Ferrofluid according to Wikipedia is “a liquid which becomes strongly magnetized in the presence of a magnetic field.”
I have seen it in several amazing experiments on Youtube and decided to make one myself.
I bought the Ferrofluid and the magnets online through this very cool Swiss store, although there are many tutorials online that explain how to make your own.
The trickiest part is finding a suspension liquid, since Ferrofluid stains everything it touches, if you put it in a bottle just by itself, it will stain the glass and you won’t be able to see anything, this is why the bottle has to be filled with another liquid where the Ferrofluid will be “suspended” in.
The problem that all online sources don’t really agree on what type of liquid that would word best, I experimented with the following:
Burning alcohol —> Ferrofluid lost many particles and became a powder
Distilled water —> Stained glass, ferrofluid shapes were very weak
Mix of distilled water and alcohol —> Stained glass a bit and ferrofluid looked weird
Calcium residue cleaner —> Ferrofluid floated
Window cleaner and alcohol —-> Promising, but ferrofluid was still looking like sand
Window cleaner —> Best results
Filling the bottle with only a windows cleaning liquid gave me the best results, the glass was not stained, ferrofluid kept it’s shape and I was able to see all the cool effects since it’s a clear liquid.
It has been more than 24 hours so far and the ferrofluid is still looking good in the bottle.
The choice of the bottle is very important, as it must be a good quality glass and squared (never rounded), otherwise you will not be able to see the ferrofluid effects due to refraction.
So I had a power outage this week and my Pi server restarted, after reboot I noticed that WordPress wouldn’t start anymore. Starting mysqld manually would cause the following error:
03:02:19 UTC – mysqld got signal 6 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware.
Most pages returned by Google say that the InnoDB is probably corrupted and suggest to force recovery in my.cnf using the flag
innodb_force_recovery = 4
The innodb_force_recovery takes a number from 1 to 6.
However, none of these options could get mysqld to start, I was always getting the same error.
Here is what I did to get it to work:
In my.cnf add innodb_force_recovery = 6 in the [mysqld] section (mySQL manual)
In my.cnf add innodb_purge_threads=0 (this what allowed mysqld to start in read only mode)
Start mysqld (“mysqld –verbose” or “/etc/init.d/mysqld start”)
Check for corruption: mysqlcheck -p –all-databases
Find the corrupt table and do: myisamchk -r -v -f <table_name> (where the data file is stored)
Using the mysql recovery command did not fix anything, it was unable to recover the error, but you are welcome to try
Backup your data: mysqldump -A > /home/user/backup_dump.sql
What’s great about Pi is that it’s tiny, powerful for it’s size, can run Linux, has many interfaces (2xUSB,1xHDMI, 100MBit Ethernet, audio and composite), low power consumption and moderately priced.
It all started with Google abandoning Reader, my favorite RSS feed reader and me unable to find a decent replacement, Feedly looks really nice in a browser but a HORRIBLE android app, old reader is a good compromise, but has no apps at all.
This is why i decided to move to Tiny, tiny RSS…which needed it’s own server and my hosting provider did not allow me to install; thus I decided to get my own hosting.
Moving my blog was a pain in the ass, the most difficult part was to mantain the redirections so search engines and feedreaders could still access my new blog using the same URLs and without the users having to change anything.
Since there was no much help online, here is how to make a 301 http redirect that will allow all requests and QUERY STRINGS passed to your root folder to be redirected somewhere else.
Save this as index.php of your old location, this way if your old feed used any querystring parameters e.g. /?feed=rss2 it will be redirected properly, also direct access to your old blog home, will be redirected to the new place.
Moftasa posted this article on how he wrote a linux script that downloads all the obituaries published in Al Ahram newspaper between 2002 and 2008, finds all the names of people with Police titles then finds the family relations between them!
The script does the following:
The first step is to convert the HTML files downloaded by curl into one giant text file.
Then to move each separate obituary into a line of it’s own.
Extract officer names sandwiched between rank and place of work into a separate text file.
Search for the names of each officer through each obituary, family links between different officers can be discovered.