Thermochemical stabilization and analysis of continuously electrospun nanofibers

Carbon nanotube (CNT)-loaded and neat polyacrylonitrile nanofibers were produced by a needleless continuous electrospinning method as carbon nanofiber precursors. The details of the stabilization, which is a crucial issue during carbon fiber production, were investigated as these nanofibers are especially sensitive to degradation. In order to determine the optimal parameters, the nanofibers were stabilized at different temperatures. The stabilized samples were analyzed by Fourier-transform infrared spectroscopic and differential scanning calorimetric (DSC) measurements and by the determination of the color changes. The chemical changes during the stabilization (the formation of the so-called ladder-polymer) can be followed by infrared spectrometry, while the conversion can be monitored by DSC. The formation of the ladder-polymer occurs according to the Gaussian distribution function, where the temperature of the stabilization is the statistical parameter, which was also determined. In the case of CNT-loaded samples, the range of stabilization temperature was wider, which provides better controllability of the process. Based on the established models, an appropriate multi-step heat-treatment program could be determined, which led to completely stabilized nanofibers, suitable for carbonization.     

2,3-Diamino-5-aryl-7-(4-nitrophenyl)-1,2,4-triazolo[1,5-a]pyrimidinium-6-olates

The corresponding triazolopyrimidinium salts and 1,2,4-triazolo[1,5-a]pyrimidinium-6-olates were formed from the reaction of 3,4,5-triamino-1,2,4-triazole and 1-aryl-3-(4-nitrophenyl)-2,3-dibromopropanones. The structure of one of the latter has been established by X-ray crystallography.     

New reactions of cyclization and recyclization of derivatives of 1,3-dimethyl-5,6-diaminouracil

The reaction of 1,3-dimethyl-5-6-diaminouracils with chalcones produced 7,9-dimethyl-2,4-diaryl-1-,7,9-triazaspiro[4,5] decene-1-6,8,10-triols. The transformation of these spiro-compounds to pyrimido[4,5-d]oxazoles was investigated.Khar'kov State University, Khar'kov 31007. Institute of Single Crystals, Academy of Sciences of Ukraine, Khar'kov 310141. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 972-983, July, 1996. Original article submitted February 20, 1996.     

Cyclocondensation of chalcones with di- and triamino-1,2,4-triazoles

We have carried out the synthesis of 2-amino-5,7-diaryl-1,2,4-triazolo[1,5-a]pyrimidines from chalcones and 3,4,5-triamino-1,2,4-triazole and synthesized them independently via the 4,7-dihydro derivatives. The course and mechanism of the cyclocondensation are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 938–941, July, 1990.     

A microscale camera using direct Fourier-domain scene capture

We demonstrate a chip-scale (<1 mm(2)) sensor, the Planar Fourier Capture Array (PFCA), capable of imaging the far field without any off-chip optics. The PFCA consists of an array of angle-sensitive pixels manufactured in a standard semiconductor process, each of which reports one component of a spatial two-dimensional (2D) Fourier transform of the local light field. Thus, the sensor directly captures 2D Fourier transforms of scenes. The effective resolution of our prototype is approximately 400 pixels.     

Asymmetrical diarylideneacetones in reactions with o-phenylenediamine

Asymmetrical diarylideneacetones were condensed with o-phenylenediamine in methanol in the presence of a tertiary amine. It is shown that the p-dimethyl-amino derivative does not react under these conditions, that the reaction takes place at the unsubstituted cinnamoyl fragment in the case of the p-methoxy and p-nitro-substituted compounds, and that the reaction takes place at the substituted fragment in the case of halo-containing ketones. The structures of the compounds obtained were confirmed by alternative synthesis (by the reaction of 4-methyl-2-pheny1-2,3-dihydro-1H-1,5-benzodiazepine with aromatic aldehydes), as well as by the IR, UV, and PMR spectra and the dipole moments. The principal physicochemical criteria for the identification of isomeric dihydrodiazepines were established. All of the synthesized compounds belong to the trans series.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 827–832, June, 1981.     

Synthesis of hydroxylated intermediate metabolites of dimetacrin

To prove the chemical structure of metabolites of the antidepressant drug (dimetacrin²) (Istonil®³), 2- and 3-hydroxy-9,9-dimethyl-10-dimethylaminopropyl-acridane and 2-hydroxy-monometacrin⁴ were synthesized using substituted alkoxy diphenylamines (V) as intermediates. The methoxy compounds on treatment with strong acids cyclized either to the corresponding acridanes or to their O-demethylated derivatives, VI (X ? OCH₃ or OH), depending on concentration and temperature.