Search results for "gradient"
showing 10 items of 725 documents
Geochemical characterization of surface waters and groundwater resources in the Managua area (Nicaragua, Central America)
2008
This paper reports new geochemical data on dissolved major and minor constituents in surface waters and ground waters collected in the Managua region (Nicaragua), and provides a preliminary characterization of the hydrogeochemical processes governing the natural water evolution in this area. The peculiar geological features of the study site, an active tectonic region (Nicaragua Depression) characterized by active volcanism and thermalism, combined with significant anthropogenic pressure, contribute to a complex evolution of water chemistry, which results from the simultaneous action of several geochemical processes such as evaporation, rock leaching, mixing with saline brines of natural or…
Effect of the Substituent Position on the Anionic Copolymerization of Styrene Derivatives: Experimental Results and Density Functional Theory Calcula…
2019
In a combined synthetic, kinetic and theoretical study, the living anionic copolymerization of styrene and its ring-methylated derivatives ortho-, meta-, and para-methylstyrene (MS) was examined by real-time 1H NMR spectroscopy in the nonpolar solvents toluene-d8 and cyclohexane-d12 as well as by density functional theory calculations. Based on the NMR kinetics data, reactivity ratios for each comonomer pair were determined by the Kelen–Tudős method and numerical integration of the copolymerization equation (Contour software). The reaction pathway was modeled and followed by density functional theory (DFT) calculations to validate and predict the experimentally derived reactivity ratios. Un…
A facile and eco-friendly route to fabricate poly(Lactic acid) scaffolds with graded pore size
2016
Over the recent years, functionally graded scaffolds (FGS) gaineda crucial role for manufacturing of devices for tissue engineering. The importance of this new field of biomaterials research is due to the necessity to develop implants capable of mimicking the complex functionality of the various tissues, including a continuous change from one structure or composition to another. In this latter context, one topic of main interest concerns the design of appropriate scaffolds for bone-cartilage interface tissue. In this study, three-layered scaffolds with graded pore size were achieved by melt mixing poly(lactic acid) (PLA), sodium chloride (NaCl) and polyethylene glycol (PEG). Pore size distr…
Validity of NMR pore-size analysis of cultutal heritage ancient building materials containing magnetic impurities
2007
NMR relaxation time distributions, obtained with laboratory and portable devices, are utilized to characterize the pore-size distributions of building materials coming from the Roman remains of the Greek-Roman Theatre of Taormina. To validate the interpretation of relaxation data in terms of pore-size distribution, comparison of results from standard and in situ NMR experiments with results of the mercury intrusion porosimetry (MIP) has been made. Although the pore-size distributions can be obtained by NMR in terms of either longitudinal (T-1) or transverse (T-2) relaxation times distributions, the shorter duration of the T-2 measurement makes it, in principle, preferable, although the dete…
Cell cooperation in coelomocyte cytotoxic activity of Paracentrotus lividus coelomocytes
2007
The coelomic fluid from the sea urchin Paracentrotus lividus contains several coelomocyte types including amoebocytes and uncoloured spherulocytes involved in immune defences. In the present paper, we show a Ca(2+)-dependent cytotoxic activity for the unfractionated coelomocytes assayed in vitro, with rabbit erythrocytes and the K562 tumour cell line. In a plaque-forming assay, whole coelomocyte preparations as well as density gradient separated coelomocyte populations revealed that cell populations enriched in uncoloured spherulocytes, exerted high cytotoxic activity by releasing lysins in the presence of amoebocytes. This cooperative effect could be dependent on soluble factors released b…
Heparan sulfate proteoglycans interact exclusively with conformationally intact HPV L1 assemblies: basis for a virus-like particle ELISA.
2004
In this article, we demonstrate that interaction of human papillomavirus-like particles (HPV-VLPs) with the putative glucosaminoglycan binding receptor is strictly dependent on conformational integrity. Such conformations are present on VLPs and capsomeres but not on monomers of the major capsid protein, L1, confirming reports that capsomeres can induce virus-neutralizing antibodies. Furthermore, we show the suitability of this specific interaction for development of VLP-based enzyme-linked immunosorbent assays (ELISAs), using heparin for indirect coupling of VLPs to microtiter plates, which may add an intrinsic quality control. This avoids presentation of linear, often highly cross-reactiv…
Identification of ERp29, an endoplasmic reticulum lumenal protein, as a new member of the thyroglobulin folding complex.
2002
Folding and post-translational modification of the thyroid hormone precursor, thyroglobulin (Tg), in the endoplasmic reticulum (ER) of the thyroid epithelial cells is facilitated by several molecular chaperones and folding enzymes, such as BiP, GRP94, calnexin, protein disulfide isomerase, ERp72, and others. They have been shown to associate simultaneously and/or sequentially with Tg in the course of its maturation, thus forming large heterocomplexes in the ER of thyrocytes. Here we present evidence that such complexes include a novel member, an ER-resident lumenal protein, ERp29, which is present in all mammalian tissues with exceptionally high levels of expression in the secretory cells. …
The production of 85 kDa N-terminal fragment of apolipoprotein B in mutant HepG2 cells generated by targeted modification of apoB gene occurs by ALLN…
2010
Abstract To study the mechanism of low levels of full length and truncated apoB in individuals heterozygous for apoB truncation, a non-sense mutation was introduced in one of the three alleles of apob gene of HepG2 cells by homologous recombination. Despite very low levels of apoB-82 (1–2%) in the media, a prominent N-terminal apoB protein of 85 kDa (apoB-15) was secreted that fractionated at d > 1.065 in density gradient ultracentrifugation. The mechanism of production of this short protein was studied by 35S-methionine pulse–chase experiment. Oleate prevented presecretory degradation of apoB-100 in the cell and resulted in increased secretion of newly synthesized apoB-100 with decreases i…
About the finite convergence of the proximal point algorithm
1988
We study the finite convergence property of the proximal point algorithm applied to the partial inverse, with respect to a subspace, of the subdifferential of a polyhedral convex function. Using examples we show how sufficient conditions providing the finite convergence can be realized and we give a case with non finite termination.
Notions of Dirichlet problem for functions of least gradient in metric measure spaces
2019
We study two notions of Dirichlet problem associated with BV energy minimizers (also called functions of least gradient) in bounded domains in metric measure spaces whose measure is doubling and supports a (1, 1)-Poincaré inequality. Since one of the two notions is not amenable to the direct method of the calculus of variations, we construct, based on an approach of Juutinen and Mazón-Rossi–De León, solutions by considering the Dirichlet problem for p-harmonic functions, p>1, and letting p→1. Tools developed and used in this paper include the inner perimeter measure of a domain. Peer reviewed