Archive for October, 2006

Virtual Laboratories

Posted in Education, Science on October 20, 2006 by Mike Procario

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.

Teaching Again

Posted in Education, physics, Science on October 18, 2006 by Mike Procario

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.

m1v1i + m2v2i= m1v1f + m2v2f

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 m1,m2, and v1f. I am left with just v2f 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.

Wasting Time with Outlook

Posted in Technology and Software on October 13, 2006 by Mike Procario

I use Microsoft Outlook at work because that is what is supplied. We are given a quota of 450 MB of storage on the Exchange Server. Much of my work centers around email, so I do find that I hit that limit quite easily if I do not aggressively archive my email. This of course introduces a new problem. Outlook 2002, which we are still running, only supports 2 GB archives. My primary archive hit that limit this Monday and I spent all morning cleaning up.

I had to decide on a strategy to split of the archive. Did I move all messages before some date to a different archive or did I grab a couple of big folders and move them to a new archive. I have 62 folders with some folders being nested four levels deep. The only way I know to move all messages before a particular date would be to search each folder individually for messages before some date. I chose to grab a handful of big folders and move them. I also had change the autoarchive settings so that new messaged would be archived to the new file. I ended up moving six related folders and the slowest part was the copying of the messages. It took all morning to get everything cleaned up.

Today I had to find a message that I recieved somewhere between 6 and 12 months ago. With my autarchive settings that meant it was in the archives, but which one? I knew it had to be in either of two archives so I had search both and I had to search all of the subfolders. It took over an hour.

In both of these cases, Outlook came up short compared to Google’s Gmail which I use for my personal email. Gmail would have found that email in minutes if not seconds. Even Google Desktop would have found it quickly, but my employer does not want to have all of my work email indexed on Google’s servers and I can understand why.

I would like to have all of my accessible in one heap and I would like it to be searchable in an effective way in a finite amount of time.

A Functional Relationship in a Health Article

Posted in health, Science on October 10, 2006 by Mike Procario

 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.

Frankenbunny

Posted in biology, Science on October 9, 2006 by Mike Procario

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.