1,890 research outputs found
Measurement of the temperature of an ultracold ion source using time-dependent electric fields
We report on a measurement of the characteristic temperature of an ultracold
rubidium ion source, in which a cloud of laser-cooled atoms is converted to
ions by photo-ionization. Extracted ion pulses are focused on a detector with a
pulsed-field technique. The resulting experimental spot sizes are compared to
particle-tracking simulations, from which a source temperature
mK and the corresponding transversal reduced emittance m rad are determined. We find that this result is
likely limited by space charge forces even though the average number of ions
per bunch is 0.022.Comment: 8 pages, 11 figure
Program transformations using temporal logic side conditions
This paper describes an approach to program optimisation based on transformations, where temporal logic is used to specify side conditions, and strategies are created which expand the repertoire of transformations and provide a suitable level of abstraction. We demonstrate the power of this approach by developing a set of optimisations using our transformation language and showing how the transformations can be converted into a form which makes it easier to apply them, while maintaining trust in the resulting optimising steps. The approach is illustrated through a transformational case study where we apply several optimisations to a small program
Transcriptome Profiles of Strawberry (Fragaria vesca) Fruit Interacting With Botrytis cinerea at Different Ripening Stages
Gray mold caused by Botrytis cinerea is a major cause of economic losses in strawberry fruit production, limiting fruit shelf life and commercialization. When the fungus infects Fragaria x ananassa strawberry at flowering or unripe fruit stages, symptoms develop after an extended latent phase on ripe fruits before or after harvesting. To elucidate the growth kinetics of B. cinerea on flower/fruit and the molecular responses associated with low susceptibility of unripe fruit stages, woodland strawberry Fragaria vesca flowers and fruits, at unripe white and ripe red stages, were inoculated with B. cinerea. Quantification of fungal genomic DNA within 72 h postinoculation (hpi) showed limited fungal growth on open flower and white fruit, while on red fruit, the growth was exponential starting from 24 hpi and sporulation was observed within 48 hpi. RNA sequencing applied to white and red fruit at 24 hpi showed that a total of 2,141 genes (12.5% of the total expressed genes) were differentially expressed due to B. cinerea infection. A broad transcriptional reprogramming was observed in both unripe and ripe fruits, involving in particular receptor and signaling, secondary metabolites, and defense response pathways. Membrane-localized receptor-like kinases and nucleotide-binding site leucine-rich repeat genes were predominant in the surveillance system of the fruits, most of them being downregulated in white fruits and upregulated in red fruits. In general, unripe fruits exhibited a stronger defense response than red fruits. Genes encoding for pathogenesis-related proteins and flavonoid polyphenols as well as genes involved in cell-wall strengthening were upregulated, while cell-softening genes appeared to be switched off. As a result, B. cinerea remained quiescent in white fruits, while it was able to colonize ripe red fruits
The point of maximum curvature as a marker for physiological time series
We present a geometric analysis of the model of Stirling. In particular we analyze the curvature of a heart rate time series in response to a step like increment in the exercise intensity. We present solutions for the point of maximum curvature which can be used as a marker of physiological interest. This marker defines the point after which the heart rate no longer continues to rapidly rise and instead follows either a steady state or slow rise. These methods are then applied to find analytic solutions for a mono exponential model which is commonly used in the literature to model the response to a moderate exercise intensity. Numerical solutions are then found for the full model and parameter values presented in Stirling
A novel broadband electro-absorption modulator based on bandfilling in n-InGaAs : design and simulations
Sustainability of fresh groundwater resources in fifteen major deltas around the world
Population growth, urbanization and intensification of irrigated agriculture in the world’s deltas boost the demand for fresh water, with extensive groundwater extraction as a result. This, in turn, leads to salt water intrusion and upconing, which poses a threat to freshwater and food security. Managing fresh groundwater resources in deltas requires accurate knowledge about the current status and behaviour of their fresh groundwater resources. However, this knowledge is scarcely present, especially for groundwater at larger depths. Here, we use three-dimensional variable-density groundwater model simulations over the last 125 ka to estimate the volume of fresh groundwater resources for 15 major deltas around the world. We estimate current volumes of onshore fresh groundwater resources for individual deltas to vary between 1010 m3 and 1012 m3. Offshore, the estimated volumes of fresh groundwater are generally smaller, though with a considerably higher variability. In 9 out of 15 simulated deltas, fresh groundwater volumes developed over thousands of years. Based on current groundwater extraction and recharge rates, we estimate the time until in-situ fresh groundwater resources are completely exhausted, partly leading to groundwater level decline and mostly replacement with river water or saline groundwater. This straightforward analysis shows that 4 out of 15 deltas risk complete exhaustion of fresh groundwater resources within 300 m depth in 200 years. These deltas also suffer from saline surface water which means their groundwater resources will progressively salinize. With a fourfold increase in extraction rates, seven deltas risk a complete exhaustion within 200 years. Of these seven deltas, six suffer from saline surface water. We stress that the groundwater of these six vulnerable deltas should be carefully managed, to avoid non-renewable groundwater use. The progressive exhaustion of fresh groundwater resources in these deltas will hamper their ability to withstand periods of water scarcity
Light Baryon Resonances: Restrictions and Perspectives
The problem of nucleon resonances N' with masses below the Delta is
considered. We derive bounds for the properties of such states. Some of these
are new, while others improve upon existing limits. We discuss the nature of N'
states, and their unitary partners, assuming their existence can be verified.Comment: 11 pages, 11 figur
Survey strategy optimization for the Atacama Cosmology Telescope
In recent years there have been significant improvements in the sensitivity
and the angular resolution of the instruments dedicated to the observation of
the Cosmic Microwave Background (CMB). ACTPol is the first polarization
receiver for the Atacama Cosmology Telescope (ACT) and is observing the CMB sky
with arcmin resolution over about 2000 sq. deg. Its upgrade, Advanced ACTPol
(AdvACT), will observe the CMB in five frequency bands and over a larger area
of the sky. We describe the optimization and implementation of the ACTPol and
AdvACT surveys. The selection of the observed fields is driven mainly by the
science goals, that is, small angular scale CMB measurements, B-mode
measurements and cross-correlation studies. For the ACTPol survey we have
observed patches of the southern galactic sky with low galactic foreground
emissions which were also chosen to maximize the overlap with several galaxy
surveys to allow unique cross-correlation studies. A wider field in the
northern galactic cap ensured significant additional overlap with the BOSS
spectroscopic survey. The exact shapes and footprints of the fields were
optimized to achieve uniform coverage and to obtain cross-linked maps by
observing the fields with different scan directions. We have maximized the
efficiency of the survey by implementing a close to 24 hour observing strategy,
switching between daytime and nighttime observing plans and minimizing the
telescope idle time. We describe the challenges represented by the survey
optimization for the significantly wider area observed by AdvACT, which will
observe roughly half of the low-foreground sky. The survey strategies described
here may prove useful for planning future ground-based CMB surveys, such as the
Simons Observatory and CMB Stage IV surveys.Comment: 14 Pages, 9 Figures, 4 Table
Group medical appointments for people with physical illness
This is the protocol for a review and there is no abstract. The objectives are as follows: To assess the effects of group medical appointments (GMAs) on the health status and well-being of patients with a primary physical illness as compared to one-to-one patient-clinician appointments
- …