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Loukanov A.R.,University of Mining and Geology St Ivan Rilski | Gagov H.,Sofia University
Microscopy Research and Technique | Year: 2012

In this study, we aimed to increase the sensitivity of protein labeling using 1.4 nm gold nanoparticles and glutamate δ2 receptor (GluD2) from the postsynaptic membrane of the Purkinje cells. The very small marker size of the particles reduces the steric hindrance between antibodies leading to a higher labeling efficiency of more than one subunit per single receptor molecule. The nanoparticles are visible in 200 kV dark-field scanning transmission electron microscope on freeze-fractured carbon replica of nervous tissue after plasma cleaning treatment. The different elemental composition of nanoparticles as Au nanogold or CdS quantum dot can be distinguished by energy dispersive X-ray spectroscopy. This method ensures detection of an average of three subunits per GluD2 and often labels all four of them with 1.4 nm Au nanoparticles. It is concluded that this high-resolution microscopic method is useful for exploring the quaternary structure of membrane proteins. © 2012 Wiley Periodicals, Inc. Source

Mintcheva N.,University of Mining and Geology St Ivan Rilski | Mintcheva N.,Tokyo Institute of Technology | Tanabe M.,Tokyo Institute of Technology | Osakada K.,Tokyo Institute of Technology
Organometallics | Year: 2011

Phenyl(iodo)platinum complexes having a 2,2′-bipyridine (bpy) or 1,2-bis(diphenylphosphino)ethane (dppe) ligand react with incompletely condensed silsesquioxane (c-C 5H 9) 7Si 7O 9(OH) 3 in the presence of Ag 2O to yield platinasilsesquioxane complexes [Pt{(c-C 5H 9) 7Si 7O 10(OH) 2}(C 6H 5)(L)] (1, L = bpy; 2, L = dppe). NMR spectroscopy revealed their square-planar structures with an O-coordinated silsesquioxanate ligand and O-H⋯O hydrogen bonds within the ligand. Both complexes undergo transmetalation of p-methoxyphenylboronic acid to afford unsymmetrical diarylplatinum complexes [Pt(C 6H 4OCH 3-p)(C 6H 5)(L)] (3, L = bpy; 4, L = dppe). © 2010 American Chemical Society. Source

Gicheva G.,University of Mining and Geology St Ivan Rilski | Yordanov G.,Sofia University
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2013

This article describes studies on the efficiency of activated carbon as adsorbent for water-dispersible silver nanoparticles. Nanoparticles of average size around 60nm and negative zeta-potential were synthesized by reduction of Ag(I) ions with sodium citrate in aqueous medium. Activated carbon (Norit® CA1) intended for water purification was found to be an efficient adsorbent for silver nanoparticles. It was found that nanoparticle adsorption on activated carbon could be described by Freundlich and Langmuir isotherms. The presence of electrolytes favored nanoparticle deposition on the surface of activated carbon. When electrolytes were used above their critical coagulation concentration aggregated nanoparticles were settling down along with the carbon particles, where carbons were acting as filter aid. This allowed complete removal of nanoparticles from the aqueous dispersions. It is expected that these studies could be important for better understanding of the interactions between nanoparticles and solid-liquid interfaces, for preparation of nanoparticle/carbon composite materials, as well as for designing of methods for removal of metal nanoparticles from contaminated water during treatment of nanowastes. © 2013 Elsevier B.V. Source

Anguelov K.,University of Mining and Geology St Ivan Rilski
Global View of Engineering Geology and the Environment - Proceedings of the International Symposium and 9th Asian Regional Conference of IAEG | Year: 2013

Structural bonds among clayey particles were investigated by a number of scientists, predominantly based on results of physical and mechanical studies [Terzaghi K., 1925; Rehbinder, 1966; Derjaguin, 1986; Shtukin, 1965; Osipov, 2012; V.N. Sokolov, 1991]. The most recent comprehensions of academician V. I. Osipov revealed that the main types of structural bonds (contacts) in clays are as follows: phase, transitional, short range coagulation and long range coagulation contacts. Nevertheless of those physical-chemical concepts, which define the significant differences in the nature of contact interactions, all the types of clays are described by the same strength parameters-angle of internal friction (φ) and cohesion (c). Those parameters (φ and c) are convincing for clays with phase and transient contacts, where contacts between the particles are direct. What, however, may be said about clays with coagulation contacts, where hybrid coatings of bound water are available among the particles? Those kinds of contacts are present in the sliding surfaces of landslides. The present report will show which strength properties may be used instead of the traditional ones "φ" and "c" for defining the stability factor. © 2013 Taylor & Francis Group, London. Source

Stavrev P.,University of Mining and Geology St Ivan Rilski | Reid A.,University of Leeds
Geophysics | Year: 2010

The concept of extended Euler homogeneity of potential fields is examined with respect to all variables of length dimension in their analytical expressions. This reveals the possible existence of positive degrees of homogeneity or corresponding negative structural indices considered as extensions of the Thompson's structural indices in Euler deconvolution. This approach is implemented for a contact gravity model, represented by a 2D semi-infinite slab with large thickness relative to its depth. Applying Euler deconvolution on synthetic and field data indicates that the positive degree of homogeneity, i.e., the extended negative structural index, is the appropriate one for the inversion of gravity anomalies from contact structures. © 2010 Society of Exploration Geophysicists. Source

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