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Cambrian Hopf algebras
No full textCambrian trees are oriented and labeled trees which fulfill local conditions around each node generalizing the conditions for classical binary search trees. Based on the bijective correspondence between signed permutations and leveled Cambrian trees, we define the Cam-brian Hopf algebra generalizing J.-L. Loday and M. Ronco's algebra on binary trees. We describe combinatorially the products and coproducts of both the Cambrian algebra and its dual in terms of operations on Cambrian trees. We also define multiplicative bases of the Cambrian algebra and study structural and combinatorial properties of their indecomposable elements. Finally, we extend to the Cambrian setting different algebras connected to binary trees, in particular S. Law and N. Reading's Baxter Hopf algebra on quadrangulations and S. Giraudo's equivalent Hopf algebra on twin binary trees, and F. Chapoton's Hopf algebra on all faces of the associahedron
Towards realistic simulation of the novel III-V/epi-Si tandem solar cell concept
No full textInternational audienceMultijunction solar cells based on III-V compounds have by far the highest conversion efficiency. However, the fabrication cost is very high. An attractive solution to lower the cost while maintaining high efficiencies is to design multijunctions on cheaper substrates such as silicon. Different routes have been taken to cope with lattice mismatch issues between Si and III-Vs: epitaxial growth of GaAs on Si with or without buffer layers or non-epitaxial techniques such as mechanical stacking. A novel approach has been recently presented consisting in direct epitaxial growth of thin Si or SiGe layers on GaAs by low temperature PECVD, where the high crystal quality reported opens a new way for making III-V/Si tandem solar cells. Yet, due to the low deposition rate, the epi-Si layers are still rather thin (~10μm), and though they are assumed to be of high quality, some defects might be still present at the interface or in the bulk. These critical aspects still have to be carefully investigated to evaluate the potential benefits of this novel concept. Here, numerical simulation has definitely a role to play. Therefore, we propose to simulate these novel structures using TCAD tools and to estimate the defect density inside the thin epi-layer based on experimental inputs. Realistic efficiencies achievable by this novel concept will thus be presented and discussed
Banc de caractérisations avancées de modules photovoltaïques de différentes technologies installé à l'observatoire atmosphérique du SIRTA
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Characterization of a-Si:H/c-Si heterojunction by temperature dependent modulated photoluminescence
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Plasma-Texturing Processes and a-Si:H Surface Passivation on c-Si Wafers for Photovoltaic Applications
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New Approaches to Improve the Performance of Thin-Film Radial Junction Solar Cells Built Over Silicon Nanowire Arrays
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A low-complexity 2D signal space diversity solution for future broadcasting systems
No full textInternational audience—DVB-T2 was the first industrial standard deploying rotated and cyclic Q delayed (RCQD)modulation to improve performance over fading channels. This enablesimportantgains compared toconventional quadrature amplitude modulations(QAM) under severe channel conditions.However, the corresponding demodulation complexitystill prevents its use forwider applications. This paper proposes several rotation angles for different QAM constellations anda corresponding low-complexity detection method. Results show that the proposed solution simplifies both the transmitter and the receiver with often betterperformancethan the proposed angles in DVB-T2. Compared with the lowest complexity demappers currently used in DVB-T2, the proposed solution achieves an additional reduction bymore than 60%. Index Terms— DVB-T2, Rotated and Cyclic Q Delayed (RCQD) Modulations, Signal Space Diversity (SSD), Fading Channel, Quadrature Amplitude Modulations (QAM), Max-Log, ComputationalComplexity
Specific GFP-binding artificial proteins ( Rep): a new tool for in vitro to live cell applications
No full textInternational audienceA family of artificial proteins, named αRep, based on a natural family of helical repeat was previously designed. αRep members are efficiently expressed, folded and extremely stable proteins. A large αRep library was constructed creating proteins with a randomized interaction surface. In the present study, we show that the αRep library is an efficient source of tailor-made specific proteins with direct applications in biochemistry and cell biology. From this library, we selected by phage display αRep binders with nanomolar dissociation constants against the GFP. The structures of two independent αRep binders in complex with the GFP target were solved by X-ray crystallography revealing two totally different binding modes. The affinity of the selected αReps for GFP proved sufficient for practically useful applications such as pull-down experiments. αReps are disulfide free proteins and are efficiently and functionally expressed in eukaryotic cells: GFP-specific αReps are clearly sequestrated by their cognate target protein addressed to various cell compartments. These results suggest that αRep proteins with tailor-made specificity can be selected and used in living cells to track, modulate or interfere with intracellular processes
Thioglycerol-functionalized CdSe quantum dots detecting cadmium ions
No full textInternational audienceWater-soluble CdSe quantum dots (QDs) were synthesized using thioglycerol (TG) as the surface capping agent through a one-step process at low temperature T (100 degrees C). The CdSe quantum dots were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, UV-visible absorption and fluorescence spectroscopies. These measurements revealed that the TG-capped CdSe QDs possess a high crystalline quality with an average diameter in the range 2.5-2.8 nm and exhibit particular optical properties. The UV-visible absorption of CdSe QDs is enhanced by the addition of cadmium ions, with a simultaneous shift of the edge band (400 nm), while seventeen other tested metal cations have no effect on the absorption of QDs. Moreover, the binding of Cd2+ ions induces a quenching of the fluorescence emission of TG-CdSe QDs. At particular absorption wavelengths, the response is linearly proportional to the cadmium ions concentration ranging from 1.0 to 22 mu M with a detection limit of 0.32 mu M (37 mu g L-1). Based on these optical properties, the TG-CdSe QDs could be used as a highly selective probe for the detection of Cd2+ ions in aqueous solutions, a species highly toxic for cells. (C) 2015 Elsevier B.V. All rights reserved
Efficiency Comparison of Inductor-, Capacitor- and Resonant-based Converters Fully Integrated in CMOS Technology
No full textInternational audienceThe full integration of DC-DC converters offers great promise for dramatic reduction in power consumption and the number of board-level components in complex systems on chip. Some papers compare the numerous published on-chip and on-die converter structures, but there is the need for an approach to accurately compare the main basic DC-DC conversion topologies. Therefore, this paper presents a method to compare the efficiencies of CMOS integrated capacitive-, inductive-and resonant-based switching converters. The loss mechanism of each structure in hard-switching conditions is detailed and the analytical equations of the power loss and output voltage are given as a function of few CMOS technology parameters. The resulting models can be used to accurately predict converter efficiency in the early design phase, to compare the basic structure in particular the technology node or to orient the passive choice. The proposed method is then applied to design, optimize and compare fully-integrated power delivery requirements on a 1mm 2 on-die area in 65nm CMOS technology over three decades of power density. The results also underline the high efficiency of the promising resonant-based converter. Index Terms—integrated switching power supply, on-chip voltage regulator, switched-capacitor converter, inductive power converter, resonant converte