Starting to unravel the toxoglossan knot: molecular phylogeny of the "turrids" (Neogastropoda: Conoidea).

The superfamily Conoidea is one of the most speciose groups of marine mollusks, with estimates of about 340 recent valid genera and subgenera, and 4000 named living species. Previous classifications were based on shell and anatomical characters, and clades and phylogenetic relationships are far from well assessed. Based on a dataset of ca. 100 terminal taxa belonging to 57 genera, information provided by fragments of one mitochondrial (COI) and three nuclear (28S, 18S and H3) genes is used to infer the first molecular phylogeny of this group. Analyses are performed on each gene independently as well as for a data matrix where all genes are concatenated, using Maximum Likelihood, Maximum Parsimony and Bayesian approaches. Several well-supported clades are defined and are only partly identifiable to currently recognized families and subfamilies. The nested sampling used in our study allows a discussion of the classification at various taxonomical levels, and several genera, subfamilies and families are found polyphyletic.

Tight and loose shapes in flat entangled dense polymers.

We investigate the effects of topological constraints (entanglements) on two-dimensional polymer loops in the dense phase, and at the collapse transition (theta-point). Previous studies have shown that in the dilute phase the entangled region becomes tight, and is thus localised on a small portion of the polymer. We find that the entropic force favouring tightness is considerably weaker in dense polymers. While the simple figure-eight structure, created by a single crossing in the polymer loop, localises weakly, the trefoil knot and all other prime knots are loosely spread out over the entire chain. In both the dense and theta conditions, the uncontracted-knot configuration is the most likely shape within a scaling analysis. By contrast, a strongly localised figure-eight is the most likely shape for dilute prime knots. Our findings are compared to recent simulations.

Elasticity of gaussian and nearly gaussian phantom networks

We study the elastic properties of phantom networks of Gaussian and nearly Gaussian springs. We show that the stress tensor of a Gaussian network coincides with the conductivity tensor of an equivalent resistor network, while its elastic constants vanish. We use a perturbation theory to analyze the elastic behavior of networks of slightly non-Gaussian springs. We show that the elastic constants of phantom percolation networks of nearly Gaussian springs have a power-law dependence on the distance of the system from the percolation threshold, and we derive bounds on the exponents.

Entropic elasticity of two-dimensional self-avoiding percolation systems

The sol-gel transition is studied on a purely entropic two-dimensional model system consisting of hard spheres (disks) in which a fraction p of neighbors are tethered by inextensible bonds. We use a new method to measure directly the elastic properties of the system. We find that over a broad range of hard sphere diameters a the rigidity threshold is insensitive to a and indistinguishable from the percolation threshold p(c). Close to p(c), the shear modulus behaves as (p-p(c))(f), where the exponent f approximately 1. 3 is independent of a and is similar to the conductivity exponent in random resistor networks.

Diabetic dermopathy and internal complications in diabetes mellitus.

BACKGROUND: Diabetic dermopathy is the most common cutaneous marker of diabetes mellitus. The relationship of diabetic dermopathy to internal complications of diabetes mellitus, such as nephropathy, retinopathy, and neuropathy, is still unknown. METHODS: The possible role of diabetic dermopathy as a clinical sign of internal complications in diabetes mellitus was investigated. One hundred and seventy-three patients with diabetes mellitus, of whom 125 (72%) had insulin-dependent diabetes mellitus and 48 (28%) had non-insulin-dependent diabetes mellitus, were studied. RESULTS: Diabetic dermopathy was present in 69 (40%) of patients, statistically more significant in patients 50 years of age and older. The mean diabetic duration was significantly higher in patients with diabetic dermopathy than in those without. The associations of diabetic dermopathy with retinopathy, nephropathy, and neuropathy were each statistically significant, and the increased frequency of diabetic dermopathy correlated with an increased number of these three complications in each patient. CONCLUSIONS: Some of the factors that affect the development of internal complications in diabetes mellitus may play a role in the development of diabetic dermopathy, and diabetic dermopathy may serve as a clinical sign of an increased likelihood of these internal complications in diabetic patients.