Branching ratio measurement of the decay K(L) --> e(+)e(-)mu(+)mu(-)

We have collected a 43 event sample of the decay K(L)-->e(+)e(-)mu(+)mu(-) with negligible backgrounds and measured its branching ratio to be (2.62+/-0.40+/-0.17)x10(-9). We see no evidence for CP violation in this decay. In addition, we set the 90% confidence upper limit on the combined branching ratios for the lepton flavor violating decays K(L)-->e(+/-)e(+/-)mu(-/+)mu(-/+) at B(K(L)-->e(+/-)e(+/-)mu(-/+)mu(-/+))< or =1.23x10(-10), assuming a uniform phase space distribution.     

Study of ancient Islamic gilded pieces combining PIXE-RBS on external microprobe with sem images

Numerous metallic objects with very aesthetic and technological qualities have been recovered by archaeological excavations. Adequate processes of restoration and conservation treatments require the accurate determination of the elemental composition and distribution within the objects, as well as the identification of the nature and distribution of the corrosion products. Ideally the identification method should cause no alteration in the sample. In this work, different archaeological pieces with a gilded look have been characterized using simultaneously PIXE and RBS at the CMAM external microprobe in order to study the gilding metalworking done in the Iberian Peninsula during the Middle Ages. The gold layer thickness and its elemental concentrations of Ag, Au and Hg were determined by both techniques and compared with the scanning electron microscopy images obtained for some fragments of pieces. PACS  29.30.Kv; 87.64.-t     

Iodomethylethers from 1,3-dioxolane and 1,3-oxathiolane: preparation of acyclic nucleoside analogs

Purine and pyrimidine anions were alkylated using the iodomethyl ether and thioether generated $\text{in}$$\text{situ}$ by the reaction of 1,3-dioxolane and 1,3-oxathiolane with trimethylsilyl iodide.     

Research for new antichagasic drugs.

A series of ten 1-[(5-nitrothenylidene)amino]azoles has been synthesized by the reaction of 5-nitrothiophene-2-carbaldehyde with 1-aminopyrazole, 1-aminoimidazole, 1- and 4- amino-1,2,4-triazoles, 1-aminoindole, 1- and 2-aminoindazoles, 1-aminobenzimidazole and 1- and 2-aminobenzotriazoles. Physical data, spectroscopic characteristics and biological properties of all the derivatives have been examined. The antiprotozoal activity has been tested against Trypanosoma cruzi, comparative to Nifurtimox (Lampit).     

Two-component system CCl4 + (CH3)3CBr: extrema in equilibria involving orientationally disordered phases

Phase equilibria involving orientationally disordered (OD) and liquid phases of the two-component system between carbon tetrachloride (CCl4) and 2-methyl-2-bromomethane ((CH3)3CBr) have been determined by means of X-ray powder diffraction and thermal analysis techniques from 210 K up to the liquid state. The isomorphism relation between the OD stable face-centered cubic (FCC) phase of (CH3)3CBr and the metastable FCC phase of CCl4 has been demonstrated throughout the continuous evolution of the lattice parameters and the existence of the two-phase equilibrium [FCC + L] for the whole range of composition, despite the monotropy of the FCC phase for the CCl4 component with respect to its OD rhombohedral (R) stable phase. A continuous series of OD R mixed crystals is found, which confirms the R lattice symmetry of the OD phase II of (CH3)3CBr, for which the crystallographic results have been long-time misinterpreted. X-ray patterns of such a phase were indexed according to the recent single-crystal results obtained by Rudman (Rudman, R. J. Mol. Struct. 2001, 569, 157). In addition, some experimental evidences are given to confirm the number of molecules per unit cell (Z = 21). The thermodynamic assessment reproduces coherently the phase diagram for the stable [R + L] and [R + FCC] two-phase equilibria as well as for the partially metastable [FCC + L] two-phase equilibrium and provides a set of data for the thermodynamic properties of nonexperimentally available phase transitions of pure components. Surprisingly, the phase equilibrium involving R and FCC OD phases appears as one of the very few showing a solid-solid equilibrium with two extremes.     

Magnesium Borohydride Confined in a Metal–Organic Framework: A Preorganized System for Facile Arene Hydroboration

In close quarters : When confined in a metal–organic framework, magnesium borohydride reacts with arenes by a hydroboration pathway (see scheme), in contrast to its reactivity under analogous homogeneous solution‐phase conditions. Framework‐imposed organization of the reactive groups is required, which is achieved by a combination of the metal coordination and two hydrogen bonds.

     

Coordination‐Directed Growth of Transition‐Metal–Crystalline‐Carbon Composites with Controllable Metal Composition

Transition‐metal–carbon (CTM) composites show ample activity in many catalytic reactions. However, control of composition, distribution, and properties is challenging. Now, a straightforward path for the synthesis of transition‐metal nanoparticles engulfed in crystalline carbon is presented with excellent control over the metal composition, amount, ratio, and catalytic properties. This approach uses molten monomers that coordinate metals ions at high temperature. At high temperatures, strong coordination bonds direct the growth of carbon material with homogeneous metals distribution and with negligible losses, owing to the liquid‐like reaction compared to the traditional solid‐state reaction. The strength of the approach is demonstrated by the synthesis of mono, binary, and trinary transition‐metal–crystalline‐carbon composites with tunable and precise elemental composition as well as good electrochemical properties as oxygen evolution reaction electrocatalysts.     

GC-NPD investigation of the recovery of organonitrogen and organophosphorus pesticides from apple samples: The effect of the extraction solvent

Summary A gas chromatographic method employing a capillary column and a selective nitrogen/phosphorus detector (NPD) has been developed for the determination of organophosphorus (OP) and organonitrogen (NP) pesticides in horticultural samples (apples). The separation of sixteen pesticides and the internal standard was performed in thirteen minutes. The analytical characteristics of the method, including linear response ranges, detection limits, and reproducibility, have been studied using a 11 mixture of ethyl acetate and xylene as extraction solvent. The possibility of mutual interference between pesticides has also been studied. A procedure for the quantitative extraction of the sixteen pesticides from apple samples has also been developed; for fifteen of the pesticides recoveries >85% were obtained after 90 minutes extraction. The effect of different solvents both on recovery and on the sensitivity of the subsequent chromatography were also investigated. It was found that the sensitivity required must be considered when the solvent for sample treatment is selected.     

Low-Temperature Synthesis of Solution Processable Carbon Nitride Polymers

Carbon nitride materials require high temperatures (>500 °C) for their preparation, which entails substantial energy consumption. Furthermore, the high reaction temperature limits the materials’ processability and the control over their elemental composition. Therefore, alternative synthetic pathways that operate under milder conditions are still very much sought after. In this work, we prepared semiconductive carbon nitride (CN) polymers at low temperatures (300 °C) by carrying out the thermal condensation of triaminopyrimidine and acetoguanamine under a N₂ atmosphere. These molecules are isomers: they display the same chemical formula but a different spatial distribution of their elements. X-ray photoelectron spectroscopy (XPS) experiments and electrochemical and photophysical characterization confirm that the initial spatial organization strongly determines the chemical composition and electronic structure of the materials, which, thanks to the preservation of functional groups in their surface, display excellent processability in liquid media.