In‐vitro Aluminum Determination and Preconcentration in Blood of Dialysis Patients Based on Ionic Liquid Dispersive Liquid‐Liquid Biomicroextraction by 2‐Amino‐3‐(1H‐imidazol‐4‐yl)propanoic Acid

In this study, trace amounts of aluminum in serum of dialysis patients were chelated with 2‐Amino‐3‐(1H‐imidazol‐4‐yl)propanoic acid (Histidine) and determined by electro‐thermal atomic absorption spectrometry (ETAAS). A fast and efficient method based on ionic liquid dispersive liquid‐liquid bio‐micro‐extraction (IL‐DLLBME) was developed for the determination of Al cation in human blood serum samples. In this work, a small amount of 1‐Hexyl‐3‐methylimmidazolum hexafluorophosphate ([HMIM] [PF₆]) as an extractant solvent was dissolved in acetone as a dispersant solvent and then the binary solution was rapidly injected by a syringe into the serum containing Al³⁺,Which have already in‐vitro chelated by Histidine amino acid (Al‐His) at pH = 6.5. After separation, the settled IL‐phase was dissolved in ethanol up to 200 μL and 20 μL of samples injected into the ET‐AAS by auto‐sampler. Various parameters have been studied and optimized for 10 mL of sample. Under the optimum conditions, the enrichment factor (EF), limit of detection (LOD) and working range (peak area mode) were obtained 53, 15 ng L^?1 and 0.05‐4.1 μg L^?1 respectively. In vitro Al chelation showed that His can significantly decrease aluminum concentration in serum of dialysis patients. Validation of methodology was confirmed by standard reference material (SRM).     

Optimization of parameters for the alcoholic-assisted dispersive liquid–liquid microextraction of estrogens in water

Extraction and determination of estrogens in water samples were performed using alcoholic-assisted dispersive liquid–liquid microextraction (AA-DLLME) and high-performance liquid chromatography (UV/Vis detection). A Plackett–Burman design and a central composite design were applied to evaluate the AA-DLLME procedure. The effect of six parameters on extraction efficiency was investigated. The factors studied were volume of extraction and dispersive solvents, extraction time, pH, amount of salt and agitation rate. According to Plackett–Burman design results, the effective parameters were volume of extraction solvent and pH. Next, a central composite design was applied to obtain optimal condition. The optimized conditions were obtained at 220 μL 1-octanol as extraction solvent, 700 μL ethanol as dispersive solvent, pH 6 and 200 μL sample volume. Linearity was observed in the range of 1–500 μg L^?1 for E2 and 0.1–100 μg L^?1 for E1. Limits of detection were 0.1 μg L^?1 for E2 and 0.01 μg L^?1 for E1. The enrichment factors and extraction recoveries were 42.2, 46.4 and 80.4, 86.7, respectively. The relative standard deviations for determination of estrogens in water were in the range of 3.9–7.2 % (n = 3). The developed method was successfully applied for the determination of estrogens in environmental water samples.     

K2Re(NCS)6: A weak ferromagnet

The preparation of the potassium salt of hexathiocyanate Re(IV) as a pure and crystalline solid is described. The crystal structure for [{K(H₂O)₂}₂{Re(NCS)₆}] (P2₁/c, a = 8.29132(8) Å, b = 15.0296(2) Å, c = 8.5249(1) Å, β = 90.885(1)°, V = 1062.21(2) Å³) revealed the formation of a 3-D coordination polymer based on K-S linkages. This organization leads to rather short intermolecular S···S contacts. The magnetic behavior for the compound is characterized by substantial antiferromagnetic interactions (with Curie-Weiss parameters C = 1.93 cm³mol⁻¹ and θ = −171 K) that in turn lead to a weak ferromagnet with T_C = 13 K.     

Nano-structured lead dioxide as a novel stationary phase for solid-phase microextraction

The first study on the high efficiency of nano-structured lead dioxide as a new fiber for solid-phase microextraction (SPME) purposes has been reported. The size of the PbO2 particles was in the range of 34-136 nm. Lead dioxide-based fibers were prepared via electrochemical deposition on a platinum wire. The extraction properties of the fiber to benzene, toluene, ethylbenzene, and xylenes (BTEX) were examined using headspace solid-phase microextraction (HS-SPME) mode coupled to gas chromatography-flame ionization detection (GC-FID). The results obtained proved the suitability of proposed fibers for the sampling of organic compounds from water. The extraction procedure was optimized by selecting the appropriate extraction parameters, including preparation conditions of coating, salt concentration, time and temperature of adsorption and desorption and stirring rate. The calibration graphs were linear in a concentration range of 0.1-100 microg l(-1) (R2 > 0.994) with detection limits below 0.012 microg l(-1) level. Single fiber repeatability and fiber-to-fiber reproducibility were less than 10.0 and 12.5%, respectively. The PbO2 coating was proved to be very stable at relatively high temperatures (up to 300 degrees C) with a high extraction capacity and long lifespan (more than 50 times). Higher chemical resistance and lower cost are among the advantages of PbO2 fibers over commercially available SPME fibers. Good recoveries (81-108%) were obtained when environmental samples were analyzed.     

A Relation Between Closure Operators on a Small Category and Its Category of Presheaves

In this paper we show that each factorization structure on a small category , satisfying certain conditions, yields a presheaf on and a morphism of presheaves . We then give connections, and set up one to one correspondences, between subclasses of the following classes: (a) closure operators on (b) subobjects of (c) morphisms from to (d) weak Lawvere–Tierney topologies (e) weak Grothendieck topologies (f) closure operators on .     

Numerical investigation of blood flow. Part II: In capillaries

In order to understand the normal and pathologic behavior of the human vascular system, detailed knowledge of blood flow and the response of blood vessels is required. In fact the ability to predict the flow hydrodynamics at any site in the vessels can lead to a better understanding of the behavior of blood flow. Simulation can play an important role in understanding the hemodynamic forces. The objective of the present attempt was to simulate the behavior of blood flow in microvessels using computational fluid dynamics (CFD). Numerical analysis is performed using a commercially available CFD package Fluent 6.2 which is based on the finite volume method. A continuum approach is proposed in which fluid structure interaction has been taken into account. Based on limitations imposed by computational resources, a more simplified model based on volume of fluid (VOF) approach is suggested to simulate movements of RBCs in capillaries and also to predict RBCs’ deformation. Three-dimensional incompressible laminar flow fields are obtained by solving continuity and Navier–Stokes equations computationally. It was found that multiphase CFD simulations may give further insight into the dynamic characteristics of blood flow under complex flow conditions.     

On Fuzzy Preordered Structures and （Fuzzy） Hyperstructures

This article presents a connection between fuzzy preordered structures and hyperstructures. Firstly, we introduce the notion of fuzzy preordered semigroup and then, we construct a semihypergroup associated with it, giving some properties of the associated hyperstructure. Secondly, we define the notion of fuzzy preordered ring in order to construct a fuzzy hyperring.     

On novel classes of iterative methods for solving nonlinear equations

In this paper, we establish two new classes of derivative-involved methods for solving single valued nonlinear equations of the form f(x) = 0. The first contributed two-step class includes two evaluations of the function and one of its first derivative where its error analysis shows a fourth-order convergence. Next, we construct a three-step high-order class of methods including four evaluations per full cycle to achieve the seventh-order of convergence. Numerical examples are included to re-verify the theoretical results and moreover put on show the efficiency of the new methods from our classes.     

Some exact solutions of F(R) gravity with charged (a)dS black hole interpretation

In this paper we obtain topological static solutions of some kind of pure F(R) gravity. The present solutions are two kind: first type is uncharged solution which corresponds with the topological (a)dS Schwarzschild solution and second type has electric charge and is equivalent to the Einstein-Λ-conformally invariant Maxwell solution. In other word, starting from pure gravity leads to (charged) Einstein-Λ solutions which we interpreted them as (charged) (a)dS black hole solutions of pure F(R) gravity. Calculating the Ricci and Kreschmann scalars show that there is a curvature singularity at r = 0. We should note that the Kreschmann scalar of charged solutions goes to infinity as r → 0, but with a rate slower than that of uncharged solutions.     

Electrochemical properties of modified carbon paste electrodes containing some amino derivatives of 9,10-anthraquinone

The preparation and aqueous electrochemistry of carbon paste electrodes modified by some amino-substituted 9,10-anthraquinones are reported. In all cases, the reduction processes studied by cyclic voltammetry reveal a quasi-reversible behavior. The half-wave potentials were calculated as a function of the solution pH and from the resulting potential-pH plots the formal potentials and pK _a ^′ values of different redox and acid-base couples involved at various pH ranges were evaluated. The diffusion coefficients of different anthraquinone derivatives used in paraffin oil were calculated by chronoamperometry. Received: 3 May 1999 / Accepted: 15 November 1999