Computational Hydrographic Printing

NASA - Aquarius Mission logo. June 17, 2015 An international Earth-observing mission launched in 2011 to study the salinity of the ocean surface ended June 8 when an essential part of the power and attitude control system for the SAC-D spacecraft, which carries NASA’s...

As fragile as a soap bubble seems, these films have remarkable powers of self-healing. The animation above shows a falling water droplet passing through a soap film without bursting it. An important factor here is that the water droplet is wet–passing a dry object through a soap film is a quick way to burst it, as those who have played with bubbles know. The droplet’s inertia deforms the soap film, creating a cavity. If the drop’s momentum were smaller, the film could actually bounce the droplet back like a trampoline, but here the droplet wins out. The film breaks enough to let the drop through, but its cavity quickly pinches off and the film heals thanks to the stabilizing effect of its soapy surfactants. (Image credit: H. Kim, source)

The Quicksort Algorithm

Quicksort is the fastest known comparison-based sorting algorithm (on average, and for a large number of elements), requiring O(n log(n)) steps. By convention, n is the number of elements to be compared and big O is a function of those elements. Quicksort is a recursive algorithm which first partitions an array according to several rules:

Pick an element, called a pivot, from the array.

Reorder the array so that all elements with values less than the pivot come before the pivot, while all elements with values greater than the pivot come after it (equal values can go either way). After this partitioning, the pivot is in its final position. This is called the partition operation.

Recursively apply the above steps to the sub-array of elements with smaller values and separately to the sub-array of elements with greater values.

Quicksort was invented by Tony Hoare and has undergone extensive analysis and scrutiny, and is known to be about twice as fast as the next fastest sorting algorithm. In the worst case, however, quicksort is a slow n² algorithm (and for quicksort, “worst case” corresponds to already sorted). (Click this link for an example of the Quicksort Algorithm written in C)

Credit: Wolfram Alpha/Wikipedia

Helping Hand

Robots, video games, and a radical new approach to treating stroke patients.

BY KAREN RUSSELL

In late October, when the Apple TV was relaunched, Bandit’s Shark Showdown was among the first apps designed for the platform. The game stars a young dolphin with anime-huge eyes, who battles hammerhead sharks with bolts of ruby light. There is a thrilling realism to the undulance of the sea: each movement a player makes in its midnight-blue canyons unleashes a web of fluming consequences. Bandit’s tail is whiplash-fast, and the sharks’ shadows glide smoothly over rocks. Every shark, fish, and dolphin is rigged with an invisible skeleton, their cartoonish looks belied by the programming that drives them—coding deeply informed by the neurobiology of action. The game’s design seems suspiciously sophisticated when compared with that of apps like Candy Crush Soda Saga and Dude Perfect 2.

Bandit’s Shark Showdown’s creators, Omar Ahmad, Kat McNally, and Promit Roy, work for the Johns Hopkins School of Medicine, and made the game in conjunction with a neuroscientist and neurologist, John Krakauer, who is trying to radically change the way we approach stroke rehabilitation. Ahmad told me that their group has two ambitions: to create a successful commercial game and to build “artistic technologies to help heal John’s patients.” A sister version of the game is currently being played by stroke patients with impaired arms. Using a robotic sling, patients learn to sync the movements of their arms to the leaping, diving dolphin; that motoric empathy, Krakauer hopes, will keep patients engaged in the immersive world of the game for hours, contracting their real muscles to move the virtual dolphin.

Many scientists co-opt existing technologies, like the Nintendo Wii or the Microsoft Kinect, for research purposes. But the dolphin simulation was built in-house at Johns Hopkins, and has lived simultaneously in the commercial and the medical worlds since its inception. “We depend on user feedback to improve the game for John’s stroke patients,” Ahmad said. “This can’t work without an iterative loop between the market and the hospital.”

In December, 2010, Krakauer arrived at Johns Hopkins. His space, a few doors from the Moore Clinic, an early leader in the treatment of AIDS, had been set up in the traditional way—a wet lab, with sinks and ventilation hoods. The research done in neurology departments is, typically, benchwork: “test tubes, cells, and mice,” as one scientist described it. But Krakauer, who studies the brain mechanisms that control our arm movements, uses human subjects. “You can learn a lot about the brain without imaging it, lesioning it, or recording it,” Krakauer told me. His simple, non-invasive experiments are designed to produce new insights into how the brain learns to control the body. “We think of behavior as being the fundamental unit of study, not the brain’s circuitry. You need to study the former very carefully so that you can even begin to interpret the latter.”

Krakauer wanted to expand the scope of the lab, arguing that the study of the brain should be done in collaboration with people rarely found on a medical campus: “Pixar-grade” designers, engineers, computer programmers, and artists. Shortly after Krakauer arrived, he founded the Brain, Learning, Animation, Movement lab, or BLAM! That provocative acronym is true to the spirit of the lab, whose goal is to break down boundaries between the “ordinarily siloed worlds of art, science, and industry,” Krakauer told me. He believes in “propinquity,” the ricochet of bright minds in a constrained space. He wanted to create a kind of “neuro Bell Labs,” where different kinds of experts would unite around a shared interest in movement. Bell Labs is arguably the most successful research laboratory of all time; it has produced eight Nobel Prizes, and inventions ranging from radio astronomy to Unix and the laser. Like Bell,BLAM! would pioneer both biomedical technologies and commercial products. By developing a “self-philanthropizing ecosystem,” Krakauer believed, his lab could gain some degree of autonomy from traditionally conservative funding structures, like the National Institutes of Health.

The first problem that BLAM! has addressed as a team is stroke rehabilitation. Eight hundred thousand people in the U.S. have strokes each year; it is the No. 1 cause of long-term disability. Most cases result from clots that stop blood from flowing to part of the brain, causing tissue to die. “Picture someone standing on a hose, and the patch of grass it watered dying almost immediately,” Steve Zeiler, a neurologist and a colleague of Krakauer’s, told me. Survivors generally suffer from hemiparesis, weakness on one side of the body. We are getting better at keeping people alive, but this means that millions of Americans are now living for years in what’s called “the chronic state” of stroke: their recovery has plateaued, their insurance has often stopped covering therapy, and they are left with a moderate to severe disability.

In 2010, Krakauer received a grant from the James S. McDonnell Foundation to conduct a series of studies exploring how patients recover in the first year after a stroke. He was already well established in the worlds of motor-control and stroke research. He had discovered that a patient’s recovery was closely linked to the degree of initial impairment, a “proportional recovery rule” that had a frightening implication: if you could use early measures of impairment to make accurate predictions about a patient’s recovery three months later, what did that say about conventional physical therapy? “It doesn’t reverse the impairment,” Krakauer said.

Nick Ward, a British stroke and neurorehabilitation specialist who also works on paretic arms, told me that the current model of rehabilitative therapy for the arm is “nihilistic.” A patient lucky enough to have good insurance typically receives an hour each per day of physical, occupational, and speech therapy in the weeks following a stroke. “The movement training we are delivering is occurring at such low doses that it has no discernible impact on impairment,” Krakauer told me. “The message to patients has been: ‘Listen, your arm is really bad, your arm isn’t going to get better, we’re not going to focus on your arm,’ ” Ward said. “It’s become accepted wisdom that the arm doesn’t do well. So why bother?”

Krakauer and his team are now engaged in a clinical trial that will test a new way of delivering rehabilitation, using robotics and the video game made by Ahmad, Roy, and McNally, who make up an “arts and engineering” group within the Department of Neurology. Krakauer hopes to significantly reduce patients’ impairment, and to demonstrate that the collaborative model of BLAM! is “the way to go” for the future study and treatment of brain disease.

Reza Shadmehr, a Johns Hopkins colleague and a leader in the field of human motor-control research, told me, “He’s trying to apply things that we have developed in basic science to actually help patients. And I know that’s what you’re supposed to do, but, by God, there are very few people who really do it.”

“You bank on your reputation, in the more conventional sense, to be allowed to take these risks,” Krakauer said. “I’m cashing in my chits to do something wild.”

In 1924, Charles Sherrington, one of the founders of modern neuroscience, said, “To move things is all that mankind can do; for such the sole executant is muscle, whether in whispering a syllable or in felling a forest.” For Sherrington, a human being was a human doing.

Yet the body often seems to go about its business without us. As a result, we may be tempted to underrate the “intelligence” of the motor system. There is a deep-seated tendency in our culture, Krakauer says, to dichotomize brains and brawn, cognition and movement. But he points out that even a movement as simple as reaching for a coffee cup requires an incredibly sophisticated set of computations. “Movement is the result of decisions, and the decisions you make are reflected in movements,” Krakauer told me.

Motor skills, like Stephen Curry’s jump shot, require the acquisition and manipulation of knowledge, just like those activities we deem to be headier pursuits, such as chess and astrophysics. “Working with one’s hands is working with one’s mind,” Krakauer said, but the distinction between skill and knowledge is an ancient bias that goes back to the Greeks, for whom techne, skill, was distinct from episteme, knowledge or science.

Keep reading

#DataMining

Poland A and Poland B might be real - Borders of Imperial Germany and the 2015 Polish Presidential Race Exit Poll Results.

Orange (Incumbent): PO (Civic Platform) Party - Liberal-Conservative

Blue: PiS (Law and Justice) Party - Interventionist & Social Conservative

More interesting correlations >>

Odor Biomarker For Alzheimer’s: Urine Test Could Predict Disease Onset

A new study from the Monell Center, the U.S. Department of Agriculture (USDA), and collaborating institutions reports a uniquely identifiable odor signature from mouse models of Alzheimer’s disease. The odor signature appears in urine before significant development of Alzheimer-related brain pathology, suggesting that it may be possible to develop a non-invasive tool for early diagnosis of Alzheimer’s disease.

The research is in Scientific Reports. (full open access)

The American Commute by Alasdair Rae.