Interval non-edge-colorable bipartite graphs and multigraphs

An edge-coloring of a graph $G$ with colors $1,...,t$ is called an interval $t$-coloring if all colors are used, and the colors of edges incident to any vertex of $G$ are distinct and form an interval of integers. In 1991 Erd\H{o}s constructed a bipartite graph with 27 vertices and maximum degree 13 which has no interval coloring. Erd\H{o}s's counterexample is the smallest (in a sense of maximum degree) known bipartite graph which is not interval colorable. On the other hand, in 1992 Hansen showed that all bipartite graphs with maximum degree at most 3 have an interval coloring. In this paper we give some methods for constructing of interval non-edge-colorable bipartite graphs. In particular, by these methods, we construct three bipartite graphs which have no interval coloring, contain 20,19,21 vertices and have maximum degree 11,12,13, respectively. This partially answers a question that arose in [T.R. Jensen, B. Toft, Graph coloring problems, Wiley Interscience Series in Discrete Mathematics and Optimization, 1995, p. 204]. We also consider similar problems for bipartite multigraphs.Comment: 18 pages, 7 figure

Multi-jet Production in Hadron Collisions

The advent of high-energy hadron colliders necessitates efficient and accurate computation of multi-jet production processes, both as QCD processes in their own right and as backgrounds for other physics. The algorithm that performs these tasks and a brief numerical study of multi-jet processes are presented.Comment: 21 pages, 9 figure

The role of accounting in handling and reporting environmental effects

The thesis investigates the broad areas of accounting's adaptability in handling and reporting environmental effects. The main purposes of the study are: firstly. to draw together the literature of environmental concern and accounting: secondly to establish whether the use of environmental accounting is practised. to ascertain whether there is a suitable medium for environmental reporting and lastly to formulate a theoretical environmental performance model. The overall orientation of the research was to consider whether accounting should break away from its traditional economic and financial principles and broaden its scope to embrace a system that echoes with "environmental concern". In order to address these issues. the methods of evaluating environmental effects are looked at, together with the methods for accounting and reporting them. For these purposes, data were collected using a cross-sectional corporate methodology. The instrument used for the survey was the postal questionnaire. The construction and content of the questionnaire were influenced by the information gleaned from the literature review and, in the main, it covered qualitative, quantitative and financial information. The evidence gathered from the research has shown that environmental accounting and reporting are being practised by a variety of companies and are also becoming more widespread, which demonstrates that accounting is playing an important role in handling environmental transactions. The research has also shown that environmental accounting and reporting are gaining a broader perspective and now embrace environmental management systems. resource efficiency, and general environmental stewardship. Overall, the study recognises and concludes that environmental accounting and reporting, although spreading. should now be supported by environmental accounting and reporting guidelines from the accountancy profession, and in time, by legislation. Also environmental reports should be verified by external auditors in order to improve their integrity and prevent them from being used as a public relations exercise

Intestinal protozoan infections among HIV positive persons with and without Antiretroviral Treatment (ART) in selected ART centers in Adama, Afar and Dire-Dawa, Ethiopia

Background: In developing countries, gastroenteritis caused by intestinal parasites may be complicated and is a major cause of morbidity, in general, and kills millions of AIDS patients annually. Thus, the consequences of parasitic diseases are among the major health problems in tropical developing countries. Methods: A total of 200 HIV positive patients on and without-ART aged from 18 to 65 years, of both sexes participated in the study. Each study participant was provided with a faecal collection vial containing 10% formalin for microscopic examination of ova, larvae, and cysts. For detection of Cryptosporidium spp, lsospora belli andCyclospora spp, the modified Zeihl-Neelsen staining method was used. Results: Most (60%) of the study participants were on antiretroviral therapy (ART). Out of those, only two (1.5%) were diagnosed with an opportunistic parasite, and 96 (48%) of the non-ART study participants were infected with at least one other intestinal parasite species. The prevalence was 16% for Giardia lamblia, 13% for Entamoeba histolytica/ E. dispar, 8% for Cryptosporidium spp, 5% for Isospora belli, 1.5% for Blastocystis hominis, 2.5% for Ascaris lumbricoides and 2% for Hymnolepis nana. Diarrhoea was significantly associated with cryptosporidiosis, giardiasis, and isosporiasis. Significant association was observed between lower CD4+ T cell count

Scientific multi-agent reinforcement learning for wall-models of turbulent flows

The predictive capabilities of turbulent flow simulations, critical for aerodynamic design and weather prediction, hinge on the choice of turbulence models. The abundance of data from experiments and simulations and the advent of machine learning have provided a boost to these modeling efforts. However, simulations of turbulent flows remain hindered by the inability of heuristics and supervised learning to model the near-wall dynamics. We address this challenge by introducing scientific multi-agent reinforcement learning (SciMARL) for the discovery of wall models for large-eddy simulations (LES). In SciMARL, discretization points act also as cooperating agents that learn to supply the LES closure model. The agents self-learn using limited data and generalize to extreme Reynolds numbers and previously unseen geometries. The present simulations reduce by several orders of magnitude the computational cost over fully-resolved simulations while reproducing key flow quantities. We believe that SciMARL creates new capabilities for the simulation of turbulent flows