32,880 research outputs found
A Generating Function for Fatgraphs
We study a generating function for the sum over fatgraphs with specified
valences of vertices and faces, inversely weighted by the order of their
symmetry group. A compact expression is found for general (i.e. non necessarily
connected) fatgraphs. This expression admits a matrix integral representation
which enables to perform semi--classical computations, leading in particular to
a closed formula corresponding to (genus zero, connected) trees.Comment: 24 pages, uses harvmac macro, 1 figure not included, Saclay preprint
SPhT/92-16
Quantum intersection rings
We examine a few problems of enumerative geometry and present their solutions
in the framework of deformed (quantum) cohomology rings.Comment: 73 p, uuencoded, uses harvmac in b mode, 6 figures include
Fully Packed O(n=1) Model on Random Eulerian Triangulations
We introduce a matrix model describing the fully-packed O(n) model on random
Eulerian triangulations (i.e. triangulations with all vertices of even
valency). For n=1 the model is mapped onto a particular gravitational 6-vertex
model with central charge c=1, hence displaying the expected shift c -> c+1
when going from ordinary random triangulations to Eulerian ones. The case of
arbitrary n is also discussed.Comment: 12 pages, 3 figures, tex, harvmac, eps
Hemodynamics of Stent Implantation Procedures in Coronary Bifurcations: an in vitro study
Stent implantation in coronary bifurcations presents unique challenges and
currently there is no universally accepted stent deployment approach. Despite
clinical and computational studies, to date, the effect of each stent
implantation method on the coronary artery hemodynamics is not well understood.
In this study the hemodynamics of stented coronary bifurcations under pulsatile
flow conditions were investigated experimentally. Three implantation methods,
provisional side branch (PSB), culotte (CUL), and crush (CRU), were
investigated using time-resolved particle image velocimetry (PIV) to measure
the velocity fields. Subsequently, hemodynamic parameters including wall shear
stress (WSS), oscillatory shear index (OSI), and relative residence time (RRT)
were calculated and the pressure field through the vessel was non-invasively
quantified. The effects of each stented case were evaluated and compared
against an un-stented case. CRU provided the lowest compliance mismatch, but
demonstrated detrimental stent interactions. PSB, the clinically preferred
method, and CUL maintained many normal flow conditions. However, PSB provided
about a 300% increase in both OSI and RRT. CUL yielded a 10% and 85% increase
in OSI and RRT, respectively. The results of this study support the concept
that different bifurcation stenting techniques result in hemodynamic
environments that deviate from that of un-stented bifurcations, to varying
degrees.Comment: 33 pages, 8 figures, 3 table
Back to the future. the crucial role of clinical registries in the era of randomized controlled trials for identifying the optimal medical therapy of heart failure
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