Minimization of convex functionals over frame operators

We present results about minimization of convex functionals defined over a finite set of vectors in a finite-dimensional Hilbert space, that extend several known results for the Benedetto-Fickus frame potential. Our approach depends on majorization techniques. We also consider some perturbation problems, where a positive perturbation of the frame operator of a set of vectors is realized as the frame operator of a set of vectors which is close to the original one.     

Exact Controllability of a Faedo–Galërkin Scheme for the Dynamics of Polymer Fluids

Journal of Optimization Theory and Applications - We describe the dynamics of fluids with scattered polymer chains through a multi-field model accounting for weakly non-local inertia and...     

Essential oil and fractions isolated of Laurel to control adults and larvae of cattle ticks

Abstract

This study, was to evaluate the acaricidal effect of the essential oil (EO) and fractions (FR) obtained from Laurus nobilis leaves on Rhipicephalus (Boophilus) microplus. Eight fractions were obtained, however FR1: sabinene (37.83%), β-pinene (13.50%), 1,8-cineole (12.66%), α-pinene (12.56%) and FR8: α-terpineol (79.19%) were highlighted as to the larvicidal potential when submitted by Larval Packet Test. The EO was tested by the Adult Immersion Test, at concentrations of 200.00; 100.00 and 50.00?µL/mL caused mortality of engorged females, egg mass reduction and hatching inhibition. Two fractions are shown to be efficient in controlling larvae FR8 (LC₅₀?=?0.13?µL/mL, LC₉₉?=?0.51?µL/mL) and FR1 (LC₅₀?=?0.20?µL/mL, LC₉₉?=?0.56?µL/mL). The fractionation of EO was determinant to elucidate which compounds were responsible for the larvicidal potential. This study opens new perspectives to direct new bioassays with the compounds obtained in the fractionation, since they present high potential on cattle tick larvae.     

Silica xerogels of tailored porosity as support matrix for optical chemical sensors. Simultaneous effect of pH, ethanol:TEOS and water:TEOS molar ratios, and synthesis temperature on gelation time, and textural and structural properties

The sensing of a chemical environment is achieved mainly in the surface by interactions of the sensor material with its chemical surroundings. Therefore, porous structure control is key in developing good chemical sensors. The aim of this work was to obtain materials of tailored porosity to be used as support matrix for optical chemical sensors. We studied the simultaneous effect of pH, temperature, ethanol:TEOS, and water:TEOS molar ratios on gelation time, and textural and structural properties. We used a 2⁴ factorial design that evaluates the effect of each independent variable and their interactions. Samples were characterized by XRD, SEM, FTIR, and gas adsorption (N₂ at 77 K and CO₂ at 273 K). The gelation time decreased with increasing temperature, water:TEOS molar ratio, and pH; and with decreasing ethanol:TEOS molar ratios. Synthesis conditions also affected the xerogels porous textures. Xerogels obtained at pH 2.5 were ultramicroporous. In general, samples synthesized at pH 4.5 and ethanol:TEOS molar ratio of 2.25:1 were mesoporous, but the material is not appropriate for use as support in fiber optical sensors.     

A label-free method based on MALDI-TOF mass spectrometry for the absolute quantitation of troponin T in mouse cardiac tissue

A label-free absolute quantitation method based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been developed. This methodology was applied to mouse heart in order to quantify cardiac troponin T (cTnT), which is considered to be a sensitive marker of heart damage. The cTnT was extracted, isolated by reversed-phase high-performance liquid chromatography, digested, and analyzed by MALDI-TOF MS. The MS-based quantitation was performed using matrix-matched calibration curves (due to a matrix effect) of two synthetic peptides, one cTnT-specific peptide and one internal standard peptide, respectively. Recoveries at three spiking levels ranged from 87–96%, with relative standard deviations of below 10%. The method detection limit and the method quantitation limit, expressed as the amount of cTnT for the amount of total sarcomeric protein extract, were 0.03 mg g⁻¹ and 0.15 mg g⁻¹, respectively. This method appears to be accurate and generally suitable for improving absolute protein quantitation.     

Novel dithiolene complexes incorporating conjugated electroactive ligands

A series of new metal (M) dithiolene complexes bearing terthiophene (3, 12, M = Ni; 4, M = Pd; 5, 6, M = Au) and 2,5-bis(para-methoxyphenyl)thiophene units (14, M = Ni; 15, 16, M = Au; 17, M = Pd) have been synthesised in 38-99% yield. The electrochemical properties of the materials have been characterised by cyclic voltammetry and UV-vis spectroelectrochemistry. The nickel complexes possess low oxidation potentials (-0.12 to -0.25 V vs Ag/AgCl) due to the electron-rich dithiolene centres and all complexes display ligand-based redox activity. The terthiophene derivatives have been polymerised by electrochemical oxidation to give stable films with, in the case of poly(3), broad absorption characteristics. Charge transfer materials have been isolated from 14 and 16 with conductivities in the range 9 x 10(-6) to 7 x 10(-8) S cm(-1).     

Receptors for organochlorine pesticides based on calixarenes

The water soluble 4-sulfocalix[n]arenes (with n?=?4,6,8) have been investigated as potential synthetic receptors for cyclodiene organochlorine pesticides. Steady state fluorescence experiments in ethanol solution have shown that only the cavitands with n equal to 6 and 8 form complexes, of comparable stability, with heptachlor. Electrochemical data, obtained in water solution, confirmed the ability of 4-sulfocalix[6]arene to bind the heptachlor, unlike the smaller calixarene. Moreover, a significant increase in the stability constant is observed in water solutions. This stability is caused by the sterical hindrance of pesticides with respect to the cavity dimension of the calixarene. This results in a selective interaction of this molecule with other organochlorine pesticides. Binding experiments, carried out with endosulfan have shown that, despite of chemical similarity, 4-sulfocalix[6]arene and 4-sulfocalix[8]arene behave in a very different way: the former is unable to bind this pesticide, while the latter shows a binding constant of 4.7?×?10⁵ with endosulfan. To investigate the molecular features of the interactions, molecular dynamic simulations of 4-sulfocalix[6]arene in presence of heptachlor in water solution have been performed. These simulations show that different configurations of heptachlor inside the calixarene cavity are equally populated and easily interconverting, suggesting that a non specific hydrophobic interaction plays a key role in the complex stability. These studies have permitted to individuate versatile synthetic receptors for organochlorine pesticides.     

On the investigation of the bilayer functionalities of 1,2-di-oleoyl-sn-glycero-3-phosphatidylcholine (DOPC) large unilamellar vesicles using cationic hemicyanines as optical probes: a wavelength-selective fluorescence approach

The behavior of the cationic hemicyanines trans-4-[4-(dimethylamino)-styryl]-1-methylpyridinium iodide (HC) and 4,(4-(dihexadecylamino)styryl-N-methyl-pyridinium iodide (DIA) were studied in large unilamellar vesicles (LUV) of 1,2-di-oleoyl-sn-glycero-3-phosphatidylcholine (DOPC) using absorption, emission, depolarization and time resolved spectroscopies. Also, thorough spectroscopic studies were performed in homogeneous media to investigate the different interactions that the dyes can experience with its microenvironment. These results help us to comprehend the dye performance under different media and, consequently find interesting features of the DOPC membrane properties. The studies in homogeneous media analyzed by the Kamlet and Taft's solvatochromic comparison method demonstrate, for the first time, that the cationic hemycianines undergo specific interactions with the medium through the solvents ability to donate an electron pair as measured by the beta parameter. Thus, the absorption bands shifts bathochromically with beta while, the emission band shifts hypsochromically. In addition, for the relaxed hemicyanines the 00 energy, nu00, is invariant with the solvent properties. The results in LUV of DOPC show that, DIA undergoes a strong association with the vesicle bilayer while HC partitions between the water and the bilayer pseudophases. To monitor directly the microenvironment and dynamics around HC and DIA inside the DOPC bilayer, we use the wavelength-selective fluorescence approach, which is based on the red edge effect in fluorescence spectroscopy, in addition with the nu00 energy of the hemicyanines. The results show that the fluid state of the DOPC bilayer resembles the microenvironment of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) reverse micelles at W=[H2O]/[AOT] below 10 where there is no free water forming the water pool. Moreover, it is demonstrated for the first time, that the region of the bilayer close to the polar head of DOPC is a powerful electron donor environment.