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Spirit and Opportunity computer guts

A post over at Slashdot and an article over at Space.com talk about the computational innards of the Spirit and Opportunity rovers. They’re surprisingly low-tech, but work well and NASA seems to find them reliable.
From the Space.com article,

RAD6000 microprocessors are radiation-hardened versions of the PowerPC chips that powered Macintosh computers in the early 1990s, with 128 megabytes of random access memory (RAM) and capable of carrying out about 20 million instructions per second.

Not as powerful as one might think, but then again I suppose you don’t need much computing power to operate a robot. They did jam it full of memory though.
What I think is more cool is

In addition to VxWorks’ reliability, the system allows users to add software patches — such as a glitch fix or upgrade — without interruption while a mission is in flight. “We’ve always had that [feature] so you don’t have to shut down, reload and restart after every patch,” Blackman said, adding that some commercial desktop systems require users to reboot their computers after a patch

Now if only Microsoft could make Windows do that…

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Journal Club: Phase Contrast Imaging

The idea behind this paper is relatively easy to get. Traditionally, x-ray imaging is examined using the ‘light as particle’ method of thinking. It works, and the math is easy. But nobody really examines x-ray imaging from the ‘light as a wave’ point of view. Recently though, there have been a number of articles looking at phase imaging for x-ray systems. This article (Wu X, Liu H, “Clinical implementation of x-ray phase-contrast imaging: Theoretical foundations and design considerations“, Med Phys 30, 2169-2179 (2003)) is one of them.

It’s a topic that I’ve been peripherally interested for a while. I’ve always wondered what x-ray imaging physics might look like formulated from the ‘light as wave’ perspective.

One thing I found interesting was that the refractive portion of the refractive index for tissue (δ, Eq 1 & 2) was much larger than the absorptive portion (β, Eq 1), the implication being that it ought to be relatively easy to do phase based imaging.

One of the interesting things in this paper is that the authors extend the theory of phase contrast imaging to real-world x-ray machines as opposed to specialized micro-focus x-ray units or monochromatic x-rays from a synchrotron (Section II.C) and end up predicting things that previous treatments did not (A Pogany, D Gao, S Wilkins, “Contrast and resolution in imaging with a microfocus x-ray source“, Rev Sci Instrum 68, 2774-2782 (1997). Mammography machines fit the resolution requirements for observing phase contrast, but an x-ray tube with a smaller focal spot is needed. Still, the requirements aren’t something you find in a run-of the mill x-ray unit. However, the fact that phase contrast imaging can be done with polychromatic beams is exciting.

Theory is tested by simulating a mammography imaging system to find optimal values for source-object and object/detector distances. Experiments also illustrate the exciting prospects of phase contrast imaging in mammography (Section IV).

A well written paper, with some very interesting and promising results. Some of the more complicated math has been glossed over, but details can be found in another paper by the same authors.

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US Patent office silliness

I’ve seen the USPTO grant some pretty ridiculous patents over the past few years, but I think patent 6,671,714 (story at Slashdot and Geek.com) takes the cake.

From the abstract of the patent:

The present invention comprises a method, apparatus and business system for allowing on-line communications with members of a group of recipients for whom the invention has been implemented. A group may, for example, comprise members of a particular business or profession. For example, a group may consist of doctors admitted to practice medicine in the United States. Individual members of the group may or may not have existing internet presences. The invention allows online users to communicate with each member of a given group regardless of whether or not the member has an existing internet presence. In one or more embodiments, the invention does so by setting up a database of contact information for members of the group, creating an internet presence for each member of such group, creating an on-line user interface allowing a user to access the member’s created internet presence, and providing means of communications between the created internet presence and the member recipient.

And furthermore, claim

  1. A method for assigning URL’s and e-mail addresses to members of a group comprising the steps of:
    • assigning each member of said group a URL of the form “name.subdomain.domain”; and
    • assigning each member of said group an e-mail address of the form “name@subdomain.domain;”
    • wherein the “name” portion of said URL and said e-mail address is the same and unique for each particular one of said members such that an only difference between said URL and said e-mail address for said member is that in said URL the “@” symbol of the e-mail address is replaced with a “.” and wherein said “subdomain” portion of said URL and said e-mail address is the same for all members of said group.
  2. The method of claim 1 wherein said members of said group comprise members of a licensed profession.

So essentially what the patent was granted for is a way of assigning domain names, URLs and email addresses like

  • tom@runspotrun.com, http://tom.runspotrun.com/
  • jane@runspotrun.com, http://jane.runspotrun.com/
  • harry@runspotrun.com, http://harry.runspotrun.com/

And they have the gall to call this an invention!

And as patent owners are prone to do, the patent owner promptly proceeded to file lawsuits against two TLD registration companies for patent infringement, essentially a form of government santioned extortion. A patent that should never have been granted if collective people at the USPTO had a brain among them. A patent for which it should be fairly trivial to find prior art for, considering the patent was only filed in 1999.

Really makes one wonder about the people who work at the USPTO and review applications. How much research gets done researching the validity of a patent? What kind of training and background do these examiners have? Some of patents that have been granted recently really want to make you smack all of them with an idiot stick.

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My Yahoo! has RSS aggregating!

Learned from Jeremy Zawodny that My Yahoo! now has an RSS aggregator module you can put on your My Yahoo! page. I might actually start using the thing again now. It’s only in beta, but I haven’t seen anything resembling a problem yet in the 5 minutes I’ve been casually using it. And you can even ping it.

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Body Challenge Week 2

Ok, it’s the end of week 2, and although I haven’t been able to squeeze in any work out sessions yet (although I’ve been doing a lot of walking around and still take the stairs everywhere I go), I’ve still managed to drop 4 pounds, so now I”m down to 172. Feels good. Really need to start doing some workouts though, but with this AAPM assignment I need to get finished by next week, I don’t seem to have much time. Maybe this coming week.