<!?tlsb=‐0.06pt>Zigzag polymer chains in catena‐poly[[[triaqua(isobutyrato‐κO)magnesium(II)]‐μ‐isobutyrato‐κ2O:O′] monohydrate]

The structure of the title compound, {[Mg(C₄H₇O₂)₂(H₂O)₃]·H₂O}_n, features one‐dimensional ...(μ₂‐ib)Mg(μ₂‐ib)Mg... zigzag chains (ib is isobutyrate) parallel to the c axis. The octahedral Mg environment is completed by three fac‐oriented terminal water ligands, as well as one further monodentate end‐on coordinated ib ligand. In the crystal structure, the hydrophobic ib groups are all oriented within one half of the coordination perimeter of each chain, whereas the water ligands, together with hydrogen‐bonded noncoordinated solvent water molecules, define the other half. Along the a axis, neighbouring strands are oriented so that both the hydrophilic and hydrophobic sides are adjacent to each other. This results in an extensive hydrogen‐bonding network within the hydrophilic areas, also involving an additional solvent water molecule per formula unit. There are van der Waals contacts between the aliphatic isopropyl groups of the hydrophobic areas.     

TETRAPHOSPHORUS TRISULFIDE IN REACTIONS WITH THIOACETALS,AMINALS, SULFENAMIDES AND DISULFIDES. INFLUENCE OF AMINES AND BENZOYL PEROXIDE

Abstract

The reactions of tetraphosphorus trisulfide with thioacetals, aminals, sulfenamides and disulfides were studied. The reactions were found to give organothiophosphorus compounds and to be facilitated by organic amines and benzoyl peroxide.     

“Helter‐Skelter‐Like” Perylene Polyisocyanopeptides

Exciton migration! Spectroscopic analyses and extensive molecular dynamics studies revealed a well‐defined 4₁ helix in which the perylene molecules (see figure) form four “helter‐skelter‐like” overlapping pathways along which excitons and electrons can rapidly migrate.

     

Direct quantitative analysis of peptides using matrix assisted laser desorption ionization

The protocol and various matrices were examined for quantification of biomolecules in both the low ca. 1200 amu and mid mass 6000-12000 amu ranges using an internal standard. Comparative studies of different matrices of MALDI quantitative analysis showed that the best accuracy and standard curve linearity were obtained for two matrices: (a) 2,5-dihydroxybenzoic acid (DHB) combined with a comatrix of fucose and 5-methoxysalicylic acid (MSA) and (b) ferulic acid/fucose. In the low mass range, the quantitative limit was in the 30 fmol range and in the mid mass range the quantitative limit was in the 250 fmol range. Linear response was observed over 2-3 decades of analyte concentration. The relative error of the standard curve slope was 1.3-1.8% with correlation coefficients of 0.996-0.998.The main problem for quantitative measurement was suppression of the signal of the less concentrated component (analyte or internal standard) by the more concentrated component. The effect was identified with saturation of the matrix by the analyte. The threshold of matrix saturation was found to be in the range of 1/(3000-5000) analyte/matrix molar ratio. To avoid matrix saturation the (analyte+internal standard) to matrix molar ratio should be below this threshold. Thus the internal standard concentration should be as low as possible.DHB/MSA/fucose and ferulic acid/fucose matrices demonstrated good accuracy and linearity for standard curves even when the internal standard had chemical properties different from the analyte. However, use of an internal standard with different chemical properties requires highly stable instrumental parameters as well as constant (analyte+internal standard)/matrix molar ratio for all samples.     

Hyperbolic chaos in a system of resonantly coupled weakly nonlinear oscillators

We show that a hyperbolic chaos can be observed in resonantly coupled oscillators near a Hopf bifurcation, described by normal-form-type equations for complex amplitudes. The simplest example consists of four oscillators, comprising two alternatively activated, due to an external periodic modulation, pairs. In terms of the stroboscopic Poincaré map, the phase differences change according to an expanding Bernoulli map that depends on the coupling type. Several examples of hyperbolic chaos for different types of coupling are illustrated numerically.     

Attractor of Smale - Williams type in an autonomous distributed system

We consider an autonomous system of partial differential equations for a one-dimensional distributed medium with periodic boundary conditions. Dynamics in time consists of alternating birth and death of patterns with spatial phases transformed from one stage of activity to another by the doubly expanding circle map. So, the attractor in the Poincaré section is uniformly hyperbolic, a kind of Smale - Williams solenoid. Finite-dimensional models are derived as ordinary differential equations for amplitudes of spatial Fourier modes (the 5D and 7D models). Correspondence of the reduced models to the original system is demonstrated numerically. Computational verification of the hyperbolicity criterion is performed for the reduced models: the distribution of angles of intersection for stable and unstable manifolds on the attractor is separated from zero, i.e., the touches are excluded. The example considered gives a partial justification for the old hopes that the chaotic behavior of autonomous distributed systems may be associated with uniformly hyperbolic attractors.     

“Yet Once More”: The Double-Slit Experiment and Quantum Discontinuity

This article reconsiders the double-slit experiment from the nonrealist or, in terms of this article, “reality-without-realism” (RWR) perspective, grounded in the combination of three forms of quantum discontinuity: (1) “Heisenberg discontinuity”, defined by the impossibility of a representation or even conception of how quantum phenomena come about, even though quantum theory (such as quantum mechanics or quantum field theory) predicts the data in question strictly in accord with what is observed in quantum experiments); (2) “Bohr discontinuity”, defined, under the assumption of Heisenberg discontinuity, by the view that quantum phenomena and the data observed therein are described by classical and not quantum theory, even though classical physics cannot predict them; and (3) “Dirac discontinuity” (not considered by Dirac himself, but suggested by his equation), according to which the concept of a quantum object, such as a photon or electron, is an idealization only applicable at the time of observation and not to something that exists independently in nature. Dirac discontinuity is of particular importance for the article’s foundational argument and its analysis of the double-slit experiment.