Impedance camera: a system for determining the spatial variation of electrical conductivity

A data collection and data interpretation method is presented for predicting, from measurements made on the periphery of the core sample, the electrical conductivity distribution within core samples. This method uses an array of electrodes on the periphery to probe through the core sample. Surprisingly accurate detail can be seen in the estimated conductivity distribution. This method has been demonstrated using synthetic examples modeled and analyzed on a computer. Extensions of the procedure may be useful in subsurface geophysical probing and remote probing methods using physical phenomena satisfying Laplace's equation

TOMOGRAPHIC INVERSION OF NORMALIZED DATA: DOUBLE-TRACE TOMOGRAPHY ALGORITHMS

Tomography is widely used in geophysics as a technique for imaging geological structures by means of data that are line integrals of physical characteristics. In some transmission measurements, due to various kinds of normalization, the measured data are related to two (the current and the reference) raypaths and can be expressed as a function of differences between line integrals. This is the case, for example, in seismo-acoustic emission measurements, when (since the exact start time is unknown) only the differences between traveltimes (differences between line integrals of the slowness) can be determined. Similarly the use of normalized Fourier amplitudes results in data dependent upon the difference between line integrals of the absorption coefficient (computed along the actual and the reference raypaths). In order to invert these data the ordinary tomography algorithms should be modified. Some generalizations are presented for series expansion tomography methods in order to make them applicable to reconstruction problems in which the input data are differences between two line integrals. The conjugate gradient and the simultaneous iterative reconstruction technique (SIRT) methods were adapted and tested. It is shown that the modified tomography algorithms are stable and sufficiently accurate for practical use. In the reconstruction of noise-free difference data, the conjugate gradient algorithm is found to be faster and more accurate while, in the case of noisy difference data, the modified SIRT algorithm is more stable and insensitive to noise

Convergence properties of ART and SOR algorithms

Elsner L, Koltracht I, Lancaster P. Convergence properties of ART and SOR algorithms. Numerische Mathematik. 1991;59(1):91-106.ART algorithms with relaxation parameters are studied for general (consistent or inconsistent) linear algebraic systems Rx = f, and a general convergence theorem is formulated. The advantage of severe underrelaxation is re-examined and clarified. The relationship to solutions obtained by applying SOR methods to the equation RR(T)y = f is investigated

Preclinical Models for Translating Regenerative Medicine Therapies for Rotator Cuff Repair

Despite improvements in the understanding of rotator cuff pathology and advances in surgical treatment options, repairs of chronic rotator cuff tears often re-tear or fail to heal after surgery. Hence, there is a critical need for new regenerative repair strategies that provide effective mechanical reinforcement of rotator cuff repair as well as stimulate and enhance the patient's intrinsic healing potential. This article will discuss and identify appropriate models for translating regenerative medicine therapies for rotator cuff repair. Animal models are an essential part of the research and development pathway; however, no one animal model reproduces all of the features of the human injury condition. The rat shoulder is considered the most appropriate model to investigate the initial safety, mechanism, and efficacy of biologic treatments aimed to enhance tendon-to-bone repair. Whereas large animal models are considered more appropriate to investigate the surgical methods, safety and efficacy of the mechanical—or combination biologic/mechanical—strategies are ultimately needed for treating human patients. The human cadaver shoulder model, performed using standard-of-care repair techniques, is considered the best for establishing the surgical techniques and mechanical efficacy of various repair strategies at time zero. While preclinical models provide a critical aspect of the translational pathway for engineered tissues, controlled clinical trials and postmarketing surveillance are also needed to define the efficacy, proper indications, and the method of application for each new regenerative medicine strategy