1,721,065 research outputs found
Agricultural commodity trade: What are the major issues?
No full textEthiopia depends heavily on agricultural commodity export as a major source of foreign currency earning and imports large amounts of agricultural items to compensate for the shortfall in food and nutrition security and raw material supply for the local food industry. It reached several milestones over recent decades. There was rapid growth of export earnings between mid-2000 and mid-2010 along with commodity diversification, which meant reduced reliance on coffee alone and increased contribution of oilseeds, grain legumes and meat. The country transitioned from a net importer to net exporter of tea and exported more meat than live animals and more processed than raw hides and skins. Despite those successes, however, 92% of the total export is not value added and there has been a continued decline of earnings between 2016 and 2020, making the country a net food importer, even with its huge potential for increased agricultural productivity and production
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Economic Evaluation of a Large-Scale PHBV Production Facility: Impact of Polymer Content on the Final Selling Price
No full textPoly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biodegradable polymer with excellent thermal and mechanical properties comparable to fossil-based plastics. Scaling up the production of this polymer could provide a viable solution for reducing the use of fossil-based materials. However, its current production capacities are limited, with only a few facilities implementing the process at pilot or semi-industrial scales. The primary challenge lies in the high production costs, with 40% of the expenses attributed to the feedstock used for fermentation. Additionally, the energy required for sterilization in processes using pure methanotrophic cultures further reduces its economic viability. In this study, the economic aspects of the PHBV production process were assessed at an industrial level (100,000 t/y PHBV), using cheap and renewable substrates such as valeric acid and methane. A mixed methanotrophic consortium was used to reduce the need for sterility. The techno-economic analysis was based on estimating both fixed investment and operating costs. Then, a sensitivity analysis was performed to analyse the effect that the polymer content has on the final selling price: the initial biomass concentration was set to 30 g L-1 and the PHBV content was considered to be 20, 30, 40, 50 and 70% wt on a dry weight basis. The results revealed that increasing the polymer content beyond 40% wt led to a more competitive PHBV selling price, thus opening significant market opportunities
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Assessing the performance of synthetic co-cultures during the conversion of methane into Poly(3-hydroxybutyrate)
No full textSynthetic co-cultures can enhance pollutant bioconversion performance through synergistic effects among co-existing species. In this study, the potential of Methylocystis hirsuta and Methylocystis parvus to support poly(3-hydroxybutyrate) (PHB) production in co-cultivation with Rhodococcus opacus and Pseudomonas putida under a CH4:O2 atmosphere was assessed batchwise. The metabolic activation of almost all co-cultures studied was faster than that of single strain cultures, bringing higher methane and oxygen consumption rates. Higher PHB yields were achieved when coupling M. hirsuta with R. opacus (63 % w w−1) or with R. opacus and P. putida (64.4 % w w−1) compared to M. hirsuta alone (38.5 % w w−1). Interestingly, the combination of both R. opacus and P. putida with M. parvus reduced PHB accumulation to 42.2 % w w−1 compared to the content observed in M. parvus monocultures (62.2 % w w−1) and M parvus + R. opacus co-cultures (66.6 % w w−1)
Exploring 1,3-Dioxolane Extraction of Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from Methylocystis hirsuta and Mixed Methanotrophic Strain: Effect of Biomass-to-Solvent Ratio and Extraction Time
No full textThe increasing need for biodegradable polymers demands efficient and environmentally friendly extraction methods. In this study, a simple and sustainable method for extracting polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHB-co-HV) from Methylocystis hirsuta and a mixed methanotrophic consortium with different biopolymer contents was presented. The extraction of biopolymers with 1,3-dioxolane was initially investigated by varying the biomass-to-solvent ratio (i.e., 1:2 w v−1, 1:4 w v−1, 1:6 w v−1, 1:8 w v−1 and 1:10 w v−1) and extraction time (6, 8 and 10 h) at the boiling point of the solvent and atmospheric pressure. Based on the results of the preliminary tests, and only for the most efficient biomass-to-solvent ratio, the extraction kinetics were also studied over a time interval ranging from 30 min to 6 h. For Methylocystis hirsuta, the investigation of the extraction time showed that the maximum extraction was reached after 30 min, with recovery yields of 87% and 75% and purities of 98.7% and 94% for PHB and PHB-co-HV, respectively. Similarly, the extraction of PHB and PHB-co-HV from a mixed methanotrophic strain yielded 88% w w−1 and 70% w w−1 recovery, respectively, with 98% w w−1 purity, at a biomass-to-solvent ratio of 6 in 30 min
Solubility of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in sustainable and green solvents: Effect of HV content and comparison between experimental results and theoretical prediction
No full textFor the first time, a quantitative analysis of the solubility of poly-3hydroxybutyrrate-co-3hydroxyvalerate (PHBV) in green solvents is proposed. The solubility of two commercial co-polymers, with hydroxyvalerate (HV) contents of 8 %mol and 12 %mol, in 1,3-dioxolane, dimethyl carbonate and butyl acetate was experimentally determined using chloroform as the benchmark and water as the control. The results showed a direct correlation between solubility and temperature, with a maximum at the boiling point of the solvent. For PHBV with an HV content of 8 %mol, solubilities of 265 mg mL−1 for 1,3-dioxolane and dimethyl carbonate and 274 mg mL−1 for butyl acetate were measured; for PHBV with an HV content of 12 %mol, solubilities of 225 mg mL−1, 197 mg mL−1 and 137 mg mL−1 for 1,3-dioxolane, dimethyl carbonate and butyl acetate were measured, respectively. Following Hansen's theory, the PHBV solubility sphere was defined to predict the solubility of the co-polymers in solvents qualitatively. The validation of the sphere was performed by the experimental results herein obtained
Techno-economic assessment of biopolymer production from methane and volatile fatty acids: effect of the reactor size and biomass concentration on the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) selling price
No full textPoly(3-hydroxybutyrate-co-3-hydroxyvalerate) is a biobased and biodegradable polymer that could efficiently replace fossil-based plastics. However, its widespread deployment is slowed down by the high production cost. In this work, the techno-economic assessment of the process for producing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from low-cost substrates, such as methane and valeric acid derived from the anaerobic digestion of organic wastes, is proposed. Several strategies for cost abatement, such as the use of a mixed consortium and a line for reagent recycling during downstream, were adopted. Different scenarios in terms of production, from 100 to 100,000 t/y, were analysed, and, for each case, the effect of the reactor volume (small, medium and large size) on the selling price was assessed. In addition, the effect of biomass concentration was also considered. Results show that the selling price of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is minimum for a production plant with 100,000 t/y capacity, accounting for 18.4 €/kg, and highly influenced by the biomass concentration since it can be reduced up to 8.6 €/kg by increasing the total suspended solids from 5 to 30 g/L, This adjustment aligns the breakeven point of PHBV with the reported average commercial price
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