# Anti-miscegenation laws

I came across this tidbit about anti-miscegenation laws in the US as applied to groups other than blacks in Randall Kennedy’s Interracial Intimacies. In these states, the groups not allowed to marry whites were:

• Arizona : Mongolians, Malayans, Hindus, Indians
• California : Mongolians, Malayans
• Georgia : Japanese, Chinese, Malayans, Asiatic Indians
• Mississippi : Mongolians
• Montana : Chinese, Japanese
• Nevada : Ethiopians, Malays, Mongolians
• Wyomimg : Malayans, Mongolians

# Tips for writing

As a postdoc at a school with a gigantic biosciences program and surrounded by other biomedical research institutes (Scripps, Burnham, etc), a lot of the professional development workshops offered here are not specifically helpful to me. For example, I went to a workshop on writing grants, but it was almost entirely focused on NIH grants; the speaker said he had never applied to the NSF for a grant. Still, I did pick up general tips and strategies about the process of writing a grant. In the same vein, I read an article in The Scientist (registration required) about improving scientific writing which offered ideas applicable to technical writing in general. One that stuck out for me was:

Write daily for 15 to 30 minutes
During your daily writing sessions, don’t think about your final manuscript. Just write journal entries, says Tara Gray, director of the teaching academy that provides training and support to New Mexico State University professors. “People think there’s two phases of a research project—doing the research and writing it up,” she says. Rather than setting aside large chunks of time for each activity, combine them to improve your writing and your research. The first time Gray encouraged a group of faculty members at New Mexico State to adhere to this schedule for three months, they wrote about twice as much as their normal output.

I think I’ll try doing this. I often complain that I live an “interrupt-driven” lifestyle, but sometimes flailing on some very involved epsilonics at the last minute to get something to work results in errors, tension, and woe.

# US drones’ video feed was wiretapped

From Bobak I saw that US drones in Iraq have been hacked because “the remotely flown planes have an unprotected communications link” but “there was no evidence that they [insurgents] were able to jam electronic signals from the aircraft.”

This illustrates nicely the difference between eavesdropping and jamming. However, a nice by-product of anti-jamming codes using shared encryption keys (here they can be easily agreed upon before the drone takes off) is that sometimes you can get both eavesdropping and jamming protection at the same time.

# Bayes-Ball in a nutshell

One of the fun thing about graphical models is that arguments can be done by looking at diagrams (kind of like a diagram chase in algebraic topology). One such trick is from R.D. Shachter’s paper in UAI called “Bayes-Ball: The Rational Pastime (for Determining Irrelevance and Requisite Information in Belief Networks and Influence Diagrams)” (see it here. for example). This is a handy method for figuring out conditional independence relations, and is a good short-cut for figuring out when certain conditional mutual information quantities are equal to 0. The diagram below shows the different rules for when the ball can pass through a node or when it bounces off. Gray means that the variable is observed (or is in the conditioning). I tend to forget the rules, so I made this little chart summary to help myself out.

# Another take on matched sources and channels

Ehsan Ardestanizadeh posed a little problem in Young-Han Kim‘s group meeting before break and Paolo Minero presented a cute solution which I thought might be of interest. It’s related to ideas my advisor, Michael Gastpar worked on in his thesis.

Suppose I have a Gaussian variable $S$ that is $\mathcal{N}(0,1)$, so zero-mean and unit variance. If I observe $Y = S + Z$ where $Z$ is also $\mathcal{N}(0,1)$ and independent of $S$, the minimum mean-square error (MMSE) estimate of $S$ given $Y$ is just

$\mathsf{MMSE}( S | Y) = \frac{1}{2} Y$

and the MSE is $\mathbb{E}[ (S - \hat{S})^2 ] = 1/2$. The question is this: can we somehow get an MSE of less than 1/2 by “encoding” $S$? Suppose now we can take any function $f$ and let $X = f(S)$, and $Y = X + Z$ but with the restriction that $\mathsf{Var}(X) \le 1$. That is, the encoding cannot take any more power.

The answer is no, and comes via an “information theoretic” argument. Consider the vector version of the problem where you have $n$ iid unit variance Gaussians $S^n$ and you want to estimate $S^n$ from $Y^n = f(S^n) + Z^n$ where $Z^n$ is iid unit variance Gaussian as well. The goal is to minimize the average per-letter distortion:

$d(\hat{S}^n, S^n) = \frac{1}{n} \sum_{i=1}^{n} \mathbb{E}[ (S_i - \hat{S}_i)^2 ]$

This is just the problem of joint source-channel coding of a Gaussian source over an AWGN channel with quadratic distortion and encoding function $f$ must satisfy a unit power constraint. For this problem the rate distortion function is

$R(D) = \frac{1}{2} \log \frac{1}{D}$

and the capacity of the channel is $\frac{1}{2} \log(1 + 1) = \frac{1}{2}$. Since separate source coding (compression) followed by channel coding (error control) is optimal, in order to get distortion $D$ the rate $R(D) \le 1/2$ so $D \ge 1/2$. Furthermore, this is achievable with no coding at all by just setting $f(S^n) = S^n$.

Now if there was a scheme for the single-letter case which got MSE less than 1/2, we could concatenate it to get a vector scheme with distortion less than 1/2. But since $D \ge 1/2$ in the optimal code, we get a contradiction. Thus encoding does not help in the single-letter case either. If $S$ isn’t Gaussian the whole story changes though.

# Concert Bleg : The Messiah

I’m singing again!

The Messiah

Orchestra Nova
Conducted by Jung-Ho Pak

Bach Collegium San Diego
Ruben Valenzuela, Music Director

Guest Artists:
Virginia Sublett, Soprano
Katherine Lundeen, Alto
Robert MacNeil, Tenor
John Polhamus, Bass

St. Paul’s Cathedral, San Diego
Thursday, December 10, 7:30 p.m.

St. James by-the-Sea Episcopal Church, La Jolla
Friday, December 11, 7:30 p.m.

Solana Beach Presbyterian Church, Solana Beach
Saturday, December 12, 7:30 p.m.

This season’s Masterpiece Messiah is an encore presentation of our dramatic video experience of the great masterpieces of art
complementing the most famous of all oratorios, George Frideric Handel’s Messiah. Joined again by Bach Collegium San Diego, our
interpretation has become well-known for its original 18th-century period approach, creating an unforgettable emotional experience that