Influence of N+ ion implantation at different temperatures on nanostructural modifications and characteristics of Al alloy surface

Thick (3.0 mm) Al samples (7049 an alloy with 15 elements) were implanted by N⁺ ions of 30 keV energy and fluence of 5 × 10 ¹⁷ N⁺ cm^?2 at different temperatures. The surface modification of the samples was studied using X-ray diffraction (XRD) and atomic force microscope (AFM) analysis. XRD spectra of the samples clearly showed the formation of different phases of AlN. Crystallite sizes (coherently diffracting domains) obtained from AlN diffraction lines showed that at a certain substrate temperature the crystallite size decreases considerably. AFM images showed the formation of grains on Al samples, and it was observed that both grain size and sample surface roughness first decrease and then increase with temperature (i.e. a minimum at a certain temperature is observed). In addition at this temperature, a minimum of intensity is also observed for the intensity of different phases of AlN and the intensity ratio of AlN (200)/AlN (311). This phenomenon is similar to those obtained for thin films and pure metal foils though the sample studied in this work is an Al alloy and the minimum for Al occurred at a value three times larger than that reported for the above cases. Alloy nature of this sample with 14 elements is responsible for the observed results because they may act as defects. Results may also be affected by the residual gases, substrate temperature, dissociation of water in the chamber and the ion energy. Results also showed that the processes of Al nitride and Al oxide formations are competing with each other; decrease of aluminium nitride phases are associated with increase of aluminium oxide phases.     

Facile synthesis and biological assays of novel 2,4-disubstituted hydrazinyl-thiazoles analogs

A convenient, one-pot multi-component synthesis of new 2,4-disubstituted hydrazinyl-thiazoles was accomplished using different aldehydes/ketones, thiosemicarbazide, and 4-methoxy phenacyl bromide in the presence of a catalytic amount of AcOH in EtOH. Products were obtained in reasonable yields and high purity. The in vitro antioxidant activity of hydrazinyl-thiazoles was evaluated by DPPH radical scavenging activity in comparison to ascorbic acid. Synthesized thiazoles 14c and 14g possessed the lowest \(\hbox {IC}_{50}\) values. Also, hydrazinyl-thiazoles were screened for their in vitro antibacterial activity against six strains of bacteria including S. aureus, M. luteus, E. coli, Ps. aeruginosa, B. subtilis, and A. hydrophila where some products showed good antibacterial activity. Moreover, compound 14a showed anticancer activity against melanoma cancerous cell lines A375 with \(\hbox {LC}_{50}= 0.55\hbox { mg}/\hbox {mL}\), slightly selective versus normal cell lines (Hu-2) with \(\hbox {LC}_{50}= 1.19\hbox { mg}/\hbox {mL}\).     

Optimization of solid phase microextraction procedure for determination of paraquat using reduction process

Headspace solid phase microextraction (HS-SPME) followed by gas chromatography–mass spectrometry was developed for the determination of paraquat in urine. The volatile product resulting from reduction of paraquat by sodium borohydride–nickel chloride was used for HS-SPME. The calibration curve was linear from 10–1000 ng/mL and the limit of detection was 0.1 ng/mL. The optimized methods were validated using 500 and 750 ng/mL concentrations of paraquat in the spiked urine samples. The recoveries obtained in this study were 98.2% for intra-day (n = 6) and 99.2% for inter-day (n = 6), respectively, with RSD lower than 1.1%.     

Composite Polymer/Oxide Hollow Fiber Contactors: Versatile and Scalable Flow Reactors for Heterogeneous Catalytic Reactions in Organic Synthesis

Flexible composite polymer/oxide hollow fibers are used as flow reactors for heterogeneously catalyzed reactions in organic synthesis. The fiber synthesis allows for a variety of supported catalysts to be embedded in the walls of the fibers, thus leading to a diverse set of reactions that can be catalyzed in flow. Additionally, the fiber synthesis is scalable (e.g. several reactor beds containing many fibers in a module may be used) and thus they could potentially be used for the large‐scale production of organic compounds. Incorporating heterogeneous catalysts in the walls of the fibers presents an alternative to a traditional packed‐bed reactor and avoids large pressure drops, which is a crucial challenge when employing microreactors.     

Stripping voltammetric determination of copper(II) in natural waters and human hairs based on the adsorption of its complex with Kryptofix 22 on the carbon paste electrode

Traces of copper(II) can be determined by adsorptive stripping voltammetry using Kryptofix 22 as complex forming reagent. First, copper(II)-Kryptofix 22 complex was adsorbed on the carbon paste electrode in phosphate buffer pH 5.3 with an accumulation potential of −0.5 V. Following this, the adsorbed complex was oxidized and detected by anodic differential pulse voltammetric scan from −0.2 to 0.1 V. The effective parameters of sensor response were examined. The detection limit of copper(II) was 1.1 μg/L and relative standard deviations for 50 and 150 μg/L of Cu(II) were 1.2 and 0.96%, respectively. The calibration curve was linear for 2–150 μg/L of copper(II). This technique does not use mercury and therefore is environmentally beneficial. The method, which is reasonably sensitive and selective, has been successfully applied to the determination of trace amounts of copper(II) in water and human hair samples.     

A strategy to enhance the thermal stability of a nanostructured polypyrrole-based coating for solid phase microextraction

We report on a nanostructured self-doped polypyrrole (SPPy) film that was prepared by an electrochemical technique in an electrolyte containing fluorosulfonic acid as the sulfonation reagent. The film was applied as a new fiber material for solid-phase microextraction (SPME) of the pesticides lindane, heptachlor, aldrin, endosulfans I and II prior to their quantitation by GC with electron capture detection. The SPPy nanoparticles have a diameter of <100?nm. The introduction of covalently bound sulfo groups into the backbone of the polymer resulted in improved temperature resistance (~350?°C) and satisfactory extraction efficiency. The thermal stability of the SPPy fiber is superior to common polypyrrole fibers. Extraction was optimized by means of the Taguchi orthogonal array experimental design with an OA₁₆ (4⁵) matrix including extraction temperature, extraction time, salt concentration, stirring rate, and headspace volume. The method displays good repeatability (RSD?<?6%) and linearity (in the range from 0.78 to 100?ng?mL^?1; with an R² of >0.998. The detection limits are <0.23?ng?mL^?1. The method was successfully applied to the analysis of the pesticides in skimmed milk and fruit juice samples, and recoveries are from 84?±?1 to 105?±?1%.

Characterizing n-Isoclinism Classes of Lie Algebras

In this article, we introduce the notion of the equivalence relation, n-isoclinism, between Lie algebras, and obtain some criterions under which Lie algebras are n-isoclinic. In particular, we show that n-isoclinic Lie algebras can be isoclinically embedded into one Lie algebra. Also, we present the notion of an n-stem Lie algebra and prove its existence within an arbitrary n-isoclinism class. In addition, similar to a result of Hekster [6 Hekster , N. S. ( 1986 ). On the structure of n-isoclinam classes of groups . J. Pure Appl. Algebra 40 : 63 – 85 .[Crossref], [Web of Science ®] , [Google Scholar]] in the group case, we characterize the n-stem Lie algebras in the n-isoclinism classes which contains at least one finitely generated Lie algebra L with dim (L ⁿ⁺¹) finite.     

Uniformly defining valuation rings in Henselian valued fields with finite or pseudo-finite residue fields

We give a definition, in the ring language, of _Zp${\mathbb{Z}}_p$ inside _Qp${\mathbb{Q}}_p$ and of _Fp[[t]]${\mathbb{F}}_p[[t]]$ inside _Fp((t))${\mathbb{F}}_p((t))$, which works uniformly for all p   and all finite field extensions of these fields, and in many other Henselian valued fields as well. The formula can be taken existential-universal in the ring language, and in fact existential in a modification of the language of Macintyre. Furthermore, we show the negative result that in the language of rings there does not exist a uniform definition by an existential formula and neither by a universal formula for the valuation rings of all the finite extensions of a given Henselian valued field. We also show that there is no existential formula of the ring language defining _Zp${\mathbb{Z}}_p$ inside _Qp${\mathbb{Q}}_p$ uniformly for all p  . For any fixed finite extension of _Qp${\mathbb{Q}}_p$, we give an existential formula and a universal formula in the ring language which define the valuation ring.     

Chemistry of aqueous silica nanoparticle surfaces and the mechanism of selective peptide adsorption

Control over selective recognition of biomolecules on inorganic nanoparticles is a major challenge for the synthesis of new catalysts, functional carriers for therapeutics, and assembly of renewable biobased materials. We found low sequence similarity among sequences of peptides strongly attracted to amorphous silica nanoparticles of various size (15-450 nm) using combinatorial phage display methods. Characterization of the surface by acid base titrations and zeta potential measurements revealed that the acidity of the silica particles increased with larger particle size, corresponding to between 5% and 20% ionization of silanol groups at pH 7. The wide range of surface ionization results in the attraction of increasingly basic peptides to increasingly acidic nanoparticles, along with major changes in the aqueous interfacial layer as seen in molecular dynamics simulation. We identified the mechanism of peptide adsorption using binding assays, zeta potential measurements, IR spectra, and molecular simulations of the purified peptides (without phage) in contact with uniformly sized silica particles. Positively charged peptides are strongly attracted to anionic silica surfaces by ion pairing of protonated N-termini, Lys side chains, and Arg side chains with negatively charged siloxide groups. Further, attraction of the peptides to the surface involves hydrogen bonds between polar groups in the peptide with silanol and siloxide groups on the silica surface, as well as ion-dipole, dipole-dipole, and van-der-Waals interactions. Electrostatic attraction between peptides and particle surfaces is supported by neutralization of zeta potentials, an inverse correlation between the required peptide concentration for measurable adsorption and the peptide pI, and proximity of cationic groups to the surface in the computation. The importance of hydrogen bonds and polar interactions is supported by adsorption of noncationic peptides containing Ser, His, and Asp residues, including the formation of multilayers. We also demonstrate tuning of interfacial interactions using mutant peptides with an excellent correlation between adsorption measurements, zeta potentials, computed adsorption energies, and the proposed binding mechanism. Follow-on questions about the relation between peptide adsorption on silica nanoparticles and mineralization of silica from peptide-stabilized precursors are raised.     

Polyaniline-coated Fe(3) O(4) nanoparticles: An anion exchange magnetic sorbent for solid-phase extraction

In this study, the capability of the prepared polyaniline-coated Fe(3) O(4) nanoparticles for magnetic solid-phase extraction of three parabens from environmental wastewater, cream, and toothpaste samples is presented. Synthesized Fe(3) O(4) nanoparticles were coated with sulfate-doped polyaniline via polymerization of aniline in the presence of Fe(3) O(4) nanoparticles and sulfuric acid. Here, polyaniline-coated Fe(3) O(4) nanoparticles are presented as anion exchange sorbent, which extract anionic form of parabens via anion exchange with dopant of polyaniline. The experimental conditions affecting extraction efficiency were further studied and optimized. The experimental results showed that maximum extraction efficiency can be obtained at 70 mL sample solution of pH 8, extraction and desorption times of 2 and 1 min, respectively, 100 μL of 3% (v/v) acetic acid in acetonitrile as eluent, and 100 mg of the adsorbent. Under these conditions, the linear dynamic ranges were 0.5-100 μg/L with good correlation coefficients (0.998-0.999). The detection limits were in the range of 0.3-0.4 μg/L and the relative standard deviations were less than 2.4 (n = 5) for the three parabens. Finally, this fast and efficient method was further employed for determination of target analytes in cream, toothpaste, and environmental wastewater samples and satisfactory results were obtained.