How to use fetchmail to collect mail from different mail servers
7 mins
This blog post tackles a common challenge in email service administration where users set up mail forwarding without implementing Sender Rewriting Scheme (SRS), which leads to problems with email authentication methods like DKIM and SPF. The suggested workaround is to reverse the forwarding process by configuring the receiving mail server to periodically fetch mail from external accounts using the `fetchmail` tool, which requires only the target server to be configured. Detailed steps explain how to configure `fetchmail` alongside a local MTA like Postfix to pull emails while bypassing SPF and DKIM checks for localhost deliveries. The author shares his personal experience using this setup during a mail service migration, emphasizing the advantages of the method while also discussing the security consideration that `fetchmail` needs access to plaintext credentials. The post includes comprehensive steps for installing and configuring `fetchmail` on a FreeBSD system, and configuring Postfix to ensure proper mail delivery without authentication checks for fetched mail.
Measuring the speed of light at Wiener Forschungsfest 2022
14 mins
This article allows you to discover how we (a group from TU Vienna and University of Vienna) brought the fascinating world of physics to life at the Wiener Forschungsfest 2022! Using a visible range laser, a bicycle wheel, and modern photodiodes, we demonstrated how to measure the speed of light in an interactive and engaging setup designed mainly for children. This hands-on experiment highlighted the incredible speed of light while also conveying the fact that light is fast but not infinitly fast and allowed visitors to influence the accuracy of the measurement themselves. This article provides a short summary about the historical context, experimental setup, and the exciting outcomes of this educational outreach project.
Temporal correlation in coherent cathodoluminescence
1 min
Presented at the 16th Multinational Congress on Microscopy (16 MCM)
OpAmp based voltage controllable current source
7 mins
A simple temperature drift compensated voltage controlled current source up to 8A (10A peak) and 30V rail to rail based on OPA549 or other power operational amplifiers
Discrimination of coherent and incoherent cathodoluminescence using temporal photon correlations
1 min
Published in Ultramicroscopy: We present a method to separate coherent and incoherent contributions of cathodoluminescence (CL) by using a time-resolved coincidence detection scheme. For a proof-of-concept experiment, we generate CL by irradiating an optical multimode fiber with relativistic electrons in a transmission electron microscope. A temporal analysis of the CL reveals a large peak in coincidence counts for small time delays, also known as photon bunching. Additional measurements allow us to attribute the bunching peak to the temporal correlations of coherent CL (Cherenkov radiation) created by individual electrons. Thereby, we show that coincidence measurements can be employed to discriminate coherent from incoherent CL and to quantify their contribution to the detected CL signal. This method provides additional information for the correct interpretation of CL, which is essential for material characterization. Furthermore, it might facilitate the study of coherent electron-matter interaction.
SSH command execution and SFTP file transfer using paramiko in Python
6 mins
Recipes to execute remote commands and transfer files using the native Python SSHv2 implementation of paramiko
The ID3 algorithm
87 mins
A short summary on the inner workings of the Iterative Dichotomiser 3 (ID3) decision tree algorithm, a small Python playground implementation and application to one toy and two real world datasets out of the world of biology and medicine
Controlling the Korad KA3005P using Python
13 mins
A short summary on how to control the Korad KA3005P power supply using Python as well as some simple samples on how to use my own control library
Developing native Python extensions in C - capturing from Video4Linux devices
30 mins
Since I was not really satisfied with various tutorials out there this is my personal summary on how to develop Python extensions in ANSI C. A simple library that captures frames from Video4Linux devices on various Unices without external dependencies will serve as an example.
Linear time dependent correlations using bivariate correlation and shifts
7 mins
A mini summary of how to use the bivariate correlation coefficient (Pearson correlation coefficient) together with shifts to get information about time based correlations between two different time series datasets
