Pruning of recurrent neural models: an optimal brain damage approach

Nonlinear Dynamics - This paper considers the problem of pruning recurrent neural models of perceptron type with one hidden layer which may be used for modelling of dynamic system. In order to...     

Distinguishing secant from cactus varieties

Foundations of Computational Mathematics - Cactus varieties are a generalization of secant varieties. They are defined using linear spans of arbitrary finite schemes of bounded length, while secant...     

Chitin and chitin-cellulose composite hydrogels prepared by ionic liquid-based process as the novel electrolytes for electrochemical capacitors

This paper reports on the preparation and electrochemical performance of chitin- and chitin-cellulose-based hydrogel electrolytes. The materials were prepared by a casting solution technique using ionic liquid-based solvents. The method of chitin dissolution in ionic liquid with the assistance of dimethyl sulfoxide co-solvent was investigated. The obtained membranes were soaked with 1-M lithium sulfate aqueous solution. The prepared materials were preliminarily characterized in terms of structural and physicochemical properties. Further, the most promising biopolymer membranes were assembled with activated carbon cloth electrodes in symmetric electrochemical capacitor cells. The electrochemical performances of these devices were studied in a 2-electrode system by commonly known electrochemical techniques, such as cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The devices operated at a maximum voltage of 0.8 V. All the investigated materials have shown high efficiency in terms of specific capacitance, power density, and cyclability. The studied capacitors exhibited specific capacitance values in the range of 92–98 F g⁻¹, with excellent capacitance retention (ca. 97–98%) after 20,000 galvanostatic charge and discharge cycles. Taking into account the above information and the eco-friendly nature of the biopolymer, it appears that the prepared chitin- and chitin-cellulose-based hydrogel electrolytes can be promising components for green electrochemical capacitors.

     

Crystal structures,electrochemical properties,antioxidant screening and in vitro cytotoxic studies on four novel Cu(II) complexes of bidentate Schiff base ligands derived from 2-methoxyethylamine

Four novel Schiff base ligands and their copper(II) complexes, [Cu(L¹)₂] (1), [Cu(L²)₂] (2), [Cu(L³)₂] (3), and [Cu(L⁴)₂] (4), were synthesized and characterized by elemental analyses, FT-IR, and UV–Vis spectroscopy. The ligands were synthesized from the condensation of 2-methoxyethylamine with various salicylaldehyde derivatives (x-salicylaldehyde for HLⁿ, x = H (n = 1), 5-Br (n = 2), 3-OMe (n = 3), and 4-OMe (n = 4)). The molecular structures of 1, 2, and 3 were determined by the single crystal X-ray diffraction technique. The redox behavior studies of the complexes in acetonitrile display the electronic effects of the groups on the redox potential. The antioxidant activity of the Schiff base ligands and their Cu(II) complexes was evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method and FRAP assay. Furthermore, the in vitro anticancer activity of compounds was screened, including MTT and migration assays against gastric cancer cell line (MKN-45). The results show that all ligands and complexes have antioxidant and anticancer activity in a concentration-dependent way.     

Experimental studies of charge density distribution in the crystals of cytisine and N-methylcytisine. Inside the <Emphasis Type="Italic">Fake Tobacco</Emphasis>

The high-resolution X-ray data for two bioactive molecules: cytisine (1) and its N-methyl derivative (2) have been collected up to sinθ/λ = 1.12 Å^?1 for 1 and 1.0 Å^?1 for 2. This data was used for modeling of the fine features of electron density distribution, including bonding density and electron lone pairs. The quality of the model was checked by, e.g., rigid bond test and RDA analysis. The topological analysis (gradient field analysis) has been also performed for both inter- and intramolecular interactions. In case of 1 a number of intermolecular interactions, from relatively strong N-H···O hydrogen bonds to weak H···H contacts was found, and their topological features were analyzed. For N-methyl derivative, only few intermolecular bonding contacts were found. The analyzed features show that besides the structural similarities of both alkaloids, the electron density distribution and consequently all its derivatives differ quite significantly in places.     

Effects of reduced inflation pressure and vehicle loading on off-road traction and soil stress and deformation state

Field experiments on off-road vehicle traction and wheel–soil interactions were carried out on sandy and loess soil surfaces. A 14 T, 6 × 6 military truck was used as a test vehicle, equipped with 14.00-20 10 PR tyres, nominally inflated to 390 kPa. Tests were performed at nominal and reduced (down to 200 kPa) inflation pressures and at three vehicle loading levels: empty weight, loaded with 3.6 and 6.0 T mass (8000, 11,600 and 14,000 kg, respectively). Traction was measured with a load cell, attached to the rear of the test vehicle as well as to another, braking vehicle. Soil stress state was determined with the use of an SST (stress state transducer), which consists of six pressure sensors. Soil surface deformation was measured in vertical and horizontal directions, with a videogrammetric system. Effects of reduced inflation pressure as well as wheel loading on traction and wheel–soil interactions were analyzed. It was noticed that reduced inflation pressure had positive effects on traction and increased stress under wheels. Increasing wheel load resulted in increasing drawbar pull. These effects and trends are different for the two soil surfaces investigated. The soil surface deformed in two directions: vertical and longitudinal. Vertical deformations were affected by loading, while longitudinal were affected by inflation pressure.