scholarly journals Positronium Confined in Nanocavities: The Role of Electron Exchange Correlations

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2350
Author(s):  
Fabrizio Castelli ◽  
Giovanni Consolati ◽  
Giacomo Tanzi Marlotti
Keyword(s):  
Experimental Data ◽  
Electron Density ◽  
General Relation ◽  
Electron Exchange ◽  
Cavity Surface ◽  
Cavity Size ◽  
Cavity Radius ◽  
Geometrical Characteristics ◽  
Reliable Interpretation

Positronium atoms (Ps) are commonly employed as a probe to characterize nanometric or subnanometric voids or vacancies in nonmetallic materials, where Ps can end up confined. The annihilation lifetime of a trapped Ps is strongly modified by pickoff and depends on the cavity size and on the electron density in the confining cavity surface. Here, we develop a theory of the Ps annihilation in nanocavities based on the fundamental role of the exchange correlations between the Ps-electron and the outer electrons, which are not usually considered but must be considered to correctly theorize the pickoff annihilation processes. We obtain an important relation connecting the two relevant annihilation rates (for the p-Psand the o-Ps) with the electron density, which has the property of being totally independent of the geometrical characteristics of the nanoporous medium. This general relation can be used to gather information on the electron density and on the average cavity radius of the confining medium, starting from the experimental data on PALS annihilation spectra. Moreover, by analyzing our results, we also highlight that a reliable interpretation of the PALS spectra can only be obtained if the rule of 1/3 between the intensities of p-Psand o-Pslifetimes can be fulfilled.

РОЛЬ ФИЗИЧЕСКОЙ РАЗМИНКИ В ПОДГОТОВКЕ К ТРЕНИРОВОЧНЫМ ЗАНЯТИЯМ И СОРЕВНОВАНИЯМ ШАХМАТИСТОВ БГУ

2019 ◽  
pp. 63-65
Author(s):  
Судоргин Е.П. ◽  
Карсакова И.Н.
Keyword(s):  
Experimental Data ◽  
Sport Performance ◽  
Warm Up ◽  
Physical Exercises ◽  
Methods Of Evaluation ◽  
Mental Fitness ◽  
Physical Preparation ◽  
Tools And Methods

Аннотация: О роли разминки перед тренировкой и соревнованиями написано много научных статьей и диссертаций. Ещё больше о значимости физической подготовки спортсменов, в том числе и шахматистов. В то же время авторы считают, что вопросу физической подготовки шахматистов и в частности разминке в научной и научно-методической литературе уделяется недостаточно внимания. В своей статье авторы приводят собственные экспериментальные данные о влиянии физических упражнений (разминки) на умственную работоспособность студентов-шахматистов БГУ и как следствие на спортивные результаты команды. Ключевые слова: Шахматы, разминка, умственная работоспособность, средства и методы разминки, методы оценки результатов. Аннотация: Машыгуунун жана мелдештердин алдында даярдоонун ролу жөнүндө көптөгөн илимий макала жана диссертация жазылган. Ошондой эле илимий жана илимий-методикалык адабияттарда шахматка даярдоого көп көңүл бурулбай жатат. Макаланын авторлору шахмат ойногон студенттерге физикалык көнүгүүлөрдүн тийгизген таасири жөнүндө өздөрүнүн эксперименталдык маалыматтарын көргөзүштү. Түйүндүү сөздөр: Шахмат, акыл-дарамет, курулуштар жана ыкмалар, баа берүү жыйынтыгы боюнча кабыл алынат. Abstract: on the role of warm-up before training and competitions written many scientific articles and theses. More about the significance of the physical preparation of athletes, including players. At the same time, the authors believe that the issue of fit- ness players and in particular workout in scientific and scientific-methodical literature neglected. In his article the authors cite their own experimental data on the influence of physical exercises (warm-up) on the mental fitness of students-BSU players and as a result the sport performance team. Keywords: chess, warm-up, mental fitness, workout tools and methods, methods of evaluation results.

scholarly journals Oxidation of Terpenoids to Achieve High-Value Flavor and Fragrances—Questioning Microalgae Oxidative Capabilities in the Biotransformation of the Sesquiterpene Valencene and of Selected Natural Apocarotenoids

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 821-830
Author(s):  
Davide De Simeis ◽  
Stefano Serra ◽  
Alessandro Di Fonzo ◽  
Francesco Secundo
Keyword(s):  
Experimental Data ◽  
Natural Products ◽  
Aqueous Medium ◽  
Photochemical Reaction ◽  
Substrate Oxidation ◽  
Market Size ◽  
Chlorella Sp ◽  
General Opinion ◽  
Natural Way

Natural flavor and fragrance market size is expected to grow steadily due to the rising consumer demand of natural ingredients. This market request is guided by the general opinion that the production of natural compounds leads to a reduction of pollution, with inherent advantages for the environment and people’s health. The biotransformation reactions have gained high relevance in the production of natural products. In this context, few pieces of research have described the role of microalgae in the oxidation of terpenoids. In this present study, we questioned the role of microalgal based oxidation in the synthesis of high-value flavors and fragrances. This study investigated the role of three different microalgae strains, Chlorella sp. (211.8b and 211.8p) and Chlorococcum sp. (JB3), in the oxidation of different terpenoid substrates: α-ionone, β-ionone, theaspirane and valencene. Unfortunately, the experimental data showed that the microalgal strains used are not responsible for the substrate oxidation. In fact, our experiments demonstrate that the transformation of the four starting compounds is a photochemical reaction that involves the oxygen as oxidant. Even though these findings cast a shadow on the use of these microorganisms for an industrial purpose, they open a new possible strategy to easily obtain nootkatone in a natural way by just using an aqueous medium, oxygen and light.

Unusually high electron density in an intermolecular non-bonding region: Role of metal substrate

2017 ◽  
Vol 28 (4) ◽  
pp. 759-764 ◽  
Author(s):  
Chen-Guang Wang ◽  
Zhi-Hai Cheng ◽  
Xiao-Hui Qiu ◽  
Wei Ji
Keyword(s):  
Electron Density ◽  
Metal Substrate ◽  
High Electron ◽  
High Electron Density

Explanation of the Influence of Inflow Air Content on the Lift of Cavitating Hydrofoils

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Lift Coefficient ◽  
Cavity Surface ◽  
Air Bubbles ◽  
Incoming Flow ◽  
Fluid Density ◽  
Air Content ◽  
Theoretical Results ◽  
Good Agreement

According to several known experiments, an increase of the incoming flow air content can increase the hydrofoil lift coefficient. The presented theoretical study shows that such increase is associated with the decrease of the fluid density at the cavity surface. This decrease is caused by entrainment of air bubbles to the cavity from the surrounding flow. The theoretical results based on such explanation are in a good agreement with the earlier published experimental data for NACA0015.

scholarly journals Elucidating the Complex Interactions between Stress and Epileptogenic Pathways

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Aaron R. Friedman ◽  
Luisa P. Cacheaux ◽  
Sebastian Ivens ◽  
Daniela Kaufer
Keyword(s):  
Experimental Data ◽  
Blood Brain Barrier ◽  
Inflammatory Cytokine ◽  
Stress Hormones ◽  
Brain Barrier ◽  
Barrier Dysfunction ◽  
Complex Interactions ◽  
Narrow Focus ◽  
Analytical Tools

Clinical and experimental data suggest that stress contributes to the pathology of epilepsy. We review mechanisms by which stress, primarily via stress hormones, may exacerbate epilepsy, focusing on the intersection between stress-induced pathways and the progression of pathological events that occur before, during, and after the onset of epileptogenesis. In addition to this temporal nuance, we discuss other complexities in stress-epilepsy interactions, including the role of blood-brain barrier dysfunction, neuron-glia interactions, and inflammatory/cytokine pathways that may be protective or damaging depending on context. We advocate the use of global analytical tools, such as microarray, in support of a shift away from a narrow focus on seizures and towards profiling the complex, early process of epileptogenesis, in which multiple pathways may interact to dictate the ultimate onset of chronic, recurring seizures.

scholarly journals Examining the role of flare-driven D-region electron density enhancement on Doppler Flash

2020 ◽  
Author(s):  
Shibaji Chakraborty ◽  
Liying Qian ◽  
J. Michael Ruohoniemi ◽  
Joseph Baker ◽  
Joseph McInerney
Keyword(s):  
Electron Density ◽  
Density Enhancement ◽  
D Region

scholarly journals Permeability of Sand-Clay Mixtures

2010 ◽  
Vol 56 (4) ◽  
pp. 299-320 ◽  
Author(s):  
G. Kacprzak ◽  
C. Boutin ◽  
T. Doanh
Keyword(s):  
Experimental Data ◽  
Actual State ◽  
Load Step ◽  
Qualitative And Quantitative ◽  
Experimental Data Point ◽  
Saturated Clay ◽  
Simplifying Assumptions ◽  
Data Point ◽  
Homogenization Methods

Abstract This study deals with the behavior of composite blends constituted of rigid and impervious grains included in saturated clay paste of kaolin, considered as permeable and deformable. Permeability tests performed during standard oedometr tests (before each load step) highlight the key role of the original and actual state of the clay paste, and show the existence of a threshold of sand grain concentration above which a structuring effect influences its permeability. In the light of these experiments some usual homogenization methods (with simplifying assumptions to make the problem manageable) are considered in order to model the mixture permeability. Qualitative and quantitative comparisons with experimental data point out their respective domain of interest and limitations of such approaches

scholarly journals ANALYSIS OF THE CURRENT STATE OF RESEARCHES OF THE DEPOSITION OF ASPHALT-RESINOUS SUBSTANCES, PARAFFIN, AND MODELING METHODS. REVIEW PART II: WAX DEPOSITION

2021 ◽  
pp. 13-23
Author(s):  
M.R. Manafov ◽  
◽  
G.S. Aliyev ◽  
A.I. Rustamova ◽  
V.I. Kerimli ◽  
...  
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Deposition Process ◽  
Real Field ◽  
Wax Deposition ◽  
Scaling Effect ◽  
Modeling Methods ◽  
Current State ◽  
Simulation Results ◽  
Reliable Interpretation

The mechanism of paraffin formation in transport pipes is briefly discussed. A kinetic model of the formation and wax deposition from oil is proposed. Comparison of the model with the available experimental data gave satisfactory results. The review considers software tools for modeling the wax deposition process. It is noted that the simulation results are not always applicable to real field cases. For a more reliable interpretation, the scaling effect must be taken into account. In the work various technologies for wax removal are considered

scholarly journals A Model for Predicting Cation Selectivity and Permeability in AMPA and NMDA Receptors Based on Receptor Subunit Composition

2021 ◽  
Vol 13 ◽  
Author(s):  
Sampath Kumar ◽  
Sanjay S. Kumar
Keyword(s):  
Experimental Data ◽  
Divalent Cations ◽  
Ion Selectivity ◽  
Gene Families ◽  
Subunit Composition ◽  
Receptor Subunit ◽  
Cation Selectivity ◽  
Subunit Stoichiometry ◽  
Ampa And Nmda Receptors

Glutamatergic AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and NMDA (N-methyl-D-aspartate) receptors are implicated in diverse functions ranging from synaptic plasticity to cell death. They are heterotetrameric proteins whose subunits are derived from multiple distinct gene families. The subunit composition of these receptors determines their permeability to monovalent and/or divalent cations, but it is not entirely clear how this selectivity arises in native and recombinantly-expressed receptor populations. By analyzing the sequence of amino acids lining the selectivity filters within the pore forming membrane helices (M2) of these subunits and by correlating subunit stoichiometry of these receptors with their ability to permeate Na+ and/or Ca2+, we propose here a mathematical model for predicting cation selectivity and permeability in these receptors. The model proposed is based on principles of charge attractivity and charge neutralization within the pore forming region of these receptors; it accurately predicts and reconciles experimental data across various platforms including Ca2+ permeability of GluA2-lacking AMPARs and ion selectivity within GluN3-containing di- and tri-heteromeric NMDARs. Additionally, the model provides insights into biophysical mechanisms regulating cation selectivity and permeability of these receptors and the role of various subunits in these processes.

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