Cross-polarization Research Articles

Bidirectional multi-beam with multi-polarizations tensor holographic metasurface using bilayer anisotropic elements.

In this paper, we present and design a tensor holographic metasurface (THMS) capable of radiating multiple beams with different polarizations in both forward and backward directions. The proposed THMS manipulates the fundamental TE mode surface waves (SWs) to produce bidirectional leaky-wave radiation using bilayer anisotropic metal patches. To achieve the independent control of the direction and polarization of bidirectional beams, the nature of the capacitive impedance element supporting TE mode SWs is exploited. A dual-feed scheme exciting orthogonal TE SWs is proposed for THMS generating circularly polarized beams with good performance. As a proof of concept, a bidirectional THMS integrated with two WR-28 waveguide sources based on the orthogonal-feeds scheme, which simultaneously radiate linear- and circular-polarized four beams, is designed, fabricated, and measured at 35 GHz. The experiment results are in good agreement with the simulated ones, achieving a peak gain of 19.2 (19.6) dBi, a -3 dB gain bandwidth of 9.14% (4.3%), for circularly-polarized (linearly-polarized) beams and a 3 dB axial ratio bandwidth of 13% for circularly-polarized beams. The sidelobe levels and cross polarization levels of all beams are below -15 dB and -22 dB, respectively.

Inference of the low-energy constants in Δ -full chiral effective field theory including a correlated truncation error

We sample the posterior probability distributions of the low-energy constants (LECs) in Δ-full chiral effective field theory (χEFT) up to third order. We use eigenvector continuation for fast and accurate emulation of the likelihood and Hamiltonian Monte Carlo to draw effectively independent samples from the posteriors. Our Bayesian inference is conditioned on the Granada database of neutron-proton (np) cross sections and polarizations. We use priors grounded in χEFT assumptions and a Roy-Steiner analysis of pion-nucleon scattering data. We model correlated EFT truncation errors using a two-feature Gaussian process, and find correlation lengths for np scattering energies and angles in the ranges 45–83 MeV and 24–39 degrees, respectively. These correlations yield a nondiagonal covariance matrix and reduce the number of independent scattering data with factors of 8 and 4 at the second and third chiral orders, respectively. The relatively small difference between the second- and third-order predictions in Δ-full χEFT suppresses the marginal variance of the truncation error and the effects of its correlation structure. Our results are particularly important for analyzing the predictive capabilities in nuclear theory. Published by the American Physical Society 2024

Digestion inhibition of potato starch-botanical proteolytic polypeptides complexes subjected to heat moisture treatment based on steric hindrance and enzymatic inhibition

The effects of food components on starch digestibility is a prominent topic within the realms of food and nutritional science. In this study, complexes of potato starch (PS) and botanical proteolytic polypeptides (BPPs), including wheat peptides, maize peptides, rice peptides, and soybean peptides, were subjected to heat-moisture treatment (HMT). The physicochemical, structural, and digestibility variations of the PS-BPPs complexes were analyzed using polarized light microscopy, DSC, X-ray, FT-IR, SAXS, and in vitro simulated digestion. Additionally, we evaluated the inhibitory effects of BPPs on porcine pancreatic α-amylase (PPA). The results showed that the polarization cross of PS-BPPs complexes was weakened after HMT. The gelatinization temperatures (To, Tp, Tc) of the PS-BPPs complexes increased significantly. The starch in the PS-BPPs complexes transitioned from B-type structure to A-type structure after HMT, accompanied by an increase in short-range ordering and semicrystalline lamella thickness. In particular, the complexes exhibited higher contents of slowly digestible starch (SDS) and resistant starch (RS). Furthermore, wheat, rice, and soybean peptides exhibited a mixed type of competitive inhibition against PPA, whereas maize peptides exhibited competitive inhibition. The findings provide valuable insights into the role of BPPs in regulating starch digestion. Moreover, BPPs hold potential for enhancing the nutritional value and health benefits of foods.

Switchable bi-functional water-based metasurface for high efficiency and wideband polarization conversion and absorption

A reconfigurable metasurface with a switchable function, wideband, and high efficiency has gained a lot of attention for the creation of compact and efficient devices. Here, for the first time, we propose a bi-functional metasurface that utilizes a water-based resonator to achieve wideband and high-efficiency absorption and cross polarization conversion in the microwave range. By controlling the water injection, the functionality of the metasurface can switch between absorption and cross-polarized conversion. Via water injection, the designed water-based metasurface can act as a wideband absorber with an absorptivity of above 90% in the broadband range of 16.5–24 GHz. Meanwhile, without water injection, it exhibits the ability for high efficiency cross-polarization conversion across a wideband in the range of 4.38–11.9 GHz. The proposed metasurface is fabricated and measured to verify its ability to switch between the dual functions of high efficiency wideband absorption and cross-polarization conversion. We believe that the metasurface platform shown here will open up new possibilities for creating compact multifunctional devices for applications in the microwave region.

Perturbative computations of neutron-proton scattering observables using renormalization-group invariant chiral effective field theory up to N3LO

We predict neutron-proton scattering cross sections and polarization observables up to next-to-next-to-next-to-leading order in a renormalization-group invariant description of the strong nucleon-nucleon interaction. Low-energy constants are calibrated to phase shifts, subleading corrections are computed in distorted-wave perturbation theory, and we employ momentum-cutoff values 500 and 2500 MeV. We find a steady order-by-order convergence and realistic descriptions of scattering observables up to a laboratory scattering energy of approximately 100 MeV. We also compare perturbative and nonperturbative calculations for phase shifts and cross sections and quantify how unitarity is gradually restored at higher orders. The perturbative approach offers an important diagnostic tool for any power counting and our results suggest that the breakdown scale in chiral effective field theory might be significantly lower than estimates obtained in nonperturbative calculations. Published by the American Physical Society 2024

Ammonothermal Synthesis and Solid-State NMR Study of the Imidonitridosilicate Rb3Si6N5(NH)6.

The imidonitridosilicate Rb3Si6N5(NH)6, being only the second representative of this compound class, was synthesized ammonothermally at 870 K and 230 MPa. Its crystal structure was solved from single-crystal X-ray diffraction data. The imidonitridosilicate crystallizes isotypically with the respective potassium compound in space group P4132 with the lattice parameter a=10.9422(4) Å forming a three-dimensional imidonitridosilicate tetrahedra network with voids for the rubidium ions. The structure model and the presence of the imide groups were verified by Fourier-Transform infrared (FTIR) and magic-angle spinning (MAS) NMR spectroscopy, using cross polarization 15N{1H} and 29Si{1H} MAS NMR experiments. Rb3Si6N5(NH)6 represents a possible intermediate during the ammonothermal synthesis of nitridosilicates. The characterization of such intermediates improves the understanding of the reaction pathway from ammonothermal solutions to nitrides. Thus, the ammonothermal synthesis is an alternative approach to the well-established high-temperature synthesis leading to the compound class of nitridosilicates.

Probing structural features in potato starch granules at moderate hydration through the modelling of 1H->13C polarization transfer kinetics

The structural arrangement of starch polymers in presence of water is known to impact the functional properties of starchy products. In this study, the hydration of potato starch granules was investigated at the molecular level through various 1H->13C polarization transfer solid-state Nuclear Magnetic Resonance (ss-NMR) experiments. The impact of increasing the water content from 12.3 % to 45.9 % was assessed using 13C Cross Polarization Magic Angle Spinning (CPMAS), Variable Contact Time (VCT-CPMAS), Variable Spin Lock (VSL-CPMAS), and T One Rho QUEnching (TORQUE) NMR sequences. Of these, VCT-CPMAS proved to be the most promising. When applied with an optimal number of contact times, it enabled the application of several mathematical models that provided detailed insights into the structuring of protons in the hydrated potato starch granules. At low hydration (12.3 %), the models enabled various structural domains to be distinguished, which we suggest are associated with helical and amorphous structures. At moderate hydration (45.9 %), we tested two fitting models. Two pools of protons were revealed, corresponding to loosely ordered structures on the scale of tens of nanometers. These findings suggest varying water distribution during starch hydration and are likely to indicate variable hydration levels in the multilamellar amorphous structures of starch granules.

WITHDRAWN: Cross polarization converter with high transmittance and near unity polarization conversion efficiency for visible light based on bilayer all-dielectric metasurface

It is highly desired to achieve high efficiency polarization converters in visible wavelength region for ultra-compact optical systems which have shown potential applications in optical sensing, communication and imaging. Due to the intrinsic property of low loss, all dielectric metasurfaces are more competitive candidates to be utilized for fabrication of polarization converters than the counterparts based on metals. In this paper, we design a bilayer all dielectric metasurface polarization converter composed of a Si double-rod resonator placed on the top of a glass block with a polymer substrate for linearly polarized visible light. The proposed bilayer metasurface structure can convert linearly polarized light to the cross-polarized light efficiently within the visible region from 542 nm to 563 nm in the transmission mode with high transmittance and near unity polarization conversion efficiency. The transmittance is larger than 0.8 in the mentioned wavelength range with a maximum transmission of 0.86 at 556 nm and polarization conversion ratio is larger than 90% in the same wavelength range with a maximum polarization conversion ratio of 99.01% at 556 nm. The underline physical mechanisms of high conversion efficiency and high transmittance are analyzed in detail with simulated distributions of surface current, electrical field distributions and the calculated multipole decompositions of the scattering power.

Dielectric resonator magnetoelectric dipole arrays with low cross polarization, backward radiation, and mutual coupling for MIMO base station applications

Dielectric resonator magnetoelectric dipole arrays with low cross polarization, backward radiation, and mutual coupling for MIMO base station applications

Multispectral Depolarization Based Living-Skin Detection: A New Measurement Principle.

Camera-based photoplethysmographic imaging enabled the segmentation of living-skin tissues in a video, but it has inherent limitations to be used in real-life applications such as video health monitoring and face anti-spoofing. Inspired by the use of polarization for improving vital signs monitoring (i.e. specular reflection removal), we observed that skin tissues have an attractive property of wavelength-dependent depolarization due to its multi-layer structure containing different absorbing chromophores, i.e. polarized light photons with longer wavelengths (R) have deeper skin penetrability and thus experience thorougher depolarization than those with shorter wavelengths (G and B). Thus we proposed a novel dual-polarization setup and an elegant algorithm (named "MSD") that exploits the nature of multispectral depolarization of skin tissues to detect living-skin pixels, which only requires two images sampled at the parallel and cross polarizations to estimate the characteristic chromaticity changes (R/G) caused by tissue depolarization. Our proposal was verified in both the laboratory and hospital settings (ICU and NICU) focused on anti-spoofing and patient skin segmentation. The clinical experiments in ICU also indicate the potential of MSD for skin perfusion analysis, which may lead to a new diagnostic imaging approach in the future.

Biradicals based on PROXYL containing building blocks for efficient dynamic nuclear polarization in biotolerant media

A versatile strategy for synthesizing tailored peptide based biradicals is presented. By labeling the protected amino acid hydroxyproline with PROXYL via the OH functionality and using this building block in solid phase peptide synthesis (SPPS), the obtained peptides become polarization agents for DNP enhanced solid-state NMR in biotolerant media. To analyze the effect of the radical position on the enhancement factor, three different biradicals are synthesized. The PROXYL spin-label is inserted in a collagen inspired artificial peptide sequence by binding through the OH group of the hydroxyproline moieties at specific position in the chain. This labeling strategy is universally applicable for any hydroxyproline position in a peptide sequence since solid-phase peptide synthesis is used to insert the building block. High performance liquid chromatography (HPLC) and mass spectrometry (MS) analyses show the successful introduction of the spin label in the peptide chain and electron paramagnetic resonance (EPR) spectroscopy confirms its activity. Dynamic nuclear polarization (DNP) enhanced solid-state nuclear magnetic resonance (NMR) experiments performed on frozen aqueous glycerol-d8 solutions containing these peptide radicals show significantly higher enhancement factors of up to 45 in 1H→13C cross polarization magic angle spinning (CP MAS) experiments compared to an analogous mono-radical peptide including this building block (ε ≈ 14). Compared to commercial biradicals such as AMUPol for which enhancement factors > 100 have been obtained in the past and which have been optimized in their structure, the obtained enhancement up to 45 for our biradicals presents a significant progress in radical design.

Cross-Polarization Solid-State NMR Quantification of Species within Pores of Metal-Organic Frameworks: A Case Study of α-Mg3(HCOO)6.

The quantitative measurement of adsorbed guest species within metal-organic framework (MOF) pores is of fundamental importance for evaluating the adsorption performance of MOFs. However, routine analytic techniques such as thermogravimetric analysis cannot distinguish the contribution from species adsorbed within pores, species adsorbed on the surface, and gas phase or liquid phase encapsulated in the inter-crystalline space. Herein, we developed a new quantification method based on the cross-polarization (CP) solid-state nuclear magnetic resonance (ssNMR) technique, in which only the species within MOF pores are selectively probed due to the dramatically reduced mobility. Using the commercialized MOF α-Mg3(HCOO)6 as an example, a good linear correlation between Areaguest/Areaframework (i. e., the integrated area of guest and framework 13C NMR signals) and guest loading can be observed for several representative molecules such as benzene, tetrahydrofuran (THF), and 1,4-dioxane, clearly revealing the feasibility of CP quantification approach. The effects of guest molecule and corresponding residual mobility on the CP quantification are further discussed by varying the geometry and size of guest molecules. This methodology thus provides an effective and irreplaceable route to evaluate the adsorption performance of porous materials in-depth, especially for liquid-phase adsorption and gas-phase adsorption in which the capillary condensation is not negligible.

Magnetic Susceptibility Modeling of Magic-Angle Spinning Modules for Part Per Billion Scale Field Homogeneity

Magic-angle spinning (MAS) solid-state NMR methods are crucial in many areas of biology and materials science. Conventional probe designs have often been specified with 0.1 part per million (ppm) or 100 part per billion (ppb) magnetic field resolution, which is a limitation for many modern scientific applications. Here we describe a novel 5-mm MAS module design that significantly improves the linewidth and line shape for solid samples by an improved understanding of the magnetic susceptibility of probe materials and geometrical symmetry considerations, optimized to minimize the overall perturbation to the applied magnetic field (B0). The improved spinning module requires only first and second order shimming adjustments to achieve a sub-Hz resolution of 13C resonances of adamantane at 150 MHz Larmor frequency (14.1Tesla magnetic field). Minimal use of third and higher order shims improves experimental reproducibility upon sample changes and the exact placement within the magnet. Furthermore, the shimming procedure is faster, and the required gradients smaller, thus minimizing thermal drift of the room temperature (RT) shims. We demonstrate these results with direct polarization (Bloch decay) and cross polarization experiments on adamantane over a range of sample geometries and with multiple superconducting magnet systems. For a direct polarization experiment utilizing the entire active sample volume of a 5-mm rotor (90 µl), we achieved full width at half maximum (FWHM) of 0.76 Hz (5 ppb) and baseline resolved the 13C satellite peaks for adamantane as a consequent of the 7.31 Hz (59 ppb) width at 2% intensity. We expect these approaches to be increasingly pivotal for high-resolution solid-state NMR spectroscopy at and above 1 GHz 1H frequencies.

Peatland carbon chemistry, amino acids and protein preservation in biogeochemically distinct ecohydrologic layers

AbstractPeatlands play a significant role in global carbon and nitrogen cycles due to their carbon storage capabilities. However, there are key knowledge gaps in our understanding of how peatland hydrology influences the biogeochemical properties that drive peatland functioning and health. This study examines peatland hydrology and biogeochemical dynamics by exploring the variations in carbon chemistry, total amino acid (‘protein’) content and amino acid composition in the ecohydrologic layers: acrotelm, mesotelm and catotelm. The dynamic movement of the water table recorded half‐hourly over 4 years was used to assist in identifying the boundaries between these layers. Peat amino acids were measured using liquid chromatography‐tandem mass spectrometry (LC‐MS/MS). Carbon chemistry was analysed by solid state Cross Polarization Magic Angle Spinning (CPMAS) 13C Nuclear Magnetic Resonance (NMR) spectroscopy, with the alkyl:O‐alkyl ratio used to quantify the extent of decomposition. Our result revealed a strong positive correlation between the extent of decomposition and total protein content, indicating selective preservation of proteinaceous materials during peat decomposition. Each ecohydrologic layer displayed a distinct amino acid composition and carbon functional group composition. The acrotelm was relatively enriched in seven amino acids and two carbon functional groups. The mesotelm was relatively enriched in four amino acids, while the catotelm was relatively enriched in three amino acids and four carbon functional groups. The variations in amino acid composition reflect differences in microbial function and efficiency, while variations in carbon functional groups provide insights into long‐term carbon sequestration in peatland. Collectively, these results provide more insights into nutrient cycling and changes in organic matter composition during peat decomposition. These findings demonstrate that peatland biogeochemistry is closely linked to ecohydrology and suggest that changes to water table dynamics could affect the ability of peatlands to sequester and store carbon in the future.

Prompt polarized J/ψ production at NICA within NRQCD and generalized parton model

In our work we consider prompt J/ψ and ψ′ production within the approaches of nonrelativistic quantum chromodynamics and generalized parton model. We use various experimental data (√s = 200 GeV and √s =19.4 GeV) of charmonium production to fit octet nonperturbative matrix elements and averaged values of initial partons’ transverse momenta. Further, we make evaluation with the extracted parameters and predict J/ψ production cross section and polarization of J/ψ and ψ′ at NICA collider energy √s = 27 GeV.

Improvement of Phased Antenna Array Applied in Focused Microwave Breast Hyperthermia.

Focused microwave breast hyperthermia (FMBH) employs a phased antenna array to perform beamforming that can focus microwave energy at targeted breast tumors. Selective heating of the tumor endows the hyperthermia treatment with high accuracy and low side effects. The effect of FMBH is highly dependent on the applied phased antenna array. This work investigates the effect of polarizations of antenna elements on the microwave-focusing results by simulations. We explore two kinds of antenna arrays with the same number of elements using different digital realistic human breast phantoms. The first array has all the elements' polarization in the vertical plane of the breast, while the second array has half of the elements' polarization in the vertical plane and the other half in the transverse plane, i.e., cross polarization. In total, 96 sets of different simulations are performed, and the results show that the second array leads to a better focusing effect in dense breasts than the first array. This work is very meaningful for the potential improvement of the antenna array for FMBH, which is of great significance for the future clinical applications of FMBH. The antenna array with cross polarization can also be applied in microwave imaging and sensing for biomedical applications.

Multifunction and switchable hybrid metasurface based on graphene and gold

This paper presents the design and numerical investigation of a graphene-based switchable terahertz (THz) metasurface for ultrawideband absorption and multiband cross polarization conversion. The device’s operational mode can be altered to absorption or reflection by using the electrostatic capabilities exhibited by graphene. The numerical calculations yield results indicating that in absorption mode, it maintains a bandwidth ratio of 152% within the frequency range of 1.04–7.74 THz. In polarization conversion mode, the design demonstrates the ability to convert linearly polarized and circularly polarized waves to their respective cross-polarization states within the frequency ranges of 1.8–2.5 THz, 3.5–4.1 THz, and 5.6 THz. Moreover, calculated results indicate that linear-to-circular conversion can be realized at 2.64, 3.45, and 5.4 THz frequencies. In addition, the absorption and polarization conversion ratio parameters were analyzed using the multiple reflection theory, which demonstrated significant agreement with the simulation results. The designed metasurface exhibits significant potential in the field of terahertz devices, including stealth technology, smart switches, and other related applications.

Compact and broadband silicon polarization splitter-rotator using adiabaticity engineering.

We propose and demonstrate a short and broadband silicon mode-conversion polarization splitter-rotator (PSR) consisting of a mode-conversion taper and an adiabatic coupler-based mode sorter both optimized by adiabaticity engineering (AE). AE is used to optimize the distribution of adiabaticity parameter over the length of the PSR, providing shortcut to adiabaticity at a shorter device length. The total length of the PSR is 85 µm. The design is compatible with standard silicon photonics platforms and requires only one patterning step. Fabricated PSR has a polarization cross talk of less than -20 dB over the entire O-band for the TE polarization and a polarization cross talk of less than -15 dB from 1267 to 1348 nm for the TM polarization. Overall, the PSR shows low polarization cross talk (-15 dB) over a bandwidth of 81 nm in the O-band. Cross-wafer measurements show that the PSR has good fabrication tolerance.

Calculating the High‐Latitude Ionospheric Electrodynamics Using a Machine Learning‐Based Field‐Aligned Current Model

AbstractWe introduce a new framework called Machine Learning (ML) based Auroral Ionospheric electrodynamics Model (ML‐AIM). ML‐AIM solves a current continuity equation by utilizing the ML model of Field Aligned Currents of Kunduri et al. (2020, https://doi.org/10.1029/2020JA027908), the FAC‐derived auroral conductance model of Robinson et al. (2020, https://doi.org/10.1029/2020JA028008), and the solar irradiance conductance model of Moen and Brekke (1993, https://doi.org/10.1029/92gl02109). The ML‐AIM inputs are 60‐min time histories of solar wind plasma, interplanetary magnetic fields (IMF), and geomagnetic indices, and its outputs are ionospheric electric potential, electric fields, Pedersen/Hall currents, and Joule Heating. We conduct two ML‐AIM simulations for a weak geomagnetic activity interval on 14 May 2013 and a geomagnetic storm on 7–8 September 2017. ML‐AIM produces physically accurate ionospheric potential patterns such as the two‐cell convection pattern and the enhancement of electric potentials during active times. The cross polar cap potentials (ΦPC) from ML‐AIM, the Weimer (2005, https://doi.org/10.1029/2004ja010884) model, and the Super Dual Auroral Radar Network (SuperDARN) data‐assimilated potentials, are compared to the ones from 3204 polar crossings of the Defense Meteorological Satellite Program F17 satellite, showing better performance of ML‐AIM than others. ML‐AIM is unique and innovative because it predicts ionospheric responses to the time‐varying solar wind and geomagnetic conditions, while the other traditional empirical models like Weimer (2005, https://doi.org/10.1029/2004ja010884) designed to provide a quasi‐static ionospheric condition under quasi‐steady solar wind/IMF conditions. Plans are underway to improve ML‐AIM performance by including a fully ML network of models of aurora precipitation and ionospheric conductance, targeting its characterization of geomagnetically active times.

Sensitivity of polarizations and spin correlations of Z boson to anomalous neutral triple gauge couplings at lepton collider with polarized beams

We investigate the effects of anomalous neutral triple gauge couplings in ZZ and Zγ production processes, followed by the leptonic decay of the Z boson, at a lepton collider with center-of-mass energy s=250 GeV and polarized beams. We use an effective Lagrangian formalism to parametrize the anomalous couplings in terms of dimension-8 operators cB˜W, cBW, cWW, and cBB, and study the sensitivity of observables such as cross section, polarization, and spin correlation as functions of these couplings. We perform a Bayesian statistical analysis using Markov Chain Monte Carlo methods to determine simultaneous limits on the anomalous couplings, taking into account various luminosities L∈{0.1 ab−1,0.3 ab−1,1 ab−1,3 ab−1,10 ab−1} and systematic uncertainties. We find that polarization and spin correlation observables significantly enhance the sensitivity to anomalous couplings, providing stringent constraints on these couplings. Published by the American Physical Society 2024