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MIT Open Access Articles

Mostrando recursos 41 - 60 de 21.786

  1. Economic impacts of climate change on water resources in the coterminous United States

    Henderson, James; Rodgers, Charles; Jones, Russell; Smith, Joel; Martinich, Jeremy; Strzepek, Kenneth
    A national-scale simulation-optimization model was created to generate estimates of economic impacts associated with changes in water supply and demand as influenced by climate change. Water balances were modeled for the 99 assessment sub-regions, and are presented for 18 water resource regions in the United States. Benefit functions are developed for irrigated agriculture, municipal and domestic water use, commercial and industrial water use, and hydroelectric power generation. Environmental flows below minimal levels required for environmental needs are assessed a penalty. As a demonstration of concept for the model, future climate is projected using a climate model ensemble for two greenhouse...

  2. Estimated effects of climate change on flood vulnerability of U.S. bridges

    Wright, Len; Chinowsky, Paul; Jones, Russell; Streeter, Richard; Mayotte, Jean-Marc; Powell, Anthony; Jantarasami, Lesley; Perkins, William; Smith, Joel B.; Strzepek, Kenneth
    We assessed the potential impacts of increased river flooding from climate change on bridges in the continental United States. Daily precipitation statistics from four climate models and three greenhouse gas (GHG) emissions scenarios (A2, A1B, and B1) were used to capture a range of potential changes in climate. Using changes in maximum daily precipitation, we estimated changes to the peak flow rates for the 100-year return period for 2,097 watersheds. These estimates were then combined with information from the National Bridge Inventory database to estimate changes to bridge scour vulnerability. The results indicate that there may be significant potential risks...

  3. Numerical simulation of the heavy rainfall caused by a convection band over Korea: a case study on the comparison of WRF and CReSS

    In, So-Ra; Han, Sang-Ok; Im, Eun Soon
    This study investigates the capability of two numerical models, namely the Weather Research and Forecasting (WRF) and Cloud Resolving Storm Simulator (CReSS), to simulate the heavy rainfall that occurred on September 21, 2010 in the middle of the Korean peninsula. This event was considered part of the typical rainfall caused by intense quasi-stationary convection band, leading to a large accumulated rainfall amount within a narrow area. To investigate the relevant characteristics of this heavy rainfall and the feasibility of the numerical models to simulate them, the experiments using both numerical models were designed with a focus on Korea with a...

  4. Storm surges in the Singapore Strait due to winds in the South China Sea

    Tkalich, Pavel; Vethamony, P.; Babu, M. T.; Rizzoli, Paola M
    Among the semi-enclosed basins of the world ocean, the South China Sea (SCS) is unique in its configuration as it lies under the main southwest-northeast pathway of the seasonal monsoons. The northeast (NE) monsoon (November–February) and southwest (SW) monsoon (June–August) dominate the large-scale sea level dynamics of the SCS. Sunda Shelf at the southwest part of SCS tends to amplify Sea Level Anomalies (SLAs) generated by winds over the sea. The entire region, bounded by Gulf of Thailand on the north, Karimata Strait on the south, east cost of Peninsular Malaysia on the west, and break of Sunda Shelf on...

  5. Probabilistic seismic hazard maps for the sultanate of Oman

    El-Hussain, I.; Deif, A.; Al-Jabri, K.; El-Hady, S.; Al-Hashmi, S.; Al-Toubi, K.; Al-Shijbi, Y.; Al-Saifi, M.; Kuleli, Huseyin Sadi; Toksoz, M. Nafi
    This study presents the results of the first probabilistic seismic hazard assessment (PSHA) in the framework of logic tree for Oman. The earthquake catalogue was homogenized, declustered, and used to define seismotectonic source model that characterizes the seismicity of Oman. Two seismic source models were used in the current study; the first consists of 26 seismic source zones, while the second is expressing the alternative view that seismicity is uniform along the entire Makran and Zagros zones. The recurrence parameters for all the seismogenic zones were determined using the doubly bounded exponential distribution except the zones of Makran, which were...

  6. Percentile indices for assessing changes in heavy precipitation events

    Schär, Christoph; Ban, Nikolina; Rajczak, Jan; Schmidli, Jürg; Frei, Christoph; Giorgi, Filippo; Sillmann, Jana; Zhang, Xuebin; Fischer, Erich M.; Karl, Thomas R.; Kendon, Elizabeth J.; Tank, Albert M. G. Klein; Zwiers, Francis W.; O'Gorman, Paul
    Many climate studies assess trends and projections in heavy precipitation events using precipitation percentile (or quantile) indices. Here we investigate three different percentile indices that are commonly used. We demonstrate that these may produce very different results and thus require great care with interpretation. More specifically, consideration is given to two intensity-based indices and one frequency-based index, namely (a) all-day percentiles, (b) wet-day percentiles, and (c) frequency indices based on the exceedance of a percentile threshold. Wet-day percentiles are conditionally computed for the subset of wet events (with precipitation exceeding some threshold, e.g. 1 mm/d for daily precipitation). We present evidence...

  7. Equity and emissions trading in China

    Zhang, Da; Springmann, Marco; Karplus, Valerie Jean
    China has embarked on an ambitious pathway for establishing a national carbon market in the next 5–10 years. In this study, we analyze the distributional aspects of a Chinese emissions-trading scheme from ethical, economic, and stated-preference perspectives. We focus on the role of emissions permit allocation and first show how specific equity principles can be incorporated into the design of potential allocation schemes. We then assess the economic and distributional impacts of those allocation schemes using a computable general equilibrium model with regional detail for the Chinese economy. Finally, we conduct a survey among Chinese climate-policy experts on the basis...

  8. Erratum to: Quantifying and monetizing potential climate change policy impacts on terrestrial ecosystem carbon storage and wildfires in the United States

    Mills, David; Jones, Russell; Carney, Karen; Ready, Richard; Crimmins, Allison; Martinich, Jeremy; Shouse, Kate; DeAngelo, Benjamin; Juliana, Alexis St.; Monier, Erwan
    This erratum article is part of a Special Issue on “A Multi-Model Framework to Achieve Consistent Evaluation of Climate Change Impacts in the United States” edited by Jeremy Martinich, John Reilly, Stephanie Waldhoff, Marcus Sarofim, and James McFarland.

  9. AE9, AP9 and SPM: New Models for Specifying the Trapped Energetic Particle and Space Plasma Environment

    Friedel, R.; Whelan, P.; Madden, D.; Morley, S.; Su, Yi-Jiun; O’Brien, T. P.; Huston, S. L.; Johnston, W. R.; Guild, T. B.; Lindstrom, C. D.; Roth, C. J.; Quinn, R. A.; Ginet, Gregory P.
    The radiation belts and plasma in the Earth’s magnetosphere pose hazards to satellite systems which restrict design and orbit options with a resultant impact on mission performance and cost. For decades the standard space environment specification used for spacecraft design has been provided by the NASA AE8 and AP8 trapped radiation belt models. There are well-known limitations on their performance, however, and the need for a new trapped radiation and plasma model has been recognized by the engineering community for some time. To address this challenge a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space...

  10. Foreword

    Russell, C. T.; Zuber, Maria
    In 1992 a small workshop in San Juan Capistrano marked the beginning of an innovation in planetary exploration, the Principal Investigator-led mission. NASA announced the establishment of a continuing “line item” in the budget for the development, launch and operation of missions led by a Principal Investigator from inside or outside NASA. These missions were to be less costly than flagship missions that addressed the major objectives of planetary exploration. They would be more focused, developed more quickly for flight, with a limited number of instruments and a limited number of investigators. They would ensure that the smaller but important...

  11. Synthesis of Molybdenum and Tungsten Alkylidene Complexes That Contain the 2,6-Bis(2,4,6-triisopropylphenyl)phenylimido (NHIPT) Ligand

    Hoveyda, Amir H.; Axtell, Jonathan; Schrock, Richard Royce; Mueller, Peter
    Molybdenum and tungsten alkylidene complexes that contain the sterically demanding hexaisopropylterphenylimido ligand, N-2,6-(2,4,6-i-Pr[subscript 3]C[subscript 6]H[subscript 2])[subscript 2]C[subscript 6]H[subscript 3] (NHIPT), have been prepared from Mo(N-t-Bu)[subscript 2]Cl[subscript 2](1,2-dimethoxyethane) or W(N-t-Bu)[subscript 2]Cl[subscript 2](pyridine)[subscript 2], employing tert-butylimido ligands as sacrificial proton acceptors. These complexes include M(NHIPT)(CH-t-Bu)Cl[subscrip 2] (M = Mo, W), Mo(NHIPT)(CH-t-Bu)(pyrrolide)[subscript 2], and Mo(NHIPT)(CH-t-Bu)(pyrrolide)(OC[subscript 6]F[subscript 5])(CH[subscript 3]CN). In all cases only anti alkylidene isomers are observed in solution, as a consequence of the steric demands of the NHIPT ligand. An X-ray structure of W(NHIPT)(CH-t-Bu)Cl[subscript 2] showed it to be a monomer with a disordered alkylidene that is 86% in the anti configuration...

  12. Sustained, low-dose intraperitoneal cisplatin improves treatment outcome in ovarian cancer mouse models

    Na, Young Jeong; Fulci, Giulia; del Carmen, Marcela G.; Birrer, Michael J.; Ye, Hongye; Tanenbaum, Laura Melanie; Mantzavinou, Aikaterini; Cima, Michael J
    Intraperitoneal (IP) chemotherapy for ovarian cancer treatment prolongs overall survival by 16 months compared to intravenous chemotherapy but is not widely practiced due to catheter-related complications and complexity of administration. An implantable, nonresorbable IP microdevice was used to release chemotherapeutic agent at a constant rate of approximately 1.3 μg/h in vitro and 1.0 μg/h in vivo. Studies conducted in two orthotopic murine models bearing human xenografts (SKOV3 and UCI101) demonstrate that continuous dosing reduces tumor burden to the same extent as weekly IP bolus drug injections. Treatment-induced toxicity was quantified via body weight loss and complete blood count. The microdevice...

  13. The Exo-S probe class starshade mission

    Turnbull, Margaret; Sparks, William; Thomson, Mark; Shaklan, Stuart B.; Roberge, Aki; Kuchner, Marc; Kasdin, N. Jeremy; Domagal-Goldman, Shawn; Cash, Webster; Warfield, Keith; Lisman, Doug; Scharf, Dan; Webb, David; Trabert, Rachel; Martin, Stefan; Cady, Eric; Heneghan, Cate; Seager, Sara
    Exo-S is a direct imaging space-based mission to discover and characterize exoplanets. With its modest size, Exo-S bridges the gap between census missions like Kepler and a future space-based flagship direct imaging exoplanet mission. With the ability to reach down to Earth-size planets in the habitable zones of nearly two dozen nearby stars, Exo-S is a powerful first step in the search for and identification of Earth-like planets. Compelling science can be returned at the same time as the technological and scientific framework is developed for a larger flagship mission. The Exo-S Science and Technology Definition Team studied two viable...

  14. The MASCOT Magnetometer

    Herčík, David; Auster, Hans-Ulrich; Blum, Jürgen; Fornaçon, Karl-Heinz; Fujimoto, Masaki; Gebauer, Kathrin; Güttler, Carsten; Hillenmaier, Olaf; Hördt, Andreas; Liebert, Evelyn; Matsuoka, Ayako; Nomura, Reiko; Richter, Ingo; Stoll, Bernd; Glassmeier, Karl-Heinz; Weiss, Benjamin P
    The Mobile Asteroid Scout (MASCOT) is a small lander on board the Hayabusa2 mission of the Japan Aerospace Exploration Agency to the asteroid 162173 Ryugu. Among the instruments on MASCOT is a fluxgate magnetometer, the MASCOT Magnetometer (MasMag). The magnetometer is a lightweight ( ∼280 g∼280 g ) and low power ( ∼0.5 W∼0.5 W ) triaxial fluxgate magnetometer. Magnetic field measurements during the landing period and during the surface operational phase shall provide information about any intrinsic magnetic field of the asteroid and its remanent magnetization. This could provide important constraints on planet formation and the thermal and aqueous...

  15. Endogenous miRNA and Target Concentrations Determine Susceptibility to Potential ceRNA Competition

    Bosson, Andrew David; Zamudio, Jesse Ray; Sharp, Phillip A
    Target competition (ceRNA crosstalk) within miRNA-regulated gene networks has been proposed to influence biological systems. To assess target competition, we characterize and quantitate miRNA networks in two cell types. Argonaute iCLIP reveals that hierarchical binding of high- to low-affinity miRNA targets is a key characteristic of in vivo activity. Quantification of cellular miRNA and mRNA/ncRNA target pool levels indicates that miRNA:target pool ratios and an affinity partitioned target pool accurately predict in vivo Ago binding profiles and miRNA susceptibility to target competition. Using single-cell reporters, we directly test predictions and estimate that ∼3,000 additional high-affinity target sites can affect active...

  16. Minor Changes in Expression of the Mismatch Repair Protein MSH2 Exert a Major Impact on Glioblastoma Response to Temozolomide

    Sangaraju, D.; Tretyakova, N.; McFaline, Jose Luis; Braun, Christian Jorg; Stanciu, Monica; Nagel, Zachary D.; Mazzucato, Patrizia; Cerniauskas, Edvinas; Barford, Kelly; Vargas, Amanda; Chen, Yimin; Lees, Jacqueline; Hemann, Michael; White, Forest M; Samson, Leona D
    Glioblastoma (GBM) is often treated with the cytotoxic drug temozolomide, but the disease inevitably recurs in a drug-resistant form after initial treatment. Here, we report that in GBM cells, even a modest decrease in the mismatch repair (MMR) components MSH2 and MSH6 have profound effects on temozolomide sensitivity. RNAi-mediated attenuation of MSH2 and MSH6 showed that such modest decreases provided an unexpectedly strong mechanism of temozolomide resistance. In a mouse xenograft model of human GBM, small changes in MSH2 were sufficient to suppress temozolomide-induced tumor regression. Using The Cancer Genome Atlas to analyze mRNA expression patterns in tumors from temozolomide-treated...

  17. The Joy of War and the Future of Humanity

    Mazlish, Bruce
    The title is in imitation of Julia Child's Joy of Cooking and Alex Comfort's Joy of Sex (although theirs are about “how to,” and mine is a critical essay.) I choose this title because there is a widespread aversion to war today in many quarters. Academic historians are often anti-war and thus unconsciously or consciously skimp in their attention to the subject. (A possible exception to this thesis is the popularity of books on the Civil War in the USA.) Yet, overall, it is clearly one of the most important subjects in the course of human events. Thus, although in...

  18. Assessing the impact of real-time communication services on the space network ground segment

    Net, Marc Sanchez; del Portillo, Inigo; Cameron, Bruce; Crawley, Edward; Sanchez Net, Marc; Del Portillo Barrios, Inigo; Cameron, Bruce Gregory; Crawley, Edward F
    Communication networks to support space missions were originally architected around non-real time data services. In fact, missions have always required real-time services (e.g. telemetry and command), but the bulk of scientific data being returned to Earth has typically been highly delay tolerant. Nevertheless, future robotic and human exploration activities are rapidly pushing towards low latency, high data rate services. Examples can be found both in the near Earth domain (e.g. near real-imagery through NASAs LANCE program) and the deep space domain (e.g. HD video from Mars). Therefore, the goal of this paper is to quantify the effect of new real-time...

  19. A Conserved Activation Cluster Is Required for Allosteric Communication in HtrA-Family Proteases

    de Regt, Anna K.; Kim, Seokhee; Sohn, Jungsan; Grant, Robert A.; Baker, Tania A.; Sauer, Robert T.
    In E. coli, outer-membrane stress causes a transcriptional response through a signaling cascade initiated by DegS cleavage of a transmembrane anti-sigma factor. Each subunit of DegS, an HtrAfamily protease, contains a protease domain and a PDZ domain. The trimeric protease domain is autoinhibited by the unliganded PDZ domains. Allosteric activation requires binding of unassembled outer-membrane proteins (OMPs) to the PDZ domains and protein-substrate binding. Here, we identify a set of DegS residues that cluster together at subunit-subunit interfaces in the trimer, link the active sites and substrate-binding sites, and are crucial for stabilizing the active enzyme conformation in response to OMP signaling....

  20. Overexpression of CupB5 activates alginate overproduction in Pseudomonas aeruginosa by a novel AlgW-dependent mechanism

    Yin, Yeshi; Withers, T. Ryan; Wang, Xin; Yu, Hongwei D.; de Regt, Anna Katherine; Baker, Tania; Sauer, Robert T
    In Pseudomonas aeruginosa, alginate overproduction, also known as mucoidy, is negatively regulated by the transmembrane protein MucA, which sequesters the alternative sigma factor AlgU. MucA is degraded via a proteolysis pathway that frees AlgU from sequestration, activating alginate biosynthesis. Initiation of this pathway normally requires two signals: peptide sequences in unassembled outer-membrane proteins (OMPs) activate the AlgW protease, and unassembled lipopolysaccharides bind periplasmic MucB, releasing MucA and facilitating its proteolysis by activated AlgW. To search for novel alginate regulators, we screened a transposon library in the non-mucoid reference strain PAO1, and identified a mutant that confers mucoidy through overexpression of...

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