Effects of a first-order chemical reaction on turbulent mass transfer

The effects of a first-order chemical reaction on turbulent mass transfer from a wall are investigated using a Lagrangian method that involves the numerical solution for the flow field in conjunction with the tracking of mass markers released from the wall. The markers react according to a Poisson distribution that is correlated to the reaction rate constant. The method allows studying a range of Schmidt number fluids and a range of Damköhler numbers. The behavior of a continuous line source of the reactant, and the behavior of the dissolution of the reactant from the wall are examined. It is found that the mass transfer coefficient increases dramatically when a first-order reaction occurs. A correlation between the mass transfer coefficient and the Damköhler number is proposed for both low and high Schmidt numbers. The fundamental reason for the change in the mass transfer properties is that each marker is affected by different parts of the turbulence velocity field depending on the Schmidt and Damköhler numbers.     

Identification of functional domains of the human glutamate transporters EAAT1 and EAAT2

Glutamate transporters serve the important function of mediating removal of glutamate released at excitatory synapses and maintaining extracellular concentrations below excitotoxic levels. Excitatory amino acid transporter subtypes EAAT1 and EAAT2 have a high degree of sequence homology and similar predicted topology and yet display a number of functional differences. Several recombinant chimeric transporters were generated to identify domains that contribute to functional differences between EAAT1 and EAAT2. Wild-type transporters and chimeric transporters were expressed in Xenopus laevis oocytes, and electrogenic transport was studied under voltage clamp conditions. The differential sensitivity of EAAT1 and EAAT2 to transport blockers, kainate, threo-3-methylglutamate, and (2S, 4R)-4-methylglutamate as well as L-serine-O-sulfate transport and chloride permeability were employed to characterize chimeric transporters. One particular region, transmembrane domains 9 and 10, plays an important role in defining these functional differences. The intracellular carboxyl-terminal region may also play a minor role in conferring an effect on chloride permeability. This study provides important insight into the identification of functional domains that determine differences among glutamate transporter subtypes.     

Basal and induced nitric oxide and cGMP productions are decreased in senescent cultured rat articular chondrocytes

The effects of interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), and lipopolysaccharide (LPS) on the productions of nitric oxide (NO) and cGMP by cultured articular chondrocyte (AC) monolayers from 1-, 8- and 18-month old male Wistar rats were studied. It was found that basal NO and cGMP productions decrease with the age of animals. The productions were more than 2-fold greater in cells from 1-month old rats then in cells from older animals. IL-1, TNF-alpha, and LPS stimulated all three types of cells to produce NO and cGMP in a time- and concentration-dependent manner. Although the cells from young animals produced more NO per microg DNA, the older counterparts were more sensitive to these agents since they produced more NO upon stimulation then the corresponding non-stimulated controls. At the concentration of 10(-3) M, the nitric oxide synthase (NOS) inhibitor, Ng-monomethyl-L-arginine (L-NMA), blocked, although incompletely, both the basal and stimulated NO and cGMP productions in cells from the 1 and 8-month old rats and only induced productions in 18-month old counterparts. These results show a decreased capacity of unstimulated- and stimulated-AC from old rats to produce NO and cGMP in culture, which may affect the ageing cells in some yet unknown way.     

Protein Corona: Impact of Lymph Versus Blood in a Complex In Vitro Environment

In biological environments, the surface of nanoparticles (NPs) are modified by protein corona (PC) that determines their biological behavior. Unfortunately, in vitro tests still give different PC than in vivo tests causing in vitro–in vivo discrepancy; hence, in vitro studies are not indicative for the NPs' behavior in vivo. Here is demonstrated that PC in vitro is strongly influenced by the type of extracellular fluid (ECF), blood or lymph, by their high and low flow conditions and transitions between ECFs, and a combination of these parameters. As a result, this in vitro study approaches fluidic and dynamic variations to which NPs are exposed in vivo: different ECF that NPs encounter first in different injection routes, different transitions in‐between ECFs during circulation, and simultaneous change in the exposed flow in these transitions. The most‐abundant proteins in PCs are found to be not the most abundant in ECFs, but those having high affinity for binding to the surface of NPs. Moreover, some proteins are differently abundant in PCs at different flows, which indicate force‐promoted binding, catch bonds. These results suggest that future in vitro studies should consider more complex incubation conditions to improve the in vitro–in vivo consistency necessary for translational research.     

Can the sprouting process applied to wheat improve the contents of vitamins and phenolic compounds and antioxidant capacity of the flour?

The content of tocopherols, B vitamins, as well as free soluble, soluble conjugated and insoluble bound phenolic compounds was determined in untreated, steeped and sprouted wheat grains. Antioxidant capacity of whole wheat grains and their phenolic fractions was also evaluated. Sprouting significantly increased the levels of tocopherols, niacin, riboflavin, as well as free and bound phenolic compounds improving nutritional value and antioxidant capacity of wheat grains/flour. After sprouting for 5 days, the content of total phenolics, flavonoids and ferulic acid calculated as the sum of its fractions was increased by 9.9, 30.7 and 21.6%, respectively. The content of α‐, β+γ‐ and δ‐tocopherols was increased for 3.59‐fold, 2.33‐fold and 2.61‐fold respectively, while the content of niacin, as predominant B vitamin, was increased for 1.19‐fold after sprouting. The total antioxidant capacity of untreated, steeped and sprouted whole wheat grains was 19.44, 20.37 and 22.70 mmol Trolox Eq/kg, respectively. Sprouted wheat, as a rich source of bioavailable phytochemicals, should be used to improve the nutritional quality of food.     

The influence of heat treatment on the sliding wear behavior of a ZA-27 alloy

The effects of heat treatment, involving solutionizing at temperature of 370 °C for a relatively short period of time (3 or 5 h), followed by quenching in water, on tribological behavior of ZA-27 alloys were examined.Dry sliding wear tests were conducted on as-cast and heat-treated ZA-27 samples using block-on-disk machine over a wide range of applied loads. To determine the wear mechanisms, the worn surfaces of the samples were examined by scanning electron microscopy (SEM). The tribological results were related to the microstructure and mechanical properties.The heat treatment resulted in reduction in the hardness and tensile strength but increase in elongation. The heat-treated alloy samples attained improved tribological behavior over the as-cast ones, both from the aspects of friction and wear. The improved tribological behavior of the heat-treated alloys, in spite of reduced hardness, could be the result of breaking the dendrite structure, when the fraction of interdendrite regions was considerably decreased and a very fine α and η mixture was formed at the same time. The wear response of the samples has been corroborated through characteristics of worn surfaces and dominant wear mechanisms.     

Buckwheat (Fagopyrum esculentum Moench) Grain and Fractions: Antioxidant Compounds and Activities

Abstract: Buckwheat (Fagopyrum esculentum Moench) is an alternative crop belonging to the Polygonaceae family. In comparison to antioxidant activity of frequently used cereals, buckwheat has been reported to possess higher antioxidant activity (AOA), mainly due to high rutin content. The objective of this work was to determine the main antioxidant compounds and AOA of buckwheat grain fractions (whole grain, hull, and groat). Buckwheat grain fractions were extracted with ethanol/water (80/20, v/v), followed by determination of total phenolic and flavonoid content. Quantification of phenolic compounds and tocopherols was performed by high‐performance liquid chromatography (HPLC). The AOA was estimated by 2 direct electron spin resonance (ESR) and 4 indirect (spectrophotometric) tests. Significantly higher contents of total phenolics and total flavonoids were found in buckwheat hull than in whole grain and groat. Protocatechuic, syringic, and sinapic acid, rutin, and quercetin were found in all tested fractions, whereas vanilic acid was found in whole grain and hull. The content of total tocopherols in investigated samples ranged from 23.3 mmol/g for hull to 61.8 mmol/g for groat. Hull was superior in scavenging activity on 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH^?), hydroxyl (^?OH), and superoxide anion (O₂^?‐) radicals, reducing activity, AOA by β‐carotene bleaching method, and chelating activity on Fe²⁺ as evidenced by its lower IC₅₀ value. Obtained results can broaden the utilization of buckwheat, especially a share of hull in whole grain flour production. Practical Application: Obtained results suggest possibility to supplement the whole grain buckwheat flour with hull, which leads toward better usage of by‐products in buckwheat production, and enhancement of antioxidant potential of the final product.     

Antioxidant, antimicrobial, and anticancer activity of 3 Umbilicaria species

Abstract: The aim of this study is to investigate in vitro antioxidant, antimicrobial, and anticancer activity of the acetone extracts of the lichens Umbilicaria crustulosa, U. cylindrica, and U. polyphylla. Antioxidant activity was evaluated by 5 separate methods: free radical scavenging, superoxide anion radical scavenging, reducing power, determination of total phenolic compounds, and determination of total flavonoid content. Of the lichens tested, U. polyphylla had largest free radical scavenging activity (72.79% inhibition at a concentration of 1 mg/mL), which was similar as standard antioxidants in the same concentration. Moreover, the tested extracts had effective reducing power and superoxide anion radical scavenging. Total content of phenol and flavonoid in extracts was determined as pyrocatechol equivalent, and as rutin equivalent, respectively. The strong relationships between total phenolic and flavonoid contents and the antioxidant effect of tested extracts were observed. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration by the broth microdilution method. The most active was extract of U. polyphylla with minimum inhibitory concentration values ranging from 1.56 to 12.5 mg/mL. Anticancer activity was tested against FemX (human melanoma) and LS174 (human colon carcinoma) cell lines using MTT method. All extracts were found to be strong anticancer activity toward both cell lines with IC₅₀ values ranging from 28.45 to 97.82 μg/mL. The present study shows that tested lichen extracts demonstrated a strong antioxidant, antimicrobial, and anticancer effects. That suggests that lichens may be used as possible natural antioxidant, antimicrobial, and anticancer agents.     

Formation of a liquid jet after detachment of a vapour bubble

Originated by the action of Laplace-pressure at the moment of break-off of a vapour bubble, a liquid jet can form, penetrate the bubble and pierce the bubble vertex at a relatively high velocity. The prehistory of the jet formation, including the detachment process of a single vapour bubble are described in the paper. Photographs of a vapour bubble, generated on a horizontal heated surface, show clearly the process of bubble detachment, the formation and the development of a liquid jet immediately after the bubble break-off. Refrigerant R113 containing 1% (mass) of oil was used as the test liquid.