Mackay,Anti-Mackay,Double-Mackay,Pseudo-Mackay,and Related Icosahedral Shell Clusters

Mackay introduced two important crystallographic concepts in a short paper published 40 years ago. One is the icosahedral shell structure (iss) consisting of concentric icosahedra displaying fivefold rotational symmetry. The number of atoms contained within these icosahedral shells and subshells agrees well with the magic numbers in rare gas clusters, (C₆₀) _N molecules, and some metal clusters determined by mass spectroscopy or simulated on energy considerations. The cluster of 55 atoms within the second icosahedral shell occurs frequently and has been called Mackay icosahedron, or simply MI, which occurs not only in various clusters, but also in intermetallic compounds and quasicrystals. The second concept is the hierarchic icosahedral structures caused by the presence of a stacking fault in the fcc packing of the successive triangular faces in the iss. For instance, a fault occurs after the ABC layers resulting an ABCB packing. This is, in fact, a hierarchic icosahedral structure of a core icosahedron connected to 12 outer icosahedra by vertex sharing, or an icosahedron of icosahedra (double MI. Contrary to Mackay's iss, a faulted hierarchic icosahedral shell is, in fact, a twinlike face capping of the underlying triangles; it is, therefore, called an anti-Mackay cluster. The hierarchic icosahedral structure in an Al-Mn-Pd icosahedral quasicrystal has a core of body-centered cube rather than an icosahedron and, therefore, is called a pseudo-Mackay cluster. The hierarchic icosahedral structures have been studied separately in the past in the fields of clusters, nanoparticles, intermetallic compounds, and quasicrystals, but the underlying geometry should be the same. In the following a unified geometrical analysis is presented.     

Microwave-assisted polymer chemistry: Heck-reaction, transesterification, Baeyer-Villiger oxidation, oxazoline polymerization, acrylamides, and porous materials

Several questions are still open concerning the different effects of microwave (MW) irradiation in organic and macromolecular chemistry. Analyzing experimental results on a relatively broad investigation area, we came to elucidate three main effects of microwave irradiation: efficient non-contact heating, an accelerating effect, and what we term a special effect. In this paper, we report the first MW-assisted synthesis of poly(2,5-dibutoxy-1,4-phenylenevinylene) via Heck-polycondensation as an example for efficient heating. The facile synthesis of the higher lactones 1-oxa-2-oxocyclooctanone and 1-oxa-2-oxocyclononanone via Baeyer-Villiger reaction offers indeed an example for the MW-accelerating effect. A survey of our recent work is also given to explain the effects more in detail and to provide examples of the special MW effect.     

Eine mikromethode der flammen-atomabsorptions- und emissionsspektrometrie (platinschlaufen-methode)—II: Die bestimmung von As,Bi, Cd,Hg, Pb,Sb, Se,Te, Tl,Zn/Li,Na, K,Cs, Sr,Ba

This paper described the continuation of the work of Part I dealing with a microanalytical method in which the sample is introduced into a flame using an electrically heated platinum loop. This device is used in connection with an atomic absorption (AA) spectrometer. The detection limits are one to two orders of magnitude better than those of conventional flame AAS. The reproducibility depends on the element and is in general 3–5% (relative standard deviation) for concentrations in the $\text{ng}\text{ml}$ range. The platinum loop method can be also applied for flame emission analysis of small amounts of sample or the determination of low concentrations (alkalis). This application gives access to determinations in the lower ng or the pg range (detection limit of lithium: 0.6 pg).     

Atomization mechanism and determination of Ag, Be, Cd, Li, Na, Sn and Zn in uranium-plutonium matrices by ETA-AAS

The atomization processes involved in the Electrothermal Atomization-Atomic Absorption Spectrometric (ETA-AAS) determination of Ag, Be, Cd, Li, Na, Sn and Zn in the presence of an uranium-plutonium matrix containing 25% Pu have been investigated. The significant fall in the absorbance signal for Ag, Cd, Na and Zn in an uranium matrix and its restoration in the presence of plutonium is probably correlated with the change in the partial pressure of oxygen released from the matrix at/below the signal appearance temperature (T_app). In case of Li and Sn, the signal remains unaffected irrespective of the U-Pu matrix which might be due to a high T_app for these analytes. Regarding Be, the steep suppression of the signal in the presence of the plutonium matrix compared to an uranium matrix can be ascribed to the formation of stable Pu-Be compounds (PuBe₁₃). Based on these studies, analytical procedures have been developed for the direct determination of nanogram amounts of these analytes in an U-Pu matrix with an average precision of 9% RSD.     

Determination of Cr,Mn, Fe,Cu, Zn,As, Se,Cd, Hg and Pb in Ginseng by Inductively Coupled Plasma Mass Spectroscopy

Inductively coupled plasma mass spectroscopy (ICP-MS) has become an established technique of multi-element trace analysis, and it has been used for the analysis for the variety of samples,especially the samples of traditional Chinese medicine.     

Open Chemistry,JupyterLab, REST,and quantum chemistry

Quantum chemistry must evolve if it wants to fully leverage the benefits of the internet age, where the worldwide web offers a vast tapestry of tools that enable users to communicate and interact with complex data at the speed and convenience of a button press. The Open Chemistry project has developed an open‐source framework that offers an end‐to‐end solution for producing, sharing, and visualizing quantum chemical data interactively on the web using an array of modern tools and approaches. These tools build on some of the best open‐source community projects such as Jupyter for interactive online notebooks, coupled with 3D accelerated visualization, state‐of‐the‐art computational chemistry codes including NWChem and Psi4, and emerging machine learning and data mining tools such as ChemML and ANI. They offer flexible formats to import and export data, along with approaches to compare computational and experimental data.     

Dendrimers Functionalized with Palladium Complexes of N-, N,N-, and N,N,N-Ligands

Pyridine, pyridine imine, and bipyridine imine ligands functionalized by a phenol have been synthesized and characterized, in many cases by X-ray diffraction. Several of these N-, N,N-, and N,N,N,-ligands have been grafted onto the surface of phosphorhydrazone dendrimers, from generation 1 to generation 3. The complexation ability of these monomers and dendrimers towards palladium(II) has been assayed. The corresponding complexes have been either isolated or prepared in situ. In both cases, the monomeric and dendritic complexes have been tested as catalysts in Heck couplings and in Sonogashira couplings. In some cases, a positive dendritic effect has been observed, that is, an increase of the catalytic efficiency proportional to the dendrimer generation.     

The versatile,functional polyether,polyepichlorohydrin: History,synthesis, and applications

Polyepichlorohydrin (PECH) is a functional polyether first synthesized in the 1950's by the catalytic ring opening polymerization of epichlorohydrin (ECH), its inexpensive epoxide pre-cursor. PECH elastomers are used in diverse commercial applications due to their unique combination of properties including low temperature flexibility and heat and oil resistance. PECH holds an interesting place in polymer history as its synthesis led to the discovery of highly effective aluminum-based catalysts for epoxide polymerizations and a new class of high molecular weight polyether elastomers by an exceptional polymer chemist, Edwin J. Vandenberg. ECH is an ideal feedstock for polymer materials as it is functional, inexpensive, and produced through environmentally friendly means. However, due to the alkyl chloride pendant, polymerizations involving ECH are difficult and limited synthetic advancement has occurred until very recently. This focused review will discuss modern polymerization methods involving ECH while giving a historical perspective on the evolution of these techniques. We will also review applications of ECH-based polymers and discuss the future development of these materials. We hope to convince the reader to explore ECH-based materials in their own work.     

规范 · 推论 · 交往 · 世界—布兰顿哲学的四个维度

布兰顿首先将“规范”当作人类活动的核心特征,并以实用主义的方式回答了规范的性质问题;然后再由规范引出推论作为语言意义的根据,并澄清了实质推论的基础地位;接着又进一步,细致解析了推论的实际运作机制,将推论落实于社会交往的过程之中,认为社会交往本质上是不同成员之间的道义计分;最后,在推论主义框架下解释了真、表象语汇的必要性,并对语言与世界的关系做出了推论主义的说明。他的哲学体系由规范、推论、交往、世界四个维度组成。它们层层递进,形成了一个具有严密内在结构的有机整体。原本分散甚至对立的论题,在此得到整合。     

Atomization mechanism and determination of Ag,Be, Cd,Li, Na,Sn and Zn in uranium-plutonium matrices by ETA-AAS

The atomization processes involved in the Electrothermal Atomization-Atomic Absorption Spectrometric (ETA-AAS) determination of Ag, Be, Cd, Li, Na, Sn and Zn in the presence of an uranium-plutonium matrix containing 25% Pu have been investigated. The significant fall in the absorbance signal for Ag, Cd, Na and Zn in an uranium matrix and its restoration in the presence of plutonium is probably correlated with the change in the partial pressure of oxygen released from the matrix at/below the signal appearance temperature (T(app)). In case of Li and Sn, the signal remains unaffected irrespective of the U-Pu matrix which might be due to a high T(app) for these analytes. Regarding Be, the steep suppression of the signal in the presence of the plutonium matrix compared to an uranium matrix can be ascribed to the formation of stable Pu-Be compounds (PuBe(13)). Based on these studies, analytical procedures have been developed for the direct determination of nanogram amounts of these analytes in an U-Pu matrix with an average precision of 9% RSD.     

The certification of the contents of Cd, Co, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se, Tl and Cr in a city waste incineration ash

Summary The analysis of ashes being of increasing importance, a reference material was prepared from fly ash of a city waste incinerator. The procedures of preparation, homogeneity and stability testing are described as well as the way of certification of elements of major importance: Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se and Tl.

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Zertifizierung der Gehalte an Cd, Co, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se, Tl und Cr in einer Stadtmüll-Verbrennungsasche

Zusammenfassung Da die Analyse von Aschen zunehmend an Bedeutung gewinnt, wurde von der Flugasche einer Stadtmüll-Verbrennungsanlage ein Referenzmaterial hergestellt. Die Methoden der Herstellung sowie der Homogenitätsund Stabilitätsprüfung werden beschrieben und die Art der Zertifizierung der Elemente von hauptsächlicher Bedeutung aufgezeigt (Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se, Tl).

     

Comparison of small metal clusters: Ni, Pd, Pt, Cu, Ag, Au

Structures of small clusters of Ni, Pd, Pt, Cu, Ag, and Au with n=2–34 and n=55 atoms are calculated as functions of number of atoms and temperature by the simulated annealing Monte Carlo method using an embedded atom potential.     

Über die Mischbarkeit von UN mit LaN,CeN, PrN,NdN, SmN,GdN, DyN,und ErN

X-Ray studies of the mixed nitride phases indicate complete miscibility in all cases. Lattice parameters generally showed negative deviations from the additivity rule.

Teilauszug aus der Dissertation des Dipl.-Ing.J. Waldhart an der Technischen Universität Wien, Österreich.     

Formation,structure, composition,and catalytic properties of Ni-, Cu-, Mn-, Fe-, and co-containing films on aluminum

Layers containing oxygen compounds of copper and nickel and(or) of one of transition metals (manganese, cobalt, iron) were formed on an aluminum alloy by the plasma-electrolytic oxidation method. The layers were characterized by means of X-ray phase analysis, X-ray fluorescence microanalysis, and scanning electron microscopy and tested in the reaction of CO oxidation to CO₂.     

Photolyse von 2, 2, 4, 4-Tetramethylcyclobutanon-Derivaten

The photochemical reactions of the 2, 2, 4, 4-tetramethylcyclobutanones 1–6 carrying various substituents in 3-position were investigated. The major reaction in alcoholic solution or in the presence of other protic compounds was the formation of the semicyclic acetals 7–12 . Parallel to this reaction decarbonylation occurred, leading to stable cyclopropane derivatives in some cases, depending on the substituents present. Cyclopropanes with an exocyclic double bond underwent ring opening easily or, in case of an exocyclic carbon-nitrogen double bond, added alcohol, thus forming cyclopropane O, N-ketals. Alkyl-acyl biradicals are proposed as common intermediates for both photoreactions. Based on analogy to similar photoreactions reported in the literature, the formation of the semicyclic acetals is assumed to involve a carbene intermediate.     

Partial synthesis of aromatic carotenoids,tedanin, agelaxanthin a,tethyatene, and renieratene

Aromatic carotenoids, tedanin, agelaxanthin A, and tethyatene were synthesized from 0- acetyl-6-citraurin derived from natural zeaxanthin, and tethyatene was further transformed into renieratene as the first example of aromatization of an alicyclic ring in carotenoids.     

Spectrochemical determination of trace As, Fe, Hg, Mn, and Pb by an argon-stabilized U-shaped DC arc

Argon-stabilized U-shaped DC arc with a system for aerosol introduction was used for the determination of As, Fe, Hg, Mn, and Pb. By applying a computer program performing a time integration of the registered signals and by optimizing the working conditions of an U-shaped arc plasma, the detection capability for As, Fe, Hg, Mn, and Pb was improved, which contributed to the lowering of the detection limits. The lowest detection limits for Fe, Mn, and Pb were achieved during an integration time of 20 s, and for As and Hg during an integration time of 30 s, and their values were 1.1, 0.1, 0.9, 15, and 2.6 ng/mL, respectively. The detection limits obtained by our method with optimal integration times were compared with the detection limits obtained using other methods: inductively coupled plasma-atomic emission spectrometry (ICP-AES), directly coupled plasma-atomic emission spectrometry (DCP-AES), microwave-induced plasma-atomic emission spectrometry (MIP-AES), inductively coupled plasma-mass spectrometry (ICP-MS), and an improved thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). The text was submitted by the authors in English.     

First comprehensive bakkane approach: stereoselective and efficient dichloroketene-based total syntheses of (+/-)- and (-)-9-acetoxyfukinanolide, (+/-)- and (+)-bakkenolide A, (-)-bakkenolides III,B, C,H, L,V, and X, (+/-)- and (-)-homogynolide A, (+/-)-homogynolide B,and (+/-)-palmosalide C

Cycloaddition of dichloroketene with dimethylcyclohexenes has been used as the key reaction in an efficient, general approach to the bakkanes. New methods and methodologies that have been developed in this work include spiro beta-methylene-gamma-butyrolactonizations, a vicinal dicarboxylation, an angelic ester preparation, a transesterification, an epoxy ketone double reduction, and a retro aldol-aldol approach to low-energy aldol isomers.