bluuebunny/crossref_metadata_2025 huggingface dataset:
Are Generalists Beneficial to Corporate Shareholders? Evidence from Exogenous Executive Turnovers
Authors: Betzer André , Lee Hye Seung (Grace) , Limbach Peter , Salas Jesus M.
Published: October 2018

This study finds a positive, economically meaningful impact of generalist chief executive officers (CEOs) on shareholder value using 164 sudden deaths and 345 non-sudden exogenous turnovers. The higher a departing CEO’s general ability index (GAI), independently and relative to her successor, the lower is the abnormal stock return to turnover announcements. Returns reflect post-turnover changes in operating performance. Further, CEOs’ and successors’ GAIs are significantly positively related, but only for non-sudden turnovers. Consistently, for sudden deaths, we find positive stock returns to appointments of generalist successors. The results provide a market-based explanation for the generalist pay premium.
‘Simple’ can be good, too: testing three hard bottom sampling methods on macrobenthic and meiobenthic assemblages
Authors: Keklikoglou Kleoniki , Chatzigeorgiou Georgios , Faulwetter Sarah , Kalogeropoulou Vassiliki , Plaiti Wanda , Maidanou Maria , Dounas Costas , Lampadariou Nikolaos , Arvanitidis Christos
Published: October 2018

Subtidal hard bottoms are of particular scientific and economic value as they are highly productive systems. They are less well studied compared with soft bottoms, as they often require manual sample collection via scuba diving. Although a multitude of sampling devices is available for soft bottoms, only a few are suitable for hard substrates, and their performance is largely unstudied. In the present study, three hard bottom sampling methods were compared, regarding their sampling efficiency and the damage they may cause to macrobenthic and meiobenthic organisms. Two of the sampling methods examined are typically employed for the study of hard bottom substrates (manual collection, airlift device), while the third involves a newly constructed sampler (MANOSS – Manual Operated Suction Sampler). All three sampling methods were tested at 12 m depth on a hard bottom substrate with algal coverage dominated by Cystoseira spp. No overall significant differences were observed between the sampling efficiency and the damage caused by the three sampling methods regarding the macrofaunal assemblages, with the exception of the MANOSS method which collected more species than the manual method. In addition, significant differences were observed in the collecting performance for the meiobenthic assemblages, presenting significantly higher densities of meiofauna sampled by the MANOSS compared with the manual collection method, while the airlift device presented an intermediate efficiency. However, taking into account other factors such as cost, ease of use and the scope of each study, none of the methods clearly outperforms the others.
The Trump Presidency and American Democracy: A Historical and Comparative Analysis
Authors: Lieberman Robert C. , Mettler Suzanne , Pepinsky Thomas B. , Roberts Kenneth M. , Valelly Richard
Published: October 2018

To many observers across the political spectrum, American democracy appears under threat. What does the Trump presidency portend for American politics? How much confidence should we have in the capacity of American institutions to withstand this threat? We argue that understanding what is uniquely threatening to democracy requires looking beyond the particulars of Trump and his presidency. Instead, it demands a historical and comparative perspective on American politics. Drawing on insights from the fields of comparative politics and American political development, we argue that Trump’s election represents the intersection of three streams in American politics: polarized two-party presidentialism; a polity fundamentally divided over membership and status in the political community, in ways structured by race and economic inequality; and the erosion of democratic norms. The current political circumstance threatens the American democratic order because of the interactive effects of institutions, identity, and norm-breaking.
Religion and Education in Romania: Social Mobilization and the “Shadow” of the European Court of Human Rights
Authors: Popa Mihai , Andreescu Liviu
Published: October 2018

In this article, we discuss the relation between the European Court of Human Rights (ECtHR) and its jurisprudence and social mobilizations around the place of religion in the society. We focus on the struggles to define the intersection of religion and public education in Romania after the fall of communism. We show that secularist and counter-secularist civil society activists contending for the place of religion in public education in this country have made strategic use of the ECtHR and its case law, both in legal battles and in debates within the national public sphere. We argue that, since references to the ECtHR and its jurisprudence can be used in discursive battles as a form of symbolic “capital”, the strategies of mobilizing actors are at times more important than the strict doctrinal content of the ECtHR's judgments for understanding if and how the ECtHR's “shadow” is cast over religion-related mobilizations.
Shifts in the Community Dynamics and Activity of Ammonia‐Oxidizing Prokaryotes Along the Yangtze Estuarine Salinity Gradient
Authors: Gao Juan , Hou Lijun , Zheng Yanling , Liu Min , Yin Guoyu , Yu Chendi , Gao Dengzhou
Published: October 2018

Ammonia oxidation, the first and rate‐limiting step in nitrification, plays a critical role in the nitrogen cycle. However, the links between the dynamics of ammonia‐oxidizing communities and ecosystem processes along the estuarine salinity gradient remain uncertain. In this study, we examined the diversity, abundance, and community structure of ammonia‐oxidizing prokaryotes, and the potential nitrification rates along the Yangtze estuarine salinity gradient. Phylogenetic analysis showed that the predominant ammonia‐oxidizing bacteria (AOB) and ammonia‐oxidizing archaea (AOA) fell within the Nitrosospira and Nitrosopumilus clusters, respectively. The AOB amoA gene abundance (4.67 × 105 to 3.90 × 107 copies per gram of dry sediment) outnumbered AOA (5.14 × 104 to 8.88 × 106 copies per gram of dry sediment). The potential nitrification rates varied between 0.13 and 0.63 μg N·g−1·day−1 and related only to AOA amoA gene abundance. Salinity had significant effects on AOA amoA gene abundance, nitrification rates, and the community structure of ammonia‐oxidizing prokaryotes. Principal coordinate analysis showed that the AOB amoA gene clones derived from the middle‐ and high‐salinity regions behaved as a cohesive group, while all the low‐salinity clone libraries were grouped together. Moreover, the distribution of AOA communities showed a distinct salinity differentiation. Overall, this study improves the understanding of the dynamic shifts in ammonia‐oxidizing microorganisms in the Yangtze Estuary.
Interdependencies and Risk to People and Critical Food, Energy, and Water Systems: 2013 Flood, Boulder, Colorado, USA
Authors: Romero‐Lankao Patricia , Norton Rachel
Published: October 2018

This paper examines the interdependencies mediating the cascading negative consequences triggered by the September 2013 flood, in Boulder, Colorado, USA. By illustrating the risks to people and critical food‐energy‐water systems of a low probability, high‐impact event, we draw lessons on what is likely to occur in the future. Other scholars have modeled the influence of interdependent infrastructures on cascading effects. But this is one of the first studies integrating stakeholders' understanding of the influence of interdependent actions, institutions, and infrastructures. These interdependencies create the conditions for vulnerability, which is a product of multiscale and dynamic sociodemographic, economic, technologic, environmental, and governance interactions. Political histories and historical decisions on where and how to design infrastructure exert a deep influence on short‐ and long‐term capacity to manage risk. Boulder's high socio‐institutional and learning capacity, while key, is not enough to influence integrative, transformative changes. Contrary to current approaches to nexus thinking, the regimes in which emergency and recovery actions are embedded are dynamically stable, thus imposing a logic for incremental change along established pathways of understanding and action. Our study offers some lessons on the challenges of bringing together diverse sectoral and jurisdictional sectors during and after an extreme event.
Evidence of Jet‐Scale Overturning Ocean Circulations in Argo Float Trajectories
Authors: Li Qian , Lee Sukyoung , Mazloff Matthew
Published: October 2018

In a recent study, it was proposed that Reynolds stress by oceanic mesoscale eddies not only drives jets such as Subantarctic Front but also can force overturning circulations that are composed of rising motion on the poleward flank and sinking motion on the equatorward flank of the jets. In that study, the thermally indirect, jet‐scale overturning circulations (JSOCs) were detected in an eddy‐resolving model simulation of the Southern Ocean. Here observational evidence of the existence of JSOCs is demonstrated by showing that the Argo floats tend to drift poleward across the jet with the maximum drift speed coinciding with the corresponding jet maximum. This finding has an implication for the observed deep mixed layer because it was previously shown that in the model the JSOCs play a key role in preconditioning the formation of a deep and narrow mixed layer at just ~1° north of the Subantarctic Front.
A Bimaterial Interface Along the Northern San Jacinto Fault Through Cajon Pass
Authors: Share Pieter‐Ewald , Ben‐Zion Yehuda
Published: October 2018

We investigate the existence of bimaterial interfaces along the San Jacinto fault zone (SJFZ) and the San Andreas fault (SAF) around their intersection at Cajon Pass (CP) to clarify if large earthquakes can rupture simultaneously parts of both faults. Analysis of fault zone head waves reveals a bimaterial interface along the northern SJFZ with a >7.5% velocity contrast (slower northeast side) that extends continuously through and perhaps slightly beyond CP. Other seismological studies show an opposite sense of velocity contrast across the nearby SAF. These observations, combined with expected properties of bimaterial ruptures, suggest that large earthquakes on the northern SJFZ are likely to propagate to the southeast and hence unlikely to trigger large SAF events. However, large earthquakes propagating on the SAF near CP can trigger continuing rupture on the SJFZ to the southeast. This inference is consistent with ruptures of large paleoseismic earthquakes and directivities of smaller events.
Seismic Anisotropy Reveals a Dynamic Link Between Adjacent Magmatic Segments Prior to Dyke Intrusion
Authors: Illsley‐Kemp Finnigan , Greenfield Tim , Keir Derek
Published: October 2018

Seismic anisotropy has increasingly been proposed as a tool in the monitoring of magmatic systems and potential forecasting of volcanic eruptions. We present a detailed study of how seismic anisotropy evolves in an active magmatic rift segment before, during, and after a dyke intrusion in the Afar depression, Ethiopia. Results show that seismic anisotropy prior to the dyke intrusion is controlled by a complex and deforming magma plumbing system beneath the adjacent Dabbahu and Manda‐Hararo magmatic segments. Approximately eight days prior to the dyke intrusion in the Dabbahu segment, the pattern of anisotropy, coupled with lower crustal seismicity, is best explained by the inflation of a lower crustal magma reservoir in the Manda‐Hararo segment. This is the only clearly observed precursory change in seismic anisotropy. During the dyke intrusion, the magnitude of seismic anisotropy increases twofold, before rapidly returning to predyke values once the intrusion has ended. Combining our observations with models of magmatically induced crustal stress, we propose that when the deep magma reservoir beneath the Dabbahu segment becomes overpressured, inflation is triggered in the magma reservoir of the neighboring Manda‐Hararo segment. This provides strong evidence for a hydraulic link between the deep magma systems of the neighboring rift segments and that magma reservoirs beneath the Dabbahu segment can be fed by the lateral flow of magma from an adjacent segment. Our results demonstrate that seismic anisotropy has the potential to be a powerful tool for monitoring deformation in the magma plumbing systems of active volcanoes.
An Improved Second‐Moment Closure Model for Langmuir Turbulence Conditions: Model Derivation and Validation
Authors: Yu W. , Song J. B. , Cao A. Z. , Yin B. S. , Guan S. D.
Published: October 2018

In this study, an improved second‐moment closure model, the so‐called k‐ω model, which takes into consideration the Langmuir turbulent effect in the transport equations of turbulent kinetic energy and turbulent frequency, was developed. The Langmuir turbulent effect was also included in the vertical eddy viscosity and diffusivity coefficient. Langmuir turbulence production, as well as buoyancy production, anisotropic production, and vorticity production induced by velocity shear, was included in the pressure covariance parameterization to derive the stability function. The Langmuir effect and relatively complete pressure covariance parameterization inclusion can account for the influences of Langmuir turbulence and stratification in the vertical eddy viscosity and vertical eddy diffusion coefficients. Based on the modified model, one‐dimensional numerical experiments for horizontally homogeneous flows were carried out. The results indicate that the modified model is more accurate than other models in terms of the vertical eddy viscosity, vertical turbulence velocity variance, kinetic energy, and mean velocity profile compared with the large eddy simulation results. The simulated sea surface temperature (SST) and mixed layer depth of the modified model were compared with observations at Ocean Station Papa. When considering Langmuir turbulent effects, the modified model overcomes the shortcoming that the simulated SST is higher than the observed SST. Numerical results indicate that the k‐ω model performs better than the k‐kl model, although both models consider the Langmuir turbulent effect in the simulation of upper mixing motions.
A Diel Method of Estimating Gross Primary Production: 1. Validation With a Realistic Numerical Model of Chesapeake Bay
Authors: Scully Malcolm E.
Published: October 2018

A method for estimating gross primary production (GPP) is presented and validated against a numerical model of Chesapeake Bay that includes realistic physical and biological forcing. The method statistically fits a photosynthesis‐irradiance response curve using the observed near‐surface time rate of change of dissolved oxygen and the incoming solar radiation, yielding estimates of the light‐saturated photosynthetic rate and the initial slope of the photosynthesis‐irradiance response curve. This allows estimation of GPP with 15‐day temporal resolution. The method is applied to the output from a numerical model that has high skill at reproducing both surface and near‐bottom dissolved oxygen variations observed in Chesapeake Bay in 2013. The rate of GPP predicted by the numerical model is known, as are the contributions from physical processes, allowing the proposed diel method to be rigorously assessed. At locations throughout the main stem of the Bay, the method accurately extracts the underlying rate of GPP, including pronounced seasonal variability and spatial variability. Errors associated with the method are primarily the result of contributions by the divergence in turbulent oxygen flux, which changes sign over the surface mixed layer. As a result, there is an optimal vertical location with minimal bias where application of the method is most accurate.
A Diel Method of Estimating Gross Primary Production: 2. Application to 7 Years of Near‐Surface Dissolved Oxygen Data in Chesapeake Bay
Authors: Scully Malcolm E.
Published: October 2018

A diel method for estimating gross primary production (GPP) is applied to nearly continuous measurements of near‐surface dissolved oxygen collected at seven locations throughout the main stem of Chesapeake Bay. The data were collected through the Chesapeake Bay Interpretive Buoy System and span the period 2010–2016. At all locations, GPP exhibits pronounced seasonal variability consistent temperature‐dependent phytoplankton growth. At the Susquehanna Buoy, which is located within the estuarine turbidity maximum, rates of GPP are negatively correlated with uncalibrated turbidity data consistent with light limitation at this location. The highest rates of GPP are located immediately down Bay from the estuarine turbidity maximum and decrease moving seaward consistent with nutrient limitation. Rates of GPP at the mouth (First Landing Buoy) are roughly a factor of 3 lower than the rates in the upper Bay (Patapsco). At interannual time scales, the summer (June–July) rate of GPP averaged over all stations is positively correlated (r2 = 0.62) with the March Susquehanna River discharge and a multiple regression model that includes spring river discharge, and summer water temperature can explain most (r2 = 0.88) of the interannual variance in the observed rate of GPP. The correlation with river discharge is consistent with an increase in productivity fueled by increased nutrient loading. More generally, the spatial and temporal patterns inferred using this method are consistent with our current understanding of primary production in the Bay, demonstrating the potential this method has for making highly resolved measurements in less well studied estuarine systems.
On the Mechanism of the Generation and Interannual Variations of the Summer Upwellings West and Southwest Off the Hainan Island
Authors: Li Yineng , Peng Shiqiu , Wang Jia , Yan Jing , Huang Hu
Published: October 2018

The generation and interannual variations of the upwellings west and southwest off the Hainan Island (hereafter denoted as UWHI and USWHI, respectively) detected from satellite‐derived sea surface temperature as well as the mechanism behind them are investigated using a 3‐D high‐resolution ocean model with a set of sensitivity experiments. The model is able to reproduce the upwellings with significant variations in the seasonal and interannual time scales. Results of sensitivity experiments show that the joint effect of tidal mixing and stratification is the main cause of the generation of both UWHI and USWHI in summer, and the offshore pattern of the upwelling centers is closely associated with that of high mixing rate centers where currents interact with steep bathymetry. In addition, the circulation changes induced by the joint effect of tidal mixing and stratification have significant impacts on the upwellings, especially on USWHI. For the interannual variations of both UWHI and USWHI, the changes of the along‐shore winds, the tidal mixing, and the boundary currents are the main causes of the variations; the weak tidal mixing, enhanced along‐shore winds, and strong boundary currents result in the weakest upwellings there in 1998, with the enhanced along‐shore wind being the largest contributor.
Seasonal Variability of the Mauritania Current and Hydrography at 18°N
Authors: Klenz T. , Dengler M. , Brandt P.
Published: October 2018

Extensive field campaigns in the Mauritanian upwelling region between 2005 and 2016 provide the database for analyzing the seasonal variability of the eastern boundary circulation (EBC) and associated water mass distribution at 18°N. The data set includes shipboard upper ocean current, hydrographic, and oxygen measurements from nine research cruises conducted during upwelling (December to April) and relaxation (May to July) seasons. During the upwelling season, the EBC closely resembles a classical eastern boundary current regime, with a poleward undercurrent flowing beneath an equatorward coastal jet. In contrast, elevated poleward flow exceeding 30 cm/s and extending from the surface down to 250‐m depth is observed during the relaxation season. The pronounced seasonal variability of the across‐shore structure of the EBC can be related to local wind forcing and is in general agreement with Sverdrup balance. The EBC transport is correlated to the wind stress curl leading the transport by 7 days. The short lead time suggests a fast response of locally forced waves adjusting the EBC to wind forcing. The seasonal and vertical water mass distribution is presented based on hydrographic observations. The meridional oxygen distribution and corresponding water mass partitioning into South and North Atlantic Central Water masses reveal a possible northerly ventilation pathway in the deeper layers of the central water stratum. Our results suggest that the poleward surface flow and the poleward undercurrent both are a consequence of the cyclonic wind stress curl forcing and thus propose to name it the Mauritania Current.
Wintertime Gas‐Particle Partitioning and Speciation of Inorganic Chlorine in the Lower Troposphere Over the Northeast United States and Coastal Ocean
Authors: Haskins Jessica D. , Jaeglé Lyatt , Shah Viral , Lee Ben H. , Lopez‐Hilfiker Felipe D. , Campuzano‐Jost Pedro , Schroder Jason C. , Day Douglas A. , Guo Hongyu , Sullivan Amy P. , Weber Rodney , Dibb Jack , Campos Teresa , Jimenez Jose L. , Brown Steven S. , Thornton Joel A.
Published: October 2018

The formation of photolabile chlorine reservoirs depend on how much chloride is available in the particle to react, which requires the chlorine partitioning to the particle in the troposphere to be well understood. However, limited measurements of gas and particle composition necessary to constrain this chemistry exist. We present measurements from the Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER) aircraft campaign that show inorganic tropospheric chlorine compounds (Cly) measured in the lower troposphere are dominated by HCl and PM4 particulate chloride (pCl−), with contributions from trace chlorine species like nitryl chloride (ClNO2), hypochlorous acid (HOCl), and molecular chlorine (Cl2). We observed elevated Cly mixing ratios over the ocean (540–625 pptv) compared to over land (178–225 pptv). Observations show 0–20% (0–0.2 μg/m3) of measured chlorine partitions into particles with a diameter less than 1 μm under typical WINTER conditions. The thermodynamic model, ISORROPIA II, overpredicts submicron pCl− by a factor of 2 but is brought into agreement, assuming a small fraction of unmeasured, refractory sea salt <0.1 μg/m3 exists. The model‐measurement disagreement could also be caused by an effective equilibrium constant for HCl that is too large. We derive a lower‐limit equilibrium function (Keq = 2.5 × 106 exp[5,208(1/T − 1/T0)] mol2·kg−2·atm−1) that lowers the model value's temperature dependency. This work provides constraints on Cly in the troposphere, addresses the sensitivity of chlorine partitioning to minor changes in environmental variables, and highlights the remaining questions interfering with our ability to correctly model pCl− concentrations.
Radiosondes Show That After Decades of Cooling, the Lower Stratosphere Is Now Warming
Authors: Philipona Rolf , Mears Carl , Fujiwara Masatomo , Jeannet Pierre , Thorne Peter , Bodeker Greg , Haimberger Leopold , Hervo Maxime , Popp Christoph , Romanens Gonzague , Steinbrecht Wolfgang , Stübi Rene , Van Malderen Roeland
Published: October 2018

Since the mid‐twentieth century, radiosonde and satellite measurements show that the troposphere has warmed and the stratosphere has cooled. These changes are primarily due to increasing concentrations of well‐mixed greenhouse gases and the depletion of stratospheric ozone. In response to continued greenhouse gas increases and stratospheric ozone depletion, climate models project continued tropospheric warming and stratospheric cooling over the coming decades. Global average satellite observations of lower stratospheric temperatures exhibit no significant trends since the turn of the century. In contrast, an analysis of vertically resolved radiosonde measurements from 60 stations shows an increase of lower stratospheric temperature since the turn of the century at altitudes between 15 and 30 km and over most continents. Trend estimates are somewhat sensitive to homogeneity assessment choices, but all investigated radiosonde data sets suggest a change from late twentieth century cooling to early 21st century warming in the lower stratosphere, which is consistent with a reversal from ozone depletion to recovery from the effects of ozone‐depleting substances. In comparison, satellite observations at the radiosonde locations show only minor early 21st century warming, possibly due to the compensating effects of continued cooling above the radiosonde altitude range.
Comparison of the Fast and Slow Climate Response to Three Radiation Management Geoengineering Schemes
Authors: Duan Lei , Cao Long , Bala Govindasamy , Caldeira Ken
Published: October 2018

Geoengineering has been proposed as a backup approach to rapidly cool the Earth and avoid damages associated with anthropogenic climate change. In this study, we use the NCAR Community Earth System Model to conduct a series of slab‐ocean and prescribed sea surface temperature simulations to investigate the climate response to three proposed radiation management geoengineering schemes: stratospheric aerosol increase (SAI), marine cloud brightening (MCB), and cirrus cloud thinning (CCT). Our simulations show that different amounts of radiative forcing are needed for these three schemes to compensate global mean warming induced by a doubling of atmospheric CO2. With radiative forcing defined in terms of top‐of‐atmosphere energy imbalances in prescribed sea surface temperature simulations with land temperature adjustments, radiative forcing efficacy for SAI is about 15% smaller than that of CO2, and the efficacy for MCB and CCT is about 10% larger than that of CO2. In our simulations, different forcing efficacies are associated with different feedback processes for these forcing agents. Also, these geoengineering schemes produce different land‐ocean temperature change contrasts. The apparent hydrological sensitivity, that is, change in equilibrium global mean precipitation per degree of equilibrium temperature change, differs substantially between CO2, SAI, MCB, and CCT forcings, which is mainly a result of different precipitation responses during fast adjustment. After removing the component of fast adjustment, the northward movement of the Intertropical Convergence Zone in response to these forcing agents is tightly related with changes in the interhemispheric energy exchange and hemispheric temperature gradient.
Long‐Range Correlation Analysis of Soil Temperature and Moisture on A'rou Hillsides, Babao River Basin
Authors: Zhang Ting , Shen Shi , Cheng Changxiu , Song Changqing , Ye Sijing
Published: October 2018

Studying the tendency of soil temperature and moisture can provide scientific support for setting soil parameters for land surface hydrological model. Previous research has shown that there is long‐range correlation of soil temperature or moisture; however, driving factors of long‐range correlation variations and the cross correlation between temperature and moisture under multiple timescales have rarely been discussed. To explore the driving factors, we compared long‐range correlation between shady and sunny slopes. Adaptive fractal analysis was utilized to analyze long‐range cross correlation (LRCC) and long‐range correlation (LRC). Experimental data were collected between 9 August 2013 and 3 December 2014 at A'rou observation stations, Babao River Basin. Results show that two slopes have some common characteristics. (1) Soil temperature and moisture display the consistent change. (2) The persistence intensity of moisture, temperature, and their interaction intensity change at 9, 6, and 6‐day timescales, respectively. (3) LRC and LRCC indices demonstrate the stratification heterogeneity. Results also show that LRC and LRCC indices on two slopes have differences. The soil system was stratified into three layers to explain these differences over large timescales. (1) At 4‐ to 20‐cm depth, with significant influence of solar radiation and evapotranspiration on sunny slope, moisture shows weaker persistence. There is stronger antipersistence of temperature and stronger hydrothermal interaction on sunny slope. (2) At 20‐ to 80‐cm depth, there is weaker persistence of soil moisture on shady slope because of unstable groundwater and side runoff supply. (3) At 80‐ to 160‐cm depth, with seasonal melt‐water effect on sunny slope, persistence of moisture was considerably weaker.
Temporal Trends in Absolute and Relative Extreme Temperature Events Across North America
Authors: Sheridan Scott C. , Lee Cameron C.
Published: October 2018

In this research, we define extreme temperature events using a recently defined excess heat factor, based on the exceedance of apparent temperature beyond the 95th percentile along with an acclimatization factor, to define extreme heat events (EHE). We extend the calculation to assess cold and develop relative metrics to complement the absolute metrics, where extremeness is based on conditions relative to season. We thus examine extreme cold events (ECE), relative extreme heat events, and relative extreme cold events in addition to EHE. We present a climatology of these variables for North America, followed by analyses of trends from 1980 to 2016. While EHE and ECE are found in the core of summer and winter, respectively, relative events tend to have a broader seasonality. Trends in relative extreme heat events and EHE are upward, and relative extreme cold events and ECE are downward; the relative events are changing more rapidly than the absolute events.
Thermal and Microphysical Effects of Ice Clouds on Torrential Rainfall Over Northern China
Authors: Zhu Haoran , Xu Huiyan , Li Xiaofan
Published: October 2018

Ice clouds are an important part of precipitation systems and their thermal (radiative and latent heat) and microphysical effects may impact rainfall. In this study, the thermal and microphysical effects of ice clouds on rainfall are investigated through the diagnostic analysis of rainfall and heat budgets of a torrential rainfall simulation in north China during July 2013. During evening, the maximum reduction in rainfall caused by the inclusion of the thermal effects of ice clouds is mainly associated with the inclusion of latent‐heat effects of ice clouds, which suppresses instability and upward motions. During early morning, the maximum increase in rainfall caused by the inclusion of the thermal effects of ice clouds is mainly related to the inclusion of radiative effects of ice clouds, which enhances radiative cooling in the upper troposphere and suppresses radiative cooling in the lower troposphere and thus increases instability and upward motions. The inclusion of microphysical effects of ice clouds increases rainfall directly by the inclusion of deposition and indirectly by the increase in condensation.
Measurement of Ionospheric Total Electron Content Using Single‐Frequency Geostationary Satellite Observations
Authors: Cooper C. , Mitchell C. N. , Wright C. J. , Jackson D. R. , Witvliet B. A.
Published: October 2018

The ionized upper portion of the atmosphere, the ionosphere, affects radio signals traveling between satellites and the ground. This degrades the performance of satellite navigation, surveillance, and communication systems. Techniques to measure and mitigate ionospheric effects and in particular to measure the total electron content (TEC) are therefore required. TEC is usually determined by analyzing the differential delay experienced by dual‐frequency signals. Here we demonstrate a technique which enables TEC to be derived using single‐frequency signals passing between geostationary satellites and terrestrial Global Positioning System (GPS) receivers. Geostationary satellites offer the key advantage that the raypaths are not moving and hence are easier to interpret than standard GPS TEC. Daily TEC time series are derived for three ground receivers from Europe over the year 2015. The technique is validated by correlation analysis both between pairs of ground receiver observations and between ground receivers and independent ionosonde observations. The correlation between pairs of receivers over a year shows good agreement. Good agreement was also seen between the TEC time series and ionosonde data, suggesting the technique is reliable and routinely produces realistic ionospheric information. The technique is not suitable for use on every GPS receiver type because drift in derived TEC values was observed for profiles calculated using receivers without links to highly stable clocks. The demonstrated technique has the potential to become a routine method to derive TEC, helping to map the ionosphere in real time and to mitigate ionospheric effects on radio systems.
Detection of Stress Anomaly Produced by Interaction of Compressive Fault Steps in the West Bohemia Swarm Region, Czech Republic
Authors: Vavryčuk Václav , Adamová Petra
Published: October 2018

Observations of the 2008–2014 seismic activity in West Bohemia, Czech Republic, provide evidence of interaction of compressive fault steps that created local stress anomaly and triggered a seismic sequence with exceptional properties. The West Bohemia is a geothermal area, characterized by persistent fluid‐driven seismicity in the form of earthquake swarms. The focal zone is formed by two weak and fluid‐eroded parallel strike‐slip faults with a step of about 200 m. The fault segments were activated successively by the 2008 and 2011 swarms with magnitudes of the strongest events of 3.8 and 3.7, respectively. In 2014, a fracture linking both segments was formed or activated by a mainshock‐aftershock sequence. The aftershock decay was very fast, and the focal mechanism of the strongest event with magnitude of 4.2 was inconsistent with the regional background stress. The stress inversion of 957 focal mechanisms revealed a stress anomaly characterized by interchanging theσ2andσ3principal stress axes in the area of fault interaction. The modeling of the Coulomb stress change confirmed that the stress anomaly could completely disturb the regional background stress and produce the rotation of the principal stress axes retrieved from focal mechanisms. The faults activated or newly formed within the compressive stress anomaly were of high strength, which caused the anomalous mainshock‐aftershock character of the 2014 activity and the rapid aftershock decay. Linking the two previously active isolated faults during the 2014 activity increased the expected moment magnitude Mwof a possible strongest earthquake from 5.0 to 5.4.
Edge-emitting polariton laser and amplifier based on a ZnO waveguide
Authors: Jamadi O. , Reveret F. , Disseix P. , Medard F. , Leymarie J. , Moreau A. , Solnyshkov D. , Deparis C. , Leroux M. , Cambril E. , Bouchoule S. , Zuniga-Perez J. , Malpuech G.
Published: October 2018

We demonstrate edge-emitting exciton-polariton (polariton) laser operation from 5 to 300 K and polariton amplifiers based on polariton modes within ZnO waveguides. The guided mode dispersion below and above the lasing threshold is directly measured using gratings placed on top of the sample, fully demonstrating the polaritonic nature of the lasing modes. The threshold is found to be smaller than that expected for radiative polaritons in planar ZnO microcavities below 150 K and comparable above. These results open up broad perspectives for guided polaritonics by enabling easier and more straightforward implementation of polariton integrated circuits that exploit fast propagating polaritons, and, possibly, topological protection.
Epigenetic intersection of BDNF Val66Met genotype with premenstrual dysphoric disorder transcriptome in a cross-species model of estradiol add-back
Authors: Marrocco Jordan , Einhorn Nathan R. , Petty Gordon H. , Li Howard , Dubey Neelima , Hoffman Jessica , Berman Karen F. , Goldman David , Lee Francis S. , Schmidt Peter J. , McEwen Bruce S.
Published: October 2018

Premenstrual dysphoric disorder (PMDD) affects over 5% of women, with symptoms similar to anxiety and major depression, and is associated with differential sensitivity to circulating ovarian hormones. Little is known about the genetic and epigenetic factors that increase the risk to develop PMDD. We report that 17β-estradiol (E2) affects the behavior and the epigenome in a mouse model carrying a single-nucleotide polymorphism of the brain-derived neurotrophic factor gene (BDNF Val66Met), in a way that recapitulates the hallmarks of PMDD. Ovariectomized mice heterozygous for the BDNF Met allele (Het-Met) and their matched wild-type (WT) mice were administered estradiol or vehicle in drinking water for 6 weeks. Using the open field and the splash test, we show that E2 add-back induces anxiety-like and depression-like behavior in Het-Met mice, but not in WT mice. RNA-seq of the ventral hippocampus (vHpc) highlights that E2-dependent gene expression is markedly different between WT mice and Het-Met mice. Through a comparative whole-genome RNA-seq analysis between mouse vHpc and lymphoblastoid cell line cultures from control women and women with PMDD, we discovered common epigenetic biomarkers that transcend species and cell types. Those genes include epigenetic modifiers of the ESC/E(Z) complex, an effector of response to ovarian steroids. Although the BDNF Met genotype intersects the behavioral and transcriptional traits of women with PMDD, we suggest that these similarities speak to the epigenetic factors by which ovarian steroids produce negative behavioral effects.
Structural reorganization of SHP2 by oncogenic mutations and implications for oncoprotein resistance to allosteric inhibition
Authors: LaRochelle Jonathan R. , Fodor Michelle , Vemulapalli Vidyasiri , Mohseni Morvarid , Wang Ping , Stams Travis , LaMarche Matthew J. , Chopra Rajiv , Acker Michael G. , Blacklow Stephen C.
Published: October 2018

Activating mutations in PTPN11, encoding the cytosolic protein tyrosine phosphatase SHP2, result in developmental disorders and act as oncogenic drivers in patients with hematologic cancers. The allosteric inhibitor SHP099 stabilizes the wild-type SHP2 enzyme in an autoinhibited conformation that is itself destabilized by oncogenic mutations. Here, we report the impact of the highly activated and most frequently observed mutation, E76K, on the structure of SHP2, and investigate the effect of E76K and other oncogenic mutations on allosteric inhibition by SHP099. SHP2E76K adopts an open conformation but can be restored to the closed, autoinhibited conformation, near-identical to the unoccupied wild-type enzyme, when complexed with SHP099. SHP099 inhibitory activity against oncogenic SHP2 variants in vitro and in cells scales inversely with the activating strength of the mutation, indicating that either oncoselective or vastly more potent inhibitors will be necessary to suppress oncogenic signaling by the most strongly activating SHP2 mutations in cancer.
Differential active site requirements for NDM-1 β-lactamase hydrolysis of carbapenem versus penicillin and cephalosporin antibiotics
Authors: Sun Zhizeng , Hu Liya , Sankaran Banumathi , Prasad B. V. Venkataram , Palzkill Timothy
Published: October 2018

New Delhi metallo-β-lactamase-1 exhibits a broad substrate profile for hydrolysis of the penicillin, cephalosporin and ‘last resort’ carbapenems, and thus confers bacterial resistance to nearly all β-lactam antibiotics. Here we address whether the high catalytic efficiency for hydrolysis of these diverse substrates is reflected by similar sequence and structural requirements for catalysis, i.e., whether the same catalytic machinery is used to achieve hydrolysis of each class. Deep sequencing of randomized single codon mutation libraries that were selected for resistance to representative antibiotics reveal stringent sequence requirements for carbapenem versus penicillin or cephalosporin hydrolysis. Further, the residue positions required for hydrolysis of penicillins and cephalosporins are a subset of those required for carbapenem hydrolysis. Thus, while a common core of residues is used for catalysis of all substrates, carbapenem hydrolysis requires an additional set of residues to achieve catalytic efficiency comparable to that for penicillins and cephalosporins.
Prefrontal projections to the thalamic nucleus reuniens mediate fear extinction
Authors: Ramanathan Karthik R. , Jin Jingji , Giustino Thomas F. , Payne Martin R. , Maren Stephen
Published: October 2018

The thalamic nucleus reuniens (RE) receives dense projections from the medial prefrontal cortex (mPFC), interconnects the mPFC and hippocampus, and may serve a pivotal role in regulating emotional learning and memory. Here we show that the RE and its mPFC afferents are critical for the extinction of Pavlovian fear memories in rats. Pharmacological inactivation of the RE during extinction learning or retrieval increases freezing to an extinguished conditioned stimulus (CS); renewal of fear outside the extinction context was unaffected. Suppression of fear in the extinction context is associated with an increase in c-fos expression and spike firing in RE neurons to the extinguished CS. The role for the RE in suppressing extinguished fear requires the mPFC, insofar as pharmacogenetically silencing mPFC to RE projections impairs the expression of extinction memory. These results reveal that mPFC-RE circuits inhibit the expression of fear, a function that is essential for adaptive emotional regulation.
The DNA binding landscape of the maize AUXIN RESPONSE FACTOR family
Authors: Galli Mary , Khakhar Arjun , Lu Zefu , Chen Zongliang , Sen Sidharth , Joshi Trupti , Nemhauser Jennifer L. , Schmitz Robert J. , Gallavotti Andrea
Published: October 2018

AUXIN RESPONSE FACTORS (ARFs) are plant-specific transcription factors (TFs) that couple perception of the hormone auxin to gene expression programs essential to all land plants. As with many large TF families, a key question is whether individual members determine developmental specificity by binding distinct target genes. We use DAP-seq to generate genome-wide in vitro TF:DNA interaction maps for fourteen maize ARFs from the evolutionarily conserved A and B clades. Comparative analysis reveal a high degree of binding site overlap for ARFs of the same clade, but largely distinct clade A and B binding. Many sites are however co-occupied by ARFs from both clades, suggesting transcriptional coordination for many genes. Among these, we investigate known QTLs and use machine learning to predict the impact of cis-regulatory variation. Overall, large-scale comparative analysis of ARF binding suggests that auxin response specificity may be determined by factors other than individual ARF binding site selection.
Author Correction: Salt-dependent Blood Pressure in Human Aldosterone Synthase-Transgenic Mice
Authors: Gu Huiying , Ma Zhizhong , Wang Jian , Zhu Timothy , Du Nicole , Shatara Adam , Yi Xin , Kowala Mark C. , Du Yansheng
Published: October 2018

A correction has been published and is appended to both the HTML and PDF versions of this paper. The error has not been fixed in the paper.
Author Correction: The role of the SWI/SNF chromatin remodeling complex in maintaining the stemness of glioma initiating cells
Authors: Hiramatsu Hiroaki , Kobayashi Kazuyoshi , Kobayashi Kyousuke , Haraguchi Takeshi , Ino Yasushi , Todo Tomoki , Iba Hideo
Published: October 2018

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
A modeling study of the Danish HIV epidemic in men who have sex with men: travel, pre-exposure prophylaxis and elimination
Authors: Palk Laurence , Gerstoft Jan , Obel Niels , Blower Sally
Published: October 2018

UNAIDS has identified the Danish HIV epidemic in men who have sex with men (MSM) as a priority for elimination. Incidence is close to the elimination threshold of one new infection per year per 1,000 individuals. However, surveillance data show that HIV strains are being imported into Denmark, mainly due to travel. We use a transmission model to predict (from 2018 to 2030) the impact of pre-exposure prophylaxis (PrEP) on incidence. Our model reflects the current epidemic and diagnosis rates in the Danish MSM community. We conduct a sensitivity analysis based on 20,000 simulations, and assume that PrEP coverage could range from zero to 50% and diagnosis rates increase up to three-fold. We predict that incidence will fall below the elimination threshold, even without the introduction of PrEP, reaching 0.87 (median, 95% Confidence Interval: 0.65–1.23) new infections per 1,000 MSM by 2030. PrEP could reduce incidence to well below the threshold, if it results in a significant increase in diagnosis rates and reduces the number of infections occurring abroad. The Danish Medicine Agency and Danish Health Authority have recommended introducing PrEP. Our study provides strong support for this recommendation, and shows the importance of Danish MSM using PrEP when abroad.
A task-experienced partner does not help dogs be as successful as wolves in a cooperative string-pulling task
Authors: Marshall-Pescini Sarah , Basin Camille , Range Friederike
Published: October 2018

Although theories of domestication have suggested that dogs evolved a greater capacity for tolerant and cooperative behaviour compared to their wild wolf cousins, the differences between wolves’ and free-ranging dogs’ social ecology, with wolves relying more on conspecific cooperation than dogs, would rather predict the opposite. In a cooperative task involving joint action on a rope to pull a tray forward, wolves systematically outperformed dogs. The dogs’ failure appeared largely due to tolerance issues, i.e. one partner avoiding interacting with the apparatus, when the other was engaged with it, rather than cognitive limitations. To verify this, in the current study we trained the dominant partner to become an ‘expert’ on the task thereby potentially enhancing their understanding that they ‘needed the partner to succeed’. Indeed both the duration of co-action on the apparatus and the success rate of dyads composed of an expert and an inexperienced dog was higher than dyads composed of two inexperienced partners. Nevertheless the dogs’ performance was substantially poorer than that of wolf dyads with equivalent experience, highlighting that despite the facilitating effect of the ‘expert’, cooperation on this task did not come easily to dogs. For both dogs and wolves, cooperation was facilitated by the closeness of the affiliative bond between individuals, but opposite rank effects emerged. Dogs further apart in rank were more successful co-operators, whereas in wolves, animals closer in rank had a higher cooperative success. The results further highlight the importance of the different socio-ecologies of wolves and dogs in understanding their behaviour.