Thermodynamic calculations for the salt crystallisation damage in porous built heritage using PHREEQC

This work considers the crystallisation mechanisms of the most common and aggressive salts that generate stress in porous building stones as a result of changing ambient conditions. These mechanisms include the salt crystallisation that result from decreasing relative humidity and changes in temperature and, in hydrated salts, the dissolution of the lower hydrated form and the subsequent precipitation of the hydrated salt. We propose a new methodology for thermodynamic calculations using PHREEQC that includes these crystallisation mechanisms. This approach permits the calculation of the equilibrium relative humidity and the parameterization of the critical relative humidity and crystallisation pressures for the dissolution–precipitation transitions. The influence of other salts on the effectives of salt crystallisation and chemical weathering is also assessed. We review the sodium and magnesium sulphate and sodium chloride systems, in both single and multicomponent solutions, and they are compared to the sodium carbonate and calcium carbonate systems. The variation of crystallisation pressure, the formation of new minerals and the chemical dissolution by the presence of other salts is also evaluated. Results for hydrated salt systems show that high crystallisation pressures are possible as lower hydrated salts dissolve and more hydrated salts precipitate. High stresses may be also produced by decreasing temperature, although it requires that porous materials are wet for long periods of time. The presence of other salts changes the temperature and relative humidity of salt transitions that generates stress rather than reducing the pressure of crystallisation, if any salt has previously precipitated. Several practical conclusions derive from proposed methodology and provide conservators and architects with information on the potential weathering activity of soluble salts. Furthermore, the model calculations might be coupled with projections of future climate to give as improved understanding of the likely changes in the frequency of phase transitions in salts within porous stone.

Gender and size diversity in top management team: evidence from Portugal

In recent years the Top Management Team (TMT) in the companies has been extensively studied and discussed by many researchers (Campbell & Mínguez-Vera, 2008; Erhardt et al, 2003; Haleblian & Finkelstein, 1993; Amason & Spienza, 1997). Thus, this theme has undergone a major evolution as well as it has been diversified progressively. Combined with the Upper Echelons Theory, it was established a new dimension of diversity of the Top Management Team that addresses, for example, the diversity of gender and the size of the team. There are several countries that have established laws and regulatory requirements in order to increase the presence of women in the business environment such as Norway, Spain, France, Holland and Italy. However, the female gender is far from equal in terms of representativeness (Torchia et al., 2011), but there are noteworthy developments yearly. It is also noticeable that the size of Top Management Teams has also increased, which can provide advantages for the company (Heleblian & Finkelstein, 1993). In the course of this dissertation it was studied the female gender ratio and the size of the Top Management Team with the profitability (ROA – Return On Assets) of 41 Portuguese companies listed on the Euronext Lisbon between 2011 - 2015. Initially, the Spearman test was applied in order to verify the correlations between the variables in study. It was created a linear regression that relates the number of women (independent variable) and ROA (dependent variable). The Mann-Whitney test was used to verify the ROA behaviour between companies with no women in TMT and companies with women in TMT. After analysis, the results demonstrated that there was a positive relationship between the number of women with ROA. Also companies that have women in TMT have better performance compared to companies with no women in the Top Management Team. As far as the size of the team is concerned, it positively influences the economic profitability, in a meaningful way.

III SEMINARIO INTERNACIONAL SOBRE RECURSOS NATURALES DE LA CUENCA DEL PACIFICO

No presenta resumen este documento.

INFLUÊNCIAS DO SISTEMA CUBANO DE PRODUÇÃO DE CANA-DE-AÇÚCAR SOBRE AS USINAS DE SÃO PAULO (BRASIL): 1875-1929

La producción de azúcar ha jugado un papel central en gran parte de la historia de Cuba, así como en Brasil. En algunos períodos de la historia de estos dos países se consideró esta actividad, tecnológicamente hablando, moderna, y en otros se mostraron retrasos y demoras.Durante el período que cubrimos, 1875-1929, el cultivo de caña de azúcar de Cuba fue el más desarrollado del mundo, presentando altos niveles de productividad. Ya la de Brasil estaba estancada en el tiempo, totalmente incapaz de competir en el mercado internacional.En Brasil, el estado de Sao Paulo se perfilaba como un productor emergente, dotado de una mayor capacidad de asimilación de la tecnología y la expansión del cultivo de caña de azúcar. En el proceso de despliegue de sus modernas plantas en primer lugar, el ejemplo de Cuba fue de grande influencia a los productores de Sao Paulo.Lo que pretendemos analizar con esta investigación es cómo el sistema cubano de transporte de la caña tuvo divulgación y fue asimilado parcialmente en el estado de Sao Paulo, que pronto se convertiría en el principal productor de azúcar en el Brasil.