PERFORMANCE DES MORTIERS ET BÉTONS A BASE DES CIMENTS CONTENANT DU METAKAOLIN ALGERIEN

L'utilisation des métakaolins obtenus à partir du traitement thermique du kaolin présente une solution très prometteuse pour la conception de bétons écologiques à faible empreinte en dioxyde de carbone et à hautes performances. Toutefois, le potentiel de cet ajout cimentaire et son comportement dans un milieu cimentaire sont encore peu étudiés à l’échelle nationale. Les principaux objectifs de cette thèse étaient d'évaluer les performances mécaniques et la durabilité des mortiers et bétons à base de ciment contenant du métakaolin fabriqué à partir de kaolin disponible localement utilisé comme additions minérales. Le métakaolin est une pouzzolane de synthèse, produite par déhydroxylation de l'argile kaolinite à des températures allant de 700 à 900 C °, à laquelle l'eau chimiquement liée est éliminée et la structure cristalline se transforme en un aluminosilicate amorphe déshydroxylé constitué de particules lamellaires. Ce matériau a fait l'objet de nombreuses études de la communauté scientifique en raison de ses effets bénéfiques sur le développement des propriétés mécaniques et sur la durabilité du béton. La première partie, de cette étude a été consacrée à l’impacte de ce matériau sur les propriétés physico - mécanique de liant et mortier. Les résultats obtenus ont montré un effet moins perceptible de MK sur la prise de ciment, et une augmentation, significatif de la demande en eau et en superplastifiant pour a voir la même propriété rhéologique que celle du mortier et béton de référence, et une amélioration remarquable des performances mécaniques du mortier et béton. Concernant les questions de durabilité de béton, liées à certain facteurs qui le dégrade, il a fait l’objet de la deuxième partie et a permis de mettre en évidence l’effet positif du MK sur la réduction de retrait de séchage, et l’amélioration de la résistance de béton aux sulfates. En revanche, les résultats d’étude ont montré une augmentation de la profondeur de carbonatation et une résistance moindre à l’acide sulfurique en comparant à celle du béton sans MK. L’étude de la microstructure de béton a permis d’évaluer d’avantage les mécanismes d’actions du métakaolin. Les résultats d’analyses ont permis de mise en évidence le rôle de l’effet pouzzolanique du métakaolin, et sa contribution à la densification de la structure et l’amélioration des propriétés mécaniques et la durabilité du béton

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Background: Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. // Methods: We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung's disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. // Findings: We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung's disease) from 264 hospitals (89 in high-income countries, 166 in middle-income countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in low-income countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. // Interpretation: Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between low-income, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Etude de l’influence de l’ajout du sable de dune et le laitier granulé finement broyés au ciment sur la stabilité de béton

Ce travail porte sur l’étude de l’influence de l’ajout du sable de dune et le laitier granulé finement broyés au ciment sur la stabilité de béton , Les résultats obtenus à travers cette étude démontrent que l’ajout du sable de dune et du laitier granulé finement broyés au ciment contribuent positivement à l’amélioration des propriétés mécaniques, lorsque le sable de dune et le laitier introduit en proportions (5% et 15%) respectivement et offrent une meilleure stabilité au ciment vis-à-vis aux agressions chimiques, et une meilleure stabilité volumétrique au gonflement. Les résultats obtenus par contre montrent que les mortiers à base de ciment avec ajout de sable de dune et de laitier développent un retrait de séchage légèrement plus élevé que celui de mortier a base de ciment sans ajout (mortier de référence), aussi bien que la substitution du ciment par 5% du sable de dune et 15% du laitier à amélioré l’imperméable du béton à l’eau, par contre augmente l’absorption du béton à l’eau. Ainsi que les déformations transversales au bien longitudinales sont d’ordre inférieur pour le béton à base de ciment avec ajout de sable de dune et laitier (5%S, 15%L) que le béton sans ajout

EVALUATION OF THE MECHANICAL PROPERTIES AND DURABILITY OF CEMENT MORTARS CONTAINING ALGERIAN METAKAOLIN

This study shows the results of an examination on the use of metakaolin (MK) as an additional cementing material to improve the mechanical properties and durability of cement paste and mortar. For MK replacement levels were employed in the study: 5%, 10%, 15% and 20% by weight of the Portland cement used. Three series of paste mixture were designed at three water-cementations materials (w/cm) ratios of 0.25, 0.30 and 0.40. The performance characteristics of the paste and mortars were evaluated by measuring compressive, drying shrinkage, and swelling. The sulfate resistance of the mortar was also examined in the present study. The results showed that the inclusion of MK exceptionally reduced the drying shrinkage strain and excellent performance of swelling, but increased the strengths of the cement paste in differing degrees, depending principally on the MK substitution levels, w/cm ratio, and age of testing. It was also affirmed that the MK provided an excellent improvement in resistance to the sulfate sodium (Na₂SO₄), especially for the high- level MK replacement

Thermal-hydraulic behavior of physical quantities at critical velocities in a nuclear research reactor core channel using plate type fuel

The thermal-hydraulic study presented here relates to a channel of a nuclear reactor core. This channel is defined as being the space between two fuel plates where a coolant fluid flows. The flow velocity of this coolant should not generate vibrations in fuel plates. The aim of this study is to know the distribution of the temperature in the fuel plates, in the cladding and in the coolant fluid at the critical velocities of Miller, of Wambsganss, and of Cekirge and Ural. The velocity expressions given by these authors are function of the geometry of the fuel plate, the mechanical characteristics of the fuel plate’s material and the thermal characteristics of the coolant fluid. The thermal-hydraulic study is made under steady-state; the equation set-up of the thermal problem is made according to El Wakil and to Delhaye. Once the equation set-up is validated, the three critical velocities are calculated and then used in the calculations of the different temperature profiles. The average heat flux and the critical heat flux are evaluated for each critical velocity and their ratio reported. The recommended critical velocity to be used in nuclear channel calculations is that of Wambsganss. The mathematical model used is more precise and all the physical quantities, when using this critical velocity, stay in safe margins

Co-inhibitory receptors in female asthmatic patients: Correlation with IL-17 and IL-26

Background: Asthma is an immunological disorder in which T helper 2 (Th2)-type cells and inflammatory cytokines have a prominent role in its pathogenesis. B- and T-lymphocyte attenuator (BTLA), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed death 1 (PD-1) are co-inhibitory receptors that regulate T cell activation. Objective: In the present study of asthmatic patients we measured the soluble isoforms of BTLA (sBTLA), CTLA-4 (sCTLA-4) and PD-1 (sPD-1) in induced sputum fluid with the aim to evaluate their utility as responsible for exacerbation. Methods: Eighty patients with asthma and 30 healthy controls (HC) were included in the study. Sputum fluid concentrations of sBTLA, sCTLA-4 and sPD-1 were measured with ELISA. Comparisons were made with Mann-Whitney U test and correlations with IL-17, IL-26 levels and FEV1 (%) were assessed with Spearman’s Rank correlation test. Results: sBTLA levels were significantly higher in the severe and moderate asthmatic patients compared to healthy controls. Significant differences were observed between severe and moderate asthmatics (p &lt; 0.0001). No significant differences were found between mild asthmatics and healthy controls (p = 0.799). Soluble PD-1 levels were higher in severe and moderate asthmatic patients compared to HC and no significant difference was observed between these two asthmatic groups (p = 0.124). Mild asthmatics and control subjects expressed similar sPD-1 levels (p = 0.856). Soluble CTLA-4 was exclusively expressed in certain severe asthmatic patients. IL-17 inflammatory cytokine was significantly correlated with BTLA and sPD-1. IL-17 and IL-26 cytokines were highly expressed in sputum asthmatic groups compared to sputum from HC. Severe asthmatic group was characterized by the highest levels of both IL-17 and IL-26 mediators. Soluble BTLA correlates positively with IL-17 (r = 0.817; p &lt; 0.0001) and IL-26 (r = 0.805; p &lt; 0.0001) inflammatory cytokines. IL-17 and IL-26 levels were associated with the asthma clinical severity from severe to mild asthma (p &lt; 0.0001). The inflammatory cytokines IL-17 and IL-26 were positively correlated with the percentages of macrophages, PNN and FEV1 (%). Conclusion: Here, we provide the first report on the increased expression of sBTLA and sPD-1 in induced sputum of severe asthmatics. IL-26 and IL-17 appeared as a novel proinflammatory axis. Both sBTLA and sPD-1 might be involved in the pathogenesis of asthma and were associated with a poor prognosis