Fisher's microscope and Haldane's ellipse

Fisher’s geometrical model was introduced to study the phenotypic size of mutations contributing to adaptation. However, as pointed out by Haldane, the model involves a simplified picture of the action of natural selection, and this calls into question its generality. In particular, Fisher’s model assumes that each trait contributes independently to fitness. Here, we show that Haldane’s concerns may be incorporated into Fisher’s model solely by allowing the intensity of selection to vary between traits. We further show that this generalization may be achieved by introducing a single, intuitively defined quantity that describes the phenotype prior to adaptation. Comparing the process of adaptation under the original and generalized models, we show that the generalization may bias results toward either larger or smaller mutations. The applicability of Fisher’s model is then discussed

An Economic Approach to the Psychology of Change: Amnesia, Inertia, and Impulsiveness

This paper models how imperfect memory affects the optimal continuity of policies. We examine the choices of a player (individual or firm) who observes previous actions but cannot remember the rationale for these actions. In a stable environment, the player optimally responds to memory loss with excess inertia, defined as a higher probability of following old policies than would occur under full recall. In a volatile environment, the player can exhibit excess impulsiveness (i.e., be more prone to follow new information signals). The model provides a memory-loss explanation for some documented psychological biases, implies that inertia and organizational routines should be more important in stable environments than in volatile ones, and provides other empirical implications relating memory and environmental variables to the continuity of decisions.Memory, inertia, amnesia, behavioral economics

Higher levels of process synchronisation

Four new synchronisation primitives (SEMAPHOREs, RESOURCEs, EVENTs and BUCKETs) were introduced in the KRoC 0.8beta release of occam for SPARC (SunOS/Solaris) and Alpha (OSF/1) UNIX workstations [1][2][3]. This paper reports on the rationale, application and implementation of two of these (SEMAPHOREs and EVENTs). Details on the other two may be found on the web [4]. The new primitives are designed to support higher-level mechanisms of SHARING between parallel processes and give us greater powers of expression. They will also let greater levels of concurrency be safely exploited from future parallel architectures, such as those providing (virtual) shared-memory. They demonstrate that occam is neutral in any debate between the merits of message-passing versus shared-memory parallelism, enabling applications to take advantage of whichever paradigm (or mixture of paradigms) is the most appropriate. The new primitives could be (but are not) implemented in terms of traditional channels, but only at the expense of increased complexity and computational overhead. The primitives are immediately useful even for uni-processors - for example, the cost of a fair ALT can be reduced from O(n) to O(1). In fact, all the operations associated with new primitives have constant space and time complexities; and the constants are very low. The KRoC release provides an Abstract Data Type interface to the primitives. However, direct use of such mechanisms still allows the user to misuse them. They must be used in the ways prescribed (in this paper and in [4]) else their semantics become unpredictable. No tool is provided to check correct usage at this level. The intention is to bind those primitives found to be useful into higher level versions of occam. Some of the primitives (e.g. SEMAPHOREs) may never themselves be made visible in the language, but may be used to implement bindings of higher-level paradigms (such as SHARED channels and BLACKBOARDs). The compiler will perform the relevant usage checking on all new language bindings, closing the security loopholes opened by raw use of the primitives. The paper closes by relating this work with the notions of virtual transputers, microcoded schedulers, object orientation and Java threads

Bayesian inference of sampled ancestor trees for epidemiology and fossil calibration

Phylogenetic analyses which include fossils or molecular sequences that are sampled through time require models that allow one sample to be a direct ancestor of another sample. As previously available phylogenetic inference tools assume that all samples are tips, they do not allow for this possibility. We have developed and implemented a Bayesian Markov Chain Monte Carlo (MCMC) algorithm to infer what we call sampled ancestor trees, that is, trees in which sampled individuals can be direct ancestors of other sampled individuals. We use a family of birth-death models where individuals may remain in the tree process after the sampling, in particular we extend the birth-death skyline model [Stadler et al, 2013] to sampled ancestor trees. This method allows the detection of sampled ancestors as well as estimation of the probability that an individual will be removed from the process when it is sampled. We show that sampled ancestor birth-death models where all samples come from different time points are non-identifiable and thus require one parameter to be known in order to infer other parameters. We apply this method to epidemiological data, where the possibility of sampled ancestors enables us to identify individuals that infected other individuals after being sampled and to infer fundamental epidemiological parameters. We also apply the method to infer divergence times and diversification rates when fossils are included among the species samples, so that fossilisation events are modelled as a part of the tree branching process. Such modelling has many advantages as argued in literature. The sampler is available as an open-source BEAST2 package (https://github.com/gavryushkina/sampled-ancestors).Comment: 34 pages (including Supporting Information), 8 figures, 1 table. Part of the work presented at Epidemics 2013 and The 18th Annual New Zealand Phylogenomics Meeting, 201

Les Franco-Ontariens : la résistance comme mode de vie

Dans un premier temps, ce texte décrit certaines des grandes transformations sociales, économiques et politiques ayant marqué la communauté franco-ontarienne depuis le dix-neuvième siècle, ainsi que certaines des conséquences de ces transformations pour l'intervention sociale et communautaire. Par la suite, l'auteur suggère des pistes de réflexions vers lesquelles la recherche et l'intervention pourraient s'orienter pour mieux s'adapter aux réalités actuelles de cette population.La toile de fond qui sous-tend cet article se base sur une vision dynamique de la communauté franco-ontarienne, vision qui présente cette population non comme victime, mais plutôt comme actrice engagée dans la transformation de la communauté

Studies in the Autecology of Juncus Squarrosus L

Studies in the autecology of Juncus squarrosus L. have been made over a three-year period, mainly in the area of high-level moorland at the head of Teesdale in the north Pennines. The morphology and anatomy of the plant are described, and an account is given of the form of the communities. Annual increments in rhizome growth of 0.5 to 2.0 cm. were recorded. About 20 sites were examined phytosociologically, Five noda were distinguished, namely the peaty gley, the podsol, the species-poor gley, the species-rich gley and the flushed-peat noda. The reproductive capacity was measured at 12 of these sites. IV here Juncus is dominant up to 8,000 seeds can be produced per square metre. Production is lower on well-drained soils, the number of florets per inflorescence being less, and when a smaller proportion of florets ripen to form capsules. In average years 50% of the florets ripen at heights up to 1800 ft. (550 m.). Larvae of the moth Goleophora alticolella eat the seeds at the lower levels, and changes in its population size have been followed. Seed viability is usually high, but experiments showed that germination requires light at the normal field temperatures. Seedling establishment was found to be uncommon, though large numbers of dormant viable seeds are present in the soil. Various observations are described which provide information on the ecology of Juncus squarrosus. Sheep grazing is held responsible for its present widespread occurrence, and a slow spread will continue in certain of the better grasslands if the grazing pressure is maintained. But this cannot be considered a serious threat to the value of the uplands as the plant has some nutritional value, and most stands contain a considerable proportion of grass. Callunetum, the climax vegetation, is of less value agronomically in the area studied