Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (602 results)

  • Article
  • Peer Reviewed
UCLA Previously Published Works (2010)
Source localization models assume brain electrical conductivities are isotropic at about 0.33 S/m. These assumptions have not been confirmed ex vivo in humans. This study determined bidirectional electrical conductivities from pediatric epilepsy surgery patients. Electrical conductivities perpendicular and parallel to the pial surface of neocortex and subcortical white matter (n = 15) were measured using the 4-electrode technique and compared with clinical variables. Mean (±SD) electrical conductivities were 0.10 ± 0.01 S/m, and varied by 243% from patient to patient. Perpendicular and parallel conductivities differed by 45%, and the larger values were perpendicular to the pial surface in 47% and parallel in 40% of patients. A perpendicular principal axis was associated with normal, while isotropy and parallel principal axes were linked with epileptogenic lesions by MRI. Electrical conductivities were decreased in patients with cortical dysplasia compared with non-dysplasia etiologies. The electrical conductivity values of freshly excised human brain tissues were approximately 30% of assumed values, varied by over 200% from patient to patient, and had erratic anisotropic and isotropic shapes if the MRI showed a lesion. Understanding brain electrical conductivity and ways to non-invasively measure them are probably necessary to enhance the ability to localize EEG sources from epilepsy surgery patients.
    Cover page: Variable Anisotropic Brain Electrical Conductivities in Epileptogenic Foci
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2010)
    Source localization models assume brain electrical conductivities are isotropic at about 0.33 S/m. These assumptions have not been confirmed ex vivo in humans. This study determined bidirectional electrical conductivities from pediatric epilepsy surgery patients. Electrical conductivities perpendicular and parallel to the pial surface of neocortex and subcortical white matter (n = 15) were measured using the 4-electrode technique and compared with clinical variables. Mean (±SD) electrical conductivities were 0.10 ± 0.01 S/m, and varied by 243% from patient to patient. Perpendicular and parallel conductivities differed by 45%, and the larger values were perpendicular to the pial surface in 47% and parallel in 40% of patients. A perpendicular principal axis was associated with normal, while isotropy and parallel principal axes were linked with epileptogenic lesions by MRI. Electrical conductivities were decreased in patients with cortical dysplasia compared with non-dysplasia etiologies. The electrical conductivity values of freshly excised human brain tissues were approximately 30% of assumed values, varied by over 200% from patient to patient, and had erratic anisotropic and isotropic shapes if the MRI showed a lesion. Understanding brain electrical conductivity and ways to non-invasively measure them are probably necessary to enhance the ability to localize EEG sources from epilepsy surgery patients. © 2010 The Author(s).
      Cover page: Variable anisotropic brain electrical conductivities in epileptogenic foci
      • Article
      LBL Publications (1967)
        Cover page: PRODUCTION OF K MESONS IN THREE-BODY STATES IN PROTON-PROTON INTERACTIONS AT 6 BeV/c
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2005)

        2-[F-18]Fluoro-A-85380 (2- [F-18]fluoro-3-(2(S)-azetidinylmethoxy)pyridine, 2-[18F]FA) is a recently developed PET radioligand for noninvasive imaging of nicotinic acetylcholine receptors. Previous radiation absorbed dose estimates for 2-[F-18]FA were limited to evaluation of activity in only several critical organs. Here, we performed 2-[F-18]FA radiation dosimetry studies on two healthy human volunteers to obtain data for all important body organs. Intravenous injection of 2.9 MBq/kg of 2-[F-18]FA was followed by dynamic PET imaging. Regions of interest were placed over images of each organ to generate time-activity curves, from which we computed residence times. Radiation absorbed doses were calculated from the residence times using the MIRDOSE 3.0 program (version 3.0, ORISE, Oak Ridge, TN). The urinary bladder wall receives the highest radiation absorbed dose (0.153 mGy/MBq, 0.566 rad/mCi, for a 2.4-h voiding interval), followed by the liver (0.0496 mGy/MBq, 0.184 rad/mCi) and the kidneys (0.0470 mGy/MBq, 0.174 rad/mCi). The mean effective dose equivalent is estimated to be 0.0278 mSv/MBq (0.103 rem/mCi), indicating that radiation dosimetry associated with 2-[F-18]FA is within acceptable limits. (c) 2005 Elsevier Inc. All rights reserved.

          Cover page: Whole-body radiation dosimetry of 2-[F-18]fluoro-A-85380 in human PET imaging studies
          • Article
          LBL Publications (1969)
            Cover page: FOUR-BODY STRANGE PARTICLE PRODUCTION IN pp COLLISIONS AT 6 BeV/c
            • Article
            LBL Publications (1967)
              Cover page: EVIDENCE FOR AN I = 3/2 BARTON RESONANCE AT 2020 MeV/c2
              • Article
              LBL Publications (1968)
                Cover page: RARE DECAY MODES OF N*(l950)
                • Article
                • Peer Reviewed
                UCLA Previously Published Works (2005)

                Background: Methamphetamine (MA) abusers have cognitive deficits, abnormal metabolic activity and structural deficits in limbic and paralimbic cortices, and reduced hippocampal volume. The links between cognitive impairment and these cerebral abnormalities are not established. Methods: We assessed cerebral glucose metabolism with [F-18]fluorodeoxyglucose positron emission tomography in 17 abstinent (4 to 7 days) methamphetamine users and 16 control subjects performing an auditory vigilance task and obtained structural magnetic resonance brain scans. Regional brain radioactivity served as a marker for relative glucose metabolism. Error rates on the task were related to regional radioactivity and hippocampal morphology Results. Methamphetamine users bad higher error rate than control subjects on the vigilance task. The groups showed different relationships between error rates and relative activity), in the anterior and middle cingulate gyrus and the insula. Whereas the MA user group showed negative correlations involving these regions, the control group showed positive correlations involving the cingulate cortex. Across groups, hippocampal metabolic and structural measures were negatively correlated with error rates. Conclusions: Dysfunction in the cingulate and insular cortices of recently abstinent MA abusers contribute to impaired vigilance and other cognitive functions requiring sustained attention. Hippocampal integrity predicts task performance in methamphetamine users as well as control subjects.

                  Cover page: Cerebral metabolic dysfunction and impaired vigilance in recently abstinent methamphetamine abusers
                  • Article
                  • Peer Reviewed
                  UC Irvine Previously Published Works (2007)
                  We present new precision measurements of the ψ (2 S) total and partial widths from excitation curves obtained in antiproton-proton annihilations by Fermilab experiment E835 at the Antiproton Accumulator in the year 2000. A new technique of complementary scans was developed to study narrow resonances with stochastically cooled antiproton beams. The technique relies on precise revolution-frequency and orbit-length measurements, while making the analysis of the excitation curve almost independent of machine lattice parameters. We study the ψ (2 S) meson through the processes over(p, ̄) p → e+ e- and over(p, ̄) p → J / ψ + X → e+ e- + X. We measure the width to be Γ = 290 ± 25 (sta) ± 4 (sys)   keV and the combination of partial widths Γe+ e- Γover(p, ̄) p / Γ = 579 ± 38 (sta) ± 36 (sys)   meV, which represent the most precise measurements to date. © 2007 Elsevier B.V. All rights reserved.
                    Cover page: Precision measurements of the total and partial widths of the ψ(2S) charmonium meson with a new complementary-scan technique in p¯p annihilationsCreative Commons 'BY' version 4.0 license
                    • Article
                    • Peer Reviewed
                    UC Irvine Previously Published Works (2005)
                    This report documents the physics case for building a 2 MW, 8 GeV superconducting linac proton driver at Fermilab.
                      Cover page: Physics at a Fermilab Proton DriverCreative Commons 'BY' version 4.0 license
                      Top