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The component Allee effect (AE) is the positive correlation between an organism's fitness component and population density. Depending on the population spatial structure, which determines the interactions between organisms, a component AE might lead to positive density dependence in the population per-capita growth rate and establish a demographic AE. However, existing spatial models impose a fixed population spatial structure, which limits the understanding of how a component AE and spatial dynamics jointly determine the existence of demographic AEs. We introduce a spatially explicit theoretical framework where spatial structure and population dynamics are emergent properties of the individual-level demographic and movement rates. This framework predicts various spatial patterns depending on its specific parametrization, including evenly spaced aggregates of organisms, which determine the demographic-level by-products of the component AE. We find that aggregation increases population abundance and allows population survival in harsher environments and at lower global population densities when compared with uniformly distributed organisms. Moreover, aggregation can prevent the component AE from manifesting at the population level or restrict it to the level of each independent aggregate. These results provide a mechanistic understanding of how component AEs might operate for different spatial structures and manifest at larger scales.

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BACKGROUND: Peripheral arterial disease (PAD) is a common and highly morbid disease. Although there have been recent advancements in the endovascular modalities to treat PAD, comparisons of these strategies, especially in the popliteal region, remain underinvestigated. The objective of this study was to compare midterm outcomes in patients with PAD undergoing treatment with both novel and SS compared with drug-coated balloon (DCB) angioplasty. METHODS: All patients at a multi-institution health system treated for PAD in the popliteal region from 2011 to 2019 were identified. Presenting features, operative details, and outcomes were included in the analysis. Patients who underwent popliteal revascularization with stents were compared with DCB. SS were compared separately with novel dedicated stents. Two-year primary patency was the primary outcome. RESULTS: We included 408 patients (72.7 ± 11.8 years old; 57.1% men) in the analysis. There were 221 (54.7%) patients who underwent popliteal stenting and 187 (45.3%) who underwent popliteal DCB. There were high rates of tissue loss in both groups (57.9% vs 50.8%; P = .14). Stented patients had longer lesions (112.4 ± 3.2 vs 100.2 ± 5.8 mm; P = .03) and higher rates of concomitant superficial femoral artery treatment (88.2% vs 39.6%; P < .01). Chronic total occlusions accounted for the majority of lesions treated (stent 62.4%, DCB 64.2%). Perioperative complications were similar between groups. Primary patency for the stented group was higher at two years than the DCB group (61.0% vs 46.1%; P = .03). When evaluating stented patients only, SS had higher 2-year patency than novel stents in the popliteal segment (69.6% vs 51.4%; P = .04). On multivariable analysis, stenosis, as opposed to chronic total occlusion, was associated with improved patency (hazard ratio, 0.49; 95% confidence interval, 0.25-0.96; P = .04), whereas novel stents were associated with worse primary patency (hazard ratio, 2.01; 95% confidence interval, 1.09-3.73; P = .03). CONCLUSIONS: In a population of patients with severe vascular disease, stents do not have inferior patency and limb salvage rates compared with DCB angioplasty when treating the popliteal region. For patients with advanced vascular disease, and especially tissue loss, stents and DCB are both beneficial when treating popliteal lesions.

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Self-organized spatial patterns are ubiquitous in ecological systems and allow populations to adopt non-trivial spatial distributions starting from disordered configurations. These patterns form due to diverse nonlinear interactions among organisms and between organisms and their environment, and lead to the emergence of new (eco)system-level properties unique to self-organized systems. Such pattern consequences include higher resilience and resistance to environmental changes, abrupt ecosystem collapse, hysteresis loops, and reversal of competitive exclusion. Here, we review ecological systems exhibiting self-organized patterns. We establish two broad pattern categories depending on whether the self-organizing process is primarily driven by nonlinear density-dependent demographic rates or by nonlinear density-dependent movement. Using this organization, we examine a wide range of observational scales, from microbial colonies to whole ecosystems, and discuss the mechanisms hypothesized to underlie observed patterns and their system-level consequences. For each example, we review both the empirical evidence and the existing theoretical frameworks developed to identify the causes and consequences of patterning. Finally, we trace qualitative similarities across systems and propose possible ways of developing a more quantitative understanding of how self-organization operates across systems and observational scales in ecology.

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We introduce and analyze a spatial Lotka-Volterra competition model with local and nonlocal interactions. We study two alternative classes of nonlocal competition that differ in how each species' characteristics determine the range of the nonlocal interactions. In both cases, nonlocal interactions can create spatial patterns of population densities in which highly populated clumps alternate with unpopulated regions. These non-populated regions provide spatial niches for a weaker competitor to establish in the community and persist in conditions in which local models predict competitive exclusion. Moreover, depending on the balance between local and nonlocal competition intensity, the clumps of the weaker competitor vary from M-like structures with higher densities of individuals accumulating at the edges of each clump to triangular structures with most individuals occupying their centers. These results suggest that long-range competition, through the creation of spatial patterns in population densities, might be a key driving force behind the rich diversity of species observed in natural ecological communities.

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We introduce an asymmetric noisy voter model to study the joint effect of immigration and a competition-dispersal tradeoff in the dynamics of two species competing for space in regular lattices. Individuals of one species can invade a nearest-neighbor site in the lattice, while individuals of the other species are able to invade sites at any distance but are less competitive locally, i.e., they establish with a probability g≤1. The model also accounts for immigration, modeled as an external noise that may spontaneously replace an individual at a lattice site by another individual of the other species. This combination of mechanisms gives rise to a rich variety of outcomes for species competition, including exclusion of either species, monostable coexistence of both species at different population proportions, and bistable coexistence with proportions of populations that depend on the initial condition. Remarkably, in the bistable phase, the system undergoes a discontinuous transition as the intensity of immigration overcomes a threshold, leading to a half loop dynamics associated to a cusp catastrophe, which causes the irreversible loss of the species with the shortest dispersal range.

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A straightforward method for the synthesis of CoFe2.7/CoFe2O4 core/shell nanowires is described. The proposed method starts with a conventional pulsed electrodeposition procedure on alumina nanoporous template. The obtained CoFe2.7 nanowires are released from the template and allowed to oxidize at room conditions over several weeks. The effects of partial oxidation on the structural and magnetic properties were studied by x-ray spectrometry, magnetometry, and scanning and transmission electron microscopy. The results indicate that the final nanowires are composed of 5 nm iron-cobalt alloy nanoparticles. Releasing the nanowires at room conditions promoted surface oxidation of the nanoparticles and created a CoFe2O4 shell spinel-like structure. The shell avoids internal oxidation and promotes the formation of bi-magnetic soft/hard magnetic core/shell nanowires. The magnetic properties of both the initial single-phase CoFe2.7 nanowires and the final core/shell nanowires, reveal that the changes in the properties from the array are due to the oxidation more than effects associated with released processes (disorder and agglomeration).

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La histoplasmosis es una micosis causada por el hongo dimorfo Histoplasma capsulatum. El síndrome hemofagocítico es una enfermedad potencialmente mortal causada por la activación inapropiada de linfocitos y macrófagos, que conduce a daño celular en múltiples órganos y sistemas. Describimos el caso de un paciente masculino de 46 años de edad, con infección VIH/SIDA, con fiebre, disnea, pérdida de peso y pancitopenia, quien presenta un síndrome hemofagocítico secundario a una histoplasmosis diseminada, diagnóstico este realizado por estudios de médula ósea.

Histoplasmosis is a mycosis caused by the dimorphic fungus Histoplasma capsulatum. Hemophagocytic syndrome is a potentially lethal condition caused by inappropriate activation of lymphocytes and macrophages, leading to cellular damage in multiple organs and systems. We describe the case of a male patient 46 years old with HIV Infection/AIDS, with fever, dyspnea, diarrhea, weight loss and pancytopenia, who presents a disseminated histoplasmosis with a secondary HFS, this diagnosis made by bone marrow studies.

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El presente artículo refleja conceptos generales clínicos relacionados con una de las enfermedades de gran impacto epidemiológico a nivel nacional, que han llevado a la movilización de diferentes recursos para su control y manejo. Se presentan criterios de gran utilidad para abordar su manejo en los servicios de urgencia tomando como referencia la normatividad aprobada para su control.

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