Thermoanalytical studies of 2,2,6,6-tetramethyl-4-oxy-4-ethynylpiperidin-1-oxyl polymerization

The structure transition temperature, monomer melting point and critical temperatures of polymerization and decomposition of 2,2,6,6-tetramethyl-4-oxy-4-ethynylpiperidin-1-oxyl were determined by means of thermal analysis. Some features of the polymerization of the acetylenic monomer were studied via thermal analysis, and IR and ESR spectroscopy.It was shown that, during non-isothermal temperature increase, the mass loss of the sample associated with the exothermic effect of polymerization occurred at the expense of the monoacetylene sublimation process (42%), a reagent explosion and decomposition of the reaction products formed (15%).

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Zusammenfassung Mittels Thermoanalyse wurde die Strukturumwandlungstemperatur, der Monomerschmelzpunkt und die kritischen Temperaturen für Polymerisierung und Zersetzung von 2,2,6,6-Tetramethyl-4-oxy-4-ethynylpiperidin-1-oxyl bestimmt. Mit Hilfe von Thermo-analyse, IR- und ESR-Spektroskopie wurden einige Eigenschaften der Polymerisierung des Acethylen-Monomers untersucht.Es wurde gezeigt, daß bei einem nichtisothermen Temperaturanstieg der Massenverlust der Probe zunimmt, verbunden mit einem exothermen Effekt der eingetretenen Polymerisierung auf Kosten des Monoacetylen-Sublimierungsprozesses [42%], der Explosion und der Zersetzung der gebildeten Reaktionsprodukte [15%].

     

Numerical investigation of optical heartbeats with external driving forces

The role of harmonic and random external forces in a phenomenological nonlinear model of optical heartbeats is investigated. External forces trigger damped oscillations at the natural frequency of the system and higher harmonics. The numerical results are compared with experimental ones.     

Specificity of Cyanine Dye L-21 Aggregation in Solutions with Nucleic Acids

Optical spectroscopy experiments were used to study the features of cyanine dye 3,3′-dimethyl-9-(2-thienyl)-thiacarbocyanine iodide (L-21) aggregation in binary solutions DMF:Tris–HCl buffer (pH = 8) containing nucleic acids (DNA or RNA). The appearance of absorption and luminescence bands associated with J-aggregates and dimers that are formed within the minor groove of DNA has been observed. The model of L-21 J-aggregate structure is proposed. It has been found that dimers are the building blocks of L-21 J-aggregates. Disorientation in dimers caused by the minor groove curvature is reason of observation of Davydov splitting in absorption spectrum of L-21 J-aggregates. In the solution containing DNA the absorption and luminescence bands of L-21 J-aggregates exhibit the specific properties that allows the dye L-21 to be used as a fluorescent probe for DNA detection.     

Four-photon laser spectroscopy of liquid water and aqueous solutions of α-chymotrypsin in the range ±5 cm<Superscript>−1</Superscript>

The resonances located at 1.2, 1.6, 2.0, and 2.3 cm^?1 with a width of ～0.2 cm^?1 were observed for the first time in the range ±5 cm^?1 of the four-photon Rayleigh wing spectra of distilled water and aqueous solutions of the protein α-chymotrypsin. The line at 2.3 cm^?1 belongs to the rotational transition 3(2, 1)–4(1, 4) of the ground vibrational state of water. In the presence of the protein, the spectrum is modified by the appearance of new lines, located at 0.74, 2.8, and 3.2 cm^?1. The modification of the spectrum observed is interpreted as a manifestation of low-frequency vibrations of large molecular fragments in aqueous protein solutions and as a result of the structuring of water in the vicinity of protein molecules.     

Pseudoisocyanine J-aggregate to optical waveguiding crystallite transition: microscopic and microspectroscopic exploration

Using fluorescent microscopy and microspectroscopy, optical properties and morphology transformations in individual pseudoisocyanine (PIC) J-aggregates in aqueous electrolyte solutions have been explored. A stringlike structure of J-aggregates with a string diameter much less than 1 microm has been observed. Photodestruction of the strings under short-wavelength excitation has been revealed. Rodlike PIC crystallites, about 1 microm in diameter, have been observed with time. The fluorescence spectrum of rodlike crystallites has been found to differ from that of stringlike J-aggregate and from PIC crystal powder spectra. The crystallites are very stable, and their photodestruction has not been observed under any excitation conditions. It has been found that rodlike crystallites in contrast to stringlike J-aggregates possess optical waveguide properties. The luminescence of crystallites can be observed only at the excitation spot and at butt ends located up to hundreds of micrometers from the excitation spot.     

Detection of a single electron in xenon-based electroluminescent detectors

It is experimentally shown that a single ionization electron can be detected by various xenon-based electroluminescent detectors with optical readout, such as a high-pressure cylindrical gas counter, a two-phase detector with gas amplification, and a two-phase detector with a plane-parallel and uniform electric field. The sensitivity of the detectors was 7, 18, and 15 photoelectrons respectively. The coordinate resolution of the two-phase detector for electrons resulting from field emission at the cathode was σ _X,Y = 5.2 mm.     

Cyclization of 1-arylthiosemicarbazides to benzothiazoles

It is known that 1-arylthiosemicarbazides are cyclized to 2-aminobenzothiazoles in acidic media. This reaction was extended to 1,3- and 1,4-disubstituted thiosemicarbazides. It is shown that the rearrangement proceeds through a step involving the formation of o-aminophenylisothioureas. The reaction conditions and substituents in the benzene ring or attached to the nitrogen atoms of the thiosemicarbazides do not have a substantial effect on the ratio of the resulting 2-amino- and 2-phenyl(methyl)aminobenzothiazoles (11). In the case of m-chlorophenylthiosemicarbazide, 5- and 7-chloro-2-aminobenzothiazoles are obtained in equimolar amounts, whereas the 7 isomer (52) is the major product from m-tolylthiosemicarbazide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 467–475, April, 1978.     

Molecular dynamics simulations,docking and MMGBSA studies of newly designed peptide-conjugated glucosyloxy stilbene derivatives with tumor cell receptors

Molecular Diversity - In this work, for the first time, we designed derivatives of beta-D-glucosyloxy-3-hydroxy-trans-stiblene-2-carboxylic acid (GHS), by conjugating GHS with tumor targeting...     

Laser photonics application in prosthetic dentistry for denture design optimization

The aim of this work is to demonstrate that holographic and speckle interferometry—laser photonics methods are compatible and useful for prosthetic stomatology. These methods allow to study the deformation of the mandible after insertion of mini-implants of various forms, and to give the practical medical recommendations.