Behavior of self-propelled acetone droplets in a Leidenfrost state on liquid substrates

It is demonstrated that non-coalescent droplets of acetone can be formed on liquid substrates. The fluid flows around and in an acetone droplet hovering on water are recorded to shed light on the mechanisms which might lead to non-coalescence. For sufficiently low impact velocities, droplets undergo a damped oscillation on the surface of the liquid substrate but at higher velocities clean bounce-off occurs. Comparisons of experimentally observed static configurations of floating droplets to predictions from a theoretical model for a small non-wetting rigid sphere resting on a liquid substrate are made and a tentative strategy for determining the thickness of the vapor layer under a small droplet on a liquid is proposed. This strategy is based on the notion of effective surface tension. The droplets show self-propulsion in straight line trajectories in a manner which can be ascribed to a Marangoni effect. Surprisingly, self-propelled droplets can become immersed beneath the undisturbed water surface. This phenomenon is reasoned to be drag-inducing and might provide a basis for refining observations in previous work

High-Q bismuth silicate nonlinear glass microsphere resonators

The fabrication and characterization of a bismuth-silicate glass microsphere resonator has been demonstrated. At wavelengths near 1550 nm, high-modes can be efficiently excited in a 179 µm diameter bismuth-silicate glass microsphere via evanescent coupling using a tapered silica fiber with a waist diameter of circa 2 µm. Resonances with Q-factors as high as were observed. The dependence of the spectral response on variations in the input power level was studied in detail to gain an insight into power-dependent thermal resonance shifts. Because of their high nonlinearity and high- factors, bismuth-silicate glass microspheres offer the potential for robustly assembled fully integrated all-optical switching devices

Glassy dynamics in thin films of polystyrene

Glassy dynamics was investigated for thin films of atactic polystyrene by complex electric capacitance measurements using dielectric relaxation spectroscopy. During the isothermal aging process the real part of the electric capacitance increased with time, whereas the imaginary part decreased with time. It follows that the aging time dependences of real and imaginary parts of the electric capacitance were primarily associated with change in volume (film thickness) and dielectric permittivity, respectively. Further, dielectric permittivity showed memory and rejuvenation effects in a similar manner to those observed for poly(methyl methacrylate) thin films. On the other hand, volume did not show a strong rejuvenation effect.Comment: 7 pages, 7 figures. Phys. Rev. E (in press

Relative Burial Depths of Nakhlites: An Update

Nakhlites are augite-rich cumulate rocks with variable amounts of olivine and groundmass plus minor Fe, Ti oxides [e.g., 1]. Our previous studies revealed that nakhlites showed correlated petrography and mineralogy that could be explained by different locations (burial depths) in a common cooling cumulate pile [e.g., 2]. We so far analyzed six of the seven currently known nakhlites, Nakhla (Nak), Governador Valadares (GV), Lafayette (Laf), NWA817, Y000593 (Y) and MIL03346 (MIL) [e.g., 2,3] and calculated cooling rates of four nakhlites (Nak, GV, Laf, and NWA817) by using chemical zoning of olivine [e.g., 4]. In this abstract, we complete our examination of petrographic and mineralogical variation of all currently known nakhlites by adding petrology and mineralogy of NWA998. We also report results of cooling calculations for Y, MIL and NWA998. Then, we update our model of the nakhlite igneous body in terms of relative burial depth of each sample

Doping dependence of the exchange energies in bilayer manganites: Role of orbital degrees of freedom

Recently, an intriguing doping dependence of the exchange energies in the bilayer manganites $La_{2-2x}Sr_{1+2x}Mn_2O_7$ has been observed in the neutron scattering experiments. The intra-layer exchange only weakly changed with doping while the inter-layer one drastically decreased. Here we propose a theory which accounts for these experimental findings. We argue, that the observed striking doping dependence of the exchange energies can be attributed to the evaluation of the orbital level splitting with doping. The latter is handled by the interplay between Jahn-Teller effect (supporting an axial orbital) and the orbital anisotropy of the electronic band in the bilayer structure (promoting an in-plane orbital), which is monitored by the Coulomb repulsion. The presented theory, while being a mean-field type, describes well the experimental data and also gives the estimates of the several interesting energy scales involved in the problem.Comment: Added references, corrected typos. To appear in Phys. Rev.

Production and trapping of carbon clusters for absolute mass measurements at ISOLTRAP

Singly-charged carbon clusters C/sub n//sup +/ (n >or= 1) have been produced by laser-induced desorption and fragmentation of C/sub 60/ fullerenes and have been injected into and stored in the Penning trap system of the ISOLTRAP mass spectrometer at ISOLDE/CERN. The present study is the first step to extend the until now direct mass measurements at ISOLTRAP to absolute mass measurements by using clusters of /sup 12/C. (10 refs)

Beam-Based Alignment of the NuMI Target Station Components at FNAL

The Neutrinos at the Main Injector (NuMI) facility is a conventional horn-focused neutrino beam which produces muon neutrinos from a beam of mesons directed into a long evacuated decay volume. The relative alignment of the primary proton beam, target, and focusing horns affects the neutrino energy spectrum delivered to experiments. This paper describes a check of the alignment of these components using the proton beam.Comment: higher resolution figures available on Fermilab Preprint Server (see SPIRES entry), accepted for publication in Nucl. Instr. and Meth.

Absolute photoionization cross section measurements of the Kr I-isoelectronic sequence

Photoionization spectra have been recorded in the 4s, 4p and 3d resonance regions for the Kr Iisoelectronic sequence using both the dual laser produced plasma technique (at DCU) to produce photoabsorption spectra, and the merged ion beam and synchrotron radiation technique (at ASTRID) to measure absolute photoionization cross sections. Profile parameters are compared for the 4s − np resonances of Rb+ and Sr2+. Many new 4p " ns, md transitions are identified with the aid of Hartree-Fock calculations, and consistent quantum defects are observed for the various ns and md Rydberg series. Absolute single and double photoionization cross sections recorded in the 3d region for Rb+ and Sr2+ ions show preferential decay via double photoionization. This is only the second report where both the DLP technique and the merged beam technique have been used simultaneously to record photoionization spectra, and the advantages of both techniques (i.e. better resolution in the case of DLP and values for absolute photoionization cross sections in the case of the merged beam technique) are highlighted

``Flux'' state in double exchange model

We study the ground state properties of the double-exchange systems. The phase factor of the hopping matrix elements arises from $t_{2g}$ spin texture in two or more dimensions. A novel ``flux'' state is stabilized against the canted antiferromagnetic and spiral spin states. In a certain range of hole doping, the phase separation occurs between the ``flux'' state and antiferromagnetic states. Constructing a trial state which provides the rigorous upper bound on the ground state, we show that the metallic canted antiferromagnetic state is not stable in the double exchange model.Comment: REVTEX, 8 pages and 4 PS figure