The magnetic‐field‐dependent spin ordering of strained BiFeO3 films is determined using nuclear resonant scattering and Raman spectroscopy. The critical field required to destroy the cycloidal ...modulation of the Fe spins is found to be significantly lower than in the bulk, with appealing implications for field‐controlled spintronic and magnonic devices.
The gas-phase nitrate radical (NO3⚫) initiated oxidation of limonene can produce organic nitrate species with varying physical properties. Low-volatility products can contribute to secondary organic ...aerosol (SOA) formation and organic nitrates may serve as a NOx reservoir, which could be especially important in regions with high biogenic emissions. This work presents the measurement results from flow reactor studies on the reaction of NO3⚫ with limonene using a High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS) combined with a Filter Inlet for Gases and AEROsols (FIGAERO). Major condensed-phase species were compared to those in the Master Chemical Mechanism (MCM) limonene mechanism, and many non-listed species were identified. The volatility properties of the most prevalent organic nitrates in the produced SOA were determined. Analysis of multiple experiments resulted in the identification of several dominant species (including C10H15NO6, C10H17NO6, C8H11NO6, C10H17NO7, and C9H13NO7) that occurred in the SOA under all conditions considered. Additionally, the formation of dimers was consistently observed and these species resided almost completely in the particle phase. The identities of these species are discussed, and formation mechanisms are proposed. Cluster analysis of the desorption temperatures corresponding to the analyzed particle-phase species yielded at least five distinct groupings based on a combination of molecular weight and desorption profile. Overall, the results indicate that the oxidation of limonene by NO3⚫ produces a complex mixture of highly oxygenated monomer and dimer products that contribute to SOA formation.
Assessing the size of a former ocean of which only remnants are found in mountain belts is challenging but crucial to understanding subduction and exhumation processes. Here we present new ...constraints on the opening and width of the Piemont–Liguria (PL) Ocean, known as the Alpine Tethys together with the Valais Basin. We use a regional tectonic reconstruction of the Western Mediterranean–Alpine area, implemented into a global plate motion model with lithospheric deformation, and 2D thermo-mechanical modeling of the rifting phase to test our kinematic reconstructions for geodynamic consistency. Our model fits well with independent datasets (i.e., ages of syn-rift sediments, rift-related fault activity, and mafic rocks) and shows that, between Europe and northern Adria, the PL Basin opened in four stages: (1) rifting of the proximal continental margin in the Early Jurassic (200–180 Ma), (2) hyper-extension of the distal margin in the Early to Middle Jurassic (180–165 Ma), (3) ocean–continent transition (OCT) formation with mantle exhumation and MORB-type magmatism in the Middle–Late Jurassic (165–154 Ma), and (4) breakup and mature oceanic spreading mostly in the Late Jurassic (154–145 Ma). Spreading was slow to ultra-slow (max. 22 mm yr−1, full rate) and decreased to ∼5 mm yr−1 after 145 Ma while completely ceasing at about 130 Ma due to the motion of Iberia relative to Europe during the opening of the North Atlantic. The final width of the PL mature (“true”) oceanic crust reached a maximum of 250 km along a NW–SE transect between Europe and northwestern Adria. Plate convergence along that same transect has reached 680 km since 84 Ma (420 km between 84–35 Ma, 260 km between 35–0 Ma), which greatly exceeds the width of the ocean. We suggest that at least 63 % of the subducted and accreted material was highly thinned continental lithosphere and most of the Alpine Tethys units exhumed today derived from OCT zones. Our work highlights the significant proportion of distal rifted continental margins involved in subduction and exhumation processes and provides quantitative estimates for future geodynamic modeling and a better understanding of the Alpine Orogeny.
Organosulfates (OSs) with ambiguous formation mechanisms are a potential source of missing secondary organic aerosol (SOA) in current atmospheric models. In this study, we chemically characterized ...OSs and nitrooxy-OSs (NOSs) formed under the influence of biogenic emissions and anthropogenic pollutants (e.g., NOx, SO42−) in summer in Beijing. An ultrahigh-resolution mass spectrometer equipped with an electrospray ionization source was applied to examine the overall molecular composition of S-containing organics. The number and intensities of S-containing organics, the majority of which could be assigned as OSs and NOSs, increased significantly during pollution episodes, which indicated their importance for SOA accumulation. To further investigate the distribution and formation of OSs and NOSs, high-performance liquid chromatography coupled with mass spectrometry was employed to quantify 10 OSs and 3 NOS species. The total concentrations of quantified OSs and NOSs were 41.4 and 13.8 ng m−3, respectively. Glycolic acid sulfate was the most abundant species among all the quantified species, followed by monoterpene NOSs (C10H16NO7S−). The total concentration of three isoprene OSs was 14.8 ng m−3 and the isoprene OSs formed via the HO2 channel were higher than those formed via the NO ∕ NO2 channel. The OS concentration coincided with the increase in acidic sulfate aerosols, aerosol acidity, and liquid water content (LWC), indicating the acid-catalyzed aqueous-phase formation of OSs in the presence of acidic sulfate aerosols. When sulfate dominated the accumulation of secondary inorganic aerosols (SIAs; sulfate, nitrate, and ammonium; SO42− ∕ SIA > 0.5), OS formation would obviously be promoted as the increasing of acidic sulfate aerosols, aerosol LWC, and acidity (pH < 2.8). Otherwise, acid-catalyzed OS formation would be limited by lower aerosol acidity when nitrate dominated the SIA accumulation. The nighttime enhancement of monoterpene NOSs suggested their formation via the nighttime NO3-initiated oxidation of monoterpene under high-NOx conditions. However, isoprene NOSs are presumed to form via acid-catalyzed chemistry or reactive uptake of oxidation products of isoprene. This study provides direct observational evidence and highlights the secondary formation of OSs and NOSs via the interaction between biogenic precursors and anthropogenic pollutants (NOx, SO2, and SO42−). The results imply that future reduction in anthropogenic emissions can help to reduce the biogenic SOA burden in Beijing or other areas impacted by both biogenic emissions and anthropogenic pollutants.
Nocturnal reactive nitrogen compounds play an important role in regional air pollution. Here we present the measurements of dinitrogen pentoxide (N2O5) associated with nitryl chloride (ClNO2) and ...particulate nitrate (pNO3-) at a suburban site of Beijing in the summer of 2016. High levels of N2O5 and ClNO2 were observed in the outflow of the urban Beijing air masses, with 1 min average maxima of 937 and 2900 pptv, respectively. The N2O5 uptake coefficients, γ, and ClNO2 yield, f, were experimentally determined from the observed parameters. The N2O5 uptake coefficient ranged from 0.012 to 0.055, with an average of 0.034 ± 0.018, which is in the upper range of previous field studies reported in North America and Europe but is a moderate value in the North China Plain (NCP), which reflects efficient N2O5 heterogeneous processes in Beijing. The ClNO2 yield exhibited high variability, with a range of 0.50 to unity and an average of 0.73 ± 0.25. The concentration of the nitrate radical (NO3) was calculated assuming that the thermal equilibrium between NO3 and N2O5 was maintained. In NOx-rich air masses, the oxidation of nocturnal biogenic volatile organic compounds (BVOCs) was dominated by NO3 rather than O3. The production rate of organic nitrate (ON) via NO3 + BVOCs was significant, with an average of 0.10 ± 0.07 ppbv h−1. We highlight the importance of NO3 oxidation of VOCs in the formation of ON and subsequent secondary organic aerosols in summer in Beijing.
Global deep‐time plate motion models have traditionally followed a classical rigid plate approach, even though plate deformation is known to be significant. Here we present a global Mesozoic–Cenozoic ...deforming plate motion model that captures the progressive extension of all continental margins since the initiation of rifting within Pangea at ~240 Ma. The model also includes major failed continental rifts and compressional deformation along collision zones. The outlines and timing of regional deformation episodes are reconstructed from a wealth of published regional tectonic models and associated geological and geophysical data. We reconstruct absolute plate motions in a mantle reference frame with a joint global inversion using hot spot tracks for the last 80 million years and minimizing global trench migration velocities and net lithospheric rotation. In our optimized model, net rotation is consistently below 0.2°/Myr, and trench migration scatter is substantially reduced. Distributed plate deformation reaches a Mesozoic peak of 30 × 106 km2 in the Late Jurassic (~160–155 Ma), driven by a vast network of rift systems. After a mid‐Cretaceous drop in deformation, it reaches a high of 48 x 106 km2 in the Late Eocene (~35 Ma), driven by the progressive growth of plate collisions and the formation of new rift systems. About a third of the continental crustal area has been deformed since 240 Ma, partitioned roughly into 65% extension and 35% compression. This community plate model provides a framework for building detailed regional deforming plate networks and form a constraint for models of basin evolution and the plate‐mantle system.
Key Points
We present a plate motion model including distributed deformation from the Triassic to the present
The model includes most major rifts and orogens formed since the breakup of the supercontinent Pangea
Our optimized mantle reference frame minimizes trench migration and net rotation
A new kinematic reconstruction that incorporates estimates of post‐20 Ma shortening and extension in the Apennines, Alps, Dinarides, and Sicily Channel Rift Zone (SCRZ) reveals that the Adriatic ...microplate (Adria) rotated counterclockwise as it subducted beneath the European Plate to the west and to the east, while indenting the Alps to the north. Minimum and maximum amounts of rotation are derived by using, respectively, estimates of crustal extension along the SCRZ (minimum of 30 km) combined with crustal shortening in the Eastern Alps (minimum of 115 km) and a maximum amount (140 km) of convergence between Adria and Moesia across the southern Dinarides and Carpatho‐Balkan orogens. When combined with Neogene convergence in the Western Alps, the best fit of available structural data constrains Adria to have moved 113 km to the NW (azimuth 325°) while rotating 5 ± 3° counterclockwise relative to Europe since 20 Ma. Amounts of plate convergence predicted by our new model exceed Neogene shortening estimates of several tens of kilometers in both the Apennines and Dinarides. We attribute this difference to crust‐mantle decoupling (delamination) during rollback in the Apennines and to distributed deformation related to the northward motion of the Dacia Unit between the southern Dinarides and Europe (Moesia). Neogene motion of Adria resulted from a combination of Africa pushing from the south, the Adriatic‐Hellenides slab pulling to the northeast, and crustal wedging in the Western Alps, which acted as a pivot and stopped farther northwestward motion of Adria relative to Europe.
Key Points
Adria has rotated 5 ± 3° counterclockwise and translated 113 km to the NW (azimuth 325°) relative to Europe since 20 Ma
Adria motion was associated with 110 km convergence relative to Moesia, 125 km in Eastern Alps, and 60 km of extension in Sicily Channel
Differences between amounts of shortening and plate convergence suggest crust‐mantle decoupling at active Adria‐Europe boundaries
Nitro-aromatic compounds (NACs) were measured hourly at a rural site in
China during wintertime to monitor the changes due to local and regional
impacts of biomass burning (BB). Concurrent and ...continuous measurements of
the concentrations of 16 NACs in the gas and particle phases were performed
with a time-of-flight chemical ionization mass spectrometer (CIMS) equipped
with a Filter Inlet for
Gases and AEROsols (FIGAERO) unit using iodide as the
reagent ion. NACs accounted for <2 % of the mass concentration of
organic matter (OM) and total particulate matter (PM), but the total
particle mass concentrations of these compounds can reach as high as 1000 ng m−3 (299 ng m−3 avg), suggesting that they may contribute
significantly to the radiative forcing effects of atmospheric particles.
Levels of gas-phase NACs were highest during the daytime (15:00–16:00 local
time, LT), with a smaller night-time peak around 20:00 LT. Box-model
simulations showed that this occurred because the rate of NAC production
from gas-phase sources exceeded the rate of loss, which occurred mainly via
the OH reaction and to a lesser degree via photolysis. Data gathered during
extended periods with high contributions from primary BB sources (resulting
in 40 %–60 % increases in NAC concentrations) were used to characterize
individual NACs with respect to gas–particle partitioning and the
contributions of regional secondary processes (i.e. photochemical smog). On
days without extensive BB, secondary formation was the dominant source of
NACs, and NAC levels correlated strongly with the ambient ozone
concentration. Analyses of individual NACs in the regionally aged plumes
sampled on these days allowed precursors such as phenol and catechol to be
linked to their NAC derivatives (i.e. nitrophenol and nitrocatechol).
Correlation analysis using the high time resolution data and box-model
simulation results constrained the relationships between these compounds and
demonstrated the contribution of secondary formation processes. Furthermore,
13 of 16 NACS were classified according to primary or secondary formation
process. Primary emission was the dominant source (accounting for 60 %–70 %
of the measured concentrations) of 5 of the 16 studied NACs, but secondary
formation was also a significant source. Photochemical smog thus has
important effects on brown carbon levels even during wintertime periods
dominated by primary air pollution in rural China.
Vascular complications (VCs) occurring in transcatheter aortic valve implantation (TAVI) procedures have frequently been reported in the past. Considering significant technical improvements in ...delivery systems and vascular closure devices, the goal of this study was to determine the incidence, impact, and prognostic factors of VCs in a recent real-world cohort.
We report a bicentric prospective analysis of 479 consecutive patients who underwent TAVI between January 2017 and December 2017. VCs were defined according to criteria set out by the Valve Academic Research Consortium (VARC)-2.
The incidence of VCs was 26.1% (n = 125 patients), of which 2.9% were major (n = 14) and 23.2% were minor (n = 111). VCs were related to the primary puncture point in 69% of cases compared with 31% at the secondary puncture site. Treatments implemented were medical in 76% of cases and surgical in 24% of cases. The risk factors for VCs were as follows: iliac morphology score, sheath to iliofemoral artery ratio (SIFAR), and moderate-severe iliofemoral calcifications or tortuosity. In the case of major VCs, only sheath to iliofemoral artery ratio was a risk factor. Major VCs significantly increased intrahospital mortality (30.7% vs 1.1% for minor VCs and 1.3% for no VCs; log-rank, P < .0001) and 1-year mortality (40.6% vs 5.6% for minor VCs and 5.6% for no VCs; log-rank, P < .0001).
Using strictly VARC-2 end point definitions, more than one-quarter of TAVI procedures were associated with VCs, primarily minor ones. Secondary puncture points were responsible for one-third of VCs and should therefore also be actively monitored. Major VCs have a significant impact on short-term and midterm survival.
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