Studies on polarization properties of scattered light from a random medium like biological tissue have received considerable attention because polarization can be used as an effective tool to discriminate against multiply scattered light (acting as a gating mechanism) and thus can facilitate high resolution imaging through tissue. Further, the polarization properties of scattered light from tissue contain wealth of morphological and functional information of potential biomedical importance. However, in a complex random medium like tissue, numerous complexities due to multiple scattering and simultaneous occurrences of many scattering and polarization events present formidable challenges both in terms of accurate measurements and in terms of analysis of the tissue polarimetry signal. Several studies have therefore been conducted in the recent past to develop appropriate measurement procedures, suitable light propagation models and polarimetry signal analysis methods to overcome these difficulties. In this review, we focus on some of the recent key developments in this area. Specifically, we describe variety of theoretical and experimental tools, illustrated with selected results, aimed at evaluating the prospect of turbid medium polarimetry for both biomedical imaging and diagnosis.

The dielectric, piezoelectric and electrical properties of relaxor ferroelectric 0.65PMN-0.20PZT-0.15PT ceramic as a function of sintering temperatures was investigated. X-ray diffraction shows that with increasing temperature from 700 °C to 800 °C the pyrochlore unwanted phase reduces and at 850 °C the single phase of perovskite be formed. The studies and reviews reveal that the outstanding electrical properties are obtained with this composition near the morphotropic phase boundary (MPB). P-E hysteresis loops emphasize that the synthesis optimum temperature is 1250 °C and observed that the best temperature that led to improved properties of dielectric constant, polarization and piezoelectric coefficients is this temperature.

We report here a comparative study of the in-plane strain states of standard GaN epilayer grown on sapphire (001) and flip-chip GaN epilayer bonded on Si (111) wafer by means of X-Ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) spectroscopy. It is confirmed that the in-plane tensile strains can be largely reduced after the flip-chip process. The reduction of the biaxial strains determined by XRD, Raman, and PL analysis is found to be consistent.

This paper reports the deposition of titanium dioxide thin films on p-type Si(100) substrates using two techniques called conventional magnetron sputtering (CMS) and hollow cathode magnetron sputtering (HCMS). The influence of the plasma parameters on the film characteristics (topography, morphology and crystallinity) was investigated. Films were deposited at different oxygen concentrations (in the Ar + O2 gas mixture) and axial distances for fixed values of working pressure (5.0 mTorr) and DC power (55 W). They were analyzed by profilometry, AFM and XRD. The gas discharge was diagnosed by single Langmuir probe and OES. Under experimental conditions used in this work, results show that HCMS favors the growing of rutile phase due to the increase of the energy on the film surface caused by the hollow cathode effect. On the other hand, films deposited by CMS present preferentially anatase phase due to the low energy transferred to the growing film. Further studies regarding the influence of plasma properties on the films formation were done in order to understand the plasma-surface correlation.

A new method to evaluate the five parameters of illuminated solar cells is described. The method is based on nonlinear least squares approach. On calculating the lsqcurvefit-function with constraints, between the experimental current-voltage I(V) characteristic and a theoretical arbitrary characteristic based on Lambert W-function. The used model is implemented as a MATLAB® script which yields the I(V) characteristics of the LILT under test. The model has been validated against by applying it to experimental I(V) characteristics. Some parameters of the model have been measured directly whereas others have been evaluated by means of direct computation on the data sheet or by means of best-fit on the measured data. The results have been compared and an analysis of the errors is presented.

The Schrödinger equation is applied to the photon-electron interaction to give a unified picture of the ponderomotive refraction effect, Kapitza-Dirac diffraction as well as near field energy gain and loss processes. Analytical solutions are studied for simple cases and the potential use of these phenomena in applications of electron microscopy is discussed.

Based on the features of diode-pumped Yb3+:Y2SiO5 (Yb:YSO) lasers, a thermal model was established. According to the latest reports and measurements on thermal parameters, and further considering the heat transfer on side surface, thermal lensing effect of Yb:YSO was studied for the first time to our knowledge. Under the pump power of 17 W, the maximum temperature (488.4 °C) and the maximum distortion (1.24 μm) were obtained by solving Poisson equation using finite difference method. Moreover, thermal lens focal length was measured through a plane-plane cavity. All the results demonstrate that the theoretical result will be closer to the reality if we take the heat transfer on side surfaces into account.

The efficiency of the metastability exchange optical pumping (MEOP) performed at elevated 3He gas pressures in high magnetic field was improved by modifying the spatial profile of the pumping laser beam in such a way that it matched the nonuniform distribution of plasma in the optical pumping cell. Comparing to a conventional Gaussian profile, at the 3He gas pressure equal to 267 mbar, both the achieved nuclear polarization (equal to 26%) and the total magnetization in the cell (equal to 1.37 sccfp) are 60% higher when the annular laser beam profile is applied.

We have prepared free-standing porous silicon (FPS) samples with various porosities using electrochemical etching. The result of a study combining absorption and photoluminescence (PL) from FPS samples with porosities in the range 53–76% is presented. A blue shift of the PL peak position and an increase of the PL intensity with enhancing porosity have been observed. Furthermore, the PL peak and intensity of porous silicon (PS) samples are compared with FPS samples. Our results show that the PL peak intensity reduces 1.5–2.5 times from PS to FPS. However, no notable shift of the PL peak position from PS to FPS has been observed.

Recent pioneering experiments combining ultrafast lasers with electron-based technology demonstrated the possibility to obtain real-time information about chemical bonds and their dynamics during reactions and phase transformation. These techniques have been successfully applied to several states of matter including gases, liquids, solids and biological samples showing a unique versatility thanks to the high sensitivity of electrons to tiny amounts of material and their low radiation damage. A very powerful tool, the time-resolved Transmission Electron Microscope (TEM), is capable of delivering information on the structure of ordered and disordered matter through diffraction and imaging, with a spatial resolution down to the atomic limit (10-10 m); the same apparatus can distinguish dynamical phenomena happening on the time-scales between fs and ms, with a dynamic range of 12 orders of magnitude. At the same time, spectroscopic information can be obtained from the loss of kinetic energy of electrons interacting with specimens in the range of interband transitions and plasmons in solids, or charge transfers in molecules, all the way up to the atomic core levels with the same time-resolution. In this contribution, we focus on the recent advances in fs Electron Energy Loss Spectroscopy (FEELS), discussing the main results and their implications for future studies.

The Fourier-transform infrared (FT-IR) spectra of magnesium phthalocyanine (MgPc) were investigated in the spectral range 500–4000 cm-1. The spectra allow characterization of vibration modes. A comparison of absorption spectra of powder, as-deposited and annealed films is presented. The dark electrical resistivity measurements were carried out at different temperatures in the range 308 to 423 K. Two activation energies ΔE1 = 0.23 eV and ΔE2 = 0.69 eV were obtained. The thermal activation energy ΔE1 is associated with impurity conduction and ΔE2 is associated with intrinsic conduction. The current density-voltage characteristics of MgPc at room temperature showed a linear ohmic conduction mechanism at low voltages. At higher voltages the space-charge-limited conduction (SCLC) accompanied as a single dominant level. The temperature dependence of current density allows the determination of some essential parameters such as the hole mobility (μh), the trapping factor Θ and the total trap concentration (Nt).

An experimental study on the pulsed laser ablation of copper by using Nd-YAG laser radiation of 1064 nm wavelength at a fluence of 13 J/cm2 is reported. A time-resolving plane Langmuir probe, placed at various angles with respect to the target surface normal, is used to record temporal variation of ion currents during the plasma expansion in vacuum. The measured angular distributions of integrated ion yields are strongly peaked in forward direction. The experimentally determined plume expansion coefficient Zinf/Xinf = 2.1±0.2 is in good agreement with the previous studies. Time-of-flight measurements indicated that the energy of various ion components is highest along target surface normal and decreases with increase of the angle, however the effect of angle is more pronounced on the faster ions. The energy spread of the ions decreases approximately from ±670 eV to ±19 eV as the probe angle increases from 0° to 60°. The measured angular dependence of ion yield and most probable ion energy nicely follows the trends predicted by Anisimov's plume expansion model.

Inelastic interaction and wave optics seem to be incompatible in that inelastic processes destroy coherence, which is the fundamental requirement for holography. In special experiments it is shown that energy transfer larger than some 10-15 eV undoubtedly destroys coherence of the inelastic electron with the elastic remainder. Consequently, the usual inelastic processes, such as phonon-, plasmon- or inner shell-excitations with energy transfer of several meV out to several 10 eV, certainly produce incoherence with the elastic ones. However, it turned out that within the inelastic wave, “newborn” by the inelastic process, there is a sufficiently wide area of coherence for generating “inelastic holograms”. This is exploited to create holograms with electrons scattered at surface-plasmons, which opens up quantum mechanical investigation of these inelastic processes.

This paper presents a new steady state model which contains fewer polarisation curve fitting parameters compared to other semi-empirical models. The established model is also defined at no load operation and can be fitted perfectly to the static polarisation curve for a wide range of cell currents. The model links the fuel cell voltage to the current by a simple function to which various useful derivative laws can be applied. As a result, many analytical expressions, for example, polarisation resistance or power density, can be evaluated directly from the model.

Fuel cell self start at negative temperature conditions is not an easy task due to the water produced by the reduction of oxygen at the cathode. This amount of water can turn into ice and block the reaction before the temperature inside the fuel cell reaches positive values. The mechanism of the physical process which leads to oxidant starvation phenomena when ice appears is not yet well identified. In order to obtain a deeper understanding of this problem, the article presents some experimental investigations conducted on a short fuel cell stack. These experiments simulate vehicle technology operated in cold start conditions not with the primary objective to reach a successful and rapid start-up but much rather to characterise and understand the cold start phenomena until starvation occurs. A number of polarisation curves, electrochemical spectroscopy and cyclic voltammetry measurements are done on the stack before, after and also during the cold starts experiments. It is observed that the process of drying and cooling down prior to cold start have a great impact on the electrochemical cathode area. The results obtained show the evolution of the stack behaviour during the low temperature operation with a slow production of frost. The consequence on the individual cells in terms of inhomogeneous degradation is highlighted.

Thin-film transistors (TFT's) may have a low-quality back channel in addition to the high-quality main channel. The presence of the back channel can deteriorate TFT turn-off characteristics. We studied properties of the back channel in bottom-gate GaInZnO TFT's grown by rf sputtering. X-ray photoelectron spectroscopy (XPS) results confirmed existence of low-quality oxide in the back channel. We observed that 200 °C annealing increased binding energies of metals and oxygen on the surface. This energy increase can be explained as a result of tighter bonding between metals and oxygen. When the top surface of GaInZnO was removed by Ar etching, XPS did not show such energy increase after the annealing. XPS also showed that the top surface has significantly higher In concentration compared to the bulk.

A dedicated STEM developed for operation at primary energies from 200 keV to 40 keV and lower is described. It has a new cold field emission gun (CFEG) that gives a normalized brightness of 3 × 108 A/(m2 sr V), and excellent short-term and long-term stability. It includes two gun lenses (one electrostatic and one electromagnetic), a fast electrostatic beam blanker, three condenser lenses, a corrector of third- and fifth-order geometric aberrations, an objective lens with low aberration coefficients, a flexible set of projector lenses, an ultra-stable sample stage, and provision for storing up to five samples under high vacuum and loading them into the microscope’s objective lens under remote control. The microscope is enclosed in a magnetically and acoustically shielding enclosure, which allows it to operate at a high performance level even in non-optimal environments. It has reached 53 pm resolution at 200 keV and 123 pm at 40 keV, and an EELS energy resolution of 0.26 eV.

The structure of crystals can be described by defining size and shape of a unit cell and the positions of the atoms within it. Many materials, however, exhibit a glassy or amorphous structure. Such disordered structures are described by structure factors. These are usually determined by small angle scattering experiments. The angular distribution recorded in these experiments is related to the structure factor. In this work we present an alternative approach using elemental maps obtained in an energy filtering transmission electron microscope. In this way we can even obtain chemically resolved partial structure factors giving additional information on the specimen.

Thin films of InSb with different thickness (t = 5, 10 and 15 kÅ) were deposited on to glass substrate by flash evaporation technique. The structural and electrical properties were investigated and the effect of films thickness on films properties was discussed. XRD analysis of the films as a function of film thickness revealed that crystallinity improves with film thickness. Temperature dependence of the Hall parameters were studied in a wide range, 20 < T < 300 K. The temperature variation of the Hall coefficient and conductivity shows an activated nature with negative temperature coefficient confirming that the prepared films of InSb are semiconducting in nature with n-type conductivity. Size effect was observed as the defect density is much smaller for thicker films and as a result electrical conductivity of the films increases with increasing film thickness with the increase of the charge carriers through the film. An increase in mobility with sample thickness has been observed. The mobility variations with temperature revealed a transition from lattice to impurity scattering in the observed temperature range.