Effect of spatial heterogeneity on level of rejuvenation in Ni80P20 metallic glass

Understanding the relation between spatial heterogeneity and structural rejuvenation is one of the hottest topics in the field of metallic glasses (MGs). In this work, molecular dynamics (MD) simulation is implemented to discover the effects of initial spatial heterogeneity on the level of rejuvenation in the Ni$_{80}$P$_{20 }$MGs. For this purpose, the samples are prepared with cooling rates of $10^{10}$ K/s-$10^{12}$ K/s to make glassy alloys with different atomic configurations. Firstly, it is found that the increase in the cooling rate leads the Gaussian-type shear modulus distribution to widen, indicating the aggregations in both elastically soft and hard regions. After the primary evaluations, the elastostatic loading is also used to transform structural rejuvenation into the atomic configurations. The results indicate that the sample with intermediate structural heterogeneity prepared with 10$^{11}$ K/s exhibits the maximum structural rejuvenation which is due to the fact that the atomic configuration in an intermediate structure contains more potential sites for generating the maximum atomic rearrangement and loosely packed regions under an external excitation. The features of atomic rearrangement and structural changes under the rejuvenation process are discussed in detail.     

X-ray crystal structures of halogen containing nucleobase derivatives in unsolvated and DMSO solvated forms

A series of halogenated nucleobase derivatives 1–4 is reported to yield solvent-free (2) and DMSO solvated crystals (1, 3, 4) on the crystallization from DMSO with one of them (4) containing an additional molecule of water. The molecular and crystal structures are described and comparatively discussed with reference to previous results on related compounds. The molecule of 1 is planar, molecules of 2 and 3 show syn alignment with reference to the heterocyclic ring and common C2′-endo conformation of the ribose residue, while 4 is also syn aligned but C4′-exo in the sugar conformation. The packing structures reveal typical aggregations created via networks of hydrogen bonds. These involve conventional N–H···N, N–H···O and O–H···O interactions between nucleobase and ribose units as well as solvent molecules, additionally supported by weak C–H···O contacts but excluding the participation of halogen···halogen interactions as well as halogen···heteroatom contacts in the supramolecular structure formation.     

Kolmogorov-Smirnov two-sample test based on regression rank scores

We derive the two-sample Kolmogorov-Smirnov type test when a nuisance linear regression is present. The test is based on regression rank scores and provides a natural extension of the classical Kolmogorov-Smirnov test. Its asymptotic distributions under the hypothesis and the local alternatives coincide with those of the classical test. (Supplement to the special issue of Appl. Math. 53 (2008), No. 3) This work was supported by the Czech Science Foundation under Grant No. 201/05/H007 and by Research Project LC06024.     

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Spectroelectrochemical Investigation of the One‐Electron Reduction of Nonplanar Nickel(II) Porphyrins

The electrochemical reduction of a series of nickel porphyrins with an increasing number of substituents was investigated in acetonitrile. A one‐electron reduction of [5,15‐bis(1‐ethylpropyl)porphyrinato]nickel(II) leads to π‐anion radicals and to efficient formation of phlorin anions, presumably by disproportionation and subsequent protonation of the doubly reduced species. The phlorin anion was identified by using cyclic voltammetry and UV/Vis and resonance Raman spectroelectrochemistry, complemented by quantum‐chemical calculations to assign the spectral signatures. The theoretical analysis of the potential‐energy landscape of the singly reduced species suggests a thermally activated intersystem crossing that populates the quartet state and thus lowers the energy barrier towards disproportionation channels. Structure–reactivity correlations are investigated by considering different substitution patterns of the investigated nickel(II) porphyrin cores, that is, for the porphyrin with additional β‐aryl ([5,15‐bis(1‐ethylpropyl)‐2,8,12,18‐tetra(p‐tolyl)porphyrinato]nickel(II)) and meso‐alkyl substitution ([5,10,15,20‐tetrakis(1‐ethylpropyl)porphyrinato]nickel(II)), no phlorin anion formation was observed under electrochemical conditions. This observation is correlated either to kinetic inhibition of the disproportionation reaction or to lower reactivity of the subsequently formed doubly reduced species towards protonation.