An aggregation model of cockroaches with fast-or-slow motion dichotomy.

We propose a mathematical model, namely a reaction-diffusion system, to describe social behaviour of cockroaches. An essential new aspect in our model is that the dispersion behaviour due to overcrowding effect is taken into account as a counterpart to commonly studied aggregation. This consideration leads to an intriguing new phenomenon which has not been observed in the literature. Namely, due to the competition between aggregation towards areas of higher concentration of pheromone and dispersion avoiding overcrowded areas, the cockroaches aggregate more at the transition area of pheromone. Moreover, we also consider the fast reaction limit where the switching rate between active and inactive subpopulations tends to infinity. By utilising improved duality and energy methods, together with the regularisation of heat operator, we prove that the weak solution of the reaction-diffusion system converges to that of a reaction-cross-diffusion system.

Early results of a Canadian laparoscopic sleeve gastrectomy experience.

BACKGROUND: Sleeve gastrectomy (SG) is a relatively new bariatric procedure with a number of advantages compared with Roux-en-Y gastric bypass. However, SG also has a number of disadvantages and associated risks. We sought to examine perioperative complications and outcomes of laparoscopic SG (LSG) in a single major Canadian bariatric surgery centre (Victoria, BC). METHODS: Since June 2008, LSG has been performed at our centre and we reviewed the cases of all patients. We conducted a retrospective chart review in April 2010. RESULTS: Thirty-four patients had LSG, and none was lost to follow-up. Indications for LSG over other bariatric procedures were patient preference (n=28), severe obesity with a body mass index (BMI) greater than 60 kg/m(2) (n=5) and severe upper abdominal adhesions (n=1). All but 1 of the cohort were women, and the average age was 48 (standard deviation [SD] 11) years. Preoperatively, the average BMI was 50.3 (SD 7.7) kg/m(2). Preoperative obesity-related comorbidity rates were 56% (n=19) for type 2 diabetes mellitus (T2DM), 50% (n=17) for hypertension, 32% (n=11) for dys lipidemia, 62% (n=21) for obstructive sleep apnea (OSA), 62% (n=21) for knee and/or hip pain and 44% (n=15) for depression and/or anxiety. The mean duration of surgery was 74 (SD 21) minutes. There were 2 major perioperative complications: 1 staple line leak and 1 staple line hemorrhage. The median stay in hospital was 1 day. Postoperative upper gastrointestinal imaging studies were conducted in 11 patients; 1 was positive for staple line leak. Histopathology on the excised gastric segments revealed chronic helicobacter pylori gastritis in 2 patients and small gastrointestinal stromal tumours in 1 patient. The mean postoperative follow-up interval was 10 months. Weight loss averaged 27.4 (SD 9.0) kg. Overall weight loss was 3.3 (SD 1.8) kg/month. Resolution occurred in 74% of patients with T2DM, 53% with hypertension, 45% with dyslipidemia, 76% with OSA, 38% with joint pain and 20% with depression/anxiety. Overall satisfaction was rated as excellent by 68% of patients, good by 29% and poor by 3% of patients. CONCLUSION: Preliminary analysis of our experience with LSG indicates that this is an effective and safe procedure for the treatment of obesity.

A five year Canadian laparoscopic adjustable gastric band experience.

BACKGROUND: The aim of this study was to review 5 years of laparoscopic adjustable gastric band (LAGB) procedures in which low-pressure bands were used. METHODS: All LAGB cases at the authors' center were retrospectively analyzed. A survey of these patients was conducted in 2008 and 2009. RESULTS: Of 90 LAGB patients, 86 were surveyed. Follow-up averaged 17.5 months. Weight loss averaged 24.8 +/- 19.4 kg. Weight loss averaged 2.7 kg/mo and did not significantly drop over the last 10.7 months (2.7 vs 1.5 kg/mo, P = .16). Excess body weight loss was 27.5%, 39.1%, and 67.2% in the first, second, and following years, respectively. Patients averaged 4.14 adjustments of their bands and vomited 2.13 times per week. The mortality rate was 0%. No band slippages or band erosion occurred. Resolution or improvement occurred in most obesity-related illness. Gastroesophageal reflux disease symptoms worsened in 25% of patients. CONCLUSIONS: These results replicate world LAGB literature. Low complication rates result either from the authors' band or their techniques.

Laparoscopic colon surgery in community practice.

BACKGROUND: The benefits of laparoscopic colon surgery have been shown in the literature. More recently, the oncologic outcomes have been shown to be similar in the laparoscopic group when compared with open colon surgery for colon cancer. However, most of the published literature is from university/academic institutions. There is limited literature on laparoscopic colon surgery from a community hospital. METHODS: A retrospective chart review was conducted of 62 laparoscopic colon surgeries from a single surgeon's practice in a community hospital from October 27, 2003, to August 31, 2006. The laparoscopic approach was performed on patients with benign and curative colon cancer. The primary outcome measures were length of operating room times, pathologic results, length of hospital stay, and complication rates. RESULTS: Of the 62 laparoscopic patients, there were 9 converted patients (14% conversion rate). There were no perioperative deaths, and no anastomotic leaks. The average length of operating room time was 190 minutes (range, 96-295 min). The median length of hospital stay was 4 days (range, 3-17 d). There were 40 laparoscopic patients for colon cancer. The resection margins all were negative, and the mean number of lymph nodes in the resected specimen was 17 (range, 5-37). The overall complication rate was 18%. CONCLUSIONS: This study showed that laparoscopic colon surgery is technically feasible in a community hospital. The results from this study are similar to the published literature from university/academic institutions.