Pseudo-solidification of dredged marine soils with cement - fly ash for reuse in coastal development

The dislodged and removed sediments from the seabed, termed dredged marine soils, are generally classified as a waste material requiring special disposal procedures. This is due to the potential contamination risks of transporting and disposing the dredged soils, and the fact that the material is of poor engineering quality, unsuitable for usage as a conventional good soil in construction. Also, taking into account the incurred costs and risk exposure in transferring the material to the dump site, whether on land or offshore, it is intuitive to examine the possibilities of reusing the dredged soils, especially in coastal development where the transportation route would be of shorter distance between the dredged site and the construction location. Pseudo-solidification of soils is not a novel idea though, where hydraulic binders are injected and mixed with soils to improve the inherent engineering properties for better load bearing capacity. It is commonly used on land in areas with vast and deep deposits of soft, weak soils. However, to implement the technique on the displaced then replaced dredged soil would require careful study, as the material is far more poorly than their land counterparts, and that the deployment of equipment and workforce in a coastal environment is understandably more challenging. The paper illustrates the laboratory investigation of the improved engineering performance of dredged marine soil sample with cement and fly ash blend. Some key findings include optimum dosage of cement and fly ash mix to produce up to 30 times of small strain stiffness improvement, pre-yield settlement reduction of the treated soil unaffected by prolonged curing period, and damage of the cementitious bonds formed by the rather small dosage of admixtures in the soil post-yield. In short, the test results show a promising reuse potential of the otherwise discarded dredged marine soils

The virulence factor regulator and quorum sensing regulate the type I-F CRISPR-Cas mediated horizontal gene transfer in Pseudomonas aeruginosa

Pseudomonas aeruginosa is capable of thriving in diverse environments due to its network of regulatory components for effective response to stress factors. The survival of the bacteria is also dependent on the ability to discriminate between the acquisition of beneficial and non-beneficial genetic materials via horizontal gene transfer (HGT). Thus, bacteria have evolved the CRISPR-Cas adaptive immune system for defense against the deleterious effect of phage infection and HGT. By using the transposon mutagenesis approach, we identified the virulence factor regulator (Vfr) as a key regulator of the type I-F CRISPR-Cas system in P. aeruginosa. We showed that Vfr influences the expression of the CRISPR-Cas system through two signaling pathways in response to changes in calcium levels. Under calcium-rich conditions, Vfr indirectly regulates the CRISPR-Cas system via modulation of the AHL-QS gene expression, which could be vital for defense against phage infection at high cell density. When encountering calcium deficiency, however, Vfr can directly regulate the CRISPR-Cas system via a cAMP-dependent pathway. Furthermore, we provide evidence that mutation of vfr reduces the CRISPR-Cas spacer acquisition and interference of HGT. The results from this study add to the regulatory network of factors controlling the CRISPR-Cas system in response to abiotic factors in the environment. The findings may facilitate the design of effective and reliable phage therapies against P. aeruginosa infections, as targeting Vfr could prevent the development of the CRISPR-Cas mediated phage resistance

Aqua­chlorido(3,5-dinitro-2-oxidobenzo­ato-κ2 O 1,O 2)(1,10-phenanthroline-κ2 N,N′)chromium(III)

In the title compound, [Cr(C7H2N2O7)Cl(C12H8N2)(H2O)], the CrIII atom displays a distorted octa­hedral coordination geometry, with the chelating phenantroline and 3,5-dinitro­salicylate ligands in trans positions. In the crystal, mol­ecules are connected via O—H⋯O hydrogen bonds into a two-dimensional framework parallel to (100). In addition, there are π–π stacking inter­actions between phenanthroline ligands along the c axis, with a mean inter­planar distance of 3.456 (4) Å

Rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae produces multiple DSF-family signals in regulation of virulence factor production

<p>Abstract</p> <p>Background</p> <p><it>Xanthomonas </it><it>oryzae </it>pv. <it>oryzae </it>(<it>Xoo</it>) is the causal agent of rice bacterial blight disease. <it>Xoo </it>produces a range of virulence factors, including EPS, extracellular enzyme, iron-chelating siderophores, and type III-secretion dependent effectors, which are collectively essential for virulence. Genetic and genomics evidence suggest that <it>Xoo </it>might use the diffusible signal factor (DSF) type quorum sensing (QS) system to regulate the virulence factor production. However, little is known about the chemical structure of the DSF-like signal(s) produced by <it>Xoo </it>and the factors influencing the signal production.</p> <p>Results</p> <p><it>Xoo </it>genome harbours an <it>rpf </it>cluster comprising <it>rpfB</it>, <it>rpfF</it>, <it>rpfC </it>and <it>rpfG</it>. The proteins encoded by these genes are highly homologous to their counterparts in <it>X. campestris </it>pv. <it>campestris </it>(<it>Xcc</it>), suggesting that <it>Xcc </it>and <it>Xoo </it>might use similar mechanisms for DSF biosynthesis and autoregulation. Consistent with <it>in silico </it>analysis, the <it>rpfF </it>mutant was DSF-deficient and the <it>rpfC </it>mutant produced about 25 times higher DSF-like activity than the wild type <it>Xoo </it>strain KACC10331. From the supernatants of <it>rpfC </it>mutant, we purified three compounds showing strong DSF-like activity. Mass spectrometry and NMR analysis revealed that two of them were the previously characterized DSF and BDSF; the third one was a novel unsaturated fatty acid with 2 double bonds and was designated as CDSF in this study. Further analysis showed that all the three DSF-family signals were synthesized via the enzyme RpfF encoded by <it>Xoo2868</it>. DSF and BDSF at a final concentration of 3 μM to the <it>rpfF </it>mutant could fully restore its extracellular xylanase activity and EPS production to the wild type level, but CDSF was less active than DSF and BDSF in induction of EPS and xylanase. DSF and CDSF shared a similar cell density-dependent production time course with the maximum production being detected at 42 h after inoculation, whereas the maximum production of BDSF was observed at 36 h after inoculation. When grown in a rich medium such as YEB, LB, PSA, and NYG, <it>Xoo </it>produced all the three signals with the majority being DSF. Whereas in nutritionally poor XOLN medium <it>Xoo </it>only produced BDSF and DSF but the majority was BDSF.</p> <p>Conclusions</p> <p>This study demonstrates that <it>Xoo </it>and <it>Xcc </it>share the conserved mechanisms for DSF biosynthesis and autoregulation. <it>Xoo </it>produces DSF, BDSF and CDSF signals in rich media and CDSF is a novel signal in DSF-family with two double bonds. All the three DSF-family signals promote EPS production and xylanase activity in <it>Xoo</it>, but CDSF is less active than its analogues DSF and BDSF. The composition and ratio of the three DSF-family signals produced by <it>Xoo </it>are influenced by the composition of culture media.</p

Noise suppression of on-chip mechanical resonators by chaotic coherent feedback

We propose a method to decouple the nanomechanical resonator in optomechanical systems from the environmental noise by introducing a chaotic coherent feedback loop. We find that the chaotic controller in the feedback loop can modulate the dynamics of the controlled optomechanical system and induce a broadband response of the mechanical mode. This broadband response of the mechanical mode will cut off the coupling between the mechanical mode and the environment and thus suppress the environmental noise of the mechanical modes. As an application, we use the protected optomechanical system to act as a quantum memory. It's shown that the noise-decoupled optomechanical quantum memory is efficient for storing information transferred from coherent or squeezed light

The yeast prion protein Ure2: Structure, function and folding

The Saccharomyces cerevisiae protein Ure2 functions as a regulator of nitrogen metabolism and as a glutathione-dependent peroxidase. Ure2 also has the characteristics of a prion, in that it can undergo a heritable conformational change to an aggregated state; the prion form of Ure2 loses the regulatory function, but the enzymatic function appears to be maintained. A number of factors are found to affect the prion properties of Ure2, including mutation and expression levels of molecular chaperones, and the effect of these factors on structure and stability are being investigated. The relationship between structure, function and folding for the yeast prion Ure2 are discussed

Nutrient Availability and Phage Exposure Alter the Quorum-Sensing and CRISPR-Cas-Controlled Population Dynamics of Pseudomonas aeruginosa

Quorum sensing (QS) coordinates bacterial communication and cooperation essential for virulence and dominance in polymicrobial settings. QS also regulates the CRISPR-Cas system for targeted defense against parasitic genomes from phages and horizontal gene transfer. Although the QS and CRISPR-Cas systems are vital for bacterial survival, they undergo frequent selection in response to biotic and abiotic factors. Using the opportunistic Pseudomonas aeruginosa with well-established QS and CRISPR-Cas systems, we show how the social interactions between the acyl-homoserine lactone (AHL)-QS signal-blind mutants (ΔlasRrhlR) and the CRISPR-Cas mutants are affected by phage exposure and nutrient availability. We demonstrate that media conditions and phage exposure alter the resistance and relative fitness of ΔlasRrhlR and CRISPR-Cas mutants while tipping the fitness advantage in favor of the QS signal-blind mutants under nutrient-limiting conditions. We also show that the AHL signal-blind mutants are less selected by phages under QS-inducing conditions than the CRISPR-Cas mutants, whereas the mixed population of the CRISPR-Cas and AHL signal-blind mutants reduce phage infectivity, which can improve survival during phage exposure. Our data reveal that phage exposure and nutrient availability reshape the population dynamics between the ΔlasRrhlR QS mutants and CRISPR-Cas mutants, with key indications for cooperation and conflict between the strains