Effects of Postlayup Borate Treatment on Appearance and Flexural Properties of Douglas-Fir Glued Laminated Beams
Abstract Preservative treatments are required whenever glued laminated beams are exposed outdoors. Treatments can be either water-based systems applied to individual laminations prior to layup or o...
Effects of post-layup ammoniacal copper zinc arsenate treatment on appearance and flexural properties of Douglas-fir glued laminated beams
Preservative treatments are required whenever glued-laminated beams are exposed outdoors. Treatments can be either water-based systems applied to individual laminations prior to lay-up or organic solvent borne systems applied after the beams are fabricated. Water-based systems are not recommended for post-treatment because of concerns over checking and the potential for reductions in flexural properties. There are no data on the effects of these treatments. The effects of ammoniacal copper zinc arsenate (ACZA) treatment on flexural properties, glueline shear, and visual appearance were investigated using Douglas-fir glued laminated beams. While treatment did result in the presence of drying checks on all of the beams, ACZA treatment followed by mild kiln drying did not produce any significant effects on modulus of rupture, modulus of elasticity, work to maximum load or glueline shear. The results indicate that treatment with waterborne preservatives affects the appearance of the beam but not its load bearing properties.ZusammenfassungEine Imprägnierung mit Holzschutzmitteln ist immer dann erforderlich, wenn Brettschichtholzträger im Außenbereich eingesetzt werden. Dabei können entweder die einzelnen Lamellen vor der Verklebung mit Wasser basierten Systemen imprägniert werden oder die fertigen Träger mit organischen Lösemitteln behandelt werden. Wasser basierte Systeme sind für eine nachträgliche Behandlung nicht empfehlenswert wegen der Gefahr einer Rissbildung und einer evtl. Beeinträchtigung der Biegeeigenschaften. Genauere Angaben darüber gibt es allerdings nicht. Die Einflüsse einer Imprägnierung mit ammoniakhaltigem Kupfer-Zink-Arsen (ACZA) auf die Biegeeigenschaften, die Scherfestigkeit der Klebstofffugen und das Aussehen wurden an Douglasien-Brettschichtholzträgern untersucht. Alle Träger wiesen nach der Imprägnierung Trocknungsrisse auf, jedoch hatte eine ACZA-Imprägnierung nach milder technischer Trocknung keinen deutlichen Einfluss auf die Biegefestigkeit, den Elastizitätsmodul, die Biegearbeit und die Scherfestigkeit der Klebstofffugen. Die Ergebnisse zeigen, dass eine Behandlung mit Wasser basierten Holzschutzmitteln das Aussehen beeinflusst, sich aber nicht auf die Biegeeigenschaften auswirkt.
Endodontic regeneration: hard shell, soft core
A loss of organs or the destruction of tissue leaves wounds to which organisms and living things react differently. Their response depends on the extent of damage, the functional impairment and the biological potential of the organism. Some can completely regenerate lost body parts or tissues, whereas others react by forming scars in the sense of a tissue repair. Overall, the regenerative capacities of the human body are limited and only a few tissues are fully restored when injured. Dental tissues may suffer severe damage due to various influences such as caries or trauma; however, dental care aims at preserving unharmed structures and, thus, the functionality of the teeth. The dentin–pulp complex, a vital compound tissue that is enclosed by enamel, holds many important functions and is particularly worth protecting. It reacts physiologically to deleterious impacts with an interplay of regenerative and reparative processes to ensure its functionality and facilitate healing. While there were initially no biological treatment options available for the irreversible destruction of dentin or pulp, many promising approaches for endodontic regeneration based on the principles of tissue engineering have been developed in recent years. This review describes the regenerative and reparative processes of the dentin–pulp complex as well as the morphological criteria of possible healing results. Furthermore, it summarizes the current knowledge on tissue engineering of dentin and pulp, and potential future developments in this thriving field.