Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

We present the design and theoretical simulation of a nano-range optical structure with an elliptical solid immersion lens (e-SIL) in a rectangular diamond substrate containing nitrogen–vacancy (NV) center in diamond. We have varied the numerical aperture of the objective lens and collected photons with a maximum collection efficiency of ∼88% for NA=1. The far field variations have been studied over a wide range of emission spectra of nitrogen–vacancy center in diamond. This highly efficient single-photon emitter has a wide range of applications in the field of nanoscale magnetic sensing and quantum information devices. © 2020 Elsevier B.V.

World University root node

Department of Chemistry

School of Advanced Sciences

Vellore Campus

Optics Communications

Novel e-SIL with embedded cone structure for the enhancement of photon collection efficiency from nitrogen–vacancy center in diamond

Objectives: Motivation of this study is to check the sensitivity of dosimetric tool gamma with 2D detector array combination when unexpected errors occur while transferring intensity-modulated radiation therapy treatment plans from planning system to treatment unit. Methods: This study consists of 17 head and neck cancer patient’s treatment plans. Nine types of verification plans are created for all 17 clinically approved treatment plans by consecutively deleting different segments (up to eight) one by one from each field of the plan. Decrement factor (χ) is introduced in our study which illustrated the degree of decay of gamma passing rate when intentional errors are introduced. We analyzed the data by two different methods—one without selecting the region of interest (ROI) in dose distributions and the other by selecting the region of interest. Results: By linear regression, the absolute value of slopes is 0.025, 0.024 and 0.015 without ROI and 0.030, 0.027 and 0.015 with ROI for 2%/2 mm, 3%/3 mm and 5%/5 mm criteria, respectively. The higher absolute value of the fitted slope indicates the higher sensitivity of this method to identify erroneous plan in treatment unit. The threshold value for 2%/2 mm equivalent to 95% passing criteria in 3%/3 mm used in clinical practice is obtained as 83.44%. Conclusions: The 2D detector array with dosimetric tool gamma is less sensitive in detecting errors when unprecedented errors of segment deletion occur within the treatment plans. © 2020, Italian Society of Medical Radiology.

Department of Physics

Radiologia Medica

A technique for quantifying the sensitivity of dosimetric tool gamma with 2D detector array in pretreatment IMRT plans by segment deletion method

Time dependent density functional theory is used to systematically examine the band gap variation of Li-substituted adamantanes upon fluorination. It is realized that the absorption wavelength of Li-Adamantane can be fine tuned within UV–Visible region by changing the degree of fluorination. The static and dynamic hyperpolarizabilities of fluorinated Li-Adamantane derivatives were computed using coupled perturbed Kohn Sham theory. In this article, we report Pockel, dc-Kerr, ESHG, degenerate four wave mixing coefficients and nonlinear refractive indices from the first and second order hyperpolarizability calculations. A high positive nonlinear refractive index and significant second harmonic generation efficiency at Nd:YAG Laser wavelength are observed in F3Li-Adm derivative. © 2018 Elsevier B.V.

Chemical Physics Letters

Effect of fluorination on bandgap, first and second order hyperpolarizabilities in lithium substituted adamantane: A time dependent density functional theory

The complexity of multiple energy levels associated with each atomic system determines the various processes related to light-matter interactions. It is necessary to understand the influence of different levels in a given atomic system. In this work we focus on multi-level atomic schemes with the application of magnetic field. We analyze the different EIT windows which appears in the presence of moderately high magnetic field (∼ 10 G) strength. © Published under licence by IOP Publishing Ltd.

Fulltext

Journal of Physics: Conference Series

Study of multi-level atomic systems with the application of magnetic field

Magnetic resonance imaging (MRI) has a wide range of applications towards imaging the human body. In this work we have solved the Bloch equations for different magnetic field gradients along the transverse direction. We have modified the magnetic field components based on the relaxation terms and solved the field gradient as well as the field components for both off-pulse and on-pulse configurations. In particular we focus on different pulse sequences and optimize them to realize the best possible output. We have analyzed the field components along transverse direction because the rotation of the object to form the image by emitting signal is along the xy plane. © Published under licence by IOP Publishing Ltd.

Optimization of Pulse Sequences in MRI Scheme

We present the variation of intensity in Doppler-free hyperfine lines for rubidium atoms with the application of magnetic field. Different polarization configurations have been studied systematically with varying magnetic fields. There is a significant increase in the intensity variation with applied magnetic field related to different polarization configurations. These variations are explained with the theoretical calculations. The calculations are performed by adopting Nakayama's four level model with the varying magnetic field induced transition probability. © Published under licence by IOP Publishing Ltd.

IOP Conference Series: Materials Science and Engineering

Magnetic field dependent intensity variation in the hyperfine split Rb D1 and D2 lines

We present the magnetic and optical field induced rotation of polarization in 87Rb and 85Rb atoms at geophysical magnetic fields. The line shape varies considerably in the presence of a magnetic field of the order of a few mG. Multiple Zeeman sublevel EIT systems involving rubidium atoms are investigated. Theoretical formalism of optical field induced polarization rotation in the presence of a magnetic field is discussed by considering all the Zeeman sublevels. It is noted that the ground state population distribution also plays a major role. © Published under licence by IOP Publishing Ltd.

Optical field induced rotation of polarization in rubidium atoms with the additional magnetic field

We present a new, efficient strategy for designing fully balanced transmission line RF circuits for solid state NMR probes based on back propagation of common impedance nodes (BPCIN). In this approach, the impedance node phenomenon is the sole means of achieving mutual RF isolation and balance in all RF channels. BPCIN is illustrated using a custom double resonance 3.2 mm MAS probe operating at 500 MHz (1H) and 125 MHz (13C). When fully optimized, the probe is capable of producing high homogeneity (810 /90 ratios of 86% and 89% for 1H and 13C, respectively) and high efficiency (γB1 = 100 kHz for 1H and 13C at 70 W and 180 W of RF input, respectively; up to 360 kHz for 1H). The probe's performance is illustrated by 2D MAS correlation spectra of microcrystals of the tripeptide N-f-MLF-OH and hydrated amyloid fibrils of the protein PI3-SH3. © 2013 Elsevier Inc. All rights reserved.

Journal of Magnetic Resonance

Efficient, balanced, transmission line RF circuits by back propagation of common impedance nodes

New and efficient solid-acid catalysts were designed and prepared by the coprecipitation-impregnation method, for the esterification of acetic acid and butanol synthesizing the butylacetate ester in fine chemical industry, in which the conventional catalyst was sulfuric acid. This work resulted in a cleaner process for acid-catalyzed reaction. The preparation parameters in the precipitation step and in the calcination were improved for a better performance. With the optimized new solid-acid catalyst, a good ester yield of 93.3% was achieved with the selectivity of 96.0%. The samples were characterized by XRD, N2-adsorption and TGA measurements, the SO4 2- anion was essential in the active structure. © 2004 Elsevier B.V. All rights reserved.

Catalysis Today

Design and elaboration of new solid acids for the synthesis of butylacetate

A series of new type catalysts of SO42-/Fe2O3-ZrO2-SiO2 solid-acid were prepared by coprecipitation-irnpregnation method and applied to catalyze the esterification of acetic acid and butanol. The effects of factors such as the Fe/Zr molar ratio, Si molar content, preparation method, precalculation temperature and calcination temperature have been examined. It was found that when the catalyst was prepared under the conditions of Si content=2% and Fe/Zr ratio=0.25 through coprecipitation-irnpregnation method, and was calcinated at 773 K, the yield and selectivity of ester could reach 93.26% and 96.00%, respectively. It was suggested that SO42- could be one of the important active components.