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Kalpataru Das

Bio: Kalpataru Das is an academic researcher from Central University, India. The author has contributed to research in topics: Lewis acids and bases & Cycloaddition. The author has an hindex of 18, co-authored 41 publications receiving 921 citations. Previous affiliations of Kalpataru Das include Dr. Hari Singh Gour University & Indian Institute of Technology Kanpur.

Papers
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Journal ArticleDOI
TL;DR: The observation that amino acids and dimethyl sulfoxide had an additive effect in augmenting the cryoprotecting potential of glycerol suggests that the mechanism of their action is different from that of Glycerol.

85 citations

Journal ArticleDOI
TL;DR: A highly regio- and stereoselective strategy for the syntheses in high yield and enantioselectivity of a variety of substituted nonracemic morpholines and their homologues is described.
Abstract: A highly regio- and stereoselective strategy for the syntheses in high yield and enantioselectivity of a variety of substituted nonracemic morpholines and their homologues is described. The reaction proceeds via an SN2-type ring opening of activated aziridines and azetidines by suitable halogenated alcohols in the presence of Lewis acid followed by base-mediated intramolecular ring closure of the resulting haloalkoxy amine.

83 citations

Journal ArticleDOI
TL;DR: Self-assembly and surface-mediated reactions of 1,3,5-tris(4-mercaptophenyl)benzene--a three-fold symmetric aromatic trithiol--are studied by means of scanning tunneling microscopy under ultrahigh-vacuum (UHV) conditions to reveal the nature of intermolecular bonds and to understand the specific role of the substrate for their formation.
Abstract: Self-assembly and surface-mediated reactions of 1,3,5-tris(4-mercaptophenyl)benzene—a three-fold symmetric aromatic trithiol—are studied on Cu(111) by means of scanning tunneling microscopy (STM) under ultrahigh-vacuum (UHV) conditions. In order to reveal the nature of intermolecular bonds and to understand the specific role of the substrate for their formation, these studies were extended to Ag(111). Room-temperature deposition onto either substrate yields densely packed trigonal structures with similar appearance and lattice parameters. Yet, thermal annealing reveals distinct differences between both substrates: on Cu(111) moderate annealing temperatures (∼150 °C) already drive the emergence of two different porous networks, whereas on Ag(111) higher annealing temperatures (up to ∼300 °C) were required to induce structural changes. In the latter case only disordered structures with characteristic dimers were observed. These differences are rationalized by the contribution of the adatom gas on Cu(111) to...

83 citations

Journal ArticleDOI
TL;DR: Ammonia has been one of the most important chemical feedstocks for the chemical industry since the discovery of the Harber–Bosch process and allies are ubiquitous and prevalent in various biologically active compounds.
Abstract: Ammonia has been one of the most important chemical feedstocks for the chemical industry since the discovery of the Harber–Bosch process. Direct synthesis of nitrogen-containing compounds from ammonia is the most desirable synthetic route, and recent achievements regarding the direct use of ammonia have been reported. 3] Among nitrogencontaining chemicals, allylamines are ubiquitous and prevalent in various biologically active compounds, 5] and are valuable synthetic intermediates for a wide range of organic compounds. 6] The direct catalytic substitution of allylic alcohols with ammonia (Scheme 1, 1!2, R = H) is considered

72 citations

Journal ArticleDOI
TL;DR: Radio-frequency electromagnetic radiation affects both calcium-ion release and AChE activity in nervous system-derived cells in culture in a common dose-dependent manner.
Abstract: Radio-frequency electromagnetic radiation (RFR) at 915 and at 147 MHz, when sinusoidally amplitude modulated (AM) at 16 Hz, has been shown to enhance release of calcium ions from neuroblastoma cells in culture. The dose-response relation is unusual, consisting of two power-density “windows” in which enhanced efflux occurs, separated by power-density regions in which no effect is observed. To explore the physiological importance of these findings, we have examined the impact of RFR exposure on a membrane-bound enzyme, acetylcholinesterase (AChE), which is intimately involved with the acetylcholine (ACh) neurotransmitter system. Neuroblastoma cells (NG108), exposed for 30 min to 147-MHz radiation, AM at 16 Hz, demonstrated enhanced AChE activity, as assayed by a procedure using 14C-labeled ACh. Enhanced activity was observed within a time window between 7.0 and 7.5 h after the cells were plated and only when the exposure occurred at power densities identified in a previous report as being effective for altering the release of calcium ions. Thus RFR affects both calcium-ion release and AChE activity in nervous system-derived cells in culture in a common dose-dependent manner. 1992 Wiley-Liss, Inc.

67 citations


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Book
01 Jan 1992
TL;DR: In this paper, the induced and contact current limits of IEEE C95.1-1991 are modified in this edition, and field strengths below which induced and current do not have to be measured are specified, spatial averaging and measurement distance requirements are clarified, and more precise definitions for averaging volume and radiated power are provided.
Abstract: IEEE C95.1-1991 gives recommendations to prevent harmful effects in human beings exposed to electromagnetic fields in the frequency range from 3 kHz to 300 GHz. The recommendations are intended to apply to exposures in controlled, as well as uncontrolled, environments. They are not intended to apply to the purposeful exposure of patients under the direction of practitioners of the healing arts. The induced and contact current limits of IEEE C95.1-1991 are modified in this edition. In addition, field strengths below which induced and contact currents do not have to be measured are specified, spatial averaging and measurement distance requirements are clarified, and more precise definitions for averaging volume and radiated power are provided.

928 citations

Journal ArticleDOI
TL;DR: The Cu-TCPP nanosheet-based sensor shows excellent fluorescent sensing performance and is used for the simultaneous detection of multiple DNA targets.
Abstract: A facile surfactant-assisted bottom-up synthetic method to prepare a series of freestanding ultrathin 2D M-TCPP (M = Zn, Cu, Cd or Co, TCPP = tetrakis(4-carboxyphenyl)porphyrin) nanosheets with a thickness of sub-10 nm is developed. As a proof-of-concept application, some of them are successfully used as new platforms for DNA detection. The Cu-TCPP nanosheet-based sensor shows excellent fluorescent sensing performance and is used for the simultaneous detection of multiple DNA targets.

851 citations

Journal ArticleDOI
TL;DR: This review summarizes the recent advances in the synthesis of 2D MOF nanosheets by using top-down methods, e.g. sonication exfoliation, mechanical ex foliation, Li-intercalation exfoliated and chemical exfolation, and bottom-up methods, i.e. interfacial synthesis, three-layer synthesis, surfactant-assisted synthesis, modulated synthesis, and sonication synthesis.
Abstract: Two-dimensional (2D) metal–organic framework (MOF) nanosheets are attracting increasing research attention due to their unique properties originating from their ultrathin thickness, large surface area and high surface-to-volume atom ratios. Many great advances have been made in the synthesis and application of 2D MOF nanosheets over the past few years. In this review, we summarize the recent advances in the synthesis of 2D MOF nanosheets by using top-down methods, e.g. sonication exfoliation, mechanical exfoliation, Li-intercalation exfoliation and chemical exfoliation, and bottom-up methods, i.e. interfacial synthesis, three-layer synthesis, surfactant-assisted synthesis, modulated synthesis, and sonication synthesis. In addition, the recent progress in 2D MOF nanosheet-based nanocomposites is also briefly introduced. The potential applications of 2D MOF nanosheets in gas separation, energy conversion and storage, catalysis, sensors and biomedicine are discussed. Finally, we give our personal insights into the challenges and opportunities for the future research of 2D MOF nanosheets and their composites.

842 citations

Journal ArticleDOI
TL;DR: The objective of the present review is to give a global overview on the topic starting from those contributions published prior to the emergence of the BH concept to the most recent and current research under the term of BH catalysis.
Abstract: The borrowing hydrogen (BH) principle, also called hydrogen auto-transfer, is a powerful approach which combines transfer hydrogenation (avoiding the direct use of molecular hydrogen) with one or more intermediate reactions to synthesize more complex molecules without the need for tedious separation or isolation processes. The strategy which usually relies on three steps, (i) dehydrogenation, (ii) intermediate reaction, and (iii) hydrogenation, is an excellent and well-recognized process from the synthetic, economic, and environmental point of view. In this context, the objective of the present review is to give a global overview on the topic starting from those contributions published prior to the emergence of the BH concept to the most recent and current research under the term of BH catalysis. Two main subareas of the topic (homogeneous and heterogeneous catalysis) have been identified, from which three subheadings based on the source of the electrophile (alkanes, alcohols, and amines) have been consid...

612 citations

Journal ArticleDOI
TL;DR: TheLyophilization mechanisms, the parameters affecting the lyoprotective effect and the techniques used in a large number of studies are reviewed and the major areas and future potential of research on lyophilized liposomes are highlighted.

423 citations