A Predictive Model for Steady State Ozone Concentration at an Urban-Coastal Site

Ground level ozone (O3) plays an important role in controlling the oxidation budget in the boundary layer and thus affects the environment and causes severe health disorders. Ozone gas, being one of the well-known greenhouse gases, although present in small quantities, contributes to global warming. In this study, we present a predictive model for the steady-state ozone concentrations during daytime (13:00–17:00) and nighttime (01:00–05:00) at an urban coastal site. The model is based on a modified approach of the null cycle of O3 and NOx and was evaluated against a one-year data-base of O3 and nitrogen oxides (NO and NO2) measured at an urban coastal site in Jeddah, on the west coast of Saudi Arabia. The model for daytime concentrations was found to be linearly dependent on the concentration ratio of NO2 to NO whereas that for the nighttime period was suggested to be inversely proportional to NO2 concentrations. Knowing that reactions involved in tropospheric O3 formation are very complex, this proposed model provides reasonable predictions for the daytime and nighttime concentrations. Since the current description of the model is solely based on the null cycle of O3 and NOx, other precursors could be considered in future development of this model. This study will serve as basis for future studies that might introduce informing strategies to control ground level O3 concentrations, as well as its precursors’ emissions

A Predictive Model for Steady State Ozone Concentration at an Urban-Coastal Site

Ground level ozone (O-3) plays an important role in controlling the oxidation budget in the boundary layer and thus affects the environment and causes severe health disorders. Ozone gas, being one of the well-known greenhouse gases, although present in small quantities, contributes to global warming. In this study, we present a predictive model for the steady-state ozone concentrations during daytime (13:00-17:00) and nighttime (01:00-05:00) at an urban coastal site. The model is based on a modified approach of the null cycle of O-3 and NOx and was evaluated against a one-year data-base of O-3 and nitrogen oxides (NO and NO2) measured at an urban coastal site in Jeddah, on the west coast of Saudi Arabia. The model for daytime concentrations was found to be linearly dependent on the concentration ratio of NO2 to NO whereas that for the nighttime period was suggested to be inversely proportional to NO2 concentrations. Knowing that reactions involved in tropospheric O-3 formation are very complex, this proposed model provides reasonable predictions for the daytime and nighttime concentrations. Since the current description of the model is solely based on the null cycle of O-3 and NOx, other precursors could be considered in future development of this model. This study will serve as basis for future studies that might introduce informing strategies to control ground level O-3 concentrations, as well as its precursors' emissions.Peer reviewe

A Predictive Model for Steady State Ozone Concentration at an Urban-Coastal Site

Ground level ozone (O3) plays an important role in controlling the oxidation budget in the boundary layer and thus affects the environment and causes severe health disorders. Ozone gas, being one of the well-known greenhouse gases, although present in small quantities, contributes to global warming. In this study, we present a predictive model for the steady-state ozone concentrations during daytime (13:00–17:00) and nighttime (01:00–05:00) at an urban coastal site. The model is based on a modified approach of the null cycle of O3 and NOx and was evaluated against a one-year data-base of O3 and nitrogen oxides (NO and NO2) measured at an urban coastal site in Jeddah, on the west coast of Saudi Arabia. The model for daytime concentrations was found to be linearly dependent on the concentration ratio of NO2 to NO whereas that for the nighttime period was suggested to be inversely proportional to NO2 concentrations. Knowing that reactions involved in tropospheric O3 formation are very complex, this proposed model provides reasonable predictions for the daytime and nighttime concentrations. Since the current description of the model is solely based on the null cycle of O3 and NOx, other precursors could be considered in future development of this model. This study will serve as basis for future studies that might introduce informing strategies to control ground level O3 concentrations, as well as its precursors’ emissions

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

Développement des nouveaux systèmes redox pour la polymérisation radicalaire

La polymérisation radicalaire redox (RFRP) est une technique courante utilisée dans la production de polymères en raison de son applicabilité dans des conditions douces (température ambiante, sous air). La stratégie est basée sur le mélange de 2 composants (2K comme abréviation de système à deux cartouches) contenant respectivement un agent oxydant et un agent réducteur.La polymérisation redox est une technique facilement industrialisable et peu énergivore (réaction à température ambiante qui se produit sans stimuli extérieurs (ni activation thermique, ni photochimique…)). De ce fait, ce procédé de polymérisation « vert » s’inscrit parfaitement dans une politique mondiale de développement durable. Ce procédé présente un second avantage, il permet l’obtention de taux de conversion élevés dans les couches profondes du matériau indépendamment de la présence de renforts (fibres, charges, …) ou d’une quelconque opacité. C’est pourquoi les systèmes redox sont déjà largement utilisés dans les revêtements, les composites et les biomatériaux (dentisterie). Cependant au jour d’aujourd’hui, les systèmes redox à base de peroxyde et d’amine (comme agents oxydants et réducteurs respectivement) dominent le marché. L’utilisation de ces composés, bien qu’extrêmement efficaces, présente de nombreux inconvénients (Toxicité avérée, instabilité, explosivité …). En conséquence, ce projet de doctorat a été pensé dans le but de fournir de nouveaux systèmes d'amorçage (Redox ou photo redox) plus sûrs et respectueux de l’environnement.Redox radical polymerization (RFRP) is a common technique used in the production of polymers due to its applicability under mild conditions (room temperature, in air). The strategy is based on the mixture of 2 components (2K as an abbreviation of two-cartridge system) containing respectively an oxidizing agent and a reducing agent.Redox polymerization is a technique that can be easily industrialized and does not consume much energy (reaction at room temperature which occurs without external stimuli (no thermal or photochemical activation, etc.)). As a result, this "green" polymerization process fits perfectly into a global policy of sustainable development. This process has a second advantage, it allows high conversion rates to be obtained in the deep layers of the material regardless of the presence of reinforcements (fibers, fillers, etc.) or of any opacity. This is why redox systems are already widely used in coatings, composites and biomaterials (dentistry).However today, peroxide and amine based redox systems (as oxidizing and reducing agents respectively) dominate the market. The use of these compounds, although extremely effective, has many drawbacks (proven toxicity, instability, explosiveness, etc.). Consequently, this doctoral project has been designed with the aim of providing new initiation systems (Redox or photo redox) that are safer and more environmentally friendly

Développement des nouveaux systèmes redox pour la polymérisation radicalaire

Redox radical polymerization (RFRP) is a common technique used in the production of polymers due to its applicability under mild conditions (room temperature, in air). The strategy is based on the mixture of 2 components (2K as an abbreviation of two-cartridge system) containing respectively an oxidizing agent and a reducing agent.Redox polymerization is a technique that can be easily industrialized and does not consume much energy (reaction at room temperature which occurs without external stimuli (no thermal or photochemical activation, etc.)). As a result, this "green" polymerization process fits perfectly into a global policy of sustainable development. This process has a second advantage, it allows high conversion rates to be obtained in the deep layers of the material regardless of the presence of reinforcements (fibers, fillers, etc.) or of any opacity. This is why redox systems are already widely used in coatings, composites and biomaterials (dentistry).However today, peroxide and amine based redox systems (as oxidizing and reducing agents respectively) dominate the market. The use of these compounds, although extremely effective, has many drawbacks (proven toxicity, instability, explosiveness, etc.). Consequently, this doctoral project has been designed with the aim of providing new initiation systems (Redox or photo redox) that are safer and more environmentally friendly.La polymérisation radicalaire redox (RFRP) est une technique courante utilisée dans la production de polymères en raison de son applicabilité dans des conditions douces (température ambiante, sous air). La stratégie est basée sur le mélange de 2 composants (2K comme abréviation de système à deux cartouches) contenant respectivement un agent oxydant et un agent réducteur.La polymérisation redox est une technique facilement industrialisable et peu énergivore (réaction à température ambiante qui se produit sans stimuli extérieurs (ni activation thermique, ni photochimique…)). De ce fait, ce procédé de polymérisation « vert » s’inscrit parfaitement dans une politique mondiale de développement durable. Ce procédé présente un second avantage, il permet l’obtention de taux de conversion élevés dans les couches profondes du matériau indépendamment de la présence de renforts (fibres, charges, …) ou d’une quelconque opacité. C’est pourquoi les systèmes redox sont déjà largement utilisés dans les revêtements, les composites et les biomatériaux (dentisterie). Cependant au jour d’aujourd’hui, les systèmes redox à base de peroxyde et d’amine (comme agents oxydants et réducteurs respectivement) dominent le marché. L’utilisation de ces composés, bien qu’extrêmement efficaces, présente de nombreux inconvénients (Toxicité avérée, instabilité, explosivité …). En conséquence, ce projet de doctorat a été pensé dans le but de fournir de nouveaux systèmes d'amorçage (Redox ou photo redox) plus sûrs et respectueux de l’environnement

USE OF PROVISIONAL SUMS IN THE UAE CONSTRUCTION INDUSTRY: AN EMPIRICAL STUDY

Provisional sums are widely used in the FIDIC (Red Book) forms of contract in the UAE construction industry. The practices on dealing with provisional sums have exposed the contracting parties to a number of risks. Therefore, this research aimed at identifying such risks and mitigation measures to limit such risks in using provisional sums in the UAE. The research started with a comprehensive literature review followed by a questionnaire survey among the UAE construction industry professionals. Based on the survey findings, six semi-structured interviews were conducted with expertise in the construction industry to verify the survey findings and close any gaps in the data. The study found that provisional sums are mainly used in the FIDIC (Red Book) forms of contract in the UAE for special works, contingencies, the works which can be only defined in the site, facilitating the appointment of nominated subcontractors and overlapping design and construction. The most common risks of using provisional sums are related to claims, variations and conflicts among the contracting parties. Defining the scope of provisional sums before tendering, incorporating the provisional sums into the project programme and limit the value of provisional sums in the contract are suggested as the key measures to minimize the risk of provisional measures

High Performance Redox Initiating Systems Based on the Interaction of Silane with Metal Complexes: A Unique Platform for the Preparation of Composites

International audienceCurrently, Redox Initiating Systems (RISs) of Free Radical Polymerization (FRP) are mainly based on the interaction of aromatic amines with peroxides (e.g., dibenzoyl peroxide (BPO)) that can be both toxic and unstable. In the present work, we aim to replace these hazardous substances in new RIS that can be peroxide-free and amine-free. Our redox two components (2K) initiating system is based on diphenylsilane (DPS) as reducing agent combined with different metal complexes (Mn(acac) 2 , Cu(AAEMA) 2 or Fe(acac) 3) as oxidizing agents. For the new proposed RIS, an excellent reactivity is found for the polymerization of benchmark methacrylate monomers under mild conditions (redox polymerization done under air and at room temperature); remarkably, it is also possible to finely control the gel time. Different techniques (optical pyrometry, Real-Time FTIR spectroscopy, Cyclic Voltammetry and Electron Spin Resonance (ESR)) were used to follow the polymerization processes but also to shed some light on the new redox chemical mechanisms

Carbazole-based compounds as photoinitiators for free radical and cationic polymerization upon near visible light illumination

International audienceSix new carbazole based compounds (Ca1-Ca6) are synthesized and proposed as high performance photoinitiators with iodonium salt (iod) and/or an amine (EDB) for both the free radical polymerization (FRP) of acrylates and the cationic polymerization (CP) of epoxides upon near UV and visible light exposure using light emitting diodes (LEDs) @385 nm and @405 nm. Excellent polymerization initiating abilities are found and high final reactive function conversions are acquired. A full picture of the involved photochemical mechanisms is given