Pure Coagulation Research Articles

Giant Fibrovascular Polyp of the Esophagus Causing Sudden Dyspnea: Endoscopic Treatment

A 76-year-old man with sudden dyspnea was admitted to our department. A fleshy mass was visualized in the labial commissure, and the flexible esophagoscopy showed the polyp prolapsed into the oropharynx, partially obstructing the airway. The polyp was encircled with a large oval snare and Endoloop, which was adjusted to stalk-basis before tightening. Pure coagulation was used to transect the lesion, which was then retrieved. The polyp measured 10 x 2.5 cm. To our knowledge, our case is the first large esophageal giant fibrovascular polyps causing sudden dyspnea in the literature that has been resected endoscopically without complications.

Analysis of four Monte Carlo methods for the solution of population balances in dispersed systems

Monte Carlo (MC) constitutes an important class of methods for the numerical solution of the general dynamic equation (GDE) in particulate systems. We compare four such methods in a series of seven test cases that cover typical particulate mechanisms. The four MC methods studied are: time-driven direct simulation Monte Carlo (DSMC), stepwise constant-volume Monte Carlo, constant number Monte Carlo, and multi-Monte Carlo (MMC) method. These MC's are introduced briefly and applied numerically to simulate pure coagulation, breakage, condensation/evaporation (surface growth/dissolution), nucleation, and settling (deposition). We find that when run with comparable number of particles, all methods compute the size distribution within comparable levels of error. Because each method uses different approaches for advancing time, a wider margin of error is observed in the time evolution of the number and mass concentration, with event-driven methods generally providing better accuracy than time-driven methods. The computational cost depends on algorithmic details but generally, event-driven methods perform faster than time-driven methods. Overall, very good accuracy can be achieved using reasonably small numbers of simulation particles, O(10 3), requiring computational times of the order 10 2−10 3 s on a typical desktop computer.

Explosion phenomena in stochastic coagulation–fragmentation models

First we establish explosion criteria for jump processes with an arbitrary locally compact separable metric state space. Then these results are applied to two stochastic coagulation–fragmentation models—the direct simulation model and the mass flow model. In the pure coagulation case, there is almost sure explosion in the mass flow model for arbitrary homogeneous coagulation kernels with exponent bigger than 1. In the case of pure multiple fragmentation with a continuous size space, explosion occurs in both models provided the total fragmentation rate grows sufficiently fast at zero. However, an example shows that the explosion properties of both models are not equivalent.

A survey of colonoscopic polypectomy practices among clinical gastroenterologists

Polypectomy techniques vary in clinical practice. The aim of this study was to determine patterns of polypectomy practices in a random sample of gastroenterologists. A total of 300 gastroenterologists were selected randomly from the membership directory of a professional society. They were asked to complete a standardized survey by telephone, electronic mail, or facsimile. The offices of 285 physicians were contacted successfully. A total of 189 (63%) chose to participate. 152 (80%) of these physicians were in private practice, and 37 (20%) were in academic practice. The mean number of years in practice was 15.5 (range 1-46 years). Forceps techniques (cold or hot) dominated other polypectomy methods for polyps 1 to 3 mm in size ( p < 0.0001), whereas electrosurgical snare resection was dominate for polyps 7 to 9 mm in diameter ( p < 0.0001). No method of polypectomy was significantly more likely to be used for polyps 4 to 6 mm in size. The proportion of physicians who had used dye spraying was 8.5%; detachable snares, 20.1%; clips, 20.1%; and submucosal saline solution injection, 82%. Of those who had used submucosal saline solution injection, 29.7% had no rules for its use, and, in the remainder, there was marked variation regarding the criteria. For polyp stalks greater than 1 cm in diameter, 69% used no method to prevent bleeding. Of those who did use preventive techniques, 76% used epinephrine injection. The electrosurgical current used for polypectomy was pure coagulation in 46%, blend in 46%, and pure-cut in 3%; 4% varied the current. At present, polypectomy technique among clinical gastroenterologists is highly variable. Some newer ancillary techniques have had extremely limited use thus far.

High Intensity-Low Duration "Hot Biopsy" Forceps Coagulation: A Safe Method

Objectives: To test the rate of complications of hot biopsy forceps polypectomy performed according to our usual method in a descriptive, prospective, open study. Methods: During 12 consecutive months every patient addressed for colonoscopy was included. Every polyp seen was destroyed by hot biopsy coagulation, if possible, according to the criteria below. If not, it was snared. Coagulation, after conventional tenting, used the minimum number of short impulses (less than 1 s) of high-intensity, pure coagulation current (setting 4 corresponding to 40 w), designed to limit the depth of the burn, according to the complex physical properties of high frequency currents. Selected large, benign-looking polyps up to 15 mm were destroyed by hot biopsy, if the neck after tenting was 5 mm large or less. Results: Among 1,228 colonoscopies, we destroyed 888 polyps in 451 patients, 727 by hot biopsy forceps, including 210 in the caecum, ascending colon and hepatic flexure and 23 over 10 mm. The complications were: one minor delayed bleeding and one benign post-polypectomy syndrome. No serious complication was encountered. No complication occurred after hot biopsy of 69 polyps among the 41 patients aged 80 and over. Conclusions: With the present technique, hot biopsy forceps coagulation is safe, even in the right colon and among selected, relatively large polyps up to 15 mm.

Endoscopic treatment of Zenker's diverticulum with an oblique-end hood attached to the endoscope

Background: The feasibility and efficacy of incision of the septum between the pharyngoesophageal (Zenker's) diverticulum and the esophagus with a flexible endoscope and needle-knife have been demonstrated. Exposure of the septum remains a critical element of the procedure. This is a report of a technical improvement in this technique: use of a transparent oblique-end hood attached to the tip of the endoscope. Methods: Ten patients (10 men, age range 67-87 years) with Zenker's diverticulum were treated. With the aid of an oblique-end hood attached to the tip of the endoscope, the septum between the Zenker's diverticulum and esophagus was incised with pure coagulation current. A 10F nasogastric tube was left in place for 48 hours after the procedure to provide nutrition. Thereafter, oral intake was progressively resumed. Results: Complete incision of the septum was achieved in a single session in all cases. Bleeding or perforation did not occur in this small series. Complete relief of dysphagia was reported by all patients during follow-up that ranged from 2 to 12 months. Conclusions: With the use of the oblique-end hood attached to the tip of the endoscope, incision of Zenker's diverticulum is simplified and can be performed as a single-session procedure.

Single species diffusion-influenced reaction A+A-->alphaA: validity of the smoluchowski approach

We investigate the single species diffusion-influenced reaction, A+A-->alphaA with a finite reactivity in all dimensions. The reaction model includes a pure coagulation (alpha=1) or a pure annihilation (alpha=0) model. We apply the hierarchical Smoluchowski approach to study the dimensional aspects of the fluctuation, reactivity, particle size, and alpha(0</=alpha</=1). The theoretical results are compared with those of the Monte Carlo simulations in one, two, and three regular dimensions. The simulation results reveal that the classical Smoluchowski approach is exact in the short time limit in all dimensions and in the long time limit in three dimensions. The hierarchical Smoluchowski approach is found to be numerically exact at all times in two and three dimensions. A numerical method to obtain the exact result of the annihilation for a finite reactivity in one dimension is presented. We also propose a quite accurate analytic solution for an arbitrary alpha for the infinite reactivity in one dimension.

Endoscopic snare mucosectomy in the esophagus without any additional equipment: a simple technique for resection of flat early cancer.

Endoscopic mucosal resection of early esophageal cancer has increasingly proved to be an effective treatment modality, especially if the tumor has not invaded the muscularis mucosae. Different techniques have been introduced, using an overtube, double-channel endoscope, or suction cap. We have not found that these devices are required for snare resection in the esophagus. Over a period of two years (1994-1996), seven patients (five men and two women, age range 59-88) with early esophageal cancer defined by endosonography (3 cm or less in size, limited to the submucosal layer) were treated using a simplified technique of endoscopic snare resection using a monopolar diathermic polypectomy snare made of monofilament steel wire. The snare was positioned around the lesion, and then closed while pressing the snare against the mucosa and applying suction to draw the lesion into the snare. Pure coagulation current was used for resection. If necessary, a piecemeal technique was used to achieve complete removal. Complete removal was achieved in one session in all seven cases. No complications were observed. Two patients underwent radical surgery with no tumor remnant or metastatic lymph node in the resected specimen. All patients have remained free of recurrence during a median follow-up period of seven months (range 3-22 months). Two patients died of cardiovascular disease four and eight months after endoscopic mucosal resection. Small early esophageal cancer can be safely removed with a simplified method of endoscopic snare resection using a standard monofilament polypectomy snare.

Analytical–Numerical Solution of the Multicomponent Aerosol General Dynamic Equation—with Coagulation

A numerical procedure based on an analytical solution is presented for solution of the full multicomponent aerosol general dynamic equation. The analytical solution for the equation, accounting for growth, removal, and particle sources, is employed in an iterative procedure to account for coagulation. The iterative process is shown to be rapidly convergent, and its performance is validated by comparison with the exact solution for pure coagulation of a single-component aerosol. A simulation is presented of the evolution of a multicomponent coagulating aerosol, where each component grows-evaporates at a different rate.

Effect of interparticle forces on the coagulation of ultrafine SiO2 particles

The mechanism of ultrafine (<100 nm) SiO2 particle production under thermal arc plasma conditions is studied by modelling. Two cases of the process are considered in the model: (i) when it is determined as a pure free-molecular coagulation; (ii) when the coagulation is influenced by the interparticle forces. The Hamaker formula is used to present the van der Waals forces between the particles. Particle size distribution functions (PSDF) are calculated for both cases. It is shown that inclusion of the interparticle interactions does not affect the self-preservation of the PSDF. The mean particle sizes are obtained from the PSDF and compared. Higher values are observed in the case that includes van der Waals forces. Comparison between experimental and calculated PSDF shows better agreement in the case considering interparticle forces.

On the Evolution of the Stellar Mass Spectrum: Possible Evidence for Stellar Evaporation

The authors continue the analysis of the results of their preceding paper where a pure coagulation model was applied to star clusters in general. By combining in a certain way the free parameters of the model, it is possible to evaluate the ratio of the total mass of the cluster as it is today to what it was at its formation, according to the model. A correlation is found between this ratio and the age of the cluster. The analysis of this correlation also gives order of magnitude estimates of dierent processes such as accretion rate, evaporation rate, and timescale of disruption by evaporation (or mean life expectancy). These estimates are found to be in agreement with other published results. It is also found that the mass-loss rate of the cluster is proportional to the amount of coagulation that occured. All in all, it is shown that the coagulation model, although simplistic, merits more attention. Accepted by Ap. J.

Endometrial ablation with the combined Nd:YAG laser-rollerball

Endometrial ablation, an effective treatment for intractable uterine bleeding, can be performed with hysteroscopic rollerball coagulation, neodymium:yttrium-aluminum-garnet (Nd:YAG) laser, and endomyometrial resection techniques. Between November 1990 and January 1995, 49 women underwent ablation with the Nd:YAG laser and a nontouch technique on the ostia, uterine fundus, and upper one-third to one-half of the posterior uterine wall, in combination with rollerball coagulation over the entire endometrial surface after 60-W Nd:YAG application. The power source of the rollerball was set at 80 W of pure coagulation current. Each patient was pretreated with a gonadotropin-releasing hormone agonist or an antiestrogenic compound. The complications were one uterine perforation with a dilator with no sequelae, and one severe infection requirinjg hysterectomy. There were no failures. Of the 48 women available to follow-up, amenorrhea was achieved in 43 (90%). Two continued to spot very slightly on occasion, but did not require minipads. Three women had light flow requiring one to two tampons for 1 to 4 days every month. The technique continues to provide a very high rate of complete amenorrhea.

The order of singularity of solutions for the stationary coagulation equation

We prove that solutions of the stationary pure coagulation equation have not less than a second-order singularity at zero. Existence of solutions possessing singularity at zero was demonstrated in a previous article by the authors.

Time evolution of the structure function and dynamical scaling in porous SnO2 dry gels

An in situ study of the structural evolution of a porous SnO2 dry gel, under isothermal conditions, was carried out by means of the SAXS technique. The time evolution of the structure function is in agreement with the predictions of computer simulations for advanced stages of phase separation in binary materials. Dynamical scaling properties of the structure function of the porous system were verified. This study suggests that the evolution of microporosity occurs by a pure coagulation mechanism.

Endometrial ablation: “Combination procedure”(Nd:YAG Laser+Roller ball together)

Endometrial ablation is an effective treatment for intractable uterine bleeding. This can be accomplished using hysteroscopic electrosurgical rollerball, Nd:YAG laser, and with endomyometrial resection techniques. All ablations in this study were accomplished using the Nd:YAG laser and a "non-touch" technique on the ostiae, uterine fundus, and the upper 1/3 to 1/2 of the posterior uterine wall in combination with rollerball coagulation over the entire uterus after the 60 watt Nd:YAG application. The power source of the rollerball was set at 80 watts of pure coagulation current in most cases. Each patient was pre-treated with a GnRH agonist or an antiestrogenic compound. A total of 40 patients were treated beginning in November of 1990 until January 1994. Complete amenorrhea was achieved in 36 patients (90%). Two patients have slight monthly spotting requiring 1 to 2 mini-pads per month and two patients have light flow requiring 1 to 2 tampons for 1 to 3 days of the month. There were no failures. The complications were one uterine perforation with a dilator with no sequelae and one severe infection requiring hysterectomy. These promising results warrant further study of this "combination procedure."

The Coagulation Rate of Small Particles When Both Gravitational Convection and Brownian Motion Simultaneously Exist

While there has been an extensive and rigorous treatment of both the pureBrownian and the pure convection-induced coagulation since Smoluchowski’s work(1971), there has been no analogous study of particle/particle aggregation when bothconvection and Brownian motions simultaneously exist. In 1964, Swift and Friedlandermade an additivity assumption which assumed that the effects of convection

On 'exact solutions for the coagulation-fragmentation equation'

It is pointed out that the equilibrium solutions for pure coagulation and pure fragmentation which Dubovskii et al (ibid., vol.25, p.4737, 1992) purport to obtain are in error, and that such solutions do not in fact exist.

Exact solutions for the coagulation-fragmentation equation

The authors present new exact equilibrium and time-dependent solutions to the two main versions of the coagulation-fragmentation equation. Equilibria are first found for the pure coagulation and pure fragmentation equations; equilibrium solutions for the full coagulation-fragmentation equation are then constructed when the kernels governing the reaction rates are chosen to be in a particular form. Time-dependent solutions are also derived for the pure fragmentation equation.

Colonoscopic snare polypectomy: analysis of 1485 resections comparing two types of current

The complications related to 1485 colonic snare polypectomies were analyzed according to the type of current which was used for resection. From January 1982 to August 1986 (period 1), blended current was used in 758 snare polypectomies, while continuous coagulation current was applied in 727 polypectomies from September 1986 to October 1989 (period 2). The incidence of complications observed in the entire series was low, consisting of 0.26% perforations and 0.9% major hemorrhages. There were no deaths in this series. Twelve of 14 hemorrhages occurred after resection of polyps larger than 1 cm. Although the incidence of complications was not statistically different in the two groups, there was a significant difference in the timing of hemorrhages. All of the major hemorrhages were immediate (eight) when the blended current was used, but delayed (six; from 2 to 8 days after polyp resection), when pure coagulation current was applied.

Simulation of multicomponent aerosol dynamics

A technique for numerical solution of the multicomponent aerosol general dynamic equation is developed and tested. The method is intended to obtain directly the multivariable size-composition distribution without any a priori assumptions about the nature of the distribution. In selecting the numerical method particular attention is paid to simulating simultaneous coagulation and condensation processes, although if condensation is the dominant process a scheme more suitable for pure condensation can be chosen. Numerical solutions are compared with analytical solutions for model problems of pure condensation, pure coagulation, and simultaneous condensation and coagulation.