Thickness dependence of the stability of the charge-ordered state in Pr0.5_{0.5}Ca0.5_{0.5}MnO3_{3} thin films

Thin films of the charge-ordered (CO) compound Pr$_{0.5}$Ca$_{0.5}$MnO$_{3}$ have been deposited onto (100)-oriented SrTiO$_{3}$ substrates using the Pulsed Laser Deposition technique. Magnetization and transport properties are measured when the thickness of the film is varied. While the thinner films do not exhibit any temperature induced insulator-metal transition under an applied magnetic field up to 9T, for thickness larger than 1100\UNICODE{0xc5} a 5T magnetic field is sufficient to melt the CO state. For this latest film, we have measured the temperature-field phase diagram. Compared to the bulk material, it indicates that the robustness of the CO state in thin films is strongly depending on the strains and the thickness. We proposed an explanation based on the distortion of the cell of the film.Comment: 9 pages, 6 figures, submitted to Phys. Rev.

High magnetic field transport measurement of charge-ordered Pr0.5_{0.5}Ca0.5_{0.5}MnO3_3 strained thin films

We have investigated the magnetic-field-induced phase transition of charge-ordered (CO) Pr$_{0.5}$Ca$_{0.5}$MnO$_3$ thin films, deposited onto (100)-oriented LaAlO$_3$ and (100)-oriented SrTiO$_3$ substrates using the pulsed laser deposition technique, by measuring the transport properties with magnetic fields up to 22T. The transition to a metallic state is observed on both substrates by application of a critical magnetic field ($H_C>10T$ at 60K). The value of the field required to destroy the charge-ordered insulating state, lower than the bulk compound, depends on both the substrate and the thickness of the film. The difference of the critical magnetic field between the films and the bulk material is explained by the difference of in-plane parameters at low temperature (below the CO transition). Finally, these results confirm that the robustness of the CO state, depends mainly on the stress induced by the difference in the thermal dilatations between the film and the substrate.Comment: 10 pages, 6 figures. To be published in Phys. Rev.

Non-linear electrical response in a non-charge-ordered manganite: Pr0.8Ca0.2MnO3

Up to now, electric field induced non-linear conduction in the Pr(1-x)CaxMnO3 system has been ascribed to a current-induced destabilization of the charge ordered phase. However, for x<0.25, a ferromagnetic insulator state is observed and charge-ordering is absent whatever the temperature. A systematic investigation of the non-linear transport in the ferromagnetic insulator Pr0.8Ca0.2MnO3 shows rather similar results to those obtained in charge ordered systems. However, the experimental features observed in Pr0.8Ca0.2MnO3 are distinct in that the collapse of the CO energy gap can not be invoked as usually done in the other members of the PCMO system. We propose interpretations in which the effectiveness of the DE is restored upon application of electric field.Comment: 6 pages, 5 figure

Measurements of the Cross Section for e+e- -> hadrons at Center-of-Mass Energies from 2 to 5 GeV

We report values of $R = \sigma(e^+e^-\to {hadrons})/\sigma(e^+e^-\to\mu^+\mu^-)$ for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider.Comment: 5 pages, 3 figure

Subsequent chemotherapy reverses acquired tyrosine kinase inhibitor resistance and restores response to tyrosine kinase inhibitor in advanced non-small-cell lung cancer

<p>Abstract</p> <p>Background</p> <p>Patients with advanced or metastatic non-small cell lung cancer (NSCLC) can develop acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (TKIs) erlotinib and gefitinib. Here, we report the successful treatment with alternating chemotherapy and TKIs of two cases of advanced NSCLC who developed resistance to TKI.</p> <p>Case presentation</p> <p>Two patients with advanced or metastatic NSCLC were treated with palliative chemotherapy followed by erlotinib/gefitinib. When TKI therapy failed, two cycles of chemotherapy were provided, which were followed by re-challenge with erlotinib or gefitinib.</p> <p>Conclusion</p> <p>NSCLC patients with acquired TKI resistance should be managed aggressively whenever possible. Subsequent chemotherapy and target treatment is one of the reasonable choices for those with an initial dramatic clinical response with erlotinib/gefitinib treatment. Further studies are warranted to substantiate the association of erlotinib /gefitinib treatment with the efficacy of NSCLC patients with acquired TKI failure.</p

Tumor growth suppression induced by biomimetic silk fibroin hydrogels

Protein-based hydrogels with distinct conformations which enable encapsulation or differentiation of cells are of great interest in 3D cancer research models. Conformational changes may cause macroscopic shifts in the hydrogels, allowing for its use as biosensors and drug carriers. In depth knowledge on how 3D conformational changes in proteins may affect cell fate and tumor formation is required. Thus, this study reports an enzymatically crosslinked silk fibroin (SF) hydrogel system that can undergo intrinsic conformation changes from random coil to β-sheet conformation. In random coil status, the SF hydrogels are transparent, elastic, and present ionic strength and pH stimuli-responses. The random coil hydrogels become β-sheet conformation after 10 days in vitro incubation and 14 days in vivo subcutaneous implantation in rat. When encapsulated with ATDC-5 cells, the random coil SF hydrogel promotes cell survival up to 7 days, whereas the subsequent β-sheet transition induces cell apoptosis in vitro. HeLa cells are further incorporated in SF hydrogels and the constructs are investigated in vitro and in an in vivo chick chorioallantoic membrane model for tumor formation. In vivo, Angiogenesis and tumor formation are suppressed in SF hydrogels. Therefore, these hydrogels provide new insights for cancer research and uses of biomaterials.The authors would like to thank the Portuguese Foundation for Science and Technology (FCT) project grants OsteoCart (PTDC/CTM-BPC/115977/2009) and Tissue2Tissue (PTDC/CTM/105703/2008) which supported this study. Research leading to these results has also received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no REGPOT-CT2012-316331-POLARIS. Le-Ping Yan was awarded a PhD scholarship from FCT (SFRH/BD/64717/2009). We also would like to thank FCT for the distinction attributed to J.M. Oliveira under the Investigador FCT program (IF/00423/2012). The authors also like to acknowledge Dr. Mariana B. Oliveira for technical assistance on the dynamic mechanical analysis of the cell-laden hydrogels

Observation of Ds+→pnˉD^+_s\rightarrow p\bar{n} and confirmation of its large branching fraction

The baryonic decay $D^+_s\rightarrow p\bar{n}$ is observed, and the corresponding branching fraction is measured to be $(1.21\pm0.10\pm0.05)\times10^{-3}$, where the first uncertainty is statistical and second systematic. The data sample used in this analysis was collected with the BESIII detector operating at the BEPCII $e^+e^-$ double-ring collider with a center-of-mass energy of 4.178~GeV and an integrated luminosity of 3.19~fb$^{-1}$. The result confirms the previous measurement by the CLEO Collaboration and is of greatly improved precision, which may deepen our understanding of the dynamical enhancement of the W-annihilation topology in the charmed meson decays

Observation and study of the decay J/ψ→ϕηη′J/\psi\rightarrow\phi\eta\eta'

We report the observation and study of the decay $J/\psi\rightarrow\phi\eta\eta'$ using $1.3\times{10^9}$ $J/\psi$ events collected with the BESIII detector. Its branching fraction, including all possible intermediate states, is measured to be $(2.32\pm0.06\pm0.16)\times{10^{-4}}$. We also report evidence for a structure, denoted as $X$, in the $\phi\eta'$ mass spectrum in the $2.0-2.1$ GeV/$c^2$ region. Using two decay modes of the $\eta'$ meson ($\gamma\pi^+\pi^-$ and $\eta\pi^+\pi^-$), a simultaneous fit to the $\phi\eta'$ mass spectra is performed. Assuming the quantum numbers of the $X$ to be $J^P = 1^-$, its significance is found to be 4.4$\sigma$, with a mass and width of $(2002.1 \pm 27.5 \pm 21.4)$ MeV/$c^2$ and $(129 \pm 17 \pm 9)$ MeV, respectively, and a product branching fraction $\mathcal{B}(J/\psi\rightarrow\eta{}X)\times{}\mathcal{B}(X\rightarrow\phi\eta')=(9.8 \pm 1.2 \pm 1.7)\times10^{-5}$. Alternatively, assuming $J^P = 1^+$, the significance is 3.8$\sigma$, with a mass and width of $(2062.8 \pm 13.1 \pm 7.2)$ MeV/$c^2$ and $(177 \pm 36 \pm 35)$ MeV, respectively, and a product branching fraction $\mathcal{B}(J/\psi\rightarrow\eta{}X)\times{}\mathcal{B}(X\rightarrow\phi\eta')=(9.6 \pm 1.4 \pm 2.0)\times10^{-5}$. The angular distribution of $J/\psi\rightarrow\eta{}X$ is studied and the two $J^P$ assumptions of the $X$ cannot be clearly distinguished due to the limited statistics. In all measurements the first uncertainties are statistical and the second systematic.Comment: 10 pages, 6 figures and 4 table