196 research outputs found
Cervicothoracic Intradural Arachnoid Cyst Misdiagnosed as Motor Neuron Disease
Recognizing syndromes which mimic ALS is crucial both to avoid giving this diagnosis erroneously and since there may be appropriate treatments. We report a 63-year-old woman diagnosed with possible ALS five years ago based on upper and lower motor neuron signs with typical electrophysiology and normal cranial MRI. At reassessment, spinal MRI revealed a cervicothoracic cyst with cord compression that was successfully treated neurosurgically. Histopathology confirmed an arachnoid origin as suspected from MRI. Spinal cysts may mimic ALS and need to be thoroughly excluded by appropriate imaging
Fuzzy Torus via q-Parafermion
We note that the recently introduced fuzzy torus can be regarded as a
q-deformed parafermion. Based on this picture, classification of the Hermitian
representations of the fuzzy torus is carried out. The result involves
Fock-type representations and new finite dimensional representations for q
being a root of unity as well as already known finite dimensional ones.Comment: 12pages, no figur
Drinfeld-Twisted Supersymmetry and Non-Anticommutative Superspace
We extend the analysis of hep-th/0408069 on a Lorentz invariant
interpretation of noncommutative spacetime to field theories on
non-anticommutative superspace with half the supersymmetries broken. By
defining a Drinfeld-twisted Hopf superalgebra, it is shown that one can restore
twisted supersymmetry and therefore obtain a twisted version of the chiral
rings along with certain Ward-Takahashi identities. Moreover, we argue that the
representation content of theories on the deformed superspace is identical to
that of their undeformed cousins and comment on the consequences of our
analysis concerning non-renormalization theorems.Comment: 1+17 pages; typos fixed, minor correction
Toric Calabi-Yau supermanifolds and mirror symmetry
We study mirror symmetry of supermanifolds constructed as fermionic
extensions of compact toric varieties. We mainly discuss the case where the
linear sigma A-model contains as many fermionic fields as there are U(1)
factors in the gauge group. In the mirror super-Landau-Ginzburg B-model, focus
is on the bosonic structure obtained after integrating out all the fermions.
Our key observation is that there is a relation between the super-Calabi-Yau
conditions of the A-model and quasi-homogeneity of the B-model, and that the
degree of the associated superpotential in the B-model is given in terms of the
determinant of the fermion charge matrix of the A-model.Comment: 20 pages, v2: references adde
On Twistors and Conformal Field Theories from Six Dimensions
We discuss chiral zero-rest-mass field equations on six-dimensional
space-time from a twistorial point of view. Specifically, we present a detailed
cohomological analysis, develop both Penrose and Penrose-Ward transforms, and
analyse the corresponding contour integral formulae. We also give twistor space
action principles. We then dimensionally reduce the twistor space of
six-dimensional space-time to obtain twistor formulations of various theories
in lower dimensions. Besides well-known twistor spaces, we also find a novel
twistor space amongst these reductions, which turns out to be suitable for a
twistorial description of self-dual strings. For these reduced twistor spaces,
we explain the Penrose and Penrose-Ward transforms as well as contour integral
formulae.Comment: v4: 66 pages, typos fixed, appendix B revise
Instanton operators in five-dimensional gauge theories
This article is distributed under the terms of the Creative Commons
Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in
any medium, provided the original author(s) and source are creditedN.L. is supported in part by STFC grant ST/J002798/1. C.P. is a Royal Society Research Fellow.N.L. is supported in part by STFC grant ST/J002798/1. C.P. is a Royal Society Research Fellow.N.L. is supported in part by STFC grant ST/J002798/1. OPen Aceess funded by SCOAP
Heritability and reliability of automatically segmented human hippocampal formation subregions
The human hippocampal formation can be divided into a set of cytoarchitecturally and functionally distinct subregions, involved in different aspects of memory formation. Neuroanatomical disruptions within these subregions are associated with several debilitating brain disorders including Alzheimer's disease, major depression, schizophrenia, and bipolar disorder. Multi-center brain imaging consortia, such as the Enhancing Neuro Imaging Genetics through Meta-Analysis (ENIGMA) consortium, are interested in studying disease effects on these subregions, and in the genetic factors that affect them. For large-scale studies, automated extraction and subsequent genomic association studies of these hippocampal subregion measures may provide additional insight. Here, we evaluated the test-retest reliability and transplatform reliability (1.5 T versus 3 T) of the subregion segmentation module in the FreeSurfer software package using three independent cohorts of healthy adults, one young (Queensland Twins Imaging Study, N=39), another elderly (Alzheimer's Disease Neuroimaging Initiative, ADNI-2, N=163) and another mixed cohort of healthy and depressed participants (Max Planck Institute, MPIP, N=598). We also investigated agreement between the most recent version of this algorithm (v6.0) and an older version (v5.3), again using the ADNI-2 and MPIP cohorts in addition to a sample from the Netherlands Study for Depression and Anxiety (NESDA) (N=221). Finally, we estimated the heritability (h(2)) of the segmented subregion volumes using the full sample of young, healthy QTIM twins (N=728). Test-retest reliability was high for all twelve subregions in the 3 T ADNI-2 sample (intraclass correlation coefficient (ICC)=0.70-0.97) and moderate-to-high in the 4 TQTIM sample (ICC=0.5-0.89). Transplatform reliability was strong for eleven of the twelve subregions (ICC=0.66-0.96); however, the hippocampal fissure was not consistently reconstructed across 1.5 T and 3 T field strengths (ICC=0.47-0.57). Between-version agreement was moderate for the hippocampal tail, subiculum and presubiculum (ICC=0.78-0.84; Dice Similarity Coefficient (DSC)=0.55-0.70), and poor for all other subregions (ICC=0.34-0.81; DSC=0.28-0.51). All hippocampal subregion volumes were highly heritable (h(2)=0.67-0.91). Our findings indicate that eleven of the twelve human hippocampal subregions segmented using FreeSurfer version 6.0 may serve as reliable and informative quantitative phenotypes for future multi-site imaging genetics initiatives such as those of the ENIGMA consortium. (C) 2016 The Authors. Published by Elsevier Inc
Twistor Strings with Flavour
We explore the tree-level description of a class of N=2 UV-finite SYM
theories with fundamental flavour within a topological B-model twistor string
framework. In particular, we identify the twistor dual of the Sp(N) gauge
theory with one antisymmetric and four fundamental hypermultiplets, as well as
that of the SU(N) theory with 2N hypermultiplets. This is achieved by suitably
orientifolding/orbifolding the original N=4 setup of Witten and adding a
certain number of new topological 'flavour'-branes at the orientifold/orbifold
fixed planes to provide the fundamental matter. We further comment on the
appearance of these objects in the B-model on CP(3|4). An interesting aspect of
our construction is that, unlike the IIB description of these theories in terms
of D3 and D7-branes, on the twistor side part of the global flavour symmetry is
realised geometrically. We provide evidence for this correspondence by
calculating and matching amplitudes on both sides.Comment: 38+12 pages; uses axodraw.sty. v2: References added, minor
clarification
Quantized Nambu-Poisson Manifolds in a 3-Lie Algebra Reduced Model
We consider dimensional reduction of the Bagger-Lambert-Gustavsson theory to
a zero-dimensional 3-Lie algebra model and construct various stable solutions
corresponding to quantized Nambu-Poisson manifolds. A recently proposed Higgs
mechanism reduces this model to the IKKT matrix model. We find that in the
strong coupling limit, our solutions correspond to ordinary noncommutative
spaces arising as stable solutions in the IKKT model with D-brane backgrounds.
In particular, this happens for S^3, R^3 and five-dimensional Neveu-Schwarz
Hpp-waves. We expand our model around these backgrounds and find effective
noncommutative field theories with complicated interactions involving
higher-derivative terms. We also describe the relation of our reduced model to
a cubic supermatrix model based on an osp(1|32) supersymmetry algebra.Comment: 22 page
On Local Calabi-Yau Supermanifolds and Their Mirrors
We use local mirror symmetry to study a class of local Calabi-Yau
super-manifolds with bosonic sub-variety V_b having a vanishing first Chern
class. Solving the usual super- CY condition, requiring the equality of the
total U(1) gauge charges of bosons \Phi_{b} and the ghost like fields \Psi_{f}
one \sum_{b}q_{b}=\sum_{f}Q_{f}, as \sum_{b}q_{b}=0 and \sum_{f}Q_{f}=0,
several examples are studied and explicit results are given for local A_{r}
super-geometries. A comment on purely fermionic super-CY manifolds
corresponding to the special case where q_{b}=0, \forall b and \sum_{f}Q_{f}=0
is also made.\bigskipComment: 17 page
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