Quasi-Upward Planarity

An upward planar drawing of a directed graph (digraph) is a planar drawing such that all the edges are represented by curves monotonically increasing in the vertical direction. In this paper we introduce and study the concept of quasi-upward planarity. Quasi-upward planarity allows us to extend the upward planarity theory to a large class of digraphs including digraphs that also have directed cycles. First, we characterize the digraphs that have a quasi-upward planar drawing. Second, we give a polynomial time algorithm for computing ``optimal'' quasi-upward planar drawings within a given planar embedding. Further, we apply branch and bound techniques to the problem of computing optimal quasi-upward planar drawings, considering all possible planar embeddings. The paper also contains experimental results about the proposed techniques.     

Quasi-Upward Planarity

Abstract. An upward planar drawing of a directed graph (digraph) is a planar drawing such that all the edges are represented by curves monotonically increasing in the vertical direction. In this paper we introduce and study the concept of quasi-upward planarity. Quasi-upward planarity allows us to extend the upward planarity theory to a large class of digraphs including digraphs that also have directed cycles. First, we characterize the digraphs that have a quasi-upward planar drawing. Second, we give a polynomial time algorithm for computing ``optimal' quasi-upward planar drawings within a given planar embedding. Further, we apply branch and bound techniques to the problem of computing optimal quasi-upward planar drawings, considering all possible planar embeddings. The paper also contains experimental results about the proposed techniques.     

A computational study of the flammability of methanol and gasoline fuel spills on hot engine manifolds

The fire hazards associated with gasoline and methanol are different because of the different physical and chemical properties of the fuels. In particular, the composition of the vapors they emit determines the comparative risk of a fire or explosion in cases of accidents or fuel leaks. This study compares the behavior of methanol and gasoline (n-octane) using mathematical models, so as to assist in determining whether there is an increased risk associated with the use of methanol fuels. The flammable zones surrounding a representative unconfined exhaust manifold were determined for methanol and n-octane at two manifold surface temperatures (700 and 1000 K) using computational fluid dynamics (CFD) techniques. Some of the CID computations were also confirmed experimentally. It was found that for a manifold surface temperature of 700 K, neither fuel would ignite, although the surface temperature is above the autoignition temperature for both fuels. At a surface temperature of 1000 K, it was found that each fuel could ignite and that this temperature would be near the minimum required for either fuel to be ignited by a hot surface. The predictions also confirm the experimentally observed phenomenon that real hot surface ignition temperatures are, generally, well above autoignition temperatures. It was concluded that the risk of spontaneous ignition is similar for both fuels for the type of leak scenario investigated (i.e. the risk with methanol is not significantly different than that of gasoline). The use of two-dimensional (2-D) steady-state CFD simulations can provide significant insight into the behavior of different fuels in what is generally a three-dimensional (3-D) transient phenomenon.     

Familial lead poisoning from contaminated wine

Three members of a family were found be suffering from lead poisoning of nonindustrial origin, the causative agent being the home-produced wine left to ferment in a glazed earthenware vat. The clinical and neurophysiological features are discussed in the light of similar cases in the literature. Correct diagnosis and early treatment of nonindustrial lead polyneuropathy are often extremely difficult because of the elusive nature of the exposure.     

Small Area Drawings of Outerplanar Graphs

We show three linear-time algorithms for constructing planar straight-line grid drawings of outerplanar graphs. The first and the second algorithm are for balanced outerplanar graphs. Both require linear area. The drawings produced by the first algorithm are not outerplanar while those produced by the second algorithm are. On the other hand, the first algorithm constructs drawings with better angular resolution. The third algorithm constructs outerplanar drawings of general outerplanar graphs with O(n ^1.48) area. Further, we study the interplay between the area requirements of the drawings of an outerplanar graph and the area requirements of a special class of drawings of its dual tree. Work partially supported by MUR under Project MAINSTREAM Algorithms for Massive Information Structures and Data Streams.     

Design of statistical databases: A methodology for the conceptual step

The aim of the conceptual step in database design is to describe data involving in the application in a formal and abstract way, without any concern to the specific model and language chosen for the implementation. In statistical applications, data are described at different levels of aggregation, from elementary facts of the reality to complex aggregations such as classifications, time series, indexes. The paper describes a methodology for conceptual design of statistical databases that provides the designer suitable strategies for defining such different levels of aggregation starting from user requirements, and checking the completeness, coherence and minimality of the conceptual schema at the different levels. The methodology makes use of two data models for the representation of data: for elementary data the Entity-Relationship model, widely used in database applications, and for summary data a new model is proposed, designed to be an effective trade-off between expressive power and simplicity of use.     

Recurrent liver failure with severe rhabdomyolysis after liver transplantation for carbon tetrachloride intoxication

Acute liver failure due to intoxication is a rare indication for liver transplantation which a usually has a good prognosis. We herein report the case of a young male, who underwent orthotopic liver transplantation for acute liver failure due to carbon tetrachloride intoxication. Apart from hepatic and renal failure, the patient also developed severe rhabdomyolysis, which has not thus far been described as a toxic effect of this chemical agent. Despite forced hyperventilation, which is known to be the most effective means of eliminating the specifically lipophylic agent, as well as excessive plasma exchange following intravenous administration of fat emulsions, liver failure recurred when blood carbon tetrachloride concentrations were already at non-toxic levels. Retransplantation of the liver together with a kidney was only temporarily successful, since the patient died due to aspergillus sepsis. Based on this experience, we would recommend that whenever possible in patients with carbon tetrachloride intoxication, liver transplant should be delayed until most of the toxic agent has been eliminated in order to prevent fatal graft damage.     

Report on inaugural workshop RSA ReHi-Network ‘Interdisciplinary connections between history & regional studies’*

The RSA Research Network on Regional Economic and Policy History (ReHi) aims to investigate the role of the historic perspective on regional studies through a series of events. During the inaugural two-day workshop, held in London in April 2017, the participants highlighted historical methodologies and approaches that establish a common thread in the various regional disciplines. They defined interdisciplinary connections that need to be addressed to overcome the discontinuous dialogue among researchers of regional studies and history. The research papers that were presented at the conference focused on improving methodologies, analysing economic strategies, developing techniques, and understanding policy development. The workshop aimed at establishing the foundation for a common research framework to improve the scientific debate and provide impact on regional policy regulations.