954 research outputs found

    Legal and political barriers and enablers to the deployment of marine renewable energy

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    Ocean energy is a promising source of clean renewable energy, with clear development targets set by the European Commission. However, the ocean energy sector faces non-technological challenges and opportunities that are frequently overlooked in deployment plans. The present study aimed to provide a critical evaluation of the ocean energy sector’s legal, institutional, and political frameworks with an identification and analysis of both barriers and enabling features for the deployment of ocean energy. In the first stage, a literature review on the current political and regulatory frameworks of a set of European countries was carried out, setting the basis for the main challenges and enabling factors faced by the sector. Secondly, a critical analysis of the main non-technological barriers and enablers was performed, which was supported by questionnaires sent to regulators, technology developers, and test-site managers. This questionnaire allowed us to collect and integrate the views, perceptions, and personal experiences of the main stakeholders of the ocean energy sector in the analysis. The most relevant insights were collected to guide future policy instruments, supports, and consenting measures in a more informed and effective manner and to help accelerate the development of the sector

    Bringing Structure to the Wave Energy Innovation Process with the Development of a Techno-Economic Tool

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    Current wave energy development initiatives assume that available designs have the potential for success through continuous learning and innovation-based cost reduction. However, this may not be the case, and potential winning technologies may have been overlooked. The scenario creation tool presented in this paper provides a structured method for the earliest stages of design in technology development. The core function of the scenario creation tool is to generate and rank scenarios of potential Wave Energy Converter (WEC) attributes and inform the user on the areas of the parameter space that are most likely to yield commercial success. This techno-economic tool uses a structured innovation approach to identify commercially attractive and technically achievable scenarios, with a scoring system based on their power performance and costs. This is done by leveraging performance and cost data from state-of-the-art wave energy converters and identifying theoretical limits to define thresholds. As a result, a list of scored solutions is obtained depending on resource level, wave energy converter hull shape, size, material, degree of freedom for power extraction, and efficiency. This scenario creation tool can be used to support private and public investors to inform strategy for future funding calls, and technology developers and researchers in identifying new avenues of innovation

    Particle Physics Models of Inflation and the Cosmological Density Perturbation

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    This is a review of particle-theory models of inflation, and of their predictions for the primordial density perturbation that is thought to be the origin of structure in the Universe. It contains mini-reviews of the relevant observational cosmology, of elementary field theory and of supersymmetry, that may be of interest in their own right. The spectral index n(k)n(k), specifying the scale-dependence of the spectrum of the curvature perturbation, will be a powerful discriminator between models, when it is measured by Planck with accuracy Δn0.01\Delta n\sim 0.01. The usual formula for nn is derived, as well as its less familiar extension to the case of a multi-component inflaton; in both cases the key ingredient is the separate evolution of causally disconnected regions of the Universe. Primordial gravitational waves will be an even more powerful discriminator if they are observed, since most models of inflation predict that they are completely negligible. We treat in detail the new wave of models, which are firmly rooted in modern particle theory and have supersymmetry as a crucial ingredient. The review is addressed to both astrophysicists and particle physicists, and each section is fairly homogeneous regarding the assumed background knowledge.Comment: 156 pages, after final proof corrections and addition

    Constraint-based, Single-point Approximate Kinetic Energy Functionals

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    We present a substantial extension of our constraint-based approach for development of orbital-free (OF) kinetic-energy (KE) density functionals intended for the calculation of quantum-mechanical forces in multi-scale molecular dynamics simulations. Suitability for realistic system simulations requires that the OF-KE functional yield accurate forces on the nuclei yet be relatively simple. We therefore require that the functionals be based on DFT constraints, local, dependent upon a small number of parameters fitted to a training set of limited size, and applicable beyond the scope of the training set. Our previous "modified conjoint" generalized-gradient-type functionals were constrained to producing a positive-definite Pauli potential. Though distinctly better than several published GGA-type functionals in that they gave semi-quantitative agreement with Born-Oppenheimer forces from full Kohn-Sham results, those modified conjoint functionals suffer from unphysical singularities at the nuclei. Here we show how to remove such singularities by introducing higher-order density derivatives. We give a simple illustration of such a functional used for the dissociation energy as a function of bond length for selected molecules.Comment: 16 pages, 9 figures, 2 tables, submitted to Phys. Rev.

    Dynamically Driven Evolution of the Interstellar Medium in M51

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    We report the highest-fidelity observations of the spiral galaxy M51 in CO emission, revealing the evolution of giant molecular clouds (GMCs) vis-a-vis the large-scale galactic structure and dynamics. The most massive GMCs (so-called GMAs) are first assembled and then broken up as the gas flow through the spiral arms. The GMAs and their H2 molecules are not fully dissociated into atomic gas as predicted in stellar feedback scenarios, but are fragmented into smaller GMCs upon leaving the spiral arms. The remnants of GMAs are detected as the chains of GMCs that emerge from the spiral arms into interarm regions. The kinematic shear within the spiral arms is sufficient to unbind the GMAs against self-gravity. We conclude that the evolution of GMCs is driven by large-scale galactic dynamics --their coagulation into GMAs is due to spiral arm streaming motions upon entering the arms, followed by fragmentation due to shear as they leave the arms on the downstream side. In M51, the majority of the gas remains molecular from arm entry through the inter-arm region and into the next spiral arm passage.Comment: 6 pages, including 3 figures. Accepted, ApJ

    Multiplex Chromosomal Exome Sequencing Accelerates Identification of ENU-Induced Mutations in the Mouse

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    Forward genetic screens in Mus musculus have proved powerfully informative by revealing unsuspected mechanisms governing basic biological processes. This approach uses potent chemical mutagens, such as N-ethyl-N-nitrosourea (ENU), to randomly induce mutations in mice, which are then bred and phenotypically screened to identify lines that disrupt a specific biological process of interest. Although identifying a mutation using the rich resources of mouse genetics is straightforward, it is unfortunately neither fast nor cheap. Here we show that detecting newly induced causal variants in a forward genetic screen can be accelerated dramatically using a methodology that combines multiplex chromosome-specific exome capture, next-generation sequencing, rapid mapping, sequence annotation, and variation filtering. The key innovation of our method is multiplex capture and sequence that allows the simultaneous survey of both mutant, parental, and background strains in a single experiment. By comparing variants identified in mutant offspring with those found in dbSNP, the unmutagenized background strains, and parental lines, induced causative mutations can be distinguished immediately from preexisting variation or experimental artifact. Here we demonstrate this approach to find the causative mutations induced in four novel ENU lines identified from a recent ENU screen. In all four cases, after applying our method, we found six or fewer putative mutations (and sometimes only a single one). Determining the causative variant was then easily achieved through standard segregation approaches. We have developed this process into a community resource that will speed up individual labs’ ability to identify the genetic lesion in mutant mouse lines; all of our reagents and software tools are open source and available to the broader scientific community

    CpG methylation potentiates pixantrone and doxorubicin-induced DNA damage and is a marker of drug sensitivity

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    DNA methylation is an epigenetic modification of the mammalian genome that occurs predominantly at cytosine residues of the CpG dinucleotide. Following formaldehyde activation, pixantrone alkylates DNA and particularly favours the CpG motif. Aberrations in CpG methylation patterns are a feature of most cancer types, a characteristic that may determine their susceptibility to specific drug treatments. Given their common target, DNA methylation may modulate the DNA damage induced by formaldehyde-activated pixantrone. In vitro transcription, mass spectrometry and oligonucleotide band shift assays were utilized to establish that pixantrone–DNA adduct formation was consistently enhanced 2–5-fold at discrete methylated CpG doublets. The methylation-mediated enhancement was exquisitely sensitive to the position of the methyl substituent since methylation at neighboring cytosine residues failed to confer an increase in pixantrone–DNA alkylation. Covalent modification of DNA by formaldehyde-activated doxorubicin, but not cisplatin, was augmented by neighbouring CpG methylation, indicating that modulation of binding by CpG methylation is not a general feature of all alkylators. HCT116 colon cancer cells vastly deficient in CpG methylation were 12- and 10-fold more resistant to pixantrone and doxorubicin relative to the wild-type line, suggesting that these drugs may selectively recognize the aberrant CpG methylation profiles characteristic of most tumour types

    From presence to consciousness through virtual reality

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    Immersive virtual environments can break the deep, everyday connection between where our senses tell us we are and where we are actually located and whom we are with. The concept of 'presence' refers to the phenomenon of behaving and feeling as if we are in the virtual world created by computer displays. In this article, we argue that presence is worthy of study by neuroscientists, and that it might aid the study of perception and consciousness
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