Sensitive Electrochemical Determination of Trifluralin at a Disposable Pencil Graphite Electrode

A sensitive differential pulse (DP) voltammetric method has been proposed for the determination of trifluralin (TFA) based on both its reduction and oxidation at a disposable pencil graphite electrode (PGE). DP voltammograms recorded under optimized conditions show that oxidation and reduction peak currents increased linearly in the range from 1.0 to 75.0 μM and from 0.50 to 100.0 μM TFA, respectively. LOD and sensitivity values have been determined as 0.39 μM and 11170 μA mM⁻¹ cm⁻² for oxidation and as 0.20 μM and 22167 μA mM⁻¹ cm⁻² for reduction. The acceptable recovery values (95.2–104.8 %) were obtained from real water samples.     

Efficiency enhancement with chloride to iodide ion exchange of benzimidazolium salt as a redox mediator

The new benzimidazolium derivative (SM-1) salt with ion exchange from the (SM-0) was fabricated and characterized by proton-nuclear magnetic resonance (¹H-NMR), carbon-nuclear magnetic resonance (¹³C-NMR), Fourier-transform infrared spectroscopy (FT-IR), electrospray ionization (EIS-MS), thermal analysis (TG), cyclic voltammetry (CV), and ultraviolet-visible spectroscopy (UV-vis), for electrolytes (liquid or dried) in the DSSC charge transportation mechanism. Also, the influence of ion exchange from chloride to iodine in the synthesized electrolytes, compared to other electrolytes (conventional or commercial), was investigated about DSSC performance efficiency. When using as a liquid electrolyte (SM-1), the power conversion efficiency (ƞ) of the working DSSC device was recorded as 1.980% and it was observed that the performances of DSSCs increased up to 56% when comparing dried electrolyte for SM-1 without conventional redox material (I^-/I₃^-). In the future, different molecular modifications of this type of benzimidazole derivatives or mixtures with conventional redox couples may further improve the performance of DSSC devices.     

Phenothiazine-based chalcones as potential dual-target inhibitors toward cholinesterases (AChE,BuChE) and monoamine oxidases (MAO-A,MAO-B)

Chalcones targeting neurodegenerative diseases have been known as attractive structures in drug design and discovery. In this study, phenothiazine-based chalcones as ChEs and MAOs inhibitors were designed and synthesized via base-catalyzed Claisen-Schmidt condensation, and chemical structures of the compounds were elucidated by NMRs and HRMS. Compounds 3 and 9 showed promising inhibition potency against AChE enzyme with IC₅₀ values of 0.221 μM and 0.053 μM while compound 9 displayed remarkable inhibition potency toward MAO-B enzyme with IC₅₀ value of 0.048 μM. Compound 9 , as a dual-target inhibitor, selectively inhibited AChE and MAO-B enzymes. This promising behavior is an advantage for the compound since MAO-B and AChE inhibition have a role in Alzheimer's disease. Fused tricyclic ring systems such as phenothiazine incorporated with chalcone moiety being multitargeting ligands may help scientists for the rational design of novel lead compounds targeting neurodegenerative illnesses.     

Enhanced sedimentation and coalescence of petroleum crude oil emulsions by the new generation of environmentally friendly yellow chemicals

This study compares by means of new and advanced destabilization protocols the efficiency of new chemistry environmentally friendly (yellow) demulsifiers with already commercially available red demulsifiers in destabilizing two types of water-in-oil (w/o) emulsions: petroleum crude oil emulsions and model dense packed layers (DPLs). Oil–water separation profiles were measured by low-field nuclear magnetic resonance (NMR), which allows monitoring the water content as well as the mean droplet size in the emulsion as function of the sample height and the time. Separation profiles measured by NMR depicted an increase of the free water release kinetics as the concentration of demulsifier as well as the sedimentation rate increased. The water resolution was not substantially improved by increasing the concentration further while the water quality was worse, most likely due to adsolubilization. There was no observation of DPL formation in these crude oil emulsions. Four different demulsifiers were tested on a model DPL and compared with normal crude oil emulsions. One chemical showed higher efficiency in destabilizing DPL than destabilizing crude oil emulsion. The interfacial rheological properties for one of the systems showed a slight increase in the elastic modulus (E′), as the concentration of demulsifier increased. The increment of the elastic modulus is not totally understood. The most central parameters were represented by principal component analysis (PCA). PCA did not contribute in a better characterization of the chemicals. The new-generation yellow demulsifiers did not reproduce the efficiency of commercially available, less environmentally friendly, (red) demulsifiers.     

Computing the integer programming gap

We determine the maximal gap between the optimal values of an integer program and its linear programming relaxation, where the matrix and cost function are fixed but the right hand side is unspecified. Our formula involves irreducible decomposition of monomial ideals. The gap can be computed in polynomial time when the dimension is fixed. Partially supported by the National Science Foundation (DMS-0200729).     

A new perspective to stress–strength models

The stress–strength models have been widely used for reliability design of systems. In these models the reliability is defined as the probability that the strength is larger than the stress. The analysis is then based on the binary reliability theory since there are two possible states for the system. In this paper, we study the stress–strength reliability in a different framework assigning more than two states to the system depending on the difference between strength and stress values. In other words, the stress–strength reliability is studied under multi-state system modeling. System state probabilities are evaluated and estimated under various assumptions on the system. The multicomponent form is also studied and some results are provided for large systems.     

Improvement of catalytic properties of Candida rugosa lipase by sol-gel encapsulation in the presence of magnetic calix[4]arene nanoparticles

Candida rugosa lipase (CRL) was encapsulated within a chemically inert sol-gel support prepared by polycondensation with tetraethoxysilane (TEOS) and octyltriethoxysilane (OTES) in the presence of N-methylglucamine based calix[4]arene magnetic nanoparticles. The results indicate that the magnetic calix[4]arene based encapsulated lipase particularly has shown high conversion and enantioselectivity. It has also been noticed that the magnetic calix[4]arene based encapsulated lipase has excellent enantioselectivity (E = 460) as compared to the free enzyme (E = 166) with an ee value of >98% for S-Naproxen.     

Catalytic effect of calix[n]arene based sol–gel encapsulated or covalent immobilized lipases on enantioselective hydrolysis of (R/S)-naproxen methyl ester

In this paper the catalytic performance of the immobilized lipases was investigated in the presence of calixarene based polymers using different immobilization techniques. For this reason, Candida rugosa lipase was encapsulated in sol–gel matrices using alkoxysilane precursors and calix[n]arene based silica polymers as additives. The hydrolytic activities of encapsulated lipases were evaluated and compared with the free lipase and covalently immobilized lipases (CnP-L). These encapsulated lipases were also used in the kinetic resolution of the R/S-Naproxen methyl ester. The results indicated that the C6P encapsulated lipase has significantly higher conversion and enantioselectivity as compared to the free lipase; other encapsulated lipases and CnP-L. The optimal pH and temperature region of the C6P encapsulated lipase in the kinetic resolution of the R/S-naproxen methyl ester were 7.0 and 55?°C. Nevertheless, the encapsulated lipases have good stability, adaptability and reusability in comparison with the free enzyme.     

Consistent empirical physical formula construction for recoil energy distribution in HPGe detectors by using artificial neural networks

The gamma-ray tracking technique is a highly efficient detection method in experimental nuclear structure physics. On the basis of this method, two gamma-ray tracking arrays, AGATA in Europe and GRETA in the USA, are currently being tested. The interactions of neutrons in these detectors lead to an unwanted background in the gamma-ray spectra. Thus, the interaction points of neutrons in these detectors have to be determined in the gamma-ray tracking process in order to improve photo-peak efficiencies and peak-to-total ratios of the gamma-ray peaks. In this paper, the recoil energy distributions of germanium nuclei due to inelastic scatterings of 1–5 MeV neutrons were first obtained by simulation experiments. Secondly, as a novel approach, for these highly nonlinear detector responses of recoiling germanium nuclei, consistent empirical physical formulas (EPFs) were constructed by appropriate feedforward neural networks (LFNNs). The LFNN-EPFs are of explicit mathematical functional form. Therefore, the LFNN-EPFs can be used to derive further physical functions which could be potentially relevant for the determination of neutron interactions in gamma-ray tracking process.