A Queueing Model to Study Ambulance Offload Delays

The ambulance offload delay problem is a well-known result of overcrowding and congestion in emergency departments. Offload delay refers to the situation where area hospitals are unable to accept patients from regional ambulances in a timely manner due to lack of staff and bed capacity. The problem of offload delays is not a simple issue to resolve and has caused severe problems to the emergency medical services (EMS) providers, emergency department (ED) staff, and most importantly patients that are transferred to hospitals by ambulance. Except for several reports on the problem, not much research has been done on the subject. Almost all research to date has focused on either EMS or ED planning and operation and as far as we are aware there are no models which have considered the coordination of these units. We propose an analytical model which will allow us to analyze and explore the ambulance offload delay problem. We use queuing theory to construct a system representing the interaction of EMS and ED, and model the behavior of the system as a continuous time Markov chain. The matrix geometric method will be used to numerically compute various system performance measures under different conditions. We analyze the effect of adding more emergency beds in the ED, adding more ambulances, and reducing the ED patient length of stay, on various system performance measures such as the average number of ambulances in offload delay, average time in offload delay, and ambulance and bed utilization. We will show that adding more beds to the ED or reducing ED patient length of stay will have a positive impact on system performance and in particular will decrease the average number of ambulances experiencing offload delay and the average time in offload delay. Also, it will be shown that increasing the number of ambulances will have a negative impact on offload delays and increases the average number of ambulances in offload delay. However, other system performance measures are improved by adding more ambulances to the system. Finally, we will show the tradeoffs between adding more emergency beds, adding more ambulances, and reducing ED patient length of stay. We conclude that the hospital is the bottleneck in the system and in order to reduce ambulance offload delays, either hospital capacity has to be increased or ED patient length of stay is to be reduced

Stimulated quantum phase slips from weak electromagnetic radiations in superconducting nanowires

We study the rate of quantum phase slips in an ultranarrow superconducting nanowire exposed to weak electromagnetic radiations. The superconductor is in the dirty limit close to the superconducting-insulating transition, where fluxoids move in strong dissipation. We use a semiclassical approach and show that external radiation stimulates a significant enhancement in the probability of quantum phase slips. This can help to outline a new type of detector for microwave to submillimetre radiations based on stimulated quantum phase slip phenomenon.Comment: 10 pages, 9 figure

Development of Microextraction-based Techniques for Quantification and Behaviour Characterization of Nanoparticles in Aquatic Environments

Ph.DDOCTOR OF PHILOSOPH

Mass Spectrometric Analysis of Bisphenol A Desorption from Titania Nanoparticles: Ammonium Acetate, Fluoride, Formate, and Hydroxide as Chemical Desorption Agents

Bisphenol A (BPA) is a widely used chemical in several consumer products and a well-studied environmental toxicant, and therefore, its accurate measurement is highly demanded. However, the co-presence of nanoparticles as an emerging class of contaminants could result in inaccurate determination of BPA due to binding of BPA onto nanoparticle surface. In this study, mass spectrometry (MS) was used to investigate desorption of BPA bound on the surface of titania (TiO2) nanoparticles in water. Ammonium acetate, fluoride, formate, and hydroxide were evaluated as chemical agents for their desorption capabilities. The percentages of recovery, adsorption, and desorption were determined by this new method without requiring any prior separation of nanoparticles from BPA. MS analysis demonstrated the desorption of BPA by 10–20 mM of ammonium hydroxide for a mixture of 5 µg/mL BPA and 10 µg/mL TiO2 nanoparticles, with a desorption efficiency of 72 ± 1%. Due to adsorption of BPA onto the nanoparticle surface that was inefficient for electrospray ionization, the resulting abundance of target ions could be reduced in the detection of BPA by mass spectrometry. As such, these findings collectively promise an accurate determination of the total BPA concentration in water whether it exists in the free or bound form. Efficient desorption of contaminants from the surface of nanoparticles would improve the accuracy of the contaminant analysis by mass spectrometry

Comparison of the Effects of Thoracic Epidural Anesthesia with General Anesthesia on Hemodynamic Changes and its Complications in Patients Undergoing Laparoscopic Cholecystectomy

Background: Epidural anesthesia (EA) today has been used extensively in surgical procedures and the management of pain associated with midwifery and chronic pain. This type of anesthesia can be done in different technical, physiological, and pharmacological ways. The aim of this study was to compare the effects of thoracic EA with general anesthesia (GA) on hemodynamic changes and its complications in patients underwent laparoscopic colonoscopy. Materials and Methods: This clinical trial study was conducted on 80 patients undergoing laparoscopic cholecystectomy with EA or GA based on inclusion and exclusion criteria. The patients were randomly divided into two groups of 40 and changes in blood pressure, systolic blood pressure (SBP) and diastolic blood pressure (DBP), heart rate (HR), and arterial blood oxygen saturation were measured. The incidence of nausea, vomiting, chills, and itching in the two groups was recorded. The analysis was performed descriptively and also using t-test and Chi-square tests. Results: The results showed that the mean of SBP and DBP, HR, and arterial blood oxygen saturation and the incidence of nausea and vomiting was statistically significant (P 0.05). Conclusion: The results of this study indicated that thoracic EA in patients with laparoscopic cholecystectomy has significant effects on factors such as SBP and DBP and arterial blood oxygen saturation. Furthermore, EA has fewer complications than GA, and it is the preferable approac

Comparing the Efficacy of Two Drugs Senalin and Bisacodyl in Treatment of Constipation in Intensive Care Units' Patients

Background: Constipation is an intestinal syndrome that can be created alone or in the context of another disease in patients admitted to intensive care units (ICUs). Given the role of sennosides in increasing the transfer rate of materials from the large intestine, we aimed to compare the effect of senalin with bisacodyl on the treatment of constipation in patients admitted to ICUs. Materials and Methods: In this randomized, double-blind study, 70 patients admitted to the ICU were divided into two groups. The senalin recipient group received senalin with a dose of 500 mg daily for 3 days. The bisacodyl recipient group received bisacodyl with a dose of 10 mg daily for 3 days. Results: The mean of defecation frequency during the 2nd day of treatment of constipation was significantly higher in the group receiving bisacodyl than in the senalin group (P < 0.01). There was no significant difference between the two groups in terms of fecal consistency in any of the study days (P < 0.05). The prevalence of complications in the 3rd day of treatment was significantly higher in bisacodyl group than in the senalin group (P = 0.04). Conclusion: Given the lack of difference in the efficacy of two drugs, fecal consistency, daily defecation frequency and fewer complications of senalin compared to bisacodyl, it s eems that this drug can be used as an appropriate treatment for constipation in patients admitted to ICUs

Prepration and Characterization of Novel Ionoic Polymers to beUsed as Artificial Muscles: Novel ionic polymers for artificial muscles

The muscle-like technology would be of enormous advantages for biomedical applications such as medical implants and human assist devices. Ionic polymer metal composites (IPMCs) are one kind of biomimetic actuators. An ionic polymer metal composite composed from an ionomer with high ion exchange capacity that packed between two thin metal layers. In the present study we focused on the preparation of a novel alternative polymeric ionomer to be used as artificial muscles. Sulfonated poly(ether ether ketone) (PEEK) have been synthesized as a new class of ionomeric membrane materials. PEEK was sulfonated at various degrees with sulfuric acid and N,N-Dimethylacetamide as a solvent. Fourier transfer infrared spectroscopy confirmed the quality of substitution reaction. Sulfonated samples showed O-H vibration at 3490 and S=O peaks at 1085 and 1100-1300 cm-1. By increasing degree of sulfonation to 80%, ion exchange capacity, water uptake and the number of water molecules per the fixed sulfone groups (λ) were increased to about 2.4 meq.g-1, 75% and 19, respectively. After calculating the optimum degree of sulfonation, the applications of these ionomers as actuators are studied. Rigid microstructure of PEEK backbone causes to slow displacement. However, this inflexible backbone showed the acceptable tip force during its actuation. These IPMC are easy to prepare and much less expensive than the commercial per-fluorinated membranes such as Nafion®. The results approve the utilization of sulfonated aromatic for artificial muscles applications as novel strong muscles with low flexibility

Chemometric Analytical Approach for the Cloud Point Extraction and Inductively Coupled Plasma Mass Spectrometric Determination of Zinc Oxide Nanoparticles in Water Samples

Cloud point extraction (CPE) with inductively coupled plasma mass spectrometry (ICPMS) was applied to the analysis of zinc oxide nanoparticles (ZnO NPs, mean diameter ∼40 nm) in water and wastewater samples. Five CPE factors, surfactant (Triton X-114 (TX-114)) concentration, pH, ionic strength, incubation temperature, and incubation time, were investigated and optimized by orthogonal array design (OAD). A three-level OAD, OA₂₇ (3¹³) matrix was employed in which the effects of the factors and their contributions to the extraction efficiency were quantitatively assessed by the analysis of variance (ANOVA). Based on the analysis, the best extraction efficiency (87.3%) was obtained at 0.25% (w/v) of TX-114, pH = 10, salt content of 15 mM NaCl, incubation temperature of 45 °C, and incubation time of 30 min. The results showed that surfactant concentration, pH, incubation time, and ionic strength exert significant effects on the extraction efficiency. Preconcentration factors of 62 and 220 were obtained with 0.25 and 0.05% (w/v) TX-114, respectively. The relative recoveries of ZnO NPs from different environmental waters were in the range 64–123% at 0.5–100 μg/L spiked levels. The ZnO NPs extracted into the TX-114-rich phase were characterized by transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDS) and UV–visible spectrometry. Based on the results, no significant changes in size and shape of NPs were observed compared to those in the water before extraction. The extracted ZnO NPs were determined after microwave digestion by ICPMS. A detection limit of 0.05 μg/L was achieved for ZnO NPs. The optimized conditions were successfully applied to the analysis of ZnO NPs in water samples