We study the formation of knots on a macroscopic ball chain, which is shaken on a horizontal plate at 12 times the acceleration of gravity. We find that above a certain critical length, the knotting probability is independent of chain length, while the time to shake out a knot increases rapidly with chain length. The probability of finding a knot after a certain time is the result of the balanc...

Recent theoretical progress has explained the physics of knotting of semiflexible polymers, yet knotting of flexible polymers is relatively unexplored. We herein develop a new theory for the size distribution of knots on a flexible polymer and the existence of metastable knots. We show the free energy of a flexible molecule in a tube can be mapped to quantitatively reproduce the free energy dis...

Small bowel obstruction is a common cause of an emergency admission in the surgical wards. Acute appendicitis presenting with small bowel obstruction due to appendiceal knotting is a very rare and unsuspected condition in an emergency scenario. We report a case of acute small bowel obstruction in a 26-year-old male who, on exploration was found to have small bowel strangulation due to appendice...

Knots appear in a wide variety of biophysical systems, ranging from biopolymers, such as DNA and proteins, to macroscopic objects, such as umbilical cords and catheters. Although significant advancements have been made in the mathematical theory of knots and some progress has been made in the statistical mechanics of knots in idealized chains, the mechanisms and dynamics of knotting in biophysi...

We report a rare case of spontaneous catheter knotting in the setting of a suprapubic cystostomy and also review previous reports and the rationale behind this event.