We discuss the probability of random knotting for a model of self-avoiding polygons whose segments are given by cylinders of unit length with radius r. We show numerically that the characteristic length of random knotting is roughly approximated by an exponential function of the chain thickness r. keyword characteristic length, random knotting, self-avoiding polygons, knot invariants,knots PACS...

The backbones of proteins form linear chains. In the case of some proteins, these chains can be characterized as forming linear open knots. The knot type of the full chain reveals only limited information about the entanglement of the chain since, for example, subchains of an unknotted protein can form knots and subchains of a knotted protein can form different types of knots than the entire pr...

Long, flexible physical filaments are naturally tangled and knotted, from macroscopic string down to long-chain molecules. The existence of knotting in a filament naturally affects its configuration and properties, and may be very stable or disappear rapidly under manipulation and interaction. Knotting has been previously identified in protein backbone chains, for which these mechanical constra...

The protein topology database KnotProt, http://knotprot.cent.uw.edu.pl/, collects information about protein structures with open polypeptide chains forming knots or slipknots. The knotting complexity of the cataloged proteins is presented in the form of a matrix diagram that shows users the knot type of the entire polypeptide chain and of each of its subchains. The pattern visible in the matrix...

Epidural block is achieved either by single injection of local anesthetic through an epidural needle or as a continuous block by infusion pump through an epidural catheter. Complications associated with epidural catheters include breakage, entrapment, and knotting. Knotting of epidural catheters is very rare, but knotting in lumbar epidural catheters has been reported in a number of studies, an...

INTRODUCTION Extracorporeal knotting in laparoscopic surgery can be used in certain situations or as a bridge to mastering more technically demanding intracorporeal suturing. We describe a simple, easy, and safe extracorporeal knotting technique. TECHNIQUE DESCRIPTION A simple knotting technique, borrowed from the art of tatting, is used. DISCUSSION This very simple and safe technique has b...

Despite the fact that in living cells DNA molecules are long and highly crowded, they are rarely knotted. DNA knotting interferes with the normal functioning of the DNA and, therefore, molecular mechanisms evolved that maintain the knotting and catenation level below that which would be achieved if the DNA segments could pass randomly through each other. Biochemical experiments with torsionally...

INTRODUCTION Abdominal trauma is a source of significant mortality and morbidity. Bowel injury as a result of blunt abdominal trauma is usually evident within hours or days of the accident. CASE PRESENTATION A 38-year-old Caucasian Greek man presented with a subtle and delayed small bowel obstruction caused by a post-traumatic ileosigmoid fistula and ileal stricture four months after a road t...