Federal University of Roraima

We investigate a nonlocal elliptic boundary value problem of logistic type involving nonlocal diffusion and global cooperative–competitive interactions:{−Δu−∫ΩK(x,y)u(y)dy=a(x)u+λ|u|p−2u∫ΩQ(x,y)|u(y)|pdy+f(x),x∈Ω,u=0,x∈∂Ω, where Ω⊂RN is a bounded smooth domain, λ∈R, 1 0. In the competitive case, we establish the existence of nonnegative weak solutions via a direct minimization argument and identify a natural spectral threshold associated with the underlying nonlocal operator. In the general case λ∈R, we employ a saddle-point framework based on Ky Fan's minimax principle to obtain existence results under suitable smallness conditions on the coefficients. These results show how the nonlocal interaction term restores coercivity and provide a unified variational framework for logistic-type elliptic problems with global interactions.

The Boa Vista Formation covers much of the Tacutu Basin in the central portion of Roraima state, northern Brazil. The genesis of this formation has been linked to geological and paleoclimatic events in the Amazon, and its stratigraphic positioning has been controversial, mainly due to the scarcity of geochronological data. In this context, the present study focuses on the geomorphological and distributional aspects of this formation in the outcrop area, integrated with facies, stratigraphic, and geochronological data (Optically Stimulated Luminescence Dating - OSL) obtained from nine outcrops in the northeastern and northwestern portions of the Tacutu Basin. The facies association allowed relating the deposition of this formation to the proximal and distal portions of a Pleistocene alluvial fan environment, based on the gravel facies (AFC) deposited by gravitational flows approximately 82.1 f 6.0 ka and the sandy facies (AFA) deposited by current flows between 66.6 f 2.2 and 39.4 f 2.7 ka, respectively. Locally, the fan deposits are overlain by aeolian facies, deposited by wind reworking approximately 2.13 f 0.3 ka ago. The data obtained are consistent with a geographic and temporal continuum of the Quaternary coverage of the Tacutu Basin, in an alluvial setting in which gravitational flow processes evolve into areas dominated by streamflows and other pertinent processes correlatable to Late Quaternary alluvial fan systems identified in the northern Amazon. In particular, the unprecedented LOE data allow us to define the sedimentation stages of the fans, allowing them to be placed within the context of recent geological evolution of Western Amazonia.

In individuals with prior dengue virus (DENV) exposure, subsequent heterotypic infection can increase the risk of severe disease. A single-dose dengue vaccine that protects against the four DENV serotypes across a wide age range and regardless of DENV serostatus is needed. Here we report the long-term safety and efficacy of Butantan dengue vaccine (Butantan-DV), a live, attenuated, tetravalent dengue vaccine, among participants ages 2-59 who were randomized 2:1 in a double-blind, placebo-controlled, phase 3 trial in Brazil. A primary objective was to evaluate vaccine efficacy (VE) against reverse transcription-PCR-positive symptomatic dengue 28 days after vaccination because of any DENV serotype, regardless of serostatus. Prespecified secondary endpoints included VE by serotype, by serostatus and against severe dengue or dengue with warning signs (combined). The primary and secondary objectives were met if the lower bound of the two-sided 95% confidence interval (CI) for VE was above 25%. Between 2016 and 2019, 16,235 participants received Butantan-DV (n = 10,259) or placebo (n = 5,976). The trial met the primary and secondary objectives. During the 5 years of follow-up, between 2016 and 2024, overall VE (95% CI) was 65.0% (57.8-71.0%). Secondary VE endpoints (95% CI) were 77.1% (67.6-83.9%) in dengue-experienced participants, 58.9% (48.0-67.6%) in dengue-naive participants, 73.0% (64.3-79.7%) against DENV-1 and 55.7% (42.3-66.1%) against DENV-2. Cases of DENV-3 or DENV-4 were not observed. VE (95% CI) against dengue with warning signs or severe dengue (secondary endpoint) was 80.5% (50.8-92.4%). The most commonly reported solicited systemic adverse event (AE) was headache (36.7% of vaccine recipients and 31.1% of placebo recipients), most of which were grade 1. The proportions of participants with unsolicited vaccine-related AEs (including serious AEs) were comparable between intervention groups. A single dose of Butantan-DV was efficacious against symptomatic virologically confirmed dengue because of DENV-1 or DENV-2, regardless of dengue serostatus at baseline, with no safety concerns observed during the 5-year follow-up (ClinicalTrials.gov: NCT02406729 ).

Soil Information Systems (SIS) are critical frameworks for collecting, managing, and disseminating soil data to guide decision-making towards sustainable agricultural and environmental policies. Despite their global importance, SIS development in Africa remains limited and fragmented. Synthesizing African experts’ knowledge on the requirements and barriers for developing robust and sustainable national SIS (NSIS) in Africa is pressing for effective and prioritized recommendations. A structured questionnaire was used to survey 81 soil information experts from twenty-seven (27) African countries. Close-ended questions were framed to comprehensively assess the understanding and the need for country-based SIS, current data infrastructure, institutional, technical, and financial challenges, stakeholder collaboration and data-sharing mechanisms within the SIS framework. The respondents are staff members of national soil information mandates. Composite indicators were generated by averaging recoded survey items within thematic sections and then subjected to Pearson correlation analysis. Results indicate that > 80 % of respondents are familiar with the SIS concept, but only a very small proportion (11 %) use it daily or weekly. A large majority of respondents (> 90 %) consider NSIS as a tool for supporting policy processes and boosting agricultural production. With regards to soil data, a substantial volume of Africa’s soil information remains confined to hardcopy archives or fragmented within legacy data systems. The major challenge in the development of NSIS includes financial constraints, with > 80 % of respondents characterizing available funding initiatives as very limited. Stakeholder collaboration and data accessibility are currently weak, as reflected in the very low composite scores, with only 30 % of respondents occasionally sharing their data. In general, there were low positive correlations between SIS familiarity/use and perceived usefulness (r = 0.29, p < 0.05) and between stakeholder collaboration and data accessibility (r = 0.28, p < 0.05), while a moderate relationship was found between data accessibility and perceived challenges (r = 0.40, p < 0.001). These findings emphasize the urgent need for harmonized methodologies, stronger institutional frameworks, capacity building, and enhanced regional cooperation to establish resilient and integrated NSIS that support sustainable land management and agricultural productivity across the continent.