Finite Difference Time Domain Simulations of Hybrid Neurotransducers Based Optical Microlasers

Different pathologies such as Alzheimer’s, Parkinson’s, Wilson’s diseases, and chronic traumatic encephalopathy due to blasts and impacts affect the brain functions altering the neuronal electrical activity. An important aspect of the brain study is the use of non-invasive, non-surgical methodologies that are suitable to the well-being of the patients. Only a portion of the electromagnetic field can be detected by applying sensors outside the scalp; in addition, surgery is often involved if sensors are applied in the subcutaneous region of the skull. Optical techniques applied to biomedical research and diagnostics have been spread during the last decades. For example, near infrared light (NIR) of spectral range goes from 800 nm to 1300 nm, it is harmless radiation for the living tissue, and can penetrate the living matter in depth as, it turns out that most of the living matter is transparent to the NIR light. Optical microlasers have been recently proposed as neurotransducers for minimally invasive neuron activity detection for the next generation of brain-computer interface (BCI) systems. They are lightweight, require low power consumption and exhibit low latency. This novel sensor that can be made of biocompatible material is coupled with a voltage sensitive dye; the fluorescence of the dye, which is excited by an external light source, is used to generate optical (laser) modes. Any variation in the neurons’ membrane electric potential via evanescent field’s perturbation turn affect the shifting of these laser modes. In order to reduce the energy required to power these devices and to improve their optical emission, metal nanoparticles can be coupled in order to use their plasmonic effect. In this paper, finite-difference timedomain (FDTD) numerical technique is used to analyze the performances on a dye-doped microlaser. Purcell effect and resonant wavelengths are observed.

Quantifying the Accuracy of a Motion Detecting Neural Prosthesis

The neural prosthesis under development is designed to improve gait in people with muscle weakness. The strategy is to augment impaired or damaged neural connections between the brain and the muscles that control walking. This third-generation neural prosthesis contains triaxial inertial measurement units (IMUs - accelerometers, gyroscopes, and processing chip) to measure body segment position and force sensitive resistors placed under the feet to detect ground contact. A study was conducted to compare the accuracy of the neural prosthesis using a traditional camera motion capture system as a reference. The IMUs were found to accurately represent the amplitude of the gait cycle components and generally track the motion. However, there are some differences in phase, with the IMUs lagging the actual motion. Phase lagged by about 10 degrees in the ankle and by about 5 degrees in the knee. Error of the neural prosthesis varied over the gait cycle. The average error for the ankle, knee and hip were 6°, 8°, and 9°, respectively. Testing showed that the neural prosthesis was able to capture the general shape of the joint angle curves when compared to a commercial camera motion capture system. In the future, measures will be taken to reduce lag in the gyroscope and reduce jitter in the accelerometer so that data from both sensors can be combination to obtain more accurate readings.

Innovative Design of Indoor-Outdoor Powerchair

People with disabilities often struggle with mobility issues, so there is a strong desire for devices such as powerchairs, which can provide more freedom. Currently, wheelchair demand in the US is increasing due to an upsurge in the elderly population. Often electric powerchairs suitable for outdoor use are extremely expensive, cannot be used indoors, and are not covered by medical insurance. In this project, these problems are addressed through the design of a chair which is suitable for both rough outdoor terrain and indoor use. This project is based on a request for a powerchair which our client’s son, who has cerebral palsy, can use on family trips in outdoor environments including grass, gravel, and sand. A photo of a previous nonfunctional prototype was provided to the team as a reference, and a full redesign was performed to resolve the problems identified. Before proceeding with the design, various sources were consulted to gain a thorough understanding of currently available technology and design methods. Many different adjustment methods and features were considered, including an adjustable frame, tracks, and a lifting system for curb mounting. The overall design selected is a welded sheet metal frame with wheels, and it was determined that the chair should have an adjustable wheelbase width to provide both outdoor stability and indoor maneuverability. Key considerations for the design include battery life, motor torque, maximum load, seat size, door width, and cost. The final specifications are based on the needs of the client, Kevin Sample, as well as an analysis of the wider consumer market. The width adjustment design uses an axle above the driving wheels, which are connected to it by sliding sleeves. Automatic adjustment is accomplished using a linear actuator. The drive wheels are large and run at low pressure to surmount obstacles and damp vibrations. Differential steering combined with rear caster wheels gives the chair a small turning radius, and its length is comparable to that of standard manual wheelchairs. The seat can be easily removed to access the battery and control system or to load the chair into a vehicle. A joystick is used to control the speed and direction of the chair, while a separate momentary switch is used for the linear actuator. Throughout the modeling process, stress analysis was performed using simulations in Inventor. Any necessary adjustments were made to ensure that none of the parts will fail, considering both failure theory and fatigue. Various grades of aluminum were selected for the majority of the manufactured parts, due to their corrosion resistance and light weight. The device is currently in the prototype manufacturing stage. If it is later marketed, a curb mounting device may also be included; this was decided against mainly due to cost and time restrictions. Space has also been left for a carrying basket, which will likely be added to the first prototype. The initial goal is to produce a single chair for our client, although the design may later be submitted for Medicare and ADA approval.

Non-Contact Measurement of Respiratory Function for Judging the Effect of Respiratory Rehabilitation in Patients With SMID

Patients with SMID (severe motor and intellectual disabilities) have severe limb disorders and severe mental disabilities. More than half of their deaths are due to respiratory disorders. Therefore, respiratory rehabilitation is important. The effect of respiratory rehabilitation is generally determined by measuring respiratory volume and rate with an expired gas analyzer. However, the equipment is expensive and requires direct contact, making it difficult to use. The purpose of this research is to develop a non-contact measurement system for respiratory function to assess the effect of respiratory rehabilitation in patients with SMID. The proposed method detects respiration by depth change of the abdomen measured using a three-dimensional camera designed to identify body tremor /motion and respiration based on respiratory parameters and individually adapted parameters. Finally, we verify the rehabilitation effect of an RTX respirator on patients with SMID and the effectiveness of the proposed method in an experiment.

Computational Modeling of Combat Helmet Performance Analysis Integrating Blunt and Blast Loadings

Combat helmets have gone through many changes, from shells made of metal to advanced composites using Kevlar and Dyneema, along with introduction of pad suspensions to provide comfort and protection. Helmets have been designed to perform against ballistic and blunt impact threats. But, in today’s warfare, combat helmets are expected to protect against all three threats, blunt, ballistic impacts and blast effects to minimize traumatic brain injury (TBI) and provide a better thermal comfort. We are developing a helmet system analysis methodology integrating the effect of multiple threats, i.e., blast and blunt impacts, to achieve an optimal helmet system design, by utilizing multi-physics computational tools. We used a validated human head model to represent the warfighter’s head. The helmet composite shell was represented by an orthotropic elasto-plastic material model. A strain rate dependent model was employed for pad suspension material. Available dynamic loading data was used to calibrate the material parameters. Multiple helmet system configurations subjected to blast and blunt loadings were considered to quantify their influence on brain biomechanical response. Parametric studies were carried out to assess energy absorption for different suspension geometry and material morphology for different loadings. The resulting brain responses were used with published injury criteria to characterize the helmet system performance through a single metric for each threat type. Approaches to combine single-threat metrics to allow aggregating performance against multiple threats were discussed.

Computational Modelling and Simulation of Pedestrian Subsystem Impactor With Sedan Vehicle and Truck Model

The increase in public transportation in the last decade has resulted in a larger pedestrian population and hence a larger number of pedestrian collisions. In the past, car-pedestrian accident prevention had been a challenge for automotive and transport safety members. Recent reports in car-pedestrian accidents have influenced many improvements to prioritize pedestrian protection for automotive industries. The number of pedestrian fatalities in U.S has raised in last decade proportionally, Car manufacturers, and transport investigation teams are implementing new product designs and adding new development methods to reduce the risk of pedestrian collisions. In this study, adult headform and upper legform is tested with a finite element vehicle model to examine the simulation results and injury behavior during impact. All finite element simulation tests are produced under Euro-NCAP Committee regulations. Finite element models are configured as per the regulation’s and testing criteria. Both upper legform impactor and adult headform finite simulation results are tested with assessing criteria limits. Finite simulation tests are carried on the LS-DYNA – Code platform. This comparative study between sedan and pickup finite vehicle models gives an injury risk prediction of pedestrian safety and assesses design parameters of automotive industries.

The Mechanism of Movement and Calculation of Blood Balance in the Flow Channel From the Left Atrium to the End of the Aorta

Today, there are a lot of works studying the mechanisms of formation and evolution of self-organizing tornado-like jets of viscous fluid. In these works, the exact solution of the Navier-Stokes equation for such a class of flows are obtained, the geometry of the generating surface for that flows is established and the necessary and sufficient conditions for the formation and evolution of such swirling jets are formulated. However, important aspects of the mechanics of such flows remain unclear — the structure of the boundary layer, the shape of streamlines in general form, the structure of such flows under a pulsating flow regime, and others. After obtaining the exact solution, attempts were made to obtain relations for streamlines in the corresponding projections. However, due to computational complexity, streamlines were constructed only for regions far from the axis of the swirling flow evolution. In this work, an alternative method of calculating streamlines was used, which made it possible to obtain general relations for these lines at each point in space. Expressions for streamlines contain easily computed functions, which simplifies their practical use Based on the expressions for streamlines, expressions were formulated declaring the conservation of the mass of the swirling blood flow from the left atrium to the aorta and the balance of the medium was calculated. The results of this work are of great theoretical and practical importance. On the one hand, the established expressions for streamlines allow a better study of the mechanisms of formation and evolution of swirling flows in the axial region. On the other hand, obtaining quantitative ratios for the balance of blood in the heart and aorta allows a more accurate study of the mechanics of blood circulation.

Regional and Layer Distribution of Residual Stresses in an Unloaded Aortic Medial Wall

The mechanical and structural characteristics of aortic media have profound effects on the physiology and pathophysiology of an aorta. However, many aspects of the aortic tissue remain poorly understood, partly due to the intrinsic layered wall structure and regionally varying residual stresses. Our recent works have demonstrated that a mechanical interaction between the elastic lamina (EL) and smooth muscle layer in the aortic media can be computationally reproduced using a simplified finite element (FE) model. However, it is questionable whether the simplified FE model we created was representative of the structure of a real medial wall and its modeling technique would be applicable to develop a more sophisticated and structure-based aortic FE model. This study aimed to computationally represent EL buckling in the aortic medial ring at an unloaded state and successfully reproduced transmural variation in EL waviness across the aortic wall. We also aimed at confirming the inner and outer layers of the medial wall are subjected to compressive and tensile residual stresses, respectively, at the unloaded state, implying that the ring model will open spontaneously when it is radially cut. Moreover, the computed residual stresses were found to be within the reasonable range of the predicted values, 1–10 kPa, supporting the validity of our modeling approach. Although further study is required, the information obtained here will greatly help improve the understanding of basic aortic physiology and pathophysiology, while simultaneously providing a basis for more sophisticated computational modeling of the aorta.

Prediction of Blood Flow Distribution in Liver Radioembolization Using Convolutional Neural Networks

We have developed a new dosimetry approach, called CFDose, for liver cancer radioembolization based on computational fluid dynamics (CFD) simulation in the hepatic arterial tree. Although CFDose overcomes some of the limitations of the current dosimetry methods such as the unrealistic assumption of homogeneous distribution of yttrium-90 in the liver, it suffers from the expensive computational cost of CFD simulations. To accelerate CFDose, we introduce a deep learning model to predict the blood flow distribution between the liver segments in a patient with hepatocellular carcinoma. The model was trained with the results of CFD simulations under different outlet boundary conditions. The model consisted of convolutional, average pooling and transposed convolution layers. A regression layer with a mean-squared-error loss function was utilized at the network output to estimate the arterial outlet blood flow. The mean-squared error and prediction accuracy were calculated to measure model performance. Results showed that the average difference between the CFD results and predicted flow data was less than 2.45% for all the samples in the test dataset. The proposed model thus estimated the blood flow distribution with high accuracy significantly faster than a CFD simulation. The network output can be used to estimate the yttrium-90 dose distribution in the liver in future studies.

Biomechanical Analysis of the Sensitivity of Brain Tissue Responses to FE Head Models in the Study of Impact-Induced TBI

A numerical investigation is conducted on the injury-related biomechanical parameters of the human head under blunt impacts. The objective of this research is twofold; first to understand the role of the employed finite element (FE) head model — with its specific components, shape, size, material properties, and mesh size — in predicting tissue responses of the brain, and second to investigate the fidelity of pressure response in validating FE head models. Accordingly, two independently established and validated FE head models are impacted in two directions under two impact severities and their predicted responses in terms of intracranial pressure (ICP) and shear stress are compared. The coup-counter ICP peak values are less sensitive to head model, mesh size, and the brain material. In all cases, maximum ICPs occur on the outer surface, vanishing linearly toward the center of the brain. Hence, it is concluded that different head models may simply reproduce the results of ICP variations due to impact. Shear stress prediction, however, is mainly affected by the head model, direction and severity of impact, and the brain material.