275 research outputs found
Observation of a Triangular to Square Flux Lattice Phase Transition in YBCO
We have used the technique of small-angle neutron scattering to observe
magnetic flux lines directly in an YBCO single crystal at fields higher than
previously reported. For field directions close to perpendicular to the CuO2
planes, we find that the flux lattice structure changes smoothly from a
distorted triangular co-ordination to nearly perfectly square as the magnetic
induction approaches 11 T. The orientation of the square flux lattice is as
expected from recent d-wave theories, but is 45 deg from that recently observed
in LSCO
Synthesis and pre-clinical evaluation of a [18F] fluoromethyl-tanaproget derivative for imaging of progesterone receptor expression
The estrogen receptor (ER) and progesterone receptor (PR) are over-expressed in ∼50% of breast cancer lesions, and used as biomarkers to stratify patients for endocrine therapy. Currently, immunohistochemical (IHC) assessment of these lesions from a core-needle biopsy in deep-sited metastases has limitations associated with sampling error and lack of standardization. An alternative solution is positron emission tomography (PET)-based probes, which are inherently quantitative and capable of imaging the entire tumor, including metastases. This work features the synthesis and biological evaluation of a novel fluorinated derivative of tanaproget, a high affinity non-steroidal PR ligand, as a candidate for imaging PR expression in vivo. Radiolabeling of the candidate was achieved in a 15% ± 4 radiochemical yield (non-decay corrected) in one step from [18F]fluoromethyltosylate in 30 min. Cell uptake studies showed a significant difference between the radioligand uptake in PR+ and PR- cell lines; however, in vivo imaging was confounded by defluorination hypothesized to occur via iminium salt formation. Investigation into high affinity, metabolically stable non-steroidal PR ligands is currently ongoing
Phenomenological theory of the 3 Kelvin phase in Sr2RuO4
We model the 3K-phase of Sr2RuO4 with Ru-metal inclusion as interface state
with locally enhanced transition temperatures. The resulting 3K-phase must have
a different pairing symmetry than the bulk phase of Sr2RuO4, because the
symmetry at the interface is lower than in the bulk. It is invariant under time
reversal and a second transition, in general, above the onset of bulk
superconductivity is expected where time reversal symmetry is broken. The
nucleation of the 3K-phase exhibits a ``capillary effect'' which can lead to
frustration phenomena for the superconducting states on different
Ru-inclusions. Furthermore, the phase structure of the pair wave function gives
rise to zero-energy quasiparticle states which would be visible in
quasiparticle tunneling spectra. Additional characteristic properties are
associated with the upper critical field Hc2. The 3K-phase has a weaker
anisotropy of Hc2 between the inplane and z-axis orientation than the bulk
superconducting phase. This is connected with the more isotropic nature
Ru-metal which yields a stronger orbital depairing effect for the inplane
magnetic field than in the strongly layered Sr$_2RuO4. An anomalous temperature
dependence for the z-axis critical field is found due to the coupling of the
magnetic field to the order parameter texture at the interface. Various other
experiments are discussed and new measurements are suggested.Comment: 10 pages, 5 figure
Detailed study of the ac susceptibility of Sr2RuO4 in oriented magnetic fields
We have investigated the ac susceptibility of the spin triplet superconductor
SrRuO as a function of magnetic field in various directions at
temperatures down to 60 mK. We have focused on the in-plane field configuration
(polar angle ), which is a prerequisite for inducing
multiple superconducting phases in SrRuO. We have found that the
previous attribution of a pronounced feature in the ac susceptibility to the
second superconducting transition itself is not in accord with recent
measurements of the thermal conductivity or of the specific heat. We propose
that the pronounced feature is a consequence of additional involvement of
vortex pinning originating from the second superconducting transition.Comment: Accepted for publication in Phys. Rev.
Acral necrosis by Stenotrophomonas maltophilia
Keywords:necrosis;skin and soft tissue infection;Stenotrophomonas maltophilia
Abstract
Background
Stenotrophomonas maltophilia (SM) has been considered a nosocomial pathogen. Nevertheless, community acquired infection may occur more frequently than usually recognized.
Case
We describe distal necrosis of the fingers by SM in a farmer, contracted in the community and successfully treated with a combination of cotrimoxazole and ciprofloxacin. The patient was diagnosed with chronic lymphocytic leukaemia 6 months later.
Conclusions
This unusual presentation shows that infection with SM should be included in the differential diagnosis of the skin and soft tissue infection, even in apparently healthy patients
Flux-Line Lattice Structures in Untwinned YBa2Cu3O
A small angle neutron scattering study of the flux-line lattice in a large
single crystal of untwinned YBa2Cu3O is presented. In fields parallel to the
c-axis, diffraction spots are observed corresponding to four orientations of a
hexagonal lattice, distorted by the a-b anisotropy. A value for the anisotropy,
the penetration depth ratio, of 1.18(2) was obtained. The high quality of the
data is such that second order diffraction is observed, indicating a well
ordered FLL. With the field at 33 degrees to c a field dependent re-orientation
of the lattice is observed around 3T.Comment: 4 pages, 4 figure
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