ABSTRACT
The aim of this study was to present a methodology for predicting changes in uric acid concentrations in the blood of chronically hemodialyzed patients based on an optical measurement of the intensity of selected wavelengths in the dialysate. Blood samples were taken from the arterial line every 30 min throughout the hemodialysis period, to measure uric acid levels. Simultaneously, optical measurements were made on dialysate flowing from the dialyzer. Uric acid concentration can be measured either directly from the blood or from dialyzer outflow with acceptable error. In addition, both methods reveal any increased dynamics in uric acid concentration in the initial phase of hemodialysis. The wavelength of the light was adjusted for optimal uric acid particle detection. Comparing the uric acid concentration measured in the blood of patients with the intensity of wave absorption in the dialysate, the functional relationship between the uric acid concentration levels was determined. Using the optical method for measuring uric acid concentration in the dialysate, the concentration of uric acid in the blood during hemodialysis can be non-invasively and accurately estimated. This method can be used to assess the adequacy of hemodialysis by computer acquisition of uric acid concentrations determined in on-line dialysate.
Subject(s)
Dialysis Solutions , Vascular Access Devices , Humans , Uric Acid , Renal DialysisABSTRACT
The problem of sound transmission through an annular aperture with perfectly rigid walls and located in a hard infinite baffle was solved analytically. The three separated regions with suitable boundary conditions were considered. There are two regions for the upper and the lower half spaces and one for the aperture. The solutions to the Helmholtz equation in each region and the continuity conditions were satisfied. The rigorous formulations describing the acoustic pressure and the transmitted and scattered acoustic powers were obtained. The obtained solutions resulted in the derivation of the modal coupling coefficients in the form of infinite integrals. The spectral mapping technique based on the Zernike circle polynomials was adopted for the annular geometry. The modal coupling impedances were presented in the form of a rapidly convergent expansion series. Finally, high accuracy and time efficiency were achieved. The problem of sound scattering and transmission through a circular aperture could be generalized for the annular aperture.
ABSTRACT
This study deals with sound radiation from a thin clamped annular plate. The fluid loading effect is included. Although it is a classical problem, using direct numerical integration to solve such a problem is usually troublesome and time consuming since the coupling integrals have certain singularities. Therefore, this study applies radial polynomials to improve the time efficiency of numerical calculations with no loss of accuracy. As radial polynomials are usually used for circular geometry, spectral mapping has been proposed to perform the necessary conversion from circular to annular geometry. The conversion is performed in the wavenumber domain. Spectral mapping makes it possible to efficiently obtain a number of numerical results for the acoustic power and acoustic field generated.
ABSTRACT
The modal low frequency noise generated by a vibrating elastically supported circular plate embedded into a flat infinite baffle has been examined. The main aim of this study is the analysis of the radiation efficiency. Low frequency approximated formulas have been presented. They are valid for all the limiting boundary conditions of the plate with its edge clamped, guided, simply supported or free as well as for all the intermediate axisymmetric boundary configurations. The formulas are expressed in the elementary form, useful for numerical computations. They are a generalization of some earlier published results. First, they are valid for axisymmetric and asymmetric modes since both kinds of modes play an important role in the low frequency range. Second, a single formula for the radiation efficiency, valid for all the axisymmetric boundary configurations, has been proposed. A numerical example for the sound power radiation has been given for some hatchway covers mounted on a ship deck.