A new filtering approach dedicated to heat sources computation from thermal field measurements

International audienceThis paper presents a new approach in heat source evaluation from thermal field measurements. A modal projection based on dynamics (Discrete Modal Decomposition) is used to estimate the spatial term of a heat diffusion problem. A numerical example is presented in order to validate this approach and compare it to a more classical spectral decompostion (based on strictly thermal considerations). Results show that the proposed projection basis not only provides closer assessement of the heat sources but is also more stable to measurement noise and side effects

A high resolution study of the Martian water cycle with a global climate model

International audienceThe martian water cycle's main source is the northern polar cap. Running high resolution models, up to 360° per 180°, help better resolve this ice cap, and better mimic the gradual retreat of the seasonal cap. Atmospheric circulation is also better resolved. Water vapor advection and the subsequent formation of clouds quite differ when we compare these brand new high resolution simulations and the usual lower resolution ones at 64 per 48 grid points

Simulation of Metal Forming Processes with a 3D Adaptive Remeshing Procedure

In this paper, a fully adaptive 3D numerical methodology based on a tetrahedral element was proposed in order to rove the finite element simulation of any metal forming process. This automatic methodology was implemented in a computational platform which integrates a finite element solver, 3D mesh generation and a field transfer algorithm. The proposed remeshing method was developed in order to solve problems associated with the severe distortion of elements subject to large deformations, to concentrate the elements where the error is large and to coarsen the mesh where the error is small. This leads to a significant reduction in the computation times while maintaining simulation accuracy . In addition, in order to enhance the contact conditions, this method has been coupled with a specific operator to maintain the initial contact between the workpiece nodes and the rigid tool after each remeshing step. In this paper special attention is paid to the data transfer methods and the necessary adaptive remeshing steps are given. Finally, a numerical example is detailed to demonstrate the efficiency of the approach and to compare the results for the different field transfer strategie

Numerical and experimental investigations of Ti-6Al-4V chip generation and thermo-mechanical couplings in orthogonal cutting

The chip formation mechanism of the Ti-6Al-4V remains a challenging problem in the machining process as well as its modeling and simulation. Starting from experimental observation on the titanium alloys Ti-6Al-4V machining shows that the ductile fracture in the chip formation is dominated by the shear phenomenon under high strain rate and temperature, the present work develops a new coupled behavior and damage model for better representation and understanding of the chip formation process. The behavior and damage of Ti-6Al-4V have been studied via hat-shaped specimen under temperature up to 900 °C and strain rate up to 1000 s−1. An inverse identification method based on Finite Element (FE) is established in order to determine the constitutive law’s parameters. The prediction of the segmented chip was analyzed through 3D finite element orthogonal cutting model which was validated by an in-situ and post-mortem orthogonal cutting machining observations. Finally, a particular attention is focused on the chip formation genesis which is described by three steps: Growth, Germination and Extraction

At the Service of Community Development: The Professionalization of Volunteer Work in Kenya and Tanzania

This article explores the changing nature of the “volunteer” as an official role within health and development interventions in East Africa. Contemporary development interventions require the engagement of volunteers to act as links between project and community. This role is increasingly professionalized within development architectures with implications for the kinds of people who can engage in volunteering opportunities. Volunteers in development interventions are likely to be drawn from public sector staff and from educated youth seeking access to positions of paid employment. Volunteering as a formal status within the organization of development programs is recognized as a kind of professional work by those seeking to engage with development organizations. Volunteers perform important work in linking development programs with beneficiaries. At the same time, volunteering provides opportunities for personal transformation

A fast and versatile method for spectral emissivity measurement at high temperatures

International audienceIn this paper, the development of a new device for high temperature emissivity measurement is described. This device aims at measuring both spectral and total emissivity for a thermal range of 600–1000 °C. The main targeted properties of this device are versatility and simplicity. To achieve this, a rigorous selection of components such as heating systems, heat sources, sample holders, and measuring devices was made. Sample dimensions and the corresponding sample holder were optimized through a ray tracing model computation. Selection of sensors to compute the total emissivity was also discussed. A near-infrared (NIR) spectrometer and two mid-infrared (MIR) cameras equipped with optical filters covering the bandwidth of 3–5 and 7.5–13 μm were chosen for spectral measurements. The major impediment was the separation of the sample signal and various spurious signals emitted by the environment. A specific measurement methodology was then made for each bandwidth to resolve this issue. Platinum was chosen as the reference material for the device validation. Spectral emissivity measurements were then compared to values from a commercial spectrometer. A good agreement was found between NIR and MIR band I measurements, and a higher error rate was seen in MIR band II which is explained by a less favorable signal to noise ratio. Integrated emissivity is then calculated and compared to values found in the literature. A good agreement between these values is found, and similar trends with temperature are observed. The device is then validated for spectral and total emissivity measurements. Device versatility and simplicity allow for an easy adaptation to a large area of applications

Green revolution in Sub-Saharan Africa: Implications of imposed innovation for the wellbeing of rural smallholders

Green Revolution policies are again being pursued to drive agricultural growth and reduce poverty in Sub-Saharan Africa. However conditions have changed since the well-documented successes of the 1960s and 1970s benefited smallholders in southern Asia and beyond. We argue that under contemporary constraints the mechanisms for achieving improvements in the lives of smallholder farmers through such policies are unclear and that both policy rationale and means of governing agricultural innovation are crucial for pro-poor impacts. To critically analyze Rwanda’s Green Revolution policies and impacts from a local perspective, a mixed methods, multidimensional wellbeing approach is applied in rural areas in mountainous western Rwanda. Here Malthusian policy framing has been used to justify imposed rather than ‘‘induced innovation”. The policies involve a substantial transformation for rural farmers from a traditional polyculture system supporting subsistence and local trade to the adoption of modern seed varieties, inputs, and credit in order to specialize in marketable crops and achieve increased production and income. Although policies have been deemed successful in raising yields and conventionally measured poverty rates have fallen over the same period, such trends were found to be quite incongruous with local experiences. Disaggregated results reveal that only a relatively wealthy minority were able to adhere to the enforced modernization and policies appear to be exacerbating landlessness and inequality for poorer rural inhabitants. Negative impacts were evident for the majority of households as subsistence practices were disrupted, poverty exacerbated, local systems of knowledge, trade, and labor were impaired, and land tenure security and autonomy were curtailed. In order to mitigate the effects we recommend that inventive pro-poor forms of tenure and cooperation (none of which preclude improvements to input availability, market linkages, and infrastructure) may provide positive outcomes for rural people, and importantly in Rwanda, for those who have become landless in recent years. We conclude that policies promoting a Green Revolution in Sub-Saharan Africa should not all be considered to be pro-poor or even to be of a similar type, but rather should be the subject of rigorous impact assessment. Such assessment should be based not only on consistent, objective indicators but pay attention to localized impacts on land tenure, agricultural practices, and the wellbeing of socially differentiated people

The Latest Mars Climate Database (MCD v5.1)

For many years, several teams around the world have developed GCMs (General Circulation Model or Global Climate Model) to simulate the environment on Mars. The GCM developed at the Laboratoire de Météorologie Dynamique in collaboration with several teams in Europe (LATMOS, France, University of Oxford, The Open University, the Instituto de Astrofisica de Andalucia), and with the support of ESA and CNES is currently used for many applications. Its outputs have also regularly been compiled to build a Mars Climate Database, a freely available tool useful for the scientific and engineering communities. The Mars Climate Database (MCD) has over the years been distributed to more than 150 teams around the world. Following the recent improvements in the GCM, a new series of reference simulations have been run and compiled into a new version (version5.1) of the Mars Climate Database, released in the first half of 2014. To summarize, MCD v5.1 provides: - Climatologies over a series of dust scenarios: standard year, cold (ie: low dust), warm (ie: dusty atmosphere) and dust storm, all topped by various cases of Extreme UV solar inputs (low, mean or maximum). These scenarios differ from those of previous versions of the MCD (version 4.x) as they have been derived from home-made, instrument-derived (TES, THEMIS, MCS, MERs), dust climatology of the last 8 Martian years. - Mean values and statistics of main meteorological variables (atmospheric temperature, density, pressure and winds), as well as surface pressure and temperature, CO2 ice cover, thermal and solar radiative fluxes, dust column opacity and mixing ratio, [H20] vapor and ice columns, concentrations of many species: [CO], [O2], [O], [N2], [H2], [O3], ... - A high resolution mode which combines high resolution (32 pixel/degree) MOLA topography records and Viking Lander 1 pressure records with raw lower resolution GCM results to yield, within the restriction of the procedure, high resolution values of atmospheric variables. - The possibility to reconstruct realistic conditions by combining the provided climatology with additional large scale and small scale perturbations schemes. At EGU, we will report on the latest improvements in the Mars Climate Database, with comparisons with available measurements from orbit (e.g.: TES, MCS) or landers (Viking, Phoenix, MSL)

Dynamics of pH-dependent self-association and membrane binding of a dicarboxylic porphyrin: a study with small unilamellar vesicles

AbstractSteady-state and stopped-flow measurements of the absorbance and fluorescence of aqueous solutions were performed to characterize the pH-dependent ionization and aggregation states of deuteroporphyrin. Porphyrin self-association promoted by neutralization of the carboxylic groups takes place within a few milliseconds impeding characterization of the monomer ionization states. Extrapolation at infinite dilution of the values obtained from steady-state measurements yielded the pKs of the carboxylic groups (6.6, 5.3) and inner nitrogens (4.1, 2.3). The kinetics of interactions of the porphyrin with unilamellar fluid state dioleoylphosphatidylcholine vesicles was examined in a large pH range, with focus on the entry step. From alkaline pH to a value of 6.5, the entrance rate is maximal (1.69×106 M−1 s−1 versus phospholipid concentration). It decreases to 2.07×105 M−1 s−1 at lower pH with an apparent pK of 5.39. This effect appears to be related to the formation of porphyrin dimer rather than to the protonation of inner nitrogen. In keeping with previous data, these results support the concept of a pH-mediated selectivity of carboxylic porphyrins for tumor. They also indicate that the propensity of these molecules to self-associate at low pH could yield to some retention in acidic intracellular vesicles of the endosome/lysosome compartment

Periostin in lymph node pre-metastatic niches governs lymphatic endothelial cell functions and metastatic colonization.

peer reviewedAlthough lymph node (LN) metastasis is an important prognostic parameter in cervical cancer, the tissue remodeling at a pre-metastatic state is poorly documented in LNs. We here identified periostin (POSTN) as a component of non-metastatic LNs by applying proteomic analyses and computerized image quantifications on LNs of patients with cervical cancer. We provide evidence for remarkable modifications of POSTN and lymphatic vessel distributions and densities in non-metastatic sentinel and metastatic human LNs, when compared to distant non-metastatic LNs. POSTN deposition at a pre-metastatic stage was demonstrated in a pre-clinical murine model (the ear sponge assay). Its expression by fibroblastic LN cells was assessed by in situ hybridization and in vitro cultures. In vitro, POSTN promoted lymphatic endothelial cell functions and tumor cell proliferation. Accordingly, the in vivo injection of recombinant POSTN together with VEGF-C boosted the lymphangiogenic response, while the metastatic potential of tumor cells was drastically reduced using a POSTN blocking antibody. This translational study also supports the existence of an unprecedented dialog "in cascade", between the primary tumor and the first pelvic nodal relay in early cervical cancer, and subsequently from pelvic LN to para-aortic LNs in locally advanced cervical cancers. Collectively, this work highlights the association of POSTN deposition with lymphangiogenesis in LNs, and provides evidence for a key contribution of POSTN in promoting VEGF-C driven lymphangiogenesis and the seeding of metastatic cells