1,099 research outputs found
Continuum and Emission-Line Properties of Broad Absorption Line Quasars
We investigate the continuum and emission-line properties of 224 broad
absorption line quasars (BALQSOs) with 0.9<z<4.4 drawn from the Sloan Digital
Sky Survey (SDSS) Early Data Release (EDR), which contains 3814 bona fide
quasars. We find that low-ionization BALQSOs (LoBALs) are significantly
reddened as compared to normal quasars, in agreement with previous work.
High-ionization BALQSOs (HiBALs) are also more reddened than the average
nonBALQSO. Assuming SMC-like dust reddening at the quasar redshift, the amount
of reddening needed to explain HiBALs is E(B-V)~0.023 and LoBALs is
E(B-V)~0.077 (compared to the ensemble average of the entire quasar sample). We
find that there are differences in the emission-line properties between the
average HiBAL, LoBAL, and nonBAL quasar. These differences, along with
differences in the absorption line troughs, may be related to intrinsic quasar
properties such as the slope of the intrinsic (unreddened) continuum; more
extreme absorption properties are correlated with bluer intrinsic continua.
Despite the differences among BALQSO sub-types and nonBALQSOs, BALQSOs appear
to be drawn from the same parent population as nonBALQSOs when both are
selected by their UV/optical properties. We find that the overall fraction of
traditionally defined BALQSOs, after correcting for color-dependent selection
effects due to different SEDs of BALQSO and nonBALQSOs, is 13.4+/-1.2% and
shows no significant redshift dependence for 1.7<z<3.45. After a rough
completeness correction for the effects of dust extinction, we find that
approximately one in every six quasars is a BALQSO.Comment: 35 pages, 11 figures (1 color), 1 table; accepted by A
Вплив екологічного стану Донецького регіону на його демографічний розвиток
В статті розглянуто важливу проблему впливу забрудненості навколишнього природного середовища на
захворюваність та смертність в регіоні.
Визначено кореляційну залежність між обсягом
викидів забруднюючих речовин та окремими видами
захворюваності, а також ступінь їх впливу, побудовано
функції, що описують їх.В статье рассмотрена важная проблема влияния
загрязненности окружающей естественной среды на
заболеваемость и смертность в регионе.
Определена корреляционная зависимость между
объемом выбросов загрязняющих веществ и отдельными видами заболеваемости, а также степень их влияния,
построены функции, которые описывают их.In the article the important problem of influence of
muddiness of natural environment is considered on morbidity
and death rate in a region.
Certainly cross-correlation dependence between the
volume of extrass of contaminents and separate types of
morbidity, and also degree of their influence, functions which
describe them are built.
Keywords: environment
Interactions, star formation and AGN activity
It has long been known that galaxy interactions are associated with enhanced
star formation. In a companion paper, we explored this connection by applying a
variety of statistics to SDSS data. In particular, we showed that specific star
formation rates of galaxies are higher if they have close neighbours. Here we
apply exactly the same techniques to AGN in the survey, showing that close
neighbours are not associated with any similar enhancement of nuclear activity.
Star formation is enhanced in AGN with close neighbours in exactly the same way
as in inactive galaxies, but the accretion rate onto the black hole, as
estimated from the extinction-corrected [O III] luminosity, is not influenced
by the presence or absence of companions. Previous work has shown that galaxies
with more strongly accreting black holes contain more young stars in their
inner regions. This leads us to conclude that star formation induced by a close
companion and star formation associated with black hole accretion are distinct
events. These events may be part of the same physical process, for example a
merger, provided they are separated in time. In this case, accretion onto the
black hole and its associated star formation would occur only after the two
interacting galaxies have merged. The major caveat in this work is our
assumption that the extinction-corrected [O III] luminosity is a robust
indicator of the bolometric luminosity of the central black hole. It is thus
important to check our results using indicators of AGN activity at other
wavelengths.Comment: v1: 10 pages, 9 figures, submitted for publication in Monthly
Notices; v2: accepted, minor changes in summary and reference list update
PhyloPat: an updated version of the phylogenetic pattern database contains gene neighborhood
Phylogenetic patterns show the presence or absence of certain genes in a set of full genomes derived from different species. They can also be used to determine sets of genes that occur only in certain evolutionary branches. Previously, we presented a database named PhyloPat which allows the complete Ensembl gene database to be queried using phylogenetic patterns. Here, we describe an updated version of PhyloPat which can be queried by an improved web server. We used a single linkage clustering algorithm to create 241 697 phylogenetic lineages, using all the orthologies provided by Ensembl v49. PhyloPat offers the possibility of querying with binary phylogenetic patterns or regular expressions, or through a phylogenetic tree of the 39 included species. Users can also input a list of Ensembl, EMBL, EntrezGene or HGNC IDs to check which phylogenetic lineage any gene belongs to. A link to the FatiGO web interface has been incorporated in the HTML output. For each gene, the surrounding genes on the chromosome, color coded according to their phylogenetic lineage can be viewed, as well as FASTA files of the peptide sequences of each lineage. Furthermore, lists of omnipresent, polypresent, oligopresent and anticorrelating genes have been included. PhyloPat is freely available at http://www.cmbi.ru.nl/phylopat
A regularity class for the roots of nonnegative functions
We investigate the regularity of the positive roots of a non-negative
function of one-variable. A modified H\"older space is
introduced such that if then . This provides sufficient conditions to overcome the usual limitation
in the square root case () for H\"older functions that
need be no more than in general. We also derive bounds on the wavelet
coefficients of , which provide a finer understanding of its local
regularity.Comment: 12 page
Asymmetric Reproductive Isolation between Two Sympatric Annual Killifish with Extremely Short Lifespans
BACKGROUND: Interspecific reproductive isolation is typically achieved by a combination of intrinsic and extrinsic barriers. Behavioural isolating barriers between sympatric, closely related species are often of primary importance and frequently aided by extrinsic factors causing spatial and temporal interspecific separation. Study systems with a severely limited role of extrinsic factors on reproductive isolation may provide valuable insights into how reproductive isolation between sympatric species is maintained. We used no-choice experimental set-up to study reproductive barriers between two closely related sympatric African killifish species, Nothobranchius furzeri and Nothobranchius orthonotus. These fish live in small temporary savannah pools and have complete spatial and temporal overlap in reproductive activities and share a similar ecology. PRINCIPAL FINDINGS: We found that the two species display largely incomplete and asymmetric reproductive isolation. Mating between N. furzeri males and N. orthonotus females was absent under standard experimental conditions and eggs were not viable when fish were forced to mate in a modified experimental setup. In contrast, male N. orthonotus indiscriminately mated with N. furzeri females, the eggs were viable, and offspring successfully hatched. Most spawnings, however, were achieved by male coercion and egg production and embryo survival were low. Behavioural asymmetry was likely facilitated by mating coercion from larger males of N. orthonotus and at relatively low cost to females. Interestingly, the direction of asymmetry was positively associated with asymmetry in post-mating reproductive barriers. SIGNIFICANCE: We showed that, in fish species with a promiscuous mating system and multiple matings each day, selection for strong mate preferences was relaxed. This effect was likely due to the small proportion of resources allocated to each single mating and the high potential cost to females from mating refusal. We highlight and discuss the fact that males of rarer species may often coercively mate with females of a related, more abundant species
Biological Invasions: Recommendations for U.S. Policy and Management
The Ecological Society of America has evaluated current U.S. national policies and practices on biological invasions in light of current scientific knowledge. Invasions by harmful nonnative species are increasing in number and area affected; the damages to ecosystems, economic activity, and human welfare are accumulating. Without improved strategies based on recent scientific advances and increased investments to counter invasions, harm from invasive species is likely to accelerate. Federal leadership, with the cooperation of state and local governments, is required to increase the effectiveness of prevention of invasions, detect and respond quickly to new potentially harmful invasions, control and slow the spread of existing invasions, and provide a national center to ensure that these efforts are coordinated and cost effective. Specifically, the Ecological Society of America recommends that the federal government take the following six actions: (1) Use new information and practices to better manage commercial and other pathways to reduce the transport and release of potentially harmful species; (2) Adopt more quantitative procedures for risk analysis and apply them to every species proposed for importation into the country; (3) Use new cost-effective diagnostic technologies to increase active surveillance and sharing of information about invasive species so that responses to new invasions can be more rapid and effective; (4) Create new legal authority and provide emergency funding to support rapid responses to emerging invasions; (5) Provide funding and incentives for cost-effective programs to slow the spread of existing invasive species in order to protect still uninvaded ecosystems, social and industrial infrastructure, and human welfare; and (6) Establish a National Center for Invasive Species Management (under the existing National Invasive Species Council) to coordinate and lead improvements in federal, state, and international policies on invasive species. Recent scientific and technical advances provide a sound basis for more cost-effective national responses to invasive species. Greater investments in improved technology and management practices would be more than repaid by reduced damages from current and future invasive species. The Ecological Society of America is committed to assist all levels of government and provide scientific advice to improve all aspects of invasive-species management
Integral field spectroscopy of four lensed quasars: analysis of their neighborhood and evidence for microlensing
CONTEXT: Gravitationally lensed quasars constitute an independent tool to
derive H0 through time-delays; they offer as well the opportunity to study the
mass distribution and interstellar medium of their lensing galaxies and,
through microlensing they also allow one to study details of the emitting
source. AIMS: For such studies, one needs to have an excellent knowledge of the
close environment of the lensed images in order to model the lensing potential:
this means observational data over a large field-of-view and spectroscopy at
high spatial resolution. METHODS: We present VIMOS integral field observations
around four lensed quasars: HE 0230-2130, RX J0911.4+0551, H 1413+117 and B
1359+154. Using the low, medium and high resolution modes, we study the quasar
images and the quasar environments, as well as provide a detailed report of the
data reduction. RESULTS: Comparison between the quasar spectra of the different
images reveals differences for HE 0230-2130, RX J0911.4+0551 and H 1413+117:
flux ratios between the images of the same quasar are different when measured
in the emission lines and in the continuum. We have also measured the redshifts
of galaxies in the neighborhood of HE 0230-2130 and RX J0911.4+0551 which
possibly contribute to the total lensing potential. CONCLUSIONS: A careful
analysis reveals that microlensing is the most natural explanation for the
(de)magnification of the continuum emitting region of the background sources.
In HE 0230-2130, image D is likely to be affected by microlensing
magnification; in RX J0911.4+0551, images A1 and A3 are likely to be modified
by microlensing de-magnification and in H 1413+117, at least image D is
affected by microlensing.Comment: 13 pages, 18 figures. Accepted for publication in A&A: January 7,
200
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