3 research outputs found
Nonlinear polarization holography of nanoscale iridium films
The phasing problem of heterodyne-detected nonlinear spectroscopy states that
the relative time delay between the exciting pulses and a local oscillator must
be known with subcycle precision to separate absorptive and dispersive
contributions. Here, a solution to this problem is presented which is the
time-domain analogue of holographic interferometry, in which the comparison of
two holograms reveals changes of an objects size and position with
interferometric precision (i.e. to fractions of a wavelength of light). The
introduced method, called nonlinear polarization holography, provides
equivalent information as attosecond nonlinear polarization spectroscopy but
has the advantage of being all-optical instead of using an attosecond streak
camera. Nonlinear polarization holography is used here to retrieve the
time-domain nonlinear response of a nanoscale iridium film to an ultrashort
femtosecond pulse. Using density matrix calculations it is shown that the
knowledge of the nonlinear response with subcycle precision allows to
distinguish excitation and relaxation mechanisms of low-energetic electrons
that depend on the nanoscale structure of the iridium film
Aircraft Noise and Quality of Life around Frankfurt Airport
In a survey of 2,312 residents living near Frankfurt Airport aircraft noise annoyance and disturbances as well as environmental (EQoL) and health-related quality of life (HQoL) were assessed and compared with data on exposure due to aircraft, road traffic, and railway noise. Results indicate higher noise annoyance than predicted from general exposure-response curves. Beside aircraft sound levels source-related attitudes were associated with reactions to aircraft noise. Furthermore, aircraft noise affected EQoL in general, although to a much smaller extent. HQoL was associated with aircraft noise annoyance, noise sensitivity and partly with aircraft noise exposure, in particular in the subgroup of multimorbid residents. The results suggest a recursive relationship between noise and health, yet this cannot be tested in cross-sectional studies. Longitudinal studies would be recommendable to get more insight in the causal paths underlying the noise-health relationship
Yellow polyketide pigment suppresses premature hatching in social amoeba
GĂŒnther M, Reimer C, Herbst R, et al. Yellow polyketide pigment suppresses premature hatching in social amoeba. Proceedings of the National Academy of Sciences. 2022;119(43).Low-molecular-weight natural products from microbes are indispensable in the development of potent drugs. However, their biological roles within an ecological context often remain elusive. Here, we shed light on natural products from eukaryotic microorganisms that have the ability to transition from single cells to multicellular organisms: the social amoebae. These eukaryotes harbor a large number of polyketide biosynthetic genes in their genomes, yet virtually none of the corresponding products can be isolated or characterized. Using complementary molecular biology approaches, including CRISPR-Cas9, we generated polyketide synthase (pks5) inactivation and overproduction strains of the social amoebaDictyostelium discoideum. Differential, untargeted metabolomics of wild-type versus mutant fruiting bodies allowed us to pinpoint candidate metabolites derived from the amoebal PKS5. Extrachromosomal expression of the respective gene led to the identification of a yellow polyunsaturated fatty acid. Analysis of the temporospatial production pattern of this compound in conjunction with detailed bioactivity studies revealed the polyketide to be a spore germination suppressor