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Archive for May, 2010

Book review: Flight of the Dragonfly (Rocheworld)

Saturday, May 22nd, 2010

Flight of the Dragonfly (Rocheworld) by Robert L. Forward (1984). A hard sf book about a one way expedition to Barnard’s Star, the second closest star system to Earth. A team of sixteen travels to the star by way of a light sail pushed by a terawatt laser originating from Mercury. The trip takes forty years and the crew’s aging is retarded during the journey by a drug. Even with the drug, the trip is one way. One of the planets around Barnard’s Star is a Roche world–a pair of co-rotating planets close enough to share atmosphere.

The crew arrives at Barnard’s Star and first explores the moons of the largest planet, a large gas giant. This is just a teaser, as most of the book describes the exploration of the Roche world. Intelligent aliens are found, and they are friendly and quite alien in form.

The book is a bit of a mismash, and it seems too short for all the elements crammed in. First, it’s a hard sf description of the engineering of a light sail trip to a nearby star. Second, it’s a hard sf look at the exploration and potential discoveries in the Barnard’s Star system, including the bizarre and wonderful Roche double planet with it’s unique physics and geography. The first two elements here feel rushed.

The most jarring part of the book is the set up in the beginning. The description of how the crew is chosen for a lifelong expedition, and why people would choose to go isn’t realistic. The crew choice seems unbelievably cavalier and the decisions of the crew aren’t really part of the book, just papered over with ‘adventure, wheee!’.

Finally, the book is an great tale of first contact and the dangerous adventure of exploring a new planet. This is the heart of the book and is well-told. This isn’t the best written book, but it has so many unique elements that it succeeds as great hard sf.

Word cloud for Flight of the Dragonfly

Messing with digestion

Sunday, May 2nd, 2010

There are several dietary products that try to minimize the calories absorbed in the GI tract. One was a non-absorbable fat, Olestra. The fat just runs through the GI tract with a side effect of diarrhea and occasional worse effects. There are also drugs that keep fat from being absorbed: Xenical, a drug that inhibits intestinal lipase and slows the breakdown and absorbtion of fat. Alli is a low dose of the same drug available OTC.

There are also several types of fiber sold as fat-trappers. It’s not clear whether they work, but they also have the same side effects as fat blockers.

There are other ideas that have been tried. Stimulants like amphetamines work fairly well with some well known side effects. So far, drugs that mess with the regulation of appetite haven’t worked well–the regulation has too many redundant pathways.

Rather than blocking fat, how about using enzymes to breakdown either sugars or fats? The simplest approach would be to use enzymes, I’m sure suitable ones could be found, grown in E. coli, isolated and taken as gel caps. To keep the proteins from getting denatured by stomach acids, a coated or time release capsule could be used. A second step would be to engineer the enzymes to resist digestion–synonomous substitutions and so on. Another possibility would be to express the enzymes as secreted proteins in a gut bacterium–one of the ones that mainly lives in the jejunum. The bacteria could be ingested in pills the way probiotics are.

A more difficult implementation would be to non-protein enzymes to digest sugar or fat. This would be harder to engineer but likely more effective.

Which enzymes? Well, that would take some study. Likely a two or three would be needed to break down the metabolite and then waste any ATP formed.