Remark on the existence results for fractional impulsive integrodifferential equations in Banach spaces

This paper deal with the study of the existence of solutions of nonlinear fractional integrodifferential equations with impulsive conditions in Banach spaces, by means of fixed point principle. The purpose of the paper is to generalize the results of [5] and correct an error in the example included in [5].     

Autonomous and non-autonomous fixed-time leader–follower consensus for second-order multi-agent systems

Nonlinear Dynamics - This paper addresses the problem of consensus tracking with fixed-time convergence, for leader–follower multi-agent systems with double-integrator dynamics, where only a...     

Coexisting aggregates in mixed aerosol OT and cholesterol microemulsions

Dynamic light scattering and NMR spectroscopic experimental evidence suggest the coexistence of two compositionally different self-assembled particles in solution. The self-assembled particles form in solutions containing water, Aerosol OT (AOT, sodium bis(2-ethylhexyl) sulfosuccinate) surfactant, and cholesterol in cyclohexane. In a similar series of studies carried out in 1-octanol only one aggregate type, that is, reverse micelles, is observed. Dynamic light scattering measurements reveal the presence of two different types of aggregates in the microemulsions formed in cyclohexane, demonstrating the coexistence of two compositionally distinct structures with very similar Gibbs energies. One particle type consists of standard AOT reverse micelles while the second type of particle consists of submicellar aggregates including cholesterol as well as small amounts of AOT and water. In microemulsions employing 1-octanol as the continuous medium, AOT reverse micelles form in a dispersed solution of cholesterol in 1-octanol. Although the size distribution of self-assembled particles is well-known for many different systems, evidence for simultaneous formation of two distinctly sized particles in solution that are chemically different is unprecedented. The ability to form microemulsion solutions that contain coexisting particles may have important applications in drug formulation and administration, particularly as applied to drug delivery using cholesterol as a targeting agent.     

Simultaneous interactions of anions and cations with cyclohexane and adamantane: aliphatic cyclic hydrocarbons as charge insulators

With ab initio MP2 computational methods, a theoretical study has been carried out to characterize the interaction between aliphatic cyclic hydrocarbons, as models of molecular hydrocarbon monolayers, with cations (Li(+), Na(+), and K(+)), anions (F(-), Cl(-), and Br(-)), and both simultaneously in opposite faces of the hydrocarbons. In addition, the energetic barrier for the cation crossing through the hydrocarbon ring has been calculated. The hydrocarbons chosen for this study are cyclohexane (C(6)H(12)) and adamantane (C(10)H(16)). The energies obtained for the M(+):hydrocarbon:X(-) complexes indicate positive cooperativity in the cases where the hydrocarbon is cyclohexane while diminutive effects are found in the adamantane complexes. The density functional theory-symmetry adapted perturbation theory analysis of the interaction energies shows that the most important term in the complexes with cations is the induction, while in the complexes with anion and with cations and anions simultaneously the most important term is the repulsion-exchange one. The electron density of the complexes has been analyzed using the atoms in molecules methodology and provides some insight to the electron transfer within the complexes.     

High‐throughput microscale extraction using ionic liquids and derivatives: A review

Ionic liquids and derivatives—mainly polymeric ionic liquids and magnetic ionic liquids—have been extensively used in microscale extraction over the past few years. Current trends in analytical sample preparation gear toward linking microextraction approaches with high‐throughput sample processing to comply with green analytical chemistry requirements. A variety of high sample throughput strategies that are coupled to both ionic‐liquid‐based solid‐phase microextraction and ionic liquid‐based liquid‐phase microextraction are herein reported. The review is focused on microscale extraction methods that use (i) custom‐made and dedicated extraction devices, (ii) parallel extraction, (iii) magnetic‐based separation, and (iv) miniaturized systems employing semi‐automatic or fully automatic flow injection methods, related micro/millifluidic devices, and robotic equipment.     

Design and Construction of an Autonomous Control System for Mössbauer Spectrometry

An autonomous control system for Mössbauer spectrometry based on two modules has been designed and built. The first module operates as a multichannel analyzer for the acquisition and storage of spectra, and the second one is a driver unit which controls and supplies the power for the velocity transducer. A microcontroller executes the digital control algorithm for the velocity transducer motion and manages the data acquisition and storage tasks. The user can monitor the system from an external PC through the serial port. A graphic interface made with the LabVIEW software allows the user to adjust digitally the control parameters for the velocity transducer motion, the channels number, to visualize as well as save spectra in a file. The microcontroller can be reprogrammed from the PC through the same serial port without intervention of a universal programmer, which allows the user to make proper software for different applications of the system. The system has been tested for linearity with several standard absorbers yielding satisfactory results. The low cost of its design, construction and maintenance make this equipment to be an attractive choice when assembling a Mössbauer spectrometer.     

Crystal structures of N,N'-(m-tolyl)thiourea and N,N'-(p-tolyl)thiourea.

C15H16N2S is monoclinic [orthorhombic], P2(1)/c [Pbcn]. Unit-cell dimensions at 293 K are a = 9.506(1), b = 7.629(1), c = 20.077(1)A, beta = 99.93(1) degrees, V= 1434.2(2)A(3), D(x) = 1.187 g/cm3, and Z = 4 [a = 11.806(2), b = 13.954(2), c = 8.466(1)A, V = 1394.7(3)A(3), D(x) = 1.221 g/cm3, and Z = 8]. The R value is 0.049 [0.045] for 1620 [1229] observed reflections. The dihedral angle between the tolyl rings is 53.6(1) degrees [47.9(1)degrees]. The crystal structures are stabilized by N-H...S hydrogen bonds and van der Waals forces.     

Photoelectrochemical processes at interfaces of nanostructured TiO<Subscript>2</Subscript>/carbon black composites studied by scanning photoelectrochemical microscopy

The local photoelectrochemical response of TiO₂/carbon black photocatalysts was studied by means of scanning photoelectrochemical microscopy performed under UV illumination and external polarization. Catalysts obtained by sol-gel techniques showed a uniform response that improved under anodic polarization, in contrast to the non-uniform response of mixtures that show enhancement under cathodic polarization. To explain the differences in photoelectrochemical activity, we performed electrochemical and capacitive studies under dark condition, finding a larger positive shift in the rest potential of sol-gel composites plus evidence of Fermi-level pinning. We propose the last is related to the presence of carbon states with a strong acceptor character formed during the sol-gel synthesis. An energy band diagram of the composites were sketched based on the data obtained.