Biomedical Engineering and Bioengineering Commons^™

Analytical Modeling With Decoupled Optimal Control Of Biomechanical Sit -To -Stand Movement, Asif Mahmood Mughal

Theses and Dissertations

Biomechanical movements with multiple degrees of freedom exhibit complex coordination and control mechanisms in the presence of physiological constraints. A human body biomechanical model which can mimic diverse 3D physiological movements is a challenging task. In this study, we develop a mathematical framework to study human sit-to-stand (STS) movement using 2D biomechanical models. This analytical framework models the physiological system for feedback controller design. A 2D 4-segment biomechanical model with optimal feedback controller design provides a motivation to extend this scheme for analytical 3D bipedal modeling. We used a newly developed mathematical modeling toolbox (Maple’s DynaFlexPro) to generate 3D 8-segment …

Linear Tactile Nanodevice With Resolution On Par With Human Finger, Ravi F. Saraf, Vivek C. Maheshwari, Chieu Nguyen

Ravi Saraf Publications

A large area thin-film nanodevice made by self-assembly containing electroluminescent nanoparticles is reported. The ~100 nm thick device on application of potential across the top and bottom surface of the film converts local pressure to light. The intensity of the electroluminescent light is linearly proportional to the applied local compressive stress. By imaging the light, the stress distribution over the area of contact is obtained at resolution on par with human finger.

A Distributed Model Of Carbohydrate Transport And Metabolism In The Liver During Rest And High-Intensity Exercise, E Chalhoub, L. Xie, V. Balasubramanian, Joanne M. Belovich

Chemical & Biomedical Engineering Faculty Publications

A model of reaction and transport in the liver was developed that describes the metabolite concentration and reaction flux dynamics separately within the tissue and blood domains. The blood domain contains equations for convection, axial dispersion, and transport to the surrounding tissue; and the tissue domain consists of reactions representing key carbohydrate metabolic pathways. The model includes the metabolic heterogeneity of the liver by incorporating spatial variation of key enzymatic maximal activities. Simulation results of the overnight fasted, resting state agree closely with experimental values of overall glucose uptake and lactate output by the liver. The incorporation of zonation …

Selective Assembly Of Nanoparticles On Block Copolymer By Surface Modification, Sanjun Niu, Ravi F. Saraf

Ravi Saraf Publications

We have developed a method to selectively deposit nanoparticles on the ordered nanoscale elements of PS–PI–PS (polystyrene– polyisoprene–polystyrene) block copolymer film. The process utilizes reactive ion plasma to selectively modify the PS surface with amine groups to electrostatically attract negatively charged Au nanoparticles. In spite of the strong interparticle Coulombic repulsion, the deposition on PS domains is significantly high. It is observed that the deposition at the edges of the domain is particularly high, forming a percolating nanoparticle necklace. The latter may lead to interesting avenues to fabricate electronic devices.

High-Resolution Thin-Film Device To Sense Texture By Touch, Vivek C. Maheshwari, Ravi F. Saraf

Ravi Saraf Publications

Touch (or tactile) sensors are gaining renewed interest as the level of sophistication in the application of minimum invasive surgery and humanoid robots increases. The spatial resolution of current large-area (greater than 1 cm²) tactile sensor lags by more than an order of magnitude compared with the human finger. By using metal and semiconducting nanoparticles, a ~100-nm-thick, large-area thin-film device is self-assembled such that the change in current density through the film and the electroluminescent light intensity are linearly proportional to the local stress. A stress image is obtained by pressing a copper grid and a United States …

The Effect Of Physiological Cyclic Stretch On The Cell Morphology, Cell Orientation And Protein Expression Of Endothelial Cells, V. Barron, Claire Brougham, K. Coghlan, C. Stenson-Cox, D. O'Mahoney, P.E. Mchugh

Articles

In vivo, endothelial cells are constantly exposed to pulsatile shear and tensile stresses. The main aim of this study was to design and build a physiological simulator, which reproduced homogenous strain profiles of the tensile strain experienced in vivo, and to investigate the effect of this cyclic tensile strain on the cell morphology, cell orientation and protein expression of endothelial cells. The biological response of human umbilical vein endothelial cells to a uniaxial cyclic stretch, in this newly developed simulator, was examined experimentally using immunohistostaining and confocal imaging and it was

found that the cells elongated and oriented at 58.9± …

Intracellular Signaling Networks In The Immune Response: Pathways Activated By Interleukin-2 And-4 Receptors And Their Roles In T Cell Proliferation, Kristen K. Comfort

Chemical and Materials Engineering Faculty Publications

Cells sense and respond to chemical and physical stimuli through signal transduction pathways, which mediate cell proliferation, differentiation, migration, and survival. The cytokines interleukin-2 (IL-2) and interleukin-4 (IL-4) are key regulators of the adaptive immune system, particularly influencing the clonal expansion and differentiation of T cells. At least in culture, both synergistic and antagonistic effects of IL-2 and -4 co-stimulation have been reported; the antagonism, when observed, is thought to arise from the utilization of a common subunit shared by IL-2 and IL-4 receptors. We have sought to characterize IL-2 and IL-4 signaling at the level of intracellular pathways activated …

Self-Assembly Of Nanoparticles On Live Bacterium: An Avenue To Fabricate Electronic Devices, Vikas Berry, Ravi F. Saraf

Ravi Saraf Publications

Lysine-capped gold nanoparticles can be electrostatically assembled on the surface of Bacillus cerius, a Gram-Positive bacterium. The conductivity of the “gold-plated” bacteria assembly immobilized between electrodes is a function of the humidity experienced by the nanoparticles.

Mechano-Biological Interactions Of Endothelial Cells, Claire Brougham, Karen Coughlan, Valerie Barron, Peter Mchugh

Conference Papers

Atherosclerosis is an ever-increasing cause of morbidity in the western world. Current surgical treatments include bypass grafts and coronary artery stents. However, there is still a need for alternative approaches especially for those who cannot receive conventional therapy. Tissue engineering is one such approach that may hold the key to the repair and regeneration. Tissue engineering is one such approach that may hold the key to the repair and regeneration of coronary arteries. Nevertheless, many questions need to be answered before a vialbe vascular tissie with the inherent properties of native tissue becomes a real contender with the surgical therapies …

Orientation Of Self-Assembled Block Copolymer Cylinders Perpendicular To Electric Field In Mesoscale Film, S. Elhadj, J. W. Woody, V. S. Niu, Ravi F. Saraf

Ravi Saraf Publications

The possibility of using self-assembled films of block polymers as templates to fabricate nanoscale structures for devices has attracted great attention towards this class of material. Self-assembly of a block copolymer can be directed by using an electric field to orient features (i.e., ~10-nm-diam cylinders) parallel to the electric field, making the material more attractive as a nanoscale lithography mask. In this letter we describe an approach to influence the electric field orientation phenomena by interfacial effects. As a result, the 15-nm-diam polystyrene cylinders of the polystyrene–polyisoprene–polystyrene triblock copolymer orient perpendicular to the electric field. The described approach along with …

Spontaneous Planarization Of Nanoscale Phase Separated Thin Film, Ravi F. Saraf, Sanjun Niu, Eric Stumb

Ravi Saraf Publications

Structure of complex fluid at mesoscales is influenced by interfacial effects. We describe the dynamic response in such films to sudden change in interfacial tension. In a self-assembled block copolymer film, the monolayer of 15 nm diam cylindrical discrete phases close to the surface commence to sink at an average rate of 0.16 nm/day in response to the interfacial tension change. Surprisingly, this spontaneous planarization occurs, even though the cylinders are covalently stitched to the matrix. A simple model explains the observed behavior. The observation may lead to approaches to tailor the structure of mesoscale thin films of complex fluids …

An Approach To Sequence Dna Without Tagging, Sanjun Niu, Ravi F. Saraf

Ravi Saraf Publications

Microarray technology is playing an increasingly important role in biology and medicine and its application to genomics for gene expression analysis has already reached the market with a variety of commercially available instruments. In these combinatorial analysis methods, known probe single-strand DNA (ssDNA) “primers” are attached in clusters of typically 100 μm × 100 μm pixels. Each pixel of the array has a slightly different sequence. On exposure to “unknown” target ssDNA, the pixels with the right complementary probe ssDNA sequence convert to double-stranded DNA (dsDNA) by a hybridization reaction. To transduct the conversion of the pixel to dsDNA, the …

Energy Loss And Stiffness Properties Of Dynamic Elastic Response Prosthetic Feet, Mark Geil

Faculty Articles

No abstract provided.

Corrosion And Protection Of A Conductive Silver Paste, V. Brusic, G. S. Frankel, J. Roldan, Ravi F. Saraf

Ravi Saraf Publications

One of the possible uses for a conductive paste is as an adhesive in interconnect technology that could replace PbSn solder. The interconnections are expected to perform under a variety of environmental conditions, and with an applied voltage. Thus knowledge of their corrosion and dissolution resistance is of utmost importance. This is a study of the dissolution and protection of polymer/metal composite films, prepared with a high loading of silver or gold particles. Electrochemical tests were conducted in a droplet of triple-distilled water with or without benzotriazole (BTA) and BTA derivatives. Results indicate that, in spite of some protection obtained …

Laser Assisted Pd Seeding For Electroless Plating On Siq2, A. G. Schrott, B. Braren, Ravi F. Saraf

Ravi Saraf Publications

Excimer laser pulses with wavelengths of 248 and 308 nm were used to selectively seed Pd on SiO₂ surfaces, making them suitable for electroless plating. This novel seeding process for insulating materials is accomplished with the sample immersed in the seeding solution, and occurs only on the areas of the substrate that are illuminated (through the liquid) by the laser light. The Pd content of the seeded samples increased with the number of pulses, but was rather independent of repetition rate. The deposition rate showed a dependence with wavelength consistent with a defect driven mechanism for electron excitation through …

Simulated Crystalline Structures Of Aromatic Polyimides, Tze Wing Poon, B. David Silverman, Ravi F. Saraf, Angelo R. Rossi, Paul S. Ho

Ravi Saraf Publications

Semicrystalline structures involving molecular packing and optimized chain conformations of three polyimides have been obtained with the CHARMM moleculardynamics program, and their densities calculated. An eclipsed conformation of face-toface stacking of polymer chains with a relative shift is observed, and the shift is found to depend upon the molecular characteristics of the planar unit and chain linearity. Threedimensional structures obtained by calculating the optimized edge-on confirmation of the stacked units yield the smallest calculated density for PMDA-ODA, namely 1.515 g/cm³, followed by BPDA-PDA with 1.644 g/cm³ and PMDA-PDA with 1.712 g/cm³. Both PMDA-ODA and BPDA-PDA …

New In Vivo And In Vitro Techniques For Quantification Of Lateral Force Levels That Cause Implants To Fail : A Progress Report On Monkey Research, V. Leroy Leggitt

Loma Linda University Electronic Theses, Dissertations & Projects

Two new techniques for quantification of forces generated by an expansion screw apparatus placed between pairs of cylindrical endosseous titanium implants are described, along with preliminary data gained from their use in Macaca rhesus monkeys. Strain gages were bonded to the expansion apparatus and were calibrated either directly by micro load cell, or indirectly by Instron Machine to reflect the applied force.

Immediate loads of up to 6 kilograms have been applied to the implants with no increase in mobility as verified by a Periotest device. No previous studies on the orthodontic uses of implants have evaluated in vivo forces …

A Comparative Analysis Of Intrusion Of Incisor Teeth Achieved In Adults And Children According To Facial Type, Ronald L. Otto

Loma Linda University Electronic Theses, Dissertations & Projects

A comparison of incisor intrusion achieved in deep bite adults and children was made. Facial type was also examined for affect upon intrusion achieved. Fifty-five cases treated with Bioprogressive mechanics were studied cephalometrically, including twenty-four adults and thirty-one children. Neither age nor facial type was found to be statistically related to the amount of incisor intrusion achieved in this sample. A method of measuring intrusion at the root apices was devised which was felt to give a more accurate indication of actual bodily intrusion. More external root changes during treatment were observed for adults than for growing children. Wide latitude …

A Method Of Analyzing Mandibular Movement, Richard B. Mccoy

Loma Linda University Electronic Theses, Dissertations & Projects

Mandibular movement is considered to be a fundamental factor in the study, analysis, and treatment of occlusion. For many years, dentists have realized that dental health depends upon the compatibility of mandibular movements and occlusion. This realization has led to the development of new methods and techniques for recording accurately and scientifically the movements of the mandible. In order for this data to be of scientific value, it must be stored in a usable form which is easily available for analysis.

The purpose of this research project was to develop a procedure for storing and recalling mandibular-movement information. Before such …

A Procedure For The Measurement Of Glosso-Maxillary Forces, Howard L. Lilly Jr.

Loma Linda University Electronic Theses, Dissertations & Projects

The purpose of this investigation was to develop a clinically feasible procedure for recording the magnitudes of glosso-maxillary forces at four palatal loci using an electronic transducer system described by Lear et, al. (1965). Of particular interest was the development of a convenient and accurate calibration device for both intraoral and extraoral application. A further object of interest was the effect an acrylic carrier plate might introduce to the magnitude of force response. Finally whether or not any significant adaptation to the carrier plate or to the transducers occurs during a reasonable testing period (six to seven hours).

A calibration …

Milking Machine Efficiency And Shed Husbandry Practices, G R. Olney

Journal of the Department of Agriculture, Western Australia, Series 4

MILKING machine efficiency on dairy farms in the Bridgetown, Greenbushes, Balingup, Boyup Brook and Nannup areas was the subject of a recent testing survey.

During the survey 106 machines were tested and the results assessed statistically to gauge the general level of machine efficiency in these districts.