Temporal variability in nutrient transport in a first-order agricultural basin in southern Ontario

This thesis examines phosphorus and nitrate transport in a first-order agricultural catchment in Southern Ontario. Specific areas of concern relate to (1) long- and short-term temporal variability in nutrient export patterns, (2) the role of drainage tiles in annual nutrient export, (3) the effects of antecedent hydrologic conditions (AHC) on nutrient export patterns and (4) temporal variability in the nutrient retention in riparian buffer strips and streams. Temporal variability in hydrochemical export from the study basin over a two-year period is described and quantified and the importance of high magnitude events is highlighted. This is the first comprehensive study to examine the role of such events in annual nutrient export from agricultural catchments (17-58% of annual nutrient export). The significance of winter thaws and in particular major snowmelt events in annual nutrient export from agricultural catchments in Southern Ontario is shown and the need to include the winter period in sampling regimes is demonstrated. The importance of sampling frequency is examined and an improved sampling strategy is suggested for the study basin. The role of drainage tiles in annual hydrochemical export from the basin is quantified and the dominance of drainage tiles as a nutrient source is shown. Tiles account for approximately 42% of annual discharge, but account for the majority of SRP, TP and NO3-export. Tiles within the study basin exhibit spatial and temporal variability in hydrochemical export patterns but the discharge from all tiles within the basin can be predicted from one continuously monitored tile. The effect of antecedent hydrologic conditions in hydrochemical export and the complex effects of successive events on hydrochemical export patterns are also demonstrated. In general, hydrochemical export increases as conditions become successively wetter, although empirical relationships between hydrological variables in the catchment and hydrochemical export are weak. Hydrologic connectivity between surface horizons and drainage tiles by macropores and preferential flowpaths appears to be critical in exporting nutrients from the catchment, and the role of these flowpaths increases as conditions become wetter. The in-stream retention of phosphate during low flows is examined. Stream sediments are unable to retain large pulses of phosphate during very low flow periods due to poor mixing in the water column. The stream is therefore unable to retain pulses of phosphate that may occur following the irrigation of fields receiving liquid manure applications or when fertilizers are directly applied into ditches. These individual studies improve our general understanding of nutrient dynamics and export from agricultural watersheds. This thesis increases our ability to predict nutrient export by (a) suggesting a new sampling strategy to improve the precision of nutrient export estimates in basins; and (b) identifying critical periods of nutrient export and linking these to antecedent hydrologic conditions in the basin

A dual maximum principle for discrete-time linear systems with economic applications,

working pape

The Bali of Anthropology and the Anthropology of Bali

falseLanham, Boulder, New York, Londo

Brief Mindfulness Meditation Improves Mental State Attribution and Empathizing

The ability to infer and understand the mental states of others (i.e., Theory of Mind) is a cornerstone of human interaction. While considerable efforts have focused on explicating when, why and for whom this fundamental psychological ability can go awry, considerably less is known about factors that may enhance theory of mind. Accordingly, the current study explored the possibility that mindfulness-based meditation may improve people's mindreading skills. Following a 5-minute mindfulness induction, participants with no prior meditation experience completed tests that assessed mindreading and empathic understanding. The results revealed that brief mindfulness meditation enhanced both mental state attribution and empathic concern, compared to participants in the control group. These findings suggest that mindfulness may be a powerful technique for facilitating core aspects of social-cognitive functioning.published_or_final_versio

Effects of magnesium treatment in a model of internal capsule lesion in spontaneously hypertensive rats

<p><b>Background and Purpose:</b> The study aim was to assess the effects of magnesium sulfate (MgSO4) administration on white matter damage in vivo in spontaneously hypertensive rats.</p> <p><b>Methods:</b> The left internal capsule was lesioned by a local injection of endothelin-1 (ET-1; 200 pmol) in adult spontaneously hypertensive rats. MgSO4 was administered (300 mg/kg SC) 30 minutes before injection of ET-1, plus 200 mg/kg every hour thereafter for 4 hours. Infarct size was measured by T2-weighted magnetic resonance imaging (day 2) and histology (day 11), and functional recovery was assessed on days 3 and 10 by the cylinder and walking-ladder tests.</p> <p><b>Results:</b> ET-1 application induced a small, localized lesion within the internal capsule. Despite reducing blood pressure, MgSO4 did not significantly influence infarct volume (by magnetic resonance imaging: median, 2.1 mm3; interquartile range, 1.3 to 3.8, vs 1.6 mm3 and 1.2 to 2.1, for the vehicle-treated group; by histology: 0.3 mm3 and 0.2 to 0.9 vs 0.3 mm3 and 0.2 to 0.5, respectively). Significant forelimb and hindlimb motor deficits were evident in the vehicle-treated group as late as day 10. These impairments were significantly ameliorated by MgSO4 in both cylinder (left forelimb use, P<0.01 and both-forelimb use, P<0.03 vs vehicle) and walking-ladder (right hindlimb score, P<0.02 vs vehicle) tests.</p> <p><b>Conclusions:</b> ET-1–induced internal capsule ischemia in spontaneously hypertensive rats represents a good model of lacunar infarct with small lesion size, minimal adverse effects, and a measurable motor deficit. Despite inducing mild hypotension, MgSO4 did not significantly influence infarct size but reduced motor deficits, supporting its potential utility for the treatment of lacunar infarct.</p&gt

Transverse multi-mode effects on the performance of photon-photon gates

The multi-mode character of quantum fields imposes constraints on the implementation of high-fidelity quantum gates between individual photons. So far this has only been studied for the longitudinal degree of freedom. Here we show that effects due to the transverse degrees of freedom significantly affect quantum gate performance. We also discuss potential solutions, in particular separating the two photons in the transverse direction.Comment: 5 pages, 3 figures, published versio

An Essential Protein that Interacts with Endosomes and Promotes Movement of the SHORT-ROOT Transcription Factor

SummaryPlant cells can communicate through the direct transport of transcription factors [1–7]. One of the best-studied examples of this phenomenon is SHORT-ROOT (SHR), which moves from the stele cells into the endodermis and root tip of Arabidopsis, where it specifies endodermal cell identity and stem cell function, respectively [8–10]. In the endodermis, SHR upregulates the transcription factors SCARECROW (SCR) [2] and JACKDAW (JKD), which in turn inhibit movement of SHR from the endodermis [11]. Although much is known about the regulatory pathways that mediate expression and activity of SHR [1, 8–14], little is known about the factors that promote its movement or the movement of other transcription factors. We have identified a novel protein, SHORT-ROOT INTERACTING EMBRYONIC LETHAL (SIEL), that interacts with SHR, CAPRICE (CPC), TARGET OF MONOPTEROUS 7 (TMO7), and AGAMOUS-LIKE 21 (AGL21). Null alleles of SIEL are embryonic lethal. Hypomorphic alleles produce defects in root patterning and reduce SHR movement. Surprisingly, both SHR and SCR regulate expression of SIEL, so that siel/scr and siel/shr double mutants have extremely disorganized roots. SIEL localizes to the nucleus and cytoplasm of root cells where it is associated with endosomes. We propose that SIEL is an endosome-associated protein that promotes intercellular movement

Assessing the Utility of Photoswitchable Fluorescent Proteins for Tracking Intercellular Protein Movement in the Arabidopsis Root

One way in which cells communicate is through the direct transfer of proteins. In plants, many of these proteins are transcription factors, which are made by one cell type and traffic into another. In order to understand how this movement occurs and its role in development, we would like to track this movement in live, intact plants in real-time. Here we examine the utility of the photoconvertible proteins, Dendra2 and (to a lesser extent) EosFP as tags for studying intracellular and intercellular protein movement in the Arabidopsis root. To this end, we made fusions between Dendra2 and six mobile transcription factors. Our results show that Dendra2 is an effective tool for studying protein movement between plant cells. Interestingly, we found that Dendra2 could not simply be swapped into existing constructs that had originally contained GFP. Most of the fusions made in this way failed to produce a fluorescent fusion. In addition we found that the optimal settings for photoconversion of Dendra2 in stably transformed roots were different from what has been published for photoconversion in transient assays in plants or in animal cells. By modifying the confocal setting, we were able to photoconvert Dendra2 in all cell layers in the root. However the efficiency of photoconversion was affected by the position of the cell layer within the root, with more internal tissues requiring more energy. By examining the Dendra2 fusions, we confirmed the mobility of the SHORT-ROOT (SHR) and CAPRICE (CPC) transcription factors between cells and we further discovered that SHR movement in stele and CPC movement in the epidermis are non-directional