Modelling biological invasions: individual to population scales at interfaces

Extracting the population level behaviour of biological systems from that of the individual is critical in understanding dynamics across multiple scales and thus has been the subject of numerous investigations. Here, the influence of spatial heterogeneity in such contexts is explored for interfaces with a separation of the length scales characterising the individual and the interface, a situation that can arise in applications involving cellular modelling. As an illustrative example, we consider cell movement between white and grey matter in the brain which may be relevant in considering the invasive dynamics of glioma. We show that while one can safely neglect intrinsic noise, at least when considering glioma cell invasion, profound differences in population behaviours emerge in the presence of interfaces with only subtle alterations in the dynamics at the individual level. Transport driven by local cell sensing generates predictions of cell accumulations along interfaces where cell motility changes. This behaviour is not predicted with the commonly used Fickian diffusion transport model, but can be extracted from preliminary observations of specific cell lines in recent, novel, cryo-imaging. Consequently, these findings suggest a need to consider the impact of individual behaviour, spatial heterogeneity and especially interfaces in experimental and modelling frameworks of cellular dynamics, for instance in the characterisation of glioma cell motility

A Prototype for the PASS Permanent All Sky Survey

A prototype system for the Permanent All Sky Survey (PASS) project is presented. PASS is a continuous photometric survey of the entire celestial sphere with a high temporal resolution. Its major objectives are the detection of all giant-planet transits (with periods up to some weeks) across stars up to mag 10.5, and to deliver continuously photometry that is useful for the study of any variable stars. The prototype is based on CCD cameras with short focal length optics on a fixed mount. A small dome to house it at Teide Observatory, Tenerife, is currently being constructed. A placement at the antarctic Dome C is also being considered. The prototype will be used for a feasibility study of PASS, to define the best observing strategies, and to perform a detailed characterization of the capabilities and scope of the survey. Afterwards, a first partial sky surveying will be started with it. That first survey may be able to detect transiting planets during its first few hundred hours of operation. It will also deliver a data set around which software modules dealing with the various scientific objectives of PASS will be developed. The PASS project is still in its early phase and teams interested in specific scientific objectives, in providing technical expertise, or in participating with own observations are invited to collaborate.Comment: Accepted for Astronomische Nachrichten (special issue for 3rd Potsdam Thinkshop 'Robotic Astronomy' in July 2004). 4 pages, 4 fig

Forest Ecosystem Services: An Analysis of Worldwide Research

The relevance of forests to sustain human well-being and the serious threats they face have led to a notable increase of research works on forest ecosystem services during the last few years. This paper analyses the worldwide research dynamics on forest ecosystem services in the period from 1998 to 2017. A bibliometric analysis of 4284 articles was conducted. The results showed that the number of published research articles has especially increased during the last five years. In total, 68.63% of the articles were published in this period. This research line experiences a growing trend superior to the general publishing trend on forest research. In spite of this increase, its relative significance within the forest research is still limited. The most productive subject areas corresponded to Environmental Science, Agricultural and Biological Sciences and Social Sciences Economic topics are understudied. The scientific production is published in a wide range of journals. The three first publishing countries are United States, China and the United Kingdom. The most productive authors are attached to diverse research centres and their contributions are relatively recent. A high level of international cooperation has been observed between countries, institutions and authors. The findings of this study are useful for researchers since they give them an overview of the worldwide research trends on forest ecosystem services

Solitons in combined linear and nonlinear lattice potentials

We study ordinary solitons and gap solitons (GSs) in the effectively one-dimensional Gross-Pitaevskii equation, with a combination of linear and nonlinear lattice potentials. The main points of the analysis are effects of the (in)commensurability between the lattices, the development of analytical methods, viz., the variational approximation (VA) for narrow ordinary solitons, and various forms of the averaging method for broad solitons of both types, and also the study of mobility of the solitons. Under the direct commensurability (equal periods of the lattices, the family of ordinary solitons is similar to its counterpart in the free space. The situation is different in the case of the subharmonic commensurability, with L_{lin}=(1/2)L_{nonlin}, or incommensurability. In those cases, there is an existence threshold for the solitons, and the scaling relation between their amplitude and width is different from that in the free space. GS families demonstrate a bistability, unless the direct commensurability takes place. Specific scaling relations are found for them too. Ordinary solitons can be readily set in motion by kicking. GSs are mobile too, featuring inelastic collisions. The analytical approximations are shown to be quite accurate, predicting correct scaling relations for the soliton families in different cases. The stability of the ordinary solitons is fully determined by the VK (Vakhitov-Kolokolov) criterion, while the stability of GS families follows an inverted ("anti-VK") criterion, which is explained by means of the averaging approximation.Comment: 9 pages, 6 figure

Contribution of hydrogeomorphology for mapping flood hazard in mediterranean ephemeral streams (ramblas)

Flood hazard mapping can be performed using different methods that, generally speaking, can be grouped into four main categories: historical and paleohydrological methods, hydrogeomorphological methods, hydrological-hydraulic methods, and the recently developed dendrogeomorphological methods. These groups of methods are not mutually exclusive and, in fact, they should be used complementarily. Unfortunately, in the case of ramblas, this combination is really difficult. On one hand, paleohydrological methods are not suitable for so small and torrential catchments as ramblas are and, on the other hand, hydrological-hydraulic methods demand a large amount of hydrologic data, non available in most of these systems. Indeed, many authors assert the inadequacy of these methods to predict extreme floods in Mediterranean small catchments. Anyway, hydrogeomorphological method is nowadays achieving more relevance. It is based on the location and typology of landforms and sediments generated during floods in order to delineate flooding areas and identify processes. It is a qualitative approach that gives a realistic image of the processes and it is enough to make decisions, with a minimum effort, in the 80% of the instances. Studies developed in the Mediterranean region of southern France and north-western Spain have demonstrated the effectiveness of this method in ephemeral streams, where channel and floodplain morphology are highly variable and changeable over time and, in addition, hydrological information is scarce or nearly inexistent. This work presents a method for mapping flood hazard in two Mediterranean small catchments -Barranc de Carraixet and Rambla de Poyo-, based on hydrogeomorphological interpretation. A synthetic hydrogeomorphological cartography was obtained supported by previous studies (carried out by Camarasa, Carmona and Ruiz) and taking into account the forms and processes developed during the great flood event of October 2000. Thirteen different landforms related to flooding processes where identified and valuated in terms of hazard, ranking from levels 1 to 8, in which level 1 represents the highest hazard (streams and critical points) and level 8 the safety areas (mountains and longshore bars). Hydrogeomorphological method has proved to be highly effective for mapping flood hazard in this kind of torrential ephemeral streams, where standard hydrological and hydraulic methods do not work properly. This method allows working with scarcity of hydrological data and, what is more, is quite adaptable to any change in flood area morphology (either natural or man made)

Contenido polínico de la atmósmera de Cataluña: resultados año 1983

Se presentan al gunos de los resultados obtenidos hasta e l momento en el Programa de estudio del contenido en polen de la atmósfera de Cataluña y Bal eares: gráficos de pol en total y de al gunos taxones i mportan tes de Barcelona, Bellaterra (U ni v. Aut ónoma de Barcelona), Girona ( aeropuerto ) , LLeida y Tarragona; gráfico de comparación de resul tactos obtenidos a partir de dos metodologías distintas de captación aplicadas a una misma estación y calendario polinice para la estación de Barcelona. Todos e l l os correspond en al año 1983.The r esults we present here are t he preliminary e nes (year 1983) o f a Study Program about atmospheric pol l eo content at severa! s i tes in Cataluña and Baleares. The annual trends of al! taxa considered coll ecti ve l ly and for sorne of the most important enes for Barcelona , Be l laterra (Univ. Autónoma de Barcelona) , Girona { airport), Lleida and Tarragona are compared. In addition we compare the effici ency of two di f ferent designs of pollen traps f rom the same local i ty. Final ly we provide the pollinic calendar of Barcelona