Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for Michael addition of mercaptans to α,β-unsaturated carbonyl compounds

Copper(II) tetrafluoroborate has been found to be a new and highly efficient catalyst for Michael addition of thiols to α,β-unsaturated carbonyl compounds under solvent-free conditions and in H₂O at room temperature. The reactions are very fast and are completed in 2 min to 1 h affording high yields. The rate of thiol addition was dependent on the steric hindrance at the β-carbon of the α,β-unsaturated carbonyl substrate. In the case of chalcones, the reactions are best carried out in MeOH as solvent.     

Bounds for the generalized Marcum function of the second kind

The Ramanujan Journal - This paper provides elementary proofs for several types of congruences involving multipartitions and self-convolutions of the divisor function. Our computations use...     

ZnO-TiO2 hybrid nanocrystal-loaded,wash durable,multifunction cotton textiles

Life-threatening diseases, especially those caused by pathogens and harmful ultraviolet radiation (UV-R), have triggered increasing demands for comfortable, antimicrobial, and UV-R protective clothing with a long service life. However, developing such textiles with exceptional wash durability is still challenging. Herein, we demonstrate how to fabricate wash durable multifunctional cotton textiles by growing in situ ZnO-TiO₂ hybrid nanocrystals (NCs) on the surface of cellulosic fabrics. The ZnO-TiO₂ hybrid NCs presented high functional efficiency, owing to their high charge transfer/separation. Ultrafine fiber surface pores, utilized as nucleating sites, endowed the uniform growth of NCs and their physical locking. The resulting fabrics presented excellent UV protection factors up to 54, displayed bactericidal efficiency of 100% against Staphylococcus aureus and Escherichia coli, and optimum self-cleaning efficacy. Moreover, the functionalized textiles exhibited robust washing durability, maintaining antibacterial and anti-UV-R efficiency even after 30 extensive washing cycles.

Graphical abstract

     

SH-waves in viscoelastic heterogeneous layer over half-space with self-weight

The effect of gravity, heterogeneity and internal friction on propagation of SH-waves (horizontally polarised shear waves) in viscoelastic layer over a half-space has been studied. Using the method of separation of variables, dispersion equation has been obtained and used to recover the damped velocity of SH-waves. Both the real and imaginary parts of dispersion equation are in well agreement with the classical Love wave equation. It has been observed that heterogeneity of the medium affects the velocity profile of SH-wave significantly. Some other peculiarities have been observed and discussed in our study.     

Influence of growth temperature and post-annealing on an n-ZnO/p-GaN heterojunction diode

We report on an n-ZnO/p-GaN heterojunction diode fabricated from zinc oxide (ZnO) films at various growth temperatures (450, 500, 550, and 600 °C) by RF sputtering. The films were subsequently annealed at 700 °C in N₂ ambient. To investigate the influence of the growth temperature of n-ZnO films, the microstructural, optical, and electrical properties were measured using scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and Hall measurements. The XRD pattern showed the preferred orientation along the c-axis (002) regardless of growth temperature. The PL spectra showed a dominant sharp near-band-edge (NBE) emission. Current–voltage (I–V) curves showed excellent rectification behavior. The turn-on voltage of the diode was observed to be 3.2 V for the films produced at 500 °C. The ideality factor of ZnO film was observed to be 1.37, which showed the best performance of the diode.     

Palladium on carbon–bromobenzene mediated esterification and transesterification

A series of carboxylic acids were converted into their corresponding esters using the Pd/C catalyzed hydrogenation conditions in the presence of catalytic bromobenzene in alcohols and the method could also be applicable for the transesterification of esters. Good to excellent yields were obtained for different aliphatic or aromatic starting materials. The success of this esterification relies on the in situ generation of hydrobromic acid (HBr) from bromobenzene which provides a mild and acidic reaction environment. The palladium catalyst exhibits a remarkable activity and is reusable for up-to three consecutive cycles.     

Molecular and Biochemical Characteristics of Recombinant β-Propeller Phytase from Bacillus licheniformis Strain PB-13 with Potential Application in Aquafeed

Phytic acid is the major storage form of organic phosphorus in nature- and plant-based animal feed. It forms insoluble complexes with nutritionally important metals and proteins that are unavailable for monogastric or agastric animals. Phytases initiate the stepwise hydrolysis of phytic acid and release inorganic orthophosphate. In the present investigation, the phytase gene from a phytase producing Bacillus licheniformis strain PB-13 was successfully expressed in Escherichia coli BL21. Recombinant phytase ‘rPhyPB13’ was found to be catalytically active, with an activity of 0.97 U/mL and specific activity of 0.77 U/mg. The rPhyPB13 was purified to 14.10-fold using affinity chromatography. Similar to other β-propeller phytases, purified rPhyPB13 exhibited maximal activity at pH 6.0–6.5 and 60 °C in the presence of 1 mM Ca²⁺ and was highly active over a wider pH range (pH 4.0–8.0) and high temperature (80 °C). It has shown maximum activity towards Na-phytate as substrate. The observed K _m , V _max and k _cat of purified rPhyPB13 were 1.064 mM, 1.32 μmol/min/mg and 27.46 s^?1, respectively. PhyPB13 was resistant to trypsin inactivation, activated in presence of Ca²⁺ and inhibited in presence of EDTA. Crude rPhyPB13 has good digestion efficiency for commercial feed and soybean meal. These results indicate that PhyPB13 is a β-propeller phytase that has application potential in aquaculture feed.     

Production of Raw Starch-Saccharifying Thermostable and Neutral Glucoamylase by the Thermophilic Mold <Emphasis Type="Italic">Thermomucor indicae-seudaticae</Emphasis> in Submerged Fermentation

Among physical and nutritional parameters optimized by “one variable at a time” approach, four cultural variables (sucrose, MgSO₄ ^.7H₂O, inoculum size, and incubation period) significantly affected glucoamylase production. These variables were, therefore, selected for optimization using response surface methodology. The p-values of the coefficients for linear effect of sucrose and inoculum size were less than 0.0001, suggesting them to be the key experimental variables in glucoamylase production. The enzyme production (34 U/ml) attained under optimized conditions (sucrose, 2%; MgSO₄ ^.7H₂O, 0.13%; yeast extract, 0.1%; inoculum size, 5 × 10⁶ spores per 50 ml production medium; incubation time, 48 h; temperature, 40°C; and pH 7.0) was comparable with the value predicted by polynomial model (34.2 U/ml). An over all 3.1-fold higher enzyme titers were attained due to response surface optimization. The experimental model was validated by carrying out glucoamylase production in shake flasks of increasing capacity (0.25–2.0 l) and 22-l laboratory bioreactors (stirred tank and airlift), where the enzyme production was sustainable. Furthermore, the fermentation time was reduced from 48 h in shake flasks to 32 h in bioreactors.     

Lie-optics, geometrical phase and nonlinear dynamics of self-focusing and soliton evolution in a plasma

It is useful to state propagation laws for a self-focusing laser beam or a soliton in group-theoretical form to be called Lie-optical form for being able to predict self-focusing dynamics conveniently and amongst other things, the geometrical phase. It is shown that the propagation of the gaussian laser beam is governed by a rotation group in a non-absorbing medium and by the Lorentz group in an absorbing medium if the additional symmetry of paraxial propagation is imposed on the laser beam. This latter symmetry, however, needs care in its implementation because the electromagnetic wave of the laser sees a different refractive index profile than the laboratory observer in this approximation. It is explained how to estimate this non-Taylor paraxial power series approximation. The group theoretical laws so-stated are used to predict the geometrical or Berry phase of the laser beam by a technique developed by one of us elsewhere. The group-theoretical Lie-optic (or ABCD) laws are also useful in predicting the laser behavior in a more complex optical arrangement like in a laser cavity etc. The nonlinear dynamical consequences of these laws for long distance (or time) predictions are also dealt with. Ergodic dynamics of an ensemble of laser beams on the torus during absorptionless self-focusing is discussed in this context. From the point of view of new physics concepts, we introduce a stroboscopic invariant torus and a stroboscopic generating function in classical mechanics that is useful for long-distance predictions of absorptionless self-focusing.