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Towards open and reproducible multi-instrument analysis in gamma-ray astronomy
No full textThe analysis and combination of data from different gamma-ray instruments involves the use of collaboration proprietary software and case-by-case methods. The effort of defining a common data format for high-level data, namely event lists and instrument response functions (IRFs), has recently started for very-high-energy gamma-ray instruments, driven by the upcoming Cherenkov Telescope Array (CTA). In this work we implemented this prototypical data format for a small set of MAGIC, VERITAS, FACT, and H.E.S.S. Crab nebula observations, and we analyzed them with the open-source gammapy software package. By combining data from Fermi-LAT, and from four of the currently operating imaging atmospheric Cherenkov telescopes, we produced a joint maximum likelihood fit of the Crab nebula spectrum. Aspects of the statistical errors and the evaluation of systematic uncertainty are also commented upon, along with the release format of spectral measurements. The results presented in this work are obtained using open-access on-line assets that allow for a long-term reproducibility of the results
Structural analysis of the intrinsically disordered splicing factor Spp2 and its binding to the DEAH-box ATPase Prp2
No full textThe spliceosome consists of five small RNAs and more than 100 proteins. Almost 50% of the human spliceosomal proteins were predicted to be intrinsically disordered or to contain disordered regions, among them the G-patch protein Spp2. The G-patch region of Spp2 binds to the DEAH-box ATPase Prp2, and both proteins together are essential for promoting the transition from the Bact to the catalytically active B* spliceosome. Here we show by circular dichroism and nuclear magnetic resonance (NMR) spectroscopy that Spp2 is intrinsically disordered in solution. Crystal structures of a complex consisting of Prp2-ADP and the G-patch domain of Spp2 demonstrate that the G-patch gains a defined fold when bound to Prp2. While the N-terminal region of the G-patch always folds into an α-helix in five different crystal structures, the C-terminal part is able to adopt two alternative conformations. NMR studies further revealed that the N-terminal part of the Spp2 G-patch, which is the most conserved region in different G-patch proteins, transiently samples helical conformations, possibly facilitating a conformational selection binding mechanism. The structural analysis unveils the role of conserved residues of the G-patch in the dynamic interaction mode of Spp2 with Prp2, which is vital to maintain the binding during the Prp2 domain movements needed for RNA translocation
A search for bottom-type, vector-like quark pair production in a fully hadronic final state in proton-proton collisions at 13 TeV
No full textA search is described for the production of a pair of bottom-type vector-like quarks (VLQs), each decaying into a b or quark and either a Higgs or a Z boson, with a mass greater than 1000 GeV. The analysis is based on data from proton-proton collisions at a 13 TeV center-of-mass energy recorded at the CERN LHC, corresponding to a total integrated luminosity of 137 fb. As the predominant decay modes of the Higgs and Z bosons are to a pair of quarks, the analysis focuses on final states consisting of jets resulting from the six quarks produced in the events. Since the two jets produced in the decay of a highly Lorentz-boosted Higgs or Z boson can merge to form a single jet, nine independent analyses are performed, categorized by the number of observed jets and the reconstructed event mode. No signal in excess of the expected background is observed. Lower limits are set on the VLQ mass at 95% confidence level equal to 1570 GeV in the case where the VLQ decays exclusively to a b quark and a Higgs boson, 1390 GeV for when it decays exclusively to a b quark and a Z boson, and 1450 GeV for when it decays equally in these two modes. These limits represent significant improvements over the previously published VLQ limits
Measurement of B(2S) and B(2S) cross section ratios in proton-proton collisions at 13 TeV
No full textThe ratios of the B(2S) to B, B(2S) to B, and B(2S) to B(2S) production cross sections are measured in proton-proton collisions at 13 TeV, using a data sample collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 143 fb. The three measurements are made in the B meson phase space region defined by the transverse momentum 15 GeV and absolute rapidity 2.4, with the excited B(2S) states reconstructed through the B, followed by the B J/ and J/ decays. The B(2S) to B, B(2S) to B, and B(2S) to B(2S) cross section ratios, including the unknown B(2S)B branching fractions, are (3.47 0.63 (stat) 0.33 (syst))%, (4.69 0.71 (stat) 0.56 (syst))%, and 1.35 0.32 (stat) 0.09 (syst), respectively. None of these ratios shows a significant dependence on the or of the B meson. The normalized dipion invariant mass distributions from the decays B(2S) are also reported
The Performance of Double Cascades Identification in IceCube-Gen2
No full textThe IceCube Neutrino Observatory is a cubic-kilometer in-ice Cherenkov detector located at the South Pole. At high energies, the neutrino flux of is expected to be observed in the ratio of 1 : 1 : 1 on Earth. A ternary particle identification technique on the basis of three event topologies,single cascades, double cascades, and tracks, has been developed. While tracks arise mainly from charged-current muon neutrino interactions, single cascades from neutral-current interactions of all neutrino flavors and many charge-current interactions of electron neutrinos. Double cascades arise from charged-current tau neutrino interactions and its subsequent non-muonic decay of the taus if the decay length is large enough to be resolved. Such double cascades are unique to tau neutrinos and can be used to identify them. The next-generation neutrino observatory, IceCube-Gen2 will have an instrumented volume nearly 10 times greater than IceCube and a different geometry with larger string spacing. In this thesis, evaluation on the performance of double cascades identification in IceCube-Gen2 is realized by analyzing the IceCube high-energy starting event sample but only using a subset of the optical sensors that is similar in layout to the future IceCube-Gen2 geometry
Angular emission distribution of O 1s photoelectrons of uniaxially oriented methanol
No full textThe angular distribution of O 1s photoelectrons emitted from uniaxially oriented methanol is studied experimentally and theoretically. We employed circularly polarized photons of an energy of hν = 550 eV for our investigations. We measured the three-dimensional photoelectron angular distributions of methanol, with the CH3–OH axis oriented in the polarization plane, by means of cold target recoil ion momentum spectroscopy. The experimental results are interpreted by single active electron calculations performed with the single center method. A comparative theoretical study of the respective molecular-frame angular distributions of O 1s photoelectrons of CO, performed for the same photoelectron kinetic energy and for a set of different internuclear distances, allows for disentangling the role of internuclear distance and the hydrogen atoms of methanol as compared to carbon monoxide
Structural characterisation of peroxisomal import receptor complexes
No full textPeroxisomes are dynamic eukaryotic organelles that require import of their membrane and matrix proteins by soluble receptors in the cytosol. Their biogenesis, protein import, and proliferation are regulated by a distinct set of proteins, collectively called peroxins.Two peroxins, Pex3 and Pex19, are involved in the insertion of various Peroxisomal Membrane Proteins (PMPs) in the peroxisomal membrane and are thus crucial for its formation. Pex3 is a PMP that acts as a docking receptor for Pex19. The role of Pex19, in turn, is to bind, stabilise, and guide PMPs to the membrane-docked Pex3, where they are inserted into the peroxisomal membrane by an unknown mechanism. Pex14 is a PMP protein that is a key component of the peroxisomal import pore. Its interaction with Pex19 is established, yet little structural information is available about their full-length complex. In this thesis we investigated the conformation of the full-length human PEX19 in complex with the cytosolic domain of PEX3. A hybrid structural and biochemical approach was employed in order to characterize this interaction. Furthermore, the role of PEX19-PEX14 binding was addressed and the full-length complex was structurally characterised, providing insight into the stoichiometry, binding and shape of the never-before-described full-length assembly, using a variety of biochemical, biophysical and structural methods.The second part of this thesis aims to shed light on the peroxisomal protein import mechanism process. Matrix proteins (cargoes) can be imported into the peroxisomal lumen using peroxisomal targeting signal 1 (PTS1), or peroxisomal targeting signal 2 (PTS2) import pathways. The PTS1 pathway is the most common, utilising peroxin Pex5p. Pex5p is a soluble receptor, cycling between a free cytoplasmic state -where it recognises and binds peroxisomal matrix proteins- and a membrane bound state, as part of the transient PTS1 pore. The interaction between Pex5p and cargo proteins occurs via the TPR domains (tetratricopeptide repeats) of Pex5p and the PTS1 sequence at the C-terminus of the cargo proteins. Two peroxisomal cargoes, Pcs60 and MIF1, were studied in this part of the PhD project. Pcs60 is a yeast peroxisomal oxalyl-CoA synthetase, while MIF1 is a plant peroxisomal cargo associated with stress response, both of which contain a PTS1 recognition signal peptide. These proteins were crystallised and structurally characterised by means of X-ray crystallography. Further characterisation of Pcs60 and its complex with Pex5p was performed by biophysical methods, small angle X-ray scattering (SAXS), and negative stain electron microscopy. Elucidation of the structure of the Pex5p-Pcs60 complex will lead to enhancing our understanding of peroxisomal protein import
Small Angle X-ray Scattering Study of Magnetic Nanofluid Exposed to an Electric Field
No full textWe report on the investigation of a transformer oil-based magnetic nanofluid exposed to an electric field by means of synchrotron small angle X-ray scattering. Two types of small angle X-ray scattering experiments were carried out. In the first one, the electric field up to 6 kV / cm was generated in the nanofluid between two immersed electrodes. The other experiment focused on the nanofluid in an external electric field up to 10 kV / cm, when the electrodes were not in a direct electrical contact with the nanofluid. In the available range (0.02–4.5 nm) of scattering vector , the non-contact mode has no effect on the scattering intensity. The contact mode yielded noticeable low- intensity variations. In comparison to small angle neutron scattering, the small angle X-rayscattering study did not prove the proportional increase in the low scattering intensity with increasing electric field, but rather stochastic variations. The observed intensity variations reflect the local structural nanofluid changes caused by the induced electrohydrodynamics. The electrical conductivity and relaxation processes are pointed out as favorable conditions for electrohydrodynamics in the magnetic nanofluid
