Category: Sciency things

Some of the papers on this month’s reading list

• Risk of Cataract after Exposure to Low Doses of Ionizing Radiation: A 20-Year Prospective Cohort Study among US Radiologic Technologists, Am. J. Epidemiol. 2008 168: 620-631
• Automatic exposure control in pediatric and adult multidetector CT examinations: A phantom study on dose reduction and image quality, Med. Phys. Volume 35, Issue 10, pp. 4567-4576
• Singular value description of a digital radiographic detector: Theory and measurements, Med. Phys. Volume 35, Issue 10, pp. 4744-4756
• Optically stimulated luminescence (OSL) dosimetry in medicine, Phys. Med. Biol. 53 R351-R379
• Evaluation of quantitative ⁹⁰Y SPECT based on experimental phantom studies, Phys. Med. Biol. 53 5689-5703
• An easy-to-use phantom and protocol for weekly PET quality assessment: A multicenter study, Med. Phys. Volume 35, Issue 9, pp. 3922-3934

A couple of them would make good journal club entries.

The Large Synoptic Survey Telescope (LSST) is a very impressive project, both in the size of the telescope (8.4m 3 mirrors), the science to be conducted, the size of the camera (3.2 Gpixels worth of CCD imagers) and the amount of data that will be generated using it (estimated at 30 TB/night). That’s a lot of data to manage. And I thought the 15TB/year of data we generate in Radiology was impressive.

The telescope will take movies of the night sky, with each frame of the movie consisting of a 15s exposure. The wide field lets the camera watch large sections of the sky while the large mirror lets the camera detect very faint objects. Multiple exposures can be added together to create the equivalent of a single long exposure image for deep field imaging.

Perhaps one of the more intriguing aspects of the project is that the data will be made freely available as it’s generated for anybody to make use of.

Q: Will LSST imaging data be available world-wide for scientific use?
A: Our goal is open-source, open-data. Currently US federal agencies and foundations support LSST R&D, and the LSST construction proposal is to a US agency. However, our goal is to make the LSST scientific data available world-wide. To realize this goal, we are working with foreign institutions and governments to share the costs. The ten LSST science collaborations are open to all US scientists, and hopefully soon to an increasing number of scientists in other countries.

This project is going to generate a lot of great data for astronomers to play with once it comes online.

That’s the fancy schmancy word for solar power.

This month’s issue of Physics Today has (in addition to the blurb on social physics) a neat article on how to set up a small solar power system for your house to run things like the TV or other appliances. Even if you don’t have the skill to put one together yourself, the article is an interesting read that shows you what goes into a PV (photovoltaic) system and how they work. It’s not a comprehensive guide though, but is still very informative. The author emphasizes the fact that you don’t need to make your house fully dependent on solar (going off the grid). Even if the system you build only powers a few appliances, you have the satisfaction of being able to use power generated by the sun and not from some power plant somewhere.

From the article:

By offsetting electricity bills, properly sized grid-tie systems can recover the cost of installation in as little as 8 years in states with rebate programs—though 15 years is a more typical time frame. Small standalone PV systems will likely not recover installation costs at today’s energy rates: Many components are necessary or desirable whether the system is large or small, but they cost similar amounts in either case. Still, few PV owners are motivated by purely economic reasons. That couldn’t be more true for me. I opted to build a small standalone system to power my modest living room, which includes a TV, DVD/VCR, stereo, and lighting. My goal was to learn the ins and outs of a personal PV system, characterize performance, and experiment with various configurations. The sense of satisfaction I get when watching a movie or reading a book using stored solar energy is reward enough.

We physicists are getting into everything. Now, it seems there’s something called ‘social physics’. There must be something to it because so far this week I’ve come across two articles in this ‘social physics’ field.

The first paper is related to food, specifically the staying power of cultural and national dishes.

Abstract:

Food is an essential part of civilization, with a scope that ranges from the biological to the economic and cultural levels. Here, we study the statistics of ingredients and recipes taken from Brazilian, British, French and Medieval cookery books. We find universal distributions with scale invariant behaviour. We propose a copy-mutate process to model culinary evolution that fits our empirical data very well. We find a cultural `founder effect’ produced by the non-equilibrium dynamics of the model. Both the invariant and idiosyncratic aspects of culture are accounted for by our model, which may have applications in other kinds of evolutionary processes.

The second article from the July issue of Physics Today. It’s a more general news article about how social networks are starting to attract physicists and mathematicians.

From the article:

Researchers studying self-organizing social networks look at how links are formed between individuals, whether some individuals or nodes are better connected than others, and the collective action or behavior of the entire network. In the past social scientists relied on surveys and questionnaires, but on the Web “social behavior is self-documenting—it leaves traces behind,” says Microsoft research sociologist Marc Smith, who studies and designs improvements for social online applications.

Some condensed-matter physicists are drawn to social network modeling because it is similar to a many-body problem, says Huberman. Like spin-glass materials that have disordered and unpaired magnetic spins, individuals have conflicting interactions with their neighbors, and their uniqueness leads to disorder, says Université de Paris-Sud physicist Marc Mézard. It’s a patent from Mézard’s spin-glass theory work that is now paying off for Microsoft: He, Chayes, and collaborators are using that patent to solve optimization problems such as sending messages from one node to others, bypassing intermediates.

See, there’s physics in everything!