287 research outputs found

    Policy Change and Patterns of Domestic Purposes Benefit Receipt: A Multiple Cohort Analysis Using Benefit Dynamics Data

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    Since 1996, the abatement regime and conditions of entitlement facing sole pare Ills in receipt of the Domestic Purposes Benefit have changed markedly. These changes were intended to increase sole parents' likelihood of supporting themselves and their families through paid employment. Were they effective in raising levels of participation in part time and full-time work? This paper addresses this question using a multiple cohort analysis based on administrative data on benefit dynamics. It finds marked differences in the declared earnings of successive cohorts that coincided with the 1996 and 1997 Employment Task Force reforms, and strongly suggest that those reforms increased DPB recipients’ participation in part-time employment. lt finds no marked differences in declared earnings propensities following the 1999 DPB reforms, but marked increases in the probability of being off benefit which appear to at least partly reflect policy impacts on full-time employment propensities. lt is possible that compositional changes associated with these increases mask changes in part-time employment propensities. This is an area for further work

    How does New Zealand compare now? International comparisons of disaggregated unemployment data

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    This article updates Hicks and Brosnan's 1982 study which compared disaggregated unemployment data for Australia, Norway, the UK and the USA with similar data from New Zealand. It is found that women, youth and non-white workers bear a disproportionate share of the unemployment burden and the unemployment burden is distributed more inequitably in New Zealand than in any of the other 4 countries

    Dense gap-junction connections support dynamic Turing structures in the cortex

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    The recent report by Fukuda et al [1] provides convincing evidence for dense gap-junction connectivity between inhibitory neurons in the cat visual cortex, each neuron making 60 +/- 12 gap-junction dendritic connections with neurons in both the same and adjoining orientation columns. These resistive connections provide a source of diffusive current to the receiving neuron, supplementing the chemical-synaptic currents generated by incoming action-potential spike activity. Fukuda et al describe how the gap junctions form a dense and homogeneous electrical coupling of interneurons, and propose that this diffusion-coupled network provides the substrate for synchronization of neuronal populations. To date, large-scale population-based mathematical models of the cortex have ignored diffusive communication between neurons. Here we augment a well-established mean-field cortical model [2] by incorporating gap-junction-mediated diffusion currents, and we investigate the implications of strong diffusive coupling. The significant result is the model prediction that the 2D cortex can spontaneously generate centimetre-scale Turing structures (spatial patterns), in which regions of high-firing activity are intermixed with regions of low-firing activity (see Fig. 1). Since coupling strength decreases with increases in firing rate, these patterns are expected to exchange contrast on a slow time-scale, with low-firing patches increasing their activity at the expense of high-firing patches. These theoretical predictions are consistent with the slowly fluctuating large-scale brain-activity images detected from the BOLD (blood oxygen-level-dependent) signal [3]

    Welfare benefits and labour supply: a review of the empirical evidence

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    Assertions about the impact of welfare benefits on labour supply have often been made in claims that the New Zealand benefit system is in need of reform. This paper provides a review of empirical evidence of the relationship between labour supply decisions and the level, duration and eligibility requirements of unemployment benefits and income support provisions such as the Domestic Purposes Benefit. No clear cut conclusions emerge from the literature. In general the empirical/ink between disincentives to work in the benefit system and actual work behaviour is either insignificant or not substantial in terms of total labour supply

    Phase transitions in single neurons and neural populations: Critical slowing, anesthesia, and sleep cycles

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    The firing of an action potential by a biological neuron represents a dramatic transition from small-scale linear stochastics (subthreshold voltage fluctuations) to gross-scale nonlinear dynamics (birth of a 1-ms voltage spike). In populations of neurons we see similar, but slower, switch-like there-and-back transitions between low-firing background states and high-firing activated states. These state transitions are controlled by varying levels of input current (single neuron), varying amounts of GABAergic drug (anesthesia), or varying concentrations of neuromodulators and neurotransmitters (natural sleep), and all occur within a milieu of unrelenting biological noise. By tracking the altering responsiveness of the excitable membrane to noisy stimulus, we can infer how close the neuronal system (single unit or entire population) is to switching threshold. We can quantify this “nearness to switching” in terms of the altering eigenvalue structure: the dominant eigenvalue approaches zero, leading to a growth in correlated, low-frequency power, with exaggerated responsiveness to small perturbations, the responses becoming larger and slower as the neural population approaches its critical point–-this is critical slowing. In this chapter we discuss phase-transition predictions for both single-neuron and neural-population models, comparing theory with laboratory and clinical measurement

    Cortical patterns and gamma genesis are modulated by reversal potentials and gap-junction diffusion

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    In this chapter we describe a continuum model for the cortex that includes both axon-to-dendrite chemical synapses and direct neuron-to-neuron gap-junction diffusive synapses. The effectiveness of chemical synapses is determined by the voltage of the receiving dendrite V relative to its Nernst reversal potential Vrev. Here we explore two alternative strategies for incorporating dendritic reversal potentials, and uncover surprising differences in their stability properties and model dynamics. In the “slow-soma” variant, the (Vrev - V) weighting is applied after the input flux has been integrated at the dendrite, while for “fast-soma”, the weighting is applied directly to the input flux, prior to dendritic integration. For the slow-soma case, we find that–-provided the inhibitory diffusion (via gap-junctions) is sufficiently strong–-the cortex generates stationary Turing patterns of cortical activity. In contrast, the fast-soma destabilizes in favor of standing-wave spatial structures that oscillate at low-gamma frequency ( 30-Hz); these spatial patterns broaden and weaken as diffusive coupling increases, and disappear altogether at moderate levels of diffusion. We speculate that the slow- and fast-soma models might correspond respectively to the idling and active modes of the cortex, with slow-soma patterns providing the default background state, and emergence of gamma oscillations in the fast-soma case signaling the transition into the cognitive state

    Instabilities of the cortex during natural sleep

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    The electrical signals generated by the human cortex during sleep have been widely studied over the last 50 years. The electroencephalogram (EEG) observed during natural sleep exhibits structures with frequencies from 0.5 Hz to over 50 Hz and complicated waveforms such as spindles and K-complexes. Understanding has been enhanced by comprehensive intra-cellular measurements from the cortex and thalamus such as those performed by Steriade et al [1] and Sanchez-Vives and McCormick [2]. Models of the cerebal cortex have been developed in order to explain many of the features observed. These can be classified in terms of individual neuron models or collective models. Since we wish to compare predictions with gross features of the human EEG, we choose a collective model, where we average over a population of neurons in macrocolumns. A number of models of this form have been developed recently; that developed at Waikato draws from a number of different sources to describe the temporal and spatial dynamics of the system
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