Blog: Science

Most of these posts were originally posted somewhere else and link to the originals. While this blog is not set up for comments, the original locations generally are, and I welcome comments there. Sorry for the inconvenience.

Things I learned on the way to looking up other things

2016-10-09 from Dreamwidth

Tags: Life, Science

I forget how I got there, but I recently found two interesting posts about my curious-but-not-very-useful "superpower". This Guardian article (from 2002) talks about animals (and people) that can see into the ultraviolet spectrum. Did you know that raptors can see into the UV? Do you know why that's important? Because rodents -- that is, prey -- emit urine trails, and urine is visible in the UV spectrum (as anybody who's tried to find and clean pets' urine stains knows).

And then there's this fascinating post from someone who sees into the UV (due to aphakia), in which he describes and shows what he sees and talks about some cool testing he did. It's hard to evaluate such things when monitor calibration is in play (do you see what I do on my monitor? probably not), but it looks like "black lights" are lighter and more purple for him than for me.

One of the ways he tested the bounds of his vision was with a simple prism. I never thought of that. Now, where can I find a prism? :-)

A belated answer and a new puzzle

2013-05-08 from Dreamwidth

Tags: Science

I don't have any lenses in my eyes. Some time back, somebody asked me what keeps my aqueous humor from mingling with my vitreous humor, since the lens usually does that. (These are two different kinds of fluid in the eye.) I wondered if they combined, or if they had different viscosities (like oil and water) and so naturally separated, or what. This morning I finally remembered to ask my ophthalmologist.

Her answer was that it's basically the latter; the aqueous humor is watery (and, by the way, exits through a duct that is often the source of glaucoma problems -- it gets plugged up, raising intra-ocular pressure), while the vitreous "has the consistency of egg whites". However, she said, the vitreous thins out as we age; parts break off and become floaters (yup, got some of those...), and it tends to liquify. So yes, in my case they'll eventually blend, and perhaps they are already. But, she said, this doesn't actually hurt anything; both exist primarily to supply nutrients to the eye and they'll keep doing that regardless. Apparently the different parts of the eye can eat each others' food, or something. (That's my conclusion, not something she said directly.)

She seemed pleased to be able to answer a question more advanced than "do I need new glasses", too. :-)

And now the new "puzzle": I wonder why the eye chart, the set of letters you read on every visit to measure your distance vision, is always the same. I understand why it was, back in the days of paper charts. But now it's all digital -- yet, on every test, it's the same set of letters on each line, in decreasing size as you go on. I have to work pretty hard to avoid memorizing this so it'll be a fair test, since I see my doctor a few times a year (not just once a year like many people). I understand why they want to have a certain mix of letters; I'm sure it's quite intentional that they use a G that can be mistaken for a C, or an F that can be mistaken for a P, and so on. But why not mix it up? Is it important that the F be on the 20/40 line and the G on the 20/50 line and so on? In the same order?

I didn't ask that question.

Natural beauty

2011-06-06 from Dreamwidth

Tags: Science

The description "midnight solar eclipse" (wait, how does that work?) got me to click through on Astronomy Picture of the Day a couple days ago. Wow, gorgeous!

Unusual galactic representation

2011-01-19 from Dreamwidth

Tags: Science

Today's entry at Astronomy Picture of the Day introduced me to the Galaxy Garden, a detailed representation of our galaxy in foliage form (1 foot = 1000 light years). Nifty! It has some very nice touches, like the gravity well at the center. If I should ever find myself in Koma I want to go take a closer look.

Medicine, drop size, and vampire blood

2009-10-18 from Dreamwidth

Tags: Work, Science, Life, Humor

A recent mailing from my employer's department of reducing health-insurance costs (that's probably not their real name) offered some advice that seemed questionable to me. They suggested splitting pills -- not, they hastened to point out, that we should take half the dosage we need, but rather, we should get pills that are twice as strong as they need to be and then split them. They suggested that a stronger drug doesn't necessarily cost any (or much) more to fill, so you can fill your prescription half as often, saving you half the copay and them a lot on the balance. (Aside: what bright person decided that your cost, if insured, should be per month rather than per some volume? If I take a medicine twice as often as you do, why shouldn't I pay twice as much for it?)

I wonder how the pill-splitting scheme could actually be implemented legally and what doctor or pharmacist would go along with it. I find it hard to believe that a large company would advise its employees to commit insurance fraud (in a manner that's traceable), so there must be a way to do it, but I'm puzzled. (The company self-insures; maybe that's why it's ok?)

I was telling this to Dani last night, and commented that even if it's kosher I can't benefit from it for my prescriptions -- the medicine I take for glaucoma is in the form of eyedrops, and I don't know how to get double-sized drops. (Nor am I going to ask my ophthamologist to write a bogus prescription.) This, combined with some recent TV viewing, led us to wonder how big a drop is, anyway. We didn't have an internet connection to hand; Dani tried to work it out theoretically while I tried to work it out empirically. (Things often fall out that way with us.) A medicine that I take once a day (two drops) comes in a 2.5ml bottle and lasts about a month (maybe a little more). Viscosity matters, of course; this stuff is closer to water than to syrup. So I posited about 25 drops/ml for my medicine. (Google later suggested 20 drops/ml of water as an approximation.)

And that's when we turned our attention to the amount by which a character in the True Blood episode we'd just watched overdosed. The character had a quarter-ounce vial of an illegal substance (vampire blood) that he was supposed to take one drop of at a time. Wikipedia tells me that the viscosity of normal blood is about three times that of water. It has no data on vampire blood. Assuming (and I don't know if that's valid) that drop size is directly correlated with viscosity, this suggests that the character overdosed by a factor of approximately 46. Ouch. :-) (Yes, it did hurt.)

Ok, fine -- what have you done with your science education lately? :-)

There is a lot of interesting discussion in the comments, including comments from pharmacists.

Interesting visualization

2009-07-02 from Dreamwidth

Tags: Judaism, Science

I just came from an interesting demonstration called a "cosmic walk". (People who were at NHC last year might have seen this there. I saw only its after-effects then.)

The presenter laid out a long rope in a spiral, maybe 8-9 feet across with spacing around a foot. (I'm too lazy to do that math.) Each eighth of an inch represents 1.5 million years. There is a pillar candle in the center and about 30 tea lights at designated places along the rope.

As one person walked the spiral lighting candles the presenter narrated. The pillar candle is the big bang, followed nearly immediately (the candles are too big to be accurate) by the formation of the universe. The progression then goes through various highlights -- the emergence of the first stars (much bigger than our current ones), the emergence of elements other than hydrogen and helium, the first cell, and so on up through the formation of land, contintental drift, the rise and fall of the dinosaurs, the rise and fall of mega-fauna, etc, ultimately leading to the emergence of homo sapiens. The presentation mapped this to the days of creation in B'reishit. (The narration continued on with milestones way too close together to be represented as candles, by the way.)

What partcularly struck me with this was the clustering. I'm sorry I wasn't in a position to take a picture. After the initial flurry there are long stretches, billions of years, where nothing happens. (You could argue that the presenter chose the points to mark, but I -- not a scientist, to clarify -- did not notice any missing.) And then, around the time of the dinosaurs, things start happening very quickly; the last dozen candles (maybe more) occupied only a few feet.

I found the spiral to be a more-effective representation than the conventional straight timeline, even though it's inherently distorting (inner legs are not the same length as outer legs). I wonder if that's just nifty or if it is in fact a better visualizaation in terms of conveying information.

20/what?

2007-11-20 from Dreamwidth

Tags: Science

The results of my distance-vision test this morning were a little better than normal. In fact, my weaker eye scored its best ever. (We only got the "denominator" into double digits in the last year...) I commented on this and my ophthamologist said it might be partially due to her newer equipment: the contrast is better on the new LCD "eye chart" than it was on the old projection chart, which in turn gives better readings than the posters of yore. (Personally, I think my gadget-assisted glasses prescription helps, particularly in the weaker eye.)

Measured visual acuity depends on the equipment. What it also depends on (based on my own observation) is operator variation. Your vision score includes a judgement call by the person administering the test. Whether you get an extra point can depend on how quickly or how certainly you read a letter. When you say "um, I think it's an F -- no, wait, it's a P", what happens to your score is not well-defined.

This doesn't really matter for an individual patient with a consistent doctor (presumably what the test was designed for); what matters is not so much your raw score but whether and how it changes from year to year. But when that score is used for other purposes, like deciding who can drive and who can fly a plane, it gives me pause. According to today's eye test, if both of my eyes were as bad as my weaker one I would still be allowed to drive (albeit only during daylight). Yikes.

Eye tests

2007-10-12 from Dreamwidth

Tags: Science, Life

I like the technician who did some routine tests for me this morning. She talks and shares reports. :-)

They have a new machine for visual field scans, so instead of taking 10-15 minutes (feels like 30) per eye, it now takes two minutes per to map the field of vision. The interface is still the same: stare at the cross-hairs and push the button when you see a flash of light anywhere. Flashes vary in position and brightness. I saw diagrams of the results showing the location of my blind spots (apparently we all have them). The machine still has the unfortunate characteristic of making noise when lights go off, which (1) makes it obvious I'm missing things and (2) enables gaming the system for those so inclined. (Gaming is obviously bad if you actually care about accurate results, but if you're a little unscrupulous and just need to pass this test to get your pilot's license, say, there'd be incentive.) Maybe they're actually clever and some of those sounds correspond to no-ops; that would be good.

Normal cornea thickness is 5.5. ("Units?" "Um, I don't know, but I can look it up for you." "That's ok; I'll ask the internet.") Both of mine are thicker than normal (6.26 right, 6.4 left). This is better than being too thin, and also means that my pressure isn't really as high as the glaucoma test says it is. I don't know if this is well-enough understood to be able to compute my actual pressure given a reading and the thickness data.

Learned in passing: the magic number for worrying about high pressure is 20. I always test in the 18-22 range, by the way. (That's with treatment; don't know what it would be without. Not inclined to find out.) So if I'm hovering at the magic line and my real pressure is probably a point or two lower, that suggests that the treatment is calibrated right.

She also took pictures of my retinas and let me see them. We had a lot of trouble with this; apparently my pupils were clenching their little fists and whining "we don't want to be dilated!". A double dose of the drops was enough to get a good picture of my right eye, but the one of the left was still kind of dark. If it's not clear enough, they should be able to redo it when I'm there for my next exam.

MBTI at work

2007-08-14 from Dreamwidth

Tags: Work, Science

Not long ago someone at my company listed his Meyers-Briggs type on his wiki page. And then someone else did, and, well, once three people do it it's a movement, so while I was on vacation someone created a page listing people by type (when known).

Of 35 people currently listed, 8 are INTJs -- seven software developers (including one of my favorite colleagues) and a hard-core designer. Yeah, these are my people. :-) According to Wikipedia, INTJs are about 2% of the general (US) population.

Granted, most of these types are being obtained by test toys found on the internet, but I don't imagine that would bias the results in a particular way, especially as people are using different tests. A few people have had more real tests in the past.

(Next-biggest group is ISTJ at 6, but that's a big group in the general population so not surprising. Ours apparently took some flack for alphabetizing the names within each section of the page; it's an ISTJ thing to do, apparently. :-) )

I just noticed something odd in the groupings. There are 16 types, grouped into four groups: NT, NF, SJ, and SP. Given the first two, I expected the other two to be ST and SF, but they're not. (That is, the first two suggested the pattern of "middle letters dominate".) I wonder what that means. (The I/E dimension gets no primary grouping at all?)

Ophthalmologist: new practice

2007-07-25 from Dreamwidth

Tags: Science, Life

My ophthalmologist left her old practice and set out on her own. This morning was my first visit in the new digs. Hey, new gadgetry!

An assistant read the prescription from my current glasses and then crafted a new one. (I hadn't asked for a refraction, but I wasn't charged for it so that's fine.) She now has a gadget similar to the one at NeoVision; I stared into the thing at an image (this one was a house in a field) and watched its focus change as the machine auto-adjusted to my eye. I love that thing; it's much less frustrating (and I imagine more accurate) than 15 minutes of "which is better, A or B?" (while they change lenses too quickly for me to focus and evaluate). They still do that to refine the prescription, but I had to evaluate no more than half a dozen configurations (so I could feasibly get them to slow down).

All that said, my ophthalmologist said "I'm not an optician; if you have one you like you should go there". I don't have one I like, but I'll keep looking. But now I know that I'm likely to get a good prescription from her if I need to -- one at least as good as what NeoVision did, anyway.

The eye chart has also been updated. Who thought there was much they could do there? But the lighting was more uniform and I think the resolution was better. (It was a display, not a projected image.) The remote control suggested to me that it could be infinitely programmable (though I didn't ask), which is refreshing. (I fear memorization giving false positives.) For the first time that I can remember, the post-slash number for my weaker eye was a two-digit number (20/80). The stronger eye also produced a better reading than usual. I know there's a great deal of variation in how those numbers are generated and interpreted (20/20 is not the universal standard you would imagine), but I have to assume that the improvement is due to the tools and not to a change in my vision. (It could be the new glasses; I didn't think to bring the old ones along for comparison.)

A small thing, but she was also able to give me printed, rather than hand-written, prescriptions. I'll bet pharmacists wish more doctors would do that. :-) The down-side of the same underlying cause: there was no physical chart for me to browse while waiting for the doctor after the preliminaries. (Hey, it's data about me and funded by me (or at least on my behalf); I should be able to look at it, right?)

I have no idea what she charges my insurance company. (My deductible, of course, has not changed.) My out-of-pocket cost actually went down; while she's farther away (= more gas), I no longer have to pay $5 for parking (and it was nowhere near $5' worth of gas). So, a win on everything except time, and the time hit isn't that bad (Fox Chapel).