Synthesis and fluorescence properties of substituted 7‐aminocoumarin‐3‐carboxylate derivatives

4‐Trifluoromethyl‐ or 6‐bromo‐substituted 7‐diethylaminocoumarin‐3‐carboxamide derivatives 2 and 3, each containing a maleimide have been synthesized as potential fluorescent labeling reagents for thiol groups in proteins and their fluorescence properties have been determined. The 4‐trifluoromethyl substituted compound 2 has a significantly greater Stokes shift than the comparable compound lacking this group, but both the new coumarins have low fluorescence quantum yields (?_f). When a 4‐trifluoromethyl substituent is present, the 3‐carboxamide is unusually labile to hydrolysis. Bromination of ethyl 7‐diethylaminocoumarin‐3‐carboxylate 17 gave the 6‐ and 8‐bromo derivatives 18 and 19 respectively, and also the 8‐bromo‐7‐monoethylamino compound 20. ?_f for the latter compound is 100‐fold greater than for its diethylamino analogue 19. Fluorescence lifetime measurements support an interpretation based on the twisted intramolecular charge transfer (TICT) model to explain these large differences in ?_f.     

Recovery of actinides extracted by Truex solvent from high level waste using complexing agents

This work deals with the batch studies on stripping of actinides extracted by a mixture octyl(phenyl)-N,N-diisobutyl-carbamoylmethylphosphine oxide (CMPO) and tri-n-butyl phosphate (TBP) in n-dodecane (Truex solvent) from simulated high level waste (HLW) solution. The stripping of americium and plutonium from acid-bearing CMPO-TBP mixture is carried out using a mixture of weak acid, weak base and complexing agent as strippant. A mixture of formic acid, hydrazine hydrate and citric acid appeared to be best suited for efficient stripping of americium and plutonium. With appropriate modifications in the concentration of individual constitutents, this strippant can be used for the recovery of actinides from loaded Truex solvent with any acid content.     

Thermal degradation kinetics of thermoresponsive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) copolymers prepared via RAFT polymerization

Reversible addition-fragmentation chain transfer polymerization at 70 °C in N,N-dimethylformamide was used to prepare poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) copolymers in various compositions to afford well-defined polymers with pre-determined molecular weight, narrow molecular weight distribution, and precise chain end structure. The copolymer compositions were determined by ¹H NMR spectroscopy. The reactivity ratios of N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMA) were calculated as r _NIPAM = 0.838 and r _DMA = 1.105, respectively, by the extended Kelen–Tüdös method at high conversions. The lower critical solution temperature of PNIPAM can be altered by changing the DMA content in the copolymer chain. Differential scanning calorimetry and thermogravimetric analysis at different heating rates were carried out on these copolymers to understand the nature of thermal degradation and to determine its kinetics. Different kinetic models were applied to estimate various parameters like the activation energy, the order, and the frequency factor. These studies are important to understand the solid state polymer degradation of N-alkyl substituted polymers, which show great potential in the preparation of miscible polymer blends due to their ability to interact through hydrogen bonding.     

Electroanalytical Sensor for Diabetic Foot Ulcer Monitoring with Integrated Electronics for Connected Health Application

L‐tyrosine is an amino acid, the concentration of which is found to be highly elevated in patients suffering from diabetic foot ulcer (DFU). The latter proves to be fatal when it turns out chronic and may lead to amputation. The conventional clinical diagnostic methods are costly and time consuming, in which case, the condition of patient(s) may deteriorate long before proper treatment commences. Herein, we report the development of smart band‐aid for real time monitoring of L‐tyrosine by employing enzymatic bio‐sensor using α‐MnO₂/tyrosinase. The smart band‐aid was further integrated with portable electronics capable of wireless data transmission to a personal digital assistant, and its tyrosine sensing performance was evaluated. Anodic current was found to vary linearly with the concentrations of L‐tyrosine in the range of 5 nM–500 μM. The developed sensor displayed a limit of detection and sensitivity of 0.71 nM and 0.67 μA/nM/mm² respectively, with a stability of 25 days. The developed sensor was validated using a commercial impedance analyzer. The impedance response was found to be consistent with the cyclic voltammogram obtained and demonstrated to be a linear function of tyrosine concentration. The developed sensing platform combines early diagnosis with connected health technologies, thus, fitting well into modern healthcare needs.     

Synthesis of Aryl Sulfides by Decarboxylative C?S Cross‐Couplings

Without the need for organohalide precursors , the convenient and general synthesis of aryl (or diaryl) sulfides can be achieved by using aryl carboxylic acids and thiols or disulfides for decarboxylative C? S cross‐coupling catalyzed by a bimetallic system (see scheme).

     

Some new solitary and travelling wave solutions of certain nonlinear diffusion-reaction equations using auxiliary equation method

Attempts are made to look for the soliton content in the exact solutions of certain types of nonlinear diffusion-reaction (DR) equations with the quadratic and cubic nonlinearities. Such equations may arise in a variety of contexts in physical problems. In this Letter using the auxiliary equation method, some new solitary and travelling wave solutions of such nonlinear DR equations are obtained in a very general form. Several interesting special cases of these general solutions are also discussed.     

Leucosceptrine--a novel sesterterpene with prolylendopeptidase inhibitory activity from Leucosceptrum canum

A novel sesterterpene, leucosceptrine, was isolated from the medicinal plant Leucosceptrum canum from Nepal. The structure was determined by single-crystal X-ray diffraction and spectroscopic techniques. The biosynthesis of leucosceptrine (1) is proposed here. Leucosceptrine (1) exhibited prolylendopeptidase inhibitory activity.     

Low-temperature synthesis of hexagonal barium ferrite (BaFe<Subscript>12</Subscript>O<Subscript>19</Subscript>) nanoparticles by annealing at 450 °C followed by quenching

Citrate precursor method has been used to obtain nanosized particles of barium hexaferrite at low temperatures. Samples were annealed at 450 °C for 3 and 5 h. Quenching of the third sample was done by taking the crucible out from the muffle furnace after annealing it for 5 h and putting it abruptly into an ice bath. The saturation magnetization has been found to be 4.36 and 0.04 emu g^?1 for the samples obtained upon annealing at 450 °C for 3 and 5 h, respectively, while that of the quenched sample has been found to be 4.61 emu g^?1. In case of the sample obtained after 5-h annealing, the squareness value was found to be maximum indicating significance in memory and switching applications. For the quenched and the 3-h annealing products, the magnetic data values are similar. Creation of spin disorders on the surface upon prolonged annealing, due to disappearance of oxygen ions and subsequent breakage of superexchange interactions between cations, has been undone upon quenching. The XRD and TEM data indicate that the particle size (9–17 nm) gets lower in case of the quenched samples. Photoluminescence study of the quenched sample furnished prominent peaks in UV, visible and near-IR regions under 200-nm excitation. The TG–DSC data were analysed for the kinetic parameters, activation energy (E), pre-exponential factor (A) using the Kissinger isoconversion and the Ozawa–Flynn–Wall methods for the first-step decomposition of the quenched sample.     

Semi-infinite medium with a cylindrical inclusion twisted by an annular die

The problem considered is that of torsion of an elastic half-space consisting of two materials which are separated by a cylindrical surface. It is assumed that there is perfect bonding at the common cylindrical surface. The torque is applied to the half-space through an annular rigid disc which is bonded to both materials. By use of integral transforms and the theory of dual integral equations the problem is reduced to that of solving a pair of simultaneous Fredholm integral equations of the second kind. These simultaneous integral equations are solved numerically. The numerical results obtained are exhibited graphically.Research for this paper was partially supported by the Natural Sciences and Engineering Research Council of Canada through NSERC Grant No. A4177.     

On the explosive instability in a three‐species food chain model with modified Holling type IV functional response

In earlier literature, a version of a classical three‐species food chain model, with modified Holling type IV functional response, is proposed. Results on the global boundedness of solutions to the model system under certain parametric restrictions are derived, and chaotic dynamics is shown. We prove that in fact the model possesses explosive instability, and solutions can explode/blow up in finite time, for certain initial conditions, even under the parametric restrictions of the literature. Furthermore, we derive the Hopf bifurcation criterion, route to chaos, and Turing bifurcation in case of the spatially explicit model. Lastly, we propose, analyze, and simulate a version of the model, incorporating gestation effect, via an appropriate time delay. The delayed model is shown to possess globally bounded solutions, for any initial condition. Copyright © 2017 John Wiley & Sons, Ltd.