Experimental investigation of flow and segregation behaviour of bulk solids in silos under high gravity conditions

Many researchers have investigated the flow and segregation behaviour in model scale experimental silos at normal gravity conditions. However it is known that the stresses experienced by the bulk solid in industrial silos are high when compared to model silos. Therefore it is important to understand the effect of stress level on flow and segregation behaviour and establish the scaling laws governing this behaviour. The objective of this paper is to understand the effect of gravity on the flow and segregation behaviour of bulk solids in a silo centrifuge model. The materials used were two mixtures composed of Polyamide and glass beads. The discharge of two bi-disperse bulk solids in a silo centrifuge model were recorded under accelerations ranging from 1g to 15g. The velocity distribution during discharge was evaluated using Particle Image Velocimetry (PIV) techniques and the concentration distribution of large and small particles were obtained by imaging processing techniques. The flow and segregation behaviour at high gravities were then quantified and compared with the empirical equations available in the literature

Aspects determining the risk of pesticides to wild bees: risk profiles for focal crops on three continents.

In order to conduct a proper risk assessment of pesticides to bees, information is needed in three areas: (i) the toxicity of the pesticide; (ii) the probability of bee exposure to that pesticide; and (iii) the population dynamics of the bee species in question. Information was collected on such factors affecting pesticide risk to (primarily wild) bees in several crops in Brazil, Kenya and The Netherlands. These data were used to construct ?risk profiles? of pesticide use for bees in the studied cropping systems. Data gaps were identified and potential risks of pesticides to bees were compared between the crops. Initially, risk profiling aims to better identify gaps in our present knowledge. In the longer term, the established risk profiles may provide structured inputs into risk assessment models for wild and managed bees, and lead to recommendations for specific risk mitigation measures.Edição dos Proceedings of the 11 International Symposium Hazards of Pesticides to Bees, Wageningen, nov. 2011

Colonization of the Mediterranean Basin by the vector biting midge species Culicoides imicola: an old story

Understanding the demographic history and genetic make-up of colonizing species is critical for inferring population sources and colonization routes. This is of main interest for designing accurate control measures in areas newly colonized by vector species of economically important pathogens. The biting midge Culicoides imicola is a major vector of Orbiviruses to livestock. Historically, the distribution of this species was limited to the Afrotropical region. Entomological surveys first revealed the presence of C. imicola in the south of the Mediterranean basin by the 1970's. Following recurrent reports of massive bluetongue outbreaks since the 1990s, the presence of the species was confirmed in northern areas. In this study, we addressed the chronology and processes of C. imicola colonization in the Mediterranean basin. We characterized the genetic structure of its populations across Mediterranean and African regions using both mitochondrial and nuclear markers, and combined phylogeographical analyses with population genetics and approximate Bayesian computation. We found a west/east genetic differentiation between populations, occurring both within Africa and within the Mediterranean basin. We demonstrated that three of these groups had experienced demographic expansions in the Pleistocene, probably because of climate changes during this period. Finally, we showed that C. imicola could have colonized the Mediterranean basin in the late Pleistocene or early Holocene through a single event of introduction; however we cannot exclude the hypothesis involving two routes of colonization. Thus, the recent bluetongue outbreaks are not linked to C. imicola colonization event, but rather to biological changes in the vector or the virus

Insect Pollinated Crops, Insect Pollinators and US Agriculture: Trend Analysis of Aggregate Data for the Period 1992–2009

In the US, the cultivated area (hectares) and production (tonnes) of crops that require or benefit from insect pollination (directly dependent crops: apples, almonds, blueberries, cucurbits, etc.) increased from 1992, the first year in this study, through 1999 and continued near those levels through 2009; aggregate yield (tonnes/hectare) remained unchanged. The value of directly dependent crops attributed to all insect pollination (2009 USD) decreased from $14.29 billion in 1996, the first year for value data in this study, to$10.69 billion in 2001, but increased thereafter, reaching $15.12 billion by 2009. The values attributed to honey bees and non-Apis pollinators followed similar patterns, reaching$11.68 billion and $3.44 billion, respectively, by 2009. The cultivated area of crops grown from seeds resulting from insect pollination (indirectly dependent crops: legume hays, carrots, onions, etc.) was stable from 1992 through 1999, but has since declined. Production of those crops also declined, albeit not as rapidly as the decline in cultivated area; this asymmetry was due to increases in aggregate yield. The value of indirectly dependent crops attributed to insect pollination declined from$15.45 billion in 1996 to $12.00 billion in 2004, but has since trended upward. The value of indirectly dependent crops attributed to honey bees and non-Apis pollinators, exclusive of alfalfa leafcutter bees, has declined since 1996 to$5.39 billion and $1.15 billion, respectively in 2009. The value of alfalfa hay attributed to alfalfa leafcutter bees ranged between$4.99 and $7.04 billion. Trend analysis demonstrates that US producers have a continued and significant need for insect pollinators and that a diminution in managed or wild pollinator populations could seriously threaten the continued production of insect pollinated crops and crops grown from seeds resulting from insect pollination

ACE2 Deficiency Enhances Angiotensin II-Mediated Aortic Profilin-1 Expression, Inflammation and Peroxynitrite Production

Inflammation and oxidative stress play a crucial role in angiotensin (Ang) II-mediated vascular injury. Angiotensin-converting enzyme 2 (ACE2) has recently been identified as a specific Ang II-degrading enzyme but its role in vascular biology remains elusive. We hypothesized that loss of ACE2 would facilitate Ang II-mediated vascular inflammation and peroxynitrite production. 10-week wildtype (WT, Ace2+/y) and ACE2 knockout (ACE2KO, Ace2−/y) mice received with mini-osmotic pumps with Ang II (1.5 mg.kg−1.d−1) or saline for 2 weeks. Aortic ACE2 protein was obviously reduced in WT mice in response to Ang II related to increases in profilin-1 protein and plasma levels of Ang II and Ang-(1–7). Loss of ACE2 resulted in greater increases in Ang II-induced mRNA expressions of inflammatory cytokines monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-1β, and IL-6 without affecting tumor necrosis factor-α in aortas of ACE2KO mice. Furthermore, ACE2 deficiency led to greater increases in Ang II-mediated profilin-1 expression, NADPH oxidase activity, and superoxide and peroxynitrite production in the aortas of ACE2KO mice associated with enhanced phosphorylated levels of Akt, p70S6 kinase, extracellular signal-regulated kinases (ERK1/2) and endothelial nitric oxide synthase (eNOS). Interestingly, daily treatment with AT1 receptor blocker irbesartan (50 mg/kg) significantly prevented Ang II-mediated aortic profilin-1 expression, inflammation, and peroxynitrite production in WT mice with enhanced ACE2 levels and the suppression of the Akt-ERK-eNOS signaling pathways. Our findings reveal that ACE2 deficiency worsens Ang II-mediated aortic inflammation and peroxynitrite production associated with the augmentation of profilin-1 expression and the activation of the Akt-ERK-eNOS signaling, suggesting potential therapeutic approaches by enhancing ACE2 action for patients with vascular diseases

Diversidad de polinizadores de girasol y sus efectos en el rendimiento de semillas en el Distrito Makueni, este de Kenia

A field experiment was carried out in 2004 and 2005 to identify the diversity of sunflower (Helianthus annuus L.) pollinators and their influence on seed yield in Makueni district, a semi-arid area in Eastern Kenya. Insect flower visitors were recorded, pollen counted from their body and pollination efficiency index for each visitor determined. Seed yield from plots where insect visitors had access to and where they were denied access was compared. The proportional difference of yield from this pollination scenario was used to estimate monetary net-gain by farmers that could be attributed to insect pollination. In total, individuals belonging to 14 insect species were observed visiting sunflower floral heads. These included six Lepidopteran species, five Hymenopteran species, two Dipteran species, and one Coleopteran species. Apis mellifera L. was the most frequent visitor and had the highest pollination efficiency index. Plots where insect visitors had access produced on average 53% more seed yield compared with plots where insect visitors were excluded. This translates to a net monetary benefit of 51% of the total annual market value of sunflower, accruing to farmers in Makueni district in 2005 due to insect pollination.Se condujo un experimento de campo entre 2004 y 2005 para determinar la diversidad de polinizadores de girasol (Helianthus annuus L.) y su influencia en el rendimiento de semillas en el distrito Makueni, una región semi-árida del Este de Kenia. Se identificaron los insectos vectores de polinización y se contó el polen adherido a sus cuerpos, a fin de determinar el índice de eficiencia de polinización de cada especie. Se comparó el rendimiento de semillas entre las parcelas visitadas y no visitadas por los vectores de polinización. Se estimó la ganancia monetaria neta de los campesinos atribuida a la polinización por insectos. En total, se observaron 14 especies de insectos visitando girasoles, que incluyeron 6 especies de Lepidópteros, 5 de Himenópteros, 2 de Dípteros y un Coleóptero. Apis mellifera L. fue la especie visitante más frecuente y obtuvo el mayor índice de eficiencia de polinización. Las parcelas a las que los insectos tuvieron acceso produjeron como promedio un 53% más semillas que las parcelas de las que los insectos fueron excluidos. Esto implica un beneficio monetario neto del 51% del valor total del mercado anual de girasol, debido a polinización por insectos, para los campesinos del distrito Makueni en 2005

Distribución y fluctuación estacional del trips de la flor (Thysanoptera: Thripidae) en la judía (Phaseolus vulgaris L.) en Kenia

The aim of this research was to study spatial distribution of flower thrips on French beans (Phaseolus vulgaris L.) in Kenya. Their build up and seasonal population dynamics was monitored using sticky blue colour traps and sampling of leaves and flowers in two seasons in 2002. Thrips infested French beans from the second week after crop emergence. Their population peaked at peak flowering. The sticky trap catches were linearly related to the actual presence of thrips on the crop and could estimate population build up of adult thrips on leaves and flowers. On the plants, most adults were on flowers. Larvae mainly inhabited leaves, buds and pods. The two thrips species, Frankliniella occidentalis (Pergande) and Megalurothrips sjostedti Trybom were spatially separated. The former colonized lower-canopy leaves and early flowers while the latter inhabited middle-canopy leaves and mature flowers. Overall, M. sjostedti was less than 5% of the total thrips population, implying that F. occidentalis was the main thrips pest of French beans. This study suggests that French bean growers should monitor thrips population before initiating any control measure. In addition, they should commence thrips control early, at pre-flowering, using larvicides to reduce the thrips pool and their migration to flowers. A combination of monitoring with sticky traps and proper sampling would contribute to sustainable thrips management.El presente estudio trató de determinar los patrones de alimentación del trips de la flor como plaga de la judía (Phaseolus vulgaris L.) en Kenia. El incremento de la población y grado de infestación de trips se evaluó usando trampas de adherencia azules en hojas y flores durante dos estaciones en el 2002. Los trips infestaron a la judía desde la segunda semana después de la emergencia del cultivo, y alcanzaron una población máxima durante la floración. Conteos en las trampas de adherencia mostraron una correlación lineal con la presencia de trips en el cultivo y pueden servir de referencia del crecimiento de las poblaciones de trips adultos en hojas y flores. En la planta, la mayoría de adultos se encontraron en las flores, mientras que las larvas se concentraron en las hojas, brotes y vainas. Las especies de trips Frankliniella occidentalis (Pergande) y Megalurothrips sjostedti Trybom se mantuvieron separadas en el espacio: mientras que la primera prefiere las hojas inferiores del dosel y las flores jóvenes, la segunda suele optar por las hojas de en medio del dosel y flores maduras. M. sjostedti representa menos del 5% de la población total de trips, lo que hace de F occidentalis la principal peste de la judía. El estudio sugiere que los agricultores deben monitorizar la dinámica poblacional de los trips antes de efectuar medidas de control, y complementariamente, deberían usar larvicidas antes de la floración previendo su posterior migración a las flores. Una adecuada combinación entre vigilancia y adecuada toma de muestras contribuiría al control sostenible de las poblaciones de trips

Economic Benefit of Crop Pollination by Bees: A Case of Kakamega Small-Holder Farming in Western Kenya

Kasina JM, Mburu J, Kraemer M, Holm-Mueller K. Economic Benefit of Crop Pollination by Bees: A Case of Kakamega Small-Holder Farming in Western Kenya. JOURNAL OF ECONOMIC ENTOMOLOGY. 2009;102(2):467-473.In most developing countries, crop production is by small scale farmers, who mainly produce for their own consumption and the extra for market, Pollination in such systems is unmanaged and is usually incidental, Supported by nearby ecosystems. One of the reasons of not managing pollination is the lack of understanding of its economic value. The "public-good" nature of pollination in these systems also discourages individual initiatives intended to conserve pollinators. We evaluate the economic returns from bee pollination in small-holder farming systems. To do this we apply the factor of production method, a form of revealed preferences methods available for valuing ecosystem services. Our analyses show that bee pollination enhances the yield of most crops grown in the farmland and improves immensely the quality of produce. Almost 40% of the annual value of crops under consideration represented the net returns derived from bee pollination. More than 99% of this benefit is attributed to pollination by feral bees. We provide in-depth valuation of pollination service and discuss applicability and limitations of the factor of production method in developing countries