760 research outputs found
Recommended from our members
Cloud-base vertical velocity statistics: a comparison between an atmospheric mesoscale model and remote sensing observations
The statistics of cloud-base vertical velocity simulated by the non-hydrostatic mesoscale model AROME are compared with Cloudnet remote sensing observations at two locations: the ARM SGP site in Central Oklahoma, and the DWD observatory at Lindenberg, Germany. The results show that, as expected, AROME significantly underestimates the variability of vertical velocity at cloud-base compared to observations at their nominal resolution; the standard deviation of vertical velocity in the model is typically 4-6 times smaller than observed, and even more during the winter at Lindenberg. Averaging the observations to the horizontal scale corresponding to the physical grid spacing of AROME (2.5 km) explains 70-80% of the underestimation by the model. Further averaging of the observations in the horizontal is required to match the model values for the standard deviation in vertical velocity. This indicates an effective horizontal resolution for the AROME model of at least 4 times the physically-defined grid spacing. The results illustrate the need for special treatment of sub-grid scale variability of vertical velocities in kilometer-scale atmospheric models, if processes such as aerosol-cloud interactions are to be included in the future
Impact of reindeer grazing on ground-dwelling Carabidae and Curculionidae assemblages in Lapland
Reindeer Rangifer tarandus L. grazing shapes forest vegetation, microclimate, and
soil respiration in Lapland, especially due to grazing on lichens (Cladina). We studied
how these changes and their magnitude affect ground-dwelling species of beetle
families Carabidae (predators) and Curculionidae (herbivores), by using pitfall traps
to collect invertebrates from pairs of grazed and ungrazed study plots over a wide
range of site types. Changes in abundance, composition, richness and diversity of
beetle assemblage were tested in relation to magnitude of the impacts on vegetation.
The species compositions of Carabidae and Curculionidae differed between grazed
and ungrazed plots in all sites. The relative difference between grazed and ungrazed
plots in the number of individuals increased linearly with the impact of reindeer on
vegetation cover. Carabid beetles, as a family, were more common in grazed plots in
all sites. Curculionid beetles were more common in ungrazed plots in the birch
dominated sites. This difference was mainly due to the species that feeds on
deciduous leaves. In the pine dominated sites with high Cladina cover and more
changes in ground vegetation, the number of curculionids feeding on conifers was
higher in grazed plots. Species richness and diversity (Hâ) of both families were higher
in grazed plots. Of the total 27 species, 11 were found only in grazed plots, while not
a single species was found only in ungrazed plots. The relative difference between
plots in diversity and evennes (Hâ/Hâmax) had humped response to the difference in
Cladina cover. The diversity values were greater in grazed plots at the intermediate
levels of grazing impact, and only in sites with very low or extremely high Cladina
cover difference was the diversity higher in ungrazed plots. The response of beetle
diversity resembled the hypotheses suggested for the relationship between grazing and
vegetation diversity: greatest positive effect at intermediate grazing intensity and
negative effects at unproductive sites
The search for common anthropogenic impacts on biodiversity : a global network
We introduce an initiative to assess and compare landscape changes related to human activities on a global scale, using a single
group of invertebrates. The GLOBENET programme uses common field methodology (pitfall trapping), to appraise assemblages
of ground beetles (Coleoptera, Carabidae) in visually-similar land-mosaics (urban-rural gradients). Carabids were selected as the
focal taxon as they are sufficiently varied (both taxonomically and ecologically), abundant and sensitive to the environment.
However, work on other taxa is comparable with the GLOBENET framework. The continuum of decreasing human pressure
from city centres into the surrounding countryside was selected to represent human-caused disturbance for this initial stage of
GLOBENET because these gradients can be found virtually all over the world. Through the broad-scale assessment envisioned
in the GLOBENET programme, we seek to separate general, repeated effects on biodiversity from those that depend on local
environments or particular biotic assemblages. Based on this understanding we aim to develop simple tools and protocols for
assessing ecological effects of human-caused landscape changes, which could help to sustainably manage landscapes for biodiversity
and for human requirements. For instance, the response of different functional groups of carabids to these landscape
changes may help guide management practices. Further GLOBENET developments and information are available at our website:
http://www.helsinki.fi/science/globenet
Ophiostoma spp. associated with pine- and spruce-infesting bark beetles in Finland and Russia
The timber and pulp industries of Finland rely heavily on importations from Russia as source of raw timber. These imports raise the risk of accidentally importing forest pests and pathogens, especially bark beetles and their associated fungi, into Finland. Although ophiostomatoid fungi have previously been reported from Finland and Russia, the risks of accidentally moving these fungi has prompted a first survey to compare the diversity of conifer-infesting bark beetles and associated fungi from boreal forests on both sides of the Finnish-Russian border. The aim of the present study was to identify and characterise Ophiostoma species isolated in association with 11 bark beetle species infesting Pinus sylvestris and Picea abies during this survey in the eastern parts of Finland and neighbouring Russia. Fungal isolates were grouped based on morphology and representatives of each morphological group were subjected to DNA sequence comparisons of the internal transcribed spaced region (ITS1, 5.8S, ITS2) and ÎČ-tubulin gene region. A total of 15 species of Ophiostoma were identified, including seven known species, five new species, and three species for which the identity remains uncertain. In the O. piceae-complex we identified O. canum, O. floccosum, O. karelicum and O. rachisporum sp. nov., and related to these, some isolates belonging to the European clade of O. minus in the O. minus-complex. Ophiostoma bicolor and O. fuscum sp. nov. were identified in the O. ips-complex, while O. ainoae, O. brunneo-ciliatum, O. tapionis sp. nov. and O. pallidulum sp. nov. were shown to group close to, but not in a strict monophyletic lineage with species of the O. ips-complex. Together with a single O. abietinum-like isolate, the only species that grouped close to the Sporothrix schenckii- O. stenoceras complex, was O. saponiodorum sp. nov
Leaf litter and the small-scale distribution of carabid beetles (Coleoptera, Carabidae) in the boreal forest
Smoking in pregnancy, adolescent mental health and cognitive performance in young adult offspring: results from a matched sample within a Finnish cohort
The association between prenatal exposure to maternal cigarette smoking (PEMCS) and adult cognition is debated, including if there are differences according to sex. We aimed to determine if there are associations between PEMCS and cognition in early adulthood in men and women and examine if observed associations were mediated by adolescent mental health factors that are associated with cognition, namely psychotic-like experiences (PLEs), inattention and hyperactivity, and other externalizing behaviors.
Participants were 471 individuals drawn from the general population-based Northern Finland 1986 Birth Cohort (NFBC 1986) followed up from pregnancy and birth to early adulthood; individuals with PEMCS were matched with those without PEMCS by socioeconomic and demographic factors. Cognitive performance in adulthood was assessed with a range of tests and their association with PEMCS was measured by sex using hierarchical linear regression, unadjusted and then controlling for potential confounders, mediators and moderators, including adolescent mental health factors.
There were no associations between PEMCS and cognitive scores in females. In males, there were associations with vocabulary (beta = -0.444, 95% CI: -0.783, -0.104) and matrix reasoning (beta = -0.379, 95% CI: -0.711, -0.047).
While associations between PEMCS and cognition were limited, observed findings with measures of general intelligence in males contribute to suggestions of differences in response to PEMCS by sex. Furthermore, observed associations may be partly mediated by earlier inattention and hyperactivity. Findings add support to efforts aimed to eliminate smoking in pregnancy.The Northern Finland Birth Cohort 1986 is funded by the University of Oulu, University Hospital of Oulu, Academy of Finland, Sigrid Juselius Foundation, European Commission (EURO-BLCS, Framework 5 award QLG1-CT-2000- 01643), and NIH/NIMH (5R01MH63706:02). Cambridge Cognition Ltd. provided support in the form of salaries for author Jennifer H. Barnett
Long-term prognosis of haemangioblastoma of the CNS: Impact of von Hippel-Lindau disease
Peer reviewe
The very massive X-ray bright binary system Wack 2134 (= WR 21a)
From the radial velocities of the N IV λ4058 and He II λ4686 emission lines, and the N v λ4604-20 absorption lines, determined in digital spectra, we report the discovery that the X-ray bright emission line star Wack 2134 (= WR 21a) is a spectroscopic binary system with an orbital period of 31.673 ± 0.002 d. With this period, the N IV and He II emission and N v absorption lines, which originate in the atmosphere of the primary component, define a rather eccentric binary orbit (e = 0.64 ± 0.03). The radial velocity variations of the N v absorptions have a lower amplitude than those of the He II emission. Such a behaviour of the emission line radial velocities could be due to distortions produced by a superimposed absorption component from the companion. High-resolution echelle spectra observed during the quadrature phases of the binary show H and He II absorptions of both components with a radial velocity difference of about 541 km s-1. From this difference, we infer quite high values of the minimum masses, of about 87 and 53 Mâ for the primary and secondary components, respectively, if the radial velocity variations of the He II emission represent the true orbit of the primary. No He i absorption lines are observed in our spectra. Thus, the secondary component in the Wack 2134 binary system appears to be an early O-type star. From the presence of H, He II and N v absorptions, and N IV and C IV emissions, in the spectrum of the primary component, it most clearly resembles those of Of/WNLha-type stars.Facultad de Ciencias AstronĂłmicas y GeofĂsicasInstituto Argentino de RadioastronomĂ
The DLV System for Knowledge Representation and Reasoning
This paper presents the DLV system, which is widely considered the
state-of-the-art implementation of disjunctive logic programming, and addresses
several aspects. As for problem solving, we provide a formal definition of its
kernel language, function-free disjunctive logic programs (also known as
disjunctive datalog), extended by weak constraints, which are a powerful tool
to express optimization problems. We then illustrate the usage of DLV as a tool
for knowledge representation and reasoning, describing a new declarative
programming methodology which allows one to encode complex problems (up to
-complete problems) in a declarative fashion. On the foundational
side, we provide a detailed analysis of the computational complexity of the
language of DLV, and by deriving new complexity results we chart a complete
picture of the complexity of this language and important fragments thereof.
Furthermore, we illustrate the general architecture of the DLV system which
has been influenced by these results. As for applications, we overview
application front-ends which have been developed on top of DLV to solve
specific knowledge representation tasks, and we briefly describe the main
international projects investigating the potential of the system for industrial
exploitation. Finally, we report about thorough experimentation and
benchmarking, which has been carried out to assess the efficiency of the
system. The experimental results confirm the solidity of DLV and highlight its
potential for emerging application areas like knowledge management and
information integration.Comment: 56 pages, 9 figures, 6 table
- âŠ