Context.
Open clusters provide unambiguous clues to understand the evolution of
7
Li at the surface of low-mass stars and its possible correlation with stellar rotation, which is a challenge for both ...stellar hydrodynamics and Galactic chemical evolution.
Aims.
We aim to quantify the efficiency of the transport processes for both angular momentum and chemicals that are required to explain simultaneously the observed behaviour of surface
7
Li (and
9
Be) and rotation as well as the internal rotation profiles inferred from helio- and asteroseismology in F- and G-type main sequence stars.
Methods.
We apply the model for the transport of angular momentum and chemicals that we tailored in a previous work for solar-type stars to an extended range of initial masses and metallicities corresponding to F- an G-type stars in a sample of 20 Galactic open clusters. We evaluate its ability to explain the
7
Li,
9
Be, and rotation periods observations. This model includes atomic diffusion, rotation-induced processes (for which we tested different prescriptions for shear turbulence), penetrative convection with a rotational dependence, parametric viscosity and turbulence, and magnetic braking.
Results.
Over the entire range of masses, metallicities, and ages explored, we reproduce the evolution of the surface rotation rates and predict, for the first time, the observed anti-correlation between the surface rotation rate and
7
Li depletion as a consequence of the penetrative convection prescription. The
7
Li behaviour and its evolution with time is well reproduced for G-type stars. However, the ability of the model to reproduce the so-called
7
Li dip centred around ∼6600 K strongly depends on the adopted prescriptions for shear turbulence. It also requires a stellar mass dependence for the parametric viscosity adopted for the transport of angular momentum, similar to the behaviour predicted for the generation and luminosity of internal gravity waves generated by stellar convective envelopes. Finally, the model predicts internal rotation profiles in good agreement with asteroseismic constraints in main sequence stars.
Conclusions.
We provide an efficient way to model G-type stars of different ages and metallicities successfully. However, the
7
Li and
9
Be dip constraints urgently call for further hydrodynamical studies to better model turbulence in stars, and for the exploration of physical processes such as tachocline mixing for the transport of chemicals and internal gravity waves for the transport of angular momentum. Finally, additional data for the internal rotation and for
9
Be in main sequence low-mass stars are definitively needed.
The nature of the crystalline basement of the Ligurian-Provence back-arc (LPB) basin is a matter debate as it remains unexplored by direct drilling methods. Several models have been proposed for the ...lower crustal structure comprising hyperextended continental crust or serpentinized mantle. In this paper, a new Vp-Vs geophysical dataset and corresponding tomography are used to propose a new petrological model for the LPB basin and for the formation of the crust of this back-arc domain. By crossing values of Vp, Vs and Vp/Vs ratios, the Messinian salt layer can be clearly identified down to 5 km depth, which highlights salt diapir structures into its overlying sedimentary cover. The 7.5 km depth corresponds to the transition with a heterogeneous basaltic oceanic crust about 4.5–5 km thick, intruded by rounded felsic gabbro plutons and underplated by a more mafic/ultramafic gabbro. This latter results from fractional crystallization of a hydrous magma inherited from the melting of a supra-subduction mantle which interacted with fluids originating from the subducting Adria slab. These magmas can be traced at the surface by magnetic anomalies punctuating the studied profile. Those new data and observations lead to conclude that the crust of the LPB basin resulted from a fast oceanic accretion during the opening of the back-arc. Its nature remains comparable to an immature oceanic crust with an overall basaltic and gabbroic composition and appears devoid of any serpentinized exhumed mantle.
•Structure of Ligurian-Provence basin is investigated by S and P-wave tomography.•∼5km basaltic crust is underlain by unaltered peridotites.•Magnetic anomalies correspond to intrusion of felsic and underplated mafic gabbro.•Ligurian-Provence basin has opened in a context of fast oceanic accretion.
The European Alps are the site where classic geologic concepts such as nappe theory, continental subduction and slab breakoff have been first proposed. However, the deep tectonic structure of the ...Alps has long been poorly constrained by independent geophysical evidence. This review paper summarizes the main results of the CIFALPS passive seismic experiment, that was launched by Chinese, French and Italian scientists in the 2010s to provide new insights on the deep tectonic structure of the Alpine region. The application of a wide range of tomographic methods to the analysis of a single fossil subduction zone makes the CIFALPS experiment a potential reference case for the analysis of other orogenic belts. Major results include: (i) the first seismic evidence of European continental crust subducted into the Adriatic upper mantle, beneath the place where coesite was first recognized in continental (U)HP rocks in the Alps; (ii) evidence of a major involvement of the mantle wedge during (U)HP rock exhumation; (iii) evidence of a serpentinized plate interface favoring continental subduction; (iv) evidence of a continuous slab beneath the Western and Central Alps, ruling out the classic model of slab breakoff magmatism; (v) evidence of a polyphase development of anisotropic fabrics in the Alpine mantle, either representing active mantle flows or fossil fabrics inherited from previous rifting stages. Detection of these major tectonic features allows to propose interpretive geologic cross‐sections at the scale of the lithosphere and upper mantle, providing a baseline for future analyses of active continental margins.
Plain Language Summary
The European Alps are the site where classic geologic concepts such as nappe theory, continental subduction, and slab breakoff have been first proposed. However, the deep tectonic structure of the Alps has long been poorly constrained by independent geophysical evidence. This review paper summarizes the main results of the CIFALPS passive seismic experiment, which allows us to propose an updated image of the deep structure of the Alps at the scale of the lithosphere and the upper mantle. The concepts and ideas summarized in this article provide a baseline for further advances in the fields of Alpine tectonics and in the analysis of active continental margins more generally.
Key Points
Summary of the main results of the CIFALPS seismic experiment provides new insights on the deep tectonic structure of the Alpine region
Application of a wide range of tomographic methods and joint interpretation with geological and petrophysical data
Interpretive geologic cross‐sections at the scale of the lithosphere and the upper mantle
Context.
Transport processes occurring in the radiative interior of solar-type stars are evidenced by the surface variation of light elements, in particular
7
Li, and the evolution of their rotation ...rates. For the Sun, inversions of helioseismic data indicate that the radial profile of angular velocity in its radiative zone is nearly uniform, which implies the existence of angular momentum transport mechanisms that are efficient over evolutionary timescales. While there are many independent transport models for angular momentum and chemical species, there is a lack of self-consistent theories that permit stellar evolution models to simultaneously match the present-day observations of solar lithium abundances and radial rotation profiles.
Aims.
We explore how additional transport processes can improve the agreement between evolutionary models of rotating stars and observations for
7
Li depletion, the rotation evolution of solar-type stars, and the solar rotation profile.
Methods.
Models of solar-type stars are computed including atomic diffusion and rotation-induced mixing with the code STAREVOL. We explore different additional transport processes for chemicals and for angular momentum such as penetrative convection, tachocline mixing, and additional turbulence. We constrain the resulting models by simultaneously using the evolution of the surface rotation rate and
7
Li abundance in the solar-type stars of open clusters with different ages, and the solar surface and internal rotation profile as inverted from helioseismology when our models reach the age of the Sun.
Results.
We show the relevance of penetrative convection for the depletion of
7
Li in pre-main sequence and early main sequence stars. The rotational dependence of the depth of penetrative convection yields an anti-correlation between the initial rotation rate and
7
Li depletion in our models of solar-type stars that is in agreement with the observed trend. Simultaneously, the addition of an ad hoc vertical viscosity
ν
add
leads to efficient transport of angular momentum between the core and the envelope during the main sequence evolution and to solar-type models that match the observed profile of the Sun. We also self-consistently compute for the first time the thickness of the tachocline and find that it is compatible with helioseismic estimations at the age of the Sun, but we highlight that the associated turbulence does not allow the observed
7
Li depletion to be reproduced. The main sequence depletion of
7
Li in solar-type stars is only reproduced when adding a parametric turbulent mixing below the convective envelope.
Conclusions.
The need for additional transport processes in stellar evolution models for both chemicals and angular momentum in addition to atomic diffusion, meridional circulation, and turbulent shear is confirmed. We identify the rotational dependence of the penetrative convection as a key process. Two additional and distinct parametric turbulent mixing processes (one for angular momentum and one for chemicals) are required to simultaneously explain the observed surface
7
Li depletion and the solar internal rotation profile. We highlight the need of additional constraints for the internal rotation of young solar-type stars and also for the beryllium abundances of open clusters in order to test our predictions.
SUMMARY
A full understanding of the dynamics of mountain ranges such as the Alps requires the integration of available geological and geophysical knowledge into a lithospheric-scale 3-D geological ...model. As a first stage in the construction of this geo-model, we derive a new 3-D shear wave velocity model of the Alpine region, with a spatial resolution of a few tens of kilometres, making it possible to compare with geological maps. We use four years of continuous vertical-component seismic noise records to compute noise correlations between more than 950 permanent broad-band stations complemented by ∼600 temporary stations from the AlpArray sea-land seismic network and the Cifalps and EASI linear arrays. A specific pre-processing is applied to records of ocean–bottom seismometers in the Liguro-Provençal basin to clean them from instrumental and oceanic noises. We first perform a 2-D transdimensional inversion of the traveltimes of Rayleigh waves to compute group-velocity maps from 4 to $150\, \mathrm{ s}$. The data noise level treated as an unknown parameter is determined with a Hierarchical Bayes method. A Fast Marching Eikonal solver is used to update ray path geometries during the inversion. We use next the group-velocity maps and their uncertainties to derive a 3-D probabilistic Vs model. The probability distributions of Vs at depth and the probability of presence of an interface are estimated at each location by exploring a set of 130 million synthetic four-layer 1-D Vs models. The obtained probabilistic model is refined using a linearized inversion. Throughout the inversion for Vs, we include the water column where necessary. Our Vs model highlights strong along-strike changes of the lithospheric structure, particularly in the subduction complex between the European and Adriatic plates. In the South-Western Alps, our model confirms the existence of a low-velocity structure at $50-80\, \mathrm{ km}$ depth in the continuation of the European continental crust beneath the subduction wedge. This deep low-velocity anomaly progressively disappears towards the North-Western and Central Alps. The European crust includes lower crustal low-velocity zones and a Moho jump of $\sim \, 8-12$ km beneath the western boundary of the External Crystalline Massifs of the North-Western Alps. The striking fit between our Vs model and the receiver function migrated depth section along the Cifalps profile documents the reliability of the Vs model. In light of this reliability and with the aim to building a 3-D geological model, we re-examine the geological structures highlighted along the Cifalps profile.
Neurovascular flow diverters are flexible, braided stent-meshes for intracranial aneurysm treatment. We applied the dynamic push-pull technique to manipulate the flow-diverter mesh density at the ...aneurysm orifice to maximize flow diversion. This study investigated the hemodynamic impact of the dynamic push-pull technique on patient-specific aneurysms by using the developed high-fidelity virtual-stenting computational modeling technique combined with computational fluid dynamics.
We deployed 2 Pipeline Embolization Devices into 2 identical sidewall anterior cerebral artery aneurysm phantoms by using the dynamic push-pull technique with different delivery-wire advancements. We then numerically simulated these deployment processes and validated the simulated mesh geometry. Computational fluid dynamics analysis was performed to evaluate detailed hemodynamic changes by deployed flow diverters in the sidewall aneurysm and a fusiform basilar trunk aneurysm (deployments implemented previously). Images of manipulated flow diverter mesh from sample clinical cases were also evaluated.
The flow diverters deployed in silico accurately replicated in vitro geometries. Increased delivery wire advancement (21 versus 11 mm) by using a dynamic push-pull technique produced a higher mesh compaction at the aneurysm orifice (50% metal coverage versus 36%), which led to more effective aneurysmal inflow reduction (62% versus 50% in the sidewall aneurysm; 57% versus 36% in the fusiform aneurysm). The dynamic push-pull technique also caused relatively lower metal coverage along the parent vessel due to elongation of the flow diverter. High and low mesh compactions were also achieved for 2 real patients by using the dynamic push-pull technique.
The described dynamic push-pull technique increases metal coverage of pure braided flow diverters over the aneurysm orifice, thereby enhancing the intended flow diversion, while reducing metal coverage along the parent vessel to prevent flow reduction in nearby perforators.
An exome-sequencing study of families with multiple breast-cancer-affected individuals identified two families with XRCC2 mutations, one with a protein-truncating mutation and one with a probably ...deleterious missense mutation. We performed a population-based case-control mutation-screening study that identified six probably pathogenic coding variants in 1,308 cases with early-onset breast cancer and no variants in 1,120 controls (the severity grading was p < 0.02). We also performed additional mutation screening in 689 multiple-case families. We identified ten breast-cancer-affected families with protein-truncating or probably deleterious rare missense variants in XRCC2. Our identification of XRCC2 as a breast cancer susceptibility gene thus increases the proportion of breast cancers that are associated with homologous recombination-DNA-repair dysfunction and Fanconi anemia and could therefore benefit from specific targeted treatments such as PARP (poly ADP ribose polymerase) inhibitors. This study demonstrates the power of massively parallel sequencing for discovering susceptibility genes for common, complex diseases.
Context.
Asteroseismology provides a unique opportunity to probe the interiors of evolved stars and constrain their internal rotation. The correct reproduction of the core rotation evolution has not ...yet been achieved, although it is key to understanding the internal processes involved in low-mass stars.
Aims.
We explore the efficiency required to reproduce the general behaviour of the transport of angular momentum along the evolution in view of asteroseismic constraints from giant low-mass stars. We analyse the consequences and predictions for lithium and beryllium surface abundances from the main sequence to red giant phase.
Methods.
We computed a series of models, which included atomic diffusion, rotation-induced mixing, magnetic braking, and additional processes tailored for main sequence low-mass stars. We extended these models to more evolved phases and investigated an updated angular momentum transport by including a time-dependent extra viscosity related to the azimuthal magneto-rotational instability. We compared our predictions to the asteroseismic measurements of the core and surface rotation of a sample of sub-giant and red giant stars. We compared the model predictions for the lithium and beryllium surface evolution with the available observations.
Results.
We confirm that a time-dependent additional viscosity
ν
add
(
t
) is required to reproduce the general behaviour of the core rotation rate along successive stellar evolutionary phases given the dependence on the differential rotation and the mass. We show that it results in stronger lithium and beryllium depletions for low-mass stars over evolution. We confirm that predicted lithium abundances at the red giant bump by classical models, commonly used as references, cannot reproduce the lithium depletion along the main sequence and evolved phases of stellar evolution. We show that the observed amount of lithium of stars less massive than 1
M
⊙
leads to a discrepancy between model predictions and observations at the red giant bump.
Conclusions.
We show that a semi-parametric model can reproduce the rotational behaviour along the first phases of evolution well, with the exception of the sharp transition observed during the sub-giant phase. This suggests that two distinct transport processes may be involved. The processes required to transport chemicals during the main sequence phase and angular momentum until the red giant phase impact the lithium depletion all along the evolutionary duration. A good prediction of the lithium abundance at young phases places strong constraints on the predicted one at more evolved phases. It also highlights discrepancies between models and observations for the lowest mass stars and impacts the threshold that defines lithium-rich giant stars, showing that classical models tend to overestimate this threshold.
As an alternative to capacity expansion, various dynamic highway traffic control measures have been introduced. Ramp metering and variable speed limits are often considered to be effective dynamic ...highway control measures. Typically, these control measures have been employed in conjunction with either optimal control methods or online feedback control. One shortcoming of feedback control is that it provides no guarantee of optimality with respect to the chosen metering rate or speed limit. Optimal control approaches, on the other hand, are limited in respect of their applicability to large traffic networks due to their significant computational expense. Reinforcement learning is an alternative solution approach, in which an agent learns a near-optimal control strategy in an online manner, with a smaller computational overhead than those of optimal control approaches. In this paper an empirical case is made for the adoption of a decentralised reinforcement learning approach towards solving the control problems posed by both ramp metering and variable speed limits simultaneously, and in an online manner. The effectiveness of this approach is evaluated in the context of a microscopic traffic simulation model of a section of the N1 national highway outbound from Cape Town in South Africa’s Western Cape Province.
Abstract Background A tubo-ovarian abscess (TOA) is a serious complication of pelvic inflammatory disease (PID), predominantly polymicrobial and present in sexually active women. TOA in virginal ...adolescent females are extremely rare but have serious and lifelong consequences. Case A 13 y.o. virginal female presented to the Emergency Room of a tertiary care pediatric hospital with abdominal pain and vomiting. Imaging suggested bowel compromise with potential perforation. An exploratory laparotomy revealed TOA which grew Escherichia Coli . This is the first reported case of Escherichia Coli TOA due to suspected bowel translocation. Conclusion Review of the literature identified 8 cases of TOA in virginal adolescents. Given the severity of outcomes following TOA, this pathology should be considered in the differential diagnosis of virginal adolescents who present with fever and abdominal pain. If suspected, a prompt gynecology consult should be initiated, followed by a first line antibiotic therapy and when indicated, surgical drainage.
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