Orfeo BELSPO Instutional Open Access Repository for Federal Organisation
Not a member yet
14207 research outputs found
Sort by
Digitizing a xylarium beyond shared meta-data: the importance of quantitative wood anatomy, images and chemistry
No full textXylaria are big institutional collections of wood samples that serve as scientific reference material. They are a result of long-term collecting efforts of multiple expeditions in the past, often in regions that are nowadays difficult to explore for logistical, conservational, or political reasons. Xylarium specimens have been key for comparative wood anatomy and establishing databases supporting botanical identification of traded timber. Strong tendencies in actual state-of-the-art research include the rising importance of quantitative approaches and the substantially improved means for producing, sharing, and analyzing images. At the same time there is a growing interest in combining microscopic observations of wood with chemical assessments. These trends urge for coordinated efforts of digitizing the invaluable information held in xylarium samples, apart from sharing metadata that are available for many xylaria. Quantitative features typically show variability, contrary to most of the qualitative characteristics commonly used in wood identification. There is indeed variability within species, but also within a single tree, e.g. vessel element or tracheid dimensions vary from pith-to-bark, in the height direction and according to different organs (trunk, roots, branches). More emphasis on quantitative features implies a statistical approach that typically needs study material consisting of more specimens than a classical wood anatomical description. This is a good reason for strengthening the network efforts between xylaria. There are also engaging perspectives for a bigger role of image-based assessments. Capturing a maximum of wood anatomical information in a collection of images involves taking pictures from the three principal angles, at different magnifications, different fields of view and using as well optical light, electron beams and X-rays. This digitizing process results in a multitude of images. Handling high resolution images in a standardized and efficient way is still challenging, but necessary to fully exploit the opportunities of deep learning. Beyond wood anatomy, several chemical analyses are also relevant for identification and provenance determination, including measurements of metabolites, stable isotopes and elemental assessments. Concerted actions will be key to share data that are maximally Findable, Interoperable and Reusable (FAIR principles
"All about Lieve". St. Godelieve Painted and Illuminated
Full text linkThis text is the joint contribution of Oliver Kik and Dominique Vanwijnsberghe, originally submitted for the publication Preserving Fragile Wisdom. Essays in Honour of Lieve Watteeuw, ed. by Wim François, Hendrik Hameeuw and Maarten Bassens (Leuven, 2025). Due to a misunderstanding, only the first part, authored by Oliver Kik, was published under a different title
Airborne soil-derived dust hazards in aviation
Full text linkAirborne mineral dust poses a safety challenge for aviation. Several fatal accidents have happened in dust-laden air due to reduced visibility, strong gusty winds, and wind shear. Dust-induced icing also contributed at least to two fatal accidents. Furthermore, atmospheric dust has long- and short-term effects on aircraft operating conditions due to corrosion and abrasion on the aircraft surfaces and molten ingress deterioration of engine hot section components. The combined impact can increase operating and maintenance costs and increase the overall cost of ownership. While the scientific community has started preparing and providing products based on atmospheric dust modeling and observation, there are still important data and information gaps in the fundamental science. These include (i) insufficient data which could be used to better understand the effects of dust on aircraft as well as on ground systems and operations (e.g., four-dimensional information of dust mineralogy, cost–benefit analysis of the impact of dust on aviation along flight routes), (ii) the identification of airborne dust monitoring and modeling products and services that could enable the flow of relevant information in commercial aviation and in decision-making workflows, and (iii) the underdeveloped, unclear, or absent role of dust hazards in regulations and operational procedures as well as in the training, skill set, and knowledge base of pilots. This review is aimed at both academic and aviation stakeholders and presents the current state-of-the-art knowledge at the intersection of dust hazards, aviation safety, and impacts on flight operations and aircraft maintenance
Core-Halo Correlations of Solar Wind Electrons and Temperature Anisotropy Instabilities
Full text linkThe properties of electrons in the heliospheric plasma are modulated by various factors, starting with the expansion and bimodal nature of the slow or fast solar wind, and continuing with the kinetic mechanisms of acceleration and energy exchange with small-scale plasma waves. The role of wave-particle interactions can be understood through rigorous kinetic modeling based on observational data. This paper presents a refined evaluation of the instabilities triggered by temperature anisotropy, that is, whistler and firehose instabilities, taking into account for the first time the correlations between the electron core and halo populations revealed by in situ observations. In establishing core-halo correlations, temperature anisotropies \$(A)\$ and plasma beta parameters \$\left({\beta }\_{\Vert }\right)\$ are of interest, as quantifiers of free (kinetic) energy at the origin of instabilities. These correlations incorporate the mutual effects of the electron populations and enable a realistic characterization of instabilities, in terms of either the core or the halo parameters. The instability thresholds can be significantly reduced under the mutual core-halo effects, and comparisons with observations prove the constraining role of self-generated instabilities, not only for the core but also for the halo electrons. The most relevant are the results for the slow solar wind, for which both the parameters and the core-halo correlations are less affected by the strahl component, which is otherwise more prominent in the fast wind. In high-speed winds, temperature anisotropies are more confined, most likely under a stronger effect of fluctuations generated by the electron strahl whose properties are not yet quantified to allow a similar analysis
First record of monogenean fish parasites in the Upper Lufira River Basin (Democratic Republic of Congo): dactylogyrids and gyrodactylids infesting Oreochromis mweruensis, Coptodon rendalli and Serranochromis macrocephalus (Teleostei: Cichlidae)
No full textBackground Monogenean parasites have never been formally reported on fishes from the Lufira River Basin. In this context, we decided to record the monogenean parasite fauna of three cichlid species found in the Upper Lufira River Basin for the first time by inventorizing their diversity (species composition) and analysing their infection parameters (prevalence, mean intensity and abundance).Methods The African cichlid fishes Oreochromis mweruensis, Coptodon rendalli and Serranochromis macrocephalus were selected for the study, given their economic value and their abundance in the Upper Lufira River Basin. Monogeneans were isolated from the gills and stomach, mounted on glass slides with either Hoyer's medium or ammonium picrate-glycerin for identification under a stereomicroscope, based on morphological analysis of genital and haptoral hard parts. Indices of diversity and infections parameters were calculated.Results A total of 13 gill monogenean parasite species (Cichlidogyrus dossoui, C. halli, C. karibae, C. mbirizei, C. papernastrema, C. quaestio, C. sclerosus, C. tiberianus, C. tilapiae, C. zambezensis, Scutogyrus gravivaginus, S. cf. bailloni and Gyrodactylus nyanzae) and one stomach monogenean (Enterogyrus malmbergi) were identified. A species richness (S) of 10 for O. mweruensis, S = 6 for C. rendalli and S = 2 for S. macrocephalus was recorded. Five parasite species were reported to be common amongst O. mweruensis and C. rendalli. According to cichlid species, the most prevalent parasite species was C. halli (prevalence [P] = 80.9%) on O. mweruensis, C. dossoui (P = 92.9%) on C. rendalli and C. karibae and C. zambezensis (both P = 9.1%) on S. macrocephalus. The parasite species with the highest mean intensity (MI) were G. nyanzae (MI = 8.7) on O. mweruensis, C. papernastrema (MI = 17.1) on C. rendalli and C. karibae (MI = 15) on S. macrocephalus. The findings indicate new host ranges for five parasites species (C. quaestio, S. cf. bailloni, E. malmbergi on O. mweruensis, C. halli on C. rendalli and C. karibae on S. macrocephalus) as well as new geographical records for all of them as they are recorded for the first time in the Lufira River Basin.Conclusions This study highlighted the richness of monogenean communities in the Upper Lufira River Basin and is a starting point for future helminthological studies, such as on the use of fish parasites as indicators of anthropogenic impact
L'édification du château de Jehay : une approche par la datation et la caractérisation des maçonneries et des bois
No full textDesign of the VenSpec-H instrument on ESA’s EnVision mission: development of critical elements, highlighting the wavefront corrector and grating
Full text linkEnVision is the European Space Agency’s upcoming mission to Venus with a launch scheduled in 2031. One of the payloads on board is the Venus Spectrometers (VenSpec) suite, containing three spectrometer channels, one of which is Venus Spectrometer with high resolution (VenSpec-H). VenSpec-H performs absorption measurements in the atmosphere of Venus in four near-infrared spectral bands. VenSpec-H is developed under Belgian management and builds on heritage from instruments on Venus Express and Trace Gas Orbiter. The operating wavelength range (1.15 to 2.5μm) imposes stringent temperature requirements on the instrument to make nightside measurements below the Venus clouds possible. Most importantly, the spectrometer’s optical components are held in a separate cold section inside the instrument, cooled down to −45°C, to remove the thermal background from the signal. Some passive optical elements in the cold spectrometer had low technological readiness at the start of the project. One of them is a wavefront corrector: the freeform corrector plate, used to compensate for aberrations introduced in the system by a parabolic mirror. This device is developed by the Brussels Photonics lab of Vrije Universiteit Brussel using a supply chain with shape-adaptive corrective polishing and dedicated metrology. Another is the echelle grating, used to disperse the incoming light into its spectral components, which is built by Advanced Mechanical and Optical Systems. We highlight the manufacturing and metrology processes of both devices. Besides that, some mechanisms, placed in the warmer part of the instrument, had to be developed: a turn window unit to protect the interior of the instrument during the aerobraking phase of the mission, a filter wheel mechanism to select the spectral bands of interest, and an integrated detector cooler assembly to register the spectra