8,158 research outputs found

    Measurements of underwater piling noise during nearshore windfarm construction in the UK potential impact on marine mammals in compliance with German UBA limit

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    Offshore construction work, such as pile and conductor driving, can potentially cause acoustic disturbance to marine mammals, such as cetaceans (whales, dolphins and por-poises), the odontocetes (toothed cetaceans) of which rely on the underwater sound field for spatial orientation, navigation, prey capture, communication, and predator avoidance. Disturbance ranges from behavioural changes, masking of communication signals, and temporary or even permanent hearing loss. There is currently no specific legal noise threshold in UK waters, but the Marine Management Organisation (MMO) has stipulated the requirement for noise monitoring during pile-driving operations when some windfarms are constructed. Measurements presented in this paper were taken during nearshore pile driving in the UK from a support vessel located 750 m from each pile (wind-turbine foun-dation). Results were compared with a threshold issued by the German Federal Environ-ment Agency (UBA). Noise level beyond the measurement location was predicted using a numerical model. Comparing results with the Southall criteria (Southall, B. L., et al., Ma-rine Mammal Noise Exposure Criteria: Initial Scientific Recommendations. Aquatic Mam-mals, 33 (4), 2007), the Joint Nature Conservation Committee (JNCC) 500 m exclusion zone offered protection for most of marine mammals during pile driving events in this particular case. Keywords: Underwater piling noise, wind-farm, marine mammals, UBA limi

    Entropy production of cyclic population dynamics

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    Entropy serves as a central observable in equilibrium thermodynamics. However, many biological and ecological systems operate far from thermal equilibrium. Here we show that entropy production can characterize the behavior of such nonequilibrium systems. To this end we calculate the entropy production for a population model that displays nonequilibrium behavior resulting from cyclic competition. At a critical point the dynamics exhibits a transition from large, limit-cycle like oscillations to small, erratic oscillations. We show that the entropy production peaks very close to the critical point and tends to zero upon deviating from it. We further provide analytical methods for computing the entropy production which agree excellently with numerical simulations.Comment: 4 pages, 3 figures and Supplementary Material. To appear in Phys. Rev. Lett.

    Nexiwave case

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    Thesis (S.M. in Engineering and Management)--Massachusetts Institute of Technology, System Design and Management Program, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 82-83).Telecommunication technology has had a profound impact on our daily lives. It has enabled organizations to be more competitive by reducing the need for physical proximity and fostering collaboration. In recent years especially, data networks have been especially prominent, with the obvious example being the Internet. Work that was once conducted by phone and fax is now increasingly being done by VolP, e-mail and IM. For years telecommunication companies had focused in making available communication between person-to-person as well as multi-person and mobile communication, but none had focused on the content of the voice communication. This thesis presents a functioning product to address the needs of such users by applying a systems thinking approach to visualize and manage complexity through the whole process from the product idea generation to the business model. A detailed assessment of the users' needs and description of the product's user-centric design is provided. User experience design principles and legal constraints were considered throughout the development process. We propose to add value and differentiate the product by providing users with options to manage the content of their calls. At the most basic level, we give free audio-to-text transcripts with built-in features that could users save time and be more productive. nexiwave was built using principles promulgated in the System Design and Management Program classes.by Cynthia Munoz Jugo [and] Benjamin Jiang.S.M.in Engineering and Managemen

    Constrained coordinated distributed control of smart grid with asynchronous information exchange

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    Smart grid constrained optimal control is a complex issue due to the constant growth of grid complexity and the large volume of data available as input to smart device control. In this context, traditional centralized control paradigms may suffer in terms of the timeliness of optimization results due to the volume of data to be processed and the delayed asynchronous nature of the data transmission. To address these limits of centralized control, this paper presents a coordinated, distributed algorithm based on distributed, local controllers and a central coordinator for exchanging summarized global state information. The proposed model for exchanging global state information is resistant to fluctuations caused by the inherent interdependence between local controllers, and is robust to delays in information exchange. In addition, the algorithm features iterative refinement of local state estimations that is able to improve local controller ability to operate within network constraints. Application of the proposed coordinated, distributed algorithm through simulation shows its effectiveness in optimizing a global goal within a complex distribution system operating under constraints, while ensuring network operation stability under varying levels of information exchange delay, and with a range of network sizes

    Discovery of Eight z ~ 6 Quasars in the Sloan Digital Sky Survey Overlap Regions

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    We present the discovery of eight quasars at z~6 identified in the Sloan Digital Sky Survey (SDSS) overlap regions. Individual SDSS imaging runs have some overlap with each other, leading to repeat observations over an area spanning >4000 deg^2 (more than 1/4 of the total footprint). These overlap regions provide a unique dataset that allows us to select high-redshift quasars more than 0.5 mag fainter in the z band than those found with the SDSS single-epoch data. Our quasar candidates were first selected as i-band dropout objects in the SDSS imaging database. We then carried out a series of follow-up observations in the optical and near-IR to improve photometry, remove contaminants, and identify quasars. The eight quasars reported here were discovered in a pilot study utilizing the overlap regions at high galactic latitude (|b|>30 deg). These quasars span a redshift range of 5.86<z<6.06 and a flux range of 19.3<z_AB<20.6 mag. Five of them are fainter than z_AB=20 mag, the typical magnitude limit of z~6 quasars used for the SDSS single-epoch images. In addition, we recover eight previously known quasars at z~6 that are located in the overlap regions. These results validate our procedure for selecting quasar candidates from the overlap regions and confirming them with follow-up observations, and provide guidance to a future systematic survey over all SDSS imaging regions with repeat observations.Comment: AJ in press (8 pages

    Novel secondary somatic mutations in Ewing's sarcoma and desmoplastic small round cell tumors.

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    BackgroundEwing's sarcoma (ES) and desmoplastic small round cell tumors (DSRCT) are small round blue cell tumors driven by an N-terminal containing EWS translocation. Very few somatic mutations have been reported in ES, and none have been identified in DSRCT. The aim of this study is to explore potential actionable mutations in ES and DSRCT.MethodologyTwenty eight patients with ES or DSRCT had tumor tissue available that could be analyzed by one of the following methods: 1) Next-generation exome sequencing platform; 2) Multiplex PCR/Mass Spectroscopy; 3) Polymerase chain reaction (PCR)-based single- gene mutation screening; 4) Sanger sequencing; 5) Morphoproteomics.Principal findingsNovel somatic mutations were identified in four out of 18 patients with advanced ES and two of 10 patients with advanced DSRCT (six out of 28 (21.4%));KRAS (n = 1), PTPRD (n = 1), GRB10 (n = 2), MET (n = 2) and PIK3CA (n = 1). One patient with both PTPRD and GRB10 mutations and one with a GRB10 mutation achieved a complete remission (CR) on an Insulin like growth factor 1 receptor (IGF1R) inhibitor based treatment. One patient, who achieved a partial remission (PR) with IGF1R inhibitor treatment, but later developed resistance, demonstrated a KRAS mutation in the post-treatment resistant tumor, but not in the pre-treatment tumor suggesting that the RAF/RAS/MEK pathway was activated with progression.ConclusionsWe have reported several different mutations in advanced ES and DSRCT that have direct implications for molecularly-directed targeted therapy. Our technology agnostic approach provides an initial mutational roadmap used in the path towards individualized combination therapy
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