The Interacting Impurity Josephson Junction: Variational Wavefunctions and Slave Boson Mean Field Theory

We investigate the Josephson coupling between two superconductors mediated through an infinite U Anderson impurity, adapting a variational wavefunction approach which has proved successful for the Kondo model. Unlike the Kondo problem, however, a crossing of singlet and doublet state energies may be produced by varying the ratio of Kondo energy to superconducting gap, in agreement with recent work of Clerk and Ambegaokar. We construct the phase diagram for the junction and discuss properties of different phases. In addition, we find the singlet and doublet state energies within a slave boson mean field approach. We find the slave boson mean field treatment is unable to account for the level crossing.Comment: 5 pages; 4 encapsulated PostScript figures; submitted to Phys. Rev.

Communication: Partial polarization transfer for single-scan spectroscopy and imaging

A method is presented to partially transfer nuclear spin polarization from one isotope S to another isotope I by the way of heteronuclear spin couplings, while minimizing the loss of spin order to other degrees of freedom. The desired I spin polarization to be detected is a design parameter, while the sequence of pulses at the two Larmor frequencies is optimized to store the greatest unused S spin longitudinal polarization for subsequent use. The unitary evolution for the case of I_NS spin systems illustrates the potentially ideal efficiency of this strategy, which is of particular interest when the spin-lattice relaxation time of S greatly exceeds that of I. Explicit timing and pulses are tabulated for the cases for which M ≤ 10 partial transfers each result in equal final polarization of 1/M or more compared to the final I polarization expected in a single transfer for N = 1, 2, or 3 I spins. Advantages for the ratiometric study of reacting molecules and hyperpolarized initial conditions are outlined

Altering the stability of the Cdc8 overlap region modulates the ability of this tropomyosin to bind cooperatively to actin and regulate myosin.

Tropomyosin (Tm) is an evolutionarily conserved ?-helical coiled-coil protein, dimers of which form end-to-end polymers capable of associating with and stabilising actin-filaments and regulate myosin function. The fission yeast, Schizosaccharomyces pombe, possesses a single essential Tm, Cdc8, which can be acetylated on its amino terminal methionine to increase its affinity for actin and enhance its ability to regulate myosin function. We have designed and generated a number of novel Cdc8 mutant proteins with amino terminal substitutions to explore how stability of the Cdc8-polymer overlap region affects the regulatory function of this Tm. By correlating the stability of each protein, its propensity to form stable polymers, its ability to associate with actin and to regulate myosin, we have shown the stability of the amino terminal of the Cdc8 ?-helix is crucial for Tm function. In addition we have identified a novel Cdc8 mutant with increased amino-terminal stability, dimers of which are capable of forming Tm-polymers significantly longer than the wild-type protein. This protein had a reduced affinity for actin with respect to wild type, and was unable to regulate actomyosin interactions. The data presented here are consistent with acetylation providing a mechanism for modulating the formation and stability of Cdc8 polymers within the fission yeast cell. The data also provide evidence for a mechanism in which Tm dimers form end-to-end polymers on the actin-filament, consistent with a cooperative model for Tm binding to actin

Three dimensional finite temperature SU(3) gauge theory in the confined region and the string picture

We determine the correlation between Polyakov loops in three dimensional SU(3) gauge theory in the confined region at finite temperature. For this purpose we perform lattice calculations for the number of steps in the temperature direction equal to six. This is expected to be in the scaling region of the lattice theory. We compare the results to the bosonic string model. The agreement is very good for temperatures T<0.7T_c, where T_c is the critical temperature. In the region 0.7T_c<T<T_c we enter the critical region, where the critical properties of the correlations are fixed by universality to be those of the two dimensional three state Potts model. Nevertheless, by calculating the critical lattice coupling, we show that the ratio of the critical temperature to the square root of the zero temperature string tension, where the latter is taken from the literature, remains very near to the string model prediction.Comment: 11 pages, 1 figure, 1 tabl

Spatially Explicit Estimates of Crop Rotation Responses

Crop Production/Industries, Environmental Economics and Policy, Land Economics/Use,

A general graphical user interface for automatic reliability modeling

Reported here is a general Graphical User Interface (GUI) for automatic reliability modeling of Processor Memory Switch (PMS) structures using a Markov model. This GUI is based on a hierarchy of windows. One window has graphical editing capabilities for specifying the system's communication structure, hierarchy, reconfiguration capabilities, and requirements. Other windows have field texts, popup menus, and buttons for specifying parameters and selecting actions. An example application of the GUI is given

Competing Interactions, the Renormalization Group and the Isotropic-Nematic Phase Transition

We discuss 2D systems with Ising symmetry and competing interactions at different scales. In the framework of the Renormalization Group, we study the effect of relevant quartic interactions. In addition to the usual constant interaction term, we analyze the effect of quadrupole interactions in the self consistent Hartree approximation. We show that in the case of repulsive quadrupole interaction, there is a first order phase transition to a stripe phase in agreement with the well known Brazovskii result. However, in the case of attractive quadrupole interactions there is an isotropic-nematic second order transition with higher critical temperature.Comment: 4 pages, no figures, version to be published in Physical Review Letters. Some scaling dimensions corrected, conclusions are the sam