Search

Strong current oscillations in a metal droplet system by point contact tunneling with a scanning tunneling microscope at 77 K have been observed. The oscillations have a periodicity equal to the single- electron charging voltage, e/C= 28 m V, where C is the metal droplet capacitance.

Investigates the tunneling characteristics of oxidized ultra small bismuth particles on Al[sub2]O[sub3] using scanning tunneling microscopy. Sample preparation; Measurement of the tunneling current and conductance as a function of bias voltage; Observations on conductance characteristics.

The article presents a study which assesses the measurement techniques in quantifying the concentration of refractory black carbon (BC) in snow samples. The comparison of the Single Particle Soot Photometer (SP2) and the Integrating Sphere/Integrating Sandwich Spectrophotometer (ISSW) in the quantification of BC concentration is outlined. Underestimates of uncertainty in the measurement of BC concentration using SP2 or ISSW are investigated.

The authors present tunneling results for junctions comprising Mn doped Al films produced by sputter deposition, with Mn concentrations in the range of 0-5000 ppm. Our results for S'/I/S', S'/I/S, and N/I/S junctions demonstrate that Al-Mn alloys can serve both as superconductors with critical temperatures reduced from that of Al and as normal metals. The authors find Al-Mn in this doping range to be otherwise identical to pure Al in terms of its BCS-like tunnel characteristics (for superconductors) and its ability to produce high-quality tunnel barriers. [ABSTRACT FROM AUTHOR]

We demonstrate cooling of the electrons and phonons of a silicon nitride (Si-N) membrane by solid-state refrigerators based on normal metal/insulator/superconductor (NIS) tunnel junctions. We report a temperature reduction of the Si-N membrane from 260 mK to 240 mK, while the electrons in the normal metal of the refrigerator are cooled to 145 mK. We explain the mechanism for cooling an isolated membrane and make quantitative comparisons between experiment and a finite-element thermal model. The model indicates that increasing the thermal conductivity of the cold-fingers, improving the transparency of the tunnel junctions, and reducing the power load through the membrane will make it possible to cool the membrane from 260 mK to below 170 mK. The refrigeration of a membrane makes it possible to integrate other cryogenic devices that require sub-Kelvin temperatures for optimal performance, such as thin-film sensors. We demonstrate this integration by combining NIS refrigerators with an x-ray Transition-Edge-Sensor (TES). [ABSTRACT FROM AUTHOR]

A circuit has been developed for the measurement of the electrical characteristics of devices sensitive to extrinsic noise and intrinsic power-supply transients. The circuit comprises two active current sources running in opposition. The current can be ramped smoothly through current excursions of a maximum of ±1 A. Provision is also made for the modulation of the dc current output by an external ac source. [ABSTRACT FROM AUTHOR]

We have measured the optical properties of cancer and normal whole cells and lysates using light transmission spectroscopy (LTS). LTS provides both the optical extinction coefficient in the wavelength range from 220 to 1100nm and (by spectral inversion using a Mie model) the particle distribution density in the size range from 1 to 3000nm. Our current work involves whole cells and lysates of cultured human oral cells in liquid suspension. We found systematic differences in the optical extinction between cancer and normal whole cells and lysates, which translate to different particle size distributions (PSDs) for these materials. Specifically, we found that cancer cells have distinctly lower concentrations of nanoparticles with diameters less than 100nm and have higher concentrations of particles with diameters from 100 to 1000nm-results that hold for both whole cells and lysates. We also found a power-law dependence of particle density with diameter over several orders of magnitude., (Copyright © 2015 Elsevier Inc. All rights reserved.)

We have observed the BCS-like density of states predicted for energy-gap suppression by nonmagnetic Anderson impurities in superconductors. We show that Mn impurities in Al exhibit no magnetic character and act exclusively as strong resonant scattering sites without producing time-reverse symmetry breaking of Cooper pairs (pair breaking).