a weird example of Persistence of Vision

Ok, you’ve probably seen this already, but let’s try to understand why our vision system creates such a weird image distortion effect. Look at the .gif image below here. Focus on the white cross and keep your eyes on that during the animation. Why does your peripheral vision see? Why normal faces become weird distorted aliens? 😀

Here’s the trick: our brain blends images together if we scroll through them quickly enough. In cinema and animation, our eyes (and brain) start blending images if the frame rate is higher than 16 frames per second.

Instead of seeing flashing separated images, our mind is able to create a more or less continuous motion between each frame and the other. That’s why, for both physical film and digital cinema systems, modern theatrical films run at 24 frames per second (even 48 in the case of Maxivision). The typical example of this phenomenon is given by the Zoetrope, that produces the illusion of motion from a rapid succession of static pictures.

The phenomenon that is responsible for this is the Phi phenomenon, defined by Wikipedia as “the optical illusion of perceiving continuous motion between separate objects viewed rapidly in succession“. Together with the Beta movement, these two perceptual illusions represent a plausible theory to explain motion perception. In more general terms, we are talking about Persistence of vision. Again with the cinema example, movies are rapid sequences of discrete images, but persistence of vision smoothes out movement, making transitions subtle and comprehensive.

other sources: one and two

Repairing and Replacing Body Parts: What’s Next

A friend of mine sent me the link to this webpage. It’s an interesting article that I simply copy and paste here! Enjoy!

🙂

Advances in medical technology have helped us live longer. Now, researchers are exploring ways to repair, refurbish, or replace human organs that have been damaged by chronic disease, traumatic injury, heart attack, stroke, or just plain aging.

“Medicine is saving people who previously we weren’t able to save,” says Dr. Doris A. Taylor, director of regenerative medicine research at the Texas Heart Institute in Houston. Even so, demand for donor organs exceeds the number available. “Each year thousands of people die while waiting for an organ,” Taylor says. That gap in supply and demand is one factor that has led researchers to ever more innovative treatments; at times these treatments can sound like science fiction come to life. Here’s a look at what repaired and replacement parts are available to patients now, which treatments are undergoing clinical trials, and what medical scientists are working to achieve in the future.

Eyesight

Here’s a new take on magnifying glasses: Surgeons can now implant a tiny telescope within the eye, to help restore some of the vision lost to end-stage age-related macular degeneration (AMD), a disease that affects 1.8 million Americans and is the leading cause of legal blindness for adults age 60 years and older. The device—which the Food and Drug Administration approved in 2010 and which is becoming more widely available to medical institutions across the country—is implanted via an hour-long outpatient procedure under local anesthesia. It requires about a month of working with an occupational therapist to get used to, says Dr. Mark Mannis, director of the Eye Center at the University of California Davis Health System. “The reason is that this is not a simple restoration of vision,” he says. “It really requires the patient to see in another way, much in the same way that a patient who loses a lower limb and then gets a prosthesis needs to learn how to walk in a new way.” In this case, the patient learns to use one eye—the one with the implant—for detailed vision and the other for peripheral vision.

Regenerative Medicine

As director of the Wake Forest Institute for Regenerative Medicine in Winston-Salem, North Carolina, Dr. Anthony Atala is researching treatments to repair or restore—or “regenerate”—damaged or failing tissues and organs by using the patient’s own cells and healing abilities. That can mean “boosting” healing by injecting stem cells, or by implanting tissues or organs that have been artificially bio-engineered in the lab starting with stem cells usually harvested from the patient, a strategy that minimizes the risk of the tissues or organs being rejected. “We’re working on about 30 different tissues and organs,” Atala says. Already a number of implants have been tried successfully in humans, including knee cartilage, skin, blood vessels, urethras, windpipes (trachea), and bladders. Clinical trials are underway to treat urinary incontinence by implanting cells to help boost functionality of the urinary valve and thus keep patients dry. Says Atala: “The future is focused on making sure that these technologies can get to as many patients and as many conditions as possible.”

“Printing” Body Parts

At Atala’s lab and other regenerative medicine research centers, 3-D printing is another experimental strategy being used to build bio-artificial body parts and organs. “We’ve printed ear lobes and nose parts and miniature kidneys and skin,” he says. “You are laying [down] the cells one layer at a time, and placing the cells right where you need them,” by customizing the different layers to form the necessary shape, he says. “If you think of your printer and your ink cartridge, instead of using ink you’re using cells and a gel.” Wake Forest is also investigating the possibility of “printing” skin cells directly onto burn wounds.

Stem Cells for Stroke Recovery

Neurologist Dr. Lawrence Wechsler of the University of Pittsburgh’s Schools of the Health Sciences is in the early stages of exploring whether stem cells, injected directly into the brain, can aid stroke victims in their recovery. The first step—now being tested in a clinical trial—is establishing that it’s safe just to try the technique. If that goes well, Wechsler says, “then we can design a study that will more reasonably look at the issue of efficacy and clinical benefit.” Such therapies wouldn’t “unparalyze” patients, he warns. But small improvements in function could yield big improvements in quality of life. “If you can begin to use your hand to grip something and do some small tasks,” Wechsler says, “or gain enough strength in your leg to help you move from being in a wheelchair to walking in some way, that change is a huge benefit.”

Growing an Artificial Heart

Perhaps the ultimate goal of regenerative medicine researchers is creating and transplanting a functioning bio-artificial heart. Is it feasible? Building complex solid organs like the heart, liver, lungs, and pancreas is challenging, and a major issue will be “where do you get those hundreds of billions of cells to do this,” says Taylor of the Texas Heart Institute. But she adds, “we’re making huge strides,” and predicts that a transplant of one kind of bio-artificial solid complex organ will be possible within five years. “And if I have anything to say about it,” Taylor says, “I will be there when it happens.”

For more, see “On Beyond 100“