Fake "legs"
A while back, I read a book that discussed (among other things) the myriad uses of cadavers in scientific research. In the case of such areas as ballistics & munitions testing (including trying out protective footwear for minefield sweepers), it was no surprise to learn that these folks don't often (hardly ever) get permission to use actual cadavers or cadaver parts (i.e. legs) in their tests. On one hand, I completely understand that these tests need to be run; on the other hand, I completely sympathize with those who withhold the permission. Who wants grandma's legs to get blown to shreds?
What they usually end up doing is casting models of bodies or body parts in ballistics gel, which apparently is a fantastic substitute for biological soft tissues. This book reported that several researchers have expressed their desire to have a more complete model of, for example, the human leg; they can see from their ballistic gel models what can happen to soft tissue, but they want a model with synthetic bone inside.
Some work has been done toward developing such a model of the human leg. So far, the "best" model produced consisted of a fiberglass "bone" at the core of the ballistic gel "leg." When tested, the fiberglass proved to be a nominally adequate bone-substitute; however, the testers complained that this "bone" just didn't behave quite right.
If I had but time and money to spare, this might be a fun project to develop. I have given the idea some preliminary thought. The compact portion of the bone could probably be fairly well-modeled with a fiberglass composite. Modeling the trabecular bone tissue, however, would present more of a challenge. Possible materials for investigation might include metallic glass foams, high-strength aerogel composites, or other cross-linked fiber composites.
The book (highly recommended, unless you get queasy):
Stiff: The Curious Lives of Human Cadavers, by Mary Roach (2004).
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Labels: literature, science
Around the world with a shoebox
I don't remember where I found this prompt, but it struck me as an interesting question: "If you were given a free plane ticket around the world and a single shoebox for luggage, what would you pack?"
The shrewd, calculating side of my brain immediately responded, "Define 'luggage.' If the shoebox is my 'carry-on,' do I get a 'personal item' like a purse or a backpack as well?"
If the answer to that question were to be "yes," well, that really kind of takes all the fun out of it. For the sake of discussion, then, let's say that anything I take with me (barring the clothes on my back) must fit in this shoebox. Obviously, I can't bring everything I would need; I would be able to purchase and discard most things along the way. So what would I wish to have on this trip that is (a) small enough to fit in a shoebox, and (b) expensive and/or difficult to obtain?
After some thought, I think that my shoebox "priority" items would be the following:
Passport
Wallet (including the usual ID, credit cards, etc.)
Cash
Contact lenses and/or glasses
Digital camera (with an extra memory card)
Extra space might go to my
Neti pot, and a couple of extra pairs of clean underwear and socks.
I'm ready to see the world!
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Labels: imagine yourself here, ponderings, travel
The Omnivore's Hundred
This list comes from the
Very Good Taste blog. As per
the given instructions, I have
bolded all the items I’ve eaten, and
crossed out any items that I would never consider eating.
1. Venison2. Nettle tea
3. Huevos rancheros4. Steak tartare
5. Crocodile
6. Black pudding -
I am repulsed by the very idea of this.7. Cheese fondue8. Carp
9. Borscht
10. Baba ghanoush11. Calamari12. Pho13. PB&J sandwich14. Aloo gobi15. Hot dog from a street cart16. Epoisses
17. Black truffle
18. Fruit wine made from something other than grapes -
Home-brewed mulled apple mead, courtesy of Matt.19. Steamed pork buns
20. Pistachio ice cream21. Heirloom tomatoes22. Fresh wild berries23. Foie gras
24. Rice and beans25. Brawn, or head cheese26. Raw Scotch Bonnet pepper -
I like my taste buds just the way they are, thanks.27. Dulce de leche
28. Oysters29. Baklava30. Bagna cauda
31. Wasabi peas32. Clam chowder in a sourdough bowl33. Salted lassi
34. Sauerkraut35. Root beer float36. Cognac with a fat cigar
37. Clotted cream tea
38. Vodka jelly/Jell-O
39. Gumbo40. Oxtail
41. Curried goat
42. Whole insects43. Phaal -
What's the point of eating something if your tongue is scorched after the first bite?44. Goat’s milk
45. Malt whisky from a bottle worth $120 or more
46. Fugu (pufferfish)
47. Chicken tikka masala48. Eel
49. Krispy Kreme original glazed doughnut50. Sea urchin
51. Prickly pear
52. Umeboshi
53. Abalone
54. Paneer
55. McDonald’s Big Mac Meal56. Spaetzle
57. Dirty gin martini
58. Beer above 8% ABV
59. Poutine
60. Carob chips61. S’mores62. Sweetbreads
63. Kaolin
64. Currywurst
65. Durian
66. Frogs’ legs
67. Beignets, churros, elephant ears or
funnel cake68. Haggis
69. Fried plantain70. Chitterlings, or andouillette -
I almost crossed this off, but 'never say never'... right?71. Gazpacho72.
Caviar and
blini -
I've had both, but not together73. Louche absinthe
74. Gjetost, or brunost
75. Roadkill -
It would have to be extremely fresh roadkill.76. Baijiu
77. Hostess Fruit Pie -
Food of the gods, seriously.78. Snail
79. Lapsang souchong
80. Bellini
81. Tom yum
82. Eggs Benedict83. Pocky84. Tasting menu at a 3-Michelin-star restaurant.
85. Kobe beef
86. Hare
87. Goulash88. Flowers89. Horse
90. Criollo chocolate
91. Spam92. Soft shell crab93. Rose harissa
94. Catfish95. Mole poblano96. Bagel and lox97. Lobster Thermidor
98. Polenta99. Jamaican Blue Mountain coffee
100. Snake
How much of an omnivore are you?
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Labels: everyday, food, my future, ponderings
The future is now?
Reading
this article in a recent issue of
Technology Review, I had to stop and think that (a) some people have really been weirdly accurate in their visions of the future, and (b) we might be able to live under Their umbrella in blissful denial and/or ignorance, but Big Brother is here and They might be more powerful than we like to think. (And that, right there, is a frightening and thorny dissertation for some other time.)
Quoting MIT professor Robert Fano, 1970:
"Computers provide access to knowledge, and knowledge is power... Big Brother may well take the form of a computerized and centralized information system which has become essential to the operation of society. Thus, the societal exploitation of computers... may continue on the automation of existing functions in human organizations, with a concomitant centralization of information and control... [which] leads to the evolution of organizations into superhuman entities with their own goals, largely insensitive to human values."
Of course, the flip side of this argument is, as Fano explained, that "societal exploitation of computers" could take the opposite direction, toward "turning the power of computers to the service of the individual." His main point was a warning: "Unless computers are made truly accessible to the population at large, there will develop a dangerous power gap between those who have access to computers and those who have not, and particularly between organizations -- whether public or private -- and the private citizen."
I think it's important to recognize the current reality of both of Fano's visions for the future. With that in mind, it's also important to note that by the very nature of the Internet, and the resultant collaborative sharing (or not) of information -- privacy rights, for example, and how private your on-line information actually is -- our situation is still growing and changing as society adapts new technology to its own ends in various ways.
(
Full article: "Community Access," by Matt Mahoney >>)
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Labels: everyday, ponderings, science
Road trip report: spring break at Grand Canyon
For spring break this year, I drove to the Grand Canyon and back with two sixteen-year-old girls (which meant that I did
all of the driving).
What was I thinking? I was thinking it might be fun. Well, it turns out I was right. I only thought about killing them once or twice; the rest of the time, we were all too busy taking pictures and laughing at each others' lame jokes. The photo highlights (and all of the hundreds of other pictures we took) can be found at
my Flickr site.
Our traveling roadshow:
Day 1, Tuesday: Boulder, CO, to Blanding, UT (440 miles): via I-70 and US-191We hit the road with a box full of canned goods (ravioli, green beans, corn, peaches, pineapple, etc.), plenty of bottled water, a huge music selection (ran the gamut from Kanye West to Madonna to Paul Oakenfold to AC/DC to the Backstreet Boys), and other assorted supplies (especially pretzels).
The first day was the biggest, mileage-wise; we hoofed it all the way out to Utah and then a good ways south, with room for sightseeing stops on the way. We stopped in Glenwood Canyon for a lovely picnic lunch of cold canned ravioli and green beans.
At a scenic rest area off I-70 in Utah, we took another break, took lots more pictures, and my gravity-defying little sister topped out on a picnic shelter and later somersaulted over a concrete retaining wall. (Actually, she says, she was attempting to vault it at a run, but her foot slipped, and she recovered by throwing her shoulder down and going into a roll. I wasn't paying very close attention, so from my perspective it looked cooler than that sounds.)
Farther down the road, just north of Moab, we drove through Arches National Park, which was gorgeous. That night, somewhere out on the open highway north of our destination, we stopped on the side of the road to look at the stars and debated over what was or wasn't the Big Dipper or Little Dipper.
Day 1 photos:
Hitting the roadEastern UtahArches National ParkDay 2, Wednesday: Blanding, UT, to Flagstaff, AZ (262 miles): via UT-95, UT-261, US-163, US-160, and US-89
We headed west from Blanding to Natural Bridges National Monument. The drive there was beautiful: blue sky, bright sun, rolling hills, towering roadcuts, surprising vistas. The park itself was chock full of picturesque sandstone. We drove the nine-mile loop road, stopped to look and take pictures at every overlook, did some meandering on foot.
Then we headed south for the Arizona border. We knew that we were coming up to a small section of road called Moki Dugway; the park ranger at Natural Bridges said it was a series of switchbacks, descending more than 1000 feet over 3 miles of road surface. Then we came to a pull-off, beyond which the road disappeared over a rise.
We stopped and walked out to the edge of a sandstone overlook, where I had a monumental "whooooaaaaaaa" moment as the view opened up in front of us. Far below, the highway zigzagged off into the distance across the wide country.
Moki Dugway, as we discovered when we finally got back in the car and continued down the road, is a narrow, side-winding gravel lane that twists back and back on itself to eke down the side of Cedar Mesa. I drove slowly, enjoying the view, and the girls screamed like it was an amusement park ride around every hairpin curve.
A little further down the highway, just north of Mexican Hat, Utah, we did some off-roading near Mexican Hat Rock. I was feeling adventurous, the girls were yelling encouragement in my ear, and I went for some of the more exciting tracks. My Subaru Forester handled it all with aplomb; I love my car.
North of the Utah-Arizona border, US-163 crosses Monument Pass; from a distance, this view struck me as particularly iconic of the great American Southwest.
Late in the afternoon we drove into Sunset Crater National Monument. It was pretty, but not terribly exciting or spectacular. We had fun clambering through a lava field.
Dinner was in Flagstaff, at a restaurant called Dara Thai that served up delicious and spicy Thai cuisine. Highly recommended!
Day 2 photos:
Southern Utah 1Natural Bridges National MonumentMoki DugwaySouthern Utah 2Sunset Crater National MonumentDay 3, Thursday: Flagstaff, AZ, to Kayenta, AZ (230 miles): via US-180, AZ-64, and US-160Once again, we were blessed with warm, sunny weather.
We cut northwest from Flagstaff through the mountains, which was a pretty drive, and then continued northward to Grand Canyon National Park.
We visited Mather Point and Yavapai Point, then did a picnic lunch in the parking lot at the park headquarters. From there we left the car for the shuttle buses, and rode up to Hermit's Rest, with a few stops at overlooks along the way.
We provided our own additional entertainment by engaging in bizarre arguments (how to best conduct and cover up a mob hit) and pointless ruminations ("if my leg muscles could speak, what would they say?"), as usual, at a volume certain to be overheard by other tourists.
Returning to the car, we drove eastward along Desert View Drive on our way out of the park, with plenty more scenic overlooks and lots of photos along the way. We made one more stop outside the park, at the Little Colorado Gorge, where we hiked in a little ways from the road and went venturing off the beaten path.
In Kayenta, the hotel desk clerk's dinner recommendation was a small local place called the Blue Coffee Pot. There, we discovered a nice family atmosphere and a down-home-style menu that featured Navajo dishes and other southwestern fare.
Day 3 photos:
Grand Canyon 1Grand Canyon 2Days 4-6, Friday-Sunday: Kayenta, AZ, to Gunnison, CO (317 miles), and Gunnison to Boulder (212 miles): via US-160, US-491, CO-145, CO-62, US-550, US-50, and US-285On Friday we headed for familiar territory. We pulled off the road at Four Corners, intending to stop and take a couple of pictures, but they wanted to charge us $3 admission per person, so we got right back on the road and kept going.
Lunch was another canned picnic, parked roadside amidst the snowbanks, somewhere in the mountains of southwest Colorado. Over the course of the afternoon we played in the snow, complained at other drivers riding their brakes downhill from the mountain passes, and ate lots of pretzels.
Towards evening, we made a little detour off US-50 west of Gunnison, up a little dirt track called Alpine Plateau Road No. 867. Thanks to the tire tracks worn into the mud and snowpack, and the hefty snowbanks to either side of the road, I had fun rumbling up and down the hills and sliding around turns. (No sarcasm, either -- I love my car!)
Friday night my parents rolled into Gunnison, a couple of hours after we did; on Saturday we went to the local climbing competition, which my little sister competed in and my dad helped run. We also hung out some with friends from the Colorado-New Mexico region who were in town for the same competition.
Sunday we drove home.
We pulled off at Kenosha Pass on US-285, and went hiking a little ways into the woods up another mud road. Then, while my parents wandered around the parking area with the dog, I took the girls in the Subaru for a spin up the same mud road. My car came back muddy;
I was duly pleased. We did lunch at Coney Island, a hot-dog-shaped hot dog stand tucked away among the evergreens just off US-285 east of Bailey, Colorado.
Days 4-6 photos:
Driving homeStatistics:1461 highway miles
742 photos/videos
4 states (US-160 actually cuts through New Mexico for about a mile)
4 national parks/monuments
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Labels: everyday, food, travel
The technological singularity: future or fantasy?
Over the weekend, I read
this fascinating series of articles in the June 2008 issue of
IEEE Spectrum, addressing the concept of the "technological singularity" which some say will happen by the year 2030.
Spectrum executive editor Glenn Zorpette describes it thus:
"The singularity is supposed to begin shortly after engineers build the first computer with greater-than-human intelligence. That achievement will trigger a series of cycles in which superintelligent machines beget even smarter machine progeny, going from generation to generation in weeks or days rather than decades or years. The availability of all that cheap, mass-produced brilliance will spark explosive economic growth, an unending, hypersonic, technoindustrial rampage that by comparison will make the Industrial Revolution look like a bingo game." (
Full article >>)
Some believe that this singularity will lead, in short order, to a kind of technological rapture. One of the skeptics, science journalist John Horgan, describes this view flippantly, but not inaccurately:
"Like paradise, technological singularity comes in many versions, but most involve bionic brain boosting. At first, we'll become cyborgs, as stupendously powerful brain chips soup up our perception, memory, and intelligence and maybe even eliminate the need for annoying TV remotes. Eventually, we will abandon our flesh-and-blood selves entirely and upload our digitized psyches into computers. We will then dwell happily forever in cyberspace where, to paraphrase Woody Allen, we'll never need to look for a parking space... Notably, singularity enthusiasts tend to be computer specialists, such as the author and retired computer scientist Vernor Vinge... and the entrepreneur Ray Kurzweil. Intoxicated by the explosive progress of information technologies captured by
Moore's Law, such singularitarians foresee a 'merger of biological and nonbiological intelligence,' as Kurzweil puts it, that will culminate in 'immortal software-based humans.' It will happen not within a millennium, or a century, but no later than 2030, according to Vinge... Kurzweil says he has adopted an antiaging regimen so that he'll 'live long enough to live forever.'" (
Full article >>)
Researcher John Casti, however, foresees the singularity going in the opposite direction:
"I think it's scientifically and philosophically on sound footing. The only real issue for me is the time frame over which the singularity will unfold. [The singularity represents] the end of the supremacy of
Homo sapiens as the dominant species on planet Earth. At that point a new species appears, and humans and machines will go their separate ways, not merge one with the other. I do not believe this necessarily implies a malevolent machine takeover; rather, machines will become increasingly uninterested in human affairs just as we are uninterested in the affairs of ants or bees. But it's more likely than not in my view that the two species will comfortably and more or less peacefully coexist -- unless human interests start to interfere with those of the machines." (
Full article >>)
Here, then, is a view of a different kind of singularity (which is, in my opinion, a more plausible one), as proposed by MIT robotics professor Rodney Brooks:
"My own view is that things will unfold very differently... an artificial intelligence could evolve in a much different way. In particular, I don't think there is going to be one single sudden technological 'big bang' that springs [a human-level artificial intelligence, or AI] into 'life.' Starting with the mildly intelligent systems we have today, machines will become gradually more intelligent, generation by generation. The singularity will be a period, not an event.
"This period will encompass a time when we will invent, perfect, and deploy, in fits and starts, ever more capable systems, driven not by the imperative of the singularity itself but by the usual economic and sociological forces. Eventually, we will create truly artificial intelligences, with cognition and consciousness recognizably similar to our own. I have no idea how, exactly, this creation will come about. I also don't know when it will happen, although I strongly suspect it won't happen before 2030, the year that some singularitarians predict.
"But I expect the [AIs] of the future -- embodied, for example, as robots that will roam our homes and workplaces -- to emerge gradually and symbiotically with our society. At the same time, we humans will transform ourselves. We will incorporate a wide range of advanced sensory devices and prosthetics to enhance our bodies. As our machines become more like us, we will become more like them." (
Full article >>)
The questions are many; the speculation runs rampant. Will machines ever be as smart as humans? Will they ever achieve "consciousness"? Will they be our helpers, our caretakers, our overseers? Eventually, time will tell -- assuming that the human race doesn't first undergo some kind of cataclysmic event (e.g., an
Andromeda strain, a nuclear holocaust, extraterrestrial enslavement, the Biblical end of days, etc.).
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Labels: engineering, my future, philosophy, ponderings, science
Clam chowder as it was meant to be
In my travels last summer, I dined one evening at
Dooger's Seafood & Grill in Cannon Beach, Oregon. The first-course soup was their own homemade clam chowder; it was amazing, perfect, melt-in-your-mouth creamy and tender. This is what clam chowder was meant to be.
The most complete recipe I could find was on
Cooks.com. It sounds right, but the cooking directions are a tad vague. Does anyone want to give this a shot? Let me know how it turns out.
Dooger's Clam Chowder:
1 lb. boiling potatoes
1 c. half & half
1/2 c. whipping cream
26 oz. canned sea clams
1/4 tsp. seasoning salt
Dash of ground thyme
Dash of white pepper
Peel and boil potatoes. Drain and mash lightly. Put clams in pot and heat. Add potatoes and seasonings. Let simmer. Heat milk, add clam mixture. Add butter.
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Labels: food, travel
Once More to the Lake
Summertime, cool morning air, the idyllic lake surrounded by towering trees: this is one of those iconic, near-perfect experiences which, once passed, we wish could have stretched for just a little longer.
"I guess I remembered clearest of all the early mornings, when the lake was cool and motionless, remembered how the bedroom smelled of the lumber it was made of and of the wet woods whose scent entered through the screen ... as I was always the first up I would dress softly so as not to wake the others, and sneak out into the sweet outdoors and start out in the canoe, keeping close along the shore in the long shadows of the pines. I remembered being very careful never to rub my paddle against the gunwale for fear of disturbing the stillness of the cathedral."
(excerpt:
"Once More to the Lake" - E.B. White, 1941)
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Labels: imagine yourself here, literature, ponderings
Modeling the cardiovascular system
There are several popular models of the cardiovascular (CV) system. Depending on your training and experience, one may make more sense than others. Personally, I prefer the fluid flow model; incidentally, this is probably the closest analog to the actual CV system itself, because blood behaves largely as a fluid.
The Windkessel fluid flow model is relatively straight-forward, with elements representing the aorta and the peripheral circulation (i.e., all of the other veins, arteries, etc. in the body). The aorta is modeled by an elastic chamber, exerting pressure on the fluid it contains, and the peripheral circulation is modeled as a rigid tube of constant resistance; the system input is given as a volume inflow rate.
Another analog to this model is that of an electrical circuit:
Fluid element ~ Circuit element
Flow rate ~ Current
Pressure ~ Voltage
Elasticity ~ Capacitance
Fluid inertia ~ Inductance
Valves ~ Diodes
Resistance ~ Resistance
The circuit can be laid out as follows:
The heart will be represented by an alternating-current (AC) current source, providing a current (blood flow rate) of specified period and amplitude (ranging from zero to a positive value). The flow will then pass through a diode (valve) to prevent backflow into the source (heart). Here, current (blood flow) can pass through the diode (valve) in one direction only.
The flow then encounters an inductor (arterial element) and resistor (aorta) in parallel. Here, the resistance is the proportionality of the voltage (pressure) across the element to the current (blood flow rate) through it; the inductor (inertial component) induces a voltage (pressure) that opposes any change in current (blood flow rate).
Following this, the flow encounters a capacitor (systemic/arterial compliance) and resistor (systemic resistance) in parallel. Here, the capacitor (compliance/elasticity) stores an amount of charge (blood volume) proportional to the voltage (pressure) across the element (aorta); i.e., it stores an amount of energy proportional to one-half the square of the voltage (pressure). Resistance here is the same as described above.
The circuit after this point goes back to the source, with a branch to common ground (blood supply, "reservoir"). Here, ground (supply) merely provides a reference "low" voltage (pressure) for the rest of the circuit.
>> Cole et al. (2005):
"A LabVIEW Model Incorporating an Open-Loop Arterial Impedance and a Closed-Loop Circulatory System," Annals of Biomedical Engineering.
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Labels: engineering, science
OK, I think my brain just exploded
This particular recurrence of Exploded Brain Syndrome may have been caused by the
sheer awesomeness of this photograph and the accompanying news articles.
Just, uh, wow. I cannot summon the words to describe just how
incredibly awesome this is. It's like my childhood dreams about flying.
Read:
>>
"Rocketman flies over Alps with jet-pack strapped to his back">>
"Holy Jetpacks, Fusion Man! Swiss Man Flies With Own Wings"--
Labels: engineering, imagine yourself here, travel
A wee taste of Geoffrey Chaucer
In the General Prologue of Chaucer's Canterbury Tales, some space is devoted to describing each of the travelers. We'll have a look at his take on the Monk. If you want to read along, the passage can be found
here, with a modern translation given alongside the original Middle English. For the convenience of the more casual reader, I will offer translations as close to the original wording as I can get.
Chaucer’s description of the Monk is fraught with the kind of sarcasm that I enjoy so much in his writing. This becomes evident beginning in lines 177-178, where Chaucer writes of the Monk's disregard for a certain text condemning his favorite pastime:
"
He thought of that text not a pulled hen,
That says that hunters are not holy men "
Clearly the Monk enjoys hunting and other things too much to let such old-fashioned religious notions get in his way. At first read Chaucer seems to agree with this philosophy (l. 183-192):
"
And I said his opinion was good.
Why should he study, and make himself mad,
Upon a book in cloister always to pore,
Or work with his hands and labor,
As Austin bids? How shall the world be served?
Let Austin have his work to him reserved!
Therefore he was a rider aright:
Greyhounds he had, as swift as fowl in flight;
Of riding and of hunting for the hare
Was all his lust, for no cost would he spare. "
Why should the Monk study and labor? "How shall the world be served?" This seems justification enough; Chaucer writes, "Therefore he was a rider aright," as if this is the best thing on which the Monk could possibly spend his time and effort. The verses that follow give a description of the Monk's person, giving him the air of a rich man who has spared no expense in the pursuit of fashionable comforts: fur-trimmed cloak, gold pin, well-conditioned boots, and, from all indications,
very fine dining.
Some might say that Chaucer genuinely agrees with the Monk's habits, being of a practical mind; the Monk can't change the world or really improve the quality of life for lesser people, so why should he waste his time?
However, especially in light of Chaucer's other works, such an observation would seem to be drastically out of character with his apparent set of moral values.
"
Suffice unto your things, though they be small,
For avarice is hateful, ...
Savor no more than behooves you "
The above, translated from Chaucer's "Ballad of Good Counsel," praises the simple lifestyle and the virtue of being satisfied with no more than you need. Considering his verses about the Monk, I find myself responding with equal sarcasm to the Monk's own set of values. "How shall the world be served," indeed?
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Labels: literature, philosophy
Culinary excellence
A little while ago, I had the opportunity to enjoy dinner at the
Flagstaff House Restaurant here in Boulder. I was impressed by many things: the location, the food, the service. This was a dining establishment the likes of which I had never experienced previously, and it may be a long time before I do so again.
The one thing which struck me most, however, was our waiter; he was a perfect gentleman, and unlike any waiter I had ever encountered in real life. Maybe "handler" was a better descriptor for his role. Regardless, what really impressed me was his commentary on every single menu selection we made: "Excellent." I'd say, "I'd like the quail, please," and he'd respond with, "Excellent." My sister would say, "Can I have the rabbit loin?" and he'd reply, "Excellent." Every single time. It seemed so very high-society, and sort of quaint in a very classy way.
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Labels: food, imagine yourself here, ponderings
It's Alive!
Robotics is a field in which I don't have a lot of experience, but I find the results terribly cool. Especially fascinating are those robots which are designed for biofidelic movement, or which mimic the movement capabilities of living creatures. Here is a perfect example: Boston Dynamics' DARPA-funded "BigDog."
Mobile Robots Take Baby Steps (full article >>)"
A robot dog could one day become a soldier's best friend -- if an Army program works out as planned."
New Video: Robot Mule Conquers Ice, Snow (full article & video >>)"
BigDog, the alarming life-like, four-legged robot, is back in action. And this time, it's trudging through snow, marching up hills, and picking itself up after slipping on some ice."
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Labels: engineering, science
ABO blood types
Here's a (relatively) simple explanation.
The four basic types are A, B, AB, and O. These types are determined by which certain antigens, or protein markers, are found on a person's blood cells. A person can have 'A' antigens only, 'B' antigens only, both 'A' and 'B' antigens, or none.
Which (if any) of these antigens a person has is determined by genetics. In a person's genetic code, the gene pair that determines these antigens can be any combination of 'A', 'B', and 'O', making for six possible genetic sequences: 'AA', 'AO', 'AB', 'BB', 'BO', and 'OO'. The genes for 'A' and 'B' are codominant, and 'O' is recessive. This means that if a person's genes code for 'AA' or 'AO' their blood cells will carry 'A' antigens (this is blood type A), 'BB' or 'BO' will yield 'B' antigens (type B), 'AB' will cause both 'A' and 'B' antigens to be produced (type AB), and 'OO' will produce no antigens (type O).
Now for the important part: anti-A and anti-B antibodies. (Antibodies are one of the human body's defensive mechanisms.)
A person with type AB blood carries both 'A' and 'B' antigens, so neither type of antibody is produced. This is what makes type AB the "universal receiver"; because it has no anti-A or anti-B antibodies, it can accept any blood type.
Type A blood carries only 'A' antigens, so in this case only anti-B antibodies are produced, which will attack only cells with 'B' antigens; vice versa, for type B with 'B' antigens, only anti-A antibodies are produced.
Type O blood carries neither 'A' nor 'B' antigen markers, so both anti-A and anti-B antibodies are produced; if these antibodies encounter any blood cells that carry 'A' or 'B' markers, they will recognize those cells as foreign and attack them. For this reason, a person with type O blood cannot accept any other blood type; each of the other types (A, B, and AB) carries 'A' and/or 'B' antigen markers. However, for this same reason, type O is the "universal donor"; these blood cells, because they carry no 'A' or 'B' antigens, can safely mingle with any other blood type.
Those are the basics of ABO blood types in a nutshell. (Bonfils gave me a complimentary keychain; I might as well know about what goes on with the blood that I've been giving away.)
The good news is that my blood type (AB+) can accept every other known blood type. The less-than-great news is that my blood cells are only acceptable to other people with the same exact type, or only about 3.4 percent of the population.
Anyone, however, can use my blood plasma, because it contains none of the blood cells (with their pesky antigens and Rh factors) that cause the incompatibility.
This warrants some thoughtful consideration.
The process by which they (the nebulous conglomerate of licensed phlebotomists) collect plasma is called plasmapheresis. This involves several iterations of a cycle in which blood is collected and separated into its components in a centrifuge, the plasma is drawn off, and the remaining components are fed back into your bloodstream. The entire process (including paperwork, donation, and prescribed downtime) takes about an hour and a half, and most donation centers offer to "compensate" plasma donors for their time.
Plasma is a fairly versatile blood product. According to several informational websites, a bone marrow or organ transplant surgery requires over a hundred units of plasma. Plasma also contains proteins that are used to treat immunodeficiency and blood coagulation disorders (such as hemophilia); for these same reasons, it is also a sought-after material for biomedical research purposes.
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Labels: everyday, science
Injury repair in the central nervous system
This is such a promising development. Also, you know, it's really cool science.
Injuries to the central nervous system (CNS) are notoriously difficult to repair, though in many cases the surrounding CNS tissues adapt to work around the resulting scar. This "glial scar" is very inhibitory to the regeneration of damaged axons, which carry outgoing signals from neurons (signal-conducting nerve cells). In order to understand the inhibitory nature of the glial scar and consequent failure of axon regeneration after CNS injury, we should first understand the cells and processes involved in the formation of the glial scar.
When CNS tissue is damaged it undergoes an injury response called reactive gliosis, or glial scarring. This consists of a series of cellular and molecular events that occur and change over a period of several days; the glial scar structure evolves over time as various cells arrive and participate at different times. The main cell types involved are the neurons themselves, as well as the surrounding glial tissue, which consists of astrocytes (general support cells, providing structural stability and helping to regulate the extracellular environment), microglia (immune cells, the "garbagemen" of the CNS), and oligodendrocytes (provide insulation for axons in the form of myelin sheaths).
Immediately following injury, myelin debris (from damaged oligodendrocytes) will be released into the neural environment as oligodendrocytes and other cells in the injured area are damaged and die. In the first few days following injury, the primary entering cells are microglia. The lesion (damaged area) also expands during this time. The mature glial scar consists mainly of a tightly-woven network of astrocyte processes.
Astrocytes around the lesion exhibit abnormal growth and some undergo cell division; the end result of this activity is the dense, predominantly astrocytic composition of the glial scar. It has been found that this tissue can be both inhibitory to and supportive of axonal regeneration, depending on changes in the CNS environment and/or the population of glial scars by an as-yet undetermined sub-type of astrocyte which is inhibitory.
Oligodendrocytes are directly damaged by traumatic injury to the CNS, causing the release of myelin debris and some oligodendrocyte death. Glial scars, therefore, usually contain some oligodendrocytes and myelin debris. It has been shown that mature oligodendrocytes and myelinated areas of the CNS are inhibitory to axon growth. Also, it has been seen that oligodendrocyte precursor cells are recruited en masse to CNS lesion sites; these cells express several proteoglycans (dense molecular complexes of proteins and polysaccharides) that are inhibitory to axon regeneration.
Microglia exhibit activation and division following injury, and migrate to the injury site, becoming more macrophage-like over time ("macrophage" essentially means "great eater," so you can guess what a macrophage does). Collective evidence suggests that microglia may actually support regeneration, as long as nothing happens to make them overtly toxic.
Interestingly, it has been shown that the eradication of all CNS glia from the lesioned area results in an environment in which robust axonal regeneration can occur for a period of about 4 days, until glia re-invade the area.
With this in mind, we turn to the potential use of a self-assembling nanofiber peptide scaffold. This novel scaffold is a hydrogel (content is over 99 percent water, with 1 to 10 milligrams of peptides per milliliter of water) that forms when a self-assembling peptide (SAP) solution is exposed to salt solution similar to that found in the human body. The figure at right (click to enlarge) shows (a) a molecular model of the SAP, (b) a microscopic image of the SAP nanofibers, (c) a microscopic image of the scaffold, and (d) a photograph of the hydrogel. The components of the scaffold are amphiphilic oligopeptides that have repeated alternating ionic hydrophilic & hydrophobic amino acids. These form beta-pleated sheets with distinct polar & non-polar surfaces. Structurally, macroscopic scaffolds have been formed in various shapes and sizes, depending on SAP concentration, total amount of SAP solution, salt concentration, and the geometry of the processing apparatus. These structures consist of individual interwoven fibers of about 10 to 20 nanometers (one-trillionth of a meter) in diameter, with the density of fibers correlating with the concentration of the SAP solution.
Here's the "really cool science" part. In one study, Holmes et al. seeded neural cells on SAP scaffolds. These cells underwent extensive outgrowth along the contours of the scaffolds; further evidence suggested that the scaffolds also supported the formation of functional neuron synapses.
In another study conducted by Ellis-Behnke et al., a tissue gap was created in the hamster midbrain (by deep transection of the optic tract). When treated with SAP solution, this gap was seen to be reduced or completely eliminated by 72 hours post-surgery and in all subsequent examinations, as compared to the saline-treated controls, which remained visible in macroscopic examination at all times post-surgery. The figure at right shows typical examples from 30 days post-surgery of (a) the saline control case and (b) the SAP-treated case. The SAP-treated animals showed axon regeneration through the injury site; the control animals showed no axon regeneration. Here the SAP treatment was generally found to support axon regeneration with a correlating return of functional vision.
Both of the above studies included tests of the body's toleration of the SAP solution; after an injection of the SAP solution into muscle tissue, examinations found no detectable toxic effects and no observable signs of structural abnormalities, muscle necrosis, inflammation, or motor impairment. Where the SAP solution was injected into brain tissue, no apparent inflammatory response was found; in addition, it was discovered that the amino acid degradation products of the scaffold are mostly eliminated from the body within 3-4 weeks post-injection.
Also, one important feature of the SAP scaffold is its ability to fill irregular voids (because it is a hydrogel) such as injury sites in damaged tissue. This allows close contact between the scaffold nanofibers and surrounding tissues.
References:
> J.W. Fawcett et al.:
"The glial scar and central nervous system repair" [PDF, 183 KB],
Brain Research Bulletin, 1999.
> T.C. Holmes et al.:
"Extensive neurite outgrowth and active synapse formation on self-assembling peptide scaffolds" [PDF, 522 KB],
Proceedings of the National Academy of Sciences, 2000.
> R.G. Ellis-Behnke et al.:
"Nano neuro knitting: Peptide nanofiber scaffold for brain repair and axon regeneration with functional return of vision" [PDF, 1.7 MB],
Proceedings of the National Academy of Sciences, 2003.
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Labels: engineering, science
