Search for γ-Emission from Isomeric Nuclei Induced by MeV Electron Beams

In this paper we study the nuclear transitions induced by incident electrons having an energy of several MeV's. We measured the cross sections for the excitation of isomeric nuclear states by 7.7 MeV electrons. The cross sections were 1.2 μb for ^111m Cd, 5.5 μb for ^113m In and 7.0 μb for ^115m In. The peak activation rates were 1.8×10⁻¹² s⁻¹ for ^111m Cd, 8.1×10⁻¹² s⁻¹ for ^113m In and 1.0×10⁻¹¹ s⁻¹ for ^115m In, for a peak power of the electron beam of 1.8×10⁶ W cm⁻². Then we describe for the first time the results of a series of experiments in which samples containing the isomeric nuclei ^166m Ho and ^186m Re have been irradiated with MeV electron beams. An upper limit of 17 mb has been determined for the cross section of electron-induced γ-emission from ^166m Ho and an upper limit of 2.2 mb has been determined for the cross section of electron-induced γ-emission from ^186m Re. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis,structural characterization and thermal analysis of the cobalt(II) oxalate obtained through the reaction of 1,2-ethanediol with Co(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> · 6H<Subscript>2</Subscript>O

The homopolynuclear coordination compound [CoL · 2.5H₂O]_n with L=C₂O₄ ²⁻ was synthesized by a new unconventional method. It consist in the redox reaction between 1,2-ethanediol and cobalt nitrate in presence of nitric acid. The coordination compound was characterized by chemical analysis, electronic and vibrational spectra respectively, thermal analysis. In the coordination compound the Co(II) ion exists in a high spin octahedral configuration and oxalate anion acts as double-bridge ligand, tetradentate, similar as in CoC₂O₄ · 2H₂O obtained by the classical method. Nonstoichiometric oxide, Co₃O_4+0.25 with deficit in cobalt and normal spinel Co₃O₄ where identified as thermal decomposition intermediates. As final product of decomposition, the oxide CoO was obtained.     

Production of nitric oxide by a fragmenting bolide: An exploratory numerical study

A meteoroid's hypersonic passage through the Earth's atmosphere results in ablational and fragmentational mass loss. Potential shock waves associated with a parent object as well as its fragments can modify the surrounding atmosphere and produce a range of physico-chemical effects. Some of the thermally driven chemical and physical processes induced by meteoroid-fragment-generated shock waves, such as nitric oxide (NO) production, are less understood. Any estimates of meteoric NO production depend not only on a quantifiable meteoroid population and a rate of fragmentation, with a size capable of producing high temperature flows, but also on understanding the physical properties of the meteor flows along with their thermal history. We performed an exploratory pilot numerical study using ANSYS Fluent, the computational fluid dynamics (CFD) code, to investigate the production of NO in the upper atmosphere by small meteoroids (or fragments of meteoroids after they undergo a disruption episode) in the size range from 10⁻² to 1 m. Our model uses the simulation of a spherical body in the continuum flow at 70- and 80-km altitude to approximate the behaviour of a small meteoroid capable of producing NO. The results presented in this exploratory study are in good agreement with previous studies.     

Quinohemoprotein alcohol dehydrogenase-based reagentless amperometric biosensor for ethanol monitoring during wine fermentation

This paper describes the development and optimization of an amperometric biosensor for monitoring ethanol in beverages. The biosensor is constructed by cross-linking a quinoprotein alcohol dehydrogenase (QH-ADH) to an Os-complex-modified poly(vinylimidazole) redox polymer using poly(ethylene glycol) diglycidyl ether. The optimum biosensor configuration was evaluated by changing the ratio between enzyme, redox polymer, and cross-linker using conventional graphite rods as basis electrodes. The optimized sensor showed a sensitivity of 0.336±0.025 A M⁻¹ cm² for ethanol and a detection limit (calculated as three times the signal-to-noise ratio) of 1 μM.This biosensor configuration was further evaluated in a conventional flow-injection system and the applicability for the determination of ethanol in diverse wine samples could be successfully demonstrated. Adaptation of this sensor configuration to screen-printed (SP) electrodes allowed their integration into an automated sequential-injection analyzer and the successful on-line monitoring of ethanol during wine fermentation processes.     

Nonisothermal decomposition kinetics of [CoC<Subscript>2</Subscript>O<Subscript>4</Subscript>·2.5H<Subscript>2</Subscript>O]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>

The authors present their results concerning the decomposition in air of the homopolynuclear coordination compound [CoC₂O₄·2.5H₂O] _n . In the temperature range 20–300 °C, the heating curves TG, DTG and DTA allowed to evidence three decomposition steps. The kinetic analysis was performed on the second step which proved to be the only workable one. The application of nonlinear regression procedure shows that this is a complex process consisting in three successive steps. The checking of the mechanism and corresponding kinetic parameters for quasi-isothermal data (T = 150 °C) shows that the obtained results could be used for prediction of the thermal behaviour of the investigated compound in both isothermal and non-isothermal conditions.     

Angular distributions for (3,4)(Lambda)H bound states in the (3,4)He(e,e(')K+) reaction

The (3,4)(Lambda)H and (4)(Lambda)H hypernuclear bound states have been observed for the first time in kaon electroproduction on (3,4)He targets. The production cross sections have been determined at Q(2)=0.35 GeV2 and W=1.91 GeV. For either hypernucleus the nuclear form factor is determined by comparing the angular distribution of the (3,4)He(e,e(')K+)(3,4)(Lambda)H processes to the elementary cross section 1H(e,e K+)Lambda on the free proton, measured during the same experiment.     

Intense laser effects on the optical properties of asymmetric GaAs double quantum dots under applied electric field

We investigated the combined effects of a non-resonant intense laser field and a static electric field on the electronic structure and the nonlinear optical properties (absorption, optical rectification) of a GaAs asymmetric double quantum dot under a strong probe field excitation. The calculations were performed within the compact density-matrix formalism under steady state conditions using the effective mass approximation. Our results show that: (i) the electronic structure and optical properties are sensitive to the dressed potential; (ii) under applied electric fields, an increase of the laser intensity induces a redshift of the optical absorption and rectification spectra; (iii) the augment of the electric field strength leads to a blueshift of the spectra; (iv) for high electric fields the optical spectra show a shoulder-like feature, related with the occurrence of an anti-crossing between the two first excited levels.