682 research outputs found
Graphene oxide-based degradation of metaldehyde: effective oxidation through a modified Fenton’s process
No full textA modified graphene oxide-based Fenton’s reaction has been investigated for the degradation of a challenging emerging contaminant which is not effectively removed in conventional water treatment. Metaldehyde, used as the challenge molecule in this study, is a common molluscicide that (like many highly soluble contaminants) has frequently breached European regulatory limits in surface waters. The new method involves graphene with higher hydrophilic characteristics (single-layer graphene oxide, SLGO) as a system that participates in a redox reaction with hydrogen peroxide and which can potentially stabilize the radical dotOH generated, which subsequently breaks down organic contaminants. The modified Fenton’s reaction has shown to be effective in degrading metaldehyde in natural waters (>92% removal), even at high contaminant concentrations (50 mg metaldehyde/L) and in the presence of high background organic matter and dissolved salts. The reaction is relatively pH insensitive. SLGO maintained its catalytic performance over 3 treatment cycles when immobilized. Its performance gradually decreased over time, reaching around 50% of starting performance on the 10th treatment cycle. X-ray photoelectron spectroscopy (XPS) analysis of modifications caused in SLGO by the oxidizing treatment indicated that the oxidation of Csingle bondC sp2 to carbonyl groups may be the cause of the decrease in performance. The proposed modified Fenton’s process has the potential to substitute traditional Fenton’s treatment although regeneration of the nanocarbon is required for its prolonged use
Agricultural wastes from wheat, barley, flax and grape for the efficient removal of Cd from contaminated water
Full text linkAgricultural production results in wastes that can be re-used to improve the quality of the environment. This work has investigated for the first time the use of abundant, un-modified agricultural wastes and by-products (AWBs) from grape, wheat, barley and flax production, to reduce the concentration of Cd, a highly toxic and mobile heavy metal, in contaminated water. At concentrations of 1.1 mg Cd per L, flax and grape waste were found superior in removing Cd compared with a granular activated carbon used in water treatment, which is both more expensive and entails greater CO2 emissions in its production. At a pH representative of mine effluents, where Cd presents its greatest mobility and risk as a pollutant, grape and flax waste showed capacity for effective bulk water treatment due to rapid removal kinetics and moderate adsorption properties: reaching equilibrium within 183 and 8 min-adsorption capacities were determined as 3.99 and 3.36 mg Cd per g, respectively. The capacity to clean contaminated effluents was not correlated with the surface area of the biosorbents. Surface chemistry analysis indicated that Cd removal is associated with exchange with Ca, and chemisorption involving CdCO3, CdS and CdO groups. This work indicates that some AWBs can be directly (i.e. without pre-treatment or modification) used in bulk to remediate effluents contaminated with heavy metals, without requiring further cost or energy input, making them potentially suitable for low-cost treatment of persistent (e.g. via mine drainage) or acute (e.g. spillages) discharges in rural and other areas.</p
Banal nationalism and soap opera
No full textAs Michael Billig (1995) argues, nationalism does not die with the establishment of relatively stable nation states- it changes from a ‘hot’ to a ‘banal’ form. In this multidisciplinary and multiperspectival study, I study nationalism (specifically Hindu nationalism or Hindutva) in its banal form within popular culture, specifically prime time television soap operas colloquially known as the K-serials. Through a conjunctural analysis, I show how banal Hindu nationalism played out on the K-serials in multiple ways. That is, these serials had an important role in the ongoing project of remaking of the Indian nation under the ideology of Hindutva, creating not just a Hindu nation but a Brahminical nation. This dissertation makes a number of contributions to different bodies of research. One, it examines how the changes in the political economy impact the way audiences are rounded up and how that influences the content of the soaps. I show how the structural limitations of the audience measurement system and the changing focus on the ‘bottom of the pyramid’ consumer influenced the arrival of Hindutva inflected content on television. (I show also, in passing, how the currency of television, TRPs, can themselves be gendered). Two, I show how the debate over secularism and religious nationalism in the political sphere get reflected in the cultural sphere, especially in texts that less obviously have anything to do with national politics. Three, I show how the agency and empowerment that other scholars have read into these soaps is derived largely from the discourses of the women’s wing of Hindu nationalism, and is therefore highly problematic, ahistorical, and limiting. Four, I show how the very structure of soaps, especially its ‘open’ ness, periodicity and everydayness can play a significant role in spreading banal nationalism. Five, I show how the operations of banal Hindutva disrupt the relationship between folk and Sanskritic practices, contributing to the homogenizing of Hinduism. And finally, I have shown how by going beyond the texts themselves, we find a bridge between the studies of soaps that look at the micropolitics of gender and those that look at macropolitics of national identity.Ph. D.Includes bibliographical referencesby Santanu Chakrabart
Competitive coordination aggregation for V-shaped [Co3] and disc-like [Co7] complexes: Synthesis, magnetic properties and catechol oxidase activity
No full textUnique dependence on the nature of metal salt and reaction conditions for coordination assembly reactions of varying architecture and nuclearity have been identified in V-shaped [Co3L4] and planar disc-like [Co7L6] compounds: [CoII3L2(μ-L)2(μ-OH2)2(CF3CO2)2] (1) and [CoII7(μ-L)6(μ-OMe)6]Cl2 (2) (HL = 2-(3-ethoxypropylimino)methyl-6-methoxyphenol). At room temperature varying reaction conditions, cobalt-ligand ratios and use of different bases allowed unique types of coordination self-assembly. The synthetic marvel lies in the nature of aggregation with respect to the two unrelated cores in 1 and 2. Complex 1 assumes a V-shaped arrangement bound to L-, water and a trifluoroacetate anion, while 2 grows around a central CoII ion surrounded by a CoII6 hexagon bound to methoxide and L-. Magnetic measurements revealed that the intermetallic interactions are antiferromagnetic in nature in the case of complex 1 and ferromagnetic in the case of 2 involving high spin cobalt(ii) ions with stabilization of the high-spin ground state in the latter case. In MeCN solutions complexes 1 and 2 showed catalytic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBCH2) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) in air. The kinetic study in MeCN revealed that with respect to the catalytic turnover number (kcat) 2 is more effective than 1 for oxidation of 3,5-DTBCH2
Enantioselective Carbon-Carbon and Carbon-Heteroatom Bond Formation : From Bifunctional to Anion-Binding Catalysis
Full text linkThe thesis entitled “Enantioselective Carbon-Carbon and Carbon-Heteroatom Bond Formation: from Bifunctional to Anion-Binding Catalysis” is divided into four chapters.
Chapter 1: Organocatalytic Asymmetric Direct Vinylogous Michael Addition of α,β-Unsaturated γ-Butyrolactam to Nitroolefins
Chiral γ-butyrolactams are privileged structural motifs present in a plethora of natural products as well as pharmaceutically important compounds, such as haplophytine and (+)-lactacystin. They are also been used as a key intermediate for the stereoselective synthesis of anti-influenza drug A-315675. Though the initial works were concentrated over 2-silyloxy pyrroles as nucleophile, the direct use of γ-butyrolactam as nucleophile in enantioselective transformation gained pace during the past decade. Direct use of α,β-unsaturated γ-butyrolactam in vinylogous Michael reaction is not only desirable but also a challenging task due to the need of controlling regio-, diastereo- and enantioselectivity simultaneously. The presence of rather poorly acidic protons at the γ-position of butyrolactam makes the activation via an organocatalyst even more difficult.
In this chapter, the first organocatalytic direct vinylogous Michael reaction of α,β-unsaturated γ-butyrolactam to nitroolefins has been demonstrated. Using quinidine and a simply modified dihydroquinine derivative as the bifunctional catalysts, both the product enantiomers are accessible as single regioisomer (only γ-addition product) and diastereomer with moderate to good enantioselectivity. A range of nitroolefins, bearing aryl, alkyl and heteroaryl substituents were found to be suitable electrophilic partner for this direct vinylogous Michael reaction. We have also successfully utilized α,β-unsaturated moiety of the butyrolactam as a Michael acceptor in a vinylogous Michael/oxa-Michael cascade reaction for the diastereo- and enantioselective synthesis of a tricyclic compound. A plausible mechanistic model is also presented to rationalize the observed stereochemical outcome.
Reference: Ray Choudhury, A.; Mukherjee, S. Org. Biomol. Chem. 2012, 10, 7313-7320.
Chapter 2: A Catalytic Sulfa-Michael Addition/Horner-Wadsworth-Emmons Cascade Reaction for Enantioselective Synthesis of Thiochromenes
Thiochromene derivatives are venerable bioactive molecules having found application as analgesics, anti-cancer, anti-inflammatory and anti-bacterial agents. Although hetero-Michael-initiated cascade reactions involving α,β-unsaturated aldehydes and ketones has been profoundly used for their enantioselective synthesis, similar reactions of the corresponding ester equivalents remained relatively underexplored and almost always require an additional binding site.
In this chapter, a catalytic enantioselective sulfa-Michael addition/Horner-Wadsworth-Emmons olefination cascade is presented. This cascade sequence is initiated by a sulfa-Michael addition to a vinylphosphonate catalyzed by a chiral bifunctional urea derivative and provides an easy access to enantioenriched 2,3-disubstituted thiochromene derivatives. Several aryl and heteroaryl substituted thiochromenes were obtained in excellent yield with high level of enantioselectivity. Our report represents the first example of the use of phosphonate as a traceless binding site in a catalytic asymmetric transformation. The use of a simple catalyst, mild reaction conditions (ambient temperature) and one-pot strategy highlights the benefits of our protocol. Synthetic utility of the products is demonstrated and a model is proposed to rationalize the stereochemical outcome of the reaction.
References: Ray Choudhury, A.; Mukherjee, S. Adv. Synth. Catal. 2013, 355, 1989-1995.
Chapter 3: Organocatalytic Enantioselective Umpolung Vinylation of Cyclic β-Ketoesters
Considering the wide abundance of natural products having vinyl containing quaternary stereocenter, we became interested in an efficient protocol for enantioselective vinylation. We became aware of the fact that all C-H vinylation reported till date couples nucleophile with β-carbon of an electron withdrawing group. However, there is no example of C-H vinylation which couples nucleophile with α-carbon of an electron withdrawing group. Considering the fact that α-carbon of an electron withdrawing group is nucleophilic in nature, such a combination would lead to “mismatched polarity” and render the reaction electronically impossible. Therefore, a reversal of polarity or umpolung reactivity would be necessary for this coupling.
In this chapter, an efficient formal enantioselective umpolung α-vinylation of cyclic β-ketoester by an one-pot two-step sequence is described. This two-step protocol consists of a catalytic enantioselective Michael reaction followed by base mediated nitrous acid elimination. The products, bearing an all-carbon quaternary stereocenter including a vinyl moiety, was synthesized in high yield with excellent er. β-Nitroenones containing substituted aryl or heteroaryl group produced the vinylated product with excellent enantioselectivity. Our protocol demonstrates the first use of β-nitroenones as an electrophilic component in an enantioselective reaction. This is also the first example of a catalytic umpolung vinylation reaction of β-ketoester. The reaction could be scaled up at least to 1.0 mmol scale without hampering the yield or enantioselectivity. A model based on the bifunctional nature of the catalyst was proposed to rationalize the observed stereochemical outcome of the reaction.
References: Ray Choudhury, A.; Manna, M. S.; Mukherjee, S. manuscript under preparation.
Chapter 4: Enantioselective Dearomatization of Isoquinolines by Anion-Binding Catalysis en Route to Cyclic α-Aminophosphonates
α-Aminophosphonates and related α-aminophosphonic acid derivatives are used extensively in medicinal and pharmaceutical sciences as surrogates of α-amino acids. The strong correlation between the biological activities of compounds containing α-aminophosphonic acids and their absolute configuration renders the enantioselective synthesis of α-aminophosphonates imperative to such studies. Considerable advancement has taken place in the catalytic enantioselective synthesis of acyclic α-aminophosphonates using various strategies. In contrast, enantioselective synthesis of cyclic α-aminophosphonates remains elusive, despite their prominent abundance in biologically active molecules.
In this chapter, the development of an enantioselective dearomatization of diversely substituted isoquinolines through acyl activation and nucleophilic addition of silyl phosphites is presented.
Using a simple and easy to prepare tert-leucine derived thiourea as the anion-binding catalyst, this base-free protocol delivers cyclic α-aminophosphonates in excellent yields with moderate to high enantioselectivities. The reaction was found to be general with respect to different isoquinolines when applied to monosubstituted isoquinolines bearing substituent at nearly every position and even to disubstituted isoquinolines. Our protocol was also found to be suitable for dihydroisoquinolines. This is the first example of the use of silyl phosphites as the nucleophile in asymmetric dearomatization reactions driven by anion-binding catalysis. In fact, this is also the first time asymmetric anion-binding catalysis has been applied to the synthesis of α-aminophosphonates. A preliminary experiment with quinoline points toward potential applicability of this strategy to other nitrogenous heteroaromatics.
References: Ray Choudhury, A.; Mukherjee, S. under revision
Dealing with fiscal constraints on public financing of human development in West Bengal.
Full text linkQuantitative analysis of adsorbed proteins by X-ray photoelectron spectroscopy
No full textProtein adsorption at solid surfaces is central to many phenomena of medical and technological interest. The determination of the amount of protein attached to the surface is a critical measurement performed by using a wide range of methods. X-ray photoelectron spectroscopy (XPS) is able to provide a straightforward quantitative analysis of the amount of protein adsorbed as an overlayer on a material surface. While XPS is commonly employed to assess qualitatively the amount of adsorbed protein, this is usually expressed in terms of the elemental fraction (or at. %) of nitrogen calculated using an assumption of depth homogeneity despite the fact that this does not linearly scale with the amount of protein. In this paper, we have shown that thicknesses derived from XPS data linearly correlated with spectroscopic ellipsometry data on the same samples with a scatter of 10%. A straightforward equation to convert the concentration of nitrogen from XPS into an equivalent thickness of a protein film is presented. We highlight some discrepancies in the absolute thicknesses determined by XPS and ellipsometry on dried films and quartz crystal microbalance on wet films, which appear likely to result from the inclusion of a contribution from water in the latter two techniques.</p
Impact Of Body Center Potential On The Electrostatics Of Undoped Body Multi Gate Transistors : A Modeling Perspective
No full textUndoped body multi gate (MG) Metal Oxide Semiconductor Field Effect Transistors (MOSFET) are appearing as replacements for single gate bulk MOSFET in forthcoming sub-45nm technology nodes. It is therefore extremely necessary to develop compact models for MG transistors in order to use them in nano-scale integrated circuit design and simulation. There is however a sharp distinction between the electrostatics of traditional bulk transistors and undoped body devices. In bulk transistor, where the substrate is sufficiently doped, the inversion charges are located close to the surface and hence the surface potential solely controls the electrostatic integrity of the device. However, in undoped body devices, gate electric field penetrates the body center, and inversion charge exists throughout the body. In contrast to the bulk transistors, depending on device geometry, the potential of the body center of undoped body devices could be higher than the surface in weak inversion regime and the current flows through the center-part of the device instead of surface. Several crucial parameters (e.g. Sub-threshold slope) sometimes become more dependable on the potential of body center rather than the surface. Hence the body-center potential should also be modeled correctly along with the surface-potential for accurate calculation of inversion charge, threshold voltage and other related parameters of undoped body multi-gate transistors. Although several potential models for MG transistors have been proposed to capture the short channel behavior in the subthreshold regime but most of them are based on the crucial approximation of coverting the 2D Poisson’s equation into Laplace equation. This approximation holds good only at surface but breaks down at body center and in the moderate inversion regime. As a result all the previous models fail to capture the potential of body center Correctly and remain valid only in weak-inversion regime.
In this work we have developed semiclassical compact models for potential distribution for double gate (DG) and cylindrical Gate-All-Around (GAA) transistors. The models are based on the analytical solution of 2D Poisson’s equation in the channel region and valid for both: a) weak and strong inversion regimes, b) long channel and short channel transistors, and, c) body surface and center. Using the proposed model, for the first time, it is demonstrated that the body potential versus gate voltage characteristics for the devices having equal channel lengths but different body thicknesses pass through a single common point (termed as crossover point). Using the concept of “crossover point” the effect of body thickness on the threshold voltage of undoped body multi-gate transistors is explained. Based on the proposed body potential model, a new compact model for the subthreshold swing is formulated. Some other parameters e.g. inversion charge, threshold voltage roll-off etc are also studied to demonstrate the impact of body center potential on the electrostatics of multi gate transistor. All the models are validated against professional numerical device simulator
Augmenting amisulpride with clozapine had led to unmasking of akathisia
No full textAmisulpride is a newer antipsychotic, which is very effective on its own, as well as augmenting other antipsychotic clozapine, which is an effective molecule for treatment resistant schizophrenia. In most cases, amisulpride is added on, in partial responders to clozapine. Here a case is reported where clozapine was added on, in an amisulpride partial responder but this produced side effect and had to be discontinued. The case later responded to clozapine alone. It has been discussed about possible reasons of this finding. It has also been suggested if sequence of introduction of medication is critical regarding getting the desired effect of the augmentation strategy
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