Large extinctions in an evolutionary model: The role of innovation and keystone species

The causes of major and rapid transitions observed in biological macroevolution as well as in the evolution of social systems are a subject of much debate. Here we identify the proximate causes of crashes and recoveries that arise dynamically in a model system in which populations of (molecular) species co-evolve with their network of chemical interactions. Crashes are events that involve the rapid extinction of many species and recoveries the assimilation of new ones. These are analyzed and classified in terms of the structural properties of the network. We find that in the absence of large external perturbation, `innovation' is a major cause of large extinctions and the prime cause of recoveries. Another major cause of crashes is the extinction of a `keystone species'. Different classes of causes produce crashes of different characteristic sizes.Comment: 8 pages, 3 figures (14 ps files

Systemische Alphabetisierung

"In vielfältigen öffentlichen Bereichen hat der systemische Blick Einzug gehalten. Der Bereich der Pädagogik ist davon bisher weitgehend verschont geblieben. In der Alphabetisierung von Jugendlichen und Erwachsenen wird dieser Ansatz ebenfalls nicht angewandt. Erst das begreifen, was dazu geführt hat, ein Lernproblem entstehen zu lassen, durch welche Bedingungen es begünstigt, ja sogar notwendig wurde, macht eine Bewältigung möglich. Dazu ist es erforderlich, sich die Bedingungen in der Herkunftsfamilie und in der damaligen Schulzeit gemeinsam mit dem Betroffenen zu vergegenwärtigen, um so erkennen zu können, was den Teilnehmer daran gehindert hat, die Schriftsprache in ausreichendem Maße zu erlernen und welchen persönlichen Gewinn er davon hatte. Wen hätte er womöglich verloren? Was würde sich in seinem Leben ändern, wenn er keine Probleme mit der Schriftsprache hätte? Welche Konsequenzen würden sich für ihn daraus ergeben?" (Autorenreferat)"In many official areas the systemic view has made its introduction. The pedagogical sphere has been widely left apart. In juvenile and adult illiteracy this method has equally not been used. For the first time the understanding, which had led to the point to let a problem of learning rise and by which conditions is has been favoured, even become a necessity, makes a solution possible. In this respect it is going to be necessary to look at the basic family of the learner, and to keep in mind this school career in his presence. All this in order to evaluate, why the client had been prevented to pick up the written language successfully and to a sufficient degree and which had been his personal success. Which person could he possibly have lost? Would considerable changes open up in his life, even if he wouldn’t have had any language problems? Which consequences would possible rise from this setting?" (author's abstract

Selfishness versus functional cooperation in a stochastic protocell model

How to design an "evolvable" artificial system capable to increase in complexity? Although Darwin's theory of evolution by natural selection obviously offers a firm foundation, little hope of success seems to be expected from the explanatory adequacy of modern evolutionary theory, which does a good job at explaining what has already happened but remains practically helpless at predicting what will occur. However, the study of the major transitions in evolution clearly suggests that increases in complexity have occurred on those occasions when the conflicting interests between competing individuals were partly subjugated. This immediately raises the issue about "levels of selection" in evolutionary biology, and the idea that multi-level selection scenarios are required for complexity to emerge. After analyzing the dynamical behaviour of competing replicators within compartments, we show here that a proliferation of differentiated catalysts and/or improvement of catalytic efficiency of ribozymes can potentially evolve in properly designed artificial cells. Experimental evolution in these systems will likely stand as beautiful examples of artificial adaptive systems, and will provide new insights to understand possible evolutionary paths to the evolution of metabolic complexity

Template coexistence in prebiotic vesicle models

The coexistence of distinct templates is a common feature of the diverse proposals advanced to resolve the information crisis of prebiotic evolution. However, achieving robust template coexistence turned out to be such a difficult demand that only a class of models, the so-called package models, seems to have met it so far. Here we apply Wright's Island formulation of group selection to study the conditions for the coexistence of two distinct template types confined in packages (vesicles) of finite capacity. In particular, we show how selection acting at the level of the vesicles can neutralize the pressures towards the fixation of any one of the template types (random drift) and of the type with higher replication rate (deterministic competition). We give emphasis to the role of the distinct generation times of templates and vesicles as yet another obstacle to coexistence.Comment: 7 pages, 8 figure

Highly ordered LB films of DHAP : a donor acceptor substituted polyene

The donor acceptor substituted polyene 5-(4-dihexadecylaminophenyl)-2-methyl-2,4-pentadienal (DHAP) is - due to its amphiphilic nature - a promising candidate for the Langmuir-Blodgett (LB) technique. The molecule was studied as a monolayer on a pure water surface under argon atmosphere. Monolayers and multilayers were transfered onto solid support. The films showed a high degree of order in the monolayer as well as in thick multilayers. LB films were investigated with polarisation dependent UV/VIS absorption spectroscopy. The film spectra showed additional absorption peaks which were not present in the spectra of the molecules in solution. The relative peak intensities were highly dependent on the orientation of the electric field vector with respect to the substrate normal. To get a detailed picture of the arrangement of the films on the molecular level, we studied the polarisation dependence of the FTIR spectra in different experimental set-ups. The spectra showed a perpendicular orientation of the conjugated system with respect to the substrate, whereas the backbone of the saturated hydrocarbon chains showed a medium tilt angle of 20.0° with respect to the substrate normal. X-ray small angle diffraction measurements were applied to investigate the thickness of the LB layers. From the position of the Bragg peaks, a thickness of 5.45 nm per bilayer can be calculated, in agreement with a bilayer model showing different molecular alignment of the molecules transferred during upstroke and downstroke

Donor-acceptor substituted polyenes : orientation in mono- and multilayers

Large molecules containing different chemical units whose interactions within the molecule result in new macroscopically observable effects, have become increasingly important.The organization of molecules of this type in ordered structures leads to functional molecular materials.Their use in molecular electronics requires that the units exhibit specific electronic properties. Recently, we reported on the intramolecular energy transfer through terminally substituted conjugated polyenes. An intramolecular electron transfer within donor-acceptor substituted polyenes can be achieved by introducing suitable terminal groups

Can Google search Data help predict macroeconomic series?

We make use of Google search data in an attempt to predict unemployment, CPI and consumer confidence for the US, UK, Canada, Germany and Japan. Google search queries have previously proven valuable in predicting macroeconomic variables in an in-sample context. However, to the best of our knowledge, the more challenging question of whether such data have out-of-sample predictive value has not yet been answered satisfactorily. We focus on out-of-sample nowcasting, and extend the Bayesian structural time series model using the Hamiltonian sampler for variable selection. We find that the search data retain their value in an out-of-sample predictive context for unemployment, but not for CPI or consumer confidence. It is possible that online search behaviours are a relatively reliable gauge of an individual’s personal situation (employment status), but less reliable when it comes to variables that are unknown to the individual (CPI) or too general to be linked to specific search terms (consumer confidence)

Etiology and Outcome of Adult and Pediatric Acute Liver Failure in Europe

Acute liver failure (ALF) is rare but life-threatening. Common causes include intoxications, infections, and metabolic disorders. Indeterminate etiology is still frequent. No systematic data on incidence, causes, and outcome of ALF across Europe are available. Via an online survey we reached out to European Reference Network Centers on rare liver diseases. Numbers and etiology of ALF cases during 2020 were retrieved and diagnostic and treatment availabilities assessed. In total, 455 cases (306 adult, 149 pediatric) were reported from 36 centers from 20 countries. Intoxication was the most common cause in adult and pediatric care. The number of cases with indeterminate etiology is low. Diagnostic tools and specific treatment options are broadly available within this network. This is the first approach to report on etiology and outcome of ALF in the pediatric and adult population in Europe. High diagnostic yield and standard of care reflects the expert status of involved centers.</p

Adherence to the screening program for HBV infection in pregnant women delivering in Greece

BACKGROUND: Hepatitis B infection (HBV) is a major Public Health Problem. Perinatal transmission can be prevented with the identification of HBsAg(+) women and administration of immunoprophylaxis to their newborns. A national prevention programme for HBV with universal screening of pregnant women and vaccination of infants is in effect since 1998 in Greece. METHODS: To evaluate adherence to the national guidelines, all women delivering in Greece between 17–30/03/03 were included in the study. Trained health professionals completed a questionnaire on demographic data, prenatal or perinatal screening for HBsAg and the implementation of appropriate immunoprophylaxis. RESULTS: During the study period 3,760 women delivered. Prenatal screening for HBsAg was documented in 91.3%. Greek women were more likely to have had prenatal testing. HBsAg prevalence was 2.89% (95%CI 2.3–3.4%). Higher prevalence of HBV-infection was noted in immigrant women, especially those born in Albania (9.8%). Other risk factors associated with maternal HBsAg (+) included young maternal age and absence of prenatal testing. No prenatal or perinatal HBsAg testing was performed in 3.2% women. Delivering in public hospital and illiteracy were identifiable risk factors for never being tested. All newborns of identified HBsAg (+) mothers received appropriate immunoprophylaxis. CONCLUSION: The prevalence of HBsAg in Greek pregnant women is low and comparable to other European countries. However, immigrant women composing almost 20% of our childbearing population, have significant higher prevalence rates. There are still women who never get tested. Universal vaccination against HBV at birth and reinforcement of perinatal testing of all women not prenatally tested should be discussed with Public Health Authorities

Value of biomarkers in osteoarthritis: Current status and perspectives

Osteoarthritis affects the whole joint structure with progressive changes in cartilage, menisci, ligaments and subchondral bone, and synovial inflammation. Biomarkers are being developed to quantify joint remodelling and disease progression. This article was prepared following a working meeting of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis convened to discuss the value of biochemical markers of matrix metabolism in drug development in osteoarthritis. The best candidates are generally molecules or molecular fragments present in cartilage, bone or synovium and may be specific to one type of joint tissue or common to them all. Many currently investigated biomarkers are associated with collagen metabolism in cartilage or bone, or aggrecan metabolism in cartilage. Other biomarkers are related to non-collagenous proteins, inflammation and/or fibrosis. Biomarkers in osteoarthritis can be categorised using the burden of disease, investigative, prognostic, efficacy of intervention, diagnostic and safety classification. There are a number of promising candidates, notably urinary C-terminal telopeptide of collagen type II and serum cartilage oligomeric protein, although none is sufficiently discriminating to differentiate between individual patients and controls (diagnostic) or between patients with different disease severities (burden of disease), predict prognosis in individuals with or without osteoarthritis (prognostic) or perform so consistently that it could function as a surrogate outcome in clinical trials (efficacy of intervention). Future avenues for research include exploration of underlying mechanisms of disease and development of new biomarkers; technological development; the ‘omics’ (genomics, metabolomics, proteomics and lipidomics); design of aggregate scores combining a panel of biomarkers and/or imaging markers into single diagnostic algorithms; and investigation into the relationship between biomarkers and prognosis. This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 3.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial