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

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

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

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

Myeloid cells in hepatocellular carcinoma

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

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

Elevated myeloid-derived suppressor cells in pancreatic, esophageal and gastric cancer are an independent prognostic factor and are associated with significant elevation of the Th2 cytokine interleukin-13

We undertook a comprehensive analysis of circulating myeloid-derived suppressor cells (MDSCs) and T regulatory cells (Tregs) in pancreatic, esophageal and gastric cancer patients and investigated whether MDSCs are an independent prognostic factor for survival. We evaluated a series of plasma cytokines and in particular re-evaluated the Th2 cytokine interleukin-13 (IL-13). Peripheral blood was collected from 131 cancer patients (46 pancreatic, 60 esophageal and 25 gastric) and 54 healthy controls. PBMC were harvested with subsequent flow cytometric analysis of MDSC (HLADR− Lin1low/− CD33+ CD11b+) and Treg (CD4+ CD25+ CD127low/− FoxP3+) percentages. Plasma IL-2, IL-4, IL-5, IL-6, IL-10, IL-12 (p70), IL-13, IL-17, G-CSF, IFN-γ, TNF-α and VEGF levels were analyzed by the Bio-Plex cytokine assay. Plasma arginase I levels were analyzed by ELISA. MDSCs and Tregs were statistically significantly elevated in pancreatic, esophageal and gastric cancer compared with controls, and MDSC numbers correlated with Treg levels. Increasing MDSC percentage was associated with increased risk of death, and in a multivariate analysis, MDSC level was an independent prognostic factor for survival. A unit increase in MDSC percentage was associated with a 22% increased risk of death (hazard ratio 1.22, 95% confidence interval 1.06–1.41). Arginase I levels were also statistically significantly elevated in upper gastrointestinal cancer patients compared with controls. There was Th2 skewing for cytokine production in all three diseases, and importantly there were significant elevations of the pivotal Th2 cytokine interleukin-13, an increase that correlated with MDSC levels

Hepatic acute-phase proteins control innate immune responses during infection by promoting myeloid-derived suppressor cell function

Acute-phase proteins (APPs) are an evolutionarily conserved family of proteins produced mainly in the liver in response to infection and inflammation. Despite vast pro- and antiinflammatory properties ascribed to individual APPs, their collective function during infections remains poorly defined. Using a mouse model of polymicrobial sepsis, we show that abrogation of APP production by hepatocyte-specific gp130 deletion, the signaling receptor shared by IL-6 family cytokines, strongly increased mortality despite normal bacterial clearance. Hepatic gp130 signaling through STAT3 was required to control systemic inflammation. Notably, hepatic gp130–STAT3 activation was also essential for mobilization and tissue accumulation of myeloid-derived suppressor cells (MDSCs), a cell population mainly known for antiinflammatory properties in cancer. MDSCs were critical to regulate innate inflammation, and their adoptive transfer efficiently protected gp130-deficient mice from sepsis-associated mortality. The hepatic APPs serum amyloid A and Cxcl1/KC cooperatively promoted MDSC mobilization, accumulation, and survival, and reversed dysregulated inflammation and restored survival of gp130-deficient mice. Thus, gp130-dependent communication between the liver and MDSCs through APPs controls inflammatory responses during infection