scholarly journals The role of acoustics in flame/vortex interactions

1993 ◽  
Vol 254 ◽  
pp. 579-603 ◽  
Author(s):  
T. L. Jackson ◽  
Michéle G. Macaraeg ◽  
M. Y. Hussaini
Keyword(s):  
Initial Temperature ◽  
Pressure Field ◽  
Ignition Time ◽  
Flame Structure ◽  
Time Varying ◽  
Vortex Interactions ◽  
Main Emphasis ◽  
One Step ◽  
And Diffusion

The role of acoustics in flame/vortex interactions is examined via asymptotic analysis and numerical simulation. The model consists of a one-step, irreversible Arrhenius reaction between initially unmixed species occupying adjacent half-planes which are allowed to mix and react by convection and diffusion in the presence of an acoustic field or a time-varying pressure field of small amplitude. The main emphasis is on the influence of the acoustics on the ignition time and flame structure as a function of vortex Reynolds number and initial temperature differences of the reactants.

Mechanisms of ATP to cAMP Conversion Catalyzed by the Mammalian Adenylyl Cyclase: A Role of Magnesium Coordination Shells and Proton Wires

2019 ◽  
Author(s):  
Bella Grigorenko ◽  
Igor Polyakov ◽  
Alexander Nemukhin
Keyword(s):  
Adenylyl Cyclase ◽  
Bond Cleavage ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Md Simulations ◽  
Coordination Shell ◽  
Energy Profile ◽  
One Step ◽  
Type V

<p>We report a mechanism of adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP) conversion by the mammalian type V adenylyl cyclase revealed in molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) simulations. We characterize a set of computationally derived enzyme-substrate (ES) structures showing an important role of coordination shells of magnesium ions in the solvent accessible active site. Several stable six-fold coordination shells of Mg<sub>A</sub><sup>2+ </sup>are observed in MD simulations of ES complexes. In the lowest energy ES conformation, the coordination shell of Mg<sub>A</sub><sup>2+ </sup>does not include the O<sub>δ1</sub> atom of the conserved Asp440 residue. Starting from this conformation, a one-step reaction mechanism is characterized which includes proton transfer from the ribose O<sup>3'</sup>H<sup>3' </sup>group in ATP to Asp440 via a shuttling water molecule and P<sup>A</sup>-O<sup>3A</sup> bond cleavage and O<sup>3'</sup>-P<sup>A</sup> bond formation. The energy profile of this route is consistent with the observed reaction kinetics. In a higher energy ES conformation, Mg<sub>A</sub><sup>2+</sup> is bound to the O<sub>δ1</sub>(Asp440) atom as suggested in the relevant crystal structure of the protein with a substrate analog. The computed energy profile initiated by this ES is characterized by higher energy expenses to complete the reaction. Consistently with experimental data, we show that the Asp440Ala mutant of the enzyme should exhibit a reduced but retained activity. All considered reaction pathways include proton wires from the O<sup>3'</sup>H<sup>3' </sup>group via shuttling water molecules. </p>

Август и Агриппа: развитие системы соправления с 29 по 18 г. до н. э.

2017 ◽  
pp. 126-169
Author(s):  
S.E. Tariverdieva
Keyword(s):  
Political Life ◽  
The Political ◽  
State Administration ◽  
Inheritance System ◽  
The Future ◽  
One Step ◽  
Formal Equality ◽  
Different Parts

The article deals with the development of the coregency system of Augustus and Agrippa from 29 to 18 BC: from formal and actual disparity of the coregents to their formal equality with the dominance of the princeps auctoritas. Particular attention is paid to the earlier stages of this development and to the crisis of 23 BC. The coregency system created by Augustus is often regarded by modern historians as means of ensuring uninterrupted succession of power. Agrippa as his coregent often is thought to have assumed the role of the regent who temporally replaces the princeps, just as it was in formal monarchies, or that of the tutor of the future rulers. However, the Roman system of state administration did not allow such type of regency. The princeps coregent, who was his equal in formal credentials but his inferior in terms of auctoritas, in case of the princeps death had to become the next princeps as his immediate successor. It is unlikely that later he was expected to voluntarily give up his power in favour of younger heir and to vanish from the political life altogether. The inheritance system under Augustus was like a ladder with the princeps at the top, the coregent who was also the immediate successor one step below, heirs of the next degree further down. In case of death of one of them, successors shifted one step up. The coregency had one more function: geographically it allowed Augustus and Agrippa to rule jointly the empire while staying in different parts of it.В статье исследуется развитие системы соправления Августа и Агриппы с 29 по 12 гг. до н. э.: от формального и фактического неравенства соправителей до их формального равенства при преобладании auctoritas принцепса, причём особое внимание уделяется раннему этапу этого развития и кризису 23 г. до н. э. Институт соправления, созданный Августом, часто рассматривается, как средство обеспечения бесперебойного перехода власти, причем Агриппе, как соправителю, НЕРЕДКО отводится роль регента, временно замещающего принцепса или воспитателя будущих правителей. Однако римская система государственного управления не предполагала регентства. Соправитель принцепса, равный ему по формальным полномочиям, но уступавший по auctoritas, в случае его смерти должен был СТАТЬ следующим принцепсом, ближайшим его наследником. Вряд ли предполагалось, что в будущем он должен добровольно уступить власть более молодому наследнику и исчезнуть из политической жизни. Система наследования при Августе представляла собой нечто вроде лестницы, на вершине которой стоял принцепс, на следующей ступени соправитель, он же избранный преемник, ниже наследники следующей очереди в случае смерти когото из них происходило продвижение наследников по ступеням вверх. Кроме того, соправление имело и иное значение позволяло Августу и Агриппе совместно управлять империей, находясь в разных ее частях.

Effect of cluster-gradient architecture of nanostructured topocomposites on features of tribointeraction with heterophased material

2020 ◽  
pp. 130-135
Author(s):  
D.N. Korotaev ◽  
K.N. Poleshchenko ◽  
E.N. Eremin ◽  
E.E. Tarasov
Keyword(s):  
Wear Resistance ◽  
Titanium Alloy ◽  
Energy Dissipation ◽  
Phase Structure ◽  
Diffusion Processes ◽  
Structural Phase ◽  
High Wear Resistance ◽  
Wear Characteristics ◽  
And Diffusion

The wear resistance and wear characteristics of cluster-gradient architecture (CGA) nanostructured topocomposites are studied. The specifics of tribocontact interaction under microcutting conditions is considered. The reasons for retention of high wear resistance of this class of nanostructured topocomposites are studied. The mechanisms of energy dissipation from the tribocontact zone, due to the nanogeometry and the structural-phase structure of CGA topocomposites are analyzed. The role of triboactivated deformation and diffusion processes in providing increased wear resistance of carbide-based topocomposites is shown. They are tested under the conditions of blade processing of heat-resistant titanium alloy.

scholarly journals Collective or Individual? What Types of Tourism Reduce Economic Inequality in Peripheral Regions?

2021 ◽  
Vol 13 (9) ◽  
pp. 4898
Author(s):  
Andrzej Tucki ◽  
Korneliusz Pylak
Keyword(s):  
Peripheral Region ◽  
Time Varying ◽  
Tourism Impacts ◽  
Economic Distress ◽  
Regional Inequalities ◽  
Local Agriculture ◽  
Northeastern Poland ◽  
Per Capita ◽  
The Impact

Regional inequalities are a major concern for governments and policymakers. There is no doubt that tourism impacts the reduction of inequalities, but this impact is not entirely clear. We consider this ambiguity to be related to both the level of study and type of accommodation. In the present study, we examine the inequality level measured by the Gini coefficient in 108 municipalities of the peripheral region of northeastern Poland from 2009 to 2018. We employ a directional spillover index to measure the impact of two accommodation types on tax incomes per capita. The empirical results indicate that collective accommodation-based tourism only reduced inequality during the financial crisis, while individual accommodation-based tourism started to reduce inequality from 2014, when Russian sanctions hit local agriculture and businesses. These results indicate that the role of accommodation types is time-varying and evident in measuring economic distress during and after shocks.

scholarly journals Millimeter (MM) wave and microwave frequency radiation produce deeply penetrating effects: the biology and the physics

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Martin L. Pall
Keyword(s):  
Magnetic Fields ◽  
Electric Fields ◽  
Cardiac Activity ◽  
Maximum Level ◽  
Voltage Sensor ◽  
The Body ◽  
Time Varying ◽  
The Brain ◽  
Mm Waves

Abstract Millimeter wave (MM-wave) electromagnetic fields (EMFs) are predicted to not produce penetrating effects in the body. The electric but not magnetic part of MM-EMFs are almost completely absorbed within the outer 1 mm of the body. Rodents are reported to have penetrating MM-wave impacts on the brain, the myocardium, liver, kidney and bone marrow. MM-waves produce electromagnetic sensitivity-like changes in rodent, frog and skate tissues. In humans, MM-waves have penetrating effects including impacts on the brain, producing EEG changes and other neurological/neuropsychiatric changes, increases in apparent electromagnetic hypersensitivity and produce changes on ulcers and cardiac activity. This review focuses on several issues required to understand penetrating effects of MM-waves and microwaves: 1. Electronically generated EMFs are coherent, producing much higher electrical and magnetic forces then do natural incoherent EMFs. 2. The fixed relationship between electrical and magnetic fields found in EMFs in a vacuum or highly permeable medium such as air, predicted by Maxwell’s equations, breaks down in other materials. Specifically, MM-wave electrical fields are almost completely absorbed in the outer 1 mm of the body due to the high dielectric constant of biological aqueous phases. However, the magnetic fields are very highly penetrating. 3. Time-varying magnetic fields have central roles in producing highly penetrating effects. The primary mechanism of EMF action is voltage-gated calcium channel (VGCC) activation with the EMFs acting via their forces on the voltage sensor, rather than by depolarization of the plasma membrane. Two distinct mechanisms, an indirect and a direct mechanism, are consistent with and predicted by the physics, to explain penetrating MM-wave VGCC activation via the voltage sensor. Time-varying coherent magnetic fields, as predicted by the Maxwell–Faraday version of Faraday’s law of induction, can put forces on ions dissolved in aqueous phases deep within the body, regenerating coherent electric fields which activate the VGCC voltage sensor. In addition, time-varying magnetic fields can directly put forces on the 20 charges in the VGCC voltage sensor. There are three very important findings here which are rarely recognized in the EMF scientific literature: coherence of electronically generated EMFs; the key role of time-varying magnetic fields in generating highly penetrating effects; the key role of both modulating and pure EMF pulses in greatly increasing very short term high level time-variation of magnetic and electric fields. It is probable that genuine safety guidelines must keep nanosecond timescale-variation of coherent electric and magnetic fields below some maximum level in order to produce genuine safety. These findings have important implications with regard to 5G radiation.

On the Role of Charged Defect States and Deep Traps in the Photocarrier Drift and Diffusion in a-Si:H

2000 ◽  
Vol 609 ◽  
Author(s):  
Paul Stradins ◽  
Akihisa Matsuda
Keyword(s):  
Particle Number ◽  
Defect States ◽  
Total Electron ◽  
Minority Carrier Diffusion Length ◽  
Continuity Equations ◽  
Effective Mobility ◽  
Almost All ◽  
Charged Defects ◽  
And Diffusion

ABSTRACTThe drift and diffusion in the presence of charged defects and photocarriers trapped in the tail states is re-examined. In continuity equations, diffusive and drift currents are related to free particles while the Poisson equation includes all charges. In order to make use of ambipolar diffusion approximation, the mobilities and diffusion coefficients should be attributed to the total electron and hole populations making them strongly particle-number dependent. Due to the asymmetry of the conduction and valence band tails, almost all trapped electrons reside in negatively charged defects (D−). A simple model of photocarrier traffic via tail and defect states allows to establish the effective mobility values and coefficients in Einstein relations. In a photocarrier grating experiment, grating of D− is counterbalanced by the grating of trapped holes. Nevertheless, electrons remain majority carriers, allowing the measurement of minority carrier diffusion length, but analysis is needed to relate the latter with μτ product.

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