Predicting user’s preferences using neural networks and psychology models

In this paper we describe a new model suitable for optimization problems with explicitly unknown optimization functions using user’s preferences. The model addresses an ability to learn not known optimization functions thus perform also a learning of user’s preferences. The model consists of neural networks using fuzzy membership functions and interactive evolutionary algorithms in the process of learning. Fuzzy membership functions of basic human values and their priorities were prepared by utilizing Schwartz’s model of basic human values (achievement, benevolence, conformity, hedonism, power, security, self-direction, stimulation, tradition and universalism). The quality of the model was tested on “the most attractive font face problem” and it was evaluated using the following criteria: a speed of optimal parameters computation, a precision of achieved results, Wilcoxon signed rank test and a similarity of letter images. The results qualify the developed model as very usable in user’s preference modeling.     

Characterization of interactions between Escherichia coli O157:H7 with epiphytic bacteria in vitro and on spinach leaf surfaces

This study characterized the types of interactions between Escherichia coli O157:H7 and spinach phylloepiphytic bacteria and identified those that influence persistence of E. coli O157:H7 on edible plants. A total of 1512 phylloepiphytic bacterial isolates were screened for their ability to inhibit or to enhance the growth of E. coli O157:H7 in vitro and on spinach leaf surfaces. Fifteen different genera, the majority belonging to Firmicutes and Enterobacteriaceae, reduced growth rates of E. coli O157:H7 in vitro by either nutrient competition or acid production. Reduced numbers of E. coli O157:H7 were recovered from detached spinach leaves that were co-inoculated with epiphytic isolates belonging to five genera. A 1.8 log reduction in E. coli O157:H7 was achieved when co-inoculated with Erwinina perscinia and 20% cellobiose, a carbon source used by the phylloepiphytes but not E. coli O157:H7. The reduction on leaves was significantly less than reduction measured in vitro. Phylloepiphytic bacteria belonging to eight different genera, increased numbers of E. coli O157:H7 when co-cultured in vitro on spent medium and when co-cultured on detached spinach leaves. The results, showing reduction of E. coli O157:H7 numbers by natural epiphytic bacteria, support the hypothesis that native plant microbiota can be used for bio-control of foodborne pathogens, however, other epiphytes may promote the persistence of enteric pathogens on the phyllosphere.     

Effect of processing for saponin removal on fungal contamination of quinoa seeds (Chenopodium quinoa Willd.)

Incidence of fungal contamination of quinoa seeds from three locations (Salar de Uyuni, Bolivia; Salta and Tucumán provinces, Argentina) was analyzed in samples with and without treatment to remove saponins (wet method). In processed samples, the percentage of infection was reduced. Distribution of the different fungal genera was not homogeneous in the three locations (p<0.05), although Penicillium and Aspergillus were the most prevalent contaminants, regardless the geographic origin of the samples. Other genera, such as Eurotium, Fusarium, Phoma, Ulocladium, Mucor and Rhizopus were less frequently isolated. Absidia, Alternaria, Cladosporium, Dreschlera, Epicoccum and Monascus were sporadically encountered. Significant differences (p<0.05) in the distribution of fungal genera in samples with and without saponins from each location were observed. In all cases, processing caused a decrease of Aspergillus incidence, while increased the proportion of Penicillium, Eurotium, Mucor and Rhizopus indicating that these genera were part of the internal mycota. A. flavus and A. niger were the dominating species of genus Aspergillus. A similar pattern of prevalent Penicillium species was observed in samples with and without saponins, since P. aurantiogriseum, P.chrysogenum, P. citrinum and P. crustosum were always present in high number, although their relative density was variable according to the geographic origin of samples. Mycotoxin-producing ability of most representative species was also determined. Toxigenic strains of A. flavus (aflatoxins and cyclopiazonic acid), A. parasiticus (aflatoxins), P. citrinum (citrinin) and P. griseofulvum (cyclopiazonic acid) were found. None of the A. niger isolates was ochratoxin A producer. The above mentioned mycotoxins were not detected in the samples analyzed.     

Biochemical characterization and process stability of polyphenoloxidase extracted from Victoria grape (Vitis vinifera ssp. Sativa)

Polyphenol oxidase (PPO) was isolated from Victoria grapes (Vitis vinifera ssp. Sativa) grown in South Africa and its biochemical characteristics were studied. Optimum pH and temperature for grape PPO activity were pH 5.0 and T = 25 °C with 10 mM catechol in McIlvaine buffer as substrate. PPO showed activity using the following substances: catechol, 4 methyl catechol, d, l-DOPA, (+) catechin and chlorogenic acid. K_m and V_max values were 52.6 ± 0.00436 mM and 653 ± 24.0 OD_400 nm/min in the case of 10 mM catechol as a substrate. Eight inhibitors were tested in this study and the most effective inhibitors were found to be ascorbic acid, l-cysteine and sodium metabisulfite. Kinetic studies showed that the thermal inactivation of Victoria grape PPO followed first-order kinetics, with an activation energy, E_a = 225 ± 13.5 of kJ/mol. Both in semipurified extract and in grape juice, PPO showed a pronounced high pressure stability.     

Profile of fatty acids, muscle structure and shear force of musculus longissimus dorsi (MLD) in growing pigs as affected by energy and protein or protein restriction followed by realimentation

Forty-eight gilts were submitted to a 30% restriction of feed (groups F and F1) or protein intake (group P) from 90 to 118 days of age, followed by realimentation from 119 to 168 days of age. Control pigs (C) were fed during the whole experiment according to a semi ad libitum scale. During realimentation all animals were fed according to semi ad libitum scale except pigs F1 which were fed ad libitum. Six pigs from each group were slaughtered at the end of restriction and realimentation. Restriction decreased the weight of musculus longissimus dorsi (MLD) and increased shear force. Restriction of feed intake depressed MUFA concentration and increased n-6/n-3 ratio while protein restriction decreased n-6/n-3 and PUFA:SFA ratios. Structure of fibers was not affected. After realimentation MLD mass was still lower in all previously restricted pigs, shear force was the lowest in F1 pigs. Only percentage of fast twich oxidative fibers was significantly greater in F1 pigs than in others. Significant correlations between parameters investigated during the study were found.     

The improvement of the resistance to Candida Albicans and Trichophyton interdigitale of some cotton textile materials by treating with oxygen plasma and chitosan

This paper presents the improvement of the resistance to fungi of some cotton textile materials by treating in the manufacturing process with oxygen plasma and chitosan. Thus, after the weaving and preliminary finishing, the fabrics were cleaned in oxygen plasma atmosphere and after dyeing, have been treated with chitosan solution with concentrations of 1 or 5 g/l, in order to confer them antimicrobial properties. The antimicrobial tests were performed with two fungi: Candida albicans and Tricophyton interdigitale. The obtained antimicrobial effect was considerably higher compared to that of the raw fabrics. The colour resistance of dyed fabrics was not significantly influenced by applying the treatment-based chitosan.     

Stiffness alterations of single cells induced by UV in the presence of nanoTiO2

Nanocrystalline titanium dioxide (nanoTiO2) has been reported to generate reactive oxygen species (ROS) under UV illumination. In our studies, changes in mechanical properties of human skin fibroblasts, exposed to the oxidative stress induced in the presence of nanoTiO2 and UV light, were studied using atomic force microscopy (AFM). The exposure of cells to the action of ROS was performed at low TiO2 concentration (4 microg/mL) and under illumination with low-intensity UVA (8 and 20 mW/cm2) or UVC (0.1 mW/ cm2). AFM measurements of the cell stiffness were carried out immediately after exposure of cells to the oxidative stress. The data suggest that under illumination with low-intensity UVA nanoTiO2 generates ROS, which, in turn, damage cellular and subcellular structures. This process was detected by AFM as a marked drop in the cellular stiffness of ca. 30-75%, which occurred rapidly, in the time frame of 1 min. The photo-oxidative stress inducing the decrease of cell stiffness was cancelled in the presence of a well-established antioxidant, beta-carotene. The results highlight the sensitivity of AFM to detect early changes in mechanical properties of cells exposed to oxidative stress.     

Comparison of inductively coupled plasma-mass spectrometry and radiochemical techniques for total uranium in environmental water samples

Inductively coupled plasma-mass spectrometry (ICP-MS) method EPA 200.8 is gradually finding acceptance as an alternative to uranium analysis. A comparison of the ICP-MS with the accepted radiochemical method EPA 908.0 has been carried out based on data from laboratory control standards, national proficiency test samples, and environmental and drinking water samples from the State of Utah. The method detection limit (MDL) for ICP-MS was determined to be 0.017 microg/L or (0.011 pCi/L), and the minimum reporting limit (MRL) was 0.17 microg/L (MDL x 10) or (0.11 pCi/L). The minimum reporting limit for radiochemical 908.0 method is 1 pCi/L. Our spiked matrix recoveries, spiked blank samples, and reference materials deviate only a few percentage from the listed true values. Results demonstrate that the ICP-MS is a superior analytical tool for the determination of uranium in drinking and environmental waters at concentrations required by the United States Environmental Protection Agency.