2,197 research outputs found
Sex differences in settlement behaviour and condition of chiffchaffs Phylloscopus collybita at a wintering site in Portugal. Are females doing better?
In passerine birds, males are generally larger
and dominant over females. In line with the dominance
theory, in all known differential migrant passerines, females
migrate further than males. However, there are
alternative explanations to the dominance hypothesis,
including the specialisation hypothesis, predicting that
females should do better than males in habitats and/or
regions to which they are specially adapted, and where
they predominate in numbers. Few studies have aimed
at comparing the behaviour and condition of males and
females wintering in locations largely dominated by
female birds. We studied a partly nomadic species, the
common chiffchaff Phylloscopus collybita, at a wintering
site in Portugal. Most individuals caught at this site
were transients. The only consistent and relatively
powerful predictor of settlement behaviour was sex.
Almost all the birds that settled in the study area were
female, while there was an almost even sex ratio in the
transient sample. Females had higher muscle and postjuvenile
moult scores when first captured. In addition, there was a significant sex-based difference in mass
trajectories, with females maintaining body mass and
males losing body mass when settled at the study site.
Results from this study suggest that the poor performance
of males was either due to inferior male
competitive ability in a region/habitat where females
predominate and/or it resulted from the fact that males
that reach these wintering grounds are of inferior individual
quality
The white-chinned petrel procellaria aequinoctialis population of the Falkland Islands
A survey of all known colonies of the White-chinned Petrel Procellaria aequinoctialis within the Falkland Islands was conducted during
the austral summers of 2004/05 and 2005/06. From these surveys, a minimum population of 55 pairs was observed. Most of these were on
Kidney and New islands, with a very small colony on Bottom Island in Port William. Although evidence of a decrease in the size of the
population on Kidney Island is limited, the population in the Falklands is likely historically to have been small
Low breeding success and sharp population decline at the largest known Falkland skua colony
The Falkland skua Stercorarius antarctica antarctica
is a poorly known seabird. Demographic studies at
the largest known colony of this taxon revealed a sharp
population decline (47%) in just 5 years, between 2004 and
2009. The decline seems to be linked with a chronic low
breeding success in the recent years and is consistent with a
situation of virtually zero recruitment. The ultimate causes
of the decline are, as of yet, unknown, but plausible explanations
are examined and discussed. The reported population
trends should be the cause of some concern, and more
research and monitoring are desired
Are blackcaps sylvia atricapilla differential distance migrants by sex?
Aims: To investigate if male and female blackcaps show differences in the amplitude of migratory
movements.
Methods: The extent of movements of male and female British blackcaps were analysed using ringing recovery
records. Furthermore, through a literature review and the collection of original field data, the
sex-ratios of blackcap samples taken at several latitudes in Europe and Africa were compared.
Results: There were no differences between British male and female blackcaps in relation to wintering
latitude or distance moved during migration. Sex-ratios of blackcap samples were quite even across a wide
range of latitudes. However, there was a significantly larger proportion of females in samples of birds that
wintered in Africa.
Conclusions: Laboratory data and morphological studies have yielded inconclusive results in relation to
the question of whether or not European blackcaps are differential distance migrants. The results from the
present study suggest that British blackcaps are not differential distance migrants. Furthermore, there is,
at best, only a weak latitudinal segregation of the sexes of blackcaps wintering in Europe and Africa. The
slightly higher proportion of males in European samples, when compared to Africa, could result from a
differential behaviour of males and females in some blackcap populations, or simply result from differences
in the sex-ratios of blackcap populations breeding and wintering in different areas. An absence of
a pronounced latitudinal segregation in the size-monomorphic blackcap is interesting, and contrasts
with the pattern found in more sexually dimorphic species, such as the chiffchaff Phylloscopus collybita
or the robin Erithacus rubecula
notes on the present distribution and conservation of the sooty mangabey (Cercocebus atys) in Guinea-Bissau, West Africa
UIDB/04038/2020 UIDP/04038/2020The West-African sooty mangabey (Cercocebus atys) is threatened by habitat loss, hunting for meat consumption, and mortality during crop-foraging events. The species’ overall demographic trend is unknown. Presence and distribution in Guinea-Bissau, a country neighbored by Senegal and Republic of Guinea, was confirmed in 1946 but the species was declared extinct in 1989 and not observed in subsequent countrywide expeditions. Narratives of its presence across southern Guinea-Bissau are scattered in reports and occurrence in the eastern part was reported in 2017, but the limits of its distribution are currently unknown. Here, we present recent geo-referenced visual and molecular-based records of the sooty mangabey for three protected areas in southern Guinea-Bissau collected as part of a region-wide survey. Individuals were observed in Cufada Lagoons Natural Park (2015) and Dulombi National Park (NP) (2016) and photographed in Boé NP (2007, 2015 and 2020). Thirty-six samples collected in Boé NP (2017) were identified as sooty mangabey using a 402 base pair fragment of the mitochondrial cytochrome b gene. Our work suggests a wider distribution in Guinea-Bissau than previously described, augments knowledge of the populations’ current habitat use and threats, and has implications for efforts to conserve the species in West Africa. Considering the sooty mangabey as the reservoir of the simian immunodeficiency virus that led to the human variant, HIV-2, confirmation that the Guinea-Bissau population is not extinct may lead to a better understanding of early viral jump to humans and consequent epidemic spread, specifically of the HIV-2 Subgroup A. We highlight the need for extra conservation measures by Guinea-Bissau authorities.publishersversionpublishe
Differential migration of chiffchaffs Phylloscopus collybita and P. ibericus in Europe and Africa
Differential migration is a widespread, but poorly understood, phenomenon in birds. In
this paper, we present the first detailed field study of differential migration in the Old
World warbler (Sylviidae) family. We studied two chiffchaff Phylloscopus [collybita ]
semispecies: the common chiffchaff P. [c. ] collybita and the Iberian chiffchaff P. [c. ]
ibericus. Using data collected at several latitudes in Europe and Africa, we present
convincing evidence for differential distance migration of sexes in chiffchaffs, with
females moving further than males. Interestingly, while there was a pronounced
gradient in the sex-ratios in Europe and North Africa (with an increasing proportion of
females with declining latitude), no clear pattern was found south of the Sahara, where
sex-ratios were more male-biased than predicted by a simple latitude model. This
suggests that, amongst the chiffchaffs wintering in West Africa, a large proportion is
composed by Iberian birds, and provides support to previous suggestions that Iberian
chiffchaffs are long distance migrants. Results from detailed studies in Senegal also
show that chiffchaffs display differential timing of spring migration, with males leaving
the winter quarters considerably earlier than females. The results are discussed in the
framework of the three main (non-mutually exclusive) hypotheses attempting to explain
the latitudinal segregation of the sexes. Given the relative failure of standard
comparative studies to discriminate between competing single-factor hypotheses to
explain differential migration, it is argued that the chiffchaff species complex might be
particularly suited to study this issue using a new approach suggested by Cristol et al.
(1999): detailed (further) comparisons between closely related species (such as the
common and the Iberian chiffchaffs) could help identifying the key factors to be
incorporated into optimality models that can predict relative distance of migration of
different sex or age classes
Oxigenación con membrana extracorpórea en el paciente COVID-19: resultados del Registro Español ECMO-COVID de la Sociedad Española de Cirugía Cardiovascular y Endovascular (SECCE)
Background and aim: COVID-19 patients with severe heart or respiratory failure are potential candidates for extracorporeal membrane oxygenation (ECMO). Indications and management of these patients are unclear. Our aim is to describe the results of a prospective registry of COVID-19 patients treated with ECMO. Methods: An anonymous prospective registry of COVID-19 patients treated with veno-arterial (V-A) or veno-venous (V-V) ECMO was created on march 2020. Clinical, analytical and respiratory preimplantation variables, implantation data and post-implantation course data were recorded. The primary endpoint was all cause in-hospital mortality. Secondary events were functional recovery and the combined endpoint of mortality and functional recovery in patients followed at least 3 months after discharge. Results: Three hundred and sixty-six patients from 25 hospitals were analyzed, 347 V-V ECMO and 18 V-A ECMO patients (mean age 52.7 and 49.5 years respectively). Patients with V-V ECMO were more obese, had less frequently organ damage other than respiratory failure and needed less inotropic support; Thirty three percent of V-A ECMO and 34.9% of V-A ECMO were discharged (P = NS). Hospital mortality was non-significantly different, 56.2% versus 50.9% respectively, mainly during ECMO therapy and mostly due to multiorgan failure. Other 51 patients (14%) remained admitted. Mean follow-up was 196 +/- 101.7 days (95%CI: 170.8-221.6). After logistic regression, body weight (OR 0.967, 95%CI: 0.95-0.99, P = 0.004) and ECMO implantation in the own centre (OR 0.48, 95%CI: 0.27-0.88, P = 0.018) were protective for hospital mortality. Age (OR 1.063, 95%CI: 1.005-1.12, P = 0.032), arterial hypertension (3.593, 95%CI: 1.06-12.19, P = 0.04) and global (2.44, 95%CI: 0.27-0.88, P = 0.019), digestive (OR 4,23, 95%CI: 1.27-14.07, P = 0.019) and neurological (OR 4.66, 95%CI: 1.39-15.62, P = 0.013) complications during ECMO therapy were independent predictors of primary endpoint occurrence. Only the post-discharge day at follow-up was independent predictor of both secondary endpoints occurrence. Conclusions: Hospital survival of severely ill COVID-19 patients treated with ECMO is near 50%. Age, arterial hypertension and ECMO complications are predictors of hospital mortality, and body weight and implantation in the own centre are protective. Functional recovery is only predicted by the follow-up time after discharge. A more homogeneous management of these patients is warranted for clinical results and future research optimization. (C) 2022 Sociedad Espanola de Cirugia Cardiovascular y Endovascular. Published by Elsevier Espana, S.L.U
Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV
Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an
Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis
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