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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Article
  • Peer Reviewed
UC San Francisco Previously Published Works (1995)
Cdc42 and Rac1 are members of the rho family of small guanosinetriphosphatases and are required for a diverse set of cytoskeleton-membrane interactions in different cell types. Here we show that these two proteins contribute differently to the organization of epithelial cells in the Drosophila wing imaginal disc. Drac1 is required to assemble actin at adherens junctions. Failure of adherens junction actin assembly in Drac1 dominant-negative mutants is associated with increased cell death. Dcdc42, on the other hand, is required for processes that involve polarized cell shape changes during both pupal and larval development. In the third larval instar, Dcdc42 is required for apico-basal epithelial elongation. Whereas normal wing disc epithelial cells increase in height more than twofold during the third instar, cells that express a dominant-negative version of Dcdc42 remain short and are abnormally shaped. Dcdc42 localizes to both apical and basal regions of the cell during these events, and mediates elongation, at least in part, by effecting a reorganization of the basal actin cytoskeleton. These observations suggest that a common cdc42-based mechanism may govern polarized cell shape changes in a wide variety of cell types.
    Cover page: CDC42 and Rac1 control different actin-dependent processes in the Drosophila wing disc epithelium.
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2015)
    The mammalian basal forebrain (BF) has important roles in controlling sleep and wakefulness, but the underlying neural circuit remains poorly understood. We examined the BF circuit by recording and optogenetically perturbing the activity of four genetically defined cell types across sleep-wake cycles and by comprehensively mapping their synaptic connections. Recordings from channelrhodopsin-2 (ChR2)-tagged neurons revealed that three BF cell types, cholinergic, glutamatergic and parvalbumin-positive (PV+) GABAergic neurons, were more active during wakefulness and rapid eye movement (REM) sleep (wake/REM active) than during non-REM (NREM) sleep, and activation of each cell type rapidly induced wakefulness. By contrast, activation of somatostatin-positive (SOM+) GABAergic neurons promoted NREM sleep, although only some of them were NREM active. Synaptically, the wake-promoting neurons were organized hierarchically by glutamatergicâ †'cholinergicâ †'PV+ neuron excitatory connections, and they all received inhibition from SOM+ neurons. Together, these findings reveal the basic organization of the BF circuit for sleep-wake control.
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2003)

      The Project for Intercomparison of Land-Surface Parameterization Schemes phase 2(d) experiment at Valdai, Russia, offers a unique opportunity to evaluate land surface schemes, especially snow and frozen soil parameterizations. Here, the ability of the 21 schemes that participated in the experiment to correctly simulate the thermal and hydrological properties of the soil on several different timescales was examined. Using observed vertical profiles of soil temperature and soil moisture, the impact of frozen soil schemes in the land surface models on the soil temperature and soil moisture simulations was evaluated. It was found that when soil-water freezing is explicitly included in a model, it improves the simulation of soil temperature and its variability at seasonal and interannual scales. Although change of thermal conductivity of the soil also affects soil temperature simulation, this effect is rather weak. The impact of frozen soil on soil moisture is inconclusive in this experiment due to the particular climate at Valdai, where the top 1 m of soil is very close to saturation during winter and the range for soil moisture changes at the time of snowmelt is very limited. The results also imply that inclusion of explicit snow processes in the models would contribute to substantially improved simulations. More sophisticated snow models based on snow physics tend to produce better snow simulations, especially of snow ablation. Hysteresis of snow-cover fraction as a function of snow depth is observed at the catchment but not in any of the models.

        Cover page: Effects of frozen soil on soil temperature, spring infiltration, and runoff: Results from the PILPS 2(d) experiment at Valdai, Russia
        • Article
        • Peer Reviewed
        UC Berkeley Previously Published Works (2002)
        BABAR, the detector for the SLAC PEP-II asymmetric e+e- B Factory operating at the γ(4S) resonance, was designed to allow comprehensive studies of CP-violation in B-meson decays. Charged particle tracks are measured in a multi-layer silicon vertex tracker surrounded by a cylindrical wire drift chamber. Electromagnetic showers from electrons and photons are detected in an array of CsI crystals located just inside the solenoidal coil of a superconducting magnet. Muons and neutral hadrons are identified by arrays of resistive plate chambers inserted into gaps in the steel flux return of the magnet. Charged hadrons are identified by dE/dx measurements in the tracking detectors and by a ring-imaging Cherenkov detector surrounding the drift chamber. The trigger, data acquisition and data-monitoring systems, VME- and network-based, are controlled by custom-designed online software. Details of the layout and performance of the detector components and their associated electronics and software are presented. © 2002 Elsevier Science B.V. All rights reserved.
          Cover page: The BABAR detectorCreative Commons 'BY' version 4.0 license
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2021)
          We present a search for quasi-monochromatic gravitational-wave signals from the young, energetic X-ray pulsar PSR J0537-6910 using data from the second and third observing runs of LIGO and Virgo. The search is enabled by a contemporaneous timing ephemeris obtained using Neutron star Interior Composition Explorer (NICER) data. The NICER ephemeris has also been extended through 2020 October and includes three new glitches. PSR J0537-6910 has the largest spin-down luminosity of any pulsar and exhibits fRequent and strong glitches. Analyses of its long-term and interglitch braking indices provide intriguing evidence that its spin-down energy budget may include gravitational-wave emission from a time-varying mass quadrupole moment. Its 62 Hz rotation frequency also puts its possible gravitational-wave emission in the most sensitive band of the LIGO/Virgo detectors. Motivated by these considerations, we search for gravitational-wave emission at both once and twice the rotation frequency from PSR J0537-6910. We find no signal, however, and report upper limits. Assuming a rigidly rotating triaxial star, our constraints reach below the gravitational-wave spin-down limit for this star for the first time by more than a factor of 2 and limit gravitational waves from the l = m = 2 mode to account for less than 14% of the spin-down energy budget. The fiducial equatorial ellipticity is constrained to less than about 3 ×10-5, which is the third best constraint for any young pulsar.
            Cover page: Diving below the Spin-down Limit: Constraints on Gravitational Waves from the Energetic Young Pulsar PSR J0537-6910Creative Commons 'BY' version 4.0 license
            • Article
            • Peer Reviewed
            UC San Francisco Previously Published Works (2021)
            To support the global restart of elective surgery, data from an international prospective cohort study of 8492 patients (69 countries) was analysed using artificial intelligence (machine learning techniques) to develop a predictive score for mortality in surgical patients with SARS-CoV-2. We found that patient rather than operation factors were the best predictors and used these to create the COVIDsurg Mortality Score (https://covidsurgrisk.app). Our data demonstrates that it is safe to restart a wide range of surgical services for selected patients.
              Cover page: Machine learning risk prediction of mortality for patients undergoing surgery with perioperative SARS-CoV-2: the COVIDSurg mortality score
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