Previous 2D Models Research Articles

Impact of nuclear heating distribution on the structural behavior of ITER first wall panel 11

The ITER blanket system safeguards the Tokamak's Vacuum Vessel and ex-vessel components from thermal and nuclear loads induced by the plasma. It comprises two parts: the First Wall panel facing the plasma and the Shield Block that provides the bulk of the shielding. The First Wall panels consist of Beryllium tiles on a CuCrZr layer, supported by stainless-steel structures which are cooled using a pressurized water circuit at 40 bar with an inlet temperature of 70 °C.Fusion for Energy has updated the thermal and mechanical analyses of ITER First Wall Panel 11 in preparation for the serial manufacturing. The panel will face heat flux up to 2 MW/m2 from plasma radiation, in addition to the volumetric nuclear heating, and the electromagnetic loads. A model with an enhanced detailed 3D geometry and heterogeneous materials indicates a 25% reduction of the deposited heating compared to the previous 2D model, from 625.4 kW (2D) to 455.4 kW (3D).The study embraces numerous thermal and mechanical analyses using Ansys software v19.2, incorporating 2D and 3D nuclear heating data. Responses are then compared and thus the possible impact of the two distributions on the thermal and mechanical behavior of the Fist Wall Panel 11 is assessed.

Reestimation of slab dehydration fronts in Kuril-Kamchatka using updated global subduction zone thermal structures

Previous subduction thermal models are inconsistent with the values of forearc heat flow (50-140 mW/m2) and global P‒T conditions of exhumed rocks, both suggesting a shallow environment 200-300°C warmer than model predictions. Here, we revaluate these problems in Kuril-Kamchatka using 3D thermomechanical modeling that satisfies the observed subduction history and slab geometry, while our refined 3D slab thermal state is warmer than that predicted by previous 2D models and better matches observational constraints. We show that warmer slabs create hierarchical slab dehydration fronts at various forearc depths, causing fast and slow subduction earthquakes. We conclude that fast-to-slow subduction earthquakes all play a key role in balancing plate coupling energy release on megathrusts trenchward of high P-T volcanism.

Exploration of Next-Generation Reinforced Concrete Corrosion Modeling with Interdependent Initiation and Propagation Stages

Most damage prediction models for reinforcing steel in concrete treat the corrosion initiation stage as being nearly independent of the propagation stage elsewhere in the system. A next-generation chloride-induced corrosion interdependent model addresses those interactions by incorporating the corrosion prevention effect of the local potential drop caused by prior active-to-passive transitions in nearby steel portions. The effect of this potential-dependent threshold (PDT) approach was examined in a 3D realization, confirming and expanding conclusions from previous 1D and 2D models. Exploratory analysis was conducted for model result sensitivity to time step duration and activation zone size. It was found that the main outcome—a strongly lowered long-term damage projection when PDT is taken into consideration was reasonably robust to changes in those variables. The precise damage amount forecast was however sensitive to an extent that needs more detailed analysis. Sensitivity to time step choice appears to be resolvable in the limit, but the selection of appropriate activation zone size needs addressing in future work.

A Parameterized Linear 3D Magnetic Equivalent Circuit for Analysis and Design of Radial Flux Magnetic Gears–Part I: Implementation

Magnetic gears can perform the same function as mechanical gears with the added benefits inherent to contactless power transfer. However, quick and accurate analysis tools are required for magnetic gears to reach their full potential. As end effects can significantly impact the slip torque of a magnetic gear, 2D models often overestimate the slip torques, so 3D models are frequently required. Therefore, this paper proposes a 3D linear Magnetic Equivalent Circuit (MEC) or reluctance network model of radial flux magnetic gears with surface mounted magnets. This is an extension of a previously developed 2D MEC model, and, like the previous 2D model, it is thoroughly parametrized so that it can be directly applied to a wide range of parametric cases. This is Part I of a two-part paper and focuses on the implementation of the 3D MEC model. Part II compares the 3D MEC model against nonlinear finite element analysis (FEA) models to validate the MEC model's accuracy and to develop guidelines for discretizing the geometry.

A 3D Smoothed Particle Hydrodynamics Study of a Non-Symmetrical Rayleigh Collapse for an Empty Cavity

In this work the first 3D Smoothed Particle Hydrodynamics model of a Rayleigh collapse for an empty cavity is proposed with the aim of improving the hydrodynamic analysis of a non-symmetrical collapse. The hydrodynamics of the model is validated against the solution of the Rayleigh-Plesset equation for a symmetrical collapse. The model is then used to simulate a non-symmetrical collapse of an empty cavity attached to a solid surface with γ=0.6 induced by an external pressure of 50 [MPa]. The results shows that is possible to identify three regions where the hydrodynamics of the collapsing cavity shows different features. For all the stages of the collapse the simulation shows smooth pressure and velocity fields in the liquid and in the solid phase with the formation of a vortex ring in the final phase of the collapse. Finally, the model is compared to a previous 2D model to highlight strong, weak points and the key differences of both approaches in final phase of the collapse.

Recent advances in the 3D kinematic Babcock–Leighton solar dynamo modeling

In this review, we explain recent progress made in the Babcock-Leighton dynamo models for the Sun, which have been most successful to explain various properties of the solar cycle. In general, these models are 2D axisymmetric and the mean-field dynamo equations are solved in the meriodional plane of the Sun. Various physical processes (e.g., magnetic buoyancy and Babcock-Leighton mechanism) involved in these models are inherently 3D process and could not be modeled properly in a 2D framework. After pointing out limitations of 2D models (e.g., Mean-field Babcock-Leighton dynamo models and Surface Flux Transport models), we describe recently developed next-generation 3D dynamo models that implement more sophisticated flux emergence algorithm of buoyant flux tube rise through the convection zone and capture Babcock-Leighton process more realistically than previous 2D models. The detailed results from these 3D dynamo models including surface flux transport counterpart are presented. We explain the cycle irregularities that are reproduced in 3D dynamo models by introducing scattering around the tilt angle only. Some results by assimilating observed photospheric convective velocity fields into the 3D models are also discussed, pointing out the wide opportunity that these 3D models hold to deliver.

3D modeling of a superconducting dynamo-type flux pump

High temperature superconducting (HTS) dynamos are promising devices that can inject large DC currents into the winding of superconducting machines or magnets in a contactless way. Thanks to this, troublesome brushes in HTS machines or bulky currents leads with high thermal losses will be no longer required. The working mechanism of HTS dynamo has been controversial during the recent years and several explanations and models have been proposed to elucidate its performance. In this paper, we present the first three-dimensional (3D) model of an HTS flux pump, which has good agreement with experiments. This model can be beneficial to clarify the mechanism of the dynamo and pinpoint its unnoticed characteristics. Employing this model, we delved into the screening current and electric field distribution across the tape surface in several crucial time steps. This is important, since the overcritical screening current has been shown to be the reason for flux pumping. In addition, we analyzed the impact of both components of electric field and screening current on voltage generation, which was not possible in previous 2D models. We also explored the necessary distance of voltage taps at different airgaps for precise measurement of the voltage across the tape in the dynamo.

Study of cathode-spot crater and droplet formation in a vacuum arc

A 3D transient model of a cathode-spot crater and droplet formation in a vacuum arc is developed. The model includes mass, momentum, heat transfer (energy), current continuity and potential equations. Using the energy flux density, current density and pressure as external parameters, the shape of the cathode-spot crater and the temperature, velocity, potential and current density distributions at each time step are determined via numerical simulation. Under symmetrical conditions, the 3D simulation results are highly consistent with those from the previous 2D model. The new cathode spot tends to appear in the direction in which the protrusion is largest because the liquid-metal velocity is lower and the liquid-metal ridge radius is larger in this direction. The effect of the external transverse magnetic field is considered by using a symmetric space function to represent the pressure and energy flux density of the plasma cloud. Simulation results show that even small changes in the plasma cloud distribution have a significant impact on the cathode-spot crater process and droplet formation. Since the pressure is asymmetric, the crater becomes asymmetric and the new cathode spot tends to appear opposite to the direction of the Ampere force. Based on this phenomenon, a possible explanation for the retrograde motion phenomenon of cathode spots is proposed.

Complex s-Plane Modeling and 2D Characterization of the Stochastic Scattering Loss in Symmetric Dielectric Slab Waveguides Exhibiting Ergodic Surface-Roughness With an Exponential Autocorrelation Function

The symmetric dielectric slab waveguide serves as an important canonical structure for the high-speed high-bandwidth optical and opto-electronic silicon-on-insulator interconnects. A stochastic model of propagation loss, due to electromagnetic wave scattering with surface-roughness of the nano-scale waveguide excited at frequencies in the 100s of THz, provides useful insights for analysis and design optimization of optical interconnects. In this work, we propose an analytic solution for the stochastic scattering integral based on contour integration of the exponential autocorrelation function in the complex s-plane that improves performance at larger autocorrelation length values, compared to previous works. An expression is proposed for computing the upper-bound value of scattering loss. Results show that the proposed 2D formulation offers reasonable correlation against data from experimental measurements of loss by previous investigators, while several discrepancies are noted compared to previous 2D models. An expression is proposed for the transverse magnetic (TM) modal field amplitude, and several discrepancies in the transverse electric (TE) modal amplitudes are noted compared to previous works. A method is proposed for computation of the effective index (and propagation constant) for arbitrary cladding that improves convergence of the Newton search method, and it is compared to two other methods. Background discussions include the stochastic theory and assumptions that lead to the stationary and ergodic treatment of the surface-roughness, extension of the ensemble-average and time-average to the spatial domain, and effective thickness due to the Goos-Hänchen shift.

A Non-normal-mode Marginal State of Convection in a Porous Box with Insulating End-Walls

The 4th order Darcy–Benard eigenvalue problem for the onset of thermal convection in a 3D rectangular porous box is investigated. We start from a recent 2D model Tyvand et al. (Transp Porous Med 128:633–651, 2019) for a rectangle with handpicked boundary conditions defying separation of variables so that the eigenfunctions are of non-normal mode type. In this paper, the previous 2D model (Tyvand et al. 2019) is extended to 3D by a Fourier component with wave number k in the horizontal y direction, due to insulating and impermeable sidewalls. As a result, the eigenvalue problem is 2D in the vertical xz-plane, with k as a parameter. The transition from a preferred 2D mode to 3D mode of convection onset is studied with a 2D non-normal mode eigenfunction. We study the 2D eigenfunctions for a unit width in the lateral y direction to compare the four lowest modes $$k_m = m \pi ~(m=0,1,2,3)$$, to see whether the 2D mode $$(m=0)$$ or a 3D mode $$(m\ge 1)$$ is preferred. Further, a continuous spectrum is allowed for the lateral wave number k, searching for the global minimum Rayleigh number at $$k=k_c$$ and the transition between 2D and 3D flow at $$k=k^*$$. Finally, these wave numbers $$k_c$$ and $$k^*$$ are studied as functions of the aspect ratio.

Unsteady three-dimensional modeling of the Fluid–Structure Interaction in the check valves of diaphragm volumetric pumps

A full 3D unsteady numerical model with dynamic meshes is developed to simulate the fluid–structure interaction in the non-returning valves of air-operated diaphragm volumetric pumps. This new three-dimensional CFD model provides a more accurate description of the flow patterns and a superior evaluation than a previous 2D model, published by the authors, regarding the dynamic response of the valves motion, which are responsible for internal volumetric losses that penalize the overall pump efficiency. Both piston-like and deformable geometries for the prescribed sinusoidal displacement of the membrane have been checked and compared in the modeling, resulting in similar behavior concerning the basic performance of the pump. Standard operation and free-delivery conditions are exhaustively analyzed, confirming more instabilities in the check valves in case of low air-supplied pressures. In particular, the exhausting valve is found to experience severe tapping with repetitive partial closures during the forward stroke due to an intense Fluid–Structure Interaction. On the contrary, the aspirating valve presents much better sealing characteristics with a partial reopening only at the initial moments of the backward stroke. All these numerical evidences have provided useful information for the pump manufacturers concerning the design, selection of materials and maintenance routines, which have been employed for the development of a series of new prototypes.

Empirical overtopping volume statistics at an OBREC

The results of a new experimental campaign on an Overtopping BReakwater for Energy Conversion (OBREC) device are presented. Previous 2D model tests carried out at Aalborg University (DK) made it possible to define new prediction methods that were used to design the first OBREC prototype breakwater which has been operating at Naples Harbor (Italy) since January 2016. The new tests were carried out at the Hydraulic Laboratory of the Catania University aiming to provide reliable methods for evaluating the energy extracted by the device. In particular, the new tests investigate the probability distribution of the individual overtopping volumes which enter the OBREC reservoir. The methods presented and validated here allow for a reliable estimate of the time distribution of the input flow, which along with the characteristics of the device, can be used to predict the energy produced by OBREC devices.

Use of surface impedances in a 3D FEM linear model for the calculation of zero‐sequence magnetising impedances of three‐phase core‐type transformers

This article shows results of using surface impedances ( Z SURFACE ) in 3D FEM linear model to calculate zero-sequence magnetising impedances ( Z 0M ) of 3-phase core-type transformers. Initially, results with and without Z SURFACE are compared to obtain certainty about model validity. Compared results are magnetising reactances and active power losses in tank during Z 0M tests. Subsequently, results of 3D models with Z SURFACE are compared with Z 0M measurements at different currents, to consider nonlinearity of tank steel. An equivalent permeability for tank steel is estimated for each test point, and accurate results from model are obtained for magnetising reactances. An approximate curve for this equivalent permeability is also found, as in a previous 2D method, and both curves are similar from each other. It is shown that active power losses in tank cannot be properly computed using these 3D linear models. This fact cannot be observed by previous 2D models and it indicates that active power losses in tank are influenced by other phenomena, which are not considered by these FEM models. Main contributions are the application of Z SURFACE as a powerful tool to compute Z 0M , and an analysis of active power losses in tank which could not be performed by previous 2D models.

Improving the thin-disk models of circumstellar disk evolution. The 2+1-dimensional model

Circumstellar disks of gas and dust are naturally formed from contracting pre-stellar molecular cores during the star formation process. To study various dynamical and chemical processes that take place in circumstellar disks prior to their dissipation and transition to debris disks, the appropriate numerical models capable of studying the long-term disk chemodynamical evolution are required. We present a new 2+1-dimensional numerical hydrodynamics model of circumstellar disk evolution, in which the thin-disk model is complemented with the procedure for calculating the vertical distributions of gas volume density and temperature in the disk. The reconstruction of the disk vertical structure is performed at every time step via the solution of the time-dependent radiative transfer equations coupled to the equation of the vertical hydrostatic equilibrium. We perform a detailed comparison between circumstellar disks produced with our previous 2D model and with the improved 2+1D approach. The structure and evolution of resulting disks, including the differences in temperatures, densities, disk masses and protostellar accretion rates, are discussed in detail. The new 2+1D model yields systematically colder disks, while the in-falling parental clouds are warmer. Both effects act to increase the strength of disk gravitational instability and, as a result, the number of gravitationally bound fragments that form in the disk via gravitational fragmentation as compared to the purely 2D thin-disk simulations with a simplified thermal balance calculation.

Abstract: Tissue Engineering a Biomimetic Platform for the Study of Breast Cancer Metastasis

INTRODUCTION: Current tissue engineering efforts are aimed towards recreating tissues to repair those that have been lost or damaged – such as the development of in vitro 3D biomimetic platforms to recapitulate in vivo conditions. Specifically, in breast cancer research, surrounding ECM in vivo has a profound effect on malignant invasion of cancer cells and it has also been clinically observed that breast tumor tissue is denser than normal tissue. However, traditional cell culture systems employed to study tumor cell behavior are limited by the significantly different cell phenotype induced under 2D culture conditions. We have created intact functional vascularized channels in biocompatible collagen constructs with proper in vivovascular physiology and alter collagen stiffness to study factors that influence tumor progression, and vascular remodeling. METHODS: Type-I collagen was enzymatically stiffened with ribose solution to create a stock collagen solution. Pluronic F127 fibers, were sacrificed in the collagen, creating a central looped microchannel with a tumor spheroid embedded in the collagen bulk. A cell suspension of human aortic smooth muscle cells (HASMC) and human umbilical vein endothelial cells (HUVEC) was seeded into the microchannel. Mechanical compression testing was completed by ElectroForce-3200 Series III. RESULTS: Confocal reflectance values showed no statistical changes of fiber length or pore area in enzymatically altered collagen, suggesting changing the stiffness would not affect bulk cell migration. Biomechanical testing of stiffened collagen revealed that 200mM of ribose dosed collagen increased the stiffness of the hydrogels to appropriate “tumor” stiffness (4kPa).1 After all time points, non-cancer containing constructs contained microchannels consisting of an anatomically correct robust vascular channel lining with increasing proliferation. However, in cancer constructs, degradation of the vascular lining and aberrantly organized HUVEC and HASMC were present. IHC and MPM imaging revealed the presence of breast cancer cells invading the endoluminal lining. Permeability studies using TexasRed Dextran revealed an increase of neovessel permeability correlating with increasing stiffness, suggesting metastatic potential of cancer also increased. CONCLUSION: This model overcomes the limitations of previous 2D and 3D culture models and may be used to investigate any type of tumor cell and can lead to the further understanding of breast cancer signaling pathways, as well as potentially provide an effective platform for high throughput analysis of patient specific breast cancer cells. Reference Citations: 1. Plewes, D., et al. Elastic moduli of normal and pathological human breast tissues: an inversion-technique-based investigation of 169 samples. Physics in Medicine and Biology. 52 (2007). 1565–76. doi:10.1088/0031-9155/52/6/002.

Two‐dimensional distributed coordination function model with finite buffer sizes

This study presents an unsaturated two-dimensional (2D) Markov model to analyse the packet collision probability and the throughput performances of the stations (STAs) in a distributed coordination function network. Compared with the previous 2D models, it takes the flexible buffer size of the STA into consideration. Compared with the 3D models, it has the advantage of low complexity by avoiding matrix operations. From the numerical results, the authors explain the approximations used in the analytical models proposed in the common existing literatures, and discuss their effect on the model accuracy.

Mimicking the Myeloma Niche: A 3D Bone-Derived Co-Culture System to Selectively Assess Bystander BMSCs and to Perform High-Throughput Drug Screening in Multiple Myeloma

Introduction: Novel substances such as the next generation IMiD pomalidomide or the recently approved next generation proteasome inhibitor carfilzomib (Cfz) have considerably expanded our treatment options in MM, both of them influencing multiple myeloma (MM) interaction with bone marrow stroma cells (BMSCs), that provides an interesting target for anti MM therapy. More compounds directed at this disease critical crosstalk are currently under investigation, however the development of novel drugs remains inefficient, displayed by a substantial drop out rate of the 376 preclinical single agents tested since 1961 (Rongvaux, Annu Rev Immunol. 2013; Schüler, Expert Opin Biol Ther. 2013; Kortüm, CLML 2014). Our focus in the projected presented here was to develop a novel bone-derived in vitro 3D co-culture model specifically adapted to mimic the BM niche to more closely study the role of bone and BM bystander cells and to perform more reliable ex vivo compound screening in MM.Methods: Previous 2D models were compared to a novel 3D co-culture model (agarose matrix interlayer, 100 microwells/cm², 1.5mm in depth, permeable for oxygen+cytokines, but not for BMSCs utilizing U266, RPMI-8226, OPM-2 and primary BM patient (pt) cells, with and without HS-5 vs. M210B4 stroma support (Fig. A + Fig. B.a. for pt characteristics). Analyses covered Trypan Blue, Annexin/PI, MTT, FACS, cell cycle analyses and H2B-mCherry/cytochrome c-GFP assays (Udi, Br J Hematol. 2013). In a next step, primary bone-derived stroma cells were acquired from bones of C57BL/6 J mice. Bones were flushed, digested and FACS sorted in order to acquire single BM and bone bystander cell subtypes (MSPCs [mesenchymal stem and progenitor cells], endothelial cells, osteoblasts, PAS [PDFGRalphaSca1] and CaRs [CXCL12-abundant reticular cells]) which were then compared to HS-5 and M210B4 with regard to growth support, cytokine secretion and protection from anti-MM substances.Results: MMCLs and pt specimens were cultured at different concentrations (10 vs. 100 cells per microwell) with and without M210B4 demonstrating a growth advantage with vs. without M210B4 (Fig. B.b). Liquid overlay technique allowed cluster formation of pt specimens leading to more reliable propagation of pt material for up to 20d of culture. Apoptotic changes were assessed by confocal microscopy of RPMI8226 co-expressing fluorescently labelled histone 2B-mCherry (red) and cytochrome c-GFP (green) as indicators of late and early apoptosis. Comparing BMSCLs with regard to their MM growth support capacities, human HS-5 proved even more beneficent than M210B4 stroma (Fig. B.b). Phenotypic analyses of pt specimens showed decreased CXCR4 expression with vs. without BMSCs suggesting a dynamic regulation of homing molecules. The model was then used as an ex-vivo platform allowing both cytotoxicity and cell cycle analyses for the combination of bortezomib (Btz) vs. Cfz with ARRY-520 (kinesin spindle protein inhibitor). Btz (10nM) and Cfz (20nM) proved significantly cytotoxic compared to the control (U266 and pt specimens, respectively) after 48h of single agent treatment Fig.B.c). Compared to Btz (10nM, B10) and Cfz (20nM, C20) as single agents, the additional combination with ARRY-520 showed stronger additive cytotoxicity for Btz (A5+B10, median: 37.5% vs. 13.1%) than for Cfz (A5+C20, 38.6% vs. 34.1%). To note, the model could also be utilized for more profound analyses as depicted for G2/M cell cycle studies in Fig.B.d. 5nM ARRY-520 (A5) led to significant accumulation of OPM-2 cells in G2/M arrest after 48h of treatment confirming prior analyses (Hernández-Garcia Blood Suppl 4710,2014; Fig. B.d). Co-culture studies with different subsets of BM and bone-derived bystander cells are currently ongoing and will be presented at the meeting (Fig. B.e).Conclusions: More complex, 3D bone-derived high-throughput in vitro models are urgently needed to better predict the potency of preclinically tested agents and to better estimate the likelihood of their later clinical adoption into phase I-II trials. With this work, we provide an innovative model which reflects the BM microenvironment as a crucial predictor for in-vivo sensitivity as shown for ARRY-5200. This ex-vivo approach helps to better incorporate MM growth support by bone and BM-derived bystander cells and thus depicts a valid tool to better characterize the role of the BM niche in myeloma. [Display omitted] DisclosuresEngelhardt:Deutsch Krebshilfe: Other: grant. Wäsch:German Cancer Aid: Research Funding; Comprehensiv Cancer Center Freiburg: Research Funding; Janssen-Cilag: Research Funding; MSD: Research Funding.

Present-day stress field in subduction zones: Insights from 3D viscoelastic models and data

3D viscoelastic FE models were performed to investigate the impact of geometry and kinematics on the lithospheric stress in convergent margins. Generic geometries were designed in order to resemble natural subduction. Our model predictions mirror the results of previous 2D models concerning the effects of lithosphere-mantle relative flow on stress regimes, and allow a better understanding of the lateral variability of the stress field. In particular, in both upper and lower plates, stress axes orientations depend on the adopted geometry and axes rotations occur following the trench shape. Generally stress axes are oriented perpendicular or parallel to the trench, with the exception of the slab lateral tips where rotations occur. Overall compression results in the upper plate when convergence rate is faster than mantle flow rate, suggesting a major role for convergence. In the slab, along-strike tension occurs at intermediate and deeper depths (>100km) in case of mantle flow sustaining the sinking lithosphere and slab convex geometry facing mantle flow or in case of opposing mantle flow and slab concave geometry facing mantle flow. Along-strike compression is predicted in case of sustaining mantle flow and concave slabs or in case of opposing mantle flow and convex slabs. The slab stress field is thus controlled by the direction of impact of mantle flow onto the slab and by slab longitudinal curvature. Slab pull produces not only tension in the bending region of subducted plate but also compression where upper and lower plates are coupled. A qualitative comparison between results and data in selected subductions indicates good match for South America, Mariana and Tonga–Kermadec subductions. Discrepancies, as for Sumatra–Java, emerge due to missing geometric (e.g., occurrence of fault systems and local changes in the orientation of plate boundaries) and rheological (e.g., plasticity associated with slab bending, anisotropy) complexities in the models.

Three-Dimensional Thermal Model of the Costa Rica-Nicaragua Subduction Zone

The thermal structure of a subduction zone controls many key processes, including subducting plate metamorphism and dehydration, the megathrust earthquake seismogenic zone and volcanic arc magmatism. Here, we present the first three-dimensional (3D), steady-state kinematic-dynamic thermal model for the Costa Rica-Nicaragua subduction zone. The model consists of the subducting Cocos plate, the overriding Caribbean Plate, and a viscous mantle wedge in which flow is driven by interactions with the downgoing slab. The Cocos plate geometry includes along-strike variations in slab dip, which induce along-strike flow in the mantle wedge. Along-strike flow occurs primarily below Costa Rica, with a maximum magnitude of 4 cm/year (~40 % of the convergence rate) for a mantle with a dislocation creep rheology; an isoviscous mantle has lower velocities. Along-margin flow causes temperatures variations of up to 80 °C in the subducting slab and mantle wedge at the volcanic arc and backarc. The 3D effects do not strongly alter the shallow (<35 km) thermal structure of the subduction zone. The models predict that the megathrust seismogenic zone width decreases from ~100 km below Costa Rica to just a few kilometers below Nicaragua; the narrow width in the north is due to hydrothermal cooling of the oceanic plate. These results are in good agreement with previous 2D models and with the rupture area of recent earthquakes. In the models, along-strike mantle flow is induced only by variations in slab dip, with flow directed toward the south where the dip angle is smallest. In contrast, geochemical and seismic observations suggest a northward flow of 6–19 cm/year. We do not observe this in our models, suggesting that northward flow may be driven by additional factors, such as slab rollback or proximity to a slab edge (slab window). Such high velocities may significantly affect the thermal structure, especially at the southern end of the subduction zone. In this area, 3D models that include slab rollback and a slab edge are needed to investigate the mantle structure and dynamics.

Formation of a laccolith by magma pulses: Evidence from modal and chemical composition of the 500 m long borehole section through the Permo-Carboniferous Landsberg laccolith (Halle Volcanic Complex)

The 500 m long section through the upper part of the Permo-Carboniferous Landsberg laccolith (Halle Volcanic Complex) was sampled every 25 meters. The modal proportions between plagioclase and K-feldspar phenocrysts vary in the section and the laccolith may be divided into four parts with different proportions of Pl/Kfs, which, in subvolcanic rocks, should reflect different proportions of these minerals in the magma plumbing system. Chemical composition of whole rock samples is uniform, but the correlations of Si and other elements with depth within all of the four sections suggest that the sections based on modal composition are also reflected in chemical composition of the rock. Also, the uppermost 100 meters of the laccolith has slightly higher contents of Fe, Ti, Zr and Nb compared to those in the rest of the laccolith and this is consistent with it being a separate magma pulse derived from a distinct source. Detailed analyses of chemical variations within each section are consistent with the model that the upper 500 meters of the Landsberg laccolith was formed by three successive pulses with slightly different chemical compositions. The best documented is the uppermost pulse, which was over-accreted on the first pulse. Another pulse was probably emplaced in the middle of the first pulse. The thickness of the pulses was 100‐300 m, which is consistent with previous 2D and 3D emplacement models of the Halle laccoliths. However, the contacts between the pulses based on modal and chemical compositional variations are not always concurrent with the presence of shearing zones, the discrepancy that is not yet well understood. In general, because silica-rich laccoliths are relatively small bodies that cool quickly due to high level of emplacement, they may preserve better evidence for separate magma pulses compared to plutonic batholiths.