366 research outputs found
Pressure induced high-spin to low-spin transition in FeS evidenced by x-ray emission spectroscopy
We report the observation of the pressure-induced high-spin to low-spin
transition in FeS using new high-pressure synchrotron x-ray emission
spectroscopy techniques. The transition is evidenced by the disappearance of
the low-energy satellite in the Fe K emission spectrum of FeS. Moreover,
the phase transition is reversible and closely related to the structural phase
transition from a manganese phosphide-like phase to a monoclinic phase. The
study opens new opportunities for investigating the electronic properties of
materials under pressure.Comment: ReVTeX, 4 pages, 3 figures inserted with epsfig. minor modifications
before submission to PR
Search for solar axions in XMASS, a large liquid-xenon detector
XMASS, a low-background, large liquid-xenon detector, was used to search for
solar axions that would be produced by bremsstrahlung and Compton effects in
the Sun. With an exposure of 5.6ton days of liquid xenon, the model-independent
limit on the coupling for mass 1keV is
(90% C.L.), which is a factor of two stronger than the existing experimental
limit. The bounds on the axion masses for the DFSZ and KSVZ axion models are
1.9 and 250eV, respectively. In the mass range of 10-40keV, this study produced
the most stringent limit, which is better than that previously derived from
astrophysical arguments regarding the Sun to date
Universal phase transitions of B1 structured stoichiometric transition-metal carbides
The high-pressure phase transitions of B1-structured stoichiometric
transition metal carbides (TMCs, TM=Ti, Zr, Hf, V, Nb, and Ta) were
systematically investigated using ab initio calculations. These carbides
underwent universal phase transitions along two novel phase-transition routes,
namely, B1\rightarrowdistorted TlI (TlI')\rightarrowTlI and/or
B1\rightarrowdistorted TiB (TiB')\rightarrowTiB, when subjected to pressures.
The two routes can coexist possibly because of the tiny enthalpy differences
between the new phases under corresponding pressures. Four new phases result
from atomic slips of the B1-structured parent phases under pressure. After
completely releasing the pressure, taking TiC as a representative of TMCs, only
its new TlI'-type phase is mechanically and dynamically stable, and may be
recovered.Comment: [email protected]
Magnetic-Field Variations of the Pair-Breaking Effects of Superconductivity in (TMTSF)2ClO4
We have studied the onset temperature of the superconductivity Tc_onset of
the organic superconductor (TMTSF)2ClO4, by precisely controlling the direction
of the magnetic field H. We compare the results of two samples with nearly the
same onset temperature but with different scattering relaxation time tau. We
revealed a complicated interplay of a variety of pair-breaking effects and
mechanisms that overcome these pair-breaking effects. In low fields, the linear
temperature dependences of the onset curves in the H-T phase diagrams are
governed by the orbital pair-breaking effect. The dips in the in-plane
field-angle phi dependence of Tc_onset, which were only observed in the
long-tau sample, provides definitive evidence that the field-induced
dimensional crossover enhances the superconductivity if the field direction is
more than about 19-degrees away from the a axis. In the high-field regime for
H//a, the upturn of the onset curve for the long-tau sample indicates a new
superconducting state that overcomes the Pauli pair-breaking effect but is
easily suppressed by impurity scatterings. The Pauli effect is also overcome
for H//b' by a realization of another state for which the maximum of
Tc_onset(phi) occurs in a direction different from the crystalline axes. The
effect on Tc_onset of tilting the applied field out of the conductive plane
suggests that the Pauli effect plays a significant role in determining
Tc_onset. The most plausible explanation of these results is that (TMTSF)2ClO4
is a singlet superconductor and exhibits Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) states in high fields.Comment: 12 pages, 10 figures. To be published in J. Phys. Soc. Jpn. (vol.77,
2008
Synthesis and Thermal Stability of Cubic ZnO in the Salt Nanocomposites
Cubic zinc oxide (rs-ZnO), metastable under normal conditions, was
synthesized from the wurtzite modification (w-ZnO) at 7.7 GPa and ~800 K in the
form of nanoparticles isolated in the NaCl matrix. The phase transition rs-ZnO
\rightarrow w-ZnO in nanocrystalline zinc oxide under ambient pressure was
experimentally studied for the first time by differential scanning calorimetry
and high-temperature X-ray diffraction. It was shown that the transition occurs
in the 370-430 K temperature range and its enthalpy at 400 K is -10.2 \pm 0.5
kJ mol-1.Comment: 12 pages, 4 figures, 1 tabl
Higher expression levels of SOCS 1,3,4,7 are associated with earlier tumour stage and better clinical outcome in human breast cancer
Background
Suppressors of cytokine signaling (SOCS) are important negative feedback regulators of the JAK/STAT signaling pathway, and have been recently investigated for their role in the development of different cancers. In this study, we examined the expression of SOCS1-7 genes in normal and breast cancer tissue and correlated this with several clinico-pathological and prognostic factors.
Methods
SOCS1-7 mRNA extraction and reverse transcription were performed on fresh frozen breast cancer tissue samples (n = 127) and normal background breast tissue (n = 31). Transcript levels of expression were determined using real-time PCR and analyzed against TNM stage, tumour grade and clinical outcome over a 10 year follow-up period.
Results
SOCS1,4,5,6 and 7 expression decreased with increased TNM stage (TNM1 vs. TNM3 p = 0.039, TNM1 vs. TNM4 p = 0.016, TNM2 vs. TNM4 p = 0.025, TNM1 vs. TNM3 p = 0.012, and TNM1 vs. TNM3 p = 0.044 respectively). SOCS2 and 3 expression decreased with increased Nottingham Prognostic Index (NPI) (NPI1 vs. NPI3 p = 0.033, and NPI2 vs. NPI3 p = 0.041 respectively). SOCS7 expression decreased with higher tumour grade (Grade 3 vs. Grade 2 p = 0.037). After a median follow up period of 10 years, we found higher levels of SOCS1,2 and 7 expression among those patients who remained disease-free compared to those who developed local recurrence (p = 0.0073, p = 0.021, and p = 0.039 respectively). Similarly, we found higher levels of SOCS 2,4, and 7 expression in those who remained disease-free compared to those who developed distant recurrence (p = 0.022, p = 0.024, and p = 0.033 respectively). Patients who remained disease-free had higher levels of SOCS1 and 2 expression compared to those who died from breast cancer (p = 0.02 and p = 0.033 respectively). The disease free survival (DFS) and overall survival (OS) curves showed that higher levels of SOCS1, 3 and 7 were significant predictors of higher DFS (p = 0.015, p = 0.024 and 0.03 respectively) and OS (p = 0.005, p = 0.013 and p = 0.035 respectively). Higher levels of SOCS 4 were significant in predicting better OS (p = 0.007) but not DFS. Immunohistochemical staining of representative samples showed a correlation between SOCS1, 3, 7 protein staining and the SOCS1, 3, 7 mRNA expression.
Conclusion
Higher mRNA expression levels of SOCS1, 3, 4 and 7 are significantly associated with earlier tumour stage and better clinical outcome in human breast cancer
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