Zusammenhang von elektrochemischkonstitutivem und kolloidem Aufbau reinster Farbsole

Zusammenfassung 1. Es werden mittels Elektrodialyse und Elektrodekantierung die hochgereinigten azidoiden blauen Farbsole aus Congorot, Congorubin, Congokorinth G, Benzopurpurin 4 B und Chicagoblau 6 B sowie zum Vergleich das basische Farbsol von Nachtblau hergestellt. 2. Diese Sole werden in bezug auf ihre elektrochemischkonstitutiven sowie Assoziations?nderungen durch Bestimmung ihrer thermischen Leitf?higkeitsabh?ngigkeit (x, t-Kurve) und deren Reversibilit?t sowie der Verdünnungs?nderung ihrer molekularen Leitf?higkeiten μ untersucht. 3. Es wird gezeigt, wie bei den genannten azidoiden Farbsolen, die s?mtliche Aminosulfos?uren darstellen, die Assoziationskr?fte mit der inneren Salzbildung wachsen und wie andererseits mit der Zunahme der polaren sauren Gruppen infolge der thermischen oder Verdünnungsaminolyse des inneren Salzes die Desassoziation erh?ht wird. Das Nachhinken der Leitf?higkeitswerte beim Wiederabkühlen ist der Ausdruck einer Assoziationshysteresis. Mit der Zeit stellt sich beim Stehen ein Assoziationsgleichgewicht ein. 4. Gegenüber dem Congoblau weisen Congorubin und Congokorinth eine Verminderung um eine NH₂-Gruppe, dagegen eine zus?tzliche OH-Gruppe auf, welche je nach ihrer Stellung den sauren Charakter mehr oder weniger verst?rkt. Die Halbierung der inneren Salzbildung und die Steigerung der Gesamtladung pr?gen sich genau in der zu erwartenden Reihenfolge steigender molekularer Leitf?higkeit und der Desassoziation aus. Auch das Verhalten des azidoiden Benzopurpurin- und Chicagoblausols ist hinsichtlich desx, t-Ganges und der μ-Werte sowie der Kolloid?quivalente durchaus das konstitutiv erwartete. 5. Es lassen sich plausible Modelle des Aufbaues der verschiedenen ionischen Micellen bei den einzelnen Farbsolen aufstellen. 6. Die Beziehungen der Farbsole zu den Seifensolen einerseits und den Proteinsolen andererseits werden kurz er?rtert.     

Development of electrochemistry in Serbia-challenges and perspectives

In this review, the development of electrochemistry in Serbia is presented, with an accent on historical moments from the beginning up to contemporary research directions. The pioneer in the establishment of electrochemical science was Professor Panta S. Tutundzic, who was elected Assistant Professor in Physical Chemistry and Electrochemistry in 1925, when the Department of Technology, previously integrated within the Technical Faculty in Belgrade, was established as a separate department. From the time of Professor Tutundzic′s group to today, a community of many eminent researchers has been involved in electrochemistry development, creating the world-renowned Belgrade School of Electrochemistry. It was not actually a formal school of electrochemistry but rather a variety of research directions, and first of all people doing excellent electrochemical science recognized at the international level. As one of the members of the contemporary active electrochemistry community from Serbia, and successors of the Belgrade School of Electrochemistry, I have both the special honor and the responsibility of presenting the historical contribution of such outstanding and internationally recognized scientists in the most appropriate way. Having in mind that any school and research area is predominantly determined by human resources, I will focus on the great contribution of the most prominent electrochemists, from the founders up to those active today. The main research directions were and still are electrodeposition, electrochemical reaction kinetics, electrocatalysis, energy production and storage, and corrosion and corrosion protection.

     

Complete (1)H NMR spectral fingerprint of huperzine A

Complete analysis of the (1)H NMR spectrum of huperzine A, 1-amino-13-ethylidene-11-methyl-6-aza-tricyclo[7.3.1.0(2, 7)]trideca-2(7),3,10-trien-5-one, a Lycopodium alkaloid and anti-Alzheimer drug lead containing an ABCD(E)(MN)(OP)X(3)Y(3)-type system of 15 nonexchangeable proton spins, is reported for the first time, and earlier assignments are corrected. The complete (1)H parameter set of 11 chemical shifts clarifies the diastereotopism of both methylene groups, and provides a total of 38 observed H,H-couplings including 31 long-range ((4-6)J) connectivities. The NMR data is consistent with the comparatively rigid alicyclic backbone predicted by molecular mechanics calculations, and forms the basis for (1)H NMR fingerprint analysis for the purpose of dereplication, purity analysis, and elucidation of structural analogs.     

Synthesis, crystal structure, spectroscopic and thermal properties of [Et4N][Ta6Br12(H2O)6]Br4·4H2O (Et=ethyl)—A new compound with the paramagnetic [Ta6Br12] cluster core

A new hexanuclear cluster compound, [Et₄N][Ta₆Br₁₂(H₂O)₆]Br₄·4H₂O (Et=ethyl) (1), with the paramagnetic [Ta₆Br₁₂]³⁺ cluster entity, was synthesized and characterized by elemental and TG/DTA analyses, IR and UV/Vis spectroscopy and by a single-crystal X-ray diffraction study. The presence of the paramagnetic [Ta₆Br₁₂]³⁺ unit was confirmed also by the room-temperature magnetic and EPR measurements. The compound crystallizes in the tetragonal I4₁/a space group, with a=14.299(5), c=21.241(5) Å, Z=4, R₁(F)/wR₂(F²)=0.0296/0.0811. The structure contains discrete [Ta₆Br₁₂(H₂O)₆]³⁺ cations with an octahedron of metal atoms edge-bridged by bromine atoms and with water molecules occupying all six terminal positions. The cluster units are positioned in the vertices of the three-dimensional (pseudo)diamond lattice. The structure shows similarities with literature reported structures of cluster compounds crystallizing in the diamond space group.     

Cimicifuga species identification by high performance liquid chromatography-photodiode array/mass spectrometric/evaporative light scattering detection for quality control of black cohosh products

Black cohosh has become one of the most important herbal products in the US dietary supplements market. It is manufactured from roots and rhizomes of Cimicifuga racemosa (Ranunculaceae). Botanical identification of the raw starting material is a key step in the quality control of black cohosh preparations. The present report summarizes a fingerprinting approach based on high performance liquid chromatography-photodiode array/mass spectrometric/evaporative light scattering detection (HPLC-PDA/MS/ELSD) that has been developed and validated using a total of 10 Cimicifuga species. These include three North American species, Cimicifuga racemosa, Cimicifuga americana, Cimicifuga rubifolia, and seven Asian species, Cimicifuga acerina, Cimicifuga biternat, Cimicifuga dahurica, Cimicifuga heracleifolia, Cimicifuga japonica, Cimicifuga foetida, and Cimicifuga simplex. The chemotaxonomic distinctiveness of the HPLC fingerprints allows identification of all 10 Cimicifuga species. The triterpene glycoside cimigenol-3-O-arabinoside (3), cimifugin (12), and cimifugin-3-O-glucoside (18) were determined to be suitable species-specific markers for the distinction of C. racemosa from the other Cimicifuga species. In addition to identification, the fingerprint method provided insight into chemical interconversion processes occurring between the diverse triterpene glycosides contained in black cohosh. The reported method has proven its usefulness in the botanical standardization and quality control of black cohosh products.     

On prestress stiffness analysis of bolt-plate contact assemblies

Bolt connections are among the most important connections used in structures. The stiffnesses of the bolt and of the connected members are the primary qualities that control the lifetime of the connection. The stiffness of the bolt can be estimated rather easily, in contrast to the member stiffness, but with finite element (FE) and contact analysis, it is possible to find the stiffness of the member. In the case of many connections and for practical applications, it is not suitable to make a full FE analysis. The purpose of the present paper is to find simplified expressions for the stiffness of the member, including the case when the width of the member is limited. The calculation of the stiffness is based on the FE, including the solution to the contact problem, and we express the stiffness as a function of the elastic energy in the structure, whereby the definition of the displacements related to the stiffness is circumvented. The contact analysis is performed using a method where iterations are not necessary, and the results are compared to alternative available results. New practical formulas for the stiffnesses are suggested.     

On a numerical exact solution to the many-body problem in one dimension

The Hamiltonian matrix for up to 30 particles has been diagonalised for three different interactions in a plane wave base, among them a hard-core potential. Restriction was made to the spin-polarised case in one space dimension. In the present feasibility study much weight is placed on the questions of convergence, numerical stability and efficiency. Some selected results on binding energies, excitation spectra, momentum distributions and spatial correlation functions are presented and discussed.