Towards Understanding Directed Evolution: More than Half of All Amino Acid Positions Contribute to Ionic Liquid Resistance of Bacillus subtilis Lipase A

Ionic liquids (ILs) are attractive (co‐)solvents for biocatalysis. However, in high concentration (>10 % IL), enzymes usually show decreased activity. No general principles have been discovered to improve IL resistance of enzymes by protein engineering. We present a systematic study to elucidate general engineering principles by site saturation mutagenesis on the complete gene bsla. Screening in presence of four [BMIM]‐based ILs revealed two unexpected lessons on directed evolution: 1) resistance improvement was obtainable at 50–69 % of all amino acid positions, thus explaining the success of small sized random mutant libraries; 2) 6–13 % of substitutions led to improved resistance. Among these, 66–95 % were substitutions by chemically different amino acids (e.g., aromatic to polar/aliphatic/charged amino acids), thus indicating that mutagenesis methods introducing such changes should, at least for lipases like BSLA, be favored to improve IL resistance.     

Influence of the injection molding process on the mechanical properties of (PA6/GF/MMT) nanocomposite

This work describes the first part of a series of studies on the effect of injection molding conditions on the mechanical properties of polyamide 6/glass fiber/montmorillonite (PA6/GF/MMT) composites, wherein the effect of the injection molding mass temperature on the mechanical properties of the composite is investigated. The results demonstrate that composites processed at lower mass temperatures exhibited higher tensile strength and flexural strength. These findings are explained by the fact that the use of different mass temperatures leads to PA6 matrices with different degrees of crystallinity. In addition, changes in the mass temperature affect the fiber–matrix adhesion of the composite and the intercalation between the matrix and the various components in the nanocomposite. POLYM. COMPOS., 36:237–244, 2015. © 2014 Society of Plastics Engineers     

A mathematical steady state model for methane bioelimination in a closed biofilter

Methane is a greenhouse gas, emitted from sources such as landfills. This paper presents a steady state model of methane biofiltration taking into consideration the impact of various parameters, such as the inlet methane concentration, the gas superficial velocity and the packing bed average temperature, on the methane biofilter efficiency. More specifically, the model developed here considers that the average bed temperature is influenced by the elimination capacity of methane in the biofilter, which is function of the methane inlet load. When using this model, it is possible to estimate the biofilter performance in terms of parameters, such as the conversion, elimination capacity and carbon dioxide production. Comparison of the model generated performance values with experimental data in the range of methane concentrations varying from 1500 to 9500 ppmv yields satisfactory results (<2–10% error, depending on the inlet methane concentration and on the performance parameter).     

Newborns discriminate the rhythm of multisyllabic stressed words.

Three experiments were run to test whether newborns were able to discriminate different stress patterns in multisyllabic stressed Italian words that varied both in consonants and in number of syllables. A high-amplitude sucking procedure was adopted in which the experimental group heard 2 sets of stimuli alternating minute by minute, whereas the control group heard only a single set of stimuli. The results showed that stress patterns were discriminated in 2 disyllabic phonetically unvaried words (Exp 1), in 2 trisyllabic consonant-varied words (Exp 2), and in 2 sets of disyllabic words varied in consonants within and between words (Exp 3). The alternation procedure proved to be suitable for examining newborns' abilities of discrimination and categorization. It also lowered the participants' rejection rate compared with the classic habituation procedure. The present results suggest that newborns are sensitive to words' rhythm, as carried by stress patterns, and that this prosodic information is salient even in the presence of substantial consonant variation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gaussian approximations of fluorescence microscope point-spread function models

We comprehensively study the least-squares Gaussian approximations of the diffraction-limited 2D-3D paraxial-nonparaxial point-spread functions (PSFs) of the wide field fluorescence microscope (WFFM), the laser scanning confocal microscope (LSCM), and the disk scanning confocal microscope (DSCM). The PSFs are expressed using the Debye integral. Under an L(infinity) constraint imposing peak matching, optimal and near-optimal Gaussian parameters are derived for the PSFs. With an L1 constraint imposing energy conservation, an optimal Gaussian parameter is derived for the 2D paraxial WFFM PSF. We found that (1) the 2D approximations are all very accurate; (2) no accurate Gaussian approximation exists for 3D WFFM PSFs; and (3) with typical pinhole sizes, the 3D approximations are accurate for the DSCM and nearly perfect for the LSCM. All the Gaussian parameters derived in this study are in explicit analytical form, allowing their direct use in practical applications.     

Effect of bacterial interactions on the spoilage of cold-smoked salmon

Cold-smoked salmon is a lightly preserved fish product in which a mixed microbial flora develops during storage and where the interactive behaviour of micro-organisms may contribute to their growth and spoilage activity. The aim of this study was to assess the effect of the bacterial interactions between the main species contaminating the cold-smoked salmon on bacterial growth, chemical and sensory changes, and spoilage. First, Carnobacterium piscicola, Photobacterium phosphoreum, Lactobacillus sakei, Vibrio sp., Brochothrix thermosphacta and Serratia liquefaciens-like were inoculated as pure cultures on sterile cold-smoked salmon. All bacterial species grew well; Vibrio sp. was the fastest and L. sakei strains developed very rapidly as well with a high maximum cell density on cold-smoked salmon blocks (up to 10(9) cfu g(-1) after 10 days at 8 degrees C). Based on sensory analysis, Vibrio sp. was identified as non-spoilage bacteria, C. piscicola as very lightly and B. thermosphacta as lightly spoiling. L. sakei and S. liquefaciens-like were found to be the most spoiling bacteria. Secondly, C. piscicola and L. sakei, two species frequently occurring in the lactic flora of the product, were inoculated together and each of them in mixed cultures with respectively P. phosphoreum, Vibrio sp., B. thermosphacta, and S. liquefaciens-like. The growth of L. sakei was shown to strongly inhibit most of the co-inoculated strains i.e. P. phosphoreum, B. thermosphacta, S. liquefaciens-like and, to a lesser extent, Vibrio sp. The growth of C. piscicola seemed to be enhanced with B. thermosphacta and to develop earlier with P. phosphoreum and Vibrio sp. Conversely, S. liquefaciens-like and P. phosphoreum were weakly inhibited by C. piscicola. The main observation resulting from the sensory evaluation was the delay in the appearance of the spoilage characteristics in the mixed cultures with L. sakei, in particular L. sakei/ S. liquefaciens-like. On the other hand, the spoilage activity of the non-spoiler strains Vibrio sp. or the moderate spoilage strains B. thermosphacta and C. piscicola was increased when they were associated together. It is concluded that the spoilage behaviour of micro-organisms in mixed culture is significantly different from pure culture and explain the difficulty to find robust quality indices for this product.     

Evolution of music performance anxiety and quality of performance during virtual reality exposure training

Virtual reality exposure is increasingly used as a method of treatment for anxiety disorders. This exploratory study examines a virtual reality exposure training (VRET) conceived for the treatment of music performance anxiety (MPA). The aim is to obtain first-level knowledge in the music field concerning VRET. This article analyzes how MPA, concentration and quality of performance evolve during VRET. Nine music students participated in six 1-h sessions of VRET spread out over 3 weeks. They were exposed to four different virtual environments representing typical audiences for musicians. The findings indicate a significant decrease in MPA between sessions. They also indicate a significant increase in performance quality within sessions and a positive correlation between absorption ability and level of anxiety at the beginning of the VRET. Further studies must be conducted to evaluate the generalizability potential of these results to real performance situations.     

How many performance measures to evaluate information retrieval systems?

Evaluating effectiveness of information retrieval systems is achieved by performing on a collection of documents, a search, in which a set of test queries are performed and, for each query, the list of the relevant documents. This evaluation framework also includes performance measures making it possible to control the impact of a modification of search parameters. The program trec_eval calculates a large number of measures, some being more used like the mean average precision or recall-precision curves. The motivation of our work is to compare all measures and to help the user to choose a small number of them when evaluating different information retrieval systems. In this paper, we present the study we carried out from a massive data analysis of TREC results. Relationships between the 130 measures calculated by trec_eval for individual queries are investigated, and we show that they can be clustered into homogeneous clusters.     

A Level Set Model for Image Classification

We present a supervised classification model based on a variational approach. This model is devoted to find an optimal partition composed of homogeneous classes with regular interfaces. The originality of the proposed approach concerns the definition of a partition by the use of level sets. Each set of regions and boundaries associated to a class is defined by a unique level set function. We use as many level sets as different classes and all these level sets are moving together thanks to forces which interact in order to get an optimal partition. We show how these forces can be defined through the minimization of a unique fonctional. The coupled Partial Differential Equations (PDE) related to the minimization of the functional are considered through a dynamical scheme. Given an initial interface set (zero level set), the different terms of the PDE's are governing the motion of interfaces such that, at convergence, we get an optimal partition as defined above. Each interface is guided by internal forces (regularity of the interface), and external ones (data term, no vacuum, no regions overlapping). Several experiments were conducted on both synthetic and real images.