Three-dimensional heat transfer in nonlinear flow: a FEM computational approach

Journal of Thermal Analysis and Calorimetry - Finite element simulations for the dynamics of Casson fluid flow over time-dependent two-dimensional stretching sheet subjected to magnetic field and...     

A new HPLC method for the simultaneous determination of ascorbic acid and aminothiols in human plasma and erythrocytes using electrochemical detection

A new, simple, economical and validated high-performance liquid chromatography linked with electrochemical detector (HPLC-ECD) method has been developed and optimized for different experimental parameters to analyze the most common monothiols and disulfide (cystine, cysteine, homocysteine, methionine, reduced (GSH) and oxidized glutathione (GSSG)) and ascorbic acid present in human plasma and erythrocytes using dopamine as internal standard (IS). Complete separation of all the targets analytes and IS at 35 °C on Discovery HS C18 RP column (250 mm × 4.6 mm, 5 μm) was achieved using 0.05% TFA:methanol (97:3, v/v) as a mobile phase pumped at the rate of 0.6 ml min⁻¹ using electrochemical detector in DC mode at the detector potential of 900 mV. The limits of detection (3 S/N) and limits of quantification (10 S/N) of the studied compounds were evaluated using dilution method. The proposed method was validated according to standard guidelines and optimization of various experimental parameters and chromatographic conditions was carried out. The optimized and validated HPLC-ECD method was successfully applied for the determination of the abovementioned compounds in human plasma and erythrocytes. The method will be quite suitable for the determination of plasma and erythrocyte profile of ascorbic acid and aminothiols in oxidative stress and other basic research studies.     

Consistent treatment of coherent and incoherent energy transfer dynamics using a variational master equation

We investigate the energy transfer dynamics in a donor-acceptor model by developing a time-local master equation technique based on a variational transformation of the underlying Hamiltonian. The variational transformation allows a minimisation of the Hamiltonian perturbation term dependent on the system parameters, and consequently results in a versatile master equation valid over a range of system-bath coupling strengths, temperatures, and environmental spectral densities. While our formalism reduces to the well-known Redfield, F?rster and polaron forms in the appropriate limits, in general it is not equivalent to perturbing in either the system-environment or donor-acceptor coupling strengths, and hence can provide reliable results between these limits as well. Moreover, we show how to include the effects of both environmental correlations and non-equilibrium preparations within the formalism.     

Determination of abamectin in citrus fruits using SPE combined with dispersive liquid–liquid microextraction and HPLC–UV detection

A new pretreatment method, SPE combined with dispersive liquid–liquid microextraction, was proposed for the determination of abamectin in citrus fruit samples for the first time. In this method, fruit samples were extracted by ultrasound‐assisted extraction followed by SPE. Then, the SPE was used as a disperser solvent in the next dispersive liquid–liquid microextraction step for further purification and enrichment of abamectin. The effects of various parameters on the extraction efficiency of the proposed method were investigated and optimized. Good linearity of abamectin was obtained from 0.005 to 10.0 mg/kg for B_1a and from 0.05 to 10.0 mg/kg for B_1b with correlation coefficient (r²) of 0.998 for B_1a and 0.991 for B_1b, respectively. The LODs were 0.001 and 0.008 mg/kg (S/N = 3) for B_1a and B_1b, respectively. The relative recoveries at three spiked levels were ranged from 87 to 96% with the RSD less than 11% (n = 3). The method has been successfully applied to the determination of abamectin in citrus fruit samples.     

Application of dispersive liquid–liquid microextraction based on solidification of floating organic drop for simultaneous determination of alachlor and atrazine in aqueous samples

Dispersive liquid–liquid microextraction based on solidification of floating organic drop coupled with HPLC‐UV detection as a fast and inexpensive technique was applied to the simultaneous extraction and determination of traces of two common herbicides, alachlor and atrazine, in aqueous samples. The critical experimental parameters, including type of the extraction and disperser solvents as well as their volumes, sample pH, salt addition, and extraction time were investigated and optimized. Under the optimum conditions, the calibration graphs found to be linear in the range of 0.1–200 μg/L with LOD in the range of 0.02–0.05 μg/L. The RSDs were in the range of 4.2–5.3% (n = 5). The relative recoveries of well, tap, and river water samples which have been spiked with different levels of herbicides were 94.0–106.0, 99.0–105.0, and 88.5–97.0%, respectively.     

Measurement of permethrin,deltamethrin and malathion pesticide residues in the wheat flour and breads and probabilistic health risk assessment: a case study in Kermanshah,Iran

ABSTRACT

This study was conducted to investigate the residues of pyrethroid and organophosphorus pesticide in flour and breads which were collected from local markets in Kermanshah province, Iran. Four different types of breads and two types of flour samples with high distribution were taken from market and their residues of pesticides were measured. A simple dispersive liquid–liquid microextraction (DLLME) method with solidification of floating organic drop was developed for the measurement. The health risk of these pesticides on adults and children health was assessed by target hazard quotient (THQ) using Monte Carlo simulation (MCS) method. About, 15% and 11.1% of total samples contained detectable levels of deltamethrin and malathion, respectively. None of the tested samples showed any permethrin residue. The results from all samples showed that none of the pesticides exceeded the maximum residue limits (MRLs). About 85% of pesticide residue detections were observed in tropical and mild weather area which is due to high consumption rate of insecticides in these areas. The percentile 95% of THQ is due to bread ingestion content of deltamethrin which was 0.033 and 0.070 for the adults and children, respectively, while this value for malathion was found to be, 0.015 and 0.030, respectively. In the adults and children for both deltamethrin and malathion, the percentile 95% of THQ value were lower than 1 (acceptable level). The non-carcinogenic health risk assessment indicated that bread consumers in Kermanshah province are not at a considerable risk because of deltamethrin and malathion.     

Coagulation of the Suspended Organic Colloids Using the Electroflocculation Technique

Electroflotation is an unconventional separation process owing its name to the bubbles generation method (i.e., electrolysis of the aqueous medium) caused by the hydrogen and hydroxide development. Collecting the colloidal particles in surface water has been a long-term issue all over the world, because of their adverse influence. In the present research, the electroflocculation technique have been use to collect the humus particles throughout the polluted wastewater. The uses of different chemical additives namely, Al₂(SO₄)₃, Al(OH)₃, CaCl₂, CaO, and Na₂SiO₃ were also successfully examined and enhanced the electroflocculation technique. Although high negatively surface electrical charge of humus causes difficulties in the conventional flocculation and coagulation technique, it enhances the flocculation process when the electroflocculation techniques have been used. The results of both Jar test and electroflocculation technique are further compared. It can be concluded that the polluted water were fully decontaminated (i.e., all of the suspended colloids through the water were removed) by using the electroflocculation technique. The removal rate after electroflocculation test were 91.8%, 98%, 93.5%, 85.3%, 95.4%, and 94% for neutral, Al₂(SO₄)₃, Al(OH)₃, CaCl₂, CaO, and Na₂SiO₃, respectively. While the removal rate after Jar test were 84.8%, 83.79%, 71.44%, 84.83%, 77.09%, and 77.09% for neutral, Al₂(SO₄)₃, Al(OH)₃, CaCl₂, CaO, and Na₂SiO₃, respectively.     

Effect of particle size and alloying with different metals on 57Fe Mössbauer spectra

Iron nanoparticles of various sizes have been synthesized using the chemical route which involves the preparation of iron bipyridine complexes in presence of different capping agents followed by thermal decomposition at 450°C in inert atmosphere. The bimetallic nanoalloys of Fe with Mg and Pd have also been prepared by following the same route. The resulting nanoparticles have been characterized by EDX-RF, XRD, AFM and ⁵⁷Fe Mössbauer spectroscopy. The appearance of quadrupole doublets in the Mössbauer spectra of Fe nanoparticles indicates the absence of magnetic interaction and variation in parameters is due to the varying particle size. The Mössbauer spectrum of Fe–Mg₂ bimetallic nanoalloy shows two doublets indicating the presence of superparamagnetism. The two doublets can be attributed to change in s-electron density of iron resulting from its two neighboring magnesium atoms. Fe–Pd nanoalloy Mössbauer spectrum is characterized by having a superparamagnetic doublet and a ferromagnetic sextet.     

Selective spin coupling through a single exciton

We present a novel scheme for performing a conditional phase gate between two spin qubits in adjacent semiconductor quantum dots through delocalized single exciton states, formed through the interdot F?rster interaction. We consider two resonant quantum dots, each containing a single excess conduction band electron whose spin embodies the qubit. We demonstrate that both the two-qubit gate and arbitrary single-qubit rotations may be realized to a high fidelity with current semiconductor and laser technology.