Investigation of Cracking in Reinforced Concrete Structures by Means of Standardized Deformation Models

In this study, a detailed analysis of the use of standardized deformation models is carried out to calculate the design characteristics of reinforced concrete elements, such as crack resistance. For theoretical verification of the values of the moment of cracking, calculation methods based on the use of a nonlinear deformation model are used.A theoretical study of cracking moment using a non-linear deformation model shows that the application of a two-line diagram of concrete deformation allows to obtain the most accurate values of cracking moment

Evolution of glyoxylate cycle enzymes in Metazoa: evidence of multiple horizontal transfer events and pseudogene formation

BACKGROUND: The glyoxylate cycle is thought to be present in bacteria, protists, plants, fungi, and nematodes, but not in other Metazoa. However, activity of the glyoxylate cycle enzymes, malate synthase (MS) and isocitrate lyase (ICL), in animal tissues has been reported. In order to clarify the status of the MS and ICL genes in animals and get an insight into their evolution, we undertook a comparative-genomic study. RESULTS: Using sequence similarity searches, we identified MS genes in arthropods, echinoderms, and vertebrates, including platypus and opossum, but not in the numerous sequenced genomes of placental mammals. The regions of the placental mammals' genomes expected to code for malate synthase, as determined by comparison of the gene orders in vertebrate genomes, show clear similarity to the opossum MS sequence but contain stop codons, indicating that the MS gene became a pseudogene in placental mammals. By contrast, the ICL gene is undetectable in animals other than the nematodes that possess a bifunctional, fused ICL-MS gene. Examination of phylogenetic trees of MS and ICL suggests multiple horizontal gene transfer events that probably went in both directions between several bacterial and eukaryotic lineages. The strongest evidence was obtained for the acquisition of the bifunctional ICL-MS gene from an as yet unknown bacterial source with the corresponding operonic organization by the common ancestor of the nematodes. CONCLUSION: The distribution of the MS and ICL genes in animals suggests that either they encode alternative enzymes of the glyoxylate cycle that are not orthologous to the known MS and ICL or the animal MS acquired a new function that remains to be characterized. Regardless of the ultimate solution to this conundrum, the genes for the glyoxylate cycle enzymes present a remarkable variety of evolutionary events including unusual horizontal gene transfer from bacteria to animals. REVIEWERS: Arcady Mushegian (Stowers Institute for Medical Research), Andrey Osterman (Burnham Institute for Medical Research), Chris Ponting (Oxford University)

Comment on the proper QCD string dynamics in a heavy-light system

The string correction to the inter-quark interaction at large distances is derived using the field theory approach to a heavy-light quark-antiquark system in the modified Fock-Schwinger gauge.Comment: LaTeX2e, 6 pages, no figures, to appear in JETP Let

Lipase Secretion and Citric Acid Production in Yarrowia lipolytica Yeast Grown on Animal and Vegetable Fat

The aim of the study was to investigate the potentiality of the utilization of raw agro- -industrial fat for the biotechnological production of valuable products (lipase and citric acid) by the yeast Yarrowia (Candida) lipolytica. Thirty strains of the aforementioned species were investigated for their capability of lipase secretion and citric acid production on media containing animal fat or rapeseed oil as a sole carbon and energy source. Strain Y. lipolytica 704, exhibiting the highest lipase activity on rapeseed oil (2760 U/mL), was selected for the study of biochemical peculiarities of cell growth, and strain Y. lipolytica 187/1, exhibiting the maximum citric acid synthesis, was selected for the subsequent studies on citric acid production. A relationship between lipase production and residual rapeseed oil concentration was studied. The essential factor for lipase production was found to be the concentration of rapeseed oil in the medium, which should be no less than 5 g/L. Under optimal conditions of cultivation, citric acid production by rapeseed-oil-grown yeast Yarrowia lipolytica 187/1 amounted to 135 g/L; specific rate of citric acid production reached m(CA)/m(cell)=127 mg/(g·h); mass yield (YCA) and energy yield (hCA) were 1.55 and 0.41, respectively

Pentaquarks in the Jaffe-Wilczek approximation

The masses of $uudd\bar s$, $uudd\bar d$ and $uuss\bar d$ pentaquarks are evaluated in a framework of both the Effective Hamiltonian approach to QCD and spinless Salpeter using the Jaffe--Wilczek diquark approximation and the string interaction for the diquark--diquark--antiquark system. The pentaquark masses are found to be in the region above 2 GeV. That indicates that the Goldstone boson exchange effects may play an important role in the light pentaquarks. The same calculations yield the mass of $[ud]^2\bar c$ pentaquark $\sim$ 3250 MeV and $[ud]^2\bar b$ pentaquark $\sim$ 6509 MeV.Comment: 14 pages, 2 tables, LaTeX2e. References correcte