Investigations of an On-body Reflectometer Probe

Radar can be utilized to detect the mechanical heart activity and is a potential alternative to today’s heartbeat monitoring techniques in medicine. It can detect details of the heart activity, such as filling and ejection of heart chambers and opening and closing of heart valves. This is due to the radars ability to detect movements and direction of motion. Compared to electrocardiogram and ultrasound it has the advantage that it is a contactless measurement. The objective of this thesis is the development of a proof-of-concept prototype of a novel microwave on-body sensor for heartbeat detection, which can be used inside an MRI system and which could provide prospective triggering information. The main idea is to use a microwave sensor (reflectometer) with an on-body antenna illuminating the heart and detecting the reflected signal. The measurement is based on the evaluation of the heart-related time-dependent reflection coefficient of the antenna, by minimizing the static and respiration-related components of the reflection coefficient. In a first step, this is done by minimizing the antenna mismatch with an automatic impedance matching circuit after the placement of the antenna on the chest of an individual; the antenna mismatch is dependent on the position and the individual body properties. In a second step the residual static and slow variation signal from respiration is suppressed by a canceller circuit (well-known from CW radar technology as reflected power canceller). With the reflectometer sensor system consisting of a CW signal generator (transmitter, Tx), on-body antenna, adaptive impedance matching circuit and demodulator circuit as part of the reflected signal canceller, the performance of each component influences the performance of the sensor system. Thus, the thesis concentrates on the design of the circuits and the antenna but also investigates the wave propagation scenario of the sensor applied to a human chest. The signals measured with the microwave sensor are compared with a standard measurement method for heart activity, a heart sound measurement. This is used in order to assess the obtained signal and relate the signal states to certain heart states. The measured radar signals are found to be sensitive to position of the sensor, the individual and the posture of the individual, making the interpretation of the signals challenging

Chemomechanics of attached and suspended cells

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 173-184).Chemomechanical coupling in single eukaryotic animal cells is investigated in the con- text of the attached (substratum-adhered) and the suspended (free-floating) states. These dichotomous configurations determine behavioral differences and commonalities relevant to therapeutic reimplantation of stem cells and to our general under- standing of the cell as an animate material. Analytical, simulation, and experimental techniques are applied to key questions including: (1) How deep can mechanosensitive attached cells "feel" into the adjacent environment? (2) In what manner do suspended cells deform, absent the prominent actomyosin stress fibers that arise upon attachment to a rigid substratum? (3) What explains the remarkable mechanical heterogeney among single cells within a population? (4) Can we leverage putative mechanical markers of useful stem cells to sort them before reimplantation in tissue generation therapies? Attached cells are found to barely detect an underlying rigid base more than 10 micrometers below the surface of a compliant coating. This conclusion, based on ex- tensions to the Boussinesq problem of elasticity theory, is validated by observations of cell morphology on compliant polyacrylamide coatings in a range of thicknesses. Analytical equations are developed for estimating the effective stiffness sensed by a cell atop a compliant layer. We also identify and consider conceptualizations of a "critical thickness," representing the minimum suitable thickness for a specific application. This parameter depends on the cell behavior of interest; the particular case of stem cell culture for paracrine extraction is presented as a case study. Suspended cells are found to exhibit no single characteristic time scale during de- formation; rather, they behave as power-law (or "soft glassy") materials. Here, optical stretching is used as a non-contact technique to show that stress fibers and probe-cell contact are not critical in enabling power-law rheological behavior of cells. Further- more, suspended cell fluidity, as characterized by both the hysteresivity of complex modulus and the power-law exponent of creep compliance, is found to be unaffected by adenosine triphosphate (ATP) depletion, showing that ATP hydrolysis is not the origin of fluidity in cells during deformation. However, ATP depletion does reduce the natural variation in hysteresivity values among cells. This finding, and the finding that changes in the power-law exponent and stiffness of single cells are correlated upon repeated loading, motivates study of how and why these parameters are coupled. To further explore this coupling, chemomechanical cues are applied to cell populations to elucidate the origin of the wide, right-skewed distribution of stiffness values that is consistently observed. The distribution and width are found to be not detectably dependent on cell-probe contact, cell lineage, cell cycle, mechanical perturbation, or fixation by chemical crosslinking. However, ATP depletion again reduces heterogeneity, now in the case of cell stiffness values. It is further found analytically that a postulated Gaussian distribution of power-law exponent values leads naturally to the log-normal distribution of cell stiffness values that is widely observed. Based on these connections, a framework is presented to improve our understanding of the appearance of mechanical heterogeneity in successively more complex assemblies of cell components. Two case studies are described to explore the implications of unavoidable intrinsic variation of cell stiffness in diagnostic and therapeutic applications. Finally, all the single-cell mechanical parameters studied so far (stiffness during creep and recovery, stiffness heterogeneity among cells, and power-law exponents in creep and recovery) are characterized in mesenchymal stem cells during twenty population doublings with the aim of developing a high-throughput sorting tool. How- ever, mechanical and structural changes that are observed in the attached state during this culture time are not observed after cell detachment from the substratum. The absence in the suspended state of these alterations indicates that they manifest themselves through stress fiber arrangement rather than cortical network arrangement. While optical stretching under the present approach does not detect mechanical markers of extended passaging that are correlated with decreased differentiation propensity, the technique is nevertheless found capable of investigating another structural transition: mechanical stiffening over tens of minutes after adherent cells are suspended. This previously unquantified transition is correlated with membrane resorption and reattachment to the cortex as the cell "remodels" after substratum detachment. Together, these quantitative studies and models of attached and suspended cells de- fine the extremes of the extracellular environment while probing mechanisms that con- tribute to cellular chemomechanical response. An integration of the results described above shows that no one existing model can describe cell chemomechanics. However, the cell can be usefully described as a material -- one in which animate mechanisms such as active contraction will generally, but not invariably, need to be considered as augmenting existing viscoelastic theories of inanimate matter.by John Mapes Maloney.Ph.D

A Biomechanical and Physiological Signal Monitoring System for Four Degrees of Upper Limb Movement

A lack of adherence to prescribed physical therapy regimens in improper healing results in poor outcomes for those affected by musculoskeletal disorders (MSDs) of the upper limb. Societal and psychological barriers to proper adherence can be addressed through the system presented in this work consisting of the following components: an ambulatory biosignal acquisition sleeve, an electromyography (EMG) based motion repetition detection algorithm, and the design of a compatible capacitive EMG acquisition module. The biosignal acquisition sleeve was untethered, unobtrusive to motion, contained only modular components, and collected biomechanical and physiological sensor data to form full motion profiles of the following four degrees of freedom: elbow flexion—extension, forearm pronation—supination, wrist flexion—extension, and ulnar--radial deviation. The piloted sleeve simultaneously collected data from four inertial sensors, two electromyography (EMG) sensors and a flex-bend sensor. A visualization application was developed to present the information in a manner meaningful to the user. As well, an EMG based motion repetition detector was developed for use within the system. It was validated using an existing database of 23 subjects with varying musculoskeletal health, achieving a success rate of 95.43%. This algorithm was modified for use with the sleeve, resulting in a 95% success rate. An electrode and analog front end module was proposed, relying on unique material structures and low-noise, precision sensing techniques. The system prototype presented a resource-conscious tool for multi-modality tracking of elbow, forearm, and wrist motion, which could eventually be integrated into upper limb MSD rehabilitation

Biomedical Photoacoustic Imaging and Sensing Using Affordable Resources

The overarching goal of this book is to provide a current picture of the latest developments in the capabilities of biomedical photoacoustic imaging and sensing in an affordable setting, such as advances in the technology involving light sources, and delivery, acoustic detection, and image reconstruction and processing algorithms. This book includes 14 chapters from globally prominent researchers , covering a comprehensive spectrum of photoacoustic imaging topics from technology developments and novel imaging methods to preclinical and clinical studies, predominantly in a cost-effective setting. Affordability is undoubtedly an important factor to be considered in the following years to help translate photoacoustic imaging to clinics around the globe. This first-ever book focused on biomedical photoacoustic imaging and sensing using affordable resources is thus timely, especially considering the fact that this technique is facing an exciting transition from benchtop to bedside. Given its scope, the book will appeal to scientists and engineers in academia and industry, as well as medical experts interested in the clinical applications of photoacoustic imaging

Bipolar Electroactive Conducting Polymers for Wireless Cell Stimulation

Electrochemical stimulation (ES) promotes wound healing and tissue regeneration in biomedical applications and clinical studies and is central to the emerging field of electroceuticals. Traditional ES such as deep brain stimulation for Parkinson’s disease, utilises metal electrodes that are hard wired to a power supply to deliver the stimulation. Bipolar electrochemistry (BPE) introduces an innovative approach to cell stimulation that is wireless. Developing conducting polymers (CPs)-based stimulation platforms wireless powdered by BPE bipolar will provide an exciting new dimension to medical bionics. In this project, Chapter 2 deals with development of a bipolar electrochemical activity testing system and bipolar electrochemical stimulation (BPES) system. Then, bipolar electroactive and biocompatible CPs grown on FTO substrate are successfully synthesised, modified, and characterised in Chapter 3 and Chapter 4 using the above systems prior to using for wireless cell stimulation. Furthermore, free standing and soft CP templates are developed (Chapter 5). More importantly, all these bipolar electroactive CPs have been applied to wireless cell stimulation using BPE (all research Chapters). Significant increase in both cell number and neurite growth has been demonstated, suggesting that the BPES system is highly efficient for stimulation of animal PC 12 cell and human SH-SY5Y cell. More specific information is presented in each chapter as below. In Chapter 3, a CP-based bipolar electrochemical stimulation (BPES) system for cell stimulation was present. Polypyrrole (PPy) films with different dopants have demonstrated reversible and recoverable bipolar electrochemical activity under a low driving DC voltage

NASA Tech Briefs, April 1991

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Advance in Energy Harvesters/Nanogenerators and Self-Powered Sensors

This reprint is a collection of the Special Issue "Advance in Energy Harvesters/Nanogenerators and Self-Powered Sensors" published in Nanomaterials, which includes one editorial, six novel research articles and four review articles, showcasing the very recent advances in energy-harvesting and self-powered sensing technologies. With its broad coverage of innovations in transducing/sensing mechanisms, material and structural designs, system integration and applications, as well as the timely reviews of the progress in energy harvesting and self-powered sensing technologies, this reprint could give readers an excellent overview of the challenges, opportunities, advancements and development trends of this rapidly evolving field

NASA Tech Briefs, October 1992

Topics covered include: Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication technology; Mathematics and Information Sciences; Life Sciences

NASA Tech Briefs, April 1992

Topics covered include: New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences

Spacelab Science Results Study

Beginning with OSTA-1 in November 1981 and ending with Neurolab in March 1998, a total of 36 Shuttle missions carried various Spacelab components such as the Spacelab module, pallet, instrument pointing system, or mission peculiar experiment support structure. The experiments carried out during these flights included astrophysics, solar physics, plasma physics, atmospheric science, Earth observations, and a wide range of microgravity experiments in life sciences, biotechnology, materials science, and fluid physics which includes combustion and critical point phenomena. In all, some 764 experiments were conducted by investigators from the U.S., Europe, and Japan. The purpose of this Spacelab Science Results Study is to document the contributions made in each of the major research areas by giving a brief synopsis of the more significant experiments and an extensive list of the publications that were produced. We have also endeavored to show how these results impacted the existing body of knowledge, where they have spawned new fields, and if appropriate, where the knowledge they produced has been applied