Numerical simulation of focused wave impact on a 2-D floating structure

Freak (Extreme, rogue) waves are extremely large water waves in ocean and may occur all over the world sea area. Such a wave may lead to damage of coastal and offshore structures. Accurate prediction of extreme wave-induced forces and motions is of importance and necessaries for researchers and engineers for the purpose of structure design and disaster prevention. Due to the complexity of nonlinear wave-structure interactions related with distorted free surface and relatively large amplitude of structure response, a great deal of effort is required to investigate the physics. Here, a Computational Fluid Dynamics (CFD) model has been developed to study focused wave impact on a floating structure and validated by a newly designed experiment. Focused waves are generated based on the mechanism of wave focusing in a two-dimensional wave tank. In the experiment, a model of a box-shaped floating body with a small freeboard is adopted in order to easily obtain green water phenomena. The computations are performed by a Constrained Interpolation Profile (CIP)-based Cartesian grid method. The CIP algorithm is adopted as the base scheme to obtain a robust flow solver of the Navier-stokes equation with free surface boundary. An improved THINC scheme (THINC, tangent of hyperbola for interface capturing), the more accurate THINC/SW scheme (THINC with Slope Weighting), is applied as the free surface/ interface capturing method. Main attentions are paid to the three degrees of freedom (3-DOF) body motions, pressure domain around the structure and nonlinear phenomena, such as water on deck. The highly nonlinear wave-structure interactions, including significant body motion and water on deck, are modeled successfully in comparison with experimental measurements. It is concluded that the present model with the aid of the CIP technique can provide with acceptably accurate numerical results on the route to practical purposes

Antibacterial effect of orange Monascus pigment against Staphylococcus aureus

The objective of this work was to research the antibacterial effects of orange pigment, which was separated from Monascus pigments, against Staphylococcus aureus. The increase of the diameter of inhibition zone treated with orange pigment indicated that orange pigment had remarkable antibacterial activities against S. aureus. Orange pigment (10 mg ml−1) had a strong destructive effect on the membrane and structure of S. aureus by the analysis of scanning electron microscopy as well as transmission electron microscopy. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) further demonstrated that the cell membrane was seriously damaged by orange pigment, which resulted in the leakage of protein from S. aureus cells. A significant decrease in the synthesis of DNA was also seen in S. aureus cells exposed to 10 mg ml−1 orange pigment. All in all, orange pigment showed excellent antibacterial effects against S. aureus

Collective Properties of Low-lying Octupole Excitations in 82208Pb126^{208}_{82}Pb_{126}, 2060Ca40^{60}_{20}Ca_{40} and 828O20^{28}_{8}O_{20}

The octupole strengths of $\beta$-stable nucleus $^{208}_{82}Pb_{126}$, a neutron skin nucleus $^{60}_{20}Ca_{40}$ and a neutron drip line nucleus $^{28}_{8}O_{20}$ are studied by using the self-consistent Hartree-Fock calculation plus the random phase approximation (RPA) with Skyrme interaction. The collective properties of low-lying excitations are analyzed by using particle-vibration coupling. The results show that the lowest isoscalar states above threshold in $^{60}_{20}Ca_{40}$ and $^{28}_{8}O_{20}$ are the superpositions of collective excitations and unperturbed transitions from bound state to nonresonance states. For these three nuclei, both the low-lying isoscalar states and giant isoscalar resonance carry isovector strength. The ratio B(IV)/B(IS) is checked. It is found that, for $^{208}_{82}Pb_{126}$, the ratios are equal to $(\frac{N-Z}{A})^2$ in good accuracy, while for $^{60}_{20}Ca_{40}$ and $^{28}_{8}O_{20}$, the ratios are much larger than $(\frac{N-Z}{A})^2$. This results from the excess neutrons with small binding energies in $^{60}_{20}Ca_{40}$ and $^{28}_{8}O_{20}$.Comment: 14 pages, 10 figure

Non-Markovian dynamics in a spin star system: The failure of thermalization

In most cases, a small system weakly interacting with a thermal bath will finally reach the thermal state with the temperature of the bath. We show that this intuitive picture is not always true by a spin star model where non-Markov effect predominates in the whole dynamical process. The spin star system consists a central spin homogeneously interacting with an ensemble of identical noninteracting spins. We find that the correlation time of the bath is infinite, which implies that the bath has a perfect memory, and that the dynamical evolution of the central spin must be non- Markovian. A direct consequence is that the final state of the central spin is not the thermal state equilibrium with the bath, but a steady state which depends on its initial state.Comment: 8 page

Stability and function of adult vasculature is sustained by Akt/Jagged1 signalling axis in endothelium.

The signalling pathways operational in quiescent, post-development vasculature remain enigmatic. Here we show that unlike neovascularization, endothelial Akt signalling in established vasculature is crucial not for endothelial cell (EC) survival, but for sustained interactions with pericytes and vascular smooth muscle cells (VSMCs) regulating vascular stability and function. Inducible endothelial-specific Akt1 deletion in adult global Akt2KO mice triggers progressive VSMC apoptosis. In hearts, this causes a loss of arteries and arterioles and, despite a high capillary density, diminished vascular patency and severe cardiac dysfunction. Similarly, endothelial Akt deletion induces retinal VSMC loss and basement membrane deterioration resulting in vascular regression and retinal atrophy. Mechanistically, the Akt/mTOR axis controls endothelial Jagged1 expression and, thereby, Notch signalling regulating VSMC maintenance. Jagged1 peptide treatment of Akt1ΔEC;Akt2KO mice and Jagged1 re-expression in Akt-deficient endothelium restores VSMC coverage. Thus, sustained endothelial Akt1/2 signalling is critical in maintaining vascular stability and homeostasis, thereby preserving tissue and organ function

Alloy design by tailoring phase stability in commercial Ti alloys.

The mechanical characteristics and the operative deformation mechanisms of a metallic alloy can be optimised by explicitly controlling phase stability. Here an integrated thermoelastic and pseudoelastic model is presented to evaluate the β stability in Ti alloys. The energy landscape of β→α′/α'' martensitic transformation was expressed in terms of the dilatational and transformational strain energy, the Gibbs free energy change, the external mechanical work as well as the internal frictional resistance. To test the model, new alloys were developed by tailoring two base alloys, Ti–6Al–4V and Ti–6Al–7Nb, with the addition of β-stabilising element Mo. The alloys exhibited versatile mechanical behaviours with enhanced plasticity. Martensitic nucleation and growth was fundamentally dominated by the competition between elastic strain energy and chemical driving force, where the latter term tends to lower the transformational energy barrier. The model incorporates thermodynamics and micromechanics to quantitatively investigate the threshold energy for operating transformation-induced plasticity and further guides alloy desig