Modeling Water Resource Systems under Climate Change: IGSM-WRS

Through the integration of a Water Resource System (WRS) component, the MIT Integrated Global System Model (IGSM) framework has been enhanced to study the effects of climate change on managed water-resource systems. Development of the WRS involves the downscaling of temperature and precipitation from the zonal representation of the IGSM to regional (latitude-longitude) scale, and the translation of the resulting surface hydrology to runoff at the scale of river basins, referred to as Assessment Sub-Regions (ASRs). The model of water supply is combined with analysis of water use in agricultural and non-agricultural sectors and with a model of water system management that allocates water among uses and over time and routes water among ASRs. Results of the IGSM-WRS framework include measures of water adequacy and ways it is influenced by climate change. Here we document the design of WRS and its linkage to other components of the IGSM, and present tests of consistency of model simulations with the historical record.The Joint Program on the Science and Policy of Global Change is funded by the U.S. Department of Energy, Office of Science under grants DE-FG02-94ER61937, DE-FG02-93ER61677, DEFG02- 08ER64597, and DE-FG02-06ER64320; the U.S. Environmental Protection Agency under grants XA-83344601-0, XA-83240101, XA-83042801-0, PI-83412601-0, RD-83096001, and RD- 83427901-0; the U.S. National Science Foundation under grants SES-0825915, EFRI-0835414, ATM-0120468, BCS-0410344, ATM-0329759, and DMS-0426845; the U.S. National Aeronautics and Space Administration under grants NNX07AI49G, NNX08AY59A, NNX06AC30A, NNX09AK26G, NNX08AL73G, NNX09AI26G, NNG04GJ80G, NNG04GP30G, and NNA06CN09A; the U.S. National Oceanic and Atmospheric Administration under grants DG1330-05-CN-1308, NA070AR4310050, and NA16GP2290; the U.S. Federal Aviation Administration under grant 06-C-NE-MIT; the Electric Power Research Institute under grant EPP32616/ C15124; and a consortium of 40 industrial and foundation sponsors (for the complete list see http://globalchange.mit.edu/sponsors/current.html)

Mutational Patterns in RNA Secondary Structure Evolution Examined in Three RNA Families

The goal of this work was to study mutational patterns in the evolution of RNA secondary structure. We analyzed bacterial tmRNA, RNaseP and eukaryotic telomerase RNA secondary structures, mapping structural variability onto phylogenetic trees constructed primarily from rRNA sequences. We found that secondary structures evolve both by whole stem insertion/deletion, and by mutations that create or disrupt stem base pairing. We analyzed the evolution of stem lengths and constructed substitution matrices describing the changes responsible for the variation in the RNA stem length. In addition, we used principal component analysis of the stem length data to determine the most variable stems in different families of RNA. This data provides new insights into the evolution of RNA secondary structures and patterns of variation in the lengths of double helical regions of RNA molecules. Our findings will facilitate design of improved mutational models for RNA structure evolution

The Diversification of the LIM Superclass at the Base of the Metazoa Increased Subcellular Complexity and Promoted Multicellular Specialization

Background: Throughout evolution, the LIM domain has been deployed in many different domain configurations, which has led to the formation of a large and distinct group of proteins. LIM proteins are involved in relaying stimuli received at the cell surface to the nucleus in order to regulate cell structure, motility, and division. Despite their fundamental roles in cellular processes and human disease, little is known about the evolution of the LIM superclass. Results: We have identified and characterized all known LIM domain-containing proteins in six metazoans and three nonmetazoans. In addition, we performed a phylogenetic analysis on all LIM domains and, in the process, have identified a number of novel non-LIM domains and motifs in each of these proteins. Based on these results, we have formalized a classification system for LIM proteins, provided reasonable timing for class and family origin events; and identified lineagespecific loss events. Our analysis is the first detailed description of the full set of LIM proteins from the non-bilaterian species examined in this study. Conclusion: Six of the 14 LIM classes originated in the stem lineage of the Metazoa. The expansion of the LIM superclass at the base of the Metazoa undoubtedly contributed to the increase in subcellular complexity required for the transition from a unicellular to multicellular lifestyle and, as such, was a critically important event in the history of animal multicellularity

The TAF-ID database Application calculations to severe accidents and irradiated fuel

International audienceTo support safety improvement and life extension for Generation II-III reactors, and the design of the Generation IV reactors there is a need of thermodynamic experimental data and modelling. These are needed to describe the complex phenomena occurring during the normal operating conditions as well as during accidental scenarios of a nuclear power plant.In 2013, the OECD-NEA Thermodynamics of Advanced Fuels International database (TAF-ID) project was started. The main objective of the TAF-ID project is to assure a comprehensive and reliable international thermodynamic Calphad-type database for the calculation of phase diagram and thermodynamic properties of fuels. This includes minor actinides (Am, Np), fission products (Cs, I, Ba, Sr, Mo, Zr, lanthanides, metallic fission products) and structural materials (steel, Zr alloy, B4C, SiC, concrete).In this work, the current version of the database has been used to investigate the thermodynamics and phase relations of corium, a partly or fully melted mixture formed during a severe accident mainly composed of nuclear fuel, cladding and structural materials. First, calculations have been compared to experimental results obtained in large scale facilities dedicated to severe accidents studies. A good agreement has been obtained. Then calculations have been performed to follow the partition of elements in each phase as a function of temperature and corium composition. For this task, representative corium compositions found in literature have been used. These calculations allow to study the role of key elements, such as Pu, in the very high temperature behavior of corium. In parallel, thermodynamic calculations have been performed to study the effect of fission products within the nuclear fuel matrix. These calculations help the understanding of UO2 based fuel behavior after irradiation. The formation of metallic phases within the oxide fuel can be predicted. Parameters such as the oxygen potential may be varied to investigate different scenarios

The TAF-ID database Application calculations to severe accidents and irradiated fuel

International audienceTo support safety improvement and life extension for Generation II-III reactors, and the design of the Generation IV reactors there is a need of thermodynamic experimental data and modelling. These are needed to describe the complex phenomena occurring during the normal operating conditions as well as during accidental scenarios of a nuclear power plant.In 2013, the OECD-NEA Thermodynamics of Advanced Fuels International database (TAF-ID) project was started. The main objective of the TAF-ID project is to assure a comprehensive and reliable international thermodynamic Calphad-type database for the calculation of phase diagram and thermodynamic properties of fuels. This includes minor actinides (Am, Np), fission products (Cs, I, Ba, Sr, Mo, Zr, lanthanides, metallic fission products) and structural materials (steel, Zr alloy, B4C, SiC, concrete).In this work, the current version of the database has been used to investigate the thermodynamics and phase relations of corium, a partly or fully melted mixture formed during a severe accident mainly composed of nuclear fuel, cladding and structural materials. First, calculations have been compared to experimental results obtained in large scale facilities dedicated to severe accidents studies. A good agreement has been obtained. Then calculations have been performed to follow the partition of elements in each phase as a function of temperature and corium composition. For this task, representative corium compositions found in literature have been used. These calculations allow to study the role of key elements, such as Pu, in the very high temperature behavior of corium. In parallel, thermodynamic calculations have been performed to study the effect of fission products within the nuclear fuel matrix. These calculations help the understanding of UO2 based fuel behavior after irradiation. The formation of metallic phases within the oxide fuel can be predicted. Parameters such as the oxygen potential may be varied to investigate different scenarios

Thermodynamic assessment of the neptunium-oxygen system: mass spectrometric studies and thermodynamic modelling

Knudsen effusion mass spectrometry measurements on neptunium dioxide are reported in this work, which have allowed to improve the understanding of its vaporization behaviour and solved discrepancies noticed in the literature: the enthalpy of formation of NpO2(g) has been re-assessed and the composition of neptunia at congruent vaporization has been determined at 2262 K. In addition, a thermodynamic model for the neptunium-oxygen system has been developed using the CALPHAD method. The non stoichiometric NpO2-x phase is described herein using the compound energy formalism with ionic constituents (Np3+;Np4+)1(O2-; V a)2, while the liquid phase is represented with the ionic two-sublattice model (Np4+)P (O2-; V aQ;O)Q. The reliability and consistency of all optimized Gibbs energies have been verified by calculating the phase equilibria, thermodynamic data, oxygen chemical potential and equilibrium partial pressures. Finally, a number of ill-defined data in the Np-O system have been identified after critical review of the literature and comparison with the present experimental results and CALPHAD model.JRC.G.I.3-Nuclear Fuel Safet

A Thermodynamic Study of the Pu-Am-O System

Vapour pressure measurements were performed on a (Pu0.756Am0.244)O2-x sample using Knudsen cell mass spectrometry. The total and partial vapour pressures of the gaseous species have been measured in the temperature range from 2000 to 2300 K. The evolution to the plutonium and americium bearing species was also determined as a function of time, in order to evaluate the congruent vapour composition. At constant temperature, the energy of ionising electrons was stepwise increased and the ionisation efficiency curves were recorded. The results were combined with the assessment of the Pu-Am-O system using the CALPHAD method. To obtain the model of this ternary system, the data on the Pu-Am and Am-O binaries have been evaluated and the optimised phase diagrams are presented. A consistent thermodynamic description of the ternary was obtained which allow calculating the ternary phase diagram, the oxygen potantial for (Pu,Am)O2+x and the equilibrium partial vapour pressures.JRC.E.3 - Materials researc