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Measurement of the branching fraction and -violating asymmetry of the decay using million bottom-antibottom meson pairs in Belle II data
No full textWe measure the branching fraction and -violating flavor-dependent rate asymmetry of decays reconstructed using the Belle II detector in an electron-positron collision sample containing pairs. Using an optimized event selection, we find signal decays in a fit to background-discriminating and flavor-sensitive distributions. The resulting branching fraction is and the -violating asymmetry is
Collective flavor conversions are interactions of neutrinos with quantized flavor waves
No full textCollective oscillations in dense neutrino gases (flavor waves) are notable for their instabilities that cause fast flavor conversion. We develop a quantum theory of interacting neutrinos and flavor wave quanta, which are analogous to plasmons, but also carry flavor. The emission or absorption of such flavor plasmons , or flavomons, changes the neutrino flavor. When an angular crossing occurs, the process is more rapid than its inverse along the direction of the crossing, triggering stimulated emission and fast instability. Calculating the rate via Feynman diagrams matches the fast instability growth rate. Our novel and kinetic equations, corresponding to quasi-linear theory, describe instability evolution without resolving the small scales of the flavomon wavelength, potentially overcoming the main challenge of fast flavor evolution
Wilson Loops with Lagrangians: Large-Spin Operator Product Expansion and Cusp Anomalous Dimension Dictionary
No full textIn the context of planar conformal gauge theory, we study five-point correlation functions between the interaction Lagrangian and four of the lightest single-trace, gauge-invariant scalar primaries. After performing two light-cone OPEs, we express this correlator in terms of the three-point functions between two leading-twist spinning operators and the Lagrangian. For finite values of spin, we compute these structure constants in perturbation theory up to two loops in Super Yang-Mills theory. Large values of spin are captured by null polygon kinematics, where we use dualities with null polygon Wilson loops as well as factorization properties to bootstrap the universal behavior of the structure constants at all loops. We find explicit maps that relate the Lagrangian structure constants with the leading-twist anomalous dimension. From the large-spin map, we recover the cusp anomalous dimension at strong and weak coupling, including genus-one terms
Set-up and characterisation of a permanent magnet-based phase shifter series for FLASH2020
No full textA compact, permanent magnet-based phase shifter was developed for theupgrade of the free-electron laser FLASH at DESY Hamburg. One phase shifter will bepositioned in each of the ten intersections between two radiator undulators and will allowfor a tuning of the electron trajectory to provide constructive interference of the radiationof adjacent undulators. Each phase shifter consists of eight permanent magnet blocksmounted on a support structure with movable gap. While building a prototype, it turnedout that angular magnetization errors of the individual magnet blocks are the main sourceof error that keeps us from achieving net zero first and second field integrals. Therefore,all 88 single magnet blocks were first characterized by stretched-wire and Helmholtz coilmeasurements individually and were then sorted according to the measurement resultsto achieve a cancellation of the angular magnetization errors. Using a dedicated guidingtool, the selected magnets were assembled into the magnet keepers. The completed phaseshifter devices were mapped by stretched-wire and Hall probe measurements. In orderto deal with small remaining kick errors, a novel tuning method was developed whichallows for a meticulous and individual correction
High-intensity X-ray pump-monochromatic X-ray probe technique across time zero
No full textA femtosecond pump–probe technique, capable of probing transient changes in intense X-ray-excited matter with monochromatic X-ray pulses and accessing data for both positive and negative delay times, is proposed. The application of this technique to single-crystal silicon revealed ultrafast X-ray-induced electron excitation occurring on a timescale of 10 fs, along with the delayed onset of atomic disordering relative to the electronic excitation. This technique will pave the way for atom-specific multidimensional spectroscopy and diagnostics of exotic states of matter created by X-ray irradiation with sophisticated probing techniques, such as single-crystal diffraction, inelastic scattering, X-ray Thomson scattering, and absorption spectroscopy
2d QCD and integrability. Part I. ’t Hooft model
Get PDFWe study analytic properties and integrable structures of the meson spectrum in large N QCD. We show that the integral equation that determines the masses of the mesons, often called the ’t Hooft equation, is equivalent to finding solutions to a TQ-Baxter equation. Our analysis extends some of previous results by Fateev et al. to general quark masses m = m = m, as a perturbative series of the mass parameter. This reformulation, together with its relation to an inhomogeneous Fredholm equation, makes accessible the analytic structure of the spectrum in the complex plane of the quark masses. We also comment on applications of our techniques to non-perturbative topological string partition functions
Introduction of sulfur into an eutectic of the Zr-Ti-Ni-Cu system: Alloy development and characterization of the ( bulk metallic glasses
Get PDFThe influence of sulfur additions to the quaternary Zr50Ti16.6Ni18.3Cu15 alloy was investigated in terms of glass forming ability, thermophysical properties and mechanical properties in high purity alloy variants as well as in industrial grade alloys. In the latter case, oxygen was found to cause only a minor reduction of glass forming ability whilst retaining good mechanical properties. Conventional powder diffraction as well as synchrotron high energy diffraction revealed that the addition of sulfur changes the primary phase that forms during casting and the glass forming properties can be enhanced by adding a specifically tailored amount of sulfur to the alloy. The resulting alloys can be tailored to either possess a large glass forming ability with a critical casting size of 6 mm with 2–3 at% S or a large supercooled liquid region for sulfur amounts above 6 at%. Mechanical properties show a compressive strength of 1.6 GPa paired with high ductility, that shows in a compressive strain to failure ≥ 5.8 %, as well as conditional fracture toughness values of KQ ≥79 MPa√m in both the high purity and in- dustrial grade variants, despite severe oxygen contamination. This indicates superior resistance against embrittlement compared to other Zr-based bulk metallic glasses.1
SidF, a dual substrate N5-acetyl-N5-hydroxy-L-ornithine transacetylase involved in Aspergillus fumigatus siderophore biosynthesis
Get PDFSiderophore-mediated iron acquisition is essential for the virulence of Aspergillus fumigatus, a fungus causing life-threatening aspergillosis. Drugs targeting the siderophore biosynthetic pathway could help improve disease management. The transacetylases SidF and SidL generate intermediates for different siderophores in A. fumigatus. A. fumigatus has a yet unidentified transacetylase that complements SidL during iron deficiency in SidL-lacking mutants.We present the first X-ray structure of SidF, revealing a two-domain architecture with tetrameric assembly. The N-terminal domain contributes to protein solubility and oligomerization, while the C-terminal domain containing the GCN5-related N-acetyltransferase (GNAT) motif is crucial for the enzymatic activity and mediates oligomer formation. Notably, AlphaFold modelling demonstrates structural similarity between SidF and SidL. Enzymatic assays showed that SidF can utilize acetyl-CoA as a donor, previously thought to be a substrate of SidL but not SidF, and selectively uses N5-hydroxy-L-ornithine as an acceptor.This study elucidates the structure of SidF and reveals its role in siderophore biosynthesis. We propose SidF as the unknown transacetylase complementing SidL activity, highlighting its central role in A. fumigatus siderophore biosynthesis. Investigation of this uncharacterized GNAT protein enhances our understanding of fungal virulence and holds promise for its potential application in developing antifungal therapies
Shared mechanisms of enhanced plasmid maintenance and antibiotic tolerance mediated by the VapBC toxin:antitoxin system
No full textToxin:antitoxin (TA) systems are widespread in bacteria and were first identified as plasmid addiction systems that kill bacteria lacking a TA-encoding plasmid following cell division. TA systems have also been implicated in bacterial persistence and antibiotic tolerance, which can be precursors of antibiotic resistance. Here, we identified a clinical isolate of Shigella sonnei (CS14) with a remarkably stable pINV virulence plasmid; pINV is usually frequently lost from S. sonnei, but plasmid loss was not detected from CS14. We found that the plasmid in CS14 is stabilized by a single nucleotide polymorphism (SNP) in its vapBC TA system. VapBC TA systems are the most common Type II TA system in bacteria, and consist of a VapB antitoxin and VapC PIN domain-containing toxin. The plasmid stabilizing SNP leads to a Q12L substitution in the DNA-binding domain of VapB, which reduces VapBC binding to its own promoter, impairing vapBC autorepression. However, VapBL12C mediates high-level plasmid stabilization because VapBL12 is more prone to degradation by Lon than wild-type VapB; this liberates VapC to efficiently kill bacteria that no longer contain a plasmid. Of note, mutations that confer tolerance to antibiotics in Escherichia coli also map to the DNA-binding domain of VapBC encoded by the chromosomally integrated F plasmid. We demonstrate that the tolerance mutations also enhance plasmid stabilization by the same mechanism as VapBL12. Our findings highlight the links between plasmid maintenance and antibiotic tolerance, both of which can promote the development of antimicrobial resistance
Identification and Protein Engineering of Galactosidases for the Conversion of Blood Type B to Blood Type O
No full textThe supply of blood products such as red blood cells poses a challenge due to rising demand and declining donor numbers. Careful matching of blood products of different types is required. Only type O of the blood types A, B, AB and O can be received by any patient without transfusion incompatibilities. Therefore, O-type blood can be considered “universal blood” and is especially needed in emergency situations. In this study, we focused on the conversion of the B antigen by enzymatic deglycosylation to generate the H antigen determining O-type blood. For this, we characterized several previously unstudied α-1,3-galactosidases belonging to the GH110 family. Our findings revealed that the α-1,3-galactosidase from Pedobacter panaciterrae (PpaGal) exhibits superior efficiency compared to previously described galactosidases. We further increased the activity of PpaGal by 2.5-fold using site-directed mutagenesis. Moreover, we solved two crystal structures of PpaGal, one in the apo-state and another in complex with d-galactose. The combination of our mutagenesis study with the solved crystal structures provides valuable information to guide further optimization of PpaGal or other B antigen converting enzymes paving the way for the easier production of universal blood from B-type blood