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On the fight between excitation and inhibition: location is everything.

Science's STKE : signal transduction knowledge environment 2004年第250期2004卷 PE44页

作者： Mel, Bartlett W Schiller, Jackie Department of Biomedical Engineering and Neuroscience Graduate Program University of Southern California Los Angeles 90089 CA United States

In the intact brain, neurons are constantly subjected to both excitatory and inhibitory inputs to their dendritic trees. Although it is accepted that the overall response of a neuron--its train of output spikes--depends on the balance of excitation and inhibition, we continue to lack specific knowledge of the rules that govern how excitatory and inhibitory inputs interact in space and time within the confines of individual neurons. In a recent paper, Liu starts by providing evidence that the relative locations and numbers of excitatory and inhibitory synapses are tightly regulated in cultured neurons from the hippocampus. This is consistent with findings in other labs that suggest neurons work hard, and in a variety of different ways, to maintain their inputs in proper balance and their outputs within appropriate ranges. On this backdrop, Liu's most important finding of a functional nature is that inhibition appears to act quite locally;that is, an inhibitory synapse effectively opposes an excitatory synapse only when it is very close by within the same dendritic branch (Fig. 1). This finding provides further support for the view--anticipated by neural theorists more than 20 years ago--that the brain's principal neurons contain a potentially large number of separate computational subunits.

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Multiple volume injection technique for high-resolution DNA sample detection utilizing planar microfluidic chip

Multiple volume injection technique for high-resolution DNA ...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： Lung-Ming Fu Che-Hsin Lin Guan-Liang Chang Graduate Institute of Materials Engineering National Pingtung University of Science and Technology Ping Tung Taiwan Department of Mechanical and Electro-Mechanical Engineering National Sun Yat-Sen University Kaohsiung Taiwan Institute of Biomedical Engineering National Cheng Kung University Tainan Taiwan

ISBN: (纸本)0780384393

This paper presents an experimental and numerical investigation into the use of high-resolution injection techniques to separate DNA fragments within electrophoresis microchips. The study addresses the principal material transport mechanisms such as electrokinetic migration, fluid flow, diffusion, variable-volume injection methods, and gives detail analyses to the double-L injection technique, which employs electrokinetic manipulations to avoid sample leakage within the microchip. We also study the sample leakage effect during sample injection and separation. The standard DNA ladder and the /spl phi/-174 DNA fragments are used to test the performance for this proposed method. Results show that this unique injection system in the current microfluidic chip presented within this paper is capable of simulating the functions of the cross, double-T form through appropriate manipulations of the electric field within its various channels. The proposed double-L injection method confirms its ability to reduce sample leakage effect during operation. The integrated microfluidic chip and double-L injection technique developed in this study has an exciting potential for use in high-quality, high-throughput chemical analysis applications and in many other applications throughout the field of micro-total-analysis systems.

关键词： DNA Microfluidics Fluorescence Electrokinetics biomedical engineering Solvents Microchannel Microscopy Voltage Plugs

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The application of advanced computational methods to the modeling of pbmr source terms

The application of advanced computational methods to the mod...

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12th International Conference on Nuclear engineering (ICONE12) - 2004

作者： Mkhosi, Margaret Msongi Denning, Richard Nakamura, Schoichiro Ohio State University Nucl. Eng. Graduate Studies Program 105 Building 1 650 Ackerman Road Columbus OH 43202 United States Ohio State University Nucl. Eng. Graduate Studies Program 105C Building 1 650 Ackerman Road Columbus OH 43202 United States Ohio State University Department of Mechanical Engineering 230 Building 1 650 Ackerman Road Columbus OH 43202 United States

Various computational methods, which were applied to the modeling of pebble bed modular reactor (PBMR) source terms, were discussed. The results of analysis performed at different velocities and fluid densities in the turbulent regime were correlated against a modified stokes number. Deposition for the time-averaged flow was found to be insensitive to the flow model. Eddy-enhanced deposition results in greater deposition at all aerosol sizes in comparison with the time-averaged results with significant deposition of aerosols were also predicted for small aerosol sizes.

关键词： Nuclear reactors

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Novel bone graft model using bead-cell sheets composed of tricalcium phosphate beads and bone marrow cells

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Materials Science and engineering: C 2004年第6-8期24卷 875-879页

作者： Shunsuke Miyauchi Katsuko S. Furukawa Yoshikazu Umezu Yasuyuki Ozeki Takashi Ushida Tetsuya Tateishi Biomedical Engineering Laboratory Department of Mechanical Engineering Graduate School of Engineering University of Tokyo 503 8th Building 7-3-1 Hongo Bunkyo Tokyo 113-8656 Japan Advance Co. Saitama Japan Division of Biomedical Materials and Systems Center for Disease Biology and Integrative Medicine School of Medicine The University of Tokyo Japan Biomaterials Center National Institute for Materials Science Ibaraki Japan

Cells on scaffold implanted in vivo need nutrient and oxygen carried on the blood stream. In this respect, many scaffolds consisting of porous ceramics cannot hold cells alive in the center of them. Therefore, osteogenesis and substitution of regenerated bone occur from the surface of graft, and the biodegradation speed is slow. To solve this problem of lack of blood stream, we developed a new bone graft sheet composed of human bone marrow stromal cells (HMSCs), and beta-tricalcium phosphate (beta-TCP) porous beads. In addition, by combining multilayered bead-cell sheets and collagen gel, we fabricated a bone graft having the space for entry of blood vessels, and implanted them subcutaneously in mice. After 3 weeks, blood vessels reaching to the focal area of graft were recognized, and near the surface of graft, osteogenesis was also observed. In conclusion, the bead-cell sheet would have good osteoconductivity, and the graft made of bead-cell sheets showed a new design concept of bone graft preparing the space for neovascularization.

关键词： Bone tissue engineering Sheet Bead Bone marrow cell

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Real time monitoring of endothelial cell actin filament disruption by cytochalasin D using a cellular impedance biosensor

Real time monitoring of endothelial cell actin filament disr...

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Computer Architectures for Machine Perception (CAMP)

作者： V. Nandakumar A.E. English A.B. Moy M. Mahfouz R. Ward K. Kruse S. Kirkpatrick M.H. Goldman Department of Mechanical AeroSpace and Biomedical Engineering University of Tennessee Knoxville TN USA Department of Internal Medicine University of Iowa Iowa IA USA Computational Physics and Engineering Division Oak Ridge National Laboratory Oak Ridge TN USA University of Tennessee Graduate School of Medicine Knoxville TN USA

Using a novel cellular impedance biosensor and confocal microscopy, this study has examined the dynamic and steady state cellular impedance response of porcine pulmonary endothelial cells to varying doses of cytochalasin D. Endothelial cell monolayer impedances were obtained using an array of gold microelectrodes coated with fibronectin to facilitate endothelial cell adhesion. Impedance measurements were acquired at 5.6 kHz by phase sensitive detection from a lock-in amplifier. The electrically measured cytochalasin D dose dependant actin disruption was successfully correlated with actin stained confocal microscopy images quantified using image-processing techniques. Based on this study, the cellular kinetic response to cytochalasin D increased systematically with the dose and saturated at a critical concentration. The real time quantification of pharmacological agents that target specific elements of the cytoskeleton using electrical impedance measurements therefore has a number of important applications in understanding the dynamic and steady state response of endothelial cells to toxins and drug induced cellular cytoskeletal micromechanics

关键词： Monitoring Biosensors Microscopy Steady-state Impedance measurement Gold Microelectrodes Adhesives Phase detection Amplifiers

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Implementation of new services to support ubiquitous computing for campus life

Implementation of new services to support ubiquitous computi...

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IEEE Workshop on Software Technologies for Future Embedded Systems

作者： Tack-Don Han Cheolho Cheong Jae-Won Ann Jong-Young Kim Hyung-Min Yoon Chang-Su Lee Hyon-Gu Shin Young-Jin Lee Hyoung-Min Yook Myoung-Hoon Jeon Jung Soo Choi Joo-Hyeon Lee Young-Woo Sohn Yoon Su Baek Sang-Yong Lee Eun-Dong Shin WooShik Kang SeongWoon Kim Department of Computer Science Yonsei University Seoul South Korea Dept. of Computer Science Yonsei University Seodaemun-gu Seoul KR Dept. of Comput. Sci. Yonsei Univ. South Korea Department of Clothing & Textiles Yonsei University Seoul South Korea Dept. of Clothing & Textiles Graduate Program in Cognitive Science Yonsei University Seoul South Korea Graduate Program in Cognitive Science Department of Mechanical Engineering Yonsei University Seoul South Korea Dept. of Mechanical Engineering Department of Psychology Yonsei University Seoul South Korea Dept. of Psychology ColorZip Media Inc. Seoul South Korea Yonsei University ColorZip Media Inc. Samsung Advanced Institute of Technology Seoul South Korea

ISBN: (纸本)0769521231

Many new services have emerged to realize ubiquitous computing environments, owing to the increasing supply of mobile devices and more widespread Internet and wireless network facilities. We introduce the U-Campus (ubiquitous computing for campus) service. This study has been conducted through interdisciplinary research by four participating departments. The U-campus project is part of the UTOPIA project (Ubiquitous computing TOwn Project: Intelligent context Awareness), which covers town- and city-wide environments. Currently, a test bed for U-campus has been constructed to support various services suck as U-profile, U-messaging and U-campus tour guide services. Students, professors, school staffs, and campus visitors can easily access the various available campus services by using image-based sensors and mobile devices such as CDMA cellular phones or WiFi smart phones. The major purpose of this research is to provide a context-aware U-campus environment to users by utilizing sensors and mobile devices currently available in the public sector and the marketplace.

关键词： Ubiquitous computing Intelligent sensors Mobile computing IP networks Web and internet services Wireless networks Context awareness Testing Educational institutions Image sensors

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The in-class use of assessment and rubrics by student groups to improve presentation performance in biomedical engineering

The in-class use of assessment and rubrics by student groups...

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2003 ASEE Annual Conference and Exposition: Staying in Tune with engineering Education

作者： Wasserman, Jack Schmidt, Monica Jendrucko, Richard University of Tennessee Knoxville Biomed. Engineering Degree Program Department of Mechanical Engineering Biomedical Engineering Program

After many years of teaching, the shift of perspective to student learning has provided the most satisfying results. The student performance has exceeded all expectations based on past courses. In addition, it is now much easier to evaluate student progress in areas that do not require a specific numerical answer. The student response has been very positive as demonstrated by a 50% improvement in attendance. The objectives of improved communication, problem solving, and team skills in addition to a background in BME applications have been successfully demonstrated with projects, papers, and presentations. This approach has provided additional benefits for the supervision of graduate students and for research planning. Although initially challenging, the benefits to cost ratio is so high that it is planned for incorporation in all courses in the curriculum.

关键词： engineering education

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Effects of Surface Roughness and Maximum Load on the mechanical Properties of Cancellous Bone Measured by Nanoindentation

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MRS Online Proceedings Library 2004年第1期823卷 W8.5.1-W8.5.6页

作者： Donnelly, Eve Baker, Shefford P. Boskey, Adele L. van der Meulen, Marjolein C. H. Sibley School of Mechanical and Aerospace Engineering Cornell University Ithaca USA Department of Materials Science and Engineering Cornell University Ithaca USA Musculoskeletal Integrity Program Hospital for Special Surgery New York USA Department of Biochemistry Weill Medical College of Cornell University New York USA Graduate Program in Physiology Biophysics and Systems Biology Weill Medical College of Cornell University New York USA

Nanoindentation was used to assess the mechanical properties of lamellar and interlamellar tissue in dehydrated rabbit cancellous bone. The effects of surface roughness and maximum nanoindentation load on the measured mechanical properties were examined in two samples of differing surface roughness using maximum loads ranging from 250-3000 μN. As the ratio of indentation depth to surface roughness decreased below approximately 3:1, the variability in material properties increased substantially. At low loads, the indentation modulus of the lamellar bone was approximately 20% greater than that of the interlamellar bone, while at high loads the measured properties of both layers converged to an intermediate value. Relatively shallow indentations made on smooth surfaces revealed significant differences in the properties of lamellar and interlamellar bone that are consistent with microstructural observations of lamellar bone as more mineralized than interlamellar bone.

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The use of asynchronous Web modules for review and just-in-time learning of mechanics

The use of asynchronous Web modules for review and just-in-t...

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2003 ASEE Annual Conference and Exposition: Staying in Tune with engineering Education

作者： Wasserman, Jack Bennett, Richard Boulet, Toby Iannelli, Joe Jendrucko, Richard Lumsdaine, Arnold Logsdon, Doug University of Tennessee Knoxville Department of Mechanical Engineering Department of Civil Engineering Freshman Engage Program College of Engineering Department of Biomedical Engineering

The development of asynchronous web modules for learning and understanding mechanics, is discussed. The modules covers special topics in Statics, Particle Dynamics, Rigid Body Dynamics and Strength of Materials. Each module contains a set of learning object (LO), based on the survey of the departmental faculty. The combination of learning styles and maturity results in a wide diversity of fundamental understanding in upper division students.

关键词： Learning systems

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Computed synovial fluid flow in a simple knee joint model

Computed synovial fluid flow in a simple knee joint model

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4th ASME/JSME Joint Fluids engineering Conference

作者： Pekkan, Kerem Nalim, Razi Yokota, Hiroki Mechanical Engineering Department Purdue Sch. of Eng. and Technology Indiana University-Purdue University Indianapolis United States Biomedical Engineering Program Purdue Sch. of Eng. and Technology Indiana University-Purdue University Indianapolis United States Cardiovasc. Fluid Mech. Laboratory Department of Biomedical Engineering Georgia Institute of Technology Atlanta United States

ISBN: (纸本)0791836967

Prediction of shear stress induced by the fluid flow on knee joint cells is the main aim of this study. Oscillatory flow of a Newtonian synovial fluid is examined in two-dimensional joint geometries. The experimental model is a fluid driven shear loader test rig, which features a finite plate oscillating at 1Hz, that is 1mm over a stationary cell culture surface. Oscillating Couette flow in the thin gap is generated by the finite span plate. An incompressible two-dimensional transient and laminar CFD model is developed using the STAR-CD® code. The infinite oscillating plate Couette flow solutions (Stoke's Second Problem with a finite gap) are reviewed and used in the grid sensitivity and validation tests of the computational finite oscillating plate model. The resulting flow features and vorticity convection are discussed and shear stress induced on the stationary plate due to an oscillating finite plate is compared with its infinite counterpart. As an extension, the effect of articular cartilage curvature is studied in a topologically equivalent model with and without menisci.

关键词： Flow of fluids

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