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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biomedical Engineering 2 (2000), S. 157-187 
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract Cryosurgery is a surgical technique that employs freezing to destroy undesirable tissue. Developed first in the middle of the nineteenth century it has recently incorporated new imaging technologies and is a fast growing minimally invasive surgical technique. A historical review of the field of cryosurgery is presented, showing how technological advances have affected the development of the field. This is followed by a more in-depth survey of two important topics in cryosurgery: (a) the biochemical and biophysical mechanisms of tissue destruction during cryosurgery and (b) monitoring and imaging techniques for cryosurgery.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4665-4672 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser-induced stresses have been studied extensively to understand macroscopic phenomenon during high-power laser ablation of solids. Recently, a norm of stress times the rate of change in stress, similar to mechanical stress power, was monitored acoustically in the target and ambient medium during high-power laser-material interactions, and compared with stress measurements. This study investigates the relationship between stress and the stress powerlike measurements (P*), and their dependence on laser energy, intensity, and spot size. The importance of different components of stress on the measurements is also considered. Results from ablation of aluminum targets by a 30 ns uv excimer laser are presented that show changes in P* with laser energy coupling, and the dependence of P* on laser intensity and stress components. Potential issues are raised for further study of stress power as a diagnostic tool of laser-material interactions and as a fundamental mechanism of laser-energy coupling. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1473-1485 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The detection of laser-induced melt at the surface of a solid in real time is demonstrated using a photothermal deflection (PTD) technique. Experimental results for indium and tin show that a local maximum and minimum pair can occur in the temporal profile of the PTD signal when melt occurs. A local minimum does not occur without phase change. Analytical work is presented which explicitly shows the effect of the latent heat of melting, thermal properties, and probe-beam size and offset on the shape of a PTD signal. Results are presented which demonstrate that the observed change in shape will not occur with planar heating, with or without phase transition. However, results derived for point-source heating show that it is possible for the maximum/minimum pair to occur when melting with a focused laser beam. The ratio of the sensible heat to the latent heat, and the ratio of the thermal diffusivities of the target and deflecting medium are the key factors which govern the deflection response. Computations for a general class of materials are given to show when the effect of latent heat can be observed at a surface. Results are also given which consider the probe-beam size and offset on the observations.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Biomedical microdevices 2 (2000), S. 305-316 
    ISSN: 1572-8781
    Keywords: membranes ; breast cancer ; oncology ; cell column regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Using microfabrication technology, we have developed a new experimental apparatus and technique which allow isolation of individual cells and which facilitate the study of kinetic volume changes and membrane permeability. The key component of the apparatus is a microdiffusion chamber which was constructed using silicon microfabrication technology and standard photolithography. The central unit of the chamber is a 1 μ m thick silicon nitride membrane with a center hole on the order of 2–3 μ m in diameter. The device is novel in its analysis of a single cell, instead of the traditional array of cells, and its avoidance of the damage artifacts and computational difficulties which are inherent in other, commonly used methods of cellular analysis. The device is used in conjunction with a predictive computer model which simulates the response of the entire membrane or a portion of the membrane to various permeant and impermeant concentrations. This study introduces the apparatus and the model, and illustrates the effectiveness of the new procedure by determining several membrane permeability coefficients for HBL-100 (healthy human breast line). The empirical data and theoretical data were combined to yield a water permability (L p) of 1.1 ± 0.5μ m/(min-atm) (mean ± 1 standard deviation) (N= 5) during the uncoupled transport of water at 22 ±C. In the presence of 6 M glycerol, the water permeability (L p), permeability coefficient (P S), and the reflection coefficient (σS) were determined to be 2.0 ± 0.63 μ m/(min-atm), 2.7E-5 ± 6.1E-6 cm-sec-1, and 0.76 ± 0.5 (N = 6). No previous values of these coefficients could be found for HBL-100 cells.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biomedical microdevices 2 (1999), S. 145-150 
    ISSN: 1572-8781
    Keywords: electroporation ; micro-electroporation chip ; cell membrane electrical currents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Electroporation is commonly used in biotechnology to introduce macromolecules into cells. We have developed a micro-electroporation chip that incorporates a live biological cell in the electrical circuit. The chip configuration forces electrical currents to pass through the cell, thereby producing electrically measurable information about the electroporation state of the cell. The cell membrane electrical properties make the cell function as a diode in the electroporation current-voltage range. The chip is transparent in the area of the cell to allow microscope viewing. during electroporation. This chip may be used to study the fundamental biophysics of cell electroporation and in biotechnology for controlled macromolecule introduction in individual cells. We describe the chip principle and show results on the electrical current-voltage pattern during reversible and irreversible electroporation in individual cells.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Breast cancer research and treatment 53 (1999), S. 185-192 
    ISSN: 1573-7217
    Keywords: breast cancer ; cryosurgery ; cellular freezing injury ; freezing damage ; surgical oncology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There is a growing interest in the use of cryosurgery to treat breast cancer, following recent breakthroughs in non-invasive imaging and in cryotechnology, as well as the recent success of cryosurgery in treating various types of cancer. However, since haphazard freezing does not guarantee tissue destruction, in order to apply this technique effectively it is essential to determine the thermal parameters that produce complete destruction of malignant tissue. This study seeks to quantitatively identify the relationship between thermal variables and the degree of freezing damage to human breast cancer cells. In order to do this, human breast cancer and normal cells were frozen with controlled thermal parameters using a directional solidification apparatus. Cell viability was determined after thawing using trypan blue, and correlated to the thermal variables used during freezing. Cellular damage is observed to increase with increasing cooling rates, due to the higher probability of intracellular ice formation. A double freeze thaw cycle significantly increases the extent of cell damage, and is sufficient to ensure complete cell destruction at final freezing temperatures of −40°c for a 25°c/min cooling rate, and −20°C for a 50°C/min cooling rate. The correlations between cell death and thermal parameters are qualitatively identical for all the cell types in this study, although there is some variation from one cell type to another in the overall susceptibility to freezing damage. The correlations established in this study can be used to design systematic and optimal breast cryosurgery protocols.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 2583-2607 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The objective of the research presented here was to develop a generic adaptive computational method for porous media evolution problems that involve coupled heat flow, fluid flow and species transport processes with sharply defined phase-change interfaces.In this paper we examine the general least squares variational approach and develop the conceptual framework for a rate least squares variational formulation of a continuously deforming mixed variable finite element method for solving highly non-linear time-dependent partial differential equations. In Part II of this paper1 we extend the formulation given here for a single evolution equation to a system of coupled evolution equations. In Part III2 we discuss in detail the numerical procedures that were implemented in a computer program and present several numerical examples that demonstrate the performance of this computational method.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 2609-2634 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The conceptual framework of a least squares rate variational approach to the formulation of continuously deforming mixed-variable finite element computational scheme for a single evolution equation was presented in Part I.1 In this paper (Part II), we extend these concepts and present an adaptively deforming mixed variable finite element method for solving general two-dimensional transport problems governed by a system of coupled non-linear partial differential evolution equations. In particular, we consider porous media problems that involve coupled heat and mass transport processes that yield steep continuous moving fronts, and abrupt, discontinuous, moving phase-change interfaces. In this method, the potentials, such as the temperature, pressure and species concentration, and the corresponding fluxes, are permitted to jump in value across the phase-change interfaces. The equations, and the jump conditions, governing the physical phenomena, which were specialized from a general multiphase, multiconstituent mixture theory, provided the basis for the development and implementation of a two-dimensional numerical simulator. This simulator can effectively resolve steep continuous fronts (i.e. shock capturing) without oscillations or numerical dispersion, and can accurately represent and track discontinuous fronts (i.e. shock fitting) through adaptive grid deformation and redistribution. The numerical implementation of this simulator and numerical examples that demonstrate the performance of the computational method are presented in Part III2 of this paper.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 2715-2760 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In Part I of this paper,1 the conceptual framework of a rate variational least squares formulation of a continuously deforming mixed-variable finite element method was presented for solving a single evolution equation. In Part II2 a system of ordinary differential equations with respect to time was derived for solving a system of three coupled evolution equations by the deforming grid mixed-variable least squares rate variational finite element method. The system of evolution equations describes the coupled heat flow, fluid flow and trace species transport in porous media under conditions when the flow velocities and constituent phase transitions induce sharp fronts in the solution domain. In this paper, we present the method we have adopted to integrate with respect to time the resulting spatially discretized system of non-linear ordinary differential equations. Next, we present computational results obtained using the code in which this deforming mixed finite element method was implemented. Because several features of the formulation are novel and have not been previously attempted, the problems were selected to exercise these features with the objective of demonstrating that the formulation is correct and that the numerical procedures adopted converge to the correct solutions.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 37 (1994), S. 1125-1141 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An inverse finite element method for solution of unknown multidimensional phase-change and material boundary shapes is presented. The method is based on minimization and requires boundary shape parametrization. The unknown boundary parameters are determined by minimizing the error between a limited number of known (e.g. measured) temperatures and the temperatures associated with the iteratively altered boundary. The algorithm presented is based on the multidimensional downhill simplex minimization method. The inverse method is illustrated and verified using a model of the plasma arc welding process. In particular, it is shown that the technique is capable of accurately determining a specified weld pool capillary interface shape using a limited number of simulated thermocouple measurements. The code's ability to determine the interface shape is investigated under various interface-thermocouple separations, using varying numbers of simulated thermocouples.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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