A discrete model for the apparent viscosity of polydisperse suspensions including maximum packing fraction

Based on the notion of a construction process consisting of the stepwise addition of particles to the pure fluid, a discrete model for the apparent viscosity as well as for the maximum packing fraction of polydisperse suspensions of spherical, non-colloidal particles is derived. The model connects the approaches by Bruggeman and Farris and is valid for large size ratios of consecutive particle classes during the construction process, appearing to be the first model consistently describing polydisperse volume fractions and maximum packing fraction within a single approach. In that context, the consistent inclusion of the maximum packing fraction into effective medium models is discussed. Furthermore, new generalized forms of the well-known Quemada and Krieger equations allowing for the choice of a second-order Taylor coefficient for the volume fraction ($\phi^2$-coefficient), found by asymptotic matching, are proposed. The model for the maximum packing fraction as well as the complete viscosity model are compared to experimental data from the literature showing good agreement. As a result, the new model is shown to replace the empirical Sudduth model for large diameter ratios. The extension of the model to the case of small size ratios is left for future work.Comment: 14 pages, 4 figure

Sustainable Tourism Marketing Strategies at UNESCO World Heritage Sites

Designation as a United Nations Educational Scientific and Cultural Organization (UNESCO) World Heritage site has a significant impact on the tourism development and sustainability of a site, city, region or country. World Heritage sites bring a certain level of prestige and international recognition, but they also have an impact on the local communities as they impact day to day life and rituals of the residents. Several paradigms exist in evaluating the success of a UNESCO World Heritage site. This paper specifically examines how marketing strategies bolster sustainable tourism efforts

Effects of near wall modeling in the Improved-Delayed-Detached-Eddy-Simulation (IDDES) methodology

The present study aims to assess the effects of two different underlying RANS models on overall behavior of the IDDES methodology when applied to different flow configurations ranging from fully attached (plane channel flow) to separated flows (periodic hill flow). This includes investigating prediction accuracy of first and second order statistics, response to grid refinement, grey area dynamics and triggering mechanism. Further, several criteria have been investigated to assess reliability and quality of the methodology when operating in scale resolving mode. It turns out that irrespective of the near wall modeling strategy, the IDDES methodology does not satisfy all criteria required to make this methodology reliable when applied to various flow configurations at different Reynolds numbers with different grid resolutions. Further, it is found that using more advanced underlying RANS model to improve prediction accuracy of the near wall dynamics results in extension of the grey area, which may delay the transition to scale resolving mode. This systematic study for attached and separated flows suggests that the shortcomings of IDDES methodology mostly lie in inaccurate prediction of the dynamics inside the grey area and demands further investigation in this direction to make this methodology capable of dealing with different flow situations reliably

Seed systems and crop genetic diversity in agroecosystems

Poster presented at the First Diversitas Open Science Conference. Oaxaca (Mexico), 9-12 Nov 200

Advanced model of squirrel cage induction machine for broken rotor bars fault using multi indicators

Squirrel cage induction machine are the most commonly used electrical drives, but like any other machine, they are vulnerable to faults. Among the widespread failures of the induction machine there are rotor faults. This paper focuses on the detection of broken rotor bars fault using multi-indicator. However, diagnostics of asynchronous machine rotor faults can be accomplished by analysing the anomalies of machine local variable such as torque, magnetic flux, stator current and neutral voltage signature analysis. The aim of this research is to summarize the existing models and to develop new models of squirrel cage induction motors with consideration of the neutral voltage and to study the effect of broken rotor bars on the different electrical quantities such as the park currents, torque, stator currents and neutral voltage. The performance of the model was assessed by comparing the simulation and experimental results. The obtained results show the effectiveness of the model, and allow detection and diagnosis of these defects

Farmers' management of rice varietal diversity in the mid-hills of Nepal: implications for on-farm conservation and crop improvement

Season-long monitoring of on-farm rice (Oryza sativa, L.) plots in Nepal explored farmers' decision-making process on the deployment of varieties to agroecosystems, application of production inputs to varieties, agronomic practices and relationship between economic return and area planted per variety. Farmers deploy varieties [landraces (LRs) and modern varieties (MVs)] to agroecosystems based on their understanding of characteristics of varieties and agroecosystems, and the interaction between them. In marginal growing conditions, LRs can compete with MVs. Within an agroecosystem, economic return and area planted to varieties have positive relationship, but this is not so between agroecosystems. LRs are very diverse on agronomic and economic traits; therefore, they cannot be rejected a priori as inferior materials without proper evaluation. LRs have to be evaluated for useful traits and utilized in breeding programmes to generate farmer-preferred materials for marginal environments and for their conservation on-farm

Assessing soil erosion and control factors by the radiometric technique in the Boussouab catchment, Eastern Rif, Morocco

The final version is available at: http://www.sciencedirect.com/science/journal/03418162In the Eastern Rif of N Morocco, soil conservation is seriously threatened by water erosion. Large areas of soil have reached an irreversible state of degradation. In this study, the 137Cs technique was used to quantify erosion rates and identify the main factors involved in the erosion process based on a representative catchment of the Eastern Rif. To estimate erosion rates in terms of the main factors affecting soil losses, samples were collected taking into account the lithology, slope and land use along six selected transects within the Boussouab catchment. The transects were representative of the main land uses and physiographic characteristics of that Rif sector. The reference inventory for the area was established at a stable, well preserved, matorral site (value of 4250 Bq m-2). All the sampling sites were eroded and 137Cs inventories varied widely (between 245 and 3670 Bq m-2). The effective soil losses were also highly variable (between 5.1 and 48.8 t ha-1 yr-1). Soil losses varied with land use. The lowest average values were on matorral and fallow land (10.5 and 15.2 t ha-1 yr-1, respectively) but much higher with alfa vegetation or cereal crops (31.6 and 27.3 t ha-1 yr-1, respectively). The highest erosion rate was on a badland transect at the more eroded part of the catchment, with rates exceeding 40 t ha-1 yr-1 and reaching a maximum of 48.8 t ha-1 yr-1.The average soil losses increased by more than 100 % when the slope increased from 10º (17.7 t ha-1 yr-1) to 25º (40. 8 t ha-1 yr-1). Similar results were obtained when comparing erosion rates in soils that were covered by matorral with respect to those under cultivation. Lithology was also a key factor affecting soil loss. Soils on marls were more erodible and the average erosion rates reached 29.36 t ha-1 yr-1, which was twice as high as soils on the glacis and old fluvial terraces (average rates of 14.98 t ha-1 yr-1 ). The radiometric approach was very useful to quantify erosion rates and to examine the pattern of soil movement. The analysis of main erosion factors can help to promote rational soil use and establish conservation strategies in the study area.This work was funded by the bilateral projects 2004MA-1005 and 18304-RM from the Agencia de Cooperación Interuniversitaria and the CICYT projects RADIERO (REN2002-02702/GLO) and REM (CGL2005-02009/BTE).Peer reviewe

Early embryonic requirement for nucleoporin Nup35/NPP-19 in nuclear assembly

11 pages, 8 figures, 3 tables.-- PMID: 19146848 [PubMed].-- Available online Dec 30, 2008.Supporting information (Suppl. figs S1-S5, movies S1-S6) available at: http://dx.doi.org/10.1016/j.ydbio.2008.12.024Nuclear pore complexes (NPCs) are gateways for transport between the nucleus and cytoplasm of eukaryotic cells and play crucial roles in regulation of gene expression. NPCs are composed of multiple copies of not, vert, similar 30 different nucleoporins (nups) that display both ubiquitous and cell type specific functions during development. Vertebrate Nup35 (also known as Nup53) was previously described to interact with Nup93, Nup155 and Nup205 and to be required for nuclear envelope (NE) assembly in vitro. Here, we report the first in vivo characterization of a Nup35 mutation, npp-19(tm2886), and its temperature-dependent effects on Caenorhabditis elegans embryogenesis. At restrictive temperature, npp-19(tm2886) embryos exhibit chromosome missegregation, nuclear morphology defects and die around mid-gastrulation. Depletion of Nup35/NPP-19 inhibits NE localization of Nup155/NPP-8, NPC assembly and nuclear lamina formation. Consequently, nuclear envelope function, including nucleo-cytoplasmic transport, is impaired. In contrast, recruitment of Nup107/NPP-5, LEM-2 and nuclear membranes to the chromatin surface is Nup35/NPP-19-independent, suggesting an uncoupling of nuclear membrane targeting and NPC assembly in the absence of Nup35/NPP-19. We propose that Nup35/NPP-19 has an evolutionary conserved role in NE formation and function, and that this role is particularly critical during the rapid cell divisions of early embryogenesis.This work was funded by grants from the Spanish Ministry of Science and Education (RYC-2003-001521, BFU-2004-01096, BFU-2007-60116) to PA. In addition, we wish to acknowledge Fundación Ramón Areces for a fellowship to ER and Junta de Andalucía for institutional support.Peer reviewe

STATE–BUILDING, CITIZENSHIP AND THE BANYARWANDA QUESTION IN THE DEMOCRATIC REPUBLIC OF CONGO

Since achieving independence in June 1960, the Democratic Republic of Congo (DRC) has been grappling with the question of the citizenship of Kinyarwanda and Kirundi-speaking populations settled on its territory at different historical periods, herein referred to as the Banyarwanda. While there is evidence of the presence of some Banyarwanda communities on current Congolese territory prior to the advent of Belgian colonisation in the area, the majority of the Banyarwanda currently living in the DRC  are descendants of those brought into the country through colonial immigration and labour recruitment processes, political exile and refuge as well as clandestine migration. Using a historical perspective, this article analyses the manner in which the question of the citizenship of the Banyarwanda has been handled in the DRC since the establishment of the Congo Free State in 1885. The article locates the roots of the problem in the poorly designed colonial policies surrounding the relocation of these populations to the Kivu region. However, the article acknowledges that the sole shortcomings on the part of colonial authorities would have never had the current consequences if it was not for the inconsistencies of the different post-colonial governments that have ruled over the DRC. Instead of resolving the citizenship question in an effective and sustainable manner, all these governments have based their respective responses to the issue on short-term political expediencies as dictated by the balance of forces within the country, the Kivu area and the Great Lakes region at a particular juncture

The challenges of power-sharing and transitional justice in post-civil war African countries: Comparing Burundi, Mozambique and Sierra Leone

This article uses the cases of Burundi, Mozambique and Sierra Leone to analyse transitional justice processes in African societies where powersharing was used as a key tool to end very protracted and violent civil wars. It is argued that, by affording warring parties a prominent role in the postsettlement political environment, power-sharing inadvertently impeded the pursuit of both restorative and criminal justice in all three countries. As an instance of ‘warriors’ justice’, power-sharing was used by such actors as an opportunity to avoid facing retributive justice. Indeed, due to the central position they held within the power-sharing dispensations, former warriors emphasised amnesty while paying lip service to reparations for victims. In all three countries, the decision to revert to the international judicial system or not was mainly motivated by political calculations rather than any genuine concern for justice. However, notwithstanding the shortcomings above, the consensus brought about by the power-sharing dispensations enabled the three countries to effect meaningful institutional reforms, albeit with limited and different levels of success.Keywords: power-sharing, transitional justice, civil war, Burundi, Mozambique, Sierra Leon