Influence of annealing temperature on Raman and photoluminescence spectra of electron beam evaporated TiO2 thin films.

Titanium dioxide (TiO(2)) thin films were deposited on fused quartz substrates by electron beam evaporation method at room temperature. The films were annealed at different temperatures in ambient air. The surface morphology/roughness at different annealing temperatures were analyzed by atomic force microscopy (AFM). The crystallinity of the film has improved with the increase of annealing temperature. The effect of annealing temperature on optical, photoluminescence and Raman spectra of TiO(2) films were investigated. The refractive index of TiO(2) films were studied by envelope method and reflectance spectra and it is observed that the refractive index of the films was high. The photoluminescence intensity corresponding to green emission was enhanced with increase of annealing temperature. The peaks in Raman spectra depicts that the TiO(2) film is of anatase phase after annealing at 300°C and higher. The films show high refractive index, good optical quality and photoluminescence characteristics suggest that possible usage in opto-electronic and optical coating applications.

Influence of Sn doping on structural, optical and electrical properties of ZnO thin films prepared by cost effective sol-gel process.

Tin (Sn) doped zinc oxide (ZnO) thin films were synthesized by sol-gel spin coating method using zinc acetate di-hydrate and tin chloride di-hydrate as the precursor materials. The films were deposited on glass and silicon substrates and annealed at different temperatures in air ambient. The agglomeration of grains was observed by the addition of Sn in ZnO film with an average grain size of 60 nm. The optical properties of the films were studied using UV-VIS-NIR spectrophotometer. The optical band gap energies were estimated at different concentrations of Sn. The MOS capacitors were fabricated using Sn doped ZnO films. The capacitance-voltage (C-V), dissipation vs. voltage (D-V) and current-voltage (I-V) characteristics were studied and the electrical resistivity and dielectric constant were estimated. The porosity and surface area of the films were increased with the doping of Sn which makes these films suitable for opto-electronic applications.

Effect of sintering on optical, structural and photoluminescence properties of ZnO thin films prepared by sol-gel process.

Zinc oxide (ZnO) thin films have been deposited on glass substrates via sol-gel technique using zinc acetate dihydrate as precursor by spin coating of the sol at 2000 rpm. Effects of annealing temperature on optical, structural and photo luminescence properties of the deposited ZnO films have been investigated. The phase transition from amorphous to polycrystalline hexagonal wurtzite structure was observed at an annealing temperature of 400 degrees C. An average transmittance of 87% in the visible region has been obtained at room temperature. The optical transmittance has slightly increased with increase of annealing temperature. The band gap energy was estimated by Tauc's method and found to be 3.22 eV at room temperature. The optical band gap energy has decreased with increasing annealing temperature. The photoluminescence (PL) intensity increased with annealing temperature up to 200 degrees C and decreased at 300 degrees C.

Optical, field-emission, and antimicrobial properties of ZnO nanostructured films deposited at room temperature by activated reactive evaporation.

ZnO nanostructures were deposited on flexible polymer sheet and cotton fabrics at room temperature by activated reactive evaporation. Room-temperature photoluminescence spectrum of ZnO nanostructured film exhibited a week intrinsic UV emission and a strong broad yellow-orange visible emission. TEM and HRTEM studies show that the grown nanostructures are crystalline in nature and their growth direction was identified to be along [002]. ZnO nanostructures grown on the copper-coated flexible polymer sheets exhibited stable field-emission characteristics with a threshold voltage of 2.74 V/mum (250 muA) and a very large field enhancement factor (beta) of 23,213. Cotton fabric coated with ZnO nanostructures show an excellent antimicrobial activity against Staphylococcus aureus bacteria (Gram positive), and approximately 73% reduction in the bacterial population is achieved compared to uncoated fabrics after 4 h in viability. Using a shadow mask technique, we also selectively deposited the nanostructures at room temperature on polymer substrates.

Optical, dielectric and morphological studies of sol-gel derived nanocrystalline TiO2 films.

Nanocrystalline TiO(2) films have been synthesized on glass and silicon substrates by sol-gel technique. The films have been characterized with optical reflectance/transmittance in the wavelength range 300-1000 nm and the optical constants (n, k) were estimated by using envelope technique as well as spectroscopic ellipsometry. Morphological studies have been carried out using atomic force microscope (AFM). Metal-Oxide-Silicon (MOS) capacitor was fabricated using conducting coating on TiO(2) film deposited on silicon. The C-V measurements show that the film annealed at 300 degrees C has a dielectric constant of 19.80. The high percentage of transmittance, low surface roughness and high dielectric constant suggests that it can be used as an efficient anti-reflection coating on silicon and other optical coating applications and also as a MOS capacitor.

Natural evolution of Perthes disease: a study of 610 children under 12 years of age at disease onset.

Records and 2,634 pairs of radiographs (anteroposterior and lateral) of 610 patients with Perthes disease were reviewed. The evolution of the disease was divided into seven stages (stages Ia, Ib, IIa, IIb, IIIa, IIIb, and IV) based on plain radiographic appearances. Intraobserver and interobserver reproducibility of this new classification system was assessed. The duration of each stage of the disease was noted. The stages at which epiphyseal extrusion and widening of the metaphysis occurred and the stages at which metaphyseal and acetabular changes appeared were identified. The shape and the size of the femoral head, the extent of trochanteric overgrowth, and the radius of the acetabulum were assessed in hips that had healed. The new classification system of the evolution of Perthes disease was reproducible and helped to identify when crucial events occur during the course of the disease. The median duration of each stage varied between 95 and 335 days. Epiphyseal extrusion and metaphyseal widening was modest in stages Ia, Ib, and IIa but increased dramatically after stage IIb. More than 20% extrusion occurred in 70% of the hips by stage IIIa. Metaphyseal changes were most frequently encountered in stage IIb, while acetabular changes were most prevalent in stage IIIa. At healing, only 24% of untreated patients had spherical femoral heads, while 52% had irregular femoral heads. The timing of epiphyseal extrusion, metaphyseal widening, and the appearance of adverse metaphyseal and acetabular changes suggest that femoral head deformation occurs by stage IIIa in untreated hips. Hence, if containment were to succeed, it should be achieved before this stage.

Optimal timing for containment surgery for Perthes disease.

To identify the optimal timing for containment surgery for Perthes disease, the outcomes following femoral osteotomy of 97 children were analyzed. Univariate and multivariate analyses were employed to identify variables that influenced the shape and size of the femoral head at healing. The timing of surgery was an important variable that had a bearing on the outcome. The chances of retaining a spherical femoral head were much higher in children operated on either during the stage of avascular necrosis or in the early part of the fragmentation stage than in those operated later. The authors conclude that containment surgery aimed at preventing femoral head deformation in Perthes disease should be performed before the advanced stage of fragmentation. Further, any study on the outcome of containment treatment of Perthes disease must consider the timing of containment as a variable that influences the outcome while interpreting the results.

Thymidylate synthase activity in leukocytes from patients with chronic myelocytic leukemia and acute lymphocytic leukemia and its inhibition by phenanthroindolizidine alkaloids pergularinine and tylophorinidine.

Thymidylate synthase (TS) (EC 2.1.1.45) provides precursors for DNA biosynthesis through a de novo pathway and is a key target enzyme for cancer chemotherapy. TS levels of human leukemic leukocytes from patients with chronic myelocytic leukemia (CML) and acute lymphocytic leukemia (ALL) were observed to be highly elevated (66- and 33-fold for CML and ALL, respectively) compared to the usual low level of basal activity in normal healthy controls. In vitro inhibition studies on the human leukemic leukocyte TS with the phenanthroindolizidine alkaloids pergularinine (PGL) and tylophorinidine (TPD) (isolated from the Indian medicinal herb Pergularia pallida) were conducted for the preliminary screening tests for their antitumor activity. The leukemic leukocyte enzyme activity was potently inhibited by PGL and TPD (IC50 = 50 microM) in both types of leukemias. These alkaloids were assessed for biological evaluation for the first time as potential antileukemic agents.

Jejunal interposition hepaticoduodenostomy for choledochal cyst.

Four cases of choledochal cyst with interesting modes of presentation were managed by excision of the cyst and biliary drainage by a new physiological and antireflux technique of jejunal loop interposition hepaticoduodenostomy. The advantages of this new technique over earlier practiced procedures are discussed.