The effect of sputtered W-based carbide diffusion barriers on the thermal stability and void formation in copper thin films

The W-based diffusion barriers W, WC and WCN barriers were investigated for Cu metallization. The thermal stability of the W, WC and WCN barriers was compared by X-ray diffraction and four point probe. It shows comparable stability for the W and WC barriers while the ternary WCN barrier has superior performance. The agglomeration of the Cu films (100 nm) on these barriers is quite different. The formation of voids was observed for the annealed copper film on the WC or WCN barriers and the activation energy values determined from Kissinger equation are low comparing with Cu on W barrier. Twins were also observed in the as-deposited and annealed Cu films on the WC and WCN barriers. The twin formation and its correlation with void formation for Cu films onto the C-containing diffusion barrier were discussed through the stress relaxation and stress-induced vacancy migration mechanism.     

Pediocin PA-1 production during repeated-cycle batch culture of immobilized Pediococcus acidilactici UL5 cells

Pediocin PA-1 production by Pediococcus acidilactici UL5 cells immobilized in kappa-carrageenan/locust bean gum gel beads was studied during repeated-cycle batch (RCB) culture with pH control in Man Rogosa and Sharpe (MRS) broth supplemented with 1% glucose and whey permeate (SWP) medium. The pediocin PA-1 production by free P. acidilactici cells pH-controlled batch culture has reached 2048 and 4096 AU ml(-1) after 11 and 12 h of incubation, with volumetric productivities of 187 and 342 AU ml(-1) h(-1) in SWP and MRS media, respectively. In RCB culture, immobilized cells reached a maximum concentration of 7.3+/-0.2 x 10(10) and 4.3+/-0.9 x 10(10) cfu g(-1) of beads in MRS and SWP media, respectively. The maximum pediocin PA-1 activity obtained during RCB fermentation was 4096 AU ml(-1); it was attained after only 0.75 and 2 h of incubation in MRS and SWP media, respectively. The corresponding volumetric productivities were 5461 and 2048 AU ml(-1) h(-1). Pediocin PA-1 production in the RCB culture was highly stable over 12 fermentation cycles carried out over 3 d in SWP media.     

Impact of the crystallisation pathway of inulin on its mono-hydrate to hemi-hydrate thermal transition

In this paper, we present the thermal properties of two inulins obtained from different crystallisation pathways. One was obtained by fractional precipitation of a saturated inulin solution and the second was from the crystallisation of a solid amorphous inulin. The thermal analyses were conducted by temperature resolved wide angle X-ray scattering (TRWAXS), differential scanning calorimetry (DSC) and thermogravimetry (TG). Although at room temperature both inulins presented similar X-ray diffractogram patterns characteristic of the mono-hydrate polymorph, they differed considerably by their thermal properties. During heating, a difference in the mono-hydrate to the hemi-hydrate polymorph transition occurred. Thermogravimetric analysis suggested a difference in the water mobility inside the material which had an impact on the thermal properties and hydrate transition of the crystalline inulin.     

Thermoelectric performance of disordered and nanostructured graphene ribbons using Green’s function method

The thermoelectric properties of defected graphene nanoribbons (GNRs) and multi-junction (MJ) GNRs coupling periodic armchair sections of different width are analyzed by means of Green’s function techniques to simulate electron and phonon transport. Among the different strategies likely to enhance the thermoelectric performance, the effects of edge disorder and random vacancies are shown to be small since they lead to the concomitant degradation of the phonon thermal conductance and of the electronic conductance, which finally reduces the thermoelectric factor ZT. However, the periodic distribution of vacancies and the structuring of GNRs in MJ-GNRs both lead to the enhancement of the figure of merit ZT. In the latter case, in addition to the strong reduction of the phonon thermal conductance, an effect of resonant tunneling of electrons allows retaining high electronic conductance and enhancing significantly the thermopower. Finally, by introducing a periodic distribution of vacancies in the MJ-GNR, the maximum value ZT=0.4 is reached at room temperature.     

Promoting robust black-box solvers through competitions

This paper presents the experiences of the organizers of the four constraint solver competitions which were held in conjunction with CP in the previous years. The paper mainly focuses on the competitions which were held in 2008 and 2009, outlines the reasons for organizing the competitions, describes how the solvers were evaluated, and presents lessons, observations, and general trends.     

Optimization of an artificial neural network dedicated to the multivariate forecasting of daily global radiation

This paper presents an application of Artificial Neural Networks (ANNs) to predict daily solar radiation. We look at the Multi-Layer Perceptron (MLP) network which is the most used of ANNs architectures. In previous studies, we have developed an ad-hoc time series preprocessing and optimized a MLP with endogenous inputs in order to forecast the solar radiation on a horizontal surface. We propose in this paper to study the contribution of exogenous meteorological data (multivariate method) as time series to our optimized MLP and compare with different forecasting methods: a naïve forecaster (persistence), ARIMA reference predictor, an ANN with preprocessing using only endogenous inputs (univariate method) and an ANN with preprocessing using endogenous and exogenous inputs. The use of exogenous data generates an nRMSE decrease between 0.5% and 1% for two stations during 2006 and 2007 (Corsica Island, France). The prediction results are also relevant for the concrete case of a tilted PV wall (1.175 kWp). The addition of endogenous and exogenous data allows a 1% decrease of the nRMSE over a 6 months-cloudy period for the power production. While the use of exogenous data shows an interest in winter, endogenous data as inputs on a preprocessed ANN seem sufficient in summer.     

Hypolipidemic and antioxidative effects of dika nut (Irvingia gabonensis) seeds and nkui (Trimphetta cordifolia) stem bark mucilages in triton WR-1339 induced hyperlipidemic rats

Two different mucilages were extracted from dika nut (Irvingia gabonensis) kernels and nkui (Trimphetta cordifolia) stem barks and the hypolipidemic and antioxidant effects were studied on Triton WR-1339 induced hyperlipidemic rats. The GC analysis revealed that, dika nut mucilage is an arabinogalactan type while nkui is a rhamnogalacturonane type. The mucilage of nkui (200 mg/kg) showed the greatest hypolipidemic effect (p<0.05). An oxidative stress marker analysis suggested that the level of malonyl dialdehyde was significantly decreased in serum by the 2 mucilages (p<0.05). There was also a significant decrease in hydroperoxide level for the tested fibers. Moreover, nkui mucilage gave the highest levels in liver homogenate and in the hemolysate and tissues (p<0.05). The results suggest that the hypolidemic effect of mucilages varies with their chemical nature. They would be effective in the prevention of increase of serum lipid levels, in the reduction of lipid peroxidation and in the improvement of antioxidant status.     

Flaxseed proteins: food uses and health benefits

Flaxseed proteins are potent multi‐functional ingredients for food formulation owing to their techno‐functionalities, food preservation capacity, and health benefits. A possible synergistic effect with mucilage on their functionalities could be valuable even though this co‐product in flaxseed may limit the protein yield during their production processes. Their techno‐functional properties could also be considered in mixture with other flax bioactive components such as lignans and fibre to enhance the value of the flaxseed meal. The present paper reviews flaxseed protein uses in food and their health benefits. New perspectives according to consumers’ demand for products with health promoting bioactive components are also suggested.     

Chemical composition and functional properties of Ulva lactuca seaweed collected in Tunisia

The chemical composition and some functional properties of the dried “Ulva lactuca” algae, collected from the littoral between the Taboulba and Sayada area, were determined. The dried “U. lactuca” algae were investigated for their soluble, insoluble and total dietary fibre content, mineral amount, amino acid and fatty acid profiles, swelling capacity (SWC), water holding capacity (WHC) and oil holding capacity (OHC). Results showed that “U. lactuca” alga powder was characterised by a high content of fibres (54.0%), minerals (19.6%), proteins (8.5%) and lipids (7.9%). The neutral fibres contain hemicellulose (20.6%), cellulose (9.0%) and lignin (1.7%). The proteinic fraction analysis indicated the presence of essential amino acids, which represent 42.0% of the total amino acids. The fatty acids profile was dominated by the palmitic acid, which represents about 60.0% of the total fatty acids, followed by oleic acid (16.0%). The study of the functional properties proved that SWC, WHC and OHC of this alga varied with temperatures and that were comparable to those of some commercial fibre rich products.