open_access
Refine
Year
Publication Type
- Article (121)
- Report (34)
- Conference Proceeding (18)
- Book (11)
- Contribution to a Periodical (5)
- Other (5)
- Bachelor Thesis (3)
- Part of a Book (3)
- Working Paper (3)
- Part of Periodical (2)
Keywords
- PIV (4)
- renewable energy (4)
- wind turbine (4)
- Blockchain (3)
- Lüftungstechnik (3)
- Nachhaltigkeit (3)
- instationäre Lüftung (3)
- BBNE (2)
- Spreadsheet Energy System Model Generator (2)
- Third culture kids (2)
Faculty
A numerical analysis of laser resonators with aberrations is presented. {T}he analysis shows that aberrations lead to large diffraction losses of laser resonators which are laid out to produce diffraction-limited beam quality. {S}tatic or dynamic compensation of the aberrations is possible and would yield much higher output power.
Adaptive laser resonators with deformable MOEMS mirrors under closed-loop control are discussed and experimental results are presented. The requirements for deformable mirrors and for closed-loop control systems of these mirrors are analyzed. Several deformable mirrors have been characterized and the results are presented. Currently available membrane mirrors deform under laser load and need further development before they can be used for aberration correction of solid state lasers above some tens of Watts. Nevertheless, the results are encouraging and the requirements are within reach of currently available technology. Finally, we demonstrate an Nd.YVO4-laser with a closed-loop adaptive resonator and more than 6 W of output power. The closed-loop system was able to compensate artificially introduced aberrations from a phase plate.
In order to avoid optical damage and non-linear effects, high-power, high-energy lasers of the petawatt class like PHELIX (petawatt high-energy laser for heavy-ion experiments) use large-aperture optics. Usually, chromatic aberration associated with these optical elements is neglected. By means of numerical simulations, we show how the chromatic aberration affects the focal intensity pattern. In particular, we make quantitative predictions of how chromatic aberration decreases the focused peak intensity. Furthermore, we prove the feasibility of a new interferometer that measures the temporal pulse front distortions which arise from expansion telescopes. We also propose a scheme that pre-compensates these distortions.
Background
Degenerative musculoskeletal disorders are among the most frequent diseases occurring in adulthood, often impairing patients' functional mobility and physical activity. The aim of the present study was to investigate and compare the impact of three frequent degenerative musculoskeletal disorders -- knee osteoarthritis (knee OA), hip osteoarthritis (hip OA) and lumbar spinal stenosis (LSS) -- on patients' walking ability.
Methods
The study included 120 participants, with 30 in each patient group and 30 healthy control individuals. A uniaxial accelerometer, the StepWatch™ Activity Monitor (Orthocare Innovations, Seattle, Washington, USA), was used to determine the volume (number of gait cycles per day) and intensity (gait cycles per minute) of walking ability. Non-parametric testing was used for all statistical analyses.
Results
Both the volume and the intensity of walking ability were significantly lower among the patients in comparison with the healthy control individuals (p < 0.001). Patients with LSS spent 0.4 (IQR 2.8) min/day doing moderately intense walking (>50 gait cycles/min), which was significantly lower in comparison with patients with knee and hip OA at 2.5 (IQR 4.4) and 3.4 (IQR 16.1) min/day, respectively (p < 0.001). No correlations between demographic or anthropometric data and walking ability were found. No technical problems or measuring errors occurred with any of the measurements.
Conclusions
Patients with degenerative musculoskeletal disorders suffer limitations in their walking ability. Objective assessment of walking ability appeared to be an easy and feasible tool for measuring such limitations as it provides baseline data and objective information that are more precise than the patients' own subjective estimates. In everyday practice, objective activity assessment can provide feedback for clinicians regarding patients' performance during everyday life and the extent to which this confirms the results of clinical investigations. The method can also be used as a way of encouraging patients to develop a more active lifestyle.
Background
Bone mineral density (BMD) accrual during childhood and adolescence is important for attaining peak bone mass. BMD decrements have been reported in survivors of childhood bone sarcomas. However, little is known about the onset and development of bone loss during cancer treatment. The objective of this cross-sectional study was to evaluate BMD in newly diagnosed Ewing's and osteosarcoma patients by means of dual-energy x-ray absorptiometry (DXA) after completion of neoadjuvant chemotherapy.
Methods
DXA measurements of the lumbar spine (L2-4), both femora and calcanei were performed perioperatively in 46 children and adolescents (mean age: 14.3 years, range: 8.6-21.5 years). Mean Z-scores, areal BMD (g/cm2), calculated volumetric BMD (g/cm3) and bone mineral content (BMC, g) were determined.
Results
Lumbar spine mean Z-score was -0.14 (95% CI: -0.46 to 0.18), areal BMD was 1.016 g/cm2 (95% CI: 0.950 to 1.082) and volumetric BMD was 0.330 g/cm3 (95% CI: 0.314 to 0.347) which is comparable to healthy peers. For patients with a lower extremity tumor (n = 36), the difference between the affected and non-affected femoral neck was 12.1% (95% CI: -16.3 to -7.9) in areal BMD. The reduction of BMD was more pronounced in the calcaneus with a difference between the affected and contralateral side of 21.7% (95% CI: -29.3 to -14.0) for areal BMD. Furthermore, significant correlations for femoral and calcaneal DXA measurements were found with Spearman-rho coefficients ranging from ρ = 0.55 to ρ = 0.80.
Conclusions
The tumor disease located in the lower extremity in combination with offloading recommendations induced diminished BMD values, indicating local osteopenia conditions. However, the results revealed no significant decrements of lumbar spine BMD in pediatric sarcoma patients after completion of neoadjuvant chemotherapy. Nevertheless, it has to be taken into account that bone tumor patients may experience BMD decrements or secondary osteoporosis in later life. Furthermore, the peripheral assessment of BMD in the calcaneus via DXA is a feasible approach to quantify bone loss in the lower extremity in bone sarcoma patients and may serve as an alternative procedure, when the established assessment of femoral BMD is not practicable due to endoprosthetic replacements.
Die Studie untersucht den didaktischen Mehrwert partizipativer Medien in der hochschulischen Lehrerbildung. Die hier entwickelten Gestaltungsgrundsätze für die Planung von Lernarrangements mit Social Media sollen dazu beitragen, die Besonderheiten dieser Medien in die didaktische Konzeption einzubinden. Auf diese Weise soll ein Beitrag dazu geleistet werden, den didaktischen Mehrwert von Social Media in Lernarrangements zu entfalten.
The effect of kinesiology tape applications on performance in amateur soccer and team handball
(2015)
Evidence supporting performance enhancing effects of kin esiotape in sports is missing . The aims of this studywere to evaluate effects of kinesiotape applications with regard to shooting and throwing performance in 26 amateursoccer and 32 handball players, and to further investigate if these effects were influenced by the players’ level ofperformance. Ball speed as the primary outcome and accuracy of soccer kicks and handball throws were analyzed withand without kinesiotape by means of radar units and video recordings. The application of kinesiotapes significantlyincreased ball speed in soccer by 1.4 km/h (p=0.047) and accuracy with a lesser di stance from the target by -6.9 cm(p=0.039). Ball velocity in handball throws also signific antly increased by 1.2 km/h (p=0.013), while accuracy wasdeteriorated with a greater distance from the target by 3.4 cm (p=0.005). Larger effects with respect to ball speed werefound in players with a lower performance level in kick ing (1.7 km/h, p=0.028) and throwing (1.8 km/h, p=0.001)compared with higher level soccer and handball players (1.2 km/h, p=0.346 and 0.5 km/h, p=0.511, respectively). Inconclusion, the applications of kinesiot ape used in this study might have beneficial effects on performance in amateursoccer, but the gain in ball speed in handball is counterac ted by a significant deterioration of accuracy. Subgroupanalyses indicate that kinesiotape may yield larger effects on ball velocity in athletes with lower kicking and throwingskills.