Variations in radioactivity of phosphate rocks from different sites in Central Eastern Desert of Upper Egypt

Natural radionuclides in the phosphate rock samples collected from Wadi Batur, Wadi Hegaza and Gabal Abu Had at Eastern Desert were determined using a high resolution 7-ray spectrometer. The experimental results concerning 226Ra, 232Th and their daughters are presented. Analyses of the measured spectra show that 226Ra is distinguished with remarkable activities with average values ranging from 22.4 to 558 Bq/kg, while 232Th activity concentration is in the range of 9.7 to 92.8 Bq/kg. The results of the analyses were found to be in a good agreement with the data obtained by others.     

A pseudo-fully stressed design approach for optimum design of steel frames

An iterative approach based on the fully-stressed design concept employing scaling to find an efficient search path to the optimum design is developed for statically indeterminate elastic frames subjected to behavioural constraints on member stresses and nodal displacements, and side constraints on member sizes. In this approach the fully stressed solution, which recognizes only the stress constraints, is scaled to the boundary of the feasible design region by employing the other constraints on the structure. The inactive constraints in an iteration are identified by the Kuhn-Tucker conditions. The computed stresses of the inactive constraints, for the time being, are considered to be the allowable values in order to develop a pseudo-fully stressed solution with a new set of allowable stresses. Convergence takes places when the normalized change in the value of the objective function between the scaled and unsealed pseudo-fully stressed designs is less than a specified tolerance. The method employs the established relationships between sectional area, section modulus and moment of inertia of W-shapes to express the objective and constraint functions in terms of one design variable for each member. The efficiency and accuracy of the method in optimization of structural steel frames is demonstrated by sample problems designed for stress, displacement and minimum size constraints. The algorithm is verified against published results.     

Synthesis of aluminium nanoparticles by arc evaporation of an aluminium cathode surface

Aluminium nanoparticles (Al Nps) are synthesized using arc discharge method by applying direct current between aluminium electrodes in liquid environment without any use of vacuum equipment, heat exchangers, high temperatures furnaces and inert gases. After synthesis of Al Nps, in situ coating process on the nanoparticles was performed immediately. The effects of media on the yield and morphology of aluminium nanoparticles were investigated. Analysis result of the samples indicated that particle size was less than 30 nm, when 120 A/cm² arc current was used. In addition, coating agent can affect arc velocity, arc stability, morphology and composition of the nanoparticles. Resultant nanoparticles were identified using X-ray powder diffraction (XRD), also their surface morphology was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and finally the accuracy of coating was assessed with infrared (IR) spectroscopy.     

Inhibition of Aluminum Alloy Corrosion in 0.5 M Nitric Acid Solution by 4-4-Dimethyloxazolidine-2-thione

The corrosion inhibition of Al-Alloy (Al2024) in 0.5 M nitric acid solution at 30 °C was achieved using 4-4-dimethyloxazolidine-2-thione (DMT) as a corrosion inhibitor. The electrochemical performance of the DMT was studied by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization measurements, and scanning electron microscopic study (SEM). The results indicated that DMT acts as an inhibitor for Al2024 in 0.5 M nitric acid. Polarization curves indicated that DMT was a mixed-type inhibitor. Inhibition efficiencies were observed to be increased with an increase in DMT concentration and attains approximately to 93.4% at 2 mM of DMT in 0.5 M nitric acid. The adsorption of DMT model on Al2024 surface obeyed in accordance with Langmuir adsorption isotherm model. The value of the free energy of adsorption ΔG _ads indicated that the adsorption of DMT molecule was a spontaneous process and was typical of physical and chemical adsorption.     

Feasibility of using various photovoltaic systems for window-type air-conditioning units under hot-arid climates

This paper reports on the feasibility of using various Photovoltaic (PV) systems namely; Grid PV (GPV), Stand-Alone PV (SAPV), Grid PV Wind (GPVW) and PV Wind (PVW) for supplying the power requirements of a window-type air-conditioning system or other small loads. It was found that the GPVW system is the best system to meet the load requirement of a window-type air-conditioning system under the climatic conditions of Oman with values ranging from $39,500 to $56,500 for the capital cost and $9,000 to $33,000 for the total net capital cost depending on the wind speed. These values are attractive for remote off grid applications.     

Electrochemical characterization of electrodeposited carbon nanotubes

Carbon nanotubes were electrodeposited in acetonitrile solution at room temperature using Cu, and Fe-Ni nanoparticles as nucleation sites on HF-etched Si(100) wafer substrate. The electrochemical behavior of the deposition was investigated by voltammetry and chronoamperometry techniques. In order to obtain the optimum growth condition, the deposition critical parameters including current density range, potential and time were studied and calculated. Carbon nanotubes with approximate external diameter of 40-100 nm were fabricated under potentiostatic condition and diffusion control at − 20 V in 4-6 h. The film crystallinity was investigated by means of X-ray diffraction and the tubes structure was revealed using scanning electron microscope and transmission electron microscope images. Raman spectroscopy was also employed to characterize the nanostructural features and single wall carbon nanotubes were detected.     

Highly Conductive Carbon Nanotube‐Graphene Hybrid Yarn

An efficient procedure for the fabrication of highly conductive carbon nanotube/graphene hybrid yarns has been developed. To start, arrays of vertically aligned multi‐walled carbon nanotubes (MWNT) are converted into indefinitely long MWNT sheets by drawing. Graphene flakes are then deposited onto the MWNT sheets by electrospinning to form a composite structure that is transformed into yarn filaments by twisting. The process is scalable for yarn fabrication on an industrial scale. Prepared materials are characterized by electron microscopy, electrical, mechanical, and electrochemical measurements. It is found that the electrical conductivity of the composite MWNT‐graphene yarns is over 900 S/cm. This value is 400% and 1250% higher than electrical conductivity of pristine MWNT yarns or graphene paper, respectively. The increase in conductivity is asssociated with the increase of the density of states near the Fermi level by a factor of 100 and a decrease in the hopping distance by an order of magnitude induced by grapene flakes. It is found also that the MWNT‐graphene yarn has a strong electrochemical response with specific capacitance in excess of 111 Fg^?1. This value is 425% higher than the capacitance of pristine MWNT yarn. Such substantial improvements of key properties of the hybrid material can be associated with the synergy of MWNT and graphene layers in the yarn structure. Prepared hybrid yarns can benefit such applications as high‐performance supercapacitors, batteries, high current capable cables, and artificial muscles.     

Preparation and characterization of foamed polyurethane/silicone rubber/graphite nanocomposite as radio frequency wave absorbing material: The role of interfacial compatibilization

A novel method for the preparation of radio frequency (RF) wave absorber polyurethane foam (PU) has been developed by impregnation of PU foam in n-hexane solution of room temperature vulcanizing (RTV) silicone rubber (SR) hybridized with graphite nanosheets (GNs) called doping solution. Extent of the GNs dispersion was optimized by the incorporation of a specific type of bifunctional compatibilizer. Insulator to conductive transition threshold as well as electromagnetic wave absorption characteristics of the fabricated nanocomposites was shown to be dependent upon the compatibilizer functionality. All PU/SR/GN nanocomposites generated from bifunctional compatibilizer exhibited higher electrical conductivity with enhanced permittivity implying enhanced formation of conductive networks by GN platelets. Permittivity of the PU/SR/GN nanocomposite based on bifunctional compatibilizer showed to be higher than uncompatibilized counterpart. Electromagnetic reflection loss behavior of the PU/SR/GN nanocomposites exhibited a non-linear correlation with the electrical conductivity. Although all PU/SR/GN prepared nanocomposites exhibited electromagnetic wave reflection loss behavior, but this revealed to be affected by the GN level as well as the size and dispersion state of the graphite nanosheets.     

Neurotoxicity of Chronic Co-Exposure of Lead and Ionic Liquid in Common Carp: Synergistic or Antagonistic?

Previous studies have indicated that the harmful heavy metal lead (Pb) contamination in aquatic systems has caused intelligence development disorders and nervous system function abnormalities in juveniles due to the increased permeability of the blood–brain barrier. Ionic liquids (ILs) are considered “green” organic solvents that can replace traditional organic solvents. Studies have found the presence of ILs in soil and water due to chemical applications or unintentional leakage. Therefore, what would happen if Pb interacted with ILs in a body of water? Could ILs enable Pb to more easily cross the blood–brain barrier? Therefore, we examined the combined exposure of Pb and ILs in common carp at low concentration (18.3 mg L⁻¹ of Pb(CH₃COO)₂•3 H₂O and 11 mg L⁻¹ of the IL 1-methyl-3-octylimidazolium chloride, 5% of their LC₅₀) for 28 days in the present study. The result of a neurobehavioral assay showed that chronic exposure of lead at lower concentrations significantly altered fish movement and neurobehaviors, indicating that lead exposure caused neurotoxicity in the carp. Increases in the neurotransmitter dopamine levels and injuries in the fish brain accounted for neurobehavioral abnormalities induced by lead exposure. Moreover, we also found that lead could easily cross the blood–brain barrier and caused significant bioaccumulation in the brain. Particularly, our study indicated that the ionic liquid could not synergistically promote blood–brain barrier permeability and hence failed to increase the absorption of lead in the fish brain, suggesting that the combined exposure of lead and ILs was not a synergistic effect but antagonism to the neurotoxicity. The results of this study suggested that ILs could recede the Pb induced neurotoxicity in fish.     

MicroRNA Expression in Clear Cell Renal Cell Carcinoma Cell Lines and Tumor Biopsies: Potential Therapeutic Targets

This study was carried out to quantitate the expression levels of microRNA-17, -19a, -34a, -155, and -210 (miRs) expressed in nine clear cell renal cell carcinoma (ccRCC) and one chromophobe renal cell carcinoma cell line with and without sarcomatoid differentiation, and in six primary kidney tumors with matching normal kidney tissues. The data in the five non-sarcomatoid ccRCC cell lines—RC2, CAKI-1, 786-0, RCC4, and RCC4/VHL—and in the four ccRCC with sarcomatoid differentiation—RCJ41T1, RCJ41T2, RCJ41M, and UOK-127—indicated that miR-17 and -19a were expressed at lower levels relative to miR-34a, -155, and -210. Compared with RPTEC normal epithelial cells, miR-34a, miR-155, and miR-210 were expressed at higher levels, independent of the sarcomatoid differentiation status and hypoxia-inducible factors 1α and 2α (HIFs) isoform expression. In the one chromophobe renal cell carcinoma cell line, namely, UOK-276 with sarcomatoid differentiation, and expressing tumor suppressor gene TP53, miR-34a, which is a tumor suppressor gene, was expressed at higher levels than miR-210, -155, -17, and -19a. The pilot results generated in six tumor biopsies with matching normal kidney tissues indicated that while the expression of miR-17 and -19a were similar to the normal tissue expression profile, miR-210, -155, -and 34a were expressed at a higher level. To confirm that differences in the expression levels of the five miRs in the six tumor biopsies were statistically significant, the acquisition of a larger sample size is required. Data previously generated in ccRCC cell lines demonstrating that miR-210, miR-155, and HIFs are druggable targets using a defined dose and schedule of selenium-containing molecules support the concept that simultaneous and concurrent downregulation of miR-210, miR-155, and HIFs, which regulate target genes associated with increased tumor angiogenesis and drug resistance, may offer the potential for the development of a novel mechanism-based strategy for the treatment of patients with advanced ccRCC.