The MTCY428.08 gene of Mycobacterium tuberculosis codes for NAD+ synthetase

The product of the MTCY428.08 gene of Mycobacterium tuberculosis shows sequence homology with several NAD+ synthetases. The MTCY428.08 gene was cloned into the expression vectors pGEX-4T-1 and pET-15b. Expression in Escherichia coli led to overproduction of glutathione S-transferase fused and His6-tagged gene products, which were enzymatically assayed for NAD synthetase activity. Our results demonstrate that the MTCY428.08 gene of M. tuberculosis is the structural gene for NAD+ synthetase.     

Statistical analysis of measurements for telecommunication-network troubleshooting

This paper presents a method for assessing network failures by means of a suitable statistical post-processing analysis of measurement data collected by nonintrusive devices. The proposed solution can be easily implemented by already available monitoring instruments for network performance surveillance and automatic detection of anomalies. The effectiveness of the method has been proven on real-life telecommunication systems, and results are reported.     

A beam model for the flexural–torsional buckling of thin-walled members with some applications

A beam model aimed at describing the flexural–torsional buckling of thin-walled members with non-symmetric cross-sections is presented. Two beam axes are introduced, and strain is defined with respect to both. The shearing strain between the cross-section and one of the two axes is assumed to vanish; the warping is supposed to be linear in the twist. Non-linear hyperelastic constitutive relations are introduced; by means of standard localization and static perturbation techniques, the field equations describing the flexural–torsional buckling are obtained. One benchmark example is given and some numerical values of the critical load for various warping constraints at the beam ends are provided.     

Stereospecific analysis of triacylglycerols in camel (Camelus dromedarius) milk fat

In the lipid fraction of camel (Camelus dromedarius) milk the percentage of saturated fatty acids (SFAs) was 62.8% with a content of palmitic acid of 28.5%. The unsaturated fatty acid (UFA) fraction was dominated by oleic and palmitoleic acids. Enzyme digestion and chemical degradation methods were used to determine the intramolecular fatty acid (FA) composition and then the intermolecular FA distribution in the three sn-positions of the triacylglycerols of the camel milk. FAs showed a specific preference for a particular position: in all samples studied, SFAs were prevalently esterified in the sn-2 position, while UFAs occupied mainly the sn-1 and sn-3 position. As the carbon chain lengthened from 8 to 16 the percentages of SFAs decreased in the sn-2 position and increased in the outer positions. Such data indicated that the length of the carbon chain could be a discriminating factor in the acylation process of SFAs.     

The stability and degradation of dietary DNA in the gastrointestinal tract of mammals: implications for horizontal gene transfer and the biosafety of GMOs

The fate of dietary DNA in the gastrointestinal tract (GIT) of animals has gained renewed interest after the commercial introduction of genetically modified organisms (GMO). Among the concerns regarding GM food, are the possible consequences of horizontal gene transfer (HGT) of recombinant dietary DNA to bacteria or animal cells. The exposure of the GIT to dietary DNA is related to the extent of food processing, food composition, and to the level of intake. Animal feeding studies have demonstrated that a minor amount of fragmented dietary DNA may resist the digestive process. Mammals have been shown to take up dietary DNA from the GIT, but stable integration and expression of internalized DNA has not been demonstrated. Despite the ability of several bacterial species to acquire external DNA by natural transformation, in vivo transfer of dietary DNA to bacteria in the intestine has not been detected in the few experimental studies conducted so far. However, major methodological limitations and knowledge gaps of the mechanistic aspects of HGT calls for methodological improvements and further studies to understand the fate of various types of dietary DNA in the GIT.     

Two-Stage vs Single-Stage Thermophilic Anaerobic Digestion: Comparison of Energy Production and Biodegradation Efficiencies

Two-stage anaerobic digestion (AD) for integrated biohydrogen and biomethane production from organic materials has been reported to promise higher process efficiency and energy recoveries as compared to traditional one-stage AD. This work presents a comparison between two-stage (reactors R1 and R2) and one-stage (reactor R3) AD systems, fed with identical organic substrates and loading rates, focusing the attention on chemical and microbiological aspects. Contrary to previous experiences, no significant differences in overall energy recovery were found for the two-stage and one-stage AD systems. However, an accumulation in R2 of undegraded intermediate metabolites (volatile fatty acids, ketones, amines, amino acids, and phenols) was observed by GC-MS. These compounds were thought to be both cause and effect of this partial inefficiency of the two-stage system, as confirmed also by the less diverse, and thereby less efficient, population of fermentative bacteria observed (by PCR-DGGE) in R2. The extreme environment of R1 (low pH and high metabolites concentrations) probably acted as selector of metabolic pathways, favoring H(2)-producing bacteria able to degrade such a wide variability of intermediate metabolites while limiting other strains. Therefore, if two-stage AD may potentially lead to higher energy recoveries, further efforts should be directed to ensure process efficiency and stability.     

Yeasts from Colombian Kumis as source of peptides with Angiotensin I converting enzyme (ACE) inhibitory activity in milk

This study investigated the possibility of using yeast strains in fermented milks to obtain products with high Angiotensin I-converting enzyme (ACE) inhibitory activity and low bitter taste. Ninety-three yeast strains isolated from Colombian Kumis in different geographic regions were molecularly identified, and their milk fermentation performances were determined. Molecular identification evidenced that Galactomyces geotrichum, Pichia kudriavzevii, Clavispora lusitaniae and Candida tropicalis, were the dominant species. Eighteen out of 93 strains produced fermented milk with ACE-inhibitory (ACEI) activity values ranging from 8.69 to 88.19%. Digestion of fermented milk samples by pepsin and pancreatin demonstrated an increase in ACEI activity, with C. lusitaniae KL4A as the best producer of ACEI peptides. Moreover, sensory analysis of the products containing the major ACE-inhibitory activity pointed out that P. kudriavzevii KL84A and Kluyveromyces marxianus KL26A could be selected as potential adjunct starter cultures in Kumis, since they made a considerable contribution to the ACE inhibitory activity and produced fermented milk without bitter taste. In this study we observed that Colombian Kumis can be an excellent vehicle for the isolation of yeasts with a potential to enhance bioactive peptides produced during milk fermentation.     

Genetic operators for hierarchical graph clustering

In this paper we propose an encoding scheme and ad hoc operators for a genetic approach to hierarchical graph clustering. Given a connected graph whose vertices correspond to points within a Euclidean space and a fitness function, a hierarchy of graphs in which each vertex corresponds to a connected subgraph of the graph below is generated. Both the number of clustering levels and the number of clusters on each level are not fixed a priori and are subject to optimization.     

Vector coding the finite-volume procedure for the CYBER 205

The paper reviews a method for the large-scale numerical simulation of fluid flow and discusses fundamental principles of vector programming in FORTRAN in order to set the stage for the main topic, the vector coding and execution of the finite-volume procedure on the CYBER 205. With the proper structure given to the data by the grid transformation each coordinate direction can be differenced throughout the entire grid in one vector operation. Boundary conditions must be interleaved which tends to inhibit the concurrency of the overall scheme, but a stragey of no data motion together with only inner-loop vectorization is judged to be the best compromise. The computed example of transonic vortex flow separating from the sharp leading edge of a delta wing demonstrates the processing performance of the procedure. Vectors over 40000 elements long are obtained, and a rate of over 125 megaflops sustained over the entire computation indicates the high degree of vectorization achieved.