Adsorption Studies of Radionuclides and Toxic Metal Ions on a Modified Mesoporous Lanthanum(III) Silicate

A new adsorbent, modified mesoporous lanthanum(III) silicate, has been prepared with various molar ratios of Si/La (10, 20, 40, 80) and cethyltrimethylammonium bromide (CTAB) as structure directing agent. XRD, nitrogen sorption, SEM, IR, thermogravimetry and sorption of radionuclides and toxic metal ions have been studied. The results show that adsorption amount of some element such as Pb(II) and Th(IV) has been increased significantly by incorporation of lanthanum ions in the framework of adsorbent. Separation of Co(II)‐Th(IV), Co(II)‐U(VI) and Mo(VI)‐U(VI) has been developed on columns of this adsorbent.     

Simultaneous Determination of Ultra Trace of Uranium and Cadmium by Adsorptive Cathodic Stripping Voltammetry Using H‐Point Standard Addition Method

A sensitive adsorptive cathodic stripping voltammetry with H‐point standard addition method for simultaneous determination of uranium and cadmium has been developed. The trace amounts of these metal ions can be simultaneously determined using the Levodpa as complexing agent. Optimal conditions were: accumulation time 50 s, accumulation potential 0.0 mV, scan rate 40 mV s^?1, supporting electrolyte 0.1 M ammonium buffer pH 9.6, and 1×10^?5 M of Levodopa. The results revealed that the cadmium and uranium could be simultaneously determined by H‐point standard addition method with different concentration ratios of uranium to cadmium. The method was successfully applied in a several of real samples.     

The pristine and carbon,silicon or germanium-substituted (10, 0) BN nanotube: A computational DFT study of NMR parameters

The geometrical structure and nuclear magnetic resonance (NMR) parameters of the pristine as well as carbon, silicon and germanium-doped (10, 0) boron-nitride (BN) nanotubes have been studied using a DFT-B3LYP method for the first time. When either a Ge, C or Si atom is substituted for a single B or N in the BN nanotube, the dopant atom extends outward from the surface of the nanotube. Our results show that Ge extends more from the surface than C or Si. It was found that the NMR parameters are significantly changed for those B and N nuclei that bond directly to C, Si or a Ge dopant. The calculations were carried out using the Gaussian 03 software package.     

Determination of BTEX Compounds by Dispersive Liquid–Liquid Microextraction with GC–FID

Rapid, inexpensive, and efficient sample-preparation by dispersive liquid–liquid microextraction (DLLME) then gas chromatography with flame ionization detection (GC–FID) have been used for extraction and analysis of BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) in water samples. In this extraction method, a mixture of 25.0 μL carbon disulfide (extraction solvent) and 1.00 mL acetonitrile (disperser solvent) is rapidly injected, by means of a syringe, into a 5.00-mL water sample in a conical test tube. A cloudy solution is formed by dispersion of fine droplets of carbon disulfide in the sample solution. During subsequent centrifugation (5,000 rpm for 2.0 min) the fine droplets of carbon disulfide settle at the bottom of the tube. The effect of several conditions (type and volume of disperser solvent, type of extraction solvent, extraction time, etc.) on the performance of the sample-preparation step was carefully evaluated. Under the optimum conditions the enrichment factors and extraction recoveries were high, and ranged from 122–311 to 24.5–66.7%, respectively. A good linear range (0.2–100 μg L⁻¹, i.e., three orders of magnitude; r ² = 0.9991–0.9999) and good limits of detection (0.1–0.2 μg L⁻¹) were obtained for most of the analytes. Relative standard deviations (RSD, %) for analysis of 5.0 μg L⁻¹ BTEX compounds in water were in the range 0.9–6.4% (n = 5). Relative recovery from well and wastewater at spiked levels of 5.0 μg L⁻¹ was 89–101% and 76–98%, respectively. Finally, the method was successfully used for preconcentration and analysis of BTEX compounds in different real water samples.

     

Theoretical calculation of excitonic binding energies and optical absorption spectra for Armchair graphene nanoribbons

In this paper the excitons of armchair graphene nanoribbons with layers of different width and thickness have been investigated. In this investigation, the band structure and energy gap of armchair graphene nanoribbons have been calculated using a tight-binding model including edge deformation effects (all edge atoms have been passivated with hydrogen atoms). Also, by calculating the conductance in armchair graphene nanoribbons (A-GNRs) optical absorption of armchair graphene nanoribbon in the single-electron approximation has been obtained. Finally, the binding energy of excitons in armchair graphene nanoribbons has been calculated using the Wannier model, Hartree-Fock approximation and the Bethe-Salpeter equation.     

Growth and investigation of antifungal properties of ZnO nanorod arrays on the glass

In this study, we have investigated the antifungal activity of ZnO nanorods prepared by the chemical solution method against Candida albicans. In the study, Zinc oxide nanorods have been deposited on glass substrates using the chemical solution method. The as-grown samples are characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). X-ray diffraction (XRD) showed zinc oxide nanorods grown in (0 0 2) orientation. The antifungal results indicated that ZnO nanorod arrays exhibit stable properties after two months and play an important role in the growth inhibitory of Candida albicans.     

XHSTT: an XML archive for high school timetabling problems in different countries

We present the progress on the benchmarking project for high school timetabling that was introduced at PATAT 2008. In particular, we announce the High School Timetabling Archive XHSTT-2011 with 21 instances from 8 countries and an evaluator capable of checking the syntax of instances and evaluating the solutions.     

A Full-Newton Step Infeasible Interior-Point Algorithm Based on Darvay Directions for Linear Optimization

We present a full-Newton step primal-dual infeasible interior-point algorithm based on Darvay’s search directions. These directions are obtained by an equivalent algebraic transformation of the centering equation. The algorithm decreases the duality gap and the feasibility residuals at the same rate. During this algorithm we construct strictly feasible iterates for a sequence of perturbations of the given problem and its dual problem. Each main iteration of the algorithm consists of a feasibility step and some centering steps. The starting point in the first iteration of the algorithm depends on a positive number ξ and it is strictly feasible for a perturbed pair, and feasibility steps find strictly feasible iterate for the next perturbed pair. By using centering steps for the new perturbed pair, we obtain strictly feasible iterate close to the central path of the new perturbed pair. The algorithm finds an ?-optimal solution or detects infeasibility of the given problem. The iteration bound coincides with the best known iteration bound for linear optimization problems.     

Preparation and biodistribution study of technetium-99m-labeled quercetin as a potential radical scavenging agent

Free radicals and oxidative stress are the primary causes of several chronic diseases such as cancer and heart disease. Quercetin is a natural compound with potent antioxidant activity. We have prepared and evaluated technetium-99m (^99mTc)-labeled quercetin as a potential radical scavenging radiotracer. A ^99mTc-quercetin complex was prepared using quercetin, SnCl₂ and Na^99mTcO₄ in a buffered solution over 30 min. The participation coefficient was measured in octanol and queues solutions. The stability was determined in phosphate buffered saline and serum. The biodistribution in normal mice was evaluated at 0.5, 2, 6 and 24 h post-injection. The radiochemical purity (>99%) was determined by thin layer chromatography (TLC) in normal saline solution as the mobile phase. It has a log P of 0.204. It was mainly cleared by the kidneys and showed negligible brain uptake at four time points measured post-injection. The pharmacological properties of quercetin, mainly its free radical scavenging, may potentially cat as a radiopharmaceutical agent for radical-targeted imaging of tissue with high levels of reactive oxygen species.