653 research outputs found
Symmetries of Abelian Orbifolds
Using the Polya Enumeration Theorem, we count with particular attention to
C^3/Gamma up to C^6/Gamma, abelian orbifolds in various dimensions which are
invariant under cycles of the permutation group S_D. This produces a collection
of multiplicative sequences, one for each cycle in the Cycle Index of the
permutation group. A multiplicative sequence is controlled by its values on
prime numbers and their pure powers. Therefore, we pay particular attention to
orbifolds of the form C^D/Gamma where the order of Gamma is p^alpha. We propose
a generalization of these sequences for any D and any p.Comment: 75 pages, 13 figures, 30 table
Counting Orbifolds
We present several methods of counting the orbifolds C^D/Gamma. A
correspondence between counting orbifold actions on C^D, brane tilings, and
toric diagrams in D-1 dimensions is drawn. Barycentric coordinates and scaling
mechanisms are introduced to characterize lattice simplices as toric diagrams.
We count orbifolds of C^3, C^4, C^5, C^6 and C^7. Some remarks are made on
closed form formulas for the partition function that counts distinct orbifold
actions.Comment: 69 pages, 9 figures, 24 tables; minor correction
Seiberg duality for Chern-Simons quivers and D-brane mutations
Chern-Simons quivers for M2-branes at Calabi-Yau singularities are best
understood as the low energy theory of D2-branes on a dual type IIA background.
We show how the D2-brane point of view naturally leads to three dimensional
Seiberg dualities for Chern-Simons quivers with chiral matter content: They
arise from a change of brane basis (or mutation), in complete analogy with the
better known Seiberg dualities for D3-brane quivers. This perspective
reproduces the known rules for Seiberg dualities in Chern-Simons-Yang-Mills
theories with unitary gauge groups. We provide explicit examples of dual
theories for the quiver dual to the Y^{p,q}(CP^2) geometries. We also comment
on the string theory derivation of CS quivers dual to massive type IIA
geometries.Comment: 32 pages+appendix; v2: added a referenc
D-branes Wrapped on Fuzzy del Pezzo Surfaces
We construct classical solutions in quiver gauge theories on D0-branes
probing toric del Pezzo singularities in Calabi-Yau manifolds. Our solutions
represent D4-branes wrapped around fuzzy del Pezzo surfaces. We study the
fluctuation spectrum around the fuzzy CP^2 solution in detail. We also comment
on possible applications of our fuzzy del Pezzo surfaces to the fuzzy version
of F-theory, dubbed F(uzz) theory.Comment: 1+42 pages, 9 figures v2: references added v3: statements on the
structure of the Yukawa couplings weakened. published versio
Wall Crossing, Quivers and Crystals
We study the spectrum of BPS D-branes on a Calabi-Yau manifold using the 0+1
dimensional quiver gauge theory that describes the dynamics of the branes at
low energies. The results of Kontsevich and Soibelman predict how the
degeneracies change. We argue that Seiberg dualities of the quiver gauge
theories, which change the basis of BPS states, correspond to crossing the
"walls of the second kind." There is a large class of examples, including local
del Pezzo surfaces, where the BPS degeneracies of quivers corresponding to one
D6 brane bound to arbitrary numbers of D4, D2 and D0 branes are counted by
melting crystal configurations. We show that the melting crystals that arise
are a discretization of the Calabi-Yau geometry. The shape of the crystal is
determined by the Calabi-Yau geometry and the background B-field, and its
microscopic structure by the quiver Q. We prove that the BPS degeneracies
computed from Q and Q' are related by the Kontsevich Soibelman formula, using a
geometric realization of the Seiberg duality in the crystal. We also show that,
in the limit of infinite B-field, the combinatorics of crystals arising from
the quivers becomes that of the topological vertex. We thus re-derive the
Gromov-Witten/Donaldson-Thomas correspondence
Methylphenidate Treatment in Children with Borderline IQ and Mental Retardation: Analysis of Three Aggregated Studies
Objective:
To determine response of low-IQ children with attention deficit hyperactivity disorder (ADHD)
symptoms to methylphenidate (MPH).
Methods:
An aggregated analysis was conducted in 90 children with low IQ who received the same dose
regimen of MPH in three independent, placebo-controlled studies. Active drug and placebo were given from
2 to 4 weeks each. Outcome measures included teacher and parent ratings on standardized behavior scales
(mean n = 84), performance on computer-controlled cognitive-motor tests (n = 62), and measures of
cardiovascular response (n = 85).
Results:
Both teachers and parents rated the children consistently as being improved on subscales assessing
attention, overactivity, and conduct problems. Some 44% of the subjects showed at least a 30% reduction
compared with placebo on teacher ratings. MPH improved accuracy on several cognitive tests, response
speed was increased on some, and seat activity declined for one of three tests; heart rate was mildly increased
(3.9 beats/minute) with MPH. Analyses of IQ and mental age as moderator variables suggested that lower
functional level (especially lower IQ) may be associated with a less favorable response to MPH.
Conclusions:
Children with low IQ and ADHD clearly respond to MPH, but their rate of beneficial response
appears to be well under that of normal-IQ children and more varied. Different attentional mechanisms may
moderate response to psychostimulants
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Micro-costing the provision of emotional support and information in UK eye clinics
Sight loss has wide ranging implications for an individual in terms of education, employment, mobility and mental health. Therefore there is a need for information and support to be provided in eye clinics at the point of diagnosis of sight threatening conditions, but these aspects of care are often missing from clinics. To meet these needs, some clinics employ an Eye Clinic Liaison Officer (ECLO) but the position has yet to be widely implemented. The aims of this study were:(1) To evaluate the forms of advice and emotional support in eye clinics provided by ECLOs.(2) To determine the cost of the ECLO service per patient
Characterisation of the Immunophenotype of Dogs with Primary Immune-Mediated Haemolytic Anaemia
Immune-mediated haemolytic anaemia (IMHA) is reported to be the most common autoimmune disease of dogs, resulting in significant morbidity and mortality in affected animals. Haemolysis is caused by the action of autoantibodies, but the immunological changes that result in their production have not been elucidated.To investigate the frequency of regulatory T cells (Tregs) and other lymphocyte subsets and to measure serum concentrations of cytokines and peripheral blood mononuclear cell expression of cytokine genes in dogs with IMHA, healthy dogs and dogs with inflammatory diseases.19 dogs with primary IMHA, 22 dogs with inflammatory diseases and 32 healthy control dogs.Residual EDTA-anti-coagulated blood samples were stained with fluorophore-conjugated monoclonal antibodies and analysed by flow cytometry to identify Tregs and other lymphocyte subsets. Total RNA was also extracted from peripheral blood mononuclear cells to investigate cytokine gene expression, and concentrations of serum cytokines (interleukins 2, 6 10, CXCL-8 and tumour necrosis factor α) were measured using enhanced chemiluminescent assays. Principal component analysis was used to investigate latent variables that might explain variability in the entire dataset.There was no difference in the frequency or absolute numbers of Tregs among groups, nor in the proportions of other lymphocyte subsets. The concentrations of pro-inflammatory cytokines were greater in dogs with IMHA compared to healthy controls, but the concentration of IL-10 and the expression of cytokine genes did not differ between groups. Principal component analysis identified four components that explained the majority of the variability in the dataset, which seemed to correspond to different aspects of the immune response.The immunophenotype of dogs with IMHA differed from that of dogs with inflammatory diseases and from healthy control dogs; some of these changes could suggest abnormalities in peripheral tolerance that permit development of autoimmune disease. The frequency of Tregs did not differ between groups, suggesting that deficiency in the number of these cells is not responsible for development of IMHA
Brane geometry and dimer models
The field content and interactions of almost all known gauge theories in AdS5/CFT4 can be expressed in terms of dimer models or bipartite graphs drawn on a torus. Associated with the fundamental cell is a complex structure parameter τ R . Based on the brane realization of these theories, we can specify a special Lagrangian (SLag) torus fibration that is the natural candidate to be identified as the torus on which the dimer lives. Using the metrics known in the literature, we compute the complex structure τ G of this torus. For the theories on ℂ3 and the conifold and for orbifolds thereof τ R = τ G . However, for more complicated examples, we show that the two complex structures cannot be equal and yet, remarkably, differ only by a few percent. We leave the explanation for this extraordinary proximity as an open challenge
Bone Microenvironment Specific Roles of ITAM Adapter Signaling during Bone Remodeling Induced by Acute Estrogen-Deficiency
Immunoreceptor tyrosine-based activation motif (ITAM) signaling mediated by DAP12 or Fcε receptor Iγ chain (FcRγ) have been shown to be critical for osteoclast differentiation and maturation under normal physiological conditions. Their function in pathological conditions is unknown. We studied the role of ITAM signaling during rapid bone remodeling induced by acute estrogen-deficiency in wild-type (WT), DAP12-deficient (DAP12-/-), FcRγ-deficient (FcRγ-/-) and double-deficient (DAP12-/-FcRγ-/-) mice. Six weeks after ovariectomy (OVX), DAP12-/-FcRγ-/- mice showed resistance to lumbar vertebral body (LVB) trabecular bone loss, while WT, DAP12-/- and FcRγ-/- mice had significant LVB bone loss. In contrast, all ITAM adapter-deficient mice responded to OVX with bone loss in both femur and tibia of approximately 40%, relative to basal bone volumes. Only WT mice developed significant cortical bone loss after OVX. In vitro studies showed microenvironmental changes induced by OVX are indispensable for enhanced osteoclast formation and function. Cytokine changes, including TGFβ and TNFα, were able to induce osteoclastogenesis independent of RANKL in BMMs from WT but not DAP12-/- and DAP12-/-FcRγ-/- mice. FSH stimulated RANKL-induced osteoclast differentiation from BMMs in WT, but not DAP12-/- and DAP12-/-FcRγ-/- mice. Our study demonstrates that although ITAM adapter signaling is critical for normal bone remodeling, estrogen-deficiency induces an ITAM adapter-independent bypass mechanism allowing for enhanced osteoclastogenesis and activation in specific bony microenvironments
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