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Search Results: 1 - 10 of 196506 matches for " Thomas E. Keller "
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Does Mutational Robustness Inhibit Extinction by Lethal Mutagenesis in Viral Populations?
Eamon B. O'Dea,Thomas E. Keller,Claus O. Wilke
PLOS Computational Biology , 2010, DOI: 10.1371/journal.pcbi.1000811
Abstract: Lethal mutagenesis is a promising new antiviral therapy that kills a virus by raising its mutation rate. One potential shortcoming of lethal mutagenesis is that viruses may resist the treatment by evolving genomes with increased robustness to mutations. Here, we investigate to what extent mutational robustness can inhibit extinction by lethal mutagenesis in viruses, using both simple toy models and more biophysically realistic models based on RNA secondary-structure folding. We show that although the evolution of greater robustness may be promoted by increasing the mutation rate of a viral population, such evolution is unlikely to greatly increase the mutation rate required for certain extinction. Using an analytic multi-type branching process model, we investigate whether the evolution of robustness can be relevant on the time scales on which extinction takes place. We find that the evolution of robustness matters only when initial viral population sizes are small and deleterious mutation rates are only slightly above the level at which extinction can occur. The stochastic calculations are in good agreement with simulations of self-replicating RNA sequences that have to fold into a specific secondary structure to reproduce. We conclude that the evolution of mutational robustness is in most cases unlikely to prevent the extinction of viruses by lethal mutagenesis.
Innovation in Collaboration: The Summer Institute on Youth Mentoring as a university-community partnership
Kevin R. Jones,Thomas E. Keller,Marc Wheeler
Gateways : International Journal of Community Research & Engagement , 2011,
Abstract: The Summer Institute on Youth Mentoring (SIYM) at Portland State University is an intensive week-long seminar designed to offer a highly interactive educational opportunity for experienced professionals and leading researchers in the field of youth mentoring. The current study explores the extent to which SIYM represents an example of a successful university-community partnership and identifies ways in which SIYM innovates on established partnership models. Using grounded theory methods and typological analysis, the researchers analysed questionnaire responses from SIYM participants and research fellows to compare key characteristics of SIYM with the elements of effective partnerships described in the literature. Findings suggest that SIYM reflects many essential partnership qualities, including the presence of a shared vision; strong, mutually beneficial relationships; and a partnering process that includes communication and work for positive change. SIYM also introduces several innovations in format and structure that could inform the improvement or development of effective partnership efforts across disciplines. Implications for service providers, researchers and other stakeholders are discussed. Keywords communication, collaboration, mutually beneficial relationships, innovation
The Benefits of Cooperation between Industry and Universities
Thomas Keller
Central European Business Review , 2012,
Abstract:
The danger of misunderstanding ‘culture’
E Keller
Madagascar Conservation & Development , 2009,
Abstract: Most conservationists working in Madagascar recognise that if conservation goals are to be achieved, conservation bodies have to work together with, rather than against, local people. One important aspect of this is taking local ‘culture’ into account. However, what is understood by ‘culture’ in such contexts tends to be extremely partial as ‘culture’ is almost always limited to taboos (fady). The article discusses the danger of such a narrow view suggesting that ‘culture’ is infinitely more complex and subtle than its immediately apparent surface. I argue that if conservationists’ commitment to take ‘culture’ seriously is genuine, it must also apply to those cultural phenomena that are in conflict with conservation programmes. This applies in particular to rural Malagasy people’s desire to have many descendants; a desire which is linked to their fundamental understanding of what represents a meaningful life.
The danger of misunderstanding ‘culture’
Keller, E.
Madagascar Conservation & Development , 2009,
Abstract: Most conservationists working in Madagascar recognise thatif conservation goals are to be achieved, conservation bodieshave to work together with, rather than against, local people.One important aspect of this is taking local ‘culture’ into account.However, what is understood by ‘culture’ in such contexts tendsto be extremely partial as ‘culture’ is almost always limited totaboos (fady). The article discusses the danger of such a narrowview suggesting that ‘culture’ is infinitely more complex andsubtle than its immediately apparent surface. I argue that if conservationists’ commitment to take ‘culture’ seriously is genuine, it must also apply to those cultural phenomena that are in conflict with conservation programmes. This applies in particular to rural Malagasy people’s desire to have many descendants; a desire which is linked to their fundamental understanding of what represents a meaningful life.
A lower bound for the number of conjugacy classes of finite groups
Thomas Michael Keller
Mathematics , 2007,
Abstract: In 2000, L. H\'{e}thelyi and B. K\"{u}lshammer proved that if $p$ is a prime number dividing the order of a finite solvable group $G$, then $G$ has at least $2\sqrt{p-1}$ conjugacy classes. In this paper we show that if $p$ is large, the result remains true for arbitrary finite groups.
Finite groups have even more conjugacy classes
Thomas Michael Keller
Mathematics , 2008,
Abstract: In his paper "Finite groups have many conjugacy classes" (J. London Math. Soc (2) 46 (1992), 239-249), L. Pyber proved the to date best general lower bounds for the number of conjugacy classes of a finite group in terms of the order of the group. In this paper we strengthen the main results in Pyber's paper.
A combinatorial problem arising in group theory
Thomas Michael Keller
Mathematics , 2014,
Abstract: We consider a combinatorial problem occurring naturally in a group theoretical setting and provide a constructive solution in a special case. More precisely, in 1999 the author established a logarithmic bound for the derived length of the quotient of a finite solvable group modulo the second Fitting subgroup in terms of the number of irreducible character degrees of the group. Along the way, in two key lemmas an inductive process was used which at its core required a solution of some weak form of the combinatorial problem studied in this paper. This problem can be stated and studied without any group theoretical background, and in this paper we present the problem, discuss what is known and what the main conjecture is, and solve the conjecture in the smallest open case.
Counting characters in linear group actions
Thomas Michael Keller
Mathematics , 2007,
Abstract: Let $G$ be a finite group and $V$ be a finite $G$--module. We present upper bounds for the cardinalities of certain subsets of $\Irr(GV)$, such as the set of those $\chi\in\Irr(GV)$ such that, for a fixed $v\in V$, the restriction of $\chi$ to $$ is not a multiple of the regular character of $$. These results might be useful in attacking the non--coprime $k(GV)$--problem.
Fixed conjugacy classes of normal subgroups and the k(GV)-problem
Thomas Michael Keller
Mathematics , 2005,
Abstract: We establish several new bounds for the number of conjugacy classes of a finite group, all of which involve the maximal number c of conjugacy classes of a normal subgroup fixed by some element of a suitable subset of the group. To apply these formulas effectively, the parameter c, which in general is hard to control, is studied in some important situations. These results are then used to provide a new, shorter proof of the most difficult case of the well-known k(GV)-problem, which occurs for p=5 and V induced from the natural module of a 5-complement of GL(2,5). We also show how, for large p, the new results reduce the k(GV)-problem to the primitive case, thereby improving previous work on this. Furthermore, we discuss how they can be used in tackling the imprimitive case of the as of yet unsolved noncoprime k(GV)-problem.
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