15 research outputs found
On the Uniform Exponential Stability of Time-Varying Systems Subject to Discrete Time-Varying Delays and Nonlinear Delayed Perturbations
This paper addresses the problem of stability analysis of systems with delayed time-varying perturbations. Some sufficient conditions for a class of linear time-varying systems with nonlinear delayed perturbations are derived by using an improved Lyapunov-Krasovskii functional. The uniform global asymptotic stability of the solutions is obtained in terms of convergence toward a neighborhood
of the origin
Estimating the burden of selected non-communicable diseases in Africa: a systematic review of the evidence
Background
The burden of non-communicable diseases (NCDs) is rapidly increasing globally, and
particularly in Africa, where the health focus, until recently, has been on infectious diseases. The
response to this growing burden of NCDs in Africa has been affected owing to a poor
understanding of the burden of NCDs, and the relative lack of data and low level of research on
NCDs in the continent. Recent estimates on the burden of NCDs in Africa have been mostly
derived from modelling based on data from other countries imputed into African countries, and
not usually based on data originating from Africa itself. In instances where few data were
available, estimates have been characterized by extrapolation and over-modelling of the scarce
data. It is therefore believed that underestimation of NCDs burden in many parts of Africa cannot
be unexpected. With a gradual increase in average life expectancy across Africa, the region now
experiencing the fastest rate of urbanization globally, and an increase adoption of unhealthy
lifestyles, the burden of NCDs is expected to rise. This thesis will, therefore, be focussing on
understanding the prevalence, and/or where there are available data, the incidence, of four major
NCDs in Africa, which have contributed highly to the burden of NCDs, not only in Africa, but
also globally.
Methods
I conducted a systematic search of the literature on three main databases (Medline, EMBASE and
Global Health) for epidemiological studies on NCDs conducted in Africa. I retained and
extracted data from original population-based (cohort or cross sectional), and/or health service
records (hospital or registry-based studies) on prevalence and/or incidence rates of four major
NCDs in Africa. These include: cardiovascular diseases (hypertension and stroke), diabetes,
major cancer types (cervical, breast, prostate, ovary, oesophagus, bladder, Kaposi, liver, stomach,
colorectal, lung and non-Hodgkin lymphoma), and chronic respiratory diseases (chronic
obstructive pulmonary disease (COPD) and asthma). From extracted crude prevalence and
incidence rates, a random effect meta-analysis was conducted and reported for each NCD. An
epidemiological model was applied on all extracted data points. The fitted curve explaining the
largest proportion of variance (best fit) from the model was further applied. The equation
generated from the fitted curve was used to determine the prevalence and cases of the specific
NCD in Africa at midpoints of the United Nations (UN) population 5-year age-group population
estimates for Africa.
Results
From the literature search, studies on hypertension had the highest publication output at 7680, 92
of which were selected, spreading across 31 African countries. Cancer had 9762 publications and
39 were selected across 20 countries; diabetes had 3701 publications and 48 were selected across
28 countries; stroke had 1227 publications and 19 were selected across 10 countries; asthma had
790 publications and 45 were selected across 24 countries; and COPD had the lowest output with
243 publications and 13 were selected across 8 countries. From studies reporting prevalence
rates, hypertension, with a total sample size of 197734, accounted for 130.2 million cases and a
prevalence of 25.9% (23.5, 34.0) in Africa in 2010. This is followed by asthma, with a sample
size of 187904, accounting for 58.2 million cases and a prevalence of 6.6% (2.4, 7.9); COPD,
with a sample size of 24747, accounting for 26.3 million cases and a prevalence of 13.4% (9.4,
22.1); diabetes, with a sample size of 102517, accounting for 24.5 million cases and a prevalence
of 4.0% (2.7, 6.4); and stroke, with a sample size of about 6.3 million, accounting for 1.94
million cases and a prevalence of 317.3 per 100000 population (314.0, 748.2). From studies
reporting incidence rates, stroke accounted for 496 thousand new cases in Africa in 2010, with a
prevalence of 81.3 per 100000 person years (13.2, 94.9). For the 12 cancer types reviewed, a total
of 775 thousand new cases were estimated in Africa in 2010 from registry-based data covering a
total population of about 33 million. Among women, cervical cancer and breast cancer had 129
thousand and 81 thousand new cases, with incidence rates of 28.2 (22.1, 34.3) and 17.7 (13.0,
22.4) per 100000 person years, respectively. Among men, prostate cancer and Kaposi sarcoma
closely follows with 75 thousand and 74 thousand new cases, with incidence rates of 14.5 (10.9,
18.0) and 14.3 (11.9, 16.7) per 100000 person years, respectively.
Conclusion
This study suggests the prevalence rates of the four major NCDs reviewed (cardiovascular
diseases (hypertension and stroke), diabetes, major cancer types, and chronic respiratory diseases
(COPD and asthma) in Africa are high relative to global estimates. Due to the lack of data on
many NCDs across the continent, there are still doubts on the true prevalence of these diseases
relative to the current African population. There is need for improvement in health information
system and overall data management, especially at country level in Africa. Governments of
African nations, international organizations, experts and other stakeholders need to invest more
on NCDs research, particularly mortality, risk factors, and health determinants to have
evidenced-based facts on the drivers of this epidemic in the continent, and prompt better,
effective and overall public health response to NCDs in Africa
The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance
INTRODUCTION
Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic.
RATIONALE
We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs).
RESULTS
Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants.
CONCLUSION
Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century
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Modulation of glucocorticoid action by 11B-hydrosysteroid dehydrogenase (11B-oxoreductase)
La compensation des systèmes à retard : les prédicteurs
Le prédicteur de smith -- Structure fonctionnelle et principes -- Équation caractéristique -- Performances dynamique et statique -- Le prédicteur analytique -- Structure fonctionnelle et principes -- Équation caractéristique -- Performances dynamique et statique -- Proposition de vogel -- Structure de vogel -- Stabilité du prédicteur de vogel -- Adaptation du contrôleur de Dahlin -- Extension pour les modèles du second degré comportant zéro -- Extension pour les modèles du troisième degré -- Stabilité de l'extension
Application des méthodes d'interpolation au design d'un compensateur robuste de systèmes avec retard
Le problème d'interpolation de nevanlinna-pick -- Algorithme de nevanlinna -- Stabilisation robuste -- Stabilisation robuste avec incertitude paramétrique
Formulation généralisée du filtre de pondération de la prédiction analytique
Ptie 1. Cas monovariable -- ptie 2. Cas multivariable -- Compensation des retards : état de l'art -- Formulation directe du filtre de pondération Frc (Z) de la prédiction analytique -- Extension du filtre de pondération du PAG au cas multivariable -- Application du principe d'invariance aux systèmes linéaires multivariables en présence du pag
High content analysis to determine cytotoxicity of the antimicrobial peptide, melittin and selected structural analogs
Antimicrobial peptides (AMPs) are naturally occurring entities with potential as pharmaceutical candidates
and/or food additives. They are present in many organisms including bacteria, insects, fish and
mammals. While their antimicrobial activity is equipotent with many commercial antibiotics, current
limitations are poor pharmacokinetics, stability and potential toxicology issues. Most elicit antimicrobial
action via perturbation of bacterial membranes. Consequently, associated cytotoxicity in human cells is
reflected by their capacity to lyse erythrocytes. However, more rigorous toxicological assessment of AMPs
is required in order to predict potential failure at a later stage of development.Wedescribe a high-content
analysis (HCA) screening protocol recently established for determination and prediction of safety in pharmaceutical
drug discovery. HCA is a powerful, multi-parameter bioanalytical tool that amalgamates the
actions of fluorescence microscopy with automated cell analysis software in order to understand multiple
changes in cellular health. We describe the application of HCA in assessing cytotoxicity of the cytolytic-helical peptide, melittin, and selected structural analogs. The data shows that structural modification
of melittin reduces its cytotoxic action and that HCA is suitable for rapidly identifying cytotoxicity.Irish Research Council for Science, Engineering and TechnologyScience Foundation IrelandMerrion PharmaceuticalsNYP: http://www.sciencedirect.com/science/article/pii/S0196978111002300 - AV 11/07/201
Effect of Verbal Encouragement on Physical Fitness, Technical Skill and Physiological Response during Small-Sided Soccer Games
This study aimed to determine the impact of teacher verbal encouragement on physical fitness performance, technical skill, and physiological responses during small-sided soccer games (SSGs) of adolescent female students’ during a physical education session. Fifty-two adolescent female students were divided into a verbal encouragement group (VEG, 15.57 ± 0.50 years) and a contrast group (CG, 15.50 ± 0.51 years). Anthropometric measurements, soccer-specific cardiorespiratory endurance (Yo-Yo Intermittent Recovery Test Level 1; YYIRT1), muscle power (countermovement jump (CMJ); 5-jump-test (5JT), agility (t-test), sprint speed (30 m)), technical skill, and heart rate (HR) responses during SSG were measured. Additionally, heart rate (HR) was recorded throughout the SSG, and video analysis was used to quantify technical actions. The independent samples Student’s t-test was used to compare the difference between the verbal encouragement group and the CG. There was no difference between the verbal encouragement group and the CG in anthropometric characteristics and 30 m speed (p > 0.05). The total distance measured with YO-YOIRT level 1, t-test performance, CMJ, and 5JT performance results of the verbal encouragement group were considerably higher than the CG (p = 0.001, ES = 1.8, large; p = 0.001, ES = 1.09, large; and p = 0.001, ES = 1.15, large, respectively). Furthermore, the ball contacts, successful balls, and average heart rate were higher in the verbal encouragement group compared with the CG (p = 0.001, ES = 3.69, large; p = 0.001, ES = 5.25, large; and p = 0.001, ES = 5.14, large, respectively). These results could inform teachers of the usefulness of verbal encouragement in the teaching-learning process in the school setting during small-sided soccer games