Hodge Theory on Metric Spaces

Hodge theory is a beautiful synthesis of geometry, topology, and analysis which has been developed in the setting of Riemannian manifolds. However, spaces of images, which are important in the mathematical foundations of vision and pattern recognition, do not fit this framework. This motivates us to develop a version of Hodge theory on metric spaces with a probability measure. We believe that this constitutes a step toward understanding the geometry of vision.     

Bioactivity and Viscoelastic Characterization of Chitosan/Bioglass® Composite Membranes

Membranes of chitosan (CTS) and composite membranes of CTS with bioglass are prepared by solvent casting. The composite membranes are shown to induce the precipitation of apatite upon immersion in SBF. The biomineralization process is followed by measuring the variation of the viscoelastic properties of the membranes immersed in SBF, both online and offline. Non‐conventional DMA is used to measure the change in the storage modulus, E′, and the loss factor, tan δ, as a function of the immersion in SBF. A simple model is used to estimate the E′ of the apatite layer formed in vitro that is about 130 MPa. This work shows that innovate mechanical tests can be useful to characterize the mechanical performance of composites under physiological conditions.

     

Electrochemical behavior of nickel in electrolytes based on 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid for capacitor applications

Electrochemical studies were performed using Ni electrodes in solutions of a mixture of ethylene glycol or of γ-butyrolactone with 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid. The aim of the study was to evaluate the use of these systems in electrochemical double-layer capacitor. Cyclic voltammetry experiments showed a potential range at which the Ni electrode behaved as a polarizable electrode. Ni oxidizes at high anodic potentials. Inside the potential range without electrochemical activity, the capacitance and the solution resistance, which were evaluated by impedance electrochemical spectroscopy, were compared for the two solutions tested. Conductivity measurements of the electrolytes with different compositions were also acquired. The results of cyclic voltammetry indicated that the Ni has a wide electrochemical window and low current peak densities of oxidation in the γ-butyrolactone medium than in ethylene glycol medium. The γ-butyrolactone and 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid solutions had the highest conductivity values. Decreased 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid content in different solvent mixtures resulted in an increase in the capacitance value at the Ni/electrolyte interface. The highest capacitance values were obtained for Ni in ethylene glycol and 1-n-butyl-3-methylimidazolium tetrafluoroborate medium.     

Effect of the deaeration on the adsorption of some cationic surfactants at the mercury/electrolyte solution interface

The effect of the deaeration on the adsorption of three cationic surfactants cetyldimethylbenzylammonium chloride (CDBACl), cetyltrimethylammonium bromide (CTAB) and octadecyltrimethylammonium bromide (OTAB) at the mercury/electrolyte solution interface is studied. The deaeration is studied using either nitrogen or helium and the effect of deaeration process and time is also studied. In all cases an effect of the deaeration time is found which is mainly observed at potentials where a condensed film is formed. Capacity-time curves at the potentials where the film is formed show a nucleation and growth mechanism with induction time that depends on the deaeration time. The deaeration slows down the kinetics of the film formation but does not change the equilibrium capacitance value of the film. The decrease of the dissolved gas from the water that perturbs its structure is perhaps the main reason for the behaviour observed during the adsorption of these surfactants.     

Drug release of pH/temperature-responsive calcium alginate/poly(N-isopropylacrylamide) semi-IPN beads

A series of semi-interpenetrating, polymer network (semi-IPN), hydrogel beads, composed of calcium alginate (Ca-alginate) and poly(N-isopropylacrylamide) (PNIPAAM), were prepared for a pH/temperature-sensitive drug delivery study. The equilibrium swelling showed the independent pH- and thermo- responsive nature of the developed materials. At pH=2.1, the release amount of indomethacin incorporated into these beads was about 10% within 400 min, while this value approached to 95% at pH=7.4. The release rate of the drug was higher at 37 degrees C than that at 25 degrees C and increased slightly with increasing PNIPAAM content. These results suggest that the Ca-alginate/PNIPAAM beads have the potential to be used as an effective pH/temperature sustainable delivery system of bioactive agents. [GRAPHS: SEE TEXT] A summary of the temperature- and pH-dependence on the release of the drug over a period of 450 min. The effect of the temperature on the swelling of the beads is shown in the inset.     

Charge distribution in Mn(salen) complexes

The charge and spin distribution in manganese‐salen complexes were analyzed using different basis sets and density functionals. Five population analysis methods [Mulliken, Löwdin, Natural population analysis (NPA), atoms in molecules (AIM), and CHelpG] were used to characterize the charge distribution. Results show that NPA and AIM were the only methods capable of giving charges with the correct sign for all cases under study. According to the analysis of the natural charge and spin distributions, the salen ligand shows a complex behavior, counteracting the effect of the chloro and oxo ligands on the metal center. Furthermore, the presence of a chloride counter ion increases the oxo‐radical character of Oxo‐Mn(salen) complexes, which may play an important role in the rationalization of the catalytic properties of Mn(salen) complexes. © 2014 Wiley Periodicals, Inc.     

Application of capillary electrophoretic methods for the analysis of plant phloem and xylem saps composition: A review

Plant vascular tissue is essential for the exchange of water, nutrients, metabolic products, and signals among distant organs in cormophytes. The compositions of phloem and xylem saps are highly dependent on many internal and external factors, and thus their analysis provides a valuable insight into plant physiology, growth, and development as well as nutrition status or presence of biotic or abiotic stresses. Capillary electrophoresis characterized by highly efficient separations and minuscule sample requirements represents a suitable analytical technique for this purpose because the sap constitutes a complex mixture with generally minimal availability. This review aims at providing a comprehensive overview of published capillary electrophoretic methods for the analysis of primary components present in the phloem and xylem saps of higher plants.     

What does an ionic liquid surface really look like? Unprecedented details from molecular simulations

We present the first intrinsic analysis of the surface of the [bmim][PF(6)] room-temperature ionic liquid. Our detailed analysis reveals unprecedented details about the structure of the interface by providing the relative prevalence of different molecular orientations. These results suggest that experimental data should be reinterpreted considering a distribution of molecular arrangements.     

Jointly handling potency and toxicity of antimicrobial peptidomimetics by simple rules from desirability theory and chemoinformatics

Today, emerging and increasing resistance to antibiotics has become a threat to public health worldwide. Antimicrobial peptides have unique action mechanisms making them an attractive therapeutic prospect to be applied against resistant bacteria. However, the major drawback is related with their high hemolytic activity which cancels out the safety requirements for a human antibiotic. Therefore, additional efforts are needed to develop new antimicrobial peptides that possess a greater potency for bacterial cells and less or no toxicity over erythrocytes. In this paper, we introduce a practical approach to simultaneously deal with these two conflicting properties. The convergence of machine learning techniques and desirability theory allowed us to derive a simple, predictive, and interpretable multicriteria classification rule for simultaneously handling the antibacterial and hemolytic properties of a set of cyclic β-hairpin cationic peptidomimetics (Cβ-HCPs). The multicriteria classification rule exhibited a prediction accuracy of about 80% on training and external validation sets. Results from an additional concordance test have shown an excellent agreement between the multicriteria classification rule predictions and the predictions from independent classifiers for complementary antibacterial and hemolytic activities, respectively, evidencing the reliability of the multicriteria classification rule. The rule was also consistent with the general mode of action of cationic peptides pointing out its biophysical relevance. We also propose a multicriteria virtual screening strategy based on the joint use of the multicriteria classification rule, desirability, similarity, and chemometrics concepts. The ability of such a virtual screening strategy to prioritize selective (nonhemolytic) antibacterial Cβ-HCPs was assessed and challenged for their predictivity regarding the training, validation, and overall data. In doing so, we were able to rank a selective antibacterial Cβ-HCP earlier than a biologically inactive or nonselective antibacterial Cβ-HCP with a probability of ca. 0.9. Our results thus indicate that promising chemoinformatics tools were obtained by considering both the multicriteria classification rule and the virtual screening strategy, which could, for instance, be used to aid the discovery and development of potent and nontoxic antimicrobial peptides.