Modelling gross primary production of a tropical semi-deciduous forest in the southern Amazon Basin

Semi-deciduous forest in the Amazon Basin is sensitive to temporal variation in surface water availability that can limit seasonal rates of leaf and canopy gas exchange. We estimated the seasonal dynamics of gross primary production (GPP) over 3 years (2005–2008) using eddy covariance and assessed canopy spectral reflectance using MODIS imagery for a mature tropical semi-deciduous forest located near Sinop, Mato Grosso, Brazil. A light-use efficiency model, known as the Vegetation Photosynthesis Model (VPM), was used to estimate seasonal and inter-annual variations in GPP as a function of the enhanced vegetation index (EVI), the land surface water index (LSWI), and local meteorology. Our results indicate that the standard VPM was incapable of reproducing the seasonal variation in GPP, primarily because the model overestimated dry-season GPP. In the standard model, the scalar function that alters light-use efficiency (ε_g) as a function of water availability (W_scalar) is calculated as a linear function of the LSWI derived from MODIS; however, the LSWI is negatively correlated with several measures of water availability including precipitation, soil water content, and relative humidity (RH). Thus, during the dry season, when rainfall, soil water content, and RH are low, LSWI, and therefore, W_scalar, are at a seasonal maximum. Using previous research, we derived new functions for W_scalar based on time series of RH and photosynthetic photon flux density (PPFD) that significantly improved the performance of the VPM. Whether these new functions perform equally well in water stressed and unstressed tropical forests needs to be determined, but presumably unstressed ecosystems would have high cloud cover and humidity, which would minimize variations in W_scalar and GPP to spatial and/or temporal variation in water availability.     

Industrial applications of product design through the inversion of latent variable models

A methodology, presented by Jaeckle and MacGregor [C.M. Jaeckle and J.F. MacGregor, Product Design Through Multivariate Statistical Analysis of Process Data, AIChE J. 44 (5) (1998) 1105–1118.], for finding a window of process operating conditions within which a product with specified quality characteristics can be produced is applied to two industrial polymerization processes. The approach uses historical data available on the process operating conditions and on the corresponding product quality for a range of existing product grades. Latent variable models — built using the existing data — are inverted to obtain a window of operating conditions, which are not only capable of yielding the desired product but are also consistent with past operating procedures and constraints. A semi-batch emulsion polymerization process for manufacturing various grades of a copolymer latex, and a batch solution polymerization process for manufacturing a range of polymer resins are considered.     

Synthesis of mordenite using kaolin as Si and Al source

The main purpose of this work was to study mordenite synthesis using kaolin as a Si and Al source. The influence of crystallization time and seed addition were studied. The obtained zeolites were characterized by: XRD, SEM, nitrogen adsorption and chemical analysis. Kaolin showed to be a promising source of Si and Al for mordenite synthesis. Seed addition led to more highly crystalline phases. Kaolin yielded mordenite whereas ZSM-5 was obtained from calcined kaolin. Longer synthesis times and seed addition favored mordenite formation.     

Which differintegration? [fractional calculus]

Despite the great advances in the theory and applications of fractional calculus, some topics remain unclear, making a systematic use difficult. In this paper, the fractional differintegration definition problem is studied from a systems point of view. Both local (Grunwald-Letnikov) and global (convolutional) definitions are considered. It is shown that the Cauchy formulation should be adopted since it is coherent with usual practice in signal processing and control applications.     

An optimisation procedure to determine the coefficients of the extended Taylor''s equation in machining

An optimum experimental design to determine the coefficients of the Extended Taylor's Equation in machining is proposed. The technique is based on the minimisation of the ratio between maximum and minimum singular values of the matrix of sensitivity of the tool life related to the machining parameter variations. This procedure generates the best set of cutting conditions to be used in tool life tests which results in a fast convergence of the coefficients and their confidence intervals. This technique was compared to the commonly used fractional factorial design when face milling AISI 1045 steel with cemented carbide cutting tools. The results showed a considerable reduction in the number of tests required to obtain a reliable equation when the optimum experimental procedure was used when compared to the factorial design.     

Influence of organic and colloidal fouling on the removal of sulphamethoxazole by nanofiltration membranes.

This study investigated the effects of organic and colloidal fouling on the removal of a representative micropollutant sulphamethoxazole by two commercially available NF membranes. Alginate, bovine serum albumin and colloidal silica were selected as model foulants to simulate hydrophilic and hydrophobic organic fractions, and colloidal matter that are often found in treated effluent and surface water. Membrane fouling was related to the membrane and foulant characteristics and subsequently the separation behaviour of the micropollutant sulphamethoxazole under different solution pH. On the basis of these results, it was confirmed that membrane fouling is strongly dependent on both the foulant and membrane characteristics. The complex relationship among retention mechanisms, fouling mechanisms and the effects of fouling on retention was systematically delineated. Of the three model foulants selected for this study, colloidal fouling resulted in the most significant reduction in retention of sulphamethoxazole as well as inorganic salts, while flux decline as a result of colloidal fouling was quite moderate. Reduction in retention caused by fouling was attributed to a phenomenon known as cake-enhance concentration polarisation, which was a predominant mechanism of colloidal fouling. In addition, the reported results suggested that the effect of fouling on retention is also membrane pore size dependent.     

Accurate environmental bioindication in floodplains in spite of an extreme flood event

The ecological reaction of species on environmental factors can differ both, temporally and geographically. Therefore, bioindicator systems must be shown to remain accurate at different places and points of time. Extreme events pose challenges for testing this robustness, which has not yet been explored systematically. The unique opportunity of the extreme flooding of the river Elbe in August 2002 was used for such a test. The bioindicator system for mean groundwater depth during the vegetation period and annual duration of inundation in floodplains studied here was developed with data collected in 1999. Data from 2003 were used to analyse the dependence of the bioindication results on the humidity of the study plots and taxonomic group (plants, molluscs and carabid beetles). For the duration of inundation, the accuracy of bioindication in 2003 was similar to that in 1999, except for the medium‐humid and dry plots using molluscs as indicators. For groundwater depth, the accuracy of bioindication in 2003 was similar to that of the reference year except in the dry plots with significantly lower accuracy for all species groups. With a few exceptions, the bioindicator system is shown to be robust and to remain accurate in spite of an extreme flood event. In conclusion, the relevance of extreme events for the robustness of bioindicator systems differs between the indicated parameters and taxonomic groups. The results stress the need to take into account the limits of the working range and the occurrence of extreme events, when testing and applying bioindicator systems. Copyright © 2009 John Wiley & Sons, Ltd.     

Polaronic effects on the collective excitation energies in a quantum wire

In this work we report a investigation of the plasmon–longitudinal-optical (LO) phonon interaction effects on the intersubband and intrasubband collective excitation energies in a GaAs–Al_νGa_1?νAs rectangular quantum well wire. We observe a resonant split of the collective excitation energy into two branches, one with energy lower and other with energy higher than the LO-optical phonon energy ?ω_LO. Our calculations are performed using a self-consistent field approximation, which includes the local-field correction within the Singwi, Tosi, Land, and Sjolander (STLS) theory at zero temperature and assuming a three-subband model, where only the first subband is occupied by electrons. The potential confining effects on the collective energies were also considered.     

Processing and characterization of a biaxially oriented conducting polymer

Two methods have been developed for the preparation of biaxially oriented poly(phenylene vinylene) from its poly(sulfonium salt) precursor. A two-stage stretching process permits non-equibiaxial stretching over a wide range of deformation ratios and a bubble expansion technique allows equibiaxial planar extension. The resulting films were examined using X-ray diffraction prior to chemical doping with SbF₅ vapor. Biaxial orientation was shown to exert considerable influence over the attainable electrical conductivity.