Synthesis and Characterization of Amorphous Si2N2O

Amorphous silicon oxynitride powder was synthesized by nitridation of high-purity silica in ammonia at 1120°C. The resulting material was X-ray amorphous, and its chemical characteristics were determined by X-ray photoelectron spectroscopy (XPS) and ²⁹Si nuclear magnetic resonance (NMR). The XPS analysis showed a shift to lower binding energies for the Si₂ p peak with increasing nitrogen content. Upon initial nitridation, the full width at half maximum (FWHM) of the Si₂ p peak increased, but decreased again at higher nitrogen contents, thus showing the formation of a silicon oxynitride phase with a single or small range of composition. The ²⁹Si NMR analysis showed the formation of (amorphous) Si₃N₄ (Si–N₄) and possibly two oxynitride phases (Si–N₃O, Si–N₂O₂). It is concluded that while XPS, FT-IR, and nitrogen analysis may show the formation of an homogeneous, amorphous silicon oxynitride (Si₂N₂O) phase, the formation of phase–pure, amorphous Si₂N₂O is extremely difficult via this route.     

Variations in the force applied to flexion tests of the distal limb of horses

A pressure-sensitive device was developed to measure the force applied to flexion tests of the distal limb of horses. The mean force applied by a group of experienced clinicians was 150 N which results in a moment on the flexed fetlock joint of about 28.5 Nm. The coefficient of variation of the force applied by one experienced clinician was only about 12 per cent, but the coefficient of variation between clinicians was considerably higher (20 per cent), irrespective of whether the clinicians were considered to be experienced or not. The mean force applied by a group of women examiners (114 N) was significantly lower than that applied by the group of male examiners. It is concluded that the flexion test used in the clinical examination of the locomotor system of the horse should be better standardised.     

Matrix metalloproteinase activity in equine synovial fluid: influence of age, osteoarthritis, and osteochondrosis

OBJECTIVE: To investigate the influence of age, osteoarthritis (OA), and osteochondrosis (OC) on the matrix metalloproteinase (MMP) activity in the synovial fluid (SF) of equine joints. METHODS: SF was collected from normal and osteoarthritic metacarpophalangeal joints (normal: 14 adult, 28 juvenile; OA: 22 adult). And from normal and osteochondrotic tarsocrural joints (5 months: 11 normal, 8 OC; 11 months: 7 normal, 6 OC). Subsequently, overall MMP activity was measured. RESULTS: The level of active MMPs was almost twofold higher in SF from juvenile horses (age up to 11 months) than in SF from mature animals (4-30 years; p < 0.001). In juvenile horses MMP activity was higher in 5 month old foals than in 11 month old foals (p < 0.01). In adult horses MMP activity was independent of age. In OA joints the activity was nearly twice as high as in normal joints (p < 0.001). In OC joints MMP activity was not significantly different from normal, age matched, control joints. CONCLUSIONS: MMP activity in SF from normal adult joints is not related to age. In juvenile joints MMP activity is significantly higher than activity in joints from adult animals. It is hypothesised that the gradual decrease in MMP activity with increasing age reflects the declining metabolic activity resulting from ceasing growth and the accompanying decrease in cartilage remodelling. The increased MMP activity in osteoarthritis joints most likely reflects matrix destruction. In osteochondrosis MMP mediated matrix degradation appears not to be different from normal joints.     

Solid-State 29Si NMR Analysis of Amorphous Silicon Nitride Powder

Solid-state ²⁹Si NMR techniques were used to characterize laser-synthesized silicon nitride powder prepared from the reaction of silane with ammonia. When the powder is exposed to water vapor, a hydrated layer rapidly forms at the surface. A comparison of ²⁹Si cross polarization (CP) and Bloch decay (BD)-MAS-NMR spectra revealed differences between surface and bulk compositions. CP-NMR identified Si-NH_x (x = 1, 2) species with a chemical shift of −45 ppm in the as-synthesized ( unexposed ) powder. In BD-NMR spectra, the nitride resonance is observed at −48 ppm. For the hydrated powder, CP-NMR identified additional =Si-OH ( Q³ ), =Si-(OH)₂ ( Q² ), and SiO₂ ( Q⁴ ) species present at the surface. The CP-NMR spectra were corrected for T_lpH relaxation effects and deconvoluted into individual components in order to extract quantitative measurements of the various species present.     

Quantification of the locomotion of Dutch Warmblood foals

To get an in-depth insight into the ontogeny of the equine locomotor apparatus, the locomotion of 28 Dutch Warmblood foals was recorded at the walk, trot and canter on a treadmill using a CODA-3 apparatus. A great similarity in joint angle-time diagrams was found, although considerable differences in kinematic gait parameters of individual foals could be detected. These results contribute to an objective comparison of the locomotor performance of foals.     

Impact of Endotoxins in Gelatine Hydrogels on Chondrogenic Differentiation and Inflammatory Cytokine Secretion In Vitro

Gelatine methacryloyl (GelMA) hydrogels are widely used in studies aimed at cartilage regeneration. However, the endotoxin content of commercially available GelMAs and gelatines used in these studies is often overlooked, even though endotoxins may influence several cellular functions. Moreover, regulations for clinical use of biomaterials dictate a stringent endotoxin limit. We determined the endotoxin level of five different GelMAs and evaluated the effect on the chondrogenic differentiation of equine mesenchymal stromal cells (MSCs). Cartilage-like matrix production was evaluated by biochemical assays and immunohistochemistry. Furthermore, equine peripheral blood mononuclear cells (PBMCs) were cultured on the hydrogels for 24 h, followed by the assessment of tumour necrosis factor (TNF)-α and C–C motif chemokine ligand (CCL)2 as inflammatory markers. The GelMAs were found to have widely varying endotoxin content (two with >1000 EU/mL and three with <10 EU/mL), however, this was not a critical factor determining in vitro cartilage-like matrix production of embedded MSCs. PBMCs did produce significantly higher TNF-α and CCL2 in response to the GelMA with the highest endotoxin level compared to the other GelMAs. Although limited effects on chondrogenic differentiation were found in this study, caution with the use of commercial hydrogels is warranted in the translation from in vitro to in vivo studies because of regulatory constraints and potential inflammatory effects of the content of these hydrogels.     

Waste disposal by shale fracturing at ORNL

The shale fracturing process is a method of waste disposal currently in use at the Oak Ridge National Laboratory (ORNL) for the permanent disposal of locally generated intermediate-level waste solutions. In this process, the waste solution is mixed with a solids blend of cement and other additives; the resulting grout is injected into an impermeable shale formation at a depth of 700–1000 ft. A few hours after completion of the injection the grout sets, fixing the radioactive waste in the shale formation. The operational experience with this process since 1966, the monitoring techniques that have been developed, and some considerations of the impact on the enviroment are discussed.