Tin and tin-titanium as catalyst components for reversible hydrogen storage of sodium aluminium hydride

This paper is concerned with the effects of adding tin and/or titanium dopant to sodium aluminium hydride for both dehydrogenation and re-hydrogenation reactions during their reversible storage of molecular hydrogen. Temperature programmed decomposition (TPD) measurements show that the dehydrogenation kinetics of NaAlH4 are significantly enhanced upon doping the material with 2 mol% of tributyltin hydride, Sn(Bu)(3)H but the tin catalyst dopant is shown to be inferior than titanium. On the other hand, in this preliminary work, a significant synergetic catalytic effect is clearly revealed in material co-doped with both titanium and tin catalysts which shows the highest reversible rates of dehydrogenation and re-hydrogenation (after their hydrogen depletion). The re-hydrogenation rates of depleted Sn/Ti/NaAlH4 evaluated at both 9.5 and 140 bars hydrogen are also found to be favourable compared to the Ti/NaAlH4, which clearly suggest the importance of the catalyst choice. Basing on these results some mechanistic insights for the catalytic reversible dehydrogenation and re-hydrogenation processes of Sn/Ti/NaAlH4 are therefore made. (C) 2006 Elsevier Ltd. All rights reserved.

On the effects of non-tariff measures on Brazilian exports

This article proposes an alternative methodology for estimating the effects of non-tariff measures on trade flows, based on the recent literature on gravity models. A two-stage Heckman selection model is applied to the case of Brazilian exports, where the second stage gravity equation is theoretically grounded on the seminal Melitz model of heterogeneous firms. This extended gravity equation highlights the role played by zero trade flows as well as firm heterogeneity in explaining bilateral trade among countries, two factors usually omitted in traditional gravity specifications found in previous literature. Last, it also proposes a economic rationale for the effects of NTM on trade flows, helping to shed some light on its main operating channels under a rather simple Cournot’s duopolistic competition framework.

On the effects of non tariff measures on Brazilian exports

This article proposes an alternative methodology for estimating the effects of non-tariff measures on trade flows, based on the recent literature on gravity models. A two-stage Heckman selection model is applied to the case of Brazilian exports, where the second stage gravity equation is theoretically grounded on the seminal Melitz model of heterogeneous firms. This extended gravity equation highlights the role played by zero trade flows as well as firm heterogeneity in explaining bilateral trade among countries, two factors usually omitted in traditional gravity specifications found in previous literature. Last, it also proposes a economic rationale for the effects of NTM on trade flows, helping to shed some light on its main operating channels under a rather simple Cournot’s duopolistic competition framework

Tracheobronchial consequences of the use of heat and moisture exchangers in dogs

Purpose: To determine the effect of heat and moisture exchange (HME) on the tracheobronchial tree (TBT) using a unidirectional anesthesic circuit with or without CO2 absorber and high or low fresh gas flow (FGF), in dogs. Methods: Thirty-two dogs were randomly allocated to four groups: G1 (n = 8) valvular circuit without CO2 absorber and high FGF (5 L·min-1); G2 (n = 8) as G1 with HME; G3 (n = 8) circuit with CO2 absorber with a low FGF (1 L·min-1); G4 (n = 8) as G3 with HME. Anesthesia was induced and maintained with pentobarbital. Tympanic temperature (TT), inhaled gas temperature (IGT), relative (RH) and absolute humidity (AH) of inhaled gas were measured at 15 (control), 60, 120 and 180 min of controlled ventilation. Dogs were euthanized and biopsies in the areas of TBT were performed by scanning electron microscopy. Results: The G2 and G4 groups showed the highest AH (>20 mgH2O·L-1) and G1 the lowest (< 10 mgH2O·L-1) and G3 was intermediate (<20 mgH2O·L-1) (P < 0.01). There was no difference of TT and IGT among groups. Alterations of the mucociliary system were greatest in G1, least in G2 and G4, and intermediate in G3. Conclusion: In dogs, introduction of HME to a unidirectional anesthetic circuit with/without CO2 absorber and high or low FGF preserved humidity of inspired gases. HME attenuated but did not prevent alterations of the mucociliary system of the TBT.

Organotins: A review of their reproductive toxicity, biochemistry, and environmental fate

The review purposes are to (1) evaluate the experimental evidence for adverse effects on reproduction and metabolism and (2) identify the current knowledge of analytical procedures, biochemistry and environmental aspects relating to organotins. Organotins are pollutants that are used as biocides in antifouling paints. They produce endocrine-disrupting effects in mollusks, such as imposex. In rodents, organotin exposure induces developmental and reproductive toxicity as well as alteration of metabolic homeostasis through its action as an obesogen. The adverse effects that appear in rodents have raised concerns about organotins' potential health risk to humans in relation to organotin exposure. At present, triorganotin, such as tributyltin, have been demonstrated to produce imposex, and mammalian reproductive and metabolic toxicity. For most mammals, triorganotin exposure predominantly occurs through the ingestion, and this compound can cross the placenta. With these risks in mind, it is important to improve our knowledge of organotins' effects on environmental health. © 2012 Elsevier Inc.

Matrix effect on butyltin analysis of sediments and fish tissues by GC-PFPD

Butyltin (BTs) quantification in environmental matrices can be affected by interfering species found primarily in complex matrices,such as sediment and biota tissues. This study investigated matrix effects in analytical procedures for butyltin (TBT,DBT and MBT) quantification and speciation in sediments and in two fish tissues (gill and liver) by gas chromatography with pulsed flame photometric detection (GC-PFPD) analysis. Unlike sediment samples,tissues exhibited a significant matrix effect,thus,the quantification should be made by curve over matrix to avoid quantification errors and loss of analytical accuracy. © 2013 Sociedade Brasileira de Química.

Estudos sobre a ocorrência de compostos organoestânicos em sedimentos marinhos superficiais na costa do estado de São Paulo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Differential organotin sensitivity in two Leucozonia species from a ship traffic area in southeastern Brazil

Tributyltin exposure is the primary cause of imposex development in gastropods, making them excellent bioindicators. The present research represents the first examination of butyltin (BT) contamination in surface sediments associated with imposex in Leucozonia nassa and L. ocellata in a harbour complex area in Espirito Santo, southeastern Brazil. The objectives of this study were to evaluate the organotin pollution in the area and to assess the sensitivity of both species to BT pollution through imposex development. Specimens were collected between 2007 and 2010 and the sediments were sampled in 2007. Imposex intensity was evaluated based on the percentage of imposexed females, the relative penis length index (RPLI) and the average value of the vas deferens sequence index (VDSI). BTs were analysed using gas chromatography equipped with a pulsed flame photometric detector (PFPD). The results demonstrated the occurrence of elevated concentrations of BTs in the sediment ranging from 383.7 to 7172.9 ng Sn g(-1), indicating a severe contamination of the area, which was confirmed by the biological monitoring results. Our findings also indicated that L. ocellata is a less sensitive species than L. nassa and that this differential sensitivity plays a key role in the distributions of the populations of both species in the studied area.

As barreiras comerciais e o meio ambiente: o comércio brasileiro com a América do Norte e União Europeia diante de notificações ambientais

Os movimentos conservacionistas, desde a década de 80, impulsionam a predileção por produtos cujos fabricantes visam à sustentabilidade, ou seja, à degradação mínima do meio ambiente na produção e no consumo da sociedade atual, de modo a não comprometer os recursos naturais para as gerações futuras. Essa tendência fez países, a início os desenvolvidos, criarem regras, regulamentos ou normas de produção visando à preservação ambiental, a serem seguidas na produção por outros países com quem desejam estabelecer comércio. O que pode se configurar, principalmente para os países em desenvolvimento, uma barreira comercial - geralmente não tarifária - difícil de transpassar. O Brasil, como país em desenvolvimento e grande fornecedor de produtos primários para o exterior, enfrenta frequentemente essas barreiras comerciais com propósitos ambientais, muitas vezes de forma não planejada. Isso provoca, especialmente em pequenas e médias empresas, um aumento dos custos de produção e dificuldades de competir no mercado internacional. Este trabalho procura expor os principais produtos que sofrem notificações ambientais, mais especificamente dos Acordos SPS e TBT, e estabelecer uma relação entre essas notificações e a pauta exportadora brasileira durante o período de 1997 a 2014

Moluscos gasterópodos como bioindicadores en el Archipiélago canario: de procesos naturales a causas antropogénicas

Se han eliminado páginas en blanco

Organismi acquatici e ambiente: meccanismi biochimici di interazione, risposta e adattamento

The research is focused on the relationship between some Mg2+-dependent ATPase activities of plasma- and mitochondrial membranes from tissues of cultured marine bivalve molluscs and potentially stressful environmental conditions, such as the exposure to contaminants both of natural origin (ammonia nitrogen, the main contaminant of aquaculture plants) and of anthropic source (alkyltins). The two filter-feeding bivalve species selected colonize different habitats: the common mussel Mytilus galloprovincialis binds to hard substrates and the Philippine clam Tapes philippinarum burrows into sea bottom sandy beds. The choice of typical species of coastal waters, extremely suitable for environmental studies due to their features of poor motility, resistance to transport and great filtering efficiency, may constitute a model to evaluate responses to contaminants of membrane-bound enzyme activities involved in key biochemical mechanisms, namely cell ionic regulation and mitochondrial energy production. In vitro and in vitro approaches have been pursued. In vitro assays were carried out by adding the contaminants (NH4Cl and alkyltins) directly to the ATPase reaction media. In vivo experiments were carried out by exposing mussels to various tributyl tin (TBT) concentrations under controlled conditions in aquaria. ATPase activities were determined spectrophotometrically according to the principles of the method of Fiske and Subbarow (1925). The main results obtained are detailed below. In Tapes philippinarum the interaction of NH4 +, the main form of ammonia nitrogen at physiological and seawater pHs, with the Na,K-ATPase and the ouabaininsensitive Na-ATPase was investigated in vitro on gill and mantle microsomal membranes. The proven replacement by NH4 +of K+ in the activation of the Na,KATPase and of Na+ in the activation of the ouabain-insensitive ATPase displayed similar enzyme affinity for the substituted cation. on the one hand this finding may represent one of the possible mechanisms of ammonia toxicity and, on the other, it supports the hypothesis that NH4 + can be transported across the plasma membrane through the two ATPases. In this case both microsomal ATPases may be involved and co-operate, at least under peculiar circumstances, to nitrogen excretion and ammonia detoxification mechanisms in bivalve molluscs. The two ATPase activities stimulated by NH4 + maintained their typical response to the glycoside ouabain, specific inhibitor of the Na,K-ATPase, being the Na++ NH4 +-activated ATPase even more susceptive to the inhibitor and the ouabain-insensitive ATPase activity activated indifferently by Na+ or NH4 + unaffected by up to 10-2 M ouabain. In vitro assays were carried out to evaluate the response of the two Na-dependent ATPases to organotins in clams and mussels and to investigate the interaction of TBT with mussel mitochondrial oligomycin-sensitive Mg-ATPase. Since no literature data were available, the optimal assay conditions and oligomycin sensitivity of mussel mitochondrial MgATPase were determined. In T. philippinarum the ouabain-insensitive Na-ATPase was found to be refractory to TBT both in the gills and in the mantle, whereas the Na,K-ATPase was progressively inhibited by increasing TBT doses; the enzyme inhibition was more pronounced in the gills than in the mantle. In both tissues of M. galloprovincialis the Na,K-ATPase inhibition by alkyltins decreased in the order TBT>DBT(dibutyltin)>>MBT(monobutyltin)=TeET(tetraethyltin) (no effect). Mussel Na-ATPase confirmed its refractorimess to TBT and derivatives both in the gills and in the mantle. These results indicate that the Na,K-ATPase inhibition decreases as the number of alkyl chains bound to tin decreases; however a certain polarity of the organotin molecule is required to yield Na,K-ATPase inhibition, since no enzyme inhibition occurred in the presence of tetraalkyl-substituted derivatives such as TeET . Assays carried out in the presence of the dithioerythritol (DTE) pointed out that the sulphhydrylic agent is capable to prevent the Na,K-ATPase inhibition by TBT, thus suggesting that the inhibitor may link to -SH groups of the enzyme complex.. Finally, the different effect of alkyltins on the two Na-dependent ATPases may constitute a further tool to differentiate between the two enzyme activities. These results add to the wealth of literature data describing different responses of the two enzyme activities to endogenous and exogenous modulators . Mussel mitochondrial Mg-ATPase was also found to be in vitro inhibited by TBT both in the gills and in the mantle: the enzyme inhibition followed non competitive kinetics. The failed effect of DTE pointed out that in this case the interaction of TBT with the enzyme complex is probably different from that with the Na,K-ATPase. The results are consistent with literature data showing that alkyltin may interact with enzyme structures with different mechanisms. Mussel exposure to different TBT sublethal doses in aquaria was carried out for 120 hours. Two samplings (after 24 and 120 hrs) were performed in order to evaluate a short-term response of gill and mantle Na,K-ATPase, ouabain-insensitive Na-ATPase and Mg-ATPase activities. The in vivo response to the contaminants of the enzyme activities under study was shown to be partially different from that pointed out in the in vitro assays. Mitochondrial Mg-ATPase activity appeared to be activated in TBTexposed mussels with respect to control ones, thus confirming the complexity of evaluating in vivo responses of the enzyme activities to contaminants, due to possible interactions of toxicants with molluscan metabolism. Concluding, the whole of data point out that microsomal and mitochondrial ATPase activities of bivalve molluscs are generally responsive to environmental contaminants and suggest that in some cases membrane-bound enzyme activities may represent the molecular target of their toxicity. Since the Na,K-ATPase, the Na-ATPase and the Mg-ATPase activities are poorly studied in marine bivalves, this research may contribute to enlarge knowledge in this quite unexplored field.

Synthetic and mechanistic investigation of new radical processes: reaction of organic azides with group-XIII Lewis acids

Dichloroindium hydride revealed to be a valid alternative to tributyltin hydride for radical reduction of organic (alkyl, aryl, acyl, solfonyl) azides. The new approach entails mild reaction conditions and provides high yields of the corresponding amines and amides, also showing high degrees of selectivity. The system dichloroindium hydride / azides can be utilised in fivemembered ring closures of g-azidonitriles, as a new source of aminyl radicals for the attractive synthesis of interesting amidine compounds in the absence of both toxic reagents and tedious purification procedures. Allylindium dichloride seems a good substitute for dichloroindium hydride for generation of indium centred radicals under photolytic conditions, since it allows allylation of electrophilic azides (e.g. phenylsulfonyl azide) and halogen or ester δ-substituted azides, the latter through a 1,5-H transfer rearrangement mechanism. Evidences of the radical nature of the reactions mechanism were provided by ESR spectroscopy, furthermore the same technique, allowed to discover that the reaction of azides with indium trichloride and other group XIII Lewis acids, in particular gallium trichloride, gives rise to strongly coloured, persistent paramagnetic species, whose structure is consistent with the radical cation of the head-to-tail dimer of the aniline corresponding to the starting azide.

Bcl-2-homologe Proteine aus dem Schwamm Geodia cydonium

'Bcl-2-homologe Proteine aus dem Schwamm Geodia cydonium: Klonierung, Charakterisierung und Funktionsanalyse von Apoptose-Regulatoren der Porifera'. Auf der Suche nach der molekularbiologischen Grundlage der Apoptose in den Porifera, dem phylogenetisch ältesten Metazoen-Tierstamm, wurden Mitglieder der apoptoseregulatorischen Bcl?2 Familie unter Anwendung diverser Techniken im Schwamm G. cydonium identifiziert: GCBHP1 und GCBHP2. Detaillierte Analysen offenbarten Bcl-2-charakteristische Signaturen sowie eine durch apoptotische Stimuli induzierbare Expression. Die parallele HSP70-Induktion zeugte von der GCBHP2-Expression als Teil einer antiapoptotischen Streßantwort zum Schutz des Organismus'. Die kontinuierliche Transkription des im Rahmen dieser Arbeit gleichfalls klonierten Proliferationsmarkers SEP1 veranschaulichte zudem die Effektivität dieser Streßreaktion. Mit der Herstellung eines rekombinanten Proteins und der Gewinnung eines Antiserums konnte auch die streßinduzierte Proteinexpression des GCBHP2 verfolgt werden. Zum Zweck der Funktionsstudie wurden Säugetierzellen (HEK-293, NIH/3T3) mit einem GCBHP2-Konstrukt stabil transfiziert und auf die Expression des Schwammproteins untersucht. Diese Zellen unterschieden sich bereits phänotypisch von mock-transfizierten Zellen. Immunzytochemische Untersuchungen enthüllten eine für antiapoptotische Bcl-2 Proteine charakteristische Assoziation mit Mitochondrien. Unter dem Einfluß zweier apoptotischer Stimuli wurde für GCBHP2-transfizierte Zellen eine vierzehn-/sechsmal höhere Vitalität und eine reduzierte Aktivierung der Caspase-Kaskade registriert (im Vergleich zu mock-transfizierten Kontrollen). Somit wurde der antiapoptotische Charakter des GCBHP2 und die Existenz apoptotischer Mechanismen in den Porifera bestätigt.

The EU and Dispute Settlement within the WTO: a strategy for the protection of the Union’s autonomy in the domestic regulation of goods?

Oggetto della ricerca è l’accertamento dell’esistenza, nonché la definizione, della strategia dall’UE in materia di controversie commerciali aventi ad oggetto l’interpretazione e l’applicazione di norme facenti capo agli Accordi OMC in materia di misure sanitarie e di barriere tecniche al commercio. Nella prima parte della tesi, si ricostruiscono gli obbiettivi perseguiti dall’UE in materia di controversie SPS e TBT. In questo contesto, un’importanza di primo piano è attribuita alla difesa dell’autonomia regolamentare dell’Unione. Ad essa si riconduce la prassi UE finalizzata a prevenire il sorgere di controversie sul piano bilaterale attraverso la conclusione di accordi di mutuo riconoscimento, la cui portata ella sottolinea essere tuttavia limitata. L’analisi di cinque controversie sorte in ambito OMC di cui l’Unione è o è stata parte convenuta e che si fondano su presunte o accertate violazioni delle norme facenti capo ai due accordi menzionati consente di classificare gli argomenti giuridici avanzati dall’Unione nel contesto di tali controversie. Nella seconda parte della ricerca, la candidata identifica i mezzi a servizio della strategia UE, in primo luogo, attraverso l’analisi del quadro giuridico relativo alla partecipazione dell’Unione e degli Stati Membri al sistema OMC di risoluzione delle controversie; in secondo luogo, attraverso lo studio, da un lato, dello status delle norme OMC nell’ordinamento UE e, dall’altro, degli effetti delle pronunce dell’Organo di Risoluzione delle Controversie e della questione della responsabilità dell’Unione per violazione del diritto OMC. Sulla base del lavoro di ricerca svolto, si conclude che una strategia dell’UE esiste nella misura in cui l’Unione persegue l’obbiettivo di preservare la propria autonomia regolamentare attraverso, anche se non esclusivamente, gli strumenti afferenti all’ordine giuridico interno analizzati nella seconda parte. La candidata conclude altresì che la riforma del diritto delle relazioni esterne operata dal Trattato di Lisbona può indurre un cambiamento di tale strategia.

Optimization of purification procedures in organic semiconductor synthesis for improving the performances of organic field-effect transistors

The aim of the research activity focused on the investigation of the correlation between the degree of purity in terms of chemical dopants in organic small molecule semiconductors and their electrical and optoelectronic performances once introduced as active material in devices. The first step of the work was addressed to the study of the electrical performances variation of two commercial organic semiconductors after being processed by means of thermal sublimation process. In particular, the p-type 2,2′′′-Dihexyl-2,2′:5′,2′′:5′′,2′′′-quaterthiophene (DH4T) semiconductor and the n-type 2,2′′′- Perfluoro-Dihexyl-2,2′:5′,2′′:5′′,2′′′-quaterthiophene (DFH4T) semiconductor underwent several sublimation cycles, with consequent improvement of the electrical performances in terms of charge mobility and threshold voltage, highlighting the benefits brought by this treatment to the electric properties of the discussed semiconductors in OFET devices by the removal of residual impurities. The second step consisted in the provision of a metal-free synthesis of DH4T, which was successfully prepared without organometallic reagents or catalysts in collaboration with Dr. Manuela Melucci from ISOF-CNR Institute in Bologna. Indeed the experimental work demonstrated that those compounds are responsible for the electrical degradation by intentionally doping the semiconductor obtained by metal-free method by Tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) and Tributyltin chloride (Bu3SnCl), as well as with an organic impurity, like 5-hexyl-2,2':5',2''-terthiophene (HexT3) at, in different concentrations (1, 5 and 10% w/w). After completing the entire evaluation process loop, from fabricating OFET devices by vacuum sublimation with implemented intentionally-doped batches to the final electrical characterization in inherent-atmosphere conditions, commercial DH4T, metal-free DH4T and the intentionally-doped DH4T were systematically compared. Indeed, the fabrication of OFET based on doped DH4T clearly pointed out that the vacuum sublimation is still an inherent and efficient purification method for crude semiconductors, but also a reliable way to fabricate high performing devices.