3D Virtual Pome Fruit Tissue Generation Based on Cell Growth Modeling

A 3D virtual fruit tissue generator is presented that can distinctly define the microstructural components of a fruit tissue and that can be used to model important physical processes such as gas transport during controlled atmosphere storage. The model is based on the biomechanics of plant cells in tissues. The main merit of this algorithm is that it can account for typical differences in intercellular air space networks and in cell size and shape found between different fruit species and tissues. The cell is considered as a closed thin walled structure, maintained in tension by turgor pressure. The cell walls of adjacent cells are modeled as parallel, linear elastic elements which obey Hooke's law. A 3D Voronoi tessellation is used to generate the initial topology of the cells. Intercellular air spaces of schizogenous origin are generated by separating the Voronoi cells along the edges where three Voronoi cells are in contact; while intercellular air spaces of lysigenous origin are generated by deleting (killing) some of the Voronoi cells randomly. Cell expansion then results from turgor pressure acting on the yielding cell wall material. To find the sequence of positions of each vertex and thus the shape of the tissue with time, a system of differential equations for the positions and velocities of each vertex is established and solved using a Matlab ordinary differential equation solver. Statistical comparison with synchrotron tomography images of fruit tissue is excellent. The virtual tissues can be used to study tissue mechanics and exchange processes of important metabolites.     

Experiments and Simulations on the Cleaning of a Swellable Soil in Plane Channel Flow

ABSTRACT

The cleaning behavior of a soil with physical properties that depend on the wetting time is studied experimentally via the local phosphorescence detection method and simulated numerically in fully developed plane channel flow for Reynolds numbers up to 30,000. A computationally inexpensive general cleaning model is proposed, adopting an existing removal model and coupling it to the turbulent flow field. The influence of the soil on the flow is neglected and the transient behavior of the soil during cleaning is modeled in the form of a transient Dirichlet boundary condition. This approach is innovative for computational fluid dynamics of this phenomenon. The way of determining the model parameters from the experiment is described. The comparison of the simulation results with experimental data reveals very good suitability of the model in the case of a starch soil. A similar good agreement is found for data for a model protein foulant in tube flow from the literature.     

The Brazilian experience of rural electrification in the Amazon with decentralized generation - The need to change the paradigm from electrification to development

There are at least 607 thousand households in the Brazilian Amazon that need to be attended with some form of regular electricity service. These households are not attended by the electricity sector through its electricity distribution companies and most of them have some form of precarious decentralized electricity generation that is not registered or regulated in the institutional framework. Diverse initiatives were taken by Brazilian government to attend these household through alternatives that relied on locally available renewable energy. This paper accesses this initiatives of rural electrification in the Brazilian Amazon. First an overview of the problems of rural electricity are discussed and its specificities in the Brazilian Amazon. Then the Brazilian institutional framework that organizes the decentralized electricity generation is described with its various limitations. The diverse initiatives undertaken to attend the rural communities in the Amazon since the 1990s are described, as well as how these initiatives are linked to the policies for rural electrification. The results shows that it can be inferred that sole market mechanisms are not sufficient to guarantee economic sustainability of these projects. This can be one of the reasons why traditional electricity distribution companies showed the lack of interest in promoting rural electrification with other means than grid extension. The most successful projects had financed efforts to integrate the generation of electricity into local development initiatives in order to guarantee sustainability and used substantial part of funding for local mobilization and organization. It needs a paradigm chance by treating these initiatives as local development initiatives and promoting alternative ways for its implementation through partnership between local new actors in the electricity sector and government and implementing policy on a local municipal level.     

Atmospheric trace gas analysis with cavity ring-down spectroscopy

Cavity ring-down spectroscopy (CRDS) is a highly sensitive laser absorption method. It can be used for quantitative analysis of molecular species at the sub-ppb level. The absorption cell (cavity) is sealed by two high-reflective mirrors on each side, which results in an effective absorption path-length of some kilometers. Our experiments for atmospheric gas analysis have been carried out so far with an Excimer pumped dye laser in the UV-VIS and a CO overtone sideband laser in the wavelength region around 3 μm. Experiments with an all solid-state difference frequency laser system will follow. In the UV-VIS region, we measured trace gas molecules like SO₂, NO₂, and CH₂O. In the mid-infrared, around 3 μm, we measured hydrocarbons like CH₄, C₂H₆, and C₂H₄ with a detection limit of less than 1 ppb. The noise equivalent absorption coefficients in the MIR are in the order of 1.7·10⁻⁹ cm⁻¹. Due to the high data acquisition rate and the high sensitivity, CRDS enables real-time detection of trace gases in ambient air.     

Are There Counter-Landscapes? On Milk Trestles and Invisible Power Lines

The paper takes its starting point from the duality in the Estonian rural landscape shaped by social practices. On the one hand, the changes and management of landscapes follow a political decision. At the same time, the old patterns of semi-legal activity offer a resistant practice. The study is illustrated with the milk trestle, a now-disappeared symbol of recent history in the Soviet countryside. The milk trestles and their role in Estonian country life are studied from a threefold perspective—their functions, meanings and the values behind this symbol. The article is based on ethnographic field work carried out between the years of 2001 and 2002 and traces the phenomenon of how living landscape transforms into deserted landscape; in other words, how story becomes history. The paper shows how the milk trestle landscape functioned as a prolongation of the former landscape behind the ideological layers of the Soviet landscapes.     

Seasonality in Estonian Traditional Landscape: The Example of Large Village Swings

Like every nation, Estonians have their own indigenous customs and habits. Village swings and the place of these swings in the landscape are focused upon as an example of such Estonian customs, and changes in landscape as related to seasonality and liminality are discussed. The word ‘swing’ is used to denote a large construction (traditionally made of wood) that is able to carry and swing at least two people. Village swings (for public use) are usually located in the middle of a village and the site is commonly used by young people as a place to meet and have a good time. Swinging takes place mostly in the spring and summer, forming one of the many seasonal activities that make up the Estonian traditional calendar. The seasonal break in swinging activity contributes to the eagerness with which swinging is resumed when spring returns, so seasonality creates frames, with the most valued time being the spring. With swinging, the spring has been celebrated as a very valuable and long-awaited season. Although the religious background for swinging has been forgotten, the place is still special and is visited mostly on certain festive occasions. As there is no comparable alternative to swing sites as a socializing place in the village, they have persisted through the centuries. The importance of preserving such unique seasonal places in Estonia's social landscape is demonstrated.