Making real progress toward more sustainable societies using decision support models and tools: Introduction to the special volume

Academics, politicians, professionals and the general public are aware that without stewarding our planet’s natural resources, man is on the pathway towards a global collapse. Over the next three decades mankind is expected to consume an estimated 140 billion tons of minerals, ores, fossil fuels and biomass per year – three times current consumption. Social welfare and human wellbeing are threatened with the scarcity of natural resources; consequently, nations and their societies are also at risk of collapse. The readers of this special volume will find a compilation of scholarly research papers with real-life applications that take the challenge of proposing decision-making models and tools to address sustainability challenges in integrative ways. The main focus of this special volume is integration of sustainability dimensions (economic, social, environmental, ethical and time) into decision-support models and to identify pathways to achieve more sustainable societies. The majority of the research in this special volume, 74 percent, focuses on environmental and economic dimensions. Only 26 percent integrated social dimensions with them. Methodologically, a range of mathematical models and tools are presented to support prescriptive decision-making, with some descriptive models integrated, to support decision-makers in solving practical problems across a variety of industries and scenarios. The breadth and complexity of issues facing organizations and society requires innovative applications of these methodologies. The concerns cover a spectrum ranging from energy to solid waste management. A multitude of levels from broad-based policy concerns to strategic inter-organizational sustainable supply chain management and significantly, shop floor operational issues are also covered. The variety of problems and solutions exemplifies the potential for modelling and operations research for addressing some of our world’s most pressing concerns

Reduction of the effects of InGaAs alloy disorder by using superlattices as the conduction channel in modulation-doped heterostructures

We present the photo-Hall electrical properties of MBE-grown modulation-doped field-effect transistors (MODFET) structures using the so-called short-period superlattices (SPS) channel of InAs and GaAs instead of the standard InGaAs alloy channel. Photo-Hall measurements present the advantage of permitting the observation of mobility versus carrier density curves so that the effect of the replacement by the SPS channel can be better understood. The variables were the indium content (y=0.08 or 0.25) and the channel thickness (80 Angstrom or 125 Angstrom), and the approach was to compare the results for the two structures. Our results indicate that for y=0.08, the electrical properties are the same for both samples, either for using the SPS or the alloy channel. On the other hand, the electrical properties differ significantly for an indium content of y=0.25. Our conclusion is that the scattering associated with the alloy disorder increases with the indium content and that this deleterious effect can be reduced by replacing the alloy channel by a SPS channel

Electron effective mass determination in asymmetric modulation-doped field-effect transistor heterostructures using InxGa1−xAs quantum well and InAs–GaAs superlattice channels

Cyclotron resonance and photoluminescence measurements have been performed on two types of modulation-doped field-effect transistor heterostructures having their bidimensional channel based, respectively, on an InxGa1-xAs quantum well and an InAs-GaAs short-period superlattice. A linear dependence of the electron effective mass as a function of indium content of the channel was obtained from cyclotron resonance measurements. For a given average value of the indium content, the effective mass in the InAs-GaAs short-period superlattice channel is found to be systematically higher than that obtained in structures with an alloy-based channel. This is attributed to larger nonparabolic effects in the former case. In our theoretical model, the electron and heavy hole energy levels and the electron wavefunction are determined self-consistently and used to estimate the nonparabolic corrections that apply to the effective mass deduced from cyclotron resonance measurements

Biodiversity of rhizobia associated with cowpea cultivars in soils of the lower half of the São Francisco River Valley Biodiversidade de rizóbio associado a cultivares de feijão-caupi em solos do submédio do Vale do São Francisco

The biodiversity of rhizobium in soils of the São Francisco Valley is unknown and can be studied using cowpea as trap plants. The objective of this study was to verify the diversity of diazotrophic bacteria that nodulate cowpea in soils of the lower half of the São Francisco River Valley by morphological and genotypic characterization. Seven soil samples (A1, A2, A3, A4, C1, C2 and MC) were collected to capture bacteria associated to five cowpea cultivars (IPA 206, BRS Pujante, BRS Marataoã, Canapu Roxo, and Sempre Verde), in a 5x7 factorial design with three replications. Thirty days after plant emergence, the nodules were collected and the bacteria isolated and analyzed in relation to their growth characteristics in YMA medium. The 581 isolates were grouped in 49 morphologic groups. Of this total, 62.3 % formed colonies in up to three days, 33.4 % grew from the 6th day on, and 4.3 % began to grow 4 to 5 days after incubation. Regarding the formation of acids and alkalis, 63 % acidified the medium, 12 % made it alkaline and 25 % maintained the medium at neutral pH. The highest diversity was observed in the A3 sample and in isolates associated with the cultivars Canapu Roxo and BRS Pujante. Thirty-eight representative isolates were chosen for the genotypic characterization, clustered in four groups based on the restriction analysis of 16s rDNA. This grouping was strongly correlated with the sampling site; 13 rhizobium isolates had an electrophoretic profile distinct from the standard rhizobium strains used in this study.<br>A biodiversidade de rizóbio de solos do Vale do São Francisco é desconhecida e pode ser estudada utilizando feijão-caupi como planta-isca. Este trabalho teve por objetivo verificar a diversidade de bactérias diazotróficas que nodulam feijão-caupi em solos do Submédio do Vale do São Francisco por meio da caracterização morfológica e genotípica. Sete amostras de solos (A1, A2, A3, A4, C1, C2 e MC) foram coletadas para a captura de bactérias, utilizando cinco cultivares de feijão-caupi (IPA 206, BRS Pujante, BRS Marataoã, Canapu Roxo e Sempre Verde), perfazendo um fatorial 5 x 7 com três repetições. Aos 30 dias após a emergência das plantas, os nódulos foram coletados e as bactérias isoladas e analisadas quanto às características culturais em meio YMA. Foram obtidos 581 isolados, que se agruparam em 49 grupos morfológicos. Desse total, 62,3 % formaram colônias em até três dias, 33,4 % cresceram a partir do sexto dia e 4,3 % cresceram entre quatro e cinco dias após a incubação. Quanto à formação de ácido e álcalis, 63 % acidificaram o meio de cultura, 12 % alcalinizaram e 25 % mantiveram o pH do meio neutro. As maiores diversidades foram encontradas nas amostras A3 e nos isolados associados às cultivares Canapu Roxo e BRS Pujante. Escolheram-se 38 isolados representativos para a caracterização genotípica, em que foram obtidos quatro grupos a partir da análise de restrição do 16s rDNA. Este agrupamento teve forte correlação com o local de origem dos isolados, mostrando 13 deles com perfil eletroforético distinto das estirpespadrão de rizóbios utilizadas no estudo