Charge and momentum transfer in supercooled melts: Why should their relaxation times differ?

The steady state values of the viscosity and the intrinsic ionic-conductivity of quenched melts are computed, in terms of independently measurable quantities. The frequency dependence of the ac dielectric response is estimated. The discrepancy between the corresponding characteristic relaxation times is only apparent; it does not imply distinct mechanisms, but stems from the intrinsic barrier distribution for $\alpha$-relaxation in supercooled fluids and glasses. This type of intrinsic ``decoupling'' is argued not to exceed four orders in magnitude, for known glassformers. We explain the origin of the discrepancy between the stretching exponent $\beta$, as extracted from $\epsilon(\omega)$ and the dielectric modulus data. The actual width of the barrier distribution always grows with lowering the temperature. The contrary is an artifact of the large contribution of the dc-conductivity component to the modulus data. The methodology allows one to single out other contributions to the conductivity, as in ``superionic'' liquids or when charge carriers are delocalized, implying that in those systems, charge transfer does not require structural reconfiguration.Comment: submitted to J Chem Phy

Analytic Solutions to the Constraint Equation for a Force-Free Magnetosphere around a Kerr Black Hole

The Blandford-Znajek constraint equation for a stationary, axisymmetric black-hole force-free magnetosphere is cast in a 3+1 absolute space and time formulation, following Komissarov (2004). We derive an analytic solution for fields and currents to the constraint equation in the far-field limit that satisfies the Znajek condition at the event horizon. This solution generalizes the Blandford-Znajek monopole solution for a slowly rotating black hole to black holes with arbitrary angular momentum. Energy and angular momentum extraction through this solution occurs mostly along the equatorial plane. We also present a nonphysical, reverse jet-like solution.Comment: 6 pages, accepted for publication in Ap

Inter-band magnetoplasmons in mono- and bi-layer graphene

Collective excitations spectrum of Dirac electrons in mono and bilayer graphene in the presence of a uniform magnetic field is investigated. Analytical results for inter-Landau band plasmon spectrum within the self-consistent-field approach are obtained. SdH type oscillations that are a monotonic function of the magnetic field are observed in the plasmon spectrum of both mono- and bi-layer graphene systems. The results presented are also compared with those obtained in conventional 2DEG. The chiral nature of the quasiparticles in mono and bilayer graphene system results in the observation of $\pi$ and $2\pi$ Berry's phase in the SdH- type oscillations in the plasmon spectrum.Comment: 9 pages, 2 figure

The Influence of Formulation, Buffering, pH and Divalent Cations on the Activity of Endothall on Hydrilla.

Endothall has been used as an aquatic herbicide for more than 40 years and provides very effective weed control of many weeds. Early research regarding the mechanism-of-action of endothall contradicts the symptomology normally associated with the product. Recent studies suggest endothall is a respiratory toxin but the mechanism-of-action remains unknown. To further elucidate the activity of endothall, several endothall formulations were evaluated for their effects on ion leakage, oxygen consumption and photosynthetic oxygen evolution from hydrilla shoot tips. The influence of pH, buffering and divalent cations was also evaluated. (PDF contains 6 pages.

J Fluorescence

The scope of this paper is to illustrate the need for an improved quality assurance in fluorometry. For this purpose, instrumental sources of error and their influences on the reliability and comparability of fluorescence data are highlighted for frequently used photoluminescence techniques ranging from conventional macro- and microfluorometry over fluorescence microscopy and flow cytometry to microarray technology as well as in vivo fluorescence imaging. Particularly, the need for and requirements on fluorescence standards for the characterization and performance validation of fluorescence instruments, to enhance the comparability of fluorescence data, and to enable quantitative fluorescence analysis are discussed. Special emphasis is dedicated to spectral fluorescence standards and fluorescence intensity standards

The effect of overconfidence and underconfidence on consumer value

Although the effect of knowledge miscalibration (i.e., the inaccuracy in subjective knowledge relative to objective knowledge) on consumer purchase decisions has been investigated, its effect in the usage stage of consumption is little understood. This paper examines the effect of knowledge miscalibration in terms of both overconfidence (i.e., when subjective knowledge is inflated) and underconfidence (i.e., when subjective knowledge is deflated) on the dimensions of consumer value (i.e., efficiency, excellence, play and aesthetics). We make the case that overconfidence and underconfidence should be treated separately as they trigger different consumption consequences. Several hypotheses are tested through two studies: a co-variance based study (Study 1) and an experimental study (Study 2). In Study 1, overconfidence and underconfidence are measured, while in Study 2 they are experimentally manipulated. Findings of both studies show that underconfidence negatively influences efficiency, excellence and aesthetics, and overconfidence negatively influences play. Also, Study 1 finds a negative effect of underconfidence on play and Study 2 finds a negative effect of overconfidence on excellence and aesthetics. Findings reveal that knowledge miscalibration negatively impacts consumers’ usage experiences. This implies that in designing product or service experiences, suppliers benefit from ensuring that consumers achieve a reduced level of knowledge miscalibration

Skyrme Crystal In A Two-Dimensional Electron Gas

The ground state of a two-dimensional electron gas at Landau level filling factors near $\nu =1$ is a Skyrme crystal with long range order in the positions and orientations of the topologically and electrically charged elementary excitations of the $\nu=1$ ferromagnetic ground state. The lowest energy Skyrme crystal is a square lattice with opposing postures for topological excitations on opposite sublattices. The filling factor dependence of the electron spin-polarization, calculated for the square lattice Skyrme crystal, is in excellent agreement with recent experiments.Comment: 3 pages, latex, 3 figures available upon request from [email protected]

From electrons to Janskys: Full stokes polarized radiative transfer in 3D relativistic particle-in-cell jet simulations

The underlying plasma composition of relativistic extragalactic jets remains largely unknown. Relativistic magnetohydrodynamic (RMHD) models are able to reproduce many of the observed macroscopic features of these outflows. The nonthermal synchrotron emission detected by very long baseline interferometric (VLBI) arrays, however, is a by-product of the kinetic-scale physics occurring within the jet, physics that is not modeled directly in most RMHD codes. This paper attempts to discern the radiative differences between distinct plasma compositions within relativistic jets using small-scale 3D relativistic particle-in-cell (PIC) simulations. We generate full Stokes imaging of two PIC jet simulations, one in which the jet is composed of an electron-proton ($e^{-}$-$p^{+}$) plasma (i.e., a normal plasma jet), and the other in which the jet is composed of an electron-positron ($e^{-}$-$e^{+}$) plasma (i.e., a pair plasma jet). We examined the differences in the morphology and intensity of the linear polarization (LP) and circular polarization (CP) emanating from these two jet simulations. We find that the fractional level of CP emanating from the $e^{-}$-$p^{+}$ plasma jet is orders of magnitude larger than the level emanating from an $e^{-}$-$e^{+}$ plasma jet of a similar speed and magnetic field strength. In addition, we find that the morphology of both the linearly and circularly polarized synchrotron emission is distinct between the two jet compositions. We also demonstrate the importance of slow-light interpolation and we highlight the effect that a finite light-crossing time has on the resultant polarization when ray-tracing through relativistic plasma.Comment: 21 pages, 13 figures; accepted for publication in A&

Anomalous Fisher-like zeros for the canonical partition function of noninteracting fermions

Noninteracting fermions, placed in a system with a continuous density of states, may have zeros in the $N$-fermion canonical partition function on the positive real $\beta$ axis (or very close to it), even for a small number of particles. This results in a singular free energy, and instability in other thermal properties of the system. In the context of trapped fermions in a harmonic oscillator, these zeros are shown to be unphysical. By contrast, similar bosonic calculations with continuous density of states yield sensible results.Noninteracting fermions, placed in a system with a continuous density of states yield sensible results.Comment: 5 pages and 5 figure

Exact results for interacting electrons in high Landau levels

We study a two-dimensional electron system in a magnetic field with a fermion hardcore interaction and without disorder. Projecting the Hamiltonian onto the n-th Landau level, we show that the Hartree-Fock theory is exact in the limit n \rightarrow \infty, for the high temperature, uniform density phase of an infinite system; for a finite-size system, it is exact at all temperatures. In addition, we show that a charge-density wave arises below a transition temperature T_t. Using Landau theory, we construct a phase diagram which contains both unidirectional and triangular charge-density wave phases. We discuss the unidirectional charge-density wave at zero temperature and argue that quantum fluctuations are unimportant in the large-n limit. Finally, we discuss the accuracy of the Hartree-Fock approximation for potentials with a nonzero range such as the Coulomb interaction.Comment: RevTex, 12 pages with figures included in same file; to appear in Physical Review