Non-native coral species dominate the fouling community on a semi-submersible platform in the southern Caribbean

A coral community was examined on a semi-submersible platform that was moored at the leeward side of Curaçao, in the southern Caribbean, from August 2016 until August 2017. This community included several non-native or cryptogenic species. Among them were two scleractinian corals (Tubastraea coccinea and T. tagusensis) and two octocorals (Chromonephthea sp. and an unidentified Nephtheidae sp.). This is the first reported presence of T. tagusensis in the southern Caribbean, and the genus Chromonephthea in the Caribbean region. An ascidian, Perophora cf. regina, is also reported from the southern Caribbean for the first time, as well as a coral-associated vermetid gastropod, Petaloconchus sp., first recorded in the Caribbean in 2014. Lack of biofouling management could potentially harm indigenous marine fauna through the introduction of non-native species. Therefore monitoring communities associated with semi-submersible platforms is essential to track the presence and dispersal of non-native, potentially invasive species

Survival-Time Distribution for Inelastic Collapse

In a recent publication [PRL {\bf 81}, 1142 (1998)] it was argued that a randomly forced particle which collides inelastically with a boundary can undergo inelastic collapse and come to rest in a finite time. Here we discuss the survival probability for the inelastic collapse transition. It is found that the collapse-time distribution behaves asymptotically as a power-law in time, and that the exponent governing this decay is non-universal. An approximate calculation of the collapse-time exponent confirms this behaviour and shows how inelastic collapse can be viewed as a generalised persistence phenomenon.Comment: 4 pages, RevTe

Simulations of the Static Friction Due to Adsorbed Molecules

The static friction between crystalline surfaces separated by a molecularly thin layer of adsorbed molecules is calculated using molecular dynamics simulations. These molecules naturally lead to a finite static friction that is consistent with macroscopic friction laws. Crystalline alignment, sliding direction, and the number of adsorbed molecules are not controlled in most experiments and are shown to have little effect on the friction. Temperature, molecular geometry and interaction potentials can have larger effects on friction. The observed trends in friction can be understood in terms of a simple hard sphere model.Comment: 13 pages, 13 figure

Macrosegregation During Dendritic Arrayed Growth of Hypoeutectic Pb-Sn Alloys: Influence of Primary Arm Spacing and Mushy Zone Length

Thermosolutal convection in the dendritic mushy zone occurs during directional solidification of hypoeutectic lead tin alloys in a positive thermal gradient, with the melt on the top and the solid below. This results in macrosegregation along the length of the solidified samples. The extent of macrosegregation increases with increasing primary dendrite spacings for constant mushy zone length. For constant primary spacings, the macrosegregation increases with decreasing mushy zone length. Presence of convection reduces the primary dendrite spacings. However, convection in the interdendritic melt has significantly more influence on the spacings as compared with that in the overlying melt, which is caused by the solutal buildup at the dendrite tips

What are we eating? Consumer information requirement within a workplace canteen

The workplace is a captive environment where the overall contribution of the meal served could be an important element of the overall diet. Despite growing demand little information is available to aid healthy dish selection. This study identifies information valued by consumers in the UK, Greece, Denmark and France using best-worst scaling. Value for Money, Nutrition and Naturalness are key elements of information that consumers require to be able to make a conscious decision about dish selection in all four countries. Latent class analysis shows that consumers align to one of five cluster groups, i.e., Value Driven, Conventionalists, Socially Responsible, Health Conscious and Locavores. Understanding key information needs can allow food operators to align their service with consumer preferences across different market segments

Real Roots of Random Polynomials and Zero Crossing Properties of Diffusion Equation

We study various statistical properties of real roots of three different classes of random polynomials which recently attracted a vivid interest in the context of probability theory and quantum chaos. We first focus on gap probabilities on the real axis, i.e. the probability that these polynomials have no real root in a given interval. For generalized Kac polynomials, indexed by an integer d, of large degree n, one finds that the probability of no real root in the interval [0,1] decays as a power law n^{-\theta(d)} where \theta(d) > 0 is the persistence exponent of the diffusion equation with random initial conditions in spatial dimension d. For n \gg 1 even, the probability that they have no real root on the full real axis decays like n^{-2(\theta(2)+\theta(d))}. For Weyl polynomials and Binomial polynomials, this probability decays respectively like \exp{(-2\theta_{\infty}} \sqrt{n}) and \exp{(-\pi \theta_{\infty} \sqrt{n})} where \theta_{\infty} is such that \theta(d) = 2^{-3/2} \theta_{\infty} \sqrt{d} in large dimension d. We also show that the probability that such polynomials have exactly k roots on a given interval [a,b] has a scaling form given by \exp{(-N_{ab} \tilde \phi(k/N_{ab}))} where N_{ab} is the mean number of real roots in [a,b] and \tilde \phi(x) a universal scaling function. We develop a simple Mean Field (MF) theory reproducing qualitatively these scaling behaviors, and improve systematically this MF approach using the method of persistence with partial survival, which in some cases yields exact results. Finally, we show that the probability density function of the largest absolute value of the real roots has a universal algebraic tail with exponent {-2}. These analytical results are confirmed by detailed numerical computations.Comment: 32 pages, 16 figure