Dynamical behavior,chaos control and synchronization of a memristor-based ADVP circuit

This paper is devoted to study the dynamical behavior of a modified Autonomous Van der Pol-Duffing (ADVP) circuit when its nonlinear element is replaced by a flux controlled memristor. The bifurcation diagrams, Lyapunov exponents, and phase portraits of the state variables are presented. Then, the chaos which appears at certain values of the system’s parameters is controlled using linear feedback control. Finally, the synchronization between two chaotic modified ADVP circuits is achieved in the case of fully unknown parameters of the system using adaptive synchronization.     

Partial entropy creation of a two-level atom with intrinsic decoherence

By using an algebraic dynamical approach, the atom–field bipartite system in mixed state is employed to investigate the influence of intrinsic decoherence and Stark shift on the partial entropy change and the entanglement. It is shown that, quality of the partial entropy is improved significantly by introducing the intrinsic decoherence and(or)Stark shift. In addition, by the concept of the lower bound of the concurrence, the entanglement between the atom and the field under the influences of intrinsic decoherence and Stark shift is also presented.     

Composition, structure and solution properties of polysaccharides extracted from leaves of Mesembryanthenum crystallinum

Water and Chelator-soluble polymers were independently isolated from the alcoholic-insoluble substance (AIS) of Mesembryanthenum crystallinum leaves. After precipitation in ethanol and ultrafiltration (40 kD cut-off) of recovered solids dissolved in water, the yield relative of the so-call Lw and LCh polymers to the AIS dry matter was 2.5 ± 0.2 and 7 ± 0.5%. The galacturonic acid contents were 67 ± 3% and 63 ± 5%. The degrees of methylesterification of ca. 45 ± 3% and 50 ± 3%, showed that Lw and LCh belonged to the fairly methylesterified pectin class. From sugar analysis, LCh was shown to contain at least two types of pectic blocks, homogalacturonan (HG: 58%) and rhamnogalacturonan-I (RG-I: 34%). Their structure were deduced after saponification, polygalacturonase treatments, size exclusion chromatography (SEC) onto Sephacryl S-200 and then sugar composition of the collected fractions. The main polymers were methylesterified HG (32%), some of them being linked to non-methylesterified HG (10%), and to polygalacturonase-resistant HG (17%). In addition, there were (1) a highly soluble RG-I with long galactan side chains (RG-I-gal accounting for 9%) and (2) a RG-I with short arabino-galactan side chains (25%), named RG-I-ara/gal that was almost totally lost during SEC analysis, due to its low solubility at room temperature and in absence of chelators.SEC coupled with differential refractive index and light scattering showed that highly methylesterified HG chains exhibited aggregate structures in solution due to intermolecular hydrophobic interactions. These interactions formed hydrophobic clusters, which have been characterized by surface tension measurements and with a polarity probe, the Coomassie Brilliant Blue dye. After alkaline treatment of LCh, the self-assembly of HG disappeared.     

Thermal decomposition study and biological characterization of zinc(II) 2-chlorobenzoate complexes with bioactive ligands

New zinc(II) 2-chlorobenzoates of general formula [Zn(2-ClC₆H₄COO)₂(L)₂] (where L = caffeine—caf, urea—u, methyl-3-pyridylcarbamate—mpc, phenazone—phen, theophylline—thp) were synthesised and characterised by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied by TG/DTG and DTA methods in nitrogen and in air atmosphere. During the thermal decomposition of the studied compounds the release of organic ligands take place followed by the decomposition of 2-chlorobenzoate anion. The volatile decomposition intermediates were proved by mass spectrometry. Zinc oxide was found as the final product of the thermal decomposition performed up to 1,000 K. The antimicrobial activity of the zinc(II) complexes against various strains of bacteria, yeasts and filamentous fungi has been investigated. It was found that the prepared compounds decreased the growth of Staphylococcus aureus, Escherichia coli, Candida albicans, Rhizopus oryzae and Microsporum gypseum, respectively. The most resistant to all tested compounds was probiotic strain of Lactobacillus plantarum. The presence of zinc and ligands in the prepared compounds increased the inhibitory effect compared to sodium salt of prepared compounds and free ligands.     

Characterization of the NIST shellfish Standard Reference Material 4358

A new shellfish Standard Reference Material 4358 was developed by the National Institute of Standards and Technology through an international interlaboratory comparison that involved twelve laboratories-participants from nine countries. The results from the participants were statistically evaluated, and the most robust certified values were based on the median of laboratories’ reported means and the uncertainties derived using the bootstrap method. Massic activity certified values were established for fourteen radionuclides, five activity ratios, and informational massic activity values for eight more radionuclides and two activity ratios.     

Existence of solutions to a global eikonal equation

We derive a geometric necessary and sufficient condition for the existence of solutions to a global eikonal equation. We also study the existence of a minimal solution to this equation, and its relation with the well-known minimal time function.     

Barrier to internal rotation of the silyl group in cyclopropylsilane from combination band spectra

Combination band spectra arising in the region 2000–2300 cm^?1 of cyclopropylsilane can be attributed to the sum and difference bands of the internal rotation with an SiH stretching mode. Analysis of these spectra leads to a potential function for the internal rotation V(cm^?1) = 693.92(1 ? cos 3φ) ? 10.28(1 ? cos 6φ), where φ is the angle of internal rotation. The barrier to internal rotation is thus 1.98 kcal/mole.     

Simultaneous determination of diloxanide furoate and metronidazole in presence of diloxanide furoate degradation products

Three methods are presented for the simultaneous determination of diloxanide furoate (DLX) and metronidazole (MTR), used for their antiprotozoal and antiamoebic effect, in the presence of DLX alkaline degradates and in pharmaceutical formulations, without previous separation. The first method is chemometric-assisted spectrophotometry, in which principal component regression and partial least squares were applied. These two approaches were successfully applied to quantify each drug in the mixture using the information included in, the absorption spectra in the range of 225-320 nm. The second method is TLC-densitometry, in which the binary mixture and degradates were separated on silica gel plates using a chloroform-acetone-glacial acetic acid (9.5 + 0.5 + 0.07, v/v/v) mobile phase and the bands were scanned at 254 nm. The last method is HPLC, in which DLX, MTR, and degradates were separated using the mobile phase acetonitrile-0.05 M dibasic potassium phosphate (25 + 75, v/v), adjusted to pH 4 with orthophosphoric acid, at a flow rate of 1 mL/min, on a C18 analytical column. Detection was at 254 nm. The proposed methods were successfully applied for the analysis of DLX and MTR in pharmaceutical formulations, and the results were statistically compared with a reported spectrophotometric method.     

New copper(II) complexes with dopamine hydrochloride and vanillymandelic acid: spectroscopic and thermal characterization

The dopamine derivatives participate in the regulation of wide variety of physiological functions in the human body and in medication life. Increase and/or decrease in the concentration of dopamine in human body reflect an indication for diseases such as Schizophrenia and/or Parkinson diseases. The Cu(II) chelates with coupled products of dopamine hydrochloride (DO.HCl) and vanillymandelic acid (VMA) with 4-aminoantipyrine (4-AAP) are prepared and characterized. Different physico-chemical techniques namely IR, magnetic and UV-vis spectra are used to investigate the structure of these chelates. Cu(II) forms 1:1 (Cu:DO) and 1:2 (Cu:VMA) chelates. DO behave as a uninegative tridentate ligand in binding to the Cu(II) ion while VMA behaves as a uninegative bidentate ligand. IR spectra show that the DO is coordinated to the Cu(II) ion in a tridentate manner with ONO donor sites of the phenolic-OH, -NH and carbonyl-O, while VMA is coordinated with OO donor sites of the phenolic-OH and -NH. Magnetic moment measurements reveal the presence of Cu(II) chelates in octahedral and square planar geometries with DO and VMA, respectively. The thermal decomposition of Cu(II) complexes is studied using thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The activation thermodynamic parameters, such as, energy of activation, enthalpy, entropy and free energy change of the complexes are evaluated and the relative thermal stability of the complexes are discussed.     

Nanoparticle assembled microcapsules for application as pH and ammonia sensor

The encapsulation of molecular probes in a suitable nanostructured matrix can be exploited to alter their optical properties and robustness for fabricating efficient chemical sensors. Despite high sensitivity, simplicity, selectivity and cost effectiveness, the photo-destruction and photo-bleaching are the serious concerns while utilizing molecular probes. Herein we demonstrate that hydroxy pyrene trisulfonate (HPTS), a pH sensitive molecular probe, when encapsulated in a microcapsule structure prepared via the assembly of silica nanoparticles mediated by poly-L-lysine and trisodium citrate, provides a robust sensing material for pH sensing under the physiological conditions. The temporal evolution under continuous irradiation indicates that the fluorophore inside the silica microcapsule is extraordinarily photostable. The fluorescence intensity alternation at dual excitation facilitates for a ratiometic sensing of the pH, however, the fluorescence lifetime is insensitive to hydrogen ion concentration. The sensing scheme is found to be robust, fast and simple for the measurement of pH in the range 5.8-8.0, and can be successfully applied for the determination of ammonia in the concentration range 0-1.2 mM, which is important for aquatic life and the environment.