Total reflection X-ray fluorescence spectrometry for the introduction of novel materials in clean-room production environments

In this paper, a number of case studies on the analysis of novel metallic contaminants on conventional and alternative substrates using the technique of total reflection X-ray fluorescence spectrometry (TXRF) is presented. Investigated materials include Si and Ge substrates, high-/spl kappa/ dielectric contaminants, and layers, and Si wafers contaminated with elements from metal gates and Cu interconnects. One focus is on the application and optimization of detection limits in direct TXRF. For the TXRF analysis of contaminants on Si wafers, a general conclusion is that a combination of three excitation sources is needed to cover the whole range of interest: a low-energy excitation (about 5 keV, e.g., WM/spl alpha/, Cr K/spl alpha/) for the low Z elements such as Na, Mg, and Al, a moderate-energy excitation (10-20 keV, e.g., WL/spl beta/, MoK/spl alpha/) for the 3d-transition elements, and a high-energy excitation (25-35 keV, e.g., W, continuum) for the analysis of elements such as Zr, Ru, Mo, and Pd. Also, for the analysis of novel substrates using direct TXRF, a careful selection of the excitation source results in better detection limits. In this way, detection limits at 10/sup 10/-10/sup 11/ at/cm/sup 2/ can be achieved, even for novel contaminants and substrates. As the International Technology Roadmap for Semiconductors (ITRS) requires control below 5/spl times/10/sup 9/ at/cm/sup 2/, the application of a preconcentration procedure such as vapor phase decomposition-droplet collection TXRF (VPD-DC-TXRF) is required. Proper use of this procedure allows the improvement of the detection limits by two to three orders of magnitude, depending on wafer size and chemical collection efficiency. The usability of this preconcentration procedure in combination with TXRF will be demonstrated for noble elements and germanium substrates.     

Adapting maize production to climate change in sub-Saharan Africa

Given the accumulating evidence of climate change in sub-Saharan Africa, there is an urgent need to develop more climate resilient maize systems. Adaptation strategies to climate change in maize systems in sub-Saharan Africa are likely to include improved germplasm with tolerance to drought and heat stress and improved management practices. Adapting maize systems to future climates requires the ability to accurately predict future climate scenarios in order to determine agricultural responses to climate change and set priorities for adaptation strategies. Here we review the projected climate change scenarios for Africa’s maize growing regions using the outputs of 19 global climate models. By 2050, air temperatures are expected to increase throughout maize mega- environments within sub-Saharan Africa by an average of 2.1°C. Rainfall changes during the maize growing season varied with location. Given the time lag between the development of improved cultivars until the seed is in the hands of farmers and adoption of new management practices, there is an urgent need to prioritise research strategies on climate change resilient germplasm development to offset the predicted yield declines.     

Crops that feed the world 6. Past successes and future challenges to the role played by maize in global food security

Maize is one of the most important food crops in the world and, together with rice and wheat, provides at least 30% of the food calories to more than 4.5 billion people in 94 developing countries. In parts of Africa and Mesoamerica, maize alone contributes over 20% of food calories. Maize is also a key ingredient in animal feed and is used extensively in industrial products, including the production of biofuels. Increasing demand and production shortfalls in global maize supplies have worsened market volatility and contributed to surging global maize prices. Climatic variability and change, and the consequent rise in abiotic and biotic stresses, further confound the problem. Unless concerted and vigorous measures are taken to address these challenges and accelerate yield growth, the outcome will be hunger and food insecurity for millions of poor consumers. We review the research challenges of ensuring global food security in maize, particularly in the context of climate change. The paper summarizes the importance of maize for food, nutrition and livelihood security and details the historical productivity of maize, consumption patterns and future trends. We show how crop breeding to overcome biotic and abiotic stresses will play a key role in meeting future maize demand. Attention needs to be directed at the generation of high yielding, stress-tolerant and widely-adapted maize varieties through judicious combination of conventional and molecular breeding approaches. The use of improved germplasm per se will not, however, be enough to raise yields and enhance adaptation to climate change, and will need to be complemented by improved crop and agronomic practices. Faced with emasculated state extension provision and imperfect markets, new extension approaches and institutional innovations are required that enhance farmers’ access to information, seeds, other inputs, finance and output markets. Over the long-term, large public and private sector investment and sustained political commitment and policy support for technology generation and delivery are needed to overcome hunger, raise the incomes of smallholder farmers and meet the challenges of growing demand for maize at the global level.     

Measuring the impact of scientific publications. The case of the biomedical sciences

The bibliometric indicators currently used to assess scientific production have a serious flaw: a notable bias is produced when different subfields are compared. In this paper we demonstrate the existence of this bias using the impact factor (IF) indicator. The impact factor is related to the quality of a published article, but only when each specific subfield is taken separately: only 15.6% of the subfields we studied were found to have homogeneous means. The bias involved can be very misleading when bibliometric estimators are used as a basis for assigning research funds. To improve this situation, we propose a new estimator, the RPU, based on a normalization of the impact factor that minimizes bias and permits comparison among subfields. The RPU of a journal is calculated with the formula: RPU=10(1-exp (-IF/x)), where IF is the impact factor of the journal and x the mean IF for the subfield in which the journal belongs. The RPU retains the advantages of the impact factor: simplicity of calculation, immediacy and objectivity, and increases homogeneous subfields from 15.6% to 93.7%.     

Improving market access and agricultural productivity growth in Africa: what role for producer organizations and collective action institutions?

The history of producer organizations in sub-Saharan Africa (SSA) is a mixed one. In the past, producer organizations often failed to provide desired services due to dependence on government support, which led to heavy political interference as well as internal leadership and managerial problems. However, the hasty retreat of the state following adjustment and market liberalization reforms left an institutional void that the private sector has failed to fill. This study reviews the role that producer organizations can play, and the challenges they face in improving access to markets and technologies for enhancing productivity of smallholder agriculture in SSA in the post-adjustment era. The paper critically examines the evidence for improving access to markets, information and technologies, and the conditions that facilitate the success of producer organizations in providing such services. Emphasis is on the characteristics of user groups, institutional arrangements, governance mechanisms, types of products (staples, perishables and other commodities), and the role of the public and private sector service providers. We conclude that while recent experiences are mixed, good governance, more homogeneous and optimal group size, transparency and market orientation can enhance the role of producer organizations in improving access to markets. However, ideally these organizations need to prioritise agribusiness opportunities over social welfare objectives even though this may mean that some households are unable to take advantage of them. Donors and governments have important roles to play in stimulating the emergence and development of economically viable and self-sustaining producer organizations. The private sector is also critical in terms of providing producer organizations with financial and business development services.     

Effect of manure and mineral fertilisation on pepper nutritional quality

BACKGROUND: The influence of farming systems on fruit quality remains controversial and the different aspects associated with each agricultural management system need to be studied separately to elucidate any specific effect on fruit quality. To this end, a greenhouse experiment was conducted to examine the effect of the usual fertilisation guidelines for pepper cultivation on the nutritional quality of fruits (sugars, vitamin C, total phenolic compounds, chlorophylls, total carotenoids and antioxidant activities in the hydrophilic (HAA) and lipophilic (LAA) fractions). Treatments included manure amendment combined with synthetic fertiliser applied at the rates recommended for organic (T1), low‐input (T2) and conventional (T3) practices. RESULTS: Pepper composition was not affected by increasing mineral fertilisation. In addition, treatment had no significant effect on HAA or LAA. The antioxidant activity of both the hydrophilic and lipophilic fractions increased from the green to the red stage of ripening. HAA contributed about 80% of the total antioxidant activity. CONCLUSION: Pepper response to mineral fertilisation seems to be less pronounced than that of other fruits, since antioxidant concentrations did not increase with increasing fertiliser application. Antioxidant activity in pepper was mainly linked to hydrophilic compounds (vitamin C and phenolic compounds). Ripening was the most important factor determining the fruit antioxidant composition. Copyright © 2009 Society of Chemical Industry     

Relationship between Fusarium spp. diversity and mycotoxin contents of mature grains in southern Belgium

Over a 4-year period (2010–13), a survey aiming at determining the occurrence of Fusarium spp. and their relations to mycotoxins in mature grains took place in southern Belgium. The most prevalent species were F. graminearum, F. avenaceum, F. poae and F. culmorum, with large variations between years and locations. An even proportion of mating type found for F. avenaceum, F. culmorum, F. cerealis and F. tricinctum is usually a sign of ongoing sexual recombination. In contrast, an unbalanced proportion of mating type was found for F. poae and no MAT1-2 allele was present in the F. langsethiae population. Genetic chemotyping indicates a majority of deoxynivalenol (DON)-producing strains in F. culmorum (78%, all 3-ADON producers) and F. graminearum (95%, mostly 15-ADON producers), while all F. cerealis strains belong to the nivalenol (NIV) chemotype. Between 2011 and 2013, DON, NIV, enniatins (ENNs) and moniliformin (MON) were found in each field in various concentrations. By comparison, beauvericin (BEA) was scarcely detected and T-2 toxin, zearalenone and α- and β-zearalenols were never detected. Principal component analysis revealed correlations of DON with F. graminearum, ENNs and MON with F. avenaceum and NIV with F. culmorum, F. cerealis and F. poae. BEA was associated with the presence of F. tricinctum and, to a lesser extent, with the presence of F. poae. The use of genetic chemotype data revealed that DON concentrations were mostly influenced by DON-producing strains of F. graminearum and F. culmorum, whereas the concentrations of NIV were influenced by the number of NIV-producing strains of both species added to the number of F. cerealis and F. poae strains. This study emphasises the need to pay attention to less-studied Fusarium spp. for future Fusarium head blight management strategies, as they commonly co-occur in the field and are associated with a broad spectrum of mycotoxins.