30 research outputs found
Anomalous Action in Gauge Invariant, Nonlocal, Dynamical Quark Model
Anomalous sector of chiral Lagrangian is calculated in a gauge invariant,
nonlocal, dynamical quark model. The Wess-Zumino term is proved coming from two
kinds of sources, one is independent on and another dependent on dynamical
quark self energy
. and more higher order anomalous sectors come only from
dependent source. After some cancellation, standard
Wess-Zumino action is obtained.Comment: 10 page
Isospin violation and the proton's neutral weak magnetic form factor
The effects of isospin violation on the neutral weak magnetic form factor of
the proton are studied using two-flavour chiral perturbation theory. The first
nonzero contributions appear at O(p^4) in the small-momentum expansion, and the
O(p^5) corrections are also calculated. The leading contributions from an
explicit Delta(1232) isomultiplet are included as well. At such a high order in
the chiral expansion, one might have expected a large number of unknown
parameters to contribute. However, it is found that no unknown parameters can
appear within loop diagrams, and a single tree-level counterterm at O(p^4) is
sufficient to absorb all divergences. The momentum dependence of the neutral
weak magnetic form factor is not affected by this counterterm.Comment: 26 pages including 9 figure
Relativistic versus Nonrelativistic Optical Potentials in A(e,e'p)B Reactions
We investigate the role of relativistic and nonrelativistic optical
potentials used in the analysis of () data. We find that the
relativistic calculations produce smaller () cross sections even in the
case in which both relativistic and nonrelativistic optical potentials fit
equally well the elastic proton--nucleus scattering data. Compared to the
nonrelativistic impulse approximation, this effect is due to a depletion in the
nuclear interior of the relativistic nucleon current, which should be taken
into account in the nonrelativistic treatment by a proper redefinition of the
effective current operator.Comment: Added one new figure, the formalism section has been enlarged and the
list of references updated. Added one appendix. This version will appear in
Phys. Rev. C. Revtex 3.0, 6 figures (not included). Full postscript version
of the file and figures available at
http://www.nikhefk.nikhef.nl/projects/Theory/preprints
Haptic Edge Detection Through Shear
Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals
Voxel-based statistical analysis of thalamic glucose metabolism in traumatic brain injury: relationship with consciousness and cognition
Objective: To study the relationship between thalamic glucose metabolism and neurological outcome after severe traumatic
brain injury (TBI).
Methods: Forty-nine patients with severe and closed TBI and 10 healthy control subjects with 18F-FDG PET were studied.
Patients were divided into three groups: MCS&VS group (n ÂĽ 17), patients in a vegetative or a minimally conscious state;
In-PTA group (n ÂĽ 12), patients in a state of post-traumatic amnesia (PTA); and Out-PTA group (n ÂĽ 20), patients who
had emerged from PTA. SPM5 software implemented in MATLAB 7 was used to determine the quantitative differences
between patients and controls. FDG-PET images were spatially normalized and an automated thalamic ROI mask was
generated. Group differences were analysed with two sample voxel-wise t-tests.
Results: Thalamic hypometabolism was the most prominent in patients with low consciousness (MCS&VS group) and the
thalamic hypometabolism in the In-PTA group was more prominent than that in the Out-PTA group. Healthy control
subjects showed the greatest thalamic metabolism. These differences in metabolism were more pronounced in the internal
regions of the thalamus.
Conclusions: The results confirm the vulnerability of the thalamus to suffer the effect of the dynamic forces generated during
a TBI. Patients with thalamic hypometabolism could represent a sub-set of subjects that are highly vulnerable to
neurological disability after TBI.Lull Noguera, N.; NoĂ©, E.; Lull Noguera, JJ.; Garcia Panach, J.; Chirivella, J.; Ferri, J.; LĂłpez-Aznar, D.... (2010). Voxel-based statistical analysis of thalamic glucose metabolism in traumatic brain injury: relationship with consciousness and cognition. Brain Injury. 24(9):1098-1107. doi:10.3109/02699052.2010.494592S10981107249Gallagher, C. N., Hutchinson, P. J., & Pickard, J. D. (2007). Neuroimaging in trauma. Current Opinion in Neurology, 20(4), 403-409. doi:10.1097/wco.0b013e32821b987bWoischneck, D., Klein, S., Reiďż˝berg, S., Dďż˝hring, W., Peters, B., & Firsching, R. (2001). Classification of Severe Head Injury Based on Magnetic Resonance Imaging. Acta Neurochirurgica, 143(3), 263-271. doi:10.1007/s007010170106Grados, M. A. (2001). Depth of lesion model in children and adolescents with moderate to severe traumatic brain injury: use of SPGR MRI to predict severity and outcome. 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