Search results for "SITES"
showing 10 items of 2851 documents
Comparison of the generation II with IV heterogeneous Ziegler-Natta catalysts used in propylene polymerizations
1998
An unsupported TiCl3-based catalyst (generation II), modified with n-butyl ether and AlEt2Cl3, was compared with a MgCl2/dibutyl phthalate/AlEt3/cyclohexylmethyldimethoxysilane catalyst system (generation IV) in propylene polymerizations. The latter (magnesium-supported) was fund to be more than 20 times as active as the former and more stereospecific, but to yield PP with a lower molecular weight (Table 2). The kinetics of the polymerizations studied with either of the catalyst, and involving the determination of concentrations of active sites [C0*] and elementary reaction rate constants (Table 4) based on earlier kinetic models, showed the C0*-values in the magnesium-supported catalyst to…
Effects of density, species interactions, and environmental stochasticity on the dynamics of British bird communities
2022
Our knowledge of the factors affecting species abundances is mainly based on time-series analyses of a few well-studied species at single or few localities, but we know little about whether results from such analyses can be extrapolated to the community level. We apply a joint species distribution model to long-term time-series data on British bird communities to examine the relative contribution of intra- and interspecific density dependence at different spatial scales, as well as the influence of environmental stochasticity, to spatiotemporal interspecific variation in abundance. Intraspecific density dependence has the major structuring effect on these bird communities. In addition, envi…
Aviokompāniju reklāmu raksturojums sociālo tīklu tīmekļa vietnēs Facebook un Twitter
2018
Reklāma ir profesionālā diskursa žanrs, kas tiek izmantots komunikācijai ar sabiedrību. Mūsdienās internets un sociālo tīklu tīmekļa vietnes tiek bieži izmantotas reklāmas nolūkos. Šī pētījuma mērķis bija analizēt lingvistiskās un paralingvistiskās iezīmes sociālo tīklu tīmekļa vietnēs Facebook un Twitter publicētajās aviokompāniju reklāmās. Pētījums tika balstīts uz Kuka (Cook, 1992) piedāvāto diskursa analīzes modeli, kas ietver teksta un konteksta analīzi. Pētījuma rezultāti parādīja, ka šo reklāmu tekstos izmantotā valoda ir vienkārša un lasītājam draudzīga, kas ir panākts, pārsvarā izmantojot vienkāršus teikumus, kā arī lietojot kontrakcijas un saīsinājumus. Tā arī imitē sarunu ar lasī…
Fast blue B functionalized silica-polymer composite to evaluate 3,5-dihy-droxyhydrocinnamic acid as biomarker of gluten intake
2021
Celiac disease is an immune-mediated systemic disorder elicited by gluten and related prolamines in genetically susceptible individuals. The current treatment is a strict and lifelong gluten-free diet. However, compliance with the gluten-free diet is not always adequate and many food products contain low concentrations of gluten. The determination of dietary transgressions is a challenge for patients, physicians and dietitians. Alkylresorcinols (AR) have been proposed as sensitive and specific biomarkers of gluten consumption. In this work silica-polymer composites doped with fast blue B reagent (FB) have been used to estimate alkylresorcinols in biological samples. The proposed colorimetri…
Biochemical and structural features of a novel cyclodextrinase from cow rumen metagenome.
2007
A novel enzyme, RA.04, belonging to the alpha-amylase family was obtained after expression of metagenomic DNA from rumen fluid (Ferrer et al.: Environ. Microbiol. 2005, 7, 1996-2010). The purified RA.04 has a tetrameric structure (280 kDa) and exhibited maximum activity (5000 U/mg protein) at 70 degrees C and was active within an unusually broad pH range from 5.5 to 9.0. It maintained 80% activity at pH 5.0 and 9.5 and 75 degrees C. The enzyme hydrolyzed alpha-D-(1,4) bonds 13-fold faster than alpha-D-(1,6) bonds to yield maltose and glucose as the main products, and it exhibited transglycosylation activity. Its preferred substrates, in the descending order, were maltooligosaccharides (C3-C…
α-Aminoalkylphosphonates as a tool in experimental optimisation of P1 side chain shape of potential inhibitors in S1 pocket of leucine- and neutral a…
2005
Abstract The synthesis and biological activity studies of the series of structurally different α-aminoalkylphosphonates were performed in order to optimise the shape of the side chain of the potential inhibitors in S1 pocket of leucine aminopeptidase [E.C.3.4.11.1]. Analysis of a series of compounds with aromatic, aliphatic and alicyclic P1 side chains enabled to find out the structural features, optimal for that fragment of inhibitors of LAP. The most active among all investigated compounds were the phosphonic analogues of homo-tyrosine ( K i = 120 nM) and homo-phenylalanine ( K i = 140 nM), which even as racemic mixtures were better inhibitors in comparison with the best till now-phosph…
Procollagen C-proteinase Enhancer Stimulates Procollagen Processing by Binding to the C-propeptide Region Only*
2011
Background: Procollagen C-proteinase enhancer-1 (PCPE-1) is an extracellular glycoprotein that increases activity of certain zinc metalloproteinases involved in tissue development and repair. Results: PCPE-1 binds uniquely to the C-propeptide region of the procollagen molecule. Conclusion: PCPE-1 enhances proteolysis by binding solely to the procollagen C-propeptides. Significance: These data may lead to future applications in the development of antifibrotic therapies.
The Sea Urchin sns Insulator Blocks CMV Enhancer following Integration in Human Cells
2001
Insulators are a new class of genetic elements that attenuate enhancer function directionally. Previously, we characterized in sea urchin a 265-bp-long insulator, termed sns. To test insulator activity following stable integration in human cells, we placed sns between the CMV enhancer and a tk promoter up-stream of a GFP transgene of plasmid or retroviral vectors. In contrast to controls, cells transfected or transduced with insulated constructs displayed a barely detectable fluorescence. Southern blot and PCR ruled out vector rearrangement following integration into host DNA; RNase protection confirmed the enhancer blocking activity. Finally, we demonstrate that two cis-acting sequences, p…
PVC silver zeolite composites with antimicrobial properties
2011
Poly(vinyl chloride) (PVC) composites containing increasing amounts (2-20%, w/w) of silver zeolite (SZ) were prepared by melt mixing and characterized by thermal, mechanical and rheological analyses. The addition of large amount of SZ did not influence the processability and the formability of the composites, if compared to neat plasticized PVC. The antibacterial activity of PVC SZ composites was tested on Escherichia coli and Staphylococcus epidermidis and resulted promising both in culture broth and on agar plate and also in sterile urine seeded with these strains, for simulation purposes. In sterile urine, composites induced a significant reduction (4-6 log units) of viability of both st…
Influence of antioxidants intercalated layered double hydroxides (AO-LDHs) on the thermo-oxidative stability of pla and pe based nanocomposites
2016
Layered double hydroxides (LDHs) are excellent host matrices for storage and delivery of antioxidants (AOs).