Romantic Love
I have in romantic relationship a number of times in my life. It hurts, I came to learn Unrequitted love from my dear friend Craig Nelson. It helped me to get out of circle. Here is an excellent article on unrequitted love.
Also look for Dear John Letter, from Craig Nelson.
Mathematics
Lemma by Dr. Pavel Grinfeld
Physics
Physics Forums to ask and read other people's queries
Engineering
Measure blood pressure (Korotkoff sound)
The Efficient Engineer YouTube channel (Poisson Ratio)
Magazine