Josephson junctions with 1 ?m dimensions and with picosecond switching times

Josephson junctions with 1 × 3 ?m dimensions have no resonances. For a current density of about 1000 A/cm2, the risetime of the switching transient from zero to the gap voltage is below 38 ps.     

Temperature Dependence of Intermodulation Power in Y1Ba2Cu3O7−δ Films on LaAlO3 Substrates

Measurements of resonators from two groups on the temperature dependence of the third-order intermodulation power of Y₁Ba₂Cu₃O_7−δ films on LaAlO₃ substrates are analyzed, evaluated, and plotted according to very similar definitions. At a fixed circulating power in the resonator both groups found a distinct minimum of the normalized intermodulation power below half the critical temperature in agreement with the theoretical prediction of Dahm and Scalapino [Appl. Phys. Lett. 69, 4248 (1996)] for d-wave superconductors. Also in agreement with theory, for Niobium as a s-wave superconductor, no intermodulation power minimum could be found down to T/T _C≈ 0.2.     

Static interferometer characteristics with many equal Josephson junctions

Flux quantum states (FQS) of interferometers with up to ten equal Josephson point junctions are characterized in the phase and current plane. Their symmetry properties are derived. Simple formulas are given to design interferometers being equivalent to uniformly distributed Josephson junctions.     

Activation of the fibrinogen binding site on platelets isolated from a patient with the Strasbourg I variant of Glanzmann's thrombasthenia

One proposed ligand binding site on platelet integrin alpha IIb beta 3 is the region of the beta 3 subunit encompassing amino acids 211-221. However, we recently showed that synthetic peptides corresponding to amino acids 211-221 inhibit fibrinogen binding to alpha IIb beta 3 by binding to alpha IIb beta 3 and not to fibrinogen. In this study, we show that AP6, a monoclonal antibody (MoAb) directed against amino acids 214-221 of beta 3, bound to immobilized active alpha IIb beta 3 but did not inhibit fibrinogen binding to the complex. We then determined whether nonfunctional alpha IIb beta 3 on platelets with a beta 3 Arg-214-->Trp mutation (Strasbourg I variant of Glanzmann's thrombasthenia or GTV) could be induced to aggregate after treatment with dithiothreitol (DTT). DTT has been shown to expose the fibrinogen receptor on normal platelets. DTT treatment of GTV platelets did result in the formation of the fibrinogen binding site as indicated by the binding of pI-55, an MoAb that only binds to the activated form of alpha IIb beta 3. Furthermore, DTT-treated GTV platelets aggregated in the presence of fibrinogen and divalent cations. This aggregation was inhibited by EDTA, RGDS, and the selective alpha IIb beta 3 antagonist, Ro 43-5054. These data show that Arg-214 of beta 3 is not required for fibrinogen binding or for platelet aggregation. However, this amino acid appears to be critical for the formation and for the maintenance of the correct tertiary structure of the fibrinogen binding site on alpha IIb beta 3.     

From nanoscale liquid spheres to anisotropic crystalline particles of tin: decomposition of decamethylstannocene in organic solvents

Routes are presented for synthesizing nano- and mesostructured β-tin particles in the form of monocrystalline spheres, cubes, and bars, as well as polycrystalline rods and needles, by the decomposition of decamethylstannocene in organic solvents under various conditions. The formation of the observed shapes is based on the presence of liquidlike and of partly crystalline droplets. These particle stages allow structure-determining processes such as entire coalescence, oriented superficial coalescence or superficial induced crystallization. Entire coalescence and oriented superficial coalescence take place in the absence of surfactants; the superficially induced crystallization occurs in the presence of ionic additives. The observed tin morphologies depend on the competition between droplet growth and crystallization behavior. The different tin particles are investigated by electron microscopy (SEM, TEM, HRTEM), selected area electron diffraction (SAED), and differential scanning calorimetry (DSC).     

Sense signal and word noise in a thin magnetic film memory with easy axis bias fields

In a thin magnetic film memory, an easy axis field due to the conducting surrounding of the cell is to be taken into account in order to evaluate the sense signal corresponding to a word pulse in the hard axis. For a simplified switching model, diagrams demonstrate the influence of the easy axis field on the sense pulse amplitude and width and the signal-to-word-noise ratios. Optimum word pulses yielding maximum signal-to-noise ratios are given. Finally, the calculated and measured sense pulse amplitudes are compared.     

A Theoretical Study of the Half-Sandwich Silicon(II) Cation [(Me<Subscript>5</Subscript>C<Subscript>5</Subscript>)Si]<Superscript>+</Superscript> and of the Cationic Complex [(Me<Subscript>5</Subscript>C<Subscript>5</Subscript>)Si (DME)]<Superscript>+</Superscript>

Ab-initio calculations have been performed for the half-sandwich cation [(Me₅C₅)Si]⁺ and its DME complex [(Me₅C₅)Si(DME)]⁺. For these cations, the ground state energies, the complexation energy, the frontier orbitals, the vertical singlet-triplet excitation energies, and the natural atomic charges have been calculated. In both cations, the “lone-pair” at silicon does not represent the HOMO. The nature of the weak dative O → Si bond can best be described in terms of electrostatic and attractive dispersion interactions. The DME coordination destabilizes the cluster orbitals and slightly enhances the positive charge at silicon.