Synthese und Eigenschaften von Bor- und Übergangsmetallkomplexen mit Curcuminoidliganden

Curcumin ist ein natürlicher Farbstoff aus curcuma longa. Curcumin und seine Derivate haben wegen ihrer biologischen und photophysikalischen Eigenschaften in den letzten Jahren viel Aufmerksamkeit erregt. Die Komplexierung mittels Bortrifluorid bewirkt eine deutliche bathochrome Verschiebung der Absorptions- und Emissionsmaxima sowie eine Erhöhung der Quantenausbeuten. Mittels einer gegenüber der Literatur verbesserten Synthesestrategie konnten eine Reihe verschiedener Curcuminoid- BF2- Komplexe synthetisiert werden. Variiert wurden die Substituenten an den terminalen Arylringen sowie die Arylringe an sich. Es konnten mit elektronenziehenden und elektronenschiebenden Substituenten derivatisierte Systeme, poly- und heteroaromatische Systeme sowie ein organometallisches System synthetisiert werden. Im Folgenden wurde die Hydrolyse der BF2-Komplexe zur Freisetzung der eigentlichen Curcuminoide eingehend untersucht, eine effektive Synthesestrategie etabliert und ein entsprechender Mechanismus vorgeschlagen. Drei der erhaltenen Curcuminoide wurden zunächst deprotoniert und dann mit organometallischen Precursor- Komplexen von Ruthenium, Rhodium, Iridium und Palladium umgesetzt, um die entsprechenden Curcuminoid- Komplexe zu erhalten. Alle neuartigen Verbindungen wurden mittels ein- und mehrdimensionaler sowie Heterokern- NMR- Spektroskopie, Schmelzpunktanalyse, Massenspektrometrie, Elementaranalyse und UV/Vis- Spektroskopie charakterisiert. Die BF2- Komplexe wurden zusätzlich per Fluoreszenzspektroskopie untersucht und deren Fluoreszenzquantenausbeuten und -lebensdauern bestimmt. Einige Derivate konnten zusätzlich mittels Einkristall- Röntgendiffraktometrie charakterisiert werden. Das Bisferrocenylderivat wurde außerdem mittels Cyclovoltammetrie untersucht

Mehr Strukturwandel für Wachstum und Beschäftigung : die deutsche Wirtschaft im Anpassungsstau.

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99% efficiency in collecting photons from a single emitter

In Nature Photonics 5, 166 (2011), we reported on a planar dielectric antenna that achieved 96% efficiency in collecting the photons emitted by a single molecule. In that work the transition dipole moment of the molecule was set perpendicular to the antenna plane. Here, we present an extension of that scheme that reaches collection efficiencies beyond 99% for emitters with arbitrarily oriented dipole moments. Our work opens important doors in a wide range of contexts including quantum optics, quantum metrology, nano-analytics, and biophysics. In particular, we provide antenna parameters to realize ultrabright single-photon sources in high-index materials such as semiconductor quantum dots and color centers in diamond, as well as sensitive detection of single molecules in nanofluidic devices

Matrix Metalloproteinases (MMPs) Regulate Fibrin-invasive Activity via MT1-MMP–dependent and –independent Processes

Cross-linked fibrin is deposited in tissues surrounding wounds, inflammatory sites, or tumors and serves not only as a supporting substratum for trafficking cells, but also as a structural barrier to invasion. While the plasminogen activator-plasminogen axis provides cells with a powerful fibrinolytic system, plasminogen-deleted animals use alternate proteolytic processes that allow fibrin invasion to proceed normally. Using fibroblasts recovered from wild-type or gene-deleted mice, invasion of three-dimensional fibrin gels proceeded in a matrix metalloproteinase (MMP)-dependent fashion. Consistent with earlier studies supporting a singular role for the membrane-anchored MMP, MT1-MMP, in fibrin-invasive events, fibroblasts from MT1-MMP–null mice displayed an early defect in invasion. However, MT1-MMP–deleted fibroblasts circumvented this early deficiency and exhibited compensatory fibrin-invasive activity. The MT1-MMP–independent process was sensitive to MMP inhibitors that target membrane-anchored MMPs, and further studies identified MT2-MMP and MT3-MMP, but not MT4-MMP, as alternate pro-invasive factors. Given the widespread distribution of MT1-, 2-, and 3-MMP in normal and neoplastic cells, these data identify a subset of membrane-anchored MMPs that operate in an autonomous fashion to drive fibrin-invasive activity

Pulse length variation causing spectral distortions in OPO-based hyperspectral coherent Raman scattering microscopy

Pilger C, Hachmeister H, Greife P, Weiss A, Wiebusch G, Huser T. Pulse length variation causing spectral distortions in OPO-based hyperspectral coherent Raman scattering microscopy. Optics Express. 2018;26(22):28312-28322.Picosecond optical parametric oscillators (OPOs) with broad wavelength tunability are frequently used as light sources in hyperspectral coherent Raman scattering (CRS) microscopy. We investigate how changes in the pulse length during OPO wavelength tuning of the pump beam affect hyperspectral CRS imaging. We find that significant distortions of the resulting CRS spectra occur if the OPO is operated without monitoring pulse length variations. By utilizing a custom-written MATLAB based control program to counteract changes in pulse length, normalized and reproducible data sets can be acquired. We demonstrate this by comparing hyperspectral data obtained from pure substances, as well as relevant biological specimens

Perceived Severity of Stressors in the Intensive Care Unit: A Systematic Review and Semi-Quantitative Analysis of the Literature on the Perspectives of Patients, Health Care Providers and Relatives

The aim of this study was to synthesize quantitative research that identified ranking lists of the most severe stressors of patients in the intensive care unit, as perceived by patients, relatives, and health care professionals (HCP). We conducted a systematic literature search in PubMed, MEDLINE, EMBASE, PsycInfo, CINAHL, and Cochrane Library from 1989 to 15 May 2020. Data were analyzed with descriptive and semi-quantitative methods to yield summarizing ranking lists of the most severe stressors. We synthesized the results of 42 prospective cross-sectional observational studies from different international regions. All investigations had assessed patient ratings. Thirteen studies also measured HCP ratings, and four studies included ratings of relatives. Data indicated that patients rate the severity of stressors lower than HCPs and relatives do. Out of all ranking lists, we extracted 137 stressor items that were most frequently ranked among the most severe stressors. After allocation to four domains, a group of clinical ICU experts sorted these stressors with good to excellent agreement according to their stress levels. Our results may contribute to improve HCPs' and relatives' understanding of patients' perceptions of stressors in the ICU. The synthesized stressor rankings can be used for the development of new assessment instruments of stressors

No Conclusive Evidence for Transits of Proxima b in MOST photometry

The analysis of Proxima Centauri's radial velocities recently led Anglada-Escud\'e et al. (2016) to claim the presence of a low mass planet orbiting the Sun's nearest star once every 11.2 days. Although the a-priori probability that Proxima b transits its parent star is just 1.5%, the potential impact of such a discovery would be considerable. Independent of recent radial velocity efforts, we observed Proxima Centauri for 12.5 days in 2014 and 31 days in 2015 with the MOST space telescope. We report here that we cannot make a compelling case that Proxima b transits in our precise photometric time series. Imposing an informative prior on the period and phase, we do detect a candidate signal with the expected depth. However, perturbing the phase prior across 100 evenly spaced intervals reveals one strong false-positive and one weaker instance. We estimate a false-positive rate of at least a few percent and a much higher false-negative rate of 20-40%, likely caused by the very high flare rate of Proxima Centauri. Comparing our candidate signal to HATSouth ground-based photometry reveals that the signal is somewhat, but not conclusively, disfavored (1-2 sigmas) leading us to argue that the signal is most likely spurious. We expect that infrared photometric follow-up could more conclusively test the existence of this candidate signal, owing to the suppression of flare activity and the impressive infrared brightness of the parent star.Comment: Accepted to ApJ. Posterior samples, MOST photometry and HATSouth photometry are all available at https://github.com/CoolWorlds/Proxim

Panel Conditioning in A Probability-based Longitudinal study: A Comparison of Respondents with Different Levels of Survey Experience

Learning effects due to repeated interviewing, also known as panel conditioning, are a major threat to response quality in later waves of a panel study. To date, research has not provided a clear picture regarding the circumstances, mechanisms, and dimensions of potential panel conditioning effects. In particular, the effects of conditioning frequency, that is, different levels of experience within a panel, on response quality are underexplored. Against this background, we investigated the effects of panel conditioning by using data from the GESIS Panel, a German mixed-mode probability-based panel study. Using two refreshment samples, we compared three panel cohorts with differing levels of experience on several response quality indicators related to the mechanisms of reflection, satisficing, and social desirability. Overall, we find evidence for both negative (i.e., disadvantageous for response quality) and positive (i.e., advantageous for response quality) panel conditioning. Highly experienced respondents were more likely to satisfice by speeding through the questionnaire. They also had a higher probability of refusing to answer sensitive questions than less experienced panel members. However, more experienced respondents were also more likely to optimize the response process by needing less time compared to panelists with lower experience levels (when controlling for speeding). In contrast, we did not find significant differences with respect to the number of “don’t know” responses, nondifferentiation, the selection of first response categories and mid-responses, and the number of nontriggered filter questions. Of the observed differences, speeding showed the highest magnitude with an average increase of 6.0 percentage points for highly experienced panel members compared to low experienced panelists

Tumor cell traffic through the extracellular matrix is controlled by the membrane-anchored collagenase MT1-MMP

As cancer cells traverse collagen-rich extracellular matrix (ECM) barriers and intravasate, they adopt a fibroblast-like phenotype and engage undefined proteolytic cascades that mediate invasive activity. Herein, we find that fibroblasts and cancer cells express an indistinguishable pericellular collagenolytic activity that allows them to traverse the ECM. Using fibroblasts isolated from gene-targeted mice, a matrix metalloproteinase (MMP)–dependent activity is identified that drives invasion independently of plasminogen, the gelatinase A/TIMP-2 axis, gelatinase B, collagenase-3, collagenase-2, or stromelysin-1. In contrast, deleting or suppressing expression of the membrane-tethered MMP, MT1-MMP, in fibroblasts or tumor cells results in a loss of collagenolytic and invasive activity in vitro or in vivo. Thus, MT1-MMP serves as the major cell-associated proteinase necessary to confer normal or neoplastic cells with invasive activity

Satisficing Response Behavior Across Time: Assessing Negative Panel Conditioning Using an Experimental Design with Six Repetitions

Satisficing response behavior can be a threat to the quality of survey responses. Past research has provided broad empirical evidence on the existence of satisficing and its consequences on data quality, however, relatively little is known about the extent of satisficing over the course of a panel study and its impact on response quality in later waves. Drawing on panel conditioning research, we use question design experiments to investigate whether learning effects across waves of a panel study cause changes in the extent of satisficing and if so, whether general survey experience (process learning) or familiarity with specific question content (content learning) accounts for those changes. We use data from a longitudinal survey experiment comprising six panel waves administered within a German non-probability online access panel. To investigate the underlying mechanism of possible learning effects, the experimental study randomly assigned respondents to different frequencies of receiving identical question content over the six panel waves. Our results show the existence of satisficing in every panel wave, which is in its magnitude similar to the extent of satisficing in the probability-based GESIS Panel that we use as a benchmark study. However, we did not find changes in the extent of satisficing across panel waves, nor did we find moderation effects of the interval between the waves, respondents’ cognitive ability, or motivation. Additional validity analyses showed that satisficing does not only affect the distribution of individual estimates by 15 percent or more but also can have an effect on associations between variables