49 research outputs found
Chaotic and pseudochaotic attractors of perturbed fractional oscillator
We consider a nonlinear oscillator with fractional derivative of the order
alpha. Perturbed by a periodic force, the system exhibits chaotic motion called
fractional chaotic attractor (FCA). The FCA is compared to the ``regular''
chaotic attractor. The properties of the FCA are discussed and the
``pseudochaotic'' case is demonstrated.Comment: 20 pages, 7 figure
Digital receivers for low-frequency radio telescopes UTR-2, URAN, GURT
This paper describes digital radio astronomical receivers used for decameter
and meter wavelength observations. This paper describes digital radio
astronomical receivers used for decameter and meter wavelength observations.
Since 1998, digital receivers performing on-the-fly dynamic spectrum
calculations or waveform data recording without data loss have been used at the
UTR-2 radio telescope, the URAN VLBI system, and the GURT new generation radio
telescope. Here we detail these receivers developed for operation in the strong
interference environment that prevails in the decameter wavelength range. Data
collected with these receivers allowed us to discover numerous radio
astronomical objects and phenomena at low frequencies, a summary of which is
also presented.Comment: 24 pages, 15 figure
A colanic acid operon deletion mutation enhances induction of early antibody responses by live attenuated salmonella vaccine strains
Colanic acid (CA) is a common exopolysaccharide produced by many genera in the Enterobacteriaceae. It is critical for biofilm formation on HEp-2 cells and on chicken intestinal tissue by Salmonella. In this study, we generated different CA synthesis gene mutants and evaluated the immune responses induced by these mutants. One of these mutations, Δ(wza-wcaM)8, which deleted the whole operon for CA synthesis, was introduced into two Salmonella vaccine strains attenuated by auxotrophic traits or by the regulated delayed attenuation strategy (RDAS). The mice immunized with the auxotrophic Salmonella vaccine strain with the deletion mutation Δ(wza-wcaM)8 developed higher vaginal IgA titers against the heterologous protective antigen and higher levels of antigen-specific IgA secretion cells in lungs. In Salmonella vaccine strains with RDAS, the strain with the Δ(wza-wcaM)8 mutation resulted in higher levels of protective antigen production during in vitro growth. Mice immunized with this strain developed higher serum IgG and mucosal IgA antibody responses at 2 weeks. This strain also resulted in better gamma interferon (IFN-γ) responses than the strain without this deletion at doses of 10(8) and 10(9) CFU. Thus, the mutation Δ(wza-wcaM)8 will be included in various recombinant attenuated Salmonella vaccine (RASV) strains with RDAS derived from Salmonella enterica serovar Paratyphi A and Salmonella enterica serovar Typhi to induce protective immunity against bacterial pathogens
Diagenesis, provenance and reservoir quality of Triassic TAGI sandstones from Ourhoud field, Berkine (Ghadames) Basin, Algeria
What Can Be Interesting in the Analysis of Crowded Solar Bursts?
International audienceAt decameter wavelengths the radio astronomy observations reveal a wide variety of solar bursts. They are associated with solar activity manifestations such as movements of electron beams and shock waves in solar corona, flare- related events, coronal mass ejections and others. The analysis of burst features allows one to use them as probing signals which comprise useful information about solar corona parameters and their changes over time. By frequency-time measurements of different types of solar bursts occurred about the same time one can provide a comparative study of their properties, complementing the missing pieces in the complex mosaic of solar events. In this purpose we discuss features of their signal processing by the gradient filtration, as applied to quasi-periodic bursts like a zebra pattern related to Bernstein modes. The measured frequency periodicity of the bursts gives a chance to determine the magnetic field strength in upper corona around the protracted solar minimum of solar activity
Comparative Analysis Of Solar Observations To A Strong Absorption On Background Of Sporadic Radio Emission From The Sun
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