https://mcc-idr.l2c2academy.co.in/xmlui/handle/123456789/878 2026-05-02T00:17:08Z https://mcc-idr.l2c2academy.co.in/xmlui/handle/123456789/891 Synthesis of Novel Bioactive Azocoumarin Derivatives: Cytotoxicity, DNA Binding, BSA Binding Study, and their in Silico Analysis. Karan, Putul The design and synthesis of novel azo-coumarin derivatives represent a promising area of research in medicinal chemistry due to their potential pharmacological activities. In this study, a series of novel azo-coumarin derivatives such as 6-[3-pyridyl]azocoumarin, 6-[Phenylazo]coumarin, 6-[2-Chlorophenylazo]coumarin, 6-[3-Chlorophenylazo]coumarin, and 6-[4-Chlorophenylazo]coumarin were synthesized using diazo-coupling reaction. The synthesized compounds were fully characterized using FT-IR, NMR, and mass spectrometry, and biological studies were carried out. The structures of the synthesized compounds were optimized using DFT calculation and the frontier molecular orbital calculations reveal that synthesized compounds were more biologically and chemically active than coumarin. The cytotoxicity of these derivatives was evaluated against human cancer cell lines LN-229 and the IC50 values were evaluated and it was found that 6-[4-Chlorophenylazo]coumarin was most effective. The interaction of these derivatives with CT-DNA was investigated using UV-visible and fluorescence spectroscopy. All the synthesized compounds bound at the minor groove of CT-DNA and the binding constant values showed the order of the binding affinities was 6-[4-Chlorophenylazo]coumarin > 6-[2-pyridyl]azocoumarin > 6-[3-Chlorophenylazo]coumarin > 6-[Phenylazo]coumarin > 6-[3-pyridyl]azocoumarin > coumarin and all the compounds bound with CT-DNA through minor groove. The BSA binding study of the synthesized compounds was also carried out using UV-visible and fluorescence spectroscopy which showed the same binding order of the compounds observed with the DNA binding study. In silico analysis supported all the experimental outcomes regarding CT-DNA and BSA binding. 2026-03-24T00:00:00Z https://mcc-idr.l2c2academy.co.in/xmlui/handle/123456789/890 Study of Temporal and Spectral Properties of X-ray Pulsars. Mandal, Manoj The accreting X-ray pulsars are binary systems that have an optical counterpart and a revolving, highly magnetized neutron star. The expelled plasma from the companion star accretes onto the compact object, resulting in pulsed X-ray emission. These sources are thought of as the only astrophysical laboratories capable of probing the properties of matter in extreme conditions, including strong magnetic fields (1012 G), high pressure, and extreme density. Considerable progress has been made in understanding these objects, both in terms of their constituent binary components and the features of their X-ray emission. However, further research is required to address many unresolved aspects, both theoretically and through observation. Some of the significant open aspects are the emission mechanism, the accretion structure’s geometry and beaming pattern, and the impact of the optical counterpart on the measured X-ray properties. Matter accreted from the optical companion interacts with the high magnetic field of the neutron star during the accretion process, following field lines to hot magnetic poles located beyond the magnetospheric radius. It is thought that an accretion column, a structure resembling a column, will develop on top of a neutron star that is home to multiple intricate processes responsible for X-ray emissions. This work presents the observational study of these processes for several X-ray pulsars driven by accretion. The luminosity and energy dependence of pulse profiles are used to study the beam function or geometry of the emission zone. Through pulse profile studies, the impact of the surrounding medium on the radiation released is also investigated. Comprehensive broadband spectroscopy of pulsars can yield valuable insights into the physical mechanisms driving radiation emission, as well as the distinctive characteristics of the matter distribution in the high-mass companion star’s accretion column, accretion stream, accretion disk, photosphere, and stellar wind. The pulsar spectra can only be explained by a few more spectral components in addition to the continuum spectra. In addition, fluorescence emission lines were also observed from matter scattered about the neutron star. Pulsar spectra exhibit absorption lines, known as cyclotron lines, which are a crucial consequence of the interaction between the magnetic field and electrons. A more precise and direct measurement of the pulsars’ magnetic fields can be obtained by detecting these lines. A thermonuclear burst is used to probe the different fundamental properties of a neutron star. The unstable fuel burning on the neutron star’s surface during a thermonuclear burst is the main reason for the sudden increase in X-ray intensity. The surface emission is more than ten times higher than the persistent emission during a Type-I burst. It can be used to distinguish between surface emission and total emission, which can be helpful in accurately calculating the different characteristics of a neutron star. The gas that powers the X-ray burst is accreted via an accretion disk by a neutron star from a low-mass companion star. The low-mass binary companion’s materials accumulate on the stellar surfaces of the neutron stars. We have detected multiple thermonuclear X-ray bursts from the millisecond pulsar MAXI J1816–195. The detailed timing and spectral properties are studied during the burst. Different fundamental parameters, such as the apparent emitting area, source distance, burst fluence, and mass accretion rate, are also estimated from the spectral study. One of the main objectives is to understand the mechanism of such types of thermonuclear flashes. Using space-based observatories like NICER, Swift, and NuSTAR, timing and spectral studies have been carried out in this work of several X-ray pulsars such as 1A 0535+262, RX J0440.9+4431, MAXI J1816–195, 2S 1417–624, and 2S 1553–542. The luminosity and energy dependence of pulse profiles and pulse fraction were also investigated in Be/Xray binary pulsars to understand the accretion mechanism and beaming patterns. Above a certain luminosity (known as critical luminosity), the timing and spectral properties evolved significantly. The accretion mode, beaming patterns, and emission mechanism evolved significantly above this luminosity. Giant outbursts were reported for two X-ray pulsars, 1A 0535+262 and RX J0440.9+4431, which were used to probe neutron star properties at such a high luminosity, which was not observed earlier. A significant evolution of temporal and spectral properties is observed during the state transition. The critical luminosity is used to estimate the magnetic field for these supercritical X-ray pulsars. For the X-ray pulsar 1A 0535+262, a giant outburst of a record-high flux of 11 Crab was detected. The combined spectro-timing study indicated a state transition from the subcritical to supercritical accretion regime during the giant outburst. A significant evolution in spectral and temporal properties was observed during the giant outburst. The Cyclotron Resonant Scattering Feature (CRSF) originates from the resonant scattering of continuum photons with electrons, resulting in an absorption-like feature in the energy spectra. The cyclotron line energy can be used to directly measure the magnetic field of the neutron star. The CRSF was detected from 1A 0535+262 during the 2020 outburst, and the magnetic field was estimated using the cyclotron line energy. The variation of the cyclotron line is probed to identify the spectral state. A significant evolution of line energy with luminosity was observed, which may be linked to the transition state in X-ray pulsars. 2026-03-24T00:00:00Z https://mcc-idr.l2c2academy.co.in/xmlui/handle/123456789/889 Detection of Complex Molecules from Millimeter Wavelength Spectra Radiating from Interstellar Medium and Planetary Objects. Manna, Arijit Studying complex organic molecules in the interstellar medium (ISM) and planetary atmospheres is crucial for understanding their chemical compositions and complex biochemistry. The high- and low-mass star-forming regions, molecular clouds, and protoplanetary disks are ideal targets for observing complex molecular lines, as various molecules are formed and destroyed in these regions through gas-phase and grain-surface chemical reactions. In this thesis, we present molecular line observations towards hot molecular cores and hot corinos using the high-resolution Atacama Large Millimeter/Submillimeter Array (ALMA). Complex molecular lines in planetary atmospheres and cometary objects were also investigated. Several complex organic molecules were detected, including the possible precursors of the simplest amino acid, glycine (NH2CH2COOH). We also successfully detected various nitrogen (N)-, oxygen (O)-, and thiol (SH)-bearing molecules in hot molecular cores and hot corinos. After detection, the column density and excitation temperature of these molecules were estimated using the local thermodynamic equilibrium (LTE) and rotational diagram models. The LTE assumption is valid in hot cores and corinos because the gas and kinetic temperatures are nearly equal. Following the column density estimation, we derived the fractional abundances of the detected molecules with respect to molecular hydrogen (H2). The detection of complex prebiotic molecules such as methylene imine (CH2NH), methylamine (CH3NH2), cyanamide (NH2CN), and aminoacetonitrile (NH2CH2CN), potential NH2CH2COOH precursors, provides insight into how complex molecules create biological environments through various chemical reactions. To understand the formation mechanisms of the detected complex organic molecules, we employed two-phase warm-up chemical modelling at different timescales using gas-grain chemical codes UCLCHEM and GGCHEMPY. Additionally, the rotational emission line of hydrogen cyanide (HCN) was detected in the atmosphere of Saturn. To derive the abundance of HCN from the atmosphere of Saturn, a planetary spectrum generator (PSG) radiative transfer model with different atmospheric layers was used. Furthermore, we detected evidence of atomic hydrogen (HI) from the comet C/2020 F3 (NEOWISE) using the Giant Metrewave Radio Telescope (GMRT). This study opens new avenues for understanding prebiotic chemistry in the universe. The detection of chemically related complex organic and prebiotic molecules in both interstellar hot cores and Solar System bodies such as comets suggests that common grain-surface chemical pathways operating on icy dust mantles may be universal, bridging the chemistry of star-forming regions and planetary systems. 2026-03-24T00:00:00Z