Bianchi types I and V bulk viscous fluid cosmological models in f(R,T) gravity theory

In this paper we present non-singular Bianchi types I and V cosmological models, in the presence of bulk viscous fluid and within the framework of f(R,T) gravity theory. Exact solutions to the field equations are obtained by choosing a particular form of the function f(R,T) and a special value for the average scale factor of the model, which corresponds to a time- dependent deceleration parameter. The cosmological models initially accelerate for a certain period of time and thereafter decelerate. The physical and kinematical properties of the models of the universe are discussed.     

Synthesis of polyhydroxylated indolizidines and piperidines from Garner's aldehyde: total synthesis of (−)-swainsonine, (+)-1,2-di-epi-swainsonine, (+)-8,8a-di-epi-castanospermine,pentahydroxy indolizidines, (−)-1-deoxynojirimycin, (−)-1-deoxy-altro-nojirimycin,and related diversity

Diastereoselective and diverse synthesis of polyhydroxylated indolizidines and piperidines have been described, where a common chiral intermediate 2-(hydroxymethyl) piperidine-3-ol is converted into (−)-swainsonine, (+)-1,2-di-epi-swainsonine, (+)-8,8a-di-epi-castanospermine, pentahydroxy indolizidines, (−)-1-deoxynojirimycin, (−)-1-deoxy-altro-nojirimycin, and related diversity. The key steps were hydroxy directed intramolecular aminomercuration, Mitsunobu cyclization, and diastereoselective dihydroxylation.     

Nanosized TiO2 as a Recyclable Heterogeneous Catalyst for the Synthesis of Tetrahydrobenzo[b]pyran Derivatives

An electrochemical reduction method was used for the preparation of TiO₂ nanoparticles in which agglomeration with formation of undesired metal powders is prevented by the presence of ammonium stabilizers. These synthesized nanoparticles were characterized by UV–Visible, XRD, SEM–EDS and TEM analysis techniques. These synthesized nanoparticles of TiO₂ were tested as heterogeneous catalyst for the synthesis of tetrahydrobenzo[b]pyran derivative using three components reaction of aromatic aldehyde, dimedione and malononitrile by simply stirring at room temperature in a solvent free condition.     

Unusual conversion of substituted-3-formylchromones to 3-(5-phenyl-3H-[1,2,4]dithiazol-3-yl)chromen-4-ones: a facile and efficient route to novel 1,2,4-dithiazoles

Substituted 3-formylchromones react with 2-phenyl-4-dimethylamino-1-thia-3-azabuta-1,3-diene (4) or thio-benzamide (7) by heating their toluene solution in a sealed tube to give novel substituted 3-(5-phenyl-3H-[1,2,4]dithiazol-3-yl)chromen-4-ones (6a-e) in high yields.     

Strategic Synthesis of Heptacoordinated FeIII Bifunctional Complexes for Efficient Water Electrolysis

In this research, highly efficient heterogeneous bifunctional (BF) electrocatalysts (ECs) have been strategically designed by Fe coordination (C_R) complexes, [Fe₂L₂(H₂O)₂Cl₂] (C1) and [Fe₂L₂(H₂O)₂(SO₄)].2(CH₄O) (C2) where the high seven C_R number synergistically modifies the electronic environment of the Fe centre for facilitation of H₂O electrolysis. The electronic status of Fe and its adjacent atomic sites have been further modified by the replacement of −Cl⁻ in C1 by −SO₄²⁻ in C2 . Interestingly, compared to C1 , the O−S−O bridged C2 reveals superior BF activity with extremely low overpotential (η) at 10 mA cm⁻² (140 mV_OER, 62 mV_HER) and small Tafel slope (120.9 mV dec⁻¹_OER, 45.8 mV dec⁻¹_HER). Additionally, C2 also facilitates a high-performance alkaline H₂O electrolyzer with cell voltage of 1.54 V at 10 mA cm⁻² and exhibits remarkable long-term stability. Thus, exploration of the intrinsic properties of metal–organic framework (MOF)-based ECs opens up a new approach to the rational design of a wide range of molecular catalysts.     

Catalyst-free one-pot synthesis of 2,4,5-tri- and 1,2,4,5-tetrasubstituted imidazoles

The present work emphasizes catalyst-free 2,4,5-tri- and 1,2,4,5-tetra substituted imidazole synthesis using diversified aldehydes with benzil, ammonium acetate, or amines. Ammonium acetate plays a vital role as a reactant catalyst by dissociating into acetic acid to afford imine and diamine formation to ascertain the 2,4,5-tri- and 1,2,4,5-tetra substituted imidazoles. The key advantages of the current approach are efficient, greener, eco-friendly, and facile, with moderate to excellent yield in shorter reaction time at the temperature of 80°C. Ethanol:water as a solvent makes the reaction process eco-friendly. Overall, the described approach offers a promising route for the efficient and sustainable synthesis of substituted imidazoles, which have a wide range of applications in various fields, including pharmaceuticals, agrochemicals, and materials science.     

Increased Availability of Tryptophan in 5-Methyltryptophan-Tolerant Shoots of Catharanthus roseus and Their Postharvest in vivo Elicitation Induces Enhanced Vindoline Production

Ten 5-methyltryprophan (5-MT)-resistant multiple shoot culture lines in three genotypes of Catharanthus roseus were selected in vitro. The variant shoot lines displayed a differential threshold tolerance limit against the analogue stress, ranged from 20 to 70?mg/l 5-MT in the medium. The lines tolerant to 40?mg/l 5-MT stress were most stable and fast proliferating. All the selected lines in the presence of 5-MT stress recorded increased level of tryptophan in their free amino acid pool. Highest tryptophan accumulation occurred in lines P40, P30, D40, and N40 (i.e., 296.5, 241.0, 200.6, and 202.0???g/g dry wt., respectively). A concomitant increase in the total alkaloid content (2.3?C3.8?% dry wt.) under the analogue stress was also noticed in these lines when compared to 1.0?C1.58?% dry wt. in the respective wild-type shoot maintained on a stress-free medium. The HPLC analysis of the alkaloid extracts of the 5-MT-tolerant lines grown under analogue stress also revealed vindoline as a major constituent with maximum accumulation in lines N40, N30, D30, D40, and P40 (0.046, 0.032, 0.034, and 0.022?% dry wt., respectively). The rooted shoots of 5-MT-tolerant lines were successfully acclimatized under glasshouse environment wherein they grew normally and set seeds. Flowering twigs or leaves excised from 1-year-old glasshouse-grown plants of 5-MT variant lines upon postharvest in vivo elicitation with 30?mg/l 5-MT or 5.0?mg/l tryptophan registered an eight-to-tenfold increment in their vindoline content within 24?C48?h.     

Efficiency enhancement of organic light emitting diode via surface energy transfer between exciton and surface plasmon

Organic light emitting diodes (OLEDs) with surface plasmon (SP) enhanced emission have been fabricated. Gold nanoclusters (GNCs) deposited using thermal evaporation technique has been used for localization of surface plasmons. Size of GNCs and distance of GNCs from the emissive layer have been optimized using steady state and time resolved photoluminescence (PL) results. 3.2 Times enhancement in PL intensity and 2.8 times enhancement in electroluminescence intensity of OLED have been obtained when GNCs of size 9.3 nm has been introduced at a distance of 5 nm from emissive layer. Distance dependence of energy transfer efficiency between exciton and SPs was found to be of 1/R⁴ type, which is typically the dependence for dipole-surface energy transfer.     

A note on the criterion for the elimination of overflow oscillations in fixed-point digital filters with saturation arithmetic and external disturbance

A recently reported criterion for the exponential stability and H_∞ performance of fixed-point digital filters with saturation arithmetic and external disturbance is reviewed. It is shown that there is a technical error in this criterion. A corrected version of the criterion is presented. Finally, a relaxed version of the criterion is made available.     

AVDR: A Framework for Migration Policy to Handle DDoS Attacked VM in Cloud

Wireless Personal Communications - The recent trends of Distributed Denial of Service (DDoS) attacks in cloud computing have revealed a new menace of DDoS attacks called collateral damages on...