S C Huang

University of California, Los Angeles, Los Angeles, California, United States

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Publications (250)1051.44 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, the ultraviolet light-emitting diodes (UV-LEDs) at 380 nm were grown on patterned sapphire substrate (PSS) by atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD). A sputtered AlN nucleation layer was utilized on the PSS to enhance the quality of the epitaxial layer. By using high-resolution X-ray diffraction, the full-width at half-maximum of the rocking curve shows that the UV-LEDs with sputtered AlN nucleation layer had better crystalline quality when compared to conventional GaN nucleation samples. From the scanning electron microscope (SEM) and transmission electron microscopy (TEM) images, it can be observed that the tip and sidewall portion of the pattern was smooth using the sputtered AlN nucleation layer. The threading dislocation densities (TDDs) are reduced from 6×107 cm−2 to 2.5×107 cm−2 at the interface between the u-GaN layers for conventional and AlN PSS devices, respectively. As a result, a much higher light output power was achieved. The light output power at an injection current of 20 mA was enhanced by 30%. Further photoluminescence (PL) measurement and numerical simulation confirm that this increase of output power can be attributed to the improvement of material quality and light extraction.
    Journal of Crystal Growth 03/2015; 414:258-262. DOI:10.1016/j.jcrysgro.2014.10.013 · 1.69 Impact Factor
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    ABSTRACT: — Maps of local tissue compression or expansion are often recovered by comparing MRI scans using nonlinear registration techniques. The resulting changes can be analyzed using tensor-based morphometry (TBM) to make inferences about anatomical differences. Numerous deformation techniques have been developed, although there has not been much theoretical development examining the mathematical/statistical validity of each technique. In this paper, we propose a basic principle that any registration technique should satisfy: realizing unbiased test statistics under null distribution of the displacement. In other words, any registration technique should recover zero change in the test statistic when comparing two images differing only in noise. Based on this principle, we propose a fundamental framework for the construction and analysis of image deformation. Moreover, we argue that logarithmic transform is instrumental in the analysis of deformation maps. Combined with the proposed framework, this leads to a theoretical connection between image registration and other branches of applied mathematics including information theory and grid generation. Index Terms-Mutual information, Image registration, Computational anatomy. 1.
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    ABSTRACT: Whether perceived changes in memory parallel changes in brain pathology is uncertain. Positron emission tomography (PET) scans using 2-(1-{6-[(2-[F-18]fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile (FDDNP) can measure levels of amyloid plaques and tau neurofibrillary tangles in vivo. Here we investigate whether degree of self-reported memory impairment is associated with FDDNP-PET binding levels in persons without dementia. Fifty-seven middle-aged and older adults without dementia (mean age ±standard deviation = 66.3 ± 10.6 years), including 25 with normal aging and 32 with mild cognitive impairment (MCI), were assessed. The outcome measures were the four factor scores of the Memory Functioning Questionnaire (MFQ) (frequency of forgetting, seriousness of forgetting, retrospective functioning, and mnemonics use) and FDDNP-PET binding levels in medial temporal, lateral temporal, posterior cingulate, parietal, frontal, and global (overall average) regions of interest. After controlling for age, higher reported frequency of forgetting was associated with greater medial temporal (r = -0.29, p = 0.05), parietal (r = -0.30, p = 0.03), frontal (r = -0.35, p = 0.01), and global FDDNP-PET binding levels (r = -0.33, p = 0.02). The remaining MFQ factor scores were not significantly associated with FDDNP-PET binding levels, and no significant differences were found between normal aging and MCI subjects. Item analysis of the frequency of forgetting factor revealed five questions that yielded similar results as the full 32-question scale (r = -0.52, p = 0.0002). These findings suggest that some forms of memory self-awareness, in particular the reported frequency of forgetting, may reflect the extent of cerebral amyloid and tau brain pathology.
    International Psychogeriatrics 02/2012; 24(7):1076-84. DOI:10.1017/S1041610212000051 · 1.89 Impact Factor
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    ABSTRACT: To determine the neuropathological load in the living brain of nondemented adults with Down syndrome using positron emission tomography with 2-(1-{6-[(2-fluorine 18-labeled fluoroethyl)methylamino]-2-napthyl}ethylidene) malononitrile ([(18)F]FDDNP) and to assess the influence of age and cognitive and behavioral functioning. For reference, [(18)F]FDDNP binding values and patterns were compared with those from patients with Alzheimer disease and cognitively intact control participants. Cross-sectional clinical study. Volunteer sample of 19 persons with Down syndrome without dementia (mean age, 36.7 years), 10 patients with Alzheimer disease (mean age, 66.5 years), and 10 controls (mean age, 43.8 years). Binding of [(18)F]FDDNP in brain regions of interest, including the parietal, medial temporal, lateral temporal, and frontal lobes and posterior cingulate gyrus, and the average of all regions (global binding). The [(18)F]FDDNP binding values were higher in all brain regions in the Down syndrome group than in controls. Compared with the Alzheimer disease group, the Down syndrome group had higher [(18)F]FDDNP binding values in the parietal and frontal regions, whereas binding levels in other regions were comparable. Within the Down syndrome group, age correlated with [(18)F]FDDNP binding values in all regions except the posterior cingulate, and several measures of behavioral dysfunction showed positive correlations with global, frontal, parietal, and posterior cingulate [(18)F]FDDNP binding. Consistent with neuropathological findings from postmortem studies, [(18)F]FDDNP positron emission tomography shows high binding levels in Down syndrome comparable to Alzheimer disease and greater levels than in members of a control group. The positive associations between [(18)F]FDDNP binding levels and age as well as behavioral dysfunction in Down syndrome are consistent with the age-related progression of Alzheimer-type neuropathological findings in this population.
    Archives of neurology 06/2011; 68(6):768-74. DOI:10.1001/archneurol.2011.104 · 7.01 Impact Factor
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    Alzheimer's and Dementia 07/2010; 6(4). DOI:10.1016/j.jalz.2010.08.100 · 17.47 Impact Factor
  • M. Wilks · H. Protas · M. Wardak · G.W. Small · J.R. Barrio · S.-C. Huang
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    ABSTRACT: In the field of quantitative imaging, the creation of accurate volumes of interest (VOIs) is often of central importance. However, the process of creating these VOIS for multiple subjects can be time-intensive and there are many chances to introduce variability on inter- and intra-investigator levels. Although previous work has shown that image normalization through cortical surface mapping can be helpful in VOI analysis, the process is complicated and labor-intensive. In this paper we present a method to eliminate this variability by warping structural and functional images to a common space in which valid VOIs already exist. We apply this method to a study of Alzheimer's disease (AD) and 2-(1-{6-[(2-[18F]fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile (FDDNP), which is known to co-localize with amyloid plaques and neurofibrillary tangles. We normalize the MRIs of control subjects and mild cognitive impairment (MCI) and AD patients, to a common space. The same normalization is applied to FDDNP PET images. The normalization technique reduces average voxel-to-voxel variance in MRIs by 54% as compared to linear normalization alone. Biologically important structures, such as the segmentation between white and gray matter, are maintained after normalization. Discriminant analysis shows that data extracted from VOIs in the common space out-performs data extracted from unnormalized PET images in classifying subjects as control, MCI, or AD. This suggests that image normalization may be useful in eliminating inter- and intra-investigator variability and increasing the predictive capability of data extracted from imaging modalities. Further study will examine the applicability of this method to predicting longitudinal changes in cognitive ability from functional imaging data.
    Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE; 01/2010
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    ABSTRACT: We report the fabrication and study of high efficiency ultraviolet light emitting diodes with inverted micropyramid structures at GaN-sapphire interface. The micropyramid structures were created by anisotropic chemical wet etching. The pyramid structures have significantly enhanced the light output efficiency and at the same time also improved the crystal quality by partially relieving the strain and reducing the dislocation defects in GaN. The electroluminescent output power at normal direction was enhanced by 120% at 20 mA injection current and the output power integrated over all directions was enhanced by 85% compared to a reference sample.
    Applied Physics Letters 07/2009; 95(4). DOI:10.1063/1.3190504 · 3.52 Impact Factor
  • S. C. Huang · W. Y. Lin · Y. M. Hsin
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    ABSTRACT: In this work, small-signal and noise model with gate-width scaling of GaAs pseudomorphic high electron mobility transistors (pHEMT) are presented. The scaling effect of the model parameters are derived from an accurate small-signal and noise equivalent circuit model for the different gate widths of pHEMTs. The experimental and model results show that noise coefficients are not dependant on the gate width while devices biasing at the same current density.
    04/2009; DOI:10.1063/1.3140458
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    ABSTRACT: Near-ultraviolet (UV) InGaN/AlGaN light-emitting diodes (LEDs) with three kinds of naturally textured surfaces were grown by atmosphere-pressure metalorganic chemical vapor deposition. The electroluminescence intensities of the 400-nm LED bare chips with nano-hole and micro-island textured morphologies show 30% and 40% in magnitude higher than that of the flat surface LED sample. Both textured surfaces greatly increased the escape probability of photons inside the LED structure. A naturally coral-like surface was developed for the near-UV LED, where the textured p-GaN layer was fabricated using the successive growth of the micro-island followed by the nano-hole p-GaN layers. As much as 31.6% increased light output power of the coral-like textured LED was achieved using this novel surface roughening technique.
    Journal of Crystal Growth 01/2009; 311(3):867-870. DOI:10.1016/j.jcrysgro.2008.09.104 · 1.69 Impact Factor
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    ABSTRACT: Information on the transport and phosphorylation rate constants (k1,k2,k3,k4,Ki) of a tracer reflects the biological state of cells. A microfluidic cell culture chip coupled with PSAPD camera (MF-PSAPD) has been developed to give continuous measurements of radioactivity in individual wells. However, constant infusion (CI) of PET tracers through the chambers would give high background activity due to the relatively large volume space of the infusing medium in the wells of cultured cells that compromise the ability of the setup to estimate the k values. New strategies of controlling the infusion and tracer level are needed to provide reliable estimates of the parameters. A switching strategy (SS) was conceived that consists of multiple medium-infusion cycles, each of which has a tracer incubation (TI) period followed by a background-removed (BR) period (tracer-free medium). In this paper, equally switching strategy (ESS) with 12 cycles of constant TI and BR periods (5 min each) was evaluated by computer simulation and by experiments on MF-PSAPD using the tracer fluorodeoxy-glucose (FDG) and the four parameter FDG model. The SS was further optimized by using a simulated annealing algorithm and D-optimal criterion to obtain optimal switching strategy (OSS). Simulations showed that the 12-cycle ESS did not perform as well (i.e., with larger estimated variability of the model parameters) as a 5-cycle OSS that also has multiple practical advantages. Patterns of OSS were found to be insensitive to the variation of cell number and k values, and all tended to have longer TI at the beginning but longer BR at later times. Estimated k values with SS have large reduction in %CV compared to those of CI, with the largest reduction for Ki--from 762% down to 26% under the same count rate conditions. The new optimized strategy of tracer incubation/measurement is able to provide reliable estimates of FDG k's in MF-PSAPD.
    IEEE Nuclear Science Symposium conference record. Nuclear Science Symposium 01/2009; DOI:10.1109/NSSMIC.2009.5401941
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    ABSTRACT: Amyloid senile plaques and tau neurofibrillary tangles are neuropathological hallmarks of Alzheimer disease that accumulate in the brains of people without dementia years before they develop dementia. Positron emission tomography (PET) scans after intravenous injections of 2-(1-{6-[(2-[F-18]fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile (FDDNP), which binds to plaques and tangles in vitro, demonstrate increased cerebral binding in patients with Alzheimer disease compared with cognitively intact controls. Here we investigated whether known risk factors for Alzheimer disease and dementia are associated with FDDNP-PET binding. To determine if impaired cognitive status, older age, apolipoprotein E-4 (APOE-4) genetic risk for Alzheimer disease, family history of dementia, and less education are associated with increased regional cerebral FDDNP-PET binding. Cross-sectional clinical study. A university research institute. Volunteer sample of 76 middle-aged and older persons without dementia (mean age, 67 years) including 36 with mild cognitive impairment. Of the 72 subjects with genetic data, 34 were APOE-4 carriers. The FDDNP-PET signal in brain regions of interest, including medial and lateral temporal, posterior cingulate, parietal, and frontal. For all regions studied, cognitive status was associated with increased FDDNP binding (P < .02 to .005). Older age was associated with increased lateral temporal FDDNP binding. Carriers of APOE-4 demonstrated higher frontal FDDNP binding than noncarriers. In the mild cognitive impairment group, age was associated with increased medial and lateral temporal FDDNP binding, and APOE-4 carriers had higher medial temporal binding than noncarriers. Impaired cognitive status, older age, and APOE-4 carrier status are associated with increased brain FDDNP-PET binding in persons without dementia, consistent with previous clinical and postmortem studies associating these risk factors with amyloid plaque and tau tangle accumulation. Stratifying subject groups according to APOE-4 carrier status, age, and cognitive status may therefore be an informative strategy in future clinical trials using FDDNP-PET.
    Archives of general psychiatry 01/2009; 66(1):81-7. DOI:10.1001/archgenpsychiatry.2008.516 · 13.75 Impact Factor
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    ABSTRACT: 3'-[F-18]fluoro-3'-deoxythymidine (FLT) traces thymidine phosphorylation catalyzed by thymidine kinase during cell proliferation. Knowing the rate of cell proliferation during cancer treatment, such as radiation therapy, would be valuable in assessing whether tumor recurrence is likely and might indicate the need for additional treatments. However, the relationship between FLT kinetics and the effects of radiation is not well-understood. Nor has the method for optimal quantification of FLT uptake within the irradiated tumor microenvironment been extensively examined. We performed dynamic FLT-positron emission tomography (PET) studies (60 min) on 22 mice implanted subcutaneously with syngeneic mammary MCaK tumors bilaterally in the shoulder area. A day before the FLT-PET imaging, the tumor on the right side was irradiated with a single dose (0, 2.5, 5, 10, or 20 Gy) or with fractionated exposures (4x2.5 Gy given in 12 h intervals). Standardized uptake value (SUVs) of FLT on tumors at 10 and 60 min post injection were calculated; model fitting was used to estimate the kinetic parameters. Significant radiation-induced changes were shown by comparing the irradiated tumor with the control tumor in the same animal and by comparing it to nonirradiated mice. The effect of radiation on MCaK cell cycle parameters and FLT uptake was also examined in vitro. In vivo FLT kinetics were sensitive to radiation doses of 5 Gy and higher (administered 1 day earlier), as judged by SUV semiquantitative measures and by modeling. Single irradiation with 10 Gy had greater impact on SUVs and kinetic parameters than fractionated exposures. Overall, the uptake constant Ki appeared to be the best marker for these radiation effects. FLT uptake by irradiated cells in vitro at various doses gave similar findings, and the in vitro FLT uptake correlated well with Ki. Radiation-induced G2/M arrest appeared to influence FLT uptake, and this was more pronounced after single than fractionated doses. The kinetics of FLT uptake into murine mammary tumors was altered 1 day after radiation treatment. The dose-dependent response correlated well with in vitro FLT cellular uptake. Parameters (e.g., Ki) derived from FLT kinetics are expected to be useful for assessing the efficacy of irradiation treatment of tumors.
    Molecular Imaging & Biology 09/2008; 10(6):325-34. DOI:10.1007/s11307-008-0158-z · 2.87 Impact Factor
  • Alzheimer's and Dementia 07/2008; 4(4). DOI:10.1016/j.jalz.2008.05.086 · 17.47 Impact Factor
  • Alzheimer's and Dementia 07/2008; 4(4). DOI:10.1016/j.jalz.2008.05.882 · 17.47 Impact Factor
  • Alzheimer's and Dementia 07/2008; 4(4). DOI:10.1016/j.jalz.2008.05.2500 · 17.47 Impact Factor
  • Alzheimer's and Dementia 07/2008; 4(4). DOI:10.1016/j.jalz.2008.05.163 · 17.47 Impact Factor
  • W.-K. Huang · S.-C. Huang · Y.-M. Hsin · J.-W. Shi · Y.-C. Kao · J.-M. Kuo
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    ABSTRACT: An optoelectronic integrated circuit (OEIC) with flip-chip technology for 1.55- m wavelength application is demonstrated. The presented flip-chip OEIC comprises an InP chip and the carrier substrate. The InP chip consists of an evanescently coupled photodiode (ECPD), an InP/InGaAs heterojunction bipolar transistor (HBT) and bonding pads. The semi-insulating GaAs carrier consists of a coplanar waveguide, bias resistances, interconnects and pads (DC, RF and bonding pads). The flip-chip technology is used to reduce InP chip size and thus save cost. The fabricated ECPD exhibits a responsivity of 0.3 A/W and an f <sub>3</sub> <sub>dB</sub> of 30 GHz. The OEIC demonstrates an f <sub>3</sub> <sub>dB</sub> of 36 GHz with a transimpedance gain of 32 dB . This is the first ECPD/HBT with flip-chip technology ever reported for OEIC.
    IET Optoelectronics 03/2008; DOI:10.1049/iet-opt:20060083 · 0.97 Impact Factor
  • J R Barrio · V Kepe · N Satyamurthy · S C Huang · G Small
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    ABSTRACT: Establish new approaches for early diagnosis of dementia, based on imaging amyloid and tau pathology, cell losses and neuronal function, in subjects with mild cognitive impairment (MCI),. The overall aim is to develop effective tools for monitoring disease progression in the living patient to facilitate discovery of early therapeutic interventions to modify the course of the disease. Use 2-(1-{6-[(2-[F- 18]fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile ([F-18]FDDNP) in combination with positron emission tomography (PET) to produce dynamic images for quantification of regional cortical brain deposition in MCI patients and compare them with controls subjects and patients with Alzheimer's disease (AD). Comparison with other molecular imaging probes for neuronal losses and function were also made. Patients are positioned supine in the tomograph bed with his/her head in the detector ring field. Upon injection of the molecular imaging probe (e.g., [F-18]FDDNP) images are obtained at very short time intervals for up to two hours. This results in dynamic sequences of brain distribution of the probe. Patients with clinical diagnosis of AD, MCI and control subjects. Subjects in the categories established above were scanned with [F-18]FDDNP-PET and quantification performed using Logan parametric graphical analysis to measure relative quantitative amyloid loads throughout the brain within patient groups. These results were compared in the same patients with cell losses in hippocampus using 4-[F-18]fluoro-N-{2-[4-(2-methoxyphenyl)- 1-piperazinyl]ethyl}-N-(2-pyridinyl)benzamide,([F-18]MPPF) and regional cerebral glucose metabolic rates using 2-deoxy-2-[F-18]fluoro-2-deoxy-D-glucose (2-[F-18]FDG). [F-18]FDDNP reliably follows neuropathological progression (amyloid plaques [SP]; neurofibrillary tangles [NFT]) in the living brain of AD patients and those with MCI. The distribution of [F-18]FDDNP brain cortical accumulation correlates well with behavioral measures (e.g., MMSE scores) and follows known patterns of pathological distribution observed at autopsy. We have also established conversion of controls to MCI and MCI to AD with precision and sensitivity in patients and control subjects in follow-up studies. Moreover, we have established that hemispheric cortical surface mapping of [F-18]FDDNP binding is a powerful tool for assessment and visualization of the rate of brain pathology deposition. A strong correlation of [F-18]FDDNP binding, cell losses in hippocampus and decreased glucose utilization ([F-18]FDG PET) in several neocortical regions was found in the same AD and MCI subjects. The combined evaluation of [F-18]FDDNP PET (targeting NFT and_SP) with neuronal losses in the hippocampus and with [F-18]FDG PET (targeting neuronal function) offers the opportunity for reliable, noninvasive detection of MCI patients at risk for AD. The approach offers a glimpse to the molecular and cellular mechanisms associated with dementia and provides a means for their assessment in the living patient. Monitoring disease progression in MCI patients demonstrates the usefulness of this imaging approach for early diagnosis and provides a means for evaluation of neuroprotective agents and drugs aimed at prevention and modification of disease progression.
    The Journal of Nutrition Health and Aging 02/2008; 12(1):61S-5S. DOI:10.1007/BF02982589 · 2.66 Impact Factor
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    ABSTRACT: The 380-nm InGaN/AlGaN light-emitting diodes (LEDs) were fabricated on a conventional and patterned sapphire substrates (PSSs) by metalorganic vapor phase epitaxy (MOVPE). Micro-photoluminescence (PL) measurements showed superior near-band-edge luminescence intensity from the overhang area as compared to the layer directly on the flat sapphire region. This was accompanied by a small redshift of the PL peak wavelength that could be attributed to a relief of compressive stress in the epitaxial lateral overgrowth region. From the temperature-dependent PL measurements, we obtain an integrated PL intensity ratio at 300–10 K of ∼13.7% and thermal activation energy of 94 meV from the InGaN/AlGaN MQW PSS LED sample. Under a 20-mA current injection, the output power increased from 3.75 to 5.06 mW, corresponding to about 35% increase in external quantum efficiency. It is evident that the increase in output power depends on both the defect reduction of epitaxial lateral overgrowth of GaN and the scattering of emitted light at the GaN/sapphire interface.
    Journal of Crystal Growth 01/2007; 298:219-222. DOI:10.1016/j.jcrysgro.2006.10.038 · 1.69 Impact Factor
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    ABSTRACT: A set of over 20 dynamic mouse FDG microPET images has been collected experimentally at UCLA and is made available to the public on the Internet. Accompanying each dynamic image set also is the radioactivity measurements of multiple sequential blood samples taken during the study. The data are expected to be useful for investigators who want to know more about the characteristics of dynamic mouse FDG microPET images before doing their own experiments, and will be especially useful for those who are interested in developing image-based methods for deriving blood activity curves from dynamic mouse microPET images.
    Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006

Publication Stats

12k Citations
1,051.44 Total Impact Points

Institutions

  • 1982–2012
    • University of California, Los Angeles
      • • Department of Molecular and Medical Pharmacology
      • • Department of Medicine
      • • Division of Cardiology
      Los Angeles, California, United States
  • 2006–2009
    • National Chung Hsing University
      • Department of Materials Science and Engineering
      臺中市, Taiwan, Taiwan
  • 1978–2005
    • Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center
      • Department of Medicine
      Torrance, California, United States
  • 2001
    • University of Sydney
      Sydney, New South Wales, Australia
  • 1999
    • Samsung Medical Center
      • Department of Nuclear Medicine
      Sŏul, Seoul, South Korea
  • 1998
    • Good Samaritan Medical Center
      West Palm Beach, Florida, United States
  • 1995
    • Chung Yuan Christian University
      臺中市, Taiwan, Taiwan
  • 1992
    • Duke University Medical Center
      • Department of Radiology
      Durham, North Carolina, United States
    • Cedars-Sinai Medical Center
      • Cedars Sinai Medical Center
      Los Ángeles, California, United States
  • 1989
    • Concordia University–Ann Arbor
      Ann Arbor, Michigan, United States
  • 1987
    • Dent Neurologic Institute
      Buffalo, New York, United States
  • 1981–1986
    • CSU Mentor
      Long Beach, California, United States
  • 1980
    • National Institutes of Health
      • Laboratory of Metabolism
      베서스다, Maryland, United States