@inproceedings{PohleFroehlichDalitzRichteretal.2020, author = {Pohle-Fr{\"o}hlich, Regina and Dalitz, Christoph and Richter, Charlotte and Hahnen, Tobias and St{\"a}udle, Benjamin and Albracht, Kirsten}, title = {Estimation of muscle fascicle orientation in ultrasonic images}, series = {Proceedings of the 15th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications - Volume 5}, booktitle = {Proceedings of the 15th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications - Volume 5}, publisher = {SciTePress}, address = {Set{\´u}bal, Portugal}, isbn = {978-989-758-402-2}, doi = {10.5220/0008933900790086}, pages = {79 -- 86}, year = {2020}, abstract = {We compare four different algorithms for automatically estimating the muscle fascicle angle from ultrasonic images: the vesselness filter, the Radon transform, the projection profile method and the gray level cooccurence matrix (GLCM). The algorithm results are compared to ground truth data generated by three different experts on 425 image frames from two videos recorded during different types of motion. The best agreement with the ground truth data was achieved by a combination of pre-processing with a vesselness filter and measuring the angle with the projection profile method. The robustness of the estimation is increased by applying the algorithms to subregions with high gradients and performing a LOESS fit through these estimates.}, language = {en} } @article{PookhalilAmoabedinyTabeshetal.2016, author = {Pookhalil, Ali and Amoabediny, Ghassem and Tabesh, Hadi and Behbahani, Mehdi and Mottaghy, Khosrow}, title = {A new approach for semiempirical modeling of mechanical blood trauma}, series = {The international journal of artificial organs}, volume = {39}, journal = {The international journal of artificial organs}, number = {4}, publisher = {Sage}, address = {London}, issn = {1724-6040}, doi = {10.5301/ijao.5000474}, pages = {171 -- 177}, year = {2016}, abstract = {Purpose Two semi-empirical models were recently published, both making use of existing literature data, but each taking into account different physical phenomena that trigger hemolysis. In the first model, hemoglobin (Hb) release is described as a permeation procedure across the membrane, assuming a shear stress-dependent process (sublethal model). The second model only accounts for hemoglobin release that is caused by cell membrane breakdown, which occurs when red blood cells (RBC) undergo mechanically induced shearing for a period longer than the threshold time (nonuniform threshold model). In this paper, we introduce a model that considers the hemolysis generated by both these possible phenomena. Methods Since hemolysis can possibly be caused by permeation of hemoglobin through the RBC functional membrane as well as by release of hemoglobin from RBC membrane breakdown, our proposed model combines both these models. An experimental setup consisting of a Couette device was utilized for validation of our proposed model. Results A comparison is presented between the damage index (DI) predicted by the proposed model vs. the sublethal model vs. the nonthreshold model and experimental datasets. This comparison covers a wide range of shear stress for both human and porcine blood. An appropriate agreement between the measured DI and the DI predicted by the present model was obtained. Conclusions The semiempirical hemolysis model introduced in this paper aims for significantly enhanced conformity with experimental data. Two phenomenological outcomes become possible with the proposed approach: an estimation of the average time after which cell membrane breakdown occurs under the applied conditions, and a prediction of the ratio between the phenomena involved in hemolysis.}, language = {en} } @article{PorschenGartzenGewehretal.1978, author = {Porschen, W. and Gartzen, J. and Gewehr, K. and M{\"u}hlensiepen, H. and Weber, Hans-Joachim and Feinedegen, L E.}, title = {In vivo assay of the radiation sensitivity of hypoxic tumour cells : influence of γ-rays, cyclotron neutrons, misonidazole, hyperthermia and mixed modalities}, series = {The British journal of cancer / Supplement}, journal = {The British journal of cancer / Supplement}, number = {3}, publisher = {Lewis}, address = {London}, issn = {0306-9443}, pages = {194 -- 197}, year = {1978}, abstract = {Tumour cell death can be evaluated in the living mouse by externally measuring the rate of loss of tumour-bound DNA tracer. By sequentially labelling the tumour-bearing animals with ¹²⁵IUdR and ¹³¹IUdR 50 h apart, the average tumour cells at the time of the second injection are labelled by ¹²⁵IUdR and the euoxic tumour cells are specifically labelled with ¹³¹IUdR. Tumour treatment at this stage of labelling permits the observation of the reaction of euoxic cells and average tumour cells and finally yields data on hypoxic cells and thus on the oxygen enhancement ratio. This information adds to results from tumour control and growth delay. With this technique effects were analysed of 60-Co γ-rays, cyclotron neutrons (E = 6 MeV), misonidazole (500 mg/kg body wt) and hyperthermia (42°C water-bath), or combinations of these. Misonidazole (15 min before irradiation) altered the oxygen enhancement ratio by a factor of 1·5 for γ-rays and of 1·1 for neutrons; when evaluated from tumour-growth delay and TCD-50 misonidazole gave a dose modifying factor of 1·47 for γ-rays and of 1·2-1·3 for neutrons. Based on percentage tumour regression 100 days after treatment, the enhancement ratio from hyperthermia (after irradiation) was 2·75 for γ-rays (at 10 Gray) and 2·2 for neutrons (at 3·2 Gray). For neutrons combined with misonidazole and hyperthermia the ratio was 2·4. These results demonstrate that effects of neutron irradiation may be modified by electron-affinic substances and/or hyperthermia.}, language = {en} } @article{PourshahidiEngelmannOffenhaeusseretal.2022, author = {Pourshahidi, Ali Mohammad and Engelmann, Ulrich M. and Offenh{\"a}usser, Andreas and Krause, Hans-Joachim}, title = {Resolving ambiguities in core size determination of magnetic nanoparticles from magnetic frequency mixing data}, series = {Journal of Magnetism and Magnetic Materials}, volume = {563}, journal = {Journal of Magnetism and Magnetic Materials}, number = {In progress, Art. No. 169969}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0304-8853}, doi = {10.1016/j.jmmm.2022.169969}, year = {2022}, abstract = {Frequency mixing magnetic detection (FMMD) has been widely utilized as a measurement technique in magnetic immunoassays. It can also be used for the characterization and distinction (also known as "colourization") of different types of magnetic nanoparticles (MNPs) based on their core sizes. In a previous work, it was shown that the large particles contribute most of the FMMD signal. This leads to ambiguities in core size determination from fitting since the contribution of the small-sized particles is almost undetectable among the strong responses from the large ones. In this work, we report on how this ambiguity can be overcome by modelling the signal intensity using the Langevin model in thermodynamic equilibrium including a lognormal core size distribution fL(dc,d0,σ) fitted to experimentally measured FMMD data of immobilized MNPs. For each given median diameter d0, an ambiguous amount of best-fitting pairs of parameters distribution width σ and number of particles Np with R2 > 0.99 are extracted. By determining the samples' total iron mass, mFe, with inductively coupled plasma optical emission spectrometry (ICP-OES), we are then able to identify the one specific best-fitting pair (σ, Np) one uniquely. With this additional externally measured parameter, we resolved the ambiguity in core size distribution and determined the parameters (d0, σ, Np) directly from FMMD measurements, allowing precise MNPs sample characterization.}, language = {en} } @article{PreissLinderWendtetal.2011, author = {Preiß, C. and Linder, Peter and Wendt, K. and Krystek, M. and Digel, Ilya and Gossmann, Matthias and Temiz Artmann, Ayseg{\"u}l and Porst, Dariusz and Kayser, Peter and Bassam, Rasha and Artmann, Gerhard}, title = {Engineering technology for plant physiology and plant stress research}, year = {2011}, abstract = {Plant physiology and plant stress: Plant physiology will be much more important for human mankind because of yield and cultivation limits of crops determined by their resistance to stress. To assess and counteract various stress factors it is necessary to conduct plant research to gain information and results on plant physiology.}, subject = {Pflanzenphysiologie}, language = {en} } @article{PresslerEsefeldScherretal.2010, author = {Pressler, Axel and Esefeld, Katrin and Scherr, Johannes and Ali, Mohammad and Hanssen, Henner and Kotliar, Konstantin and Lanzl, Ines and Halle, Martin and Kaemmerer, Harald and Schmidt-Trucks{\"a}ss, Arno and Hager, Alfred}, title = {Structural alterations of retinal arterioles in adults late after repair of aortic isthmic coarctation}, series = {The American Journal of Cardiology}, volume = {105}, journal = {The American Journal of Cardiology}, number = {5}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0002-9149}, doi = {10.1016/j.amjcard.2009.10.070}, pages = {740 -- 744}, year = {2010}, abstract = {Patients after coarctation repair still have an increased risk of cardiovascular or cerebrovascular events. This has been explained by the persisting hypertension and alterations in the peripheral vessels. However, involvement of the central vessels such as the retinal arteries is virtually unknown. A total of 34 patients after coarctation repair (22 men and 12 women; 23 to 58 years old, age range 0 to 32 years at surgical repair) and 34 nonhypertensive controls underwent structural and functional retinal vessel analysis. Using structural analysis, the vessel diameters were measured. Using functional analysis, the endothelium-dependent vessel dilation in response to flicker light stimulation was assessed. In the patients after coarctation repair, the retinal arteriolar diameter was significantly reduced compared to that of the controls (median 182 μm, first to third quartile 171 to 197; vs 197 μm, first to third quartile 193 to 206; p <0.001). These findings were independent of the peripheral blood pressure and age at intervention. No differences were found for venules. The functional analysis findings were not different between the patients and controls (maximum dilation 3.5\%, first to third quartile 2.1\% to 4.5\% vs 3.6\%, first to third quartile 2.2\% to 4.3\%; p = 0.81), indicating preserved autoregulative mechanisms. In conclusion, the retinal artery diameter is reduced in patients after coarctation repair, independent of their current blood pressure level and age at intervention. As a structural marker of chronic vessel damage associated with past, current, or future hypertension, retinal arteriolar narrowing has been linked to stroke incidence. These results indicate an involvement of cerebral microcirculation in aortic coarctation, despite timely repair, and might contribute to explain the increased rate of cerebrovascular events in such patients.}, language = {en} } @article{ProbstBehbahaniBorrmannetal.2010, author = {Probst, M. and Behbahani, Mehdi and Borrmann, E. and Elgeti, S. and Nicolai, M. and Behr, M.}, title = {Hemodynamic Modeling for Numerical Analysis and Design of Medical Devices}, year = {2010}, language = {en} } @article{PoettgenEdererAltherretal.2015, author = {P{\"o}ttgen, Philipp and Ederer, Thorsten and Altherr, Lena and Pelz, Peter F.}, title = {Developing a control strategy for booster stations under uncertain load}, series = {Applied Mechanics and Materials}, volume = {807}, journal = {Applied Mechanics and Materials}, number = {807}, publisher = {Trans Tech Publications}, address = {B{\"a}ch}, isbn = {1662-7482}, doi = {10.4028/www.scientific.net/AMM.807.241}, pages = {241 -- 246}, year = {2015}, abstract = {Booster stations can fulfill a varying pressure demand with high energy-efficiency, because individual pumps can be deactivated at smaller loads. Although this is a seemingly simple approach, it is not easy to decide precisely when to activate or deactivate pumps. Contemporary activation controls derive the switching points from the current volume flow through the system. However, it is not measured directly for various reasons. Instead, the controller estimates the flow based on other system properties. This causes further uncertainty for the switching decision. In this paper, we present a method to find a robust, yet energy-efficient activation strategy.}, language = {en} } @article{QuittmannAbelAlbrachtetal.2020, author = {Quittmann, Oliver J. and Abel, Thomas and Albracht, Kirsten and Meskemper, Joshua and Foitschik, Tina and Str{\"u}der, Heiko K.}, title = {Biomechanics of handcycling propulsion in a 30-min continuous load test at lactate threshold: Kinetics, kinematics, and muscular activity in able-bodied participants}, series = {European Journal of Applied Physiology}, journal = {European Journal of Applied Physiology}, number = {120}, publisher = {Springer}, address = {Heidelberg}, issn = {1439-6327}, doi = {10.1007/s00421-020-04373-x}, pages = {1403 -- 1415}, year = {2020}, abstract = {Purpose This study aims to investigate the biomechanics of handcycling during a continuous load trial (CLT) to assess the mechanisms underlying fatigue in upper body exercise. Methods Twelve able-bodied triathletes performed a 30-min CLT at a power output corresponding to lactate threshold in a racing recumbent handcycle mounted on a stationary ergometer. During the CLT, ratings of perceived exertion (RPE), tangential crank kinetics, 3D joint kinematics, and muscular activity of ten muscles of the upper extremity and trunk were examined using motion capturing and surface electromyography. Results During the CLT, spontaneously chosen cadence and RPE increased, whereas crank torque decreased. Rotational work was higher during the pull phase. Peripheral RPE was higher compared to central RPE. Joint range of motion decreased for elbow-flexion and radial-duction. Integrated EMG (iEMG) increased in the forearm flexors, forearm extensors, and M. deltoideus (Pars spinalis). An earlier onset of activation was found for M. deltoideus (Pars clavicularis), M. pectoralis major, M. rectus abdominis, M. biceps brachii, and the forearm flexors. Conclusion Fatigue-related alterations seem to apply analogously in handcycling and cycling. The most distal muscles are responsible for force transmission on the cranks and might thus suffer most from neuromuscular fatigue. The findings indicate that peripheral fatigue (at similar lactate values) is higher in handcycling compared to leg cycling, at least for inexperienced participants. An increase in cadence might delay peripheral fatigue by a reduced vascular occlusion. We assume that the gap between peripheral and central fatigue can be reduced by sport-specific endurance training.}, language = {en} } @article{QuittmannAbelAlbrachtetal.2019, author = {Quittmann, Oliver J. and Abel, Thomas and Albracht, Kirsten and Str{\"u}der, Heiko K.}, title = {Reliability of muscular activation patterns and their alterations during incremental handcycling in able-bodied participants}, series = {Sports Biomechanics}, journal = {Sports Biomechanics}, number = {Article in press}, publisher = {Taylor \& Francis}, address = {London}, issn = {1752-6116}, doi = {10.1080/14763141.2019.1593496}, year = {2019}, language = {en} } @article{QuittmannAbelAlbrachtetal.2022, author = {Quittmann, Oliver J. and Abel, Thomas and Albracht, Kirsten and Str{\"u}der, Heiko K.}, title = {Biomechanics of all-out handcycling exercise: kinetics, kinematics and muscular activity of a 15-s sprint test in able-bodied participants}, series = {Sports Biomechanics}, volume = {21}, journal = {Sports Biomechanics}, number = {10}, publisher = {Taylor \& Francis}, address = {London}, issn = {1752-6116 (Onlineausgabe)}, doi = {10.1080/14763141.2020.1745266}, pages = {1200 -- 1223}, year = {2022}, abstract = {This study aims to quantify the kinematics, kinetics and muscular activity of all-out handcycling exercise and examine their alterations during the course of a 15-s sprint test. Twelve able-bodied competitive triathletes performed a 15-s all-out sprint test in a recumbent racing handcycle that was attached to an ergometer. During the sprint test, tangential crank kinetics, 3D joint kinematics and muscular activity of 10 muscles of the upper extremity and trunk were examined using a power metre, motion capturing and surface electromyography (sEMG), respectively. Parameters were compared between revolution one (R1), revolution two (R2), the average of revolution 3 to 13 (R3) and the average of the remaining revolutions (R4). Shoulder abduction and internal-rotation increased, whereas maximal shoulder retroversion decreased during the sprint. Except for the wrist angles, angular velocity increased for every joint of the upper extremity. Several muscles demonstrated an increase in muscular activation, an earlier onset of muscular activation in crank cycle and an increased range of activation. During the course of a 15-s all-out sprint test in handcycling, the shoulder muscles and the muscles associated to the push phase demonstrate indications for short-duration fatigue. These findings are helpful to prevent injuries and improve performance in all-out handcycling.}, language = {en} } @article{QuittmannMeskemperAbeletal.2018, author = {Quittmann, Oliver J. and Meskemper, Joshua and Abel, Thomas and Albracht, Kirsten and Foitschik, Tina and Rojas-Vega, Sandra and Str{\"u}der, Heiko K.}, title = {Kinematics and kinetics of handcycling propulsion at increasing workloads in able-bodied subjects}, series = {Sports Engineereing}, volume = {21}, journal = {Sports Engineereing}, number = {21}, publisher = {Springer Nature}, address = {Cham}, issn = {1460-2687}, doi = {10.1007/s12283-018-0269-y}, pages = {283 -- 294}, year = {2018}, abstract = {In Paralympic sports, biomechanical optimisation of movements and equipment seems to be promising for improving performance. In handcycling, information about the biomechanics of this sport is mainly provided by case studies. The aim of the current study was (1) to examine changes in handcycling propulsion kinematics and kinetics due to increasing workloads and (2) identify parameters that are associated with peak aerobic performance. Twelve non-disabled male competitive triathletes without handcycling experience voluntarily participated in the study. They performed an initial familiarisation protocol and incremental step test until exhaustion in a recumbent racing handcycle that was attached to an ergometer. During the incremental test, tangential crank kinetics, 3D joint kinematics, blood lactate and ratings of perceived exertion (local and global) were identified. As a performance criterion, the maximal power output during the step test (Pmax) was calculated and correlated with biomechanical parameters. For higher workloads, an increase in crank torque was observed that was even more pronounced in the pull phase than in the push phase. Furthermore, participants showed an increase in shoulder internal rotation and abduction and a decrease in elbow flexion and retroversion. These changes were negatively correlated with performance. At high workloads, it seems that power output is more limited by the transition from pull to push phase than at low workloads. It is suggested that successful athletes demonstrate small alterations of their kinematic profile due to increasing workloads. Future studies should replicate and expand the test spectrum (sprint and continuous loads) as well as use methods like surface electromyography (sEMG) with elite handcyclists.}, language = {de} } @article{QuittmannMeskemperAlbrachtetal.2020, author = {Quittmann, Oliver J. and Meskemper, Joshua and Albracht, Kirsten and Abel, Thomas and Foitschik, Tina and Str{\"u}der, Heiko K.}, title = {Normalising surface EMG of ten upper-extremity muscles in handcycling: Manual resistance vs. sport-specific MVICs}, series = {Journal of Electromyography and Kinesiology}, volume = {51}, journal = {Journal of Electromyography and Kinesiology}, number = {Article 102402}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1050-6411}, doi = {10.1016/j.jelekin.2020.102402}, year = {2020}, abstract = {Muscular activity in terms of surface electromyography (sEMG) is usually normalised to maximal voluntary isometric contractions (MVICs). This study aims to compare two different MVIC-modes in handcycling and examine the effect of moving average window-size. Twelve able-bodied male competitive triathletes performed ten MVICs against manual resistance and four sport-specific trials against fixed cranks. sEMG of ten muscles [M. trapezius (TD); M. pectoralis major (PM); M. deltoideus, Pars clavicularis (DA); M. deltoideus, Pars spinalis (DP); M. biceps brachii (BB); M. triceps brachii (TB); forearm flexors (FC); forearm extensors (EC); M. latissimus dorsi (LD) and M. rectus abdominis (RA)] was recorded and filtered using moving average window-sizes of 150, 200, 250 and 300 ms. Sport-specific MVICs were higher compared to manual resistance for TB, DA, DP and LD, whereas FC, TD, BB and RA demonstrated lower values. PM and EC demonstrated no significant difference between MVIC-modes. Moving average window-size had no effect on MVIC outcomes. MVIC-mode should be taken into account when normalised sEMG data are illustrated in handcycling. Sport-specific MVICs seem to be suitable for some muscles (TB, DA, DP and LD), but should be augmented by MVICs against manual/mechanical resistance for FC, TD, BB and RA.}, language = {en} } @article{RabehiGarlanAchtsnichtetal.2018, author = {Rabehi, Amine and Garlan, Benjamin and Achtsnicht, Stefan and Krause, Hans-Joachim and Offenh{\"a}usser, Andreas and Ngo, Kieu and Neveu, Sophie and Graff-Dubois, Stephanie and Kokabi, Hamid}, title = {Magnetic detection structure for Lab-on-Chip applications based on the frequency mixing technique}, series = {Sensors}, volume = {18}, journal = {Sensors}, number = {6}, publisher = {MDPI}, address = {Basel}, issn = {1424-8220}, doi = {10.3390/s18061747}, pages = {14 Seiten}, year = {2018}, abstract = {A magnetic frequency mixing technique with a set of miniaturized planar coils was investigated for use with a completely integrated Lab-on-Chip (LoC) pathogen sensing system. The system allows the detection and quantification of superparamagnetic beads. Additionally, in terms of magnetic nanoparticle characterization ability, the system can be used for immunoassays using the beads as markers. Analytical calculations and simulations for both excitation and pick-up coils are presented; the goal was to investigate the miniaturization of simple and cost-effective planar spiral coils. Following these calculations, a Printed Circuit Board (PCB) prototype was designed, manufactured, and tested for limit of detection, linear response, and validation of theoretical concepts. Using the magnetic frequency mixing technique, a limit of detection of 15 µg/mL of 20 nm core-sized nanoparticles was achieved without any shielding.}, language = {en} } @inproceedings{RabnerShacham2006, author = {Rabner, Arthur and Shacham, Yosi}, title = {A concept for a sensitive micro total analysis system for high throughput fluorescence imaging}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:a96-opus-1456}, year = {2006}, abstract = {This paper discusses possible methods for on-chip fluorescent imaging for integrated bio-sensors. The integration of optical and electro-optical accessories, according to suggested methods, can improve the performance of fluorescence imaging. It can boost the signal to background ratio by a few orders of magnitudes in comparison to conventional discrete setups. The methods that are present in this paper are oriented towards building reproducible arrays for high-throughput micro total analysis systems (µTAS). The first method relates to side illumination of the fluorescent material placed into microcompartments of the lab-on-chip. Its significance is in high utilization of excitation energy for low concentration of fluorescent material. The utilization of a transparent µLED chip, for the second method, allows the placement of the excitation light sources on the same optical axis with emission detector, such that the excitation and emission rays are directed controversly. The third method presents a spatial filtering of the excitation background.}, subject = {Biosensor}, language = {en} } @inproceedings{RamanJungHorvathetal.2019, author = {Raman, Aravind Hariharan and Jung, Alexander and Horv{\´a}th, Andr{\´a}s and Becker, Nadine and Staat, Manfred}, title = {Modification of a computer model of human stem cell-derived cardiomyocyte electrophysiology based on Patch-Clamp measurements}, series = {3rd YRA MedTech Symposium 2019 : May 24 / 2019 / FH Aachen}, booktitle = {3rd YRA MedTech Symposium 2019 : May 24 / 2019 / FH Aachen}, editor = {Staat, Manfred and Erni, Daniel}, publisher = {Universit{\"a}t Duisburg-Essen}, address = {Duisburg}, organization = {MedTech Symposium}, isbn = {978-3-940402-22-6}, doi = {10.17185/duepublico/48750}, pages = {10 -- 11}, year = {2019}, abstract = {Human induced pluripotent stem cells (hiPSCs) have shown to be promising in disease studies and drug screenings [1]. Cardiomyocytes derived from hiPSCs have been extensively investigated using patch-clamping and optical methods to compare their electromechanical behaviour relative to fully matured adult cells. Mathematical models can be used for translating findings on hiPSCCMs to adult cells [2] or to better understand the mechanisms of various ion channels when a drug is applied [3,4]. Paci et al. (2013) [3] developed the first model of hiPSC-CMs, which they later refined based on new data [3]. The model is based on iCells® (Fujifilm Cellular Dynamics, Inc. (FCDI), Madison WI, USA) but major differences among several cell lines and even within a single cell line have been found and motivate an approach for creating sample-specific models. We have developed an optimisation algorithm that parameterises the conductances (in S/F=Siemens/Farad) of the latest Paci et al. model (2018) [5] using current-voltage data obtained in individual patch-clamp experiments derived from an automated patch clamp system (Patchliner, Nanion Technologies GmbH, Munich).}, language = {en} } @article{RamoshabaHuismanLammertynetal.2020, author = {Ramoshaba, Nthai E. and Huisman, Hugo W. and Lammertyn, Leandi and Kotliar, Konstantin and Schutte, Aletta E. and Smith, Wayne}, title = {Retinal microvasculature and masked hypertension in young adults: the African-PREDICT study}, series = {Hypertension Research}, journal = {Hypertension Research}, number = {43}, publisher = {Springer Nature}, address = {Osaka}, issn = {1348-4214}, doi = {10.1038/s41440-020-0487-0}, pages = {1231 -- 1238}, year = {2020}, abstract = {Masked hypertension is known to induce microvascular complications. However, it is unclear whether early microvascular changes are already occurring in young, otherwise healthy adults. We therefore investigated whether retinal microvascular calibers and acute responses to a flicker stimulus are related to masked hypertension. We used the baseline data of 889 participants aged 20-30 years who were taking part in the African Prospective study on the Early Detection and Identification of Cardiovascular Disease and Hypertension. Clinic and 24-h ambulatory blood pressure were measured. The central retinal artery equivalent (CRAE) and central retinal vein equivalent were calculated from fundus images, and retinal vessel dilation was determined in response to flicker light-induced provocation. A smaller CRAE was observed in those with masked hypertension vs. those with normotension (157.1 vs. 161.2 measuring units, P < 0.001). In forward multivariable-adjusted regression analysis, only CRAE was negatively related to masked hypertension [adjusted R² = 0.267, β = -0.097 (95\% CI = -0.165; -0.029), P = 0.005], but other retinal microvascular parameters were not associated with masked hypertension. In multivariable logistic regression analyses, masked hypertension [OR = 2.333, (95\% CI = 1.316; 4.241), P = 0.004] was associated with a narrower CRAE. In young healthy adults, masked hypertension was associated with retinal arteriolar narrowing, thereby reflecting early microvascular alterations known to predict cardiovascular outcomes in later life.}, language = {en} } @article{RauschHarbrechtKahmannetal.2020, author = {Rausch, Valentin and Harbrecht, Andreas and Kahmann, Stephanie Lucina and Fenten, Thomas and Jovanovic, Nebojsa and Hackl, Michael and M{\"u}ller, Lars P. and Staat, Manfred and Wegmann, Kilian}, title = {Osteosynthesis of Phalangeal Fractures: Biomechanical Comparison of Kirschner Wires, Plates, and Compression Screws}, series = {The Journal of Hand Surgery}, volume = {45}, journal = {The Journal of Hand Surgery}, number = {10}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0363-5023}, doi = {10.1016/j.jhsa.2020.04.010}, pages = {987.e1 -- 987.e8}, year = {2020}, abstract = {Purpose The aim of this study was to compare several osteosynthesis techniques (intramedullary headless compression screws, T-plates, and Kirschner wires) for distal epiphyseal fractures of proximal phalanges in a human cadaveric model. Methods A total of 90 proximal phalanges from 30 specimens (index, ring, and middle fingers) were used for this study. After stripping off all soft tissue, a transverse distal epiphyseal fracture was simulated at the proximal phalanx. The 30 specimens were randomly assigned to 1 fixation technique (30 per technique), either a 3.0-mm intramedullary headless compression screw, locking plate fixation with a 2.0-mm T-plate, or 2 oblique 1.0-mm Kirschner wires. Displacement analysis (bending, distraction, and torsion) was performed using optical tracking of an applied random speckle pattern after osteosynthesis. Biomechanical testing was performed with increasing cyclic loading and with cyclic load to failure using a biaxial torsion-tension testing machine. Results Cannulated intramedullary compression screws showed significantly less displacement at the fracture site in torsional testing. Furthermore, screws were significantly more stable in bending testing. Kirschner wires were significantly less stable than plating or screw fixation in any cyclic load to failure test setup. Conclusions Intramedullary compression screws are a highly stable alternative in the treatment of transverse distal epiphyseal phalangeal fractures. Kirschner wires seem to be inferior regarding displacement properties and primary stability. Clinical relevance Fracture fixation of phalangeal fractures using plate osteosynthesis may have the advantage of a very rigid reduction, but disadvantages such as stiffness owing to the more invasive surgical approach and soft tissue irritation should be taken into account. Headless compression screws represent a minimally invasive choice for fixation with good biomechanical properties.}, language = {en} } @article{RauschKahmannBaltschunetal.2020, author = {Rausch, Valentin and Kahmann, Stephanie Lucina and Baltschun, Christoph and Staat, Manfred and M{\"u}ller, Lars P. and Wegmann, Kilian}, title = {Pressure distribution to the distal biceps tendon at the radial tuberosity: a biomechanical study}, series = {The Journal of Hand Surgery}, volume = {45}, journal = {The Journal of Hand Surgery}, number = {8}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0363-5023}, doi = {10.1016/j.jhsa.2020.01.006}, pages = {776.e1 -- 776.e9}, year = {2020}, abstract = {Purpose Mechanical impingement at the narrow radioulnar space of the tuberosity is believed to be an etiological factor in the injury of the distal biceps tendon. The aim of the study was to compare the pressure distribution at the proximal radioulnar space between 2 fixation techniques and the intact state. Methods Six right arms and 6 left arms from 5 female and 6 male frozen specimens were used for this study. A pressure transducer was introduced at the height of the radial tuberosity with the intact distal biceps tendon and after 2 fixation methods: the suture-anchor and the cortical button technique. The force (N), maximum pressure (kPa) applied to the radial tuberosity, and the contact area (mm²) of the radial tuberosity with the ulna were measured and differences from the intact tendon were detected from 60° supination to 60° pronation in 15° increments with the elbow in full extension and in 45° and 90° flexion of the elbow. Results With the distal biceps tendon intact, the pressures during pronation were similar regardless of extension and flexion and were the highest at 60° pronation with 90° elbow flexion (23.3 ± 53.5 kPa). After repair of the tendon, the mean peak pressure, contact area, and total force showed an increase regardless of the fixation technique. Highest peak pressures were found using the cortical button technique at 45° flexion of the elbow and 60° pronation. These differences were significantly different from the intact tendon. The contact area was significantly larger in full extension and 15°, 30°, and 60° pronation using the cortical button technique. Conclusions Pressures on the distal biceps tendon at the radial tuberosity increase during pronation, especially after repair of the tendon. Clinical relevance Mechanical impingement could play a role in both the etiology of primary distal biceps tendon ruptures and the complications occurring after fixation of the tendon using certain techniques.}, language = {en} } @article{ReisertGeisslerFlorkeetal.2011, author = {Reisert, Steffen and Geissler, H. and Florke, R. and Wagner, P. and Wagner, Torsten and Sch{\"o}ning, Michael Josef}, title = {Controlling aseptic sterilization processes by means of a multi-sensor system}, publisher = {IEEE}, address = {New York}, pages = {18 -- 22}, year = {2011}, language = {en} }