bluuebunny/crossref_metadata_2025_split huggingface dataset:
Uncertainty quantification of elastic material responses: testing, stochastic calibration and Bayesian model selection
Authors: Fitt Danielle , Wyatt Hayley , Woolley Thomas E. , Mihai L. Angela 
Published: November 2019

AbstractMotivated by the need to quantify uncertainties in the mechanical behaviour of solid materials, we perform simple uniaxial tensile tests on a manufactured rubber-like material that provide critical information regarding the variability in the constitutive responses between different specimens. Based on the experimental data, we construct stochastic homogeneous hyperelastic models where the parameters are described by spatially independent probability density functions at a macroscopic level. As more than one parametrised model is capable of capturing the observed material behaviour, we apply Baye theorem to select the model that is most likely to reproduce the data. Our analysis is fully tractable mathematically and builds directly on knowledge from deterministic finite elasticity. The proposed stochastic calibration and Bayesian model selection are generally applicable to more complex tests and materials.
The clustering of risk behaviours in adolescence and health consequences in middle age
Authors: Akasaki Mifuyu , Ploubidis George B. , Dodgeon Brian , Bonell Chris P. 
Published: November 2019

ABSTRACTIntroductionThere is increasing interest in the clustering of risk behaviours in adolescence. However, few studies have examined what clusters of risk behaviours exist among adolescents, their early‐life predictors, and their associations with later health.MethodsWe analysed data derived from 8754 participants (women 53.3%) in the 1970 British Cohort Study. Latent class analysis was used to identify clusters of risk behaviours at age 16. Regression modelling was then used to examine predictors of clusters and their consequences of risk behaviours and health outcomes at age 42.ResultsWe identified two latent classes: a risky‐behaviour (men: 20.0%, women: 23.6%) and less‐risky‐behaviour class. Among men, those in the risky‐behaviour class were more likely to report smoking, multiple binge drinking, sexual debut before 16, involvement in fights and delinquency than were women. Membership in risky‐behaviour class was mainly predicted by sociodemographic and parental risk behaviours and monitoring. The risky‐behaviour class at age 16 was associated with the following outcome age 42: smoking status (more strongly among women), excessive alcohol consumption (more strongly among men), worse self‐rated health (more strongly among men), and psychological distress (only among women).ConclusionsEngagement in multiple risk behaviours in adolescence is an important driver of health inequalities later in life. Early life intervention, for example via school‐based interventions, may be warranted for favourable lifelong health.
Simplicial complexity of surface groups
Authors: Borghini Eugenio , Minian Elías Gabriel 
Published: November 2019

AbstractThe simplicial complexity is an invariant for finitely presentable groups which was recently introduced by Babenko, Balacheff, and Bulteau to study systolic area. The simplicial complexity κ(G) was proved to be a good approximation of the systolic area σ(G) for large values of κ(G). In this paper we compute the simplicial complexity of all surface groups (both in the orientable and in the non-orientable case). This partially settles a problem raised by Babenko, Balacheff, and Bulteau. We also prove that κ(G * ℤ) = κ(G) for any surface group G. This provides the first partial evidence in favor of the conjecture of the stability of the simplicial complexity under free product with free groups. The general stability problem, both for simplicial complexity and for systolic area, remains open.
Before and After Bin ͑Ali : Comparing Two Attempts at Political Liberalization in Tunisia
Authors: Henneberg Sabina 
Published: November 2019

AbstractThis article examines changes in Tunisian political and societal life that allowed the country's second attempt at political opening (beginning in 2011) to introduce deeper, more long-lasting changes in its political system as compared to the first attempt (beginning in 1987).1The article argues that three such changes in particular—the increased role of regime moderates; the development of a network of civil society groups and political activists; and the use of inclusion, negotiation, and consensus—allowed the second attempt to unfold differently. The article also briefly discusses developments in the international context between the two attempts. The article contributes to existing studies of regime change and political transition as well as to historical considerations of Tunisian political developments more broadly.
Generative Modeling of InSAR Interferograms
Authors: Rongier Guillaume , Rude Cody , Herring Thomas , Pankratius Victor 
Published: November 2019

AbstractInterferometric synthetic aperture radar (InSAR) has become an essential technique to detect surface variations due to volcanoes, earthquakes, landslides, glaciers, and aquifers. However, Earth's ionosphere, atmosphere, vegetation, surface runoff, etc., introduce noise that requires post‐processing to separate its components. This work defines a generator to create interferograms that include each of those components. Our approach leverages deformation models with real data, either directly or through machine learning using geostatistical methods. These methods result from previous developments to more efficiently and better simulate spatial variables and could replace some statistical approaches used in InSAR processing. We illustrate the use of the generator to simulate an artificial interferogram based on the 2015 Illapel earthquake and discuss the improved performance offered by geostatistical approaches compared with classical statistical ones. The generator establishes a tool for multiple applications (1) to evaluate InSAR correction workflows in controlled scenarios with known ground truth; (2) to develop training sets and generative methods for machine learning algorithms; and (3) to educate on InSAR and its principles.
Earth's Van Allen Radiation Belts: From Discovery to the Van Allen Probes Era
Authors: Li W. , Hudson M.K. 
Published: November 2019

AbstractDiscovery of the Earth's Van Allen radiation belts by instruments flown on Explorer 1 in 1958 was the first major discovery of the Space Age. The observation of distinct inner and outer zones of trapped megaelectron volt (MeV) particles, primarily protons at low altitude and electrons at high altitude, led to early models for source and loss mechanisms including Cosmic Ray Albedo Neutron Decay for inner zone protons, radial diffusion for outer zone electrons and loss to the atmosphere due to pitch angle scattering. This scattering lowers the mirror altitude for particles in their bounce motion parallel to the Earth's magnetic field until they suffer collisional loss. A view of the belts as quasi‐static inner and outer zones of energetic particles with different sources was modified by observations made during the Solar Cycle 22 maximum in solar activity over 1989–1991. The dynamic variability of outer zone electrons was measured by the Combined Radiation Release and Effects Satellite launched in July 1990. This variability is caused by distinct types of heliospheric structure that vary with the solar cycle. The launch of the twin Van Allen Probes in August 2012 has provided much longer and more comprehensive measurements during the declining phase of Solar Cycle 24. Roughly half of moderate geomagnetic storms, determined by intensity of the ring current carried mostly by protons at hundreds of kiloelectron volts, produce an increase in trapped relativistic electron flux in the outer zone. Mechanisms for accelerating electrons of hundreds of electron volts stored in the tail region of the magnetosphere to MeVenergies in the trapping region are described in this review: prompt and diffusive radial transport and local acceleration driven by magnetospheric waves. Such waves also produce pitch angle scattering loss, as does outward radial transport, enhanced when the magnetosphere is compressed. While quasilinear simulations have been used to successfully reproduce many essential features of the radiation belt particle dynamics, nonlinear wave‐particle interactions are found to be potentially important for causing more rapid particle acceleration or precipitation. The findings on the fundamental physics of the Van Allen radiation belts potentially provide insights into understanding energetic particle dynamics at other magnetized planets in the solar system, exoplanets throughout the universe, and in astrophysical and laboratory plasmas. Computational radiation belt models have improved dramatically, particularly in the Van Allen Probes era, and assimilative forecasting of the state of the radiation belts has become more feasible. Moreover, machine learning techniques have been developed to specify and predict the state of the Van Allen radiation belts. Given the potential Space Weather impact of radiation belt variability on technological systems, these new radiation belt models are expected to play a critical role in our technological society in the future as much as meteorological models do today.
Longitudinal Variations of the Occurrence Probability of the Ionospheric F1 Layer Peak at Middle and High Latitudes
Authors: Li Zhenxing , Luan Xiaoli , Ren Dexin 
Published: November 2019

AbstractThis study focuses on the longitudinal variations of the ionospheric F1 layer occurrence probabilities from middle to high latitudes (40–70°) in the daytime in summer under low solar activity conditions. The ionospheric electron density profiles retrieved from the Constellation Observing System for Meteorology, Ionosphere, and Climate observations are used. The patterns of the F1 layer occurrence probabilities are constructed with latitude, longitude, and local time in both hemispheres. The results illustrate a new feature that the occurrence probability of the F1 layer changes with longitude in both hemispheres. Specifically, the F1 layer generally occurs more frequently in the longitudes within ~160°E–90°W at 40–70°N and within 0–150°E at 40–70°S. The peak occurrence probabilities occur around 150°W (>0.6) and 60°E (>0.8) in the Northern and Southern Hemispheres, respectively. The valleys with values near 0 are located at about 120°W at 40–70°S. A minor peak (~0.4) also occurs within ~0–90°E at 40–70°N. These locations depend on latitude and local time. A simulation using the Thermosphere Ionosphere Electrodynamics General Circulation Model （(TIEGCM）) reproduces the observed longitudinal pattern well. Further TIEGCM simulations show that the higher F1 layer occurrence probabilities can be largely explained by longitudinal variations of the O/N2 ratios and also that the dynamic processes, such as the neutral winds above the F1 layer, have additional contributions. These results reveal that the low O/N2 ratios deplete the ionospheric electron density above the F1 layer at middle and high latitudes and thus makes the F1 layer stand out.
Deposition Potential and Flow‐Response Dynamics of Emergent Sandbars in a Braided River
Authors: Alexander Jason S. , McElroy Brandon , Huzurbazar Snehalata , Elliott Caroline , Murr Marissa L. 
Published: November 2019

AbstractSandbars are ubiquitous in sandy‐braided rivers throughout the world. In the Great Plains of the United States, recovery and expansion of emergent sandbar habitat (ESH) has been a priority in lowland rivers where the natural extent of sandbars has been degraded. Recovery efforts are aimed at protection of populations of the interior least tern (Sterna antillarum) and piping plover (Charadrius melodus). But quantitative observations of deposition and erosion dynamics of populations of sandbars across long segments of rivers are rare. We present a three‐part case study which used Bayesian regression models to examine relations between hydrology, channel morphology, and ESH responses in the Platte River, eastern Nebraska. Logistic regression indicates presence of ESH is positively related to the Parker, (1976) stability criterion and a gradient in sediment transport mode, and negatively related to presence of vegetation. Hierarchical linear regression modeling shows direct coupling between sandbar top‐surface height and formative flood magnitude, but the gap between formative flood stage and sandbar top‐surface increases with increasing discharge. Finally, linear regression modeling of sandbar erosion demonstrates rates of ESH erosion are on the order of 10−1 ha/day during high‐flow periods and 10−2 during low‐flow periods, but sandbar persistence is largely a function of sandbar starting size. The collective observations highlight the importance of large floods (>3‐year recurrence) in creating very large sandbars that persist as high‐quality ESH over periods of years whereas lower‐magnitude, more‐frequent flood events create lower‐quality ESH that typically does not persist into the following nesting season.
The Effect of the 21 August 2017 Total Solar Eclipse on the Phase of VLF/LF Signals
Authors: Rozhnoi A. , Solovieva M. , Shalimov S. , Ouzounov D. , Gallagher P. , Verth G. , McCauley J. , Shelyag S. , Fedun V. 
Published: November 2019

AbstractAn experimental study of the phase and amplitude observations of sub‐ionospheric very low and low frequency (VLF/LF) signals is performed to analyze the response of the lower ionosphere during the 21 August 2017 total solar eclipse in the United States of America. Three different sub‐ionospheric wave paths are investigated. The length of the paths varies from 2,200 to 6,400 km, and the signal frequencies are 21.4, 25.2, and 40.75 kHz. The two paths cross the region of the total eclipse, and the third path is in the region of 40–60% of obscuration. None of the signals reveal any noticeable amplitude changes during the eclipse, while negative phase anomalies (from −33° to −95°) are detected for all three paths. It is shown that the effective reflection height of the ionosphere in low and middle latitudes is increased by about 3–5 km during the eclipse. Estimation of the electron density change in the lower ionosphere caused by the eclipse, using linear recombination law, shows that the average decrease is by 2.1 to 4.5 times.
Effects of a Realistic O+ Source on Modeling the Ring Current
Authors: Menz A. M. , Kistler L. M. , Mouikis C. G. , Spence H. E. , Henderson M. G. 
Published: November 2019

AbstractWe use the UNH‐IMEF electric field model to simulate the convection of O+ from the near‐earth plasma sheet into the ring current during the 17 March 2015 storm. Using Van Allen Probes data from the night side apogee, we reconstruct a realistic O+ source. Modeling this storm using the UNH‐IMEF electric field and a dipole magnetic field has previously been found to have good agreement. Using the realistic source along with drift times and charge exchange loss from these results, we model an inbound pass near the peak of the storm where O+ is increasingly dominant over H+. We find that the time‐varying realistic O+ source is necessary to reproduce the observed spectral features and the O+ pressure enhancements at low L‐shells, while our previous results showed that the H+ was able to be modeled sufficiently with a simple, unchanging boundary condition. Further, our results show that adiabatic convective transport of O+ from the near‐earth plasma sheet (L ~ 6) can explain the observed ring current enhancements.
Systematic Uncertainties in Plasma Parameters Reported by the Fast Plasma Investigation on NASA's Magnetospheric Multiscale Mission
Authors: Gershman Daniel J. , Dorelli John C. , Avanov Levon A. , Gliese Ulrik , Barrie Alexander , Schiff Conrad , Da Silva Daniel E. , Paterson William R. , Giles Barbara L. , Pollock Craig J. 
Published: November 2019

AbstractSystematic uncertainties in the conversion of measured counts to phase space density by charged particle instrumentation result in errors in reported plasma moments (e.g., density, velocity, and temperature). Unlike previous particle instrumentation that relied on a spacecraft spin to sample all look‐directions, the Fast Plasma Investigation (FPI) suite on NASA's Magnetospheric Multiscale mission nearly simultaneously images the full sky. This configuration results in unprecedented time resolution but also introduces the possibility of spin tones in plasma moments, in particular electron bulk velocity. Here we characterize the effect of systematic linear errors of corrected FPI phase space densities on its reported plasma moments. We find that the flat‐fielding correction factors (i.e., scale factor errors) of FPI are typically accurate to within a few percent but can nonetheless result in significant spin tones in magnetospheric plasmas.
A Statistical Study of Pi2 Pulsations Observed in the Upper Ionosphere Using Swarm Magnetic Field Data
Authors: Park Jae‐Hee , Kim Khan‐Hyuk , Kwon Hyuck‐Jin , Jee Geonhwa , Hwang Junga 
Published: November 2019

AbstractThe properties of Pi2 pulsations observed in the upper ionosphere are studied using magnetic field data acquired by the Swarm A spacecraft in low Earth orbit and at the low‐latitude Bohyun ground station (BOH, L=1.3) for January 2014 to June 2015. From time intervals when Swarm A was on the nightside (magnetic local time (MLT) = 1800–0600 hr) and the BOH station was near midnight (MLT = 2100–0300 hr), we identified 621 Pi2 events in the horizontal H component of the BOH data. For each event we examined the coherence between the horizontal H component on the ground and the Bx (radial), By (azimuthal), or Bz (compressional) components at Swarm A. Out of 621 events, the Bx−H high‐coherence (> 0.7) events are ∼6%, the By−H high‐coherence events are ∼2%, and the Bz−H high‐coherence events are ∼25%. The ground satellite high‐coherence events occurred when the spacecraft was located at magnetic latitudes between −50° and 50°. Using the ground satellite high‐coherence events, we statistically examined the latitudinal structure of the relative amplitude and phase of the ionospheric Pi2 pulsations and found that their latitudinal variations is consistent with the north‐south mode structure expected from the plasmaspheric resonance model. Our statistical results indicate that the source of ionospheric Pi2 pulsations is the plasmaspheric resonance.
Late Paleozoic Exhumation of the West Junggar Mountains, NW China
Authors: Gillespie Jack , Glorie Stijn , Jepson Gilby , Xiao Wenjiao , Collins Alan S. 
Published: November 2019

AbstractThe Tianshan and Altai mountain belts dominate the present‐day topography of central Asia and are major constituents of the Central Asian Orogenic Belt. These mountain belts have been extensively studied using low‐temperature thermochronology to understand their uplift and exhumation history. In comparison, few studies have focused on the spatial extent and timing of intracontinental deformation in the intervening ranges, such as the West Junggar Mountains. Apatite fission track (AFT) and apatite U‐Pb dating of igneous samples from the West Junggar Mountains reveals AFT central ages ranging from latest Carboniferous to Middle Jurassic and mean confined track lengths between 14.1 and 12.0 µm, which are negatively correlating to AFT central ages. Apatite U‐Pb dating produced mid‐Carboniferous‐early Permian ages within uncertainty of zircon U‐Pb crystallization ages, indicating cooling to below ∼450–550 °C immediately following emplacement. Thermal history modeling of our AFT data combined with published (U‐Th)/He data predicts rapid cooling to <60 °C during the early‐middle Permian (285–260 Ma), followed by slower cooling rates during the Mesozoic‐Cenozoic. The rapid cooling event coincides with (1) the timing of major basinward thrusting in the Junggar Basin adjacent to the study area and (2) exhumation in the Chinese Altai to the north. In contrast to previous studies, our results imply that the West Junggar Mountains do not record significant exhumation during the Mesozoic‐Cenozoic. This suggests that Mesozoic deformation of the Central Asian Orogenic Belt was less pervasive and widespread than previously assumed.
Modeling the Seismic Response of Unstable Rock Mass With Deep Compliant Fractures
Authors: Burjánek Jan , Kleinbrod Ulrike , Fäh Donat 
Published: November 2019

AbstractAn experimental quantification of the strength and volume of real, heterogeneous, fractured rock masses is crucial when assessing rock slope stability. In order to quantitatively characterize the internal structure of fractured rock slopes, we present three‐dimensional numerical simulations of seismic wave propagation and compare with observations. We introduce a simple, effective model for fractured rock mass, which can easily be applied to simulate weak‐motion seismic wave propagation. The macroscopic compliant fractures cutting the rock mass are modeled as finite‐width zones of reduced elastic parameters characterized by shear and normal stiffness. The widths of such zones are not fixed and can be adjusted to fit the grid step in the numerical method. The proposed rock mass model is applied and tested for the Walkerschmatt site in southwest Switzerland. Synthetic ambient vibrations are generated using a finite‐difference method for the fractured rock mass, shaped by the real terrain geometry, and compared with the measurements. The observed seismic response is satisfactorily reproduced in a broad frequency range (0.5–10 Hz). The synthetized response is primarily controlled by the stiffness, depth, number of fractures, and inertial mass of the fractured rock. The simulated amplification and ground‐motion directionality correspond with the observed levels, unless (1) the simplified cracks reach depths of 200–300 m; and (2) the fracture network is larger with respect to the mapped network. This illustrates the potential of ambient vibration methods in combination with numerical simulations to infer depth, volume, and mechanical characteristics of slope instability.