In operando XAS investigation of reduction and oxidation processes in cobalt and iron mixed spinels during the chemical loop reforming of ethanol

FeCo2O4 and CoFe2O4 nanoparticles have been studied as oxygen carriers for the Chemical Loop Reforming (CLR) of ethanol. By using in operando X-ray absorption spectroscopy we have followed in real time the chemical and structural changes that take place on the materials as a function of temperature and reactive atmosphere (i.e. ethanol/water streams). During the first step of CLR for both oxides the most active chemical species are the cations in the tetrahedral sites, irrespective of their chemical nature. Quite rapidly the spinel structure is transformed into a mix of wustite-type oxide and metal alloys, but the formation of a metal phase is easier in the case of cobalt, while iron shows a marked preference to form wustite type oxide. Despite the good reducibility of FeCo2O4 imparted by the high amount of cobalt, its performance in the production of hydrogen is quite poor due to an inefficient oxidation by water steam, which is able to oxidize only the outer shell of the nanoparticles. In contrast, CoFe2O4 due to the residual presence of a reducible wustite phase shows a higher hydrogen yield. Moreover, by combining the structural information provided by X-ray absorption spectroscopy with the analysis of the byproducts of ethanol decomposition we could infer that FeCo2O4 is more selective than CoFe2O4 for the selective dehydrogenation of ethanol to acetaldehyde because of the higher amount of Fe(III) ions in tetrahedral sites

Unofficial answers to the Uniform certified public accountants examination, May 1948 to November 1950

https://egrove.olemiss.edu/aicpa_exam/1111/thumbnail.jp

Signatures of electron-boson coupling in half-metallic ferromagnet Mn5_5Ge3_3: study of electron self-energy Σ(ω)\Sigma(\omega) obtained from infrared spectroscopy

We report results of our infrared and optical spectroscopy study of a half-metallic ferromagnet Mn$_5$Ge$_3$. This compound is currently being investigated as a potential injector of spin polarized currents into germanium. Infrared measurements have been performed over a broad frequency (50 - 50000 cm$^{-1}$) and temperature (10 - 300 K) range. From the complex optical conductivity $\sigma(\omega)$ we extract the electron self-energy $\Sigma(\omega)$. The calculation of $\Sigma(\omega)$ is based on novel numerical algorithms for solution of systems of non-linear equations. The obtained self-energy provides a new insight into electron correlations in Mn$_5$Ge$_3$. In particular, it reveals that charge carriers may be coupled to bosonic modes, possibly of magnetic origin

Schoolyard Microclimate

The natural world exhibits substantial variation in climate, which influences the distribution, reproductive success, and survival of plants and animals. Although students are aware of weather, their understanding of climate is typically less clear, especially the concept of microclimate-the climate of a specific place within an area as contrasted with the climate of the entire area. Microclimate can influence where birds place their nests (Lloyd and Martin 2004), where insects reside (Lorenzo and Lazzari 1999), and where plants successfully germinate (Tomimatsu and Ohara 2004). Therefore, microclimate can have a profound effect on local community structure and biodiversity, particularly on plants, which are unable to move and thus often limited by local environmental conditions

Unofficial answers to the uniform certified public accountants examination of the American Institute of Accountants, May 1, 1951 to November 1953

https://egrove.olemiss.edu/aicpa_exam/1152/thumbnail.jp

Even Galois Representations and the Fontaine--Mazur conjecture II

We prove, under mild hypotheses, that there are no irreducible two-dimensional_even_ Galois representations of \Gal(\Qbar/\Q) which are de Rham with distinct Hodge--Tate weights. This removes the "ordinary" hypothesis required in previous work of the author. We construct examples of irreducible two-dimensional residual representations that have no characteristic zero geometric (= de Rham) deformations.Comment: Updated to take into account suggestions of the referee; the main theorems remain unchange

Metabolic origins of spatial organization in the tumor microenvironment.

The genetic and phenotypic diversity of cells within tumors is a major obstacle for cancer treatment. Because of the stochastic nature of genetic alterations, this intratumoral heterogeneity is often viewed as chaotic. Here we show that the altered metabolism of cancer cells creates predictable gradients of extracellular metabolites that orchestrate the phenotypic diversity of cells in the tumor microenvironment. Combining experiments and mathematical modeling, we show that metabolites consumed and secreted within the tumor microenvironment induce tumor-associated macrophages (TAMs) to differentiate into distinct subpopulations according to local levels of ischemia and their position relative to the vasculature. TAMs integrate levels of hypoxia and lactate into progressive activation of MAPK signaling that induce predictable spatial patterns of gene expression, such as stripes of macrophages expressing arginase 1 (ARG1) and mannose receptor, C type 1 (MRC1). These phenotypic changes are functionally relevant as ischemic macrophages triggered tube-like morphogenesis in neighboring endothelial cells that could restore blood perfusion in nutrient-deprived regions where angiogenic resources are most needed. We propose that gradients of extracellular metabolites act as tumor morphogens that impose order within the microenvironment, much like signaling molecules convey positional information to organize embryonic tissues. Unearthing embryology-like processes in tumors may allow us to control organ-like tumor features such as tissue repair and revascularization and treat intratumoral heterogeneity