Federal University of Roraima

We investigate a nonlocal elliptic boundary value problem of logistic type involving nonlocal diffusion and global cooperative-competitive interactions: {-Delta u-integral K-Omega (x, y)u(y) dy = a(x)u + lambda|u|(p-2)u integral(Omega) Q(x, y)|u(y)|(p) dy+f(x), x is an element of Omega u = 0, x is an element of partial derivative Omega, where Omega C R(N)is a bounded smooth domain, lambda is an element of R, 1 < p < 2*, K, Q is an element of L-infinity(Omega & times; Omega), a is an element of L-infinity(Omega), and f is an element of L-2(Omega). The model combines local diffusion, nonlocal dispersal, and a nonlinear global interaction term of cooperative-competitive type. We distinguish between the competitive case lambda < 0 and the general case E E R, which includes cooperative interactions when lambda > 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 lambda is an element of 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.

In this work, we are concerned with presenting a comparison result for sub- and super solutions of infinite energy in nonreflexive fractional Orlicz–Sobolev spaces, for the class of problems(Ps,Φ,f){(−ΔΦ)su=f(x,u),inΩ,u=0,inRN∖Ω, based on this, we establish the existence and uniqueness results for positive solutions to Brézis–Oswald type problems (finite energy) and strongly singular problems (infinite energy), both derived from (Ps,Φ,f). To overcome the natural difficulties arising from the non reflexivity of the underlying fractional Orlicz–Sobolev spaces and the strong singularity, we refined classical tools and arguments originally developed for reflexive spaces such as comparison theorem and regularities results.

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 ).

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.

We investigate the qualitative dynamics of smooth solutions to the radially symmetric isentropic compressible Euler equations, focusing specifically on the evolution of rarefactive and compressive wave characters across three distinct configurations: the outward supersonic, subsonic, and inward supersonic regimes. For each case, we establish structural restrictions on wave-character transitions and identify invariant sign domains for gradient variables under specific initial data conditions. While our findings refine existing invariance properties in the outward supersonic regime, they reveal novel asymmetric transition mechanisms in the subsonic and inward regimes that are absent in purely supersonic expanding cases. Consequently, we derive sufficient conditions for finite-time singularity formation. To complement the analytical results where closed-form solutions are unavailable, we provide numerical experiments using a Semi-Discrete Lagrangian-Eulerian (SDLE) formulation. These simulations reproduce the predicted wave-character dynamics and offer qualitative evidence that supports our theoretical findings, providing a unified description of wave transitions in radially symmetric isentropic gas dynamics.