Thermogravimetric analysis of cellulose insulation and determination of activation energy of its thermo‐oxidation using non‐isothermal,model‐free methods

The aim of the work was to determine the effect of heating rate on initial decomposition temperature and phases of thermal decomposition of cellulose insulation. The activation energy of thermo‐oxidation of insulation was also determined. Individual samples were heated in the air flow in the thermal range of 100°C to 500°C at rates from 1.9°C min^?1 to 20.1°C min^?1. The initial temperatures of thermal decomposition ranged from 220°C to 320°C, depending on the heating rate. Three regions of thermal decomposition were observed. The maximum rates of mass loss were measured at the temperatures between 288°C and 362°C. The activation energies, which achieved average values between 75 and 80.7 kJ mol^?1, were calculated from the obtained results by non‐isothermal, model‐free methods. Copyright © 2014 John Wiley & Sons, Ltd.     

The influence of the substrate temperature on the preparation of DNA films for studies under vacuum conditions

Experiments were carried out to determine the dependence of the physical form of supercoiled DNA films on the initial temperature of the substrate. Such films are often used in irradiation experiments involving low energy particles, like electrons or photons. In order to obtain absolute values for cross sections for such experiments, the spatial distribution of the sample in the film has to be well estimated. These investigations aim to correlate the size and form of a DNA film with the initial temperature of the substrate, on which the liquid sample is deposited prior to evacuation. From our previous studies we concluded that the presence of agents preventing DNA structural water evaporation is required in order to preserve the supercoiled plasmid DNA form under vacuum conditions. Therefore, we examined the temperature dependence on films prepared from plasmid suspended in solutions containing magnesium hydroxide, Tris-Cl buffer and various concentrations of sodium hydroxide. To visualise the films we used a conventional light microscope with a CCD camera and a scanning electron microscope. The results revealed a significant influence of the temperature of the substrate on both the area of the substrate covered by the film as well as on the spatial distribution of DNA molecules. An increase in the amount of sodium hydroxide that stabilises supercoiled DNA under vacuum increases DNA aggregation. After these investigations we conclude that the best temperature of the substrate to produce uniform and thin films should be between –5 °C and -10 °C for substrates which are not atomically flat and above 0 °C for atomically flat substrates.     

Reactions of N-substituted allylacetic acid amides with selenium and tellurium tetrahalides

The addition of selenium tetrabromide to the olefinic bond of N-substituted allylacetic acid amides (reagent molar ratio 21) proceeds counter to Markownikoff's rule with the formation of tetrahydrofuran derivatives. The addition of tellurium tetrahalides under the same conditions (reagent molar ratio 11) proceeds in accordance with Markownikoff's rule with the formation of tetrahydropyran derivatives.Communication 10 in the series Electrophilic reactions of halides of elements of the sixth group; see [1] for Communication 9.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 743–745, June, 1989.     

Electrophilic reactions of group six element halides. 11. Synthesis of the condensed system selen (tellur) azino-[2, 3-g,h] carbazole

2-Halomethylidene-1,4-selen (tellur) azino [2, 3-g, h] carbazoles are prepared by the seleno (telluro) halogenation of N-propargylcarbazole under heterogeneous reaction conditions.See [1] for Communication 10.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 126–128, January, 1990.     

On the Exponential sum over r-Free Integers

We determine, up to a constant factor, the L ¹ mean of the exponential sum formed with the r-free integers. This improves earlier results of Brüdern, Granville, Perelli, Vaughan and Wooley. As an application, we improve the known bound for the L ¹ norm of the exponential sum defined with the Möbius function.     

Preservation of the Pt(100) surface reconstruction after growth of a continuous layer of graphene

Scanning tunneling microscopy shows that a layer of graphene can be grown on the hex-reconstructed Pt(100) surface and that the reconstruction is preserved after growth. A continuous sheet of graphene can be grown across domain boundaries and step edges without loss of periodicity or change in direction. Density functional theory calculations on a simple model system support the observation that the graphene can have different rotation angles relative to the hex-reconstructed Pt surface. The graphene sheet direction can be changed by incorporating pentagon-heptagon defects giving rise to accommodation of edge dislocations. The defect formation energy and the induced buckling of the graphene have been characterized by DFT calculations.