Artin–Schreier curves and weights of two-dimensional cyclic codes

Let be the finite field with q elements of characteristic p, be the extension of degree m>1 and f(x) be a polynomial over . The maximum number of affine -rational points that a curve of the form y^q−y=f(x) can have is q^m+1. We determine a necessary and sufficient condition for such a curve to achieve this maximum number. Then we study the weights of two-dimensional (2-D) cyclic codes. For this, we give a trace representation of the codes starting with the zeros of the dual 2-D cyclic code. This leads to a relation between the weights of codewords and a family of Artin–Schreier curves. We give a lower bound on the minimum distance for a large class of 2-D cyclic codes. Then we look at some special classes that are not covered by our main result and obtain similar minimum distance bounds.     

Use of Benzoylthiourea Immobilized on Silica Gel for Separation and Preconcentration of Uranium(VI)

Benzoylthiourea immobilized on silica gel was prepared by two-step post-synthesis modification. The capacity of the chelating silica gel, which was characterized by FTIR, was 3.21 mmol · g⁻¹. The separation and enrichment of uranium(VI) from solutions was investigated. Effective extraction conditions were optimized in both batch and column methods prior to determination by spectrophotometry using arsenazo(III). The optimum pH range for quantitative adsorption is 4–7. Quantitative recovery of U(VI) was achieved by stripping with 0.1 mol · L⁻¹ HCl. The sorption capacity of modified silica gel was 0.85 mmol · g⁻¹ uranium(VI). Recovery of U(VI) was 99.1 ± 2.3% with a detection limit of 2 μg · L⁻¹. The preconcentration factor was 250, and the relative standard deviation was 1.53% for a 1 μg · L⁻¹ U(VI) solution. The method was used for the determination of uranium in synthetic samples and a soil sample.     

Iron uptake and toxicity in Caco-2 cells

The differences between the in vitro effects of iron attributed to valence, chelation, and complexation are known in terms of markers of oxidative stress. Few studies, however, describe the effects of iron on general markers of toxicity used in the testing of cell cultures. The aim of the present study was to determine the toxicity and uptake of different salts and iron complexes in the human intestinal cell line, Caco-2.Cells were incubated with 1.5 mM of different species of iron [FeCl₃/nitrilotriacetic acid (NTA) (1:2), FeCl₃/citric acid (1:2), FeCl₃ and FeSO₄] for 22–24 h. Thereafter, toxicological and uptake experiments were performed.The iron uptake, viability (via MTT assay), and membrane stability (via LDH release) of Caco-2 cells incubated with various iron forms differed significantly from untreated controls which showed no detrimental effects on cells and less iron uptake. The lowest signal for cell viability (MTT assay) was found after the incubation of the cells with FeCl₃/citric acid, being significantly different to treatment with FeCl₃, where the highest MTT signal was detected (p=0.002). No differences between the tested iron species could be found regarding cell proliferation (via serial cell counting) and viability using the trypan blue exclusion test. The lowest membrane damage (via LDH release) was registered in cells treated with FeCl₃/citric acid (1:2), whereas the highest LDH release could be found in cells incubated with FeCl₃/NTA (1:2). The highest intracellular iron concentration (measured via GFAAS) was detected after the treatment of Caco-2 cells with FeCl₃ and FeCl₃/NTA (1:2).This study substantiates the importance of the choice of complexes, as NTA seemed to enhance the toxicity of iron, while citric acid inhibited iron uptake and toxicity.     

Reductive Cleavage of Carbon Monoxide by a Disilenide

The complete reductive cleavage of the triple bond in carbon monoxide was achieved using a lithium disilenide at room temperature. The C? C‐coupled product can be regarded as a silanone dimer with pending alkyne and silirene moieties and incorporates two equivalents of CO per disilenide unit. A formation mechanism via ketenyl intermediates is proposed on the basis of DFT calculations and elucidated experimentally by employing Group 6 metal carbonyls as both stabilizing entity and source of CO in the reaction with disilenide. The isolation of cyclic silylene complexes with weakly donating ketenyl donor groups further supports the mechanistic scenario.     

Reducing disparities in large-scale emergency medical service systems

Emergency Medical Service (EMS) systems operate under the pressure of knowing that human lives might be directly at stake. In the public eye there is a natural expectation of efficient response. There is abundant literature on the topic of efficient planning of EMS systems (maximizing expected coverage or minimizing response time). Other objectives have been considered but the literature available is very sparse compared to efficiency-based works. Furthermore, while real size EMS systems have been studied, the use of exact models is usually hindered by the amount of computational time required to obtain solutions. We approach the planning of large-scale EMS systems including fairness considerations using a Tabu Search-based heuristic with an embedded approximation procedure for the queuing submodel. This allows for the analysis of large-scale real systems, extending the approach in which strategic decisions (location) and operative decisions (dispatching) are combined to balance efficiency and fairness.     

On the sound absorption performance of a felt sound absorber

In this work, we have developed an analytical model of a multilayer porous material based on the transfer matrix method to predict the absorption behavior at plane wave incidence. The aim of this study is to modify/tune the sound absorption coefficient of a felt to obtain an improved absorbing performance in the mid frequency range without increasing its weight. To achieve this target, the developed model has been used to find the best combination of each layer type and thickness. The analytical results were validated by test results.     

Detection of Sn(II) ions via quenching of the fluorescence of carbon nanodots

We report that fluorescent carbon nanodots (C-dots) can act as an optical probe for quantifying Sn(II) ions in aqueous solution. C-dots are synthesized by carbonization and surface oxidation of preformed sago starch nanoparticles. Their fluorescence is significantly quenched by Sn(II) ions, and the effect can be used to determine Sn(II) ions. The highest fluorescence intensity is obtained at a concentration of 1.75 mM of C-dots in aqueous solution. The probe is highly selective and hardly interfered by other ions. The quenching mechanism appears to be predominantly of the static (rather than dynamic) type. Under optimum conditions, there is a linear relationship between fluorescence intensity and Sn(II) ions concentration up to 4 mM, and with a detection limit of 0.36 μM.

Natural convection flow under a magnetic field in an inclined square enclosure differentialy heated on adjacent walls

Steady, laminar, natural-convection flow in the presence of a magnetic field in an inclined square enclosure differentially heated along the bottom and left vertical walls while the other walls are kept isothermal was considered. The governing equations were solved numerically for the stream function, vorticity and temperature ratio using the differential quadrature method for various Grashof and Hartmann numbers, inclination angle of the enclosure and direction of the magnetic field. The orientation of the enclosure changes the temperature gradient inside and has a significant effect on the flow pattern. Magnetic field suppresses the convective flow and its direction also influences the flow pattern, causing the appearance of inner loops and multiple eddies. The surface heat flux along the bottom wall is slightly increased by clockwise inclination and reduced by half by the counterclockwise inclination. The surface heat flux along the upper portion of the left side wall is reversed by the rise of warmer fluids due to the convection currents for no inclination and clockwise inclination of the enclosure.     

Arbitrary laser beam propagation in free space

The propagation of arbitrary laser beams in free space is examined. For this purpose, starting with an incident field of arbitrary field distribution, the intensity at the receiver plane is formulated via Huygens Fresnel diffraction integral. Arbitrary source field profile is produced by decomposing the source into incremental areas (pixels). The received field through the propagation in free space is found by superposing the contributions from all source incremental areas. The proposed method enables us to evaluate the received intensity originating from any type of source field. Using the arbitrary beam excitation, intensity of various laser beams such as cos-Gaussian, cosh-Gaussian, general type beams are checked to be consistent with the already existing results in literature, and the received intensity distributions are obtained for some original arbitrary beam field profiles. Our received intensity formulation for the arbitrary source field profiles presented in this paper can find application in optics communication links, reflection from rough surfaces, optical cryptography and optical imaging systems.