229 research outputs found
Fixed point data of finite groups acting on 3-manifolds
We consider fully effective orientation-preserving smooth actions of a given
finite group G on smooth, closed, oriented 3-manifolds M. We investigate the
relations that necessarily hold between the numbers of fixed points of various
non-cyclic subgroups. In Section 2, we show that all such relations are in fact
equations mod 2, and we explain how the number of independent equations yields
information concerning low-dimensional equivariant cobordism groups. Moreover,
we restate a theorem of A. Szucs asserting that under the conditions imposed on
a smooth action of G on M as above, the number of G-orbits of points x in M
with non-cyclic stabilizer G_x is even, and we prove the result by using
arguments of G. Moussong. In Sections 3 and 4, we determine all the equations
for non-cyclic subgroups G of SO(3).Comment: Published by Algebraic and Geometric Topology at
http://www.maths.warwick.ac.uk/agt/AGTVol3/agt-3-24.abs.htm
Chromatic roots and limits of dense graphs
In this short note we observe that recent results of Abert and Hubai and of
Csikvari and Frenkel about Benjamini--Schramm continuity of the holomorphic
moments of the roots of the chromatic polynomial extend to the theory of dense
graph sequences. We offer a number of problems and conjectures motivated by
this observation.Comment: 9 page
Modular Invariance and Uniqueness of Conformal Characters
We show that the conformal characters of various rational models of
W-algebras can be already uniquely determined if one merely knows the central
charge and the conformal dimensions. As a side result we develop several tools
for studying representations of SL(2,Z) on spaces of modular functions. These
methods, applied here only to certain rational conformal field theories, may be
useful for the analysis of many others.Comment: 21 pages (AMS TeX), BONN-TH-94-16, MPI-94-6
Semi-infinite cohomology of W-algebras
We generalize some of the standard homological techniques to \cW-algebras,
and compute the semi-infinite cohomology of the \cW_3 algebra on a variety of
modules. These computations provide physical states in \cW_3 gravity coupled
to \cW_3 minimal models and to two free scalar fields.Comment: 15 page
Flexible Lipid Bilayers in Implicit Solvent
A minimalist simulation model for lipid bilayers is presented. Each lipid is
represented by a flexible chain of beads in implicit solvent. The hydrophobic
effect is mimicked through an intermolecular pair potential localized at the
``water''/hydrocarbon tail interface. This potential guarantees realistic
interfacial tensions for lipids in a bilayer geometry. Lipids self assemble
into bilayer structures that display fluidity and elastic properties consistent
with experimental model membrane systems. Varying molecular flexibility allows
for tuning of elastic moduli and area/molecule over a range of values seen in
experimental systems.Comment: 5 pages, 5 figure
Temperature-sensitive colloidal phase behavior induced by critical Casimir forces
We report Monte Carlo simulations of phase behavior of colloidal suspensions with near-critical binary solvents using effective pair potentials from experiments. At off-critical solvent composition, the calculated phase diagram agrees well with measurements of the experimental system, indicating that many-body effects are limited. Close to the critical composition, however, agreement between experiment and simulation becomes poorer, signaling the increased importance of many-body effects. Both at and off the critical solvent concentration, the colloidal phase diagram is qualitatively similar to those of molecular systems and obeys the principle of corresponding states with one striking difference: it occurs in a narrow temperature interval of <1C below the solvent phase separation temperature.This work was supported by the Foundation for Fundamental Research on Matter (FOM). P. S. acknowledges support from the Innovational Research Incentives Scheme (VIDI grant) of the Netherlands Organization for Scientific Research (NWO). A. V. V. acknowledges financial support by the Department of Theory and Bio-Systems at the Max Planck Institute of Colloids and Interfaces. We thank A. Maciolek and D. T. F. Mohry for helpful discussions
BRST Analysis of Physical States for 2D (Super) Gravity Coupled to (Super) Conformal Matter
We summarize some recent results on the BRST analysis of physical states of
2D gravity coupled to c<=1 conformal matter and the supersymmetric
generalization.Comment: 11 page
On a possible new R^2 theory of supergravity
We consider a new MacDowell-Mansouri R^2-type of supergravity theory, an
extension of conformal supergravity, based on the superalgebra Osp(1|8).
Invariance under local symmetries with negative Weyl weight is achieved by
imposing chirality-duality and double-duality constraints on curvatures, along
with the usual constraint of vanishing supertorsion. An analysis of the
remaining gauge symmetries shows that those with vanishing Weyl weight are
invariances of the action at the linearized level. For the symmetries with
positive Weyl weight we find that invariance of the action would require
further modifications of the transformation rules. This conclusion is supported
by a kinematical analysis of the closure of the gauge algebra.Comment: 52 pages, Late
Ichthyosis follicularis, alopecia, and photophobia (IFAP) syndrome
The IFAP syndrome is a rare X-linked genetic disorder reported in nearly 40 patients. It is characterized by the triad of Ichthyosis Follicularis, Alopecia, and Photophobia from birth. Other features such as short stature, intellectual disability, and seizures may develop in the first few years of life. Skin histopathology is non-specific and consists of dilated hair follicles with keratin plugs extending above the surface of the skin, decreased or absent sebaceous glands, and decreased desmosomes in number and size. The disorder results from mutations in the MBTPS2 gene that impairs cholesterol homeostasis and the ability to cope with endoplasmic reticulum stress. Follicular hyperkeratosis can be treated using topical keratolytics, emollients and urea preparations. A moderate response to acitretin therapy has been noted in some patients. Intensive lubrication of the ocular surface is essential. Life expectancy in patients with IFAP syndrome can vary from death in the neonatal period to normal surviving. Cardiopulmonary complications remain the major cause of death
Protein crystals in adenovirus type 5-infected cells: requirements for intranuclear crystallogenesis, structural and functional analysis
Intranuclear crystalline inclusions have been observed in the nucleus of epithelial cells infected with Adenovirus serotype 5 (Ad5) at late steps of the virus life cycle. Using immuno-electron microscopy and confocal microscopy of cells infected with various Ad5 recombinants modified in their penton base or fiber domains, we found that these inclusions represented crystals of penton capsomers, the heteromeric capsid protein formed of penton base and fiber subunits. The occurrence of protein crystals within the nucleus of infected cells required the integrity of the fiber knob and part of the shaft domain. In the knob domain, the region overlapping residues 489–492 in the FG loop was found to be essential for crystal formation. In the shaft, a large deletion of repeats 4 to 16 had no detrimental effect on crystal inclusions, whereas deletion of repeats 8 to 21 abolished crystal formation without altering the level of fiber protein expression. This suggested a crucial role of the five penultimate repeats in the crystallisation process. Chimeric pentons made of Ad5 penton base and fiber domains from different serotypes were analyzed with respect to crystal formation. No crystal was found when fiber consisted of shaft (S) from Ad5 and knob (K) from Ad3 (heterotypic S5-K3 fiber), but occurred with homotypic S3K3 fiber. However, less regular crystals were observed with homotypic S35-K35 fiber. TB5, a monoclonal antibody directed against the Ad5 fiber knob was found by immunofluorescence microscopy to react with high efficiency with the intranuclear protein crystals in situ. Data obtained with Ad fiber mutants indicated that the absence of crystalline inclusions correlated with a lower infectivity and/or lower yields of virus progeny, suggesting that the protein crystals might be involved in virion assembly. Thus, we propose that TB5 staining of Ad-infected 293 cells can be used as a prognostic assay for the viability and productivity of fiber-modified Ad5 vectors
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