Determination of cadmium and zinc in water samples by flame atomic absorption spectrometry after cloud-point extraction

The phase-separation phenomenon of nonionic surfactants occurring in an aqueous solution was used for the extraction of Cd and Zn from water samples. After complexation with 6-(4-nitrophenyl)-2,4-diphenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene (NDDBH) in hydrochloric acid medium (pH 1), the analytes were quantitatively extracted after centrifugation into the phase rich in the nonionic surfactant octylphenoxypolyethoxyethanol (Triton X-114). Tetrahydrofuran acidified with 0.1 M HCl was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry. The adopted concentrations for NDDBH, Triton X-114 and hydrochloric acid were all optimized. Detection limits (3σ) of 0.33 and 0.85 ng/mL along with enrichment factors of 157 and 118 for Cd and Zn, respectively, were achieved. The proposed method was applied to the determination of Cd and Zn in acidic solutions of certified reference materials. A comparison with certified values was performed for an evaluation of the accuracy, resulting in a good agreement according to the t-test at a 95% confidence level. The high efficiency of the cloud-point extraction to carry out the determination of the studied analytes in complex matrices was, therefore, demonstrated. The text was submitted by the authors in English.     

Sulfonic acid-functionalized LUS-1: an efficient catalyst for tetrahydropyranylation/depyranylation of alcohols

Efficient acidic functionalization of mesoporous silica LUS-1 (Laval University Silica) and its application as a recyclable heterogeneous catalyst for DHP (3,4-dihydro-2H-pyran) protection of alcohols and the subsequent removal of the corresponding protecting group have been reported. This green method offers a number of advantages such as short reaction time, good yields of protection and deprotection, simple work-up procedure, recyclable catalyst, and environmentally friendly conditions.     

Application of SBA-Pr-SO<Subscript>3</Subscript>H in the synthesis of 2,3-dihydroquinazoline-4(1<Emphasis Type="Italic">H</Emphasis>)-ones: characterization,UV–Vis investigations and DFT studies

An efficient one-pot synthesis of 2,3-dihydroquinazoline-4(1H)-one derivatives 4a–l is described using SBA-Pr-SO₃H as a heterogeneous acid catalyst. The present methodology resulted in various derivatives of 2,3-dihydroquinazoline-4(1H)-one in good yield via a three-component reaction of isatoic anhydride, aldehydes and ammonium acetate. SBA-Pr-SO₃H played a significant role as an efficient mesoporous catalyst due to its pore size of 6 nm. Additionally, UV–Vis spectrum of the products was studied in order to investigate their application as UV absorbers.     

A closed-form solution for nonlinear oscillation and stability analyses of the elevator cable in a drum drive elevator system experiencing free vibration

Responses of the dynamical systems to some extent are affected by the natural frequencies. In the present paper, the parameter expansion method (PEM) is employed to investigate nonlinear oscillation and stability of the elevator’s drum as a single-degree-of-freedom (SDOF) swing system. A sensitivity analysis to observe the influence of various parameters on the nonlinear dynamic response, stability and natural frequency is performed. Comparing the results of the proposed closed-form analytical solution, the traditional numerical iterative time integration solution, and the linearized governing equations confirm the accuracy and efficiency of the proposed approach. Based on the results of the proposed closed-form solution, the linearization errors in calculating the natural frequencies in different cases are discussed as well. In contrast to the available numerical methods, the proposed method is free from the numerical damping and the time integration accumulated errors. Moreover, in comparison with the traditional multistep numerical iterative time integration methods, a much less computational time is required for the method in this research. Results reveal that for nonlinear systems, the natural frequency is remarkably affected by the initial conditions. Furthermore, the stability decreases as the dimensions of the mechanism increase.     

Synthesis and antibacterial activity of N-[2-(2-naphthyl)ethyl]piperazinyl quinolones

A series of N-[2-(2-naphthyl)ethyl]piperazinyl quinolones containing a carbonyl related functional groups (oxo- or oxyimino-) on the ethyl spacer was synthesized and evaluated for antibacterial activity. The synthesis of N-[2-(2-naphthyl)ethyl]piperazinyl quinolones was achieved through the versatile and efficient synthetic route that involved reaction of piperazinyl quinolones with appropriate α-bromoketone or α-bromooxime derivatives. The structures of new compounds were confirmed by elemental analysis, IR and NMR spectra. Antibacterial data indicated that some of the new N-[2-(2-naphthyl)ethyl]piperazinyl quinolones showed good antibacterial activity and modification of the position 8 and N-1 substituent on quinolone ring, and ethyl spacer functionality produced significant changes in activity against Gram-positive and Gram-negative bacteria.     

State‐of‐the‐Art and Trends in Synthesis,Properties, and Application of Quantum Dots‐Based Nanomaterials

Quantum dots (QDs) with a nanoscale size range have attracted significant attention in various areas of nanotechnology due to their unique properties. Different strategies for the synthesis of QD nanoparticles are reported in which various factors, such as size, impurities, shape, and crystallinity, affect the QDs fundamental properties. Consequently, to obtain QDs with appropriate physical properties, it is required to select a synthesis method which allows enough control over the surface chemistry of QDs through fine‐tuning of the synthesis parameters. Moreover, QDs nanocrystals are recently used in multidisciplinary research integrated with biological interfaces. The state‐of‐the‐art methods for synthesizing QDs and bioconjugation strategies to provide insight into various applications of these nanomaterials are discussed herein.     

Simplification of Double Folding Model Calculations in Study of Interaction Between Two Deformed Nuclei

The Double Folding （DF） model calculation of the internuclear potential in heavy-ion interactions when the participant nuclei are deformed in their ground states involves a six-dimensional integral. Using the multipole expansion in these calculations, the DF six-dimensional integral reduce to the sum of the products of three single-dimensional integrals. In this paper we have presented a procedure for the calculation of the radius dependent functions in the multipole expansion of the nuclear density and their Fourier transforms. We have also reduced the DF model integrals to the sum of the single dimensional integrals using the obtained relations for the radius dependent functions in the multipole expansion and their Fourier transforms.     

Application of SBA-Pr-SO<Subscript>3</Subscript>H as a nanoreactor in the one-pot synthesis of spiroquinazolinones

An efficient method for the synthesis of spiroquinazolinones was developed using isatoic anhydride, hydrazides and cyclic ketones, through a rapid one-pot three-component reaction in the presence of SBA-Pr-SO₃H under solvent-free conditions. SBA-Pr-SO₃H was an efficient heterogeneous nanoreactor with a pore size of 6 nm which can be easily handled and removed from the reaction mixture by simple filtration and can be reused several times without any loss of activity. The main advantages of using this nanoreactor are high product yields, being environmentally benign, short reaction times, and easy handling.