17,346 research outputs found
Trident: A three-pronged galaxy survey. I. Lyman alpha emitting galaxies at z~2 in GOODS North
Context. Lyman alpha emitting galaxies (LAEs) are used to probe the distant
universe and are therefore important for galaxy evolution studies and for
providing clues to the nature of the epoch of reionization, but the exact
circumstances under which Lyman alpha escapes a galaxy are still not fully
understood.
Aims. The Trident project is designed to simultaneously examine Lyman alpha,
H-alpha and Lyman Continuum emission from galaxies at redshift z~2, thus
linking together these three aspects of ionising radiation in galaxies. In this
paper, we outline the strategy of this project and examine the properties of
LAEs in the GOODS North field.
Methods. We performed a narrowband LAE survey in GOODS North using existing
and two custom made filters at the Nordic Optical Telescope with MOSCA. We use
complementary broad band archival data in the field to make a careful candidate
selection and perform optical to near-IR SED fitting. We also estimate
far-infrared luminosities by matching our candidates to detections in
Spitzer/MIPS 24{\mu}m and Herschel/PACS catalogs.
Results. We find a total of 25 LAE candidates, probing mainly the bright end
of the LAE luminosity function with L_Ly {\alpha} ~ 1-15e42 erg/s. They display
a range of masses of ~0.5-50e9 M_solar, and average ages from a few tens of Myr
to 1 Gyr when assuming a constant star formation history. The majority of our
candidates also show signs of recent elevated star formation. Three candidates
have counterparts in the GOODS-Herschel far-IR catalogue, with luminosities
consistent with ultra-luminous infrared galaxies (ULIRGs).
Conclusions. The wide range of parameters derived from our SED fitting, as
well as part of our sample being detected as ULIRGs, seems to indicate that at
these Lyman alpha luminosities, LAEs do not necessarily have to be young
dwarfs, and that a lack of dust is not required for Lyman alpha to escape.Comment: 16 pages, 12 figures. Accepted version for publication in A&
Effects of air pollution on natural vegetation and crops
The present report is being submitted for the consideration of the Working Group on Effects in accordance with the request of the Executive Body for the Convention on Longrange Transboundary Air Pollution in the 2012–2013 workplan for the implementation of the Convention (ECE/EB.AIR/109/Add.2, items 3.1 (c) and 3.5).
The report of the International Cooperative Programme on Effects of Air Pollution on Natural Vegetation and Crops presents the results of ozone impacts on ecosystem
services and biodiversity, and the results of the pilot study on mosses as biomonitors of persistent organic pollutants as part of the European moss survey conducted in 2010/11. In addition, the results of the workplan items common to all programmes are presented
Programmed schedule holds for improving launch vehicle holds
Baseline definition and system optimization are used for the analysis of programmed holds developed through prelaunch system analysis. Identification of design specifications for ground support equipment and maintenance concepts, and design specifications are used to describe the functional utilization of the overall flow process
Quantum Density Fluctuations in Classical Liquids
We discuss the density fluctuations of a fluid due to zero point motion.
These can be regarded as density fluctuations in the phonon vacuum state. We
assume a linear dispersion relation with a fixed speed of sound and calculate
the density correlation function. We note that this function has the same form
as the correlation function for the time derivative of a relativistic massless
scalar field, but with the speed of light replaced by the speed of sound. As a
result, the study of density fluctuations in a fluid can be a useful analog
model for better understanding fluctuations in relativistic quantum field
theory. We next calculate the differential cross section for light scattering
by the zero point density fluctuations, and find a result proportional to the
fifth power of the light frequency. This can be understood as the product of
fourth power dependence of the usual Rayleigh cross section with the linear
frequency dependence of the spectrum of zero point density fluctuations. We
give some estimates of the relative magnitude of this effect compared to the
scattering by thermal density fluctuations, and find that it can be of order
0.5% for water at room temperature and optical frequencies. This relative
magnitude is proportional to frequency and inversely proportional to
temperature. Although the scattering by zero point density fluctuation is
small, it may be observable.Comment: 7 page
Curiosity killed the cat: no evidence of an association between cat ownership and psychotic symptoms at ages 13 and 18 years in a UK general population
Congenital or early life infection with Toxoplasma gondii has been implicated in schizophrenia aetiology. Childhood cat ownership has been hypothesized as an intermediary marker of T. gondii infection and, by proxy, as a risk factor for later psychosis. Evidence supporting this hypothesis is, however, limited.
We used birth cohort data from the Avon Longitudinal Study of Parents and Children (ALSPAC) to investigate whether cat ownership in pregnancy and childhood (ages 4 and 10 years) was associated with psychotic experiences (PEs) in early (age 13, N = 6705) and late (age 18, N = 4676) adolescence, rated from semi-structured interviews. We used logistic regression to examine associations between cat ownership and PEs, adjusting for several sociodemographic and socioeconomic factors, household characteristics and dog ownership. Missing data were handled via multiple imputation.
Cat ownership during pregnancy was not associated with PEs at age 13 years [adjusted odds ratio (OR) 1.15, 95% confidence interval (CI) 0.97–1.35] or 18 years (OR 1.08, 95% CI 0.86–1.35). Initial univariable evidence that cat ownership at ages 4 and 10 years was associated with PEs at age 13 years did not persist after multivariable adjustment (4 years: OR 1.18, 95% CI 0.94–1.48; 10 years: OR 1.12, 95% CI 0.92–1.36). There was no evidence that childhood cat ownership was associated with PEs at age 18 years.
While pregnant women should continue to avoid handling soiled cat litter, given possible T. gondii exposure, our study strongly indicates that cat ownership in pregnancy or early childhood does not confer an increased risk of later adolescent PEs
Twenty eight years of ICP Vegetation: an overview of its activities
Here we look back at the activities and achievements in the 28 years of the International Cooperative Programme on the Effects of Air Pollution on Natural Vegetation and Crops (ICP Vegetation). The ICP Vegetation is a subsidiary body of the Working Group on Effects of the UNECE Convention on Long-range Transboundary Air Pollution (LTRAP), established in 1979. An important role of the ICP Vegetation is to provide evidence for air pollution impacts on vegetation in support of policy development and review of the LRTAP Convention and its Protocols. The activities and participation in the ICP Vegetation have grown over the years. The main activities include:
• Collate evidence of ozone impacts on vegetation, assess spatial patterns and temporal trends across Europe;
• Develop dose-response relationships, establish critical levels for vegetation and provide European risk maps of ozone impacts;
• Reviewing the literature on ozone impacts on vegetation and produce thematic scientific reports and policy-relevant brochures;
• Determine spatial patterns and temporal trends of heavy metals, nitrogen and persistent organic pollutants concentrations in mosses as a biomonitoring tool of atmospheric deposition of these compounds
Optical BCS conductivity at imaginary frequencies and dispersion energies of superconductors
We present an efficient expression for the analytic continuation to arbitrary
complex frequencies of the complex optical and AC conductivity of a homogeneous
superconductor with arbitrary mean free path. Knowledge of this quantity is
fundamental in the calculation of thermodynamic potentials and dispersion
energies involving type-I superconducting bodies. When considered for imaginary
frequencies, our formula evaluates faster than previous schemes involving
Kramers--Kronig transforms. A number of applications illustrates its
efficiency: a simplified low-frequency expansion of the conductivity, the
electromagnetic bulk self-energy due to longitudinal plasma oscillations, and
the Casimir free energy of a superconducting cavity.Comment: 20 pages, 7 figures, calculation of Casimir energy adde
Parents' involvement in child care: do parental and work identities matter?
The current study draws on identity theory to explore mothers' and fathers' involvement in childcare. It examined the relationships between the salience and centrality of individuals’ parental and work-related identities and the extent to which they are involved in various forms of childcare. A sample of 148 couples with at least one child aged 6 years or younger completed extensive questionnaires. As hypothesized, the salience and centrality of parental identities were positively related to mothers' and fathers' involvement in childcare. Moreover, maternal identity salience was negatively related to fathers' hours of childcare and share of childcare tasks. Finally, work hours mediated the negative relationships between the centrality of work identities and time invested in childcare, and gender moderated this mediation effect. That is, the more central a mother's work identity, the more hours she worked for pay and the fewer hours she invested in childcare. These findings shed light on the role of parental identities in guiding behavioral choices, and attest to the importance of distinguishing between identity salience and centrality as two components of self-structure
- …