145 research outputs found
Modelling global livestock diversity : a fuzzy cognitive mapping approach
For modelling global trends in agrobiodiversity better insight in the relationship between drivers (and related pressures) and agrobiodiversity is needed. In a previous study of the authors a number of indicators for genetic diversity were proposed as being suitable for modelling. In this working document it was investigated if a global agrobiodiversity map for livestock could be produced based on one of these earlier suggested indicators. The Global Domestic Animal Diversity Information System (DAD-IS) was interrogated for one livestock species (cattle) to investigate whether sufficient data of good quality is available to produce such a global map. Additionally, a fuzzy cognitive mapping approach was used to make a qualitative description of livestock diversity in relation to drivers of change. In the FCM 21 factors were identified by the workshop participants to describe the livestock diversity system, of which 10 appeared to be most influential. For these most important factors a list of relevant (proxy) indicators with their potential for use was suggested. These suggested indicators could be the basis for further research in which the so-called archetype methodology could be used to get insight in hotspots of livestock diversity
Doelgroepen inventarisatie Nagoya Protocol
Access and Benefit-Sharing (ABS) betreft de regulering van de toegang tot en het gebruik van genetische bronnen, en het delen van de voordelen voortkomend uit dit gebruik tussen leveranciers en gebruikes. Er zijn internationale ABS regels overeengekomen, vastgelegd in de Convention on Biological Diversity, het Nagoya Protocol en de International Treaty for Plant Genetic Resources for Food and Agriculture. Omdat de Europese Unie een Verordening in voorbereiding heeft waarin de plichten van gebruikers en overheden van lidstaten worden geformuleerd, is een inventarisatie gemaakt van gebruikers van genetische bronnen
Fermions, T-duality and effective actions for D-branes in bosonic backgrounds
We find the effective action for any D-brane in a general bosonic background
of supergravity. The results are explicit in component fields up to second
order in the fermions and are obtained in a covariant manner. No interaction
terms between fermions and the field , characteristic of the bosonic
actions, are considered. These are reserved for future work. In order to obtain
the actions, we reduce directly from the M2-brane world-volume action to the
D2-brane world-volume action. Then, by means of T-duality, we obtain the other
Dp-brane actions. The resulting Dp-brane actions can be written in a single
compact and elegant expression.Comment: 22 pages, latex, version published by JHEP plus typos corrected in
eq.(44) and eq.(47
Families of N=2 Strings
In a given 4d spacetime bakcground, one can often construct not one but a
family of distinct N=2 string theories. This is due to the multiple ways N=2
superconformal algebra can be embedded in a given worldsheet theory. We
formulate the principle of obtaining different physical theories by gauging
different embeddings of the same symmetry algebra in the same ``pre-theory.''
We then apply it to N=2 strings and formulate the recipe for finding the
associated parameter spaces of gauging. Flat and curved target spaces of both
(4,0) and (2,2) signatures are considered. We broadly divide the gauging
choices into two classes, denoted by alpha and beta, and show them to be
related by T-duality. The distinction between them is formulated topologically
and hinges on some unique properties of 4d manifolds. We determine what their
parameter spaces of gauging are under certain simplicity ansatz for generic
flat spaces (R^4 and its toroidal compactifications) as well as some curved
spaces. We briefly discuss the spectra of D-branes for both alpha and beta
families.Comment: 66+1 pages, 2 tables, latex 2e, hyperref. ver2: typos corrected,
reference adde
Emotion processing, reappraisal and craving in alcohol dependence: A functional Magnetic Resonance Imaging study
FdR â Publicaties niet-programma gebonde
Superparticle Models with Tensorial Central Charges
A generalization of the Ferber-Shirafuji formulation of superparticle
mechanics is considered. The generalized model describes the dynamics of a
superparticle in a superspace extended by tensorial central charge coordinates
and commuting twistor-like spinor variables. The D=4 model contains a
continuous real parameter and at a=0 reduces to the SU(2,2|1)
supertwistor Ferber-Shirafuji model, while at a=1 one gets an OSp(1|8)
supertwistor model of ref. [1] (hep-th/9811022) which describes BPS states with
all but one unbroken target space supersymmetries. When 0<a<1 the model admits
an OSp(2|8) supertwistor description, and when a>1 the supertwistor group
becomes OSp(1,1|8). We quantize the model and find that its quantum spectrum
consists of massless states of an arbitrary (half)integer helicity. The
independent discrete central charge coordinate describes the helicity spectrum.
We also outline the generalization of the a=1 model to higher space-time
dimensions and demonstrate that in D=3,4,6 and 10, where the quantum states are
massless, the extra degrees of freedom (with respect to those of the standard
superparticle) parametrize compact manifolds. These compact manifolds can be
associated with higher-dimensional helicity states. In particular, in D=10 the
additional ``helicity'' manifold is isomorphic to the seven-sphere.Comment: 32 pages, LATEX, no figure
A model independent spin analysis of fundamental particles using azimuthal asymmetries
Exploiting the azimuthal angle dependence of the density matrices we
construct observables that directly measure the spin of a heavy unstable
particle. A novelty of the approach is that the analysis of the azimuthal angle
dependence in a frame other than the usual helicity frame offers an independent
cross-check on the extraction of the spin. Moreover, in some instances when the
transverse polarisation tensor of highest rank is vanishing, for an accidental
or dynamical reason, the standard azimuthal asymmetries vanish and would lead
to a measurement with a wrong spin assignment. In a frame such as the one we
construct, the correct spin assignment would however still be possible. The
method gives direct information about the spin of the particle under
consideration and the same event sample can be used to identify the spins of
each particle in a decay chain. A drawback of the method is that it is
instrumental only when the momenta of the test particle can be reconstructed.
However we hope that it might still be of use in situations with only partial
reconstruction. We also derive the conditions on the production and decay
mechanisms for the spins, and hence the polarisations, to be measured at a
collider experiment. As an example for the use of the method we consider the
simultaneous reconstruction, at the partonic level, of the spin of both the top
and the in top pair production in in the semi-leptonic channel.Comment: 42 pages, 7 figures, 4 table
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