Water Soluble Derivatives of Camptothecin/Homocamptothecin

Camptothecin and homocamptothecin analogs and derivatives are provided incorporating alkylamine and polyalkylamine moieties

Simulation and evaluation of sustainable climate trajectories for aviation

In 2019, aviation was responsible for 2.6% of world CO2 emissions as well as additional climate impacts such as contrails. Like all industrial sectors, the aviation sector must implement measures to reduce its climate impact. This paper focuses on the simulation and evaluation of climate scenarios for air transport. For this purpose, a specific tool (CAST for “Climate and Aviation - Sustainable Trajectories”) has been developed at ISAE-SUPAERO. This tool follows a methodology for the assessment of climate impacts adapted to aviation. Firstly, models for the main levers of action, such as air traffic, aircraft energy consumption and energy decarbonization, are provided using trend projections from historical data or assumptions from the literature. Second, the evaluation of scenarios is based on aviation carbon budgets, which are also extended to non-CO2 effects using the concept of GWP*. Several scenario analyses are performed in this paper using CAST allowing different conclusions to be drawn. For instance, the modelling of the scenarios based on the more recent ATAG (Air Transport Action Group) commitments shows that aviation would consume 6.5% of the world carbon budget for +1.5 ◦C. Some illustrative scenarios are also proposed. By allocating 2.6% of the world carbon budget to aviation, it is shown that air transport is compatible with a +2 ◦C trajectory when the annual growth rate of air traffic varies between +1.8% and +2.9%, depending on the technological improvements considered. However, using the same methodology for a +1.5 ◦C trajectory shows that a drastic decrease in air traffic is necessary. Lastly, analyses including non- CO2 effects emphasize the importance of implementing specific strategies for mitigating contrails

Modeling and Design Optimization of an Electric Environmental Control System for Commercial Passenger Aircraft

The aircraft environmental control system (ECS) is the second-highest fuel consumer system, behind the propulsion system. To reduce fuel consumption, one research direction intends to replace conventional aircraft with more electric aircraft. Thus, new electric architectures have to be designed for each system, such as for the ECS. In this paper, an electric ECS is modeled and then sized and optimized for different sizing scenarios with the aim of minimizing fuel consumption at the aircraft level. For the system and for each component, such as air inlets and heat exchangers, parametric models are developed to allow the prediction of relevant characteristics. These models, developed in order to be adapted to aircraft design issues, are of different types, such as scaling laws and surrogate models. They are then assembled to build a preliminary sizing procedure for the ECS by using a multidisciplinary design analysis and optimization (MDAO) formulation. Results show that the ECS design is highly dependent on the sizing scenario considered. An approach to size the ECS globally with respect to all the sizing scenarios leads to an ECS that accounts for around 200 N of drag, 190 kW of electric power, and 1500 kg of mass for the CeRAS aircraft

Aircraft fleet models using a bottom-up approach for simulating aviation technological prospective scenarios

Modeling prospective scenarios for aviation in the context of climate issues is a scientific topic of major interest. For this purpose, the development of models to integrate technological improvements in these scenarios is necessary. This paper focuses on the use of a bottom-up approach to establish aircraft fleet models, in order to integrate them into CAST, an open-source tool for simulating and evaluating prospective scenarios for air transport. These models are based on logistic functions which allow representing the gradual replacement of current aircraft by future aircraft architectures obtained from overall aircraft design. The efficiency improvement of the aircraft fleet can then be assessed. To illustrate the use of the models, some case studies, considering for example turboprop and hydrogen aircraft, are performed for analyzing efficiency scenarios for air transport. Also, the effect of accelerated fleet renewal and earlier introduction of new aircraft architectures is studied

Sizing and optimization of a more electric aircraft integrating short-term incremental technologies

In order to reduce the environmental impact of aviation, one of the solutions is to develop more efficient aircraft. These gains can be achieved in different fields such as propulsion, aerodynamics or electrification of systems. This paper focuses on the sizing and optimization of BEITA, a short-medium range aircraft architecture available in the short term by 2025-2030. The aircraft is based on incremental technologies for propulsion, aerostructure and bleedless systems. Light-weight models are proposed for the different improvements, particularly for more electric systems. FAST-OAD, an open source framework for rapid overall aircraft design based on multidisciplinary design analysis and optimization, is used to size the new architecture and a specific life cycle assessment module is used to estimate the environmental impacts. BEITA allows a reduction in fuel consumption of 15% compared to the CeRAS reference aircraft. Optimizations of this architecture are achieved minimizing different cost functions. This study ends with a sizing on a shorter range based on specific payload-range diagrams

Mangrove Facies Drives Resistance and Resilience of Sediment Microbes Exposed to Anthropic Disturbance

Mangrove forests are coastal ecosystems continuously affected by various environmental stresses and organized along constraint gradients perpendicular to the coastline. The aim of this study was to evaluate the resistance and resilience of sediment microbial communities in contrasted vegetation facies, during and after exposure to an anthropic disturbance. Our hypothesis was that microbial communities should be the most stable in the facies where the consequences of the anthropic disturbance are the most similar to those of natural disturbances. To test this, we focused on communities involved in N-cycle. We used an in situ experimental system set up in Mayotte Island where 2 zones dominated by different mangrove trees are daily exposed since 2008 to pretreated domestic wastewater (PW) discharges. These freshwater and nutrients inputs should increase microbial activities and hence the anoxia of sediments. We monitored during 1 year the long-term impact of this disturbance, its short-term impact and the resilience of microbial communities on plots where PW discharges were interrupted. Microorganism densities were estimated by qPCR, the nitrification (NEA) and denitrification (DEA) enzyme activities were evaluated by potential activity measurements and pigment analyses were performed to assess the composition of microbial photosynthetic communities. At long-term PW discharges significantly modified the structure of phototrophic communities and increased the total density of bacteria, the density of denitrifying bacteria and DEA. Similar effects were observed at short-term, notably in the facies dominated by Ceriops tagal. The results showed a partial resilience of microbial communities. This resilience was faster in the facies dominated by Rhizophora mucronata, which is more subjected to tides and sediment anoxia. The higher stability of microbial communities in this facies confirms our hypothesis. Such information should be taken into account in mangrove utilization and conservation policies