Polar Order Research Articles

Synthesis and Magnetic Properties of the Multiferroic [C(NH2)3]Cr(HCOO)3 Metal-Organic Framework: The Role of Spin-Orbit Coupling and Jahn-Teller Distortions.

We report for the first time the synthesis of [C(NH2)3]Cr(HCOO)3 stabilizing Cr2+ in formate perovskite, which adopts a polar structure and orders magnetically below 8 K. We discuss in detail the magnetic properties and their coupling to the crystal structure based on first-principles calculations, symmetry, and model Hamiltonian analysis. We establish a general model for the orbital magnetic moment of [C(NH2)3]M(HCOO)3 (M = Cr, Cu) based on perturbation theory, revealing the key role of the Jahn-Teller distortions. We also analyze their spin and orbital textures in k-space, which show unique characteristics.

GENERALISED AUTOMORPHIC SHEAVES AND THE PROPORTIONALITY PRINCIPLE OF HIRZEBRUCH-MUMFORD

AbstractWe axiomatise the algebraic properties of toroidal compactifications of (mixed) Shimura varieties and their automorphic vector bundles. A notion of generalised automorphic sheaf is proposed which includes sheaves of (meromorphic) sections of automorphic vector bundles with prescribed vanishing and pole orders along strata in the compactification, and their quotients. These include, for instance, sheaves of Jacobi forms and weakly holomorphic modular forms. Using this machinery, we give a short and purely algebraic proof of the proportionality theorem of Hirzebruch and Mumford.

Manipulation of plasmonic vortex fields using positive elliptically polarized beams

Several studies have investigated methods for the direct excitation of surface plasmon polariton (SPP) vortex fields by using scalar beams with linear and circular polarization. In this paper, we propose novel devices for generating SPP vortex fields by using positive elliptically polarized beams. These devices excited SPP vortices with a uniform electric field intensity distribution, that did not vary arbitrarily with changes in the incident beam amplitude ratio. Moreover, when the incident scalar beam was transformed into a vector beam with different amplitude ratios at every point in space, the topological charge of the SPP vortex field could be dynamically modulated by changing the polarization order and rotation direction of the incident vector beam. The fields generated by different structures after the superposition of SPP vortices had spatial intensity distributions that varied with changes in the incident beam amplitude ratio. These properties provide a new idea for realizing different spatial intensity distributions for a dynamic modulation SPP field.

Antidiabetic Activity of Apigenin (4, 5, 7 – Trihydroxy Flavone) from Leaves of Stachytarpheta jamaicensis (L) Vahl (Verbennaceae)

Background: Apigenin is a polyphenolic compound that belongs to the class of flavonoids and is considered highly therapeutic.
 Aim: To evaluate the antidiabetic activity of apigenin isolated from dichloromethane: methanol extract of leaves of Stachytarpheta jamiacensis (L) Vahl (Verbennaceae) in alloxan-induced diabetic rats.
 Methods: Cold maceration was used to extract the S. jamiacensis powdered leaves with dichloromethane: methanol (1:1). Hexane, dichloromethane, and aqueous methanol fractions of the extract were obtained through fractionation. To isolate the bioactive molecule, the dichloromethane fraction (DCMF) was then subjected to column chromatography and eluted with several solvent mixtures in ascending polarity order. With the aid of data from FTIR, UV, GC-MS, 1HNMR (400MHz), and 13CNMR (101MHz), the structure of the isolated compound was identified. The Phytochemical analysis of the isolate and acute toxicity study was done following standard procedures. The anti-diabetic potential of the isolate was assessed by determining fasting blood glucose levels on alloxan-induced rats at the dose of 25 and 50 mg/kg body weight.
 Results: The compound was identified as apigenin (4, 5, 7 – trihydroxy flavones) and showed significant (p<0.05) reduction of 79.56 and 81.74 % in fasting blood glucose levels at the dose of 25 and 50 mg/kg respectively when compared with the standard drug (glibenclamide 83.40 %). The isolate's phytochemical analysis revealed flavonoids and the LD50 test demonstrates that apigenin was not harmful.
 Conclusion: The findings show that the apigenin from Stachytarpheta jamaicensis (L) Vahl has potent anti-diabetic properties.

Justicia adhatoda L. vasicin and vasicinone as bioactive phytochemical compounds: Isolation, characterization, and computational studies

Justicia adhatoda L. has wide applications in traditional and modern medicine. Its major potency is due to the presence of two alkaloids viz. Vasicine and Vasicinone. In industry, the demand for both marker compounds as well as quality Justicia adhatoda L. material is very high. The isolation of bioactive phytochemical compounds for the development of an in-house phytochemical reference standard library to verify quality control is of prime demand for an analytical chemist. For these reasons, the objective of the present study was to isolate two members of the alkaloids Vasicine and Vasicinone marker compounds from Justicia adhatoda L. Extraction was carried out by using a cold percolation method in a successive manner by increasing the order of polarity of the solvents from petroleum-ether to ethanol. Isolation was achieved for the above said two maker compounds by using separation, purification though column chromatography on silica-gel using mobile phase chloroform, and ethanol. Characterization of the isolated compounds was carried out by UV–VIS, IR, 1H NMR, 13C NMR and mass spectroscopy techniques. The isolated and purified solid compounds were confirmed as Vasicine and Vasicinone by comparison and co-relating with observed spectroscopy data and literature data. The compounds had a good to high amount of yield (0.4 % to 0.63 %) with high purity (98–100 %) through HPL. Lastly, frontier molecular orbital analysis (HOMO and LUMO), and global descriptive parameters (such as chemical potential, electronegativity, hardness, softness, etc.) were analyzed using computational approaches. Results revealed a good correlation with experimental data except for a few alternations in 1H NMR data.

To Be or Not To Be Polar: The Ferroelectric and Antiferroelectric Nematic Phases.

We report two new series of compounds that show the ferroelectric nematic, NF, phase in which the terminal chain length is varied. The longer the terminal chain, the weaker the dipole-dipole interactions of the molecules are along the director and thus the lower the temperature at which the axially polar NF phase is formed. For homologues of intermediate chain lengths, between the non-polar and ferroelectric nematic phases, a wide temperature range nematic phase emerges with antiferroelectric character. The size of the antiparallel ferroelectric domains critically increases upon transition to the NF phase. In dielectric studies, both collective ("ferroelectric") and non-collective fluctuations are present, and the "ferroelectric" mode softens weakly at the N-NX phase transition because the polar order in this phase is weak. The transition to the NF phase is characterized by a much stronger lowering of the mode relaxation frequency and an increase in its strength, and a typical critical behavior is observed.

Strong electron-phonon coupling driven pseudogap modulation and density-wave fluctuations in a correlated polar metal

There is tremendous interest in employing collective excitations of the lattice, spin, charge, and orbitals to tune strongly correlated electronic phenomena. We report such an effect in a ruthenate, Ca3Ru2O7, where two phonons with strong electron-phonon coupling modulate the electronic pseudogap as well as mediate charge and spin density wave fluctuations. Combining temperature-dependent Raman spectroscopy with density functional theory reveals two phonons, B2P and B2M, that are strongly coupled to electrons and whose scattering intensities respectively dominate in the pseudogap versus the metallic phases. The B2P squeezes the octahedra along the out of plane c-axis, while the B2M elongates it, thus modulating the Ru 4d orbital splitting and the bandwidth of the in-plane electron hopping; Thus, B2P opens the pseudogap, while B2M closes it. Moreover, the B2 phonons mediate incoherent charge and spin density wave fluctuations, as evidenced by changes in the background electronic Raman scattering that exhibit unique symmetry signatures. The polar order breaks inversion symmetry, enabling infrared activity of these phonons, paving the way for coherent light-driven control of electronic transport.

Bulk photovoltaic and photoconductivity effects in two-dimensional ferroelectric CuInP2S6 based heterojunctions

The construction of two-dimensional heterojunctions has significantly expanded the modulation degrees of freedom in two-dimensional materials, which has led to the emergence of numerous advanced microelectronics and optoelectronic devices. Extensive research has been conducted on the photovoltaic and photoconductivity effects to achieve higher photodetection performance in heterojunction-based devices. However, the bulk photovoltaic effect, which has excellent potential for applications in self-powered optoelectronics, microelectronics, and energy conversion devices, has not received enough attention. Herein, we construct a two-dimensional ferroelectric heterojunction using multi-layered CuInP2S6 (CIPS) and MoS2 nanoflakes and investigate its photoconductivity effect for photodetection. Furthermore, we observe and analyze the bulk photovoltaic effect in the heterojunction. The photoelectric effect in the MoS2 layer contributes to the photoconductivity effect of the heterojunction, while the room-temperature polar ordering in CIPS contributes to the bulk photovoltaic effect. The heterojunction exhibits high specific detectivity (D*) of 1.89 × 109 Jones, when the optical power intensity is 4.71 mW/cm2. Moreover, the short-circuit photocurrent density is high, reaching about 1.23 mA/cm2 when the optical power intensity is 0.35 W/cm2. This work highlights the potential application of two-dimensional ferroelectric materials in multifunction devices with self-powered detection and energy conversion capabilities.

High uniformity splitter with great inhibition of ±1st orders

A transmissive double-groove grating under vertical incidence is proposed in this paper. The grating has a total of five diffraction orders, and the effect of a three-channel beam splitter is achieved by inhibiting the diffraction efficiency of ±1st orders. This is a polarization-independent micro-nano structure that achieves triple beam splitting under both TE and TM polarization. The diffraction efficiency of the 0th order and ±2nd orders for TE polarization orders can reach 32.55% and 32.72%, respectively. And the diffraction efficiency of 0th order and ±2nd orders for TM polarization can reach 32.28% and 32.59%, respectively. Both TE and TM polarization can achieve 99% uniformity. The grating performs well in terms of manufacturing tolerances and immunity to interference.

Multi-wavelength Q-plate arithmetic in an all-liquid-crystal modular setup

Vortex beams are a type of structured light characterized by phase rotation around the propagation axis, resulting in orbital angular momentum. Their properties make them useful in various applications such as high-resolution microscopy, optical tweezing, and telecommunications. This has led to a comprehensive development of methods for their generation, ranging from using single-purpose glass elements to utilizing computer-generated holograms using spatial light modulators. One of the most commonly used elements for vortex transformation is a vortex half-wave retarder called a q-plate, which can transform a Gaussian beam into a scalar vortex or vector beam depending on the input polarization. Although the commercially available ones are limited in the range of possible output topological charges, they can be stacked to perform arithmetic operations to expand them. However, changing the output or working wavelength requires rearranging the elements. We present an improvement to this method that solves these problems by introducing Q-modules, easy-to-fabricate, electrically tunable liquid crystal devices that combine the features of q-plates and half-wave plates and can be used as building blocks in modular assemblies. Electrical tuning makes it possible to change the working wavelength as well as the topological output charge or polarization order without the need to interact mechanically with the setup.

Parameters identification of closely spaced modes with the covariance-drivern stochastic subspace and damping ratio dispersion method

Electromechanical equipment with quasi-symmetric and partially symmetrical structures is widespread in the industry, which not only makes the dynamic characteristics of the system more complex but also leads to severe closely spaced modes. The existence of closely spaced modes can lead to more confusion, because severe closely spaced modes have similar frequency eigenvalues and some singular eigenvalues are prone to generate spurious modes in matrix computations. In this paper, the covariance-drivern stochastic subspace and damping ratio dispersion (SSI-COV-DRD) method is proposed, which in comparison with previous methods, identification process directly is performed in the stochastic subspace by solving the system matrix of the time domain signal to overcome modal aliasing of the frequency-based method. Firstly, a Toeplitz matrix is constructed with a time series signal and then the system modal parameters are gained from the system matrix after performing singular value decomposition (SVD) to the Toeplitz matrix. Subsequently, the poles of the continuous model order are classified by a hierarchical clustering algorithm to obtain stabilization diagram and the real physical modes are automatically extracted from the stabilization diagram according to the choice criteria. Finally, the damping ratio dispersion index is calculated to express the nonlinear distribution characteristic of the damping ratio. Numerical examples for the five-order free vibration simulation signals with noise-free and noise indicate that the proposed method can simultaneously identify the modal frequency and damping ratio with high accuracy in severe closely spaced modes, especially for the repeated frequency modes. Since the bolt connection rotor of the aero-engine usually produces severe closely spaced modes in vibration due to the structural symmetry, the frequency and damping ratio are extracted and the damping ratio dispersion index is calculated from different bolt loosening states, which is helpful for the bolt loosening detection of aviation safety assurance and maintenance.

Acaricidal effects of Tagetes minuta L. (Asteraceae) against Tetranychus truncatus Ehara (Prostigmata: Tetranychidae)

ABSTRACT The study evaluated the efficacy of solvent fractions of Mexican marigold, Tagetes minuta against the spider mite, Tetranychus truncatus. The dried and pulverized botanical was subjected to sequential extraction using three solvents viz., hexane, chloroform and water in the increasing order of polarity. Solvent fractions were evaluated for their ovicidal and adulticidal activities against T. truncatus in the laboratory at five different concentrations viz., 0.025, 0.05, 0.1, 0.15 and 0.2 %. Results indicated that only hexane fraction at higher concentrations of 0.15 and 2.0 % exhibited significant ovicidal action, causing 100.00 and 81.33 per cent egg mortality, respectively. However, all the fractions recorded significant adulticidal effect at higher concentrations with hexane fractions at 0.2 and 0.15 % recording significantly higher adult mortality (>90 %), followed by chloroform fraction. The best concentrations of the three solvent fractions identified in the laboratory study were evaluated against T. truncatus on amaranthus, in a pot culture experiment. Fourteen days post treatment, hexane fraction at 0.2 % reduced mite population by 88.78 per cent and was superior to neem oil emulsion at 2% (76.44 % reduction), which was on par with chloroform and aqueous fractions. Results of the study identified Mexican marigold as a potential candidate in mite pest management, which may be further validated through multi-locational field trials.

Unusual magnetic properties of (Sr, Mn)-substituted BiFeO3 near the polar/antipolar phase boundary

Investigations of the crystal structure and magnetic properties of the Bi0.85Sr0.15Fe1-xMnxO3 (0.1 ≤ x ≤ 0.5) ferromanganites were carried out. The materials maintain the single-phase polar R3c structure of the pure bismuth ferrite up to x = 0.35 (a further increase in the Mn content stabilizes the antipolar Pnam phase), thus exhibiting the coexistence of spontaneous polarization and magnetic order over a wide range of Mn concentrations, sufficient to influence the cycloidal antiferromagnetic arrangement typical of the parent compound and contribute to the canted antiferromagnetic phase formation (at room temperature). A complex magnetic behaviour with irregular changes in remanent magnetization and coercive field suggesting the temperature-driven modification of the canted antiferromagnetic structure near the polar/antipolar phase boundary has also been found.

Revealing the Polarizations of Molecular Ferroelectrics via SHG Polarimetry at the Nanoscale.

Multifarious molecular ferroelectrics with multipolar axial characteristics have emerged in recent years, enriching the scenarios for energy harvesting, sensing, and information processing. The increased polar axes have enhanced the urgency of distinguishing different polarization states in material design, mechanism exploration, etc. However, conventional methods hardly meet the requirements of in situ, fast, microscale, contactless, and nondestructive features due to their inherent limitations. Herein, SHG polarimetry is introduced to probe the multioriented polarizations on a nanosized multiaxial molecular ferroelectric, i.e., TMCM-CdCl3 nanoplates, as an example. Combined with the analysis of the second-order susceptibility tensor, SHG polarimetry could serve as an effective method to detect the polarization orders and domain distributions of molecular ferroelectrics. Profiting from the full-optical feature, SHG polarimetry can even be performed on samples covered by transparent mediums, 2D materials, or thin metal electrodes. Our research might spark further fundamental studies and expand the application boundaries of next-generation ferroelectric materials.

Spin angular momentum and angular harmonics spectrum of two-order polarization vortices at the tight focus

We investigate the spin angular momentum (SAM) of two-order cylindrical vector beams at the tight focus. Such beams are a generalization of the conventional cylindrical vector beams since the transverse field components on the Cartesian axes have different polarization orders. Using the Richards-Wolf approximation, we derive an expression for the longitudinal component of the SAM density distribution. We show that if the polarization indices are of different parity then, an optical spin Hall effect arises at the tight focus, meaning that alternating areas with positive and negative SAM are originated although the initial light field is linearly polarized. We study the angular harmonics spectrum of all the components of the focused light field and determine the predominant angular harmonics. Then, neglecting the insignificant harmonics, we define the shape of the longitudinal component of the SAM density distribution and demonstrate the possibility of generating a focal SAM distribution where the areas with positive and negative SAM reside on a circle as alternating pairs or separated into different half-circles.

BIOASSAY GUIDED HEPATOPROTECTIVE ACTIVITY OF POLYGONATUM CIRRHIFOLIUM AGAINST ISONIAZID AND RIFAMPICIN INDUCED HEPATOTOXICITY IN RATS

The present investigation was performed to examine the hepatoprotective effect of the aqueous ethanolic extract of Polygonatum cirrhifolium in antitubercular drug-induced liver damage. P. cirrhifolium rhizomes were crushed, dissolved in various solvents (in order of polarity), and then tested for phytochemicals. Based on their findings, mass extraction utilizing the ethanol-water mixture (50: 50) was carried out using the Soxhlet method. The doses for animal research were established through acute toxicity tests. The hepatoprotective potential of aqueous ethanolic extract (50:50) of rhizomes was determined in Wistar rats at doses of 200 mg kg-1 and 400 mg kg-1 p.o. per day. Blood samples were examined for the biochemical markers SGOT, SGPT, ALP, total bilirubin, and albumin. Histopathology of the liver was also conducted followed by in vitro anti-oxidant studies. Simultaneously, the extract was subjected to LCMS characterization. P. cirrhifolium extract at both the doses 200 mg kg-1 and 400 mg kg-1 has shown significant hepatoprotective activity against hepatotoxicity induced by INH+ RIF in a dose-dependent manner, as depicted by the significant changes in the values of blood biomarkers and in vitro anti-oxidant studies. Histopathological studies showed that the treatment with 200 mg kg-1 and 400 mg kg-1 of P. cirrhifolium exhibited regeneration of liver architecture and portal system by reducing the haemorrhage and inflammatory infiltrate. LC-MS characterization showed serpentine, 5-hydroxy methylfurfural and cephalotaxine as active constituents. It can be inferred that hydroethanolic extract of P. cirrhifolium protects the liver from anti-TB induced toxicity and this protection could be due to the active phytoconstituents.

Polar response and Fréedericksz transition in cybotactic nematic fluids of unsymmetrical bent-core molecules

The appearance of polar order in nematic fluids is of broad interest rejuvenating affluent concepts of physics and chemistry. In bent-core nematics (BCNs), ferroelectric switching is a challenging quest of considerable interest after its primary observation in 1,2,4-oxadiazole-based BCNs. Herein, we observed induced polar switching in the cybotactic nematic phase (Ncyb) with a polarization value of ∼185 nC/cm2 in an unsymmetrical bent-core compound 8-F-OH. Temperature-dependent SAXS/WAXS analysis and dielectric measurements revealed nano-sized cybotactic clustering within the nematic phase. Electric-field-induced Fréedericksz transitions (FT) in the Ncyb phase at different frequencies and temperatures were investigated. Compound 8-F-OH exhibited two domains that formed and competed when the system was driven by an ac field. Thus, the build-up process of FT involved the reorientation of molecules and the transport of domains, where each had a distinctive characteristic time. We envisage that these detailed investigations can pave a bright way toward the development of advanced-level optical and electro-optical applications of BCN systems.

Anticonvulsant potential of Grewia tiliaefolia in pentylenetetrazole induced epilepsy: insights from in vivo and in silico studies.

Epilepsy, a chronic neurological condition, impacts millions of individuals globally and remains a significant contributor to both illness and mortality. Available antiepileptic drugs have serious side effects which warrants to explore different medicinal plants used for the management of epilepsy reported in Traditional Indian Medicinal System (TIMS). Therefore, we explored the antiepileptic potential of the Grewia tiliaefolia (Tiliaeceae) which is known for its neuroprotective properties. Aerial parts of G. tiliaefolia were subjected to extraction with increasing order of polarity viz. hexane, chloroform and methanol. Antioxidant potential of hexane, chloroform and methanol extracts ofG. tiliaefoliawas evaluated by 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) assay, total antioxidant capacity (TAC) assay, reducing power assay (RPA) and DNA nicking assay. Additionally, quantitative antioxidant assays were also conducted to quantify total phenolic (TPC) and total flavonoid content (TFC). As revealed by in vitro assays, methanol extract was found to contain more phenolic content. Hence, the methanol extract was further explored for its anticonvulsant potential in pentylenetetrazole (PTZ) induced acute seizures in mice. The methanol extract (400mg/kg) significantly increased the latency to occurrence of myoclonic jerks and generalized tonic clonic seizures (GTCS). Additionally, it also reduced duration and seizure severity score associated with GTCS. The Grewia tiliaefolia methanol extract was further screened by Ultra High-Performance Liquid Chromatography (UHPLC) for presence of polyphenolic compounds, among which gallic acid and kaempferol were present in higher amount and were further analysed by in silico study to predict their possible binding sites and type of interactions these compounds show with gamma amino butyric acid (GABA) receptor and glutamate α amino-3- hydroxyl-5-methyl-4-isoxazolepropionic acid (Glu-AMPA) receptor. It was revealed that gallic acid and kaempferol had shown agonistic interaction for GABA receptor and antagonistic interaction for Glu-AMPA receptor. We concluded thatG. tiliaefoliashowed anticonvulsant potential possibly because of gallic acid and kaempferol possibly mediated through GABA and Glu-AMPA receptor.

Mapping Polar Distortions using Nanobeam Electron Diffraction and a Cepstral Approach.

Measuring local polar ordering is key to understanding ferroelectricity in thin films, especially for systems with small domains or significant disorder. Scanning nanobeam electron diffraction (NBED) provides an effective local probe of lattice parameters, local fields, polarization directions, and charge densities, which can be analyzed using a relatively low beam dose over large fields of view. However, quantitatively extracting the magnitudes and directions of polarization vectors from NBED remains challenging. Here, we use a cepstral approach, similar to a pair distribution function, to determine local polar displacements that drive ferroelectricity from NBED patterns. Because polar distortions generate asymmetry in the diffraction pattern intensity, we can efficiently recover the underlying displacements from the imaginary part of the cepstrum transform. We investigate the limits of this technique using analytical and simulated data and give experimental examples, achieving the order of 1.1 pm precision and mapping of polar displacements with nanometer resolution.

Improved energy storage performance in rare-earth modified lead-free BNT-based relaxor ferroelectric ceramics

Dielectric ceramic capacitors with high energy storage performance are indispensable components in high-power pulse electronic systems. Herein, a collaborative optimization design is employed to achieve excellent energy storage performance in rare-earth oxides modified 0.76(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-0.24Sr0.7Bi0.2TiO3 (BNBT-SBT) ceramics by simultaneously enhancing the breakdown field strength (Eb) and relaxor behavior. To this end, ferroelectric domains are partially transformed into polar nanoregions by introducing relaxor ferroelectric SBT, while a smaller grain size is produced by doping rare-earth elements to improve the Eb and further disrupt the long-range order of ferroelectric polarization. It is found that the La-doped BNBT-SBT ceramic simultaneously exhibits a superior energy storage density of 4.4 J cm−3 and an ultrahigh efficiency of ∼91% under a moderate electric field of 300 kV/cm. The good temperature stability (30–120 °C), frequency endurance (1–100 Hz), electric fatigue resistance (1–106 cycles), and excellent power density (108 MW cm−3) are also obtained in the lead-free Bi0.5Na0.5TiO3-based relaxor ferroelectric ceramics. These prominent properties indicate that the La-doped BNBT-SBT ceramic is a promising candidate for applications of high-energy storage capacitors.