Refine
Year of publication
Institute
- Fachbereich Medizintechnik und Technomathematik (1692) (remove)
Language
- English (1692) (remove)
Document Type
- Article (1359)
- Conference Proceeding (212)
- Book (43)
- Part of a Book (43)
- Doctoral Thesis (18)
- Other (6)
- Patent (4)
- Preprint (3)
- Lecture (2)
- Habilitation (1)
Keywords
- Biosensor (25)
- Finite-Elemente-Methode (12)
- Einspielen <Werkstoff> (10)
- CAD (8)
- civil engineering (8)
- Bauingenieurwesen (7)
- FEM (6)
- Limit analysis (6)
- Shakedown analysis (6)
- shakedown analysis (6)
- Clusterion (5)
- Air purification (4)
- Hämoglobin (4)
- LAPS (4)
- Lipopolysaccharide (4)
- Luftreiniger (4)
- Natural language processing (4)
- Plasmacluster ion technology (4)
- Raumluft (4)
- hydrogen peroxide (4)
- impedance spectroscopy (4)
- limit analysis (4)
- CellDrum (3)
- Einspielanalyse (3)
- Field-effect sensor (3)
- Information extraction (3)
- Kohlenstofffaser (3)
- Label-free detection (3)
- Light-addressable potentiometric sensor (3)
- Paired sample (3)
- Shakedown (3)
- Sonde (3)
- Technische Mechanik (3)
- Traglastanalyse (3)
- biosensor (3)
- biosensors (3)
- lipopolysaccharides (3)
- shakedown (3)
- Analytischer Zulaessigkeitsnachweis (2)
- Bacillus atrophaeus (2)
- Biocomposites (2)
- Boundary integral equations (2)
- Bruchmechanik (2)
- Capacitive field-effect sensor (2)
- Clustering (2)
- Conductive boundary condition (2)
- Einspiel-Analyse (2)
- Eisschicht (2)
- Empirical process (2)
- Erythrozyt (2)
- Fibroblast (2)
- Force (2)
- Goodness-of-fit test (2)
- Incomplete data (2)
- Independence test (2)
- Iterative learning control (2)
- Machine learning (2)
- Natural fibres (2)
- Parametric bootstrap (2)
- Pflanzenphysiologie (2)
- Pflanzenscanner (2)
- Polymer-matrix composites (2)
- Potentiometry (2)
- Raman spectroscopy (2)
- Simulation (2)
- Stickstoffmonoxid (2)
- Stiffness (2)
- Stress concentrations (2)
- Tobacco mosaic virus (TMV) (2)
- Traglast (2)
- Transmission eigenvalues (2)
- acetoin (2)
- biopotential electrodes (2)
- capacitive field-effect sensors (2)
- carbonized rice husk (2)
- celldrum technology (2)
- constructive alignment (2)
- damage (2)
- examination (2)
- field-effect sensor (2)
- frequency mixing magnetic detection (2)
- gas sensor (2)
- likelihood ratio test (2)
- limit load (2)
- locomotion (2)
- long-term retention (2)
- multimodal (2)
- muscle fascicle behavior (2)
- nanostructured carbonized plant parts (2)
- nanostrukturierte carbonisierte Pflanzenteile (2)
- nitric oxide gas (2)
- not identically distributed (2)
- plant scanner (2)
- practical learning (2)
- ratchetting (2)
- sterilisation (2)
- surface modification (2)
- tobacco mosaic virus (TMV) (2)
- ultrasound (2)
- ultrasound imaging (2)
- (Bio)degradation (1)
- 3-nitrofluoranthene (1)
- Acceleration (1)
- Achilles tendon (1)
- Active learning (1)
- Adaptive control (1)
- Adsorption (1)
- Afterload (1)
- Ageing (1)
- Agent-based modeling (1)
- Agent-based simulation (1)
- AlterG (1)
- Alternating plasticity (1)
- Alzheimer's disease (1)
- Analysis (1)
- Analytical models (1)
- Anastomose (1)
- Anastomosis (1)
- Anastomotic leakage (1)
- Anatomy (1)
- Annulus Fibrosus (1)
- Architectural design (1)
- Architectural gear ratio (1)
- Assistive technology (1)
- Asymptotic efficiency (1)
- Asymptotic relative efficiency (1)
- Autofluoreszenzverfahren (1)
- Autolysis (1)
- Automatic control (1)
- Axialbelastung (1)
- Axially cracked pipe (1)
- BTEX compounds (1)
- Bacillus atrophaeus spores (1)
- Bacillus sp (1)
- Bacterial cellulose (1)
- Bakterien (1)
- Balance (1)
- Basis Reduktion (1)
- Basis reduction (1)
- Bicharakteristikenverfahren (1)
- Bio-Sensors (1)
- Bioabsorbable (1)
- Biomechanical simulation (1)
- Biomechanics (1)
- Biomechanik (1)
- Biomedizinische Technik (1)
- Biomolecular logic gate (1)
- Biophoton (1)
- Bioreaktor (1)
- Biosensorik (1)
- Biosolubilization (1)
- Bladder (1)
- Blitzschutz (1)
- Blutzellenlagerung (1)
- Bone quality and biomechanics (1)
- Bone sawing (1)
- Booster Station (1)
- Bootstrap (1)
- Bootstrapping (1)
- Boundary integral equations, (1)
- Brownian Pillow (1)
- CAD ; (1)
- CNOT (1)
- CO (1)
- Calorimetric gas sensor (1)
- Capacitive field-effect (1)
- Capacitive model (1)
- Carbon sources (1)
- Cardiac myocytes (1)
- Cardiac tissue (1)
- Categorial variable (1)
- Cell permeability (1)
- Cellular force (1)
- Cellulose nanostructure (1)
- Cement infiltration (1)
- Cementoblast (1)
- Censored data (1)
- Chance constrained programming (1)
- Chemical images (1)
- Chemical imaging (1)
- Chemical imaging sensor (1)
- Chemical sensor (1)
- Circular Dichroism (1)
- Cloud Computing (1)
- Cloud Service Broker (1)
- Co-managed care (1)
- Coal (1)
- Coat protein (1)
- Coefficient of ocular rigidity (1)
- Collective risk model (1)
- Comparative simulation (1)
- Competitiveness (1)
- Complex System (1)
- Complex-valued eigenvalues (1)
- Compliance (1)
- Compression (1)
- Computational biomechanics (1)
- Concomitant (1)
- Conducing polymer (1)
- Conductive Boundary Condition (1)
- Conservation laws (1)
- Constitutive model (1)
- Contractile tension (1)
- Contractility (1)
- Convex optimization (1)
- Corneo-scleral shell (1)
- Cost-effectiveness (1)
- Coverage probability (1)
- Cramér-von-Mises statistic (1)
- Cramér-von-Mises test (1)
- Cross border adjustment mechanism (1)
- Crámer–von-Mises distance (1)
- Culture media (1)
- C–V method (1)
- DNA (1)
- DNA biosensor (1)
- DNA hybridization (1)
- DPA (dipicolinic acid) (1)
- Damage mechanics theory (1)
- Database (1)
- Dattel (1)
- Decomposition (1)
- Deep learning (1)
- Deformation (1)
- Dehydrogenase (1)
- Dekontamination (1)
- Design-by-analysis (1)
- Diaphorase (1)
- Differential tonometry (1)
- Dimensional splitting (1)
- Disc Degeneration (1)
- Discontinuous fractures (1)
- Discrete Optimization (1)
- Druckbeanspruchung (1)
- Druckbehälter (1)
- Druckbelastung (1)
- Druckgeräte (1)
- Drug simulation (1)
- Dry surfaces (1)
- E-Mobility (1)
- E. coli detection (1)
- ECT (1)
- EEG (1)
- EIS capacitive sensor (1)
- ELISA (1)
- EPN (1)
- ES-FEM (1)
- Eigenvalue trajectories (1)
- Einspiel-Kriterium (1)
- Einspielen (1)
- Elastizität (1)
- Elastodynamik (1)
- Elastostatics (1)
- Elderly (1)
- Electrolyte–insulator–semiconductor (1)
- Electromagnetism (1)
- Electromechanical modeling (1)
- Elektrodynamik (1)
- Elemental (1)
- End-to-end colorectal anastomosis (1)
- Endothelial cells (1)
- Endothelial dysfunction (1)
- Endothelzelle (1)
- Energy dispatch (1)
- Energy market (1)
- Energy market design (1)
- Energy-intensive industry (1)
- Enterprise information systems (1)
- Entropy solution (1)
- Environmental impact (1)
- Enzymatic biosensor (1)
- Enzyme biosensor (1)
- Enzyme coverage (1)
- Enzyme logic gate (1)
- Enzyme nanocarrier (1)
- Enzyme-linked immunosorbent assay (1)
- Epithel (1)
- Equivalence test (1)
- Esophageal Doppler monitor (1)
- Evolution of damage (1)
- Exact Ilyushin yield surface (1)
- Experiment (1)
- Exponential Euler scheme, (1)
- Exponential time differencing (1)
- Extension fracture (1)
- Extension strain criterion (1)
- External knee adduction moments (1)
- Eyeball (1)
- FGF23 (1)
- FS-FEM (1)
- Fall prevention (1)
- Fault approximation (1)
- Fault detection (1)
- Fehlerstellen (1)
- Festkörper (1)
- Field effect (1)
- Field-effect biosensor (1)
- Field-effect device (1)
- Finite difference methods (1)
- Finite element analysis (1)
- Finite element analysis (FEA) (1)
- Finite element method (1)
- Finite element modelling (1)
- First Order Reliabiblity Method (1)
- First-order reliability method (1)
- Fließgrenze (1)
- Floor prices (1)
- Fluorescence (1)
- Focusing (1)
- Forces (1)
- Fracture configuration (1)
- Fracture simulation (1)
- Freeze–thaw process (1)
- Frequency adaption (1)
- Frequency mixing magnetic detection (1)
- Functional Delta Method (1)
- GaAs hot electron injector (1)
- Gamma distribution (1)
- Gas sensor (1)
- Geriatric (1)
- German (1)
- Glaucoma (1)
- Global and local collapse (1)
- Glucose biosensor (1)
- Glucose oxidase (1)
- Gold nanoparticle (1)
- Gold nanoparticles (1)
- Goodness-of-fit tests for uniformity (1)
- Grenzwertberechnung (1)
- Grid Computing (1)
- Ground-level falls (1)
- Growth modelling (1)
- Gunn diode (1)
- H2 (1)
- Hadamard differentiability (1)
- Haemodialysis (1)
- Handbike (1)
- Harnleiter (1)
- Heart tissue culture (1)
- Heavy metal detection (1)
- Helmholtz equation (1)
- Hemoglobin structure (1)
- Heterostructure (1)
- High throughput experimentation (1)
- Higher-order codes (1)
- Hip fractures (1)
- Hodgkin–Huxley models (1)
- Hoeffding-Blum-Kiefer-Rosenblatt independence test (1)
- Homogenization (1)
- Hotelling’s T² test (1)
- Hotplate (1)
- Human-Computer interaction (1)
- Hydrodynamik (1)
- Hydrogel (1)
- Hydrogen peroxide (1)
- Hydrogen sensor (1)
- Hydrogenotrophic methanogens (1)
- Hämoglobinstruktur (1)
- I3S 2005 (1)
- ISFET (1)
- Image Reconstruction (1)
- Impedance Spectroscopy (1)
- Impedance spectroscopy (1)
- Implicit methods (1)
- Induced pluripotent stem cells (1)
- Information Extraction (1)
- Inotropic compounds (1)
- Instruments (1)
- Integrated empirical distribution (survival) function (1)
- Interior Neumann eigenvalues (1)
- Interior transmission eigenvalues (1)
- Interior transmission problem (1)
- International Symposium on Sensor Science (1)
- Intervertebral Disc (1)
- Intradiscal Pressure (1)
- Inverse Scattering (1)
- Inverse dynamic problem (1)
- Inverse kinematic problem (1)
- Inverse scattering (1)
- Inverse scattering problem (1)
- Inverse spectral problem (1)
- Ion channels (1)
- Kinematics (1)
- Kinetic energy (1)
- Kinetics (1)
- Klotho (1)
- Knee (1)
- Knochen (1)
- Knochenbildung (1)
- Knochenchirugie (1)
- Knochendichte (1)
- Körpertemperatur (1)
- LED chip (1)
- LPS (1)
- Lab-on-Chip (1)
- Langevin theory (1)
- Layer-by-layer adsorption (1)
- LbL films (1)
- Level sensor (1)
- Lichtstreuungsbasierte Instrumente (1)
- Light-addressable Potentiometric Sensor (1)
- Liver (1)
- Load modeling (1)
- Long COVID (1)
- MCDA (1)
- MEMS (1)
- MOS (1)
- Magnetic nanoparticles (1)
- Main sensitivity (1)
- Manipulated variables (1)
- Marginal homogeneity (1)
- Marginal homogeneity test (1)
- Market modeling (1)
- Master stamp (1)
- Materialermüdung (1)
- Matrix exponential (1)
- Measurement (1)
- Mechanical simulation (1)
- Mechanics (1)
- Mechanische Beanspruchung (1)
- Mechanotransduction (1)
- Medusomyces gisevi (1)
- Metascintillator (1)
- Methane (1)
- Methanogenesis (1)
- Microbial adhesion (1)
- Microcirculation (1)
- Micromagnetic simulation (1)
- Microreactors (1)
- Mild cognitive impairment (1)
- Mobility (1)
- Mobility tests (1)
- Mobility transition (1)
- Model-driven software engineering (1)
- Mohr–Coulomb criterion (1)
- Monotone methods (1)
- Multi-criteria decision analysis (1)
- Multi-dimensional partial differential equations (1)
- Multi-dimensional wave propagation (1)
- Multi-sample problem (1)
- Multianalyte detection (1)
- Multicell (1)
- Multimode failure (1)
- Multiple TOF kernels (1)
- Multiplexing (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)
- Nano Materials (1)
- Nanomaterial (1)
- Nanoparticles (1)
- Nanopartikel (1)
- Nanostructuring (1)
- Nanotechnologie (1)
- Nanotechnology ; Microelectronics ; Biosensors ; Superconductor ; MEMS (1)
- Natriumhypochlorit (1)
- Natural Language Processing (1)
- Natural language understanding (1)
- Negative impedance convertor (1)
- Neural Network (1)
- Niacin (1)
- Nichtlineare Gleichung (1)
- Nichtlineare Optimierung (1)
- Nichtlineare Welle (1)
- Nitric Oxide (1)
- Nitric Oxide Donor (1)
- Non-linear optimization (1)
- Non-parallel fissures (1)
- Nonequilibrium dynamics (1)
- Nonlinear Dynamics (1)
- Nonlinear PDEs (1)
- Nonlinear eigenvalue problems (1)
- Nucleus Pulposus (1)
- Numerical inversion of Laplace transforms (1)
- Numerical linear algebra (1)
- Numerics (1)
- O2 plasma (1)
- Ocular blood flow (1)
- Open Data (1)
- Open source (1)
- Organic light-emitting diode display (1)
- Organkultur (1)
- Organophosphorus (1)
- Ostazine Orange (1)
- Osteoporose (1)
- Osteoporosis (1)
- PFM (1)
- PTH (1)
- Parabolic SPDEs (1)
- Paralympic sport (1)
- Passive stretching (1)
- Pelvic floor dysfunction (1)
- Pelvic muscle (1)
- Penicillin (1)
- Permeability (1)
- Permeabilität (1)
- Peroxidase (1)
- Pflanzenstress (1)
- Pharmacology (1)
- Phenylalanine determination (1)
- Phosphate (1)
- Photolithographic mimics (1)
- Physiology (1)
- Plant virus (1)
- Plastizität (1)
- Poly(allylamine hydrochloride) (1)
- Poly(d,l-lacticacid) (1)
- Polyimide (1)
- Polylactide acid (1)
- Post-COVID-19 syndrome (1)
- Potential theory (1)
- Preference assessment (1)
- Pressure loaded crack-face (1)
- Pressure-volume relationship (1)
- Prevention (1)
- Process model (1)
- Product-integration (1)
- Profile Extraction (1)
- Profile extraction (1)
- Progressive plastic deformation (1)
- Prophylaxis (1)
- Proteine (1)
- Proximal humerus fracture (1)
- Pseudomonas putida (1)
- Pulsations (1)
- Pump System (1)
- Quartz crystal microbalance (1)
- Quartz crystal nanobalance (QCN) (1)
- Quartz micro balances (1)
- Query learning (1)
- RVA (1)
- Random variable (1)
- Ratcheting (1)
- Ratchetting (1)
- Reaction-diffusion (1)
- Reaction-diffusion systems (1)
- Real distinct pole (1)
- Real-time monitoring (1)
- Recombinant activated protein C (1)
- Reconstruction (1)
- Red blood cell storage (1)
- Refining (1)
- Regionalization (1)
- Rehabilitation Technology and Prosthetics (1)
- Rehabilitation engineering (1)
- Relation classification (1)
- Reliability analysis (1)
- Reliability of structures (1)
- Renewable energy sources (1)
- Reproducible research (1)
- Resampling test (1)
- Resistive temperature detector (1)
- Resolvent Operator (1)
- Resonance-mode measurement (1)
- Retinal vessel analysis (1)
- Retinal vessels (1)
- Riboflavin (1)
- Robotic rehabilitation (1)
- Rohr (1)
- Rohrbruch (1)
- Rotator cuff (1)
- Running (1)
- S-FEM (1)
- Sampling methods (1)
- ScaLAPACK (1)
- Schwammknochen (1)
- Semi-parametric random censorship model (1)
- Sensitivity (1)
- Sepsis (1)
- Septic cardiomyopathy (1)
- Shakedown criterion (1)
- Silk fibroin (1)
- Simultaneous determination (1)
- Skeletal muscle (1)
- Sleep EEG (1)
- Small Aral Sea (1)
- Sn₃O₄ (1)
- Software and systems modeling (1)
- Solid amalgam electrodes (1)
- Source term (1)
- Spleen (1)
- Stahl (1)
- Statics (1)
- Steel industry (1)
- Sterilisation process (1)
- Stochastic programming (1)
- Strukturanalyse (1)
- Supraleiter (1)
- Surface imprinted polymer (1)
- Surface microorganisms (1)
- Surgical Navigation and Robotics (1)
- Surgical staplers (1)
- Survival analysis (1)
- Swabbing (1)
- TMV adsorption (1)
- TOF PET (1)
- Ta₂O₅ gate (1)
- Technical Operations Research (TOR) (1)
- Temperaturabhängigkeit (1)
- Tendon Rupture (1)
- Tendon properties (1)
- Tendons (1)
- Tension (1)
- Text Mining (1)
- Text mining (1)
- Thiamine (1)
- Time-series (1)
- Tin oxide (1)
- Tinetti test (1)
- Tissue Engineering (1)
- Tobacco mosaic virus (1)
- Training (1)
- Transmission Eigenvalues (1)
- Trustworthy artificial intelligence (1)
- UML (1)
- Ultrasound (1)
- Uniaxial compression test (1)
- Unified Modeling Language (1)
- Ureter (1)
- Vapnik–Čhervonenkis class (1)
- Variable height stapler design (1)
- Vascular response (1)
- Vasomotions (1)
- Velocity (1)
- Vertebroplastie (1)
- Vertebroplasty (1)
- Viscous flow (1)
- Viskose Strömung (1)
- Viskosität (1)
- Visual field asymmetry (1)
- Vitamin A (1)
- Vitamin B (1)
- Vitamin D (1)
- Volterra integral equation (1)
- Volume of confidence regions (1)
- Volume status (1)
- Volumes of confidence regions (1)
- Wafer (1)
- Wasserbrücke (1)
- Wasserstoffperoxid (1)
- Wellen (1)
- Wolff's Law (1)
- Wolffsches Gesetz (1)
- Workflow (1)
- Workflow Orchestration (1)
- Wundheilung (1)
- XOR (1)
- Zeta potential (1)
- Zug-Druck Belastung (1)
- acetoin reductase (1)
- achilles tendon (1)
- actin cytoskeleton (1)
- activated nanostructured carbon (1)
- adipose-derived stromal cells (ASCs) (1)
- adsorption (1)
- agility (1)
- aktivierte nanostrukturierte Kohlenstofffaser (1)
- alcoholic beverages (1)
- allocation (1)
- alternierend Verformbarkeit (1)
- ammonia gas sensors (1)
- amperometric biosensors (1)
- amperometric sensor (1)
- anaesthetic complications (1)
- anisotropy (1)
- annealing (1)
- antimony doped tin oxide (1)
- aortic perfusion (1)
- aquaculture (1)
- aromatic amines (1)
- artificial olfactory image (1)
- asymptotic relative efficiency (1)
- atomic layer deposition (1)
- autofluorescence-based detection system (1)
- barium strontium titanate (1)
- biaxial tensile experiment (1)
- bicharacteristics (1)
- bioburdens (1)
- biocompatible (1)
- biocompatible materials (1)
- biodegradabl (1)
- biodegradable electronic devices (1)
- biomechanics (1)
- bone density (1)
- bone structure (1)
- bootstrap (1)
- burst pressure (1)
- burst tests (1)
- calorimetric gas sensor (1)
- calorimetric gas sensor;hydrogen peroxide;wireless sensor system (1)
- cancellous bone (1)
- capacitive electrolyte–insulator–semiconductor sensors (1)
- capacitive field-effect biosensor (1)
- capacitive field-effect sensor (1)
- capillary micro-droplet cell (1)
- carbon electrodes (1)
- carcinogens (1)
- cardiomyocyte biomechanics (1)
- catalytic decomposition (1)
- catalytic metal (1)
- cell aerosolization (1)
- cell atomization (1)
- central symmetry test (1)
- cerebral small vessel disease (1)
- chance constrained programming (1)
- chemical reduction method (1)
- chemical sensor (1)
- chip-based sensor setup (1)
- cognitive impairment (1)
- community dwelling (1)
- complete block symmetry (1)
- computational fluid dynamics analysis (1)
- conditional excess distribution (1)
- conditional expectation principle (1)
- confidence interval (1)
- connective tissue (1)
- constitutive modeling (1)
- contactless conductivity sensor (1)
- contractile tension (1)
- correlation (1)
- coupled Néel–Brownian relaxation dynamics (1)
- covariance principle (1)
- cross sensitivity (1)
- cytosolic water diffusion (1)
- date palm tree (1)
- dental trauma (1)
- design-by-analysis (1)
- dialysis (1)
- difficult airway (1)
- direct method (1)
- distorted element (1)
- doped metal oxide (1)
- doped silicon (1)
- doping (1)
- double-lumen tube intubation (1)
- drop jump (1)
- ecological structure (1)
- eigensolvers (1)
- elastic scattering (1)
- elastic solids (1)
- electrical capacitance tomography (1)
- electrical conductivity of liquids (1)
- electro-migration (1)
- electrolyte-insulator semiconductor sensor (EIS) (1)
- electromyography (1)
- electronic nose (1)
- electronic noses dendronized polymers inverted mesa technology (1)
- encapsulation materials (1)
- endoluminal (1)
- endospores (1)
- energy absorption (1)
- energy dissipation (1)
- enzymatic (bio)degradation (1)
- enzymatic biosensor (1)
- enzymatic methods (1)
- enzyme cascade (1)
- enzyme immobilisation (1)
- enzyme immobilization (1)
- epithelization (1)
- exchangeability test (1)
- extracorporeal membrane oxygenation (1)
- fatigue analyses (1)
- fenitrothion (1)
- fibroin (1)
- field-effect structure (1)
- finite element analysis (1)
- flaw (1)
- fluidic (1)
- force generation (1)
- forecast (1)
- forehead EEG (1)
- fortschreitende plastische Deformation (1)
- frequency mixing (1)
- functional data (1)
- gait (1)
- gas sensor array (1)
- glucose (1)
- glucose oxidase (GOx) (1)
- goodness-of-fit test (1)
- graphene oxide (1)
- healthy aging (1)
- heater metallisation (1)
- heavy metals (1)
- hemoglobin (1)
- hemoglobin dynamics (1)
- hiPS cardiomyocytes (1)
- high-intensity exercise (1)
- high-k material (1)
- high-temperature stability (1)
- horseradish peroxidase (HRP) (1)
- huge dimensional data (1)
- human dermal fibroblasts (1)
- humic acid (1)
- humidity (1)
- hydrogel (1)
- hydroxylation (1)
- hyper-gravity (1)
- hyperelastic (1)
- hypo-gravity (1)
- image sensor (1)
- imaging (1)
- immobilization (1)
- in-ear EEG (1)
- in-situ monitoring (1)
- independence test (1)
- intraclass correlation coefficient (1)
- ion-selective electrodes (1)
- key performance indicators (1)
- kontraktile Spannung (1)
- konvexe Optimierung (1)
- lab-on-a-chip (1)
- lab-on-chip (1)
- lable-free detection (1)
- large language models (1)
- layer expansion (1)
- layer-by-layer technique (1)
- lenslet array (1)
- light scattering analysis (1)
- light-addressable potentiometric sensor (1)
- light-addressing technologies (1)
- lightning flash (1)
- lignite (1)
- limit and shakedown analysis (1)
- linear kinematic hardening (1)
- lipopolysaccharide (1)
- load limit (1)
- lower bound theorem (1)
- magnetic actuation (1)
- magnetic beads (1)
- magnetic biosensing (1)
- magnetic nanoparticles (1)
- magnetic particles (1)
- magnetic relaxation (1)
- magnetic sandwich immunoassay (1)
- magnetic sensing (1)
- magnetic separation (1)
- magnetic tweezers (1)
- magnetophoretic velocity (1)
- material shakedown (1)
- matrix method (1)
- mechanical buffer (1)
- mechanical waves (1)
- metagenomics (1)
- metal oxide (1)
- metal-oxide-semiconductor structure (1)
- method of fundamental solutions (1)
- microbial diversity (1)
- microfluidics (1)
- micromagnetic simulation (1)
- microreactor (1)
- microwave generation (1)
- modeling biosensor (1)
- modelling (1)
- modified electrode (1)
- multi-functional material (1)
- multi-interface measurement (1)
- multinomial distribution (1)
- multiparametric immunoassays (1)
- multivariate normal distribution (1)
- muscle mechanics (1)
- nanobelts (1)
- nanomaterials (1)
- naphtols (1)
- nitrogen oxides (1)
- non-simplex S-FEM elements (1)
- nonlinear kinematic hardening (1)
- nonlinear optimization (1)
- nonlinear solids (1)
- nonlinear tensor constitutive equation (1)
- novel photoexcitation method (1)
- optical sensor setup (1)
- optical spore trapping (1)
- optical trapping (1)
- organic PVC membranes (1)
- organosilanes (1)
- overload (1)
- pH sensors (1)
- pH-based biosensing (1)
- parabolic flight (1)
- pattern-size reduction (1)
- penicillin (1)
- penicillinase (1)
- performance analysis (1)
- performance testing (1)
- phenols (1)
- photoelectrochemistry (1)
- physiology (1)
- pipes (1)
- plant stress (1)
- plant virus detection (1)
- plasma generated ions (1)
- plug-based microfluidic device (1)
- poly(d, l-lactic acid) (1)
- polyaniline (1)
- polymer composites (1)
- porous Pt electrode (1)
- portfolio risk (1)
- prevention (1)
- principal component (1)
- probabilistic fracture mechanics (1)
- protein (1)
- psychosocial (1)
- quantum charging (1)
- random effects (1)
- random effects meta-regression model (1)
- rehabilitation (1)
- reliability (1)
- reliability analysis (1)
- reliability of structures (1)
- retinal microvasculature (1)
- retinal vessels (1)
- rhAPC (1)
- running (1)
- sEMG (1)
- sarcomere operating length (1)
- scanned light pulse technique (1)
- screen-printing (1)
- second-order reliability method (1)
- self-aligned patterning (1)
- semantic role labeling (1)
- sensing properties (1)
- sensors (1)
- separable Hilbert space (1)
- series elastic element behavior (1)
- shakedown analyses (1)
- shotgun sequencing (1)
- shoulder (1)
- silanization (1)
- simulation (1)
- smooth muscle contraction (1)
- spatial resolution (1)
- speaker attribution (1)
- sprint start (1)
- standard error of measurement (1)
- sterility tests (1)
- sterilization (1)
- sterilization conditions (1)
- sterilization efficacy (1)
- sterilization methods (1)
- stiffness (1)
- stochastic programming (1)
- strain energy function (1)
- stretch reflex (1)
- stretch-shortening cycle (1)
- subsurface ice research (1)
- subsurface probe (1)
- superparamagnetic bead (1)
- superparamagnetic nanoparticles (1)
- surface functionalization (1)
- survival (1)
- swift heavy ions (1)
- temperature (1)
- tendon rupture (1)
- tension–torsion loading (1)
- test-retest reliability (1)
- thermal ratcheting (1)
- thermometry (1)
- thick-film technology (1)
- thin-film microsensors (1)
- tilted constant illumination (1)
- titanium dioxide photoanode (1)
- training simulator (1)
- tri-lineage differentiation (1)
- turnip vein clearing virus (TVCV) (1)
- twin-fluid atomizer (1)
- ultrasonography (1)
- ultrathin gate insulators (1)
- uniformly most powerful invariant test (1)
- unloading (1)
- validation methods (1)
- vessels (1)
- videolaryngoscopy (1)
- virgin passive (1)
- virtual reality (1)
- viscoelasticity (1)
- visualization (1)
- voltammetry (1)
- wafer-level testing (1)
- walking (1)
- walking gait (1)
- water bridge phenomenon (1)
- wound healing (1)
- yield stress (1)
Frequency mixing magnetic detection (FMMD) is a sensitive and selective technique to detect magnetic nanoparticles (MNPs) serving as probes for binding biological targets. Its principle relies on the nonlinear magnetic relaxation dynamics of a particle ensemble interacting with a dual frequency external magnetic field. In order to increase its sensitivity, lower its limit of detection and overall improve its applicability in biosensing, matching combinations of external field parameters and internal particle properties are being sought to advance FMMD. In this study, we systematically probe the aforementioned interaction with coupled Néel–Brownian dynamic relaxation simulations to examine how key MNP properties as well as applied field parameters affect the frequency mixing signal generation. It is found that the core size of MNPs dominates their nonlinear magnetic response, with the strongest contributions from the largest particles. The drive field amplitude dominates the shape of the field-dependent response, whereas effective anisotropy and hydrodynamic size of the particles only weakly influence the signal generation in FMMD. For tailoring the MNP properties and parameters of the setup towards optimal FMMD signal generation, our findings suggest choosing large particles of core sizes dc > 25 nm nm with narrow size distributions (σ < 0.1) to minimize the required drive field amplitude. This allows potential improvements of FMMD as a stand-alone application, as well as advances in magnetic particle imaging, hyperthermia and magnetic immunoassays.
Analyzing electroencephalographic (EEG) time series can be challenging, especially with deep neural networks, due to the large variability among human subjects and often small datasets. To address these challenges, various strategies, such as self-supervised learning, have been suggested, but they typically rely on extensive empirical datasets. Inspired by recent advances in computer vision, we propose a pretraining task termed "frequency pretraining" to pretrain a neural network for sleep staging by predicting the frequency content of randomly generated synthetic time series. Our experiments demonstrate that our method surpasses fully supervised learning in scenarios with limited data and few subjects, and matches its performance in regimes with many subjects. Furthermore, our results underline the relevance of frequency information for sleep stage scoring, while also demonstrating that deep neural networks utilize information beyond frequencies to enhance sleep staging performance, which is consistent with previous research. We anticipate that our approach will be advantageous across a broad spectrum of applications where EEG data is limited or derived from a small number of subjects, including the domain of brain-computer interfaces.
The growing body of political texts opens up new opportunities for rich insights into political dynamics and ideologies but also increases the workload for manual analysis. Automated speaker attribution, which detects who said what to whom in a speech event and is closely related to semantic role labeling, is an important processing step for computational text analysis. We study the potential of the large language model family Llama 2 to automate speaker attribution in German parliamentary debates from 2017-2021. We fine-tune Llama 2 with QLoRA, an efficient training strategy, and observe our approach to achieve competitive performance in the GermEval 2023 Shared Task On Speaker Attribution in German News Articles and Parliamentary Debates. Our results shed light on the capabilities of large language models in automating speaker attribution, revealing a promising avenue for computational analysis of political discourse and the development of semantic role labeling systems.
Muscle function is compromised by gravitational unloading in space affecting overall musculoskeletal health. Astronauts perform daily exercise programmes to mitigate these effects but knowing which muscles to target would optimise effectiveness. Accurate inflight assessment to inform exercise programmes is critical due to lack of technologies suitable for spaceflight. Changes in mechanical properties indicate muscle health status and can be measured rapidly and non-invasively using novel technology. A hand-held MyotonPRO device enabled monitoring of muscle health for the first time in spaceflight (> 180 days). Greater/maintained stiffness indicated countermeasures were effective. Tissue stiffness was preserved in the majority of muscles (neck, shoulder, back, thigh) but Tibialis Anterior (foot lever muscle) stiffness decreased inflight vs. preflight (p < 0.0001; mean difference 149 N/m) in all 12 crewmembers. The calf muscles showed opposing effects, Gastrocnemius increasing in stiffness Soleus decreasing. Selective stiffness decrements indicate lack of preservation despite daily inflight countermeasures. This calls for more targeted exercises for lower leg muscles with vital roles as ankle joint stabilizers and in gait. Muscle stiffness is a digital biomarker for risk monitoring during future planetary explorations (Moon, Mars), for healthcare management in challenging environments or clinical disorders in people on Earth, to enable effective tailored exercise programmes.
Advances in polymer science have significantly increased polymer applications in life sciences. We report the use of free-standing, ultra-thin polydimethylsiloxane (PDMS) membranes, called CellDrum, as cell culture substrates for an in vitro wound model. Dermal fibroblast monolayers from 28- and 88-year-old donors were cultured on CellDrums. By using stainless steel balls, circular cell-free areas were created in the cell layer (wounding). Sinusoidal strain of 1 Hz, 5% strain, was applied to membranes for 30 min in 4 sessions. The gap circumference and closure rate of un-stretched samples (controls) and stretched samples were monitored over 4 days to investigate the effects of donor age and mechanical strain on wound closure. A significant decrease in gap circumference and an increase in gap closure rate were observed in trained samples from younger donors and control samples from older donors. In contrast, a significant decrease in gap closure rate and an increase in wound circumference were observed in the trained samples from older donors. Through these results, we propose the model of a cell monolayer on stretchable CellDrums as a practical tool for wound healing research. The combination of biomechanical cell loading in conjunction with analyses such as gene/protein expression seems promising beyond the scope published here.
Pulmonary arterial cannulation is a common and effective method for percutaneous mechanical circulatory support for concurrent right heart and respiratory failure [1]. However, limited data exists to what effect the positioning of the cannula has on the oxygen perfusion throughout the pulmonary artery (PA). This study aims to evaluate, using computational fluid dynamics (CFD), the effect of different cannula positions in the PA with respect to the oxygenation of the different branching vessels in order for an optimal cannula position to be determined. The four chosen different positions (see Fig. 1) of the cannulas are, in the lower part of the main pulmonary artery (MPA), in the MPA at the junction between the right pulmonary artery (RPA) and the left pulmonary artery (LPA), in the RPA at the first branch of the RPA and in the LPA at the first branch of the LPA.
Magnetic nanoparticles (MNP) are investigated with great interest for biomedical applications in diagnostics (e.g. imaging: magnetic particle imaging (MPI)), therapeutics (e.g. hyperthermia: magnetic fluid hyperthermia (MFH)) and multi-purpose biosensing (e.g. magnetic immunoassays (MIA)). What all of these applications have in common is that they are based on the unique magnetic relaxation mechanisms of MNP in an alternating magnetic field (AMF). While MFH and MPI are currently the most prominent examples of biomedical applications, here we present results on the relatively new biosensing application of frequency mixing magnetic detection (FMMD) from a simulation perspective. In general, we ask how the key parameters of MNP (core size and magnetic anisotropy) affect the FMMD signal: by varying the core size, we investigate the effect of the magnetic volume per MNP; and by changing the effective magnetic anisotropy, we study the MNPs’ flexibility to leave its preferred magnetization direction. From this, we predict the most effective combination of MNP core size and magnetic anisotropy for maximum signal generation.
Motile cilia are hair-like cell extensions present in multiple organs of the body. How cilia coordinate their regular beat in multiciliated epithelia to move fluids remains insufficiently understood, particularly due to lack of rigorous quantification. We combine here experiments, novel analysis tools, and theory to address this knowledge gap. We investigate collective dynamics of cilia in the zebrafish nose, due to its conserved properties with other ciliated tissues and its superior accessibility for non-invasive imaging. We revealed that cilia are synchronized only locally and that the size of local synchronization domains increases with the viscosity of the surrounding medium. Despite the fact that synchronization is local only, we observed global patterns of traveling metachronal waves across the multiciliated epithelium. Intriguingly, these global wave direction patterns are conserved across individual fish, but different for left and right nose, unveiling a chiral asymmetry of metachronal coordination. To understand the implications of synchronization for fluid pumping, we used a computational model of a regular array of cilia. We found that local metachronal synchronization prevents steric collisions and improves fluid pumping in dense cilia carpets, but hardly affects the direction of fluid flow. In conclusion, we show that local synchronization together with tissue-scale cilia alignment are sufficient to generate metachronal wave patterns in multiciliated epithelia, which enhance their physiological function of fluid pumping.
During rapid deceleration of the body, tendons buffer part of the elongation of the muscle-tendon unit (MTU), enabling safe energy dissipation via eccentric muscle contraction. Yet, the influence of changes in tendon stiffness within the physiological range upon these lengthening contractions is unknown. This study aimed to examine the effect of training-induced stiffening of the Achilles tendon on triceps surae muscle-tendon behavior during a landing task. Twenty-one male subjects were assigned to either a 10-week resistance-training program consisting of single-leg isometric plantarflexion (n = 11) or to a non-training control group (n = 10). Before and after the training period, plantarflexion force, peak Achilles tendon strain and stiffness were measured during isometric contractions, using a combination of dynamometry, ultrasound and kinematics data. Additionally, testing included a step-landing task, during which joint mechanics and lengths of gastrocnemius and soleus fascicles, Achilles tendon, and MTU were determined using synchronized ultrasound, kinematics and kinetics data collection. After training, plantarflexion strength and Achilles tendon stiffness increased (15 and 18%, respectively), and tendon strain during landing remained similar. Likewise, lengthening and negative work produced by the gastrocnemius MTU did not change detectably. However, in the training group, gastrocnemius fascicle length was offset (8%) to a longer length at touch down and, surprisingly, fascicle lengthening and velocity were reduced by 27 and 21%, respectively. These changes were not observed for soleus fascicles when accounting for variation in task execution between tests. These results indicate that a training-induced increase in tendon stiffness does not noticeably affect the buffering action of the tendon when the MTU is rapidly stretched. Reductions in gastrocnemius fascicle lengthening and lengthening velocity during landing occurred independently from tendon strain. Future studies are required to provide insight into the mechanisms underpinning these observations and their influence on energy dissipation.
Comparison of different training algorithms for the leg extension training with an industrial robot
(2018)
In the past, different training scenarios have been developed and implemented on robotic research platforms, but no systematic analysis and comparison have been done so far. This paper deals with the comparison of an isokinematic (motion with constant velocity) and an isotonic (motion against constant weight) training algorithm. Both algorithms are designed for a robotic research platform consisting of a 3D force plate and a high payload industrial robot, which allows leg extension training with arbitrary six-dimensional motion trajectories. In the isokinematic as well as the isotonic training algorithm, individual paths are defined i n C artesian s pace by sufficient s upport p oses. I n t he i sotonic t raining s cenario, the trajectory is adapted to the measured force as the robot should only move along the trajectory as long as the force applied by the user exceeds a minimum threshold. In the isotonic training scenario however, the robot’s acceleration is a function of the force applied by the user. To validate these findings, a simulative experiment with a simple linear trajectory is performed. For this purpose, the same force path is applied in both training scenarios. The results illustrate that the algorithms differ in the force dependent trajectory adaption.
Training-induced increase in Achilles tendon stiffness affects tendon strain pattern during running
(2019)
Background
During the stance phase of running, the elasticity of the Achilles tendon enables the utilisation of elastic energy and allows beneficial contractile conditions for the triceps surae muscles. However, the effect of changes in tendon mechanical properties induced by chronic loading is still poorly understood. We tested the hypothesis that a training-induced increase in Achilles tendon stiffness would result in reduced tendon strain during the stance phase of running, which would reduce fascicle strains in the triceps surae muscles, particularly in the mono-articular soleus.
Methods
Eleven subjects were assigned to a training group performing isometric singleleg plantarflexion contractions three times per week for ten weeks, and another ten subjects formed a control group. Before and after the training period, Achilles tendon stiffness was estimated, and muscle-tendon mechanics were assessed during running at preferred speed using ultrasonography, kinematics and kinetics.
Results
Achilles tendon stiffness increased by 18% (P <0:01) in the training group, but the associated reduction in strain seen during isometric contractions was not statistically significant. Tendon elongation during the stance phase of running was similar after training, but tendon recoil was reduced by 30% (P <0:01), while estimated tendon force remained unchanged. Neither gastrocnemius medialis nor soleus fascicle shortening during stance was affected by training.
Discussion
These results show that a training-induced increase in Achilles tendon
stiffness altered tendon behaviour during running. Despite training-induced changes in tendon mechanical properties and recoil behaviour, the data suggest that fascicle shortening patterns were preserved for the running speed that we examined. The asymmetrical changes in tendon strain patterns supports the notion that simple inseries models do not fully explain the mechanical output of the muscle-tendon unit during a complex task like running.
The MYOTONES experiment is the first to monitor changes in the basic biomechanical properties (tone, elasticity and stiffness) of the resting human myofascial system due to microgravity with a oninvasive, portable device on board the ISS. The MyotonPRO device applies several brief mechanical stimuli to the surface of the skin, and the natural oscillation signals of the tissue beneath are detected and computed by the MyotonPRO. Thus, an objective, quick and easy determination of the state of the underlying tissue is possible.
Two preflight, four inflight and four post flight measurements were performed on a male astronaut using the same 10 measurement points (MP) for each session. MPs were located on the plantar fascia, Achilles tendon, M. soleus, M. gastrocnemius, M. multifidus, M. splenius capitis, M. deltoideus anterior, M. rectus femoris, infrapatellar tendon, M. tibialis anterior. Subcutaneous tissues thickness above the MPs was measured using ultrasound imaging. Magnetic resonance images (MRI) of lower limb muscles and functional tests were also performed pre- and postflight.
Our first measurements on board the ISS confirmed increased tone and stiffness of the lumbar multifidus muscle, an important trunk stabilizer, dysfunction of which is known to be associated with back pain. Furthermore, reduced tone and stiffness of Achilles tendon and plantar fascia were observed inflight vs. preflight, confirming previous findings from terrestrial analog studies and parabolic
flights. Unexpectedly, the deltoid showed negative inflight changes in tone and stiffness, and increased elasticity, suggesting a potential risk of muscle atrophy in longer spaceflight that should be addressed by adequate inflight countermeasure protocols. Most values from limb and back MPS showed deflected patterns (in either directions) from inflight shortly after the re-entry phase on the landing day and one week later. Most parameter values then normalized to baseline after 3 weeks likely due to 1G re-adaptation and possible outcome of the reconditioning protocol. No major changes in subcutaneous tissues thickness above the MPs were found inflight vs preflight, suggesting no bias (i.e., fluid shift, extreme tissue thickening or loss). Pre- and postflight MRI and functional tests showed negligible changes in calf muscle size, power and force, which is likely due to training effects from current inflight exercise protocols.
The MYOTONES experiment is currently ongoing to collect data from further crew members. The potential impact of this research is to better understand the effects of microgravity and countermeasures over the time course of an ISS mission cycle. This will enable exercise countermeasures to be tailored
Effective training requires high muscle forces potentially leading to training-induced injuries. Thus, continuous monitoring and controlling of the loadings applied to the musculoskeletal system along the motion trajectory is required. In this paper, a norm-optimal iterative learning control algorithm for the robot-assisted training is developed. The algorithm aims at minimizing the external knee joint moment, which is commonly used to quantify the loading of the medial compartment. To estimate the external knee joint moment, a musculoskeletal lower extremity model is implemented in OpenSim and coupled with a model of an industrial robot and a force plate mounted at its end-effector. The algorithm is tested in simulation for patients with varus, normal and valgus alignment of the knee. The results show that the algorithm is able to minimize the external knee joint moment in all three cases and converges after less than seven iterations.
Neuromuscular strength training of the leg extensor muscles plays an important role in the rehabilitation and prevention of age and wealth related diseases. In this paper, we focus on the design and implementation of a Cartesian admittance control scheme for isotonic training, i.e. leg extension and flexion against a predefined weight. For preliminary testing and validation of the designed algorithm an experimental research and development platform consisting of an
industrial robot and a force plate mounted at its end-effector has been used. Linear, diagonal and arbitrary two-dimensional motion trajectories with different weights for the leg extension and flexion part are applied. The proposed algorithm is easily adaptable to trajectories consisting of arbitrary six-dimensional poses and allows the implementation of individualized trajectories.
To prevent the reduction of muscle mass and loss of strength coming along with the human aging process, regular training with e.g. a leg press is suitable. However, the risk of training-induced injuries requires the continuous monitoring and controlling of the forces applied to the musculoskeletal system as well as the velocity along the motion trajectory and the range of motion. In this paper, an adaptive norm-optimal iterative learning control algorithm to minimize the knee joint loadings during the leg extension training with an industrial robot is proposed. The response of the algorithm is tested in simulation for patients with varus, normal and valgus alignment of the knee and compared to the results of a higher-order iterative learning control algorithm, a robust iterative learning control and a recently proposed conventional norm-optimal iterative learning control algorithm. Although significant improvements in performance are made compared to the conventional norm-optimal iterative learning control algorithm with a small learning factor, for the developed approach as well as the robust iterative learning control algorithm small steady state errors occur.
Achilles tendon rupture (ATR) patients have persistent functional deficits in the triceps surae muscle–tendon unit (MTU). The complex remodeling of the MTU accompanying these deficits remains poorly understood. The purpose of the present study was to associate in vivo and in silico data to investigate the relations between changes inMTU properties and strength deficits inATR patients. Methods: Elevenmale subjects who had undergone surgical repair of complete unilateral ATR were examined 4.6 ± 2.0 (mean ± SD) yr after rupture. Gastrocnemius medialis (GM) tendon stiffness, morphology, and muscle architecture were determined using ultrasonography. The force–length relation of the plantar flexor muscles was assessed at five ankle joint angles. In addition, simulations (OpenSim) of the GM MTU force–length properties were performed with various iterations of MTU properties found between the unaffected and the affected side. Results: The affected side of the patients displayed a longer, larger, and stiffer GM tendon (13% ± 10%, 105% ± 28%, and 54% ± 24%, respectively) compared with the unaffected side. The GM muscle fascicles of the affected side were shorter (32% ± 12%) and with greater pennation angles (31% ± 26%). A mean deficit in plantarflexion moment of 31% ± 10% was measured. Simulations indicate that pairing an intact muscle with a longer tendon shifts the optimal angular range of peak force outside physiological angular ranges, whereas the shorter muscle fascicles and tendon stiffening seen in the affected side decrease this shift, albeit incompletely. Conclusions: These results suggest that the substantial changes in MTU properties found in ATR patients may partly result from compensatory remodeling, although this process appears insufficient to fully restore muscle function.
Performing tasks, such as running and jumping, requires activation of the agonist and antagonist muscles before (motor unit pre-activation) and during movement performance (Santello and Mcdonagh, 1998). A well-timed and regulated muscle activation elicits a stretch-shortening cycle (SSC) response, naturally occurring in bouncing movements (Ishikawa and Komi, 2004; Taube et al., 2012). By definition, the SSC describes the stretching of a pre-activated muscle-tendon complex immediately followed by a muscle shortening in the concentric push-off phase (Komi, 1984).
Given the importance of SSC actions for human movement, it is not surprising that many studies investigated the biomechanics of this phenomenon; in particular, drop jumps (DJs) represent a good paradigm to study muscle fascicle and tendon behavior in ballistic movements involving the SSC.
Within a DJ, three main phases [pre-activation, braking, and push-off (PO; Komi, 2000)] have been recognized and extensively studied in common and challenging conditions, such as changes in load, falling height, or simulated hypo-gravity (Avela et al., 1994; Arampatzis et al., 2001; Fukashiro et al., 2005; Ishikawa et al., 2005; Sousa et al., 2007; Ritzmann et al., 2016; Helm et al., 2020).
These studies show that the timing and amount of triceps-surae muscle-tendon unit pre-activation in DJs are differentially regulated based on the load applied to the muscle, being optimal in normal “Earth” gravity conditions (Avela et al., 1994), but decreased in simulated hypo-gravity, hyper-gravity (Avela et al., 1994; Ritzmann et al., 2016), or unknown conditions (i.e., unknown falling heights; Helm et al., 2020). Some authors indicated that, when falling from heights different from the optimal one [defined as the drop height giving a maximum DJ performance indicated as peak ground reaction force (GRF) or jump high], electromyographic (EMG) activity of the plantar flexors increases from lower than optimal to higher than optimal heights (Ishikawa and Komi, 2004; Sousa et al., 2007).
These findings highlight the ability of the central nervous system to regulate the timing and amount of pre-activation according to different jumping conditions, thus regulating muscle fascicle length, tendon and joint stiffness as well as position, in order to safely land on the ground and quickly re-bounce.
Similarly, to pre-activation, also in the braking phase, the plantar flexors are differentially regulated. In optimal height (i.e., load) jumping conditions, gastrocnemius medialis (GM) fascicles shorten at early ground contact (possibly due to the intervention of the stretch reflex; Gollhofer et al., 1992) and behave quasi-isometrically in the late braking phase, enabling tendon elongation, and storage of elastic energy (Gollhofer et al., 1992; Fukashiro et al., 2005; Sousa et al., 2007). When increasing the falling height (augmenting the impact GRF), the quasi-isometric behavior of fascicles disappears, and fast fascicle lengthening occurs (Ishikawa et al., 2005; Sousa et al., 2007).
In the third and last PO phase, fascicles shorten and the tendon releases the elastic energy previously stored. Bobbert et al. (1987) reported no influence of jumping height on the work done and on the net vertical impulse assessed during PO; this observation suggests that, despite an optimal DJ performance might be achieved only in specific conditions (falling heights, loads), the central nervous system seems to be able to regulate muscle behavior in order to effectively perform the required task also in challenging situations.
Although the regulation of triceps-surae muscle-tendon unit in DJs has been extensively investigated, very few studies focused on sarcomeres behavior during the performance of this SSC movement (Kurokawa et al., 2003; Fukashiro et al., 2005, 2006). Sarcomeres represent muscle contractile units and are known to express different amounts of force depending on their length (Gordon et al., 1966; Walker and Schrodt, 1974); thus, understanding the time course of their responses during DJs is fundamental to gain further insights into muscle force-generating capacity. In vivo measurement of sarcomere length in humans has been so far been performed only in static positions and under highly controlled experimental conditions (Llewellyn et al., 2008; Sanchez et al., 2015). Instead, human sarcomere length estimation (achieved by dividing GM measured fascicle length for a fixed sarcomere number) in dynamic contractions provided an indirect measure of sarcomere operating range during squat jump, countermovement jump, and DJ (Fukashiro et al., 2005, 2006; Kurokawa et al., 2003). The results of these studies showed that sarcomeres operate in the ascending limb of their length-tension (L-T) relationship in all types of jumps, and particularly so in DJ.
However, most of the available observations on sarcomere and muscle fascicle behavior were made in condition of constant gravity. Thus, in order to understand how sarcomere and muscle fascicle length are regulated in variable gravity conditions, we performed experiments in a parabolic flight, involving variable gravity levels, ranging from about zero-g to about double the Earth’s gravity (1 g; Waldvogel et al., 2021).
Specifically, the aims of the present study were as follows:
1. To investigate the ability of the neuromuscular system in regulating fascicle length in response to conditions of variable gravity.
2. To estimate sarcomere operative length in the different DJ phases, in order to calculate its theoretical force production and its possible modulation in conditions of variable gravity.
We hypothesized that muscle fascicles would be differentially regulated in different gravity conditions compared to 1 g, particularly in anticipation of landing and re-bouncing in unknown gravity levels. In addition, we hypothesized that sarcomeres would operate in the upper part of the ascending limb of their L-T relationship, possibly lengthening during the braking phase (especially in hyper-gravity) while operating quasi-isometrically in 1 g.
The compliant nature of distal limb muscle-tendon units is traditionally considered suboptimal in explosive movements when positive joint work is required. However, during accelerative running, ankle joint net mechanical work is positive. Therefore, this study aims to investigate how plantar flexor muscle-tendon behavior is modulated during fast accelerations. Eleven female sprinters performed maximum sprint accelerations from starting blocks, while gastrocnemius muscle fascicle lengths were estimated using ultrasonography. We combined motion analysis and ground reaction force measurements to assess lower limb joint kinematics and kinetics, and to estimate gastrocnemius muscle-tendon unit length during the first two acceleration steps. Outcome variables were resampled to the stance phase and averaged across three to five trials. Relevant scalars were extracted and analyzed using one-sample and two-sample t-tests, and vector trajectories were compared using statistical parametric mapping. We found that an uncoupling of muscle fascicle behavior from muscle-tendon unit behavior is effectively used to produce net positive mechanical work at the joint during maximum sprint acceleration. Muscle fascicles shortened throughout the first and second steps, while shortening occurred earlier during the first step, where negative joint work was lower compared with the second step. Elastic strain energy may be stored during dorsiflexion after touchdown since fascicles did not lengthen at the same time to dissipate energy. Thus, net positive work generation is accommodated by the reuse of elastic strain energy along with positive gastrocnemius fascicle work. Our results show a mechanism of how muscles with high in-series compliance can contribute to net positive joint work.