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THE HEMIHELIX: Scientists discover a new shape while messing around with rubber bands.  Warning: perversions are involved.

Figure 1. Illustration of a helix (top), a hemihelix with one perversion marked by an arrow (middle) and a hemihelix with multiple perversions (bottom).  The scale bar is 5 cm for each image. Credit: Jiangshui Huang

Figure 2. Sequence of operations leading to the spontaneous creation of hemihelices and helices.  Credit: Jia Liu

  • Starting with two long elastomer strips of different lengths,
  • the shorter one is stretched to the same length as the other.
  • While the stretching force, P, is maintained,
  • the two strips are joined side-by-side.
  • Then, as the force is slowly released,
  • the bi-strip twists and bends to create either a helix or a hemihelix. 

Figure 4. Snapshots recorded from the finite element simulations, illustrating the formation of (A) a helix, (B) a hemihelix with single perversion and (C) a hemihelix with 12 perversions.

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Jia Liu, Jiangshui Huang, Tianxiang Su, Katia Bertoldi, David R. Clarke:
"Structural Transition from Helices to Hemihelices  in the journal PLoS ONE — 23 April 2014

Nature abounds with complex, three-dimensional shapes. Of these, the helix and spiral are amongst the most ubiquitous, often emerging during growth from initially straight or flat 2-D configurations. For instance, initially straight roots form helical shapes while attempting to penetrate more compact soils.

NOTE:  Something is said to be chiral if it is not identical in shape to its mirror image; the simplest example is the human hand. 

Similarly, as seed pods open, a chirality-creating mechanism turns an initially flat pod valve into a helix. In other instances, the chirality can switch during growth as noted by Asa Gray and Darwin in their studies of plant tendrils. They noted that as a growing plant tendril circumnutates [that is, twists around] it can attach to another object and then, being fixed at both ends, its chirality reverses in between to maintain its topology as it continues to grow.

This reversal of chirality - often referred to as a perversion - forms what we term here a simple hemihelix. More generally, we introduce the term hemihelix to describe multiple reversals in chirality connected by perversions

Read more about this in a general way at Physics.org News …

For the math and a lot of discussion, go to PLoS ONE

archiemcphee:

Discussion of cosplay usually concerns the creation of awesome costumes. But some people don’t need to use a single piece of fabric, fiberglass, Wonderflex or EVA foam to create a spectacular look. Such is the case with Alexys Fleming, aka MadeYewLook, a completely self-taught make-up artist who can completely transform herself into anyone or anything using make-up, thoughtful lighting and sometime contact lenses and the occasional homemade headpiece or hat. Each character is so well-realized that some of the photos require a good long stare in order to find Lex’s actual facial features. And some of them are truly terrifying.

MadeYewLook also posts excellent tutorials on both her Facebook page and her YouTube channel. Even if you don’t want to try your hand at personal transformation with makeup, be sure to visit both her Facebook and YouTube accounts simply to check out many more of her incredible cosplay creations.

[via Kotaku Cosplay]

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