Inhibitory power of kefir: the role of organic acids

Milk and MRS broth fermented with kefir grains from different households were examined for inhibitory activity toward gram-negative and gram-positive strains. Fermented milk obtained with 10 g per 100 ml of inoculum (final pH 3.32 to 4.25) and MRS broth fermented with 1 and 10 g per 100 ml of inocula (final pH 4.18 to 5.25) had inhibitory power demonstrated by spot test and agar well diffusion assay. This inhibitory effect could be assigned to the undissociated form of lactic and acetic acid produced during the fermentation process. Kefir supernatants inhibited the growth of Escherichia coli 3 in nutrient broth at 37 degrees C for 24 h. However, supernatants of yogurt or milk artificially acidified with lactic and acetic acids allowed the growth of E. coli 3 in the same conditions. A bacteriostatic effect of milk fermented with kefir grains over E. coli 3 was also demonstrated.     

Effect of electrolyte composition on initial cycling and impedance characteristics of lithium-ion cells

Hybrid-electric vehicles require lithium-battery electrolytes that form stable, low impedance passivation layers to protect the electrodes, while allowing rapid lithium-ion transport under high current charge/discharge pulses. In this article, we describe data acquired on cells containing LiNi_0.8Co_0.15Al_0.05O₂-based positive electrodes, graphite-based negative electrodes, and electrolytes with lithium hexafluorophosphate (LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium bis(oxalato)borate (LiBOB) and lithium difluoro(oxalato) borate (LiF₂OB) salts. The impedance data were collected in cells containing a Li–Sn reference electrode to determine effect of electrolyte composition and testing temperature on individual electrode impedance. The full cell impedance data showed the following trend: LiBOB > LiBF₄ > LiF₂OB > LiPF₆. The negative electrode impedance showed a trend similar to that of the full cell; this electrode was the main contributor to impedance in the LiBOB and LiBF₄ cells. The positive electrode impedance values for the LiBF₄, LiF₂OB, and LiPF₆ cells were comparable; the values were somewhat higher for the LiBOB cell. Cycling and impedance data were also obtained for cells containing additions of LiBF₄, LiBOB, LiF₂OB, and vinylene carbonate (VC) to the EC:EMC (3:7 by wt.) + 1.2 M LiPF₆ electrolyte. Our data indicate that the composition and morphology of the graphite SEI formed during the first lithiation cycle is an important determinant of the negative electrode impedance, and hence full cell impedance.     

A line search approach for high dimensional function optimization

This paper proposes a modified line search method which makes use of partial derivatives and re-starts the search process after a given number of iterations by modifying the boundaries based on the best solution obtained at the previous iteration (or set of iterations). Using several high dimensional benchmark functions, we illustrate that the proposed Line Search Re-Start (LSRS) approach is very suitable for high dimensional global optimization problems. Performance of the proposed algorithm is compared with two popular global optimization approaches, namely, genetic algorithm and particle swarm optimization method. Empirical results for up to 10,000 dimensions clearly illustrate that the proposed approach performs very well for the tested high dimensional functions.     

Automated scanning electron microscopy and x-ray microanalysis for in situ quantification of gadolinium deposits in skin

Gadolinium (Gd) has been identified as a possible causative agent of an emerging cutaneous and systemic fibrosing disorder, nephrogenic systemic fibrosis (NSF), which can cause serious disability and even death. To date, there are only two known associations with this disorder--renal insufficiency and Gd enhanced magnetic resonance imaging (MRI). We developed an automated quantitative scanning electron microscopy (SEM) and Energy dispersive x-ray spectroscopy (EDS) method for Gd in tissue of NSF patients. Freshly cut paraffin block surfaces examined using the variable pressure mode under standardized conditions and random search of the tissue area allow in situ detection and semiquantitative morphometric (volumetric) analysis of insoluble higher atomic number features using backscattered electron imaging. We detected Gd ranging from 1 to 2270 cps/mm2 in 57 cutaneous biopsies of NSF. Gd was associated with P, Ca, and usually Na in tissue deposits. Our method reproducibly determines the elemental composition, relative concentration, and spatial distribution of detected features within the tissue. However, we cannot detect features below our spatial resolution, nor concentrations below the detection limit of our SEM/EDS system. The findings confirm transmetallation and release of toxic Gd ions in NSF and allow dose-response analysis at the histologic level.     

The effects of sex and region on the carcass yield and m longissimus lumborum proximate composition of impala

Physical morphological measurements and m longissimus lumborum proximate chemical composition of impala (Aepyceros melampus) and the effects of age, sex and region on these parameters were investigated. Impala were randomly sampled from Mara (n = 40, 24 males, 16 females), situated in the Arid Sweet Bushveld region, and Musina (n = 28, 15 males, 13 females), situated in the Mopane Bushveld region in the Limpopo Province of South Africa. The live weights of the Mara (50.23 ± 9.32 kg) animals were higher (p < 0.05) than those of the Musina animals (44.25 ± 10.81 kg). The male animals from both regions were significantly heavier than the females (p < 0.05), particularly for the older animals (～5 kg for 30‐month‐old animals and ～10 kg for 42‐month‐old animals); however, the dressing percentages between the sexes did not differ. The Mara female group (～62%) had significantly (p < 0.05) higher mean dressing percentages than the Musina females (～58%). The mean proportions of external and internal offal were relatively higher in the Musina animals. No significant differences in the dressing percentages between the five age groups were found. Carcass measurements increased linearly with age. Age showed no effect on the m longissimus lumborum chemical carcass composition. Female animals (～19.4 g kg^?1) had higher (p < 0.05) lipid contents for both regions than the males (～14.0 g kg^?1) but the sex of the animal had no effect on the remaining chemical carcass composition parameters. The crude protein content of the Musina animals (248.8 ± 10.44 g kg^?1) was higher (p < 0.05) than for the Mara animals (238.0 ± 8.404 g kg^?1). The mean ash content of the impala m longissimus lumborum was ～12 g kg^?1. The results indicated that age effects are caused by the increases in size brought about by the growth of the animal and by the development of sexual dimorphism. Age, however, had no effect on the m longissimus lumborum proximate chemical composition. Regional differences were also shown for both the physical parameters as well as for the proximate chemical composition of the muscle. Similarly, females also differed from males for the parameters measured. These factors will have to be taken into consideration by the meat trade when purchasing, processing and marketing impala game meat. Copyright © 2004 Society of Chemical Industry     

Identification of estrogenic compounds in fish bile using bioassay-directed fractionation

Conjugates of estrogenic chemicals, endogenous as well as xenobiotic, are mainly excreted via bile into the intestine. Therefore, measurement of estrogenic activity in bile yields useful information about an organism's internal exposure to (xeno-)estrogens. Although previous studies in The Netherlands have reported estrogenic activity in male fish bile, the contribution of natural hormones and xenobiotic substances to this activity is unknown. To identify compounds responsible for estrogenic activity in fish bile, we developed a bioassay-directed fractionation method for estrogenic chemicals. In this approach, the in vitro reporter gene assay ER-CALUX (Estrogen Responsive Chemical Activated Luciferase Gene Expression) was used to assess estrogenic activity in deconjugated bile samples and to direct RP-HPLC fractionation and chemical analysis (by GC-MS) of estrogenic compounds. The method was applied to bile from male breams (Abramis brama) collected at three locations in The Netherlands. At one of these locations, the River Dommel, extremely high levels of plasma vitellogenin and a high incidence of intersex gonads in these male breams have previously been observed, indicating the exposure to estrogens. In this study, the natural hormones 17beta-estradiol, estrone, and estriol accounted for the majority of estrogenic activity in male bream bile. At the River Dommel, the synthetic contraceptive pill component ethynylestradiol was found in effective concentrations as well. The detected natural and synthetic hormones may be responsible forthe estrogenic effects observed in wild bream from this location. Furthermore, a large number of xenobiotic chemicals was detected at relatively high levels in bile, including triclosan, chloroxylenol, and clorophene. Although chloroxylenol was shown for the first time to be weakly estrogenic, these compounds did not contribute significantly to the estrogenic activity observed.     

Purification and hypotensive activity of rapeseed protein-derived renin and angiotensin converting enzyme inhibitory peptides

Rapeseed protein isolate (RPI) was hydrolyzed with Alcalase followed by reverse-phase high performance liquid chromatography (RP-HPLC) purification of bioactive peptides. The rapeseed protein hydrolysate (RPH) obtained after 4 h digestion with Alcalase had a degree of hydrolysis (DH) of ～11%. Gel permeation chromatography separation showed high contents of low molecular weight peptides in the RPH when compared to the RPI. After preparative and analytical RP-HPLC separations, three peptides (LY, TF and RALP) were purified and amino acid sequence determined by tandem mass spectrometry. LY (IC₅₀, 0.11 mM) was the most potent (p < 0.05) against ACE activity when compared to TF (IC₅₀, 0.81 mM) and RALP (IC₅₀, 0.65 mM). However, RALP (IC₅₀, 0.97 mM) was the most potent (p < 0.05) against renin activity when compared to LY (IC₅₀, 1.87 mM) and TF (IC₅₀, 3.1 mM). Single oral administration (30 mg/kg body weight) to spontaneously hypertensive rats showed LY and RALP to be the more effective hypotensive agents with maximum blood pressure reduction of ?26 and 16 mmHg, respectively when compared to TF (?12 mmHg). The results suggest that the higher number of hydrophobic amino acid residues LY and RALP contributed to their higher in vitro and in vivo activities when compared to TF.     

High power fuel cell simulator based on artificial neural network

Artificial Neural Network (ANN) has become a powerful modeling tool for predicting the performance of complex systems with no well-known variable relationships due to the inherent properties. A commercial Polymeric Electrolyte Membrane fuel cell (PEMFC) stack (5 kW) was modeled successfully using this tool, increasing the number of test into the 7 inputs – 2 outputs-dimensional spaces in the shortest time, acquiring only a small amount of experimental data. Some parameters could not be measured easily on the real system in experimental tests; however, by receiving the data from PEMFC, the ANN could be trained to learn the internal relationships that govern this system, and predict its behavior without any physical equations. Confident accuracy was achieved in this work making possible to import this tool to complex systems and applications.     

Formation of pyrazines in hydroxyacetaldehyde and glycine nonenzymatic browning Maillard reaction: A computational study

By considering the formation of pyrazines (C₄N₂H₆ and C₄N₂H₄) as one of the possible final Maillard flavour compounds, Density Functional Theory computations at the standard state have been performed on the proposed mechanisms of glyoxal and glycine in the advanced stage of hydroxyacetaldehyde and glycine nonenzymatic browning reaction under different pH conditions. The results reveal that the basic condition is the most favourable for the production of pyrazines (Pzs), and the aqueous solution is more favourable than that of the gaseous state. The reactions at the isoelectric point of glycine and under neutral conditions are the second and third most favourable for the production of Pzs, respectively. The reaction under acidic conditions is the least feasible for the production of Pzs. Amino acetaldehyde is the most likely precursor of the pyrazine ring in the reaction. Presence of air or oxygen is necessary for the production of 2,3,5,6-tetrahydropyrazine (C₄N₂H₄) from 3,6-dihydropyrazine (C₄N₂H₆). Water is necessary with glyoxal and glycine species for the formation of Pzs and water is produced as a by-product during the formation of Pzs.