tony kakkar | University Of Petroleum And Energy Studies (original) (raw)

Papers by tony kakkar

We report the fabrication of planar optical waveguides using multi ion diffusion by femtosecond l... more We report the fabrication of planar optical waveguides using multi ion diffusion by femtosecond laser ablation. A real-time implantation of Te3+, Zn2+, Na+ ions along with rare earth ion Er3+ in oxygen plasma is achieved (fig.1). The planar waveguides are analysed using prism coupling method to understand the modal behaviour. Optical characteristics specify a high refractive index contrast optical waveguide layer formation, ensuring a thickness up to 3.2 µm with 1.6 refractive index at 1550 nm optical communication wavelength. An overall optical transparency >90% is well observed in the 800-1700 nm NIR range using transmission spectroscopy (Fig.2), making it suitable for photonic applications. The effect of various process parameters like laser pulse energy, pulse repetition rate, pressure and temperature effects are studied in detail. The impact of these parameters on guide layer formation will be presented in this work. The distinctive prospect of engineering the silica glass u...

eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fullte... more eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher’s website.

Journal of Biophotonics, 2018

Rare-earth (RE) doped optical materials, compatible with CMOS processing, are essential for the d... more Rare-earth (RE) doped optical materials, compatible with CMOS processing, are essential for the development of planar optical loss-less circuits and amplifiers to facilitate the progress of next generation optical interconnects[1]. However, the lack of a suitable optical material with high (~1022 atoms/cm3) RE solubility and long fluorescent lifetime(milliseconds) is hindering the realization of dielectric based integrated planar amplifiers at present[2]. We report a novel technique, ultrafast laser plasma implantation (ULPI)[3], that enables the simultaneous implantation of multiple, atomically dissimilar ions into a silica optical platform, enabling silica to contain a record high Er3+-ion concentration of 1.4 at.% and the highest lifetime-density product 8.94×1019 s.cm-3. This was achieved through the integration of chemically incompatible materials, RE doped tellurite and silica, assisted by ablation of RE (Er/Yb) enriched tellurite target glass using ultrashort pulse(100 fs) la...

The advent of combinatorial chemistry has led to a deluge of new chemical entities whose metaboli... more The advent of combinatorial chemistry has led to a deluge of new chemical entities whose metabolic pathways need to be determined. A significant issue involves determination of the ability of new agents to inhibit the metabolism of existing drugs as well as its own susceptibility for altered metabolism. There is need to estimate the enzyme inhibition parameters and mechanism or mechanisms of inhibition with minimal experimental effort. We examined a minimal experimental design for obtaining reliable estimates of K(i) (and V(max) and K(m)). Simulations have been applied to a variety of experimental scenarios. The least experimentally demanding case involved three substrate concentrations, [S], for the control and one substrate-inhibitor pair, [S]-[I]. The control and inhibitor data (with 20% coefficient of variance random error) were simultaneously fit to the full nonlinear competitive inhibition equation [simultaneous nonlinear regression (SNLR)]. Excellent estimates of the correct ...

There are a variety of methods available to calculate the inhibition constant (Ki) that character... more There are a variety of methods available to calculate the inhibition constant (Ki) that characterizes substrate inhibition by a competitive inhibitor. Linearized versions of the Michaelis-Menten equation (e.g., Lineweaver-Burk, Dixon, etc.) are frequently used, but they often produce substantial errors in parameter estimation. This study was conducted to compare three methods of analysis for the estimation of Ki: simultaneous nonlinear regression (SNLR); nonsimultaneous, nonlinear regression, "KM,app" method; and the Dixon method. Metabolite formation rates were simulated for a competitive inhibition model with random error (corresponding to 10% coefficient of variation). These rates were generated for a control (i.e., no inhibitor) and five inhibitor concentrations with six substrate concentrations per inhibitor and control. The KM/Ki ratios ranged from less than 0.1 to greater than 600. A total of 3 data sets for each of three KM/Ki ratios were generated (i.e., 108 rates...

Scientific reports, Jan 15, 2015

Chemical dissimilarity of tellurium oxide with silica glass increases phase separation and crysta... more Chemical dissimilarity of tellurium oxide with silica glass increases phase separation and crystallization tendency when mixed and melted for making a glass. We report a novel technique for incorporating an Er(3+)-doped tellurite glass composition into silica substrates through a femtosecond (fs) laser generated plasma assisted process. The engineered material consequently exhibits the spectroscopic properties of Er(3+)-ions, which are unachievable in pure silica and implies this as an ideal material for integrated photonics platforms. Formation of a well-defined metastable and homogeneous glass structure with Er(3+)-ions in a silica network, modified with tellurite has been characterized using high-resolution cross-sectional transmission electron microscopy (HRTEM). The chemical and structural analyses using HRTEM, Rutherford backscattering spectrometry (RBS) and laser excitation techniques, confirm that such fs-laser plasma implanted glasses may be engineered for significantly hig...

Drug metabolism and disposition: the biological fate of chemicals, 1999

A gas chromatographic-mass spectrometric (GC-MS) assay was developed for the quantitative analysi... more A gas chromatographic-mass spectrometric (GC-MS) assay was developed for the quantitative analysis of methyl salicylate (MeS), ethyl salicylate (ES) and salicylic acid (SA) from biological fluids. The method was validated from 100-microl rat liver homogenate preparations (5 mg/ml protein) in 70 mM KH2PO4 (pH 7.4) buffer and from 100 microl rat plasma. The samples were extracted with chloroform, derivatized with BSTFA and quantitated by GC-MS in the SIM mode. The standard curves ranged from 31 ng/ml to 800 or 1250 ng/ml. Relative standard deviations and bias were less than 11% in plasma and homogenate for all compounds except SA which evidenced greater variability. The assay was used in preliminary experiments to characterize the pharmacokinetics of MeS in rats.

3551 Background: AMG102 is a fully human IgG2 monoclonal antibody against HGF that prevents tumor... more 3551 Background: AMG102 is a fully human IgG2 monoclonal antibody against HGF that prevents tumorigenesis in preclinical models through blockade of the HGF/c-Met receptor tyrosine kinase pathway. We describe interim results from the first-in-human study of AMG102. Methods: This ongoing phase 1, open-label, dose-escalation study is evaluating safety, pharmacokinetics (PK), and preliminary pharmacodynamics (PD) of AMG102 after single and multiple intravenous doses in pts with advanced solid tumors. Sequential dose cohorts of 4–6 pts were administered AMG102 at 0.5, 1, 3, 5, 10, or 20 mg/kg. Pts received a single dose, followed by a 4-wk treatment- free period during which safety and PK were assessed. If no dose-limiting toxicity (DLT) was observed, treatment was resumed every 2 wks at the same dose until pts exhibited drug intolerance or disease progression. Results: As of 10 August 2006, 31 pts have been treated with AMG102 at doses up to 20 mg/kg ( Table ). AMG102 appears to be well tolerated. One pt with non-small cell lung cancer had a grade 3 DLT of dyspnea/hypoxia after the first dose (0.5 mg/kg); a second pt with pancreatic cancer had a grade 3 DLT/serious adverse event of gastrointestinal hemorrhage after the first dose (1 mg/kg). The most frequently reported, treatment-related adverse events (AEs) have been fatigue (13%), constipation (10%), anorexia (6%), nausea (6%), and vomiting (6%). No anti-AMG102 antibodies have been detected. Initial PK analysis indicates approximately linear PK in the dose range of 0.5 to 20 mg/kg. The overall mean (SD) [median] clearance and half-life estimates based on day-1 dosing were 12.1 (5.21) [10.7] mL/hr and 15.4 (5.84) [15.5] days, respectively. Tumor response is described ( Table ). Conclusions: In this study, interim results suggest that AMG102 at doses up to 20 mg/kg appears to be well-tolerated, with preliminary PK data supporting every-2-wk administration. [Table: see text] No significant financial relationships to disclose.

ABSTRACT We demonstrate the simultaneous growth of multiple optically functional crystalline stru... more ABSTRACT We demonstrate the simultaneous growth of multiple optically functional crystalline structures through a complex implantation and diffusion process. This includes ZnTe, ZnO and as-yet undefined silica crystallites doped with Er3+ or Tm3+ which are each characterized optically and structurally.

Baba Farid …, 2011

The assay of saliva is an increasing area of research with implications for basic and clinical pu... more The assay of saliva is an increasing area of research with implications for basic and clinical purposes. Although this biological fluid is easy to manipulate and collect, careful attention must be directed to limit variation in specimen integrity. Recently, the use of saliva has ...