Refine
Year of publication
Institute
- IfB - Institut für Bioengineering (542)
- Fachbereich Medizintechnik und Technomathematik (453)
- Fachbereich Luft- und Raumfahrttechnik (136)
- Fachbereich Chemie und Biotechnologie (11)
- Kommission für Forschung und Entwicklung (6)
- Senat (2)
- Arbeitsstelle fuer Hochschuldidaktik und Studienberatung (1)
- Fachbereich Maschinenbau und Mechatronik (1)
Has Fulltext
- no (601) (remove)
Language
- English (601) (remove)
Document Type
- Article (437)
- Conference Proceeding (108)
- Part of a Book (34)
- Book (9)
- Other (4)
- Patent (4)
- Doctoral Thesis (3)
- Conference: Meeting Abstract (1)
- Talk (1)
Keywords
- solar sail (5)
- CellDrum (3)
- GOSSAMER-1 (3)
- MASCOT (3)
- Biocomposites (2)
- Iterative learning control (2)
- Limit analysis (2)
- Mars (2)
- Natural fibres (2)
- Polymer-matrix composites (2)
- Shakedown analysis (2)
- Solar sail (2)
- Spacecraft (2)
- Stiffness (2)
- Stress concentrations (2)
- Trajectory Optimization (2)
- bacterial cellulose (2)
- biopotential electrodes (2)
- damage (2)
- locomotion (2)
- multiple NEA rendezvous (2)
- muscle fascicle behavior (2)
- prebiotic (2)
- small spacecraft (2)
- ultrasound (2)
- ultrasound imaging (2)
- Achilles tendon (1)
- Adaptive control (1)
- Ageing (1)
- AlterG (1)
- Alzheimer's disease (1)
- Analogue Environments (1)
- Anastomotic leakage (1)
- Anatomy (1)
- Annulus Fibrosus (1)
- Antarctic Glaciology (1)
- Antarctica (1)
- Architectural gear ratio (1)
- Assistive technology (1)
- Asteroid Deflection (1)
- Attitude dynamics (1)
- Autolysis (1)
- Automated Optimization (1)
- Automatic control (1)
- Bacillus sp (1)
- Biomechanical simulation (1)
- Biosolubilization (1)
- Bladder (1)
- Bone sawing (1)
- Cardiac myocytes (1)
- Cardiac tissue (1)
- Cell permeability (1)
- Cellular force (1)
- Cementoblast (1)
- Chance constrained programming (1)
- Circular Dichroism (1)
- Coal (1)
- Coefficient of ocular rigidity (1)
- Collagen fibrils (1)
- Compression (1)
- Computational biomechanics (1)
- Connective tissues (1)
- Constitutive model (1)
- Contractile tension (1)
- Corneo-scleral shell (1)
- Cryobot (1)
- DLR-ESTEC GOSSAMER roadmap for solar sailing (1)
- Damage mechanics theory (1)
- Decomposition (1)
- Differential tonometry (1)
- Disc Degeneration (1)
- Discontinuous fractures (1)
- Drug simulation (1)
- Dry surfaces (1)
- EEG (1)
- ES-FEM (1)
- Electromechanical modeling (1)
- End-to-end colorectal anastomosis (1)
- Endothelial cells (1)
- Endothelial dysfunction (1)
- Evolution of damage (1)
- Evolutionary Neurocontrol (1)
- Extension fracture (1)
- Extension strain criterion (1)
- External knee adduction moments (1)
- Extracellular matrix (ECM) (1)
- Extraterrestrial Glaciology (1)
- Eyeball (1)
- FGF23 (1)
- FS-FEM (1)
- Finite element analysis (1)
- Finite element analysis (FEA) (1)
- Finite element modelling (1)
- Force (1)
- Forces (1)
- Fracture configuration (1)
- Fracture simulation (1)
- Freeze–thaw process (1)
- Frequency adaption (1)
- Glaciological instruments and methods (1)
- Glaucoma (1)
- Gossamer (1)
- Gossamer structures (1)
- Growth modelling (1)
- H2 (1)
- Haemodialysis (1)
- Handbike (1)
- Heart tissue culture (1)
- Hodgkin–Huxley models (1)
- Homogenization (1)
- Human-Computer interaction (1)
- Hybrid Propellants (1)
- Hydrogenotrophic methanogens (1)
- Ice Melting (1)
- Ice melting probe (1)
- Ice penetration (1)
- Icy Moons (1)
- Icy moons (1)
- Impedance Spectroscopy (1)
- Induced pluripotent stem cells (1)
- Inotropic compounds (1)
- Interplanetary flight (1)
- Interstellar objects (1)
- Intervertebral Disc (1)
- Intradiscal Pressure (1)
- Inverse dynamic problem (1)
- Inverse kinematic problem (1)
- Ion channels (1)
- Jupiter (1)
- Klotho (1)
- Knee (1)
- LPS (1)
- Lactobacillus rhamnosus GG (1)
- Lipopolysaccharide (1)
- Liver (1)
- Load modeling (1)
- Long COVID (1)
- Low-Thrust Propulsion (1)
- Machine learning (1)
- Manipulated variables (1)
- Mechanical simulation (1)
- Mechanical stability (1)
- Mechanotransduction (1)
- Melting Efficiency (1)
- Melting Performance (1)
- Melting Probe (1)
- Methane (1)
- Methanogenesis (1)
- Microbial adhesion (1)
- Microcirculation (1)
- Mild cognitive impairment (1)
- Missions (1)
- Mohr–Coulomb criterion (1)
- Multimode failure (1)
- Multiphase (1)
- Muscle (1)
- Muscle Fascicle (1)
- Muscle Force (1)
- Muscle fibers (1)
- Musculoskeletal model (1)
- Musculoskeletal system (1)
- Myocardial infarction and cardiac death (1)
- NONOate (1)
- Niacin (1)
- Nitric Oxide (1)
- Nitric Oxide Donor (1)
- Non-linear optimization (1)
- Non-parallel fissures (1)
- Nucleus Pulposus (1)
- Ocean Worlds (1)
- Ocean worlds (1)
- Ocular blood flow (1)
- Orbital dynamics (1)
- PHILAE (1)
- PTH (1)
- Paralympic sport (1)
- Passive stretching (1)
- Pelvic floor dysfunction (1)
- Pelvic muscle (1)
- Pharmacology (1)
- Phosphate (1)
- Physiology (1)
- Planetary Protection (1)
- Planetary exploration (1)
- Post-COVID-19 syndrome (1)
- Pressure-volume relationship (1)
- Proximal humerus fracture (1)
- Pulsations (1)
- RVA (1)
- Recombinant activated protein C (1)
- Reconstruction (1)
- Rehabilitation Technology and Prosthetics (1)
- Rehabilitation engineering (1)
- Reliability analysis (1)
- Reliability of structures (1)
- Retinal vessel analysis (1)
- Retinal vessels (1)
- Reusable Rocket Engines (1)
- Riboflavin (1)
- Robotic rehabilitation (1)
- Rotator cuff (1)
- Running (1)
- S-FEM (1)
- Sampling methods (1)
- Septic cardiomyopathy (1)
- Sequence-Search (1)
- Simulation (1)
- Sleep EEG (1)
- Small Solar System Body Lander (1)
- Small Spacecraft (1)
- Small spacecraft (1)
- Solar Power Sail (1)
- Solar Sail (1)
- Spacecraft Trajectory Optimization (1)
- Spleen (1)
- Stochastic programming (1)
- Subclacial exploration (1)
- Subglacial lakes (1)
- Surface microorganisms (1)
- Surgical Navigation and Robotics (1)
- Surgical staplers (1)
- Swabbing (1)
- Tapered ends (1)
- Tendon Rupture (1)
- Tendon properties (1)
- Tension (1)
- Thiamine (1)
- Training (1)
- Trajectories (1)
- Uniaxial compression test (1)
- Ureter (1)
- Variable height stapler design (1)
- Vascular response (1)
- Vasomotions (1)
- Visual field asymmetry (1)
- Vitamin A (1)
- Vitamin B (1)
- Vitamin D (1)
- achilles tendon (1)
- actin cytoskeleton (1)
- adipose-derived stromal cells (ASCs) (1)
- adsorption (1)
- agility (1)
- anaesthetic complications (1)
- anisotropy (1)
- aortic perfusion (1)
- asteroid lander (1)
- asteroid sample return (1)
- attitude dynamics (1)
- biaxial tensile experiment (1)
- biofilms (1)
- biomechanics (1)
- carbonized rice husk (1)
- cardiomyocyte biomechanics (1)
- cell aerosolization (1)
- cell atomization (1)
- cerebral small vessel disease (1)
- chance constrained programming (1)
- coculture (1)
- cognitive impairment (1)
- community dwelling (1)
- computational fluid dynamics analysis (1)
- connective tissue (1)
- constitutive modeling (1)
- constructive alignment (1)
- correlation (1)
- crop yield (1)
- dental trauma (1)
- dialysis (1)
- difficult airway (1)
- distorted element (1)
- double-lumen tube intubation (1)
- drop jump (1)
- electromyography (1)
- endoluminal (1)
- energy absorption (1)
- energy dissipation (1)
- examination (1)
- exopolysaccharides (1)
- extracorporeal membrane oxygenation (1)
- flotilla missions (1)
- force generation (1)
- forehead EEG (1)
- gait (1)
- habitability (1)
- healthy aging (1)
- heliosphere (1)
- hiPS cardiomyocytes (1)
- high-intensity exercise (1)
- humic acid (1)
- hyper-gravity (1)
- hyperelastic (1)
- hypo-gravity (1)
- ice moons (1)
- icy moons (1)
- immobilization (1)
- impedance spectroscopy (1)
- in-ear EEG (1)
- intraclass correlation coefficient (1)
- ion propulsion (1)
- life detection (1)
- lignite (1)
- limit analysis (1)
- lipopolysaccharide (1)
- long-term retention (1)
- low-rank coal (1)
- low-thrust (1)
- low-thrust trajectory optimization (1)
- mechanical buffer (1)
- multimodal (1)
- muscle mechanics (1)
- near-Earth asteroid (1)
- non-simplex S-FEM elements (1)
- orbit control (1)
- orbital dynamics (1)
- overload (1)
- parabolic flight (1)
- performance testing (1)
- physiology (1)
- planetary defence (1)
- practical learning (1)
- prevention (1)
- psychosocial (1)
- pullulan (1)
- rehabilitation (1)
- reliability of structures (1)
- responsive space (1)
- retinal microvasculature (1)
- retinal vessels (1)
- running (1)
- sEMG (1)
- sailcraft (1)
- sample return (1)
- sarcomere operating length (1)
- sensors (1)
- series elastic element behavior (1)
- shakedown analysis (1)
- shoulder (1)
- simulation (1)
- small solar system body characterisation (1)
- small spacecraft asteroid lander (1)
- small spacecraft solar sail (1)
- smooth muscle contraction (1)
- soil amendment (1)
- soil health (1)
- soil remediation (1)
- solar sails (1)
- solar system (1)
- space missions (1)
- sprint start (1)
- standard error of measurement (1)
- stiffness (1)
- stochastic programming (1)
- strain energy function (1)
- stretch reflex (1)
- stretch-shortening cycle (1)
- surface modification (1)
- survival (1)
- system engineering (1)
- tendon rupture (1)
- test-retest reliability (1)
- training simulator (1)
- tri-lineage differentiation (1)
- twin-fluid atomizer (1)
- ultrasonography (1)
- underwater vehicle (1)
- unloading (1)
- videolaryngoscopy (1)
- virgin passive (1)
- virtual reality (1)
- viscoelasticity (1)
- walking (1)
- walking gait (1)
Influence of a freeze–thaw cycle on the stress–stretch curves of tissues of porcine abdominal organs
(2012)
The paper investigates both fresh porcine spleen and liver and the possible decomposition of these organs under a freeze–thaw cycle. The effect of tissue preservation condition is an important factor which should be taken into account for protracted biomechanical tests. In this work, tension tests were conducted for a large number of tissue specimens from twenty pigs divided into two groups of 10. Concretely, the first group was tested in fresh state; the other one was tested after a freeze-thaw cycle which simulates the conservation conditions before biomechanical experiments. A modified Fung model for isotropic behavior was adopted for the curve fitting of each kind of tissues. Experimental results show strong effects of the realistic freeze–thaw cycle on the capsule of elastin-rich spleen but negligible effects on the liver which virtually contains no elastin. This different behavior could be explained by the autolysis of elastin by elastolytic enzymes during the warmer period after thawing. Realistic biomechanical properties of elastin-rich organs can only be expected if really fresh tissue is tested. The observations are supported by tests of intestines.
Suburethral slings as well as different meshes are widely used treating stress urinary incontinence and prolaps in women. With the development of MiniSlings and special meshes using less alloplastic material anchorage systems become more important to keep devices in place and to put some tension especially on the MiniSlings. To date, there are many different systems of MiniSlings of different companies on the market which differ in the structure of the used meshes and anchors. A new objective measurement method to compare different properties of MiniSling systems (mesh and anchor) is presented in this article. Ballistic gelatine acts as soft tissue surrogate. Significant differences in parameters like pull-out strength of anchors or shrinkage of meshes under loading conditions have been determined. The form and size of the anchors as well as the structural stability of the meshes are decisive for a proper integration. The tested anchorings sytems showed markedly different mechanical function at their respective load bearing capacity. As the stable fixation of the device in tissue is a prerequisite for a permanet reinforcement, the proposed test system permits further optimisation of anchor and mesh devices to improve the success of the surgical treatment
The impact of surgical staplers on tissues has been studied mostly in an empirical manner. In this paper, finite element method was used to clarify the mechanics of tissue stapling and associated phenomena. Various stapling modalities and several designs of circular staplers were investigated to evaluate the impact of the device on tissues and mechanical performance of the end-to-end colorectal anastomosis. Numerical simulations demonstrated that a single row of staples is not adequate to resist leakage due to non-linear buckling and opening of the tissue layers between two adjacent staples. Compared to the single staple row configuration, significant increase in stress experienced by the tissue at the inner staple rows was observed in two and three rows designs. On the other hand, adding second and/or third staple row had no effect on strain in the tissue inside the staples. Variable height design with higher staples in outer rows significantly reduced the stresses and strains in outer rows when compared to the same configuration with flat cartridge.
Thermodynamic stability, configurational motions and internal forces of haemoglobin (Hb) of three endotherms (platypus, Ornithorhynchus anatinus; domestic chicken, Gallus gallus domesticus and human, Homo sapiens) and an ectotherm (salt water crocodile, Crocodylus porosus) were investigated using circular dichroism, incoherent elastic neutron scattering and coarse-grained Brownian dynamics simulations. The experimental results from Hb solutions revealed a direct correlation between protein resilience, melting temperature and average body temperature of the different species on the 0.1 ns time scale. Molecular forces appeared to be adapted to permit conformational fluctuations with a root mean square displacement close to 1.2 Å at the corresponding average body temperature of the endotherms. Strong forces within crocodile Hb maintain the amplitudes of motion within a narrow limit over the entire temperature range in which the animal lives. In fully hydrated powder samples of human and chicken, Hb mean square displacements and effective force constants on the 1 ns time scale showed no differences over the whole temperature range from 10 to 300 K, in contrast to the solution case. A complementary result of the study, therefore, is that one hydration layer is not sufficient to activate all conformational fluctuations of Hb in the pico- to nanosecond time scale which might be relevant for biological function. Coarse-grained Brownian dynamics simulations permitted to explore residue-specific effects. They indicated that temperature sensing of human and chicken Hb occurs mainly at residues lining internal cavities in the β-subunits.
Heterogeneous Composites on the Basis of Microbial Cells and Nanostructured Carbonized Sorbents
(2012)
The fact that microorganisms prefer to grow on liquid/solid phase surfaces rather than in the surrounding aqueous phase was noticed long time ago [1]. Virtually any surface – animal, mineral, or vegetable – is a subject for microbial colonization and subsequent biofilm formation. It would be adequate to name just a few notorious examples on microbial colonization of contact lenses, ship hulls, petroleum pipelines, rocks in streams and all kinds of biomedical implants. The propensity of microorganisms to become surface-bound is so profound and ubiquitous that it vindicates the advantages for attached forms over their free-ranging counterparts [2]. Indeed, from ecological and evolutionary standpoints, for many microorganisms the surface-bound state means dwelling in nutritionally favorable, non-hostile environments [3]. Therefore, in most of natural and artificial ecosystems surface-associated microorganisms vastly outnumber organisms in suspension and often organize into complex communities with features that differ dramatically from those of free cells [4].
We present a new approach to the problem of optimal control of solar sails for low-thrust trajectory optimization. The objective was to find the required control torque magnitudes in order to steer a solar sail in interplanetary space. A new steering strategy, controlling the solar sail with generic torques applied about the spacecraft body axes, is integrated into the existing low-thrust trajectory optimization software InTrance. This software combines artificial neural networks and evolutionary algorithms to find steering strategies close to the global optimum without an initial guess. Furthermore, we implement a three rotational degree-of-freedom rigid-body attitude dynamics model to represent the solar sail in space. Two interplanetary transfers to Mars and Neptune are chosen to represent typical future solar sail mission scenarios. The results found with the new steering strategy are compared to the existing reference trajectories without attitude dynamics. The resulting control torques required to accomplish the missions are investigated, as they pose the primary requirements to a real on-board attitude control system.
There is common agreement within the scientific community that in order to understand our local galactic environment it will be necessary to send a spacecraft into the region beyond the solar wind termination shock. Considering distances of 200 AU for a new mission, one needs a spacecraft traveling at a speed of close to 10 AU/yr in order to keep the mission duration in the range of less than 25 yrs, a transfer time postulated by European Space Agency (ESA). Two propulsion options for the mission have been proposed and discussed so far: the solar sail propulsion and the ballistic/radioisotope-electric propulsion (REP). As a further alternative, we here investigate a combination of solar-electric propulsion (SEP) and REP. The SEP stage consists of six 22-cms diameter RIT-22 ion thrusters working with a high specific impulse of 7377 s corresponding to a positive grid voltage of 5 kV. Solar power of 53 kW at begin of mission (BOM) is provided by a lightweight solar array.
Effectiveness of the edge-based smoothed finite element method applied to soft biological tissues
(2012)
Visual Virology
(2012)
Determination of the frictional coefficient of the implant-antler interface : experimental approach
(2012)
The similar bone structure of reindeer antler to human bone permits studying the osseointegration of dental implants in the jawbone. As the friction is one of the major factors that have a significant influence on the initial stability of immediately loaded dental implants, it is essential to define the frictional coefficient of the implant-antler interface. In this study, the kinetic frictional forces at the implant-antler interface were measured experimentally using an optomechanical setup and a stepping motor controller under different axial loads and sliding velocities. The corresponding mean values of the static and kinetic frictional coefficients were within the range of 0.5–0.7 and 0.3–0.5, respectively. An increase in the frictional forces with increasing applied axial loads was registered. The measurements showed an evidence of a decrease in the magnitude of the frictional coefficient with increasing sliding velocity. The results of this study provide a considerable assessment to clarify the suitable frictional coefficient to be used in the finite element contact analysis of antler specimens.
Background
Minor changes in protein structure induced by small organic and inorganic molecules can result in significant metabolic effects. The effects can be even more profound if the molecular players are chemically active and present in the cell in considerable amounts. The aim of our study was to investigate effects of a nitric oxide donor (spermine NONOate), ATP and sodium/potassium environment on the dynamics of thermal unfolding of human hemoglobin (Hb). The effect of these molecules was examined by means of circular dichroism spectrometry (CD) in the temperature range between 25°C and 70°C. The alpha-helical content of buffered hemoglobin samples (0.1 mg/ml) was estimated via ellipticity change measurements at a heating rate of 1°C/min.
Results
Major results were:
1) spermine NONOate persistently decreased the hemoglobin unfolding temperature T u irrespectively of the Na + /K + environment,
2) ATP instead increased the unfolding temperature by 3°C in both sodium-based and potassium-based buffers and
3) mutual effects of ATP and NO were strongly influenced by particular buffer ionic compositions. Moreover, the presence of potassium facilitated a partial unfolding of alpha-helical structures even at room temperature.
Conclusion
The obtained data might shed more light on molecular mechanisms and biophysics involved in the regulation of protein activity by small solutes in the cell.
Upper and lower bound theorems of limit analyses have been presented in part I of the paper. Part II starts with the finite element discretization of these theorems and demonstrates how both can be combined in a primal–dual optimization problem. This recently proposed numerical method is used to guide the development of a new class of closed-form limit loads for circumferential defects, which show that only large defects contribute to plastic collapse with a rapid loss of strength with increasing crack sizes. The formulae are compared with primal–dual FEM limit analyses and with burst tests. Even closer predictions are obtained with iterative limit load solutions for the von Mises yield function and for the Tresca yield function. Pressure loading of the faces of interior cracks in thick pipes reduces the collapse load of circumferential defects more than for axial flaws. Axial defects have been treated in part I of the paper.