Illuminating the dark corridor in graphene: polarization dependence of angle-resolved photoemission spectroscopy on graphene

We have used s- and p-polarized synchrotron radiation to image the electronic structure of epitaxial graphene near the K-point by angular resolved photoemission spectroscopy (ARPES). Part of the experimental Fermi surface is suppressed due to the interference of photoelectrons emitted from the two equivalent carbon atoms per unit cell of graphene's honeycomb lattice. Here we show that by rotating the polarization vector, we are able to illuminate this 'dark corridor' indicating that the present theoretical understanding is oversimplified. Our measurements are supported by first-principles photoemission calculations, which reveal that the observed effect persists in the low photon energy regime.Comment: 5 pages, 4 figure

Quasiparticles in the superconducting state of Bi2Sr2CaCu2O8

Recent improvements in momentum resolution by a factor of 32 lead to qualitatively new ARPES results on the spectra of Bi2Sr2CaCu2O8 (Bi2212) along the (pi,pi) direction, where there is a node in the superconducting gap. With improved resolution, we now see the intrinsic lineshape, which indicates the presence of true quasiparticles at the Fermi momentum in the superconducting state, and lack thereof in the normal state. The region of momentum space probed here is relevant for charge transport, motivating a comparison of our results to conductivity measurements by infrared reflectivity.Comment: revised paper with new figure

HOMO band structure and anisotropic effective hole mass in thin crystalline Pentacene films

The band dispersion of the two highest occupied molecular orbital (HOMO)-derived bands in thin crystalline Pentacene films grown on Bi(001) was determined by photoemission spectroscopy. Compared to first-principles calculations our data show a significantly smaller band width and a much larger band separation indicating that the molecular interactions are weaker than predicted by theory--a direct contradiction to previous reports by Kakuta et al. [Phys. Rev. Lett. 98, 247601 (2007)]. The effective hole mass m* at M-bar is found to be anisotropic and larger than theoretically predicted. Comparison of m* to field effect mobility measurements shows that the band structure has a strong influence on the mobility even at room temperature where we estimate the scattering rate to be tau ~3 fs.Comment: 20 pages, 4 figures, 1 table and appendi

Las estrategias de crecimiento de la industria química alemana en España, 1880-1936: exportación e inversión directa

Editada en la Fundación Empresa PúblicaEn este trabajo se reconstruyen y examinan las dos grandes estrategias de crecimiento de las empresas químicas alemanas en España entre 1880 y 1936: la exportación y la inversión directa. Ambas fueron, en todo el mundo, importantes vías de transferencia tecnológica especialmente después de la Primera Guerra Mundial. Para averiguar por qué en la industria química española los efectos modemizadores del primer mversor mundial fueron tan escasos, se abordan dos tareas: 1) valorar la estratega de las firmas alemanas en España a la luz de las desplegadas en todo el mundo, y 2) analizar las medidas que las empresas y la Administración españolas aplicaron para defender el mercado nacional y fomentar el surgmuento y la consolidación de la industria química española.This paper reconstructs and examines the growth strategies displayed by the German chemical industry in Spain between 1880 and 1936: exports and direct investment. Elsewhere both became instrumental for the transfer of technology and managerial skills, particularly after World War I. In order to understand why the effects of the fírst world chemical investor were so poor on the Spanish industry, the German strategies are analyzed in the light of those followed elsewhere. Furthermore, those policies applied both by the Spanish firms and Administration to encourage the rise and development of the local industry are also examined.Publicad

Tumor-induced STAT3 activation in monocytic myeloid-derived suppressor cells enhances stemness and mesenchymal properties in human pancreatic cancer

Pancreatic cancer (PC) mobilizes myeloid cells from the bone marrow to the tumor where they promote tumor growth and proliferation. Cancer stem cells (CSCs) are a population of tumor cells that are responsible for tumor initiation. Aldehyde dehydrogenase-1 activity in PC identifies CSCs, and its activity has been correlated with poor overall prognosis in human PC. Myeloid cells have been shown to impact tumor stemness, but the impact of immunosuppressive tumor-infiltrating granulocytic and monocytic myeloid-derived suppressor cells (Mo-MDSC) on ALDH1(Bright) CSCs and epithelial to mesenchymal transition is not well understood. In this study, we demonstrate that Mo-MDSC (CD11b(+)/Gr1(+)/Ly6G(−)/Ly6C(hi)) significantly increase the frequency of ALDH1(Bright) CSCs in a mouse model of PC. Additionally, there was significant upregulation of genes associated with epithelial to mesenchymal transition. We also found that human PC converts CD14(+) peripheral blood monocytes into Mo-MDSC (CD14(+)/HLA-DR(low/−)) in vitro, and this transformation is dependent on the activation of the STAT3 pathway. In turn, these Mo-MDSC increase the frequency of ALDH1(Bright) CSCs and promote mesenchymal features of tumor cells. Finally, blockade of STAT3 activation reversed the increase in ALDH1(Bright) CSCs. These data suggest that the PC tumor microenvironment transforms monocytes to Mo-MDSC by STAT3 activation, and these cells increase the frequency of ALDH1(Bright) CSCs. Therefore, targeting STAT3 activation may be an effective therapeutic strategy in targeting CSCs in PC. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00262-014-1527-x) contains supplementary material, which is available to authorized users

ARPES Line Shapes in FL and non-FL Quasi-Low-Dimensional Inorganic Metals

Quasi-low-dimensional (quasi-low-D) inorganic materials are not only ideally suited for angle resolved photoemission spectroscopy (ARPES) but also they offer a rich ground for studying key concepts for the emerging paradigm of non-Fermi liquid (non-FL) physics. In this article, we discuss the ARPES technique applied to three quasi-low-D inorganic metals: a paradigm Fermi liquid (FL) material TiTe$_{2}$, a well-known quasi-1D charge density wave (CDW) material K$_{0.3}$MoO$_{3}$ and a quasi-1D non-CDW material Li$_{0.9}$Mo$_{6}$O$_{17}$. With TiTe$_2$, we establish that a many body theoretical interpretation of the ARPES line shape is possible. We also address the fundamental question of how to accurately determine the {\bf k}$_F$ value from ARPES. Both K$_{0.3}$MoO$_{3}$ and Li$_{0.9}$Mo$_{6}$O$_{17}$ show quasi-1D electronic structures with non-FL line shapes. A CDW gap opening is observed for K$_{0.3}$MoO$_{3}$, whereas no gap is observed for Li$_{0.9}$Mo$_{6}$O$_{17}$. We show, however, that the standard CDW theory, even with strong fluctuations, is not sufficient to describe the non-FL line shapes of K$_{0.3}$MoO$_{3}$. We argue that a Luttinger liquid (LL) model is relevant for both bronzes, but also point out difficulties encountered in comparing data with theory. We interpret this situation to mean that a more complete and realistic theory is necessary to understand these data.Comment: 23 pages, including 21 figures; to appear in a special issue of J. Elec. Spectr. Rel. Pheno

The Role of T-Cadherin (CDH13) in Treatment Options with Garcinol in Melanoma

Targeted therapies with chemotherapeutic agents and immunotherapy with checkpoint inhibitors are among the systemic therapies recommended in the guidelines for clinicians to treat melanoma. Although there have been constant improvements in the treatment of melanoma, resistance to the established therapies continues to occur. Therefore, the purpose of this study was to explore the function of garcinol with regards to specific cancer properties such as proliferation and apoptosis. Garcinol, a natural compound isolated from the plant also known as mangosteen (Garcinia mangostana), is a newly discovered option for cancer treatment. Numerous pharmaceutical substances are derived from plants. For example, the derivates of camptothecin, extracted from the bark of the Chinese tree of happiness (Camptotheca acuminate), or paclitaxel, extracted from the bark of the Western yew tree (Taxus brevifolia), are used as anti-cancer drugs. Here, we show that garcinol reduced proliferation and induced apoptosis in melanoma cell lines. In addition, we found that those cells that are positive for the expression of the cell–cell adhesion molecule T-cadherin (CDH13) respond more sensitively to treatment with garcinol. After knock-down experiments with an siRNA pool against T-cadherin, the sensitivity to garcinol decreased and proliferation and anti-apoptotic behavior of the cells was restored. We conclude that patients who are T-cadherin-positive could especially benefit from a therapy with garcinol.</jats:p

Myeloid cells in hepatocellular carcinoma

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113692/1/hep27867.pd