The present work reports the temperature and frequency dependence of a.c. conductivity in glassy Se70Te30−x Znx (x = 0, 2, 4 and 6) alloys in the temperature range 300–500 K and frequency range 1 kHz. An agreement between experimental and theoretical results suggests that the a.c. conductivity behaviour of the present samples can be successfully explained by correlated barrier hopping (CBH) model. The density of defect states has been determined using this model for all the glassy alloys. The results show that bipolaron hopping dominates over single-polaron hopping in this glassy system. This is explained in terms of lower values of the maximum barrier height for single-polaron hopping.

Organic photovoltaic cells based on the multilayers structure, indium tin oxide (ITO)/copper-phthalocyanine(CuPc)/fullerene(C60)/aluminium tris(8-hydroxyquinoline) (Alq3)/aluminium, have been studied. When an ultra-thin metal layer is deposited onto the surface of the ITO anode the power conversion efficiency of the cells is significantly improved. The improvement depends on the ITO used. These differences have been attributed to the difficulty to control the surface chemistry of ITO. The best result has been obtained with a gold layer thick of about 0.5 nm. We propose that the gold ultra-thin film, which is too thin to be continuous, allows to improve the agreement between the work function of the anode and the highest occupied molecular orbital (HOMO) of the organic donor CuPc and to passivate the surface contamination of ITO.

Polymer sheets are currently used worldwide in a wide range of applications. The manufacturing process of these sheets involves extruding machines that stretch the material in both lateral and longitudinal directions with respect to the machine direction, thus inducing birefringence. In most cases, the film obtained is optically biaxial. Polarimetric spectroscopy (Ellipsometry and Mueller Matrix) combined with conoscopic observation are the methods of choice to study these properties. In this work we report an analysis of commercially available polyethylene terephtalate (PET) films used as substrate for food packaging as well as for embedded electronic devices such as solar cells or flexible displays. Initial observation of these films through polarizing microscope in conoscopic mode reveals first the trace of optical axis plane with respect to the film surface and second, whether the optical axis is acute or not. This preliminary study allows optimal sample positioning for further polarimetric studies. The measurements and modelling are done in both reflection and transmission mode on several spectroscopic polarimetric setups from UV to NIR. The models give as a main result, the dielectric tensor of the film as well as its orientation with respect to the laboratory reference frame.

Kinetic electron emission from MgO film under the impact of 50–300 eV rare-gas ions has been investigated by Monte Carlo simulation. The program includes excitation of the target electrons (by projectile ions, recoiling target atoms and fast primary electrons), subsequent transport and escape of these electrons from the target surface. Potential electron yields due to Auger neutralization of various ions are obtained by comparing the calculated kinetic electron yield with the experimental data. The program generates partial yields of the secondary electrons excited by projectile ions, recoiling target atoms and electron cascades. The partial yields of the electrons excited by projectile ions and electron cascades fluctuate with mass of the projectile ion like the electronic stopping. Moreover, lateral and depth distribution of the electrons excited by three excitation processes were quite different. For the range of investigated ion energies, the average electron escape depth was independent of the mass of the incident ion, which indicates that electron escape depth is a material property.

Well-aligned ZnO nanocones were self-assembled on amorphous carbon using manganese oxide assisted thermal chemical vapor transport and condensation, without any metal catalysts. Compared with the ZnO nanowires fabricated without the manganese oxide assistance, the field emission performance of the ZnO nanocones was greatly improved, lower turn-on electronic fields and higher current densities were achieved with these emitters. Experimental analyses showed that the ZnO nanocones grow vertically and epitaxially on the [0002] oriented ZnO intermediate layer between nanocones and substrate The manganese oxide seems to play a crucial role in the formation of this ZnO intermediate layer.

The fabrication of a hybrid micro/nano-fluidic device to study electropreconcentration of biomolecules is presented. A nanoslit surrounded by glass is formed between two access microchannels and an “H” configuration bio-analysis system is developed. The optimized know-how for this biochip fabrication is transferred and the key steps are discussed. Fluorescence spatiotemporal profile in the preconcentration area is recorded and quantitatively analyzed. The reliability of the applied technology for studies of charged biomolecule transport phenomena across nanochannels is proven giving two examples for different preconcentration geometries.

The intensity spectrum of modulated noisy light on optical microwave signal processing and on conversion of FM noise to intensity noise in optical links is investigated theoretically and experimentally with a good agreement. We have applied a model that uses a 1550 nm distributed feedback (DFB) laser and an unbalanced Mach-Zehnder interferometer (UMZI) considering the external phase modulator. Numerical calculations show the influence of the phase modulation index, modulation frequency, and interferometric delay in the phase-to-intensity noise conversion by lowest-order group-velocity dispersion in optical fiber. The results can be employed to estimate the influence of the chromatic dispersion in phase-to-intensity noise conversion, which use either self-delayed interferences or interferometers.

In image processing, the Wavelet Transform (WT) islargely used. However, time requirements for large two-dimensionalimage transforms are hard to meet with sequential implementations.Parallel implementation decreases the processing time and allowsto reach a real-time operation in image coding. Unfortunately,this parallel coding increases the hardware complexity.We propose an optical implementation of the JPEG2000 compressionusing a special implementation of the WT. Special attention ispaid to propose a simple all optical setup carrying out theoptical implementation of JPEG2000 compression for gray-levelimages. Finally, an adaptation of our technique to colored imagesis proposed. Wb

The methods to control the pulse width of a laser-diode end-pumped doubly Q-switched Nd:YVO4/YVO4 composite crystal laser with acoustic-optic (AO) and GaAs saturable absorber has been theoretically and experimentally studied. By varying the laser beam radius in the Q-switchers and the pump beam radius in the gain medium, we provide efficient means to control the pulse duration. The coupled rate equations are used to analyze the process of the laser. The experimental results are consistent with the theoretical results.

Photoinduced changes in a Sudan I doped PMMA thin film were investigated. The dependence of photoinduced birefringence of the thin film on light intensity was studied, with a continuous wave (CW) 532 nm laser as pump light and a CW 650 nm laser as probe light. For all the light intensities (100–1000 mW/cm2), the thin film possessed large photoinduced birefringence (Δn ~ 10−4). With a CW 532 nm laser at relatively low light intensity, a reversible polarization hologram has been recorded in the thin film. Moreover, Z-scan measurements showed that the thin film possessed large nonlinear refractive index (−7.93 ×10−5  cm 2/W) and nonlinear absorption coefficient (−5.50 W/cm) under a CW 532 nm excitation.

Analysis of the optical generation of three bands of continuously tunable millimeter-wave signals using an optical phase modulator (OPM) and an optical notch filter is presented. Three bands of millimeter-wave signals are tuned by using an optical phase modulator and a polarization state rotation filter (PSRF) as optical notch filter. The effect of the chromatic dispersion on wide-band continuously tunable millimeter-wave signal which using an OPM and a PSRF is investigated. The spectrum of the generated millimeter-wave signal after transmission over a 25 km standard single-mode fiber (SSMF) is obtained.

A recent claim [Eur. Phys. J. Appl. Phys. 40, 293 (2007)] demonstrating a nuclear process triggered by electrolysis is challenged. An analysis, based on relative diameters, is used to demonstrate that predominant pits could not possibly be attributed to alpha particles, or to less massive nuclear projectiles. This conclusion is supported not only by positive results from a replication experiment, but also by results from the experiment on which the original claim was based. While the numerous SPAWAR-type pits seem to be highly reproducible, their interpretation is not yet clear.

Earlier we reported, in this journal, that the pits generated in CR-39 detectors during Pd/D co-deposition experiments are consistent with thoseobserved for pits that are of a nuclear origin. Recently, that interpretation has been challenged. In this communication, additional experimental data and further analysis of our earlier results are providedthat support our original conclusions.

It is theoretically shown that an attractive effective potential isgenerated via optical phonon exchange between two quasi-free, differentparticles in deuterated Pd which, in turn, enhances the probability oftheir nuclear fusion reaction. Mechanisms, thatmay be responsible for extra heat production and nuclear isomer formation,are also discussed. Creation of 4He pairs dueto the significantly increased probability of the p + 7Li $\rightarrow$ 24He + 17.35 MeV and d + 6Li $\rightarrow$ 24He + 22.37 MeVnuclear reactions is predicted. Some of the basic questions of fusion reactions insolids seem to be successfully explained.

In order to improve our knowledge of the emitted signal of forests at L-band (1.4 GHz) we focused this study on permittivity measurements of heterogenic natural media such as soil or litter consisting of plant debris and organic matter. This study was done in the context of the upcoming SMOS (Soil Moisture and Ocean Salinity) satellite mission that will attempt to map surface soil moisture from L-band (1.4 GHz) passive microwave measurements. In the field of passive microwaves, very little information exists about the behaviour of the L-band signal of forests especially when litter is included in the soil-vegetation system. To date very few analyses have investigated the dielectric behaviour of the litter layer and its influence on the microwave emission of forests is generally neglected.

This paper presents a dynamical non linear model of the spatial time-dependant evolution of A3 point during a particular sequence of resistance spot welding in steel material. The model is based on a solution to the heat equation, expressed in cylindrical coordinates inside the joint area, and when the source term is attributed to the electrical power. By the mean of the steel binary Fe–C diagram and the deduced t-dependant temperature rise profile, an estimation of the A3 point spatial range date is given and compared to further results. The obtained temperature profile is yielded, taking into account main parameters variations, as a guide to non-destructive protocols and thermal characteristics investigation