Floristic and structural changes in secondary forests following agricultural disturbances: the case of Lama forest reserve in Southern Benin

Structural changes in secondary forests are less known in West Africa, and this precludes their management. This study aims at providing quantitative information on floristic composition and structure of the Lama secondary forests (Benin), so as to contribute to their restoration, and fill part of knowledge gaps on West African secondary forests. Data of 77 permanent plots each of 0.5 ha were used to analyze the floristic composition, the trajectory of the recovery and the recovery of stocking in these forests, compared to nearby old-growth forests. The results showed that the forests were less diversified with few species very common in the forest stands; the most dominant were Lonchocarpus sericeus and Anogeissus leiocarpa in the secondary forests, and Dialium guineense, Diospyros mespiliformis and Afzelia africana in the old-growth forests. The secondary forests hold more species than the mature ones. Their compositions will recover that of the original forest because species of the original forest were actively regenerating in the secondary forests. About 28 years after recovery, large trees were insufficient and basal area was about 60% of those of the mature forests. Further studies are needed to elucidate barriers to tree regeneration and dynamics of tree population.© 2016 International Formulae Group. All rights reserved.Keywords: Secondary forest, recovery, diversity, species composition, timber stock, Beni

Declines in Pediatric Bacterial Meningitis in the Republic of Benin Following Introduction of Pneumococcal Conjugate Vaccine: Epidemiological and Etiological Findings, 2011-2016.

BACKGROUND: Pediatric bacterial meningitis (PBM) remains an important cause of disease in children in Africa. We describe findings from sentinel site bacterial meningitis surveillance in children <5 years of age in the Republic of Benin, 2011-2016. METHODS: Cerebrospinal fluid (CSF) was collected from children admitted to Parakou, Natitingou, and Tanguieta sentinel hospitals with suspected meningitis. Identification of Streptococcus pneumoniae (pneumococcus), Haemophilus influenzae, and Neisseria meningitidis (meningococcus) was performed by rapid diagnostic tests, microbiological culture, and/or polymerase chain reaction; where possible, serotyping/grouping was performed. RESULTS: A total of 10 919 suspected cases of meningitis were admitted to the sentinel hospitals. Most patients were 0-11 months old (4863 [44.5%]) and there were 542 (5.0%) in-hospital deaths. Overall, 4168 CSF samples were screened for pathogens and a total of 194 (4.7%) PBM cases were confirmed, predominantly caused by pneumococcus (98 [50.5%]). Following pneumococcal conjugate vaccine (PCV) introduction in 2011, annual suspected meningitis cases and deaths (case fatality rate) progressively declined from 2534 to 1359 and from 164 (6.5%) to 14 (1.0%) in 2012 and 2016, respectively (P < .001). Additionally, there was a gradual decline in the proportion of meningitis cases caused by pneumococcus, from 77.3% (17/22) in 2011 to 32.4% (11/34) in 2016 (odds ratio, 7.11 [95% confidence interval, 2.08-24.30]). Haemophilus influenzae meningitis fluctuated over the surveillance period and was the predominant pathogen (16/34 [47.1%]) by 2016. CONCLUSIONS: The observed decrease in pneumococcal meningitis after PCV introduction may be indicative of changing patterns of PBM etiology in Benin. Maintaining vigilant and effective surveillance is critical for understanding these changes and their wider public health implications

Efficient analysis of planar, arbitrarily shaped, and (Bi)-anisotropic metasurface antennas

An efficient method of moments (MoM) scheme is presented for the analysis of planar, possibly cascaded meta- surfaces (MTSs) implementing high-impedance surfaces. The MTS can be designed on an arbitrarily shaped domain and is accounted for as a set of cascaded electric sheet impedances. In the proposed method, the shaped MTS is included in a larger rectangular domain meshed with rooftop basis functions, resulting in a Toeplitz–block Toeplitz structure for the sub- strate impedance matrix, which enables fast Fourier transform (FFT)-based acceleration of matrix–vector products. The basis functions lying in the rectangular domain but outside the MTS are disabled by including zeros in the impedance matrix. The obtained linear system of equations is well conditioned, does not require any specific near-field treatment, and can be solved itera- tively using the generalized minimal residual (GMRES) method. It has been demonstrated that the algorithm is able to handle efficiently any MTS antenna shape in single-layer or multilayer configuration with almost linear complexity. It is shown that the high-impedance sheets improve the convergence rate. MTSs with more than 40 wavelengths size, meshed with more than 1 million basis functions, can be analyzed on a conventional computer in less than 15 min. A very good agreement is shown through comparison with results from other software packages

Metasurface Antennas Design: Full-Wave Feeder Modeling and Far-Field Optimization

This article addresses the optimization of the radiation pattern of surface-wave (SW)-based metasurface (MTS) antennas. Those antennas are considered a promising alternative to parabolic reflectors and phased arrays due to their extremely low profile and their ability to provide high gain, shaped beams and multibeams. However, pattern synthesis with MTS antennas is very challenging because of the single active control point and the need to control surface and leaky waves through the MTS. An accurate optimization of the radiation pattern, along with the sidelobe level requires full-wave modeling of the feeding structure, including its coupling with the MTS. MTS synthesis methods existing in the literature usually approximate the feeder model, and neglect its coupling with the MTS. Such approximation may lead to more than 1 dB error in the predicted antenna directivity. This article presents a technique for optimization of the far-field pattern, built on a Method of Moments (MoM) analysis tool in which the MTS coupling with the feeder, a coax probe, is fully considered. The MTS is modeled as an arbitrarily shaped, spatially modulated electric sheet impedance in a layered medium. At each optimization iteration, the complexity of the underlying analysis is O(N logN) owing to the use of a fast Fourier transforms (FFT)-based acceleration. The effectiveness of the method is demonstrated through the optimization of MTSs radiating a pencil beam and a conical beam with orbital angular momentum (OAM)

Simulation of shaped metasurface antennas including the feeder coupling

An effective Method of Moment (MoM) tool able to rapidly and accurately analyze arbitrarily shaped metasurface (MTS) antennas is provided. The MTS is assumed to be fed by a coax probe as is usually the case in practice. The feed as well as the MTS are meshed with local basis functions. The calculation of the interactions between the MTS basis functions, which are the dominant unknowns, is accelerated with the FFT. The surface current is then computed iteratively using the GMRES algorithm. Once the currents on the MTS and on the feed are obtained, the efficiency of the antenna can be derived. The method is validated with an in-house numerical tool developed for the particular case of circular MTSs. An excellent comparison is observe

Load-Dependent Prefrontal Cortex Activation Assessed by Continuous-Wave Near-Infrared Spectroscopy during Two Executive Tasks with Three Cognitive Loads in Young Adults

International audienceThe present study examined the evolution of the behavioral performance, subjectively perceived difficulty, and hemodynamic activity of the prefrontal cortex as a function of cognitive load during two different cognitive tasks tapping executive functions. Additionally, it investigated therelationships between these behavioral, subjective, and neuroimaging data. Nineteen right-handed young adults (18–22 years) were scanned using continuous-wave functional near-infrared spectroscopy during the performance of n-back and random number generation tasks in three cognitiveload conditions. Four emitter and four receptor optodes were fixed bilaterally over the ventrolateral and dorsolateral prefrontal cortices to record the hemodynamic changes. A self-reported scale measured the perceived difficulty. The findings of this study showed that an increasing cognitive loaddeteriorated the behavioral performance and increased the perceived difficulty. The hemodynamic activity increased parametrically for the three cognitive loads of the random number generation task and in a two-back and three-back compared to a one-back condition. In addition, the hemodynamic activity was specifically greater in the ventrolateral prefrontal cortex than in the dorsolateral prefrontal cortex for both cognitive tasks (random number generation and n-back tasks). Finally, the results highlighted some links between cerebral oxygenation and the behavioral performance, but not the subjectively perceived difficulty. Our results suggest that cognitive load affects the executive performance and perceived difficulty and that fNIRS can be used to specify the prefrontal cortex’s implications for executive tasks involving inhibition and working memory updating

Investigation of the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH) model as a function of cardiorespiratory fitness

International audienc

Prefrontal cortex activation in young adults during an updating working memory task with varying levels of complexity

International audienc

Testing the behavioral and neurohemodynamic compensation effects of cardiorespiratory fitness on the aging of working memory updating

National audienc

Working Memory, Cognitive Load and Cardiorespiratory Fitness: Testing the CRUNCH Model with Near-Infrared Spectroscopy

The present study aimed to examine the effects of chronological age and cardiorespiratory fitness (CRF) on cognitive performance and prefrontal cortex activity, and to test the compensation-related utilization of neural circuits hypothesis (CRUNCH). A total of 19 young adults (18&#8315;22 years) and 37 older ones (60&#8315;77 years) with a high or low CRF level were recruited to perform a working memory updating task under three different cognitive load conditions. Prefrontal cortex hemodynamic responses were continuously recorded using functional near-infrared spectroscopy, and behavioral performances and perceived difficulty were measured. Results showed that chronological age had deleterious effects on both cognitive performance and prefrontal cortex activation under a higher cognitive load. In older adults, however, higher levels of CRF were related to increased bilateral prefrontal cortex activation patterns that allowed them to sustain better cognitive performances, especially under the highest cognitive load. These results are discussed in the light of the neurocognitive CRUNCH model