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91.
Modifications to bicarbonate conductivity: A way to increase phosphate removal during hemodialysis? Proof of concept
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Jean‐Philippe Bertocchio Médérick Mohajer Khaled Gaha Laurent Ramont Hervé Maheut Philippe Rieu 《Hemodialysis international. International Symposium on Home Hemodialysis》2016,20(4):601-609
Introduction Hyperphosphatemia and cardiovascular mortality are associated particularly with end‐stage renal disease. Available therapeutic strategies (i.e., diet restriction, calcium [or not]‐based phosphate binders, calcimimetics) are associated with extrarenal blood purification. Compartmentalization of phosphate limits its depuration during hemodialysis. Several studies suggest that plasmatic pH is involved in the mobilization of phosphate from intracellular to extracellular compartments. Consequently, the efficiency of modified bicarbonate conductivity to purify blood phosphate was tested. Methods Ten hemodialysis patients with chronic hyperphosphatemia (>2.1 mmol/L) were included in the two three–sessions‐per week periods. Bicarbonate concentration was fixed at 40 mmol/L and 30 mmol/L in the first and second periods, respectively. Phosphate depuration was evaluated by phosphate mobilization clearance (KM). Findings Although bicarbonatemia was lower during the second period (21.0 ± 2.7 vs. 24.4 ± 3.1 mmol/L, P < 0.01), no difference was observed in phosphatemia (2.4 ± 0.5 vs. 2.3 ± 0.4 mmol/L, P = NS). The in‐session variation of phosphate was lower (?1.45 ± 0.42 vs. ?1.58 ± 0.44 mmol/L, P < 0.05) and KM was higher during the second period (82.94 ± 38.00 vs. 69.74 ± 24.48 mL/min, P < 0.05). Discussion The decrease of in‐session phosphate and the increase in KM reflect phosphate refilling during hemodialysis. Thus, modulation of serum bicarbonate may play a role in controlling the phosphate pool. Even though correcting metabolic acidosis during hemodialysis remains important, alkaline excess can impair phosphate mobilization clearance. Clinical trials are needed to test the efficiency and relevance of a strategy where bicarbonatemia is corrected less at the beginning of sessions. 相似文献
92.
A new approach of direct adaptive control of single input single output nonlinear systems in affine form using single-hidden layer neural network (NN) is introduced. In contrast to the algorithms in the literature, the weights adaptation laws are based on the control error and not on the tracking error or its filtered version. Since the control error is being expressed in terms of the NN controller, hence its weights updating laws are obtained via back-propagation concept. A fuzzy inference system (FIS) with heuristically defined rules is introduced to provide an estimate of this error based on the past history of the system behaviour. The stability of the closed loop is studied using Lyapunov theory. A fixed structure is then proposed for the FIS and the design parameters reduce to the parameters of the NN. The method is reproducible and does not require any pre-training of the network weights. 相似文献
93.
In this paper, the equations of motion for a general multi-link inverted pendulum system are derived. Assumptions previously employed to simplify such formulation are removed. The pendulum system is more general and includes nonlinear friction terms to suit various engineering applications. The generalized equations are first developed in the absolute coordinate system using Lagrange's technique, then a simple linear transformation is proposed to obtain the set of nonlinear equations in the DevanitHartenberg coordinate system. The equations of motion for double and triple link inverted pendulum systems are given as examples for such dynamics equations. 相似文献
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The reaction process of polycarbosilane (PCS) fiber cured by cyclohexene vapor has been studied and compared with that of PCS fiber cured by air. The influence of curing temperature on Si? H bond reaction degree and gel content, the structure and composition of PCS were investigated by FTIR, EA, TGA, NMR, and GC‐MS. The results showed that, Si? H bond in the molecular structure of PCS reacted during cyclohexene curing process and the reaction degree increased when the curing temperature increases. Simultaneously, gel content of PCS fiber rapidly increased till PCS fiber became infusible. Si? H radical and Si? CH2 radicals formed Si? CH2? Si crosslinking of PCS molecules through the agency of cyclohexene. Some cyclohexyls linked to principal chain of PCS, which was proven by 13C‐CPMAS‐NMR, and broke off, and cyclohexane and some monosilane are generated as byproducts when temperature increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
96.
The corrosion inhibition and adsorption characteristics of three selected imidazole derivatives namely, 2-amino-4,5-imidazoledicarbonitril
(AID), 5-amino-4-imidazolecarboxamide (AIC) and imidazole (IM) on aluminum in 1.0 M HCl was investigated at 25 °C. Measurements
were carried out under various experimental conditions using chemical (weight loss), and electrochemical (Tafel polarization
and impedance) methods. Molecular dynamics (MD) method and density functional theory were also applied here for theoretical
study. Results obtained showed that inhibition efficiency of these compounds increases with increase in their concentrations
due to the formation of a surface film on the aluminum surface. Adsorption energy as well as hydrogen bond length calculations
showed that AID was the best corrosion inhibitor among the tested imidazole derivatives. Polarization measurements reveal
that the selected imidazole derivatives function mainly as cathodic-type inhibitors. Physisorption, followed by chemisorption
was proposed as the mechanism for the inhibition process. Adsorption via H-bond formation was also considered here. Results
obtained from theoretical study were found to confirm experimental findings. 相似文献
97.
The corrosion behaviour of steel at various concentrations of perchloric acid was studied by weight loss method in temperature range from 298 to 323 K. Results obtained show that corrosiveness of acid increases with its concentration and temperature. The logarithm of corrosion rate was plotted against the acid concentration and values of Hammett Ho and Strehlow Ro(H) acidity functions. The activation energies, enthalpies and entropies of the corrosion process of steel were also determined and fitted against Ro(H). 相似文献
98.
99.
Khaled Ali Alfadhel 《Chemical engineering science》2005,60(11):2911-2926
We study the development of a mathematical model that describes isothermal microfluidic steady flow in a membrane microreactor, i.e., a silicon microreactor that houses a permeable membrane in one wall. The model employs the Navier-Stokes equation with appropriate boundary conditions for fluid permeation through the membrane and velocity slip at the walls to account for high Knudsen number. The model equations are solved analytically using finite Fourier transforms. The model solution is used to evaluate the effect of fluid permeation through the membrane and the Knudsen number on the velocity profile and pressure drop. For the simplified cases of no permeation and/or no slip, the derived solution is in excellent agreement with published experimental and theoretical results available in the literature. The utility of the model is illustrated by applying the results to a membrane microseparator used to separate hydrogen from the other effluents in a microreformer. 相似文献
100.