A Class of Super Dense Stars Models Using Charged Analogues of Hajj-Boutros Type Relativistic Fluid Solutions

We present a spherically symmetric solution of the general relativistic field equations in isotropic coordinates for perfect charged fluid, compatible with a super dense star modeling. The solution is well behaved for all the values of Schwarzschild parameter u lying in the range 0 < u < 0.1727 for the maximum value of charge parameter K = 0.08163. The maximum mass of the fluid distribution is calculated by using stellar surface density as ρ _b = 4.6888×10¹⁴g cm^?3. Corresponding to K = 0.08 and u _max = 0.1732, the resulting well behaved solution has a maximum mass M = 0.9324M _⊙ and radius R = 8.00 and by assuming ρ _b = 2×10¹⁴g cm^?3 the solution results a stellar configuration with maximum mass M = 1.43M _⊙ and radius R _b = 12.25 km. The maximum mass is found increasing with increasing K up to 0.08. The well behaved class of relativistic stellar models obtained in this work might has astrophysical significance in the study of internal structure of compact star such as neutron star or self-bound strange quark star like Her X-1.     

Conductivity relaxation in Ag+ ion conducting PEO–PMMA–PEG polymer blends

In this paper, the electrical conductivity and relaxation studies in two different temperature regions (T?<?T _m and T?>?T _m) on plasticized PEO–PMMA blend polymer electrolyte system with AgNO₃ salt are reported. The polymer electrolyte system has been prepared by solution cast technique and characterized by X-ray diffraction and differential scanning calorimetry. The conduction and relaxation processes at various temperatures have been investigated in the framework of modulus formalism. The distribution of relaxation times is discussed using Argand plot. Variation in ionic conductivity of polymer blends is discussed with the increase of PEO as well as with temperature.     

Syntheses of 1,5-Benzothiazepines-Part XXXI: Syntheses and Antimicrobial Studies of 10-Substituted-7- (monochlorophenyl/dichlorophenyl)-6H-6a,7-dihydro-6-phenyl[1]benzopyrano[3,4-c]-[1,5]benzothiazepines

Abstract

Two flavindogenides, 3-(2-chlorobenzylidene)-flavanone and 3-(2,4-dichloro- benzylidene)-flavanone reacted with six 5-substituted-2-aminobenzenethiols, the substituents being fluoro, chloro, bromo, methyl, methoxyl, and ethoxyl, to give respective 12 new compounds, 10-substituted-7-(2-chlorophenyl/2,4-dichlorophenyl)- 6H-6a,7-dihydro-6-phenyl[1]benzopyrano[3,4?c][1,5]benzothiazepines (5a–l) in 60–70% yields. The products were characterized on the basis of microanalytical data for elements and IR, ¹ H, and ¹³ C NMR and mass spectral studies. All the synthesized compounds were evaluated for their antimicrobial activity against the bacteria,Escherichia coli and GFC,and the fungi,Aspergillus niger, Aspergillus flavus,and Curvularia lunata.     

Synthesis,Characterization and Catalytic Behaviour of Silica Supported Zinc Salicylaldimine Complex

Zinc salicylaldimine complex immobilized on silica gel was used as a promising catalyst for the transesterification reaction of dimethyl terephthalate (DMT) and ethylene glycol (EG).The catalyst was characterized by Fourier transform infra‐red spectroscopy (FT‐IR), thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS). The product bis‐(2‐hydroxyethyl)terephthalate (BHET)was confirmed by mass and ¹H‐NMR studies. In comparison to zinc acetate i.e., homogeneous catalyst, a polymer supported catalyst showed better stability, catalytic activity and ease of separation from the reaction product. The catalyst can be reutilized during successive catalytic cycles.     

Conductometry and Thermodynamics Study of Metal Dodecyl Sulfates in Aqueous Solution

The aggregation behavior of metal dodecyl sulfates (MDS), [Na¹⁺, Mg²⁺, Mn²⁺, Co²⁺, and Ni²⁺] in water has been studied by electrical conductivity (at 293.15–333.15 K) and surface tension methods (at 303.15 K). Critical micelle concentrations (CMCs), degree of counterion dissociation (β) evaluated from conductivity data. Using law of mass action model, the thermodynamic parameters viz. Gibbs energy (ΔG_m ⁰), enthalpy (ΔH_m ⁰), and entropy (ΔS_m ⁰) were evaluated. The enthalpy of micellization decreases strongly with increasing temperature. ΔG is always negative (thermodynamically favored process) and slightly temperature and counterion dependent. Gibbs energy and entropy exploit micellization as thermodynamic favorable process. The electrostatic repulsions between ionic head groups, which prevent the aggregation, are progressively screened as the ionic character decreases with the size of the counterion. The plots of differential conductivity, (dk/dc) _T,P , versus the total surfactant concentration enables us to determine the CMC values more precisely than the conventional method. Surfactants with strong condense counterion are adapted to rodlike micelle better than to a spherical micelle. The data are explained in terms of molecular characteristics of surfactants viz. degree of dissociation, polar head group size and counterion.     

Solution Behavior of Poly(n-Isopropylacrylamide) in Water: Effect of Additives

The effect of different kinds of additives (electrolytes, nonelectrolytes, hydrotropes, and surfactants) on the cloud point (CP) of low molecular weight and narrow dispersed poly(n-isopropylacrylamide) (PNIPAM) synthesized via reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization was examined. The CP showed a concentration dependent variation and it is greatly modified in the presence of additives. The size of the random polymer coil at 30°C obtained from dynamic light scattering (DLS) measurements is often influenced by the presence of additives. We have explained the effects of different additives on PNIPAM in terms of their interaction with polymer and resultant changes in the coil structure.     

Leak detection in a high-pressure heat exchanger system in a refinery using radiotracer technique

A radiotracer investigation was carried out in a diesel hydrotreater (DHDT) unit in a refinery for leak detection in a breech-lock heat exchanger system. The main objectives of the study were to identify the leaking heat exchanger in a system with six heat exchangers and estimate the leak rate. Bromine-82 as dibromobiphenyl was selected and used as radiotracer for the investigation. The radiotracer was instantaneously injected into the suction end of the feed pump line to the heat exchanger of the DHDT unit. The movement of the tracer was measured at strategically selected locations using NaI(Tl) scintillation detectors. Based upon the results of the radiotracer investigation, it was found that out of six heat exchangers, exchanger E-1F was leaking.     

Numerical Investigation of Graphene as a Back Surface Field Layer on the Performance of Cadmium Telluride Solar Cell

This paper numerically explores the possibility of ultrathin layering and high efficiency of graphene as a back surface field (BSF) based on a CdTe solar cell by Personal computer one-dimensional (PC1D) simulation. CdTe solar cells have been characterized and studied by varying the carrier lifetime, doping concentration, thickness, and bandgap of the graphene layer. With simulation results, the highest short-circuit current (I_sc = 2.09 A), power conversion efficiency (η = 15%), and quantum efficiency (QE~85%) were achieved at a carrier lifetime of 1 × 10³ μs and a doping concentration of 1 × 10¹⁷ cm⁻³ of graphene as a BSF layer-based CdTe solar cell. The thickness of the graphene BSF layer (1 μm) was proven the ultrathin, optimal, and obtainable for the fabrication of high-performance CdTe solar cells, confirming the suitability of graphene material as a BSF. This simulation confirmed that a CdTe solar cell with the proposed graphene as the BSF layer might be highly efficient with optimized parameters for fabrication.     

Green synthesis and characterization of silver nanoparticles by Allium cepa L. to produce silver nano‐coated fabric and their antimicrobial evaluation

This research work was proposed to study the antimicrobial activity of the silver nanocoated fabric with the purpose of producing good dressing and clothing material. We synthesized simple, ecofriendly, cost‐effective and sustainable silver nanoparticles by using the aqueous extract of Allium cepa L. Here, A. cepa L. acts as a good reducing and capping agent that produced stable silver nanoparticles having particle size of range 36 ± 1 to 98 ± 2 nm, Poly dispersiblity index 0.234 ± 0.61 to 1.023 ± 0.33 and Zeta potential ‐12 ± 1.5 mV to ‐26 ± 1.2 mV. The effect of temperature and extract volume used was considered for optimization of synthetic procedure. The nanocoated fabric was characterized for morphological study, size (using transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE‐SEM) and zeta‐potential (Zeta Potentiometer). The presence of functional groups were observed by using attenuated total reflection‐Fourier transform infrared (ATR‐FTIR) and Raman spectroscopy. The crystallinity and structural property of the synthesized silver nanoparticles were studied in terms of Powder X‐ray diffraction (PXRD). An IC₅₀ value and zone of inhibition was studied which demonstrate that the silver nanocoated fabric have an excellent antibacterial property against Gram‐negative (Escherichia coli) and Gram‐positive (Staphylococcus aureus) bacteria. Further nanocoated fabric material was washed (with function of time 0, 10, 25, and 50 laundry cycles) and still retained their anti‐bacterial activity towards both strain. Initially there was 52 μg/ml of silver nanoparticles on the cotton fabric but after 50 laundry cycle in 500 ml of distilled water the fabric showed 92% efficiency against gram positive and 90% efficacy toward gram negative bacteria. It was found that 4.16 μg/ml nano particles leached in case of S. Aureus and 5.2 μg/mL silver nanoparticles leached in case of E. coli. Nanocoated fabric material synthesized using green synthesis was found to be economical with good resistance to washing.     

Visible regime application of zone plate coded incoherent holography

Unlike conventional optical holography which requires coherent radiation, zone plate coded holography (ZPCH) offers the possibility of encoding 3D information of an incoherent radiation source. But ZPCH with its coherent optical reconstruction (COR) is unsuitable to be used in the visible regime. However, proposed digital ZPCH scheme for visible regime uses digital decoding instead of COR and overcomes this limitation. This paper discusses the issues of visible regime ZPCH and presents experimental results of applying the modified scheme to encode and successfully decode a visible source, for the first time, to our knowledge. In addition to imaging of incoherent radiation sources, visible regime incoherent holography may find use in constructing holograms of live cells or objects, like retina, where coherent illumination can be detrimental.