Trace Complexity of Chaotic Reversible Cellular Automata

Delvenne, K\r{u}rka and Blondel have defined new notions of computational complexity for arbitrary symbolic systems, and shown examples of effective systems that are computationally universal in this sense. The notion is defined in terms of the trace function of the system, and aims to capture its dynamics. We present a Devaney-chaotic reversible cellular automaton that is universal in their sense, answering a question that they explicitly left open. We also discuss some implications and limitations of the construction.Comment: 12 pages + 1 page appendix, 4 figures. Accepted to Reversible Computation 2014 (proceedings published by Springer

Cost and Capacity of Signaling in the Escherichia coli Protein Reaction Network

In systems biology new ways are required to analyze the large amount of existing data on regulation of cellular processes. Recent work can be roughly classified into either dynamical models of well-described subsystems, or coarse-grained descriptions of the topology of the molecular networks at the scale of the whole organism. In order to bridge these two disparate approaches one needs to develop simplified descriptions of dynamics and topological measures which address the propagation of signals in molecular networks. Here, we consider the directed network of protein regulation in E. coli, characterizing its modularity in terms of its potential to transmit signals. We demonstrate that the simplest measure based on identifying sub-networks of strong components, within which each node could send a signal to every other node, indeed partitions the network into functional modules. We then suggest measures to quantify the cost and spread associated with sending a signal between any particular pair of proteins. Thereby, we address the signalling specificity within and between modules, and show that in the regulation of E.coli there is a systematic reduction of the cost and spread for signals traveling over more than two intermediate reactions.Comment: 21 pages, 6 figure

Motivating doctors into leadership and management: a cross-sectional survey

Purpose: Calls for doctors to enter management are louder as the benefits of medical leadership become clearer. But supply is not meeting demand. This study asks doctors: what might encourage you to go into leadership, and what do you see as the disincentives? The same was asked about leadership training. First, the paper attempts to understand doctors’ motivation to lead, specifically, to explore the job characteristics that might act as incentives and disincentives. Second, the study points to organisational obstacles that further shrink the medical leadership pipeline. Method: Doctors were surveyed through the Organization of Danish Medical Societies. Our key variables included: 1) willingness to take on a management or leadership position; 2) the incentives to go into leadership or management; 3) disincentives to do so; and 4) incentives for participating in leadership training. Our sample includes 3534 doctors (17% response rate). Findings: Nearly 70% of doctors said that they would consider leadership or management positions. Overwhelmingly, the main incentive reported was to have a positive impact. Doctors are put off by fears of extra administration, longer hours, burnout, lack of resources, and by organisational cultures resistant to change. But they are fully aware of their need for leadership training. Practical implications: Health systems should adapt to reflect the motivations of their potential medical leaders, especially the best talent, who may not be the first to apply for management positions. It is also essential they offer leadership training. These findings, that aid succession planning, are especially important as more is known about the influence of medical leaders on organisational outcomes, and at a time of high reported stress, burnout, and staff recruitment and retention challenges

A functional calcium-transporting ATPase encoded by chlorella viruses

Calcium-transporting ATPases (Ca2+ pumps) are major players in maintaining calcium homeostasis in the cell and have been detected in all cellular organisms. Here, we report the identification of two putative Ca2+ pumps, M535L and C785L, encoded by chlorella viruses MT325 and AR158, respectively, and the functional characterization of M535L. Phylogenetic and sequence analyses place the viral proteins in group IIB of P-type ATPases even though they lack a typical feature of this class, a calmodulin-binding domain. A Ca2+ pump gene is present in 45 of 47 viruses tested and is transcribed during virus infection. Complementation analysis of the triple yeast mutant K616 confirmed that M535L transports calcium ions and, unusually for group IIB pumps, also manganese ions. In vitro assays show basal ATPase activity. This activity is inhibited by vanadate, but, unlike that of other Ca2+ pumps, is not significantly stimulated by either calcium or manganese. The enzyme forms a 32P-phosphorylated intermediate, which is inhibited by vanadate and not stimulated by the transported substrate Ca2+, thus confirming the peculiar properties of this viral pump. To our knowledge this is the first report of a functional P-type Ca2+-transporting ATPase encoded by a virus

Capabilitarian Sufficiency: Capabilities and Social Justice

This paper suggests an account of sufficientarianism—that is, that justice is fulfilled when everyone has enough—laid out within a general framework of the capability approach. In doing so, it seeks to show that sufficiency is especially plausible as an ideal of social justice when constructed around key capabilitarian insights such as freedom, pluralism, and attention to empirical interconnections between central capabilities. Correspondingly, we elaborate on how a framework for evaluating social justice would look when constructed in this way and give reasons for why capabilitarians should embrace sufficientarianism. We do this by elaborating on how capabilitarian values underpin sufficiency. On this basis, we identify three categories of central capabilities; those related to biological and physical needs, those to fundamental interests of a human agent, and those to fundamental interests of a social being. In each category, we argue, achieving sufficiency requires different distributional patterns depending on how the capabilities themselves work and interrelate. This argument adds a new dimension to the way capabilitarians think about social justice and changes how we should target instances of social justice from social-political viewpoint

Unequally egalitarian? Defending the credentials of social egalitarianism

In his new book, Luck Egalitarianism, Kasper Lippert-Rasmussen responds to challenges raised by social egalitarians against luck egalitarianism. Social egalitarianism is the view according to which a just society is one where people relate to each other as equals, while the basic premise of luck egalitarianism is that it is unfair if people are worse-off than others through no fault or choice of their own. Lippert-Rasmussen argues that the most important objections to luck egalitarianism made by social egalitarians can either be largely accommodated by luck egalitarians or lack the argumentative force that its proponents believe them to have. While Lippert-Rasmussen does offer a version of luck egalitarianism that seems to avoid some of the main lines of criticism, he mischaracterizes parts of both the form and the content of the disagreement, and thus ultimately misses the mark. In this paper, we provide a substantive, a methodological and a political defense of social egalitarianism by elaborating on this mischaracterization. More work must be done, we argue, if social egalitarianism is to be dismissed and its concerns genuinely incorporated in the luck egalitarian framework. Until this is done, the supposed theoretical superiority of luck egalitarianism remains contested