title: Timing in Possums: Accounting for Resurgence in the Peak Procedure

authors: Stanley, Christopher D.

abstract: This study attempted to account for resurgence on the Peak Procedure using 6 possums (Trichosurus vulpecula) as subjects. The Peak Procedure is made up of randomly mixed fixed intervals (FI) and peak intervals (PI), with the ratio of FI trials to PI trials being 4:1 respectively. Conditions 1-4 were used to replicate Church et al.’s (1991) procedure from their second experiment. The authors found that when the PI trial length was variable, data from PI trials showed that responding did not resurge, as it did when the PI duration was fixed.  Condition 1 used a FI 20 s and a variable PI with a mean of 80 s. Responding did not resurge, but rather decreased to a low level throughout the PI trial. Condition 2 used a FI 20 and a fixed PI of 100 s. Responding resurged for this condition. Condition 3 and 4 repeated Condition 1 and 2 respectively to give an ABAB design. Responding again decreased and increased as the PI changed to being variable and fixed respectively. These results are similar to that found by Church et al. (1991), and show support for what Sanabria and Killeen (2007) call the anticipation theory (where escape from a non-reinforced PI trial is negatively reinforcing). The PI duration was shortened to twice the FI length in Condition 5 and lengthened to 300 s, or 15 times the FI in Condition 6. This was in order to investigate whether responding would resurge at very short and very long PI durations. Responding did not resurge at the shorter PI length, and this may be due to there not being enough time to do so. At the extreme length of 300 s, responding was seen to resurge; a result that is not consistent with other studies that used a similar procedure (Sanabria & Killeen, 2007). When the procedure returned to using a FI 20 s and a variable PI with a mean of 80 s in Condition 7, resurgence decreased to a minimum and remained stable till the end of the trial. 
Results from the present study support Church et al.’s (1991) anticipation theory, and that as long as the animals can track the end of the PI trial, responding will resurge; if it is variable, animals cannot predict the end of the trial and so response resurgence does not occur.

text: Timing in Possums: Accounting for Resurgence in the Peak Procedure This study attempted to account for resurgence on the Peak Procedure using 6 possums (Trichosurus vulpecula) as subjects. The Peak Procedure is made up of randomly mixed fixed intervals (FI) and peak intervals (PI), with the ratio of FI trials to PI trials being 4:1 respectively. Conditions 1-4 were used to replicate Church et al.’s (1991) procedure from their second experiment. The authors found that when the PI trial length was variable, data from PI trials showed that responding did not resurge, as it did when the PI duration was fixed.  Condition 1 used a FI 20 s and a variable PI with a mean of 80 s. Responding did not resurge, but rather decreased to a low level throughout the PI trial. Condition 2 used a FI 20 and a fixed PI of 100 s. Responding resurged for this condition. Condition 3 and 4 repeated Condition 1 and 2 respectively to give an ABAB design. Responding again decreased and increased as the PI changed to being variable and fixed respectively. These results are similar to that found by Church et al. (1991), and show support for what Sanabria and Killeen (2007) call the anticipation theory (where escape from a non-reinforced PI trial is negatively reinforcing). The PI duration was shortened to twice the FI length in Condition 5 and lengthened to 300 s, or 15 times the FI in Condition 6. This was in order to investigate whether responding would resurge at very short and very long PI durations. Responding did not resurge at the shorter PI length, and this may be due to there not being enough time to do so. At the extreme length of 300 s, responding was seen to resurge; a result that is not consistent with other studies that used a similar procedure (Sanabria & Killeen, 2007). When the procedure returned to using a FI 20 s and a variable PI with a mean of 80 s in Condition 7, resurgence decreased to a minimum and remained stable till the end of the trial. 
Results from the present study support Church et al.’s (1991) anticipation theory, and that as long as the animals can track the end of the PI trial, responding will resurge; if it is variable, animals cannot predict the end of the trial and so response resurgence does not occur.

year: 2013

title: Dynamic magnetic reconnection at an X-type neutral point

authors: Craig, Ian J.D.

abstract: The relaxation of a two-dimensional "X-type" neutral point magnetic field disturbed from equilibrium is considered. Perturbations are shown to possess well-defined azimuthal modes which allow an exact determination of the magnetic annihilation rate. Free magnetic energy is dissipated by oscillatory reconnection which couples resistive diffusion at the neutral point to global advection of the outer field. The decay of azimuthally symmetric (m = 0) modes - the only modes associated with topological reconnection - is limited by the dissipation time scale of the "fundamental" (n = 0) mode with no radial nodes. This mode decays over typically 100 Alfvén times. An analytic treatment shows that the oscillation and decay time scales couple according to τosc ≈ 2 ln S and τdecay ≈ τosc 2/(2π2), where S is the Lundquist number (4π/c2)υA R/η and the times are in units of R/υA, with R the distance from the neutral point to the boundary, υA the Alfvén speed at the boundary, and η the resistivity.

text: Dynamic magnetic reconnection at an X-type neutral point The relaxation of a two-dimensional "X-type" neutral point magnetic field disturbed from equilibrium is considered. Perturbations are shown to possess well-defined azimuthal modes which allow an exact determination of the magnetic annihilation rate. Free magnetic energy is dissipated by oscillatory reconnection which couples resistive diffusion at the neutral point to global advection of the outer field. The decay of azimuthally symmetric (m = 0) modes - the only modes associated with topological reconnection - is limited by the dissipation time scale of the "fundamental" (n = 0) mode with no radial nodes. This mode decays over typically 100 Alfvén times. An analytic treatment shows that the oscillation and decay time scales couple according to τosc ≈ 2 ln S and τdecay ≈ τosc 2/(2π2), where S is the Lundquist number (4π/c2)υA R/η and the times are in units of R/υA, with R the distance from the neutral point to the boundary, υA the Alfvén speed at the boundary, and η the resistivity.

year: 1991

title: Mouri matters Contextualizing mouri in Māori health discourse

authors: Penehira, Mera

abstract: The vision statement of Te Reo o Taranaki, “Tuku reo, tuku mouri: language, culture, crossing generations”, embodies the essence of an understanding of mouri which goes beyond the simple dictionary translations of “life force” or “life essence”. Indeed, there are numerous oral narratives—whakataukī (proverbs), waiata (songs), haka (dance), karanga (ceremonial call), whaikōrero (formal speech), karakia (prayers and incantations)—from the present day to our earliest records of Māori history that engage the notion of mouri. The purpose of this paper is to examine current understandings of mouri and, by linking the concept with linguistic, cultural and intergenerational terms—as in the Taranaki example—it will be argued that mouri is something of significance to our “being” and to our wellbeing.

text: Mouri matters Contextualizing mouri in Māori health discourse The vision statement of Te Reo o Taranaki, “Tuku reo, tuku mouri: language, culture, crossing generations”, embodies the essence of an understanding of mouri which goes beyond the simple dictionary translations of “life force” or “life essence”. Indeed, there are numerous oral narratives—whakataukī (proverbs), waiata (songs), haka (dance), karanga (ceremonial call), whaikōrero (formal speech), karakia (prayers and incantations)—from the present day to our earliest records of Māori history that engage the notion of mouri. The purpose of this paper is to examine current understandings of mouri and, by linking the concept with linguistic, cultural and intergenerational terms—as in the Taranaki example—it will be argued that mouri is something of significance to our “being” and to our wellbeing.

year: 2011