Information theoretic combination of pattern classifiers

Combining several classifiers has proved to be an effective machine learning technique. Two concepts clearly influence the performances of an ensemble of classifiers: the diversity between classifiers and the individual accuracies of the classifiers. In this paper we propose an information theoretic framework to establish a link between these quantities. As they appear to be contradictory, we propose an information theoretic score (ITS) that expresses a trade-off between individual accuracy and diversity. This technique can be directly used, for example, for selecting an optimal ensemble in a pool of classifiers. We perform experiments in the context of overproduction and selection of classifiers, showing that the selection based on the ITS outperforms state-of-the-art diversity-based selection techniques.     

Influence of woody elements of a Norway spruce canopy on nadir reflectance simulated by the DART model at very high spatial resolution

A detailed sensitivity analysis investigating the effect of woody elements introduced into the Discrete Anisotropic Radiative Transfer (DART) model on the nadir bidirectional reflectance factor (BRF) for a simulated Norway spruce canopy was performed at a very high spatial resolution (modelling resolution 0.2 m, output pixel size 0.4 m). We used such a high resolution to be able to parameterize DART in an appropriate way and subsequently to gain detailed understanding of the influence of woody elements contributing to the radiative transfer within heterogeneous canopies. Three scenarios were studied by modelling the Norway spruce canopy as being composed of i) leaves, ii) leaves, trunks and first order branches, and finally iii) leaves, trunks, first order branches and small woody twigs simulated using mixed cells (i.e. cells approximated as composition of leaves and/or twigs turbid medium, and large woody constituents). The simulation of each scenario was performed for 10 different canopy closures (CC = 50-95%, in steps of 5%), 25 leaf area index (LAI = 3.0-15.0 m² m^− 2, in steps of 0.5 m² m^− 2), and in four spectral bands (centred at 559, 671, 727, and 783 nm, with a FWHM of 10 nm). The influence of woody elements was evaluated separately for both, sunlit and shaded parts of the simulated forest canopy, respectively. The DART results were verified by quantifying the simulated nadir BRF of each scenario with measured Airborne Imaging Spectroradiometer (AISA) Eagle data (pixel size of 0.4 m). These imaging spectrometer data were acquired over the same Norway spruce stand that was used to parameterise the DART model.The Norway spruce canopy modelled using the DART model consisted of foliage as well as foliage including robust woody constituents (i.e. trunks and branches). All results showed similar nadir BRF for the simulated wavelengths. The incorporation of small woody parts in DART caused the canopy reflectance to decrease about 4% in the near-infrared (NIR), 2% in the red edge (RE) and less than 1% in the green band. The canopy BRF of the red band increased by about 2%. Subsequently, the sensitivity on accounting for woody elements for two spectral vegetation indices, the normalized difference vegetation index (NDVI) and the angular vegetation index (AVI), was evaluated. Finally, we conclude on the importance of including woody elements in radiative transfer based approaches and discuss the applicability of the vegetation indices as well as the physically based inversion approaches to retrieve the forest canopy LAI at very high spatial resolution.     

Dimeric character of a basic phospholipase A2 from cobra venom: experimental and modelling study

When it is gel filtered on Sephadex in the absence of calciumions, basic phospholipase A₂ from Naja nigricollis venom elutesas a dimer. In order to study the possibility of this dimerizationfrom a structural point of view, three-dimensional models ofboth monomeric and dimeric N. nigricollis phospholipases A havebeen graphically built on the basis of homologies with the phospholipasesA₂ from pancreatic bovine and Crotalus atrox venom. The buildingof a duneric model is made possible by the deletion of a particularloop of the bovine structure. The predicted models of N. nigricollisphospholipase A₂ have been checked using molecular mechanicsand molecular dynamics techniques according to a suitable protocolwhich has been developed starting from refined X-ray structuresof phospholipases A₂ as the test case. The observed stabilityof the dimeric model, in the absence of calcium, agrees withthe hypothesis of the dimerization of the basic phospholipaseA Particularly, Arg31, which replaces the hydrophobic residuepresent in pancreatic bovine and C.atrox venom phospholipasesA₂, contributes to this stability.     

Étude des Caractéristiques de l'Ecoulement créé par une Turbine à Barreaux croisés dans une Cellule de Flottation — Influence du Nombre de Barreaux et de la Viscosité du Liquide I. • Détermination de la Capacité de Pompage et de l'Intensité de Turbulence

Time-smoothed velocities, velocity fluctuations, pumping capacity and turbulence intensity in the discharge flow of a turbine made of crossed bars in a flotation cell have been measured at different speeds by hot film anemometry. Influences of the number of bars and of the viscosity of the liquid have been studied.     

Larvicidal Effect of a Cell-Wall Fraction Isolated from Alder Decaying Leaves

Decaying alder leaves in water from Alpine Aedes breeding sites, particularly their toxicity to larval Culicidae, were investigated and characterized with comparative toxicological and chemical methods. Bioassays that used third-instar Aedes aegypti as a reference species indicated that the larvicidal effect of crude leaf litter varied with decaying age of the litter, while no toxicity was detected from leaching water of the mosquito breeding sites. Ten-month-old leaf litter was the most toxic. Comparison of the different soluble and insoluble fractions obtained after sequential extraction of decomposed litter allowed us to localize the toxicity factor to an insoluble cell-wall fraction. The toxicity seems to be linked to phenolic activity. It is higher than that found for tannic acid solutions used as a reference to mimic the larvicidal effects of the molecules naturally occurring in decaying litter. The pattern of establishing the larvicidal effect of alder leaf litter in water of Alpine Aedes breeding sites is discussed.     

Infra-red spectrum of the tight (110) fold in n-C198H398

The alkane n-C₁₉₈H₃₉₈ has been crystallised in both extended chain and once-folded forms and annealed to produce materials with low concentrations of gauche bonds. The concentrations of the specific conformers detected by FTIR spectroscopy at −173 °C are calculated, using measurements on liquid n-hexadecane for calibration: values are all generally less than 2.0 per 100 carbon atoms, with extended chain samples showing values less than 1.0 per 100 carbon atoms. A subtraction spectrum (Once-folded chain sample minus Extended chain sample) shows positive bands at 1298, 1340, 1347 and 1369 cm⁻¹, which are predicted in earlier calculations for a (110) fold, while additional positive bands at 1353 and 1363 cm⁻¹ are assigned, respectively, to gg conformers and (tentatively) to strained gtg or gtg′ conformations.     

Tunable photoactivation of a post-translationally modified signaling protein and its unmodified counterpart in live cells

An ideal technology for direct imaging of post-translationally modified proteins would be one in which the appearance of a fluorescent signal is linked to a modification dependent protein-activation event. Herein, we utilize the protein semisynthesis technique, expressed protein ligation (EPL), to prepare caged analogues of the signaling protein Smad2; the function and fluorescence of the analogues were then photocontrolled in a correlated fashion. We show that this strategy permits titration of the cellular levels of active phosphorylated Smad2 in its biologically relevant, full-length form. We also prepared a nonphosphorylated, caged full-length Smad2 analogue labeled with an orthogonal fluorophore, and simultaneously imaged the phosphorylated and nonphosphorylated forms of the protein in the same cell. This strategy should enable the dissection of the cellular consequences of post-translational modifications (PTMs) by direct comparison of the behavior of the modified and unmodified forms of the protein following uncaging.     

Behaviour of pathogenic and indicator bacteria during urban wastewater treatment and sludge composting, as revealed by quantitative PCR

Two enteric pathogens, Salmonella spp. and Campylobacter jejuni, and two bacteria commonly used as indicators, Escherichia coli and Clostridium perfringens, were monitored using quantitative real-time PCR during municipal wastewater treatment and sludge composting. The results were compared with those obtained using standard culture methods. A reduction of all bacteria was observed during wastewater treatment and during the thermophilic phase of composting. However, the bacterial groups studied behaved differently during the process, and the main differences were observed during biological treatment in activated sludge basins. In particular, Salmonella spp. and C. jejuni survived better during activated sludge treatment than E. coli. C. jejuni was the most resistant to wastewater treatment among the four bacterial groups. Overall, differences in survival were observed for all bacteria studied, when submitted to the same environmental pressure. This holds both for differences between indicators and pathogenic bacteria and between pathogenic bacteria. These results show the difficulty in defining reliable indicators.     

Competition between planktonic and fixed microorganisms during the start-up of methanogenic biofilm reactors

The influence of the hydraulic retention time (HRT) on the start-up phase of a methanogenic inverse turbulent bed bioreactor was investigated. Two identical reactors were monitored, the only differing parameter being the HRT: one of the reactors was fed with a diluted wastewater at a constant HRT of 1 day, the organic loading rate (OLR) being increased by decreasing the substrate dilution; the second reactor was fed at a constant influent concentration of 20 g COD L(-1), the OLR being increased by decreasing the HRT from 40 days to 1 day. After 45 days of start-up, both reactors were operated at an OLR of 20 g COD L(-1)d(-1) and a HRT of 1 day. However, strong differences were observed on biofilm growth. In the reactor operated at a constant short HRT, biofilm concentration was 4.5 as high as in the reactor operated at an increasing HRT. This difference was attributed to the competition between planktonic and biofilm microorganisms in the latter reactor, whereas suspended biomass was quickly washed out in the former reactor because of the low HRT.     

Lead shot contribution to blood lead of First Nations people: the use of lead isotopes to identify the source of exposure

Although lead isotope ratios have been used to identify lead ammunition (lead shotshell pellets and bullets) as a source of exposure for First Nations people of Canada, the actual source of lead exposure needs to be further clarified. Whole blood samples for First Nations people of Ontario, Canada, were collected from participants prior to the traditional spring harvest of water birds, as well as post-harvest. Blood-lead levels and stable lead isotope ratios prior to, and after the harvest were determined by ICP-MS. Data were analyzed by paired t-tests and Wilcoxon Signed-Ranks tests. All participants consumed water birds harvested with lead shotshell during the period of study. For the group excluding six males who were potentially exposed to other sources of lead (as revealed through a questionnaire), paired t-tests and Wilcoxon Signed-Ranks tests showed consistent results: significant (p<0.05) increases in blood-lead concentrations and blood levels of (206)Pb/(204)Pb and (206)Pb/(207)Pb towards the mean values we previously reported for lead shotshell pellets; and a significant decrease in (208)Pb/(206)Pb values towards the mean for lead shotshell pellets. However, when we categorized the group further into a group that did not use firearms and did not eat any other traditional foods harvested with lead ammunition other than waterfowl, our predictions for (206)Pb/(204)Pb, (206)Pb/(207)Pb and (208)Pb/(206)Pb hold true, but there was not a significant increase in blood-lead level after the hunt. It appears that the activity of hunting (i.e., use of a shotgun) was also an important route of lead exposure. The banning of lead shotshell for all game hunting would eliminate a source of environmental lead for all people who use firearms and/or eat wild game.