Search

In this paper, the dielectric performance of calcium copper titanate (CCTO) synthesized by various possible routes is investigated. The effect of sintering temperature on dielectric, structural, morphological properties is conferred in text. X-ray diffraction spectroscopy reveals the presence of Im3 space group and body centred cubic structure. The results confirmed that 950 °C temperature is appropriate temperature for synthesis of oxide via various routes. The average particle size of CCTO is estimated to be 500 nm by field emission scanning electron microscope. The good capacitive dielectric performance of 500 °C and 1000 °C temperature sintered pellets is examined by LCR meter at frequency range of 40 Hz to 8 MHz. It is quite evidenced that oxalate co-precipitation and sono-chemical technique attributed to remarkable dielectric permittivity of 12,000 and 10,980 with minimum dielectric loss at high sintering temperature, as the temperature plays a major role in drastic enhancement in dielectric performance of a perovskites. [ABSTRACT FROM AUTHOR]

In the present study, a multilayer reflective optical filter consisting of 24 alternate layers of SiO 2 and TiO 2 was designed and fabricated on BK7 glass substrate using Ion Assisted electron beam Deposition (IAD) technique. The spectroscopic characterization of the filter was carried out in Vis-NIR range with Universal Measurement Accessory (UMA) to measure its optical performance at normal and oblique angles of incidences. The measurements confirmed the optical peak reflectance of more than 99.98% at design wavelength of Nd:YAG laser centred at 1064 nm. The tuning of refractive indices of the constituent layers during deposition resulted in a Full-Width at Half-Maximum (FWHM) bandwidth of 330 nm of the fabricated filter which enables its use at any angle of incidences between 0 and 60° for manipulating the laser beam. Qualitative assessment of the mechanical stability of the coated filter with respect to its adhesion and abrasion resistance was carried out in accordance with MIL-F-48616 and MIL-E−12397 respectively. The achieved optical performance of the coated filter is suited for beam steering and folding of high power laser beams for metal cutting, diamond processing and in other laser based material processing instruments. [ABSTRACT FROM AUTHOR]

With the rising incidences of cancer cases, the quest for new metal based anticancer drugs has led to extensive research in cancer biology. Zinc complexes of amino acid residue side chains are well recognized for hydrolysis of phosphodiester bond in DNA at faster rate. In the presented work, a Zn(II) complex of cyclen substituted with two l -tryptophan units, Zn(II)-Cyclen-(Trp) 2 has been synthesized and evaluated for antiproliferative activity. Zn(II)-Cyclen-(Trp) 2 was synthesized in ∼70% yield and its DNA binding potential was evaluated through QM/MM study which suggested good binding (G = −9.426) with B-DNA. The decrease in intensity of the positive and negative bands of CT-DNA at 278 nm and 240 nm, respectively demonstrated an effective unwinding of the DNA helix with loss of helicity. The complex was identified as an antiproliferative agent against U-87 MG cells with 5 fold increase in apoptosis with respect to control (2 h post incubation, IC 50 25 µM). Electrophoresis and comet assay studies exhibited an increase in DNA breakage after treatment with complex while caspase-3/β-actin cleavage established a caspase-3 dependent apoptosis pathway in U-87 MG cells after triggering DNA damage. In vivo tumor specificity of the developed ligand was validated after radiocomplexation with 99m Tc (>98% radiochemical yield and specific activity of 2.56 GBq/µmol). Avid tumor/muscle ratio of >6 was depicted in biodistribution and SPECT imaging studies in U-87 MG xenograft model nude mice. [ABSTRACT FROM AUTHOR]

Abstract: Ferroelectric c-oriented Bi2VO5.5 (BVO) thin films (thickness ≈300nm) were fabricated by pulsed laser deposition on corning glass substrates. Nonlinear refractive index (n 2) and two photon absorption coefficient (β) were measured by Z-scan technique at 532nm wavelength delivering pulses with 10ns duration. Relatively large values of n 2 =2.05±0.2×10−10 cm2/W and β =9.36±0.3cm/MW were obtained for BVO thin films. Origin of the large optical nonlinearities in BVO thin films was discussed based on bond–orbital theory of transition metal oxides. [Copyright &y& Elsevier]

Abstract: The optical properties of Bi2V1−x Mn x O5.5−x {x =0.05, 0.1, 0.15 and 0.2 at.%} thin films fabricated by pulsed laser deposition on platinized silicon substrates were studied in UV–visible spectral region (1.51–4.17eV) using spectroscopic ellipsometry. The optical constants and thicknesses of these films have been obtained by fitting the ellipsometric data (Ψ and Δ) using a multilayer four-phase model system and a relaxed Lorentz oscillator dispersion relation. The surface roughness and film thickness obtained by spectroscopic ellipsometry were found to be consistent with the results obtained by atomic force and scanning electron microscopy. The refractive index measured at 650nm does not show any marginal increase with Mn content. Further, the extinction coefficient does not show much decrease with increasing Mn content. An increase in optical band gap energy from 2.52 to 2.77eV with increasing Mn content from x =0.05 to 0.15 was attributed to the increase in oxygen ion vacancy disorder. [Copyright &y& Elsevier]

Abstract: Titanium nitride and titanium oxynitride films were deposited by varying the plasma current density from 10 mA/cm2 to 40 mA/cm2 using DC magnetron sputtering at constant gas flow rate and deposition time. Samples were characterized by Grazing Incidence X-Ray Diffraction, XPS, Nanoindentation and colorimetric analysis. Different coloured films like golden, blue, pink and green were obtained at different current densities. At lower current density (10 mA/cm2), golden coloured stoichiometric titanium nitride film was formed. At higher current densities (20, 30 and 40 mA/cm2), non stoichiometric Titanium oxynitride films of colour blue, pink and green were formed respectively. The thickness of the films increased with plasma current density from 43 nm to 117 nm. It was found that the colour variation was not only due to thickness of the film but also due to oxygen atoms replacing the nitrogen positions in TiN lattice. Hardness and Young Modulus of the films were found to decrease from 17.49 GPa to 7.05 GPa and 319.58 GPa–246.77 GPa respectively with increasing plasma current density. This variation of hardness and Young Modulus of the films can be speculated due to change in crystal orientation caused by oxygen incorporation in the films. The film resistivity increased from 16.46 × 10−4 to 3.28 × 10−1 Ω cm for increasing plasma current density caused due to oxygen incorporation in the crystal lattice. [Copyright &y& Elsevier]

Abstract: Bi2V1−x Nb x O5.5 {(x =0, 0.1, 0.2, 0.3, 0.4), (BVN)} thin films were grown by pulsed laser deposition on (111) Pt/TiO2/SiO2/Si and Corning glass substrates and investigated systematically for their microstructural, optical and ac conduction properties. The undoped bismuth vanadate, Bi2VO5.5 (BVO) thin films were highly textured and have been associated with the c-axis oriented grains of the layered perovskite structure, while the Nb doped films consisted of randomly oriented crystallites. The scanning electron microscopy of the films indicates that the grain size increases with increase in Nb content. The optical transmission studies carried out on the samples deposited on Corning glass substrates revealed that these films were nearly 80% transparent in the 400–900nm range and the band gap of Nb doped BVO thin films was slightly higher (3.13eV for x =0.4) than that of the undoped (2.91eV) films. The dielectric constant of the Nb doped films increased with increase in Nb content, while the dielectric loss decreased especially in the 3–100kHz frequency range. At a particular frequency, the conductivity decreased with increase in Nb content in the BVN thin films. In the higher temperature range, the activation energy varied from 0.61eV (x =0.1) to 0.76eV (x =0.4) measured at 100Hz. The frequency analysis of the dielectric and ac conduction properties of these films suggests the conduction process in these films to be via oxygen ion vacancy motion through various defect sites. [Copyright &y& Elsevier]

Abstract: Ferroelectric bismuth vanadate Bi2VO5.5 (BVO) thin films have been successfully grown on p-type Si(100) substrate by using chemical solution decomposition (CSD) technique followed by rapid thermal annealing (RTA). The crystalline nature of the films has been studied by X-ray diffraction (XRD). Atomic force microscopy (AFM) was used to study the microstructure of the films. The dielectric properties of the films were studied. The capacitance–voltage characteristics have been studied in metal–ferroelectric–insulator–semiconductor (MFIS) configuration. The dielectric constant of BVO thin films formed on Si(100) is about 146 measured at a frequency of 100kHz at room temperature. The capacitance–voltage plot of a Bi2VO5.5 MFIS capacitor subjected to a dc polarizing voltages shows a memory window of 1.42V during a sweep of ±5V gate bias. The flatband voltage (V f) shifts towards the positive direction rather than negative direction. This leads to the asymmetric behavior of the C–V curve and decrease in memory window. The oxide trap density at a ramp rate of 0.2V/s was estimated to be as high as 1.45×1012 cm−2. [Copyright &y& Elsevier]

Duffy suggested the use of double-aperture imaging system for the measurement of in-plane displacement component. In this arrangement, twin apertures are placed symmetrically over the imaging lens. This imaging system is used in speckle metrology to measure component of displacement parallel to the line joining the two apertures. The imaging lens used in such configuration need not be diffraction limited over the entire lens aperture, but only over the two small areas encompassed by the two apertures. In present work, compact holographic lenses have been used to generate the two apertures of Duffy''s double-aperture interferometer. This imaging system has been used in speckle metrology to measure crack mouth opening displacement (CMOD) in an aluminium beam specimen having central edge crack subjected to three point bending. Experimental results are in good agreement with theoretical predictions. Present experimental investigation reveals that compact holographic lenses can be used advantageously to generate apertures of double-aperture speckle interferometer for its use in the measurement of in-plane displacement component. [Copyright &y& Elsevier]

High transmission optical filters require specific filter characteristics and set of optimisation methods since precision in output performance plays a vital role in such applications. In this paper, an improved genetic algorithm approach to optimise high transmission optical filter is described. High transmission of around 99% in the wavelength region of 525–575 nm without any dips in between is the main performance requirement desired. The optimisation parameters are layer thickness, refractive index and number of layers and design wavelength is 550 nm in visible region. The method integrates the Taguchi method and genetic algorithm. First, Taguchi method is used to reduce the number of design experiments and find the minimum possible number of optimised set of values that represents the quality performance of the system. Then, genetic algorithm is applied to search the optimal design parameters. The performance is determined in terms of transmittance. Three levels for each optimisation parameter were considered. The total number of design experiments to be performed (in worst case) using genetic algorithm only with three optimisation variables and three levels is approximately 33 = 27 for obtaining the best design that matches the desired performance whereas Taguchi integrated genetic method helped in finding the best matching design with 9 design experiments. The best transmission performance was obtained for 24 layers, with thickness range 10–123.75 nm and high and low refractive index of 2.1 and 1.38. This method is a very robust approach that can be used for design parameter optimisation of optical filters for high transmission applications. [ABSTRACT FROM AUTHOR]

Micro heat exchangers are the integral part of advanced technologies such as space technologies. However, the cooling of these micro heat exchangers encounters various challenges due to large aspect ratios. Further, the conventional coolants could not dissipate the heat due to limited thermal conductivity and specific heat. Hence, suspension of nanoparticles in such coolants would increase the efficiency of micro heat exchanges. Nanofluids are widely used in biomedical applications, as coolants in transportation, industrial cooling, nuclear reactor cooling and defense applications due to their higher stability, higher heat transfer capabilities and reduced particle clogging. In the present work, the thermophysical properties of Al 2 O 3 , SiO 2 , SiC, CuO and TiO 2 nanoparticles in Liquid Nitrogen (LN 2 ) are studied with the volume concentration of 3%. It is observed that thermal conductivity of nanofluid is enhancing with the increase in volume concentration of nanoparticles which result in enhancing the heat transfer rate in micro heat exchangers. In order to confirm this fact, a computational investigation on pressure drop and heat transfer is performed with Liquid Nitrogen as a base fluid and CuO, SiO 2 , SiC, Al 2 O 3 and TiO 2 as nanoparticles. A computational geometry is developed in ANSYS ® and the pressure drop and heat transfer analysis is done using FLUENT ® . Relevant boundary conditions are applied to reflect the practical operating conditions of micro heat exchangers. It is observed from the results that the decrease in pressures drop with the suspension of CuO nanoparticle is low. Further, the heat transfer is observed to be increasing with the addition of Al 2 O 3 and SiO 2 nanoparticles with the concentration of 3% by volume. Finally, it can be concluded that the dispersion of the nanoparticles in Liquid Nitrogen (LN 2 ) is beneficial to be used in micro heat exchangers. [ABSTRACT FROM AUTHOR]

Urea-aided solution combustion (SC) method has been employed to generate monoclinic structure-based Dy (III) doped Ba 2 BiV 3 O 11 nanophosphors. X-ray diffraction (XRD) and the Rietveld refinement techniques confirmed that the developed nanophosphors are crystallized in a monoclinic crystal system with space group as P21/a. The crystallite size was assessed via Scherrer's equation and Williamson-Hall (W–H) plot. SEM and TEM images confirm the agglomerated particle with a non-uniform shape lies in the nano range. An energy dispersive X-ray (EDAX) study is executed to assess various constitute elements and their relative dispersal was analyzed via mapping spectrum. The highly intense emission peak at 577 nm is ascribed to 4F 9/2 → 6H 13/2 electronic transition of the Dy3+ ion when energized at 327 nm wavelength. The band gap values for the host matrix and the optimized sample were measured using a DR spectrophotometer. Auzel's model was utilized to establish the values of quantum efficiency (68.21 %), non-radiative rates (597.08 s−1), and intrinsic lifetime (0.7803 ms). Furthermore, PL (photoluminescence) data is exercised to attain chromatic quantities viz. color coordinates (x and y), and correlated color temperature (CCT), which are strongly endorsed for their usage as near UV-based advanced solid-state illuminating devices. • Dy3+- doped Ba 2 BiV 3 O 11 nanophosphors were prepared via solution combustion method. • Crystallite size was calculated via Scherrer's equation and Williamson-Hall (W–H) plot. • Unit cell parameters have been calculated via Rietveld refinement technique. • The emission peak at 577 nm with 4F 9/2 → 6 H 13/2 transition is responsible for white color. • Dipole-dipole interactions are responsible for concentration quenching in synthesized phosphors. [ABSTRACT FROM AUTHOR]

An orthorhombic symmetry type BaGd 2 ZnO 5 :Dy3+ nanocrystals with luminance of cool white-color light have been fabricated via urea assisted combustion methodology. Morphological analysis revealed the agglomerated particles with non-uniform shape having crystal-size of 30–40 nm. Optimized amount of dopant (Dy3+) was examined to be x = 3 mol%, after the occurrence of quenching phenomenon. The logical pathways for quenching mechanism has been determined as non-radiative (NR) relaxations of energy via exchange-type interrelations as validated by Inokuti-Hirayama (I-H) and Dexter's theory. Fabricated nano-powders represents two band located at 492 nm (bluish) and at 581 nm (yellowish). Band gap, decay life time and quantum efficiency of optimal powder were found as 4.71 eV, 0.7049 ms and 93.9% respectively. White-light emanation is reflected in terms of CIE color-parameters like color-coordinates of white regions (0.2869, 0.3876), color purity of 30 × 10−2 and CCT values as 7206.2 K, which have been in congruence with standard coordinates of commercial LEDs and NTSE and thus, authenticate their optimistic applicability for advanced illuminating devices. [Display omitted] • White-color light emanating BaGd 2 ZnO 5 :Dy3+ nanocrystals fabricated for first time via solution combustion approach. • The detailed structural and photoluminescence investigations are done effectively. • The band-gap energy has been determined using Kubelka-Munk function. • Versatile luminescent features have also been determined. • Widen new prospects for opto-electronic and solid state lighting applications. [ABSTRACT FROM AUTHOR]

• A deposition method of Al 2 O 3 graded films is presented using a customized jig with varying substrate leaning angles. • The customized jig allows coating of substrates at different leaning angles ranging from 10 to 80° in same deposition run. • Correlation of thickness of Al 2 O 3 films from the microscopy images of SEM, CCI and reflectometer studies are presented. • Results of thickness estimation using envelope technique is also compared for films deposited at different leaning angles. • Wettability and the EDAX data of the graded Al 2 O 3 films are also presented for additional insights on the films properties. Present work describes the evaporation of aluminium oxide (Al 2 O 3) in the form of thin films on glass and silicon substrates at different leaning angles (10−80°) using Ion-Assisted E-beam deposition (IAD). The optical, morphological and wettability studies of the films reveal a variation in film properties. Refractive index of the film material was found to be varied from 1.67 to 1.64 for 10 to 80° leaning angles. Films thickness was calculated using transmission data with envelope method. The obtained film thickness value was further compared with the thickness data of cross-sectional scanning electron microscopy (SEM) micrographs and coherence co-relation interferometer (CCI) results. Fabricated Al 2 O 3 films show decreased values of refractive index and contact angle with higher leaning angles. [ABSTRACT FROM AUTHOR]

Aim: We aim to examine the association of plasma leucine-rich-α-2-glycoprotein 1 (LRG1) with diabetic retinopathy (DR) in type 2 diabetes.Methods: At baseline visit, plasma LRG1 levels were assessed using ELISA. Central arterial stiffness was estimated by carotid-femoral pulse wave velocity (PWV). At follow-up visit (median = 3.2 years), digital color fundus photographs were assessed for DR. DR severity was categorized into non-proliferative DR (NPDR) and proliferative DR (PDR).Results: DR was diagnosed in 396 (32.8%) of 1206 patients. DR has higher LRG1 than non-DR (19.5 ± 11.3vs.16.9 ± 8.9 μg/ml, p ≪ 0.001). After adjustment, LRG1 was not associated with DR (OR = 1.2, [95% CI, 0.96-1.30], p = 0.16). LRG1 was higher in PDR (n = 107) than NPDR (n = 270) (23.2 ± 15.4vs.18.1 ± 8.9 μg/ml, n = 270, p ≪ 0.001). After adjustment, with 1-SD increase in LRG1, the relative risk of NPDR and PDR was 0.99 ([0.83-1.18], p = 0.91) and 1.42 ([95% CI, 1.14-1.76], p = 0.002) (p-trend = 0.01), respectively. We didn't observe significant improvement in AUC after adding LRG1 into the model. Baseline PWV mediated 12.0% of the association between LRG1 and PDR (p = 0.03).Conclusion: Baseline plasma LRG1 is associated with PDR, suggesting it maybe a promising biomarker for prediction for advanced proliferative stages of DR. The mediation result indicates the potential benefit of ameliorating central arterial stiffness to prevent PDR. [ABSTRACT FROM AUTHOR]

Purpose To investigate the independent impact of the incidence and progression of diabetic retinopathy (DR) on visual functioning (VF). Design Population-based cohort study. Participants A total of 518 participants aged 40 to 80 years (baseline visit 2007–2009 and second visit 6 years later, 2013–2015), with diabetes, clinical data, and VF information at both visits. Main Outcome Measures VF-7 scores, converted to interval-level person measures (in logits) using Rasch analysis. Methods Incident DR was defined using the Modified Airlie House classification as “none or minimal” DR at baseline and at least mild nonproliferative DR at follow-up; incident vision-threatening DR (VTDR; severe nonproliferative DR, proliferative DR, and/or clinically significant macular edema) as no VTDR at baseline, and present at follow-up; and DR progression as at least a 1-step worsening in DR at follow-up from mild or worse status at baseline. The longitudinal associations between incident DR, VTDR, and DR progression, as well as change in composite and individual item scores of VF, were assessed using multivariable linear regression models. Results Of the 518 participants (mean age ± standard deviation [SD] 59.8±9.0 years; 47.7% female), 42 (9.8%), 14 (2.8%), and 32 (42.7%) had incident DR, incident VTDR, and DR progression, respectively, at follow-up. In models adjusting for traditional confounders, persons with incident DR and VTDR had a 13.7% (β = −0.60; 95% confidence interval [CI], −0.96 to −0.24; P = 0.001) and 23% (β = −1.00; 95% CI, −1.61 to −0.38; P = 0.001) reduction in mean VF scores at follow-up. Furthermore, individuals with incident DR had similar independent reductions in scores for 7 individual items of the VF-7, whereas those with incident VTDR had the largest reductions for activities like cooking (31%; P = 0.003), reading the newspaper (29.6%; P < 0.001), and seeing street signs (28%, P = 0.001) at follow-up. Progression of DR was not independently associated with change in overall VF (β = −0.18; 95% CI, −1.00, 0.64; P = 0.660). Conclusions Incident DR, particularly vision-threatening stages, has a substantial negative impact on people's overall vision-dependent functioning and specific activities such as cooking, seeing street signs, and reading the newspaper. Our findings reinforce the need for strategies to prevent or delay the development of DR. [ABSTRACT FROM AUTHOR]

A simple, non-hazardous and cost effective, solution combustion fabrication route was adopted to prepare novel BaSrY 4(1− x) Er 4 x O 8 (x = 0.5−5 mol%) nanocrystals. Investigations related to crystal structure and phase purity of the prepared nanophosphors were made by using X-Ray Diffraction (XRD) based Rietveld refinement analysis technique. Crystallite size of the prepared nanocrystals was analyzed from Transmission Electron Microscopy (TEM) technique and the morphological examinations were done with the help of Scanning Electron Microscopy (SEM) measurements. Optical properties of the fabricated nanophosphors were analyzed from photoluminescence (PL) excitation-emission spectra. By fixing excitation at 379 nm, the emission spectra depicted peak at 549 nm (most intense) corresponding to 4S 3/2 → 4I 15/2 transition. The optimum content of Er3+ in BaSrY 4 O 8 matrix was determined as x = 0.02. Further, the DR (diffuse reflectance) analysis revealed the band gap (E gap) values for host BaSrY 4 O 8 (5.79 eV) and doped BaSrY 3.92 Er 0.08 O 8 (5.38 eV) powder samples. CIE (Commission International de I′Eclairage) color coordinates were found to be in green region which proclaims the potential use of combustion fabricated nanophosphors in optical display devices, mainly white LEDs, lasers and optical sensors. [Display omitted] • Novel BaSrY 4 O 8 : x Er3+ nanocrystals have been prepared via solution combustion approach. • Cell parameters and refinement factors are evaluated for host and best luminescent composition. • The band-gap energy has been determined using Kubelka-Munk function. • Optical properties have been studied in detail. • Potential candidates for optical display applications, mainly RGB based WLEDs, lasers and optical sensors. [ABSTRACT FROM AUTHOR]

Microwave absorbing materials consisting of neodymium (Nd) doped strontium hexaferrites, Sr 1-x Nd x Fe 12 O 19 (X = 0.1, 0.2 and 0.3), were developed using auto-combustion route. The XRD spectrum confirmed the formation of pure ferrite phase with no impurity. The Nd acted as an inhibitor for the growth of hexaferrite particles which resulted in a decrease in the average particle size of ferrite from 638.02 nm to 478.19 nm. The hysteresis loop revealed that the undoped ferrite has high saturation magnetization which further observed to decrease from 41.185 emu/g to 37.145 emu/g with the increasing neodymium doping concentration. The coercivity of the doped strontium hexaferrites also showed similar pattern which decreased from 387.97 G to 278.37 G due to the weakening of uniaxial magnetocystalline anisotropy. The impedance matching and reflection loss improved with the increase in the doping concentration of neodymium. The optimum value of attenuation constant and reflection loss was observed for the sample, X = 0.3. The maximum reflection loss value of −40.595 dB at 9.62 GHz was obtained with −10 dB bandwidth of 3.13 GHz (≈75% of the X-band). • Microwave absorption behavior of Sr 1-x Nd x Fe 12 O 19 (X = 0.1, 0.2, 0.3) is investigated. • Doping resulted in high dielectric and magnetic losses. • The improved impedance matching resulted in increased reflection losses. • Maximum reflection loss of -40. 59 dB is observed at 9.62 GHz with thickness 2.35 mm. • The - 10 dB bandwidth reached to 3. 13 GHz (≈75% of the X-band). [ABSTRACT FROM AUTHOR]

Present study investigates the optical properties and film thickness estimation of tantalum oxide (Ta 2 O 5) thin films of various thicknesses, deposited by physical evaporation technique. The optical constants and thickness of deposited films were estimated by using envelope method. The thickness value obtained from this method has been compared with in-situ (quartz crystal thickness monitor) as well as Ex-situ (Coherence Correlation Interferometry) thickness estimation techniques. Refractive index calculated by envelope method was also validated using Reflectometer. These thickness values were used for the estimation of other optical constants such as refractive index, absorption and extinction coefficients. Contact angle measurement studies are also performed on uncoated as well as Ta 2 O 5 coated glass substrates, which indicate the hydrophobic nature of these films. [ABSTRACT FROM AUTHOR]