Estimation of chemical traits in poplar short-rotation coppice at stand level

In order to improve qualitative traits of harvestable biomass and enhance its conversion into second generation biofuels (e.g. bioethanol), much attention should be paid to manage woody-energy plantations. This work represents an attempt to estimate chemical composition of biomass at stand level in poplar plantations. Based on the relationship between chemical traits of stem cross-sections and the corresponding distribution of diameter classes within the whole plantations, three different harvesting cycles were compared in terms of biomass yield and chemical composition. Under 2-year rotation, the stand showed the lower biomass annual yield (11.7 tDM ha^?1 y^?1) and the lower cellulose (42.5%) and the higher lignin (22%) proportion. On the contrary, under the 4-year cutting cycle, annual yield was not only higher (18.4 tDM ha^?1 y^?1), but the biomass also presented the highest cellulose (51.6%) and the lower lignin (19%) share. These results suggest that different management practices, including the cutting cycle, may affect not only yields but also qualitative traits of harvestable biomass of poplar short-rotation coppice.     

Simultaneously All-Optical Inverted and Noninverted Wavelength Conversion Employing Ultra-Small Silicon-on-Insulator Waveguide

We propose single-to-dual all-optical wavelength conversion based on stimulated Raman effect on silicon waveguides. Simulation results of non-return-to-zero (NRZ) pseudorandom bit sequence (2⁷–1 code) at 10, 50, and 200-Gbit/s rates of conversion in an ultra-small silicon-on-insulator waveguide are presented. The main goal in the proposed scheme is that the converted signal can be obtained simultaneously inverted, at the 1550 nm channel (down-conversion) and non-inverted, at the 1846 nm channel (up-conversion), for original signal fixed at 1686 nm.     

Robust real-time parameter estimation for linear systems affected by external noises and uncertainties

A robust adaptive parameter estimation method, based on the application of a full-order filter capable of rejecting exogenous disturbances, is proposed in this article. A linear matrix inequality condition is proposed to synthesize the desired robust filter, assuming the presence of a known input control with constraints. The filter uses the output of the system to estimate the desired signal that will be employed in the adaptive estimation procedure and, to assure robustness to exogenous noise and unstructured uncertainties, the guaranteed cost is minimized in the synthesis condition. The filtered signals are then applied to an adaptive procedure to estimate the unknown system's internal parameters, which is also proposed in this article. It is shown that lower values for the guaranteed cost from the disturbance input to the error output of the filter imply more accurate estimations of the parameters. The efficiency of the proposed estimation technique is illustrated through a simulated model and a physical system has been considered to validate real-time estimation.     

Electron Transfer in Cuprates,Pnictides, and Metallic Superconductors

The charge distribution and electronic properties of several materials that become superconductors at a low temperature are examined by using Density Functional Theory cluster calculations. For cuprates, charge transfer occurs between copper atoms only for the cluster with the oxygen vacancy. For pnictides, charge transfer with positive and negative atoms in the FeAs layer is observed in fluorine-doped clusters but not in undoped clusters. For metallic superconductors, alternating positive and negative layers are found in the clusters. These calculated charge distributions are analyzed as a result of electron transfer occurring in the superconducting state involving unsynchronized resonances, as predicted by the RVB theory of Pauling. From this analysis, combinations of chemical elements and their relationship with the superconducting transition temperature are discussed.     

Sensitivity of Cylindrotheca closterium to copper: Influence of three test endpoints and two test methods

The present study checked the suitability of Cylindrotheca closterium (Bacillariophyceae) as a test species for ecotoxicology studies. To date, only limited use has been made of microphytobenthos in ecotoxicology, and C. closterium has been employed as a target organism in this study because the biological group is considered to be very relevant ecologically. The main objective was to assess the response of C. closterium to a contaminant-type (copper) using three different test endpoints (esterase activity, chlorophyll fluorescence and population growth) and two different test methods (Erlenmeyer flasks and microplates), to evaluate which combination of test conditions would provide the most sensitive approach for assessment of effects. Regardless of the endpoints, the response of C. closterium to copper was very similar; however lower sensitivity (EC₅₀ of 27.8 ± 0.7 µg Cu L^− 1) was observed when tests were carried out in microplates. Chlorophyll fluorescence measured by flow cytometry as total FL3 was slightly more sensitive (EC₅₀ of 4.7 ± 0.1 µg Cu L^− 1) than the other parameters measured, probably because it takes into account the effect on chlorophyll fluorescence and cell density simultaneously. The test method (Erlenmeyer flask or microplate) was the determining factor for the observed differences in sensitivity. These differences found for the two methods are explained by the higher metal adsorption capacity of microplate vessel walls (more than 40%), which decreases the available copper. C. closterium was demonstrated to be a suitable organism for adoption in ecotoxicological studies, given the reliability of the three endpoints and also of the two test methods evaluated here.     

Influence of the Germanium content on the amorphization of silicon–germanium alloys during ion implantation

We have studied by transmission electron microscopy the amorphization of silicon–germanium (SiGe) alloys by Ge⁺ implantation. We show that when implanted with the same amorphization dose, the resulting amorphous layers get narrower when the Ge content increases. The experimental results can be simulated using the critical damage energy density model assuming that the amorphization threshold rises linearly with the Ge content from 3 eV/at for pure Si to 5 eV/at for pure Ge. These results and simulations are needed to optimize the fabrication of highly doped regions in SiGe alloys.     

Nature and mechanisms of loss of motivation.

Loss of motivation refers either to the weakening of a motive q or to the loss of energy and persistence with which some subordinate goal p is planned for and pursued in view of q. Although interrelated, such aspects can be kept distinct, and the present work focuses on the loss of strength of the subordinate goal. An analysis is provided of such mental attitudes as subjective frustration, negative expectation, disappointment, and discouragement so as to clarify their respective roles in favoring loss of motivation. The necessary cognitive conditions for the occurrence of loss of motivation are singled out; namely, goal p should be an intention, and a disappointment should occur in regard to the instrumental relationship between p and q , p's attainability, or p's convenience. Both advantages and limits of the model are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)