Adaptive learning method in self-organizing map for edge preservingvector quantization

The Kohonen's self-organizing map algorithm for vector quantization of images is modified to reduce the edge degradation in the coded image. The learning procedure is performed by adaptive learning rates that are determined according to the image block activity. The simulation result of 4x4 vector quantization for 512x512 image coding demonstrates the feasibility of the proposed method.     

Magnetic coupling phenomena in EuS/Pb thin film double layers

The magnetic properties of EuS/Pb double layers (a ferromagnetic insulator on a superconducting metal) were investigated by means of 50 Hz hysteresis. The magnetic coupling between the two layers does not set in spontaneously. Two procedures for achieving magnetic coupling are described: first, by means of a d.c. magnetic field perpendicular to the film plane; secondly, with an a.c. field in the film plane. The coupled states are characterized by a slowing of the 50 Hz magnetization reversals. The degree of slow-down depends on the strength of the magnetic coupling.     

Major histocompatibility complex class I viral antigen processing in the secretory pathway defined by the trans-Golgi network protease furin

Classical antigen presentation by major histocompatibility complex class I molecules involves cytosolic processing of endogenously synthesized antigens by proteasomes and translocation of processed peptides into the endoplasmic reticulum (ER) by transporters associated with antigen presentation (TAP). Alternative pathways for processing of endogenous antigens, generally involving the ER, have been suggested but not fully proved. We analyzed the potential for class I presentation of proteolytic maturation of secretory antigens in the exocytic pathway. We found that hepatitis B (HB) virus secretory core protein HBe can efficiently deliver COOH-terminally located antigenic peptides for endogenous class I loading in the absence of TAP. Antigen presentation to specific cytotoxic T lymphocytes correlates with protein maturation at the COOH terminus, since modification of maturation and transport of HBe through the secretory pathway alters antigen presentation. Both maturation and a necessary processing step occur in the Golgi or post-Golgi compartment. Antigen presentation is independent of proteasome activity, but inhibitors of the trans-Golgi network resident protease furin inhibit both HBe maturation and antigen presentation. These results define a new antigen processing pathway located in the secretory route, with a central role for proteolytic maturation mediated by the subtilisin protease family member furin as an efficient source for antigen presentation.     

The characteristics of the coordinated activity of functionally identified hypothalamic neurons under different motivational-emotional states

Simultaneous impulse activity of pairs of neurons in hypothalamus was analysed in different natural functional states of rats (hunger, satiation after food deprivation, cry of a victim) and those induced by electrical stimulation of the emotionally positive (lateral hypothalamus, lateral preoptic area) and negative (dorso-medial tegmentum) reinforcing hypothalamic structures. Two classes of neurons were separated according to the pattern of their activity determined by the motivational state or reinforcement. Characteristic features were revealed in the patterns of conjugate activity of the functionally identified neurons. They were determined by the dominance of motivational or emotional component in the behaviour of an animal and manifested in a specificity of temporal delays in impulsation of one of the neurons in respect to the other one, in magnitude and number of positive and negative correlations. The results suggest the different ways of realization of the motivational and reinforcing hypothalamic influences mediated by the neurons of the motivational and reinforcing systems, on the cortical processes at different stages of learning which also differ in the balance between the motivational and emotional components of the animal behaviour.     

Preparation of chloromethylated and aminated gel‐type poly(styrene‐co‐divinylbenzene) microparticles with controlled degree of functionalization

The possibility of adjusting the degree of hydrophilic functionalization in polymeric microparticles with a hydrophobic skeleton makes it possible to obtain adsorbents and catalyst microparticles that may show better performance. In this regard, in this study, gel‐type poly(styrene‐co‐divinyl benzene) microparticles were chloromethylated and subsequently aminated, and the quantitative effect of the chloromethylation reaction conditions on the final degree of functionalization achieved were examined. In the chloromethylation route, methylal, thionyl chloride, and a Friedel–Craft catalyst were used. From the experimental results, two models were obtained by multiple linear regression relating the chloromethylation conditions to the anion‐exchange capacity (AEC) achieved and to the replaceable chlorine content, according to which the achievement of a high degree of useful functionalization within the microparticles entailed chloromethylation with low methylal/polymer molar ratios and high thionyl chloride/polymer molar ratios, relatively high temperatures, and short reaction times; all of these values were within the ranges used in this study. Additionally, we found that the highest values of AEC could be reached with a methylal/thionyl chloride molar ratio close to unity. The models obtained could be useful for the synthesis of microparticles with required degrees of functionalization, that is, with the chosen hydrophilicity/hydrophobicity ratio. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4054–4065, 2013     

Effect of mass transfer on biodesulfurization kinetics of alkylated forms of dibenzothiophene by Pseudomonas putida CECT5279

BACKGROUND: An important problem exists for the implementation of biodesulfurization technology of fuels related to the influence of mass transfer on the overall reaction rate and process yield. Pseudomonas putida CECT5279 has been shown to be one of the most promising biocatalysts, but most kinetic studies were done at small scale and their capability for the transformation of alkyl substituted forms (Cx–DBTs) has not yet been reported. RESULTS: Conversion yields and kinetic parameters were calculated under aqueous and biphasic resting cell conditions in a 2 L stirred tank reactor. In aqueous reaction media, 100% conversion of DBT, 4MDBT and 4,6DMDBT was achieved while the conversions in the presence of an organic liquid were 38% for DBT, 19.5% for 4MDBT and 16.5% for 4,6DMDBT, showing that the process is strongly affected by mass transfer between liquids. Laboratory scale–up of P. putida CECT5279 growing step was successfully carried out using a 15 L stirred tank, on the basis of the volumetric mass transfer coefficient (k_La). CONCLUSIONS: P. putida CECT5279 is capable of removing Cx–DBT compounds successfully in aqueous resting cell conditions using stirred tank reactors, but in biphasic media, mass transfer between liquids controls the process, increasing time of reaction and lowering process yield. © 2012 Society of Chemical Industry     

Algebraic Reasoning about Reactions: Discovery of Conserved Properties in Particle Physics

Kocabas (1991) describes a situation from particle physics in which quantum properties and conservation laws are postulated from lists of observed and unobserved reactions. Kocabas also presents a program named BR-3 that can rediscover some accepted quantum properties from textbook data, although it fails on a more difficult example from the same source. This paper describes PAULI, a program that solves the same task as BR-3 but uses a different problem-solving model. PAULI produces different, simpler solutions than does BR-3, and it can also handle the problematic example. After comparing the two programs, we conclude that PAULI offers distinct advantages over its predecessor, which we attribute to analgebraic approach to reasoning about sets of reactions.     

Proton-Conductive Melanin-Like Fibers through Enzymatic Oxidation of a Self-Assembling Peptide

Melanin pigments have various properties that are of technological interest including photo- and radiation protection, rich coloration, and electronic functions. Nevertheless, laboratory-based synthesis of melanin and melanin-like materials with morphologies and chemical structures that are specifically optimized for these applications, is currently not possible. Here, melanin-like materials that are produced by enzymatic oxidation of a supramolecular tripeptide structures that are rich in tyrosine and have a 1D morphology are demonstrated, that are retained during the oxidation process while conducting tracks form through oxidative tyrosine crosslinking. Specifically, a minimalistic self-assembling peptide, Lys–Tyr–Tyr (KYY) with strong propensity to form supramolecular fibers, is utilized. Analysis by Raman spectroscopy shows that the tyrosines are pre-organized inside these fibers and, upon enzymatic oxidation, result in connected catechols. These form 1D conducting tracks along the length of the fiber, which gives rise to a level of internal disorder, but retention of the fiber morphology. This results in highly conductive structures demonstrated to be dominated by proton conduction. This work demonstrates the ability to control oxidation but retain a well-defined fibrous morphology that does not have a known equivalent in biology, and demonstrate exceptional conductivity that is enhanced by enzymatic oxidation.