bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of spin orientation in antiferromagnetic NiO by epitaxial strain and spin–flop coupling
Authors: Kozioł-Rachwał A. , Ślęzak M. , Zając M. , Dróżdż P. , Janus W. , Szpytma M. , Nayyef H. , Ślęzak T.
Published: June 2020

A ferromagnet/antiferromagnet (FM/AFM) Fe/NiO bilayer was grown using molecular beam epitaxy on MgO(001) and Cr buffered MgO(001) substrates. X-ray linear dichroism measurements showed a dominating out-of-plane component for the NiO spins in Fe/NiO/MgO and an in-plane spin direction for NiO layers grown on the Cr buffer. Furthermore, systematic studies on the magnetic properties of Fe/NiO grown on the wedge-shaped Cr buffer revealed a continuous strain-induced spin reorientation transition from out-of-plane to in-plane NiO spin directions when the Cr thickness increased from 0 nm to 3.5 nm. The analysis of the in-plane magnetic structure of NiO in Fe/NiO/Cr showed a pronounced uniaxial anisotropy in thin AFM layers. The AFM spins are perpendicular to the Fe spins due to spin–flop interaction. These results demonstrate the feasibility of using strain and coupling with FMs to manipulate spin structures in NiO.
Real Segre cubics, Igusa quartics and Kummer quartics
Authors: Krasnov V. A.
Published: June 2020

We prove some properties of real Segre cubics. In particular, we find the topological types of the real parts of Segre cubics as well as the topological types of the real parts of the complements of the Segre planes. We prove some differential-geometric properties of the real parts of real Segre cubics and Kummer quartics. We study the automorphism groups of real Segre cubics and, in particular, their action on the real parts of these cubics.
Methylation-directed glycosylation of chromatin factors represses retrotransposon promoters
Authors: Boulard Mathieu , Rucli Sofia , Edwards John R. , Bestor Timothy H.
Published: June 2020

The mechanisms by which methylated mammalian promoters are transcriptionally silenced even in the presence of all of the factors required for their expression have long been a major unresolved issue in the field of epigenetics. Repression requires the assembly of a methylation-dependent silencing complex that contains the TRIM28 protein (also known as KAP1 and TIF1β), a scaffolding protein without intrinsic repressive or DNA-binding properties. The identity of the key effector within this complex that represses transcription is unknown. We developed a methylation-sensitized interaction screen which revealed that TRIM28 was complexed with
O-
linked β-
N
-acetylglucosamine transferase (OGT) only in cells that had normal genomic methylation patterns. OGT is the only glycosyltransferase that modifies cytoplasmic and nuclear protein by transfer of
N
-acetylglucosamine (
O
-GlcNAc) to serine and threonine hydroxyls. Whole-genome analysis showed that
O-
glycosylated proteins and TRIM28 were specifically bound to promoters of active retrotransposons and to imprinting control regions, the two major regulatory sequences controlled by DNA methylation. Furthermore, genome-wide loss of DNA methylation caused a loss of
O-
GlcNAc from multiple transcriptional repressor proteins associated with TRIM28. A newly developed Cas9-based editing method for targeted removal of
O-
GlcNAc was directed against retrotransposon promoters. Local chromatin de-GlcNAcylation specifically reactivated the expression of the targeted retrotransposon family without loss of DNA methylation. These data revealed that
O
-linked glycosylation of chromatin factors is essential for the transcriptional repression of methylated retrotransposons.
A selective inference approach for false discovery rate control using multiomics covariates yields insights into disease risk
Authors: Yurko Ronald , G’Sell Max , Roeder Kathryn , Devlin Bernie
Published: June 2020

To correct for a large number of hypothesis tests, most researchers rely on simple multiple testing corrections. Yet, new methodologies of selective inference could potentially improve power while retaining statistical guarantees, especially those that enable exploration of test statistics using auxiliary information (covariates) to weight hypothesis tests for association. We explore one such method, adaptiveP-value thresholding (AdaPT), in the framework of genome-wide association studies (GWAS) and gene expression/coexpression studies, with particular emphasis on schizophrenia (SCZ). Selected SCZ GWAS associationPvalues play the role of the primary data for AdaPT; single-nucleotide polymorphisms (SNPs) are selected because they are gene expression quantitative trait loci (eQTLs). This natural pairing of SNPs and genes allow us to map the following covariate values to these pairs: GWAS statistics from genetically correlated bipolar disorder, the effect size of SNP genotypes on gene expression, and gene–gene coexpression, captured by subnetwork (module) membership. In all, 24 covariates per SNP/gene pair were included in the AdaPT analysis using flexible gradient boosted trees. We demonstrate a substantial increase in power to detect SCZ associations using gene expression information from the developing human prefrontal cortex. We interpret these results in light of recent theories about the polygenic nature of SCZ. Importantly, our entire process for identifying enrichment and creating features with independent complementary data sources can be implemented in many different high-throughput settings to ultimately improve power.
First-principles experimental demonstration of ferroelectricity in a thermotropic nematic liquid crystal: Polar domains and striking electro-optics
Authors: Chen Xi , Korblova Eva , Dong Dengpan , Wei Xiaoyu , Shao Renfan , Radzihovsky Leo , Glaser Matthew A. , Maclennan Joseph E. , Bedrov Dmitry , Walba David M. , Clark Noel A.
Published: June 2020

We report the experimental determination of the structure and response to applied electric field of the lower-temperature nematic phase of the previously reported calamitic compound 4-[(4-nitrophenoxy)carbonyl]phenyl2,4-dimethoxybenzoate (RM734). We exploit its electro-optics to visualize the appearance, in the absence of applied field, of a permanent electric polarization density, manifested as a spontaneously broken symmetry in distinct domains of opposite polar orientation. Polarization reversal is mediated by field-induced domain wall movement, making this phase ferroelectric, a 3D uniaxial nematic having a spontaneous, reorientable polarization locally parallel to the director. This polarization density saturates at a low temperature value of ∼6 µC/cm
2
, the largest ever measured for a fluid or glassy material. This polarization is comparable to that of solid state ferroelectrics and is close to the average value obtained by assuming perfect, polar alignment of molecular dipoles in the nematic. We find a host of spectacular optical and hydrodynamic effects driven by ultralow applied field (E ∼ 1 V/cm), produced by the coupling of the large polarization to nematic birefringence and flow. Electrostatic self-interaction of the polarization charge renders the transition from the nematic phase mean field-like and weakly first order and controls the director field structure of the ferroelectric phase. Atomistic molecular dynamics simulation reveals short-range polar molecular interactions that favor ferroelectric ordering, including a tendency for head-to-tail association into polar, chain-like assemblies having polar lateral correlations. These results indicate a significant potential for transformative, new nematic physics, chemistry, and applications based on the enhanced understanding, development, and exploitation of molecular electrostatic interaction.
Rationing social contact during the COVID-19 pandemic: Transmission risk and social benefits of US locations
Authors: Benzell Seth G. , Collis Avinash , Nicolaides Christos
Published: June 2020

To prevent the spread of coronavirus disease 2019 (COVID-19), some types of public spaces have been shut down while others remain open. These decisions constitute a judgment about the relative danger and benefits of those locations. Using mobility data from a large sample of smartphones, nationally representative consumer preference surveys, and economic statistics, we measure the relative transmission reduction benefit and social cost of closing 26 categories of US locations. Our categories include types of shops, entertainments, and service providers. We rank categories by their trade-off of social benefits and transmission risk via dominance across 13 dimensions of risk and importance and through composite indexes. We find that, from February to March 2020, there were larger declines in visits to locations that our measures indicate should be closed first.
Palenquero origins
Authors: Parkvall Mikael , Jacobs Bart
Published: June 2020

Palenquero is a Spanish-lexified creole spoken in Columbia. We argue that existing hypotheses regarding its birth are problematic in several regards. This article addresses the inconsistencies in these hypotheses and provides an alternative, more coherent account. More precisely, we take issue with the following three claims: (a) Palenquero is the result of a two-language encounter; (b) it has its roots in a West African Afro-Portuguese proto-variety; (c) an ancestral form of the creole emerged in the port city of Cartagena. We then set out to present our own, more economical, formation scenario, according to which Palenquero was formed in the early 1600s in the linguistically heterogenous maroon communities of the Cartagenan hinterlands.
L2 writing and L2 learning: Transfer, self-regulation, and identities
Authors: Cumming Alister
Published: June 2020

Can aspects of a second language (L2) be learned through writing the language? Research addressing
this question has focused on (a) the transfer of knowledge and skills; (b) attention, self-regulation, knowledge
consolidation, or collaboration while composing; or (c) development of identities within particular discourse
communities and complex dynamic systems. This chapter reviews research and theories from these three perspectives,
which suggest 10 tentative claims about diverse ways in which L2 writing may foster L2 learning. These claims are
analyzed from the perspectives of behaviorist, cognitive, sociocultural, and complexity theories of learning.
A dual-process model of L1 writing processes
Authors: Galbraith David , Al-Saadi Zulaikha
Published: June 2020

Current models of the cognitive processes involved in L1 writing treat them as problem-solving
processes, and characterize expert / novice differences as a contrast between a knowledge-transforming approach and a
knowledge-telling approach. Empirical research informed by these models has typically used this distinction as a
characterization of the processes involved but has not explicitly tested what effect these have on the writer’s
knowledge. In this chapter, we argue that these models neglect the implicit nature of much of the writer’s knowledge,
and present an alternative dual-process model of writing, which is designed to take this into account. We then
describe recent studies in L1 that support the main claims of the dual-process model, call into question some of the
assumptions of problem-solving models and suggest that an alternative rough-drafting strategy may help overcome the
conflict between text quality and the development of the writer’s understanding. We conclude by discussing the
implications for research into L2 writing processes and drafting strategies.
Toward an agenda for researching L2 writing and language learning
Authors: Byrnes Heidi
Published: June 2020

Taking an educational linguistics perspective, the chapter highlights four areas that have the
potential of illuminating possible effects of L2 writing for L2 learning. They address pressing issues by (a)
theorizing writing as textual meaning-making; (b) emphasizing the pivotal role of the educational context, in its
conceptualization and its practice; (c) affirming the long-term nature of developing literate forms of language use
under a longitudinal optic; and d) privileging an extended, well-conceptualized curricular framework. The chapter
suggests that these dimensions can yield important insights regarding the long-term development of both L2 composing
and L2 abilities, especially when they are informed by a textually oriented theory of language, such as Systemic
Functional Linguistics, and contemporary thinking in Complex Dynamic Systems Theory.
L2 writing-to-learn
Authors: Leow Ronald P.
Published: June 2020

Given the current contextual focus on the cognitive processes employed during L2 written production
in ISLA with a focus on L2 writing-to-learn in relation to written corrective feedback (WCF), this
chapter provides (1) a description of the curricular context in which the writing-to-learn
perspective lies, together with its associated learning outcomes and assumed pedagogical ramifications derived from
empirical research; (2) a succinct review of theoretical underpinnings postulated to account for cognitive processes
employed during the phase of addressing WCF; (3) a critical report of L2 WCF studies premised on these underpinnings,
their curricular association, and potential pedagogical extrapolations; and (4) a curricular approach that involves
potential directions for future research premised on understanding and promoting such processes during this writing
process in relation to L2 development.
Investigating the relationship between peer interaction and writing processes in computer-supported collaborative
L2 writing
Authors: Stiefenhöfer Laura , Michel Marije C.
Published: June 2020

Twenty-first century technology has created new digital contexts (e.g., shared online writing
platforms) that influence the potential of collaborative writing for second language (L2) learning. Making a
methodological contribution to studying L2 computer-supported collaborative writing (CSCW), the present chapter
reports on an exploratory yet innovative investigation triangulating data from text mining, interaction analyses,
eye-tracking, and stimulated recall. Eight international students in the UK used Google Docs for paired collaborative
writing tasks. Results of quantitative and qualitative analyses reveal the many ways in which peers interact with each
other and the nature of the emerging text during CSCW. Findings illustrate the complexities of CSCW and indicate how
triangulating different methods facilitates the study of the affordances of CSCW and its potential contribution to L2
learning.
The meaning-making potential of collaborative L2 writing at tertiary level
Authors: Saller Marcus
Published: June 2020

This chapter reports on a longitudinal study on collaborative writing by advanced L2 university
students. In an attempt to elucidate the language-learning potential of collaborative writing over one semester, a
mixed-method, descriptive, exploratory study with students writing essays in digital environments individually
(n = 11) and in pairs (n = 15) was designed. Data consisted of the audio
recordings of dyadic interaction, surveys, and expository essays. Results provide evidence of dyads deliberating upon
complex meaning-making decisions, indicate positive responses to collaborative writing, and suggest heterogeneous
development of syntactic complexity features characteristic of academic writing between the groups. Findings will be
discussed from the point of view of research and pedagogy.
An ISLA perspective on L2 learning through writing
Authors: Manchón Rosa M. , Leow Ronald P.
Published: June 2020

This chapter argues for the relevance of framing L2 writing research associated with language
learning as part of a language curriculum within an instructed second language acquisition (ISLA)
perspective. In line with current ISLA theorizing, we argue that the field should prioritize the conduct of additional
studies of the processing dimension of writing and we envisage this future work as contributing to both
applied ISLA and ISLA applied. We synthesize past research on writing processes
and, against this background, we propose several future avenues and methodological directions for a process-oriented
agenda in the domain. We conclude with a synthesis of the ideas discussed and with an assessment of what our optic
offers to the collective inquiry into writing as a site for language learning that this book attempts to provide.
The language learning potential of L2 writing
Authors: Manchón Rosa M.
Published: June 2020

In this final chapter I articulate how the book contributes to advancing previous intersectional work
between the fields of L2 writing and ISLA/SLA. To this end, I discuss the volume’s expansion of theoretical and
empirical knowledge on writing as a site for language development in terms of (a) new empirical insights provided on
the learning affordances of L2 writing and the variables mediating observed effects, and (b) future research
directions suggested, primarily in terms of domains to be researched, empirical questions to be addressed, and methods
of inquiry to be employed.
Bonding across Chinese social media
Authors: Xie Chaoqun , Tong Ying , Yus Francisco
Published: June 2020

This paper explores social bonding in language play via the construction of ‘Chinese character (annotation)’ on two major social media platforms (Sina WeiboandWeChat) in China. The Chinese characters and their bracketed annotations under study, despite their one-to-one matching in sequence, never match each other either in meaning or in pronunciation. They convey a sense of playfulness among social media users who may be acquaintances or strangers to each other. While research on language play has uncovered systematic interpersonal meanings and social functions, our analysis of screen-based and user-based data shows that such linguistic behavior in a virtual community of practice contributes to social bonding among social media players. Within such structure and with different substitutes for both characters and annotations, social media users frame their expressions in evaluative or emotive ways to facilitate their presentation of an alternative self and of individual or community values.
Elite athletes’ experiences of interpersonal violence in organized sport in Germany, the Netherlands, and Belgium
Authors: Ohlert Jeannine , Vertommen Tine , Rulofs Bettina , Rau Thea , Allroggen Marc
Published: June 2020

Interpersonal violence in sport occurs in different forms, from emotional abuse, overtraining, bullying, physical aggression and pressuring to punishment and sexual abuse. Due to the use of different definitions, a comparison of prevalence estimates between studies in different countries has not been possible to date. The aim of the current study was thus to present the prevalence estimates of interpersonal violence in elite sport for the Netherlands, Belgium (Flanders), and Germany and to examine the overlap of three types of interpersonal violence. Data from two different surveys (one in the Netherlands and Flanders and another in Germany) of a total of 1,665 elite athletes (n = 533 from the Netherlands and Flanders, n = 1,132 from Germany) were used. Athletes were asked to answer questions about their experiences of psychological, physical, and sexual violence in the context of organized sport. In general, lifetime prevalence estimates for all three types of interpersonal violence are more than 24% in elite athletes, with the highest numbers for psychological violence. Compared to representative population samples the prevalence rate of psychological violence seems to be particularly high. Gender differences were only evident for sexual violence, with female athletes showing higher prevalence estimates than male athletes. Furthermore, a high overlap of experiences of the three different forms of interpersonal violence was found for all three countries. The differences in prevalence estimates between the three countries are discussed.
Conflict, cooperation or competition in the Caspian Sea region: A critical review of the New Great Game paradigm
Authors: Bayramov Agha
Published: June 2020

This article critically reviews the New Great Game image of the Caspian Sea region and the assumptions, concepts, and mechanisms (revolving around actors, aims, and motivations) this image is based on. More specifically, this review essay answers the following questions: How does the academic literature interpret the impact of competition between great powers on social, political and economic developments in the Caspian Sea region? Which actors are presented as the dominant players? The essay also introduces the existing criticism of the New Great Game concept and alternatives to it that have already been put forward. By identifying the gaps and limits of existing scholarship, this article offers new avenues for alternative theoretical and empirical interpretations. More specifically, this article argues that the New Great Game literature promotes unsystematic and shallow discussion as it ignores and misunderstands historical, material, political, economic, and normative differences in the Caspian Sea region. Within this discussion, actors, interests, identities, social contexts, and principles are taken to be fixed, i.e. not prone to change or to any sort of adjustment.
Poor quality Vβ recombination signal sequences stochastically enforce TCRβ allelic exclusion
Authors: Wu Glendon S. , Yang-Iott Katherine S. , Klink Morgann A. , Hayer Katharina E. , Lee Kyutae D. , Bassing Craig H.
Published: June 2020

The monoallelic expression of antigen receptor (AgR) genes, called allelic exclusion, is fundamental for highly specific immune responses to pathogens. This cardinal feature of adaptive immunity is achieved by the assembly of a functional AgR gene on one allele, with subsequent feedback inhibition of V(D)J recombination on the other allele. A range of epigenetic mechanisms have been implicated in sequential recombination of AgR alleles; however, we now demonstrate that a genetic mechanism controls this process for Tcrb. Replacement of V(D)J recombinase targets at two different mouse Vβ gene segments with a higher quality target elevates Vβ rearrangement frequency before feedback inhibition, dramatically increasing the frequency of T cells with TCRβ chains derived from both Tcrb alleles. Thus, TCRβ allelic exclusion is enforced genetically by the low quality of Vβ recombinase targets that stochastically restrict the production of two functional rearrangements before feedback inhibition silences one allele.
In-situ control of microdischarge characteristics in unipolar pulsed plasma electrolytic oxidation of aluminum
Authors: Hermanns Patrick , Boeddeker Simon , Bracht Vera , Bibinov Nikita , Awakowicz Peter
Published: June 2020

Microdischarges occurring during plasma electrolytic oxidation are the main mechanism promoting oxide growth compared to classical anodization. When the dissipated energy by microdischarges during the coating process gets too large, high-intensity discharges might occur, which are detrimental to the oxide layer. In bipolar pulsed plasma electrolytic oxidation a so called ‘soft-sparking’ mode limits microdischarge growth. This method is not available for unipolar pulsing and for all material combinations. In this work, the authors provide a method to control the size- and intensity distributions of microdischarges by utilizing a multivariable closed-loop control. In-situ detection of microdischarge properties by CCD-camera measurements and fast image processing algorithms are deployed. The visible size of microdischarges is controlled by adjusting the duty cycle in a closed-loop feedback scheme, utilizing a PI-controller. Uncontrolled measurements are compared to controlled cases. The microdischarge sizes are controlled to a mean value of

A
=
5
⋅

10

−
3

m
m

2

and

A
=
7
⋅

10

−
3

m
m

2

, respectively. Results for controlled cases show, that size and intensity distributions remain constant over the processing time of 35 minutes. Larger, high-intensity discharges can be effectively prevented. Optical emission spectra reveal, that certain spectral lines can be influenced or controlled with this method. Calculated black body radiation fits with very good agreement to measured continuum emission spectra (

T
=
3200
 

K

). Variance of microdischarge size, emission intensity and continuum radiation between consecutive measurements is reduced to a large extent, promoting uniform microdischarge and oxide layer properties. A reduced variance in surface defects can be seen in SEM measurements, after coating for 35 minutes, for controlled cases. Surface defect study shows increased number density of microdischarge impact regions, while at the same time reducing pancake diameters, implying reduced microdischarge energies compared to uncontrolled cases.
On the choice of proper average lifetime formula for an ensemble of emitters showing non-single exponential photoluminescence decay
Authors: Zatryb G , Klak M M
Published: June 2020

In this paper, we investigate non-single exponential photoluminescence decays in various disordered condensed-matter systems. For such materials, two formulas for the average lifetime of system’s excited state are commonly used in the analysis of experimental data. In many cases, the choice of formula is arbitrary and lacks a clear physical justification. For this reason, our main goal is to show that the choice of correct mathematical formula should be based on the interpretation of measured photoluminescence decay curve. It is shown that depending on the investigated system, after appropriate normalization, photoluminescence decay curve can represent either a survival probability function or a probability density function of lifetime and for this reason two different formulas for the average lifetime are required. It is also shown that, depending on luminescence quantum yield, some information on the probability density function of lifetime can be lost in the process of measurement, which results in underestimated values of average lifetime. Finally, we provide an interpretation of total decay rate distributions which are frequently obtained by phenomenological modeling of non-single exponential photoluminescence decays.
Hot-carrier separation in heterostructure nanowires observed by electron-beam induced current
Authors: Fast Jonatan , Barrigon Enrique , Kumar Mukesh , Chen Yang , Samuelson Lars , Borgström Magnus , Gustafsson Anders , Limpert Steven , Burke Adam , Linke Heiner
Published: June 2020

The separation of hot carriers in semiconductors is of interest for applications such as thermovoltaic photodetection and third-generation photovoltaics. Semiconductor nanowires offer several potential advantages for effective hot-carrier separation such as: a high degree of control and flexibility in heterostructure-based band engineering, increased hot-carrier temperatures compared to bulk, and a geometry well suited for local control of light absorption. Indeed, InAs nanowires with a short InP energy barrier have been observed to produce electric power under global illumination, with an open-circuit voltage exceeding the Shockley-Queisser limit. To understand this behaviour in more detail, it is necessary to establish control over the precise location of electron-hole pair-generation in the nanowire. In this work we perform electron-beam induced current measurements with high spatial resolution, and demonstrate the role of the InP barrier in extracting energetic electrons.We interprete the results in terms of hot-carrier separation, and extract estimates of the hot carriers’ mean free path.
Alternative physics to understand wall turbulence: Navier–Stokes equations with modified linear dynamics
Authors: Lozano-Durán Adrián , Nikolaidis Marios-Andreas , Constantinou Navid C. , Karp Michael
Published: June 2020

Despite the nonlinear nature of wall turbulence, there is evidence that the energy-injection mechanisms sustaining wall turbulence can be ascribed to linear processes. The different scenarios stem from linear stability theory and comprise exponential instabilities from mean-flow inflection points, transient growth from non-normal operators, and parametric instabilities from temporal mean-flow variations, among others. These mechanisms, each potentially capable of leading to the observed turbulence structure, are rooted in simplified theories and conceptual arguments. Whether the flow follows any or a combination of them remains unclear. In the present study, we devise a collection of numerical experiments in which the Navier–Stokes equations are sensibly modified to quantify the role of the different linear mechanisms. This is achieved by direct numerical simulation of turbulent channel flows with constrained energy extraction from the streamwise-averaged mean-flow. We demonstrate that (i) transient growth alone is not sufficient to sustain wall turbulence and (ii) the flow remains turbulent when the exponential instabilities are suppressed. On the other hand, we show that (iii) transient growth combined with the parametric instability of the time-varying mean-flow is able to sustain turbulence.
Large-scale structures predicted by linear models of wall-bounded turbulence
Authors: Symon S. , Illingworth S. J. , Marusic I.
Published: June 2020

The objective of this article is to determine for which scales stochastic forcing of the linearized Navier-Stokes equations, recast as the resolvent operator, is sufficient to reproduce second-order statistics in turbulent channel flow. Our focus is on the large scales at a friction Reynolds number of Reτ = 2003. We consider a molecular resolvent operator, where only the kinematic viscosity appears, and an eddy resolvent operator, where the kinematic viscosity is augmented with an eddy viscosity profile. The molecular resolvent operator is able to identify the wall-normal height where the maximum energy of a structure is located, but it fails to predict the most energetic wave speed. It also overestimates the streamwise velocity component and underestimates the spatial support of the structures in the wall-normal direction. When the eddy resolvent operator identifies the most energetic wave speed, it also predicts the correct statistics for a given spatial scale. For spatial scales where this criterion is not met, the eddy viscosity overdamps the linear response. As a result, it predicts energetic wave speeds which are too low and velocity structures which are too energetic close to the wall. We conclude that eddy viscosity works best for structures which are most energetic in the wake region while its performance deteriorates for structures that are active in the log region.
Dynamic mode decomposition analysis of coherent structures in rotating plane Couette flow
Authors: Sacco Francesco , Ostilla-Mónico Rodolfo , Verzicco Roberto
Published: June 2020

Large scale structures have been observed in many turbulent wall bounded flows, such as pipe, Couette or square duct flows. Many efforts have been made in order to capture such structures to understand and model them. However, commonly used methods have their limitations, such as arbitrariness in parameter choice or specificity to certain setups. In this manuscript we attempt to overcome these limitations by using two variants of Dynamic Mode Decomposition (DMD). We apply these methods to (rotating) Plane Couette flow, and verify that DMD-based methods are adequate to detect the coherent structures and to extract the distinct properties arising from different control parameters. In particular, these DMD variants are able to capture the influence of rotation on large-scale structures by coupling velocity components. We also show how high-order DMD methods are able to capture some complex temporal dynamics of the large-scale structures. These results show that DMD-based methods are a promising way of filtering and analysing wall bounded flows.
Turbulent flow over spanwise-varying roughness in a minimal streamwise channel
Authors: Xie Michael X , Chung Daniel , Hutchins Nicholas
Published: June 2020

We report direct numerical simulations in a minimal streamwise domain of turbulent channel flow over spanwise-alternating patches of rough and smooth walls. Despite the minimal streamwise domain overpredicting streamwise-velocity fluctuations and inhibiting the meandering of long turbulent structures, it captures the rotational behaviour of mean secondary flows also observed in other studies with spanwise-varying roughness. To extend the study of spanwise-varying roughness, we prescribe a lateral velocity to the wall roughness to mimic flow over oblique patches of roughness. Far from the wall, long-lived turbulent structures are convected in the direction of the moving roughness, but their speeds are only weakly perturbed from a preferential value of around 40% of the friction velocity. The turbulence-driven secondary flows laterally convect at comparable speeds, but depend on the roughness patch width.
In vitro characterization of osteoblast cells on polyelectrolyte multilayers containing detonation nanodiamonds
Authors: Balakin Sascha , Yun Young-Shik , Lee Jihye , Kang Eun-Hye , Spohn Juliane , Yun In-Sik , Opitz Jörg , Cuniberti Gianaurelio , Yeo Jong-Souk
Published: June 2020

Nanoparticle-enhanced coatings of bone implants are a promising method to facilitate sustainable wound healing, leading to an increase in patient well-being. This article describes the in vitro characterization of osteoblast cells interacting with polyelectrolyte multilayers, which contain detonation nanodiamonds (NDs), as a novel class of carbon-based coating material, which presents a unique combination of photoluminescence and drug-binding properties. The cationic polyelectrolyte, namely polydiallyldimethylammonium chloride (PDDA), has been used to immobilize NDs on silica glass. The height of ND-PDDA multilayers varies from a minimum of 10 nm for one bilayer to a maximum of 90 nm for five bilayers of NDs and PDDA. Human fetal osteoblasts (hFOBs) cultured on ND-PDDA multilayers show a large number of focal adhesions, which were studied via quantitative fluorescence imaging analysis. The influence of the surface roughness on the filopodia formation was assessed via scanning electron microscopy and atomic force microscopy. The nano-rough surface of five bilayers constrained the filopodia formation. The hFOBs grown on NDs tend to show not only a similar cell morphology compared to cells cultured on extracellular matrix protein-coated silica glass substrates, but also increased cell viability by about 40%. The high biocompatibility of the ND-PDDA multilayers, indicated via high cell proliferation and sound cell adhesion, shows their potential for biomedical applications such as drug-eluting coatings and biomaterials in general.
Electrospun PCL-based nanofibers Arrabidaea chica Verlot – Pterodon pubescens Benth loaded: synergic effect in fibroblast formation
Authors: Costa Salles Tais Helena , Volpe-Zanutto Fabiana , de Oliveira Sousa Ilza Maria , Machado Daisy , Zanatta Ana Caroline , Vilegas Wagner , Lancellotti Marcelo , Foglio Mary Ann , d’Ávila Marcos Akira
Published: June 2020

The guided tissue regeneration (GTR) technique can be applied in dentistry and other medical specializations, such as orthopedics. In modern dentistry, GTR has been used in periodontics and implantology to treat periodontal defects, to reconstruct lost, damaged and atrophied bone tissue in dental implant procedures, and to preserve alveolar bases after tooth extraction. In order to create and improve new therapies and to develop new biomaterials that restore, improve and prevent aggravation of compromised tissue function, poly (ϵ-caprolactone) (PCL) polymer membranes were obtained by the electrospinning process and were associated with two plant extracts: Pterodon pubescens Benth (P. pubescens) and Arrabidaea chica Verlot (A. chica) which are characterized by their pharmacological activities of anti-inflammatory and healing actions, respectively. Fiber morphology was analyzed using scanning electron microscopy (SEM), where fiber average diameter was measured from SEM images. Contact angle measurements were performed in order to evaluate the hydrophilicity of electrospun membranes containing vegetal extract. High-performance liquid chromatography was used to evaluate the ability to release active ingredients. Cytotoxicity and cell proliferation assays were performed in vitro on NIH-3T3 cells for 1, 3 and 7 d. Electrospun PCL membranes associated with plant extracts P. pubescens and/or A. chica presented a controlled release profile of the active compounds induced fibroblast formation, suggesting that they are promising and suitable for applications in GTR.
Modulation of the optical properties of transition metal doped PbSe quantum dots in silicate glasses
Authors: Tesfamariam Belay Brehane , P Janaki Ramulu
Published: June 2020

Optical properties of lead chalcogenide quantum dots (QDs) can be controlled by tuning its bandgaps. We prepared silicate glasses using the melt-quenching method and heat-treated 510 °C–540 °C for 10 h to precipitate transition metal ions into PbSe QDs. Transition metals oxide such as TiO, MnO & NiO were used in our experiment due to relative ease of incorporation of Ti2+, Mn2+, or Ni2+ ions in PbSe crystal structure lattice compared to rare-earth ions. Emission spectra of PbSe QDs were tuned in a wide wavelength range through changing concentration of transition metals oxide in glasses. For instance, photoluminescence bands of Pb1−xTixSe QDs QDs moved from 1890 nm to 1625 nm with increasing TiO from 0.0 to 0.5 mol% at heat treatment 530 °C for 10 h. Absorption bands of QDs also shifted to shorter wavelength sides as concentration of TiO or MnO increased under constant thermal treatment conditions mainly due to the change in the bandgap of QDs. However, absorption & PL peaks moved to longer wavelength sides (red-shifted) with increasing the duration of thermal annealing while keeping the amount of transition metal oxides constant mainly due to enlargement of the QDs sizes with thermal treatment. Tunable optical properties of QDs make them a promising candidate for various photoelectric devices, for example, fiber-optics amplifiers in optical communication and fiber lasers.
A Systematic Review and Meta-Analysis of Interventions for Orphans and Vulnerable Children Affected by HIV/AIDS Worldwide
Authors: Thomas Tina , Tan Mei , Ahmed Yusra , Grigorenko Elena L
Published: June 2020

Background

Worldwide, there are more than 13.3 million orphans and vulnerable children affected by Human immunodeficiency virus infection and acquired immune deficiency syndrome (HIV/AIDS) (HIV OVC), defined as individuals below the age of 18 who have lost one or both parents to HIV/AIDS or have been made vulnerable by HIV/AIDS; they are at risk for negative psychosocial and cognitive outcomes.

Purpose

This meta-analysis aimed to examine the scientific literature on available interventions for HIV OVC, with a focus on community-based interventions (CBI).

Methods

Systematic electronic searches were conducted from four databases between October 2016 and April 2017 to identify articles investigating the effectiveness of interventions for HIV OVC. Effect sizes were calculated for each article which provided enough information and data points for analyses.

Results

Seventy-four articles were reviewed, including psychosocial interventions (d = 0.30), cognitive interventions (d = 0.14), social protection interventions (d = 0.36), and community-based interventions (CBI; d = 0.36). Study-specific effect sizes varied widely, ranging from −1.09 to 2.26, that is, from a negative effect to an impressively large positive one, but the majority of studies registered small to medium effects (the overall effect size for all studies was 0.32, SE = 0.03, 95% CI: 0.26–0.37). Social protection interventions had the highest positive outcomes whereas CBI tended to have the fewest significant positive outcomes, with some outcomes worsening instead of improving.

Conclusions

Overall, interventions provided to OVC have potential for improving cognitive, psychosocial, and risk-behavior outcomes. Social protection interventions and CBI had the highest effect sizes, but CBI had positive effects on fewer outcomes and demonstrated some negative effects. CBI warrant scrutiny for improvement, as they represent an important form of culturally embedded services with potentially long-term benefits to OVC, yet appear to be differentially effective. Successful components of other types of intervention were identified, including cash grants, mentorship, and family therapy. In addition, more research is needed that attends to which interventions may be more effective for specific populations, or that studies cost-effectiveness.
Prevalence of Coronavirus Disease 2019 Infection and Outcomes Among Symptomatic Healthcare Workers in Seattle, Washington
Authors: Mani Nandita S , Budak Jehan Z , Lan Kristine F , Bryson-Cahn Chloe , Zelikoff Allison , Barker Gwendolyn E C , Grant Carolyn W , Hart Kristi , Barbee Carrie J , Sandoval Marissa D , Dostal Christine L , Corcorran Maria , Ungerleider Hal M , Gates Jeff O , Olin Svaya V , Bryan Andrew , Hoffman Noah G , Marquis Sara R , Harvey Michelle L , Nasenbeny Keri , Mertens Kathleen , Chew Lisa D , Greninger Alexander L , Jerome Keith R , Pottinger Paul S , Dellit Timothy H , Liu Catherine , Pergam Steven A , Neme Santiago , Lynch John B , Kim H Nina , Cohen Seth A
Published: June 2020

Background

Healthcare workers (HCWs) who serve on the front lines of the coronavirus disease 2019 (COVID-19) pandemic have been at increased risk for infection due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in some settings. Healthcare-acquired infection has been reported in similar epidemics, but there are limited data on the prevalence of COVID-19 among HCWs and their associated clinical outcomes in the United States.

Methods

We established 2 high-throughput employee testing centers in Seattle, Washington, with drive-through and walk-through options for symptomatic employees in the University of Washington Medicine system and its affiliated organizations. Using data from these testing centers, we report the prevalence of SARS-CoV-2 infection among symptomatic employees and describe the clinical characteristics and outcomes among employees with COVID-19.

Results

Between 12 March 2020 and 23 April 2020, 3477 symptomatic employees were tested for COVID-19 at 2 employee testing centers; 185 (5.3%) employees tested positive for COVID-19. The prevalence of SARS-CoV-2 was similar when comparing frontline HCWs (5.2%) with nonfrontline staff (5.5%). Among 174 positive employees reached for follow-up at least 14 days after diagnosis, 6 reported COVID-related hospitalization; all recovered.

Conclusions

During the study period, we observed that the prevalence of positive SARS-CoV-2 tests among symptomatic HCWs was comparable to that of symptomatic nonfrontline staff. Reliable and rapid access to testing for employees is essential to preserve the health, safety, and availability of the healthcare workforce during this pandemic and to facilitate the rapid return of SARS-CoV-2–negative employees to work.
Preventing COVID-19 Collateral Damage
Authors: Shepherd James , Friedland Gerald
Published: June 2020

The lockdown in response to coronavirus disease 2019 (COVID-19) risks damaging the response to many infectious diseases. We recommend integrating the COVID-19 response into existing public health programs, strengthening both.
Development of an Ordinal Scale Treatment Endpoint for Adults Hospitalized With Influenza
Authors: Lee Nelson , Smith Stephanie W , Hui David S C , Ye Ming , Zelyas Nathan , Chan Paul K S , Drews Steven J , Zapernick Lori , Wong Rity , Labib Mary , Shokoples Sandy , Eurich Dean T
Published: June 2020

Background

An obstacle in influenza therapeutics development is the lack of clinical endpoints, especially in hospitalized patients. A single time-point binary outcome measure is limited by patients’ diverse clinical trajectories and low event rates.

Methods

A 6-point ordinal scale with ascending clinical status severity (scoring: discharged; subacute care; acute care without/with respiratory failure; intensive care unit [ICU]; death) was proposed to study outcomes of adults hospitalized with influenza. Individual patient data from 2 active surveillance cohorts’ datasets (2015/2016−2017/2018; Edmonton, Hong Kong) was used for evaluation. The impact of neuraminidase inhibitor (NAI) treatment on longitudinal ordinal outcome changes over 30 days was analyzed using mixed-effects ordinal logistic regression and group-based trajectory models.

Results

Patient (n = 1226) baseline characteristics included age (mean 68.0 years), virus-type (A 78.1%, B 21.9%), respiratory failure (57.2%), ICU admittance (14.4%), and NAI treatment within 5 days of illness (69.2%). Outcomes at 30 days included discharged (75.2%), subacute care (13.7%), acute care (4.5%), and death (6.6%). Two main clinical trajectories were identified, predictive by baseline scoring (mean ± SD, 4.3 ± 0.6 vs 3.5 ± 0.6, P < .001). Improved outcomes with NAI treatment within 5 days were indicated by significantly lower clinical status scores over time (unadjusted odds ratio [OR], 0.53; 95% confidence interval [CI], .41−.69; P < .001; adjusted OR, 0.62; 95% CI, .50−.77; P < .001, for baseline score, age, and within-patient correlations). In subanalysis, influenza vaccination was also associated with lower scores (adjusted OR, 0.67; 95% CI, .50−.90; P = .007). Analyses of binary endpoints showed insignificant results.

Conclusions

The ordinal outcome scale is a potentially useful clinical endpoint for influenza therapeutic trials, which could account for the diverse clinical trajectories of hospitalized patients, warranting further development.