789 research outputs found

    Book Review: Water delivery: Public or private?

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    Teaching/Communication/Extension/Profession,

    Opportunistic behaviour by private irrigators within a capacity-sharing regime

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    The concept of capacity-sharing (as a specific type of demand-orientated water management strategy) is a relatively newcomer on the South African water management regime and much debate is currently under way regarding the viability of the concept for the South African context. One of the main features is that it decentralises and integrates water management to a much greater degree than state-dominated management regimes. However, as the concept of capacity-sharing allows a greater degree of decision-making autonomy to the private decision-maker, the question could be asked to what extent the management of a capacity-sharing regime would be exposed to opportunistic behaviour from private irrigators. If it is heavily exposed, there are considerable scope for opportunistic decision-making behaviour under private decision-makers and therefore problems of moral hazard / adverse selection and rent seeking could present itself. Therefore, the question arises what safety features do capacity sharing present to confine possible opportunistic decision-making practices. This article discusses two areas within a capacity-sharing regime that are likely to be exposed to opportunistic decision-making behaviour. Possible safety-features from capacity sharing to account for this type of behaviour are identified and discussed briefly. This article concludes with the notion that capacity sharing does feature some properties that could minimise opportunistic behaviour from private decision-makers.Resource /Energy Economics and Policy,

    Towards more inclusive long-term bulk water resource management

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    Fresh water resources provide a platform for complex and often emotional issues to develop, particularly in resource scarcity situations. Bulk water infrastructure contains elements of a public good and proved vulnerable to failures in market and government driven allocation strategies. Common to both are uncaptured costs and benefits due to shortcomings in cost quantification techniques. Natural ecosystems stands to lose the most since ecosystem services are often not quantifiable in monetary terms and therefore neglected in allocation decision-making. This paper took on the challenge of expanding current decision-support in order to promote more inclusive long-term water management. A case-study approach with the focus on a choice related problem regarding different long-term bulk water resource management options was applied in the Western Cape province. The paper incorporated components of economic valuation theory, a public survey and a modified Delphi expert panel technique. Both spatial and temporal dimensions of the decision-making context were expanded. Two surveys were completed to accommodate these expansions. The first focused on public preference in water allocation management and the relative merit of accommodating public preference in highly specialised decision-making such as long-term water allocation decision-making. The second survey utilized a modified Delphi technique in which an expert panel indicated the relative merit of two alternative long-term allocation strategies. A willingness to pay for 'greener' water was observed and may be used to motivate a paradigm shift from management's perspective to consider, without fear of harming their own political position, 'greener' water supply options more seriously even if these options imply higher direct costs to public.water management, decision-support, public participation, Resource /Energy Economics and Policy,

    Rainfall threshold for initiating effective stress decrease and failure in weathered tephra slopes

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    Rainfall is one of the most important triggers of slope failure. Weathered pyroclastic (tephra) deposits are especially vulnerable to slope failure because they commonly form slopes of high porosity and high clay content. Empirically derived thresholds for the triggering of landslides are commonly based on rainfall conditions and have been widely applied in volcanic soils. However, so far only few researchers utilized pore water pressure in the slope as additional variable for the threshold calibration. Here, we derived a new rainfall threshold for initiating the decrease in effective stress in the slope by analyzing a long-term record of rainfall and piezometer data from a slide-prone coastal area in northern New Zealand that consists of clayey, halloysitic tephra deposits. The level of effective stress decrease increased with rainfall intensity and duration. We observed highest effective stress decrease of up to 36% during rainfall events that triggered landslides in our study area. The effective stress threshold exhibits a satisfactory predictive capability. The probability of correctly predicting a decrease in effective stress is 53%. The effective stress threshold contributes towards the implementation of the decrease in effective stress into rainfall thresholds for the occurrence of landslides

    Increased Postnatal Cardiac Hyperplasia Precedes Cardiomyocyte Hypertrophy in a Model of Hypertrophic Cardiomyopathy

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    Rationale: Hypertrophic cardiomyopathy (HCM) occurs in ~0.5% of the population and is a leading cause of sudden cardiac death (SCD) in young adults. Cardiomyocyte hypertrophy has been the accepted mechanism for cardiac enlargement in HCM, but the early signaling responsible for initiating hypertrophy is poorly understood. Mutations in cardiac myosin binding protein C (MYBPC3) are among the most common HCM-causing mutations. Ablation of Mybpc3 in an HCM mouse model (cMyBP-C−/−) rapidly leads to cardiomegaly by postnatal day (PND) 9, though hearts are indistinguishable from wild-type (WT) at birth. This model provides a unique opportunity to explore early processes involved in the dramatic postnatal transition to hypertrophy.Methods and Results: We performed microarray analysis, echocardiography, qPCR, immunohistochemistry (IHC), and isolated cardiomyocyte measurements to characterize the perinatal cMyBP-C−/− phenotype before and after overt hypertrophy. cMyBP-C−/− hearts showed elevated cell cycling at PND1 that transitioned to hypertrophy by PND9. An expanded time course revealed that increased cardiomyocyte cycling was associated with elevated heart weight to body weight ratios prior to cellular hypertrophy, suggesting that cell cycling resulted in cardiomyocyte proliferation. Animals heterozygous for the cMyBP-C deletion trended in the direction of the homozygous null, yet did not show increased heart size by PND9.Conclusions: Results indicate that altered regulation of the cell cycling pathway and elevated proliferation precedes hypertrophy in the cMyBP-C−/− HCM model, and suggests that increased cardiomyocyte number contributes to increased heart size in cMyBP-C−/− mice. This pre-hypertrophic period may reflect a unique time during which the commitment to HCM is determined and disease severity is influenced

    Transcriptome Analysis of Cardiac Hypertrophic Growth in MYBPC3-Null Mice Suggests Early Responders in Hypertrophic Remodeling

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    Rationale: With a prevalence of 1 in 200 individuals, hypertrophic cardiomyopathy (HCM) is thought to be the most common genetic cardiac disease, with potential outcomes that include severe hypertrophy, heart failure, and sudden cardiac death (SCD). Though much research has furthered our understanding of how HCM-causing mutations in genes such as cardiac myosin-binding protein C (MYBPC3) impair contractile function, it remains unclear how such dysfunction leads to hypertrophy and/or arrhythmias, which comprise the HCM phenotype. Identification of early response mediators could provide rational therapeutic targets to reduce disease severity. Our goal was to differentiate physiologic and pathophysiologic hypertrophic growth responses and identify early genetic mediators in the development of cardiomegaly in the cardiac myosin-binding protein C-null (cMyBP-C-/-) mouse model of HCM.Methods and Results: We performed microarray analysis on left ventricles of wild-type (WT) and cMyBPC-/- mice (n = 7 each) at postnatal day (PND) 1 and PND 9, before and after the appearance of an overt HCM phenotype. Applying the criteria of ≥2-fold change, we identified genes whose change was exclusive to pathophysiologic growth (n = 61), physiologic growth (n = 30), and genes whose expression changed ≥2-fold in both WT and cMyBP-C-/- hearts (n = 130). Furthermore, we identified genes that were dysregulated in PND1 cMyBP-C-/- hearts prior to hypertrophy, including genes in mechanosensing pathways and potassium channels linked to arrhythmias. One gene of interest, Xirp2, and its protein product, are regulated during growth but also show early, robust prehypertrophic upregulation in cMyBP-C-/- hearts. Additionally, the transcription factor Zbtb16 also shows prehypertrophic upregulation at both gene and protein levels.Conclusion: Our transcriptome analysis generated a comprehensive data set comparing physiologic vs. hypertrophic growth in mice lacking cMyBP-C. It highlights the importance of extracellular matrix pathways in hypertrophic growth and early dysregulation of potassium channels. Prehypertrophic upregulation of Xirp2 in cMyBP-C-/- hearts supports a growing body of evidence suggesting Xirp2 has the capacity to elicit both hypertrophy and arrhythmias in HCM. Dysregulation of Xirp2, as well as Zbtb16, along with other genes associated with mechanosensing regions of the cardiomyocyte implicate stress-sensing in these regions as a potentially important early response in HCM
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