21,947 research outputs found
Self-shrinkers of the mean curvature flow in arbitrary codimension
For hypersurfaces of dimension greater than one, Huisken showed that compact
self-shrinkers of the mean curvature flow with positive scalar mean curvature
are spheres. We will prove the following extension: A compact self-similar
solution in arbitrary codimension and of dimension greater than one is
spherical, i.e. contained in a sphere, if and only if the mean curvature vector
\be H\ee is non-vanishing and the principal normal \be\nu\ee is parallel in the
normal bundle. We also give a classification of complete noncompact
self-shrinkers of that type.Comment: 19 pages, 1 figur
Reducing behaviour problems in young people through social competence programmes
There is a relatively strong relationship between the concepts of behavioural problems
and social competence, in that social competence is regarded as one of the most
important protective factors in the prevention of behavioural problems. This paper
argues that the concept of social competence should include social skills, social practice
and empathic understanding. It identifies the components that form part of an effective
social competence programme, including enhancing an understanding of social
situations, increasing the generation of adequate social skills, improving the management
of provocations which may lead to uncontrolled anger, and developing empathic
understanding. The evidence also suggests that effective social competence programmes
for children and young people should be multi modal and consist of mixed groups of
pupils with and without difficulties. The paper concludes with a brief description of
Aggression Replacement Training as an example of a programme which follows the
recommended guidelines.peer-reviewe
Deservingness Transfers
This article seeks to cause trouble for a brand of consequentialism known as ‘desertarianism’. In somewhat different ways, views of this kind evaluate outcomes more favourably, other things equal, the better the fit between the welfare different people enjoy and the welfare they each deserve. These views imply that we can improve outcomes by redistributing welfare to fit desert, which seems plausible enough. Unfortunately, they also imply that we can improve outcomes by redistributing desert to fit welfare: in other words, by making happy people more deserving, at the cost of making unhappy people less deserving. Extant versions of desertarianism predict that such ‘deservingness transfers’ are improvements and that we ought to carry them out. Even worse, they will sometimes rank deservingness transfers higher than simply benefitting deserving people who are poorly off
The uncertainty in regional innovation policy: some ration-ales and tools for learning in policy making
This paper deals with two major dilemmas in regional innovation policy making: The dilemma that theory does not provide sufficient answers for the formulation of specific innovation policy measures addressing the problem configurations of single regions and the dilemma that role models are used as a substitute for orientation. In order to support policy learning, different approaches like evaluation, the development of innovation strategies and regional foresight are discussed. --
Pulse propagation in time dependent randomly layered media
We study cumulative scattering effects on wave front propagation in time
dependent randomly layered media. It is well known that the wave front has a
deterministic characterization in time independent media, aside from a small
random shift in the travel time. That is, the pulse shape is predictable, but
faded and smeared as described mathematically by a convolution kernel
determined by the autocorrelation of the random fluctuations of the wave speed.
The main result of this paper is the extension of the pulse stabilization
results to time dependent randomly layered media. When the media change slowly,
on time scales that are longer than the pulse width and the time it takes the
waves to traverse a correlation length, the pulse is not affected by the time
fluctuations. In rapidly changing media, where these time scales are similar,
both the pulse shape and the random component of the arrival time are affected
by the statistics of the time fluctuations of the wave speed. We obtain an
integral equation for the wave front, that is more complicated than in time
independent media, and cannot be solved analytically, in general. We also give
examples of media where the equation simplifies, and the wave front can be
analyzed explicitly. We illustrate with these examples how the time
fluctuations feed energy into the pulse
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