On new conditions for evaluate long-time scales in superstatistical time series

In this article, we introduce an additional condition for the criterion previously presented in order to extract the update time scale of the intensive parameter, in superstatistical time series. With these modifications, such criterion is capable of evaluating the actual long-time scale. In addition, the criterion permits a valuable way to verify whether the process under study is superstatistical or not.     

Synthesis and characterization of tetrahedral and square planar Bis(iminopyrrolyl) complexes of cobalt(II)

A series of 2-iminopyrrole ligand precursors with increasing bulkiness [HNC4H3C(R)=N-2,6-R'2C6H3] (R = R' = H, 1a; R = Me, R'= H, 1b; R = H, R' = Me, 1c; R = R' = Me, 1d; R = H, R' = iPr, 1e; R = Me, R' = iPr, 1f) were synthesized and deprotonated with NaH to give the corresponding iminopyrrolyl sodium salts 2a-f. A set of homoleptic bis-ligand Co(II) complexes of the type [Co(kappa2N,N'-NC4H3C(R)=N-2,6-R'2C6H3)2] (R = R'= H, 3a; R = Me, R'= H, 3b; R = H, R' = Me, 3c; R = R' = Me, 3d; R = H, R' = iPr, 3e; R = Me, R' = iPr, 3f) was prepared by reaction of CoCl2 with the corresponding iminopyrrolyl sodium salts 2a-f. The new complexes were characterized by elemental analysis, magnetic susceptibility measurements, in powder and in solution, UV/vis/NIR, and, in some cases, X-ray crystallography. According to X-ray diffraction and magnetic measurements, the Co complexes 3a-e proved to be tetrahedral, which is the preferred geometry for Co(II) compounds. However, a square planar geometry is observed in the case of 3f, as determined by several characterization techniques. In this case, DFT calculations suggest the square planar geometry is slightly more stable than the tetrahedral one probably due to a combination of steric and electronic reasons.     

Recycling of the used automotive lubricating oil by ionizing radiation process

The recycling process of the used mineral oils has been gaining a very important gap in the context of environmental protection. Among mineral oils from petroleum, the lubricating oils are not entirely consumed during their use; therefore, it is necessary to apply a treatment for recuperation seeking their reuse. Moreover, the environmental legislation of countries does not allow their discard in any type of soils, rivers, lakes, oceans or sewerage systems.The conventional treatment has shown certain difficulties in the recuperation process for used oils. The ionizing radiation process is renowned in the industrial effluents treatments due to its high efficiency in the degradation of organic compounds and in the removal of metals by the action of OH, H and e_aq radicals.In this work, used automotive lubricating oil was treated by the ionizing radiation process for metal removal and degradation of organic compounds. The samples were irradiated with 100 and 200 kGy irradiation doses. Determination of the elements Mg, Al, P, S, Cl, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Se, Mo, Nb, Cd, Sn, Ba, Bi and Pb, before and after the irradiation, was done by X-ray fluorescence technique and the organic profile was obtained by infrared spectroscopy.     

Molecular dynamics simulations of charged dendrimers: low-to-intermediate half-generation PAMAMs

We have performed atomistic molecular dynamics simulations of PAMAM dendrimers of generations 0.5, 1.5, 2.5, 3.5, and 4.5. The simulated systems comprise the charged dendrimer and its counterions embedded in a dielectric continuum (i.e., without explicit solvent). Structural properties of these dendrimers, like the radius of gyration, the principal moments of inertia, and the segment density profiles, were evaluated from the simulations. The average radius of gyration obtained for the intermediate half-generations 2.5, 3.5, and 4.5 follows the same scaling law that was previously inferred from simulations of full-generation PAMAMs, Rg approximately M1/3, and is characteristic of space-filling objects. The low half-generations 0.5 and 1.5 deviate, however, to greater Rg values. The shape of the smaller dendrimers is approximately that of a prolate ellipsoid, which becomes more spherical for higher generations. The segment density profiles show features identical to those obtained in other simulations of flexible-chain dendrimers, like dendron-backfolding. Two slightly different configurations, in terms of size and shape, were identified for generation 2.5. The radial distributions of counterions extracted from the simulations compare well with the solutions of Poisson-Boltzmann cell model, and the dendrimer's effective charge was estimated using the Bjerrum criterion. The influence of electrostatic interactions in the dendrimer's conformation due to repulsion between the charged end-groups and its relation to counterion effects is discussed for the several generations simulated. The form factors calculated from the simulations are compared with the model of a homogeneous ellipsoid of revolution. The overall results are in agreement with the previously established morphological transition of PAMAM dendrimers toward a more spherical and compact conformation above generations 3 or 4.     

Nicotine: on the potential role of ionic liquids for its processing and purification

Marked solubility differences of nicotine in the ionic liquids [C(2)mim][NTf(2)], [C(2)mim][EtOSO(3)], and [C(n)mim]Cl, 6 相似文献   

Peptidomic analysis of human acquired enamel pellicle

Human acquired enamel pellicle is the result of a selective interaction of salivary proteins and peptides with the tooth surface. In the present work, the characterization of the peptides as well as the type of interactions established with the enamel surface was performed. Peptides from in vivo bovine enamel implants in the human oral cavity were sequentially extracted using guanidine and trifluoroacetic acid solutions and the fractions obtained were analysed by LC-MS and LC-MS/MS. Based on the LC-MS data, six phosphorylated peptides were identified in an intact form, strongly adsorbed to the enamel surface. Data from the LC-MS/MS analyses allowed us to identified 30 fragment peptides non-covalently bonded to enamel [basic proline-rich proteins, histatins (1 and 3) and acidic proline-rich protein classes]. The tandem mass spectrometry experiments showed the existence of a pattern of amide bond cleavage for the different identified peptide classes suggesting a selective proteolytic activity. For histatins, a predominance of cleavage at Arg, Lys and His residues was observed, while for basic proline-rich proteins, cleavage at Arg and Pro residues prevailed. In the case of acidic proline-rich proteins, a clearly predominance of cleavage of the Gln-Gly amide bond was evident.     

Probing the mechanism of direct Mannich-type alpha-methylenation of ketoesters via electrospray ionization mass spectrometry

Reactions promoting direct Mannich-type alpha-methylenation of alpha, beta and gamma-ketoesters have been monitored via electrospray ionization mass and tandem mass spectrometric experiments. Key intermediates of the catalytical cycle of this synthetically useful reaction have been intercepted and characterized. The mechanistic information provided by electrospray ionization mass spectrometry/mass spectrometry (ESI-MS/MS) guided the optimization of reaction conditions, allowing alpha-methyleneketoesters to be prepared in high yields (80-95%) and in high-enough purity for immediate further manipulation.     

3-Oxo-12alpha-hydroxyfriedelane from Maytenus gonoclada: structure elucidation by (1)H and (13)C chemical shift assignments and 2D-NMR spectroscopy

The compounds 3-oxofriedelane (1), 3beta-hydroxyfriedelane (2), 3,11-dioxofriedelane (3), 3,16-dioxofrie delane (4) and 3-oxo-12alpha-hydroxyfriedelane (5) were isolated from the hexane extract of Maytenus gonoclada Mart. (Celastraceae) leaves. Structural formula and the stereochemistry of the new pentacyclic triterpene 3-oxo-12alpha-hydroxyfriedelane (5) were established through (1)H and (13)C NMR and DEPT 135 spectral data including 2D experiments (HMBC, HMQC, COSY, and NOESY) and mass spectrometry (GC-MS).     

Organorhenium(VII) and organomolybdenum(VI) oxides: synthesis and application in oxidation catalysis

Methyltrioxorhenium(VII) has found numerous applications in various catalytic processes. In olefin epoxidation its activity can be enhanced by the addition of aromatic Lewis base nitrogen donor ligands, e.g. pyridines and pyrazoles. Due to the comparatively weak coordination of these ligands, a significant excess has to be used. Therefore the MTO/chiral Lewis base/H₂O₂ system is not very useful for chiral epoxidations. In contrast to this, dimethyldioxomolybdenum­(VI) MoO₂(CH₃)₂ undergoes a significantly stronger interaction with Lewis bases and seems, despite its generally somewhat lower activity, a reasonable candidate for application in chiral epoxidation reactions together with an appropriate chiral Lewis base ligand. Complexes of the type MoO₂(CH₃)₂L are accessible via MoO₂X₂L (X = Cl, Br). These latter compounds are even more active in olefin epoxidation than MoO₂(CH₃)₂L. Unfortunately, however, all the Mo(VI) complexes mentioned above need t‐butyl hydroperoxide as oxidizing agent and do not show activity in the presence of H₂O₂.