Effects of mutual excitations in the fusion of carbon isotopes

Fusion data for $^{13}$C+$^{13}$C, $^{12}$C+$^{13}$C and $^{12}$C+$^{12}$C are analyzed by coupled-channels calculations that are based on the M3Y+repulsion, double-folding potential. The fusion is determined by ingoing-wave-boundary conditions (IWBC) that are imposed at the minimum of the pocket in the entrance channel potential. Quadrupole and octupole transitions to low-lying states in projectile and target are included in the calculations, as well as mutual excitations of these states. The effect of one-neutron transfer is also considered but the effect is small in the measured energy regime. It is shown that mutual excitations to high-lying states play a very important role in developing a comprehensive and consistent description of the measurements. Thus the shapes of the calculated cross sections for $^{12}$C+$^{13}$C and $^{13}$C+$^{13}$C are in good agreement with the data. The fusion cross sections for $^{12}$C+$^{12}$C determined by the IWBC are generally larger than the measured cross sections but they are consistent with the maxima of some of the observed peak cross sections. They are therefore expected to provide an upper limit for the extrapolation into the low-energy regime of interest to astrophysics.Comment: 34 pages, 17 figure

NbTiN superconducting nanowire detectors for visible and telecom wavelengths single photon counting on Si3N4 photonic circuits

We demonstrate niobium titanium nitride superconducting nanowires patterned on stoichiometric silicon nitride waveguides for detecting visible and infrared photons. The use of silicon nitride on insulator on silicon substrates allows us to simultaneously realize photonic circuits for visible and infrared light and integrate them with nanowire detectors directly on-chip. By implementing a traveling wave detector geometry in this material platform, we achieve efficient single photon detection for both wavelength regimes. Our detectors are an ideal match for integrated quantum optics as they provide crucial functionality on a wideband transparent waveguide material.Comment: 5 pages, 3 figure

Large oscillating non-local voltage in multi-terminal single wall carbon nanotube devices

We report on the observation of a non-local voltage in a ballistic one-dimensional conductor, realized by a single-wall carbon nanotube with four contacts. The contacts divide the tube into three quantum dots which we control by the back-gate voltage $V_g$. We measure a large \emph{oscillating} non-local voltage $V_{nl}$ as a function of $V_g$ with zero mean. Though a classical resistor model can account for a non-local voltage including change of sign, it fails to describe the magnitude properly. The large amplitude of $V_{nl}$ is due to quantum interference effects and can be understood within the scattering-approach of electron transport

Wave Propagation In A Fluid-Filled Fracture-An Experimental Study

A laboratory experimental study has been carried out to investigate the mode trapping characteristics of a fluid-filled fracture between two elastic solids. Using a small circular cylindrical receiver of 2.7 mm diameter, we were able to measure the wave motion directly inside a 2.8 mm thick fracture and to obtain array data for the propagating waves. The data was processed using Prony's method to give velocity of the wave modes as a function of frequency. The experimental results agree with the theoretical predictions quite well. Specifically, in a "hard" (aluminum) fracture where the shear velocity of the solid is greater than the fluid velocity, four normal modes were detected in the frequency range up to 2.4 MHz. Whereas in a "soft" (lucite) fracture where the shear velocity is smaller than the fluid velocity, four leaky-P modes were detected in the same frequency range. In both cases, a fundamental mode analogous to Stoneley waves in a borehole was detected. In particular, the velocity of this mode approaches zero in the low frequency limit, as indicated by the theory and confirmed by the experiment in a low frequency range down to 25 kHz.Massachusetts Institute of Technology. Full Waveform Acoustic Logging ConsortiumUnited States. Dept. of Energy (Grant DE-FG02-86ERI3636

A review of satellite positioning systems for civil engineering

This paper informs and updates civil engineers of the status and advances of global navigation satellite systems, and how this will affect the profession in the near future. An overview of the various global and regional systems is given. Real data are used to show the potential precision of the US Global Positioning System and other global navigation satellite systems, as well as the advantages of using a multi-system approach. The results illustrate that there is a clear increase in the availability of satellites through a multisystem approach, as well as an improvement in the resulting coordinate precision