34 research outputs found
The long cross-over dynamics of capillary imbibition
Spontaneous capillary imbibition is a classical problem in interfacial fluid dynamics with a broad range of applications, from microfluidics to agriculture. Here we study the duration of the cross-over between an initial linear growth of the imbibition front to the diffusive-like growth limit of Washburn's law. We show that local-resistance sources, such as the inertial resistance and the friction caused by the advancing meniscus, always limit the motion of an imbibing front. Both effects give rise to a cross-over of the growth exponent between the linear and the diffusive-like regimes. We show how this cross-over is much longer than previously thought - even longer than the time it takes the liquid to fill the porous medium. Such slowly slowing-down dynamics is likely to cause similar long cross-over phenomena in processes governed by wetting
Cultural Competency Observation Tool
This observational assessment rubric includes rating of the elements of patient centered communication defined in the Kalamazoo Consensus Statement regarding patient centered communication: These are augmented with sections that highlight factors that emerged in our observations specific to intercultural communication such as language and interpreters, nonverbal communication, mental and social issues with a large cultural overlay (mental health, pain, and disability). In addition, the tool incorporates issues specific to the medical context such as professional competence and professional regard. The rubric is also informed by the developmental model of intercultural sensitivity and Dreyfus\u27s phenomenology of skill acquisition with skill levels progressing through the stages: novice, beginner, competence, proficient, mastery
Patient-led active tuberculosis case-finding in the Democratic Republic of the Congo.
OBJECTIVE: To investigate the effect of using volunteer screeners in active tuberculosis case-finding in South Kivu, the Democratic Republic of the Congo, especially among groups at high risk of tuberculosis infection. METHODS: To identify and screen high-risk groups in remote communities, we trained volunteer screeners, mainly those who had themselves received treatment for tuberculosis or had a family history of the disease. A non-profit organization was created and screeners received training on the disease and its transmission at 3-day workshops. Screeners recorded the number of people screened, reporting a prolonged cough and who attended a clinic for testing, as well as test results. Data were evaluated every quarter during the 3-year period of the intervention (2014-2016). FINDINGS: Acceptability of the intervention was high. Volunteers screened 650 434 individuals in their communities, 73 418 of whom reported a prolonged cough; 50 368 subsequently attended a clinic for tuberculosis testing. Tuberculosis was diagnosed in 1 in 151 people screened, costing 0.29 United States dollars (US 44 per person diagnosed. Although members of high-risk groups with poorer access to health care represented only 5.1% (33 002/650 434) of those screened, they contributed 19.7% (845/4300) of tuberculosis diagnoses (1 diagnosis per 39 screened). The intervention resulted in an additional 4300 sputum-smear-positive pulmonary tuberculosis diagnoses, 42% (4 300/10 247) of the provincial total for that period. CONCLUSION: Patient-led active tuberculosis case-finding represents a valuable complement to traditional case-finding, and should be used to assist health systems in the elimination of tuberculosis
Épidémiologie clinique et grande diversité génétique parmi les isolats de Cryptococcus spp. infectant les personnes vivant avec le VIH à Kinshasa, République démocratique du Congo
Neuromeningeal cryptococcosis (NMC) is a life-threatening opportunistic infection in advanced HIV disease patients (AHDP). It is caused by Cryptococcus spp. complexes and mainly occurs in sub-Saharan Africa. In this study, we performed molecular characterization and antifungal susceptibility profiling of Cryptococcus isolates from AHDP in Kinshasa (DRC). Additionally, we investigated a possible association between NMC severity factors and the Cryptococcus neoformans (Cn) multilocus sequence typing (MLST) profiles. We characterized the isolates using PCR serotyping, MALDI-TOF MS, internal transcribed spacer (ITS) sequencing, and MLST. Susceptibility testing for the major antifungal drugs was performed according to the EUCAST guidelines. Parameters associated with NMC severity, such as hypoglycorrhachia ( 30 cm H2O), and poor therapeutic outcome were compared with the Cn MLST sequences type (ST). Twenty-three out of 29 Cryptococcus isolates were identified as serotype A using PCR serotyping (79.3%; 95% IC: 65.5-93.1), while six (20.7%; 95% IC: 6.9-34.5) were not serotypable. The 29 isolates were identified by ITS sequencing as follows: Cryptococcus neoformans (23/29, 79.3%), Cutaneotrichosporon curvatus (previously called Cryptococcus curvatus) (5/29, 17.2%), and Papiliotrema laurentii (Cryptococcus laurentii) (1/29, 3.5%). Using the ISHAM MLST scheme, all Cn isolates were identified as molecular type VNI. These comprised seven different STs: ST93 (n = 15), ST5 (n = 2), ST53 (n = 1), ST31 (n = 1), ST4 (n = 1), ST69 (n = 1), and one novel ST that has not yet been reported from other parts of the world and was subsequently assigned as ST659 (n = 2). Of the included strains, only Papiliotrema laurentii was resistant to amphoterin B (1/29, 3.5%), 6.8% (2/29) were resistant to 5-flucytosine (the single Papiliotrema laurentii strain and one Cryptococcus neoformans isolate), and 13.8% (4/29) to fluconazole, including two of five (40%) Cutaneotrichosporon curvatus and two of 23 (8.7%) C. neoformans strains. We found a significative association between poor therapeutic outcome and a non-ST93 sequence type of causative strains (these concerned the less common sequence types: ST53, ST31, ST5, ST4, ST659, and ST69) (87.5% versus 40%, p = 0.02). Molecular analysis of Cryptococcus spp. isolates showed a wide species diversity and genetic heterogenicity of Cn within the VNI molecular type. Furthermore, it is worrying that among included strains we found resistances to several of the commonly used antifungals.Cryptococcose chez les personnes vivant avec le VIH à Kinshasa : étude épidémiologique et moléculaire3. Good health and well-bein
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
Radiation Risk Assessment Associated with TGFs for Aircraft Passengers: Estimations of the Probability for a Commercial Flight to Be Hit by a TGF
International audienceTerrestrial Gamma ray Flashes (TGFs) are bursts of high-energy photons lasting less than 100 μs [Fishman et al., JGR, 116, A07304, 2011]. They are produced in common thunderstorms [e.g., Chronis et al., BAMS, 97, 639, 2016 ; Splitt et al., JGR, 115, A00E38, 2010] and Briggs et al. [JGR, 118, 3805-3830, 2013] estimated in 2013 that more than 400,000 Fermi-GBM detectable TGFs are produced each year on Earth. With a typical production altitude between 10 and 15 km [Cummer et al., GRL, 38, L14810, 2011; GRL, 41, 8586-8593, 2014; GRL, 42, 7792-7798, 2015], TGF sources are close to commercial flight altitudes, and therefore these high-energy events could represent an additional exposure to ionizing radiation for aircraft passengers and aircrews [Dwyer et al., JGR, 115, D09206, 2010]. In a recent work, we showed that doses delivered by gamma rays have been seemed to be relatively low, whereas extremely high doses have been estimated to be delivered in the electron acceleration region although in compact areas (hundreds of meters of radius) [Pallu et al., JGR, 126, e2020JD033907, 2021]. Currently, in most of the countries, the monitoring of aircrews exposure, mainly driven by cosmic rays, is performed by software, but these systems ignore the possible TGF contribution. Therefore, the need for a thorough risk assessment associated with TGFs for aircraft passengers and aircrews is called for by the predicted doses. In this work, we present a statistical study using TGF data from the first Fermi-GBM TGF catalog [Roberts et al., JGR, 123, 4381-4401, 2018] and both simulated and real commercial flight routes, in order to estimate an upper bound of the probability for a commercial flight to find itself in a TGF electron acceleration region and draw conclusions about the overall risk incurred by aircrews
Structural model performance and reinforced pavement technology in unstable location in the south of the Republic of Benin (West Africa)
The main cities in West Africa have been characterized by the development of infrastructure in past decade. This paper examined the performance of the soil and of pavement in Benin (West Africa). In this research, four objectives have been adopted in-depth on the performance characteristics of West African soil and aim to (i) accessing characteristics of soil types in the region; (ii) assessing the performance of these soils with 3% of lime, with the combination of 3% lime and 3% cement; (iii) using geogrid to evaluate the performance of pavement on clayey soil; (iv) proposing a new pavement model strategy considering economic aspects of construction. The methods used to examine these objectives are experimental tests according to standard French test. Design of flexible pavement is largely based on empirical methods according to the transport research laboratory (TRL) Note 31 with WinJulea software and compared with a designed and evaluated pavement structure adopting the center experimental of building and public works (CEBTP) method. In addition, the research quantified the percentage of biaxial geogrid impacting the performance of pavement in a diminishing perspective. Flexible pavements (with and without geogrids) were built and subjected to 127.49 kN load applications. This paper firstly reveals the unstable and stable areas in southern Benin (West Africa) with the presence of clay soil, and secondly reveals that the use of 3% lime and the combination of 3% lime and 3% cement are limited in subgrade. In addition, the TRL Note 31 with WinJulea software is more economical while the one of CEBTP highly performs. More so, the paper confirms that the use of biaxial geogrid reinforcement in pavement structures highly reduces the construction cost. As conclusion, firstly, the pavement made from the recycled asphalt pavement materials with biaxial geogrid in subgrade is the best in the clayey area