Mass spectra of N-arylaminosulphonylcarbethoxydiazoacetamides

The electron impact mass spectra of N-arylaminosulphonylcarbethoxydiazoacetamides were studied. On the basis of high-resolution mass spectrometric data, mass-analysed ion kinetic energy Spectrometry and linked scan experiments a detailed scheme of the fragmentation is proposed. A number of possibilities of charge Iocalization are revealed in the complex decomposition processes of the molecular ions.     

Synthesis and properties of analogs of 5(4)-aminoimidazole-4(5)-carboxamide and purines. 11. Investigation of the structure and reactivity of imidazolethioamides

The IR, UV, and PMR spectra of 5(4)-mercaptoimidazole-4(5)-carboxamide, 5(4)-hydroxyimldazole-4(5)-thiocarboxyamide, 5(4)-mercaptoimidazole-4(5)-thiocarboxamide, and the corresponding methyl derivatives were studied. It is shown that the mercaptoimidazoles obtained exist in the form of zwitterions in solution. The methylation of the mercapto- and hydroxyimidazoles with various methylating agents in solvents was investigated, and the reaction of the thioamides with hydrazine was carried out.See [1] for Communication 10.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 957–962, July, 1982.     

Synthesis and properties of analogs of 5(4)-aminoimidazole-4(5)-carboxamide and purines. 14. Acylation of 5(4)-aminoimidazole derivatives

The acylation of 5(4)-aminoimidazole derivatives was studied. It is shown that acylation by means of carboxylic acid anhydrides and chlorides takes place at the amino group, whereas acylation by means of chlorocarbonic acid esters takes place at the nitrogen atoms of the imidazole ring. Methods for the selective introduction of a carbomethoxy group in the 1, 3, and 5 positions of the 5(4)-aminoimidazole-4(5)-carboxamide molecule were developed.See [1] for communication 13.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 247–252, February, 1984.     

Resummation in QCD fractional analytic perturbation theory

An analytic approach in the QCD perturbation theory that has its origin in studies by Jones, Solovtsov, and Shirkov is briefly summarized. Basic propositions of the fractional analytic perturbation theory (FAPT) are also briefly taken into account with a fixed number of quark flavors and allowing for heavy-quark thresholds in a global FAPT version. Summation of perturbative series in (F)APT is examined. Application of the developed global FAPT version to calculations of the width of Higgs boson decay H → b $ \bar b $ \bar b is described.     

Electrochemical microfluidic biosensor for the detection of nucleic acid sequences

A microfluidic biosensor with electrochemical detection for the quantification of nucleic acid sequences was developed. In contrast to most microbiosensors that are based on fluorescence for signal generation, it takes advantage of the simplicity and high sensitivity provided by an amperometric and coulorimetric detection system. An interdigitated ultramicroelectrode array (IDUA) was fabricated in a glass chip and integrated directly with microchannels made of poly(dimethylsiloxane) (PDMS). The assembly was packaged into a Plexiglas housing providing fluid and electrical connections. IDUAs were characterized amperometrically and using cyclic voltammetry with respect to static and dynamic responses for the presence of a reversible redox couple-potassium hexacyanoferrate (ii)/hexacyanoferrate (iii) (ferri/ferrocyanide). A combined concentration of 0.5 microM of ferro/ferricyanide was determined as lower limit of detection with a dynamic range of 5 orders of magnitude. Background signals were negligible and the IDUA responded in a highly reversible manner to the injection of various volumes and various concentrations of the electrochemical marker. For the detection of nucleic acid sequences, liposomes entrapping the electrochemical marker were tagged with a DNA probe, and superparamagnetic beads were coated with a second DNA probe. A single stranded DNA target sequence hybridized with both probes. The sandwich was captured in the microfluidic channel just upstream of the IDUA via a magnet located in the outside housing. Liposomes were lysed using a detergent and the amount of released ferro/ferricyanide was quantified while passing by the IDUA. Optimal location of the magnet with respect to the IDUA was investigated, the effect of dextran sulfate on the hybridization reaction was studied and the amount of magnetic beads used in the assay was optimized. A dose response curve using varying concentrations of target DNA molecules was carried out demonstrating a limit of detection at 1 fmol assay(-1) and a dynamic range between 1 and 50 fmol. The overall assay took 6 min to complete, plus 15-20 min of pre-incubation and required only a simple potentiostat for signal recording and interpretation.     

Complex magnetic ordering as a driving mechanism of multifunctional properties of Heusler alloys from first principles

First-principles calculations are used to study the structural, electronic and magnetic properties of (Pd, Pt)-Mn-Ni-(Ga, In, Sn, Sb) alloys, which display multifunctional properties like the magnetic shape-memory, magnetocaloric and exchange bias effect. The ab initio calculations give a basic understanding of the underlying physics which is associated with the complex magnetic behavior arising from competing ferro- and antiferromagnetic interactions with increasing number of Mn excess atoms in the unit cell. This information allows to optimize, for example, the magnetocaloric effect by using the strong influence of compositional changes on the magnetic interactions. Thermodynamic properties can be calculated by using the ab initio magnetic exchange parameters in finite-temperature Monte Carlo simulations. We present guidelines of how to improve the functional properties. For Pt-Ni-Mn-Ga alloys, a shape memory effect with 14% strain can be achieved in an external magnetic field.     

The effect of N-heterocyclic carbene ligands in the palladium-catalyzed cross-coupling reaction of K[C6F5BF3] with aryl iodides and aryl bromides

The effect of N-heterocyclic carbene (NHC) ligands on the catalytic activity of in situ generated palladium complexes in the model cross-coupling reaction of K[C₆F₅BF₃] with 4-FC₆H₄I was studied. Based on the obtained results, a series of pentafluorobiphenyls C₆F₅C₆H₄X were prepared from K[C₆F₅BF₃] and XC₆H₄I or 4-CF₃C₆H₄Br in high yields under aerobic conditions.     

Behaviour of pure water and water mixture with benzene or chloroform adsorbed onto ordered mesoporous silicas

Structural characteristics of synthesized ordered mesoporous silicas MCM-41, MCM-48 and SBA-15 were studied using XRD, nitrogen adsorption and FTIR methods. Pure water and mixtures with water/benzene and water/chloroform-d adsorbed onto silicas were studied by ¹H NMR spectroscopy with layer-by-layer freezing-out of bulk and interfacial liquids. Concentrated aqueous suspensions of MCM-48 and SBA-15 were studied by thermally stimulated depolarization current (TSDC) method. Benzene and chloroform-d can displace a portion of water to broad pores from the pore walls and from narrower pores, especially in the case of a large excess of an organic solvent. This process is accompanied by diminution of both interaction energy of water with an adsorbent surface and freezing temperature depression of adsorbed water. The effect of nonpolar benzene on pore water is much stronger than that of weakly polar chloroform-d. Modifications of the Gibbs-Thomson relation to describe the freezing point depression of mixtures of immiscible liquids confined in pores allow us to determine distribution functions of sizes of structures with unfrozen pore water and benzene. Former address: Pisarzhevskii Institute of Physical Chemistry, 31 Prospect Nauki, Kiev, Ukraine     

Synthesis of fluoroquinoxalin-2(1<Emphasis Type="Italic">H</Emphasis>)-one derivatives containing substituents in the pyrazine and benzene fragments

6,7-Difluoroquinoxalin-2-one reacted with indoles, 5,5-dimethylcyclohexane-1,3-dione, 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one, resorcinol, and pyrogallol on heating in acetic acid to give products of hydrogen substitution in the heterocyclic fragment. Heating of 6,7-difluoro-3-(1H-indol-3-yl)quinoxalin-2(1H)-ones with N-methylpiperazine gave the corresponding 7-(4-methylpiperazin-1-yl) derivatives.     

Synthesis and heteroelectrocyclization of unsymmetrically substituted diazomalonamides

A selective procedure was developed for the synthesis of 1,2,3-triazoles and unsymmetrically substituted diazomalonamides. Cyclization of unsymmetrically substituted diazomalonamides to 1,2,3-triazoles was studied by the method of intramolecular competitive reactions. The kinetic and thermodynamic characteristics of the process were determined. Quantum-chemical calculations for the monorotatory electrocyclic and nonrotatory heteroelectrocyclic mechanisms of cyclization were carried out. N-Aryldiazomalonamides undergo cyclization according to the heteroelectrocyclic mechanism, whereas cyclization of N-alkyldiazomalonamides proceeds by the monorotatory mechanism. The experimental constant of competition between these processes is (1.3—8.3)·10³ (DMSO-d₆) and (45.2—72.4)·10³ (CD₃OD).