The ultrafast scattering dynamics of intersubband polaritons in dispersive cavities embedding GaAs/AlGaAs quantum wells are studied directly within their band structure using a non-collinear ...pump-probe geometry with phase-stable mid-infrared pulses. Selective excitation of the lower polariton at a frequency of 25 THz and at a finite in-plane momentum, k||, leads to the emergence of a narrowband maximum in the probe reflectivity at k|| = 0. A quantum mechanical model identifies the underlying microscopic process as coherent polariton-polariton scattering. These results mark an important milestone towards quantum control and bosonic lasing in custom-tailored polaritonic systems in the mid and far-infrared.
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Electron microscopy, X-ray energy dispersive spectroscopy, and tomographic reconstructions were used to characterize a high entropy alloy predominantly composed of refractory elements. The ...intragranular microstructure was found to consist of a periodic two phase mixture, where a disordered bcc phase is aligned orthogonally in an ordered B2 phase. The phases were found to exhibit continuous lattice registry and an orientation relationship given by bcc// B2, {001}bcc//{001}B2. X-ray energy dispersive spectroscopy was used to determine the compositions of the phases, and spectral images were used in the tomographic reconstruction of the alloy to reveal the morphology and the elemental partitioning between phases.
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Precise helicity-dependent cross sections and the double-polarization observable \(E\) were measured for \(\eta\) photoproduction from quasi-free protons and neutrons bound in the deuteron. The ...\(\eta\rightarrow 2\gamma\) and \(\eta\rightarrow 3\pi^0\rightarrow 6\gamma\) decay modes were used to optimize the statistical quality of the data and to estimate systematic uncertainties. The measurement used the A2 detector setup at the tagged photon beam of the electron accelerator MAMI in Mainz. A longitudinally polarized deuterated butanol target was used in combination with a circularly polarized photon beam from bremsstrahlung of a longitudinally polarized electron beam. The reaction products were detected with the electromagnetic calorimeters Crystal Ball and TAPS, which covered 98\% of the full solid angle. The results show that the narrow structure observed earlier in the unpolarized excitation function of \(\eta\) photoproduction off the neutron appears only in reactions with antiparallel photon and nucleon spin (\(\sigma_{1/2}\)). It is absent for reactions with parallel spin orientation (\(\sigma_{3/2}\)) and thus very probably related to partial waves with total spin 1/2. The behavior of the angular distributions of the helicity-dependent cross sections was analyzed by fitting them with Legendre polynomials. The results are in good agreement with a model from the Bonn-Gatchina group, which uses an interference of \(P_{11}\) and \(S_{11}\) partial waves to explain the narrow structure.
The evolution of marine microbes over billions of years predicts that the composition of microbial communities should be much greater than the published estimates of a few thousand distinct kinds of ...microbes per liter of seawater. By adopting a massively parallel tag sequencing strategy, we show that bacterial communities of deep water masses of the North Atlantic and diffuse flow hydrothermal vents are one to two orders of magnitude more complex than previously reported for any microbial environment. A relatively small number of different populations dominate all samples, but thousands of low-abundance populations account for most of the observed phylogenetic diversity. This "rare biosphere" is very ancient and may represent a nearly inexhaustible source of genomic innovation. Members of the rare biosphere are highly divergent from each other and, at different times in earth's history, may have had a profound impact on shaping planetary processes.
We report on the light sterile neutrino search from the first four-week science run of the KATRIN experiment in 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are ...analyzed by a high-resolution MAC-E filter down to 40 eV below the endpoint at 18.57 keV. We consider the framework with three active neutrinos and one sterile neutrino. The analysis is sensitive to the mass, m_{4}, of the fourth mass state for m_{4}^{2}≲1000 eV^{2} and to active-to-sterile neutrino mixing down to |U_{e4}|^{2}≳2×10^{-2}. No significant spectral distortion is observed and exclusion bounds on the sterile mass and mixing are reported. These new limits supersede the Mainz results for m_{4}^{2}≲1000 eV^{2} and improve the Troitsk bound for m_{4}^{2}<30 eV^{2}. The reactor and gallium anomalies are constrained for 100<Δm_{41}^{2}<1000 eV^{2}.
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beta-amyloid peptide (Abeta) and "Advanced glycation endproducts" (AGEs) are components of the senile plaques in Alzheimer's disease patients. It has been proposed that both AGEs and Abeta exert many ...of their effects, which include the upregulation of pro-inflammatory cytokines, through RAGE ("receptor for advanced glycation endproducts"). To investigate whether Abeta and AGEs cause similar or identical effects on cell survival and energy metabolism, we have compared the effects of a model-AGE and Abeta on cell viability, ATP level, glucose consumption and lactate production in the neuroblastoma cell line SH-SY5Y. The results show that AGEs and Abeta increase glucose consumption and decrease ATP levels in a dose dependent manner. Furthermore, both compounds decrease mitochondrial activity measured by the MTT assay. However, only AGEs decrease the number of cells and significantly increase lactate production. These data indicate that both AGEs and Abeta can cause differential disturbances in neuronal metabolism, which may contribute to the pathophysiological findings in Alzheimer's disease. However, their signalling pathways are apparently quite distinct, a fact which should stimulate a more detailed investigation in this field, e.g. for the purpose of a rational design of potential "neuroprotective" RAGE antagonists.
Uveal melanomas are molecularly distinct from cutaneous melanomas and lack mutations in BRAF, NRAS, KIT, and NF1. Instead, they are characterized by activating mutations in GNAQ and GNA11, two highly ...homologous α subunits of Gαq/11 heterotrimeric G proteins, and in PLCB4 (phospholipase C β4), the downstream effector of Gαq signaling. We analyzed genomics data from 136 uveal melanoma samples and found a recurrent mutation in CYSLTR2 (cysteinyl leukotriene receptor 2) encoding a p.Leu129Gln substitution in 4 of 9 samples that lacked mutations in GNAQ, GNA11, and PLCB4 but in 0 of 127 samples that harbored mutations in these genes. The Leu129Gln CysLT2R mutant protein constitutively activates endogenous Gαq and is unresponsive to stimulation by leukotriene. Expression of Leu129Gln CysLT2R in melanocytes enforces expression of a melanocyte-lineage signature, drives phorbol ester-independent growth in vitro, and promotes tumorigenesis in vivo. Our findings implicate CYSLTR2 as a uveal melanoma oncogene and highlight the critical role of Gαq signaling in uveal melanoma pathogenesis.
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