497 research outputs found
Effect of Background, Attitudinal and Social Network Variables on PhD Students’ Academic Performance. A Multimethod Approach
The aim of this paper is to predict the
academic performance of PhD students understood as
publications and presentations at conferences.
MATERIALS AND METHODS: We use a multimethod approach,
a quantitative web survey of PhD students and
their supervisors and in-depth interviews. We surveyed
all PhD students at the University of Girona (Spain) in
their 4th and 5th year, who held either a PhD grant or
a teaching position at the university.
RESULTS: The explanatory variables of PhD performance
are of three types: characteristics of the PhD students’
research groups understood as social networks, background
variables and attitudinal characteristics. The
quantitative analyses show the importance of some
background and attitudinal variables like supervisor performance,
having a grant, or motivation. The qualitative
results show networking to be also important. Policy
implications are drawn at country and university level.
DISCUSSION: Policy implications are drawn at country
and university level
Fast adiabatic transport of single laser-cooled Be ions in a cryogenic Penning trap stack
High precision mass and -factor measurements in Penning traps have enabled
groundbreaking tests of fundamental physics. The most advanced setups use
multi-trap methods, which employ transport of particles between specialized
trap zones. Present developments focused on the implementation of sympathetic
laser cooling will enable significantly shorter duty cycles and better
accuracies in many of these scenarios. To take full advantage of these
increased capabilities, we implement fast adiabatic transport concepts
developed in the context of trapped-ion quantum information processing in a
cryogenic Penning trap system. We show adiabatic transport of a single
ion initially cooled to 2 mK over a 2.2 cm distance within 15
ms and with less than 10\,mK energy gain at a peak velocity of 3 m/s. These
results represent an important step towards the implementation of quantum logic
spectroscopy in the \ppbar system. Applying these developments to other
multi-trap systems has the potential to considerably increase the data-sampling
rate in these experiments.Comment: 15 pages, 7 figure
Religion in Dutch society 2005. Documentation of a national survey on religious and secular attitudes and behaviour in 2005
Contains fulltext :
129193pub.pdf (publisher's version ) (Closed access
Rainfall interception and redistribution by a common North American understory and pasture forb, \u3cem\u3eEupatorium capillifolium\u3c/em\u3e (Lam. dogfennel)
In vegetated landscapes, rain must pass through plant canopies and litter to enter soils. As a result, some rainwater is returned to the atmosphere (i.e., interception, I) and the remainder is partitioned into a canopy (and gap) drip flux (i.e., throughfall) or drained down the stem (i.e., stemflow). Current theoretical and numerical modeling frameworks for this process are almost exclusively based on data from woody overstory plants. However, herbaceous plants often populate the understory and are the primary cover for important ecosystems (e.g., grasslands and croplands). This study investigates how overstory throughfall (PT,o) is partitioned into understory I, throughfall (PT) and stemflow (PS) by a dominant forb in disturbed urban forests (as well as grasslands and pasturelands), Eupatorium capillifolium (Lam., dogfennel). Dogfennel density at the site was 56 770 stems ha−1, enabling water storage capacities for leaves and stems of 0.90±0.04 and 0.43±0.02 mm, respectively. As direct measurement of PT,o (using methods such as tipping buckets or bottles) would remove PT,o or disturb the understory partitioning of PT,o, overstory throughfall was modeled (PT,o′ role= presentation \u3eP′T,o) using on-site observations of PT,o from a previous field campaign. Relying on modeled PT,o′ role= presentation \u3eP′T,o, rather than on observations of PT,o directly above individual plants means that significant uncertainty remains with respect to (i) small-scale relative values of PT and PS and (ii) factors driving PS variability among individual dogfennel plants. Indeed, PS data from individual plants were highly skewed, where the mean PS:PT,o′ role= presentation \u3ePS:P′T,o per plant was 36.8 %, but the median was 7.6 % (2.8 %–27.2 % interquartile range) and the total over the study period was 7.9 %. PS variability (n=30 plants) was high (CV \u3e 200 %) and may hypothetically be explained by fine-scale spatiotemporal patterns in actual overstory throughfall (as no plant structural factors explained the variability). The total PT:PT,o′ role= presentation \u3ePT:P′T,o was 71 % (median PT:PT,o′ role= presentation \u3ePT:P′T,o per gauge was 72 %, with a 59 %–91 % interquartile range). Occult precipitation (mixed dew and light rain events) occurred during the study period, revealing that dogfennel can capture and drain dew to their stem base as PS. Dew-induced PS may help explain dogfennel\u27s improved invasion efficacy during droughts (as it tends to be one of the most problematic weeds in the improved grazing systems in the southeastern US). Overall, dogfennel\u27s precipitation partitioning differed markedly from the site\u27s overstory trees (Pinus palustris), and a discussion of the limited literature suggests that these differences may exist across vegetated ecosystems. Thus, more research on herbaceous plant canopy interactions with precipitation is merited
Optical stimulated-Raman sideband spectroscopy of a single 9Be+ ion in a Penning trap
We demonstrate optical sideband spectroscopy of a single 9Be+ ion in a cryogenic 5 tesla Penning trap using two-photon stimulated-Raman transitions between the two Zeeman sublevels of the 1s22s ground state manifold. By applying two complementary coupling schemes, we accurately measure Raman resonances with and without contributions from motional sidebands. From the latter we obtain an axial sideband spectrum with an effective mode temperature of (3.1±0.4) mK. These results are a key step for quantum logic operations in Penning traps, applicable to high-precision matter-antimatter comparison tests in the baryonic sector of the standard model
Resolved-sideband cooling of a single Be ion in a Penning trap
Manipulating individual trapped ions at the single quantum level has become
standard practice in radio-frequency ion traps, enabling applications from
quantum information processing to precision metrology. The key ingredient is
ground-state cooling of the particle's motion through resolved-sideband laser
cooling. Ultra-high-presicion experiments using Penning ion traps will greatly
benefit from the reduction of systematic errors offered by full motional
control, with applications to atomic masses and -factor measurements,
determinations of fundamental constants or related tests of fundamental
physics. In addition, it will allow to implement quantum logic spectroscopy, a
technique that has enabled a new class of precision measurements in
radio-frequency ion traps. Here we demonstrate resolved-sideband laser cooling
of the axial motion of a single Be ion in a cryogenic 5 Tesla Penning
trap system using a two-photon stimulated-Raman process, reaching a mean phonon
number of . This is a fundamental step in the
implementation of quantum logic spectroscopy for matter-antimatter comparison
tests in the baryonic sector of the Standard Model and a key step towards
improved precision experiments in Penning traps operating at the quantum limit.Comment: 6 pages, 5 figure
Contextual factors and prejudice at the beginning of the migrant influx: The Moroccan case in Seville, Spain
Studies addressing contextual factors associated with anti‐immigrant prejudice have focused on out‐group size and rapid demographic changes in receiving locations. However, the territorial concentration and distribution of ethnic minorities at a local and intraurban level has received little attention. We analyse the relationship between emerging territorial concentration points—alongside other contextual variables—by Moroccans and receiving society's growing prejudice towards them in a city experiencing the start of a migrant influx. We combine survey and census data from five Seville districts (southern Spain). Our results show how rapid changes in the general population's ethnic composition, coupled with Moroccan and economic migrants' territorial concentration, correlate strongly with negative attitudes towards Moroccans at this early stage. However, a weaker relationship between the immigrant percentage and degree of prejudice by the receiving group is observed. We also discuss guidelines for ensuring good, local diversity management to prevent socioterritorial fragmentation in multicultural cities.Ministerio de Economía, Industria y Competitividad de España CSO2014‐55780‐C3‐1‐PMinisterio de Economía, Industria y Competitividad de España SEJ2006-14470Junta de Andalucí
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The effect of spatial throughfall patterns on soil moisture patterns at the hillslope scale
Improving the understanding of the controls on subsurface stormflow generation has been the goal of numerous experimental and modeling studies. However, the effect of the spatial variability of throughfall on soil moisture patterns and subsurface stormflow (SSF) generation has not yet been studied in detail. The objectives of this study are threefold: (1) to investigate the influence of a spatially variable throughfall pattern on soil moisture; (2) to investigate if soil moisture patterns reflect a balance between a throughfall and bedrock topography patterns; and (3) to investigate how this balance changes when soil depth, storm size and slope angle are varied. Virtual experiments are used to address these questions. A virtual experiment is a numerical experiment driven by collective field intelligence. It provides a learning tool to investigate the effect of individual processes in a complex system. In our virtual experiment we combined spatial throughfall data from the Huewelerbach catchment in Luxembourg with the topography of a well-studied hillslope within the Panola Mountain Research Watershed, Georgia, USA. We used HYDRUS-3D as a modeling platform. The virtual experiment shows that throughfall patterns influence soil moisture patterns, but only during and shortly after a storm. With a semi-variogram analysis we showed how the effective range of the soil moisture pattern (i.e., the main descriptor of a spatial pattern in case of a small nugget to sill ratio), is similar to the effective range of the throughfall pattern during the storm and gradually returns to the effective range of the bedrock topography after throughfall has ceased. The same analysis was carried out to investigate how this balance changes due to changes in storm size, soil depth, and slope. The analysis showed that the throughfall pattern is more important during large storms on gentle slopes. For steeper slopes the bedrock topography becomes more important.Keywords: Variability, Water dynamics, Georgia, Beech forest, Stand, Floor interception, Runoff, Subsurface stormflow, Tropical rainforest, Canop
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