Nonlinear Optical Switching in Regioregular Porphyrin Covalent Organic Frameworks

Covalent organic frameworks (COFs) have garnered immense scientific interest among porous materials because of their structural tunability and diverse properties. However, the response of such materials toward laser‐induced nonlinear optical (NLO) applications is hardly understood and demands prompt attention. Three novel regioregular porphyrin (Por)‐based porous COFs—Por‐COF‐HH and its dual metalated congeners Por‐COF‐ZnCu and Por‐COF‐ZnNi—have been prepared and present excellent NLO properties. Notably, intensity‐dependent NLO switching behavior was observed for these Por‐COFs, which is highly desirable for optical switching and optical limiting devices. Moreover, the efficient π‐conjugation and charge‐transfer transition in ZnCu‐Por‐COF enabled a high nonlinear absorption coefficient (β=4470 cm/GW) and figure of merit (FOM=σ₁/σ_o, 3565) value compared to other state‐of‐the‐art materials, including molecular porphyrins (β≈100–400 cm/GW), metal–organic frameworks (MOFs; β≈0.3–0.5 cm/GW), and graphene (β=900 cm/GW).     

Multielemental characterisation of cobalt by glow discharge quadrupole mass spectrometry

Multielemental determination and the assessment of purity of cobalt metal used in the preparation of Ni-based super-alloys have been carried out by glow discharge quadrupole mass spectrometry (GD-QMS). Relative sensitivity factors (RSF) generated from certified iron matrix reference samples (NIST 663 and 664 low alloy steel pin standards) could be used for the determination of different trace element constituents of the sample. Different wet chemical procedures were also carried out for the determination of the trace constituents in the sample. The GD-QMS results are in reasonably good agreement with those obtained from wet chemical procedures, validating the use of the RSF values generated on low alloy steel standards for the computation of trace element concentrations in cobalt metal. A variety of molecular ions formed through the reaction of cobalt (matrix) with the discharge gas (argon) were also detected.     

Extractive spectrophotometric determination of molybdenum as a thiocyanate-2-acetylpyridinethiosemicarbazone complex

A new spectrophotometric method for the determination of molybdenum is based on the extraction of the orange red molybdenum thiocyanate-2-acetylpyridinethiosemicarbazone complex into chloroform from hydrochloric acid. The complex has an absorption maximum at 470 nm with a molar absorptivity of 1.7 × 10⁴ liters mol^?1 cm^?1. Beer's law is valid from 0.1 to 6.5 ppm of molybdenum. The equilibrium shift method indicated a 1:4:2 complex. The method has been used successfully for the determination of molybdenum in molybdenum steels.     

Validated liquid chromatography–tandem mass spectrometry method for simultaneous quantitation of bendamustine and copanlisib in mouse plasma: Application to a pharmacokinetic study in mice

In this study, we report the development and validation of an LC–tandem mass spectrometry method for the simultaneous quantitation of bendamustine and copanlisib in mouse plasma as per the US FDA regulatory guidelines. The sample processing involves extraction of bendamustine and copanlisib along with internal standard (IS; warfarin) from 50 μL mouse plasma using a liquid–liquid extraction method. The chromatographic separation of bendamustine, copanlisib and the IS was achieved on an Atlantis dC₁₈ column using an isocratic mobile phase (5 mM ammonium acetate:methanol, 20:80 v/v). Bendamustine, copanlisib and the IS eluted at 0.88, 1.39 and 0.74 min, respectively, with a total run time of 2.5 min. The calibration curve ranged from 3.99–2996 and 4.33–3248 ng/mL for bendamustine and copanlisib, respectively. Inter- and intra-day precision and accuracy, stability in processed samples and upon storage, dilution integrity and incurred sample reanalysis were investigated for both the analytes. The intra- and inter-day precisions were in the ranges of 2.01%–5.05% and 2.74%–6.13% and 1.98%–7.64 and 8.62%–9.04% for bendamustine and copanlisib, respectively. Stability studies showed that both analytes were stable on bench top for 6 h, in auto-sampler for 24 and at −80°C for 30 days. The validated method was successfully applied to a pharmacokinetic study in mice.     

Synthesis,antioxidant, and antimicrobial activity of 3-(1H-indole-3-carbonyl)-2H-chromen-2-ones

A simple and convenient method for the one-pot synthesis of 3-(1H-indole-3-carbonyl)-2H-chromen-2-one derivatives from the reaction of 3-cyanoacetyl indole and salicylaldehyde in the presence of Na₂CO₃ in water: methanol (1:1) is described. Wider substrate scope, high yields, operational simplicity, and simple purification process make the protocol highly applicable in the synthesis of 3-(1H-indole-3-carbonyl)-2H-chromen-2-ones. For the first time, in vitro antioxidant and antimicrobial activity was studied. Compounds 5e , 7a , and 7b exhibits good radical scavenging ability against DPPH free radical. Compounds 7b , 5f , and 5g possess lower EC₅₀ values than the Standards AA and BHA and thus proving their high reducing power. Compounds 5d and 5f show good antibacterial activity against gram-positive bacteria (MRSA) while compounds 5c , 7a , and 7b exhibits good antibacterial activity against Bacillus sp. Compounds 5b and 5e show good antibacterial activity against gram negative bacterial strains (Escherichia coli, Klebsiella pneumoniae) and compounds 5g and 5h exhibits good antifungal activity against Candida albicans.     

Low temperature fluorination of sulphur compounds with elemental fluorine

Low temperature fluorination technique is adopted for fluorination of the following sulphur compounds in freon-11 medium (1) Sulphur dioxide (2) Thionyl chloride (3) Sulphuryl chloride (4) Tetrasulphur tetra nitride and (5) Sulphur bromide. All the compounds undergo oxidative fluorination to give rise to sulphur-fluorine compounds except sulphuryl chloride which resists fluorination. Sulphuryl chloride thus behaves as a good solvent medium for fluorination of other reactive compounds like elemental sulphur. Details of the experimental procedures adopted and the identification of the products will be presented.     

Steady flow generated by the differential rotation of a porous disk of finite thickness

When a body of fluid bounded by a porous disk of finite thickness is disturbed from a state of rigid rotation by an enhanced (or reduced) angular velocity of the disk, a few authors followed Darcys model and observed that the centrifugal pumping occurs through the entire porous layer regarded as a convection zone. The shear stress can develop only at the edge of the porous layer. We use a porous disk of high permeability that allows the fluid in the porous disk to deform in response to the changing angular velocity. Based on the Birkmans model, we solve for the steady non-linear flow and observe that there arises (i) a convection zone of nearly uniform angular velocity at the boundary (within the porous layer) and (ii) a transition zone adjacent to the convection zone which provides a smooth transition to the interior. This makes the model relevant to some astrophysical situations as described by some authors [1, 3]. The two point boundary value problem is solved subject to the boundary conditions, the far field conditions, and the matching conditions at the fluid-porous medium interface. The solution is obtained using a numerical procedure known as the method of Adjoints.Received: June 13, 2002; revised: July 7, 2003     

Thin films of metal-organic compounds and metal nanoparticle-embedded polymers for nonlinear optical applications

Thin films based on two very different metal-organic systems are developed and some nonlinear optical applications are explored. A family of zinc complexes which form perfectly polar assemblies in their crystalline state are found to organize as uniaxially oriented crystallites in vapor deposited thin films on glass substrate. Optical second harmonic generation from these films is investigated. A simple protocol is developed for thein-situ fabrication of highly monodisperse silver nanoparticles in a polymer film matrix. The methodology can be used to produce free-standing films. Optical limiting capability of the nanoparticle-embedded polymer film is demonstrated     

Hopf-Cole transformation to some systems of partial differential equations

In this paper we study a system of nonlinear partial differential equations which we write as a Burgers equation for matrix and use the Hopf-Cole transformation to linearize it. Using this method we solve initial value problem and initial boundary value problems for some systems of parabolic partial differential equations. Also we study an initial value problem for a system of nonlinear partial differential equations of first order which does not have solution in the standard distribution sense and construct an explicit solution in the algebra of generalized functions of Colombeau. Received November 1999     

Problems on matchings and independent sets of a graph

Let $G$ be a finite simple graph. For $X?V\left(G\right)$, the difference of $X$, $d\left(X\right)?\left|X\right|?\left|N\left(X\right)\right|$ where $N\left(X\right)$ is the neighborhood of $X$ and $max\{d\left(X\right):X?V\left(G\right)\}$ is called the critical difference of $G$. $X$ is called a critical set if $d\left(X\right)$ equals the critical difference and $\ker \left(G\right)$ is the intersection of all critical sets. $\mathrm{diadem}\left(G\right)$ is the union of all critical independent sets. An independent set $S$ is an inclusion minimal set with$d\left(S\right)>0$ if no proper subset of $S$ has positive difference.A graph $G$ is called a König–Egerváry graph if the sum of its independence number $\alpha \left(G\right)$ and matching number $\mu \left(G\right)$ equals $\left|V\left(G\right)\right|$.In this paper, we prove a conjecture which states that for any graph the number of inclusion minimal independent set $S$ with $d\left(S\right)>0$ is at least the critical difference of the graph.We also give a new short proof of the inequality $\left|\ker \left(G\right)\right|+\left|\mathrm{diadem}\left(G\right)\right|\le 2\alpha \left(G\right)$.A characterization of unicyclic non-König–Egerváry graphs is also presented and a conjecture which states that for such a graph $G$, the critical difference equals $\alpha \left(G\right)?\mu \left(G\right)$, is proved.We also make an observation about $\ker \left(G\right)$ using Edmonds–Gallai Structure Theorem as a concluding remark.