Tunka-Rex is a radio detector for cosmic-ray air showers in Siberia, triggered by Tunka-133, a co-located air-Cherenkov detector. The main goal of Tunka-Rex is the cross-calibration of the two ...detectors by measuring the air-Cherenkov light and the radio signal emitted by the same air showers. This way we can explore the precision of the radio-detection technique, especially for the reconstruction of the primary energy and the depth of the shower maximum. The latter is sensitive to the mass of the primary cosmic-ray particles. In this paper we describe the detector setup and explain how electronics and antennas have been calibrated. The analysis of data of the first season proves the detection of cosmic-ray air showers and therefore, the functionality of the detector. We confirm the expected dependence of the detection threshold on the geomagnetic angle and the correlation between the energy of the primary cosmic-ray particle and the radio amplitude. Furthermore, we compare reconstructed amplitudes of radio pulses with predictions from CoREAS simulations, finding agreement within the uncertainties.
Aims. We present a study of the spectrophotometric properties of dwarf planet Ceres in the visual-to-infrared (VIS-IR) spectral range by means of hyper-spectral images acquired by the VIR imaging ...spectrometer on board the NASA Dawn mission. Methods. Disk-resolved observations with a phase angle within the 7° <α < 132° interval were used to characterize Ceres’ phase curve in the 0.465–4.05 μm spectral range. Hapke’s model was applied to perform the photometric correction of the dataset to standard observation geometry at VIS-IR wavelength, allowing us to produce albedo and color maps of the surface. The V-band magnitude phase function of Ceres has been computed from disk-resolved images and fitted with both the classical linear model and H-G formalism. Results. The single-scattering albedo and the asymmetry parameter at 0.55 μm are w = 0.14 ± 0.02 and ξ = −0.11 ± 0.08, respectively (two-lobe Henyey-Greenstein phase function); at the same wavelength, Ceres’ geometric albedo as derived from our modeling is 0.094 ± 0.007; the roughness parameter is \hbox{$\bar{\theta}=29^{\circ} \pm 6^{\circ}$}θ̅ = 29° ± 6°. Albedo maps indicate small variability on a global scale with an average reflectance at standard geometry of 0.034 ± 0.003. Nonetheless, isolated areas such as the Occator bright spots, Haulani, and Oxo show an albedo much higher than average. We measure a significant spectral phase reddening, and the average spectral slope of Ceres’ surface after photometric correction is 1.1% kÅ-1 and 0.85% kÅ-1 at VIS and IR wavelengths, respectively. Broadband color indices are V−R = 0.38 ± 0.01 and R−I = 0.33 ± 0.02. Color maps show that the brightest features typically exhibit smaller slopes. The H-G modeling of the V-band magnitude phase curve for α < 30° gives H = 3.14 ± 0.04 and G = 0.10 ± 0.04, while the classical linear model provides V(1,1,0°) = 3.48 ± 0.03 and β = 0.036 ± 0.002. The comparison of our results with spectrophotometric properties of other minor bodies indicates that Ceres has a less back-scattering phase function and a slightly higher albedo than comets and C-type objects. However, the latter represents the closest match in the usual asteroid taxonomy.
N‐Glycans direct protein function, stability, folding and targeting, and influence immunogenicity. While most glycosidases that process N‐glycans cleave a single sugar residue at a time, enzymes from ...glycoside hydrolase family 99 are endo‐acting enzymes that cleave within complex N‐glycans. Eukaryotic Golgi endo‐1,2‐α‐mannosidase cleaves glucose‐substituted mannose within immature glucosylated high‐mannose N‐glycans in the secretory pathway. Certain bacteria within the human gut microbiota produce endo‐1,2‐α‐mannanase, which cleaves related structures within fungal mannan, as part of nutrient acquisition. An unconventional mechanism of catalysis was proposed for enzymes of this family, hinted at by crystal structures of imino/azasugars complexed within the active site. Based on this mechanism, we developed the synthesis of two glycosides bearing a spiro‐epoxide at C‐2 as electrophilic trap, to covalently bind a mechanistically important, conserved GH99 catalytic residue. The spiro‐epoxyglycosides are equipped with a fluorescent tag, and following incubation with recombinant enzyme, allow concentration, time and pH dependent visualization of the bound enzyme using gel electrophoresis.
Eukaryotic endomannosidase from glycosyl hydrolase family 99 (GH99) is involved in the processing of immature N‐linked glycans, whereas bacterial GH99 endomannanase orthologs hydrolyze high‐mannose oligosaccharides. Based on the proposed unusual hydrolytic mechanism of these enzymes, two fluorescent spiro‐epoxyglycosides were synthesized and we show that these compounds function as activity‐based probes for these enzymes.
The KASCADE-Grande air shower experiment 1 consists of, among others, a large scintillator array for measurements of charged particles, Nch, and of an array of shielded scintillation counters used ...for muon counting, Nμ. KASCADE-Grande is optimized for cosmic ray measurements in the energy range 10PeV to about 2000PeV, where exploring the composition is of fundamental importance for understanding the transition from galactic to extragalactic origin of cosmic rays. Following earlier studies of the all-particle and the elemental spectra reconstructed in the knee energy range from KASCADE data 2, we have now extended these measurements to beyond 200PeV. By analysing the two-dimensional shower size spectrum Nch vs. Nμ for nearly vertical events, we reconstruct the energy spectra of different mass groups by means of unfolding methods over an energy range where the detector is fully efficient. The procedure and its results, which are derived based on the hadronic interaction model QGSJET-II-02 and which yield a strong indication for a dominance of heavy mass groups in the covered energy range and for a knee-like structure in the iron spectrum at around 80PeV, are presented. This confirms and further refines the results obtained by other analyses of KASCADE-Grande data, which already gave evidence for a knee-like structure in the heavy component of cosmic rays at about 80PeV 3.
LOPES, the LOFAR prototype station, was an antenna array for cosmic-ray air showers operating from 2003 to 2013 within the KASCADE-Grande experiment. Meanwhile, the analysis is finished and the data ...of air-shower events measured by LOPES are available with open access in the KASCADE Cosmic Ray Data Center (KCDC). This article intends to provide a summary of the achievements, results, and lessons learned from LOPES. By digital, interferometric beamforming the detection of air showers became possible in the radio-loud environment of the Karlsruhe Institute of Technology (KIT). As a prototype experiment, LOPES tested several antenna types, array configurations and calibration techniques, and pioneered analysis methods for the reconstruction of the most important shower parameters, i.e., the arrival direction, the energy, and mass-dependent observables such as the position of the shower maximum. In addition to a review and update of previously published results, we also present new results based on end-to-end simulations including all known instrumental properties. For this, we applied the detector response to radio signals simulated with the CoREAS extension of CORSIKA, and analyzed them in the same way as measured data. Thus, we were able to study the detector performance more accurately than before, including some previously inaccessible features such as the impact of noise on the interferometric cross-correlation beam. These results led to several improvements, which are documented in this paper and can provide useful input for the design of future cosmic-ray experiments based on the digital radio-detection technique.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We reconstructed the energy and the position of the shower maximum of air showers with energies E ∼> 100 PeV applying a method using radio measurements performed with Tunka-Rex. An event-to-event ...comparison to air-Cherenkov measurements of the same air showers with the Tunka-133 photomultiplier array confirms that the radio reconstruction works reliably. The Tunka-Rex reconstruction methods and absolute scales have been tuned on CoREAS simulations and yield energy and X{sub max} values consistent with the Tunka-133 measurements. The results of two independent measurement seasons agree within statistical uncertainties, which gives additional confidence in the radio reconstruction. The energy precision of Tunka-Rex is comparable to the Tunka-133 precision of 15%, and exhibits a 20% uncertainty on the absolute scale dominated by the amplitude calibration of the antennas. For X{sub max}, this is the first direct experimental correlation of radio measurements with a different, established method. At the moment, the X{sub max} resolution of Tunka-Rex is approximately 40 g/cm{sup 2}. This resolution can probably be improved by deploying additional antennas and by further development of the reconstruction methods, since the present analysis does not yet reveal any principle limitations.
Cryo-electron microscopy yields 3D density maps of macromolecules from single-particle images, tomograms, or 2D crystals. An optimal visualization of the density map is important for its proper ...interpretation. We have developed a method to improve the visualization of density maps by using general statistical information about proteins for the sharpening process. In particular, the packing density of atoms is highly similar between different proteins, which allows for building a pseudo-atomic model to approximate the true mass distribution. From this model the radial structure factor and density value histogram are estimated and applied as constraints to the 3D reconstruction in reciprocal- and real-space, respectively. Interestingly, similar improvements are obtained when using the correct radial structure factor and density value histogram from a crystal structure. Thus, the estimated pseudo-atomic model yields a sufficiently accurate mass distribution to optimally sharpen a density map.
•The effective muon attenuation and absorption lengths of air showers are investigated.•Air shower data of the KASCADE-Grande observatory is analyzed.•Predictions of the models SIBYLL 2.1, EPOS-LHC, ...QGSJET-II-02 and -04 are tested.•The studied models fail to describe consistently the attenuation of the muon data.
The evolution of the muon content of very high energy air showers (EAS) in the atmosphere is investigated with data of the KASCADE-Grande observatory. For this purpose, the muon attenuation length in the atmosphere is obtained to Λμ=1256±85−232+229(syst)g/cm2 from the experimental data for shower energies between 1016.3 and 1017.0 eV. Comparison of this quantity with predictions of the high-energy hadronic interaction models QGSJET-II-02, SIBYLL 2.1, QGSJET-II-04 and EPOS-LHC reveals that the attenuation of the muon content of measured EAS in the atmosphere is lower than predicted. Deviations are, however, less significant with the post-LHC models. The presence of such deviations seems to be related to a difference between the simulated and the measured zenith angle evolutions of the lateral muon density distributions of EAS, which also causes a discrepancy between the measured absorption lengths of the density of shower muons and the predicted ones at large distances from the EAS core. The studied deficiencies show that all four considered hadronic interaction models fail to describe consistently the zenith angle evolution of the muon content of EAS in the aforesaid energy regime.
Glucocerebrosidase (GBA), a lysosomal retaining β‐d‐glucosidase, has recently been shown to hydrolyze β‐d‐xylosides and to transxylosylate cholesterol. Genetic defects in GBA cause the lysosomal ...storage disorder Gaucher disease (GD), and also constitute a risk factor for developing Parkinson's disease. GBA and other retaining glycosidases can be selectively visualized by activity‐based protein profiling (ABPP) using fluorescent probes composed of a cyclophellitol scaffold having a configuration tailored to the targeted glycosidase family. GBA processes β‐d‐xylosides in addition to β‐d‐glucosides, this in contrast to the other two mammalian cellular retaining β‐d‐glucosidases, GBA2 and GBA3. Here we show that the xylopyranose preference also holds up for covalent inhibitors: xylose‐configured cyclophellitol and cyclophellitol aziridines selectively react with GBA over GBA2 and GBA3 in vitro and in vivo, and that the xylose‐configured cyclophellitol is more potent and more selective for GBA than the classical GBA inhibitor, conduritol B‐epoxide (CBE). Both xylose‐configured cyclophellitol and cyclophellitol aziridine cause accumulation of glucosylsphingosine in zebrafish embryo, a characteristic hallmark of GD, and we conclude that these compounds are well suited for creating such chemically induced GD models.
New selective GBA inhibitor: We show that the β‐d‐xylose configured epoxide and aziridine are potent selective inhibitors towards GBA in vitro and in vivo, and their selectivity and inhibitory effect towards GBA are superior to the widely used GBA inhibitor Conduritol B‐epoxide (CBE).
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