[Emergency laparoscopy in the treatment of perforated gastroduodenal ulcers]

OBJECTIVE

To compare the results of endoscopic and open treatment of perforated gastroduodenal ulcers.

MATERIAL AND METHODS

There were 445 patients with perforated gastroduodenal ulcers between 2013 and 2021. Endoscopic suturing of perforation was performed in 172 patients (38.7%), 273 ones underwent open surgery.

RESULTS

Among 172 patients scheduled for endoscopy, 160 (93.6%) ones underwent laparoscopic suturing of perforation. Morbidity rate was 5.0% (n=8), postoperative mortality rate - 1.3% (n=2). Comparison of the outcomes after laparoscopic suturing of ulcers in 160 patients and open surgery in 134 patients showed that laparoscopy was followed by 2.5 times lower incidence of complications and 3 times lower postoperative mortality.

CONCLUSION

Diagnostic laparoscopy is advisable in patients with perforated ulcers and no contraindications. In most cases, surgery can be successfully and effectively completed without conversion to laparotomy. Endoscopic closure of ulcerative defect is preferable since this procedure has certain advantages over traditional intervention, contributes to significant reduction in morbidity, mortality and hospital-stay.

Rotational Brownian motion of axisymmetric particles in a Maxwell fluid

A theory of non-Markovian rotational Brownian motion is developed for axisymmetric particles moving in a Maxwell fluid in the presence of an external field. Both the inertial and viscoelastic effects are taken into account. A kinetic equation for the joint probability distribution of orientation, angular velocity, and acceleration of a particle without spin is derived starting from the rotational Langevin equation with relaxed hydrodynamic and random torques. A third-order stochastic differential equation for the particle orientation vector is also derived. Directly from this equation, the set of nonlinear evolution equations for one-time moments is derived in a noninertial approximation. The expressions for a linear response to a time-dependent external field and dynamic susceptibility of particle are obtained by direct averaging of particle orientation equation. Appendices derive the rotational mobility of axisymmetric particles in a general linear viscoelastic fluid, and the evolution equations for one-time moments of the orientation vector for axisymmetric particles moving in a Maxwell fluid in the presence of an external field.

An Approach to Chemorheology of a Filled SBR Compound

Three steps in complex chemorheological studies are necessary for complete rheological characterization of filled rubbers during cross-linking reaction. They include: (i) kinetic studies of cross-linking reaction, (ii) rheological studies of green rubber compounds, and (iii) correlation between the rheological parameters and the degree of cure. Basic experiments in the steps (i)–(iii) and their modeling are presented in this paper on the example of a filled SBR compound with sulfur accelerated vulcanization. The approach provides a unique possibility to trace therheological properties of rubber compounds from the green to completely cured states.

A Study of the Vulcanization Kinetics of an Accelerated-Sulfur SBR Compound

Vulcanization kinetics for a SBR compound was studied by using both curemeter and DSC methods by a kinetic approach. A simplified but realistic model reaction scheme was used to simulate both induction and curing periods simultaneously. Model parameters were extracted from isothermal curemeter experiments. The model prediction demonstrated a good agreement with isothermal curemeter data over a temperature range of 120°C to 180°C. The variation of equilibrium modulus with temperature, observed from cure curves, can also be predicted. However, DSC experiments showed a different reaction behavior in the curing period as compared to model calculations. This was explained by the assumption that the reaction heat observed in DSC is due to all possible exothermal reactions, and the formation of crosslinks is only a part of these reactions. Hence, the curemeter can provide a good indication of crosslink formation, while DSC displays the entire reaction heat released during the vulcanization process. The kinetic approach allows one to incorporate vulcanization kinetics into the practical simulation of reactive processing operations.