Arimaa is a highly competitive strategy game. It was designed to be:
* Difficult for computers.
* Playable with a standard chess set.
* Fun and interesting for humans.
Arimaa Tutorial. It looks interesting.
Author Archives: curiouscat
YouTube Architecture
This very interesting post by Todd Hoff gives an overview of the YouTube Architecture and thus some interesting ideas on large scale web application architecture.
Each video hosted by a mini-cluster. Each video is served by more than one machine.
* Using a a cluster means:
– More disks serving content which means more speed.
– Headroom. If a machine goes down others can take over.
– There are online backups.
* Servers use the lighttpd web server for video:
– Apache had too much overhead.
– Uses epoll to wait on multiple fds.
– Switched from single process to multiple process configuration to handle more connections.
* Most popular content is moved to a CDN (content delivery network):
– CDNs replicate content in multiple places. There’s a better chance of content being closer to the user, with fewer hops, and content will run over a more friendly network.
– CDN machines mostly serve out of memory because the content is so popular there’s little thrashing of content into and out of memory.
* Less popular content (1-20 views per day) uses YouTube servers in various colo sites.
– There’s a long tail effect. A video may have a few plays, but lots of videos are being played.
* Using a a cluster means:
– More disks serving content which means more speed.
– Headroom. If a machine goes down others can take over.
– There are online backups.
* Servers use the lighttpd web server for video:
– Apache had too much overhead.
– Uses epoll to wait on multiple fds.
– Switched from single process to multiple process configuration to handle more connections.
* Most popular content is moved to a CDN (content delivery network):
– CDNs replicate content in multiple places. There’s a better chance of content being closer to the user, with fewer hops, and content will run over a more friendly network.
– CDN machines mostly serve out of memory because the content is so popular there’s little thrashing of content into and out of memory.
* Less popular content (1-20 views per day) uses YouTube servers in various colo sites.
– There’s a long tail effect. A video may have a few plays, but lots of videos are being played.
I have noticed a large increase in significant delays (taking 10-20 seconds to start playing) with YouTube in the last few months.
Contradictory Medical Studies
I have written before about false research findings. This is an important topic – we need to remember that the interpritation of one study (or many studies) in not necessarily conclusive. Another article – When Medical Studies Collide:
Two years ago, the headlines blared that echinacea was a bust. Millions of people who believed the best-selling herbal remedy was warding off colds were probably deluding themselves, according to The New England Journal of Medicine. Now echinacea is back in the news. This time, it works! So says a study in The Lancet Infectious Diseases.
How could two studies come to such different conclusions—especially when there have been no new trials of the herb? While the New England Journal reported on one clinical trial, authors of the latest report combined data from previous studies, a controversial approach called a meta-analysis. Its conclusion is dramatically different—not just from that of the New England Journal paper, but also from a review last year of the same studies.
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The problem is, the world of medical and health research is messier than most people realize. Black-and-white answers are rare, even when it comes to a single drug trial.
Just remember those last two sentences. Very simple. And most people would agree if you showed them those two sentences and asked if they agreed. But then they see a headline and away they go… Just force yourself to repeat that idea every time you see a health report. Don’t believe the headline without strong support.
An interesting tidbit from the article. The coneflower is the source of echinacea. I tried to find photos that I am pretty sure I have on my hard drive of the flowers in my back yard, but I couldn’t.
Related: Correlation is Not Causation – Another Paper Questions Scientific Paper Accuracy
High Pay for Engineering Graduates – July 2007
From the National Association of Colleges and Employers survey , Starting Salary Offers to Class of 2007 Continue to Rise.
| Degree | Average Salary Offer | Increase over 2006 |
|---|---|---|
| Chemical Engineering | $59,361 | 5.4% |
| Civil Engineering | $48,509 | 5.4% |
| Computer Engineering | $56,201 | 4.8% |
| Computer Science | $53,396 | 4.1% |
| Mechanical Engineering | $54,128 | 4.6% |
| Electrical Engineering | $55,292 | 3.2% |
| Information sciences and systems | $50,852 | 4.6% |
Economics was the next highest pay reported by NACE at $48,483. So once again engineering graduates are being paid well. Some other majors: Accounting – $46,718; English – $32,553 and Psychology $31,631.
Related: Lucrative college degrees – Engineering Graduates Get Top Salary Offers (2006) – Engineering Starting Salaries (2005) – science and engineering career related posts
Research on Why Healthy Living Leads to Longer Life
New Clue into How Diet and Exercise Enhance Longevity
In their experiments, the researchers sought to understand the role of the insulin-like signaling pathway in extending lifespan. This pathway governs growth and metabolic processes in cells throughout the body. The pathway is activated when insulin and insulin-like growth factor-1 switch on proteins inside the cell called insulin receptor substrates (Irs).
Other researchers had shown that reducing the activity of the pathway in roundworms and fruitflies extends lifespan. Despite those tantalizing clues, White said, “The idea that insulin reduces lifespan is difficult to reconcile with decades of clinical practice and scientific investigation to treat diabetes.” “In fact, based on our work on one of the insulin receptor substrates, Irs2, in liver and pancreatic beta cells, we thought more Irs2 would be good for you,” said White. “It reduces the amount of insulin needed in the body to control blood glucose, and it promotes growth, survival and insulin secretion from pancreatic beta cells.
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“Diet, exercise and lower weight keep your peripheral tissues sensitive to insulin. That reduces the amount and duration of insulin secretion needed to keep your glucose under control when you eat. Therefore, the brain is exposed to less insulin. Since insulin turns on Irs2 in the brain, that means lower Irs2 activity, which we’ve linked to longer lifespan in the mouse.”
Related: Eat food. Not too much. Mostly plants. – Regular Exercise Reduces Fatigue – Diabetes Breakthrough – $500 Million Over the Next 5 Years to Help Reduce Childhood Obesity in USA
Evolutionary Design
Evolutionary algorithms now surpass human designers by Paul Marks:
Evolutionary Algorithms take two parent designs – for a boat hull, say – and blend components of each, perhaps taking the surface area of one and the curvature of another, to produce multiple hull offspring that combine the features of the parents in different ways. Then the algorithm selects those offspring it considers are worth re-breeding – in this case those with the right combination of parameters to make a better hull. The EA then repeats the process. Although many offspring will be discarded, after thousands of generations or more, useful features accumulate in the same design, and get combined in ways that likely would not have occurred to a human designer. This is because a human does not have the time to combine all the possibilities for each feature and evaluate them, but an EA does.
Evolving new designs is very cool. One point I would like to make (I am biased since my father did a great deal of work in this area) is the power of design of experiments to allow experimenting on multiple factors at once. This is a methodology that is still used far too little. Regardless, evolutionary design is very cool. The Human-Competitive awards highlight some examples.
Related: Statistics for Experimenters – Invention Machine – Evo-Devo – Evolution In Action
National Science and Technology Medals
The 2005 and 2006 National Medals for Science and Technology were awarded at a White House Ceremony this week. The National Science and Technology Medals Foundation web site has photos of each award winner receiving their medals this year and a list of all winners. The National Medal of Science was established by Congress in 1959 as a Presidential award, has recognized 441 of America’s leading scientists and engineers. The evaluation criteria is based on the total impact an individual’s work has had on the present state of physical, chemical, biological, mathematical, engineering, behavioral or social sciences.
The National Medal of Technology was established by Congress in 1980 as a Presidential award, has recognized 146 individuals and 26 companies whose accomplishments have generated jobs and created a better standard of living. Their accomplishments best embody technological innovation and support the advancement of global U.S. competitiveness.
Related: 2004 Medal of Science Winners (including Norman E. Borlaug) – 2004 National Medal of Science and Technology Ceremony – 2007 Draper Prize to Berners-Lee – Shaw Laureates 2007 – Millennium Technology Prize to Dr. Shuji Nakamura
List of all winners from the White House press release: Continue reading
Time
Planck time—the smallest unit of time that has any physical meaning—is 10-43 second, less than a trillionth of a trillionth of an attosecond. Beyond that? Tempus incognito. At least for now. Efforts to understand time below the Planck scale have led to an exceedingly strange juncture in physics. The problem, in brief, is that time may not exist at the most fundamental level of physical reality.
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Einstein’s theories also opened a rift in physics because the rules of general relativity (which describe gravity and the large-scale structure of the cosmos) seem incompatible with those of quantum physics (which govern the realm of the tiny). Some four decades ago, the renowned physicist John Wheeler, then at Princeton, and the late Bryce DeWitt, then at the University of North Carolina, developed an extraordinary equation that provides a possible framework for unifying relativity and quantum mechanics. But the Wheeler-ÂDeWitt equation has always been controversial, in part because it adds yet another, even more baffling twist to our understanding of time.
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Einstein’s theories also opened a rift in physics because the rules of general relativity (which describe gravity and the large-scale structure of the cosmos) seem incompatible with those of quantum physics (which govern the realm of the tiny). Some four decades ago, the renowned physicist John Wheeler, then at Princeton, and the late Bryce DeWitt, then at the University of North Carolina, developed an extraordinary equation that provides a possible framework for unifying relativity and quantum mechanics. But the Wheeler-ÂDeWitt equation has always been controversial, in part because it adds yet another, even more baffling twist to our understanding of time.
“One finds that time just disappears from the Wheeler-DeWitt equation,” says Carlo Rovelli, a physicist at the University of the Mediterranean in Marseille, France. “It is an issue that many theorists have puzzled about. It may be that the best way to think about quantum reality is to give up the notion of time—that the fundamental description of the universe must be timeless.”
Interesting. As usual, quantum actions seem bizarre. Related: Quantum Mechanics Made Relatively Simple Podcasts – Physicists Observe New Property of Matter – Particles and Waves – Quantum Theory Fails Reality Checks – Physics Concepts in 60 Seconds
Light-harvesting Bacterium Discovered in Yellowstone
Surprising new species of light-harvesting bacterium discovered in Yellowstone
In the hot springs of Yellowstone National Park, a team of researchers has discovered a novel bacterium that transforms light into chemical energy.
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Remarkably, the new genus and species Cab. thermophilum also belongs to a new phylum, Acidobacteria. The discovery marks only the third time in the past 100 years that a new bacterial phylum has been added to the list of those with chlorophyll-producing members. Although chlorophyll-producing bacteria are so abundant that they perform half the photosynthesis on Earth, only five of the 25 major groups, or phyla, of bacteria previously were known to contain members with this ability.
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Remarkably, the new genus and species Cab. thermophilum also belongs to a new phylum, Acidobacteria. The discovery marks only the third time in the past 100 years that a new bacterial phylum has been added to the list of those with chlorophyll-producing members. Although chlorophyll-producing bacteria are so abundant that they perform half the photosynthesis on Earth, only five of the 25 major groups, or phyla, of bacteria previously were known to contain members with this ability.
“The microbial mats give the hot springs in Yellowstone their remarkable yellow, orange, red, brown and green colors,” explained Bryant. “Microbiologists are intrigued by Octopus and Mushroom Springs because their unusual habitats house a diversity of microorganisms, but many are difficult or impossible to grow in the lab. Metagenomics has given us a powerful new tool for finding these hidden organisms and exploring their physiology, metabolism and ecology.”
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Unexpectedly, the new bacterium has special light-harvesting antennae known as chlorosomes, which contain about 250,000 chlorophylls each. No member of this phylum nor any aerobic microbe was known to make chlorosomes before this discovery. The team found that Cab. thermophilum makes two types of chlorophyll that allow these bacteria to thrive in microbial mats and to compete for light with cyanobacteria.
This discovery is particularly important because members of the Acidobacteria have proven very hard to grow in laboratory cultures, which means their ecology and physiology are very poorly understood. Most species of Acidobacteria have been found in poor or polluted soils that are acidic, with a pH below 3. However, the Yellowstone environments are more alkaline, about pH 8.5 (on a scale of 1 to 14). Bryant noted, “Judging from their 16S rRNA sequences, the closest relatives of Cab. thermophilum are found around Mammoth Hot Springs in Yellowstone and hot springs in Tibet and Thailand. As we look more closely, we may find relatives of Cab. thermophilum in the microbial mats of thermal sites worldwide.”
Photo of Mammoth Hot Springs, Yellowstone National Park by John Hunter.
Related: Yellowstone National Park Photo Essay – Bacterium Living with High Level Radiation – Where Bacteria Get Their Genes
Camera Fashion
Another merging of fashion and technology. Images are printed that are not visible to the eye but are to a camera. It does bring to mind some interesting applications.
Related: Hug Shirt – Gadgets and Gifts