Picosecond studies of excited states in conjugated polymers

This thesis reports on the interplay between molecular structure and photophysics in light emitting conjugated polymers revealed by steady state and picosecond time-resolved fluorescence spectroscopy. The fundamental excited state relaxation of a polyfluorene derivative is compared to that of two oligofluorenes using isolated molecules in dilute solution. Their long-time time-dependent spectral dynamics are monitored by means of picosecond streak camera and single photon counting techniques. Excited state relaxation in oligofluorenes is entirely conformational and depends on solvent viscosity. The intrachain photophysics of the polyfluorene is dominated by fast excitation migration with a slow conformational component. A rigid ladder-type polymer exhibits only migrational relaxation. In analogy, the spectral dynamics of an alkoxy-substituted polyspirobifluorene are studied in dilute solution. Their qualitative dependence on solvent viscosity is elucidated by further femtosecond photobleaching measurements. Two excited states are proposed with the lower energy state involving strong spiroconjugation as confirmed by electronic structure calculations. Conversion between them occurs via conformational relaxation of the fluorene side groups. The sensitive reaction of these photophysics to the substitution pattern of the polymer suggests an easy chemical tunability of polyspirobifluorenes towards optimised charge carrier transport properties. Finally, the formation of the beta phase in amorphous polydioctylfluorene is investigated as a function of spin coating fabrication in the solid state. It is suggested that it forms by condensation at colloidal sites, which arise from incomplete solvation in the master solution. A further room temperature phase exists in the absence of these nuclei. The excited state relaxation after energy transfer from amorphous to beta phase is monitored via time-resolved spectroscopy. Within the beta phase, exciton migration is restricted as confirmed by steady state anisotropy data. This evidence for exciton confinement is an important step towards the application of the beta phase as a polymer laser

The influence of interchain interactions on the photophysics of conjugated polymers

This thesis presents findings on the photoluminescence properties of two conjugated polymers with special interest paid to interchain interactions and chemical degradation. The delayed luminescence of thin films of poly(3-methyl-4-octyl-thiophene) (PMOT) has been observed via time-resolved photoluminescence spectroscopy (TRS) in different temperature regimes. While at 15 K the emission consists of delayed fluorescence (DF) and phosphorescence (Ph) originating from radiatively decaying singlet and triplet excitons, room temperature emission is red-shifted with respect to the DF and originates from excimers. Supportingly, photo-induced absorption experiments detect very long-lived excitations allocated to the triplet counterparts of the emitting excimers. Furthermore, the influence of the photo-oxidisation of polyfluorenes on their luminescence is investigated. A series of polyfluorene/polyfluorenone co-polymers (PFO/PFl) with varying percentages of fluorenone repeat units was analysed via TRS as well as steady-state absorption, photoluminescence and photoexcitation spectroscopy in solid state and solution. Fluorenone repeat units (or keto defects) arising from polyfluorene photo-oxidation are the origin of the green luminescence band affecting the colour purity and quantum yield of polyfluorene devices. Fluorenone triplets play a major role and can be directly photo-excited. Moreover, they form upon polyfluorene degradation. Efficient energy transfer takes place from PFO singlets to fluorenone triplets entailing two types of triplet-triplet interaction processes, which lead to the formation of fluorenone excimers as well as polyfluorene-fluorenone exciplexes. Two types of the green emission can be assigned to emission from these states. This could be confirmed by the decay kinetics, thermal behaviour and keto level dependence of the emissions

Evaluating the interreader agreement and intrareader reproducibility of Visual Field Defects in Thyroid Eye Disease- Compressive Optic Neuropathy

PURPOSE To categorize visual field (VF) defects according to Freitag and Tanking's (FT) classification in Thyroid Eye Disease-Compressive Optic Neuropathy (TED-CON) and evaluate the interreader agreement and intrareader reproducibility of the classification. SUBJECTS AND METHODS In this retrospective, observational study we included medical reports of 96 eyes (51 patients), who underwent VF testing with TED-CON in Ludwig-Maximilians-University (2008-2019). Two readers separately examined the VFs at the time of the TED-CON diagnosis, each offering two readings of the same VF in a time interval of 1 month. None of our patients were diagnosed with only VF testing. The visual field testing was only performed when the inclusion criteria for TED-CON were met. RESULTS The most common VF defects upon TED-CON diagnosis were stage 1b defects in FT classification (34.4% for reader 1, 35.4% for reader 2), followed by stage 2b (10.4% for reader 1, 14.6% for reader 2), and stage 3 (10.4% for both readers). The overall interreader agreement between 2 examiners was substantial for the first reading (69.8% agreement, kappa 0.635 (95% CI 0.525-0.745)) and moderate for the second reading (66.7{\%} agreement, kappa 0.598 (95{\%} CI 0.488-0.708)). The intrareader reproducibility ranged from substantial to almost perfect (78.1{\%} agreement) between readings (kappa 0.736 (95{\%}CI 0.638-0.834)) for reader 1 and 90.6{\%} agreement (kappa 0.885 (95{\%}CI 0.814-0.956)) for reader 2. CONCLUSION We found good BCVA (LogMAR $\leq$ 0.2), in nearly half of the cases (44 eyes, 45.8{\%}) and also, strikingly near perfect visual acuity (BCVA LogMAR $\leq$0.1) in 22.9{\%} of the cases (22 eyes) with TED-CON. We conclude that clinicians should be alert to VF defects in the inferior region (stage 1a/1b in the FT classification) even in patients with a good BCVA

A pathological indicator for dysthyroid optic neuropathy: tritan color vision deficiency

PURPOSE To investigate the sensitivity of the color vision test by Arden in patients with dysthyroid optic neuropathy (DON) to improve diagnosis. METHODS In this observational, retrospective study, we included the medical records of 92 eyes (48 patients) with diagnosis of DON between 2008 and 2019 in order to evaluate the full spectrum of findings from the color vision test by Arden, and to determine potential importance of this test. Thirty-five patients were female, and 13 patients were male. The mean age was 58.0~years (range: 34-79) at the time of the DON diagnosis. RESULTS Forty-one eyes displayed relatively good BCVA with ≤ 0.2 LogMAR. We found a protan value exceeding the threshold of ≥ 8% in 57 eyes (30 patients) at the time of the diagnosis. The sensitivity of protan was 61.9% (95% CI 51.2-71.8%), while that of tritan was a striking 98.9% (95% CI 94.1-99.9%). We discovered one pathological sign, tritan deficiency (based on a threshold of ≥ 8%) consistently in all eyes but one at the time of the diagnosis, regardless of the visual field defects or any changes in best-corrected visual acuity (BCVA). CONCLUSION We found blue-yellow (tritan) deficiency, to be a sensitive and reliable indicator of dysthyroid optic neuropathy. We conclude that, in cases with suspected DON, a color vision test that can detect tritan deficiency is an essential tool for the adequate assessment, diagnosis, and treatment of DON

The taste of the pandemic—contemporary review on the current state of research on gustation in coronavirus disease 2019 (COVID‐19)

Subjectively perceived impairment of taste is a common and distinct symptom of coronavirus disease 2019 (COVID-19). Large meta-analyses identified this symptom in approximately 50% of cases. However, this high prevalence is not supported by blinded and validated psychophysical gustatory testing, which showed a much lower prevalence in up to 26% of patients. This discrepancy may be due to misinterpretation of impaired retronasal olfaction as gustatory dysfunction. In addition, we hypothesized that COVID-19–associated hyposmia is involved in the decrease of gustatory function, as found for hyposmia of different origin. This indirect mechanism would be based on the central-nervous mutual amplification between the chemical senses, which fails in COVID-19–associated olfactory loss. However, further research is necessary on how severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) may directly impair the gustatory pathway as well as its subjective perception

Topical Administration of Mometasone Is Not Helpful in Post-COVID-19 Olfactory Dysfunction

Persistent olfactory dysfunction is a major concern post-COVID-19, affecting up to 5% of all patients. Different therapeutic options, including mometasone nasal spray, have been recommended, only some of which have been validated for post-COVID-19 olfactory dysfunction. In this study we psychophysically assessed the effect of intranasally applied mometasone furoate on the recovery of olfaction. The spray was applied with a long applicator so that the olfactory cleft could be reached effectively. After olfactory dysfunction had been confirmed psychophysically using Sniffin’ Sticks, patients were randomly assigned to two different treatment arms: the study group (n = 40) underwent olfactory training and intranasal administration of mometasone furoate twice daily, whereas the control group (n = 46) performed olfactory training only. After a study duration of three months, psychophysical testing of olfaction was repeated using Sniffin’ Sticks. We found no benefit of an additional topical administration of mometasone furoate compared to olfactory training alone. These results psychophysically confirm two previous studies which were based on patients’ subjective self-ratings. Our findings are in contrast to current recommendations for the management of olfactory dysfunction post-COVID-19, which might have to be adapted accordingly

Combined positron emission tomography/computed tomography (PET/CT) for imaging of orbital tumours and tumours extending into the orbit

Objective To assess clinical and radiological performance of combined positron emission tomography/computed tomography (PET/CT) in patients with secondary and primary intraorbital tumours. Methods 14 adults with secondary and 1 child with primary orbital masses underwent combined whole-body PET/CT. Radiopharmaceutical tracers applied were (18F)-fluorodeoxyglucose, (18F)-fluoroethylcholine (FEC) and (68Ga)-DOTATATE. Histopathology and/or all conventional radiographic work-up and clinical course served as standard of reference. Descriptive statistics and Fisher's exact test were used for analysis. Results PET/CT detected all orbital masses. All 15 patients had malignant disease. Local osseous infiltration was correctly identified in 11 patients. Lymph node metastases were present in two of eight patients (25%) with haematogenous orbital metastases and in five of six patients (83%) with infiltrative carcinoma (p=0.05). Further distant metastases were present in all eight patients suffering from orbital metastases, but only one patient with infiltrative carcinoma (17%) presented with disseminated disease (p=0.003). In one metastasis, PET/CT excluded vital orbital tumour tissue after radiation therapy. Local recurrence was detected in another patient suffering from prostate cancer. Conclusion PET/CT is a sensitive tool for the detection and localisation of orbital masses, enabling assessment of both morphology and cell metabolism. Detailed imaging of the head and neck region with a small field-of-view should be performed when suspecting lymphatic metastases. As metastatic disease to the orbit is associated with advanced disease, focus should be laid on whole-body imaging for staging of these patients. Different radiopharmaceutical tracers can be applied to distinguish the origin of orbital metastases

Hertel-exophthalmometry-like multi-detector-row-CT-exophthalmometry: inter-disciplinary inter-observer reproducibility of measurements

Objectives: To investigate the interdisciplinary interobserver reproducibility of Hertel-exophthalmometry-like protrusion measurements on multidetector-row-computed-tomography- (MDCT-) images of the orbit to facilitate structured evaluation of the orbit and mid-face. Methods: Respective reproducibility of base-length along the interfronto-zygomatic line, right and left ocular protrusion, and deriving interocular difference was measured in this retrospective (04/2009-03/2020) single-centre observational study. MDCT-series and slice-positions were selected independently, using picture-archiving-and-communication-system- (PACS-) tools on tilt-corrected axial MDCT-images (slice-thickness 0.6–3.0 mm, window/centre 350/50 HU) in 37 selected adult patients (24 female, age 57 ± 13 years, average±standard-deviation) with clinical indication for Hertel-exophthalmometry, by one radiology-attending, two ophthalmology-attendings, one critical-care-attending, and one ear-nose-throat-surgery resident, respectively. Bland-Altman plots and Wilcoxon-matched-pairs-signed-rank-tests compared interobserver results. Results: Mean and median interobserver and intraobserver (radiology-attending) deviations were within 1 mm of respective averages of base-length (98 ± 4 mm), right and left ocular protrusion (21 ± 4 mm) and interocular difference (2 ± 1 mm). Relative interobserver deviations were within 2.0% of average (all patients) for base-length, and 5.0% (>80% of patients) for ocular protrusion. Pairwise interobserver comparison showed no significant differences between interocular differences of protrusion. Conclusions: Respective measurements of base-length, ocular protrusion, and deriving interocular difference show high interdisciplinary interobserver reproducibility in tilt-corrected axial MDCT-images of the orbit or mid-face. Advances in knowledge: Hertel-exophthalmometry-like protrusion measurements did not depend on the years of experience or the medical subspecialty of the observer. Measurements are objective, well reproducible and important for multiple medical disciplines and should thus be included in pertinent radiology reports

Pronounced Olfactory Habituation with Age

Objectives Olfactory habituation is a transient decrease in olfactory sensitivity caused by prolonged odor exposure, aiding in the discernment of new olfactory stimuli against the background. We explored the impact of subclinical olfactory impairment on odor habituation using age as a proxy. Methods Before the actual experiment, the individual olfactory threshold for the rose-like odorant phenylethyl alcohol (PEA) was assessed separately for the left and right nostril using the “Sniffin’ Sticks” test, and ratings for odor intensity and pleasantness were collected. After applying a nasal clip continuously delivering PEA odor to one nostril for 10 min and 2 h, respectively, threshold, intensity, and pleasantness were reassessed immediately after clip removal. Results In the group of 80 participants (younger adults-mean age 27.7 ± 4.5 years; older adults-mean age 61.5 ± 4.7 years), olfactory thresholds were already significantly elevated after just 10 min, and this habituation was even more pronounced after 2 h. This effect could be observed bilaterally even though significantly more distinct on the exposed side. Older participants generally exhibited a more pronounced habituation on the exposed side after 2 h compared to the younger participants. Conclusion The results indicate that older people experience more notable habituation after extended exposure to odors. This is most likely due to the compromised olfactory function in age. Although older and younger subjects scored in the normosmic range when tested with standardized olfactory tests, the stress on the system after exposure to an odor clearly revealed the lower functionality of the aging sense of smell