TY - JOUR A1 - Gilbert, F. A1 - Meffert, R. H. A1 - Schmalzl, J. A1 - Weng, A. M. A1 - Köstler, H. A1 - Eden, L. T1 - Grade of retraction and tendon thickness correlates with MR-spectroscopically measured amount of fatty degeneration in full thickness supraspinatus tears JF - BMC Musculoskeletal Disorders N2 - Background: The amount of fatty degeneration (FD) has major impact on the clinical result and cuff integrity after rotator cuff repair. A quantitative analysis with magnet resonance imaging (MRI) spectroscopy was employed to analyze possible correlation of FD with tendon retraction, tendon thickness and patients’ characteristics in full thickness supraspinatus tears. Methods: Forty-two patients with full-thickness supraspinatus tears underwent shoulder MRI including an experimental spectroscopic sequence allowing quantification of the fat fraction in the supraspinatus muscle belly. The amount of fatty degeneration was correlated with tendon retraction, tendon thickness, patients’ age, gender, smoker status, symptom duration and body mass index (BMI). Patients were divided in to three groups of retraction (A) 0-10 mm (n=), (B) 11-20 mm (n=) and (C) < 21 mm (n=) and the means of FD for each group were calculated. Results: Tendon retraction (R = 0.6) and symptom duration (R = 0.6) correlated positively, whereas tendon thickness correlated negatively (R = − 0.6) with the amount of FD. The fat fraction increased significantly with tendon retraction: Group (A) showed a mean fat mount of 3.7% (±4%), group (B) of 16.7% (±8.2%) and group (C) of 37.5% (±19%). BMI, age and smoker-status only showed weak to moderate correlation with the amount of FD in this cohort. Conclusion: MRI spectroscopy revealed significantly higher amount of fat with increasing grade of retraction, symptom duration and decreased tendon thickness. Thus, these parameters may indirectly be associated with the severity of tendon disease. KW - rotator cuff KW - MRI KW - spectroscopy KW - muscle degeneration Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-176116 VL - 19 IS - 197 ER - TY - JOUR A1 - Sung, Jooyoung A1 - Kim, Pyosang A1 - Fimmel, Benjamin A1 - Würthner, Frank A1 - Kim, Dongho T1 - Direct observation of ultrafast coherent exciton dynamics in helical π-stacks of self-assembled perylene bisimides JF - Nature Communications N2 - Ever since the discovery of dye self-assemblies in nature, there have been tremendous efforts to exploit biomimetic supramolecular assemblies for tailored artificial photon processing materials. This feature necessarily has resulted in an increasing demand for understanding exciton dynamics in the dye self-assemblies. In a sharp contrast with pi-type aggregates, however, the detailed observation of exciton dynamics in H-type aggregates has remained challenging. In this study, as we succeed in measuring transient fluorescence from Frenkel state of π-stacked perylene tetracarboxylic acid bisimide dimer and oligomer aggregates, we present an experimental demonstration on Frenkel exciton dynamics of archetypal columnar π-π stacks of dyes. The analysis of the vibronic peak ratio of the transient fluorescence spectra reveals that unlike the simple π-stacked dimer, the photoexcitation energy in the columnar π-stacked oligomer aggregates is initially delocalized over at least three molecular units and moves coherently along the chain in tens of femtoseconds, preceding excimer formation process. KW - systems KW - molecules KW - J-aggregate behavior KW - absorption KW - spectroscopy KW - photoluminescence KW - diffusion KW - fluorescence KW - excimer formation KW - organic semiconductors Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148157 VL - 6 IS - 8646 ER - TY - JOUR A1 - Reichmuth, Anne A1 - Henning, Lea A1 - Pinnel, Nicole A1 - Bachmann, Martin A1 - Rogge, Derek T1 - Early detection of vitality changes of multi-temporal Norway spruce laboratory needle measurements—the ring-barking experiment JF - Remote Sensing N2 - The focus of this analysis is on the early detection of forest health changes, specifically that of Norway spruce (Picea abies L. Karst.). In this analysis, we planned to examine the time (degree of early detection), spectral wavelengths and appropriate method for detecting vitality changes. To accomplish this, a ring-barking experiment with seven subsequent laboratory needle measurements was carried out in 2013 and 2014 in an area in southeastern Germany near Altötting. The experiment was also accompanied by visual crown condition assessment. In total, 140 spruce trees in groups of five were ring-barked with the same number of control trees in groups of five that were selected as reference trees in order to compare their development. The laboratory measurements were analysed regarding the separability of ring-barked and control samples using spectral reflectance, vegetation indices and derivative analysis. Subsequently, a random forest classifier for determining important spectral wavelength regions was applied. Results from the methods are consistent and showed a high importance of the visible (VIS) spectral region, very low importance of the near-infrared (NIR) and minor importance of the shortwave infrared (SWIR) spectral region. Using spectral reflectance data as well as indices, the earliest separation time was found to be 292 days after ring-barking. The derivative analysis showed that a significant separation was observed 152 days after ring-barking for six spectral features spread through VIS and SWIR. A significant separation was detected using a random forest classifier 292 days after ring-barking with 58% separability. The visual crown condition assessment was analysed regarding obvious changes of vitality and the first indication was observed 302 days after ring-barking as bark beetle infestation and yellowing of foliage in the ring-barked trees only. This experiment shows that an early detection, compared with visual crown assessment, is possible using the proposed methods for this specific data set. This study will contribute to ongoing research for early detection of vitality changes that will support foresters and decision makers. KW - laboratory measurements KW - derivatives KW - spectroscopy KW - forest health KW - ring-barking KW - random forest KW - index analysis Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159253 VL - 10 IS - 1 ER - TY - JOUR A1 - Wolter, Steffen A1 - Aizezers, Janis A1 - Fennel, Franziska A1 - Seidel, Marcus A1 - Würthner, Frank A1 - Kühn, Oliver A1 - Lochbrunner, Stefan T1 - Size-dependent exciton dynamics in one-dimensional perylene bisimide aggregates JF - New Journal of Physics N2 - The size-dependent exciton dynamics of one-dimensional aggregates of substituted perylene bisimides are studied by ultrafast transient absorption spectroscopy and kinetic Monte-Carlo simulations as a function of the excitation density and the temperature in the range of 25-90 degrees C. For low temperatures, the aggregates can be treated as infinite chains and the dynamics is dominated by diffusion-driven exciton-exciton annihilation. With increasing temperature the aggregates dissociate into small fragments consisting of very few monomers. This scenario is also supported by the time-dependent anisotropy deduced from polarization-dependent experiments. KW - rotational diffusion KW - spectroscopy KW - dyes KW - annihilation KW - migration KW - films Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-135190 VL - 14 IS - 105027 ER - TY - JOUR A1 - Gilbert, Fabian A1 - Böhm, Dirk A1 - Eden, Lars A1 - Schmalzl, Jonas A1 - Meffert, Rainer H. A1 - Köstler, Herbert A1 - Weng, Andreas M. A1 - Ziegler, Dirk T1 - Comparing the MRI-based Goutallier Classification to an experimental quantitative MR spectroscopic fat measurement of the supraspinatus muscle JF - BMC Musculoskeletal Disorders N2 - Background The Goutallier Classification is a semi quantitative classification system to determine the amount of fatty degeneration in rotator cuff muscles. Although initially proposed for axial computer tomography scans it is currently applied to magnet-resonance-imaging-scans. The role for its clinical use is controversial, as the reliability of the classification has been shown to be inconsistent. The purpose of this study was to compare the semi quantitative MRI-based Goutallier Classification applied by 5 different raters to experimental MR spectroscopic quantitative fat measurement in order to determine the correlation between this classification system and the true extent of fatty degeneration shown by spectroscopy. Methods MRI-scans of 42 patients with rotator cuff tears were examined by 5 shoulder surgeons and were graduated according to the MRI-based Goutallier Classification proposed by Fuchs et al. Additionally the fat/water ratio was measured with MR spectroscopy using the experimental SPLASH technique. The semi quantitative grading according to the Goutallier Classification was statistically correlated with the quantitative measured fat/water ratio using Spearman’s rank correlation. Results Statistical analysis of the data revealed only fair correlation of the Goutallier Classification system and the quantitative fat/water ratio with R = 0.35 (p < 0.05). By dichotomizing the scale the correlation was 0.72. The interobserver and intraobserver reliabilities were substantial with R = 0.62 and R = 0.74 (p < 0.01). Conclusion The correlation between the semi quantitative MRI based Goutallier Classification system and MR spectroscopic fat measurement is weak. As an adequate estimation of fatty degeneration based on standard MRI may not be possible, quantitative methods need to be considered in order to increase diagnostic safety and thus provide patients with ideal care in regard to the amount of fatty degeneration. Spectroscopic MR measurement may increase the accuracy of the Goutallier classification and thus improve the prediction of clinical results after rotator cuff repair. However, these techniques are currently only available in an experimental setting. KW - rotator cuff KW - MRI KW - spectroscopy KW - goutallier KW - classification KW - shoulder surgery Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-147788 VL - 17 IS - 355 ER - TY - JOUR A1 - Kasprzak, J. A1 - Sivalertporn, K. A1 - Albert, F. A1 - Schneider, C. A1 - Höfling, S. A1 - Kamp, M. A1 - Forchel, A. A1 - Muljarov, E. A. A1 - Langbein, W. T1 - Coherence dynamics and quantum-to-classical crossover in an exciton-cavity system in the quantum strong coupling regime JF - New Journal of Physics N2 - Interaction between light and matter generates optical nonlinearities, which are particularly pronounced in the quantum strong coupling regime. When a single bosonic mode couples to a single fermionic mode, a Jaynes-Cummings (JC) ladder is formed, which we realize here using cavity photons and quantum dot excitons. We measure and model the coherent anharmonic response of this strongly coupled exciton-cavity system at resonance. Injecting two photons into the cavity, we demonstrate a \(\sqrt 2\) larger polariton splitting with respect to the vacuum Rabi splitting. This is achieved using coherent nonlinear spectroscopy, specifically four-wave mixing, where the coherence between the ground state and the first (second) rung of the JC ladder can be interrogated for positive (negative) delays. With increasing excitation intensity and thus rising average number of injected photons, we observe spectral signatures of the quantum-to-classical crossover of the strong coupling regime. KW - Jaynes-Cummings ladder KW - spectral interferometry KW - photon KW - dot KW - spectroscopy KW - oscillations KW - microcavity KW - resonance KW - light Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-123005 SN - 1367-2630 VL - 15 IS - 045013 ER - TY - JOUR A1 - Dauth, M. A1 - Wiessner, M. A1 - Feyer, V. A1 - Schöll, A. A1 - Puschnig, P. A1 - Reinert, F. A1 - Kuemmel, S. T1 - Angle resolved photoemission from organic semiconductors: orbital imaging beyond the molecular orbital interpretation JF - New Journal of Physics N2 - Fascinating pictures that can be interpreted as showing molecular orbitals have been obtained with various imaging techniques. Among these, angle resolved photoemission spectroscopy (ARPES) has emerged as a particularly powerful method. Orbital images have been used to underline the physical credibility of the molecular orbital concept. However, from the theory of the photoemission process it is evident that imaging experiments do not show molecular orbitals, but Dyson orbitals. The latter are not eigenstates of a single-particle Hamiltonian and thus do not fit into the usual simple interpretation of electronic structure in terms of molecular orbitals. In a combined theoretical and experimental study we thus check whether a Dyson-orbital and a molecular-orbital based interpretation of ARPES lead to differences that are relevant on the experimentally observable scale. We discuss a scheme that allows for approximately calculating Dyson orbitals with moderate computational effort. Electronic relaxation is taken into account explicitly. The comparison reveals that while molecular orbitals are frequently good approximations to Dyson orbitals, a detailed understanding of photoemission intensities may require one to go beyond the molecular orbital picture. In particular we clearly observe signatures of the Dyson-orbital character for an adsorbed semiconductor molecule in ARPES spectra when these are recorded over a larger momentum range than in earlier experiments. KW - Dyson orbitals KW - electronic structure KW - PTCDA KW - AG(110) KW - density-functional theory KW - approximation KW - energies KW - monolayers KW - spectroscopy KW - NTCDA KW - ARPES KW - orbital imaging KW - photoemission spectroscopy Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-115180 SN - 1367-2630 VL - 16 ER -