Copper (II)-supported polyethylenimine-functionalized magnetic graphene oxide as a catalyst for the green synthesis of 2-arylquinazolin-4(3H)-ones

A novel copper (II) catalyst supported on polyethylenimine-functionalized magnetic graphene oxide (denoted Cu@PEI-MGO) has been developed and applied for the cyclization of benzylacetamide with 2-aminobenzamide to afford 2-arylquinazolin-4(3H)-ones in acetonitrile as an inexpensive, non-toxic and reusable solvent medium. Cu@PEI-MGO was characterized by transmission electron microscopy, scanning electron microscopy, thermo-gravimetric analysis, and Fourier-transform infra-red spectroscopy.     

On a class of bilevel linear mixed-integer programs in adversarial settings

We consider a class of bilevel linear mixed-integer programs (BMIPs), where the follower’s optimization problem is a linear program. A typical assumption in the literature for BMIPs is that the follower responds to the leader optimally, i.e., the lower-level problem is solved to optimality for a given leader’s decision. However, this assumption may be violated in adversarial settings, where the follower may be willing to give up a portion of his/her optimal objective function value, and thus select a suboptimal solution, in order to inflict more damage to the leader. To handle such adversarial settings we consider a modeling approach referred to as \(\alpha \)-pessimistic BMIPs. The proposed method naturally encompasses as its special classes pessimistic BMIPs and max–min (or min–max) problems. Furthermore, we extend this new modeling approach by considering strong-weak bilevel programs, where the leader is not certain if the follower is collaborative or adversarial, and thus attempts to make a decision by taking into account both cases via a convex combination of the corresponding objective function values. We study basic properties of the proposed models and provide numerical examples with a class of the defender–attacker problems to illustrate the derived results. We also consider some related computational complexity issues, in particular, with respect to optimistic and pessimistic bilevel linear programs.     

Development of carbon‐nanotube‐assisted electromembrane extraction in the two‐phase mode combined with GC for the determination of basic drugs

In this work, carbon‐nanotube‐assisted electromembrane extraction in the two‐phase mode combined with GC was developed for the preconcentration and determination of basic drugs in body fluids. The multiwalled carbon nanotubes dispersed in organic solvent are held in the pores of the porous fiber wall by capillary forces and sonification. The membrane with immobilized carbon nanotubes acts as a sorbent and provides an additional pathway for analyte transport. This study demonstrates that the immobilization of carbon nanotubes in the supported liquid membrane is an excellent approach to enhance the performance of the extraction. Optimization of the variables affecting this method was carried out in order to achieve the best extraction efficiency. Optimal extractions were accomplished with octanol as the extraction solvent, 50 V as the driving force and pH 7.4 in the sample solution with the whole assembly agitated at 1000 rpm for 20 min. Under the optimized extraction conditions, the proposed technique provided good linearity (R² > 0.9990), repeatability (3.5–3.8%), low LODs (1.5 ng/mL), good preconcentration factors (292–316) and high recoveries (80–87%). Finally, this method was successfully used for the determination of tramadol and methadone in different body fluids including plasma and urine samples.     

Electrochemical determination of homocysteine using carbon nanotubes modified paste electrode and isoprenaline as a mediator

Homocysteine (HCy) is an important amino acid containing thiol group and is known as a risk factor in relation to ischemic heart disease and stroke. In this study the electrochemical determination of homocysteine (HCy) has been described using isoprenaline hydrochloride (ISP) as a mediator on multiwall carbon nanotubes modified paste electrode (MWCNTPE). Electrochemical behavior of homocysteine was investigated by cyclic voltarrtmetry and chronoamperometry. The cyclic voltammograms showed that the electrocatalytic oxidation of homocysteine occurs in the presence of ISP on the surface of MWCNTPE at a potential about 640 mV. Also, results showed that the oxidatation peak current of HCy at the modified carbon nanotubes electrode was more than unmodified electrode. The diffusion coefficient and the kinetic parameters including electron transfer coefficient and rate constant of electrocatalytic reaction were determined using electrochemical approaches. Linear sweep voltammetry results showed that electrocatalytic oxidation peak current of HCy had linear dynamic range in the range of 5.0 to 800 μmol L^?1 with a detection limit of 3.3 μmol L^?1 in pH 3.5 (universal buffer).     

Unlocking the Secrets of Cancer Stem Cells with γ-Secretase Inhibitors: A Novel Anticancer Strategy

The dysregulation of Notch signaling is associated with a wide variety of different human cancers. Notch signaling activation mostly relies on the activity of the γ-secretase enzyme that cleaves the Notch receptors and releases the active intracellular domain. It is well-documented that γ-secretase inhibitors (GSIs) block the Notch activity, mainly by inhibiting the oncogenic activity of this pathway. To date, several GSIs have been introduced clinically for the treatment of various diseases, such as Alzheimer’s disease and various cancers, and their impacts on Notch inhibition have been found to be promising. Therefore, GSIs are of great interest for cancer therapy. The objective of this review is to provide a systematic review of in vitro and in vivo studies for investigating the effect of GSIs on various cancer stem cells (CSCs), mainly by modulation of the Notch signaling pathway. Various scholarly electronic databases were searched and relevant studies published in the English language were collected up to February 2020. Herein, we conclude that GSIs can be potential candidates for CSC-targeting therapy. The outcome of our study also indicates that GSIs in combination with anticancer drugs have a greater inhibitory effect on CSCs.     

Application of nanoparticles in the potentiometric ion selective electrodes

Among the various analytical techniques available, the use of ion-selective electrodes is a wellestablished routine analytical technique. Good ion-selective electrodes (ISEs) possess many advantages over traditional methods for analysis and provide accurate, reproducible, fast, and regular selective determination of various ionic species. Modification of ISEs with nanoparticles has shown interesting ability toward various ions and biological molecules. In this article we review some of developments about applications of nanoparticles in the construction of ISEs in recent years.     

Optimization of the separation of chlorophenols with stepwise gradient elution in reversed phase liquid chromatography

An optimization technique based on gradient elution was used to separate eleven chlorophenols by reversed phase liquid chromatography. The separation was based on gradient elution with a stepwise variation pattern of the volume fraction of organic modifier, phi, in the mobile phase. Initially, two-, three-, and four-parameter equations which describe the dependence of ln k' upon phi, were examined for their ability to fit the experimental data. It was found that, among these equations, the four-parameter equation gave the best fit of the experimental data. In addition to separation optimization, a non-linear least squares program with a grid search for initial estimates was used to determine the best variation pattern. The best variation pattern was obtained with phi(1)= 0.27, phi(2)= 0.39, phi(3)= 0.62, t(1) = 33 min, and t(2) = 11 min. This pattern allowed the chromatographic separation of the chlorophenols with a good resolution and a total analysis time of 51 min. Good agreement was observed between predicted and experimental values of the retention times under optimal condition.     

Efficient synthesis of chromeno[4,3-b]pyrano[3,4-e]pyridine-6,8-dione derivatives via multicomponent one-pot reaction under mild reaction conditions in water

10-Methyl-7-aryl-7,12-dihydro-6H,8H-chromeno[4,3-b]pyrano[3,4-e]pyridine-6,8-dione derivatives are significant class of compounds and this is critical to develop methods in water using commercially available and non-toxic catalysts. In this paper, an efficient method is introduced for the synthesis of 10-methyl-7-aryl-7,12-dihydro-6H,8H-chromeno[4,3-b]pyrano[3,4-e]pyridine-6,8-dione derivatives. For the synthesis of the desired products, a multicomponent reaction was designed and performed between 4-hydroxycoumarin, an aldehyde, 6-methyl-2H-pyran-2,4(3H)-dione, and ammonium acetate. The products are obtained under green conditions in water in the presence of a catalytic amount of L-proline (10 mol%). The advantage of this method is no need to any toxic solvent, which is critical from the environmental viewpoint. A possible mechanism was suggested, which confirms the role of L-proline in the reaction as the catalyst.

     

BiVO4‐Silica Composites Containing Cobalt Phthalocyanine Groups: Synthesis,Characterization and Application in Photodegradation of 2,4,6‐Trichlorophenol

BiVO₄‐Silica composites were prepared and grafted with sulfonated cobalt phthalocyanine. The structural and chemical properties including crystalline phase, specific surface area, UV–Visible diffuse reflectance behavior, morphology and photocatalytic activity were investigated. Depending on the silica content and subsequently amounts of loaded phthalocyanine, various catalytic activities were observed. The sample containing nominal 15% silica and grafted with phthalocyanine showed less aggregated form of this organic dye, smaller and nanometric particles, and higher photocatalytic activity in degradation of 2,4,6‐trichlorophenol.