Robust dynamic control algorithm for uncertain powered wheelchairs based on sliding neural network approach

The dynamic model of mobile wheelchair technology requires developing and implementing an intelligent control system to improve protection, increasing performance efficiency, and creating precise maneuvering in indoor and outdoor spaces. This work aims to design a robust tracking control algorithm based on a reference model for operating the kinematic model of powered wheelchairs under the variation of system parameters and unknown disturbance signals. The control algorithm was implemented using the pole placement method in combination with the sliding mode control (PP-SMC) approach. The design also adopted a neural network approach to eliminate system uncertainties from perturbations. The designed method utilized the sinewave signal as an essential input signal to the reference model. The stability of a closed-loop control system was achieved by adopting the Goa reaching law. The performance of the proposed tracking control system was evaluated in three scenarios under different conditions. These included assessing the tracking under normal operation conditions, considering the tracking performance by changing the dynamic system's parameters and evaluating the control system in the presence of uncertainties and external disturbances. The findings demonstrated that the proposed control method efficiently tracked the reference signal within a small error based on mean absolute error (MAE) measurements, where the range of MAE was between 0.08 and 0.12 in the presence of uncertainties or perturbations

Knowledge and perceptions regarding Coronavirus (COVID-19) among pediatric dentists during lockdown period

Aim: To assess the knowledge and perceptions of COVID-19 among pediatric dentists based on their dependent source of information. Methods: A descriptive-analytical cross-sectional survey using a self-administered questionnaire with 23 questions was sent via Google forms to pediatric dentists. All participants were divided into three groups [postgraduate residents (PGs), private practitioners (PP), and faculty (F)]. The comparison of knowledge and perception scores was made based on occupation, source of information, and descriptive statistics used for the analysis using SPSS 21.0 (IBM, Armonk, NY, USA). Results: A total of 291 pediatric dentists completed the survey, and the majority of them were females (65%). Overall, good mean scores were obtained for knowledge (9.2 ± 1.07) and perceptions (5.6 ± 1.5). The majority of the participants used health authorities (45%) to obtain updates on COVID-19, while social media (35.1%) and both (19.6%) accounted for the next two. A statistically significant difference (p < 0.05) was found among different pediatric dentists groups for relying on the source of information. Conclusion: Overall good pediatric dentists showed sufficient knowledge regarding COVID-19. The pediatric dentists’ age, occupation, and source of information influenced knowledge regarding COVID-19, whereas perceptions were influenced by age and gender of the participants. Health authorities successfully educated pediatric dentists than the social medi

Non-Invasive Analyses of Electrophysiological Properties of Primary Cell Culture

The model of efficacy and toxicity testing has been largely based on a model of high quantities of low quality data gathered in vitro. Recent advances in nanotechnology offer an alternative strategy. Soft lithography has made microscale tissue engineering possible. It is now feasible to create the cellular microenvironments of healthy and diseased tissues and engineer biological systems with high fidelity. Further, development of multielectrode array (MEA) platforms by precise location of metal electrodes on glass substrates has proven to be a robust innovative tool to use with cells that generate electrical activity. In this study, we first fabricated polydimethylsiloxane (PDMS) stamps for microcontact (µC) printing extra cellular protein along microscale features through soft lithography techniques. Engineering anisotropic cardiac monolayers on glass substrate without an underlying of PDMS coating was achieved to mimic the aligned architecture of myocardium without the hydrophobic polymer. Direct microcontact printing on glass is an important development for engineering anisotropic cellular layers on top of MEAs. Additionally, we investigated physical and protein cues from extracellular matrix to engineer anisotropic cardiac tissues as highly aligned monolayers on top of MEA. Non-invasive measurements of beating rate and conduction velocity were collected over different days of culture to determine the ideal substrate. While anisotropic cardiac tissues started to delaminate in early time point on µC fibronectin and gelatin substrates, the anisotropic tissues stayed intact for a long-culture time on micromolded (µM) gelatin hydrogels and provided synchronized beating and steady conduction velocity that was close to the physiological values. Ultimately, 3D micromolded gelatin hydrogel that recapitulated myocardial stiffness improved the synchronicity and conduction velocity of neonatal rat ventricular myocytes (NRVM) without any stimulation. In a second study, we validated the usage of MEA to measure the electrical activity induced by glucose response in dissociated human islets. First, we solved the obstacle of adhering 3D islets on planar electrodes MEA by successfully dissociating the 3D islets into dissociated singular cells and small cell clusters, which helped the cells to adhere in a single layer for a long culture time. The planar cell contact on the electrodes allowed us to start testing islet functionality from the first day by recording the electrical activity with low glucose and then high glucose incubation. MEA recordings captured higher electrical activities of islet cells under high glucose than low glucose conditions. While traditional functional assay showed an insulin response to glucose challenge at only early time points, spiking activity from MEA recordings corresponding to high and low glucose was consistently recorded up to a week in culture. Overall, we report important developments in primary cardiac and islet cell culture techniques that further enable MEA as a non-invasive real time platform for functional evaluation of electrophysiology.</p

In vitro methods for evaluating therapeutic ultrasound exposures: present-day models and future innovations

Although preclinical experiments are ultimately required to evaluate new therapeutic ultrasound exposures and devices prior to clinical trials, in vitro experiments can play an important role in the developmental process. A variety of in vitro methods have been developed, where each of these has demonstrated their utility for various test purposes. These include inert tissue-mimicking phantoms, which can incorporate thermocouples or cells and ex vivo tissue. Cell-based methods have also been used, both in monolayer and suspension. More biologically relevant platforms have also shown utility, such as blood clots and collagen gels. Each of these methods possesses characteristics that are well suited for various well-defined investigative goals. None, however, incorporate all the properties of real tissues, which include a 3D environment and live cells that may be maintained long-term post-treatment. This review is intended to provide an overview of the existing application-specific in vitro methods available to therapeutic ultrasound investigators, highlighting their advantages and limitations. Additional reporting is presented on the exciting and emerging field of 3D biological scaffolds, employing methods and materials adapted from tissue engineering. This type of platform holds much promise for achieving more representative conditions of those found in vivo, especially important for the newest sphere of therapeutic applications, based on molecular changes that may be generated in response to non-destructive exposures

Microelectrode Array based Functional Testing of Pancreatic Islet Cells

Electrophysiological techniques to characterize the functionality of islets of Langerhans have been limited to short-term, one-time recordings such as a patch clamp recording. We describe the use of microelectrode arrays (MEAs) to better understand the electrophysiology of dissociated islet cells in response to glucose in a real-time, non-invasive method over prolonged culture periods. Human islets were dissociated into singular cells and seeded onto MEA, which were cultured for up to 7 days. Immunofluorescent imaging revealed that several cellular subtypes of islets; &beta;, &delta;, and &gamma; cells were present after dissociation. At days 1, 3, 5, and 7 of culture, MEA recordings captured higher electrical activities of islet cells under 16.7 mM glucose (high glucose) than 1.1 mM glucose (low glucose) conditions. The fraction of the plateau phase (FOPP), which is the fraction of time with spiking activity recorded using the MEA, consistently showed distinguishably greater percentages of spiking activity with high glucose compared to the low glucose for all culture days. In parallel, glucose stimulated insulin secretion was measured revealing a diminished insulin response after day 3 of culture. Additionally, MEA spiking profiles were similar to the time course of insulin response when glucose concentration is switched from 1.1 to 16.7 mM. Our analyses suggest that extracellular recordings of dissociated islet cells using MEA is an effective approach to rapidly assess islet functionality, and could supplement standard assays such as glucose stimulate insulin response

Microelectrode Array based Functional Testing of Pancreatic Islet Cells

Electrophysiological techniques to characterize the functionality of islets of Langerhans have been limited to short-term, one-time recordings such as a patch clamp recording. We describe the use of microelectrode arrays (MEAs) to better understand the electrophysiology of dissociated islet cells in response to glucose in a real-time, non-invasive method over prolonged culture periods. Human islets were dissociated into singular cells and seeded onto MEA, which were cultured for up to 7 days. Immunofluorescent imaging revealed that several cellular subtypes of islets; β, δ, and γ cells were present after dissociation. At days 1, 3, 5, and 7 of culture, MEA recordings captured higher electrical activities of islet cells under 16.7 mM glucose (high glucose) than 1.1 mM glucose (low glucose) conditions. The fraction of the plateau phase (FOPP), which is the fraction of time with spiking activity recorded using the MEA, consistently showed distinguishably greater percentages of spiking activity with high glucose compared to the low glucose for all culture days. In parallel, glucose stimulated insulin secretion was measured revealing a diminished insulin response after day 3 of culture. Additionally, MEA spiking profiles were similar to the time course of insulin response when glucose concentration is switched from 1.1 to 16.7 mM. Our analyses suggest that extracellular recordings of dissociated islet cells using MEA is an effective approach to rapidly assess islet functionality, and could supplement standard assays such as glucose stimulate insulin response

Engineering anisotropic cardiac monolayers on microelectrode arrays for non-invasive analyses of electrophysiological properties

A standard culture of cardiac cells as unorganized monolayers on tissue culture plastic or glass does not recapitulate the architectural or the mechanical properties of native myocardium. We investigated the physical and protein cues from the extracellular matrix to engineer anisotropic cardiac tissues as highly aligned monolayers on top of the microelectrode array (MEA). The MEA platform allows non-invasive measurement of beating rate and conduction velocity. The effect of different extracellular proteins was tested by using the most common extracellular matrix proteins in the heart, fibronectin and gelatin, after aligning myocytes using a microcontact (μC) printing technique. Both proteins showed similar electrophysiological results before the monolayer began to delaminate after the sixth day of culture. Additionally, there were no significant differences on day 4 between the two microcontact printed proteins in terms of sarcomere alignment and gap junction expression. To test the effect of substrate stiffness, a micromolded (μM) gelatin hydrogel was fabricated in different concentrations (20% and 2%), corresponding to the elastic moduli of approximately 33 kPa and 0.7 kPa, respectively, to cover both spectra of the in vivo range of myocardium. Cardiac monolayers under micromolded conditions beat in a much more synchronized fashion, and exhibited conduction velocity that was close to the physiological value. Both concentrations of gelatin hydrogel conditions yielded similar sarcomere alignment and gap junction expression on day 4 of culture. Ultimately, the 3D micromolded gelatin hydrogel that recapitulated myocardial stiffness improved the synchronicity and conduction velocity of neonatal rat ventricular myocytes (NRVM) without any stimulation. Identifying such microenvironmental factors will lead to future efforts to design heart on a chip platforms that mimic in vivo environment and predict potential cardiotoxicity when testing new drugs

Correction to: A Chemically Defined Common Medium for Culture of C2C12 Skeletal Muscle and Human Induced Pluripotent Stem Cell Derived Spinal Spheroids

[This corrects the article DOI: 10.1007/s12195-020-00624-1.]

A Chemically Defined Common Medium for Culture of C2C12 Skeletal Muscle and Human Induced Pluripotent Stem Cell Derived Spinal Spheroids

Multicellular platforms and linked multi organ on chip devices are powerful tools for drug discovery, and basic mechanistic studies. Often, a critical constraint is defining a culture medium optimal for all cells present in the system. In this study, we focused on the key cells of the neuromuscular junction i.e., skeletal muscle and motor neurons. Formulation of a chemically defined medium for the co-culture of C2C12 skeletal muscle cells and human induced pluripotent stem cell (hiPSC) derived spinal spheroids (SpS) was optimized. C2C12 cells in 10 experimental media conditions and 2 topographies were evaluated over a 14-day maturation period to determine the ideal medium formulation for skeletal muscle tissue development. During early maturation, overexpression of genes for myogenesis and myopathy was observed for several media conditions, corresponding to muscle delamination and death. Together, we identified 3 media formulations that allowed for more controlled differentiation, healthier muscle tissue, and long-term culture duration. This evidence was then used to select media formulations to culture SpS and subsequently assessed axonal growth. As axonal growth in SpS cultures was comparable in all selected media conditions, our data suggest that the neuronal basal medium with no added supplements is the ideal medium formulation for both cell types. Optimization using both topographical cues and culture media formulations provides a comprehensive analyses of culture conditions that are vital to future applications for NMJ models