3,743 research outputs found
Spectroscopy of Sc and ab initio calculations of strengths
The GRIFFIN spectrometer at TRIUMF-ISAC has been used to study excited states
and transitions in Sc following the -decay of Ca.
Branching ratios were determined from the measured -ray intensities,
and angular correlations of rays have been used to firmly assign the
spins of excited states. The presence of an isomeric state that decays by an
transition with a strength of 13.6(7)\,W.u. has been confirmed. We
compare with the first {\it ab initio} calculations of ) strengths in
light and medium-mass nuclei from the valence-space in-medium similarity
renormalization group approach, using consistently derived effective
Hamiltonians and operator. The experimental data are well reproduced for
isoscalar transitions when using bare -factors, but the strength of
isovector transitions are found to be underestimated by an order of
magnitude
Magnetic Ordering, Orbital Ordering and Resonant X-ray Scattering in Perovskite Titanates
The effective Hamiltonian for perovskite titanates is derived by taking into
account the three-fold degeneracy of orbitals and the strong
electron-electron interactions. The magnetic and orbital ordered phases are
studied in the mean-field approximation applied to the effective Hamiltonian. A
large degeneracy of the orbital states in the ferromagnetic phase is found in
contrast to the case of the doubly degenerate orbitals. Lifting of this
orbital degeneracy due to lattice distortions and spin-orbit coupling is
examined. A general form for the scattering cross section of the resonant x-ray
scattering is derived and is applied to the recent experimental results in
YTiO. The spin wave dispersion relation in the orbital ordered YTiO is
also studied.Comment: 10 pages, 6 figure
Release and activity of rifampicin from biodegradable polymer formulations
Implantation of an indwelling medical device is often required in order to successfully treat a serious medical issue. However, infection of such devices is an ongoing problem, and can occur when microorganisms, predominantly Staphylococcus species, adhere to the device surface1 . Biodegradable polymer drug delivery technology may be of use in some devices as a means of delivering a high local dose of antimicrobial in order to help prevent infection pathogenesis. In this study the broad spectrum antibiotic rifampicin has been formulated with the polymers PLA (Poly(L-Lactide)) and PLGA (Poly(D,L-lactic-co-glycolic acid(65:35)) and the in vitro drug release over 1 week analysed. Based on the release data (Fig. 1A), the PLGA:rifampicin formulations of 50:50 and 60:40 were selected for further analysis. A 4 week drug release study showed that over the examined period >95% of the rifampicin load was released from both formulations, however increasing the ratio of polymer to drug significantly changed the percentage release profile (Fig. 1B). Investigation of antimicrobial activity revealed that both formulations were able to produce consistently large zones of inhibition in disk diffusion assays over the 4 weeks examined, indicating successful bacterial inhibition (Fig. 1C). What this preliminary study has revealed is that rifampicin can be readily released from PLA and PLGA, and that release can be controlled by adjusting the ratio of polymer to drug. It has also shown that the antimicrobial activity of the rifampicin can be retained for at least 4 weeks. Therefore biodegradable polymers may represent a promising material for use in implanted medical devices as a means of delivering a high local concentration of antimicrobial to help prevent infection pathogenesis
MicroRNA-143 activation regulates smooth muscle and endothelial cell crosstalk in pulmonary arterial hypertension
Rationale: The pathogenesis of PAH remains unclear. The four microRNAs representing the miR-143 and miR-145 stem loops are genomically clustered.
Objective: To elucidate the transcriptional regulation of the miR-143/145 cluster, and the role of miR-143 in PAH.
Methods and Results: We identified the promoter region that regulates miR-143/145 miRNA expression in pulmonary artery smooth muscle cells (PASMCs). We mapped PAH-related signalling pathways, including estrogens receptor (ER), liver X factor/retinoic X receptor (LXR/RXR), TGF-β (Smads), and hypoxia (HRE) that regulated levels of all pri-miR stem loop transcription and resulting miRNA expression. We observed that miR-143-3p is selectively upregulated compared to miR-143-5p during PASMC migration. Modulation of miR-143 in PASMCs significantly altered cell migration and apoptosis. In addition, we found high abundance of miR-143-3p in PASMCs-derived exosomes. Using assays with pulmonary arterial endothelial cells (PAECs) we demonstrated a paracrine pro-migratory and pro-angiogenic effect of miR-143-3p enriched exosomes from PASMC. Quantitative PCR and in situ hybridisation showed elevated expression of miR-143 in calf models of PAH as well as in samples from PAH patients. Moreover, in contrast to our previous findings that had not supported a therapeutic role in vivo, we now demonstrate a protective role for miR-143 in experimental PH in vivo in miR-143-/- and antimiR143-3p-treated mice exposed to chronic hypoxia in both preventative and reversal settings.
Conclusions: MiR-143-3p modulated both cellular and exosome-mediated responses in pulmonary vascular cells, while inhibition of miR-143-3p blocked experimental PH. Taken together these findings confirm an important role for the miR-143/145 cluster in PAH pathobiology
Orbital Wave and its Observation in Orbital Ordered Titanates and Vanadates
We present a theory of the collective orbital excitation termed orbital wave
in perovskite titanates and vanadates with the triply degenerate
orbitals. The dispersion relations of the orbital waves for the orbital ordered
LaVO, YVO and YTiO are examined in the effective spin-orbital
coupled Hamiltonians associated with the Jahn-Teller type couplings. We propose
possible scattering processes for the Raman and inelastic neutron scatterings
from the orbital wave and calculate the scattering spectra for titanates and
vanadates. It is found that both the excitation spectra and the observation
methods of the orbital wave are distinct qualitatively from those for the
orbital ordered systems.Comment: 9 pages, 7 figure
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