Comparative study of particle size analysis of hydroxyapatite-based nanomaterials

The purpose of this work was to compare hydroxyapatite (HAP) and composites of HAP, HAP with chitosan (CS), and HAP with poly(vinyl pyrrolidone) (PVP), in terms of their particle size and morphology, using different methods, such as Coulter counter analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Although many researchers have studied HAP and CS/HAP and PVP/HAP composites extensively, there is no evidence of a comparative study of their particle sizes. For this reason, different complementary methods have been used so as to provide a more complete image of final product properties — particle size — from the perspective of possible applications. The syntheses of HAP and HAP with polymer nanoparticles were carried out employing a precipitation method. Variation in particle size with synthesis time and influence of the reactants’ concentration on the materials’ preparation were systematically explored. Crystallite size calculated from XRD data revealed nanosized particles of HAP, CS/HAP, and PVP/HAP materials in the range of 2.5–9.2 nm. Coulter counter analysis revealed mean particle sizes of one thousand orders of magnitude larger, confirming that this technique measures agglomerates, not individual particles. In addition, the particles’ morphology and an assessment of their binding mode were completed by TEM measurements.     

The Liquid Junction Potential in Potentiometric Titrations. VII. On Emf Titrations Proposed for the Determination of Some Interaction Coefficients

Certain galvanic cells without liquid junctions, used together with a titration technique, are proposed to determine interaction coefficients for the various ion pairs present in the solutions: The experimental values of the interaction coefficients are needed in calculations of the total emf of cells with liquid junctions considered in other papers of this series.     

Construction of CPs-Stratified Algebras

The results of [7 Dlab , V. , Ringel , C. M. ( 1992 ). The module theoretical approach to quasi-hereditary algebras. In: Tachikawa, H., Brenner, S. eds. Representations of Algebras and Related Topics, London Math. Society Lecture Note Series 168:200–224 . [Google Scholar]] and [2 Ágoston , I. , Dlab , V. , Lukács , E. ( 2011 ). Constructions of stratified algebras . Comm. Algebra 39 : 2545 – 2553 .[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]] gave a recursive construction for all quasi-hereditary and standardly stratified algebras starting with local algebras and suitable bimodules. Using the notion of stratifying pairs of subcategories, introduced in [3 Ágoston , I. , Lukács , E. Stratifying pairs of subcategories for CPS-stratified algebras . To appear in Journal of Algebra and Its Applications , p. 11 . [Google Scholar]], we generalize these earlier results to construct recursively all CPS-stratified algebras.     

Ocadaic acid treatment causes tyrosine phosphorylation of caveolin-2 and induces internalization of caveolae in rat peritoneal macrophages

In this paper, we provide evidences that protein phosphatases could regulate the internalization cycle of caveolae in rat peritoneal cells. Ocadaic acid (OA)—a serine/threonine phosphatase inhibitor—was used in various concentrations (4 and 100 nM) to study the internalization of horseradish peroxidase (HRP) in resident and elicited macrophages. We have found that OA in both concentrations has significantly decreased HRP uptake in resident and elicited cells. The results of our morphometrical analysis showed that in OA-treated cells, the number of surface-connected caveolae has been dramatically decreased. Simultaneously large, endosome-like vacuoles containing small vesicles appeared in the cytoplasm. The membrane of these small vesicles was labeled with anti-caveolin-1 antibody. Immunoprecipitation and Western blot analysis revealed that in OA-treated cells a 29 kDa protein identified as caveolin-2 in macrophages was phosphorylated on tyrosine residues. These data support the idea that there is a close correlation between the phosphorylation of caveolin-2 and endocytosis of caveolae: the tyrosine phosphorylation of this 29 kDa protein can drive caveolae to pinch off from the plasma membrane and causes accumulation of caveolae in a multivesicular body-like cellular compartment, which was never found to contain lysosomal enzymes. As a result of OA treatment caveolin-2 remains phosphorylated and the phosphorylation of these protein might inhibit the recycling of caveolae.     

Hydroxyapatite modified with silica used for sorption of copper(II)

This paper aims to increase the sorption capacity of hydroxyapatite and to find the best apatite-based material for metal ions sorption. The sorption process of copper ions from water solutions by HAP and structurally modified HAP was carried out in this work. Structural modifications of HAP were realized in the preparation phase by an addition of sodium silica into the reaction medium. The prepared materials were characterized by physical-chemical methods: IR, electron-microscopy and X-ray diffraction. The composites characterized were tested in kinetic studies regarding ion exchange and adsorption of Cu²⁺. It was revealed that the silica content, particle size and initial copper ion concentration influence the process rate. Presented at the 8th Conference on Solid State Chemistry, Bratislava, Slovakia, 6–11 July 2008.     

The <Emphasis Type="Italic">Mitsunobu</Emphasis> Inversion Reaction of Sterically Hindered 17-Hydroxy Steroids

Summary. The Mitsunobu inversion reaction of 3-methoxyestra-1,3,5(10)-trien-17-ol is dramatically influenced by the acidic component. There appears to be a relationship between the dissociation constant of the electron-withdrawing substituent on the aryl acid and the overall effectiveness of the reaction, with more acidic species generally providing a higher yield of inverted product.     

Finitistic dimension of standardly stratified algebras

We prove that the projectively and the injectively defined finitistic dimensions of a standardly stratified algebra are always finite by giving the optimal bound for these numbers in terms of the number of simple modules.     

Vibrational Spectroscopy of Intercalated Kaolinites. Part I.

Abstract

The industrial application of kaolinite is closely related to its reactivity and surface properties. The reactivity of kaolinite can be tested by intercalation; that is, via the insertion of low-molecular-weight organic compounds between the kaolinite layers resulting in the formation of a nano-layered organo-complex. Although intercalation of kaolinite is an old and ongoing research topic, there is limited knowledge available on the reactivity of different kaolinites and the mechanism of complex formation, as well as on the structure of the complexes formed. Grafting and incorporation of exfoliated kaolinite in polymer matrices and other potential applications can open new horizons in the study of kaolinite intercalation. This article attempts to summarize (without completion) the most recent achievements in the study of kaolinite organo-complexes obtained with the most common intercalating compounds such as urea, potassium acetate, dimethyl sulphoxide, formamide, and hydrazine using vibrational spectroscopy combined with X-ray powder diffraction and thermal analysis.     

Characterization of antioxidant phenolics in Syringa vulgaris L. flowers and fruits by HPLC‐DAD‐ESI‐MS

In this study the polyphenolic composition of lilac flowers and fruits was determined for the first time. For the identification of compounds, accurate molecular masses and formulas, acquired by LC and ESI‐TOF‐MS and fragmentation pattern given by LC‐ESI/MS/MS analyses, were used. Our chromatographic system in conjunction with tandem MS was found to be valuable in the rapid separation and determination of the multiple constituents in methanolic extracts of lilac flowers and fruits. Altogether 34 phenolics, comprising 18 secoiridoids, seven phenylpropanoids, four flavonoids and five low‐molecular‐weight phenols, were identified. As marker compounds two secoiridoids (oleuropein and nuzhenide), two phenylpropanoids (acteoside and echinacoside) and rutin were quantified by validated methods. As a result of quantitative analysis, it was confirmed that flowers contain significant amounts of phenylpropanoids (acteoside, 2.48%; echinacoside, 0.75%) and oleuropein (0.95%), while in fruits secoiridoid oleuropein (1.09%) and nuzhenide (0.42%) are the major secondary metabolites. The radical scavenging activities of the extracts and the constituents were investigated by DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) and ABTS [2,2′‐azino‐bis‐(3‐ethylbenzothiazoline‐6‐sulfonic acid)] assays. Both extracts show remarkable antioxidant activities. Our results clearly show that lilac flowers and fruits are inexpensive, readily available natural sources of phenolic compounds with pharmacological and cosmetic applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Homological characterization of lean algebras

Certain classes of lean quasi-hereditary algebras play a central role in the representation theory of semisimple complex Lie algebras and algebraic groups. The concept of a lean semiprimary ring, introduced recently in [1] is given here a homological characterization in terms of the surjectivity of certain induced maps between Ext¹-groups. A stronger condition requiring the surjectivity of the induced maps between Ext ^k -groups for allk≥1, which appears in the recent work of Cline, Parshall and Scott on Kazhdan-Lusztig theory, is shown to hold for a large class of lean quasi-hereditary algebras. Research partially supported by NSERC of Canada and by Hungarian National Foundation for Scientific Research grant no. 1903 Research partially supported by NSERC of Canada