BeppoSAX Observations of Unprecedented Synchrotron Activity in the BL Lac Object Mkn 501

The BL Lac object Mkn 501, one of the only three extragalactic sources (with Mkn 421 and 1ES 2344+514) so far detected at TeV energies, was observed with the BeppoSAX satellite on 7, 11, and 16 April 1997 during a phase of high activity at TeV energies, as monitored with the Whipple, HEGRA and CAT Cherenkov telescopes. Over the whole 0.1-200 keV range the spectrum was exceptionally hard (alpha =< 1, with F_nu ~ nu^{-alpha}) indicating that the X-ray power output peaked at (or above) ~100 keV. This represents a shift of at least two orders of magnitude with respect to previous observations of Mkn 501, a behavior never seen before in this or any other blazar. The overall X-ray spectrum hardens with increasing intensity and, at each epoch, it is softer at larger energies. The correlated variability from soft X-rays to the TeV band points to models in which the same population of relativistic electrons produces the X-ray continuum via synchrotron radiation and the TeV emission by inverse Compton scattering of the synchrotron photons or other seed photons. For the first time in any blazar the synchrotron power is observed to peak at hard X-ray energies. The large shift of the synchrotron peak frequency with respect to previous observations of Mkn 501 implies that intrinsic changes in the relativistic electron spectrum caused the increase in emitted power. Due to the very high electron energies, the inverse Compton process is limited by the Klein-Nishina regime. This implies a quasi-linear (as opposed to quadratic) relation of the variability amplitude in the TeV and hard X-ray ranges (for the SSC model) and an increase of the inverse Compton peak frequency smaller than that of the synchrotron peak frequency.Comment: 11 pages, Latex, 4 Postscript figures, to appear in The Astrophysical Journal Letter

Observing the Evolution of the Universe

How did the universe evolve? The fine angular scale (l>1000) temperature and polarization anisotropies in the CMB are a Rosetta stone for understanding the evolution of the universe. Through detailed measurements one may address everything from the physics of the birth of the universe to the history of star formation and the process by which galaxies formed. One may in addition track the evolution of the dark energy and discover the net neutrino mass. We are at the dawn of a new era in which hundreds of square degrees of sky can be mapped with arcminute resolution and sensitivities measured in microKelvin. Acquiring these data requires the use of special purpose telescopes such as the Atacama Cosmology Telescope (ACT), located in Chile, and the South Pole Telescope (SPT). These new telescopes are outfitted with a new generation of custom mm-wave kilo-pixel arrays. Additional instruments are in the planning stages.Comment: Science White Paper submitted to the US Astro2010 Decadal Survey. Full list of 177 author available at http://cmbpol.uchicago.ed

Ecological and environmental transition across the forested-to-open bog ecotone in a west Siberian peatland

Climate change may cause increasing tree cover in boreal peatlands, and the impacts of this encroachment will be noted first at forested-to-open bog ecotones. We investigate key metrics of ecosystem function in five such ecotones at a peatland complex in Western Siberia. Stratigraphic analysis of three cores from one of these transects shows that the ecotone has been dynamic over time with evidence for recent expansion of forested peatland. We observed that the two alternative states for northern boreal peatlands (forested/open) clearly support distinct plant and microbial communities. These in turn drive and respond to a number of feedback mechanisms. This has led to steep ecological gradients across the ecotones. Tree cover was associated with lower water tables and pH, along with higher bulk density, aquatic carbon concentrations, and electrical conductivity. We propose that the conditions found in the forested peatland of Western Siberia make the carbon sink more vulnerable to warmer and drier conditions

Preserving Iron Gall Ink Objects in Collections in South and Central America and the Caribbean, Part 1: Assessing Preservation Needs of Ink-Corroded Materials

Most museums, libraries, and archives throughout the world have to deal with paper damaged by iron gall ink. For more than a decade international research has been devoted to the topic in an attempt to provide practical treatments for objects and formulate guidelines for the preservation of iron gall ink collections. A working group of conservators in South and Central America and the Caribbean have developed a program to disseminate research findings, collect data about the condition of iron gall ink collections in their countries and identify imminent training needs. The goal of this project is to combine the latest research with existing and acceptable conservation practices and share information about risk management, proper housing, examination and treatment of iron gall ink inscribed artefacts-at risk. Communications among colleagues were established to learn more about the current resources available in collections from various countries

A single immunization with MVA expressing GnGc glycoproteins promotes epitope-specific CD8+-T cell activation and protects immune-competent mice against a lethal RVFV infection

BACKGROUND: Rift Valley fever virus (RVFV) is a mosquito-borne pathogen causing an important disease in ruminants often transmitted to humans after epizootic outbreaks in African and Arabian countries. To help combat the spread of the disease, prophylactic measures need to be developed and/or improved. METHODOLOGY/PRINCIPAL FINDINGS: In this work, we evaluated the immunogenicity and protective efficacy of recombinant plasmid DNA and modified vaccinia virus Ankara (rMVA) vectored vaccines against Rift Valley fever in mice. These recombinant vaccines encoded either of two components of the Rift Valley fever virus: the viral glycoproteins (Gn/Gc) or the nucleoprotein (N). Following lethal challenge with live RVFV, mice immunized with a single dose of the rMVA-Gn/Gc vaccine showed no viraemia or clinical manifestation of disease, but mounted RVFV neutralizing antibodies and glycoprotein specific CD8+ T-cell responses. Neither DNA-Gn/Gc alone nor a heterologous prime-boost immunization schedule (DNA-Gn/Gc followed by rMVAGn/Gc) was better than the single rMVA-Gn/Gc immunization schedule with regards to protective efficacy. However, the rMVA-Gn/Gc vaccine failed to protect IFNAR(-/-) mice upon lethal RVFV challenge suggesting a role for innate responses in protection against RVFV. Despite induction of high titer antibodies against the RVFV nucleoprotein, the rMVA-N vaccine, whether in homologous or heterologous prime-boost schedules with the corresponding recombinant DNA vaccine, only conferred partial protection to RVFV challenge. CONCLUSIONS/SIGNIFICANCE: Given the excellent safety profile of rMVA based vaccines in humans and animals, our data supports further development of rMVA-Gn/Gc as a vaccine strategy that can be used for the prevention of Rift Valley fever in both humans and livestock

The Origin of the Universe as Revealed Through the Polarization of the Cosmic Microwave Background

Modern cosmology has sharpened questions posed for millennia about the origin of our cosmic habitat. The age-old questions have been transformed into two pressing issues primed for attack in the coming decade: How did the Universe begin? and What physical laws govern the Universe at the highest energies? The clearest window onto these questions is the pattern of polarization in the Cosmic Microwave Background (CMB), which is uniquely sensitive to primordial gravity waves. A detection of the special pattern produced by gravity waves would be not only an unprecedented discovery, but also a direct probe of physics at the earliest observable instants of our Universe. Experiments which map CMB polarization over the coming decade will lead us on our first steps towards answering these age-old questions