249 research outputs found

    Energy price risk management

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    The price of electricity is far more volatile than that of other commodities normally noted for extreme volatility. Demand and supply are balanced on a knife-edge because electric power cannot be economically stored, end user demand is largely weather dependent, and the reliability of the grid is paramount. The possibility of extreme price movements increases the risk of trading in electricity markets. However, a number of standard financial tools cannot be readily applied to pricing and hedging electricity derivatives. In this paper we present arguments why this is the case

    Free-Free Spectral Energy Distributions of Hierarchically Clumped HII Regions

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    In an effort to understand unusual power-law spectral slopes observed in some hypercompact HII regions, we consider the radio continuum energy distribution from an ensemble of spherical clumps. An analytic expression for the free-free emission from a single spherical clump is derived. The radio continuum slope (with F_\nu \nu^\alpha) is governed by the population of clump optical depths N(tau), such that (a) at frequencies where all clumps are thick, a continuum slope of +2 is found, (b) at frequencies where all clumps are optically thin, a flattened slope of -0.11 is found, and (c) at intermediate frequencies, a power-law segment of significant bandwidth with slopes between these two limiting values can result. For the ensemble distribution, we adopt a power-law distribution N(tau) tau^{-\gamma}, and find that significant power-law segments in the SED with slopes from +2 to -0.11 result only for a relatively restricted range of γ\gamma values of 1 to 2. Further, a greater range of clump optical depths for this distribution leads to a wider bandwidth over which the intermediate power-law segment exists. The model is applied to the source W49N-B2 with an observed slope of \alphab +0.9, but that may be turning over to become optically thin around 2 mm. An adequate fit is found in which most clumps are optically thin and there is little shadowing of rearward clumps by foreground clumps (i.e., the geometrical covering factor C<<1). The primary insight gained from our study is that in the Rayleigh-Jeans limit for the Planck function that applies for the radio band, it is the distribution in optical depth of the clump population that is solely responsible for setting the continuum shape, with variations in the size and temperature of clumps serving to modulate the level of free-free emission.Comment: Astrophysical Journal, in pres

    Sustainable Municipal Operations: Independence, Oregon

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    Portland State University, Hatfield School of Government (PSU), and Northwest Energy Efficiency Alliance (NEEA), has formed a partnership to develop Sustainable Municipal Operations Plans that documents sustainability and energy management best practices. The goal of this partnership is to determine how a City/municipality can actively manage energy as a controllable expense by following a predetermined operation protocol. The PSU team developed a framework of best practices for sustainable municipal operations in different categories including facilities, fleet, purchasing, operations and the work environment. After identifying pilot jurisdictions, the team applied these best practices to the current operations of local governments in Oregon with limited capacity to do so independently. A list of criteria was used to select the jurisdictions based on the commitment to sustainability and executive level management support. Independence was selected as a pilot for these reasons following detailed conversations with City administrators and management staff on the issues the team would be investigating. The results of this project are intended to both serve as a foundation for each jurisdiction to move forward with implementing improvements, and also as a starting point in learning new and innovative approaches to sustainable operations in municipal and City governments. The PSU team, compiled of experienced practitioners, worked with Independence initially to provide clarity around the goals and deliverables of the project, solidifying the commitment of the City to provide information and relevant data for the purpose of drafting this report. We visited the City on numerous occasions to understand the current operations, state of facilities, challenges and opportunities for the City and staff. The following report provides an overview of our process working with Independence to collect and gather information, our findings and recommendations for both the immediate and long term, as well as suggested strategies for implementation

    Supporting Conservation and Decision-Making in the Northwoods: Mapping Forest Values, Services, and Threats

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    Land managers and resource and conservation professionals across political and organizational boundaries (e.g. state and federal agencies, non-governmental organizations, private landowners) often lack a common framework for planning and coordinated decision-making on a regional scale. We created and implemented such a framework and demonstrated its application through Story Maps, an interactive web-based communication tool. Story Maps facilitate collective understanding and decision-making by displaying interactive maps and spatial data with narrative text and multimedia. We developed a framework for coordinated development of Story Maps, integrating both the Ecosystem Services and Human Well-Being frameworks used by conservation planners in order to understand the following: (1) how people value the Northwoods forest ecosystem of Michigan, Wisconsin, and Minnesota; and (2) threats to these values. For this pilot study, we used our framework to map three human well-being values and threats to those values across the Northwoods region of Minnesota, Wisconsin, and Michigan. The three values included forest products sector jobs, water quality, and non-consumptive recreational experiences in nature (outdoor recreation). Each value was explored in a story map designed to communicate through spatial indicators, descriptive text, and graphics the extent and distribution of values and threats.Master of ScienceNatural Resources and EnvironmentUniversity of Michiganhttps://deepblue.lib.umich.edu/bitstream/2027.42/136554/1/314_MappingForestValuesintheNorthwoods2017.pd

    First Detection of an H2CO 6 cm Maser Flare: A Burst in IRAS 18566+0408

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    We report the discovery of a short-duration (less than 3 months) outburst of the H2CO 6 cm maser in IRAS 18566+0408 (G37.55+0.20). During the flare, the peak flux density of the maser increased by a factor of 4; after less than a month, it decayed to the preflare value. This is the first detection of a short, burstlike variability of an H2CO 6 cm maser. The maser shows an asymmetric line profile that is consistent with the superposition of two Gaussian components. We did not detect a change in the velocity or the line width of the Gaussian components during the flare. If the two Gaussian components trace two separate maser regions, then very likely an event outside the maser gas triggered simultaneous flares at two different locations

    NOMINAL VALUES FOR SELECTED SOLAR AND PLANETARY QUANTITIES: IAU 2015 RESOLUTION B3

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    In this brief communication we provide the rationale for and the outcome of the International Astronomical Union (IAU) resolution vote at the XXIXth General Assembly in Honolulu, Hawaii, in 2015, on recommended nominal conversion constants for selected solar and planetary properties. The problem addressed by the resolution is a lack of established conversion constants between solar and planetary values and SI units: a missing standard has caused a proliferation of solar values (e.g., solar radius, solar irradiance, solar luminosity, solar effective temperature, and solar mass parameter) in the literature, with cited solar values typically based on best estimates at the time of paper writing. As precision of observations increases, a set of consistent values becomes increasingly important. To address this, an IAU Working Group on Nominal Units for Stellar and Planetary Astronomy formed in 2011, uniting experts from the solar, stellar, planetary, exoplanetary, and fundamental astronomy, as well as from general standards fields to converge on optimal values for nominal conversion constants. The effort resulted in the IAU 2015 Resolution B3, passed at the IAU General Assembly by a large majority. The resolution recommends the use of nominal solar and planetary values, which are by definition exact and are expressed in SI units. These nominal values should be understood as conversion factors only, not as the true solar/planetary properties or current best estimates. Authors and journal editors are urged to join in using the standard values set forth by this resolution in future work and publications to help minimize further confusion

    A Novel Enzymatic System against Oxidative Stress in the Thermophilic Hydrogen-Oxidizing Bacterium Hydrogenobacter thermophilus

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    Rubrerythrin (Rbr) is a non-heme iron protein composed of two distinctive domains and functions as a peroxidase in anaerobic organisms. A novel Rbr-like protein, ferriperoxin (Fpx), was identified in Hydrogenobacter thermophilus and was found not to possess the rubredoxin-like domain that is present in typical Rbrs. Although this protein is widely distributed among aerobic organisms, its function remains unknown. In this study, Fpx exhibited ferredoxin:NADPH oxidoreductase (FNR)-dependent peroxidase activity and reduced both hydrogen peroxide (H2O2) and organic hydroperoxide in the presence of NADPH and FNR as electron donors. The calculated Km and Vmax values of Fpx for organic hydroperoxides were comparable to that for H2O2, demonstrating a multiple reactivity of Fpx towards hydroperoxides. An fpx gene disruptant was unable to grow under aerobic conditions, whereas its growth profiles were comparable to those of the wild-type strain under anaerobic and microaerobic conditions, clearly indicating the indispensability of Fpx as an antioxidant of H. thermophilus in aerobic environments. Structural analysis suggested that domain-swapping occurs in Fpx, and this domain-swapped structure is well conserved among thermophiles, implying the importance of structural stability of domain-swapped conformation for thermal environments. In addition, Fpx was located on a deep branch of the phylogenetic tree of Rbr and Rbr-like proteins. This finding, taken together with the wide distribution of Fpx among Bacteria and Archaea, suggests that Fpx is an ancestral type of Rbr homolog that functions as an essential antioxidant and may be part of an ancestral peroxide-detoxification system

    The Natural Variation of a Neural Code

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    The way information is represented by sequences of action potentials of spiking neurons is determined by the input each neuron receives, but also by its biophysics, and the specifics of the circuit in which it is embedded. Even the “code” of identified neurons can vary considerably from individual to individual. Here we compared the neural codes of the identified H1 neuron in the visual systems of two families of flies, blow flies and flesh flies, and explored the effect of the sensory environment that the flies were exposed to during development on the H1 code. We found that the two families differed considerably in the temporal structure of the code, its content and energetic efficiency, as well as the temporal delay of neural response. The differences in the environmental conditions during the flies' development had no significant effect. Our results may thus reflect an instance of a family-specific design of the neural code. They may also suggest that individual variability in information processing by this specific neuron, in terms of both form and content, is regulated genetically
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