 | Belltown Crane Erection: in 1999 a new apartment building was built right outside my apartment window in Seattle's Belltown. I happened to be home the day they erected the tower crane and I made a time-lapse movie of the 14-hour process. |
 | My Mother the Car: A video from April 2008 in our Seattle kitchen |
 | The Bed Cave: A video from April 2008 of the girls playing in our Seattle house |
 | New Swing Set: from June 2008. While the girls were visiting grandparents I assembled the new swing set. When they got out of the car from the trip home they jumped right on. |
 | Thomas Stop-motion: a stop-motion animation experiment from March 2008. |
 | Scared Bot: a robot I built with LEGO Mindstorms in June 2008. It is afraid of everything. |
Sunday, April 17, 2011
New Old Videos
I recently received notice that Google Video is moving from dormancy to complete shutdown, so I had to rescue some old videos and move them to my current video host: Vimeo. I thought methot.net readers might like to take a little trip down memory lane.
Thursday, April 7, 2011
Fairies and Birds
On March 20 we visited the Wenham Museum for a workshop run by fabric artist Elizabeth Golz Rush. She provided kits she had prepared and the girls (about a dozen were in attendance) assembled the dolls and then decorated them as they wished. Audrey and Charlotte loved it.
Neither Carol or I felt like fighting the hair-brushing battle on the way out the door, but then we were a little embarrassed to have girls with rats' nest heads. Especially with one of the museum volunteers taking photos. Oh well. Live and learn.
After the workshop we wandered around the museum. There was a wonderful temporary exhibit of miniature houses. And a very cool permanent exhibit of dolls, doll houses and doll clothing. There was also a very small photography exhibit that included two film cameras that kids could handle. I tried explaining the concept of "film" to the girls but I don't think it really sunk in.
By then we were hungry and headed to the town of Hamilton very nearby for some lunch. In the Boston area there is a particular kind of casual food joint. They all have the same menu (pizza, subs, gyros, maybe spaghetti) and in fact they all have the exact same physical menu (example). The Hamilton House of Pizza was typical. And good.
The towns of Wenham and Hamilton border the south edge of the Ipswich River Audubon Sanctuary (which by now you know has become our favorite place) so we headed there next. We had finally bought our own bird seed after relying on the generosity of others on previous visits so we were excited to try it out.
Upon our arrival, though, we first of course had to visit the Rockery - the 50' tall pile of washing-machine-size boulders that were arranged 100 years ago into an artificial mountain with stairs and paths and a grotto. Unfortunately, the paths were all still covered with compacted snow and ice (the Rockery is very shaded) and it was treacherous. So we went off on a hike instead.
We often go geocaching for fun. I had discovered that there was a fairly new cache in the sanctuary so we set off toward that. Along the way we found a spot near the Old Stone Bridge where the birds were especially hungry. We fed them for a long time. Then I finally coaxed the girls to continue on to the cache. We had to travel down a trail that was new to us, along an esker. There was a cold wind blowing off the marsh, so we hurried along. We found the cache, and we also found a very friendly nuthatch so Audrey spent some time feeding him (they are much more shy than the chickadees). Then we found another new trail that was a shortcut back to the car. A very fun day.
Neither Carol or I felt like fighting the hair-brushing battle on the way out the door, but then we were a little embarrassed to have girls with rats' nest heads. Especially with one of the museum volunteers taking photos. Oh well. Live and learn.
After the workshop we wandered around the museum. There was a wonderful temporary exhibit of miniature houses. And a very cool permanent exhibit of dolls, doll houses and doll clothing. There was also a very small photography exhibit that included two film cameras that kids could handle. I tried explaining the concept of "film" to the girls but I don't think it really sunk in.
By then we were hungry and headed to the town of Hamilton very nearby for some lunch. In the Boston area there is a particular kind of casual food joint. They all have the same menu (pizza, subs, gyros, maybe spaghetti) and in fact they all have the exact same physical menu (example). The Hamilton House of Pizza was typical. And good.
The towns of Wenham and Hamilton border the south edge of the Ipswich River Audubon Sanctuary (which by now you know has become our favorite place) so we headed there next. We had finally bought our own bird seed after relying on the generosity of others on previous visits so we were excited to try it out.
Upon our arrival, though, we first of course had to visit the Rockery - the 50' tall pile of washing-machine-size boulders that were arranged 100 years ago into an artificial mountain with stairs and paths and a grotto. Unfortunately, the paths were all still covered with compacted snow and ice (the Rockery is very shaded) and it was treacherous. So we went off on a hike instead.
We often go geocaching for fun. I had discovered that there was a fairly new cache in the sanctuary so we set off toward that. Along the way we found a spot near the Old Stone Bridge where the birds were especially hungry. We fed them for a long time. Then I finally coaxed the girls to continue on to the cache. We had to travel down a trail that was new to us, along an esker. There was a cold wind blowing off the marsh, so we hurried along. We found the cache, and we also found a very friendly nuthatch so Audrey spent some time feeding him (they are much more shy than the chickadees). Then we found another new trail that was a shortcut back to the car. A very fun day.
Charlotte & Dad One-on-One Day
Back in mid-March Audrey and Carol had a plan to go skiing with a friend for his birthday. He ended up canceling because he was sick, but Carol and Audrey went anyway. So Charlotte and I had a one-on-one day.
We started by going ice skating at the local public rink. Charlotte was nervous at first and used a milk crate, but after about half an hour she put the crate away and skated all on her own. She was even doing some turns in place! It took me a while to get my skating legs back but it came to me. It was also my first time on hockey skates and I decided I like them better than figure skates.
After skating for more than an hour we went and refueled with donuts. Charlotte got pink sprinkles, of course.
Then we drove to the T and rode it into town to visit the Children's Museum. I had never been and Charlotte had only been once. We had two hours until closing and it went by very quickly. There is a huge climbing structure in the main entrance area. Charlotte was tentative at first and would only climb up to about 6 feet off the floor. But I pointed out that she couldn't really fall anywhere and she started pushing her boundaries. Before you know it, she was climbing all the way to the top - three stories off the floor. After that she couldn't get enough and she went all the way down and back up three more times.
That used up at least half of our time before closing, so I coaxed Charlotte out of the tower and we explored a few other areas. She got to light up some lights by pedaling a bike and she got to ride in a vertical rail chair that I could raise and lower with a rope and pulleys. The we chased each other around a boat playground area.
We definitely didn't get enough time there and have to return. I finally broke down and bought a membership so we'll go there often.
The girls hardly ever get solo time with a parent. Carol and I decided we'll make it a regular occurrence: every couple of months we'll swap kids and take them off by ourselves on an adventure.
By the way, Carol and Audrey had a great time skiing but Carol was having so much fun she didn't take many photos.
We started by going ice skating at the local public rink. Charlotte was nervous at first and used a milk crate, but after about half an hour she put the crate away and skated all on her own. She was even doing some turns in place! It took me a while to get my skating legs back but it came to me. It was also my first time on hockey skates and I decided I like them better than figure skates.
After skating for more than an hour we went and refueled with donuts. Charlotte got pink sprinkles, of course.
Then we drove to the T and rode it into town to visit the Children's Museum. I had never been and Charlotte had only been once. We had two hours until closing and it went by very quickly. There is a huge climbing structure in the main entrance area. Charlotte was tentative at first and would only climb up to about 6 feet off the floor. But I pointed out that she couldn't really fall anywhere and she started pushing her boundaries. Before you know it, she was climbing all the way to the top - three stories off the floor. After that she couldn't get enough and she went all the way down and back up three more times.
That used up at least half of our time before closing, so I coaxed Charlotte out of the tower and we explored a few other areas. She got to light up some lights by pedaling a bike and she got to ride in a vertical rail chair that I could raise and lower with a rope and pulleys. The we chased each other around a boat playground area.
We definitely didn't get enough time there and have to return. I finally broke down and bought a membership so we'll go there often.
The girls hardly ever get solo time with a parent. Carol and I decided we'll make it a regular occurrence: every couple of months we'll swap kids and take them off by ourselves on an adventure.
By the way, Carol and Audrey had a great time skiing but Carol was having so much fun she didn't take many photos.
Friday, April 1, 2011
What the heck are all those different units of radiation?
If you've been reading very much press about the ongoing nuclear disaster in Japan, then you have likely been confused by the wide variety of units in which radiation measurements are reported. I was. Yesterday I spent some time reading various Wikipedia articles (see links in text below) and organized the information into a guide that I hope is useful for someone with moderate scientific knowledge.
There are three aspects of radiation that are measured by various units: what is happening in the radioactive material; what exposure does a nearby object experience; and if that object is a living organism what biological effects does that exposure produce.
The material is undergoing radioactive decay. Unstable isotopes are decaying and emitting alpha particles, beta particles and gamma rays (there are other forms of ionizing radiation but these are the ones of concern with regard to nuclear fuels and their by-products).
There are three aspects of radiation that are measured by various units: what is happening in the radioactive material; what exposure does a nearby object experience; and if that object is a living organism what biological effects does that exposure produce.
The material is undergoing radioactive decay. Unstable isotopes are decaying and emitting alpha particles, beta particles and gamma rays (there are other forms of ionizing radiation but these are the ones of concern with regard to nuclear fuels and their by-products).
The most basic measurement is the total number of disintegrations occurring per unit time in the material:
1 becquerel (SI unit) = 1 disintegration/second
1 curie (traditional unit) = 37 billion disintegrations/second
The emissions are in all directions. At a detector the most basic measurement is Counts Per Minute (CPM): the total number of disintegrations (alpha particles, beta particles and gamma rays) arriving at the detector. Keep in mind that the detector does not typically completely surround the source, so CPM is only the emissions that reach the detector.
Emissions encountering an object accumulate in that object and add up to "exposure". Exposure units have a complicated history and taxonomy.
A roentgen (traditional unit) is "the amount of radiation required to liberate positive and negative charges of one electrostatic unit of charge (esu) in 1 cm³ of dry air at standard temperature and pressure (STP). This corresponds to the generation of approximately 2.08×109 ion pairs." Use of roentgen units is now discouraged.
A rad (traditional unit) is "the dose causing 0.01 joule of energy to be absorbed per kilogram of matter"
1 roentgen = 1 rad, approximately.
A gray (SI unit) is "the absorption of 1 joule of radiation energy per kilogram of absorbing material". 1 Gy is approximately equal to 115 roentgens.
The effect of the radiation exposure on the object depends on the composition of the radiation (the proportion of alpha, beta and gamma radiation) and the object's material. So subsequent units use a conversion factor ("quality factor", Q) that reflects the biological effects on humans. Q ranges from 1 for x-rays, gamma rays and beta particles to 10 for neutrons to 20 for alpha particles.
A rem ("roentgen equivalent in man", traditional unit) is a measure of "radiation dose equivalent" and is the product of the quality factor times rads (or roentgens).
rems = Q x rads
The SI unit of radiation dose equivalent is the sievert. 1 sievert (SI unit) = 100 rems.
But that's just a measurement of energy absorbed adjusted for biological effect on human tissue without regard to duration of exposure. One could absorb a given amount of energy in a minute or in a lifetime. The Wikipedia sievert article lists doses for single events like dental x-rays as well as dose/time examples such as average background radiation exposure for an American resident per year.
The sievert article also gives symptom benchmarks:
1 becquerel (SI unit) = 1 disintegration/second
1 curie (traditional unit) = 37 billion disintegrations/second
The emissions are in all directions. At a detector the most basic measurement is Counts Per Minute (CPM): the total number of disintegrations (alpha particles, beta particles and gamma rays) arriving at the detector. Keep in mind that the detector does not typically completely surround the source, so CPM is only the emissions that reach the detector.
Emissions encountering an object accumulate in that object and add up to "exposure". Exposure units have a complicated history and taxonomy.
A roentgen (traditional unit) is "the amount of radiation required to liberate positive and negative charges of one electrostatic unit of charge (esu) in 1 cm³ of dry air at standard temperature and pressure (STP). This corresponds to the generation of approximately 2.08×109 ion pairs." Use of roentgen units is now discouraged.
A rad (traditional unit) is "the dose causing 0.01 joule of energy to be absorbed per kilogram of matter"
1 roentgen = 1 rad, approximately.
A gray (SI unit) is "the absorption of 1 joule of radiation energy per kilogram of absorbing material". 1 Gy is approximately equal to 115 roentgens.
The effect of the radiation exposure on the object depends on the composition of the radiation (the proportion of alpha, beta and gamma radiation) and the object's material. So subsequent units use a conversion factor ("quality factor", Q) that reflects the biological effects on humans. Q ranges from 1 for x-rays, gamma rays and beta particles to 10 for neutrons to 20 for alpha particles.
A rem ("roentgen equivalent in man", traditional unit) is a measure of "radiation dose equivalent" and is the product of the quality factor times rads (or roentgens).
rems = Q x rads
The SI unit of radiation dose equivalent is the sievert. 1 sievert (SI unit) = 100 rems.
But that's just a measurement of energy absorbed adjusted for biological effect on human tissue without regard to duration of exposure. One could absorb a given amount of energy in a minute or in a lifetime. The Wikipedia sievert article lists doses for single events like dental x-rays as well as dose/time examples such as average background radiation exposure for an American resident per year.
In most countries the current maximum permissible dose to radiation workers is 20 mSv per year averaged over five years, with a maximum of 50 mSv in any one year. This is over and above background exposure, and excludes medical exposure.
The sievert article also gives symptom benchmarks:
Symptoms of acute radiation (dose received within one day):[20]
- 0 – 0.25 Sv (0 – 250 mSv): None
- 0.25 – 1 Sv (250 – 1000 mSv): Some people feel nausea and loss of appetite; bone marrow, lymph nodes, spleendamaged.
- 1 – 3 Sv (1000 – 3000 mSv): Mild to severe nausea, loss of appetite, infection; more severe bone marrow, lymph node, spleen damage; recovery probable, not assured.
- 3 – 6 Sv (3000 – 6000 mSv): Severe nausea, loss of appetite; hemorrhaging, infection, diarrhea, peeling of skin,sterility; death if untreated.
- 6 – 10 Sv (6000 – 10000 mSv): Above symptoms plus central nervous system impairment; death expected.
- Above 10 Sv (10000 mSv): Incapacitation and death.
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