Nonlinear fractional optimal control problems with neural network and dynamic optimization schemes

Nonlinear Dynamics - This paper deals with a numerical technique for fractional optimal control problems (FOCPs) based on a neural network scheme. The fractional derivative in these problems is in...     

Benford’s law predicted digit distribution of aggregated income taxes: the surprising conformity of Italian cities and regions

Core-level photoemission spectra of the Fabre salts with X = SbF₆ and PF₆ were taken using hard X-rays from PETRA III, Hamburg. In these salts TMTTF layers show a significant stack dimerization with a charge transfer of 1e per dimer to the anion SbF₆ or PF₆. At room temperature and slightly below the core-level spectra exhibit single lines, characteristic for a well-screened metallic state. At reduced temperatures progressive charge localization sets in, followed by a 2nd order phase transition into a charge-ordered ground state. In both salts groups of new core-level signals occur, shifted towards lower kinetic energies. This is indicative of a reduced transverse-conductivity across the anion layers, visible as layer-dependent charge depletion for both samples. The surface potential was traced via shifts of core-level signals of an adsorbate. A well-defined potential could be established by a conducting cap layer of 5 nm aluminum which appears “transparent” due to the large probing depth of HAXPES (8–10 nm). At the transition into the charge-ordered phase the fluorine 1s line of (TMTTF)₂SbF₆ shifts by 2.8 eV to higher binding energy. This is a spectroscopic fingerprint of the loss of inversion symmetry accompanied by a cooperative shift of the SbF₆ anions towards the more positively charged TMTTF donors. This shift does not occur for the X = PF₆ compound, most likely due to smaller charge disproportion or due to the presence of charge disorder.     

Synthesis of Macrobicyclic Polyamines by Direct Macrobicyclisation via Tripode-Tripode Coupling

The synthesis of five macrobicyclic polyamines 1 – 5 is described following a route in which the macrobicycle is formed by the coupling of two tripodal subunits. Such a sequence is appreciably shorter than the stepwise construction via a macrocycle, and may give higher yields, as illustrated by the case of bis-tren 3 , which has been synthesized following both routes.     

Alkylation des pyrimidines en catalyse par transfert de phase

We report here the first operationally simple and efficient study concerning the phase transfer catalysed alkylation of ambident pyrimidine dianions derived from uracil, thymine, 5-nitrouracil, 5-fluorouracil, 6-chlorouracil, 1,2,3,4-tetrahydro-2,4-dioxoquinazoline, giving selectively the corresponding N₁,N₃-dialkyl derivatives in high yield.     

What Flow Injection has to Offer in the Environmental Analytical Field

NO plays an important role in the regulation of physiological and pathophysiological mechanisms, and quite a lot of investigations have been focused on this kind of special molecule. It is difficult to achieve reliable ex vivo NO measurements with the existing analytical methods, and developing a reliable in vivo monitoring method for NO is still an urgent task. In this review, the techniques utilized for the determination of endogenous NO formed by enzymatic action and its reactions with other biological substances found in living organisms are discussed with respect to applications both in vivo or in vitro. In addition, various NO (micro)sensors and trap probes based on different principles are presented with their respective advantages and limitations. Finally, an NO monitoring system based on the combination of microdialysis sampling and chemiluminescence is introduced which is considered to be a prospective method for in vivo monitoring.     

Rhodium-catalysed tetradehydro-Diels–Alder reactions of enediynes via a rhodium-stabilized cyclic allene

Efficient methods for the synthesis of fused-aromatic rings is a critical endeavour in the creation of new pharmaceuticals and materials. A direct method for preparing these systems is the tetradehydro-Diels–Alder reaction, however this is limited by the need for harsh reaction conditions. A potential, but underdeveloped, route to these systems is via transition metal-catalysed cycloaromatisation of ene-diynes. Herein, tethered unconjugated enediynes have been shown to undergo a facile room-temperature Rh^I-catalysed intramolecular tetradehydro-Diels–Alder reaction to produce highly substituted isobenzofurans, isoindolines and an indane. Furthermore, experimental and computational studies suggest a novel mechanism involving an unprecedented and complex Rh^I/Rh^III/Rh^I/Rh^III redox cycle involving the formation of an unusual strained 7-membered rhodacyclic allene intermediate and a Rh^III-stabilized 6-membered ring allene complex.

Room temperature Rh-catalysed tetradehydro-Diels–Alder reaction via an unusual Rh-stabilised allene.     

A novel flow-through microdialysis separation unit with integrated differential potentiometric detection for the determination of chloride in soil samples

In this paper, a novel and miniaturised flow-through dialysis-based potentiometric detector is proposed for the determination of chloride in soil samples. The outstanding feature of the designed unit is the integration of analyte isolation from matrix constituents via membrane separation with differential potentiometric detection. Two identical tubular all-solid-state Ag/AgCl ion selective electrodes (ISEs) were assembled respectively at the inlet and outlet of the acceptor channel. Thus, as a consequence of the continuous forward flow of solutions through the microdialyser the outlet tube becomes the indicator electrode for the analyte diffusate while the nested tube at the entrance serves as reference electrode. The effect of physical and chemical parameters on the mass transfer efficiency is discussed in detail and compared with conventional configurations involving downstream detection. The membrane morphology for optimum dialysis performance is also thoroughly evaluated in terms of thickness, porosity and molecular weight cut-off. Higher dialysis efficiency and reduction of dilution factors up to a value of 5 were attained by halting the recipient stream temporarily. Under the optimised conditions, a dynamic working range of 5-5000 mg l(-1) chloride with a linear interval between 10 and 5000 mg l(-1) (for 1 min stopped-flow and 200 microl sample volume), a repeatability better than 3.0% and a 3 sigma(blank) detection limit of 1.2 mg l(-1) chloride were the analytical figures of merit of the devised configuration. The potentiometric dialysis sensor features extreme tolerance to high molecular weight interfering matrix compounds (> 1000 mg l(-1) humic acid), which makes it specially suited for the interference-free potentiometric determination of chloride in soils containing high levels of organic matter. The miniature size, low-reagent consumption and high analytical throughput (25-40 h(-1)) also warrant its applicability to in-field monitoring or screening schemes. The accuracy of the measurements was assessed using ion-chromatography as an external reference method. A mean t-test showed no statistical differences between both methodologies at the 95% confidence level.     

A Numerical Approach for Multicomponent Vapor Solid Equilibrium Calculations in Gas Hydrate Formation

A new numerical approach has been developed for vapor solid equilibrium calculations and for predicting vapor solid equilibrium constant and composition of vapor and solid phases in gas hydrate formation. Equation of state methods generally do a good job of determining vapor phase properties, but for solid phase it is much more difficult and inaccurate. This proposed new model calculates vapor solid equilibrium constant and vapor and solid phase composition as a function of temperature and partial pressure. The results of this proposed numerical approach, for vapor solid equilibrium, have a good agreement with the available reported data. This new numerical model also has an advantage to tune coefficients, to cover different sets of experimental data accurately.     

The effect of pulse repetition frequency on the uptake into electropermeabilized cells in vitro with possible applications in electrochemotherapy

Electrochemotherapy is a technique where electric pulses in combination with chemotherapeutic agents are applied to tumor cells. In general, patients find electrochemotherapy tolerable, in spite of unpleasant sensations associated with contraction of muscles located beneath or in the vicinity of the electrodes. These contractions are due to the intensity of the electric pulses required for effective electropermeabilization of tumor cell membranes. Since a train of eight electric pulses with repetition frequency of 1 Hz is usually applied to the tumors, each pulse in the train excites underlying nerves and provokes muscle contractions. Therefore, for patients involved in electrochemotherapy, the use of pulses with repetition frequency higher than the frequency of tetanic contraction would represent reduced number of muscle contractions and associated unpleasant sensations. Our results of the uptake of Lucifer Yellow into electropermeabilized cells in vitro show that with increased repetition frequency the uptake stays at similar levels even at frequencies up to 8.3 kHz. On the basis of these results the possibilities for the clinical use of pulses with high repetition frequency in electrochemotherapy are considered.     

Chemiluminescence determination of sodium 2-mercaptoethane sulfonate by flow injection analysis using cerium(IV) sensitized by quinine

A flow injection method with chemiluminescence (CL) detection is proposed for the determination of sodium 2-mercaptoethane sulfonate (MESNA), a drug often used to reduce the urotoxic effects of antineoplastic alkylating agents. The procedure is based on the reaction of the thiol with Ce(IV) in a sulfuric acid medium and measurement of the CL intensity produced by quinine used as a sensitizer. The optimum conditions for CL emission were investigated. Using the CL peak height as the analytical parameter, MESNA was determined over the concentration range 0.29–2.21 ng (1.97–9.85 μg·l⁻¹) with a detection limit of 0.21 ng (1.38 μg·l⁻¹) and a relative standard deviation (R.S.D.) of 4.1%. The method was applied satisfactorily to the determination of MESNA in pharmaceutical preparations with percentages of recovery between 94 and 105.