SideLink: automated side-chain assignment of biopolymers from NMR data by relative-hypothesis-prioritization-based simulated logic

Previously we published the development of AutoLink, a program to assign the backbone resonances of macromolecules. The primary limitation of this program has proven to be its inability to directly recognize spectral data, relying on the user to define peak positions in its input. Here, we introduce a new program for the assignment of side-chain resonances. Like AutoLink, this new program, called SideLink, uses Relative Hypothesis Prioritization to emulate "human" logic. To address the higher complexity of side-chain assignment problems, the RHP algorithm has itself been advanced, making it capable of processing almost any combinatorial logic problem. Additionally, SideLink directly examines spectral data, overcoming the need and limitations of prior data interpretation by users.     

Facile Access to Optically Active 2,6‐Dialkyl‐1,5‐Diazacyclooctanes

The chiral substituted 1,5‐diazacyclooctane (1,5‐DACO) is of considerable importance and has attracted attention from a wide range of fields due to their unique chemical and biological properties. Despite the application potential, further study has not been optimized due to difficulties in their synthetic accessibility. Here, we report that the 1,5‐DACO bearing a chiral auxiliary obtained from the formal [4+4] cycloaddition of N‐alkyl‐α,β‐unsaturated imines can be further derivatized by nucleophilic alkylation to give various chiral substituted 1,5‐DACO derivatives. The removal of the chiral auxiliary was effectively carried out using hydrogenation over Pearlman's catalyst. This methodology allows the production of a broad range of unprecedented optically active 2,6‐dialkyl‐1,5‐DACO, which could not be accessed by other methods.     

Comparison of diluted antiferromagnetic Ising models on frustrated lattices in a magnetic field

We study diluted antiferromagnetic Ising models on triangular and kagome lattices in a magnetic field, using the replica-exchange Monte Carlo method. We observe seven and five plateaus in the magnetization curve of the diluted antiferromagnetic Ising model on the triangular and kagome lattices, respectively, when a magnetic field is applied. These observations contrast with the two plateaus observed in the pure model. The origin of multiple plateaus is investigated by considering the spin configuration of triangles in the diluted models. We compare these results with those of a diluted antiferromagnetic Ising model on the three-dimensional pyrochlore lattice in a magnetic field pointing in the [111] direction, sometimes referred to as the “kagome-ice” problem. We discuss the similarity and dissimilarity of the magnetization curves of the “kagome-ice” state and the two-dimensional kagome lattice.     

Lorentz-boosted evanescent waves

Polarization, spin, and helicity are important properties of electromagnetic waves. It is commonly believed that helicity is invariant under the Lorentz transformations. This is indeed so for plane waves and their localized superpositions. However, this is not the case for evanescent waves, which are well-defined only in a half-space, and are characterized by complex wave vectors. Here we describe transformations of evanescent electromagnetic waves and their polarization/spin/helicity properties under the Lorentz boosts along the three spatial directions.     

Experimental modeling of percolation of molten iron through polycrystalline olivine matrix at 2.0–5.5 GPa and 1600°C

The present work was aimed to understand the role of light elements for the penetration of Fe melt through the olivine matrix at high P–T parameters. We studied the mechanism of Fe melt percolation through the olivine matrix, whose interstices are filled with carbon and sulfur. The experiments were performed using a ‘split-sphere’ type multi-anvil high pressure apparatus at pressures 2.0 and 5.5?GPa and a temperature of 1600°C. It was demonstrated that the Fe melt penetrated through the olivine matrix at a relatively high rates in the presence of carbon or sulfur in the interstices. The percolation occurs due to fast dissolution of the light elements into Fe melt and filling of these interstices by the melt.     

Spreadsheets to calculate P–V–T relations,thermodynamic and thermoelastic properties of silicates in the MgSiO3–MgO system

Modified equations of state (EoS) of forsterite, wadsleyite, ringwoodite, akimotoite, bridgmanite and post-perovskite based on the Helmholtz free energy are described using Microsoft Excel spreadsheets. The equations of state were set up by joint analysis of reference experimental data and can be used to calculate thermodynamic and thermoelastic parameters and P–V–T properties of the Mg-silicates. We used Visual Basic for Applications module in Microsoft Excel and presented a simultaneous calculation of full set of thermodynamic and thermoelastic functions using only T–P and T–V data as input parameters. Phase transitions in the MgSiO₃–MgO system play an important role in the interpretation of the seismic boundaries of the upper Earth’s mantle and in the D″ layer. Therefore, proposed EoSes of silicates in the MgSiO₃–MgO system have clear geophysical implications. The developed software will be interesting to specialists who are engaged to study the mantle mineralogy and Earth’s interior.     

Calculation of off‐resonance Raman scattering intensities with parametric models

The paper reviews applications of parametric models for calculations of the Raman scattering intensity of materials with the main emphasis on the performance of the bond polarizability model. The use of the model in studies of polymers, aluminosilicates, and nanostructures is discussed and the existing sets of electro‐optical parameters as well as their transferability are analyzed. The paper highlights the interplay between the first‐principles and parametric approaches to the Raman intensity calculations and suggests further developments in this field. Copyright © 2009 John Wiley & Sons, Ltd.     

Localization on Quantum Graphs with Random Edge Lengths

The spectral properties of the Laplacian on a class of quantum graphs with random metric structure are studied. Namely, we consider quantum graphs spanned by the simple ${\mathbb Z^d}$ -lattice with δ-type boundary conditions at the vertices, and we assume that the edge lengths are randomly independently identically distributed. Under the assumption that the coupling constant at the vertices does not vanish, we show that the operator exhibits the Anderson localization near the spectral edges situated outside a certain forbidden set.