n/a

Sedimentological features of the Paimogo site, 6 km NNW of Lourinhã, western central Portugal are presented. More than one hundred theropod dinosaur eggs (some containing embryo bones) ascribed to Lourinhanosaurus antunesi Mateus 1998, three crocodilian eggs and some other fossils were found at the 32 m2 excavated area of the egg-bearing horizon (Mateus et al., 1998). The stratigraphic position of the site is the Praia Azul member (Lourinhã Formation), roughly corresponding to the Kimmeridgian-Tithonian boundary or, more likely lowermost Tithonian. The maximum flooding surface of the basinal transgressive event where the horizon is located corresponds to the base of the H depositional sequence defined by Pena dos Reis et al. (2000) and probably correlates to the base of sequence Ti1 identified within western European basins (Jacquin et al., 1998), dated as 150 Ma. Possibly during the normal river discharge, the theropods congregated in nesting colonies at the backswamp of an extensive flood plain with small meandering channels and freshwater ponds. There are no evidences that the nest was dug or the eggs buried. The eggs have probably been laid on a flat, shaded, muddy area near the bank of a large pond. It is probable that the eggs have not been actively incubated. The larger number of eggs suggest that they were laid near simultaneously by, at least, six females. The fossil record shows that crocodilians, mammals, gastropods and fish were also present. A flood event occurred when theropod embryos had attained a late stade of ontogenetic development, probably just before hatching. The overflow from a nearby channel flooded the plain, including the area where the eggs had been laid. The sheet flood flowing over the nest resulted into the scattering and breaking up of some dinosaur eggs. Eggshell and embryos skeletal parts fragments were displaced to an adjacent area where, due to hydrodynamic decline, the flow submerged other clutches and moderately dragged their eggs. The flooding caused the drowning of the embryos and covered the eggs with fine-grained sediment, hiding them from predators and scavengers. Hydrodynamic interpretation of the arrangement of the theropod eggs and egg-fragments suggests that the flow came from the NW. When the floodwaters receded, the fine-grained deposits became exposed to subaerial weathering. Although the sediment surface was often wet and small bodies of standing water may still have existed, the sediments were oxidized and plant remains have consequently been destroyed. Some carbonate cementation and redenning resulted from pedogenesis under alternating dry and moist conditions, in a semiarid/ sub-tropical climate under seasonal changing, contrasting conditions. The thick, stratigraphically above and below the nesting horizon mudrocks indicate a long persistence of periodic flooding, alternating with pedogenesis. During the early stages of diagenesis, vertical pressure crushed the eggs. Silt penetration into the inner part of each egg inhibited later flattening during the burial process.

We prove Fredholm criteria for singular integral operators of the form
\[
P_++M_bP_-+M_uUP_-,
\]
where \(P_\pm\) are the Riesz projections, \(U\) is the flip operator, and \(M_b,M_u\) are operators of multiplication by functions \(b,u\), respectively, on a reflexive rearrangement-invariant space with nontrivial Boyd indices over the unit circle. We assume a priori that \(M_b\) is bounded, but \(M_u\) may be unbounded. The function \(u\) belongs to a class of, in general, unbounded functions that relates to the Douglas algebra \(H^\infty+C\).

In this paper, the author proves that the set of all integrable functions whose sequences of negative (resp. nonnegative) Fourier coefficients belong to \(\ell^1\cap\ell^\Phi_{\varphi,w}\) (resp. to \(\ell^1\cap\ell^\Psi_{\psi,\varrho}\)), where \(\ell^\Phi_{\varphi,w}\) and \(\ell^\Psi_{\psi,\varrho}\) are two-weighted Orlicz sequence spaces, forms an algebra under pointwise multiplication whenever the weight sequences
\[
\varphi=\{\varphi_n\},\quad
\psi=\{\psi_n\},\quad
w=\{w_n\},\quad
\varrho=\{\varrho_n\}
\]
increase and satisfy the \(\Delta_2\)-condition.

The aim of this work is to present a process able to allow a fast method to clean plasma enhanced chemical vapour deposition (PECVD) systems used to produce amorphous silicon films and their alloys, and a proper device patterning when required. In this work we propose to study CF4/O2 or SF6 as etchant gases at room temperature to perform cleaning and films patterning. The aim is to select the process that leads to a faster cleaning process without formation of residual contaminants or to anisotropic patterning of very thin layers. The influence of some plasma parameters, such as pressure (p), power (P) and flow (f) for the etchant gases used will be also analysed.

Using a recently developed procedure combining isothermal and non-isothermal current measurements space charge trapping and transport in LDPE was successfully studied. Unaged, thermally and electrically aged samples were investigated. The samples were conditioned before each measurement in order to obtain reproducible results. In the non-isothermal measurements appeared a broad peak (40degreesC to 50degreesC) that was possible to decompose into two or three peaks (35, 45 and 65degreesC). At even higher temperature another peak was sometimes present (85degreesC) depending on the prior sample conditioning. The space charge is trapped near the surface in deep traps (maximum depth of approximate to 15 mum). Relaxation times, mobilities and activation energies have been calculated for different charging/discharging conditions. For unaged samples the reproducibility of the results was poor while for the aged polyethylene it was quite good, meaning that aging helps conditioning. In the electrically aged LDPE there is a decrease of conductivity and the broad peak of the non-isothermal spectra shows a slight shift towards higher temperatures when compared with the data found in the thermally aged polymer.

Using a recently developed procedure combining isothermal and non-isothermal current measurements space charge trapping and transport in LDPE was successfully studied. Unaged, thermally and electrically aged samples were investigated. The samples were conditioned before each measurement in order to obtain reproducible results. In the non-isothermal measurements appeared a broad peak (40degreesC to 50degreesC) that was possible to decompose into two or three peaks (35, 45 and 65degreesC). At even higher temperature another peak was sometimes present (85degreesC) depending on the prior sample conditioning. The space charge is trapped near the surface in deep traps (maximum depth of approximate to 15 mum). Relaxation times, mobilities and activation energies have been calculated for different charging/discharging conditions. For unaged samples the reproducibility of the results was poor while for the aged polyethylene it was quite good, meaning that aging helps conditioning. In the electrically aged LDPE there is a decrease of conductivity and the broad peak of the non-isothermal spectra shows a slight shift towards higher temperatures when compared with the data found in the thermally aged polymer.

In this work we report the study of spectral response on large area amorphous silicon solar cells (30×40 cm2), deposited through plasma enhanced chemical vapour deposition technique (PECVD) at excitation frequencies of 27.12MHz. To perform this work, the solar cells were split in units of area of 0.126 cm2, which allows determining the device homogeneity over all the entire solar cell. Emphasis of this work is put the role of thickness and optical band gap of p-doped layer on the collection efficiency, spectral response, current density-voltage curves under standard condition and spectroscopy impedance. The results show that high transparent p-doped layer can be deposited at 42mW/cm2, which allows increasing the collection efficiency in 45%, at the blue region. The spectroscopy impedance performed showed to be efficient in analyzing the device shunt resistance, interfaces role on the device performances and the behaviour of the device depletion region, for the range of frequencies analysed.

Silicon nitride films were produced on glass and crystalline silicon substrates using r.f. magnetron sputtering to select the best process conditions (substrate temperature, gas pressure and r.f. power) to grow dielectrics for device applications such as low temperature thin film transistors, where special care has to be taken concerning the film's compactness and bulk defects. The films produced were analysed by different techniques such as ultra violet - visible - near infrared spectroscopy Fourier transformed infrared spectroscopy and capacitance measurements, aiming to correlate the films properties with its composition and degree of compactness. The role of the deposition pressure is notorious since films deposited at high pressures are more compact, presenting low oxygen incorporation after deposition. The increase of the substrate temperature up to 373 °K has the same effect, not changing the film's amorphous structure. These data will be discussed aiming to produce films with the required compactness and stoichiometry to grow very thin insulating layers (<10 nm) to be used in MIS structures or devices like thin film transistors.