@article {46183, title = {Fiber optic Fabry-Perot interferometer sensor: an efficient and fast approach for ammonia gas sensing}, journal = {Journal of the Optical Society of America B-Optical Physics}, volume = {36}, year = {2019}, month = {MAR }, pages = {684-689}, type = {Article}, abstract = {

In this work, we propose and demonstrate a Fabry-Perot-interferometer-based polydimethylsiloxane (PDMS) and poly(methyl methacrylate) (PMMA)-composite-coated optical sensor for ammonia and volatile organic compounds (VOCs) detection at room temperature. The principle of sensing is based on change in the cavity length of the FP cavity in the presence of varied concentrations of gases, which results in changes in the total reflectance due to the shift in wavelength of an interference pattern. The sensing composite material was coated on a single-mode optical fiber by using a simple dip-coating technique and explored it for sensing. The ammonia and VOCs measurements were performed for concentrations ranging from 5 to 500 ppm. The corresponding sensitivity and limit of detection of the developed sensor for ammonia gas detection was observed of the order of around 4.16 pm/ppm and 4.8 ppm, respectively. The response and recovery times of the sensor were found to be of the order of 50 s and 10 s, respectively, for the ammonia gas. This sensor provides a simple, cost-effective, highly sensitive, and repeatable approach to measure ammonia gas and other VOCs at room temperature and could fulfill the demands of industrial applications. (C) 2019 Optical Society of America

}, issn = {0740-3224}, doi = {10.1364/JOSAB.36.000684}, author = {Kanawade, Rajesh and Kumar, Ajay and Pawar, Dnyandeo and Late, Dattatray and Mondal, Samir and Sinha, Ravindra K.} } @article {46173, title = {Negative axicon tip-based fiber optic interferometer cavity sensor for volatile gas sensing}, journal = {Optics Express}, volume = {27}, year = {2019}, month = {MAR }, pages = {7277-7290}, type = {Article}, abstract = {

In this research work we demonstrated negative axicon optical fiber tip filled with Polydimethylsiloxane (PDMS) as a sensor platform for volatile organic gases detection at room temperature. The response of the sensor was measured with various Volatile Organic Compounds (VOCs) such as Chloroform, Hexane, Isopropanol, Acetone, Toluene and Methanol in the concentration ranging from 5 to 200 ppm. The corresponding sensitivity and limit of detection (LOD) of the developed sensor for the measured VOCs were observed between the order of around 23.7 to 3.2 pm/ppm and 0.84 to 6.10 ppm, respectively. The response and recovery time of sensor were found between the order of 30 to 57 seconds and 8 to 25 seconds respectively for the measured VOCs. Thermal stability of the developed sensor was also studied at 30-70 degrees C with intervals of 10 degrees C. The principle of sensing is based on change in the length of the Fabry-Perot Interferometric (FPI) cavity in the presence of varied concentrations of VOCs, which results in changes in the shift in wavelength of an interference pattern attributed to the change in PDMS filling the cavity length (swelling). The experimentally observed trends in the relative swelling of PDMS with VOCs are found in agreement with the theoretically calculated values obtained from the Hansen solubility parameter (HSP). The developed gas sensor has the potential to fulfill the demands of industrial applications.

}, issn = {1094-4087}, doi = {10.1364/OE.27.007277}, author = {Kanavvade, Rajesh and Kumar, Ajay and Pawar, Dnyandeo and Vairagi, Kaushal and Late, Dattatray and Sarkar, Sudipta and Sinha, Ravindra K. and Mondal, Samir} } @conference {48195, title = {Skin mimicking solid optical tissue phantom fulfillment and its characterization}, booktitle = {Photonics in Dermatology and Plastic Surgery 2022}, year = {2022}, publisher = {SPIE}, organization = {SPIE}, address = {1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA}, abstract = {

Skin mimicking optical tissue phantoms are widely used in diagnostics systems for characterization, optimization, routine calibration and validation. In general, solid phantoms are more preferred in comparison to liquid phantoms. Therefore, our aim is to prepare and characterize the solid tissue phantoms having skin equivalent optical properties. In this work, we have used epoxy resin and hardener as a base material and titanium oxide (TiO2) nanoparticles and ink as a scatterer and absorber media, respectively. The total transmission (Tt), collimated transmission (Tc), and diffuse reflectance (Rd) spectra of the developed phantoms were measured with an integrating sphere installed in UV-VIS spectrometer within the wavelength range 400-700 nm. To characterize the optical properties such as absorption (mu(a)), reduced scattering (mu(s){\textquoteright}), and anisotropy factor (g) of the developed tissue phantoms, the numerical model based on Inverse Adding Doubling (IAD) has been used. With various concentrations of absorber and scatterer, a calibration curve was prepared. The calculated experimental optical properties from IAD matched with the predicted intrinsic optical properties of the skin. Thus, the preliminary results suggest that the recipe used in this study may be used as an alternative approach to developing skin mimicking solid optical phantom for diagnostics system applications.

}, keywords = {Absorption, anisotropy factor, scattering, skin mimicking, solid tissue phantom}, isbn = {978-1-5106-4740-4; 978-1-5106-4739-8}, doi = {10.1117/12.2609577}, author = {Kumar, Ajay and Hinge, Sarika and Dixit, Hemant and Kanawade, Rajesh and Kulkarni, Gauri}, editor = {Choi, B and Zeng, H} } @article {48814, title = {Response of cardiac pulse parameters in humans at various inclinations via 360{\textdegree} rotating platform for simulated microgravity perspective}, journal = {NPJ Microgravity}, volume = {9}, year = {2023}, month = {JUL}, pages = {54}, type = {Article}, abstract = {

On the Earth, the human body is designed and adapted to function under uniform gravitational acceleration. However, exposure to microgravity or weightlessness as experienced by astronauts in space causes significant alterations in the functioning of the human cardiovascular system. Due to limitations in using real microgravity platforms, researchers opted for various ground-based microgravity analogs including head-down tilt (HDT) at fixed inclination. However, in the present study, an investigation of response of various cardiac parameters and their circulatory adaptation in 18 healthy male subjects was undertaken by using an indigenously developed 360 \& DEG; rotating platform. Cardiac pulse was recorded from 0 \& DEG; to 360 \& DEG; in steps of 30 \& DEG; inclination using piezoelectric pulse sensor (MLT1010) and associated cardiac parameters were analyzed. The results showed significant changes in the pulse shape while an interesting oscillating pattern was observed in associated cardiac parameters when rotated from 0 \& DEG; to 360 \& DEG;. The response of cardiac parameters became normal after returning to supine posture indicating the ability of the cardiovascular system to reversibly adapt to the postural changes. The observed changes in cardiac parameters at an inclination of 270 \& DEG;, in particular, were found to be comparable with spaceflight studies. Based on the obtained results and the proposed extended version of fluid redistribution mechanism, we herewith hypothesize that the rotation of a subject to head down tilt inclination (270 \& DEG;) along with other inclinations could represent a better microgravity analog for understanding the cumulative cardiac response of astronauts in space, particularly for short duration space missions.

}, doi = {10.1038/s41526-023-00301-3}, author = {Jagtap, Sagar and Kumar, Ajay and Mahale, Bhoopesh and Dixit, Jyotsana and Kalange, Ashok E. and Kanawade, Rajesh and Gangal, Shashikala and Vidyasagar, Pandit} } @article {48826, title = {Synthesis, biological evaluation and docking studies of silicon incorporated diarylpyrroles as MmpL3 inhibitors: an effective strategy towards development of potent anti-tubercular agents}, journal = {European Journal of Medicinal Chemistry}, volume = {259}, year = {2023}, month = {NOV }, pages = {115633}, type = {Article}, abstract = {

Growing global demand for new molecules to treat tuberculosis has created an urgent need to develop novel strategies to combat the menace. BM212 related compounds were found to be potent anti-TB agents and they inhibit mycolic acid transporter, MmpL3, a known potent drug target from Mycobacterium tuberculosis. In order to enhance their inhibitory potency, several silicon analogues of diarylpyrroles related to BM212 were designed, synthesized, and evaluated for anti-tubercular activities. In Alamar blue assay, most of the silicon-incorporated compounds were found to be more potent than the parent compound (BM212), against Mycobacterium tuberculosis (MIC = 1.7 \& mu;M, H37Rv). Docking results from the crystal structure of MmpL3 and silicon analogues as pharmacophore model also strongly correlate with the biological assays and suggest that the incorporation of silicon in the inhibitor scaffold could enhance their potency by stabilizing the hydrophobic residues at the binding pocket. The best docking hit, compound 12 showed an MIC of 0.1 \& mu;M against H37Rv with an acceptable in vitro ADME profile and excellent selectivity index. Overall, the present study indicates that, the designed silicon analogues, especially compound 12 could be a good inhibitor for an intrinsically flexible drug-binding pocket of MmpL3 and has potential for further development as anti-tubercular agents.

}, keywords = {antibiotic, BM212, docking studies, MmpL3 inhibitor, Silicon analogue, tuberculosis}, issn = {0223-5234}, doi = {10.1016/j.ejmech.2023.115633}, author = {Vasudevan, N. and Motiwala, Zenia and Ramesh, Remya and Wagh, Sachin B. and Shingare, Rahul D. and Katte, Revansiddha and Anand, Amitesh and Choudhary, Sushil and Kumar, Ajay and Gokhale, Rajesh S. and Kulkarni, Kiran A. and Reddy, D. Srinivasa} }