Evidence for negative thermal expansion in the superconducting precursor phase SmFeAsO.

The fluorine-doped rare-earth iron oxypnictide series SmFeAsO1-x F x (0 [Formula: see text] 0.10) was investigated with high resolution powder x-ray scattering. In agreement with previous studies (Margadonna et al 2009 Phys. Rev. B. 79 014503), the parent compound SmFeAsO exhibits a tetragonal-to-orthorhombic structural distortion at [Formula: see text] = 130 K which is rapidly suppressed by [Formula: see text] 0.10 deep within the superconducting dome. The change in unit cell symmetry is followed by a previously unreported magnetoelastic distortion at 120 K. The temperature dependence of the thermal expansion coefficient [Formula: see text] reveals a rich phase diagram for SmFeAsO: (i) a global minimum at 125 K corresponds to the opening of a spin-density wave instability as measured by pump-probe femtosecond spectroscopy (Mertelj et al 2010 Phys. Rev. B 81 224504) whilst (ii) a global maximum at 110 K corresponds to magnetic ordering of the Sm and Fe sublattices as measured by magnetic x-ray scattering (Nandi et al 2011 Phys. Rev. B 84 055419). At much lower temperatures than [Formula: see text], SmFeAsO exhibits a significant negative thermal expansion on the order of -40 ppm · K-1 in contrast to the behaviour of other rare-earth oxypnictides such as PrFeAsO (Kimber et al 2008 Phys. Rev. B 78 140503) and the actinide oxypnictide NpFeAsO (Klimczuk et al 2012 Phys. Rev. B 85 174506) where the onset of [Formula: see text] 0 only appears in the vicinity of magnetic ordering. Correlating this feature with the temperature and doping dependence of the resistivity and the unit cell parameters, we interpret the negative thermal expansion as being indicative of the possible condensation of itinerant electrons accompanying the opening of a SDW gap, consistent with transport measurements (Tropeano et al 2009 Supercond. Sci. Technol. 22 034004).

Gankyrin promotes breast cancer cell metastasis by regulating Rac1 activity.

Tumor metastasis is responsible for most cancer patients' deaths. Understanding the mechanism of metastasis is crucial for improving the cure rate for cancer. Here, we report that Gankyrin, a chaperone of ubiquitin-proteasome, has an essential role in breast cancer metastasis. We find that Gankyrin is highly overexpressed in human breast cancers and the expression correlates strongly with lymph node metastasis. Knocking down Gankyrin expression in highly metastatic human breast cancer cells significantly decreases cancer cell migration and invasion. Furthermore, we demonstrate that depletion of Gankyrin inhibits intrinsic Rac1 activity and induces large focal adhesions. Overexpression of Gankyrin accelerates focal adhesion turnover and increases cell migration. Notably, reduction of Gankyrin expression in mouse mammary tumor cell significantly decreases tumor metastasis to lung in animal models. Therefore, our findings suggest that Gankyrin is crucial for breast cancer metastasis and highlight the potential of Gankyrin as a therapeutic target for tumor metastasis.

Clinical feature and DYT1 mutation screening in primary dystonia patients from South-West China.

BACKGROUND: Clinical presentation and DYT1 status amongst Chinese patients with primary dystonia have not been well studied. METHODS: One hundred and twenty patients with primary dystonia from South-West China were studied in a prospective survey for 3.5 years. Severity and the resulting disability were assessed using the Burke-Fahn-Marsden dystonia rating scale (BFMDRS). Health related quality of life (HRQL) was measured through the 36-item short-form (SF-36). The Hospital Anxiety and Depression Scale (HADS) was utilized to identify and quantify depression and anxiety. Mutations in the DYT1 exon 5 were screened by direct sequencing. RESULTS: Cervical dystonia was found to be the most frequent form of focal dystonia and was discovered to occur at an early age. Pain and tremor were the common associated symptoms. Family history was positive in 19.5% of the cases, with a trend of earlier onset. Depression (14.5%) and anxiety (6.6%) were the main HRQL impairments. Multiple linear regression analysis suggested that gender, depression, anxiety and functional disability were amongst the principal determinants of lower HRQL. Only one instance of DYT1 GAG deletion (1.4%) was detected in 71 patients. CONCLUSION: Our data on a cohort of Chinese patients show some difference from descriptions in other ethnic groups. This includes an earlier age of onset, a lower incidence of depression and female serving as a predictor factor of a HRQL. Similar to other cohorts, DYT1 gene mutations are rare.

Transport properties and the large anisotropic magnetoresistance of Cu(x)NbS(2) single crystals.

The transport properties of Cu(x)NbS(2) (x = 0.09, 0.44 and 0.55) single crystals were systematically studied. The in-plane and out-of-plane resistivities decrease with increasing Cu content, and a transition with hysteresis shows up for the crystals with x = 0.44 and 0.55. The thermopower and Hall coefficient of Cu(x)NbS(2) show opposite signs, indicating that there are two kinds of carriers in this system. The angular dependences of the in-plane magnetoresistance (MR(ab) = (ρ(ab)(H)-ρ(ab)(0))/ρ(ab)(0) × 100%) at different temperatures were also studied. The single crystals with x = 0.44 and 0.55 show a strong anisotropic MR(ab). For the x = 0.55 sample, MR(ab) reaches 80% with a magnetic field of 14 T applied along the c-axis, while MR(ab) is less than 5% for the magnetic field applied within the ab-plane. These results can be well understood in the light of the anisotropic Fermi surface in the multiband system.

Anomalous transport properties and phase diagram of the FeAs-based SmFeAsO1-xFx superconductors.

We report the detailed phase diagram and anomalous transport properties of Fe-based high-T_{c} superconductors SmFeAsO1-xFx. It is found that superconductivity emerges at x approximately 0.07, and optimal doping takes place in the x approximately 0.20 sample with the highest T_{c} approximately 54 K. T_{c} increases monotonically with doping; the anomaly in resistivity from structural phase or spin-density-wave order is rapidly suppressed, suggesting a quantum critical point around x approximately 0.14. As manifestations, a linear temperature dependence of the resistivity shows up at high temperatures in the x<0.14 regime but at low temperatures just above T_{c} in the x>0.14 regime; a drop in carrier density evidenced by a pronounced rise in the Hall coefficient is observed below the temperature of the anomaly peak in resistivity. A scaling behavior is observed between the Hall angle and temperature: cottheta_{H} proportional, variantT;{1.5} for all samples with different x in SmFeAsO1-xFx system.

Superconductivity at 43 K in SmFeAsO1-xFx.

Since the discovery of high-transition-temperature (high-T(c)) superconductivity in layered copper oxides, extensive effort has been devoted to exploring the origins of this phenomenon. A T(c) higher than 40 K (about the theoretical maximum predicted from Bardeen-Cooper-Schrieffer theory), however, has been obtained only in the copper oxide superconductors. The highest reported value for non-copper-oxide bulk superconductivity is T(c) = 39 K in MgB(2) (ref. 2). The layered rare-earth metal oxypnictides LnOFeAs (where Ln is La-Nd, Sm and Gd) are now attracting attention following the discovery of superconductivity at 26 K in the iron-based LaO(1-x)F(x)FeAs (ref. 3). Here we report the discovery of bulk superconductivity in the related compound SmFeAsO(1-x)F(x), which has a ZrCuSiAs-type structure. Resistivity and magnetization measurements reveal a transition temperature as high as 43 K. This provides a new material base for studying the origin of high-temperature superconductivity.

Giant anisotropy of the magnetoresistance and the 'spin valve' effect in antiferromagnetic Nd(2-x)Ce(x)CuO(4).

We have studied anisotropic magnetoresistance (MR) and magnetization with a rotating magnetic field (B) within the CuO(2) plane in lightly doped AF Nd(2-x)Ce(x)CuO(4). A giant anisotropy in the MR is observed at low temperature, below 5 K. The c-axis resistivity can be tuned over about one order of magnitude just by changing the B direction within the CuO(2) plane, and a scaling behavior for the out-of-plane and in-plane MR is found. A 'spin valve' effect is proposed for explaining the giant anisotropy of the out-of-plane MR and the evolution of the scaling parameters with the external field. It is found that the field-induced spin-flop transition of the Nd(3+) layer under high magnetic field is the key to understanding the giant anisotropy. These results suggest that a novel entanglement of charge and spin dominates the underlying physics.