43 research outputs found
The Centurion 18 telescope of the Wise Observatory
We describe the second telescope of the Wise Observatory, a 0.46-m Centurion
18 (C18) installed in 2005, which enhances significantly the observing
possibilities. The telescope operates from a small dome and is equipped with a
large-format CCD camera. In the last two years this telescope was intensively
used in a variety of monitoring projects.
The operation of the C18 is now automatic, requiring only start-up at the
beginning of a night and close-down at dawn. The observations are mostly
performed remotely from the Tel Aviv campus or even from the observer's home.
The entire facility was erected for a component cost of about 70k$ and a labor
investment of a total of one man-year.
We describe three types of projects undertaken with this new facility: the
measurement of asteroid light variability with the purpose of determining
physical parameters and binarity, the following-up of transiting extrasolar
planets, and the study of AGN variability. The successful implementation of the
C18 demonstrates the viability of small telescopes in an age of huge
light-collectors, provided the operation of such facilities is very efficient.Comment: 16 pages, 13 figures, some figures quality was degraded, accepted for
publication in Astrophysics and Space Scienc
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
Plant community persistence strategy is elevation‐specific
Aims
Persistence plays a key role in both plant population and community dynamics as it allows withstanding temporarily habitat conditions unsuitable for growth and reproduction. Plants can exploit three different strategies to persist in situ (building soil seed banks, increasing adult longevity and/or clonal reproduction), the dominance of which in a community might vary along environmental gradients. Yet, their relative role in plant persistence has never been investigated.
Location
The Bavarian Alps, Germany.
Methods
We collected data on seed soil persistence, adult longevity and clonality for 290 species occurring in 18 grasslands located along an elevational gradient of 1,000 metres and examined their contribution to persistence in a community. Linear models were used to estimate the relationship between elevation and these persistence strategies.
Results
We found that dominance of a certain persistence strategy varied depending on environmental variability. Specifically, persistence in lowlands was mainly achieved by persistent and dense soil seed banks along with extended clonal growth (larger spread distances and higher number of offspring). Contrastingly, the main persistence strategy in the alpine communities was increased adult longevity.
Conclusions
The changes in relative contribution of each strategy to community persistence along the elevational gradient are interrelated suggesting a trade-off among them. We conclude that this trade-off plays an important role in species co-existence and community assembly, and might be useful to understand vegetation dynamics under ongoing climate change and improve restoration efforts of upland ecosystems
Topical Review: Medical Trauma During Early Childhood
OBJECTIVE: Early childhood is a high-risk period for exposure to traumatic medical events due to injury/illness. It is also one of the most important and vulnerable periods due to rapid development in neurobiological systems, attachment relationships, cognitive and linguistic capacities, and emotion regulation. The aim of this topical review is to evaluate empirical literature on the psychological impact of medical trauma during early childhood (0-6 years) to inform models of clinical care for assessing, preventing, and treating traumatic stress following injury/illness. METHODS: Topical review of empirical and theoretical literature on pediatric medical traumatic stress (PMTS) during early childhood. RESULTS: There are important developmental factors that influence how infants and young children perceive and respond to medical events. The emerging literature indicates that up to 30% of young children experience PMTS within the first month of an acute illness/injury and between 3% and 10% develop posttraumatic stress disorder. However, significant knowledge gaps remain in our understanding of psychological outcomes for infants and young children, identification of risk-factors and availability of evidence-based interventions for medical trauma following illness. CONCLUSIONS: This topical review on medical trauma during early childhood provides: (a) definitions of key medical trauma terminology, (b) discussion of important developmental considerations, (c) summary of the empirical literature on psychological outcomes, risk factors, and interventions, (d) introduction to a stepped-model-of-care framework to guide clinical practice, and (e) summary of limitations and directions for future research
Topical Review: Medical Trauma During Early Childhood
OBJECTIVE: Early childhood is a high-risk period for exposure to traumatic medical events due to injury/illness. It is also one of the most important and vulnerable periods due to rapid development in neurobiological systems, attachment relationships, cognitive and linguistic capacities, and emotion regulation. The aim of this topical review is to evaluate empirical literature on the psychological impact of medical trauma during early childhood (0-6 years) to inform models of clinical care for assessing, preventing, and treating traumatic stress following injury/illness. METHODS: Topical review of empirical and theoretical literature on pediatric medical traumatic stress (PMTS) during early childhood. RESULTS: There are important developmental factors that influence how infants and young children perceive and respond to medical events. The emerging literature indicates that up to 30% of young children experience PMTS within the first month of an acute illness/injury and between 3% and 10% develop posttraumatic stress disorder. However, significant knowledge gaps remain in our understanding of psychological outcomes for infants and young children, identification of risk-factors and availability of evidence-based interventions for medical trauma following illness. CONCLUSIONS: This topical review on medical trauma during early childhood provides: (a) definitions of key medical trauma terminology, (b) discussion of important developmental considerations, (c) summary of the empirical literature on psychological outcomes, risk factors, and interventions, (d) introduction to a stepped-model-of-care framework to guide clinical practice, and (e) summary of limitations and directions for future research