Construction of the avian skull, as demonstrated by direct magnifying microfocal radiography (Aves)
SummaryThe new microfocus X-ray technique works with X-ray sources smaller than 10 Μm in diameter. Thus, in contrast to conventional X-ray systems, it is possible to obtain direct magnifications with high spatial resolution, i.e., well-focused radiographs with better contrast and “depth of focus”. In this connection, specific construction principles of the avian skull are elucidated, comparing several bird groups. The typical pneumatization effects are demonstrated, as are other biologically important anatomical features, in particular those of the bills/beaks as related to mechanical demands.
Konstruktionsprinzipien des Schnabelskeletts beim schlupfreifen Jungvogel
Unter Einsatz einer neuartigen, direkt vergrößernden Röntgentechnologie wurde die Konstruktion des Schnabelskeletts von schlupfreifen Jungvögeln untersucht. Wie die bei Verwendung sog. Mikrofokus-Röntgengeräte erzielten Röntgenaufnahmen erkennen lassen, weist das Schnabelskelett der Schlüpflinge — unabhängig vom Entwicklungsmodus — bei allen untersuchten Formen einen recht einheitlichen Bau auf. Sowohl der Ossifikationsgrad der Kiefer als auch die spezifische Osteoarchitektur der Knochenelemente des Schnabelapparates, insbesondere im Bereich der Substantia spongiosa des Os praemaxillare können als anatomische Anpassungen an die beim Sprengen der Eischale auftretenden mechanischen Belastungen des Kieferskeletts gewertet werden. The structure of the beak skeleton of hatchlings was analysed using a new direct magnifying X-ray technique. The application of these microfocus X-ray systems reveals a quite uniform construction of the beak skeleton in the hatchlings, independent from the mode of development of the bird species groups studied (precocial, altricial etc.). The amount of ossification as well as the specific osteoarchitecture of the jaw bones of the beak apparatus — especially in the region of Substantia spongiosa of the Os praemaxillare — may be considered as an anatomical adaptation to mechanical stress of the jaw bones during picking of the eggshell.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.