The wrinkling of thin elastic sheets occurs over a range of length scales, from the fine scale patterns in substrates on which cells crawl to the coarse wrinkles seen in clothes. Motivated by the wrinkling of a stretched elastic sheet, we deduce a general theory of wrinkling, valid far from the onset of the instability, using elementary geometry and the physics of bending and stretching. Our ma...

Nonlinear wrinkling of a compressed film on a soft substrate in the presence of inhomogeneous swelling actuation strain caused by solvent diffusion is studied. The simulation relies on a continuum model which integrates phase field microelasticity and Föppl-von Kármán plate theory. We show that the wrinkling morphologies developed in the diffusive domain exceeding a critical compression are con...

during a two-year (2004-2005) survey of alfalfa aphids and their natural enemies in isfahan, a total of four aphid species and 58 species of their natural enemies comprised of 45 predatory species, 11 parasitoid species and two species of parasitic mites were collected and identified. moreover, five hyperparasitoid species were collected. on each sampling date, six 20-sweep samples were taken u...

The within-plant distribution of soybean aphid, Aphis glycines Matsumura has been attributed to various causes, yet it is unclear which factor or combination of factors most influence aphid within-plant distribution. Understanding soybean aphid distribution within the soybean canopy is important both in developing sampling programs and in evaluating injury. Because natural enemies have the pote...

We consider the wrinkling of highly stretched, thin rectangular sheets – a problem that has attracted the attention of several investigators in recent years, nearly all of which employ the classical Föppl-von Kármán (F-K) theory of plates. (See Figure 1 below for a schematic diagram.) We first propose a rational model that correctly accounts for large mid-plane strain. We then carefully perform...

Aphidius transcaspicus Telenga, a mealy plum aphid (Hyalopterus pruni Geoffroy) parasitoid from the Mediterranean, was recently introduced into Hawaii for control of invasive aphids. Under laboratory conditions the parasitoid successfully attacked several important aphid pests in Hawaii, including the melon aphid Aphis gossypii Glover, the banana aphid Pentalonia nigronervosa (Coquerel), the gr...

We present a new wrinkling-based measurement technique for quantifying the viscoelastic properties of confined polymer thin films. This approach utilizes real-time laser-light scattering to observe the kinetics of thermally-induced surface wrinkling, which evolves isothermally as a function of annealing time. Specifically, wrinkling is induced by applying a thermal stress to a polystyrene film ...

In the north central United States, populations of the exotic soybean aphid, Aphis glycinesMatsumura (Hemiptera: Aphididae), are highly variable across space, complicating effective aphid management. In this study we examined relationships of plant nutrients, landscape structure, andnatural enemieswith soybeanaphid abundance across Iowa,Michigan,Minnesota, andWisconsin, representing the range o...

Self-organized wrinkling patterns of a liquid crystalline polymer, dictated by the chemico-physically anisotropic nature of surface wettability, are demonstrated in confined geometries. The symmetry of the geometrical constraints of the confinement primarily governs the periodic wrinkling patterns of such a polymer in the wetting region. In a circular geometry, the number of the radial domains ...