Free entry in infrastructure

With a policy of free entry, individuals, firms, or community groups who wish to supply power, water, and sanitation services can do so with minimal legal restrictions. Free entry is the opposite of"exclusivity"or"legal monopoly". Free entry is allowed in most industries, but governments usually allow only one provider of power, water, and sanitation in any given area. This is supposed to prevent wasteful duplication and ensure a supply of essential services to poor and marginal areas. But monopoly water and power utilities often operate at high cost, lack funds to invest, and provide low-quality, unreliable service. Worse, poor and marginal areas are often unserved. When the monopoly model doesn't work, it is time to look at alternatives. The authors provide examples of alternative solutions in developing countries: *In Karachi, Pakistan, the Orangi Pilot Project provides sanitation in an unplanned settlement. Roughly 800,000 working class people lived in an area where sanitary conditions were medievaland a long-hoped-for sewerage system never came. Starting in 1980, a charitable group developed a low-cost approach to piped sanitation, explained the technology to the community, and catalyzed community action. Householders and neighborhoods funded the construction of household pourflush latrines and sewerage lines. * In Paraguay, 300 to 400 private individuals and aguateros supply good quality piped water to areas unserved by the public water company. Unlike the public company, the aguateros allow payment of connection fees on installment, making it easier for low-income consumers to connect. * In Yemen, small-scale electricity providers innovatively meet the rural and village demand for electricity that the public utility does not meet. These entrants seldom duplicate investments, although some government intervention to ensure interconnection could improve efficiency. Limitations on entry may sometimes be justified for environmental reasons or to promote private sector investment, but those cases are rare. Legalizing alternative providers will allow them to expand and meet new needs. Limits on their entry may be needed sometimes, but limits should be the exception, not the rule, the authors argue. Generally, free entry should be allowed in power, water, and sanitation.Health Economics&Finance,Decentralization,Water and Industry,Economic Theory&Research,Environmental Economics&Policies,Town Water Supply and Sanitation,Environmental Economics&Policies,Health Economics&Finance,Water and Industry,Economic Theory&Research

Nonlinear model identification and spectral submanifolds for multi-degree-of-freedom mechanical vibrations

In a nonlinear oscillatory system, spectral submanifolds (SSMs) are the smoothest invariant manifolds tangent to linear modal subspaces of an equilibrium. Amplitude-frequency plots of the dynamics on SSMs provide the classic backbone curves sought in experimental nonlinear model identification. We develop here a methodology to compute analytically both the shape of SSMs and their corresponding backbone curves from a data-assimilating model fitted to experimental vibration signals. Using examples of both synthetic and real experimental data, we demonstrate that this approach reproduces backbone curves with high accuracy.Comment: 32 pages, 4 figure

Discrete transparent boundary conditions for the mixed KDV-BBM equation

International audienceIn this paper, we consider artificial boundary conditions for the linearized mixed Korteweg-de Vries (KDV) Benjamin-Bona-Mahoney (BBM) equation which models water waves in the small amplitude, large wavelength regime. Continuous (respectively discrete) artificial boundary conditions involve non local operators in time which in turn requires to compute time convolutions and invert the Laplace transform of an analytic function (respectively the Z-transform of an holomor-phic function). In this paper, we propose a new, stable and fairly general strategy to carry out this crucial step in the design of transparent boundary conditions. For large time simulations, we also introduce a methodology based on the asymptotic expansion of coefficients involved in exact direct transparent boundary conditions. We illustrate the accuracy of our methods for Gaussian and wave packets initial data

Rho GTPase Signaling Activates Microtubule Severing to Promote Microtubule Ordering in Arabidopsis

SummaryBackgroundOrdered cortical microtubule (MT) arrays play a critical role in the spatial control of cell division and expansion and are essential for plant growth, morphogenesis, and development. Various developmental, hormonal, and mechanical signals and a large number of MT-associated proteins are known to impact cortical MT organization, but the underlying mechanisms remain poorly understood. Our previous studies show that auxin signaling, which is mediated by the ROP6 Rho GTPase and its effector RIC1, promotes the ordering of cortical MTs in pavement cells, but it is unknown how RIC1 controls the organization of cortical MTs into well-ordered arrays.ResultsOur genetic screens identified the conserved MT-severing protein katanin (KTN1) as a downstream component of the ROP6-RIC1 signaling pathway leading to well-ordered arrangement of cortical MTs. KTN1 and RIC1 proteins displayed overlapping localization. In vivo and in vitro studies showed that RIC1 physically interacts with and promotes the MT-severing activity of KTN1. Live-cell imaging reveals a role for RIC1 in promoting detachment of branched MTs that is known to rely on KTN1.ConclusionWe have demonstrated that a Rho GTPase signaling pathway regulates katanin-mediated MT severing in plant cells and uncovered an explicit regulatory mechanism underpinning the alignment and ordering of cortical MTs in plants. Our findings provide new insights into regulatory mechanisms underlying growth stimuli such as auxin promote the organization of cortical MTs into parallel arrays in plants

Vision, challenges and opportunities for a Plant Cell Atlas

With growing populations and pressing environmental problems, future economies will be increasingly plant-based. Now is the time to reimagine plant science as a critical component of fundamental science, agriculture, environmental stewardship, energy, technology and healthcare. This effort requires a conceptual and technological framework to identify and map all cell types, and to comprehensively annotate the localization and organization of molecules at cellular and tissue levels. This framework, called the Plant Cell Atlas (PCA), will be critical for understanding and engineering plant development, physiology and environmental responses. A workshop was convened to discuss the purpose and utility of such an initiative, resulting in a roadmap that acknowledges the current knowledge gaps and technical challenges, and underscores how the PCA initiative can help to overcome them