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A light dimuon resonance in B decays?
No full textThe observed deviations from the Standard Model in several processes can be explained in terms of a new vector boson produced on-shell in B meson decays. A mass of 2.5-3 GeV and a total width of 10-20% allow to hide the associated dimuon bump in the poorly known charmonium region, and the large invisible decay width can be interpreted in terms of Dark Matter. This proposal predicts a contribution to the muon anomalous magnetic moment, that could explain the long-standing tension with the Standard Model. It also predicts sizeable invisible decays and a peculiar -dependence of the lepton flavor universality ratios and , that could be tested at the LHCb and Belle-II. This proceeding is based on arXiv:1704.06188, and slightly extends it with comments about Dark Matter
Deciphering role of the Fe substitution in modulating the structural, magnetic and magnetocaloric properties of
No full textA detailed magnetic study on the Fe substituted is presented. Phase purity of polycrystalline prepared by conventional solid-state technique has been confirmed by synchrotron X-ray diffraction (SXRD). Temperature-dependent magnetization (MT) measurements indicate a transition to an antiferromagnetic (AFM) type of magnetic ordering at 10 K. AFM type of order is also supported by magnetocaloric data. Magnetic hysteresis as well as a type of magnetic relaxation behavior collected below (at 5 K) indicate the presence of weak ferromagnetism
HRTEM analysis of the high-temperature phases of the newly developed high-temperature Ni-base superalloy VDM 780 Premium
No full textVDM 780 Premium is a recently developed Ni-based superalloy designed for working at high service temperatures (above 650 °C) while keeping the good workability of alloy 718. VDM 780 Premium is based on the austenitic matrix (gamma phase) strengthened by intermetallic Ni3Al-like precipitates (gamma’ phase, fcc L12 structure). Other co-precipitates may be formed in function of the applied heat treatment, such as Ni3Nb-based (delta phase, orthorhombic DOa structure) or Ni3Ti-based (eta phase, hexagonal DO24 structure) precipitates. The amount as well as the size and morphology of the different precipitates depend on the heat treatments performed on the alloy, playing an important role in improving the creep properties or the behavior during forging and recrystallization. This work contains a complex study using various techniques of analytical electron microscopy and synchrotron diffraction intended to clarify the structure of the high-temperature phase formed in the newly developed VDM 780 Premium alloy. The atomic structure of the high-temperature plate-like precipitates formed in VDM 780 Premium after two different thermal treatments has been investigated in relation with the surrounding matrix lattice, proving the stacked d/h structure of the precipitates
A comparison study of dislocation density, recrystallization and grain growth among nickel, FeNiCo ternary alloy and FeNiCoCrMn high entropy alloy
No full textThe microstructural evolutions in terms of dislocation density, annealing twin density as well as with respect to microstructural changes due to recrystallization and grain growth were investigated in pure Ni, equiatomic FeNiCo alloy, and FeNiCoCrMn high entropy alloy (HEA) during the thermomechanical process. All samples were single phase and showed a face-centered cubic (FCC) lattice structure. This was maintained during thermomechanical processing comprising of cold swaging by 85% reduction of cross-sectional area and subsequent annealing at 800 °C. The level of dislocation accumulation during cold swaging increased with the number of constituent elements. The FeNiCoCrMn HEA obtained the highest dislocation density, followed by the FeNiCo and Ni, respectively. After the annealing at 800 °C for 0.5 h, all samples achieved the large fraction of recrystallized grains with minor fraction of substructured grains and no deformed grain. The FeNiCoCrMn HEA obtained the smallest recrystallized grain size (∼5 μm) after the annealing at 800 °C for 0.5 h. This could be a result of the highest dislocation density generated during cold swaging prior to the annealing. The prolonged annealing at 800 °C for up to 24 h led to a grain growth for all the samples, however, at different growth rates. The FeNiCoCrMn HEA revealed the lowest rate of grain growth, but the microstructural changes during the annealing were not significantly different between the FeNiCo and Ni samples. Besides the effect of the number of constituent elements, the type and the combination of constituent elements have an effect on the microstructural evolution during the annealing
Tracking Structural Phase Transitions in Lead‐Halide Perovskites by Means of Thermal Expansion
No full textThe extraordinary properties of lead‐halide perovskite materials have spurred intense research, as they have a realistic perspective to play an important role in future photovoltaic devices. It is known that these materials undergo a number of structural phase transitions as a function of temperature that markedly alter their optical and electronic properties. The precise phase transition temperature and exact crystal structure in each phase, however, are controversially discussed in the literature. The linear thermal expansion of single crystals of APbX3 (A = methylammonium (MA), formamidinium (FA); X = I, Br) below room temperature is measured using a high‐resolution capacitive dilatometer to determine the phase transition temperatures. For δ‐FAPbI3, two wide regions of negative thermal expansion below 173 and 54 K, and a cascade of sharp transitions for FAPbBr3 that have not previously been reported are uncovered. Their respective crystal phases are identified via powder X‐ray diffraction. Moreover, it is demonstrated that transport under steady‐state illumination is considerably altered at the structural phase transition in the MA compounds. The results provide advanced insights into the evolution of the crystal structure with decreasing temperature that are essential to interpret the growing interest in investigating the electronic, optical, and photonic properties of lead‐halide perovskite materials
Anomalous Dynamics of Concentrated Silica-PNIPAm Nanogels
No full textWe present the structure and dynamics of highly concentrated core–shell nanoparticles composed of a silica core and a poly(N-isoproylacrylamide) (PNIPAm) shell suspended in water. With X-ray photon correlation spectroscopy, we are able to follow dynamical changes over the volume phase transition of PNIPAm at LCST = 32 °C. On raising the temperature beyond LCST, the structural relaxation times continue to decrease. The effect is accompanied by a transition from stretched to compressed exponential shape of the intensity autocorrelation function. Upon further heating, we find a sudden slowing down for the particles in their collapsed state. The q dependence of the relaxation time shows an anomalous change from to . Small angle X-ray scattering data evidence a temperature-induced transition from repulsive to attractive forces. Our results indicate a temperature-induced phase transition from a colloidal liquid with polymer-driven dynamics toward a colloidal gel
Relativistic bubble collisions—a closer look
No full textWe study scalar bubble collisions in first-order phase transitions focusing on the relativistic limit. We propose `trapping equation' which describes the wall behavior after collision, and test it with numerical simulations in several setups. We also examine the energy dynamics after collision and discuss its implications to gravitational wave production
Understanding a New NASICON‐Type High Voltage Cathode Material for High‐Power Sodium‐Ion Batteries
No full textThe cathode materials for sodium‐ion batteries have always been one of the key issues for the ultimate success of large‐scale energy storage systems. Here, we introduce a 4.0 V class high‐voltage cathode material with a newly recognized sodium superionic conductor (NASICON)‐type structure with cubic symmetry (space group P 2 1 3), Na 3 V(PO 3 ) 3 N. We synthesize an N‐doped graphene oxide wrapped Na 3 V(PO 3 ) 3 N composite with a uniform carbon coating layer, and it shows both excellent rate performance and outstanding cycling stability. Its air/water stability and all‐climate performance are carefully investigated in detail. Near‐zero volume change (~0.40%) is clearly observed for the first time based on in‐situ synchrotron X‐ray diffraction, and the in‐situ X‐ray absorption spectra reveal the V 3.2+ /V 4.2+ redox reaction with high reversibility. Its three‐dimensional sodium diffusion pathways are explicitly demonstrated with distinctive low energy barriers. Higher reversible capacity and a higher working platform can surely be achieved if the electrolyte possesses a wider voltage tolerance window above 4.8 V. Our comprehensive results indicate that this high‐voltage new NASICON‐type Na 3 V(PO 3 ) 3 N composite can be considered as a competitive candidate cathode material for sodium‐ion batteries and will receive more extensive attention and studies in the future
Electronic structure based design of thin film metallic glasses with superior fracture toughness
No full textHigh fracture toughness is crucial for the application of metallic glasses as structural materials to avoid catastrophicfailure of the material in a brittle manner. One fingerprint for fracture toughness in metallic glasses isthe fraction of hybridized bonds, which is affected by alloying Pd57.4Al23.5Y7.8M11.3 with M = Fe, Ni, Co, Cu, Os,Ir, Pt, and Au. It is shown that experimental fracture toughness data is correlated to the fraction of hybridizedbondswhich scalewith the localized bonds at the Fermi level. Thus, the localized bonds at the Fermi level are utilizedquantitatively as a measure for fracture toughness. Based on ab initio calculations, the minimum fraction ofhybridized bonds was identified for Pd57.4Al23.5Y7.8Ni11.3. According to the ansatz that the crystal orbital overlappopulation at the Fermi level scales with fracture toughness, for Pd57.4Al23.5Y7.8Ni11.3 a value of around 95 ±20 MPa·m0.5 is predicted quantitatively for the first time. Consistent with this prediction, in micro-mechanicalbeam bending experiments Pd57.4Al23.5Y7.8Ni11.3 thin films show pronounced plasticity and absence of crackgrowth
Orthogonal Techniques to Study the Effect of pH, Sucrose, and Arginine Salts on Monoclonal Antibody Physical Stability and Aggregation During Long-term Storage
No full textUnderstanding the effects of additives on therapeutic protein stability is of paramount importance for obtaining stable formulations. In this work, we apply several high- and medium-throughput methods to study the physical stability of a model monoclonal antibody at pH 5.0 and 6.5 in the presence of sucrose, arginine hydrochloride, and arginine glutamate. In low ionic strength buffer, the addition of salts reduces the antibody colloidal and thermal stability, attributed to screening of electrostatic interactions. The presence of glutamate ion in the arginine salt partially reduces the damaging effect of ionic strength increase. The addition of 280 mM sucrose shifts the thermal protein unfolding to a higher temperature. Arginine salts in the used concentration reduce the relative monomer yield after refolding from urea, whereas sucrose has a favorable effect on antibody refolding. In addition, we show 12-month long-term stability data and observe correlations between thermal protein stability, relative monomer yield after refolding, and monomer loss during storage. The monomer loss during storage is related to protein aggregation and formation of subvisible particles in some of the formulations. This study shows that the effect of commonly used additives on the long-term antibody physical stability can be predicted using orthogonal biophysical measurements