Synthesis and characterization of spinel LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles prepared by high-energy milling and hydrothermal method

Spinel LiMn₂O₄ has been known to be a technologically important, environmental-friendly, and low-cost cathode material used in Li-based rechargeable batteries, and it is also widely available. Nanoparticle spinel LiMn₂O₄ has been synthesized by the top-down, high-energy milling, and hydrothermal methods. SEM images, X-ray diffraction patterns, and neutron high-resolution powder diffraction patterns have confirmed the nanocrystalline nature of the spinel LiMn₂O₄ samples. Raman and Fourier transform infrared (FTIR) measurements show typical absorption and vibration spectra typical for the spinel LiMn₂O₄ showing the formation of various metallic bonds in the sample. The strongest Raman and FTIR signals come from the higher frequency region, with weaker signals appearing in the lower frequency range.     

Imaging and correlation used for guided laser lithotripsy

High-speed imaging of phenomena akin to laser lithotripsy is performed. A new method for guiding laser light for the stone destruction is proposed. This is based on a combination of signals obtained from the correlation of fluorescent and ballistic images.     

Hadamard speckle contrast reduction

The condition for a diffuser to produce the maximum speckle contrast reduction with the minimum number of distinct phase patterns is derived. A binary realization of this optimum diffuser is obtained by mapping the rows or columns of a Hadamard matrix to the phase patterns. The method is experimentally verified in the Grating Light Valve laser projection display.     

Structure,composition and optical properties of ZnO:Ga films electrodeposited on flexible substrates

Thin films of ZnO:Ga are electrodeposited on stainless steel from zinc chloride solutions containing gallium with a Ga/Zn molar ratio in the range 1–10%. The surface morphology, structure, composition, and the optical properties of these films are studied using SEM, XRD, EDX, XPS, photoluminescence and transmittance spectroscopy. Results reveal that films with embedded platelets can be grown with a Ga/Zn molar ratio up to 60%. In as-grown films, Ga is present in the form of oxide, hydroxide or hydroxychloride compounds which decompose by annealing. Films annealed at 400°C are composed only from ZnO and Ga₂O₃ phases. The incorporation of Ga in ZnO films does not make a considerable change in the optical transmittance and the photoluminescence properties of the films.     

ZnO films grown by successive chemical solution deposition

ZnO films were grown from 0.1-M zincate solutions on stainless-steel and aluminosilicate glass substrates by the successive chemical solution deposition method. The structure, morphology, composition, and optical emission properties of the films were studied by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and photoluminescence techniques. Results revealed that the as-grown film contains a substantial amount of amorphous zinc hydroxide (15–25%), at least on its surface. This can be reduced to 7% by annealing the film in argon (350 °C, 1 h). Despite the presence of the hydroxide phase, the films hexagonal lattice constants match the standard values. The films surface texture and the grains shape and preferential orientation depend on the type of the substrate and its surface conditioning. The UV photoluminescence emission from as-grown films at 3.22±0.04 eV (380–390 nm) and its suppression due to the effect of chlorine are addressed. PACS 81.16.Be; 81.05.Dz; 78.55.Et; 79.60.-i; 68.55.Jk     

Laser spectroscopy and imaging of gallbladder stones, tissue and bile

Laser spectroscopic study of billary calculi and tissues is described. Fluorescence spectra of human gallbladder stones, bile and tissues were recorded with streak camera in the frequency and time domain. Potential of fluorescence as a diagnostic tool to discriminate between the intended target and the surrounding tissues and bile is evaluated. Initiation of fragmentation process is visualized by high-speed shadowgraphy, interferometry performed during the laser impact and generation of plasma causing growth and collapse of bubbles.     

Higher-moment and diffraction-order computation for deformation measurement

Higher moment and diffraction orders are computed and used for deformation measurement. For a given two-dimenstional function lower-order moments are calculated. It is shown that simplified results can be obtained if an appropriate pattern is used for the calculation. The obtained results are employed for calculation of higher-order mements. Optical implementation and their use for deformation measurement is shown. High diffraction orders are introduced by using a projected grill-pattern on the model surface. This is performed by selecting higher frequency spots in the Fourier-Transform plane. Selection of the high-frequency diffraction orders and calculation of high-order moments are two image processing approaches useful for deformation measurement. Accuracy of the measurement for in-plane deformation and out-of-plane rotation is calculated. It is shown that accuracy of measurement is increased when higher orders are used.     

Identification of discontinuities in plasma plume evolution

The ejection of material during laser ablation gives rise to the development of discontinuities in the ambient gas. Several of these discontinuities are observed and characterized, including externally and internally propagating shock waves, contact surface, and the ionization front. Qualitative experimental observations and analysis of these discontinuities are presented. Results from shadowgraphy enabled determination of an irradiance threshold between two different ablation mechanisms, and determination of several stages of plasma plume evolution. Consideration of the refractive index as a dynamic sum of the contributions from gas and electrons led to separate identification of ionization front from the contact surface. Furthermore, ionization front was observed to lead the shock wave at the earlier stage of the ablation.     

Laser ablation of gall bladder stones.

Study of laser interaction with calculi is presented. A system of Nd-Yag and Ho-Yag pulsed lasers were used to produce fluorescence and plasma signals at the stone surface surrounded by saline and bile fluids. Fourth harmonic from Nd-Yag laser was transmitted to the samples by graded UV optical fibres. Gall bladder stones of various compositions were subjected to the high power Ho-Yag laser. Temporal transients and spectral evolution of plasma and fluorescence signals were monitored by a streak camera. A profile of acoustic pressures generated by shock waves was recorded with sensitive hydrophones placed in the surrounding fluids. Ablation threshold, cavitation process and fluorescence dependence on the laser parameters were studied in detail. Potential of stone identification by fluorescence and possible hydrodynamic model for ablation of biological samples is discussed.     

Successive chemical solution deposition of ZnO films on flexible steel substrate: structure, photoluminescence and optical transitions

Zinc oxide is an attractive optoelectronic material with wide applications. Thin ZnO films were prepared on steel foil by successive chemical solution deposition (SCSD). The film structure, room-temperature photoluminescence (PL) and optical absorption characteristics were investigated. This study revealed that films of high structural and optical quality can be prepared by the SCSD method. PL of as-grown films shows a weak green peak at 560 nm and a strong UV peak at 380 nm. Annealing in either air or argon suppresses the green peak and red shifts the UV emission towards 390 nm. The presence of chlorine in the deposition solution destroys the PL of as-grown films. A strong UV emission, however, develops after annealing the films in air. Several optical transitions measured from the film PL and optical absorption coefficients are shown to be related to transitions through the known defect levels in ZnO, such as E₁, L₁, E₃ and V_O ²⁺ levels. PACS 81.16.Be; 81.05.Dz; 78.55.Et; 78.66.Hf; 68.55.Jk