Experimental Study on the Low-velocity Impact Behavior of Foam-core Sandwich Panels

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97064/1/AIAA2012-1701.pd

Transcriptional Analysis of Lactobacillus brevis to N-Butanol and Ferulic Acid Stress Responses

The presence of anti-microbial phenolic compounds, such as the model compound ferulic acid, in biomass hydrolysates pose significant challenges to the widespread use of biomass in conjunction with whole cell biocatalysis or fermentation. Currently, these inhibitory compounds must be removed through additional downstream processing or sufficiently diluted to create environments suitable for most industrially important microbial strains. Simultaneously, product toxicity must also be overcome to allow for efficient production of next generation biofuels such as n-butanol, isopropanol, and others from these low cost feedstocks.This study explores the high ferulic acid and n-butanol tolerance in Lactobacillus brevis, a lactic acid bacterium often found in fermentation processes, by global transcriptional response analysis. The transcriptional profile of L. brevis reveals that the presence of ferulic acid triggers the expression of currently uncharacterized membrane proteins, possibly in an effort to counteract ferulic acid induced changes in membrane fluidity and ion leakage. In contrast to the ferulic acid stress response, n-butanol challenges to growing cultures primarily induce genes within the fatty acid synthesis pathway and reduced the proportion of 19:1 cyclopropane fatty acid within the L. brevis membrane. Both inhibitors also triggered generalized stress responses. Separate attempts to alter flux through the Escherichia coli fatty acid synthesis by overexpressing acetyl-CoA carboxylase subunits and deleting cyclopropane fatty acid synthase (cfa) both failed to improve n-butanol tolerance in E. coli, indicating that additional components of the stress response are required to confer n-butanol resistance.Several promising routes for understanding both ferulic acid and n-butanol tolerance have been identified from L. brevis gene expression data. These insights may be used to guide further engineering of model industrial organisms to better tolerate both classes of inhibitors to enable facile production of biofuels from lignocellulosic biomass

Modelisation parametrique et classification automatique de signaux de forme transitoire

La présente communication décrit une procédure de classification automatique mise en place sur une banque de signaux tests, préalablement expertisés, de type complexe et issus de contrôle non destructif. L'étape de classification intervient après une phase de détection-segmentation et une phase de modélisation paramétrique (Prony étendue) des transitoires du signal, représentatifs d'événements que l'on désire classifier. Sur les vecteurs de paramétres obtenus _ paramètres autorégressifs, coefficients cepstraux, coefficients de réflexion, tous introduits à partir d'une modélisation autorégressive _ on mesure les performances, en pourcentage de bien classés, de plusieurs métriques sur des classes définies à priori. Nous mettons en évidence la supériorité de la métrique associée à la matrice d'inertie _ de covariance totale (métrique de Mahalanobis) et interclasse _ opérant sur les coefficients cepstraux

Effective static and dynamic finite element modeling of a double swept composite rotor blade

The paper concerns mechanical responses of helicopter blades made of composite materials. Structures with complicated geometries are modeled by using both beam and solid finite elements. The adopted one-dimensional kinematics only encompasses pure displacements; therefore, the connection with three-dimensional elements can be carried out with ease. Contributions to elastic and inertial matrices deriving from nodes shared by beams and solids are merely summed together through a standard assembling procedure. Stress, free vibration, and time response analyses have been performed on different configurations. A straight metallic rotating structure and a swept-tip blade made of an orthotropic material have been considered for verification and validation purposes. Current results have been compared with experimental data and numerical solutions available in the literature. Furthermore, a straight and a double-swept blade with a realistic airfoil have been studied. For the straight configuration, the one-dimensional results have been compared with finite element solutions obtained with commercial software. The methodology enabled complicated stress distributions and coupling phenomena to be predicted with reasonable accuracy and affordable computational efforts

a topological approach

of grids conforming to geological structures

Acid Resistance Systems Required for Survival of Escherichia coli O157:H7 in the Bovine Gastrointestinal Tract and in Apple Cider Are Different

Escherichia coli O157:H7 is a highly acid-resistant food-borne pathogen that survives in the bovine and human gastrointestinal tracts and in acidic foods such as apple cider. This property is thought to contribute to the low infectious dose of the organism. Three acid resistance (AR) systems are expressed in stationary-phase cells. AR system 1 is σ(S) dependent, while AR systems 2 and 3 are glutamate and arginine dependent, respectively. In this study, we sought to determine which AR systems are important for survival in acidic foods and which are required for survival in the bovine intestinal tract. Wild-type and mutant E. coli O157:H7 strains deficient in AR system 1, 2, or 3 were challenged with apple cider and inoculated into calves. Wild-type cells, adapted at pH 5.5 in the absence of glucose (AR system 1 induced), survived well in apple cider. Conversely, the mutant deficient in AR system 1, shown previously to survive poorly in calves, was susceptible to apple cider (pH 3.5), and this sensitivity was shown to be caused by low pH. Interestingly, the AR system 2-deficient mutant survived in apple cider at high levels, but its shedding from calves was significantly decreased compared to that of wild-type cells. AR system 3-deficient cells survived well in both apple cider and calves. Taken together, these results indicate that E. coli O157:H7 utilizes different acid resistance systems based on the type of acidic environment encountered