NIR emitting ytterbium chelates for colourless luminescent solar concentrators

A new oxyiminopyrazole-based ytterbium chelate enables NIR emission upon UV excitation in colorless single layer luminescent solar concentrators for building integrated photovoltaics.     

Synthesis of Fullerene Derivatives for Incorporation in Sol-Gel Glasses

We report on the synthesis of fullerene derivatives containing a trialkoxysilane moiety that exhibit enhanced solubility in solvents commonly used for sol-gel processing. These derivatives have been successfully embedded in glassy bulk samples and thin films that show very promising optical limiting properties.     

Basic Substances,a Sustainable Tool to Complement and Eventually Replace Synthetic Pesticides in the Management of Pre and Postharvest Diseases: Reviewed Instructions for Users

Synthetic pesticides are widely used to protect crops from pathogens and pests, especially for fruits and vegetables, and this may lead to the presence of residues on fresh produce. Improving the sustainability of agriculture and, at the same time, reducing the adverse effects of synthetic pesticides on human health requires effective alternatives that improve the productivity while maintaining the food quality and safety. Moreover, retailers increasingly request fresh produce with the amounts of pesticides largely below the official maximum residue levels. Basic substances are relatively novel compounds that can be used in plant protection without neurotoxic or immune-toxic effects and are still poorly known by phytosanitary consultants (plant doctors), researchers, growers, consumers, and decision makers. The focus of this review is to provide updated information about 24 basic substances currently approved in the EU and to summarize in a single document their properties and instructions for users. Most of these substances have a fungicidal activity (calcium hydroxide, chitosan, chitosan hydrochloride, Equisetum arvense L., hydrogen peroxide, lecithins, cow milk, mustard seed powder, Salix spp., sunflower oil, sodium chloride, sodium hydrogen carbonate, Urtica spp., vinegar, and whey). Considering the increasing requests from consumers of fruits and vegetables for high quality with no or a reduced amount of pesticide residues, basic substances can complement and, at times, replace the application of synthetic pesticides with benefits for users and for consumers. Large-scale trials are important to design the best dosage and strategies for the application of basic substances against pathogens and pests in different growing environments and contexts.     

催化膜和催化膜反应器:整合的高效和环保催化过程

 The design of new heterogeneous photooxygenation systems able to employ visible light, oxygen, mild temperatures, and solvent with a low environmental impact has been investigated. In particular, the heterogenization of decatungstate (W10O4-32), a polyoxometalate with photocatalytic activity in oxidation reactions, has been carried out in polymeric membranes of polyvinylidenefluoride. The polymeric catalytic membranes prepared by phase inversion technique have been successfully applied in the aerobic mineralization of phenol in water, which was used as an example of organic pollutant. In order to evaluate the effect of the polymeric environment on the overall catalyst behavior, we have also heterogenized the decatungstate (opportunely functionalized) in perfluorinated membrane made of Hyflon. The photocatalytic composite membranes are characterized by different and tuneable properties depending on the nature of the polymeric micro-environment, in which the catalyst is confined. Moreover, the selective separation function of the membrane results in enhanced performance in comparison with homogeneous reactions.     

σ−π Contributions in metal-co bond: A theoretical study of RhCO and PdCO

The electronic structure of linear RhC0 and PdCO molecules has been studied by means of effective core potential calculations including configuration interaction. The study of the ⁴Δ and ²Σ⁺ states of RhCO and the ³Σ⁺ and ¹Σ⁺ states of PdCO has shown that their low-spin states are bound and their high-spin states are repulsive. The binding energies of RhCO and PdCO are 4.0 and 7.2 kcal/mol, for the equilibrium bond lengths of 3.87 and 4.03 au, respectively. The interaction between the diffuse 5s metal orbital and the carbon lone pair produces a repulsion in the α-space, as depicted by the negative region along the metal-carbon axis in the electron density difference contour maps. The bonding in low-spin states of RhCO and PdCO is due to the metal-CO π “backdonation”. The present investigation on RhCO and PdCO, preliminary results on ScCO, as well as published results on FeCO, NiCO, CuCO and PtCO allows us to make a general conjecture that a low occupancy of the outer s atomic orbital of the transition metal atom in the complex favours the bonding interaction with the CO moiety. The analogy with properties of LiCO and NaCO systems is pointed out.     

The lift computation for an oscillating flat plate in incompressible potential flow

The initial aim of this work was the estimation of the lift acting on a flat plate performing small oscillations in a plane uniform stream by means of a simplified model based on one or at the most two lumped vortices, and the assessment of its results by comparison to those that were exact. The model was found to work well up to a reduced frequency of about 1 or 2, above which the results diverged from those that were correct. In order to improve the model, its behaviour at very high frequencies was then investigated, discovering: (i) that if the number of lumped vortices is greater than one the possibility to impose all boundary conditions is subject to certain geometrical constraints; (ii) that the asymptotical behaviour is not the right one. A straightforward extension of this conclusion to the exact case of a continuous, vorticity distribution simulating the motion of the plate and to the classical equation describing it leads apparently to an incorrect result. The reason for the discrepancy is found in the singularity displayed by the integral equation which cannot be reproduced by the discrete model. It this therefore concluded that the latter can be trusted at low and middle frequencies but its extension to higher ones is fundamentally uncorrect.

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Sommario Lo scopo iniziale di questo lavoro era il calcolo approssimato della portanza agente su una lamina piana soggetta a piccole oscillazioni in una corrente bidimensionale uniforme per mezzo di un modello semplificato basato su uno o al più due vortici concentrati, e il confronto dei risultati con quelli esatti. Il modello risulta funzionare bene per frequenze ridotte inferiori ad 1 o 2, sopra le quali, tuttavia, i risultati si allontanano da quelli corretti. Per migliorarlo si è allora studiato il suo comportamento alle frequenze molto alte, scoprendo che: (i) la possibilità di imporre tutte le condizioni al contorno quando il numero dei vortici concentrati è superiore a uno è soggetta a certe limitazioni sulla configurazione geometrica; (ii) che il comportamento asindotico non è quello corretto. Un'estensione automatica di questa conclusione al caso esatto in cui il moto della lamina è simulato da una distribuzione continua di vorticità e alla classica equazione che lo descrive sembra condurre ad un risultato errato. La ragione di questa discrepanza viene individuata nella singolarità contenuta nell'equazione integrale, che non può essere riprodotta dal modello discreto. Se ne conclude perciò che esso è utilizzabile alle basse e medie frequenze ma che una sua estensione alle alte è fondamentalmente errata.

     

Problemi e convergenze variazionali su domini non limitati

Summary We introduce a class of second order elliptic operators from H ₀ ¹ () to his dual space H^–1(), where is an open set in Rⁿ that we allow to be unbounded. We prove that such operators are continuously invertible and that the constant majoryzing the norm of their inverses depends only on the parameters of the class. We prove moreover that if T H^–1() is given then the set of the L^–1T, where L belongs to the mentioned class is relatively compact in L²(). Next we study the relationships between several kinds of convergence (one of them is the G-convergence) and we study in what cases the spectrum function is semicontinuous or continuous on certain subsets of our class of operators.     

More Than 12 % Polarization and 20 Minute Lifetime of 15N in a Choline Derivative Utilizing Parahydrogen and a Rhodium Nanocatalyst in Water

Hyperpolarization techniques are key to extending the capabilities of MRI for the investigation of structural, functional and metabolic processes in vivo. Recent heterogeneous catalyst development has produced high polarization in water using parahydrogen with biologically relevant contrast agents. A heterogeneous ligand‐stabilized Rh catalyst is introduced that is capable of achieving ¹⁵N polarization of 12.2±2.7 % by hydrogenation of neurine into a choline derivative. This is the highest ¹⁵N polarization of any parahydrogen method in water to date. Notably, this was performed using a deuterated quaternary amine with an exceptionally long spin‐lattice relaxation time (T₁) of 21.0±0.4 min. These results open the door to the possibility of ¹⁵N in vivo imaging using nontoxic similar model systems because of the biocompatibility of the production media and the stability of the heterogeneous catalyst using parahydrogen‐induced polarization (PHIP) as the hyperpolarization method.     

Chiral Diselenides from Benzylamines: Catalysts in the Diethylzinc Addition to Aldehydes

A series of new chiral diselenides with a N-atom in the side chain was prepared by a short synthetic sequence (Scheme 1). Only 1 mol-% of these diselenides catalyzed very effectively the diethylzinc addition to various aromatic and α,β-unsaturated aldehydes yielding the secondary alcohols in up to 98% ee (Scheme 2 and Tables 1 and 2). An asymmetric amplification was observed with these catalysts. Detailed NMR studies were performed to characterize the catalytically active species.     

Accurate Determination of 1H‐15N Dipolar Couplings Using Inaccurate Settings of the Magic Angle in Solid‐State NMR Spectroscopy

Magic‐angle spinning (MAS) is an essential ingredient in a wide variety of solid‐state NMR experiments. The standard procedures to adjust the rotor angle are not highly accurate, resulting in a slight misadjustment of the rotor from the magic angle ( ) on the order of a few millidegrees. This small missetting has no significant impact on the overall spectral resolution, but is sufficient to reintroduce anisotropic interactions. Shown here is that site‐specific ¹H‐¹⁵N dipolar couplings can be accurately measured in a heavily deuterated protein. This method can be applied at arbitrarily high MAS frequencies, since neither rotor synchronization nor particularly high radiofrequency field strengths are required. The off‐MAS method allows the quantification of order parameters for very dynamic residues, which often escape an analysis using existing methods.