5,003 research outputs found
The Cluster Abundance in Flat and Open Cosmologies
We use the galaxy cluster X-ray temperature distribution function to
constrain the amplitude of the power spectrum of density inhomogeneities on the
scale corresponding to clusters. We carry out the analysis for critical density
universes, for low density universes with a cosmological constant included to
restore spatial flatness and for genuinely open universes. That clusters with
the same present temperature but different formation times have different
virial masses is included. We model cluster mergers using two completely
different approaches, and show that the final results from each are extremely
similar. We give careful consideration to the uncertainties involved, carrying
out a Monte Carlo analysis to determine the cumulative errors. For critical
density our result agrees with previous papers, but we believe the result
carries a larger uncertainty. For low density universes, either flat or open,
the required amplitude of the power spectrum increases as the density is
decreased. If all the dark matter is taken to be cold, then the cluster
abundance constraint remains compatible with both galaxy correlation data and
the {\it COBE} measurement of microwave background anisotropies for any
reasonable density.Comment: Uuencoded package containing LaTeX file (uses mn.sty) plus 7
postscript figures incorporated using epsf. Total length 10 pages. Final
version, to appear MNRAS. COBE comparison changed to 4yr data. No change to
results or conclusion
Mapping road network communities for guiding disease surveillance and control strategies
Human mobility is increasing in its volume, speed and reach, leading to the
movement and introduction of pathogens through infected travelers. An
understanding of how areas are connected, the strength of these connections and
how this translates into disease spread is valuable for planning surveillance
and designing control and elimination strategies. While analyses have been
undertaken to identify and map connectivity in global air, shipping and
migration networks, such analyses have yet to be undertaken on the road
networks that carry the vast majority of travellers in low and middle income
settings. Here we present methods for identifying road connectivity
communities, as well as mapping bridge areas between communities and key
linkage routes. We apply these to Africa, and show how many highly-connected
communities straddle national borders and when integrating malaria prevalence
and population data as an example, the communities change, highlighting regions
most strongly connected to areas of high burden. The approaches and results
presented provide a flexible tool for supporting the design of disease
surveillance and control strategies through mapping areas of high connectivity
that form coherent units of intervention and key link routes between
communities for targeting surveillance.Comment: 11 pages, 5 figures, research pape
Early Enrichment of the Intergalactic Medium and its Feedback on Galaxy Formation
Supernova-driven outflows from early galaxies may have had a large impact on
the kinetic and chemical structure of the intergalactic medium (IGM). We use
three-dimensional Monte Carlo cosmological realizations of a simple linear
peaks model to track the time evolution of such metal-enriched outflows and
their feedback on galaxy formation. We find that at most 30% of the IGM by
volume is enriched to values above 10^-3 solar in models that only include
objects that cool by atomic transitions. The majority of enrichment occurs
relatively early (5 < z < 12) and resulting in a mass-averaged cosmological
metallicity between 10^-3 and 10^-1.5 solar. The inclusion of Population III
objects that cool through H2 line emission has only a minor impact on these
results: increasing the mean metallicity and filling factor by at most a factor
of 1.4, and moving the dawn of the enrichment epoch to a redshift of
approximately 14 at the earliest. Thus enrichment by outflowing galaxies is
likely to have been incomplete and inhomogeneous, biased to the areas near the
starbursting galaxies themselves. Models with a 10% star formation efficiency
can satisfactorily reproduce the nearly constant (2 < z < 5, Z approximately
3.5 x 10^-4 solar) metallicity of the low column density Ly-alpha forest
derived by Songaila (2001), an effect of the decreasing efficiency of metal
loss from larger galaxies. Finally, we show that IGM enrichment is intimately
tied to the ram-pressure stripping of baryons from neighboring perturbations.
This results in the suppression of at least 20% of the dwarf galaxies in the
mass range 10^8.5 to 10^9.5 solar, in all models with filling factors greater
than 2%, and an overall suppression of approximately 50% of dwarf galaxies in
the most observationally-favored model.Comment: 8 pages, 5 figures, accepted to Ap
Cosmological Implications of the Fundamental Relations of X-ray Clusters
Based on the two-parameter family nature of X-ray clusters of galaxies
obtained in a separate paper, we discuss the formation history of clusters and
cosmological parameters of the universe. Utilizing the spherical collapse model
of cluster formation, and assuming that the cluster X-ray core radius is
proportional to the virial radius at the time of the cluster collapse, the
observed relations among the density, radius, and temperature of clusters imply
that cluster formation occurs in a wide range of redshift. The observed
relations favor the low-density universe. Moreover, we find that the model of
is preferable.Comment: 7 pages, 4 figures. To be published in ApJ Letter
INFLUÊNCIA DO CONSUMO DE FARINHA DE YACON NA GLICEMIA, PERFIL LIPÍDICO, COMPOSIÇÃO CORPORAL E CONSUMO ALIMENTAR COM MULHERES COM DIABETES TIPO 2 E COM EXCESSO DE PESO
O yacon é uma raiz tuberosa ainda pouco consumida no Brasil, sendo ultimamente muito estudada na saúde humana devido à presença dos fruto-oligossacarídeos (FOS). No presente estudo foi produzida a farinha de yacon e avaliou-se a influência de sua ingestão por mulheres portadoras de diabetes tipo 2 durante 60 dias (T0: início; T30: após 30 dias; T60: após 60 dias). As participantes foram divididas em grupo controle (GC: n = 29) e grupo yacon (GY: n = 23), que consumiu 11 g de FOS presentes na farinha de yacon. Foram avaliados os parâmetros de glicose em jejum, perfil lipídico, composição corporal e consumo alimentar, adotando um nível de 5% de significância nos testes estatísticos. A farinha de yacon apresentou 6,50% de rendimento, 1,15% de umidade, 4,52% de proteína total, 0,33% de gordura, 2,94% de cinzas, 10,23% de fibra bruta, 91,0% de carboidratos totais e 35,06% de FOS. No GY foi encontrado aumento significativo do HDL entre os três tempos do estudo (p < 0,0001) e também de colesterol total de T0 para T60 (p = 0,03) e redução significativa do percentual de gordura corporal de T0 para T60 (p = 0,03). No GC, um aumento significativo foi encontrado no HDL de T0 e T30 para T60 (p < 0,0001) e de triacilgliceróis de T0 para T30 (p = 0,01). Em relação ao consumo alimentar, houve diferença significativa entre os grupos em relação às fibras em T30 e T60 (p = 0,01/p = 0,009). O GY apresentou uma redução significativa de calorias (p = 0,02) e ácidos graxos saturados (p = 0,02) de T0 para T60, enquanto o GC apresentou redução significativa da ingestão de carboidratos de T0 para T30 (p = 0,03). A diminuição do percentual de gordura corporal e da ingestão energética do GY sugere um possível efeito benéfico dos FOS
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