title: Effects of a modified zeolite on P and N processes and fluxes across the lake sediment–water interface using core incubations

authors: Gibbs, Max M.

subjects: internal load

abstract: A new locally produced P-inactivation agent, Z2G1, was tested on sediment cores from Lake Okaro, New Zealand, for phosphorus (P) removal efficacy and any non-target side effects prior to a whole lake trial to manage internal P loading. Z2G1 is a granular product which settles rapidly, and was designed as a sediment capping material. It is a modified zeolite which acts as a carrier for the aluminium (Al)-based P-binding agent. It was found to have a high affinity for P and did not release Al into the water column. Continuous-flow incubation study results showed that a thin layer of Z2G1 (~2 mm) could completely block the release of P from the sediment under aerobic and anoxic conditions, and remove P from the overlying water in contact with the capping layer. The Z2G1 capping layer neither released metals itself nor did it induce the release of metals from the sediments, and the zeolite substrate absorbed arsenic and mercury from the geothermally influenced Lake Okaro sediments. In general, zeolites are strong cation absorbers and the zeolite substrate of Z2G1 absorbed ammoniacal nitrogen, making it the only sediment capping material to actively remove both P and N. There were, however, indications of a suppression effect on microbial denitrification by the Z2G1 capping layer under aerobic conditions. Overall, the Z2G1 sediment capping material is a highly effective P-inactivation agent which might be a useful material for managing internal P loads in eutrophic lakes.

text: Effects of a modified zeolite on P and N processes and fluxes across the lake sediment–water interface using core incubations A new locally produced P-inactivation agent, Z2G1, was tested on sediment cores from Lake Okaro, New Zealand, for phosphorus (P) removal efficacy and any non-target side effects prior to a whole lake trial to manage internal P loading. Z2G1 is a granular product which settles rapidly, and was designed as a sediment capping material. It is a modified zeolite which acts as a carrier for the aluminium (Al)-based P-binding agent. It was found to have a high affinity for P and did not release Al into the water column. Continuous-flow incubation study results showed that a thin layer of Z2G1 (~2 mm) could completely block the release of P from the sediment under aerobic and anoxic conditions, and remove P from the overlying water in contact with the capping layer. The Z2G1 capping layer neither released metals itself nor did it induce the release of metals from the sediments, and the zeolite substrate absorbed arsenic and mercury from the geothermally influenced Lake Okaro sediments. In general, zeolites are strong cation absorbers and the zeolite substrate of Z2G1 absorbed ammoniacal nitrogen, making it the only sediment capping material to actively remove both P and N. There were, however, indications of a suppression effect on microbial denitrification by the Z2G1 capping layer under aerobic conditions. Overall, the Z2G1 sediment capping material is a highly effective P-inactivation agent which might be a useful material for managing internal P loads in eutrophic lakes.

year: 2011

title: Insider threat modeling: An adversarial risk analysis approach

authors: Joshi, Chaitanya

abstract: Insider threats entail major security issues in geopolitics, cyber security and business organizations. Most earlier work in the field has focused on standard game theoretic approaches. We provide here two alternative, more realistic models based on adversarial risk analysis (ARA). ARA does not assume common knowledge and solves the problem from the point of view of just one of the players, the defender (typically), taking into account their knowledge and uncertainties regarding the choices available to them, to their adversaries, the possible outcomes, their payoffs/utilities and their opponents payoffs/utilities. The first model depicts the problem as a standard Defend-AttackDefend model. The second model segments the set of involved agents in three classes of users and considers both sequential as well as simultaneous actions. A data security example illustrates the discussion.

text: Insider threat modeling: An adversarial risk analysis approach Insider threats entail major security issues in geopolitics, cyber security and business organizations. Most earlier work in the field has focused on standard game theoretic approaches. We provide here two alternative, more realistic models based on adversarial risk analysis (ARA). ARA does not assume common knowledge and solves the problem from the point of view of just one of the players, the defender (typically), taking into account their knowledge and uncertainties regarding the choices available to them, to their adversaries, the possible outcomes, their payoffs/utilities and their opponents payoffs/utilities. The first model depicts the problem as a standard Defend-AttackDefend model. The second model segments the set of involved agents in three classes of users and considers both sequential as well as simultaneous actions. A data security example illustrates the discussion.

year: 2019

title: Evidence for late polynesian colonization of New Zealand: University of Waikato radiocarbon measurements

authors: Hogg, Alan G.

subjects: radiocarbon

abstract: We present radiocarbon determinations for 271 New Zealand archaeological samples measured at the University of Waikato Radiocarbon Dating Laboratory between 1975 and 1995. A discard protocol is applied to the series and the list culled to winnow the acceptable dates from those that may incorporate error. None of the 221 acceptable ¹⁴C determinations older than 600 BP (in the case of terrestrial samples) or 930 BP (in the case of marine and estuarine shell) extends beyond cal AD 1250. This conclusion supports the short chronology model of New Zealand prehistory presented by Anderson (1991).

text: Evidence for late polynesian colonization of New Zealand: University of Waikato radiocarbon measurements We present radiocarbon determinations for 271 New Zealand archaeological samples measured at the University of Waikato Radiocarbon Dating Laboratory between 1975 and 1995. A discard protocol is applied to the series and the list culled to winnow the acceptable dates from those that may incorporate error. None of the 221 acceptable ¹⁴C determinations older than 600 BP (in the case of terrestrial samples) or 930 BP (in the case of marine and estuarine shell) extends beyond cal AD 1250. This conclusion supports the short chronology model of New Zealand prehistory presented by Anderson (1991).

year: 1997