A nonparametric approach for histogram segmentation.

In this work, we propose a method to segment a 1-D histogram without a priori assumptions about the underlying density function. Our approach considers a rigorous definition of an admissible segmentation, avoiding over and under segmentation problems. A fast algorithm leading to such a segmentation is proposed. The approach is tested both with synthetic and real data. An application to the segmentation of written documents is also presented. We shall see that this application requires the detection of very small histogram modes, which can be accurately detected with the proposed method.     

Use of electrochemical microsensors for hydrodynamics study in crossing microchannels

The study of microfluidic systems is an important research challenge related to the design of microdevices for chemical processes. The understanding of physical phenomena, such as flow behaviour and heat and mass transfer performance is needed in order to develop these microsystems for industrial applications as mixers, reactors or heat exchangers. This work aims at characterizing two flow pattern behaviours, by using an electrochemical method, in a microdevice composed of crossing microchannels. A nonintrusive electrodiffusion method involving an electrochemical reaction of active species on an electrode flush-mounted into a wall is used to investigate wall shear stress. The measured limiting diffusion current is related to the wall shear rate in the vicinity of the electrode. The experimental cell consists of two crossing microchannels intersecting at right angle. Two channels sections are investigated, respectively 500 and 833 μm in hydraulic diameter. In each case, the influence of the crossing on the flow behaviour and on the mixing performance are characterized locally by using microelectrodes implemented at several positions on the wall of the channels located after the crossing. The experimental results are analyzed and a comparison with the results of CFD simulations using Fluent is performed.     

Numerical schemes for investment models with singular transactions

This paper considers an infinite horizon investment-consumption model in which a single agent consumes and distributes his wealth between two assets, a bond and a stock. The problem of maximization of the total utility from consumption is treated, when state (amount allocated in assets) and control (consumption, rates of trading) constraints are present. The value function is characterized as the unique viscosity solution of the Hamilton-Jacobi-Bellman equation which, actually, is a Variational Inequality with gradient constraints. Numerical schemes are then constructed in order to compute the value function and the location of the free boundaries of the so-called transaction regions. These schemes are a combination of implicit and explicit schemes; their convergence is obtained from the uniqueness of viscosity solutions to the HJB equation.     

Semantic categorical flexibility and aging: Effect of semantic relations on maintenance and switching.

The authors studied the effects of aging on the flexible use of categorization rules based on thematic and taxonomic relations. Two components of flexibility were distinguished: maintenance of a categorical relation, and switching between two relations. Results showed that age affects these two components. In older adults, an effect of the nature of the categorical relations to be used was revealed. Older adults demonstrated a specific difficulty in the flexible use of taxonomic relations. Moreover, all adults, independent of their age, showed better performance in maintaining the use of a categorical relation than in switching between two categorical relations. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Extended and global phylogenetic view of the Bacillus cereus group population by combination of MLST, AFLP, and MLEE genotyping data

The Bacillus cereus group of bacteria includes species that can cause food-poisoning or spoilage, such as B. cereus, as well as Bacillus anthracis, the cause of anthrax. In the present report we have conducted a multi-datatype analysis using tools from the HyperCAT database (http://mlstoslo.uio.no/) that we recently developed, combining data from multilocus sequence typing (Tourasse et al., 2010), amplified fragment length polymorphism, and multilocus enzyme electrophoresis typing techniques. We provide a comprehensive snapshot of the B. cereus group population, incorporating 2213 isolates including 450 from food and dairy products, in the form of both phylogenetic supertrees and superclusters of genetically closely related isolates. Our main findings include the detection of phylogenetically separated groups of isolates possibly representing novel evolutionary lineages within the B. cereus group, a putative new branch of B. anthracis, as well as new groups of related strains containing both environmental and clinical isolates. In addition, the multi-datatype analysis revealed to a larger extent than previously recognized that food-borne isolates can share identical genotyping profiles with strains from various other origins. Altogether, the global analysis confirms and extends the results underlining the opportunistic nature of B. cereus group organisms, and the fact that isolates responsible for disease outbreaks and contamination of foodstuffs can originate from various genetic backgrounds.     

Modification of poly(styrene-b-(ethylene-co-butylene)-b-styrene) via free-radical grafting and its photo-crosslinking

Poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) is functionalized via radical grafting with 4-vinyl-1-cyclohexene 1,2-epoxide (VCHO) initiated using 2,5-Bis(tert-butylperoxy)-2,5-dimethylhexane. The existence of the epoxide group on the SEBS backbone is evidenced by ¹H nuclear magnetic resonance. A size exclusion chromatography (SEC) study reveals some chain coupling, and this phenomenon is limited by controlling the quantities of peroxide and monomer reagents used during the radical grafting. Photo-crosslinking of SEBS-g-VCHO under ultraviolet irradiation in the presence of a cationic initiator is then successfully performed with resultant gel contents higher than 85%. Mechanical properties of SEBS and crosslinked materials are measured by tensile tests on thin films. On the one hand, those tests reveal a significant increase of Young's modulus of the crosslinked materials. On the other hand, the diminution of elongation at break is much more limited; crosslinked materials retain their elastomeric properties with an elongation at break greater than 200%. Finally, the photosensitive SEBS-g-VCHO is used to show the adhesion performance of the photo-crosslinking coating as well as a resin for the stereolithography process.