Technical note: A geostatistical fixed-lag Kalman smoother for atmospheric inversions

International audienceInverse modeling methods are now commonly used for estimating surface fluxes of carbon dioxide, using atmospheric mass fraction measurements combined with a numerical atmospheric transport model. The geostatistical approach to flux estimation takes advantage of the spatial and/or temporal correlation in fluxes and does not require prior flux estimates. In this work, a geostatistical implementation of a fixed-lag Kalman smoother is developed to improve the computational efficiency of the inverse problem. This method makes it feasible to perform multi-year inversions, at fine resolutions, and with large amounts of data. The new method is applied to the recovery of global gridscale carbon dioxide fluxes for 1997 to 2001 using pseudodata representative of a subset of the NOAA-ESRL Cooperative Air Sampling Network

I love judges, and I love courts: Chief Justice William H. Taft and reform in the federal judiciary.

As the only former president to ever serve as the Chief Justice of the United States Supreme Court, William Howard Taft’s legacy is best exemplified through his impact on the federal judiciary. Taft proved in time that the judiciary was his one true passion, undertaking revolutionary federal court reform that expanded the federal district courts, introduced the Judicial Conference, strengthened the chief justiceship, expanded the Supreme Court’s discretionary jurisdiction, and established a freestanding Supreme Court building. Following the reform trends of the period, Taft accomplished his reforms with the help of his political connections and experience, his colleagues on his Court, and his expert judicial management skills. Through transforming the third branch of government from one with neither force nor will, into a branch with the necessary tools for effective delivery of justice and its own agenda, Taft’s federal court reform can still be felt across the United States today. Although the origins of Taft’s judicial reform proved unusual, Taft completed his reforms within the boundaries of the power of the chief justice as delegated by the United States Constitution. The modern federal courts’ structure and mere ability to function should be accredited to Taft, and Taft’s historical reputation should not rely on his hefty figure and mediocre presidency, but rather his respect for and dedication to the federal judiciary

Theory of Tunneling Spectroscopy in a Mn12_{12} Single-Electron Transistor by Density-Functional Theory Methods

We consider tunneling transport through a Mn$_{12}$ molecular magnet using spin density functional theory. A tractable methodology for constructing many-body wavefunctions from Kohn-Sham orbitals allows for the determination of spin-dependent matrix elements for use in transport calculations. The tunneling conductance at finite bias is characterized by peaks representing transitions between spin multiplets, separated by an energy on the order of the magnetic anisotropy. The energy splitting of the spin multiplets and the spatial part of their many-body wave functions, describing the orbital degrees of freedom of the excess charge, strongly affect the electronic transport, and can lead to negative differential conductance.Comment: 4 pages, 3 figures, a revised version with minor change

A Tidally-Disrupted Asteroid Around the White Dwarf G29-38

The infrared excess around the white dwarf G29-38 can be explained by emission from an opaque flat ring of dust with an inner radius 0.14 of the radius of the Sun and an outer radius approximately equal to the Sun's. This ring lies within the Roche region of the white dwarf where an asteroid could have been tidally destroyed, producing a system reminiscent of Saturn's rings. Accretion onto the white dwarf from this circumstellar dust can explain the observed calcium abundance in the atmosphere of G29-38. Either as a bombardment by a series of asteroids or because of one large disruption, the total amount of matter accreted onto the white dwarf may have been comparable to the total mass of asteroids in the Solar System, or, equivalently, about 1% of the mass in the asteroid belt around the main sequence star zeta Lep.Comment: ApJ Letters, in pres

Electron-magnon coupling and nonlinear tunneling transport in magnetic nanoparticles

We present a theory of single-electron tunneling transport through a ferromagnetic nanoparticle in which particle-hole excitations are coupled to spin collective modes. The model employed to describe the interaction between quasiparticles and collective excitations captures the salient features of a recent microscopic study. Our analysis of nonlinear quantum transport in the regime of weak coupling to the external electrodes is based on a rate-equation formalism for the nonequilibrium occupation probability of the nanoparticle many-body states. For strong electron-boson coupling, we find that the tunneling conductance as a function of bias voltage is characterized by a large and dense set of resonances. Their magnetic field dependence in the large-field regime is linear, with slopes of the same sign. Both features are in agreement with recent tunneling experiments.Comment: 4 pages, 2 figure

Large Magnetoresistance in Co/Ni/Co Ferromagnetic Single Electron Transistors

We report on magnetotransport investigations of nano-scaled ferromagnetic Co/Ni/Co single electron transistors. As a result of reduced size, the devices exhibit single electron transistor characteristics at 4.2K. Magnetotransport measurements carried out at 1.8K reveal tunneling magnetoresistance (TMR) traces with negative coercive fields, which we interpret in terms of a switching mechanism driven by the shape anisotropy of the central wire-like Ni island. A large TMR of about 18% is observed within a finite source-drain bias regime. The TMR decreases rapidly with increasing bias, which we tentatively attribute to excitation of magnons in the central island.Comment: 12 pages (including 4 figures). Accepted for publishing on AP

Editorial: Endoplasmic Reticulum and Its Role in Tumor Immunity.

Published onlineJournal ArticleN/