Biocoacervation extraction combined with dispersive solid phase extraction using a reversed-phase core–shell magnetic molecularly imprinted sorbent for 2,4-dichlorophenoxyacetic acid prior to its determination by HPLC

In this study, efficient preconcentration method has been developed for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D) using biosorption based on microassemblies combined with core–shell magnetic molecularly imprinted polymers (mag-MIP) nanoparticles followed by high-performance liquid chromatography. The method involves three steps: (1) The bioaggregates is added to the sample. The analyte is extracted into the colloidal phase formed by aggregation of the rhamnolipid. (2) Mag-MIPs are added in order to selectively extract 2,4-D from the bioaggregate. (3) The mag-MIPs are then collected from the solution by a strong magnet placed underneath the test tube, and 2,4-D is desorbed from the surface of the mag-MIP with an acetonitrile: methanol mixture. This material has a high adsorption capacity and yields high upconcentrations, which is reusable and chemically stable. Under optimum conditions, the enrichment factor was 265. The linear dynamic range and limit of detection are 0.16–40 and 0.053 µg L^?1, respectively. The relative standard deviations for six replicate measurements are 5.2 %.     

CFD modeling of convection heat transfer using 1.7 MHz and 24 kHz ultrasonic waves: a comparative study

The effects of 24 kHz and 1.7 MHz ultrasonic waves on heat transfer from a thin platinum wire are investigated. The results revealed that the 1.7 MHz ultrasound waves could increase the heat transfer rate more efficiently than the lower frequency one. The CFD modeling of ultrasonication was performed to compare heat transfer, predict fluid flow patterns. The CFD results were validated by the experimental results with an excellent agreement.     

In-phantom neutron dose distribution for bladder cancer cases treated with high-energy photons

This work presents an estimation of the neutron dose distribution for common bladder cancer cases treated with high-energy photons of 15 MV therapy accelerators. Neutron doses were measured in an Alderson phantom, using TLD 700 and 600 thermoluminescence dosimeters, resembling bladder cancer cases treated with high-energy photons from 15 MV LINAC and having a treatment plan using the four-field pelvic box technique. Thermal neutron dose distribution in the target area and the surrounding tissue was estimated. The sensitivity of all detectors for both gamma and neutrons was estimated and used for correction of the TL reading. TLD detectors were irradiated with a Co⁶⁰ gamma standard source and thermal neutrons at the irradiation facility of the National Institute for Standards (NIS). The TL to dose conversion factor was estimated in terms of both Co⁶⁰ neutron equivalent dose and thermal neutron dose. The dose distribution of photo-neutrons throughout each target was estimated and presented in three-dimensional charts and isodose curves. The distribution was found to be non-isotropic through the target. It varied from a minimum of 0.23 mSv/h to a maximum of 2.07 mSv/h at 6 cm off-axis. The mean neutron dose equivalent was found to be 0.63 mSv/h, which agrees with other published literature. The estimated average neutron equivalent to the bladder per administered therapeutic dose was found to be 0.39 mSv Gy^?1, which is also in good agreement with published literature. As a consequence of a complete therapeutic treatment of 50 Gy high-energy photons at 15 MV, the total thermal neutron equivalent dose to the abdomen was found to be about 0.012 Sv.     

A pure geometric approach to stellar structure

The present work represents a step in dealing with stellar structure using a pure geometric approach. Geometric field theory is used to construct a model for a spherically symmetric configuration. In this case, two solutions have been obtained for the field equations. The first represents an interior solution which may be considered as a pure geometric one in the sense that the tensor describing the material distributions is not a phenomenological object, but a part of the geometric structure used. A general equation of state for a perfect fluid, is obtained from, and not imposed on, the model. The second solution gives rise to Schwarzschild exterior field in its isotropic form. The two solutions are matched, at a certain boundary, to evaluate the constants of integration. The interior solution obtained shows that there are different zones characterizing the configuration: a central radiation dominant zone, a probable convection zone as a physical interpretation of the singularity of the model, and a corona like zone. The model may represent a type of main sequence stars. The present work shows that Einstein’s geometerization scheme can be extended to gain more physical information within material distribution, with some advantages.     

Study on structural, thermal, sintering and conductivity of Cu-Co doubly substituted Bi4V2O11

Doubly substitution of vanadium by Cu and Co in the limit of 10% in Bi₄V₂O₁₁, has led to the formation of the Bi₄V_1.8Cu_0.2−xCo_xO_10.7 solid solution. X-ray diffraction shows that all the compositions present a tetragonal symmetry. The thermal analysis has revealed that the polymorph γ' phase, which is formed by a partial ordering of oxygen ions in the γ high temperature form, is stabilized at room temperature. The influence of sintering temperature on the microstructure of the samples was investigated by the scanning electron microscopy (SEM). The ceramics sintered at 820 °C for more than 3 hours present micro-craks. The evolution of the electrical conductivity with temperature and the degree of substitution has been investigated by impedance spectroscopy. The sample with x=0.1 presents the highest value of the conductivity ≈4.6×10⁻² S·cm⁻¹ at 600 °C.     

Null-controllability of some reaction–diffusion systems with one control force

This work is concerned with the null-controllability of semilinear parabolic systems by a single control force acting on a subdomain.     

Chemical composition,antioxidant and antibacterial properties of Pteranthus dichotomus from Algerian Sahara

The phytochemical study of ethyl acetate and n-butanol extracts of Pteranthus dichotomus Forssk. led to the isolation and identification of 11 compounds, including three glycolipids 1–3, one lignan 4, three flavonoids 5–7 and four phytosterols 8–11. Structures of the isolated compounds have been elucidated by analysis of 1D and 2D NMR data, and mass spectrometry EI-MS and ESI-MS and by comparison with literature data. Furthermore, the ethyl acetate and n-butanol extracts were examined for their antioxidant and antibacterial activities. The results showed that both extracts (PDAC and PDBU) had a moderate antioxidant activity (IC50 = 375.514 μg/mL and 691.333 μg/mL) respectively.