15,380 research outputs found
Low-Energy Heavy-Ion Reactions and the Skyrme Effective Interaction
The Skyrme effective interaction, with its multitude of parameterisations,
along with its implemen- tation using the static and time-dependent density
functional (TDHF) formalism have allowed for a range of microscopic
calculations of low-energy heavy-ion collisions. These calculations allow
variation of the effective interaction along with an interpretation of the
results of this variation informed by a comparison to experimental data.
Initial progress in implementing TDHF for heavy-ion collisions necessarily used
many approximations in the geometry or the interaction. Over the last decade or
so, the implementations have overcome all restrictions, and studies have begun
to be made where details of the effective interaction are being probed. This
review surveys these studies in low energy heavy-ion reactions, finding
significant effects on observables from the form of the spin-orbit interaction,
the use of the tensor force, and the inclusion of time-odd terms in the density
functional.Comment: submitted to Prog. Part. Nucl. Phy
A benign, low Z electron capture agent for negative ion TPCs
We have identified nitromethane (CHNO) as an effective electron
capture agent for negative ion TPCs (NITPCs).
We present drift velocity and longitudinal diffusion measurements for
negative ion gas mixtures using nitromethane as the capture agent.
Not only is nitromethane substantially more benign than the only other
identified capture agent, CS, but its low atomic number will enable the use
of the NITPC as a photoelectric X{}-ray polarimeter in the 1{}-10 keV band
The magical language of un-realistic venture ideas in social entrepreneurship
As social entrepreneurship gains maturity, research has begun to explore the less alluring aspects of the field, including the heroic stance of social entrepreneurs, the assumed moral superiority of their intentions, and the misleading emphasis on solutionism. In this paper, we explore a central component of this criticism, which is the construction of un-realistic venture ideas in social entrepreneurs’ pitches for social change. We analysed social venture business plans and the written feedback provided by judges during a social venture competition, and we used speech act theory to analyse the claims and promises triggering judges’ disbelief. We discovered three linguistic artefacts that underlie the construction of un-realistic venture ideas in social entrepreneurship, which we label holism, devotion, and enlightenment. While these artefacts trigger disbelief, they also play an expressive role as they channel both contestation and dreams. We leverage magical realism to forward an alternative explanation of how venture ideas in social entrepreneurship can act as a cultural form of social protest, which can be seen as a historically contingent, modern revolution
On initialization of milling paths for 5-axis flank CNC machining of free-form surfaces with general milling tools
We propose a path-planning algorithm for 5-axis flank CNC machining with general tools of varying curvature. Our approach generalizes the initialization strategy introduced for conical tools [Bo et al., 2017] to arbitrary milling tools. Given a free-form (NURBS) surface and a rotational milling tool, we look for its motion in 3D to approximate the input reference surface within a given tolerance. We show that for a general shape of the milling tool, there exist locally and generically four 3D directions in which the point-surface distance follows the shape of the tool up to second order. These directions form a 3D multi-valued vector field and its integration gives rise to a set of integral curves. Among these integral curves, we seek straight line segments that correspond to good initial positions of the axes of the milling tool. We validate our method against synthetic examples with known exact solutions and, on industrial datasets, we detect approximate solutions that meet fine machining tolerances. We also demonstrate applicability of our method for efficient flank milling of convex regions that is not possible using traditional conical tools.RYC-2017-2264
Search for correlation effects in linear chains of trapped ions
We report a precise search for correlation effects in linear chains of 2 and
3 trapped Ca+ ions. Unexplained correlations in photon emission times within a
linear chain of trapped ions have been reported, which, if genuine, cast doubt
on the potential of an ion trap to realize quantum information processing. We
observe quantum jumps from the metastable 3d 2D_{5/2} level for several hours,
searching for correlations between the decay times of the different ions. We
find no evidence for correlations: the number of quantum jumps with separations
of less than 10 ms is consistent with statistics to within errors of 0.05%; the
lifetime of the metastable level derived from the data is consistent with that
derived from independent single-ion data at the level of the experimental
errors 1%; and no rank correlations between the decay times were found with
sensitivity to rank correlation coefficients at the level of |R| = 0.024.Comment: With changes to introduction. 5 pages, including 4 figures. Submitted
to Europhys. Let
Optimal Computation of Avoided Words
The deviation of the observed frequency of a word from its expected
frequency in a given sequence is used to determine whether or not the word
is avoided. This concept is particularly useful in DNA linguistic analysis. The
value of the standard deviation of , denoted by , effectively
characterises the extent of a word by its edge contrast in the context in which
it occurs. A word of length is a -avoided word in if
, for a given threshold . Notice that such a word
may be completely absent from . Hence computing all such words na\"{\i}vely
can be a very time-consuming procedure, in particular for large . In this
article, we propose an -time and -space algorithm to compute all
-avoided words of length in a given sequence of length over a
fixed-sized alphabet. We also present a time-optimal -time and
-space algorithm to compute all -avoided words (of any
length) in a sequence of length over an alphabet of size .
Furthermore, we provide a tight asymptotic upper bound for the number of
-avoided words and the expected length of the longest one. We make
available an open-source implementation of our algorithm. Experimental results,
using both real and synthetic data, show the efficiency of our implementation
Urban planning for healthy cities a review of the progress of the european healthy cities programme
The purpose of this paper is to evaluate the progress made by European cities in relation to Healthy Urban Planning (HUP) during Phase IV of the World Health Organization's Healthy Cities programme (2003-2008). The introduction sets out the general principle of HUP, identifying three levels or phases of health and planning integration. This leads on to a more specific analysis of the processes and substance of HUP, which provide criteria for assessment of progress. The assessment itself relies on two sources of data provided by the municipalities: the Annual Review Templates (ARTs) 2008 and the response to the Phase IV General Evaluation Questionnaire. The findings indicate that the evidence from different sources and questions in different sections are encouragingly consistent. The number of cities achieving a good level of understanding and activity inHUP has risen very substantially over the period. In particular, those achieving effective strategic integration of health and planning have increased. A key challenge for the future will be to develop planning frameworks which advance public health concerns in a spatial policy context driven often by market forces. A health in all policies approach could be valuable. © 2012 The New York Academy of Medicine
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