Vaccination coverage against COVID-19 in a Tunisian general hospital

Lettor to the editor

Variability of Acid-Base Status in Acetate-Free Biofiltration 84&#x0025; <i>versus </i>Bicarbonate Dialysis

The ultimate goal of hemodialysis (HD) treatment is to achieve the highest level of efficacy in the presence of maximal clinical tolerance. With an aim to offer good hemodynamic stability, as observed during the acetate-free biofiltration 14&#x0025; (AFB 14&#x0025;) to patients who are intolerant to bicarbonate dialysis (BD) and with less cost, we have developed since June 1994, a new HD technique, namely AFB 84&#x0025;. This study was carried out to analyze acid-base variations during the AFB 84&#x0025; in comparison to BD in hemodynamically stable patients on regular HD. This was a prospective randomized crossover study carried out on 12 patients (6 males and 6 females) for a total of 144 HD sessions (72 BD and 72 AFB <i>84&#x0025;). </i>Patients with decompensated cardiomyopathy, respiratory diseases or uncontrolled hypertension were not included in the trial. All the patients were treated with BD or AFB <i>84&#x0025;; </i>the latter is characterized by the absence of acetate in the dialysate and a complete correction of buffer balance by post-dilutional infusion of bicarbonate-based replacement solution. The comparison of pre-dialysis arterial acid-base and blood-gas parameters revealed no significant differences of pH, HCO₃^- and paCO₂ levels between the two techniques. Analysis of post-dialysis parameters showed that, among patients dialyzed with BD, there was over correction of metabolic acidosis with a tendency towards metabolic alkalosis. In contrast, in patients dialyzed with AFB <i>84&#x0025;, </i>we observed a significant improvement in pH and HCO₃^- levels but the increase in paCO2</sub> level was not significant. A comparison of these parameters between the two techniques showed statistically significant difference in pH, HCO3^- and paCO2</sub> levels, but not for paO2 level. AFB <i>84&#x0025; </i>can offer some important advantages with the complete absence of acetate from the substitution fluids, and permits a better correction of metabolic acidosis than BD, without causing alkalosis

An Artificially Intelligent Technique to Generate Synthetic Geomechanical Well Logs for the Bakken Formation

Artificially intelligent and predictive modelling of geomechanical properties is performed by creating supervised machine learning data models utilizing artificial neural networks (ANN) and will predict geomechanical properties from basic and commonly used conventional well logs such as gamma ray, and bulk density. The predictive models were created by following the approach on a large volume of data acquired from 112 wells containing the Bakken Formation in North Dakota. The studied wells cover a large surface area of the formation containing the five main producing counties in North Dakota: Burke, Mountrail, McKenzie, Dunn, and Williams. Thus, with a large surface area being analyzed in this research, there is confidence with a high degree of certainty that an extensive representation of the Bakken Formation is modelled, by training neural networks to work on varying properties from the different counties containing the Bakken Formation in North Dakota. Shear wave velocity of 112 wells is also analyzed by regression methods and neural networks, and a new correlation is proposed for the Bakken Formation. The final goal of the research is to achieve supervised artificial neural network models that predict geomechanical properties of future wells with an accuracy of at least 90% for the Upper and Middle Bakken Formation. Thus, obtaining these logs by generating it from statistical and artificially intelligent methods shows a potential for significant improvements in performance, efficiency, and profitability for oil and gas operators

Integrated inventory ranking system for oilfield equipment industry

Purpose: This case study is motivated by the subcontracting problem in an oilfield equipment and service company where the management needs to decide which parts to manufacture in-house when the capacity is not enough to make all required parts. Currently the company is making subcontracting decisions based on management’s experience. Design/methodology/approach: Working with the management, a decision support system (DSS) is developed to rank parts by integrating three inventory classification methods considering both quantitative factors such as cost and demand, and qualitative factors such as functionality, efficiency, and quality. The proposed integrated inventory ranking procedure will make use of three classification methods: ABC, FSN, and VED. Findings: An integration mechanism using weights is developed to rank the parts based on the total priority scores. The ranked list generated by the system helps management to identify about 50 critical parts to manufacture in-house. Originality/value: The integration of all three inventory classification techniques into a single system is a unique feature of this research. This is important as it provides a more inclusive, big picture view of the DSS for management’s use in making business decisions

Hybrid Imperialist Competitive and Grey Wolf Algorithm to Solve Multiobjective Optimal Power Flow with Wind and Solar Units

The optimal power flow (OPF) module optimizes the generation, transmission, and distribution of electric power without disrupting network power flow, operating limits, or constraints. Similarly to any power flow analysis technique, OPF also allows the determination of system&rsquo;s state of operation, that is, the injected power, current, and voltage throughout the electric power system. In this context, there is a large range of OPF problems and different approaches to solve them. Moreover, the nature of OPF is evolving due to renewable energy integration and recent flexibility in power grids. This paper presents an original hybrid imperialist competitive and grey wolf algorithm (HIC-GWA) to solve twelve different study cases of simple and multiobjective OPF problems for modern power systems, including wind and photovoltaic power generators. The performance capabilities and potential of the proposed metaheuristic are presented, illustrating the applicability of the approach, and analyzed on two test systems: the IEEE 30 bus and IEEE 118 bus power systems. Sensitivity analysis has been performed on this approach to prove the robustness of the method. Obtained results are analyzed and compared with recently published OPF solutions. The proposed metaheuristic is more efficient and provides much better optimal solutions

Comparative study of perdialytic volemia variability in chronic dialysis patients between acetate- free biofiltration and bicarbonate hemodialysis

We have developed since 1994 a new hemodialysis (HD) technique called acetate biofiltration 84% (AFB 84%) that is characterized by the absence of acetate in the dialysate and the complete correction of buffer balance by post- dilutional infusion of bicarbonate- based replacement solution. Our study aimed to compare the variability of perdialytic volemia [net ultrafiltration (UF) rate, total UF, Δweight (T4- T0)] during AFB 84% and bicarbonate dialysis (BD) for stable chronic hemodynamic patients. This was a prospective crossover study carried out on 14 patients for a total of 168 HD sessions (84 AFB 84% and 84 BD). Optical measurement of hemoglobin (Hb) concentration was incorporated into the dialysis monitor to allow the study of the relative blood volume. For both techniques, Hb measured by Hemoscan® correlated well with the laboratory measurements. Moreover, the comparison of the averages of the different indicators of the perdialytic volemia did not disclose any significant statistical differences. Nevertheless, the comparison of the variability of perdialytic volemia between both techniques showed less Δ volemia (T4- T0) during the AFB 84% than the BD (- 7.909% for BD and - 6.960% for ABF 84%, P = 0.0036). We conclude that the absence of acetate and maintaining an optimal osmolarity at the origin of a better plasma refilling rate are key factors that make AFB 84% a technique assuring a better perdialyitic hemodynamic tolerance in comparison with BD in chronic HD patients