Airborne forward pointing UV Rayleigh lidar for remote clear air turbulence (CAT) detection: system design and performance

A high-performance airborne UV Rayleigh lidar system was developed within the European project DELICAT. With its forward-pointing architecture it aims at demonstrating a novel detection scheme for clear air turbulence (CAT) for an aeronautics safety application. Due to its occurrence in clear and clean air at high altitudes (aviation cruise flight level), this type of turbulence evades microwave radar techniques and in most cases coherent Doppler lidar techniques. The present lidar detection technique relies on air density fluctuations measurement and is thus independent of backscatter from hydrometeors and aerosol particles. The subtle air density fluctuations caused by the turbulent air flow demand exceptionally high stability of the setup and in particular of the detection system. This paper describes an airborne test system for the purpose of demonstrating this technology and turbulence detection method: a high-power UV Rayleigh lidar system is installed on a research aircraft in a forward-looking configuration for use in cruise flight altitudes. Flight test measurements demonstrate this unique lidar system being able to resolve air density fluctuations occurring in light-to-moderate CAT at 5 km or moderate CAT at 10 km distance. A scaling of the determined stability and noise characteristics shows that such performance is adequate for an application in commercial air transport.Comment: 17 pages, 19 figures. Pre-publish to Applied Optics (OSA

Aeronautics Lidar Applications - Airborne LIDAR Detection of Clear Air Turbulence (CAT) within the FP7 DELICAT project

Turbulence encounters are the leading cause for passenger and flight crew injuries in non-fatal airline incidents. Turbulence occurring in clear air, accounting to nearly half of all turbulence incidents, remains one of the open issues in flight safety since it is not detectable by conventional means, such as weather radar. The frequency of ‘Clear Air Turbulence’ (CAT) encounters that arise from shear and wave motion in cruise altitudes, is further expected to increase due to climatic change. Here we report on a research activity generated within the EC FP6 FLYSAFE and implemented within the FP7 DELICAT project. In the DELICAT project, with the objective of concept and technology demonstration, an airborne LIDAR instrument for the remote detection of CAT was designed, built and integrated on a jet research aircraft. A flight campaign aiming for turbulent conditions was performed in 2013, successfully proving the instrument’s capabilities. In the future, LIDAR systems could be used, alongside radars, for ahead detection of CAT (besides other atmospheric phenomena as icing conditions, volcanic ash, etc.) for timely warning of the flight crew, ultimately increasing safety for passengers, crew and vehicle

Clear air turbulence detection and characterisation in the delicat airborne lidar project

We report on a development of a long-range airborne UV high spectral resolution lidar, intended for the detection and characterisation of clear air turbulence (CAT). The detection of turbulence is based on the measurement of density fluctuations associated with the movement of turbulent air masses. These density fluctuations are measured by the variations in the molecular backscatter coefficient which is determined from the lidar signal by spectrally separating it from the aerosol backscatter. After an introduction, we review the CAT detection principle and describe the lidar system design. We then present the expected performance of the system and give an overview on the planned measurement campaign

ATC-Wake: Integrated Wake Vortex Safety and Capacity System

With the steady increase in air traffic, civil aviation authorities are under continuous pressure to increase aircraft handling capacity. One potential approach is to reduce the separation distance between aircraft at takeoff and landing witliout compromising safety. ATC-Wake aims to develop and build an integrated system for ATC (Air Traffic Control) that would allow variable aircraft separation distances, as opposed to the fixed distances presently applied at airports. The ATC-Wake project has developed and built an integrated ATC Wake Vortex Safety and Capacity platform. A variety of subsystems is integrated and used within a test bed role: - To evaluate the interoperability of ATC-Wake with existing ATC systems currently used at various European airports; - To assess the safety and capacity improvements that can be obtained by local installation of the ATC-Wake system at various European airports; - To evaluate operational usability and acceptability of the ATC-Wake system; The ATC-Wake system is used in the planning phase where weather and wake vortex forecast information are used together with aircraft separation rules to establish the arrival and/or departure sequence. For approaches, the aim is to manage separation distances down to 2.5 nautical miles, in favorable weather conditions, for all aircraft types regardless of size. For departures, the aim is to reduce the time separation between departing aircraft to 90 seconds (in favorable wind conditions). Weather nowcasting and wake vortex prediction and detection information is used in the tactical phase to monitor and control safe separation. Wind forecast data is used to determine time frames suitable for reduced separation. Criteria on crosswind and associated safe separation minima are derived from safety assessment results obtained with the NLR WAke Vortex Induced Risk assessment (WAVIR) methodology. As main conclusion the ATC-Wake technical and operational feasibility analyses and the safety and capacity studies have built sufficient confidence in the operational concept and system design for the application of reduced separations to represent a sound evolution from existing ATC procedures and working practices, to deliver significant benefits for runway throughput and average delay per flight without major rework to the current ATC systems,while maintaining safety. The next step will be to complete the validation through production of a Safety Case, Human Factors Case, Business Case, and a Technology Case towards installation of the ATC-Wake at one or more European airports. The best would be to continue with airport shadow mode field trials, i.e., with direct involvement of airports and air traffic control centers

Flight Tests of the DELICAT Airborne LIDAR System for Remote Clear Air Turbulence Detection

An important aeronautics application of lidar is the airborne remote detection of Clear Air Turbulence which cannot be performed with onboard radar. We report on a DLR-developed lidar system for the remote detection of such turbulent areas in the flight path of an aircraft. The lidar, consisting of a high-power UV laser transmitter and a direct detection system, was installed on a Dutch research aircraft. Flight tests executed in 2013 demonstrated the performance of the lidar system to detect local subtle variations in the molecular backscatter coefficient indicating the turbulence some 10 to 15 km ahead

Genetic and Phenotypic Study of the \emphPectobacterium\emph Versatile Beta-Lactamase, the Enzyme Most Similar to the Plasmid-Encoded TEM-1

International audienceThis study aimed to compare the chromosomal beta-lactamase from Pectobacterium versatile , PEC-1, with the well-known and globally distributed TEM-1 in terms of genetic and functional properties. Despite the similarities between the enzymes, we obtained no definitive proof of gene transfer for the emergence of bla PEC-1 from bla TEM-1 . , ABSTRACT Genus Pectobacterium bacteria include important agricultural pathogens. Pectobacterium versatile isolates contain a chromosome-borne beta-lactamase, PEC-1. This enzyme is the closest relative of TEM-1, a plasmid-borne beta-lactamase widespread in the Enterobacterales . We performed bioinformatics and phenotypic analyses to investigate the genetic and phenotypic features of PEC-1 and its frequency and ability to spread within genus Pectobacterium . We also compared the characteristics of PEC-1 and TEM-1 and evaluated the likelihood of transfer. We found that bla PEC-1 was present principally in a small number of genetic environments in P. versatile . Identical bla PEC-1 genetic environments were present in closely related species, consistent with the high frequency of genetic exchange within the genus Pectobacterium . Despite the similarities between PEC-1 and TEM-1, their genetic environments displayed no significant identity, suggesting an absence of recent transfer. Phenotypic analyses on clonal constructs revealed similar hydrolysis spectra. Our results suggest that P. versatile is the main reservoir of PEC-1, which seems to transfer to closely related species. The genetic distance between PEC-1 and TEM-1, and the lack of conserved elements in their genetic environments, suggest that any transfer that may have occurred must have taken place well before the antibiotic era. IMPORTANCE This study aimed to compare the chromosomal beta-lactamase from Pectobacterium versatile , PEC-1, with the well-known and globally distributed TEM-1 in terms of genetic and functional properties. Despite the similarities between the enzymes, we obtained no definitive proof of gene transfer for the emergence of bla PEC-1 from bla TEM-1 . Indeed, given the limited degree of sequence identity and the absence of a common genetic environment, it seems unlikely that any transfer of this gene has occurred recently. However, although bla PEC-1 was found mostly in one specific clade of the P. versatile species, certain isolates from other closely related species, such as Pectobacterium brasiliense and Pectobacterium polaris , may also carry this gene inserted into common genetic environments. This observation suggests that genetic exchanges are frequent, accounting for the diffusion of bla PEC-1 between isolates from different Pectobacterium species and, potentially, to exogenous mobile genetic elements

Genetic and Phenotypic Study of the \emphPectobacterium\emph Versatile Beta-Lactamase, the Enzyme Most Similar to the Plasmid-Encoded TEM-1

International audienceThis study aimed to compare the chromosomal beta-lactamase from Pectobacterium versatile , PEC-1, with the well-known and globally distributed TEM-1 in terms of genetic and functional properties. Despite the similarities between the enzymes, we obtained no definitive proof of gene transfer for the emergence of bla PEC-1 from bla TEM-1 . , ABSTRACT Genus Pectobacterium bacteria include important agricultural pathogens. Pectobacterium versatile isolates contain a chromosome-borne beta-lactamase, PEC-1. This enzyme is the closest relative of TEM-1, a plasmid-borne beta-lactamase widespread in the Enterobacterales . We performed bioinformatics and phenotypic analyses to investigate the genetic and phenotypic features of PEC-1 and its frequency and ability to spread within genus Pectobacterium . We also compared the characteristics of PEC-1 and TEM-1 and evaluated the likelihood of transfer. We found that bla PEC-1 was present principally in a small number of genetic environments in P. versatile . Identical bla PEC-1 genetic environments were present in closely related species, consistent with the high frequency of genetic exchange within the genus Pectobacterium . Despite the similarities between PEC-1 and TEM-1, their genetic environments displayed no significant identity, suggesting an absence of recent transfer. Phenotypic analyses on clonal constructs revealed similar hydrolysis spectra. Our results suggest that P. versatile is the main reservoir of PEC-1, which seems to transfer to closely related species. The genetic distance between PEC-1 and TEM-1, and the lack of conserved elements in their genetic environments, suggest that any transfer that may have occurred must have taken place well before the antibiotic era. IMPORTANCE This study aimed to compare the chromosomal beta-lactamase from Pectobacterium versatile , PEC-1, with the well-known and globally distributed TEM-1 in terms of genetic and functional properties. Despite the similarities between the enzymes, we obtained no definitive proof of gene transfer for the emergence of bla PEC-1 from bla TEM-1 . Indeed, given the limited degree of sequence identity and the absence of a common genetic environment, it seems unlikely that any transfer of this gene has occurred recently. However, although bla PEC-1 was found mostly in one specific clade of the P. versatile species, certain isolates from other closely related species, such as Pectobacterium brasiliense and Pectobacterium polaris , may also carry this gene inserted into common genetic environments. This observation suggests that genetic exchanges are frequent, accounting for the diffusion of bla PEC-1 between isolates from different Pectobacterium species and, potentially, to exogenous mobile genetic elements

Aircraft Wake Vortex State-of-the-Art & Research Needs

This report has been compiled by the partners of the WakeNet3-Europe consortium with the support of several external experts. It describes the present international state-of-the-art in wake vortex research and application – focusing on recent developments in the various involved disciplines – and specifically evaluates research activities needed in order to provide operational benefits in line with ongoing SESAR developments, in response to ACARE goals and following Europe’s vision for aviation, Flightpath 2050

Robespierre. De la Nation artésienne à la République et aux Nations

Ce volume est l'aboutissement du colloque organisé à Arras en avril 1993 et auquel ont participé près de cinquante historiens de plusieurs pays. Il rassemble 35 contributions, les synthèses de trois jours de débats, le compte rendu d'une table ronde sur "la politique, la morale et le sacré". L'ouvrage concerne le lecteur soucieux de comprendre un personnage qui porte en lui la complexité de la Révolution française ; il sollicite aussi le citoyen qui s'interroge sur l'évolution de la démocratie et de la République