Oligo(ethylene oxide) side‐chain steric screening effects on conductimetric properties of grafted poly(4‐vinylpyridinium) salts in aqueous solutions

A set of poly[N‐oligo(ethylene oxide)yl 4‐vinylpyridinium tosylate] (P4VOEOOTs) has been prepared by spontaneous polymerization of 4‐vinylpyridine. This method gives a grafted polyelectrolyte having a positive charge on every backbone pyridinic moiety. The P4VP15Ts, P4VP164Ts, P4VP350Ts and P4VP750Ts aqueous solution conductivities were determined in the concentration range from 6 × 10^?4 to 10^?2 M at 25 °C. The variation of the conductivity versus concentration of the investigated system exhibits typical polyelectrolyte behaviour. The polyelectrolyte mobility was found to be dependent on the oligo(ethylene oxide) (OEO) side‐chain length. Manning's rod‐like model fails to describe these results. A simple steric effect is proposed to explain the influence of the OEO length. Copyright © 2003 Society of Chemical Industry     

Fast Object Segmentation by Growing Minimal Paths from a Single Point on 2D or 3D Images

In this paper, we present a new method for segmenting closed contours and surfaces. Our work builds on a variant of the minimal path approach. First, an initial point on the desired contour is chosen by the user. Next, new keypoints are detected automatically using a front propagation approach. We assume that the desired object has a closed boundary. This a-priori knowledge on the topology is used to devise a relevant criterion for stopping the keypoint detection and front propagation. The final domain visited by the front will yield a band surrounding the object of interest. Linking pairs of neighboring keypoints with minimal paths allows us to extract a closed contour from a 2D image. This approach can also be used for finding an open curve giving extra information as stopping criteria. Detection of a variety of objects on real images is demonstrated. Using a similar idea, we can extract networks of minimal paths from a 3D image called Geodesic Meshing. The proposed method is applied to 3D data with promising results.

A step by step methodology to analyze the IGBT failure mechanisms under short circuit and turn-off inductive conditions using 2D physically based device simulation

A systematic methodology is developed in order to clarify the punch through trench insulated gate bipolar transistor (T-IGBT) failure mechanisms which can occur under extreme operating conditions such as short circuit and clamped inductive switching. By considering a 2D dimensional physically based device simulation, and by analyzing some T-IGBT physical parameters, it is possible to identify if the failure mechanism is due to a breakdown, a latchup or a thermal runaway phenomenon.     

Laser‐induced breakdown spectroscopy for photovoltaic silicon wafer analysis

The principal subject matter of this work is the application of laser‐induced breakdown spectroscopy for the multi‐elemental analytical characterization of different qualities of solid silicon. The physical process upon which the technique is based is the temporally resolved observation of emission spectra emitted by a micro‐plasma generated by a laser focused on the surface of a given sample. The optimal environmental parameters such as the composition of the buffering gas for the identification and measurement of several metallic, non‐metallic, and dopant impurities were determined. Particular attention was given to boron. A detection limit of 2.10⁻⁴ mg/g of boron was found using a calibration curve, which was made in the range of 1 to 100 ppmw. Silicon samples from different production techniques (4C and directional solidification), which permit the segregation of different impurities along the length of the silicon ingot were analyzed using laser‐induced breakdown spectroscopy. Copyright © 2011 John Wiley & Sons, Ltd.     

Poly(3-hexylthiophene)/C60 heterojunction solar cells: Implication of morphology on performance and ambipolar charge collection

The performance of heterojunction organic solar cells is critically dependent on the morphology of the donor and acceptor components in the active film. We report results of photovoltaic devices consisting of bilayers and bulk heterojunctions using poly(3-hexylthiophene) (P3HT) and Buckminsterfullerene C₆₀. White light power efficiencies of η2.2% (bulk heterojunction) and 2.6% (bilayer) were measured after a thermal annealing step on completed devices. Optical and structural investigations on non-annealed bilayer thin films indicated a distinct porosity of the spin-coated polymer, which allows C₆₀ to penetrate the P3HT layer and to touch the anode. This resulted for these bilayer solar cells in the experimental observation that electrons were collected predominantly at the cathode after photo-excitation of P3HT, but predominantly at the anode after C₆₀ excitation. A morphological model to explain the ambipolar charge collection phenomenon is proposed.     

Chemical composition and antimicrobial activity of the essential oils from four Ruta species growing in Algeria

Antimicrobial properties of plants essential oils have been investigated in order to suggest them as potential tools to overcome the microbial drug resistance and the increasing incidence of food borne diseases problems. The aim of this research is to study the antibacterial and antifungal effects of four traditional plants essential oils, Ruta angustifolia, Ruta chalepensis, Ruta graveolens and Ruta tuberculata, against standard bacterial and fungal strains. The chemical compounds of the oils were examined by GC/MS. Results revealed a powerful antifungal activity against filamentous fungi. Aspergillus fumigatus and Cladosporium herbarum are the most sensitive strains to these oils with MIC values less than 3.5 μg ml⁻¹ for certain oils, reaching 7.8 μg ml⁻¹ for other. GC/MS essay exhibited ketones as the most abundant constituent of these oils except for R. tuberculata essential oil which has a completely different composition, monoterpenes alcohols being the most abundant. These compositions explain their potential antifungal activity.     

Tabu search for a parallel-machine scheduling problem with periodic maintenance,job rejection and weighted sum of completion times

Journal of Scheduling - We consider in this work a bicriteria scheduling problem on two different parallel machines with a periodic preventive maintenance policy. The two objectives considered...     

Characterization of high quality RTCVD relaxed Si1−xGex grown on ge graded buffer layers on Si by photoluminescence spectroscopy

Relaxed Si_1−xGe_x layers grown by rapid thermal chemical vapor deposition (RTCVD) have been characterized by photoluminescence (PL) spectroscopy. The structures consist of a Si_1−xGe_x capping layer with a 0.32 and 0.52 Ge concentration, grown on a compositionally graded Si_1−xGe_x buffer layer. The effect of the composition grading rate on the layer quality has been intensively studied. Well-resolved near band edge luminescence (excitonic lines with no-phonon and phonon replica similar as in bulk SiGe alloys) coming from the relaxed alloy capping layer and dislocation-related bands (Dl, D2, D3, D4 lines) in the graded buffer layer have been measured. The electronic quality of this relaxed capping layer, controlled by the design of the compositionally graded buffer layer, has been determined by the excitonic photoluminescence. A detailed analysis of the energy of the D4 dislocation band demonstrates that the main misfit dislocations remain confined in the first steps of the graded buffer layer. Si_1−xGe_x layers grown on these pseudo-substrates either under compressive or tensile strain and the well-defined PL results obtained are discussed on the bases of strain symmetrization and of high quality of the layers. This points out the possibility of using such high quality relaxed Si_1−xGe_x layers as substrates for the integration of new devices associated with Si technology.