Brilliant angle-independent structural colours preserved in weevil scales from the Swiss Pleistocene

Extant weevils exhibit a remarkable colour palette that ranges from muted monochromatic tones to rainbow-like iridescence, with the most vibrant colours produced by three-dimensional photonic nanostructures housed within cuticular scales. Although the optical properties of these nanostructures are well understood, their evolutionary history is not fully resolved, in part due to a poor knowledge of their fossil record. Here, we report three-dimensional photonic nanostructures preserved in brightly coloured scales of two weevils, belonging to the genus Phyllobius or Polydrusus, from the Pleistocene (16–10 ka) of Switzerland. The scales display vibrant blue, green and yellow hues that resemble those of extant Phyllobius/Polydrusus. Scanning electron microscopy and small-angle X-ray scattering analyses reveal that the subfossil scales possess a single-diamond photonic crystal nanostructure. In extant Phyllobius/Polydrusus, the near-angle-independent blue and green hues function primarily in crypsis. The preservation of far-field, angle-independent structural colours in the Swiss subfossil weevils and their likely function in substrate matching confirm the importance of investigating fossil and subfossil photonic nanostructures to understand the evolutionary origins and diversification of colours and associated behaviours (e.g. crypsis) in insects

Substrate Suppression of Thermal Roughness in Stacked Supported Bilayers

We have fabricated a stack of five 1,2-dipalmitoyl-sn-3-phosphatidylethanolamine (DPPE) bilayers supported on a polished silicon substrate in excess water. The density profile of these stacks normal to the substrate was obtained through analysis of x-ray reflectivity. Near the substrate, we find the layer roughness and repeat spacing are both significantly smaller than values found in bulk multilayer systems. The reduced spacing and roughness result from suppression of lateral fluctuations due to the flat substrate boundary. The layer spacing decrease then occurs due to reduced Helfrich repulsion.This work was partially supported by NSF Grants No. DMR-0706369 and No. DMR-0706665. Use of the Advanced Photon Sourcewas supported by theUSDepartment of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. SKS and ANP wish to acknowledge support from the Office of Basic Energy Sciences, US Department of Energy, via Grant No. DE-FG02- 04ER46173. We would also like to thank Suresh Narayanan for his support of the experimental work at Sector 8-ID

Oral insulin-mimetic compounds that act independently of insulin

The hallmarks of insulin action are the stimulation and suppression of anabolic and catabolic responses, respectively. These responses are orchestrated by the insulin pathway and are initiated by the binding of insulin to the insulin receptor, which leads to activation of the receptor's intrinsic tyrosine kinase. Severe defects in the insulin pathway, such as in types A and B and advanced type 1 and 2 diabetes lead to severe insulin resistance, resulting in a partial or complete absence of response to exogenous insulin and other known classes of antidiabetes therapies. We have characterized a novel class of arylalkylamine vanadium salts that exert potent insulin-mimetic effects downstream of the insulin receptor in adipocytes. These compounds trigger insulin signaling, which is characterized by rapid activation of insulin receptor substrate-1, Akt, and glycogen synthase kinase-3 independent of insulin receptor phosphorylation. Administration of these compounds to animal models of diabetes lowered glycemia and normalized the plasma lipid profile. Arylalkylamine vanadium compounds also showed antidiabetic effects in severely diabetic rats with undetectable circulating insulin. These results demonstrate the feasibility of insulin-like regulation in the complete absence of insulin and downstream of the insulin receptor. This represents a novel therapeutic approach for diabetic patients with severe insulin resistance

Anomalous phase transitions in soft colloid-polymer binary mixtures

We have shown earlier [1] that these PGNPs resemble star polymers or spherical brushes in terms of their morphology in the melt. However, these particles show dynamics in melt which is quite different from other soft colloidal particles. Since most of the work on soft colloidal particles have been performed in solutions we have now explored the phase behavior of the PGNPs in good solvent using microscopic structural and dynamical measurements on binary mixtures of homopolymers and soft colloids consisting of polymer grafted nanoparticles. We observe anomalous structural and dynamical phase transitions of these binary mixtures, including appearance of spontaneous orientational alignment and logarithmic structural relaxations, as a function of added homopolymers of different molecular weights. Our experiments points to the possibility of exploiting the phase space in density and homopolymer size, of such hybrid systems, to create new materials with unique properties

Observation of a Low-viscosity Interface Between Immiscible Polymer Layers

この論文は国立情報学研究所の電子図書館事業により電子化されました。研究会報告X-ray Photon Correlation Spectroscopy (XPCS) was employed in a surface standing wave geometry in order to resolve the thermally diffusive in-plane dynamics at both the surface/vacuum (top) and polymer/polymer (bottom) interfaces of a thin Polystyrene (PS) film on top of Poly (4-bromo styrene) (PBrS) and supported on a Si substrate. The top vacuum interface shows two relaxation modes: one fast and one slow, while the buried polymerpolymer interface shows a single slow mode. The slow mode of the top interface is similar in magnitude and wavevector dependence to the single mode of the buried interface. The dynamics are consistent with a low-viscosity mixed layer between the PS and PBrS and coupling of the capillary wave fluctuations between this layer and the PS

Evolution of single gyroid photonic crystals in bird feathers

Vivid, saturated structural colors are conspicuous and important features of many animals. A rich diversity of three-dimensional periodic photonic nanostructures is found in the chitinaceous exoskeletons of invertebrates. Three-dimensional photonic nanostructures have been described in bird feathers, but they are typically quasi-ordered. Here, we report bicontinuous single gyroid β-keratin and air photonic crystal networks in the feather barbs of blue-winged leafbirds (Chloropsis cochinchinensis sensu lato), which have evolved from ancestral quasi-ordered channel-type nanostructures. Self-assembled avian photonic crystals may serve as inspiration for multifunctional applications, as they suggest efficient, alternative routes to single gyroid synthesis at optical length scales, which has been experimentally elusive.ISSN:0027-8424ISSN:1091-649