Radioactivity in Montenegro beach sands and assessment of the corresponding environmental risk

Activity concentrations of the naturally occurring radionuclides ²²⁶Ra, ²³²Th, ⁴⁰K and anthropogenic ¹³⁷Cs in sand samples collected from 20 renowned beaches on the Coast of Montenegro have been determined using an HPGe (high purity Ge spectrometer). The average activity concentrations were found to be 7.4, 5.2, 97.3 and 0.5 Bq kg^?1, respectively. For all sand samples, the radium equivalent activity has been evaluated and found to be lower than the limit of 370 Bq kg^?1. External and internal hazard indices were less than unity. The gonadal dose equivalent was estimated to be on average 75 μSv y^?1, which is about four times lower than the global average for soil (0.3 mSv y^?1). Calculated values of absorbed dose rates showed the range from 3.1 to 28 nGy h^?1, which is below the world median of average values (57 nGy h^?1). The effective dose rate in the range from 3.8 to 34.4 μSv y^?1 was significantly below the recommended limit value for the public (1 mSv y^?1). The highest dose rate was found for the Velika Plaza locality, which also showed heavy metal contents (As, B, Cd, Hg, Cr, Cu, Mn, Ni, Pb, Zn and Ba) significantly higher than in the sand from Jaz, a locality with one of the lowest dose rates.     

Bestimmung von niedrigen Gehalten und Spuren von Molybd?n in geologischen Proben mit induktiv gekoppeltem Plasma

Ohne Zusammenfassung

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Determination of minor and trace contents of molybdenum in geological samples by inductively coupled plasma

     

On almost periodic processes in impulsive fractional-order competitive systems

In this paper an impulsive model for the dynamics of competitive Lotka–Volterra systems using the Caputo fractional-order derivative is developed. The existence and uniqueness of almost periodic solutions are investigated. Applying the fractional Lyapunov method, we give sufficient conditions for global perfect uniform-asymptotic stability of the almost periodic solution and sufficient conditions to save these qualities at the uncertain case. Since the competitive relationship in ecosystem models is relevant in various contexts, including many population, neural nets or chemical kinetics problems, our results can be applied in the investigation of almost periodic processes in a wide range of competitive systems of diverse interest.     

Determination of the stereochemistry of rotenoids by1H-NMR spectroscopy in C6D6

The application of¹H-NMR spectroscopy in C₆D₆ for the determination of configurations at C_12a and C_6a in rotenoids is discussed.

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Bestimmung der Stereochemie von Rotenoiden mittels¹H-NMR-Spektroskopie in C₆D₆

Zusammenfassung Es wird die Anwendung der¹H-NMR-Spektroskopie in C₆D₆ zur Bestimmung der Konfigurationen an C_12a und C_6a in Rotenoiden diskutiert.

     

Synthesis, Characterization, and Biological Activity of Amino Acid Derivatives of the Heteropolytungstophosphoric Acid

Summary. Compounds of phosphotungstic acid (WPA) containing the amino acids alanine (WPA–Ala) or glycine (WPA–Gly) as counter cations were synthesized and characterized by elemental analysis, thermal analysis, and IR spectroscopy. Cellular toxicity was assessed by the trypan blue exclusion method, and the antiviral activity of WPA and the modified WPA compounds was tested against herpes simplex viruses (HSV) type 1 and type 2. Biological assays indicate that the newly synthesized compounds exhibit no evident cytotoxic effects on Vero cells and negligible antiviral activity against HSV-1 and HSV-2.     

Mass spectrometric investigation of some [1]benzopyrano[3,4-c]pyrazole and [1]benzopyrano[4,3-d]isoxazole derivatives

The fragmentation behaviour of some [1]benzopyrano[3,4-c]pyrazole and [1]benzopyrano[4,3-d]isoxazole derivatives under electron impact is described.     

Reactions of Alkenediazonium Salts. Part 1. 2,2-Diethoxyethene-diazonium hexachloroantimonate: A diazonium,a carbenium or an oxonium salt?

Reactions of the title compound 1 with various nucleophiles have been studied. The salt behaves like an alkylating agent towards ethers, alcohols and water forming ethyl diazoacetate ( 2 ), which reacts further with excess of the nucleophile. A solvent cage mechanism accounting for the observed products is proposed. Thermal decomposition in inert solvents leads to the alkylation of the counter-ion, i.e. formation of chloroethane, and in anisole, alkylation and chlorination of the solvent are also observed. With a standard coupling component, 2-naphtholate ion, no azo coupling reaction of 1 is observed, but instead 14-methyl-14 H-dibenzo[a,j]xanthene ( 17 ) is formed. The products of the reaction with diethylamine are diethylcyanoformamide ( 18 ) and ethyl diethylcarbamate ( 19 ). None of the chemistry of salt 1 is explained by the intervention of vinyl cations expected to be formed in a heteroytic dediazoniation. The predominant pathways seem to involve reactions of an oxonium salt (alkylating properties) or, in the case of diethylamine, a carbenium salt (primary nucleophilic attack on the β-C-atom of 1 ). The free energy barrier to C?C rotation in 1 is estimated to be 75 to 77 kJ/mol (18.0 to 18.5 kcal/mol), a value which falls between those expected for a double and a single bond.     

Preparation and stereochemical characterization of some N-acyl-[1]benzopyrano[3,4-c]pyrazole derivatives from rotenoids

Summary Several new N-acyl derivatives of 1-(4-hydroxy-2,3-dihydrobenzofuran-5-yl)-7,8-di methoxy-1,9 b,2,3,3 a,4-hexahydro-[1]benzopyrano[3,4-c]pyrazole-1-ene have been prepared by appropriate chemical transformation of isohydrazones of rotenone and amorphigenin. A study of their¹H- and¹³C-NMR spectra confirmed the presence of the twocis 3a, 9b, 2 and 3a, 9b, 2 diastereomers in the parent isohydrazones and revealed the strong predominance of the conformers withendo orientation of the 3-NAc group. The conformations due to rotation about the 1,5-bond between rings C and D in the 4-OH and 4-O-substituted compounds were also determined by taking into account the anisotropic effect of aromatic rings A and D, and the hydrogen bond between 4-OH and the 2-N atom, as well as by inspecting the Dreiding models.

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Darstellung und stereochemische Charakterisierung einiger N-Acyl-[1]benzopyrano[3,4-c]pyrazol-Derivate von Rotenoiden

Zusammenfassung Mittels geeigneter chemischer Transformationen von Isohydrazonen von Rotenon und Amorphigenin wurden einige neue N-Acyl-Derivate von 1-(4-Hydroxy-2,3-dihydrobenzofuran-5-yl)-7,8-dimethoxy-1,9 b,2,3,3 a,4-hexahydro-[1]benzopyrano[3,4-c]pyrazol-1-en hergestellt. Eine Untersuchung ihrer¹H und¹³C-NMR-Spektren zeigt die Gegenwart von zweicis 3a, 9b, 2- und 3a, 9b, 2-Diastereomeren in den Ausgangs-Isohydrazonen und eine starke Bevorzugung der Konformeren mitendo-Orientierung der 3-NAc-Gruppe. Die Konformationen bezüglich der Rotation um die 1,5-Bindung zwischen Ring C und D werden für die 4-OH und 4-O-substituierten Verbindungen unter Berücksichtigung von Anisotropie-Effekten der aromatischen A- und D-Ringe, der Wasserstoffbrücken zwischen 4-OH und dem 2-N Atom und auch der Betrachtung der entspechenden Dreiding-Modelle diskutiert.

     

Hindered, 1,1-disubstituted monomers. Chain transfer to benzene in the radical polymerisation of di-n-butyl itaconate

The transfer constant to benzene in the radical polymerisation of di-n-butyl itaconate, DBI, was measured at 60 °C and found to have the value of 2.2 × 10⁻³. This value is surprisingly high considering that benzene has no readily extractable hydrogen atoms and is usually considered to be a relatively inert solvent in radical polymerisations. The high values of transfer constants in the radical polymerisation of itaconates must be taken into consideration when planning the tailored polymerisation of these monomers.