Survival of the Fittest Nanojar: Stepwise Breakdown of Polydisperse Cu27−Cu31 Nanojar Mixtures into Monodisperse Cu27(CO3) and Cu31(SO4) Nanojars

Nanojars are emerging as a class of anion sequestration agents of unparalleled efficiency. Dinegative oxoanions (e.g., carbonate, sulfate) template the formation of a series of homologous nanojars [Cu(OH)(pyrazolato)]_n (n=27–31). Pyridine selectively transforms less stable, larger CO₃^2? nanojars (n=30, 31) into more stable, smaller ones (n=27, 29), but leaves all SO₄^2? nanojars (n=27–29, 31) intact. Ammonia, in turn, transforms all less stable nanojars into the most stable one and allows the isolation of pure [CO₃^2??{Cu(OH)(pz)}₂₇] and [SO₄^2??{Cu(OH)(pz)}₃₁]. A comprehensive picture of the solution and solid‐state intricacies of nanojars was revealed by a combination of variable temperature NMR spectroscopy, tandem mass spectrometry, and X‐ray crystallography.     

High dose implantation of Eu into α-Fe

Abstract

At the UNILAC injector at GSI ¹⁵¹Eu was implanted into an α-Fe foil [8]. According to our simulation code of the energy loss of the implanted ions an energy of 1.5 MeV was chosen to minimize the sputter yield during implantation and to produce the highest possible Eu concentration near the surface of the sample. After the irradiation with a dose of 3.6 · 10¹⁷ Eu/cm² the implantation profile should reach its maximum of 8 at. % Eu at the surface of the sample and its width should be 1700 Å.     

Photoelectric charging of coal and pyrite powders using excimer-UV-light sources

Coal and pyrite powders have been irradiated by narrow-band excimer-UV-radiation. A new type of Xenon and Xenonchloride sources were used that have the potential to fit to industrial processes. The powders get charged by photoemission of electrons under high-vacuum conditions. No photoemission-charging was detected in air. Saturation of the photocharge was observed with increasing irradiation time and-intensity.     

The Miniaturized Mössbauer Spectrometer MIMOS II for Extraterrestrial and Outdoor Terrestrial Applications: A Status Report

Hyperfine Interactions -     

Students constructing meaning for the number line in small-group discussions: negotiation of essential epistemological issues of visual representations

In mathematics classroom interaction, the multiple meanings of mathematical visual diagrams are often ignored; instead, depending on the given situation, they are read in a well-defined and unitary way. Mathematical visual representations are thus used even less in their epistemological function for learning, but more as pre-given subject matter. The purpose of this paper is to elaborate opportunities for negotiating and clarifying differences, dealing with a great variety of ways of interpreting visual diagrams that are brought into focus in interaction. Theory-based qualitative analyses of two exemplifying video episodes of small-group discussions negotiating their ideas on the topic “number line” show differences of meaning and the importance of conventions followed by mathematical deductions. Two mutually exclusive teacher behaviors within the communicative acts, reconstructed as a dominating way of instruction and a moderating way of focusing, are identified.     

Adjacent Lone Pair (ALP) Effect: A Computational Approach for Its Origin

The adjacent lone pair (ALP) effect is an experimental phenomenon in certain nitrogenous heterocyclic systems exhibiting the preference of the products with lone pairs separated over other isomers with lone pairs adjacent. A theoretical elucidation of the ALP effect requires the decomposition of intramolecular energy terms and the isolation of lone pair–lone pair interactions. Here we used the block‐localized wavefunction (BLW) method within the ab initio valence bond (VB) theory to derive the strictly localized orbitals which are used to accommodate one‐atom centered lone pairs and two‐atom centered σ or π bonds. As such, interactions among electron pairs can be directly derived. Two‐electron integrals between adjacent lone pairs do not support the view that the lone pair–lone pair repulsion is responsible for the ALP effect. Instead, the disabling of π conjugation greatly diminishes the ALP effect, indicating that the reduction of π conjugation in deprotonated forms with two σ lone pairs adjacent is one of the major causes for the ALP effect. Further electrostatic potential analysis and intramolecular energy decomposition confirm that the other key factor is the favorable electrostatic attraction within the isomers with lone pairs separated.     

Compatibility study of oxide and olivine cathode materials with lithium aluminum titanium phosphate

The compatibility of the solid electrolyte Li_1.5Al_0.5Ti_1.5(PO₄)₃ (LATP) with the cathode materials LiCoO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, and LiMn_0.5Fe_0.5PO₄ was investigated in a co-sintering study. Mixtures of LATP and the different cathode materials were sintered at various temperatures and subsequently analyzed by thermal analysis, X-ray diffraction, and electron microscopy. Oxide cathode materials display a rapid decomposition reaction with the electrolyte material even at temperatures as low as 500 °C, while olivine cathode materials are much more stable. The oxide cathode materials tend to decompose to lithium-free compounds, leaving lithium to form Li₃PO₄ and other metal phosphates. In contrast, the olivine cathode materials decompose to mixed phosphates, which can, in part, still be electrochemically active. Among the olivine cathode materials, LiFePO₄ demonstrated the most promising results. No secondary phases were detected by X-ray diffraction after sintering a LATP/LiFePO₄ mixture at temperatures as high as 700 °C. Electron microscopy revealed a small secondary phase probably consisting of Li₂FeTi(PO₄)₃, which is ionically conductive and should be electrochemically active as well.     

A direct integration method for analysis of a certain class of non-linear dynamic problems

Summary A new efficient algorithm for direct integration of a classs of non-linear dynamic systems is presented. The systems which can be effectively solved by the proposed algorithm stem usually from spatial discretization of problems in non-linear elasticity and some related fields. For this sort of equations the algorithm is proven to be unconditionally stable. The global (accumulated) truncation error is of order t², hence relatively high precision is attained without iteration of integration steps. A series of examples is successfully solved for testing purposes.

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Übersicht Es wird ein neuer effizienter Algorithmus für die direkte Integration einer Klasse von nichtlinearen dynamischen Systemen angegeben. Systeme, die mit Hilfe des vorgeschlagenen Algorithmus effektiv gelöst werden können, entstehen meist bei der räumlichen Diskretisierung von Problemen der nicht-linearen Elastizität und verwandten Gebieten. Für Gleichungen dieser Art wird die unbedingte Stabilität des Algorithmus bewiesen. Da der globale (akkumulierte) Abbruchsfehler eine Größenordnung von t ² hat, kann eine relativ hohe Genauigkeit ohne Iteration der Integrationsschritte erreicht werden. Einige Testbeispiele wurden erfolgreich gelöst.

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The author wishes to express his gratitude to the Alexander-von-Humboldt-Foundation and to the Institut für Allgemeine Bauingenieurmethoden, TU Berlin, for creation of the conditions enabling carrying out of this research. He wishes to thank S. Ginsburg for his help in programming and for the supplying of comparable material.