The effect of the nanocarbon structures from laser pyrolysis on microorganisms evolution

The carbon nanoparticles existing in environment are an important factor on healthy either by their toxicity or by interaction with pathogen microorganisms, which can make them more resistant or induce a specific mutagenesis. To understand the role of the nanocarbon particles, a series of carbon nanopowders was synthesized by gas-phase laser pyrolysis from different hydrocarbon-based mixture and used to design cell culture media for Escherichia coli and Staphylococcus aureus. The microorganisms, grown in a given incubation time, were investigated by fluorescent markers (water soluble quantum dots). We report that structure and properties of the nanocarbons influence the behaviour of the aerobic microorganisms. We show that carbon nanopowders are oxygen supplier for microorganisms and, at the same time, due to the presence of polyaromatics or heterogeneous atoms existent in the reactive gas mixture, could have an inhibition/poisoning effect.     

Atomic hydrogen in circularly polarized,high-intensity and high frequency laser fields

We present the application of a recently developed nonperturbative theory for electronatom interactions in intense, high-frequency laser fields to the calculation of the structure of atomic hydrogen in a monochromatic, circularly polarized plane wave. This theory predicts that the atom is stable in the high-frequency limit and that the levels are given by a time-independent Schrödinger equation containing a “dressed” Coulomb potential. The laser frequency and intensity enter only combined in a parameter α₀. The energy eigenvalue equation was solved in the angular momentum representation by adopting the “decoupledl-channels approximation”. The weak field limit (α₀ → 0) of the levels could be solved analytically using perturbation theory. Our numerical calculation gives the eigenvalues corresponding to principal quantum numbern≦4, over an extended range of α₀:0≦α₀≦100. The results are compared with those for the case of linear polarization obtained earlier by a similar approximation. The rapid decrease of the ionization potential at fixed (high) frequency and increasing intensity shows a remarkable resemblance in the two cases. This decrease is shown to be connected with a steady increase with α₀ of the average of the radial coordinater, such that the atom in its ground state may attain Rydberg sizes at values of α₀ presently achieved in experiment. Further, the existence of a new symmetry in the strong field limit (α₀→∞) is signalled, leading to a peculiar multiplet structure. Finally, predictions are made concerning the energy spectrum of the electrons ionized at high (but finite) frequencies. In contrast to current experiments, no suppression of peaks can occur in our case, and large shifts of the peaks towards higher energies in comparison to the weak field case are expected.     

Radiative corrections to photoeffect and the high-frequency end of the Bremsstrahlung spectrum

Radiative corrections to K-shell atomic photoeffect assuming a point Coulomb atomic potential and sufficiently high photoelectron velocities (αZ/β ? 1) are evaluated to lowest order in αZ. The result describes also the radiative corrections to the high-frequency end of the bremsstrahlung spectrum. The low- and high-energy limits are presented and discussed.     

The influence of ultrasound on the capacity of lead accumulators

An increase of 12%–40% in the capacity of lead accumulators is obtained by the action of ultrasound. Simultaneously, the number of discharge cycles is increased. These achievements are important when considering the problem of energy. A few causes of the results obtained are explained.     

Ultrafast switching of hard X‐rays

A new concept for shortening hard X‐ray pulses emitted from a third‐generation synchrotron source down to few picoseconds is presented. The device, called the PicoSwitch, exploits the dynamics of coherent acoustic phonons in a photo‐excited thin film. A characterization of the structure demonstrates switching times of ≤ 5 ps and a peak reflectivity of ～10^?3. The device is tested in a real synchrotron‐based pump–probe experiment and reveals features of coherent phonon propagation in a second thin film sample, thus demonstrating the potential to significantly improve the temporal resolution at existing synchrotron facilities.     

Spectral, magnetic and thermal characterisation of new Co(II), Ni(II) and Cu(II) complexes with Schiff base 5-bromo-N,N′-bis-(salicylidene)-o-tolidine

Starting from 5-bromo-N,N′-bis-(salicylidene)-o-tolidine (H₂L) new complexes with Co(II), Ni(II) and Cu(II) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR, UV–Vis–NIR and EPR spectra, magnetic data at room temperature as well as thermal analysis. IR data are in accordance with bischelate nature of the deprotonated ligand that coordinates through azomethinic nitrogen and phenolic oxygen. The electronic spectra display the characteristic pattern of tetrahedral stereochemistry for [CoL]·H₂O complex and octahedral one for [NiL(OH₂)₂]·H₂O complex. The electronic spectra correlated with magnetic susceptibility measurements indicate a square-planar surrounding for [ML] (M:Ni, Cu) species, while the EPR spectrum of copper complex sustains the proposed stereochemistry. The thermal analysis evidenced that thermal transformations are complex processes according to TG, DTA and DTG curves including (crystallization or coordination) water elimination, thermolyses and oxidative degradation of Schiff base. All these processes lead to the most stable metallic oxides as final product.     

Ultrafast temperature jump in liquid water studied by a novel infrared pump-x-ray probe technique

We report the first infrared pump-x-ray probe study of the structural dynamics of liquid water. Femtosecond infrared excitation via the O–H stretching band induces an ultrafast temperature jump that gives rise to changes in the hydrogen bond network. Such changes are probed via the transient x-ray absorption at the oxygen K edge using 70 ps x-ray pulses from a storage ring source. We measure spectra and time evolution of the transient x-ray absorption and calibrate the absolute change of temperature. Our work paves the way for future studies with femtosecond x-ray probe pulses.