The Wet-Dog Shake: How wet mammals dry themselves

The drying of wet fur is a critical to mammalian heat regulation. This fluid dynamics video demonstrates how hirsute animals rapidly oscillate their bodies to shed water droplets, nature's analogy to the spin cycle of a washing machine.

High-speed videography and fur-particle tracking is employed to determine the angular position of the animal's shoulder skin as a function of time. X-ray cinematography is used to track the motion of the skeleton. Particular attention is paid to rationalizing the relationship between animal size and oscillation frequency required to self-dry.

http://arxiv.org/abs/1010.3279, ArXiv, 15 Oct 2010

A fun little game: GenePool

GenePool is an evolution simulation game in which hundreds of little virtual organisms called swimbots are subject to the forces of darwinian evolution by making them compete for food and sex in a small aquatic environment.

A typical starting pool, zoomed in

The creatures are generated randomly at the start from a number of geometric pieces of different shape and size, and they immediately begin to pursue one of the two objectives their 2-bit brain is capable of: eat and mate.

mine? mine! mine mine mine!!!

When hungry, two little green bars resembling a mouth will sprout from their bodies and they will try to swim towards the nearest little green pellet, the pool's only food source.

At first, the swimbots are very inefficient. They flail their limbs randomly when trying to go in a particular direction, and many end up swimming in circles, or even away from the pellet. Only those that can coordinate their movements well enough survive, leaving the rest to die a slow death at the hands of natural selection.

Betty! How could you?!

When the swimbot's hunger is satiated it's time to quell their other need. The little mouth turns into an arrow and the swimmer starts looking for a suitable mate. Swimbots can mate with any other member of the pool. They prefer, by default, one that matches their color scheme, but the sexual preference can be set to a number of other criteria: size, speed, length, etc.


After mating they leave behind a little swimbot, a genetic average of the two parents, which rapidly matures. Sometimes the offspring will be born with a small mutation, which might help it survive and spread its genes, thus driving evolution forward in the pool.

After leaving the simulation run for a while, one or two species will start dominating the pool. These will be much more efficient swimmers than their ancestors, having gone through several generations of evolution in a single afternoon.

Zerg rush kekekeke

Gene Pool was created by Jeffrey Ventrella

The latest version of the game, for both Mac and PC, can be downloaded for FREE from here http://www.swimbots.com/

From the Uncanny Valley: Actroid-F

Actroids are a brand of humanoid androids developed by Osaka University and manufactured by Kokoro Company Ltd. The skin is composed of a silicone compound that gives them a staggering human-like visual appereance, and they posses an array of internal sensors that allow Actroid models to react with a natural appearance by way of air actuators placed at many points of articulation in the upper body.

Their latest model, the Actroid-F, can track the operator’s facial expressions and head movements, and replicate them with impressive accuracy. The android is being positioned as an observer in hospitals to gauge patient reactions.
SOURCE: RoboTimes

How do jellyfish eat?

Video of the pulsing dynamics and the resulting fluid flow generated by the upside down jellyfish, Cassiopea spp. Medusae of this genus are unusual in that they typically rest upside down on the ocean floor and pulse their bells to generate feeding currents, only swimming when significantly disturbed. The pulsing kinematics and fluid flow around these upside down jellyfish is investigated using a combination of videography, flow visualization, and numerical simulation. Coherent vortex rings are not seen in the wake above the jellyfish, but starting and stopping vortices are observed before breaking up as they pass through the elaborate oral arms (if extended). Feeding Currents Generated by Upside Down Jellyfish, ArXiv, 16 Oct 2010

It's nice to know people have their priorities straight

The atheist's nightmare... peanut butter

Universal robotic gripper

Gripping and holding of objects are key tasks for robotic manipulators. The development of universal grippers able to pick up unfamiliar objects of widely varying shape and surface properties remains, however, challenging. Most current designs are based on the multifingered hand, but this approach introduces hardware and software complexities. These include large numbers of controllable joints, the need for force sensing if objects are to be handled securely without crushing them, and the computational overhead to decide how much stress each finger should apply and where.

In this robotic hand, individual fingers are replaced by a single mass of granular material that, when pressed onto a target object, flows around it and conforms to its shape. Upon application of a vacuum the granular material contracts and hardens quickly to pinch and hold the object without requiring sensory feedback. "Universal robotic gripper based on the jamming of granular material", PNAS, 17 Sept 2010

Floating water bridge between two beakers

The interaction of electrical fields and liquids can lead to phenomena that defies intuition. Some famous examples can be found in Electrohydrodynamics as Taylor cones, whipping jets or non-coalescing drops. A less famous example is the Floating Water Bridge: a slender thread of water held between two glass beakers in which a high voltage difference is applied. Surprisingly, the water bridge defies gravity even when the beakers are separated at distances up to 2 cm. "Building water bridges in air: Electrohydrodynamics of the Floating Water Bridge", ArXiv, 19 Oct 2010.

Mass of ants behaving as a fluid

Fire ants use their claws to grip diverse surfaces, including each other. As a result of their mutual adhesion and large numbers, ant colonies flow like inanimate fluids. This sequence of films shows how ants behave similarly to the spreading of drops, the capillary rise of menisci, and gravity-driven flow down a wall. By emulating the flow of fluids, ant colonies can remain united under stressful conditions. “Ants as Fluids: Physics-Inspired Biology”, ArXiv, 15 Oct 2010.