The presence of <i>Megachasma</i> (Chondrichthyes: Lamniformes) in the Neogene of Belgium, first occurrence in Europe

Fossil teeth of the genus Megachasma Taylor, Compagno & Struhsaker, 1983 are recorded for the first time in Europe. Isolated teeth have been recovered from the transgressive layer at the base of the Belgian Pliocene, extending the known paleogeographic range of this genus. These teeth are compared with fossil specimens from Greece, Chile, USA and extant specimens. The Belgian teeth seem to fit well in the gap between the early Miocene teeth from California and those of the extant taxon Megachasma pelagios Taylor, Compagno & Struhsaker, 1983; while the megamouth teeth found in Late Miocene to Early Pliocene sediments worldwide (Chile, North Carolina, Florida, and Greece) appear to be giant versions of modern teeth. Juvenile teeth of modern Megachasma pelagios are illustrated for the first time, showing a distinct ontogenetic variation in the roots and crown surface

<i>Carcharias vorax</i> (Le Hon, 1871) (Chondrichthyes, Lamniformes), from the Miocene of Belgium: redescription and designation of a neotype and paraneotype

Carcharias vorax (Le Hon, 1871) is poorly defined with one single tooth only. The holotype could not be found in the Type Collection of the IRScNB (Brussels) and recognition of the holotype is impossible based on the poor drawing in Le Hon (1871). A neotype and paraneotype are designated for the lost holotype. A temporary outcrop at a construction site southeast of the city of Antwerp is chosen as type locality. The basal part of the Middle Miocene Antwerpen Sands Member is selected as type horizon. An artificial tooth set is constructed and illustrated, confirming the attribution of this species to the genus Carcharias. Carcharias vorax (Le Hon, 1871) appears to be closely related to Carcharias cuspidatus (Agassiz, 1843) and seems to have a restricted geographical and temporal distribution, focused on the North Sea Basin only during the Burdigalian-Tortonian interval. The disappearance of Carcharias vorax during the Late Miocene is discussed. A maximum total body length of approximately 280 cm is estimated for this Miocene shark species

Large <i>Centrophorus</i> (Chondrichthyes, Squaliformes) of the Belgian Neogene continental shelf

A number of isolated teeth of gulper sharks (genus Centrophorus Müller & Henle, 1837) have been recovered from Neogene sands in the Antwerp area, marking the first occurrence of the genus Centrophorus in the fossil record of Belgium and the North Sea Basin. The precise stratigraphic origin of these teeth could not be established, but the taphonomic condition strongly suggests a Late Miocene or Early Pliocene age, although reworking from older Miocene strata cannot be excluded. These teeth are remarkable for the presence of serrated cutting edges of both upper and lower teeth as well as their large size. The teeth, that measure up to 1 cm, are the largest fossil Centrophorus reported in literature. The subtle differences between the teeth of different Centrophorus species and the paucity of comparative extant material prohibit specific attribution, but the teeth pertain to individuals that equalled the largest extant species. The occurrence of these large Centrophorus in the Belgian deposits is remarkable as Centrophorus usually prefers deeper waters

Tropical analogues of a Dempe-Franke bilevel optimization problem

We consider the tropical analogues of a particular bilevel optimization problem studied by Dempe and Franke and suggest some methods of solving these new tropical bilevel optimization problems. In particular, it is found that the algorithm developed by Dempe and Franke can be formulated and its validity can be proved in a more general setting, which includes the tropical bilevel optimization problems in question. We also show how the feasible set can be decomposed into a finite number of tropical polyhedra, to which the tropical linear programming solvers can be applied.Comment: 11 pages, 1 figur

Experimental study of formwork tightness as a function of rheological properties of SCC

Several studies relating formwork pressure to rheology exist, however the relationship between rheology and leakage through formwork joints remains to be investigated. In practice, standard documents are used to define formwork tightness requirements, typically using a qualitative approach. To try bridge this gap in knowledge, we developed a test set-up to study tightness of formwork joints under pressure as a function of varying rheological properties. Coupled with standard rheology tests, this new test set-up provides means of linking flow rate, formwork pressure, flow area, and the rheological properties. The study seeks to provide insight on measurable governing parameters and thus inform formwork tightness requirements in a more quantifiable manner. This paper presents a test set-up designed to study the flow of fresh paste through small openings. It highlights a preliminary study on the pressure-driven flow of limestone paste through a bottom orifice in a cylindrical container. While this new device may not be directly representative of the actual conditions in formwork, it provides a good base for a fundamental study that can then be extrapolated to a more representative test operation. Preliminary results show a linear relationship between the flow rate and the applied pressure. The results also show that increasing the flow area by a factor of 2.33 had a higher impact than an increase in yield stress and viscosity by a factor of 2.54 and 3.80 respectively. However, more tests need to be carried out to obtain clear trends

Structural build-up of cementitious paste under external magnetic fields

Engineering application processes of fresh concrete include transporting, pumping, formwork casting, etc. Each process is a significant factor influencing properties of fresh and hardened concrete. However, many contradicting requirements of fresh concrete performances (such as structuration rate) exist in these operation processes. Therefore, advanced techniques need to be proposed to satisfy future challenges. Actively controlling the stiffness by applying external magnetic fields would be a potential solution for the contradicting requirements, and could make the pumping and casting processes smarter and more reliable. In the present paper, the effects of magnetic field strength and magnetizing time on structural build-up of cementitious paste are discussed. The results show that higher magnetic field strengths result in higher percolation time and lower phase angle at equilibrium state. However, the application of external magnetic fields with low flux density has little effects on the viscoelastic behaviour of cementitious paste. Under high magnetic field strengths, the viscousliquid behaviour dominates the elastic-solid behaviour at early stage, while the solid-like behaviour becomes more dominant with magnetizing time

Struggling for food in a time of crisis: A comment on Caplan in this issue

This commentary sets Caplan’s arguments about food banks and food poverty in the broader context of changes to the welfare state, the ‘charitization’ of state welfare and the need to address food poverty within a framework of dignity rather than charity