Derivatives with respect to metrics and applications: subgradient marching algorithm

This paper introduces a subgradient descent algorithm to compute a Riemannian metric that minimizes an energy involving geodesic distances. The heart of the method is the Subgradient Marching Algorithm to compute the derivative of the geodesic distance with respect to the metric. The geodesic distance being a concave function of the metric, this algorithm computes an element of the subgradient in O(N 2 log(N)) operations on a discrete grid of N points. It performs a front propagation that computes a subgradient of a discrete geodesic distance. We show applications to landscape modeling and to traffic congestion. Both applications require the maximization of geodesic distances under convex constraints, and are solved by subgradient descent computed with our Subgradient Marching. We also show application to the inversion of travel time tomography, where the recovered metric is the local minimum of a non-convex variational problem involving geodesic distance

Etude physicochimique et microbiologique de l’huile essentielle de Thymus fontanesii Boiss & Reut

Thymus fontanesii (thym) est une plante aromatique, répandue en Algérie et très utilisée par les populations locales pour ses vertus médicinales. L’huile essentielle de cette plante originaire de l’ouest algérien, fait l’objet dans cet article d’une étude physicochimique et microbiologique. L’extraction de l’huile essentielle a été effectuée par entraînement à la vapeur d’eau. Le rendement obtenu à partir des feuilles (2%) est intéressant pour l’exploitation industrielle. La densité spécifique (0.9219), l’indice de réfraction à 20° (1.4999), le pouvoir rotatoire (+3.4313), la miscibilité à l’éthanol (0.6V/1V), le point de congélation

Study of the Biological Activities of the Seeds of the Plant Ceratonia Siliqua L. Recovered in the Bejaia Region

Background: Ceratonia siliqua is a plant that belongs to the Fabaceae family. It is frequently used in our culinary and medical traditions to fight cholesterol, acute diarrhea and digestive disorders. Methods: The hydrogen atom or electron donation abilities of the corresponding extracts and some pure compounds were measured from the bleaching of the purple-colored methanol solution of 2, 20-diphenylpicrylhydrazyl (DPPH), studying the anti-inflammatory effect by measuring the volume of the edema of the paw that has received carrageenan 1%. Antimicrobial activity in vitro was screened by using disc diffusion and micro-dilution methods. Results: The determination of the polyphenols of the methanolic extracts of the seeds reveals the richness of our extracts in polyphenols is 30 mg of gallic acid / g of extract. The aqueous and methanolic extract flavonoid assay shows that they contain high levels of flavonoids with contents of 07 and 10 mg equivalent of quercetin / g of extract respectively. The aqueous and methanolic extracts of Ceratonia siliqua seeds from the Bejaia region could bring the stable free radical 2.2 diphenyl-1-picrylhydrazyl (DPPH) to yellow-colored diphenylpicrylhydrazine with respective IC 50 values of 0.7 mg/ml and 0.2 mg/ml. They exhibit lower antioxidant activity than ascorbic acid (0.038 μg / ml). Determination of anti-inflammatory activity revealed that our aqueous and methanolic extracts of Ceratonia siliqua L seeds are able to reduce edema up to 81.89%. The methanoid extracts of Ceratonia siliqua L. seeds have a medium antibacterial action against bacteria: E. coli (13 mm), Staphylococcus aureus (12 mm) and Pseudomonas aeruginosa (12 mm). On the other hand, the aqueous extracts of the seeds of Ceratonia siliqua L have a weak antibacterial action against the same bacteria with a diameter of inhibition of 9 mm. However, the aqueous extracts of Ceratonia siliqua L seeds are endowed with a very important inhibitory action against candida albicans and it is similar to that of the antibiotic, antifungal Econazole (1%). Conclusion: According to the results observed, the two extracts of the seeds and pods have a potential anti-free radical and antioxidant measured compared to the standard antioxidant used. The results of the antimicrobial activity carried out in vitro on the 3 bacterial strains indicate that the two methanolic extracts of this plant have low antibacterial activity

Sub-Riemannian Fast Marching in SE(2)

We propose a Fast Marching based implementation for computing sub-Riemanninan (SR) geodesics in the roto-translation group SE(2), with a metric depending on a cost induced by the image data. The key ingredient is a Riemannian approximation of the SR-metric. Then, a state of the art Fast Marching solver that is able to deal with extreme anisotropies is used to compute a SR-distance map as the solution of a corresponding eikonal equation. Subsequent backtracking on the distance map gives the geodesics. To validate the method, we consider the uniform cost case in which exact formulas for SR-geodesics are known and we show remarkable accuracy of the numerically computed SR-spheres. We also show a dramatic decrease in computational time with respect to a previous PDE-based iterative approach. Regarding image analysis applications, we show the potential of considering these data adaptive geodesics for a fully automated retinal vessel tree segmentation.Comment: CIARP 201

Derivatives with respect to metrics and applications: subgradient marching algorithm

This paper introduces a subgradient descent algorithm to compute a Riemannian metric that minimizes an energy involving geodesic distances. The heart of the method is the Subgradient Marching Algorithm to compute the derivative of the geodesic distance with respect to the metric. The geodesic distance being a concave function of the metric, this algorithm computes an element of the subgradient in O(N (2) log(N)) operations on a discrete grid of N points. It performs a front propagation that computes a subgradient of a discrete geodesic distance. We show applications to landscape modeling and to traffic congestion. Both applications require the maximization of geodesic distances under convex constraints, and are solved by subgradient descent computed with our Subgradient Marching. We also show application to the inversion of travel time tomography, where the recovered metric is the local minimum of a non-convex variational problem involving geodesic distances

Reversible stimulus-responsive Cu(i) iodide pyridine coordination polymer

We present a structurally flexible copper–iodide–pyridine-based coordination polymer showing drastic variations in its electrical conductivity driven by temperature and sorption of acetic acid molecules. The dramatic effect on the electrical conductivity enables the fabrication of a simple and robust device for gas detection. X-ray diffraction studies and DFT calculations allow the rationalisation of these observations.We are thankful for support from MICINN (MAT2013-46753-C2-1-P, MAT2013-46502-C2-1/2-P and CTQ2011-26507), Eusko Jaurlaritza (S-PE13UN016) and Generalitat Valenciana PrometeoII/2014/076

Photoinduced hole-transfer in semiconducting polymer/low-bandgap cyanine dye blends: evidence for unit charge separation quantum yield

Power-conversion efficiencies of organic heterojunction solar cells can be increased by using semiconducting donor-acceptor materials with complementary absorption spectra extending to the near-infrared region. Here, we used continuous wave fluorescence and absorption, as well as nanosecond transient absorption spectroscopy to study the initial charge transfer step for blends of a donor poly(p-phenylenevinylene) derivative and low-band gap cyanine dyes serving as electron acceptors. Electron transfer is the dominant relaxation process after photoexcitation of the donor. Hole transfer after cyanine photoexcitation occurs with an efficiency close to unity up to dye concentrations of similar to 30 wt%. Cyanines present an efficient self-quenching mechanism of their fluorescence, and for higher dye loadings in the blend, or pure cyanine films, this process effectively reduces the hole transfer. Comparison between dye emission in an inert polystyrene matrix and the donor matrix allowed us to separate the influence of self-quenching and charge transfer mechanisms. Favorable photovoltaic bilayer performance, including high open-circuit voltages of similar to 1 V confirmed the results from optical experiments. The characteristics of solar cells using different dyes also highlighted the need for balanced adjustment of the energy levels and their offsets at the heterojunction when using low-bandgap materials, and accentuated important effects of interface interactions and solid-state packing on charge generation and transport

The measuring systems of the wire tension for the MEG II Drift Chamber by means of the resonant frequency technique

The ultra-low mass Cylindrical Drift Chamber designed for the MEG experiment upgrade is a challenging apparatus made of 1728 phi = 20 micron gold plated tungsten sense wires, 7680 phi = 40 micron and 2496 phi = 50 micron silver plated aluminum field wires. Because of electrostatic stability requirements all the wires have to be stretched at mechanical tensions of about 25, 19 and 29 g respectively which must be controlled at a level better than 0.5 g. This chamber is presently in acquisition, but during its construction about 100 field wires broke, because of chemical corrosion induced by the atmospheric humidity. On the basis of the experience gained with this chamber we decided to build a new one, equipped with a different type of wires less sensitive to corrosion. The choice of the new wire required a deep inspection of its characteristics and one of the main tools for doing this is a system for measuring the wire tension by means of the resonant frequency technique, which is described in this paper. The system forces the wires to oscillate by applying a sinusoidal signal at a known frequency, and then measures the variation of the capacitance between a wire and a common ground plane as a function of the external signal frequency. We present the details of the measuring system and the results obtained by scanning the mechanical tensions of two samples of MEG II CDCH wires and discuss the possible improvements of the experimental apparatus and of the measuring technique.Comment: Ten pages, twelve figures, to be submitted to Nuclear Instruments and Methods

Production, characterization, and antigen specificity of recombinant 62-71-3, a candidate monoclonal antibody for rabies prophylaxis in humans

Rabies kills many people throughout the developing world every year. The murine monoclonal antibody (mAb) 62-71-3 was recently identified for its potential application in rabies postexposure prophylaxis (PEP). The purpose here was to establish a plant-based production system for a chimeric mouse-human version of mAb 62-71-3, to characterize the recombinant antibody and investigate at a molecular level its interaction with rabies virus glycoprotein. Chimeric 62-71-3 was successfully expressed in Nicotiana benthamiana. Glycosylation was analyzed by mass spectroscopy; functionality was confirmed by antigen ELISA, as well as rabies and pseudotype virus neutralization. Epitope characterization was performed using pseudotype virus expressing mutagenized rabies glycoproteins. Purified mAb demonstrated potent viral neutralization at 500 IU/mg. A critical role for antigenic site I of the glycoprotein, as well as for two specific amino acid residues (K226 and G229) within site I, was identified with regard to mAb 62-71-3 neutralization. Pseudotype viruses expressing glycoprotein from lyssaviruses known not to be neutralized by this antibody were the controls. The results provide the molecular rationale for developing 62-71-3 mAb for rabies PEP; they also establish the basis for developing an inexpensive plant-based antibody product to benefit low-income families in developing countries.—Both, L., van Dolleweerd, C., Wright, E., Banyard, A. C., Bulmer-Thomas, B., Selden, D., Altmann, F., Fooks, A. R., Ma, J. K.-C. Production, characterization, and antigen specificity of recombinant 62-71-3, a candidate monoclonal antibody for rabies prophylaxis in humans

Performances of a new generation tracking detector: the MEG II cylindrical drfit chamber

The cylindrical drift chamber is the most innovative part of the MEG~II detector, the upgraded version of the MEG experiment. The MEG~II chamber differs from the MEG one because it is a single volume cylindrical structure, instead of a segmented one, chosen to improve its resolutions and efficiency in detecting low energy positrons from muon decays at rest. In this paper, we show the characteristics and performances of this fundamental part of the MEG~II apparatus and we discuss the impact of its higher resolution and efficiency on the sensitivity of the MEG~II experiment. Because of its innovative structure and high quality resolution and efficiency the MEG~II cylindrical drift chamber will be a cornerstone in the development of an ideal tracking detector for future positron-electron collider machines.Comment: 27 pages, 41 figures, to be submitted to EPJ