Not feeling to inspired to write today. But here are some fun science links:
Danielle thought that these pictures were neat:
(Ultraviolet pictures of the sun from SOHO.)
Caroline likes the Birdhouse cams.
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10
10 years = 3653 days = 87,672 hours = 315,619,200 seconds
(also equal to 260.928571 fortnights)
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Knitting Club
This week at knitting club I painted a picture. Becka says it was more fun to be at knitting when I was there. How sweet!
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Some bird pictures
Here is a slideshow of some bird pictures I took last weekend.
If the slideshow doesn’t work, let me know. It is kind of an experiment.
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Macromolecules
Becka says I should write something science-like so my page isn’t blank.
I thought I would relate one of my Bio prof’s pet peeves. It has to do with Macromolecules ( not to be confused with Macromedia ). Macromolecules are large molecules (usually protein) – they are measured in a unit called “daltons” or “kilodaltons” (kDa). One dalton is a measure of the mass of a molecule, and actually it is the same as the molecular mass. But I think biochemists use the term Dalton just so they can confuse people…. or because a dalton is usually measured using a centrifuge or electrophoresis, instead of with more exacting means such as mass spectrometry.
So the impressive thing about macromolecules is just how large they can be. For example a small molecule like water has a molecular mass of 18. Keratin, a major constituent of skin weighs in at 67,000 (67 kDa). Yeah, that’s big. But that’s nothing compared to polymers; polymers are repeating chains of molecules. DNA is a polymer. Lots of structural proteins are polymers, too. For example, collagen, microtubules, and intermediate filaments. In their polymer form, these things weigh in a millions and millions of Daltons. Actually, taken to the extreme, a car tire is actually one giant molecule — a polymer or polymers. How many Daltons is a car tire? Well, it is on the order of 6.02 times 1023…
Diffusion across a membrane is greatly affected by the size of a molecule. Small molecules can fit through the small gaps in the membrane whereas large ones can’t. That’s why you can lose water through your skin on a hot dry day without ever sweating. That’s also how your lungs can take oxygen out of the air you breathe. Or maybe you’ve noticed that if you go swimming in fresh water after a while you really need to pee even though you haven’t been drinking anything; the water diffused into your body. But you don’t need to worry about most bad things getting into your skin when you swim. They’re usually too big to diffuse through your skin.
Anyhow, my Bio Prof’s peeve was for the hand lotion commercials that talked about how their product revitalized skin. They would have a diagram showing a cross section of the skin, with arrows showing the deep penetration of the collagen in the lotion. The problem is that collagen is a gigantic macromolecule; it cannot diffuse into your skin because it is too large. Instead it just sits on the surface and is all slimy or maybe after a while it gets crusty. Probably the only thing in lotion that does penetrate the skin is the water and oils; so some vaseline or shortening is probably just as effective.
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I’m a d20
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Ambition
Yeah, the same markers that Becka used…. She said it reminded her of bitter dregs, even though he played the Euphonium, not the sousaphone.
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What is a low interest rate worth?
I’m considering buying a new car. Becka and I have gotten by with one car for ten years, but now with us both working and both jobs too far away to walk to and no good public transit, we’re going to need a second car.
We test drive some Volkswagons this afternoon. I thought I remembered reading that they offered a special 1.2% financing rate. This is a classic sales technique : confuse the consumer. So what, exactly, is 1.2% financing worth?
Loans work over a period of time, at the end of which the principle owed is zero. The amount of the payment owed is a function of the initial value of the loan and the interest rate. If the interest rate is zero, then the payment is simply the initial value divided by the number of payments.
What is interesting about that is that the payment on a loan is a function of two inputs : Initial value and interest rate. Now I do not believe that the car dealer has access to a pool of money at a lower interest rate than everyone else. When they sell you a car, they secretly “contribute” to your loan to make the interest rate lower. They in effect sell you the car for less than you agreed upon — but don’t ever tell you this.
Why should we care? Well, for one thing, you’re paying more taxes than you need to. But the reason I really care is that we might be able to buy our car with either separate financing (through an independent lender) or with cash. In that situation, you really want to know what the present value of the loan at the discounted interest rate is really worth.
This is one situation where Excel is useful. First I studied how interest rate affects payments. For typical car interest rates (between zero and 6 percent), the payment seems to correlate more or less linearly with the interest rate. That’s nice because it means I can make an assumption that simplifies my next calculation. Which is:
=PV((2+E$28)/1200,72,PMT(2/1200,72,$D29))
Where cell E$28 contains the “MSRP”, or price you negotiated. And cell $D29 contains the difference in interest rate between what the car dealer is offering and what current interest rates really are, as quoted by your bank or the internet. Basically I use to financial functions to find out what the present value of a loan with such and such payments over six years is worth today at the real interest rate.
Download a printable version of this table
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I.Fri.
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Wolf eyes.
I took the fancy new “Hubble” lens to the Wolf Center in Forest Lake last weekend. It is the 50-500 Sigma “Bigma” lens. It is not an image stabliized lens.
Nevertheless, I feel I got a few nice pictures with it!
I want to take people up there to see it. There is the Canine Carnival in a few weeks. Also, it is right near the Carlos Avery Wildlife area, which looks like it would be a nice place to take a bike ride.