KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Settings

Subject: search.filters.subject.Dextran

Search Results

Now showing 1 - 2 of 2
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    Spatiotemporal variations of sand hydraulic conductivity by microbial application methods
    (2024-01-01)
    Kamchoom, Viroon
    ;
    Khattiwong, Thiti
    ;
    Treebupachatsakul, Treesukon
    ;
    Keawsawasvong, Suraparb
    ;
    Leung, Anthony Kwan
    The spatiotemporal distributions of microbes in soil by different methods could affect the efficacy of the microbes to reduce the soil hydraulic conductivity. In this study, the specimens of bio-mediated sands were prepared using three different methods, i.e. injecting, mixing, and pouring a given microbial solution onto compacted sand specimens. The hydraulic conductivity was measured by constant-head tests, while any soil microstructural changes due to addition of the microbes were observed by scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) tests. The amount of dextran concentration produced by microbes in each type of specimen was quantified by a refractometer. Results show that dextran production increased exponentially after 5–7 d of microbial settling with the supply of culture medium. The injection and mixing methods resulted in a similar amount and uniform distribution of dextran in the specimens. The pouring method, however, produced a nonuniform distribution, with a higher concentration near the specimen surface. As the supply of culture medium discontinued, the dextran content near the surface produced by the pouring method decreased dramatically due to high competition for nutrients with foreign colonies. Average dextran concentration was negatively and correlated with hydraulic conductivity of bio-mediated soils exponentially, due to the clogging of large soil pores by dextran. The hydraulic conductivity of the injection and mixing cases did not change significantly when the supply of culture medium was absent.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    Electrospun dextran fibrous membranes
    (2008-06-01)
    Ritcharoen, Watadta
    ;
    Thaiying, Yaowaporn
    ;
    Saejeng, Yupa
    ;
    Jangchud, Ittipol
    ;
    Rangkupan, Ratthapol
    Ultra-fine fiber mats of dextran (powder; M<inf>w</inf> = 64,000-76,000 Da) were fabricated by electrospinning, using water as the solvent. The effects of solution concentration (i.e., 0.7-1.3 g mL<sup>-1</sup>) and applied electric field (9-21 kV/15 cm) on morphological appearance and size of the obtained fibers were investigated. Under a fixed electric field of 15 kV/15 cm and a fixed solution flow rate of 0.25 mL h<sup>-1</sup>, beaded fibers were observed up to a critical concentration of about 0.9 g mL<sup>-1</sup>, beyond which only smooth fibers were obtained. The average diameter of these fibers increased monotonically with increasing the solution concentration (i.e., from ∼290 to ∼1950 nm). For the dextran solutions investigated, increasing the electric field generally caused the diameters of the obtained fibers to increase, with the average diameter of the obtained fibers ranging between 520 and 1760 nm. To improve the usefulness of the electrospun dextran fiber mats in an aqueous medium, cross-linking with glutaraldehyde was necessary. The effects of curing temperature (i.e., 70-90 °C), curing time (i.e., 3-48 h), and added MgCl<inf>2</inf> catalyst (i.e., 0.01-0.03 g) on physical integrity of the cross-linked dextran membranes in water were investigated. Both the swelling and the weight loss in water of the cross-linked membranes were generally found to decrease with increasing curing temperature, curing time, and MgCl<inf>2</inf> loading and the cross-linking did not affect the morphology of the obtained membranes. © Springer Science+Business Media B.V. 2008.