Regeneration from seed affects species assembly in plant communities, and temperature is the most important environmental factor controlling the germination process. Thermal dependence of seed germination is thus associated with species occurrence in an ecosystem. Hence, we aimed to investigate the role of temperature on seed germination of ten tree species from the western Brazilian Amazon. Seeds were collected in the state of Rondônia, Brazil, and set to germinate under constant temperatures ranging from 10 to 40°C in germination chambers. We calculated germination capacity (G%), germination rate (GR50, reciprocal of germination time), and thermal parameters, such as cardinal temperatures and thermal time requirements. Most species had a large range of temperatures showing G% ≥80%, with optimal temperature varying from 20 to 40°C. Base temperature ranged from 6 to 12°C and ceiling temperatures were mainly >40°C. Astronium lecointei and Parkia nitida showed high germination capacity under temperatures of 35–40°C, while germination of Theobroma cacao dropped from 100% to zero under temperatures between 37 and 40°C. The climax species Cedrela fissilis had the slowest germination time (10 days) and highest thermal time requirement, while seeds of Enterolobium schomburgkii (a late-successional species) germinated within the first day of the experiment. Rapid recruitment of Amazon species could be favoured with treefall disturbance, which increases temperatures in the understory, but sharp limits might be found in the supra-optimal range of temperatures. Such patterns might indicate different regeneration strategies in the tropical rainforest, providing important information regarding seed germination among Amazon species.

Different GaAs-matched epitaxial structures based on InGaP and InGaAlP layers were prepared by LP MOVPE. The suitable p- and n-type sequence of these layers will be used as active elements in high efficiency solar cells. The layers were grown on (001) GaAs substrates oriented 2° off towards (110) using trimethylgallium (TMG), trimethylaluminium (TMA), trimethylindium (TMI), arsine (AsH3) and phosphine (PH3) as main reagents and dimethylzinc (DMZ) and silane (SiH4) as p- and n-type doping reagents, respectively. The layers have been analyzed as regards their compositional homogeneity, interface abruptness and doping concentration by different techniques such as SIMS, TEM and AFM. The combined analysis of SIMS and TEM has been of great usefulness in order to define the abruptness of composition change. Moreover an analysis of autodoping effects is reported as regards the arsenic diffusion in InGaP matrix and the analysis of different samples is reported.

Optical (refractive index) and structural properties of silicon oxynitride (SiON) and amorphous silicon (a-Si) multilayers grown by RF sputtering with thickness in the 10–30 nm range have been analysed by ellipsometry and TEM. Satisfactory agreement between the two techniques is obtained as regards the thickness determination of the SiON films. Disagreement with values obtained by the stylus method by extrapolation for the two types of layers is discussed. The interfaces of the SiON films are very good when n-type P doped Si is used as a target. They are wavy with average periodicity and amplitude on the order of 50 and 2 nm, respectively, when a semi-insulating Si target is used, despite the presence of a buffer layer. Hypothesis is made that P incorporation may improve the reconstruction of the SiON surface.

We present a simple and reproducible method to obtain TiO2 and Fe2O3 mixed-oxide thin films by reactive radio-frequency sputtering. The influence of iron concentration on the structural properties of the layers has been studied. Structural characterization, carried out by electron microscopy analysis, allowed one to correlate the inhibition of the grain growth of titania to the presence of iron oxide and to its segregation at grain boundaries. This behavior should be ascribed to a superficial-tension phenomenon. As a possible application of these thin films, we have investigated the gas-sensing properties toward CO, with particular focus on the role of Fe. The layers were capable to sense CO down to the level requested for environmental monitoring.

Impurity atmospheres around dislocations have been studied in n-type Si-doped liquid encapsulated Czochralski (LEC) GaAs substrates by micro-Raman spectroscopy, diluted Sirtl-like etching with light (DSL) method, and electron-beam-induced current (EBIC). A complete morphological study of the recombinative atmospheres revealed by photoetching was achieved by phase stepping microscopy (PSM), which is an optical interferometry technique allowing to obtain the surface topography with a high vertical resolution (in the nanometer range). The minority carrier diffusion length was measured by EBIC at different points of the atmospheres. Structural distortion at the regions surrounding the dislocation core were observed by micro-Raman spectroscopy. The carrier depletion depth and the recombination of the photogenerated carriers were also studied by Raman spectroscopy, obtaining a good agreement with the EBIC data and the photoetching rates. Impurity gettering and diffusion and defect reactions involving As interstitials are assumed to play a major role in the formation of the recombinative atmospheres.

High energy (2 MeV) ion implantation of Fe in InP has been investigated by means of Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM) and secondary ions mass spectrometry (SIMS). The implanted doses ranged between 5×l013 and 5×l014 at/cm2. Annealing in the 650–800 °C range was performed and the primary as well as secondary damage evolution has been studied. The correlations between defect structure and Fe redistribution properties have been carefully analysed. The results show the role of the primary defect structure in determining the annealing properties, both for damage recovery and Fe redistribution. The latter is also influenced by the doping of the substrate.

Two regimes of defect generation have been found in MOVPE GaAs/Ge layers upon changing the V/III ratio between 1.3 and 11.8. For low V/III ratio the layers contained misfit dislocations along with stacking faults that had been generated by dissociation of the misfit dislocations. The stacking fault density increased with decreasing V/III ratio. This might be explained by an enhanced mobility of the dissociated partials due the reduced unintentional doping of the layer caused by reduced Ge outdiffusion from the substrate when V/III is small. The secon regime corresponds to high V/III ratios and is characterized by the absence of misfit dislocations and the presence of a high density of planar defects. This means that breakdown of the 2D layer-by-layer growth occurred and 3D island growth prevailed.

The recovery of the implant-induced damage and the defects present after thermal annealing at 650 °C in Fe-implanted InP have been investigated by TEM, RBS and X-ray diffractometry as a function of the annealing time that was varied betweeen 0.5 and 2 h. The near-surface damaged layer was removed only for annealing times ≥ 1.5 h. The annealed samples contained stacking fault tetrahedra of vacancy type, extrinsic dislocation loops and microdefects. These extended defects were mostly localized in a band corresponding to the region of transition between amorphous top layer and crystalline substrate as was detected in the as-implanted sample. Stacking fault tetrahedra and loops have also been observed before and beyond this band, respectively. Such defects could be due to either shear strains at the recrystallization front or implant-induced point defects.

Quantitative energy-dependent EBIC measurements have been used to calibrate the photoetching rate in HF-CrO3 aqueous solutions (DSL method: Diluted Sirtl-like etching with the use of Light) as a function of dopant concentration in LEC grown n-type GaAs samples containing growth striations. The relative DSL etching rate depends on the width of the surface depletion region associated with the semiconductor-etching solution interface, i. e. greater etch rates correspond to smaller dopant concentrations. These results are in agreement with the electrochemical model of GaAs etching in the DSL etching system.

By studying InP epitaxies it has been found that optimum growth conditions are not achieved under low growth rate regimes, which, on the contrary, yield a defect density nearly as high as under high growth rate conditions, due to the creation of a very high density of point defects from which dislocation loops originate. Such loops are generated not only at the substrate-epilayer interface but also throughout the layer and depend on the supersaturation of the feeding phases. Under conditions yielding high dislocation density both layer and hillock growth mainly occur by spiral growth.

Important modifications in ambulance design were suggested and introduced by Safar in 1965 and in 1971. However, most of these modifications have not reached the developing countries. The present “ambulance” in these countries are low ceiling and carry no equipment or trained personnel. They could be better defined as “taxis for horizontal transportation.” Recently, we have been able to introduce onto the market of these countries, a new ambulance that is competitive in price and adapted to the availability of materials, equipment, and personnel.