SECM Imaging of Interfacial Processes in Defective Organic Coatings Applied on Metallic Substrates Using Oxygen as Redox Mediator

Operation of the SECM in feedback mode over a coated metal allows changes in the state of the surface to be monitored using dissolved oxygen in the test environment as redox mediator. The system investigated consisted in mild steel samples coated with a polyurethane film in which a defect was deliberately introduced into it. Accurate approach curves under negative‐feedback condition were obtained using a platinum microelectrode over regions of the intact coating. Imaging experiments were also carried out over the artificial defect on the coating. Under these conditions, corrosion of the exposed metal substrate at the defects could be monitored.     

Construction of -structures and equivalences of derived categories

We associate a -structure to a family of objects in , the derived category of a Grothendieck category . Using general results on -structures, we give a new proof of Rickard's theorem on equivalence of bounded derived categories of modules. Also, we extend this result to bounded derived categories of quasi-coherent sheaves on separated divisorial schemes obtaining, in particular, Belinson's equivalences.

     

On Conditional Tsallis Entropy

There is no generally accepted definition for conditional Tsallis entropy. The standard definition of (unconditional) Tsallis entropy depends on a parameter α that converges to the Shannon entropy as α approaches 1. In this paper, we describe three proposed definitions of conditional Tsallis entropy suggested in the literature—their properties are studied and their values, as a function of α, are compared. We also consider another natural proposal for conditional Tsallis entropy and compare it with the existing ones. Lastly, we present an online tool to compute the four conditional Tsallis entropies, given the probability distributions and the value of the parameter α.     

Routine analysis by high precision gas chromatography/mass selective detector/isotope ratio mass spectrometry to 0.1 parts per mil

Stable isotope methods are potentially quite useful for validating natural or enhanced mineral degradation of contaminants. For this reason, a continuous flow gas chromatograph (GC), isotope ratio mass spectrometer (IRMS) has been coupled with a quadrupole mass selective detector (MSD) to allow simultaneous mass spectral and stable carbon isotope ratio data to be obtained from a single chromatographic analysis. This allows the target contaminant and any extra-cellular degradation intermediates to be both qualified and quantified. Previously acceptable limits of precision (0.3 parts per mil) are undesirable given the small fractionation observed during aerobic degradation. To further understand the fate of organic contaminants and to gain information about the metabolic degradative pathway employed by a microorganism, routine isotopic analyses on a range of analytes have been performed. Quantities of sample producing mass-44 ion beam signal (I(44)) of 2 x 10(-10) to 1 x 10(-8) A were analysed. When the IRMS was tuned for high sensitivity, ion source nonlinearities were overcome by peak height correction from an algorithm that was produced using known isotopic standards of varying concentrations. This led to sample accuracy of <0.01 per thousand and sample precision of 0.1 per thousand. Copyright 1999 John Wiley & Sons, Ltd.     

Frequency scan for the analysis of high mass ions generated by matrix-assisted laser desorption/ionization in a paul trap

An ion trap has been modified for the analysis of high mass ions generated by matrix-assisted laser desorption/ionization. Samples are deposited on a probe tip and introduced directly onto the hyperbolically shaped surface of one endcap. All three electrodes - both the endcaps and the ring electrode - are insulated so that the radio frequency (Rf) voltage may be applied to the center ring electrode and the inverted Rf voltage to the endcaps. By using low frequencies (below 100 kHz) and low amplitudes (below 200 V), high mass singly charged ions may be trapped and analyzed by a frequency sweep at constant amplitude. In the high mass range (60-160 kDa), this instrument showed good sensitivity, signal-to-noise ratios, and mass resolution. Copyright 1999 John Wiley & Sons, Ltd.     

Superlinear problems without Ambrosetti and Rabinowitz growth condition

Superlinear elliptic boundary value problems without Ambrosetti and Rabinowitz growth condition are considered. Existence of nontrivial solution result is established by combining some arguments used by Struwe and Tarantello and Schechter and Zou (also by Wang and Wei). Firstly, by using the mountain pass theorem due to Ambrosetti and Rabinowitz is constructed a solution for almost every parameter λ by varying the parameter λ. Then, it is considered the continuation of the solutions.     

Loading of praziquantel in the crystal lattice of solid lipid nanoparticles

Praziquantel (PZQ) is the drug of choice for oral treatment of schistosomiasis and other fluke infections that affect humans. Its low oral bioavailability demands the development of innovative strategies to overcome the first pass metabolism. In this article, solid lipid nanoparticles loaded with PZQ (PZQ-SLN) were prepared by a modified oil-in-water microemulsion method selecting stearic acid as lipid phase after solubility screening studies. The mean particle size (Z-Ave) and zeta potential (ZP) were 500 nm and −34.0 mV, respectively. Morphology and shape of PZQ-SLN were analysed by scanning electron microscopy revealing the presence of spherical particles with smooth surface. Differential scanning calorimetry suggested that SLN comprised a less ordered arrangement of crystals and the drug was molecularly dispersed in the lipid matrix. No supercooled melts were detected. The entrapment efficiency (EE) and loading capacity of PZQ, determined by high performance liquid chromatography, were 99.06 ± 0.3 and 17.48 ± 0.05, respectively. Effective incorporation of PZQ into the particles was confirmed by small angle X-ray scattering revealing the presence of a lipid lamellar structure. Stability parameters of PZQ-SLN stored at room temperature (25 °C) and at 4 °C were checked by analysing Z-Ave, ZP and the EE for a period of 60 days. Results showed a relatively long-term physical stability after storage at 4 °C, without drug expulsion.