37 research outputs found
Bridging the sim2real gap. Investigating deviations between experimental motion measurements and musculoskeletal simulation results—a systematic review
Musculoskeletal simulations can be used to estimate biomechanical variables like muscle forces and joint torques from non-invasive experimental data using inverse and forward methods. Inverse kinematics followed by inverse dynamics (ID) uses body motion and external force measurements to compute joint movements and the corresponding joint loads, respectively. ID leads to residual forces and torques (residuals) that are not physically realistic, because of measurement noise and modeling assumptions. Forward dynamic simulations (FD) are found by tracking experimental data. They do not generate residuals but will move away from experimental data to achieve this. Therefore, there is a gap between reality (the experimental measurements) and simulations in both approaches, the sim2real gap. To answer (patho-) physiological research questions, simulation results have to be accurate and reliable; the sim2real gap needs to be handled. Therefore, we reviewed methods to handle the sim2real gap in such musculoskeletal simulations. The review identifies, classifies and analyses existing methods that bridge the sim2real gap, including their strengths and limitations. Using a systematic approach, we conducted an electronic search in the databases Scopus, PubMed and Web of Science. We selected and included 85 relevant papers that were sorted into eight different solution clusters based on three aspects: how the sim2real gap is handled, the mathematical method used, and the parameters/variables of the simulations which were adjusted. Each cluster has a distinctive way of handling the sim2real gap with accompanying strengths and limitations. Ultimately, the method choice largely depends on various factors: available model, input parameters/variables, investigated movement and of course the underlying research aim. Researchers should be aware that the sim2real gap remains for both ID and FD approaches. However, we conclude that multimodal approaches tracking kinematic and dynamic measurements may be one possible solution to handle the sim2real gap as methods tracking multimodal measurements (some combination of sensor position/orientation or EMG measurements), consistently lead to better tracking performances. Initial analyses show that motion analysis performance can be enhanced by using multimodal measurements as different sensor technologies can compensate each other’s weaknesses
Lifetime and performance of the very latest microchannel-plate photomultipliers
The PANDA experiment at the FAIR facility at GSI will study hadron physics
using a high intensity antiproton beam of up to 15 GeV/c momentum to perform
high precision spectroscopy. Two DIRC detectors with their image planes
residing in an 1 T magnetic field will be used in the experiment. The
only suitable photon detectors for both DIRCs were identified to be
Microchannel-Plate Photomultipliers (MCP-PMTs). Since the aging problems of
MCP-PMTs were solved recently by coating the MCPs with the so-called
ALD-technique (atomic layer deposition) we are investigating devices which are
significantly improved with respect to other parameters, as, e.g., the
collection efficiency (CE) and the quantum efficiency (QE). The latest
generation of MCP-PMTs can reach a detective quantum efficiency DQE = QE - CE
of 30%. This paper will present the performance of the most advanced 53
53 mm ALD-coated MCP-PMTs from Photonis (8 8 and 3
100 anodes) and Photek (8 8 anodes), also inside the magnetic
field. With a picosecond laser and a multi-hit capable DAQ system which allows
read out up to 300 pixels simultaneously, parameters like darkcount rate,
afterpulse probability and time resolution can be investigated as a function of
incident photon position.Comment: Proceedings contribution to NDIP20 (9th Conference on New
Developments in Photodetection
Performance of the most recent Microchannel-Plate PMTs for the PANDA DIRC detectors at FAIR
In the PANDA experiment at the FAIR facility at GSI two DIRC (Detection of
Internally Reflected Cherenkov light) detectors will be used for /K
separation up to 4 GeV/c. Due to their location in a high magnetic field and
other stringent requirements like high detection efficiency, low dark count
rate, radiation hardness, long lifetime and good timing, MCP-PMTs
(microchannel-plate photomultiplier) were the best choice of photon sensors for
the DIRC detectors in the PANDA experiment. This paper will present the
performance of some of the latest 22 inch MCP-PMTs from Photek and
Photonis, including the first mass production tubes for the PANDA Barrel DIRC
from Photonis. Performance parameters like the collection efficiency (CE),
quantum efficiency (QE), and gain homogeneity were determined. The effect of
magnetic fields on some properties like gain and charge cloud width was
investigated as well. Apart from that the spatial distribution of many internal
parameters like time resolution, dark count rate, afterpulse ratio, charge
sharing crosstalk and recoil electrons were measured simultaneously with a
multihit capable DAQ system. The latest generation of Photonis MCP-PMTs shows
an unexpected "escalation" effect where the MCP-PMT itself produces photons.Comment: Proceedings contribution to RICH2022 (11th International Workshop on
Ring Imaging Cherenkov Detectors
Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR
This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented
PANDA Phase One - PANDA collaboration
The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future antiProton ANnihilations at DArmstadt (PANDA or P¯ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton–nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the Phase One setup. The physics programme that is achievable during Phase One is outlined in this paper
Precision resonance energy scans with the PANDA experiment at FAIR: Sensitivity study for width and line shape measurements of the X(3872)
This paper summarises a comprehensive Monte Carlo simulation study for precision resonance energy scan measurements. Apart from the proof of principle for natural width and line shape measurements of very narrow resonances with PANDA, the achievable sensitivities are quantified for the concrete example of the charmonium-like X(3872) state discussed to be exotic, and for a larger parameter space of various assumed signal cross-sections, input widths and luminosity combinations. PANDA is the only experiment that will be able to perform precision resonance energy scans of such narrow states with quantum numbers of spin and parities that differ from J P C = 1 - -
A split-intein-based method for the efficient production of circularized nanodiscs for structural studies of membrane proteins.
Phospholipid nanodiscs are a native-like membrane mimetic that is suitable for structural studies of membrane proteins. Although nanodiscs of different sizes exist for various structural applications, their thermal and long-term stability can vary considerably. Covalently circularized nanodiscs are a perfect tool to overcome these limitations. Existing methods for the production of circularized nanodiscs can be time-consuming and technically demanding. Therefore, an easy in vivo approach, in which circularized membrane scaffold proteins (MSPs) can be directly obtained from Escherichia coli culture, is reported herein. Nostoc punctiforme DnaE split-intein fusions with MSPs of various lengths are used and consistently provide circularized nanodiscs in high yields. With this approach, a large variety of circularized nanodiscs, ranging from 7 to 26 nm in diameter, that are suitable for NMR spectroscopy and electron microscopy (EM) applications can be prepared. These nanodiscs are superior to those of the corresponding linear versions in terms of stability and size homogeneity, which affects the quality of NMR spectroscopy data and EM experiments. Due to their long-term stability and homogeneity, the presented small circular nanodiscs are suited for high-resolution NMR spectroscopy studies, as demonstrated with two membrane proteins of 17 or 32 kDa in size. The presented method will provide easy access to circularized nanodiscs for structural studies of membrane proteins and for applications in which a defined and stable nanodisc size is required