Browsing by Author "Chang, H. M."

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A semi-automatic method for neuron centerline extraction in confocal microscopic image stack
(2008)
Lee, Ping-Chang
;
Ching, Yu-Tai
;
Chang, H. M.
;
Chiang, Ann-Shyn
;
資訊工程學系
An algorithm for extracting the centerlines of neurons from 3-D image stack collected from a laser scanning confocal microscope is presented. Recovery of neuronal structure from image stack is critical for quantitative analysis of neuron-morphology. Many methods have been proposed to extract the centerline from the tubular structure in medical images, such as vessels. But the same methods do not work well in processing of neurons. One of the reasons is that the physical limitations of the spatial resolution of the image stack collect by confocal microscopy in the z-direction is much worse than the resolution in x and y directions. In our studied cases the mean voxel size of the image stack is 0.17 x 0.17 x 1.0 mu m(3) i.e., the resolution in z-direction cannot reflect the fact that the neuron has a tubular structure. In this paper, we propose an almost automatic neuron-tracing algorithm for a set of confocal microscopic images of neuron. The method is designed based on finding a minimal path in the volume to extract the centerlines of a neuron.
Computation of brain neurodegeneration in the Alzheimer's fly
(2006-01-01)
Lee, P. C.
;
Huang, Y. R.
;
Chang, H. M.
;
Chiang, A. S.
;
Ching, Y. T.
Expression of human A beta 42 peptide in the Drosophila brain induces pathological phenotypes resembling Alzheimer's disease (PNAS 101, 6623-6628). Three-dimensional confocal imaging reveals extensive vacuoles caused by neurodegeneration in the brain of aged but not young A beta 42 flies. Here, we report a three-dimensional computation algorisin allowing semi-automatic measurement of numbers and volumes of brain vacuoles. The method employed matched filters, alpha-shape, and the active-contour techniques. Using this method, a good result depicting the contours of the vacuoles can be obtained. A more accurate algorithm is still under development. Accurate evaluation of brain pathology in Alzheimer's flies may facilitate the understanding of molecular mechanisms underlying A beta. toxicity and the discovery of novel therapeutic targets for Alzheimer's disease.
Computation of brain neurodegeneration in the Alzheimer's fly - art. no. 61433E
(2006)
Lee, P. C.
;
Huang, Y. R.
;
Chang, H. M.
;
Chiang, A. S.
;
Ching, Y. T.
Expression of human A beta 42 peptide in the Drosophila brain induces pathological phenotypes resembling Alzheimer's disease (PNAS 101, 6623-6628). Three-dimensional confocal imaging reveals extensive vacuoles caused by neurodegeneration in the brain of aged but not young A beta 42 flies. Here, we report a three-dimensional computation algorisin allowing semi-automatic measurement of numbers and volumes of brain vacuoles. The method employed matched filters, alpha-shape, and the active-contour techniques. Using this method, a good result depicting the contours of the vacuoles can be obtained. A more accurate algorithm is still under development. Accurate evaluation of brain pathology in Alzheimer's flies may facilitate the understanding of molecular mechanisms underlying A beta. toxicity and the discovery of novel therapeutic targets for Alzheimer's disease.
Electrical measurements on iridium dioxide nanorods
(2006)
Lin, Y. H.
;
Lee, T. C.
;
Lin, J. J.
;
Chang, H. M.
;
Huang, Y. S.
Iridium dioxide (IrO2) nanorods have been prepared by metal-organic chemical vapor deposition method. Applying the standard electron-beam lithography technique, a single nanorod with a diameter of I 10 nm is contacted by three Cr/Au fingers from above. The resistance measurements on this nanorod have been performed between 10 and 300 K, using different probe configurations. We observe that the resistivity rho of the nanorod has a value <= 120 mu Omega cm at 300 K. On the other hand, the temperature dependence of the contact resistance R obeys the law logR proportional to T-1/2 below 100 K. The conduction process through the contact is ascribed to the transport of electrons via hopping in granular metals accidentally formed at the contact region.
Electrical transport studies of individual IrO(2) nanorods and their nanorod contacts
(2008-01-30)
Lin, Y. H.
;
Sun, Y. C.
;
Jian, W. B.
;
Chang, H. M.
;
Huang, Y. S.
We have studied the electrical transport properties of individual single-crystalline IrO(2) nanorods prepared by the metal-organic chemical vapour deposition method. With the help of the standard electron-beam lithographic technique, individual nanorods are contacted by Cr/Au submicron electrodes from above. Utilizing two-probe, three-probe and four-probe measurement configurations, not only the intrinsic electrical transport properties of the individual nanorods but also the electronic contact resistances, Rc(T), have been determined from 300 K down to liquid-helium temperatures. Our measured resistivity behaviour of the nanorods is in close agreement with the current theoretical understanding of this rutile material. On the other hand, we found that the temperature behaviour of the electronic contact resistance obeys the law log R(C) alpha T(-1/2) over an extremely wide temperature range, from approximately 100 K down to liquid-helium temperatures. This latter conduction process is ascribed to the hopping of electrons through nanoscale Cr granules and/or an amorphous coating incidentally formed at the interface between the submicron Cr/Au electrode and the nanorod.
Electrical transport studies of individual IrO2 nanorods and their nanorod contacts
(2008-01-30)
Lin, Y. H.
;
Sun, Y. C.
;
Jian, W. B.
;
Chang, H. M.
;
Huang, Y. S.
We have studied the electrical transport properties of individual single-crystalline IrO2 nanorods prepared by the metal-organic chemical vapour deposition method. With the help of the standard electron-beam lithographic technique, individual nanorods are contacted by Cr/Au submicron electrodes from above. Utilizing two-probe, three-probe and four-probe measurement configurations, not only the intrinsic electrical transport properties of the individual nanorods but also the electronic contact resistances, Rc(T), have been determined from 300 K down to liquid-helium temperatures. Our measured resistivity behaviour of the nanorods is in close agreement with the current theoretical understanding of this rutile material. On the other hand, we found that the temperature behaviour of the electronic contact resistance obeys the law log R-C alpha T-1/2 over an extremely wide temperature range, from approximately 100 K down to liquid-helium temperatures. This latter conduction process is ascribed to the hopping of electrons through nanoscale Cr granules and/or an amorphous coating incidentally formed at the interface between the submicron Cr/Au electrode and the nanorod.
The Reliability Study and Device Modeling for p-HEMT Microwave Power Transistors
(2011)
Liu, S. L.
;
Chang, H. M.
;
Chang, T.
;
Kao, H. L.
;
Cheng, C. H.
In this paper, the commercial 0.5-mu m AlGaAs/InGaAs/GaAs pseudo-morphic high electron mobility transistors were subjected to both high-drain voltage and high-temperature stresses for investigating reliability issues. The results reveal that the stress-induced trapping phenomena near two-dimensional electron gas layer should be responsible for the different drain current collapses. The decay level of the DC and the small-signal characteristics increases with the stress voltage and/or the operation temperature. The self-consistent model was established through the de-embedded and the non-linear fitting processes, which can be used to estimate the DC and RF small-signal characteristics degradation under high-drain voltage and high-temperature stress.