gregburek
gregburek on Hacker News
The press release (edit: and I) skipped a step: "A portion of the laser beam is split off with a glass plate and directed to a photodetector that provides the syn- chronization signal for the camera. The camera images the incoming light on a slit and this slit on a photocathode where photons excite electrons. These electrons are accelerated in a vacuum tube and deflected by an electric field perpendicular to their direction of motion and perpendicular to the direction of the slit. The signal generating this field is obtained by filtering and amplifying the synchronization signal from the laser. The image is thus spread out over time in a “streak” that hits a micro channel plate at the far end of the vacuum tube that further amplifies the electrons and directs them to a phosphor screen where they are converted back to photons. The screen is than imaged on a conventional low noise CCD camera. The complete time interval captured in this way spans about 1 nanosecond." [Picosecond Camera for Time-of-Flight Imaging]
So a photo cathode generates electrons which are deflected.
The MIT News Office article has more details than the PR video and a link to the paper:
http://web.mit.edu/newsoffice/2011/trillion-fps-camera-1213....The actual imaging device is just a long line of photosensors. The camera aperture uses a varying electric field to deflect photons that arrive later to sensors further down the line, producing an image in effective 2D - 1D of space and 1D of time. By repeating the scene and slowly scanning the camera's mirror, a composite video is built that shows diffusion of a picosecond laser pulse.
Enable javascript to load current positions.
I have an electrical engineering background and all this FP VS IP sounds like Async Logic VS State Machines. How far off base is that description?
I'm getting the feeling that with all the unique server setups in use, monitoring and metrics systems are going to be just as unique and specific.
There are some interesting process monitoring projects out there like god, monit and bluepill, as well as ec2/cloud specific stuff from ylastic, rightscale and librato silverline. Have you ever used any of those tools?
Fitting all these together for my setup is trial and error, but it really does force me to think hard about my tools and assumptions even before I get hard data.
How does everyone here gather and analyze their metrics? What do you have always deployed and what do you use when shit hits the fan?
[Edit for typo]
Unfortunately, this last AWS problem affected multiple AZs in the us-east region. The OP very well may have had an alternate AZ failover plan, but like Quora, Sencha, Reddit, FourSquare and Heroku, they probably kept it region specific.
As for backing up to multiple regions, I can imagine them thinking that sending everything over the public internet as being a bad idea. However, not having a multi-region/multi-provider failover plan was a worse one.
I think that Microsoft Corp. v. i4i Limited Partnership, which was argued before the Supreme Court on April 18, may change how this plays out in the end.
"Since 1983, the courts have followed a clear, firm rule: In order to overcome the statutory presumption that a patent is valid, a litigant must provide clear and convincing evidence that a patent is invalid. That's a high hurdle to overcome. ... Many observers expect the Supreme Court will reject the current bright-line rule and, at least under some circumstances, make it easier for parties to attack the validity of patents." - http://www.abajournal.com/magazine/article/court_may_make_it...
Previously on HN: http://news.ycombinator.com/item?id=2453895 and http://news.ycombinator.com/item?id=2464698
I found a benchmark from 2008 that details the problems with RAID10 and sourced it in a comment above [1]. These are just raw disk transfer numbers, though. I can only imagine how they would change as CPU usage/postgres load climbs. IIRC disk IO is network traffic and network traffic is CPU dependent, so as load increases, IO will suffer greatly.
[1] http://news.ycombinator.com/item?id=2341425
Duly noted. I started with this talk and have been using it as a guide to scaling edge cases with python as well as AWS. I thought raid10 was overkill before I started digging into the postgres/EBS mess, but now it seem almost routine enough that Amazon should have it as a configuration option.
Thanks for the extra info! I'm doing a lot of work now with python on EC2 and the reddit write ups + presentations have been a huge help. Thanks again.
So, I assume instances reddit uses have instance storage root volumes instead of EBS root vols. I've always assumed the persistence of ebs AMIs was a plus without a downside. Why would you opt for instance-storage AMIs instead of ebs root volume EC2 AMIs?
On page 500, under Discussion:
"Blood tests assessing IgG levels against foods did not predict which foods might have a deleterious behavioural effect. ... We recorded no difference in behavioural effects after challenge with high-IgG or low-IgG foods. These results suggest that use of IgG blood tests to identify which foods are triggering ADHD is not advisable. However, IgG blood tests might be useful in other diseases."
That conclusion was really buried in there. Some form of confirmation bias on the part of a reader, perhaps?
The hypothesis was that IgG tests may pinpoint foods that in some way trigger ADHD symptoms. This was found to be incorrect.
"We recorded no difference in behavioural effects after challenge with high-IgG or low-IgG foods. These results suggest that use of IgG blood tests to identify which foods are triggering ADHD is not advisable. However, IgG blood tests might be useful in other diseases." [1]
To me, this says that any deviation from restricted diet caused a relapse in ADHD symtoms. A less technical explaination about IgG testing here: http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html
[1] http://marrym.web-log.nl/files/adhd-and-elimination-diet-rct...
kgo may have been referring to how the contents of /private/tmp, /private/var/log and /private/var/tmp are not encrypted and may contain private information, such as com.apple.QuickLook.thumbnailcache.
I've had some success using scripts on the following website to plug these holes, but recently, I have been more concerned with my data's survivability than my privacy. Once that grad degree is done, I hope to return to a more secure approach.
http://xercestech.com/fixing-filevault-random-key-disposable...
In my experience with business school and engineering school, EVERYONE asserts power before they earn it. Others may call it "fake it till you make it", but I would say that over-confidence and power games are rewarded in social constructs which make me (and other techies I know) very uncomfortable.