1,924 research outputs found

    Impacts of CO2 Mandates for New Cars in the European Union

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    CO2 emissions mandates for new light-duty passenger vehicles have recently been adopted in the European Union (EU), which require steady reductions to 95 g CO2/km in 2021. Using a computable general equilibrium (CGE) model, we analyze the impact of the mandates on oil demand, CO2 emissions, and economic welfare, and compare the results to an emission trading scenario that achieves identical emissions reductions. We find that the mandates lower oil expenditures by about €6 billion, but at a net added cost of €12 billion in 2020. Emissions from transport are about 50MtCO2 lower with the vehicle emission standards, but with the economy-wide emission trading, lower emissions in transport allow an equal increase in emissions elsewhere in the economy. We estimate that tightening CO2 standards further after 2020 would cost the EU economy an additional €24–63 billion in 2025 compared with achieving the same reductions with an economy-wide emission trading system.The paper benefitted from comments of participants on an earlier draft of the paper presented at a workshop on the EU fuels standards held in Brussels on February 26, 2015, organized by General Motors. The MIT Joint Program on the Science and Policy of Global Change, where the authors are affiliated, is supported by the U.S. Department of Energy, Office of Science under grants DE-FG02-94ER61937, DE-FG02-08ER64597, DE-FG02-93ER61677, DE-SC0003906, DE-SC0007114, XEU-0-9920-01; the U.S. Department of Energy, Oak Ridge National Laboratory under Subcontract 4000109855; the U.S. Environmental Protection Agency under grants XA-83240101, PI-83412601-0, RD-83427901-0, XA-83505101-0, XA-83600001-1, and subcontract UTA12-000624; the U.S. National Science Foundation under grants AGS-0944121, EFRI-0835414, IIS-1028163, ECCS-1128147, ARC-1203526, EF-1137306, AGS-1216707, and SES-0825915; the U.S. National Aeronautics and Space Administration under grants NNX06AC30A, NNX07AI49G, NNX11AN72G and Sub Agreement No. 08-SFWS-209365.MIT; the U.S. Federal Aviation Administration under grants 06-C-NE-MIT, 09-C-NE-MIT, Agmt. No. 4103-30368; the U.S. Department of Transportation under grant DTRT57-10-C-10015; the Electric Power Research Institute under grant EP-P32616/C15124, EP-P8154/C4106; the U.S. Department of Agriculture under grant 58-6000-2-0099, 58-0111-9-001; and a consortium of 35 industrial and foundation sponsors (for the complete list see: http://globalchange.mit.edu/sponsors/all)

    Dynamics of semiclassical Bloch wave - packets

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    The semiclassical approximation for electron wave-packets in crystals leads to equations which can be derived from a Lagrangian or, under suitable regularity conditions, in a Hamiltonian framework. In the plane, these issues are studied %in presence of external fields using the method of the coadjoint orbit applied to the ``enlarged'' Galilei group.Comment: 15 pages, Talk given at Nonlinear Physics. Theory and Experiment. IV,Gallipoli (Lecce), Italy - June 22 - July 1, 200

    Anomalous Hall Effect and Skyrmion Number in Real- and Momentum-space

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    We study the anomalous Hall effect (AHE) for the double exchange model with the exchange coupling JH|J_H| being smaller than the bandwidth t|t| for the purpose of clarifying the following unresolved and confusing issues: (i) the effect of the underlying lattice structure, (ii) the relation between AHE and the skyrmion number, (iii) the duality between real and momentum spaces, and (iv) the role of the disorder scatterings; which is more essential, σH\sigma_H (Hall conductivity) or ρH\rho_H (Hall resistivity)? Starting from a generic expression for σH\sigma_H, we resolve all these issues and classify the regimes in the parameter space of JHτJ_H \tau (τ\tau: elastic-scattering time), and λs\lambda_{s} (length scale of spin texture). There are two distinct mechanisms of AHE; one is characterized by the real-space skyrmion-number, and the other by momentum-space skyrmion-density at the Fermi level, which work in different regimes of the parameter space.Comment: 4 pages, 1 figure, REVTe

    Sequencing of folding events in Go-like proteins

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    We have studied folding mechanisms of three small globular proteins: crambin (CRN), chymotrypsin inhibitor 2 (CI2) and the fyn Src Homology 3 domain (SH3) which are modelled by a Go-like Hamiltonian with the Lennard-Jones interactions. It is shown that folding is dominated by a well-defined sequencing of events as determined by establishment of particular contacts. The order of events depends primarily on the geometry of the native state. Variations in temperature, coupling strengths and viscosity affect the sequencing scenarios to a rather small extent. The sequencing is strongly correlated with the distance of the contacting aminoacids along the sequence. Thus α\alpha-helices get established first. Crambin is found to behave like a single-route folder, whereas in CI2 and SH3 the folding trajectories are more diversified. The folding scenarios for CI2 and SH3 are consistent with experimental studies of their transition states.Comment: REVTeX, 12 pages, 11 EPS figures, J. Chem. Phys (in press

    Theory of Anomalous Hall Effect in a Heavy fermion System with a Strong Anisotropic Crystal Field

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    In a heavy fermion system, there exists the anomalous Hall effect caused by localized ff-orbital freedom, in addition to the normal Hall effect due to the Lorentz force. In 1994, we found that the Hall coefficient caused by the anomalous Hall effect (RHAHER_H^{AHE}) is predominant and the relation RHAHEρ2R_H^{AHE} \propto \rho^2 (ρ\rho is the electrical resistivity) holds at low temperatures in many compounds. In this work, we study the system where the magnetic susceptibility is highly anisotropic due to the strong crystalline electric field on ff-orbitals. Interestingly, we find that RHAHER_H^{AHE} is nearly isotropic in general. This tendency is frequently observed experimentally, which has casted suspicion that the anomalous Hall effect may be irrelevant in real materials. Our theory corresponds to corrections and generalizations of the pioneering work on ferromagnetic metals by Karplus and Luttinger.Comment: 4 pages, revtex, to be published in J. Phys. Soc. Jpn. (No.8

    Some Recent Advances in Bound-State Quantum Electrodynamics

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    We discuss recent progress in various problems related to bound-state quantum electrodynamics: the bound-electron g factor, two-loop self-energy corrections and the laser-dressed Lamb shift. The progress relies on various advances in the bound-state formalism, including ideas inspired by effective field theories such as Nonrelativistic Quantum Electrodynamics. Radiative corrections in dynamical processes represent a promising field for further investigations.Comment: 12 pages, nrc1 LaTeX styl

    One Loop Multiphoton Helicity Amplitudes

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    We use the solutions to the recursion relations for double-off-shell fermion currents to compute helicity amplitudes for nn-photon scattering and electron-positron annihilation to photons in the massless limit of QED. The form of these solutions is simple enough to allow {\it all}\ of the integrations to be performed explicitly. For nn-photon scattering, we find that unless n=4n=4, the amplitudes for the helicity configurations (+++...+) and (-++...+) vanish to one-loop order.Comment: 27 pages + 4 uuencoded figures (included), Fermilab-Pub-93/327-T, RevTe

    Design Equation: A Novel Approach to Heteropolymer Design

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    A novel approach to heteropolymer design is proposed. It is based on the criterion by Kurosky and Deutsch, with which the probability of a target conformation in a conformation space is maximized at low but finite temperature. The key feature of the proposed approach is the use of soft spins (fuzzy monomers) that leads to a design equation, which is an analog of the Boltzmann machine learning equation in the design problem. We implement an algorithm based on the design equation for the generalized HP model on the 3x3x3 cubic lattice and check its performance.Comment: 7 pages, 3 tables, 1 figures, uses jpsj.sty, jpsjbs1.sty, epsf.sty, Submitted to J. Phys. Soc. Jp

    Collapse of Randomly Self-Interacting Polymers

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    We use complete enumeration and Monte Carlo techniques to study self--avoiding walks with random nearest--neighbor interactions described by v0qiqjv_0q_iq_j, where qi=±1q_i=\pm1 is a quenched sequence of ``charges'' on the chain. For equal numbers of positive and negative charges (N+=NN_+=N_-), the polymer with v0>0v_0>0 undergoes a transition from self--avoiding behavior to a compact state at a temperature θ1.2v0\theta\approx1.2v_0. The collapse temperature θ(x)\theta(x) decreases with the asymmetry x=N+N/(N++N)x=|N_+-N_-|/(N_++N_-)Comment: 8 pages, TeX, 4 uuencoded postscript figures, MIT-CMT-

    Protein structures and optimal folding emerging from a geometrical variational principle

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    Novel numerical techniques, validated by an analysis of barnase and chymotrypsin inhibitor, are used to elucidate the paramount role played by the geometry of the protein backbone in steering the folding to the correct native state. It is found that, irrespective of the sequence, the native state of a protein has exceedingly large number of conformations with a given amount of structural overlap compared to other compact artificial backbones; moreover the conformational entropies of unrelated proteins of the same length are nearly equal at any given stage of folding. These results are suggestive of an extremality principle underlying protein evolution, which, in turn, is shown to be associated with the emergence of secondary structures.Comment: Revtex, 5 pages, 5 postscript figure
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