Intervertebral disc response to cyclic loading--an animal model.

The viscoelastic response of a lumbar motion segment loaded in cyclic compression was studied in an in vivo porcine model (N = 7). Using surgical techniques, a miniaturized servohydraulic exciter was attached to the L2-L3 motion segment via pedicle fixation. A dynamic loading scheme was implemented, which consisted of one hour of sinusoidal vibration at 5 Hz, 50 N peak load, followed by one hour of restitution at zero load and one hour of sinusoidal vibration at 5 Hz, 100 N peak load. The force and displacement responses of the motion segment were sampled at 25 Hz. The experimental data were used for evaluating the parameters of two viscoelastic models: a standard linear solid model (three-parameter) and a linear Burger\u27s fluid model (four-parameter). In this study, the creep behaviour under sinusoidal vibration at 5 Hz closely resembled the creep behaviour under static loading observed in previous studies. Expanding the three-parameter solid model into a four-parameter fluid model made it possible to separate out a progressive linear displacement term. This deformation was not fully recovered during restitution and is therefore an indication of a specific effect caused by the cyclic loading. High variability was observed in the parameters determined from the 50 N experimental data, particularly for the elastic modulus E1. However, at the 100 N load level, significant differences between the models were found. Both models accurately predicted the creep response under the first 800 s of 100 N loading, as displayed by mean absolute errors for the calculated deformation data from the experimental data of 1.26 and 0.97 percent for the solid and fluid models respectively. The linear Burger\u27s fluid model, however, yielded superior predictions particularly for the initial elastic response

Engaging diverse experts in the global science-policy interface: Learning experiences from the process of the IPBES Values Assessment

This longitudinal study explores evidence of learning and reflexivity among experts involved in the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) Values Assessment from 2018 to 2022. As part of an online survey administered at yearly intervals, experts self-reported their views on: i) the aims they attributed to the Values Assessment, ii) their epistemic worldviews, iii) the definition of the multiple values of nature, and iv) their personal learning experiences in the assessment process. The represented epistemic worldviews corresponded to Constructivist, Transformative, Pragmatist, and Post-positivist. Across the three surveys, 59% of the respondents shifted their epistemic worldviews. However, these same experts did not change their core perspectives regarding the motivation behind the Values Assessment. At the same time, experts holding a Post-positivist worldview came to express more engagement-inclined themes and openness to dialogue with diverse knowledge systems. While enhanced reflexivity stimulated overall learning, cutting across all learning dimensions, it was itself a multilayered learning outcome. This study illustrates how diverse experts critically reflected and changed their own underlying assumptions during the inter- and transdisciplinary process of the Values Assessment. It further reveals that learning experiences in the Values Assessment were embedded in epistemic worldviews and connected to cognitive, relational, and transformative dimensions of learning. Our findings have broader implications for the design of inclusive and reflexive learning processes in future work of organisations aiming to facilitate inter- and transdisciplinary practices at the science-policy interface.publishedVersionPeer reviewe

'Inoculation injuries in the Lothian region'.

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Study of the PM Gas-Phase Filter Artifact Using a Setup for Mixing Diesel-Like Soot and Hydrocarbons

The filter artifact is a significant source of error in gravimetric measurements of particulate matter (PM) exhaust. However, only a few studies on the subject exist. Results from these studies show a large discrepancy mainly because the experiments were performed using real diesel vehicle exhaust with varying exhaust composition. In this study, a setup for mixing diesel-like soot and hydrocarbon vapor was constructed for generating a stable exhaust aerosol with adjustable composition. The particle size distribution of the diesel-fueled soot generator (GMD [geometric mean diameter] adjustable between 27 and 164 nm) was found to represent “real” exhaust particulate emission. This setup was applied for studying the filter artifact on Teflon-coated glass fiber filters using pentadecane as the hydrocarbon vapor. Experiments were performed using particle and hydrocarbon concentrations of 130–700 μg/m3 and 10–12 ppm, respectively. It was found that the particle concentration of the aerosol affects the filter artifact. At lower particle concentrations, more hydrocarbon adsorption was detected. In the absence of particles, the adsorption was highest. Furthermore, filter soot load, corresponding to 0.13%–0.66% of the clean filter mass, was found to affect adsorption. Sooty filters adsorbed less vapor than clean filters. However, increasing the soot load resulted in more adsorption. Moreover, it was found that the backup filter serves as a reasonable estimate of the filter artifact only for low particle concentrations and filter soot loads. These results indicate that the filter soot load is an important parameter influencing the filter artifact, and therefore, it should be considered when performing gravimetric sampling. The setup was proven to be a unique tool for quantitative studies of the filter artifact

Neurophysiological and mitochondrial abnormalities in MuSK antibody seropositive myasthenia gravis compared to other immunological subtypes

Objective: To compare the electrophysiological and histopathological features of immunological myasthenia gravis (MG) subtypes. Methods: Fifty MG patients underwent clinical examination, MuSK-Ab and AChR-Ab analysis. The majority underwent quantitative and single-fiber electromyography (QEMG, SFEMG), repetitive nerve stimulation and deltoid muscle biopsy. From muscle specimens with histological mitochondrial dysfunction, we amplified mitochondrial DNA (mtDNA). In specimens with mtDNA deletions, the nuclear gene POLG1 was sequenced. Results: Five AChR-Ab seropositive [AChR(+)] and 5 seronegative [AChR(-)] patients were MuSK-Ab seropositive [MuSK(+)]. Five of 7 neurophysiologically examined MuSK(+) patients (71%) had proximal myopathic pattern, compared to 7 of 31 MuSK(-)/AChR(+) patients (23%) (P=0.012). SFEMG was abnormal in all examined MuSK(+) patients. All 7 biopsied MuSK(+) and 32 MuSK(-) patients (89%) had cytochrome c oxidase (COX) negative fibers. Three of five MuSK(+) and 13 of 20 MuSK(-) patients analyzed had multiple mtDNA deletions but no POLG1 mutations. Conclusions: Similar degree of SFEMG abnormalities was present in proximal muscles among MuSK(+) and AChR(+) patients. Proximal myopathy was over-represented in MuSK(+) patients; however, both MuSK(+) and MuSK(-) patients had mild myopathy with frequent mitochondrial abnormalities. Significance: The weakness in MuSK(+) patients is most likely due to disturbed neuromuscular transmission. The frequently encountered mitochondrial dysfunction in MG warrants further study. \ua9 2006 International Federation of Clinical Neurophysiology