176 research outputs found
Conceptualizing and Measuring Psychological Resilience of Lower Secondary School Students: A Variable- and Person-Centered Approach
Influence of crystallographic orientation of biogenic calcite on <i>in situ</i> Mg XANES analyses
Micro X-ray absorption near-edge spectroscopy at the Mg <i>K</i>-edge is a useful technique for acquiring information about the environment of Mg<sup>2+</sup> in biogenic calcite. These analyses can be applied to shell powders or intact shell structures. The advantage of the latter is that the XANES analyses can be applied to specific areas, at high (e.g. micrometre) spatial resolution, to determine the environment of Mg<sup>2+</sup> in a biomineral context. Such in situ synchrotron analysis has to take into account the potential effect of crystallographic orientation given the anisotropy of calcite crystals and the polarized nature of X-rays. Brachiopod shells of species with different crystallographic orientations are used to assess this crystallographic effect on <i>in situ</i> synchrotron measurements at the Mg <i>K</i>-edge. Results show that, owing to the anisotropy of calcite, <i>in situ</i> X-ray absorption spectra (XAS) are influenced by the crystallographic orientation of calcite crystals with a subsequent potentially erroneous interpretation of Mg<sup>2+</sup> data. Thus, this study demonstrates the importance of crystallography for XAS analyses and, therefore, the necessity to obtain crystallographic information at high spatial resolution prior to spectroscopic analysis
The Censor’s Stele: Religion, Salt-Production and Labour in the Temple of the God of the Salt Lake in Southern Shanxi Province
This case study analyses religious and technological changes that occurred during the last seventy years of the Ming dynasty (1574-1644) around the Hedong Salt Lake, situated south of Yuncheng City in southern Shanxi province. Based on a close reading of inscriptions found on stone steles at the Temple of the God of the Salt Lake and of different kinds of gazetteers, the article documents the processes and analyses the factors that shaped the expanding pantheon of local salt-production-related deities during this period. I argue that these religious changes need to be under-stood in the context of a wider sociotechnical system around the Salt Lake, especially the emergence of new salt production methods that were intro-duced at this time under the increasingly affirmative leadership of local salt merchants, as well as the changing conditions of local labour management. The larger methodological point the article makes is about the necessity to take stone steles themselves in their spatial and material dimensions as evidence of historical processes: this will allow us to see that by means of these steles and their inscriptions the temple became an architectural discursive space that facilitated new forms of social participation and of administrative intervention, while offering simultaneously a nexus be-tween the sphere of human intervention and the relevant ‘natural’ factors of the salt production at the Salt Lake. Accordingly, the article proposes novel ways to understand the role of religious institutions such as temples in their relation to ‘natural’ and ‘technological’ processes
Role of magnetic and orbital ordering at the metal-insulator transition in NdNiO3
Soft x-ray resonant scattering at the Ni L2,3 edges is used to test models of
magnetic and orbital-ordering below the metal-insulator transition in NdNiO3.
The large branching ratio of the L3 to L2 intensities of the (1/2,0,1/2)
reflection and the observed azimuthal angle and polarization dependence
originates from a non collinear magnetic structure. The absence of an orbital
signal and the non collinear magnetic structure show that the nickelates are
materials for which orbital ordering is absent at the metal-insulator
transition.Comment: 10 pages, 4 figures, Physical Review B rapid communication, to be
publishe
Pionic charge exchange on the proton from 40 to 250 MeV
The total cross sections for pionic charge exchange on hydrogen were measured
using a transmission technique on thin CH2 and C targets. Data were taken for
pi- lab energies from 39 to 247 MeV with total errors of typically 2% over the
Delta-resonance and up to 10% at the lowest energies. Deviations from the
predictions of the SAID phase shift analysis in the 60 to 80 MeV region are
interpreted as evidence for isospin-symmetry breaking in the s-wave amplitudes.
The charge dependence of the Delta-resonance properties appears to be smaller
than previously reported
Magnetic and electronic Co states in layered cobaltate GdBaCo2O5.5-x
We have performed non-resonant x-ray diffraction, resonant soft and hard
x-ray magnetic diffraction, soft x-ray absorption and x-ray magnetic circular
dichroism measurements to clarify the electronic and magnetic states of the
Co3+ ions in GdBaCo2O5.5. Our data are consistent with a 3+ Py Co HS state at
the pyramidal sites and a 3+ Oc Co LS state at the octahedral sites. The
structural distortion, with a doubling of the a axis (2ap x 2ap x 2ap cell),
shows alternating elongations and contractions of the pyramids and indicates
that the metal-insulator transition is associated with orbital order in the t2g
orbitals of the 3+ Py Co HS state. This distortion corresponds to an
alternating ordering of xz and yz orbitals along the a and c axes for the 3+ Py
Co . The orbital ordering and pyramidal distortion lead to deformation of the
octahedra, but the 3+ Oc Co LS state does not allow an orbital order to occur
for the 3+ Oc Co ions. The soft x-ray magnetic diffraction results indicate
that the magnetic moments are aligned in the ab plane but are not parallel to
the crystallographic a or b axes. The orbital order and the doubling of the
magnetic unit cell along the c axis support a non-collinear magnetic structure.
The x-ray magnetic circular dichroism data indicate that there is a large
orbital magnetic contribution to the total ordered Co moment
Phase-shift analysis of low-energy elastic-scattering data
Using electromagnetic corrections previously calculated by means of a
potential model, we have made a phase-shift analysis of the
elastic-scattering data up to a pion laboratory kinetic energy of 100 MeV. The
hadronic interaction was assumed to be isospin invariant. We found that it was
possible to obtain self-consistent databases by removing very few measurements.
A pion-nucleon model was fitted to the elastic-scattering database obtained
after the removal of the outliers. The model-parameter values showed an
impressive stability when the database was subjected to different criteria for
the rejection of experiments. Our result for the pseudovector
coupling constant (in the standard form) is . The six
hadronic phase shifts up to 100 MeV are given in tabulated form. We also give
the values of the s-wave scattering lengths and the p-wave scattering volumes.
Big differences in the s-wave part of the interaction were observed when
comparing our hadronic phase shifts with those of the current GWU solution. We
demonstrate that the hadronic phase shifts obtained from the analysis of the
elastic-scattering data cannot reproduce the measurements of the
charge-exchange reaction, thus corroborating past evidence that the hadronic
interaction violates isospin invariance. Assuming the validity of the result
obtained within the framework of chiral perturbation theory, that the mass
difference between the - and the -quark has only a very small effect on
the isospin invariance of the purely hadronic interaction, the
isospin-invariance violation revealed by the data must arise from the fact that
we are dealing with a hadronic interaction which still contains residual
effects of electromagnetic origin.Comment: 43 pages, 6 figure
Multipole analysis of pion photoproduction based on fixed t dispersion relations and unitarity
We have analysed pion photoproduction imposing constraints from fixed t
dispersion relations and unitarity. Coupled integral equations for the S and P
wave multipoles were derived from the dispersion relations and solved by the
method of Omnes and Muskhelishvili. The free parameters were determined by a
fit to the most recent data for \pi^{+} and \pi^{0} production on the proton as
well as \pi^{-} production on the neutron, in the energy We have analysed pion
photoproduction imposing constraints from fixed t dispersion relations and
unitarity. Coupled integral equations for the S and P wave multipoles were
derived from the dispersion relations and solved by the method of Omnes and
Muskhelishvili. The free parameters were determined by a fit to the most recent
data for \pi^{+} and \pi^{0} production on the proton as well as \pi^{-}
production on the neutron, in the energy range 160 MeV \leq E_{\gamma} \leq 420
MeV. The lack of high precision data on the neutron and of polarization
observables leads to some limitations of our results. Especially the multipole
M_{1-} connected with the Roper resonance P_{11}(1440) cannot be determined to
the required precision. Our predictions for the threshold amplitudes are in
good agreement with both the data and chiral perturbation theory. In the region
of the \Delta(1232) we have determined the ratio of electric quadrupole and
magnetic dipole excitation. The position of the resonance pole is obtained in
excellent agreement with pion-nucleon scattering, and the complex residues of
the multipoles are determined with the speed-plot technique.Comment: 46 pages LATEX including 29 postscript figure
- …