2 simple oak shelves, 4 feet long, total cost: $79.50 DIY

simple oak shelves.  Total cost $75.75




Temperature Effects in Nuclear Quadrupole Resonance Spectroscopy

How to clone all Github repositories for a given user

It’s a hack, but it’ll work. You’ll need either:

  • Linux
  • OSX
  • Windows, running the git-bash app (highly recommended). Download it here: Git – Downloads




How long does it take a new Bitcoin full node to sync to the blockchain in 2016? Does libsecp256k1 speed up the sync?

Bitcoin-Core version 12.0.0 shipped with a new heavily optimized elliptic curve math library. Prior to the release, there were whispers that the new library would significantly speed up the blockchain sync – a sync which was taking me 12-24 hours to complete. Excited for the potential speed up, I decided to benchmark the sync and talk about it on reddit live. Needless to say I was amazed at the difference. Thanks to the core developers for this!

How long does it take a new Bitcoin full node to sync to the blockchain? Does the recently merged libsecp256k1 speed up the sync?

687474703a2f2f692e696d6775722e636f6d2f6f62634c6a44442e706e67

These are good questions, so I wrote a small bash script that gives us some data about the sync time of the new release candidate, whose new optimized library for elliptic curve operations has been rumored to give up to a “700%” increase in the speed of verifying transactions. Disclaimer: it’s not wonderfully modular or well thought out; I did it quickly just to see how the performance was.

So let’s benchmark bitcoin-core with the new libsecp256k1 to see this speedup ourselves. Here is a script for making a log and getting a birds eye view of the sync process. Spoilers: it was really, really fast.

Motivation

This is the kind of thing I always thought about doing, but never did. It’s a simple thing to do, however it just takes time to write up a useful albeit simple script to give you the data you want. Not only that, but previously, when syncs were taking days to complete, this sort of test would eat up my machine.

Since I have been involved with bitcoin, I have known the user base to be (I love you guys) …well, prone to getting carried about with the fear of an impending doom of the BTC — especially if the inevitable doom will be brought upon by some physical limitations of the client, its capacity, and scalability.

In fact, back in 2012-2013, the total size of the blockchain was really all the rage, and the buzzword of the times was “blockchain pruning”. This involved lot of media focus on this problem, as well as efforts by developers and theorists alike to put forth a concerted effort to find a method for reduction of the very scary, problematic growth rate of the block chain!

That’s right everyone was talking about the block chain being too large on disk already, and growing too fast. How bloody ironic, eh.  I won’t say it.  Don’t even say it!

Over time I have built up a thick skin for these sorts of mobs of fear and uncertainty.  I just keep using my coins and really tend to take the doomsday scenarios with less than a grain of salt, because I have seen bitcoin overcome obstacle after obstacle, so many times that it becomes almost illogical to be anything but calm through it all, and feel as though we are in good hands with the devlopers (we are).

But node sync time has been a subtle concern to me for many months – not because I read it on www.scary-bitcoin-news.ninja, but because I noticed this sync time change over a long period of time and become a real hassle to me and running my node as a casual.

In early 2013, it took “pretty damn long” to bootstrap a new node. But I was able to run a full node that year, all year, on a mid level laptop, that I would wipe and re sync every few months.  But by the end of 2014 I was no longer running the laptop node and noticed long sync times on my main high performance monster of a desktop. I felt it took so much longer in fact, that I considered not even running the node, which would have really sucked for me, and put a big damper in the way I got used to used bitcoin. By the end of 2015 I was just trying to avoid a fresh node sync at all costs, which is hard as a man who re-installs his OS every few months. The sync would, on either of my computers, take between 36 and 96 hours for me, depending on how uninterrupted I could run the process and the state of my internet service, and other variables.




It dawned on me at some point that if I was dreading a sync, I couldn’t have been the only one. And so I did consider whether node sync time was a real deterrent to running a node.

However I decided to go for it because I thought if the figures I heard are true, and this library gives a significant speedup, it might require less than a day. And when I inquired in the IRC channel, I was told “could be as fast as 4 hours.” Hot damn – this I had to so. So I finally did it.  Result: Sp happy!  It finished in a blazing 4 hrs, 4 minutes, and 4 seconds!  Sweet victory for node operators and bitcoin as a whole!

This did truly make me very happy as it served my purposes and the community as a whole in no small part.  I was stoked, and to such a degree that had to spread the joy around the community, encouraging others to take note of the speedy sync time by benching it themselves.  I made a reddit post, and put the code on github, along with the data from my 4 hour full bootstrapping of bitcoin core.

Well anyway, I enjoyed this little treat from the devs, and hope y’all do as well.  Thanks guys! Long live the core!




Search for Nuclear Quadrupole Resonance in an Organic Quantum Magnet

SEARCH FOR NUCLEAR QUADRUPOLE RESONANCE IN AN ORGANIC QUANTUM MAGNET

By
ALLEN R. MAJEWSKI
A QUALIFYING EXAM PAPER PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
2015

Using LS_COLORS to colorize your shell by filename / filetype

Messing with LS_COLORS


Before and after

Small steps

I’ll first set LS_COLOR='' Below, you’ll see that nothing is colored, except for the directories which are blue, because of another environment variable called DIR_COLORS. We are going to learn how to tell LS_COLORS to colorize files by name.

I usually had colored by files by whether or not they were executable, a symbolic link, etc, which something like LS_COLORS='di=96:fi=0:ln=33:ex=1;92' which sets

  • directories to 96 (cyan)
  • files to 0 (default)
  • links to 33 (yellow)
  • executables to 92 (green)

and so on.




Go further

I realized recently you can set LS_COLORS to colorize files by name. This is useful in times where you know many types of files will be present in a directory and you want to see what they are right away. Or even if its not that useful, it’s still pretty cool.

Here I know I have .tex, .aux, .log, .bib, .png, .zip, and .pdf all in this directory. I do LS_COLORS='*.png=96:*.aux=90:*.bib=94:*.log=1;90:*.pdf=1;93:*.tex=93:*.zip=91:di=1;94'




Notice how you can set bold and a color with 1;COLOR.

 

Extreme Measures

Since you can take this to extremes, I did.  I quite like it – I use colored pens in real life, so when I discovered this, I just had to …

LS_COLORS='di=96:fi=0:ln=33:pi=5:so=5:bd=5:cd=5:or=37:mi=0:ex=91:*.rpm=90:*.deb=92:*.run=1;92:*.png=34:*.jpg=94:*.JPG=94:*.JPEG=94:*.xcf=34:*.tiff=1;34:*.TIFF=1;34:*.gif=1;94:*.aux=90:*.bib=34:*.log=1;90:*.pdf=1;93:*.tex=33:*.zip=31:*.tar.gz=91:*.tar.bz2=91:*.exe=1;94;100:*.doc=1;94;100:*.xlsx=1;94;100:*.xls=1;94;100:*.pptx=1;94;100:*.nb=31:*.math=91:*.m=31:*.py=93:*.sh=92:*.rb=95:*.pl=1;94:*.c=31:*.h=91:*.md=1;33:*README=1;33:*LICENSE=33:*.txt=93:*.ipynb=1;33:*.mp3=31:*.mp4=91:*.mov=1;91:*.html=95:*.js=35:*.css=1;95:*rc=32:*config=1;32:*makefile=1;91'

🙂 Enjoy the pretty prompts!



Making your command line prompt cool – exploring PS1, PROMPT_COMMAND and other environment variables

Let’s start with an extremely basic prompt so we can see how subtle changes affect it. If you export PS1=’a string of text’, your prompt will be exactly ‘a string of text’, unless you use one of the special PS1 codes ‘\u, \h, \w’:

Other PS1 codes include:

u - the current user's username
h - the current machine's hostname
j - the number of jobs managed by this shell
@ - the current time (12 hour format)
d - the current date
w - path of the current working directory
W - just the current working directory
e - an ASCII escape character (033)
n - adds a newline character

Adding colors is the next step. Bash reads a color code and colorizes everything after that, until it reads a new one. And I mean everything. You need to end your PS1 with the color code you want to type in.

In pseudocode,
export PS1='code1 item code2 item2 coode3 item3'

This results in item having color for “colorcode”, item2 having colorcode2, item3 having colorcode3, and we exit with colorcode4 which will be the color of your commands you type.

We can combine several codes together if they are compatible. For example, 0 is default, 1 is bold. So 1;32 means bold and yellow. \033[1;36m means, to bash “beginning a color code, make it bold, and make it cyan.” You can keep adding color codes, and if they don’t override the last one, they will just add:

echo -e '\033[1m make it bold, and \033[36m make it \033[31m red \033[31;103m with a yellow background'

My usual PS1 is: export PS1='\[\033[1;33m\]\u\[\033[0;36m\]@\[\033[1;32m\]\h\[\033[1;37m\]:\[\033[1;31m\]\w \[\033[1;96m\]\$ \[\033[0m\]', or something like this. Let’s break it down by bolding the color codes

export PS1='\[\033[1;33m\]\u\[\033[0;36m\]@\[\033[1;32m\]\h\[\033[1;37m\]:\[\033[1;31m\]\w \[\033[1;36m\]\$ \[\033[0m\]'

export PS1='\[\033[1;33m\]\u\[\033[0;36m\]@\[\033[1;32m\]\h\[\033[1;37m\]:\[\033[1;31m\]\w \[\033[1;96m\]\$ \[\033[0m\]'

The PROMPT_COMMAND environment variable executes a command each time your prompt returns to you. It can be used to give your PS1 some dynamic ability – the ability to update depending on the current state of the system, outside of the limited PS1 codes. The only way I’ve been able to use it meaningfully is to print the system memory available.


export PROMPT_COMMAND='echo -en "\033[m\033[38;5;2m"$(( `sed -n "s/MemFree:[\t ]\+\([0-9]\+\) kB/\1/p" /proc/meminfo`/1024))"\033[1;38;5;22m/"$((`sed -n "s/MemTotal:[\t ]\+\([0-9]\+\) kB/\1/Ip" /proc/meminfo`/1024 ))MB ""'

Messing with LS_COLORS

I’ll first set LS_COLOR='' Below, you’ll see that nothing is colored, except for the directories which are blue, because of another environment variable called DIR_COLORS. We are going to learn how to tell LS_COLORS to colorize files by name.

I usually had colored by files by whether or not they were executable, a symbolic link, etc, which something like LS_COLORS='di=96:fi=0:ln=33:ex=1;92' which sets

  • directories to 96 (cyan)
  • files to 0 (default)
  • links to 33 (yellow)
  • executables to 92 (green)

and so on.

I realized recently you can set LS_COLORS to colorize files by name. This is useful in times where you know many types of files will be present in a directory and you want to see what they are right away. Or even if its not that useful, it’s still pretty cool.

Here I know I have .tex, .aux, .log, .bib, .png, .zip, and .pdf all in this directory. I do LS_COLORS='*.png=96:*.aux=90:*.bib=94:*.log=1;90:*.pdf=1;93:*.tex=93:*.zip=91:di=1;94'

Notice how you can set bold and a color with 1;COLOR.

 

Since you can take this to extremes, I did.  I quite like it – I use colored pens in real life, so when I discovered this, I just had to …

 

🙂 Enjoy the pretty prompts!

Useful shell aliases

Redo the last command as if I had sudoed

alias please='sudo $(fc -ln -1)'

Use this all the time

(Ubuntu) Install a package I don’t have but tried to use

alias ok='eval $($(fc -ln -1) 2>&1 | sed -n 2p)'

Go back to previous directory


alias back='cd $OLDPWD'

I use this one most of all when copying files to destinations outside of the current directory, especially if the paths involved are pretty long. Sometimes after copying, I may follow the file to the destination just to check what I just did by changing directory to the destination directory. ‘back’ lets me return to where I was before pretty effortlessly. This alias takes advantage of the OLDPWD environment variable.

Free up system memory

alias freemem='echo "echo 1 > /proc/sys/vm/drop_caches" | sudo sh'

For this example, I started to copy a 4 GB file so that I knew my ram would start to be used up. Here, you can see my memory available on the left is decreasing as I hit enter for purposes of demonstration. (displaying my system memory is done using the PROMPT_COMMAND environment variable). You can see when I use freemem, I get my memory back.

Colorize cat!

alias dog='pygmentize -g'




This works like cat in that it dumps the contents of a file to the screen. It does not concatenate files. But it does read the shebang and print the code with syntax highlighting, if it can. Requires python-pygmentize

Find a file or directory in working dir matching a string.

I use this one a LOT! Ignores case and prints line number.

alias lsg='ls -la| grep -ni'

I have many variants of this one, most notably to do this recursively through directories beneath you: ls -laR | grep -in




If you don’t have pygmentize for my dog alias, make installing it a breeze

(Ubuntu) obviously

alias gimme='sudo apt-get install'




Bitcoin-data manipulaton and plotting in python

 

plot.png - https://i0.wp.com/raw.githubusercontent.com/Altoidnerd/bitcoin-price/master/plot.png?resize=840%2C474&ssl=1
I wrote a python mini-api to manipulate and visualize the price of bitcoin historically using the coinbase version 1 api.

bitcoin-price (python module)

Get bitcoin price data from the coinbase API and parse it into an easily manipulated form.

>>> from fast_dump_v22 import *
>>> get_page(1)

Will return all the data on page 1 of coinbase’s bitcoin price API (this is the latest data).

You can almost always turn on optional debug statements

>>> get_first_N(3, show=True)
... fetching first 3

You can get all the price data that coinbase has

>>> get_all(show=True)
... getting page 1
... getting page 2
... getting page 3
... getting page 4
... getting page 5
... getting page 6
... getting page 7
... getting page 8
... getting page 9
... etc ...

All the ‘get_*’ functions return a price_data string, which is interlaced timestamps and prices littered with newlines and commas. You can print them to see what is going on more clearly:

>>> print(get_page(1))
2015-09-11T06:44:04-05:00,241.14
2015-09-11T06:34:04-05:00,240.8
2015-09-11T06:24:04-05:00,240.75
2015-09-11T06:14:05-05:00,240.68
2015-09-11T06:04:04-05:00,240.83
2015-09-11T05:54:05-05:00,240.92
2015-09-11T05:44:04-05:00,240.64
2015-09-11T04:34:04-05:00,241.27
2015-09-11T04:24:04-05:00,240.73
...

Turn on the optional show switch for printing large vectors

>>> prices(get_page(11), show=True)
... returning 11000 prices in specified range ...
['239.9',
'239.9',
'239.4',
'239.77',
'239.33',
'239.99',
'239.81',
'240.28',
'240.4',

You can use prices(data)[k] and timestamps()[j] to return the kth price in data, or the jth timestamp in data.

>>> data = get_page(1)
>>> prices(data)[4]
'241.2'
>>> prices(data, index=4)
'241.2'

are two equivalent ways of returning only the 4th price in the requested range (in this case, page 1). This also works for timestamps.

>>> timestamps(get_page(1)+get_page(2))[1166] == timestamps(get_first_N(2), index=1166)
True

This shows the expressiveness of this module. In general:

>>> prices(get_page(2)) == parse(get_page(2))[0]
True

prices() and timestamps() are just functions that return a parsed() object having a specific index, or indices.

>>> parse(get_page(1)+get_page(2)+get_page(3))[0] == prices(get_first_N(3))
True
>>> parse(get_page(2)+get_page(3))[0] == prices(get_range(2,3))
True

The parse() function is there to manually control the outputs instead of just getting prices, or timestamps

>>> x = parse(get_page(1))
>>> x[0][0]
'241.2'
>>> x[0][1]
'241.14'
>>> x[1][1]
'2015-09-11T04:34:04-07:00'

As you can see, parse(price_data)[0][k] returns the kth price in the list. Indices [1][k] return the kth timestamp.

The parse() function takes care of some weird edge cases:

>>> get_first_N(3) == get_page(1)+get_page(2)+get_page(3)
False
>>> parse(get_first_N(3)) == parse(get_page(1)+get_page(2)+get_page(3))
True
>>> x = get_page(1)
>>> y = get_range(2,7)
>>> prices(get_first_N(7)) == prices(x+y)
True

In general,

OPERATOR( get_page(1) + get_page(2) + ... + get_page(k) ) == OPERATOR(get_first_N(k))

where OPERATOR is parsed(), prices(), or timestamps(). We also know prices() can obviously display and return ranges of values. When returning large vectors, you can verify their length by setting show=True. The “show” parameter is optional for all get_* functions and provides some information about the operation being performed.

>>> print( prices(get_first_N(11), show=True) )
... returning 11000 prices in specified range...

since each page is a thousand pairs of values (timestamp, price).

>>> len(prices(get_page(2))
1000
>>> prices(get_page(2)) # returns a long list
['230.11',
'229.64',
'230.04',
'229.71',
'229.69',
'229.74',
'229.92',
'229.43',
'229.43',
'229.41',
...

fast_dump_v1* are older versions that are somewhat different. They are designed to store the fetched data in the .data directory. This in v2*, this was abandoned in favor of stdout redirection.
// 2015 altodinerd.com

Getting started with Bitcoin the “right way” – encrypted wallets, bitcoin core, and linux

A brief introduction to getting started with bitcoin on a linux distribution

For the impatient: Skip to step 1

Bitcoin is one of the most interesting technologies we have seen emerge in the past ten years. And it confuses everyone who sets out to use it.  This post is my definitive guide to beginning your journey with bitcoin the right way.

tuxbig

To me, the right way includes, but is not limited to:

  • Running bitcoin on a linux machine.  My reasons for this are too many to really list here, but suffice it to say that since linux is widely regarded as the most secure operating system available, and the usage of bitcoin involves being your own bank, using bitcoin on linux is the best way to ensure your coins stay safe.
  • Using the bitcoin-core wallet software.  There are other wallets available.  You actually don’t even need a wallet software to own bitcoins or even spend bitcoins.  However, if you want to understand how bitcoin works under the hood – which you should, because you are going to be your own bank, you should use this software.
  • Using the command line to do bitcoin things. Actually, using both the GUI and the command line is the way to go.  This tutorial (this is part 1 of 2) will be a command-line-centric description because afterall, I’m trying to show you the right way to do things.

But that’s just, like, your opinion man.

It is. This is my blog.

You shouldn’t necessarily trust me or anyone – bitcoin isn’t about trust. But if you google “altoidnerd”, you’ll find that I have been around the bitcoin eco-system for quite some time. That’s all I can tell you.

Screen Shot 2015-09-10 at 8.31.28 PM

There are just so many wallets available – why bitcoin-core?  Because I have been using it for years, I have a very good method of keeping my coins safe, and that is what I am sharing with you today.  Use it- it is THE wallet.

But altoidnerd, I don’t want to run linux. I like windows / OSX

I am a linux and an OSX user.  So please understand the scope of my knowledge includes these operating systems. If you want to use OSX, most of this tutorial will make sense with minor changes perhaps.

Screen Shot 2015-09-10 at 8.32.59 PM

If you want to use windows, that’s ok, I’m not going to judge you. Bitcoin-core is available for windows as well. Please understand however, I am not a windows user, so I will not be able to give you “the definitive bitcoin windows guide”. You can still read on, however, since you can apply much of this tutorial to usage of bitcoin-qt’s debug window instead of the command line.

Step 1: Download and install bitcoin-core

Navigate to bitcoin.org’s official download page and select the bitcoin-core distribution for your operating system. And do choose linux (tgz).  Do that because you should be running linux.  But if you aren’t, even though you should be, choose the distribution for your operating system. Extract and install the client.






The “right way”

To really take control of things, and understand what is happening, you’re going to want to run bitcoin software from the command line. Though it isn’t really necessary to download the thing from the command line, I’m going to describe that here because this tutorial is the first installment of a start to finish command line approach. For a sneak peak of what I mean, see an earlier post where I described how to use bitcoin-core to generate QR codes without having to trust shady ass websites.

Go to your home directory and create a new directory just for bitcoin.  This is not a necessary step, but once again, this is my “right way” tutorial and I will explain reasons for this later on.  Enter the directory, and download the tarball with the “wget” command.  The extract the tarball like so:

    cd ~

    mkdir bitcoin

    cd bitcoin

    wget 'https://bitcoin.org/bin/bitcoin-core-0.11.0/bitcoin-0.11.0-linux64.tar.gz'

    tar -xzvf bitcoin-0.11.0-linux64.tar.gz

bitcointerm1

 

Sweet.  Now change directory to where the binaries are,

    cd bitcoin-0.11.0/bin/

and launch “bitcoin-qt” (qt means its the GUI version).

./bitcoin-qt

It’s going to show you the dialogue box below and ask you if you’d like to use the default directory. Do it. Click “OK”.

 

default

 

You’ll see a friendly startup screen if you’ve done things right!

bitcointerm2

 




 

Step 2: Encrypt your wallet, and wait a few days

Bitcoin-core is called a “full-node” implementation, which means the first time you start it on your machine, it’s going to download every single bitcoin transaction that has ever taken place.  Wait until the blockchain is synced to start making transactions.

In the mean time, you need to set a passphrase for your wallet.  This is super important.  In the upper left corner of bitcoin-qt, go to settings -> Encrypt Wallet, and set a very strong passphrase.

encrypt

This will make it impossible for anyone to send bitcoins from your wallet without entering your password:

PASSWORD

Just make sure you:

    • Make your password extremely long. I don’t know if there is a length limit in the bitcoin-core code or not. Regardless, seriously push your personal boundaries on what you think a safe password is. Make it super duper long, and impossible to guess. Wise men have discussed password strength to a great extent. Pick a strong password. 20+ characters. Go for 30. No 40. Just make it long, and keep it an absolute secret.
    • Never, ever lose or forget this password. If you lose or forgot your password, your coins will be unspendable forever. Neither you, nor anybody on earth, nor God himself will be able to spend your coins. Your coins will be effectively lost.





Picking a strong passphrase makes security so, so easy

Once you encrypt your wallet, you can copy and store wallet.dat everywhere (I explain wallet.dat in great detail in “Step 3”). I literally have copies of my main wallet.dat on 6 or 7 computers, because come hell or highwater, I will always be able to find a copy of my wallet.dat file. I suggest you do the same. Here is why strong encryption and insane redundancy works:

  • If your password is ridiculously long, you can be very lazy and downright cavelier about where you keep your wallet.dat, because even if someone finds the wallet file, they wont be able to do a damn thing with it. They won’t be able to spend your coins without your passphrase.
  • This means that you can make copies of wallet.dat and store them like literally everywhere, on all your machines, three times over. In the cloud. On your mom’s computer. Hell, theoretically speaking, you can post your encrypted wallet.dat on the internet and just about everyone will have a copy, and be unable to spend your coins, because they don’t know your password. Someone remind me to put some coins into an address, and post the encrypted wallet online to prove my point.

    Bottom Line

    If you encrypt your wallet like a boss, you never forget your password, you never tell anyone your password, and you copy the file to everywhere you possibly can imagine, you will never lose your coins. And nobody will be able to steal them from you. Seriously, nobody. It is computationally impossible.

    Step 3: Understand what you just did on your computer

    Let’s break it down this way. Here are some things that just happened when you launched bitcoin-qt for the first time:

    • A hidden directory ~/.bitcoin was created. It contains among other things the single most important thing ever: a file called wallet.dat. This file is critical. ~/.bitcoin/wallet.dat contains all of your private keys. wallet.dat is life. When you see in headlines in the news like “Frustrated gentleman quite upset having lost a usb jump drive containing 100,000 BTC“, it means he doesn’t have a copy of wallet.dat, so neither he, nor anyone on earth, nor God himself can spend his coins anymore.
    • Your computer started downloading the blockchain. The blockchain is a record of every bitcoin transaction ever to have taken place. This will take a few days. As of today, the blockchain is about 42 gigabytes. Make sure you have space for it.

    Do not delete your wallet.dat file. Just don’t. If you want to start a new wallet, instead of deleting wallet.dat, just rename it to something else, like wallet.dat.old, restart bitcoin-qt, and it will create a new wallet for you. Keep your wallets people. Keep them good.

    wallet

    Notice how I have a file called wallet.dat.default? That’s because I never delete a wallet. When I installed bitcoin on this computer, I moved the wallet.dat that stores my coins into ~/.bitcoin/, but first I renamed the existing file so I can keep it. Because, why not? I’m telling you – don’t delete a file called wallet.dat, because mistakes happen, and its better to have hundreds of files named wallet.dat.* than it is to lose your coins.

In my next post, I will describe some of the features of the bitcoin-qt debug window, bitcoind and its helper bitcoin-cli.  You can do interesting things, like import new keys, or convert keys to qr-codes.




If you have ay questions, please feel free to comment or contact me.
If you liked this post, you can donate bitcoins to me here: 12gKRdrz7yy7erg5apUvSRGemypTUvBRuJ
Learn about the author here:
http://www.phys.ufl.edu/~majewski