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BACKGROUND CONTEXT: Targeted delivery of osteoinductive bone morphogenetic Proteins (eg, GDF5) in bioresorbable calcium phosphate cement (CPC), potentially suitable for vertebroplasty and kyphoplasty of osteoporotic vertebral fractures, may be required to counteract augmented local bone catabolism and to support complete bone regeneration. The biologically optimized GDF5 Mutant BB-1 may represent an attractive drug candidate for this purpose.
PURPOSE: The aim of the current study was to test an injectable, poly (l-lactide-co-glycolide) acid (PLGA) fiber-reinforced, brushite-forming CPC containing low-dose BB-1 in a sheep lumbar osteopenia model.
STUDY DESIGN/ SETTING: This is a prospective experimental animal study.
METHODS: Bone defects (diameter 5 mm) were generated in aged, osteopenic female sheep and were filled with fiber-reinforced CPC alone (L4; CPC+fibers) or with CPC containing different dosages.
To assess the clinical course of a sheep stifle joint model for osteochondral (OC) defects, medial femoral condyles (MFC) were exposed without patella luxation using medial parapatellar skin (3–4 cm) and deep incisions (2–3 cm). Two defects (7 mm diameter; 10 mm depth; OC punch) were left empty or refilled with osteochondral autologous transplantation cylinders (OATS) and explanted after six weeks. Incision-to-suture time, anesthesia time, and postoperative wound or impairment scores were compared to those in sham-operated animals. Implant performance was assessed by X-ray, micro-computed tomography, histology, and immunohistology (collagens 1, 2; aggrecan). There were no surgery-related infections or patellar luxations. Operation, anesthesia, and time to complete stand were short (0.5, 1.4, and 1.5 h, respectively). The wound trauma score was low (0.4 of maximally 4; day 7). Empty-defect and OATS animals reached an impairment score of 0 significantly later than sham animals (7.4 and 4.0 days, respectively, versus 1.5 days). Empty defects showed incomplete healing and dedifferentiation/heterotopic differentiation; OATS-filled defects displayed advanced bone healing with remaining cartilage gaps and orthotopic expression of bone and cartilage markers. Minimally-invasive, medial parapatellar surgery of OC defects on the sheep MFC allows rapid and low-trauma recovery and appears well-suited for implant testing.
Zur Charakterisierung von luftgekoppelten Ultraschallwandlern werden mehrere verschiedene Methoden und Verfahren angewendet. Durch die unterschiedlichen Herangehensweisen werden oft unterschiedliche Prüfkopfpara-meter und Schallfeldgrößen ermittelt, was einen direkten Vergleich von Datenblättern erschwert. Für die Charakterisierung von Kontakt- und Tauchtechnikprüfköpfen hat sich ISO 22232-2:2021 bereits etabliert, allerdings ist diese Norm nicht auf die luftgekoppelten Wandlertechnologien direkt übertragbar. Daher erkannten Hersteller, Forschungseinrichtungen und Anwender den Bedarf an einer Richtlinie zur einheitlichen Charakterisierung von luftgekoppelten Wandlern. Gemeinsam arbeiten sie aktuell im Rahmen des Unterausschusses „Luftgekoppelte Ultraschallprüfung“ der DGZfP an der Erstellung einer solcher Richtlinie mit dem Anspruch, die bestehende Normung um die luftgekoppelte Prüfung zu erweitern und somit die Vereinheitlichung der Charakterisierung dieser Wandler zu erleichtern.
In diesem Beitrag wird ein Überblick über den geplanten Inhalt der Richtlinie und über die Methoden zur akustischen Charakterisierung von luftgekoppelten Ultraschallwandlern gegeben. Insbesondere werden verschiedene Methoden der Ermittlung von wichtigen Wandlerparametern wie z.B. Empfindlichkeit, Mittenfrequenz, Bandbreite, Fokusgröße und Fokusabstand dargestellt und verglichen.
In accordance with IAEA SSR-6 para 306 a management system shall be established and implemented to ensure compliance with the relevant provisions of the IAEA regulations. BAM has issued an update of the guideline: the BAM-GGR 011. The new revision describes necessary quality assurance measures for design, manufacture, testing, documentation, use, maintenance and inspection of packagings for package designs requiring competent authority approval for the transport of radioactive material.
The measures can be categorised as system-related and design-related. They are independently approved and monitored by the German competent authority BAM and its authorised expert (BAM/T). The qualification of the organisation applying for the design approval certificate is reviewed in the context of the design approval procedure. The quality assurance measures for manufacture consist of three main steps. Pre-assessment of manufacturing documents such as quality plans, specifications etc., Manufacturing inspections according the pre-assessed documents and inspection before commissioning including documentation review. Periodic inspections during operation as well as relevant specifications for use and maintenance ensure that the properties specified in the approval certificate are preserved over the package life time. Special provisions for the return on
experience regarding operational feedback for design, manufacture, use, maintenance and inspection are given. Special focus shall be given here to the rearranged and meanwhile established system of manufacturing inspections. This includes more transparent roles for a) the Producers authorised inspection 11282 representative, b) the independent inspection expert (S), acting on behalf of the manufacturer with acceptance of BAM, and c) BAM or its authorised expert (BAM/T). Additional attention shall be drawn to the management of deviations during manufacturing and provisions for maintenance and periodic inspections.
The finite element method was used to simulate the thermo-mechanical behaviour of a solder bump configuration on Al2O3 substrate under thermo-cyclic loading between -55 °C and 125 °C. Chaboche's viscoplastic material model was used to describe the Bauschinger effect and the creep/plasticity interaction for the tin-lead solder material. The influence of two different viscoelastic underfill materials (Epoxy+50 % SiO2, Epoxy+70 % SiO2) on the inelastic deformation of the tin-lead solder was analyzed and compared. It may be shown that the thermally matched 'hard' underfiller (Epoxy+70 % SiO2) significantly reduces the accumulated inelastic strain in the bump compared to 'soft' underfiller or no underfill material. On the other hand, the maximum lateral normal stress will increase slightly.
BACKGROUND CONTEXT:
Bioresorbable calcium phosphate cement (CPC) may be suitable for vertebroplasty/kyphoplasty of osteoporotic vertebral fractures. However, additional targeted de-
livery of osteoinductive bone morphogenetic Proteins (BMPs) in the CPC may be required to counteract the augmented local bone catabolism and support complete bone regeneration.
PURPOSE:
This study aimed at testing an injectable, poly (l-lactide-co-glycolide) acid (PLGA) fiber-reinforced, brushite-forming cement (CPC) containing low-dose bone morphogenetic Protein BMP-2 in a sheep lumbar osteopenia model.
STUDY DESIGN/ SETTING:
This is a prospective experimental animal study.
METHODS:
Bone defects (diameter 5 mm) were generated in aged, osteopenic female sheep and filled with fiber-reinforced CPC alone (L4; CPC+ fibers) or with CPC containing different dosages of BMP-2 (L5; CPC+ fibers + BMP-2; 1, 5, 100, and 500g BMP-2; n=5 or 6 each). The results were
compared with those of untouched controls (L1). Three and 9 months after the operation, structural and functional effects of the CPC (±BMP-2) were analyzed ex vivo by measuring
(1) bone Mineral density (BMD);
(2) bone structure, that is, bone volume/total volume (assessed by micro-computed tomography [micro-CT] and histomorphometry), trabecular thickness, and trabecular number;
(3) bone formation, that is, osteoid volume/bone volume, osteoid surface/bone surface, osteoid thickness, mineralizing surface/bone surface, mineral Apposition rate, and bone formation rate/bone surface;
(4) bone resorption, that is, eroded surface/bone surface; and
(5) compressive strength.
RESULTS:
Compared with untouched controls (L1), CPC+ fibers (L4) and/or CPC+ fibers + BMP-2(L5) significantly improved all parameters of bone formation, bone resorption, and bone structure.
These effects were observed at 3 and 9 months, but were less pronounced for some parameters at 9 months. Compared with CPC without BMP-2, additional significant effects of BMP-2 were demonstrated for bone structure (bone volume/total volume, trabecular thickness, trabecular number) and formation (osteoid surface/bone surface and mineralizing surface/bone surface), as well as for the compressive strength. The BMP-2 effects on bone Formation at 3 and 9 months were dose-dependent, with 5–100g as the optimal dosage.
CONCLUSIONS:
BMP-2 significantly enhanced the bone formation induced by a PLGA fiber-reinforced CPC in sheep lumbar osteopenia. A single local dose as low as ≤100g BMP-2 was sufficient
to augment middle to long-term bone formation. The novel CPC+ BMP-2 may thus represent an alternative to the bioinert, supraphysiologically stiff polymethylmethacrylate cement presently used to treat osteoporotic vertebral fractures by vertebroplasty/kyphoplasty.
Influence of the dispersant on the parts quality in slurry-based binder jetting of SiC ceramics
(2022)
Binder jetting is establishing more and more in the ceramic industry to produce large complex shaped parts. A parameter with a great impact on the quality of the parts is the binder–powder interaction. The use of ceramic slurries as feedstock for this process, such as in the layerwise slurry deposition–print technology, allows a great flexibility in the composition. Such slurries are typically composed of ceramic powder, water, and small amounts of various additives. The understanding of the effect of these components on the printing quality is thus essential for the feedstock development. Four models were developed regarding the impact of additives, such as dispersants on printing. These models were confirmed or rebutted by experiments performed for an SiC slurry system with two different concentrations of a dispersant and a commercial phenolic resin used as a binder. It is shown that for this system the influence of the dispersant on the curing behavior and the clogging of the pores by dispersant can be neglected. The redispersion of the dispersant after the curing of the resin has no or only a minor effect. However, the wetting behavior determined by the surface energies of the system seem to be most crucial. In case the surface energy of the slurry additive is significantly lower than the surface energy of the binder, the strength of the green parts and the printing quality will be low. This was shown by inverse gas chromatography, contact angle measurement, rheological characterization, and mechanical tests with casted samples.
This guideline was drafted following and complementing the norm ISO 22232-2:2020(E) to include air-coupled ultrasonic transducers. This document specifies the characteristics of probes used for non-destructive air-coupled ultrasonic testing with center frequencies above 20 kHz, with focusing or without focusing means.
Current light microscopic methods such as serial sectioning, confocal microscopy or multiphoton microscopy are severely limited in their ability to analyse rather opaque biological structures in three dimensions, while electron optical methods offer either a good three-dimensional topographic visualization (scanning electron microscopy) or high-resolution imaging of very thin samples (transmission electron microscopy). However, sample preparation commonly results in a significant alteration and the destruction of the three-dimensional integrity of the specimen. Depending on the selected photon energy, the interaction between X-rays and biological matter provides semi-transparency of the specimen, allowing penetration of even large specimens. Based on the projection-slice theorem, angular projections can be used for tomographic imaging. This method is well developed in medical and materials science for structure sizes down to several micrometres and is considered as being non-destructive. Achieving a spatial and structural resolution that is sufficient for the imaging of cells inside biological tissues is difficult due to several experimental conditions. A major problem that cannot be resolved with conventional X-ray sources are the low differences in density and absorption contrast of cells and the surrounding tissue. Therefore, X-ray monochromatization coupled with a sufficiently high photon flux and coherent beam properties are key requirements and currently only possible with synchrotron-produced X-rays. In this study, we report on the three-dimensional morphological characterization of articular cartilage using synchrotron-generated X-rays demonstrating the spatial distribution of single cells inside the tissue and their quantification, while comparing our findings to conventional histological techniques.