Solid phase extraction of heavy metals on chemically modified silica-gel with 2-(3-silylpropylimino) methyl)-5-bromophenol in food samples

Trace amounts of Fe³⁺, Pb²⁺, Cu²⁺, Ni²⁺, Co²⁺ and Zn²⁺ ions were efficiently enriched following complexation with silica-gel chemically functionalized with 2-((3-silylpropylimino)methyl)-5-bromophenol. The enriched metal ions efficiently eluted with 6?mL of 4.0?mol?L^?1 nitric acid and their metal contents were determined by flame atomic absorption spectrometry (FAAS). The influences of the analytical parameters and experimental variables on the recoveries of the metal ions under study were investigated and optimized. The method has high sorption preconcentration efficiency even in the presence of various interfering ions. At optimum values of all variables the method is applicable for analysis of real samples with recoveries in the range of 95 to 105% with RSD lower than 4.2% and detection limits between 1.4 and 2.8?µg?L^?1.     

A New and Efficient Procedure for the Production of 1,1-Diacetate from Corresponding Aldehydes Promoted by Silica Chromate (SiO2-O-CrO2-O-SiO2)

Abstract

A wide range of aromatic aldehydes has been selectively converted to 1,1-diacetates using silica chromate (SiO₂?O?CrO₂?O?SiO₂) under solvent-free conditions at room temperature in moderate to good yields. This protocol is mild and efficient compared to other reported methods.

GRAPHICAL ABSTRACT     

Sulfamic Acid–Catalyzed Oxidation of Sulfides to Sulfoxides and Sulfones Using H2O2: Green and Chemoselective Method

A mild, efficient, green, and selective oxidation method of sulfides to sulfoxides or sulfones using H₂O₂ in the presence of catalytic amounts of sulfamic acid has been developed. Various substituted sulfides having functional groups such as alcohol, ester, and aldehyde are successfully and selectively oxidized without affecting the sensitive functionalities in good to excellent yields at room temperature.     

Electronic and optical properties of V doped AlN nanosheet: DFT calculations

Electronic and optical properties of pure and V-doped AlN nanosheet have been investigated using density functional theory, and the dielectric tensor is calculated using the random phase approximation (RPA). The results of structural calculations show that the V atoms tend to replace instead of aluminum atoms with the lowest formation energy. In addition, study of the electronic properties shows that pure AlN nanosheet is a p-type semiconductor that by increasing one V atom, it possesses the metallic properties and magnetic moment becomes Zero. Moreover, by replacing two V atoms, the half-metallic behavior with 100% spin polarization can be found, and each supercell gains a net magnetic moment of 3.99 µ_B. Optical properties like the dielectric function, the energy loss function, the absorption coefficients, the refractive index are calculated for both parallel and perpendicular electric field polarizations, and the results show that the optical spectra are anisotropic.     

Biodegradation of Alprazolam in Pharmaceutical Wastewater Using Mesoporous Nanoparticles-Adhered Pseudomonas stutzeri

The release of pharmaceutical wastewaters in the environment is of great concern due to the presence of persistent organic pollutants with toxic effects on environment and human health. Treatment of these wastewaters with microorganisms has gained increasing attention, as they can efficiently biodegrade and remove contaminants from the aqueous environments. In this respect, bacterial immobilization with inorganic nanoparticles provides a number of advantages, in terms of ease of processing, increased concentration of the pollutant in proximity of the cell surface, and long-term reusability. In the present study, MCM-41 mesoporous silica nanoparticles (MSN) were immobilized on a selected bacterial strain to remove alprazolam, a persistent pharmaceutical compound, from contaminated water. First, biodegrading microorganisms were collected from pharmaceutical wastewater, and Pseudomonas stutzeri was isolated as a bacterial strain showing high ability to tolerate and consume alprazolam as the only source for carbon and energy. Then, the ability of MSN-adhered Pseudomonas stutzeri bacteria was assessed to biodegrade alprazolam using quantitative HPLC analysis. The results indicated that after 20 days in optimum conditions, MSN-adhered bacterial cells achieved 96% biodegradation efficiency in comparison to the 87% biodegradation ability of Pseudomonas stutzeri freely suspended cells. Kinetic study showed that the degradation process obeys a first order reaction. In addition, the kinetic constants for the MSN-adhered bacteria were higher than those of the bacteria alone.     

Reliability of Algorithms Interpreting Topological and Geometric Properties of Porous Media for Pore Network Modelling

Pore network models (PNMs) offer a computationally efficient way to analyse transport in porous media. Their effectiveness depends on how well they represent the topology and geometry of real pore systems, for example as imaged by X-ray CT. The performance of two popular algorithms, maximum ball and watershed, is evaluated for three porous systems: an idealised medium with known pore throat properties and two rocks with different morphogenesis—carbonate and sandstone. It is demonstrated that while the extracted PNM simulates simple flow (permeability) with acceptable accuracy, their topological and geometric properties are significantly different. This suggests that such PNM may not serve more complex studies, such as reactive/convective transport of contaminants or bacteria, and further research is necessary to improve the interpretation of real pore spaces with networks. Linear topology–geometry relations are derived and presented to stimulate development of more realistic PNM.

     

Dielectrophoresis microbial characterization and isolation of Staphylococcus aureus based on optimum crossover frequency

Characterization of antibiotic-resistant bacteria is a significant concern that persists for the rapid classification and analysis of the bacteria. A technology that utilizes the manipulation of antibiotic-resistant bacteria is key to solving the significant threat of these pathogenic bacteria by rapid characterization profile. Dielectrophoresis (DEP) can differentiate between antibiotic-resistant and susceptible bacteria based on their physical structure and polarization properties. In this work, the DEP response of two Gram-positive bacteria, namely, Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-susceptible S. aureus (MSSA), was investigated and simulated. The DEP characterization was experimentally observed on the bacteria influenced by oxacillin and vancomycin antibiotics. MSSA control without antibiotics has crossover frequencies ($f_{x0}$) from 6 to 8 MHz, whereas MRSA control is from 2 to 3 MHz. The $f_{x0}$ changed when bacteria were exposed to the antibiotic. As for MSSA, the $f_{x0}$ decreased to 3.35 MHz compared to $f_{x0}$ MSSA control without antibiotics, MRSA, $f_{x0}$ increased to 7 MHz when compared to MRSA control. The changes in the DEP response of MSSA and MRSA with and without antibiotics were theoretically proven using MyDEP and COMSOL simulation and experimentally based on the modification to the bacteria cell walls. Thus, the DEP response can be employed as a label-free detectable method to sense and differentiate between resistant and susceptible strains with different antibiotic profiles. The developed method can be implemented on a single platform to analyze and identify bacteria for rapid, scalable, and accurate characterization.     

The Newton-Kleinman method for the optimal control of stable weakly regular linear systems

We give an algorithm to find the approximate solution of the linear-quadratic optimal control problem for stable weakly regular linear systems. This algorithm can be understood as a generalization of the Newton-Kleinman method known from the finite-dimensional theory. The central characteristic of our approach is the possibility to solve problems with unbounded control and observation operators, which is motivated by partial differential equations with boundary control and observation. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)