22 research outputs found
Degree distribution in random planar graphs
We prove that for each , the probability that a root vertex in a
random planar graph has degree tends to a computable constant , so
that the expected number of vertices of degree is asymptotically ,
and moreover that .
The proof uses the tools developed by Gimenez and Noy in their solution to
the problem of the asymptotic enumeration of planar graphs, and is based on a
detailed analysis of the generating functions involved in counting planar
graphs. However, in order to keep track of the degree of the root, new
technical difficulties arise. We obtain explicit, although quite involved
expressions, for the coefficients in the singular expansions of the generating
functions of interest, which allow us to use transfer theorems in order to get
an explicit expression for the probability generating function . From this we can compute the to any degree of accuracy, and derive
the asymptotic estimate for large values of ,
where is a constant defined analytically
Asymptotic enumeration and limit laws for graphs of fixed genus
It is shown that the number of labelled graphs with n vertices that can be
embedded in the orientable surface S_g of genus g grows asymptotically like
where , and is the exponential growth rate of planar graphs. This generalizes the
result for the planar case g=0, obtained by Gimenez and Noy.
An analogous result for non-orientable surfaces is obtained. In addition, it
is proved that several parameters of interest behave asymptotically as in the
planar case. It follows, in particular, that a random graph embeddable in S_g
has a unique 2-connected component of linear size with high probability
On the diameter of random planar graphs
International audienceWe show that the diameter of a random (unembedded) labelled connected planar graph with vertices is asymptotically almost surely of order , in the sense that there exists a constant such that for small enough and large enough . We prove similar statements for rooted -connected and -connected embedded (maps) and unembedded planar graphs
Physiological parameters for Prognosis in Abdominal Sepsis (PIPAS) Study : a WSES observational study
BackgroundTiming and adequacy of peritoneal source control are the most important pillars in the management of patients with acute peritonitis. Therefore, early prognostic evaluation of acute peritonitis is paramount to assess the severity and establish a prompt and appropriate treatment. The objectives of this study were to identify clinical and laboratory predictors for in-hospital mortality in patients with acute peritonitis and to develop a warning score system, based on easily recognizable and assessable variables, globally accepted.MethodsThis worldwide multicentre observational study included 153 surgical departments across 56 countries over a 4-month study period between February 1, 2018, and May 31, 2018.ResultsA total of 3137 patients were included, with 1815 (57.9%) men and 1322 (42.1%) women, with a median age of 47years (interquartile range [IQR] 28-66). The overall in-hospital mortality rate was 8.9%, with a median length of stay of 6days (IQR 4-10). Using multivariable logistic regression, independent variables associated with in-hospital mortality were identified: age > 80years, malignancy, severe cardiovascular disease, severe chronic kidney disease, respiratory rate >= 22 breaths/min, systolic blood pressure 4mmol/l. These variables were used to create the PIPAS Severity Score, a bedside early warning score for patients with acute peritonitis. The overall mortality was 2.9% for patients who had scores of 0-1, 22.7% for those who had scores of 2-3, 46.8% for those who had scores of 4-5, and 86.7% for those who have scores of 7-8.ConclusionsThe simple PIPAS Severity Score can be used on a global level and can help clinicians to identify patients at high risk for treatment failure and mortality.Peer reviewe