278 research outputs found
A minimal stochastic model for influenza evolution
We introduce and discuss a minimal individual-based model for influenza
dynamics. The model takes into account the effects of specific immunization
against viral strains, but also infectivity randomness and the presence of a
short-lived strain transcending immunity recently suggested in the literature.
We show by simulations that the resulting model exhibits substitution of viral
strains along the years, but that their divergence remains bounded. We also
show that dropping any of these features results in a drastically different
behavior, leading either to the extinction of the disease, to the proliferation
of the viral strains, or to their divergence
Pemanfaatan Tempat Pendaratan Ikan (Tpi) di Kecamatan Rangsang Kabupaten Kepulauan Meranti
Building Fish Landing Places (TPI) that ther stimuli are buildings constructed for thefishermen land their catch of fish. These buildings have been built but not yet enabled bythe local government, especially the Department of Marine and Fisheries Meranti IslandsRegency. This is because the Department has the authority to regulate and supervise theactivities of marine and fisheries. Peneliitian purpose of this is to know the problemsfaced by the Department of Marine and Fisheries in the functioning of Fish LandingPlaces (TPI).Arrangement is to create a way to make a pekerjan have goals, direction to be achieved,sby knowing the existing procedures. This study used a qualitative descriptive method.Data were obtained from the interview data, documentary studies, and field observations.Informants in this study are those relating to the discussion of the function of FishLanding Places (TPI) is.The results showed that in the discussion of the function of pemanfaataan Fish LandingPlaces (TPI) is not able to function because of the absence of directives from the centralgovernment to the regions, and because of inadequate facilities. Furthermore, theconstraints for the fishermen are long distance and weather influences.Keywords. Place Pendaratn Fish, Function Department, Local Governmen
Electrical modeling of the photoelectric effect induced by a pulsed laser applied to an SRAM cell
International audienceThis abstract presents an electrical model of an SRAM cell exposed to a pulsed Photoelectrical Laser Stimulation (PLS), based on our past model of MOS transistor under laser illumination. The validity of our model is assessed by the very good correlation obtained between measurements and electrical simulation. These simulations are capable to explain some specific points. For example, in theory, a SRAM cell under PLS have four sensitive areas. But in measurements only three areas were revealed. A hypothesis was presented in this paper and confirm by electrical simulation. The specific topology of the cell masks one sensitive area. Therefore the electrical model could be used as a tool of characterization of a CMOS circuits under PLS
On the accuracy of language trees
Historical linguistics aims at inferring the most likely language
phylogenetic tree starting from information concerning the evolutionary
relatedness of languages. The available information are typically lists of
homologous (lexical, phonological, syntactic) features or characters for many
different languages.
From this perspective the reconstruction of language trees is an example of
inverse problems: starting from present, incomplete and often noisy,
information, one aims at inferring the most likely past evolutionary history. A
fundamental issue in inverse problems is the evaluation of the inference made.
A standard way of dealing with this question is to generate data with
artificial models in order to have full access to the evolutionary process one
is going to infer. This procedure presents an intrinsic limitation: when
dealing with real data sets, one typically does not know which model of
evolution is the most suitable for them. A possible way out is to compare
algorithmic inference with expert classifications. This is the point of view we
take here by conducting a thorough survey of the accuracy of reconstruction
methods as compared with the Ethnologue expert classifications. We focus in
particular on state-of-the-art distance-based methods for phylogeny
reconstruction using worldwide linguistic databases.
In order to assess the accuracy of the inferred trees we introduce and
characterize two generalizations of standard definitions of distances between
trees. Based on these scores we quantify the relative performances of the
distance-based algorithms considered. Further we quantify how the completeness
and the coverage of the available databases affect the accuracy of the
reconstruction. Finally we draw some conclusions about where the accuracy of
the reconstructions in historical linguistics stands and about the leading
directions to improve it.Comment: 36 pages, 14 figure
Modeling microevolution in a changing environment: The evolving quasispecies and the Diluted Champion Process
Several pathogens use evolvability as a survival strategy against acquired
immunity of the host. Despite their high variability in time, some of them
exhibit quite low variability within the population at any given time, a
somehow paradoxical behavior often called the evolving quasispecies. In this
paper we introduce a simplified model of an evolving viral population in which
the effects of the acquired immunity of the host are represented by the
decrease of the fitness of the corresponding viral strains, depending on the
frequency of the strain in the viral population. The model exhibits evolving
quasispecies behavior in a certain range of its parameters, ans suggests how
punctuated evolution can be induced by a simple feedback mechanism.Comment: 15 pages, 12 figures. Figures redrawn, some additional clarifications
in the text. To appear in Journal of Statistical Mechanics: Theory and
Experimen
Off-shore and underwater sampling of aquatic environments with the aerial-aquatic drone MEDUSA
Monitoring of aquatic habitats for water quality and biodiversity requires regular sampling, often in off-shore locations and underwater. Such sampling is commonly performed manually from research vessels, or if autonomous, is constrained to permanent installations. Consequentially, high frequency ecological monitoring, such as for harmful algal blooms, are limited to few sites and/or temporally infrequent. Here, we demonstrate the use of MEDUSA, an Unmanned Aerial-Aquatic Vehicle which is capable of performing underwater sampling and inspection at up to 10 m depth, and is composed of a multirotor platform, a tether management unit and a tethered micro Underwater Vehicle. The system is validated in the task of vertical profiling of Chlorophyll-a levels in freshwater systems by means of a custom solid sample filtering mechanism. This mechanism can collect up to two independent samples per mission by pumping water through a pair of glass-fibre GF/F filters. Chlorophyll levels measured from the solid deposits on the filters are consistent and on par with traditional sampling methods, highlighting the potential of using UAAVs to sample aquatic locations at high frequency and high spatial resolution
Permeability of anti-fouling PEGylated surfaces probed by fluorescence correlation spectroscopy
The present work reports on in situ observations of the interaction of organic dye probe molecules and dye-labeled protein with different poly(ethylene glycol) (PEG) architectures (linear, dendron, and bottle brush). Fluorescence correlation spectroscopy (FCS) and single molecule event analysis were used to examine the nature and extent of probećś EG interactions. The data support a sieve-like model in which size-exclusion principles determine the extent of probećś EG interactions. Small probes are trapped by more dense PEG architectures and large probes interact more with less dense PEG surfaces. These results, and the tunable pore structure of the PEG dendrons employed in this work, suggest the viability of electrochemically-active materials for tunable surfaces
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