11,862 research outputs found
Polarization effects on the effective temperature of an ultracold electron source
The influence has been studied of the ionization laser polarization on the
effective temperature of an ultracold electron source, which is based on
near-threshold photoionization. This source is capable of producing both
high-intensity and high-coherence electron pulses, with applications in for
example electron diffraction experiments. For both nanosecond and femtosecond
photoionization, a sinusoidal dependence of the temperature on polarization
angle has been found. For most experimental conditions, the temperature is
minimal when the polarization coincides with the direction of acceleration.
However, surprisingly, for nanosecond ionization a regime exists when the
temperature is minimal when the polarization is perpendicular to the
acceleration direction. This shows that in order to create electron bunches
with the highest transverse coherence length, it is important to control the
polarization of the ionization laser. The general trends and magnitudes of the
temperature measurements are described by a model, based on the analysis of
classical electron trajectories; this model further deepens our understanding
of the internal mechanisms during the photoionization process. Furthermore, for
nanosecond ionization, charge oscillations as a function of laser polarization
have been observed; for most situations the oscillation amplitude is small
Biological hydrogen production from sucrose and sugar beet by Caldicellulosiruptor Saccharolyticus
Variability and nature of the binary in the Red Rectangle Nebula
We present new observations of the central binary inside the Red Rectangle
nebula. The detection of zinc in the optical spectrum confirms that the
peculiar photospheric abundances are due to accretion of circumstellar gas.
Grey brightness variations with the orbital period are observed. They are
interpreted as being due to the variation of the scattering angle with orbital
phase. The small orbital separation of the system is not compatible with
previous normal evolution of the primary on the AGB. We point out the
similarity of the orbital history of this and other similar systems with those
of some close Barium stars and suggest that the nonzero eccentricity of the
orbit is the result of tidal interaction with the circumbinary disk.Comment: 4 pages, 3 figures, A&A Letters accepte
Infrared High-Resolution Spectroscopy of Post-AGB Circumstellar Disks. I. HR 4049 - The Winnowing Flow Observed?
High-resolution infrared spectroscopy in the 2.3-4.6 micron region is
reported for the peculiar A supergiant, single-lined spectroscopic binary HR
4049. Lines from the CO fundamental and first overtone, OH fundamental, and
several H2O vibration-rotation transitions have been observed in the
near-infrared spectrum. The spectrum of HR 4049 appears principally in emission
through the 3 and 4.6 micron region and in absorption in the 2 micron region.
The 4.6 micron spectrum shows a rich 'forest' of emission lines. All the
spectral lines observed in the 2.3-4.6 micron spectrum are shown to be
circumbinary in origin. The presence of OH and H2O lines confirm the
oxygen-rich nature of the circumbinary gas which is in contrast to the
previously detected carbon-rich material. The emission and absorption line
profiles show that the circumbinary gas is located in a thin, rotating layer
near the dust disk. The properties of the dust and gas circumbinary disk and
the spectroscopic orbit yield masses for the individual stars, M_AI~0.58 Msolar
and M_MV~0.34 Msolar. Gas in the disk also has an outward flow with a velocity
of 1 km/s. The severe depletion of refractory elements but near-solar
abundances of volatile elements observed in HR 4049 results from abundance
winnowing. The separation of the volatiles from the grains in the disk and the
subsequent accretion by the star are discussed. Contrary to prior reports, the
HR 4049 carbon and oxygen isotopic abundances are typical AGB values:
12C/13C=6^{+9}_{-4} and 16O/17O>200.Comment: 42 pages, 14 figures, Accepted by Ap
Interventions for promoting reintegration and reducing harmful behaviour and lifestyles in street-connected children and young people (Review)
Background
Millions of street-connected children and young people worldwide live or work in street environments. They are vulnerable to many risks, whether or not they remain connected to families of origin, and despite many strengths and resiliencies, they are excluded from mainstream social structures and opportunities.
Objectives
Primary research objectives
To evaluate and summarise the effectiveness of interventions for street-connected children and young people that aim to:
• promote inclusion and reintegration;
• increase literacy and numeracy;
• facilitate access to education and employment;
• promote mental health, including self esteem;
• reduce harms associated with early sexual activity and substance misuse.
Secondary research objectives
• To explore whether effects of interventions differ within and between populations, and whether an equity gradient influences theseeffects, by extrapolating from all findings relevance for low- and middle-income countries (LMICs) (Peters 2004).
• To describe other health, educational, psychosocial and behavioural effects, when appropriate outcomes are reported.
• To explore the influence of context in design, delivery and outcomes of interventions.
Interventions for promoting reintegration and reducing harmful behaviour and lifestyles in street-connected children and young people 1
(Review)
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
To explore the relationship between numbers of components and duration and effects of interventions.
• To highlight implications of these findings for further research and research methods to improve evidence in relation to the primary
research objective.
• To consider adverse or unintended outcomes.
Search methods
We searched the following bibliographic databases, searched for the original review, from inception to 2012, and various relevant non-governmental and organisational websites: Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE and PreMEDLINE;EMBASE and EMBASE Classic; Cumulative Index to Nursing and Allied Health Literature (CINAHL); PsycINFO; Education Resource Information Center (ERIC); Sociological Abstracts; Social Services Abstracts; Social Work Abstracts; Healthstar; Latin American Caribbean Health Sciences Literature (LILACS); System for Grey literature in Europe (OpenGrey); ProQuest Dissertations and Theses; EconLit; IDEAS Economics and Finance Research; JOLIS Library Catalog of the holdings of the World Bank Group and International Monetary Fund (IMF) Libraries; British Library for Development Studies (BLDS); Google and Google Scholar. We
updated the search in April 2015 for the review update, using the same methods.
Selection criteria
This review includes data from harm reduction or reintegration intervention studies that used a comparison group study design; all were randomised or quasi-randomised studies. Studies were included if they evaluated interventions provided for street-connected children and young people, from birth to 24 years, in all contexts.
Data collection and analysis
Two review authors independently extracted data and assessed risk of bias and other factors presented in the Discussion and Summary quality assessment (Grades of Recommendation, Assessment, Development and Evaluation (GRADE)). We extracted data on intervention delivery, context, process factors, equity and outcomes, and grouped outcomes into psychosocial outcomes, risky sexual behaviours or substance use. We conducted meta-analyses for outcomes where the outcome measures were sufficiently similar. We evaluated other outcomes narratively.
Main results
We included 13 studies evaluating 19 interventions from high-income countries (HICs). We found no sufficiently robust evaluations conducted in low- and middle-income countries (LMICs). Study quality overall was low and measurements used by studies variable. Participants were classified as drop-in and shelter-based. No studies measured the primary outcome of reintegration and none reported on adverse effects.We found no consistent results on a range of relevant outcomes within domains of psychosocial health, substance misuse and sexually risky behaviours . Interventions evaluated consisted of time-limited therapeutically based programmes that proved no more effective than standard shelter or drop-in services and other control interventions used for most outcomes in most studies.
Favourable changes from baseline were reported for outcomes for most participants following therapy interventions and standard services. We noted considerable heterogeneity between studies and inconsistent reporting of equity data. No studies measured the primary outcome of reintegration or reported on adverse effects.
Authors’ conclusions
Analysis revealed no consistently significant benefit for focused therapeutic interventions compared with standard services such as dropin centres, case management and other comparable interventions for street-connected children and young people. Commonly available services, however, were not rigorously evaluated. Robust evaluation of interventions, including comparison with no intervention, would establish a more reliable evidence base to inform service implementation. More robust research is needed in LMICs to examine interventions for street-connected children and young people with different backgrounds and service needs
Cruise report hydro acoustic survey for blue whiting (Micromesistius poutassou) with R.V. Tridens, 17 March - 04 April 2008
This is the report of the Dutch part of the international North East Atlantic hydro acoustic survey for blue whiting. The survey is coordinated by ICES and has been executed annually. The purpose of the survey is to estimate the blue whiting stock of the North East Atlantic. The ICES uses this estimation is as a “tuning index” to assess the North East Atlantic blue whiting stock. The applied method was echo integration. By sailing transects over the survey area, the total acoustic cross-section can be calculated by surface area sampled. Trawling identified species composition of localized schools. The length composition of each species was determined. Blue whiting was examined on age and fecundity from which a split up stock structure was mad
Analysing Personal Characteristics of Lone-Actor Terrorists: Research Findings and Recommendations
This Research Note presents the outcome of a project that looked at the personal characteristics of lone-actor terrorists. It is part of the larger Countering Lone-Actor Terrorism (CLAT) project. The project described here aimed to improve understanding of, and responses to, the phenomenon of (potentially) violent lone-actors based on an analysis of 120 cases from across Europe. The Research Note focuses on the personal characteristics of lone-actor terrorists. First of all, it presents the main findings of the general analysis of the study into personal variables of lone-actor terrorists. Subsequently, the authors outline a set of recommendations based on the key findings. In the beginning, we present the main research questions of the CLAT project and the working definition of lone-actor terroris
Tracer Measurements in Growing Sea Ice Support Convective Gravity Drainage Parameterizations
Gravity drainage is the dominant process redistributing solutes in growing sea ice. Modeling gravity drainage is therefore necessary to predict physical and biogeochemical variables in sea ice. We evaluate seven gravity drainage parameterizations, spanning the range of approaches in the literature, using tracer measurements in a sea ice growth experiment. Artificial sea ice is grown to around 17 cm thickness in a new experimental facility, the Roland von Glasow air‐sea‐ice chamber. We use NaCl (present in the water initially) and rhodamine (injected into the water after 10 cm of sea ice growth) as independent tracers of brine dynamics. We measure vertical profiles of bulk salinity in situ, as well as bulk salinity and rhodamine in discrete samples taken at the end of the experiment. Convective parameterizations that diagnose gravity drainage using Rayleigh numbers outperform a simpler convective parameterization and diffusive parameterizations when compared to observations. This study is the first to numerically model solutes decoupled from salinity using convective gravity drainage parameterizations. Our results show that (1) convective, Rayleigh number‐based parameterizations are our most accurate and precise tool for predicting sea ice bulk salinity; and (2) these parameterizations can be generalized to brine dynamics parameterizations, and hence can predict the dynamics of any solute in growing sea ic
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