16 research outputs found
The Tumor Microenvironment: The Making of a Paradigm
What has been will be again, what has been done will be done again; there is nothing new under the su
Supernova remnants: the X-ray perspective
Supernova remnants are beautiful astronomical objects that are also of high
scientific interest, because they provide insights into supernova explosion
mechanisms, and because they are the likely sources of Galactic cosmic rays.
X-ray observations are an important means to study these objects.And in
particular the advances made in X-ray imaging spectroscopy over the last two
decades has greatly increased our knowledge about supernova remnants. It has
made it possible to map the products of fresh nucleosynthesis, and resulted in
the identification of regions near shock fronts that emit X-ray synchrotron
radiation.
In this text all the relevant aspects of X-ray emission from supernova
remnants are reviewed and put into the context of supernova explosion
properties and the physics and evolution of supernova remnants. The first half
of this review has a more tutorial style and discusses the basics of supernova
remnant physics and thermal and non-thermal X-ray emission. The second half
offers a review of the recent advances.The topics addressed there are core
collapse and thermonuclear supernova remnants, SN 1987A, mature supernova
remnants, mixed-morphology remnants, including a discussion of the recent
finding of overionization in some of them, and finally X-ray synchrotron
radiation and its consequences for particle acceleration and magnetic fields.Comment: Published in Astronomy and Astrophysics Reviews. This version has 2
column-layout. 78 pages, 42 figures. This replaced version has some minor
language edits and several references have been correcte
First lacustrine varve chronologies from Mexico: impact of droughts, ENSO and human activity since AD 1840 as recorded in maar sediments from Valle de Santiago
Disease: A Hitherto Unexplored Constraint on the Spread of Dogs (Canis lupus familiaris) in Pre-Columbian South America
First lacustrine varve chronologies from Mexico: impact of droughts, ENSO and human activity since AD 1840 as recorded in maar sediments from Valle de Santiago
We present varve chronologies for sediments from two maar lakes in the Valle de Santiago region (Central Mexico): Hoya La Alberca (AD 1852â1973) and Hoya RincĂłn de Parangueo (AD 1839â1943). These are the first varve chronologies for Mexican lakes. The varved sections were anchored with tephras from Colima (1913) and ParicutĂn (1943/1944) and 210Pb ages. We compare the sequences using the thickness of seasonal laminae and element counts (Al, Si, S, Cl, K, Ti, Mn, Fe, and Sr) determined by micro X-ray fluorescence spectrometry. The formation of the varve sublaminae is attributed to the strongly seasonal climate regime. Limited rainfall and high evaporation rates in winter and spring induce precipitation of carbonates (high Ca, Sr) enriched in 13C and 18O, whereas rainfall in summer increases organic and clastic input (plagioclase, quartz) with high counts of lithogenic elements (K, Al, Ti, and Si). Eolian input of Ti occurs also in the dry season. Moving correlations (5-yr windows) of the Ca and Ti counts show similar development in both sequences until the 1930s. Positive correlations indicate mixing of allochthonous Ti and autochthonous Ca, while negative correlations indicate their separation in sublaminae. Negative excursions in the correlations correspond with historic and reconstructed droughts, El Niño events, and positive SST anomalies. Based on our data, droughts (3â7 year duration) were severe and centred around the following years: the early 1850s, 1865, 1880, 1895, 1905, 1915 and the late 1920s with continuation into the 1930s. The latter dry period brought both lake systems into a critical state making them susceptible to further drying. Groundwater overexploitation due to the expansion of irrigation agriculture in the region after 1940 induced the transition from calcite to aragonite precipitation in Alberca and halite infiltration in RincĂłn. The proxy data indicate a faster response to increased evaporation for RincĂłn, the lake with the larger maar dimensions, solar radiation receipt and higher conductivity, whereas the smaller, steeper Alberca maar responded rapidly to increased precipitation
C-type lectins in immunity and homeostasis
The authors thank the Wellcome Trust, the UK Medical Research Council (MRC), the MRC Centre for Medical Mycology at the University of Aberdeen and Arthritis Research UK for financial support. The authors apologize to colleagues whose many valuable contributions could not be cited owing to space constraints.Peer reviewedPostprintPostprintPostprintPostprin