articles+ search results

holographic optical elements, III‐V alloys, multijunction, photovoltaic, solar energy, spectrum splitting photovoltaics, Technology, and Science

Abstract Spectrum‐splitting photovoltaics incorporate optical elements to separate sunlight into frequency bands, which can be targeted at solar cells with bandgaps optimized for each sub‐band. Here, we present the design of a holographic diffraction grating‐based spectrum‐splitting photovoltaic module integrating eight III‐V compound semiconductor cells as four dual‐junction tandems. Four stacks of simple sinusoidal volume phase holographic diffraction gratings each simultaneously split and concentrate sunlight onto cells with bandgaps spanning the solar spectrum. The high‐efficiency cells get an additional performance boost from concentration incorporated using a single or a compound trough concentrator, providing up to 380X total concentration. Cell bandgap optimization incorporated an experimentally derived bandgap‐dependent external radiative efficiency function. Simulations show 33.2% module conversion efficiency is achievable. One grating stack is experimentally fabricated and characterized.

energy efficiency, rotor position detection, sensorless drive, switched reluctance motor, Engineering (General). Civil engineering (General), TA1-2040, Electronic computers. Computer science, and QA75.5-76.95

Abstract A switched reluctance motor (SRM) is a low‐cost motor with a simple structure and variable speed industrial and home applications. This article presents the design, simulation, and development of a low‐cost, accurate, and small‐size sensorless driver for a 6/4 three‐phase SRM. In the algorithm, the (nonlinear) relation of the flux, current, and rotor (FCR) position is linearized to achieve a modified FCR model, in which the values of the most important points of the primary FCR are emphasized. The SRM parameters required for the design process are obtained using a 3D finite‐element method (FEM). The proposed method is simulated and then tested under different load and speed conditions. The results are compared with a conventional sensorless algorithm's results, and the reference data are obtained by a direct with‐sensor algorithm. The algorithm estimates the rotor position (error of 1.3%) between low to nominal speed of the selected SRM under both nominal and no‐load conditions. In comparison with the conventional algorithm, the proposed FCR model significantly reduces the calculation cost and memory demand by 66%. Finally, the proposed algorithm decreases the driver size and price by 64% and 85%, respectively.

Adult, Electrons, Female, Follow-Up Studies, Humans, Male, Middle Aged, Mandibular Reconstruction methods, Surgery, Computer-Assisted methods, Surgical Mesh, and Titanium

Background: Immediate mandibular reconstruction was performed using a patient-specific titanium mesh tray fabricated by electron beam melting (EBM) /rapid prototyping techniques.
Methods: Patient-specific titanium trays were virtually designed and fabricated using EBM technology/rapid prototyping for patients requiring mandibular resection and immediate reconstruction using an iliac crest bone graft. Dental implants were placed in the grafted sites and the patients received prosthetic rehabilitation with a follow-up of one year. Clinical data, postoperative bone formation and complications were evaluated.
Results: A symmetric appearance of facial contours was achieved. The titanium tray incorporated the particulate iliac crest bone graft that provided significant bone formation (mean 18.97 ± 1.45 mm) and predictable results. Stability of the dental implants was achieved.
Conclusion: The patient-specific titanium meshes and immediate particulate autogenous bone graft showed satisfactory clinical and surgical results in improving patients' quality of life and decreasing the overall treatment time with adequate functional rehabilitation.
(Copyright © 2018 John Wiley & Sons, Ltd.)

Algorithms, Brain diagnostic imaging, Humans, Signal-To-Noise Ratio, Image Processing, Computer-Assisted methods, and Magnetic Resonance Imaging methods

Purpose: To introduce a framework for rapid prototyping of MR pulse sequences.
Methods: We propose a simple file format, called "TOPPE", for specifying all details of an MR imaging experiment, such as gradient and radiofrequency waveforms and the complete scan loop. In addition, we provide a TOPPE file "interpreter" for GE scanners, which is a binary executable that loads TOPPE files and executes the sequence on the scanner. We also provide MATLAB scripts for reading and writing TOPPE files and previewing the sequence prior to hardware execution. With this setup, the task of the pulse sequence programmer is reduced to creating TOPPE files, eliminating the need for hardware-specific programming. No sequence-specific compilation is necessary; the interpreter only needs to be compiled once (for every scanner software upgrade). We demonstrate TOPPE in three different applications: k-space mapping, non-Cartesian PRESTO whole-brain dynamic imaging, and myelin mapping in the brain using inhomogeneous magnetization transfer.
Results: We successfully implemented and executed the three example sequences. By simply changing the various TOPPE sequence files, a single binary executable (interpreter) was used to execute several different sequences.
Conclusion: The TOPPE file format is a complete specification of an MR imaging experiment, based on arbitrary sequences of a (typically small) number of unique modules. Along with the GE interpreter, TOPPE comprises a modular and flexible platform for rapid prototyping of new pulse sequences. Magn Reson Med 79:3128-3134, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
(© 2017 International Society for Magnetic Resonance in Medicine.)

Luminescent Proteins chemistry, Luminescent Proteins genetics, Luminescent Proteins metabolism, Polymerase Chain Reaction, Protein Biosynthesis, Time Factors, Cell-Free System, Nucleic Acid Amplification Techniques methods, Recombinant Proteins chemistry, Recombinant Proteins genetics, and Recombinant Proteins metabolism

In this study, we present a minimal template design and accompanying methods to produce assayable quantities of custom sequence proteins within 24 hr from receipt of inexpensive gene fragments from a DNA synthesis vendor. This is done without the conventional steps of plasmid cloning or cell-based amplification and expression. Instead the linear template is PCR amplified, circularized, and isothermally amplified using a rolling circle polymerase. The resulting template can be used directly with cost-optimized, scalably-manufactured Escherichia coli extract and minimal supplement reagents to perform cell-free protein synthesis (CFPS) of the template protein. We demonstrate the utility of this template design and 24 hr process with seven fluorescent proteins (sfGFP, mVenus, mCherry, and four GFP variants), three enzymes (chloramphenicol acetyltransferase, a chitinase catalytic domain, and native subtilisin), a capture protein (anti-GFP nanobody), and 2 antimicrobial peptides (BP100 and CA(1-7)M(2-9)). We detected each of these directly from the CFPS reaction using colorimetric, fluorogenic, and growth assays. Of especial note, the GFP variant sequences were found from genomic screening data and had not been expressed or characterized before, thus demonstrating the utility of this approach for phenotype characterization of sequenced libraries. We also demonstrate that the rolling circle amplified version of the linear template exhibits expression similar to that of a complete plasmid when expressing sfGFP in the CFPS reaction. We evaluate the cost of this approach to be $61/mg sfGFP for a 4 hr reaction. We also detail limitations of this approach and strategies to overcome these, namely proteins with posttranslational modifications.
(© 2018 Wiley Periodicals, Inc.)

Equipment Design, Pilot Projects, Image Interpretation, Computer-Assisted instrumentation, Image Interpretation, Computer-Assisted methods, Magnetic Resonance Imaging instrumentation, Magnetic Resonance Imaging methods, Signal Processing, Computer-Assisted instrumentation, and Software

Purpose: Implementing new magnetic resonance experiments, or sequences, often involves extensive programming on vendor-specific platforms, which can be time consuming and costly. This situation is exacerbated when research sequences need to be implemented on several platforms simultaneously, for example, at different field strengths. This work presents an alternative programming environment that is hardware-independent, open-source, and promotes rapid sequence prototyping.
Methods: A novel file format is described to efficiently store the hardware events and timing information required for an MR pulse sequence. Platform-dependent interpreter modules convert the file to appropriate instructions to run the sequence on MR hardware. Sequences can be designed in high-level languages, such as MATLAB, or with a graphical interface. Spin physics simulation tools are incorporated into the framework, allowing for comparison between real and virtual experiments.
Results: Minimal effort is required to implement relatively advanced sequences using the tools provided. Sequences are executed on three different MR platforms, demonstrating the flexibility of the approach.
Conclusion: A high-level, flexible and hardware-independent approach to sequence programming is ideal for the rapid development of new sequences. The framework is currently not suitable for large patient studies or routine scanning although this would be possible with deeper integration into existing workflows. Magn Reson Med 77:1544-1552, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
(© 2016 International Society for Magnetic Resonance in Medicine.)

3D printing, compartmentalized devices, fast prototyping, human neural stem cells, neurite guidance, nigrostriatal pathway, and Science

Abstract Compartmentalized microfluidic platforms are an invaluable tool in neuroscience research. However, harnessing the full potential of this technology remains hindered by the lack of a simple fabrication approach for the creation of intricate device architectures with high‐aspect ratio features. Here, a hybrid additive manufacturing approach is presented for the fabrication of open‐well compartmentalized neural devices that provides larger freedom of device design, removes the need for manual postprocessing, and allows an increase in the biocompatibility of the system. Suitability of the method for multimaterial integration allows to tailor the device architecture for the long‐term maintenance of healthy human stem‐cell derived neurons and astrocytes, spanning at least 40 days. Leveraging fast‐prototyping capabilities at both micro and macroscale, a proof‐of‐principle human in vitro model of the nigrostriatal pathway is created. By presenting a route for novel materials and unique architectures in microfluidic systems, the method provides new possibilities in biological research beyond neuroscience applications.

Cell Count, Cells, Cultured, Gene Expression Profiling, Humans, Time Factors, Cell Culture Techniques instrumentation, Cell Culture Techniques methods, and Chondrocytes physiology

Three-dimensional (3D) culture models are widely used in basic and translational research. In this study, to generate and culture multiple 3D cell spheroids, we exploited laser ablation and replica molding for the fabrication of polydimethylsiloxane (PDMS) multi-well chips, which were validated using articular chondrocytes (ACs). Multi-well ACs spheroids were comparable or superior to standard spheroids, as revealed by glycosaminoglycan and type-II collagen deposition. Moreover, the use of our multi-well chips significantly reduced the operation time for cell seeding and medium refresh. Exploiting a similar approach, we used clinical-grade fibrin to generate implantable multi-well constructs allowing for the precise distribution of multiple cell types. Multi-well fibrin constructs were seeded with ACs generating high cell density regions, as shown by histology and cell fluorescent staining. Multi-well constructs were compared to standard constructs with homogeneously distributed ACs. After 7 days in vitro, expression of SOX9, ACAN, COL2A1, and COMP was increased in both constructs, with multi-well constructs expressing significantly higher levels of chondrogenic genes than standard constructs. After 5 weeks in vivo, we found that despite a dramatic size reduction, the cell distribution pattern was maintained and glycosaminoglycan content per wet weight was significantly increased respect to pre-implantation samples. In conclusion, multi-well chips for the generation and culture of multiple cell spheroids can be fabricated by low-cost rapid prototyping techniques. Furthermore, these techniques can be used to generate implantable constructs with defined architecture and controlled cell distribution, allowing for in vitro and in vivo investigation of cell interactions in a 3D environment.
(© 2015 Wiley Periodicals, Inc.)

Animals, Biocompatible Materials chemistry, Cells, Cultured, Extracellular Matrix ultrastructure, Humans, Models, Anatomic, Polymers chemistry, Robotics, Tissue Engineering trends, Tissue Scaffolds trends, Tissue Engineering methods, and Tissue Scaffolds chemistry

Advances in scaffold design and fabrication technology have brought the tissue engineering field stepping into a new era. Conventional techniques used to develop scaffolds inherit limitations, such as lack of control over the pore morphology and architecture as well as reproducibility. Rapid prototyping (RP) technology, a layer-by-layer additive approach offers a unique opportunity to build complex 3D architectures overcoming those limitations that could ultimately be tailored to cater for patient-specific applications. Using RP methods, researchers have been able to customize scaffolds to mimic the biomechanical properties (in terms of structural integrity, strength, and microenvironment) of the organ or tissue to be repaired/replaced quite closely. This article provides intensive description on various extrusion based scaffold fabrication techniques and review their potential utility for TE applications. The extrusion-based technique extrudes the molten polymer as a thin filament through a nozzle onto a platform layer-by-layer and thus building 3D scaffold. The technique allows full control over pore architecture and dimension in the x- and y- planes. However, the pore height in z-direction is predetermined by the extruding nozzle diameter rather than the technique itself. This review attempts to assess the current state and future prospects of this technology.
(Copyright © 2011 Wiley Periodicals, Inc.)

CEM, computational electromagnetics, modeling, rapid virtual prototyping, simulation, Engineering (General). Civil engineering (General), TA1-2040, Electronic computers. Computer science, and QA75.5-76.95

Have you ever wondered why we use certain computational electromagnetics methods and how we decide on the choice of tools for modeling problems in electromagnetics? Though true for any field, particularly in electrodynamics, there is a gap between current practitioners' knowledge and knowhow about different tools and the state‐of‐the‐art developments. Rapid advancements made in material science and (nano)‐fabrication techniques are demanding new tools with multiscale and multiphysics capabilities. In this article, we cover the recent developments and highlight capabilities and limitations of different electromagnetic modeling tools. One has to answer a series of questions about modeling constraints and objectives before picking the appropriate tool. We aim to clarify some of the misconceptions, discuss limits and capabilities of some of the popular electromagnetic modeling tools, and provide a few practical tips, so that applied physicists and engineers can make informed decisions while choosing appropriate tools for their applications.

Molecular dynamics (MD) simulation involves solving Newton's equations of motion for a system of atoms, by calculating forces and updating atomic positions and velocities over a timestep Deltat. Despite the large amount of computing power currently available, the timescale of MD simulations is limited by both the small timestep required for propagation, and the expensive algorithm for computing pairwise forces. These issues are currently addressed through the development of efficient simulation methods, some of which make acceptable approximations and as a result can afford larger timesteps. We present MDLab, a development environment for MD simulations built with Python which facilitates prototyping, testing, and debugging of these methods. MDLab provides constructs which allow the development of propagators, force calculators, and high level sampling protocols that run several instances of molecular dynamics. For computationally demanding sampling protocols which require testing on large biomolecules, MDL includes an interface to the OpenMM libraries of Friedrichs et al. which execute on graphical processing units (GPUs) and achieve considerable speedup over execution on the CPU. As an example of an interesting high level method developed in MDLab, we present a parallel implementation of the On-The-Fly string method of Maragliano and Vanden-Eijnden. MDLab is available at http://mdlab.sourceforge.net.
(Copyright 2009 Wiley Periodicals, Inc.)

Blood Flow Velocity physiology, Computer Simulation, Contrast Media, Feasibility Studies, Gadolinium DTPA, Hemodynamics, Humans, Phantoms, Imaging, Pulsatile Flow, Aorta, Thoracic physiology, Imaging, Three-Dimensional, Magnetic Resonance Angiography methods, and Magnetic Resonance Imaging methods

The knowledge of local vascular anatomy and function in the human body is of high interest for the diagnosis and treatment of cardiovascular disease. A comprehensive analysis of the hemodynamics in the thoracic aorta is presented based on the integration of flow-sensitive 4D MRI with state-of-the-art rapid prototyping technology and computational fluid dynamics (CFD). Rapid prototyping was used to transform aortic geometries as measured by contrast-enhanced MR angiography into realistic vascular models with large anatomical coverage. Integration into a flow circuit with patient-specific pulsatile in-flow conditions and application of flow-sensitive 4D MRI permitted detailed analysis of local and global 3D flow dynamics in a realistic vascular geometry. Visualization of characteristic 3D flow patterns and quantitative comparisons of the in vitro experiments with in vivo data and CFD simulations in identical vascular geometries were performed to evaluate the accuracy of vascular model systems. The results indicate the potential of such patient-specific model systems for detailed experimental simulation of realistic vascular hemodynamics. Further studies are warranted to examine the influence of refined boundary conditions of the human circulatory system such as fluid-wall interaction and their effect on normal and pathological blood flow characteristics associated with vascular geometry.
((c) 2008 Wiley-Liss, Inc.)

Aged, Aged, 80 and over, Arthroplasty, Replacement, Hip instrumentation, Equipment Design, Female, Hip Prosthesis, Humans, Imaging, Three-Dimensional, Male, Middle Aged, Robotics instrumentation, Robotics methods, Surgery, Computer-Assisted instrumentation, Surgical Instruments, Tomography, X-Ray Computed, Arthroplasty, Replacement, Hip methods, and Surgery, Computer-Assisted methods

Background: A surgical guide made by the rapid prototyping (RP) technique for cup insertion in total hip arthroplasty might be useful to avoid malalignment of the cup, which indicates postoperative complications.
Methods: To address this research question, we applied a RP-based guide to 24 patients with their CT images. We designed it to fit onto the acetabular edge and to insert a Kirschner wire (K-wire) which indicated a planned cup direction. We intraoperatively placed it on the acetabular edge, inserted the K-wire through the guide on the superior acetabulum and implanted the cup while observing the alignment of the K-wire. We also recorded the additional time needed to use the guide.
Results: The mean cup accuracy between planned and postoperative alignments was 2.8 degrees (SD = 2.1 degrees ) for abduction and 3.7 degrees (SD = 2.7 degrees ) for anteversion. The mean additional time was 3.5 (range 2-6) min.
Conclusion: We can use this guide with acceptable accuracy and without consuming an excessive amount of time.

Computer Simulation, Computer-Aided Design, Humans, Male, Maxillary Fractures diagnostic imaging, Models, Neurological, Orbital Fractures diagnostic imaging, Robotics methods, Skull diagnostic imaging, Surgery, Computer-Assisted methods, Tomography, X-Ray Computed, User-Computer Interface, Young Adult, Zygomatic Fractures diagnostic imaging, Imaging, Three-Dimensional, Maxillary Fractures surgery, Models, Anatomic, Orbital Fractures surgery, and Zygomatic Fractures surgery

Background: With the advent of CAD/CAM and rapid prototyping (RP), a technical revolution in oral and maxillofacial trauma was promoted to benefit treatment, repair of maxillofacial fractures and reconstruction of maxillofacial defects.
Methods: For a patient with zygomatico-facial collapse deformity resulting from a zygomatico-orbito-maxillary complex (ZOMC) fracture, CT scan data were processed by using Mimics 10.0 for three-dimensional (3D) reconstruction. The reduction design was aided by 3D virtual imaging and the 3D skull model was reproduced using the RP technique. In line with the design by Mimics, presurgery was performed on the 3D skull model and the semi-coronal incision was taken for reduction of ZOMC fracture, based on the outcome from the presurgery.
Results: Postoperative CT and images revealed significantly modified zygomatic collapse and zygomatic arch rise and well-modified facial symmetry.
Conclusions: The CAD/CAM and RP technique is a relatively useful tool that can assist surgeons with reconstruction of the maxillofacial skeleton, especially in repairs of ZOMC fracture.

Alloys chemistry, Kinetics, Microscopy, Electron, Scanning, Oxides chemistry, Strontium chemistry, Temperature, Titanium chemistry, Biocompatible Materials chemistry, Ceramics chemistry, Materials Testing, and Nanostructures chemistry

The significance of kinetics on the development of microstructures in connection with sintering of ceramics is well recognized. In practice, however, it still remains a challenge to prepare designed microstructures via engineering the sintering kinetics because of an insufficient understanding of the different operative mechanisms that are in many cases overlapping. In this article the kinetic issues involved in sintering are described and discussed with respect to their potential for prototyping microstructures that yield desired properties. By exploiting and mastering the differences present in the kinetics of grain sliding, densification, chemical reactions, and grain growth, respectively, we have established processing principles for producing bulk ceramics with microstructures consisting of nano-sized grains, aligned grains, and/or non-equilibrium-phase constitutions, and for achieving radically improved superplasticity in brittle ceramics. Although the studies quoted in this article were mainly carried out by spark plasma sintering, more general implications of them are expected, including efficient particle sliding, deformation-induced dynamic ripening, superplastic deformation-induced dynamic ripening, and non-equilibrium integration.
(Copyright (c) 2005 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.)

Bone-Implant Interface, Computer-Aided Design, Humans, Dental Implants, Mandibular Neoplasms surgery, Mandibular Reconstruction methods, Osteotomy methods, and Surgery, Computer-Assisted methods

Objectives: The objective of this study was to provide the generalized methodology for design and development of a customized implant and customized surgical osteotomy guide (CSOG) for precise mandibular tumor resection and placement of a customized implant in ablative tumor surgery for accurate mandibular reconstruction.
Methods: Medical imaging technique, image processing, virtual surgical planning (VSP), biomedical computer-aided design (CAD), and rapid prototyping (RP) were used to develop CSOG and customized implant. A mock surgical test and an experimental analysis were performed on the biomodel (RP assisted diseased model) to check the effectiveness of the CSOG.
Results: The paired t test showed the statistically significant result with the use of CSOG as compared to the without using CSOG in ablative mandibular tumor surgery.
Conclusions: A mock test and an experimental analysis proved that, the precise tumor resection and customized implant placement with minimal gap between bone-implant junctions in mandibular reconstruction using CSOG.
(© 2019 John Wiley & Sons, Ltd.)

Objective: The objective of this study was to assess the accuracy of physical reproductions of plaster orthodontic study casts fabricated by two different rapid prototyping techniques: Fused Deposition Modeling (FDM) and Digital Light Processing (DLP).
Materials and Methods: Twenty pairs of pretreatment plaster models were prepared from randomly selected patients at the Orthodontic Department, University of Damascus Dental School. Twenty-one reference points were placed on plaster models, followed by scanning and printing of these models using FDM and DLP techniques. Forty measurements were made on these models using a digital caliper. Paired t tests were used to detect significant differences in the measurements between the 3D printed replicas and the original plaster models (Gold Standard). Alpha level was adjusted due to the multiplicity of the tests.
Results: The intraclass correlation coefficients for all the comparisons made between the 3D replicas and the gold standard models were greater than 0.80 with ICCs ranging from 0.802 to 0.990 and from 0.853 to 0.990 for the FDM and DLP techniques, respectively. This indicated an excellent agreement. No statistically significant differences could be detected between the 3D-printed models and their corresponding plaster models. The overall mean difference was -0.11 mm and 0.00 ranging from -0.49 to 0.17 mm and from -0.42 to 0.50 mm, for the FDM and DLP techniques, respectively.
Conclusion: The accuracy of the 3D models produced by the DLP and FDM techniques was acceptable. However, for the fabrication of clear aligners, the optimum fit of the produced plates in the patients' mouths is not completely guaranteed.
(© 2020 The Authors. Clinical and Experimental Dental Research published by John Wiley & Sons Ltd.)

Female, Humans, Needs Assessment, Netherlands, Pregnancy, Stakeholder Participation, Midwifery education, Parturition, Patient Advocacy, Program Development methods, and Students, Nursing

Women want positive birth experiences with high quality maternity care that is neither too much, too soon, nor too little, too late. Research confirms the effectiveness of midwifery care, and the midwifery approach to birth as physiologic may counter the upward trend of the unnecessary medicalization of birth. The role of guardian of physiologic birth is seen as central to midwifery practice; however, medical hegemony has led to the subordination of midwives, which inhibits them in fulfilling the role as guardian of physiologic birth. Learning to become powerful advocates of physiologic birth creates midwives able to speak up for effective, evidence-based maternity care and challenge the unnecessary use of obstetric intervention. Midwifery education has a role to fulfil in molding midwives who are able to assume this role. This brief report describes the development of an educational prototype aimed at increasing student midwife agency as an advocate of physiologic birth. This was done using rapid prototyping (RP) methodology, in which important stakeholders gave input and feedback during the educational design and development process. Input from stakeholders led to the inclusion of persuasive communication strategies and discussion and debate as teaching methodologies in order to increase student midwife agency to argue for physiologic birth. Reflective evidence-based practice, using the Optimality Index-Netherlands, allowed students to reflect on their practice while providing a framework for discussion. Working with the RP methodology allowed for the development of a prototype that reflected the needs of midwifery stakeholders and was mindful of material and human resources.
(© 2019 by the American College of Nurse-Midwives.)

We report the development of a versatile system based on the oscillating-flow methodology in a thermal gradient system for nucleic acid analysis. Analysis of DNA and RNA samples were performed in the device, without additional temperature control and complexity. The technique reported in this study eliminates the need for predetermined fluidic channels for thermocycles, and complexity involved with additional incubation steps required for RNA amplification. A microfluidic device was fabricated using rapid prototyping by simply sandwiching dual side adhesive Kapton tape and a polydimethylsiloxane spacer between glass microscope slides. Amplification of the 181-bp segment of a viral phage DNA (ΦX174) and B2M gene in human RNA samples was demonstrated using the system. The developed system enables simultaneous acquisition of amplification and melt curves, eliminating the need for postprocessing. A direct comparison between the oscillating-flow system and a commercial real-time polymerase chain reaction (PCR) instrument showed complete agreement in PCR data and improved sample-to-result time by eliminating an additional 30 min melt curve step required in commercial PCR systems.
(© 2020 Wiley Periodicals, Inc.)