Geometrical Constructs Research Articles

In-situ Printability Maps (IPM): A new approach for in-situ printability assessment with application to extrusion-based bioprinting

3D Bioprinting is an emerging field with many highly valuable applications. The most common and versatile technology is extrusion-based bioprinting, which requires extensive experimental campaigns to achieve appropriate quality of the bioprinted constructs when new bioinks or complex geometrical constructs need to be considered. This paper presents a new approach to easily guide operators and scientists to evaluate the probability of successful bioprinting in a defined window of the process parameters, starting from a small experimental campaign and relying on in-situ quality data. The proposed method consists of defining printability maps based on a probabilistic approach. These maps assess the printing outcome considering a specified acceptable deviation from the nominal geometry, which is predefined by the end-user depending on the application at hand. Even if shown with reference to extrusion-based bioprinting, the proposed method can be used with any other bioprinting process and any quality index, including categorical assessment classification. Eventually, the paper shows how the map can be combined with different quality criteria (e.g., productivity, cell viability) to define the appropriate setting, depending on the application at hand. Furthermore, the map provides a practical tool for rapid material printability assessment and robust process optimization. It offers an enhanced visual representation of the process domain, acceptable region boundaries, and their resilience to variation and uncertainties. Eventually, in-situ printability maps represent a further leap for the advancement of bioprinting toward the digital transformation, aiming at increasing the controllability and scalability of the bioprinting process.

Curcumin nanoparticles as a multipurpose additive to achieve high-fidelity SLA-3D printing and controlled delivery

Light-based three-dimensional (3D) printing has been under use extensively to fabricate complex geometrical constructs which find a vast application in the fields of drug delivery and tissue engineering fields due to its ability to recapitulate the intricate biological architecture and thus provides avenues to achieve previously unachievable biomedical devices. The inherent problem associated with light-based 3D printing (from a biomedical perspective) is that of light scattering causing inaccurate and defective prints which results in erroneous drug loading in 3D printed dosage forms and can also render the environment of the polymers toxic for the biological cells and tissues. In this regard, an innovative additive comprising of a nature-derived drug-cum-photoabsorber (curcumin) entrapped in naturally derived protein (bovine serum albumin) is envisaged to act as a photoabsorbing system that can improve the printing quality of 3D printed drug delivery formulations (macroporous pills) as well as provide stimuli-responsive release of the same upon oral ingestion. The delivery system was designed to endure the chemically and mechanically hostile gastric environment and deliver the drug in the small intestine to improve absorption. A 3 × 3 grid macroporous pill was designed (specifically to withstand the mechanically hostile gastric environment) and 3D printed using Stereolithography comprising of a resin system including acrylic Acid, PEGDA and PEG 400 along with curcumin loaded BSA nanoparticles (Cu-BSA NPs) as a multifunctional additive and TPO as the photoinitiator. The 3D printed macroporous pills were found to show excellent fidelity to CAD design as evident from the resolution studies. The mechanical performance of the macroporous pills was found to be extremely superior to monolithic pills. The pills found to release curcumin in pH responsive manner with slower release at acidic pH but faster release at intestinal pH due to its similar swelling behavior. Finally, the pills were found to be cytocompatible to mammalian kidney and colon cell lines.

Optimization of Freeform Reversible Embedding of Suspended Hydrogel Microspheres for Substantially Improved Three-Dimensional Bioprinting Capabilities.

Three-dimensional (3D) bioprinting demonstrates technology that is capable of producing structures comparable to native tissues in the human body. The freeform reversible embedding of suspended hydrogels (FRESH) technique involves hydrogel-based bio-inks printed within a thermo-reversible support bath to provide mechanical strength to the printed construct. Smaller and more uniform microsphere sizes of FRESH were reported to aid in enhancing printing resolution and construct accuracy. Therefore, we sought to optimize the FRESH generation protocol, particularly by varying stir speed and stir duration, in hopes to further improve microsphere size and uniformity. We observed optimal conditions at a stir speed of 600 rpm and stir duration for 20 h that generated the smallest microspheres with the best uniformity. Comparison of using the optimized FRESH to the commercial FRESH LifeSupport to bioprint single filament and geometrical constructs revealed reduced single filament diameters and higher angular precision in the optimized FRESH bio-printed constructs compared with those printed in the commercial FRESH. Overall, our refinement of the FRESH manufacturing protocol represents an important step toward enhancing 3D bioprinting resolution and construct fidelity. Improving such technologies allows for the fabrication of highly accurate constructs with anatomical properties similar to native counterparts. Such work has significant implications in the field of tissue engineering for producing accurate human organ model systems. Impact statement Freeform reversible embedding of suspended hydrogels (FRESH) is a method of sacrificial three-dimensional (3D) bioprinting that offers support to reinforce bio-ink extrusion during printing. During FRESH generation, the stir speed and stir duration of the mixture can significantly impact FRESH microsphere characteristics. In this study, we optimized FRESH microspheres to significantly improve resolution and accuracy in bioprinting. This advancement in FRESH-based 3D bioprinting technologies allows for the fabrication of highly accurate constructs with anatomical properties similar to native counterparts and has significant implications in the field of tissue engineering and translational medicine.

ARCHITECTURAL DESIGN WITH GENERATIVE ALGORITHM AND VIDEO PROJECTION MAPPING

The innovative and creative approach that is produced for architectural design problems involves quite complex stages. In architectural design, the designer's approach and numerical data make the design process a multi-layered structure. The integration of parametric modeling programs and generative algorithms makes it easy to carry out multi-layered design processes. Generative systems defined through generative algorithms enable conceptual approaches, various geometrical constructs, and different forms to be created in digital environments in solving design problems. The creation of the generative algorithm of the design eliminates the restrictive role of modeling software in the architectural design. The designer gets the opportunity to create every parameter and design criteria specific to his approach. 
 In this study, our aim is to develop a generative algorithm in a computer environment by using the principles of fractal geometry function. The generative system creates by overlaying the developed generative algorithm with the environmental factor parameters. In this system proposal, the goal is to produce various facade design proposals by coding the algorithm fractal functions and to make use of the visualization of various potentials of the generative algorithm in parametric facade proposals. Video projection mapping method is chosen to discuss the functionality of the parameters in the proposed generative system of the developed generative algorithm. Computation of the transformation relating consecutive image frames is an essential operation in video mapping. In this context, the design created with the generative system is reflected on a real scale medium , specifically a column in this study, and various image frames letting new design proposals produced by the algorithm were evaluated. In concluding rmarks, the advantages of architectural designs modeled by coding with the generative algorithm compared to the algorithms obtained directly with the software are discussed.

Modeling Alkyl Aromatic Hydrocarbons with Dissipative Particle Dynamics.

Building on previous work studying alkanes, we develop a dissipative particle dynamics (DPD) model to capture the behavior of the alkyl aromatic hydrocarbon family under ambient conditions of 298 K and 1 atmosphere. Such materials are of significant worldwide industrial importance in applications such as solvents, chemical intermediates, surfactants, lubricating oils, hydraulic fluids, and greases. We model both liquids and waxy solids for molecules up to 36 carbons in size and demonstrate that we can correctly capture both the freezing transition and liquid-phase densities in pure substances and mixtures. We also demonstrate the importance of including specialized bead types into the DPD model (rather than solely relying on generic bead types) to capture specific local geometrical constructs such as the benzene ring found in the benzyl chemical group; this can be thought of as representing subtle real-world many-body effects via customized pairwise non-bonded potentials.

Motion Polytopes in Virtual Reality for Shared Control in Remote Manipulation Applications.

In remote applications that mandate human supervision, shared control can prove vital by establishing a harmonious balance between the high-level cognition of a user and the low-level autonomy of a robot. Though in practice, achieving this balance is a challenging endeavor that largely depends on whether the operator effectively interprets the underlying shared control. Inspired by recent works on using immersive technologies to expose the internal shared control, we develop a virtual reality system to visually guide human-in-the-loop manipulation. Our implementation of shared control teleoperation employs end effector manipulability polytopes, which are geometrical constructs that embed joint limit and environmental constraints. These constructs capture a holistic view of the constrained manipulator’s motion and can thus be visually represented as feedback for users on their operable space of movement. To assess the efficacy of our proposed approach, we consider a teleoperation task where users manipulate a screwdriver attached to a robotic arm’s end effector. A pilot study with prospective operators is first conducted to discern which graphical cues and virtual reality setup are most preferable. Feedback from this study informs the final design of our virtual reality system, which is subsequently evaluated in the actual screwdriver teleoperation experiment. Our experimental findings support the utility of using polytopes for shared control teleoperation, but hint at the need for longer-term studies to garner their full benefits as virtual guides.

Multimodal Microscale Imaging of Textured Perovskite-Silicon Tandem Solar Cells.

Halide perovskite/crystalline silicon (c-Si) tandem solar cells promise power conversion efficiencies beyond the limits of single-junction cells. However, the local light-matter interactions of the perovskite material embedded in this pyramidal multijunction configuration, and the effect on device performance, are not well understood. Here, we characterize the microscale optoelectronic properties of the perovskite semiconductor deposited on different c-Si texturing schemes. We find a strong spatial and spectral dependence of the photoluminescence (PL) on the geometrical surface constructs, which dominates the underlying grain-to-grain PL variation found in halide perovskite films. The PL response is dependent upon the texturing design, with larger pyramids inducing distinct PL spectra for valleys and pyramids, an effect which is mitigated with small pyramids. Further, optimized quasi-Fermi level splittings and PL quantum efficiencies occur when the c-Si large pyramids have had a secondary smoothing etch. Our results suggest that a holistic optimization of the texturing is required to maximize light in- and out-coupling of both absorber layers and there is a fine balance between the optimal geometrical configuration and optoelectronic performance that will guide future device designs.

Incisive Approach to Fermi-Walker Transport

A rational approach to the Fermi-Walker transport equation is proposed by deriving it from a condition of “non-rotation”. First, the condition is applied to a tetrad basis and then generalized to an arbitrary space-time four-vector. The method is conceptually simple and apart from the use of tetrad bases in four-dimensional space-time, does not require the effort of visualizing abstract geometrical constructs in spaces of more than three dimensions. The argument develops in the context of the flat space-time of special relativity theory but the final result can be immediately extended to curved space-time.

Comment on 'Metamorphic olivine after dehydration embrittlement in Serpentinite: Case study from the Shiraga Serpentinite mass in the Sanbagawa high P/T metamorphic belt, central Shikoku, Japan' by Fukumura, Okamoto and Terabayashi, https://doi.org/10.1111/iar.12293

Comment on 'Metamorphic olivine after dehydration embrittlement in Serpentinite: Case study from the Shiraga Serpentinite mass in the Sanbagawa high P/T metamorphic belt, central Shikoku, Japan' by Fukumura, Okamoto and Terabayashi, https://doi.org/10.1111/iar.12293

Nydus One Syringe Extruder (NOSE): A Prusa i3 3D printer conversion for bioprinting applications utilizing the FRESH-method

<h2>Abstract</h2> Bioprinting, combined with other tissue engineering techniques, is a promising method to create engineered tissues or standardized 3D cell culturing models. It has potential applications in the development of animal free models for drug toxicity screenings or for personalized medicine approaches. Here we report the conversion of the worldwide used open source 3D printer (RepRap, Prusa i3) to a functional and affordable bioprinter by substituting the common plastic-extruder with the <b>N</b>ydus <b>O</b>ne <b>S</b>yringe <b>E</b>xtruder (<b>NOSE</b>). The <b>NOSE</b> modification enables mechanical hydrogel extrusion as well as a tunable deposition precision and volume by featuring a modular syringe-holder concept. A cost effective and simple hardware design including a custom software (termed ‘composer') was developed to prove that this technique can be made accessible for a broader public. Furthermore, the printing procedure was optimized for the peer-reviewed FRESH-method by Hinton et al. which allows to print geometrical complex cell-laden constructs. We provide a detailed protocol on the creation of the FRESH-gel to ensure the reproducibility of this state of the art method. As a proof of concept HEK293 cells as well as mouse embryonic stem cells (mESC) were utilized for cell-laden printing. Depending on the cellular source the survival rates range from 60% up to 95%. Automatized quantitative viability analysis was performed using the open source image analysis tool Icy, in particular the "spot detector" plugin. A detailed protocol allows the recreation of the assay. Further data utilizing a support bath printing technique reveal limitations regarding the printing and residential time of cell-laden constructs.

Decoding Gestural Iconicity.

Speakers frequently perform representational gestures to depict concepts in an iconic fashion. For example, a speaker may hold her index finger and thumb apart to indicate the size of a matchstick. However, the process by which a physical handshape is mentally transformed into abstract spatial information is not well understood. We present a series of experiments that investigate how people decode the physical form of an articulator to derive imaginary geometrical constructs, which we call "gesture form." We provide quantitative evidence for several key properties that play a role in this process. First, "profiling," the ability to focus on a structural subunit within the complex form of the physical hand. Second, "perspective," for which we show that one and the same handshape seen from different perspectives can lead to different spatial interpretations. Third, "selectivity," the fact that gestures focus on specific spatial features at the expense of others. Our results provide a first step toward mapping out the process of how representational gestures make the communication of spatial information possible.

Advanced geometrical constructs in a Pueblo ceremonial site, c 1200 CE

Summer 2015 marked the 100th anniversary of the excavation by J.W. Fewkes of the Sun Temple in Mesa Verde National Park, Colorado; an ancient complex prominently located atop a mesa, constructed by the ancestral Pueblo peoples approximately 800years ago. While the D-shaped structure is generally recognized by modern Pueblo peoples as a ceremonial complex, the exact uses of the site are unknown, although the site has been shown to have key solar and lunar alignments.In this study, we examined the potential that the site was laid out using advanced knowledge of geometrical constructs. Using aerial imagery in conjunction with ground measurements, we performed a survey of key features of the site. We found apparent evidence that the ancestral Pueblo peoples laid out the site using the Golden rectangle, Pythagorean 3:4:5 triangles, equilateral triangles, and 45° right triangles.The survey also revealed that a single unit of measurement, L=30.5±0.5cm, or one third of that, appeared to be associated with many key features of the site. Further study is needed to determine if this unit of measurement is common to other ancestral Pueblo sites, and also if geometric constructs are apparent at other sites.These findings represent the first potential quantitative evidence of knowledge of advanced geometrical constructs in a prehistoric North American society, which is particularly remarkable given that the ancestral Pueblo peoples had no written language or number system.

Absorbed fractions and dose factors for a model of the mouse skeleton

A general model for skeletal dosimetry in mice is presented. Geometrical constructs were made for four general regions in the mouse skeleton, and dose factors for 90Sr and 90Y were calculated using the MCNP Monte Carlo transport code. Then, an overall skeletal dose factor for the whole skeleton was derived based on the individual values and the fraction of the total skeleton that they were assumed to represent. The whole skeleton average values were 1.56 × 10−11 Gy/dis for 90Sr and 1.74 × 10−11 Gy/dis for 90Y.

Periodic Orbits in the Elliptical Relative Motion Problem with Space Surveillance Applications

Periodic orbits with respect to an object in an eccentric Keplerian reference orbit can be found in a variety of ways, including the use of Tschauner–Hempel equations and orbital element differences, which both admit linearized solutions, as well as through direct analyses of two orbits. An alternative parameterization of the last approach is proposed in the current study, using an inertial frame and simple geometrical constructs inherent to the relative motion problem. In this manner, an intuitive and straightforward characterization of periodic orbits is established that retains the nonlinear dynamics. The resulting multidimensional space that defines the periodic orbits is surveyed, archiving 336 orbits and their characteristics, and direct comparisons are made with the Tschauner–Hempel equations to assess the linear region of validity. Applications focus on resident space object (RSO) surveillance and circumnavigation orbits. An orbit’s effectiveness is analyzed in terms of object coverage using coverage figures of merit, including the concept of “RSO tracks”, the analogy of ground tracks on the body-fixed surface of an RSO.

Quantum polyhedra, definitions, statistics and the construction of a collective quantum similarity index

Quantum polyhedra (QP) are geometrical constructs whose vertices are made by quantum mechanical density functions (DF). In this paper a QP centroid and a variance are defined at two levels: functional and numerical. The numerical QP variance can be shown associated to a collective QP squared distance involving the whole DF set composing the QP vertices. In this manner, a global dissimilarity index corresponding to the set of QP vertices can be defined. Extension of the mathematical and computational techniques developed on QP to shape functions polyhedra and to classical descriptor N-dimensional multimolecular polyhedra, are also discussed.

A geometric tool for the analysis of position and force constraints in wave energy converters

Most wave energy devices are subject to finite constraints on both the power take-off (PTO) stroke length and the maximum force that the PTO can tolerate. It is also often the case that greater stroke lengths can reduce the maximum force in the PTO and vice versa. Ultimately, some informed choice of PTO constraints must be made in order to ensure that PTO constraints are not violated and that the trade-off between position and force constraints is made in such as way that maximum energy is captured by the converter. This paper presents a tool to allow device developers to check the satisfaction of constraints for a given hydrodynamic model and set of sea conditions and, where constraints are not satisfied, shows how to relax the constraints to maximize energy capture. The tool is algebraic, requiring no simulation and the results are presented through intuitive geometrical constructs. Sample application results are presented for single- and two-body wave energy systems.

Simple Engineering Applications Recycled as Effective Training Aids

Summary Technical advances have led to both expansion and increased specialization in the engineering skills employed in our industry. In many cases, these specializations involve the use of complex engineering calculations involving a bewildering number of inputs and outputs to match real-world situations. Another problem with high-end applications is that they are costly and their logic is often presented as a "black box"—disclosure may be hampered by intellectual-property concerns. Although such high-fidelity applications may be essential for operations, simpler models with few inputs are better for scoping exercises or training. The rapid and effective transfer of knowledge and experience to new hires with diverse backgrounds remains a key challenge. Though information technology and richer media have helped standardize delivery methods, accessing appropriate engineering applications for training purposes remains a challenge. The important requirements are to communicate the fundamentals and build on knowledge gained at university. At the same time, the teaching methods and modules should instill curiosity and encourage critical assessment of the models and methods used. Therefore, the models should not be too far from reality. Technical progress and refinement of a broad range of topics are inherent in the content and structure of the SPE paper library. The application to training is illustrated using examples including the simple 2D bottomhole-assembly (BHA) algorithm presented by Walker (1973). This paper shows how key refinements have been included by use of simple geometrical constructs and how the model has been used effectively in spreadsheet form to develop an understanding of BHA behavior and directional-survey-sag correction, and to identify and correct programmatic errors. It is suggested that greater use can be made of the SPE library as a ready source of cost-effective training material and that the descriptions of the simpler engineering applications it contains can be recycled as valuable training aids.

Population-Based Optimization Algorithms for History Matching and Uncertainty Quantification: PUNQ-S3

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 136861, ’Comparative Study of Novel Population-Based Op timization Algorithms for History Matching and Uncertainty Quantification: PUNQ-S3 Revisited,’ by Yasin Hajizadeh, SPE, Mike Christie, SPE, and Vasily Demyanov, Institute of Petroleum En gineering, Heriot-Watt University, prepared for the 2010 Abu Dhabi International Petroleum Exhibition &amp; Conference, Abu Dhabi, UAE, 1-4 November. The paper has not been peer reviewed. Multiple history-matched models are essential for a realistic uncertainty estimate of the field’s future behavior. This study compared application of ant-colony optimization (ACO), differential evolution (DE), and neighborhood algorithms (NAs) for history matching and uncertainty quantification of the PUNQ-S3 reservoir, a synthetic benchmark case with challenging parameterization, history-matching, and uncertainty-quantification steps. Introduction History matching of reservoir models and uncertainty quantification of the predictions are two important steps in any field-management process. In the history-matching phase, simulation models are calibrated on the basis of the observed production history of the reservoir. Parameters of the reservoir model are perturbed, and the model’s output is compared with available fluid-production rates or pressure measurements. This procedure is repeated with new parameter values until good agreement is obtained between output of the simulation and observations. History matching is an inverse problem with nonunique solutions. Multiple combinations of reservoir properties can provide a good match to observed field behavior. To quantify the uncertainty of predictions realistically, multiple history-matched reservoir models are required. Diverse models are likely to show different production behavior in the future because of different reservoir parameters. Recently, ACO and DE algorithms have been applied to history matching of a simple reservoir model with a small number of unknowns (eight). The subject methods for history matching were applied to a more-complex reservoir with 45 uncertain parameters, and the results were compared to those from NA. Originally, ACO was proposed for problems with discrete parameter space, and it later was adopted to handle continuous-optimization problems. DE is a powerful global-optimization algorithm that is a parallel-population-based search algorithm. The NA is a recent stochastic-optimization method that uses simple geometrical constructs called Voronoi cells to find good-fitting regions of the search space. Voronoi cell is a method to decompose the search space into n cells around n points by centering on the generated points. Each of these cells is the nearest neighborhood region of the points. Case Study The PUNQ-S3 reservoir-simulation model is a five-layer model. The top depth of PUNQ-S3 reservoir is 2430 m. It has a 1.5° dip angle and is bounded by faults to the east and south. A relatively strong aquifer on the north and west provides pressure support. Because of this pressure support, no injection wells have been drilled in this reservoir. There also is a small gas cap in the reservoir in Layer 1, and no wells are completed in this layer because of the effect of free-gas production on recovery from the reservoir. There are six production wells, all near the initial gas/oil contact. Three producers are perforated in Layers 4 and 5. Two producers are completed in Layers 3 and 4, and one producer is perforated only in Layer 4. One of the producers is completed near the aquifer, and water breakthrough was observed in the seventh year. Free-gas production starts in Years 4 and 5 in two of the producers. There also are positions for five infill wells.

Application of low energy ion blocking for adsorption site determination of Na Atoms on a Cu(111) surface

Ion blocking in the low keV energy range is demonstrated to be a sensitive method for probing surface adsorption sites by means of the technique of time-of-flight scattering and recoiling spectroscopy (TOF-SARS). Adsorbed atoms can block the nearly isotropic backscattering of primary ions from surface atoms in the outmost layers of a crystal. The relative adsorption site position can be derived unambiguously by simple geometrical constructs between the adsorbed atom site and the surface atom sites. Classical ion trajectory simulations using the scattering and recoiling imaging code (SARIC) and molecular dynamics (MD) simulations provide the detailed ion trajectories. Herein we present a quantitative analysis of the blocking effects produced by sub-monolayer Na adsorbed on a Cu(111) surface at room temperature. The results show that the Na adsorption site preferences are different at different Na coverages. At a coverage θ = 0.25 monolayer, Na atoms preferentially populate the fcc threefold surface sites with a height of 2.7 ± 0.1 Å above the 1st layer Cu atoms. At a lower coverage of θ = 0.10 monolayer, there is no adsorption site preference for the Na atoms on the Cu(111) surface.

Geometry, Light, and Cosmology in the Church of Hagia Sophia

Designed by a physicist and a mathematician, the Hagia Sophia church in Istanbul, Turkey acted as an experimental test case in which advanced knowledge of geometrical constructs, sophisticated understanding of light behavior, and religious and cosmological beliefs combined to create a magnificent structure. While some of its design concepts are known, many remain hidden. Earthquakes have demolished parts of the church—such as the original dome. Researchers have in the past misinterpreted their observations and perpetuated false conclusions. Lastly, the lack of digital tools has until now prevented verification and analysis of prior findings. In this paper, we integrate traditional historical research, parametric digital analysis, and lighting simulation to analyze several aspects of the church. In particular, we focus on the geometry of the floor plan, the geometry of the apse, and light behavior in the original dome. Our findings point to the potential of digital tools in the discovery of a structure's hidden features and design rules.