Dibrugarh University is a collegiate public state university in the Indian state of Assam. It is located at Dibrugarh, Assam, India. It was set up in 1965 under the provisions of the Dibrugarh University Act, 1965 enacted by the Assam Legislative Assembly.
In this work, we probe the well known thermodynamic phase structure of black hole through the lens of its quasi-periodic oscillations (QPOs). Can QPOs be influenced by black hole phase transitions? Do they carry any signature of such transitions in their observational patterns? These were the central questions guiding our study. Using both RN AdS and Kerr black hole backgrounds across different QPO models, we analyzed the behavior of upper and lower QPO frequencies as functions of the Hawking temperature. Our results shows that QPO frequencies trace out distinct thermodynamic phases and also reflect their stability properties. As the black hole transitions between different thermodynamic phases, the trend of QPO frequencies with respect to temperature also shifts. Due to lack of observational data, the present work is primarily more on the mathematical side, as the underlying mechanism responsible for the Hawking temperature has not yet been fully understood or experimentally verified. Moreover, given the speculative nature of black hole phase transitions, it would be unfair to claim that our results establish a definitive connection between an observable quantity such as the QPO frequency and the thermodynamic phase behavior of black holes. Nevertheless, our analysis suggests a possibility that changes in black hole geometry could be one of the contributing factors influencing QPO behavior.
Abstract Heat stress has emerged as a critical environmental issue in rapidly growing tropical cities. However, grid-level assessment linking heat stress to exposed population remains limited in tier-III cities of Assam. The study examined UTFVI (Urban Thermal Field Variance Index) induced heat stress exposure across 7 prominent urban centers of Assam. Landsat 8 data of May and December 2023 were analyzed along with gridded population data. Kruskal Wallis test & Dunn’s post hoc test were employed to evaluate inter-city variations and pair wise comparison of LST (land surface temperature). The composite Z-score analysis was utilized to classify grid-level heat stress zones for assessing exposed population in selected cities. Results revealed that all cities exhibit a high mean LST in summer with highest observed in Nagaon (28.36 °C) and lowest in Tezpur (26.61 °C). In winter, Silchar records the highest mean LST (20.81 °C), while Tinsukia exhibits the lowest (17.92 °C). Statistical analysis reveals significant inter-city disparity of LST. UTFVI reveals Dibrugarh and Tezpur cities contain major areas under strongest UHI (Urban heat island), whereas Silchar and Nagaon occupy considerable Non-UHI zones. The Z-score analysis reveals Silchar and Dibrugarh occupy larger area under very high heat stress exposure (VHHSE) class. However, Nagaon records the highest number of residents exposed to VHHSE, while Sivasagar exhibits the lowest exposure. In all cities, only a minimal population resides in the very low heat stress exposure (VLHSE) zone. Findings reflect the emergence of thermally stressed cities and provide a useful framework for heat mitigation in rapidly urbanizing tropical cities.
Revealing deep insides of light-matter interactions in two-dimensional transition-metal dichalcogenides under resonant excitation is essential for next-generation nanoscale optoelectronics, valley photonics, and polarisation-sensitive devices. Among these dichalcogenides, MoS2 monolayer shows especially distinct vibrational and optical behaviour under resonant excitation. In this work, a comprehensive first-principle Density Functional Theory (DFT) investigation focusing resonant Raman response of a vacancy-induced MoS2 monolayer root 13 & times; root 13R13.9 degrees supercell with 37 atoms has been performed using Quantum Espresso software. The phonon modes and Raman spectra at commonly used lasers viz: 445, 488, 532, and 635 nm, that mimic real experimental conditions have been computed. This reveals strong excitation-energy dependent enhancement of specific phonon modes linked to excitonic transitions in the visible regime. Furthermore, the calculated Raman tensors under in-plane and out-of-plane polarized light show a pronounced anisotropic response, highlighting the selective activation and suppression of A(1g), E-2g(1) , and zone-folded low-symmetry modes. This polarization dependence uncovers the interplay between lattice symmetry, excitonic resonance, and electron-phonon coupling in the supercell. This work demonstrates that resonant Raman spectroscopy of large MoS2 supercells offers a powerful way to detect subtle structural effects such as long-wavelength distortions, twist-induced symmetry breaking, zone folding induced activation of normally inactive Raman or silent phonon modes and provide a deeper insight into defect like and long-wavelength phonon contributions. These findings open up new possibilities for designing polarization-sensitive and strain-adaptive two-dimensional photonic devices.
Shillong Meghalaya Plateau in NE India represents the eastern continuation of the Indian peninsular shield separated by Garo-Rajmahal graben. The plateau consists of basement granite gneisses, granites, migmatites and granulites of the Paleoproterozoic age and Shillong Group of rocks as the cover sequence. Granites of the Neoproterozoic and Cambrian ages (Pan-African) have intruded the basement gneisses and Shillong Group of rocks. These granites are equigranular to porphyritic and consist of microgranular enclaves with no significant evidence of deformation in the field. An attempt has been made to understand the deformation fabric of the macroscopically undeformed granitoids exposed within the Shillong Group of rocks from the field and microstructural observations. In this study we have carried out a detailed petrographic investigation of Pan-African Granites of the Shillong plateau. It is observed that the granites preserve magmatic, high-T solid-state as well as low-T solid-state fabrics. It is thus concluded that these granites are deformed.
Helminth infection continues to adversely affect poultry health and productivity, especially in tropical and subtropical areas whereby resistance to traditional anthelmintic drugs is becoming common. The traditional medicinal plants can become a viable alternative because they are readily available, cheap and contain a variety of bioactive compounds. The indigenous communities of Assam use Sarcochlamys pulcherrima (Urticaceae) to treat various helminthic infections, but its anthelmintic effect is not scientifically verified. The present study evaluates the in vitro anthelmintic potential of the methanolic extract of S. pulcherrima leaves against Raillietina echinobothrida. Anthelmintic activity was evaluated in terms of motility index. The morphological changes were studied by scanning electron microscopy (SEM) and biochemical assays were performed to study the ATPase, AcPase and AlkPase activity. Our finding revealed that the plant extract (30 mg/ml) caused rapid paralysis with total loss of motility in 6 h, an earlier event compared to the standard drug. Major tegumental changes were noted with SEM, such as tegument erosion, wrinkling and folding and scolex and sucker deformities. Biochemical tests proved that there was a great inhibition of acid phosphatase (64
