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Results for “PH-VALUE”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Different feeding patterns affect meat quality of Tibetan pigs associated with intestinal microbiota alterations

This study aimed to investigate the effects of different feeding patterns on meat quality, gut microbiota and its metabolites of Tibetan pigs. Tibetan pigs with similar body weight were fed the high energy diets ( HEP , 20 pigs) and the regular diets ( RFP , 20 pigs), and free-ranging Tibetan pigs ( FRP , 20 pigs) were selected as the reference. After 6 weeks of experiment, meat quality indexes of semitendinosus muscle ( SM ) and cecal microbiota were measured. The results of meat quality demonstrated that the shear force of pig SM in FRP group was higher than that in HEP and RFP groups ( p < 0.001); the pH-value of SM in HEP pigs was higher at 45 min ( p < 0.05) and lower at 24 h ( p < 0.01) after slaughter than that in FRP and RFP groups; the SM lightness ( L* value) of FRP pigs increased compared with RFP and HEP groups ( p < 0.001), while the SM redness ( a* value) of FRP pigs was higher than that of RFP group ( p < 0.05). The free fatty acid ( FA ) profile exhibited that the total FAs and unsaturated FAs of pig SM in HEP and RFP groups were higher than those in FRP group ( p < 0.05); the RFP pigs had more reasonable FA composition with higher n-3 polyunsaturated FAs ( PUFAs ) and lower n-6/n-3 PUFA ratio than HEP pigs ( p < 0.05). Based on that, we observed that Tibetan pigs fed high energy diets (HEP) had lower microbial α-diversity in cecum ( p < 0.05), and distinct feeding patterns exhibited a different microbial cluster. Simultaneously, the short-chain FA levels in cecum of FRP and RFP pigs were higher compared with HEP pigs ( p < 0.05). A total of 11 genera related to muscle lipid metabolism or meat quality, including Alistipes , Anaerovibrio , Acetitomaculun , etc., were identified under different feeding patterns ( p < 0.05). Spearman correlation analysis demonstrated that alterations of free FAs in SM were affected by the genera Prevotellaceae_NK3B31_group , Prevotellaceae UCG-003 and Christensenellaceae_R-7_group ( p < 0.05). Taken together, distinct feeding patterns affected meat quality of Tibetan pigs related to gut microbiota alterations.

Zhu, Yanbin↗
NASA NTRS1999

Water transport by the bacterial channel alpha-hemolysin

This study is an investigation of the ability of the bacterial channel alpha-hemolysin to facilitate water permeation across biological membranes. alpha-Hemolysin channels were incorporated into rabbit erythrocyte ghosts at varying concentrations, and water permeation was induced by mixing the ghosts with hypertonic sucrose solutions. The resulting volume decrease of the ghosts was followed by time-resolved optical absorption at pH 5, 6, and 7. The average single-channel permeability coefficient of alpha-hemolysin for water ranged between 1.3x10-12 cm/s and 1.5x10-12 cm/s, depending on pH. The slightly increased single-channel permeability coefficient at lower pH-values was attributed to an increase in the effective pore size. The activation energy of water transport through the channel was low (Ea=5.4 kcal/mol), suggesting that the properties of water inside the alpha-hemolysin channel resemble those of bulk water. This conclusion was supported by calculations based on macroscopic hydrodynamic laws of laminar water flow. Using the known three-dimensional structure of the channel, the calculations accurately predicted the rate of water flow through the channel. The latter finding also indicated that water permeation data can provide a good estimate of the pore size for large channels.

Non-NASA Center↗
DOE OSTI2016

Laboratory Experiments on Bentonite Samples: FY16 Progress

The primary goal of this study is to improve the understanding of U(VI) sorption and diffusion behavior in sodium-montmorillonite in order to support the development of realistic conceptual models describing these processes in performance assessment models while (1) accounting for potential changes in system conditions over time and space, (2) avoiding overly conservative transport predictions, and (3) using a minimum number of fitting parameters.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗