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Somnath Ghosh

Bio: Somnath Ghosh is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Microstructured optical fiber & Optical fiber. The author has an hindex of 28, co-authored 287 publications receiving 3318 citations. Previous affiliations of Somnath Ghosh include University of Calcutta & Indian Institute of Science.


Papers
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TL;DR: The photochemical decomposition of the said diazoketoneg (4 a, 11 and 16 ) gave products depending on the length of the side chain present in the substrates as mentioned in this paper.

22 citations

Journal ArticleDOI
TL;DR: Despite activation of same repair molecules such as ATM and BRCA1, differences in low and high LET damage responses might be due to their distinct macromolecular complexes rather than their individual activation and the activation of cytoplasmic pathways such as ERK.
Abstract: Carbon beams (5.16 MeV/u, LET = 290 keV/μm) are high linear energy transfer (LET) radiation characterized by higher relative biological effectiveness than low LET radiation. The aim of the current study was to determine the signaling differences between γ-rays and carbon ion-irradiation. A549 cells were irradiated with 1 Gy carbon or γ-rays. Carbon beam was found to be three times more cytotoxic than γ-rays despite the fact that the numbers of γ-H2AX foci were same. Percentage of cells showing ATM/ATR foci were more with γ-rays however number of foci per cell were more in case of carbon irradiation. Large BRCA1 foci were found in all carbon irradiated cells unlike γ-rays irradiated cells and prosurvival ERK pathway was activated after γ-rays irradiation but not carbon. The noteworthy finding of this study is the early phase apoptosis induction by carbon ions. In the present study in A549 lung adenocarcinoma, authors conclude that despite activation of same repair molecules such as ATM and BRCA1, differences in low and high LET damage responses might be due to their distinct macromolecular complexes rather than their individual activation and the activation of cytoplasmic pathways such as ERK, whether it applies to all the cell lines need to be further explored.

22 citations

Journal ArticleDOI
TL;DR: Bystander signaling was found to exist between RAW 264.7 (macrophage) and EL-4 (lymphoma) cells and active iNOS in the irradiated cells was essential for bystander response.
Abstract: Purpose The present report describes the bystander effects of radiation between similar and dissimilar cells and the role of iNOS in such communication. Materials and Methods EL-4 and RAW 264.7 cells were exposed to 5 Gy γ-irradiation. The medium from irradiated cells was transferred to unirradiated cells. Results Irradiated EL-4 cells as well as those cultured in the presence of medium from γ-irradiated EL-4 cells showed an upregulation of NF-κB, iNOS, p53, and p21/waf1 genes. The directly irradiated and the bystander EL-4 cells showed an increase in DNA damage, apoptosis, and NO production. Bystander signaling was also found to exist between RAW 264.7 (macrophage) and EL-4 (lymphoma) cells. Unstimulated or irradiated RAW 264.7 cells did not induce bystander effect in unirradiated EL-4 cells, but LPS stimulated and irradiated RAW 264.7 cells induced an upregulation of NF-κB and iNOS genes and increased the DNA damage in bystander EL-4 cells. Treatment of EL-4 or RAW 264.7 cells with L-NAME significantly reduced the induction of gene expression and DNA damage in the bystander EL-4 cells, whereas treatment with cPTIO only partially reduced the induction of gene expression and DNA damage in the bystander EL-4 cells. Conclusions It was concluded that active iNOS in the irradiated cells was essential for bystander response.

22 citations

Journal Article
TL;DR: In this paper, the effect of alkali content in geopolymer mortar specimens exposed to sulphuric acid was investigated and the findings of an experimental investigation was presented to study the effect.
Abstract: This paper presents the findings of an experimental investigation to study the effect of alkali content in geopolymer mortar specimens exposed to sulphuric acid. Geopolymer mortar specimens were manufactured from Class F fly ash by activation with a mixture of sodium hydroxide and sodium silicate solution containing 5% to 8% Na2O. Durability of specimens were assessed by immersing them in 10% sulphuric acid solution and periodically monitoring surface deterioration and depth of dealkalization, changes in weight and residual compressive strength over a period of 24 weeks. Microstructural changes in the specimens were studied with Scanning electron microscopy (SEM) and EDAX. Alkali content in the activator solution significantly affects the durability of fly ash based geopolymer mortars in sulphuric acid. Specimens manufactured with higher alkali content performed better than those manufactured with lower alkali content. After 24 weeks in sulphuric acid, specimen with 8% alkali still recorded a residual strength as high as 55%. Keywords—Alkali content, acid attack, compressive strength, geopolymer

22 citations

Journal ArticleDOI
TL;DR: In this paper, photolysis of 9-aroyl carbazoles in polar solvent has been used for the first time to obtain the first synthesis of the unknown 1-carbazole.

21 citations


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08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
04 Jan 2019-Science
TL;DR: The topic of exceptional points in photonics is reviewed and some of the possible exotic behavior that might be expected from engineering such systems are explored, as well as new angle of utilizing gain and loss as new degrees of freedom, in stark contrast with the traditional approach of avoiding these elements.
Abstract: BACKGROUND Singularities are critical points for which the behavior of a mathematical model governing a physical system is of a fundamentally different nature compared to the neighboring points. Exceptional points are spectral singularities in the parameter space of a system in which two or more eigenvalues, and their corresponding eigenvectors, simultaneously coalesce. Such degeneracies are peculiar features of nonconservative systems that exchange energy with their surrounding environment. In the past two decades, there has been a growing interest in investigating such nonconservative systems, particularly in connection with the quantum mechanics notions of parity-time symmetry, after the realization that some non-Hermitian Hamiltonians exhibit entirely real spectra. Lately, non-Hermitian systems have raised considerable attention in photonics, given that optical gain and loss can be integrated as nonconservative ingredients to create artificial materials and structures with altogether new optical properties. ADVANCES As we introduce gain and loss in a nanophotonic system, the emergence of exceptional point singularities dramatically alters the overall response, leading to a range of exotic functionalities associated with abrupt phase transitions in the eigenvalue spectrum. Even though such a peculiar effect has been known theoretically for several years, its controllable realization has not been made possible until recently and with advances in exploiting gain and loss in guided-wave photonic systems. As shown in a range of recent theoretical and experimental works, this property creates opportunities for ultrasensitive measurements and for manipulating the modal content of multimode lasers. In addition, adiabatic parametric evolution around exceptional points provides interesting schemes for topological energy transfer and designing mode and polarization converters in photonics. Lately, non-Hermitian degeneracies have also been exploited for the design of laser systems, new nonlinear optics phenomena, and exotic scattering features in open systems. OUTLOOK Thus far, non-Hermitian systems have been largely disregarded owing to the dominance of the Hermitian theories in most areas of physics. Recent advances in the theory of non-Hermitian systems in connection with exceptional point singularities has revolutionized our understanding of such complex systems. In the context of optics and photonics, in particular, this topic is highly important because of the ubiquity of nonconservative elements of gain and loss. In this regard, the theoretical developments in the field of non-Hermitian physics have allowed us to revisit some of the well-established platforms with a new angle of utilizing gain and loss as new degrees of freedom, in stark contrast with the traditional approach of avoiding these elements. On the experimental front, progress in fabrication technologies has allowed for harnessing gain and loss in chip-scale photonic systems. These theoretical and experimental developments have put forward new schemes for controlling the functionality of micro- and nanophotonic devices. This is mainly based on the anomalous parameter dependence in the response of non-Hermitian systems when operating around exceptional point singularities. Such effects can have important ramifications in controlling light in new nanophotonic device designs, which are fundamentally based on engineering the interplay of coupling and dissipation and amplification mechanisms in multimode systems. Potential applications of such designs reside in coupled-cavity laser sources with better coherence properties, coupled nonlinear resonators with engineered dispersion, compact polarization and spatial mode converters, and highly efficient reconfigurable diffraction surfaces. In addition, the notion of the exceptional point provides opportunities to take advantage of the inevitable dissipation in environments such as plasmonic and semiconductor materials, which play a key role in optoelectronics. Finally, emerging platforms such as optomechanical cavities provide opportunities to investigate exceptional points and their associated phenomena in multiphysics systems.

1,276 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive review of shape-memory polymers (SMPs) and their derivatives, such as composites and compound structures, as well as their current applications are presented.

1,034 citations

Journal ArticleDOI
19 Apr 2013-Polymer
TL;DR: An up-to-date review on shape memory polymer composites with potential applications in biomedical devices, aerospace, textiles, civil engineering, bionics engineering, energy, electronic engineering, and household products is presented.

981 citations