A study of the bubble point test for membrane characterisation

Filtration is a commonly used separation process. Many researchers have looked at the different properties affecting the performance of filter media and many methods have been considered for testing their efficiency. The performance of a filtration process is mainly dependent on the status of the filter medium and its ability to act as perfect barrier within the process, and from there arose the importance of defining its properties and integrity. In this research we are looking at the bubble point test as one of the more useful, economical tests for examining a particular type filter medium. 0.2 µm, 5 µm and 12 µm Nuclepore track etched membranes were used in this research as their pore dimensions are close to cylindrical. The main parameters investigated were the minimum and mean pore size in addition to the bubble point. Two types of porometers were used in this research, the PMI and the Coulter II, and the results obtained by both were in good agreement with the ranges specified by the manufacturers. The selection of Nuclepore track etched membranes is made due to the uniqueness of the shapes of their pores. The cylindrical shape of the pores in this type of membranes simplifies the approach towards modelling the bubble point test, and thus understanding the microhydrodynamics occurring inside the membrane. This knowledge is obtained from this research by simulating both velocity and pressure profiles as well as gas-liquid interaction inside single and multiple pores, thus providing comprehensive understanding on the behaviour of the gas and the liquid phase inside the membrane. Such knowledge will help improve the design for a better system to accurately measure the bubble point test. Different mathematical methods can be applied, but the ability of the penalty scheme finite element method in dealing with complex geometries and such complex phenomena made it the preferred method. On the other hand the use of the volume of fluid method to detect the interfacial surface between the gas and the wetting liquid inside a pore microstructure has not been fully addressed before and thus considered as a novel part of this research

Adherence of Healthcare Professionals to Evidence-based Clinical Practice Guidelines in the Management of Hemodialysis Patients, Khartoum State, Sudan

Introduction: Hemodialysis (HD) is a complex procedure with many specifications and requires adherence to a set of particular clinical practice guidelines. These guidelines had already been established by globally acclaimed renal authorities and their implementation was shown to correlate with patients’ morbidity and mortality. This study was conducted to evaluate the adherence of healthcare professionals to the evidence-based clinical practice patterns in Khartoum State HD units.Methods: A cross-sectional study was conducted in Khartoum State HD units during the period from September 2010 to January of 2011. Data was collected from the healthcare professionals using a specially designed checklist. The checklist included the evidence-based clinical practice guidelines for the HD vascular access, HD adequacy, anemia of chronic kidney disease (CKD), nutrition, cardiovascular risk assessment, and hepatitis B and C virus infection control. Implementation of these guidelines was evaluated, and further graded using a Likert-type scale.Results: Four randomly selected HD units were included in the study. The rate of implementation of the HD vascular access guidelines was 54.8%, adequacy guidelines 57%, anemia of CKD 68.8%, nutrition 58.4%, cardiovascular risk assessment 57%, and hepatitis B and C infection control guidelines was 79.2%. Overall, the four HD units assessed showed moderate deviations from the practice guidelines of anemia of CKD and hepatitis B and C infection control. Extreme deviations from the clinical practice guidelines were seen in HD vascular access practices, adequacy assessments, nutrition and cardiovascular risk assessment.Conclusion: Hemodialysis services in Khartoum State are in need of great improvements regarding adherence to protocols and the standards of care.Key words: Clinical practice guidelines; Hemodialysis; Suda

Clinical presentation, treatment and outcome of paraphenylene-diamine induced acute kidney injury following hair dye poisoning: a cohort study

Introduction: in Africa and Asia hair dye is applied together with henna to decorate the hands and feet. Paraphenylene-diamine (PPD), a highly toxic constituent of hair dye can lead to acute kidney injury (AKI). Methods: a cohort study was conducted during the period from April 2012 to March 2013 in Khartoum Teaching Hospital, Sudan. It targeted adults presenting acutely with an evident history and clinical  features of hair dye poisoning, together with AKI as per the RIFLE criteria. Analysis of data was done using SPSS. Results: 30 adults were included, their mean age was 25.6 ± 4.2 years, 93.3% were females. Exposure to PPD was suicidal in 86.7%. The mean duration to onset of renal symptoms was 34.8 ± 7.6 hours,  maximum median serum creatinine was 8.6 ± 2.3 mg/dl, 86.7% had loss of kidney function as per the RIFLE  classification and required dialysis. Initial renal recovery was seen after a mean duration of 9.8 ± 2.2 days. One patient died, 3.3%; all others, 96.7%, recovered normal kidney function. The amount of ingested PPD correlated significantly to the severity of symptoms, number of dialysis sessions required and time for renal recovery with P values < 0.05. Conclusion: hair dye poisoning was associated with prolonged hospital stay, requirement of dialysis and increased morbidity. The severity of symptoms directly correlates to the dose of PPD ingested, with the kidney damage being reversible in almost all survivors.Key words: Hair dye poisoning, paraphenylene-diamine, acute kidney injur

Active Tuberculous Infection among Adult Sudanese Patients on Long Term Peritoneal Dialysis

Introduction: The prevalence of tuberculosis in Sudan is 209 cases per 100,000 populations. There are no reports available regarding the prevalence of tuberculosis among the end-stage kidney disease and dialysis populations.Methods: We reviewed the medical records of all adults who were on peritoneal dialysis (PD) in the Sudan Peritoneal Dialysis Program, during the period from June 2005 to December 2011. Those diagnosed ashaving active tuberculous infections were retrospectively studied regarding their demography, clinical presentation and outcomes.Results: Out of 350 patients in our program, 19 were diagnosed as having active tuberculosis (5.4%). All patients were diagnosed during their first year on peritoneal dialysis, 74% were males; the mean age was37 ± 11 years, extrapulmonary tuberculosis was seen in 16/19 (84%) patients and it was abdominal in nine of the 16 (47%) patients. In addition to high clinical suspicion, the diagnosis of active tuberculosis was supported by tissue biopsy findings in 16%, positive polymerase chain reaction in 26%, exudative ascites with suggestive radiological features in 21%, strongly positive tuberculin test in 21% and a favourable response to empirical antituberculous therapy in 26% of patients. HIV test wasnegative in all 19 patients and only one patient tested positive for hepatitis B viral infection. Antituberculous drugs side effects were seen in 68% of patients. Forty seven percent of patients showed complete recovery and continued on peritoneal dialysis. Our case fatality was 32%.Conclusion: Abdominal tuberculosis is common among PD patients and its diagnosis should always be considered in suspected patients

Clinical features and antinuclear antibodies profile among adults with systemic lupus erythematosus and lupus nephritis: a cross-sectional study

Introduction: Limited data is available regarding the clinical manifestations and pattern of Systemic Lupus Erythematosus (SLE) in Sudan. This study aimed to determine the clinical manifestations and Antinuclear Antibodies (ANA) profile among Sudanese adults with SLE and lupus nephritis (LN).Methods: A descriptive study was conducted in Omdurman Military Hospital, Sudan. It included all adults with SLE and on regular follow-up during the study period (December 2012 to May 2013). These were investigated regarding their demographic details, clinical features, and immunological profile (ANA, anti-double stranded DNA, and ANA profile 3 levels). Patients with LN had their pattern of renal involvement described; furthermore, associations between the various SLE reactive antibodies and the histological diagnosis of lupus were studied.Results: Sixty-two Sudanese adults with SLE were included, their mean age was 31 ± 10.9 year. Females made 93.5% of patients. A clear predominance of those of Arab ancestry was seen, with most patients being from the Ja'alin and Shaigiya ethnic groups accounting for 29% and 12.9%, respectively. Arthritis was the dominant clinical manifestation seen in 85.5%, whereas renal involvement was seen in 66.1% of patients. Lupus nephritis class III was the dominant histological lesion, seen in 39% of patients. On correlating the ANA profile to the histopathological diagnosis of LN, anti-Nucleosomes and anti-AMA-M2 autoantibodies were found to be significantly associated with LN class IV and class VI, respectively (P values < 0.05).Conclusion: Further epidemiological studies regarding SLE and its ANA profile remain essential as they might help predicting the clinical patterns of the disease and its prognosis.Keywords: SLE, lupus nephritis, ANA profile, Suda

Numerical analyses of bubble point tests used for membrane characterisation: model development and experimental validation

A numerical model for simulating the microhydrodynamics inside different pore sizes was developed in this work, using a continuous penalty finite element scheme. This scheme combines the flexibility in modelling two phase systems, as the one simulated in this work with accuracy. The volume of fluid (VOF) method was applied to track the motion of the gasliquid interfacial boundary as an approach to monitor the repulsion of the wetting liquid from the pores to detect their bubble pressures. To resolve the complexities arising from the inclusion of the surface tension at the liquid-gas interface as an unknown dynamic condition it is treated as a resistance force in the equations of motion. The effects of the surface tension and other forces such as the buoyancy are then determined by model calibration with respect to a set of experimental data. To obtain the experimental data, the bubble point test was used to characterise different Nuclepore track etched membrane samples, which provided insights into the mechanisms underlying the test and into the interpretation of the pore size distribution. The experimental data are used to calibrate the numerical model. The calibrated model was, in turn, used to predict the outcome of bubble point tests for a range of inlet boundary conditions. The results obtained from these simulations are shown to be in good agreement with of the experimental data, indicating the ability of the developed model to accurately predict the bubble point pressure

Field Load Tests of Open-Deck Timber Trestle Railroad Bridges

A field load test program was conducted to evaluate three open-deck timber railroad trestle bridges. The bridges included part of a 31-span bridge, a four-span bridge with skewed interior bents and a three-span bridge. Piles of the chords of the bridges were evaluated non-destructively for material properties using an ultrasonic stress wave device. The bridges were modeled using typical frame analysis techniques to predict response to loads. Deflection and strain measurements were recorded from the load testing. The responses of the bridges to various loads are compared to the predicted responses from several analytical modeling assumptions. The diagnostic testing used loads applied statically by axles of a test train and ramp loads applied by a specially designed railroad test car. Rolling train loads were conducted using the axles of the test train. Displaced chord and ground reference deflections plus some strain measurements were recorded at selected locations. The bridges performed within the expected range of behavior predicted by the analytical models. The chord systems of the bridges performed as beams semi-continuous over multiple supports. Two forms of support motion were observed; motion of the caps and gap closing between individual piles and the supporting caps. Load sharing among individual piles was examined empirically. No definable pattern for load sharing of the piles was identified