Knocking Out P_k-free Graphs

A parallel knock-out scheme for a graph proceeds in rounds in each of which each surviving vertex eliminates one of its surviving neighbours. A graph is KO-reducible if there exists such a scheme that eliminates every vertex in the graph. The Parallel Knock-Out problem is to decide whether a graph G is KO-reducible. This problem is known to be NP-complete and has been studied for several graph classes since MFCS 2004. We show that the problem is NP-complete even for split graphs, a subclass of P 5-free graphs. In contrast, our main result is that it is linear-time solvable for P 4-free graphs (cographs)

An Investigative Study Of Patents From An Engineering Design Perspective

Preservation and reuse of valuable design experience aids in the design of new products and processes. Product design repositories are presently being used as a means to preserve and later reuse design knowledge. As such, patent databases such as the United States Patent office and the European Patent Office offer design knowledge in the form of patents. Unfortunately, these sources of novel design solutions do not appear to have been have not been effectively used in the context of engineering design. In this research, the role of patents in a systematic design process is reviewed understand its utility in the design process. A major hurdle, in the reuse of patent design knowledge, is the lack of formal tools to support designers in understanding and applying the available information to new problems. Information theory fundamentals are used to study patent claim text which describes the subject matter of the patent and to develop an understanding of the information content within the text claim and other representations of the claim. Graph based representations are recognized as an effective way to represent design information. They are considered as ideal for modeling patent claims as they enable the direct use of the information as input to existing design processes and tools, such as function models, the core product model, and function-behavior-structure scheme. This new approach provides a designer-friendly model of patent claims and also enables the use of intelligent search mechanisms. Existing graph based product representation schemas are studied for their suitability to model patent claims. A new representation tailored for patent claims is proposed since, the existing schemas where found to be insufficient to efficiently model patent claim. Patent claims modeled using multiple representation schemas are compared with the models developed using the proposed representation, for the information content captured from claim text. The representation technique proposed here may aid in the retrieval of the relevant patent design information, thereby promoting use of patent information to aid designers. Further refinement and evaluation of the scheme along with the development of grammar and ontologies for a vocabulary is needed. This representation scheme, with existing search and retrieval methods, should help designers in generating both novel and practical concepts based on patent information

Self-Evaluation Applied Mathematics 2003-2008 University of Twente

This report contains the self-study for the research assessment of the Department of Applied Mathematics (AM) of the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS) at the University of Twente (UT). The report provides the information for the Research Assessment Committee for Applied Mathematics, dealing with mathematical sciences at the three universities of technology in the Netherlands. It describes the state of affairs pertaining to the period 1 January 2003 to 31 December 2008

A theoretical assessment of fuel combustion attributes to enhance the operational envelope of HCCI engines

Includes bibliographical references.Homogeneous Charge Compression Ignition (HCCI) is an alternative internal combustion (IC) engine that can provide high efficiencies while producing ultra-low nitrous oxides (NOx) and particulate matter (PM) emissions compared to existing compression ignition (CI) and spark ignition (SI) engines. HCCI engines operate on the principle of having a dilute, premixed charge that reacts and burns volumetrically throughout the cylinder as it is compressed by the piston. The large amounts of charge dilution also dramatically reduce the peak burned gas temperatures resulting in low NOx emissions. Since there is no fuel-rich diffusion burning taking place, the PM emissions are at near zero levels. In theory, HCCI combustion can be achieved with any fuel that evaporates readily and autoignite under the conditions typically found in an internal combustion engine. In some regards, HCCI incorporates the best features of both SI and CI engine. As in a SI engine, the charge is well mixed, which minimises particulate emissions and as in a CI engine, the charge is compression ignited and has no throttling losses, which leads to high thermal efficiencies. However, unlike either of these conventional engines, the combustion occurs simultaneously throughout the combustion chamber without a flame front, eliminating the flammability limits associated with SI combustion. The HCCI engine can provide efficiencies as high as compression ignition engines while generating extremely low NOx emissions, as low as 1-5% tailpipe NOx of a conventional SI engine

From Dakar to Brasilia: Monitoring Unesco´s Education Goals

Active participation of Brazilian civil society, coupled with the 2007 education development plan, launched by the Brazilian government provides an interesting example of the influences of the Dakar Goals. The two domestic initiatives share the same name, spirit and direction proposed in Dakar 2000. We analyse here changes in the Brazilian policies and indicators related to the Dakar Education Goals since its creation, we note: (i) an increase in enrolment over the relevant period; (ii) access to primary education was nearly universal by 2000; (iii) over-aged youth and adult students fell considerably during the period, but access did not expand; (iv) illiteracy has been falling at a rate which, if sustained, will enable us to meet the goal; (v) gender discrimination did not take place in Brazil; (vi) most pupil proficiency indicators have progressively deteriorated from what was already a low standard. In summary, quantity indicators did improve over the period while most quality indicators worsened.

Renormalization Group Approach to Interacting Fermions

The stability of nonrelativistic fermionic systems to interactions is studied within the Renormalization Group framework. A brief introduction to $\phi^4$ theory in four dimensions and the path integral formulation for fermions is given. The strategy is as follows. First, the modes on either side of the Fermi surface within a cut-off $\Lambda$ are chosen and a path integral is written to describe them. An RG transformation which eliminates a part of these modes, but preserves the action of the noninteracting system is identified. Finally the possible perturbations of this free-field fixed point are classified as relevant, irrelevant or marginal. A $d=1$ warmup calculation involving a system of fermions shows how, in contrast to mean-field theory, the RG correctly yields a scale invariant system (Luttinger liquid) In $d=2$ and 3, for rotationally invariant Fermi surfaces, {\em automatically} leads to Landau's Fermi liquid theory, which appears as a fixed point characterized by an effective mass and a Landau function $F$, with the only relevant perturbations being of the superconducting (BCS) type The functional flow equations for the BCS couplings are derived and separated into an infinite number of flows, one for each angular momentum. It is shown that similar results hold for rotationally non-invariant (but time-reversal invariant) Fermi surfaces also, A study of a nested Fermi surface shows an additional relevant flow leading to charge density wave formation. For small $\Lambda / K_F$, a 1/N expansion emerges, with $N = K_F/ \Lambda$, which explains why one is able to solve the narrow cut-off theory. The search for non-Fermi liquids in $d=2$Comment: 191 pages, Latex, Yale, July 1993; 18 EPS figures appende

Learning instructional communication skills in peer collaborative problem solving : a case of moving referent.

The present work is an attempt to combine two traditions of communication study: referential communication approach and sociolinguistic approach. The purpose was to examine how children ages 5 and 7 years learn to give instructions to each other in a peer collaborative problem solving situation. In an effort to identify interaction patterns and possible developmental progressions, various coding and categorization schemes were developed to analyze the processes of: negotiation of themes, establishing a common perspective toward the task, co-constructing messages and shared names. A comparison was made between the children\u27s development of spatial terms for a stationary referent and a moving referent. The analysis shows that 7-year-olds shared themes more actively, using explicit means, compared to 5-year-olds. The older children\u27s instructions were more informative and made in the task-appropriate referential perspective. For the purpose of establishing shared names, the older children engaged themselves in the naming process less often because they used names that can be more easily shared. The development of spatial terms for a moving referent seems to lag behind the development of those for a stationary referent. The children gradually learned, across ages and sessions, to participate to maximize the team effectiveness. Finally, dynamic changes in instructional messages were analyzed using a mode of graphic representation

Towards a Theory of Scale-Free Graphs: Definition, Properties, and Implications (Extended Version)

Although the ``scale-free'' literature is large and growing, it gives neither a precise definition of scale-free graphs nor rigorous proofs of many of their claimed properties. In fact, it is easily shown that the existing theory has many inherent contradictions and verifiably false claims. In this paper, we propose a new, mathematically precise, and structural definition of the extent to which a graph is scale-free, and prove a series of results that recover many of the claimed properties while suggesting the potential for a rich and interesting theory. With this definition, scale-free (or its opposite, scale-rich) is closely related to other structural graph properties such as various notions of self-similarity (or respectively, self-dissimilarity). Scale-free graphs are also shown to be the likely outcome of random construction processes, consistent with the heuristic definitions implicit in existing random graph approaches. Our approach clarifies much of the confusion surrounding the sensational qualitative claims in the scale-free literature, and offers rigorous and quantitative alternatives.Comment: 44 pages, 16 figures. The primary version is to appear in Internet Mathematics (2005

targetTB: A target identification pipeline for Mycobacterium tuberculosis through an interactome, reactome and genome-scale structural analysis

<p>Abstract</p> <p>Background</p> <p>Tuberculosis still remains one of the largest killer infectious diseases, warranting the identification of newer targets and drugs. Identification and validation of appropriate targets for designing drugs are critical steps in drug discovery, which are at present major bottle-necks. A majority of drugs in current clinical use for many diseases have been designed without the knowledge of the targets, perhaps because standard methodologies to identify such targets in a high-throughput fashion do not really exist. With different kinds of 'omics' data that are now available, computational approaches can be powerful means of obtaining short-lists of possible targets for further experimental validation.</p> <p>Results</p> <p>We report a comprehensive <it>in silico </it>target identification pipeline, targetTB, for <it>Mycobacterium tuberculosis</it>. The pipeline incorporates a network analysis of the protein-protein interactome, a flux balance analysis of the reactome, experimentally derived phenotype essentiality data, sequence analyses and a structural assessment of targetability, using novel algorithms recently developed by us. Using flux balance analysis and network analysis, proteins critical for survival of <it>M. tuberculosis </it>are first identified, followed by comparative genomics with the host, finally incorporating a novel structural analysis of the binding sites to assess the feasibility of a protein as a target. Further analyses include correlation with expression data and non-similarity to gut flora proteins as well as 'anti-targets' in the host, leading to the identification of 451 high-confidence targets. Through phylogenetic profiling against 228 pathogen genomes, shortlisted targets have been further explored to identify broad-spectrum antibiotic targets, while also identifying those specific to tuberculosis. Targets that address mycobacterial persistence and drug resistance mechanisms are also analysed.</p> <p>Conclusion</p> <p>The pipeline developed provides rational schema for drug target identification that are likely to have high rates of success, which is expected to save enormous amounts of money, resources and time in the drug discovery process. A thorough comparison with previously suggested targets in the literature demonstrates the usefulness of the integrated approach used in our study, highlighting the importance of systems-level analyses in particular. The method has the potential to be used as a general strategy for target identification and validation and hence significantly impact most drug discovery programmes.</p