Academic Search

The radial behavior of hollow cathode discharge (HCD) proper emission function has been studied by using a double Fabri–Perot interferogram, i.e., simultaneous recording of spectral line shapes, emitted from two different regions. Radial inhomogeneity and shift of the line shape center are established at buffer gas pressure lower than 0.3 Torr. At these pressures electric field in cathode dark space

D. Zhechev; N. Parvanova

2002-01-01

165

Apparatus and Method for Minimizing Polarization-Induced Signal Fading in an Interferometric Fiber-Optic Sensor Using Input-Polarization Modulation.  

National Technical Information Service (NTIS)

An apparatus for minimizing polarization-induced signal fading in an interferometric fiber optic sensor is disclosed. The apparatus includes an optical source for providing an input light beam, a polarization modulator for modulating the state of polariza...

A. A. Kersey M. J. Marrone

1989-01-01

166

The nano-gap and the emitting molecule: Control of polarization and spectral shape  

NASA Astrophysics Data System (ADS)

The realization of single-molecule surface-enhanced Raman scattering (SERS) from molecules positioned within nano-gaps between metallic nanopraticles has opened up exciting opportunities for studying plasmonic fields and their effects on quantum emitters. We recently showed that constructs made of pairs of nanoparticles with an individual molecules bridging their gap can be systematically formed and studied [1]. By changing the size of the particles, we were able to tune the position of the plasmon resonance spectrum, so that the overlap with different parts of the molecular Raman spectrum changed, leading to significant modulation of its shape. More intricate control over molecular properties can be achieved if a third particle is added to the contstruct. It was found that by breaking the dimer symmetry, a third particle can couple strongly to the emitted Raman field and modulate its polarization in a wavelength-dependent fashion [2]. This surprising experimental result was backed up by a series of Generalized Mie calculations, showing the effect of the distance of the third particle, its size and position [3]. Interestingly, the refractive index of the surrounding medium serves as another control parameter that allows changing the coupling between the particles and modulating the polarization of emitted light. [4pt] [1] Dadosh T, et al. (2009) Plasmonic Control of the Shape of the Raman Spectrum of a Single Molecule in a Silver Nanoparticle Dimer. Acs Nano 3:1988-1994. [0pt] [2] Shegai T, et al. (2008) Managing light polarization via plasmon-molecule interactions within an asymmetric metal nanoparticle trimer. Proc Natl Acad Sci USA 105:16448-16453. [0pt] [3] Li ZP, Shegai T, Haran G, Xu HX (2009) Multiple-Particle Nanoantennas for Enormous Enhancement and Polarization Control of Light Emission. Acs Nano 3:637-642.

Haran, Gilad

2010-03-01

167

Orthogonal polarization spectral (OPS) imaging: a new technique for the visualization and study of microcirculation  

NASA Astrophysics Data System (ADS)

OPS-imaging is a novel technique which can be used to obtain images of the microcirculation using reflected light. High contrast transillumination quality images can be collected not only from thin tissues, but from the surface of solid organs as well. In OPS-imaging the tissue is illuminated with light that has been linearly polarized in one plane. The light is then both scattered and reflected by the tissue. In front of the camera there is a second polarizer which is oriented in a plane precisely orthogonal to that of the illuminating light. This means that light which is directly reflected by the tissue, which maintains its polarization, is rejected by the polarizer in front of the camera. The only light which enters the camera and forms the image is light which has become depolarized, which typically requires at least 10 scattering events. Thus, the light which forms the image comes from deep (0.5 mm) within the tissue and effectively back-illuminates the absorbing material in the foreground. When the light has a wavelength within the hemoglobin absorption spectrum (548 nm), the scattered light is absorbed by the hemoglobin in the red cells, making it possible to visualize the blood vessels as in transillumination intravital microscopy. Thus, images of the microcirculation of solid organs can be obtained without the use of fluorescent dyes. OPS-imaging has been incorporated into a small, hand held device which is easily transportable (CYTOSCAN). Because of these two advantages, it is possible to not only use OPS-imaging in the laboratory, but also in the clinic on patients.

Harris, A. G.; Sinitsina, I.; Pahernik, S.; Langer, S.; von Dobschuetz, E.; Biberthaler, P.; Uhl, E.; Genzel, O.; Messmer, K.

2001-05-01

168

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

NASA Astrophysics Data System (ADS)

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

Lesmes, David P.; Frye, Kevin M.

2001-01-01

169

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

DOEpatents

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

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

2003-12-16

170

Induced polarization signatures of cations exhibiting differential sorption behaviors in saturated sands  

NASA Astrophysics Data System (ADS)

Two sets of experiments were designed to understand the change in induced polarization associated with the sorption of copper and sodium, exhibiting distinct sorption behavior on a silica sand. A sand column experiment was first performed to see the change in the complex conductivity during the advective transport of a copper sulfate solution. A second set of experiments was done with the sand at equilibrium with various solutions of NaCl and CuSO4. In the first experiment, the copper sulfate solution replaced a sodium chloride solution, keeping the electrical conductivity of the solution nearly constant. During the passage of the copper sulfate solution, the apparent phase angle decreased from 3 ± 0.2 to 0.5 ± 0.2 mrad, while the magnitude of the conductivity of the sand remained nearly constant. A quantitative model is proposed to explain the change in the complex conductivity as a function of the chemistry assuming a polarization mechanism associated with the Stern layer (the inner part of the electrical double layer coating the water-mineral interface). The Stern layer polarization is combined with a complexation model describing the competitive sorption of copper and sodium at the pore water interface. The change of the phase lag is directly associated with the ion exchange between sodium and copper at the surface of the silica grains. The explanation of the observed phase differences between Na and Cu relies on their different complexation behaviors, with Na being loosely absorbed, while Cu forms relatively strong complexation with both inner (monodentate) and outer sphere (bidentate) complexes. The replacement of Cu2+ by Na+ is less favorable; therefore, the kinetics of such a replacement is much slower than for the opposite replacement (Na+ by Cu2+). We were able to reproduce the changes in the phase lags at thermodynamic equilibrium near the relaxation frequency and in the frequency domain. These measurements and modeling results open the door to the quantitative interpretation of spectral induced polarization data in the field in terms of quantification of the sorption processes.

Vaudelet, P.; Revil, A.; Schmutz, M.; Franceschi, M.; BéGassat, P.

2011-02-01

171

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

NASA Astrophysics Data System (ADS)

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

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

2005-02-01

172

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

NASA Astrophysics Data System (ADS)

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

Quintana, Joel; Gonzalez, Virgilio

2014-04-01

173

Time-resolved spectral investigations of laser light induced microplasma  

NASA Astrophysics Data System (ADS)

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

Nánai, L.; Hevesi, I.

1992-01-01

174

Effects of polarization on laser-induced electron-ion recombination  

SciTech Connect

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

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

2011-03-15

175

Parahydrogen Induced polarization by homogeneous catalysis: theory and applications.  

PubMed

The alignment of the nuclear spins in parahydrogen can be transferred to other molecules by a homogeneously catalyzed hydrogenation reaction resulting in dramatically enhanced NMR signals. In this chapter we introduce the involved theoretical concepts by two different approaches: the well known, intuitive population approach and the more complex but more complete density operator formalism. Furthermore, we present two interesting applications of PHIP employing homogeneous catalysis. The first demonstrates the feasibility of using PHIP hyperpolarized molecules as contrast agents in (1)H MRI. The contrast arises from the J-coupling induced rephasing of the NMR signal of molecules hyperpolarized via PHIP. It allows for the discrimination of a small amount of hyperpolarized molecules from a large background signal and may open up unprecedented opportunities to use the standard MRI nucleus (1)H for, e.g., metabolic imaging in the future. The second application shows the possibility of continuously producing hyperpolarization via PHIP by employing hollow fiber membranes. The continuous generation of hyperpolarization can overcome the problem of fast relaxation times inherent in all hyperpolarization techniques employed in liquid-state NMR. It allows, for instance, the recording of a reliable 2D spectrum much faster than performing the same experiment with thermally polarized protons. The membrane technique can be straightforwardly extended to produce a continuous flow of a hyperpolarized liquid for MRI enabling important applications in natural sciences and medicine. PMID:23536243

Buljubasich, Lisandro; Franzoni, María Belén; Münnemann, Kerstin

2013-01-01

176

Solvent polarity-induced conformational unlocking of asparagine.  

PubMed

Classical and Car-Parrinello molecular dynamics simulations are performed to study the solvent effect on the conformational distribution of asparagine. Conformational populations obtained from the simulations in gas phase and in nonpolar chloroform solvent are in agreement with the most probable single conformation of asparagine in the gas phase measured in recent laser ablation with molecular beam Fourier transform microwave spectroscopy experiments. We rationalize that intramolecular hydrogen bonding and dipole-dipole interactions between carbonyl groups dictate such a conformational locking to a single asparagine conformer. The solvent polarity induced interlocking or intermolecular hydrogen bonding with water solvent molecules destabilizes the (NH···O?C) bonding between side chain and terminal groups of asparagine, while not essentially affecting the (NH···O?C) intramolecular hydrogen bondings within the side chain nor within the terminal groups. Such a conformational unlocking or cage effect is observed in asparagine within aqueous solution. We observed a spontaneous conversion of neutral to zwitterionic isomer of asparagine in aqueous solution, which is in agreement with interpretation of Raman spectroscopy results. Using Møller-Plesset second order perturbation theory, we show that a tautomeric shift from neutral to zwitterionic occurs on asparagine in between DMSO and water solvents. The ramification of these findings for the conformational character of asparagine is briefly discussed. PMID:23110399

Selvaraj, Ananda Rama Krishnan; Murugan, N Arul; Ågren, Hans

2012-11-29

177

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

USGS Publications Warehouse

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

Sadek, Hamdy S.

1983-01-01

178

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

SciTech Connect

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

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

2011-05-01

179

Geometric phase and Pancharatnam phase induced by light wave polarization  

NASA Astrophysics Data System (ADS)

We use the quantum kinematic approach to revisit geometric phases associated with polarizing processes of a monochromatic light wave. We give the expressions of geometric phases for any, unitary or non-unitary, cyclic or non-cyclic transformations of the light wave state. Contrarily to the usually considered case of absorbing polarizers, we found that a light wave passing through a polarizer may acquire in general a nonzero geometric phase. This geometric phase exists despite the fact that initial and final polarization states are in phase according to the Pancharatnam criterion and cannot be measured using interferometric superposition. Consequently, there is a difference between the Pancharatnam phase and the complete geometric phase acquired by a light wave passing through a polarizer. We illustrate our work with the particular example of total reflection based polarizers.

Lages, José; Giust, Remo; Vigoureux, Jean-Marie

2014-05-01

180

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

PubMed

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

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

2014-05-01

181

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

182

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

NASA Technical Reports Server (NTRS)

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

Fineschi, Silvano; Degl'innocenti, Egidio L.

1992-01-01

183

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

PubMed Central

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.

2013-01-01

184

Phase Resolved X-Ray Spectral Analysis of Intermediate Polars EX Hya and FO Aqr  

NASA Astrophysics Data System (ADS)

Intermediate Polars (IPs): EX Hya and FO Aqr whichs are a subclass of Cataclysmic Variables (CVs) where a white dwarf with magnetic field strength of about 1-10MG accretes material from a main sequence companion through a truncated disc. In this talk we present orbital and spin phase-resolved X-ray spectroscopy of EX Hya and orbital phase-resolved X-ray spectroscopy of FO Aqr. We utilize XMM-Newton archive data of these objects for analysis. We investigate the change of the source spectrum over the spin and orbital periods. This analysis enhances our understanding about the accretion structure in these systems, temperature and composition of the X-ray emitting region together with the structure of the outer accretion disc and absorption in the system

Pekön, Yakup; Balman, ?lölen

2014-01-01

185

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

SciTech Connect

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.

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

186

Inhibition of cyclophosphamide-induced oxidative stress in rat brain by polar and non-polar extracts of Annatto ( Bixa orellana) seeds  

Microsoft Academic Search

Annatto (Bixa orellana) seeds are widely distributed throughout the Tropics and have been used to provide both colour and flavour to food. This study sought to assess the ability of dietary inclusion of polar (water) and non-polar (chloroform) extracts of Annatto (B. orellana) seeds on cyclophosphamide-induced oxidative stress in rat brain. The total phenol content and antioxidant activities of polar

Ganiyu Oboh; Toyin L. Akomolafe; Stephen A. Adefegha; Abayomi O. Adetuyi

2011-01-01

187

INDUCED POLARIZATION: A STUDY OF ITS CAUSES AND MAGNITUDES IN GEOLOGIC MATERIALS. Final Report  

Microsoft Academic Search

The causes of induced electrical polarization include not only the ; polarization of metal-solution interfaces, but also effects asscciated with the ; coupling of different flows. Electro-osmotic, thermal electric, and ion ; diffusion effects are among such examples. A study of the physical properties of ; geologic materials indicates that only electrode interface and diffusion flow ; phenomenon are important

T. R. Madden; D. J. Marshall

1959-01-01

188

Electrode polarity effects on the shock-induced transmembrane potential distribution in the canine heart  

Microsoft Academic Search

Experimental measurements have indicated that for implantable cardioverter defibrillators (ICDs), the defibrillation threshold is different for reversed shock electrode polarity. In this research we offer a possible explanation for this observation. We examine, through large scale computer simulations, the effects of electrode polarity on the transmembrane potential distribution induced throughout the myocardium by defibrillation shock. The tissue preparation is a

N. Trayanova; J. Eason; C. S. Henriquez

1995-01-01

189

A LABORATORY INVESTIGATION OF INDUCED POLARIZATION. Interim Report for 1957-58  

Microsoft Academic Search

Various experimental methods used in the induced polarization study of ; rock sainples are d~scussed. These methods include electrical measurements and ; mineralogical analyses for clays and sulfides. A measurement system has been ; developed whlch can measure polarization effects of less than 1%. Practical ; methods for carrylng out the Fourier analysis have been worked out, and frequency ;

T. R. Madden; D. J. Marshall

1958-01-01

190

Integrated optical waveguide polarizer based on photobleaching-induced birefringence in an electrooptic polymer  

Microsoft Academic Search

A TE-pass waveguide polarizer is fabricated by utilizing the photobleaching-induced birefringence at room temperature in an electrooptic polymer. The polarizer consists of the photobleached waveguide supporting only TE mode, which is integrated in the middle of the etched rib waveguide supporting both TE and TM modes. It has a simple structure and requires no high temperature process like poling. The

Sang-Shin Lee; Seh-Won Ahn; Sang-Yang Shin

1997-01-01

191

TM-pass polarizer based on a photobleaching-induced waveguide in polymers  

Microsoft Academic Search

An integrated optical TM-pass polarizer was fabricated by utilizing a photobleaching-induced birefringence in polymers. The polarizer is implemented by integrating a photobleached waveguide supporting only the TM mode between input and output etched rib waveguides supporting both TE and TM modes. The photobleaching has been controlled to reduce the excess loss by closely matching the mode profiles of the waveguides.

Sang-Shin Lee; Sean Garner; Antao Chen; Vadim Chuyanov; William H. Steier; Seh-Won Ahn; Sang-Yung Shin

1998-01-01

192

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

193

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

PubMed

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

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

2011-07-14

194

Research on the Use of Induced Polarization Measurements to Study the Mechanical Properties of Unconsolidated Materials.  

National Technical Information Service (NTIS)

It has been suggested by previous investigators that measurements of induced polarization made on clay-bearing materials can be used to determine the permeability to fluids or the mechanical properties of those materials. A laboratory and field study was ...

G. V. Keller

1977-01-01

195

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

DOEpatents

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

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

1989-01-01

196

Simultaneous laser-induced fluorescence and sub-Doppler polarization spectroscopy of the CH radical  

NASA Astrophysics Data System (ADS)

The first application of polarization spectroscopy (PS) to the CH radical is demonstrated. In particular, we report on the simultaneous application of laser-induced fluorescence (LIF) and sub-Doppler PS to CH. The conventional experimental setup for PS was supplemented with a second detection system in order to collect the LIF emission. At the same time a Fabry-Perot etalon and molecular iodine were utilized to obtain a precise relative and absolute frequency scale, respectively. CH was investigated in a low pressure methane-oxygen flame. The R 2(5) transition of the B-X (0, 0) band corresponding to a wavelength around 387.3 nm was scanned while fluorescence emission was collected in the spectral region around 431 nm from the B-X (0, 1), A-X (1, 1) and A-X (0, 0) bands. The saturation behavior of both techniques is investigated as well as line broadening effects due to the pump laser pulse energy or rather fluence. Saturation fluence for LIF was found to be more than one order of magnitude higher as compared to PS.

Kiefer, Johannes; Li, Zhongshan; Zetterberg, Johan; Linvin, Martin; Aldén, Marcus

2007-02-01

197

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

198

Alignment and orientation of diatomic molecules induced by polarized electron impact  

NASA Astrophysics Data System (ADS)

We report measurements of linear and circular fluorescence polarizations for molecular transitions in H2, D2, and N2 induced by spin-polarized electron impact. Circular polarizations resulting from some Fulcher-? transitions in H2 and D2 are found to be significant, while the null results from nitrogen's second positive system are consistent with an earlier measurement by the Münster group. We compare this nitrogen data to that from our previous study of nitrogen's first negative system. Emphasis is placed on understanding the mechanisms that cause the values of circular polarization from N2 to be relatively small compared to those observed from H2 and D2 molecules.

Maseberg, J. W.; Gay, T. J.

2010-02-01

199

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

PubMed

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

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

2012-02-01

200

Ultraviolet irradiation induced polarization restoration in electrically fatigued ferroelectric polymer films  

SciTech Connect

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

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

2013-03-21

201

Ion-induced emission of spin-polarized electrons to study surface magnetism  

NASA Astrophysics Data System (ADS)

A novel technique, ion-induced, angle- and energy-resolved, spin-polarized electron emission spectroscopy (SPEES) has been used to probe the electron spin polarization (ESP) at the surface of Ni(110) picture-frame single crystals which are well characterized using AES, LEED, RHEED and STM. The energy distribution of the emitted electrons (0-70 eV), which includes spin-polarized Auger electrons, is significantly different from that of electron-induced secondary electrons and contains fundamental, spin-dependent information on the local surface magnetic structure of Ni(110).

Waters, K.; Rau, C.

1991-02-01

202

Shock-induced polarized hydrogen emission lines in omicron Ceti  

NASA Astrophysics Data System (ADS)

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

Fabas, N.; Lèbre, A.; Gillet, D.

2012-05-01

203

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

204

Optimizing a spectral element for modeling PZT-induced Lamb wave propagation in thin plates  

NASA Astrophysics Data System (ADS)

Use of surface-mounted piezoelectric actuators to generate acoustic ultrasound has been demonstrated to be a key component of built-in nondestructive detection evaluation (NDE) techniques, which can automatically inspect and interrogate damage in hard-to-access areas in real time without disassembly of the structural parts. However, piezoelectric actuators create complex waves, which propagate through the structure. Having the capability to model piezoelectric actuator-induced wave propagation and understanding its physics are essential to developing advanced algorithms for the built-in NDE techniques. Therefore, the objective of this investigation was to develop an efficient hybrid spectral element for modeling piezoelectric actuator-induced high-frequency wave propagation in thin plates. With the hybrid element we take advantage of both a high-order spectral element in the in-plane direction and a linear finite element in the thickness direction in order to efficiently analyze Lamb wave propagation in thin plates. The hybrid spectral element out-performs other elements in terms of leading to significantly faster computation and smaller memory requirements. Use of the hybrid spectral element is proven to be an efficient technique for modeling PZT-induced (PZT: lead zirconate titanate) wave propagation in thin plates. The element enables fundamental understanding of PZT-induced wave propagation.

Ha, Sungwon; Chang, Fu-Kuo

2010-01-01

205

Nuclear spin polarization induced by ultrashort laser pulses  

SciTech Connect

We theoretically show that the use of the hyperfine interaction together with a static electric field leads to ultrafast nuclear spin polarization. The idea is specifically applied to the isotopes of alkaline-earth atoms such as 27Mg (I = 1/2) and 37 Ca (I = 3/2), and we find that spin polarization as high as 88 % and 62 %, respectively, can be attained within the time scale of a few to tens of ns. This technique can be very effective not only for stable nuclei but also unstable nuclei.

Nakajima, Takashi [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

2007-06-13

206

Inducing elliptically polarized high-order harmonics from aligned molecules with linearly polarized femtosecond pulses  

SciTech Connect

A recent paper reported elliptically polarized high-order harmonics from aligned N{sub 2} using a linearly polarized driving field [X. Zhou et al., Phys. Rev. Lett. 102, 073902 (2009)]. This observation cannot be explained in the standard treatment of the Lewenstein model and has been ascribed to many-electron effects or the influence of the Coulomb force on the continuum electron. We show that nonvanishing ellipticity naturally appears within the Lewenstein model when using a multicenter stationary-phase method for treating the dynamics of the continuum electron. The reason for this is the appearance of additional contributions, which can be interpreted as quantum orbits in which the active electron is ionized at one atomic center within the molecule and recombines at another. The associated exchange harmonics are responsible for the nonvanishing ellipticity and result from a correlation between the ionization site and the recombination site in high-order harmonic generation.

Etches, Adam; Madsen, Christian Bruun; Madsen, Lars Bojer [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

2010-01-15

207

Continental lithospheric thickness and deglaciation induced true polar wander  

Microsoft Academic Search

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

W. R. Peltier; Patrick Wu

1983-01-01

208

A meteorological model for rain-induced cross polarization  

Microsoft Academic Search

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

GERT BRUSSAARD

1976-01-01

209

Wide-angle and polarization-independent electromagnetically induced transparency-like effect based on pentacyclic structure  

NASA Astrophysics Data System (ADS)

A pentacyclic structure analog wide-angle and polarization-independent electromagnetically induced transparency-like (EIT-like) effect is numerically and experimentally demonstrated. The unit cell of the structure is composed of four identical circular inner rings surrounded by a larger circular outer ring. A wide-angle and polarization-independent transparency window is clearly observed in the spectral overlapping region of absorption bands of the inner and outer rings. The resonant feature of the transparency effect is investigated by the surface current distribution. We find that the coupling fields between rings play key roles and lead to the classical EIT-like effect. It is also shown that the polarization direction in our structure can be used to tune the position of the localized electric field enhancement. In addition, the effective group index and the effective refractive index are extracted to verify the slow light property with low loss. It is shown that our structure can reduce the group velocity of light by a factor of 64.

Zhu, Lei; Dong, Liang; Meng, Fan Yi; Wu, Qun

2014-01-01

210

Spontaneous polarization induced by natural thermalization of incoherent light.  

PubMed

We analyze theoretically the polarization properties of a partially coherent optical field that propagates in a nonlinear Kerr medium. We consider the standard model of two resonantly coupled nonlinear Schrödinger equations, which account for a wave-vector mismatch between the orthogonal polarization components. We show that such a phase-mismatch is responsible for the existence of a spontaneous repolarization process of the partially incoherent optical field during its nonlinear propagation. The repolarization process is characterized by an irreversible evolution of the unpolarized beam towards a highly polarized state, without any loss of energy. This unexpected result contrasts with the commonly accepted idea that an optical field undergoes a depolarization process under nonlinear evolution. The repolarization effect can be described in details by simple thermodynamic arguments based on the kinetic wave theory: It is shown to result from the natural tendency of the optical field to approach its thermal equilibrium state. The theory then reveals that it is thermodynamically advantageous for the optical field to evolve towards a highly polarized state, because this permits the optical field to reach the ???most disordered state???, i.e., the state of maximum (nonequilibrium) entropy. The theory is in quantitative agreement with the numerical simulations, without adjustable parameters. The physics underlying the reversible property of the repolarization process is briefly discussed in analogy with the celebrated Joule???s experiment of free expansion of a gas. Besides its fundamental interest, the repolarization effect may be exploited to achieve complete polarization of unpolarized incoherent light without loss of energy. PMID:18957998

Picozzi, Antonio

2008-10-27

211

A mass spectral library based on chemical ionization and collision-induced dissociation  

Microsoft Academic Search

A so-called CI–CID mass spectral library based on GC–CI-MS–MS, LC–TSP-MS–MS, LC–ESI-MS–MS and LC–APCI-MS–MS data has been created and evaluated. The main advantage of the CI–CID spectral library is the independence of the chemical ionization and\\/or collision-induced dissociation procedure and the system apparatus used. Comparison of MS–MS spectra from different ionization methods indicate that fragment ions most often have the same

P. G. M Kienhuis; R. B Geerdink

2002-01-01

212

Reconstruction of laser-induced plasma spectral emissivity in non-axisymmetric conditions  

NASA Astrophysics Data System (ADS)

The problem of determining the spectral emissivity in each spatial position of a laser induced plasma is extremely important in order to calculate the spatial distributions of physical and thermodynamical parameters characterizing the plume. Supposing that the plume is optically thin and axisymmetric, the problem is theoretically solved by the Abel inversion of the integral spectral emission. The work presented here is a generalization of the Aguilera et al. method of solving the Abel inversion, based on the modelization of the plume by discrete shells of constant emissivity, in the case of slightly non-axisymmetric plasmas. Some tests and examples of the application of the new algorithm are given.

Cristoforetti, G.; Legnaioli, S.; Palleschi, V.; Salvetti, A.; Tognoni, E.; Tomassini, P.

2005-08-01

213

Laser-induced hole filling and spectral diffusion of aluminum phthalocyanine tetrasulfonate in hyperquenched glassy films  

SciTech Connect

Laser-induced hole filling and spectral diffusion for the dye aluminum phthalocyanine tetrasulfonate in hyperquenched glassy films of water, ethanol, and methanol are investigated. Burning multiple holes into these films reveals a dependence on the burn direction, which is explained by the asymmetry of the antihole produced in the burning process. Spectral diffusion rates are shown to be dependent on sample annealing at temperatures well below the glass transition temperature, T{sub g}. This is interpreted in terms of a {beta}-relaxation process of the glass and is identified with transport of free volume. {copyright} {ital 1999 American Institute of Physics.}

Reinot, T.; Hayes, J.M.; Small, G.J. [Ames Laboratory and Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)] [Ames Laboratory and Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)

1999-03-01

214

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

SciTech Connect

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.

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

2008-11-01

215

Accuracy improvement on polymer identification using laser-induced breakdown spectroscopy with adjusting spectral weightings.  

PubMed

A new approach to polymer identification by laser-induced breakdown spectroscopy (LIBS) with adjusting spectral weightings (ASW) was developed in this work aiming at improving the identification accuracy. This approach has been achieved through increasing the intensities of specific characteristic spectral lines which are important to polymer identification but difficult to be excited. Using the ASW method, the identification accuracies of all 11 polymers were increased to nearly 100%, while the accuracies of PE, PU, PP and PC were only 98%, 74%, 90% and 98%, respectively, without using the ASW method. PMID:24663709

Yu, Y; Guo, L B; Hao, Z Q; Li, X Y; Shen, M; Zeng, Q D; Li, K H; Zeng, X Y; Lu, Y F; Ren, Z

2014-02-24

216

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

PubMed

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

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

2008-11-01

217

Nonequilibrium nuclear polarization and induced hyperfine and dipolar magnetic fields in semiconductor nanostructures  

NASA Astrophysics Data System (ADS)

We investigate the dynamic nuclear polarization (DNP) caused by hyperfine coupling between nonequilibrium electronic spins and nuclear spins in semiconductor nanostructures. We derive the time and position dependence of the resulting hyperfine and dipolar magnetic fields. In GaAs quantum wells the induced nuclear spin polarization greatly exceeds the polarization of the electronic system that causes the DNP. The induced magnetic fields vary between tens of tesla for the electronic hyperfine field acting on nuclei, to hundreds of gauss for the nuclear hyperfine field acting on electrons, to a few gauss for the induced nuclear dipolar fields that act on both nuclei and electrons. The field strengths should be measurable via optically induced nuclear magnetic resonance or time-resolved Faraday rotation experiments. We discuss the implications of our calculations for low-dimensional semiconductor nanostructures.

?ifrea, Ionel; Flatté, Michael E.

2011-10-01

218

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

219

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

SciTech Connect

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

Mueller, N.; Khalil, T.; Pohl, M.; Uphues, T.; Heinzmann, U. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Polcik, M. [Fritz-Haber-Institut der MPG, D-14195 Berlin (Germany); Rader, O. [BESSY, D-12489 Berlin (Germany); Heigl, F.; Starke, K. [Freie Universitaet Berlin, Fachbereich Physik, D-14195 Berlin (Germany); Fritzsche, S. [Institut fuer Physik, Universitaet Kassel, D-34132 Kassel (Germany); Kabachnik, N. M. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Institute of Nuclear Physics, Moscow State University, Moscow 119992 (Russian Federation)

2006-10-15

220

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

NASA Technical Reports Server (NTRS)

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

Ryff, Luis Carlos B.

1994-01-01

221

Simulation of sub-wavelength 3D photomask induced polarization effect by RCWA  

NASA Astrophysics Data System (ADS)

In 45nm technology node and beyond with hyper NA and Off-axis Illumination (OAI) lithography, mask induced polarization effect is remarkable. At this scale, traditional Kirchhoff approximation, in which the masks are considered to be infinitely thin objects, is no longer valid. Rigorous three-dimensional (3D) mask model is required for precise evaluation of mask diffraction. In this paper, a general 3D mask model based on the rigorous coupled-wave analysis (RCWA) is presented, and the change of polarization state as a function of mask and incident light properties is evaluated. The masks considered are the binary chrome mask and 10% Si-Si3N4 attenuated phase shifting mask. The results show that the mask induced polarization effects depend on the mask and incident light properties, such as mask material, absorber thickness, mask pitch, feature size, the polarization and incident angle of the light.

Yang, Liang; Li, Yanqiu; Liu, Lihui; Wang, Jianfeng

2012-10-01

222

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

Microsoft Academic Search

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

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

2004-01-01

223

Laser-induced damage resistance of thin-film polarizers prepared by ion-assisted deposition  

NASA Astrophysics Data System (ADS)

Design is reported of thin film polarizer for a high power laser system having an operating wavelength of 1064 nm. A TiO2/Ta2O5 mixture and SiO2 were used as high index and low index materials respectively. Laser damage test was performed with pulsed Nd:glass lasers. Improvement of laser induced damage threshold of the polarizers by low energy ion assisted deposition is reported.

Gu, P. F.; Tang, J. F.

1994-01-01

224

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

SciTech Connect

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

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

1997-05-01

225

Fatty acid oxidation is dispensable for human macrophage IL-4-induced polarization.  

PubMed

Macrophage polarization elicits various metabolic alterations which in turn influence the polarized phenotype. Activation of glycolytic metabolism accompanies and supports macrophage pro-inflammatory M1 polarization. In contrast, M2 polarization of murine macrophages in response to the Th2 cytokine interleukin-4 (IL-4) was linked to the up-regulation of mitochondrial oxidative metabolism and fatty acid oxidation (FAO), which was necessary for coining an IL-4-polarized phenotype. Here we investigated whether similar mechanisms operate in human macrophages stimulated with IL-4. IL-4 causes only moderate changes of mitochondrial oxidative metabolism and FAO, correlating with an unaltered expression of peroxisome proliferator-activated receptor-? coactivator 1 ?/? (PGC-1?/?), the master transcriptional regulators of mitochondrial biogenesis. Furthermore, attenuating FAO had no effect on IL-4-induced polarization-associated gene expression. Apparently, FAO is dispensable for IL-4-induced polarization of human macrophages, pointing to fundamental differences in the metabolic requirements of macrophage phenotype alterations between mice and humans. PMID:24960101

Namgaladze, Dmitry; Brüne, Bernhard

2014-09-01

226

Irradiation induced phase and polarization phenomena in optical fibers  

Microsoft Academic Search

A theory is developed for evaluation of irradiation induced phase phenomena in optical fibers. The new optical method for control of various ionizing radiations is discussed. The special interest represents the potential ability for control of thermal neutrons and charged particles of low energies. The base of the method makes up the phenomena: the irradiation induced changes of elastic characteristics

F. N. Ignatiev

2003-01-01

227

Imaging the human retina in vivo with combined spectral-domain polarization-sensitive optical coherence tomography and scanning laser ophthalmoscopy  

NASA Astrophysics Data System (ADS)

Polarization-sensitive (PS) optical coherence tomography (OCT) allows for depth-resolved measurement of light polarizing properties of different layers in the human retina. Since their inherent polarizing properties are different, the retinal structures can be identified using PS-OCT. We present an improved PS-OCT instrument for in vivo imaging of healthy and diseased human retinas. The system is based on spectral-domain (SD) PS-OCT operating at an A-line rate of 20 kHz. Different scan patterns and trigger signals are controlled by a field-programmable gate array (FPGA). By integration of an additional detection channel in the source arm of the OCT system, scanning laser ophthalmoscope (SLO) images can be recorded. Images of healthy and diseased human retinas are presented.

Baumann, Bernhard; Pircher, Michael; Götzinger, Erich; Sattmann, Harald; Wurm, Martin; Stifter, David; Schütze, Christopher; Ahlers, Christian; Geitzenauer, Wolfgang; Schmidt-Erfurth, Ursula; Hitzenberger, Christoph K.

2009-02-01

228

Shock induced polarized hydrogen emission lines in omicron Ceti  

NASA Astrophysics Data System (ADS)

We have performed a spectropolarimetric survey of the variable Mira star omicron Ceti along three pulsation cycles. We present those new data collected with the Narval instrument mounted on the Télescope Bernard Lyot in Pic du Midi, France. We have detected time variable polarimetric signatures (on QUV Stokes spectra) associated with Balmer hydrogen emission lines supposed to be formed behind the front of a shock wave propagating throughout the stellar atmosphere. We associate the linear polarization of Balmer emission lines in Mira stars to the presence and the structure of the radiative shock wave.

Fabas, N.; Lèbre, A.; Gillet, D.

2010-12-01

229

Shock-Induced Polarized Hydrogen Emission Lines in Omicron Ceti  

NASA Astrophysics Data System (ADS)

We have performed a spectropolarimetric survey of the variable Mira star omicron Ceti along three pulsation cycles. We present those new data collected with the Narval instrument mounted on the Telescope Bernard Lyot (TBL) in Pic du Midi, France. We have detected time variable polarimetric signatures (on QUV Stokes spectra) associated with Balmer hydrogen emission lines supposed to be formed behind the front of a shock wave propagating throughout the stellar atmosphere. We associate the linear polarization of Balmer emission lines in Mira stars to the presence and the structure of the radiative shock wave.

Fabas, N.; Lèbre, A.; Gillet, D.

2011-04-01

230

Shock-Induced Polarized Hydrogen Emission Lines in omicron Ceti  

NASA Astrophysics Data System (ADS)

We have performed a spectropolarimetric survey of the variable Mira star omicron Ceti along three pulsation cycles. We present those new data collected with the Narval instrument mounted on the Telescope Bernard Lyot (TBL) in Pic du Midi, France. We have detected time variable polarimetric signatures (on QUV Stokes spectra) associated with Balmer hydrogen emission lines supposed to be formed behind the front of a shock wave propagating throughout the stellar atmosphere. We associate the linear polarization of Balmer emission lines in Mira stars to the presence and the structure of the radiative shock wave.

Lèbre, A.; Fabas, N.; Gillet, D.

2011-12-01

231

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

SciTech Connect

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

Pikulik, L G; Chernyavskii, V A; Grib, A F [Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, Minsk (Belarus)

2000-06-30

232

Spectral Reflectivity and Emissivity Measurements of Solid and Liquid UO sub 2 at 458, 514.5 and 647 NM as a Function of Polarization and Angle of Incidence.  

National Technical Information Service (NTIS)

The directional spectral reflectivity of UO sub 2 was measured in the temperature range between 2000 and 4000 K with an integrating-sphere laser reflectometer. The measurements were carried out with monochromatic light polarized parallel and perpendicular...

M. Bober J. Singer K. Wagner

1980-01-01

233

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

SciTech Connect

The CLAS Collaboration is using the p(e, e'K{sup +}p){pi}{sup -} reaction to measure the induced polarization of the electroproduced {Lambda}(1116). In this experiment a 5.499-GeV electron beam was incident upon an unpolarized liquid-hydrogen target. The CEBAF Large Acceptance Spectrometer (CLAS) was used to detect the scattered electron, the kaon, and the decay proton from the {Lambda} hyperon. CLAS allowed for a large kinematic acceptance in Q{sup 2}(0.75{<=}Q{sup 2{<=}}3.5 GeV{sup 2}) and W(1.6{<=}W{<=}3.0 GeV), as well as the kaon center-of-mass scattering angle. The goal is to map out the kinematic dependencies for the induced polarization in order to provide new constraints on models of K-hyperon production. Along with previously published photo- and electroproduction cross sections and polarization observables from CLAS, LEPS, SAPHIR, and GRAAL, these new induced polarization data are needed in coupled-channel analyses to search for previously unobserved s-channel resonances. Preliminary polarization results are presented.

Gabrielyan, Marianna; Raue, Brian; Dhamija, Seema [Florida International University, Miami, FL 33199 (United States); Carman, Daniel S. [Jefferson Laboratory, Newport News, VA 23606 (United States)

2010-08-05

234

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

SciTech Connect

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

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

2010-08-01

235

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

236

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

237

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

PubMed

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

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

2014-07-10

238

LFZ fibre texture modification induced by electrical polarization  

Microsoft Academic Search

Preliminary results of electric current flux application during LFZ growth of BSCCO fibres show a dramatic effect on fibre texture. The solute electromigration modifies the ionic transport and consequently the phase development, inducing a randomly crystal orientation on the as-grown fibres. After heat treatment, fibres grown with reverse electric current are three times more resistive at room temperature than those

F. M. Costa; M. F. Carrasco; N. Ferreira; R. F. Silva; J. M. Vieira

2004-01-01

239

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

NASA Astrophysics Data System (ADS)

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.

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

240

Birefringent gratings induced by polarized laser in azobenzene-doped poly(methyl methecrylate) optical fibers  

NASA Astrophysics Data System (ADS)

Birefringence gratings induced by 532nm polarized laser in an azobenzene doped polymethyl methacrylate (PMMA) fiber and perform block were investigated. Significant photo-induced birefringence has been observed from the fiber. The maximum induced index change is about 3.1x10+MIN5) from this material. The induced birefringence was attributed to the nonlinear absorption at 532nm wavelength. It is found there is the threshold intensity of 0.29mW/cm2. The birefringence decayed little by little when laser turned off, a certain amount of saturation was remained. The dynamics process of the birefringence was studied. This birefringent grating may apply in the polarization dispersion compensation of the fiber communication.

Xu, Xingsheng; Ming, Hai; Ma, Hui; Sun, Xiaohong; Cheng, Wei; Ye, Jichun; Zhang, Qijin; Xie, Jiangping

2001-10-01

241

A Class of Hybrid Polar Inducers of Transformed Cell Differentiation Inhibits Histone Deacetylases  

Microsoft Academic Search

Hybrid polar compounds (HPCs) have been synthesized that induce terminal differentiation and\\/or apoptosis in various transformed cells. We have previously reported on the development of the second-generation HPCs suberoylanilide hydroxamic acid (SAHA) and m-carboxycinnamic acid bishydroxamide (CBHA) that are 2,000-fold more potent inducers on a molar basis than the prototype HPC hexamethylene bisacetamide (HMBA). Herein we report that CBHA and

Victoria M. Richon; Stephane Emiliani; Eric Verdin; Yael Webb; Ronald Breslow; Richard A. Rifkind; Paul A. Marks

1998-01-01

242

Induced-Polarization Measurements at Roosevelt Hot Springs Thermal Area, Utah.  

National Technical Information Service (NTIS)

An induced polarization survey was conducted at Roosevelt Hot Springs, using the dipole-dipole array. The survey consisted of two profile lines, one across the southern end of the system (2200N) and another across the northern portion (5950N). A total of ...

J. J. Chu W. R. Sill S. H. Ward

1979-01-01

243

Inversion of two-dimensional resistivity and induced-polarization data  

Microsoft Academic Search

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

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

1978-01-01

244

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

Microsoft Academic Search

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

Lee D. Slater; Stewart K. Sandberg

2000-01-01

245

Study of Optical Effects Due to an Induced Polarization Third Order in the Electric Field Strength  

Microsoft Academic Search

This paper presents the results of a series of experiments in which a giant pulsed ruby laser is used to study several different nonlinear optical effects arising from an induced optical polarization third order in the electric field strength. The various phenomena studied are special cases of either frequency mixing or intensity-dependent changes in the complex refractive index, including Raman

P. D. Maker; R. W. Terhune

1965-01-01

246

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

DOEpatents

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

Ward, S.H.

1989-10-17

247

Induced polarization signatures of cations exhibiting differential sorption behaviors in saturated sands  

Microsoft Academic Search

Two sets of experiments were designed to understand the change in induced polarization associated with the sorption of copper and sodium, exhibiting distinct sorption behavior on a silica sand. A sand column experiment was first performed to see the change in the complex conductivity during the advective transport of a copper sulfate solution. A second set of experiments was done

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

2011-01-01

248

Spectral Broadening of Excitation induced by Ultralong-range Interaction in a Cold Gas of Rydberg Atoms  

SciTech Connect

Preliminary results of calculating the broadening of spectral lines of excited atoms induced by ultralong- range (100 Bohr radii) interactions in a cold gas of Rb atoms within the 'own pressure' approximation and perturbation theory formalism are presented.

Loboda, A. V.; Mischenko, E. V.; Gurnitskaya, E. P. [Odessa University, P.O.Box 24a, Odessa-9, South-East, 65009 (Ukraine); Glushkov, A. V. [Odessa University, P.O.Box 24a, Odessa-9, South-East, 65009 (Ukraine); Institute for Spectroscopy of Russian Academy of Sciences, Troitsk, Moscow reg., 142090 (Russian Federation); Khetselius, O. Yu. [Odessa University, P.O.Box 24a, Odessa-9, South-East, 65009 (Ukraine); UK National Acad. of Sciences and Bookdata Co., London SW1Y 5AG (United Kingdom)

2008-10-22

249

Stark widths of several Pb III spectral lines in a laser-induced lead plasma  

NASA Astrophysics Data System (ADS)

Context: Data on Stark widths of spectral lines are relevant not only for atomic structure research, but also for astrophysics and analytical techniques of plasma diagnosis. Aims: Stark widths of ten doubly ionized lead spectral lines that belong to 7s-7p, 6d-7p and 6p2-7p transitions have been measured. Methods: We observe the emission lines from an optically thin laser induced plasma from a lead target in an argon atmosphere. The studied plasma has a temperature of about 25 200 K and an electron density of about 1017 cm-3. Local thermodynamic equilibrium conditions and plasma homogeneity have been checked. Special attention was paid to the possible selfabsorption of the different transitions. Results: We report ten new experimental values for Stark widths (FWHM) of Pb III lines.

Alonso-Medina, A.; Colón, C.

2007-04-01

250

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

PubMed

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

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

2014-07-01

251

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

PubMed Central

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

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

2014-01-01

252

Molecular frame photoemission in multiphoton ionization of small molecules induced by linearly and circularly polarized light  

NASA Astrophysics Data System (ADS)

We report results for one-color multiphoton dissociative ionization (MPDI) of NO2 induced by linearly (P) and circularly (k, ê) polarized femtosecond (fs) pulses centered at 400 nm. The experiments were performed by combining the use of 1 kHz femtosecond laser sources (SLIC, Saclay) and the electron-ion vector correlation method. The recoil frame photoelectron angular distributions (RFPADs), derived from the analysis of the (Ve, VNO+) velocity vector correlation, are analyzed using a new formalism. It generalizes the expression of the MFPADs for one-photon photoionization of linear molecules, and models the reaction as n-1 bound-to-bound transitions and ionization induced by the nth photon. The polar and azimuthal angle dependences of the RFPAD are characterized. We illustrate the discussion by the RFPADs measured for a MPDI process induced by five-photon absorption.

Lucchese, R. R.; Elkharrat, C.; Picard, Y.; Billaud, P.; Dowek, D.

2009-11-01

253

Early stage expansion and time-resolved spectral emission of laser-induced plasma from polymer  

NASA Astrophysics Data System (ADS)

In the nanosecond laser ablation regime, absorption of laser energy by the plasma during its early stage expansion critically influences the properties of the plasma and thus its interaction with ambient air. These influences can significantly alter spectral emission of the plasma. For organic samples especially, recombination of the plasma with the ambient air leads to interfering emissions with respect to emissions due to native species evaporated from the sample. Distinguishing interfering emissions due to ambient air represents a critical issue for the application of laser-induced breakdown spectroscopy (LIBS) to the analysis of organic materials. In this paper, we report observations of early stage expansion and interaction with ambient air of the plasma induced on a typical organic sample (nylon) using time-resolved shadowgraph. We compare, in the nanosecond ablation regime, plasmas induced by infrared (IR) laser pulses (1064 nm) and ultraviolet (UV) laser pulses (266 nm). Nanosecond ablation is compared with femtosecond ablation where the post-ablation interaction is absent. Subsequent to the early stage expansion, we observe for each studied ablation regime, spectral emission from CN, a typical radical for organic and biological samples. Time-resolved LIBS allows identifying emissions from native molecular species and those due to recombination with ambient air through their different time evolution behaviors.

Boueri, Myriam; Baudelet, Matthieu; Yu, Jin; Mao, Xianglei; Mao, Samuel S.; Russo, Richard

2009-09-01

254

Polarization effects induced by a two-mirror laser beam scanner  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

255

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

PubMed

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

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

2010-06-21

256

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

NASA Astrophysics Data System (ADS)

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.

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

1995-10-01

257

Dual-spectral plasmon electromagnetically induced transparency in planar metamaterials based on bright-dark coupling  

NASA Astrophysics Data System (ADS)

The optical properties of a planar metamaterials, composed of asymmetric two gold wire pairs located at the two sides of the gold bar, have been investigated theoretically in this paper. The calculated results show that this structure can exhibit dual-spectral plasmonic electromagnetically-induced transparency analogous to the quantum optical phenomenon. The electric field distributions demonstrate that the double transparency windows originate from dual bright-dark coupling modes. Moreover, in accompany with the double tunable transparency windows modulated by the symmetry-reduced displacement, two large group indexes for multi-band slow light applications are also found.

He, Xun-jun; Wang, Jian-min; Tian, Xiao-hua; Jiang, Jiu-xing; Geng, Zhao-xin

2013-03-01

258

Multi-spectral plasmon induced transparency via in-plane dipole and dual-quadrupole coupling.  

PubMed

We experimentally demonstrated an approach based on dipole and dual-quadrupole coupling to construct a planar metamaterial supporting multi-spectral plasmon induced transparency. The structure consists of two short silver wires (dipole) and two long silver wires (dual-quadrupole). The in-plane coupling between the dipole and the dual-quadrupole leads to two transmission windows even in the absorbance linewidth of the dipole. This phenomenon is well described and understood by numerical analyses and a classical oscillator model. PMID:24921261

Miyata, Masashi; Hirohata, Jumpei; Nagasaki, Yusuke; Takahara, Junichi

2014-05-19

259

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

260

Relationship between Hydrological Parameters and Induced Polarization Spectra of Soil Samples  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

261

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

PubMed

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

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

2014-07-01

262

Electron spin polarization induced by linearly polarized light in a (110) GaAs quantum-well waveguide.  

PubMed

We report an experimental demonstration of generating electron spin polarization with linearly polarized light in a (110) GaAs quantum well. A detailed frequency-domain pump-probe study shows that the dynamic nuclear spin polarization arising from the oriented electron spins results in a strong dependence of the electron spin splitting on the photon energy and intensity of the linearly polarized excitation laser. PMID:19519059

Crankshaw, Shanna; Sedgwick, Forrest G; Moewe, Michael; Chang-Hasnain, Connie; Wang, Hailin; Chuang, Shun-Lien

2009-05-22

263

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

264

Tau-induced traffic jams reflect organelles accumulation at points of microtubule polar mismatching.  

PubMed

It is currently accepted that tau overexpression leads to impaired organelle transport and thus to neuronal degeneration. Nevertheless, the underlying mechanisms that lead to impaired organelle transport are not entirely clear. Using cultured Aplysia neurons and online confocal imaging of human tau, microtubules (MTs), the plus-end tracking protein - end-binding protein 3, retrogradely and anterogradely transported organelles, we found that overexpression of tau generates the hallmarks of human tau pathogenesis. Nevertheless, in contrast to earlier reports, we found that the tau-induced impairment of organelle transport is because of polar reorientation of the MTs along the axon or their displacement to submembrane domains. 'Traffic jams' reflect the accumulation of organelles at points of MT polar discontinuations or polar mismatching rather than because of MT depolymerization. Our findings offer a new mechanistic explanation for earlier observations, which established that tau overexpression leads to impaired retrograde and anterograde organelle transport, while the MT skeleton appeared intact. PMID:18182010

Shemesh, Or A; Erez, Hadas; Ginzburg, Irith; Spira, Micha E

2008-04-01

265

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

SciTech Connect

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

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

2000-03-15

266

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

SciTech Connect

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

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

2012-01-01

267

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

NASA Astrophysics Data System (ADS)

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

Tripathi, Neeraj

268

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

EPA Science Inventory

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

269

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

Microsoft Academic Search

Jeffrey Heenan, Dimitrios Ntarlagiannis, Lee Slater Department of Earth and Environmental Sciences, Rutgers University, Newark NJ Microbial Enhanced Oil Recovery (MEOR) is an established, cost effective, method for enhancing tertiary oil recovery. Although not commonly used for shallow heavy oils, it could be a viable alternative since it can offer sustainable economic recovery and minimal environmental impact. A critical component

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

2010-01-01

270

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

SciTech Connect

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

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

1984-04-24

271

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

272

Detection of global tropospheric clouds and polar stratospheric clouds over Antarctica using thermal infrared spectral data observed by TANSO-FTS/GOSAT  

NASA Astrophysics Data System (ADS)

Global tropospheric cloud distribution was derived from thermal infrared band data observed by Thermal And Near infrared Sensor for carbon Observation - Fourier Transform Spectrometer (TANSO-FTS) onboard Greenhouse gases Observation SATellite (GOSAT). It is expected that this band has ability to detect optically thin clouds compared with Cloud and Aerosol Imager (CAI) which is the other sensor on GOSAT. In addition, polar stratospheric clouds (PSCs) which can be harder to detect than the tropospheric clouds because of high reflectivity or low temperature of the surface and their low optical thickness were also detected. We have modified CO2 slicing method which was developed as one of the cirrus cloud detection techniques using thermal infrared band data to detect thin clouds more stably. The pseudo spectral channels were defined as sets of several actual spectral channels between 700cm-1 and 750cm-1 which have weighting function peak height in a same height range for each 0.5km. These pseudo channels were optimized with simulation studies using a multi-scattering radiative transfer code, Polarized radiance System for Transfer of Atmospheric Radiation (Pstar) 3 for several temperature profile patterns prepared based on latitudes and temperature at 500hPa. GOSAT data was analyzed with the combination of these pseudo channels determined for each of observation points from these simulations and the results were compared with the observational results from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) / Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The comparisons about global cloud are based on the coincident observations in 2010. Monthly occurrences of Antarctic PSCs were compared for each grid area from June to September in 2010. As a result, the correlation coefficients in each month are 0.76, 0.71, 0.75, and 0.61 relatively. Though that is low value in September, it can be explained by decrease of occurrences.

Someya, Yu; Imasu, Ryoichi; Ota, Yoshifumi; Saitoh, Naoko

2014-05-01

273

Efficient design of polarization insensitive polymer optical waveguide devices considering stress-induced effects.  

PubMed

We present an approach for the efficient design of polarization insensitive polymeric optical waveguide devices considering stress-induced effects. In this approach, the stresses induced in the waveguide during the fabrication process are estimated first using a more realistic model in the finite element analysis. Then we determine the perturbations in the material refractive indices caused by the stress-optic effect. It is observed that the stresses cause non-uniform optical anisotropy in the waveguide materials, which is then incorporated in the modal analysis considering a multilayer structure of waveguide. The approach is exploited in the design of a Bragg grating on strip waveguide. Excellent agreement between calculated and published experimental results confirms the feasibility of our approach in the accurate design of polarization insensitive polymer waveguide devices. PMID:24787822

Hossain, Md Faruque; Chan, Hau Ping; Kouzani, Abbas Z

2014-04-21

274

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

SciTech Connect

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

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

1998-01-19

275

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

Microsoft Academic Search

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

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

2003-01-01

276

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

Microsoft Academic Search

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

Carlo Capsoni; Aldo Paraboni; Francesco Fedi; Dario Maggiori

1981-01-01

277

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

Microsoft Academic Search

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

Jeffrey J. Daniels

1977-01-01

278

Detection of gravity-induced polarity of cytoplasmic streaming in Chara  

Microsoft Academic Search

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

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

1995-01-01

279

Optically induced angular alignment of trapped birefringent micro-objects by linearly polarized light  

Microsoft Academic Search

Optically induced mechanical angular alignment of trapped birefringent micrometer-sized objects resulting from the transfer of angular momentum produced by birefringence using linearly polarized light has been experimentally demonstrated. Fluorinated polyimide (PMDA\\/TFDB) micro-objects having a large birefringence of Deltan=nslow-nfast=0.13 (refractive indices nslow=1.62, nfast=1.49), which were fabricated by micromachining (reactive ion etching) and suspended in water (n=1.33), were trapped and manipulated by

E. Higurashi; R. Sawada; T. Ito

1999-01-01

280

Saturation effects on polarized-light-pulse propagation and the resultant laser-induced fluorescence  

Microsoft Academic Search

We consider the nonlinear propagation of an intense short pulse of polarized light through a molecular medium with ground- and excited-state absorption, excited-state emission, and fluorescence from the excited state to the ground state and possibly to a lower-lying excited state. We incorporate the effects of saturation, field-induced alignment, and rotational diffusion of the molecules in the medium. Our approach

Yehuda B. Band

1986-01-01

281

Stress induced polarization switching and coupled hysteretic dynamics in ferroelectric materials  

NASA Astrophysics Data System (ADS)

The dynamic responses of ferroelectric materials upon external mechanical and electrical stimulations are inherently nonlinear and coupled. In the current paper, a macroscopic differential model is constructed for the coupled hysteretic dynamics via modeling the orientation switching induced in the materials. A non-convex potential energy is constructed with both mechanic and electric field contributions. The governing equations are formulated as nonlinear ordinary differential equations by employing the Euler-Lagrange equation, and can be easily recast into a state space form. Hysteresis loops associated with stress induced polarization switching and butterfly-shaped behavior in ferroelectric materials are also successfully captured. The effects of mechanical loadings on the electrically induced switching are numerically investigated, as well as the mechanically-induced switching with various bias electric fields.

Wang, Linxiang; Melnik, Roderick; Lv, Fuzai

2011-09-01

282

Influence of Polarization and Pulse Shape of Femtosecond Initial Laser Pulses on Spectral Broadening in Microstructure Fibers  

NASA Astrophysics Data System (ADS)

We theoretically studied the influence of initial parameters of laser pulses, such as polarization, pulse shape and frequency chirp, on the broadening of spectrum during pulse propagation through microstructure fibers (MSFs). We utilized two coupled-mode equations based on the nonlinear Schrödinger equation using an intermediate-broadening model for a Raman response function, and the dispersion coefficients from 2nd to 7th orders for the slow and fast axes, respectively, of highly birefringent MSFs.

Tianprateep, Montian; Tada, Junji; Kannari, Fumihiko

283

Induced polarized state in intentionally grown oxygen deficient KTaO3 thin films  

NASA Astrophysics Data System (ADS)

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.

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

284

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

NASA Astrophysics Data System (ADS)

We are using the p(e, e' K+p)?- reaction to perform a measurement of the induced polarization of the electroproduced L(1116) using its p?- parity-violating weak decay. This study uses the CEBAF Large Acceptance Spectrometer (CLAS) to detect the scattered electron, the kaon, and the decay proton over the kinematics 0.8 <= Q2 <= 3.5 GeV2, 1.6 <= W <= 3.0 GeV, and the full kaon CM angle range. In this experiment a 5.5 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. The goal is to map out the kinematic dependencies for this polarization observable to provide new constraints for models of the electromagnetic production of K-hyperon final states. Along with previously published photo- and electroproduction cross sections and polarization observables from CLAS, SAPHIR, LEPS, and GRAAL, these data are needed in a coupled-channel analysis to identify previously unobserved s-channel resonances. Preliminary polarization results will be presented.

Gabrielyan, M.; Raue, B.; Carman, D. S.; Park, K.; CLAS Collaboration

2012-04-01

285

Measurement of the induced polarization of ?(1116) in kaon electroproduction with CLAS  

NASA Astrophysics Data System (ADS)

The CLAS Collaboration is using the p(e, e? K+ p)pi- reaction to perform a measurement of the induced polarization of the electroproduced ?(1116). The parity-violating weak decay of the ? into ppi- (64%) allows extraction of the recoil polarization of the ?. The present study uses the CEBAF Large Acceptance Spectrometer (CLAS) to detect the scattered electron, the kaon, and the decay proton. CLAS allows for a large kinematic acceptance in Q2 (0.8 ? Q2 ? 3.5 GeV2 ), W (1.6 ? W ? 3.0 GeV), as well as the kaon scattering angle. In this experiment a 5.499 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. The goal is to map out the kinematic dependencies for this polarization observable to provide new constraints for theoretical models of the electromagnetic production of kaon-hyperon final states. Along with previously published photo- and electroproduction cross sections and polarization observables from CLAS, SAPHIR, and GRAAL, these data are needed in a coupled-channel analysis to identify previously unobserved s-channel resonances.

Gabrielyan, Marianna Y.

286

Measurement of Induced Polarization of ?(1116) in Kaon Electroproduction With CLAS  

NASA Astrophysics Data System (ADS)

The CLAS Collaboration is using the p(e,e'K^+p)&-circ; reaction to perform a measurement of the induced polarization of the electroproduced ?(1116). The parity-violating weak decay of the ? into p&-circ; (64%) allows extraction of the recoil polarization of the ?. This study uses the CEBAF Large Acceptance Spectrometer (CLAS) to detect the scattered electron, the kaon, and the decay proton. CLAS allows for a large kinematic acceptance in Q^2 (0.73<=Q^2<=3.5 GeV^2), W (1.6<=W <=3.0 GeV), as well as the kaon scattering angle. In this experiment a 5.499 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. The goal is to map out the kinematic dependencies for this polarization observable to provide new constraints for models of the electromagnetic production of K-hyperon final states. Along with previously published photo- and electroproduction cross sections and polarization observables from CLAS, SAPHIR, and GRAAL, these data will ultimately be useful in coupled-channel analyses and will potentially help identify previously unobserved or poorly determined s-channel resonance terms. Preliminary results will be presented.

Gabrielyan, M. Y.; Raue, B. A.; Dhamija, S.; Carman, D. S.

2009-10-01

287

Fully spin-polarized transport induced by B doping in graphene nanoribbons  

NASA Astrophysics Data System (ADS)

B-doping induced spin polarization in zigzag-edged graphene nanoribbons is studied by density functional calculations by two kinds of doping: (1) doping only one B atom in the central scattering region; (2) periodically doping in the whole system. It is found that even a single B dopant may cause large spin polarization in the current, which can be understood by the breaking of spin-degeneracy due to the impurity atoms and the Fermi level shift resulting from the hole-donating of the B atoms. More interestingly, 100% spin polarized current under finite bias is obtained through periodical doping although the transmission function around the Fermi level is not 100% spin polarized. This can be interpreted by a rigid shift model of the special band structures of the left and right leads in this case. It demonstrates that only transmission function at equilibrium conditions is not sufficient in the study of electron transport, but current should be considered in certain situations.

Ding, Hong; Zheng, X. H.

2014-05-01

288

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

SciTech Connect

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

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

2012-04-01

289

Spectral characterization of laser-induced air plasma by pulsed CO2 laser  

NASA Astrophysics Data System (ADS)

The spectral characterization of laser-induced air plasma by a pulsed TEA CO2 laser with a GaAs lens is reported. The data were collected using an ICCD spectrograph. The spectra of laser-induced plasma in the range of 300-900 nm and their spatial and temporal behaviors were investigated. Emission spectra of the N II lines occurring between 490 and 520nm were analyzed in detail. The intensity peaks during the laser pulse approximately 0.7 ?s and the peak emission spectra decay over the first 1.5 ?s. The spectra of plasma at different position were measured in the directions both perpendicular and parallel to the laser propagation respectively. And the spectra of laser-induced air plasma produced by different focal length lens were compared. The affection of different focal length lens for the plasma was described. The shapes of horizontal directions were smaller with the shorter focal length and the intensities of the plasma were higher. In addition, the temperature of plasma was evaluated from the emission intensities. The peak temperature was more than 10000K.

Jiu, Zhixian; Tang, Jian; Yang, Chenguang; Li, Qiang; Zuo, Duluo; Cheng, Zuhai

2008-12-01

290

Method and apparatus for determining shaliness and oil saturations in earth formations using induced polarization in the frequency domain  

SciTech Connect

An apparatus is disclosed for borehole measurements of the induced polarization of earth formations. The apparatus consists of an induced polarization logger capable of measuring both in-phase and quadrature conductivities in the frequency domain. A method is described which uses these measurements to determine cation exchange capacity per unit pore volume, Qv, brine conductivity, Cw, and oil and water saturations, So and Sw, in shaly sands.

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

1982-11-16

291

Serum from patients with systemic vasculitis induces alternatively activated macrophage M2c polarization.  

PubMed

Anti-neutrophil cytoplasmic antibody associated vasculitides (AAV) are conditions defined by an autoimmune small vessel inflammation. Dying neutrophils are found around the inflamed vessels and the balance between infiltrating neutrophils and macrophages is important to prevent autoimmunity. Here we investigate how sera from AAV patients may regulate macrophage polarization and function. Macrophages from healthy individuals were differentiated into M0, M1, M2a, M2b or M2c macrophages using a standardized protocol, and phenotyped according to their expression surface markers and cytokine production. These phenotypes were compared with those of macrophages stimulated with serum from AAV patients or healthy controls. While the healthy control sera induced a M0 macrophage, AAV serum promoted polarization towards the M2c subtype. No sera induced M1, M2a or M2b macrophages. The M2c subtype showed increased phagocytosis capacity compared with the other subtypes. The M2c polarization found in AAV is consistent with previous reports of increased levels of M2c-associated cytokines. PMID:24631966

Ohlsson, Susanne M; Linge, Carl Petrus; Gullstrand, Birgitta; Lood, Christian; Johansson, Asa; Ohlsson, Sophie; Lundqvist, Andrea; Bengtsson, Anders A; Carlsson, Fredric; Hellmark, Thomas

2014-01-01

292

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

NASA Astrophysics Data System (ADS)

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.

Yu, Peiqiang; Damiran, Daalkhaijav

2011-06-01

293

Polarized spectral properties and 1.5-1.6 ?m laser operation of Er:Sr3Yb2(BO3)4 crystal  

NASA Astrophysics Data System (ADS)

Undoped and Er3+-doped Sr3Yb2(BO3)4 crystals were grown by the Czochralski method. Room temperature polarized spectral properties of the Er:Sr3Yb2(BO3)4 crystal were investigated. The efficiency of the energy transfer from Yb3+ to Er3+ ions in this crystal was calculated to be about 95%. End-pumped by a diode laser at 970 nm in a hemispherical cavity, a 0.75 W quasi-CW laser at 1.5-1.6 ?m with a slope efficiency of 7% and an absorbed pump threshold of 3.8 W was achieved in a 0.5-mm-thick Z-cut crystal glued on a 5-mm-thick pure YAG crystal with UV-curable adhesive.

Lin, F. L.; Huang, J. H.; Chen, Y. J.; Gong, X. H.; Lin, Y. F.; Luo, Z. D.; Huang, Y. D.

2013-10-01

294

[Spectral properties of the green alga Trebouxia--a phycobiont of cryptoendolithic lichens in the high-latitude polar regions of Antarctica].  

PubMed

An algologically pure culture of the green alga Trebouxia, a phycobiont of cryptoendolithic lichens, was isolated from the sandstone samples collected in the high-altitude polar regions of Antarctica. The absorption and the second-derivative absorption spectra of the acetone extract of the Antarctic phycobiont cells were studied in comparison with those of the Trebouxia phycobiont isolated recently from the Parmeliaceae lichen in the Mid-European climatic zone. The cells of the Antarctic phycobiont were characterized by a lower content of chlorophyll a and a higher ratio of chlorophyll b and carotenoids to chlorophyll a as compared to the Mid-European phycobiont. Furthermore, the carotenoids of the Antarctic phycobiont were more diverse. The low-temperature fluorescence spectra of the Antarctic phycobiont were characterized by an increased intensity of the short-wavelength fluorescence peak of chlorophyll a and a diminished intensity of fluorescence in the long-wavelength spectral region. PMID:15521176

Erokhina, L G; Shatilovich, A V; Kaminskaia, O P; Gilichinski?, D A

2004-01-01

295

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

PubMed Central

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

Zhang, Xiaoming; Zhao, Mingwen

2014-01-01

296

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

297

Three-dimensional inversion of induced polarization data from simulated waste1  

NASA Astrophysics Data System (ADS)

The Idaho National Laboratory (INEL) Cold Test Pit (CTP) has been carefully constructed to simulate buried hazardous waste sites. An induced polarization (IP) survey of the CTP shows a very strong polarization and a modest resistivity response associated with the simulated waste. A three-dimensional (3-D) inversion algorithm based on the simultaneous iterative reconstruction technique (SIRT) and finite difference forward modelling has been applied to generate a subsurface model of complex resistivity. The lateral extents of the waste zone are well resolved. Limited depth extent is recognized, but the bottom of the waste appears too deep. With a modelling experiment, the intrinsic polarizability of the waste material is determined. Since IP is a technique for detection of diffuse occurrences of metallic material, this method holds promise as a method to distinguish buried waste from conductive soil material.

Weller, A.; Frangos, W.; Seichter, M.

2000-05-01

298

Three-dimensional inversion of induced polarization data from simulated waste  

NASA Astrophysics Data System (ADS)

The Idaho National Laboratory (INEL) Cold Test Pit (CTP) has been carefully constructed to simulate buried hazardous waste sites. An induced polarization (IP) survey of the CTP shows a very strong polarization and a modest resistivity response associated with the simulated waste. A three-dimensional (3-D) inversion algorithm based on the simultaneous iterative reconstruction technique (SIRT) and finite difference forward modelling has been applied to generate a subsurface model of complex resistivity. The lateral extents of the waste zone are well resolved. Limited depth extent is recognized, but the bottom of the waste appears too deep. With a modelling experiment, the intrinsic polarizability of the waste material is determined. Since IP is a technique for detection of diffuse occurrences of metallic material, this method holds promise as a method to distinguish buried waste from conductive soil material.

Weller, A.; Frangos, W.; Seichter, M.

1999-02-01

299

Vector magnetometry based on electromagnetically induced transparency in linearly polarized light  

SciTech Connect

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

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

2010-09-15

300

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

301

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

NASA Astrophysics Data System (ADS)

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

Å koda, Václav

2013-11-01

302

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

SciTech Connect

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.

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

303

Flexoelectric polarization changes induced by light in a nematic liquid crystal  

NASA Astrophysics Data System (ADS)

In a nematic liquid crystal where the director field has a splay-bend deformation mediated by the boundary conditions there is a certain intrinsic polarization density distribution characteristic of the flexoelectric properties of the medium. By application of an electric field perpendicular to the director, a twist is induced which is a measure of the flexoelectric anisotropy [I. Dozov, Ph. Martinot-Lagarde, and G. Durand, J. Phys. (Paris) Lett. 43, L-365 (1982)]. We show that in molecules susceptible to a photoinduced configurational change we may change the volume polarization by UV illumination and relate the change in flexoelectric coefficients to the configurational change in the molecule. In the experiment we use the British Drug House (Merck) nematic mixture E7 doped with 5 wt % of the dye 4-hexyloxy-(4'-hexyl)azobenzene. The photoinduced trans-cis configurational change leads to an increase by 40% in the flexoelectric anisotropy (es-eb)/K.

Hermann, D. S.; Rudquist, P.; Ichimura, K.; Kudo, K.; Komitov, L.; Lagerwall, S. T.

1997-03-01

304

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

PubMed

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 naïve T cells, polarized CD4(+) and CD8(+) T cells to secrete IFN-? 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. PMID:21782792

Heo, Deok Rim; Shin, Sung Jae; Kim, Woo Sik; Noh, Kyung Tae; Park, Jin Wook; Son, Kwang Hee; Park, Won Sun; Lee, Min-Goo; Kim, Daejin; Shin, Yong Kyoo; Jung, In Duk; Park, Yeong-Min

2011-08-01

305

13C hyperpolarization of a barbituric acid derivative via parahydrogen induced polarization  

NASA Astrophysics Data System (ADS)

Significant 13C NMR signal enhancement by a factor of 5000 of a barbituric acid derivative (5-methyl-5-propenyl-barbituric acid) via parahydrogen induced polarization is presented. This hyperpolarization is achieved by hydrogenating 5-methyl-5-propargyl-barbituric acid with 98% enriched para-H 2 under elevated temperature and pressure and transferring the initially created 1H hyperpolarization with an INEPT-derived pulse sequence to 13C. The polarization can be selectively transferred to different carbons in the barbituric acid derivative by applying different pulse delays in the INEPT pulse sequence. These results demonstrate the potential of using hyperpolarized barbituric acid derivatives as " active" contrast agents in MRI and visualizing their pharmacokinetics in vivo.

Roth, Meike; Koch, Achim; Kindervater, Petra; Bargon, Joachim; Spiess, Hans Wolfgang; Münnemann, Kerstin

2010-05-01

306

Shock-induced polarized hydrogen emission lines in the Mira star o Ceti  

NASA Astrophysics Data System (ADS)

Context. In the spectra of variable pulsating stars, especially Mira stars, the detection of intense hydrogen emission lines has been explained by the presence of a radiative and hypersonic shock wave, periodically propagating throughout the stellar atmosphere. Previous observation of the Mira star o Ceti around one of its brightest maximum light led to the detection of a strong level of linear polarization associated to Balmer emissions, although the origin of this phenomenon is not fully explained yet. Aims: With the help of spectropolarimetry, we propose to investigate the nature of shock waves propagating throughout the stellar atmosphere and present, for o Ceti (the prototype of Mira stars), a full observational study of hydrogen emission lines formed in the radiative region of such a shock. Methods: Using the instrument NARVAL mounted on the Télescope Bernard Lyot (TBL) in Pic du Midi Observatory (France), we performed a spectropolarimetric monitoring of o Ceti during three consecutive pulsation cycles. For this survey, the four Stokes parameters (I for intensity, Q and U for linear polarization, and V for circular polarization) were systematically collected, with a particular emphasis on the maxima of luminosity, i.e. when a radiative shock wave is supposed to emerge from the photosphere and starts to propagate outward. Results: On hydrogen Balmer lines, over a large part of the luminosity cycle, we report clear detection of polarimetric structures in Q and U Stokes spectra (and also in V Stokes spectra but to a lesser extent). We report a temporal evolution of these spectropolarimetric signatures, which appear strongly correlated to the presence of an intense shock wave responsible for the hydrogen emission lines. We establish that the hydrogen lines are polarized by a physical process inherent to the mechanism responsible for the emission line formation: the shock wave itself. Two mechanisms are thus considered: a global one that implies a polarization induced by some giant convective cells located around the photosphere and a local one that implies a charge separation due to the passage of the shock wave, inducing an electrical current. Combined with the existing turbulence, this may generate a magnetic field, hence polarization. Based on spectropolarimetric observations obtained at the Télescope Bernard Lyot (TBL at Observatoire du Pic du Midi, CNRS and Université de Toulouse, France).

Fabas, N.; Lèbre, A.; Gillet, D.

2011-11-01

307

Dysregulation of Cell Polarity Proteins Synergize with Oncogenes or the Microenvironment to Induce Invasive Behavior in Epithelial Cells  

PubMed Central

Changes in expression and localization of proteins that regulate cell and tissue polarity are frequently observed in carcinoma. However, the mechanisms by which changes in cell polarity proteins regulate carcinoma progression are not well understood. Here, we report that loss of polarity protein expression in epithelial cells primes them for cooperation with oncogenes or changes in tissue microenvironment to promote invasive behavior. Activation of ErbB2 in cells lacking the polarity regulators Scribble, Dlg1 or AF-6, induced invasive properties. This cooperation required the ability of ErbB2 to regulate the Par6/aPKC polarity complex. Inhibition of the ErbB2-Par6 pathway was sufficient to block ErbB2-induced invasion suggesting that two polarity hits may be needed for ErbB2 to promote invasion. Interestingly, in the absence of ErbB2 activation, either a combined loss of two polarity proteins, or exposure of cells lacking one polarity protein to cytokines IL-6 or TNF? induced invasive behavior in epithelial cells. We observed the invasive behavior only when cells were plated on a stiff matrix (Matrigel/Collagen-1) and not when plated on a soft matrix (Matrigel alone). Cells lacking two polarity proteins upregulated expression of EGFR and activated Akt. Inhibition of Akt activity blocked the invasive behavior identifying a mechanism by which loss of polarity promotes invasion of epithelial cells. Thus, we demonstrate that loss of polarity proteins confers phenotypic plasticity to epithelial cells such that they display normal behavior under normal culture conditions but display aggressive behavior in response to activation of oncogenes or exposure to cytokines.

Chatterjee, Samit; Seifried, Laurie; Feigin, Michael E.; Gibbons, Don L.; Scuoppo, Claudio; Lin, Wei; Rizvi, Zain H.; Lind, Evan; Dissanayake, Dilan; Kurie, Jonathan; Ohashi, Pam; Muthuswamy, Senthil K.

2012-01-01

308

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

SciTech Connect

Highlights: {yields} Treatment with Rv0462 induces the expression of surface molecules and the production of cytokines in DCs. {yields} Rv0462 induces the activation of MAPKs. {yields} Rv0462-treated DCs enhances the proliferation of CD4{sup +} T cells. -- Abstract: Mycobacterium tuberculosis, the etiological factor of pulmonary tuberculosis, causes significant morbidity and mortality worldwide. Activation of host immune responses for containment of mycobacterial infections involves participation of innate immune cells, such as dendritic cells (DCs). In this study, we demonstrated that the gene encoding lipoamide dehydrogenase C (lpdC) from M. tuberculosis, Rv0462, induce maturation and activation of DCs involved in the MAPKs signaling pathway. Moreover, Rv0462-treated DCs activated naive T cells, polarized CD4{sup +} and CD8{sup +} T cells to secrete IFN-{gamma} in syngeneic mixed lymphocyte reactions, which would be expected to contribute to Th1 polarization of the immune response. Our results suggest that Rv0462 can contribute to the innate and adaptive immune responses during tuberculosis infection, and thus modulate the clinical course of tuberculosis.

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

2011-08-05

309

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

NASA Astrophysics Data System (ADS)

InGaN/GaN light-emitting diodes (LEDs) grown along the polar orientations significantly suffer from the quantum confined Stark effect (QCSE) caused by the strong polarization induced electric field in the quantum wells, which is a fundamental problem intrinsic to the III-nitrides. Here, we show that the QCSE is self-screened by the polarization induced bulk charges enabled by designing quantum barriers. The InN composition of the InGaN quantum barrier graded along the growth orientation opportunely generates the polarization induced bulk charges in the quantum barrier, which well compensate the polarization induced interface charges, thus avoiding the electric field in the quantum wells. Consequently, the optical output power and the external quantum efficiency are substantially improved for the LEDs. The ability to self-screen the QCSE using polarization induced bulk charges opens up new possibilities for device engineering of III-nitrides not only in LEDs but also in other optoelectronic devices.

Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Wei Sun, Xiao; Volkan Demir, Hilmi

2014-06-01

310

Performance degradation induced by polarization-dependent loss in optical fiber transmission systems with and without polarization-mode dispersion  

Microsoft Academic Search

The performance degradation caused by polarization-dependent loss (PDL) in optical fiber transmission systems in both the absence and presence of polarization-mode dispersion (PMD) is studied. First a simple theory is given to show how PDL affects the system performance and then extensive simulation results are presented. We show that PDL causes a much larger fluctuation of optical-signal-to-orthogonal-noise ratio (OSNRort) than

Chongjin Xie; Linn F. Mollenauer

2003-01-01

311

Induced spin polarization in ferromagnetic Gd62.4Y37.6  

NASA Astrophysics Data System (ADS)

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.

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

2000-06-01

312

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

SciTech Connect

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.

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

313

Lymphocyte-Polarized Dendritic Cells Are Highly Effective in Inducing Tumor-Specific CTLs  

PubMed Central

High activity of dendritic cells (DCs) in inducing cytotoxic T cells (CTLs) led to their application as therapeutic cancer vaccines. The ability of DCs to produce IL-12p70 is one of the key requirements for effective CTL induction and a predictive marker of their therapeutic efficacy in vivo. We have previously reported that defined cocktails of cytokines, involving TNF? and IFN?, induce mature type-1 polarized DCs (DC1s) which produce strongly elevated levels of IL-12 and CXCL10/IP10 upon CD40 ligation compared to “standard” PGE2-matured DCs (sDCs; matured with IL-1?, IL-6, TNF?, and PGE2) and show higher CTL-inducing activity. Guided by our observations that DC1s can be induced by TNF?- and IFN?-producing CD8+ T cells, we have tested the feasibility of using lymphocytes to generate DC1s in a clinically-compatible process, to limit the need for clinical-grade recombinant cytokines and the associated costs. CD3/CD28 activation of bulk lymphocytes expanded them and primed them for effective production of IFN?and TNF?following restimulation. Restimulated lymphocytes, or their culture supernatants, enhanced the maturation status of immature (i)DCs, elevating their expression of CD80, CD83 and CCR7, and the ability to produce IL-12p70 and CXCL10 upon subsequent CD40 ligation. The “lymphocyte-matured” DC1s showed elevated migration in response to the lymph-node-directing chemokine, CCL21, when compared to iDCs. When loaded with antigenic peptides, supernatant-matured DCs induced much high levels of CTLs recognizing tumor-associated antigenic epitope, than PGE2-matured DCs from the same donors. These results demonstrate the feasibility of generation of polarized DC1s using autologous lymphocytes.

Berk, Erik; Muthuswamy, Ravikumar; Kalinski, Pawel

2012-01-01

314

Modeling the impact of spectral sensor configurations on the FLD retrieval accuracy of sun-induced chlorophyll fluorescence  

Microsoft Academic Search

Chlorophyll fluorescence is related to photosynthesis and can serve as a remote sensing proxy for estimating photosynthetic energy conversion and carbon uptake. Recent advances in sensor technology allow remote measurements of the sun-induced chlorophyll fluorescence signal (Fs) at leaf and canopy scale. The commonly used Fraunhofer Line Depth (FLD) principle exploits spectrally narrow atmospheric oxygen absorption bands and relates Fs

Alexander Damm; André Erler; Walter Hillen; Michele Meroni; Michael E. Schaepman; Wout Verhoef; Uwe Rascher

2011-01-01

315

Phonon anomalies induced by polar nano-regions in a relaxor ferroelectric  

NASA Astrophysics Data System (ADS)

Inelastic neutron scattering was used to measure both acoustic and optic phonons polarized along (110) (T2 mode) in the relaxor ferroelectric compound PZN-4.5PT. In the low temperature rhombohedral phase, a single domain state was achieved by cooling the single crystal sample under an external electric field of 2 kV/cm along the [111] direction. Phonon measurements were performed near the (2,2,0) and (2,-2,0) Bragg peaks. We have found that the TA2 phonon couples closely to the diffuse scattering, which arises from polar nano-regions in the system. With the redistribution of diffuse scattering under the external field (see Ref. 1), a clear hardening of TA2 mode was observed near the (2,2,0) Bragg peak, while the TA2 mode near (2,-2,0) Bragg peak softens significantly and becomes over-damped. Our results indicate local inhomogeneities such as the PNR can have direct and significant effects on the lattice dynamics and stability of the whole system. Ref. 1: ``Electric-field-induced redistribution of polar nano-regions in a relaxor ferroelectric'', Guangyong Xu, Z. Zhong, Y. Bing, Z.-G. Ye, and G. Shirane, Nature Materials 5, 134, (2006).

Xu, Guangyong; Wen, Jinsheng; Stock, Chris; Gehring, Peter

2007-03-01

316

Magnetically-induced ferroelectric polarization in a molecule-based quantum magnet  

NASA Astrophysics Data System (ADS)

Ferroelectricity coupled to antiferromagnetic (AFM) order has been observed in the organic S=1/2 chain compound CDC (CuCl2 2(CH3)2SO). For magnetic fields along the orthorhombic c-axis, AFM order occurs below TN = 0.93 K and H ˜ 4 T. A spin-flop transition above Hsf = 0.35 T leads to a magnetically ordered state that breaks inversion symmetry along the b-axis for 0.35 T < H < 4 T. Measurements of the pyroelectric effect and the dielectric constant along b indicate ferroelectricity occurring in this same region of HT phase space with the spin polarization closely tracking the magnetic order parameter. The ferroelectric polarization is observed without electrically poling the material, and polarization switching can be observed by consecutive field sweeps in the same direction. While the magnetically-induced ferroelectricity in CDC is far from practical temperatures and fields, it nevertheless demonstrates that this phenomena can occur in a whole new class of compounds.

Zapf, Vivien; Fabris, Frederik; Kenzelmann, Michel; Balakirev, Fedor; Chen, Ying; Broholm, Colin

2008-03-01

317

Self-induced polarization rotation of laser beam in fullerene (C70) solutions  

NASA Astrophysics Data System (ADS)

Nonlinear self-rotation of elliptically polarized laser pulses (? = 532 nm, ?FWHM ~ 12 ns) in toluene, benzene and binary mixture (toluene + ethanol) solutions of fullerene C70 has been investigated experimentally. Absolute values and signs of the nonlinear refractive indices (n2) and nonlinear optical susceptibilities ?(3)(?, - ?, ?) of C70 solutions in toluene and benzene at different values of polarization ellipse (? = 0.2 ÷ 0.8) have been determined. High-resolution transmission electron microscope studies of C70 solutions showed that in toluene + ethanol mixtures ball-shaped C70 clusters are formed with particle sizes in the range ~ 100 ÷ 500 nm. It has been demonstrated, that the clusters sizes depend on the C70 concentration and volume fraction of ethanol in toluene. Correlation between the processes of C70 clusters formation in solutions and the values of polarization self-rotation angle of transmitted laser beam has been demonstrated. Physical mechanisms of laser induced optical activity in fullerene solutions have been discussed.

Kokhkharov, A. M.; Bakhramov, S. A.; Makhmanov, U. K.; Kokhkharov, R. A.; Zakhidov, E. A.

2012-06-01

318

Nuclear lamin A/C deficiency induces defects in cell mechanics, polarization, and migration.  

PubMed

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 deficiency induces significant separation of the microtubule organizing center (MTOC) from the nuclear envelope. Investigations using ballistic intracellular nanorheology reveal that lamin A/C deficiency also dramatically affects the micromechanical properties of the cytoplasm. Both the elasticity (stretchiness) and the viscosity (propensity of a material to flow) of the cytoplasm in Lmna(-/-) MEFs are significantly reduced. Disassembly of either the actin filament or microtubule networks in Lmna(+/+) MEFs results in decrease of cytoplasmic elasticity and viscosity down to levels found in Lmna(-/-) MEFs. Together these results show that both the mechanical properties of the cytoskeleton and cytoskeleton-based processes, including cell motility, coupled MTOC and nucleus dynamics, and cell polarization, depend critically on the integrity of the nuclear lamina, which suggest the existence of a functional mechanical connection between the nucleus and the cytoskeleton. These results also suggest that cell polarization during cell migration requires tight mechanical coupling between MTOC and nucleus, which is mediated by lamin A/C. PMID:17631533

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

2007-10-01

319

Parahydrogen-induced polarization of carboxylic acids: a pilot study of valproic acid and related structures.  

PubMed

Parahydrogen-induced polarization (PHIP) is a promising new tool for medical applications of MR, including MRI. The PHIP technique can be used to transfer high non-Boltzmann polarization, derived from parahydrogen, to isotopes with a low natural abundance or low gyromagnetic ratio (e.g. (13) C), thus improving the signal-to-noise ratio by several orders of magnitude. A few molecules acting as metabolic sensors have already been hyperpolarized with PHIP, but the direct hyperpolarization of drugs used to treat neurological disorders has not been accomplished until now. Here, we report on the first successful hyperpolarization of valproate (valproic acid, VPA), an important and commonly used antiepileptic drug. Hyperpolarization was confirmed by detecting the corresponding signal patterns in the (1) H NMR spectrum. To identify the optimal experimental conditions for the conversion of an appropriate VPA precursor, structurally related molecules with different side chains were analyzed in different solvents using various catalytic systems. The presented results include hyperpolarized (13) C NMR spectra and proton images of related systems, confirming their applicability for MR studies. PHIP-based polarization enhancement may provide a new MR technique to monitor the spatial distribution of valproate in brain tissue and to analyze metabolic pathways after valproate administration. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24812006

Lego, Denise; Plaumann, Markus; Trantzschel, Thomas; Bargon, Joachim; Scheich, Henning; Buntkowsky, Gerd; Gutmann, Torsten; Sauer, Grit; Bernarding, Johannes; Bommerich, Ute

2014-07-01

320

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

PubMed Central

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 deficiency induces significant separation of the microtubule organizing center (MTOC) from the nuclear envelope. Investigations using ballistic intracellular nanorheology reveal that lamin A/C deficiency also dramatically affects the micromechanical properties of the cytoplasm. Both the elasticity (stretchiness) and the viscosity (propensity of a material to flow) of the cytoplasm in Lmna?/? MEFs are significantly reduced. Disassembly of either the actin filament or microtubule networks in Lmna+/+ MEFs results in decrease of cytoplasmic elasticity and viscosity down to levels found in Lmna?/? MEFs. Together these results show that both the mechanical properties of the cytoskeleton and cytoskeleton-based processes, including cell motility, coupled MTOC and nucleus dynamics, and cell polarization, depend critically on the integrity of the nuclear lamina, which suggest the existence of a functional mechanical connection between the nucleus and the cytoskeleton. These results also suggest that cell polarization during cell migration requires tight mechanical coupling between MTOC and nucleus, which is mediated by lamin A/C.

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

2007-01-01

321

Inhibition of cyclophosphamide-induced oxidative stress in rat brain by polar and non-polar extracts of Annatto (Bixa orellana) seeds.  

PubMed

Annatto (Bixa orellana) seeds are widely distributed throughout the Tropics and have been used to provide both colour and flavour to food. This study sought to assess the ability of dietary inclusion of polar (water) and non-polar (chloroform) extracts of Annatto (B. orellana) seeds on cyclophosphamide-induced oxidative stress in rat brain. The total phenol content and antioxidant activities of polar (water) and non-polar (chloroform) extracts of Annatto seeds were determined in vitro and in vivo. The results of the study showed that intraperitoneal administration of cyclophosphamide (75 mg/kg of body weight) caused a significant increase (P<0.05) in the malondialdehyde (MDA) content of the brain; however, dietary inclusion of Annatto seed extracts (0.1% and 0.2%) caused dose-dependent significant decrease (P<0.05) in the MDA content of the brain. Likewise, the extracts also caused dose-dependent inhibition of the elevated serum glutamate oxaloacetate transaminase (SGOT), glutamate pyruvate transaminase (SGPT), alkaline phosphatase and total bilirubin. However, the non-polar extract had significantly higher inhibitory effects on the elevated MDA production in brain and serum liver function markers. This higher protective effect of the non-polar extract could be attributed to its higher antioxidant properties as typified by its significantly higher (P<0.05) reducing power, free-radical scavenging and Fe (II) chelating ability. Therefore, dietary inclusion of Annato seed extracts as food colourant could prevent oxidative stress occasioned by cyclophosphamide administration, but the non-polar extract is a better protectant. PMID:20137904

Oboh, Ganiyu; Akomolafe, Toyin L; Adefegha, Stephen A; Adetuyi, Abayomi O

2011-03-01

322

Assessment of system penalties induced by polarization mode dispersion in a 5 Gb\\/s optically amplified transoceanic link  

Microsoft Academic Search

The system penalties induced by polarization mode dispersion (PMD) in a 5 Gb\\/s optically amplified link are analyzed. A relation between differential group delays and system penalties is obtained from numerical simulations and used to derive analytic formulas for probability density functions of system penalties. Cumulated probabilities show that PMDs higher than 20 ps can induce significant fluctuations of the

F. Bruyere; O. Audouin

1994-01-01

323

Photophysics of indole in polar solvent: Analysis of fluorescence lifetime distributions and time-dependence spectral shifts  

SciTech Connect

The fluorescence lifetime distribution of indole in isobutanol is described by the Maximum Entropy Method (MEM) by a main slow emission decay component and a second fast one which is due to spectral kinetics processes. These latter components are associated with positive amplitudes at short emission wavelengths and with negative amplitudes with the same mean decay time value at the long-wavelength edge of the fluorescence spectrum. Both positive and negative rapid components sharply decline or even disappear if the excitation is performed at the long-wavelength edge of the absorption spectrum (300 nm). As expected, these components are very sensitive to temperature. The variation is linear in Arrhenius coordinates and results in activation energies of 7.5 kcal/mol. The shifts of emission spectra as a function of time (TRES) have allowed to obtain relaxation times in the same range as observed in lifetime distributions. The C(t) function defined by the centers of the time-dependent emission spectrum, can be described by MEM as a sum of two or three discrete components depending on the temperature and not by continuous distributions. The longuest one displays a similar value as that of the longuest longitudinal relaxation time of isobutanol as determined by dielectric measurements in the same temperature range. The excited state stabilization energy is around 3.7 kcal/mol. This set of results are consistent with a mechanism of general dielectric solvent relaxation rather than formation of binary excited state complexes in the time range studied.

Vincent, Michel; Gallay, Jacques; Demchenko, Alexander P. [L.U.R.E. Laboratoire pour l'Utilisation du Rayonnement Electromagnetique, Universite Paris-Sud, batiment 209D, 91405-Orsay (France); Department of Biophysics, A. V. Palladin Institute of Biochemistry, Kiev, 252030 (Ukraine)

1996-04-01

324

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

SciTech Connect

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

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

1984-04-24

325

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

PubMed

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

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

2013-11-15

326

Magnetic coupling between Fe nanoislands induced by capping-layer magnetic polarization  

NASA Astrophysics Data System (ADS)

A study on the interislands interaction in granular Fe(110) thin films grown on c-sapphire as a function of the islands size and the capping layer induced magnetization is presented. Islands size (ranging from 10 to 50 nm in diameter) and physical contact between them can be monitored with the deposition time. While Al and MgO cappings do not modify the magnetic hysteresis loop of free islands surface, Pd and Pt give rise to a superparamagnetic-ferromagnetic transition in structures formed by small islands and a stronger interisland coupling in those formed by larger ferromagnetic islands. This improvement in the exchange interactions between islands is due to the induced magnetization of Pt and Pd localized at the interfaces between Pt-Fe ( Pd-Fe ) as evidenced by polar Kerr spectroscopy measurements and simulations.

Navarro, E.; Huttel, Y.; Clavero, C.; Cebollada, A.; Armelles, G.

2004-06-01

327

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

NASA Astrophysics Data System (ADS)

Hydrodynamically interacting active particles in an external harmonic potential form a self-assembled fluid pump at large enough Péclet numbers. Here, we give a quantitative criterion for the formation of the pump and show that particle orientations align in the self-induced flow field in surprising analogy to ferromagnetic order where the active Péclet number plays the role of inverse temperature. The particle orientations follow a Boltzmann distribution ?(p)˜exp(Apz) where the ordering mean field A scales with the active Péclet number and polar order parameter. The mean flow field in which the particles' swimming directions align corresponds to a regularized Stokeslet with strength proportional to swimming speed. Analytic mean-field results are compared with results from Brownian dynamics simulations with hydrodynamic interactions included and are found to capture the self-induced alignment very well.

Hennes, Marc; Wolff, Katrin; Stark, Holger

2014-06-01

328

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

NASA Astrophysics Data System (ADS)

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.

Derakhshan, Vahid; Cheraghchi, Hosein

2014-05-01

329

Time lapse electrical resistivity and induced polarization monitoring of near-surface CO2 injection  

NASA Astrophysics Data System (ADS)

Field experiments were carried out to investigate the efficiency and the reliability of electrical geophysical methods to detect and monitor CO2 leakages at field scale. Each test consisted of injecting CO2 for approximately four hours at five meters depth, corresponding to a cumulative mass of gas of around six kilograms. Electrical resistivity tomography and temporal induced polarization were acquired at the surface before, during and after injections along profiles centered to the injection well. Time lapse measurements were compared to a reference acquisition performed before the injection. We observe that both methods are sensitive to variations in terms of gas saturation, the chargeability measurements being more sensitive to the presence of CO2 than electrical resistivity. During the injection, an increase of chargeability and a decrease of the measured resistivity are observed at depth in the vinicity of the injection well. Afterwards, the medium equilibrates and retrieves its original state, corresponding to the reference acquisition. The temporal variations of electrical resistivity and induced polarization responses are interpreted in terms of gas dissolution and water/gas saturation.

Allègre, V.; Kremer, T.; Williard, E.; Schmutz, M.; Maineult, A. J.

2013-12-01

330

Mycobacterium avium subsp. paratuberculosis Fibronectin Attachment Protein Activates Dendritic Cells and Induces a Th1 Polarization ?  

PubMed Central

Paratuberculosis is a chronic infectious disorder and a major problem in farmed ruminants. This disease is caused by Mycobacterium avium subsp. paratuberculosis. M. avium subsp. paratuberculosis is an important pathogen that causes Johne's disease in animals and also has been implicated as a possible cause of Crohn's disease in humans, but little is known about the protective immune responses to this microorganism. Fibronectin attachment protein (FAP) is a member of a family of fibronectin-binding proteins produced by several species of mycobacteria which is important in the pathogenesis of M. avium. Addition of recombinant FAP to human respiratory tract organ cultures inhibits M. avium binding to areas where there is epithelial damage. We characterized the role of FAP in promoting adaptive and innate immune responses. FAP functionally activated dendritic cells by augmenting the expression of CD80, CD86, major histocompatibility complex class I, and major histocompatibility complex class II. Moreover, FAP induced the allogeneic immunostimulatory capacity of dendritic cells by stimulating dendritic cell production of Th1-promoting interleukin-12. FAP also increased the production of gamma interferon by T cells in mixed-lymphocyte reactions, which would be expected to contribute to the Th1 polarization of the immune response. The expression of surface markers and cytokine production in dendritic cells was mediated by both mitogen-activated protein kinases and NF-?B pathways. These results show that FAP modulates the adaptive immune responses to M. avium subsp. paratuberculosis by inducing maturation and activation of dendritic cells, which drives Th1 polarization.

Lee, Jun Sik; Shin, Sung Jae; Collins, Michael T.; Jung, In Duk; Jeong, Young-Il; Lee, Chang-Min; Shin, Yong Kyoo; Kim, Daejin; Park, Yeong-Min

2009-01-01

331

The human Lgl polarity gene, Hugl-2, induces MET and suppresses Snail tumorigenesis.  

PubMed

Lethal giant larvae proteins have key roles in regulating polarity in a variety of cell types and function as tumour suppressors. A transcriptional programme initiated by aberrant Snail expression transforms epithelial cells to potentially aggressive cancer cells. Although progress in defining the molecular determinants of this programme has been made, we have little knowledge as to how the Snail-induced phenotype can be suppressed. In our studies we identified the human lethal giant larvae homologue 2, Hugl-2, (Llgl2/Lgl2) polarity gene as downregulated by Snail. Snail binds E-boxes in the Hugl-2 promoter and represses Hugl-2 expression, whereas removal of the E-boxes releases Hugl-2 from Snail repression. We demonstrate that inducing Hugl-2 in cells with constitutive Snail expression reverses the phenotype including changes in morphology, motility, tumour growth and dissemination in vivo, and expression of epithelial markers. Hugl-2 expression reduced the nuclear localization of Snail and thus binding of Snail to its target promoters. Our results placing Hugl-2 within the Snail network as well as its ability to suppress Snail carcinogenesis identifies Hugl-2 as a target molecule driving cascades, which may have preventative and therapeutic promise to minimize cancer progression. PMID:22580609

Kashyap, A; Zimmerman, T; Ergül, N; Bosserhoff, A; Hartman, U; Alla, V; Bataille, F; Galle, P R; Strand, S; Strand, D

2013-03-14

332

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

PubMed

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

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

2012-12-17

333

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

NASA Astrophysics Data System (ADS)

We report the controlled synthesis of free-standing ZnO nanobelts whose surfaces are dominated by the large polar surfaces. The nanobelts grow along the a axis, their large top/bottom surfaces are the +/-(0001) polar planes, and the side surfaces are (0110). Owing to the positive and negative ionic charges on the zinc- and oxygen-terminated +/-(0001) surfaces, respectively, the nanobelts form multiloops of nanohelixes/nanosprings/nanospirals for the sake of reducing electrostatic energy introduced by the polar surfaces as well as balancing the difference in surface tension. The polar surface dominated ZnO nanobelts are likely to be an ideal system for understanding piezoelectricity and polarization induced phenomena at nanoscale.

Kong, Xiang Yang; Wang, Zhong Lin

2004-02-01

334

Spectral characterization of biological aerosol particles using two-wavelength excited laser-induced fluorescence and elastic scattering measurements.  

PubMed

A two-wavelength laser-induced fluorescence (LIF) instrument has been developed and used to characterize individual biological aerosol particles, including biological warfare (BW) agent surrogates. Fluorescence in discrete spectral bands from widely different species, and also from similar species under different growth conditions were measured and compared. The two-wavelength excitation approach was found to increase discrimination among several biological materials, and especially with respect to diesel exhaust particles, a common interferent for LIF BW detection systems. The spectral characteristics of a variety of biological materials and ambient air components have been studied as a function of aerosol particle size and incident fluence. PMID:21451645

Sivaprakasam, Vasanthi; Lin, Horn-Bond; Huston, Alan L; Eversole, Jay D

2011-03-28

335

Ultraviolet-light-induced multi-physics behaviors of 0-3 polarized transparent PLZT plates: I. Experimental testing  

NASA Astrophysics Data System (ADS)

This paper presents a novel experimental and numerical investigation into ultraviolet-light-induced multi-physics responses of 0-3 polarized PbLaZrTi (PLZT) plates with transparent indium tin oxide (ITO) electrodes on both surfaces. Part I details the testing set-up, procedure and results for the 0.3 mm thick PLZT sample polarized at room temperature and an electrical field strength of 1200 V mm-1. The measured time-dependent curves and steady state results are presented for the photo-induced electrical voltage and current, temperature and transverse displacement of a 0-3 polarized PLZT plate with double-sided ITO electrodes. It is worth noting that there exists no report on the measurement of transverse displacements of 0-3 polarized PLZT plates, which plays an important role in validating the novel finite element formulation for their multi-physics fields in part II.

Luo, Quantian; Tong, Liyong

2011-11-01

336

Note: reducing polarization induced sidebands in Rayleigh backscattering spectra for accurate distributed strain measurement using optical frequency-domain reflectometry.  

PubMed

We describe a phenomenon called polarization-induced sidebands (PIS) in Rayleigh backscatter spectra (RBS) and discuss its deteriorating effects on the distributed strain measurement using an optical frequency-domain reflectometry. We propose using a special polarization diversity detection scheme to remove PIS and successfully demonstrate accurate distributed strain measurement in the range of 0.75 ??-225 ?? in a 50 m standard single mode fiber, with a good linearity between the strain and the spectra shift in RBS. PMID:23464263

Ding, Zhenyang; Yao, X Steve; Liu, Tiegen; Du, Yang; Liu, Kun; Han, Qun; Meng, Zhuo; Li, Dingjie

2013-02-01

337

The X-ray spectrum and spectral energy distribution of FIRST J155633.8+351758: a LoBAL quasar with a probable polar outflow  

NASA Astrophysics Data System (ADS)

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 ? = 1.7 or flatter at a >99 per cent confidence for a neutral hydrogen absorber model). Absorption is present, with a column density a few times 1023 cm-2, with both partially ionized models and partially covering neutral hydrogen models providing good fits. We present several lines of argument that suggest the fraction of X-ray emissions associated with the radio jet is not large. We combine our Chandra data with observations from the literature to construct the spectral energy distribution of FIRST J1556+3517 from radio to X-ray energies. We make corrections for Doppler beaming for the pole-on radio jet, optical dust reddening and X-ray absorption, in order to recover a probable intrinsic spectrum. The quasar FIRST J1556+3517 seems to be an intrinsically normal radio-quiet quasar with a reddened optical/UV spectrum, a Doppler-boosted but intrinsically weak radio jet and an X-ray absorber not dissimilar from that of other broad absorption line quasars.

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

2013-12-01

338

Polarized laser-induced fluorescence technique to measure localized electric field induced perpendicularly to magnetic field in the plasma-edge  

NASA Astrophysics Data System (ADS)

To develop a direct measurement of the weak electric field induced in a magnetically confined edge plasma, the crossed magnetic- and electric-field effect was investigated on the linear polarization of laser-induced fluorescence. The fluorescence was induced by laser excitation of metastable He atoms 2 1S to 4 1D state due to Stark-induced electric dipole and electric quadrupole moments. In a model-type experiment carried out in a cylindrical hollow cathode plasma column, the radial distribution of the polarization of fluorescence was analyzed to determine the electric field dependence. The measured degree of polarization agreed with estimates from a theoretical model based on the selection rules of the spontaneous radiative transition. The minimum detectable electric field is estimated to be a few tens of V/cm in our scheme. We briefly discuss techniques to increase our measurement sensitivity by the interference between both the forbidden transitions in the laser excitation.

Takiyama, K.; Watanabe, M.; Oda, T.

339

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

340

Reduction of polarization-induced artifacts in grating-based spectrometers  

Microsoft Academic Search

An optical device that converts unpolarized light into a single polarization state is described. The device is based on a polarizing beam splitter that separates the two polarization directions. The beam splitter is combined with two pairs of equilateral prisms that are used to collimate the two beams in terms of both propagation and polarization directions. When it is used

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

2005-01-01

341

Precise extraction of the induced polarization in the {sup 4}He(e,e'p(pol){sup 3}H reaction.  

SciTech Connect

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

Malace, S. P.; Paolone, M.; Strauch, S.; Albayrak, I.; Arrington, J.; Solvignon, P.; The E03-104 Collaboration (Physics); (Univ. of South Carolina); (Hampton Univ.)

2011-01-31

342

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

SciTech Connect

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

S.P. Malace, M. Paolone, S. Strauch

2011-01-01

343

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

PubMed

We measured with unprecedented precision the induced polarization P(y) in (4)He(e,e'p)(3)H at Q(2)=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. PMID:21405386

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

344

Morphologies of laser-induced damage in hafnia-silica multilayer mirror and polarizer coatings  

NASA Astrophysics Data System (ADS)

Hafnia-silica multilayer mirrors and polarizers were deposited by e-beam evaporation onto BK7 glass substrates. The mirrors and polarizers were coated for operation at a wavelength of 1053 nm at 45 degrees and at Brewster's angle (56 degrees), respectively. They were tested with a single 3-ns laser pulse. The morphology of the laser-induced damage was characterized by optical and scanning electron microscopy. Four distinct damage morphologies were found: pits, flat bottom pits, scalds, and delaminates. The pits and flat bottom pits (less than 30 micrometer in diameter) were detected at lower fluences (as low as 5 J/cm2). The pits seemed to result from ejection of nodular defects by causing local enhancement of the electric field. Scalds and delaminates could be observed at higher fluences (above 13 J/cm2) and seemed to result from the formation of plasmas on the surface. These damage types often originated at pits and were typically less than 300 micrometer in diameter; their size increased almost linearly with fluence. Finally, the effects of the damage on the characteristics of the beam (reflectivity degradation and phase modulations) were measured.

Genin, Francois Y.; Stolz, Christopher J.

1996-11-01

345

Thermally induced birefringence changes in cartilage using polarization-sensitive optical coherence tomography  

NASA Astrophysics Data System (ADS)

Thermodynamic induced changes in birefringence of nasal septal cartilage following Nd:YAG laser irradiation were investigated using a polarization-sensitive optical coherence tomography (PSOCT) system. Birefringence in cartilage is due to the asymmetrical collagen fibril structure and may change if the underlying structure is disrupted due to local heat generation by absorption of laser radiation. A PSOCT instrument and an infrared imaging radiometer were used to record, respectively, depth-resolved images of the Stokes parameters of light backscattered from ex vivo porcine nasal septal cartilage and radiometric temperature following laser irradiation. PSOCT images of cartilage were recorded before (control), during, and after laser irradiation. From the measured Stokes parameters (I,Q,U, and V), an estimate of the relative phase retardation between two orthogonal polarizations was computed to determine birefringence in cartilage. Stokes parameter images of light backscattered from cartilage show significant changes due to laser irradiation. From our experiments we differentiate dehydration and thermal denaturation effects and observe the birefringence changes only in the dehydration effect. Therefore, a dynamic measurement of birefringence changes in cartilage using PSOCT as a feedback control methodology to monitor thermal denaturation is problematic in non-ablative surgical procedures such as laser assisted cartilage reshaping.

Youn, Jong-In; Vargas, Gracie; Ducros, Mathieu G.; Telenkov, Sergey A.; Wong, Brian J.; Milner, Thomas E.

2001-07-01

346

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

PubMed Central

We have developed and characterized a system to analyze light effects on auxin transport independent of photosynthetic effects. Polar transport of [3H]indole-3-acetic acid through hypocotyl segments from etiolated cucumber (Cucumis sativus L.) seedlings was increased in seedlings grown in dim-red light (DRL) (0.5 ?mol m?2 s?1) relative to seedlings grown in darkness. Both transport velocity and transport intensity (export rate) were increased by at least a factor of 2. Tissue formed in DRL completely acquired the higher transport capacity within 50 h, but tissue already differentiated in darkness acquired only a partial increase in transport capacity within 50 h of DRL, indicating a developmental window for light induction of commitment to changes in auxin transport. This light-induced change probably manifests itself by alteration of function of the auxin efflux carrier, as revealed using specific transport inhibitors. Relative to dark controls, DRL-grown seedlings were differentially less sensitive to two inhibitors of polar auxin transport, N-(naphth-1-yl) phthalamic acid and 2,3,5-triiodobenzoic acid. On the basis of these data, we propose that the auxin efflux carrier is a key target of light regulation during photomorphogenesis.

Shinkle, James R.; Kadakia, Rajan; Jones, Alan M.

1998-01-01

347

Errors induced when polarization is neglected in radiance calculations for an atmosphere-ocean system  

NASA Astrophysics Data System (ADS)

Virtually all calculations to date dealing with radiance calculations in an atmosphere-ocean system have been performed using a scalar theory approach where polarization effects have been neglected. This approach is always in error; however, neither the nature nor the magnitude of the errors induced has been studied. We have written a large scale Monte Carlo program to calculate the complete four component Stokes vector at any region in a fully inhomogenous atmosphere-ocean system with inclusion of a wind ruffled stochastic interface. The program uses as input the Mueller matrices for both the aerosols in the atmosphere as well as the hydrosols in the ocean. The Mueller matrix for the stochastic interface is also accurately accounted for. The correlated sampling technique is used to compute radiance distributions for both the scalar and the Stokes vector formulations in a single computer run, thus allowing a direct comparison of the errors induced. Results are presented for a realistic atmosphere-ocean system to show the effects of the volume scattering function, the dielectric interface, and waves on the induced errors.

Kattawar, George W.; Adams, Charles N.

1992-12-01

348

Nesprin-3 regulates endothelial cell morphology, perinuclear cytoskeletal architecture, and flow-induced polarization  

PubMed Central

Changes in blood flow regulate gene expression and protein synthesis in vascular endothelial cells, and this regulation is involved in the development of atherosclerosis. How mechanical stimuli are transmitted from the endothelial luminal surface to the nucleus is incompletely understood. The linker of nucleus and cytoskeleton (LINC) complexes have been proposed as part of a continuous physical link between the plasma membrane and subnuclear structures. LINC proteins nesprin-1, -2, and -4 have been shown to mediate nuclear positioning via microtubule motors and actin. Although nesprin-3 connects intermediate filaments to the nucleus, no functional consequences of nesprin-3 mutations on cellular processes have been described. Here we show that nesprin-3 is robustly expressed in human aortic endothelial cells (HAECs) and localizes to the nuclear envelope. Nesprin-3 regulates HAEC morpho­logy, with nesprin-3 knockdown inducing prominent cellular elongation. Nesprin-3 also organizes perinuclear cytoskeletal organization and is required to attach the centrosome to the nuclear envelope. Finally, nesprin-3 is required for flow-induced polarization of the centrosome and flow-induced migration in HAECs. These results represent the most complete description to date of nesprin-3 function and suggest that nesprin-3 regulates vascular endothelial cell shape, perinuclear cytoskeletal architecture, and important aspects of flow-mediated mechanotransduction.

Morgan, Joshua T.; Pfeiffer, Emily R.; Thirkill, Twanda L.; Kumar, Priyadarsini; Peng, Gordon; Fridolfsson, Heidi N.; Douglas, Gordon C.; Starr, Daniel A.; Barakat, Abdul I.

2011-01-01

349

Ligand induced circular dichroism and circularly polarized luminescence in CdSe quantum dots.  

PubMed

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 postsynthetic 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. Time Dependent Density Functional Theory (TDDFT) 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 origin of the induced chirality is consistent with the hybridization of highest occupied CdSe molecular orbitals with those of the chiral ligand. PMID:24200288

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

2013-12-23

350

Circularly polarized luminescence from individual microstructures of conjugated polymer aggregates with solvent-induced chirality.  

PubMed

We report a microscopic study of circularly polarized luminescence (CPL) from R and S isomers of aggregates of the conjugated polymer , a copolymer containing fluorene and thiophene monomer units. Chirality in the aggregates is induced by addition of either (R)- or (S)-limonene during aggregation in solution. Solid-state samples are prepared either by drop-casting or spin-coating of the aggregate solution. CPL dissymmetry parameter g measured for individual aggregate microstructures shows a broad distribution of values ranging from positive to negative even for the same isomer. The difference in the centers of the g distribution between the R and S isomers reflects the intrinsic CPL from the chiral aggregates, and is found to depend on the size of the aggregate structures. On the other hand, the large widths of the distributions are ascribed to an optical effect arising from phase retardation along the optical path of the CPL inside the sample. PMID:25050630

Katayama, Kenta; Hirata, Shuzo; Vacha, Martin

2014-07-30

351

Mapping polarization induced surface band bending on the Rashba semiconductor BiTeI  

PubMed Central

Surfaces of semiconductors with strong spin-orbit coupling are of great interest for use in spintronic devices exploiting the Rashba effect. BiTeI features large Rashba-type spin splitting in both valence and conduction bands. Either can be shifted towards the Fermi level by surface band bending induced by the two possible polar terminations, making Rashba spin-split electron or hole bands electronically accessible. Here we demonstrate the first real-space microscopic identification of each termination with a multi-technique experimental approach. Using spatially resolved tunnelling spectroscopy across the lateral boundary between the two terminations, a previously speculated on p-n junction-like discontinuity in electronic structure at the lateral boundary is confirmed experimentally. These findings realize an important step towards the exploitation of the unique behaviour of the Rashba semiconductor BiTeI for new device concepts in spintronics.

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

352

Rotation of scissioning nuclei observed in ternary fission induced by polarized neutrons  

NASA Astrophysics Data System (ADS)

Angular distributions of light charged particles relative to the momentum of the light fission fragment were studied in ternary fission induced by cold polarized neutrons. It was discovered that the angular distribution is asymmetric with respect to a plane determined by the direction of incident neutron spin and the light fragment momentum. The violation of the mirrorlike symmetry was established at the level of ~10-2-10-4 for three reactions studied: 233U(n,f), 235U(n,f) and 239Pu(n,f). In spite of the smallness of the effects the neutron spin flip method allowed to make reliable measurements. The current status of the experimental studies of the effect and its interpretation are presented. Perspectives for further studies of the new phenomenon are discussed.

Gagarski, A.; Petrov, G.; Guseva, I.; Zavarukhina, T.; Gönnenwein, F.; Mutterer, M.; von Kalben, J.; Kopatch, Yu.; Tiourine, G.; Trzaska, W.; Sillanpää, M.; Soldner, T.; Nesvizhevsky, V.

2009-10-01

353

Mapping polarization induced surface band bending on the Rashba semiconductor BiTeI.  

PubMed

Surfaces of semiconductors with strong spin-orbit coupling are of great interest for use in spintronic devices exploiting the Rashba effect. BiTeI features large Rashba-type spin splitting in both valence and conduction bands. Either can be shifted towards the Fermi level by surface band bending induced by the two possible polar terminations, making Rashba spin-split electron or hole bands electronically accessible. Here we demonstrate the first real-space microscopic identification of each termination with a multi-technique experimental approach. Using spatially resolved tunnelling spectroscopy across the lateral boundary between the two terminations, a previously speculated on p-n junction-like discontinuity in electronic structure at the lateral boundary is confirmed experimentally. These findings realize an important step towards the exploitation of the unique behaviour of the Rashba semiconductor BiTeI for new device concepts in spintronics. PMID:24898943

Butler, Christopher John; Yang, Hung-Hsiang; Hong, Jhen-Yong; Hsu, Shih-Hao; Sankar, Raman; Lu, Chun-I; Lu, Hsin-Yu; Yang, Kui-Hon Ou; Shiu, Hung-Wei; Chen, Chia-Hao; Kaun, Chao-Cheng; Shu, Guo-Jiun; Chou, Fang-Cheng; Lin, Minn-Tsong

2014-01-01

354

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

355

Spatiotemporal mapping of concentration polarization induced pH changes at nanoconstrictions.  

PubMed

Under an applied electric field, concentration polarization (CP) arises from ion permselectivity of most nanoporous materials and biological ion channels. We present novel methods to quantitatively assess CP-induced spatiotemporal changes of pH that may significantly impact transport dynamics, device functionality, and physicochemical properties of molecular analytes in devices with nanofluidic constrictions. We measured pH fluctuations of >1.5 pH units and changes extending over 100's of micrometers from nanoconstrictions. The degree of change depends on key system parameters including buffer composition, surface charge, and strength of electric field. The results highlight the importance of neglected contributions of pH changes, and the approach can aid characterization and manipulation of mass transport in nanofluidic systems. PMID:23061977

Mai, Junyu; Miller, Hanna; Hatch, Anson V

2012-11-27

356

COMPLEX RESISTIVITY OF FAULT GOUGE AND ITS SIGNIFICANCE FOR EARTHQUAKE LIGHTS AND INDUCED POLARIZATION.  

USGS Publications Warehouse

The authors measured complex resistivity of 2 water-saturated San Andreas fault gouges from 10** minus **3 to 10**6 Hz and confining pressures of 0. 2 to 200 MPa. Consistent with earlier observations of clays and common rocks, large low-frequency permittivities were observed in all cases. Comparisons were made to induced polarization (IP) measurements by inversion of the data into the time domain, where it was found that principal features of the IP response curves were due to these large low-frequency permittivities. The results also suggest that following large earthquakes, significant electrical charge could remain for many seconds and could result in a variety of reported electromagnetic effects. Refs.

Lockner, David, A.; Byerlee, James, D.

1985-01-01

357

Spectral and biological changes induced in nicotinic acid and related compounds by ultraviolet light  

PubMed Central

1. Irradiation of nicotinic acid, nicotinamide, nicotinamide N-oxide, N?-methyl-4-pyridone-3-carboxamide, reduced nicotinamide–adenine dinucleotide and pyridine with ultraviolet light at 253·7m? leads to striking spectral changes. 2. Nicotinic acid and nicotinamide are broken down to photosensitive intermediates which in turn undergo photodecomposition. 3. A major photoproduct of [7-14C]nicotinic acid is radioactive and absorbs ultraviolet light, but is inactive as a growth factor for Candida pseudotropicalis. 4. Irradiation of nicotinamide gives rise to small quantities of a biologically active photoproduct having the same RF as nicotinic acid. A second photoproduct is also formed, but its identity has not yet been established. 5. Irradiation of nicotinamide N-oxide leads to the formation of several photoproducts, one of which has the same RF as nicotinamide, absorbs ultraviolet light, and is biologically active. 6. Evidence is presented that irradiation of ethanolic solutions of N?-methyl-4-pyridone-3-carboxamide gives rise to acetaldehyde. 7. Irradiation of reduced nicotinamide–adenine dinucleotide in the presence of acetaldehyde leads to the formation of oxidized nicotinamide–adenine dinucleotide, which in turn can break down to nucleotide and/or nucleoside (depending on the conditions of the reaction). 8. The quantum yields of photolysis and the molar photosensitivities have been determined for N?-methyl-4-pyridone-3-carboxamide and nicotinamide N-oxide. 9. The possible biological significance of these photoreactions is discussed in relation to photosynthesis, visual-pigment metabolism and ultraviolet-light-induced cell damage. 10. A four-step theory is presented for the biochemical evolution of oxidation–reduction systems, involving photoactivated transformations of pyridine derivatives. ImagesFig. 3.Fig. 6.

Abelson, Denis; Parthe, E.; Lee, K. W.; Boyle, A.

1965-01-01

358

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

SciTech Connect

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.

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

359

?2 Integrin Induces TCR ?-Syk-PLC-? Phosphorylation and Paxillin-dependent Granule Polarization in Human NK cells1  

PubMed Central

Cytotoxic lymphocytes kill target cells through polarized release of the content of lytic granules at the immunological synapse. In human natural killer (NK) cells, signals for granule polarization and for degranulation can be uncoupled: Binding of ?2 integrin LFA-1 to ICAM is sufficient to induce polarization but not degranulation, whereas CD16 binding to IgG triggers unpolarized degranulation. Here we investigated the basis for this difference. IL-2 expanded human NK cells were stimulated by incubation with plate-bound ligands of LFA-1 (ICAM-1) and CD16 (human IgG). Surprisingly, LFA-1 elicited signals similar to those induced by CD16, including tyrosine phosphorylation of the TCR ? chain, tyrosine kinase Syk, and phospholipase C (PLC)-?. Whereas CD16 activated Ca2+ mobilization and LAT phosphorylation, LFA-1 did not, but induced strong Pyk2 and paxillin phosphorylation. LFA-1-dependent granule polarization was blocked by inhibition of Syk, PLC-?, and PKC, and by paxillin knockdown. Therefore, common signals triggered by CD16 and LFA-1 bifurcate to provide independent control of Ca2+-dependent degranulation and paxillin-dependent granule polarization.

March, Michael E.; Long, Eric O.

2013-01-01

360

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

PubMed

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

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

2014-01-01

361

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

362

The mechanism for continuum polarization in laser induced breakdown spectroscopy of Si(111)  

NASA Astrophysics Data System (ADS)

Polarization of the plasma luminescence produced by both nanosecond and femtosecond laser ablation of Si(111) was analyzed under different conditions of fluence and detection geometry. It is shown that the luminescence is partially polarized and is directed in the plane of the crystal. The time evolution of the plasma emission signal was also investigated with the use of a streak camera. The mechanism for polarization is proposed to be preferential reflection of s-polarized light (i.e., light polarized normal to the plane of laser incidence) by the melted surface, in agreement with the Fresnel equations. Earlier reports of much stronger polarization are shown to be erroneous.

Penczak, John S., Jr.; Liu, Yaoming; Schaller, Richard D.; Rich, Daniel H.; Gordon, Robert J.

2012-08-01

363

Numerical Simulation of Flow Induced by a Spinning Sphere Using Spectral Methods.  

National Technical Information Service (NTIS)

A direct numerical simulation, based on spectral methods, has been used to investigate viscous, incompressible, steady, rotationally symmetric flow due to a sphere rotating with a constant angular velocity about a diameter. The equations of motion have be...

B. Zeybek

1997-01-01

364

Electric field-induced polarization of charged cell surface proteins does not determine the direction of galvanotaxis.  

PubMed

Galvanotaxis, that is, migration induced by DC electric fields, is thought to play a significant role in development and wound healing, however, the mechanisms by which extrinsic electric fields orchestrate intrinsic motility responses are unknown. Using mammalian cell lines (3T3, HeLa, and CHO cells), we tested one prevailing hypothesis, namely, that electric fields polarize charged cell surface molecules, and that these polarized molecules drive directional motility. Negatively charged sialic acids, which contribute the bulk of cell surface charge, redistribute preferentially to the surface facing the direction of motility, as measured by labeling with fluorescent wheat germ agglutinin. We treated cells with neuraminidase to remove sialic acids; as expected, this decreased total cell surface charge. We also changed cell surface charge independent of sialic acid moieties, by conjugating cationic avidin to the surface of live cells. Neuraminidase inhibited the electric field-induced directional polarization of membrane ruffling and alpha4 integrin, while avidin treatment actually reversed the directional polarization of sialic acids. Neuraminidase treatment inhibited directionality but did not alter speed of motility. Surprisingly, avidin treatment did not significantly alter either directionality or speed of motility. Thus, our results demonstrate that electric field-induced polarization of charged species indeed occurs. However, polarization of the bulk of charged cell surface proteins is neither necessary nor sufficient to cause motility, thus contradicting the second part of our hypothesis. Because neuraminidase inhibited directional motility, we also conclude that sialic acids are required constituents of some cell surface molecule(s) through which electric fields mount a polarized transmembrane response. PMID:17685443

Finkelstein, Erik I; Chao, Pen-hsiu Grace; Hung, Clark T; Bulinski, Jeannette Chloë

2007-11-01

365

Spectral integration plasticity in cat auditory cortex induced by perceptual training  

Microsoft Academic Search

We investigated the ability of cats to discriminate differences between vowel-like spectra, assessed their discrimination\\u000a ability over time, and compared spectral receptive fields in primary auditory cortex (AI) of trained and untrained cats. Animals\\u000a were trained to discriminate changes in the spectral envelope of a broad-band harmonic complex in a 2-alternative forced choice\\u000a procedure. The standard stimulus was an acoustic

M. Diane Keeling; Barbara M. Calhoun; Katharina Krüger; Daniel B. Polley; Christoph E. Schreiner

2008-01-01

366

Spectral hole burning and uniaxial stress study of radiation-induced defects in diamond  

Microsoft Academic Search

A persistent spectral hole-burning technique has been employed to investigate the impact of uniaxial stress on the defects created by neutron irradiation in natural Ia-type diamond. Shifts of the spectral holes in the 649, 681, and 774 nm zero-phonon lines (ZPLs) have been measured. The values of the shifts, 2.2, 1.2, and 0.65 cm?1\\/kbar, obtained from these measurements have been

A. Osvet; V. Palm; I. Sildos

1996-01-01

367

Ionization-induced refractive index and polarization effects in LiNbO3:Ti directional coupler waveguides  

NASA Astrophysics Data System (ADS)

Exposure of an LiNbO3:Ti directional coupler to pulsed 16-MeV electrons was observed to nonequivalently affect the transverse electric-transverse magnetic (TE-TM) polarized transmission of a continuous wave 1300-nm optical signal through the channel waveguides. Two distinct ionization-induced attenuation responses were observed to depend on the magnitude of the optical power in the guides and on the polarization states. An hypothesis for these phenomena is advanced based on the presence of localized space charge fields arising from ionization-induced transient color centers, free carriers within or near the light guiding regions, and polarization conversion initiated through decreased mode confinement and scattering. Transient space charge fields causing localized changes to the refractive indexes in and near the guiding regions are believed to have caused both the loss of guiding and the onset of photorefractive-like processes.

Taylor, Edward W.

1991-03-01

368

Humidity-induced spectral shift in a cross-dispersion echelle spectrometer and its theoretical investigation.  

PubMed

The relationship between ambient relative humidity H and the position shift of a spectral line was investigated both experimentally and theoretically. An echelle-based ICP emission spectrometer equipped with a CID detector was used for experimental verification of the derived model. The shift of a spectral line is quantitatively described by two defined spectral shift functions: delta lambda x(x, lamda, H) (in the x direction of the CID detector) and delta lambda y(y, lambda, H) (in the y direction of the CID detector). Experimental results indicate that delta lamda x(x, lambda, H) does not change with a variation in ambient relative humidity, but delta lamda y(y, lambda, H) does. A spectral shift equation, i.e., an empirical second-order polynomial equation, can be used to describe the relationship between delta lamda y(y, lambda, H) and H. Based on the classical dipole model, classical mechanics and electrodynamics the empirical spectral-shift equation involving delta lambda y(y, lambda, H) and H was theoretically deduced. The theoretical result is in good agreement with the experimental findings. The theoretical results indicate that the coefficients of the empirical spectral-shift equation are related to the basic physical parameters of materials and the geometric configuration of the echelle CID ICP-AES, and also provide physical meaning to the coefficients of the empirical shift equation obtained experimentally. PMID:21090510

Liu, Ke-ling; Huang, Mao; Hieftje, Gary M

2010-09-01

369

Vector photochromism in polarization-sensitive materials.  

PubMed

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

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

2014-07-01

370

Polar agents with differentiation inducing capacity potentiate tumor necrosis factor-mediated cytotoxicity in human myeloid cell lines  

Microsoft Academic Search

Cotreatment or pretreatment of several hu- man myeloid cell lines (KG!, HL6O, U937, THP1) with the differentiation inducer DMSO was found to potenti- ate the antiproliferative and cytotoxic effects of TNF. In addition, TNF-resistant monocytic cell lines could be sen- sitized to TNF cytotoxicity by DMSO treatment. Other highly polar molecules, known to be potent differentia- tion inducers, showed similar

Stany Depraetere; Bart Vanhaesebroeckt; Walter Fierst; Jean Willems; Marcel Joniau

371

Induced polarization, resistivity, and self-potential: a case history of contamination evaluation due to landfill leakage  

Microsoft Academic Search

This article compares the efficiency of induced polarization (IP) and resistivity in characterizing a contamination plume\\u000a due to landfill leakage in a typical tropical environment. The resistivity survey revealed denser electrical current flow\\u000a that induced lower resistivity values due to the high ionic content. The increased ionic concentration diminished the distance\\u000a of the ionic charges close to the membrane, causing

José Domingos Faraco Gallas; Fabio Taioli; Walter Malagutti Filho

2011-01-01

372

Effect of light polarization and dimensions of ?-type three level cylindrical quantum dot on electromagnetically induced transparency  

NASA Astrophysics Data System (ADS)

In this paper, electromagnetically induced transparency (EIT) is investigated in a GaAs cylindrical quantum dot (QD) with parabolic potential. The Schrödinger equation is solved in effective mass, eigenfunctions and eigenvalues of QD. Using obtained eigenfunctions and eigenvalues, susceptibility of cylindrical QD is found. Dependence of electromagnetically induced transparency on radius and height of cylindrical QD, polarization of probe and control lasers, Rabi and probe frequencies, decay rate and detuning of the control laser are also investigated.

Raki, Z.; Askari, H. R.

2014-01-01

373

Angular correlations in emission of prescission neutrons from {sup 235}U fission induced by slow polarized neutrons  

SciTech Connect

A new approach to searching for and studying scission neutrons, which is based on the analysis of specific angular correlations in nuclear fission induced by polarized neutrons, is described and used to evaluate the fraction of scission neutrons in the total number of prompt neutrons of {sup 235}U fission emitted perpendicularly to the fission axis.

Danilyan, G. V., E-mail: danilyan@itep.r [Institute of Theoretical and Experimental Physics (Russian Federation); Wilpert, T.; Granz, P. [Hahn-Meitner Institute (Germany); Krakhotin, V. A. [Institute of Theoretical and Experimental Physics (Russian Federation); Mezei, F. [Hahn-Meitner Institute (Germany); Novitsky, V. V.; Pavlov, V. S. [Institute of Theoretical and Experimental Physics (Russian Federation); Russina, M. V. [Hahn-Meitner Institute (Germany); Shatalov, P. B. [Institute of Theoretical and Experimental Physics (Russian Federation)

2008-12-15

374

Interferon Tau Alleviates Obesity-Induced Adipose Tissue Inflammation and Insulin Resistance by Regulating Macrophage Polarization  

PubMed Central

Chronic adipose tissue inflammation is a hallmark of obesity-induced insulin resistance and anti-inflammatory agents can benefit patients with obesity-associated syndromes. Currently available type I interferons for therapeutic immunomodulation are accompanied by high cytotoxicity and therefore in this study we have examined anti-inflammatory effects of interferon tau (IFNT), a member of the type I interferon family with low cellular toxicity even at high doses. Using a diet-induced obesity mouse model, we observed enhanced insulin sensitivity in obese mice administered IFNT compared to control mice, which was accompanied by a significant decrease in secretion of proinflammatory cytokines and elevated anti-inflammatory macrophages (M2) in adipose tissue. Further investigations revealed that IFNT is a potent regulator of macrophage activation that favors anti-inflammatory responses as evidenced by activation of associated surface antigens, production of anti-inflammatory cytokines, and activation of selective cell signaling pathways. Thus, our study demonstrates, for the first time, that IFNT can significantly mitigate obesity-associated systemic insulin resistance and tissue inflammation by controlling macrophage polarization, and thus IFNT can be a novel bio-therapeutic agent for treating obesity-associated syndromes and type 2 diabetes.

Ying, Wei; Kanameni, Srikanth; Chang, Cheng-An; Nair, Vijayalekshmi; Safe, Stephen; Bazer, Fuller W.; Zhou, Beiyan

2014-01-01

375

Pressure-induced polar phases in multiferroic delafossite CuFeO2  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

376

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

PubMed

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

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

2012-12-01

377

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

NASA Astrophysics Data System (ADS)

Data on Stark widths of spectral lines are of high interest for astrophysics and analytical techniques of stellar plasma diagnosis. Stark widths of 43 spectral lines of Sn I and 27 spectral lines of Sn II has been measured in a laser-induced plasma (LIP) at an electron temperature of 11,000 K and an electron density of 1.1×1016 cm-3. The LIP optical emission spectroscopy generated by a 10640 Å radiation, with a flux of 1.4×1010 W cm-2 on several tin and lead targets in an atmosphere of argon was recorded at 2.5 ?s and analyzed between 1890 and 7000 Å. The population level distribution and the corresponding temperatures were obtained using Boltzmann plots. The plasma electron densities were determined using well-known Stark broadening parameters of spectral lines. Special attention was dedicated to the possible self-absorption of the different transitions. The local thermodynamic equilibrium (LTE) conditions and plasma homogeneity have been checked. The experimental results obtained have been compared with the experimental and theoretical values given by other authors. The results obtained in this study will allow a substantial improvement in the interpretation of the data of the ultraviolet spectrum of the tin observed by the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope. These atomic data are relevant to the analysis of the isotopic abundances of tin in stellar atmospheres.

Alonso-Medina, A.; Colón, C.

2008-01-01

378

Spectral element formulation for analysis of high-frequency dynamic responses induced by surface-bonded piezoelectric transducers  

NASA Astrophysics Data System (ADS)

This paper presents spectral element formulation which simulates high frequency dynamic responses generated by PZT transducers bonded on a thin plate. A two layer beam model under 2-D plane strain condition is developed to represent fundamental Lamb wave modes induced by a piezoelectric (PZT) layer rigidly bonded on a base plate. Mindlin- Herrmann and Timoshenko beam theories are employed to represent the first symmetric and anti-symmetric Lamb wave modes on a base plate, respectively. The Euler-Bernoulli beam theory and 1-D linear piezoelectricity are used to model the electro-mechanical behavior of a PZT layer. The equations of motions of a two layer beam model are derived through Hamilton's principle. The necessary boundary conditions associated with the electro-mechanical properties of a PZT layer are formulated in the context of dual functions of a PZT layer as an actuator and a sensor. General spectral shape functions of response field and the associated boundary conditions are obtained through equations of motion transformed into frequency domain. Detailed spectral element formulation for composing the dynamic stiffness matrix of a two layer beam model is presented as well. The validity of the proposed spectral element is demonstrated through a numerical example.

Park, Hyun Woo; Lim, Ki Lyong; Kim, Eun Jin; Sohn, Hoon

2009-03-01

379

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

Microsoft Academic Search

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

Ka Lok Ng; Kin-Wang Ng

1994-01-01

380

Application of the new comprehensive X-ray spectral model to the two brightest intermediate polars EX Hydrae and V1223 Sagittarii  

NASA Astrophysics Data System (ADS)

We applied the new comprehensive X-ray spectral model for the post-shock accretion column (PSAC) of the intermediate polars (IPs) constructed by Hayashi and Ishida to the Suzaku data of the two brightest IPs EX Hydrae and V1223 Sagittarii. The white dwarf (WD) mass and the specific accretion rate of EX Hya are estimated to be M_WD= 0.63_{-0.14}^{+0.17} M? and a=0.049_{-0.035}^{+0.66} g cm-2 s-1. Our WD mass of EX Hya is greater than that of previous X-ray estimations (˜0.4-0.5 M?), where higher specific accretion rate than ours is assumed, and marginally consistent with 0.790 ± 0.026 M? measured by Beuermann and Reinsch using a binary motion. On the other hand, with the aid of the PSAC height of V1223 Sgr hV1223 < 0.07RWD, we estimated M_WD= 0.87_{-0.06}^{+0.10} M_{?} and a > 2.0 g cm-2 s-1 for V1223 Sgr. We evaluated the fractional accreting area of EX Hya and V1223 Sgr at 0.0033_{-0.0030}^{+0.0067} and <0.007, respectively. Calculation of the hydrodynamical equations with these best-fitting parameters show that the PSAC height of EX Hya is 0.33 RWD = 2.8 × 108 cm. The maximum temperature of the EX Hya and V1223 Sgr are calculated at 18.0 keV and 43.1 keV, respectively. In EX Hya, the temperature distribution is flatter and the density at the top of the PSAC is smaller than those of the previous PSAC models because of its low specific accretion rate.

Hayashi, Takayuki; Ishida, Manabu

2014-07-01

381

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

Microsoft Academic Search

ABSTRACT In response to mating pheromones, cells of the yeast Saccharomyces cerevisiae adopt a polarized “shmoo” morphology, in which the cytoskeleton and proteins involved in mating are localized to a cell- surface projection. This polarization , yet to be determined. We discuss the possible roles of these gene products in establishing cell polarity during mating. M ANY cell types generate

Janet Chenevert; Nicole Val; Ira Herskowitz

382

Experimental evidence of Brillouin-induced polarization wheeling in highly birefringent optical fibers.  

PubMed

We study the influence of Stimulated Brillouin Scattering on the polarization stabilization of a light beam propagating in a highly-birefringent optical fiber. In particular, due to a saturation effect, we find that the output polarization lies on a ring when the polarization is represented onto the Poincaré sphere. PMID:19654665

Fatome, Julien; Pitois, Stéphane; Millot, Guy

2009-07-20

383

Errors induced by the neglect of polarization in radiance calculations for Rayleigh-scattering atmospheres  

NASA Technical Reports Server (NTRS)

Although neglecting polarization and replacing the rigorous vector radiative transfer equation by its approximate scalar counterpart has no physical background, it is a widely used simplification when the incident light is unpolarized and only the intensity of the reflected light is to be computed. We employ accurate vector and scalar multiple-scattering calculations to perform a systematic study of the errors induced by the neglect of polarization in radiance calculations for a homogeneous, plane-parallel Rayleigh-scattering atmosphere (with and without depolarization) above a Lambertian surface. Specifically, we calculate percent errors in the reflected intensity for various directions of light incidence and reflection, optical thicknesses of the atmosphere, single-scattering albedos, depolarization factors, and surface albedos. The numerical data displayed can be used to decide whether or not the scalar approximation may be employed depending on the parameters of the problem. We show that the errors decrease with increasing depolarization factor and/or increasing surface albedo. For conservative or nearly conservative scattering and small surface albedos, the errors are maximum at optical thicknesses of about 1. The calculated errors may be too large for some practical applications, and, therefore, rigorous vector calculations should be employed whenever possible. However, if approximate scalar calculations are used, we recommend to avoid geometries involving phase angles equal or close to 0 deg and 90 deg, where the errors are especially significant. We propose a theoretical explanation of the large vector/scalar differences in the case of Rayleigh scattering. According to this explanation, the differences are caused by the particular structure of the Rayleigh scattering matrix and come from lower-order (except first-order) light scattering paths involving right scattering angles and right-angle rotations of the scattering plane.

Mishchenko, M. I.; Lacis, A. A.; Travis, L. D.

1994-01-01

384

Over-limiting currents and deionization "shocks" in current-induced polarization: local-equilibrium analysis.  

PubMed

The problem is considered theoretically of dynamics of current-induced concentration polarization of interfaces between ideally perm-selective and non-ideally perm-selective ("leaky") ion-exchange media in binary electrolyte solutions under galvanostatic conditions and at negligible volume flow. In contrast to the previous studies, the analysis is systematically carried out in terms of local thermodynamic equilibrium in the approximation of local electric neutrality in virtual solution. For macroscopically homogeneous media, this enables one to obtain model-independent results in quadratures for the stationary state as well as an approximate scaling-form solution for the transient response to the step-wise increase in electric-current density. These results are formulated in terms of such phenomenological properties of the "leaky" medium as ion transport numbers, diffusion permeability to salt and specific chemical capacity. An easy-to-solve numerically 1D PDE is also formulated in the same terms. A systematic parametric study is carried out within the scope of fine-pore model of "leaky" medium in terms of such properties as volumetric concentration of fixed electric charges and diffusivities of ions of symmetrical electrolyte. While previous studies paid principal attention to the shape and propagation rate of the so-called deionization "shocks", we also consider in detail the time evolution of voltage drop and interface salt concentration. Our analysis confirms the previously predicted pattern of propagating deionization "shocks" within the "leaky" medium but also reveals several novel features. In particular, we demonstrate that the deionization-shock pattern is really pronounced only at intermediate ratios of fixed-charge concentration to the initial salt concentration and at quite high steady-state voltages where the model used in this and previous studies is applicable only at relatively early stages of concentration-polarization process. PMID:22947188

Yaroshchuk, Andriy

2012-11-15

385

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

SciTech Connect

The authors demonstrate the use of resistivity/induced polarization (IP) monitoring of salt transport under natural hydraulic loads. Electrical monitoring of saline tracer transport during forced injection has been demonstrated previously. Detection of tracer transport under natural hydraulic loading is difficult because neither the hydraulic load nor the tracer resistivity can be controlled. In one study, the authors identify the electrical response to salt transport in a dynamic beach environment. Resistivity/IP imagine resolved the structure of the saltwater-freshwater interface and evidence for tide-induced groundwater transport. Resistivity increases in the near surface and at depth, upbeach of the high-tide mark, accompanied by tidal transgression. They attribute this to desaturation and decreasing salinity in the near surface and to decreasing salinity at depth, despite tidal transgression. Monitoring of groundwater levels indicates a phase lag between the tide level and groundwater level, supporting the electrical data. IP was insensitive to groundwater salinity variation. In a second study, the authors identify the electrical response to recharge-induced salt transport from a road-sale storage facility. Conductivity and IP models for monitoring lines, located on the basis of an EM31 survey, resolved the subsurface salt distribution, IP modeling resolved the sediment-bedrock interface. Modeling of monthly conductivity differences revealed conductivity increases and decreases at the locations of salt contamination, which correlate with the recharge pattern. They attribute near-surface conductivity increases after heavy rainfall to increasing saturation and ion dissolution. Corresponding conductivity decreases at depth are attributed to flushing of the bedrock with freshwater. Essentially, the opposite response was observed during a quiet monitoring period following heavy recharge. Near-surface IP changes are consistent with this interpretation. Salt transport occurring under natural hydraulic conditions was monitored with resistivity imaging. IP improved characterization of the hydrogeologic framework but was of limited value in monitoring salt transport in these environments.

Slater, L.D.; Sandberg, S.K.

2000-04-01

386

Light-induced spectral diffusion in single self-assembled quantum dots  

NASA Astrophysics Data System (ADS)

Small ensembles of In0.55Al0.45As self-assembled quantum dots have been studied at low temperatures using near-field scanning optical microscopy. We observe spectral diffusion in individual quantum dot luminescence lines. The phenomenon increases in magnitude with optical power density, but is not visible at low powers. We believe the spectral diffusion to be caused by long time-scale trapping and untrapping of charges created by photoionization or thermal ionization in the immediate vicinity of the quantum dots.

Robinson, H. D.; Goldberg, B. B.

2000-02-01

387

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

PubMed

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

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

2014-01-31

388

Dirac {ital R} Matrix Modeling of Spin-Induced Asymmetry in the Scattering of Polarized Electrons from Polarized Cesium Atoms  

Microsoft Academic Search

Recent experiments by Baum, Raith, and co-workers to measure the spin-induced asymmetries in electron scattering from cesium have stimulated theoretical work to interpret these measurements. We present Dirac R -matrix calculations of the interference asymmetry function, and of the spin-orbit and spin-exchange asymmetries, for comparison with experimental data at 7 and 13.5eV and with nonrelativistic predictions of the spin-exchange asymmetry

S. Ait-Tahar; I. P. Grant; P. H. Norrington

1997-01-01

389

Dirac R-Matrix Modeling of Spin-Induced Asymmetry in the Scattering of Polarized Electrons from Polarized Cesium Atoms  

Microsoft Academic Search

Recent experiments by Baum, Raith, and co-workers to measure the spin-induced asymmetries in electron scattering from cesium have stimulated theoretical work to interpret these measurements. We present Dirac R-matrix calculations of the interference asymmetry function, and of the spin-orbit and spin-exchange asymmetries, for comparison with experimental data at 7 and 13.5 eV and with nonrelativistic predictions of the spin-exchange asymmetry

S. Ait-Tahar; I. P. Grant; P. H. Norrington

1997-01-01

390

Cytoskeleton-dependent surface blebbing induced by the polar solvent N-methylformamide.  

PubMed

In vivo and in vitro studies performed on the polar solvent N-methylformamide (NMF), as well as on its association with chemotherapeutic agents or X rays, have clearly demonstrated that this compound is capable of inducing changes in biological characteristics of tumor cells, e.g., cell differentiation. However, the mechanism of action of NMF is far from being elucidated. Hence, in order to better clarify such a mechanism an in vitro study was carried out by using mouse fibroblasts in primary culture (MEF) and human melanoma cultured cells (M14). Results obtained by immunocytochemical and ultrastructural methods with doses of NMF ranging from 0.1 to 7% are reported here. As a general rule, a different sensitivity (in terms of cytopathologic changes induced by NMF) was found between the cell types considered. In fact, melanoma cells appeared to be highly susceptible to the action of the drug, undergoing severe morphological modifications represented mainly by a reversible dose and time-dependent cell rounding and surface blebbing. In contrast, NMF-induced injury in MEF cells was characterized mainly by a simple retraction of the cell body. A cytochemical analysis of the expression of certain membrane antigens (e.g., glycoproteins, epidermal growth factor receptor, B2 microglobulin) in NMF-treated M14 cells undergoing blebbing was also carried out. A randomly distributed labeling of such molecules was observed. Accordingly, freeze-fracturing electron microscopic analysis also displayed a random distribution of intramembrane particles over the plasma membrane. When subcellular changes induced by the drug were investigated, a remarkable modification of cytoskeletal components was detected in both cell types. In particular, cross-linked actin microfilament bundles were easily observed in NMF-exposed MEF cells. Finally, when different experimental conditions which perturb calcium ion homeostasis or restore protein thiol group reduced state were analyzed, a noticeable impairment of the blebbing phenomenon was observed. Thus, a target effect of NMF on the microfilament system, probably leading, in turn, to several subcellular changes and cell surface blebbing, can be hypothesized. Such a cytoskeletal element-dependent cytopathology appears to be related to changes of the oxidized state of such molecules as well as to calcium ion perturbations. PMID:1426160

Malorni, W; Meschini, S; Arancia, G

1992-10-01

391

Relationships between Hydrological Parameters obtained from Multi-Step Outflow Experiments and Induced Polarization Spectra of Soil Samples  

NASA Astrophysics Data System (ADS)

The investigation of relationships between complex electrical parameters and hydrological properties of soil samples is necessary to allow an interpretation of spectral induced polarization (SIP) data in terms of soil hydrological properties. Therefore, laboratory SIP measurements in a frequency range between 0.01 Hz and 100 Hz and hydrological multi-step outflow (MSO) experiments are performed on different samples of unconsolidated sediments. The investigated material includes a fine sand sample with a narrow grain size distribution between 0.1 and 0.3 mm and soil samples from different locations in the vicinity of Braunschweig. The SIP measurements were performed on samples fully saturated with a sodium chloride solution and a calcium chloride solution, respectively. Both solutions had a salt concentration of 0.001 mol/l. From the measured SIP spectra the mean relaxation time, the normalized total chargeability and a parameter describing the spreading of the relaxation time distribution were derived with the Debye decomposition approach. After finishing all SIP measurements, the MSO experiments were carried out to obtain the retention curves and hydraulic conductivity functions. The parameters of these functions, obtained by fitting the van Genuchten-Mualem model to the MSO data, were then compared with the parameters resulting from the Debye decomposition of the SIP spectra to find relationships between the electrical and hydrological properties. Evaluation of the first measurements indicates a correlation between the mean relaxation time and the van Genuchten-Mualem parameter ?. In literature, the mean relaxation time or equivalent parameters of models fitted to SIP spectra are often related to a characteristic pore size of the investigated material. The van Genuchten-Mualem parameter ? correlates with the inverse of the air entry pressure head of soils and thus can also be related to a pore size. The evidence for a relationship will be further studied by extending the number of investigated soil samples. A second pair of electrical and hydrological parameters promising a correlation is the so called non-uniformity parameter U? resulting from the Debye decomposition of SIP spectra and the van Genuchten-Mualem parameter n. Both parameters are related to the distribution of relaxation times and pore sizes, respectively.

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

2012-04-01

392

Characterization of Natural Attenuation in a uranium-contaminated site by means of Induced Polarization Imaging  

NASA Astrophysics Data System (ADS)

Field experiments at the U.S. Department of Energy's (DOE) Integrated Field Research Challenge site (IFRC) in Rifle, Colorado (USA) have repeatedly demonstrated the ability of microorganisms to reductively immobilize uranium (U) in U tailings-contaminated groundwater accompanying organic carbon amendment. At the same time, geophysical monitoring during such amendment experiments has proven that Induced Polarization (IP) datasets can provide valuable information regarding geochemical changes induced by stimulated microbial activity, such as precipitation of metallic minerals (e.g. FeS) and accumulation of reactive, electroactive ions (Fe[II]). Based on these findings, we present a novel, modified application of the IP imaging method. Specifically, we utilized an IP characterization approach to delineate areas where fluvially deposited organic material, within aquifer sediments, naturally stimulates the activity of subsurface microflora, leading to both the natural immobilization of uranium and accumulation of reduced end-products (minerals and pore fluids) capable of generating anomalous IP signatures. These so-called 'naturally reduced zones' (NRZ's) are characterized by elevated rates of microbial activity relative to sediments having a lower concentration of organic matter. As noted and based on our previous experiments at the site, the accumulation of metallic minerals represents suitable targets for the exploration with IP tomographic methods. Here, we explore the application of the IP imaging method for the characterization of NRZ's at the scale of the floodplain. We present imaging results obtained through the inversion of 70 independent lines distributed along the floodplain (~600 m2). Imaging results are validated through comparisons with lithological data obtained from wells drilled at the site and laboratory analysis of sediment and groundwater samples. Our results show the applicability of the IP method for characterizing regions of the subsurface having a greater propensity for elevated rates of microbial activity, with such regions (themselves often highly localized within a larger sedimentary matrix) exerting an outsized control on contaminant (e.g. U) fate and transport.

Flores Orozco, Adrián; Bücker, Matthias; Williams, Kenneth

2014-05-01

393

Polarized linewidth-controllable double-trapping electromagnetically induced transparency spectra in a resonant plasmon nanocavity.  

PubMed

Surface plasmons with ultrasmall optical mode volume and strong near field enhancement can be used to realize nanoscale light-matter interaction. Combining surface plasmons with the quantum system provides the possibility of nanoscale realization of important quantum optical phenomena, including the electromagnetically induced transparency (EIT), which has many applications in nonlinear quantum optics and quantum information processing. Here, using a custom-designed resonant plasmon nanocavity, we demonstrate polarized position-dependent linewidth-controllable EIT spectra at the nanoscale. We analytically obtain the double coherent population trapping conditions in a double-? quantum system with crossing damping, which give two transparent points in the EIT spectra. The linewidths of the three peaks are extremely sensitive to the level spacing of the excited states, the Rabi frequencies and detunings of pump fields, and the Purcell factors. In particular the linewidth of the central peak is exceptionally narrow. The hybrid system may have potential applications in ultra-compact plasmon-quantum devices. PMID:24096943

Wang, Luojia; Gu, Ying; Chen, Hongyi; Zhang, Jia-Yu; Cui, Yiping; Gerardot, Brian D; Gong, Qihuang

2013-01-01

394

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

PubMed Central

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.

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

2001-01-01

395

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

NASA Astrophysics Data System (ADS)

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.

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

2001-01-01

396

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

PubMed

The elucidation of cell metabolic mechanisms is the modern underpinning of the diagnosis, treatment, and in some cases the prevention of disease. Para-Hydrogen induced polarization (PHIP) enhances magnetic resonance imaging (MRI) signals over 10 000 fold, allowing for the MRI of cell metabolic mechanisms. This signal enhancement is the result of hyperpolarizing endogenous substances used as contrast agents during imaging. PHIP instrumentation hyperpolarizes Carbon-13 ((13)C) based substances using a process requiring control of a number of factors: chemical reaction timing, gas flow, monitoring of a static magnetic field (Bo), radio frequency (RF) irradiation timing, reaction temperature, and gas pressures. Current PHIP instruments manually control the hyperpolarization process resulting in the lack of the precise control of factors listed above, resulting in non-reproducible results. We discuss the design and implementation of a LabVIEW based computer program that automatically and precisely controls the delivery and manipulation of gases and samples, monitoring gas pressures, environmental temperature, and RF sample irradiation. We show that the automated control over the hyperpolarization process results in the hyperpolarization of hydroxyethylpropionate. The implementation of this software provides the fast prototyping of PHIP instrumentation for the evaluation of a myriad of (13)C based endogenous contrast agents used in molecular imaging. PMID:24784636

Agraz, Jose; Grunfeld, Alexander; Li, Debiao; Cunningham, Karl; Willey, Cindy; Pozos, Robert; Wagner, Shawn

2014-04-01

397

Disorder-induced reversal of spin polarization in the Heusler alloy Co{sub 2}FeSi  

SciTech Connect

We study the spin polarization in the conduction band of Co{sub 2}FeSi layers with a different degree of structural order. The injected spin polarization in Co{sub 2}FeSi/(Al,Ga)As spin light-emitting diodes as well as the planar Hall effect measured for the Co{sub 2}FeSi injectors exhibit a sign reversal between injectors crystallized in the ordered L2{sub 1} phase and the Fe-Si disordered B2 phase. These results are explained by a disorder-induced change in the spin polarization at the Fermi energy of Co{sub 2}FeSi. Support for the occurrence of such a striking change in the electronic band structure is obtained by first principles calculations.

Bruski, P.; Ramsteiner, M.; Brandt, O.; Friedland, K.-J.; Farshchi, R.; Herfort, J.; Riechert, H. [Paul-Drude Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany); Erwin, S. C. [Center for Computational Materials Science, Naval Research Laboratory, Washington, DC 20375 (United States)

2011-04-01

398

Parahydrogen-induced polarization transfer to 19F in perfluorocarbons for 19F?NMR spectroscopy and MRI.  

PubMed

Fluorinated substances are important in chemistry, industry, and the life sciences. In a new approach, parahydrogen-induced polarization (PHIP) is applied to enhance (19)F?MR signals of (perfluoro-n-hexyl)ethene and (perfluoro-n-hexyl)ethane. Unexpectedly, the end-standing CF3 group exhibits the highest amount of polarization despite the negligible coupling to the added protons. To clarify this non-intuitive distribution of polarization, signal enhancements in deuterated chloroform and acetone were compared and (19)F-(19)F?NOESY spectra, as well as (19)F T1 values were measured by NMR spectroscopy. By using the well separated and enhanced signal of the CF3 group, first (19)F?MR images of hyperpolarized linear semifluorinated alkenes were recorded. PMID:23526596

Plaumann, Markus; Bommerich, Ute; Trantzschel, Thomas; Lego, Denise; Dillenberger, Sonja; Sauer, Grit; Bargon, Joachim; Buntkowsky, Gerd; Bernarding, Johannes

2013-05-10

399

Dirac {ital R} -Matrix Modeling of Spin-Induced Asymmetry in the Scattering of Polarized Electrons from Polarized Cesium Atoms  

SciTech Connect

Recent experiments by Baum, Raith, and co-workers to measure the spin-induced asymmetries in electron scattering from cesium have stimulated theoretical work to interpret these measurements. We present Dirac R -matrix calculations of the interference asymmetry function, and of the spin-orbit and spin-exchange asymmetries, for comparison with experimental data at 7 and 13.5eV and with nonrelativistic predictions of the spin-exchange asymmetry from the convergent close coupling method. We find that a simple relativistic target model provides a basis for the understanding and analysis of ongoing experiments. {copyright} {ital 1997} {ital The American Physical Society}

Ait-Tahar, S.; Grant, I.P. [Mathematical Institute, Oxford University, 24-29 St.Giles, Oxford OX1 3LB (United Kingdom)] [Mathematical Institute, Oxford University, 24-29 St.Giles, Oxford OX1 3LB (United Kingdom); Norrington, P.H. [Department of Applied Mathematics and Theoretical Physics, The Queen University of Belfast, Belfast BT7 1NN (United Kingdom)] [Department of Applied Mathematics and Theoretical Physics, The Queen University of Belfast, Belfast BT7 1NN (United Kingdom)

1997-10-01

400

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

SciTech Connect

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