Cycle Quark

XKCD got written up in the NY Times. I discovered from the article that the author is a physics major. I knew he had to be a geek, but physics is as good as it gets.

I don’t know, but I am seeing many attempts to answer it. The first was a study about women who were postdocs in the D-Zero collaboration which runs the D-Zero experiment at Fermilab. This study was interesting. It used a database of internal notes, conference presentations, and where postdocs went after leaving D-Zero. The conclusion was that women received fewer opportunities to present D-Zero results at conferences than equally qualified men and this hurt their ability to get faculty positions.

I read the actual study and it struck me a serious piece of work that cannot be lightly dismissed. If I understood the paper correctly, it claims that by the metric used in the study the women in the cohort were more productive than the men but were only offered faculty positions at the same rate. There was one element that struck me as odd. It limited the study to men and women who went on to faculty positions at universities. Staff scientist positions at laboratories are very comparable to faculty positions. I know of quite a number of women who are staff scientists at Fermilab. I am curious what would have happened if lab staff scientists were also studied. Do women prefer lab positions over university ones?

The second study I saw was written up in the Boston Globe. It covered science and engineering more broadly than the first one. It argues that women self select against the hard sciences and engineering.

Now two new studies by economists and social scientists have reached a perhaps startling conclusion: An important part of the explanation for the gender gap, they are finding, are the preferences of women themselves. When it comes to certain math- and science-related jobs, substantial numbers of women - highly qualified for the work - stay out of those careers because they would simply rather do something else.

One study of information-technology workers found that women’s own preferences are the single most important factor in that field’s dramatic gender imbalance. Another study followed 5,000 mathematically gifted students and found that qualified women are significantly more likely to avoid physics and the other “hard” sciences in favor of work in medicine and biosciences.

The third article was in the Fashion & Style section of the New York Times, an odd positioning for this topic. On the day that I read it there was large swimsuit ad next to it.

This article cites a study to be published in the Harvard Business Review and claims that scientific workplaces are pretty bad places for women to work.

“It’s almost a time warp,” said Sylvia Ann Hewlett, the founder of the Center for Work-Life Policy, a nonprofit organization that studies women and work. “All the predatory and demeaning and discriminatory stuff that went on in workplaces 20, 30 years ago is alive and well in these professions.”

I can’t say that I recognize this as describing anyplace I have worked. If there has been discrimination going on, it has been much more subtle like that described in the first study I mentioned.

There is a nice article in the New York Times about creating new habits. It discusses the advantage to the brain of stretching yourself to keep your mind sharp. I taught myself to use the vi editor a couple of years back just to prove to myself that I could. It was clear to me that my older colleagues were loath to learn a new editor as we switched to using Unix when I was a postdoc. I wanted to prove that I was still capable of picking up something new. It looks like this type of exercise is useful as are lots of other ones that are less technical.

“Getting into the stretch zone is good for you,” Ms. Ryan says in “This Year I Will… .” “It helps keep your brain healthy. It turns out that unless we continue to learn new things, which challenges our brains to create new pathways, they literally begin to atrophy, which may result in dementia, Alzheimer’s and other brain diseases. Continuously stretching ourselves will even help us lose weight, according to one study. Researchers who asked folks to do something different every day — listen to a new radio station, for instance — found that they lost and kept off weight. No one is sure why, but scientists speculate that getting out of routines makes us more aware in general.”

Mythbusters, Zombie Feynman and a meditation on the meaning of science. What more can you ask for?

Mahalo Daily is a short video podcast hosted by Veronica Belmont that covers a different topic everyday. One day it is hangover cures and another it is the perfect grilled cheese sandwich. Well I checked on the recent ones today and I saw that there was a podcast about SLAC. It is not as good as a real visit, but you should check it out anyway.

An article in the New York Times discusses a review by the College Board of the role of virtual laboratories in advanced placement.

“Professors are saying that simulations can be really good, that they use them to supplement their own lab work, but that they’d be concerned about giving credit to students who have never had any experience in a hands-on lab,” said Trevor Packer, the board’s executive director for Advanced Placement. “You could have students going straight into second-year college science courses without ever having used a Bunsen burner.”

I think as a pedagogical tool these virtual laboratories are a great tool. They tend to constrain the mistakes that students can make. Becoming skilled in a laboratory is an important hurdle for future scientists, but for non-scientists it the effort is probably too much work for the benefit. In a previous post I mention the advantage of doing a bunch of conservation of momentum measurements. I think simulated collisions would do a very good job at teaching the concept.

My youngest daughter is taking algebra based physics in high school. The middle one is taking AP calculus in high school, and the oldest is taking honors calculus-based physics. They are keeping me busy.

My youngest was asking me about conservation of momentum problems last night. The book did something that I liked. It did not ask for actual numerical answers, but instead asked if the available information was enough to solve the problem. For example, you know the masses and momenum of two objects before a collision and the velocity of one after the collision. Can you find the velocity of the other after the collision. After doing a few of these I instructed her to write the equation for conservation of momentum.

m₁v_1i + m₂v_2i= m₁v_1f + m₂v_2f

Now cross out each item that you know and ask if there is only one unkown left. I get to cross out both terms on the left side since I know the initial momenta and I can cross out m_1,m_2, and v_1f. I am left with just v_2f so I can solve for it.Well it turns out that writing that equation which is just second nature to me is a big stumbling block for a new student. I immediately switch to abstract thinking. There is a lot of content in my choices of labels. 1 and 2 indicate that there are two different mass objects and they can have different velocities. The i and f indicate that the velocity can change in the collision. The fact that there is no i and f on the masses means that objects do not stick to gether or fall apart.How does one encourage that conceptual leap? Do you do many concrete examples and hope the student begins to infer the abstraction or do you lead them through it?

Update: I think some experimental introduction is probably the best approach. Measure a bunch of momenta before and after a collision and see that the momentum is always conserved.

 I have long complained about the simplistic analyses given in health articles. Saturated fats are bad. Trans fats are bad. Hormone replacement therapy prevents heart attacks. Hormone replacement therapy causes heart attacks. In reality things are much more complex because of the difficulties in experimenting with living being and particularly people, it can take a very long time to sort out all of the complexities. An article today on trans fats actually pointed out the beginnings of this sorting out.

The most vocal critics of trans fats believe that the relationship between their intake and heart disease is linear. Even tiny amounts pose some threat, they say. But an interesting study by Dr. Lichtenstein suggests that it’s more complicated than that.

She and her colleagues put 36 volunteers on diets with various amounts of trans fats, then measured blood levels of L.D.L. and H.D.L. cholesterol.

Increased trans fats were associated with increased blood levels of bad cholesterol in a linear fashion, she found. But good cholesterol was significantly diminished only in subjects who consumed trans fats in the greatest amounts — nearly 7 percent of their daily calories — and even then just barely. H.D.L. was not affected in subjects consuming less.

This finding and others like it suggest that for consumers eating modest amounts of trans fat, the gain from reduced intake may not be as great as some might hope. In any event, the benefit is likely to accrue mostly for people who have elevated cholesterol to begin with. That’s one in four New Yorkers, according to the city’s health department.

“Cumulatively, this small step could have a beneficial effect,” Dr. Lichtenstein said. “But it’s not going to be a panacea.”

The boldface was added by me. I can never remember seeing a popular press article mention a linear relationship between two variables. In addition, the article goes on to point out that the linear relationship holds for LDL but not HDL.  This turns out to be very important to me since my LDL is quite good, but HDL is just outside the acceptable range. If this result is true cutting trans fats are unlikely to help me.

Scientists in England are planning to introduce human DNA into rabbit egg cells in order to learn about how to produce stem cells. They hope that this will mitigate some of the moral objections to using human eggs.

I read the preprint of CDF’s on the observation of B_s mesons. It took a remarkable amount of work. Large high energy physics collaborations have large author lists due to the large contributions made by many people to operate and calibrate the detector, simulate and process the data. But the analysis described in most papers is done by a very small group of people, usually a graduate student and his or her adviser or a postdoc.

This analysis requires the observation of B_s mesons and a measurement of their momentum and decay point. In addition it is necessary to determine whether it was produced as a B_s meson or the antiparticle. In order to get a large enough sample to be statistically significant, CDF had to use many decay modes of the B_s and some of these were only partially reconstructed, which means that one particle escaped detection which hurts the momentum resolution and can increase the background. CDF also had to use multiple techniques, called tags, to identify whether the original B_s was a particle or antiparticle.

A graduate student could be expected to do an analysis that used one tag and a small number of similar decay modes. Clearly this work had to split up among a number of people. Some of the partially reconstructed modes using leptons would require very detailed studies to understand the effect on the momentum resolution. Combining the results in the end is also a big job. Making sure that the various data samples were independent or that any correlations were understood is critical.

This is a very impressive result. Having studied B mesons for many years, I can appreciate the amount of work that must have gone into this analysis.