A search for internal isotopic tracers in metallurgical materials

On the basis of the results obtained it can be concluded that none of the examined elements could be used as internal tracer for studying processes, which take place during production of steel in chosen steel-works. However, some of the examined elements could be used as inactive tracers. The results of the determination of lanthanum are particularly interesting in view of the fact that this element was used as inactive tracer for examination of the origin of exogenic inclusions.     

Use of charge-transfer complexation in the spectrophotometric analysis of certain cephalosporins

Three simple, rapid and sensitive spectrophotometric procedures were developed for the analysis of cephapirin sodium (1), cefazoline sodium (2), cephalexin monohydrate (3), cefadroxil monohydrate (4), cefotaxime sodium (5), cefoperazone sodium (6) and ceftazidime pentahydrate (7) in pure form as well as in their pharmaceutical formulations. The methods are based on the reaction of these drugs as n-electron donors with the σ-acceptor iodine, and the π-acceptors: 2,3-dichloro-5,6-dicyano-p-benzo-quinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Depending on the solvent polarity, different coloured charge-transfer complexes and radicals were developed. Different variables and parameters affecting the reactions were studied and optimized. The obtained charge-transfer complexes were measured at 364 nm for iodine (in 1,2-dichloroethane), 460 nm for DDQ (in methanol) and 843 nm for TCNQ (in acetonitrile). Ultraviolet–visible, infrared and ¹H-nuclear magnetic resonance techniques were used to study the formed complexes. Due to the rapid development of colours at ambient temperature, the obtained results were used on thin-layer chromatograms for the detection of the investigated drugs. Beer's plots were obeyed in a general concentration range of 6–50, 40–300 and 4–24 μg ml⁻¹ with iodine, DDQ and TCNQ, respectively, with correlation coefficients not less than 0.9989. The proposed procedures could be applied successfully to the determination of the investigated drugs in vials, capsules, tablets and suspensions with good recovery; percent ranged from 96.47 (±1.14) to 98.72 (±1.02) in the iodine method, 96.35 (±1.62) to 98.51 (±1.30) in the DDQ method, and 95.98 (±0.78) to 98.40 (±0.87) in the TCNQ method. The association constants and standard free energy changes using Benesi–Hildebrand plots were studied. The binding of cephalosporins to proteins in relation to their molar absorptivities was studied.     

Effects of activation conditions on the structural and adsorption characteristics of pinecones derived activated carbons

This study was conducted to understand and optimize the activation process for the production of a low-cost activated carbon (AC) using a renewable and plentiful biomass waste, pinecones. This was achieved by tracking the changes in porous structure, surface chemistry and adsorption properties of the AC produced using different activating agents, activation temperatures, holding times and heating rates. Generally, produced ACs were predominantly microporous with small external surface area and were different in terms of H/C and O/C ratios. Study of Pb²⁺ cations adsorption on these samples proved the high affinity of the pinecones derived ACs to this cation. The best adsorption behaviour was recognized in sample prepared by impregnation with H₃PO₄ at weight ratio of 2, then heating at 400?°C for 2?h at 5?°C/min heating rate. This sample possessed the highest BET surface area (1335 m²/g). The adsorption process obeyed the pseudo-first-order and Freundlich model slightly better than the pseudo-second-order kinetics and Langmuir model. The high Langmuir maximum adsorption capacity of 418?mg/g supports the applicability of the produced AC for the removal of Pb²⁺ cations from wastewater.     

Surface free energy of ultra-high molecular weight polyethylene modified by electron and gamma irradiation

Surface free energy of biocompatible polymers is important factor which affects the surface properties such as wetting, adhesion and biocompatibility. In the present work, the change in the surface free energy of ultra-high molecular weight polyethylene (UHMWPE) samples, which is produced by electron beam and gamma ray irradiation were, investigated. Mechanism of the changes in surface free energy induced by irradiations of doses ranging from 25 to 500 kGy was studied. FTIR technique was applied for sample analysis. Contact angle measurements showed that wettability and surface free energy of samples have increased with increasing the irradiation dose, where the values of droplet contact angle of the samples decrease gradually with increasing the radiation dose. The increase in the wettability and surface free energy of the irradiated samples are attributed to formation of hydrophilic groups on the polymer surface by the oxidation, which apparently occurs by exposure of irradiated samples to the air.     

On the simple and mixed first-order theories for functionally graded plates resting on elastic foundations

In this article, the bending response of a functionally graded plate resting on elastic foundations and subjected to a transverse mechanical load is investigated. An accurate solution for the functionally graded plate with simply supported edges resting on elastic foundations is presented. The interaction between the plate and the elastic foundations is considered and included in the equilibrium equations. Pasternak’s model is used to describe the two-parameter elastic foundations, and get a special case of Winkler’s model by considering one-parameter of elastic foundation. A relationship between the simple and mixed first-order transverse shear deformation theories is presented. Numerical results for deflections and stresses of functionally graded plates are investigated. Comparisons between the results of the simple and mixed first-order theories are made, and appropriate conclusion is formulated. Additional boundary conditions at the edges of the present plates are investigated.     

Periodic motions of spinning rigid spacecraft under influence of gravitational and magnetic fields

The motion of a magnetized axisymmetric spacecraft about its center of mass in a circular orbit is considered, taking the gravitational and magnetic effects of the central body into account. Equations of motion of the reduced system are transformed to equations of plane motion of a charged particle under the action of electric and magnetic fields. Stationary motions of the system are determined and periodic motions near to them are constructed using the Lyapounoff theorem of the holomorphic integral.     

MOS Realization of the Conjectured Simplest Chaotic Equation

This paper presents a general block diagram of a third-order linear differential equation using current mode techniques. The realization of the conjectured simplest chaotic equation of Elwakil and Kennedy based on G_m – C technology is given. The metal oxide semiconductor circuit is composed of 20 transistors and three grounded capacitors, can operate from a supply voltage as low as ±1.5 V, and covers a very wide range of frequencies. PSpice simulation results using 0.5 µm Mietec technology are given. A numerical solution is also included to verify the circuit operation.     

Electrogravitational instability of cylindrical interface acted upon by a varying electric field

The electrodynamic instability of a self-gravitating dielectric fluid penetrated by a uniform axial electric field surrounded by a self-gravitating vacuum pervaded by a varying electric field is investigated. A general eigenvalue relation valid to all possible (symmetric and asymmetric) modes of perturbation for all (short and long) wavelengths is derived and discussed in detail. The model is gravitationally stable to the pure asymmetric disturbances modes while to symmetric modes it is as if the longitudinal wavenumber normalized with respect to the jet radius is equal to or greater than 1.0668 and vice versa. The axial electric fields pervaded interior and exterior to the cylinder are stabilizing for all disturbances modes according to some restrictions. The transverse varying electric field is purely stabilizing in the symmetric disturbance for all wavelengths, while it is stabilizing in the asymmetric disturbance under some restrictions. The electrodynamic force has a strong stabilizing influence in the symmetric mode and can suppress the gravitational instability above a certain value of the basic electric field.     

The Recognition of and Reactions to Nucleic Acid Nanoparticles by Human Immune Cells

The relatively straightforward methods of designing and assembling various functional nucleic acids into nanoparticles offer advantages for applications in diverse diagnostic and therapeutic approaches. However, due to the novelty of this approach, nucleic acid nanoparticles (NANPs) are not yet used in the clinic. The immune recognition of NANPs is among the areas of preclinical investigation aimed at enabling the translation of these novel materials into clinical settings. NANPs’ interactions with the complement system, coagulation systems, and immune cells are essential components of their preclinical safety portfolio. It has been established that NANPs’ physicochemical properties—composition, shape, and size—determine their interactions with immune cells (primarily blood plasmacytoid dendritic cells and monocytes), enable recognition by pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) and RIG-I-like receptors (RLRs), and mediate the subsequent cytokine response. However, unlike traditional therapeutic nucleic acids (e.g., CpG oligonucleotides), NANPs do not trigger a cytokine response unless they are delivered into the cells using a carrier. Recently, it was discovered that the type of carrier provides an additional tool for regulating both the spectrum and the magnitude of the cytokine response to NANPs. Herein, we review the current knowledge of NANPs’ interactions with various components of the immune system to emphasize the unique properties of these nanomaterials and highlight opportunities for their use in vaccines and immunotherapy.