Polarization Spectra Research Articles

A bottom-up perspective on photodynamics and photoprotection in light-harvesting complexes using anti-Brownian trapping.

Single-molecule fluorescence spectroscopy allows direct, real-time observation of dynamic photophysical changes in light harvesting complexes. The Anti-Brownian ELectrokinetic (ABEL) trap is one such single-molecule method with useful advantages. This approach is particularly well-suited to make detailed spectroscopic measurements of pigment-protein complexes in a solution phase because it enables extended-duration single-molecule observation by counteracting Brownian motion. This Perspective summarizes recent contributions by the authors and others that have utilized the unique capabilities of the ABEL trap to advance our understanding of phycobiliproteins and the phycobilisome complex, the primary light-harvesting apparatus of cyanobacteria. Monitoring the rich spectroscopic data from these measurements, which include brightness, fluorescence lifetime, polarization, and emission spectra, among other measurable parameters, has provided direct characterization of pigments and energy transfer pathways in the phycobilisome, spanning scales from single pigments and monomeric phycobiliproteins to higher order oligomers and protein-protein interactions of the phycobilisome complex. Importantly, new photophysical states and photodynamics were observed to modulate the flow of energy through the phycobilisome and suggest a previously unknown complexity in phycobilisome light harvesting and energy transport with a possible link to photoadaptive or photoprotective functions in cyanobacteria. Beyond deepening our collective understanding of natural light-harvesting systems, these and future discoveries may serve as inspiration for engineering improved artificial light-harvesting technologies.

Nontarget screening of production waste samples from Leuckart amphetamine synthesis using liquid chromatography - high-resolution mass spectrometry as a complementary method to GC-MS impurity profiling.

The established approaches of suspect and nontarget screening (NTS) using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) are usually applied in the field of environmental and bioanalytical analysis. Herein, these approaches were employed on a forensic-toxicological application by analyzing different production waste samples from controlled amphetamine synthesis via Leuckart route to evaluate the suitability of this methodology for identification of route-specific organic substances in such waste samples. For analysis, two complementary LC techniques were used to cover a broad polarity spectrum. After data processing and peak picking using the enviMass software and further manual data restriction, 17 features were tentatively identified as suspects, three of which were subsequently identified with reference substances. All suspects had been previously identified in studies, in which gas chromatography-mass spectrometry (GC-MS) was successfully applied for synthesis marker assessment in waste and amphetamine samples. Remaining features with high signal intensity and assigned sum formula were selected for the attempt of structure elucidation. Seven potential synthesis markers were tentatively identified, which were not yet reported, except the sum formula of one compound, and which were partly also detected in real case waste samples afterward. The innovative application of the NTS approach using LC-HRMS for the analysis of aqueous amphetamine synthesis waste samples showed its suitability as extension to GC-MS analysis as it was possible to successfully identify seven new potential marker compounds, which are specific either for the conversion of the pre-precursors α-phenylacetoacetonitrile and α-phenylacetoacetamide to benzyl methyl ketone or for the subsequent Leuckart synthesis route after their conversion.

Coded aperture full-stokes imaging spectropolarimeter

A coded aperture full-Stokes imaging spectropolarimeter (CAFIS) based on a combination of coded aperture spectral imager and polarization spectrum modulation is demonstrated. The CAFIS uses a rotatable retarder and a rotatable polarizer as polarization spectrum modulation components to modulate the polarization information on the spectrum first, then the CAFIS achieves aperture coding with a digital micromirror device (DMD). After passing through a dispersive element, the coded polarization modulated spectral images are recorded by a CCD camera. The polarization modulated spectral images with the camera’s intrinsic spatial resolution are estimated with sparsity-constrained optimization from the acquired images, and the full-Stokes spectral images are computed by the demodulation algorithm. The principle and feasibility are verified via simulations. The relationship between the configuration of polarization spectrum modulation components and the reconstruction quality is investigated in this paper as well.

Polarization and entanglement spectrum in non-Hermitian systems

The entanglement spectrum is a useful tool to study topological phases of matter, and contains valuable information about the ground state of the system. Here, we study its properties for free non-Hermitian systems for both point-gapped and line-gapped phases. While the entanglement spectrum only retains part of the topological information in the former case, it is very similar to Hermitian systems in the latter. In particular, it not only mimics the topological edge modes, but also contains all the information about the polarization, even in systems that are not topological. Furthermore, we show that the Wilson loop is equivalent to the many-body polarization and that it reproduces the phase diagram for the system with open boundaries, despite being computed for a periodic system.

Polarization Spectrum of Near-Infrared Zodiacal Light Observed with CIBER

Abstract We report the first measurement of the zodiacal light (ZL) polarization spectrum in the near-infrared between 0.8 and 1.8 μm. Using the low-resolution spectrometer on board the Cosmic Infrared Background Experiment, calibrated for absolute spectrophotometry and spectropolarimetry, we acquire long-slit polarization spectral images of the total diffuse sky brightness toward five fields. To extract the ZL spectrum, we subtract the contribution of other diffuse radiation, such as the diffuse galactic light, the integrated starlight, and the extragalactic background light. The measured ZL polarization spectrum shows little wavelength dependence in the near-infrared, and the degree of polarization clearly varies as a function of the ecliptic coordinates and solar elongation. Among the observed fields, the North Ecliptic Pole shows the maximum degree of polarization of ∼20%, which is consistent with an earlier observation from the Diffuse Infrared Background Experiment on board on the Cosmic Background Explorer. The measured degree of polarization and its solar elongation dependence are reproduced by an empirical scattering model in the visible band and also by a Mie scattering model for large absorptive particles, while a Rayleigh scattering model is ruled out. All of our results suggest that the interplanetary dust is dominated by large particles.

Assessment of corrosivity of emulsions from a petroleum sample on X80 steel

PurposeThe purpose of this paper is to study the corrosion process by examining the deterioration of X80 steel exposed to a real petroleum sample containing condensed hydrocarbon plus oilfield-produced water, which were subjected to stimulated emulsions in flowing media at 50°C.Design/methodology/approachThe impedance and polarization spectra were used to assess the aggressiveness of the petroleum sample and tried to find a washing process using condensed hydrocarbon with deionized water. Mössbauer technique was used to identify the phases in precipitated ions obtained during an oven-drying procedure of the oilfield produced water.FindingsThe emulsion, chloride, sulphur compounds, heavy metals and the use of a double hydrodynamic system were the most important factors affecting the corrosion of X80 steel. The corrosion rate of this steel increased when oilfield-produced water was stimulated by a double hydrodynamic system (4.56 mm/year). It was determined to be 7.66 mm/year and 4.01 mm/year when steel was exposed to a stimulated emulsion using the petroleum sample and condensed hydrocarbon with deionized water at 24 h, respectively, suggesting that a significant process of hydrocarbon washing could occur and a more corrosive solution was highlighted. Mössbauer results showed that the ions precipitates included the following phases at Wt.%: magnetite (20.0), greigeite (22.8), siderite (3.2), pyrite (2.9), marcasite (26.7) and mackinawite (24.4).Originality/valueA stimulated hydrocarbon/water emulsions with a more homogeneous solution containing high concentrations of saline compounds and heavy metals were used to simulate the susceptibility to corrosion on the internal pipeline steels exposed to any type of immiscible liquids such as condensed hydrocarbon, or crude oil, containing water. A practical application of the presented research could provide a novel framework for understanding the internal corrosion in pipelines from the simulation of washed hydrocarbons after the stimulated emulsions that can be found in the field. Because more susceptibility to corrosion for pipeline steels would be expected at the end of the transportation of the fluid. It is possible to investigate the possible corrosion mechanisms by using a dried oilfield-produced water sample interacting with the pipeline steels.

Crystal growth, polarization spectral analysis derived from the broadband emission from the 1D2 level of Pr:GdScO3 crystal

Pr3+-doped GdScO3 single crystal was successfully grown by the Czochralski (Cz) method. Polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves were measured at room temperature. The polarized spectroscopic property of Pr:GdScO3 crystal for new-wavelength transition in the near infrared (NIR) region was discussed for the first time. The absorption cross-sections at 600 nm were calculated to be 0.39×10−20 cm2 (E∥a), 0.32×10−20 cm2 (E∥b) and 0.4×10−20 cm2 (E∥c). The emission cross sections at 1053 nm of 1D2 energy level were calculated to be 0.86×10−20 cm2 (E∥a), 0.79×10−20 cm2 (E∥b) and 0.78×10−20 cm2 (E∥c), with FWHM of 57.54 nm, 57.96 nm and 58.96 nm, respectively. The fluorescence lifetime and radiative lifetime of the 1D2 energy levels of Pr3+ ions were 45.46 µs and 393.94 µs, respectively. Those results show that the Pr:GdScO3 crystal should be the potential near infrared laser gain medium originated from the 1D2 transition.

Polarization Estimation With Vector Sensor Array in the Underdetermined Case

Ship target detection using radar is an important application in military and civilian fields. For the polarization estimation of scattering waves in the underdetermined case, i.e., the number of scattering waves from ships is larger than the number of sensors, this paper proposes two estimation methods with different measurement models. 1) For the single-vector-sensor model, this paper proposes the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">polarization-invariant</i> ESPRIT-based method. This method can estimate the polarization of signals containing target echo, interference, and noise, which can cure the problem that the accuracy of existing method is poor under low interference signal ratio. 2) For the multi-vector-sensor model, this paper proposes an improved ESPRIT method based on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">spatial-invariant and time-invariant</i> simultaneously, which can increase the degree of freedom without increasing hardware cost. As for another problem of multi-vector-sensor, i.e., almost all existing methods assume that the number of scattering waves is known, this paper introduces <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">the polarization spectrum</i> for the first time, which can estimate the polarization parameters when the number of scattering waves is unknown. Finally, we analyze the two proposed ESPRIT-based methods comparing with some existing methods through Monte Carlo simulation, which results demonstrate the efficience of the proposed methods.

Synthesis of polymeric CdS and its optical properties investigation

Producing of polymeric cadmium sulfide in polyvinyl alcohol matrix is reported. The result was achieved through solid state sulfurization of hybrid interpolymeric complex of polyvinyl alcohol with cadmium chloride. In this process CdS inherits polymeric chain structure of CdCl2 complexing with polyvinyl alcohol due to diffusion restriction. One-dimensional structure of CdS was verified by high degree of luminescence polarization and Raman spectra behavior. It was observed that Raman spectrum of produced material is similar to spectrum of polyacetylene. This similarity disappears at impurities addition. Appearance of Raman band at 228 cm-1 indicates formation of CdS chain structure. Resulting polyvinyl alcohol --- CdS system has a structure of Little's high temperature superconductor. Keywords: one-dimensional structures, inorganic polymers, conjugated polymers, hybrid polymeric complexes, polyvinyl alcohol, CdS.

Estimation of Time Evolution of Muon Spin Polarization in 14N and 15N Systems

In muon spin rotation and relaxation (SR) method, time evolution of muon spin polarization provides the information about local electronic and spin dynamic states of the material. Quantum simulation and estimated frequency of calculated the spectra help to interpret the observed polarization spectra. Based on spin dipole interaction between the muon and nearby nuclei (14N, 15N and proton) in zero field measurement case, muon spin polarization spectra and corresponding frequencies are estimated using the quantum simulation. The oscillation frequency increases with approaching the muon towards the nuclei. Variation of separation between frequency positions with changing distance between muon and nuclei indicates the distribution of the magnetic field at the muon site. This study will help to distinguish the origin of oscillation in zero field μSR spectra in the isolated system containing 14N and 15N nuclei (e.g., glycine with 14N, glycine with 15N).

Electrochemical and microscopic analysis on corrosion behavior of steel bars in slag/fly ash-cement paste subjected to seawater attack

A series of corrosion experiments of cement paste-steel bar specimens with different contents of slag and fly ash were performed to investigate the influence of slag/fly ash on the corrosion behavior of steel bars in concrete under seawater. In this investigation, the corrosion behavior of specimen was electrochemically monitored by open-circuit potential (OCP), Tafel polarization (TP) and electro chemical impedance spectra (EIS). Meanwhile, SEM/EDS and XRD were applied to microscopically analyze the microstructure deterioration of materials. Results showed that, replacing cement with slag/fly ash caused a decrease in Ca(OH)2 as well as an increase in C-S-H gel and Friedel's salt in concrete, which can improve the chloride-solidification ability and slow down the chloride diffusion in concrete by both physical adsorption and chemical binding, and thereafter promoting the corrosion resistance of steel bars in concrete in marine environment. Compared to slag, the equal replacing content of fly ash can contribute to a better improving effect on the corrosion resistance of reinforced concrete in marine environment. In this study, a replacement of cement by 20% slag+20% fly ash led to an optimum improving effect on its corrosion resistance. In addition, the results also indicate that the corrosion of reinforced concrete caused by seawater attack does not occur at a uniform rate, but it can firstly maintain a long-term uncorroded state, and then develops rapidly after pitting corrosion occurs.

Vanadium and Tannic Acid-Based Composite Conversion Coating for 6063 Aluminum Alloy

In this study, a vanadium (V) and tannic acid-based composite conversion coating (VTACC) was prepared on 6063 aluminum alloy (AA6063) to increase its corrosion resistance. The surface morphology and compositions of the VTACCs were characterized using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the coatings was investigated by linear polarization and electrochemical impedance spectra (EIS). The self-healing ability of the coating was detected by SEM, EDS, and scanning vibrating electrode technique (SVET) measurements. The coating mainly consisted of metal oxides, including Al2O3, VO2, V2O3, and V2O5, and metal organic complexes (Al and V-complexes). The electrochemical measurement results indicated that the best corrosion resistance of VTACC was acquired when the treatment time was 12 min. Furthermore, because a new coating with vanadium rich oxide was developed on the scratch area, artificial scratch VTACC surfaces were repaired after several days of immersion in 3.5-wt% NaCl solution.

Terahertz circular polarization sensing for protein denaturation based on a twisted dual-layer metasurface.

Protein denaturation has very important research value in nutrition, biomedicine, and the food industry, which is caused by the changes in the molecular structure of the protein. Since the collective vibrational and torsional modes of protein molecules are within the terahertz (THz) frequency range, THz spectroscopy can characterize the protein denaturation with several advantages of non-contact, label-free, real-time, and non-destructive. Therefore, we proposed a reflective THz time-domain polarization spectroscopy sensing method, and use a flexible twisted dual-layer metasurface film as a sensor to realize the thermal denaturation sensing, concentration sensing, and types identification of protein aqueous solutions. The experiment tested three proteins (bovine serum albumin, whey protein, and ovalbumin), and the results show that: for the thermal denaturation sensing, its detection sensitivity can reach 6.30 dB/% and the detection accuracy is 0.77%; for the concentration sensing, the detection sensitivity and detection accuracy reach 52.9 dB·mL/g and 3.6·10-5 g/mL, respectively; in addition, different protein types can be distinguished by the difference of the circular polarization spectra.

The mechanism for tuning the corrosion resistance and pore density of plasma electrolytic oxidation (PEO) coatings on Mg alloy with fluoride addition

Here we prepared PEO coatings on Mg alloys in silicate–NaOH–phosphate electrolyte containing different concentrations of NaF addition. The detailed microstructural characterizations combining with potentiodynamic polarization and electrochemical impedance spectra (EIS) were employed to investigate the roles of fluoride in the growth and corrosion properties of PEO coating on Mg. The result shows the introduction of NaF led to a fluoride-containing nanolayer (FNL) formed at the Mg/coating interface. The FNL consists of MgO nanoparticles and insoluble MgF2 nanoparticles (containing rutile phase and cubic phase). The increase in the NaF concentration of the electrolyte increases the thickness and the MgF2 content in the FNL. When anodized in the electrolyte containing 2 g/L NaF, the formed FNL has the highest thickness of 100–200 nm along with the highest value of x of ∼0.6 in (MgO)1-x(MgF2)x resulted in the highest corrosion performance of PEO coating. In addition, when anodized in the electrolyte containing a low NaF concentration (0.4–0.8 g/L), the formed FNL was thin and discontinuous, which would decrease the pore density and increase the coating's uniformness simultaneously.

Detection model of copper based on polarization degree induced by low-energy density laser.

In order to analyze the mechanism of plasma polarization characteristics and the improvement effect of spectral signal-to-back ratio, the intensity formulas of continuous spectrum and discrete spectrum were derived by exploring the path of the radiation spectrum. At the Brewster angle, the model of polarization degree was established based on the measured spectral data to identify the radiation intensity of plasma. The experimental results showed that the polarization characteristics of the background and discrete spectrum were both observed in the plasma spectrum of a copper element, and there were obvious differences in polarization degree and vibration direction. Moreover, cadmium and chromium were used to verify the detection model. It was found that the characteristic signals of the polarization spectrum were more than the effective peaks in laser-induced breakdown spectroscopy, and the variation trend was relatively gentle. The model retained the effective information in the continuum spectrum and fully explored the basic polarization mechanism of plasma. The measured data were not only convenient to observe the characteristic signal peaks of elements, but also greatly improved the recognition effect. This method could extract effective information of illumination plasma under the condition of low incident light intensity and reduce the damage of medium surface, which is a more effective nondestructive testing technology.

Estimation of Rock Characteristics Based on Polarization Spectra: Surface Roughness, Composition, and Density

Surface polarization characteristics provide crucial structural information of the Earth's surface. As two key elements of the natural geographical environment, rocks and soils play an important role in the study of surface processes. Inherent surface characteristics, such as surface roughness, composition, and density are critical parameters for the remote monitoring of land surfaces as they affect the polarization characteristics of scattered light waves. In this study, we investigated the relationship between surface roughness, composition, and density, and the polarization spectra of limestone-dolomite series rock. Results reveal a power function relationship between the surface roughness and the degree of polarization peaks among different detection zenith and azimuth angles. The depth and position of the absorbing waveband are significantly correlated with the characteristic component contents. The rock density was determined via the polarized reflection spectra, with the Earth's surface density calculations associated with a 2.6% divergence from the current recognized data. Our results demonstrate the ability of polarized spectra to retrieve surface roughness, composition, and density, with potential for further development in future work.

CMB anisotropies and linear matter power spectrum in models with non-thermal neutrinos and primordial magnetic fields

Angular power spectra of temperature anisotropies and polarization of the cosmic microwave background (CMB) as well as the linear matter power spectra are calculated for models with three light neutrinos with non-thermal phase-space distributions in the presence of a primordial stochastic magnetic field. The non-thermal phase-space distribution function is assumed to be the sum of a Fermi-Dirac and a gaussian distribution. It is found that the known effective description of the non-thermal model in terms of a twin thermal model with extra relativistic degrees of freedom can also be extended to models including a stochastic magnetic field. Numerical solutions are obtained for a range of magnetic field parameters.

Hyperspectral polarimetry of eight Apollo soils

The reflected light from the lunar surface is polarized and contains perpendicular (I⊥) and parallel (I∥) branches. To provide supporting data for the first polarimetric camera (PolCam) on board the Korean Pathfinder lunar orbiter, in this work, we built a polarimeter and measured the polarized spectra for eight Apollo soils that span a wide range in composition and maturity. We found a linear correlation between reflectance R and the difference of perpendicular and parallel branches: R+a′⋅(I⊥−I∥)=b′, and b’ might be sensitive to the grain size of lunar soils. The regression coefficient b’ can be derived from both positive and negative polarization spectra and has little dependence on wavelength, thus it has great potential in estimating grain size for lunar soils. We also used radiative transfer equations to calculate the real index of optical constants and to reproduce the perpendicular and parallel polarized spectra for the lunar soils. We correlated polarimetry indexes including polarization degree (P=(I⊥−I∥)/(I⊥+I∥)) and the difference of the perpendicular and parallel branches (I⊥−I∥) with the abundances of FeO and TiO2 and soil maturity, and our result indicates that these two polarimetry indexes show dependence on both the compositions and soil maturity.

Polarization spectroscopy of an excited state transition in Rubidium

We investigate polarization spectroscopy of an excited state transition in room-temperature rubidium vapor. By applying a circularly polarized coupling beam, resonant with the 52S1/2 → 52P3/2 transition, we induce anisotropy in the atomic medium that is then probed by scanning a probe beam across the 52P3/2 → 62S1/2 transition. By performing polarimetry on the probe beam, a dispersive spectral feature is observed. We characterize the excited-state polarization spectrum as a function of coupling intensity for both isotopes and find that at high intensities, Autler-Townes splitting results in a sub-feature, which theoretical modelling shows is enhanced by Doppler averaging. This spectroscopic technique produces a narrow dispersive signal which is ideal for laser frequency stabilization to excited-state transitions.

Fast UHPLC-MS/MS for the Simultaneous Determination of Azithromycin, Erythromycin, Fluoxetine and Sotalol in Surface Water Samples

Chromatographic development for the determination of pharmaceuticals in environmental water samples is particularly challenging when the analytes have significantly different physico-chemical properties (solubility, polarity, pKa) often requiring multiple chromatographic methods for each active component. This paper presents a method for the simultaneous determination of azithromycin, erythromycin (antibiotics), fluoxetine (anti-depressant) and sotalol (b-blocker) in surface waters by ultra-high-performance liquid chromatography coupled with ultra-high-resolution time-of-flight mass spectrometry. These pharmaceuticals—presenting a broad spectrum of polarity (0.24 ≤ log Kow ≤ 4.05)—were separated on a C-18 analytical column, after a simple filtration step for freshwater samples or after a liquid–liquid extraction with Methyl-tertio-butyl ether (MTBE) for seawater samples. The optimized separation method (in terms of nature of column and eluent, elution gradient, and of mass spectrometric parameters), enable one to reach limits of detection ranging between 2 and 7 ng L−1 and limits of quantification between 7 and 23 ng L−1 for the four targeted molecules, within a three minute run. This method was validated using samples collected from three different surface waters in Lebanon (freshwater and seawater) and analytical results were compared with those obtained in surface waters sampled in a French river, equivalent in terms of human activities. Using this method, we report the highest concentration of pharmaceuticals found in surface water (up to 377 ng L−1 and 268 ng L−1, respectively, for azithromycin and erythromycin, in the Litani river, Lebanon).