Developing Design Storm Hydrographs for Small Tropical Catchments with Limited Data

Hydrographs are vital tools in the design and construction of water-control structures in urban and rural systems. The purpose of this study was to explore the development of design storm hydrographs for the small tropical catchment with limited data. In this study, Clark’s Unit Hydrograph method was used to develop synthetic hydrographs for the University of Ilorin Agricultural and Biosystems Engineering field plot. This method was selected for evaluation because the field plot has very limited stream flow data. Kunrun stream, which is the discharge outlet for the watershed, has no gauge stations. Clark's method was evaluated in this study for peak discharge and storm hydrograph analysis of the field plot. The total area of the field plot measures 18.4 ha and is characterized according to its land use: pasture range land (34%), cultivated land (49%), wood or forest land (9%) and 'dirt' (8%). The three necessary inputs needed for the development of the synthetic hydrograph using Clark’s method are: time of concentration, a storage coefficient, and a time-area histogram. The  time of concentration was estimated using the Natural Resources Conservation Service method (NRCS) with the lag time determined from Snyder’s equation. The storage coefficient was estimated at 0.75 hr while the time of concentration was 1.98 hr. Convolution procedures were used in determining the storm hydrograph from the unit hydrograph. Runoff volume and peak discharge from the unit hydrograph were estimated to be 2.4 x 104 m3 and 1.02 m3/s, respectively. According to the 24hour, 100year storm hydrograph, the runoff volume was 5.23 x 104 m3 while the peak discharge was 2.15 m3/s. It was found that Clark's Unit Hydrograph Method was very suitable in the development of design storm hydrograph for small tropical catchment with limited data.Keywords: Clark’s unit hydrograph, Storm hydrograph, Peak discharge,  ungauged watershed

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

The study of diurnal and seasonal variations in total electron content (TEC) over Nigeria has been prompted by the recent increase in the number of GPS continuously operating reference stations (CORSs) across Nigeria as well as the reduced costs of microcomputing. The GPS data engaged in this study were recorded in the year 2012 at nine stations in Nigeria located between geomagnetic latitudes – 4.33 and 0.72° N. The GPS data were used to derive GPS TEC, which was analysed for diurnal and seasonal variations. The results obtained were used to produce local GPS TEC maps and bar charts. The derived GPS TEC across all the stations demonstrates consistent minimum diurnal variations during the pre-sunrise hours 04:00 to 06:00 LT, increases with sharp gradient during the sunrise period (∼ 07:00 to 09:00 LT), attains postnoon maximum at about 14:00 LT, and then falls to a minimum just before sunset. Generally, daytime variations are found to be greater than nighttime variations, which range between 0 and 5 TECU. The seasonal variation depicts a semi-annual distribution with higher values (∼ 25–30 TECU) around equinoxes and lower values (∼ 20–25 TECU) around solstices. The December Solstice magnitude is slightly higher than the June Solstice magnitude at all stations, while March Equinox magnitude is also slightly higher than September Equinox magnitude at all stations. Thus, the seasonal variation shows an asymmetry in equinoxes and solstices, with the month of October displaying the highest values of GPS TEC across the latitudes

The role of laboratory confirmations and molecular epidemiology in global eradication of measles

This review reports on the role of laboratory confirmation and molecular epidemiology in global eradication of measles. The role of laboratory confirmation and molecular epidemiology in defining the origins of measles outbreaks cannot be overemphasized. New serological tests based on recombinant proteins detect only a fraction of the total measles virus (MV) specific antibodies. Several assays based on recombinant MV-haemagglutinin (ELISA and flow cytometry) or MV-fusion protein (flow cytometry) as well as neutralization and haemagglutination test have been evaluated using a large panel of lowtitre and negative sera. Isolation of measles virus confirmed the diagnosis. Phylogenetic trees are invaluable tools for monitoring the progress of immunization activities. Recent advances in genomic sequencing technology have lent its support to the monitoring and evaluation of vaccination programmes. More so, indigenous prepared measles antigens has been advocated to be produced, refined further and reproduced massively. This will be highly cost effective especially in field for seromonitoring and surveillance of measles. There is therefore, continual need for simpler diagnostic tests in elimination and eventual eradication of measles

"Near-miss" obstetric events and maternal deaths in Sagamu, Nigeria: a retrospective study

AIM: To determine the frequency of near-miss (severe acute maternal morbidity) and the nature of near-miss events, and comparatively analysed near-miss morbidities and maternal deaths among pregnant women managed over a 3-year period in a Nigerian tertiary centre. METHODS: Retrospective facility-based review of cases of near-miss and maternal death which occurred between 1 January 2002 and 31 December 2004. Near-miss case definition was based on validated disease-specific criteria, comprising of five diagnostic categories: haemorrhage, hypertensive disorders in pregnancy, dystocia, infection and anaemia. The near-miss morbidities were compared with maternal deaths with respect to demographic features and disease profiles. Mortality indices were determined for various disease processes to appreciate the standard of care provided for life-threatening obstetric conditions. The maternal death to near-miss ratios for the three years were compared to assess the trend in the quality of obstetric care. RESULTS: There were 1501 deliveries, 211 near-miss cases and 44 maternal deaths. The total near-miss events were 242 with a decreasing trend from 2002 to 2004. Demographic features of cases of near-miss and maternal death were comparable. Besides infectious morbidity, the categories of complications responsible for near-misses and maternal deaths followed the same order of decreasing frequency. Hypertensive disorders in pregnancy and haemorrhage were responsible for 61.1% of near-miss cases and 50.0% of maternal deaths. More women died after developing severe morbidity due to uterine rupture and infection, with mortality indices of 37.5% and 28.6%, respectively. Early pregnancy complications and antepartum haemorrhage had the lowest mortality indices. Majority of the cases of near-miss (82.5%) and maternal death (88.6%) were unbooked for antenatal care and delivery in this hospital. Maternal mortality ratio for the period was 2931.4 per 100,000 deliveries. The overall maternal death to near-miss ratio was 1: 4.8 and this remained relatively constant over the 3-year period. CONCLUSION: The quality of care received by critically ill obstetric patients in this centre is suboptimal with no evident changes between 2002 and 2004. Reduction of the present maternal mortality ratio may best be achieved by developing evidence-based protocols and improving the resources for managing severe morbidities due to hypertension and haemorrhage especially in critically ill unbooked patients. Tertiary care hospitals in Nigeria could also benefit from evaluation of their standard of obstetric care by including near-miss investigations in their maternal death enquiries

Maternal death review and outcomes : an assessment in Lagos State, Nigeria

Strong political will by hospital management and supervising government agencies are a prerequisite for effectively addressing the human and infrastructural deficits that predispose to maternal mortality in Lagos State. Failure to address the patients and facility-related causes of maternal mortality could account for the persistently high maternal mortality ratio (MMR) in the hospitals. Interventions aimed at redressing all causes identified in the reviews will likely reduce MMRs. The study investigates results of Maternal and Perinatal Death Surveillance and Response (MPDSR) conducted in three referral hospitals in Lagos State, Nigeria over a two-year period and reports outcomes and lessons learned

An Estimate of the Incidence of Prostate Cancer in Africa: A Systematic Review and Meta-Analysis

Prostate cancer (PCa) is rated the second most common cancer and sixth leading cause of cancer deaths among men globally. Reports show that African men suffer disproportionately from PCa compared to men from other parts of the world. It is still quite difficult to accurately describe the burden of PCa in Africa due to poor cancer registration systems.We systematically reviewed the literature on prostate cancer in Africa and provided a continentwide incidence rate of PCa based on available data in the regio

Another Look at the “Abdominal Cocoon”

Abdominal cocoon is a rare cause of bowel obstruction. The condition was first described three decades ago and about 106 cases have so far been reported in the English literature. It is found mainly among adolescent females in tropical and sub-tropical countries. It is characterized by a thick fibrous membrane encapsulating the small intestines partially or completely. It should be differentiated from Encapsulating Peritoneal Sclerosis (EPS) and Peritoneal Encapsulation (PE) which are sometimes referred to as abdominal cocoon but are of different aetio-pathology. Patients present with features of intestinal obstruction and the diagnosis is usually made intraoperatively. Surgical excision of the membrane with adhesiolysis in an emergency exploratory laparotomy results in complete recovery. Appropriate management of this condition requires adequate knowledge about the disease. We present a review of this rare entity. Key words: abdominal cocoon, intestinal obstructio

Effect of transmission rate in an SIR epidemic model

We extend the transmission rate to nonlinear orders and show that S+I+R is still attractive. When the nonlinearity order is greater than 1, we show that the basic reproduction number decreases as the recruitment increases. We provide the patterns of the stability of the equilibrium states.Keywords: transmission rate, SIR model, basic reproduction number, stability