Numerical Investigation of Sound Generation due to Laminar Flow Past Elliptic Cylinders

Numerical investigation of sound generation due to unsteady laminar flow past elliptic cylinders has been carried out using direct numerical simulation $(DNS)$ approach at a free-stream Mach number of $0.2$. Effects of aspect ratio $(0.6\le AR\le 1.0)$ and Reynolds number $(100\le Re \le 160)$ on the characteristics of radiated sound fields are analyzed. Two-dimensional compressible fluid flow equations are solved on a refined grid using high resolution dispersion relation preserving $(DRP)$ schemes. Using present $DNS$ data, equivalent noise sources as given by various acoustic analogies are evaluated. Amplitudes and frequencies associated with these noise sources are further related to characteristics of disturbance pressure fields. Disturbance pressure fields are intensified with increase in Reynolds number and aspect ratio. Thus, radiated sound power increases with increase in Reynolds number and aspect ratio. Among various cases studied here, minimum and maximum values of radiated sound power are found at $Re=120$ & $AR=0.6$ and $Re=160$ & $AR=1.0$, respectively. Directivity patterns show that the generated sound fields are dominated by the lift dipole for all cases. Next, proper orthogonal decomposition $(POD)$ technique has been implemented for decomposing disturbance pressure fields. The $POD$ modes associated with the lift and the drag dipoles have been identified. $POD$ analyses also clearly display that the radiated sound fields are dominated by the lift dipole only. Further, acoustic and hydrodynamic modes obtained using Doak's decomposition method have confirmed the patterns of radiated sound field intensities.     

Conditionally Negative Definite Functions

Let \(f:[0,\infty )\rightarrow [0,\infty )\) be an operator monotone function and \(g: \mathbb {R}\rightarrow [0,\infty )\) be a conditionally negative definite(in short cnd) function. We obtain that \(f\circ g:\mathbb {R}\rightarrow [0,\infty )\) is also conditionally negative definite. This generalizes and subsumes several existing results. A versatile direct connection between cnd functions and functions having Weierstrass factorization is established and consequently a reasonable account for cnd functions is presented.     

Ultrasound promoted asymmetric transfer hydrogenation of ketones using Ru(II)arene/amino alcohol catalyst system

Asymmetric transfer hydrogenation of ketones using Ru(II)arene/amino alcohol catalyst system proceeds with significant rate enhancement by ultrasound promotion. Comparison of the silent reactions carried out at 25 degrees C with reactions under sonochemical activation at 25 degrees C clearly showed enhancement in catalytic activity by 5-10 times without significantly affecting the enantioselectivity.     

Microwave‐Assisted Synthesis and Antituberculosis Screening of Some 4‐((3‐(Trifluoromethyl)‐5,6‐dihydro‐[1,2,4]triazolo[4,3‐a]pyrazin‐7(8H)‐l)methyl)benzenamine Hybrids

In the present investigation, a series of 4‐((3‐(trifluoromethyl)‐5,6‐dihydro‐[1,2,4]triazolo[4,3‐a]pyrazin‐7(8H)‐yl)methyl)benzenamine analogs 6a–o were synthesized and characterized by IR, NMR (¹H and ¹³C), and mass spectra. All newly synthesized compounds 6a–o were prepared under conventional and microwave irradiation methods. These compounds obtained in higher yields and in shorter reaction times in the microwave irradiation method when compared with the conventional method. Synthesized compounds 6a–o were inspected for their in vitro antitubercular activity against Mycobacterium tuberculosis H₃₇Ra using an established XTT reduction menadione assay. Among the screened compounds, 6i (IC₅₀: 1.82 μg/mL), 6j (IC₅₀: 1.02 μg/mL), and 6k (IC₅₀: 1.59 μg/mL) showed excellent activity. Furthermore, compound 6i showed MIC₉₀ value of 16.02 μg/mL. In summary, the results indicate the identification of some novel, selective, and specific inhibitors against M. tuberculosis that can be explored further for the potential antitubercular drug.     

Design,Synthesis, In Vitro Antimicrobial,Antioxidant Evaluation,and Molecular Docking Study of Novel Benzimidazole and Benzoxazole Derivatives

A series of novel 2‐substituted benzimidazole and benzoxazole derivatives as a potential antimicrobial and antioxidant agent were synthesized via coupling of N‐methyl‐o‐phenylenediamine or 2‐amino‐phenol with aromatic aldehyde and acid in the presence of polyphosphoric acid as an efficient catalyst as well as solvent by conventional method in short reaction times with excellent yield. The newly synthesized benzimidazole and benzoxazole derivatives were evaluated for antimicrobial and antioxidant activity and exhibited excellent to good activities compared to the standard drugs. Furthermore, the theoretical predictions based on molecular docking against microbial DNA gyrase could provide an insight into the plausible mechanism of action and establish a link between the observed antimicrobial activity and the binding affinity shedding light on specific thermodynamic (bonded and nonbonded) interactions governing the activity. Furthermore, the synthesized compounds were analyzed for absorption, distribution, metabolism, and excretion properties and exhibited potential properties to build up as good oral drug candidates.     

Iodine-transfer polymerization and CuAAC “click” chemistry: A versatile approach toward poly(vinylidene fluoride)-based amphiphilic triblock terpolymers

This study presents the synthesis and properties of linear PVDF-based amphiphilic triblock terpolymers with PS and PEO, [PVDF-b-PS-b-PEO], by adopting a procedure that involves: (a) iodine-transfer polymerization (ITP) of VDF with 1-iodoperfluorohexane (C₆F₁₃I) serving as chain-transfer agent (CTA) to afford C₆F₁₃-PVDF-I, (b) ITP of styrene with the C₆F₁₃-PVDF-I macromolecular-CTA to obtain C₆F₁₃-PVDF-b-PS-I diblock copolymer, (c) end-group exchange from iodo- to azido-group by nucleophilic substitution reaction with NaN_3, and (d) copper-catalyzed azide-alkyne cycloaddition (CuAAC) with alkyne-terminated PEO to achieve C₆F₁₃-PVDF-b-PS-b-PEO triblock terpolymers. The ¹H and ¹⁹F NMR spectroscopy confirmed the presence of all blocks, while gel permeation chromatography traces showed the living nature of ITP technique. The self-assembly of these terpolymers was investigated in films (atomic force microscopy and DSC), as well as in aqueous and organic solvents (DLS). The analysis of crystalline phases based on the FTIR spectroscopy indicated the conversion of PVDF α-phase into α + β-phases and β + γ-phases upon the incorporation of PS and PEO blocks, respectively. The synthesized amphiphilic copolymers were evaluated (fluorescence spectroscopy) as carriers of small hydrophobic molecules in water. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 163–171     

CsF promoted rapid synthesis of spirooxindole-pyran annulated heterocycles at room temperature in ethanol

A newer, versatile, and straightforward synthetic strategy for the construction of functionalized spirooxindole-pyran annulated heterocycles is described. The procedure is based on CsF-promoted rapid tandem Knoevenagel-Michael-Cyclocondensation reaction of isatin, malononitrile, and 4-hydroxycoumarin/barbituric acids/pyrazolone at room temperature in ethanol. This methodology has various advantages like easy operational, excellent yields within short reaction time (3-25 min), and simple isolation of products. The CsF has a dual role as a base and carbonyl activator.     

One‐pot Synthesis of Fully Substituted Pyrimidines Using Amidine and Ketene Dithioacetals as Synthons and Their Antimicrobial Activity

A simple, convenient, and efficient one‐pot synthesis of fully substituted pyrimidines was developed by cyclocondensation of α‐oxo ketene dithioacetals with amidine in the presence of potassium carbonate in good yield. Structures of all the newly synthesized compounds were elucidated by elemental analysis and spectral analysis. All the newly synthesized compounds are tested toward different microorganisms.     

Studies on photodissociation dynamics of butadiene monoxide at 193 nm

Butadiene monoxide (BMO) undergoes the S(0)-->S(1) transition, involving the excitation of both pi and n electrons to pi(*) orbital, at 193 nm. After relaxing to the ground electronic state via internal conversion, BMO molecules undergo intramolecular rearrangement and subsequently dissociate to form unexpected OH radicals, which were detected state selectively by laser-induced fluorescence technique, and the energy state distribution was measured. OH is produced vibrationally cold, OH(nu(")=0,J(")), with the rotational population characterized by a rotational temperature of 456+/-70 K. The major portion (approximately 60%) of the available energy is partitioned into internal degrees of the photofragments, namely, vibration and rotation. A considerable portion (25%-35%) also goes to the relative translation of the products. The Lambda doublet and spin-orbit ratios of OH were measured to be nearly unity, implying statistical distribution of these states and, hence, no preference for any of the Lambda doublet (Lambda+ and Lambda-) and spin-orbit (Pi(3/2) and Pi(1/2)) states. Formation time of the nascent OH radical was measured to be <100 ns. Different products, such as crotonaldehyde and methyl vinyl ketone, were detected by gas chromatography as stable products of photodissociation. A reaction mechanism for the formation of all these photoproducts, transient and stable, is proposed. The multiple pathways by which these products can be formed have been theoretically optimized, and energies have been calculated. Absorption cross section of BMO at 193 nm was measured, and quantum yield of OH generation channel was also determined.     

High-performance thin-layer chromatography densitometric method for the quantification of harmine, harmaline, vasicine, and vasicinone in Peganum harmala

Peganum harmala Linn. seed is a reputed drug of the Indian systems of medicine. We report a simple high-performance thin-layer chromatography (HPTLC) densitometric method for the quantification of 4 alkaloids, viz., harmine, harmaline, vasicine, and vasicinone from P. harmala seed. The 4 compounds were resolved in ethyl acetate-methanol-ammonia (7 + 1 + 0.3, v/v/v) mobile phase. The method was validated for precision, repeatability, and accuracy. Instrumental precision was 0.27, 1.53, 0.39, and 1.15% [relative standard deviation (RSD)] and repeatability of the method was 1.01, 0.79, 0.13, and 1.62% RSD for harmine, harmaline, vasicine, and vasicinone, respectively. Accuracy of the method was checked by a recovery study conducted at 3 different levels, and the average recovery was 97.88% for harmine, 97.69% for harmaline, 98.38% for vasicine, and 98.28% for vasicinone. The 4 compounds were quantified in P. harmala seed using the method, and it was found to contain 0.44, 0.096, 0.25, and 0.0007% (w/w) of each, respectively. The proposed HPTLC densitometric method for the quantification of the 4 compounds was found to be simple, precise, specific, sensitive, and accurate. It can be used for routine quality control of P. harmala seed and has the ability to quantify the 4 marker compounds in the formulations containing P. harmala. It also can be used to quantify any of these marker compounds in other herbal drugs.