The Physics Police

The Physics Police

Wednesday, July 24, 2013

Turmeric and Depression

It's bad-science-o-clock!

Efficacy and Safety of Curcumin in Major Depressive Disorder: A Randomized Controlled Trial

The study concludes:
This study provides first clinical evidence that curcumin may be used as an effective and safe modality for treatment in patients with MDD...
This is a lie, of course, because the study's flawed design makes this conclusion impossible.

Instead, it effectively tests the placebo effect, substituting a sugar pill for a pill full of turmeric.

So, what is flawed about the design? Well, the study consisted of 60 participants, in three groups of 20 people. The first group was given Prozac, the second group was given turmeric, and the third group was given both (presumably, two separate pills).

At this point, it should be immediately obvious why the title of the article is fallacious. There is no placebo control group, without which, the efficacy of turmeric, or any drug, cannot be tested. You can't call this a "controlled trial" at all. It's a "comparative study" where Prozac is pit against turmeric.

To be conducted correctly, this study would have to include a placebo group, given a sugar pill.

Because the placebo effect is so strong, there's no statistically significant difference:
The proportion of responders as measured by the HAM-D17 scale was higher in the combination group (77.8%) than in the fluoxetine (64.7%) and the curcumin (62.5%) groups; however, these data were not statistically significant (P = 0.58). Interestingly, the mean change in HAM-D17 score at the end of six weeks was comparable in all three groups (P = 0.77).
Basically, the study tests for nothing, and finds precisely that.

I guess that's what passes for science in the Government Medical College at Bhavnagar.

I'm sure it's a coincidence that this study, like turmeric itself, comes from India...

Tuesday, July 23, 2013

Local Dark Matter

I share with you this splendid example of terrible journalism:
The Incredible Dark Matter Mystery: Why Astronomers Say it is Missing in Action
This article attempts to invent a controversy where none, in fact, exists:
So astronomers are left scratching their heads. On the one hand, they say dark matter must hold our galaxy together with a vice-like gravitational grip. On the other, its gravitational effect on the Solar System is negligible. Something has to give.
This implies some contradiction between theory and experiment. There is no such contradiction!

Look no further than the physics paper cited in the news article, Constraints on Dark Matter in the Solar System, which concludes:
Our results show that the mass of the dark matter, if present, and its density are much lower than the present-day errors in these parameters.
The author of the news article (actually, a blog post, really) seems to have misunderstood the idea of a limit. In scientific parlance, a "limit" is the maximum (or minimum) amount of some measurable quantity that may exist. We get limits by doing experiments.

In this case, previous work has set maximum limits on dark matter density in the solar system. This paper sets some new limits based on several planetary orbits. Cool, new limits, yeah!

So the question remains, do these new limits contradict theories of dark matter?

The paper finds an upper limit of 1.1 * 10-20 g/cm3, whereas it's generally accepted that the dark matter density near Earth is about 0.3 GeV/cm3, or 20,000 times smaller!

M / V = (E / c2) / V = ((0.3 GeV) / c2) / (1 cm3) = 5.35 * 10-25 g/cm3

This expected dark matter density is infinitesimal compared to the new upper-limit set by the paper. That means, while the paper has gotten us one step closer to testing theory, we aren't there just yet. Experimental error is still too large to detect local dark matter.
Now astronomers say they can find no evidence of dark matter’s gravitational influence on the planets. What gives?
Yeah, what gives? I'll tell you what gives!

MIT Technology Review just got policed!

Tuesday, July 16, 2013

Arsenic Chicken

There's a drug fed to chickens called Roxarsone. This molecule contains an atom of arsenic.

A new study titled Roxarsone, Inorganic Arsenic, and Other Arsenic Species in Chicken concludes:
Conventional chicken meat had higher [inorganic arsenic] concentrations than did conventional antibiotic-free and organic chicken meat samples.
Predictably, the birdbrains have already start running around like decapitated chickens. Let's inoculate ourselves against their anti-science rhetoric, shall we?

Of foremost importance, when discussing any frightening chemical, is to consider its concentration.

Conventional chickens were found to contain 3.4 ppb arsenic.
Antibiotic-free chickens were found to contain 2.0 ppb arsenic.

EPA tolerance for arsenic in drinking water is 10 ppb.
FDA tolerance for arsenic in chicken meat is 500 ppb.
FDA tolerance for arsenic in shellfish 86,000 ppb.

So, just how much chicken breast would you have to eat, to reach the daily safe intake of 50 µg?
(50 micrograms) / (3.4 / 1 billion) = 32.4 lbs
That's more than 7 whole chickens! I think, after such a meal, I'd have greater concerns than my daily intake of arsenic...

Anyway, back in 2011, the FDA put out a press release when the company that produces Roxarsone (also called 3-Nitro) pulled it from the market. They sum up the issue nicely:
...the levels of inorganic arsenic detected were very low and that continuing to eat chicken as 3-Nitro is suspended from the market does not pose a health risk.
So the drug isn't even being fed to chickens anymore, at least, not in the USA!

Now that we have the facts, lets examine some of the birdbrained fear tactics:

Fear tactic #1: Conspiracy theory.
After years of sweeping the issue under the rug and hoping no one would notice, the FDA has now finally admitted that chicken meat sold in the USA contains arsenic...
In order to discredit any rational, scientific argument, the fear monger accuses the FDA of hiding something. The reader is then primed to distrust the scientific conclusions made by the FDA, such as the lack of danger due to the insignificance of the low levels of arsenic.

Fear tactic #2: Appeal to tribalism.
... it's just what the poultry industry wanted everybody to believe.
In order to discredit scientific consensus, the fear monger introduces an imaginary enemy, the poultry industry. Faced with this threat, the reader suspends reason, becomes reactionary, and rejects the scientific consensus, which the reader perceives as belonging to an out-group or foreign tribe. As in this example, this is best used in conjunction with conspiracy theory.

Fear tactic #2: Trigger words.
... arsenic, cancer-causing toxic chemical that's fatal in high doses.
... poisoning us with their deadly ingredients.
... vaccines containing chemical adjuvants that are injected into children.
... they're eating second-hand chicken crap.
In order to stop the reader from thinking clearly, the fear monger includes words which are likely to trigger an emotional response. Most people know someone who has died from cancer (mentioned 5 times in the article), making this an extremely effective trigger word. The words "toxic" and "chemical" (mentioned 4 times) are trigger words for people who have impaired scientific understanding.

Despite the doses in question being tremendously low, the fear monger is sure to add that bit about arsenic being "fatal" in high doses, because the alluded to threat of death is so effective at triggering the reader's emotions.

The fear monger takes every opportunity to put emphasis on "children" in order to evoke parental emotion in readers.

In the last example, the fear monger brings up feces in a conversation about food, provoking an involuntary disgust reaction on the part of the reader.

Fear tactic #3: Vicious circle.
... it's okay to eat arsenic, but dangerous to drink elderberry juice or raw milk.
... arsenic that's pooped out by the chickens gets consumed and concentrated in the tissues of cows.
The fear monger waves yarns that complete a vicious circle, or self-reinforcing narrative. In the first example above, this issue is tied together with other issues likely to cause an emotional reaction in the reader. The reader is assumed to also be outraged by the controversy over raw milk and elderberry juice. This triggers an emotional response on recall of that outrage, which suspends reason, and reinforces a narrow-minded, tribal mentality.

In other words, the reader who has already jumped on the raw milk band wagon will be biased towards agreeing with the opinion of the fear monger, because the fear monger has used the other issue to gain trust of the reader.

The second narrative draws on unnamed fear of contamination from cow meat. This is a red herring, having nothing to do with the scientific question. But it serves the fear monger by engendering their misplaced trust among a broader range of their readership. Namely, those subconsciously triggered by mad cow disease, bovine growth hormone, etc.

Don't be fooled. Don't be scared. Be smart.

Wouldn't Arsenic Chicken be a cool band name? lol

Monday, July 15, 2013

Fish Oil

Good news, everyone! I've got some terrible science to share with you. This study was published online last week by the Journal of the National Cancer Institute:
Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial
The study concludes that:
The consistency of these findings suggests that these fatty acids are involved in prostate tumorigenesis. Recommendations to increase LCω-3PUFA intake should consider its potential risks.
The conclusion means to scare people away from taking supplemental fish oils, rich in omega-3 fatty acids, by saying it causes prostate cancer.

This is a grand overstatement of their results, and almost certainly untrue.

First of all, data used are from a case-cohort study. That means, measurements of blood serum levels were taken only once per participant. It is impossible to establish causality in such a study.

If omega-3 fatty acids actually cause prostate cancer, we would expect a dose-response. But:
... there was no dose response.
Which means their conclusion is wrong. Omega-3 fats don't cause cancer. That's just silly.

Then why is there more omega-3 fat in the blood of men with prostate cancer?

Well, as it turns out, many people diagnosed with prostate cancer take fish oil supplements, because they are said to have cancer-protective properties. Fish oil as a cure-all may be cliche, but people still quaff the stuff when they are diagnosed.

In other words, prostate cancer causes a higher omega-3 levels, not the other way around!

Still, in the news, you get headlines like:
Study confirms link between ... omega-3 fatty acids and ... aggressive prostate cancer
Whenever a study is reported to confirm a "link" between two things, my hobby is to assume causality going the opposite direction as implied. That's my right as a vehement skeptic. Though, sometimes, I just yell, "correlation is does not equal causation!" over and over...

So, I've seen a complaint in response to this story which is common in the health news section:
but I thought omega-3 was good for you?
There is a tendency, with regards to health science in particular, for laypeople to engage in black and white thinking. The media will oversimplify things like omega-3 fats, coffee, or vitamins as being either good or bad, and not always consistently. The resulting contradiction is upsetting to those black-and-white-thinking laypersons.

My advice to those laypersons is to stop considering yourself a layperson! Anyone with a High School education is (theoretically) equipped to navigate the world of science. All you need is a healthy skepticism, and a motivation to be informed.

Granted, it takes a whole lot of time and effort to stay informed. (This is the story of my life.)

My goal with this blog is to demystify, debunk (when necessary), and inform. Hopefully, too, this blog will save you, the not-so-layperson, a bit of time. Maybe, also, a whole lot of effort.

Special thanks to Kurtis Frank over at Examine blog for his informative post on this topic.

Another, more detailed summary can be found here and here.

Thursday, July 11, 2013

Human-Powered Helicopter

Powered by Todd Reichert, the Atlas human-powered helicopter won the Sikorsky Prize. This achievement realizes a dream that dates back to Leonardo da Vinci's ornithopter.

Just how much power did Todd have to produce to lift the craft 3.3 meters 10 seconds?
P = mgh/t = (55 kg + 80 kg) (9.8 m/s2) (3.3 m) / (10 s) = 436 W
Todd was able to output about 890 W during the first ten seconds of a power test. That means about half of the power went into lift, which is pretty impressive.

I would have expected more energy loss due to conversion along those long drive wires, and from air drag and turbulence.

Clearly, a lot of thought went into the design.

According to this graph, lighter "healthy men" stand a good chance to lift off with this vehicle.

Makes me want to give it a try!

Oh wait, I might not be light enough...

Imidacloprid and Bee DNA

Today I read a paper titled Transient Exposure to Low Levels of Insecticide Affects Metabolic Networks of Honeybee Larvae. While the title is impressive, the experiment and conclusion are much less so.

The study examined the expression for 10,736 genes in bee larva from 6 hives. In addition to 3 control hives, 3 hives were exposed to plausible quantities (2 ppb) of a neonicotinoid insecticide called imidacloprid.

Statistical analysis found 300 genes that were differently expressed between the larva from exposed vs. control hives:

For example, the greatest difference was seen in a gene called GB19113. That sounds pretty significant, right? Let's take a look at the data:

What's up with control hive 3??

It seems to have very different gene expression going on than the rest. Probably, some accident of timing, temperature, pheromones, or wild food supply resulted in some biological process going on in there, but not in the other hives.

This begs the question, what would be the expected variance between any two hives? We get 300 statistically significant genes different expressed when we bin based on exposure vs. control. But what if we bin the larva differently? What if we bin the larva based on other permutations of their hives?

This would seem a necessary control to determine the systemic error caused by any between-hive variance. From what I know about genetics, and about bees, we might expect this variance to be quite large.

Larval development is a time in a bees life where genes involved in growth are turning on and off quite often. One bee hive might have accelerated larval breeding compared with another. This might easily have nothing to do with imidacloprid exposure in the parts per billion.

Since the authors don't supply all the data, but only the data for the 300 genes in their list, I can't calculate the extent of this systemic error.

Without knowing the systemic error, no conclusion can be reached with regard to the safety of imidacloprid use on bee populations.

Another flaw with the study is the lack of testing for dose-response. In studies of this type, it is typical to expose different doses. This allows the support of a causal relationship by correlating increased dose with increased effect.

Maybe Reinhard Stöger, the experiment's designer, hasn't heard of dose-response?

Flaws aside, this is a worthy area of research. Many studies have found imidacloprid safe, but it probably does have some effect on bees, even in small doses. It is important to measure and understand the nature of this minor stress, especially during larval development.

In the wake of the knee-jerk decision by the EU to ban neonicotinoids, science like this needs to be approached with calm and patience. Some people will take this study out of context. They will ignore the experimental flaws. They will exaggerate its conclusions, and likely amend them with more extreme claims, implying danger and mongering fear.

I trust the reader will not be fooled by any such deception.

Methane vs. Coal

Josh Fox, creator of the film Gassland, opposes fracking for many reasons. One reason is the danger that leaked or "fugitive" methane emissions will contribute to global warming. He cites the fact that methane is a more potent greenhouse gas than is carbon dioxide. This is true, but he exaggerates to make his (incorrect) point:
Methane is a super greenhouse gas. It's 100 times more potent than CO2. (Source)
First of all, the ratio of the radiative efficiency of methane to that of carbon dioxide is:
(3.7 * 10-4) / (1.4 * 10-5) = 26.4
So, it's really only 26 and a half times as "potent" as carbon dioxide.

But that doesn't even take into account atmospheric lifetime. Methane leaves the atmosphere after just 12 years, compared to the century long lifetime of carbon dioxide. So, depending on how long of a view you take, the climate forcing from some mass of methane, compared with the same mass of carbon dioxide, changes.

As you can see, taking the long view of 500+ years, methane is only 7.6 times as strong a greenhouse gas. This is the number that the planet cares about. But the 100-year time horizon is more often used by climate scientists.

Fox himself admits that methane burns "50% cleaner" (18:40) than coal; and by that, he means it produces 50% less carbon dioxide per kilowatt.

Just for fun, let's calculate this ourselves!

The molar mass of methane is 16.04 grams per mole. Each molecule of methane has one carbon atom, which, after burning, becomes part of one carbon dioxide molecule. Carbon dioxide has a molar mass of 44.01 grams per mole.

So, 16 tonnes of methane burns to create 44 tonnes of carbon dioxide. Wow, how can the waste weigh more than the fuel? Because the carbon binds to two oxygen atoms, the resulting molecule is much heavier!

How about coal? 2,000 pounds of coal will generate about 5,720 pounds of carbon dioxide. (Source)

That leaves fuel efficiency. In current power plants, 1.07 pounds of coal produces the same amount of electricity as 226 liters of natural gas. (Source)

Annoyingly, the units aren't the same, so we have to convert to pounds of natural gas:
226 liters * (0.6556 grams per liter) = 0.327 pounds
So, the ratio of carbon dioxide output from methane compared with coal is:
(0.327 * (44.01 / 16.04)) / (1.07 * (5720 / 2000)) = 0.293
The next question is leakage. The highest estimate for methane leakage is 5.75%, even though the EPA estimate is only 2.3%.

If, like most climate scientists, we use the 100-year global warming potential for methane, equal to 25, we can now calculate the global warming potential of emissions from methane compared to coal:
(100% + (5.75% * 25)) * 0.293 = 71.4%
So, Josh Fox has no right to oppose fracking on the grounds that it contributes to global warming, when you compare it to the current alternative, coal.

I will be sure to respond to his other reasons for opposing fracking once I've watched Gassland.

In any case, fracking is the lesser of two evils, in terms of carbon dioxide emissions.

But remember kids, the only good carbon dioxide molecule is a sequestered carbon dioxide molecule.

Unless you're a plant.

Monday, July 8, 2013

Cucumber Vitamins

There's a cute raw foods article floating around which claims that:
Cucumbers contain most of the vitamins you need every day
This claim has a subtle deception in it. A cucumber is part of a plant, so, of course it contains some amount of all vitamins. Vitamins are equally important plant and human cells. Whereas plants produce their own vitamins, we need to get certain vitamins from our diet.

But the title of the article implies you get all your daily value of the vitamins listed below, from some reasonable serving of cucumber. This is false.

To reach recommended daily value for any of the listed vitamins, you'd need to eat more than 7 whole cucumbers in a day! Even then, you'd only be set for Vitamin C and Potassium.

A slice of white bread has more Niacin, Thiamin, and Folate than one whole cucumber.

Now, I'm not bashing on cucumbers! I eat them tons, and you should, too.

But this article is really silly, with unsubstantiated claims like:
Take a slice of cucumber and press it to the roof of your mouth with your tongue for 30 seconds to eliminate bad breath, the phytochemcials will kill the bacteria in your mouth responsible for causing bad breath.
Yeah right.

Vitamin Cucumber1, 2 Bread1, 3 Number4
Vitamin B1 (Thiamin)5820.00
Vitamin B2 (Riboflavin)6516.67
Vitamin B3 (Niacin)15100.00
Vitamin B5 (Pantothenic acid)8112.50
Vitamin B66116.67
Folic Acid (Folate)5720.00
Vitamin C1407.14

  1: Percent daily value.
  2: Cucumber, with peel, raw (whole)
  3: Bread, white, commercially prepared (slice)
  4: Number of cucumbers you need to eat to get daily value.