545 research outputs found
The implicit theory of historical change in the work of Alan S. Milward
Alan S. Milward was an economic historian who developed an implicit theory of historical change. His interpretation which was neither liberal nor Marxist posited that social, political, and economic change, for it to be sustainable, had to be a gradual process rather than one resulting from a sudden, cataclysmic revolutionary event occurring in one sector of the economy or society. Benign change depended much less on natural resource endowment or technological developments than on the ability of state institutions to respond to changing political demands from within each society. State bureaucracies were fundamental to formulating those political demands and advising politicians of ways to meet them. Since each society was different there was no single model of development to be adopted or which could be imposed successfully by one nation-state on others, either through force or through foreign aid programs. Nor could development be promoted simply by copying the model of a more successful economy. Each nation-state had to find its own response to the political demands arising from within its society. Integration occurred when a number of nationâ states shared similar political objectives which they could not meet individually but could meet collectively. It was not simply the result of their increasing interdependence. It was how and whether nation-states responded to these domestic demands which determined the nature of historical change.historical change,development,World Wars,Third Reich,Blitzkrieg,New Order,Vichy,Fascism,Grossraumwirtschaft,German question,reconstruction,golden age,integration,supranationality,Bretton Woods
Fast determination of coarse grained cell anisotropy and size in epithelial tissue images using Fourier transform
Mechanical strain and stress play a major role in biological processes such
as wound healing or morphogenesis. To assess this role quantitatively, fixed or
live images of tissues are acquired at a cellular precision in large fields of
views. To exploit these data, large numbers of cells have to be analyzed to
extract cell shape anisotropy and cell size. Most frequently, this is performed
through detailed individual cell contour determination, using so-called
segmentation computer programs, complemented if necessary by manual detection
and error corrections. However, a coarse grained and faster technique can be
recommended in at least three situations. First, when detailed information on
individual cell contours is not required, for instance in studies which require
only coarse-grained average information on cell anisotropy. Second, as an
exploratory step to determine whether full segmentation can be potentially
useful. Third, when segmentation is too difficult, for instance due to poor
image quality or too large a cell number. We developed a user-friendly, Fourier
transform-based image analysis pipeline. It is fast (typically cells per
minute with a current laptop computer) and suitable for time, space or ensemble
averages. We validate it on one set of artificial images and on two sets of
fully segmented images, one from a Drosophila pupa and the other from a chicken
embryo; the pipeline results are robust. Perspectives include \textit{in vitro}
tissues, non-biological cellular patterns such as foams, and stacks.Comment: 13 pages; 9 figure
Quantum cavitation in liquid helium
Using a functional-integral approach, we have determined the temperature
below which cavitation in liquid helium is driven by thermally assisted quantum
tunneling. For both helium isotopes, we have obtained the crossover temperature
in the whole range of allowed negative p essures. Our results are compatible
with recent experimental results on 4He.Comment: Typeset using Revtex, 10 pages and 2 figures, Phys. Rev B (1996
Gene body DNA methylation in seagrasses: inter- and intraspecific differences and interaction with transcriptome plasticity under heat stress
The role of DNA methylation and its interaction with gene expression and transcriptome plasticity is poorly understood, and current insight comes mainly from studies in very few model plant species. Here, we study gene body DNA methylation (gbM) and gene expression patterns in ecotypes from contrasting thermal environments of two marine plants with contrasting life history strategies in order to explore the potential role epigenetic mechanisms could play in gene plasticity and responsiveness to heat stress. In silico transcriptome analysis of CpG(O/E) ratios suggested that the bulk of Posidonia oceanica and Cymodocea nodosa genes possess high levels of intragenic methylation. We also observed a correlation between gbM and gene expression flexibility: genes with low DNA methylation tend to show flexible gene expression and plasticity under changing conditions. Furthermore, the empirical determination of global DNA methylation (5-mC) showed patterns of intra and inter-specific divergence that suggests a link between methylation level and the plants' latitude of origin and life history. Although we cannot discern whether gbM regulates gene expression or vice versa, or if other molecular mechanisms play a role in facilitating transcriptome responsiveness, our findings point to the existence of a relationship between gene responsiveness and gbM patterns in marine plants
A king and vassals' tale: Molecular signatures of clonal integration in Posidonia oceanica under chronic light shortage
Under unfavourable conditions, clonal plants benefit from physiological integration among ramets, sharing resources and information. Clonal integration can buffer against environmental changes and lets the plant clone work as a âmacroâ organism. Molecular signals that regulate this phenomenon are completely unknown in marine plants. Here we present a first comprehensive study providing insights into the metabolic role of different types of ramets (i.e. apical vs. vertical) in the foundation species Posidonia oceanica. Plants were exposed to 80% diminishing irradiance level (LL) in a controlled mesocosm system. Subsequent multiscale variations in whole transcriptome expression, global DNA methylation level, photo-physiology, morphology and fitness-related traits, were explored at different exposure times. We tested the hypothesis that vertical shoots (the âvassalsâ) can provide vital resources to apical shoots (the âkingsâ) under energy shortage, thus safeguarding the whole clone survival. Whole transcriptome analysis of leaves and shoot-apical meristems (SAMs) emphasized signatures of molecular integration among ramets, which strongly correlated with higher organization-level responses. In both shoots types, the exposure to LL resulted in a growth slowdown throughout the experiment, which started from immediate signals in SAMs. In apical shoots, this was linked to an acclimative response, where they were suffering a mild stress condition, while in vertical ones it fell in a more severe stress response. Yet, they suffered from sugar starvation and showed a clear cellular stress response in terms of protein refolding and DNA repair mechanisms. Several epigenetic mechanisms modulated the observed gene-expression patterns and the cross-talk between DNA methylation and the cellular energetic status appeared to regulate shoot metabolism under LL. Synthesis. Our results demonstrate a high level of specialization of integrated ramets within seagrass clones and a âdivision of labourâ under adverse conditions. Vertical shoots appear to do âmost of the jobâ especially in terms of resource providing, whereas activated functions in apical shoots were restricted to few important processes, according to an âenergy-savingâ strategy. The response of vertical shoots could be seen as a âsacrificing responseâ allowing the survival of âthe kingâ that is key for ensuring propagation and population maintenance, and for the colonization of new environments
DNA methylation dynamics in a coastal foundation seagrass species under abiotic stressors
DNA methylation (DNAm) has been intensively studied in terrestrial plants in response to environmental changes, but its dynamic changes in a temporal scale remain unexplored in marine plants. The seagrass Posidonia oceanica ranks among the slowest-growing and longest-living plants on Earth, and is particularly vulnerable to sea warming and local anthropogenic pressures. Here, we analysed the dynamics of DNAm changes in plants collected from coastal areas differentially impacted by eutrophication (i.e. oligotrophic, Ol; eutrophic, Eu) and exposed to abiotic stressors (nutrients, temperature increase and their combination). Levels of global DNAm (% 5-mC) and the expression of key genes involved in DNAm were assessed after one, two and five weeks of exposure. Results revealed a clear differentiation between plants, depending on environmental stimuli, time of exposure and plants' origin. % 5-mC levels were higher during the initial stress exposure especially in Ol plants, which upregulated almost all genes involved in DNAm. Contrarily, Eu plants showed lower expression levels, which increased under chronic exposure to stressors, particularly to temperature. These findings show that DNAm is dynamic in P. oceanica during stress exposure and underlined that environmental epigenetic variations could be implicated in the regulation of acclimation and phenotypic differences depending on local conditions
Spread of the invasive alga Caulerpa racemosa var. cylindracea (Caulerpales, Chlorophyta) along the Mediterranean Coast of the Murcia region (SE Spain)
The aim of this paper was to document the appearance and spread of the green alga Caulerpa racemosa along the coast of Murcia in southâeastern Spain. It was found for the first time in the area in 2005 and over the next two years the number of new sightings increased almost exponentially. In the period 2005â2007 the total surface area colonised by the alga in the region was estimated to be at least 265 ha. Benthic assemblages colonised by the alga were rocky bottoms with photophilic algae, dead P. oceanica rhizomes, infralittoral and circalittoral soft bottoms and maerl beds. No penetration of the alga was observed in P. oceanica meadows, except in one locality. Biometric analysis indicated high vegetative development in the established colonies in comparison to those described in other Mediterranean areas. Rapid spreading dynamics observed in the Murcia region is a potential threat for native benthic communities.
Key words: Biological invasions, Caulerpa racemosa var. cylindracea, Colonised surface area, Distribution, Mediterranean Sea, Spain.En el presente trabajo se documenta la apariciĂłn y dispersiĂłn del alga verde Caulerpa racemosa a lo largo de la costa de Murcia, regiĂłn situada en el sureste español. El alga fue detectada por primera vez en el año 2005 y durante los dos años consecutivos se observĂł un crecimiento casi exponencial en el nĂșmero de ĂĄreas colonizadas. La superficie total colonizada por el alga en Murcia durante el periodo 2005â2007 ha sido estimada en 265 ha., siendo las comunidades bentĂłnicas afectadas algas fotĂłfilas sobre sustrato rocoso, "mata muerta" de P. oceanica, fondos blandos infralitorales y circalitorales y fondos con comunidades de maĂ«rl. La presencia del alga dentro de praderas de P. oceanica solamente fue detectada en una localidad. Los estudios biomĂ©tricos realizados muestran un elevado desarrollo vegetativo de las poblaciones de C. racemosa en Murcia en comparaciĂłn con colonias de otras ĂĄreas del MediterrĂĄneo, siendo esta rĂĄpida dinĂĄmica de expansiĂłn una amenaza potencial para las comunidades bentonicas nativas.
Palabras clave: Invasiones biolĂłgicas, Caulerpa racemosa var. cylindracea, Superficie colonizada, Mar
Mediterraneo, España.The aim of this paper was to document the appearance and spread of the green alga Caulerpa racemosa along the coast of Murcia in southâeastern Spain. It was found for the first time in the area in 2005 and over the next two years the number of new sightings increased almost exponentially. In the period 2005â2007 the total surface area colonised by the alga in the region was estimated to be at least 265 ha. Benthic assemblages colonised by the alga were rocky bottoms with photophilic algae, dead P. oceanica rhizomes, infralittoral and circalittoral soft bottoms and maerl beds. No penetration of the alga was observed in P. oceanica meadows, except in one locality. Biometric analysis indicated high vegetative development in the established colonies in comparison to those described in other Mediterranean areas. Rapid spreading dynamics observed in the Murcia region is a potential threat for native benthic communities.
Key words: Biological invasions, Caulerpa racemosa var. cylindracea, Colonised surface area, Distribution, Mediterranean Sea, Spain
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