Use of laparoscopic equipment for colonoscopy intraoperatively in case of lack of colonoscope

Abstract

In the case where intraoperative endoscopy is necessary and there is no endoscope available in the hospital, there is a solution, the use of available laparoscopic equipment. The technique is simple and without being time consuming. All its needed is a laparoscopic video- camera, and laparoscopic ports. The whole procedure takes place in the surgical field and provides an immediate solution for the endoscopic inspection of stomach, small intestine and large intestine. We describe the first case where it takes place in an open right colectomy in a patient with colon cancer and a suspicious lesion at the left colon. Further studies are needed to evaluate the indications and the effectiveness of the method.

Control instabilities and incite slow-slip in generalized Burridge-Knopoff models

“…This transition is made in a characteristic distance D c (Kanamori & Brodsky, 2004). This characteristic distance, together with the friction coefficient drop and the applied effective normal force, determine the apparent frictional weakening during sliding and render the system unstable leading to sudden slip (stick-slip motion Ruina, 1983;Stefanou, 2019). Alternatively, the classical rateand-state friction law could be used, but this model is mathematically singular for very low (and very high) sliding velocities, as the ones developed herein when the system is under control, and therefore it is not appropriate without proper regularization (Ben-Zion, 2008).…”

“…Stability analysis using Lyapunov methods can show the exact conditions for which this system becomes unstable (cf. Stefanou, 2019). When several blocks are considered, the system presents a chaotic, SOC behavior, which makes its dynamical behavior extremely rich and challenging to control (see for instance Carlson & Langer, 1989;Schmittbuhl et al, 1996;Becker, 2000;Erickson et al, 2011).…”

“…This might be at first counter-intuitive, if stabilization is thought as a simple process of adjusting pressure in order to satisfy the frictional stability condition of the system. For the single springslider model, frictional stability is guaranteed when the stiffness of the loading system is higher than a critical softening stiffness, which depends on the exact frictional parameters and rheology (see Ruina, 1983;Scholz, 2019;Stefanou, 2019). For the GBK model, the stability conditions are qualitatively similar.…”

“…This can be quite important for industrial projects involving fluid injections in depth. Some preliminary, practical numerical examples on the base of the simple spring-slider model were given in Stefanou (2019), where pressure reduction is found again to be needed for stabilization. In these examples tracking was achieved by increasing the effective stress by ∼ 15%.…”

“…For the simulations, we first calculate the minimum displacement of the driver plate that can trigger the sliding of at least one block. In this way we avoid simulating the slow-dynamics (Stefanou, 2019), quasi-static behavior of the system and we only integrate numerically the dynamic equations of motion of the system for determining its fast dynamic, unstable response. After each dynamic event, the system reaches a new equilibrium (local minimum potential energy state).…”