A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances

This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cassiopeia A, taken overnight on 18–19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across an observing bandwidth of 10–80 MHz. Delay-Doppler spectra (the 2-D FFT of the dynamic spectrum) from the first hour of observation showed two discrete parabolic arcs, one with a steep curvature and the other shallow, which can be used to provide estimates of the distance to, and velocity of, the scattering plasma. A cross-correlation analysis of data received by the dense array of stations in the LOFAR “core” reveals two different velocities in the scintillation pattern: a primary velocity of ~20–40 ms−1 with a north-west to south-east direction, associated with the steep parabolic arc and a scattering altitude in the F-region or higher, and a secondary velocity of ~110 ms−1 with a north-east to south-west direction, associated with the shallow arc and a scattering altitude in the D-region. Geomagnetic activity was low in the mid-latitudes at the time, but a weak sub-storm at high latitudes reached its peak at the start of the observation. An analysis of Global Navigation Satellite Systems (GNSS) and ionosonde data from the time reveals a larger-scale travelling ionospheric disturbance (TID), possibly the result of the high-latitude activity, travelling in the north-west to south-east direction, and, simultaneously, a smaller-scale TID travelling in a north-east to south-west direction, which could be associated with atmospheric gravity wave activity. The LOFAR observation shows scattering from both TIDs, at different altitudes and propagating in different directions. To the best of our knowledge this is the first time that such a phenomenon has been reported

The LOFAR Two-metre Sky Survey V. Second data release

In this data release from the ongoing LOw-Frequency ARray (LOFAR) Two-metre Sky Survey we present 120a 168 MHz images covering 27% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44 30a and 1h00m +28 00a and spanning 4178 and 1457 square degrees respectively. The images were derived from 3451 h (7.6 PB) of LOFAR High Band Antenna data which were corrected for the direction-independent instrumental properties as well as direction-dependent ionospheric distortions during extensive, but fully automated, data processing. A catalogue of 4 396 228 radio sources is derived from our total intensity (Stokes I) maps, where the majority of these have never been detected at radio wavelengths before. At 6a resolution, our full bandwidth Stokes I continuum maps with a central frequency of 144 MHz have: a median rms sensitivity of 83 μJy beama 1; a flux density scale accuracy of approximately 10%; an astrometric accuracy of 0.2a; and we estimate the point-source completeness to be 90% at a peak brightness of 0.8 mJy beama 1. By creating three 16 MHz bandwidth images across the band we are able to measure the in-band spectral index of many sources, albeit with an error on the derived spectral index of > a ±a 0.2 which is a consequence of our flux-density scale accuracy and small fractional bandwidth. Our circular polarisation (Stokes V) 20a resolution 120a168 MHz continuum images have a median rms sensitivity of 95 μJy beama 1, and we estimate a Stokes I to Stokes V leakage of 0.056%. Our linear polarisation (Stokes Q and Stokes U) image cubes consist of 480a A a 97.6 kHz wide planes and have a median rms sensitivity per plane of 10.8 mJy beama 1 at 4a and 2.2 mJy beama 1 at 20a; we estimate the Stokes I to Stokes Q/U leakage to be approximately 0.2%. Here we characterise and publicly release our Stokes I, Q, U and V images in addition to the calibrated uv-data to facilitate the thorough scientific exploitation of this unique dataset

Tiende CRL-Salmonella ringonderzoek (2005) voor de typering van Salmonella spp.

Het tiende ringonderzoek voor de typering van Salmonella werd in maart 2005 georganiseerd door het Communautair Referentie Laboratorium voor Salmonella (CRL-Salmonella, Bilthoven, Nederland) in samenwerking met de Health Protection Agency (HPA, Londen, Verenigd Koninkrijk) en het Centraal Instituut voor Dierziekte Controle (CIDC, Lelystad, Nederland). Zesentwintig Nationale Referentie Laboratoria voor Salmonella (NRLs-Salmonella) inclusief Noorwegen en 14 Enter-Net Laboratoria (ENLs) namen deel aan de studie. Twintig stammen van species Salmonella enterica subspecies enterica werden geselecteerd voor de serotypering. Tien stammen van Salmonella Enteritidis (SE) en 10 stammen van Salmonella Typhimurium (STM) werden geselecteerd voor faagtypering. Tien stammen van Salmonella spp. werden geselecteerd voor antimicrobiele gevoeligheidsbepalingen. In het algemeen werden geen problemen gevonden met de typering van de O-antigenen. Negenennegentig procent van de NRLs en 100 % van de ENLs typeerden de O-antigenen correct. Slechts enkele laboratoria hadden problemen met het typeren van de H-antigenen. De H-antigenen werden correct getypeerd door 97 % van de NRLs en door 99 % van de ENLs. Vierennegentig procent van de NRLs en 99 % van de ENLs gaven de 20 serotyperingsstammen de goede serovar naam. De meeste laboratoria vonden goede resultaten met de faagtypering. Ook de kwaliteit van de antimicrobiele gevoeligheidsbepalingen uitgevoerd door zowel de NRLs als door de ENLs was goed.The tenth interlaboratory comparison study on the typing of Salmonella was organised by the Community Reference Laboratory for Salmonella (CRL-Salmonella, Bilthoven, The Netherlands) in collaboration with the Health Protection Agency (HPA, London, United Kingdom) and the Central Institute for Animal Disease Control (CIDC, Lelystad, The Netherlands) in March 2005. Twenty-six National Reference Laboratories for Salmonella (NRLs-Salmonella), including Norway and 14 Enter-Net Laboratories (ENLs), participated in the study. In total, 20 strains of the species Salmonella enterica subspecies enterica were selected for serotyping. Ten strains of Salmonella Enteritidis (SE) and 10 strains of Salmonella Typhimurium (STM) were selected for phage typing. Ten strains of Salmonella spp. were selected for antimicrobial susceptibility testing. In general, no problems were encountered with the typing of the O antigens. Ninety-nine per cent of the NRLs and 100 % of the ENLs were able to correctly type the O antigens. A few laboratories had problems typing the H antigens. The H antigens were typed correctly by 97% of the NRLs and by 99% of the ENLs. Ninety-four per cent of the NRLs and 99% of the ENLs indicated correct serovar names for the 20 serotyping strains. The phage typing results of the majority of the laboratories were found to be good. This was also valid for the quality of the antimicrobial susceptibility testing of both the NRLs and the ENLs.European CommissionLegislation Veterinaire et Zootechniqu

Tiende CRL-Salmonella ringonderzoek (2005) voor de typering van Salmonella spp.

The tenth interlaboratory comparison study on the typing of Salmonella was organised by the Community Reference Laboratory for Salmonella (CRL-Salmonella, Bilthoven, The Netherlands) in collaboration with the Health Protection Agency (HPA, London, United Kingdom) and the Central Institute for Animal Disease Control (CIDC, Lelystad, The Netherlands) in March 2005. Twenty-six National Reference Laboratories for Salmonella (NRLs-Salmonella), including Norway and 14 Enter-Net Laboratories (ENLs), participated in the study. In total, 20 strains of the species Salmonella enterica subspecies enterica were selected for serotyping. Ten strains of Salmonella Enteritidis (SE) and 10 strains of Salmonella Typhimurium (STM) were selected for phage typing. Ten strains of Salmonella spp. were selected for antimicrobial susceptibility testing. In general, no problems were encountered with the typing of the O antigens. Ninety-nine per cent of the NRLs and 100 % of the ENLs were able to correctly type the O antigens. A few laboratories had problems typing the H antigens. The H antigens were typed correctly by 97% of the NRLs and by 99% of the ENLs. Ninety-four per cent of the NRLs and 99% of the ENLs indicated correct serovar names for the 20 serotyping strains. The phage typing results of the majority of the laboratories were found to be good. This was also valid for the quality of the antimicrobial susceptibility testing of both the NRLs and the ENLs.Het tiende ringonderzoek voor de typering van Salmonella werd in maart 2005 georganiseerd door het Communautair Referentie Laboratorium voor Salmonella (CRL-Salmonella, Bilthoven, Nederland) in samenwerking met de Health Protection Agency (HPA, Londen, Verenigd Koninkrijk) en het Centraal Instituut voor Dierziekte Controle (CIDC, Lelystad, Nederland). Zesentwintig Nationale Referentie Laboratoria voor Salmonella (NRLs-Salmonella) inclusief Noorwegen en 14 Enter-Net Laboratoria (ENLs) namen deel aan de studie. Twintig stammen van species Salmonella enterica subspecies enterica werden geselecteerd voor de serotypering. Tien stammen van Salmonella Enteritidis (SE) en 10 stammen van Salmonella Typhimurium (STM) werden geselecteerd voor faagtypering. Tien stammen van Salmonella spp. werden geselecteerd voor antimicrobiele gevoeligheidsbepalingen. In het algemeen werden geen problemen gevonden met de typering van de O-antigenen. Negenennegentig procent van de NRLs en 100 % van de ENLs typeerden de O-antigenen correct. Slechts enkele laboratoria hadden problemen met het typeren van de H-antigenen. De H-antigenen werden correct getypeerd door 97 % van de NRLs en door 99 % van de ENLs. Vierennegentig procent van de NRLs en 99 % van de ENLs gaven de 20 serotyperingsstammen de goede serovar naam. De meeste laboratoria vonden goede resultaten met de faagtypering. Ook de kwaliteit van de antimicrobiele gevoeligheidsbepalingen uitgevoerd door zowel de NRLs als door de ENLs was goed

Negende CRL-Salmonella ringonderzoek (2004) voor de typering van Salmonella spp

The ninth interlaboratory comparison study on the typing of Salmonella was organised by the Community Reference Laboratory for Salmonella (CRL-Salmonella, Bilthoven, the Netherlands) in collaboration with the Health Protection Agency (HPA, London, United Kingdom) and the Central Institute for Animal Disease Control (CIDC, Lelystad, the Netherlands) in spring 2004. Twenty-five National Reference Laboratories for Salmonella (NRLs-Salmonella) including Norway and Candidate Country Romania and eighteen Enter-Net Laboratories (ENLs) participated in the study. In total, 20 strains of the species Salmonella enterica subspecies enterica were selected for serotyping. Ten strains of Salmonella Enteritidis (SE) and 10 strains of Salmonella Typhimurium (STM) were selected for phage typing. Ten strains of Salmonella spp. were selected for antimicrobial susceptibility testing. In general, no problems were encountered with the typing of the O-antigens. Some laboratories had problems with typing of the H-antigens. Many problems occurred with the distinction between S. Banana and S. California. Ninety-eight percent of all participating laboratories were able to correctly type the O-antigens. The H-antigens were typed correctly by 90 % of the NRLs and by 96 % of the ENLs. Ninety percent of the NRLs and 95 % of the ENLs indicated correct serovar names for the 20 serotyping strains. The phage typing of some of the Salmonella Enteritidis strains caused problems for the NRLs as well as for the ENLs. Most laboratories performed the antimicrobial susceptibility testingtowards a panel of fourteen antibiotics. Some problems occurred with the interpretation of the results obtained with antibiotics amoxicillin-clavanulate and trimethoprim/sulphamethoxazole. This study demonstrated that less deviating results were produced by Minimal Inhibition Concentration determinations than by disc diffusion.Het negende ringonderzoek voor de typering van Salmonella werd in de lente van 2004 georganiseerd door het Communautair Referentie Laboratorium voor Salmonella (CRL-Salmonella, Bilthoven, Nederland) in samenwerking met Health Protection Agency (HPA, Londen, Verenigd Koninkrijk) en het Centraal Instituut voor Dierziekte Controle (CIDC, Lelystad, Nederland). Vijfentwintig Nationale Referentie Laboratoria voor Salmonella (NRLs-Salmonella) inclusief Noorwegen en Kandidaat lidstaat Roemenie en 18 Enter-Net Laboratoria (ENLs) namen deel aan de studie. Twintig stammen van species Salmonella enterica subspecies enterica werden geselecteerd voor de serotypering. Tien stammen van Salmonella Enteritidis (SE) en 10 stammen van Salmonella Typhimurium (STM) werden geselecteerd voor faagtypering. Tien stammen van Salmonella spp. werden geselecteerd voor antimicrobiele gevoeligheidsbepalingen. In het algemeen werden geen problemen gevonden met de typering van de O-antigenen. Enkele laboratoria hadden problemen met het typeren van de H-antigenen. Veel problemen traden op met de onderscheiding tussen S.Banana en S. California. Achtennegentig procent van alle deelnemende laboratoria typeerden de O-antigenen correct. De H-antigenen werden correct getypeerd door 90 % van de NRLs en door 96 % van de ENLs. Negentig procent van de NRLs en 95 % van de ENLs gaven de 20 serotyperingsstammen de goede serovar naam. De faagtypering van enkele van de Salmonella Enteritidis stammen zorgden voor problemen voor zowel de NRLs als de ENLs. De meeste laboratoria testten de antimicrobiele gevoeligheids bepalingen tegen een panel van veertien antibiotica. Sommige problemen deden zich voor met de interpretatie van de resultaten verkregen met de antibiotica amoxicillin-clavanulaat en trimethoprim/sulphamethoxazole. Deze studie toonde aan dat minder afwijkende resultaten werden verkregen met de Minimal Inhibition Concentration methode dan met de disk diffusie test

Negende CRL-Salmonella ringonderzoek (2004) voor de typering van Salmonella spp

Het negende ringonderzoek voor de typering van Salmonella werd in de lente van 2004 georganiseerd door het Communautair Referentie Laboratorium voor Salmonella (CRL-Salmonella, Bilthoven, Nederland) in samenwerking met Health Protection Agency (HPA, Londen, Verenigd Koninkrijk) en het Centraal Instituut voor Dierziekte Controle (CIDC, Lelystad, Nederland). Vijfentwintig Nationale Referentie Laboratoria voor Salmonella (NRLs-Salmonella) inclusief Noorwegen en Kandidaat lidstaat Roemenie en 18 Enter-Net Laboratoria (ENLs) namen deel aan de studie. Twintig stammen van species Salmonella enterica subspecies enterica werden geselecteerd voor de serotypering. Tien stammen van Salmonella Enteritidis (SE) en 10 stammen van Salmonella Typhimurium (STM) werden geselecteerd voor faagtypering. Tien stammen van Salmonella spp. werden geselecteerd voor antimicrobiele gevoeligheidsbepalingen. In het algemeen werden geen problemen gevonden met de typering van de O-antigenen. Enkele laboratoria hadden problemen met het typeren van de H-antigenen. Veel problemen traden op met de onderscheiding tussen S.Banana en S. California. Achtennegentig procent van alle deelnemende laboratoria typeerden de O-antigenen correct. De H-antigenen werden correct getypeerd door 90 % van de NRLs en door 96 % van de ENLs. Negentig procent van de NRLs en 95 % van de ENLs gaven de 20 serotyperingsstammen de goede serovar naam. De faagtypering van enkele van de Salmonella Enteritidis stammen zorgden voor problemen voor zowel de NRLs als de ENLs. De meeste laboratoria testten de antimicrobiele gevoeligheids bepalingen tegen een panel van veertien antibiotica. Sommige problemen deden zich voor met de interpretatie van de resultaten verkregen met de antibiotica amoxicillin-clavanulaat en trimethoprim/sulphamethoxazole. Deze studie toonde aan dat minder afwijkende resultaten werden verkregen met de Minimal Inhibition Concentration methode dan met de disk diffusie test.The ninth interlaboratory comparison study on the typing of Salmonella was organised by the Community Reference Laboratory for Salmonella (CRL-Salmonella, Bilthoven, the Netherlands) in collaboration with the Health Protection Agency (HPA, London, United Kingdom) and the Central Institute for Animal Disease Control (CIDC, Lelystad, the Netherlands) in spring 2004. Twenty-five National Reference Laboratories for Salmonella (NRLs-Salmonella) including Norway and Candidate Country Romania and eighteen Enter-Net Laboratories (ENLs) participated in the study. In total, 20 strains of the species Salmonella enterica subspecies enterica were selected for serotyping. Ten strains of Salmonella Enteritidis (SE) and 10 strains of Salmonella Typhimurium (STM) were selected for phage typing. Ten strains of Salmonella spp. were selected for antimicrobial susceptibility testing. In general, no problems were encountered with the typing of the O-antigens. Some laboratories had problems with typing of the H-antigens. Many problems occurred with the distinction between S. Banana and S. California. Ninety-eight percent of all participating laboratories were able to correctly type the O-antigens. The H-antigens were typed correctly by 90 % of the NRLs and by 96 % of the ENLs. Ninety percent of the NRLs and 95 % of the ENLs indicated correct serovar names for the 20 serotyping strains. The phage typing of some of the Salmonella Enteritidis strains caused problems for the NRLs as well as for the ENLs. Most laboratories performed the antimicrobial susceptibility testingtowards a panel of fourteen antibiotics. Some problems occurred with the interpretation of the results obtained with antibiotics amoxicillin-clavanulate and trimethoprim/sulphamethoxazole. This study demonstrated that less deviating results were produced by Minimal Inhibition Concentration determinations than by disc diffusion.European CommissionLegislation Veterinaire et Zootechniqu

Test resultaten van Salmonella typering door de NRLs-Salmonella in de Lidstaten van de EU en door de EnterNet Laboratoria

The eighth collaborative typing study for Salmonella was organised by the Community Reference Laboratory for Salmonella (CRL-Salmonella, Bilthoven, The Netherlands) in collaboration with the Public Health Laboratory Services (PHLS, London, United Kingdom) and the Central Institute for Animal Disease Control - Section Infectious Diseases (CIDC, Lelystad, The Netherlands).Seventeen National Reference Laboratories for Salmonella (NRLs-Salmonella) and fifteen Enter-Net laboratories (ENLs) participated in the study. Three of the NRLs for Salmonella are also ENL. The results obtained by these three NRL-ENL laboratories will only be evaluated in conjunction with the results of the 17 NRLs for Salmonella. In total, 20 strains of the species Salmonella enterica subspecies enterica were selected for serotyping, 10 strains of Salmonella Enteritidis (SE) and 10 strains of Salmonella Typhimurium (STM) for phage typing and 10 strains of Salmonella spp. for antimicrobial susceptibility testing. In general, no problems were encountered with the typing of the O-antigens. However, some laboratories had problems with typing the H-antigens. Some laboratories showed minor differences in phage typing. Some ENLs had considerable problems with the phage typing of the SE strains. Ten strains of various Salmonella serotypes were tested by most laboratories for their antimicrobial susceptibility towards a panel of twelve antibiotics. The NRLs and ENLs were free to choose whether to use the Minimal Inhibition Concentration (MIC) or the disc diffusion test. Over 95% of all tests were recorded correctly. Most problems occurred with testing against streptomycin.Het Communautair Referentie Laboratorium voor Salmonella (CRL-Salmonella, Bilthoven, Nederland) organiseerde in samenwerking met Public Health Laboratory Service (PHLS), London, Verenigd Koninkrijk en het Central Institute for Animal Disease Control - Sectie Infectieziekten (CIDC, Lelystad, Nederland) een achtste ringonderzoek aangaande de typering van Salmonella. Zeventien Nationale Referentie Laboratoria voor Salmonella (NRLs-Salmonella) en 15 EnterNet Laboratoria (ENLs) namen deel aan deze studie. Drie van deze NRLs zijn eveneens ENL. De resultaten van deze drie NRL-ENL laboratoria werden alleen geevalueerd bij de 17 NRLs voor Salmonella. In totaal werden 20 stammen van het species Salmonella enterica subspecies enterica geselecteerd voor serotypering terwijl 10 stammen van Salmonella Typhimurium (STM) en 10 stammen van Salmonella Enteritidis (SE) werden geselecteerd voor faagtypering. In het algemeen waren er geen problemen met het typeren van de O-antigenen. Sommige laboratoria hadden problemen met het typeren van de H-antigenen. Bijna alle laboratoria hadden weinig problemen met het faag-typeren. Enige ENLs hadden problemen met het faagtyperen van de SE stammen. Tien stammen van verschillende Salmonella serotypen werden getest op hun resistentie patronen tegen een panel van 12 antibiotica door bijna alle laboratoria. De NRLs en ENLs waren vrij om te kiezen tussen de Minimale Inhibitie Concentratie (MIC) of de disc diffusie test. Meer dan 95% van alle testen werden goed uitgevoerd. De meeste problemen werden veroorzaakt door streptomycine

Test resultaten van Salmonella typering door de NRLs-Salmonella in de Lidstaten van de EU en door de EnterNet Laboratoria

Het Communautair Referentie Laboratorium voor Salmonella (CRL-Salmonella, Bilthoven, Nederland) organiseerde in samenwerking met Public Health Laboratory Service (PHLS), London, Verenigd Koninkrijk en het Central Institute for Animal Disease Control - Sectie Infectieziekten (CIDC, Lelystad, Nederland) een achtste ringonderzoek aangaande de typering van Salmonella. Zeventien Nationale Referentie Laboratoria voor Salmonella (NRLs-Salmonella) en 15 EnterNet Laboratoria (ENLs) namen deel aan deze studie. Drie van deze NRLs zijn eveneens ENL. De resultaten van deze drie NRL-ENL laboratoria werden alleen geevalueerd bij de 17 NRLs voor Salmonella. In totaal werden 20 stammen van het species Salmonella enterica subspecies enterica geselecteerd voor serotypering terwijl 10 stammen van Salmonella Typhimurium (STM) en 10 stammen van Salmonella Enteritidis (SE) werden geselecteerd voor faagtypering. In het algemeen waren er geen problemen met het typeren van de O-antigenen. Sommige laboratoria hadden problemen met het typeren van de H-antigenen. Bijna alle laboratoria hadden weinig problemen met het faag-typeren. Enige ENLs hadden problemen met het faagtyperen van de SE stammen. Tien stammen van verschillende Salmonella serotypen werden getest op hun resistentie patronen tegen een panel van 12 antibiotica door bijna alle laboratoria. De NRLs en ENLs waren vrij om te kiezen tussen de Minimale Inhibitie Concentratie (MIC) of de disc diffusie test. Meer dan 95% van alle testen werden goed uitgevoerd. De meeste problemen werden veroorzaakt door streptomycine.The eighth collaborative typing study for Salmonella was organised by the Community Reference Laboratory for Salmonella (CRL-Salmonella, Bilthoven, The Netherlands) in collaboration with the Public Health Laboratory Services (PHLS, London, United Kingdom) and the Central Institute for Animal Disease Control - Section Infectious Diseases (CIDC, Lelystad, The Netherlands).Seventeen National Reference Laboratories for Salmonella (NRLs-Salmonella) and fifteen Enter-Net laboratories (ENLs) participated in the study. Three of the NRLs for Salmonella are also ENL. The results obtained by these three NRL-ENL laboratories will only be evaluated in conjunction with the results of the 17 NRLs for Salmonella. In total, 20 strains of the species Salmonella enterica subspecies enterica were selected for serotyping, 10 strains of Salmonella Enteritidis (SE) and 10 strains of Salmonella Typhimurium (STM) for phage typing and 10 strains of Salmonella spp. for antimicrobial susceptibility testing. In general, no problems were encountered with the typing of the O-antigens. However, some laboratories had problems with typing the H-antigens. Some laboratories showed minor differences in phage typing. Some ENLs had considerable problems with the phage typing of the SE strains. Ten strains of various Salmonella serotypes were tested by most laboratories for their antimicrobial susceptibility towards a panel of twelve antibiotics. The NRLs and ENLs were free to choose whether to use the Minimal Inhibition Concentration (MIC) or the disc diffusion test. Over 95% of all tests were recorded correctly. Most problems occurred with testing against streptomycin.European CommissionLegislation Veterinaire et Zootechniqu