Tracking through equality

We give a tracker solution for the quintessence scalar field for Ratra--Peebles or SUGRA potentials, holding before, during and after the equality epoch (\rho_m=\rho_r) and nicely fitting the numerical behavior.Comment: submitted to New Astronom

Modelling of a standard gas mixtures generator with computational fluid dynamics

Monitoring VOC for climate change and for indoor and outdoor air quality at trace level concentrations need reference standard materials at high metrological performance. To improve this performance, the description of phenomena involved in mixtures generation by rigorous models is mandatory. A model to describe diffusion cells of a primary generator was developed and validated with experimental data. A good agreement was found between the uncertainties of measurements and calculations

Uncertainty in cell confluency measurements

Pharmaceutical industries have declared their need of metrology in the cellular field, to improve new drugs developing time and costs by high-content screening technologies. Cell viability and proliferation tests largely use confluency of cells on a bi-dimensional (2D) surface as a biological measurand. The confluency is measured from images of 2D surface acquired via microscopy techniques. The plethora of algorithms already in use aims at recognizing objects from images and identifies a threshold to distinguish objects from the background. The reference method is the visual assessment from an operator and any objective uncertainty estimation is not yet available. A method to estimate the image analysis contribution to confluency uncertainty is here proposed. A maximum and a minimum threshold are identified from a visual assessment of the free edge of the cells. An application to a fluorescence microscopy image of 2D of PT-45 cell cultures is reported. Results shows that the method can be a promising solution to associate an uncertainty to cell confluency measurements to enhance reliability and efficiency of high-content screening technologies

Uncertainty and Reliability of Comparison of Energetic Scenarios

Background: Comparison of scenarios that involve devices for conversion or production of energy needs energetic criteria. Energy Payback Time is a typical energetic parameter used to compare the performances of systems under specific scenarios. To discriminate between scenarios the difference of parameter values is considered. The significance of the difference makes the confidence on the result and the reliability of a comparison, it depends on the difference and its uncertainty. Objective: This paper shows and discusses how to evaluate the uncertainty of the difference of parameters, defines a target uncertainty to achieve reliable discrimination. A case study on photovoltaic scenarios is used to apply methodology, commercial modules monocrystalline Si, amorphous Si and polycrystalline Si were considered for comparison. Results: Scenarios were compared by their energy payback time. All uncertainty sources were quantified and discussed and energy payback time uncertainty was calculated. Confidence of comparisons was lower than 95% and a target uncertainty was calculated. Conclusion: The use of uncertainty approach gives a much more detailed information on comparison. Confidence is the reliability of the comparison. Uncertainty analysis identify the opportunities to reduce uncertainty and enhance confidence in comparison result

Impact of agricultural interventions on food and nutrition security in Ethiopia: Uncovering pathways linking agriculture to improved nutrition

Achieving sustainable food and nutrition security calls for multi-sectoral coordination mechanisms in implementing, among others, nutrition-sensitive agricultural interventions. Despite progresses made in evaluating the effectiveness/impact of these interventions in some countries, very little is known about the nature and causal effect of these interventions in Ethiopia. Therefore, this systematic review aims to provide evidence on the impact of nutrition-sensitive agricultural interventions and pathways linking agriculture to improved nutrition. Based on a comprehensive advanced literature search using keywords in various databases and setting inclusion/screening criteria, we identify 25 relevant studies conducted between 2008 and 2018. Overall, we find positive effects on knowledge, attitude, and practice of complementary feeding and economic indicators (income, poverty and asset accumulation). We also find an overwhelming positive effect on food consumption, dietary diversity, and food security indicators. However, we also note mixed effectiveness in relation to child anthropometry. The most important pathways linking agriculture to improved nutrition center on its role as a source of food and income, and its effect on food prices/market. Hence, enhancing community-based nutrition education, accelerating adoption of improved technologies, improving access to farm inputs and technical information, integrating farmers to markets, and boosting enabling environments and capacities should be emboldened

Food Price Volatility over the Last Decade in Niger and Malawi: Extent, Sources and Impact on Child Malnutrition

Recently, considerable attention has rightly been paid to the nutritional impact of the sharp hikes in international food prices which took place in 2007-8 and, again, in 2010-11. While sacrosanct, this growing focus has somewhat obscured the effect of other factors which do affect malnutrition in the Sub-Saharan Africa context, i.e. the long term impact of agricultural policies, huge and persistent seasonal variation in domestic food prices, and the impact of famines which still regularly stalk the continent. This paper focuses on the relative weight of these factors in explaining child malnutrition (proxied by the number of child admissions to feeding centers) in Malawi and Niger, two prototypical countries in the region. The analysis shows that the drivers of domestic food staple prices and of the ensuing child malnutrition have to be found not only – or not primarily – in the changes of international food prices but mainly in the impact of agricultural policies on food production, the persistence of a strong food price seasonality, and recurrent and often poorly attended famines. Indeed, even during years of declines in international food prices, these factors often exert a huge upward pressures on domestic food prices and child malnutrition

Simulation of boron rejection by seawater reverse osmosis desalination

yesBoron is a vital element for growth of creations, but excessive exposure can cause detrimental effects to plants, animals, and possibly humans. Reverse Osmosis (RO) technique is widely used for seawater desalination as well as for waste water treatment. The aim of this study is to identify how different operating parameters such as pH, temperature and pressure can affect boron concentrations at the end of RO processes. For this purpose, a mathematical model for boron rejection is developed based on solution-diffusion model which can describe solvent and solute transport mechanism through the membranes. After a wide and thorough research, empirical correlations developed in the past are filtered, adopted and calibrated in order to faction with reliability as part of the solution-diffusion model of this work. The model is validated against a number of experimental results from the literature and is used in further simulations to get a deeper insight of the RO process. The general findings of the boron rejection model are supporting the case that with increasing pH and operating pressure of the feed water, the boron rejection increases and with increasing feed water temperature the boron rejection decreases

Dynamic images to address conceptual nodes about mechanical waves: Example materials and preliminary results of the experimentation of the teacher training module IMAGONDE

In the framework of the 2002-03 project “Fisica per la Formazione Culturale - FORMazione Insegnanti” funded by Italy ministry of Education, a set of training materials, focused on mechanical waves, has been developed. The core of the materials is represented by animated images purposely designed in order to: 1) address intrinsically dynamic aspects of one-dimensional impulses/waves propagation on a string; 2) have the trainees reflect upon students’ difficulties in reading/interpreting static images (as the ones which are featured in common textbooks) and animations. In this paper we discuss example materials concerning transversal impulses on strings to address conceptual nodes such as: 1) configuration of the string at a given time and its abstract representation; 2) displacement vs. time graph of a string element and its abstract representation; 3) relationships between the two abstract representations; 4) modelization of mechanical wave propagation in one dimension. Moreover the results of the experimentation of the training materials in the framework of the Post Graduate School to Became Physics Teacher in Secondary Schools are presented and commented