A Unifying and Rigorous Shape from Shading Method Adapted to Realistic Data and Applications

We propose a new method for the Lambertian Shape From Shading (SFS) problem based on the notion of Crandall-Lions viscosity solution. This method has the advantage of requiring the knowledge of the solution (the surface to be reconstructed) only on some part of the boundary and/or of the singular set (the set of the points at maximal intensity). Moreover it unifies in an unique mathematical formulation the works of Rouy et al. [34, 50], Falcone et al. [21], Prados et al. [46, 48, 49], based on the notion of viscosity solutions and the work of Dupuis and Oliensis [17] dealing with classical solutions and value functions. Also, it allows to generalize their results to the “perspective SFS” problem recently simultaneously introduced in [13,46,55]. While the theoretical part has been developed in [44], in this paper we give some stability results and we describe numerical schemes for the SFS based on this method. We construct provably convergent and robust algorithms. Finally, we apply our SFS method to real images and we suggest some real-life applications.     

Testing for association in 2?×?2 contingency tables with very small sample sizes.

Applied statistics textbooks generally recommend the use of the chi-square tests of homogeneity and independence with 2?×?2 contingency tables only when the expected frequency of each cell is 5 or more. Recent research has shown this rule-of-thumb criterion to be unnecessarily restrictive, but has not explored the accuracy of the chi-square tests when the total number of observations is less than 20 or when the expected frequencies fall well below one—the primary issues considered in this article. The chi-square tests of homogeneity and independence were found to provide reasonably accurate estimates of Type I error probability for N?≥?8. Certain alternatives to the chi-square tests are considered. (61 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tuning photoresponse through size control of Cu nanoparticles deposited on multi wall carbon nanotubes

In this paper we illustrate a simple method for the production of multiwall carbon nanotubes thin films decorated with copper metal nanoparticles. The structural information obtained from the transmission electron microscopy study performed on samples differing in the quantity of deposited Copper was linked to the opto-electronic properties evaluated with photo-electrochemical measurements. The photo-response evaluated in terms of incident photon-to-charge carrier generation efficiency varied for different sized-Cu-multiwall carbon nanotubes samples across all the visible and near-ultraviolet photon energy range with respect to the response of bare carbon tubes. The photo-response from the sample covered with of 0.5 nm Cu nominal thickness, reached 10.2%, a value 2 times higher than that measured for bare carbon tubes of 5.9%. While this value decreased to 2.8% when the Cu nominal coverage thickened up to 3 nm. The increase in the photo-response found was interpreted as being the result of a remarkable charge transfer between the Cu metal nanoparticles and the carbon atoms in the tube due to the formation of a strong ionic bond at their interface. The results obtained prove that the metal nanoparticle-carbon nanotube composites have optical, electrical and structural properties that can be applied in a variety of nanoscale architectures for novel photo-electrochemical devices.     

Photovoltaic response of carbon nanotube-silicon heterojunctions: effect of nanotube film thickness and number of walls

We report on the multiwall carbon nanotube application as energy conversion material to fabricate thin film solar cells, with nanotubes acting as photogeneration sites as well as charge separators, collectors and carrier transporters. The device consists of a semitransparent thin film of nanotubes coating a n-type crystalline silicon substrate. Under illumination electron-hole (e-h) pairs, generated in the nanotubes and in the silicon substrate underneath, are split and charges are transported through the nanotubes (electrons) and the n-Si (holes). We found that a suitable thickness of the nanotube thin film, high density of Schottky junctions between nanotubes and n-Si and lowest number of nanotube walls are all fundamental parameters to improve the device incident photon to electron conversion efficiency. Multiwall carbon nanotubes have been synthesized by chemical vapour deposition in an ultra high vacuum chamber by evaporating a given amount of iron at room temperature and then exposing the substrate kept at 800 degrees C at acetylene gas. The amount of deposited iron is found to directly affect the nanotube size distribution (inner and outer diameter) and therefore the number of walls of the nanotubes.     

The interaction of epsin and Eps15 with the clathrin adaptor AP-2 is inhibited by mitotic phosphorylation and enhanced by stimulation-dependent dephosphorylation in nerve terminals

Clathrin-mediated endocytosis was shown to be arrested in mitosis due to a block in the invagination of clathrin-coated pits. A Xenopus mitotic phosphoprotein, MP90, is very similar to an abundant mammalian nerve terminal protein, epsin, which binds the Eps15 homology (EH) domain of Eps15 and the alpha-adaptin subunit of the clathrin adaptor AP-2. We show here that both rat epsin and Eps15 are mitotic phosphoproteins and that their mitotic phosphorylation inhibits binding to the appendage domain of alpha-adaptin. Both epsin and Eps15, like other cytosolic components of the synaptic vesicle endocytic machinery, undergo constitutive phosphorylation and depolarization-dependent dephosphorylation in nerve terminals. Furthermore, their binding to AP-2 in brain extracts is enhanced by dephosphorylation. Epsin together with Eps15 was proposed to assist the clathrin coat in its dynamic rearrangements during the invagination/fission reactions. Their mitotic phosphorylation may be one of the mechanisms by which the invagination of clathrin-coated pits is blocked in mitosis and their stimulation-dependent dephosphorylation at synapses may contribute to the compensatory burst of endocytosis after a secretory stimulus.     

Influence of Cu nanoparticle size on the photo-electrochemical response from Cu-multiwall carbon nanotube composites

We show that Cu metal nanoparticle-multiwall carbon nanotube (MWCNT) assemblies can act as a new hybrid photoactive layer in photo-electrochemical devices. The carbon nanotube (CNT) composites were formed by a controlled thermal deposition of copper which produced crystalline metal nanoparticles localized on the carbon tube outer walls. The photoresponse evaluated in terms of IPCE (incident photon-to-charge carrier generation efficiency) varied for different sized-Cu-MWCNT samples across all the visible and near ultraviolet photon energy range with respect to the response of bare MWCNTs. In the case of 0.2 nm Cu nominal thickness, the IPCE increased, reaching 15%, a value 2.5 times higher than that measured for bare MWCNTs. As the Cu nominal coverage thickened, the IPCE started to decrease and become totally ineffective after 1 nm deposited Cu. The IPCE increase found was interpreted as being the result of a remarkable charge transfer between the Cu metal nanoparticles and the CNTs due to the formation of a strong ionic bond at their interface. The results obtained prove that the metal nanoparticle-CNT composites have optical, electrical and structural properties that can be applied in a variety of nanoscale architectures for novel photo-electrochemical devices.     

Role of phosphorylation in regulation of the assembly of endocytic coat complexes

Clathrin-mediated endocytosis involves cycles of assembly and disassembly of clathrin coat components and their accessory proteins. Dephosphorylation of rat brain extract was shown to promote the assembly of dynamin 1, synaptojanin 1, and amphiphysin into complexes that also included clathrin and AP-2. Phosphorylation of dynamin 1 and synaptojanin 1 inhibited their binding to amphiphysin, whereas phosphorylation of amphiphysin inhibited its binding to AP-2 and clathrin. Thus, phosphorylation regulates the association and dissociation cycle of the clathrin-based endocytic machinery, and calcium-dependent dephosphorylation of endocytic proteins could prepare nerve terminals for a burst of endocytosis.