Electron scattering in intrananotube quantum dots.

Intratube quantum dots showing particle-in-a-box-like states with level spacings up to 200 meV are realized in metallic single-walled carbon nanotubes by means of low dose medium energy Ar(+) irradiation. Fourier-transform scanning tunneling spectroscopy compared to results of a Fabry-Perot electron resonator model yields clear signatures for inter- and intravalley scattering of electrons confined between consecutive irradiation-induced defects (interdefects distance

Electronic and atomic shell structure in aluminium nanowires.

We report experiments on aluminium nanowires in ultra-high vacuum at room temperature that reveal a periodic spectrum of exceptionally stable structures. Two 'magic' series of stable structures are observed: at low conductance, the formation of stable nanowires is governed by electronic shell effects whereas for larger contacts atomic packing dominates. The crossover between the two regimes is found to be smooth. A detailed comparison of the experimental results to a theoretical stability analysis indicates that, while the main features of the observed electron-shell structure are similar to those of alkali and noble metals, a sequence of extremely stable wires plays a unique role in aluminium. This series appears isolated in conductance histograms and can be attributed to 'superdeformed' non-axisymmetric nanowires.

Zener enhancement of quantum tunneling in a two-level superconducting circuit.

We have investigated the macroscopic quantum tunneling (MQT) of the phase across a Josephson junction embedded in a superconducting circuit. This system is equivalent to a spin 1/2 particle in a potential energy well. The MQT escape rate of such a particle was recently predicted to be strongly modified when a crossing of its inner Zeeman levels occurs while tunneling. In this regime, we observe a significant enhancement of the MQT rate and compare it to theory.

Coulomb drag shot noise in coupled Luttinger liquids.

Coulomb drag shot noise has been studied theoretically for 1D interacting electron systems, which are realized, e.g., in single-wall nanotubes. We show that under adiabatic coupling to external leads, the Coulomb drag shot noise of two coupled or crossed nanotubes contains surprising effects, in particular, a complete locking of the shot noise in the tubes. In contrast to Coulomb drag of the average current, the noise locking is based on a symmetry of the underlying Hamiltonian and is not limited to asymptotically small energy scales.

Coulomb blockade of tunneling between disordered conductors.

We determine the zero-bias anomaly of the conductance of tunnel junctions by an approach unifying the conventional Coulomb blockade theory for ultrasmall junctions with the diffusive anomalies in disordered conductors. Both electron-electron interactions within the electrodes and electron-hole interactions between the electrodes are taken into account nonperturbatively. Explicit results are given for one- and two-dimensional junctions, and the crossover to ultrasmall junctions is discussed.

Strong friction limit in quantum mechanics: the quantum Smoluchowski equation.

For a quantum system coupled to a heat bath environment the strong friction limit is studied starting from the exact path integral formulation. Generalizing the classical Smoluchowski limit to low temperatures, a time evolution equation for the position distribution is derived and the strong role of quantum fluctuations in this limit is revealed.

Semiclassical time evolution of the density matrix and tunneling

The time dependent density matrix of a system with potential barrier is studied using path integrals. The characterization of the initial state, which is assumed to be restricted to one side of the barrier, and the time evolution of the density matrix lead to a threefold path integral which is evaluated in the semiclassical limit. The semiclassical trajectories are found to move in the complex coordinate plane and barrier penetration only arises due to fluctuations. Both the form of the semiclassical paths and the relevant fluctuations change significantly as a function of temperature. The semiclassical analysis leads to a detailed picture of barrier penetration in the real time domain and the changeover from thermal activation to quantum tunneling. Deep tunneling is associated with quasizero modes in the fluctuation spectrum about the semiclassical orbits in the long time limit. The connection between this real time description of tunneling and the standard imaginary time instanton approach is established. Specific results are given for a double well potential and an Eckart barrier.

Current bistability and hysteresis in strongly correlated quantum wires

Nonequilibrium transport properties are determined exactly for an adiabatically contacted single-channel quantum wire containing one impurity. Employing the Luttinger liquid model with interaction parameter g, for very strong interactions g less, similar0.2, and sufficiently low temperatures, we find an S-shaped current-voltage relation. The unstable branch with negative differential conductance gives rise to current oscillations and hysteretic effects. These nonperturbative and nonlinear features appear only out of equilibrium.

Prognostic value of the histopathologic private characteristics of breast cancer in patients with no axillary lymph node involvement.

The biological behavior of breast cancer supports the impression that it is often a systemic disease which can recur many years after the treatment of the local lesion. Since 35% of patients without axillary nodal metastasis will have recurrence of the disease after mastectomy, prognostic indicators are necessary to identify the high-risk patients to allow a more rational adjuvant therapy. We studied the prognostic value of fatty tissue invasion, perineural involvement and lymphatic and venous peritumoral embolization in T2NOMO primary breast carcinomas. Fifty-three patients were studied after initial treatment (only Halsted mastectomy). They were divided into two groups: A (control), with 25 patients with 15 years of survival without clinical and laboratory evidence of metastasis, and group B, with 28 patients who developed metastasis after initial treatment. The results were analysed by the chi-square test (p < 0.05). The fatty tissue invasion was identified in 56.0% and 78.5% in the A and B groups respectively, while venous embolization was only detected in 8.0% of the group A tumors and in 10.7% of those in group B. Neither showed significant variation when analyzed according to the chi-square test. Lymphatic embolization and perineural involvement were found respectively in 36.0% and 40.0% in the group A tumors and in 67.8% and 71.4% of those in group B, exhibiting a significant statistical variation. When analysing the histopathological characteristics in the pre- and post-menopausal patients, the chi-square test disclosed that lymphatic embolization and perineural involvement had a significantly higher incidence only in premenopausal patients in group B.