Distribution of critical values of miniversal deformations of parabolic singularities

Summary We consider, in this paper, the critical values mapping, which associates with any polynomial from underdiagonal miniversal deformation of the family of parabolic singularities, the set of its critical values. We showed that the restriction of this mapping to the subset of polynomials withk different critical values,k2, is a covering of the space of unorderedk-tuples of different complex numbers. In particular, it is proved that the connected components of such subsets areK(, 1) spaces.     

Anionic Indole N-carbamoyl N --> C translocation. A directed remote metalation route to 2-Aryl- and 2-heteroarylindoles. synthesis of benz[a]carbazoles and Indeno[1,2-b]indoles

A new LDA-induced anionic N-C carbamoyl migration of 2-arylindoles (7) is reported. Treatment of N-carbamoylindoles 10 and 13, readily available by direct and ipso-borodesilylative Suzuki-Miyaura cross-coupling routes from 8 and 12, respectively, provides a general route to functionalized 2-arylindoles 11 and 14, respectively (Tables 1 and 2). The reaction has been applied to the synthesis of benzo[ a]carbazoles 16 and indeno[1,2- b]indoles 18, and its intramolecularity has been established by a crossover experiment (Scheme 4).     

Subgraphs of Random Match-Graphs

 A simple graph (match-graph) generated by two-cycles of a general model of a random digraph is considered. Based on relations between a special case of such a graph and a classical model of a random graph, some results about the existence and the number of subgraphs of a given type in a random match-graph are presented. Received: December 8, 1997 Final version received: September 16, 1999     

Temperature Compensation by Embedded Temperature Variation Method for an AC Voltammeric Analyzer of Electroplating Baths

An in‐situ sensor utilizing a variety of DC‐ and AC‐voltammetric techniques is an integral component of the on‐line monitoring system that provides a complete chemical analysis of different plating solutions by predicting concentration values of all deliberately‐added bath constituents with a single device despite differences in the constituents’ chemical properties. Such sensors are employed routinely for electroplating process control in semiconductor manufacturing. This voltammetric approach exploits quantitatively the physicochemical processes (like adsorption) which are temperature dependent. Therefore the accuracy of analyte concentration predictions can be affected adversely by temperature fluctuations. This paper introduces a novel comprehensive method which allows the mitigation of temperature variation effects on voltammetric scans allowing accurate concentration prediction. Specifically, this study introduces a multi‐step rigorous routine for the development and subsequent validation of the analytical method utilizing a chemometric model with temperature variation embedded in regression for exemplary determination of leveler additive concentration. This approach analyses the effect on AC voltammograms resulting from two qualitatively indistinguishable sources of variation: leveler concentration and temperature. A critical step of this routine of fundamental novelty, which aims to select the variables (index points of voltammogram) to be utilized for building of the analytical model in the presence of two concurrent sources of variation, is introduced to incorporate temperature variation.     

Temperature dependences of dual fluorescence as criterion for determining character of photoreactions

We performed comparative studies of the temperature quenching of dual fluorescence of acetonitrile solutions of several molecular probes with proton transfer reaction in an excited singlet state of 4′-(dieth-ylamino)-3-hydroxyflavone (FET), 1-methyl-2-(4-methoxy)phenyl-3-hydroxy-4(1H)-quinolone (QMOM), and 3-hydroxyflavone (3HF) parent molecule at different energies of excitation quanta. In accordance with expressions obtained from balance equations for photoreactions of the kinetic and thermodynamic character, the intensity ratios of fluorescence bands as functions of the degree of quenching behave differently. Namely, the quenching increases the relative intensity of bands normal form/tautomer for reactions of the kinetic type, retaining this ratio unchanged for reactions of the thermodynamic character. Our experimental studies showed that, for fluorescent probes with the kinetic reaction (3HF and QMOM), the intensity ratio fluorescence bands increases almost linearly with the degree of quenching, whereas, in the thermodynamic case (FET), this ratio is independent of this parameter. Conclusions about the character of reactions that we obtained in this work agree well with data of independent investigations of these molecules by laser spectroscopy with high time resolution, and the obtained relations allow us also to judge the mechanism of temperature quenching in the case of the reaction of the kinetic type. The method can be used for comparatively simple express selection of molecular probes, candidate for new applications.     

Mathematics teaching development as a human practice: identifying and drawing the threads

The didactic triangle links mathematics, teachers and students in a consideration of teaching?Clearning interactions in mathematics classrooms. This paper focuses on teachers and teaching in the development of fruitful learning experiences for students with mathematics. It recognises primarily that teachers are humans with personal characteristics, subject to a range of influences through the communities of which they are a part, and considers aspects of teachers?? personhood, identity and agency in designing teaching for the benefit of their students. Teaching is seen as a developmental process in which inquiry plays a central role, both in doing mathematics in the classroom and in exploring teaching practice. The teacher-as-inquirer in collaboration with outsider researchers leads to growth of knowledge in teaching through development of identity and agency for both groups. The inclusion of the outsider researcher brings an additional node into the didactic triangle.     

High performance Na-doped PbTe-PbS thermoelectric materials: electronic density of states modification and shape-controlled nanostructures

Thermoelectric heat-to-power generation is an attractive option for robust and environmentally friendly renewable energy production. Historically, the performance of thermoelectric materials has been limited by low efficiencies, related to the thermoelectric figure-of-merit ZT. Nanostructuring thermoelectric materials have shown to enhance ZT primarily via increasing phonon scattering, beneficially reducing lattice thermal conductivity. Conversely, density-of-states (DOS) engineering has also enhanced electronic transport properties. However, successfully joining the two approaches has proved elusive. Herein, we report a thermoelectric materials system whereby we can control both nanostructure formations to effectively reduce thermal conductivity, while concurrently modifying the electronic structure to significantly enhance thermoelectric power factor. We report that the thermoelectric system PbTe-PbS 12% doped with 2% Na produces shape-controlled cubic PbS nanostructures, which help reduce lattice thermal conductivity, while altering the solubility of PbS within the PbTe matrix beneficially modifies the DOS that allow for enhancements in thermoelectric power factor. These concomitant and synergistic effects result in a maximum ZT for 2% Na-doped PbTe-PbS 12% of 1.8 at 800 K.     

Design,synthesis, antitubercular and antibacterial activities of pyrrolo[3,2-b]pyridine-3-carboxamide linked 2-methoxypyridine derivatives and in silico docking studies

Abstract

A novel series pyrrolo[3,2-b]pyridine-3-carboxamide linked 2-methoxypyridine derivatives have been designed, synthesized and confirmed by FT-IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR, MS, and elemental analysis. The synthesized compounds were screened for their antitubercular activity using microplate alamar blue assay method and antibacterial activity. Among the tested compounds, 4- fluorophenyl (8m), 4- chlorophenyl (8n) and 4-methoxyphenyl (8i) showed potent anti-TB activity (3.12?µg/mL) in comparison with reference drug, Pyrazinamide ((3.12?µg/mL). In addition, all compounds were docked into DprE1 (PDB code: 4KW5) to explore their binding interactions at the active site. The compounds exhibited essential key interactions as that of reported DprE1 inhibitors and hence, the synthesized compounds may be considered as molecular scaffolds for antitubercular activity. Compounds, 4-chlorophenyl (8n) and 4-flurophenyl (8m) showed significant antibacterial activity against Escherichia coli and Staphylococcus aureus strains. In silico prediction of toxicities, druglikeness and drug score profiles of the tested compounds are promising.     

Synthons for syntheses of spiro[2.4]heptane analogues of prostaglandins

Methods for the preparation of synthons for syntheses of spiro[2.4]heptane analogues of prostaglandins are described. Two of them (1a and1b) enable the syntheses of 11-deoxy-type compounds and were prepared from spiro[2.4]heptan-4-one (3) which after transformation into the 5-phenylthio-,-unsaturated ketone5 was subjected to conjugate addition of organocuprate reagent6. The third synthon (2)-a potential intermediate in syntheses of complete spiro[2.4]heptane analogues of prostaglandins-was prepared from the bicyclic ketone10 byBaeyer-Villiger oxidation followed by epoxidation.

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Ausgangsverbindungen für die Synthese von Prostaglandin-analogen Spiro[2.4]heptanen

Zusammenfassung Es werden Synthesewege für Spiro[2.4]hepane als Analoge zu Prostaglandinen beschrieben. Zwei davon (1a und1b) ermöglichen die Synthese von Verbindungen des 11-Deoxy-Typs; sie wurden aus Spiro[2.4]heptan-4-on (3) dargestellt, das nach der Umwandlung zum 5-phenylthio-,-ungesättigten Keton5 einer konjugierten Addition von Organocuprat-Reagens6 unterworfen wurde. Das dritte (2), ein potentielles Zwischenprodukt in der Synthese von vollständigen Spiro[2.4]heptan-Analogen zu Prostaglandinen, wurde aus dem bicyclischen Keton10 durchBaeyer-Villiger-Oxidation gefolgt von einer Epoxidierung dargestellt.