78 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
Fauna of euglossina (Hymenoptera: Apidae) from southwestern Amazonia, Acre, Brazil
Male orchid bees were collected between December 2005 and September 2006 in 11 forest areas of different sizes in the region of Rio Branco, Acre, Southwestern Amazonia, Brazil. The bees were attracted by 6 aromatic compounds and collected by insect nets and scent baited traps. A total of 3,675 males of Euglossina in 4 genera and 36 species were collected. Eulaema cingulata (Fabricius) was the most common (24.6%), followed by Eulaema meriana (Olivier) (14.6%), Euglossa amazonica Dressler (10.5%), Eulaema nigrita Lepeletier (10.5%) and Eulaema pseudocingulata (Oliveira) (7.2%). Cineole was the scent that attracted the greatest number of individuals (23.8%) and methyl salicylate the greatest number of species (28) for both methods of sampling. Thirty one bees of 9 species with pollinar orchid attached to their bodies were collected. The accumulative number of species stabilized after the 48th collection. Few species were abundant; the great majority were represented by less than 50 bees. The lack of standardized sample protocols limited very much the conclusions derived from comparisons among the majority of studies on Euglossina assemblages. However, the results presented here suggest that the State of Acre is very rich in those bees compared to other regions.Machos de abelhas Euglossina foram coletados entre dezembro de 2005 e setembro de 2006 em 11 áreas florestais de diferentes tamanhos na regiĂŁo de Rio Branco, Acre, AmazĂ´nia Sul-Ocidental. As abelhas foram atraĂdas por 6 substâncias odorĂferas e coletadas com rede entomolĂłgica e armadilhas. Um total de 3.675 machos de Euglossina pertencentes a 4 gĂŞneros e 36 espĂ©cies foi coletado. Eulaema cingulata (Fabricius) foi a espĂ©cie mais comum (24,6%), seguida por Eulaema meriana (Olivier) (14,6%), Euglossa amazonica Dressler (10,5%), Eulaema nigrita Lepeletier (10,5%) e Eulaema pseudocingulata (Oliveira) (7,2%). Cineol foi a substância que atraiu maior nĂşmero de indivĂduos (23,8%) e metil salicilato o maior nĂşmero de espĂ©cies (28) para ambos os mĂ©todos de coleta. Foram coletados 31 indivĂduos pertencentes a 9 espĂ©cies portando polinários. O nĂşmero acumulado de espĂ©cies coletadas na regiĂŁo estabilizou a partir da 48ÂŞ coleta. Poucas espĂ©cies foram abundantes, a maioria representada por menos que 50 indivĂduos. A falta de um protocolo amostral padronizado tem limitado comparações entre trabalhos realizados em diferentes regiões. Contudo, os resultados aqui apresentados indicam que o Acre apresenta elevada riqueza dessas abelhas
Upregulation of vascular endothelial growth factor (VEGF) in the retinas of transgenic mice overexpressing interleukin-1Ăź (IL-1Ăź) in the lens and mice undergoing retinal degeneration
IL-1Ăź is a pro-inflammatory agent associated
with angiogenesis and increased vascular permeability.
To determine whether IL-1Ăź elicits these responses
through an upregulation of VEGF, transgenic mice that
overexpress IL-1Ăź in the lens were evaluated at various
time points for the localization of VEGF, the location
and extent of blood-retinal barrier (BRB) breakdown,
and the origin and extent of neovascularization (NV). In
homozygous and heterozygous transgenic mice, but not
controls, intense VEGF immunoreactivity was scattered
throughout the retina at postnatal days 5-7 (P5-7), just
after the onset of inflammatory cell infiltration. VEGF
staining in the retina remained widespread, but weak
from P9-15. Beginning at P15, the intensity of VEGF
immunoreactivity achieved a second peak, which it
maintained through adulthood. This peak coincided with
significant retinal destruction due to massive
inflammation. The onset of BRB breakdown coincided
with the upregulation of VEGF (P5-7) and widespread
BRB breakdown was demonstrated from about P9. From
P9-12, aggregates of cells positive for Griffonia
simplicifolia isolectin-B4, a marker for vascular
endothelial cells, formed on the retinal surface. These
cells migrated into the retina at P12-15 with the more
superficial cells forming a network of vessels and the
deeper cells remaining in small clusters, thus
demonstrating that NV occurs much later than BRB breakdown. Non-transgenic FVB/N mice, which
undergo retinal degeneration beginning at about P9, also
demonstrate the latter peak of VEGF upregulation and
the accompanying BRB breakdown, but not the early
upregulation. VEGF immunostaining of transgenic and
non-transgenic mouse retinas was eliminated by preincubation
of the VEGF antibodies with VEGF peptide.
The data suggest that the early peak of VEGF upregulation (P5-7) and its accompanying BRB
breakdown is due to IL-1Ăź expression and is likely to be
dependent on inflammatory cell infiltration. The latter
peak appears to be related to retinal destruction
An Agency Theory Perspective on Corruption in Sport: The Case of the International Olympic Committee
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