Efficient Data Representation by Selecting Prototypes with Importance Weights

Prototypical examples that best summarizes and compactly represents an underlying complex data distribution communicate meaningful insights to humans in domains where simple explanations are hard to extract. In this paper we present algorithms with strong theoretical guarantees to mine these data sets and select prototypes a.k.a. representatives that optimally describes them. Our work notably generalizes the recent work by Kim et al. (2016) where in addition to selecting prototypes, we also associate non-negative weights which are indicative of their importance. This extension provides a single coherent framework under which both prototypes and criticisms (i.e. outliers) can be found. Furthermore, our framework works for any symmetric positive definite kernel thus addressing one of the key open questions laid out in Kim et al. (2016). By establishing that our objective function enjoys a key property of that of weak submodularity, we present a fast ProtoDash algorithm and also derive approximation guarantees for the same. We demonstrate the efficacy of our method on diverse domains such as retail, digit recognition (MNIST) and on publicly available 40 health questionnaires obtained from the Center for Disease Control (CDC) website maintained by the US Dept. of Health. We validate the results quantitatively as well as qualitatively based on expert feedback and recently published scientific studies on public health, thus showcasing the power of our technique in providing actionability (for retail), utility (for MNIST) and insight (on CDC datasets) which arguably are the hallmarks of an effective data mining method.Comment: Accepted for publication in International Conference on Data Mining (ICDM) 201

Cognitive penetration of early vision in face perception

Cognitive and affective penetration of perception refers to the influence that higher mental states such as beliefs and emotions have on perceptual systems. Psychological and neuroscientific studies appear to show that these states modulate the visual system at the visuomotor, attentional, and late levels of processing. However, empirical evidence showing that similar consequences occur in early stages of visual processing seems to be scarce. In this paper, I argue that psychological evidence does not seem to be either sufficient or necessary to argue in favour of or against the cognitive penetration of perception in either late or early vision. In order to do that we need to have recourse to brain imaging techniques. Thus, I introduce a neuroscientific study and argue that it seems to provide well-grounded evidence for the cognitive penetration of early vision in face perception. I also examine and reject alternative explanations to my conclusion

1.55 μm direct bandgap electroluminescence from strained n-Ge quantum wells grown on Si substrates

Electroluminescence from strained n-Ge quantum well light emitting diodes grown on a silicon substrate are demonstrated at room temperature. Electroluminescence characterisation demonstrates two peaks around 1.55 μm and 1.8 μm, which correspond to recombination between the direct and indirect transitions, respectively. The emission wavelength can be tuned by around 4% through changing the current density through the device. The devices have potential applications in the fields of optical interconnects, gas sensing, and healthcare

Acute toxicity tests of two herbicides diuron and atrazine on the beetle Crenitis sp in Volta Basin, Burkina Faso

Acute toxicity tests were performed on Crenitis spp (Coleoptera; Hydrophilidae) using two herbicides, atrazine and diuron in the laboratory. The experiment was to investigate the effect of high doses of these pollutants in individually and together for 12 h each on Crenitis spp a species that abounds during the dry period in the shallow hydro-agricultural waters reservoirs of the Volta Basin. Individual macroinvertebrates were collected from puddle areas of the shoreline of Bama Reservoir in the Volta basin. The dry period is the period of rest for agricultural activities at the reservoir. Tests have shown that the toxic effects of the two herbicides on the species of beetles can be enhanced when the both products act synergistically. For diuron, the effective concentration that immobilizes 50% (EC50) of the insects is 44.96 g/l only, but drops to 11.72 g/l in the mixture; while in the same order, atrazine shows 11.75 g/l only and then drops to 7.33 g/l in synergy. It is concluded from this study that works on ecotoxicology should consider the additive or synergistic effects of herbicides to define the bio-ecological traits of macroinvertebrate species living in frequently polluted hydro-agricultural systems

Spatio-temporal dynamics of population structure for macro invertebrates families in a continuum dam - effluent - river in irrigated system. Volta Basin (Burkina Faso)

A monthly sampling of benthic macro invertebrates was carried out at the hydro-agricultural dam of Boura in the Volta watershed basin (Burkina) during the period of February through July 2012 in order to describe the structuring of insect succession along with changes occurring in habitats of this irrigated dam farming system. The samples of insects were collected from 6 stations located inside the littoral (Station I), the sublittoral (Station II), the sewage channel or effluent (Stations III, IV, V) and the Mouhoun River (Station VI). The sampling method employed is a conventional method by the European Union named ” Directive Cadre sur l’Eau (DCE) ” recommended for the survey of benthic macro invertebrates. The survey reveals a community composed majorly of insects (more than 75%) variously distributed. On one hand at the shoreline and the coastal- adjoining zone in the dam, 23 families of macro invertebrates were identified; mostly belonging to the shoreline except for 10 families identified as endemic to the adjoining zone of the coastline. These two zones of the dam shelter the same malacological fauna consisting of the Unionidae, Lymneidae, Ampullariidae, Planorbidae, Valvatidae and Bulinidae families. The survey reveals otherwise that the differences between the Shannon biological diversity indices for these two zones were more pronounced during the month of July, the rainy period in the basin. On the other hand, concerning the dam-effluent-river continuum, a total of 35 families are sampled: 27 from dam water and stations near the irrigated zones; and 32 from the station of the sewage channel far from the irrigated zone and the river. The identification of individuals belonging to the family of the Baetidae and the Ephemerellidae (order of Ephemeroptera) in the river water highlights a subsequent reconstruction of the biodiversity in the river as the presence of both families is an indicator of fertile water. Further analysis on the spatial and temporal distribution involved 17 families out of the 35 sampled not common to all habitats. This lead to the conclusion that changes in natural habitats dictate the clustering patterns of macro invertebrates populations during the year long

Inventaire et distribution spatio-temporelle des macroinvertébrés bioindicateurs de trois plans d’eau du bassin de la Volta au Burkina Faso

Une étude des macroinvertébrés dans deux lacs de barrages hydro- agricoles (Bama et de Boura) et dans le lac naturel de Bala a permis de mettre en évidence la distribution spatio-temporelle des macroinvertébrésbioindicateurs de la qualité des eaux. La collecte des échantillons a été inspirée de la méthode conventionnelle de la Directive Cadre sur l’Eau de l’Union Européenne (DCE). L’étude a permis d’identifier 26405 individusde macroinvertébrés répartis en 71 espèces et 33 familles au total sur les trois sites de Bama (25 familles), Boura (23 familles) et Bala (30 familles). Les polluo-sensibles ont été décrites au lac naturel de Bala : des crustacés de l’ordre des Cladocères et 7 familles d’insectes (Gyrinidés, Pleidés, Baetidés Ephémérélidés, Tabanidés, Cératopogonidés et Canaceidés). L’étude a noté la présence de l’espèce Hydrocanthus ferruginicollis (Notéridés) particulièrement dominante dans les retenues hydro-agricoles de Bama (30,52% des Coléoptères) et Boura (27,32% des Coléoptères) ; tandis qu’elle ne représente que 7,51% des Coléoptères récoltés dans le lac naturel de Bala. Cette étude considère que les polluo-sensibles et les polluo-résitants décrits respectivement à Bala et à Bama et Boura peuvent être considérés comme de potentiels bioindicateurs des plans d’eau du bassin de la Volta.Mots clés : Macroinvertébrés, distribution, bioindicateurs, petits plans d’eau, bassin de la Volta, Burkina Faso

Beam energy measurement at linear colliders using spin precession

Linear collider designs foresee some bends of about 5-10 mrad. The spin precession angle of one TeV electrons on 10 mrad bend is 23.2 rad and it changes proportional to the energy. Measurement of the spin direction using Compton scattering of laser light on electrons before and after the bend allows determining the beam energy with an accuracy about of 10^{-5}. In this paper the principle of the method, the procedure of the measurement and possible errors are discussed. Some remarks about importance of plasma focusing effects in the method of beam energy measurement using Moller scattering are given.Comment: 7 pages, Latex, 4 figures(.eps). In v.3 corresponds to journal publication. Talk at 26-th Advanced ICFA Beam Dynamic Workshop on Nanometre-Size Colliding Beams (Nanobeam2002), Lausanne, Switzerland, Sept 2-6, 200