Showing papers by "Somnath Ghosh published in 2011"
TL;DR: In this paper, a highly efficient photochemical methodology has been developed for the condensation of Meldrum's acid with aromatic aldehydes in water-ethanol solution without any catalyst, support or promoter.
38 citations
TL;DR: In this paper, the synthesis of 2-aryl/alkylbenzofurans has been achieved in high yields under photochemical conditions from readily accessible and suitably substituted phosphonium bromides by an intramolecular photochemical Wittig reaction onto aryloxy carbonyl groups.
36 citations
TL;DR: In this paper, an eight-bilayer chitosan/silver (Cs/Ag)8 hybrid was prepared having a known concentration of silver, and atomic force microscopy (AFM) studies were carried out for the first time on the microbe to know the morphological changes affected by the hybrid film.
Abstract: Antibacterial efficacy of silver nanoparticles (Ag NPs) deposited alternatively layer by layer (LBL) on chitosan polymer in the form of a thin film over a quartz plate and stainless steel strip has been studied. An eight-bilayer chitosan/silver (Cs/Ag)8 hybrid was prepared having a known concentration of silver. Techniques such as UV-visible spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES), and atomic force microscopy (AFM) were carried out to understand and elucidate the physical nature of the film. Gram-negative bacteria, Escherichia coli (E. coli), were used as a test sample in saline solution for antibacterial studies. The growth inhibition at different intervals of contact time and, more importantly, the antibacterial properties of the hybrid film on repeated cycling in saline solution have been demonstrated. AFM studies are carried out for the first time on the microbe to know the morphological changes affected by the hybrid film. The hybrid films on aging (3 months) are found to be as bioactive as before. Cytotoxicity experiments indicated good biocompatibility. The hybrid can be a promising bioactive material for the prevention of biofilms specific to E. coli and in purification of water for safe drinking.
31 citations
TL;DR: In this paper, the authors investigate how the transverse localization of light in evanescently coupled, disordered, lossless waveguide lattices depends on the shape and size of an input beam.
27 citations
Journal Article•
25 Dec 2011-World Academy of Science, Engineering and Technology, International Journal of Civil, Environmental, Structural, Construction and Architectural Engineering
TL;DR: In this paper, the effect of incorporating silica fume on physico-mechanical properties and durability of resulting fly ash geopolymers was investigated, and it was shown that the addition of fume significantly enhanced the physico and structural properties of fly ash.
Abstract: This paper presents results of an experimental study performed to investigate effect of incorporating silica fume on physico-mechanical properties and durability of resulting fly ash geopolymers. Geopolymer specimens were prepared by activating fly ash incorporated with additional silica fume in the range of 2.5% to 5%, with a mixture of sodium hydroxide and sodium silicate solution having Na2O content of 8%. For studying durability, 10% magnesium sulphate solution was used to immerse the specimens up to a period of 15 weeks during which visual observation, weight changes and strength changes were monitored regularly. Addition of silica fume lowers performance of geopolymer pastes. However, in mortars, addition of silica fume significantly enhanced physico-mechanical properties and durability. Keywords—Fly ash; Silica fume; Geopolymer; Apparent porosity; Sorptivity;compressive strength; durability
26 citations
TL;DR: In this article, a new synthetic approach for the synthesis of flavones and pyranoflavone was developed by light induced intramolecular photochemical Wittig reaction in water onto aryloxy carbonyl groups and suitably substituted phosphonium bromides without any phase transfer catalyst or promoter.
25 citations
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
TL;DR: Durability of fly ash based geopolymer mortar specimens in Nitric acid solution was investigated on three different series of specimens manufactured by activating fly ash with a mixture of sodium hydroxide and sodium silicate solution containing Na2O.
Abstract: Durability of fly ash based geopolymer mortar specimens in Nitric acid solution was investigated on three different series of specimens manufactured by activating fly ash with a mixture of sodium hydroxide and sodium silicate solution containing Na2O ranging from 5% to 8% of fly ash. Specimens were exposed in 10% by weight Nitric acid solution up to 24 weeks. The effect of alkali (%Na2O) content on durability of geopolymer mortar specimens were studied in terms of visual appearance, change in weight and change in compressive strength. Mineralogical and microstructure changes due to nitric acid attack were also investigated. Geopolymer mortar specimens showed excellent durability in terms of extremely less weight loss as well as high retention of compressive strength. Specimens with higher alkali content exhibited better durability in nitric acid.
21 citations
TL;DR: The design of an all-solid, soft glass-based, large mode area Bragg fiber for effective single mode operation with mode effective area exceeding 1100 µm(2) across the wavelength range of 2-4 μm is reported.
Abstract: The design of an all-solid, soft glass-based, large mode area Bragg fiber for effective single mode operation with mode effective area exceeding 1100 µm2 across the wavelength range of 2 – 4 μm is reported. The design adopts a new strategy to induce large differential loss between the fundamental and higher order modes for effective single-mode operation within few tens of centimetres length of an otherwise multimode fiber. In addition to having the potential for the targeted application in high power laser delivery systems; complemented by a zero dispersion wavelength at 2.04 µm and rapidly developing mid-IR optical sources, the proposed fiber should also be attractive for generation of high power, single mode and less divergent supercontinuum light over this mid-IR window.
19 citations
TL;DR: The noteworthy finding of this study is the activation of the sensor proteins, ATM and ATR by oxygen irradiation and the significant activation of Chk1, Chk2 and p53 only in the oxygen beam irradiated cells.
Abstract: Oxygen beams 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- and oxygen ion-irradiation. Activation of various signaling molecules was looked in A549 lung adenocarcinoma cells irradiated with 2Gy oxygen, 2Gy or 6Gy γ-radiation. Oxygen beam was found to be three times more cytotoxic than γ-radiation. By 4h there was efficient repair of DNA in A549 cells exposed to 2Gy or 6Gy gamma radiation but not in cells exposed to 2Gy oxygen beam as determined by γ-H2AX counting. Number of ATM foci was found to be significantly higher in cells exposed to 2Gy oxygen beam. Percentage of cells showing ATR foci were more with gamma however number of foci per cell were more in case of oxygen beam. Oxygen beam irradiated cells showed phosphorylation of Chk1, Chk2 and p53. Many apoptotic nuclei were seen by DAPI staining in cells exposed to oxygen beam. The noteworthy finding of this study is the activation of the sensor proteins, ATM and ATR by oxygen irradiation and the significant activation of Chk1, Chk2 and p53 only in the oxygen beam irradiated cells.
TL;DR: Equilibrium and dynamic electrowetting behavior of ultrathin liquid films of surfactant (SDS) laden water over silicon substrate (with native oxide) is investigated and contact line instability resulting in emission of droplets from the curved meniscus has been observed.
Abstract: Equilibrium and dynamic electrowetting behavior of ultrathin liquid films of surfactant (SDS) laden water over silicon substrate (with native oxide) is investigated. A nonobtrusive optical method, namely, image analyzing interferometry, is used to measure the meniscus profile, adsorbed film thickness, and the curvature of the capillary meniscus. Significant advancement of the contact line of the liquid meniscus, as a result of the application of electric field, is observed even at relatively lower values of applied voltages. The results clearly demonstrate the balance of intermolecular and surface forces with additional contribution from Maxwell stress at the interline. The singular nature of Maxwell stress is exploited in this analysis to model the equilibrium meniscus profile using the augmented Young–Laplace equation, leading to the in situ evaluation of the dispersion constant. The electrowetting dynamics has been explored by measuring the velocity of the advancing interline. The interplay of differen...
TL;DR: In this article, the visible light induced, uncatalyzed and unsupported photochemical process can be also carried out under microwave irradiation over alumina, and it is shown that it can be done under a variety of conditions.
Abstract: The visible light induced, uncatalyzed and unsupported photochemical process can be also carried out under microwave irradiation over alumina.
TL;DR: In this article, the synthesis of Au/PbSe and Au/copper indium diselenide (CIS) core/shell nanowires was reported.
Abstract: Here, we report the synthesis of Au/PbSe and Au/copper indium diselenide (CIS) core/shell nanowires. The nanowires were synthesized by the aqueous electrodeposition of either PbSe or CIS onto gold nanowires prepared by lithographically patterned nanowire electrodeposition. The resulting nanowires are nanocrystalline, exhibit a sharp boundary between the gold core and the semiconducting coating, and are photoconductive, with enhanced light absorption in smaller nanowires.
TL;DR: In this paper, the intramolecular Wittig reaction of phosphonium salts (I) gave better yields under photochemical conditions than under microwave irradiation, and showed that I gives better yields than I under both photochemical and microwave conditions.
Abstract: In general, the intramolecular Wittig reaction of phosphonium salts (I) gives better yields under photochemical conditions than under microwave irradiation.
06 Mar 2011
TL;DR: In this paper, an all-solid LMA Bragg fiber (mode area exceeding 1100µm2) is presented for mid-infrared applications, based on a new design strategy that induces large differential loss between fundamental and higher order modes for effective single-mode operation.
Abstract: An all-solid LMA Bragg fibre (mode area exceeding 1100µm2) is presented for mid-infrared applications, based on a new design strategy that induces large differential loss between fundamental and higher order modes for effective single-mode operation.
TL;DR: This paper introduces batch extension that gradually extends the shareholders' collaboration boundary by more than one hop at a time around the service requestor, to find at least the threshold number of the unknown shareholders, reducing the redundancy use of reply routes, decreasing the required packet transmission, and lessening the service delay.
Abstract: The collaboration of at least a threshold number of secret shareholders in a threshold secret sharing scheme is a strict requirement to ensure its intended functionality. Due to its promising characteristics, such a scheme has been proposed to solve a range of security problems in mobile ad hoc networks. However, discovering a sufficient number of secret shareholders in such dynamic and unpredictable networks is not easy. In this paper, we propose a more efficient shareholder discovery mechanism compared to our previous work. The discovery process is performed in a multihop fashion to adapt to the mobile ad hoc network environment. We introduce batch extension that gradually extends the shareholders' collaboration boundary by more than one hop at a time around the service requestor, to find at least the threshold number of the unknown shareholders. Through the batch extension, reply aggregation is applicable, hence reducing the redundancy use of reply routes, decreasing the required packet transmission, and lessening the service delay, compared to the previously proposed mechanism. Our simulation results show that, with the appropriate batch size, the latest mechanism is more efficient with an insignificant increase of control overhead.
01 May 2011-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, loss of H monitored by on-line elastic recoil detection analysis (ERDA) technique from passivated Hg1−xCdxTe (MCT) wafers due to irradiation by 80 MeV Ni9+, 120 MeV Au15+ and 200 MeV Ag10+.
Abstract: We report here loss of H monitored by on-line elastic recoil detection analysis (ERDA) technique from passivated Hg1−xCdxTe (MCT) wafers due to irradiation by 80 MeV Ni9+, 120 MeV Au15+ and 200 MeV Ag10+. The loss of H is more in case of the wafer irradiated by Ag ions as compared to other two because of higher electronic energy loss (Se). For same Se value, H loss is more in case of the wafer having x = 0.29 as compared to the one having x = 0.204. This is due to higher band gap of the former as compared to the later, which is an important data for proper use of these materials as IR detector in intense radiation zone. These results are explained on the basis of thermal spike model of ion–solid interaction.
TL;DR: In this paper, the signature of transverse localization of light in laser-inscripted disordered array of evanescently coupled one-dimensional optical waveguides in an Er-doped Bismuthate glass was observed.
Abstract: We report direct observation of the signature of transverse localization of light in laser-inscripted disordered array of evanescently coupled one-dimensional optical waveguides in an Er-doped Bismuthate glass.