Fixed points of non-Newtonian contraction mappings on non-Newtonian metric spaces

The study of non-Newtonian calculi was started in 1972 by Grossman and Katz. These calculi provide an alternative to the classical calculus and they include the geometric, anageometric and bigeometric calculi, etc. Recently, Çakmak and Ba?ar (2002) have studied the concept of non-Newtonian metric. Also they have given the triangle and Minkowski’s inequalities in the sense of non-Newtonian calculus. In this paper, we introduce a fixed point theory by defining some topological structures of the relevant non-Newtonian metric space.     

Site-specific interactions of Cu(II) with alpha and beta-synuclein: bridging the molecular gap between metal binding and aggregation

The aggregation of alpha-synuclein (AS) is a critical step in the etiology of Parkinson's disease (PD) and other neurodegenerative synucleinopathies. Protein-metal interactions play a critical role in AS aggregation and might represent the link between the pathological processes of protein aggregation and oxidative damage. Our previous studies established a hierarchy in AS-metal ion interactions, where Cu(II) binds specifically to the protein and triggers its aggregation under conditions that might be relevant for the development of PD. In this work, we have addressed unresolved structural details related to the binding specificity of Cu(II) through the design of site-directed and domain-truncated mutants of AS and by the characterization of the metal-binding features of its natural homologue beta-synuclein (BS). The structural properties of the Cu(II) complexes were determined by the combined application of nuclear magnetic resonance, electron paramagnetic resonance, UV-vis, circular dichroism spectroscopy, and matrix-assisted laser desorption ionization mass spectrometry (MALDI MS). Two independent, noninteracting copper-binding sites with significantly different affinities for the metal ion were detected in the N-terminal regions of AS and BS. MALDI MS provided unique evidence for the direct involvement of Met1 as the primary anchoring residue for Cu(II) in both proteins. Comparative spectroscopic analysis of the two proteins allowed us to deconvolute the Cu(II) binding modes and unequivocally assign the higher-affinity site to the N-terminal amino group of Met1 and the lower-affinity site to the imidazol ring of the sole His residue. Through the use of competitive chelators, the affinity of the first equivalent of bound Cu(II) was accurately determined to be in the submicromolar range for both AS and BS. Our results prove that Cu(II) binding in the C-terminal region of synucleins represents a nonspecific, very low affinity process. These new insights into the bioinorganic chemistry of PD are central to an understanding of the role of Cu(II) in the fibrillization process of AS and have implications for the molecular mechanism by which BS might inhibit AS amyloid assembly.     

Core-shell nanoparticles: characterization and study of their use for the encapsulation of hydrophobic fluorescent dyes

Core-shell nanocapsules intended to be used as drug scavengers were prepared using a surfactant mixture containing octadecyltrimethoxysilane (OTMS) as a reactive amphiphile, to form spherical templates. A siloxane shell was grown on the surface of the templates by reacting tetramethoxysilane (TMOS) with the silanol groups obtained after the hydrolysis and condensation of OTMS. Dynamic light scattering (DLS) showed that particles with diameters in the range of 100-200 nm were obtained, with core and shell sizes controlled by varying component compositions. Atomic force microscopy (AFM) was used to study the effect of the silica coating of the templates on their robustness after deposition on a substrate. Subsequently, we present studies on the encapsulation of two hydrophobic fluorescent dyes, which are sensors of polarity and rigidity. Steady-state fluorescence spectroscopy was used to examine the fluorescence response of the dyes before and after shell growth. Changes in the emission of the encapsulated dyes were related to changes in the polarity and rigidity of the microenvironment where the dyes were located and correlated to the AFM results. Finally, dye-free core-shell particles were used to sequester the dyes from aqueous suspensions. Fluorescence of the sequestered species was compared to the dye-loaded particles to determine the final fate of the fluorophores in the nanoparticles.     

Electron density topological properties are useful to assess the difference between hydrogen and dihydrogen complexes

B3LYP/6-31++G(d,p) and MP2/6-31++G(d,p) calculations for a series of hydrogen- and dihydrogen-bonded systems have been carried out in order to analyze the topology of the electron density and the energy densities at the respective energy-optimized bond critical points. Even though there are no significant differences when these properties are represented as a function of the dimerization energy, they can be separated into two well-defined sets if those properties are correlated with intermolecular distances. When analyzing the dependence of various properties with equilibrium bond lengths, the specific trends of dihydrogen bond systems consist of (a) lower electron density at the bond critical point, and (b) lower concentration/depletion of that density which can be translated in a different behavior for the Laplacian components. Furthermore, the sets of molecules form two different plots which allow for a valuable classification between hydrogen- and dihydrogen-bonded systems.     

Polystyrene-block-poly(ethylene oxide) stars as surface films at the air/water interface

Star diblock copolymers containing polystyrene (PS) and poly(ethylene oxide) (PEO) were investigated as surface films at the air/water interface. Both classic and dendritic-like stars were prepared containing either a PS core and PEO corona or the reverse. The investigated polymers, consisting of systematic variations in architectures and compositions, were spread at the air/water interface, generating reproducible surface pressure-area isotherms. All of the films could be compressed to higher pressures than would be possible for pure PEO. For stars containing 20% or more PEO, three distinct regions appeared. At higher areas, the PEO absorbs in pancakelike structures at the interface with PS globules sitting atop. Upon compression, a pseudoplateau transition region appeared. Both regions strongly depended on PEO composition. The pancake area and the pseudoplateau width and pressure increased in a linear fashion with an increasing amount of PEO. In addition, minimum limits of PEO chain length and mass percentage were determined for observing a pseudoplateau. At small areas, the film proved less compressible, producing a rigid film in which PS dominated. Here, the film area increased with both molecular weight and the amount of PS. Comparison with pure linear PS showed the stars spread more, occupying greater areas. Among the stars, the PEO-core stars were more compact while the PS-core stars spread more. The influence of architecture in terms of the core/corona polymers and branching were also examined. The effects of architecture were subtle, proving less important than PEO chain length or mass percentage.     

Fine-tuning the electronic properties of highly stable organometallic Cu(III) complexes containing monoanionic macrocyclic ligands

A family of highly stable organometallic Cu(III) complexes with monoanionic triazamacrocyclic ligands (L(i)) with general formula [CuL(i)]+ have been prepared and isolated, and their structural, spectroscopic, and redox properties thoroughly investigated. The HL(i) ligands have been designed in order to understand and quantify the electronic effects exerted by electron donor and electron-withdrawing groups on either the aromatic ring or the central secondary amine or on both. In the solid state the Cu(III) complexes were mainly characterized by single-crystal X-ray diffraction analysis, whereas in solution their structural characterization was mainly based on 1H NMR spectroscopy given the diamagnetic nature of the d(8) square-planar Cu(III) complexes. Cyclic voltammetry together with 1H NMR and UV/Vis spectroscopy have allowed us to quantify the electronic effects exerted by the ligands on the Cu(III) metal center. A theoretical analysis of this family of Cu(III) complexes has also been undertaken by DFT calculations to gain a deeper insight into the electronic structure of these complexes, which has in turn allowed a greater understanding of the nature of the UV/Vis transitions as well as the molecular orbitals involved.     

Adsorption of Cu(II) ions from aqueous solution by hazelnut husk activated carbon prepared with potassium acetate

Hazelnut husk (HH), an agricultural waste, was converted to carbonaceous material by chemical activation using potassium acetate. The produced activated carbon (KAHHAC) was characterized by FTIR, SEM, N₂ adsorption–desorption experiments, CHN elemental analysis, and determination of moisture, ash, and point of zero charge. KAHHAC was used for the batch adsorption of Cu(II) ions from aqueous solutions. Optimum pH and contact time were found to be 5.0 and 240 minutes, respectively. The adsorption equilibrium data were described well by the Langmuir equation providing 105.3?mg?g^?1 Cu(II) adsorption capacity. The pseudo-second-order model successfully described the kinetic of Cu(II) adsorption by KAHHAC. The adsorbed Cu(II) onto KAHHAC was completely desorbed by 0.5?M nitric acid. In conclusion, HH activated carbon (AC) produced by the potassium acetate activation method is a very useful and efficient sorbent material for the removal of Cu(II) from aqueous solution.     

Difference based ridge and Liu type estimators in semiparametric regression models

We consider a difference based ridge regression estimator and a Liu type estimator of the regression parameters in the partial linear semiparametric regression model, y=Xβ+f+ε. Both estimators are analyzed and compared in the sense of mean-squared error. We consider the case of independent errors with equal variance and give conditions under which the proposed estimators are superior to the unbiased difference based estimation technique. We extend the results to account for heteroscedasticity and autocovariance in the error terms. Finally, we illustrate the performance of these estimators with an application to the determinants of electricity consumption in Germany.     

Determination of Effective Properties of MMC by Computational Homogenization

On the macrolevel Metal Matrix Composites (MMCs) resemble a homogeneous material. However, on the microlevel they show an inhomogeneous microstructure. This paper will have how heterogeneities affect the overall properties and the behaviour of a material (i. e. the effective properties). This is done using computational homogenization techniques. Finite element (FE) simulations were conducted in ABAQUS in connection with MATLAB, using material parameters for aluminium alloy AA2124 and SiC to develop a representative volume element (RVE) of the MMC AMC217xe. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Medium- and long-chain 3-hydroxymonocarboxylic acids: analysis by gas chromatography combined with mass spectrometry

Medium- and long-chain 3-hydroxymonocarboxylic acids represent intermediates in the beta-oxidation of fatty acids: they accumulate in the plasma of patients with an inherited deficiency of long-chain 3-hydroxyacylcoenzyme A dehydrogenase. 3-Hydroxy acids with chain lengths varying from 6 to 16 were synthesized by a Reformatzky reaction. Capillary gas chromatography of the pertrimethylsilyl derivatives was performed on a CP-Sil 19 CB column, coupled to a quadrupole mass spectrometer in the electron impact mode. Calculation of the retention indices showed that the separation of the 3-hydroxy acids from the homologous straight-chain fatty acids may be troublesome, stressing the need for mass spectrometric identification.