Study of the Resonance Energy Transfer Between Two Dye Cations Embedded in Layered Silicates

The Langmuir – Blodgett (LB) method is one of the useful techniques to prepare ultra-thin films with precise organization of embedded dye cations. The main limitations for the preparation of LB films is that the surfactants, building blocks of the LB films, must be amphiphiles and not soluble in water. In our study we used laser dye cation (rhodamine) with long alkyl chain in the structure, which makes this cation sufficiently hydrophobic. The alkylammonium chain helps to prevent dye molecular aggregation. The objective of this study was to prepare LB films built from synthetic saponite particles and adsorbed alkylammonium and organic dye cations. Energy transfer between two dye cations in LB films was studied. Oxazine 4 – energy acceptor molecules - does not represent an amphiphilic molecule, and is soluble in water. This problem we solved using long chain alkylammonium solution as the third component. We found out RET proceeded with high yields. The molecules of rhodamine played the role of molecular antennas absorbing green light (energy donor). Resonance energy transfer was detected as a quenching of light emission from rhodamine (580 nm) in favour of the red light luminescence from oxazine ( 623 nm), playing the role of energy acceptor. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3530

Accession Site Does Not Influence the Risk of Stroke after Diagnostic Coronary Angiography or Intervention: Results from a Large Prospective Registry

INTRODUCTION: Periprocedural stroke represents a rare but serious complication of cardiac catheterization. Pooled data from randomized trials evaluating the risk of stroke following cardiac catheterization via transradial versus transfemoral access showed no difference. On the other hand, a significant difference in stroke rates favoring transradial access was found in a recent meta-analysis of observational studies. Our aim was to determine if there is a difference in stroke risk after transradial versus transfemoral catheterization within a contemporary real-world registry. METHODS: Data from 14,139 patients included in a single-center prospective registry between 2009 and 2016 were used to determine the odds of periprocedural transient ischemic attack (TIA) and stroke for radial versus femoral catheterization via multivariate logistic regression with Firth's correction. RESULTS: A total of 10,931 patients underwent transradial and 3,208 underwent transfemoral catheterization. Periprocedural TIA/stroke occurred in 41 (0.29%) patients. Age was the only significant predictor of TIA/stroke in multivariate analysis, with each additional year representing an odds ratio (OR) = 1.09 (CI 1.05-1.13, p < 0.000). The choice of accession site had no impact on the risk of periprocedural TIA/stroke (OR = 0.81; CI 0.38-1.72, p = 0.577). CONCLUSION: Observational data from a large prospective registry indicate that accession site has no influence on the risk of periprocedural TIA/stroke after cardiac catheterization

Links Between Hydrothermal Environments, Pyrophosphate, Na+, and Early Evolution

The discovery that photosynthetic bacterial membrane-bound inorganic pyrophosphatase (PPase) catalyzed light-induced phosphorylation of orthophosphate (Pi) to pyrophosphate (PPi) and the capability of PPi to drive energy requiring dark reactions supported PPi as a possible early alternative to ATP. Like the proton-pumping ATPase, the corresponding membrane-bound PPase also is a H+-pump, and like the Na+-pumping ATPase, it can be a Na+-pump, both in archaeal and bacterial membranes. We suggest that PPi and Na+ transport preceded ATP and H+ transport in association with geochemistry of the Earth at the time of the origin and early evolution of life. Life may have started in connection with early plate tectonic processes coupled to alkaline hydrothermal activity. A hydrothermal environment in which Na+ is abundant exists in sediment-starved subduction zones, like the Mariana forearc in the W Pacific Ocean. It is considered to mimic the Archean Earth. The forearc pore fluids have a pH up to 12.6, a Na+-concentration of 0.7 mol/kg seawater. PPi could have been formed during early subduction of oceanic lithosphere by dehydration of protonated orthophosphates. A key to PPi formation in these geological environments is a low local activity of water

Surface properties of illite-smectite minerals as detected by interactions with Rhodamine 6G dye

Interactions between smectite clay minerals and various organic dyes have been studied extensively, but little information has accumulated from dye interactions with mixed-layer illite-smectite (I-S) minerals, especially regarding relationships with clay layer expandability, layer charge, particle size/shape, and molecular aggregation of organic dye molecules. The purpose of this study was to investigate the surface interactions of a set of mixed-layer illite-smectites from different geological environments with Rhodamine 6G dye. The samples used have different amounts of expandable smectite interlayers, different particle size and/or shape, and different layer-charge density at the surface. Five smectites with differences in layer charge and some non-expandable layer silicates were also tested. The interactions detected by UV-vis spectroscopy show no reaction between R6G and non-expandable minerals (kaolinite, mica), and intense reactions forming H-aggregates and monomers with smectites and illite-smectites. The intensity of H-aggregate formation increases with increase in the layer charge of smectites. Mixed-layer illite-smectites interact with R6G more intensely than do smectites. H-aggregate and monomer formation increases with the illitization process for randomly ordered illite-smectites (R = 0) and decreases in the course of illitization for the ordered illite-smectites (R > 0)

Preparation and infrared spectroscopic characterization of reduced-charge montmorillonite with various Li contents

A series of reduced-charge montmorillonites (RCMs) was prepared from Li-montmorillonite from Jel&scaron;ov&yacute; Polok (Slovakia) by heating at various temperatures (105-210&deg;C) for 24 h. The amount of fixed Li, 0.09-0.67 per O 20 (OH) 4 , increased with increasing temperature, confirming preparation of a set of samples of variable layer charge from the same parent Li-montmorillonite by varying only the preparation temperature. Infrared spectroscopy revealed that Li was trapped in the hexagonal cavities of the tetrahedral sheet at all temperatures. Partial deprotonation of the samples, reflected in the decrease of the intensities of the OH-bending bands, was observed after treatments above 120&deg;C. Analysis of the OH-stretching region showed Li in the previously vacant octahedra in the samples heated above 150&deg;C. Weak inflections near 660 and 720 cm -1 confirmed development of local trioctahedral character of octahedral cations coordinated with OH groups in the sample heated at 210&deg;C. Gradual decrease of the layer charge due to Li fixation led to a shift of the Si-O stretching hand to higher frequencies and to the appearance of new, pyrophyllite-like bands at 1120 and 419 cm -1