2,104 research outputs found
Automatic Sampling of Geographic objects
Today, one's disposes of large datasets composed of thousands of geographic
objects. However, for many processes, which require the appraisal of an expert
or much computational time, only a small part of these objects can be taken
into account. In this context, robust sampling methods become necessary. In
this paper, we propose a sampling method based on clustering techniques. Our
method consists in dividing the objects in clusters, then in selecting in each
cluster, the most representative objects. A case-study in the context of a
process dedicated to knowledge revision for geographic data generalisation is
presented. This case-study shows that our method allows to select relevant
samples of objects
Influence of temperature and pH on S. bayanus var. uvarum growth; impact of a wine yeast interspecific hybridization on these parameters
The species Saccharomyces bayanus var. uvarum possesses interesting enological characteristics but produces high
concentration of volatile fermentative compounds not desirable in Sauvignon blanc wines. Interspecific hybrids between Saccharomyces cerevisiae and S. bayanus var. uvarum were made in order to join the main parental advantages. Two hybrids were selected on the basis of their fermentation characteristics and their karyotypes, i.e. they have a different mitochondrial DNA. In order to produce these hybrids as active dry yeast to be used as starter in winemaking, their optimal environmental
conditions for growth, i.e. temperature and pH, were determined as the objective of our work. Using a two-level factorial design it was found that the two parental strains have different optimal temperature but for the two strains, pH does not have a significant influence on growth. The influence of temperature on biomass productivity for hybrid strains were strictly identical, so we suppose that the main genes coding for temperature sensitivity were not contained in mitochondrial DNA, but in nuclear
DNA. Moreover the reactions of hybrid strains to the temperature variations were similar to the one of S. bayanus var.uvarum. This latter strain could have a majority of genes responsible of temperature sensitivity dominant in comparison with those of the strain S. cerevisiae
Quantitative study of interactions between Saccharomyces cerevisiae and Oenococcus oeni strains
This study examines the interactions that occur between Saccharomyces cerevisiae and Oenococcus oeni strains during the process of winemaking. Various yeast/bacteria pairs were studied by applying a sequential fermentation strategy which simulated the natural winemaking process. First, four yeast strains were tested in the presence of one bacterial strain leading to the inhibition of the bacterial component. The extent of inhibition varied widely from one pair to another and closely depended on the specific yeast strain chosen. Inhibition was correlated to weak bacterial growth rather than a reduction in the bacterial malolactic activity. Three of the four yeast strains were then grown with another bacteria strain. Contrary to the first results, this led to the bacterial stimulation, thus highlighting the importance of the bacteria strain. The biochemical profile of the four yeast fermented media exhibited slight variations in ethanol, SO2 and fatty acids produced as well as assimilable consumed nitrogen. These parameters were not the only factors responsible for the malolactic fermentation inhibition observed with the first bacteria strain. The stimulation of the second has not been reported before in such conditions and remains unexplained
Knowledge revision in systems based on an informed tree search strategy : application to cartographic generalisation
Many real world problems can be expressed as optimisation problems. Solving
this kind of problems means to find, among all possible solutions, the one that
maximises an evaluation function. One approach to solve this kind of problem is
to use an informed search strategy. The principle of this kind of strategy is
to use problem-specific knowledge beyond the definition of the problem itself
to find solutions more efficiently than with an uninformed strategy. This kind
of strategy demands to define problem-specific knowledge (heuristics). The
efficiency and the effectiveness of systems based on it directly depend on the
used knowledge quality. Unfortunately, acquiring and maintaining such knowledge
can be fastidious. The objective of the work presented in this paper is to
propose an automatic knowledge revision approach for systems based on an
informed tree search strategy. Our approach consists in analysing the system
execution logs and revising knowledge based on these logs by modelling the
revision problem as a knowledge space exploration problem. We present an
experiment we carried out in an application domain where informed search
strategies are often used: cartographic generalisation.Comment: Knowledge Revision; Problem Solving; Informed Tree Search Strategy;
Cartographic Generalisation., Paris : France (2008
Impact of the co-culture of Saccharomyces cerevisiae–Oenococcus oenion malolactic fermentation and partial characterization of a yeast-derived inhibitory peptidic fraction
The present study was aimed to evaluate the impact of the co-culture on the output of malolactic fermentation and to further investigate the reasons of the antagonism exerted by yeasts towards bacteria during sequential cultures. The Saccharomyces cerevisiae D strain/Oenococcus oeni X strain combination was tested by applying both sequential culture and co-culture strategies. This pair was chosen amongst others because the malolactic fermentation was particularly difficult to realize during the sequential culture. During this traditional procedure, malolactic fermentation started when alcoholic fermentation was achieved. For the co-culture, both fermentations were conducted together by inoculating yeasts and bacteria into a membrane bioreactor at the same time. Results obtained during the sequential culture and compared to a bacterial control medium, showed that the inhibition exerted by S. cerevisiae D strain in term of decrease of the malic acid consumption rate was mainly due to ethanol (75%) and to a peptidic fraction (25%) having an MW between 5 and 10 kDa. 0.4 g l-1 of L-malic acid was consumed in this case while 3.7 g l-1 was consumed when the co-culturewas applied. In addition, therewas no risk of increased volatile acidity during the co-culture. Therefore, the co-culture strategy was considered effective for malolactic fermentation with the yeast/bacteria pair studied
Effect of ammonium concentration on alcoholic fermentation kinetics by wine yeasts for high sugar content
Kinetics of alcoholic fermentation by Saccharomyces cerevisiae wine strains in a synthetic
medium with high sugar content were established for different nitrogen initial content and are
presented for 4 strains. The composition of the medium was close to grape must except that
the nitrogen source consisted mainly in ammonium and was varied from 120 to 290 mg N/L
assimilable nitrogen. The overall nitrogen consumed was also estimated in order to determine
nitrogen requirement variability.
The effect of assimilable nitrogen was in general greater on sugar consumption rates than on
growth and 3 kinds of effect on sugar consumption rates were observed: i) existence of an
optimal initial nitrogen level for a maximal sugar consumption rate (inhibition if excess), ii)
no effect of nitrogen beyond the intermediary level (saturation), iii) sugar consumption rate
proportional to the initial nitrogen level (activation).
In all cases, the amount of consumed nitrogen increased with its initial concentration and so
did the fructophilic capacity of the strains. The optimal requirement varied from 0.62 to 0.91
mg N per g of sugars according to the different strains. There was no general correlation
between the sugar assimilation rates and the nitrogen requirement
The Kalai-Smorodinski solution for many-objective Bayesian optimization
An ongoing aim of research in multiobjective Bayesian optimization is to
extend its applicability to a large number of objectives. While coping with a
limited budget of evaluations, recovering the set of optimal compromise
solutions generally requires numerous observations and is less interpretable
since this set tends to grow larger with the number of objectives. We thus
propose to focus on a specific solution originating from game theory, the
Kalai-Smorodinsky solution, which possesses attractive properties. In
particular, it ensures equal marginal gains over all objectives. We further
make it insensitive to a monotonic transformation of the objectives by
considering the objectives in the copula space. A novel tailored algorithm is
proposed to search for the solution, in the form of a Bayesian optimization
algorithm: sequential sampling decisions are made based on acquisition
functions that derive from an instrumental Gaussian process prior. Our approach
is tested on four problems with respectively four, six, eight, and nine
objectives. The method is available in the Rpackage GPGame available on CRAN at
https://cran.r-project.org/package=GPGame
Nanotechnology Through the Lenses of Science Fiction: Case Study of the Manga Ganmu (Battle Angel Alita) by Kishiro Yukito.
Nanotechnology has emergerd as a rapidly growing field whose dynamics and prospects pose many challenges to society at large. One of them is to overcome the radical opposition between nanophilic and nanophobic perspectives, whose science fictional rhetoric blurs the boundaries between "real" science and SF. However, if we assume, as Colin Milburn has pointed out, that nanotechnology is a "science fiction", it should be worth considering the ways science-fiction explores its so-called social and ethical implications. Japan offers an interesting example inasmuch as manga and animation, as a modern medium for SF, has dealt a lot with the political, economical, social and ethical impacts of nanotechnology. I will thus focus on the manga Ganmu 銃夢(Gunnm) by Kishiro Yukito 木城 ゆきとto analyse how Japan apprehends a nanotechnologically modified future
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