Single Pulse-Laser Induced Breakdown Spectroscopy in aqueous solution

In this paper the flexibility of Laser Induced Breakdown Spectroscopy (LIBS) has been proved for the analysis of water solutions. The plasma is generated directly in the bulk of a water solution by a Q-switched Nd:YAG laser (1064). The emission signal of four different solutions has been studied: AlCl₃, NaCl, CaCO₃ and LiF. The basic mechanisms influencing the emission signal and the experimental tricks for the optimization of the detection mode have been pointed out. PACS 52.70.Kz; 52.80.Wq; 39.30.+p     

Modification of surface properties of electrospun polyamide nanofibers by means of a perfluorinated acridine

Polyamide 6 (PA6) nanofibers were prepared from formic acid solutions by using electrospinning technique. The fibers were smooth, defects free and with diameters smaller than 200 nm. Small amounts of a perfluorinated acridine were added as dopant to the feed solution to modify the wettability of the fibers. The effect of doping on the contact angle values is well apparent. The contact angle values go from 50° of pure PA6 to 120° when 6% of acridine is added. A comparison between fibers and films of pure and doped polyamide 6 was carried out in order to determine the effect of morphology on wettability. Thermal annealing near the T_g of the polymer promoted the segregation of the molecules to the surface, reaching contact angles of 131° with smaller amounts (4%) of acridine. The surface segregation was also promoted by time aging.     

Dynamics of quark-gluon plasma from field correlators

It is argued that strong dynamics in the quark-gluon plasma and bound states of quarks and gluons is mostly due to nonperturbative effects described by field correlators. The emphasis in the paper is made on two explicit calculations of these effects from first principles—one analytic using gluelump Green’s functions and another using independent lattice data on correlators. The resulting hadron spectra are investigated in the range T _c ≤ T < 2T _c . The spectra of charmonia, bottomonia, light s mesons, glueballs, and quark-gluon states calculated numerically are in general agreement with lattice MEM data. The possible role of these bound states in the thermodynamics of quark—gluon plasma is discussed. The text was submitted by the authors in English.     

Dynamical phases of the Hindmarsh-Rose neuronal model: studies of the transition from bursting to spiking chaos

The dynamical phases of the Hindmarsh-Rose neuronal model are analyzed in detail by varying the external current I. For increasing current values, the model exhibits a peculiar cascade of nonchaotic and chaotic period-adding bifurcations leading the system from the silent regime to a chaotic state dominated by bursting events. At higher I-values, this phase is substituted by a regime of continuous chaotic spiking and finally via an inverse period doubling cascade the system returns to silence. The analysis is focused on the transition between the two chaotic phases displayed by the model: one dominated by spiking dynamics and the other by bursts. At the transition an abrupt shrinking of the attractor size associated with a sharp peak in the maximal Lyapunov exponent is observable. However, the transition appears to be continuous and smoothed out over a finite current interval, where bursts and spikes coexist. The beginning of the transition (from the bursting side) is signaled from a structural modification in the interspike interval return map. This change in the map shape is associated with the disappearance of the family of solutions responsible for the onset of the bursting chaos. The successive passage from bursting to spiking chaos is associated with a progressive pruning of unstable long-lasting bursts.     

On the possibility of detecting gluon condensation from the spectra of heavy quarkonia

We compute the effect of the gluon condensate on the spectra of heavy quarkonia, taking into account the condensate correlation length. We compare the results obtained for the hydrogen-like model with a more realistic model. The effects are shown to be very small both in bottomonium and toponium.     

Immobilized TiO<Subscript>2</Subscript> nanoparticles produced by flame spray for photocatalytic water remediation

Anatase/rutile mixed-phase titanium dioxide (TiO₂) photocatalysts in the form of nanostructured powders with different primary particle size, specific surface area, and rutile content were produced from the gas-phase by flame spray pyrolysis (FSP) starting from an organic solution containing titanium (IV) isopropoxide as Ti precursor. Flame spray-produced TiO₂ powders were characterized by means of X-ray diffraction, Raman spectroscopy, and BET measurements. As-prepared powders were mainly composed of anatase crystallites with size ranging from 7 to 15 nm according to the synthesis conditions. TiO₂ powders were embedded in a multilayered fluoropolymeric matrix to immobilize the nanoparticles into freestanding photocatalytic membranes. The photocatalytic activity of the TiO₂-embedded membranes toward the abatement of hydrosoluble organic pollutants was evaluated employing the photodegradation of rhodamine B in aqueous solution as test reaction. The photoabatement rate of best performing membranes significantly overcomes that of membranes produced by the same method and incorporating commercial P25-TiO₂.     

Quantum learning algorithms for quantum measurements

We study quantum learning algorithms for quantum measurements. The optimal learning algorithm is derived for arbitrary von Neumann measurements in the case of training with one or two examples. The analysis of the case of three examples reveals that, differently from the learning of unitary gates, the optimal algorithm for learning of quantum measurements cannot be parallelized, and requires quantum memories for the storage of information.