bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of magnetic field on perturbation evolution in homogeneously sheared flows
Authors: Praturi Divya Sri , Collard Diane , Girimaji Sharath S.
Published: November 2018

The goal of this paper is to identify and characterize the fundamental mechanisms that contribute toward flow stabilization in sheared plasma flows. Toward that end, we investigate the evolution of velocity and magnetic field perturbations in homogeneously sheared magnetohydrodynamic (MHD) flows subjected to an imposed streamwise magnetic field. The influences of magnetic field strength ($B_{0}$) and perturbation wavevector orientation ($\unicode[STIX]{x1D6FD}$) are characterized using linear analysis and direct numerical simulations. The linear analysis of ideal MHD indicates that the perturbation evolution is governed by four processes: pressure redistribution, kinetic energy production, kinetic–magnetic energy exchange and magnetic energy production due to magnetic stretching. The interplay between these processes can be characterized by the ratio of shear-to-magnetic timescales ($R_{A}\equiv V_{A}\unicode[STIX]{x1D705}/S$) and $\unicode[STIX]{x1D6FD}$, where $V_{A}$, $\unicode[STIX]{x1D705}$ and $S$ are Alfvén wave speed, initial wavenumber and mean flow shear, respectively. For cases with low values of $\boldsymbol{R}_{\boldsymbol{A}}~(\ll \mathbf{1})$, a three-stage perturbation evolution is seen. At the first stage, pressure redistribution and production dominate leading to hydrodynamic-type behaviour. In the second stage, the onset of magnetic stretching process leads to an increase in magnetic energy. At late stages, production subsides and the dynamics is dominated by harmonic exchange between velocity and magnetic fields. For cases of $\boldsymbol{R}_{\boldsymbol{A}}\approx \mathbf{1}$, the magnetic field reacts rapidly enough that hydrodynamic and magnetic production stages occur simultaneously followed by harmonic exchange. In the case of $\boldsymbol{R}_{\boldsymbol{A}}\gg 1$, all three stages occur simultaneously leading to harmonic exchange between kinetic and magnetic energies without any perturbation growth. For all cases considered, the late stage harmonic exchange results in equipartition between perturbation magnetic and kinetic energies. For a given $R_{A}$, the effect of increasing $\unicode[STIX]{x1D6FD}$ is to reduce the intensity of coupling and progressively slow down the three stages of evolution. For spanwise wavevector perturbations, the velocity–magnetic field interaction mechanism vanishes and there is no effect of pressure or magnetic field on individual velocity components.
A versatile taxonomy of low-dimensional vortex models for unsteady aerodynamics
Authors: Darakananda Darwin , Eldredge Jeff D.
Published: November 2018

Inviscid vortex models have been demonstrated to capture the essential physics of massively separated flows past aerodynamic surfaces, but they become computationally expensive as coherent vortex structures are formed and the wake is developed. In this work, we present a two-dimensional vortex model in which vortex sheets represent shear layers that separate from sharp edges of the body and point vortices represent the rolled-up cores of these shear layers and the other coherent vortices in the wake. We develop a circulation transfer procedure that enables each vortex sheet to feed its circulation into a point vortex instead of rolling up. This procedure reduces the number of computational elements required to capture the dynamics of vortex formation while eliminating the spurious force that manifests when transferring circulation between vortex elements. By tuning the rate at which the vortex sheets are siphoned into the point vortices, we can adjust the balance between the model’s dimensionality and dynamical richness, enabling it to span the entire taxonomy of inviscid vortex models. This hybrid model can capture the development and subsequent shedding of the starting vortices with insignificant wall-clock time and remain sufficiently low-dimensional to simulate long-time-horizon events such as periodic bluff-body shedding. We demonstrate the viability of the method by modelling the impulsive translation of a wing at various fixed angles of attack, pitch-up manoeuvres that linearly increase the angle of attack from$0^{\circ }$to$90^{\circ }$, and oscillatory pitching and heaving. We show that the proposed model correctly predicts the dynamics of large-scale vortical structures in the flow by comparing the distributions of vorticity and force responses from results of the proposed model with a model using only vortex sheets and, in some cases, high-fidelity viscous simulation.
Numerical investigation of laminar–turbulent transition in laminar separation bubbles: the effect of free-stream turbulence
Authors: Hosseinverdi Shirzad , Fasel Hermann F.
Published: November 2018

The role of free-stream turbulence (FST) in the hydrodynamic instability mechanisms and transition to turbulence in laminar separation bubbles (LSBs) was investigated using direct numerical simulations (DNS). Towards this end, a set of highly resolved DNS have been carried out, where isotropic FST fluctuations with intensities from 0.1 % to 3 % are introduced to investigate the relevant physical mechanisms governing the interaction of separation and transition in LSBs. For disturbance-free simulations, i.e. without FST, laminar–turbulent transition involves a Kelvin–Helmholtz (KH) instability of the separated shear layer. For LSBs subjected to FST, vortical FST fluctuations penetrate the approaching attached laminar boundary layer upstream of the separation location and induce slowly growing low-frequency disturbances, so-called Klebanoff (K) modes, which cause a spanwise modulation with a distinct spanwise wavelength. Simultaneously, the FST enhances the initial levels of instability waves with frequencies in the frequency range of the KH instability, but at much smaller amplitude levels compared to the K-modes. Results from the calculations based on the linearized Navier–Stokes equations and comparison with DNS results reveal that the K-mode exhibits exponential growth in the separated shear layer until it reaches a peak amplitude. At the same time, two-dimensional (2D) disturbance waves are also exponentially amplified, in fact at larger growth rate compared to the K-mode, due to the primary (convective) shear-layer instability mechanism until they saturate downstream of the peak amplitude associated with the K-mode. Therefore, based on detailed spectral analysis and modal decompositions for the separation bubbles investigated, the transition process is the result of two different mechanisms: (i) strong amplification of high-frequency (order of the shedding frequency), essentially 2D or weakly oblique fluctuating disturbances and (ii) low-frequency, three-dimensional K-modes caused by FST. Depending on the intensity of the FST, one of these mechanisms would dominate the transition process, or both mechanisms act together and contribute simultaneously. The net effect of these two events is an acceleration of transition for an increased level of FST intensity, which in turn leads to a reduction of the extent of the separation bubble in streamwise and wall-normal directions. The ‘roll-up’ into spanwise large-scale vortical structures resulting from the shear-layer instability, and the eventual breakdown of these structures, strongly contribute to the reattachment process. The spanwise coherence of these ‘rollers’ deteriorates due to the presence of large-amplitude K-modes, thus effectively weakening their strength for high levels of FST intensities ($Tu>1\,\%$).
Computing heteroclinic orbits using adjoint-based methods
Authors: Farano M. , Cherubini S. , Robinet J.-C. , De Palma P. , Schneider T. M.
Published: November 2018

Transitional turbulence in shear flows is supported by a network of unstable exact invariant solutions of the Navier–Stokes equations. The network is interconnected by heteroclinic connections along which the turbulent trajectories evolve between invariant solutions. While many invariant solutions in the form of equilibria, travelling waves and periodic orbits have been identified, computing heteroclinic connections remains a challenge. We propose a variational method for computing orbits dynamically connecting small neighbourhoods around equilibrium solutions. Using local information on the dynamics linearized around these equilibria, we demonstrate that we can choose neighbourhoods such that the connecting orbits shadow heteroclinic connections. The proposed method allows one to approximate heteroclinic connections originating from states with multi-dimensional unstable manifold and thereby provides access to heteroclinic connections that cannot easily be identified using alternative shooting methods. For plane Couette flow, we demonstrate the method by recomputing three known connections and identifying six additional previously unknown orbits.
THE POLITICS OF RECOGNIZABILITY: GIVING AN ACCOUNT OF IRANIANGAYMEN’S LIVES UNDER REPRESSIVE CONDITIONS OF SEXUALITY GOVERNANCE
Authors: Martino Wayne , Kjaran Jón Ingvar
Published: November 2018

In this article we examine accounts of self-identifying Iranian gay men. We draw on a range of evidentiary sources—interpretive, historical, online, and empirical—to generate critical and nuanced insights into the politics of recognition and representation that inform narrative accounts of the lived experiences of self-identifiedgayIranian men, and the constitution of same-sex desire for these men under specific conditions of Iranian modernity. In response to critiques of existinggayinternationalist and liberationist accounts of the Iraniangaymale subject as a persecuted victim of the Islamic Republic of Iran's barbarism, we address interpretive questions of sexuality governance in transnational contexts. Specifically, we attend to human rights frameworks in weighing social justice and political claims made by and on behalf of sexual and gender minorities in such Global South contexts. In this sense, our article represents a critical engagement with the relevant literature on sexuality governance and the politics of same-sex desire for Iraniangaymen that is informed by empirical analysis.
The Icon and the Text: American Book History and the Construction of the World's Largest-Grossing Illustrated Book, Madonna'sSex(1992)
Authors: RATTI MANAV
Published: November 2018

Madonna's bookSex(1992) is the world's largest-grossing illustrated book, selling 1.4 million copies worldwide and earning US$70 million in sales at retail. This essay is the first to use methods from the discipline of bibliography to analyze the book's production, distribution, and reception. This article extends scholarship on Madonna, including about her iconicity and visuality, from her songs and videos to her print culture. I demonstrate howSex– both as a printed book and as an expression of national culture – is part of a dynamic American book history that constructs notions of America, including freedom of speech, thought, and religion.
Effect of Trading Relationships on Execution Costs in Low-Information-Asymmetry Over-the-Counter Markets
Authors: Issa George , Jarnecic Elvis
Published: November 2018

Traders can reduce search costs in dealership markets by entering relationships with dealers. However, dealers draw little informational benefit from these relationships in Treasury markets, due to low risk and information asymmetry. We investigate the extent, duration, effects on pricing, and potential benefits of client–dealer relationships. We find that relationship strength leads to higher execution costs for clients, more so during stressed market conditions but less so in the presence of information asymmetry and when trading in corporate bonds. Relationship traders are compensated with immediacy at times when search is costly.
Projection-operator methods for classical transport in magnetized plasmas. Part 2. Nonlinear response and the Burnett equations
Authors: Krommes John A.
Published: November 2018

The time-independent projection-operator formalism of Breyet al. (PhysicaA, vol. 109, 1981, pp. 425–444) for the derivation of Burnett equations is extended and considered in the context of multispecies and magnetized plasmas. The procedure provides specific formulas for transport coefficients in terms of two-time correlation functions involving both two and three phase-space points. It is shown how to calculate those correlation functions in the limit of weak coupling. The results are used to demonstrate, with the aid of a particular non-trivial example, that the Chapman–Enskog methodology employed by Catto & Simakov (CS) (Phys. Plasmas, vol. 11, 2004, pp. 90–102) to calculate the contributions to the parallel viscosity driven by temperature gradients is consistent with formulas previously derived from the two-time formalism by Brey (J. Chem. Phys., vol. 79, 1983, pp. 4585–4598). The work serves to unify previous work on plasma kinetic theory with formalism usually applied to turbulence. Additional contributions include discussions of (i) Braginskii-order interspecies momentum exchange from the point of view of two-time correlations; and (ii) a simple stochastic model, unrelated to many-body theory, that exhibits Burnett effects. Insights from that model emphasize the role of non-Gaussian statistics in the evaluation of Burnett transport coefficients, including the effects calculated by CS that stem from the nonlinear collision operator. Together, Parts 1 and 2 of this series provide an introduction to projection-operator methods that should be broadly useful in theoretical plasma physics.
Bias-contingent attention bias modification and attention control training in treatment of PTSD: a randomized control trial
Authors: Lazarov Amit , Suarez-Jimenez Benjamin , Abend Rany , Naim Reut , Shvil Erel , Helpman Liat , Zhu Xi , Papini Santiago , Duroski Ariel , Rom Rony , Schneier Franklin R. , Pine Daniel S. , Bar-Haim Yair , Neria Yuval
Published: November 2018

Background

Randomized control trials (RCTs) comparing attention control training (ACT) and attention bias modification (ABM) in posttraumatic stress disorder (PTSD) have shown mixed results. The current RCT extends the extant literature by comparing the efficacy of ACT and a novel bias-contingent-ABM (BC-ABM), in which direction of training is contingent upon the direction of pre-treatment attention bias (AB), in a sample of civilian patients with PTSD.

Methods

Fifty treatment-seeking civilian patients with PTSD were randomly assigned to either ACT or BC-ABM. Clinician and self-report measures of PTSD and depression, as well as AB and attention bias variability (ABV), were acquired pre- and post-treatment.

Results

ACT yielded greater reductions in PTSD and depressive symptoms on both clinician-rated and self-reported measures compared with BC-ABM. The BC-ABM condition successfully shifted ABs in the intended training direction. In the ACT group, there was no significant change in ABV or AB from pre- to post-treatment.

Conclusions

The current RCT extends previous results in being the first to apply ABM that is contingent upon AB at pre-treatment. This personalized BC-ABM approach is associated with significant reductions in symptoms. However, ACT produces even greater reductions, thereby emerging as a promising treatment for PTSD.
THE CORPORATION'S GOVERNMENTAL PROVENANCE AND ITS SIGNIFICANCE
Authors: Singer Abraham A.
Published: November 2018

Corporations cannot exist, scholars rightly note, without being constituted by government. However, many take a further step, claiming that corporations are normatively distinct from other market actors because of this governmental provenance. They are mistaken. Like corporations, markets and contracts also require government for their creation. Governmental provenance does not distinguish corporations normatively because our coercive social institutions are pro tanto justified in re-arranging both corporate and non-corporate market activities on behalf of social and political values. The corporation is distinct only practically and prudentially, in that it represents a more proximate instrument for effecting morality in the economy.
Inequality and Political Trust in China: The Social Volcano Thesis Re-examined
Authors: Zhou Yingnan Joseph , Jin Shuai
Published: November 2018

The social volcano thesis states that the rising inequality in China threatens regime stability. This idea, although widely held in the media and in academia, is backed by little positive evidence but by much negative evidence. Two primary pieces of negative evidence are that the Chinese people trust the central government and that they are highly tolerant of inequality. This paper discusses the shortcomings of the negative evidence and re-examines the thesis in a rigorous and direct way. Our multilevel analysis shows that provincial inequality has negative effects on individuals’ trust in the local government but not in the central government, and this negative effect holds for both the rich and the poor. Because distrust in the local government implies distrust in the central government, we conclude that a social volcano exists.
When Voluntary Donations Meet the State Monopoly: Understanding Blood Shortages in China
Authors: Guan Yue
Published: November 2018

China's blood-borne HIV catastrophe in the 1990s prompted the government to adopt a blood-collection system that combines voluntary donations with the state's monopoly on blood services. Juxtaposing fieldwork and survey data, this study examines how the intricate interplay between government manoeuvres and citizen reactions has led to blood shortages that are serious yet manageable. This article reveals that even though voluntary blood donations are adversely affected by a public distrust of state-run collection agencies, owing to political concerns healthcare officials shirk from engaging with citizens to overcome the distrust. It also finds that the blood shortages are nevertheless largely manageable because the authorities have the capacity to recruit captive donors through work units, with the caveat that such captive practices are used sparingly. Overall, this study argues that the lack of state–society synergy in voluntary donations, while exacerbated by government involvement, is also partially remedied by the government's mobilization of captive donors.
‘As Modern as Tomorrow’: Australian Entrepreneurs and Japanese Entertainment, 1957–1968
Authors: BOLLEN JONATHAN
Published: November 2018

This article compares the efforts of two Australian entrepreneurs to import Japanese entertainments for theatres in mid-twentieth-century Australia. David N. Martin of the Tivoli Circuit and Harry Wren, an independent producer, were rivals in the business of touring variety-revue. Both travelled to Japan in 1957, the year that the governments of Australia and Japan signed a landmark trade agreement. Whereas Martin's efforts were hampered by the legacy of wartime attitudes, Wren embraced the post-war optimism for trade. Wren became the Australian promoter for the Toho Company of Japan, touring a series of Toho revues until 1968. These Toho tours have been overlooked in Australian histories of cultural exchange with Japan. Drawing on evidence from archival sources and developing insights from foreign policy of the time, this article examines why Australian entrepreneurs turned to Japan, what Toho sent on tour, and how Toho's revues played in Australia. It analyses trade in touring entertainment as a form of entrepreneurial diplomacy that sought to realize the prospects of regional integration.
Comparing Hydrological Postprocessors Including Ensemble Predictions Into Full Predictive Probability Distribution of Streamflow
Authors: Biondi D. , Todini E.
Published: November 2018

Although not matching the formal definition of the predictive probability distribution, meteorological and hydrological ensembles have been frequently interpreted and directly used to assess flood‐forecasting predictive uncertainty. With the objective of correctly assessing the predictive probability of floods, this paper introduces ways of taking into account the measures of uncertainty provided in the form of ensemble forecasts by modifying a number of well‐established uncertainty postprocessors, such as Bayesian Model Averaging and Model Conditional Processor. The uncertainty postprocessors were developed on the assumption that the future unknown quantity (predictand) is uncertain while model forecasts (predictors) are given, which imply that they are perfectly known. With this in mind, we propose to relax this assumption by considering ensemble predictions, in analogy to measurement errors, as expressions of errors in model predictions to be integrated in the postprocessors coefficients estimation process. The analyses of the methodologies proposed in this work are conducted on a real case study based on meteorological ensemble predictions for the Po River at Pontelagoscuro in Italy. After showing how improper can be the direct use of ensemble predictions to describe the predictive probability distribution, results from the modified postprocessors are compared and discussed.
Tropical Ionization Trough in the Ionosphere Seen by Swarm‐A Satellite
Authors: Lee Woo Kyoung , Kil Hyosub , Paxton Larry J.
Published: November 2018

A new type of ionization trough, the tropical ionization trough, is identified in the tropical F region from the Swarm‐A satellite observations in December 2013 to January 2017. The trough is formed around midnight near 25° magnetic latitudes in the winter hemisphere during the solstices. The trough is pronounced around 330°E longitude in the Southern Hemisphere (negative magnetic declination) during the June solstices and around 210°E longitude in the Northern Hemisphere (positive magnetic declination) during the December solstices. Weak signatures of the trough also appear at those locations during the equinoxes. We interpret the formation of the trough in the winter hemisphere during the solstices by the convergence of meridional winds in the winter tropics. The longitudinal variation of the trough intensity is explained by the magnetic declination control of the zonal wind effect and the longitudinal variation of the meridional wind velocity.
Toward Data‐Driven Weather and Climate Forecasting: Approximating a Simple General Circulation Model With Deep Learning
Authors: Scher S.
Published: November 2018

It is shown that it is possible to emulate the dynamics of a simple general circulation model with a deep neural network. After being trained on the model, the network can predict the complete model state several time steps ahead—which conceptually is making weather forecasts in the model world. Additionally, after being initialized with an arbitrary model state, the network can through repeatedly feeding back its predictions into its inputs create a climate run, which has similar climate statistics to the climate of the general circulation model. This network climate run shows no long‐term drift, even though no conservation properties were explicitly designed into the network.
Effect of the Reconnection Electric Field on Electron Distribution Functions in the Diffusion Region of Magnetotail Reconnection
Authors: Bessho N. , Chen L.‐J. , Wang S. , Hesse M.
Published: November 2018

Electron distribution functions in the electron diffusion region during symmetric magnetic reconnection are investigated by means of theory and fully kinetic simulations. Crescent‐like striations are formed in distribution functions in the velocity plane perpendicular to the magnetic field. Using an analytical current sheet, we solve the equation of motion for electrons, and derive the shape of a crescent distribution, as a function of the distance from the neutral line, field gradients, and the reconnection electric field. Each crescent is tilted in the velocity plane because of the acceleration by the reconnection electric field, and multiple stripes appear due to multiple meandering bounces. Applying the theory to distribution functions observed in Earth's magnetotail, we deduce the amplitude of the reconnection electric field.
The Energetics of Extensive Meltwater Flooding of Level Arctic Sea Ice
Authors: Diaz A. , Ehn J. K. , Landy J. C. , Else B. G. T. , Campbell K. , Papakyriakou T. N.
Published: November 2018

During the spring‐to‐summer transition, the snow cover on Arctic sea ice melts and meltwater pools on the surface to form melt ponds; however, the timing and extent of the ponding vary between years. In Dease Strait (Nunavut), this transition was particularly dramatic in 2014 when on 18 June meltwater had flooded >95% of the surface. In this study, continuous surface energy balance measurements throughout the transition highlight how the timing of transient weather events influenced seasonal shifts in distinct ice melt stages. The keys to the extensive flooding were (1) the level ice cover, (2) a strong low‐pressure system on 24 May that deposited ~10 cm of snow, and (3) freeze‐thaw cycling and a subsequent return to subzero air temperatures on 30 May that led to superimposed and interposed ice formation. Without these, melt ponds would have likely developed within days from an initial melt onset on 28 May. After a 2‐week delay, snow‐melt resumed and lead to near‐complete flooding of the surface for 4 days. The albedo of the flooded ice remained high (0.35–0.40), as a result of the bubble‐laden superimposed ice layer. Once this layer eroded, the albedo over melt ponds decreased to a more typical level (~0.20). Our observations suggest that the formation of superimposed and interposed ice prevented the vertical drainage of meltwater to the ocean. Future challenges remain to measure the presence of these layers and understand their effect on sea ice permeability and pond evolution, while sea ice temperatures are near the melting point.
Observations of Reduced Turbulence and Wave Activity in the Arctic Middle Atmosphere Following the January 2015 Sudden Stratospheric Warming
Authors: Triplett Colin C. , Li Jintai , Collins Richard L. , Lehmacher Gerald A. , Barjatya Aroh , Fritts David C. , Strelnikov Boris , Lübken Franz‐Josef , Thurairajah Brentha , Harvey V. Lynn , Hampton Donald L. , Varney Roger H.
Published: November 2018

Measurements of turbulence and waves were made as part of the Mesosphere‐Lower Thermosphere Turbulence Experiment (MTeX) on the night of 25–26 January 2015 at Poker Flat Research Range, Chatanika, Alaska (65°N, 147°W). Rocket‐borne ionization gauge measurements revealed turbulence in the 70‐ to 88‐km altitude region with energy dissipation rates between 0.1 and 24 mW/kg with an average value of 2.6 mW/kg. The eddy diffusion coefficient varied between 0.3 and 134 m2/s with an average value of 10 m2/s. Turbulence was detected around mesospheric inversion layers (MILs) in both the topside and bottomside of the MILs. These low levels of turbulence were measured after a minor sudden stratospheric warming when the circulation continued to be disturbed by planetary waves and winds remained weak in the stratosphere and mesosphere. Ground‐based lidar measurements characterized the ensemble of inertia‐gravity waves and monochromatic gravity waves. The ensemble of inertia‐gravity waves had a specific potential energy of 0.8 J/kg over the 40‐ to 50‐km altitude region, one of the lowest values recorded at Chatanika. The turbulence measurements coincided with the overturning of a 2.5‐hr monochromatic gravity wave in a depth of 3 km at 85 km. The energy dissipation rates were estimated to be 3 mW/kg for the ensemble of waves and 18 mW/kg for the monochromatic wave. The MTeX observations reveal low levels of turbulence associated with low levels of gravity wave activity. In the light of other Arctic observations and model studies, these observations suggest that there may be reduced turbulence during disturbed winters.
Vertical Characterization of Aerosol Particle Composition in Beijing, China: Insights From 3‐Month Measurements With Two Aerosol Mass Spectrometers
Authors: Zhou Wei , Sun Yele , Xu Weiqi , Zhao Xiujuan , Wang Qingqing , Tang Guiqian , Zhou Libo , Chen Chen , Du Wei , Zhao Jian , Xie Conghui , Fu Pingqing , Wang Zifa
Published: November 2018

Despite extensive studies for characterization of aerosol chemistry near ground level, long‐term vertical characterization of aerosol particle composition in Beijing is very limited. In this work, non‐refractory submicron aerosol (NR‐PM1) species were simultaneously measured at ground level and 260 m on a meteorological tower from 14 October 2014 to 18 January 2015 in Beijing using two aerosol mass spectrometers. Our results showed overall lower concentrations of NR‐PM1 at 260 m by 2%–36% than ground level in both heating and non‐heating seasons, and also larger vertical gradients during clean periods than polluted episodes. The vertical ratios and correlations of aerosol species between ground level and 260 m presented higher values in daytime and lower ones at nighttime mainly due to the influences of planetary boundary layer and local source emissions, respectively. Nitrate showed ubiquitously higher ratio of 260 m to ground (ratio260m/ground) than sulfate due to a higher formation potential from gas‐particle partitioning and heterogeneous reactions at higher heights. A detailed analysis of vertical evolution showed relatively stable ratios260m/ground for secondary aerosol species during the early formation stage of haze episodes, which decreased simultaneously along with mixing layer height during the later severely polluted periods with NR‐PM1 concentration above 150 μg/m3. Our results demonstrated that the evolution of vertical differences in megacities is subject to the influences from both physical (e.g., regional transport, mountain‐valley winds, inversions of temperature and relative humidity, and mixing layer height) and chemical processes (e.g., gas‐particle partitioning and aqueous‐phase processing).
Effects of Langmuir Turbulence on Upper Ocean Carbonate Chemistry
Authors: Smith K. M. , Hamlington P. E. , Niemeyer K. E. , Fox‐Kemper B. , Lovenduski N. S.
Published: November 2018

Effects of wave‐driven Langmuir turbulence on the air‐sea flux of carbon dioxide (CO2) are examined using large eddy simulations featuring actively reacting carbonate chemistry in the ocean mixed layer at small scales. Four strengths of Langmuir turbulence are examined with three types of carbonate chemistry: time‐dependent chemistry, instantaneous equilibrium chemistry, and no reactions. The time‐dependent model is obtained by reducing a detailed eight‐species chemical mechanism using computational singular perturbation analysis, resulting in a quasi steady state approximation for hydrogen ion (H+); that is, fixed pH. The reduced mechanism is then integrated in two half‐time steps before and after the advection solve using a Runge‐Kutta‐Chebyshev scheme that is robust for stiff systems of differential equations. The simulations show that as the strength of Langmuir turbulence increases, CO2 fluxes are enhanced by rapid overturning of the near‐surface layer, which rivals the removal rate of CO2 by time‐dependent reactions. Equilibrium chemistry and nonreactive models are found to bring more and less carbon, respectively, into the ocean as compared to the more realistic time‐dependent model. These results have implications for Earth system models that either neglect Langmuir turbulence or use equilibrium, instead of time‐dependent, chemical mechanisms.
Convective‐Reactive CO2 Dissolution in Aquifers With Mass Transfer With Immobile Water
Authors: Babaei Masoud , Islam Akand
Published: November 2018

The objective of this paper is to study the impact of immobile water, its fraction, and its mass transfer with the flowing region on efficiency of CO2 dissolution in aquifers with an immobile water zone. A continuum scale code is developed with underlying assumptions of spatially homogeneous and temporally invariable partitioning fraction of the porous media, first‐order mass transfer between the mobile and immobile zones, and simplified reaction of CO2 aqueous solution with calcium carbonate rock. Using ranges of values for Damköhler number (Da), fraction of the total pore volume, and mass transfer coefficient rate (α), 96 simulations are conducted. It is shown that due to a lower intensity of reaction in the mobile region, intermediate values of α serve as a threshold below which the mass transfer coefficient is not affecting the overall CO2 storage and above which overall CO2 storage increases as a function of mass transfer coefficient. Additionally, we found that (i) when α is high and geochemistry is intensive (high Da), the overall CO2 storage decreases with increase in fraction of mobile water. This is because CO2 storage through consumption of rock in immobile water with higher geochemistry is reduced. (ii) When α is high but Da is low, the system is effectively a single porosity medium with no chemistry‐influenced discrimination between mobile and immobile zones, and therefore, overall CO2 storage increases with fraction of mobile water. (iii) When α is low, the magnitude of Da does not influence the overall CO2 storage.
New Semi‐Analytical Insights Into Stress‐Dependent Spontaneous Imbibition and Oil Recovery in Naturally Fractured Carbonate Reservoirs
Authors: Haghi Amir H. , Chalaturnyk Richard , Geiger Sebastian
Published: November 2018

Fluid injection and withdrawal in a porous medium create changes in pore pressure that alter effective stresses within the medium. This leads to pore volume changes, which can be described by the poroelastic theory. These changes in pore volume can influence fluid flow processes, such as capillary diffusion and imbibition, potentially altering multiphase flow characteristics in subsurface reservoirs with a focus on oil recovery in the naturally fractured carbonate reservoirs. In this study, a semi‐analytical model is developed to analyze the impact of stress‐dependent spontaneous imbibition. The model allows us to study the influence of stress‐dependent effects on porosity, absolute permeability, relative permeability, and capillary pressure on the imbibition and oil recovery mechanisms of both intact rock and fracture in naturally fractured carbonate reservoirs. In order to capture the geomechanical interactions involved, pure compliance poroelastic definitions and nonlinear joint normal stiffness equations are used to assess the deformation of intact rock and fracture, respectively. The model shows that increasing effective confining stress shifts the imbibition capillary pressure curve upward, resulting in improved absorption of the wetting phase into the smaller pores and enhanced extraction of the nonwetting phase. Model calculations provide a rationale for how and why irreducible water saturation increases during compression of mixed‐wet carbonates and decreases in the case of initially strong water‐wet carbonates. It is also shown how higher relative permeability of the wetting phase leads to a greater diffusion of the wetting phase and improved oil recovery for the less deformed mixed‐wet rock.
Promotion of tumor progression and cancer stemness by MUC15 in thyroid cancer via the GPCR/ERK and integrin-FAK signaling pathways
Authors: Choi Cheolwon , Thi Thao Tran Nguyen , Van Ngu Trinh , Park Sae Woong , Song Min Suk , Kim Sung Hyun , Bae Yun-Ui , Ayudthaya Penchatr Diskul Na , Munir Javaria , Kim Eunbit , Baek Moo-Jun , Song Sujung , Ryu Seongho , Nam Kee-Hyun
Published: November 2018

Thyroid cancer is the fifth most common cancer diagnosed in women worldwide. Notwithstanding advancements in the prognosis and treatment of thyroid cancer, 10–20% of thyroid cancer patients develops chemotherapeutic resistance and experience relapse. According to previous reports and TCGA database, MUC15 (MUCIN 15) upregulation is highly correlated with thyroid cancer progression. However, the role of MUC15 in tumor progression and metastasis is unclear. This study aimed to investigate factors mediating cancer stemness in thyroid cancer. MUC15 plays an important role in sphere formation, as an evident from the expression of stemness markers including SOX2, KLF4, ALDH1A3, and IL6. Furthermore, ectopic expression of MUC15 activated extracellular signal-regulated kinase (ERK) signaling via G-protein–coupled receptor (GPCR)/cyclic AMP (cAMP) and integrin/focal adhesion kinase pathways. Interestingly, ectopic expression of MUC15 did not affect RAF/mitogen-activated protein kinase kinase (MEK)-mediated ERK activation. The present findings may provide novel insights into the development of diagnostic, prognostic, and therapeutic applications of MUC15 in thyroid cancer.
Prognostic and therapeutic significance of phosphorylated STAT3 and protein tyrosine phosphatase-6 in peripheral-T cell lymphoma
Authors: Han Jing Jing , O’byrne Megan , Stenson Mary J. , Maurer Matthew J. , Wellik Linda E. , Feldman Andrew L. , McPhail Ellen D. , Witzig Thomas E. , Gupta Mamta
Published: November 2018

Peripheral T cell lymphomas (PTCL) is a heterogenous group of non-Hodgkin lymphoma and many patients remain refractory to the frontline therapy. Identifying new prognostic markers and treatment is an unmet need in PTCL. We analyzed phospho-STAT3 (pSTAT3) expression in a cohort of 169 PTCL tumors and show overall 38% positivity with varied distribution among PTCL subtypes with 27% (16/59) in PTCL-NOS; 29% (11/38) in AITL, 57% (13/28) in ALK-negative ALCL, and 93% in ALK-pos ALCL (14/15), respectively. Correlative analysis indicated an adverse correlation between pSTAT3 and overall survival (OS). PTPN6, a tyrosine phosphatase and potential negative regulator of STAT3 activity, was suppressed in 62% of PTCL-NOS, 42% of AITL, 60% ALK-neg ALCL, and 86% of ALK-pos ALCL. Loss of PTPN6 combined with pSTAT3 positivity predicted an infwere considered significantferior OS in PTCL cases. In vitro treatment of TCL lines with azacytidine (aza), a DNA methyltransferase inhibitor (DNMTi), restored PTPN6 expression and decreased pSTAT3. Combining DNMTi with JAK3 inhibitor resulted in synergistic antitumor activity in SUDHL1 cell line. Overall, our results suggest that PTPN6 and activated STAT3 can be developed as prognostic markers, and the combination of DNMTi and JAK3 inhibitors as a novel treatment for patients with PTCL subtypes.
Hydroxyurea prevents arterial and late venous thrombotic recurrences in patients with myeloproliferative neoplasms but fails in the splanchnic venous district. Pooled analysis of 1500 cases
Authors: De Stefano Valerio , Rossi Elena , Carobbio Alessandra , Ghirardi Arianna , Betti Silvia , Finazzi Guido , Vannucchi Alessandro M. , Barbui Tiziano
Published: November 2018

We collected 1500 patients with myeloproliferative neoplasms (MPN) and arterial or venous thrombosis (935/565), pooling three independent cohorts previously reported. Long-term treatment with antiplatelet drugs or vitamin K-antagonists (VKA) was given to 1391 (92.7%) patients; 975 (65%) patients received hydroxyurea (HU). We recorded 348 recurrences (venous in 142 cases) over 6075 patient-years, with an incidence rate of 5.7 per 100 pt-years (95% CI 5.1–6.4). The site of the first thrombosis predicted the site of recurrence. Independent factors influencing the rate of novel arterial thrombosis were HU (HR 0.67, 95% CI 0.46–0.98), antiplatelet treatment (HR 0.54, 95% CI 0.35–0.82), and VKA (HR 0.58, 95% CI 0.35–0.96). On the contrary, the recurrence of venous thromboses was significantly diminished only by VKA (HR 0.60, 95% CI 0.37–0.95), while HU prevented late but not early recurrences after venous thrombosis at common sites. Of note, we failed to demonstrate a positive effect of HU in the prevention of recurrent splanchnic vein thrombosis. In conclusion, in MPN patients, HU plays a role in the prevention of arterial thrombosis, together with aspirin and VKA, whereas its action in the prevention of recurrent venous thrombosis is uncertain. Such findings call for future studies to optimize and personalize secondary prophylaxis after MPN-related thrombosis.
Brain injury induces HIF-1α-dependent transcriptional activation of LRRK2 that exacerbates brain damage
Authors: Bae Yun-Hee , Joo Hyejin , Bae Jinhyun , Hyeon Seung Jae , Her Song , Ko Eunhwa , Choi Hwan Geun , Ryu Hoon , Hur Eun-Mi , Bu Youngmin , Lee Byoung Dae
Published: November 2018

Leucine-rich repeat kinase 2 (LRRK2), originally identified as a causative genetic factor in Parkinson’s disease, is now associated with a number of pathologies. Here, we show that brain injury induces a robust expression of endogenous LRRK2 and suggest a role of LRRK2 after injury. We found that various in vitro and in vivo models of traumatic brain injury (TBI) markedly enhanced LRRK2 expression in neurons and also increased the level of hypoxia-inducible factor (HIF)-1α. Luciferase reporter assay and chromatin immunoprecipitation revealed direct binding of HIF-1α in LRRK2 proximal promoter. We also found that HIF-1α-dependent transcriptional induction of LRRK2 exacerbated neuronal cell death following injury. Furthermore, application of G1023, a specific, brain-permeable inhibitor of LRRK2, substantially prevented brain tissue damage, cell death, and inflammatory response and alleviated motor and cognitive defects induced by controlled cortical impact injury. Together, these results suggest HIF-1α-LRRK2 axis as a potential therapeutic target for brain injury.
A delayed diagnosis of Pallister-Hall syndrome in an adult male following the incidental detection of a hypothalamic hamartoma
Authors: Courtney Eliza , Swee Du Soon , Ishak Diana , Ngeow Joanne
Published: November 2018

Pallister-Hall syndrome is a rare autosomal dominant condition that is associated with polydactyly and hypothalamic hamartoma and is caused predominantly by frameshift or nonsense pathogenic variants in the GLI3 gene. The majority of cases are identified during childhood; however, rare reports of diagnoses during adulthood exist. Here, we describe the identification of a novel nonsense GLI3 pathogenic variant in an adult male following the incidental detection of a hypothalamic hamartoma.
A majority of HIV persistence during antiretroviral therapy is due to infected cell proliferation
Authors: Reeves Daniel B. , Duke Elizabeth R. , Wagner Thor A. , Palmer Sarah E. , Spivak Adam M. , Schiffer Joshua T.
Published: November 2018

Antiretroviral therapy (ART) suppresses viral replication in people living with HIV. Yet, infected cells persist for decades on ART and viremia returns if ART is stopped. Persistence has been attributed to viral replication in an ART sanctuary and long-lived and/or proliferating latently infected cells. Using ecological methods and existing data, we infer that >99% of infected cells are members of clonal populations after one year of ART. We reconcile our results with observations from the first months of ART, demonstrating mathematically how a fossil record of historic HIV replication permits observed viral evolution even while most new infected cells arise from proliferation. Together, our results imply cellular proliferation generates a majority of infected cells during ART. Therefore, reducing proliferation could decrease the size of the HIV reservoir and help achieve a functional cure.
Mechanism of copper-free Sonogashira reaction operates through palladium-palladium transmetallation
Authors: Gazvoda Martin , Virant Miha , Pinter Balazs , Košmrlj Janez
Published: November 2018

The seminal contributions by Sonogashira, Cassar and Heck in mid 1970s on Pd/Cu- and Pd-catalysed (copper-free) coupling of acetylenes with aryl or vinyl halides have evolved in myriad applications. Despite the enormous success both in academia and in industry, however, critical mechanistic questions of this cross-coupling process remain unresolved. In this study, experimental evidence and computational support is provided for the mechanism of copper-free Sonogashira cross-coupling reaction. In contrast to the consensus monometallic mechanism, the revealed pathway proceeds through a tandem Pd/Pd cycle linked via a multistep transmetallation process. This cycle is virtually identical to the Pd/Cu tandem mechanism of copper co-catalysed Sonogashira cross-couplings, but the role of CuI is played by a set of PdII species. Phosphine dissociation from the square-planar reactants to form transient three-coordinate Pd species initiates transmetallation and represents the rate-determining step of the process.
Multiple forest attributes underpin the supply of multiple ecosystem services
Authors: Felipe-Lucia María R. , Soliveres Santiago , Penone Caterina , Manning Peter , van der Plas Fons , Boch Steffen , Prati Daniel , Ammer Christian , Schall Peter , Gossner Martin M. , Bauhus Jürgen , Buscot Francois , Blaser Stefan , Blüthgen Nico , de Frutos Angel , Ehbrecht Martin , Frank Kevin , Goldmann Kezia , Hänsel Falk , Jung Kirsten , Kahl Tiemo , Nauss Thomas , Oelmann Yvonne , Pena Rodica , Polle Andrea , Renner Swen , Schloter Michael , Schöning Ingo , Schrumpf Marion , Schulze Ernst-Detlef , Solly Emily , Sorkau Elisabeth , Stempfhuber Barbara , Tschapka Marco , Weisser Wolfgang W. , Wubet Tesfaye , Fischer Markus , Allan Eric
Published: November 2018

Trade-offs and synergies in the supply of forest ecosystem services are common but the drivers of these relationships are poorly understood. To guide management that seeks to promote multiple services, we investigated the relationships between 12 stand-level forest attributes, including structure, composition, heterogeneity and plant diversity, plus 4 environmental factors, and proxies for 14 ecosystem services in 150 temperate forest plots. Our results show that forest attributes are the best predictors of most ecosystem services and are also good predictors of several synergies and trade-offs between services. Environmental factors also play an important role, mostly in combination with forest attributes. Our study suggests that managing forests to increase structural heterogeneity, maintain large trees, and canopy gaps would promote the supply of multiple ecosystem services. These results highlight the potential for forest management to encourage multifunctional forests and suggest that a coordinated landscape-scale strategy could help to mitigate trade-offs in human-dominated landscapes.
Cellular metabolism constrains innate immune responses in early human ontogeny
Authors: Kan Bernard , Michalski Christina , Fu Helen , Au Hilda H. T. , Lee Kelsey , Marchant Elizabeth A. , Cheng Maye F. , Anderson-Baucum Emily , Aharoni-Simon Michal , Tilley Peter , Mirmira Raghavendra G. , Ross Colin J. , Luciani Dan S. , Jan Eric , Lavoie Pascal M.
Published: November 2018

Pathogen immune responses are profoundly attenuated in fetuses and premature infants, yet the mechanisms underlying this developmental immaturity remain unclear. Here we show transcriptomic, metabolic and polysome profiling and find that monocytes isolated from infants born early in gestation display perturbations in PPAR-γ-regulated metabolic pathways, limited glycolytic capacity and reduced ribosomal activity. These metabolic changes are linked to a lack of translation of most cytokines and of MALT1 signalosome genes essential to respond to the neonatal pathogenCandida. In contrast, they have little impact on house-keeping phagocytosis functions. Transcriptome analyses further indicate a role for mTOR and its putative negative regulatorDNA Damage Inducible Transcript 4-Likein regulating these metabolic constraints. Our results provide a molecular basis for the broad susceptibility to multiple pathogens in these infants, and suggest that the fetal immune system is metabolically programmed to avoid energetically costly, dispensable and potentially harmful immune responses during ontogeny.