This paper studies numerically the temperature reached by atomic force microscope tips illuminated by femtosecond laser pulses, in which the laser focusing dependence of tip heating is investigated in detail and the laser heating effects on different tips are discussed too. The results show that tip heating can be significantly reduced if the femtosecond laser is focused tightly on the tip apex.

Ultrasonic velocity (U), density (ρ) and viscosity (η) measurements have been carried out in three ternarymixtures of glucose with amylase in aqueous medium at 298.15 K. The experimental data have been used to calculate somederived parameters such as acoustical impedance (Z), relative association (R A ), Rao's constant (R), Wada's constant (W), relaxation time (τ), relaxation amplitude (α/f 2), relaxation strength (r), and some excessthermodynamical properties like excess adiabatic compressibility (βE ), excess free length (L f E ) excessfree volume (V f E ), excess internal pressure (π i E ) and excess acoustical impedance (ZE ). The above parameters have been evaluated and discussed in light of molecular interactions in the mixture.

Using spectroscopic and small angle X-ray scattering analyses, temporal evolution of ionic and neutral silver clusters inside and on the surface of a glass matrix has been studied during the ion-exchange process. It is found that in the beginning of the ion-exchange process the ionic clusters (Ag $_{N}^{+}$ ; where N is the number of atoms of the ionic silver cluster) form and start to grow. But, with continuation of the process the generated ionic silver clusters begin fragmentation and resizing which, in turn, results in modification of the interaction with the glass matrix. Our results show that, longer ion-exchange processing time results in re-growing of the ionic silver clusters. Simultaneously, the index of refraction of the ion-exchanged glass first increases, then decreases and increases again. Our findings imply that, there is no simple linear relation between the index of refraction and the ion-exchange duration time. Some of the ionic clusters may transform to neutral ones by absorbing electrons available in the glass matrix. X-ray and AFM analyses confirm that, at the same time, some neutral silver nanoparticles form on the surface of the samples, and their evolution follows the evolution of the forming ionic clusters. Resizing, movement toward the surface and aggregation of the clusters, are the most important consequences of the interaction of the forming clusters with the glass matrix observed in this study.

In this investigation, transparent TiO2 nanotube arrays prepared on a FTO substrate are employed as 1D nanostructuresproviding elongated direct pathways for electron transport and collection in solid-state dye-sensitized solar cell (SDSC). Donor-antenna (D-A) dyes provide an exciting route for improving the light harvesting efficiency in dye sensitized solar cells owing to their high molar extinction coefficients and the effective spatial separation of charges in the charge-separated state. Hence in this study we fabricated SDSC devices with different thicknesses of transparent TiO2 nanotube array electrodes sensitized with Ru-(II)-donor-antenna dye and spiro-OMeTAD as a hole conductor. At AM 1.5 G, 100 mW/cm2 illumination intensity, a power conversion efficiency of 1.94% was achieved when the TiO2 nanotubes are initially subjected to TiCl4 treatment. Furthermore, a linear increase in the cell current without loss in fill factor is observed for increasing length of TiO2 nanotubes. The structural and morphological characteristics of the transparent TiO2 nanotube arrays as well as the optimal conditions for the fabrication of SDSCs with transparentTiO2 nanotubes on FTO glass are reported.

We study resonant tunneling through a layered medium with a passive negative index medium (NIM) slab as a constituent layer. Using a causalmodel for susceptibilities with the parameters of a recently reported metamaterial [G. Dolling, C. Enkrich, M. Wegener, C.M. Soukoulis, S. Linden, Opt. Lett. 31, 1800 (2006)] we show that resonant tunnelling and the associated delay are mostly suppressed. This is in sharp contrast with the naive approach of retaining phase velocity dispersion with arbitrary low losses, predicting sharp resonances with large associated delays. This is shown to be a nontrivial issue because of the necessity of losses for NIM behaviour, while their presence spoils the quality factor of the resonant devices.

The atomic edges of graphene nanoribbons with anomalous geometry structure were very recently observed in experimental evidence by [Koskinen et al., Phys. Rev. B 80, 073401 (2009)]. We present first-principles calculation to investigate the electronic structures and transport properties of graphene nanoribbon with anomalous edges (two configurations, namely 5-7-7 edge and 5-6 edge). Electronic band results demonstrate that the Fermi level is downward shifted due to the formation of the anomalous edges in these configurations. The band gap is substantially increased as a result of the presence of the 5-7-7 edge. Furthermore, the conductance below the Fermi level presents more prominent variation in the 5-6 edge configuration, indicating that this defect mainly affecting its valence bands. Our results provide the possibility of new approaches to control the electronic transport properties of graphene nanoribbons via tailoring the atomic structure of their edges.

Since they first appearance at the end of the 1980's, organic transistors have been experiencing a growing interest from both academic and industrial institutions. In this short review, we address the current state-of-the-art of this new kind of electronic device. In particular, we try to define what characterizes an organic semiconductor, and in what it differs from its inorganic counterpart. As far as the applications are concerned, we show that the organic transistor must not be viewed as a direct competitor to silicon; instead, its future lies in the opportunity to implement new low-cost fabrications techniques, and in the possibility to realize flexible devices on polymer substrates.

The vortex dynamics of (Y, Nd)Ba2Cu3O7−δ ((Y, Nd)123) superconductors have been studied using magnetic relaxation measurements obtained at different sweep rates. The temperature dependence of the dynamic relaxation rate (Q) is found to be not vanishing at T = 0 K, and also showed well developed maxima becoming broader and tending to move to higher temperatures with decreasing magnetic field. At temperatures close to the critical temperature (T c ), Q(T) showed well-developed minima becoming deeper and tending to move to lower temperatures with increasing field. These minima appeared to occur approximately at the same reduced temperature position [ T/T c ]as that of oxygen-controlled-melt-grown (OCMG)-Nd(123) samples, thus providing further support for pinning similarities between both systems. Both the field dependence of the characteristic pinning energy [ U c ]and relaxation rate showed significant inconsistency with the collective pinning theory but full agreement with the results of [Perkins et al., Phys. Rev. B 54, 12551 (1996)].

The diffraction of Gaussian vortex beams in uniaxial crystals orthogonal to the optical axis is studied. Analytical expressions for the components of the diffraction field are derived and illustrated by numerical examples. Results indicate that, upon diffraction of Gaussian vortex beams inside uniaxial crystals, components of the transversal and longitudinal electric fields would vary and show different characteristics. Effects of anisotropic crystals on intensity distributions of Gaussian vortex beams are also investigated. It demonstrates that, upon diffraction, intensity distributions would be distorted and rotated into elliptical profiles with the variation of the ratio of refractive indices. These influences may finally cause the non-symmetry of the intensity distributions of laser beams.

A technique based on a tree-cotree decomposition, called Spanning Tree Technique (STT) in this paper, has been shown to be simple and efficient to compute the generalized source magnetic fields for h-oriented magnetostatic formulations when solenoidal source electric currents over the faces of the mesh are given as input. Yet, it has been recently shown that STT may frequently fail in practice.Other techniques, which circumvent STT problems, have been proposed in literature. However, all of them greatly worsen the computational complexity and memory requirements regarding the source field computation.The aim of this paper is to present a generalization of STT called Extended Spanning Tree Technique (ESTT), which is provably general and it retains the STT computational efficiency.

The study presented in this paper is a first step of an EMC (Electromagnetic Compatibility) analysisof the behaviour of a railway power substation at high frequency. Before on site intensive experimentation, theapproach is performed with a reduced scale model. The mock-up of the substation is powered by a 220 Vthree-phase voltage supplied by a 15 kV A power transformer, a rectifier and loads. The study consists in designing an equivalent electrical circuit of power transformer in high frequency, available over a large panelof loads. The model of power transformer was deduced from measurements in frequency domain within the range 40 Hz to 30 MHz.

The formation of the chemical products produced in an atmospheric glow discharge fed by a N2-CH4 gas mixture has been studied using Fourier Transform InfraRed (FTIR) and Optical Emission Spectrometry (OES). The measurements were carried out in a flowing regime at ambient temperature and pressure with CH4 concentrations ranging from 0.5% to 2%. In the recorded emission spectra the lines of the second positive system CN system and the first negative system of N2 were found to be the most intensive but atomic H $^{\alpha}$ , H $^{\beta}$ , and C (247 nm) lines were also observed. FTIR-measurements revealed HCN and NH3 to be the major products of the plasma with traces of C2H2. These same molecules have been detected in Titan's atmosphere and the present experiments may provide some novel insights into the chemical and physical mechanisms prevalent in Titan's atmosphere with these smaller species believed to be the precursors of heavier organic species in Titan's atmosphere and on its surface.

The elastic and thermodynamic properties of fcc-6LiF under high temperatures and pressures are investigated using the ab initio method and quasi-harmonic Debye model. The lattice constant of 6LiF at ground state is a little larger than that of LiF. When pressure is less than 10 GPa, crystal lattice is compressed easily at low temperature, and when P> 10 GPa, lattice can be compressed easily at high temperature. C 11 increases with pressure and reduces with temperature sensitively. C 12 and C 44 raise or decrease just a little with increasing pressure and temperature. Heat capacity of different pressure increases with temperature and closes to the Dulong-Petit limit at higher temperatures. Debye temperature decreases with temperature, and increases with pressure. Furthermore, under lower pressure, thermal expansion coefficient raise rapidly with temperature, and the increasing trend will get slow at higher pressure.

We studied the structural and dielectric properties of new Tetragonal Tungsten Bronze (TTB) ceramics Pb1.85K1.15Li0.15Nb5O15 that was synthesized by solid-state reaction. We pay a special attention to the diffuse phase transition (DPT) that occurs close to 425 °C. Using dielectric measurements in a frequency range of 10 Hz–1 MHz and in the temperature range 30–560 °C, we have shown that the real permittivity close to DPT is well described by Santos-Eiras phenomenological model. Space-charge polarization, relaxation phenomena and free charges conductivity have been analyzed using dielectric spectroscopy impedance and modulus characterization. Cole-Cole plots show a non-Debye (polydispersive) type relaxation. In paraelectric phase the Arrhenius activation energy was determined as Eτ = 0.72 eV. We demonstrated that frequency dependence of ac conductivity at different temperatures obeys the Jonscher's universal law: σac = σdc + A(ω)n.

In this paper the design of a multiband compact antenna for the integration into the new multi function mobile phones is presented. The antenna is matched to operate at GSM 920 MHz, WI-Fi 2.4 GHz and HiperLan 5.1 GHz standards with low SAR levels. Return loss coefficient and radiation pattern of this antenna are computed in free space as well as in the presence of head. The specific absorption rate (SAR) of the planar antenna is calculated and compared with that of the monopole antenna. To examine the performance of this antenna, a prototype was designed, fabricated and measured; the simulation analysis was performed using the HFSS software, good agreement with the simulation providing validation of the design procedure.

This paper deals with a technique for calculating the 3D E-field components knowing only the two components (H x and H y ) of the H-field in near-zone. The originality of the under study technique lies on the possibility to take into account the evanescent wave influences. The presented E-field extraction process is based on the exploitation of the Maxwell-Ampere relation combined with the plane wave spectrum (PWS) method. The efficiency of the proposed technique is evidenced by comparing the E-field deduced from H-field and the own E-field radiated by the association of electrical- and also magnetic- elementary dipoles in different configurations by using Matlab text programming environment. In addition, as a concrete demonstrator, the concept was also validated with the computation of EM-wave radiated by an open-end microstrip transmission line. As result of comparison, very good agreement between the exact E-field and that one extracted from the H-field was realized by considering the near-field scanned at the height, z = 5 mm and 8 mm above the under test structure at the operating frequency, f = 1 GHz. The presented technique can simplify the difficulties about the E-near-field measurement in EMC applications.

The local structures and the spin Hamiltonian parameters for the substitutional Nb4+ centers in MO2 (M = Sn, Ti and Ge) crystals are theoretically studied using the perturbation formulas of these parameters for a 4d1 ion in a rhombically compressed octahedron. The above Nb4+ centers are found to experience the Jahn-Teller distortions, characteristic of the relative axial compressions (~ 0.01–0.02 Å) and the non-axial (planar) angular increases (~ 3°). As a result, the ligand octahedra are transformed from original elongation on host tetravalent cation sites to compression in the impurity centers, with additional non-axial distortions smaller than those in the hosts. The influences of the Jahn-Teller distortions and the ligand orbital contributions are also analyzed.

In this paper we extract the characteristic impedance of Back End Of Line (BEOL) interconnections from radio frequency (RF) scattering parameter measurements. Quantification of the electric interconnection performance on a broad frequency band requires a good knowledge of the characteristic impedance Z c and the propagation exponent γ. Propagation exponent is easily obtained by measuring two interconnections with different lengths. However, because of the complex test structure with mismatched ports where interconnections are embedded, the extraction of Z c from scattering parameter measurements remains challenging. To solve this problem, we propose an approach based on the Winkel method without using simplified assumptions. Limits of validity for our de-embedding procedure to extract characteristic impedance are also analyzed.

A gas phase kinetic model combined to a 3D atomic etching model have been developed to study the etching process of InP under Cl2-Ar ICP plasma discharge. A gas phase global kinetic model is used to calculate the reactive particle fluxes implied in the etching mechanisms. The 3D atomic InP etching model is based on the Monte Carlo kinetic approach where the plasma surface interactions are described in the probability way. The coupling between the plasma chemistry model and the surface etching model is an interesting approach to predict the etched surface properties in terms of the etch rate, the surface roughness and surface steochiometry as a function of the operating conditions. A satisfactory agreement is obtained by comparing the experimental and the simulation results concerning the evolution of the main plasma discharge parameters such as the electron density and temperature versus the ICP source power for a surface recombination coefficient of atomic chlorine fixed at γ Cl = 0.04. On the other hand, simulation results show the effect of the operating conditions on the etched surface roughness and the etch rate evolutions with time in the early stage. Moreover, the simulation results show the correlation between the decrease of the ion to chlorine flux ratio and the decrease of the RRMS as a function of the pressure.