Trace Minerals Management in Cattle

in XVIII Congreso Internacional Anembe de Medicina Bovina (2013, April)

La censure au pluriel

in Matière & l'Esprit (La) (2013), 25-27(avril-novembre), 5-6

Templated TiO2 mesoporous films used as highly efficient photoelectrode in Dye-Sensitized Solar Cells

Doctoral thesis (2013)

The present thesis is dedicated to the synthesis and characterization of the TiO2 semiconductor layer used as photoelectrode in dye-sensitized solar cells (DSSCs), with the aim to improve their ... [more ▼]

The present thesis is dedicated to the synthesis and characterization of the TiO2 semiconductor layer used as photoelectrode in dye-sensitized solar cells (DSSCs), with the aim to improve their photovoltaic efficiencies. DSSCs have been reported by O’Regan and Grätzel in the early nineties as a very promising alternative to conventional silicon devices. Main benefits of these cells are their low cost and their mild manufacturing process. In most of the specific literature, DSSCs are made of TiO2 films prepared by doctor-blade or screen-printing of anatase nanoparticles paste. However due to the random organization of the nanoparticles, pore accessibility by the dye and electrolyte could be incomplete and some anatase crystallites could be not connected impeding electron transfer. The strategy adopted to improve the films properties and thus PV efficiencies involves a surfactant-assisted process allowing the preparation of highly porous layers with well-ordered and accessibles pores as well as improved crystallites connectivity. The main goal of this work is to increase the film surface area and perfectly control the mesostructure in terms of thickness, pore size, pore organization and pore accessibility in order to maximize the adsorption of active dye and the electrolyte infiltration inside the porous network. Special attention was paid to the tuning of the experimental settings such as the relative humidity conditions, the withdrawal speed and the choices of substrate and surfactant. Moreover, for DSSCs applications, TiO2 film has to be crystallized in form of anatase. Perfect balance between high crystallinity and mesostructure preservation was studied in order to enhance the cells efficiencies. Besides, templated films challenge is to obtain thick layers. Indeed, monolayer films are only a few hundred nanometers thick. To increase the film thickness and thus the quantity of active material, a multilayer process was tuned. Special effort was paid to overcome the surface area limitation induced by the repeated thermal treatments applied during multilayer process. We propose an alternative thermal treatment in order to limit the mesostructure degradation. We also define the maximum crystal size compatible with the preservation of the mesoarchitecture initially induced by templating. Thick films up to 4 µm were prepared from this multilayer process and show excellent efficiency in combination with N-719 dye (6.1%) when compared to values reported in the literature. Such mesostructured templated films were compared in terms of photovoltaic performances with TiO2 nanoparticles films, generally used in DSSCs. In a second part, as the goal of this thesis is to improve the current nanoparticles-based DSSCs and prove the viability of the templating alternative, a comparison of the long-term stability of both technologies was performed. To our knowledge, long-term stability of templated DSSCs has never been reported at this time. However, in case of templated films, the surface area is highly improved and the negative effects of thermal stress, light soaking and UV exposure could be heightened. Due to their higher active interface, templated films are more sensitive than nanoparticles samples to UV illumination, what can be easily solved by the use of a UV filter. However, they are as stable as nanoparticles samples under visible light soaking (UV filtered) and under thermal stress. In addition, cells were characterized by electrochemical impedance spectroscopy (EIS). Templated cells show lower transfer resistance, as well as longer electron lifetime compared to nanoparticles DSSCs. Using templated films in DSSCs is therefore really promising because higher conversion efficiencies are reached without any increase in cells degradation. Finally, stability limitation encountered by DSSCs are mostly related to the use of liquid electrolytes, which can leak out the cell. Solid-state hole transporting materials are investigated in order to overcome this issue. However, in solid-state DSSCs, TiO2 films thickness is limited to a few microns allowing the adsorption of a limited amount of photoactive dye and thus leading to a poor light harvesting. Moreover, solid-state DSSCs are characterized by incomplete electrolyte filling, impeding the dye regeneration. Both limitations further lead to low photovoltaic efficiencies. Due to the surface area improvement as well as the perfect control of the pore organization and the pore size, the templating strategy was investigated to overcome light harvesting and pore filling limitations. Templated films were prepared from different structuring agents. They show an efficient electrolyte infiltration and a two times higher dye loading compared to nanoparticles layers. Corresponding photovoltaic performances in liquid-state and solid-state DSSCs have also been evaluated. While templating allows improving the liquid-state cells efficiencies, we cannot conclude for solid-state DSSCs due to device assembly issue and/or bad contacts between the electrodes and the sample holder during the I-V measurements. We hope that the achievements of this thesis brought a significant contribution to the field of DSSCs. Indeed, the templating strategy is proved to improve the liquid-sate cells efficiency. However, the assembly of solid-state devices and subsequent I-V tests have to be investigated further. Besides, new pathways are envisaged for interesting future work in both fundamental and applied research fields, such as the synthesis of templated films with hierarchical porosity or scale-up and industrialization of the templated devices. [less ▲]

SOUTHERN BLUES NIGHT , Heerlen (NL) 17e ed. , 15 mars 2013

E-print/Working paper (2013)

C.R. de la 17e Southern Blues Night , le 15 mars 2013 à Heerlen ( Nl) + photos ; Khalif Wailin' Walter , Mud Morganfield, Heritage Blues Orchestra, James Harman, Enrico Crivellaro, Gene Taylor, ....

Substrate Marking by an Invasive Ladybeetle: Seasonal Changes in Hydrocarbon Composition and Behavioral Responses

in PLoS ONE (2013), 8(4),

The multicolored Asian ladybeetle, Harmonia axyridis (Pallas), aggregates inside dwellings during the winter to survive the cold. Recent published reports have highlighted that overwintering individuals ... [more ▼]

The multicolored Asian ladybeetle, Harmonia axyridis (Pallas), aggregates inside dwellings during the winter to survive the cold. Recent published reports have highlighted that overwintering individuals use hydrocarbon markings deposited on surfaces by conspecifics to orient toward aggregation sites. In the current study, monthly GC-MS analyses revealed seasonal modifications in the chemical profile of substrate markings deposited by moving individuals. The markings of overwintering ladybeetles contained larger proportions of heptacosadiene, nonacosadiene, hentriacontadienes, and methyl-nonacosanes, along with a lower proportion of heptacosene and nonacosene. This finding suggests the importance of the unsaturated and/or branched hydrocarbons in the H. axyridis aggregation process. Subsequently, we conducted behavioral assays to test whether (1) there is seasonal variation in the behavioral response of H. axyridis individuals toward substrate markings deposited by conspecifics in the same physiological state and (2) the observed behavioral modification is due to a change in ladybeetle sensitivity and/or a change in the chemical composition of the substrate marking. The results indicate that overwintering individuals exhibit a stronger ‘‘following’’ response toward conspecific substrate markings. This behavior is linked to both the physiological state of ladybeetles and the specific chemical profile of the marking biomolecules deposited under overwintering conditions. [less ▲]

Trente ans de lutte contre le racisme en Belgique : bilan et perspectives

in Revue Nouvelle (2013), année 68(numéro 4),

Nonparametric subspace identification of nonlinear structures - Application to a spacecraft

in Proceedings of the 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference (2013, April)

The objective of the present paper is to address the identification of a strongly nonlinear satellite structure by exploiting a new nonlinear subspace identification method formulated in the frequency ... [more ▼]

The objective of the present paper is to address the identification of a strongly nonlinear satellite structure by exploiting a new nonlinear subspace identification method formulated in the frequency domain, referred to as the FNSI method. The modal parameters of the underlying linear structure and the coefficients of the nonlinear internal forces will be estimated by this approach. Moreover, because a priori knowledge about nonlinear behaviour may be limited, the paper also proposes a nonparametric spline-based modelling strategy, encapsulated in the FNSI method. The application of interest is the SmallSat spacecraft developed by EADS-Astrium, which possesses an impact-type nonlinear device consisting of eight mechanical stops limiting the motion of an inertia wheel mounted on an elastomeric interface. [less ▲]

Testing the bootstrap constraints in the strange sector

in Journal of High Energy Physics [=JHEP] (2013), 1304

In this paper the bootstrap conditions that follow from the general postulates of effective scattering theory (EST) are checked in the strange sector. We construct the system of tree level bootstrap ... [more ▼]

In this paper the bootstrap conditions that follow from the general postulates of effective scattering theory (EST) are checked in the strange sector. We construct the system of tree level bootstrap constraints for the renormalization prescriptions fixing the physical content of the theory. Then we perform the numerical testing of corresponding sum rules for the parameters of strange resonances. It is shown that, generally, the bootstrap constraints turn out consistent with presently known data on the strange resonance parameters. At the same time we point out few sum rules which cannot be saturated with modern data and discuss the possible reasons for such discrepancies. [less ▲]

Comparative study of four safflower oils (Carthamus tinctorius) varieties grown in eastern of Morocco

Poster (2013, April)

Quadratization of symmetric pseudo-Boolean functions

Conference (2013, April)

We consider the problem of minimizing an arbitrary pseudo-Boolean function f(x), that is, a real-valued function of 0-1 variables. In recent years, several authors have proposed to reduce this problem to ... [more ▼]

We consider the problem of minimizing an arbitrary pseudo-Boolean function f(x), that is, a real-valued function of 0-1 variables. In recent years, several authors have proposed to reduce this problem to the quadratic case by expressing f(x) as min{g(x,y):y∈{0,1}^m}, where g(x,y) is a quadratic pseudo-Boolean function of x and of additional binary variables y. We say that g(x,y) is a quadratization of f. In this talk, we investigate the number of additional variables needed in a quadratization when f is a symmetric function of the x-variables. The cases where f is either a positive or a negative monomial are of particular interest, but some of our techniques also extend to more complex functions, like k-out-of-n or parity functions. Joint work with Martin Anthony, Endre Boros and Aritanan Gruber [less ▲]