conductivity mechanism
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AIM: To compare pH and conductivity used in the determination of growth in reconstituted skim milk (RSM), to determine whether the presence of one or two plasmids in Lactococcus lactis had any influence on growth, and whether AbiS improved bacteriophages resistance of L. lactis.
- MeSH
- analýza kolonii tvořících jednotek MeSH
- bakteriální proteiny genetika MeSH
- bakteriální transformace MeSH
- bakteriofágy fyziologie MeSH
- elektrická vodivost MeSH
- fermentace MeSH
- financování organizované MeSH
- koncentrace vodíkových iontů MeSH
- Lactococcus lactis genetika růst a vývoj MeSH
- mléko mikrobiologie MeSH
- plazmidy aplikace a dávkování MeSH
- potravinářská mikrobiologie MeSH
- sýr MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- srovnávací studie MeSH
The effect of ionic surfactants and manufacturing methods on the separation and distribution of multi-wall carbon nanotubes (CNTs) in a silicone matrix are investigated. The CNTs are dispersed in an aqueous solution of the anionic surfactant dodecylbenzene sulfonic acid (DBSA), the cationic surfactant cetyltrimethylammonium bromide (CTAB), and in a DBSA/CTAB surfactant mixture. Four types of CNT-based composites of various concentrations from 0 to 6 vol.% are prepared by simple mechanical mixing and sonication. The morphology, electrical and thermal conductivity of the CNT-based composites are analyzed. The incorporation of both neat and modified CNTs leads to an increase in electrical and thermal conductivity. The dependence of DC conductivity versus CNT concentration shows percolation behaviour with a percolation threshold of about 2 vol.% in composites with neat CNT. The modification of CNTs by DBSA increases the percolation threshold to 4 vol.% due to the isolation/separation of individual CNTs. This, in turn, results in a significant decrease in the complex permittivity of CNT–DBSA-based composites. In contrast to the percolation behaviour of DC conductivity, the concentration dependence of thermal conductivity exhibits a linear dependence, the thermal conductivity of composites with modified CNTs being lower than that of composites with neat CNTs. All these results provide evidence that the modification of CNTs by DBSA followed by sonication allows one to produce composites with high homogeneity.
- MeSH
- benzensulfonáty chemie MeSH
- cetrimoniové sloučeniny chemie MeSH
- elektrická vodivost * MeSH
- impedanční spektroskopie MeSH
- nanokompozity chemie ultrastruktura MeSH
- nanotrubičky uhlíkové chemie ultrastruktura MeSH
- povrchově aktivní látky chemie MeSH
- silikonové elastomery chemie MeSH
- tepelná vodivost * MeSH
- termogravimetrie MeSH
- vibrace ultrazvukové MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Kidney international. Supplement, ISSN 0098-6577 no. 89, July 2004
24 s. : tab., grafy ; 28 cm
- MeSH
- biologické modely MeSH
- dialýza ledvin přístrojové vybavení MeSH
- dialyzační roztoky farmakokinetika MeSH
- difuze MeSH
- elektřina MeSH
- koronární cirkulace MeSH
- membrány umělé MeSH
- močovina krev MeSH
- osmolární koncentrace MeSH
- plicní oběh MeSH
- sodík krev MeSH
- vodní a elektrolytová rovnováha MeSH
- Publikační typ
- časopisecké články MeSH
- Konspekt
- Patologie. Klinická medicína
- NLK Obory
- nefrologie
This paper deals with the development and characteristics of the properties of a permeable water-resistant heat insulation panel based on recycled materials. The insulation panel consists of a thermal insulation core of recycled soft polyurethane foam and winter wheat husk, a layer of geopolymer that gives the entire sandwich composite strength and fire resistance, and a nanofibrous membrane that permits water vapor permeability, but not water in liquid form. The observed properties are the thermal conductivity coefficient, volumetric heat capacity, fire resistance, resistance to long-term exposure of a water column, and the tensile strength perpendicular to the plane of the board. The results showed that while the addition of husk to the thermal insulation core does not significantly impair its thermal insulation properties, the tensile strength perpendicular to the plane of these boards was impaired by the addition of husk. The geopolymer layer increased the fire resistance of the panel for up to 13 min, and the implementation of the nanofibrous membrane resulted in a water flow of 154 cm2 in the amount of 486 g of water per 24 h at a water column height of 0.8 m.
BACKGROUND AND AIMS: The increasing frequency of disturbances in temperate forests is responsible for the greater numbers of trees with mechanically damaged cambial zones. Adjustment of wood anatomical structure to balance between safe and efficient water conductivity is one mechanism trees employ to cope with mechanical damage. The relative role of disturbances, tree age and climate in shaping xylem conduits and affecting xylem hydraulic conductivity remains unknown. METHODS: We performed an experiment with five different mechanical treatments simulating natural disturbances of juvenile Betula pendula trees (stem scarring, tilting, decapitation, root exposure and stem-base burial). After 3 years, trees were cut down, conduit size and density were measured, and specific hydraulic conductivity of each tree ring was calculated. Between-tree and between-year variability in xylem conductivity was decomposed into effects of tree age, climate and disturbances using linear mixed-effects models. KEY RESULTS: Xylem-specific hydraulic conductivity decreased significantly after treatment in decapitated, tilted and scarred trees. In the last treatment, wood anatomical adjustment was restricted to the area next to the callus tissue zone; in contrast, specific hydraulic conductivity declined over the entire stem circumference after tilting or decapitation. The response of trees with buried stems and exposed roots was generally weak. The overall effect of disturbances on inter-annual variability of wood anatomical structure was greater than the contribution of tree age and climate. CONCLUSIONS: The results indicate that disturbances are important drivers of xylem hydraulic conductivity. Expected increases in the frequency and intensity of disturbances may alter the theoretical capacity of forest stands for water conductance with a feedback to climate.
In the sustained presence of agonist, the opening of P2X7R channel is followed by pore dilatation, which causes an increase in its permeability to larger organic cations, accompanied by receptor sensitization. To explore the molecular mechanisms by which the conductivity and sensitivity are increased, we analyzed the electrophysiological properties and YO-PRO-1 uptake of selected alanine mutants in the first and second transmembrane domains of the rat P2X7R. Substitution of residues Y40, F43, G338, and D352 with alanine reduced membrane trafficking, and the D352A was practically non-functional. The Y40A and F43A mutants that were expressed in the membrane lacked pore dilation ability. Moreover, the Y40A and Y40F displayed desensitization, whereas the Y40W partially recovered receptor function. The G338A/S mutations favored the open state of the channel and displayed instantaneous permeability to larger organic cations. The G338P was non-functional. The L341A and G345A displayed normal trafficking, current amplitude, and sensitization, but both mutations resulted in a decreased pore formation and dye uptake. These results showed that the increase in P2X7R conductivity and sensitivity is critically dependent on residues Y40 and F43 in the TM1 domain and that the region located at the intersection of TM2 helices controls the rate of large pore opening. We investigated the mechanism of the proapoptotic receptor P2X7R's large pore opening and its sensitization. We found that aromatic residues in the upper part of the first transmembrane domain (TM1) are critical for both the P2X7R channel pore opening and receptor sensitization, and residues located at or below the intersection of the second transmembrane domains (TM2) control the rate of pore opening. These findings identify new residues involved in pore formation of P2X7R.
- MeSH
- HEK293 buňky MeSH
- krysa rodu rattus MeSH
- lidé MeSH
- metoda terčíkového zámku MeSH
- molekulární sekvence - údaje MeSH
- mutace MeSH
- mutageneze cílená MeSH
- purinergní receptory P2X7 chemie metabolismus MeSH
- sekvence aminokyselin MeSH
- terciární struktura proteinů MeSH
- transfekce MeSH
- transport proteinů MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Polyaniline cryogel is a new unique form of polyaniline combining intrinsic electrical conductivity and the material properties of hydrogels. It is prepared by the polymerization of aniline in frozen poly(vinyl alcohol) solutions. The biocompatibility of macroporous polyaniline cryogel was demonstrated by testing its cytotoxicity on mouse embryonic fibroblasts and via the test of embryotoxicity based on the formation of beating foci within spontaneous differentiating embryonic stem cells. Good biocompatibility was related to low contents of low-molecular-weight impurities in polyaniline cryogel, which was confirmed by liquid chromatography. The adhesion and growth of embryonic stem cells, embryoid bodies, cardiomyocytes, and neural progenitors prove that polyaniline cryogel has the potential to be used as a carrier for cells in tissue engineering or bio-sensing. The surface energy as well as the elasticity and porosity of cryogel mimic tissue properties. Polyaniline cryogel can therefore be applied in bio-sensing or regenerative medicine in general, and mainly in the tissue engineering of electrically excitable tissues.
- MeSH
- algoritmy MeSH
- aniliny chemie MeSH
- biokompatibilní materiály chemie MeSH
- buněčné kultury MeSH
- elektrická vodivost MeSH
- fibroblasty MeSH
- kryogely chemie MeSH
- mechanické jevy MeSH
- modul pružnosti MeSH
- myši MeSH
- poréznost MeSH
- teoretické modely MeSH
- testování materiálů MeSH
- tkáňové inženýrství MeSH
- viabilita buněk MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
