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The small Plio-Quaternary volcanic centre of Cabezo Negro de Tallante in SE Spain includes a thick deposit of polymictic pyroclastic tuff-breccia, whose fragments are agglutinated by a carbonate-rich component. This feature is also observed in other monogenetic volcanic centres cropping out in the Tallante-Cartagena volcanic district. The carbonate fraction has been recently interpreted in literature as representing a mantle component, therefore pointing to the existence of a diffuse carbonatitic activity in the area. Based on detailed sedimentological (presence of pisoids and root remnants), petrographic (presence of plagioclase and absence of euhedral silicate minerals in the calcite plagues), mineral chemistry (Ba-Sr-poor calcite composition), whole-rock chemistry (overall low incompatible element content in the pure carbonate fraction and a monotonous trace element negative correlation with CaO) as well as isotopic constraints (perfect correlations between Sr-Nd-Pb isotopic ratios with CaO in the basaltic and carbonate fraction, as well as heavy δ18O and light δ13C isotopic composition of the carbonate fraction), we propose a secondary origin for the carbonate component, excluding any contribution of mantle carbonatite melts. The presence of carbonates infiltrating the abundant mantle and crustal xenolith fragments found in the pyroclastic breccia is not related to the presence of carbonatitic melts at mantle to lower crustal depths, but to in-situ fragmentation of the Strombolian tuff-breccia deposit, followed by secondary carbonate infiltration. The pyroclastic breccia was indeed affected by an alternation of carbonate precipitation and dissolution in a vadose zone, where the activity of bacteria, fungi, roots and meteoric water led to the formation of a calcrete (caliche)-type deposits. Basaltic rocks (hawaiites and basanites) occur in the area as scoria and lava fragments in the pyroclastic breccia as well as small lava flows. They have been modelled with a low-degree partial melting of an amphibole-bearing peridotitic mantle close to the lithosphere-asthenosphere boundary. The origin of the mildly alkaline sodic basaltic activity in SE Spain post-dates the abundant and long-lasting subduction-related volcanic phase in the Betic Chain. Its origin is explained without requiring the presence of any thermal anomaly, but simply as consequence of the difference of lithospheric depths and edge-driven-type small-scale convection.

The Pleistocene (~460-265 ka) San Venanzo volcanic complex belongs to the IAP (Intra-Apennine Province) in central Italy, which comprises at least four small Pleistocene monogenetic volcanoes plus several unrooted pyroclastic deposits with peculiar mineralogical and whole-rock chemical compositions. San Venanzo products are strongly SiO-undersaturated, CaO- and MgO-rich and show ultrapotassic serial character. The relatively common occurrence of calcite in the pyroclastic rocks and the overall high CaO content are interpreted in literature as primary mineral. The main rock facies at San Venanzo are calcite-rich scoria and lapilli tuffs, with minor massive lava flows, and a rare pegmatoid variant (melilitolitic pockets). All the San Venanzo rocks are feldspar-free, with a typical paragenesis of forsteritic olivine, non-stoichiometric Ca-rich diopside, melilite, leucite, kalsilite, opaque minerals, nepheline, phlogopite, calcite, apatite, cuspidine, wollastonite, kirschsteinite-monticellite s.s. ± glass and other minor and very rare minerals typical of agpaitic melts. Based on petrographic analyses, the studied rocks can be classified as olivine melilitites, olivine leucite melilitites, venanzites (a local variant of kamafugites), calcite leucite melilitolites and Ca-rich olivine leucite melilitite tuffs. Mass balance calculations indicate a direct genetic link between the lava bodies and the pegmatoid melilitolitic pocket through a fractional crystallization process characterized by the removal of ~74% of a melilite-bearing uganditic cumulate made up of melilite, leucite, olivine, kalsilite and chromite. Primitive mantle-normalized patterns of the lavas and tuffs are rather spiked and share negative anomalies for Ba, Nb, Ta, P and Ti resembling typical magmas generated by supra-subduction mantle wedge. These compositions are very different from the only two other kamafugite localities outside Italy (Toro Ankole and Virunga in the East Africa Rift and Alto Paranaiba Igneous Province in SE Brazil). The melilitolite sample is more incompatible element-enriched than the other San Venanzo volcanic rocks, coherently with its evolved liquid composition proposed here. Major and trace element contents indicate a general depletion proportional to the amount of CaO content. The negative trends in Harker-type diagrams with CaO as abscissa are compatible with a process of variable interaction between a silicate magma with sedimentary marly carbonates/limestones. The presence of Mg-rich (Fo) and rim-ward CaO-enriched (up to 1.72 wt%) euhedral olivine, as well as the presence of thin kirschsteinite rim around olivine crystals agree with a process of crustal carbonate assimilation by an originally strongly SiO-undersaturated silicate magma. On the other hand, the lack of feldspars even in the rocks with the highest SiO, the high CaO content, and the extreme SiO-undersaturation of San Venanzo rocks exclude their derivation from a simple peridotitic source. In order to generate these peculiar compositions, the presence of a SiO-KO-CaO-rich HO-bearing component, identified in a carbonated phlogopite peridotite is required. The results of different isotopic systematics (Sr-Nd-Pb-He-Ne-Ar) presented here are compatible with a process of crustal contamination both at mantle source levels (to explain the general N-S isotopic trends recorded in Quaternary volcanic rocks of Italian peninsula and Sicily) and with interaction of ultrabasic melts with limestones at shallow crustal depths.

A vinyl-terminated polycaprolactone has been developed for tissue engineering applications using a one-step synthesis and functionalization method based on ring opening polymerization (ROP) of ?-Caprolactone, with hydroxyl ethyl vinyl ether (HEVE) acting both as the initiator of ROP and as photo-curable functional group. The proposed method employs a catalyst based on aluminium, instead of the most popular Tin(II) 2-ethylhexanoate, to reduce the cytotoxicity. Following the synthesis of the vinyl-terminated polycaprolactone, its reaction with fumaryl chloride (FuCl) results in a divinyl-fumarate polycaprolactone (VPCLF). The polymers obtained were thoroughly characterized using Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) techniques. The polymer has been successfully employed, in combination with N-vinyl pyrrolidone (NVP), to fabricate films and computer-designed porous scaffolds by micro-stereolithography (?-SL) with gyroid and diamond architectures. Characterization of the networks indicated the influence of NVP content on the network properties. Human mesenchymal stem cells adhered and spread onto VPCLF/NVP networks showing good biological properties and no cytotoxic effect. Copyright © 2016 John Wiley & Sons, Ltd.

The presence of "free" trimethylaluminum (TMA) in methylalumoxane (MAO) solutions can be highly detrimental to the performance of metallocene and "post-metallocene" olefin polymerization catalysts. The most used strategy to remove "free" TMA is to evaporate MAO solutions to dryness, until a free-flowing white powder ("solid MAO") is left. This procedure is tedious and potentially hazardous, because in some cases the distillate is a concentrated hydrocarbon solution of TMA. Moreover, "solid MAO" is poorly soluble in common polymerization media, and once in solution it can regenerate TMA to some extent. This communication reports on a facile alternative, which consists in the controlled addition of a sterically hindered phenol, such as 2,6-di-tert-butylphenol, effectively trapping "free" TMA. We show here that 2,6-di-tert-butylphenol/MAO solutions activate equally well the dichloro-precursors of well-known zirconocene and bis(phenoxyimine)Ti catalysts, and that their use in propene polymerization results in a substantially higher productivity, polymer stereoregularity, and/or average molecular mass compared with activation by MAO alone.

The term disentangled refers to polymers with fewer entanglements in the amorphous regions, a metastable condition that can significantly affect the material&rsquo, s properties and processing behavior. The lower entanglement density in ultra-high molecular weight polyethylene (dis-UHMWPE) facilitates the solid-state processability into uniaxially-oriented specimens reaching very high draw ratios and crystallinities. In this study, Au/dis-UHMWPE nanocomposites were formulated and processed at variable draw ratios. Polarized light microscopy suggests gold nanoparticles are oriented in arrays following the drawing of polymer chains. The structural features, upon orientation, are studied by means of Raman spectroscopy, wide- and small-angle X-ray scattering, and near-infrared spectrophotometry. Crystallinity is found to increase by 15%, as calculated by wide-angle X-ray scattering. The change in optical absorbance in the visible spectrum indicates that, with orientation, the average size of gold aggregates increases, supported quantitatively by small-angle X-ray scattering. Since the gold nanoparticles are expected to be found within amorphous chain segments, the aforementioned findings are attributed to the increase of crystallinity and thus the decrease of available (amorphous) space.

After five decades of largely serendipitous (albeit formidable) progress, catalyst design in Ziegler–Natta olefin polymerization, i.e., the rational implementation of new active species to target predetermined polyolefin architectures, has ultimately become a realistic ambition, thanks to a much deeper fundamental understanding and major advances in the tools of computational chemistry. In this article, we discuss, as a case history, a unique class of stereorigid C 2 -symmetric bis(phenoxy-amine)Zr(IV) catalysts with controlled kinetic behavior. A large variety of polypropylene microstructures have been obtained with these catalysts by modulating the steric demand of one key substituent, without altering the nature and symmetry of the ancillary ligand framework, under the guidance of computer modeling. This unusual achievement is relevant per se and for the perspective implications in catalyst discovery.

In this communication, we report on the direct measurement of dormant chain concentration and of the relative reactivity of authentic primary and secondary Zr-polymeryls toward propene, ethene, and H2 under practical conditions for a new highly regio- and stereoselective postmetallocene polymerization catalyst with controlled kinetic behavior. The results, in particular, confirm the poor reactivity toward propene of secondary M-polymeryls and the possible accumulation of dormant chains in propene homopolymerization.

The block copolymerization polypropylene under highly isotactic stereocontrol, using a new catalyst obtained by means of rational ligand design, was discussed. Moderately isotactic polypropylenes of very low average molecular mass in reasonable yields was obtained. NMR analysis of samples prepared at different propene concentrations revealed a 1,2 insertion regiochemistry and pointed to trans-alkylation by the Al-alkyl and β-H transfer to the monomer as the dominating chain transfer pathways. The results are in agreement with quantum mechanics/molecular mechanics (QM/MM) calculations.

The propene/ethene-[1-13C] copolymerization method has been applied to measure precisely the regioselectivity of two modern MgCl2-supported Ziegler-Natta catalyst systems for the industrial production of isotactic polypropylene, namely MgCl2/di(isobutyl)-o-phthalate/TiCl4-cyclohexylmethyldimethoxysilane/AlR3 (1) and MgCl2/2,2-di(isobutyl)-1,3-dimethoxypropane/TiCl4-AlR3 (2). System 2 turned out to be slightly less regioselective than system 1 (on average, 0.26% 2,1 misinsertions instead of 0.18%), but the distribution of the regiodefects throughout the polymer was found to be more uniform, most likely as a result of a lower differentiation of the active species. This provides a simple explanation for the different response of the two catalysts to molecular hydrogen as a chain transfer agent. In system 1, indeed, part of the active species are almost completely regioselective, which means that H2 finds very few preferential "cutting points" in the form of growing chains with a sterically hindered 2,1 last-inserted unit; therefore, a higher H2 partial pressure is neededcompared with system 2in order to achieve the same decrease of average polymer molecular mass.

The synthesis of PE-block-iPP with a Zr-based postmetallocene catalyst was carried out. 13C NMR provided direct and complete evidence of a true block nature for a polyolefin-based material containing a polypropylene block of any tacticity.

In a previous letter, we proposed the synthesis and C-13 NMR characterization of propene/ethene-[1-C-13] copolymers at low ethene-[1-C-13] content as a convenient tool for measuring the regioselectivity of coordinated propene polyinsertion, in case 13C NMR fails to detect the regiomistakes in propene homopolymers. In the present article, we introduce the foundations of the approach in more detail, and illustrate how its scope can be extended to the evaluation of catalyst "dormancy" due to regiochemical monomer inversion. The method was calibrated for two well-known C-2-symmetric ansa-metallocene catalysts (namely, rac-Me2Si(1-indenyl)(2)ZrCl2 and rac-Me2Si(2-Me-4-phenyl-1-indenyl)(2)ZrCl2), by means of a cross-check with results of a C-13 NMR characterization of samples of poly(propene-[3-C-13]) prepared under corresponding experimental conditions. In particular, it was proved that the fraction of consecutive 2,1 insertions in propene homopolymerization promoted by the quoted catalysts, although nonzero, is low enough not to invalidate the propene/ethene-[1-C-13] copolymerization approach.

We report here the presence of N6-methyladenine (MeAde) in the macronuclear DNA (maDNA) of Blepharisma japonicum vegetative cells. We have further investigated the relationship between DNA methylation and cell union in cells activated for conjugation. Such activation was induced by treating cells of mating type I with complementary gamone 2. We found a reduction of about 24% of MeAde content in gamone-treated cells ready for cell union. First indications of the presence and reduction of MeAde content came from electrophoresis of maDNA digested by appropriate restriction endonucleases. Chromatographic determination of the amount of methylated base by HPLC substantiated these observations. In vegetative cells, 1.576 ± 0.02% of total adenine was found to be methylated as opposed to 1.193 ± 0.04% in activated cells. The HPLC analysis of maDNA also revealed a peak with a retention time corresponding to that of 5-hydroxymethyluracil, already found in some species of dinoflagellates. In that gamone treatment is correlated with a differential gene expression (indicated by a differential RNA and protein synthesis), our results suggest that there is a relationship between macronuclear genome activation and demethylation of maDNA. This is the first report of a correlation between gene activation and adenine demethylation in a eukaryotic organism.