Spontaneous Knotting Research Articles

Compression of a confined semiflexible polymer under direct and oscillating fields.

The folding transition of biopolymers from the coil to compact structures has attracted wide research interest in the past and is well studied in polymer physics. Recent seminal works on DNA in confined devices have shown that these long biopolymers tend to collapse under an external field, which is contrary to the previously reported stretching of the chain. In this work, we capture the compression of a confined semiflexible polymer under direct and oscillating fields using a coarse-grained computer simulation model in the presence of long-range hydrodynamics. In the case of a semiflexible polymer chain, the inhomogeneous hydrodynamic drag from the center to the periphery of the coil couples with the chain bending to cause a swirling movement of the chain segments, leading to structural intertwining and compaction. Contrarily, a flexible chain of the same length lacks such structural deformation and forms a well-established tadpole structure. While bending rigidity profoundly influences the chain's folding favorability, we also found that subject to the direct field, chains in stronger confinements exhibit substantial compaction, contrary to the one in moderate confinements or bulk where such compaction is absent. However, an alternating field within an optimum frequency can effectuate this compression even in moderate or no confinement. This field-induced collapse is a quintessential hydrodynamic phenomenon, resulting in intertwined knotted structures even for shorter chains, unlike other spontaneous knotting experiments where it happens exclusively for longer chains.

Spontaneous knotting of an antegrade continent enema catheter

Malone antegrade continent enema (ACE) is a procedure in which an appendicostomy is performed to effectively control intractable fecal incontinence. In this procedure, spontaneous knotting of the enema catheter inside the cecum may occur, albeit rarely. In such a situation, the knot of the ACE catheter in the cecum could not be removed easily. Here, we aimed to report two cases of spontaneous knotting of the ACE catheter during routine ACE. Moreover, we aimed to discuss the mechanism of spontaneous knotting of the catheter during ACE, preventive methods, and methods to remove the knotted catheters.

Spontaneous knotting of a flexible fiber in chaotic flows.

We consider the problem of an inextensible but flexible fiber advected by a steady chaotic flow, and ask the simple question of whether the fiber can spontaneously knot itself. Using a one-dimensional Cosserat model, a simple local viscous drag model and discrete contact forces, we explore the probability of finding knots at any given time when the fiber is interacting with the ABC class of flows. The bending rigidity is shown to have a marginal effect compared to that of increasing the fiber length. Complex knots are formed up to 11 crossings, but some knots are more probable than others. The finite-time Lyapunov exponent of the flow is shown to have a positive effect on the knot probability. Finally, contact forces appear to be crucial since knotted configurations can remain stable for times much longer than the turnover time of the flow, something that is not observed when the fiber can freely cross itself.

Time-dependent knotting of agitated chains.

Agitated strings serve as macroscale models of spontaneous knotting, providing valuable insight into knotting dynamics at the microscale while allowing explicit analysis of the resulting knot topologies. We present an experimental setup for confined macroscale knot formation via tumbling along with a software interface to process complex knot data. Our setup allows characterization of knotting probability, knot complexity, and knot formation dynamics for knots with as many as 50 crossings. We find that the probability of knotting saturates below 80% within 100s of the initiation of tumbling and that this saturation probability does not increase for chains above a critical length, an indication of nonequilibrium knot-formation conditions in our experiment. Despite the saturation in knot formation, we show that longer chains, while being more confined, will always tend to form knots of higher complexity since the free end can access a greater number of loops during tumbling.

Spontaneous knotting of foley’s catheter in urinary bladder: A case report

We are presenting a case of spontaneous knotting of Foley’s catheter in a 64 year old male. Suprapubic ultrasonographic-guided puncture of balloon of Foley’s catheter was done under local anaesthesia. Knotted Foley’s catheter was gently removed after pushing anaesthetic jelly in urethra by the side of Foley’s catheter. Mild but sustained traction helped the removal of the Foley’s catheter without causing any injury to the urethra. Though the spontaneous knotting of Foley’s catheter is a rare incidence but it occurs and that’s why whoever inserts Foley’s catheter per urethra in urinary bladder must keep in mind spontaneous knotting.

Pore translocation of knotted DNA rings

We use an accurate coarse-grained model for DNA and stochastic molecular dynamics simulations to study the pore translocation of 10-kbp-long DNA rings that are knotted. By monitoring various topological and physical observables we find that there is not one, as previously assumed, but rather two qualitatively different modes of knot translocation. For both modes the pore obstruction caused by knot passage has a brief duration and typically occurs at a late translocation stage. Both effects are well in agreement with experiments and can be rationalized with a transparent model based on the concurrent tensioning and sliding of the translocating knotted chains. We also observed that the duration of the pore obstruction event is more controlled by the knot translocation velocity than the knot size. These features should advance the interpretation and design of future experiments aimed at probing the spontaneous knotting of biopolymers.

Spontaneous Knotting of a Foley Catheter in the Urinary Bladder: A Case Report

Urinary bladder catheterization and drainage are the commonly done procedures in hospitalized patients. We are reporting a rare occurrence of spontaneous knotting of a Foley catheter in a 10 year’s old agitated boy after 12 h of successful catheterization and adequate drainage. Trans-abdominal ultrasound-guided suprapubic puncture of the none deflating Foley catheter balloon followed by gentle and sustained traction was used to remove the spontaneously knotted Foley catheter inside the urinary bladder. We recommend health care providers should consider spontaneous knotting of Foley catheter as cause of none draining Foley catheter. Securing the catheter and control of agitation can prevent this complication.

Spontaneous Knotting and Unknotting of Flexible Linear Polymers: Equilibrium and Kinetic Aspects

We report on a computational study of the statics and dynamics of long flexible linear polymers that spontaneously knot and unknot. Specifically, the equilibrium self-entanglement properties, such as the knotting probability, knot length and position, are investigated with extensive Monte Carlo sampling of chains of up to 15,000 beads. Tens of such equilibrated chains of up to 4, 096 beads are next used as starting points for Langevin dynamics simulations. The complex interplay of chain dynamics and self-knotting is addressed by monitoring the time evolution of various metric and entanglement properties. In particular, the extensive duration of the simulations allows for observing the spontaneous formation and disappearance of prime and composite physical knots in linear chains. Notably, a sizeable fraction of self-knotting and unknotting events is found to involve regions that are far away from the chain termini. To the best of our knowledge this represents the first instance where spontaneous changes in knotting for linear homopolymers are systematically characterized using unbiased dynamics simulations.

Spontaneous knotting of a feeding tube in the bladder

Urinary catheterization is often performed in the pediatric age group. The procedure although safe, is not free of complications. Knotting of the urinary catheter is a rare but serious complication. A seven-year-old boy presented with left-sided neuroblastoma and underwent an exploratory laparotomy during which it was found that he had an inoperable tumor. There was a nodule obstructing the left ureter. This was resected and an end-to-end anastomosis of the ureter was carried out. A size 8 French (Fr) feeding tube was introduced through the urethra to monitor the patient's urine output and fluid balance in the absence of a self-retaining pediatric catheter. An attempt at removal 48 h later was unsuccessful. The patient was afterwards, on the sixth postoperative day, anaesthetized and the tube was pulled out. It was noticed that the catheter was knotted. The case is reported with a limited discussion of relevant literature. Spontaneous knotting of a catheter is a rare complication. With availability of appropriate catheters and adequate knowledge and skill, this complication can be reduced to the barest minimum.

Spontaneous knotting of self-trapped waves

We describe theory and simulations of a spinning optical soliton whose propagation spontaneously excites knotted and linked optical vortices. The nonlinear phase of the self-trapped light beam breaks the wave front into a sequence of optical vortex loops around the soliton, which, through the soliton's orbital angular momentum and spatial twist, tangle on propagation to form links and knots. We anticipate similar spontaneous knot topology to be a universal feature of waves whose phase front is twisted and nonlinearly modulated, including superfluids and trapped matter waves.

Spontaneous knotting of peritoneal catheter: A report of an asymptomatic patient

Spontaneous knotting of peritoneal catheter: A report of an asymptomatic patient

Spontaneous Urethral Catheter Kinking or Knotting in Male Dogs: Four Cases

Four dogs were diagnosed with urethral catheter malfunction. The catheter was kinked in three dogs and knotted in one dog. In two dogs, kinking of the catheter was associated with presence of urethroliths in the perineal urethra. Diagnosis was based on the difficulty encountered retrieving the catheter in all dogs and swelling in the scrotal or perineal area in two dogs. Diagnosis of catheter kinking or knotting was confirmed after catheter retrieval. Catheter removal was achieved in two dogs after traction under anesthesia, whereas scrotal or perineal urethrotomy were used in the other two dogs. No complications associated with urination were reported in any of the dogs after 7 to 12 mo.

Knotting of two central venous catheters: a rare complication of pulmonary artery catheterization

To the Editor: A unique complication of pulmonary artery (PA) catheter use is knotting. We describe a case of a knot between a central venous catheter and a PA catheter, and the successful nonsurgical unknotting and removal of the catheter. A 31-year-old pregnant woman in cardiogenic shock resulting from a tachycardia-induced cardiomyopathy was transferred to the intensive care unit. On admission, a triple-lumen central venous catheter was introduced via the right internal jugular vein. Despite sufficient hydration and continuous infusion of inotropic agents, her blood pressure was unstable. Circulatory supports by intraaortic balloon pump (IABP) and percutaneous cardiopulmonary support system (PCPS) were introduced for severe heart failure (ejection fraction was 10%). On the 6th ICU day, a PA catheter was inserted through the left internal jugular vein to monitor hemodynamic status during weaning from PCPS. The catheter was inserted without difficulty and advanced easily, and the correct position was confirmed on the chest X-ray. Weaning from the PCPS was completed on the 6th ICU day, and the IABP was removed on the 7th ICU day because her hemodynamic status became relatively stable. However, as she still had multiple organ failure, we retained the PA catheter. Although a chest X-ray showed normal configuration of the catheters on the morning of the 11th ICU day, monitoring failure of pulmonary arterial pressure happened abruptly about 9 p.m. without any catheter manipulations. We attempted to remove the PA catheter in the usual manner. However, resistance was felt during withdrawal of the catheter, and repeated traction was unsuccessful. Then, we confirmed a loose knot between the central venous catheter and the PA catheter in the superior vena cava on the chest X-ray (Fig. 1). As the knotting was relatively loose, we pushed the PA catheter forward to unknot the catheters, and then the catheter was successfully removed. The case of knotting of two catheters is rare [1–3]. Cases of knotted catheters functioning normally for several days have not been previously reported. We suspected that the catheter knotted when sudden malfunction of the catheter was found; in fact, the catheter was in normal configuration in the morning. The cause of knotting was not clear, and the catheter was not manipulated before discovery of the knotting. Several technical methods for removal of the knotting have been developed in cases that are more difficult to handle. One approach is to tighten the knot as much as possible so that it may be removed through the vein insertion site. Alternative approaches are to use a retrieval basket, a loop snare formed by a double-over guide wire or loop snares, endomyocardial biopsy forceps, or an inflated angiography balloon to expand the diameter of the knot [4]. Open surgical removal of knotted catheters is reserved for large, multiple loop knots or knots that are fixed within the cardiac chamber. In summary, we experienced a case of a spontaneous knotting between a central venous catheter and a PA catheter several days after placement. A catheter knotting should be considered when malfunction of the catheter is encountered. Withdrawal of a PA catheter should be performed cautiously, and a chest X-ray should be taken S. Hida (&) S. Ohashi H. Kinoshita T. Honda S. Yamamoto J. Kazama H. Endoh Department of Emergency and Critical Care Medicine, Niigata University Faculty of Medicine, 1-757 Asahimachi, Niigata 951-8510, Japan e-mail: ukhida@med.niigata-u.ac.jp

Spontaneous knotting of an agitated string

It is well known that a jostled string tends to become knotted; yet the factors governing the "spontaneous" formation of various knots are unclear. We performed experiments in which a string was tumbled inside a box and found that complex knots often form within seconds. We used mathematical knot theory to analyze the knots. Above a critical string length, the probability P of knotting at first increased sharply with length but then saturated below 100%. This behavior differs from that of mathematical self-avoiding random walks, where P has been proven to approach 100%. Finite agitation time and jamming of the string due to its stiffness result in lower probability, but P approaches 100% with long, flexible strings. We analyzed the knots by calculating their Jones polynomials via computer analysis of digital photos of the string. Remarkably, almost all were identified as prime knots: 120 different types, having minimum crossing numbers up to 11, were observed in 3,415 trials. All prime knots with up to seven crossings were observed. The relative probability of forming a knot decreased exponentially with minimum crossing number and Möbius energy, mathematical measures of knot complexity. Based on the observation that long, stiff strings tend to form a coiled structure when confined, we propose a simple model to describe the knot formation based on random "braid moves" of the string end. Our model can qualitatively account for the observed distribution of knots and dependence on agitation time and string length.

Spontaneous Knotting — From Oligoamide Threads to Trefoil Knots.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Spontaneous Knotting—From Oligoamide Threads to Trefoil Knots

Tying up loose ends: Oligoamide thread molecules can spontaneously transform into open knots, whose terminal functional groups can subsequently be chemically linked to form closed, cyclic knots (see scheme; left: threads; middle: open knots; right: molecular knots; X=N, C).

Spontaneous Knotting of Urinary Catheters

Urinary catheters are known to spontaneously knot inside the bladder. Approximately 40 cases of this complication have been recorded in the world literature. Clinical observation in 4 children and simulation experiments done using a balloon model are described herein. Risk factors identified in this study includes catheter size less than 10 Fr, overdistended bladder and insertion of more than 10 cm length of catheter inside the bladder. Water-current generated by the flow of urine appears to play an important role in the pathogenesis of catheter knotting.

Migration and spontaneous knotting of feeding jejunostomy tube: an unusual complication

Migration and spontaneous knotting of feeding jejunostomy tube: an unusual complication

Migration and spontaneous knotting of feeding jejunostomy tube: an unusual complication

Migration and spontaneous knotting of feeding jejunostomy tube: an unusual complication