Reversible click chemistry at the service of macromolecular materials

The application of the reversible Diels-Alder (DA) reaction to the realm of furan polymers has recently bloomed, because of its potential for the preparation of a wide variety of novel macromolecular materials based on renewable resources, possessing, among other properties, thermoreversible, mendable and recycling features. In this study, the synthesis and characterisation of novel furan-maleimide monomers, viz. AB-type molecules, and their polycondensation by means of the DA reaction, are presented. These systems represent an interesting alternative to the traditional linear DA polycondensations, because they ensure the ideal initial stoichiometry. The behaviour of two A-B monomers was investigated with the maleimide group protected in the form of a furan-DA adduct in order to obtain a stable monomer and thus avoid premature polymerization. Their polycondensation was then followed after the in situ deprotection at high temperature, followed by the cooling to the appropriate temperature for the DA polymerization to occur.FCT - SFRH/BD/ 28271/2006REEQ/515/CTM/2005POCI 2010FEDE

The functions of social interaction in the knowledge-creative economy: between co-presence and ICT-mediated social relations

This article investigates the role and functions of interaction among knowledge-creative workers in Milan. While a large body of literature supports the relevance of co-presence for the building of social capital in creative scenes, a growing body of empirical and theoretical research shows in fact that, under certain circumstances, social relations mediated by digital tools are equally important. The extent to which professionals in these industries are embedded in \u201cspaces\u201d which are physical as well as digital, and how these have come to be so, remains nevertheless an under-explored research question. Building on findings from two distinct qualitative researches on knowledge-creative workers in Milan, undertaken in 2008 and 2011-2013, it is here argued that knowledge-creative professionals are embedded in a wider \u201cspace\u201d of relations where exchanges mediated via ICTs productively intertwine with face-to-face interaction to determine new ways of searching for jobs and practicing work. The paper highlights what changes when proximity becomes physical and digital as a mixture of face-to-face and ICT-mediated interaction, and discusses contradictions and implications of their blending, showing the necessity to overcome the rigid distinction between face-to-face and digital interaction that still characterises the empirical study of knowledge-creative economies

Robust Control Architecture for Waste Heat Harvesting with Non-Inverting Buck-Boost Converter

Thermoelectric generators (TEG) can be used to harvest wasted heat. TEGs are characterized by a wide output voltage range and a considerable output resistance leading to a maximum power point dependent on the working temperature. Non-Inverting Buck-Boost converter is used to manage, from one side, the wide voltage range, and from the other a battery. This article investigates a robust control architecture to recover the maximum energy from the exhaust's heat avoiding instability issues and maximizing converter efficiency

Preferential expression of the transcription coactivator HTIF1alpha gene in acute myeloid leukemia and MDS-related AML

HTIF1α, a transcription coactivator which is able to mediate RARα activity and functionally interact with PML, is encoded by a gene on chromosome 7q32–34, which is a critical region in acute myeloid leukemias (AML). With the assumption that this gene may be related to AML, we investigated the HTIF1α DNA structure and RNA expression in leukemic cells from 36 M1–M5 AML patients (28 ‘de novo’ and eight ‘secondary’ to myelodysplastic syndrome (MDS)). Abnormal HTIF1α DNA fragments were never found, whereas loss of HTIF1α DNA was observed in the patients with chromosome 7q32 deletion and translocation, and in one case without detectable chromosome 7 abnormality. HTIF1α RNA was found in acute myelocytic leukemic blasts, and was almost undetectable in normal mononuclear cells. The expression varied among the patients: higher in M1 to M3 subtypes, with the highest values in M1; low levels were constantly observed in M4 and M5 AML. In addition, HTIF1α was significantly overexpressed in MDS-related AML (MDR-AML), but not in MDS. We also found that HTIF1α expression was high in myeloid cell lines. In myeloblastic HL60 and promyelocytic NB4 cells, induced to differentiate along the monocytic–macrophage pathway by TPA or vitamin D3, HTIF1α expression decreased, whereas it was maintained at high levels on induction to granulocytic differentiation by RA or DMSO. In K562 cells, HTIF1α RNA levels did not change after hemin-induced erythroid differentiation. These results suggest that HTIF1α could play a role in myeloid differentiation, being distinctly regulated in hematopoietic lineages

Spherical orbit closures in simple projective spaces and their normalizations

Let G be a simply connected semisimple algebraic group over an algebraically closed field k of characteristic 0 and let V be a rational simple G-module of finite dimension. If G/H \subset P(V) is a spherical orbit and if X is its closure, then we describe the orbits of X and those of its normalization. If moreover the wonderful completion of G/H is strict, then we give necessary and sufficient combinatorial conditions so that the normalization morphism is a homeomorphism. Such conditions are trivially fulfilled if G is simply laced or if H is a symmetric subgroup.Comment: 24 pages, LaTeX. v4: Final version, to appear in Transformation Groups. Simplified some proofs and corrected minor mistakes, added references. v3: major changes due to a mistake in previous version

Cambios en la estructura de la comunidad y contenido de carbono orgánico del meio- y macrobentos entre las áreas de planicies de marea y marismas colonizadas por Spartina alterniflora en el Estuario de Bahía Blanca (Atlántico SO)

Salt marshes are regarded as among the most productive coastal ecosystems, important “blue carbon” sinks and a support for benthic communities with large abundances, whose structure may be strongly influenced by salt marsh vegetation. During the last few decades, Spartina alterniflora has been colonizing bare mudflats in the Bahía Blanca estuary, and a large increase in the area covered by salt marshes has been reported. This colonization can strongly influence the structure of benthic fauna and its role in the carbon cycle. The hypothesis of this study was that the community structure and the organic carbon contained in the meio- and macrobenthos change between tidal flats and salt marshes recently colonized by S. alterniflora. Response variables studied to compare the tidal flat and salt marsh were density, biomass and production to biomass (P/B) ratio of macro- and meiobenthos. Density and biomass of Gastropoda and P/B ratio of Nematoda were higher on the salt marsh than on the tidal flat. By contrast, density and biomass of Polychaeta were higher on the tidal flat. These results suggest that the expansion of S. alterniflora marshes on tidal flats produces changes in the structure of the macro- and meiobenthos community (taxonomic composition and biomass) that have an influence on carbon cycling.Las marismas son consideradas uno de los ecosistemas costeros más productivos, importantes sumideros de “carbono azul” y soporte para comunidades bentónicas con grandes abundancias, cuya estructura puede estar fuertemente influenciada por la vegetación de las marismas. Durante las últimas décadas, Spartina alterniflora ha estado colonizando las planicies de mareas sin vegetación en el estuario de Bahía Blanca, reportándose un gran incremento del área cubierta por las marismas. Esta colonización puede influir fuertemente en la estructura de la fauna bentónica y en su rol en el ciclo de carbono. La hipótesis de este estudio fue que la estructura de la comunidad y el carbono orgánico contenido en el meiobentos y macrobentos cambian entre las planicies de marea y las marismas recientemente colonizadas por S. alterniflora. Las variables de respuesta estudiadas para comparar la planicie de marea y la marisma fueron la densidad, biomasa y la relación producción/biomasa (P/B) del macrobentos y meiobentos. La densidad y biomasa de Gastropoda y la relación P/B de Nematoda fueron mayores en la marisma que en la planicie de marea. Por el contrario, la densidad y biomasa de Polychaeta fueron mayores en la planicie de marea. Estos resultados sugieren que la expansión de las marismas de S. alterniflora sobre las planicies de marea genera cambios en la estructura de la comunidad del macrobentos y meiobentos (composición taxonómica y biomasa) que influyen en el ciclo del carbono

On the limiting mechanism of irradiation enhancement of I/sub c/

Irradiation may significantly increase I/sub c/ in HTS. A systematic pattern occurs: R=I/sub c/(afterirr.)/I/sub c/(beforeirr.) increases at low defect density, d. It reaches a peak, and then it falls below 1 at high d. The pinning center mechanism, which causes R to increase, has been extensively studied. The falloff in R has not. It has been considered a secondary effect. Here, we will show that the fall-off plays an important role in determining the maximum I/sub c/ enhancement achievable. A phenomenological model to describe the R-vs.-d curve, over the entire d range, is proposed. The idea is that R is the product of two competing effects. (i) Irradiation damage acts as pinning centers, hence increases critical current density, J/sub c/. (ii) Damage reduces the flow-area. Hence, it decreases the net critical current. Data on U/n processed Bi-2223 tapes are fitted to this model. The fitting indicates: (1) the reduction of the flow-area accounts for the majority of the R falloff; and (2) It is sufficient to describe J/sub c/ enhancement as linear with d, and it depending on field and temperature only through the ratio b=B/B/sub irr/, where B/sub irr/ is the irreversible field before irradiation

Determination of the Hydroxy and Carboxylic Acid Groups in Natural Complex Mixtures of Hydroxy Fatty Acids by (1)H Nuclear Magnetic Resonance Spectroscopy

The use of trichloroacetyl isocyanate (TAI) to mark both hydroxyl and carboxyl groups borne by the hydrolysis or methanolysis of suberin fragments (a complex mixture of hydroxy fatty acids), allowed the quantitative assessment of the ratio between carboxyl and hydroxy groups, as well as the ratio between primary and secondary hydroxy groups, to be carried out reliably by (1)H nuclear magnetic resonance (NMR) spectroscopy. All the samples thus analyzed displayed an excess of CO(2)H (or CO(2)CH(3)) functions with respect to the OH counterparts, albeit to a variable extent, depending on the procedure adopted to isolate the suberin fragments. The precise knowledge of the molar ratio of these two reactive moieties is fundamental for the correct utilization of suberin monomers in polymerization reactions leading to aliphatic polyesters.FCT - SFRH/ BD/38890/200