901 research outputs found
Ecological investigations on selected species at the Meikle Kilrannoch Ultramafic Outcrops, Scotland.
Ecological and ecophysiological investigations carried out at the ultramafic outcrop near
Meikle Kilrannoch, Angus, Scotland are reported. The outcrop is botanically famous for
its rare plant species, particularly the endemic Cerastium fontanum ssp. scoticum and
the nationally rare Lychnis alnina. The studies were made on the main outcrop (called
MK1) which is dome shaped, and on a much smaller low-lying area (called MK1.5)
about 300 m from it.
The overall aim of the studies was to investigate the relationship between the soil
physico-chemical environment and species distribution on the open areas of the
ultramafic site and to experimentally test for causality; and to offer an explanation for
the open character of the vegetation on the skeletal soils.
Variograms which were constructed for soil properties and vegetation data to investigate
soil micro-spatial variation and vegetation pattern showed differing levels of spatial
dependence, always indicating high intrinsic variability. The cause of this high
variability was probably cryoturbation for the soil and morphological characters for
plants.
The gradient analyses (Principal Components Analysis and its canonical form,
Redundancy Analysis) used to study soil - vegetation correlations suggested that
A ostis vinealis, Cerastium fontanum ssp. scoticum and Lychnis alpina were most
abundant in areas up-slope with lower concentrations of soil magnesium; Cochlearia
pyrenaica ssp. alpina and Festuca rubra were associated with bigger stone sizes, and the
latter occurred in wetter areas with higher of ions.
A comparative solution culture experiment based on the local soil chemistry was used
to study the growth responses to magnesium and nickel of Cerastium fontanum ss.
scoticum, Cochlearia pyrenaica ssp. al ina and Festuca rubra. The results for Festuca
and Cerastium were in agreement with the findings of the gradient analysis: Festuca was
indifferent to both magnesium and nickel and Cerastium was susceptible to high
magnesium; the reduction of dry weight by nickel in the Cochlearia conflicted with its
suggested association with high soil nickel in the gradient analysis.
The impacts on the photosynthetic systems of three Cochlearia species of different
concentrations of iron and nickel were identifiable only in the non-ultramafic C.
pyrenaica where the addition of nickel decreased photosynthesis but the effect could be
ameliorated by the addition of high concentrations of iron.
The open character of the skeletal soil at the MK1 site was discussed in terms of
'carrying capacity'. Vegetation development was suggested to be controlled at least
partly by large stones covering the soil surface. Further factors such as space
fragmentation, possible plant-to-plant interactions, and low density of flowering
individuals and restricted seed dispersal were also considered.
To test if major nutrients were limiting plant growth, major nutrients (NPK) were
applied to the MK1.5 skeletal soil. The significantly higher X's and recruitment and
change in life history traits (larger rosette sizes, earlier maturing and higher seed
production) in the fertilised populations of C. pyrenaica ssp. alpina resulted in a
significantly higher plant cover in the fertilised quadrats. The better growth of plants
in the fertilised quadrats was reflected in their lower total non-structural carbohydrate
(TNC) concentrations in May and their higher TNC in August.
The present series of investigations found that magnesium and nickel toxicity had an
effect on the intra-site distribution of the ultramafic species and also confirmed earlier
reports on the importance of magnesium and nickel toxicity in ultsamafic exclusion.
Large stones and low soil phosphorus concentration are proposed as limiting factors for
the development of closed vegetation on the skeletal soil areas of the sites
Nuclear receptor signalling in dendritic cells connects lipids, the genome and immune function
Dendritic cells (DCs) are sentinels of the immune system and represent a heterogeneous cell population. The existence of distinct DC subsets is due to their inherent plasticity and to the changing microenvironment modulating their immunological properties. Numerous signalling pathways have impacts on DCs. It appears that besides cytokines/chemokines, lipid mediators also have profound effects on the immunogenicity of DCs. Some of these lipid mediators exert an effect through nuclear hormone receptors. Interestingly, more recent findings suggest that DCs are able to convert precursors to active hormones, ligands for nuclear receptors. Some of these DC-derived lipids, in particular retinoic acid (RA), have a central function in shaping T-cell development and effector functions. In this review, we summarize and highlight the function of a set of nuclear receptors (PPARÎł, RA receptor, vitamin D receptor and glucocorticoid receptor) in DC biology. Defining the contribution of nuclear hormone receptor signalling in DCs can help one to understand the regulatory logic of lipid signalling and allow the exploitation of their potential for therapeutic intervention in various immunological diseases
Scattering Induced Attenuation of Ultrasonic Backscattering
Scattering induced ultrasonic attenuation offers a simple way to characterize material inhomogeneities. This method has a wide range of applications from tissue characterization [1,2] to ultrasonic NDE, such as grain size measurement in polycrystalline materials [3,4], structural diagnostics in ceramics [5,6], porosity assessment in cast metals [7,8] and composites [9], etc. The scattering induced attenuation of a through transmitted coherent ultrasonic wave can be readily related to certain characteristics of the average inhomogeneity via its total scattering cross-section. In many cases however, ultrasonic attenuation measurement is not feasible except from the backscattered signal. For want of better approximation, the scattering induced attenuation is presumed to have the same relation to the average inhomogeneity as if it were measured by the simpler transmission technique. It was recently reported [10] that this approximation breaks down in porosity assessment, and it probably does not work in many other NDE applications either
Association des Oulemas : une tendance de lâislam politique algĂ©rien (Epoque dâentre les deux grandes guerres)
The article presents how Algeriansâ national awareness was born. At that time, the country was still a French colony (a department belonging to a metropolis). The author mentions two important figures: Abdelkader ibn Muhieddine and Ben Badis, both of them are important when the process of rousing Algeriansâ Islamic and national awareness is taken into consideration. Abdelkader and Badis were ulamas; Islamic intellectuals who tried to rouse Algerians by restoring importance of their language and culture. They did not want to rouse political awareness in people, but rather identity coming from moderate Islam. Moderate Islam was supposed to be the basis of resistance against âmaking the country more Frenchâ and at the same time depriving dignity. The author quotes fragments of Ben Badisâ reply directed to Ferhat Abbasa (who represented Members of Parliament compliant with France). The reply is of a great value when Algeriansâ national liberation movement is taken into consideration.The article presents how Algeriansâ national awareness was born. At that time, the country was still a French colony (a department belonging to a metropolis). The author mentions two important figures: Abdelkader ibn Muhieddine and Ben Badis, both of them are important when the process of rousing Algeriansâ Islamic and national awareness is taken into consideration. Abdelkader and Badis were ulamas; Islamic intellectuals who tried to rouse Algerians by restoring importance of their language and culture. They did not want to rouse political awareness in people, but rather identity coming from moderate Islam. Moderate Islam was supposed to be the basis of resistance against âmaking the country more Frenchâ and at the same time depriving dignity. The author quotes fragments of Ben Badisâ reply directed to Ferhat Abbasa (who represented Members of Parliament compliant with France). The reply is of a great value when Algeriansâ national liberation movement is taken into consideration
Bovine brucellosis: A study of the serological aspects of the disease
A study of bovine brucellosis was carried out on a herd of mixed vaccination history with a view to evaluating the various methods of diagnosis used under field conditions in Great Britain. It was shown that the milk ring and whey agglutination tests were largely negative in calfhood-vaccinated brucella-free animals (85.1% and 96.1% respectively). In animals vaccinated as adults or repeat vaccinated, the milk ring test appears to be valueless as an indicator of field infection because of the very high percentage of falsely positive results (47.7%). The whey agglutination test was shown to be as valuable in these cattle as in calfhood-vaccinated cows, provided that the level of significance of whey agglutinins was taken as 1:10. The whey agglutinin titres appear to be influenced by the stage of lactations and there is a rise in the percentage of positives with advancing gestation. It is suggested that the milk ring and whey agglutination tests on them are of little value in the detection of infected animals since these are detected more readily by repeat serum agglutination test alone, but they are valuable as moderators in cases where the serum agglutination test gave doubtful results. The results of the vaginal mucus agglutination test indicate that tis value is very similar to that of the whey agglutination test in that it does not help significantly in the detection of infected animals but does serve to indicate absence of brucella infection in animals giving doubtful serum agglutinin titres. Over-age vaccination of cattle with Br.abortus S19 diminishes the value of the serum agglutination test to a considerable degree. The vaccinal serum agglutinin titre persists much longer in adult-vaccinated animals than in calfhood-vaccinated stock. There is a marked tendency for the serum titres of adult and also of calfhood-vaccinated animals, born and vaccinated in an infected environment, to show fluctuation of serum titres. One result of this fluctuation is that, on occasions, non-infected animals may show higher titres than animals known to be infected with Br.abortus. It is suggested that the too rigid application of the accepted criteria to the interpretation of serum agglutinin titres of adult-vaccinated cows may cause the disposal of many cows which may never constitute any danger for the rest of the herd. The examination of milk and vaginal mucus samples may be of real value in this situation. The results of cultural and biological examination of milk, vaginal mucus, post-partum and autopsy specimens indicated that the time and expense involved in these tests, purely for the diagnosis of brucella infection, is not proportionate to their value. However, where maximum safety is required their use may be justified. (Abstract shortened by ProQuest.)
La Grande Guerre 14-18 et le mouvement national maghrébin (Algérie, Tunisie)
The mobilisation causes a great social mobility, never seen before, in the maghrebiens countries: more of two hundred thousand men have been presents in the war operations, and almost hundred and fifty thousand have gone to work in the metropolitan factories. They have discovered a new world: a more egalitarian society than that of his country. They have been influenced by new ideologies: nationalism, Pan-Islamism, bolshevism, Wilsonâs President program. The contact with the working world transforms them in thinking beings â tells one of them spokesmen, the emir Khaled. The author presents the activities of Charles- AndrĂ© Julien (1891â1991), social-communist militant (in 1924, he left the Communist Party) in favour of the taking of conscience by the Maghrebies (the ânativesâ) of them national and social situation. And this militant, after high historian of Maghreb, have given a great contribution to do of the colonial problem an important matter in the French poltitical life at the beginning of Twenties
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