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1.
Mon Not R Astron Soc ; 459(3): 2681-2689, 2016 Jul 01.
Article in English | MEDLINE | ID: mdl-27279782

ABSTRACT

The eclipses of certain types of binary millisecond pulsars (i.e. 'black widows' and 'redbacks') are often studied using high-time-resolution, 'beamformed' radio observations. However, they may also be detected in images generated from interferometric data. As part of a larger imaging project to characterize the variable and transient sky at radio frequencies <200 MHz, we have blindly detected the redback system PSR J2215+5135 as a variable source of interest with the Low-Frequency Array (LOFAR). Using observations with cadences of two weeks - six months, we find preliminary evidence that the eclipse duration is frequency dependent (∝ν-0.4), such that the pulsar is eclipsed for longer at lower frequencies, in broad agreement with beamformed studies of other similar sources. Furthermore, the detection of the eclipses in imaging data suggests an eclipsing medium that absorbs the pulsed emission, rather than scattering it. Our study is also a demonstration of the prospects of finding pulsars in wide-field imaging surveys with the current generation of low-frequency radio telescopes.

2.
Mon Not R Astron Soc ; 459(3): 3161-3174, 2016 Jul 01.
Article in English | MEDLINE | ID: mdl-27279785

ABSTRACT

We report on the results of a search for radio transients between 115 and 190 MHz with the LOw-Frequency ARray (LOFAR). Four fields have been monitored with cadences between 15 min and several months. A total of 151 images were obtained, giving a total survey area of 2275 deg2. We analysed our data using standard LOFAR tools and searched for radio transients using the LOFAR Transients Pipeline. No credible radio transient candidate has been detected; however, we are able to set upper limits on the surface density of radio transient sources at low radio frequencies. We also show that low-frequency radio surveys are more sensitive to steep-spectrum coherent transient sources than GHz radio surveys. We used two new statistical methods to determine the upper limits on the transient surface density. One is free of assumptions on the flux distribution of the sources, while the other assumes a power-law distribution in flux and sets more stringent constraints on the transient surface density. Both of these methods provide better constraints than the approach used in previous works. The best value for the upper limit we can set for the transient surface density, using the method assuming a power-law flux distribution, is 1.3 × 10-3 deg-2 for transients brighter than 0.3 Jy with a time-scale of 15 min, at a frequency of 150 MHz. We also calculated for the first time upper limits for the transient surface density for transients of different time-scales. We find that the results can differ by orders of magnitude from previously reported, simplified estimates.

3.
Farmaco ; 59(11): 863-8, 2004 Nov.
Article in English | MEDLINE | ID: mdl-15544790

ABSTRACT

The different analogues of ebselen-unsubstituted benzisoselenazol-3(2H)-one (2a) 2-pyridylbenzisoselenazol-3(2H)-ones (2b-h) and 7-azabenzisoselenazol-3(2H)-ones (3a-j) were designed as new selenium-containing antiviral and antimicrobial agents and synthesized. Some of them were found in the antiviral assay in vitro to be strong inhibitors of cythopatic activity of herpes simplex virus type 1--HSV-1 (compounds 2a,b,f,h, 3a-j) and encephalomyocarditis virus--EMCV (compounds 2a,h, 3a-f,k,l). The compounds 2a,h and 3a-e,j were found to have an appreciable activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus) in vitro, some of them inhibited growth of pathogenic yeasts (Candida albicans) (3a,b) and filamentous fungi (3a-e,f).


Subject(s)
Anti-Bacterial Agents/chemical synthesis , Antifungal Agents/chemical synthesis , Antiviral Agents/chemical synthesis , Azoles/chemical synthesis , Azoles/pharmacology , Organoselenium Compounds/chemical synthesis , Organoselenium Compounds/pharmacology , Anti-Bacterial Agents/pharmacology , Antifungal Agents/pharmacology , Antiviral Agents/pharmacology , Aza Compounds/chemical synthesis , Aza Compounds/pharmacology , Candida albicans/drug effects , Cell Line , Encephalomyocarditis virus/drug effects , Encephalomyocarditis virus/pathogenicity , Herpesvirus 1, Human/drug effects , Herpesvirus 1, Human/pathogenicity , Humans , Isoindoles , Microbial Sensitivity Tests , Vesicular stomatitis Indiana virus/drug effects , Vesicular stomatitis Indiana virus/pathogenicity
4.
Z Lebensm Unters Forsch ; 194(5): 465-8, 1992 May.
Article in English | MEDLINE | ID: mdl-1621449

ABSTRACT

The action of gamma-irradiated patulin on Saccharomyces cerevisiae LOCK 2144 in liquid culture was studied. Patulin irradiated in an aqueous solution with doses ranging over 0.34-1.36 kGy inhibited the yeast growth in a proportion to the concentration of undestroyed toxin. Patulin disappearance in the growth medium occurred between 12-72 h of incubation at 30 degrees C. The patulin content did not essentially change in the period of log phase of yeast growth which is accompanied by rapid glucose uptake.


Subject(s)
Patulin/pharmacology , Saccharomyces cerevisiae/drug effects , Chromatography, High Pressure Liquid , Culture Media , Gamma Rays , Glucose/metabolism , Kinetics , Patulin/analysis , Patulin/radiation effects , Saccharomyces cerevisiae/growth & development
5.
Z Lebensm Unters Forsch ; 188(4): 348-50, 1989 Apr.
Article in English | MEDLINE | ID: mdl-2502886

ABSTRACT

The bacteriological toxicity of patulin irradiated in aqueous solutions was investigated using two strains of bacteria, Bacillus subtilis and B.megaterium. The results of the plate cultivation test showed that the growth inhibition of both strains decreased in relation to absorbed dose. A dose of 1.8 kGy was sufficient to eliminate the bacteriological toxicity of patulin at an initial concentration of 125 micrograms/ml. There was good correlation between the concentration of patulin in the irradiated solution as measured spectrophotometrically and that calculated from the diameter of the inhibition zone.


Subject(s)
Bacillus megaterium/drug effects , Bacillus subtilis/drug effects , Patulin/radiation effects , Pyrans/radiation effects , Bacillus megaterium/growth & development , Bacillus subtilis/growth & development , Gamma Rays , Patulin/pharmacology , Patulin/toxicity , Spectrophotometry
6.
Acta Microbiol Pol ; 32(1): 73-85, 1983.
Article in English | MEDLINE | ID: mdl-6194669

ABSTRACT

The new isolated yeasts were very good producers of biomass from methanol. Their taxonomic studies were based on classical classification, GC content of DNA, proton magnetic resonance spectrum of the cell wall mannans and mannan and glucan and chitin contents in the cell walls. The isolates could not be identified with any species described in literature. Considering their special features and some relation to the known species, the isolated yeasts were classified as follows: C-16 as Candida bimundalis var. chlamydospora, C-4 as Candida melinii var. melibiosica, D-3 as Candida silvicola var. melibiosica and M-1 as Torulopsis candida var. nitratophila.


Subject(s)
Candida/classification , Methanol/metabolism , Base Composition , Candida/cytology , Candida/metabolism , Cell Wall/analysis , DNA, Fungal/analysis , Mannans/analysis , Polysaccharides/analysis
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