Dehydration and ionic conductance quantization in nanopores

There has been tremendous experimental progress in the last decade in identifying the structure and function of biological pores (ion channels) and fabricating synthetic pores. Despite this progress, many questions still remain about the mechanisms and universal features of ionic transport in these systems. In this paper, we examine the use of nanopores to probe ion transport and to construct functional nanoscale devices. Specifically, we focus on the newly predicted phenomenon of quantized ionic conductance in nanopores as a function of the effective pore radius - a prediction that yields a particularly transparent way to probe the contribution of dehydration to ionic transport. We study the role of ionic species in the formation of hydration layers inside and outside of pores. We find that the ion type plays only a minor role in the radial positions of the predicted steps in the ion conductance. However, ions with higher valency form stronger hydration shells, and thus, provide even more pronounced, and therefore, more easily detected, drops in the ionic current. Measuring this phenomenon directly, or from the resulting noise, with synthetic nanopores would provide evidence of the deviation from macroscopic (continuum) dielectric behavior due to microscopic features at the nanoscale and may shed light on the behavior of ions in more complex biological channels.Comment: 13 pages, 10 figure

Study of Organic Self-Assembled Nanosystems by Means of High-Frequency ESR/ENDOR: The Case of Oil Asphaltenes

© 2018, Pleiades Publishing, Ltd. An approach to investigate self-assembly of oil disperse systems based on high-field electron nuclear double resonance has been suggested. As exemplified by asphaltenes, the oil components most prone to self-assembly, the formation of planar rather than multilayer structures has been directly evidenced experimentally. The suggested method can be applied to elucidate the self-assembly mechanism in wide range of organic objects

In Situ Identification of Various Structural Features of Vanadyl Porphyrins in Crude Oil by High-Field (3.4 T) Electron-Nuclear Double Resonance Spectroscopy Combined with Density Functional Theory Calculations

© 2017 American Chemical Society.Structural characterization of metalloporphyrins in complex systems, such as native hydrocarbons, has been the focus of scientific and industrial interests for many years. We describe electron-nuclear double resonance (ENDOR) of crude oil from the well without any additional sample treatment (i.e., in the native environment) in the magnetic field of about 3.4 T and temperature of 50 K by applying microwave pulses at 94 GHz (W band) and radio frequency pulses at near the proton Larmor frequencies of 144 MHz to probe the paramagnetic vanadyls. By means of density functional theory calculations, ENDOR features are explained and ascribed to certain vanadyl porhyrin structural forms known to be present in crude oil

«Analog» and «Digital» Generation of Media Audience: the Basic Behavioral Characteristics

В исследовании выявлены и описаны поведенческие характеристики «аналогового» и «цифрового» поколения аудитории СМИ. К «аналоговому» отнесены 3 поколения: «оттепели», «строителей»/«застоя», «странников» (согласно теории поколений Н. Хоува и В. Штрауса, концепции поколений Ю. Левады). К цифровому отнесены поколения Y и Z (по Хоуву и Штраусу, Е. Шамис и А. Антипову). «Аналоговое» поколение интересуется общественно-политической обстановкой, обращается чаще других к первично аналоговым СМИ (радио, телевидение) и печати, при этом ценит качество содержания больше, чем звука и «картинки». «Цифровое» поколение – аудитория «экономики впечатлений», предпочитают мобильное потребление коротких медиатекстов в мультимедийных форматах, контент «рассматривают», ценят качество изображения и звука больше, чем содержание.The study identified and described the behavioral characteristics of the «analog» and «digital» generations of media audiences. 3 generations are attributed to the «analog»: «thaws», «builders» / «stagnation», «wanderers» (according to the theory of the generations of N. How and W. Strauss, the concept of the generations of Y. Levada). Generations Y and Z (according to How and Strauss, E. Shamis and A. Antipov) are referred as «digital». The «analog» generation is interested in the socio-political situation, appeals more often than others to the primary analog media (radio, television) and the press, while appreciating the quality of the content more than the sound and the «picture». The «digital» generation – audience of the «economy of impressions» prefers mobile consumption of short media texts in multimedia formats, content is «viewed», they value image and sound quality more than content.Исследование проведено при поддержке РНФ (грант №19-18-00264)

ENDOR study of nitrogen hyperfine and quadrupole tensors in vanadyl porphyrins of heavy crude oil

© Kazan Federal University (KFU).We report the observation of pulsed electron-nuclear double resonance (ENDOR) spectrum caused by interactions of the nitrogen nuclei14N with the unpaired electron of the paramagnetic vanadyl complexes VO2+ of vanadyl porphyrins in natural crude oil. We provide detailed experimental and theoretical characterization of the nitrogen hyperfine and quadrupole tensors

Toward the Asphaltene Structure by Electron Paramagnetic Resonance Relaxation Studies at High Fields (3.4 T)

© 2016 American Chemical Society.A series of 12 asphaltene samples extracted from heavy oils and the oxidized bitumen of different origin has been studied with high-frequency W-band (94 GHz) pulsed electron paramagnetic resonance (EPR) spectroscopy. Transverse (T2e) and longitudinal (T1e) relaxation times of the free radical (FR) and the vanadyl porphyrin (VO2+) were measured for each sample. A significant contribution of the spectral diffusion to T2e has been revealed and ascribed to the dipole-dipole interaction between the FR and VO2+. This indicates that the distance between the FR and VO2+ does not exceed a few nanometers, which means, in turn, that VO2+ can participate in construction of the asphaltene aggregates via the intermolecular interactions

Ischemic Changes in the Mucous Membrane of the Transverse Colon as a Complication of Acute Pancreatitis

Aim: to present a clinical case of a patient with a complicated course of acute pancreatitis.Key points. A 31-year-old patient was admitted to the surgical department with a clinical picture of acute alcoholic pancreatitis. Signs of anemia were regarded as a consequence of gastrointestinal bleeding. Computed tomography with contrast enhancement, along with an increase in the size of the pancreas, the presence of foci of pancreatic necrosis with multiple fluid accumulations in the parapancreatic space, revealed smoothed gaustration and thickening of the walls of the predominantly transverse colon. During colonoscopy, ischemic changes of the colon mucosa were detected in a timely manner. Negative results of analysis for toxins A and B of Clostridioides difficile and pathogenic intestinal flora were obtained. By the means of intensive care, it was possible to achieve complete stabilization of the patient's condition, normalization of laboratory blood parameters and relief of ischemic processes in the colon wall.Conclusion. Ischemic changes of the colon can serve as a complication of acute pancreatitis. A thorough analysis of the results of computed tomography at the first signs of colon lesion and colonoscopy contributed to the rapid detection of complications and prevention of irreversible colon ischemia

Experimental manifestations of the Nb^{4+}-O^{-} polaronic excitons in KTa_{0.988}Nb_{0.012}O_{3}

The formation of the photo-polaronic excitons in ABO_{3} perovskite type oxides has been detected experimentally by means of the photoinduced electron paramagnetic resonance studies of KTa_{0.998}Nb_{0.012}O_{3} crystals. The corresponding microwave X-band spectrum at T < 10 K consists of a narrow, nearly isotropic signal located at g ~ 2 and a strongly anisotropic component. The first signal, which has a rich structure due to hyperfine interactions with the lattice nuclei, is attributed to the single trapped charge carriers: the electrons and/or the holes. The anisotropic spectrum is caused by the axial centers oriented along the C_{4} pseudo-cubic principal crystalline axes. The spectrum angular dependence can be described well by an axial center with S = 1, g_{\parallel) = 0.82, g_{\perp} = 0.52 and D = 0.44 cm^{-1}. The anisotropic spectrum is attributed to the Nb^{4+}-O^{-} polaronic excitons. The temperature dependence of the anisotropic component is characterized by two activation energies: the internal dynamics activation E_{a1} = 3.7\pm0.5 meV, which makes the EPR spectrum unobservable above 10 K, and the destruction energy E_{a2} = 52\pm4 meV. By comparing the anisotropic photo-EPR spectrum and the photoinduced optical absorption temperature dependencies, we found that the Nb^{4+}-O^{-} polaronic excitons also manifested themselves via the ~0.7 eV wide absorption band arising under UV light excitation in the weakly concentrated KTaO_{3}:Nb crystals.Comment: PDF, 15 pages, 6 figures (submitted to Physical review B

The general fault in our fault lines

Pervading global narratives suggest that political polarization is increasing, yet the accuracy of such group meta-perceptions has been drawn into question. A recent US study suggests that these beliefs are inaccurate and drive polarized beliefs about out-groups. However, it also found that informing people of inaccuracies reduces those negative beliefs. In this work, we explore whether these results generalize to other countries. To achieve this, we replicate two of the original experiments with 10,207 participants across 26 countries. We focus on local group divisions, which we refer to as fault lines. We find broad generalizability for both inaccurate meta-perceptions and reduced negative motive attribution through a simple disclosure intervention. We conclude that inaccurate and negative group meta-perceptions are exhibited in myriad contexts and that informing individuals of their misperceptions can yield positive benefits for intergroup relations. Such generalizability highlights a robust phenomenon with implications for political discourse worldwide