Effect of quantization and positron concentration on shielding potentials in electron-positron-ion plasma

The kinetic theory of plasma has been employed to compute the test-charge potential distributions accounting for quantization effects in magnetized electron-positron-ion (EPI) plasmas. In this regard, the degenerate positrons and electrons are assumed to follow the Fermi-Dirac distribution, while inertial ions are modelled by Maxwellian velocity distribution. By solving the Fourier-transformed Vlasov–Poisson equations, a modified dielectric function and electrostatic potential is obtained. By imposing various constraints on the test-charge speed, the potential profile has been analysed in terms of Debye–Hückel (DH), far-field (FF), and wake-field (WF) potentials. It has been found that the amplitude of DH and FF potentials increases by the inclusion of quantization effects, and it becomes the opposite for the WF potential profile. Furthermore, the variation of positron concentration significantly affects the DH, FF, and WF potentials. The present findings are important to understand the shielding phenomenon in degenerate multi-species plasmas.     

Well Oriented ZnO Nanorods Array: Negative Resistance and Optical Switching

Well‐oriented ZnO nanorods (NRs) arrays were grown on Si, alumina, quartz, and FTO substrates through a ZnO seed layer followed by low temperature wet chemical process. The influence of sputtered ZnO seed layer thickness (100, 50, 32, and 16 nm), annealing temperature and CuO_x coverage on the characteristics of ZnO NRs were investigated in this study. The crystalline structural, chemical, morphological, optical, and electrical properties of ZnO NRs arrays were studied by X‐ray diffraction (XRD), field emission‐ scanning electron microscopy equipped by energy dispersive X‐ray spectroscopy (FE‐SEM/EDX), Raman scattering, UV/Vis ‐ near IR absorption spectroscopy and current‐voltage characteristic. XRD and Raman spectra measurement revealed that the synthesize ZnO displayed hexagonal wurtzite structure. The individual rod diameter, density, and orientation can be controlled by varying the seed layer thickness. The mean diameter and maximum length of ZnO NRs are around 55–66 nm and 282 nm, respectively. ZnO NRs/ ZnO thin film structure shows optical switching and negative differential resistance behavior as applicable to ON/OFF gate and memory devices.     

Efficient Syntheses of Some New Thiophene‐Based Heterocycles

In this effort, 2‐aminothiophene‐3‐carboxylate ( 1 ) was prepared using Gewald's methodology. This 2‐aminothiophene derivative was diazotized and coupled with malononitrile to obtain the nitrile derivative ( 2 ), which was utilized as key synthon for the synthesis of polyfunctionally substituted heterocycles via its reactions with some nitrogen and carbon nucleophiles. On the other hand, a facile and convenient syntheses of thiazolidinone, pyrrolidinone, and chromene derivatives incorporating thiophene moiety via the versatile, readily accessible 2‐aminothiophene‐3‐carboxylate ( 1 ) were also described.     

Solubility prediction of deferiprone in N-methyl-2-pyrrolidone + ethanol mixtures at various temperatures using a minimum number of experimental data

Experimental solubility of deferiprone (DFP) in N-methyl-2-pyrrolidone (NMP) + ethanol (EtOH) mixtures at 293.2, 298.2, 303.2 and 308.2 K was determined and mathematically represented using various models. The trained versions of the van’t Hoff equation, its combined version with log-linear model, Jouyban–Acree model and a combination of van’t Hoff + Jouyban–Acree model were reported to simulate DFP solubility in the binary mixture compositions at various temperatures. The mean percentage deviation (MPD) was used as an accuracy criterion. The obtained overall MPDs for back-calculated and predicted solubility of DFP in NMP + EtOH mixtures varied from 1.1% to 3.2% and 2.6% to 6.6%, respectively. Some of apparent thermodynamic quantities for the dissolution processes of DFP are also reported.     

Highly selective detection of Cu2+ based on a thiosemicarbazone triphenylacetylene fluorophore

A novel thiosemicarbazone fluorophore (3) was successfully synthesized in 3 steps via Sonogashira coupling and Knoevenagel condensation using baker's yeast (Saccharomyces cerevisiae) as a biocatalyst. Compound 3 contains triphenylacetylene, which acts as a fluorophore, and thiosemicarbazone, which acts as a copper probe. Compound 3 exhibited highly selective detection of Cu²⁺ ions based on photoinduced electron transfer (PET) in 10 mM HEPES buffer pH 7.4/propylene glycol (70% (v/v)). A linear relationship was observed for Cu²⁺ concentrations between 0.1 nM and 10 μM, and the detection limit of the method was 0.14 nM. Additionally, 3 was utilized to detect Cu²⁺ in wastewater with satisfactory results, which highlighted its potential for real sample applications.     

Solvent-free synthesis of dibenzo[b,j][1,10]phenanthroline derivatives using Eaton’s reagent as catalyst

A new class of dibenzo[b,j][1,10]phenanthrolines has been prepared. The synthon acridones were achieved in very good yield by a one-pot reaction of 2-amino-5-chloro or 2′-chloro/flouro-substituted benzophenones with 1,2-cyclohexanedione in the presence of freshly prepared Eaton’s reagent (phosphorus pentoxide–methanesulfonic acid) without solvent, through Friedländer synthesis. Then these intermediates were reacted with 2-amino-3,5-dibromobenzaldehyde to afford 1,3-dibromo-10-chloro-8-aryl-6,7-dihydrodibenzo[b,j][1,10]phenanthroline. Also an one-pot reaction between 2?mol of 2-amino-5-chloro aryl benzophenones with 1?mol of 1,2-cyclohexanedione to get 3,10-dichloro-5,8-diaryl-6,7-dihydrodibenzo[b,j][1,10]phenanthroline has also been reported. The newly synthesized structures of the compounds were deduced by spectroscopic techniques.     

Parabola-Hyperbola P-H kinetic model for NR sulphur vulcanization

A Parabola-Hyperbola (P-H) kinetic model for NR sulphur vulcanization is presented. The idea originates from the fitting composite Parabola-Parabola-Hyperbola (P-P-H) function used by the authors in [1,2] to approximate experimental rheometer curves with the knowledge of a few key parameters of vulcanization, such as the scorch point, initial vulcanization rate, 90% of vulcanization, maximum point and reversion percentage. After proper normalization of experimental data (i.e. excluding induction and normalizing against maximum torque), the P-P-H model reduces to the discussed P-H composite function, which is linked to the kinetic scheme originally proposed by Han and co-workers [3]. Typically, it is characterized by three kinetic constants, where classically the first two describe incipient curing and stable/instable crosslinks and the last reproduces reversion.The powerfulness of the proposed approach stands into the very reduced number of input parameters required to accurately fit normalized experimental data (i.e. rate of vulcanization at scorch, vulcanization at 90%, maximum point and reversion percentage), and the translation of a mere geometric data-fitting into a kinetic model. Kinetic constants knowledge from simple geometric fitting allows characterizing rubber curing also at temperature different from those experimentally tested.The P-H model can be applied also in the so-called backward direction, i.e. assuming Han's kinetic constants known from other models and deriving the geometric fitting parameters as result.Some existing experimental data available, relying into rheometer curves conducted at 5 different temperatures on the same rubber blend are used to benchmark the P-H kinetic approach proposed, in both backward and forward direction. Very good agreement with previously presented kinetic approaches and experimental data is observed.     

Viscosity based droplet size controlling in negative pressure driven droplets generator for large‐scale particle synthesis

The poor control and regulation of droplets limit the applications of negative pressure driven droplet generator (NPDDG). Here, we present a simple method to control droplet size in NPDDG via varying the oil viscosity. Depending on the infinite intersolubility of high viscous mineral oil and low viscous hexadecane, we obtain a series of oils with kinematic viscosities linearly varied from 4.2 to 194.6 mm²/s. By using these oils as continuous phases, monodisperse droplets are fabricated with controllable size in NPDDG. This viscosity‐based droplet regulation method is effective, reliable, and compatible with scale‐up processes. Compared with droplet generator driven by positive pressure, the presented method can fabricate hydrogel particles massively, without complicated multilayer chip structure and complex fluid controlling, which may extend the potential of NPDDG in droplets based high‐throughput assay or large‐scale materials synthesis.     

A novel method for the determination of diffusion coefficients in amorphous poly(3-hydroxybutyrate)

A novel approach is proposed for the determination of the diffusion coefficient of certain drugs in amorphous poly(hydroxybutyrate) (PHB), which can be a reliable alternative to the conventional permeation based measurements. The method requires the preparation of PHB films with various concentrations of the drug and if the latter absorbs in the visible wavelength range, its concentration gradient in the polymer film as well as the time dependence of the latter can be analyzed quantitatively by following changes in color. Color can be converted into concentration with the help of adequate calibration and thus the dependence of additive concentration on space (x) and time (t), i.e. the c(x,t) function, can be determined relatively easily. The fitting of the numerical solution of Fick's second law onto the measured values provides directly the targeted diffusion coefficient. The comparison of diffusion coefficients obtained by the proposed approach to values published in the literature proved that the new method provides reliable results and requires reasonable time and effort at the same time.     

Thermoelastoplastic axisymmetric stress-strain state of laminated orthotropic shells

A method is proposed for the numerical analysis of the thermoelastoplastic stress-strain state of laminated shells of revolution, made of isotropic and orthotropic materials, under axisymmetric loading. The method is based on the Kirchhoff-Love hypotheses for a layer stack, the theory of deformation along paths of small curvature for isotropic materials, and Hills theory of flow with isotropic hardening for orthotropic materials. The problem is solved by the method of successive approximations. A numerical example is given.__________Translated from Prikladnaya Mekhanika, Vol. 40, No. 12, pp. 84–91, December 2004.