2,051 research outputs found
Multi-Pulse Laser Wakefield Acceleration: A New Route to Efficient, High-Repetition-Rate Plasma Accelerators and High Flux Radiation Sources
Laser-driven plasma accelerators can generate accelerating gradients three
orders of magnitude larger than radio-frequency accelerators and have achieved
beam energies above 1 GeV in centimetre long stages. However, the pulse
repetition rate and wall-plug efficiency of plasma accelerators is limited by
the driving laser to less than approximately 1 Hz and 0.1% respectively. Here
we investigate the prospects for exciting the plasma wave with trains of
low-energy laser pulses rather than a single high-energy pulse. Resonantly
exciting the wakefield in this way would enable the use of different
technologies, such as fibre or thin-disc lasers, which are able to operate at
multi-kilohertz pulse repetition rates and with wall-plug efficiencies two
orders of magnitude higher than current laser systems. We outline the
parameters of efficient, GeV-scale, 10-kHz plasma accelerators and show that
they could drive compact X-ray sources with average photon fluxes comparable to
those of third-generation light source but with significantly improved temporal
resolution. Likewise FEL operation could be driven with comparable peak power
but with significantly larger repetition rates than extant FELs
Spatio-temporal analysis of spatial accessibility to primary health care in Bhutan
© 2015 by the authors; licensee MDPI, Basel, Switzerland. Geographic information systems (GIS) can be effectively utilized to carry out spatio-temporal analysis of spatial accessibility to primary healthcare services. Spatial accessibility to primary healthcare services is commonly measured using floating catchment area models which are generally defined with three variables; namely, an attractiveness component of the service centre, travel time or distance between the locations of the service centre and the population, and population demand for healthcare services. The nearest-neighbour modified two-step floating catchment area (NN-M2SFCA) model is proposed for computing spatial accessibility indices for the entire country. Accessibility values from 2010 to 2013 for Bhutan were analysed both spatially and temporally by producing accessibility ranking maps, plotting Lorenz curves, and conducting spatial clustering analysis. The spatial accessibility indices of the 205 sub-districts show great disparities in healthcare accessibility in the country. The mean-and median-based classification results indicate that, in 2013, 24 percent of Bhutan's population have poor access to primary healthcare services, 66 percent of the population have medium-level access, and 10 percent have good access
On Torsion-Free Crawley Groups
The notion of a Crawley p-group is well known in Abelian group theory. In this present work, a corresponding concept is introduced for torsion-free groups. The principal result, which uses the set-theoretic notions of the diamond and Martinâs axiom, establishes an independence result for N1-free Crawley groups
The Moderating Effects of âDarkâ Personality Traits and Message Vividness on the Persuasiveness of Terrorist Narrative Propaganda
Terrorism researchers have long discussed the role of psychology in the radicalization process. This work has included research on the respective roles of individual psychological traits and responses to terrorist propaganda. Unfortunately, much of this work has looked at psychological traits and responses to propaganda individually and has not considered how these factors may interact. This study redresses this gap in the literature. In this experiment (N = 268), participants were measured in terms of their narcissism, Machiavellianism, subclinical psychopathy, and everyday sadismâcollectively called the Dark Tetrad. Participants were then exposed to a vivid or nonvivid terrorist narrative (or a control message). Results indicate that Machiavellianism interacts with both narrative exposure and narrative vividness to amplify the persuasive effect of terrorist narratives. Neither narcissism, subclinical psychopathy, nor everyday sadism had such an effect. These results highlight the importance of considering the psychological traits of audiences when evaluating proclivity for radicalization via persuasion by terrorist narratives
CaNaSTA - Crop Niche Selection for Tropical Agriculture, a Spatial Decision Support System
Farmers in the developing world frequently find themselves in uncertain and risky environments, often having to make decisions based on very little information. Risks for smallholder farmers are often critical because of their poverty. In addition, in the tropics and subtropics, the natural environment is spatially and temporally variable and often harsh, thereby increasing the uncertainty faced by these farmers. This research aims to improve forage adoption decisions in the developing world, thereby increasing sustainable intensification and ultimately contributing to increased sustainable world food production and the alleviation of under-nutrition
Day convolution for monoidal bicategories
Ends and coends can be described as objects which are
universal amongst extranatural transformations. We describe a cate-
gorification of this idea, extrapseudonatural transformations, in such a way that
bicodescent objects are the objects which are universal amongst such transfor-
mations. We recast familiar results about coends in this new setting, providing
analogous results for bicodescent objects. In particular we prove a Fubini theorem
for bicodescent objects.
The free cocompletion of a category C is given by its category of presheaves
[C^op ,Set]. If C is also monoidal then its category of presheaves can be pro-
vided with a monoidal structure via the convolution product of Day.
This monoidal structure describes [C^op ,Set] as the free monoidal cocompletion
of C. Dayâs more general statement, in the V-enriched setting, is that if C is
a promonoidal V-category then [C^op ,V] possesses a monoidal structure via the
convolution product. We define promonoidal bicategories and go on to show
that if A is a promonoidal bicategory then the bicategory of pseudofunctors
Bicat(A^op ,Cat) is a monoidal bicategory
Laserwire at the Accelerator Test Facility 2 with Sub-Micrometre Resolution
A laserwire transverse electron beam size measurement system has been
developed and operated at the Accelerator Test Facility 2 (ATF2) at KEK.
Special electron beam optics were developed to create an approximately 1 x 100
{\mu}m (vertical x horizontal) electron beam at the laserwire location, which
was profiled using a 150 mJ, 71 ps laser pulse with a wavelength of 532 nm. The
precise characterisation of the laser propagation allows the non-Gaussian
transverse profiles of the electron beam caused by the laser divergence to be
deconvolved. A minimum vertical electron beam size of 1.07 0.06 (stat.)
0.05 (sys.) {\mu}m was measured. A vertically focussing quadrupole just
before the laserwire was varied whilst making laserwire measurements and the
projected vertical emittance was measured to be 82.56 3.04 pm rad.Comment: 17 pages, 26 figures, submitted to Phys. Rev. ST Accel. Beam
âCSA Planâ: A guide to scaling climate-smart agriculture - Concepts and lessons from designing CSA programs and policies in sub-Saharan Africa
Large scale investment is needed to create climate-smart agriculture (CSA) systems. While many government and development agencies are integrating CSA into their policies, programmes, plans and projects, there is little guidance for operational planning and implementation on ways to be climate-smart. Here we present âCSA-Planâ. CSA-Plan frames actions needed to design and execute CSA programs into four componentsâ1) situation analysis, 2) targeting and prioritizing, 3) program design, and 4) monitoring and evaluation. Each component yields concrete information to operationalize CSA development separating it from traditional agriculture development. Already, CSA-Plan has shown the capacity to change the discussion around CSA implementation. With iterative co-development, the approaches will become only more useful, relevant and legitimate to governments, civil society and the private sector alike
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