title: Denitrification potential in lake sediment increases across a gradient of catchment agriculture

authors: Bruesewitz, Denise A.

subjects: nitrogen

abstract: Intensification of catchment agriculture has increased nutrient loads and accelerated eutrophication in some lakes, often resulting in episodic harmful algal blooms or prolonged periods of anoxia. The influence of catchment agriculture on lake sediment denitrification capacity as a nitrogen (N) removal mechanism in lakes is largely unknown, particularly in contrast to research on denitrification in agricultural streams and rivers. We measured denitrification enzyme activity (DEA) to assess sediment denitrification potential in seven monomictic and three polymictic lakes that range in the proportion of agriculture in the catchment from 3 to 96% to determine if there is a link between agricultural land use in the lake catchment and sediment denitrification potential. We collected sediment cores for DEA measurements over 3 weeks in austral spring 2008 (October– November). Lake Okaro, with 96% catchment agriculture, had approximately 15 times higher DEA than Lake Tikitapu, with 3% catchment agriculture (232.2 ± 55.9 vs. 15.9 ± 4.5 lg N gAFDM -1 h-1, respectively). Additionally, sediment denitrification potential increased with the proportion of catchment in agriculture (R2 = 0.85, P < 0.001). Our data suggest that lakes retain a high capacity to remove excessNvia denitrification under increasing N loads from higher proportions of catchment agriculture. However, evidence from the literature suggests that despite a high capacity for denitrification and longer water residence times, lakes with high N loads will still remove a smaller proportion of their N load. Lakes have a denitrification potential that reflects the condition of the lake catchment, but more measurements of in situ denitrification rates across lake catchments is necessary to determine if this capacity translates to high N removal rates.

text: Denitrification potential in lake sediment increases across a gradient of catchment agriculture Intensification of catchment agriculture has increased nutrient loads and accelerated eutrophication in some lakes, often resulting in episodic harmful algal blooms or prolonged periods of anoxia. The influence of catchment agriculture on lake sediment denitrification capacity as a nitrogen (N) removal mechanism in lakes is largely unknown, particularly in contrast to research on denitrification in agricultural streams and rivers. We measured denitrification enzyme activity (DEA) to assess sediment denitrification potential in seven monomictic and three polymictic lakes that range in the proportion of agriculture in the catchment from 3 to 96% to determine if there is a link between agricultural land use in the lake catchment and sediment denitrification potential. We collected sediment cores for DEA measurements over 3 weeks in austral spring 2008 (October– November). Lake Okaro, with 96% catchment agriculture, had approximately 15 times higher DEA than Lake Tikitapu, with 3% catchment agriculture (232.2 ± 55.9 vs. 15.9 ± 4.5 lg N gAFDM -1 h-1, respectively). Additionally, sediment denitrification potential increased with the proportion of catchment in agriculture (R2 = 0.85, P < 0.001). Our data suggest that lakes retain a high capacity to remove excessNvia denitrification under increasing N loads from higher proportions of catchment agriculture. However, evidence from the literature suggests that despite a high capacity for denitrification and longer water residence times, lakes with high N loads will still remove a smaller proportion of their N load. Lakes have a denitrification potential that reflects the condition of the lake catchment, but more measurements of in situ denitrification rates across lake catchments is necessary to determine if this capacity translates to high N removal rates.

year: 2011

title: Exact and quasiexact solvability of second-order superintegrable quantum systems: I. Euclidean space preliminaries

authors: Kalnins, Ernie G.

subjects: Mathematics

abstract: We show that second-order superintegrable systems in two-dimensional and three-dimensional Euclidean space generate both exactly solvable (ES) and quasiexactly solvable (QES) problems in quantum mechanics via separation of variables, and demonstrate the increased insight into the structure of such problems provided by superintegrability. A principal advantage of our analysis using nondegenerate superintegrable systems is that they are multiseparable. Most past separation of variables treatments of QES problems via partial differential equations have only incorporated separability, not multiseparability. Also, we propose another definition of ES and QES. The quantum mechanical problem is called ES if the solution of Schrödinger equation can be expressed in terms of hypergeometric functions mFn and is QES if the Schrödinger equation admits polynomial solutions with coefficients necessarily satisfying a three-term or higher order of recurrence relations. In three dimensions we give an example of a system that is QES in one set of separable coordinates, but is not ES in any other separable coordinates. This example encompasses Ushveridze's tenth-order polynomial QES problem in one set of separable coordinates and also leads to a fourth-order polynomial QES problem in another separable coordinate set.

text: Exact and quasiexact solvability of second-order superintegrable quantum systems: I. Euclidean space preliminaries We show that second-order superintegrable systems in two-dimensional and three-dimensional Euclidean space generate both exactly solvable (ES) and quasiexactly solvable (QES) problems in quantum mechanics via separation of variables, and demonstrate the increased insight into the structure of such problems provided by superintegrability. A principal advantage of our analysis using nondegenerate superintegrable systems is that they are multiseparable. Most past separation of variables treatments of QES problems via partial differential equations have only incorporated separability, not multiseparability. Also, we propose another definition of ES and QES. The quantum mechanical problem is called ES if the solution of Schrödinger equation can be expressed in terms of hypergeometric functions mFn and is QES if the Schrödinger equation admits polynomial solutions with coefficients necessarily satisfying a three-term or higher order of recurrence relations. In three dimensions we give an example of a system that is QES in one set of separable coordinates, but is not ES in any other separable coordinates. This example encompasses Ushveridze's tenth-order polynomial QES problem in one set of separable coordinates and also leads to a fourth-order polynomial QES problem in another separable coordinate set.

year: 2006-03

title: Re-designing the national imaginary: The development of Matariki as a contemporary festival

authors: Hardy, Ann

subjects: Aotearoa/New Zealand

abstract: This article considers the factors shaping the contemporary redevelopment in Aotearoa/ New Zealand of the indigenous commemoration of the rising of the constellation Matariki as a marker of seasonal change.  Through interviews with producers of media materials celebrating Matariki, it examines the ideological, cultural, and economic factors determining the encoding of the materials, investigating in particular the ways in which Matariki can resource a marketplace for spiritual commodities.

text: Re-designing the national imaginary: The development of Matariki as a contemporary festival This article considers the factors shaping the contemporary redevelopment in Aotearoa/ New Zealand of the indigenous commemoration of the rising of the constellation Matariki as a marker of seasonal change.  Through interviews with producers of media materials celebrating Matariki, it examines the ideological, cultural, and economic factors determining the encoding of the materials, investigating in particular the ways in which Matariki can resource a marketplace for spiritual commodities.

year: 2012