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Extracellular growth factors signal to transcription factors via a limited number of cytoplasmic kinase cascades. It remains unclear how such cascades encode ligand identities and concentrations. In this paper, we use live-cell imaging and statistical modeling to study FOXO3, a transcription factor regulating diverse aspects of cellular physiology that is under combinatorial control. We show that FOXO3 nuclear-to-cytosolic translocation has two temporally distinct phases varying in magnitude with growth factor identity and cell type. These phases comprise synchronous translocation soon after ligand addition followed by an extended back-and-forth shuttling; this shuttling is pulsatile and does not have a characteristic frequency, unlike a simple oscillator. Early and late dynamics are differentially regulated by Akt and ERK and have low mutual information, potentially allowing the two phases to encode different information. In cancer cells in which ERK and Akt are dysregulated by oncogenic mutation, the diversity of states is lower.

Granular material is vibro-fluidized in N connected compartments. For sufficiently strong shaking the particles are statistically uniformly distributed over the compartments, but if the shaking intensity is lowered this uniform distribution gives way to a clustered state. The clustering transition is experimentally shown to be of 2nd order for N = 2 compartments and of 1st order for N ≥ 3. In particular, the latter is hysteretic, involves long-lived transient states, and exhibits a striking lack of time reversibility. In the strong shaking regime, a cluster breaks down very abruptly and in its further decay shows anomalous diffusion, with the length scale going as t 1/3 rather than the standard t 1/2. We focus upon the self-similar nature of this process. The observed phenomena are all accounted for within a flux model.

It is by now generally accepted that the recently discovered superconductor MgB2 is a superconductor with two energy gaps. Here we discuss how this happens and address some of its unusual implications. The anisotropy ratio of the upper critical field in MgB2 single crystals shows an unusual strong temperature dependence. Measurements of the microwave conductivity on MgB2 thin films have shown an anomalous coherence peak appearing at significantly lower temperatures than in conventional superconductors. We argue that both of these observations are natural consequences of the existence of the two gaps, if the special Fermi surface structure of MgB2 is taken into account. We also examine consequences for the expected intrinsic nonlinear microwave response in MgB2. Calculations including impurity scattering indicate that under certain circumstances impurity scattering might improve the microwave properties of this material.

We investigate the influence of a perpendicular magnetic field on the spectral and spin properties of a ballistic quasi-one-dimensional electron system with Rashba effect. The magnetic field strongly alters the spin-orbit induced modification to the subband structure when the magnetic length becomes comparable to the lateral confinement. A new subband-dependent energy splitting at k=0 is found which can be much larger than the Zeeman splitting. This is due to the breaking of a combined spin orbital-parity symmetry., Comment: 6 pages, 4 figures

The problem of identifying the pairing mechanism in high-T c superconductors is discussed. The pairing interaction in a superconductor cannot be measured directly by experiment, but can only be seen through its effects on different observable properties. These difficulties are discussed first for the conventional superconductors and it will be shown how the electron-phonon interaction can be identified as the pairing mechanism in this case using controlled approximations. For the high-T c superconductors the situation is much more difficult because of the complexity of these materials and the lack of accurate theories. Recent studies of the spinfluctuation mechanism within the FLEX-approximation are reviewed and it is shown that this mechanism has a number of features, which are qualitatively different from the conventional phonon mechanism, but have similarities with observations on the high-T c compounds.

We investigate the dynamical interplay between currents and electromagnetic fields in frequency-dependent transport through a single-channel quantum wire with an impurity potential in the presence of electron-electron interactions. We introduce and discuss a formalism which allows a self-consistent treatment of currents and electromagnetic fields., 4 pages

We investigate the nonlinear ac transport through a quantum wire with an impurity in the presence of finite range electron-electron interactions. We discuss the influence of the spatial shape of the ac electric field onto transport properties of the system and find that the scaling behavior of the occupation probability of the sidebands depends on the range of the voltage drop., 4 pages, ndes99.sty, 3 figures

The complex ac-response of a quasi-one dimensional electron system in the one-band approximation with an interaction potential of finite range is investigated. It is shown that linear response is exact for this model. The influence of the screening of the electric field is discussed. The complex absorptive conductance is analyzed in terms of resistive, capacitive and inductive behaviors.

The non-linear current-voltage characteristic of a tunnel junction between two Luttinger systems is calculated for an interaction with finite range. Coulomb blockade features are found. The dissipative resistance, the capacitance and the external impedance, which were introduced ad hoc in earlier theories, are obtained in terms of the electron-electron interaction. The frequency dependence of the impedance is given by the excitation spectrum of the electrons.

We show that the non-linear dc transport in a Luttinger liquid with interaction of finite range in the presence of an impurity is governed by a sum rule which causes the charging energy to vanish.

We study the subgap transport properties of a small capacitance normal metal-superconductor tunnel junction coupled to an external electromagnetic environment. Mesoscopic interference between the electrons in the normal metal strongly enhances the subgap conductance with decreasing bias voltage. On the other hand, quantum fluctuations of the environment destroy electronic phase coherence and suppress the subgap conductance at low bias (Coulomb blockade).The competition between charging effects and mesoscopic interference leads to a non-monotonic dependence of the differential subgap conductance on the applied bias voltage. This feature is pronounced, even if the coupling to the environment is weak and the charging energy is small., Comment: RevTeX, 4 pages, 4 eps figures, (tar,gzip,uuencode)

The low-temperature AC conductance of a one-dimensional electron system with a strong interaction of finite range is calculated by using linear response theory. The conductance factorizes into parts which depend on the internal properties of the system, and the external probe. For short-range interaction, the result resembles that for non-interacting electrons, but with the zero-frequency limit and the Fermi velocity renormalized by the interaction strength. For strong and long-range interaction, the conductance shows a peak that is related to charge-wave excitations. In this limit, the AC conductance can be simulated by a quantum capacitance and a quantum inductance.

The spectral properties of up to four interacting electrons confined within a quasi one--dimensional system of finite length are determined by numerical diagonalization including the spin degree of freedom. The ground state energy is investigated as a function of the electron number and of the system length. The limitations of a description in terms of a capacitance are demonstrated. The energetically lowest lying excitations are physically explained as vibrational and tunneling modes. The limits of a dilute, Wigner-type arrangement of the electrons, and a dense, more homogeneous charge distribution are discussed., Comment: 10 pages (excl. Figures), Figures added in POSTSCRIPT, LaTeX