About the screening of the charge of a proton migrating in a metal

The amount of screening of a proton in a metal, migrating under the influence of an applied electric field, is calculated using different theoretical formulations. First the lowest order screening expression derived by Sham (1975) is evaluated. In addition 'exact' expressions are evaluated which were derived according to different approaches. For a proton in a metal modeled as a jellium the screening appears to be 15 +/- 10 %, which is neither negligible not reconcilable with the controversial full-screening point of view of Bosvieux and Friedel (1962). In reconsidering the theory of electromigration, a new simplified linear-response expression for the driving force is shown to lead to essentially the same result as found by Sorbello (1985), who has used a rather complicated technique. The expressions allow for a reduction such that only the scattering phase shifts of the migrating impurity are required. Finally it is shown that the starting formula for the driving force of Bosvieux and Friedel leads exactly to the zero-temperature limit of well-established linear response descriptions, by which the sting of the controversy has been removed.Comment: 14 pages, 5 figure

Examining barriers to healthcare access and utilization of antenatal care services: evidence from demographic health surveys in sub-Saharan Africa

Background:Antenatal care utilization is one of the means for reducing the high maternal mortality rates in sub-Saharan Africa. This study examined the association between barriers to healthcare access and implementation of the 2016 WHO antenatal care services model among pregnant women seeking antenatal care in selected countries in sub-Saharan Africa. Methods: This study considered only Demographic and Health Survey data collected in 2018 in sub-Saharan Africa. Hence, the Demographic and Health Survey data of four countries in sub-Saharan Africa (Nigeria, Mali, Guinea and Zambia) were used. A sample of 6761 from Nigeria, 1973 from Mali, 1690 from Guinea and 1570 from Zambia was considered. Antenatal care visits, categorized as  3 months (as per the WHO recommendations) were the outcome variables for this study. Both descriptive statistics and ordinal logistic regression were used to analyze the data. Crude odds ratios (cOR) and adjusted odds ratios (aOR) and p-values < 0.05 were used for the interpretation of results. Results: With timing of antenatal care visits, getting money needed for treatment (aOR = 1.38, 95% CI = 1.03–1.92) influenced early timing of antenatal care visits in Mali whereas getting permission to visit the health facility (aOR = 1.62, 95% CI = 1.15–2.33) motivated women to have early timing of antenatal care visits in Guinea. We found that women who considered getting money needed for treatment as not a big problem in Nigeria were more likely to have the recommended number of antenatal care visits (aOR = 1.38, 95% CI= 1.11–1.73). On the contrary, in Guinea, Zambia and Mali, getting permission to visit health facilities, getting money for treatment, distance to the health facility and not wanting to go alone were not barriers to having ≥ 8 antenatal care visits. Conclusion: Our study has emphasized the role played by barriers to healthcare access in antenatal care utilization across sub-Saharan African countries. There is the need for governmental and non-governmental organizations to ensure that policies geared towards improving the quality of antenatal care and promoting good interaction between health care seekers and health care providers are integrated within the health system

Quantum field theoretic approach to neutrino oscillations in matter

We consider neutrino oscillations in non-uniform matter in a quantum field theoretic (QFT) approach, in which neutrino production, propagation and detection are considered as a single process. We find the conditions under which the oscillation probability can be sensibly defined and demonstrate how the properly normalized oscillation probability can be obtained in the QFT framework. We derive the evolution equation for the oscillation amplitude and discuss the conditions under which it reduces to the standard Schr\"odinger-like evolution equation. It is shown that, contrary to the common usage, the Schr\"odinger-like evolution equation is not applicable in certain cases, such as oscillations of neutrinos produced in decays of free pions provided that sterile neutrinos with $\Delta m^2\gtrsim 1$ eV$^2$ exist.Comment: LaTeX, 24 pages + 16 pages of appendices, 1 figure. V2: typos correcte

Noncompliance with the WHO's Recommended Eight Antenatal Care Visits among Pregnant Women in Sub-Saharan Africa: A Multilevel Analysis.

Background: In 2016, the World Health Organization (WHO) introduced a minimum of eight antenatal care (ANC) visits for positive pregnancy outcomes. This study examined the prevalence of noncompliance with 8+ ANCvisits and its associated factors in sub-Saharan Africa (SSA). Methods: We used data from the Demographic and Health Surveys of eight countries in SSA. A pooled sample of 63,266 pregnant women aged 15-49 years who had given birth to children within 5 years prior to the surveys was included in this study. To examine the factors associated with noncompliance with ANC 8+ visits, multilevel binary logistic regression analysis was conducted, and the results were reported using odds radios at 95% confidence interval (CI). Results: The pooled prevalence of noncompliance with ANC 8+ visits was 92.3% (95% CI: 91.1%-93.3%) with the highest and lowest prevalence in Zambia (98.7%, 95% CI: 98.3%-99.1%) and Libya (73.4%, 95% CI: 70.4%-76.2%), respectively. With the individual level factors, women's age (44-49 years-aOR = 0.33, 9% CI: 0.14-0.78), health insurance registration, (yes-aOR = 0.53, 95% CI: 0.29-0.98), and economic status (richest-aOR = 0.16, 95% CI: 0.05-0.49) were negatively associated with noncompliance with 8+ ANC visits, while parity (five or more children-aOR = 1.68, 95% CI: 1.12-2.52) was positively associated with noncompliance with 8+ ANC visit. With the community level factors, community level literacy was negatively associated with noncompliance with 8+ ANC visit (high-aOR = 0.56, 95% CI: 0.32-0.99). Conclusion: About eight out of ten pregnant women did not comply with the WHO's recommended minimum of eight ANC visits for positive pregnancy outcomes in SSA. Empowering the economic status of women , enhancing health insurance and education coverage, and giving more attention to young pregnant women and those with more children are crucial for improving the coverage of ANC 8+ visits in the region

Central Mediterranean Sea forecast: effects of high-resolution atmospheric forcings

International audienceOcean forecasts over the Central Mediterranean, produced by a near real time regional scale system, have been evaluated in order to assess their predictability. The ocean circulation model has been forced at the surface by a medium, high or very high resolution atmospheric forcing. The simulated ocean parameters have been compared with satellite data and they were found to be generally in good agreement. High and very high resolution atmospheric forcings have been able to form noticeable, although short-lived, surface current structures, due to their ability to detect transient atmospheric disturbances. The existence of the current structures has not been directly assessed due to lack of measurements. The ocean model in the slave mode was not able to develop dynamics different from the driving coarse resolution model which provides the boundary conditions

Leadership for professional learning towards educational equity: a systematic literature review

Abstract: This systematic review of recent research explored the uncharted intersection of literature on educational leadership, professional learning, and educational equity. It investigated leadership approaches to shaping the professional development and on-going learning of educators that supports more equitable outcomes for students. The underlying motivation for the work is our concern for the educational experiences and achievements of marginalised students, and for professional learning to address these inequalities. Guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement, and iterative selection of literature based on relevance and quality judged by weight of evidence assessments, we identified 41 empirical items for detailed analysis. The outcome was five themes: Critical framing of social justice issues; Dialogue and enquiry; Learning and identity development; Context, resources, and motivations; Normalising inclusion and shared leadership. A further six articles informed a conceptual framework linking professional learning and outcomes that developed existing models. Critique of linear conceptualisations of learning, and affinity with the values and philosophy of the process model of education championed by Lawrence Stenhouse, prompted proposing the themes as nascent principles. These require further research, yet they have immediate practical utility for educational leaders and teachers working in pursuit of educational equity. Keywords: Professional Learning; Leadership; Educational Equity; Review of Researc

Long-Distance Wind-Dispersal of Spores in a Fungal Plant Pathogen: Estimation of Anisotropic Dispersal Kernels from an Extensive Field Experiment

Given its biological significance, determining the dispersal kernel (i.e., the distribution of dispersal distances) of spore-producing pathogens is essential. Here, we report two field experiments designed to measure disease gradients caused by sexually- and asexually-produced spores of the wind-dispersed banana plant fungus Mycosphaerella fijiensis. Gradients were measured during a single generation and over 272 traps installed up to 1000 m along eight directions radiating from a traceable source of inoculum composed of fungicide-resistant strains. We adjusted several kernels differing in the shape of their tail and tested for two types of anisotropy. Contrasting dispersal kernels were observed between the two types of spores. For sexual spores (ascospores), we characterized both a steep gradient in the first few metres in all directions and rare long-distance dispersal (LDD) events up to 1000 m from the source in two directions. A heavy-tailed kernel best fitted the disease gradient. Although ascospores distributed evenly in all directions, average dispersal distance was greater in two different directions without obvious correlation with wind patterns. For asexual spores (conidia), few dispersal events occurred outside of the source plot. A gradient up to 12.5 m from the source was observed in one direction only. Accordingly, a thin-tailed kernel best fitted the disease gradient, and anisotropy in both density and distance was correlated with averaged daily wind gust. We discuss the validity of our results as well as their implications in terms of disease diffusion and management strategy

Drivers of desire for more children among childbearing women in sub-Saharan Africa: implications for fertility control.

BackgroundDespite the extensive research on fertility desires among women the world over, there is a relative dearth of literature on the desire for more children in sub-Saharan Africa (SSA). This study, therefore, examined the desire for more children and its predictors among childbearing women in SSA.MethodsWe pooled data from 32 sub-Saharan African countries' Demographic and Health Surveys. A total of 232,784 married and cohabiting women with birth history, who had complete information on desire for more children made up the sample for the study. The outcome variable for the study was desire for more children. Multilevel logistic regression analysis was conducted. Results were presented using adjusted odds ratios (aOR), with their corresponding 95% confidence intervals (CI).ResultsThe overall prevalence of the desire for more children was 64.95%, ranging from 34.9% in South Africa to 89.43% in Niger. Results of the individual level predictors showed that women aged 45-49 [AOR = 0.04, CI = 0.03-0.05], those with higher education [AOR = 0.80, CI = 0.74-0.87], those whose partners had higher education [AOR = 0.88; CI = 0.83-0.94], women with four or more births [AOR = 0.10, CI = 0.09-0.11], those who were using contraceptives [AOR = 0.68, CI = 0.66-0.70] and those who had four or more living children [AOR = 0.09 CI = 0.07-0.12] were less likely to desire for more children. On the other hand, the odds of desire for more children was high among women who considered six or more children as the ideal number of children [AOR = 16.74, CI = 16.06-17.45] and women who did not take decisions alone [AOR = 1.58, CI = 1.51-1.65]. With the contextual factors, the odds of desire for more children was high among women who lived in rural areas compared to urban areas [AOR = 1.07, CI = 1.04-1.13].ConclusionsThis study found relatively high prevalence of women desiring more children. The factors associated with desire for more children are age, educational level, partners' education, parity, current contraceptive use, ideal number of children, decision-making capacity, number of living children and place of residence. Specific public health interventions on fertility control and those aiming to design and/or strengthen existing fertility programs in SSA ought to critically consider these factors

Theory for the electromigration wind force in dilute alloys

A multiple scattering formulation for the electromigration wind force on atoms in dilute alloys is developed. The theory describes electromigration via a vacancy mechanism. The method is used to calculate the wind valence for electromigration in various host metals having a close-packed lattice structure, namely aluminum, the noble metals copper, silver and gold and the $4d$ transition metals. The self-electromigration results for aluminum and the noble metals compare well with experimental data. For the $4d$ metals small wind valences are found, which make these metals attractive candidates for the experimental study of the direct valence.Comment: 18 pages LaTeX, epsfig, 8 figures. to appear in Phys. Rev. B 56 of 15/11/199