Substituted Thiadiazole, Oxadiazole, Triazole and Triazinone as Antimicrobial and Surface Activity Compounds

Stearic acid ( 1 ) was utilized as a new cheap starting material in the manufacture of important biologically active heterocycles as thiadiazole, oxadiazole, triazole and triazinone derivatives ( 2 – 11 ) by treating with different nucleophiles. These heterocycles bears active hydrogen atom (SH, NH and NH₂) which could be propoxylated by different moles of propylene oxide (5, 10, 15 mol) to produce nonionic compounds ( 12 – 21 ) a – c having functions as surface and antimicrobial activities. The structural elucidation of these compounds is based on IR, ¹H NMR, ¹³C NMR and elemental analysis. The surface properties (surface and interfacial tension, cloud point, witting time, foaming properties and emulsion stability) and the biodegradability were screened beside these compounds have been tested for their antimicrobial activity.     

Multiple access interference cancelation technique in optical CDMA systems

This paper presents a simple and efficient multiple access interference (MAI) cancelation technique in optical code division multiple access (OCDMA) system. The proposed technique is based on hybrid frequency shift keying (FSK) with an enhanced modified prime code as a signature sequence for coding techniques. Coherent FSK modulation along with incoherent demodulation using Arrayed-Waveguide Grating has been examined in the transceiver structure. In the proposed technique, a reference signal is constructed by using one of the addressed spreading sequences, and MAI cancelation is performed by subtracting the reference signal from the received signal of the desired user. The performance of the proposed FSK-OCDMA system is compared with the performance of the existing pulse position modulation (PPM)–OCDMA system. The simulation results reveal that the bit-error rate performance of the proposed technique is superior to the performance of the pulse position modulation (PPM) technique. Also, the results indicate that the proposed technique is very power efficient, and when the bit rate is constant, the network capacity can be expanded to accommodate a large number of simultaneous active users with low error rate. Moreover, the proposed technique simplifies the hardware of the receiver design.     

A Study on the Thixotropy of Egyptian Bentonite Suspensions

The rheology behavior of water bentonite suspensions has been studied through recording the viscosity measurements to study the thixotropy of the suspensions using local Egyptian bentonite at 5.0%, 6.40%, and 7.5.0% concentrations in the a presence of different salt concentration as 0.0 M, 0.01 M, and 0.1 M NaCl according to API stander, rheological data was calculated by viscometer, deriving first the D0 curve, from 600 to 3 rpm, followed by a typical thixotropic loop, getting the U curve from 3 to 600 rpm, and then the D curve from 600 to 3 rpm. Three rheograms have been derived for each suspension after intensive preshearing, from high to low, from low to high, and from high to low shear rates. Positive thixotropy is observed for all suspensions at 0.0 M and 0.01 M but not at 0.1 M salt concentrations. Thixotropic indexes computed from the normal thixotropic loop, low to high to low shear rates, have been computed and vary from positive to negative. The higher the bentonite concentration, the higher the index for the suspensions with no salt, while in the presence of salt, variations of the thixotropy index are obtained with the degree of variation dependent on bentonite concentration and salt concentration The suspension with no salt and 0.01 M salt exhibited thixotropy, estimated from the D0-U curves, while the 0.1-M suspensions showed no thixotropy. Thixotropy indices vary and depend on bentonite type and concentration and on the presence and amount of salt.     

Effects of Surfactants on the Properties of Styrene/Methacrylate–Type Superplasticizer in Cement Paste

Copolymer emulsion lattices based on styrene (St) with methacrylate monomers, were synthesized with composition ratio (5/5) in the presence of a co-surfactants that consists of dodecyl benzene sodium sulfonate with polyvinyl alcohol (DBSS/PVA) and DBBS with polyoxyethylene glycol monomethyl ether (DBBS/POE). The obtained latices were characterized by ¹H NMR, rheological and morphological techniques. The effect of latices on the physicomechanical properties of ordinary Portland cement (OPC) pastes was investigated. The results showed that the addition of water mixed to the cement with copolymer improves most of the specific characteristics of OPC.     

The beneficial effect of ruthenium additions on the passivation of duplex stainless steel corrosion in sodium chloride solutions

The effect of varying ruthenium contents of 0.00, 0.14, 0.22, and 0.28% on the corrosion of 22%Cr-9%Ni-3%Mo duplex stainless steel (DSS) after different immersion intervals in 3.5% NaCl solutions has been investigated. The study was carried out using open-circuit potential, potentiodynamic cyclic polarization, chronoamperometry, electrochemical impedance spectroscopy, and weight-loss measurements. Particular attention was paid to the effect of Ru on the pitting corrosion of DSS in the chloride solutions. Electrochemical measurements indicated that the presence of Ru passivates the DSS alloy by decreasing its corrosion parameters. Furthermore, it shifts the corrosion and pitting potentials to more positive values. This effect was found to increase with increasing Ru content and also with increased immersion time of the alloy in the chloride solution before measurements. Weight-loss time data after varied exposure periods (4-20 days) showed that the weight-loss and corrosion rate of DSS significantly decrease with increasing Ru contents.     

Flow and heat transfer over shallow cavities

The flow over a shallow cavity heated with constant heat flux form the bottom side has been studied experimentally and numerically. In the experimental part, pressure coefficient and Nusselt number have been measured along the cavity floor. In the numerical simulation, the conservation equations of mass, momentum, and energy have been solved. The standard k–? turbulence model is used to account for the turbulent fluctuations. In both experimental and numerical part, the effect of changing cavity aspect ratio and Reynolds number has been studied. It is found that, a single elongated eddy has been formed for aspect ratio lower than 7. As the aspect ratio increases the flow impinges with the cavity floor creating two eddies, one beside the upstream cavity side and the second beside the downstream cavity side. Local Nusselt number along the cavity floor is affected mainly by the flow structure inside the cavity and the average Nusselt number has increased with increasing the aspect ratio up to 10 and with increasing Reynolds number. A correlation for the average Nusselt number, as a function of Reynolds number and cavity aspect ratio, is developed.     

Application of prepared waterborne polyurethane extended with chitosan to impart antibacterial properties to acrylic fabrics

In this study, isophorone diisocyanate (IPDI), 2,2-bis (hydroxylmethyl)-propionic acid and polyethylene glycol (PEG) were employed to polymerize waterborne polyurethane. The polyurethane prepolymer was extended with chitosan of two different molecular weight (100,000 and 150,000), and used as finishing agent for acrylic fabrics. The antibacterial activity of the acrylic fabric treated with the polyurethane-chitosan solution was improved even after 15 washing times. Pretreatment of acrylic fabrics with hydrazine hydrate was found to improve the uptake of the polymer by the fabric. The effects of hydrazine and polyurethane treatments on some of the inherent properties of acrylic were assessed. The functional groups of polyurethane prepolymer as well as polyurethane extended with chitosan were confirmed with the analysis of the spectra of Fourier transform infrared spectroscopy (FT-IR).     

Delamination Buckling and Growth in Rings under Pressure

A delaminated composite ring under external pressure is studied to understand the effect of curvature on delamination buckling and growth. Examples with differing crack lengths and delamination locations were considered. In all cases, the delamination surfaces come in contact rather early in the loading history, no matter what the initial imperfections are assumed to be. Furthermore, the delaminated part never becomes separated from the main ring. The modes of buckling given by standard linear stability analysis do not play any role in the behavior. Strain energy release rates were computed with the objective of predicting possible crack growth. Because of the contact, total energy release rate is dominated by the shear mode. Because the critical values of energy release rates are generally much higher in the shear mode than in the opening mode, one may conclude that shells tend to be more delamination tolerant than plates in which the opening modes tend to dominate.     

Inhibition of copper corrosion in acidic chloride pickling solutions by 5-(3-aminophenyl)-tetrazole as a corrosion inhibitor

Inhibition of copper corrosion in acidic chloride pickling (0.5 M HCl) solutions by 5-(3-Aminophenyl)-tetrazole (APT) as a corrosion inhibitor has been studied using potentiodynamic polarization, chronoamperometry (CA), electrochemical impedance spectroscopy (EIS), weight-loss and Raman spectroscopy investigations. Electrochemical measurements showed that the presence of APT and the increase of its concentration significantly decrease the cathodic, anodic, and corrosion currents as well as corrosion rates. This effect also decreases the dissolution currents of copper at 200 mV vs. Ag/AgCl, and greatly increases surface and polarization resistances and inhibition efficiency as indicated by CA and EIS measurements. Weight-loss data revealed that the corrosion rate of copper decreases to a minimum and the inhibition efficiency increases to a maximum in the presence of APT and upon increasing of its concentration even after 72 h of copper coupons immersion. Comparing the Raman spectrum obtained on the copper surface after its immersion in HCl solution containing 1.0 mM APT for 72 h to the spectrum obtained for the solid APT alone indicated that APT molecules inhibit the corrosion of copper via their adsorption onto its surface.     

Complex susceptibility analysis of magneto-fluids: Optical band gap and surface studies on the nanomagnetite-based particles

An aqueous stable magnetic fluid containing Fe₃O₄ nano-particles with a mean diameter of 4–7 nm, which is in the range of super-paramagnetism, is prepared. The particles are synthesized via co-precipitation method from ferrous and ferric solutions. X-ray diffraction, transmission electron microscopy, transformer method are used to study the physical properties of the magnetic fluids and powders. A method is given to analyze and resolve the real and imaginary parts of the measured complex susceptibility of magnetic fluids. The band gap parameters of the magneto-nanopowders such as the direct-, indirect-band gap energies, Fermi energy and Urbach energy are determined. A comparative study between the different techniques used to calculate the powder particle size is presented. Adsorption of nitrogen gas is used to identify and determine the particles mean diameter and to study their microstructure, the magnetic properties and surface porosity. The study showed that the total pore system of the magnetic nano-powders consists mainly of mesopores.