Invasion of a sticky random solid: self-established potential gradient, phase separation, and criticality.

Invasion of a sticky random solid by an aqueous solution is modeled through a chemical reaction. In this reaction, the solid elements dissolve in the solution and redeposit back on the rough interface. A self-established potential gradient (SEPG) in the binding energy of the solid is developed spontaneously and the system gets phase separated into "hard" and "soft" solids. The solution profile is found drifted slowly into the solid by the SEPG with a constant velocity. The system tunes itself to the percolation threshold in the steady state. In the steady state, the system is found consisting of finite clusters of solution molecules followed by a path of redeposited solid as an invasion percolation cluster. A diffusive growth of the interface and the solution inside the solid is found to occur. The nonequilibrium steady state of this dynamical system is found critical and characterized by a power-law distribution of cluster size with an exponent approximately -2 .

Ensemble distribution for immiscible two-phase flow in porous media.

We construct an ensemble distribution to describe steady immiscible two-phase flow of two incompressible fluids in a porous medium. The system is found to be ergodic. The distribution is used to compute macroscopic flow parameters. In particular, we find an expression for the overall mobility of the system from the ensemble distribution. The entropy production at the scale of the porous medium is shown to give the expected product of the average flow and its driving force, obtained from a black-box description. We test numerically some of the central theoretical results.

Effective Rheology of Two-Phase Flow in Three-Dimensional Porous Media: Experiment and Simulation.

We present an experimental and numerical study of immiscible two-phase flow of Newtonian fluids in three-dimensional (3D) porous media to find the relationship between the volumetric flow rate (Q) and the total pressure difference ([Formula: see text]) in the steady state. We show that in the regime where capillary forces compete with the viscous forces, the distribution of capillary barriers at the interfaces effectively creates a yield threshold ([Formula: see text]), making the fluids reminiscent of a Bingham viscoplastic fluid in the porous medium. In this regime, Q depends quadratically on an excess pressure drop ([Formula: see text]). While increasing the flow rate, there is a transition, beyond which the overall flow is Newtonian and the relationship is linear. In our experiments, we build a model porous medium using a column of glass beads transporting two fluids, deionized water and air. For the numerical study, reconstructed 3D pore networks from real core samples are considered and the transport of wetting and non-wetting fluids through the network is modeled by tracking the fluid interfaces with time. We find agreement between our numerical and experimental results. Our results match with the mean-field results reported earlier.

Local load-sharing fiber bundle model in higher dimensions.

We consider the local load-sharing fiber bundle model in one to five dimensions. Depending on the breaking threshold distribution of the fibers, there is a transition where the fracture process becomes localized. In the localized phase, the model behaves as the invasion percolation model. The difference between the local load-sharing fiber bundle model and the equal load-sharing fiber bundle model vanishes with increasing dimensionality with the characteristics of a power law.

Effect of Adherence to the World Health Organization Surgical Safety Checklist on Morbidity and Mortality in a Defined Surgical Patient Population

To improve patient safety and prevent complications, WHO introduced surgical safety checklist (WHO SSC). However, the actual effect of WHO SSC on patient morbidity, particularly surgical site infections (SSI), and mortality on post-operative patients is one of the least studied area. Our study was to measure the effects surgical safety checklists have in reducing morbidities and complications, particularly surgical site infections, post-operative length of stay and mortality resulting from the surgical procedures. Methods: A prospective observational comparative study was conducted among all patients who underwent elective general surgical procedures from 01st July 2015 to 30th June 2016 in the Main OT Complex (OT1 and OT2), Indoor Surgical Wards and higher dependency units (ITU & CCU) of IPGMER & SSKM Hospital, Kolkata, after applying proper exclusion criteria. Pre-implementation (before implementation of WHO Surgical Safety Checklist) data was collected for first 6 months, then WHO Surgical Safety Checklist was implemented over next 6 months. Pre and post-implementation cohorts were compared and analysed. Results: Total 382 patients (187 Control group and 195 implementation group) were included. Both groups matched regarding age, sex, type of surgery, type of anaesthesia, post-operative length of stay. However, incidence of SSI significantly decreased (30.48% to 16.41%, p value 0.002, <0.05, statistically significant). Overall complication rate, unplanned return to operating room (OR) also decreased though the results were statistically not significant. Conclusion: Implementation of WHO SSC decreases morbidity related to SSI significantly. Further studies are required to assess the effects on mortality and unplanned return to OR.

Role of Closed Suction Drain in the Prevention of SSI in Elective Surgery

Presence of haematoma, serous fluid, and dead space in a wound increase the risk of infection as they act as a culture media. Multiple options had been mentioned to reduce these risks. We tried to assess the incidence of SSI following placement of closed suction drains following elective surgeries. Methods: A prospective observational study was conducted in the Department of General Surgery, IPGMER & SSKM Hospital, Kolkata from January 2016 to June 2017. Patients who were given a subcutaneous suction drain after an elective general surgical procedure were included in the study. Patients unwilling to take part in the study, patients from paediatric age group, on steroids, with Class 4 wounds and those underwent Laparoscopic Surgery were excluded. Outcome was measured in the form of presence or absence of SSI and data was analysed. Results: No statistically significant decrease of incidence of SSI was found in terms of different age, sex, socio-economic status, duration of hospital stays, smoking or alcoholism. Increased incidence of SSI was detected among Diabetics even after using closed suction drainage. Conclusion: Placement of closed suction drain did not significantly reduce incidence of SSI following elective general surgical procedures.

“Ligation of Intersphincteric Fistula Tract (Lift)" The Solution in Perianal Fistulae? – A Prospective Observational Study in 30 Simply Randomised Cases

Ligation of Intersphincteric Fistulous Tract (LIFT) is a novel and promising technique in the management of Fistula in ano. We tried to assess the outcome of LIFT procedure in our institute in terms of healing rate, incontinence and recurrences. Methods: A prospective observational study was performed in the Department of General Surgery, IPGMER and SSKM Hospital, Kolkata, India between January 2016 and August 2017. Thirty patients were selected with simple randomization after applying all inclusion and exclusion criteria and all underwent LIFT procedure. Results: Among the 30 patients included in our study, the healing rate varied from 76.7% in 2-week follow-up to 93.3% on 6 months follow-up. One patient had Grade B incontinence from which he recovered within 1 month. One diabetic patient had recurrence of the disease. Conclusion: LIFT is a promising procedure for both simple or complex fistulas with single or multiple tracts with minimum incidence of incontinence or recurrence. However, larger randomised controlled trials with large study population is required.

A Novel Technique for Protection of Facial Nerve during Parotidectomy

Identification and protection of Facial Nerve is of prime importance during surgery of parotid glands. Several techniques are available in literature to identify and preserve FN. We present here a case series with dissection of FN in a novel technique during parotidectomy which has significantly lowered the morbidity due to injury of the FN. Methods: All data, from all the patients who underwent Parotidectomy in our unit (conducted or supervised by a single surgeon) in the Department of General Surgery, IPGMER and SSKM Hospital, Kolkata, between March 2014 to March 2019, using our novel technique for identification and protection of FN, was retrospectively analysed. Outcome measurement was expressed in terms of type of surgery, duration, estimated blood loss, any intra-operative or post-operative complications, length of hospital stay, duration of drain in place, Histopathological (HPE) reports, size of the tumour, margin and lymph node status, Facial Nerve weakness and other complications. Results: Total 13 patients underwent Parotidectomy (Total or Superficial) following our technique of identifying and protecting Facial Nerve (FN). Four of them had temporary FN paresis in immediate post-op period. None of the patients had FN paresis on follow-up at 1 year. Conclusion: The novel technique described in our study for identification and protection of FN is a promising technique for Parotid Surgery.

Effective rheology of bubbles moving in a capillary tube.

We calculate the average volumetric flux versus pressure drop of bubbles moving in a single capillary tube with varying diameter, finding a square-root relation from mapping the flow equations onto that of a driven overdamped pendulum. The calculation is based on a derivation of the equation of motion of a bubble train, considering the capillary forces and the entropy production associated with the viscous flow. We also calculate the configurational probability of the positions of the bubbles.

History independence of steady state in simultaneous two-phase flow through two-dimensional porous media.

It is well known that the transient behavior during drainage or imbibition in multiphase flow in porous media strongly depends on the history and initial condition of the system. However, when the steady-state regime is reached and both drainage and imbibition take place at the pore level, the influence of the evolution history and initial preparation is an open question. Here, we present an extensive experimental and numerical work investigating the history dependence of simultaneous steady-state two-phase flow through porous media. Our experimental system consists of a Hele-Shaw cell filled with glass beads which we model numerically by a network of disordered pores transporting two immiscible fluids. From measurements of global pressure evolution, histograms of saturation, and cluster-size distributions, we find that when both phases are flowing through the porous medium, the steady state does not depend on the initial preparation of the system or on the way it has been reached.

Unicentric Castleman's Disease Masquerading Pancreatic Neoplasm.

Castleman's disease is a rare nonclonal proliferative disorder of the lymph nodes with an unknown etiology. Common locations of Castleman's disease are mediastinum, neck, axilla, and abdomen. Castleman's disease of a peripancreatic location masquerading as pancreatic neoplasm is an even rarer entity. On search of published data, we came across about 17 cases published on peripancreatic Castleman's disease until now. Here we are reporting a case of retropancreatic Castleman's disease masquerading as retroperitoneal neoplasm in a 46-year-old male patient.

Isolated traumatic bilateral first rib fracture: a rare entity.

Since the first rib is protected very well by the overlying soft tissue and bones, its fracture is a major injury and a considerable force is required to do it. Therefore, an isolated fracture of this rib is unusual. A 28-year-old healthy female had an accident while crossing the road and a heavy object fell on her. She had severe pain behind her clavicle region and was immediately hospitalized and examined. Thorough clinical examination and different relevant investigations surprisingly disclosed isolated bilateral first rib fracture which is a very rare clinical condition.

Local wettability reversal during steady-state two-phase flow in porous media.

We study the effect of local wettability reversal on remobilizing immobile fluid clusters in steady-state two-phase flow in porous media. We consider a two-dimensional network model for a porous medium and introduce a wettability alteration mechanism. A qualitative change in the steady-state flow patterns, destabilizing the percolating and trapped clusters, is observed as the system wettability is varied. When capillary forces are strong, a finite wettability alteration is necessary to move the system from a single-phase to a two-phase flow regime. When both phases are mobile, we find a linear relationship between fractional flow and wettability alteration.