Unsupervised Bump Hunting Using Principal Components

Principal Components Analysis is a widely used technique for dimension reduction and characterization of variability in multivariate populations. Our interest lies in studying when and why the rotation to principal components can be used effectively within a response-predictor set relationship in the context of mode hunting. Specifically focusing on the Patient Rule Induction Method (PRIM), we first develop a fast version of this algorithm (fastPRIM) under normality which facilitates the theoretical studies to follow. Using basic geometrical arguments, we then demonstrate how the PC rotation of the predictor space alone can in fact generate improved mode estimators. Simulation results are used to illustrate our findings.Comment: 24 pages, 9 figure

On the explanatory power of principal components

We show that if we have an orthogonal base ($u_1,\ldots,u_p$) in a $p$-dimensional vector space, and select $p+1$ vectors $v_1,\ldots, v_p$ and $w$ such that the vectors traverse the origin, then the probability of $w$ being to closer to all the vectors in the base than to $v_1,\ldots, v_p$ is at least 1/2 and converges as $p$ increases to infinity to a normal distribution on the interval [-1,1]; i.e., $\Phi(1)-\Phi(-1)\approx0.6826$. This result has relevant consequences for Principal Components Analysis in the context of regression and other learning settings, if we take the orthogonal base as the direction of the principal components.Comment: 10 pages, 3 figure

Fusion excitation function revisited

We report on a comprehensive systematics of fusion-evaporation and/or fusion-fission cross sections for a very large variety of systems over an energy range 4-155 A.MeV. Scaled by the reaction cross sections, fusion cross sections do not show a universal behavior valid for all systems although a high degree of correlation is present when data are ordered by the system mass asymmetry.For the rather light and close to mass-symmetric systems the main characteristics of the complete and incomplete fusion excitation functions can be precisely determined. Despite an evident lack of data above 15A.MeV for all heavy systems the available data suggests that geometrical effects could explain the persistence of incomplete fusion at incident energies as high as 155A.MeV.Comment: 8 pages, 5 figures, contribution to the NN2012 Proceeding

Facteurs déterminants l’adoption des mesures de gestion intégrée de la fertilité des sols (GIFS) au nord du Bénin : une application du modèle probit multivarié au cas de producteurs de maïs

La baisse du niveau de fertilité des terres cultivables du fait des pratiques agricoles inadaptées, de la déforestation et du changement climatique reste l’une des contraintes majeures de l’agriculture béninoise. Les mesures de Gestion Intégrée de la Fertilité des Sols (GIFS) en sont une des approches de gestion durales des terres à l’échelle des exploitations agricoles. Ainsi, l’étude a fait usage d’un modèle probit multivarié pour identifier les déterminants de l’adoption des mesures de GIFS au sein des exploitations agricoles productrices de maïs au Nord-Bénin. Elle a été conduite sur un échantillon de 100 producteurs de maïs sélectionnés suivant un sondage aléatoire stratifié. Les résultats ont révélé l’existence d’une interdépendance et de complémentarités dans l’adoption des différentes mesures de GIFS. Aussi, la majorité des producteurs de maïs enquêtés préfèrent adopter une combinaison de deux mesures de GIFS (32%) ou de trois mesures (26%). Par ailleurs, la distance du village au champ, l’appartenance à un groupement, le contact avec la vulgarisation, la superficie  emblavée en maïs, la taille du cheptel et le nombre d’actifs agricoles restent les principaux facteurs déterminants l’adoption de ces mesures de GIFS par les producteurs.Mots clés : Bénin, changement climatique, gestion durable des terres, Gestion Intégrée de la Fertilité des Sols, pratiques agricoles, probit multivarié. English title: Adoption of integrated soil fertility management measures in northern Benin: an application of the multivariate probit model to the case of maize producers The decline in the level of fertility of arable land due to unsuitable agricultural practices, deforestation and climate change remains one of the major constraints of agriculture in Benin. Integrated Soil Fertility Management measures (GIFS) are one of the sustainable land management approaches that have been promoted at the level of farmers’ communities. Thus, the study made use of a multivariate probit model to identify the determinants of the adoption of GIFS measures within maize-producing farms in North Benin. It was carried out on a sample of 100 maize farmers selected following a stratified random survey. The results revealed the existence of interdependence and complementarities in the adoption of different GIFS measures. The majority of maize producers surveyed prefer to adopt a combination of two (32%) or three GIFS measures (26%). In addition, the distance from the village to the field, the membership of a group, the contact with the extension service, the area sown with maize, the size of the herd and the number of agricultural workers were identified as the important factors determining the adoption of these GIFS methods by producers.Keywords: Benin, climate change, sustainable land management, Integrated Soil Fertility Management measures, agricultural practices, multivariate probit

Graphene/Ionic Liquid Ultracapacitors: Does Ionic Size Correlate with Storage Energy Performance?

An electric double layer ultracapacitor stores energy in an electric double layer formed near its electrolyte/electrode interfaces. Graphene-based ultracapacitors, because of their outstanding performance, have attracted significant research interest. Optimization of ultracapacitor performance requires understanding the correlation of molecular characteristic of the device (such as structure, inter-ionic and ion-electrode interactions) with its macroscopic properties. Herein, we report molecular dynamics study of how an ionic volume impacts a double-layer capacitance. Four systems were probed: large cation + large anion, large cation + small anion, small cation + large anion, small cation + small anion. Our results show that the structuring of the ionic liquid is driven by the electrolyte-electrode interactions in the ultracapacitor, which are predominantly of the van der Waals type. Storage density energies are similar for all ultracapacitors, being in the range of 24 to 28 J cm-3 at 5.0V. Our results present a comparative analysis of the performances of four different ILs confined between two graphene electrodes. Although the best performance has been observed for the IL with ions (cations and anions) of equal sizes, no definite conclusion about the correlation of the performance to the ionic size ratio can be made from the present study.Instituto de Ciência e Tecnologia, Universidade Federal de São Paulo, São José dos Campos, SP, BrazilP.E.S., Vasilievsky Island, Saint Petersburg, Leningrad Oblast, Russian FederationDepartment of Physics, St. Petersburg State University, St. Petersburg, Russian FederationInstituto de Ciência e Tecnologia, Universidade Federal de São Paulo, São José dos Campos, SP, Brazi

Expression of a bacterial 3-dehydroshikimate dehydratase reduces lignin content and improves biomass saccharification efficiency.

Lignin confers recalcitrance to plant biomass used as feedstocks in agro-processing industries or as source of renewable sugars for the production of bioproducts. The metabolic steps for the synthesis of lignin building blocks belong to the shikimate and phenylpropanoid pathways. Genetic engineering efforts to reduce lignin content typically employ gene knockout or gene silencing techniques to constitutively repress one of these metabolic pathways. Recently, new strategies have emerged offering better spatiotemporal control of lignin deposition, including the expression of enzymes that interfere with the normal process for cell wall lignification. In this study, we report that expression of a 3-dehydroshikimate dehydratase (QsuB from Corynebacterium glutamicum) reduces lignin deposition in Arabidopsis cell walls. QsuB was targeted to the plastids to convert 3-dehydroshikimate - an intermediate of the shikimate pathway - into protocatechuate. Compared to wild-type plants, lines expressing QsuB contain higher amounts of protocatechuate, p-coumarate, p-coumaraldehyde and p-coumaryl alcohol, and lower amounts of coniferaldehyde, coniferyl alcohol, sinapaldehyde and sinapyl alcohol. 2D-NMR spectroscopy and pyrolysis-gas chromatography/mass spectrometry (pyro-GC/MS) reveal an increase of p-hydroxyphenyl units and a reduction of guaiacyl units in the lignin of QsuB lines. Size-exclusion chromatography indicates a lower degree of lignin polymerization in the transgenic lines. Therefore, our data show that the expression of QsuB primarily affects the lignin biosynthetic pathway. Finally, biomass from these lines exhibits more than a twofold improvement in saccharification efficiency. We conclude that the expression of QsuB in plants, in combination with specific promoters, is a promising gain-of-function strategy for spatiotemporal reduction of lignin in plant biomass

Solvent extraction aplied to the recovery of heavy metals from galvanic sludges

In this study, a hydrometallurgical treatment involving the solvent extraction and recovery of some heavy metals from a sulphuric acid leach solution of galvanic sludge, using di-(2-ethylhexyl)-phosphoric acid (D2EHPA) and bis-(2,4,4- trimethylpentyl)-phosphinic acid (Cyanex 272), both diluted in kerosene, has been investigated. The preliminary tests revealed the necessity to remove other metal species than zinc and nickel, contained in the leach solution, and therefore, processes to cement copper and precipitate chromium were then applied to finally obtain a Zn and Ni pregnant solution prior to solvent extraction. For the experimental conditions studied, Cyanex 272 showed a good recovery of Zn after the stripping stage using H2SO4, but D2EHPA effectively promoted a higher Zn extraction than Cyanex 272 did. The dependence of the solvent extraction method on variables such as pH, contact time and concentration of extractant, as well as the effect of different concentrations of sulphuric acid on stripping, are discussed. The discussion also includes the previous conditions developed to separate the main interfering metallic species from the leach solution in order to improve the extraction and recovery of zinc by solvent extraction. The final objective has been to achieve a solution as pure as possible to recover nickel sulphate.Estudou-se o desenvolvimento de um processo metalúrgico para a extracção de metais a partir de lamas galvânicas, passando por fases e extracção com solventes orgânico

Leaching behaviour of a galvanic sludge in sulphuric acid and ammoniacal media

Leaching studies of a sludge produced by the physico-chemical treatment of astewaters generated by a Ni/Cr plating plant were carried out in both sulphuric acid and ammoniacal media aiming to decide which of them would be the best treatment for this kind of waste material. The dissolution behaviour of some metals (Cu, Ni, Cr and Zn) was studied in order to assure the best metal recovery conditions in subsequent processes by the use of some separation methods such as solvent extraction and precipitation techniques. Therefore, the study here presented deals with the first chemical stage of an integrated treatment process. For the sulphuric acid leaching, maximal conversions obtained were 88.6% Cu, 98.0% Ni and 99.2% Zn for the following experimental conditions: a 100 g L−1 acid concentration, a 5:1 liquid-to-solid ratio (L/S), a particle size less than 1 mm, a digestion time of 1 h, a stirring speed of 700 rpm (all at room temperature and under atmospheric pressure). As expected, no selectivity was achieved for the sulphuric acid leaching, despite this option yielding much higher metal ion dissolution when compared with that reached by ammoniacal leaching. The use of this latter medium allowed the extraction of Cu and Ni without Cr species, but rates of conversion were only about 70% for Cu and 50% for Ni, much lower than those obtained for sulphuric acid leaching

Effect of experimental variables on the inertization of galvanic sluges in clay-based ceramics

The incorporation of several industrial wastes in ceramic matrixes had been attempted as an effective low expense technique for the fixation of metallic species in usable products or simply to reduce the residue volume for further disposal. However, the dominant mechanism of the inertization process and the relevant influent parameters are still unknown, mostly due to the complexity of the systems. This work reports the effect of several processing parameters such as the mixing time, the calcination temperature and duration, the relative amount of sludge, and the physical aspect of the sample (powdered or pressed pellets) on the fixing level of relevant species (SiO2, SO4 2−, Zn, Ni, Ca, Cu, Cr) by leaching in different media (aqueous, acetate, and citrate). Statistical tools were used to define the relevance of each experimental variable on the inertization process of the used galvanic sludge. The relative amount of sludge in the mixture, the calcination temperature and the agglomeration state of the sample were found to be the most influent parameters of the inertization process. The incipient reaction between sludge and ceramic matrix components points out for the dominance of a macro- encapsulation mechanism