New stereoselective routes to macrocyclic ligands

Reaction of bis(ethane-1,2-diamine)copper(II) with acetaldehyde and nitromethane in methanol leads, stereoselectively, to the new macrocyclic complex (trans-5(R),7(R),12(S),14(S))-tetramethyl-6,13-dinitro-1,4,8,11-tetraazacyclotetradecane)copper(II) perchlorate alpha-[CuL1](ClO4)(2) in good yield. Reduction of the nitro groups affords the hexaamine (L-2), which was crystallized as [H4L2](ClO4)(4) . 2H(2)O and characterized by an X-ray crystal structure study (monoclinic P2(1)/n, a = 9.763(2) Angstrom, b = 12.1988(7) Angstrom, c = 13.036(2) Angstrom, beta = 105.668(7)degrees, Z = 2) and complexed with Cu-II to produce the complex beta-[Cu(H2L2)](ClO4)(4) . 2H(2)O, which has also been characterized by X-ray crystallography (monoclinic P2(1)/n, a = 9.717(4) Angstrom, b = 12.174(2) Angstrom, c = 13.036(5) Angstrom, beta = 106.51(2)degrees, Z = 2). Reaction of alpha-[CuL1](2+) with either basic hydrogen peroxide or dilute nitrous acid leads to mild reduction of the nitro groups to afford the ketoxime L-3 as its N-based isomeric Cu-II complexes, trans-I [CuL3](ClO4)(2) and trans-II [Cu(L-3)Cl]Cl . 7H(2)O, the latter of which has been characterized structurally: triclinic, <P(1)over bar> a = 10.8441(5) Angstrom, b = 11.6632(9) Angstrom, c = 11.8723(9) Angstrom, alpha = 113.634(7)degrees, beta = 95.744(5), gamma = 94.851(5)degrees Z = 2. Variations in the configurations of the coordinated amines in [CuL1](2+), [CuL2](2+), and [CuL3](2+) have a profound effect on the spectroscopy and electrochemistry of their complexes.

Variable temperature and pressure study of the aquation reactions of cobalt(III) and chromium(III) penta- and tetra-amines

Preparation of a series of specific penta- and tetra-amine derivatives of Co-III and Cr-III with a neutral leaving ligand has been carried out in order to accomplish a fine tuning of the associativeness/dissociativeness of their substitution reactions. Spontaneous aquation reactions of the neutral ligands have been studied at variable temperature and pressure. Although rate constants and thermal activation parameters show an important degree of scatter, the values determined for the activation volumes of the substitution process illustrate the mechanistic fine tuning that may be achieved for these reactions. In all cases, in the absence of important steric constraints in the molecule, electronic inductive effects seem to be the most important factor accounting for the dissociative shifts observed both for pentaamine (i.e.Delta V double dagger=+4.0 or +14.0 cm(3) mol(-1) and +5.2 or +16.5 cm(3) mol(-1) for the aquation of cis- or trans-[Co(MeNH2)(NH3)(4)(DMF)](3+) and cis- or trans-[CoL15(DMF)](3+) respectively, where L-15 represents a pentaamine macrocyclic ligand), and tetraamine systems (i.e.Delta V double dagger=+4.1 or +8.4 cm(3) mol(-1) and -10.8 or -7.4 cm(3) mol(-1) for the aquation of cis-[Co(NH3)(4)Cl(DMAC)](2+) (DMAC=dimethylacetamide) or cis-[Co(en)(2)Cl(DMAC)](2+) and cis-[Cr(NH3)(4)Cl(DMF)](2+) or cis -[Cr(en)(2)Cl(DMF)](2+)). From the results, clear evidence is obtained which indicates that, only when the situation is borderline I-a/I-d, or the steric demands are increased dramatically, dissociative shifts are observed; in all other cases electronic inductive effects seem to be dominant for such a tuning of the substitution process.

Effects of oxide promoters on metal dispersion and metal-support interactions in Ni catalysts supported on activated carbon

Various oxide-promoted Ni catalysts supported on activated carbon were prepared, and the effect of promoters on the surface structure and properties of Ni catalysts was studied. Physical adsorption (Na adsorption), thermogravimetric analysis (TGA), temperature-programmed desorption (TPD), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts. It is found that nickel is fairly uniformly distributed in the pores of the carbon support. Addition of promoters produces a more homogeneous distribution of nickel ion in carbon. However, distributions of promoters in the pores are varying. Addition of promoters increases the dispersion of nickel in carbon. Promoters also change the interaction between the carbon and Ni, resulting in significantly different behaviors of catalysts under various environments. CaO and MgO promoters improve the reactivity of nickel catalysts with O-2 but retard the interaction between nickel oxide and carbon. La2O3 shows some inhibiting effect on the interactions between nickel oxide and oxygen as well as carbon.

P2X4 receptors interact with both P2X2 and P2X7 receptors in the form of homotrimers

BACKGROUND AND PURPOSE The P2X receptor family consists of seven subunit types - P2X1-P2X7. All but P2X6 are able to assemble as homotrimers. In addition, various subunit permutations have been reported to form heterotrimers. Evidence for heterotrimer formation includes co-localization, co-immunoprecipitation and the generation of receptors with novel functional properties; however, direct structural evidence for heteromer formation, such as chemical cross-linking and single-molecule imaging, is available in only a few cases. Here we examined the nature of the interaction between two pairs of subunits - P2X2 and P2X4, and P2X4 and P2X7. EXPERIMENTAL APPROACH We used several experimental approaches, including in situ proximity ligation, co-immunoprecipitation, co-isolation on affinity beads, chemical cross-linking and atomic force microscopy (AFM) imaging. KEY RESULTS Both pairs of subunits co-localize upon co-transfection, interact intimately within cells, and can be co-immunoprecipitated and co-isolated from cell extracts. Despite this, chemical cross-linking failed to show evidence for heteromer formation. AFM imaging of isolated receptors showed that all three subunits had the propensity to form receptor dimers. This self-association is likely to account for the observed close interaction between the subunit pairs, in the absence of true heteromer formation. CONCLUSIONS AND IMPLICATIONS We conclude that both pairs of receptors interact in the form of distinct homomers. We urge caution in the interpretation of biochemical evidence indicating heteromer formation in other cases.

A field study conducted at Kidston Gold Mine, to evaluate the impact of arsenic and zinc from mine tailing to grazing cattle

The grazing trial at Kidston Gold Mine, North Queensland, was aimed specifically to assess the uptake of metals from the tailing and the potential for unacceptable contamination of saleable meat. Further aims included estimating metal dose rates and identifying potential exposure pathways including plant uptake of heavy metals, mine tailings adhered to plants and direct ingestion of mine tailing. It was found that of the 11 metals analysed (As, Zn, Co, Cd, Cr, Sn, Pb, Sb, Hg, Se and Ni) in the animal's liver, muscle and blood during the 8-month trial period, only accumulation of arsenic and zinc occurred. A risk assessment including these two metals was conducted to determine the potential for chronic metal toxicity and long-term contamination, using the estimates of metal dose rate. It was concluded that no toxicity or long-term contamination in cattle was likely at this site. Management procedures were therefore not required at this site; however, the results highlight percent ground cover and standing dry matter (DM) as important factors in decreasing metal exposure from direct ingestion of tailings and dust adhered to plants. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.

Política(s) de saúde no trabalho : um inquérito sociológico às empresas portuguesas

Resumo Política(s) de saúde no trabalho: um inquérito sociológico às empresas portuguesas A literatura portuguesa sobre políticas, programas e actividades de Segurança, Higiene e Saúde no Trabalho (abreviadamente, SH&ST) é ainda escassa. Com este projecto de investigação pretende-se (i) colmatar essa lacuna, (ii) melhorar o conhecimento dos sistemas de gestão da saúde e segurança no trabalho e (iii) contribuir para a protecção e a promoção da saúde dos trabalhadores. Foi construída uma tipologia com cinco grupos principais de políticas, programas e actividades: A (Higiene & Segurança no Trabalho / Melhoria do ambiente físico de trabalho); B (Avaliação de saúde / Vigilância médica / Prestação de cuidados de saúde); C (Prevenção de comportamentos de risco/ Promoção de estilos de vida saudáveis); D (Intervenções a nível organizacional / Melhoria do ambiente psicossocial de trabalho); E (Actividades e programas sociais e de bem-estar). Havia uma lista de mais de 60 actividades possíveis, correspondendo a um índice de realização de 100%. Foi concebido e desenhado, para ser auto-administrado, um questionário sobre Política de Saúde no Local de Trabalho. Foram efectuados dois mailings, e um follow-up telefónico. O trabalho de campo decorreu entre a primavera de 1997 e o verão de 1998. A amostra (n=259) é considerada representativa das duas mil maiores empresas do país. Uma em cada quatro é uma multinacional. A taxa de sindicalização rondava os 30% da população trabalhadora, mas apenas 16% dos respondentes assinalou a existência de representantes dos trabalhadores eleitos para a SH&ST. A hipótese de investigação principal era a de que as empresas com um sistema integrado de gestão da SH&ST seriam também as empresas com um (i) maior número de políticas, programas e actividades de saúde; (ii) maior índice de saúde; (iii) maior índice de realização; e (iv) maior percentagem dos encargos com a SH&ST no total da massa salarial. As actividades de tipo A e B, tradicionalmente associadas à SH&ST, representavam, só por si, mais de 57% do total. Os resultados, correspondentes às respostas da Secção C do questionário, apontam, para (i) a hipervalorização dos exames de medicina do trabalho; e por outro para (ii) o subaproveitamento de um vasto conjunto de actividades (nomeadamente as de tipo D e E), que são correntemente levadas a cabo pelas empresas e que nunca ou raramente são pensadas em termos de protecção e promoção da saúde dos trabalhadores. As actividades e os programas de tipo C (Prevenção de comportamentos de risco/Promoção de estilos de vida saudáveis), ainda eram as menos frequentes entre nós, a seguir aos Programas sociais e de bem-estar (E). É a existência de sistemas de gestão integrados de SH&ST, e não o tamanho da empresa ou outra característica sociodemográfica ou técnico-organizacional, que permite predizer a frequência de políticas de saúde mais activas e mais inovadores. Os três principais motivos ou razões que levam as empresas portuguesas a investir na protecção e promoção da saúde dos seus trabalhadores eram, por ordem de frequência, (i) o absentismo em geral; (ii) a produtividade, qualidade e/ou competitividade, e (iii) a filosofia de gestão ou cultura organizacional. Quanto aos três principais benefícios que são reportados, surge em primeiro lugar (i) a melhoria da saúde dos trabalhadores, seguida da (ii) melhoria do ambiente do ambiente de trabalho e, por fim, (iii) a melhoria da produtividade, qualidade e/ou competitividade.Quanto aos três principais obstáculos que se põem, em geral, ao desenvolvimento das iniciativas de saúde, eles seriam os seguintes, na percepção dos respondentes: (i) a falta de empenho dos trabalhadores; (ii) a falta de tempo; e (iii) os problemas de articulação/ comunicação a nível interno. Por fim, (i) o empenho das estruturas hierárquicas; (ii) a cultura organizacional propícia; e (iii) o sentido de responsabilidade social surgem, destacadamente, como os três principais factores facilitadores do desenvolvimento da política de saúde no trabalho. Tantos estes factores como os obstáculos são de natureza endógena, susceptíveis portanto de controlo por parte dos gestores. Na sua generalidade, os resultados deste trabalho põem em evidência a fraqueza teóricometodológica de grande parte das iniciativas de saúde, realizadas na década de 1990. Muitas delas seriam medidas avulsas, que se inserem na gestão corrente das nossas empresas, e que dificilmente poderão ser tomadas como expressão de uma política de saúde no local de trabalho, (i) definida e assumida pela gestão de topo, (ii) socialmente concertada, (iii) coerente, (iv) baseada na avaliação de necessidades e expectativas de saúde dos trabalhadores, (v) divulgada, conhecida e partilhada por todos, (vi) contingencial, flexível e integrada, e, por fim, (vii) orientada por custos e resultados. Segundo a Declaração do Luxemburgo (1997), a promoção da saúde engloba o esforço conjunto dos empregadores, dos trabalhadores, do Estado e da sociedade civil para melhorar a segurança, a saúde e o bem-estar no trabalho, objectivo isso que pode ser conseguido através da (i) melhoria da organização e das demais condições de trabalho, da (ii) participação efectiva e concreta dos trabalhadores bem como do seu (iii) desenvolvimento pessoal. Abstract Health at work policies: a sociological inquiry into Portuguese corporations Portuguese literature on workplace health policies, programs and activities is still scarce. With this research project the author intends (i) to improve knowledge on the Occupational Health and Safety (shortly thereafter, OSH) management systems and (ii) contribute to the development of health promotion initiatives at a corporate level. Five categories of workplace health initiatives have been identified: (i) Occupational Hygiene and Safety / Improvement of Physical Working Environment (type A programs); (ii) Health Screening, Medical Surveillance and Other Occupational Health Care Provision (type B programs); (iii) Preventing Risk Behaviours / Promoting Healthy Life Styles (type C programs); (iv) Organisational Change / Improvement of Psycho-Social Working Environment (type D programs); and (v) Industrial and Social Welfare (type E programs). A mail questionnaire was sent to the Chief Executive Officer of the 1500 largest Portuguese companies, operating in the primary and secondary sectors (≥ 100 employees) or tertiary sector (≥ 75 employees). Response rate has reached about 20% (259 respondents, representing about 300 companies). Carried out between Spring 1997 and Summer 1998, the fieldwork has encompassed two direct mailings and one phone follow-up. Sample is considered to be representative of the two thousand largest companies. One in four is a multinational. Union membership rate is about 30%, but only 16% has reported the existence of a workers’ health and safety representative. The most frequent workplace health initiatives were those under the traditional scope of the OSH field (type A and B programs) (57% of total) (e.g., Periodical Medical Examinations; Individual Protective Equipment; Assessment of Working Ability). In SMEs (< 250) it was less likely to find out some time-consuming and expensive activities (e.g., Training on OSH knowledge and skills, Improvement of environmental parameters as ventilation, lighting, heating).There were significant differences in SMEs, when compared with the larger ones (≥ 250) concerning type B programs such as Periodical medical examinations, GP consultation, Nursing care, Other medical and non-medical specialities (e.g., psychiatrist, psychologist, ergonomist, physiotherapist, occupational social worker). With regard to type C programs, there were a greater percentage of programs centred on Substance abuse (tobacco, alcohol, and drug) than on Other health risk behaviours. SMEs representatives reported very few prevention- oriented programs in the field of Drug abuse, Nutrition, Physical activity, Off- job accidents, Blood pressure or Weight control. Frequency of type D programs included Training on Human Resources Management, Training on Organisational Behaviour, Total Quality Management, Job Design/Ergonomics, and Workplace rehabilitation. In general, implementation of this type of programs (Organisational Change / Improvement of Psychosocial Working Environment) is not largely driven by health considerations. Concerning Industrial and Social Welfare (Type E programs), the larger employers are in a better position than SMEs to offer to their employees a large spectrum of health resources and facilities (e.g., Restaurant, Canteen, Resting room, Transport, Infra-structures for physical activity, Surgery, Complementary social protection, Support to recreational and cultural activities, Magazine or newsletter, Intranet). Other workplace health promotion programs like Training on Stress Management, Employee Assistance Programs, or Self-help groups are uncommon in the Portuguese worksites. The existence of integrated OSH management systems, not the company size, is the main variable explaining the implementation of more active and innovative workplace health policies in Portugal. The three main prompting factors reported by employers for health protection and promotion initiatives are: (i) Employee absenteeism; (ii) Productivity, quality and/or competitiveness; and (iii) Corporate culture/management philosophy. On the other hand, (i) Improved staff’s health, (ii) Improved working environment and (iii) Improved productivity, quality and/or competitiveness were the three main benefits reported by companies’ representatives, as a result of successful implementation of workplace health initiatives. (i) Lack of staff commitment; (ii) Lack of time; and (iii) Problems of co-operation and communication within company or establishment (iii) are perceived to be the main barriers companies must cope with. Asked about the main facilitating factors, these companies have pointed out the following ones: (i) Top management commitment; (ii) Corporate culture; and (iii) Sense of social responsibility. This sociological research report shows the methodological weaknesses of workplace health initiatives, carried out by Portuguese companies during the last ‘90s. In many cases, these programs and actions were not part of a corporate health strategy and policy, (i) based on the assessment of workers’ health needs and expectancies, (ii) advocated by the employer or the chief executive officer, (ii) planned and implemented with the staff consultation and participation or (iv) evaluated according to a cost-benefit analysis. In short, corporate health policy and action were still rather based on more traditional OSH approaches and should be reoriented towards Workplace Health Promotion (WHP) approach. According to the Luxembourg Declaration of Workplace Health Promotion in the European Union (1997), WHP is “a combination of: (i) improving the work organisation and environment; (ii) promoting active participation; (iii) encouraging personal development”.Résumée Politique(s) de santé au travail: une enquête sociologique aux entreprises portugaises Au Portugal on ne sait presque rien des politiques de santé au travail, adoptés par les entreprises. Avec ce projet de recherche, on veut (i) améliorer la connaissance sur les systèmes de gestion de la santé et de la sécurité au travail et, au même temps, (ii) contribuer au développement de la promotion de la santé des travailleurs. Une typologie a été usée pour identifier les politiques, programmes et actions de santé au travail: A. Amélioration des conditions de travail / Sécurité au travail; B. Médecine du travail /Santé au travail; C. Prévention des comportements de risque / Promotion de styles de vie sains; D. Interventions organisationnelles / Amélioration des facteurs psychosociaux au travail; E. Gestion de personnel et bien-être social. Un questionnaire postal a été envoyé au représentant maximum des grandes entreprises portugaises, industrielles (≥ 100 employés) ou des services (≥ 75 employés). Le taux de réponse a été environ 20% (259 répondants, concernant trois centaines d’entreprises et d’établissements). La recherche de champ, conduite du printemps 1997 à l’été 1998, a compris deux enquêtes postales et un follow-up téléphonique. L´échantillon est représentatif de la population des deux miles plus grandes entreprises. Un quart sont des multinationales. Le taux de syndicalisation est d’environ 30%. Toutefois, il y a seulement 16% de lieux de travail avec des représentants du personnel pour la santé et sécurité au travail. Les initiatives de santé au travail les plus communes sont celles concernant le domaine plus traditionnel (types A et B) (57% du total): par exemple, les examens de médecine du travail, l’équipement de protection individuelle, les tests d’aptitude au travail. En ce qui concerne les programmes de type C, les plus fréquents sont le contrôle et la prévention des addictions (tabac, alcool, drogue). Les interventions dans le domaine de du système technique et organisationnelle du travail peuvent comprendre les courses de formation en gestion de ressources humaines ou en psychosociologie des organisations, l’ergonomie, le travail posté ou la gestion de la qualité totale. En général, la protection et la promotion de la santé des travailleurs ne sont pas prises en considération dans l’implémentation des initiatives de type D. Il y a des différences quand on compare les grandes entreprises et les moyennes en matière de politique de gestion du personnel e du bien-être (programmes de type E, y compris l’allocation de ressources humaines ou logistiques comme, par exemple, restaurant, journal d’entreprise, transports, installations et équipements sportifs). D’autres activités de promotion de la santé au travail comme la formation en gestion du stress, les programmes d’ assistance aux employés, ou les groupes de soutien et d’auto-aide sont encore très peu fréquents dans les entreprises portugaises. C’est le système intégré de gestion de la santé et de la sécurité au travail, et non pas la taille de l’entreprise, qui aide à prédire l’existence de politiques actives et innovatrices dans ce domaine. Les trois facteurs principaux qui encouragent les actions de santé (prompting factors, en anglais) sont (i) l’absentéisme (y compris la maladie), (ii) les problèmes liés à la productivité, qualité et/ou la compétitivité, et aussi (iii) la culture de l’entreprise/philosophie de gestion. Du coté des bénéfices, on a obtenu surtout l’amélioration (i) de la santé du personnel, (ii) des conditions de travail, et (iii) de la productivité, qualité et/ou compétitivité.Les facteurs qui facilitent les actions de santé au travail sont (i) l’engagement de la direction, (ii) la culture de l’entreprise, et (iii) le sens de responsabilité sociale. Par contre, les obstacles à surmonter, selon les organisations qui ont répondu au questionnaire, seraient surtout (i) le manque d’engagement des travailleurs et de leur représentants, (ii) le temps insuffisant, et (iii) les problèmes de articulation/communication au niveau interne de l’entreprise/établissement. Ce travail de recherche sociologique montre la faiblesse méthodologique des services et activités de santé et sécurité au travail, mis en place par les entreprises portugaises dans les années de 1990, à la suite des accords de concertation sociale de 1991. Dans beaucoup de cas, (i) ces politiques de santé ne font pas partie encore d’un système intégré de gestion, (ii) il n’a pas d’évaluation des besoins et des expectatives des travailleurs, (iii) c’est très bas ou inexistant le niveau de participation du personnel, (iv) on ne fait pas d’analyse coût-bénéfice. On peut conclure que les politiques de santé au travail sont plus proches de la médecine du travail et de la sécurité au travail que de la promotion de la santé des travailleurs. Selon la Déclaration du Luxembourg sur la Promotion de la Santé au Lieu de Travail dans la Communauté Européenne (1997), celle-ci « comprend toutes les mesures des employeurs, des employés et de la société pour améliorer l'état de santé et le bien être des travailleurs » e « ceci peut être obtenu par la concentration des efforts dans les domaines suivants: (i) amélioration de l'organisation du travail et des conditions de travail ; (ii) promotion d'une participation active des collaborateurs ; (iii) renforcement des compétences personnelles ».

Liver histology in co-infection of hepatitis C virus (HCV) and Hepatitis G virus (HGV)

As little is known about liver histology in the co-infection of hepatitis C virus (HCV) and hepatitis G virus (HGV), HGV RNA was investigated in 46 blood donors with hepatitis C, 22 of them with liver biopsy: co-infection HCV / HGV (n = 6) and HCV isolated infection (n = 16). Besides staging and grading of inflammation at portal, peri-portal and lobular areas (Brazilian Consensus), the fibrosis progression index was also calculated. All patients had no symptoms or signs of liver disease and prevalence of HGV / HCV co-infection was 15.2%. Most patients had mild liver disease and fibrosis progression index, calculated only in patients with known duration of infection, was 0.110 for co-infection and 0.130 for isolated HCV infection, characterizing these patients as "slow fibrosers". No statistical differences could be found between the groups, although a lesser degree of inflammation was always present in co-infection. In conclusion co-infection HCV / HGV does not induce a more aggressive liver disease, supporting the hypothesis that HGV is not pathogenic.

Multiresponsive supramolecular systems for information processing at the molecular level

Dissertação para obtenção do Grau de Doutor em Química Sustentável

Novel insights into the action of antimicrobial agents against human pathogens

Dissertation presented to obtain the Ph.D degree in Biochemistry

A matter of time: Phases of customer co-creation community participation and their impact on customer behavior

Despite the growing relevance of co-creating customer communities only little scientific evidence is available on their impact on transactional behavior of participants. Previous research has mostly used self-reported data or distinguished only between during and pre-community phases obtaining mixed results. However, the author proposes that co-creating community activity takes place in five distinguishable phases and changes in transactional behavior are limited to certain phases. Using 33 months of transactional data of a Dutch online auction provider a study was conducted covering all five phases of the community co-creation process from community planning over community set-up, co-development and co-testing to post-launch. The overall results indicate mixed effects of community participation on the different transactional variables during the co-creation process. Community participation had positive effects on auctions listing behavior at the community set-up, co-development and post-launch phases, whereby the number of auctions listed peaked during the community set-up phase. These results suggest that the impact on transactional behavior differs between co-creation phases and different psychological mechanism limited to certain phases might trigger the respective changes.

Para cá e para lá dos muros: relações familiares na interface entre o interior e o exterior da prisão

Tese de Doutoramento em Sociologia

Reprogramming energy metabolism and inducing angiogenesis : co-expression of monocarboxylate transporters with VEGF family members in cervical adenocarcinomas

Reprogramming energy metabolism and inducing angiogenesis: co-expression of monocarboxylate transporters with VEGF family members in cervical adenocarcinomas.

Production of medium-chain fatty acids and higher alcohols by a synthetic co-culture grown on carbon monoxide or syngas

Synthesis gas, a mixture of CO, H2, and CO2, is a promising renewable feedstock for bio-based production of organic chemicals. Production of medium-chain fatty acids can be performed via chain elongation, utilizing acetate and ethanol as main substrates. Acetate and ethanol are main products of syngas fermentation by acetogens. Therefore, syngas can be indirectly used as a substrate for the chain elongation process.

Primary Commodity Prices: Co-movements, Common Factors and Fundamentals

The behavior of commodities is critical for developing and developed countries alike. This paper contributes to the empirical evidence on the co-movement and determinants of commodity prices. Using nonstationary panel methods, we document a statistically significant degree of co-movement due to a common factor. Within a Factor Augmented VAR approach, real interest rate and uncertainty, as postulated by a simple asset pricing model, are both found to be negatively related to this common factor. This evidence is robust to the inclusion of demand and supply shocks, which both positively impact on the co-movement of commodity prices.

Estudi de l'estabilitat tèrmica de l'espinel·la NiCo2O4 mesoporosa

Els materials mesoporos (amb una mida controlada de porus entre els 2 i 50 nm) tenen com a tret diferencial la seva gran superfície específica, la qual els fa aptes per a aplicacions molt diverses. L’espinel·la de NiCo2O4 és aplicable com a sensor de gasos, com a catalitzador de les reaccions d’evolució i reducció d’oxigen o com a elèctrode en electrosíntesi inorgànica i orgànica. Hom preveu que l’obtenció de NiCo2O4 mesoporós podria ampliar el ventall d’aplicacions d’aquest material o millorar les prestacions de les ja existents. L’objectiu del projecte és el de determinar el rang de temperatures d’ús dels dispositius que incorporin l’espinel·la de NiCo2O4 mesoporosa. Per tal d’analitzar l’estabilitat tèrmica d’aquest material, es realitza un procés de síntesi complet de mostres d’aquestes característiques. S’inicia un procés d’obtenció de nanomotlles de sílice amb mesoestructura SBA-15 i KIT-6 pel mètode de soft-templating. Aquests templates es validen per TEM i EDX i són els emprats per a la síntesi de mostres de NiCo2O4 per hard-templating. Un cop sintetitzades les mostres de NiCo2O4 SBA-15 i KIT-6, es procedeix a validar la qualitat de la seva mesoestructura per TEM, i la seva composició química per EDX i de fases per XRD. Aquestes dues mostres as-prepared passen a ser sotmeses a un seguit de tractaments tèrmics a temperatures de 400ºC, 450ºC, 500ºC, 550ºC i 600ºC. Això permetrà observar per TEM el col·lapse de la mesoestructura i per XRD serà possible detectar i quantificar la segregació de NiO que podria malmetre les propietats del material en qualsevol de les seves aplicacions. Segons l’aparició d’aquests dos efectes negatius, es determinarà una temperatura crítica de funcionalitat del NiCo2O4 mesoporós. També es farà una anàlisi termogravimètrica dels precursors emprats per a la síntesi del NiCo2O4 confinats en templates de sílice: nitrat de cobalt i nitrat de níquel per separat, i una mescla d’ambdós amb proporcions 0,5:1 Ni(II):Co(II). Es podrà observar en quines temperatures tenen lloc el processos físicoquímics patits per aquests precursors, quan té lloc la formació dels òxids pertinents i com afecta la presència dels nanomotlles a cada un d’ells. Finalment, aquest projecte també incideix en l’estudi de la reproductibilitat per hard-templating de l’espinel·la de FeCo2O4, un material força desconegut en format mesoporós. I la caracterització de les mostres as-prepared per TEM, EDX i XRD.