The Generation and Dissipation of Interstellar Turbulence - Results from Large Scale High Resolution Simulations

We study, by means of adaptive mesh refinement hydro- and magnetohydrodynamical simulations that cover a wide range of scales (from kpc to sub-parsec), the dimension of the most dissipative structures and the injection scale of the turbulent interstellar gas, which we find to be about 75 pc, in agreement with observations. This is however smaller than the average size of superbubbles, but consistent with significant density and pressure changes in the ISM, which leads to the break-up of bubbles locally and hence to injection of turbulence. The scalings of the structure functions are consistent with log-Poisson statistics of supersonic turbulence where energy is dissipated mainly through shocks. Our simulations are different from previous ones by other authors as (i) we do not assume an isothermal gas, but have temperature variations of several orders of magnitude and (ii) we have no artificial forcing of the fluid with some ad hoc Fourier spectrum, but drive turbulence by stellar explosions at the Galactic rate, self-regulated by density and temperature thresholds imposed on the ISM gas.Comment: Five pages and three figures. Accepted for publication in Astrophysical Journal (Letters

The Portuguese real exchange rate, 1995-2010 : competitiveness or price effects?

We disentangle the extent to which the real exchange rate appreciation in Por- tugal during 1995-2010 re ected the emergence of wage-productivity misalignments or, instead, changes in the relative price of tradable and non-tradable goods. The available data suggests that the latter e ect dominated at the aggregate level. The evidence is consistent with the view that the external imbalance that character- ized the Portuguese economy during the 1990s and early 2000s was triggered by the liberalization of capital ows, and not by dysfunctional wage setting institu- tions. Using the Fundamental Equilibrium Exchange Rate approach, we nd that recent oil price shocks played an important role in explaining the real exchange rate overvaluation in Portugal.COMPETE; QREN; FEDER; Fundação para a Ciência e a Tecnologia (FCT

An accurate density functional theory for the vapor-liquid interface of associating chain molecules based on the statistical associating fluid theory for potentials of variable range.

Published versio

HT Cas - eclipsing dwarf nova during its superoutburst in 2010

We present results of a world-wide observing campaign of the eclipsing dwarf nova - HT Cas during its superoutburst in November 2010. Using collected data we were able to conduct analysis of the light curves and we calculated $O-C$ diagrams. The CCD photometric observations enabled us to derive the superhump period and with the timings of eclipses the orbital period was calculated. Based on superhump and orbital period estimations the period excess and mass ratio of the system were obtained

IX Draconis - a curious ER UMa-type dwarf nova

We report results of an extensive world-wide observing campaign devoted to a very active dwarf nova star - IX Draconis. We investigated photometric behaviour of the system to derive its basic outburst properties and understand peculiarities of IX Dra as well as other active cataclysmic variables, in particular dwarf novae of the ER Uma-type. In order to measure fundamental parameters of the system, we carried out analyses of the light curve, O-C diagram, and power spectra. During over two months of observations we detected two superoutbursts and several normal outbursts. The V magnitude of the star varied in the range 14.6 - 18.2 mag. Superoutbursts occur regularly with the supercycle length of 58.5+/-0.5 d. When analysing data over the past 20 years, we found that the supercycle length is increasing at a rate of P_dot = 1.8 * 10^{-3}. Normal outbursts appear to be irregular, with typical occurrence times in the range 3.1 - 4.1 d. We detected a double-peaked structure of superhumps during superoutburst, with the secondary maximum becoming dominant near the end of the superoutburst. The mean superhump period observed during superoutbursts equals 0.066982(36) d, which is constant over the last two decades of observations. Based on the power spectrum analysis, the evaluation of the orbital period was problematic. We found two possible values: the first one, 0.06641(3) d, which is in agreement with previous studies and our O-C analysis (0.06646(2) d), and the second one, 0.06482(3) d, which is less likely. The evolutionary status of the object depends dramatically on the choice between these two values. A spectroscopic determination of the orbital period is needed. We updated available information on ER UMa-type stars and present a new set of their basic statistics. Thereby, we provide evidence that this class of stars is not uniform.Comment: Accepted for publication in MNRAS; 15 pages, 15 figures, 6 tables; typo correcte

Operationalizing psychic distance International Market Selection based on a knowledge perspective : the case of Miitik, a Portuguese beachwear company

Back in the days, Internationalization was a process exclusive to companies of great dimension. It requires a rather high amount of resources, reason why it was difficult and expensive for smaller companies to achieve. However, as the years went by, communication channels have improved and the world has become closer as information costs decreased. Given this, nowadays not only big multinationals but also Micro, Small and Medium Enterprises (SME’s) have increased its operations abroad. If in the past internationalizing was considered an option, but some support that it has become a necessity given the high market concentration across many industries. Nevertheless, although it is advantageous to expand operations, it doesn’t mean it has become an easy process. In fact, SME’s still face several obstacles that must be considered and tackled. As an example of the previous lines, I found Miitik. Miitik is a retailing beachwear start-up based in Portugal. The company started its operations 4 years ago and currently operates only in Portugal. Although it has sold some products abroad, it is not representative at all in the total sales. At the moment, the beachwear industry in Portugal is rather saturated both by big multinationals and also by other small actors, as Miitik. Due to this, Miitik has been struggling to achieve its financial goals. One of the options would be to internationalize, however the company is lacking resources and some insights about with countries to chase. This thesis has the aim to support Miitik with its International Market Selection.No passado, Internacionalização era um processo adoptado essencialmente por grandes multinacionais. Tal acontecia, pois consiste num processo que involve diversos recursos, o que tornava bastante dificil e dispendioso para pequenas empresas de obter. No entanto, com o decorrer dos anos, os canais de comunicação evoluiram bastante, o que levou a que a obtenção de informação se tenha tornado mais fácil e o mundo tenha ficado mais próximo. Posto isto, hoje em dia não apenas as grandes multinacionais, mas também as pequenas e médias empresas têm expandido as suas operações no estrangeiro. Se no passado internacionalização era considerado uma opção, hoje em dia é uma necessidade. Ainda que internacionalizar seja de facto vantajoso, não significa que seja um processo fácil, viste que continuam a existir diversas barreiras no processo. Como exemplo do previamente exposto, temos a Miitik, uma start-up de comércio de fatos de banho sediada em Portugal. A empresa iniciou as suas operarações há 4 anos e atua principalmente no mercado português. Apesar de ter efectuado algumas vendas no estrangeiro, estas não são representativas no total de vendas. Actualmente, a indústria de fatos de banho em Portugal, encontra-se especialmente saturada tanto por grandes multinacionais como por PME’s. Por consequente, a empresa não tem conseguido alcançar os resultados desejados. Uma das soluções passaria por expandir as suas operações no estrangeiro, no entanto a empresa escasseia em recursos e tem pouco conhecimento acerca de mercados estrangeiros. Esta tese tem o objectivo de ajudar a Miitik quanto à sua selecção de mercados

New results for Petrov type D pure radiation fields

We present a new family of Petrov type D pure radiation spacetimes with a shear-free, non-diverging geodesic principal null congruence.Comment: 4 pages; changed the appearance of some v's and nu'