Browsing by Author "Chen, Hui-Fen"

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Design, simulation and experimental validation of a novel flexible neural probe for deep brain stimulation and multichannel recording
(2012-06-01)
Lai, Hsin-Yi
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Liao, Lun-De
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Lin, Chin-Teng
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Hsu, Jui-Hsiang
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He, Xin
An implantable micromachined neural probe with multichannel electrode arrays for both neural signal recording and electrical stimulation was designed, simulated and experimentally validated for deep brain stimulation (DBS) applications. The developed probe has a rough three-dimensional microstructure on the electrode surface to maximize the electrode-tissue contact area. The flexible, polyimide-based microelectrode arrays were each composed of a long shaft (14.9 mm in length) and 16 electrodes (5 mu m thick and with a diameter of 16 mu m). The ability of these arrays to record and stimulate specific areas in a rat brain was evaluated. Moreover, we have developed a finite element model (FEM) applied to an electric field to evaluate the volume of tissue activated (VTA) by DBS as a function of the stimulation parameters. The signal-to-noise ratio ranged from 4.4 to 5 over a 50 day recording period, indicating that the laboratory-designed neural probe is reliable and may be used successfully for long-term recordings. The somatosensory evoked potential (SSEP) obtained by thalamic stimulations and in vivo electrode-electrolyte interface impedance measurements was stable for 50 days and demonstrated that the neural probe is feasible for long-term stimulation. A strongly linear (positive correlation) relationship was observed among the simulated VTA, the absolute value of the SSEP during the 200 ms post-stimulus period (Sigma SSEP) and c-Fos expression, indicating that the simulated VTA has perfect sensitivity to predict the evoked responses (c-Fos expression). This laboratory-designed neural probe and its FEM simulation represent a simple, functionally effective technique for studying DBS and neural recordings in animal models.
Direct infrared observation of hydrogen chloride anions in solid argon
(2017-09-21)
Huang, Tzu-Ping
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Chen, Hui-Fen
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Liu, Meng-Chen
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Chin, Chih-Hao
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Durrant, Marcus C.
To facilitate direct spectroscopic observation of hydrogen chloride anions (HCl-), electron bombardment of CH3Cl diluted in excess Ar during matrix deposition was used to generate this anion. Subsequent characterization were performed by IR spectroscopy and quantum chemical calculations. Moreover the band intensity of HCl fi decays slowly when the matrix sample is maintained in the dark for a prolonged time. High-level ab inito calculation suggested that HCl fi is only weakly bound. Atom-in-molecule charge analysis indicated that both atoms of HCl fi are negatively charged and the Cl atom is hypervalent. Published by AIP Publishing.
Distribution of internal states of CO from O (D-1) + CO determined with time-resolved Fourier transform spectroscopy
(2006-11-09)
Chen, Hui-Fen
;
Lee, Yuan-Pern
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應用化學系
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應用化學系分子科學碩博班
;
Department of Applied Chemistry
Following collisions of O (D-1) with CO, rotationally resolved emission spectra of CO (1 e V e 6) in the spectral region 1800-2350 cm(-1) were detected with a step-scan Fourier transform spectrometer. O (D-1) was produced by photolysis of O-3 with light from a KrF excimer laser at 248 nm. Upon irradiation of a flowing mixture of O-3 (0.016 Torr) and CO (0.058 Torr), emission of CO (v <= 6) increases with time, reaches a maximum similar to 10 mu s. At the earliest applicable period (2-3 mu s), the rotational distribution of CO is not Boltzmann; it may be approximately described with a bimodal distribution corresponding to temperatures similar to 8000 and similar to 500 K, with the proportion of these two components varying with the vibrational level. A short extrapolation from data in the period 2-6 As leads to a nascent rotational temperature of similar to 10170 +/- 600 K for v = 1 and similar to 1400 +/- 40 K for v = 6, with an average rotational energy of 33 (6 kJ mol(-1). Absorption by CO (v = 0) in the system interfered with population of low J levels of CO (V) 1). The observed vibrational distribution of (v = 2):(v = 3):(v = 4):(v = 5):(v = 6) = 1.00: 0.64: 0.51: 0.32: 0.16 corresponds to a vibrational temperature of 6850 +/- 750 K. An average vibrational energy of 40 (4 kJ mol(-1) is derived based on the observed population of CO (2 e V e 6) and estimates of the population of CO (V) 0, 1, and 7) by extrapolation. The observed rotational distributions of CO (1 <= v <= 3) are consistent with results of previous experiments and trajectory calculations; data for CO (4 <= v <= 6) are new.
Distribution of Vibrational States of CO(2) in the Reaction O((1)D) + CO(2) from Time-Resolved Fourier Transform Infrared Emission Spectra
(2009-04-16)
Chen, Hui-Fen
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Chiang, Hung-Chu
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Matsui, Hiroyuki
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Tsuchiya, Soji
;
Lee, Yuan-Pern
A mixture Of O(3) and CO(2) was irradiated with light from a KrF laser at 248 nm; time-resolved infrared emission Of CO(2) in the region 2000-2400 cm(-1) was observed with a Fourier transform spectrometer. This emission involves one quantum in the asymmetric stretching mode (nu(3)) Of CO(2) in highly vibrationally excited states. The band contour agrees satisfactorily with a band shape calculated based on a simplified polyad model of CO(2) and a vibrational distribution estimated through a statistical partitioning of energy of similar to 13 000 cm(-1), similar to 3100 cm(-1) smaller than the available energy, into the vibrational modes Of CO(2). From this model, approximately 44% and 5% of the available energy of O((1)D) + CO(2) is converted into the vibrational and rotational energy of product CO(2), respectively, consistent with previous reports of similar to 50% for the translational energy. An extent of rotational excitation Of CO(2) much smaller than that expected from statistical calculations indicates a mechanism that causes a small torque to be given to CO(2) when an O atom leaves the complex CO(3) on the triplet exit surface of potential energy, consistent with quantum-chemical calculations.
Distribution of Vibrational States of CO2 in the Reaction O(D-1) + CO2 from Time-Resolved Fourier Transform Infrared Emission Spectra
(2009-04-16)
Chen, Hui-Fen
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Chiang, Hung-Chu
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Matsui, Hiroyuki
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Tsuchiya, Soji
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Lee, Yuan-Pern
A mixture Of O-3 and CO2 was irradiated with light from a KrF laser at 248 nm; time-resolved infrared emission Of CO2 in the region 2000-2400 cm(-1) was observed with a Fourier transform spectrometer. This emission involves one quantum in the asymmetric stretching mode (nu(3)) Of CO2 in highly vibrationally excited states. The band contour agrees satisfactorily with a band shape calculated based on a simplified polyad model of CO2 and a vibrational distribution estimated through a statistical partitioning of energy of similar to 13 000 cm(-1), similar to 3100 cm(-1) smaller than the available energy, into the vibrational modes Of CO2. From this model, approximately 44% and 5% of the available energy of O(D-1) + CO2 is converted into the vibrational and rotational energy of product CO2, respectively, consistent with previous reports of similar to 50% for the translational energy. An extent of rotational excitation Of CO2 much smaller than that expected from statistical calculations indicates a mechanism that causes a small torque to be given to CO2 when an O atom leaves the complex CO3 on the triplet exit surface of potential energy, consistent with quantum-chemical calculations.
Dynamics of reactions O((1)D)+C(6)H(6) and C(6)D(6)
(2008-11-07)
Chen, Hui-Fen
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Liang, Chi-Wei
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Lin, Jim J.
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Lee, Yuan-Pern
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Ogilvie, J. F.
The reaction between O((1)D) and C(6)H(6) (or C(6)D(6)) was investigated with crossed-molecular-beam reactive scattering and time-resolved Fourier-transform infrared spectroscopy. From the crossed-molecular-beam experiments, four product channels were identified. The major channel is the formation of three fragments CO+C(5)H(5)+H; the channels for formation of C(5)H(6)+CO and C(6)H(5)O+H from O((1)D)+C(6)H(6) and OD+C(6)D(5) from O((1)D)+C(6)D(6) are minor. The angular distributions for the formation of CO and H indicate a mechanism involving a long-lived collision complex. Rotationally resolved infrared emission spectra of CO (1 <=upsilon <= 6) and OH (1 <=upsilon <= 3) were recorded with a step-scan Fourier-transform spectrometer. At the earliest applicable period (0-5 mu s), CO shows a rotational distribution corresponding to a temperature of similar to 1480 K for upsilon=1 and 920-700 K for upsilon=2-6, indicating possible involvement of two reaction channels; the vibrational distribution of CO corresponds to a temperature of similar to 5800 K. OH shows a rotational distribution corresponding to a temperature of similar to 650 K for upsilon=1-3 and a vibrational temperature of similar to 4830 K. The branching ratio of [CO]/[OH]=2.1 +/- 0.4 for O((1)D)+C(6)H(6) and [CO]/[OD]>2.9 for O((1)D)+C(6)D(6) is consistent with the expectation for an abstraction reaction. The mechanism of the reaction may be understood from considering the energetics of the intermediate species and transition states calculated at the G2M(CC5) level of theory for the O((1)D)+C(6)H(6) reaction. The experimentally observed branching ratios and deuterium isotope effect are consistent with those predicted from calculations.
FORMATION AND IDENTIFICATION OF INTERSTELLAR MOLECULE LINEAR C(5)H FROM PHOTOLYSIS OF METHANE DISPERSED IN SOLID NEON
(2009-08-10)
Wu, Yu-Jong
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Chen, Hui-Fen
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Camacho, Cristopher
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Witek, Henryk A.
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Hsu, Sheng-Chuan
Photolysis of methane dispersed (1/1000) in solid Ne at 3 K with vacuum-ultraviolet light from a synchrotron produced infrared absorption lines of several products, including new lines at 3319.3 and 1955.5 cm(-1). Based on experiments with isotopic labeling and results of quantum-chemical calculations, these lines are assigned to the C-H stretching and C=C stretching modes, respectively, of interstellar molecule linear C(5)H radicals.
FORMATION AND IDENTIFICATION OF INTERSTELLAR MOLECULE LINEAR C5H FROM PHOTOLYSIS OF METHANE DISPERSED IN SOLID NEON
(2009-08-10)
Wu, Yu-Jong
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Chen, Hui-Fen
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Camacho, Cristopher
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Witek, Henryk A.
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Hsu, Sheng-Chuan
Photolysis of methane dispersed (1/1000) in solid Ne at 3 K with vacuum-ultraviolet light from a synchrotron produced infrared absorption lines of several products, including new lines at 3319.3 and 1955.5 cm(-1). Based on experiments with isotopic labeling and results of quantum-chemical calculations, these lines are assigned to the C-H stretching and C=C stretching modes, respectively, of interstellar molecule linear C5H radicals.
Identification of a Simplest Hypervalent Hydrogen Fluoride Anion in Solid Argon
(2017-06-07)
Liu, Meng-Chen
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Chen, Hui-Fen
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Chin, Chih-Hao
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Huang, Tzu-Ping
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Chen, Yu-Jung
Hypervalent molecules are one of the exceptions to the octet rule. Bonding in most hypervalent molecules is well rationalized by the Rundle-Pimentel model (three-center four-electron bond), and high ionic bonding between the ligands and the central atom is essential for stabilizing hypervalent molecules. Here, we produced one of the simplest hypervalent anions, HF-, which is known to deviate from the Rundle-Pimentel model, and identified its ro-vibrational features. High-level ab inito calculations reveal that its bond dissociation energy is comparable to that of dihalides, as supported by secondary photolysis experiments with irradiation at various wavelengths. The charge distribution analysis suggested that the F atom of HF-is negative and hypervalent and the bonding is more covalent than ionic.
Infrared absorption spectra of vinyl radicals isolated in solid Ne
(2008-05-28)
Wu, Yu-Jong
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Lin, Meng-Yeh
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Cheng, Bing-Ming
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Chen, Hui-Fen
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Lee, Yuan-Pern
Irradiation of samples of solid Ne near 3.0 K containing ethene (C(2)H(4)) with vacuum ultraviolet radiation at 120 nm from synchrotron yielded new spectral lines at 3141.0, 2953.6, 2911.5, 1357.4, 677.1, 895.3, and 857.0 cm(-1). These features are assigned to alpha-CH stretching (nu(1)), CH(2) antisymmetric stretching (nu(2)), CH(2) symmetric stretching (nu(3)), CH(2)-bending (nu(5)), HCCH cis bending (nu(7)), CH(2) out-of-plane bending (nu(8)), and alpha-CH out-of-plane bending (nu(9)) modes of C(2)H(3), respectively, based on results of (13)C- and D-isotopic experiments and quantum-chemical calculations. These calculations using density-functional theory (B3LYP and PW91PW91/aug-cc-pVTZ) predict vibrational wavenumbers, IR intensities, and isotopic ratios of vinyl radical that agree satisfactorily with our experimental results. (C) 2008 American Institute of Physics.
Photochemistry and infrared spectrum of single-bridged diborane(5) anion isolated in solid argon
(2016-08-21)
Liu, Meng-Chen
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Chen, Hui-Fen
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Huang, Wei-Jie
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Chin, Chih-Hao
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Chen, Sian-Cong
Three-center two-electron bonds are important for understanding electron-deficient molecules. To examine such a molecule, we produced a diborane(5) anion with a single-bridged structure upon electron bombardment during matrix deposition of Ar containing a small proportion of diborane(6). The diborane(5) anion was destroyed upon photolysis at 180, 220, 385, and 450 nm, but not at 532 nm. Moreover, the possible formation of neutral diborane(5) was observed upon photolysis at 385 and 450 nm, whereas neutral diborane(3) was observed upon photolysis at 180 and 220 nm. The observed line wavenumbers, relative intensities, and isotopic ratios of the diborane(5) anion agreed satisfactorily with those predicted by density functional theory calculations at the B3LYP/aug-cc-pVTZ level of theory. Thus, this method produced the boron hydride anion of interest with few other fragments, which enabled us to clearly identify the IR spectrum of the diborane(5) anion. Published by AIP Publishing.