Thursday, 22 November 2012

09:01 – Barbara is leaving late this morning to meet her parents and sister to spend the day celebrating Thanksgiving. I’m not much for holidays, and certainly not religious holidays, so today is just another work day for me. Barbara will bring me food when she returns this evening, I hope not including any turkey. It’s not that I dislike the taste of turkey so much as that I think it’s a bad idea to eat something so stupid that it can literally drown while drinking because it forgets to take its head out of the water.

I ran out of chromatography paper envelopes while I was building kits yesterday, so Barbara is going to label and stuff another 60 of those before she leaves. That gives me enough to finish building 30 each of the chemistry kits and biology kits, as well as some prototypes of the two new kits. I also have a case of glass Petri dishes that’ll be in one of the new kits. We have to figure out how to package those so they can survive shipping. I know we’ll use bubble-wrap; I’m just not sure yet which type or how much.

Barbara has been encouraging me to get a tablet. I’ve hesitated because I really prefer something with a real keyboard. I’d been thinking about buying a ChromeBook, so yesterday I went ahead and ordered one from Google. I’ll probably give it to Barbara, but I may use it from time to time.

11:45 – In designing science kits, I end up doing all kinds of little experiments that have nothing directly to do with the lab sessions covered by the kits. I’m doing one of those today.

One of the new kits I’m designing right now is the LK01 Life Science Kit. Life Science is basically middle-school biology, a simplified version of a first-year high school biology course. One of the classic experiments that’s covered at both levels is antibiotic resistance in bacteria. Our full biology kit includes four antibiotics: amoxicillin capsules, chlortetracycline and sulfadimethoxine powder, and neomycin liquid. But to simplify things for 7th and 8th graders and to keep the cost of the kit down, I decided that the LK01 kit would include three antibiotic test papers–amoxicillin, neomycin, and sulfadimethoxine–rather than the actual antibiotics.

I’m going to make the antibiotic test papers myself, by soaking letter-size sheets of chromatography paper in solutions of the antibiotics. But I need to have at least an approximate idea of the concentrations of the antibiotics in micrograms per square centimeter. To do that, I need to know how much liquid one sheet (about 600 square centimeters) of chromatography paper will absorb. Knowing that, I can calculate how concentrated the antibiotic solutions need to be. So, to determine that factor, I’ll weigh a sheet of dry chromatography paper, soak it in water, reweigh it, and determine how much liquid it absorbs. I don’t expect a lot of variability, but I’ll do several sheets just to get a reasonable idea of how much actual variation there’ll be.

But I can’t simply use blank sheets of chromatography paper. The test papers included in the kit will be roughly 4 by 5 centimeter pieces, so I need to pre-print each sheet with “amoxicillin” or whatever in tiny little print. That may affect the absorbency, so it has to be taken into account.

14:06 – Well, it is a national holiday, so I’ve decided to take the rest of the afternoon off and watch Heartland re-runs. I only have 1.5 episodes left on Netflix streaming, so it’s time to fish out the boxed set of series three to watch the four remaining episodes in series three and then start series four on disc.