In search of an evolutionary coding style

In the near future, all the human genes will be identified. But understanding the functions coded in the genes is a much harder problem. For example, by using block entropy, one has that the DNA code is closer to a random code then written text, which in turn is less ordered then an ordinary computer code; see \cite{schmitt}. Instead of saying that the DNA is badly written, using our programming standards, we might say that it is written in a different style -- an evolutionary style. We will suggest a way to search for such a style in a quantified manner by using an artificial life program, and by giving a definition of general codes and a definition of style for such codes.Comment: 14 pages, 7 postscript figure

War of attrition with implicit time cost

In the game-theoretic model war of attrition, players are subject to an explicit cost proportional to the duration of contests. We construct a model where the time cost is not explicitly given, but instead depends implicitly on the strategies of the whole population. We identify and analyse the underlying mechanisms responsible for the implicit time cost. Each player participates in a series of games, where those prepared to wait longer win with higher certainty but play less frequently. The model is characterised by the ratio of the winner's score to the loser's score, in a single game. The fitness of a player is determined by the accumulated score from the games played during a generation. We derive the stationary distribution of strategies under the replicator dynamics. When the score ratio is high, we find that the stationary distribution is unstable, with respect to both evolutionary and dynamical stability, and the dynamics converge to a limit cycle. When the ratio is low, the dynamics converge to the stationary distribution. For an intermediate interval of the ratio, the distribution is dynamically but not evolutionarily stable. Finally, the implications of our results for previous models based on the war of attrition are discussed.Comment: Accepted for publication in Journal of Theoretical Biolog

Pseudovetenskap – Hur rustar vi våra studenter att bemöta detta?

Pseudovetenskap – Hur rustar vi våra studenter att bemöta detta? <p> Sammanfattning: Genom att kontrastera mot pseudovetenskap kan våra studenter lära sig om just vetenskap (nature of science) och vetenskaplig metodik. I denna workshop arbetar vi med hur man kan använda pseudovetenskapliga exempel för studenters lärande. Förutom kritiskt tänkanade kan man fokusera på färdigheter i vetenskapligt skrivande. Vi problematiserar och letar möjligheter ihop. Våra studenter förväntas kunna göra bedömningar i komplexa frågeställningar genom tillämpning av vetenskaplig metodik och kritiskt tänkande. [1] Men klarar de att tillämpa detta vid bedömningar av pseudovetenskapliga påståenden – och kan de hantera de etiska aspekterna av att kommunicera med allmänheten om pseudovetenskap? Hur rustar vi dem inför detta? Ingår detta ens i ingenjörsrollen? Varför bry sig? Homeopati, spöken, slagrutor och astrologi hör väl inte hemma på Chalmers? För en definition och förteckning av exempel på pseudovetenskap, se [2]. Vi kan vända på steken och lära oss om god vetenskaplig metodik och väletablerad kunskap just genom att uttala skillnaden mot pseudovetenskapen. Ofta uttrycks detta på engelska som ”the nature of science, NOS”. [3] Ingenjören är en ofta högaktad bärare av teknisk och naturvetenskaplig kompetens i arbetslivet och i samhället, och vi kan rusta våra studenter bättre än idag för att tydligt kommunicera om vad som är ”sant” i frågor som går att avgöra vetenskapligt. Ofta viftar vi bort ”tokiga” idéer som fått fäste i samhället som orimliga men ofarliga. Men, det finns många situationer där pseudovetenskaplig idéspridning får allvarliga konsekvenser. [4] Det kan röra sig om allt ifrån individens ekonomi, hälsa och överlevnad till planetens långsiktiga klimatförändringar. I denna workshop kommer vi att låta deltagarna konkretisera sina egna möjliga roller i främjandet av studenternas lärande kring pseudovetenskap och dess bemötande. Kan jag som lärare hitta något exempel inom mitt eget ämnesområde? T.ex. i kursen Laser Engineering kan man nagelfara påståenden om att hårbortfall kan behandlas med ”soft laser”. Exempel på andra lärosäten som utnyttjar pseudovetenskapliga exempel i vetenskapligt syfte diskuteras. [5-8]. Lärande om vetenskaplig text som genre är en sidoeffekt som påpekas av Dixon [9]. Vi kommer att gemensamt problematisera att man över huvud taget omnämner pseudovetenskap inom utbildningen. [10] Sprider man inte villfarelse genom att omnämna det? Kan man få motsatt effekt mot vad man avsåg när folk hör att pseudovetenskap tas upp med studenterna? Vi diskuterar om det är etiskt försvarbart att argumentera emot pseudovetenskap då så många människor kan bli upprörda av olika skäl – personlig eller religiös övertygelse, eller ekonomisk vinning. Men de samhälleliga och etiska konsekvenserna av det motsatta – att inte själva bemöta pseudovetenskapliga påståenden och att inte rusta studenterna att bemöta pseudovetenskap – samtalar vi kring under workshopen.</p> Referenser, nerladdade 2012-12-03 <p> 1. Nationella examensmål för bl.a. civilingenjörsexamen. https://www.chalmers.se/insidan/SV/utbildning-och-forskning/grundutbildning/hogskoleverkets/nationella-examensmal 2012-12-03</p> <p> 2. Pseudovetenskap http://en.wikipedia.org/wiki/List_of_topics_characterized_as_pseudoscience 2012-12-03</p> <p> 3. Duncan, D. “Teaching the nature of science using pseudoscience” http://casa.colorado.edu/~dduncan/pseudoscience/ 2012-12-03</p> <p> 4. What’s the harm? http://whatstheharm.net/ 2012-12-03</p> <p> 4. Good Science, Bad Science, Dreadful Science, and Pseudoscience. Kitcher, Philip, Journal of College Science Teaching v14 n3 p168-73 Dec-Jan 1984-85</p> <p> 5. Using Bad Science to Teach Good Chemistry. Epstein, Michael S., Journal of Chemical Education v. 75 n. 11 p1399-1404 Nov 1998 http://pubs.acs.org/doi/pdfplus/10.1021/ed075p1399 </p> <p> 6. Rasmussen, S.C., “The history of science as a tool to identify and confront pseudoscience”, J. of Chem. Education v. 84, nr. 6, pp 949-951, 2007 http://pubs.acs.org/doi/pdfplus/10.1021/ed084p949 </p> <p> 7. “A learning cycle approach to dealing with pseudoscience beliefs of prospective elementary teachers” Journal of science teacher education [1046-560X] Rosenthal, D B yr:1993 vol:4 iss:2 pg:33 -36 http://link.springer.com/article/10.1007%2FBF02628883#page-1 </p> <p> 8. Turgut, H. “The Context of Demarcation in Nature of Science Teaching: The Case of Astrology” Science and Education, v. 20, nr. 5-6, pp 491-515, 2011 http://link.springer.com/article/10.1007%2Fs11191-010-9250-2?LI=true#page-1 </p> <p> 9. Dixon, D. “Teaching Science with Pseudoscience” http://www.randi.org/site/index.php/swift-blog/1897-teaching-science-with-pseudoscience.html 2012-12-03</p> <p> 10. Häggström, O. ”Homeopati hör inte hemma på Chalmers” http://haggstrom.blogspot.se/2012/10/homeopati-hor-inte-hemma-pa-chalmers.html 2012-12-03</p

Grass/clover silage for growing/finishing pigs – effect of silage pre-treatment and feeding strategy on growth performance and carcass traits

This study evaluated the influence of feeding strategy and grass/clover silage pre-treatment on pig growth performance and carcass traits. In total, 128 pigs weighing 30–110 kg were fed either a commercial control feed or received silage in a pellet (SP) or in a total mixed ratio (TMR) containing chopped silage (SC) or intensively treated silage (SE). Silage replaced 20% of dietary crude protein content (g/kg). Diet affected weight gain (P = 0.001), with pigs fed the SP diet showing best overall growth performance. Pigs fed the SC diet had the lowest weight gain (P = 0.001), while pigs fed the SE diet performed similarly to those fed the control diet. Carcass weight and dressing percentage differed between the diets (P = 0.016 and P = 0.018), but there was no difference in lean meat content (P = 0.832). The results show satisfactory growth performance and carcass traits, indicating that silage can replace other protein sources in growing/finishing pig diets

Vetenskapligt förhållningssätt i samhällsfrågor

Vetenskapliga frågor med samhällsrelevans är ofta mycket komplexa. En del är känt, en del är okänt. En förståelse för problemen kräver ofta djupa specialkunskaper inom många olika ämnen och ett samarbete mellan experter inom olika områden är därför väsentligt. Data kan ofta vara ofullständiga och kontrollerade experiment kan av olika skäl vara olämpliga eller omöjliga. Hur dessa frågor skall kunna presenteras på ett rimligt korrekt och begripligt sätt för allmänheten är naturligtvis inte en strikt naturvetenskaplig fråga, men naturvetare som skall arbeta med komplexa frågor behöver förståelse även för dessa aspekter

A Model of Sympatric Speciation Through Reinforcement

Sympatric speciation, i.e. the evolutionary split of one species into two in the same environment, has been a highly troublesome concept. It has been a questioned if it is actually possible. Even though there have been a number of reported results both in the wild and from controlled experiments in laboratories, those findings are both hard to get and hard to analyze, or even repeat. In the current study we propose a mathematical model which addresses the question of sympatric speciation and the evolution of reinforcement. Our aim has been to capture some of the essential features such as: phenotype, resources, competition, heritage, mutation, and reinforcement, in as simple a way as possible. Still, the resulting model is not too easy to grasp with purely analytical tools, so we have also complemented those studies with stochastic simulations. We present a few results that both illustrates the usefulness of such a model, but also rises new biological questions about sympatric speciation and reinforcement in particular

Estimating the probability of coexistence in cross-feeding communities

The dynamics of many microbial ecosystems are driven by cross-feeding interactions, in which metabolites excreted by some species are metabolised further by others. The population dynamics of such ecosystems are governed by frequency-dependent selection, which allows for stable coexistence of two or more species. We have analysed a model of cross-feeding based on the replicator equation, with the aim of establishing criteria for coexistence in ecosystems containing three species, given the information of the three species’ ability to coexist in their three separate pairs, i.e. the long term dynamics in the three two-species component systems. The triple-system is studied statistically and the probability of coexistence in the species triplet is computed for two models of species interactions. The interaction parameters are modelled either as stochastically independent or organised in a hierarchy where any derived metabolite carries less energy than previous nutrients in the metabolic chain. We differentiate between different modes of coexistence with respect to the pair-wise dynamics of the species, and find that the probability of coexistence is close to 1/2 for triplet systems with three pair-wise coexistent pairs and for the so-called intransitive systems. Systems with two and one pair-wise coexistent pairs are more likely to exist for random interaction parameters, but are on the other hand much less likely to exhibit triplet coexistence. Hence we conclude that certain species triplets are, from a statistical point of view, rare, but if allowed to interact are likely to coexist. This knowledge might be helpful when constructing synthetic microbial communities for industrial purposes

An ecological and economical assessment of Integrated Amaranth (Amaranthus hybridus) and Nile Tilapia (Oreochromis niloticus) farming in Dar es Salaam, Tanzania

Organic wastes can be recycled in an ecologically sound way in fishponds by applying integrated agriculture and aquaculture systems (IAA). This kind of waste recycling can help to protect the environment from pollution and improve fishpond yields. Additionally, IAA provides an opportunity for diversification of the output from two or more existing subsystems leading to higher overall farm economic returns. This study explored the potential application of amaranth wastes (AW) as a dietary ingredient for tilapia in a tilapia-amaranths integrated system (ITA). An experimental diet (AD) contained 10% (based on the control diet, CD) inclusion of AW collected from a nearby vegetable market. The experiments included triplicate treatments with; (i) fish fed on AD, where the pond water was used for irrigating the amaranth plants (IAA-fish), and (ii) fish fed on CD, where no pond water was used for irrigating the amaranth plants (non-IAA fish). 90 days after fish stocking, eighteen 4 m2 amaranth plots were prepared and treated with (i) tap water without fertilization (control amaranths), (ii) water from IAA-fish pond and organically fertilized (IAA amaranths), and (iii) tap water and inorganically fertilized (non-IAA amaranths). The use of AW improved the fish feed conversion ratio. The overall net income from ITA was 3.2, 2.3, 2.6, and 1.8 higher than from non-IAA amaranths, IAA-amaranths, non-IAA fish, and IAA fish sub-systems respectively

Good-bye slippage - a new fusion to tackle bandage slippage on the foot

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