Shift Anisotropy Research Articles

Video tooning

We describe a system for transforming an input video into a highly abstracted, spatio-temporally coherent cartoon animation with a range of styles. To achieve this, we treat video as a space-time volume of image data. We have developed an anisotropic kernel mean shift technique to segment the video data into contiguous volumes. These provide a simple cartoon style in themselves, but more importantly provide the capability to semi-automatically rotoscope semantically meaningful regions.In our system, the user simply outlines objects on keyframes. A mean shift guided interpolation algorithm is then employed to create three dimensional semantic regions by interpolation between the keyframes, while maintaining smooth trajectories along the time dimension. These regions provide the basis for creating smooth two dimensional edge sheets and stroke sheets embedded within the spatio-temporal video volume. The regions, edge sheets, and stroke sheets are rendered by slicing them at particular times. A variety of styles of rendering are shown. The temporal coherence provided by the smoothed semantic regions and sheets results in a temporally consistent non-photorealistic appearance.

Harmonics of Daily Variations in Cosmic-Ray Intensity

The high/low amplitude anisotropic wave-train events (HAE/LAE) in cosmic-ray intensity have been investigated during the period 1991-94, using the neutron monitor data for different latitudes. In all, 16 HAE and 13 LAE cases have been studied. An inter-comparison of the first three harmonics during these events has been made so as to understand the basic reason causing the occurrence of these types of events. It has been observed that the phase of diurnal anisotropy shifts towards earlier hours for HAEs; similarly, it shifts towards earlier hour as compared to 18-Hr direction for LAEs. For semi-diurnal anisotropy phase remains statistically the same for both HAE as well as for LAE. Further in case of tri-diurnal anisotropy phase is evenly distributed for both types of events. The interplanetary magnetic field and solar-wind plasma parameters during these events are also investigated. It has been also observed that HAE/LAEs are weakly dependent on solar-wind velocity.

Anisotropic exchange interaction in CdTe/Cd 0.75Mn 0.25Te quantum wires

We observed anisotropic large peak-energy shift of photoluminescence (PL) from CdTe/Cd 0.75Mn 0.25Te quantum wires (QWRs). The large PL-peak-energy shift is caused by the exchange interaction between excitons in the non-magnetic QWR and Mn ions in the DMS barrier. The exchange interaction is enhanced when magnetic field is perpendicular to the QWR.

Molecular Orientation and Conformation of Phosphatidylinositides in Membrane Mimetics Using Variable Angle Sample Spinning (VASS) NMR

For many biological molecules, determining their geometry as they exist in a membrane environment is a crucial step in understanding their function. Variable angle sample spinning (VASS) NMR provides a new route to obtaining geometry information on membrane-associating molecules; it has been used here to scale and separate anisotropic contributions to phosphorus chemical shifts in NMR spectra of phosphatidylinositol phosphates. The procedure allows spectral assignment via correlation with isotropic chemical shifts and determination of a family of probable headgroup orientations via interpretation of anisotropic shift contributions. The molecules studied include phosphtidylinositol-4-phosphate (PI(4)P) and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2). A membrane-like environment is provided by a dispersion of alkyl-poly(ethylene) glycols and n-alcohols that forms a field-orienting liquid crystal with a director that can be manipulated by varying the sample spinning axis. The experiments presented indicate that the variable angle sample spinning method will provide a direct approach for assignment and extraction of structural information from membrane-associating biomolecules labeled with a wider variety of NMR active isotopes.

A Xanthone‐Based Neutral Receptor for Zwitterionic Amino Acids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

High-temperature magnetic order and coexisting spin dynamics inPrCu2:Manifestations of multipolar effects

We present a comprehensive muon-spin-rotation/relaxation $(\ensuremath{\mu}\mathrm{SR})$ study of the high-temperature magnetic order ${(T}_{N}\ensuremath{\simeq}65\mathrm{K})$ in ${\mathrm{PrCu}}_{2},$ first observed quite unexpectedly in 1998 [A. Schenck et al., Phys. Rev. B $58,$ 5205 (1998)]. Measurements in zero and longitudinal fields as a function of temperature, orientation of the single-crystal sample, and strength of applied magnetic field ${H}_{\mathrm{ext}}$ confirmed the previous findings and allowed us to determine the properties of the internal spontaneous fields $\mathit{B}$ in detail. It is found that $\mathit{B}$ is strictly confined to the crystallographic $(a,c)$ plane and encloses on average an angle $\ensuremath{\theta}$ of $30\ifmmode^\circ\else\textdegree\fi{}\ensuremath{-}45\ifmmode^\circ\else\textdegree\fi{}$ with the a axis, depending on temperature. Both $|\mathit{B}|$ and $\ensuremath{\theta}$ display a large variation. This is consistent with, but does not unambiguously prove, the incommensurately modulated antiferromagnetic structure observed below $\ensuremath{\sim}50\mathrm{mK}$ by neutron scattering [S. Kawarazaki and J. Arthur, J. Phys. Soc. Jpn. $57,$ 1077 (1988)]. The estimated ordered electronic moment of $\ensuremath{\sim}0.29{\ensuremath{\mu}}_{B}$ is smaller than the value quoted by Kawarazaki et al. $(0.54{\ensuremath{\mu}}_{B}).$ The temperature dependence of $|\mathit{B}|$ is highly unusual and scales perfectly with the temperature dependence of the elastic constant ${C}_{66}$ [R. Settai et al., J. Phys. Soc. Jpn $67,$ 636 (1998)], implying that the ordered moment is proportional to the strain susceptibility involving the ${O}_{\mathrm{xy}}$ quadrupole moment. ${\ensuremath{\mu}}^{+}$ is also found to be exposed to fluctuating field components inducing spin-lattice relaxation. The relaxation rate $\ensuremath{\lambda}$ consists of a field-independent but rather anisotropic term and an essentially isotropic but field-dependent term. The first term reflects the Jahn-Teller transition at 7.5 K by a cusplike anomaly. Transverse-field measurements at 6 kOe and above 100 K allowed us to determine the anisotropic Knight shift, or the dipolar coupling tensor, from which it follows that ${\ensuremath{\mu}}^{+}$ are located at $4e$ sites. At lower temperatures, we find evidence that the contact-hyperfine coupling constant becomes temperature and orientation dependent.

Improvement of resolution in solid state NMR spectra with J-decoupling: an analysis of lineshape contributions in uniformly 13C-enriched amino acids and proteins

In magic angle spinning (MAS) NMR spectra of highly and uniformly 13C, 15N-enriched amino acids and proteins, homo-nuclear coupling interactions contribute significantly to the 13C linewidths, particularly for moderate applied magnetic field strengths and sample spinning frequencies. In this work, we attempted to dissect, analyze, and control the contributions of J-coupling and residual homo-nuclear dipolar coupling interactions to the linewidths of uniformly 13C, 15N-enriched crystalline alanine; these studies were carried out at 9.4 T using a range of spinning frequencies from 5 to 15 kHz. The anisotropic second-order dipolar shifts and the J-splittings are comparable in their contribution to the linewidths, but behave very differently in terms of experimental protocols for line narrowing. In contrast to the J-coupling interactions, the second-order dipolar broadening cannot be refocused using selective pulses on the passively coupled spin. We carried out experiments to remove or refocus the 13C J-coupling interactions ( ω 1 J-decoupling) using a selective DANTE pulse in the center of the indirect evolution period. Inversion profiles and bandwidths of selective DANTE pulses acting on transverse magnetization, in the regime of moderate spinning frequencies, were characterized computationally and experimentally. A dramatic improvement in the resolution of the 2D spectrum was achieved when this decoupling protocol was employed.

A xanthone-based neutral receptor for zwitterionic amino acids

Combination of a xanthone and crown ether provides a receptor that extracts phenylalanine from water. Strong anisotropic shifts were observed for the guest aromatic ring in the complex. The ninhydrin test was used to assess the amount of other amino acids extracted by this receptor.

Dependence of Magnetic Properties on Sputtering Pressure for Fe–Al–O Alloy Films Made by Carousel-Type Sputtering

We have investigated the magnetic anisotropy and permeability of FeAlO films with Bs∼1.8 T and ρ∼1 µΩm. The films were prepared using a carousel-type sputtering system. Although an aligning magnetic field to induce uniaxial magnetic anisotropy was not applied to the substrates during deposition, the FeAlO films in the as-deposited state had uniaxial magnetic anisotropy. The anisotropy strongly depends on sputtering pressure. The direction of the magnetic anisotropy shifts 90° from the rotation direction to the radial direction of the substrate holder as the sputtering pressure increases. In the pressure range of 0.3–0.4 Pa, the measured µ–f properties are largely different from the theoretical one because of magnetic anisotropy dispersion. The anisotropy dispersion can be explained by a model with two orthogonal anisotropy components.

Metal‐stabilized rare tautomers: N4 metalated cytosine (M = Li+, Na+, K+, Rb+ and Cs+), theoretical views

AbstractAb initio calculations indicate that metalation of the exocyclic amino group of cytosine by the elements of Group IA (Li, Na, K, Rb and Cs) induces protonation of a nucleobase ring nitrogen atom, and hence causes a proton shift from an exocyclic to an endocyclic nitrogen atom. Thus, this metal‐assisted process leads to the generation of rare nucleobase tautomers. The calculations suggest that this kind of metalation increases the protonation energies of the aromatic ring of the nucleobase. The present study reports the quantum chemistry analysis of the metal‐assisted tautomerization. The calculations clearly demonstrate that metalation of the exocyclic amino group of the nucleobase significantly increases the protonation energy of the aromatic rings of the nucleobase. Also, absolute anisotropy shift, molecular orbital and natural bond orbital calculations are compatible with these results. Copyright © 2003 John Wiley & Sons, Ltd.

59Co, 23Na NMR and electric field gradient calculations in the layered cobalt oxides NaCoO 2 and HCoO 2

59Co and 23Na NMR has been applied to the layered cobalt oxides NaCoO 2 and HCoO 2 at three different magnetic field strengths (4.7, 7.1 and 11.7 T). The 59Co and 23Na quadrupole and anisotropic shift tensors have been determined by iterative fitting of the NMR line shapes at the three magnetic field strengths. Due to the large 59Co quadrupole interaction in NaCoO 2, a frequency-swept irradiation procedure was used to alleviate the limited bandwidth of the excitation. While the 59Co and 23Na shift and quadrupole coupling tensors in NaCoO 2 are found to be coincident and axially symmetric in agreement with the crystal symmetry requirements, the fits of the 59Co NMR spectra clearly show the presence of structural disorder in HCoO 2. The 23Na chemical shift anisotropy can be reproduced by shift tensor calculations using a point dipole model and considering that the magnetic susceptibility in NaCoO 2 is due to Van Vleck paramagnetism for Co 3+. Electric field gradient calculations using either the empirical point charge model or the ab initio full potential-linearized augmented plane wave method are compared with the experimental NMR data.

Electronic Inhomogeneity and Possible Pseudogap Behavior of Spin Susceptibility in the Electron-Doped Superconductor Sr 0.93 La 0.07 CuO 2 : 63 Cu NMR Study

The magnetic susceptibility, NMR spectra, nuclear spin-lattice relaxation rate (T 1 −1)α and the echo-decay rate (T 2 −1) of 63Cu were measured for the electron-doped infinite-layer superconductor Sr0.93La0.07CuO2/T c onset = 42.4 K). The results obtained revealed a clear tendency toward frustrated phase separation in this nominally underdoped high-T c material. Above T c the 63Cu Knight shift is found to decrease upon cooling giving an evidence for a pseudogap-like decrease of the spin susceptibility. It is shown that unusual anisotropy of the 63Cu Knight shift in the electron-doped CuO2 layer can be understood as a “compensation effect” between the isotropic hyperfine coupling, mediated by the 4s Fermi-contact and 3d core-polarization exchange interactions, and the anisotropic on-site spin-dipolar hyperfine interaction of the Cu nuclei with the itinerant carriers, whose states near the Fermi energy have a sizeable admixture of Cu(4pz) and/or Cu(3dz 2) orbitals.

Relaxation Equations in Operator Representation for a Multipolar Spin System (1/2, 5/2)

The theoretical description of relaxation processes in a scalar-coupled two-spin system containing a quadrupole nucleus (I = 1/2, S = 5/2) is presented, presuming that the relaxation is determined by dipole interaction between I and S spins, quadrupole interactions of the nucleus S, and the anisotropy of the chemical shift of both nuclei CSA (I) and CSA (S). The interference terms (cross correlation terms) between these types of interactions D-Q, D-CSA, and Q-CSA are also taken into account. Within the framework of the theory of a density matrix in the second order of perturbation theory, the relaxation equations in the operator representation for describing the longitudinal and transverse relaxation of a nucleus with spin 1/2 are derived. A formalism for the angular momentum operators of scalar coupled spins IS is developed, which makes it possible to calculate a spectrum pattern of a nucleus with a half spin, scalar coupled to a quadrupole nucleus with any spin. The proposed procedure has allowed us to find linear combinations of operators which can be considered as the projective operators responsible for each spectral component of spin 1/2, scalar coupled to a quadrupole nucleus (S = 5/2). The relaxation equations allowing investigation of the longitudinal and transverse relaxation of each component of the spectrum of a half-spin nucleus are obtained. The rates of longitudinal and transverse relaxation and also the rate of cross relaxation between the components are determined.

Magnetic and optical properties of one-dimensional π–d system with axially substituted iron(III) phthalocyanine

We have measured the angular dependence of the ESR spectra on DMDP[Fe III 0.01Co III 0.99(Pc)(CN) 2] (DMDP=dimethyldiphenylphosphonium, Pc=phthalocyanine), which is the alloy system of magnetic Fe III and non-magnetic Co III. The spectra exhibit giant anisotropic shift in g-value of iron(III). We also report the temperature dependence of the polarized reflectance spectra of one-dimensional conductors, TPP[Fe III(Pc)(CN) 2] 2 and TPP[Co III(Pc)(CN) 2] 2 (TPP=tetraphenylphosphonium). With lowering the temperature, the plasma edge drastically shifts to a higher wavenumber in both salts.

NMR study of the influence of iodine substitution in the Chevrel compounds Mo 6Te 8− xI x and Mo 6Se 8− xI x

We have obtained the 125Te and 77Se nuclear magnetic resonance spectra of the Chevrel type compounds Mo 6Te 8− x I x ( x=0,1,2) at room temperature and Mo 6Se 8− x I x ( x=0,0.5,1.0,1.5,2.0) over the temperature range 70–300 K, in order to study the effect of I doping in these materials. The spectra consisted of the superposition of two separate anisotropic Knight shifts corresponding to the two different crystallographic sites of the Se and Te nuclei within their respective compounds. The distinction between the two lines became more blurred with the increase of the iodine concentration. Analysis of the results tends to favor the supposition that in the case of the Se compound, the iodine favors the replacement of the Se ternary sites, although some temperature dependence on the choice of site was discerned. In the case of the Te compounds, the experimental evidence showed that even for x=2, both the ternary and the non-ternery sites were occupied. An abrupt change in the NMR parameters for Mo 6Se 8 near T=100 K was found.

13C NMR spectral assignments for nematic liquid crystals by 2D chemical shift γ-encoding NMR

A novel method to accomplish 13C NMR spectral assignments for nematic liquid crystals is proposed. The two-dimensional (2D) isotropic/anisotropic chemical shift correlation spectrum is observed in which the anisotropic shift parameters are represented as sharp lines by γ-encoding. The 13C spectral assignments can be made from the 2D spectrum with the aid of the 13C isotropic shift assignments for the same compound in the isotropic liquid state. The experiments were performed on p-methoxybenzilidene- p- n-butylaniline.

MIXING OF SINGLET AND TRIPLET PAIRING FOR SURFACE SUPERCONDUCTIVITY

We consider structure of the Cooper wave function for superconductivity in a surface layer. Broken space inversion at the surface results in lifted spin degeneracy and in two branches of the gapped energy spectrum as caused by the spin-orbit interaction. The pair wave function consists of a mixture of both singlet and triplet components. Anisotropy of the Knight shift measurable in the NMR experiments is calculated in the whole temperature regime. Implications for a few known experimental situations is briefly discussed.

2"-Chartreusin-monoacetate, a New Natural Product with Unusual Anisotropy Effects from the Marine Isolate Streptomyces sp. B5525, and its 4"-Isomer

The marine Streptomycete isolates B5342 and B5525 forms, beside large amounts of the antitumor antibiotic chartreusin (1a), two chartreusin monoacetates as trace components. Whereas the chemical shift of the acetate methyl in 1c is in the normal range, the methyl group of the 2"-acetate residue in 1b and also in the tetra- and pentaacetates shows an extreme upfield shift. The structures of the monoacetates were confirmed by extensive NMR experiments, the anisotropic shift is explained by semi-empirical calculations.

Field-induced magnetization distribution and antiferroquadrupolar order in CeB(6).

The anisotropic Knight shift of implanted positive muons (micro(+)) in CeB(6) has been studied between 2.2 and 200 K in a field of 0.6 T. The results imply that the field-induced magnetization distribution is not only found at the Ce sites but also in other regions of the unit cell (e.g., near or inside the B6 molecule, as proposed by Saitoh et al. [J. Phys. Soc. Jpn. Suppl. 71, 106-108 (2002)]). While above the antiferroquadrupolar ordering temperature T(Q) approximately 3.55 K this additional magnetization appears to be antiparallel to the Ce moments, a drastic change is observed below T(Q), and the additional magnetization is eventually aligned parallel to the Ce moments.

β-VO 2—a V(IV) or a mixed-valence V(III)–V(V) oxide—studied by 51V MAS NMR spectroscopy

Analysis of high-field (9.4 and 14.1 T) 51V MAS NMR spectra for the low-temperature non-metallic β-form of VO 2 unambiguously shows the presence of only one V(IV) site for this semiconductor phase. Magnitudes and relative orientation of the 51V quadrupole coupling and chemical shift tensor have been precisely determined. Variable-temperature 51V MAS NMR studies (25–90 °C) show that the phase transition from non-metallic (β) to metallic (α) VO 2 is accompanied by a large change in Knight shift from 2115 to −4788 ppm. Approximate values for the 51V quadrupole coupling and shift anisotropy are reported for the V(IV) site in α-VO 2.