287 results on '"Kumar, Ravi"'
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2. Facile Mechanochemical Synthesis of Compositionally Complex Spinel‐type Oxides, (Co, Fe, Mn)3O4, (Co, Fe, Mn, Ni)3O4, and (Co, Cr, Fe, Mn, Ni)3O4.
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Teppala, Dharma Teja, Bernauer, Jan, Drouillard, Esteve, Kumar Geddam, Yaswanth, Chen, Guoxing, Widenmeyer, Marc, Trapp, Maximilian, Kleebe, Hans‐Joachim, Kumar, Ravi, Mathur, Sanjay, and Ionescu, Emanuel more...
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AMMONIUM bicarbonate ,OXIDE ceramics ,TRANSITION metals ,LOW temperatures ,NITRATES - Abstract
In the current work, a simple mechanochemical route has been employed to preparatively access three spinel‐type compositionally complex ceramics, i. e., (Co, Fe, Mn)3O4, (Co, Fe, Mn, Ni)3O4, and (Co, Cr, Fe, Mn, Ni)3O4. Hydrated nitrate salts of the respective transition metal elements were mechanically ground with ammonium hydrogen carbonate. The resulting paste‐like mixture of metal hydroxides, oxyhydroxides, and carbonates was rinsed with water to remove the byproduct (NH4NO3) and converted into the respective single‐phase spinel‐type oxides via calcination. In situ X‐ray diffraction (XRD) revealed the formation of the spinel‐type structure (Fd3‾ ${\bar{3}}$ m) already at temperatures as low as 150 °C. Typically, the calcination of the precursors at temperatures beyond 500 °C led to the formation of well‐crystallized, single‐phase spinel‐type oxides with nearly equimolar composition and highly homogeneous distribution of the transition metals within the structure. The mechanochemical synthesis route in the present study is considered to be an easy, straightforward, and scalable access to compositionally complex oxides. [ABSTRACT FROM AUTHOR] more...
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- 2024
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Catalog
3. Porous Pd‐Loaded IRMOF‐9 as Highly Efficient Recyclable Material Towards the Reduction of Nitroaromatics in Aqueous Media.
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Rimi, Kumar, Ravi, and Uttam, Bhawna
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NITROAROMATIC compounds , *RECYCLABLE material , *WASTE recycling , *POROUS materials , *POLLUTANTS - Abstract
Nitroaromatic compounds (NACs) cause severe hazardous impacts on human health as well as on the environment. Therefore, there is dire need to develop a robust material to reduce the toxicity of these organic pollutants. In this regard, our group developed a series of porous MOF materials viz., Pdx@IRMOF‐9 (x=2 %, 5 % and 10 %) by loading different concentration of Pd(II) on IRMOF‐9 and explored them towards reduction of different nitroaromatic compounds. Pd10%@IRMOF‐9showed ~30 % greater efficiency for the reduction of 4‐NP as compared to Pd2%@IRMOF‐9. Pd10%@IRMOF‐9showed excellent reduction ability (>85 %) towards 4‐NP, 2‐NP, 2‐NA, 3‐NA and 2,4‐DNPH. The kinetic studies indicates that the reduction follows the pseudo‐first‐order kinetics. Moreover, the rate constant value for reduction of 3‐NA was ~9 times higher than that of 2‐NP. Based on the kinetic parameters, the t1/2 values for all the nitroaromatics have been calculated. The kinetic parameters, Km and Vmax have been calculated from double reciprocal Lineweaver‐Burk plot and found to be 65.984 μM and 116×10−6 Mmin−1 respectively. Pd10%@IRMOF‐9showed excellent recyclability towards the reduction of 4‐NP for few consecutive cycles without any remarkable loss in its activity. Thus, highly efficient, porous and robust material for the reduction of nitroaromatic compounds in aqueous media have been demonstrated. [ABSTRACT FROM AUTHOR] more...
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- 2024
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4. Numerical Simulation of Heat Transfer Characteristics for Optimum Air Flow Rate in Triangular PV/T System.
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Sharma, Amit, Rajoria, C. S., Bhadu, Mahendra, Singh, Dharmendra, Kumar, Ravi, and Ahmed, Mahmoud
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TEMPERATURE distribution ,SPACE heaters ,AIR flow ,HEAT transfer ,ATMOSPHERIC temperature - Abstract
The aim of this numerical study is to investigate the heat transfer characteristics of the air flowing in the triangular photovoltaic thermal (PV/T) array/system at variable velocities. The PV/T array in the present analysis is composed of seven photovoltaic (PV) panels connected in series along with a triangular duct throughout its length. The heat transfer analysis in the PV panel (solid component) and visualization of temperature distribution in the PV/T system has been simulated by the use of system coupling of steady state thermal and CFX tools in ANSYS 18.2. Experiment was initially performed at velocity of 1.5 m/s inside the duct by the use of ANSYS software to predict the glass temperature, outlet air temperature, and tedlar temperature of triangular PV/T system. Further, the velocity has been incremented by 1 m/s up to 6.5 m/s to see the overall performance of the system. The validation of simulation results showed a good agreement with the experimental results under reasonable limit. The gain in temperature with the increase in velocity becomes marginal (only 7%) after 4.5 m/s. The temperature contours from the numerical simulation also revealed that cooling up to the last panel is not significant beyond 4.5 m/s. Similar tendency is documented in the overall exergy efficiency which significantly increased to 4.5 m/s and became marginal with further increment in velocity. It can be inferred that the optimum velocity which can fulfill the requirement of cooling of all PV panels along with reasonable thermal output is 4.5 m/s. The thermal energy gain gradually increases as the day progresses and becomes maximum at 2:00 PM. The average thermal energy gain being 9.6% higher than that in the morning (10:00 AM) indicates its suitability for applications requiring moderately high temperature. The present numerical investigation focuses on improving the overall performance of the system without the involvement of any additional cost. The system can be used in various applications like crop drying, space heating, etc. Owing to different outlet air temperatures during the day, the applications can either be utilized independently or can be combined to be used at different times according to the temperature requirement. [ABSTRACT FROM AUTHOR] more...
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- 2024
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5. Novel Lewis Acid‐Base Interactions in Polymer‐Derived Sodium‐Doped Amorphous Si−B−N Ceramic: Towards Main‐Group‐Mediated Hydrogen Activation.
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Tada, Shotaro, Terashima, Motoharu, Shimizu, Daisuke, Asakuma, Norifumi, Honda, Sawao, Kumar, Ravi, Bernard, Samuel, and Iwamoto, Yuji
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LEWIS pairs (Chemistry) ,LEWIS bases ,SILICON nitride ,LEWIS acids ,HETEROGENEOUS catalysis - Abstract
Interest is growing in transition metal‐free compounds for small molecule activation and catalysis. We discuss the opportunities arising from synthesizing sodium‐doped amorphous silicon‐boron‐nitride (Na‐doped a‐SiBN). Na+ cations and 3‐fold coordinated BIII moieties were incorporated into an amorphous silicon nitride network via chemical modification of a polysilazane followed by pyrolysis in ammonia (NH3) at 1000 °C. Emphasis is placed on the mechanisms of hydrogen (H2) activation within Na‐doped a‐SiBN structure. This material design approach allows the homogeneous distribution of Na+ and BIII moieties surrounded by SiN4 units contributing to the transformation of the BIII moieties into 4‐fold coordinated geometry upon encountering H2, potentially serving as frustrated Lewis acid (FLA) sites. Exposure to H2 induced formation of frustrated Lewis base (FLB) N−= sites with Na+ as a charge‐compensating cation, resulting in the in situ formation of a frustrated Lewis pair (FLP) motif (≡BFLA⋅⋅⋅Hδ−⋅⋅⋅Hδ+⋅⋅⋅:N−(Na+)=). Reversible H2 adsorption‐desorption behavior with high activation energy for H2 desorption (124 kJ mol−1) suggested the H2 chemisorption on Na‐doped a‐SiBN. These findings highlight a future landscape full of possibilities within our reach, where we anticipate main‐group‐mediated small molecule activation will have an important impact on the design of more efficient catalytic processes and the discovery of new catalytic transformations. [ABSTRACT FROM AUTHOR] more...
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- 2024
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6. Single‐Site Heterogenized Molecular Catalysts towards CO2 Hydrogenation to Formates, Formamides and Methanol.
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Mandal, Tanmoy, Kumar, Ravi, Kumar, Saurabh, and Choudhury, Joyanta
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HETEROGENEOUS catalysis , *HOMOGENEOUS catalysis , *CATALYST supports , *METAL catalysts , *CATALYTIC hydrogenation , *HETEROGENEOUS catalysts - Abstract
Harnessing CO2 in conjunction with inexpensive reusable H2 for catalytic hydrogenation is a viable method for lowering the environmental impact of industrial operations while producing useful chemicals and fuels. To make the process more sustainable, particular emphasis was paid to the heterogeneous catalyst system in this regard. Intending to profit from both homogeneous and heterogeneous catalysis in real‐world circumstances for the CO2 hydrogenation reaction, heterogenized molecular catalysts are receiving a lot of attention among heterogeneous catalysts. This review is devoted to significant developments in single‐site heterogenized molecular catalysts for CO2 hydrogenation reactions. Attempting to illustrate the state‐of‐the‐art developments in this domain, the present work meticulously summarizes several recently reported heterogenized molecular catalysts for the CO2 hydrogenation process producing formic acid/formate, N‐formamide, and methanol. The fundamental structure–activity relationships and mechanistic understanding are given particular attention since they offer solid foundations for sensible catalyst architectural design. Important variables that influence catalytic activity are also emphasized, such as electron density, metal dispersion, porous nature, surface area, a robust backbone, and coordination environment of metal sites. Finally, a short assessment is given as potential directions for further research. [ABSTRACT FROM AUTHOR] more...
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- 2024
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7. Thermal decomposition of oxygen‐containing Ta3N5${\rm {Ta}}_3{\rm {N}}_5$.
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Moharana, Niraja, Ghosh, Chanchal, Dasgupta, Arup, Maezono, Ryo, Kumar, Ravi, and Kumar, K. C. Hari
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NITRIDES ,ELECTRON energy loss spectroscopy ,TRANSITION metal nitrides ,THERMODYNAMICS ,SCANNING transmission electron microscopy ,BULK modulus ,ELASTIC constants - Abstract
Transition metal nitrides, especially tantalum nitrides, are pivotal for applications in extreme environments demanding excellent mechanical properties and thermodynamic stability. Among them, θ$\utheta$‐TaN, a high‐pressure polymorph of tantalum nitride with its exceptional bulk modulus (362 GPa) and hardness (31.7 GPa) promises to have many technological uses. Another nitride, Ta3N5${\rm {Ta}}_3{\rm {N}}_5$, has gained importance as a photocatalyst for water splitting using visible light. The Ta–N phase diagram indicates that the thermal decomposition of pure Ta3N5${\rm {Ta}}_3{\rm {N}}_5$ leads to the formation of ε$\uepsilon$‐TaN. However, Ta3N5${\rm {Ta}}_3{\rm {N}}_5$ usually has some amount of oxygen as an impurity mainly due to its synthesis route. We found that the θ$\utheta$‐TaN phase, which is usually observed at high pressures, is formed during the thermal decomposition of oxygen containing Ta3N5${\rm {Ta}}_3{\rm {N}}_5$. The presence of θ$\utheta$‐TaN is verified using several experimental techniques such as X‐ray diffraction, Raman spectra, high‐angle annular dark field scanning transmission electron microscopy (STEM‐HAADF), and electron energy loss spectroscopy (EELS). Elemental distribution analyzed through energy dispersion X‐ray spectroscopy (XEDS) in STEM reveals about 7 at.% of oxygen in θ$\utheta$‐TaN. First‐principle calculations are performed to examine the thermodynamic stability of oxygen substituted θ$\utheta$‐TaN and pure θ$\utheta$‐TaN via formation enthalpies, elastic constants, and phonon dispersion calculations. The computational studies confirm that oxygen in θ$\utheta$‐TaN enhances its thermodynamic stability. The calculated electron localization functions establish the bonding characteristics between Ta, N, and O, confirming the same. [ABSTRACT FROM AUTHOR] more...
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- 2024
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8. Structural stability and proton beam irradiation effects on simulated metal fluoride waste–loaded iron phosphate glass.
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Joshi, Akhilesh C., Roy, Mainak, Dutta, Dimple P., Mishra, Raman K., Meena, Sher Singh, and Kumar, Ravi
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PROTON beams ,PHOSPHATE glass ,STRUCTURAL stability ,MOLTEN salt reactors ,ALKALI metals ,FLUORIDES ,FISSION products ,NUCLEAR reactors - Abstract
Next‐generation nuclear reactor technologies such as the molten salt reactor utilize alkali metal fluoride salts as both fuel and coolant. In the present study, the suitability of iron phosphate glass (IPG) as a vitrification matrix for alkali metal fluoride (NaF, CaF2) and simulated fission product loaded fluoride (NdF3, CeF3, SmF3) waste has been explored. The structural change in the metal fluoride–loaded IPG has been analyzed thoroughly using Raman and fourier transform infrared (FTIR) spectroscopy. Thermal analysis showed that the stability and glass forming ability of IPG improved upon loading the same with various mixed metal fluorides. Mössbauer data and X‐ray absorption spectroscopy at Fe K‐edge explored the minute changes in the local structure. The effect of radiation emanating from radioactive wastes in the fluoride‐loaded IPG has been scrutinized via 4.5 MeV proton beam irradiation. Our study firmly establishes the applicability of IPG as suitable vitrification matrix for radioactive metal fluoride–loaded nuclear wastes. [ABSTRACT FROM AUTHOR] more...
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- 2024
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9. Ultranarrow Band UV Detection in GaN with Simple Device Architecture.
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Chatterjee, Abhishek, Khamari, Shailesh K., Kumar, Ravi, Porwal, Sanjay, Bose, Aniruddha, Raghavendra, S., Dixit, Vijay Kumar, and Sharma, Tarun Kumar
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GALLIUM nitride ,VALENCE bands ,THERMAL equilibrium ,SURFACE photovoltage ,HIGH temperatures - Abstract
An ultranarrow‐band ultraviolet (UV) GaN detector with a simple device architecture is presented. The device displays an ultranarrow band response centred at 366 nm with only ≈5 nm width, a UV–visible rejection ratio of >2 × 103, and detectivity of 1.3 × 1010 Jones at room temperature. The device is tested over a wide temperature range where the maximum response is recorded at 200 K. Temperature dependence of device response is explained by considering the thermal activation of shallow donors in low‐temperature regime and the establishment of thermal equilibrium of the donor level with conduction band at elevated temperatures. Moreover, the device displays three orders UV‐to‐visible rejection ratio over a wide temperature range of 150–350 K, showing great potential for narrowband UV detection even at elevated temperatures. Conventional and pump‐probe surface photovoltage spectroscopy measurements are performed with UV and infrared lasers to identify the electronic transitions associated with the narrowband response. It is understood that carrier excitation from valance band to shallow donor level in the interfacial depletion region is responsible for the observed behavior. The results presented here demonstrate an innovative methodology for achieving a stable and high spectrum‐selective UV photodetection without involving complex device architecture. [ABSTRACT FROM AUTHOR] more...
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- 2024
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10. Weed seedbank as influenced by tillage and herbicide in direct seeded rice‐mustard cropping sequence in lateritic soil of eastern India.
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Jaiswal, Deepak Kumar, Duary, Buddhadeb, Kumar, Ravi Ranjan, and Nath, Chaitanya P.
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CROP rotation ,HERBICIDES ,NO-tillage ,WEEDS ,TILLAGE ,WEED control ,TURNIPS - Abstract
The above‐ground community dynamics of weeds represent the soil weed seedbank in an agro‐ecosystem. Hence, understanding the seedbank will offer an idea for future weed management tactics. We aimed to determine the density of weed seedbank and emergence of major weeds in direct seeded rice (DSR) (Oryza sativa L.)—mustard (Brassica campestris L. var. yellow sarson) cropping sequence under varied tillage and herbicide combinations. The present study on weed seedbank was conducted using seedling emergence method after collecting the soils at the harvest of mustard at the completion of 2 years field experimentation. The experiment was conducted in split‐plot design with two tillage practices [zero tillage (ZT) and conventional tillage (CT)] in main plot and eight weed management practices in DSR [oxadiargyl followed by (fb) bispyribac‐sodium, penoxsulam + cyhalofop‐butyl, oxadiargyl fb penoxsulam + cyhalofop‐butyl, fenoxaprop‐p‐ethyl + ethoxysulfuron, oxadiargyl fb fenoxaprop‐p‐ethyl + ethoxysulfuron, pendimethalin fb bispyribac‐sodium, unweeded control, and weed free check] as subplot. The carry‐over effect of tillage and weed management practices were recorded in mustard crop. Seed emergence study revealed that ZT reduced the emergence of grassy weeds (by 13.7%) and total weed emergence (19.5%) in comparison to the CT (p < 0.05). However, emergence of broadleaf weeds was 24.5% higher in ZT than in CT. The higher infestation was recorded for Ludwigia parviflora (Jacq.) Raven under penoxsulam + cyhalofop‐butyl, fenoxaprop‐p‐ethyl + ethoxysulfuron, Cyperus iria (L.) under fenoxaprop‐p‐ethyl + ethoxysulfuron, and Eleusine indica (L.) Gaertn. under pendimethalin fb bispyribac‐sodium, oxadiargyl fb bispyribac‐sodium. Sole application of post‐emergence (POE) herbicide decreased the total weed emergence by 22.2%–28.1% than unweeded control (p < 0.05). Whereas, sequential application of PRE + POE herbicides decreased the total weed emergence by 32.8%–36.9% than unweeded control (p < 0.05). Notably, sedge weeds such as Cyperus iria (L.) and Fimbristylis miliacea (L.) Vahl were lower in ZT than in CT under herbicide treated plots (by 66.6%–84.3%) than unweeded control. Thus, ZT with oxadiargyl 90 g a.i. ha−1fb fenoxaprop‐p‐ethyl + ethoxysulfuron (90 + 15 g a.i. ha−1) as tank‐mix can be effectively used to lower the weed seedbank density vis‐à‐vis managing complex weed flora in DSR and rice‐mustard cropping sequence. [ABSTRACT FROM AUTHOR] more...
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- 2024
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11. Small but mighty: Peptides regulating abiotic stress responses in plants.
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Datta, Tapasya, Kumar, Ravi S., Sinha, Hiteshwari, and Trivedi, Prabodh K.
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ABIOTIC stress , *AMINO acid residues , *PEPTIDES , *SIGNAL peptides , *RECEPTOR-like kinases , *BRASSINOSTEROIDS - Abstract
Throughout evolution, plants have developed strategies to confront and alleviate the detrimental impacts of abiotic stresses on their growth and development. The combat strategies involve intricate molecular networks and a spectrum of early and late stress‐responsive pathways. Plant peptides, consisting of fewer than 100 amino acid residues, are at the forefront of these responses, serving as pivotal signalling molecules. These peptides, with roles similar to phytohormones, intricately regulate plant growth, development and facilitate essential cell‐to‐cell communications. Numerous studies underscore the significant role of these small peptides in coordinating diverse signalling events triggered by environmental challenges. Originating from the proteolytic processing of larger protein precursors or directly translated from small open reading frames, including microRNA (miRNA) encoded peptides from primary miRNA, these peptides exert their biological functions through binding with membrane‐embedded receptor‐like kinases. This interaction initiates downstream cellular signalling cascades, often involving major phytohormones or reactive oxygen species‐mediated mechanisms. Despite these advances, the precise modes of action for numerous other small peptides remain to be fully elucidated. In this review, we delve into the dynamics of stress physiology, mainly focusing on the roles of major small signalling peptides, shedding light on their significance in the face of changing environmental conditions. Summary statement: Small peptides, each containing fewer than 100 amino acid residues, emerge as pivotal regulators influencing diverse physiological processes, notably stress responses in plants. This review discusses about the intricate regulatory roles played by a spectrum of these peptides during abiotic stresses. [ABSTRACT FROM AUTHOR] more...
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- 2024
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12. Transcriptional dynamics in source-sink tissues identifies molecular factors regulating the corm development process in saffron (Crocus sativus L.).
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Jose-Santhi, Joel, Sheikh, Firdous Rasool, Kalia, Diksha, Sood, Riya, Kumar, Ravi, Acharya, Vishal, and Singh, Rajesh Kumar
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SAFFRON crocus ,UNDERGROUND storage ,CELL division ,GROWING season ,AUTUMN ,MOLECULAR clock - Abstract
Aims: Geophytic plants have evolved to develop underground storage organs (USO) in the active growing season to withstand harsh environments as well as to coordinate growth and reproduction when conditions are favourable. Saffron is an autumn flowering geophyte and an expensive spice crop restricted to certain geographical locations in the world. Saffron, being sterile, does not produce seeds and thus propagates only through corms, the quality of which determines its yield. Corm development in saffron is unexplored and the underlying molecular mechanism is still elusive. In this study, we performed an extensive characterisation of the transcriptional dynamics in the source (leaf) and sink (corm) tissues during corm development in saffron. Key results: Via morphological and transcriptome studies, we identified molecular factors regulating corm development process in saffron, which defined corm development into three stages: the initiation stage demonstrates enhanced vegetative growth aboveground and swelling of shoot base belowground due to active cell division & carbohydrate storage; the bulking stage comprises of increased source and sink strength, active photosynthesis, circadian gating and starch accumulation; the maturation stage represents reduced source and sink strength, lowered photosynthesis, sugar transport, starch synthesis and cell cycle arrest. Utility: The global view of transcriptional changes in source and sink identifies similar and new molecular factors involved in the saffron corm development process compared to USO formation in other geophytes and provides a valuable resource for dissecting the molecular network underlying the corm development. We propose a hypothetical model based on data analysis, of how molecular factors via environmental cues can regulate the corm development process in saffron. [ABSTRACT FROM AUTHOR] more...
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- 2024
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13. New Isoxazole‐Substituted Aryl Iodides: Metal‐Free Synthesis, Characterization and Catalytic Activity.
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Rimi, Uttam, Bhawna, Zhdankin, Viktor V., and Kumar, Ravi
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ARYL iodides ,SULFOXIDES ,ISOXAZOLES ,CATALYTIC activity ,RING formation (Chemistry) ,CATALYTIC oxidation ,X-ray crystallography - Abstract
A series of new isoxazole‐substituted aryl iodides 1 a–1 d have been synthesized by DIB‐mediated [3+2] cycloaddition reaction of 2‐iodo‐1,3‐bis(prop‐2‐yn‐1‐yloxy) benzene (4) with corresponding benzaldehyde oximes 5 a–5 d. Structure of the synthesized aryl iodides 1 were characterized by IR, 1H NMR, 13C NMR and HRMS. The structure of 1 a was also confirmed by single‐crystal X‐ray crystallography. Further, catalytic activity of iodoarenes 1 a–1 d was screened for the oxidation of hydroquinones and sulfides. On oxidation using aryl iodides 1 with m‐CPBA as terminal oxidant, hydroquinones afforded benzoquinones while sulfides gave corresponding sulfoxides in good to excellent yields. Iodoarene 1 b showed the best catalytic activity for the oxidation of sulfides and hydroquinones. Moreover, iodoarene 1 b, was also utilized for α‐oxytosylation of acetophenones. [ABSTRACT FROM AUTHOR] more...
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- 2024
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14. Rebound or Cage Escape? The Role of the Rebound Barrier for the Reactivity of Non‐Heme High‐Valent FeIV=O Species.
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Kumar, Ravi, Ansari, Azaj, Comba, Peter, and Rajaraman, Gopalan
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IRON , *CYCLOHEXADIENE , *SPECIES , *HYDROXYLATION , *CHARGE exchange - Abstract
Owing to their high reactivity and selectivity, variations in the spin ground state and a range of possible pathways, high‐valent FeIV=O species are popular models with potential bioinspired applications. An interesting example of a structure–reactivity pattern is the detailed study with five nonheme amine‐pyridine pentadentate ligand FeIV=O species, including N4py: [(L1)FeIV=O]2+ (1), bntpen: [(L2)FeIV=O]2+ (2), py2tacn: [(L3)FeIV=O]2+ (3), and two isomeric bispidine derivatives: [(L4)FeIV=O]2+ (4) and [(L5)FeIV=O]2+ (5). In this set, the order of increasing reactivity in the hydroxylation of cyclohexane differs from that with cyclohexadiene as substrate. A comprehensive DFT, ab initio CASSCF/NEVPT2 and DLPNO‐CCSD(T) study is presented to untangle the observed patterns. These are well reproduced when both activation barriers for the C−H abstraction and the OH rebound are taken into account. An MO, NBO and deformation energy analysis reveals the importance of π(pyr) → π*xz(FeIII‐OH) electron donation for weakening the FeIII‐OH bond and thus reducing the rebound barrier. This requires that pyridine rings are oriented perpendicularly to the FeIII‐OH bond and this is a subtle but crucial point in ligand design for non‐heme iron alkane hydroxylation. [ABSTRACT FROM AUTHOR] more...
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- 2024
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15. A robust and secure user authentication scheme based on multifactor and multi‐gateway in IoT enabled sensor networks.
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Kumar, Ravi, Singh, Samayveer, Singh, Deepti, Kumar, Mohit, and Gill, Sukhpal Singh
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SENSOR networks , *WIRELESS sensor networks , *INTERNET of things , *MULTI-factor authentication , *DATA transmission systems - Abstract
The Internet of Things (IoT) enabled wireless sensor networks (WSNs) are used to collect data from various nodes in hostile environments, but it is essential to authenticate legitimate nodes to prevent malicious attacks. Traditional authentication schemes may be vulnerable to attack, necessitating the development of more secure authentication techniques. To address this problem, we propose a novel authentication technique for multi‐gateway IoT‐enabled WSNs that achieves effective and secure data communication. The proposed scheme is based on biological information, hash, and XOR operations, which reduce computational costs. Passwords, biometric information, and session keys are updated securely to maintain forward and backward secrecy during communication. We provide an informal security analysis of the proposed scheme and a formal security analysis of the session key using the real‐or‐random (ROR) model. We also use the AVISPA simulation toolkit to verify the proposed user authentication scheme. Experimental results demonstrate that our proposed scheme is more effective than previous multi‐factor multi‐gateway authentication protocols. [ABSTRACT FROM AUTHOR] more...
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- 2024
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16. Ultimate fate, transformation, and toxicological consequences of herbicide pretilachlor to biotic components and associated environment: An overview.
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Dhanda, Vidhi, Kumar, Ravi, Yadav, Neelam, Sangwan, Sarita, and Duhan, Anil
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HERBICIDE residues ,HERBICIDES ,WEED control ,HAZARDOUS waste sites ,CROP yields ,BIOCONVERSION - Abstract
Herbicides are applied for effective weed management in order to increase the crop yield. In recent decades, the overuse of these chemicals has posed adverse effects on different biotic components of the environment. Pretilachlor has been widely used during last few decades for weed management in paddy crop. Its excessive use may prove fatal for environment, various organisms, and nontarget plants. Thus, it is pertinent to know the extent to which herbicide residues remain in environment. The potential mobility and the release rate of herbicide in the soil are important factors governing ecotoxicological impact and degradation rate. Therefore, several techniques are being investigated for its effective removal from the contaminated sites. Furthermore, efforts have also been made to study the degradation of pretilachlor by various physicochemical processes, resulting into the formation of different types of metabolites. This review summarizes the available information on environmental fate, various degradation processes, microbial biotransformation, metabolites formed, ecotoxicological effects, techniques for detection in environmental samples, effect of safener, and various control release formulations for sustained release of pretilachlor in applied fields. The information so obtained will be very advantageous in deciding the future policies for safe and judicious use of the herbicide by maintaining health and environmental sustainability. Herbicidal toxicity is a matter of great concern nowadays. In this review, the effect of pretilachlor on environment is discussed. Various metabolites formed due to degradation are also outlined. Further, the adverse effect of pretilachlor on various organisms and nontarget plants is illustrated. Various methods to detect the accumulated residues and remediation techniques to minimize toxicity are also summarized. [ABSTRACT FROM AUTHOR] more...
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- 2024
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17. Single Pyrrole Unit Functionalized Electron Deficient Porphyrins and Their Metal Complexes: Synthesis, Structural, Spectral and Electrochemical Properties.
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Arif, Waseem and Kumar, Ravi
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METAL complexes , *PYRROLES , *REDUCTION potential , *SCHIFF bases , *POLYPYRROLE , *BAND gaps , *ELECTRONS , *METALLOPORPHYRINS - Abstract
A family of electron‐deficient regioselective β‐disubstituted meso‐tetraphenylporphyrins, H2TPP(R)2 (where R=trifluoromethyl (CF3) and cyano (CN) and its metal complexes (Co(II), Ni(II), Cu(II) and Zn(II)) were synthesized from versatile precursor H2TPPBr2 by palladium‐catalyzed trifluoromethylation and nucleophilic aromatic cyanation respectively. The absorption spectrum of H2TPP(CF3)2 and H2TPP(CN)2 exhibited a notable shift towards longer wavelengths both in the Soret (Δλmax=16–17 nm) and longest wavelength band, Qx(0,0) (Δλmax=34–52 nm) as compared to precursor porphyrin, H2TPPBr2. The first ring reduction potential of H2TPP(CF3)2 and H2TPP(CN)2 are centred at −0.69 and −0.68 respectively which show drastic anodic shift as compared to precursor H2TPPBr2 (−1.01 V) and parent porphyrin H2TPP (−1.25 V). The anodic shift trend for first ring reduction potentials follows as H2TPP(CN)2>H2TPP(CF3)2>H2TPP(Br)2>H2TPP. Introducing two highly electron withdrawing substituents (CN and CF3) at the single pyrrole unit of the porphyrin macrocycle via regioselective substitution has led to a significant reduction in the HOMO‐LUMO energy gap (0.15 V–0.39 V) in comparison to the precursor H2TPPBr2 (2.08 V). The analysis of the crystal structures for ZnTPP(CN)2 and H2TPP(CF3)2 revealed nearly planar and distinct saddle conformations respectively which are further supported by DFT calculations. [ABSTRACT FROM AUTHOR] more...
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- 2023
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18. Large‐scale synthesis of centrifugally spun tantalum oxynitride fiber electrocatalysts for hydrogen evolution reaction.
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Mukkavilli, Raghunath Sharma, Saxena, Abhinav, Ji, Seulgi, Thiyagarajan, Ganesh Babu, Choi, Heechae, Mathur, Sanjay, and Kumar, Ravi
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HYDROGEN evolution reactions ,OXYGEN evolution reactions ,TANTALUM ,X-ray photoelectron spectroscopy ,ELECTROCATALYSTS ,FIBERS - Abstract
Tantalum oxynitride (TaOxN1−x) fibers were synthesized and evaluated for their electrocatalytic hydrogen activity using an in‐house developed centrifugal spinning setup. By tailoring the composition of the spinning solution and optimizing collector distance and rotation speed of the spinneret, bead‐free TaOxN1−x fibers with a diameter of 800 nm were obtained. The fibers were structurally characterized through phase and elemental analysis, confirming the formation of monoclinic TaOxN1−x with clear splitting of the X‐ray photoelectron spectroscopy peaks indicating Ta was in +5 oxidation state. The resulting oxynitride fibers exhibited superior electrocatalytic performance with low overpotentials (250 mV) to generate 10 mA/cm2 compared to Ta2O5 oxide fibers. Interestingly, the enhanced activity of oxynitride fibers was observed to be suppressed in basic medium due to the high oxophilicity of tantalum ions and a negative Gibbs adsorption‐free energy, leading to poisoning of the active sites. This work demonstrates a facile pathway for the fabrication of high‐performance electrocatalysts, based on TaOxN1−x fibers, from a cost‐effective and energy‐efficient centrifugal spinning technique. [ABSTRACT FROM AUTHOR] more...
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- 2023
- Full Text
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19. An Imidazolylidene‐Based Mesoionic Carbene–Mn(I) Complex and Its Catalytic Potential in N‐Heteroarene Hydrogenation.
- Author
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Kumar, Ravi, Pandey, Madhusudan K., Pandey, Indresh K., Kumar, Abhishek, and Choudhury, Joyanta
- Subjects
- *
HYDROGENATION , *CATALYTIC hydrogenation , *ELECTRON density , *FOURIER transform infrared spectroscopy , *MASS spectrometry , *CARBENE synthesis , *KEGGIN anions - Abstract
Herein we report the first mesoionic carbene (MIC)‐Mn(I) complex Mn‐bim‐MICimz derived from imidazolylidene motif. Structurally the octahedral Mn(I) complex Mn‐bim‐MICimz was assembled with an anionic benzimidazolato‐anchored imidazolylidene MIC‐based bidentate ligand (bim‐MICimz) and four CO ligands, as supported by detailed characterization using NMR and FTIR spectroscopy, mass spectrometry, and single crystal X‐ray diffraction study. We reckoned that the bim‐MICimz ligand would provide a robust and stable bonding with the Mn(I) centre, and also enhance electron density at the Mn(I) centre through its stronger σ‐donating/weaker π‐accepting property. These structural and electronic attributes triggered to exploit Mn‐bim‐MICimz in catalytic hydrogenation of N‐heteroarenes, where efficient hydride (Mn−H) delivery is a key step. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
20. Step‐by‐Step Guide for Synthesis and Delamination of Ti3C2Tx MXene.
- Author
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Thakur, Anupma, Chandran B.S., Nithin, Davidson, Karis, Bedford, Annabelle, Fang, Hui, Im, Yooran, Kanduri, Vaishnavi, Wyatt, Brian C., Nemani, Srinivasa Kartik, Poliukhova, Valeriia, Kumar, Ravi, Fakhraai, Zahra, and Anasori, Babak more...
- Subjects
ELECTRIC conductivity ,ATOMIC force microscopy ,SCANNING electron microscopy ,TITANIUM carbide ,LITHIUM chloride ,HYDROFLUORIC acid - Abstract
To advance the MXene field, it is crucial to optimize each step of the synthesis process and create a detailed, systematic guide for synthesizing high‐quality MXene that can be consistently reproduced. In this study, a detailed guide is provided for an optimized synthesis of titanium carbide (Ti3C2Tx) MXene using a mixture of hydrofluoric and hydrochloric acids for the selective etching of the stoichimetric‐Ti3AlC2 MAX phase and delamination of the etched multilayered Ti3C2Tx MXene using lithium chloride at 65 °C for 1 h with argon bubbling. The effect of different synthesis variables is investigated, including the stoichiometry of the mixed powders to synthesize Ti3AlC2, pre‐etch impurity removal conditions, selective etching, storage, and drying of MXene multilayer powder, and the subsequent delamination conditions. The synthesis yield and the MXene film electrical conductivity are used as the two parameters to evaluate the MXene quality. Also the MXenes are characterized with scanning electron microscopy, x‐ray diffraction, atomic force microscopy, and ellipsometry. The Ti3C2Tx film made via the optimized method shows electrical conductivity as high as ≈21,000 S/cm with a synthesis yield of up to 38 %. A detailed protocol is also provided for the Ti3C2Tx MXene synthesis as the supporting information for this study. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
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21. Enhancing Diradical Character of Chichibabin's Hydrocarbon through Fluoride Substitution.
- Author
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Kundu, Gargi, Dash, Soumya Ranjan, Kumar, Ravi, Vanka, Kumar, Ghosh, Aryya, and Sen, Sakya S.
- Subjects
HYDROCARBONS ,BAND gaps ,DOUBLE bonds ,TETRAFLUOROBORATES - Abstract
In this work, 5‐SIDipp [SIDipp=1,3‐bis(2,6‐diisopropylphenyl)‐imidazolin‐2‐ylidene] (1) derived Chichibabin's hydrocarbon with an octafluorobiphenylene spacer (3) has been reported. The addition of two equivalents of 5‐SIDipp with decafluorobiphenyl in presence of BF3 gives the double C−F bond activated imidazolium salt with two tetrafluoroborate anions, 2. Further reduction of 2 gives the fluorine substituted 5‐SIDipp based Chichibabin's hydrocarbon, 3. Quantum chemical calculations suggested a singlet state of 3 with a singlet–triplet energy gap (ΔES‐T) of 3.7 kcal mol−1, which is substantially lower with respect to the hydrogen substituted NHC‐based Chichibabin's hydrocarbons (10.7 kcal mol−1, B3LYP). As a result, the diradical character (y) of 3 (y=0.62) is also noticeably higher than the hydrogen substituted CHs (y=0.41–0.43). The ▵ES‐T was found to be higher in CASSCF (22.24 kcal mol−1) and CASPT2 (11.17 kcal mol−1) for 3 and the diradical character (d) is 44.6 %. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
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22. Development of a thin‐layer chromatographic method for detection of lipstatin produced by Streptomyces toxytricini.
- Author
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Jatain, Indu, Kumar, Ravi, Dubey, Kashyap Kumar, Yadav, Karuna, and Nitharwal, Ram Gopal
- Subjects
- *
STREPTOMYCES , *HIGH performance liquid chromatography , *PINK , *SIMVASTATIN , *LIPASE inhibitors , *ORLISTAT - Abstract
Lipstatin or its saturated analog (orlistat), being the irreversible inhibitor of intestinal lipase, is widely used for the treatment of obesity. The bacterium Streptomyces toxytricini is the main source for the production of lipstatin/orlistat. There are continuous attempts to increase the production of lipstatin in S. toxytricini. For optimization of best conditions/strains for lipstatin production, there are requirements for a fast, simple, and reliable method to detect/estimate lipstatin. At present, highly sophisticated methods such as high‐performance liquid chromatography, mass spectrometry, and so forth are available for the detection and estimation of lipstatin/orlistat. These methods are very costly, time‐consuming, and require state of the art facility. Here we report a simple, fast, cost‐effective method based on thin‐layer chromatography for the detection of lipstatin in S. toxytricini. The optimized mobile phase was acetone: ethanol in a ratio of 3:7. Development of thin‐layer chromatography was done by ρ‐anisaldehyde staining that showed the pink color to the silica plate and greenish‐blue color to the lipstatin/orlistat drug. Conclusively, here we mention a simple and reproducible method of detection of orlistat and lipstatin samples extracted from S. toxytricini. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
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23. Effect on structure, stability, and H+ irradiation on Nd3+/Ru4+‐loaded iron phosphate glass for nuclear applications.
- Author
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Joshi, Akhilesh C., Roy, Mainak, Dutta, Dimple P., Mishra, Raman K., Meena, Sher Singh, Kumar, Ravi, and Tyagi, Avesh K.
- Subjects
PHOSPHATE glass ,PROTON beams ,IRON ,RADIOACTIVE waste disposal ,NUCLEAR energy ,MOSSBAUER effect ,IRRADIATION ,X-ray absorption - Abstract
Nuclear energy generation technology is critically linked with the safe disposal of radioactive waste. In this context, iron phosphate glass (IPG) is gaining predominance as nuclear waste vitrification matrix that necessitates a thorough study on the effect of the loading of various nuclear fission waste materials in it. In this study, the effect of the loading of Nd3+ (which acts as a surrogate for radioactive curium (Cm)) and Ru4+ (which is a fission product of 235U) in IPG has been assessed. The optimum loading of Nd3+/Ru4+ leading to the formation of homogenous melt has been ascertained via powder X‐ray diffraction and scanning electron microscopy techniques. The modification in the Fe3+/Fe2+ ratio in IPG and the consequent change in its average coordination number with Nd3+/Ru4+ loading has been deduced from the Mössbauer studies. Local structure analysis has been done using X‐ray absorption spectroscopy at Nd/Ru/Fe K‐edge (as applicable) for all the single and co‐loaded IPG samples. All the co‐loaded samples show enhanced glass stability and glass forming ability compared to unloaded IPG which has been ascertained via detailed thermal studies. The variation in IPG network structure on the addition of Nd2O3 and RuO2 has been ascertained through spectroscopic techniques like Fourier transform infrared (FTIR) and Raman. The base glass and a few representative homogenous single and co‐loaded IPG samples have been irradiated with 4.5 MeV proton beam to simulate the hosting of radioactive elements and the radiation effect on glass structure has been ascertained using FTIR and Raman spectroscopies. The suitability of IPG as nuclear waste vitrification matrix for Nd3+ and Ru4+ is established through all the above analyses. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
24. Performance dependency of LSTM and NAR beamformers with respect to sensor array properties in millimeter‐wave V2I scenario.
- Author
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Kumar, Ravi and Singh, Hardeep
- Subjects
- *
WIRELESS channels , *SENSOR arrays , *COMPLEX variables , *BEAMFORMING , *TIME series analysis - Abstract
Interference prediction is a challenging problem in millimeter‐wave V2I scenarios. The implementation of a practical V2I network is limited because of the interference due to the random nature of the wireless channel. This paper proposes an adaptive beamforming technique for mitigation of interference in V2I networks. In this work, long short‐term memory (LSTM) and nonlinear autoregressive (NAR)‐based regressors have been employed to predict the angles between the RSU and UE. Advance prediction of transmit and receive signals enables reliable V2I communication. Instead of predicting the beamforming matrix directly, we predict the main features using LSTM for learning dependencies in the input time series where complex variables were taken as input states and the final beamformed signal was the output. Simulation results have confirmed that the proposed LSTM model achieves comparable performance in terms of system throughput compared to the NAR method implemented as an artificial neural network. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
25. Synthesis, characterization and catalytic activities of Zn(II) and Cd(II) complexes supported by unsymmetrical aryl thiourea ligands.
- Author
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Banerjee, Indrani, Bhattacharjee, Jayeeta, Kumar, Ravi, Pal, Kuntal, and Panda, Tarun K.
- Subjects
THIOUREA ,CATALYTIC activity ,LIGANDS (Chemistry) ,CADMIUM compounds ,BORONIC esters ,METAL complexes - Abstract
We report a series of Zn(II) and Cd(II) metal complexes [L12(ZnCl2)] (1), [L12(ZnBr2)] (2), [L12(CdCl2)] (3), [L12(CdI2)] (4), [L22(ZnCl2)] (5), [L22(ZnBr2)] (6), [L22(ZnI2)] (7), [L22(CdCl2)] (8), [L32(CdCl2)] (9) and [L42(ZnBr2)] (10), synthesized using various unsymmetrical aryl thiourea ligands: 1‐(2,6‐diisopropylphenyl)‐3‐phenylthiourea (L1), 1‐mesityl‐3‐phenylthiourea (L2), 1‐(2‐fluorophenyl)‐3‐phenylthiourea (L3) and symmetrical 1,3‐bis(2‐fluorophenyl)thiourea (L4). The ligands and metal complexes were characterized by 1H, 13C{1H} NMR, FT‐IR analysis. Solid‐state structures of the zinc and cadmium metal complexes (1–8) were established using the single‐crystal diffraction analysis technique. Furthermore, the catalytic activities of the Zn(II) complexes towards hydroboration of aldehydes and ketones (‐C=O) as substrates were studied. Excellent yields of the corresponding boronate esters were achieved. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
26. Generalized quantitative electroluminescence method for the performance evaluation of defective and unevenly degraded crystalline silicon photovoltaic module.
- Author
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Puranik, Vishal E., Kumar, Ravi, and Gupta, Rajesh
- Subjects
SOLAR cells ,ELECTRIC potential measurement ,QUANTITATIVE research ,ELECTROLUMINESCENCE ,EVALUATION methodology ,PHOTOVOLTAIC power systems ,BUILDING-integrated photovoltaic systems - Abstract
Photovoltaic (PV) module experiences multiple cell defects and degradation in a field operation, which significantly reduces module output. Hence, quantitative assessment of a PV module is essential to ensure module operation within a desirable limit. This article proposes the generalized quantitative electroluminescence (g‐QUEL) method to evaluate the performance of a defective and unevenly degraded PV module from the EL images. Four module classes are considered from the view of field applications, such as new, PID‐s affected, field aged shunted, and nonshunted modules. The effects of defects and degradation on fundamental cell electroluminescence (EL) characteristics and constants are analyzed for each class. Based on this analysis, the g‐QUEL method is developed, which utilizes module multiple EL images, datasheet information, and terminal voltage measurements for quantification. First, a test module is qualitatively assessed to identify the present defects and classified into one of four classes. In the second part, the g‐QUEL algorithm is applied to a test module in a customized manner to extract five or seven parameters of a PV cell. Subsequently, a single or two diode model simulation is carried out at a module, submodule, or cell level to estimate module output by generating I‐V curve. Experimental verification of the proposed method was conducted on five test modules of each class. Results demonstrate the accuracy and effectiveness of the g‐QUEL method as it evaluates the output power of new to field‐aged modules with a relative error ≤±3%. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
27. Single source precursor‐derived SiOC/TiOxCy as an anode component for Li‐ion batteries.
- Author
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Vendra, SS Lokesh, Singh, Gurpreet, and Kumar, Ravi
- Subjects
LITHIUM-ion batteries ,X-ray photoelectron spectroscopy ,ANODES ,AMORPHOUS silicon ,STRUCTURAL stability - Abstract
Amorphous silicon oxycarbides are known to be an effective anode material for lithium‐ion batteries. Despite their exceptional properties and high charge capacities, however, their practical uses are limited by their significant first‐cycle loss, considerable hysteresis, and low cyclic ability. Comparatively, SiOC/metal oxide materials have demonstrated increased rate capability and cyclic stability. This study utilized a liquid precursor‐derived ceramic method to modify SiOC with titanium (IV) butoxide precursor to synthesize SiOC/TiOxCy. X‐ray diffractograms confirmed the amorphous nature of SiOC/TiOxCy. The elemental composition and bonding properties were investigated using X‐ray photoelectron spectroscopy, and electron microscopy was used to explore morphological features. In the first cycle, the reversible capacity of pyrolyzed SiOC/TiOxCy was 520 mAh g−1, which then increased to 736 mAh g−1 for the 1200°C annealed SiOC/TiOxCy due to the increased free carbon network and TiC conductive phases. The irreversible capacity of the first cycle was 568 mAh g−1, which was lower than the annealed SiOC irreversible capacity of 695 mAh g−1. Interestingly, the rate stability of the pyrolyzed SiOC/TiOxCy performed more stability than the annealed sample. Localized carbothermal reactions between amorphous SiOC/TiOxCy and free carbon at annealing temperatures resulted in loss of structure stability. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
- Full Text
- View/download PDF
28. Exploring the Electronic Influence of β‐Br Substitutions in CuTPP on Electrochemical Overall Water Splitting in Alkaline Medium.
- Author
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Ahmad Lone, Ishfaq and Kumar, Ravi
- Subjects
- *
POLAR effects (Chemistry) , *ELECTRON density , *HYDROGEN evolution reactions - Abstract
Beta substitution has a marked influence on the electronic environment of porphyrin ring atoms and the structure of the substituted porphyrin. In this work, we explore the influence of the bromo (Br) substitution at the β‐positions of copper tetraphenylporphyrin (CuTPP) and its consequent influence on the electrocatalytic alkaline overall water splitting. The β‐Br substitution is expected to exercise a strong influence on the electronic environment of central Cu through the electronic effects of Br. The overall influence of electronic effects is seen to lead to the net increase in the electron density of the central Cu (observed from XPS shifts) which is ultimately reflected in their different HER and OER performance in the alkaline medium. We observe the HER overpotentials (for 10 mA cm−2) of 697 mV, 760 mV, 838 mV, and 883 mV for the unsubstituted, bisubstituted, tetrasubstituted, and octasubstituted [Cu(TPP)]. The OER performance on the contrary depicts the reverse order with the overpotentials of 1118 mV, 827 mV, 637 mV, and 420 mV respectively for unsubstituted, bisubstituted, tetrasubstituted, and octasubstituted [Cu(TPP)]. The observed shifts in the catalytic performance can directly be attributed to increasing charge density on the central metal Cu2+ with the increase in the number of Br groups which in turn has opposite consequences for HER and OER performance. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
29. One‐Pot Electrochemical Synthesis of Citric Acid Functionalized Iron Oxide Magnetic Nanoparticles for Congo Red Adsorption.
- Author
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Pawar, Aditya Amrut, Kumar, Ravi, Sharma, Shilpa, and Satyanarayana, Tulasi
- Subjects
- *
CONGO red (Staining dye) , *CITRIC acid , *ADSORPTION (Chemistry) , *ADSORPTION isotherms , *GENTIAN violet , *LANGMUIR isotherms , *ADSORPTION capacity , *IRON oxide nanoparticles , *HETEROGENEOUS catalysts - Abstract
Azo dyes, like Congo red (CR), are persistent contaminants that cause detrimental consequences on living organisms in various habitats. In the present study, a novel and facile one‐pot citric acid functionalized iron oxide magnetic nanoparticles (Fe3O4@CA NPs) through an electrochemical method are synthesized and characterized for adsorbing CR dye present in an aqueous solution is reported. The influence of various factors on the adsorption of CR dye, namely pH of the CR solution, Fe3O4@CA NPs concentration, initial CR dye concentration, contact time, temperature, and agitation speed, are examined. The adsorption isotherms and kinetic studies for CR adsorption on Fe3O4@CA NPs are also investigated. The equilibrium results correspond well to the Langmuir isotherm having maximum dye uptake of 46.948 mg g−1, while the adsorption follows the pseudo‐second‐order kinetics model. The adsorption process appears to be spontaneous and endothermic, according to the thermodynamic parameters. The mechanism of CR adsorption on Fe3O4@CA NPs is also suggested. The synthesized nanoadsorbent shows more than 90% recyclability during five consecutive adsorption–desorption cycles. The simple and cost effective synthesis, high adsorption capacity, and recyclable nature of Fe3O4@CA NPs suggest the potential to eliminate CR from aqueous sources. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
30. Amelioration of Radiation-Induced Cell Death in Neuro2a Cells by Neutralizing Oxidative Stress and Reducing Mitochondrial Dysfunction Using N-Acetyl-L-Tryptophan.
- Author
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Kumar, Ravi, Kumari, Pratibha, Pandey, Swapnil, Singh, Shravan Kumar, and Kumar, Raj
- Published
- 2022
- Full Text
- View/download PDF
31. Diamond Surfaces with Clickable Antifouling Polymer Coating for Microarray‐Based Biosensing.
- Author
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Kumar, Ravi, Yang, Bingquan, Barton, Jan, Stejfova, Miroslava, Schäfer, Andreas, Koenig, Meike, Knittel, Peter, Cigler, Petr, and Hirtz, Michael
- Subjects
DIAMOND surfaces ,BINDING site assay ,REACTIVE polymers ,SURFACE coatings ,POLYMERS ,SIGNAL-to-noise ratio ,BIOMACROMOLECULES - Abstract
Diamond enables the construction of various (bio)sensors, including those with quantum‐based detection. However, bare diamond interfaces are susceptible to unspecific adhesion of proteins and other macromolecules from biological media or complex samples. This impairs selectivity in biosensing, leads to low signal‐to‐noise ratio in fluorescence‐based applications, and introduces the need for blocking steps in incubation protocols. Here, a stable, protein‐repellent, and clickable reactive polymer coating is introduced, abolishing unspecific protein adhesion while concurrently enabling covalent immobilization of functional compounds as recognition elements. The polymer coating has two segments, an antifouling poly(N‐(2‐hydroxypropyl) methacrylamide) and an alkyne‐terminated poly(propargyl methacrylamide) providing the click functionality. The antifouling properties and click‐reactivity of the polymers are demonstrated by selective protein binding assays on micropatterns written by microchannel cantilever spotting (µCS). The assays demonstrated the successful functionalization of both diamond and glass surfaces and the excellent antifouling properties of the polymer coating. The coating procedure is compatible with oxidized diamond surfaces thus well‐suitable for diamond‐based quantum technology. The results can directly impact applications of diamond materials in optically detected quantum sensing or fluorescence sensing in general. The polymer functionalization can also be used for any case where highly specific interaction with low fouling is desired. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
32. Challenges and opportunities of brand corporate social responsibility classification: A review, new conceptualization and future research agenda.
- Author
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Prasad, Ashok A. and Kumar, Ravi Shekhar
- Subjects
SOCIAL responsibility of business ,FOLKSONOMIES ,HOUSE brands ,SOCIAL marketing - Abstract
Scholars have outlined several corporate social responsibility (CSR) classifications to analyse the wide range of CSR initiatives. The usage of diverse CSR types has resulted in independent and fragmented research. Previous literature reviews have analysed the overall CSR domain or focused on specific CSR activity, like cause‐related marketing. A comprehensive review of CSR classifications is not available to the best of the authors' knowledge. This article synthesizes the literature on CSR classification and proposes a holistic brand CSR mechanism classification schema. We review the CSR classifications outlined in 104 academic resources published between 1979 and 2021 (across 47 ABDC listed journals and one book). The review utilizes the 5W1H—Who, Why, What, When, Where and How—analytical framework to reveal the underlying rationale of different CSR classifications. The 5W1H analysis indicates that the majority of CSR classifications are from the overall business perspective rather than the product brand perspective. It also suggests the importance of the CSR delivery mechanism, that is, how CSR is delivered. The review finds a lack of conceptual basis in the extant brand CSR mechanism classifications. To address these challenges, we propose a conceptually grounded classification schema for brand CSR mechanisms with 10 classes to capture the feasible options holistically and parsimoniously. We describe the proposed classes and sub‐classes, provide real‐life illustrations, and assess the proposed classification's robustness. The implications of this study for theory, practice, and consumers are discussed. Leveraging the proposed classification, we identify several avenues for further research. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
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33. Density Functional‐Based Tight‐Binding Simulations of Pristine and Aluminum‐Modified Silica.
- Author
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Dernov, Andrei, Tong, Zhen, Kumar, Ravi, Agarwal, Pulkit, Frauenheim, Thomas, and Dumitrică, Traian
- Subjects
YOUNG'S modulus ,PERMITTIVITY ,SILICA ,POTENTIAL energy ,BAND gaps - Abstract
Using self‐consistent density functional tight‐binding simulations it is shown that Aluminum (Al) content in amorphous silica (a‐SiO2) changes its ideal microscopic structure in a manner compatible to densification. Similar to the structure of pressure‐densified a‐SiO2, the Al‐modified a‐SiO2 comprises a network of Silicon (Si)‐centered tetrahedra as well as unquenchable pentahedra and, to a smaller extent, hexahedra coordination defects. Al itself acts not only as a network former, with fourfold coordination, but also as a center for fivefold and sixfold coordination defects. Al content promotes densification since it shifts the potential energy minima at densities larger than in their pristine counterpart. Calculations uncover that Young's modulus (Y) and static dielectric constants (ε0) can be effectively doubled through densification. Oxygen starvation promotes network polymerization, which further increases Y and ε0. However, the small rings formation through Si─Si bonding and presence of undercoordinated Si introduce electronic states in the electronic band gap. The results provide guidance for the bottom‐up design of amorphous silica with tunable microscopic structure and properties desirable for advancing electronic applications. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
34. Alphavirus antivirals targeting RNA‐dependent RNA polymerase domain of nsP4 divulged using surface plasmon resonance.
- Author
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Pareek, Akshay, Kumar, Ravi, Mudgal, Rajat, Neetu, Neetu, Sharma, Monica, Kumar, Pravindra, and Tomar, Shailly
- Subjects
- *
RNA replicase , *SURFACE plasmon resonance , *ANTIVIRAL agents , *SMALL molecules , *CHLOROGENIC acid , *VIRUS-induced enzymes - Abstract
Alphaviruses are continuously re‐emerging and pose a global threat to human health and currently no antiviral drug is commercially available for alphaviral infections. Alphavirus non‐structural protein nsP4, which possesses RNA‐dependent RNA polymerase (RdRp) activity, is a potential antiviral target. To date, no antiviral drug is commercially available against alphaviruses. Since RdRp is the key virus‐specific enzyme involved in viral genome replication, this study identifies and validates the antiviral efficacy of small molecules targeting alphavirus RdRp. Purified nsP4 was characterized using the surface plasmon resonance (SPR) assay, and the binding affinities of divalent metal ions, ribonucleotides, and in vitro transcribed viral RNA oligonucleotides were obtained in the micromolar (μm) range. Further, four potential inhibitors, piperine (PIP), 2‐thiouridine (2TU), pyrazinamide (PZA), and chlorogenic acid (CGA), were identified against nsP4 RdRp using a molecular docking approach. The SPR assay validated the binding of PIP, 2TU, PZA, and CGA to purified nsP4 RdRp with KD of 0.08, 0.13, 0.66, and 9.87 µm, respectively. Initial testing of these molecules as alphavirus replication inhibitors was done using SINV‐IRES‐Luc virus. Detailed assessment of antiviral efficacy of molecules against CHIKV was performed by plaque reduction assay, qRT‐PCR, and immunofluorescence assay. PIP, 2TU, PZA, and CGA showed antiviral potency against CHIKV with EC50 values of 6.68, 27.88, 36.26, and 53.62 µm, respectively. This study paves the way towards the development of novel broad‐spectrum alphavirus antivirals targeting nsP4 RdRp. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
35. Performance and Emission Analysis of Waste Cooking Oil Biodiesel Mixed with Titanium Oxide Nano-Additives.
- Author
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Kumar, Raj, Arunkumar, M., Shan, D. Priestly, Patil, Pravin P., Kumar, Ravi, Singh, Bharat, and Chowdary, Velivela Lakshmikanth
- Subjects
EDIBLE fats & oils ,TITANIUM oxides ,ENERGY dispersive X-ray spectroscopy ,DIESEL motors ,TRANSMISSION electron microscopy ,FATTY acid methyl esters - Abstract
People are using biodiesel in compression ignition engines because it is more environmentally friendly and can be used as a good alternative to diesel. There is a new technology called nanoparticles that can change the way a fuel works. Because waste cooking has a lot of oil in it, it can make biodiesel. To make biodiesel, transesterification was used to turn nonedible oil from waste cooking oil into biodiesel that could be used. Nanoparticles made of titanium oxide were studied by using scanning electron microscopy, transmission electron microscopy, as well as energy dispersive X-ray analysis, among other things. TiO2 nanoparticles are spread out in different amounts in the biodiesel blend. The dosage levels range from 25, 50, 75, and 100 ppm. Tests on how titanium nanoparticles in a waste cooking oil biodiesel blend affect a diesel engine's performance and how it emits were conducted in this study too. At a steady speed, the engine was used when there was a lot of work to do. Tests show that the WCOME 20 TiO2 100 ppm blend worked well. With the increase in the concentration of nanoparticles, there is an increase in brake thermal efficiency and at the same time, there is a decrease in BSFC. It is also less harmful to the environment than other blends, except for NOx, which does no't change. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
36. Multiplexed Covalent Patterns on Double‐Reactive Porous Coating.
- Author
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Das, Supriya, Kumar, Ravi, Yang, Bingquan, Bag, Sudipta, Sauter, Eric, Hussain, Navid, Hirtz, Michael, and Manna, Uttam
- Subjects
- *
INK-jet printing , *SURFACE coatings , *POROUS materials , *SUPERHYDROPHOBIC surfaces , *FLUOROPHORES , *ADDITION reactions - Abstract
We have conceptualized and demonstrated an approach based on the combination of hydrophobicity, a substrate‐independent dip coating as porous material with double residual chemical reactivities for implementing multiplexed, miniaturized and unclonable bulk‐infused patterns of different fluorophores following distinct reaction pathways. The embedded hydrophobicity (∼102°) restricted the unwanted spreading of beaded aqueous ink on the coating. The constructions of micropatterns on porous dip‐coating via ink‐jet printing or microchannel cantilever spotting offered orthogonal read‐out and remained readable even after removal of the exterior of the coating. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
37. Evaluation of Dibenzocyclooctyne and Bicyclononyne Click Reaction on Azido‐Functionalized Antifouling Polymer Brushes via Microspotting.
- Author
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Yang, Bingquan, Wang, Yangxin, Vorobii, Mariia, Sauter, Eric, Koenig, Meike, Kumar, Ravi, Rodriguez‐Emmenegger, Cesar, and Hirtz, Michael
- Abstract
Strain‐promoted alkyne‐azide cycloaddition (SPAAC) has become an indispensable tool in bioorthogonal conjugation and surface immobilization. While numerous studies have focused on enhancing the reactivity of cyclooctynes, a facile method to evaluate the binding efficiency for cyclooctyne‐azide‐based immobilization without any sophisticated facilities is still missing. In the present work, different derivatives of dibenzocyclooctyne/bicyclononyne (DBCO/BCN) linked to either a fluorophore or a biotin‐moiety are patterned on ultra‐low fouling polymer brushes, which can avoid unspecific protein contamination without any prior blocking steps. The polymer brushes are composed of an antifouling bottom block and azide‐terminated top block. The assessment of binding efficiency is conducted on ordered arrays spotted by microchannel cantilever spotting (μCS) with a normal fluorescent microscope. Both cyclooctynes demonstrate reliable binding performance with azide‐bearing diblock polymer brushes via μCS, but DBCO shows a higher surface density of molecular immobilization according to the protein binding assays. This work provides a reference for choosing appropriate cyclooctyne to couple with azides and can be useful for the design of biosensors or bio‐platforms for analyte detection, cell capture, and other biological applications. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
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38. Experimental investigation on burning characteristics of diesel pool fires in naturally ventilated compartment.
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Tiwari, Mahesh Kumar, Gupta, Akhilesh, Kumar, Ravi, and Sharma, Pavan Kumar
- Subjects
HEAT release rates ,FLAME spread ,ENTHALPY ,HEAT flux ,DIESEL fuels ,FIRE testing - Abstract
Summary: In this study, experiments were performed in a 4 m × 4 m × 4 m compartment having a door size of 2 m × 1 m in the front wall. The pan diameter has been varied from 0.2 to 1.0 m in order to evaluate parameters, such as mass loss rate, CO/CO2 yield, global equivalence ratio (GER), flame height, flame pulsation frequency and total heat flux within the compartment. Experimental mass loss flux was found to be 0.23 times lesser than the mass loss flux obtained with an open fire test. A correlation was developed to estimate the flame height for compartment fire as the function of pool diameter and heat release rate. Pulsation frequency has been well correlated with previous studies for smaller pool sizes, due to no interaction between the flame tip and upper smoke layer. However, for a larger pool, this seems to be deviated due to a larger smoke layer thickness. Heat flux variations were observed to follow power law trends for all the inner surfaces of the compartment with respect to pool diameters. This investigation is also essential for better understanding of diesel (sooty) fuel burning effects with respect to pool size in a compartment having well‐ventilated door opening. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
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39. Capacity factor characteristics for a multi‐tubular sensible energy storage system with wire coil inserts.
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Kumar, Ravi, Kumar, Manoj, and Patil, Anil Kumar
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ENERGY storage ,SPECIFIC heat capacity ,HEAT transfer fluids ,WIRE ,ATMOSPHERIC temperature - Abstract
Summary: The transient energy storage in a sensible energy storage system (SESS) depends on the rate of energy stored in the system. The rate of energy stored in a sensible energy system is a strong function of spatial temperature distribution that governs the energy distribution in the storage medium. The present study explores the energy and capacity factor characteristics of a wire coil fitted multi‐tubular SESS. A storage system is molded using M30 grade concrete of density (ρc= 2200 kg/m3) and specific heat capacity (Cps= 850 J/kg/K). The inlet temperature of the air, used as heat transfer fluid, is varied from 45°C to 75°C. The pitch to diameter (p/d) ratio of the wire coil insert is varied from 0.25 to 0.75 to examine its effect on energy storage/release and capacity factor. Using a (p/d) ratio of 0.5 for wire coil inserts, the maximum capacity factor of 0.98 is achieved during the charging phase of sensible energy storage at 55°C inlet air temperature and 0.029 kg/s mass flow rate of heat transfer fluid (HTF). With respect to the smooth SESS, the maximum improvement in capacity factor is found to be 29%. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
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40. A Plausible Prebiotic One‐Pot Synthesis of Orotate and Pyruvate Suggestive of Common Protometabolic Pathways.
- Author
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Clay, Alyssa P., Cooke, Rachel E., Kumar, Ravi, Yadav, Mahipal, Krishnamurthy, Ramanarayanan, and Springsteen, Greg
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KREBS cycle ,PYRUVATES ,NUCLEOSIDE synthesis ,AMINO acids ,PYRIMIDINES ,HYDANTOIN ,FORMYLATION - Abstract
A reaction between two prebiotically plausible building blocks, hydantoin and glyoxylate, generates both the nucleobase orotate, a precursor of biological pyrimidines, and pyruvate, a core metabolite in the citric acid cycle and amino acid biosynthesis. The reaction proceeds in water to provide significant yields of the two widely divergent chemical motifs. Additionally, the reaction of thiohydantoin and glyoxylate produces thioorotate in high yield under neutral aqueous conditions. The use of an open‐chain thiohydantoin derivative also enables the potential pre‐positioning of a nucleosidic bond prior to the synthesis of an orotate nucleoside. The observation that diverse building blocks of modern metabolism can be produced in a single reaction pot, from common reactants under mild conditions, supports the plausibility of orthogonal chemistries operating at the origins of chemical evolution. [ABSTRACT FROM AUTHOR] more...
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- 2022
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41. Catalytic Hydroboration and Reductive Amination of Carbonyl Compounds by HBpin using a Zinc Promoter.
- Author
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Kumar, Ravi, Rawal, Parveen, Banerjee, Indrani, Pada Nayek, Hari, Gupta, Puneet, and Panda, Tarun K.
- Subjects
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AMINATION , *CARBONYL compounds , *HYDROBORATION , *ZINC , *ZINC compounds , *ZINC catalysts , *BORONIC esters - Abstract
The chemoselective hydroboration of aldehydes and ketones, catalyzed by Zinc(II) complexes [κ2‐(PyCH=NR)ZnX2] [R=CPh3, X=Cl (1) and R=Dipp (2,6‐diisoropylphenyl) and X=I (2)], in the presence of pinacolborane (HBpin) at ambient temperature and under solvent‐free conditions, which produced the corresponding boronate esters in high yield, is reported. Zinc metal complexes 1 and 2 were derived in 80–90% yield from the reaction of iminopyridine [PyCH=NR] with anhydrous zinc dichloride in dichloromethane at room temperature. The solid‐state structures of both zinc complexes were confirmed using X‐ray crystallography. Zinc complex 1 was also used as a competent pre‐catalyst in the reductive amination of carbonyl compounds with HBpin under mild and solvent‐free conditions to afford a high yield (up to 97%) of the corresponding secondary amines. The wider substrate scope of both reactions was explored. Catalytic protocols using zinc as a pre‐catalyst demonstrated an atom‐economic and green method with diverse substrates bearing excellent functional group tolerance. Computational studies established a plausible mechanism for catalytic hydroboration. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
42. Metamorphic evolution of the pelitic and mafic granulites from Daltonganj, Chhotanagpur Granite Gneiss Complex, India: Constraints from zircon U–Pb age and phase equilibria modelling.
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Kumar, Ravi Ranjan, Kawaguchi, Kenta, Dwivedi, Shyam Bihari, and Das, Kaushik
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- *
GRANULITE , *ZIRCON , *LASER ablation inductively coupled plasma mass spectrometry , *PHASE equilibrium , *CORDIERITE , *GNEISS , *SILLIMANITE - Abstract
The Daltonganj region is located on the northwestern extension of the Chhotanagpur Granite Gneiss Complex in the eastern Indian Peninsula, which is characterized by pelitic and mafic assemblages of granulite facies rock. The pelitic granulites contain garnet, cordierite, biotite, plagioclase, K‐feldspar, sillimanite, and quartz. Petrographical interpretations divulge prograde and retrograde metamorphic events within mafic granulites, which consist of clinopyroxene, orthopyroxene, amphibole, plagioclase, biotite, and quartz. Field observation, petrography, phase equilibrium modelling, and U–Pb zircon geochronology of the pelitic granulites reveal two stages of metamorphic events along the clockwise P–T path. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) zircon U–Pb age dating of pelitic granulites shows the detrital zircon ages from ~1,734 Ma to 1,677 Ma, and the possible metamorphic domains show the weighted mean age of 1,638 ± 22 Ma, which represents the timing of metamorphism. Subsequently, the magmatic emplacement of mafic granulites was recorded at 1,629 ± 6 Ma age by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) zircon U–Pb dating which coincide with the timing of metamorphism of the pelitic granulite. Phase equilibrium modelling in the NCKFMASHTO system divulges the pre‐peak metamorphic stage at ~3.2 kbar and ~620°C and the first stage which is characterized by a peak metamorphic condition that ranges from 7.40 to 9.10 kbar and from 815 to 835°C during ~1,638 Ma with the mineral assemblage of garnet + sillimanite + biotite + plagioclase + K‐feldspar + melt + quartz + ilmenite. Sequentially, the retrograde metamorphism is observed by a nearly isothermal decompression stage at ~4.0 kbar/~790°C after 1,638 Ma, due to the appearance of garnet + cordierite + biotite + plagioclase + K‐feldspar + melt + quartz + ilmenite + magnetite. The formation of cordierite is due to the decompression and dehydration melting phases. The Nb, Sr, and Ti negative anomalies suggest their generation from crustal sources. The geochemical analyses constrain that the sedimentation of pelitic sediments was recorded along the convergent margin and encountered by a subduction‐related tectonic setting. The geochemical interpretation provides significant evidence that the protoliths of pelitic granulites were derived from the Singhbhum Mobile Belt, Mahakoshal Supracrustal Belt, and Bundelkhand Craton, while their metamorphism was processed by the continent–continent collision and followed by exhumation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
43. Asymmetric Direct/Stepwise Dearomatization Reactions Involving Hypervalent Iodine Reagents.
- Author
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Kumar, Ravi, Singh, Fateh V., Naoko Takenaga, and Toshifumi Dohi
- Subjects
- *
HYPERVALENCE (Theoretical chemistry) , *IODINE compounds , *IODINE , *CATALYSTS - Abstract
A remarkable growth in hypervalent iodine-mediated oxidative transformations as stoichiometric reagents as well as catalysts has been well-documented due to their excellent properties, such as mildness, easy handling, high selectivity, environmentally friendly nature, and high stability. This review aims at highlighting the asymmetric oxidative dearomatization reactions involving hypervalent iodine compounds. The present article summarizes asymmetric intraand intermolecular dearomatization reactions using chiral hypervalent iodine reagents/catalysts as well as hypervalent iodine-mediated dearomatization reactions followed by desymmetrization. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
44. Molecular analysis of severe hemophilia B in Indian families: Identification of mutational hotspot and novel variants.
- Author
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Agrawal, Neha, Kumar, Ravi, Masih, Suzena, Srivastava, Priyanka, Singh, Parshw, Jaiswal, Sushil Kumar, Moirangthem, Amita, Saxena, Deepti, Phadke, Shubha R., and Mandal, Kausik
- Subjects
- *
HEMOPHILIA , *DISEASE clusters , *GENETIC mutation , *DNA , *PROTEASE inhibitors , *MOLECULAR pathology , *TERTIARY care , *SEVERITY of illness index , *MOLECULAR biology , *SERINE , *STATISTICAL correlation - Abstract
Introduction: Hemophilia B is associated with molecular heterogeneity, with more than 1200 unique variants in the F9 gene. We hereby describe the mutational spectrum of severe hemophilia B patients presenting in a tertiary‐care center in India. Method: DNA was extracted from peripheral blood samples of 35 diagnosed severe hemophilia B patients belonging to 32 families, and were subjected to Sanger sequencing. Determination of the effect of novel variants on the protein structure and correlation between genotype and phenotype was attempted using in‐silico tools. Results: Twenty‐seven different mutations were detected in 30 probands, including 20 known and 7 novel variants. Also, we found one suspected case of whole gene deletion. The serine peptidase domain harbored most of the variants (48.1%). Inhibitory antibodies were found in two patients. Conclusions: This study provides a comprehensive mutational spectrum and mutation screening strategy by Sanger sequencing of F9 gene in severe hemophilia B patients, in a resource‐constraint setting. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
45. Hyperglycaemia‐induced human hepatocellular carcinoma (HepG2) cell proliferation through ROS‐mediated P38 activation is effectively inhibited by a xanthophyll carotenoid, lutein.
- Author
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Maradagi, Tehreem, Kumar, Ravi, and Ponesakki, Ganesan
- Subjects
- *
XANTHOPHYLLS , *PROTEIN kinases , *FLOW cytometry , *HYPERGLYCEMIA , *WESTERN immunoblotting , *LUTEIN , *ANTIOXIDANTS , *CELL cycle proteins , *SIGNAL peptides , *RISK assessment , *CAROTENOIDS , *MOLECULAR biology , *GENE expression , *CELL proliferation , *REACTIVE oxygen species , *HEPATOCELLULAR carcinoma , *DISEASE risk factors , *DISEASE complications - Abstract
Aims: Diabetic population have a twofold to threefold increased risk of developing liver cancer, and hyperglycaemia is a prime causative factor that propends the tumour cells to undergo aggressive metabolic growth. In this study, we aimed to examine the molecular mechanism by which lutein inhibits hyperglycaemia‐induced human hepatocarcinoma (HepG2) cell proliferation. Methods: The effect of lutein on high glucose‐induced proliferation was measured using the WST‐1 reagent. Its effect on intracellular reactive oxygen species (ROS) levels was measured by DCF assay. The effect on the expression of antioxidant enzymes, cell cycle regulatory proteins and intracellular protein kinases was analysed by western blotting. The modulatory effect of lutein on different phases of the cell cycle was analysed by flow cytometry. Results: The data showed that lutein at 5 µM concentration significantly blocked glucose‐promoted HepG2 cell proliferation. Suppression of high glucose‐induced cell proliferation by lutein was not associated with apoptosis induction, but it was linked with inhibition of hyperglycaemia‐mediated elevated ROS and upregulated expression of high glucose‐mediated repressed heme oxygenase 1 (HO1). Furthermore, G2/M phase cell cycle arrest and associated phosphorylation of Cdk1 and P53 were found to be linked with suppressed hyperglycaemia‐mediated cell proliferation by lutein. In addition, lutein inhibited hyperglycaemia‐induced activation of P38 which relates to high glucose‐induced ROS‐mediated growth suppression and modulated the phosphorylation of Erk, JNK and Akt in hyperglycaemic HepG2 cells. Conclusion: Our findings portray that sufficient intake of lutein may offer a negative impact on diabetes‐associated tumour growth. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
46. Recent Progress in Enolonium Chemistry under Metal‐Free Conditions.
- Author
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Kumar, Ravi, Nguyen, Quynh H., Um, Tae‐Woong, and Shin, Seunghoon
- Subjects
- *
UMPOLUNG , *CLASSICAL conditioning , *HYPERVALENCE (Theoretical chemistry) , *NUCLEOPHILES , *ELECTRON donors , *ENOLATES , *ALKYLATION - Abstract
Umpolung approach through inversion of the polarity of conventional enolates, has opened up an unprecedented opportunity in the cross‐coupling via alkylation. The enolonium equivalents can be accessed either by hypervalent iodine reagents, activation/oxidation of amides, or the oxidation of alkynes. Under umpolung conditions, highly basic conditions required for classical enolate chemistry can be avoided, and they can couple with unmodified nucleophiles such as heteroatom donors and electron‐rich arenes. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
47. Advances in development of biodegradable food packaging material from agricultural and agro‐industry waste.
- Author
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Birania, Sapna, Kumar, Sunil, Kumar, Nitin, Attkan, Arun Kumar, Panghal, Anil, Rohilla, Priyanka, and Kumar, Ravi
- Subjects
PACKAGING materials ,AGRICULTURAL wastes ,FOOD packaging ,BIODEGRADABLE materials ,SOCIAL responsibility of business ,FOOD industrial waste ,PACKAGING recycling - Abstract
The preferment for farm mechanization and advancement in industrialization has augmented the agro‐industrial waste generation. The management of such numerous waste is a challenging and resource‐intensive task. The current practices involve releasing this waste into the water bodies and open landfills which causes water, air, and soil pollution. These wastes have the potential to be used as a raw material for the development of value‐added products, generation of renewable energy, extraction of food‐use compounds, and manufacturing of packaging material. In the current scenario, agro‐based materials are captivating the packaging industries toward the development of renewable, biodegradable, and sustainable packaging materials. These agro‐based materials have great capability to replace petrochemical‐based plastic materials in packaging industries because of their ample availability and biodegradability. Biodegradable packaging materials can be derived from agro‐industrial waste either directly or by chemical synthesis or by genetically modified organisms. Agro‐based polymers have a scintillating future for a wide range of applications in the food industry and pharmaceuticals, including advances in active and smart packaging with bio‐functional characteristics. The present review comprehensively discusses the potential of different agricultural and agro‐industrial wastes that can be used for extracting different natural biopolymers and their further use in manufacturing biodegradable food packaging. Practical Applications: Information about the potential agricultural and agro‐industrial waste suggests development, optimization, customization, and scale‐up of production of biodegradable packaging material to promote its commercial usage. The major patents granted in biodegradable packing, properties of these materials, and the current status of their commercial availability will provide a compiled source of information, start‐ups, innovation, research, and future advancements to the industrialists, students, researchers, and entrepreneurs. As an alternative to plastics, biodegradable packaging materials open opportunities for sustainable and environment‐friendly solutions to industries and help in fulfilling their corporate social responsibility. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
48. Endogenous dipeptide‐carnosine supplementation ameliorates hypobaric hypoxia‐induced skeletal muscle loss via attenuating endoplasmic reticulum stress response and maintaining proteostasis.
- Author
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Agrawal, Akanksha, Rathor, Richa, Kumar, Ravi, Singh, Som Nath, Kumar, Bhuvnesh, and Suryakumar, Geetha
- Subjects
SKELETAL muscle ,ENDOPLASMIC reticulum ,MUSCLE proteins ,CREATINE kinase ,CALPAIN ,DIETARY supplements ,HYPOXIA-inducible factor 1 - Abstract
High altitude is an environmental stress that is accompanied with numerous adverse biological responses, including skeletal muscle weakness and muscle protein loss. Skeletal muscle wasting is an important clinical problem, progressing to critical illness, associated with increased morbidity and mortality. The present study explores the protective efficacy of endogenous dipeptide, carnosine (CAR), supplementation in ameliorating skeletal muscle protein loss under hypobaric hypoxia (HH). Male Sprague–Dawley rats (n = 5) were randomly divided into control group, HH‐exposed group (3 days HH exposure equivalent to 7,620 m), and HH‐exposed rats supplemented with carnosine (3 days; 150 mg/kg b.w, orally) (HH + CAR). HH‐exposed rats supplemented with CAR ameliorated HH‐induced oxidative protein damage, lipid peroxidation, and maintained pro‐inflammatory cytokines levels. HH‐associated muscle protein degradative pathways, including calpain, ubiquitination, endoplasmic reticulum stress, autophagy, and apoptosis were also regulated in carnosine‐supplemented rats. Further, the muscle damage marker, the levels of serum creatine phosphokinase were also reduced in HH + CAR co‐supplemented rats which proved the protective efficacy of CAR against hypobaric hypoxia‐induced muscle protein loss. Altogether, CAR supplementation ameliorated HH‐induced skeletal muscle protein loss via performing multifaceted ways, mainly by maintaining redox homeostasis and proteostasis in skeletal muscle. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
- Full Text
- View/download PDF
49. Comprehensive Overview of Progress in Functionalization of 2‐Pyridone and 2, 4 ‐Dihydroxy Pyridine: Key Constituents of Vital Natural Products.
- Author
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Yadav, Neelam, Sangwan, Sarita, Kumar, Ravi, Chauhan, Sonu, Duhan, Anil, Singh, Ajay, and Arya, Rajesh K.
- Subjects
NATURAL products ,TRANSITION metals ,PYRIDINE ,SCIENTIFIC community ,PYRIDONE - Abstract
Nitrogen heterocycles have found a key role in biologically active natural products. Pyridones, specifically 2‐pyridone and 2,4‐dihydoxypyridine are an extensive class of compounds with reported occurrence in many natural products. Therefore, the methods for generation of functionalized pyridones are of great interest since their discovery. From traditional coupling to transition metal catalyzed C−H functionalization and transition metal free C−H functionalization, this field has witnessed enormous growth. In the present review, we aim to present a comprehensive overview of pyridone functionalization for young researchers and invite the scientific community to come up with more environment friendly, economic and transition metal free methodologies for corresponding functionalizations. [ABSTRACT FROM AUTHOR] more...
- Published
- 2021
- Full Text
- View/download PDF
50. Investigation of Indole‐3‐piperazinyl Derivatives as Potential Antidepressants: Design, Synthesis, In‐Vitro, In‐Vivo and In‐Silico Analysis.
- Author
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Kumar, Ravi R., Kumar, Vijay, Kaur, Dilpreet, Nandi, Nilay K., Dwivedi, Ashish R., Kumar, Vinod, and Kumar, Bhupinder
- Subjects
- *
ANTIDEPRESSANTS , *MOLECULAR docking , *YOUNG adults , *TEENAGERS , *DRUG standards , *KETAMINE , *INDOLE - Abstract
Depression is declared the second leading cause of disability worldwide. Recently, cases of depression have increased significantly in adolescents, young adults as well as in elder population. Monoamine oxidase‐A (MAO‐A) is considered one of the major targets for the treatment of depression. In the current study, we have designed and synthesized various indole functionalized piperazinyl derivatives and evaluated them for in vitro MAO‐A inhibitory activity and in vivo antidepressant‐like activity. Most of the compounds were found to possess potent MAO‐A inhibitory activity with IC50 values in the sub‐micromolar range along with significant selectivity over MAO‐B. Compounds RP1 and RP9 emerged as the most promising reversible MAO‐A inhibitors with IC50 values of 0.11±0.03 μM and 0.14±0.02 μM and displayed selectivity of 193 folds and 178 folds over Monoamine oxidase‐B (MAO‐B), respectively. In the series, RP1 showed good intracellular ROS inhibitory activity along with neuroprotective properties. These compounds were found nontoxic against SH‐SY5Y cells and explored antidepressant activities. In the in vivo Forced swimming test (FST) and Tail suspension test (TST) studies, RP1 exhibited potential antidepressant‐like behavior similar to standard drug fluoxetine while compound RP9 showed antidepressant‐like activity only in the TST studies. The molecular docking and dynamics studies further supported the results obtained in the in vitro and in vivo studies. Thus, the indole functionalized piperazinyl derivatives were found to be promising ligands and can be developed as new antidepressant molecules. [ABSTRACT FROM AUTHOR] more...
- Published
- 2021
- Full Text
- View/download PDF
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