Compressed Distortion Research Articles

Characterizing a Joint Reflection-Distortion OAE Profile in Humans With Endolymphatic Hydrops.

Endolymphatic hydrops (EH), a hallmark of Meniere disease, is an inner-ear disorder where the membranes bounding the scala media are distended outward due to an abnormally increased volume of endolymph. In this study, we characterize the joint-otoacoustic emission (OAE) profile, a results profile including both distortion- and reflection-class emissions from the same ear, in individuals with EH and speculate on its potential utility in clinical assessment and monitoring. Subjects were 16 adults with diagnosed EH and 18 adults with normal hearing (N) matched for age. Both the cubic distortion product (DP) OAE, a distortion-type emission, and the stimulus-frequency (SF) OAE, a reflection-type emission, were measured and analyzed as a joint OAE profile. OAE level, level growth (input/output functions), and phase-gradient delays were measured at frequencies corresponding to the apical half of the human cochlea and compared between groups. Normal hearers and individuals with EH shared some common OAE patterns, such as the reflection emissions being generally higher in level than distortion emissions and showing more linear growth than the more strongly compressed distortion emissions. However, significant differences were noted between the EH and N groups as well. OAE source strength (a metric based on OAE amplitude re: stimulus level) was significantly reduced, as was OAE level, at low frequencies in the EH group. These reductions were more marked for distortion than reflection emissions. Furthermore, two significant changes in the configuration of OAE input/output functions were observed in ears with EH: a steepened growth slope for reflection emissions and an elevated compression knee for distortion emissions. SFOAE phase-gradient delays at 40 dB forward-pressure level were slightly shorter in the group with EH compared with the normal group. The underlying pathology associated with EH impacts the generation of both emission types, reflection and distortion, as shown by significant group differences in OAE level, growth, and delay. However, hydrops impacts reflection and distortion emissions differently. Most notably, DPOAEs were more reduced by EH than were SFOAEs, suggesting that pathologies associated with the hydropic state do not act identically on the generation of nonlinear distortion at the hair bundle and intracochlear reflection emissions near the peak of the traveling wave. This differential effect underscores the value of applying a joint OAE approach to access both intracochlear generation processes concurrently.

Theoretical studies on the g-factors and the local structure of W5+ ions in tungsten phosphate glasses

In this work, we adopt the three-order perturbation formulae for g-factors (g//, g^) of d1 ions in the octahedral environment to calculate the g-factors of W5+ ions in tungsten phosphate glasses containing lithium (P2O5-Li2WO4-Li2O). In the light of the high valence state of the studied W5+ centers and hence the strong covalency of the studied octahedral [WO6]7- cluster, we consider the contributions to g-factors from the ligand orbital and spin-orbit (SO) coupling interactions based on the cluster approach. The required tetragonal crystal-field parameters are calculated from the local structure of W5+ ions based on the superposition model. According to the theoretical calculations, we find that the octahedral [WO6]7- clusters possess the tetragonally compressed distortion with a shorter W-O bond length (≈1.54 Å) and a longer one (≈2.26 Å) along C4 axis and four normal W-O bond length (≈1.94 Å) in the perpendicular plane, which infers that the W5+ ions are in the form of tungstyl ions (i.e., WO3-). Based on the local structural data, the theoretical values of g// and g^ agree well with the experimental values.

Subjective and Objective Video Quality Assessment for Windowed-6DoF Synthesized Videos

Video Quality Assessment (VQA) for windowed six Degree of Freedom (windowed-6DoF) synthesized viewpoints is conducive to the development and broadcasting of 6DoF immersive video system. To explore this new field, we propose the subjective and objective VQA studies for windowed-6DoF synthesized videos. Stage one, a pioneering windowed-6DoF synthesized video quality database with compressed distortion, rendering distortion, and viewing path discomfort are presented, in which overall 128 videos are synthesized from four sequences with different distortion combinations. Stage two, a no-reference objective VQA method is proposed. Firstly, the video is converted into one traditional spatio-temporal domain (XY-T domain) and two new spatio-temporal domains (XT-Y and TY-X domains). Secondly, the emerging rendering distortion and viewing path discomfort are measured in the XT-Y and TY-X domains based on their respective characteristic statistical models, and the common compressed distortion is measured in XY-T domain. Thirdly, the image numbers of new domains are accurately determined through optical flow based depth estimation. Finally, the regression model plus weighting strategy is used to obtain the ultimate quality score of windowed-6DoF synthesized video. Experimental results on three synthesized video databases illustrate that the proposed objective NR VQA method has a good performance in evaluating various synthesized videos, compared with other classic and state-of-the-art 2D/3D IQA/VQA metrics.

Theoretical analysis of single-ion anisotropy in d3 Mott insulators

An effective spin model for Mott insulators is determined by the symmetries involved among magnetic sites, electron fillings, and their interactions. Such a spin Hamiltonian offers insight to mechanisms of magnetic orders and magnetic anisotropy beyond the Heisenberg model. For a spin moment S bigger than 1/2, single-ion anisotropy is in principle allowed. However, for $d^3$ Mott insulators with large cubic crystal field splitting, the single-ion anisotropy is absent within the LS coupling, despite S = 3/2 local moment. On the other hand, preferred magnetic moment directions in $d^3$ materials have been reported, which calls for a further theoretical investigation. Here we derive the single-ion anisotropy interaction using the strong-coupling perturbation theory. The cubic crystal field splitting including $e_g$ orbitals, trigonal distortions, Hund's coupling, and spin-orbit coupling beyond the LS scheme are taken into account. For compressed distortion, the spin-orbit coupling at magnetic sites can favor either the easy-axis or the easy-plane while that of anions leads to easy-axis anisotropy. We apply the theory on $\rm{CrX}_3$ with X = Cl and I, and show the dependence of the single-ion anisotropy on the strength of the spin-orbit couplings of both magnetic and anion sites. Significance of the single-ion anisotropy in ideal two-dimensional magnets is also discussed.

Modulation of cancer therapy using nano-organometallic compounds: preparation, spectroscopic characterization and cytotoxic evaluation.

New series of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) organometallic complexes with hydroxyl benzylidene malonohydrazide ligand have much potential as therapeutic and diagnostic agents. The ligand allows the thermodynamic and kinetic reactivity of the metal ion to be controlled and also provide a scaffold for functionalization. The establishment of structure activity relationships and elucidation of the specification of complexes under conditions relevant to drug testing and formulation are crucial for the further development of promising medicinal applications of organometallic complexes. Specific examples involving the design of metal complexes as anticancer agents are discussed. These complexes have been synthesized and characterized by (1H-NMR, mass, IR, UV-VIS and ESR) spectroscopy, as well as magnetic moments, conductance, elemental and thermal analyses. Molar conductance in DMF solution indicates that, the complexes are non-electrolytes. The ESR spectra of solid Cu(II) complexes (7) and (8) showed isotropic and anisotropic types indicating an octahedral geometry with covalent bond character. However, Co(II) complexes (3) and (4) showed anisotropic type where, g┴ > g|| >2.0023, indicating compressed tetragonal distortion around Co(II) ion. Cytotoxic evolution of the ligand and its complexes have been carried out. Complexes showed enhanced activity in comparison to the parent ligand or standard drug applied.

Determination of charge-compensated C 3υ (II) centers for Er3+ ions in CdF2 and CaF2 crystals* *Project supported by the National Natural Science Foundation of China (Grant No. 1170513), the Natural Science Foundation of Shaanxi Province, China (Grant No. Z20200051), the Foundation of the Education Department of Shaanxi Provincial Government, China (Grant No. 16JK1461), and the Scientific Research Foundation of Xi’an

A unified theoretical method is established to determine the charge-compensated C 3v (II) centers of Er3+ ions in CdF2 and CaF2 crystals by simulating the electron paramagnetic resonance (EPR) parameters and Stark energy levels. The potential (Er3+–F−–) and (Er3+––O2–) structures for the C 3v (II) centers of Er3+ ions in CdF2 and CaF2 crystals are checked by diagonalizing 364 × 364 complete energy matrices in the scheme of superposition model. Our studies indicate that the C 3v (II) centers of Er3+ ions in CdF2 and CaF2 may be ascribed to the local (Er3+–F−–) structure, where the upper ligand ion F− undergoes an off-center displacement by ΔZ ≈ 0.3 Å for CdF2 and ΔZ ≈ 0.29 Å for the CaF2 along the C 3 axis. Meanwhile, a local compressed distortion of the cluster is expected to be ΔR ≈ 0.07 Å for CdF2:Er3+ and ΔR ≈ 0.079 Å for CaF2:Er3+. The considerable g-factor anisotropy for Er3+ ions in each of both crystals is explained reasonably by the obtained local parameters. Furthermore, our studies show that a stronger covalent effect exists in the C 3v (II) center for Er3+ in CaF2 or CaF2, which may be due to the stronger electrostatic interaction and closer distance between the central Er3+ ion and ligand O2– with the (Er3+–F−–) structure.

Theoretical Study of Electron Paramagnetic Resonance Spectra and Local Lattice Distortion for Mn2+ in Zn(ClO4)2·6(H2O)Mg(ClO4)2·6(H2O)

The electron paramagnetic resonance (EPR) spectra of trigonal Mn2+ centers in Zn(ClO4)2·6(H2O) and Mg(ClO4)2·6(H2O) crystals were studied on the basis of the complete energy matrices for a d5 configuration ion in a trigonal ligand field. It was demonstrated that the local lattice structure around a trigonal Mn2+ center has an compressed distortion along the crystalline c3 axis, and when Mn2+ is doped in the Zn(ClO4)2·6(H2O) and Mg(ClO4)2·6(H2O) crystals, there is a similar local distortion. From the EPR calculation, the local lattice structure parameters R=2.183 2 A, for Zn(ClO4)2·6(H2O), R=2.130 2 A, for Mg(ClO4)2·6(H2O) have been determined.

Theoretical Studies of the Electron Paramagnetic Resonance Parameters and Local Structure for VO2+ in Oxyfluoroborate Glasses

The electron paramagnetic resonance parameters (g factors g‖, g⊥ and hyperfine structure constants A‖, A⊥) of a tetragonal V4+ center in oxyfluoroborate glasses (20Li2O-10Li2F2-70B2O3) are theoretically investigated by using the perturbation formulas for a 3d1 ion in tetragonally compressed octahedra. The calculated results are in good agreement with the experimental data. Local structure parameters of [VO6]8- clusters are obtained from the calculation (i.e., R‖ ≈ 1.74 Å and R⊥ ≈ 1.985 Å for the metal-ligand distances parallel and perpendicular to the C4 axis, respectively). It is shown that the local structure around the V4+ ion possesses a compressed tetragonal distortion along C4 axis. The signs of the hyperfine structure constants A‖ and A⊥ for V4+ centers in oxyfluoroborate glasses were also suggested in the discussion.

1s2p Resonant Inelastic X-ray Scattering Magnetic Circular Dichroism as a probe for the local and non-local orbitals in CrO2

We have determined the magnetic ground state of the half-metal CrO2 based on 1s2p Resonant Inelastic X-ray Scattering Magnetic Circular Dichroism (RIXS-MCD) experiments. The two-dimensional RIXS-MCD map displays the 1s X-ray absorption spectrum combined with the 1s2p X-ray emission decay, where there is a large MCD contrast in the final state involving the 2p core hole.Our measurements show that the Cr K pre-edge structure is dominated by dipolar contributions and the quadrupole peak is invisible in direct K pre-edge absorption. Using RIXS-MCD, we reveal that the quadrupole 1s3d pre-edge has a large MCD contrast, which appears at lower energy with respect to the K pre-edge maximum.We use crystal field multiplet calculations to model the excitonic RIXS-MCD spectral shape in tetragonal (D4h) symmetry. The RIXS-MCD is strongly sensitive to the ground state distortion of the Cr4+ sites. The calculations of the RIXS-MCD maps suggest that the 3d spin–orbit interaction is fully quenched (ζ3d=0meV) and the ground state electron configuration must contain a 3B2g (D4h) contribution, which is required to explain the appearance of the Magnetic Circular Dichroism (MCD) in the Cr K pre-edge. This is in apparent contrast with the compressed tetragonal distortion.

Chemical pressure effects on crystal and magnetic structures of bilayer manganites PrA2Mn2O7 (A = Sr or Ca)

The crystal and magnetic structures of the bilayer manganites PrSr2Mn2O7 (PSMO) and PrCa2Mn2O7 (PCMO) have been studied by neutron powder diffraction. It was found that PSMO crystallizes in space group I4/mmm, while PCMO adopts space group Cmc21 at room temperature. The difference in the structure arises from chemical pressure induced by the Ca substitution for Sr on the A sites, which causes different Jahn-Teller distortions. In PSMO, the MnO6 octahedra suffer a small elongated distortion, while those in PCMO adopt strong compressed distortion along the axial direction. In addition, the octahedra in PCMO show a+b0c0 rotation and a0b+c+ tilting in the Glazer notation in comparison to PSMO. As a result, these two compounds adopt very different magnetic structures: The magnetic structure of PSMO is an A-type magnetic structure (Im'm'm) with propagation vector k = (0, 0, 1) and magnetic moments in the ab plane. In contrast, a C-type antiferromagnetic magnetic structure (Cm'c2′1) with the multiple propagation vectors (k = (0, 12, 12) and (0, 12, 0)) and magnetic moments mainly along the b axis is found in PCMO. The critical exponent of the magnetic phase transition is around 0.345 for PSMO and 0.235 for PCMO, indicating 3D and 2D XY transitions, respectively. The strong Jahn-Teller distortion induced by the chemical pressure is believed to suppress the double exchange and favour super-exchange in PCMO, leading to the dramatic difference in the magnetic structure.

EPR investigation of local structure for the [Mn(H2O)6]2+cluster in M(ClO4)2· 6H2O:Mn2+(M = Cd, Hg) systems at different temperatures

Local lattice structure distortion studies of the octahedral Mn 2+ center in M(ClO 4 ) 2 · 6H 2 O:Mn 2+ (M = Cd, Hg) systems have been performed systematically based on the diagonalization of the complete energy matrices of electron-electron repulsion, spin-orbit coupling and trigonal ligand-field interaction for a d 5 configuration ion in a trigonal ligand field. From the EPR calculation, the local structure distortion parameters R and θ are determined, respectively. Results show that the local lattice structure around a trigonal Mn 2+ center has a compressed distortion along the crystalline C 3 axis. The compression distortion may be ascribed to the fact that the radius of the Mn 2+ ion is smaller than that of the Hg 2+ ion and the Cd 2+ ion. The local lattice structure parameters for Mn 2+ in M(ClO 4 ) 2 · 6H 2 O:Mn 2+ (M = Cd, Hg) systems are determined at liquid-nitrogen temperature and room temperature.

Distortion correction in EPI using an extended PSF method with a reversed phase gradient approach.

In echo-planar imaging (EPI), such as commonly used for functional MRI (fMRI) and diffusion-tensor imaging (DTI), compressed distortion is a more difficult challenge than local stretching as spatial information can be lost in strongly compressed areas. In addition, the effects are more severe at ultra-high field (UHF) such as 7T due to increased field inhomogeneity. To resolve this problem, two EPIs with opposite phase-encoding (PE) polarity were acquired and combined after distortion correction. For distortion correction, a point spread function (PSF) mapping method was chosen due to its high correction accuracy and extended to perform distortion correction of both EPIs with opposite PE polarity thus reducing the PSF reference scan time. Because the amount of spatial information differs between the opposite PE datasets, the method was further extended to incorporate a weighted combination of the two distortion-corrected images to maximize the spatial information content of a final corrected image. The correction accuracy of the proposed method was evaluated in distortion-corrected data using both forward and reverse phase-encoded PSF reference data and compared with the reversed gradient approaches suggested previously. Further we demonstrate that the extended PSF method with an improved weighted combination can recover local distortions and spatial information loss and be applied successfully not only to spin-echo EPI, but also to gradient-echo EPIs acquired with both PE directions to perform geometrically accurate image reconstruction.

Theoretical investigation of ESR spectra and local structure for VO 2+ in Ba 2Zn(HCOO) 6(H 2O)

The electron spin resonance spectra (characterized by g factors g , g ⊥ and hyperfine structure constants A  and A ⊥) of Ba 2Zn(HCOO) 6(H 2O) (BZFA): VO 2+ crystal are calculated from high order perturbation formulas. The calculated results are in good agreement with the observed values. The local structure parameters of [VO(H 2O) 5] 2+ clusters are also obtained from the calculation. The magnitudes of the metal–ligand distances parallel and perpendicular to the C 4-axis are, respectively, R ≈0.163 nm and R ⊥≈0.210 nm. It is shown that the local structure around the V 4+ ion possesses a compressed tetragonal distortion along C 4-axis.

Investigation of the local structure and the effects of the orbit reduction factor on the EPR g-factors for octahedral (CrO6)9− cluster in TiO2:Cr3+ and MgO:Cr3+ systems

A theoretical method for studying the inter-relation between electronic and molecular structure has been proposed based on the complete energy matrices for a d(3) configuration ion in a tetragonal ligand-field. By means of this method, the local structure for Cr(3+) ion doped in oxides TiO(2) (anatase) and MgO has been determined. The calculated results indicate that the local structure of the (CrO(6))(9-) cluster in TiO(2):Cr(3+) and MgO:Cr(3+) systems exists as a compressed distortion relative to the regular octahedron. Meanwhile, the dependence of the EPR zero-field splitting parameter D on the local structure parameter Delta R (Delta R = R(1)-R(2)) has been revealed. In addition, the relation between the EPR g-factors (g(II),g(perpendicular to),Delta g) and the orbit reduction factor k has been discussed for the two systems, suggesting that the orbit reduction factor k is very important to understand the EPR g-factors. (C) 2009 Elsevier B.V. All rights reserved.

Investigations of the electron paramagnetic resonance parameters and the tetragonal local structure for (VCl6)4− coordination complex in MCl:V2+ (M = Na, K, Rb) systems

By simulating the electron paramagnetic resonance (EPR) and optical spectra on the basis of the 120 × 120 complete energy matrix, this paper determines the local lattice structure parameters R1 and R2 for MCl:V2+ (M = Na, K, Rb) systems at 77 K, 195 K and RT (room temperature 295 K or 302 K), respectively. The theoretical results indicate that there exists a compressed distortion in MCl:V2+ systems. Meanwhile, it finds that the structure parameters R1, R2 and |ΔR| ( = R1 − R2) increase with the rising temperature. Subsequently, from the analysis it concludes that the relation of EPR parameter D vs. ΔR is approximately linear. Finally, the effects of orbital reduction factor k on the g factors for the three systems have been discussed.

An Unusual Stable Mononuclear MnIII Bis‐terpyridine Complex Exhibiting Jahn–Teller Compression: Electrochemical Synthesis, Physical Characterisation and Theoretical Study

The mononuclear manganese bis-terpyridine complex [Mn(tolyl-terpy)(2)](X)(3) (1(X)(3); X=BF(4), ClO(4), PF(6); tolyl-terpy=4'-(4-methylphenyl)-2,2':6',2"-terpyridine), containing Mn in the unusual +III oxidation state, has been isolated and characterised. The 1(3+) ion is a rare example of a mononuclear Mn(III) complex stabilised solely by neutral N ligands. Complex 1(3+) is obtained by electrochemical oxidation of the corresponding Mn(II) compound 1(2+) in anhydrous acetonitrile. Under these conditions the cyclic voltammogram of 1(2+) exhibits not only the well-known Mn(II)/Mn(III) oxidation at E(1/2)=+0.91 V versus Ag/Ag(+) (+1.21 V vs. SCE) but also a second metal-based oxidation process corresponding to Mn(III)/Mn(IV) at E(1/2)=+1.63 V (+1.93 V vs. SCE). Single crystals of 1(PF(6))(3)2 CH(3)CN were obtained by an electrocrystallisation procedure. X-ray analysis unambiguously revealed its tetragonally compressed octahedral geometry and high-spin character. The electronic properties of 1(3+) were investigated in detail by magnetic measurements and theoretical calculations, from which a D value of +4.82 cm(-1) was precisely determined. Density functional and complete active space self consistent field ab initio calculations both correctly predict a positive sign of D, in agreement with the compressed tetragonal distortion observed in the X-ray structure of 1(PF(6))(3)2 CH(3)CN. The different contributions to D were calculated, and the results show that 1) the spin-orbit coupling part (+2.593 cm(-1)) is predominant compared to the spin-spin interaction (+1.075 cm(-1)) and 2) the excited triplet states make the dominant contribution to the total D value.

Tetragonal Distortion of Structural Defects in Cr3+ Doped in Several Perovskites Calculated from the EPR and Optical Data: A Complete Energy Matrix Study

This paper describes a novel application of a ligand field model in the study of the local molecular structure of the (CrF 6) (3-) coordination complex. Based on the ligand field model, the complete energy matrix which contains the electron-electron repulsion interaction, the ligand field interaction, the spin-orbit coupling interaction, and the Zeeman interaction, has been constructed for a d (3) configuration ion in a tetragonal ligand field. In order to study the relation between the EPR, the optical spectra, and the local lattice structures around the centers with tetragonal symmetry in AMF 3 codoped with Cr (3+) and Li (+) ions, a three-layer-ligand model is proposed. By diagonalizing the complete energy matrix and employing the three-layer-ligand model, the variational ranges of the local structural parameters around the Cr (3+) ions are determined, respectively. The results show that the local lattice structures around the Cr (3+) ions in AMF 3 exhibit a compressed distortion, and the magnitude of distorted parameter Delta R 1 of the Cr (3+)-V M center is different from that of the Cr (3+)-Li (+) center in AMF 3. The compressed distortion is ascribed to the fact that the radius of the Cr (3+) ion is smaller than those of M (2+) (M = Cd, Mg, Zn). Moreover, a linear correlation between the difference in the magnitude of distortion parameterDelta R for two different defect centers and the difference in the corresponding values of the zero-field-splitting parameter Delta D are found first.

Theoretical investigation on the optical absorption spectra and local lattice structure of α-Al 2O 3:Yb 3+ crystals

In this paper, the optical absorption spectra of Yb 3+ in the α-Al 2O 3 crystal are reasonably explained by using the superposition model and local lattice structure analysis. Based on these studies, we find that the local geometrical structure around the Yb 3+ ions possesses an elongated trigonal distortion above the O 2−-triangle and a compressed trigonal distortion in the lower one.

Investigation of local lattice structure around Cr3+ ions at the trigonal and tetragonal sites in RbCdF3: Cr3+ crystal

The local lattice structure and EPR, optical spectra for Cr3+ doped in RbCdF3 crystal have been studied by diagonalizing the complete energy matrices. The results show that the local structure of the Cr3+ ions in RbCdF3 exhibits a compressed distortion at the trigonal and tetragonal sites. The compressed distortion can be ascribed to the fact that the radius of Cr3+ ion is smaller than that of Cd2+ ion, and therefore Cr3+ ion will draw the fluorin ligands inwards. The variational ranges of the local structural parameters for Cr3+ doped in RbCdF3 crystal R = 1.9491 Å ∼ 1.9814 Å, θ = 55.234° ∼ 55.286° at the trigonal site and R 1 = 1.8617 Å ∼ 1.8928 Å, R 2 = 1.9527 Å ∼ 1.9851 Å at tetragonal site are obtained respectively, and the EPR and optical spectra agree well with the experimental results.

EPR theoretical study of hydrostatic pressure and temperature dependence of local lattice structure for [Mn(H 2O) 6] 2+ octahedral complex in the Zn(BF 4) 2 · 6H 2O:Mn 2+ system

The effect of hydrostatic pressure and temperature on the local molecular structure for Mn 2+ ions in the Zn(BF 4) 2 · 6H 2O:Mn 2+ system have been investigated by diagonalizing the complete energy matrices for a d 5 configuration ion in a trigonal ligand-field. By simulating the EPR parameters D and ( a − F), the local lattice structure parameters R and θ under different conditions have been determined. The results show that the local lattice structure of the [Mn(H 2O) 6] 2+ octahedron has a compressed distortion with increasing the pressure, and a elongated distortion with the temperature rising. Moreover, the electronic transition energies for Mn 2+ ions in the Zn(BF 4) 2 · 6H 2O crystal at 293 K are reported for the first time.