70 research outputs found
A new method for the estimation of variance matrix with prescribed zeros in nonlinear mixed effects models
We propose a new method for the Maximum Likelihood Estimator (MLE) of
nonlinear mixed effects models when the variance matrix of Gaussian random
effects has a prescribed pattern of zeros (PPZ). The method consists in
coupling the recently developed Iterative Conditional Fitting (ICF) algorithm
with the Expectation Maximization (EM) algorithm. It provides positive definite
estimates for any sample size, and does not rely on any structural assumption
on the PPZ. It can be easily adapted to many versions of EM.Comment: Accepted for publication in Statistics and Computin
Harvest of endangered marine invertebrates in a priority area for conservation in Brazil
The harvesting of marine organisms for aquarium and ornamental art crafts is a very common and widespread activity, threatening a number of coral reef species. The goal of this manuscript is to report the intensive harvesting of two marine invertebrate species, the starfish Oreaster reticulatus and the gorgonian Phyllogorgia dilatata, in reef environments of a national priority area for the creation of a Marine Protected Area (MPA) in the Espírito Santo State, central coast of Brazil. These species were present on the 2003 Brazilian Red List of Endangered species as threatened of extinction, but P. dilatata was removed from the most recent 2014 Brazilian Red List, while O. reticulatus is currently considered vulnerable. Neither species have been assessed by IUCN. The harvest of these invertebrates was registered in 17% of the 51 days of monitoring (ten expeditions between March 2005 and February 2006), with catches of up to 24 starfishes and 1000 gorgonians in a single day. Starfishes used to be sold to local traders for US 0.15. This starfish is already in decline on a regional scale, and the actual harvesting rate of the gorgonian could lead to the extinction of the local population in about 17 years of exploitation. Due to the ecological importance of these two endangered species, their harvest threatens the entire local rocky reef ecosystem. Further ecological and fisheries studies on these species should be conducted, and the definition and creation of the MPA could help to manage all the unsustainable activities conducted and expected in the region
Hydrological influence on the evolution of a subtropical mangrove ecosystem during the late Holocene from Babitonga Bay, Brazil
Mangroves are key ecosystems which respond to global changes in tropical and subtropical regions worldwide. We describe late Holocene mangroves that established close to the southernmost limit (28°S) for this type of ecosystem in South America. Our findings are based on a C dated core obtained from Babitonga Bay, Santa Catarina State, Brazil (26°12′S, 48°33′W). Analysis of palynology, sedimentary facies, isotopic and elemental data shows that mangrove establishment took place ~500 yrs. B.C.E., following an increase in humidity, and expanded further during the Roman Warm Period and at the end of Dark Age Cold Period. Mangrove and precipitation proxies records appear to be sensitive to rainfall patterns imposed both by the expansion/retraction of the Intertropical Convergence Zone and also the interaction with the South Atlantic Subtropical Anticyclone which affects coastal region due to sea surface temperature variations.The authors thank the Coastal Dynamic Laboratory (LADIC-UFPA) , C-14 Laboratory of the Center for Nuclear Energy in Agriculture (CENA-USP) , University of Joinville (UNIVILLE) and Radiocarbon Laboratory (LAC-UFF) for all infrastructure and support. We also thank three anonymous Reviewers and Prof. H. Falcon-Lang for their constructive comments. The first and third author thanks Brazilian Council for Technology and Science-CNPq for fellowship (process 131813/2016-1 , 165911/2015-8 and 305074/2017-2 ). This study was financed by CNPq ( 445111/2014-3 , 405060/2013- 0 ) and FAPESP ( 2011/00995-7 , 2017/03304-1, and 2020/13715-1 ). This study also was financed in part by the Coordenação de Aperfeiçoamento de Pessoal Nível Superior – Brazil (CAPES) – Finance Code 001
Determination of non-isothermal crystallization rate constant of a rotational molding grade LLDPE
Selection of bee species for environmental risk assessment of GM cotton in the Brazilian Cerrado
Desempenho e características de carcaça de frangos de corte alimentados com rações contendo farelo da castanha de caju tratado ou não com antioxidante
Remoção biológica de fenol por uso de reator contínuo com inóculo de Aspergillus niger
Protracted deformation during cooling of the Paleoproterozoic arc system as constrained by 40Ar/39Ar ages of muscovite from brittle faults: the Transamazonan Bacajá Terrane, Brazil
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