Simple Geometric Model Research Articles

Sun-induced chlorophyll fluorescence is more strongly related to photosynthesis with hemispherical than nadir measurements: Evidence from field observations and model simulations

Solar-induced chlorophyll fluorescence (SIF) has been shown to be a novel proxy for terrestrial gross primary production (GPP). A growing number of ground-based automatic SIF observation systems equipped with hemispherical-conical and bi-hemispherical observation configurations have been developed in synergy with EC flux measurements across different ecosystems. However, the difference in the canopy SIF observed by these two types of configurations has not been well studied, which poses challenges in evaluating their performance in tracking GPP. In this study, we investigated SIF from both hemispherical-conical and bi-hemispherical observation configurations for their ability to track GPP in a maize field during the 2020 growth season. We found that bi-hemispherical SIF observations (SIFHemis) showed higher correlations with GPP at both diurnal and seasonal scales, and the superiority of SIFHemis for GPP estimation was also supported by Soil-Canopy-Observation of Photosynthesis and the Energy balance (SCOPE) model simulations. In addition, we found that the SIFHemis-GPP model established at a satellite overpass time (e.g., 09:30) outperformed the corresponding SIFNadir-GPP model in estimating both the half-hourly and daily GPP. The underlying mechanism for the advantage of this SIFHemis-GPP relationship was elucidated by a simplified geometrical optical model, which showed that the diurnal patterns of the observed sunlit and shaded leaves for the SIFHemis were consistent with those of the canopy GPP. Our study recommends a bi-hemispherical configuration setup for its superiority in monitoring GPP dynamics.

A phase space model of a Versa HD linear accelerator for application to Monte Carlo dose calculation in a real-time adaptive workflow.

PurposeThis study aims to develop and validate a simple geometric model of the accelerator head, from which a particle phase space can be calculated for application to fast Monte Carlo dose calculation in real‐time adaptive photon radiotherapy. With this objective in view, the study investigates whether the phase space model can facilitate dose calculations which are compatible with those of a commercial treatment planning system, for convenient interoperability.Materials and methodsA dual‐source model of the head of a Versa HD accelerator (Elekta AB, Stockholm, Sweden) was created. The model used parameters chosen to be compatible with those of 6‐MV flattened and 6‐MV flattening filter‐free photon beams in the RayStation treatment planning system (RaySearch Laboratories, Stockholm, Sweden). The phase space model was used to calculate a photon phase space for several treatment plans, and the resulting phase space was applied to the Dose Planning Method (DPM) Monte Carlo dose calculation algorithm. Simple fields and intensity‐modulated radiation therapy (IMRT) treatment plans for prostate and lung were calculated for benchmarking purposes and compared with the convolution‐superposition dose calculation within RayStation.ResultsFor simple square fields in a water phantom, the calculated dose distribution agrees to within ±2% with that from the commercial treatment planning system, except in the buildup region, where the DPM code does not model the electron contamination. For IMRT plans of prostate and lung, agreements of ±2% and ±6%, respectively, are found, with slightly larger differences in the high dose gradients.ConclusionsThe phase space model presented allows convenient calculation of a phase space for application to Monte Carlo dose calculation, with straightforward translation of beam parameters from the RayStation beam model. This provides a basis on which to develop dose calculation in a real‐time adaptive setting.

First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass

In this paper we quantify the temporal variability and image morphology of the horizon-scale emission from Sgr A*, as observed by the EHT in 2017 April at a wavelength of 1.3 mm. We find that the Sgr A* data exhibit variability that exceeds what can be explained by the uncertainties in the data or by the effects of interstellar scattering. The magnitude of this variability can be a substantial fraction of the correlated flux density, reaching ∼100% on some baselines. Through an exploration of simple geometric source models, we demonstrate that ring-like morphologies provide better fits to the Sgr A* data than do other morphologies with comparable complexity. We develop two strategies for fitting static geometric ring models to the time-variable Sgr A* data; one strategy fits models to short segments of data over which the source is static and averages these independent fits, while the other fits models to the full data set using a parametric model for the structural variability power spectrum around the average source structure. Both geometric modeling and image-domain feature extraction techniques determine the ring diameter to be 51.8 ± 2.3 μas (68% credible intervals), with the ring thickness constrained to have an FWHM between ∼30% and 50% of the ring diameter. To bring the diameter measurements to a common physical scale, we calibrate them using synthetic data generated from GRMHD simulations. This calibration constrains the angular size of the gravitational radius to be μas, which we combine with an independent distance measurement from maser parallaxes to determine the mass of Sgr A* to be M ⊙.

Geometric modeling predicts architectural adaptations are not responsible for the force deficit following tenotomy in the rotator cuff

Tenotomy, or the severing of then tendinous connection between muscle and bone, is an experimental model frequently used to assess muscular changes in response to unloading with retraction. It is most translationally relevant to rotator cuff (RC) tendon tears as these frequently progress to chronic muscle retraction and thus most recent tenotomy animal models have used RC muscles. Tenotomy induces chronic changes to muscle architecture including reduced muscle mass, muscle length, fiber length and pennation angle. However, most RC studies evaluating the physiological consequences of tenotomy do not account for changes in architecture, in part because these are difficult to measure in RC muscles. This is a critical omission as architectural changes can dramatically impact muscle force generating capacity. In this work, we develop a geometric model to predict changes in fiber length and pennation angle of the mouse supraspinatus and infraspinatus muscles given a measured muscle length. We then validate this model with detailed architectural measurements in tenotomized muscles and show a close match between predicted and experimental values. Finally, using this model, we find that predicted changes in architecture cannot explain the force deficit in tenotomized muscle. The contributions of this work are 1) a simple geometric model that predicts changes in architecture with retraction, validated in the mouse RC but with potential application across muscles and species and 2) data indicating that architectural adaptation is not solely responsible for the force deficit with tenotomy which suggests future research should focus on intrinsic changes to the myofiber.

Determine Corneal Biomechanical Parameters by Finite Element Simulation and Parametric Analysis Based on ORA Measurements.

Purpose: The Ocular Response Analyzer (ORA) is one of the most commonly used devices to measure corneal biomechanics in vivo. Until now, the relationship between the output parameters and corneal typical biomechanical parameters was not clear. Hence, we defined the output parameters of ORA as ORA output parameters. This study aims to propose a method to determine corneal biomechanical parameters based on ORA measurements by finite element simulation and parametric analysis. Methods: Finite element analysis was used to simulate the mechanics process of ORA measurements with different intraocular pressure (IOP), corneal geometrical parameters and corneal biomechanical parameters. A simplified geometrical optics model was built to simulate the optical process of the measurements to extract ORA output parameters. After that, 70% of the simulated data was used to establish the quantitative relationship between corneal biomechanical parameters and ORA output parameters by parametric analysis and 30% of the simulated data was used to validate the established model. Besides, ten normal subjects were included to evaluate the normal range of corneal biomechanical parameters calculated from ORA. Results: The quantitative relationship between corneal biomechanical parameters and ORA output parameters is established by combining parametric analysis with finite element simulation. The elastic modulus (E) and relaxation limit (G ∞) of the ten normal subjects were 0.65 ± 0.07 MPa and 0.26 ± 0.15, respectively. Conclusions: A method was proposed to determine corneal biomechanical parameters based on the results of ORA measurements. The magnitude of the corneal biomechanical parameters calculated according to our method was reasonable.

On the Counter‐intuitive Heterogeneous Electron Transfer Barrier Properties of Alkanethiolate Monolayers on Gold: Smooth versus Rough Surfaces

AbstractAlkanethiolate monolayers formed on rough gold surfaces can, somewhat surprisingly, act as stronger barriers to heterogeneous electron transfer than those on smooth gold surfaces. This paper presents a possible explanation for this observation by constructing simple geometric models of a “rough” and “smooth” gold surface to examine how microscopic roughness differences can affect the nucleation/growth of the adlayer and size/density of structural defects. Expectedly, the number of defects predicted for adlayers formed on smooth gold is lower than any of those for rough gold. The counter‐intuitive result is that the sizes of a small portion of the defects in the adlayer on the smooth surface are larger than any of those found on the rough surface. The potential implications of these results are discussed.

Build Surface Roughness and Internal Oxide Concentration for Laser Powder Bed Fusion of IN718

Oxidation of hot spatter during laser powder bed fusion results in the deposition of oxides on the build surface. In the case of IN718—as studied in this work—the oxide is alumina. While some of this surface oxide may be incorporated in the build, an oxygen mass balance indicates some oxygen removal during the building process. This work tested an expected effect of the roughness of the build surface on the concentration of micron-sized oxide inclusions that are incorporated in test coupons during building. The roughness of the build surface responded to changes in hatch spacing, in line with a simple geometric model of the overlap between adjacent beads. Samples with deeper grooves retained more oxide, resulting in a much larger concentration of oxide inclusions within the samples. The conclusion is that parts with lower inclusion concentrations can be produced by decreasing the hatch spacing, at the cost of a lower build rate.

Variability of right ventricular linear measurements of size and function using a standardized echocardiographic protocol

Abstract Funding Acknowledgements Type of funding sources: None. Background Right ventricular size and function have a prognostic value not only in right heart conditions (pulmonary hypertension, congenital heart disease), but also in left ventricular (LV) disease states. The right ventricle (RV) has a unique shape, for which a simple geometrical model is not achievable as is the case for the LV. In clinical practice simple measurements are used for the RV, since these are considered to be most reliable and reproducible: linear cavity dimensions, tricuspid annular plane systolic excursion (TAPSE) and tissue Doppler systolic velocity s’ at the tricuspid annulus. The latest RV quantitation guidelines made important modifications to RV measurements, in particular, by shifting from the apical 4-chamber view to the RV focused apical view. Very scarce data exist on the variability of these measurements. Purpose In this study we aim to analyze the intra and inter-observer variability of the linear measurements of RV size and function using a standardized methodology. Methods A mixed cohort, randomly selected from the echocardiographic database, comprising 50 patients, was retrospectively analyzed. We measured linear diameters (basal = 1, longitudinal = 2, mid = 3) in apical RV-focused view, TAPSE and s’. Based on computer simulations, we propose a step-by-step approach: tracing the longitudinal diameter as perpendicular to the mid of the basal and generally parallel with the interventricular septum, and the mid as perpendicular to the middle of the longitudinal (Figure). Two observers measured independently the same images at baseline, three (inter-observer) and six months (intra-observer). Results The longitudinal diameter had the lowest relative bias (3% inter and 4% intra-observer), followed by the basal (7% and 2%), and mid (6% and 6%). The limits of agreement (LOA) were small for s’ (-3 to 1 intra and -1 to 1mm inter-observer), TAPSE (-6 to 5 and -3 to 3mm), and larger for diameters (1=-5 to 10 and -8 to 6; 2=-13 to 17 and -11 to 6; 3=-11 to 7 and -9 to 4mm). ICCs for individual measurements were very good (1= 0.94 intra and 0.94 inter; 2 = 0.78 and 0.94; 3: 0.72 and 0.56; TAPSE: 0.86 and 0.94; s’=0.94 and 0.98), p < 0.001 for all (Table). Conclusion A systematic approach to linear RV-focused apical view measurements may lead to reproducible results. It is essential that size measurements be performed in the RV focused view. Our study shows best consistency and reproducibility for the basal diameter and the linear functional parameters. Echocardiographic laboratories may benefit from implementing a consistent analysis protocol and assessing its reproducibility. Abstract Figure: linear RV measurements Abstract Table: variability results

Dependence of cell-free-layer width on rheological parameters: Combining empirical data on flow separation at microvascular bifurcations with geometrical considerations.

When blood flows through vessel networks, red blood cells (RBCs) are typically concentrated close to the vessel center line, creating a lubrication layer near the vessel wall. As RBCs bind oxygen, the width of this cell-free layer (CFL) impacts not only the blood rheology inside the vasculature, but also oxygen delivery to the tissues they perfuse and, hence, their function. Existing attempts to relate the width of the CFL to the rheological properties of the blood and the geometrical properties of the vessel are based on an analysis of the forces acting on RBCs suspended in the blood. However, the complexity of interactions in the blood makes this a challenging task. Here, we propose an alternative, two-step approach to derive such a functional relationship. First, we extend widely accepted empirical fits describing the minimum flow fraction needed for RBCs to enter a daughter vessel downstream of a microvascular bifurcation so that it depends not only on the diameter and discharge haematocrit of the parent vessel, but also on its average shear rate. Second, we propose a simple geometrical model for the minimum flow fraction based on the cross-sectional blood flow profile within the parent vessel upstream of the bifurcation-considering uniform, parabolic, and blunt velocity profiles-and derive the leading-order approximation to this model for small CFL widths. By equating the functional relationships obtained using these two approaches, we derive expressions relating the CFL width to the vessel diameter, discharge haematocrit, and mean shear rate. The resulting expressions are in good agreement with available in vivo data and represent a promising basis for future research.

Regulating and Directionally Controlling Electron Emission from Gold Nanorods with Silica Coatings.

Dielectric coatings offer a versatile means of manipulating hot carrier emission from nanoplasmonic systems for emerging nanocatalysis and photocathode applications, with uniform coatings acting as regulators and nonuniform coatings providing directional photocurrent control. However, the mechanisms for electron emission through dense and mesoporous silica (SiO2) coatings require further examination. Here, we present a systematic investigation of photoemission from single gold nanorods as a function of dense versus mesoporous silica coating thicknesses. Studies with dense coatings on gold nanostructures clarify the short (∼1 nm) attenuation length responsible for severely reduced transmission through the silica conduction band. By contrast, mesoporous silica is much more transmissive, and a simple geometric model quantitatively recapitulates the electron escape probability through nanoscopic porous channels. Finally, photoelectron velocity map imaging (VMI) studies of nanorods with coating defects verify that photoemission occurs preferentially through the thinner regions, illustrating new opportunities for designing photocurrent distributions on the nanoscale.

Studies of the radiation environment on the Mars surface using the Geant4 toolkit

The radiation environment on the surface of Mars is a potential threat for future manned exploration missions to this planet. In this study, a simple geometrical model was built for simulating the radiation environment on the Mars surface caused by galactic cosmic rays; the model was built and studied using the Geant4 toolkit. The simulation results were compared with the data reported by a radiation assessment detector (RAD). The simulated spectra of neutrons, photons, protons, alpha particles, and particle groups Z=3–5, Z=6–8, Z=9–13, and Z=14–24 were in a reasonable agreement with the RAD data. However, for deuterons, tritons, and ,^{3}{mathrm{He}}, the simulations yielded much smaller values than for the corresponding RAD data. In addition, the particles’ spectra within the 90^{circ } zenith angle were also obtained. Based on these spectra, we calculated the radiation dose that would have been received by an average human body on Mars. The distribution of the dose throughout the human body was not uniform. The absorbed and equivalent doses for the brain were the highest among all of the organs, reaching 62.0 ± 1.7 mGy/y and 234.1 ± 8.0 mSv/y, respectively. The average absorbed and equivalent doses for the entire body were approximately 44 mGy/y and 153 mSv/y, respectively. Further analysis revealed that most of the radiation dose was owing to alpha particles, protons, and heavy ions. We then studied the shielding effect of the Mars soil with respect to the radiation. The body dose decreased significantly with increasing soil depth. At the depth of 1.5 m, the effective dose for the entire body was 17.9 ± 2.4 mSv/y, lower than the dose limit for occupational exposure. At the depth of 3 m, the effective dose to the body was 2.7 ± 1.0 mSv/y, still higher than the accepted dose limit.

Challenges and Solutions for Antennas in Vehicle-to-Everything Services

Autonomous vehicle is being developed for widespread deployment. Its reliability and safety are critically dependent on advanced wireless technologies, e.g., vehicle-to-everything (V2X) communication. The frontend of a V2X system needs an antenna module that enables the vehicle to reliably connect to all other networks. Designing V2X antenna is challenging due to the complex in-vehicle environment, trend for hidden antenna solution, long simulation time and need for omnidirectional coverage. In this article, we survey these challenges as well as existing V2X antenna solutions. In view of the drawbacks in the existing solutions, we propose an efficient design methodology for V2X antennas to provide the desired coverage. The method utilizes a simple geometrical model of the vehicle that captures the shadowing effects of the vehicle body to obtain candidate antenna locations that offer the best coverage via multi-antenna diversity. Hence, complex full-wave simulation can be avoided. The approach is validated through comprehensive full-wave simulations and pattern measurements on two car models. The results confirm that, at 5.9GHz, line-of-sight shadowing has more dominant effect on the received power than multipath propagation due to the car body. In cases of strong diffraction and surface waves, a simple rule-of-thumb can be devised to improve the accuracy of the method.

Cooperation of unmanned systems for agricultural applications: A case study in a vineyard

Fully-autonomous vehicles, both aerial and ground, could provide great benefits in the Agriculture 4.0 framework when operating within cooperative architectures, thanks to their ability to tackle difficult tasks, particularly within complex irregular and unstructured scenarios such as vineyards on sloped terrains. A decentralised multi-phase approach has been proposed as an alternative to more common cooperative schemes. When perennial crops are considered, it is advantageous to build a simplified geometrical (and georeferenced) crops model, which can be identified by using 3D point clouds acquired during a-priori explorative missions by unmanned aerial vehicles. This model can be used to plan the tasks to be performed within the crops by the in-field aerial and ground drones. In this companion paper, the proposed strategy is applied to a specific case study involving a vineyard on a sloped terrain, located in the Barolo region in Piedmont, Italy. Ad-hoc technologies and guidance, navigation and control algorithms were designed and implemented. The main objectives were to improve the autonomous driving capabilities of the drones involved and to automate the process of retrieving low-complexity maps from the data collected with preliminary remote sensing missions to make them available for the autonomous navigation by a quadrotor and an unmanned 4-wheel steering ground vehicle within the vine rows. Preliminary results highlight the benefits achievable by exploiting the tailored technologies selected and applied to improve each of the analysed mission phases.

Mapping shifts in nanopore signal to changes in protein and protein-DNA conformation.

Solid-state nanopores have been used extensively in biomolecular studies involving DNA and proteins. However, the interpretation of signals generated by the translocation of proteins or protein-DNA complexes remains challenging. Here, we investigate the behavior of monovalent streptavidin and the complex it forms with short biotinylated DNA over a range of nanopore sizes, salts, and voltages. We describe a simple geometric model that is broadly applicable and employ it to explain observed variations in conductance blockage and dwell time with experimental conditions. The general approach developed here underscores the value of nanopore-based protein analysis and represents progress toward the interpretation of complex translocation signals.

Unfolded Hybrid Beamforming With GAN Compressed Ultra-Low Feedback Overhead

Optimizing a hybrid beamforming transmitter is a non-convex problem and requires channel state information, leading in most cases to nontrivial feedback overhead. We propose a methodology relying on the principles of deep generative models and unfolding to achieve near-optimal hybrid beamforming with reduced feedback and computational complexity. We first represent the channel as a low-dimensional manifold via a generative adversarial network (GAN) and search the optimum digital and analog precoders in this low-dimensional space. To decrease the search complexity, we find an iteration rule by formulating hybrid beamforming as a bi-level optimization problem and then unfold each iteration as a neural layer. This results in a novel model-based deep neural network that incorporates domain knowledge. Our results show that this method (i) approaches the capacity-achieving spectral efficiency, (ii) provides a superior energy and spectral efficiency tradeoff, (iii) decreases feedback overhead, and (iv) reduces the complexity significantly, by optimizing a single low-dimensional vector per channel coherence time, with the neural network itself trained offline. The achieved spectral efficiency is robust when tested with realistic 3GPP channel models, even if the offline training relies on a simple geometric channel model.

Geant4 Monte Carlo simulation study of the secondary radiation fields at the laser-driven ion source LION

At the Center for Advanced Laser Applications (CALA), Garching, Germany, the LION (Laser-driven ION Acceleration) experiment is being commissioned, aiming at the production of laser-driven bunches of protons and light ions with multi-MeV energies and repetition frequency up to 1 Hz. A Geant4 Monte Carlo-based study of the secondary neutron and photon fields expected during LION’s different commissioning phases is presented. Goal of this study is the characterization of the secondary radiation environment present inside and outside the LION cave. Three different primary proton spectra, taken from experimental results reported in the literature and representative of three different future stages of the LION’s commissioning path are used. Together with protons, also electrons are emitted through laser-target interaction and are also responsible for the production of secondary radiation. For the electron component of the three source terms, a simplified exponential model is used. Moreover, in order to reduce the simulation complexity, a two-components simplified geometrical model of proton and electron sources is proposed. It has been found that the radiation environment inside the experimental cave is either dominated by photons or neutrons depending on the position in the room and the source term used. The higher the intensity of the source, the higher the neutron contribution to the total dose for all scored positions. Maximum neutron and photon ambient dose equivalent values normalized to 109 simulated incident primaries were calculated at the exit of the vacuum chamber, where values of about 85 nSv (109 primaries)−1 and 1.0 μSv (109 primaries)−1 were found.

Detection of Substructures in Young Transition Disk WL 17

Abstract WL 17 is a young transition disk in the Ophiuchus L1688 molecular cloud complex. Even though WL 17 is among the brightest disks in L1688 and massive enough to expect dust self-scattering, it was undetected in polarization down to Atacama Large Millimeter/submillimeter Array’s (ALMA’s) instrument sensitivity limit. Such low polarization fractions could indicate unresolved polarization within the beam or optically thin dust emission. We test the latter case by combining the high-sensitivity 233 GHz Stokes I data from the polarization observations with previous ALMA data at 345 and 100 GHz. We use simple geometric shapes to fit the observed disk visibilities in each band. Using our simple models and assumed dust temperature profiles, we estimate the optical depth in all three bands. The optical depth at 233 GHz peaks at τ 233 ∼ 0.3, which suggests the dust emission may not be optically thick enough for dust self-scattering to be efficient. We also find the higher-sensitivity 233 GHz data show substructure in the disk for the first time. The substructure appears as brighter lobes along the major axis, on either side of the star. We attempt to fit the lobes with a simple geometric model, but they are unresolved in the 233 GHz data. We propose that the disk may be flared at 1 mm such that there is a higher column of dust along the major axis than the minor axis when viewed at an inclination. These observations highlight the strength of high-sensitivity continuum data from dust polarization observations to study disk structures.

Hydrocavitation Piezoelectric Ocean Wave Energy Harvesting

Abstract The possibility to convert the ocean wave energy into electrical energy by piezoelectric layers has excited the imagination of ocean wave energy conversion designers for decades owing to its relative robustness (no mechanical parts are needed), the capability to cover large areas, and its relatively low cost. Unfortunately, the very poor efficiency featured by piezoelectric layers in the application of ocean waves has prevented its application even as an energy harvester. Here, the possibility to induce hydrocavitation and then working with higher local pressures for substantial efficiency enhancement is discussed. Utilizing a simplified geometrical and physical model and the linear and potential theory, a first theoretical estimation for the energy enhancement driven by hydrocavitation was calculated. It was found that the power could be enhanced several orders of magnitude which, although still rather low, however, the enhanced electric outputs can be used now as energy harvesters. Additional R&D is encouraged in order to explore the possibilities to harness hydrocavitation to enhance piezoelectric converters.

Simulation of magnetic nanoparticles crossing through a simplified blood-brain barrier model for Glioblastoma multiforme treatment

Background and ObjectivesGlioblastoma multiforme is considered as one of the most aggressive types of cancer, while various treatment techniques have been proposed. Magnetic nanoparticles (MNPs) loaded with drug and magnetically controlled and targeted to tissues affected by disease, is considered as a possible treatment. However, MNPs are difficult to penetrate the central nervous system and approach the unhealthy tissue, because of the blood-brain barrier (BBB). This study investigates numerically the delivery of magnetic nanoparticles through the barrier driven by normal pressure drop and external gradient magnetic fields, employing a simplified geometrical model, computational fluid dynamics and discrete element method. The goal of the study is to provide information regarding the permeability of the BBB under various conditions like the imposed forces and the shape of the domain, as a preliminary predictive tool. MethodsTo achieve that, the three-dimensional Navier-Stokes equations are solved in the margin of a blood vessel along with a discrete model for the MNPs with various acting forces. The numerical results are compared with experimental measurements showing that the model can predict acceptably the flow behavior. ResultsThe effect of nanoparticles’ size, external magnetic field and blood flow in the vessel, on the brain-barrier's permeability are investigated. Three different cases of available area among the endothelial cells per the MNPs’ size ratio are also examined, showing that the MNPs’ size and available area is not the dominant parameter affecting the permeability of the BBB. The results indicate that the applied magnetic field enhances the drug delivery into the central nervous system (CNS). When larger MNPs (∼100 nm) are exposed to an external magnetic field, the permeability can be improved up to 30%, while it is shown that smaller MNPs (∼10 nm) cannot be driven by the applied magnetic field and in this case the permeability remains relatively unchanged. Finally, the blood flow increase leads to a permeability improvement up to 15%. ConclusionsThe applied magnetic field improves up to 45% the permeability of the BBB for MNPs of 100 nm. The geometric characteristics of the endothelial cells, the nanoparticles’ size and the blood flow are not so decisive parameters for the drug delivery into the CNS, compared to the external magnetic force.

Room-Temperature Electrochemical Healing of Structural Steel through Pulsed Plating and Tailored Electrolyte Chemistry

Low-carbon steel is a widely used structural metal that, when fractured, can be repaired with high temperature processes such as arc welding. There are many applications, however, that would benefit from a room-temperature repair process which maintains the steel microstructure and prevents adjacent materials and electronics from overheating. We seek to enable effective room-temperature healing of steel using electrochemistry by understanding how ion transport and electrolyte chemistry influence growth and strength in fractured steel wires repaired with nickel electrodeposition. Experiments and simulations show that pulsed electroplating mitigates diffusion-limited growth to enable smooth and dense nickel deposits that have 4x higher adhesion to steel than nickel deposited by potentiostatic electroplating. We also investigate the effect of various nickel electrolyte chemistries on nickel-steel adhesion and the recovery of strength in healed steel. By combining pulsed electroplating with judicious use of electrolyte chemistry, fully fractured steel wires could be repaired to achieve up to 69% of their pristine strength.Finally, we propose a simple geometric model to estimate the energy and time requirements of electrochemical healing across length scales. Our model shows that if crack width can be minimized, over eight hundred 10-mm steel reinforcing bars (commonly used in construction) could be healed in under one minute using only one smartphone battery (5,000 mAh).This work is the first demonstration of electrochemical healing of a metal other than nickel (see our prior work: Hsain and Pikul, Adv. Funct. Mater. 29, 2019) and opens the possibility of healing a variety of structural metals using electrodeposition. With its low energy and time requirements, as well as its effective recovery of strength, electrochemical healing can be used to minimize weight in aerospace structures, extend the service life of structural parts, and more efficiently employ scarce resources in energy-constrained systems or remote environments.