We demonstrate the use of an ordinary white-light microscope for the study of the $q$-dependent dynamics of colloidal dispersions. Time series of digital video images are acquired in bright field with a fast camera, and image differences are Fourier analyzed as a function of the time delay between them. This allows for the characterization of the particle dynamics independent of whether or not they can be resolved individually. The characteristic times are measured in a wide range of wave vectors and the results are found to be in good agreement with the theoretically expected values for Brownian motion in a viscous medium.

Using a combination of density functional theory and recursive Green‘s functions techniques, we present a full description of a large scale sensor, accounting for disorder and different coverages. Here, we use this method to demonstrate the functionality of nitrogen-rich carbon nanotubes as ammonia sensors as an example. We show how the molecules one wishes to detect bind to the most relevant defects on the nanotube, describe how these interactions lead to changes in the electronic transport properties of each isolated defect, and demonstrate that there are significative resistance changes even in the presence of disorder, elucidating how a realistic nanosensor works.

We present the first measurements of the Berry phase in a superconducting Cooper pair pump. A fixed amount of Berry phase is accumulated to the quantum-mechanical ground state in each adiabatic pumping cycle, which is determined by measuring the charge passing through the device. The dynamic and geometric phases are identified and measured quantitatively from their different response when pumping in opposite directions. Our observations, in particular, the dependencies of the dynamic and geometric effects on the superconducting phase bias across the pump, agree with the basic theoretical model of coherent Cooper pair pumping.

The dynamics of water dimers was investigated at the single-molecule level by using a scanning tunneling microscope. The two molecules in a water dimer, bound on a Cu(110) surface at 6 K, were observed to exchange their roles as hydrogen-bond donor and acceptor via hydrogen-bond rearrangement. The interchange rate is $\sim 60$ times higher for $({\mathrm{H}}_2\mathrm{O}{)}_2$ than for $({\mathrm{D}}_2\mathrm{O}{)}_2$, suggesting that quantum tunneling is involved in the process. The interchange rate is enhanced upon excitation of the intermolecular mode that correlates with the reaction coordinate.

We report a study of colloidal suspensions of highly monodisperse semiflexible chiral rodlike viruses, denoted $fd$, in the range of high concentrations. Small angle x-ray scattering experiments reveal the existence of two hexagonal phases: the first one is crystalline and the second one is hexatic columnar, as shown by its short-range positional order. The suspension of rodlike viruses is the first experimental system showing the whole phase sequence with increasing particle concentration theoretically predicted for systems of hard rods, ranging from the chiral nematic via the smectic to columnar and crystalline phases.

The excitation of a high density of carriers in semiconductors can induce an order-to-disorder phase transition due to changes in the potential-energy landscape of the lattice. We report the first direct resolution of the structural details of this phenomenon in freestanding films of polycrystalline and (001)-oriented crystalline Si, using 200-fs electron pulses. At excitation levels greater than $\sim 6\%$ of the valence electron density, the crystalline structure of the lattice is lost in $<500\mathrm{fs}$, a time scale indicative of an electronically driven phase transition. We find that the relaxation process along the modified potential is not inertial but rather involves multiple scattering towards the disordered state.

We report low-temperature specific-heat studies on the single-crystalline ternary-iron silicide superconductor ${\mathrm{Lu}}_2{\mathrm{Fe}}_3{\mathrm{Si}}_5$ with $T_c=6.1\mathrm{K}$ down to $\sim T_c/20$. We confirm a reduced normalized jump in specific heat at $T_c$, and find that the specific heat divided by temperature $C/T$ shows a sudden drop at $\sim T_c/5$ and goes to zero with further decreasing temperature. These results indicate the presence of two distinct superconducting gaps in ${\mathrm{Lu}}_2{\mathrm{Fe}}_3{\mathrm{Si}}_5$, similar to the typical two-gap superconductor ${\mathrm{MgB}}_2$. We also report Hall coefficients, band structure calculations, and the anisotropy of upper critical fields for ${\mathrm{Lu}}_2{\mathrm{Fe}}_3{\mathrm{Si}}_5$, which support the anisotropic multiband nature and reinforce the existence of two superconducting gaps in ${\mathrm{Lu}}_2{\mathrm{Fe}}_3{\mathrm{Si}}_5$.

When a classical black hole is perturbed, its relaxation is governed by a set of quasinormal modes with complex frequencies $\omega ={\omega }_R+i{\omega }_I$. We show that this behavior is the same as that of damped harmonic oscillators whose real frequencies are $({\omega }_R^2+{\omega }_I^2{)}^{1/2}$, rather than simply ${\omega }_R$. Since, for highly excited modes, ${\omega }_I\gg {\omega }_R$, this observation changes drastically the physical understanding of the black hole spectrum and forces a reexamination of various results in the literature. In particular, adapting a derivation by Hod, we find that the area of the horizon of a Schwarzschild black hole is quantized in units $\Delta A=8\pi l_{\mathrm{Pl}}^2$, in contrast with the original result $\Delta A=4\log (3)l_{\mathrm{Pl}}^2$.

Enantiomers, or stereoisomers, have crystal structures that are mirror images of each other and are thus handed, like our right and left hands. The physical properties of enantiomers are identical except for optical activity, which rotates linearly polarized light by equal amounts but in opposite directions. While conventional x-ray Bragg diffraction can determine crystal structures, it does not distinguish between right- and left-handed crystals. We show resonant Bragg diffraction using circularly polarized x rays reveals the handedness of crystals by coupling x-ray helicity to a crystal screw axis. The intensity of resonantly allowed reflection of $\alpha$-quartz is well described by an admixture of a parity-even and a parity-odd process. Our results are of general importance and demonstrate a new method to directly study chiral motifs in structures that include biomaterials, liquid crystals, magnets, multiferroics, etc.

We present an extensive computer simulation study of structure formation in amphiphilic block copolymer solutions after a quench from a homogeneous state. By using a mesoscopic field-based simulation method, we are able to access time scales in the range of a second. A “phase diagram” of final structures is mapped out as a function of the concentration and solvent philicity of the copolymers. A rich spectrum of structures is observed, ranging from spherical and rodlike micelles and vesicles to toroidal and net-cage micelles. The dynamical pathways leading to these structures are analyzed in detail, and possible ways to control the structures are discussed briefly.

We present an experimental study of the elastic properties of a superhydrophobic surface in the Cassie regime, due to the gas bubbles trapped at the liquid-solid interface. We use a surface force apparatus to measure the force response to an oscillating drainage flow between a sphere and the surface. We show that the force response allows to determine the surface elasticity without contact, using the liquid film as a probe. The elasticity of the bubble mattress is dominated by the meniscii stiffness, and its determination enables us to probe the shape of these meniscii. Another effect of surface elasticity is to decrease the viscous friction. We show that this effect can be wrongly attributed to rate dependant boundary slippage if elastohydrodynamics is not taken into account.

We demonstrate the feasibility of time-resolved diffuse reflectance measurements at small source-detector separations using a single-photon avalanche diode operated in time-gated mode. Photon time distributions at an interfiber distance of 2 mm were obtained on a homogeneous tissue phantom with a dynamic range of ${10}^6$ and collecting photons at arrival times up to 4 ns. Moreover, we were able to detect a local inhomogeneity deeply buried within a diffusive medium with better spatial resolution, higher signal intensity, and same contrast of a larger (20 mm) interfiber distance. Finally, the proposed approach proved valuable to detect in vivo a task-related brain activation.

A measurement using a one-electron quantum cyclotron gives the electron magnetic moment in Bohr magnetons, $g/2=1.00115965218073(28)$ [0.28 ppt], with an uncertainty 2.7 and 15 times smaller than for previous measurements in 2006 and 1987. The electron is used as a magnetometer to allow line shape statistics to accumulate, and its spontaneous emission rate determines the correction for its interaction with a cylindrical trap cavity. The new measurement and QED theory determine the fine structure constant, with ${\alpha }^{-1}=137.035999084(51)$ [0.37 ppb], and an uncertainty 20 times smaller than for any independent determination of $\alpha$.

We search for the radiative penguin decays $B_s^0\to \varphi \gamma$ and $B_s^0\to \gamma \gamma$ in a $23.6{\mathrm{fb}}^{-1}$ data sample collected at the ${\rm Y}(5S)$ resonance with the Belle detector at the KEKB $e^{+}{e}^{-}$ asymmetric-energy collider. We observe for the first time a radiative penguin decay of the $B_s^0$ meson in the $B_s^0\to \varphi \gamma$ mode and we measure $\mathcal{B}(B_s^0\to \varphi \gamma )=\mathbf{(}{57}_{-15}^{+18}(\mathrm{stat}{)}_{-11}^{+12}(\mathrm{syst})\mathbf{)}\times {10}^{-6}$. No significant $B_s^0\to \gamma \gamma$ signal is observed and we set a 90% confidence level upper limit of $\mathcal{B}(B_s^0\to \gamma \gamma )<8.7\times {10}^{-6}$.

We prove that the 2D Ising model is complete in the sense that the partition function of any classical $q$-state spin model (on an arbitrary graph) can be expressed as a special instance of the partition function of a 2D Ising model with complex inhomogeneous couplings and external fields. In the case where the original model is an Ising or Potts-type model, we find that the corresponding 2D square lattice requires only polynomially more spins with respect to the original one, and we give a constructive method to map such models to the 2D Ising model. For more general models the overhead in system size may be exponential. The results are established by connecting classical spin models with measurement-based quantum computation and invoking the universality of the 2D cluster states.

We report the first observation of $e^{+}{e}^{-}\to {\rm Y}(1S){\pi }^{+}{\pi }^{-}$, ${\rm Y}(2S){\pi }^{+}{\pi }^{-}$, and first evidence for $e^{+}{e}^{-}\to {\rm Y}(3S){\pi }^{+}{\pi }^{-}$, ${\rm Y}(1S)K^{+}{K}^{-}$, near the peak of the ${\rm Y}(5S)$ resonance at $\sqrt{s}\sim 10.87\mathrm{GeV}$. The results are based on a data sample of $21.7{\mathrm{fb}}^{-1}$ collected with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. Attributing the signals to the ${\rm Y}(5S)$ resonance, the partial widths $\Gamma \mathbf{(}{\rm Y}(5S)\to {\rm Y}(1S){\pi }^{+}{\pi }^{-}\mathbf{)}=0.59\pm 0.04(\mathrm{stat})\pm 0.09(\mathrm{syst})\mathrm{MeV}$ and $\Gamma \mathbf{(}{\rm Y}(5S)\to {\rm Y}(2S){\pi }^{+}{\pi }^{-}\mathbf{)}=0.85\pm 0.07(\mathrm{stat})\pm 0.16(\mathrm{syst})\mathrm{MeV}$ are obtained from the observed cross sections. These values exceed by more than 2 orders of magnitude the previously measured partial widths for dipion transitions between lower ${\rm Y}$ resonances.

Laser-based angle-resolved photoemission measurements with superhigh resolution have been carried out on an optimally doped ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_8$ high temperature superconductor. New high energy features at $\sim 115\mathrm{meV}$ and $\sim 150\mathrm{meV}$, in addition to the prominent $\sim 70\mathrm{meV}$ one, are found to develop in the nodal electron self-energy in the superconducting state. These high energy features, which cannot be attributed to electron coupling with single phonon or magnetic resonance mode, point to the existence of a new form of electron coupling in high temperature superconductors.

We report on angle-resolved photoemission studies of the electronic $\pi$ states of high-quality epitaxial graphene layers on a Ni(111) surface. In this system the electron binding energy of the $\pi$ states shows a strong dependence on the magnetization reversal of the Ni film. The observed extraordinarily large energy shift up to 225 meV of the graphene-derived $\pi$ band peak position for opposite magnetization directions is attributed to a manifestation of the Rashba interaction between spin-polarized electrons in the $\pi$ band and the large effective electric field at the graphene/Ni interface. Our findings show that an electron spin in the graphene layer can be manipulated in a controlled way and have important implications for graphene-based spintronic devices.

The High Resolution Fly’s Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes’ measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of $6\times {10}^{19}\mathrm{eV}$, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of $4\times {10}^{18}\mathrm{eV}$. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.

The time scale of proton transfer between ${\mathrm{H}}_2\mathrm{O}$ and OH adsorbed on a Pt(111) surface was determined by a combination of laser-induced thermal desorption (LITD) and microscale x-ray photoelectron spectroscopy (micro-XPS). The patterned distribution $\mathrm{OH}+{\mathrm{H}}_2\mathrm{O}/{\mathrm{H}}_2\mathrm{O}/\mathrm{OH}+{\mathrm{H}}_2\mathrm{O}$ was initially prepared on the Pt(111) surface by the LITD method and the time evolution of the spatial distribution of ${\mathrm{H}}_2\mathrm{O}$ and OH was observed by the micro-XPS technique. From quantitative analyses based on a diffusion equation, we found two proton-transfer pathways with different time scales of $5.2\pm 0.9\mathrm{ns}$ and $48\pm 12\mathrm{ns}$ at 140 K, which were attributed to direct proton transfer to the neighbor site and ${\mathrm{H}}_3{\mathrm{O}}^{+}$-mediated transfer to the next-nearest site, respectively.