Numerical simulation of hydraulic jumps. part 2: Recent results and future outlook

During the past two decades, hydraulic jumps have been investigated using Computational Fluid Dynamics (CFD). The second part of this two-part study is devoted to the state-of-the-art of the numerical simulation of the hydraulic jump. First, the most widely-used CFD approaches, namely the Reynolds-Averaged Navier–Stokes (RANS), the Large Eddy Simulation (LES), the Direct Numerical Simulation (DNS), the hybrid RANS-LES method Detached Eddy Simulation (DES), as well as the Smoothed Particle Hydrodynamics (SPH), are introduced pointing out their main characteristics also in the context of the best practices for CFD modeling of environmental flows. Second, the literature on numerical simulations of the hydraulic jump is presented and discussed. It was observed that the RANS modeling approach is able to provide accurate results for the mean flow variables, while high-fidelity methods, such as LES and DES, can properly reproduce turbulence quantities of the hydraulic jump. Although computationally very expensive, the first DNS on the hydraulic jump led to important findings about the structure of the hydraulic jump and scale effects. Similarly, application of the Lagrangian meshless SPH method provided interesting results, notwithstanding the lower research activity. At the end, despite the promising results still available, it is expected that with the increase in the computational capabilities, the RANS-based numerical studies of the hydraulic jump will approach the prototype scale problems, which are of great relevance for hydraulic engineers, while the application at this scale of the most advanced tools, such as LES and DNS, is still beyond expectations for the foreseeable future. Knowledge of the uncertainty associated with RANS modeling may allow the careful design of new hydraulic structures through the available CFD tools

Role and regulation of ACC deaminase gene in Sinorhizobium meliloti: is it a symbiotic, rhizospheric or endophytic gene?

Plant-associated bacteria exhibit a number of different strategies and specific genes allow bacteria to communicate and metabolically interact with plant tissues. Among the genes found in the genomes of plant-associated bacteria, the gene encoding the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase (acdS) is one of the most diffused. This gene is supposed to be involved in the cleaving of plant-produced ACC, the precursor of the plant stress-hormone ethylene toning down the plant response to infection. However, few reports are present on the actual role in rhizobia, one of the most investigated groups of plant-associated bacteria. In particular, still unclear is the origin and the role of acdS in symbiotic competitiveness and on the selective benefit it may confer to plant symbiotic rhizobia. Here we present a phylogenetic and functional analysis of acdS orthologs in the rhizobium model-species Sinorhizobium meliloti. Results showed that acdS orthologs present in S. meliloti pangenome have polyphyletic origin and likely spread through horizontal gene transfer, mediated by mobile genetic elements. When acdS ortholog from AK83 strain was cloned and assayed in S. meliloti 1021 (lacking acdS), no modulation of plant ethylene levels was detected, as well as no increase in fitness for nodule occupancy was found in the acdS-derivative strain compared to the parental one. Surprisingly, AcdS was shown to confer the ability to utilize formamide and some dipeptides as sole nitrogen source. Finally, acdS was shown to be negatively regulated by a putative leucine-responsive regulator (LrpL) located upstream to acdS sequence (acdR). acdS expression was induced by root exudates of both legumes and non-leguminous plants. We conclude that acdS in S. meliloti is not directly related to symbiotic interaction, but it could likely be involved in the rhizospheric colonization or in the endophytic behavior

Draft Genome Sequence of Chromate-Resistant and Biofilm-Producing Strain Pseudomonas alcaliphila 34

We report the draft genome sequence of Pseudomonas alcaliphila 34, a Cr(VI)-hyperresistant and biofilm-producing bacterium that might be used for the bioremediation of chromate-polluted soils. The genome sequence might be helpful in exploring the mechanisms involved in chromium resistance and biofilm formation

Draft genome sequence and overview of the purple non sulfur bacterium Rhodopseudomonas palustris 42OL

Rhodopseudomonas palustris strain 42OL was isolated in 1973 from a sugar refinery waste treatment pond. The strain has been prevalently used for hydrogen production processes using a wide variety of waste-derived substrates, and cultured both indoors and outdoors, either freely suspended or immobilized. R. palustris 42OL was suitable for many other applications and capable of growing in very different culturing conditions, revealing a wide metabolic versatility. The analysis of the genome sequence allowed to identify the metabolic pathways for hydrogen and poly-β-hydroxy-butyrate production, and confirmed the ability of using a wide range of organic acids as substrates

Response of rumen microbial ecosystem to diets integrated with chestnut or quebracho tannins in dairy ewes

The aim of this study was to evaluate the response of rumen microbial ecosystem to diets integrated with chestnut or quebracho tannins in dairy ewes. The experiment was conducted as 3 X 3 Latin square design and the trial was repeated 2 times. Three fistulated ewes fed 3 diets based on chopped grass hay ad libitum administered and on 800 g / head and day of 3 experimental concentrates containing 84.5 g of soybean oil / kg of DM and 52.8 g / kg DM of bentonite (CON) or chestnut tannin extract (CHT) or quebracho tannin extract (QUE). At the end of each experimental period rumen liquor was analysed for fatty acid and microbial profiles. On the basis of the molar stoichiometric relations between rumen volatile fatty acid and CH4 production (CH4=0.45 x acetate-0.275 x propionate + 0.4 x butyrate), the CH4 emission was also predicted for each diet. A canonical correspondence analysis (CCA) was performed in order to find potential connection between microbial community, fatty acid composition of rumen liquor and potential CH4 emission, and how these connections are influenced by the different diets. DGGE bands were used as "species" data, while fatty acids and potential CH4 emission as "environmental" variables. The microbial profile was affected by the presence of tannins. The bacterial community of QUE and CHT samples of rumen liquor was positively correlated to vaccenic acid, conjugated linoleic acid and C18:2 trans-11 cis-15. Moreover, the bacterial communities as affected by CHT resulted mainly positively correlated to butyric acid, acetic acid and with potential CH4 emission. In contrast, the bacterial communities as affected by CON resulted mainly correlated positively to C18:2 cis-9 cis-12 and C18:0 production