9,493 research outputs found
Face pairing graphs and 3-manifold enumeration
The face pairing graph of a 3-manifold triangulation is a 4-valent graph
denoting which tetrahedron faces are identified with which others. We present a
series of properties that must be satisfied by the face pairing graph of a
closed minimal P^2-irreducible triangulation. In addition we present
constraints upon the combinatorial structure of such a triangulation that can
be deduced from its face pairing graph. These results are then applied to the
enumeration of closed minimal P^2-irreducible 3-manifold triangulations,
leading to a significant improvement in the performance of the enumeration
algorithm. Results are offered for both orientable and non-orientable
triangulations.Comment: 30 pages, 57 figures; v2: clarified some passages and generalised the
final theorem to the non-orientable case; v3: fixed a flaw in the proof of
the conical face lemm
Considerations on grapevine selection and certification
Different viruses and virus-like diseases can be detrimental to grapevines and their products. The protocols of the assays used to evaluate the impact of viruses have evolved with the progress of the knowledge in aetiology and diagnosis. A wrong interpretation of the data from experiments that compare the performance of virus-infected and non-infected vines may lead to erroneous conclusions. Even if some experiments show that virus infections induce an increase of sugar content, a better evaluation of the experimental data may show that the conclusion drawn is incorrect. The role viruses may play in clonal variability is also discussed
A note on dimer models and McKay quivers
We give one formulation of an algorithm of Hanany and Vegh which takes a
lattice polygon as an input and produces a set of isoradial dimer models. We
study the case of lattice triangles in detail and discuss the relation with
coamoebas following Feng, He, Kennaway and Vafa.Comment: 25 pages, 35 figures. v3:completely rewritte
Corporate Governance and Transparency: A Research Study Investigating CEO Duality in Fortune Ranked Companies
The fiduciary oversight expected from the board of directors has intensified because of corporate scandals of corruption and fraudulent financial reporting within the US. The Federal Government, Securities and Exchange Commission, American stock exchanges, and shareholders are demanding corporate transparency in these matters. This longitudinal study examines CEO duality of the largest firms in the US as a whole and by industry sector. Concentrating on the agency theory, this paper investigates the two-tier compliance status within the largest 500 firms in the US, as reported by Fortune Magazine in 2008 and 2010. This study seeks to reveal the degree to which CEO duality roles exist today in large US publicly traded corporations. The investigation began by reviewing the 2008 CEO duality status. Further analysis incorporated the 2010 top 500 revenue-generating firms in the US. The combination of titles held by CEOs remained consistent from 2008 to 2010. However, in 2008, CEO/Chairman title ranked first and it ranked third in 2010, which is a 68.4 percent decrease from 2008 to 2010. Further review reveals CEO/President title witnessed a 110 percent increase from 2008 to 2010 and ranks first in 2010. The 2010 increase in CEO/President titles and a decrease in CEO/Chairman titles are consistent with the principal-agency theory. There is a gap within the existing literature addressing the current governance trends within large US companies in order to heighten corporate disclosure and transparency. This research study can have global implications because of the internationalization of capital markets and the volume of cross-listings
Convex plumbings in closed hyperbolic 4-manifolds
We show that every plumbing of disc bundles over surfaces whose genera satisfy a simple inequality may be embedded as a convex submanifold in some closed hyperbolic four-manifold. In particular its interior has a geometrically finite hyperbolic structure that covers a closed hyperbolic four-manifold
Hyperbolic 5-manifolds that fiber over S1
We exhibit some finite-volume cusped hyperbolic 5-manifolds that fiber over the circle. These include the smallest hyperbolic 5-manifold known, discovered by Ratcliffe and Tschantz. As a consequence, we build a finite type subgroup of a hyperbolic group that is not hyperbolic
MicroRNA-222 regulates muscle alternative splicing through Rbm24 during differentiation of skeletal muscle cells
A number of microRNAs have been shown to regulate skeletal muscle development and differentiation. MicroRNA-222 is downregulated during myogenic differentiation and its overexpression leads to alteration of muscle differentiation process and specialized structures. By using RNA-induced silencing complex (RISC) pulldown followed by RNA sequencing, combined with in silico microRNA target prediction, we have identified two new targets of microRNA-222 involved in the regulation of myogenic differentiation, Ahnak and Rbm24. Specifically, the RNA-binding protein Rbm24 is a major regulator of muscle-specific alternative splicing and its downregulation by microRNA-222 results in defective exon inclusion impairing the production of muscle-specific isoforms of Coro6, Fxr1 and NACA transcripts. Reconstitution of normal levels of Rbm24 in cells overexpressing microRNA-222 rescues muscle-specific splicing. In conclusion, we have identified a new function of microRNA-222 leading to alteration of myogenic differentiation at the level of alternative splicing, and we provide evidence that this effect is mediated by Rbm24 protei
Multidomain switching in the ferroelectric nanodots
Controlling the polarization switching in the ferroelectric nanocrystals,
nanowires and nanodots has an inherent specificity related to the emergence of
depolarization field that is associated with the spontaneous polarization. This
field splits the finite-size ferroelectric sample into polarization domains.
Here, based on 3D numerical simulations, we study the formation of 180 polarization domains in a nanoplatelet, made of uniaxial ferroelectric
material, and show that in addition to the polarized monodomain state, the
multidomain structures, notably of stripe and cylindrical shapes, can arise and
compete during the switching process. The multibit switching protocol between
these configurations may be realized by temperature and field variations
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