2,338 research outputs found
Radiative corrections to the three-body region of the Dalitz plot of baryon semileptonic decays with angular correlation between polarized emitted baryons and charged leptons: The initial-baryon rest frame case
We complement the results for the radiative corrections to the s2.l angular
correlation of baryon semileptonic decays of Ref. [1] with the final results in
the rest frame of the decaying baryon.Comment: 7 pages, Revtex4, no figure
Compressibility of the nitridosilicate SrYb[Si4N7] and the oxonitridoaluminosilicates MYb[Si4âxAlxOxN7âx] (x = 2; M = Sr, Ba)
The compressibilities of the nitridosilicate SrYb[Si4N7] and the oxonitridoaluminosilicates MYb[Si4âxAlxOxN7âx] (x = 2; M = Sr, Ba) were investigated by in situ high-pressure X-ray powder diffraction. Pressures up to 42â
GPa were generated using the diamondâanvil cell technique. The title compounds are structurally stable to the highest pressure obtained. A fit of a third-order BirchâMurnaghan equation-of-state to the pâV data results in V0 = 302.91â
(6)â
Ă
3, B0 = 176â
(2)â
GPa and BⲠ= 4.4â
(2) for SrYb[Si4N7]; V0 = 310.4â
(1)â
Ă
3, B0 = 161â
(2)â
GPa and BⲠ= 4.6â
(2) for SrYb[Si4âxAlxOxN7âx]; and V0 = 317.3â
(5)â
Ă
3, B0 = 168â
(2)â
GPa and BⲠ= 4.7â
(2) for BaYb[Si4âxAlxOxN7âx]. While the linear compressibilities of the a and c axes of BaYb[Si4âxAlxOxN7âx] are very similar up to 30â
GPa, distinct differences were observed for SrYb[Si4N7] and SrYb[Si4âxAlxOxN7âx], with the c axis being the most compressible axis. In all of the investigated compounds the bulk compressibility is dominated by the compression behaviour of the tetrahedral network, while the size of the substituted cation plays a minor role
Spin-Orbit Coupling and Ion Displacements in Multiferroic TbMnO3
The electronic and magnetic properties of TbMnO3 leading to its ferroelectric
(FE) polarization were investigated on the basis of relativistic density
functional theory (DFT) calculations. In agreement with experiment, we show
that the spin-spiral plane of TbMnO3 can be either the bc- or ab-plane, but not
the ac-plane. As for the mechanism of FE polarization, our work reveals that
the "pure electronic" model by Katsura, Nagaosa and Balatsky (KNB) is
inadequate in predicting the absolute direction of FE polarization. For the
ab-plane spin-spiral state of TbMnO3, the direction of FE polarization
predicted by the KNB model is opposite to that predicted by DFT calculations.
In determining the magnitude and the absolute direction of FE polarization in
spin-spiral states, it is found crucial to consider the displacements of the
ions from their ecntrosymmetric positions
Synchrotron radiation photoionization mass spectrometry of laser ablated species
The present paper describes an experimental apparatus suitable to create and study free clusters by combining laser ablation and synchrotron radiation. First tests on sulfur samples, S, showed the production, through laser ablation, of neutral Sn clusters (n = 1â8). These clusters were ionized using synchrotron radiation at photon energies from 160 eV to 175 eV, across the S 2p core edge. The feasibility of such combined ablationâsynchrotron radiation experiments is demonstrated, opening new possibilities on the investigation of free clusters and radical
Splash control of drop impacts with geometric targets
Drop impacts on solid and liquid surfaces exhibit complex dynamics due to the
competition of inertial, viscous, and capillary forces. After impact, a liquid
lamella develops and expands radially, and under certain conditions, the outer
rim breaks up into an irregular arrangement of filaments and secondary
droplets. We show experimentally that the lamella expansion and subsequent
break up of the outer rim can be controlled by length scales that are of
comparable dimension to the impacting drop diameter. Under identical impact
parameters, ie. fluid properties and impact velocity, we observe unique
splashing dynamics by varying the target cross-sectional geometry. These
behaviors include: (i) geometrically-shaped lamellae and (ii) a transition in
splashing stability, from regular to irregular splashing. We propose that
regular splashes are controlled by the azimuthal perturbations imposed by the
target cross-sectional geometry and that irregular splashes are governed by the
fastest-growing unstable Plateau-Rayleigh mode
Optimization of the investment casting process
Rapid prototyping is an important technique for manufacturing. This work refers to the manufacture of hollow patterns made of polymeric materials by rapid prototyping technologies for its use in the preparation of ceramic molds in the investment casting process. This work is focused on the development of a process for manufacturing patterns different from those that currently exist due to its hollow interior design, allowing its direct use in the fabrication of ceramic molds; avoiding cracking and fracture during the investment casting process, which is an important process for the foundry industry
Optimiranje postupka kalupljenja u ljevaÄkom procesu
Rapid prototyping is an important technique for manufacturing. This work refers to the manufacture of hollow patterns made of polymeric materials by rapid prototyping technologies for its use in the preparation of ceramic molds in the investment casting process. This work is focused on the development of a process for manufacturing patterns different from those that currently exist due to its hollow interior design, allowing its direct use in the fabrication of ceramic molds; avoiding cracking and fracture during the investment casting process, which is an important process for the foundry industry.Brzo razvijanje prototipa vaĹžna je proizvodna tehnika. Ovaj se rad odnosi na proizvodnju ĹĄupljih kalupa izraÄenih od polimerskih materijala pomoÄu tehnologija brzog razvijanja prototipa za uporabu u izradi keramiÄkih modela u postupku kalupljenja ljevaÄkog procesa. Ovaj rad je usmjeren na razvijanje postupka za proizvodnju kalupa drukÄijih od onih kakvi trenutno postoje i to zbog svoje ĹĄuplje unutarnje izvedbe Äime se omoguÄava izravna uporaba u izradi keramiÄkih modela te se izbje gava pucanje i lom tijekom postupka kalupljenja ljevaÄkog procesa koji predstavlja vaĹžan postupak u ljevaoniÄkoj industriji
- âŚ