Original Geometry Research Articles

In-Vitro Flow Validation of Third-Generation Ventricular Assist Devices: Feasibility and Challenges.

Computational fluid dynamics (CFD) is a powerful tool for the in-silico evaluation of rotodynamic blood pumps (RBPs). Corresponding validation, however, is typically restricted to easily accessible, global flow quantities. This study showcased the HeartMate 3 (HM3) to identify feasibility and challenges of enhanced in-vitro validation in third-generation RBPs. To enable high-precision acquisition of impeller torques and grant access for optical flow measurements, the HM3 testbench geometry was geometrically modified. These modifications were reproduced in silico , and global flow computations validated along 15 operating conditions. The globally validated flow in the testbench geometry was compared with CFD-simulated flows in the original geometry to assess the impact of the necessary modifications on global and local hydraulic properties. Global hydraulic properties in the testbench geometry were successfully validated (pressure head: r = 0.999, root mean square error [RMSE] = 2.92 mmHg; torque: r = 0.996, RMSE = 0.134 mNm). In-silico comparison with the original geometry demonstrated good agreement ( r > 0.999, relative errors < 11.97%) of global hydraulic properties. Local hydraulic properties (errors up to 81.78%) and hemocopatibility predictions (deviations up to 21.03%), however, were substantially affected by the geometric modifications. Transferability of local flow measures derived on advanced in-vitro testbenches toward original pump designs is challenged by significant local effects associated with the necessary geometrical modifications.

Assessing 3D Seismic Plastic Damages of Arch Dams Considering Optimum Mesh Spaces Based on FOS Analyses and 2023 Kahramanmaraş, Hatay, Malatya, and Gaziantep Earthquakes in Turkey

In this paper, the three-dimensional (3D) seismic plastic damage performance of the Ermenek Arch Dam (220 m), which was built in Karaman, Turkey, in 2009, is investigated by including different gallery spaces. 3D modeling of the dam is performed using the finite-difference method, and four various gallery spaces are added to the dam model considering their original oval geometries. WIPP-Drucker (WD) material model is utilized for the dam’s concrete material in creep and seismic damage analyses. Moreover, the Mohr–Coulomb material model is utilized for the foundation. Quiet nonreflecting and free-field boundary conditions are taken into account in the earthquake analyses, and reflecting (fix) boundary condition is used in the factor of safety (FOS) analyses in order to minimize the reflection of earthquake waves at the boundaries. First, the FOS analyses of the Ermenek Dam are performed considering the WD material model, and the optimum mesh space is determined according to FOS analyses. Then, 3D earthquake analyses are performed for 10 important strong ground motions that occurred in Kahramanmaraş, Hatay, Malatya, and Gaziantep in 2023. As a result of the FOS analyses, it is suggested that the mesh length of arch dams should not be chosen randomly while performing the earthquake analyses, and the FOS analyses of arch dams should be carried out using the WD material model before choosing the mesh space. Besides, it is concluded that selected ground motions for seismic analyses have created significant plastic damage around the galleries of the Ermenek Arch Dam, and gallery spaces are of great importance for the seismic plastic damage behavior of arch dams.

Geometry-Aware Planar Embedding of Treelike Structures

The growing complexity of spatial and structural information in 3D data makes data inspection and visualization a challenging task. We describe a method to create a planar embedding of 3D treelike structures using their skeleton representations. Our method maintains the original geometry, without overlaps, to the best extent possible, allowing exploration of the topology within a single view. We present a novel camera view generation method which maximizes the visible geometric attributes (segment shape and relative placement between segments). Camera views are created for individual segments and are used to determine local bending angles at each node by projecting them to 2D. The final embedding is generated by minimizing an energy function (the weights of which are user adjustable) based on branch length and the 2D angles, while avoiding intersections. The user can also interactively modify segment placement within the 2D embedding, and the overall embedding will update accordingly. A global to local interactive exploration is provided using hierarchical camera views that are created for subtrees within the structure. We evaluate our method both qualitatively and quantitatively and demonstrate our results by constructing planar visualizations of line data (traced neurons) and volume data (CT vascular and bronchial data).

A technique for quantification of quaternary ground tilting as recorded by alluvial fill terraces: An example from the northern Gulf of Mexico coastal plain

To quantify the degree of Quaternary structural tilting, we examined topographic slopes of treads of alluvial fill terraces. Like strath terrace treads, fill terrace treads can serve as a structural datum if restored to their pre-erosion geometry. Their slope degree and direction can then be compared to the slope of the modern floodplain to assess neotectonic tilting. On the northern Gulf of Mexico coastal plain, a ~45km-wide flight of seven Pleistocene alluvial fill terraces of the Ouachita River records a preferred southwestward migration of the river, and previous authors attribute this lateral migration to Quaternary structural tilting. The original geometries of Ouachita River terrace treads are needed as structural datums, but the treads are dissected by tributary streams. On younger treads, we observe concordant elevations of tributary divides and stronger soil development on divides than on tributary valley flanks. This indicates that divides are minimally eroded and preserve parts of the original treads. In order to restore terrace treads to their pre-dissection geometries, we constructed a topographic envelope model using elevations of tread remnants on tributary divides. This model effectively ‘fills’ the tributary valleys on the treads. We extracted each restored tread from the model and determined the tread's best-fit plane. We used three planes with R2 values >0.9 as datums. Consistent with westward tilting, directions of topographic slope of middle/late Pleistocene treads are rotated 80o toward the south-southwest, and treads have slopes that increase with terrace age from 0.017° to 0.09° (0.3 to 1.6 m/km). This quantitative estimate of late Quaternary westward regional tilting reveals a 10-fold increase in slope relative to the Holocene floodplain (0.14 m/km).

GAM: Gradient Attention Module of Optimization for Point Clouds Analysis

In the point cloud analysis task, the existing local feature aggregation descriptors (LFAD) do not fully utilize the neighborhood information of center points. Previous methods only use the distance information to constrain the local aggregation process, which is easy to be affected by abnormal points and cannot adequately fit the original geometry of the point cloud. This paper argues that fine-grained geometric information (FGGI) plays an important role in the aggregation of local features. Based on this, we propose a gradient-based local attention module to address the above problem, which is called Gradient Attention Module (GAM). GAM simplifies the process of extracting the gradient information in the neighborhood to explicit representation using the Zenith Angle matrix and Azimuth Angle matrix, which makes the module 35X faster. The comprehensive experiments on the ScanObjectNN dataset, ShapeNet dataset, S3DIS dataset, Modelnet40 dataset, and KITTI dataset demonstrate the effectiveness, efficientness, and generalization of our newly proposed GAM for 3D point cloud analysis. Especially in S3DIS, GAM achieves the highest index in the current point-based model with mIoU/OA/mAcc of 74.4%/90.6%/83.2%.

CFD Study of the Impacts of a Turbocharger’s Various Wastegate and Bypass Configurations on the Efficiency and the Flow Field of its Radial Turbine

Turbocharger systems enhance the engine power and efficiency, reduce its pollution, and downsize the engine volume. As the significance of exploiting turbochargers in gasoline engines is surging among automobile manufacturers, the necessity of improvement in the system components becomes more critical. This paper investigates the impacts of a turbocharger turbine bypass and wastegate geometry alterations on the performance and the flow field characteristics via numerical simulations. The numerical method verification and mesh independence study are performed for the original geometry. The simulation results of the altered geometries indicate that better alignment between the bypassed and the bulk flows leads to higher efficiency of the turbocharging system. In addition, the bent or elbow-shaped and protruded turbine walls immediately downstream of the wheel are found to be unfavorable. It is also uncovered that if the wastegate shape and the housing walls are designed in such a way that the effects of ensuing vortices are minimized, it improves the stage efficiency, which is desirable for two-stage turbochargers. Furthermore, a novel manufacturable design is proposed in this study, which increases the efficiency and useful power by 19.9% and 6.7%, respectively.

Modelling and Simulating Eulerian Venturi Effect of SBM to Increase the Rate of Penetration with Roller Cone Drilling Bit

Drilling bits are essential downhole hardware that facilitates drilling operations in high-pressure, high-temperature regions and in most carbonate reservoirs in the world. While the drilling process can be optimized, drilling operators and engineers become curious about how drill bits react during rock breaking and penetration. Since it is experimentally expensive to determine, the goal of the study is to maximize the rate of penetration by modeling fluid interactions around the roller cone drilling bit (RCDB), specifying a suitable number of jet nozzles and venturi effects for non-Newtonian fluids (synthetic-based muds), and examining the effects of mud particles and drill cuttings. Ansys Fluent k-epsilon turbulence viscous model, a second order upwind for momentum, turbulent kinetic energy, and dissipation rate, were used to model the specified 1000 kg/m3 non-Newtonian fluid around the roller cone drill bit. The original geometry of the nozzles was adapted from a Chinese manufacturer whose tricone had three jet nozzles. The results of our six redesigned jet nozzles (3 outer, 39.12 mm, and 3 proximal, 20 mm) sought to offer maximum potential for drilling optimization. However, at a pressure of 9.39 × 104 Pa, the wellbore with particle sizes between 0.10 mm and 4.2 mm drill cuttings observed an improved rate of penetration with a rotation speed of 150 r/min.

Fiber Bragg gratings inscribed in nanobore fibers.

The nanobore fiber (NBF) is a promising nanoscale optofluidic platform due to its long nanochannel and unique optical properties. However, so far, the applications of NBF have been based only on its original fiber geometry without any extra functionalities, in contrast with various telecom fiber devices, which may limit its wide applications. Here, we provide the first, to the best of our knowledge, demonstration of NBF-based fiber Bragg gratings (FBGs) introduced by either the femtosecond (fs) laser direct writing technique or the ultraviolet (UV) laser phase mask technique. Moreover, the FBG fabricated via the UV laser was optimized, achieving a high reflectivity of 96.89% and simultaneously preserving the open nanochannel. The NBF-based FBGs were characterized in terms of temperature variation and the infiltration of different liquids, and they showed high potential for nanofluidic applications.

Sensing High 17β-Estradiol Concentrations Using a Planar Microwave Sensor Integrated with a Microfluidic Channel.

The global issue of pollution caused by endocrine-disrupting chemicals (EDCs) has been gaining increasing attention. Among the EDCs of environmental concern, 17β-estradiol (E2) can produce the strongest estrogenic effects when it enters the organism exogenously through various routes and has the potential to cause harm, including malfunctions of the endocrine system and development of growth and reproductive disorders in humans and animals. Additionally, in humans, supraphysiological levels of E2 have been associated with a range of E2-dependent disorders and cancers. To ensure environmental safety and prevent potential risks of E2 to human and animal health, it is crucial to develop rapid, sensitive, low cost and simple approaches for detecting E2 contamination in the environment. A planar microwave sensor for E2 sensing is presented based on the integration of a microstrip transmission line (TL) loaded with a Peano fractal geometry with a narrow slot complementary split-ring resonator (PF-NSCSRR) and a microfluidic channel. The proposed technique offers a wide linear range for detecting E2, ranging from 0.001 to 10 mM, and can achieve high sensitivity with small sample volumes and simple operation methods. The proposed microwave sensor was validated through simulations and empirical measurements within a frequency range of 0.5-3.5 GHz. The E2 solution was delivered to the sensitive area of the sensor device via a microfluidic polydimethylsiloxane (PDMS) channel with an area of 2.7 mm2 and sample value of 1.37 µL and measured by a proposed sensor. The injection of E2 into the channel resulted in changes in the transmission coefficient (S21) and resonance frequency (Fr), which can be used as an indicator of E2 levels in solution. The maximum quality factor of 114.89 and the maximum sensitivity based on S21 and Fr at a concentration of 0.01 mM were 1746.98 dB/mM and 40 GHz/mM, respectively. Upon comparing the proposed sensor with the original Peano fractal geometry with complementary split-ring (PF-CSRR) sensors without a narrow slot, several parameters were evaluated, including sensitivity, quality factor, operating frequency, active area, and sample volume. The results showed that the proposed sensor exhibited an increased sensitivity of 6.08% and had a 40.72% higher quality factor, while the operating frequency, active area, and sample volume showed decreases of 1.71%, 25%, and 28.27%, respectively. The materials under tests (MUTs) were analyzed and categorized into groups using principal component analysis (PCA) with a K-mean clustering algorithm. The proposed E2 sensor has a compact size and simple structure that can be easily fabricated with low-cost materials. With the small sample volume requirement, fast measurement with a wide dynamic range, and a simple protocol, this proposed sensor can also be applied to measure high E2 levels in environmental, human, and animal samples.

In-situ tensile-shear test in SEM and DIC analysis of two pearlitic steel microstructures: undeformed-coarse and deformed-refined

The deformation and fracture behaviors of undeformed-coarse (UC) and deformed-refined (DR) pearlitic steel microstructure were investigated via in-situ tensile-shear (TS) test in scanning electron microscopy (SEM). An original TS sample geometry was designed. Secondary Electron (SE) images were recorded in real-time and digital image correlation technique was applied to them. Due to the DR's refined microstructure, SE images, backscatter electron images, and electron backscatter diffraction techniques were additionally employed in the DR condition under an interrupted TS test. The results showed that the DR pearlitic microstructure presented a higher shear strength and absorbed energy, compared to UC, during the TS performance. UC's pearlitic microstructure experienced a high degree of microstructural deformation, while DR seemed to be highly rigid. Strain concentration was mainly observed in the UC's colony boundaries, in the DR's GBs-α, and in the DR's colony with lamellae parallel to the tensile direction. The decohesion phenomenon was observed at colony boundaries and ferrite/cementite interfaces, respectively, for UC and DR specimens. These decohesion phenomena were related to crack nucleation in both pearlitic microstructure conditions. Finally, the shear rupture occurred abruptly for UC and slowly for DR, resulting in fractures mainly comprised of a sheared flat surface and dimples, respectively.

The Campinas-Jaguariúna Sill, NE Paraná Magmatic Province, Brazil: Insights on the mechanisms of emplacement and differentiation from geochemical and magnetic data

The Paraná Magmatic Province (PMP), one of the largest magmatic provinces on Earth, is composed of lava flows, dike swarms and sills that occupy thousands of kilometers across central-eastern South America. The Campinas-Jaguariúna Sill (CJS) is a large (>50 m thick and ±150 km2) diabase intrusion showing frequent medium- to coarse-grained gabbroic segregations and was emplaced at the interface between the Precambrian basement and sedimentary rocks in the northeastern Paraná Basin. This paper applies airborne magnetic and geochemical modeling to help understand the emplacement mechanisms and petrological evolution of the CJS. Magnetic field filtering techniques demonstrate that the CJS continues for tens of kilometers in the subsurface; analogous features are shown to be associated with other neighbor diabase occurrences, creating lobe-shaped structures that seem to freeze their original geometry and are not fully exposed by the current erosion levels. Petrological modeling indicates that the parental magma of the CJS was emplaced at ∼1 kbar, 1000 ppm H2O, and oxygen fugacity near FMQ-1. The gabbroic segregations, exposed as cm- to dm-sized sheets and eye-shaped lenses, are more evolved than the host diabase and can be shown by geochemical modeling to correspond to residual melts formed by crystal fractionation in a closed system. The parent magma of the CJS is akin to the more primitive Paranapanema magma type of the PMP, and we tested the possibility that sills intruding upper sedimentary layers may be part of a single episode of intrusions. For this purpose, we used geochemical data from the well-studied Limeira Sill, which is akin to the more evolved Pitanga magma type. Our modeling shows that, under crystal fractionation in the representative system condition, the CJS starting compositions cannot generate the Limeira rocks.

High-dimensional CFD optimization of a low-flow coefficient S–CO2 centrifugal compressor for enhanced oil recovery systems

The design of low-flow coefficient (∼0.01) centrifugal compressors with supercritical CO2 as working fluid is still a challenge for engineers due to its increased friction losses at the impeller. However, the reinjection pressure required for Enhanced Oil Recovery (EOR) systems is achieved by compression trains with stages of high-Pressure Ratios (PR > 3) which can only be obtained by lowering the flow coefficient of the equipment. The carbon dioxide mitigation, due to the reinjection process, also increases oil productivity and extraction lifetime. A four-staged compression system was considered and the preliminary geometry of its last stage was considered herein after a 1D optimization that decreased the total required power of the system. In order to further increase the systems' performance, a CFD model was developed and submitted to Sensitivity Analysis (SA) and parametric optimization procedure, considering polar angles, meridional profile and vaneless diffuser passage (25 variables). The assessment of the sequential SA using, Morris' screening method Design of Experiment (DoE) and SS-ANOVA for variable ranking and response surface training, has exposed the method's limitation in recognizing interaction between variables since low-quality Response Surfaces (RS) were trained. However, the Incremental Space Filler (ISF) sampling has complemented the sample space screening, guarantying adequate RS at a low computational cost. This indirect optimization strategy that increased the equipment's polytropic efficiency by 1.19%, diminishing total entropy generation by 8.5% can deliver important cost reductions to the operation of EOR compression systems. The ‘entropy-guided’ phenomenology analysis strategy combined with SA results, identified that the narrowing of the vaneless diffuser has extinguished the recirculation present in the original geometry's impeller/diffuser interface region, which was the largest difference in the entropy histogram. Moreover, the enlargement of the impeller's meridional profile has smoothed the fluid flow change of direction (from axial to radial) and displaced the swirl structures that restricted the fluid flow in the main passage.

The optimal geometric design of a v-corrugated absorber solar air heater integrated with twisted tape insert

The proper design of a solar air heater depends on the highest thermal performance of the solar collector. In the present paper, proposed a method to find an optimal dimension of V-corrugated absorber solar air heater (VSAH) combined with a twisted tape insert (TTI). The design variables of the VSAH-TTI are length, width, number of channels, and twisted tape ratio. The effect of each design variable is examined and studied under various ranges of Reynolds number (Re). Given the complexity in changing design variables of solar collector having a V-corrugated absorbing plate with twisted tape insert (VSAH -TTI) to find the highest thermal performances, the multi-objective function genetic algorithm is used to find the optimal dimensions of VSAH-TTI based on maximizing the heat gain, thermal and effective efficiency as well as minimizing the pressure drop on solar collector. The range of each design variable of the VSAH-TTI by means of length (1 – 2.5 m), width (0.5 – 1.5 m), number of channels (4 – 14), and twisted tape ratio (1 – 8) are specified in paper based on the most common practical values of the solar collector. The results showed for the case under study that each design variable of VSAH-TTI affect the thermal performance and the optimized geometry by using a genetic algorithm (Ga) can find the optimal geometric dimensions of VSAH-TTI. The optimal dimension by using Ga can increase the heat gain by more than 8% and increase the effective and thermal efficiency of more than 7% for the original geometry. Furthermore, the optimized geometry can reduce more than 29% for the original geometry. These improvements in optimized geometry for VSAH- TTI without introducing any additional items.

A combined cuff electrode array for organ-specific selective stimulation of vagus nerve enabled by Electrical Impedance Tomography.

Previously developed spatially-selective Vagus Nerve Stimulation (sVNS) allows the targeting of specific nerve fascicles through current steering in a multi-electrode nerve cuff but relies on a trial-and-error strategy to identify the relative orientation between electrodes and fascicles. Fast Neural Electrical Impedance Tomography (FN-EIT) has been recently used for imaging neural traffic in the vagus nerves of pigs in a cross-correlation study with sVNS and MicroCT fascicle tracking. FN-EIT has the potential for allowing targeted sVNS; however, up to now, stimulation and imaging have been performed with separate electrode arrays. In this study, different options were evaluated in-silico to integrate EIT and stimulation into a single electrode array without affecting spatial selectivity. The original pig vagus EIT electrode array geometry was compared with a geometry integrating sVNS and EIT electrodes, and with direct use of sVNS electrodes for EIT imaging. Modelling results indicated that both new designs could achieve image quality similar to the original electrode geometry in all tested markers (e.g., co-localisation error <100 µm). The sVNS array was considered to be the simplest due to the lower number of electrodes. Experimental results from testing evoked EIT imaging of recurrent laryngeal activity using electrodes from the sVNS cuff returned a signal-to-noise ratio similar to our previous study (3.9 ± 2.4 vs. 4.1 ± 1.5, N = 4 nerves from 3 pigs) and a lower co-localisation error (≈14% nerve diameter vs. ≈25%, N = 2 nerves from 2 pigs). Performing FN-EIT and sVNS on the same nerve cuff will facilitate translation to humans, simplify surgery and enable targeted neuromodulation strategies.

Radiometric Terrain Flattening of Geocoded Stacks of SAR Imagery

We have described an efficient approach to radiometrically flatten geocoded stacks of calibrated synthetic aperture radar (SAR) data for terrain-related effects. We have used simulation to demonstrate that, for the Sentinel-1 mission, one static radiometric terrain-flattening factor derived from actual SAR imaging metadata per imaging geometry is sufficient for flattening interferometrically compliant stacks of SAR data. We have quantified the loss of precision due to the application of static flattening factors, and show that these are well below the stated requirements of change-detection algorithms. Finally, we have discussed the implications of applying radiometric terrain flattening to geocoded SAR data instead of the traditional approach of flattening data provided in the original SAR image geometry. The proposed approach allows for efficient and consistent generation of five different Committee of Earth-Observation Satellites (CEOS) Analysis-Ready Dataset (ARD) families—Geocoded Single-Look Complex (GSLC), Interferometric Radar (InSAR), Normalized Radar Backscatter (NRB), Polarimetric Radar (POL) and Ocean Radar Backscatter (ORB) from SAR missions in a common framework.

Effects of the mouthpiece and chamber of Turbuhaler® on the aerosolization of API-only powder formulations

Powder dispersion in dry powder inhalers (DPIs) is affected by powder formulations as well as the design of a device. This paper conducted a numerical investigation based on the coupled computational fluid dynamics (CFD) and discrete element method (DEM) to evaluate the changes of the design of a commercial DPI device Turbuhaler® on the aerosolization of an API-only formulation. Six different designs were proposed by modifying the mouthpiece and chamber of the original geometry which was reconstructed from a CT-scan of the Turbuhaler, and their performances in terms of powder deposition in the device and fine powder fraction (FPF) were evaluated. The resistance of the device was observed to vary with different designs. For the change of the mouthpiece, the device with a cylindrical mouthpiece had the least resistance and the lowest FPF emitted among all the devices, confirming the important role of the spiral mouthpiece on powder dispersion. Reducing the mouthpiece size caused more powder deposition in the inhaler due to higher airflow velocity, but FPF emitted increased compared to the original design as more powder dispersion occurred inside the mouthpiece. The half-length mouthpiece design reduced device resistance to increase airflow velocity and average collision energy, resulting in an increase in FPF loaded but a decrease in the number of collisions. For the change of the chamber, the domed chamber design increased the powder dispersion time and thus enhanced the frequency and energy of particle collisions, which eventually led to an increase in FPF loaded. At fixed flow rates, the powder dispersion efficiency was a function of the device resistance with higher device resistance causing an increase in the FPF loaded. However, it is important for the patient’s attainable pressure drop to be considered in this context. Correlations between the aerosolization efficiency and the ratio of the average collision energy and cohesion energy were established based on model-predicted quantities.

Three-dimensional modeling and defect quantification of existing concrete bridges based on photogrammetry and computer aided design

Bridge infrastructure is aging and deteriorating and requires innovative condition monitoring and assessment to ensure safety and maintain serviceability. Current practices for bridge condition assessment depend mainly on visual inspection. Innovative data collection technologies can assist in bridge inspection and defect identification and circumvent the limitations of traditional visual inspection. This research aims to apply photogrammetry principles and image processing techniques to develop a full-scale three-dimensional (3D) bridge structure model for defect identification and quantification. The data source to establish the point cloud models is a set of digital images taken at the bridge site. The point cloud models are developed by analyzing high-resolution images captured using a Nikon D4S camera. The images are captured from different positions/locations to provide extensive stereo coverage and maximum overlapping. Two hundred images of the bridge are processed with PhotoModeler software along with the calibration information, and ground control points (GCPs) coordinates to create the models. A standard digital close-range image processing is implemented to generate the 3D points cloud model. The calibration and orientation processes are made over a deformed situation. However, the developed CAD bridge drawings depict the original undeformed geometry. The extracted bridge inventory data from the 3D model, including bridge geometry information and bridge damage quantification, can provide a baseline for the bridge monitoring system to detect bridge deterioration over the years. The developed photogrammetric 3D model has an RMSE of 0.0081 m and uncertainty of ± 0.0041 m. Future research can aim at developing reusable parametric objects for bridges in Revit and coding scripts using programming languages such as Dynamo or Python to perform further analysis of the captured information.

3D bioprinting as a prospective therapeutic strategy for corneal limbal epithelial stem cell deficiency.

Limbal epithelial stem cells (LESCs) are responsible for the maintenance and repair of the corneal surface. Injuries and diseases of the eye may result in a vision condition called limbal stem cell deficiency (LSCD). Without limbal stem cells, the cornea becomes opaque, vascularized, and inflamed. Cultured LESC therapy as a treatment method was first described in 1997, and LESCs cultured from either patients or donors have been used to treat LSCD successfully. However, the main source of cornea for LSCD treatment is from donors, which are too few to meet the demand (less than 1:70 of cases). The global shortage of donor cornea promotes the need for studies exploring corneal limbus alternatives. Many problems still remain unresolved, such as original geometry reconstruction, corneal epithelial regeneration, and ocular optical function restoration. 3D bioprinting has garnered tremendous attention in recent years, and significant advances have been made in fabricating cell-laden scaffolds. These advancements could lead to a promising treatment for LSCD. It is possible that alternative limbus stem cells can be constructed using 3D printing, which, in corneal limbus regeneration, enables personalized corneal implants and fabrication of single- or multilayer corneal limbus equivalents with corneal limbal stem cells. In this review, the progress, applications, and limitations of the most influential works regarding current treatments of LESC deficiency are discussed. The advantages of 3D bioprinting are illustrated, and some first promising steps toward the creation of a functional cornea limbus with 3D bioprinting are discussed. Finally, insights into the prospects and technical challenges facing the future research of 3D bioprinting of corneal limbus alternatives in vivo and in vitro are provided.

Elastic Interaction Between a Mesoscale Eddy‐Pair and an Axisymmetrical Eddy

AbstractWe investigate numerically the elastic interaction between an eddy‐pair and an axisymmetrical eddy in inviscid isochoric two‐dimensional (2D) flows, as well as in three‐dimensional (3D) flows under the quasi‐geostrophic (QG) approximation. The eddy‐pair is a straight moving Lamb‐Chaplygin dipole where the absolute value of either its positive or negative amount of vorticity equals the vorticity of the axisymmetrical eddy. The results for the 2D and 3D cases show that interactions with almost no vorticity exchange, or vorticity loss to the background field between ocean eddies, but causing changes in their displacement velocity, are possible. When the eddy‐pair approaches the axisymmetrical eddy, their respective potential flows interact, the eddy‐pair's trajectory acquires curvature and their vorticity poles separate. In the QG dynamics, the eddies suffer little vertical deformation, being the barotropic effects dominant. At the moment of highest interaction, the anticyclonic eddy of the pair elongates, simultaneously the cyclonic eddy of the pair evolves toward spherical geometry, and the axisymmetrical eddy acquires prolate ellipsoidal geometry in the vertically stretched QG space. Once the eddy‐pair moves away from the axisymmetrical eddy, its poles close, returning to their original geometry, and the anticyclonic and cyclonic eddies continue as an eddy‐pair with a straight trajectory but along a new direction. The interaction is sensitive to the initial conditions and, depending on the initial position of the eddy‐pair, as well as on small changes in the vorticity distribution of the axisymmetrical eddy, inelastic interactions may instead occur.

Identifying local vs. regional drainage using multiproxy provenance tracers – Tracking the Moroccan Late Triassic fluvial system

The Kerrouchen Basin is an understudied rift basin in the Middle Atlas of Morocco, where over 600 m of Triassic stratigraphy is well exposed. It was partially inverted during the Atlasic orogeny whilst preserving the original basin geometry. Within the Kerrouchen Basin, two distinct fluvial systems are present. The first, recorded by the K3 Formation, is a braided-meandering fluvial system showing vertical and lateral amalgamation. The K3 is an axial fluvial system that shows a predominant drainage direction towards the north-north-east, parallel to the rift zone axis, ultimately draining towards the Tethys Ocean. The K4 Formation records a secondary, Tributary Fluvial System (TFS), with facies spanning a range of alluvial-fluvial processes. Paleoflows predominantly record drainage to the SSW, transverse to the basin axis.Heavy mineral and petrographic analysis of the two fluvial systems indicates two distinct sedimentary provenances for the depositional system. The K3 system records a higher proportion of sediment sourced from igneous rocks. In contrast, the K4 system records a local provenance signal derived from adjacent low-medium grade metamorphic terranes exposed to the east. Comparison of the provenance and stratigraphic trends within the Kerrouchen Basin with work undertaken in the Central and Western High Atlas suggests a shared source region for the through going axial fluvial systems recorded in the High Atlas and Kerrouchen basins. Our study provides evidence for a linked fluvial system spanning the High and Middle Atlas rifts during the Triassic, indicating that a regional fluvial system was present within Central Pangea from Middle-Late Triassic times. Identifying regional and local drainage networks within the Triassic rift basins has key implications for paleogeographic reconstructions and future exploration efforts for hydrocarbons and CCS sites within Morocco.