Stochastic models in population biology and their deterministic analogs

In this paper we introduce a class of stochastic population models based on "patch dynamics". The size of the patch may be varied, and this allows one to quantify the departures of these stochastic models from various mean field theories, which are generally valid as the patch size becomes very large. These models may be used to formulate a broad range of biological processes in both spatial and non-spatial contexts. Here, we concentrate on two-species competition. We present both a mathematical analysis of the patch model, in which we derive the precise form of the competition mean field equations (and their first order corrections in the non-spatial case), and simulation results. These mean field equations differ, in some important ways, from those which are normally written down on phenomenological grounds. Our general conclusion is that mean field theory is more robust for spatial models than for a single isolated patch. This is due to the dilution of stochastic effects in a spatial setting resulting from repeated rescue events mediated by inter-patch diffusion. However, discrete effects due to modest patch sizes lead to striking deviations from mean field theory even in a spatial setting.Comment: 47 pages, 9 figure

Resolving the compact dusty discs around binary post-AGB stars using N-band interferometry

We present the first mid-IR long baseline interferometric observations of the circumstellar matter around binary post-AGB stars. Two objects, SX Cen and HD 52961, were observed using the VLTI/MIDI instrument during Science Demonstration Time. Both objects are known binaries for which a stable circumbinary disc is proposed to explain the SED characteristics. This is corroborated by our N-band spectrum showing a crystallinity fraction of more than 50 % for both objects, pointing to a stable environment where dust processing can occur. Surprisingly, the dust surrounding SX Cen is not resolved in the interferometric observations providing an upper limit of 11 mas (or 18 AU at the distance of this object) on the diameter of the dust emission. This confirms the very compact nature of its circumstellar environment. The dust emission around HD 52961 originates from a very small but resolved region, estimated to be ~ 35 mas at 8 micron and ~ 55 mas at 13 micron. These results confirm the disc interpretation of the SED of both stars. In HD 52961, the dust is not homogeneous in its chemical composition: the crystallinity is clearly concentrated in the hotter inner region. Whether this is a result of the formation process of the disc, or due to annealing during the long storage time in the disc is not clear.Comment: 12 pages, 10 figures, accepted for publication in A &

Analysis of schizophrenia-related genes and electrophysiological measures reveals ZNF804A association with amplitude of P300b elicited by novel sounds

Several genes have recently been identified as risk factors for schizophrenia (SZ) by genome-wide association studies (GWAS), including ZNF804A which is thought to function in transcriptional regulation. However, the downstream pathophysiological changes that these genes confer remain to be elucidated. In 143 subjects (68 clinical high risk, first episode or chronic cases; 75 controls), we examined the association between 21 genetic markers previously identified by SZ GWAS or associated with putative intermediate phenotypes of SZ against three event-related potential (ERP) measures: mismatch negativity (MMN), amplitude of P300 during an auditory oddball task, and P300 amplitude during an auditory novelty oddball task. Controlling for age and sex, significant genetic association surpassing Bonferroni correction was detected between ZNF804A marker rs1344706 and P300 amplitude elicited by novel sounds (beta=4.38, P=1.03 × 10−4), which is thought to index orienting of attention to unexpected, salient stimuli. Subsequent analyses revealed that the association was driven by the control subjects (beta=6.35, P=9.08 × 10−5), and that the risk allele was correlated with higher novel P300b amplitude, in contrast to the significantly lower amplitude observed in cases compared to controls. Novel P300b amplitude was significantly correlated with a neurocognitive measure of auditory attention under interference conditions, suggesting a relationship between novel P300b amplitude and higher-order attentional processes. Our results suggest pleiotropic effects of ZNF804A on risk for SZ and neural mechanisms that are indexed by the novel P300b ERP component

Community between Europe and Africa

'Die Studie untersucht den Typ von Gemeinschaft, der durch die verschiedenen Lome Konventionen etabliert wurde. Die Beziehung zwischen der EG/ EU und den AKP-Staaten ist einem tiefgreifenden Wandel unterworfen. Während am Anfang die Beziehung auf der (kontrafaktischen) Unterstellung der Gleichheit der Vertragspartner und fairem Austausch basierte, wurde das Ungleichgewicht zwischen den Partnern im weiteren Verlauf immer offensichtlicher. Wurden die AKP-Staaten anfänglich als Klienten betrachtet, so wurden sie immer mehr zu Bittstellern, weil sich die sozio-ökonomischen und politischen Grundlagen veränderten, auf der die Fiktion der Gleichheit basierte. Das spezielle, als 'post-kolonial' charakterisierte Verhältnis zwischen der EG/ EU und den AKP-Staaten geht aller Wahrscheinlichkeit seinem Ende entgegen, genau so wie die besondere Form der Gemeinschaft, die sich zwischen diesen Staatengruppen entwickelt hatte. Auch in der Vergangenheit war das Verhältnis durch politische und ökonomische Konditionalität gekennzeichnet, die auf interne politische Reformen, Konfliktprävention und Armutsbekämpfung ausgerichtet war. So lange die EG/ EU nicht bereit und willens ist, direkt in diesen Staaten zu intervenieren, wird sie weiterhin die Entwicklungshilfe als indirektes Mittel benützen, um ihren politischen Interessen Geltung zu verschaffen. Dazu zählen neuerdings die Flüchtlingsproblematik, der Kampf gegen die Verbreitung von epidemischen Seuchen und der Kampf gegen den wachsenden Drogenhandel.' (Autorenreferat)'The study analyses the kind of community which was established through the various Lome Conventions. The relationship between the EC/ EU and the ACP countries has undergone profound changes. While in the beginning the relationship was based on the (contrafactual) supposition of equality between the partners and fair exchange the situation turned into a more openly unbalanced one. The real status of the ACP countries turned from client to supplicant because the socio-economic and political rational for upholding the fiction of equality vanished. The special 'post-colonial' relationship between the EC/ EU and the ACP countries is likely to come to an end as is the particular form of community between these two groups of states. Even in the past the relationship was characterised by political and economic conditionality aimed at internal political reform, conflict prevention, and poverty alleviation. Nevertheless, as long as the EC/ EU is not ready and willing to directly intervene in these countries it will rely on development aid as an indirect means to address its political concerns which now include refugee flight, the spread of cross border epidemic disease, and the growth of narcotics trade.' (author's abstract)

Preventing yellow fever epidemics in Asian megacities: how can cities control mosquito-transmitted diseases?

The COVID-19 pandemic has reminded us of the ever present threat from infectious diseases, this includes the ones we know about already and future unknowns. The mosquito-transmitted disease yellow fever has claimed thousands of lives over the centuries and it hasn’t gone away. It is still endemic in tropical areas of Africa and Latin America, where it is kept at bay through constant surveillance, mass vaccination campaigns and some natural immunity within local populations. Despite this there are serious outbreaks from time to time. The Aedes mosquitoes capable of transmitting the virus from person to person, are now widespread in warmer countries worldwide, moreover they thrive in urban areas. With increased international movement, the fear is that infected travellers could unwittingly introduce the virus into countries where people have little or no immunity. Densely populated Asian megacities are a major concern. There are simple measures citizens can take to protect themselves and their homes from the bite of infected mosquitoes, but city leaders must be at the forefront of a coordinated response bringing together diverse stakeholders to ensure a robust and sustainable defence

Community in Europe: a historical lexicon

Eines der Hauptargumente für die EU ist die anhaltende hohe Arbeitslosigkeit in allen Ländern der Union. Das vorliegende Arbeitspapier zeigt, dass die EU bei Bekämpfung der Arbeitslosigkeit sich in fast allen ihren Statements und Forderungen zwischen mehr Wettbewerbsfähigkeit auf den Märkten einerseits und 'sozialem Schutz', 'sozialer Balance' und 'sozialer Verantwortung' andererseits bewegt. Die schwierige Frage ist dabei die nach der Vereinbarkeit zwischen individueller Eigenverantwortlichkeit und staatlichen Interventionen und Regulierungen, die häufig mit den Freiheitsrechten des Einzelnen in Konflikt geraten. Die Kollision zwischen Selbständigkeit und dem Anspruch auf wohlfahrtsstaatliche Hilfe ist nur zu lösen, wenn der Verlust an subsidiären Solidarleistungen durch eine sozial vertretbare Form der kollektiven Hilfeleistungen kompensiert werden kann. (ICAÜbers)'One of the main causes of flagging support for the EU has been the persistence of high levels of unemployment in virtually all member states of the Union. Our paper shows that in combating unemployment, present policy as set out in EU documents is forced to steer a course between 'competitiveness' of markets and what is variously referred to as 'social protection', 'social balance' or 'social responsibility'. The difficult question which then arises is how an injunction for individual responsibility can be enforced through rules and regulations which run against the principle of freedom to which responsibility is attached. When freedom is associated with social custom or convention, and that it is customary for individuals to have a state-provided social benefit, a 'community' of social responsibility and the like becomes so problematic. The task is finding the means of persuasion that makes the loss of local custom and individual dependence appear as a socially responsible but private gain of livelihood.' (author's abstract)

Molecular Profiles of Pyramidal Neurons in the Superior Temporal Cortex in Schizophrenia

Disrupted synchronized oscillatory firing of pyramidal neuronal networks in the cerebral cortex in the gamma frequency band (i.e., 30–100 Hz) mediates many of the cognitive deficits and symptoms of schizophrenia. In fact, the density of dendritic spines and the average somal area of pyramidal neurons in layer 3 of the cerebral cortex, which mediate both long-range (associational) and local (intrinsic) corticocortical connections, are decreased in subjects with this illness. To explore the molecular pathophysiology of pyramidal neuronal dysfunction, we extracted ribonucleic acid (RNA) from laser-captured pyramidal neurons from layer 3 of Brodmann’s area 42 of the superior temporal gyrus (STG) from postmortem brains from schizophrenia and normal control subjects. We then profiled the messenger RNA (mRNA) expression of these neurons, using microarray technology. We identified 1331 mRNAs that were differentially expressed in schizophrenia, including genes that belong to the transforming growth factor beta (TGF-β) and the bone morphogenetic proteins (BMPs) signaling pathways. Disturbances of these signaling mechanisms may in part contribute to the altered expression of other genes found to be differentially expressed in this study, such as those that regulate extracellular matrix (ECM), apoptosis, and cytoskeletal and synaptic plasticity. In addition, we identified 10 microRNAs (miRNAs) that were differentially expressed in schizophrenia; enrichment analysis of their predicted gene targets revealed signaling pathways and gene networks that were found by microarray to be dysregulated, raising an interesting possibility that dysfunction of pyramidal neurons in schizophrenia may in part be mediated by a concerted dysregulation of gene network functions as a result of the altered expression of a relatively small number of miRNAs. Taken together, findings of this study provide a neurobiological framework within which specific hypotheses about the molecular mechanisms of pyramidal cell dysfunction in schizophrenia can be formulated

The airtightness and air leakage characteristics of new UK holiday homes

It is estimated that in the UK, 200,000 residents live in park and holiday homes all year round, the majority of which are elderly and on low incomes. As these homes are often thermally inefficient and leaky, these residents are some of the most susceptible in society to fuel poverty. Despite this, there is a dearth of empirical data available on the in situ fabric performance of these homes. This paper presents the results obtained from undertaking a series of pressurisation tests and leakage identification on new build holiday homes. While the sample size reported is small, the results indicate almost a factor of two variation in the airtightness performance of the homes. In spite of this, all of the homes achieved an air permeability significantly lower than the default value incorporated within the industry standard Energy Efficiency Rating Calculator, suggesting that a much lower figure may be more appropriate. The results also suggest that the use of the air permeability metric within the Calculator potentially biases the performance of holiday homes due to their particular form factor, and that this bias could be mitigated against by adopting the air leakage metric within any future revisions to the Calculator