Ingenieurwissenschaften und zugeordnete Tätigkeiten
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- 2016 (3) (entfernen)
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- Englisch (3)
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- Bioerosion (1)
- Bone marrow extrusion (1)
- Brushite-forming calcium phosphate cement (1)
- Carbonate substrate (1)
- Cement injection (1)
- Computed tomography (1)
- Epoxy resin (1)
- Ex vivo (1)
- Fire residue (1)
- Flame retardancy (1)
Biological erosion is a key process for the recycling of carbonate and the formation of calcareous sediments in the oceans. Experimental studies showed that bioerosion is subject to distinct temporal variability, but previous long-term studies were restricted to tropical waters. Here, we present results from a 14-year bioerosion experiment that was carried out along the rocky limestone coast of the island of Rhodes, Greece, in the Eastern Mediterranean Sea, in order to monitor the pace at which bioerosion affects carbonate substrate and the sequence of colonisation by bioeroding organisms. Internal macrobioerosion was visualised and quantified by micro-computed tomography and computer-algorithm-based segmentation procedures. Analysis of internal macrobioerosion traces revealed a dominance of bioeroding sponges producing eight types of characteristic Entobia cavity networks, which were matched to five different clionaid sponges by spicule identification in extracted tissue. The morphology of the entobians strongly varied depending on the species of the producing sponge, its ontogenetic stage, available space, and competition by other bioeroders. An early community developed during the first 5 years of exposure with initially very low macrobioerosion rates and was followed by an intermediate stage when sponges formed large and more diverse entobians and bioerosion rates in-creased. After 14 years, 30 % of the block volumes were occupied by boring sponges, yielding maximum bioerosion rates of 900 g m.
Vertebroplasty or kyphoplasty of osteoporotic vertebral fractures bears the risk of pulmonary cement embolism (3.5%–23%) caused by leakage of commonly applied acrylic polymethylmethacrylate (PMMA) cement to spongious bone marrow or outside of the vertebrae. Ultraviscous cement and specific augmentation systems have been developed to reduce such adverse effects. Rapidly setting, resorbable, physiological calcium phosphate cement (CPC) may also represent a suitable alternative.
PURPOSE: This study aimed to compare the intravertebral extrusion of CPC and PMMA cement in an ex vivo and in vivo study in sheep.
STUDY DESIGN/SETTING: A prospective experimental animal study was carried out. METHODS: Defects (diameter 5 mm; 15 mm depth) were created by a ventrolateral percutane-ous approach in lumbar vertebrae of female Merino sheep (2–4 years) either ex vivo (n = 17) or in vivo (n = 6), and injected with: (1) CPC (L3); (2) CPC reinforced with 10% poly(l-lactide-co-glycolide) (PLGA) fibers (L4); or (3) PMMA cement (L5; Kyphon HV-R). Controls were untouched (L1) or empty defects (L2). The effects of the cement injections were assessed in vivo by blood gas analysis and ex vivo by computed tomography (CT), micro-CT (voxel size: 67 µm), histology, and biomechanical testing.
Synergistic multicomponent systems containing melamine poly(metal phosphate)s have been recently proposed as flame retardants. This work focuses on the decomposition pathways, molecular mechanisms and morphology of the fire residues of epoxy resin (EP) flame retarded with melamine poly(zinc phosphate) (MPZnP) to explain the modes of action and synergistic effects with selected synergists (melamine polyphosphate (MPP) and AlO(OH), respectively). The total load of flame retardants was always 20 wt.%. The decomposition pathways were investigated in detail via thermogravimetric Analysis coupled with Fourier transform infrared spectroscopy. The fire residues were investigated via elemental analysis und solid-state nuclear magnetic resonance spectroscopy. The morphology of intumescent fire residues was investigated via micro-computed tomography and scanning electron microscopy.
EP + (MPZnP + MPP) formed a highly voluminous residue that showed structural features of both EP + MPZnP and EP + MPP, resulting in a highly effective protection layer. EP + (MPZnP + AlO(OH)) preserved the entire quantity of phosphorus content during combustion due to the Formation of Zn₂P₂O₇ and AlPO₄.