187,745 research outputs found
Bananes et ananas : production et commerce en Guinée française / par Yves Henry,... ; avec la collaboration de M. P. Ammann,... et de M. P. Teissonnier,...
No full textCollection : Bibliothèque d'agriculture colonialeCollection : Bibliothèque d'agriculture colonialeAppartient à l’ensemble documentaire : NmBA001Appartient à l’ensemble documentaire : NmBA003Contient une table des matièresAvec mode text
Maintaining replicated authorizations in distributed database systems
No full textWe consider the propagation of authorizations in distributed database systems. We present an optimistic replica control algorithm that ensures that the authorization table at any given site evolves consistently with respect to other sites. The motivation for using optimistic replica control to maintain authorizations is that site and communication failures do not needlessly delay authorization changes. In addition, the semantics of the authorization operations we employ can be exploited to resolve transient inconsistencies without the expense of an undo-redo mechanism. Instead, we give efficient, direct algorithms whereby a site scans its log of authorization requests and updates its authorization table correspondingly. From the system perspective, any inconsistencies in the authorization table replicas maintained at different sites are transient and are eliminated by further communication. We show how a site can prune its authorization log by the use of a matrix that records how current remaining sites in the system are
Is biotechnology a victim of anti-science bias in scientific journals?
No full textPrimarily outside the scientific community, misapprehensions and misinformation about recombinant DNA-modified (also known as 'genetically modified', or 'GM') plants have generated significant 'pseudo-controversy' over their safety that has resulted in unscientific and excessive regulation (with attendant inflated development costs) and disappointing progress. But pseudo-controversy and sensational claims have originated within the scientific community as well, and even scholarly journals' treatment of the subject has been at times unscientific, one-sided and irresponsible. These shortcomings have helped to perpetuate 'The Big Lie' - that recombinant DNA technology applied to agriculture and food production is unproven, unsafe, untested, unregulated and unwanted. Those misconceptions, in turn, have given rise to unwarranted opposition and tortuous, distorted public policy
Today’s vegetation and woody flora
No full textConsidered over long time scales, today's vegetation is only the last realization of a dynamic process and not a static concept. On the one hand, knowledge of modern vegetation is essential for our understanding of vegetation history, on the other hand, considering this history allows a deeper understanding of the present vegetation. In Europe this comparison is made difficult because of the human impact on the environment over millennia: what we observe as the modern plant cover is only rarely the end product of a natural vegetation history.
A distinction was often made between ‘modern natural vegetation’ (plant cover without any human impact) and ‘modern potential natural vegetation’ (plant cover including human impact but as it would be after the cessation of this influence). Both are concepts based on soils, climate and biogeography, but they remain constructions with large uncertainties (Tüxen, 1956; Frenzel, 1968; Neuhäusl, 1991; Bohn et al., 2003; Birks, 2019).
For our purpose a map of the modern potential natural vegetation on a small scale will be sufficient showing the ‘zonal vegetation’ that depends on large-scale factors such as temperature and precipitation and that omits the ‘azonal vegetation’ depending on edaphic conditions (for example riparian forests, mires, halophytic habitats). Moreover, the elevational belts of mountain systems cannot be fully shown on this scale. A higher spatial resolution can be found in Ozenda (1979) and Bohn et al. (2003). As an overview we can distinguish five vegetation zones (biomes) in Europe:
• The arctic and alpine zone with treeless dwarf shrub, meadow or tall herb vegetation (A)
• The boreal zone with a dominance of conifers (B)
• The temperate zone with mainly forests of deciduous trees (T)
• The Mediterranean zone with co-dominance (mesomediterranean) or dominance (thermomediterranean) of evergreen broadleaved trees and shrubs (M)
• The Pannonic-Pontic-Anatolian zone with forest steppes, steppes and semi-deserts (P) Most limits are spatially not clearly delimited and this can be expressed in terms such as ‘forest- tundra’ or ‘subarctic’ – belts that can be very broad for example in north-west Russia
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Gap asymptotics of the directions in an Ammann-Beenker-like quasicrystal
No full textIt is known that the limiting gap distribution of the directions to visible points in planar quasicrystals of cut-and-project type exists as a continuous function . In this article we study the asymptotic behaviour of said limiting gap distributionin the particular case of an Ammann-Beenker-like quasicrystal ; more precisely we show that in this case as with an explicit constant .</p
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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