Determination of the structure of fusaproliferin by1H-NMR and distance geometry

The absolute configuration of fusaproliferin, a toxic metabolite produced byFusarium proliferation, was determined by the combined use of¹H NMR and distance geometry. The configuration of double bonds has been determined in agreement with NOESY buildup data. An R configuration for C10 was determined using Mosher's method. Processing the constraints obtained from NOESY experiments with a distance geometry program, a limited number (80) of possible structures was derived. An agglomerative nonhierarchical method of clustering was used in order to place these structures into classes suggested by the data, and not previously defined in any way. This statistical method showed that indeed the structures could be grouped in four classes. One of these classes is represented by a single structure, with the highest sum of violations and was discarded. All other structures have the same chirality; respectively S for C14 and R for C15. In solution the overall conformation is quite well defined in the region of the five-member ring and the planes of double bonds C2–C3 and C11–C12, while near to C8 and C9 internal flexibility appears evident.     

An asymptotic approach to the torsion problem in thin rectangular domains

A rather straightforward derivation of the Γ-limit of the torsion problem on a thin rectangle as the thickness goes to zero is obtained. The limit stresses are evaluated and the distributional nature of one of the stress components is clarified.     

Photoelectrochemistry on TiO2/Ti anodes as a tool to increase the knowledge about some photo‐oxidation mechanisms in CH3CN

Through current efficiency measurements, obtained from the photoelectrochemical oxidation at TiO₂ (rutile)/Ti anodes, further mechanistic information has been obtained regarding the TiO₂ photosensitized oxidation of benzylic alcohols, ethers and 1,2‐diols in CH₃CN. In deaerated medium, two electrons are captured by the semiconductor from all the considered substrates (one from the substrate, the second from the intermediate benzylic radical). In contrast, in aerated CH₃CN, the number of TiO₂‐captured electrons can be reduced to one because, depending on its oxidizability, the benzylic radical can be competitively captured by oxygen. Copyright © 2008 John Wiley & Sons, Ltd.     

On the use of information theory for the analysis of the relationship between neural and imaging signals

Functional magnetic resonance imaging (fMRI) is a widely used method for studying the neural basis of cognition and of sensory function. A potential problem in the interpretation of fMRI data is that fMRI measures neural activity only indirectly, as a local change of deoxyhemoglobin concentration due to the metabolic demands of neural function. To build correct sensory and cognitive maps in the human brain, it is thus crucial to understand whether fMRI and neural activity convey the same type of information about external correlates. While a substantial experimental effort has been devoted to the simultaneous recordings of hemodynamic and neural signals, so far, the development of analysis methods that elucidate how neural and hemodynamic signals represent sensory information has received less attention. In this article, we critically review why the analytical framework of information theory, the mathematical theory of communication, is ideally suited to this purpose. We review the principles of information theory and explain how they could be applied to the analysis of fMRI and neural signals. We show that a critical advantage of information theory over more traditional analysis paradigms commonly used in the fMRI literature is that it can elucidate, within a single framework, whether an empirically observed correlation between neural and fMRI signals reflects either a similar stimulus tuning or a common source of variability unrelated to the external stimuli. In addition, information theory determines the extent to which these shared sources of stimulus signal and of variability lead fMRI and neural signals to convey similar information about external correlates. We then illustrate the formalism by applying it to the analysis of the information carried by different bands of the local field potential. We conclude by discussing the current methodological challenges that need to be addressed to make the information-theoretic approach more robustly applicable to the simultaneous recordings of neural and imaging data.     

Local Structure and Coordination Define Adsorption in a Model Ir1/Fe3O4 Single‐Atom Catalyst

Single‐atom catalysts (SACs) bridge homo‐ and heterogeneous catalysis because the active site is a metal atom coordinated to surface ligands. The local binding environment of the atom should thus strongly influence how reactants adsorb. Now, atomically resolved scanning‐probe microscopy, X‐ray photoelectron spectroscopy, temperature‐programmed desorption, and DFT are used to study how CO binds at different Ir₁ sites on a precisely defined Fe₃O₄(001) support. The two‐ and five‐fold‐coordinated Ir adatoms bind CO more strongly than metallic Ir, and adopt structures consistent with square‐planar Ir^I and octahedral Ir^III complexes, respectively. Ir incorporates into the subsurface already at 450 K, becoming inactive for adsorption. Above 900 K, the Ir adatoms agglomerate to form nanoparticles encapsulated by iron oxide. These results demonstrate the link between SAC systems and coordination complexes, and that incorporation into the support is an important deactivation mechanism.     

ZnII Complexes for Bioimaging and Correlated Applications

Zinc is a biocompatible element that exists as the second most abundant transition metal ion and an indispensable trace element in the human body. Compared to traditional metal‐organic complexes systems, d¹⁰ metal Zn^II complexes not only exhibit a large Stokes shift and good photon stability but also possess strong emission and low cytotoxicity with a relatively small molecular weight. The use of Zn^II complexes has emerged in the last decade as a versatile and convenient tool for numerous biological applications, including bioimaging, molecular and protein recognition, as well as photodynamic therapy. Herein, we review recent developments involving Zn^II metal complexes applied as specific subcellular compartment imaging probes and their correlated utilizations.     

Chemoselective esterification of phenolic acids and alcohols

[formula: see text] The Mitsunobu reaction can distinguish between alcohol and phenol hydroxyls in esterification reactions, providing an expeditious and broadly applicable entry into various phenolics and polyphenolics of biomedical and nutritional relevance.     

Un problema ai limiti ellittico in un dominio non limitato

Summary For a class of operators described in § 2 we study an elliptic boundary value problem in an unbounded domain ofR ⁿ (half space). The main result is established using pseudo-differential techniques. Lavoro eseguito nell'ambito del G.N.A.F.A. del C.N.R. Entrata in Redazione il 4 maggio 1972.