Electrokinetic phenomena in aqueous suspended films and foams

Electrokinetic phenomena in liquid foams is at a junction between two areas. On one side is the investigation of liquid foam drainage, and on the other side is electrokinetics of surface driven flow on solid-liquid interfaces. However, the electrokinetic phenomena in liquid foam films significantly lack understanding. Therefore, the novelty of the thesis is to address the mentioned gap in three stages. The outcome has potential applications in a novel separation approaches of biological molecules such as proteins and DNA. In the first stage, the electrokinetic flow of a sufficiently thick (180 µm) free liquid film was investigated using cationic and anionic surfactants by confocal micron-resolution particle image velocimetry (µ-PIV). The reverse of the surface charge resulted in a shift in charge of the electrical double layer at the free liquid film interface, which caused the direction of the electroosmotic velocity to reverse. In each surfactant type used, the fluid velocity profiles were measured at different depths of the free liquid film (different z-planes). It was found how the fluid velocity varied with depth. Numerical simulations of the electroosmotic flow in the same system were also performed using Finite Element Method to understand the flow dynamics. A reasonably good agreement was found between the numerical simulations and the experimental results validating the model. In the second stage, instead of flow visualisation particles, rhodamine B (RB) and fluorescein isocyanate (FICT) dye were added to the free liquid film. Under the initial conditions of pH 7.2, RB is a neutral dye, and FICT has a -2 charge. Under an imposed electric field pH variations were detected and an interesting flow profile was observed. The CFD model developed earlier (stage one) was modified to include the local pH variation. The behaviour of the simulated pH had a good agreement with the behaviour of the FICT. Further confirmation of local pH variation was undertaken using extra new experiments which also showed a good agreed with the simulation. In the third stage, a liquid foam electrokinetic separation chamber was designed to extend the study to include practical applications. The first challenge was to achieve a stable foam under external electric field. A polymer-surfactant mixture can solve the stability problem. However, the mixture of polymers required an alkaline pH (>9) condition for the polymer mixture to be soluble in the aqueous system. Lectin and tetramethylrhodamine goat anti-rabbit (IgG) protein mixture with different molecular mass to charge ratio (50 kDa and 150 kDa) were injected near the anode. The system was monitored in three location: (a) in a vicinity of the injection region, (b) between the two electrodes and (c) in a vicinity of the cathode. In the region (a), a decay of the luminescence intensity of the fluorescein of the two proteins was noted with varying rate. In region (b), an increase followed by a decrease in fluorescein intensity of the proteins was observed again at a varying rate. In region (c), an increase of the dye concentration was observed and again at a different rate. The observed difference was caused by difference of the electrophoretic velocity of the two proteins. The setup proved that proteins could be separated based on their electrophoretic mobility inside a liquid foam. The findings from the thesis show the ability to manipulate fluid flow within a free liquid film, and inside a liquid foam system by an external DC electric field, is not only interesting academically but has potential application in a novel separation approach of biological molecules and beyond. The result show, with the correct surfactant formulation, it possible to make a stable foam under an electric field which can be set up for separation of proteins using foam electrokinetics

On Measuring the Criticality of Various Variables and Processes in Organization Information Systems: Proposed Methodological Procedure

This paper proposes methodological procedures to be used by the accounting, organizational and managerial researchers and executives to ascertain the criticality of the variables and the processes in the measurement of management control system. We have restricted the validation of proposed methods to the extraction of critical success factors (CSF) in this study. We have also provided a numerical illustration and tested our methodological procedures using a dataset of an empirical study conducted for the purpose of ascertaining the CSFs. The proposed methods can be used by the researchers in accounting, organizational information systems, economics, and business and also in other relevant disciplines of organizational sciences. The main contribution of this paper is the extension of Rockart’s work [33] on critical success factors. We have extended the theory of CSF beyond the initially suggested domain of information into management control system decision making. The methodological procedures developed by us are expected to enrich the literature of analytical and empirical studies in accounting and organizational areas where it can prove helpful in understanding the criticality of individual variables, processes, methods or success factors.Success Factors, Criticality Analysis, Perceptual Criticality, Critical Success Factors

Patient vital signs in relation to ICU admission in treatment of acute leukemia: a retrospective chart review

Objectives: The objective of the current study was to investigate the relationship between changes in vital signs and intensive care unit (ICU) admission. Windsor Regional Hospital treats 15–20 new patients a year with acute leukemia. These patients are at increased risk of neutropenic fevers and admission to the ICU following induction chemotherapy. Methods: Retrospective review examined the correlation between acute leukemia patient vitals and ICU admission. The analysis included 37 patients: 7 ICU versus 30 controls. Changes were compared to baseline over 24 hours prior to ICU admission or 5 days after the initiation of induction chemotherapy in the following vital signs: heart rate (HR), mean arterial pressure (MAP), temperature (T), respiratory rate (RR), and fraction of inspired oxygen (FiO2) required to maintain a stable oxygen saturation. Results: RR and FiO2 demonstrated significant change over baseline leading up to ICU admission within the ICU group. T, HR and MAP did not demonstrate significant changes over time in either group. RR, FiO2 and HR were significantly higher in the ICU group at time zero compared with the control group. RR was recorded least frequently in the 24 hours leading up to ICU admission. Discussion: Changes in RR and FiO2 predicted clinical deterioration requiring ICU admission in acute leukemia patients. This is consistent with the predominant reason for ICU admission which was respiratory failure. Conclusion: We present preliminary evidence to support enhanced monitoring of RR and FiO2 in acute leukemia patients following induction chemotherapy with early intervention if identified

Determining electroosmotic velocity in a free liquid film

The flow field within a free liquid film under an applied external electric field was measured using confocal micro-PIV system. Free liquid films of thickness ∼ 200 μm were formed in a rectangular frame with electrodes in direct contact with the fluid and stabilised by cationic surfactant. The flow field induced by an external electric field of ∼1600 V/m was visualised using 2 μm tracer particles on several depth wise planes. The observed particle velocities were used to determine the fluid velocities within the film by accounting for the electrophoresis of the tracer particles

Electroosmotic flow in free liquid films: Understanding flow in foam plateau borders

Liquid flow in foams mostly proceeds through Plateau borders where liquid content is the highest. A sufficiently thick (~180 µm) free liquid film is a reasonable model for understanding of electrokinetic phenomena in foam Plateau borders. For this purpose, a flow cell with a suspended free liquid film has been designed for measurement of electrokinetic flow under an imposed electric potential difference. The free liquid film was stabilised by either anionic (sodium lauryl sulfate (NaDS)) or cationic (trimethyl(tetradecyl) ammonium bromide (TTAB)) surfactants. Fluid flow profiles in a stabilised free liquid film were measured by micron-resolution particle image velocimetry (µ-PIV) combined with a confocal laser scanning microscopy (CLSM) setup. Numerical simulations of electroosmotic flow in the same system were performed using the Finite Element Method. The computational geometry was generated by CLSM. A reasonably good agreement was found between the computed and experimentally measured velocity profiles. The features of the flow profiles and the velocity magnitude were mainly determined by the type of surfactant used. Irrespective of the surfactants used, electroosmotic flow dominated in the midfilm region, where the film is thinnest, while backflow due to pressure build-up developed near the glass rods, where the film is thickest

Electroosmotic flow measurements in a freely suspended liquid film: Experiments and numerical simulations

Fluid flow profiles in free liquid films stabilised by anionic and cationic surfactants under an external electric field were investigated. Depthwise velocity fields were measured at the mid region of the free liquid film by confocal μ-PIV and corresponding numerical simulations were performed using Finite Element Method (FEM) to model the system. Depthwise change in velocity profiles was observed with electroosmotic flow dominating in the vicinity of the gas-liquid and solid-liquid interfaces while backpressure drives fluid in the opposite direction at the core of the film. It was also found that the direction of the flow at various sections of the films depends on the type of surfactant used, but flow features remained the same. Numerical simulations predicted the flow profiles with reasonable accuracy; however, asymmetry of the actual film geometry caused deviations at the top half of the computational domain. Overall, electroosmotic flow profiles within a free liquid film is similar to that of the closed-end solid microchannel. However, the flow direction and features of the velocity profiles can be changed by selecting various types of surfactants. The free liquid films thickness was selected to match dimensions of foam Plateau border. Hence these findings will be useful in developing a separation system based on foam electrokinetics

Prevalence of Poultry Coccidiosis and Associated Risk Factors in Intensive Farm and Individual Small Holder Poultry Farm in Benadir Region, Somalia

A cross sectional study was conducted from September2021 to February2022 in Mogadishu, Somalia to determine the prevalence of poultry coccidiosis and associated risk factors in intensive farm and Individual smallholder poultry farm in Benadir region-Somalia. The objective of the study was to determine the prevalence of poultry coccidiosis, to assess the risk factors associated with poultry coccidiosis. However, floatation technique was used for isolation of coccidian oocysts obtained from 384 fecal samples of chicken and the prevalence revealed was 19.8%. There was no statistically significant difference in poultry coccidiosis between the different ages of chicken (P>0.05) Where the young chickens (chicks) had shown slightly higher prevalence (20.4%) than adult chickens (18.8%). The effect of sex on the disease prevalence was assessed and relatively slightly higher prevalence was recorded in male chickens (20%) than female (19.4%). However, the difference between sex groups was not statistically significant (P>0.05). According to the management system of the chickens, the study had shown a significant difference between extensive and intensive management systems, with the extensive system having a higher prevalence (25.5%) than intensive system (14%) with P-value (0.003). There was a significant difference in poultry coccidiosis between the different body condition score of chickens (P<0.05), where those poor body condition (26.6%) are more prevalence than middle (16%) and good (8.8%) chickens. The study also revealed a statistically significant association between infection rate and housing methods with the chickens kept in floor house had a higher prevalence (25.5%) than cage house (14%) with P-value (0.003) However, appropriate control strategies should be designed considering important risk factors such as age, management system and housing system. Especially, focus should be given to biosecurity practices in the prevention and control of coccidiosis, and in addition, further studies are needed to be conducted to identify the prevalent Eimeria species for strategic control

Risk and Benefit of Warfarin for Primary Prevention in Atrial Fibrillation Patients on Hemodialysis: A Retrospective Pilot Study

Rationale: Although warfarin is an established anticoagulation therapy for prevention of ischemic strokes in patients with atrial fibrillation, studies reporting INR values with correlation to warfarin efficacy and safety outcomes in patients on hemodialysis with atrial fibrillation are scarce. The purpose of this study was provide additional information to aid in optimizing future clinical anticoagulation decisions for patients with atrial fibrillation on hemodialysis. Methods: A retrospective cohort study was conducted from April 2011 to January 2019 at a regional kidney dialysis centre in southwestern Ontario, Canada. The primary objective of this study was to correlate achieved INR measurements with the efficacy and safety of warfarin anticoagulation. Results: A total of 286 patients were reviewed and 25 patients were included. No ischemic strokes were reported and six bleeding episodes occurred. The mean INR of the 25 patients was 2.4 (SD±0.47) with an average follow up of 336 days. Using a Cox Proportional Hazards Model, univariate correlations between risk of bleeding and baseline characteristics were examined and no statistically significant correlations were found. Conclusion: Patients on hemodialysis with atrial fibrillation may have a higher bleeding rate while on warfarin despite having therapeutic IN Rs. This may be attributed to the small sample size, duration of observation and factors such as intra-dialysis heparin use and uremic platelet dysfunction. Therefore, initiating warfarin for primary prevention in this patient population requires a careful assessment of bleeding risk factors. Further studies are warranted

Procedures used in electrokinetic investigations of surfactant-laden interfaces, liquid films and foam system

Electrokinetic phenomena in liquid foam media are at a junction between two well-developed fields. On the one side is the study of liquid foam drainage, which is well documented, and on the other side is electrokinetics of surface driven flow on solid-liquid interfaces, which is equally well understood. However, electrokinetic phenomena in foams with deformable air-liquid interfaces have gained significant attention only recently. In pursuit of understanding electrokinetics of foams, the model systems adopted by investigators can be summarised as: (i) free liquid films; (ii) flow cells (iii) a single bubble sandwiched between two electrodes; (iv) foam column and (v) numerical simulations. A new experimental approach for system monitoring and visualisation is proposed for foam electrokinetics. The results obtained from preliminary experiments are compared with the numerical simulations performed using Finite Element Method. The model predictions closely agree with the experimental data validating the model

Electrokinetic transport of a charged dye in a freely suspended liquid film: Experiments and numerical simulations

Electrokinetic transport of a charged dye within a free liquid film stabilised by a cationic surfactant, trimethyl(tetradecyl)ammonium bromide (TTAB), subjected to an external electric field was investigated. Confocal laser scanning microscopy was used to visualise fluorescein isocyanate (FICT) separation within the stabilised liquid film. Numerical simulations were performed using Finite Element Method to model the dynamics of charged dye separation fronts observed in the experiments. Due to the electrochemical reactions at the electrodes, significant spatial and temporal pH changes were observed within the liquid film. These local pH changes could affect the local zeta potential at the gas-liquid and solid-liquid film boundaries; hence the flow field was found to be highly dynamic and complex. The charged dye (FICT) used in the experiments is pH sensitive, therefore electrophoresis of the dye also depended on the local pH. The pH and the electroosmotic flow field predicted from the numerical simulations were useful for understanding charged dye separation near both the anode and the cathode