Polarization Measurements Research Articles

Distortions correction in HR-(S)TEM and low resolution TEM images: Absolute size, strain and polarization measurements

Distortions correction in HR-(S)TEM and low resolution TEM images: Absolute size, strain and polarization measurements

Vector meson polarisation in heavy-ion collisions at the LHC

Heavy quarks, i.e. charm and beauty, are produced in the initial stage of heavy-ion collisions, on a time scale shorter than the medium formation time, and are sensitive to the large initial magnetic field produced perpendicular to the reaction plane, defined by the impact parameter direction and beam direction, in non-central heavy-ion collisions. In the presence of a large initial magnetic field, the charm quark can be polarised. The quark polarisation is then expected to be transferred to the hadron in the hadronisation process. We will present the first measurement of D*+ polarisation in Pb–Pb collisions at √SNN = 5.02 TeV, exploiting the large data sample collected by the ALICE Collaboration during the LHC Run 2 and we will compare these new results with the existing J/ψ polarisation measurements.

Room-temperature ferroelectric nematic liquid crystal showing a large and diverging density.

The ferroelectric nematic phase (NF) is a recently discovered phase of matter in which the orientational order of the conventional nematic liquid crystal state is augmented with polar order. Atomistic simulations suggest that the polar NF phase would be denser than conventional nematics owing to contributions from polar order. Using an oscillating U-tube densitometer, we obtain detailed temperature-dependent density values for a selection of conventional liquid crystals with excellent agreement with earlier reports. Having demonstrated the validity of our method, we then record density as a function of temperature for M5, a novel room-temperature ferroelectric nematic material. We present the first experimental density data for a NF material as well as density data for a nematic that has not previously been reported. We find that the room-temperature NF material shows a large (>1.3 g cm-3) density at all temperatures studied, notably including phases without polar order. An increase in density at phase transitions is observed. The magnitude of the increase for the intermediate-to-ferroelectric nematic (NX-NF) transition is an order of magnitude smaller than the isotropic-nematic (I-N) transition. We then probe potential consequences that may result from an elevated density through measurement of the refractive indices (no and ne). The navg of M5 is compared with 5CB and polar smectic liquid crystals. We observe how the highly polar nature of the system counteracts the effects of an increase in density. With knowledge of experimental density, we are able to derive an approximation that yields the polar order parameter, 〈P1〉, from polarisation measurements. Present results may be typical of ferroelectric nematic materials, potentially guiding material development, and is especially relevant for informing ongoing studies into this emerging class of materials.

Optical characterization of a single molecule complete spatial orientation using intra-molecular triplet-triplet absorption.

Progress in single molecule fluorescence experiments have enabled an in-depth characterization of fluorophores, ranging from their photophysical rates to the orientation of their emission dipole moments in three dimensions. However, one crucial spatial information remains elusive: the molecule orientation relative to its emission dipole moment. One can retrieve the latter only by the use of another non-colinear transition dipole moment. We experimentally demonstrate the optical retrieval of this information for single terrylene (Tr) molecules in a 30 nm thin para-terphenyl matrix. We show, through second-order correlation measurements at varying excitation power and polarization, that Tr molecules experience an optically induced deshelving of their triplet states, mediated by two orthogonal intra-molecular triplet-triplet absorption dipole moments. We take advantage of these two transition dipole moments to retrieve the full orientation of the Tr molecule, employing a 3-level scheme for the molecule photophysics and analytical calculations for the exciting electric field distribution. This modelling approach enables us to accurately describe both varying power and polarization measurements, giving access to the molecule's photophysical rates and to its complete orientation in three dimensions. This includes the orientation of the singlet emission dipole moment in the laboratory frame, and the orientation of the molecule plane with respect to the singlet emission dipole moment.

Hyperon polarization in heavy ion collisions at STAR

In these proceedings, we present the measurements of global polarization for Λ, ¯Λ with the high-statistics data collected by the STAR experiment for isobar (Ru+Ru, Zr+Zr) collisions at √SNN = 200 GeV and Au+Au collisions at √SNN = 19.6, 27 GeV. These measurements allow us to study possible magnetic field driven effects through the polarization difference between Λ and ¯Λ and system size dependence of global polarization. Furthermore, we present the first measurements of Λ, ¯Λ hyperon local polarization in isobar collisions at √SNN = 200 GeV and Au+Au collisions at √SNN = 19.6, 27 GeV. Comparisons with previous measurements in Au+Au and Pb+Pb collisions at RHIC and LHC provide important insights into the collision system size and energy dependence of the vorticities. The local polarization measurements at lower beam energies can probe the predicted baryonic spin hall effect in a dense baryonic environment in heavy-ion collisions.

Recent advances in application-oriented new generation diluted magnetic semiconductors

Diluted ferromagnetic semiconductors (DMSs) have attracted widespread attention in last decades, owing to their potential applications in spintronic devices. But classical group-III-IV, and -V elements based DMS materials, such as (Ga,Mn)As which depend on heterovalent (Ga<sup>3+</sup>, Mn<sup>2+</sup>) doping, cannot separately control carrier and spin doping, and have seriously limited chemical solubilities, which are disadvantages for further improving the Curie temperatures. To overcome these difficulties, a new-generation DMS with independent spin and charge doping have been designed and synthesized. Their representatives are I-II-V based Li(Zn,Mn)As and II-II-V based (Ba,K)(Zn,Mn)<sub>2</sub>As<sub>2</sub>. In these new materials, doping isovalent Zn<sup>2+</sup> and Mn<sup>2+</sup> introduces only spins, while doping heterovalent non-magnetic elements introduces only charge. As a result, (Ba,K)(Zn,Mn)<sub>2</sub>As<sub>2</sub> achieves Curie temperature of 230 K, a new record among DMS where ferromagnetic orderings are mediated by itinerate carriers. Herein, we summarize the recent advances in the new-generation DMS materials. The discovery and synthesis of several typical new-generation DMS materials are introduced. Physical properties are studied by using muon spin relaxation, angle-resolved photoemission spectroscopy and pair distribution function. The physical and chemical pressure effects on the title materials are demonstrated. The Andreev reflection junction based on single crystal and the measurement of spin polarization are exhibited. In the end, we demonstrate the potential multiple-parameter heterojunctions with DMSs superconductors and antiferromagnetic materials.

Electrochemical and DFT insights into 2-amino-4-(4-hydroxy-3-methoxyphenyl)-7-methyl-4H-chromene-3-carbonitrile: an innovative strategy for antibacterial activity and corrosion protection of carbon steel.

This study explored the potential of a newly synthesized derivative, 2-amino-4-(4-hydroxy-3-methoxyphenyl)-7-methyl-4H-chromene-3-carbonitrile (AHMCC), as a broad-spectrum antibacterial agent and a corrosion inhibitor for carbon steel (C.STL) in 0.5 M HCl solution. AHMCC demonstrated remarkable antibacterial efficacy against Gram-negative (Escherichia coli, Klebsiella pneumoniae) and Gram-positive (Bacillus subtilis, Staphylococcus aureus) bacteria, as evidenced by agar plate tests and cell viability assays. In the corrosion inhibition studies, AHMCC exhibited mixed-type inhibitor behavior as revealed by potentiodynamic polarization (PDP) measurements. The inhibition efficiency increased with rising AHMCC concentration, confirmed by a significant enhancement in charge transfer resistance (R ct) observed in electrochemical impedance spectroscopy (EIS) analysis. Electrochemical frequency modulation (EFM) data with obtained CF2 and CF3 values further corroborated these findings. Langmuir isotherm modeling suggested AHMCC molecules followed a monolayer adsorption pattern on the C.STL surface. UV-visible spectroscopy indicated the formation of a protective layer through chemical interaction between AHMCC and the metal surface. Atomic force microscopy (AFM) provided visual confirmation of this protective film shielding the C.STL from the corrosive environment. Additionally, theoretical calculations supported the proposed adsorption mechanism of AHMCC molecules onto the C.STL surface.

Comprehensive study of the synthetic tychite, Na6Mg2(CO3)4SO4: synthesis, structure and conductive properties.

The structural and conductive properties of the synthetic tychite Na6Mg2(CO3)4SO4 (space group: Fd3̄) were explored. Optimal synthesis parameters were selected by varying the molar ratio of reagents, synthesis temperature and time. For structural descriptions, we carried out scanning electron microscopy, thermal analysis, and Raman and Fourier-transform infrared spectroscopy. We carried out theoretical and experimental studies of conductivity. Theoretical calculations were obtained using geometrical-topological analysis based on Voronoi partitioning (the evaluation of geometrical sizes of voids and channels), the bond valence site energy (BVSE) method (the fast calculation of migration energies, Em), kinetic Monte Carlo simulation (the estimation of ionic conductivity at different temperatures), and density functional theory (the precise assessment of Em and vacancy formation energies). The experimental techniques included electrochemical impedance spectroscopy EIS (total conductivity determination) and direct current DC polarization (electronic conductivity assessment) measurements. Na6Mg2(CO3)4SO4 was found to have a three-periodic Na+-ion migration map with an Em of 0.37 eV and 0.18 eV from BVSE and DFT results, respectively. The theoretical value of cationic conductivity was 2.6 × 10-7 S cm-1 at 100 °C. The experimental total conductivity was equal to 6.0 × 10-7 S cm-1 at 100 °C, which is close to theoretical results. Using additional DC polarization, the electronic contribution to the total conductivity was characterized as insignificant.

Membrane fluidity properties of lipid-coated polylactic acid nanoparticles.

Lipid coating is considered a versatile strategy to equip nanoparticles (NPs) with a biomimetic surface coating, but the membrane properties of these nanoassemblies remain in many cases insufficiently understood. In this work, we apply C-Laurdan generalized polarization (GP) measurements to probe the temperature-dependent polarity of hybrid membranes consisting of a lipid monolayer adsorbed onto a polylactic acid (PLA) polymer core as function of lipid composition and compare the behavior of the lipid coated NPs (LNPs) with that of liposomes assembled from identical lipid mixtures. The LNPs were generated by nanoprecipitation of the polymer in aqueous solutions containing two types of lipid mixtures: (i) cholesterol, dipalmitoylphosphatidylcholine (DPPC), and the ganglioside GM3, as well as (ii) dioleoylphosphatidylcholine (DOPC), DPPC and GM3. LNPs were found to exhibit more distinct and narrower phase transitions than corresponding liposomes and to retain detectable phase transitions even for cholesterol or DOPC concentrations that yielded no detectable transitions in liposomes. These findings together with higher GP values in the case of the LNPs for temperatures above the phase transition temperature indicate a stabilization of the membrane through the polymer core. LNP binding studies to GM3-recognizing cells indicate that differences in the membrane fluidity affect binding avidity in the investigated model system.

EFFECT OF SURFACE TREATMENT ON THE ELECTROCHEMICAL ACTIVITY OF Ti3SiC2/TiC/TiSi COMPOSITE MATERIAL IN THE HYDROGEN EVOLUTION REACTION

The effect of treatment of the surface layer of the Ti3SiC2/TiC/TiSi composite material on its electrochemical activity in the of hydrogen evolution reaction in 0.5M H2SO4 has been studied. Surface treatment has been carried out by chemical etching in solutions of 15, 30, 45% HF for 15, 30, 45 min at 25 and 60 °C. It has been established that the cathodic polarization curves of the Ti3SiC2/TiC/TiSi-electrode without and with surface treatment have a Tafel section with a slope of 0.060–0.076 V and they are characterized by an overvoltage value of 0.20–0.26 V at i = 1 mA/cm2. The rate of the cathodic reaction as a result of treatment increases by ~1.6-9.8 times. The greatest increase is caused by high-temperature etching in a solution of 30% HF for 30 min while stirring the solution. The impedance spectra of the Ti3SiC2/TiC/TiSi-electrode at Tafel region potentials consist of a capacitive semicircle with a displaced center. On the impedance graphs of the treated electrode, a straight section with a slope above 45º was registered in the region of the highest frequencies, indicating the presence of pores in the surface layer of the electrode. To describe the hydrogen evolution reaction on Ti3SiC2/TiC/TiSi, we used an equivalent electrical circuit, the Faraday impedance of which consists of charge transfer resistances R1 connected in series and a parallel R2C2-chain corresponding to the adsorption of atomic hydrogen on the electrode surface. The equivalent circuit also includes the electrolyte resistance Rs and the double layer capacitance impedance, which is modeled by the constant phase element CPE1. It has been shown that the results of polarization and impedance measurements agree satisfactorily with the discharge–electrochemical desorption mechanism with a quasi-equilibrium discharge stage when the logarithmic Temkin adsorption isotherm for adsorbed atomic hydrogen is fulfilled. It has been concluded that the composite material Ti3SiC2/TiC/TiSi in sulfuric acid electrolyte is a promising electrode material for the electrochemical production of hydrogen.

Preparation and anticorrosion performance of graphene-reinforced epoxy powder coating

Existing studies have reported that graphene can enhance the corrosion resistance of solvent-based organic coatings. However, the role of graphene in organic powder coatings remains to be obscure. In the present study, the graphene powder was prepared through liquid-phase exfoliation of graphite followed by freeze drying and the effects of graphene on structures, anticorrosion performance and adhesion strength of epoxy powder coatings were investigated. Scanning electron microscopy (SEM) demonstrated that graphene reduced surface micropores and enhanced structural compactness of the epoxy powder coatings. Electrochemical impedance spectra, Tafel polarization measurement and salt spray test indicated that a small amount (0.0125, 0.025 and 0.05 wt%) of well-dispersed graphene powder would be sufficient to effectively reinforce the anticorrosion performance of the epoxy powder coatings, especially for the coating with 0.025 wt% graphene, of which the impedance modulus maintained the highest values of nearly 107 and 105.8 Ω cm2 after immersion in 3.5 % NaCl solution for 21 and 30 days. Pull-off test confirmed that graphene enhanced the adhesion strength of coatings after salt spray test for 240 h, while the coating with 0.025 wt% graphene exhibited the highest adhesion strength up to 3.88 MPa. In addition, differential scanning calorimetry (DSC) indicated that graphene sheets could improve the thermal conductivity and promote curing reactions of epoxy powder. The mechanism for the reinforcement of epoxy powder coating by graphene has also been proposed.

Effect of Vaporized Hydrogen Peroxide and Nitrogen Dioxide Sterilization on Nitinol.

Background: Nitinol is used as the structural framework in numerous types of medical devices (e.g., guidewires, transcatheters, stents). The desire to understand the material compatibility of nitinol with vaporized hydrogen peroxide (VH2O2) and nitrogen dioxide (NO2) sterilization is increasing in healthcare technology. As a result of increased regulatory pressure and capacity limitations related to ethylene oxide (EO) sterilization, the industry is seeking alternative, sustainable sterilization options. Objective: This study sought to characterize the corrosion resistance of nitinol metal alloy wire when exposed to varying levels of VH2O2 and NO2 sterilization. Methods: Scanning electron microscopy (SEM) imaging and energy-dispersive X-ray spectroscopy (EDS) scans were performed to understand the effects of VH2O2 and NO2 sterilization treatments on the surface morphology and chemical composition of nitinol. Results: From the SEM-EDS results, no notable difference was observed when comparing VH2O2 and NO2 test samples with nonsterile control samples. In addition, cyclic potentiodynamic polarization measurements were performed per ASTM F2129-19a to determine corrosion susceptibility. No considerable changes were detected in the electrochemical potential after VH2O2 and NO2 sterilization treatments, when compared with the nonsterile control samples. Conclusion: SEM-EDS and corrosion test results indicated no considerable changes in the surface properties or electrochemical potential of the sterilized samples compared with the nonsterilized control samples. Therefore, nitinol metal showed promising results for compatibility with VH2O2 and NO2 sterilization.

Optical Frequency Domain Distributed Polarization Measurement Technology and Applications (Invited)

Optical Frequency Domain Distributed Polarization Measurement Technology and Applications (Invited)

High Hard X-Ray Polarization in Cygnus X-1 Confined to the Intermediate Hard State: Evidence for a Variable Jet Component

Cygnus X-1, the well-known accreting black hole system, exhibits several observational features hinting at an intricate interplay between the accretion disk, its atmosphere known as the corona, and the putative relativistic jet. It has been extensively studied using all available observational methods, including using the newly available technique of sensitive X-ray polarimetry. X-ray polarization characteristics are distinct for coronal and jet emissions. The low X-ray polarization measured below ∼100 keV is understood as arising from the corona. In contrast, the high polarization measurements reported above ∼400 keV required a separate jet-dominated spectral component, which spectroscopy does not demonstrate conclusively. Here we report precise polarization measurements in the 100–380 keV region made during three different subclasses of spectral states of the source using the CZTI instrument onboard AstroSat. A high polarization (23% ± 4%) is found mainly in the Intermediate Hard State of the source, and the energy-resolved measurements smoothly connect the coronal and the jet regimes. When high polarization is observed, the simultaneous spectral data hints at a separate power-law component above 100 keV. We examine the possible sources of this energy-dependent high polarization in Cygnus X-1.

Comparative evaluation of freeze-dried and hot air-dried Spirulina Platensis extracts as green inhibitors for mild steel corrosion

ABSTRACT Spirulina, a commercially farmed cyanobacteria, offers potential as a nontoxic corrosion inhibitor. However, traditional drying methods deteriorate its protective feature and this challenge must be overcome to enhance corrosive resistance. The present study compares the corrosive inhibitor performance of Spirulina extracts from freeze (SP1) and hot air drying (SP2). The electrochemical and microscopic techniques revealed that freeze-dried-derived Spirulina inhibited over 90% of corrosion through the chemisorption process where freeze-dried-derived Spirulina maximises the inhibitory compounds binding to steel. Polarisation measurements showed that SP1 provided higher inhibition efficiencies of over 93% at certain concentrations compared to around 88% for SP2. At the optimal concentration of 2 g/L, Rp values increased from 35.17 Ω/cm2 (uninhibited) to 531.3 Ω/cm2 for SP1 and 282.7 Ω/cm2 for SP2. Negative ΔGads values (−42.4 kJ/mol for SP2, −46.3 kJ/mol for SP1) and Langmuir isotherm fit indicated chemisorption-controlled adsorption. SEM/EDX showed SP1 and SP2 formed barrier layers inhibiting surface damage compared to blank steel. SP1 layer provided better protection. In short, through innovative applications of marine resources, greener corrosion management is enabled.

StockTwits classified sentiment and stock returns

We classify the sentiment of a large sample of StockTwits messages as bullish, bearish or neutral, and create a stock-aggregate daily sentiment polarity measure. Polarity is positively associated with contemporaneous stock returns. On average, polarity is not able to predict next-day stock returns. But when we condition on specific events, defined as sudden peaks of message volume, polarity has predictive power on abnormal returns. Polarity-sorted portfolios illustrate the economic relevance of our sentiment measure.

Detection of Hydrogen Bubbles Produced by Corrosion Inhibition of Metal Weldment Using Machine Learning

This study analyzes the corrosion inhibition efficiency of sodium molybdate (SM) solution on weldment specimens in 1 M HCl, based on H2 bubbles detection. The detection of the bubbles produced by the corrosion process is achieved by a YOLOv4 deep learning algorithm. The results indicate that the corrosion rate is higher on the weld metal zone than on the base metal zone in the same solution, which might be attributed to the coarser grain of the weld metal zone and the stability of the produced oxide layer. The addition of sodium molybdate was discovered to boost the stability of the oxide layer, hence enhancing the specimens’ corrosion resistance. The overall inhibitory efficiency of the sodium molybdate solution was 59% for the weld metal (WM) (0.4 g/L), 52% for the heat-affected zone (HAZ) (0.2 g/L), and 37% for the base metal (BM) (0.2 g/L). The object detection algorithm models showed 97% for the mAP and 0.98 for recall. The minimum average bubble detected for the WM was 0.353 /mm2 at an SM concentration of 0.4 g/L, while the HAZ was 0.612 /mm2 at 0.2 g/L, and the BM was 1.055 /mm2 at 0.2 g/L. The results of the bubbles detection appeared to be consistent with the corrosion experiment outcomes obtained by the potentiodynamic polarization and hydrogen volume measurement tests. This experiment validates the distinctiveness of the different weld zones in terms of the inhibitor concentration required for successful corrosion prevention, as well as the potential of analyzing corrosion using machine learning algorithms for object detection.

From nature to protection: Unleashing the protective potential of Hedera helix leaves against corrosion in harsh acidic environments using experimental and theoretical insights

The corrosion of metals is a major problem in many industrial sectors. To develop sustainable and naturally friendly alternatives to classical corrosion inhibitors, the use of plant extracts has attracted increasing interest. Plant extracts contain a variety of bioactive substances, such as polyphenols, which have corrosion-inhibitory properties. Plant extracts are biodegradable and pose minimal risk to human health and ecosystems. Consistent with the prevailing research trends in this field, in this study, the ability of Hedera helix leaf extract (HHLE) to protect XC18 steel from corrosion in 1 M HCl was evaluated. The polyphenols present in HHLE were identified using HPLC-DAD analysis. The weight loss, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) measurements were examined. Six phenolic compounds were detected in HHLE. The results showed that the inhibitory efficiency of the leaf extract increased with increasing concentration. At 298 K, weight loss corrosion and electrochemical tests demonstrated that the greatest protection efficiency of 92.67 % for the steel was achieved at a concentration of 1000 mg/L of HHLE. This was attributed to a reduction in the cathodic currents and the obstruction of the active corroding sites. Thermodynamic analysis indicated an endothermic process governed by physisorption, and the Langmuir adsorption isotherm model highlighted the influence of both physical and chemical mechanisms on the adsorption process. Scanning electron microscopy (SEM) was used to confirm the reduction in XC18 steel corrosion in the presence of HHLE. Density functional theory (DFT) was employed to carry out quantum chemistry studies on the two primary components of the extract: kaempferol (KMP) and trans-chalcone (CHL). The quantum parameters obtained from the calculations were used to explore the active sites and interactions between donor and acceptor molecules, as well as the interfacial mechanism behavior of HHLE molecules on the metal surface.

Prompt GRB polarization from non-axisymmetric jets

ABSTRACT Time-resolved linear polarization (Π) measurements of the prompt gamma-ray burst emission can reveal its dominant radiation mechanism. A widely considered mechanism is synchrotron radiation, for which linear polarization can be used to probe the jet’s magnetic-field structure, and in turn its composition. In axisymmetric jet models, the polarization angle (PA) can only change by 90°, as Π temporarily vanishes. However, some time-resolved measurements find a continuously changing PA, which requires the flow to be non-axisymmetric in at least one out of its emissivity, bulk Lorentz factor, or magnetic field. Here, we consider synchrotron emission in non-axisymmetric jets, from an ultrarelativistic thin shell, comprising multiple radially expanding mini-jets (MJs) or emissivity patches within the global jet, that yield a continuously changing PA. We explore a wide variety of possibilities with emission consisting of a single pulse or multiple overlapping pulses, presenting time-resolved and integrated polarization from different magnetic field configurations and jet angular structures. We find that emission from multiple incoherent MJs/patches reduces the net polarization due to partial cancellation in the Stokes plane. When these contain a large-scale ordered field in the plane transverse to the radial direction, Π always starts near maximal and then declines over the single pulse or shows multiple highly polarized peaks due to multiple pulses. Observing $\Pi \lesssim 40~{{\ \rm per\ cent}}$ (15 per cent) integrated over one (several) pulse(s) will instead favour a shock-produced small-scale field either ordered in the radial direction or tangled in the plane transverse to it.

Assessment of in-vivo corrosion of Ti and CoCrMo joint implants by electrochemical measurements in human synovial liquids

Understanding the corrosion behavior of biomedical materials in the human body is an essential step for the development of improved materials and clinical procedures in arthroplasty. In this work, the corrosion behavior of Ti and CoCrMo alloys in human synovial fluids directly extracted from patients was investigated through an electrochemical experimental protocol, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results show that the corrosion behavior of both materials largely depends on patients. The obtained corrosion rates of both materials correspond well to the metal ion release rate detected in patients with joint implants revealing the adequateness of the electrochemical experimental protocol for quantifying in-vivo corrosion of biomedical implants. Based on the results, no significant risk of galvanic corrosion of Ti/CoCrMo coupling is anticipated. The rates of wear-accelerated corrosion (one of the main degradation mechanisms of metallic artificial hip joints) were theoretically extracted from the present electrochemical measurements using an established tribocorrosion model. Those material loss rates are patient-dependent and can be up to two orders of magnitude higher than the static corrosion rates, indicating that the nature of the patient can critically affect the degradation rate of the joint implant.