Asymptotically matched sheath and presheath in a dense plasma

1998 ◽  
Vol 59 (3) ◽  
pp. 505-536 ◽  
Author(s):  
LINDSEY D. THORNHILL ◽  
PRATEEN V. DESAI
Keyword(s):  
Rapid Change ◽  
Debye Length ◽  
Mean Free Path ◽  
Boundary Region ◽  
Surface Erosion ◽  
Leading Order ◽  
Power Flux ◽  
Temperature Plasma ◽  
Recombination Length ◽  
The Impact

Asymptotically matched solutions for electron and ion density, electron and ion velocity, and electric potential are obtained in the boundary region of a dense low-temperature plasma adjacent to perfectly absorbing walls – walls that absorb, without reflection, incident electrons and ions. Leading-order composite solutions, valid throughout the boundary region, are constructed from solutions in three subdomains distinguished by different physical length scales: the geometric length, the ion mean free path and the Debye length. The composite solutions are used to assess the impact of electron–ion recombination in the ionization nonequilibrium region on sheath and presheath profiles, and on quantities evaluated at the wall. While, at leading order, the velocity profiles throughout the boundary region are not influenced by recombination, the density and potential profiles are significantly altered when recombination is included. These results show that the region of rapid change in these profiles lies closer to the wall when recombination is explicitly included in the model. The influence of recombination on the presheath potential, and consequently the wall potential, is found to scale as the natural logarithm of the recombination length. The broadening of the density profile results in a larger flux of ions accelerating through the sheath and impacting on the wall. The influence of recombination on the ion power flux to the wall is found to scale with the inverse recombination length. This scaling influences the prediction of surface erosion rates in technological applications that utilize these plasmas.

Impurity leakage and radiative cooling in the first nitrogen and neon seeding study in the slot divertor at DIII-D

2021 ◽  
Author(s):  
Livia Casali ◽  
David Eldon ◽  
Adam G McLean ◽  
Tom H Osborne ◽  
Anthony W Leonard ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Mean Free Path ◽  
Flow Reversal ◽  
Momentum Balance ◽  
Ionization Source ◽  
Power Flux ◽  
Impurity Transport ◽  
Plasma Drifts ◽  
High Level ◽  
The Impact

Abstract A comparative study of nitrogen versus neon has been carried out to analyze the impact of the two radiative species on power dissipation, SOL impurity distribution, divertor and pedestal characteristics. The experimental results show that N remains compressed in the divertor, thereby providing high radiative losses without affecting the pedestal profiles and displacing carbon as dominant radiator. Neon, instead, radiates more upstream than N thus reducing the power flux through the separatrix leading to a reduced ELM frequency and compression in the divertor. A significant amount of neon is measured in the plasma core leading to a steeper density gradient. The different behaviour between the two impurities is confirmed by SOLPS-ITER modelling which for the first time at DIII-D includes multiple impurity species and a treatment of full drifts, currents and neutral-neutral collisions. The impurity transport in the SOL is studied in terms of the parallel momentum balance showing that N is mostly retained in the divertor whereas Ne leaks out consistent with its higher ionization potential and longer mean free path. This is also in agreement with the enrichment factor calculations which indicate lower divertor enrichment for neon. The strong ionization source characterizing the SAS divertor causes a reversal of the main ions and impurity flows. The flow reversal together with plasma drifts and the effect of the thermal force contribute significantly in the shift of the impurity stagnation point affecting impurity leakage. This work provides a demonstration of the impurity leakage mechanism in a closed divertor structure and the consequent impact on pedestal. Since carbon is an intrinsic radiator at DIII-D, in this paper we have also demonstrated the different role of carbon in the N vs Ne seeded cases both in the experiments and in the numerical modeling. Carbon contributes more when neon seeding is injected compared to when nitrogen is used. Finally, the results highlight the importance of accompanying experimental studies with numerical modelling of plasma flows, drifts and ionization profile to determine the details of the SOL impurity transport as the latter may vary with changes in divertor regime and geometry. In the cases presented here, plasma drifts and flow reversal caused by high level of closure in the slot upper divertor at DIII-D play an important role in the underlined mechanism.

scholarly journals Music Modulates Cognitive Flexibility? An Investigation of the Benefits of Musical Training on Markers of Cognitive Flexibility

2021 ◽  
Vol 11 (4) ◽  
pp. 451
Author(s):  
Miriam Gade ◽  
Kathrin Schlemmer
Keyword(s):  
Everyday Life ◽  
Cognitive Flexibility ◽  
Musical Training ◽  
Rapid Change ◽  
Task Sequence ◽  
Switch Costs ◽  
Classification Tasks ◽  
Professional Contexts ◽  
The Impact ◽  
Task Sequences

Cognitive flexibility enables the rapid change in goals humans want to attain in everyday life as well as in professional contexts, e.g., as musicians. In the laboratory, cognitive flexibility is usually assessed using the task-switching paradigm. In this paradigm participants are given at least two classification tasks and are asked to switch between them based on valid cues or memorized task sequences. The mechanisms enabling cognitive flexibility are investigated through two empirical markers, namely switch costs and n-2 repetition costs. In this study, we assessed both effects in a pre-instructed task-sequence paradigm. Our aim was to assess the transfer of musical training to non-musical stimuli and tasks. To this end, we collected the data of 49 participants that differed in musical training assessed using the Goldsmiths Musical Sophistication Index. We found switch costs that were not significantly influenced by the degree of musical training. N-2 repetition costs were small for all levels of musical training and not significant. Musical training did not influence performance to a remarkable degree and did not affect markers of mechanisms underlying cognitive flexibility, adding to the discrepancies of findings on the impact of musical training in non-music-specific tasks.

scholarly journals Charged current Drell-Yan production at N3LO

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Claude Duhr ◽  
Falko Dulat ◽  
Bernhard Mistlberger
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Production Cross Section ◽  
Production Cross ◽  
Hadron Collider ◽  
Charge Asymmetry ◽  
Charged Current ◽  
Leading Order ◽  
Neutrino Pair ◽  
The Impact

Abstract We present the production cross section for a lepton-neutrino pair at the Large Hadron Collider computed at next-to-next-to-next-to-leading order (N3LO) in QCD perturbation theory. We compute the partonic coefficient functions of a virtual W± boson at this order. We then use these analytic functions to study the progression of the perturbative series in different observables. In particular, we investigate the impact of the newly obtained corrections on the inclusive production cross section of W± bosons, as well as on the ratios of the production cross sections for W+, W− and/or a virtual photon. Finally, we present N3LO predictions for the charge asymmetry at the LHC.

scholarly journals Mixed NNLO QCD×electroweak corrections of $$ \mathcal{O} $$(Nfαsα) to single-W/Z production at the LHC

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Stefan Dittmaier ◽  
Timo Schmidt ◽  
Jan Schwarz
Keyword(s):  
Z Bosons ◽  
Leading Order ◽  
Current Standard ◽  
Gauge Invariant ◽  
Mass Distributions ◽  
Self Energy ◽  
Electroweak Gauge Boson ◽  
First Results ◽  
Invariant Part ◽  
The Impact

Abstract First results on the radiative corrections of order $$ \mathcal{O} $$ O (Nfαsα) are presented for the off-shell production of W or Z bosons at the LHC, where Nf is the number of fermion flavours. These corrections comprise all diagrams at $$ \mathcal{O} $$ O (αsα) with closed fermion loops, form a gauge-invariant part of the next-to-next-to-leading-order corrections of mixed QCD×electroweak type, and are the ones that concern the issue of mass renormalization of the W and Z resonances. The occurring irreducible two-loop diagrams, which involve only self-energy insertions, are calculated with current standard techniques, and explicit analytical results on the electroweak gauge-boson self-energies at $$ \mathcal{O} $$ O (αsα) are given. Moreover, the generalization of the complex-mass scheme for a gauge-invariant treatment of the W/Z resonances is described for the order $$ \mathcal{O} $$ O (αsα). While the corrections, which are implemented in the Monte Carlo program Rady, are negligible for observables that are dominated by resonant W/Z bosons, they affect invariant-mass distributions at the level of up to 2% for invariant masses of ≳ 500 GeV and are, thus, phenomenologically relevant. The impact on transverse-momentum distributions is similar, taking into account that leading-order predictions to those distributions underestimate the spectrum.

scholarly journals Metallic conduction through van der Waals interfaces in ultrathin $$\hbox{Bi}_2\hbox{Te}_3$$ films

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shinichiro Hatta ◽  
Ko Obayashi ◽  
Hiroshi Okuyama ◽  
Tetsuya Aruga
Keyword(s):  
Photoelectron Spectroscopy ◽  
Van Der Waals ◽  
Vertical Direction ◽  
Conductivity Measurement ◽  
Spatial Separation ◽  
Mean Free Path ◽  
Conduction Path ◽  
Conductivity Increase ◽  
The Impact

AbstractWhile the van der Waals (vdW) interface in layered materials hinders the transport of charge carriers in the vertical direction, it serves a good horizontal conduction path. We have investigated electrical conduction of few quintuple-layer (QL) $$\hbox {Bi}_2\hbox {Te}_3$$ Bi 2 Te 3 films by in situ four-point probe conductivity measurement. The impact of the vdW (Te–Te) interface appeared as a large conductivity increase with increasing thickness from 1 to 2 QL. Angle-resolved photoelectron spectroscopy and first-principles calculations reveal the confinement of bulk-like conduction band (CB) state into the vdW interface. Our analysis based on the Boltzmann equation showed that the conduction of the CB has a long mean free path compared to the surface-state conduction. This is mainly attributed to the spatial separation of the CB electrons and the donor defects located at the Bi sites.

scholarly journals Wetting transition of ionic liquids at metal surfaces: A computational molecular approach to electronic screening using a virtual Thomas-Fermi fluid

2020 ◽  
Author(s):  
Alexander Schlaich ◽  
Dongliang Jin ◽  
Lyderic Bocquet ◽  
Benoit Coasne
Keyword(s):  
Ionic Liquids ◽  
Energy Storage ◽  
Electrostatic Interactions ◽  
Debye Length ◽  
Wetting Transition ◽  
Molecular Fluids ◽  
Thomas Fermi ◽  
Electronic Screening ◽  
Novel Approach ◽  
The Impact

Abstract Of particular relevance to energy storage, electrochemistry and catalysis, ionic and dipolar liquids display a wealth of unexpected fundamental behaviors – in particular in confinement. Beyond now well-documented adsorption, overscreening and crowding effects1,2,3, recent experiments have highlighted novel phenomena such as unconventional screening4 and the impact of the electronic nature – metallic versus insulating – of the confining surface on wetting/phase transitions5,6. Such behaviors, which challenge existing theoretical and numerical modeling frameworks, point to the need for new powerful tools to embrace the properties of confined ionic/dipolar liquids. Here, we introduce a novel atom-scale approach which allows for a versatile description of electronic screening while capturing all molecular aspects inherent to molecular fluids in nanoconfined/interfacial environments. While state of the art molecular simulation strategies only consider perfect metal or insulator surfaces, we build on the Thomas-Fermi formalism for electronic screening to develop an effective approach that allows dealing with any imperfect metal between these asymptotes. The core of our approach is to describe electrostatic interactions within the metal through the behavior of a `virtual' Thomas-Fermi fluid of charged particles, whose Debye length sets the Thomas-Fermi screening length λ in the metal. This easy-to-implement molecular method captures the electrostatic interaction decay upon varying λ from insulator to perfect metal conditions, while describing very accurately the capacitance behavior – and hence the electrochemical properties – of the metallic confining medium. By applying this strategy to a nanoconfined ionic liquid, we demonstrate an unprecedented wetting transition upon switching the confining medium from insulating to metallic. This novel approach provides a powerful framework to predict the unsual behavior of ionic liquids, in particular inside nanoporous metallic structures, with direct applications for energy storage and electrochemistry.

scholarly journals Spontaneous HTLV-1 transcription is accompanied by distinct epigenetic changes in the 5′ and 3′ long terminal repeats

2018 ◽  
Vol 3 ◽  
pp. 105 ◽  
Author(s):  
Michi Miura ◽  
Paola Miyazato ◽  
Yorifumi Satou ◽  
Yuetsu Tanaka ◽  
Charles R.M. Bangham
Keyword(s):  
Histone Modifications ◽  
Insertion Site ◽  
Rapid Change ◽  
Epigenetic Modifications ◽  
The Body ◽  
Ctcf Binding ◽  
Ctcf Binding Site ◽  
Long Terminal Repeats ◽  
Terminal Repeats ◽  
The Impact

Background:The human retrovirus HTLV-1 inserts the viral complementary DNA of 9 kb into the host genome. Both plus- and minus-strands of the provirus are transcribed, respectively from the 5′ and 3′ long terminal repeats (LTR). Plus-strand expression is rapid and intense once activated, whereas the minus-strand is transcribed at a lower, more constant level. To identify how HTLV-1 transcription is regulated, we investigated the epigenetic modifications associated with the onset of spontaneous plus-strand expression and the potential impact of the host factor CTCF.Methods:Patient-derived peripheral blood mononuclear cells (PBMCs) and in vitro HTLV-1-infected T cell clones were examined. Cells were stained for the plus-strand-encoded viral protein Tax, and sorted into Tax+and Tax–populations. Chromatin immunoprecipitation and methylated DNA immunoprecipitation were performed to identify epigenetic modifications in the provirus. Bisulfite-treated DNA fragments from the HTLV-1 LTRs were sequenced. Single-molecule RNA-FISH was performed, targeting HTLV-1 transcripts, for the estimation of transcription kinetics. The CRISPR/Cas9 technique was applied to alter the CTCF-binding site in the provirus, to test the impact of CTCF on the epigenetic modifications.Results:Changes in the histone modifications H3K4me3, H3K9Ac and H3K27Ac were strongly correlated with plus-strand expression. DNA in the body of the provirus was largely methylated except for the pX and 3′ LTR regions, regardless of Tax expression. The plus-strand promoter was hypomethylated when Tax was expressed. Removal of CTCF had no discernible impact on the viral transcription or epigenetic modifications.Conclusions:The histone modifications H3K4me3, H3K9Ac and H3K27Ac are highly dynamic in the HTLV-1 provirus: they show rapid change with the onset of Tax expression, and are reversible. The HTLV-1 provirus has an intrinsic pattern of epigenetic modifications that is independent of both the provirus insertion site and the chromatin architectural protein CTCF which binds to the HTLV-1 provirus.

scholarly journals Re-thinking Public Health Education in Aotearoa New Zealand: Factory Model to Personalized Learning

2021 ◽  
Vol 6 ◽  
Author(s):  
Cath Conn ◽  
Shoba Nayar ◽  
Margaret Hinepo Williams ◽  
Radilaite Cammock
Keyword(s):  
Public Health ◽  
Rapid Change ◽  
Public Health Education ◽  
Personalized Learning ◽  
Project Based Learning ◽  
Public Health Workforce ◽  
Fostering Creativity ◽  
Educational Paradigm ◽  
Societal Expectations ◽  
The Impact

Key drivers of change in the 21st century—pandemic, technology advance, social disparity—are shaping the public health industry, including employment and education. In 2020, COVID-19 brought rapid change to the teaching of public health in higher education. In this reflective essay, we move beyond the delivery of existing curricula shifting from classroom to online, and consider the greater agenda of a transformative educational paradigm. This is broadly conceptualized as a shift from a “factory model education” to one of “personalized learning” with an emphasis on fostering creativity and heutagogical (student-driven) models, underpinned by technology, and real world application involving problem and project-based learning in a changing industry. Such change has stemmed both from the impact of COVID-19 on the education system, and in response to a more momentous transformation in public health careers and societal expectations of a public health workforce.

scholarly journals Dynamics of Gender-Specific Behaviors in the Digital Educational Environment

2021 ◽  
Vol 15 (24) ◽  
pp. 155-166
Author(s):  
Jeļena Badjanova ◽  
Dzintra Iliško ◽  
Svetlana Ignatjeva ◽  
Margarita Nesterova
Keyword(s):  
Information And Communication Technologies ◽  
Rapid Change ◽  
Female Gender ◽  
Well Being ◽  
Educational Environment ◽  
Digital Learning ◽  
And Gender ◽  
Teachers Professional Development ◽  
The Impact ◽  
Gender Specific

During the social distancing, an increasing number of people use communication applications, various types of digital tools and programs. Various video conferencing platforms are regularly used in the educational environment. The study presents the analyses how intensive is the use of Information and Communication Technologies (ICT) in the educational environment and how it can change cognitive-behavioral gender differences. This is particularly important to pay a special attention to the analysis of gender as a dynamic category, to take into account the processes of gender socialization and transformation of gender identification in the changing social environment. The research methods also included a set of additional methods, such as a focus group on different aspects of gender-specific behavior in the digital learning environment, putting together collages, as well as the method of the unfinished sentence related to the impact of ICT on teachers' professional development and well-being. In the course of the study, it was recognised that the design of social models of male and female gender-specific behaviour includes more than the basic gender identity and gender stability: in today's society, there is a multiplicity of views on the similarities and differences of gender-specific behaviours, and a rapid change in the accepted social guidelines and behavioural patterns is in progress, socio-cultural norms that define the psychological characteristics of women and men, their patterns of behaviour.

scholarly journals Does Prenatal Stress Management Enhance Maternal And Fetal Outcomes?

2016 ◽  
Vol 12 (27) ◽  
pp. 129
Author(s):  
Ghada Mohammad Abu Shosha
Keyword(s):  
Pregnant Women ◽  
Stress Management ◽  
Stress Reduction ◽  
Maternal Stress ◽  
Rapid Change ◽  
Fetal Outcomes ◽  
Reduction Techniques ◽  
Antenatal Stress ◽  
Fetal Organs ◽  
The Impact

Background: Antenatal period is a time of rapid change during which fetal organs are vulnerable to various stressors. Studies have suggested that psychosocial stressors during pregnancy could adversely influence physical and behavioral outcomes of the infant. Aim: This paper aimed to discusses the importance of antenatal stress assessment and management on both mothers' and infants' health status. Method: This review aggregated evidence from various studies that examined the impact of maternal stress management and its outcomes on pregnant women and their infants. Results: Maternal stress is generally associated with unpleasant fetal outcomes. The use of stress reduction techniques was approved to reduce psychological stress in pregnant women. Conclusion: Ongoing assessment of antenatal stress using a standardized process promotes proper stress handling strategy.

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