U of M News Wire: May 10, 2007
Spider-Man 3’s nemesis Sandman, a villain shiftier than the Sahara, says U of M sand and superhero expert
- Professor explains the science of sand -
By Deane Morrison
U of M News Wire
The new blockbuster movie Spider-Man 3 is packing theaters and among those in the audience is University of Minnesota physics professor James Kakalios. A diehard fan of superhero comics, he takes a double interest in Spidey foe Sandman, who can transform all or part of his body into living sand.
It doesn't always happen, but in the case of Sandman the writers manage to get much of the science right, Kakalios says. After 10 years researching the physics of sand and other granular materials -- not to mention writing the bestselling book "The Physics of Superheroes" -- he is delighted to see sand finally getting the billing it deserves.
One characteristic of sand that comes through in the movie is its changeling nature.
"Sand can go from light and fluffy in its loose-packed state to hard and rigid when densely packed," Kakalios explains. "Think of getting hit with a sandbag."
That's exactly what Sandman has in mind as he battles Spider-Man. When Spidey tries to punch his shifty nemesis in the stomach, his fist sails right through Sandman's powdery midsection. But in the next instant, Sandman packs the sand grains of his fists into dense, rock-hard clubs and proceeds to pummel the hapless hero.
The powders that be
At first glance, working on the physics of sand and similar materials may seem a little odd. Kakalios, who once wrote a paper titled "Granular physics or nonlinear dynamics in a sandbox," would agree. But such studies are of intense interest to U.S. industries such as pharmaceutical, agriculture, and construction, which together spend about $80 billion a year in powder processing. Take the pills in your medicine cabinet, for example.
"The segregation of granular materials ... is a major concern for the pharmaceutical industry, for example, where granular systems need to be well mixed and homogenous over length scales of a pill diameter or less," Kakalios points out.
In fact, he says, nearly 80 percent of everything manufactured or grown in the United States exists at some point as a granular material, and three percent of all electrical energy in the United States goes into grinding metal ores into powders.
The physics of grains also applies to breakfast cereals, boxes of which usually arrive in stores almost half empty and bearing the apologetic disclaimer "Contents may have settled during shipping." Even Isaac Newton was aware of the settling problem and studied how spherical objects could best be packed in containers. Perhaps he was influenced, Kakalios speculates, by a desire to wring more profit from the apple orchard he owned.
The times of sand
When we walk on a sandy ocean beach, we're treading on tiny grains of rock that were born on mountaintops lifted up by movements of the Earth's crust. As plants and the elements erode rock into smaller pieces, they find their way into valleys, where water washes the finer particles toward the sea. On average, says Kakalios, a grain of sand takes about 10,000 years to complete each mile of its journey. And there are plenty of journeys.
"There is a lot of sand on the planet-approximately 10 million cubic miles, all told," he says. "That's enough to cover the United States three miles deep."
Sandman may not know it, but as he changes the density of his body sand he is actually altering the stacking pattern of individual grains in rather startling ways. Sand, says Kakalios, is full of spaces between the grains that resist being squashed. In fact, the spaces expand when pressure is applied from the top. This explains why a person walking on wet beach sand leaves footprints that are temporarily dry. With each step, the pressure causes new spaces and pores to open up through the matrix of grains. Water drains in to fill the expanded voids, leaving the top surface of the prints drier than the surrounding sand.
The presence of spaces also explains why sand, and not water, is used in hourglasses. Normal fluids respond to the pressure of their own weight by initially shooting through a hole in the bottom of their container rapidly, but their speed slackens as the chamber empties and the pressure head decreases. Sand's resistance to compression, however, keeps it from packing at the bottom and allows it to flow at an even rate.
Another surprising ability of granular materials becomes evident when grains of different sizes are poured into a narrow space such as an ant farm. For example, if sand and sugar are well mixed and poured together, they will at first form an ordinary-looking pile. But after a while, the pile will display alternate horizontal stripes as the sand and sugar sort themselves out.
Perhaps more astonishing is what happens when grains of different sizes are mixed in a rotating cylinder. If a uniform mixture of rice and dried peas, for example, is put into a horizontal glass cylinder and the cylinder is rotated at the right speed, the peas and rice will sort themselves into separate bands like rings on a finger.
The physics behind these phenomena still fascinates Kakalios, although he has switched his research focus to semiconductor materials and neurological systems. As Hollywood continues to produce superhero movies, he hopes viewers will take home a lesson or two when the science is correct, and take the rest with a grain of salt.
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UMC researcher may have found way to save money on animal feed
By Justin Ware
U of M News Wire
With the rising costs of corn and soybeans, farmers have been looking for ways to save money on feed for their animals. A University of Minnesota-Crookston (UMC) researcher might have found a way to do that.
According to Harouna Maiga, UMC department of agriculture professor, substituting some of the soybean meal and all of the beet pulp in the animal's diet with mustard bran increased daily milk production by about 4 pounds and did not change milk composition or feed intake. The mustard bran did not cause any changes in milk flavor or color, and, it is a less expensive option than other feeds; something that could be especially important as more feed crops are used for biofuels like ethanol.
"The study concludes that mustard bran could be used to lower feed cost and increase milk production," said Maiga. "It could be fed to beef cattle, sheep and swine."
Mustard bran is a by-product of mustard milling. It is the outer-layer of whole mustard seed. Maiga is available to answer questions about the use of mustard bran as a replacement feed for dairy cattle.
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Growing Concerns
A parenting column with Dr. Martha Erickson of the University of Minnesota
Question: I have a 3-week-old baby boy whom I tried to breastfeed. But despite lots of effort and all kinds of outside help, it just didn't work. I've read that breastfeeding is very important to the development of mother-child attachment, which worries me. Is there anything I can do to make sure our attachment is good even though I have to bottle feed him?
Answer: Although breastfeeding has many benefits, it is not essential for the development of a good, secure attachment between parents and their baby. Consider, for example, that many babies have great attachments with their fathers, even though breastfeeding isn't an option. The important thing is that your baby learns you are there to comfort him when he's distressed, to respond warmly and sensitively to his needs, and to delight in his smiles, babbles, first words and first steps. Through those simple day-to-day interactions, your son will learn he can count on you to be his safe haven and his secure base from which he can go out and explore the world.
In simple terms, here are things both you and the father of your baby can do in these early months to make sure your son has that solid foundation of a secure attachment to both mom and dad:
• During feeding, hold him closely as you would if breastfeeding. Create a calm, cozy, quiet atmosphere and follow his lead when he wants to start or stop feeding.
• When your baby fusses or cries, try to figure out what he is telling you. Does he need to be held? Fed? Talked to? Does he need you to change his diaper? Or does he just need to know you're nearby while he settles himself?
• When playing with your baby, follow his lead. Provide a clean, safe environment in which he can explore freely. Offer toys, but don't over-direct his play. For example, if he wants to bang the stacking rings together instead of stacking them the "right way," cheer him on.
• Most of all, remember that you are his most important play partner. Sing songs, dance, read stories, get down on the floor and play games that make him smile and laugh. This is the stuff of which attachment is made.
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