167 research outputs found

    Local convergence analysis of the Gauss–Newton method under a majorant condition

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    AbstractThe Gauss–Newton method for solving nonlinear least squares problems is studied in this paper. Under the hypothesis that the derivative of the function associated with the least square problem satisfies a majorant condition, a local convergence analysis is presented. This analysis allows us to obtain the optimal convergence radius and the biggest range for the uniqueness of stationary point, and to unify two previous and unrelated results

    Systematics of species of the genus Akodon (Rodentia: Sigmodontinae) in southeastern Brazil and implications for the biogeography of the Campos de Altitude.

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    Faunal inventories of the highest peaks of the Atlantic forests of South America, in the Caparaó and Itatiaia mountain ranges in Southeastern Brazil, have revealed a new community of small mammals. The species making up this community appear to be restricted to the highest altitudinal zones and are found in close association with scattered montane grasslands (campos de altitude). Their phylogenetic relationships can provide insights into speciation in mountaintop communities of the Atlantic forest. In this paper we review the taxonomic identity and systematic relationships of Akodon mystax, a high- altitude endemic described from Caparaó. We demonstrate that populations from Itatiaia previously assigned to mystax are morphologically, cytogenetically and genetically distinct from that species and appear to represent a northern isolate of Akodon paranaensis, and that Akodon mystax is closely related to Akodon lindberghi from the Central Brazilian grasslands. Phylogenetic relationships among these populations demonstrate that differentiation of the mountaintop endemics of Caparaó and Itatiaia is not solely attributable the isolation of campos de altitude from southern grasslands of Brazil and Uruguay as grasslands retreated southward, phylogenetic analyses of some groups suggest connections between the campos de altitude and Central Brazil."http://deepblue.lib.umich.edu/bitstream/2027.42/102734/1/MP197.pd

    Relative Growth Of Carcass Tissues Of Goat Kids From Five Breed Types Finished On Pasture Or Feedlot

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    The aim of this study was to evaluate the effect of cross breeding, finishing system, and gender on the relative growth of carcass tissues of dairy kids. Seventy eight kids (39 male and 39 female) from five breed types were used: Alpine; 1/2 Boer + 1/2 Alpine (1/2 BA); 1/2 Nubian + 1/2 Alpine (1/2 ANA); 3/4 Boer + 1/4 Alpine (3/4 BA); and 1/2 Nubian + 1/4 Boer + 1/4 Alpine (TC). Kids were distributed into two finishing systems: in pasture with doe (FS1) and weaned in feedlot (FS2). Kids were slaughtered at a mean age of 128.4 ± 7.9 days and mean live weight of 22.07 kg. The mean weight of half carcasses was 5.09 kg. To determine allometric growth, we used the exponential equation Y= aXb. In the half carcass, muscle tissue showed comparatively early growth in group 1/2 BA, whereas fat tissue of animals in FS1 had relatively late growth. Females exhibited early growth of muscle tissue, while in males this tissue was intermediate. The 1/2 BA first-cross improved carcass characteristics by enhancing the growth of muscle tissue.37298999

    Movements of hatchery-reared dusky groupers released in a Northeast Atlantic Coastal Marine Protected Area.

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    No-take areas are key instruments to promote the effectiveness of Marine Protected Areas (MPAs), particularly concerning the protection of endangered species such as the dusky grouper (Epinephelus marginatus). However, despite the establishment of no-take areas and the prohibition of catching this species in a southwestern Portuguese MPA (SACVMP—‘Sudoeste Alentejano’ and ‘Costa Vicentina’ Marine Park) since 2011, there is still no evidence of population recovery. By using acoustic biotelemetry, this work aimed to evaluate the feasibility of restocking hatchery-reared adult dusky groupers in two no-take areas within the SACVMP. In 2019 and 2021, thirty groupers were tagged with acoustic transmitters and the site attachment and movements of the groupers were assessed in the releasing sites (no-take areas). None of the tagged fish settled down in either of the areas, leaving the no-take areas mainly at dusk and night. Some individuals displayed extended movements of more than a hundred kilometers along the Portuguese coast which was rarely reported for this species. At least in some coastal stretches, those movements were performed close to the shore, which may evidence the importance of coastal MPAs to protect and promote the connectivity of species more associated with rocky reef habitats. Following studies should focus on the conditions that promote site attachment and fidelity by hatchery-reared dusky groupers so that future large-scale restocking programs can be successful in MPAs with appropriate habitats

    Efeito do alumínio sobre a absorção, o acúmulo e o fracionamento do fósforo em sorgo

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    O trabalho teve como objetivo estudar o efeito do Al sobre a absorção, o acúmulo e o fracionamento do P em duas cultivares de sorgo. As plantas foram expostas a níveis tóxicos de Al durante dez dias e, então, colhidas e determinados o crescimento em tamanho e produção de massa seca, os teores de Al e de P total e as diversas formas de P nas duas partes das plantas. Avaliou-se, também, o efeito do Al sobre a absorção de P pelas raízes de plantas intactas. O Al reduziu o crescimento da raiz seminal e a produção de matéria seca de raízes e parte aérea nas duas cultivares, especialmente na sensível. Os teores de Al e de P total aumentaram nas raízes, mas não foram modificados na parte aérea nas duas cultivares. A absorção de P, entretanto, decresceu na presença de Al nas duas cultivares, principalmente na sensível. O Al, de modo geral, modificou as concentrações das várias formas de P solúvel (Pi e Porg) e insolúvel (P RNA e Presidual), exceto a da forma P LIP. Algumas dessas modificações parecem ser importantes e podem estar relacionadas com o mecanismo de tolerância ao Al em sorgo.The objective of this work was to evaluate Al effect on uptake, accumulation and fractionation of P in two sorghum cultivars. Plants were treated with toxic levels of Al during ten days and then they were harvested and growth, dry matter yield, Al and total P contents and concentrations of the various P forms in the two parts of the plants were determined. Aluminum effect on P uptake was also evaluated in intact plants. Aluminum reduced the growth of the seminal root and dry matter yield in roots and tops of both cultivars, especially in the sensitive one. Aluminum and P contents increased in roots but did not change in the top of both cultivars. Phosphate uptake by roots, however, decreased in the presence of Al in both cultivars, especially in the sensitive one. Aluminum, in general, changed concentrations of all soluble (Pi e Porg) and insoluble P forms (P RNA e Presidual), except of the P LIP form. Some of these modifications seem to be important and may be related to Al tolerance mechanism in sorghum
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