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Open Access Publications from the University of California

Scholarly Works (279 results)

  • Article
  • Peer Reviewed
UC Irvine Previously Published Works (2006)
Basel cell carcinoma (BCC) is the most common human skin malignancy. Its incidence has increased significantly in Australia, Europe and North America over the past decade. A number of modalities are currently used for treatment of BCC, including cryosurgery which offers a potential for high cure rate, low cost, minimal bleeding and good cosmetic effect. However, cryosurgery is not used frequently for BCC because no current method exists to design adequate treatment parameters. We present a numerical analysis on the thermal history of the target tissue during cryosurgery of a nodular BCC using liquid nitrogen (LN2) spray. The model uses Pennes equation to describe the heat transfer within the target tissue. A convective thermal boundary is used to describe the heat interaction between the tissue and LN2, and the apparent heat capacity method is applied to address the tissue phase change process. A parametric study is conducted on the convective heat transfer coefficient (hs: 104-106 W/m 2·K), cooling site area (rs/R0: 0.5-1.0) and spray time (t: 0-30 sec.), with the objective to understand the thermal history during tissue freezing, including lethal temperature (-50°C) and cooling rate (CR). Results demonstrate that propagation of the lethal isotherm is sensitive to the convective heat transfer coefficient, hs, with a range of 104-5×104 W/m2·K. Increasing the cooling site area can significantly enhance cooling efficiency, producing dramatic increase in the amount of tissue encompassed by the lethal isotherm. The cooling rate (CR) shows a highly dynamic distribution during the cooling process: the highest CR drops quickly from 140°C/sec. (t=0.5 sec.) to 20°C/sec. (t=5 sec.). The highest CR is initially located close to the cooling site but moves toward the inside of the tissue as treatment proceeds. The model presented herein provides a simulation tool for treatment planning of cryosurgery using LN2 spray, in which the protocol parameters, e.g. cooling site area and spray time, can be determined for an optimal outcome. The quantitative predictions on the propagation of lethal isotherm and the distribution of CR should help to optimize cryosurgery efficacy. Copyright © 2006 by ASME.
    Cover page: Thermal Analysis for Cryosurgery of Nodular Basal Cell CarcinomaCreative Commons 'BY' version 4.0 license
    • Article
    • Peer Reviewed
    UC Irvine Previously Published Works (2004)

    Cryogen spray cooling (CSC) is used to minimize the fisk of epidermal damage during dermatologic therapy. However, the dominant mechanisms of heat transfer during the transient cooling process are incompletely understood. The objective of this study is to elucidate the physics of CSC by measuring the effect of initial substrate temperature (T-0) on cooling dynamics. Cryogen was delivered by a straight-tube nozzle onto a skin phantom. A fast-response thermocouple was used to record the phantom temperature changes before. during and after the cryogen spray. Surface heat fluxes (q") and heat-transfer coefficients (h) were computed using an inverse heat conduction algorithm. The maximum surface heat flux (q"(max)) was observed to increase with T-0. The surface temperature corresponding to q" also increased with T-0 but the latter has no significant effect on h. It is concluded that heat transfer between the cryogen spray and skin phantom remains in the nucleate boiling region even if T-0 is 80 degreesC.

      Cover page: Heat-transfer dynamics during cryogen spray cooling of substrate at different initial temperatures
      • Article
      • Peer Reviewed
      UC San Francisco Previously Published Works (2015)
      © 2015 Zhang et al.Staphylococcus aureus is one of the most common pathogens causing keratitis. Surfactant protein D (SP-D) plays a critical role in host defense and innate immunity. In order to investigate the role of SP-D in ocular S. aureus infection, t
        • Article
        • Peer Reviewed
        UC Berkeley Previously Published Works (2015)
        Co-seismic groundwater-level changes induced by earthquakes have been reported for thousands of years. The M8.0 Wenchuan earthquake caused co-seismic groundwater-level responses across the Chinese mainland. Three types of changes were recorded in 197 monitoring wells: co-seismic oscillations ranging in amplitude from 0.004 to 1.1 m, immediate co-seismic step changes ranging from 0.0039 to 9.188 m, and more gradual postseismic changes ranging from 0.014 to 1.087 m. We find that the co-seismic groundwater-level response is complex. There is neither a clear relationship between the response amplitude and the distance from the epicenter, nor a clear relationship between the groundwater response and lithology at the continental scale. Both the sign and amplitude of water-level changes are random at the continental scale, and a poroelastic response to the co-seismic static strain cannot explain most of the co-seismic changes. However, wells located near the edges of tectonically active blocks have larger response amplitudes than those in the middle of these 'stable' blocks. Considered together, these observations indicate that permeability enhancement caused by the earthquake is a significant or dominant mechanism causing water-level changes. These data indicate that large earthquakes can cause the widespread permeability changes in the shallow crust although the magnitude of permeability change is uncertain.
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2005)
          It is common in some cryosurgical procedures to rely on freeze-thaw cycle(s) to destroy undesirable tissues. Most research in cryosurgery focuses on the freezing process and much less attention has been paid to thawing or re-warming. However, as ice melts during thawing, the extracellular solution can become locally hypotonic, driving water into cells, resulting in cell expansion and ultimately, membrane rupture. Therefore, the thermal history of the target tissue during both the freezing and thawing processes is critical for cell viability. To better understand and predict the thermal history during cryosurgery, we developed a two-dimensional numerical model to describe the complete freeze-thaw cycle during liquid nitrogen cutaneous cryosurgery. A stratified anatomical structure of human skin is considered in the model. The numerical simulation applies temperature-dependent thermal and physical properties for human skin tissue and considers the typical thermal boundary conditions for clinical practice. Parametric studies are performed to explore the influence of spray cooling, spray duration and surface heating. Results are discussed concentrating on iceball front propagation, lethal temperature isotherm evolution, tissue temperature variation and cooling rates. These results are expected to provide both quantitative and graphical support to cutaneous cryosurgery and suggest approaches to optimize current cryosurgical protocols. Copyright © 2005 by ASME.
            Cover page: Numerical Modeling of the Tissue Freezing-Thaw Cycle During Cutaneous Cryosurgery Using Liquid Nitrogen SprayCreative Commons 'BY' version 4.0 license
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2021)
            A combined Doppler backscattering/cross-polarization scattering (DBS/CPS) system is being deployed on MAST-U for simultaneous measurements of local density turbulence, turbulence flows, and magnetic turbulence. In this design, CPS shares the probing beam with the DBS and uses a separate parallel-viewing receiver system. In this study, we utilize a modified GENRAY 3D ray-tracing code to simulate the propagation of the probing and scattered beams. The contributions of different scattering locations along the entire beam trajectories are considered, and the corresponding local B̃ wavenumbers are estimated using the wavevector matching criterion. The wavenumber ranges of the local B̃ that are detectable to the CPS system are explored for simulated L- and H-mode plasmas.
              • Article
              • Peer Reviewed
              UC Davis Previously Published Works (1995)

              A bacterial artificial chromosome (BAC) library consisting of 11,000 clones with an average DNA insert size of 125 kb was constructed from rice nuclear DNA. The BAC clones were stable in E. coli after 100 generations of serial growth. Transformation of the BAC clones by electroporation into E. coli was highly efficient and increased with decreasing size of the DNA inserts. The library was evaluated for the presence of organellar, repeated, and telomeric sequences. A very low percentage (< 0.3%) of the library consisted of chloroplast and mitochondrial clones. Eighteen BACs were identified that hybridized with an Arabidopsis telomere repeat. Sixteen BACs hybridized with the AA genome-specific repetitive sequence pOs48. Twelve clones were isolated that hybridized with three DNA markers linked to the Xa-21 disease resistance locus. The results indicate that the BAC system can be used to clone and manipulate large pieces of plant DNA efficiently.

                Cover page: Construction of a rice bacterial artificial chromosome library and identification of clones linked to the Xa-21 disease resistance locus.
                • Article
                • Peer Reviewed
                UC San Diego Previously Published Works (2005)

                A composite metal-polymer electrode is designed to investigate electric-field-induced changes of the dielectric function of gate insulators in metal-oxide-semiconductor structures using infrared spectroscopy. We studied structures based on TiO2 dielectric insulator on doped silicon, a combination commonly used in field-effect transistors. It is shown that the voltage-induced changes of the dielectric constant in TiO2 originate from a modification of the lattice vibration modes of this compound. (c) 2005 American Institute of Physics.

                  Cover page: An infrared probe of tunable dielectrics in metal-oxide-semiconductor structures
                  • Article
                  • Peer Reviewed
                  UC Irvine Previously Published Works (2012)
                  Cryosurgery is a surgical technique that employs freezing to destroy target tumor tissue. While the main objective during a cryosurgical procedure is to ensure tissue destruction within the cryolesion, the greatest challenge is how to spare the surrounding healthy tissues from cryoablation. In this work, a historical review of the field of cryosurgery is presented followed by a theoretical study where a mathematical model is developed for cryosurgery on a basal cell carcinoma (BCC) using liquid nitrogen (LN2) spray. The model takes into consideration the anatomic structure of skin tissue and the irregular geometry of BCC. In particular, a methodology for quantitatively determining the extent of the intracellular ice formation (IIF) zone based on the tissue temperature and cooling rate (CR) is proposed, which can directly relate to the necrosis of the cancer cells after cryosurgery. The model is then used to analyze formation of the IIF zone during cryosurgery on a BCC and quantification is provided for the volume of the final IIF zone. A parametric study is also carried out to investigate the effect of various protocol parameters on the final IIF zone. The results should be useful for dermatologists for pre-treatment surgery planning.
                    Cover page: Numerical Prediction of the Intracellular ICE Formation Zone during Cryosurgery on a Nodular Basal Cell Carcinoma Using Liquid Nitrogen SprayCreative Commons 'BY' version 4.0 license
                    • Article
                    • Peer Reviewed
                    UC San Francisco Previously Published Works (2014)
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