Using chaos indicators to determine vaccine influence on epidemic stabilization.

Virus outbreaks have the potential to be a source of severe sanitarian and economic crisis. We propose a new methodology to study the influence of several parameter combinations on the dynamical behavior of simple epidemiological compartmental models. Using this methodology, we analyze the behavior of a simple vaccination model. We find that for susceptible-infected-recovered (SIR) models with seasonality and natural death rate, a new vaccination can reduce the chaoticity of epidemic trajectories, even with nonvaccinated adults. This strategy has little effect on the first infection wave, but it can stop subsequent waves.

The utility of esophagogastroduodenoscopy and Helicobacter pylori screening in the preoperative assessment of patients undergoing bariatric surgery: A cross-sectional, single-center study in Saudi Arabia.

BACKGROUND/AIM: Esophagogastroduodenoscopy (EGD) and Helicobacter pylori screening are routine parts of the preoperative assessment of patients undergoing bariatric surgery at many centers around the world. The reason for this step is to identify abnormalities that may change the surgical approach. In this study, we aim to evaluate the extent to which endoscopic findings and H. pylori testing affect the plan of care in bariatric patients. PATIENTS AND METHODS: We retrospectively reviewed the investigational processes of 356 patients planned for bariatric surgery (2014-2016) at our center. Patients were categorized into two main groups (4 subgroups) from endoscopic findings. One group included patients with normal EGD and patients who had abnormal findings that did not change the surgical approach, whereas the other included patients who had findings that changed or canceled the surgical plan. A logistic regression analysis was used to evaluate how strongly can factors such as patient demographics, BMI, comorbidities, symptomatology, and H. pylori status predict the risk of having plan-changing endoscopic abnormalities. RESULTS: The ages ranged between 15 and 66 years with a mean ± SD of 37 ± 11 years, and 56% were females. The majority of patients (75%; 95% CI: 73 - 82%) had either no findings (41%) or had abnormalities that did not change the surgical approach (34%). Only 25% (95% CI: 21-29%) were found to have pathologies that altered the surgical approach, and 0.6% of them had findings that were considered contraindications for surgery. In spite the relatively high prevalence of H. pylori in our cohort (41%; 95% CI 36-46%), the proportion of patients who had plan-changing abnormalities did not differ markedly from other studies. Gastroesophageal reflux disease (GERD) and obstructive sleep apnea symptoms were the only significant predictors of EGD findings (P = 0.009). CONCLUSIONS: GERD and sleep apnea symptoms can be strong predictors of EGD abnormalities. However, this evidence is still not enough to safely recommend changing the current practice. Therefore, until a sensitive clinical prediction score is derived and validated according to the symptoms, we suggest that EGD should continue as the standard of care in all patients undergoing bariatric surgery.

Applicability of Low-Cost Binders for the Quantitative Elemental Analysis of Urinary Stones Using EDXRF Based on Fundamental Parameter Approach.

The pressed powder sample is a common method for elemental analysis using X-ray fluorescence analysis whereas suitable light hydrocarbon materials should be added to the sample as a binder. The present study demonstrates the applicability of using different commercial binders for elemental analysis of urinary stone samples. In order to confirm the obtained results, a comparison with pure chemical grade binders was presented. Different commercial and pure binders were tested for quantitative elemental analysis of urinary stones, namely, cellulose, starch, wax, and urea. Energy dispersive X-ray fluorescence (EDXRF) was used for elemental analysis. Differential thermal analysis was used to estimate the loss on ignition (LOI) in the urinary stone samples. The signal to background ratios (I/IB) of the different detected elements in the commercial and pure binders were calculated, compared, and studied at eight different photon energies starting from 2.5 up to 37 keV. Standard-less quantitative analysis method based on the fundamental parameter approach was applied for elemental analysis of selected urinary stones. The commercial and low-cost binders could be an excellent alternative binder for urinary stone analysis using energy dispersive X-ray fluorescence. The commercial binders could provide an advantage as pure chemical grade binders or even better especially at photon energy higher than 10 keV. The best commercial binder candidate was found to be the wax. The quantitative analysis results using commercial and pure chemical grade binders give good agreement results, which indicate the applicability of commercial binders for quantitative elemental analysis of urinary stones in the form of pressed powder samples.

Blends of thermoplastic polyurethane and polydimethylsiloxane rubber: assessment of biocompatibility and suture holding strength of membranes.

In the present investigation, a compatibilized blend of thermoplastic polyurethane (TPU) and polydimethylsiloxane (PDMS) is prepared by using copolymer of ethylene and methyl acrylate (EMA) as a reactive compatibilizer. Detailed in vitro biocompatibility studies were carried out for this compatibilized blend and the material was found noncytotoxic towards L929 mouse fibroblast subcutaneous connective tissue cell line. Microporosity was created on the surface of membranes prepared from the blend material by adopting the crazing mechanism. Cell proliferation and growth studies on the membranes surface showed that the microporous surface favoured ingrowth of the cells compared with a nonmicroporous surface. Suture holding strength studies indicate that the microporous membranes have enough strength to withstand the cutting and tearing forces through the suture hole. This blend material could be evaluated further to find its suitability in various implant applications.