Category: Sci general


The artificial sweetener aspartame is about 200 times sweeter than sugar. It is widely consumed in large quantities–diet sodas contain 140-185mg per 12 oz., so a person drinking a lot of diet soda may consume a gram a day. The FDA recommends 40mg per kg body weight as a safe daily dose–about 2 grams per day for a average sized person.

In the human gut aspartame breaks down into three components: two amino acids, phenylalanine and aspartic acid, and methanol. Phenylalanine and aspartic acid, being amino acids, are a normal part of the human diet. Methanol is absorbed from the gut and converted by the liver to into formaldehyde and formic acid, both nasty but non-specific poisons. In the small amounts formed from aspartame they are thought to not be dangerous. Some foods, some normal body processes, and alcohol consumption produce methanol, though I don’t have figures as to how much.

There has been some controversy over whether aspartame is safe. There have been a few studies showing some cancer risk in animals, three recent mouse studies from Soffritti et. al. being the most convincing. Any cancer risk is thought to come from the methanol. Recent studies in animals seem to running about 10:1 no cancer:cancer. As aspartame has been in food for thirty years, there have been some large human studies, and none of them show increased cancer due to eating aspartame.

Here are American Cancer Society and National Cancer Institute pages assessing aspartame.

The other concern brought up is whether the phenylalanine and aspartic acid that aspartame breaks down into have an effect on the nervous system. In addition to being used for making protein, these amino acids are also feedstock for making catecholamine neurotransmitters. There is some evidence that a large ingestion of these two amino acids alone might throw off normal neurotransmitter levels. It’s not clear what, if any, effect this has on human brains–it clearly has no striking consequence. Any effect is of course relative–aspartame is often consumed with caffeine, a substance that clearly effects brain function. :)

This 2008 review article makes a number of alarmist suggestions but has almost no actual evidence. It’s a very odd article. A large human dose of aspartame is about 1 gram a day. The RDA for protein consumption is 0.8 g / kg day, which contains about 2 grams of phenylalanine and aspartic acid. Not all foods have an even balance of amino acids, so animals must have fair ability to buffer a diet rich in one or another.

Aspartame has been well-studied and is safe. It is still being studied–it may turn out to be a very weak carcinogen, too weak to show up clearly in the studies so far. Or have a subtle effect that screws up the rare person’s brain. Risks are relative–aspartame is certainly much better for a person’s health than the sugar it replaces. On the other hand, you can’t go wrong drinking water.

How big is a nanobot?

Nanobots are miniature molecular machines. So far they are just an idea as no one knows how to design or build one. But there is discussion of them, and certain properties be considered. For example, how big is a nanobot?

A ‘simple’, dumb miniature machine could be quite small, for example an antibody attached to a viral-like particle that binds to particular cells, get absorbed by the cell and opens to release the DNA into the cell. But that’s not a very interesting machine, the really interesting nanobots are miniature robots with sensors, computer logic to make decisions, and hands to grab or manipulate things.

So what’s the minimum size for a smart nanobot? It has 100,000 bytes of memory, 1,000,000 bits, and 10 atoms/bit. Let’s figure the same number of atoms for the computer logic. Add an equivalent number for energy storage and generation, structure, sensors, and manipulators. Thirty million atoms in total.

If it is mostly carbon, atoms will be 1 Å apart. Assume a spherical shape, and look at protein structures to estimate packing of atoms in a compact structure. From this, the core of the nanobot will be an estimated 1000 Å or roughly 100 nm.

An E. coli is roughly 1 &#181m long, so a nanabot would be a about a 1/10 the size of a bacteria. This is small, about the size of an average virus particle, small enough to exist inside cells. A nanobot is large enough to be recognized and engulfed by immune cells, and to need a specific mechanism to enter cells.

T4 bacteriophage

Parasitic diseases are common in the eastern Kentucky Appalachian region. This is one of the topics of a report in June 2008 PLoS Neglected Tropical Diseases.


The diseases mentioned, Strongyloidiasis and Ascariasis, are parasitic nematode infections!

Strongyloides stercoralis
Strongyloides stercoralis
Ascaris lumbricoides
Ascaris lumbricoides
Here is a diagram of the Strongyloides lifecycle from the CDC:

Strongyloides LifeCycle

And the Ascaris lifecycle. The Ascaris worms are huge, 20-49 cm long!

Ascariasis LifeCycle

Wind power!

Two recent posts on the look at the question of wind power. The first post looks at the how practical it is to fit wind power into the US power grid. The main problem with wind power are that sometimes the wind doesn’t blow, so the power grid has to have excess generating capacity to meet the demand. Critics say that because of the ‘no blow’ times, wind power can’t replace base capacity, so even if lots of windmills get installed, the US still needs all the coal, nuclear, and gas power plants.

The article considers the problem and concludes if wind farms are spread out and high capacity transmission lines are built to pool the power wind farms should be able to provide base power at about a quarter of the total installed windmill capacity. The power grid should be able to accommodate somewhere between 25% to 50% of US power coming from windmills.

‘Smart grid’ capability, having devices like A/C that temporarily shut off when demand is too high is also an option. Wind power is also nicely complementary to hydroelectric generation, as a dam stores power and the turbines can be spun up and down quickly as average wind strength varies.

The other article looks at the cost of wind power and at whether anything limits the prospect of building lots of windmills today. There appear to be no resource that constrains windmill production. Today windmills are cheaper than anything but coal in the US, and modest carbon taxes would make wind power the cheapest power source:

Cost of different power sources

It is time to build windmills, and lots of them!

Pepper spray antidote

Pepper spray has been around for years now, but there is not commonly available antidote. And we know how the active ingredient, capsaicin acts to active, or hold open, the ion channels that transduce pain signals. In fact, a quick Google shows that capsaicin binds and activates a receptor called the vanilloid receptor subtype 1 (VR1), a member of a group of related receptors called TRP ion channels that are activated by temperature changes.

Capsaicin chemical structure
Capsaicin chemical structure (from Wikipedia)

So an antidote would be an inhibitor of the VR1 receptor, and such a thing should be easy to find, or create, and in fact another Google shows that several have been created. Capsazepine was the first inhibitor discovered, way back in 1994. Activators and inhibitors of this receptor have many potential uses as analgesics and anti-inflammation compounds so there is a lot of research interest.

Capsaicin inhibitor capsazepine (from Wikipedia)

A spray containing one of these inhibitors should be an effective antidote for pepper spray. But surprisingly no such inhibitor is available! The small quantities of purified inhibitors are available in small quantities for research purposes (i.e. capsazepine, 50mg for $455 but I can’t find anyone who has made an antidote preparation. This should be safe and fairly easy. Safe, because it would be applied mainly externally, and because pepper spray is itself fairly safe–aside from the pain and shock it is used to cause. It doesn’t have other, non-specific side effects. And relatively easy to make because the literature describes the synthesis of inhibitors from capsaicin itself. So the starting product used to make an inhibitor can be capsaicin, and capsaicin is readily available in large quantities!

Wikipedia: Discovery and development of TRPV1 antagonists

A variation on windmill design

Neat idea for ocean multi-stage windmills, a design by Selsam called SuperTurbines.

They think the design has advantages over single static windmills:

Like a flock of geese, each rotor favorably affects the next in line. Like a set of louvres, the tilted rotors pull in fresh wind from above, deflecting their wakes downward to insure fresh wind for succeeding rotors and, like a stack of kites, to add overall lift which helps support the driveshaft against gravity and downwind thrust forces. The rotors act as gyroscopes or spinning tops, stabilizing the driveshaft where they are attached.

Selsam ocean superturbine

No prototypes made so far.

The Late Discovery of the Gorilla

I read today that gorillas weren’t known to people in the West until 1847 when Thomas Staughton Savage described the gorilla from skeletons he obtained. And it wasn’t until later, in 1861 that Paul du Chaillu sent back specimens to England, and the general public became aware of them.

I hadn’t realized that gorillas were discovered in the West so recently. So many fundamental, basic things about the world were first understood in the 1800s. Scientifically it was a time of much greater change than any time before or since.

Chimpanzees and orangutans were sent to Europe in the 17th century. It sounds crazy, but the relationship of humans/chimps/gorillas (human-chimp closest, gorillas more distantly related) wasn’t definitively established until molecular biology techniques were applied in the 1970s! I wonder what Africans thought about chimps and gorillas, and their relationship? I think their ranges overlap in West Africa.

When did scientists become aware of global warming?

In 1997, the Kyoto Protocol agreement to reduce green gases was signed by 30+ nations including (as best I can tell) all the Western countries except the US. So it was clear in 1997 that the world was warming and green house gas emissions needed to be reduced, but *when* exactly did scientists figure this out?

My memory of the issue with a little proding stretches back to the 1992 climate agreement signed by George HW Bush, officially called the U.N. Framework Convention of Climate Change. It called on countries to cut green house gas emissions but didn’t set binding targets. So global warming was understood back in ’92, and must have been known about years earlier for political action to have been taken then. I didn’t know about research earlier than the 1970s modeling research.

A great talk laying out the history of global warming science by historian Naomi Oreskes is on the web:

She lays out a number of landmarks. She gives an interesting talk–I’ve pared it away and just list the landmarks here:

  • 1931, E. O. Hulbert, increasing atmospheric CO2 2-3X will lead to 4-7°K increase in world temperature.
  • 1938, G. S. Calender, increasing CO2 leading to increased temps, 1880-1930s
  • 1957, Suess and Revelle paper pointing out that dumping back into the atmosphere over a few decades CO2 stored over millions of years in coal and oil could heat up the world. Calls for detailed research into the world CO2 budget–where will the CO2 go, and what secondary effects will there be?
  • 1964, NAS committee warns of “inadvertent weather modification” caused by CO2 from burning fossil fuels.
  • 1965, Keeling, about 1/2 of CO2 from burning fossil fuels will end up in the atmosphere.
  • 1965, President’s Science Advisory Committee, Board on Environmental Pollution, by 2000 there will 25% more CO2 in the atmosphere and marked and uncontrollable changes in climate could occur.
  • 1979, JASON committee reports that predicted increases in atmospheric CO2 will increase world temperature 2.4°C or 2.8°C (two different JASON models). Further, the increase will be much greater at the poles, 10-12°C [Now observed].
  • 1979, Charney report summarizes climate science “If CO2 continues to increase, [we] find no reason to doubt that climate changes will result, and no reason to believe that these changes will be negligible.”
  • 1988, IPCC created to study climate and suggest solutions.
  • 1988, US National Energy Policy Act, “to establish a national energy policy that will quickly reduce the generation of CO2 and trace gases as quickly as is feasible in order to slow the pace and degree of atmospheric warming…to protect the global environment.”
  • 1992, U.N. Framework Convention of Climate Change
  • 1997, the Kyoto Protocol

Hydroponics solution

I’m going to make up my own hydroponics solution. Looking around the web it is hard to find a site with a recipe.

Here’s one at U of Wisconsin-Madison:

0.4 NH4H2PO4; 2.4 KNO3; 1.6 Ca(NO3)2; 0.8 MgSO4; 0.1 Fe as Fe-chelate; 0.023 B as B(OH)3 [boric acid]; 0.0045 Mn as MnCl2; 0.0003 Cu as CuCl2; 0.0015 Zn as ZnCl2; 0.0001 Mo as MoO3 or (NH4)6Mo7O24; Cl as chlorides of Mn, Zn, and Cu (all concentrations in units of millimoles/liter).

Good information from UIUC

and USD.