Monitoring water and salt movement during a leaching irrigation using time domain reflectometry

Non-Peer ReviewedTime domain reflectometry (TDR) has become an accepted method of measuring soil water content. Laboratory results have indicated that it may also be possible to measure soil electrical conductivity (EC) using TDR. The objectives of this experiment were to investigate the utility of TDR as a field measurement of EC and to illustrate a potential application of the technique. Field research was conducted at the Saskatchewan Irrigation Development Centre on a field which has been reclaimed from salinity over the past 10 years by the installation of tile drains and a fall leaching program. To test the accuracy of bulk soil EC measurements made by TDR (ECr), EC was also measured on water samples from suction lysimeters which sampled at the same depths as the TDR waveguides and converted to a bulk soil basis (EC8). Comparisons between ECT and EC8 were made three times during the 1992 growing season (when the soil was relatively dry) and four times during the fall leaching period (when the soil was much wetter). ECr was significantly correlated (p<0.001) to EC8. However, the measurement of ECT was affected by soil moisture content and an empirical function had to be used to eliminate this source of variability. Good agreement (R2=0.93) was obtained between ECT and EC8 when this function was applied. During the leaching irrigation, water and salt movement was monitored by TDR. At most sites, a salt bulge could be clearly identified moving downward through the profile as the volume of water applied increased. With further investigation into the relationship between ECT and water content, the rapid simultaneous measurement of water content and electrical conductivity made possible by TDR should prove useful in studies of salt movement

Leaching of nitrates and herbicides under low pressure (high volume) irrigation

Non-Peer ReviewedThe potential for contamination of groundwater by nitrates or pesticides from irrigated soils has not been fully evaluated. This project was initiated to monitor nitrate and herbicide leaching in a tile-drained field at SIDC in Outlook. Water samples were collected using suction lysimeters and analyzed for nitrate and four herbicides (2, 4-D, dicamba, bromoxynil and diclofop). The concentrations of nitrates at depth were maintained by the downward movement of applied andmineralized N. Trace amounts of 2, 4-D and diclofop were leached to 180 cm but bromoxynil and dicamba were not found below 60 cm depth. Dicamba and diclofop persisted longer in the soil than 2, 4-D or bromoxynil but were only present in trace amounts at the end of August

Observing Supermassive Black Holes across cosmic time: from phenomenology to physics

In the last decade, a combination of high sensitivity, high spatial resolution observations and of coordinated multi-wavelength surveys has revolutionized our view of extra-galactic black hole (BH) astrophysics. We now know that supermassive black holes reside in the nuclei of almost every galaxy, grow over cosmological times by accreting matter, interact and merge with each other, and in the process liberate enormous amounts of energy that influence dramatically the evolution of the surrounding gas and stars, providing a powerful self-regulatory mechanism for galaxy formation. The different energetic phenomena associated to growing black holes and Active Galactic Nuclei (AGN), their cosmological evolution and the observational techniques used to unveil them, are the subject of this chapter. In particular, I will focus my attention on the connection between the theory of high-energy astrophysical processes giving rise to the observed emission in AGN, the observable imprints they leave at different wavelengths, and the methods used to uncover them in a statistically robust way. I will show how such a combined effort of theorists and observers have led us to unveil most of the SMBH growth over a large fraction of the age of the Universe, but that nagging uncertainties remain, preventing us from fully understating the exact role of black holes in the complex process of galaxy and large-scale structure formation, assembly and evolution.Comment: 46 pages, 21 figures. This review article appears as a chapter in the book: "Astrophysical Black Holes", Haardt, F., Gorini, V., Moschella, U and Treves A. (Eds), 2015, Springer International Publishing AG, Cha

Cloaked websites: propaganda, cyber-racism and epistemology in the digital era

This article analyzes cloaked websites, which are sites published by individuals or groups who conceal authorship in order to disguise deliberately a hidden political agenda. Drawing on the insights of critical theory and the Frankfurt School, this article examines the way in which cloaked websites conceal a variety of political agendas from a range of perspectives. Of particular interest here are cloaked white supremacist sites that disguise cyber-racism. The use of cloaked websites to further political ends raises important questions about knowledge production and epistemology in the digital era. These cloaked sites emerge within a social and political context in which it is increasingly difficult to parse fact from propaganda, and this is a particularly pernicious feature when it comes to the cyber-racism of cloaked white supremacist sites. The article concludes by calling for the importance of critical, situated political thinking in the evaluation of cloaked websites

Para-infectious brain injury in COVID-19 persists at follow-up despite attenuated cytokine and autoantibody responses

To understand neurological complications of COVID-19 better both acutely and for recovery, we measured markers of brain injury, inflammatory mediators, and autoantibodies in 203 hospitalised participants; 111 with acute sera (1–11 days post-admission) and 92 convalescent sera (56 with COVID-19-associated neurological diagnoses). Here we show that compared to 60 uninfected controls, tTau, GFAP, NfL, and UCH-L1 are increased with COVID-19 infection at acute timepoints and NfL and GFAP are significantly higher in participants with neurological complications. Inflammatory mediators (IL-6, IL-12p40, HGF, M-CSF, CCL2, and IL-1RA) are associated with both altered consciousness and markers of brain injury. Autoantibodies are more common in COVID-19 than controls and some (including against MYL7, UCH-L1, and GRIN3B) are more frequent with altered consciousness. Additionally, convalescent participants with neurological complications show elevated GFAP and NfL, unrelated to attenuated systemic inflammatory mediators and to autoantibody responses. Overall, neurological complications of COVID-19 are associated with evidence of neuroglial injury in both acute and late disease and these correlate with dysregulated innate and adaptive immune responses acutely