Solid-phase extraction and simultaneous spectrophotometric determination of trace amounts of Co, Ni and Cu using partial least squares regression

A novel sensitive and simple method for rapid extraction, preconcentration and determination of cobalt, nickel and copper as their 1-(2-pyridilazo)-2-naphthol (PAN) complexes using polytetrafluoroethylene filter as solid phase and multivariate calibration of spectrophotometric data is presented. The analytical wavelengths of 400-700 nm were chosen and the experimental calibration matrix for partial least squares (PLS) was designed with 21 samples of 5.90-41.25, 0.30-29.35 and 0.64-41.30 ng ml⁻¹ for cobalt, nickel and copper, respectively. The cross-validation method was used for selecting the number of components. The root-mean-square errors of predictions (RMSEPs) were between 0.48 and 1.37 ng ml⁻¹. In this work we could reach preconcentration factors of 100 or even higher by using polytetrafluoroethylene as solid phase which is cheap and can be used in a wide range of pH, flow rates and for many times. The proposed method was successfully applied to the simultaneous determination of Co, Ni and Cu in tap and pit water samples.     

A new peptide nucleotide acid biosensor for electrochemical detection of single nucleotide polymorphism in duplex DNA via triplex structure formation

In this paper, we report a new PNA biosensor for electrochemical detection of point mutation or single nucleotide polymorphism (SNP) in p53 gene corresponding oligonucleotide based on PNA/ds-DNA triplex formation following hybridization of PNA probe with double-stranded DNA (ds-DNA) sample without denaturing the ds-DNA into single-stranded DNA (ss-DNA). As p53 gene is mutated in many human tumors, this research is useful for cancer therapy and genomic study. In this approach, methylene blue (MB) is used for electrochemical signal generation and the interaction between MB and oligonucleotides is studied by differential pulse voltammety (DPV). Probe-modified electrode is prepared by self-assembled monolayer (SAM) formation of thiolated PNA molecules on the surface of Au electrode. A significant increase in the reduction signal of MB following hybridization of the probe with the complementary double-stranded oligonucleotide (ds-oligonucleotide) confirms the function of the biosensor. The selectivity of the PNA sensor is investigated by non-complementary ds-oligonucleotides and the results support the ability of the sensor to detect single-base mismatch directly on ds-oligonucleotide. The influence of probe and ds-DNA concentrations on the effective discrimination against complementary sequence and point mutation is studied and the concentration of 10^?6 M is selected as appropriate concentration. Diagnostic performance of the biosensor is described and the detection limit is found to be 4.15 × 10^?12 M.     

Multiobjective Problems: Enhanced Necessary Conditions and New Constraint Qualifications through Convexificators

In this paper, we study necessary optimality conditions for local Pareto and weak Pareto solutions of multiobjective problems involving inequality and equality constraints in terms of convexificators. We develop the enhanced Karush–Kuhn–Tucker conditions and introduce the associated pseudonormality and quasinormality conditions. We also introduce several other new constraint qualifications which entirely depend on the feasible set. Then a connecting link between these constraint qualifications is presented. Moreover, we provide several examples that clarify the interrelations between the different results that we have established.     

Synthesis and characterization of RuO<Subscript>2</Subscript>@ZrO<Subscript>2</Subscript> core–shell nano particles as heterogeneous catalyst for oxidation of benzylic alcohols in different conditions

In this study, new RuO₂@ZrO₂ core–shell nanoparticles have been produced using simple procedure and characterized by the spectroscopic methods (XRD and HR-TEM techniques). Catalytic activity of the synthesized nano powders has been investigated in the liquid-phase selective oxidation of benzyl alcohols. Also, the effect of some parameters such as optimum weight ratio for Ru doping, catalyst, oxidant type and various solvents was studied in room temperature, reflux, ultrasound, microwave conditions and UV–vis irradiation. The catalyst exhibits excellent activity and high conversion under mild conditions. Furthermore, this reagent was recycled and reused three times in the model reaction.     

Experimental and numerical study on simultaneous effects of scattering and absorption on fluorescence spectroscopy of a breast phantom

Detection of dysplastic lesions can decrease morbidity and mortality caused by cancer. The fluorescence spectroscopy is a noninvasive method of detecting dysplasia in several organs. During dysplastic progression, fluorescence intensity of spectrum is changed due to variation in absorption and scattering coefficients of tissue. In this work we have experimentally verified simultaneous effects of scattering and absorption coefficients on fluorescence intensity of different tissue like phantoms with the same optical properties as the human breast ductal carcinoma. The results are compared with those obtained by Monte Carlo simulation and good agreement between them is observed. This provides an important detecting method to discriminate dysplastic tissue from normal tissue.     

A finite volume method for solving the two-sided time-space fractional advection-dispersion equation

We present a finite volume method to solve the time-space two-sided fractional advection-dispersion equation on a one-dimensional domain. The spatial discretisation employs fractionally-shifted Grünwald formulas to discretise the Riemann-Liouville fractional derivatives at control volume faces in terms of function values at the nodes. We demonstrate how the finite volume formulation provides a natural, convenient and accurate means of discretising this equation in conservative form, compared to using a conventional finite difference approach. Results of numerical experiments are presented to demonstrate the effectiveness of the approach.     

Metal matrix composites for sustainable lotus-effect surfaces

The lotus effect involving roughness-induced superhydrophobicity is a way to design nonwetting, self-cleaning, omniphobic, icephobic, and antifouling surfaces. However, such surfaces require micropatterning, which is extremely vulnerable to even small wear rates. This limits the applicability of the lotus effects to situations when wear is practically absent. To design sustainable superhydrophobic surfaces, we suggest using metal matrix composites (MMCs) with hydrophobic reinforcement in the bulk of the material, rather than only at its surface. Such surfaces, if properly designed, provide roughness and heterogeneity needed for superhydrophobicity. In addition, they are sustainable, since when the surface layer is deteriorated and removed due to wear, hydrophobic reinforcement and roughness remains. We present a model and experimental data on wetting of MMCs. We also conducted selected experiments with graphite-reinforced MMCs and showed that the contact angle can be determined from the model. In order to decouple the effects of reinforcement and roughness, the experiments were conducted for initially smooth and etched matrix and composite materials.