Nature and Nuclear Reactions

I've blogged about toilets evolving in nature, but apparently nature also created self-sustaining nuclear reactions:
Perrin and the other French scientists concluded that the only other uranium samples with similar levels of the isotopes found at Oklo could be found in the used nuclear fuel produced by modern reactors. They found that the percentages of many isotopes at Oklo strongly resembled those in the spent fuel generated by nuclear power plants, and, therefore, reasoned that a similar natural process had occurred.
Scientists think these natural reactors could have functioned intermittently for a million years or more. Natural chain reactions stopped when the uranium isotopes became too sparse to keep the reactions going.
It is amazing to me that the random motion of matter can create a self-sustaining nuclear reaction with an average power output in the 100 kW range. This interesting anecdote of a complex system arising from random processes is evidence that long time periods and random processes can create surprising, complex systems. Maybe even life?


Google Wave Invites

Even after sending many invites, I still have a few left over. Let me know if you want one.



I'm sorry I haven't posted. I've been so stressed out lately that it has taken everything I have to focus on getting an iota of work done every day. I tried writing a long, thoughtful post about what is happening, but it just sounded lame.

I'm not dead, I know I'll eventually have things to blog about, but those things just aren't going to happen any time soon, at least not until I'm back in the states for vacation. You can check out today's PhD strip for a decent run-down on the current events in my life...only imagine someone who is convinced that working now will lead to laziness later, but instead this working is leading to more trouble with working. Or some other non-sense like that.



Last week I went to an astronaut's speech on the future of commercial space flight. The astronaut, Steve Smith, worked on the Hubble Space Telescope while it was in orbit. I got to meet and talk with him personally for a few minutes, and loved every second of it.

He had a lot of interesting anecdotes, but the one that I'm still thinking about is this: the space program rejected him as an astronaut candidate four times before being accepting him. You can only apply once every two years, so he was living in a state of space-program rejection for eight years before being accepted. I wish I had had the foresight to ask him whether this was normal for astronaut candidates, or if he was an exception. Either way, the fact that he keep reaching for his dream, even after eight years of rejection, is amazing and inspiring to me.



My 2.5 by 2 mm^2 integrated circuit design was finalized yesterday. Maybe now I can stop stressing out so much?

Probably not.


Randomizing a Coin Toss

Way to report only the problem, Freakonomics blog:
But it may be that the the random coin toss isn’t so random. A 2007 study found that a vigorously flipped coin is likely to land on the same side it started on at least 51 percent of the time, possibly more depending on the person doing the flipping.
Say you have a coin with a bias that doesn't change from flip to flip. You can remove the bias by flipping the coin twice, and taking the first result if the second result differs from the first or repeating if it lands the same way both times.

Mathematically, if the probability of landing heads is P, then:

  • P^2 = Prob[HH]
  • P*(1-P) = Prob[HT]
  • (1-P)*P = Prob[TH]
  • (1-P)^2 = Prob[TT]

Since the probability of HT is the same as TH, taking the first element removes the bias.

Mad props to von Neumann for inventing this trick (publication was "Various techniques used in connection with random digits"), along with fundamental portions of the theory for quantum mechanics, cryptography, and game theory. They don't make mathematicians like they used to.



I don't normally blog about personal things, because I think they're lame and I really hate putting personal information onto the interweb. But I figured I've got to try most things once and see how it turns out.

I lost my temper today. It was pretty bad. If you know me, I may not seem like the kind of person who loses it very easily, and in general I think I keep my cool pretty well. Today just wasn't my day.

Today at work, one of my officemates made a passing remark about gay people and how they were decreed to be killed in his home country. He was talking to another person at the time (not me), but I thought the way he phrased it was completely inappropriate. What I thought I heard was a statement supporting violence against people based on their sexual preference. What he probably said or intended to say was a factual statement about what happens in his home country because of the laws. In retrospect, as he isn't a native English speaker, the intention of the statement and what were said were probably different. I think the words "should," "could" and "would" are particularly difficult for non-native speakers to grasp. Even native speakers aren't clear with their intentions in everyday conversation.

Anyways, I then asked him if he would please keep the hate speech out of this country.

A large fight ensued where I lost my cool. He claimed the remark wasn't for public consumption, but at the same time I heard it and pointed out that other people use our room. When he makes remarks like the one he made, other people listen and he implicitly represents our group, and hence me in such remarks. We ended up taking the issue to our adviser, who as head of our group is mostly responsible for our group image.

My adviser agreed with me about our room and our remarks being public. My adviser warned my colleague to be more careful with his words in the future. My adviser told me I needed to be less strict in my interpretations of what people, especially non-native speakers, say, and that I shouldn't assume their intentions from their speech. He also said not to overreact so much. I think I agree with him on all statements. I lost my cool, and need to be more understanding of the slipperiness in communications.

I would be lying if I said there hasn't been a build-up to this, or to the other times I've lost my cool. The way my officemate structures his speech would be extremely rude in Iowa. I've tried explaining it, but so far without much success. Maybe the problem is with me? I don't know. Things aren't really great between us. He accused me of being a spy today (I don't think he knows what the word means), and I think I've burned too many bridges to try and explain to him how he is subtly insulting me. He probably wouldn't believe me anyways - I'm a spy, right?

I'm been having some problems with my temper lately (when I say lately, I mean over the past two years, since leaving university). At my last job, I had pretty big issues with how long it took to accomplish things. I'm a pretty lazyefficient person, and when I do work I want it to matter. I get angry when it doesn't, or if I did unnecessary work. Making sure I take the right approach to getting things working is very important to me, and I think it makes me a good engineer. I know I can focus my anger when things don't go well. I distinctly remember times in middle school when I did poorly on a test and studied non-stop because I was angry about it, and the next tests always came back with high marks. At the same time, it seems over the past few years my temper has starting to get in the way of getting things done in the most efficient manner. I should have asked my officemate to clarify his statement, not immediately assumed a bigoted intention. I should have known that getting things done quickly is different for a very constrained university assignment than for work in the corporate world.

I thought I'd share this moment of anger with you. While writing about it has been a bit cathartic, I'll still be fuming for the next few days.


How are Our Children Going to Get Out of Bathrooms?

It was roughly 2 am on a standard night at MIT. Pacing the hallways with my trusty football, I asked a few people if they wanted to hit up a local shop for some late night chocolate milk and Italian subs. Receiving an affirmative, I told them I'd be back in a moment. I really had to go to the bathroom.

Having finished my business and washed my heads, I went to unlock the bathroom door. The knob turned, but the latch did not retract. I looked at my football. We were stuck in the bathroom.

After yelling and attracting the attention of some local residents, I asked if they had any bright ideas. One suggested re-locking and unlocking the door, which had allowed her to escape a similar situation several days ago. Alas, it did not work. I looked at my football again. Still stuck in the bathroom.

But wait! I had my trusty Gerber multi-tool with me! Holding my football a bit steadier, I whipped out the mini-screwdriver, took off the doorknob casing, had some friends help take apart the rest of the doorknob, pulled out the latch, and escaped the clutches of the bathroom (EDIT: this sentence was modified to properly attribute work to people missed on the initial post).

Today, the NYTimes ran an article on schools punishing children for carrying multi-tools. I want to know from these multi-tool nay-sayers: Who is going to get our children out of the bathrooms at 2 am? Because I don't think it is going to be you.

The Invention of Google Wave: A Play in One Act

Date: roughly one year ago. Two twenty-something google engineers (both decked out in blue google t-shirts and jeans) sit on their fitness balls. One sips some strange coffee-like concoction while the other downs an Odwalla drink. Engineer one checks his e-mail.

One: That jerk Larry from HR keeps top-replying to my emails. Seriously. Who the h#** uses top-reply these days?

Two: Everyone but nerds uses top-reply. Didn't you talk with new girl? She was an M$ intern last year, and apparently M$ mandates top-reply in their emails.

One: And what if you want to respond to multiple points in the e-mail?

Two: I think Outlook would have crashed by then.

One: Seriously, this is non-sense. We need to get some giant conspiracy going to make bottom-reply the default.

Two: I have an idea. How about we claim we're merging IM functionality with e-mail. But in reality we'll just be forcing people to use the indent-reply conventions nerds have been using for the past 40 years, and give people too stupid to setup IM notifications of email events the chance to get e-mail instantly.

One: That sounds awesome. We'll dress it up to look fancy, so people aren't so intimidated by the less than signs that would normally occupy the start of the line.

Two: I know. Heaven forbid people learn how to use conventions, or look at plain text.

One: Oh, and we can put in annoying features that geeks would hate! Maybe we can have it immediately show the person's reply, while they're typing! Heaven forbid people think before they respond, like us introverted nerds do with emails, so the hundreds of people getting our emails don't have to sit through our mistakes. We can cut out the subject line, too - it isn't like people use that to its potential.

Two: Those sound like exactly the sorts of nerd-hating features that'll launch this project into the big time! Let's get coding.

Curtains close as furious keyboard pounding commences.



If you've talked with me lately, I've probably told you how stressed out I am about something called a "tape-out." The phrase refers to production of an integrated circuit. According to my adviser, 20 or 30 years ago, before the internet was around, circuit designers would send physical tapes to the chip manufacturers. Hence the term tape-out. Thus when an electrical engineer is creating an integrated circuit, (s)he uses the term tape-out to describe the process.

Today I thought I'd share a little bit of the designer process, so you can understand what I'm talking about when I say I've been staring at colored polygons all day. Circuits perform a lot of tasks, from the main processing in our computers, to capturing images in some of our cameras, or detecting events in the world around us.

To create circuits to do all these things, engineers start simple and build up. The basic unit in an integrated circuit is the transistor, which acts as a switch in digital logic. The switch is on or off depending on the electrical signals we send to the transistor. I've taken public domain pictures from Wikipedia that shows the behavior when the transistor is off (first picture) or on (second picture).

The basis for transistor construction is the placement of materials with different characteristics. The "n" and "p" labels above are on materials with different elements. Placing these materials at proper distances from one another is critical to proper operation of the switches.

When electrical engineers create circuits, we need ways to control where the materials go, and then we can control the behavior of the circuit. Thus when I talk about colored polygons, I am talking about visualizing the locations of different types of material that determine a circuit's operation. I've labeled the drawings above with the colors of the layers, and including a screenshot of what I look at when I am using software to "create" a transistor. The wikipedia images are from the side, whereas engineers view things from the top.

The red polygon, representing the gate, interfaces with the control signal for the transistor. The green layer represents the 'n' implant into the 'p' type silicon. The blue layer is a metal routing layer on top - there are other metal layers for routing, along with via layers such as the teal layer above that connect metal layers to other layers.

You'll notice I don't specify all the layers. The silicon dioxide layer, dashed in the figure, doesn't have a corresponding polygon. Some layers are auto-generated from other layers; this can create problems when you want to do something fancy.

Starting from these simple layers, we can quickly build up complicated devices. I didn't mention this before, but there are actually two types of complementary transistors on most integrated circuits. This is the basis for the term CMOS, or complementary metal oxide semiconductor. The next picture shows both types of transistors. You can check out the CMOS Wikipedia page if you're interested in the two types.

The structure you're looking at is an inverter, as it outputs the opposite of the input signal after some time. If you're confused by the layers, follow the red polygon (the gate) to the green areas - the overlap area would be the two transistors. The yellow and white dotted layers help describe which type of transistor is to be created. The big orange box around the top portion would change the material in a large area, and is required for one of the two transistor types. The teal / cyan squares are vias that connect the metal to other material. Though vias only connect to the green layers in the transistor I showed above, they can also connect to other layers.

There are additional metal routing layers than the metal one I've shown so far. The next picture shows a custom structure I have made. This structure includes yellow and white polygons, which represent metals at different heights than the metal in the previous images.

The purple and orange squares represent vias between the various metal layers. The structure that you're looking at is a variable-delay buffer. It takes a control signal and an input signal, and outputs the input signal after a delay which is set by the control signal.

I've included measurements on the side of the structure in microns, or one-thousandth of a millimeter. A micron is also one-millionth of a meter. When you hear people talk about different integrated circuits production processes, they'll usually use the minimum accuracy of the gate size as a first-order statement of how advanced the process is. This is a 0.35 micron process, meaning that the minimum gate size is 0.35 microns, or 350 nanometers. The current processor in your computer is probably a 45, 90 or 130 nanometer process.

You might ask why people care about the construction of the circuit - don't we really just care about the behavior? Digital engineers do tend to care more about the behavior than the construction itself, and they usually don't lay out circuits by hand. They usually specify the behavior using some type of code, and run this code through a bunch of fancy tools to get the material locations.

However, if you work with sensors, it is often more difficult to specify the exact characteristics of the structures than simply laying out the structures by hand. This is the case for most of the work my group does.

There is the additional problem that messing up means the entire circuit might not work. This is why I'm constantly stressed out - while one mistake can cost a software person months of their life, simple things are enough to easily prevent this. This often isn't the case in hardware, as creating the circuit takes months, and you're stuck with the circuit.

Well, I hope you enjoyed my post on tape-outs. I cannot post pictures of my more complex structures, as a lot of the cells I work with are proprietary, and the man would come after me. I'm finished with this tape-out in early November, and then it will be a few months before I know whether it was a waste of time. I'll probably be drinking a lot of egg nog at xmas time.


Worst People

I'm beginning to think Google is out to get me.


Architecture around TU Delft

The weather was nice a few weekends ago, so I went out and snapped a few photos. Enjoy!

This is a picture from the window of my new apartment. I now have a view of the canal. Sorry for the tilt, my head isn't on straight so it looks normal to me.

TNO is a large defense contractor in Delft.

A south view from my building.

A west view from my building, towards the part of town with the high-rise apartment buildings.
I've circled a bunch of the high rise buildings. As I've previously described, most of the development in Delft occurs on the outskirts of town. This preserves the town center as is.

You can see that along the canal there are a lot of industrial type buildings. A lot of heavy freight is shipped along the canals instead of roads, which means that the roads require less maintainence.

Some apartments near the university. You can see part of my building in the background.

Some apartments near the university. They stand over a pond.

Due to all of the bicycle traffic, it can be difficult to know whether a bicycle is supposed to go on a path or not. The people who designed the park in the middle of campus included environmental cues to help. First, the rocks are close enough together that a bicycle would have trouble going between them. Next, the gray sections of the path are rough; riding over the alternating path sections feels unnatural on a bicycle. The path goes down a few steps out of sight, so it is important that bicyclists don't go on this path. People don't seem to like signs here, Delft has a lot of these environmental cues around the city to help bicyclists with whether or not they belong in certain places.

The main bicycle path next to the mechanical engineering building. Exposed stairwells are very common here, I think architects like them.

My building.

The civil engineering building, which also contains administrative offices. Another building with exposed stairwells.

A set of dorm rooms are by my building.

Two Hogeschools (or vocational schools) have opened up next to TUDelft. When they were building this school, they had water in the lot that is now under construction. This building looked like one of those beach buildings on stilts. The empty lot will soon contain housing.

Another vocational school. This one is interesting because it contains a parking lot on the roof!



The town of Drachten in the northern part of the Netherlands took its main traffic intersection and changed it drastically in 2003 -- all traffic signs and lights were removed! Below are pictures from before and after the rebuilding of the city square.

My favorite note from the summarizing report is that respondents think the traffic situation is less safe now (appendix 6c from the report), whereas the number of accidents has fallen to under 20% of previous levels. I think something called the Peltzman effect is behind the discrepancy between the increased safety but decreased view of safety. When human beings feel safe, they might engage in riskier behavior. By playing on the fears of people, the intersection has (so far) been much safer. I have previously blogged about this effect in a post on condoms.

Oddly enough, people ranked the "quality" of the re-designed space much better than before, even though they thought the re-design was less safe. In addition, the transit times across the intersection improved.

I think this effect has strong implications for how we can misunderstand our own rationality, and helps explain why it is important to study information objectively by examining accident rates and transit times, getting a full picture of how our emotions steer us in all situations.

Tip of the hat to reddit for still providing signal, even though most of your links are now noise.

Copyright note - the publication with these pictures didn't include explicit copyright information, but did contain a logo for a sponsoring institution, a Gemeente, meaning they should be in the public domain. If you are a random visitor with more information, please let me know if you are aware of the copyright situation of these photographs.


Drawing the US

As a follow-up to my earlier post, I drew the U.S. today. I managed to get all the states, though a few have some major issues. I colored in what I meant to draw, and I'm not really sure what happened at the MO / IL / KY border...hmmm...

If you think you can do better you should give it a shot!


Farewell, Norman Borlaug

Norman Borlaug has died:
Norman E. Borlaug, the plant scientist who did more than anyone else in the 20th century to teach the world to feed itself and whose work was credited with saving hundreds of millions of lives, died Saturday night. He was 95 and lived in Dallas.
In high school biology class, we had a population unit that included articles on Borlaug. As a fellow Iowan, Norman Borlaug was the center of several important discussions, especially his premonition that "If the world population continues to increase at the same rate, we will destroy the species."

There are a lot of slow, dangerous effects that we hear about every now and then - I think that people, myself included, don't think enough about the drastic increases in population that will come with better health-care and nourishment in every part of the world.


High SNR Sentences: Identifying You in Data

It was found that 87% (216 million of 248 million) of the population in the United States had reported characteristics that likely made them unique based only on {5-digit ZIP, gender, date of birth}.
The sentence was from a CMU researcher working in 2000 on 1990 census data. Unfortunately the paper is behind a wall, but a different, available paper with a decent methodology puts the number at 63%. I was not comforted by the lower estimate. Tip of the hat to Ars Technica for an interesting discussion on "anonymizing" data.


Drawing the US from Memory

I used to challenge people to draw the US from memory, it was usually hilarious when people who weren't from the mid-west tried to draw the region. I can do a respectable job, I almost always hit all the states and the shapes aren't too bad...but holy cow, Al Franken, you're my hero.


Timing Properties of SPADs

I've gotten requests for more technical material, so here ya go:

Today I'm going to talk about some applications of SPADs. If you want a reminder of the basics of SPADs, you can read my introductory post or my post on noise. SPADs are single-photon detectors that use feedback systems in conjunction with one another to accurately time the arrival of single-photons. Accurately timing a photon's arrival time is important in many applications, but today I'll be talking about rangefinding.

In rangefinding applications, such as laser-based rangefinding for land surveying, a laser fires a pulse of photons and a detector times the difference between the pulse and the photon detection time. Photons, being light, travel at the speed of light. You'll usually here the speed of light quoted as 300,000,000 meters per second, but optics people prefer to quote the speed of light as
  • 30 centimeters per nanosecond
  • 300 millimeters per nanosecond
  • 300 micrometers (microns) per picosecond
  • 30 millimeters per 100 picoseconds
We use these values because modern electronics usually have around 100 picoseconds of accuracy. In the future, I think the 300 microns per picosecond value will become more common.

Anyways, we have to accurately time this photon arrival so we can determine the time of flight. The timing inaccuracy is termed jitter; we use various metrics to quantify the jitter, but most of these metrics just capture the usual case. For SPADs, the jitter depends on a few things.

First, the temperature is very important. In a silicon integrated circuit, increasing the temperature increases the ambient energy available to electrons, the main information carriers in the circuit. The introduction of additional energy modifies a carrier's behavior, and thus changing the temperature will change the characteristics of both the fast and slow feedback loops in SPADs.

Next, the color of the light is also important. Different colors of light have different wavelengths. The wavelength describes how frequently the energy moves around in space. Since silicon has a repeating structure, the wavelengths will help determine how likely it is that the light interacts with the crystal, producing the primary electron that could cause an avalanche. It turns out that blue light is optimal for the current generation of SPADs - the optimal wavelength is a balance between how far light usually penetrates into the silicon and where the avalanche region is (remember that we moved the region away from the surface to avoid the noise-causing irregularities at the surface).

Within the avalanche region, the build-up time of the avalanche is obviously important. During the initial portion of the positive feed-back loop, when there are very few carriers active, the variation in each carrier can change the build-up time. Current understanding is that it takes between 0 and 15 picoseconds to generate enough carriers to average out these variations, though this build-up process depends on characteristics like the temperature and strength of the applied force (the electric field).

So what is the end result? Well it depends on what you need and what you have available. If you have a lot of area available on a silicon chip, you can use more complex current detectors to get the jitter as low as 15 or 20 picoseconds. On the other hand, if you're short on area you can raise the jitter as much as you like, but you'd be hard-pressed to raise it above nanoseconds and still have a viable application. Keep in mind that you'll be changing how close the SPADs are, so the cross-talk will change.

When you're making a range-finder, you might care only about one specific range, or you might be trying to acquire a bunch of ranges to get a 3D pictures. If you only care about one range, you can use a lot of area to achieve the 20 picosecond resolution. This corresponds to an uncertainty in space around 6 millimeters. If you have an array of SPADs and timing circuitry, you're more likely to have an error in the 100 picosecond range. 100 picoseconds corresponds to an error of 3 cm in space. You can lower this uncertainty by taking multiple measurements, and since the measurements are so fast the accuracy can easily be one millimeter or less.

Anyways, I hope this post helped you understand about the timing uncertainty in SPADs. The uncertainty affects other applications besides rangefinding, things like quantum-based encryption algorithms, biological imaging, and cancer detection, but those applications are a bit more complicated to explain! I'll be attempting in future posts, and we'll see how it goes.

Another Airbrushing Site

I stumbled across a really interesting airbrushing site today...I can never click through enough of these to remind me how much people are mis-represented in print and online media. (earlier post)



Why are TVs and computer monitors horizontally long, but paper is vertically long? I suppose it makes sense that monitors and TVs are horizontal, as this matches our visual field, but then why is paper tall, rather than wide?



It has been a year! Here are some of the things I've done in the past year:

1) Forgot / lost passport, had to travel 3 hours to get it back
2) Setup an experiment using somewhat dangerous radiation while I was suffering a headache from lack of sleep
3) Was the last person on a plane, having nearly missed it (this experience is over-rated)
4) Laid out a portion of an integrated ciricuit that (if it works, crosses fingers!) will have 5.12 GBps going through it
5) Lost PhD topic
5.5) Lost PhD topic
6) Found PhD topic (errrr.....I think?)
7) Went all-in and won a poker pot, went all-in and lost a poker pot, successfully spotted a bluff at a poker table, successfully set a trap at a poker table
8) Gone to one of those fancy European clubs in Paris (it was worse than I thought and I will not be returning)
9) Bought plane tickets, booked a hotel, flew on plane and checked into hotel within 5 hours of one another
10) Successfully found apartment in a foreign country and moved into it from another apartment
11) Gotten a first-hand view of how difficult it is to be an immigrant
12) Earned the title Expatriate

Things I haven't done:

1) Successfully had a conversation in Dutch (I haven't had many successful ones in English over here, either)
2) Joined a choir
3) Written a paper (I'm working on one right now, and I have two in various stages of the paper pipeline)
4) Used tools to go from VHDL to ASIC

By the numbers:

Guitars purchased - 1
Bicycles purchased - 1
Haircuts - 2
"Original" research ideas that someone else had actually tried but adviser didn't know about - 3
Canned hot dogs consumed - 4
Moose seen - 4 (two real, two mascots)
Shoes purchased - 6
Countries book was purchased in - 5 (6 if you separate England and Scotland, 7 if you include online purchases)
Countries "visited" - 7 (Scotland, US, Canada, Switzerland, Ghana, France, Belgium)
Passport resources used - 27 boxes from stamps, 2 pages from visas
Train tickets purchased - ~100 (I go through about 8 a month)
PB&J Sandwichs consumed - ~150 (they have this awesome sour cherry jam over here)
Emails sent - 2,088 (more than I thought, 25 were to myself)
Emails received - 2,698 (fewer than I thought)
Most lines of code written in a single day - ~3,200 (most of it was test code...firmware test code can be pretty massive to go through the appropriate states)
Lines of code written overall - ~16,000 (again, around 14,000 lines are test code)
Heartbeats - ~37,000,000 (the heart is a work of art)

And finally:

Dutch postcards sent - 0 (yeeeeeeeah...I still owe a lot of people postcards.....)

$500 for a Bicycle

The Freakonomics blog has a great post on the cost of bicycles in bicycle-crazy Portland:
Yeah, the bike guy answered, he had something super-cheap for me ... I could have it, he said, for $475.

So I went to another store. Same deal, more or less. There was one bike for $275, but it was a girl’s Raleigh from the 1960’s with a wicker basket.


At Portland’s Costco, meanwhile — on the outskirts of the city — you can buy a brand-new Schwinn Midtown city bike with Shimano shifters for around $200. But, according to the clerk there, those Schwinns aren’t moving.

I bought an inexpensive, new bicycle in Delft for just over $500, though the university reimbursed most of the cost through a travel program. I was expecting to find a nice, new one for around $250.

We don't have CostCo here, and sadly Ikea doesn't sell bicycles. I'll just keep dreaming.


A Test for Rental Scams

I'm looking for an apartment, and I seem to get an awful lot of e-mails from people that have beautiful apartments for low, low prices but for whatever reason they won't show me the places. Or they say they'll meet me and when I show up a confused woman answers the door and says, "No, there is no apartment for rent here."

Today I'm going to describe to you how you can check if you are being scammed. Go into your email client and turn on all of the headers (in Thunderbird, this is View->Headers->All). You'll see a giant chain of "received" headers that look like:

Received: from [] by n75.bullet.mail.sp1.yahoo.com with NNFMP;
22 Jul 2009 20:09:46 -0000
Received: from [] by t3.bullet.sp1.yahoo.com with NNFMP;
22 Jul 2009 20:09:46 -0000
Received: from [] by t3.bullet.mail.gq1.yahoo.com with NNFMP;
22 Jul 2009 20:09:46 -0000
Received: from [] by omp109.mail.gq1.yahoo.com with NNFMP;
22 Jul 2009 20:09:46 -0000

At one end of these headers will be your e-mail provider, while at the other end will be the IP address of the computer that sent the email address:

Received: from SRV502.tudelft.net ([]) by ...
Received: from [] by web111904.mail.gq1.yahoo.com via HTTP;
Wed, 22 Jul 2009 13:09:45 PDT

Sometimes the address of the originating computer is listed a bit differently:

Received: from BLU116-W26 ([]) by ...
X-Originating-IP: []

The person might have masked the IP of their computer, but this is complicated and most scammers are idiots. Anyways, you can take this IP to a handy geolocation look-up service and find out the originating location.

Host: dial-pool07.ab.starcomms.net
Country: Nigeria

Every now and then the country won't be listed, but the host name you get back has information you can use to determine the country. For example, resolves to 35-6.rv.ipnxtelecoms.com but the geolocation service doesn't give a country for this IP. ipNX Telecom has its headquarters in...Lagos, Nigeria.

I suppose in the future I'll have to screen any email about apartments. Sometimes I really hate people.

EDIT: Your email client actually uses the same method I describe above to label some emails as being probable scams. Usually IP blocks assigned to certain ISPs and sometimes even entire countries are labeled as suspect.

Sentences that Make Me Laugh

If we ignore (thing one), (thing two), (thing three), (thing four) and assume (thing five), then the problem becomes tractable using only elementary results from field X.
Sadly I wrote the sentence...though it was followed by:
Subsequent sections will discuss the effects of (thing one), (thing two), (thing three) and (thing five), cumulating with results from a simulation including all these effects. The authors plan to revisit (thing four) in later work.
Planning to revisit something is a total cop-out.


CEOs and Pay

While I was home the issue of executive compensation came up several times. I'm a person who thinks that a CEO could easily deserve tens of millions a year or more. The main reason behind this is two-fold.

First, I've worked at a company that has undergone restructuring at a management level. From personal experience, small changes in strategic direction have a massive impact on people at the bottom of the "job-food" chain. It is easy to lose months, probably even years of work because someone above you made the wrong call. Since a CEO helps determine the strategic direction of the company, it seems reasonable to me that the pay of the CEO should scale with the sum pay of every other member of the company.

Second, there are a few studies which show a CEO's personal circumstances can have a percentage-point effect on a company's performance. A great example is a study of the effect on profit by a death in the immediate family of a CEO. Excerpt:
Sorting by the number of children we find the biggest effects on firm profitability in cases where the CEO only has one child. Specifically, one-child death shocks correlate with a 5 percentage point decline in firm profitability irrespective of the age of the child.
The study goes on to show that the deaths of a spouse or child are significant events for a firm. I think the study underscores the importance of choosing the correct CEO. Though the study doesn't show the variation in profit during standard circumstances, to me it seems like a reasonable conclusion that variations in a CEO's ability to carry themselves through tough times will have a large effect on firm profit. For a company with hundreds of billions in profits per year, like an oil company, the CEO's personal circumstances could have an effect in the billion dollar range, meaning if the CEO themselves only received a fraction of this pay it would still be in the tens of millions range.

My math is a bit fuzzy here, but as always you're welcome to disagree in the comments and point out any mistakes I've made.


It's All About the Teachers

I've been on vacation for the past, well, month, and I had a lot of interesting conversations. Aside from the very personal ones, the most engaging ones were on the topic of teachers. I had lunch with an old class-mate who is now a teacher at a high school. We talked a little bit about evaluating teachers. There isn't really a coherent point to this post, but if there was it would be that there is enormous room for improvement in the way we allocate resources to educate and invest in our next generation.

There is a lot of interesting quantitative data in how we invest in students. My class-mate and I talked about how too many smart people opt out of teaching. As the feminist movement has matured, a lot of really smart women no longer become teachers and the quality of teachers has suffered. I think the take-away is not that the feminist movement is bad, but rather we as a society don't have a great understanding of the importance of good teachers.

Another subject we talked about was the politics of teaching. If you haven't heard it, I suggest the TED speech of Bill Gates, the education portion begins at about 8 minutes. He talks, amongst other things, about how it is illegal in New York to use performance-based data to evaluate a teacher's performance. Coincidentally my old class-mate was for qualitative data like committees but against quantitative performance-based data. She claimed the quantitative data would have too much variance. I think I dissuaded her from this stance, but I do agree that quantitative data is not perfect. Any one metric can be taken advantage of. As an engineer, however, I have more faith in a well-designed system with numbers than a well-designed system with committees.

Finally, we went over the cost of education at private schools. There is a huge debate about whether private schools outperform public schools. The debate is quite contentious, especially when trying to account for socioeconomic and ethnic diversity factors. She said that public schools are critical to integrating immigrants into society. I do not have a great link to summarize this stance, as I haven't seen anything like this online - please comment and send along a link if you have one. I said that I thought public schools were wasteful due to the political pressure and lack of transparency into the teachers.

Anyways, I think the high level take-away is that evaluating teacher performance is a complex problem that has to touch politics and statistics, though a lot of information suggests there are inefficiencies. It would be interesting to attempt to evaluate schools, but creating a non-partisan report that accurately represents the facts seems to be near impossible. The only thing I know for sure is that I don't have a clue how parents choose schools for their children.


Big Pimpin'

Sometimes it helps to remember your fashion roots.

Only a select few can go pantsless with combat boots and diapers. I am one of these few.

Sometimes, though, you've got to break out those whale pants.

When I was big in the 80's, I wore jump suits for a while. I think my life-long relationship with red started around this time.

I also tried the grunge scene in the 80's. Or the potato chip scene. They were kinda the same thing.

After the grunge scene I classed it up a little.

Speaking of classy, nothing says classy like gray shoes and a bow tie.

Sometimes it was hard being with other people who didn't get it. Going as a mouse to Halloween was so last year. Being a pre-schooler was where it was at.


Toilets Evolved?

How awesome is evolution?
Using isotopic analysis, they estimate that shrew feces deposited in N. lowii’s pitchers are a significant source of nitrogen for the plants...Tree shrews visit the plants to eat nectar that oozes from the bowl’s open lid, positioning themselves directly over the bowl
Nature, how about you evolve me a starship? I promise I'll provide it with nutrients.

Errrrr, maybe I'll just build it myself.

Also, this is at least my fourth post on toilets, and those are just the ones I've tagged. How disturbing.


Shushing Doom

According to space.com, the military is shushing incoming space objects:
A recent U.S. military policy decision now explicitly states that observations by hush-hush government spacecraft of incoming bolides and fireballs are classified secret and are not to be released, SPACE.com has learned.
I'd like to think they're trying to keep the location of orbiting platforms secret, but I know it's really a cover-up of a secret government program which has angered aliens previously posing as Gods who have sent a giant ball of explosives (posing as an asteroid) to wipe out our solar system and only an oddball team of four individuals (one carrying such an alien himself) can prevent the asteroid from hitting Earth by traveling to it and having their simple scheme fail while they'll still save the day with a more complex, 1 in a 1,000,000 chance scheme. Whew.


Mixed Nuts

Sometimes you end up at the strangest pages on Wikipedia:
Modifying words like "fancy" or "choice" have not historically carried any legal meaning in the United States, and they remain absent from the current regulations.[1] In a 1915 federal case against "fancy mixed nuts" that were argued by competitors to be an inferior grade, U. S. v. 25 Bags of Nuts, N. J. No. 4329 (1915), the court declined to accept a trade standard.

Most Useful Undergraduate Classes

Today I was thinking about how small the knowledge intersection has been between my undergraduate courses and my jobs. I made a list of all the classes I found directly useful at either of my two jobs, and it was shockingly small.

Classes I found useful at my previous, finance job (in order of usefulness):

1.  6.111 - Digital Design Lab / FPGA-based design lab
2. 6.001 - Intro to ComSci with LISP

Classes I've found useful at my current, graduate school job (in order of usefulness):

1.  6.111 - Digital Design Lab, or FPGA-based design lab
2. 6.004 - Computation Structures, or Build a CPU
3. 6.002 - Intro to Circuit Design
4. 17.477 - Technology and Policy of Weapons Systems
5. 6.001 - Intro to ComSci with LISP
6. 6.041 - Intro Probability

I think a lot of the other classes I took, such as the math classes and signal processing courses, have had a large impact on how I think and approach problems, but I haven't used this knowledge directly in my day to day life. I was shocked that 6.046, my algorithms course, isn't on the list. I haven't used any of the important concepts from 6.046 in either of my jobs. Just the other day I wrote a one-liner for bubble sort when I needed to sort data.

I'm not sure why there are so few classes on the lists, but I was thinking yesterday about why my design class, 6.111, was so high on both lists. I think it has to do with the design project, which was the first "real" design project I ever had. In 6.001, the programming introduction course, there was also a design project, but 6.001 worked on the principle of building up proven components. You wrote something and checked that it worked. Building bigger things meant building up the system one proven component at a time. When you were handed code, you read through and tested the code to check that it worked.

Unfortunately real life is more messy than this. Components are usually too complex to verify for yourself, and sometimes you have to work around interfaces that were designed for another task. My 6.111 project had to deal with these issues, along with the issues found in building up a proven and known system. My team created an electronic version of Labyrinth, the old tilting maze game wherein one tilts a board to guide a ball through a maze to a goal, avoiding hole traps along the way. Not only did we create a pretty big custom system, we also had to interface our system with a lot of 3rd party components, including tilt sensors, circuits that converted the tilt sensors into something understandable, a VGA controller and an LCD.

This was the first time that something I created had to work with sloppy, complex components. The components we interfaced with included complex but standard interfaces, like the LCD, and sloppy and non-standard ones, like the components written by the teaching assistants for the course. I still remember, four years on, that the tilt sensors could enter an error state during the read-out. This error state required a lot of hand-holding to work correctly. I also remember fighting for a week with the start-up sequence because of nuances with the timing.

It makes me sad that none of the theory courses I took actually have anything to do with my job, but the theory courses that I took don't really have much to do with anything. I indirectly use this theoretical knowledge every know and then, but rarely directly. Whenever I do digital circuit design, for example, my tools use the graph algorithms that I learned in 6.046, but this is abstracted away from me. I don't think I've used a single academic thing I learned in my senior year. What a waste of money. Sigh.


"He Thinks the Lavatory in his Cell is Fantastic"

Or so swoon Somali pirates about Dutch toilets.

I think civilized people have a different opinion.


Let's Really Be Equal Here

Insurance companies claim that women, especially child-bearing ones, use more health care than men, and hence pay higher premiums. Of course some people think this reason is non-sense, among them some law-makers introducing legislation to equalize the payments:
Senator John Kerry today introduced legislation that would improve health care benefits for women in the individual market by preventing insurers from charging them more, denying or limiting coverage based on their pregnancy status or delivery method, and ensuring comprehensive maternity coverage.

In related news, it was noticed that women live longer than men. Senator Kerry plans to fix this with a bill which would kill off specific women, equalizing the average lifetimes. He hasn't talked about his plans to equalize the "unmentionable parts of the human body."


Feeling Good About Being Stupid

I wish I had some people's tolerance for their own ignorance:
Second, we don't do a good enough job of teaching our students how to be productively stupid – that is, if we don't feel stupid it means we're not really trying...Focusing on important questions puts us in the awkward position of being ignorant.
Aside from the isolating nature of graduate school, constantly feeling stupid is probably the hardest thing to adapt to. I still haven't found a good way to focus in the face of infinite possibilities.

Oh, right, I read reddit to help me focus. Nevermind.




I've been staring at colored polygons for the past month, so I don't have anything interesting to say. You know the stress is getting to you when you run across random quotes on the internet and they bounce around inside your head. Enjoy the memes...or, rather, let the memes enjoy you.

Since its foundation nearly two decades earlier, Nato had had its headquarters in France. Now Nato would have to move. Furthermore, de Gaulle added, it was his intention that all American service personnel should be removed from French soil. "Does that include," [Lyndon B] Johnson is said to have replied, "those buried in it?"

When I was in the military they gave me a medal for killing two men and a discharge for loving one.

My father told me I had three career options. I could be a doctor, an engineer or a failure.

...any competent programmer, if given a chance to learn on the job, can become productive in a new software technology within a few weeks... [FYI I strongly disagree with the spirit of this quote, though the meaning is a bit truthful]

We hold these Truths to be self-evident, that all Men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty, and the pursuit of Happiness—-That to secure these Rights, Governments are instituted among Men, deriving their just Powers from the Consent of the Governed, that whenever any Form of Government becomes destructive of these Ends, it is the Right of the People to alter or abolish it, and to institute a new Government, laying its Foundation on such Principles, and organizing its Powers in such Form, as to them shall seem most likely to effect their Safety and Happiness.

Life is good, everyone just overreacts. Even me.


Accidentally Posted

I seemed to have accidentally posted a draft before it was ready, I apologize to anyone who saw the post, "Firsts." It wasn't supposed to go up yet. Maybe in August.



Ears Making Noise?

Did you know your ears make noise? And people want to use the noise as identification?

Called otoacoustic emissions (OAEs), the ear-generated sounds emanate from within the spiral-shaped cochlea in the inner ear. They are thought to be produced by the motion of hair cells within the outer part of the cochlea.
My hearing and speech class at MIT, 6.551, went over this phenomenon. Your ear contains an active amplifier that can also create sound. Under normal conditions the emissions are very pure tones that occur at frequencies specific to each ear. The 6.551 professors had a few interesting anecdotes about the OAEs - one knew a conductor who memorized the frequency of one of his OAEs, and used it for "perfect pitch."

IIRC, though, not everyone's ears have OAEs. Aside from the problems mentioned in the article above, the Wikipedia article goes over a few details that could hamper using OAEs for biometric passwords. Another, small issue is that your ears have different OAEs, so you'd have to calibrate any system for both ears.



I have been a bit surprised about the topics in my Dutch language courses. My previous foreign language courses were in high school, and American high schools avoid controversial topics. My Dutch courses tackle the difficult topics head-on. Our most recent lesson, "Are you married?", briefly went over some of the differences between marriage in the Netherlands and elsewhere. Weak English translation:
Dutch teacher: Do you have children?
Female student: No, after all I am not yet married.
Male teacher: Must you be married before you can have kids? Do you really need that? Is it really necessary?
Female student: Maybe not in the Netherlands, but in my society that is absolutely necessary.
Male teacher: What happens if a women is expecting a child while she isn't married?
Female student: Then you must immediately marry. Preferably with the father of the child.
Teacher: Not so long ago that also held for the Netherlands...the last 30 years, though, have seen many changes to marriage. People still marry, but frequently they'll live together first...You can also register with the government as "living together." Then you will be treated almost the same as if you are married, and it is a bit easier.
Another student: What is the difference between marriage and living together in the government's policy.
Teacher: That is indeed small, it is mostly the vows you've taken.

Aside from marriage, the book also goes over the population policy of the government, parties, alcohol, the police, and how the Dutch are friendly but difficult to know really well. I do not believe the policy on drugs is mentioned.

I'm not sure what to think about mentioning controversial topics with public opinions in the language course. They are only a small part of the course. I also think it is critical for immigrants to know about government policies and the values of the people. I think it is important that people make informed choices about where they live, the values of the people they live with, and what policies they support with their tax money. People are given a chance to share what their own country values during the discussion classes.

On the other hand, language courses are required for the spouses and other family members of any long-term immigrants. No one knows enough Dutch to explain the complex ideas behind the social values. It feels a bit like the government is forcing public opinion down the throats of minorities.

In the bigger picture, though, the language courses are one of the least controversial aspects of immigrating. Dutch law requires most new immigrants to watch a social orientation video containing gay men kissing and women on a crowded top-less beach. The video is so racy that an edited version of it was made specifically for Middle Eastern countries.

(I'm waiting for the sequel before I see it. I hear there is going to be an action sequence involving sheep)



Radioactive Ball

I thought they were talking about a dance, not a deadly pile of Cs137:
Officials told the BBC that they had detected what may be the missing Caesium-137, adding that it may have been melted down...The BBC's Quentin Sommerville in Beijing says China has an appalling record on industrial safety - there are around 30 cases of radioactive material being lost every year.

Earlier I posted about how radioactive sources are used in construction sites and old factories. I think this instance is interesting because the Chinese government controls the media, and I'm confused why they would admit something like this. I don't think an incident like this is very dangerous, but people panic when they hear the term radiation. Did the government decide it wasn't all that dangerous, and it would gain the trust of its citizenship if it gave out the information? Was there a leak? Are they worried about keeping quiet and something blowing up in their face? If you controlled the media, would you admit that someone lost a "ball" of radioactive material?

[Insert snarky joke about radioactive balls here]


Blame Condoms or Human Nature?

Do condoms spread HIV? Some recent comments by the Pope are causing quite a stir. But the Pope might be right. At play is something called the Peltzmann effect or risk compensation. When humans feel safer, they sometimes engage in riskier behavior. With the "safety" of a condom, people almost certainly engage in sex they would not normally have. Too much safer sex can be more dangerous than a little risky sex. Safer sex still has risks.

I wish I had time to dig into this, but I'm hosed.

EDIT: The exact comments under question are that HIV/AIDS in Africa is:
a tragedy that cannot be overcome by money alone, that cannot be overcome through the distribution of condoms, which can even increase the problem

The part about condoms sounds reasonable to me. The part about money is pretty non-sensical. He asserts a bit of wackoness right after, when he claims:
the traditional teaching of the Church has proven to be the only failsafe way to prevent the spread of HIV/Aids

That is bull$#!+.


Follow-up: Inches Overseas

Europeans measure the strangest things with inches:
... wearing six-inch heels confirm ... with four inches becoming the norm ... wore a five-inch-high pair ...
Does America really export that much fashion?

Earlier I posted pictures showing how monitor sizes are still quoted in inches.


Rants on Media Continued: Misleading Graphs

USA Today has a very misleading graph on the change in the American, Catholic population. The graph is meant to show the change in regional catholic population, but I found two problems between the graph and its mission. For the first problem, take a second and think about the circled states:

California and Texas have large increases in their Roman Catholic populations, and Florida has a sizable increase. These three states comprise 25% of the population of the US. This graph, which was supposed to represent growth in various regions, instead portrays a very inaccurate picture of overall growth. Yahoo! News breaks it down correctly:
Nationally, Catholics remain the largest religious group, with 57 million people saying they belong to the church. The tradition gained 11 million followers since 1990, but its share of the population fell by about a percentage point to 25 percent.

Would you have guessed, after looking at the graph above, that the Catholic population in the US increased? Or that the percentage of Catholics in the population dropped one percentage point, which is a drop in the portion of the population of roughly four percentage points (26 to 25)? By focusing on the four percentage point drop in the population portion data (even making this drop appear larger than it is), the graph misses both overall growth and the one percentage point drop in the overall population. USA Today's article text doesn't even mention the overall growth.

Forgoing the big picture to explain a less important point is the second problem with the graph. How would you visually show the information from the quote above? The more I have to create visual data, the more I'm struck by how much a sentence can communicate.

(Yahoo! News even links to the study. I still stand by my last rant, however.)


Short Rant: Lack Of Transparency in Online Media

Some Japanese scientists think that riding motorcycles is good for you. The study sounds pretty suspicious to me...funded by a motorbike company? Studying only twenty men? The other group rode either bicycles or cars? Only looking at whether scores go up, not starting levels?

So I want to call b$#!+ on this study....except I cannot find it. I googled "Kawashima motorcycle", but not one of the top five Google results links to the study or reports where the study is published. Kawashima's publication pages currently lack the study (hopefully this will change later on).

It drives me crazy when the media reports the results of a study without linking directly to it (or at least stating where said study was published). How can people state a conclusion without offering insight into the supporting process and information? This "internet" thing lets you link to the original data if it is available. At the very least there could be a link to a gated version.

Shame on Yahoo! News for failing to leverage the transparency of the internet.

And stay off my lawn!


Lost in Translation

Last weekend a few friends and I went skiing / snowboarding. I got up early to make pancakes, as there appeared to be pancake material available, but the pancakes tasted like cream of wheat. On close examination the "baking powder" looked a bit odd:

Perhaps I should have looked harder at that first word: mais-stärke.


100th Post

I made it to post 100. I think I have been posting too much, so I'm going to roll back my expectations for myself to four posts a month, with one of them a big post. Otherwise I think I will end up posting too many secondary links.

Things that I've learned:

- writing long posts is hard, but it has been good practice for my writing abilities
- most random links I still email to one person only. It has been tempting to post them to the blog, but I am happier when I don't
- comments are really rewarding, I now find myself leaving comments at other blogs (though I only rarely post a link back to my own).
- there was a lot to say about my big move at first, but I don't have much to say anymore
- I still have a few mementos ("I'll write about this later") that I haven't gotten around to researching. I thought I would find out about these things, but they haven't sprung up in conversation
- I now schedule a lot of my posts rather than write them on the spot.


Some Ugly Truths about Human Trafficking

The UN's Office on Drugs and Crime released its annual Global Report on Trafficking in Persons a few weeks ago.

The Dutch fared poorly. A uniform comparison across countries is difficult since reported data varies by country. Countries provide some sub-set of people prosecuted, convicted, investigated or suspected of trafficking. A quick look through the data suggests that the Netherlands is either much better at prosecuting people, or that human trafficking is a problem for the Dutch. Conviction and prosecution rates per capita in Holland were eight times as high as the UK. The UK has roughly four times the population of the Netherlands, but the UK prosecuted and convicted less than half the number of people that Holland did.

Another interesting anomaly was the gender breakdown of convictions in Eastern Europe. In Latvia, for example, women are convicted of less than 10% of all crimes, but they account for over half of human trafficking convictions.

Anyways, the big picture is very dim. Sometimes it is easy to forget that it is 2009.


Reddit Round-Up: Photoshop, Gender Biases when Rating Teachers, and Nuclear Reactors

Some interesting photoshop examples (EDIT on 2009-06-09: link is borked, my apologies). Who knows if they're real - maybe they were reverse photoshopped?

Apparently high school students like male physics teachers more, even when the numbers say something else.

Iran is starting computer tests for its budding nuclear reactor at Bushehr.


On Dirty Bombs and Construction Sites

Last week I got to play around with dangerous radiation, which was fun. But what was even better was talking to the people who work with the radiation. Apparently the Swiss government has a radiation "SWAT" team. I talked with a guy who was on the team about what they did, and he told me some crazy tales.

He said that he was routinely called to construction sites to deal with radiation problems. Apparently radioactive materials are commonly used on construction sites, especially in equipment that surveys the ground (sends waves into the ground and reads back the results). Bulldozers will sometimes accidentally drive over this equipment and expose the radiation source(s).

He told me the horror story of a factory worker in Chile who picked up an iridium source. Old factories use radiation sources for a variety of things, including flow meters, density sensors, and heating of all things! The source looked like a pen, and the worker picked it up. He tossed it from hand to hand (because it was so hot), and then put it in his back pocket.

At this point my colleague's story diverges from the internet. According to the IAEA, the worker showed the source to a few other people before some of them started to be sick. According to my colleague, the worker walked into a cafeteria and dosimeters of workers started going crazy.

They flew the worker to a French military hospital and immediately amputated a giant sphere (~10 cm diameter) of flesh from his butt, close to where he had the source. The French doctors used stem cells to treat him, and managed to save his life.

It was pretty fun to shot the breeze with this guy, especially on the subjects of dirty bombs and terrorism. We talked about how the current generation of bomb detectors at the borders was absurd. Shielding a uranium bomb from the border detectors or sneaking a bomb through under a common false alarm condition (hide the bomb in a truck with kitty litter and old electronics like CRTs) are not difficult feats of engineering. We talked about dirty bombs, and whether Cs-137 or Co-60 would make better "dirt".

The crazy part of my work with radiation is that now I feel a lot safer at Delft's nuclear facility than at a random construction site. If something horrible did happen, the people at nuclear facilities have the know-how to clean it up. Also, there are stringent regulations at the nuclear / radiation facilities I have been to.

If you need further proof of safety, just look at the moat at Delft's facility. Sadly the architect couldn't convince the university to spring for the draw-bridge option.


Don't Rub Beryllium Tools on your Skin

Cool fact: beryllium scissors, screwdrivers and pliers are used near MRI machines since the metal doesn't react (noticeably) to the magnetic field. I looked into getting some Be-tools, but apparently the metal is highly toxic and the tool sets are really expensive. $4,000 a tool-set expensive. Weak.


No French Hamsters?

I was wandering around Lausanne and saw an odd movie poster for "Volt", the translated version of the American movie "Bolt". I suppose hamsters are American, with their obesity and refusal to translate things:

I'd Focus Her Ion Beam

Over the past week I've been doing a bunch of stuff in Lausanne, Switzerland. Unfortunately most of it failed. Sigh.

But I got to play around with EPFL's focused ion beam (FIB) for another project. EPFL's FIB is a combination of an electron microscope, a platinum depositor, and a Gallium microscope/etcher.

What was I doing with the FIB? I was fixing integrated circuits. One fixes circuits by etching away parts of the chip (the equivalent of cutting a line), and then using the platinum depositor to short other lines. This re-routes the signals, and fixes your design mistake. The etching is performed by the Ga microscope. Normally the number of Ga ions does not drastically effect the surface, but if you use a lot of Ga ions, then you can etch away parts of the chip. The etching occurs even when you're using the Ga microscope as a microscope - in other words, if you use the microscope for too long, you etch away the entire surface off the chip. As far as I know electron microscopes don't have sufficient energy to etch the surface, but it wouldn't surprise me if a high-energy electron microscope could also etch a chip.

The etching is mechanical, so the etched atoms spray above the chip. The etching is performed in a vacuum so that these atoms don't (hopefully don't) end up on the surface of the chip and interfere with surface electronics.

Anyways, that is enough theory. One of the other groups has been having trouble properly simulating a design, so they wanted to use the FIB at EPFL to test something. Since I was going to be in Switzerland, I oversaw the FIB use.

A high level overview is that we needed to re-route a grounded signal. A line was shorted to ground, and we needed to short it to the power rail instead. I'll call the line we're working with line "Q". First, we had to cut line Q. Next, we exposed line Q a distance away. We then exposed the power line. Finally, we shorted line Q's exposure to the power line's exposure. Well, at least we think we did. No one has tested the chips yet.

You might ask yourself why we didn't just short the power line to line Q's cut directly. The platinum (Pt) deposition isn't easily controlled (we're working with nanometers of distance), and we would have risked shorting both sides of the cut to the power rail if we tried to short the power rail to Q at the cut. Risking a power rail to ground short is bad. Very bad.

First up, we cut line Q. Here is a picture:

The hole near the bottom-middle of the L-shaped objects is the cut. I believe the L-shaped and square objects are support patterns on the surface of the chip. Silicon foundries yell at you if you don't use a minimum amount of metal for each layer. Something like a third of the layer must be used. I'm not sure if it is an issue with the lower layers supporting the upper layers or the implant process, but either way it is easier to put patterns on the un-used parts of the chip than having the foundry yell at you. You can see some lower layer patterns in the cut, they're the twelve or so little dots. We use different patterns for different layers, ostensibly for better chip support. Or something. I'm not 100% sure about reasons behind the patterns, so take everything I saw about them with a grain of salt.

Anyways, next up we needed to expose the Q line farther down:

I've circled the exposed Q line, which runs vertically. Ga ions interact differently with conductors, and the results is that conductors show up more brightly in pictures from this Ga microscope. If this pictures doesn't convince you that we hit the line, I wasn't convinced either. Due to the support patterns, the Ga ions etch through the chip at different speeds, and it was impossible to get a picture-perfect exposure. Also, please keep in mind that the line is about 500 nm wide. This was the best result of several failed attempts on previous chips.

Similarly, we found the power supply line, which ran horizontally:

Finally, we used the Pt depositor to short the two:

As you can see, some of the surface material was sucked into the hole when we deposited the Pt bypass. I don't know if the material melted or was pulled down from a mechanical force.

As I previously said, we haven't tested these chips. Even if they don't work, it was a very interesting event to see. Please feel free to ask any questions, though I'm not sure I'll be able to answer them. Single bypass surgery on integrated circuits isn't my specialty.