Clusters of galaxies : observational properties of the diffuse radio emission

Clusters of galaxies, as the largest virialized systems in the Universe, are ideal laboratories to study the formation and evolution of cosmic structures...(abridged)... Most of the detailed knowledge of galaxy clusters has been obtained in recent years from the study of ICM through X-ray Astronomy. At the same time, radio observations have proved that the ICM is mixed with non-thermal components, i.e. highly relativistic particles and large-scale magnetic fields, detected through their synchrotron emission. The knowledge of the properties of these non-thermal ICM components has increased significantly, owing to sensitive radio images and to the development of theoretical models. Diffuse synchrotron radio emission in the central and peripheral cluster regions has been found in many clusters. Moreover large-scale magnetic fields appear to be present in all galaxy clusters, as derived from Rotation Measure (RM) studies. Non-thermal components are linked to the cluster X-ray properties, and to the cluster evolutionary stage, and are crucial for a comprehensive physical description of the intracluster medium. They play an important role in the cluster formation and evolution. We review here the observational properties of diffuse non-thermal sources detected in galaxy clusters: halos, relics and mini-halos. We discuss their classification and properties. We report published results up to date and obtain and discuss statistical properties. We present the properties of large-scale magnetic fields in clusters and in even larger structures: filaments connecting galaxy clusters. We summarize the current models of the origin of these cluster components, and outline the improvements that are expected in this area from future developments thanks to the new generation of radio telescopes.Comment: Accepted for the publication in The Astronomy and Astrophysics Review. 58 pages, 26 figure

Phosphorylcholine Allows for Evasion of Bactericidal Antibody by Haemophilus influenzae

The human pathogen Haemophilus influenzae has the ability to quickly adapt to different host environments through phase variation of multiple structures on its lipooligosaccharide (LPS), including phosphorylcholine (ChoP). During colonization with H. influenzae, there is a selection for ChoP+ phase variants. In a murine model of nasopharyngeal colonization, this selection is lost in the absence of adaptive immunity. Based on previous data highlighting the importance of natural antibody in limiting H. influenzae colonization, the effect of ChoP expression on antibody binding and its bactericidal activity was investigated. Flow cytometric analysis revealed that ChoP+ phase variants had decreased binding of antibody to LPS epitopes compared to ChoP− phase variants. This difference in antibody binding correlated with increased survival of ChoP+ phase variants in the presence of antibody-dependent, complement-mediated killing. ChoP+ phase variants were also more resistant to trypsin digestion, suggesting a general effect on the physical properties of the outer membrane. Moreover, ChoP-mediated protection against antibody binding correlated with increased resilience of outer membrane integrity. Collectively, these data suggest that ChoP expression provides a selective advantage during colonization through ChoP-mediated effects on the accessibility of bactericidal antibody to the cell surface

Giant Cell Lesions in Noonan Syndrome: Case Report and Review of The Literature

Noonan-like/multiple giant cell lesion syndrome (NS/MGCLS) is a rare condition with phenotypic overlap with Noonan syndrome (NS). Once thought to be a specific and separate entity, it is now suggested to be a variant of the NS spectrum. We report a patient with classical cardinal features of NS, including short stature, mild ptosis, hypertelorism, down-slating palpebral fissures, low-set and posteriorly angulated ears, short neck, pectus excavatum, widely spaced nipples and cryptochidism, which were associated with bilateral central giant cell lesions in the mandible and germ-line mutation (C218T, Thr73Ile) in the exon 3 of the PTPN11 gene. The similar clinical and genetic aspects support the observation that NS/MGCLS is a variant of NS and giant cell lesions are an integrant part of this disorder

Attention substances of the environmental policy in the Netherlands - Survey 1994

In dit rapport wordt een overzicht gegeven van de stand van zaken met betrekking tot aandachtstoffen, dat wil zeggen, de stoffen die zijn opgenomen in de Regeling aandachtstoffen Wet milieugevaarlijke stoffen 1992 (Staatscourant 138, 21 juli 1992). De aandachtstoffen omvatten ook de stoffen die prioritair zijn in het Nederlandse milieubeleid. De belangrijkste doelstellingen van het rapport zijn de volgende: 1. het geven van een overzicht van het onderzoek dat reeds aan aandachtstoffen is verricht of wordt verricht ; 2. het sturen en prioriteren van nieuw uit te zetten onderzoek aan aandachtstoffen ; 3. het doen van aanbevelingen ten aanzien van de doorvoer van stoffen in het aandachtstoffenwerk en de afvoer van stoffen van de aandachtstoffenlijst. Voor wat betreft de tweede doelstelling is het rapport in de eerste plaats gericht op het onderzoek dat in opdracht van de Directie Stoffen, Veiligheid en Straling van het Directoraat-Generaal Milieubeheer wordt uitgezet, zoals onderzoek in het kader van de nationale lijn van het project Bestaande Stoffen, maar deze doelstelling moet zo breed mogelijk worden gezien. Het rapport geeft per aandachtstof of aandachtstoffengroep een overzicht van de belangrijkste gegevens ten aanzien van emissies, voorkomen in milieucompartimenten en voeding, de vigerende milieukwaliteitsdoelstellingen en -eisen, onderzoek (monitoring/meetprogramma's en overig onderzoek dat relevant is in het kader van het aandachtstoffenwerk) en van beleidsontwikkeling en beleidsmaatregelen. Voor wat betreft de milieukwaliteitsdoelstellingen en -eisen wordt zowel een overzicht gegeven van toxicologische advieswaarden (maximaal toelaatbare risiconiveaus en verwaarloosbare risiconiveaus) als van de beleidsmatig vastgestelde waarden (streef-, richt- en grenswaarden; interventiewaarden bodemsanering). Uitgaande van de MTR's respectievelijk VR's en zo recent mogelijke blootstellingsgegevens is een risicobeoordeling voor mens en milieu gemaakt. Op basis van de beschikbare gegevens, maar vooral vanuit het oogpunt van het mogelijke risico voor mens en milieu, is per stof een aanbeveling gedaan voor handhaving als (prioritaire) aandachtstof of voor afvoer van de stof van de aandachtstoffenlijst. Bij een aanbeveling voor handhaving wordt aangeven welke verdere activiteiten gewenst zijn, toegespitst op onderzoek dat relevant is voor de (verdere) risicobeoordeling of beleidsontwikkeling. Op basis van het concept-rapport is in oktober jl. het "Onderzoeksplan aandachtstoffen 1995" uitgebracht. Dit adviesrapport is als bijlage in het onderhavige rapport opgenomen. Een deel van de in het onderzoeksplan opgenomen concrete onderzoeksvoorstellen is op basis hiervan reeds opgenomen in de planning van het RIVM-programma voor 1995.This report contains an overview of "attention substances", substances placed on a list which is issued each year by the Minister of Housing, Physical Planning and Environment, according to section 22 of the Chemical Substances Act. The substances (or preparations) on that list are requiring special attention because of their possible risk to man or the environment. Attention substances include all priority substances. The main goals of the report are to provide background information for a research plan on these attention substances and to make recommendations for the removal of substances from the attention substances list, primarily on the basis of risk assessment. For each substance the report summarizes key data on emissions, actual environmental concentrations, current environmental quality objectives, and research activities (including national monitoring programmes). The risk assessment for each substance is based on a comparison of exposure levels and toxicological recommended levels (maximum permissible risk levels, "MTR" and negligible risk levels, "VR"). The latter is defined as 1% of the MTR. According to the environmental policy, a substance can be removed from the attention list when the environmental concentrations fall below the negligible risk levels.DGM/SVS/

Observing pulsars and fast transients with LOFAR

Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in the lowest 4 octaves of the ionospheric "radio window": 10-240MHz, that will greatly facilitate observing pulsars at low radio frequencies. Through the huge collecting area, long baselines, and flexible digital hardware, it is expected that LOFAR will revolutionize radio astronomy at the lowest frequencies visible from Earth. LOFAR is a next-generation radio telescope and a pathfinder to the Square Kilometre Array (SKA), in that it incorporates advanced multi-beaming techniques between thousands of individual elements. We discuss the motivation for low-frequency pulsar observations in general and the potential of LOFAR in addressing these science goals. We present LOFAR as it is designed to perform high-time-resolution observations of pulsars and other fast transients, and outline the various relevant observing modes and data reduction pipelines that are already or will soon be implemented to facilitate these observations. A number of results obtained from commissioning observations are presented to demonstrate the exciting potential of the telescope. This paper outlines the case for low frequency pulsar observations and is also intended to serve as a reference for upcoming pulsar/fast transient science papers with LOFAR

Observing pulsars and fast transients with LOFAR

Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in the lowest 4 octaves of the ionospheric “radio window”: 10–240 MHz, that will greatly facilitate observing pulsars at low radio frequencies. Through the huge collecting area, long baselines, and flexible digital hardware, it is expected that LOFAR will revolutionize radio astronomy at the lowest frequencies visible from Earth. LOFAR is a next-generation radio telescope and a pathfinder to the Square Kilometre Array (SKA), in that it incorporates advanced multi-beaming techniques between thousands of individual elements. We discuss the motivation for low-frequency pulsar observations in general and the potential of LOFAR in addressing these science goals. We present LOFAR as it is designed to perform high-time-resolution observations of pulsars and other fast transients, and outline the various relevant observing modes and data reduction pipelines that are already or will soon be implemented to facilitate these observations. A number of results obtained from commissioning observations are presented to demonstrate the exciting potential of the telescope. This paper outlines the case for low frequency pulsar observations and is also intended to serve as a reference for upcoming pulsar/fast transient science papers with LOFAR. </p