Assessment of the geological heritage of Cape Mondego Natural Monument (Central Portugal)

In the western coast of Portugal, Cape Mondego is a well-known set of outcrops due to its international stratigraphic relevance given by the establishment of two stratotypes: the Global Boundary Stratotype Section and Point (GSSP) for the base of the Bajocian Stage and the Auxiliary Stratotype Section and Point (ASSP) for the base of the Bathonian Stage.     

Can the Intermediate Western Boundary Current recirculation trigger the Vitória Eddy formation?

Ocean Dynamics - South of the Vitória-Trindade Ridge, a seamount chain off East Brazil, the Brazil Current (BC) meanders cyclonically within Tubarão Bight, occasionally forming the...     

Impact of stress and disturbance factors on the phytoplankton communities in Northeastern Brazil reservoir

The ecology of phytoplankton reservoir communities plays a pivotal role in their management and in the development of inland fisheries in the water scarce semi-arid regions of Rio Grande do Norte State, Brazil. The hydrological conditions characterizing these reservoirs include infrequent rainfall and high evaporative loses. The phytoplankton assemblages in tropical climate are structured primarily on dry and wet cycles, not the annual temperature and light regime. The purpose of the current study was to investigate the ecological aspects of phytoplankton communities from three reservoirs during the period of July 2003–June 2004, which include atypical summer rainfall and reservoir overflow. The environmental data broadly divided into two categories, stress factors and disturbance factors. The stress factors deals with the impact of high particulate organic matter and low dissolved oxygen concentrations and disturbance factors, linked to water level fluctuation through flushing and reservoir drawdown, and these events are associated with the phytoplankton assemblages. Results indicated that the three distinct hydroperiods determined the structure of phytoplankton and chlorophyll levels and limited the presence and relative abundance of cyanobacterial species. Phytoplankton succession accompanied changes in clear and turbid water phase represented by the alternate dominance between diatoms and chlorophytes. Inundation and complete filling of reservoir stimulated “s” and “r” strategists species (<20 um) of unicellular and some colonial members of chlorophytes and cryptomonads in highly turbid water environment, and “c” strategist species in rest of the wet period following disturbance gradients. Statistical analysis elicited a significant relationship between particulate organic matter and relative abundance of smaller chlorophytes, which was deemed as stress factor. The flushing and reservoir drawdown indicate disturbance gradient and as a consequence high diversity. Furthermore, a substantial reduction in chlorophyll levels was registered in turbid water phase is related to the reduction of light penetration and re-suspension of sediments. Considering these results, it can be suggested that the well-managed reservoir drawdown can possibly maintain an environment free of eutrophication and cyanobacterial dominance.     

Homogeneity assessment of a station climate series (1933–2005) in the Metropolitan Area of S?o Paulo: instruments change and urbanization effects

This work assessed homogeneity of the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG) weather station climate series, using various statistical techniques. The record from this target station is one of the longest in Brazil, having commenced in 1933 with observations of precipitation, and temperatures and other variables later in 1936. Thus, it is one of the few stations in Brazil with enough data for long-term climate variability and climate change studies. There is, however, a possibility that its data may have been contaminated by some artifacts over time. Admittedly, there was an intervention on the observations in 1958, with the replacement of instruments, for which the size of impact has not been yet evaluated. The station transformed in the course of time from rural to urban, and this may also have influenced homogeneity of the observations and makes the station less representative for climate studies over larger spatial scales. Homogeneity of the target station was assessed applying both absolute, or single station tests, and tests relatively to regional climate, in annual scale, regarding daily precipitation, relative humidity, maximum (TMax), minimum (TMin), and wet bulb temperatures. Among these quantities, only precipitation does not exhibit any inhomogeneity. A clear signal of change of instruments in 1958 was detected in the TMax and relative humidity data, the latter certainly because of its strong dependence on temperature. This signal is not very clear in TMin, but it presents non-climatic discontinuities around 1953 and around 1970. A significant homogeneity break is found around 1990 for TMax and wet bulb temperature. The discontinuities detected after 1958 may have been caused by urbanization, as the observed warming trend in the station is considerably greater than that corresponding to regional climate.     

The Oued Mellègue: Mining activity,stream sediments and dispersion of base metals in natural environments,North-western Tunisia

In the Northwest of Tunisia, mining works have occurred in an area of vital water reserves and resources (Oued Mellègue and Oued Mejerda), which represent nearly 81% of total potential of water in the region. Demographic growth, insufficient drinkable water, agriculture and industrial plants are factors responsible for the strong demand of this resource. Water supply is done by an interconnected battery of dams built on the major watercourses, the first of which, the Mellègue dam, was erected in the 1960s. Nowadays, most of the mines are closed for almost two decades although one is still active: (Jerissa for Fe). It is important to emphasise the fact that there are millions of cubic metres of abandoned tailings, mainly from Pb–Zn–Ba mines, which are not surveyed, representing a serious threat to the environment.     

Ongoing research on seismic safety assessment

Research on seismic safety assessment has been the centre of great interest among the scientific community in recent years. Although the devastating impact of earthquakes on current society should be incentive enough to increase research, the development of more realistic mechanical behaviour models and the continuous enhancement of computation capabilities are paramount factors contributing a great deal to the increase of such interest. In this context, three research areas can be identified as currently leading to important developments: code related research, especially in Europe where new design codes are in the implementation process; risk analysis, namely concerning the definition of methodologies for safety assessment that involve the evaluation of the failure probability and could be included in future generations of codes; and experimental characterization of constitutive laws which provides support for the development and calibration of accurate and realistic numerical models for seismic analysis and for the adequate characterization of limit state capacities. The paper will present some of the current scientific research trends on these three seismic safety assessment related topics. Studies addressing the seismic safety assessment of structures, either probabilistically or based on code provisions, and that consider realistic nonlinear mechanical behaviour models will be focussed. Reference will also be made to experimental research on the seismic behaviour of structural elements, emphasizing its crucial role to support the development of numerical models simulating the effects of different seismic strengthening techniques. Finally, given the development of studies leading to new trends and perspectives for performance based earthquake engineering, a possible scenario for seismic design in the future is presented, emphasizing the key issues for its implementation.     

Constraints on cosmological parameters from recent measurements of cosmic microwave background anisotropy

A key prediction of cosmological theories for the origin and evolution of structure in the Universe is the existence of a 'Doppler peak' in the angular power spectrum of cosmic microwave background (CMB) fluctuations. We present new results from a study of recent CMB observations which provide the first strong evidence for the existence of a 'Doppler peak' localized in both angular scale and amplitude. This first estimate of the angular position of the peak is used to place a new direct limit on the curvature of the Universe, corresponding to a density of Ω = 0.7^+0.8_−0.5, consistent with a flat universe. Very low-density 'open' universe models are inconsistent with this limit unless there is a significant contribution from a cosmological constant. For a flat standard cold dark matter dominated universe we use our results in conjunction with big bang nucleosynthesis constraints to determine the value of the Hubble constant as H ₀ = 30 − 70 km s⁻¹ Mpc⁻¹ for baryon fractions Ω_b = 0.05 to 0.2. For H ₀ = 50 km s⁻¹ Mpc⁻¹ we find the primordial spectral index of the fluctuations to be n  = 1.1 ± 0.1, in close agreement with the inflationary prediction of n  ≃ 1.0.     

10-GHz Tenerife cosmic microwave background observations at 8° resolution and their analysis using a new maximum entropy method

The complete set of data from the Tenerife 10-GHz (8° FWHM) twin-horn, drift scan experiment is described. These data are affected by both long-term atmospheric baseline drifts and short-term noise. A new maximum entropy procedure, utilizing the time invariance and spatial continuity of the astronomical signal, is used to achieve a clean separation of these effects from the astronomical signal, and to deconvolve the effects of the beam-switching. We use a fully positive/negative algorithm to produce two-dimensional maps of the intrinsic sky fluctuations. Known discrete sources and Galactic features are identified in the deconvolved map. The data from the 10-GHz experiment, after baseline subtraction with MEM, are then analysed using conventional techniques, and new constraints on Galactic emission are made.