Effect of SiO2 Addition on Chromium Transitions in Borate Glasses

Silicon - Melt-quenching technique was used to prepare borosilicate glasses of composition xSiO2- (75-x) B2O3–24.7Li2O-0.3Cr2O3 (x = 0, 10, 20, 30, 40 and 50 mol%). With...     

Application of nanostructured titanium dioxide pigments in paper coating: a comparison between prepared and commercially available ones

Nano-TiO₂ pigments in pure crystallographic anatase and rutile phases have been successfully prepared by hydrothermal at 120°C and hydrolysis methods, respectively. The laboratory-prepared pigments were characterized parallel to two commercial pigments of the same crystal structure. All pigments were applied in paper coating mixtures, and their influence on coated paper properties was systematically investigated. X-ray diffraction investigation showed that the laboratory-prepared pigments using the hydrothermal method at 120°C were pure anatase, whereas hydrolysis method produced pure rutile phase pigment. The application of the prepared nanopigments and the corresponding commercial TiO₂ phases in paper coating revealed that clay/rutile nano-TiO₂ pigments in paper coating mixture decreased coated paper roughness more than blending clay with anatase nano-TiO₂ pigments. Commercial nano-TiO₂ pigments increased porosity of coated paper at both the 30% and 50% addition of nano-TiO₂ pigments to clay, while laboratory-prepared nano-TiO₂ pigments highly decreased it at 30% addition of nano-TiO₂ to clay, compared to clay only. Blending of clay/nano-TiO₂ pigments improved both brightness and opacity of the coated paper where commercial pigments are more effective. Burst, tensile strength, stretching, and TEA were improved in the case of all pigments. The 50% addition of the prepared and commercial nanopigments in conjunction with clay improved the mechanical coated paper properties more than 30% addition (except the cases of stretching and TEA of the commercial pigments). The coated paper samples were offset printed. It was found that blending of clay/nano-TiO₂ pigments improved print density. Commercial nano-TiO₂ pigments improved print gloss more than the laboratory-prepared ones. This result was found consistent with the results of coated paper roughness.     

The role of surface roughness in the friction of sliding contacts

Results are presented of studies to assess the role of surface roughness in the friction of sliding contacts. A model of the surface roughness uses conical steel needles. A theoretical model based on the mechanics of interaction is included. Experimental and calculated results are discussed in relation to real engineering surfaces and the models compared     

Antitumor activity and antioxidant role of a novel water-soluble carboxymethyl chitosan-based copolymer

In this study, a natural polymer, chitosan (CS) has been converted through modified procedures to produce a water-soluble nontoxic form that has been evaluated as a novel potential antitumor drug. CS was carboxymethylated and then further modified in mild aqueous medium via graft copolymerization using a new simple and reproducible method. The synthesized new derivative of carboxymethylated CS (DCMC) was fully characterized by numerous techniques including Fourier transform infrared spectroscopy (FT-IR), elemental analyzer (EA), scanning electron microscopy (SEM), two-dimensional wide-angle X-ray scattering (2D-WAXS), and differential scanning calorimetry (DSC). The anticancer activity of the DCMC was investigated using mice bearing Ehrlich ascites tumor cells (EAC) at different doses dissolved in isotonic saline. It has been found that treatment with DCMC significantly inhibited tumor growth in a dose-dependent manner. To better understand the molecular mechanism explaining the DCMC effect on cancer cells, we tested the response of EAC cells in vivo to DCMC using flow cytometry cell cycle analysis. The cell cycle analysis revealed a G?/M phase accumulation as well as a significant increase in sub-G? phase cells after treatment with DCMC. This indicates an induction of apoptosis in EAC cells associated with a highly significant decrease in tumor volume. In general, our results indicated that the DCMC is a regulator of tumor cell growth and differentiation not only by causing G?/M cell cycle arrest but also inducing their apoptotic death. Moreover, the estimated hematological profile such as hemoglobin, RBCs, as well as WBCs counts revealed normal levels in mice treated with DCMC, indicating the possibility of using the DCMC in cancer chemotherapy without causing anemia like other drugs. Biochemical assays also revealed that treatment with DCMC has led to an augmentation of the antioxidant defense system without affecting lipid peroxidation in EAC-bearing mice.     

Tribological Properties of PVD Silver Films

This paper presents an experimental study made on physical-vapor-deposited (PVD) silver films. A conventional ion plating unit was used in depositing ion-plated, vacuum-deposited, and gas-deposited silver films.

Experimental work on nucleation, growth, and interface formation is briefly presented. Some adhesion, microhardness, and x-ray test results are also included. Friction and wear test results are reported in details.

The good lubrication properties are attributed initially to the low shear strength in the direction of sliding, and also to the transfer-back-transfer mechanism. The wear mechanism however, is initially a microcutting process, followed by wear debris abrasion process and, finally, a fatigue wear process.     

Characterization and sustainable management strategies of municipal solid waste in Egypt

Clean Technologies and Environmental Policy - The aim of the present study was to establish a national database of waste characteristics for Egypt to support the assessment of various waste...     

Rheological characteristics of modified calcium grease with graphene nanosheets

The effect of graphene nanosheets (GNS) on the rheological characteristics and thermal conductivity of calcium grease used in marine applications, and water pumps for lower demanding applications, has been experimentally evaluated in this paper. Various volume fractions of GNS (0.5, 1, 2, 3, and 4% wt.) have been immersed in the grease aiming at finding the better percentages that improve the properties of nanogrease. The rheological characteristics and thermal conductivity were evaluated with a Brookfield Rheometer DV-III ULTRA and KD2 thermal analyzer, respectively. The results of the modified calcium grease indicated that the best concentration of GNS is 3% wt. The rheological characteristics of the grease with a different volume fraction of GNS indicated a non-Newtonian behavior. Thermal conductivity of nanogreas also increases with an increase of GNS volume fraction. Moreover, the apparent viscosity, shear stress and dropping point increase by 59%, 52%, and 65%, respectively, with increasing GNS volume fraction.     

Mass transfer at the gas evolving inner electrode of a concentric cylindrical reactor

Mass transfer coefficients for an oxygen evolving vertical PbO₂ coated cylinder electrode were measured for the anodic oxidation of acidified ferrous sulphate above the limiting current. Variables studied included the ferrous sulphate concentration, the anode height, the oxygen discharge rate and the anode surface roughness. The mass transfer coefficient was found to increase with increasing O₂ discharge rate,V, and electrode height,h, according to the proportionality expressionK V ^0.34 h ^0.2. Surface roughness with a peak to valley height up to 2.6 mm was found to increase the rate of mass transfer by a modest amount which ranged from 33.3 to 50.8% depending on the degree of roughness and oxygen discharge rate. The present data, as well as previous data at vertical oxygen evolving electrodes where bubble coalescence is negligible, were correlated by the equationJ=7.63 (Re. Fr)^–0.12, whereJ is the mass transferJ factor (St. Sc ^0.66).Notation a ₁,a ₂ constants - A electrode area (cm²) - C concentration of Fe²⁺ (M) - d bubble diameter (cm) - D diffusivity (cm² s^–1) - e electrochemical equivalent (g C^–1) - F Faraday's constant - g acceleration due to gravity (cm s^–2) - h electrode height (cm) - I _Fe ²⁺ current consumed in Fe²⁺ oxidation A - I _{o 2} current consumed in O₂ evolution, A - K mass transfer coefficient (cm s^–1) - m amount of Fe²⁺ oxidized (g) - P gas pressure (atm) - p pitch of the threaded surface (cm) - Q volume of oxygen gas passing any point at the electrode surface (cm³ s^–1) - R gas constant (atm cm³ mol^–1 K^–1) - r peak-to-valley height of the threaded surface (cm) - t time of electrolysis (s) - T temperature (K) - solution viscosity (g cm^–1 s^–1) - V oxygen discharge velocity as defined by Equation 3 (cm s^–1) - Z number of electrons involved in the reaction - Sh Sherwood number (Kd/D) - Re Reynolds number (Vd/) - Sc Schmidt number (v/D) - J mass transferJ factor (St. Sc ^0.66) - St Stanton number (K/V) - Fr Froude number (V ²/dg) - Solution density, g cm^–3 - v Kinematic viscosity (cm² s^–1) - bubble geometrical parameter defined in [31] - fractional surface coverage - diffusion layer thickness (cm)     

Mechanical properties of coated paper: Influence of coating properties and pigment Blends

The effect of percentage solids content, coating film thickness and plastic pigment on mechanical properties of coated paper was studied. The results showed that the tensile strength, TEA, stretch and tensile stiffness were improved as the percentage solids content and the coating film thickness were increased. Bending stiffness slightly increased when solids content was increased and showed higher values on increasing the coating film thickness. The addition of plastic pigment to both clay based and GCC based coating mixtures improved the mechanical properties considered in this study. Although tensile strength and tensile stiffness increased with the addition of plastic pigment of smaller particle size, stretch and TEA showed a reverse trend.