Modelling of reinforced‐concrete structures providing crack‐spacing based on X‐FEM,ED‐FEM and novel operator split solution procedure

In this work, we present a novel approach to the finite element modelling of reinforced‐concrete (RC) structures that provides the details of the constitutive behavior of each constituent (concrete, steel and bond‐slip), while keeping formally the same appearance as the classical finite element model. Each component constitutive behavior can be brought to fully non‐linear range, where we can consider cracking (or localized failure) of concrete, the plastic yielding and failure of steel bars and bond‐slip at concrete steel interface accounting for confining pressure effects. The standard finite element code architecture is preserved by using embedded discontinuity (ED‐FEM) and extended (X‐FEM) finite element strain representation for concrete and slip, respectively, along with the operator split solution method that separates the problem into computing the deformations of RC (with frozen slip) and the current value of the bond‐slip. Several numerical examples are presented in order to illustrate very satisfying performance of the proposed methodology. Copyright © 2010 John Wiley & Sons, Ltd.     

Dynamics and species diversity of communities of lactic acid bacteria and acetic acid bacteria during spontaneous cocoa bean fermentation in vessels

To speed up research on the usefulness and selection of bacterial starter cultures for cocoa bean fermentation, a benchmark cocoa bean fermentation process under natural fermentation conditions was developed successfully. Therefore, spontaneous fermentations of cocoa pulp-bean mass in vessels on a 20 kg scale were tried out in triplicate. The community dynamics and kinetics of these fermentations were studied through a multiphasic approach. Microbiological analysis revealed a limited bacterial species diversity and targeted community dynamics of both lactic acid bacteria (LAB) and acetic acid bacteria (AAB) during fermentation, as was the case during cocoa bean fermentations processes carried out in the field. LAB isolates belonged to two main (GTG)₅-PCR clusters, namely Lactobacillus plantarum and Lactobacillus fermentum, with Fructobacillus pseudofilculneus occurring occasionally; one main (GTG)₅-PCR cluster, composed of Acetobacter pasteurianus, was found among the AAB isolates, besides minor clusters of Acetobacter ghanensis and Acetobacter senegalensis. 16S rRNA-PCR-DGGE revealed that L. plantarum and L. fermentum dominated the fermentations from day two until the end and Acetobacter was the only AAB species present at the end of the fermentations. Also, species of Tatumella and Pantoea were detected culture-independently at the beginning of the fermentations. Further, it was shown through metabolite target analyses that similar substrate consumption and metabolite production kinetics occurred in the vessels compared to spontaneous cocoa bean fermentation processes. Current drawbacks of the vessel fermentations encompassed an insufficient mixing of the cocoa pulp-bean mass and retarded yeast growth.     

Exergy analysis for Generation IV nuclear plant optimization

This paper deals with the application of the exergy concept to an energy production system involving a very high temperature reactor coupled with an innovative electricity‐generating cycle. The objective is to propose a general approach to quantify exergy destruction of the involved process components, modelled by a thermodynamic simulator Proceedings of the Conference on High Temperature Reactors, Beijing, China, 22–24 September 2004, International Atomic Agency, Vienna (Austria), HTR‐2004; 1–11). The minimization of exergy destruction is then identified as the optimization criterion used in an optimization framework based on a genetic algorithm, in which the model is embedded. Finally, the approach is applied to electrical production by a Brayton–Rankine combined cycle connected to a nuclear reactor. Some typical results are presented. The perspectives of this work including the cogeneration of hydrogen and electricity are highlighted. Copyright © 2009 John Wiley & Sons, Ltd.     

Streptococcus macedonicus ACA-DC 198 produces the lantibiotic, macedocin, at temperature and pH conditions that prevail during cheese manufacture

Streptococcus macedonicus ACA-DC 198, a natural cheese isolate, produces the anticlostridial bacteriocin, macedocin. Bacteriocin activity was detected from the mid-exponential growth phase and remained constant during the stationary phase. A secondary model was setup to describe the influence of temperature (20-45 degrees C) and pH (5.1-6.9) on cell growth of and bacteriocin production by S. macedonicus ACA-DC 198 during in vitro laboratory fermentations. The optimum temperature for bacteriocin production (20-25 degrees C) was markedly lower than the optimum growth temperature (42.3 degrees C). In contrast, the specific macedocin production was maximal around pH 6.0, whereas growth was optimal at pH 6.4. Consequently, the maximum bacteriocin activity was reached between pH 6.0 and 6.5.     

Assessment of maple syrup physico-chemistry and typicity by means of fluorescence spectroscopy

Maple syrup is a natural sweetener obtained from the transformation of maple sap collected mostly from sugar maple (Acer saccharum Marsh) in North America. At present, simple physico-chemical tests are used for routine quality control. Inspectors also taste all batches on the market to ensure authenticity. Because of the presence of various aromatic compounds in sap and syrup, intrinsic fluorescence was tested as a means to characterize the physico-chemistry and typicity of maple syrup. Two hundred samples of sap and their corresponding syrup were obtained from various farms in 2003 and 2004. They were analysed by conventional physico-chemical tests and by fluorescence spectroscopy. Two major regions of fluorescence were found, which were mostly the same for sap and syrup. The first one was at 320 nm, excited at 275 nm, and the second one at 460 nm, excited at 360 (syrup) or 370 nm (sap). The first peak diminishes as harvesting season progresses, while the second peak increases, making it possible to predict the harvesting period of syrup from its spectra (r² = 0.88 in 2003 and 0.81 in 2004). Color of syrup (r² = 0.91 and 0.88) and bacterial counts in sap (r² = 0.75 and 0.78) were also predicted from syrup spectra. Results show that sap spectra are related to syrup spectra and could potentially be used as predictor of quality prior to transformation. Discriminant analysis revealed that between 71% and 95% of syrup samples were correctly classified according to the farm of origin in 2003, and between 78% and 100% in 2004. Proximity was not always a factor of explanation of misclassification, suggesting that precise farm location, rather than the broad region of production is the major factor of typicity.     

Update on potential of edible mushrooms: high-value compounds,extraction strategies and bioactive properties

The traditional and growing importance of mushrooms due to their rich composition in nutritive and bioactive compounds converts the whole feedstock and their fractions into versatile attractive ingredients for food and nutraceuticals. The processing conditions are critically relevant to selectively recover high-valuable compounds in a sustainable way. This short review, covering scientific papers published in the last 2 years, offers an updated vision of the study and applications of edible mushroom bioactive compounds, covering aspects in relation to the novelties in the cultivation, isolation, identification, characterisation of chemical and biological properties, extraction technologies and purification, as well as food applications, particularly in novel foods.     

Associations between CXCR1 polymorphisms and pathogen-specific incidence rate of clinical mastitis,test-day somatic cell count,and test-day milk yield

The CXCR1 gene plays an important role in the innate immunity of the bovine mammary gland. Associations between single nucleotide polymorphisms (SNP) CXCR1c.735C>G and c.980A>G and udder health have been identified before in small populations. A fluorescent multiprobe PCR assay was designed specifically and validated to genotype both SNP simultaneously in a reliable and cost-effective manner. In total, 3,106 cows from 50 commercial Flemish dairy herds were genotyped using this assay. Associations between genotype and detailed phenotypic data, including pathogen-specific incidence rate of clinical mastitis (IRCM), test-day somatic cell count, and test-day milk yield (MY) were analyzed. Staphylococcus aureus IRCM tended to associate with SNP c.735C>G. Cows with genotype c.735GG had lower Staph. aureus IRCM compared with cows with genotype c.735CC (rate ratio = 0.35, 95% confidence interval = 0.14–0.90). Additionally, a parity-specific association between Staph. aureus IRCM and SNP c.980A>G was detected. Heifers with genotype c.980GG had a lower Staph. aureus IRCM compared with heifers with genotype c.980AG (rate ratio = 0.15, 95% confidence interval = 0.04–0.56). Differences were less pronounced in multiparous cows. Associations between CXCR1 genotype and somatic cell count were not detected. However, MY was associated with SNP c.735C>G. Cows with genotype c.735GG out-produced cows with genotype c.735CC by 0.8 kg of milk/d. Results provide a basis for further research on the relation between CXCR1 polymorphism and pathogen-specific mastitis resistance and MY.     

Multi-enzyme production by pure and mixed cultures of Saccharomyces and non-Saccharomyces yeasts during wine fermentation

Saccharomyces and non-Saccharomyces yeasts release enzymes that are able to transform neutral compounds of grape berries into active aromatic compounds, a process that enhances the sensory attributes of wines. So far, there exists only little information about enzymatic activity in mixed cultures of Saccharomyces and non-Saccharomyces during grape must fermentations. The aim of the present work was to determine the ability of yeasts to produce extracellular enzymes of enological relevance (β-glucosidases, pectinases, proteases, amylases or xylanases) in pure and mixed Saccharomyces/non-Saccharomyces cultures during fermentation. Pure and mixed cultures of Saccharomyces cerevisiae BSc562, Hanseniaspora vinae BHv438 and Torulaspora delbrueckii BTd259 were assayed: 1% S. cerevisiae/99% H. vinae, 10% S. cerevisiae/90% H. vinae, 1% S. cerevisiae/99% T. delbrueckii and 10% S. cerevisiae/90% T. delbrueckii. Microvinifications were carried out with fresh must without pressing from Vitis vinifera L. c.v. Pedro Jiménez, an autochthonous variety from Argentina. Non-Saccharomyces species survived during 15-18days (BTd259) or until the end of the fermentation (BHv438) and influenced enzymatic profiles of mixed cultures. The results suggest that high concentrations of sugars did not affect enzymatic activity. β-Glucosidase and pectinase activities seemed to be adversely affected by an increase in ethanol: activity diminished with increasing fermentation time. Throughout the fermentation, Saccharomyces and non-Saccharomyces isolates assayed produced a broad range of enzymes of enological interest that catalyze hydrolysis of polymers present in grape juice. Vinifications carried out by a pure or mixed culture of BTd259 (99% of T. delbrueckii) showed the highest production of all enzymes assayed except for β-glucosidase. In mixed cultures, S. cerevisiae outgrew H. vinae, and T. delbrueckii was only detected until halfway the fermentation process. Nevertheless, their secreted enzymes could be detected throughout the fermentation process. Our results may contribute to a better understanding of the microbial interactions and the influence of some enzymes on vinification environments.     

Screening for Human Milk Amino Acids by HPLC-ESI-MS/MS

Amino acids have a determining effect on the nutritional status of the newborn, and their appropriate levels in breast milk are vital for this first stage of life. The amino acids tryptophan, arginine, glutamate, and taurine, for example, are suggested to have a positive effect on immune functions. The purpose of the present study was to develop a new method for the assay of amino acids in human milk by high-performance liquid chromatography–electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) after hydrolysis. Breast milk samples were collected from 77 healthy mothers living in the community of Extremadura (Spain) with less than 2 months of lactation. The samples were then stored at −80 °C. The HPLC-ESI-MS/MS technique proved to be a sensitive and efficient tool for the assay of amino acids in breast milk. The method could be used for the qualitative screening of 40 underivatized amino acids, and for the assay of 20. The resulting data will serve to improve commercial infant formula milks and bring them closer to the reference standard represented by human milk.