Intramolecular cyclization of ω‐haloalkylsubstituted thiophosphorylacetonitriles: Synthesis and stereochemistry of 3‐cyano‐2‐oxo‐1,2‐thiaphosphacyclanes

Intramolecular S‐alkylation in a series of ω‐haloalkyl‐substituted thiophosphorylacetonitriles 5–7 presents an effective synthetic route to the hitherto unknown 3‐cyano‐2‐oxo‐1,2‐thiaphospholanes 14 and thiaphosphinanes 15 . The compounds were obtained as a mixture of cis‐ and trans‐isomers that were resolved to individual stereoisomers in most cases. For some of them, X‐ray diffraction analysis has been performed. It was shown that ³¹P NMR spectroscopy can be used to assign the stereochemistry of 3‐cyano‐2‐oxo‐1,2‐thiaphosphacyclanes. © 2002 John Wiley & Sons, Inc. Heteroatom Chem 13:1–21, 2002; DOI 10.1002/hc.1101     

Crystal Growth of Lanthanum Beryllium Hexaaluminate LaBeAl11O19 and Fields of Crystallization in the System La2O3–BeO–Al2O3

The fields of crystallization in the system La₂O₃–BeO–Al₂O₃ are investigated. Single crystals of LaBeAl₁₁O₁₉ were grown by the Czochralski technique.     

Structure and interactions in homopolymers and blends as studied by the methods of vibrational and nmr spectroscopy

The combination of IR, Raman and NMR spectroscopy was used in the study of the blends of semicrystalline and amorphous polymers with considerably different strength of intermolecular interactions: poly(ϵ-caprolactam)/polystyrene (PCL/PS), poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) and poly(N-methyllaurolactam)/poly(4-vinylphenol) (PNMLL/PVPh). In the vibrational and NMR spectra of the blends composed of non-interacting polymers (PCL/PS) and weakly interacting polymers (PEO/PMMA), no band changes were observed which would indicate changes of the conformational structures. ¹H NMR relaxation of the PCL and PS components in the blends is the same as in the respective homopolymers similarly treated. In the blends of weakly interacting polymers (PEO/PMMA), the crystallinity of PEO is influenced by the presence of PMMA and is negligible in the blends with less than 30 wt.-% of PEO. The rotating-frame spin-lattice relaxation time for protons T^H_1p of PMMA indicates close contact of the PMMA and PEO chains. In the blends PNMLL/PVPh with strong hydrogen-bonding interactions, both components are intimately mixed on a scale of 3–4 nm and significant shifts of some bands both in vibrational and in NMR spectra reveal changes of structure.     

Synthesis and reactivity of 1,2,4-triazolo[1,5-c]quinazolines

The preparation of 1,2,4-triazolo[1,5-c]quinazolines 4a-d , 5 , 8a-d by cyclocondensation of 1a-c with carboxylic acids and carboxylic anhydrides, respectively, is described. By different pathways, the 5-thioxo-5,6-dihydro-1,2,4-triazolo[1,5-c]quinazolines 4a-d react with hydrazine hydrate or amines with the formation of 5-substituted 1,2,4-triazolo[1,5-c]quinazolines 9 and 10a-d . Cyclocondensation of 9 with carboxylic acids, carboxylic anhydrides, and nitrous acid, respectively, leads to the new anellated heterocycles bis-1,2,4-triazolo[4,3-a:1,5-c]quinazoline 13 and tetrazolo [1,5-a]-1,2,4-triazolo[1,5-c]quinazoline ( 14 ).     

Syllable intelligibility for temporally filtered LPC cepstral trajectories.

The intelligibility of syllables whose cepstral trajectories were temporally filtered was measured. The speech signals were transformed to their LPC cepstral coefficients, and these coefficients were passed through different filters. These filtered trajectories were recombined with the residuals and the speech signal reconstructed. The intelligibility of the reconstructed speech segments was then measured in two perceptual experiments for Japanese syllables. The effect of various low-pass, high-pass, and bandpass filtering is reported, and the results summarized using a theoretical approach based on the independence of the contributions in different modulation bands. The overall results suggest that speech intelligibility is not severely impaired as long as the filtered spectral components have a rate of change between 1 and 16 Hz.     

On the Neutrosophic,Pythagorean and Some Other Novel Fuzzy Sets Theories Used in Decision Making: Invitation to Discuss

In this short paper, a critical analysis of the Neutrosophic, Pythagorean and some other novel fuzzy sets theories foundations is provided, taking into account that they actively used for the solution of the decision-making problems. The shortcomings of these theories are exposed. It is stated that the independence hypothesis, which is a cornerstone of the Neutrosophic sets theory, is not in line with common sense and therefore leads to the paradoxical results in the asymptotic limits of this theory. It is shown that the Pythagorean sets theory possesses questionable foundations, the sense of which cannot be explained reasonably. Moreover, this theory does not completely solve the declared problem. Similarly, important methodological problems of other analyzed theories are revealed. To solve the interior problems of the Atanassov’s intuitionistic fuzzy sets and to improve upon them, this being the reason most of the criticized novel sets theories were developed, an alternative approach based on extension of the intuitionistic fuzzy sets in the framework of the Dempster–Shafer theory is proposed. No propositions concerned with the improvement of the Cubic sets theory and Single-Valued Neutrosophic Offset theory were made, as their applicability was shown to be very dubious. In order to stimulate discussion, many statements are deliberately formulated in a hardline form.     

Anion-exchange chromatography on short reversed-phase columns modified with amphoteric (N-dodecyl-N,N-dimethylammonio)alcanoates

Short reversed-phase columns (50 mm x 4.6 mm Gemini C(18)) were dynamically coated with carboxybetaines of the general structure, C(12)H(25)N(+)(CH(3))(2)(CH(2))(n)COOH, namely (N-dodecyl-N,N-dimethylammonio)undecanoate, DDMAU (n=10) and (N-dodecyl-N,N-dimethylammonio)butyrate, DDMAB (n=3), and investigated for the separation of inorganic anions in ion chromatography. The role of the ionic strength of coating surfactant solutions on their adsorption and resultant column capacity was studied. The retention of inorganic anions was investigated with different eluents at various concentrations and pH. Interestingly, no retention for anions was found with pure water as the eluent, but the addition of small amounts of electrolytes, up to 0.1 mM, caused a sharp increase in the retention of analytes. The effect of increasing anion retention with an increase in eluent cation charge was also observed. Based on this effect a new cation charge gradient concept was proposed and applied to the separation of a standard mixture of anions.     

An evaluation of the experimental approaches to detection of small ions in CE

This review points out some important trends in the development of the detection techniques for small ions in CE. On the basis of selected literature references it briefly discusses some general requirements on detection techniques in CE. Various optical measurements, mass spectrometric approaches and electrochemical detection techniques are dealt with. Some specific features of microchip CE separation and detection are pointed out and possibilities of dual detection are mentioned. The principal parameters of the above detection techniques are then briefly compared.