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Abstract: In the present study, four different locally available waste glass materials (bottle glass-BG, glass wool-GW, stone wool-SW and cathode-ray tube glass-CRTG) were treated with hot concentrated potassium hydroxide (KOH) in order to obtain alternative alkali activators (AAAs). We evaluated the suitability of the solutions obtained for use as AAAs in the production of AAMs. AAMs were prepared using electric arc furnace slag and selected AAAs with a higher content of dissolved Si. We evaluated the performance of the AAMs in comparison to that of slags activated with KOH or potassium-silicate (K-silicate). The compressive strength of the AAMs prepared with KOH-based AAAs were high when Si and Al were simultaneously abundant in the AAA (9.47 MPa when using the activator sourced from the CRTG), and low with the addition of KOH alone (1.97 MPa). The AAM produced using commercial K-silicate yielded the highest compressive strength (27.7 MPa). The porosity of the KOH-based AAM was lowest when an alternative BG-based activator was used (24.1%), when it was similar to that of the AAM prepared with a K-silicate. The BG-based activator had the highest silicon content (33.1 g/L), and NMR revealed that Si was present in the form of Q0, Q1 and Q2. The concentrations of toxic trace elements in the AAAs used for alkali activation of the slag were also determined, and leaching experiments were performed on the AAMs to evaluate the immobilisation potential of alkali-activated slag. In the SW AAAs the results show acceptable concentrations of trace and minor elements with respect to the regulations on waste disposal sites, while in the activators prepared from BG, CRTG and GW some elements exceeded the allowable limits (Pb, Ba, Sb, and As).
Keywords: alkali activated materials/geopolymers, alternative activators, NMR, leaching
Published in DiRROS: 08.06.2023; Views: 332; Downloads: 212
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Abstract: The renin-angiotensin-aldosterone system (RAAS) plays a key role in the regulation of blood pressure. Renin is the rate limiting enzyme of the RAAS and aliskiren is a highly potent and selective inhibitor of the human renin. Renin is known to be active both in the circulating blood stream as well as locally, when bound to the (pro)-renin receptor ((P)RR). In this study we have investigated a possible mechanism of action of aliskiren, in which its accumulation in the plasma membrane is considered as an essential step for effective inhibition. Aliskiren's interactions with model membranes (cholesterol rich and poor) have been investigated by applying different complementary techniques: differential scanning calorimetry (DSC), Raman spectroscopy, magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and small- and wide-angle X-ray scattering (SAXS and WAXS). In addition, in silico molecular dynamics (MD) calculations were applied for further confirmation of the experimental data. Aliskiren's thermal effects on the pre- and main transition of dipalmitoyl-phosphatidylcholine (DPPC) membranes as well as its topographical position in the bilayer show striking similarities to those of angiotens.in II type 1 receptor (AT1R) antagonists. Moreover, at higher cholesterol concentrations aliskiren gets expelled from the membrane just as it has been recently demonstrated for the angiotensin receptor blocker (ARB) losartan. Thus, we propose that both the AT1R and the (P)RR-bound renin active sites can be efficiently blocked by membrane-bound ARBs and aliskiren when cholesterol rich membrane rafts/caveolae are formed in the vicinity of the receptors.
Keywords: aliskiren, renin, PRR, DPPC bilayers, raman spectroscopy, solid state NMR spectroscopy, SAXS and WAXS, MD simulations
Published in DiRROS: 26.01.2015; Views: 4355; Downloads: 314
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