Energy- and flux-budget (EFB) turbulence closure model for the stably stratified flows. Part I: Steady-state, homogeneous regimes

We propose a new turbulence closure model based on the budget equations for the key second moments: turbulent kinetic and potential energies: TKE and TPE (comprising the turbulent total energy: TTE = TKE + TPE) and vertical turbulent fluxes of momentum and buoyancy (proportional to potential temperature). Besides the concept of TTE, we take into account the non-gradient correction to the traditional buoyancy flux formulation. The proposed model grants the existence of turbulence at any gradient Richardson number, Ri. Instead of its critical value separating - as usually assumed - the turbulent and the laminar regimes, it reveals a transition interval, 0.1< Ri <1, which separates two regimes of essentially different nature but both turbulent: strong turbulence at Ri<<1; and weak turbulence, capable of transporting momentum but much less efficient in transporting heat, at Ri>1. Predictions from this model are consistent with available data from atmospheric and lab experiments, direct numerical simulation (DNS) and large-eddy simulation (LES).Comment: 40 pages, 6 figures, Boundary-layer Meteorology, resubmitted, revised versio

Giant liver hemangioma resected by trisectorectomy after efficient volume reduction by transcatheter arterial embolization: a case report

<p>Abstract</p> <p>Introduction</p> <p>Liver hemangiomas are the most common benign liver tumors, usually small in size and requiring no treatment. Giant hemangiomas complicated with consumptive coagulopathy (Kasabach-Merritt syndrome) or causing severe incapacitating symptoms, however, are generally considered an absolute indication for surgical resection. Here, we present the case of a giant hemangioma, which was, to the best of our knowledge, one of the largest ever reported.</p> <p>Case presentation</p> <p>A 38-year-old Asian man was referred to our hospital with complaints of severe abdominal distension and pancytopenia. Examinations at the first visit revealed a right liver hemangioma occupying the abdominal cavity, protruding into the right diaphragm up to the right thoracic cavity and extending down to the pelvic cavity, with a maximum diameter of 43 cm, complicated with "asymptomatic" Kasabach-Merritt syndrome. Based on the tumor size and the anatomic relationship between the tumor and hepatic vena cava, primary resection seemed difficult and dangerous, leading us to first perform transcatheter arterial embolization to reduce the tumor volume and to ensure the safety of future resection. The tumor volume was significantly decreased by two successive transcatheter arterial embolizations, and a conventional right trisectorectomy was then performed without difficulty to resect the tumor.</p> <p>Conclusions</p> <p>To date, there have been several reports of aggressive surgical treatments, including extra-corporeal hepatic resection and liver transplantation, for huge hemangiomas like the present case, but because of its benign nature, every effort should be made to avoid life-threatening surgical stress for patients. Our experience demonstrates that a pre-operative arterial embolization may effectively enable the resection of large hemangiomas.</p

Nitrous oxide may not increase the risk of cancer recurrence after colorectal surgery: a follow-up of a randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>Even the best cancer surgery is usually associated with minimal residual disease. Whether these remaining malignant cells develop into clinical recurrence is at least partially determined by adequacy of host defense, especially natural killer cell function. Anesthetics impair immune defenses to varying degrees, but nitrous oxide appears to be especially problematic. We therefore tested the hypothesis that colorectal-cancer recurrence risk is augmented by nitrous oxide administration during colorectal surgery.</p> <p>Methods</p> <p>We conducted a 4- to 8-year follow-up of 204 patients with colorectal cancer who were randomly assigned to 65% nitrous oxide (n = 97) or nitrogen (n = 107), balanced with isoflurane and remifentanil. The primary outcome was the time to cancer recurrence. Our primary analysis was a multivariable Cox-proportional-hazards regression model that included relevant baseline variables. In addition to treatment group, the model considered patient age, tumor grade, dissemination, adjacent organ invasion, vessel invasion, and the number of nodes involved. The study had 80% power to detect a 56% or greater reduction in recurrence rates (i.e., hazard ratio of 0.44 or less) at the 0.05 significance level.</p> <p>Results</p> <p>After adjusting for significant baseline covariables, risk of recurrence did not differ significantly for nitrous oxide and nitrogen, with a hazard ratio estimate (95% CI) of 1.10 (0.66, 1.83), <it>P </it>= 0.72. No two-way interactions with the treatment were statistically significant.</p> <p>Conclusion</p> <p>Colorectal-cancer recurrence risks were not greatly different in patients who were randomly assigned to 65% nitrous oxide or nitrogen during surgery. Our results may not support avoiding nitrous oxide use to prevent recurrence of colorectal cancer.</p> <p>Implications Statement</p> <p>The risk of colorectal cancer recurrence was similar in patients who were randomly assigned to 65% nitrous oxide or nitrogen during colorectal surgery.</p> <p>Trial Registration</p> <p>Current Controlled Clinical Trials NCT00781352 <url>http://www.clinicaltrials.gov</url></p

Determining the role of external beam radiotherapy in unresectable intrahepatic cholangiocarcinoma: a retrospective analysis of 84 patients

<p>Abstract</p> <p>Background</p> <p>Intrahepatic cholangiocarcinoma (ICC) is the second most common type of primary liver cancer. Only few studies have focused on palliative radiotherapy used for patients who weren't suitable for resection by surgery. This study was conducted to investigate the effect of external beam radiotherapy (EBRT) for patients with unresectable ICC.</p> <p>Methods</p> <p>We identified 84 patients with ICC from December 1998 through December 2008 for retrospective analysis. Thirty-five of 84 patients received EBRT therapy five times a week (median dose, 50 Gy; dose range, 30-60 Gy, in fractions of 1.8-2.0 Gy daily; EBRT group); the remaining 49 patients comprised the non-EBRT group. Tumor response, jaundice relief, and survival rates were compared by Kaplan-Meier analysis. Patient records were reviewed and compared using Cox proportional hazard analysis to determine factors that affect survival time in ICC.</p> <p>Results</p> <p>After EBRT, complete response (CR) and partial response (PR) of primary tumors were observed in 8.6% and 28.5% of patients, respectively, and CR and PR of lymph node metastases were observed in 20% and 40% of patients. In 19 patients with jaundice, complete and partial relief was observed in 36.8% and 31.6% of patients, respectively. Median survival times were 5.1 months for the non-EBRT group and 9.5 months for the EBRT group (<it>P </it>= 0.003). One-and two-year survival rates for EBRT versus non-EBRT group were 38.5% versus 16.4%, and 9.6% versus 4.9%, respectively. Multivariate analysis revealed that clinical symptoms, larger tumor size, no EBRT, multiple nodules and synchronous lymph node metastases were associated with poorer prognosis.</p> <p>Conclusions</p> <p>EBRT as palliative care appears to improve prognosis and relieve the symptom of jaundice in patients with unresectable ICC.</p

An Electrode Array for Limiting Blood Loss During Liver Resection: Optimization via Mathematical Modeling

Liver resection is the current standard treatment for patients with both primary and metastatic liver cancer. The principal causes of morbidity and mortality after liver resection are related to blood loss (typically between 0.5 and 1 L), especially in cases where transfusion is required. Blood transfusions have been correlated with decreased long-term survival, increased risk of perioperative mortality and complications. The goal of this study was to evaluate different designs of a radiofrequency (RF) electrode array for use during liver resection. The purpose of this electrode array is to coagulate a slice of tissue including large vessels before resecting along that plane, thereby significantly reducing blood loss. Finite Element Method models were created to evaluate monopolar and bipolar power application, needle and blade shaped electrodes, as well as different electrode distances. Electric current density, temperature distribution, and coagulation zone sizes were measured. The best performance was achieved with a design of blade shaped electrodes (5 × 0.1 mm cross section) spaced 1.5 cm apart. The electrodes have power applied in bipolar mode to two adjacent electrodes, then switched sequentially in short intervals between electrode pairs to rapidly heat the tissue slice. This device produces a ~1.5 cm wide coagulation zone, with temperatures over 97 ºC throughout the tissue slice within 3 min, and may facilitate coagulation of large vessels

Disease-Free Survival after Hepatic Resection in Hepatocellular Carcinoma Patients: A Prediction Approach Using Artificial Neural Network

Background: A database for hepatocellular carcinoma (HCC) patients who had received hepatic resection was used to develop prediction models for 1-, 3- and 5-year disease-free survival based on a set of clinical parameters for this patient group. Methods: The three prediction models included an artificial neural network (ANN) model, a logistic regression (LR) model, and a decision tree (DT) model. Data for 427, 354 and 297 HCC patients with histories of 1-, 3- and 5-year disease-free survival after hepatic resection, respectively, were extracted from the HCC patient database. From each of the three groups, 80 % of the cases (342, 283 and 238 cases of 1-, 3- and 5-year disease-free survival, respectively) were selected to provide training data for the prediction models. The remaining 20 % of cases in each group (85, 71 and 59 cases in the three respective groups) were assigned to validation groups for performance comparisons of the three models. Area under receiver operating characteristics curve (AUROC) was used as the performance index for evaluating the three models. Conclusions: The ANN model outperformed the LR and DT models in terms of prediction accuracy. This study demonstrated the feasibility of using ANNs in medical decision support systems for predicting disease-free survival based on clinical databases in HCC patients who have received hepatic resection