Interaction of Gd(III) MRI contrast agents with membranes: a review of recent EPR studies

Rational development of new selective paramagnetic contrast agents (PCAs) requires a detailed understanding of their interactions with biological macromolecules. This report shows how some of these interactions can be studied with electron paramagnetic resonance (EPR) through examples of Gd³⁺ complexes interactions with model phospholipid membranes. It is shown that the spin label EPR method can be used to detect: (i) presence and possible location of lipophilic contrast agents in the model membranes, (ii) changes and distortions in membrane organization upon interaction with the PCAs, and (iii) changes in the local polarity of the bilayer and its phase behavior due to addition of Gd³⁺ complexes. This work demonstrates that interaction of Gd³⁺ complexes with phospholipid bilayers can be observed directly from changes in their continuous wave (CW) EPR spectra obtained at frequencies higher than X-band (9.5 GHz), where signals arising from aqueous and lipid-bound Gd³⁺ complexes become resolved. Analysis of frequency dependence of the effectiveg-factors of the EPR signal provides estimates of zero-field splitting (ZFS) parameter for these complexes at physiological conditions and information on how this parameter is affected by interaction with lipids. Multifrequency EPR experiments at high magnetic fields are also useful in providing data on the frequency dispersion of electronic relaxation caused mainly by a modulation of the electron-electron dipolar interaction (ZFS) of these high spin ions.     

Cobalt-Catalyzed Green Cross-Dehydrogenative C(sp<Superscript>2</Superscript>)-H/P-H Coupling Reactions

Joined electrolysis of arenes (benzene or coumarin derivatives) and diethyl-H-phosphonate (EtO)₂P(O)H in the presence of [CoCl₂(bpy)] catalyst (5%) in an ethanol-aqueous solution in reductive conditions allows obtaining the desired products in a single step by aromatic C–H bonds phosphonation with yields up to 70%. The only by-product is hydrogen; the reaction proceeds at room temperature and does not require specially added reducing agents and oxidants or other initiators. Radical mechanism has been confirmed for the catalytic reaction proceeding via bicobalt phosphonates with Co–P bond, the structure of which also has been identified.     

BaO−B2O3 system and its mysterious member Ba3B2O6

The first systematic study of the BaO–B₂O₃ system and barium orthoborate Ba₃B₂O₆ (3BaO·B₂O₃) was reported in 1949. Thereafter, the system was repeatedly refined but the structure of Ba₃B₂O₆ compound has not been adequately studied yet. In our study we have, for the first time, obtained the crystalline samples of Ba₃B₂O₆. The solved structure (Pbam, a = 13.5923(4) Å, b = 13.6702(4) Å, c = 14.8894(3) Å) belongs to the class of ‘anti‐zeolite’ borates with a pseudotetragonal [Ba₁₂(BO₃)₆]⁶⁺ cation pattern which contains channels along the c axis filled with anionic clusters. The Ba₃B₂O₆ compound may be regarded as a fluorine‐free end‐member of the Ba₃(BO₃)_2–xF_3x solid solution. The BaO–B₂O₃ phase diagram presented in our study is based on our research and literature data.     

A regional algorithm for separating light absorption by chlorophyll-a and coloured detrital matter in the Black Sea,using 480–560 nm bands from ocean colour scanners

The aim of this study is to modify the regional algorithm for Moderate Resolution Imaging Spectroradiometer (MODIS) and Medium-spectral Resolution Imaging Spectrometer (MERIS) bands using newly available data of seasonal and spatial variability of light absorption by all optically active components in the Black Sea, and to obtain a merged product based on data retrieved from all the colour scanners that have operated since September 1997. Comparison of chlorophyll-a concentration (chl-a) simulated by the standard National Aeronautics and Space Administration (NASA) algorithm with in situ chl-a measurements showed that the NASA algorithm provided incorrect chl-a assessment of Black Sea shelf and deep-sea waters during spring?summer. Originally the standard NASA algorithm could be applied if there was a high correlation between light absorption by phytoplankton (a_ph) and that by coloured dissolved and suspended organic matter (a_CDM), which is not the case in the Black Sea. Consequently, development of the correct regional chl-a algorithm requires splitting of light absorption into a_ph and a_CDM. This issue has been resolved by the proposed regional algorithm developed for the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) using remote-sensing reflectance in three (as minimum) spectral bands from 480 to 560 nm. Operation of the SeaWiFS and MERIS colour scanners ceased in December 2010 and April 2012, respectively, while the MODIS scanner is still working on the Terra and Aqua satellites. In this research, level 2 data (products of standard atmosphere correction at three bands filtered by masks/flags) of SeaWiFS, MODIS (on Terra and Aqua satellites), and MERIS scanners were retrieved for their mission lifetime. The regional algorithm was validated independently for each scanner, based on the adequacy of the algorithm-derived chl-a and a_CDM to in situ-measured data for the same day. The results suggest a satisfactory accuracy of the modified regional algorithm.     

Distributive mereotopology: extended distributive contact lattices

The notion of contact algebra is one of the main tools in the region based theory of space. It is an extension of Boolean algebra with an additional relation C called contact. The elements of the Boolean algebra are considered as formal representations of spatial regions as analogues of physical bodies and Boolean operations are considered as operations for constructing new regions from given ones and also to define some mereological relations between regions as part-of, overlap and underlap. The contact relation is one of the basic mereotopological relations between regions expressing some topological nature. It is used also to define some other important mereotopological relations like non-tangential inclusion, dual contact, external contact and others. Most of these definitions are given by means of the operation of Boolean complementation. There are, however, some problems related to the motivation of the operation of Boolean complementation. In order to avoid these problems we propose a generalization of the notion of contact algebra by dropping the operation of complement and replacing the Boolean part of the definition by that of a distributive lattice. First steps in this direction were made in (Düntsch et al. Lect. Notes Comput. Sci. 4136, 135–147, 2006, Düntsch et al. J. Log. Algebraic Program. 76, 18–34, 2008) presenting the notion of distributive contact lattice based on the contact relation as the only mereotopological relation. In this paper we consider as non-definable primitives the relations of contact, nontangential inclusion and dual contact, extending considerably the language of distributive contact lattices. Part I of the paper is devoted to a suitable axiomatization of the new language called extended distributive contact lattice (EDC-lattice) by means of universal first-order axioms true in all contact algebras. EDC-lattices may be considered also as an algebraic tool for a certain subarea of mereotopology, called in this paper distributive mereotopology. The main result of Part I of the paper is a representation theorem, stating that each EDC-lattice can be isomorphically embedded into a contact algebra, showing in this way that the presented axiomatization preserves the meaning of mereotopological relations without considering Boolean complementation. Part II of the paper is devoted to topological representation theory of EDC-lattices, transferring into the distributive case important results from the topological representation theory of contact algebras. It is shown that under minor additional assumptions on distributive lattices as extensionality of the definable relations of overlap or underlap one can preserve the good topological interpretations of regions as regular closed or regular open sets in topological space.     

Analyzing multicomponent receptive fields from neural responses to natural stimuli

The challenge of building increasingly better models of neural responses to natural stimuli is to accurately estimate the multiple stimulus features that may jointly affect the neural spike probability. The selectivity for combinations of features is thought to be crucial for achieving classical properties of neural responses such as contrast invariance. The joint search for these multiple stimulus features is difficult because estimating spike probability as a multidimensional function of stimulus projections onto candidate relevant dimensions is subject to the curse of dimensionality. An attractive alternative is to search for relevant dimensions sequentially, as in projection pursuit regression. Here we demonstrate using analytic arguments and simulations of model cells that different types of sequential search strategies exhibit systematic biases when used with natural stimuli. Simulations show that joint optimization is feasible for up to three dimensions with current algorithms. When applied to the responses of V1 neurons to natural scenes, models based on three jointly optimized dimensions had better predictive power in a majority of cases compared to dimensions optimized sequentially, with different sequential methods yielding comparable results. Thus, although the curse of dimensionality remains, at least several relevant dimensions can be estimated by joint information maximization.     

Self‐Assembled Hybrid Materials Based on Organic Nanocrystals and Carbon Nanotubes

Organic crystalline materials are used as dyes/pigments, pharmaceuticals, and active components of photonic and electronic devices. There is great interest in integrating organic crystals with inorganic and carbon nanomaterials to create nanocomposites with enhanced properties. Such efforts are hampered by the difficulties in interfacing organic crystals with dissimilar materials. Here, an approach that employs organic nanocrystallization is presented to fabricate solution‐processed organic nanocrystal/carbon nanotube (ONC/CNT) hybrid materials based on readily available organic dyes (perylene diimides (PDIs)) and carbon nanotubes. The hybrids are prepared by self‐assembly in aqueous media to afford free‐standing films with tunable CNT content. These exhibit excellent conductivities (as high as 5.78 ± 0.56 S m^?1), and high thermal stability that are superior to common polymer/CNT hybrids. The color of the hybrids can be tuned by adding various PDI derivatives. ONC/CNT hybrids represent a novel class of nanocomposites, applicable as optoelectronic and conductive colorant materials.     

ACE2 Is an Adjacent Element of Atherosclerosis and COVID-19 Pathogenesis

COVID-19 is a highly contagious new infection caused by the single-stranded RNA Sars-CoV-2 virus. For the first time, this infection was recorded in December 2019 in the Chinese province of Wuhan. The virus presumably crossed the interspecies barrier and passed to humans from a bat. Initially, the disease was considered exclusively in the context of damage to the respiratory system, but it quickly became clear that the disease also entails serious consequences from various systems, including the cardiovascular system. Among these consequences are myocarditis, myocardial damage, subsequent heart failure, myocardial infarction, and Takotsubo syndrome. On the other hand, clinical data indicate that the presence of chronic diseases in a patient aggravates the course and outcome of coronavirus infection. In this context, the relationship between COVID-19 and atherosclerosis, a condition preceding cardiovascular disease and other disorders of the heart and blood vessels, is particularly interesting. The renin-angiotensin system is essential for the pathogenesis of both coronavirus disease and atherosclerosis. In particular, it has been shown that ACE2, an angiotensin-converting enzyme 2, plays a key role in Sars-CoV-2 infection due to its receptor activity. It is noteworthy that this enzyme is important for the normal functioning of the cardiovascular system. Disruptions in its production and functioning can lead to various disorders, including atherosclerosis.     

Thermal analysis of new ITER FW and divertor design during VDE energy deposition

Further developments and investigations in the area of fusion energy devices require extensive and comprehensive computer simulations with great precision to evaluate reactor components behavior during normal and transient events. In this work we performed detailed study of the first wall (FW) subjected to high heat flux during a vertical displacement event (VDE) with various initial steady-state conditions and heat flux histories for the transient plasma energy deposition. We calculated the spatial temperature profile through out the entire module and the maximum surface temperature, as well as melting and vaporization thickness of Be surface during VDE and just before thermal quench (TQ). We further studied possible potential damage to plasma facing components (PFC) and structural materials for VDEs with higher energy loads than currently estimated.