In situ study of Ge(100) surfaces with tertiarybutylphosphine supply in vapor phase epitaxy ambient

GaInP nucleation on Ge(100) often starts by annealing of the Ge(100) substrates under supply of phosphorus precursors. However, the influence on the Ge surface is not well understood. Here, we studied vicinal Ge(100) surfaces annealed under tertiarybutylphosphine (TBP) supply in MOVPE by in situ reflection anisotropy spectroscopy (RAS), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). While XPS reveals a P termination and the presence of carbon on the Ge surface, LEED patterns indicate a disordered surface probably due to by-products of the TBP pyrolysis. However, the TBP annealed Ge(100) surface exhibits a characteristic RA spectrum, which is related to the P termination. RAS allows us to in situ control phosphorus desorption dependent on temperature

Theory of inelastic lifetimes of low-energy electrons in metals

Electron dynamics in the bulk and at the surface of solid materials are well known to play a key role in a variety of physical and chemical phenomena. In this article we describe the main aspects of the interaction of low-energy electrons with solids, and report extensive calculations of inelastic lifetimes of both low-energy electrons in bulk materials and image-potential states at metal surfaces. New calculations of inelastic lifetimes in a homogeneous electron gas are presented, by using various well-known representations of the electronic response of the medium. Band-structure calculations, which have been recently carried out by the authors and collaborators, are reviewed, and future work is addressed.Comment: 28 pages, 18 figures, to appear in Chem. Phy

MARCH1: An Exploration of its Domains and Understanding its Role in the Mechanism of Antigen-Presentation and the Potential Sequela of Dysregulation

Current research of membrane-associated ring finger –C3HC4-1 (MARCH1) suggests that its role in mammalian immunity is more complex than was previously thought. MARCH1 is an E3 ubiquitin ligase expressed by antigen-presenting cells of the immune system, where it inhibits antigen presentation by downregulation of its substrates, MHC class II and CD86. We have studied how MARCH1 expression is regulated and determined that the protein levels are regulated, in part, through its inherent instability. We have shown that MARCH1 has distinct regions responsible for both its stability and function. The amino terminus contains a region needed for destabilization of the protein, while the amino acid residues 229-257 are missing: it appears to lead to a loss of function. Preliminary studies into dysregulation of antigen processing, inhibited by loss of MARCH1 expression in mice, have shown inclinations toward a metabolically diseased state. Knock-out (KO) MARCH1 mice have increased amounts of visceral adipose tissue relative to wild type. In addition, our preliminary results, examining transcript levels, suggest that a pro-inflammatory environment may result from the loss of MARCH1 in these fat depots, potentially resulting in metabolic disease. Our results indicate that changes in MARCH1 levels lead to a potentially dysregulated inflammatory environment

A corrosão do bolso das famílias

Copia digital. Madrid : Ministerio de Cultura. Subdirección General de Coordinación Bibliotecaria, 200