Regge oscillations in integral cross sections for proton impact on atomic hydrogen

The integral cross sections for elastic scattering and spin exchange for proton impact on atomic hydrogen show several oscillations in the energy range 0.01-1.0 eV that cannot be associated with resonances or the glory effect. A complex angular momentum analysis using computed Regge trajectories shows that each peak of the oscillatory structure is predominantly associated with at most three trajectories. In this way, the peaks are related to the L=0 bound states of H+ 2. The complex angular momentum theory for integral cross sections that we introduce shows that such oscillations are a general feature of potential scattering.     

Anomalous diffusion in living yeast cells

The viscoelastic properties of the cytoplasm of living yeast cells were investigated by studying the motion of lipid granules naturally occurring in the cytoplasm. A large frequency range of observation was obtained by a combination of video-based and laser-based tracking methods. At time scales from 10(-4) to 10(2) s, the granules typically perform subdiffusive motion with characteristics different from previous measurements in living cells. This subdiffusive behavior is thought to be due to the presence of polymer networks and membranous structures in the cytoplasm. Consistent with this hypothesis, we observe that the motion becomes less subdiffusive upon actin disruption.     

Sodium pyroxene NaTiSi2O6: possible haldane spin-1 chain system

Using a density functional approach, we study the structural and magnetic properties of the pyrox-ene compound NaTiSi2O6. While all previous workers are taking that NaTiSi2O6 is a quasi-one-dimensional S=1/2 system, our theoretical results indicate that this is a Haldane S=1 chain compound below the phase transition at 210 K. A good agreement is obtained between the calculated and the measured Ti-Ti distances in the dimerized low temperature phase. We present a simple explanation of the flow of the unusual phase transition which is taking place in this compound.     

Magnetic-field dependence of the anomalous noise behavior in a two-dimensional electron system in silicon

Studies of low-frequency resistance noise show that the dramatic change in the dynamics of the two-dimensional electron system (2DES) in Si that occurs near the metal-insulator transition (MIT) persists in high parallel magnetic fields B such that the 2DES is fully spin polarized. This strongly suggests that charge, as opposed to spin, degrees of freedom are responsible for this effect. In the metallic phase, however, noise is suppressed by a parallel B, pointing to the role of spins. At low B, the temperature dependence of conductivity in the metallic phase provides evidence for a MIT.     

Electron-electron interaction in strong electromagnetic fields: the two-electron contribution to the ground-state energy in He-like uranium

Radiative recombination transitions into the ground state of cooled bare and hydrogenlike uranium ions were measured at the storage ring ESR. By comparing the corresponding x-ray centroid energies, this technique allows for a direct measurement of the electron-electron contribution to the ionization potential in the heaviest He-like ions. For the two-electron contribution to the ionization potential of He-like uranium we obtain a value of 2248+/-9 eV. This represents the most accurate determination of two-electron effects in the domain of high-Z He-like ions, and the accuracy reaches already the size of the specific two-electron radiative QED corrections.     

Photoinduction of surface-relief gratings during all-optical poling of polymer films

Using the all-optical poling method, we observed the formation of a surface-relief grating (SRG) in an amorphous polymer film containing azo dye molecules in side chain positions. The experiment consists of a seeding-type process. We used a recently described experimental setup that permits a periodic nonlinear pattern to be produced by the index dispersion of glass. The particular configuration permits photoinduced translation diffusion of the azo chromophores to be observed as the origin of the SRG formation. Analyses of the gratings recorded by use of s (TE) and p (TM) polarization of the writing beams are conducted by atomic-force microscopy. The effect is attributed to mass transport from regions of high isomerization activity to regions of lower activity.     

Microwave assisted IMDAF# reaction: microwave irradiation applied with success to cycloaddition reaction of N-propargyl-N-p-tolyl-N-2-furfurylamines

The new tertiary furfurylamine with triple bond as a dienophylic part i.e. N-(5-methyl-2-furfuryl)-N-prop-2-ynyl-p-toluidine (1) was prepared and the intramolecular Diels-Alder reaction of the amine (1) was performed under microwave irradiation conditions and by heating a benzene solution of the amine under nitrogen. Comparing the results of the usual thermal and the MAOS reaction, we confirmed our expectations that MAOS could promote the outcome of IMDA reaction of the suitably N-substituted tertiary 2-furfuryl-amines. In the present example, N-p-tolyl-5-methyl-5,7a-dihydro-5,7a-epoxyisoindoline was obtained in much better yield and of higher purity.     

All-optical transistor action with bistable switching in a photonic crystal cross-waveguide geometry

We demonstrate all-optical switching action in a nonlinear photonic crystal cross-waveguide geometry with instantaneous Kerr nonlinearity, in which the transmission of a signal can be reversibly switched on and off by a control input. Our geometry accomplishes both spatial and spectral separation between the signal and the control in the nonlinear regime. The device occupies a small footprint of a few micrometers squared and requires only a few milliwatts of power at a 10-Gbit/s switching rate by use of Kerr nonlinearity in AlGaAs below half the electronic bandgap. We also show that the switching dynamics, as revealed by both coupled-mode theory and finite-difference time domain simulations, exhibits collective behavior that can be exploited to generate high-contrast logic levels and all-optical memory.     

Pseudogap Fermi-Bose Kondo model

We consider a magnetic impurity coupled to both fermionic quasiparticles with a pseudogap density of states and bosonic spin fluctuations. Using renormalization group and large-N calculations we investigate the phase diagram of the resulting Fermi-Bose Kondo model. We show that the Kondo temperature is strongly reduced by low-energy spin fluctuations, and make connections to experiments in cuprate superconductors. Furthermore, we derive an exact exponent for the critical behavior of the conduction electron T matrix, and propose our findings to be relevant for certain scenarios of local quantum criticality in heavy-fermion metals.