articles+ search results

Humans, Vision, Ocular, Macula Lutea physiology, and Vision, Entoptic

Entoptic phenomena are visual artifacts arising from the interaction of light with the specific anatomic structure of the human eye. While they are usually too subtle to actually enable additional visual abilities, their perception can provide indirect information on the physiological conditions of the visual system. Among the most famous ones, Haidinger's brushes consist in the appearance of a yellowish bow tie perceived in the presence of linearly polarized white light and originate from the particular spatial distribution of dichroic carotenoid molecules forming a sort of embedded radial polarizer in the foveal region. In this work, we develop a compact and versatile optical setup for the psychophysical analysis of the perceptual threshold of such entoptic effect. The tests performed on a group of 113 healthy individuals under conditions of maximum contrast (blue light) reveal the capability to perceive an average polarization degree around 16%. The developed prototype outlines a new optical platform to train the users in the perception of the phenomenon and infer information on the polarization-degree sensitivity of the human visual system.
(Copyright © 2022 Elsevier Ltd. All rights reserved.)

Electrodes, Ion-Selective Electrodes, Ions, Potassium, Potentiometry, Printing, Three-Dimensional, Sodium, Internet of Things, and Robotics

We report automated fabrication of solid-contact sodium-selective (Na + -ISEs) and potassium-selective electrodes (K + -ISEs) using a 3D printed liquid handling robot controlled with Internet of Things (IoT) technology. The printing system is affordable and can be customized for the use with micropipettes for applications such as drop-casting, biological assays, sample preparation, rinsing, cell culture, and online analyte monitoring using multi-well plates. The robot is more compact (25 × 30 × 35 cm) and user-friendly than commercially available systems and does not require mechatronic experience. For fabrication of ion-selective electrodes, a carbon black intermediate layer and ion-selective membrane were successively drop-cast on the surface of stencil-printed carbon electrode using the dispensing robot. The 3D-printed robot increased ISE robustness while decreasing the modification time by eliminating manual steps. The Na + -ISEs and K + -ISEs were characterized for their potentiometric responses using a custom-made, low-cost (<$25) multi-channel smartphone-based potentiometer capable of signal processing and wireless data transmission. The electrodes showed Nernstian responses of 58.2 ± 2.6 mV decade -1 and 56.1 ± 0.7 mV decade -1 for Na + and K + , respectively with an LOD of 1.0 × 10 -5  M. We successfully applied the ISEs for multiplexed detection of Na + and K + in urine and artificial sweat samples at clinically relevant concentration ranges. The 3D-printed pipetting robot cost $100 and will pave the way for more accessible mass production of ISEs for those who cannot afford the expensive commercial robots.
(Copyright © 2022 Elsevier B.V. All rights reserved.)

Equipment Design, Phantoms, Imaging, Software, Algorithms, and Magnetic Resonance Imaging methods

Purpose: An automated algorithm for generating realizable MR gradient and shim coil layouts based on the boundary element method is presented here. The overall goal is to reduce postprocessing effort and thus enable for rapid prototyping of new coil designs. For a given surface mesh and target field, the algorithm generates a connected, non-overlapping wire path.
Methods: The proposed algorithm consists of several steps: Stream function optimization, two-dimensional surface projection, potential discretization, topological contour sorting, opening and interconnecting contours, and finally adding non-overlapping return paths. Several technical parameters such as current strength, inductance and field accuracy are assessed for quality control.
Results: The proposed method is successfully demonstrated in four different examples. All exemplary results demonstrate high accuracy with regard to reaching the respective target field. The optimal discretization for a given stream function is found by generating multiple layouts while varying the input parameter values.
Conclusion: The presented algorithm allows for a rapid generation of interconnected coil layouts with high flexibility and low discretization error. This enables to reduce the overall post-processing effort. The source code of this work is publicly available ( https://github.com/Philipp-MR/CoilGen).
(© 2022 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)

Animals, Aquaculture, Ergonomics methods, Farmers, Feasibility Studies, Humans, Pilot Projects, Seafood, Bivalvia, Low Back Pain therapy, Occupational Diseases prevention control, and Self-Management

Objectives. Lower back pain (LBP) is extremely prevalent in seafood harvesters who often have limited or no access to ergonomic consultation, occupational health support and rehabilitation services. This pilot study aimed to describe a participatory ergonomic approach and determine the feasibility and extent of adoption of self-management strategies in clam farmers with LBP. Methods. A rapid prototype participatory ergonomic approach was used to develop context-specific self-management strategies. Options to adjust lifting and repetitive stress were introduced using video clips, demonstrations and discussions in the workplace. Workers chose and implemented three strategies for 8 weeks with weekly reminders. Survey and qualitative data from focus groups were analyzed. Results. Team strategies were the most popular, but individual options were used more often. Strategies were considered feasible, acceptable and relatively easy to use. Strategies were implemented relatively consistently, and most improved productivity with decreased pain. Challenges for uptake included changing habit, culture and team dynamics. Conclusions. Participatory rapid prototyping provided a feasible and efficient option to introduce strategies for clam farmers with small teams, variable work processes and workloads, and time restrictions. Strategies were considered acceptable and easy to use, and most increased productivity. These methods show potential for future research.

The growing use of 3D printing in the biomedical sciences demonstrates its utility for a wide range of research and healthcare applications, including its potential implementation in the discipline of breath analysis to overcome current limitations and substantial costs of commercial breath sampling interfaces. This technical note reports on the design and construction of a 3D-printed mouthpiece adapter for sampling exhaled breath using the commercial respiration collector for in-vitro analysis (ReCIVA) device. The paper presents the design and digital workflow transition of the adapter and its fabrication from three commercial resins (Surgical Guide, Tough v5, and BioMed Clear) using a Formlabs Form 3B stereolithography (SLA) printer. The use of the mouthpiece adapter in conjunction with a pulmonary function filter is appraised in comparison to the conventional commercial silicon facemask sampling interface. Besides its lower cost - investment cost of the printing equipment notwithstanding - the 3D-printed adapter has several benefits, including ensuring breath sampling via the mouth, reducing the likelihood of direct contact of the patient with the breath sampling tubes, and being autoclaveable to enable the repeated use of a single adapter, thereby reducing waste and associated environmental burden compared to current one-way disposable facemasks. The novel adapter for breath sampling presented in this technical note represents an additional field of application for 3D printing that further demonstrates its widespread applicability in biomedicine.
(© 2022. The Author(s).)

Background: Patients with Bipolar Disorder (BD) report a lower quality of life and lower levels of well-being than the general population. Despite the growing availability of psychotherapeutic and self-management interventions, there are still important unmet needs. These unmet needs are closely linked to positive psychology domains. Although a growing number of studies evaluated the impact of positive psychology interventions (PPIs) on patients with severe mental illness in general, only few addressed the application of positive psychology in BD.
Objective: The current study aimed to gain insight into the opinion of patients with BD and health care professionals about (online) PPIs for BD and to develop and pilot-test an app containing PPIs specifically designed for patients with BD.
Methods: The study was conducted in accordance with the Center for eHealth and Disease Management (CeHRes) roadmap principles and incorporated co-creation and designing for implementation. Data was collected using focus group discussions (FGs), questionnaires, rapid prototyping (RPT), and online feedback on a prototype from the participants. Three FGs were held with eight BD patients and five professionals. The collected data was used to develop a smartphone app containing short PPIs. The content was based on PPIs for which a solid base of evidence is available. Finally, a Pilot Test (PT) was used to test the app.
Results: FGs revealed that positive psychology interventions as part of the current BD treatment could potentially meet the following needs: offering hope, increasing self-esteem, expressing feelings, acceptance, and preventing social isolation. Some patients expressed concern that PPIs may provoke a (hypo)manic episode by increasing positive affect. The pilot test of the app showed that the PPIs are moderate to highly valued by the participants. There were no adverse effects such as an increase of (hypo)manic symptoms.
Conclusions: With the systematic utilisation of user involvement (patients and professionals) in all steps of the development process, we were able to create an app that can potentially fulfil some of the current unmet needs in the treatment of BS. We reached consensus among consumers and professionals about the potential benefits of positive psychology interventions to address unmet needs of BD patients. The use of PPI in BD is intriguing and could be usefully explored in further research. We emphasise that more evaluation studies (quantitative and qualitative) should be carried out that are focused on the effect of PPIs in the treatment of BD. In addition, to establish the working mechanisms in BD, explorative qualitative designed studies are also required to reveal if PPIs indeed can cover unmet needs in BD.

Background: Facial deformities often demand reconstructive surgery and the placement of three-dimensional (3D) printed craniomaxillofacial prostheses. Prostheses manufacturing requires patients' computed tomography (CT) images. Poor quality images result in incorrectly sized prostheses, necessitating repeat imaging and refitting. The Centre for Rapid Prototyping and Manufacturing (CRPM) produces most facial prostheses in South Africa but does not have a prescribed optimised CT protocol. Therefore, this study was undertaken.
Methods: A collection of CRPM STLs used in the design and manufacturing of craniomaxillofacial prostheses is available. The image quality of stereolithography (STL) files of CRPM CT scans was evaluated to determine what constitutes good image quality. This collection was scrutinised for inclusion in the image quality evaluation. After scrutiny, 35 STLs of individuals ≥15 years of age were selected and included metadata attached to the DICOM file. Furthermore, only STLs created without manipulation by the same designer were included in the collection. Before the qualitative evaluation of the STLs, eight different critical anatomical reference points (CARPs) were identified with the assistance of an expert team. A visual acuity rating scale of three categories was devised for each CARP, where 1 was allocated to poor visual acuity, 2 to partial, and 3 to good visual acuity. Similarly, rating scales were devised for the presence of concentric rings and the overall impression score awarded by the two designers involved in the design and manufacturing of the prostheses. This stereolithography measurement rubric (SMR) was then applied to the 35 STLs by a team of three experts, including the two designers, during a structured evaluation session. The scores were used to calculate summary and inferential statistics.
Results: Scores grouped around the central rating of partial visual acuity. The three evaluators' mean total CARP scores ranged from 13.1 to 14.4 (maximum possible score 24), while the mean total CARP + ring scores ranged from 15.8 to 17.1 (maximum possible score 27). No significant differences were detected between the evaluators' scores.
Conclusion: This SMR appears to be the first of its kind. This image quality assessment of STLs provides the groundwork for finer CT image quality evaluation to formulate a CT imaging protocol for the CRPM to design and manufacture accurate internal cranial prostheses.
(© 2022. The Author(s).)

Purpose: Navigational strategies create a scenario whereby percutaneous needle-based interventions of the liver can be guided using both pre-interventional 3D imaging datasets and dynamic interventional ultrasound (US). To score how such technologies impact the needle placement process, we performed kinematic analysis on different user groups.
Methods: Using a custom biopsy phantom, three consecutive exercises were performed by both novices and experts (n = 26). The exercise came in three options: (1) US-guidance, (2) US-guidance with pre-interventional image-registration (US + Reg) and (3) US-guidance with pre-interventional image-registration and needle-navigation (US + Reg + Nav). The traveled paths of the needle were digitized in 3D. Using custom software algorithms, kinematic metrics were extracted and related to dexterity, decision making indices to obtain overall performance scores (PS).
Results: Kinematic analysis helped quantifying the visual assessment of the needle trajectories. Compared to US-guidance, novices yielded most improvements using Reg (PS avg(US)  = 0.43 vs. PS avg(US+Reg)  = 0.57 vs. PS avg(US+Reg+Nav)  = 0.51). Interestingly, the expert group yielded a reversed trend (PS avg(US)  = 0.71 vs PS avg(US+Reg)  = 0.58 vs PS avg(US+Reg+Nav)  = 0.59).
Conclusion: Digitizing the movement trajectory allowed us to objectively assess the impact of needle-navigation strategies on percutaneous procedures. In particular, our findings suggest that these advanced technologies have a positive impact on the kinematics derived performance of novices.
(© 2022. The Author(s).)

Magnetic Phenomena, Microscopy, Electron, Scanning, Imaging, Three-Dimensional methods, and Spectrometry, Mass, Secondary Ion

The structural, morphological, and chemical characterization of samples is of utmost importance for a large number of scientific fields. Furthermore, this characterization very often needs to be performed in three dimensions and at length scales down to the nanometer. Therefore, there is a stringent necessity to develop appropriate instrumentational solutions to fulfill these needs. Here we report on the deployment of magnetic sector secondary ion mass spectrometry (SIMS) on a type of instrument widely used for such nanoscale investigations, namely, focused ion beam (FIB)-scanning electron microscopy (SEM) instruments. First, we present the layout of the FIB-SEM-SIMS instrument and address its performance by using specific test samples. The achieved performance can be summarized as follows: an overall secondary ion beam transmission above 40%, a mass resolving power ( M /Δ M ) of more than 400, a detectable mass range from 1 to 400 amu, a lateral resolution in two-dimensional (2D) chemical imaging mode of 15 nm, and a depth resolution of ∼4 nm at 3.0 keV of beam landing energy. Second, we show results (depth profiling, 2D imaging, three-dimensional imaging) obtained in a wide range of areas, such as battery research, photovoltaics, multilayered samples, and life science applications. We hereby highlight the system's versatile capability of conducting high-performance correlative studies in the fields of materials science and life sciences.

Face surgery, Fibula, Humans, Maxilla surgery, Surgical Flaps blood supply, and Reconstructive Surgical Procedures methods

Purpose: Midface reconstruction poses a complex set of challenges for reconstructive surgeons. The optimal midface reconstruction must possess a durable underlying bone construct capable of integrating dental implants. Facial contour is restored by the overlying microvascular soft tissue reconstruction with reestablishment of the oral cavity. A plethora of microvascular flaps used in clinical practice have been described including those harvested from the iliac crest, scapula, fibula, forearm and back (latissimus dorsi). The objective was to share our experiences with each of these treatment options that have continued to evolve over time for the benefit of patients.
Methods: Our institution has over three decades of experience in reconstructing complex midface defects and this article summarizes midface reconstruction from an evolutionary perspective (for type II, III and IV defect; Browns classification, Supplementary Table I). We broadly divide this into (i) flaps supplied by the subscapular system (ii) autologous reconstruction with titanium mesh and (iii) fibula microvascular flaps using 3D planning.
Results: The advantages and disadvantages for each approach are discussed (Supplementary Table II).
Conclusion: In the future, it is expected that 3D planning coupled with rapid prototyping, intraoperative navigation and CT imaging will become standard procedural practice.
(© 2022. Crown.)

Curriculum, Humans, Schools, Medical, Surveys and Questionnaires, Education, Medical, Undergraduate, and Students, Medical psychology

Problem: The extent of medical student unwellness is well documented. Learner distress may impact patient care, workforce adequacy, and learners' performance and personal health. The authors describe the philosophy, structure, and content of the novel REACH (Recognize, Empathize, Allow, Care, Hold each other up) curriculum and provide a preliminary evaluation.
Approach: The REACH curriculum is a mandatory, longitudinal well-being curriculum for first- and second-year medical students at the Medical College of Wisconsin (MCW) designed to prepare them for the emotional life of being a physician. The curriculum uses a framework, core concepts, and skills from the field of trauma stewardship. It builds on effective medical student well-being interventions (e.g., mindfulness-based training) and the sharing of personal stories by instructors during didactic and small-group sessions that are integrated into the regular MCW curriculum. During the first 2 years of implementation (2018-2019 and 2019-2020), the curriculum was evaluated using mid- and postcurriculum student surveys.
Outcomes: Over 700 students have completed the REACH curriculum as of March 2022. Overall, most students who responded to the surveys in 2018-2020 reported that they felt the REACH curriculum material was important, that the curriculum met their expectations for a quality medical school course, and that they would recommend other schools incorporate a similar curriculum. Respondents to the 2019-2020 postcurriculum survey indicated the REACH curriculum helped them develop self-care (84% [85/101]), mindfulness (76% [76/101]), and help-seeking (71% [72/101]) skills.
Next Steps: The initial outcomes show that integrating a mandatory well-being curriculum is feasible and acceptable to medical students. The authors plan to examine the relationships between student-reported well-being metrics, academic and clinical performance data, and professional identity formation. They are also prototyping electronic dashboards that will allow students to interact with their well-being data to promote timely help-seeking and behavior change.
(Copyright © 2022 by the Association of American Medical Colleges.)

Metal patterning via additive manufacturing has been phasing-in to broad applications in many medical, electronics, aerospace, and automotive industries. While previous efforts have produced various promising metal-patterning strategies, their complexity and high cost have limited their practical application in rapid production and prototyping. Herein, a one-step gold printing technique based on anion-assisted photochemical deposition (APD), which can directly print highly conductive gold patterns (1.08 × 10 7 S m -1 ) under ambient conditions without post-annealing treatment, is introduced. Uniquely, the APD uses specific ion effects with projection lithography to pattern Au nanoparticles and simultaneously sinter them into tunable porous gold structures. The significant influence of kosmotropic or chaotropic anions in the precursor ink on tuning the morphologies and conductivities of the printed patterns by employing a series of different ions, including Cl - ions, in the printing process is presented. Additionally, the resistance stabilities and the electrochemical properties of the APD-printed gold patterns are carefully investigated. The high conductivity and excellent conformability of the printed Au electrodes are demonstrated with reliable performance in electrophysiological signal delivery and acquisition for biomedical applications. This work exploits the potential of photochemical-deposition-based metal patterning in flexible electronic manufacturing.
(© 2022 Wiley-VCH GmbH.)

Humans, Phantoms, Imaging, Printing, Three-Dimensional, and Tomography, X-Ray Computed methods

Introduction: Additive production refers to the process of prototyping, which allows the production of highly complex medical devices and products. Interpretation of additive manufacturing (AM) material in Computed Tomography (CT) has not been widely investigated. The aim of this study was to determine the CT number values of commercially available fused deposition modelling (FDM) and stereolithography (SLA) AM materials.
Methods: Total of 15 AM materials, 7 FMD and 8 SLA, were selected and scanned on CT to determine the HU value and appearance on the images. All test object were designed as rectangular blocks and after their production physical description were calculated. AM materials were scanned on CT operating at 80, 100, 120 and 135 kV.
Results: All materials correspond to a certain human tissue and they have uniformity when printed with 100% infill. CT number ranged from a minimum of -188.0 HU to a maximum of 189.1 HU, for FDM materials, and from -15.8 HU to 167.3 HU, for SLA materials.
Conclusion: Knowing the CT number of an AM materials can allow the design of medical or rehabilitation products with a specific appearance on CT images. Analysed and collected data can find application in the design and manufacture of immobilization devices that can be easily distinguished from other materials or human tissue.
Implications for Practice: This study provides information that can be used in the design and fabrication of anthropomorphic diagnostic and therapeutic phantoms. There is significant potential for the use of AM material for sophisticated test objects when used in medical image modality testing. Knowing actual CT numbers of frequently used AM materials allows manufacturing anthropomorphic phantoms to investigate radiation doses in diagnostic radiology and radiotherapy.
(Copyright © 2022 The College of Radiographers. Published by Elsevier Ltd. All rights reserved.)

Biopsy, Education, Medical, Graduate methods, Feedback, Female, Humans, Bone Marrow, and Fellowships and Scholarships

Introduction: Hematology/oncology fellows must achieve bone marrow biopsy proficiency. However, opportunities for fellows to perform bone marrow biopsies on patients are highly dependent on clinical volume. An easily accessible and feasible system to practice these procedures repetitively has not been described. Other specialties use 3-dimensional (3D)-printed models to practice procedures, but hematology/oncology has not yet incorporated this novel medical education tool, which has the potential to provide such an accessible and feasible system for procedural practice.
Methods: We used design thinking to develop and pilot a bone marrow biopsy simulation using 3D-printed pelvis models. We printed and optimized 2 models through iterative prototyping. In July 2019, we conducted a 1-hour session with 9 fellows. After an anatomy review, fellows practiced biopsies using the models with faculty feedback. To evaluate feasibility, we reviewed session evaluations, measured fellow comfort, surveyed supervising attendings, and gathered fellow and attending feedback.
Results: Fellows rated the 3D session highly. Fellow comfort improved after orientation. Supervisors noted no difference between the 2019 fellows and prior years. Fellows praised the opportunity to rehearse mechanics, receive feedback, and internalize anatomy. Fellows suggested incorporating a female pelvis and more soft tissue. Attending feedback on the model aligned with fellow feedback. We implemented the session again in 2020 with adjustments based on feedback.
Conclusions: Three-dimensional printing represents an accessible and feasible educational tool. Three-dimensional-printed models provide opportunities for iterative practice, feedback, and anatomy visualization. Future iterations should continue to incorporate user feedback to optimize model utility.
(Copyright © 2021 Society for Simulation in Healthcare.)

Aged, Equipment Design, Humans, Muscle, Skeletal physiology, Printing, Three-Dimensional, Biomimetics, and Robotics

Biomimetic machines able to integrate with natural and social environments will find ubiquitous applications, from biodiversity conservation to elderly daily care. Although artificial actuators have reached the contraction performances of muscles, the versatility and grace of the movements realized by the complex arrangements of muscles remain largely unmatched. Here, we present a class of pneumatic artificial muscles, named GeometRy-based Actuators that Contract and Elongate (GRACE). The GRACEs consist of a single-material pleated membrane and do not need any strain-limiting elements. They can contract and extend by design, as described by a mathematical model, and can be realized at different dimensional scales and with different materials and mechanical performances, enabling a wide range of lifelike movements. The GRACEs can be fabricated through low-cost additive manufacturing and even built directly within functional devices, such as a pneumatic artificial hand that is fully three-dimensionally printed in one step. This makes the prototyping and fabrication of pneumatic artificial muscle-based devices faster and more straightforward.

This case-report described the 3-dimensional (3D) evaluation of airway changes using 3D printing technology in a patient with mandibular prognathism, treated via mandibular setback surgery with maxillary posterior impaction. The airway dimensions, following orthognathic surgery, were printed using 3D printing technology and the sequential airway changes were visualized. The patient underwent orthognathic surgery for the correction of mandibular prognathism. Five years later, the airway changes were visualized and evaluated using rapid prototyping. The 3D visualization of the airway changes following surgery alerted clinicians of patients with mandibular prognathism and facilitated effective communication with their patients. This case-report documented the long-term evaluation and visualization of the postoperative airway changes in patients with mandibular prognathism using cone-beam computed tomography and 3D printing technology.
(Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc.)

Protein cages are attractive as molecular scaffolds for the fundamental study of enzymes and metabolons and for the creation of biocatalytic nanoreactors for in vitro and in vivo use. Virus-like particles (VLPs) such as those derived from the P22 bacteriophage capsid protein make versatile self-assembling protein cages and can be used to encapsulate a broad range of protein cargos. In vivo encapsulation of enzymes within VLPs requires fusion to the coat protein or a scaffold protein. However, the expression level, stability, and activity of cargo proteins can vary upon fusion. Moreover, it has been shown that molecular crowding of enzymes inside VLPs can affect their catalytic properties. Consequently, testing of numerous parameters is required for production of the most efficient nanoreactor for a given cargo enzyme. Here, we present a set of acceptor vectors that provide a quick and efficient way to build, test, and optimize cargo loading inside P22 VLPs. We prototyped the system using a yellow fluorescent protein and then applied it to mevalonate kinases (MKs), a key enzyme class in the industrially important terpene (isoprenoid) synthesis pathway. Different MKs required considerably different approaches to deliver maximal encapsulation as well as optimal kinetic parameters, demonstrating the value of being able to rapidly access a variety of encapsulation strategies. The vector system described here provides an approach to optimize cargo enzyme behavior in bespoke P22 nanoreactors. This will facilitate industrial applications as well as basic research on nanoreactor-cargo behavior.

Objectives: The Vocal Tract Organ has had a number of iterations resulting from advances in available technology as well as requirements of perceptual experiments and performance paradigms. The objective of this paper is to relate the development history of the Vocal Tract Organ from the original vision to what it is today as a modern version of the Vox Humana pipe organ stop for application in voice production and perception research.
Study Design: Descriptive METHODS/DESIGN: The latest Vocal Tract Organ is a polyphonic eight-channel eight-stop one manual Vocal Tract Organ that enables tab stop selected three-D printed vocal tracts to be used to create sound. This version includes eight stops (four for female vowel oral tracts and four for male vowel oral tracts). The stops are implemented using conventionally engraved pipe organ stop tabs labeled "Vox Humana Female" or "Vox Humana Male" followed by the three-D printed vowel: "EE", "AH", "ER" or "UU." This is described alongside the development stages from which it emerged and covers all previous versions of the Vocal Tract Organ. At the heart of the latest instrument is a Bela BeagleBone Black with a Bela cape audio expander board which incorporates eight 16-bit audio outputs at 44.1 kHz sampling rate (earlier versions based on the Arduino Mega board were limited to 8-bit audio at an audio sampling rate of 16.384 kHz which limited the overall output spectrum). The latest Vocal Tract Organ is programmed using the audio graphical programming language Pure Data which is directly compatible with the Bela system. The Pure Data patch creates eight larynx outputs at the pitches set by the keys depressed on the keyboard and these are routed to Vocal Tract Organ loudspeakers with three-D printed vocal tracts attached.
Results: The Bela system has enabled real-time synthesis of eight-note polyphonic sounds to eight separate three-D printed vocal tracts, each being selectable via an organ tab stop switch. The instrument has been cased in a purpose-designed and built prototype laser-cut enclosure that incorporates the eight tab stops, a MIDI keyboard input, a pipe organ style swell (volume) pedal connection, four stereo (eight channels) audio amplifiers and terminal connections for the eight loudspeakers.
Conclusions: The Vocal Tract Organ functions as a musical instrument for performance and as an instrument for vowel and pitch perception research. Implementing it with the Bela family of processors allows for low audio latency of 1 ms and rapid prototyping due to being able to program directly with the high-level graphical audio programming language, Pure data (Pd).
(Crown Copyright © 2022. Published by Elsevier Inc. All rights reserved.)

Population density techniques can be used to simulate the behavior of a population of neurons which adhere to a common underlying neuron model. They have previously been used for analyzing models of orientation tuning and decision making tasks. They produce a fully deterministic solution to neural simulations which often involve a non-deterministic or noise component. Until now, numerical population density techniques have been limited to only one- and two-dimensional models. For the first time, we demonstrate a method to take an N-dimensional underlying neuron model and simulate the behavior of a population. The technique enables so-called graceful degradation of the dynamics allowing a balance between accuracy and simulation speed while maintaining important behavioral features such as rate curves and bifurcations. It is an extension of the numerical population density technique implemented in the MIIND software framework that simulates networks of populations of neurons. Here, we describe the extension to N dimensions and simulate populations of leaky integrate-and-fire neurons with excitatory and inhibitory synaptic conductances then demonstrate the effect of degrading the accuracy on the solution. We also simulate two separate populations in an E-I configuration to demonstrate the technique's ability to capture complex behaviors of interacting populations. Finally, we simulate a population of four-dimensional Hodgkin-Huxley neurons under the influence of noise. Though the MIIND software has been used only for neural modeling up to this point, the technique can be used to simulate the behavior of a population of agents adhering to any system of ordinary differential equations under the influence of shot noise. MIIND has been modified to render a visualization of any three of an N-dimensional state space of a population which encourages fast model prototyping and debugging and could prove a useful educational tool for understanding dynamical systems.
(Copyright © 2022 Osborne and de Kamps.)