Conductivity and Local Structure of LaNiO3 Thin Films

A marked conductivity enhancement is reported in 6–11 unit cell LaNiO₃ thin films. A maximal conductivity is also observed in ab initio calculations for films of the same thickness. In agreement with results from state of the art scanning transmission electron microscopy, the calculations also reveal a differentiated film structure comprising characteristic surface, interior, and heterointerface structures. Based on this observation, a three‐element parallel conductor model is considered and leads to the conclusion that the conductivity enhancement for films of 6–11 unit cells, stems from the onset of intercompetition between the three local structures in the film depth.     

Contribution à la modélisation de lignes hyperfréquences supraconductrices à haute température critique par la méthode FDTD

The purpose of this study is to determine the electrical behaviour of high-Tc superconductor microstrip lines. TheFdtd method is used to put into discrete terms Maxwell’s equations. The two-fluid model has been chosen to describe the behaviour of the superconductor. The variation of electrical parameters such as surface resistance as a function of frequency up to 60 GHz is presented.     

A plot drainage network as a conceptual tool for the spatial representation of surface flow pathways in agricultural catchments

The drainage network must take the farming systems and the landscape structure into consideration to describe flow pathways in the agricultural catchment. A new approach is proposed to build the drainage network which is based on the identification of the inlets and outlets for surface water flow on each farmers’ field (or plot), estimating the relative areas contributing to the surface yield. The delineation of these areas and their links in terms of surface flow pathways provides us with a pattern of relationships between individual plots, i.e. going from each plot to the other plots over the entire catchment. In this approach, flow directions are firstly calculated in the usual way by taking account of slope direction. Plot outlets are defined from the digital elevation model (DEM) and then linked together using a tree structure. If present, linear networks such as hedges modify both the flow directions and the location of plot outlets, hence modify this tree structure. In a final step, the plots are themselves linked together using a graph structure illustrated by an arrow diagram. This drainage network based on plot outlets is applied to a 15-km² catchment area represented by 38,300 pixels and 2000 plots. This new drainage network takes into consideration 5300 plot outlets, which greatly reduces the number of objects in comparison with a drainage network made up of pixels or DEM cells. This method leads to a simple and functional representation of surface flow pathways in an agricultural catchment. It allows us to identify the key plots controlling stream water pollution where converging flow pathways are coming from numerous or large-sized plots. Finally, it produces a functional representation for decision support.     

A column generation and branch-and-cut algorithm for the channel assignment problem

We present an exact algorithm for solving the channel assignment problem in cellular telephony networks. This problem consists of assigning sets of channels to the network cells in such a way that the channel demand is satisfied, while avoiding co-channel interference and adjacent channel interference and respecting the channel spacing constraint for each antenna. In a previous article [Jaumard B, Marcotte O, Meyer C, Vovor T. Comparison of column generation models for channel assignment in cellular networks. Discrete Applied Mathematics 2002; 118:299–322], we formulated this problem as a covering problem in two different ways and compared these two formulations and another formulation both from a theoretical and computational point of view (by solving their linear relaxations). In the present article we focus on the best set covering formulation, where the subsets are sets of cells that can be assigned the same channel, and we actually solve two versions of the integer program. In the first version, we seek to minimize the unmet demand, while in the second, we seek to minimize the overall interference while assigning the required number of channels to each cell. In either version, the integer program is solved by an algorithm combining the column generation technique and a branch-and-cut scheme. Finally, we present the solutions produced by these algorithms for some instances of European networks and real-life instances supplied by the Bell Mobilité company.     

Synthesis and characterization of interpenetrating networks from polycarbonate and cellulose acetate butyrate

Polycarbonates (PC) are currently used for organic optical glass; nevertheless they show a poor impact resistance which may be increased by combination with cellulose acetate butyrate (CAB) into a PC/CAB interpenetrating polymer network (IPN), without altering the material transparency as we show here. A series of rigid IPNs based on an aliphatic polycarbonate and CAB was prepared through in situ polymerization techniques. The kinetics of the formation of two networks in the IPNs were studied by FTIR spectroscopy. Effects of the CAB cross-linking and weight proportions of the two components in the IPNs were investigated by dynamic mechanical thermal analysis.     

A perimeter algorithm applied to lung pathology

A new image analyser, the NS 2000, explores the image using 256 photodiodes and, according to an adjustable threshold, converts it into a set of digital points of logical level 0 or 1. The method of fitting squares of increasing size consists of checking the presence of a square of a given size and of a given logical value throughout the image studied and gives the areas of successive erosions of the image. Using the parameters provided by the device one can obtain the total boundary B_A per unit area for the phase studied, which is proportional to the number of squares having points of the two logical levels. Errors in length measurement as a function of orientation and for isotropic structures are compared to other automatic perimeter algorithms and to manual square grid measurement. Using the parameters provided by the device for the quantitative evaluation of lesions of elastase induced emphysema in hamster lungs, the values obtained for internal surface area (ISA) of alveoli, are lower by about 40% in elastase treated hamsters when compared to normal controls. This difference is highly significant (P < 0.001) and the results obtained by the described method are in good agreement with those obtained by the classical manual procedure. Efficiency, defined as the precision of the estimate per unit measurement time on a given set of sample units (pictures in this paper), is given for both NS 2000 and manual procedures. The results obtained show comparable values but the automatic procedure includes a statistical treatment and it is significantly faster on histological sections than on micrographs, which was not the case with the manual method.     

Characterization of starch and cell walls from mature-green ambarella (Spondias cytherea Sonnerat) and their enzymatic hydrolysis

Juice from mature-green ambarella contains starch, a characteristic detrimental to its visual appearance due to the white sediment formed upon storage. The purpose of this work was to evaluate the effects of starch and cell wall degrading enzymes on juice residual starch and content in soluble sugars. Starch and cell walls from mature-green ambarella fruits were purified and characterized. Starch was found to contain 21.0% amylose, 78.1% amylopectin and 0.9% other minors compounds. Its average granule size was 20 μm. Its thermal characteristics were: temperatures of onset (T _o = 57.8 °C), peak (T _p = 65.6 °C), and conclusion (T _c = 72.6 °C) of gelatinization and the endothermic enthalpy (ΔH _{gelatinisation} = 12.4 J g^?1). Cell walls represented 2.8% of the edible fresh matter and were mainly constituted of highly methylated (HM) pectic substances and cellulose. The amylolytic preparations we tested, AMG^® 300 L and Hazyme^® C, showed similar behaviours in terms of starch hydrolysis and profit of Brix degree obtained. With 200 μg g^?1 of AMG^® 300 L or Hazyme^® C, the degree of amylolysis of coarse ambarella puree was close to 50% and its increased up to 70% with enzymes concentrations higher than 1,000 μg g^?1 (gelatinization at 75 ± 5 °C for 15 min followed by starch amylolysis at 60 ± 5 °C for 15 min). Total hydrolysis of ambarella starch is possible when pectinolysis occurred before amylolysis treatment, probably because of the fluidification of the medium by the pectocellulolytic enzymes. Pectinex^® Ultra SP-L was the most efficient preparation to degrade the ambarella pectins (～80% of cell wall uronides liberated from 120 mg g^?1 of purified cell walls within 1 h at 30 °C, pH 2.7).     

Physicochemical properties of talc ore from three deposits of Lamal Pougue area (Yaounde Pan-African Belt, Cameroon), in relation to industrial uses

Three talc deposits were discovered at Ngoung, Lamal Pougue and Bibodi Lamal (Cameroon). They derived from ultramafic rocks and are enclosed in a Pan-African garnet and muscovite-bearing mica schist of the Yaoundé series. The physico-chemical properties of these talc deposits have been investigated by different techniques including Scanning Electron and Transmission Microscopy (SEM and TEM), chemical analyses, X-ray diffraction (XRD), infrared spectroscopy, particle size analysis by laser diffraction and low temperature gas absorption–desorption. The mineralogical composition deduced from XRD is wide (talc + chlorite + tremolite ± anthophyllite ± chromite ±serpentine ± brucite ± magnesite ± dolomite), but due to the high talc contents (≈ 90%) the samples are close to monomineralic. SEM studies reveal that all talc deposits comprise bundles of platy talc and a few prismatic crystals of amphiboles and other contaminating minerals. Laser diffraction confirms the coarse particle size of the talc crystals. Mode values are as high as 105–170 μm (except two samples displaying 76 and 42 μm) and d50 ranges from 107 to 25 μm. The values of specific surface area measured by BET and t-plot methods range from 1 to 6 m²/g and are correlated with external specific surface area measured by laser diffraction. Discrepancies from the trend are due to the semi-crystalline texture of the samples and mostly to intra-crystalline structural defects revealed by TEM observations. In infrared spectra, specific absorption bands are distinguished for talc, chlorite, tremolite, carbonates, serpentine, brucite and water. Occasional substitutions in minerals led to a shift in some absorption bands. The chemical composition criteria important for most of the industrial applications such as ceramics and pharmaceutics are closely complied with in untreated samples from these deposits. In summary, high talc proportions, chemical compositions, platy morphology and coarse grain size of its crystals lead to the conclusion that the studied deposits are economically attractive. The data set of the present work is an important tool for choosing the beneficiation methods for specific applications.     

The Male Abdominal Glands of <Emphasis Type="Italic">Leucophaea maderae</Emphasis>: Chemical Identification of the Volatile Secretion and Sex Pheromone Function

In Leucophaea maderae, male calling behavior involves the release of a sex pheromone from the abdominal sternal glands. An extract of sternal glands attracted conspecific females over a distance. The compounds present were identified as hydroxy-3-butan-2-one, (2R, 3R)-butanediol, senecioic acid, and (E)-2-octenoic acid. The same components are also present in male tergal glands. The identified compounds were tested on their own and in mixtures. Their biological function is discussed.