Origin of the single chain magnet behavior of the Co(H2L)(H2O) compound with a 1D structure

The paper is aimed at the elucidation of the main factors responsible for the single-chain magnet behavior of the cobalt(II) disphosphonate compound Co(H2L)(H2O) with a 1D structure. The model takes into account the spin-orbit interaction, the axial component of the octahedral crystal field acting on the ground-state cubic 4T1 terms of the Co(II) ions, the antiferromagnetic exchange interaction between Co(II) ions as well as the difference in the crystallographic positions of these ions. The conditions that favor the single-chain magnet behavior based on spin canting in a 1D chain containing inequivalent Co(II) centers are discussed. The peculiarities of this behavior in chains containing orbitally degenerate ions are revealed. The qualitative explanation of the experimental data is given.     

Modulation instability: The beginning

We discuss the early history of an important field of “sturm and drang” in modern theory of nonlinear waves. It is demonstrated how scientific demand resulted in independent and almost simultaneous publications by many different authors on modulation instability, a phenomenon resulting in a variety of nonlinear processes such as envelope solitons, envelope shocks, freak waves, etc. Examples from water wave hydrodynamics, electrodynamics, nonlinear optics, and convection theory are given.     

Classification of Random Image Fields Using Synthetic Discriminant Functions: Spectral Statistical Approach and Its Computer-Optical Realization

The problem of classification of images that have a perfectly random nature is considered. We propose a new approach to solve this problem that is based on the use of the synthetic discriminant functions being synthesized to separate linearly the power spectra of random image fields to be classified. In the stage of both discriminant function synthesis and classification, the statistical technique of power spectrum estimation is employed. The realization of the proposed approach by means of a hybrid computer-optical technique is discussed, and its efficiency is illustrated by two examples of real-world texture classification.     

Polynomial estimation of probability densities

We propose a new quality criterion and an iterative algorithm for polynomial estimation of probability densities of a random quantity. The properties of the optimal estimate are studied and the conditions and rate of its convergence are found. Antiaircraft Command High School of Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 11, pp. 1416–1432, November, 1997.     

Threshold Laws for Four-Particle Fragmentation: Mass Effects

Hyperfine Interactions - The threshold laws for break-up of an atomic particle into N charged fragments reflect dynamics of long-range Coulomb correlation. Progress in experimental technique makes...     

Highly anisotropic orbitally dependent superexchange in cyano-bridged clusters containing Mn(III) and Mn(II) ions.

We study the orbitally dependent magnetic exchange in cyanide-based clusters as a source of the barrier for reversal magnetization. We consider the Mn(III)-CN-Mn(II) dimer and linear Mn(II)-NC-Mn(III)-CN-Mn(II) trimer containing octahedrally coordinated Mn(III) and Mn(II) ions with special emphasis on the magnetic manifestations of the orbital degeneracy of the Mn(III) ion. The kinetic exchange mechanism involves the electron transfer from the single occupied t(2) orbitals of the Mn(II) ion [6A1(t2(3)e2) ground state] to the singly occupied t(2) orbitals of the Mn(III) ion [3T1(t2(4)) ground state] resulting in the charge-transfer 5T2(t2(2)e2)Mn(III) - 2T2(t2(5))Mn(II) state of the pair. The deduced effective exchange Hamiltonian that takes into account orbital degeneracy leads to an essentially non-Heisenberg energy pattern. The energy levels are shown to be dependent on both spin and orbital quantum numbers, thus providing direct information about the magnetic anisotropy of the system. Along with the magnetic exchange, the model includes an axial component of the crystal field and spin-orbit coupling operating within the ground 3T1(t2(4)) cubic term of the Mn(III) ion. We have shown that under certain conditions both named interactions lead to the occurrence of the barrier for the reversal of magnetization, which significantly increases when passing from the dimer to the trimer. This provides a possible way for raising the magnetic barrier in the family of cyano-bridged manganese clusters.     

Deuterium Rotating Frame NMR Relaxation Measurements in the Solid State under Static Conditions for Quantification of Dynamics

The feasibility of static deuterium rotating frame NMR relaxation measurements for characterization of slow timescale motions in powder systems is demonstrated. Using a model compound dimethyl sulfone-d₆, we show that these measurements yield conformational exchange rates and activation energy values in accordance with results obtained with other techniques. Furthermore, we demonstrate that the full Liouvillian approach as opposed to the Redfield approximation is necessary to analyze the experimental data.     

Comparative Hydrophobic Core Dynamics Between Wild-Type Amyloid-β Fibrils,Glutamate-3 Truncation,and Serine-8 Phosphorylation

Post-translational modifications (PTMs) of amyloid-β (Aβ) species are implicated in the modulation of overall toxicities and aggregation propensities. We investigated the internal dynamics in the hydrophobic core of the truncated ΔE3 mutant fibrils of Aβ_1–40 and compared them with prior and new data for wild-type fibrils as well as with phosphorylated S8 fibrils. Deuteron static solid-state NMR techniques, spanning line-shape analysis, longitudinal relaxation, and chemical exchange saturation transfer methods, were employed to assess the rotameric jumps of several methyl-bearing and aromatic groups in the core of the fibrils. Taken together, the results indicate the rather significant influence of the PTMs on the hydrophobic core dynamics, which propagates far beyond the local site of the chemical modification. The phosphorylated S8 fibrils display an overall rigidifying of the core based on the higher activation barriers of motions than the wild-type fibrils, whereas the ΔE3 fibrils induce a broader variety of changes, some of which are thermodynamic in nature rather than the kinetic ones.