Relevant Geometries Research Articles

Dosimetric dependencies on target geometry and size in radioiodine therapy for differentiated thyroid cancer

Purpose Radioiodine therapy is used in most disease stages for differentiated thyroid cancer. Its success depends on several factors, such as lesion size, completeness of surgery, extent of metastasis and tumoural iodine avidity. We aimed to investigate the importance of non-spherical geometries and size of metastases and thyroid remnants for the absorbed dose delivered. Methods Absorbed doses and energy depositions from homogeneously distributed iodine-131 in clinically relevant geometries and sizes were calculated using Monte Carlo simulations with MCNP6. A total of 162 volumes with different sizes and geometries corresponding to spheres, and prolate or oblate spheroids were simulated. Results Oblate and prolate spheroids had worse radiation coverage compared to spheres for equal masses, up to a difference of 38% for the most eccentric oblate spheroids and smallest masses simulated (a micrometastasis of mass 0.005 g). The differences in coverage could be explained by different volume - to - surface - area ratios of the spheroids. The impact of size alone caused up to 71% lower absorbed doses per decay in a spherical target mass of 0.005 g compared to 50 g. Conclusions While the iodine avidity, and therefore the total amount of decays, is the predominant contributing factor to absorbed dose in radioiodine therapy, eccentric spheroids and small target sizes can receive substantially lower absorbed doses from the same administration of radioiodine.

Unconventional spin Hall effects in nonmagnetic solids

Direct and inverse spin Hall effects lie at the heart of novel applications that utilize spins of electrons as information carriers, allowing generation of spin currents and detecting them via the electric voltage. In the standard arrangement, applied electric field induces transverse spin current with perpendicular spin polarization. Although conventional spin Hall effects are commonly used in spin-orbit torques or spin Hall magnetoresistance experiments, the possibilities to configure electronic devices according to specific needs are quite limited. Here, we investigate unconventional spin Hall effects that have the same origin as conventional ones, but manifest only in low-symmetry crystals where spin polarization, spin current and charge current are not enforced to be orthogonal. Based on the symmetry analysis for all 230 space groups, we have identified crystal structures that could exhibit unusual configurations of charge-to-spin conversion. The most relevant geometries have been explored in more detail; in particular, we have analyzed the collinear components yielding transverse charge and spin current with spin polarization parallel to one of them, as well as the longitudinal ones, where charge and spin currents are parallel. In addition, we have demonstrated that unconventional spin Hall effect can be induced by controllable breaking the crystal symmetries by an external electric field, which opens a perspective for external tuning of spin injection and detection by electric fields. The results have been confirmed by density functional theory calculations performed for various materials relevant for spintronics. We are convinced that our findings will stimulate further computational and experimental studies of unconventional spin Hall effects.

SciKit-SurgeryGlenoid, an Open Source Toolkit for Glenoid Version Measurement.

Correct understanding of the geometry of the glenoid (the socket of the shoulder joint) is key to successful planning of shoulder replacement surgery. This surgery typically involves placing an implant in the shoulder joint to restore joint function. The most relevant geometry is the glenoid version, which is the angular orientation of the glenoid surface relative to the long axis of the scapula in the axial plane. However, measuring the glenoid version is not straightforward and there are multiple measurement methods in the literature and used in commercial planning software. In this paper we introduce SciKit-SurgeryGlenoid, an open source toolkit for the measurement of glenoid version. SciKit-SurgeryGlenoid contains implementations of the 4 most frequently used glenoid version measurement algorithms enabling easy and unbiased comparison of the different techniques. We present the results of using the software on 10 sets of pre-operative CT scans taken from patients who have subsequently undergone shoulder replacement surgery. We further compare these results with those obtained from a commercial implant planning software. SciKit-SurgeryGlenoid currently requires manual segmentation of the relevant anatomical features for each method. Future work will look at automating the segmentation process to build an automatic and repeatable pipeline from CT or radiograph to quantitative glenoid version measurement.

Simulation of the Impact of Point Defects and Edge Dislocations on X‐Ray Diffraction in Hexagonal (Ni,Co)1+2xTi1−xO3 Thin Films

A computer code for simulating high‐resolution X‐ray diffraction (XRD) data from disordered crystals with arbitrary spatial composition and local lattice parameters is developed. Simulated patterns are compared with the experimental data collected on a single phase, highly crystalline (Ni0.42Co0.58)2.22Ti0.39O3 solid‐solution thin film exhibiting a large number of subsidiary minima. As a case study, the edge dislocations in hexagonal (Ni,Co)3O3 thin films with Burgers vector parallel and perpendicular to the a‐axis and c‐axis, respectively, are modeled. No peak profiles are assumed and thus issues related to profile fitting are avoided. Both macroscopic features, such as film thickness, and atomic‐scale structure, such as dislocations, are simultaneously modeled. Simulations are run on a desktop machine. Commonly applied database‐based phase identification routines can result in wrong phase identification, unless intensities are properly modeled. Modeling tools of diffractometer manufacturers are compared with the present approach. An example of how simulated reciprocal lattice patterns can be used to choose relevant measurement geometries in defected thin films is given.

Look-up table approach for uncertainty determination for operational vicarious calibration of Earth imaging sensors.

Understanding the uncertainty of a vicarious calibration is essential for any application to Earth imaging sensors. The Radiometric Calibration Network provides SI-traceable spectral top-of-atmosphere (TOA) reflectance from a network of ground sites and uses a look-up table (LUT) approach for uncertainty determination. The uncertainty LUT was derived using Monte Carlo techniques applied to the relevant solar geometry, surface, and atmospheric variables. While surface reflectance is typically the dominant uncertainty source, atmospheric contributions do play an important role, depending upon the exact scenario and conditions. This approach allows knowledge of TOA reflectance uncertainty to within 0.5%.

Advances in 3D printing of composite scaffolds for the repairment of bone tissue associated defects.

The conventional methods of using autografts and allografts for repairing defects in bone, the osteochondral bone, and the cartilage tissue have many disadvantages, like donor site morbidity and shortage of donors. Moreover, only 30% of the implanted grafts are shown to be successful in treating the defects. Hence, exploring alternative techniques such as tissue engineering to treat bone tissue associated defects is promising as it eliminates the above-mentioned limitations. To enhance the mechanical and biological properties of the tissue engineered product, it is essential to fabricate the scaffold used in tissue engineering by the combination of various biomaterials. Three-dimensional (3D) printing, with its ability to print composite materials and with complex geometry seems to have a huge potential in scaffold fabrication technique for engineering bone associated tissues. This review summarizes the recent applications and future perspectives of 3D printing technologies in the fabrication of composite scaffolds used in bone, osteochondral, and cartilage tissue engineering. Key developments in the field of 3D printing technologies involves the incorporation of various biomaterials and cells in printing composite scaffolds mimicking physiologically relevant complex geometry and gradient porosity. Much recently, the emerging trend of printing smart scaffolds which can respond to external stimulus such as temperature, pH and magnetic field, known as 4D printing is gaining immense popularity and can be considered as the future of 3D printing applications in the field of tissue engineering.

Design of the Test Section for the Experimental Validation of Antipermeation and Corrosion Barriers for WCLL BB

Tritium permeation into the Primary Heat Transfer System (PHTS) of DEMO and ITER reactors is one of the challenging issues to be solved in order to demonstrate the feasibility of nuclear fusion power plants construction. Several technologies were investigated as antipermeation and corrosion barriers to reduce the tritium permeation flux from the breeder into the PHTS. Within this frame, alumina coating manufactured by Pulsed Laser Deposition (PLD) and Atomic Layer Deposition (ALD) are two of the main candidates for the Water Cooled Lithium Lead (WCLL) Breeder Blanket (BB). In order to validate the performance of the coatings on relevant WCLL BB geometries, a mock-up was designed and will be characterized in an experimental facility operating with flowing lithium-lead, called TRIEX-II. The present work aims to illustrate the preliminary engineering design of a WCLL BB mock-up in order to deeply investigate permeation of hydrogen isotopes through PHTS water pipes. The permeation tests are planned in the temperature range between 330 and 500 °C, with hydrogen and deuterium partial pressure in the range of 1–1000 Pa. The hydrogen isotopes transport analysis carried out for the design and integration of the mock-up in TRIEX-II facility is also shown.

Meltelectrowriting of Polycaprolactone Thin Membranes with High Porosity

An emerging polymer fiber-forming, additive manufacturing (AM) technique, “Melt Electrowriting” (MEW), has been used to build polymer scaffolds for tissue engineering applications (TE). Compared to other polymer forming AM technologies, MEW is a solvent-free process that we are using to produce extremely fine fibers with accurate positioning. This is suitable for the production of biologically relevant pore geometries that may encourage cell attachment, production of extracellular matrix, vascularization, and tissue-specific physiology. In regards to restoring or creating tissue-specific physiological function, MEW is also one of the few biofabrication modalities capable of forming thin sheets (i.e., thin membranes) with controlled seeding densities (e.g., as thin as a single cell thick) that can be positioned contiguously. The interaction of adjacent layers of different cell types is a functional requirement of many organs. In order to expand the variety of geometries that can be manufactured, our device separately controls nozzle position and the collector platform, such as a flat surface or a spinning mandrel. With our MEW device we can modulate parameters involved in the process such as voltage, pressure, and collector translation/rotation speed, to obtain thin membranes of stacked micro-fibers that produce pore sizes of approximately 1000-, 500-, and 250 μm Achieving that level of accuracy of fiber deposition requires the programming of kinematics (i.e, simultaneous movement) that is implied by these and other MEW parameters.

Distance Matrix and Markov Chain Based Sensor Localization in WSN

Applications based on Wireless Sensor Networks (WSN) have shown to be quite useful in monitoring a particular geographic area of interest. Relevant geometries of the surrounding environment are essential to establish a successful WSN topology. But it is literally hard because constructing a localization algorithm that tracks the exact location of Sensor Nodes (SN) in a WSN is always a challenging task. In this research paper, Distance Matrix and Markov Chain (DM-MC) model is presented as node localization technique in which Distance Matrix and Estimation Matrix are used to identify the position of the node. The method further employs a Markov Chain Model (MCM) for energy optimization and interference reduction. Experiments are performed against two well-known models, and the results demonstrate that the proposed algorithm improves performance by using less network resources when compared to the existing models. Transition probability is used in the Markova chain to sustain higher energy nodes. Finally, the proposed Distance Matrix and Markov Chain model decrease energy use by 31% and 25%, respectively, compared to the existing DV-Hop and CSA methods. The experimental results were performed against two proven models, Distance Vector-Hop Algorithm (DV-HopA) and Crow Search Algorithm (CSA), showing that the proposed DM-MC model outperforms both the existing models regarding localization accuracy and Energy Consumption (EC). These results add to the credibility of the proposed DC-MC model as a better model for employing node localization while establishing a WSN framework.

Dynamic response and roughening of ferroelectric domain walls driven at planar electrode edges

Understanding and controlling the motion, stability, and equilibrium configuration of ferroelectric domain walls is key for their integration into potential nanoelectronic applications, such as ferroelectric racetrack memories. Using piezoresponse force microscopy, we analyze the growth and roughness of ferroelectric domains in epitaxial thin film Pb(Zr0.2Ti0.8)O3, driven by the electric fields at straight edges of planar electrodes at two different temperatures. This device relevant geometry allows us to confirm that the domain walls are well described as one-dimensional monoaffine elastic interfaces driven in random-bond disorder. However, we observe a progressive increase in roughness as initially flat domain walls move through the disorder landscape, which could prove a significant limiting factor for racetrack-type memories using ferroelectrics.

Geometry dependence of micron-scale NMR signals on NV-diamond chips

Small volume nuclear magnetic resonance spectroscopy (NMR) has recently made considerable progress due to rapid developments in the field of quantum sensing using nitrogen vacancy (NV) centers. These optically active defects in the diamond lattice have been used to probe unprecedented small volumes in the picoliter range with high spectral resolution. However, the NMR signal size depends strongly on both the diamond sensor’s and sample’s geometry. Using Monte-Carlo integration of sample spin dipole moments, the magnetic field projection along the orientation of the NV center for different geometries has been analyzed. We show that the NMR signal strongly depends on the NV-center's orientation with respect to the diamond surface. While the signal of currently used planar diamond sensors converges as a function of the sample volume, more optimal geometries lead to a logarithmically diverging signal. Finally, we simulate the expected signal for spherical, cylindrical and nearly-2D sample volumes, covering relevant geometries for interesting applications in NV-NMR such as single-cell biology or NV-based hyperpolarization. The results provide a guideline for NV-NMR spectroscopy of microscopic objects.

Abstract 14158: Cardiac Leaflet Enhancement (CARLEN) Treats Functional Mitral Regurgitation While Preserving the Native Valve Dynamics

Introduction: Interventional repair of functional mitral regurgitation (FMR) is rapidly replacing traditional surgical correction as surgery is contraindicated in most FMR patients. Current treatments reduce FMR acutely but unfavorably alter mitral valve (MV) geometry resulting in MR recurrence over time and are restricted to use in specific anatomies. We developed a new focal leaflet augmentation approach ( Fig. 1A ) that augments a single leaflet to correct FMR without the disturbing MV dynamics. Hypothesis: We hypothesize that Cardiac leaflet enhancing (CARLEN) implant can effectively correct regurgitation in different geometries seen clinically in FMR patients. Methods: CARLEN was laser cut from a thin sheet of nitinol and shape set to form a 3D structure with two arms that grasp the leaflet and a balloon like section that enables leaflet enhancement ( Fig. 1B ). A trans-septal delivery system was developed and the feasibility of deployment was tested in a swine model ( Fig. 2 ). CARLEN functionality was tested and compared to Edge-to-Edge repair (EE) in an in-vitro left heart simulator with an isolated pig MV (n=6) in different valve geometries seen in FMR patients: a) Annular dilation (AD) alone (aFMR), b) AD+asymmetric tethering (iFMR), and c) AD+symmetric tethering (dFMR). Results: CARLEN consistently and significantly decreased FMR in all geometries (aFMR: 14.79±3.11% vs 6.79±1.90%; iFMR: 20.52±2% vs 6.64±2.16%; dFMR: 21.93±7.2% vs 7.12±2.83%, p<0.05). However, significant reduction after EE was seen only in iFMR and dFMR ( Fig. 3 ). CARLEN did not perturb leaflet kinematics whereas leaflet mobility was significantly decreased after EE ( Fig. 4 ) in all geometries. Conclusion: Focal leaflet enhancement with CARLEN can effectively correct regurgitation in all clinically relevant valve geometries associated with FMR, potentially expanding the opportunity for transcatheter repair to a larger patient population.

Extraction of Thickness and Water-Content Gradients in Hydrogel-Based Water-Backed Corneal Phantoms Via Submillimeter-Wave Reflectometry

Absolute thickness and free-water-content gradients in gelatin-based corneal phantoms with physiologically accurate radii of curvature and aqueous backing were extracted via coherent submillimeter-wave reflectometry at 220–330 GHz. Fourier-domain-based calibration methods, utilizing temporal and spatial gating, were developed and yielded peak-to-peak amplitude and phase clutter of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> and 0.1°, respectively, for signal-to-noise ratios (SNRs) between 40 and 50 dB. Total 12 phantoms were fabricated. Calibration methods enabled quantification of target sphericity that strongly correlated with optical-coherence tomography-based sphericity metrics via image segmentation. The extracted free-water volume fraction varied less than 5% in the five phantoms whose fabrication yielded the most spherical geometry. Submillimeter-wave-based thickness accuracy was better than 111 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m (∼λ/9) with an average of 65 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m (∼λ/17) and standard deviation of 44 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m (∼λ/25) for phantoms with physiologically relevant geometry. Monte-Carlo simulations of measurement noise and uncertainty limits agree with the experimental data analysis and indicate a lower thickness accuracy limit of 33 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m, and water-content sensitivities of 0.5% and 11.8% for the anterior and posterior segments, respectively. Numerical analysis suggests that the measurement fidelity was SNR limited and identified optical path length ambiguities within the cornea where a continuum of thickness/water gradient pairs produces statistically insignificant differences in complex reflection coefficient for finite SNR. This is the first known submillimeter-wave measurement technique, which is able to extract both the thickness and water-content gradients from a soft-tissue phantom, with a water backing, without the need for ancillary measurements.

Investigation of the Performance Characteristics of the Angle-based Proportional Navigation Guidance Law

Guidance commands generated by the proportional navigation guidance (PNG) law which constitutes the most popular one among the guidance laws applied on the guidance munition fired against predetermined targets are in the form of linear acceleration or angular speed as dictated by the relevant engagement geometry. As a result of the studies in which notable linear acceleration- and angle-based guidance laws are compared, it is seen the lateral acceleration values obtained with the PNG law occur in a lower level than the results of the angle-based guidance laws. However, the angle-based guidance laws lead to lower final miss distances. In this study, the PNG law is so adapted that it yields angle-based guidance commands and then it is applied upon a short range air-to-surface missile against a maneuvering surface target as well as the velocity pursuit guidance law that is nothing but a version of PNG law, linear homing guidance law, and body pursuit guidance law. After the computer simulations, it is observed that the angle-based PNG law produces smaller final miss distances compared to its original form. The resulting lateral accelerations are in admissible levels. Also, the engagement duration values with the target happen to be almost the same.

Modal Decomposition and Linear Modeling of Swirl Fluctuations in the Mixing Section of a Model Combustor Based on Particle Image Velocimetry Data

Abstract In order to determine the flame transfer function of a combustion system, different mechanisms have been identified that need to be modeled. This study focuses on the generation and propagation of one of these mechanisms, namely, the swirl fluctuations downstream of a radial swirl combustor under isothermal conditions. Swirl fluctuations are generated experimentally by imposing acoustic perturbations. Time-resolved longitudinal and crosswise particle image velocimetry (PIV) measurements are conducted inside the mixing tube and combustion chamber to quantify the evolution of the swirl fluctuations. The measured flow response is decomposed using spectral proper orthogonal decomposition to unravel the contributions of different dynamical modes. In addition a resolvent analysis is conducted based on the linearized Navier–Stokes equations to reveal the intrinsically most amplified flow structures. Both, the data-driven and analytic approach, show that inertial waves are indeed present in the flow response and an inherent flow instability downstream of the swirler, which confirms recent theoretical works on inertial waves. However, the contribution of the identified inertial waves to the total swirl fluctuations turns out to be very small. This is suggested to be due to the very structured forcing at the swirler and the additional amplification of shear-driven modes. Overall, this work confirms the presence of inertial waves in highly turbulent swirl combustors and evaluates its relevance for industry-related configurations. It further outlines a methodology to analyze and predict their characteristics based on mean fields only, which is applicable for complex geometries of industrial relevance.

Mode-Matching Analysis of Acoustic Wave Propagation along a Rigid Coaxial Pipe with an Internal Impedance Loading

Mathematical analysis of the acoustic wave propagation along the coaxial waveguide, whose right part of the outer wall is impedance-coated, is considered. By determining the boundary conditions corresponding to the relevant geometry, the boundary value problem is solved by applying the Mode-Matching technique. At the end of the analysis, numerical computations are carried out to illustrate the affect of some parameters. The results demonstrate the significance of the absorbing lining in reducing the unwanted noise.

A two‐stage recursive ray tracing algorithm to automatically identify external building objects in building information models

AbstractThe internal or external attribute of building information modeling (BIM) objects is vital information for many BIM‐based engineering analyses such as building energy analysis and cost estimation. Unfortunately, such information is often inaccurate, incomplete, or missing entirely in most BIM models. Manually checking, correcting, or inputting this data for large‐scale BIM models can be time‐consuming, laborious, and error‐prone. This study proposes a two‐stage ray tracing algorithm to automatically identify external BIM objects, based on the idea that external objects of a building can be viewed from somewhere outside the building. The first‐stage ray tracing samples viewpoints from the six faces of an offset axis‐aligned bounding box (AABB) of the building and emits a ray for each viewpoint to detect relevant external objects. The second‐stage ray tracing recursively searches for any remaining external objects from the view of the external objects that have been detected in the previous round of ray tracing. Both stages are carefully designed for efficiency. Furthermore, a two‐tier AABB tree is introduced to spatially index building objects on both model and object levels to accelerate relevant geometry operations. The proposed algorithm is validated with one synthetic and two large‐scale real‐world building models. The results show that all the external objects in the three models are accurately and efficiently identified, and the two‐tier spatial indexing and other acceleration techniques improve the algorithm's efficiency significantly.

Force microscopy cantilevers locally heated in a fluid: Temperature fields and effects on the dynamics

Atomic force microscopy cantilevers are often, intentionally or not, heated at their extremity. We describe a model to compute the resulting temperature field in the cantilever and in the surrounding fluid on a wide temperature range. In air and for common geometries, the heat fluxes in the cantilever and to the environment are of comparable magnitude. We then infer how the fluid–structure interaction is modified due to heating and predict the induced changes in the dynamics of the system. In particular, we describe how the resonance frequencies of the cantilever shift with a temperature increase due to two competing processes: softening of the cantilever and decrease of the fluid inertial effects. Our models are illustrated by experiments on a set of cantilevers spanning the relevant geometries to explore the relative importance of both effects.

Engineering large, anatomically shaped osteochondral constructs with robust interfacial shear properties

Despite the prevalence of large (>5 cm2) articular cartilage defects involving underlying bone, current tissue-engineered therapies only address small defects. Tissue-engineered, anatomically shaped, native-like implants may address the need for off-the-shelf, tissue-repairing therapies for large cartilage lesions. This study fabricated an osteochondral construct of translationally relevant geometry with robust functional properties. Scaffold-free, self-assembled neocartilage served as the chondral phase, and porous hydroxyapatite served as the osseous phase of the osteochondral constructs. Constructs in the shape and size of an ovine femoral condyle (31 × 14 mm) were assembled at day 4 (early) or day 10 (late) of neocartilage maturation. Early osteochondral assembly increased the interfacial interdigitation depth by 244%, interdigitation frequency by 438%, interfacial shear modulus by 243-fold, and ultimate interfacial shear strength by 4.9-fold, compared to late assembly. Toward the development of a bioprosthesis for the repair of cartilage lesions encompassing up to an entire condylar surface, this study generated a large, anatomically shaped osteochondral construct with robust interfacial mechanical properties and native-like neocartilage interdigitation.

Computing the local ion concentration variations for electric-double-layer-modulation microscopy

Modulation of the electric potential on a conducting electrode is presented to generate an optical contrast for scattering microscopy that is sensitive to both surface charge and local topography. We dub this method electric-double-layer-modulation microscopy. We numerically compute the change in the local ion concentration that is the origin of this optical contrast for three experimentally relevant geometries: nanosphere, nanowire, and nanohole. In absence of plasmonic effects and physical absorption, the observable optical contrast is proportional to the derivative of the ion concentration with respect to the modulated potential. We demonstrate that this derivative depends on the size of the object and, less intuitively, also on its surface charge. This dependence is key to measuring the surface charge, in an absolute way, using this method. Our results help to identify the experimental conditions such as dynamic range and sensitivity that will be necessary for detecting the elementary charge jumps. We conclude that the nanohole is the most suitable geometry of the three for achieving elementary charge sensitivity.