Eucalypt wood is known worldwide as a raw-material for pulping but only a few species are used by the industry. One of the important features for pulping is the wood structure and anatomy, including cell biometry and cell type proportion. This work makes a prospective study of nine eucalypt species aiming at a pulping use by an early assessment of wood anatomical features. Young 50-month-old trees grown in the same environment of Eucalyptus camaldulensis, Eucalyptus globulus, Eucalyptus maculata, Eucalyptus melliodora, Eucalyptus ovata, Eucalyptus propinqua, Eucalyptus sideroxylon, Eucalyptus tereticornis and Eucalyptus viminalis were studied in relation to wood anatomy, cell biometry and proportion, and morphological fibre ratios. The nine species are structurally similar with typical eucalypt wood features, e.g. diffuse porosity with predominantly solitary vessels and simple perforations plates, and most anatomical differences between species related to rays and axial parenchyma. The wood is in general uniform and the radial variation of cellular dimensions is of small magnitude. The species showed a higher diversity regarding proportion of fibres (15-50%) and morphological characteristics e.g. slenderness ratio (39-48) and flexibility coefficient (0.37-0.65). The eucalypt species position themselves differently as regards the combination of morphological parameters, therefore allowing species targeting for specific paper properties. By considering these indicators, and the relative species growth, it seems promising to further study E. maculata, E. ovata and E. sideroxylon as potential new paper making eucalypt species, in parallel to the prized E. globulus and the already used E. camaldulensis.

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In this work, we present the results of photoconductivity measurements performed in the temperature range of 12 K-300 K on a 150 nm-thick Bi 2 Te 3 film grown by molecular beam epitaxy on a (111) BaF 2 substrate. A transition from negative to positive photoconductivity is found to occur around 125 K. Resistivity and Hall data measured under light and dark conditions qualitatively elucidate the observed phenomena. The Arrhenius plot of recombination times obtained from photoconductivity decay curves measured at different temperatures gives the activation energy associated with the bulk trap level. Using this activation energy as the effective trap potential, we calculated the generation and recombination rates as a function of temperature. The analysis provides a quantitative explanation that predicts the transition effect observed in the experiment. No evidence of contribution from surface states is found from the magnetoresistance curves measured at low temperatures.

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We investigated the photoconductivity effect in n-type PbTe/Pb0.88Eu0.12Te quantum wells for a temperature range of 300–10 K using infrared light. The measurements revealed that at high temperatures, the photoresponse has small amplitude. As temperature decreases to T ∼ 75 K, however, the photoconductivity amplitude increases reaching a maximum value 10 times higher than the original value before illumination. From Hall measurements performed under dark and light conditions, we show that this effect is a result of the carrier concentration increase under illumination. Unexpectedly, for further reduction of temperature, the amplitude starts to decrease again. The electrical resistance profiles indicate that the transport occurs through barriers and the well that behave as two parallel channels. For temperatures below 75 K, transport is more effective in the quantum well, where the signal reduction can be associated with the electron-electron scattering due to the increase in the carrier concentration that occurs under illumination. We also used the random potential model to explain the origin of the persistent effect observed in the photoconductivity curves.

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