Fachbereich Medizintechnik und Technomathematik
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Anpassung der Halswirbelsäule in der Schwerelosigkeit und das Risiko von Bandscheibenvorfällen
(2025)
Astronaut*innen haben ein etwa 20-mal höheres Risiko für Bandscheibenvorfälle (BSV) in der Halswirbelsäule (HWS) als Menschen auf der Erde. Die genauen Ursachen sind noch unklar. Durch die Untersuchung der Bindegewebe-, Muskel- und Knochenadaption der HWS vor und nach dem Aufenthalt im Weltall sollen die Mechanismen aufgeklärt werden, die das erhöhte Risiko von BSV in der HWS begünstigen.
Background: The aim of this study was to assess the agreement between different analysis protocols for the determination of retinal vessel dilation response to flicker light (FL) and its relation to static and metabolic parameters of retinal vessels in healthy subjects.
Methods: In total, 24 right eyes of 24 healthy controls (mean age: 36.04 ± SD 14.4 years) who underwent dynamic and static retinal diameter and oxygen saturation measurements on a Retinal Vessel Analyzer (RVA, Imedos, Jena, Germany) were included. Using repeated video analyses, responses to FL were measured with RVA. These measurements were conducted at three specific retinal locations: within the superotemporal area—within a distance of less than one optic disk (OD) diameter to optic nerve head (ONH) (group 1); greater than one OD diameter to ONH (group 2); and areas near the ONH within the VesselMap region (group 3). For comparability, the static and oxygen saturation parameters were also calculated in the superotemporal peripapillary area using the VesselMap tool of the RVA and were evaluated in relation to the corresponding dynamic area (group 3).
Results: In all groups, the vascular FL response of arteries was less pronounced compared to venules (p = 0.0014). Even though FL responses (mean ± SD: FL-A; FL-V) in group 1 were more pronounced (3.36 ± 2.31; 4.42 ± 1.69) compared to those in group 2 (2.97 ± 2.40; 4.08 ± 1.55) and group 3 (2.84 ± 2.29; 4.21 ± 2.03), they did not reach statistically significant values. The mean flicker response of venules (VDil) in all groups showed negative correlations to the corresponding static parameter: central retinal venous equivalent (CRV) (r = −0.0437; p = 0.015). The mean flicker response of arteries (ADil) in all groups showed negative correlations to the corresponding metabolic parameter: arterio-venous oxygen extraction fraction (r = −0.101; p = 0.041).
Conclusions: Our study confirms that the flicker light response, despite slight variations in its duration and location, allows for reliable measurements, proving the Retinal Vessel Analyzer to be a valuable diagnostic tool. Furthermore, we were able to highlight the relationship between the dynamic and metabolic components of retinal supply, which enables early diagnosis concerning the development of diseases within this spectrum.
The bioconversion of salinized land into healthy agricultural systems by utilizing low-rank coal (LRC) is a strategic approach for sustainable agricultural development. The aims of this study were: (1) to isolate bacterial strains associated with the rhizosphere of native plants in coal-containing soils, (2) to characterize their plant growth-promoting (PGP) and coal-solubilizing capabilities under laboratory conditions and (3) to evaluate their influence on the germination and growth of chia seeds under saline stress. Fourteen bacterial cultures were isolated from the rhizosphere of Artemisia annua L. using culture media containing salt and coal. Based on their PGP activities (nitrogen fixation, phosphate solubilization, siderophore and indole-3-acetic acid production), five strains were selected, belonging to the genera Bacillus, Phyllobacterium, Arthrobacter, and Pseudomonas. Solubilization assays were conducted to confirm the ability of these strains to utilize coal efficiently. Finally, the selected strains were inoculated with chia seeds (Salvia hispanica L.) to evaluate their ameliorating effect under saline stress conditions in coal-containing media. Inoculation with A. subterraneus Y1 resulted in the highest germination and growth metrics of chia seeds. A positive but comparatively weaker response was observed with P. frederiksbergensis AMA1 and B. paramycoides Lb-1 as inoculants. Coal inoculated with halotolerant bacteria can serve as the foundation for humified organic matter in salt-affected environments. The selected halotolerant bacteria enhance coal biotransformation while exhibiting PGP traits.
Background: Numerous single- and double-row repair techniques with simple and modified stitches have been described for subscapularis tendon tears.
Purpose/Hypothesis: This study aimed to uniformly evaluate the influence of 4 different repair techniques on the biomechanical performance of fixation for full-thickness subscapularis tendon tears. It was hypothesized that (1) the 2 modified single-row repair techniques would require more cycles to result in 3- and 5-mm gap formation and have a higher load to failure after cyclic loading than the simple single-row repair technique and (2) the double-row repair technique would also require more cycles to result in 3- and 5-mm gap formation and have a significantly higher load to failure after cyclic loading compared to the simple single-row repair technique.
Study Design: Controlled laboratory study.
Methods: Full-thickness subscapularis tendon tears were created in 32 fresh-frozen cadaveric shoulders, and the tears were treated in 1 of 4 ways: (1) single-row repair with the mattress stitch, (2) single-row repair with the modified lasso-loop stitch, (3) single-row repair with the modified Mason-Allen stitch, or (4) double-row repair. After repair, specimens were progressively cyclically loaded to 200 N, and the number of cycles to obtain a 3- and 5-mm gap was recorded. After cyclic loading, the specimens were loaded to failure at 500 mm/min, and ultimate failure loads were measured.
Results: There were no significant differences between either of the modified single-row repair techniques and the simple single-row repair technique. Double-row repair withstood significantly more cycles until 3-mm (P < .001) and 5-mm (P = .004) gap formation and had a higher ultimate failure load (P = .015) compared to the simple single-row repair technique, and double-row repair withstood more cycles until 3-mm gap formation (P = .003) compared with single-row repair with the modified lasso-loop stitch. No significant differences were found between double-row repair and single-row repair with the modified Mason-Allen stitch.
Conclusion: Findings indicated that (1) there was no significant biomechanical advantage of the modified single-row repair techniques over the simple single-row repair technique and (2) while the double-row repair technique was biomechanically superior to the simple single-row repair technique, there was no significant difference between single-row repair with the modified Mason-Allen stitch and double-row repair.
Clinical Relevance: Considering that double-row repair might not be useful in some tears because of the risk of overtensioning, modified single-row repair techniques appear to be an adequate refixation alternative.
This work presents a new model for the shakedown analysis of Kirchhoff plates under uncertain conditions of the plastic moment by the direct method. The stochastic models of the plastic moment are normal or lognormal distribution. New formulations are derived to compute the lower bound and upper shakedown loads and a dual algorithm is established to calculate the upper and lower bound shakedown load factors simultaneously for a chosen structural reliability level. An example is examined to illustrate the algorithm and shows robust results of the stochastic analysis.
