Malcolm Gladwell on the importance of stubbornness

A very interesting speech of Malcolm Gladwell on stubbornness in below YouTube video.

He makes references to

Also see Malcolm Gladwell’s article on the Flynn effect: What I.Q. doesn’t tell you about race.

Importing Calendar Data to Google-Calendar

Importing calendar data to Google is still troublesome for a number of reasons. What seems to work goes like this:

  1. Force-stop calendar data in your Android phone
  2. Clear all calendar data in your Android phone
  3. Shut down your Android phone
  4. Log-off from all other Google accounts
  5. Shut down your browser (I am not sure whether this step is really necessary, but better safe)
  6. Fire up your browser once again and log-in to Google
  7. Import your data, see screenshot below (I use the iCalendar format)

importCal1

Continue reading

Two Free Invites for the OnePlus One, #2

I have two free invites for the OnePlus One. Below are the links:

  1. GLYP-ATVO-YQ8K-D969
  2. GLGQ-A0LM-I7RL-EKGB

Please do not click on the links if you do not want to actually buy the phone, because the invites are then reserved and cannot be used by others.

For a review of the phone see Review of the OnePlus One Smartphone.

Addendum 22-Mar-2015: Both invites unfortunately expired. So people clicked on it without actually wanting to buy a phone.

On Differential Forms

Abstract. This article will give a very simple definition of k-forms or differential forms. It just requires basic knowledge about matrices and determinants. Furthermore a very simple proof will be given for the proposition that the double outer differentiation of k-forms vanishes.

MSC 2010: 58A10

1. Basic definitions.

We denote the submatrix of A=(a_{ij})\in R^{m\times n} consisting of the rows i_1,\ldots,i_k and the columns j_1,\ldots,j_k with

\displaystyle{          [A]{\textstyle\!{\scriptstyle j_1\atop\scriptstyle i_1}          \!{\scriptstyle\ldots\atop\scriptstyle\ldots}          \!{\scriptstyle j_k\atop\scriptstyle i_k}} := \begin{pmatrix}                  a_{i_1j_1} & \ldots & a_{i_1j_k}\\                  \vdots     & \ddots & \vdots\\                  a_{i_kj_1} & \ldots & a_{i_kj_k}\\          \end{pmatrix}  }

Continue reading

Testing file-size limits

For testing purposes you may want to provoke a file-size error. Here are the steps. Open a new bash/xterm. Set a file-size limit with ulimit, then write a file with dd.

ulimit -f 1
dd bs=1 iflag=count_bytes count=5000 if=/dev/zero of=yourFile

The resulting error is

File size limit exceeded (core dumped)

just as expected.

Using GnuPG for encryption and decryption

On Ubuntu install with:

apt-get install gnupg

First generate private and public key:

gpg --gen-key

Generating this key can take some time, because it needs enough randomness.

Store your public key in a file:

gpg -a --export

Although it is not necessary to store this public key, you usually will provide this public key to other people, see for example my public key.

Import public keys from other people by

gpg --import my-friend.pub

Now encrypt a message for my-friend:

gpg -aers my-friend your-file

These options have the following effect:

  • -a: create base64 encoded output (“ASCII armored”). This is not necessary, so you can skip this option. If skipped the output is binary.
  • -e: encrypt
  • -r: recipient, here your-friend
  • -s: add signature. This is not necessary. You could drop this option from above.

Decrypting a file is the easiest part. Just type

gpg encrypted-file