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Ting C.M.,Center for Biomedical Engineering
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2012

This paper applies an expectation-maximization (EM) based Kalman smoother (KS) approach for single-trial event-related potential (ERP) estimation. Existing studies assume a Markov diffusion process for the dynamics of ERP parameters which is recursively estimated by optimal filtering approaches such as Kalman filter (KF). However, these studies only consider estimation of ERP state parameters while the model parameters are pre-specified using manual tuning, which is time-consuming for practical usage besides giving suboptimal estimates. We extend the KF approach by adding EM based maximum likelihood estimation of the model parameters to obtain more accurate ERP estimates automatically. We also introduce different model variants by allowing flexibility in the covariance structure of model noises. Optimal model selection is performed based on Akaike Information Criterion (AIC). The method is applied to estimation of chirp-evoked auditory brainstem responses (ABRs) for detection of wave V critical for assessment of hearing loss. Results shows that use of more complex covariances are better estimating inter-trial variability. Source


News Article
Site: http://www.rdmag.com/rss-feeds/all/rss.xml/all

Imitation may be the sincerest form of flattery, but the best way to make something is often to co-opt the original process and make it work for you. In a sense, that’s how scientists at Brown Univ. accomplished a new advance in tissue engineering. In Biomaterials, the team reports culturing cells to make extracellular matrix (ECM) of two types and five different alignments with the strength found in natural tissue and without using any artificial chemicals that could make it incompatible to implant. ECM is the fibrous material between cells in tissues like skin, cartilage, or tendon that gives them their strength, stretchiness, squishiness and other mechanical properties. To help patients heal wounds and injuries, engineers and physicians have strived to make ECM in the lab that’s aligned, as well as it is when cells make it in the body. So far, though, they’ve struggled to recreate ECM. Using artificial materials provides strength, but those don’t interact well with the body. Attempts to extract and build upon natural ECM have yielded material that’s too weak to re-implant. The Brown team tried a different approach to making both collagen, which is strong, and elastin, which is stretchy, with different alignments of their fibers. They cultured ECM-making cells in specially designed molds that promoted the cells to make their own natural but precisely guided ECM. “What we hypothesized is that the cells are making it the same way they do in the body, because we’re starting them in a more natural environment,” said lead author Jacquelyn Schell, assistant professor (research) of molecular pharmacology, physiology and biotechnology. “We’re not adding exogenous materials.” The strategy built on the insight that when cells clump together and grow in culture, they pull on each other and communicate as they would in the body, Schell said. The molds therefore were made from agarose so that cells wouldn’t stick to the sides or bottom. Instead they huddled together. To guide ECM growth in particular alignments, the researchers used molds with very specific shapes, often constrained by pegs the cells had to grow around. For instance, to make a rod with collagen fibers aligned along its length (like a tendon) they cultured chondrocyte cells in a dog bone-shaped mold with loops on either end. To make a skin-like “trampoline” of elastin, where the ECM fibers run in all directions, they cultured fibroblast cells to grow in an open area suspended at the center of a honeycomb shape. “The placement of the pegs that this group of cells wraps itself around and then exerts force on each other is what dictates their alignment and the direction of the ECM they are going to synthesize,” said senior author Jeffrey Morgan, professor of medical science and engineering and co-director of Brown’s Center for Biomedical Engineering. “That’s a new ability to control the cells’ synthesis of extracellular matrix.” After the researchers grew various forms of ECM, they did some stress testing. They took the dog bone-shaped tissues to the lab of Christian Franck, assistant professor of engineering, and together made precise measurements of the tissue strength under the force of being pulled apart. The measurements confirmed the self-assembled tissue was about as strong as that found in some of the body’s tissues, such as skin, cartilage or blood vessels. The team’s next goal is to identify a prospective clinical application, Morgan said. The lab will pursue the needed testing to see if this new way of growing ECM can help future patients. The highly-anticipated educational tracks for the 2015 R&D 100 Awards & Technology Conference feature 28 sessions, plus keynote speakers Dean Kamen and Oak Ridge National Laboratory Director Thom Mason.  Learn more.


News Article
Site: http://www.biosciencetechnology.com/rss-feeds/all/rss.xml/all

Imitation may be the sincerest form of flattery but the best way to make something is often to co-opt the original process and make it work for you. In a sense, that’s how scientists at Brown University accomplished a new advance in tissue engineering. In the journal Biomaterials, the team reports culturing cells to make extracellular matrix (ECM) of two types and five different alignments with the strength found in natural tissue and without using any artificial chemicals that could make it incompatible to implant. ECM is the fibrous material between cells in tissues like skin, cartilage, or tendon that gives them their strength, stretchiness, squishiness, and other mechanical properties. To help patients heal wounds and injuries, engineers and physicians have strived to make ECM in the lab that’s aligned as well as it is when cells make it in the body. So far, though, they’ve struggled to recreate ECM. Using artificial materials provides strength, but those don’t interact well with the body. Attempts to extract and build upon natural ECM have yielded material that’s too weak to reimplant. The Brown team tried a different approach to making both collagen, which is strong, and elastin, which is stretchy, with different alignments of their fibers. They cultured ECM-making cells in specially designed molds that promoted the cells to make their own natural but precisely guided ECM. “What we hypothesized is that the cells are making it the same way they do in the body, because we’re starting them in a more natural environment,” said lead author Jacquelyn Schell, assistant professor (research) of molecular pharmacology, physiology and biotechnology. “We’re not adding exogenous materials.” The strategy built on the insight that when cells clump together and grow in culture, they pull on each other and communicate as they would in the body, Schell said. The molds therefore were made from agarose so that cells wouldn’t stick to the sides or bottom. Instead they huddled together. To guide ECM growth in particular alignments, the researchers used molds with very specific shapes, often constrained by pegs the cells had to grow around. For instance, to make a rod with collagen fibers aligned along its length (like a tendon) they cultured chondrocyte cells in a dog bone-shaped mold with loops on either end. To make a skin-like “trampoline” of elastin, where the ECM fibers run in all directions, they cultured fibroblast cells to grow in an open area suspended at the center of a honeycomb shape. “The placement of the pegs that this group of cells wraps itself around and then exerts force on each other is what dictates their alignment and the direction of the ECM they are going to synthesize,” said senior author Jeffrey Morgan, professor of medical science and engineering and co-director of Brown’s Center for Biomedical Engineering. “That’s a new ability to control the cells’ synthesis of extracellular matrix.” After the researchers grew various forms of ECM, they did some stress testing. They took the dog bone-shaped tissues to the lab of Christian Franck, assistant professor of engineering, and together made precise measurements of the tissue strength under the force of being pulled apart. The measurements confirmed the self-assembled tissue was about as strong as that found in some of the body’s tissues, such as skin, cartilage or blood vessels. The team’s next goal is to identify a prospective clinical application, Morgan said. The lab will pursue the needed testing to see if this new way of growing ECM can help future patients. The Department of Defense and the National Science Foundation funded the study.


News Article
Site: http://phys.org/biology-news/

In the journal Biomaterials, the team reports culturing cells to make extracellular matrix (ECM) of two types and five different alignments with the strength found in natural tissue and without using any artificial chemicals that could make it incompatible to implant. ECM is the fibrous material between cells in tissues like skin, cartilage, or tendon that gives them their strength, stretchiness, squishiness, and other mechanical properties. To help patients heal wounds and injuries, engineers and physicians have strived to make ECM in the lab that's aligned as well as it is when cells make it in the body. So far, though, they've struggled to recreate ECM. Using artificial materials provides strength, but those don't interact well with the body. Attempts to extract and build upon natural ECM have yielded material that's too weak to reimplant. The Brown team tried a different approach to making both collagen, which is strong, and elastin, which is stretchy, with different alignments of their fibers. They cultured ECM-making cells in specially designed molds that promoted the cells to make their own natural but precisely guided ECM. "What we hypothesized is that the cells are making it the same way they do in the body, because we're starting them in a more natural environment," said lead author Jacquelyn Schell, assistant professor (research) of molecular pharmacology, physiology and biotechnology. "We're not adding exogenous materials." The strategy built on the insight that when cells clump together and grow in culture, they pull on each other and communicate as they would in the body, Schell said. The molds therefore were made from agarose so that cells wouldn't stick to the sides or bottom. Instead they huddled together. To guide ECM growth in particular alignments, the researchers used molds with very specific shapes, often constrained by pegs the cells had to grow around. For instance, to make a rod with collagen fibers aligned along its length (like a tendon) they cultured chondrocyte cells in a dog bone-shaped mold with loops on either end. To make a skin-like "trampoline" of elastin, where the ECM fibers run in all directions, they cultured fibroblast cells to grow in an open area suspended at the center of a honeycomb shape. "The placement of the pegs that this group of cells wraps itself around and then exerts force on each other is what dictates their alignment and the direction of the ECM they are going to synthesize," said senior author Jeffrey Morgan, professor of medical science and engineering and co-director of Brown's Center for Biomedical Engineering. "That's a new ability to control the cells' synthesis of extracellular matrix." After the researchers grew various forms of ECM, they did some stress testing. They took the dog bone-shaped tissues to the lab of Christian Franck, assistant professor of engineering, and together made precise measurements of the tissue strength under the force of being pulled apart. The measurements confirmed the self-assembled tissue was about as strong as that found in some of the body's tissues, such as skin, cartilage or blood vessels. The team's next goal is to identify a prospective clinical application, Morgan said. The lab will pursue the needed testing to see if this new way of growing ECM can help future patients. Explore further: Development of 'matrix' material controlling differentiation of stem cells


Tang Y.,Center for Biomedical Engineering | Hill E.H.,Center for Biomedical Engineering | Zhou Z.,Center for Biomedical Engineering | Zhou Z.,University of New Mexico | And 3 more authors.
Langmuir | Year: 2011

Three series of cationic oligo p-phenyleneethynylenes (OPEs) have been synthesized to study their structure-property relationships and gain insights into the transition from molecular to macromolecular properties. The absorbance maxima and molar extinction coefficients in all three sets increase with increasing number of repeat units; however, the increase in Imax between the oligomers having 2 and 3 repeat units is very small, and the oligomer having 3 repeat units shows virtually the same spectra as a p-phenyleneethynylene polymer having 49 repeat units. A computational study of the oligomers using density functional theory calculations indicates that while the simplest oligomers (OPE-1) are fully conjugated, the larger oligomers are nonplanar and the limiting "segment chromophore" may be confined to a near-planar segment extending over three or four phenyl rings. Several of the OPEs self-assemble on anionic "scaffolds", with pronounced changes in absorption and fluorescence. Both experimental and computational results suggest that the planarization of discrete conjugated segments along the phenylene-ethynylene backbone is predominantly responsible for the photophysical characteristics of the assemblies formed from the larger oligomers. The striking differences in fluorescence between methanol and water are attributed to reversible nucleophilic attack of structured interfacial water on the excited singlet state. © 2011 American Chemical Society. Source

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