laser safety

July 31, 2006 at 1:22 pm | | lab safety

The Moerner lab had its annual laser-safety training (by W.E.), which is always interesting and exciting. I’ve calculated some safety parameters for one of the lasers I use: an Ar-ion laser operating at 11 W. First, it is important to know the minimum permissible exposure (MPE), or the amount of laser energy your eyes may receive without being damaged. This is deterimed by the color of the source and the viewing time. With visible light, assuming an exposure time equal to the blink response, the MPE = 2.1×10-3 W/cm2.

I can now use the MPE to determine safe viewing distances of intra-beam and diffuse reflections (e.g. off a card). The region where is it unsafe to view the beam—i.e. where you will exceed the MPE—is called the nominal hazard zone (NHZ). For intra-beam viewing, the NHZ = 2 km, so you have to be over 2 km away to be able to look directly in the beam for the time it takes you to blink. Our lab isn’t that big. To view the beam within the lab, you would need goggles with OD > 5 to avoid damage. Cool!

As for diffuse reflections, the NHZ is 40 cm. So if you hold the card at arms length, you should be ok. But use goggles, anyway!

The equations for all these calculations are found in the appendix in the American National Standards Institute book on laser safety. Have fun!

stanford chem’s new website

July 28, 2006 at 11:07 pm | | news, wild web

We have a new website design, and it’s OK. The old site wasn’t so great (I mean, who is that guy?)—we weren’t really even trying. Now it’s a little better. I mean, the pictures with the silly words (Understanding) should go. But all in all, I think it looks better and is organized in a more obvious manner.

Constest: Which chem dept has the best website? Personally, I think my alma mater at least beats Stanford Chemistry.

chilled water

July 24, 2006 at 1:43 pm | | everyday science, news

The chilled water system at Stanford has been basically down for the last month and—now that the weather is getting ridiculously hot—we’re on the brink of the apocalypse. We can’t run our big lasers because they need to be cooled by the chilled water and the temperature in the offices and some of the labs it approaching hott with two “t”s. I mean, my office is in the basement and I’m sweating; the offices upstairs and in Mudd building are much warmer than outside (where the temperature is 90 F).

Thankfully, the most essential locations on campus (like the hospital) still get chilled water routed to them. Also, LINX, a for-profit cafeteria on the first floor of the BioX building, still is nice and cool. Thank god!

Check out this link for more cool (ha!) facts.

Tamiflu – July Molecule of the Month

July 23, 2006 at 11:28 pm | | nerd, wild web

From the wild, wild web comes a pretty fun site: Molecule of the Month (MOTM), brought to you by Dr. Paul May of Bristol University Dept of Chemistry. I recommend you check this out when you’ve got 5 minutes to kill while that ol’ laser is warming up.
Tamiflu, in all its glory:

Some neat tidbits on Tamiflu, care of the excellent MOTM Tamiflu Page:

  • Tamiflu is made from a complicated 10 step synthesis that requires shikimic acid, a product extracted with great pain (and cost) from anise seeds.
  • Tamiflu is our best bet against avian influenza. It binds to the neuraminidase protein on the viral coat and reduces the virus from exiting an infiected cell, thereby reducing the number of infected cells.
  • There comes a point when the number of infected cells is too large for the tamiflu to work effectively therefore it must be taken as early as possible.

A Call to Arms – for Science!

July 22, 2006 at 9:52 am | | nerd, science@home

Its time to rally the troops against the forces of darkness – literally. Today, I’m embarking on my solar-oven-building adventure. Why? you ask.

Burning Man!!!!

What is burning man? you ask. Shame on you. Now go google until you finally learn something useful in college.

The solar oven is relatively simple – basically a box with a bunch of reflectors that shoot the light inside and can cook food in sunny environments. I plan to build several for the upcoming BMan’06 . The best part is running all the controls to determine optimal cooking conditions: insulation type, angle relative to sun and time of day, black paint or no paint, oh so much science it makes my knees weak!

Pictures of the type of box I am building:


Let me know if you’re interested in helping out with this fun weekend project. If you have some 1337 woodcutting SkillZ or ToolZ that’d be cool. I also have an extra BMan ticket at the lowest price point that I can part with. There will be a group of Stanford chemists going up with me and you’re welcome to join our camp on the playa.


2 Inch Improvements

July 21, 2006 at 11:29 am | | cool results

We use a few parabolic mirrors on our optics table to align and focus a couple of beams to a tight spot. It’s important that these mirrors be well aligned because power density is really important for our (non-linear) purposes.

The mirrors need to be replaced from time to time. Last week the big 2 inch mirror was removed, as shown in Figure 1. Replacing the mirrors can be a little

Figure 1. It’s dirty, also the coating is improper.

worrisome. Of course, there is no signal without the mirror in place, and proper alignment can be difficult because one of the beams is almost invisible. No worries, though. Once the system was working again, we got twice the previous signal, as shown in Figure 2. 2x is mighty fine.

Figure 2. Sort of hard to tell if this is good or bad. It’s OK.


July 19, 2006 at 2:44 pm | | great finds, hardware, nerd

I found a great calculator in lab today. I actually think it was from the old Pecora lab, because we took a few of their rooms. It’s a TI-1250, circa 1975. Wow!

Figure 1. A TI-1250, not a calculator from the future.

At first, I thought it was a calculator from the future: I have a new calculator, and it’s only the TI-89. But it quickly became apparent that this was an older piece of scientific equipment. You can’t tell from the picture above, but the screen is on. You can only read the display at very precise angles and the whole screen flashes every time you press a button. It has an AC adapter, so you have to be plugged into the wall if you don’t have a 9-volt battery.

The best part is on the back, where it tells you how to do math:

Figure 2. What’s the point of the calculator when they print all the answers right on the back?

And look how thick this monster is!

Figure 3. Is that a TI-1250 in your pocket? Unlikely.

Note the on-off switch on the side. I just find that amusing. Plus, check out this website, where some guy with access to an X-ray machine shows us the insides of one of these beasts.

Thermite: A Classic

July 18, 2006 at 11:46 pm | | lab safety, science and the public

There are a handful of reactions used almost exclusively to convince undergrads that chemistry is hip and/or cool. You’ve got your oscillating reactions, exploding hydrogen balloons, and all sorts of pretty colors turning clear. But, the granddaddy of them all is the thermite reaction. (Our friend Dylan at Tenderbutton contributed the melting slot machine).

One of the summer classes just fired off this classic reaction, and I happened to be there to record it. Check it out.


Impressive Caleb, but check out the masters.

Deflections 2.0?

July 14, 2006 at 2:57 pm | | nerd, science@home

I came across this product advertisment recently:
Wanna shoot my pharoah?

Zap the pharaoh. No, that’s not slang for a questionable act, but the object of the first ever board game to use real lasers! Deflexion is a high-tech game of strategy in which two players try to zap each other’s pharaoh by bouncing a laser beam off Egyptian-themed game pieces bearing one, two, or no mirrored surfaces.

That got me thinking. I’ve got an empty 4 x 8 laser table, more optical elements and mounts than I know what to do with, and plenty of lasers (manly class IV, too)…


July 14, 2006 at 12:00 pm | | cool results, crazy figure contest

Some Data I took recently with David Pearson – cool, huh?

Easy on the Eyes

July 11, 2006 at 11:50 am | | cool results

I work with fluorescent proteins. Can you tell which FPLC fraction contains my sample? Not only can you see the purple fraction of victory, but the ones that follow are a little green with an immature form of the protein. See Figure 1.


Figure 1. Sweet jesus, that’s some good ‘tein.

Cornell researchers break Galileo codes

July 8, 2006 at 9:59 pm | | news

So a couple of researchers at Cornell broke the PRN codes for Europe’s Galileo GPS satellites. It’s a $4 billion dollar investment that, unlike the US satellites, was supported by private investors expecting to charge for access. Except they protected the system with codes that were broken in 1 week, without any serious computing power, using only Matlab and a dish receiver, by non-crypographers. There’s also a lot of background story to the issue, since the US doesn’t have the ability to turn Galileo off, should we decide who’s next to liberate.

The first satellite was at 36 degrees declination from NY, so I’m not sure if its visible from CA, but here’s the PRN. Maybe they’ll do a better job next time.

Lab Agriculture

July 6, 2006 at 3:49 pm | | everyday science

I like to have a little life in lab. So, I plant various crops. In particular, cotton it a nice choice for any budding scientist, as shown in Figure 1. A nice pepper plant is also a good idea. The pepper is well suited for indoor growth, as shown in Figures 2 and 3.


Figure 1. God’s Q-tip.

pepper 11.JPG

Figure 2. Great stems.

pepper 21.JPG

Figure 3. Right after this picture was taken, my dog was run over by a tractor and a horse kicked my father.

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