Micromechanical modelling and simulation of chopped random fiber reinforced polymer composites with progressive debonding damage

The aim of the present paper is to provide a quantitative prediction of the elastic-damage behaviour of randomly oriented fiber polymer composites. A constitutive model based on micromechanical considerations is presented. The nucleation and growth of voids induced by progressive fiber debonding is combined with the constitutive relationship. Failure resulting of excessive damage accumulation is captured by a critical void volume criterion and a vanishing element technique. Experimentally, damage accumulation in random glass fiber–polyester composites was monitored by a videoextensometry technique able to control the local strain rate. Good agreement of model predictions with experimental data is pointed out. The model was implemented into a finite element program and numerical applications on composite structures (a tensile specimen and a plate containing a central hole) are presented to illustrate the capability of the approach. Digital image correlation method was also used to measure the full-field strain in a notched specimen under tensile loading. The simulated results compared favourably with those obtained from experiments.     

On a non-linear geometrical inverse problem of Signorini type: identifiability and stability

This paper deals with a non-linear inverse problem of identification of unknown boundaries, on which the prescribed conditions are of Signorini type. We first prove an identifiability result, in both frameworks of thermal and elastic testing. Local Lipschitz stability of the solutions with respect to the boundary measurements is also established, in case of unknown boundaries which are parts of 𝒞^{1, β} Jordan curves, with β>0. © 1998 B. G. Teubner Stuttgart—John Wiley & Sons, Ltd.     

Determination of 3J(H3í, Pi+1) and 3J(H5í/5i, Pi) coupling constants in 13C-labeled nucleic acids using constant-time HMQC.

A novel 1H-13C correlated two-dimensional experiment, CT-HMQC-J, for the measurement of three-bond proton-phosphorus coupling constants in 13C-labeled DNA is described. The experiment is based on the intensity difference of 1H-13C cross peaks in the presence and absence of the proton-phosphorus coupling interaction during the constant-time period in HMQC experiment. The 3J(H, P) coupling constants can be easily extracted from the intensity ratios of the two experiments. The method has been applied to a uniformly 13C, 15N-labeled d(GGAGGAT) 7-mer DNA sample. The proton-phosphorus coupling constants determined from CT-HMQC-J, together with the other three-bond coupling constants, are used to determine beta and epsilon torsion angles. The introduction of beta and epsilon restraints has improved the convergence as well as the quality of d(GGAGGAT) structure.     

Palm cryobanking

We describe the development of an efficient cryopreservation protocol for proembryogenic masses (PEMs) of date palm variety 'Barhee'. Proembryos were induced by inoculating small pieces of juvenile leaves on MS medium supplemented with 0.3 mg per liter 2,4-D. Application of these in vitro conditions led to true-to-type plants as observed after plant fructification. When compared to the standard vitrification protocol, the ultra-rapid droplet-vitrification technique proved to be superior. Sucrose preculture considerably increased post-cryopreservation recovery. The highest regeneration after cryogenic exposure reached 63.3 percent when PEMs were treated with PVS2 for 30 min at 0 degree C and 56.7 percent when PVS2 treatment lasted for 15 min at 25 degree C. The first signs of regrowth of cryopreserved PEMs were observed after 2 to 3 weeks. Cryopreservation did not affect the morphogenetic capacities of the plant material. Moreover, highly proliferating suspension cultures could be established from the cryopreserved material. The overall production of somatic embryos from 500 mg cryopreserved PEMs reached 1030 +/- 50 units after 1 month. The morphological study of date palms regenerated from cryopreserved material confirmed the stability of clonal material following cryopreservation.     

Sequential MCR/Fisher indolization strategy for the construction of polycyclic carbazole derivatives

A one-pot method for the synthesis of novel polycyclic carbazole derivatives from readily available starting materials using a sequential multicomponent reaction/Fisher indolization strategy is described.     

Effet de l'orientation d'un champ magnétique horizontal sur la stabilité de l'écoulement de HadleyEffet of the orientation of a horizontal magnetic field on the stability of Hadley flow

A numerical study based on the linear stability analysis is undertaken, in order to determine the influence of a horizontal magnetic field on the marginal modes occuring in a fluid layer subjected to a horizontal temperature gradient. A particular interest is devoted to the influence of the magnetic field orientation on both nature and critical values of the unstable modes. Calculations show, that when it is subjected to such a magnetic field, this type of flow, known as Hadley flow, can present oblique waves, hitherto non-existent when no magnetic field is applied and even when a vertical, a transverse or a longitudinal magnetic field is imposed. A new asymptotic behavior is also observed for the stabilizing effects. To cite this article: S. Kaddeche et al., C. R. Mecanique 331 (2003).     

Inhibition of Fungi and Gram-Negative Bacteria by Bacteriocin BacTN635 Produced by Lactobacillus plantarum sp. TN635

The aim of this study was to evaluate 54 lactic acid bacteria (LAB) strains isolated from meat, fermented vegetables and dairy products for their capacity to produce antimicrobial activities against several bacteria and fungi. The strain designed TN635 has been selected for advanced studies. The supernatant culture of this strain inhibits the growth of all tested pathogenic including the four Gram-negative bacteria (Salmonella enterica ATCC43972, Pseudomonas aeruginosa ATCC 49189, Hafnia sp. and Serratia sp.) and the pathogenic fungus Candida tropicalis R2 CIP203. Based on the nucleotide sequence of the 16S rRNA gene of the strain TN635 (1,540 pb accession no FN252881) and the phylogenetic analysis, we propose the assignment of our new isolate bacterium as Lactobacillus plantarum sp. TN635 strain. Its antimicrobial compound was determined as a proteinaceous substance, stable to heat and to treatment with surfactants and organic solvents. Highest antimicrobial activity was found between pH 3 and 11 with an optimum at pH?=?7. The BacTN635 was purified to homogeneity by a four-step protocol involving ammonium sulfate precipitation, centrifugal microconcentrators with a 10-kDa membrane cutoff, gel filtration Sephadex G-25, and C18 reverse-phase HPLC. SDS-PAGE analysis of the purified BacTN635, revealed a single band with an estimated molecular mass of approximately 4 kDa. The maximum bacteriocin production (5,000 AU/ml) was recorded after a 16-h incubation in Man, Rogosa, and Sharpe (MRS) medium at 30?°C. The mode of action of the partial purified BacTN635 was identified as bactericidal against Listeria ivanovii BUG 496 and as fungistatic against C. tropicalis R2 CIP203.     

The use of selected ion flow tube mass spectrometry to detect and quantify polyamines in headspace gas and oral air

Polyamines are a class of aliphatic compounds which include putrescine, cadaverine, spermine and spermidine. They are involved in a variety of cellular processes and have been implicated in a number of different pathophysiological mechanisms. Polyamines are volatile compounds having a distinctive odour normally perceived as being unpleasant. The measurement of their abundance has, however, been restricted to compounds present in the aqueous phase. Using selected ion flow tube mass spectrometry (SIFT‐MS) we have shown that the polyamines react with the ions H₃O⁺, NO⁺ and O to form distinctive product ions allowing their levels to be quantified in the vapour phase. The low volatility of spermine did not allow extensive analysis of this compound by SIFT‐MS while the adherent properties of cadaverine and putrescine required the use of PTFE transfer lines and couplers. Our data suggested the presence of cadaverine and putrescine in both oral air and the headspace of putrefying bovine muscle, while product ions corresponding to putrescine and spermidine were found in the headspace of human semen. SIFT‐MS therefore appears to be a practical means of measuring vapour‐phase polyamine levels, having applications in biology, medicine and dentistry, and food science. Copyright © 2009 John Wiley & Sons, Ltd.     

Join-Irreducible Boolean Functions

This paper is a contribution to the study of a quasi-order on the set Ω of Boolean functions, the simple minor quasi-order. We look at the join-irreducible members of the resulting poset [(W)\tilde]\tilde{\Omega}. Using a two-way correspondence between Boolean functions and hypergraphs, join-irreducibility translates into a combinatorial property of hypergraphs. We observe that among Steiner systems, those which yield join-irreducible members of [(W)\tilde]\tilde{\Omega} are the − 2-monomorphic Steiner systems. We also describe the graphs which correspond to join-irreducible members of [(W)\tilde]\tilde{\Omega}.     

Determination of isotope cluster patterns in mass spectra of GC-MS analyses by a chemometric detector

The computer program ISODET recognizes isotope cluster patterns in the mass spectra of the GC-MS analysis of atoms of chlorine, bromine, sulphur and chlorine/bromine combinations. The decision parameters used in the algorithm of the method were calculated by treating 2, 535 mass spectra from the NBS database. The result of the analysis is a graphic output (isotope cluster chromatograms) and tabulated output. The applicability and the reliability of the isotope detector and the mode of using the input program parameters are discussed. The reliability of the correct recognition of isotope clusters evaluated by means of the spectra from the NBS database was 92% for chlorinated and brominated compounds but only 51%, for sulphur containing compounds.