A multifrequency analysis of radio variability of blazars

We have carried out a multifrequency analysis of the radio variability of blazars, exploiting the data obtained during the extensive monitoring programs carried out at the University of Michigan Radio Astronomy Observatory (UMRAO, at 4.8, 8, and 14.5 GHz) and at the Metsahovi Radio Observatory (22 and 37 GHz). Two different techniques detect, in the Metsahovi light curves, evidences of periodicity at both frequencies for 5 sources (0224+671, 0945+408, 1226+023, 2200+420, and 2251+158). For the last three sources consistent periods are found also at the three UMRAO frequencies and the Scargle (1982) method yields an extremely low false-alarm probability. On the other hand, the 22 and 37 GHz periodicities of 0224+671 and 0945+408 (which were less extensively monitored at Metsahovi and for which we get a significant false-alarm probability) are not confirmed by the UMRAO database, where some indications of ill-defined periods about a factor of two longer are retrieved. We have also investigated the variability index, the structure function, and the distribution of intensity variations of the most extensively monitored sources. We find a statistically significant difference in the distribution of the variability index for BL Lac objects compared to flat-spectrum radio quasars (FSRQs), in the sense that the former objects are more variable. For both populations the variability index steadily increases with increasing frequency. The distribution of intensity variations also broadens with increasing frequency, and approaches a log-normal shape at the highest frequencies. We find that variability enhances by 20-30% the high frequency counts of extragalactic radio-sources at bright flux densities, such as those of the WMAP and Planck surveys.Comment: A&A accepted. 12 pages, 16 figure

Towards the Event Horizon - The Vicinity of AGN at Micro-Arcsecond Resolution

We summarize the present status of VLBI experiments at 3 mm (86 GHz), 2 mm (129-150 GHz) and 1.3 mm (215-230 GHz). We present and discuss a new 3 mm VLBI map of M87 (Virgo A), which has a spatial resolution of only approx. 20 Schwarzschild radii. We discuss recent VLBI results for SgrA* and argue in favor of new observations within an extended European mm-VLBI network, in order to search for variability. We discuss the possibilities to image the `event horizon' of a super-massive black hole at wavelengths < 2mm, and conclude that the addition of large and sensitive millimetre telescopes such as CARMA, the SMA, the LMT and ALMA will be crucial for this.Comment: 4 pages, 2 figures, Proceedings of the 7th European VLBI Network Symposium held in Toledo, Spain on October 12-15, 2004. Editors: R. Bachiller, F. Colomer, J.-F. Desmurs, P. de Vicent

VLBI observations at 147 GHz: first detection of transatlantic fringes in bright AGN

At 147 GHz (2mm wavelength), we detected three prominent AGN (NRAO150, 3C279, 1633+382) with Very Long Baseline Interferometry (VLBI) with an angular resolution of only 18 micro-arcseconds on the baseline between two antennas in Arizona (10m HHT and 12m KittPeak) and the IRAM 30m antenna on Pico Veleta in Spain. This is a new world record in radio interferometry and astronomical imaging and opens fascinating future possibilities to directly image and study the innermost regions in Quasars and other Active Galactic Nuclei.Comment: 4 pages, 3 figures, appears in: Proceedings of the 6th European VLBI Network Symposium held on June 25th-28th in Bonn, Germany. Edited by: E. Ros, R.W. Porcas, A.P. Lobanov, and J.A. Zensu

Isotopic Composition of Light Nuclei in Cosmic Rays: Results from AMS-01

The variety of isotopes in cosmic rays allows us to study different aspects of the processes that cosmic rays undergo between the time they are produced and the time of their arrival in the heliosphere. In this paper we present measurements of the isotopic ratios 2H/4He, 3He/4He, 6Li/7Li, 7Be/(9Be+10Be) and 10B/11B in the range 0.2-1.4 GeV of kinetic energy per nucleon. The measurements are based on the data collected by the Alpha Magnetic Spectrometer, AMS-01, during the STS-91 flight in 1998 June.Comment: To appear in ApJ. 12 pages, 11 figures, 6 table

A Nanoparticle-Based Approach for the Detection of Extracellular Vesicles

The analysis of extracellular vesicles (EVs) typically requires tedious and time-consuming isolation process from bio-fluids. We developed a nanoparticle-based time resolved fluorescence immunoassay (NP-TRFIA) that uses biotinylated antibodies against the proteins of tetraspanin family and tumor-associated antigens for capturing EVs from urine samples and cell culture supernatants without the need for isolation. The captured-EVs were detected either with Eu3+-chelate or Eu3+-doped nanoparticle-based labels conjugated either to antibodies against the tetraspanins or lectins targeting the glycan moieties on EVs surface. The NP-TRFIA demonstrated specific capturing and detection of EVs by antibodies and lectins. Lectin-nanoparticle based assays showed 2–10 fold higher signal-to-background ratio compared with lectin-chelate assays. The nanoparticle assay concept allowed surface glycosylation profiling of the urine derived-EVs with lectins. It was also applied to establish an assay showing differential expression of tumor-associated proteins on more aggressive (higher ITGA3 on DU145- and PC3-EVs) compared to less aggressive (higher EpCAM on LNCaP-EVs) PCa- cell lines derived-EVs. This NP-TRFIA can be used as a simple tool for analysis and characterization of EVs in urine and cell culture supernatants. Such approach could be useful in identification of disease-specific markers on the surface of patient-derived urinary EVs

Order and structure in syntax I: Word order and syntactic structure

This book reconsiders the role of order and structure in syntax, focusing on fundamental issues such as word order and grammatical functions. The first group of papers in the collection asks what word order can tell us about syntactic structure, using evidence from V2, object shift, word order gaps and different kinds of movement. The second group of papers all address the issue of subjecthood in some way, and examine how certain subject properties vary across languages: expression of subjects, expletive subjects, quirky and locative subjects. All of the papers address in some way the tension between modelling what can vary across languages whilst improving our understanding of what might be universal to human language. This book is complemented by Order and structure in syntax II: Subjecthood and argument structure &nbsp

Order and structure in syntax I: Word order and syntactic structure

This book reconsiders the role of order and structure in syntax, focusing on fundamental issues such as word order and grammatical functions. The first group of papers in the collection asks what word order can tell us about syntactic structure, using evidence from V2, object shift, word order gaps and different kinds of movement. The second group of papers all address the issue of subjecthood in some way, and examine how certain subject properties vary across languages: expression of subjects, expletive subjects, quirky and locative subjects. All of the papers address in some way the tension between modelling what can vary across languages whilst improving our understanding of what might be universal to human language. This book is complemented by Order and structure in syntax II: Subjecthood and argument structure &nbsp

Order and structure in syntax I: Word order and syntactic structure

This book reconsiders the role of order and structure in syntax, focusing on fundamental issues such as word order and grammatical functions. The first group of papers in the collection asks what word order can tell us about syntactic structure, using evidence from V2, object shift, word order gaps and different kinds of movement. The second group of papers all address the issue of subjecthood in some way, and examine how certain subject properties vary across languages: expression of subjects, expletive subjects, quirky and locative subjects. All of the papers address in some way the tension between modelling what can vary across languages whilst improving our understanding of what might be universal to human language. This book is complemented by Order and structure in syntax II: Subjecthood and argument structure &nbsp

Order and structure in syntax I: Word order and syntactic structure

This book reconsiders the role of order and structure in syntax, focusing on fundamental issues such as word order and grammatical functions. The first group of papers in the collection asks what word order can tell us about syntactic structure, using evidence from V2, object shift, word order gaps and different kinds of movement. The second group of papers all address the issue of subjecthood in some way, and examine how certain subject properties vary across languages: expression of subjects, expletive subjects, quirky and locative subjects. All of the papers address in some way the tension between modelling what can vary across languages whilst improving our understanding of what might be universal to human language. This book is complemented by Order and structure in syntax II: Subjecthood and argument structure &nbsp

Order and structure in syntax I: Word order and syntactic structure

This book reconsiders the role of order and structure in syntax, focusing on fundamental issues such as word order and grammatical functions. The first group of papers in the collection asks what word order can tell us about syntactic structure, using evidence from V2, object shift, word order gaps and different kinds of movement. The second group of papers all address the issue of subjecthood in some way, and examine how certain subject properties vary across languages: expression of subjects, expletive subjects, quirky and locative subjects. All of the papers address in some way the tension between modelling what can vary across languages whilst improving our understanding of what might be universal to human language. This book is complemented by Order and structure in syntax II: Subjecthood and argument structure &nbsp