Controlling the propagation of broadband light pulses by Electromagnetically Induced Transparency

We present an experimental and theoretical investigation, performed on hot sodium atoms in a ladder scheme, showing the control of the absorption and of the propagation velocity of a probe light pulse with a spectral bandwidth as large as 1.8 GHz. The predictions of the theoretical model compare favorably with the experimental results.     

Tautomerism in liquid 1,2,3-triazole: a combined energy-dispersive X-ray diffraction, molecular dynamics, and FTIR study

In this work, we report a multitechnique (energy-dispersive X-ray diffraction, computational methods, and FTIR spectroscopy) study of the tautomeric equilibrium of 1,2,3-triazole, one of the few small nitrogen-containing eterocycles liquid at room temperature. The T-2H form (C _2v symmetry) is found to be strongly favored in gas and solid phases, whereas the neat liquid gives diffraction patterns that can be interpreted satisfactorily with the structure functions calculated from some molecular dynamics results for both T-2H and T-1H tautomers, although the T-2H form gives a slightly better agreement.     

Additive-Free Chemoselective Acylation of Amines

Aliphatic and aromatic amines are efficiently acylated by acetic, pivalic, benzoic, phthalic, or maleic anhydrides in ethyl acetate at room temperature. Under the same experimental conditions, amino alcohols are chemoselectively acylated at the amino group.     

Unexpected high ordering of a [60]Fullerene nitroxide in the nematic phase of 4-4′-azoxyanisole

A nitroxide [60]fullerene adduct containing a pyrrolidine-1-oxyl group has been synthesized. Its orientational order in the nematic phase of the liquid crystal solvent 4,4′-azoxyanisole (PAA) has been measured from the variation of the EPR spectral parameters on passing from the isotropic to the nematic phase. Highly resolved EPR lines allow for precise evaluation of the shifts of the g, a _N and a _H values. Since the g and the hyperfine tensors are known, the order matrix could be obtained. This is compared with the one calculated with a theoretical model based on short range solute-solvent interactions, which predicts a considerable degree of orientation of the molecular axes, despite the almost spherical shape of the molecule. The agreement with experimental findings is quite good and it is further improved if a bent structure of the pyrrolidine ring is taken into account.     

Osteopontin: A Uranium Phosphorylated Binding‐Site Characterization

Herein, we describe the structural investigation of one possible uranyl binding site inside a nonstructured protein. This approach couples spectroscopy, thermodynamics, and theoretical calculations (DFT) and studies the interaction of uranyl ions with a phosphopeptide, thus mimicking a possible osteopontin (OPN) hydroxyapatite growth‐inhibition site. Although thermodynamical aspects were investigated by using time‐resolved laser fluorescence spectroscopy (TRLFS) and isothermal titration calorimetry (ITC), structural characterization was performed by extended X‐ray absorption fine structure (EXAFS) at the U L_III‐edge combined with attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy. From the vibrational and fluorescence spectra, several structural models of a UO₂²⁺/peptide complex were developed and subsequently refined by using theoretical calculations to fit the experimental EXAFS obtained. The structural effect of the pH value was also considered under acidic to moderately acidic conditions (pH 1.5–5.5). Most importantly, the uranyl/peptide coordination environment was similar to that of the native protein.     

Catalyst‐ and Solvent‐Dependent Stereodivergence in the Intramolecular Et2Zn/Pd0‐Promoted Carbonyl Propargylation: Mechanistic Implications

Carbonyl‐tethered propargylic benzoates undergo intramolecular carbonylpropargylation upon treatment with Et₂Zn in the presence of a catalytic amount of Pd⁰ with the formation of 2‐alkynylcyclopentanol products. A ligand/solvent effect on the cis/trans selectivity (referring to the relative positions of alkynyl and OH groups) of ring‐closure has been found. In a non‐coordinating solvent (benzene), increasing the electron‐donating ability of the phosphine ligand (while decreasing its dissociation ability) leads to an increased tendency towards the trans product. On the other hand, the combination of a coordinating solvent (THF) and PPh₃, an easily dissociated phosphine, results in the exclusive formation of cis products. Experimental and computational results are compatible with a divergent behavior of an allenylethylpalladium intermediate that partitions between competitive carbonyl‐addition and transmetalation pathways, each leading to a different diastereoisomer. These results also suggest that the dissociating ability of the phosphine regulates that behavior.     

Macrocyclic ZnII and CuII complexes as guests of the hybrid composites based on the layered MnPS3 phase. Comparison of spectroscopic properties

A family of macrocyclic complexes [M₂LⁿCl₂] have been synthesized and characterized (M: Cu^II or Zn^II; Lⁿ: macrocyclic ligand derived from 2-hydroxy-5-methyl-1,3-benzenedicarbaldehyde and different aliphatic diamines and o-phenylenediamine). The influence of the aromaticity of the ligand and the metal center on the spectroscopic properties of the complexes (absorption and emission) has been studied. Making use of the weak interactions between hydrated potassium ions and the layers of the K_0.4Mn_0.8PS₃ precursor, the obtained macrocyclic complexes have been intercalated in the interlamellar space by a microwave assisted cationic exchange reaction. The optical properties of the obtained hybrid materials are reported. The absorption edge, recorded by solid state reflectance spectroscopy for Cu^II and the Zn^II macrocycle-based composites, is 1.67–1.76 eV, both shifted to lower energy compared with that of the pristine MnPS₃.     

Metabolism of JWH-015, JWH-098, JWH-251, and JWH-307 in silico and in vitro: a pilot study for the detection of unknown synthetic cannabinoids metabolites

This pilot study was performed to study the main metabolic reactions of four synthetic cannabinoids: JWH-015, JWH-098, JWH-251, and JWH-307 in order to setup a screening method for the detection of main metabolites in biological fluids. In silico prediction of main metabolic reactions was performed using MetaSite^? software. To evaluate the agreement between software prediction and experimental reactions, we performed in vitro experiments on the same JWHs using rat liver slices. The obtained samples were analyzed by liquid chromatography-quadrupole time-of-flight and the identification of metabolites was executed using Mass-MetaSite^? software that automatically assigned the metabolite structures to the peaks detected based on their accurate masses and fragmentation. A comparison between the experimental findings and the in silico metabolism prediction using MetaSite^? software showed a good accordance between experimental and in silico data. Thus, the use of in silico metabolism prediction might represent a useful tool for the forensic and clinical toxicologist to identify possible main biomarkers for synthetic cannabinoids in biological fluids, especially urine, following their administration.

Stability analysis of the flow past miniature vortex generators in a Blasius boundary layer

It is shown in the literature that Tollmien−Schlichting waves can be damped and transition delayed by a proper modulation of the streamwise velocity in a boundary layer (BL), which can be obtained using miniature vortex generators (MVGs). Experiments show that the amplitude of TS waves is not always monotonically damped past the MVGs. In this study, direct numerical simulations and local stability analysis have been performed in order to provide an interpretation of the experiments and to characterize further the stabilization mechanism induced by this type of control. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)