bluuebunny/crossref_metadata_2025 huggingface dataset:
Drag of a heated sphere at low Reynolds numbers in the absence of buoyancy
Authors: Ganguli Swetava , Lele Sanjiva K.
Published: April 2019

Fully resolved simulations are used to quantify the effects of heat transfer in the absence of buoyancy on the drag of a spatially fixed heated spherical particle at low Reynolds numbers ($Re$) in the range $10^{-3}\leqslant Re\leqslant 10$ in a variable-property fluid. The case where buoyancy is present is analysed in a subsequent paper. This analysis is carried out without making any assumptions on the amount of heat addition from the sphere and thus encompasses both the heating regime where the Boussinesq approximation holds and the regime where it breaks down. The particle is assumed to have a low Biot number, which means that the particle is uniformly at the same temperature and has no internal temperature gradients. Large deviations in the value of the drag coefficient as the temperature of the sphere increases are observed. When $Re<O(10^{-2})$, these deviations are explained using a low-Mach-number perturbation analysis as irrotational corrections to a Stokes–Oseen base flow. Correlations for the drag and Nusselt number of a heated sphere are proposed for the range of Reynolds numbers $10^{-3}\leqslant Re\leqslant 10$ which fit the computationally obtained values with less than 1 % and 3 % errors, respectively. These correlations can be used in simulations of gas–solid flows where the accuracy of the drag law affects the prediction of the overall flow behaviour. Finally, an analogy to incompressible flow over a modified sphere is demonstrated.
Weakly nonlinear theory for a gate-type curved array in waves
Authors: Michele S. , Renzi E. , Sammarco P.
Published: April 2019

We analyse the effect of gate surface curvature on the nonlinear behaviour of an array of gates in a semi-infinite channel. Using a perturbation-harmonic expansion, we show the occurrence of new detuning and damping terms in the Ginzburg–Landau evolution equation, which are not present in the case of flat gates. Unlike the case of linearised theories, synchronous excitation of trapped modes is now possible because of interactions between the wave field and the curved boundaries at higher orders. Finally, we apply the theory to the case of surging wave energy converters (WECs) with curved geometry and show that the effects of nonlinear synchronous resonance are substantial for design purposes. Conversely, in the case of subharmonic resonance we show that the effects of surface curvature are not always beneficial as previously thought.
scaling enabled by multiscale wall roughness in Rayleigh–Bénard turbulence
Authors: Zhu Xiaojue , Stevens Richard J. A. M. , Shishkina Olga , Verzicco Roberto , Lohse Detlef
Published: April 2019

In turbulent Rayleigh–Bénard (RB) convection with regular, mono-scale, surface roughness, the scaling exponent$\unicode[STIX]{x1D6FD}$in the relationship between the Nusselt number$Nu$and the Rayleigh number$Ra$,$Nu\sim Ra^{\unicode[STIX]{x1D6FD}}$can be${\approx}1/2$locally, provided that$Ra$is large enough to ensure that the thermal boundary layer thickness$\unicode[STIX]{x1D706}_{\unicode[STIX]{x1D703}}$is comparable to the roughness height. However, at even larger$Ra$,$\unicode[STIX]{x1D706}_{\unicode[STIX]{x1D703}}$becomes thin enough to follow the irregular surface and$\unicode[STIX]{x1D6FD}$saturates back to the value for smooth walls (Zhuet al.,Phys. Rev. Lett., vol. 119, 2017, 154501). In this paper, we prevent this saturation by employing multiscale roughness. We perform direct numerical simulations of two-dimensional RB convection using an immersed boundary method to capture the rough plates. We find that, for rough boundaries that contain three distinct length scales, a scaling exponent of$\unicode[STIX]{x1D6FD}=0.49\pm 0.02$can be sustained for at least three decades of$Ra$. The physical reason is that the threshold$Ra$at which the scaling exponent$\unicode[STIX]{x1D6FD}$saturates back to the smooth wall value is pushed to larger$Ra$, when the smaller roughness elements fully protrude through the thermal boundary layer. The multiscale roughness employed here may better resemble the irregular surfaces that are encountered in geophysical flows and in some industrial applications.
Effect of background mean flow on PSI of internal wave beams
Authors: Fan Boyu , Akylas T. R.
Published: April 2019

An asymptotic model is developed for the parametric subharmonic instability (PSI) of finite-width nearly monochromatic internal gravity wave beams in the presence of a background constant horizontal mean flow. The subharmonic perturbations are taken to be short-scale wavepackets that may extract energy via resonant triad interactions while in contact with the underlying beam, and the mean flow is assumed to be small so that its advection effect on the perturbations is as important as dispersion, triad nonlinearity and viscous dissipation. In this ‘distinguished limit’, the perturbation dynamics are governed by the same evolution equations as those derived in Karimi & Akylas (J. Fluid Mech., vol. 757, 2014, pp. 381–402), except for a mean flow term that affects the group velocity of the perturbations and imposes an additional necessary condition for PSI, which stabilizes very short-scale perturbations. As a result, it is possible for a small amount of mean flow to weaken PSI dramatically.
Histoire coloniale. Les tribulations des collections archéologiques de l'Algérie
Authors: Nacéra Benseddik
Published: April 2019

From the Musée Algérien established at the Louvre in Paris by Captain Delamare, to the Bibliothèque-musée created by A. Berbrugger in 1838 in the former Janissaries barracks in Algiers, to the short-lived Musée Africain, the archaeological collections of Algeria did not have a real museum space until 19 April 1897, when the Musée des Antiquités Algériennes et d'Art Musulman was inaugurated in the Parc de Galland (today the Parc de la Liberté). Independent Algeria placed the museum under the Ministère de l’éducation nationale until 1970, and then it was moved to the Ministère de l'information et de la culture, and the Musée Stéphane Gsell became the Musée National des Antiquités, financially autonomous in 1985 under the Ministère de la culture. Have the true missions of a museum been fulfilled? And what is the situation at the Louvre where only a few ancient Algerian works are now on display?
Variation of Surface Radiocarbon in the North Pacific During Summer Season 2004–2016
Authors: Aramaki T , Nakaoka S , Terao Y , Kushibashi S , Kobayashi T , Osonoi Y , Mukai H , Tohjima Y
Published: April 2019

Surface radiocarbon (Δ14C) in the North Pacific has been monitored using a commercial volunteer observation ship since the early 2000s. Here we report the temporal and spatial variations in Δ14C in the summer surface water when the surface ocean is vertically stratified over a 13-yr period, 2004–2016. The long-term Δ14C decreasing trend after the late 1970s in the subtropical region has continued to the present and the rate of decrease of the Kuroshio and Kuroshio Extension, North Pacific and California current areas is calculated to be –3.3, –5.2 and –3.3 ‰/yr, respectively. After 2012 the Δ14C of the Kuroshio and Kuroshio Extension area, however, has remained at an approximately constant value of around 50‰. The result may indicate that subtropical surface Δ14C in the western North Pacific has reached an equilibrium with atmospheric Δ14CO2. The Δ14C in the subarctic region is markedly lower than values in the subtropical region and it seems that the decreasing tendency of surface Δ14C has changed to an increasing tendency after 2010. The results may indicate that bomb-produced 14C, which has accumulated below the mixed layer in the past few decades, has been entrained into the surface layer by deep convection.
The Dynamics of Latin American Agricultural Production Growth, 1950–2008
Authors: Martín-Retortillo Miguel , Pinilla Vicente , Velazco Jackeline , Willebald Henry
Published: April 2019

This article is the first of its kind to offer a quantitative estimation of the evolution of Latin American agricultural production and productivity between 1950 and 2008. It also uncovers the extent to which the increases in production were due to increases in factors of production or to efficiency gains. Our findings reveal that efficiency gains made a rather modest contribution to the substantial increase in production, although their role became increasingly large over time and were highly significant between 1994 and 2008. Capital was the most important productive factor in explaining increases in output.
Influence of electroconvulsive therapy on white matter structure in a diffusion tensor imaging study
Authors: Repple Jonathan , Meinert Susanne , Bollettini Irene , Grotegerd Dominik , Redlich Ronny , Zaremba Dario , Bürger Christian , Förster Katharina , Dohm Katharina , Stahl Felix , Opel Nils , Hahn Tim , Enneking Verena , Leehr Elisabeth J. , Böhnlein Joscha , Leenings Ramona , Kaehler Claas , Emden Daniel , Winter Nils R. , Heindel Walter , Kugel Harald , Bauer Jochen , Arolt Volker , Benedetti Francesco , Dannlowski Udo
Published: April 2019

Background

Electroconvulsive therapy (ECT) is a fast-acting intervention for major depressive disorder. Previous studies indicated neurotrophic effects following ECT that might contribute to changes in white matter brain structure. We investigated the influence of ECT in a non-randomized prospective study focusing on white matter changes over time.

Methods

Twenty-nine severely depressed patients receiving ECT in addition to inpatient treatment, 69 severely depressed patients with inpatient treatment (NON-ECT) and 52 healthy controls (HC) took part in a non-randomized prospective study. Participants were scanned twice, approximately 6 weeks apart, using diffusion tensor imaging, applying tract-based spatial statistics. Additional correlational analyses were conducted in the ECT subsample to investigate the effects of seizure duration and therapeutic response.

Results

Mean diffusivity (MD) increased after ECT in the right hemisphere, which was an ECT-group-specific effect. Seizure duration was associated with decreased fractional anisotropy (FA) following ECT. Longitudinal changes in ECT were not associated with therapy response. However, within the ECT group only, baseline FA was positively and MD negatively associated with post-ECT symptomatology.

Conclusion

Our data suggest that ECT changes white matter integrity, possibly reflecting increased permeability of the blood–brain barrier, resulting in disturbed communication of fibers. Further, baseline diffusion metrics were associated with therapy response. Coherent fiber structure could be a prerequisite for a generalized seizure and inhibitory brain signaling necessary to successfully inhibit increased seizure activity.
School success in childhood and subsequent prodromal symptoms and psychoses in the Northern Finland Birth Cohort 1986
Authors: Lassila M. , Nordström T. , Hurtig T. , Mäki P. , Jääskeläinen E. , Oinas E. , Miettunen J.
Published: April 2019

Background

Low IQ is a risk factor for psychosis, but the effect of high IQ is more controversial. The aim was to explore the association of childhood school success with prodromal symptoms in adolescence and psychoses in adulthood.

Methods

In the general population-based Northern Finland Birth Cohort 1986 (n= 8 229), we studied the relationship between teacher-assessed learning deficits, special talents and general school success at age 8 years and both prodromal symptoms (PROD-screen) at age 15–16 years and the occurrence of psychoses by age 30 years.

Results

More prodromal symptoms were experienced by those talented in oral presentation [boys: adjusted odds ratio (OR) 1.49; 95% confidence interval 1.14–1.96; girls: 1.23; 1.00–1.52] or drawing (boys: 1.44; 1.10–1.87). Conversely, being talented in athletics decreased the probability of psychotic-like symptoms (boys: OR 0.72; 0.58–0.90). School success below average predicted less prodromal symptoms with boys (OR 0.68; 0.48–0.97), whereas above-average success predicted more prodromal symptoms with girls (OR 1.22; 1.03–1.44). The occurrence of psychoses was not affected. Learning deficits did not associate with prodromal symptoms or psychoses.

Conclusions

Learning deficits in childhood did not increase the risk of prodromal symptoms in adolescence or later psychosis in this large birth cohort. Learning deficits are not always associated with increased risk of psychosis, which might be due to, e.g. special support given in schools. The higher prevalence of prodromal symptoms in talented children may reflect a different kind of relationship of school success with prodromal symptoms compared to full psychoses.
Are there temporal subtypes of premenstrual dysphoric disorder?: using group-based trajectory modeling to identify individual differences in symptom change
Authors: Eisenlohr-Moul Tory A. , Kaiser Gudrun , Weise Cornelia , Schmalenberger Katja M. , Kiesner Jeff , Ditzen Beate , Kleinstäuber Maria
Published: April 2019

Background

Premenstrual dysphoric disorder (PMDD) is a new Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 diagnosis characterized by the cyclical emergence of emotional and physical symptoms in the luteal phase of the menstrual cycle, with symptom remission in the follicular phase. Converging evidence highlights the possibility of distinct subtypes of PMDD with unique pathophysiologies, but temporal subgroups have yet to be explored in a systematic way.

Methods

In the current work, we use group-based trajectory modeling to identify unique trajectory subgroups of core emotional and total PMDD symptoms across the perimenstrual frame (days −14 to +9, where day 0 is menstrual onset) in a sample of 74 individuals prospectively diagnosed with DSM-5 PMDD.

Results

For the total daily symptom score, the best-fitting model was comprised of three groups: a group demonstrating moderate symptoms only in the premenstrual week (65%), a group demonstrating severe symptoms across the full 2 weeks of the luteal phase (17.5%), and a group demonstrating severe symptoms in the premenstrual week that were slow to resolve in the follicular phase (17.5%).

Conclusions

These trajectory groups are discussed in the context of the latest work on the pathophysiology of PMDD. Experimental work is needed to test for the presence of possible pathophysiologic differences in trajectory groups, and whether unique treatment approaches are needed.
Stepping-Stone or Dead End: To What Extent Does Part-Time Employment Enable Progression Out of Low Pay for Male and Female Employees in the UK?
Authors: NIGHTINGALE MADELINE
Published: April 2019

Using data from Understanding Society and the British Household Panel Survey, this article explores the relationship between working part-time and progression out of low pay for male and female employees using a discrete-time event history model. The results show that working part-time relative to full-time decreases the likelihood of progression out of low pay, defined as earning below two-thirds of the median hourly wage. However, part-time workers who transition to full-time employment experience similar rates of progression to full-time workers. This casts doubt on the idea that part-time workers have lower progression rates because they have lower abilities or work motivation and reinforces the need to address the quality of part-time jobs in the UK labour market. The negative effect of working part-time is greater for men than for women, although women are more at risk of becoming trapped in low pay in the sense that they tend to work part-time for longer periods of time, particularly if they have children. Factors such as childcare policy and Universal Credit (UC) incentivise part-time employment for certain groups, although in the right labour market conditions UC may encourage some part-time workers to increase their working hours.
Artistic Work as a Practice of Translation on the Global Art Market: The Example of “African” Dancer and Choreographer Germaine Acogny
Authors: Klein Gabriele
Published: April 2019

Identity, difference, and translation are important theoretical concepts in the field of translation studies and postcolonial studies. It is a basic assumption of this text that aesthetic and cultural translation is exposed to the paradox of identity and difference and that this paradox is particularly evident in artistic performance practices such as dance and choreography. Focusing on the artistic work of choreographer and dancer Germaine Acogny (Senegal), the text addresses artistic translation practices under postcolonial conditions in the global art market of so-called “contemporary dance.” The aim is to illustrate how contradictory, hybrid, and fragmented the cultural and aesthetic translation process is, how the global art market shapes the artistic strategies of translation, and how aesthetic productivity lies in the impossibility of translating cultural experience artistically.
Emerging Frameworks for Engaging Precarity and “Otherness” in Greek Contemporary Dance Performances
Authors: Zervou Natalie
Published: April 2019

At the dawn of the European refugee crisis, and in the middle of the ongoing sociopolitical and financial crisis in Greece, Greek choreographers started creating dance works that engaged immigrants and refugees. In most such initiatives, improvisation became the tool for bridging the disparity between the professional dancers and the “untrained” participants, who were often the vulnerable populations of refugees and asylum seekers. In this essay, I question the ethics and aesthetics of these methodological approaches utilized for staging encounters between natives and migrants through dance. In particular, I consider the significance of improvisation as potentially perpetuating hierarchical inequalities in the framework of Western concert dance, while I also highlight the ways that such artistic endeavors end up presenting immigrants and refugees as “Others.”
Democracy's Body, Neoliberalism's Body: The Ambivalent Search for Egalitarianism Within the Contemporary Post/Modern Dance Tradition
Authors: Reynoso Jose L.
Published: April 2019

This article analyzes ways in which dance as labor and artist as a specific subjectivity relate to the material conditions of their production within contexts shaped by neoliberal notions of freedom, ideologies of liberal democracy, and the logic of global capitalism. The discussion focuses on contemporary dance practices that embody some of these values by striving to be more egalitarian, thus giving performers more agency in how they participate in creative processes that lead to a collectively created performance work. This analysis emphasizes the tension between these collaborative practices and modes of producing and distributing financial and symbolic, as well as cultural forms of capital in ways that resist and/or reproduce exploitative aspects of capitalism. Examining some works by Yvonne Rainer, Xavier Le Roy, and Tino Sehgal enables the theorization of the entrepreneurial artistic archive as well as practices of crediting creative labor in relation to notions of capital, ownership, collaboration, and consequently who dance-art makers and performers become as politically progressive artists.
Species turnover drives the spatial distribution of frog beta diversity in farmland ponds
Authors: Tavares Henrique Nascimento , da Silva Fernando Rodrigues
Published: April 2019

Studies integrating variation in species composition among sites are useful in understanding the impacts of land-use changes on the spatial distribution of biodiversity. However, the failure to recognize the distinction between beta diversity components, dissimilarity due to species replacement (i.e. turnover) and dissimilarity due to species loss from site to site (i.e. nestedness), can lead to inappropriate use of some indices. Here, we evaluated how the spatial distribution of anuran beta diversity components, turnover and nestedness, is associated with local and landscape descriptors in a tropical agricultural landscape with a recent history of agriculture expansion in south-eastern Brazil. Overall, 27 anuran species were found in the region with average ± SD species richness in each pool of 9.5 ± 3.5 species, ranging from 4 to 15 species. We observed that species turnover was the major component for anuran dissimilarity among pools, indicating that anuran species occurring in species-poor pools are not subsets of anuran species occurring in species-rich pools. Local variables and geographic distance were not important descriptors explaining the variation of anuran beta diversity. In contrast, the distance of the pools to the nearest forest fragment explained 16% of the variance in total beta diversity, 5% of the nestedness component and 2% of spatial turnover. Our results show that pools distributed across farmland landscapes are harbouring different anuran species composition, and together, these pools are contributing to the regional diversity of anurans in this region which is considered one of the most deforested and fragmented within Brazil.
La formation des cités grecques
Authors: Zurbach Julien
Published: April 2019

On oppose couramment aujourd’hui deux conceptions des sociétés grecques archaïques,liées pour l’une à une définition juridique et statique des groupes de statut, pour l’autre à un statut social individuel, fluide et produit de stratégies de distinction diverses. Cet article vise à dépasser cette opposition en examinant l’histoire des groupes de statut à l’époque archaïque. Après une analyse des grandes étapes de l’historiographie complexe existant sur la question, il propose une histoire des statuts dans les cités grecques en formation. La création de statuts nouveaux est un trait essentiel de l’histoire des cités, liée notamment à la dette et la guerre. Les statuts sont collectifs et souvent imposés, mais ils n’en ont pas moins une histoire qui se situe au cœur même de la formation des cités grecques. De nouveaux groupes sont créés pour répondre au besoin de main-d’œuvre des aristocraties du VIIesiècle av. J.-C. Les conflits qui en résultent aboutissent à des évolutions des systèmes alimentaires et fonciers, et cette réorganisation de l’entitlement, réponse des communautés à la crise qui les frappe, passe par la manipulation des statuts. Ce sont des conflits de classe qui amènent la définition d’un nouveau système de statuts.
Les statuts de travail des esclaves et des affranchis dans les grands ports du monde romain(Iersiècle av. J.-C.-IIesiècle apr. J.-C.)
Authors: Tran Nicolas
Published: April 2019

Cet article porte sur le rapport au travail des esclaves et des affranchis impliqués dans les économies portuaires du monde romain, entre le Ier siècle av. J.-C. et le IIesiècle apr. J.-C.La documentation textuelle, épigraphique ou issue de la tradition manuscrite révèle la grande diversité de conditions qui régnaient dans ces milieux. Cette hétérogénéité était liée au degré de technicité des tâches accomplies et donc à la qualification professionnelle des dépendants, comme dans d’autres environnements urbains. Néanmoins, des facteurs propres aux économies portuaires, de nature spatiale en particulier, entraient en ligne de compte. Le clivage entre travailleurs de peine et homme de confiance ne recouvre qu’une partie de ce large spectre. La complexité observée réside dans l’absence de coïncidence,voire dans les dissonances, entre le statut juridique, le statut social et le statut de travail des individus.
Innovation and business sustainability (IBS): empirical evidence from Indian pharmaceutical industry (IPI)
Authors: Pal Brajaballav , Nandy Mithun
Published: April 2019

The aim of our study is to investigate how innovation is taking place through different research and development (R&D) activities and to establish a link between innovation and business sustainability in the context of Indian pharmaceutical companies. Our study is based on the secondary data. Sample data of 37 Indian pharmaceutical companies listed on the National Stock Exchange have been used based on the stratified sampling technique. For empirical analysis we have performed descriptive statistics, correlation matrix, and panel regression analysis as statistical techniques with the help of STATA 12.0 statistical package. R2 value can predict 100 and 98.20% variability in return on assets (ROA) and return on equity (ROE) in model 1 and model 2, respectively. In model 1, the value of c2 is 1.48 and its corresponding p value is 0.00 (<0.05) which means that the model is a good fit for interpretation. R&D intensity is having a positive effect on ROA and the effect is statistically significant at 1% level. Advertising and marketing intensity, capital intensity, leverage ratio and operating expenditure to the total assets ratio are having positive effect on ROA but the effect is not statistically significant. In model 2, the value of F statistics is 8025.62 and its corresponding p value is 0.00 which is <0.05. It means that the model is a good fit for study. R&D intensity is having a positive effect on ROE and the effect is statistically significant at 1% level. Advertising and marketing intensity, capital intensity and operating expenditure to the total assets ratio have positive effect on ROE and the effect is statistically significant at 1% level. Leverage ratio is having a negative effect on ROE but the effect is statically significant at 10% level.
All the ACEs: A Chaotic Concept for Family Policy and Decision-Making?
Authors: White Sue , Edwards Rosalind , Gillies Val , Wastell David
Published: April 2019

This article will consider Adverse Childhood Experiences (ACEs) as a chaotic concept that prioritises risk and obscures the material and social conditions of the lives of its objects. It will show how the various definitions of ACEs offer no cohesive body of definitive evidence and measurement, and lead to a great deal of over-claiming. It discusses how ACEs have found their time and place, locating a variety of social ills within the child’s home, family and parenting behaviours. It argues that because ACEs are confined to intra-familial circumstances, and largely to narrow parent-child relations, issues outside of parental control are not addressed. It concludes that ACEs form a poor body of evidence for family policy and decision-making about child protection and that different and less stigmatising solutions are hiding in plain sight.
The Indonesian Throughflow and the Circulation in the Banda Sea: A Modeling Study
Authors: Liang Linlin , Xue Huijie , Shu Yeqiang
Published: April 2019

To investigate the relationship between the Indonesian ThroughFlow (ITF) and the Banda Sea circulation, we set up a high‐resolution ocean circulation model for the western Pacific and northern Indian Oceans. This well‐validated model demonstrates complex distributions of the along‐channel velocity in different straits, with vertically sheared flows in the Makassar and Maluku straits but horizontally sheared flows in the Halmahera, Timor, and Ombai straits. The model also reveals a three‐layer circulation pattern in the Banda Sea: clockwise, counterclockwise, and clockwise in the upper (<500 m), middle (500–2,250 m), and lower (>2,250 m) water column, respectively. The Lagrangian tracking code TRACMASS is used to diagnose the sources and sinks of Banda Sea waters. The backward/forward tracking experiment pinpoints the inflows/outflows in the straits surrounding the Indonesian Archipelago (IA), which directly affect the Banda Sea. These TRACMASS results imply active vertical exchanges in the Banda Sea, which result in fast flushing with a typical time scale of 8 years. Based on the profiles of net transport into and out of the Banda Sea estimated from the tracking experiments, the three‐layer circulations of the Banda Sea are dynamically explained in terms of the potential vorticity (PV) integral constraint: the PV flux across the boundary and the wind stress curl act in concert with approximately equal order of magnitude for the clockwise circulation in the upper layer, while the positive (negative) PV flux to the middle (bottom) layer corresponds to the counterclockwise (clockwise) circulation.
Charge Structure of Two Tropical Thunderstorms in Colombia
Authors: López Jesús A. , Montanyà Joan , van der Velde Oscar A. , Pineda Nicolau , Salvador Albert , Romero David , Aranguren Daniel , Taborda John
Published: April 2019

Charge structure derived from lightning leader development of tropical thunderstorms comprising equatorial latitudes of less than ±10° has not been investigated yet. In this work, using a lightning mapping array installed in northern Colombia, the charge structure, lightning leader initiations, and the cloud‐to‐ground strokes rates of two thunderstorms have been analyzed. Additionally, radar information is also included. The identification of the charge regions has been obtained by analyzing the propagation of lightning leader developments. Flashes initiate between 4‐ and 15‐km altitude. High initiation rates are different in the two storms. In one case the high rates are found between 8 and 13 km. In the other case, the initiation heights are found between 10 and 15 km. The storms show typical tripolar charge structure where the upper positive charge is present at 10 to ~15 km, the midlevel negative charge is found between 6 and 9 km, and the lower positive charge between 4 and 6 km altitude. Intracloud lightning flashes with inverted polarity have been identified for short period. In other periods, screening layer flashes have been detected at 14–15 km. The overall results show that the charge structures in the two Colombian storms are similar to the structures reported in North Central Florida, but with the significant difference that the flash initiation altitudes  are 2 km higher in Colombia. The vertical configuration of the charge regions and the leader development of these thunderstorms may help explain the occurrence of terrestrial gamma‐ray flashes in tropical thunderstorms.
More Than Emissions and Chemistry: Fire Size, Dilution, and Background Aerosol Also Greatly Influence Near‐Field Biomass Burning Aerosol Aging
Authors: Hodshire A. L. , Bian Q. , Ramnarine E. , Lonsdale C. R. , Alvarado M. J. , Kreidenweis S. M. , Jathar S. H. , Pierce J. R.
Published: April 2019

Biomass burning emits particles (black carbon and primary organic aerosol) and precursor vapors to the atmosphere that chemically and physically age in the atmosphere. This theoretical study explores the relationships between fire size (determining the initial plume width and concentration), dilution rate, and entrainment of background aerosol on particle coagulation, organic aerosol (OA) evaporation, and secondary organic aerosol (SOA) condensation in smoke plumes. We examine the impacts of these processes on aged smoke OA mass, geometric mean diameter (Dg), peak lognormal modal width (σg), particle extinction (E), and cloud condensation nuclei (CCN) concentrations. In our simulations, aging OA mass is controlled by competition between OA evaporation and SOA condensation. Large, slowly diluting plumes evaporate little in our base set of simulations, which may allow for net increases in mass, E, CCN , and Dg from SOA condensation. Smaller, quickly diluting fire plumes lead to faster evaporation, which favors decreases in mass, E, CCN, and Dg. However, the SOA fraction of the smoke OA increases more rapidly in smaller fires due to faster primary organic aerosol evaporation leading to more SOA precursors. Net mass changes for smaller fires depend on background OA concentrations; increasing background aerosol concentrations decrease evaporation rates. Although coagulation does not change mass, it can decrease the number of particles in large/slowly diluting plumes, increasing Dg and E, and decreasing σg. While our conclusions are limited by being a theoretical study, we hope they help motivate future smoke‐plume analyses to consider the effects of fire size, meteorology, and background OA concentrations.
Role of Tidal Wetland Stability in Lateral Fluxes of Particulate Organic Matter and Carbon
Authors: Ganju Neil K. , Defne Zafer , Elsey‐Quirk Tracy , Moriarty Julia M.
Published: April 2019

Tidal wetland fluxes of particulate organic matter and carbon (POM, POC) are important terms in global budgets but remain poorly constrained. Given the link between sediment fluxes and wetland stability, POM and POC fluxes should also be related to stability. We measured POM and POC fluxes in eight microtidal salt marsh channels, with net POM fluxes ranging between −121 ± 33 (export) and 102 ± 28 (import) g OM·m−2·year−1 and net POC fluxes ranging between −52 ± 14 and 43 ± 12 g C·m−2·year−1. A regression employing two measures of stability, the unvegetated‐vegetated marsh ratio (UVVR) and elevation, explained >95% of the variation in net fluxes. The regression indicates that marshes with lower elevation and UVVR import POM and POC while higher elevation marshes with high UVVR export POM and POC. We applied these relationships to marsh units within Barnegat Bay, New Jersey, USA, finding a net POM import of 2,355 ± 1,570 Mg OM/year (15 ± 10 g OM·m−2·year−1) and a net POC import of 1,263 ± 632 Mg C/year (8 ± 4 g C·m−2·year−1). The magnitude of this import was similar to an estimate of POM and POC export due to edge erosion (−2,535 Mg OM/year and − 1,291 Mg C/year), suggesting that this system may be neutral from a POM and POC perspective. In terms of a net budget, a disintegrating wetland should release organic material, while a stable wetland should trap material. This study quantifies that concept and demonstrates a linkage between POM/POC flux and geomorphic stability.
Wildfire Particulates Raise Cardiopulmonary Health Concerns
Authors: Derouin Sarah
Published: April 2019

New research reveals that exposure to smoky air and the particulates created in wildfires can cause increased cardiovascular and respiratory hospitalizations for people 65 and older.
Geo‐fO2: Integrated Software for Analysis of Magmatic Oxygen Fugacity
Authors: Li Weikai , Cheng Yuanqi , Yang Zhiming
Published: April 2019

Oxygen fugacity (fO2) is a fundamental thermodynamic property governing redox potential in solid Earth systems. Analysis of magmatic fO2 aids our understanding of the valence state and solubility of multivalent elements during magma evolution. Specialized software, Geo‐fO2, was developed for calculating magmatic fO2 on the basis of oxybarometers and thermobarometers for common minerals (amphibole, zircon, and biotite) in intermediate‐silicic magmas. With user‐friendly interfaces, it is easy to input files (.csv or Excel files), output data in Excel files, and plot results as binary diagrams that can be saved as vector graphics and modified using image‐processing software.
Rate of Magma Supply Beneath Mammoth Mountain, California, Based on Helium Isotopes and CO2 Emissions
Authors: Lewicki Jennifer L. , Evans William C. , Montgomery‐Brown Emily K. , Mangan Margaret T. , King John C. , Hunt Andrew G.
Published: April 2019

Mammoth Mountain, California, has exhibited unrest over the past ~30 years, characterized by seismicity over a broad range of depths, elevated 3He/4He ratios in fumarolic gas, and large‐scale diffuse CO2 emissions. This activity has been attributed to magmatic intrusion, but minimal ground deformation and the presence of a shallow crustal gas reservoir beneath Mammoth Mountain pose a challenge for estimating magma supply rate. Here, we use the record of fumarolic 3He/4He ratios and CO2 emissions to estimate that of the ~5.2 Mt of CO2 released from Mammoth Mountain between 1989 and 2016, 1.6 Mt was associated with active intrusion and degassing of ~0.05–0.07 km3 of basaltic magma. Intrusion at an average rate of ~0.002–0.003 km3/year into a postulated zone of partial melt at ~15‐km depth could occur without detection by local Global Navigation Satellite System stations.
Model states for a class of chiral topological order interfaces
Authors: Crépel V. , Claussen N. , Estienne B. , Regnault N.
Published: April 2019

Interfaces between topologically distinct phases of matter reveal a remarkably rich phenomenology. To go beyond effective field theories, we study the prototypical example of such an interface between two Abelian states, namely the Laughlin and Halperin states. Using matrix product states, we propose a family of model wavefunctions for the whole system including both bulks and the interface. We show through extensive numerical studies that it unveils both the universal properties of the system, such as the central charge of the gapless interface mode and its microscopic features. It also captures the low energy physics of experimentally relevant Hamiltonians. Our approach can be generalized to other phases described by tensor networks.
Microscopic study of the Halperin–Laughlin interface through matrix product states
Authors: Crépel V. , Claussen N. , Regnault N. , Estienne B.
Published: April 2019

Interfaces between topologically distinct phases of matter reveal a remarkably rich phenomenology. We study the experimentally relevant interface between a Laughlin phase at filling factor ν = 1/3 and a Halperin 332 phase at filling factor ν = 2/5. Based on our recent construction of chiral topological interfaces (Nat. Commun. https://doi.org/10.1038/s41467-019-09168-z; 2019), we study a family of model wavefunctions that captures both the bulk and interface properties. These model wavefunctions are built within the matrix product state framework. The validity of our approach is substantiated through extensive comparisons with exact diagonalization studies. We probe previously unreachable features of the low energy physics of the transition. We provide, amongst other things, the characterization of the interface gapless mode and the identification of the spin and charge excitations in the many-body spectrum. The methods and tools presented are applicable to a broad range of topological interfaces.
Asgard archaea capable of anaerobic hydrocarbon cycling
Authors: Seitz Kiley W. , Dombrowski Nina , Eme Laura , Spang Anja , Lombard Jonathan , Sieber Jessica R. , Teske Andreas P. , Ettema Thijs J. G. , Baker Brett J.
Published: April 2019

Large reservoirs of natural gas in the oceanic subsurface sustain complex communities of anaerobic microbes, including archaeal lineages with potential to mediate oxidation of hydrocarbons such as methane and butane. Here we describe a previously unknown archaeal phylum, Helarchaeota, belonging to the Asgard superphylum and with the potential for hydrocarbon oxidation. We reconstruct Helarchaeota genomes from metagenomic data derived from hydrothermal deep-sea sediments in the hydrocarbon-rich Guaymas Basin. The genomes encode methyl-CoM reductase-like enzymes that are similar to those found in butane-oxidizing archaea, as well as several enzymes potentially involved in alkyl-CoA oxidation and the Wood-Ljungdahl pathway. We suggest that members of the Helarchaeota have the potential to activate and subsequently anaerobically oxidize hydrothermally generated short-chain hydrocarbons.
Primary cilia regulate hematopoietic stem and progenitor cell specification through Notch signaling in zebrafish
Authors: Liu Zhibin , Tu Haiqing , Kang Yunsi , Xue Yuanyuan , Ma Dongyuan , Zhao Chengtian , Li Huiyan , Wang Lu , Liu Feng
Published: April 2019

Hematopoietic stem and progenitor cells (HSPCs) are capable of producing all mature blood lineages, as well as maintaining the self-renewal ability throughout life. The hairy-like organelle, cilium, is present in most types of vertebrate cells, and plays important roles in various biological processes. However, it is unclear whether and how cilia regulate HSPC development in vertebrates. Here, we show that cilia-specific genes, involved in primary cilia formation and function, are required for HSPC development, especially in hemogenic endothelium (HE) specification in zebrafish embryos. Blocking primary cilia formation or function by genetic or chemical manipulations impairs HSPC development. Mechanistically, we uncover that primary cilia in endothelial cells transduce Notch signal to the earliest HE for proper HSPC specification during embryogenesis. Altogether, our findings reveal a pivotal role of endothelial primary cilia in HSPC development, and may shed lights into in vitro directed differentiation of HSPCs.
Thermally robust spin correlations between two 85Rb atoms in an optical microtrap
Authors: Sompet Pimonpan , Szigeti Stuart S. , Schwartz Eyal , Bradley Ashton S. , Andersen Mikkel F.
Published: April 2019

The complex collisional properties of atoms fundamentally limit investigations into a range of processes in many-atom ensembles. In contrast, the bottom-up assembly of few- and many-body systems from individual atoms offers a controlled approach to isolating and studying such collisional processes. Here, we use optical tweezers to individually assemble pairs of trapped 85Rb atoms, and study the spin dynamics of the two-body system in a thermal state. The spin-2 atoms show strong pair correlation between magnetic sublevels on timescales exceeding one second, with measured relative number fluctuations 11.9 ± 0.3 dB below quantum shot noise, limited only by detection efficiency. Spin populations display relaxation dynamics consistent with simulations and theoretical predictions for 85Rb spin interactions, and contrary to the coherent spin waves witnessed in finite-temperature many-body experiments and zero-temperature two-body experiments. Our experimental approach offers a versatile platform for studying two-body quantum dynamics and may provide a route to thermally robust entanglement generation.
The cyclooxygenase-1/mPGES-1/endothelial prostaglandin EP4 receptor pathway constrains myocardial ischemia-reperfusion injury
Authors: Zhu Liyuan , Xu Chuansheng , Huo Xingyu , Hao Huifeng , Wan Qing , Chen Hong , Zhang Xu , Breyer Richard M. , Huang Yu , Cao Xuetao , Liu De-Pei , FitzGerald Garret A. , Wang Miao
Published: April 2019

The use of nonsteroidal anti-inflammatory drugs that inhibit cyclooxygenase (COX)-1 and COX-2, increases heart failure risk. It is unknown whether microsomal (m) prostaglandin (PG) E synthase (S)-1, a target downstream of COX, regulates myocardial (M) ischemia/reperfusion (I/R) injury, a key determinant of heart failure. Here we report that COX-1 and mPGES-1 mediate production of substantial amounts of PGE2 and confer cardiac protection in MI/R. Deletion of mPges-1 impairs cardiac microvascular perfusion and increases inflammatory cell infiltration in mouse MI/R. Consistently, mPges-1 deletion depresses the arteriolar dilatory response to I/R in vivo and to acetylcholine ex vivo, and enhances leukocyte-endothelial cell interaction, which is mediated via PGE receptor-4 (EP4). Furthermore, endothelium-restricted Ep4 deletion impairs microcirculation, and exacerbates MI/R injury, irrespective of EP4 agonism. Treatment with misoprostol, a clinically available PGE analogue, improves microcirculation and reduces MI/R injury. Thus, mPGES-1, a key microcirculation protector, constrains MI/R injury and this beneficial effect is partially mediated via endothelial EP4.
Bacterial chemotaxis in a microfluidic T-maze reveals strong phenotypic heterogeneity in chemotactic sensitivity
Authors: Salek M. Mehdi , Carrara Francesco , Fernandez Vicente , Guasto Jeffrey S. , Stocker Roman
Published: April 2019

Many microorganisms have evolved chemotactic strategies to exploit the microscale heterogeneity that frequently characterizes microbial habitats. Chemotaxis has been primarily studied as an average characteristic of a population, with little regard for variability among individuals. Here, we adopt a classic tool from animal ecology – the T-maze – and implement it at the microscale by using microfluidics to expose bacteria to a sequence of decisions, each consisting of migration up or down a chemical gradient. Single-cell observations of clonal Escherichia coli in the maze, coupled with a mathematical model, reveal that strong heterogeneity in the chemotactic sensitivity coefficient exists even within clonal populations of bacteria. A comparison of different potential sources of heterogeneity reveals that heterogeneity in the T-maze originates primarily from the chemotactic sensitivity coefficient, arising from a distribution of pathway gains. This heterogeneity may have a functional role, for example in the context of migratory bet-hedging strategies.
Towards super-clean graphene
Authors: Lin Li , Zhang Jincan , Su Haisheng , Li Jiayu , Sun Luzhao , Wang Zihao , Xu Fan , Liu Chang , Lopatin Sergei , Zhu Yihan , Jia Kaicheng , Chen Shulin , Rui Dingran , Sun Jingyu , Xue Ruiwen , Gao Peng , Kang Ning , Han Yu , Xu H. Q. , Cao Yang , Novoselov K. S. , Tian Zhongqun , Ren Bin , Peng Hailin , Liu Zhongfan
Published: April 2019

Impurities produced during the synthesis process of a material pose detrimental impacts upon the intrinsic properties and device performances of the as-obtained product. This effect is especially pronounced in graphene, where surface contamination has long been a critical, unresolved issue, given graphene’s two-dimensionality. Here we report the origins of surface contamination of graphene, which is primarily rooted in chemical vapour deposition production at elevated temperatures, rather than during transfer and storage. In turn, we demonstrate a design of Cu substrate architecture towards the scalable production of super-clean graphene (>99% clean regions). The readily available, super-clean graphene sheets contribute to an enhancement in the optical transparency and thermal conductivity, an exceptionally lower-level of electrical contact resistance and intrinsically hydrophilic nature. This work not only opens up frontiers for graphene growth but also provides exciting opportunities for the utilization of as-obtained super-clean graphene films for advanced applications.
Genome-wide association study of medication-use and associated disease in the UK Biobank
Authors: Wu Yeda , Byrne Enda M. , Zheng Zhili , Kemper Kathryn E. , Yengo Loic , Mallett Andrew J. , Yang Jian , Visscher Peter M. , Wray Naomi R.
Published: April 2019

Genome-wide association studies (GWASs) of medication use may contribute to understanding of disease etiology, could generate new leads relevant for drug discovery and can be used to quantify future risk of medication taking. Here, we conduct GWASs of self-reported medication use from 23 medication categories in approximately 320,000 individuals from the UK Biobank. A total of 505 independent genetic loci that meet stringent criteria (P < 10−8/23) for statistical significance are identified. We investigate the implications of these GWAS findings in relation to biological mechanism, potential drug target identification and genetic risk stratification of disease. Amongst the medication-associated genes are 16 known therapeutic-effect target genes for medications from 9 categories. Two of the medication classes studied are for disorders that have not previously been subject to large GWAS (hypothyroidism and gastro-oesophageal reflux disease).