Long-term Effects of Tillage on the Retention and Transport of Soil Water

Quantitative measurements were made of the physical and chemical properties of two virgin prairie soils, Crowley and Jay, that remain in their native Arkansas environments and of similar soils that had been tilled extensively. Comparisons were made of soil properties at several depths. When compared with the tilled soils the virgin soils had higher organic matter contents, saturated hydraulic conductivities and water retained at several applied pressures. Bulk densities and hydraulic resistances were lower in the virgin soils. For the Crowley silt loam, values of pH and elemental contents of the virgin soil were higher than those of the tilled soil. Determinations also were made of the effects of a 14-year addition of winter cover crops on a Dubbs-Dundee soil in continuous cotton production. In general, the winter cover crops tended to increase hydraulic conductivity~. ·porosity and organic matter content. These results indicated that the detrimental effects of long-term tillage on soil hydraulic properties could partially be overcome with the planting of these crops during the winter. However, the rate of improvement in the hydraulic properties was not dramatic

HST images and properties of the most distant radio galaxies

We present Hubble Space Telescope images of 11 high redshift radio galaxies (between $z=2.3$ and $z=3.6$). The galaxies were observed with the WFPC2 camera in a broad band filter (F606W or F707W, roughly equivalent to V or R-band), for 2 orbits each. We find that on the scale of the HST observations there is a wide variety of morphological structures of the hosting galaxies: most objects have a clumpy, irregular appearance, consisting of a bright nucleus and a number of smaller components, suggestive of merging systems. Some observed structures could be due (at least partly) to the presence of dust distributed through the galaxies. The UV continuum emission is generally elongated and aligned with the axis of the radio sources, however the characteristics of the ``alignment effect'' differ from case to case, suggesting that the phenomenon cannot be explained by a single physical mechanism. We compare the properties of our radio galaxies with those of the UV dropout galaxies and conclude that (i) the most massive radio galaxies may well evolve from an aggregate of UV dropout galaxies and (ii) high redshift radio galaxies probably evolve into present day brightest cluster galaxies.Comment: 22 pages, 30 figures, accepted by A&

Trends in Kaposi's sarcoma-associated Herpesvirus antibodies prior to the development of HIV-associated Kaposi's sarcoma: a nested case-control study

HIV-associated Kaposi's sarcoma (KS) is a public health challenge in sub-Saharan Africa since both the causative agent, Kaposi's sarcoma associated-herpesvirus (KSHV), and the major risk factor, HIV, are prevalent. In a nested case-control study within a long-standing clinical cohort in rural Uganda, we used stored sera to examine the evolution of antibody titres against the KSHV antigens K8.1 and latency-associated nuclear antigen (LANA) among 30 HIV-infected subjects who subsequently developed HIV-related KS (cases) and among 108 matched HIV/KSHV coinfected controls who did not develop KS. Throughout the 6 years prior to diagnosis, antibody titres to K8.1 and LANA were significantly higher among cases than controls (p < 0.0001), and titres increased prior to diagnosis in the cases. K8.1 titres differed more between KS cases and controls, compared to LANA titres. These differences in titre between cases and controls suggest a role for lytic viral replication in the pathogenesis of HIV-related KS in this setting

The MURALES survey II. Presentation of MUSE observations of 20 3C low-z radio galaxies and first results

We present observations of a complete sub-sample of 20 radio galaxies from the Third Cambridge Catalog (3C) with redshift <0.3 obtained from VLT/MUSE optical integral field spectrograph. These data have been obtained as part of the survey MURALES (a MUse RAdio Loud Emission line Snapshot survey) with the main goal of exploring the Active Galactic Nuclei (AGN) feedback process in a sizeable sample of the most powerful radio sources at low redshift. We present the data analysis and, for each source, the resulting emission line images and the 2D gas velocity field. Thanks to their unprecedented depth (the median 3 sigma surface brightness limit in the emission line maps is 6X10^-18 erg s-1 cm-2 arcsec-2, these observations reveal emission line structures extending to several tens of kiloparsec in most objects. In nine sources the gas velocity shows ordered rotation, but in the other cases it is highly complex. 3C sources show a connection between radio morphology and emission line properties. Whereas, in three of the four Fanaroff and Riley Class I radio galaxies (FRIs), the line emission regions are compact, ~1 kpc in size; in all but one of the Class II radiogalaxies FRIIs, we detected large scale structures of ionized gas with a median extent of 17 kpc. Among the FRIIs, those of high and low excitation show extended gas structures with similar morphological properties, suggesting that they both inhabit regions characterized by a rich gaseous environment on kpc scale.Comment: Accepted for publication in A&

The Nascent Red Sequence at z~2

We present new constraints on the evolution of the early-type galaxy color-magnitude relation (CMR) based on deep near-infrared imaging of a galaxy protocluster at z=2.16 obtained using NICMOS on-board the Hubble Space Telescope. This field contains a spectroscopically confirmed space-overdensity of Lyman-alpha and H-alpha emitting galaxies which surrounds the powerful radio galaxy MRC 1138-262. Using these NICMOS data we identify a significant surface-overdensity (= 6.2x) of red J-H galaxies in the color-magnitude diagram (when compared with deep NICMOS imaging from the HDF-N and UDF). The optical-NIR colors of these prospective red-sequence galaxies indicate the presence of on-going dust-obscured star-formation or recently formed (<~ 1.5 Gyr)stellar populations in a majority of the red galaxies. We measure the slope and intrinsic scatter of the CMR for three different red galaxy samples selected by a wide color cut, and using photometric redshifts both with and without restrictions on rest-frame optical morphology. In all three cases both the rest-frame $U-B$ slope and intrinsic color scatter are considerably higher than corresponding values for lower redshift galaxy clusters. These results suggest that while some relatively quiescent galaxies do exist in this protocluster both the majority of the galaxy population and hence the color-magnitude relation are still in the process of forming, as expected.Comment: 8 pages, 7 figures, accepted for publication in ApJ (to appear June 1, 2008, v679n2