221 research outputs found
Biomarkers of ventricular remodelling in African hypertensives.
No full textIncludes abstract.Includes bibliographical references.There is substantial evidence that the burden of hypertension, hypertension with left ventricular hypertrophy and hypertensive heart failure is very enormous in sub-Saharan Africa. There is therefore the need to look for easier and faster means, compared to electrocardiography and echocardiography of diagnosing and differentiating the different effects of long standing hypertension on cardiac remodelling which ultimately lead to systolic and diastolic dysfunctions as this affects the prognosis, management and treatment modalities of hypertension. We studied 210 subjects who were subdivided into three groups after echocardiography: those without left ventricular hypertrophy (HT) (n=83); those with left ventricular hypertrophy (HTLVH) (n=50) and those with hypertensive heart failure (HHF) (n=77)
Reliability Analysis of the Nezahualcoyotl Dike in the Aztec City of Tenochtitlan
No full textBefore the Spanish conquest of Mexico, around the year 1519, the Valley of Mexico was a closed basin. As a result, at the bottom of the valley, an extensive system of shallow lakes, lagoons, and swamps was formed due to precipitation and permanent river’s discharge from the Sierra Nevada mountains. This lacustrine system occupied around 1000km2 of the total surface of the valley. Lakes Zumpango, Xaltocan, Chalco, Xochimilco, Texcoco, and Mexico were distinguished. The capital of the Aztec empire, Tenochtitlan, was founded and built on an island in the middle of Lake Mexico.The Aztecs were known for their impressive constructions and hydraulic structures. At the time of the Spanish conquest, they had a complex system of approximately 95 hydraulic structures (Palerm, 1973), of which the most impressive one was the Nezahualcoyotl dike. This structure was roughly sixteen kilometers long, eight meters’ height and three and a half meters’ width. Its principal function was to protect the city of Tenochtitlan from high water levels in Lake Texcoco.Nowadays, there are no remains of the dike and most of the lakes were drained. The purpose of this thesis is to characterize the lacustrine system and the Nezahualcoyotl at the time of the Spanish conquest of Mexico City dike by using historical documentation and present-day climate and terrain data. This in order to assess the reliability of the dike as a flood defense mechanism and to compare it to modern safety levels. The dike was tested for one failure mechanism: Overflow. A Markov chain and Copula models are proposed in order to create a synthetic time series of precipitation and evaporation. Through a hydrological balance, the water elevation at Lake Texcoco was obtained. In this way, it was possible to provide an estimation of the water level fluctuation in the lake each year during the wet season. In total, a thousand years of synthetic data were generated. To the author’s knowledge, this is the first time that an attempt is made to compare the Aztec design criteria with present time standards. This research illustrates, from an engineering point of view, the possible design criteria of the Nezahualcoyotl dike and the uncertainties surrounding it. This work can be used as a guideline to assess the reliability of other ancient structures or present-day constructions all over the world whose design is largely based on informal criteria where information for the reliability assessment is scarce.Civil Engineering | Hydraulic Engineering | Hydraulic Structures and Flood Ris
Probabilistic design and risk analysis for the Duong river dike in the Red River delta in Vietnam
No full textTraditionally, the design of sea and river dikes in Vietnam is primarily based on a water level with a particular frequency of being exceeded. The frequencies of exceedence of design levels and governing discharge are widely regarded as constituting a standard for the safety of the region protected by the dikes and are interpreted in terms of inundation probabilities. However, this is not fully correct since the inundation probability is not only determined by the frequency of exceedence of design levels, but it is also caused by other mechanisms below that design levels. Normally, the dike crest exceeds the design water level to a certain extent, thus, the probability of overtopping is smaller than the design frequency. However, some parts of the dike may already be critically loaded before the design water level is reached. Water logging may lead to slide planes through the dike or piping may undermine the body of the dike, with sudden failure as a consequence. In short, there are other failure mechanisms that can lead to flooding of the protected area than overtopping. In fact, if all possible causes of dike failure at high water level such as overtopping, piping, macro instability, and micro instability etc. could be listed and the associated probabilities of their occurrence be ascertained, then, in principle, the probability of inundation could be calculated. As a next step, a new approach to safety of the design of dikes, embankments, and other flood defenses was developed. This is the probabilistic design method. The probabilistic approach aims to determine the true probability of flooding of a river system and to judge its acceptability in view of the consequences. In this approach, the stochastic character of the various load and strength parameters is taken into account and the design is based on an analysis of failure probabilities. This new approach is called "risk-based" approach. During this study, the probabilistic design method is applied for a case study in Vietnam, which is the dike improvement for the right Duong River dike in the Red River Delta in Vietnam. Due to lack of time, only the failure probabilities caused by overflowing, piping, and sliding mechanisms and the failure probability caused by hydraulic structures have been calculated. For each mechanism, uncertainties for various variables are considered by mean of statistica I tools. The failure probability of each mechanism was determined based on the defined reliability function and, as aresuit, the inundation probability of the dike was calculated by combining all the mechanism failure probabilities. By considering the risk and the cost for the improvement, the optimization of the dike design is reached. From the economic point of view, the optimal dike crest elevation is the point corresponding with the minimum total cost. Following this study this leads to a crest level that can withstand a 1/500-year flood approximately.KWP-collectio
Nigeria Healthcare Worker SARS-CoV-2 Serology Study: Results from a Prospective, Longitudinal Cohort
No full textQuantifying the effect of woody vegetation on the wave loads on a dike using remote sensing: Large scale physical model tests
No full textIt is already acknowledged that Nature-based Solutions can be used to attenuate waves, however it is still uncertain to what extent the vegetation can contribute to decreasing the flood risk. So far mainly small-scale tests have been performed to quantify wave attenuating properties of vegetation. To quantify the effect of more extreme wave conditions (high-water levels and wave heights), full scale tests are required. In the Delta flume of Deltares large-scale physical model tests with a willow forest of 40 meters in front of a dike are conducted. Three different measuring methods: visual measurements, terrestrial laser scanning and video imaging, are used to quantify the wave run-up and wave-overtopping on the dike. This is the first time a ‘Machine Learning algorithm’ is used to obtain the wave run-up heights on a dike from video footages. It is also new that the wave overtopping volumes are determined by a laser scanner without using a wave overtopping tank, which was initially used to collect and measure the real overtopping volume.Results by the laser scanner show an overestimation of the overtopping discharges at high water level for higher crest freeboards, making these results less reliable. However, more research and a thorough validation are required to confirm the accuracy of this method. From results obtained by flume experiments can be concluded that remote sensing: laser scanner and video imaging, are accurate methods to measure the run-up on a dike. Thus, the camera in combination with Machine Learning is an accurate, simple and low-cost technique, to measure the wave run-up on a dike. Results from the camera not only give the run-up height, but also give new insights in the variations of the wave run-up over the dike. It can also be concluded that a willow forest of 40 meters causes a significant reduction in the wave run-up and overtopping, for both willows in summer and winter state. Further research is needed, so these significant reductions can be implemented in the design and assessment of dikes.The most commonly used models for designing a dike are the TAW (2002) and EurOtop. Comparing the obtained results, show that the determined wave run-up from the experiments are underestimated by the TAW (2002). The TAW is an empirical formula, based on a large data set of mainly small-scale experiments. Therefore, the difference between the test results and the TAW could likely be attributed to scale effects. However, more measurements at full scale are needed to confirm this.WOODYWoods versus WavesCivil Engineering | Hydraulic Engineerin
Soluble ST2 correlates with some indicators of right ventricular function in hypertensive heart failure
No full textDike B Ojji,1,2 Sandrine Lecour,2 Olusoji M Adeyemi,3 Karen Sliwa2,4 1Cardiology Unit, Department of Medicine, University of Abuja Teaching Hospital, Gwagwalada, Abuja, Nigeria; 2Department of Medicine, Faculty of Health Sciences, Hatter Institute for Cardiovascular Research in Africa, University of Cape Town, Cape Town, South Africa; 3Department of Medical Laboratory Sciences, University of Abuja Teaching Hospital, Gwagwalada, Abuja, Nigeria; 4Mary McKillop Institute for Health Research, ACU, Melbourne, VIC, Australia Purpose: ST2 receptor, which is a member of the Toll-like/interleukin-1 (IL-1) receptor family, has been found to be increased in the serum of patients 1 day after myocardial infarction. Several other studies have shown that soluble ST2 levels correlate with severity of heart failure (HF), left ventricular ejection fraction, creatinine clearance, B-type natriuretic peptide and C-reactive protein, and are predictors of mortality in HF. Most of these studies were not only limited to ischemic heart disease but also concentrated on left-sided HF. We therefore decided to study the relationship between soluble ST2 and some markers of right ventricular (RV) function in a cohort of hypertensive HF subjects.Patients and methods: This is a prospective cohort study of hypertensive HF patients presenting to the University of Abuja Teaching Hospital, Abuja, over a 12-month period. ST2 was measured in plasma sample by the enzyme-linked immunosorbent assay (ELISA) method. Right ventricular diameters in diastole (RVDD) and right atrial area (RAA) were obtained on echocardiography, while right ventricular systolic pressure (RVSP) was estimated from echocardiography by the addition of the pressure gradient between the right ventricle and right atrium (RA) to the pressure in the RA.Results: There was a significant correlation between RVSP and soluble ST2 (t=0.75, p<0.0001), RVDD (t=0.28, p=0.004) and RAA (t=0.46, p=0.002).Conclusion: In a cohort of hypertensive HF subjects, soluble ST2 correlates significantly with RVSP, RVDD and RAA. Keywords: RV function, ST2, hypertensive heart failur
Best practices in serials management: a Kenneth Dike Library model
No full textSerials are described as a group of important information resources which contain primary cutting edge information, especially in an academic library like the Kenneth Dike Library, University of Ibadan, Nigeria. The various processes involved in the effective management of serials are highlighted in this paper. Automation of serials collection and electronic serials were discussed; serials workflow diagrams representing manual and automated serials management systems were also developed by the author
BresDefender: A potential emergency measure to prevent or postpone a dike breach
No full textDikes are designed to withstand a load, with a certain finite probability of occurrence. In case of crises regarding to flood safety, the military is expected to prevent low-laying areas against flooding. Historical attempts show that the effectiveness of emergency measures and strategies are mainly successful caused by the adequate acts of the local people in charge. Based on a literature analysis of breach development, the available time for the application of emergency measures is estimated. This paper introduces the BresDefender strategy, an emergency response strategy, used by the military, to prevent or postpone dike failure. The current BresDefender strategy is a floating pontoon, which can placed on a weakened dike section. It is expected that it can be applied during two scenario’s. In the first scenario, the BresDefender is applied during the early stages of breach formation. In the second scenario, it restores the original crest height, where overflow is expected in the near future e.g. in case of macro instability. The BresDefender is expected to stabilize the weakened dike section.Hydraulic Structures and Flood Ris
Nigeria Healthcare Worker SARS-CoV-2 Serology Study: Results from a Prospective, Longitudinal Cohort
No full textThis study demonstrates baseline, 3-month and 6-month follow-up prevalence of IgG antibodies to SARS-CoV-2 during the first two waves of the COVID-19 pandemic in Nigeria among a cohort of unvaccinated frontline healthcare workers, including primary healthcare workers despite low symptomatology
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