8,639 research outputs found

    From dilute matter to the equilibrium point in the energy--density--functional theory

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    Due to the large value of the scattering length in nuclear systems, standard density--functional theories based on effective interactions usually fail to reproduce the nuclear Fermi liquid behavior both at very low densities and close to equilibrium. Guided on one side by the success of the Skyrme density functional and, on the other side, by resummation techniques used in Effective Field Theories for systems with large scattering lengths, a new energy--density functional is proposed. This functional, adjusted on microscopic calculations, reproduces the nuclear equations of state of neutron and symmetric matter at various densities. Furthermore, it provides reasonable saturation properties as well as an appropriate density dependence for the symmetry energy.Comment: 4 figures, 2 table

    Magnetic blackbody shift of hyperfine transitions for atomic clocks

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    We derive an expression for the magnetic blackbody shift of hyperfine transitions such as the cesium primary reference transition which defines the second. The shift is found to be a complicated function of temperature, and has a T^2 dependence only in the high-temperature limit. We also calculate the shift of ground-state p_1/2 hyperfine transitions which have been proposed as new atomic clock transitions. In this case interaction with the p_3/2 fine-structure multiplet may be the dominant effect

    A frequency-adjustable electromagnet for hyperthermia measurements on magnetic nanoparticles

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    We describe a low-cost and simple setup for hyperthermia measurements on colloidal solutions of magnetic nanoparticles (ferrofluids) with a frequency-adjustable magnetic field in the range 5-500 kHz produced by an electromagnet. By optimizing the general conception and each component (nature of the wires, design of the electromagnet), a highly efficient setup is obtained. For instance, in a useful gap of 1.1 cm, a magnetic field of 4.8 mT is generated at 100 kHz and 500 kHz with an output power of 3.4 W and 75 W, respectively. A maximum magnetic field of 30 mT is obtained at 100 kHz. The temperature of the colloidal solution is measured using optical fiber sensors. To remove contributions due to heating of the electromagnet, a differential measurement is used. In this configuration the sensitivity is better than 1.5 mW at 100 kHz and 19.3 mT. This setup allows one to measure weak heating powers on highly diluted colloidal solutions. The hyperthermia characteristics of a solution of Fe nanoparticles are described, where both the magnetic field and the frequency dependence of heating power have been measured

    High Dimensional Classification with combined Adaptive Sparse PLS and Logistic Regression

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    Motivation: The high dimensionality of genomic data calls for the development of specific classification methodologies, especially to prevent over-optimistic predictions. This challenge can be tackled by compression and variable selection, which combined constitute a powerful framework for classification, as well as data visualization and interpretation. However, current proposed combinations lead to instable and non convergent methods due to inappropriate computational frameworks. We hereby propose a stable and convergent approach for classification in high dimensional based on sparse Partial Least Squares (sparse PLS). Results: We start by proposing a new solution for the sparse PLS problem that is based on proximal operators for the case of univariate responses. Then we develop an adaptive version of the sparse PLS for classification, which combines iterative optimization of logistic regression and sparse PLS to ensure convergence and stability. Our results are confirmed on synthetic and experimental data. In particular we show how crucial convergence and stability can be when cross-validation is involved for calibration purposes. Using gene expression data we explore the prediction of breast cancer relapse. We also propose a multicategorial version of our method on the prediction of cell-types based on single-cell expression data. Availability: Our approach is implemented in the plsgenomics R-package.Comment: 9 pages, 3 figures, 4 tables + Supplementary Materials 8 pages, 3 figures, 10 table

    Urban Agriculture and Other Green Uses: Remaking the Shrinking City

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    For many decades, the primary challenge of land use law has been how to promote and channel growth and development. Nobody wants stagnation; the cure is growth, and lately the cure has been “smart growth.” In the last several years, however, some cities have begun openly to address a previously unacknowledged truth: some cities will and do shrink. They lose population and have no foreseeable prospect of ever regaining it. The land use planning community has begun to grapple with the issue of the shrinking city, asking how we can achieve managed, “smart” shrinkage To some extent, the answer is to shift density and promote green uses of various kinds This brings us to the legal question Does an organized effort to help a city shrink pose any distinctive legal issues? What constraints might the law impose on a city’s goals of diminishing its infrastructure responsibilities, downzoning its land to less intensive uses, or taking other steps consistent with a goal of managed shrinkage This paper explores a few of those issues, using Cleveland, Ohio as an example. It considers legal challenges the shrinking city might face, particularly when downzoning urban property to promote urban agriculture and other green uses, focusing on the application of takings law It also briefly considers the fairness issues associated with downzoning and the limitations of the current legal structure for revitalizing Brownfields in a setting where traditional redevelopment is unlikely

    Urban Green Uses: The New Renewal

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    As they confront dramatically reduced population and little prospect of significant near-term growth, several cities in the rust belt have turned to innovative tactics to put excess land to beneficial use. These measures include the creation of active land banks, downzoning for green uses such as urban agriculture, possible consolidation of population and abandonment of utility and public services, and installation of green infrastructure, such as stormwater retention and renewable power generation facilities, on publicly owned land. In the process, these cities face intriguing legal questions: What steps are needed to form an effective land bank? What is the liability of land banks for cleanup of contaminated properties? Are cities required to provide municipal services to unpopulated areas within their boundaries? In the unlikely event that a city uses eminent domain to relocate owners of sparsely-populated areas, what is “just compensation” for this action? What issues might arise with zoning land for less intensive uses such as urban farms? Some of the answers are emerging. For example, state authorizing legislation has been enacted to establish the type of active land bank successfully implemented in St. Louis, Cleveland, and other cities, and it appears that cities need not provide infrastructure and services throughout their land area, though they are best advised retain any rights of way or easements that may be needed in the event of future development. Other questions – both legal and practical - have yet to be fully answered, as rust belt cities lead the way in what might tentatively be called The New Renewal – a form of sustainable development that dovetails well with the policies of cities that seek to combat and adapt to climate change

    Density-matrix functionals for pairing in mesoscopic superconductors

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    A functional theory based on single-particle occupation numbers is developed for pairing. This functional, that generalizes the BCS approach, directly incorporates corrections due to particle number conservation. The functional is benchmarked with the pairing Hamiltonian and reproduces perfectly the energy for any particle number and coupling.Comment: 4 pages, 4 figures, revised versio

    Urban Green Uses: The New Renewal

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    As they confront dramatically reduced population and little prospect of significant near-term growth, several cities in the rust belt have turned to innovative tactics to put excess land to beneficial use. These measures include the creation of active land banks, downzoning for green uses such as urban agriculture, possible consolidation of population and abandonment of utility and public services, and installation of green infrastructure, such as stormwater retention and renewable power generation facilities, on publicly owned land. In the process, these cities face intriguing legal questions: What steps are needed to form an effective land bank? What is the liability of land banks for cleanup of contaminated properties? Are cities required to provide municipal services to unpopulated areas within their boundaries? In the unlikely event that a city uses eminent domain to relocate owners of sparsely-populated areas, what is “just compensation” for this action? What issues might arise with zoning land for less intensive uses such as urban farms? Some of the answers are emerging. For example, state authorizing legislation has been enacted to establish the type of active land bank successfully implemented in St. Louis, Cleveland, and other cities, and it appears that cities need not provide infrastructure and services throughout their land area, though they are best advised retain any rights of way or easements that may be needed in the event of future development. Other questions – both legal and practical - have yet to be fully answered, as rust belt cities lead the way in what might tentatively be called The New Renewal – a form of sustainable development that dovetails well with the policies of cities that seek to combat and adapt to climate change

    Urban Agriculture and Other Green Uses: Remaking the Shrinking City

    Get PDF
    For many decades, the primary challenge of land use law has been how to promote and channel growth and development. Nobody wants stagnation; the cure is growth, and lately the cure has been “smart growth.” In the last several years, however, some cities have begun openly to address a previously unacknowledged truth: some cities will and do shrink. They lose population and have no foreseeable prospect of ever regaining it. The land use planning community has begun to grapple with the issue of the shrinking city, asking how we can achieve managed, “smart” shrinkage To some extent, the answer is to shift density and promote green uses of various kinds This brings us to the legal question Does an organized effort to help a city shrink pose any distinctive legal issues? What constraints might the law impose on a city’s goals of diminishing its infrastructure responsibilities, downzoning its land to less intensive uses, or taking other steps consistent with a goal of managed shrinkage This paper explores a few of those issues, using Cleveland, Ohio as an example. It considers legal challenges the shrinking city might face, particularly when downzoning urban property to promote urban agriculture and other green uses, focusing on the application of takings law It also briefly considers the fairness issues associated with downzoning and the limitations of the current legal structure for revitalizing Brownfields in a setting where traditional redevelopment is unlikely
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