December 29, 2004

New Math

From a Washington Post article, Math Educators Find Common Denominator:


The program [Everyday Mathematics] is being used in many schools across the country, including Annandale Terrace Elementary School. On a recent day at the Northern Virginia school, teacher Abigale Braun presented this problem for 21 second-graders to solve: 15+5+9=__. Then she asked them how they got their answers.

Dennis Segovia-Ramirez said he put 15 plus 5 together to make 20 and then added 9. Sarah Velegaleti said she knew 5+9 was 14 and just added 15. Laila Elahi put down 15 tally marks on her white board, then 5, then 9, and added them all up.

Braun praised them, telling them that there was no single correct method and that it was important for them to figure out the way that worked best for them.

OK, fine. There's no single correct method - although both Dennis and Sarah are using the associative property of addition [ (x + y) + z = x + (y + z) ] to solve the problem.

But Laila's method was badly wrong, even though she came up with the right answer. Counting things out the way she did is infinitely more time-consuming and prone to error. I hope that one of her parents notices and gets her math help before she falls hopelessly behind.


UPDATE: Looks like the Washington Post author may not have been providing the full story. Ms. Braun left the following in the comments:

I am the teacher whose class is featured in this article. The information in the article only represented part of the lesson. What was not included in the article was the class discussion we had about why Leila's method would not be practical. We talked about what would happen if the question was something like 43+98+65. Then it would be extremely time consuming to make tally marks, and as you stated, very prone to error. She then used the associative property to solve the problem as most of the other children did. Thank you for your comments.

So it sounds like Ms. Braun is the sort of teacher that Leila needs.

Posted by jeffreyb at 01:37 PM | Comments (1)

December 26, 2004

Is it Alzheimer's or is it Art?

From a review of "De Kooning: An American Master" in the Washington Times:

[T]here is the tragedy of de Kooning's late years. Beginning around the mid-1980s, de Kooning began exhibiting symptoms of Alzheimer's Disease. Still, he kept painting. What is one to make of these works? Are they heroic strivings in the face of diminishing capacity, a great last flowering like the cutouts of Henri Matisse? Or are they little more than a child's scrawls put down by a man groping his way through a gathering mental twilight?

As my Dad commented, if this had been Michaelangelo, you'd be able to tell.

Posted by jeffreyb at 10:19 PM | Comments (0)

December 21, 2004

Rite Aid Hostages

Looks like hostages are being held after a failed robbery attempt a few blocks from where I work.

There's a Washington Post story here.

I find it... very Washington-Postlike that a story about a "hostage situation" leads and closes with its impact on local traffic.

Update: As it turns out, there weren't any hostages, or hostage-takers. MPD spent many hours surrounding an empty store, the bad guys having evidently departed immediately after the robbery.

Posted by jeffreyb at 11:55 AM | Comments (0)

December 14, 2004

Chicken genome sequencing, condensed

Here are the main points from the chicken genome sequencing articles below.


  • The chicken is both the first bird to be sequenced and the first agricultural animal to be sequenced.
  • It's a nice middle point between the us mammals (humans, mice, chimps) that have been sequenced, and the much more distantly related plants, fish, and fungus.
  • The chicken genome is much smaller than the mammalian. This is mainly due to reduced duplication and "junk" DNA.

    "The nearly threefold difference in size between the chicken and mammalian genomes reflects a substantial reduction in interspersed repeat content, pseudogenes and segmental duplications within the chicken genome."
    ...
    "There is a paucity of retroposed pseudogenes in the chicken genome, in contrast to mammalian genomes, greatly simplifying the classification of chicken gene content."

    I saw someone positing that the relatively small chicken genome was due to the more stringent weight requirements posed for birds by the needs of flight. Given that the sum total weight of all the DNA in a human is so ridiculously small, this theory strikes me as a non-starter.
  • The chicken sequenced was a Burmese Red Jungle Fowl hen. The Jungle Fowl is believed to be the ancestral species from which all domestic chickens derived; thus it was the best representative.

    Why a hen? Well, as any poultry fan knows, hens are the heterogametic sex in chickens. The female chicken has two different sex chromosomes, Z and W. Roosters have two copies of Z. This is the reverse situation from humans, where females are XX, and males are XY.

  • "Rare as hen's teeth" is going to be a valid saying without some serious genetic engineering of the chicken. Chickens are have no genes for the enamel required. You won't be able to milk chickens either -- no genes for casein milk proteins exist.
  • Transposition is evidently uncommon in the chicken. Transposition occurs when sections of the genome "jump" from one position in a chromosome to another, or even to a different chromosome entirely. Chicken genes pretty much seem to stay put. See above comments relating to the efficiency of chicken DNA.

Posted by jeffreyb at 11:37 PM | Comments (0)

December 09, 2004

Chicken Genome Sequenced

Today is a day that will go down in poultry history. The chicken genome has been sequenced by the International Chicken Genome Sequencing Consortium. Results have been published in the journal "Nature". This is dynamite stuff.

The paper is entitled Sequence and comparative analysis of the chicken genome provide unique perspectives on vertebrate evolution.

Additional articles are A genetic variation map for chicken with 2.8 million single-nucleotide polymorphisms and A physical map of the chicken genome

The National Institutes of health is hosting a Chicken Genome Resources page, with all kinds of information and links to data. BLAST away!

Several of the news articles I've seen off of Google News are disagreeing with each other on the particulars. I'll spend some time with the papers and do my best to give an accurate summary later.

Posted by jeffreyb at 09:35 PM | Comments (0)