The Urine Anion Gap: Common Misconceptions

Two papers, one in 1986 and another one in 1988, reported a strong inverse correlation between urinary anion gap (UAG) and urine ammonia excretion (UNH4) in patients with metabolic acidosis and postulated that UAG could be used as an indirect measure of UNH4. This postulation has persisted until now and is widely accepted. In this review, we discuss factors regulating UAG and examine published evidence to uncover errors in the postulate and the design of the original studies. The essential fact is that, in the steady state, UAG reflects intake of Na, K, and Cl. Discrepancy between intake and urinary output of these electrolytes (i.e., UAG) indicates selective extrarenal loss of these electrolytes or nonsteady state. UNH4 excretion, which depends, in the absence of renal dysfunction, mainly on the daily acid load, has no consistent relationship to UAG either theoretically or in reality. Any correlation between UAG and UNH4, when observed, was a fortuitous correlation and cannot be extrapolated to other situations. Furthermore, the normal value of UAG has greatly increased over the past few decades, mainly due to increases in dietary intake of potassium and widespread use of sodium salts with anions other than chloride as food additives. The higher normal values of UAG must be taken into consideration in interpreting UAG.

Electroplating of iron and its alloys

Analytical review of information on electrodeposition of iron and its alloys from aqueous solutions is carried out. Processes of electroplating of iron and its alloys from aqueous solutions and the principal fields of application of these galvanic coatings are discussed. The principal technological advantages of using iron coatings in the reconditioning of steel parts are considered. Compositions of electrolytes and conditions for plating of iron coatings are provided. Technological parameters of electroplating of iron from industrial electrolytes are considered. Data are presented on the effect of some organic additives on the iron plating process. The effect of the concentration of Fe3+ ions in iron plating electrolytes on electroplating of iron coatings and their physic-mechanical properties is discussed. The data are presented on physic-mechanical properties of iron coatings obtained in different electrolysis modes. Nonsteady-state electrolysis modes are discussed that are used in industry for application of iron coatings. The effect of coating plating conditions on their mechanical properties is studied. Technological parameters of electroplating of iron alloys are considered. Co-deposition of iron with nickel, chromium, titanium, phosphorus, molybdenum, vanadium and tungsten is described. Data are provided on compositions of electrolytes and conditions of electroplating of these alloys. Main fields of application of electroplated iron alloys are discussed. Information is provided.

Nonsteady-state mathematical modelling of H2SO4-catalysed alkylation of isobutane with alkenes

H2SO4-catalysed isobutane alkylation with alkenes is an important industrial process used to obtain high-octane alkylate. In this process, the concentration of H2SO4 is one of the main parameters. For alkylation, sulphuric acid containing 88%–98% monohydrate is typically used. However, only a H2SO4 concentration of 95%–96% enables alkylate with the maximum octane number to be obtained. Changes in H2SO4 concentration due to decontamination are the main cause of process variations. Therefore, it is necessary to maintain the reactor acid concentration at a constant level by regulating the supply of fresh catalyst and pumping out any spent acid. The main reasons for the decrease in the H2SO4 concentration are accumulation of high-molecular organic compounds and dilution by water. One way to improve and predict unsteady alkylation processes is to develop a mathematical model that considers catalyst deactivation. In the present work, the formation reactions of undesired substances were used in the description of the alkylation process, indicating the sensitivity of the prediction to H2SO4 activity variations. This was used for calculation the optimal technological modes ensuring the maximum selectivity and stability of the chemical–technological system under varying hydrocarbon feedstock compositions.

Gas exchange calculation may estimate changes in pulmonary blood flow during veno-arterial extracorporeal membrane oxygenation in a porcine model

Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is used as rescue therapy for severe cardiopulmonary failure. We tested whether the ratio of CO2 elimination at the lung and the V-A ECMO (V˙co2ECMO/V˙co2Lung) would reflect the ratio of respective blood flows and could be used to estimate changes in pulmonary blood flow (Q˙Lung), i.e., native cardiac output. Four healthy pigs were centrally cannulated for V-A ECMO. We measured blood flows with an ultrasonic flow probe. V˙co2ECMO and V˙co2Lung were calculated from sidestream capnographs under constant pulmonary ventilation during V-A ECMO weaning with changing sweep gas and/or V-A ECMO blood flow. If ventilation-to-perfusion ratio (V˙/Q˙) of V-A ECMO was not 1, the V˙co2ECMO was normalized to V˙/Q˙ = 1 (V˙co2ECMONorm). Changes in pulmonary blood flow were calculated using the relationship between changes in CO2 elimination and V-A ECMO blood flow (Q˙ECMO). Q˙ECMO correlated strongly with V˙co2ECMONorm ( r2 0.95–0.99). Q˙Lung correlated well with V˙co2Lung ( r2 0.65–0.89, P < = 0.002). Absolute Q˙Lung could not be calculated in a nonsteady state. Calculated pulmonary blood flow changes had a bias of 76 (−266 to 418) mL/min and correlated with measured Q˙Lung ( r2 0.974–1.000, P = 0.1 to 0.006) for cumulative ECMO flow reductions. In conclusion, V˙co2 of the lung correlated strongly with pulmonary blood flow. Our model could predict pulmonary blood flow changes within clinically acceptable margins of error. The prediction is made possible with normalization to a V˙/Q˙ of 1 for ECMO. This approach depends on measurements readily available and may allow immediate assessment of the cardiac output response.

Experimental Identification of Steady-State Turbomachinery Heat Transfer Using Nondimensional Groups

Diabatic performance modeling is a prerequisite for engine condition monitoring based on nonsteady-state data points (e.g., Putz et al. 2017, “Jet Engine Gas Path Analysis Based on Takeoff Performance Snapshots,” ASME J. Eng. Gas Turbines Power, 139(11), p. 111201.). The importance of diabatic effects increases with decreasing engine size. Steady-state diabatic modeling of turbomachinery components is presented using nondimensional parameters derived from a dimensional analysis. The resulting heat transfer maps are approximated using the analytic solution for a pipe. Experimental identification of the maps requires the measurement of casing and gas path temperatures. This approach is demonstrated successfully using a small turboshaft engine as a test vehicle. A limited amount of measurements was needed to generate a steady-state heat transfer map which is valid for a wide range of operating points.