46 research outputs found
Pressure-induced changes of the vibrational modes of spin-crossover complexes studied by nuclear resonance scattering of synchrotron radiation
Nuclear inelastic scattering (NIS) spectra were recorded for the
spin-crossover complexes STP and ETP (STP =
[Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg- ethane)](ClO4)2 and
ETP =
[Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg-butane)](ClO4)2) at
30 K and at room temperature and also at ambient pressure and applied pressure
(up to 2.6 GPa). Spin transition from the high-spin (HS) to the low-spin (LS)
state was observed by lowering temperature and also by applying pressure at
room temperature and has been assigned to the hardening of iron-bond stretching
modes due to the smaller volume in the LS isomer
Ethics of primate use
This article provides an overview of the ethical issues raised by the use of
non-human primates (NHPs) in research involving scientific procedures which
may cause pain, suffering, distress or lasting harm. It is not an exhaustive
review of the literature and views on this subject, and it does not present
any conclusions about the moral acceptability or otherwise of NHP research.
Rather the aim has been to identify the ethical issues involved and to
provide guidance on how these might be addressed, in particular by carefully
examining the scientific rationale for NHP use, implementing fully the 3Rs
principle of Russell and Burch (1959) and applying a robust "harm-benefit
assessment" to research proposals involving NHPs
Ce-L3-XAS study of the temperature dependence of the 4f occupancy in the Kondo system Ce2Rh3Al9
We have used temperature dependent x-ray absorption at the Ce-L3 edge to
investigate the recently discovered Kondo compound Ce2Rh3Al9. The systematic
changes of the spectral lineshape with decreasing temperature are analyzed and
found to be related to a change in the occupation number, n_f, as the
system undergoes a transition into a Kondo state. The temperature dependence of
indicates a characteristic temperature of 150K, which is clearly related
with the high temperature anomaly observed in the magnetic susceptibility of
the same system. The further anomaly observed in the resistivity of this system
at low temperature (ca. 20K) has no effect on n_f and is thus not of Kondo
origin.Comment: 7 pages, three figures, submitted to PR
Elastic and vibrational properties of alpha and beta-PbO
The structure, electronic and dynamic properties of the two layered alpha
(litharge) and beta (massicot) phases of PbO have been studied by density
functional methods. The role of London dispersion interactions as leading
component of the total interaction energy between layers has been addressed by
using the Grimme's approach, in which new parameters for Pb and O atoms have
been developed. Both gradient corrected and hybrid functionals have been
adopted using Gaussian-type basis sets of polarized triple zeta quality for O
atoms and small core pseudo-potential for the Pb atoms. Basis set superposition
error (BSSE) has been accounted for by the Boys-Bernardi correction to compute
the interlayer separation. Cross check with calculations adopting plane waves
that are BSSE free have also been performed for both structures and vibrational
frequencies. With the new set of proposed Grimme's type parameters structures
and dynamical parameters for both PbO phases are in good agreement with
experimental data.Comment: 8 pages, 5 figure
Phonon spectroscopy of oriented hcp iron
High-pressure phonon spectroscopy was performed on iron in the bcc and hcp phase up to 40 GPa using the nuclear inelastic scattering (NIS) of synchrotron radiation (SR). In hcp iron we observe differences in the density of phonon states for spectra measured with different orientations of the diamond anvil cell (DAC) with respect to the SR beam. These differences are attributed to a preferred orientation of the hexagonal c-axis along the load axis of the DAC. These texture effects are used, in conjunction with theoretical calculations, to extract density of phonon states as seen parallel and perpendicular to the c-axis of hcp iron