Probing the Phase Diagram of Bi2Sr2CaCu2O8+d with Tunneling Spectroscopy

Tunneling measurements are performed on Ca-rich single crystals of Bi2Sr2CaCu2O8+d (Bi2212), with various oxygen doping levels, using a novel point contact method. At 4.2 K, SIN and SIS tunnel junctions are obtained with well-defined quasiparticle peaks, robust dip and hump features and in some cases Josephson currents. The doping dependence of tunneling conductances of Ca-rich Bi2212 are analyzed and compared to stoichiometric Bi2212. A similar profile of energy gap vs. doping concentration is found although the Ca-rich samples have a slighly smaller optimum Tc and therefore smaller gap values for any doping level. The evolution of tunneling conductance peak height to background ratios with hole concentration are compared. For a given doping level, the Ca-rich spectra showed more broadened features compared to the stoichiometric counterparts, most likely due to increased disorder from the excess Ca. Comparison of the dip and hump features has provided some potential insights into their origins.Comment: 4 pages, 4 figures; presented at the Applied Superconductivity Conference (August 4-9, 2002) in Houston, TX; to be published in IEEE Trans. Appl. Supercon

Single Junction and Intrinsic Josephson Junction Tunneling Spectroscopies of Bi2Sr2CaCu2O8+d

Tunneling spectroscopy measurements are reported on optimally-doped and overdoped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ single crystals. A novel point contact method is used to obtain superconductor-insulator-normal metal (SIN) and SIS break junctions as well as intrinsic Josephson junctions (IJJ) from nanoscale crystals. Three junction types are obtained on the same crystal to compare the quasiparticle peaks and higher bias dip/hump structures which have also been found in other surface probes such as scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy. However, our IJJ quasiparticle spectra consistently reveal very sharp conductance peaks and no higher bias dip structures. The IJJ conductance peak voltage divided by the number of junctions in the stack consistently leads to a significant underestimate of $\Delta$ when compared to the single junction values. The comparison of the three methods suggests that the markedly different characteristics of IJJ are a consequence of nonequilibrium effects and are not intrinsic quasiparticle features.Comment: 4 pages, 4 figures; presented at the Applied Superconductivity Conference (October 3-8, 2004) in Jacksonville, FL; to be published in IEEE Trans. Appl. Supercon

A one-compartment, direct glucose fuel cell for powering long-term medical implants

We present the operational concept, microfabrication, and electrical performance of an enzyme-less direct glucose fuel cell for harvesting the chemical energy of glucose from body fluids. The spatial concentrations of glucose and oxygen at the electrodes of the one-compartment setup are established by self-organization, governed by the balance of electro-chemical depletion and membrane diffusion. Compared to less stable enzymatic and immunogenic microbial fuel cells, this robust approach excels with an extended life time, the amenability to sterilization and biocompatibility, showing up a clear route towards an autonomous power supply for long-term medical implants without the need of surgical replacement and external refueling. Operating in physiological phosphate buffer solution containing 0.1 wt% glucose and having a geometrical cathode area of 10 cm2, our prototype already delivers 20 µ W peak power over a period of 7 days

Evolution of mixing state of black carbon particles: Aircraft measurements over the western Pacific in March 2004

We report the evolution of the mixing state of black carbon (BC) particles in urban plumes measured by an airborne single particle soot photometer. The aircraft observations were conducted over the ocean near the coast of Japan in March 2004. The number fiaction of coated BC particles with a core diameter of 180 mn increased from 0.35 to 0.63 within 12 hours (h), namely 2.3% h-1, after being emitted from the Nagoya urban area in Japan. BC particles with a core diameter of 250 nm increased at the slower rate of 1.0% h-1. The increase in coated BC particles was associated with increases in non-sea salt sulfate and water-soluble organic carbon by a factor of approximately two, indicating that these compounds contributed to the coating on the BC particles. These results give direct evidence that BC particles become internally mixed on a time scale of 12 h in urban plumes. Copyright 2007 by the American Geophysical Union

The Experimental plan of the 4m Resonant Sideband Extraction Prototype for The LCGT

The 4m Resonant Sideband Extraction (RSE) interferometer is a planned prototype of the LCGT interferometer. The aim of the experiment is to operate a powerrecycled Broadband RSE interferometer with suspended optics and to achieve diagonalization of length signals of the central part of the interferometer directly through the optical setup. Details of the 4m RSE interferometer control method as well as the design of the experimental setup will be presented

Two Sizes of Superconducting Gaps on an Under-doped Bi2.1Sr1.9Ca2Cu3O10+δ with TC ∼ 101K by Tunneling Spectroscopy

AbstractWe measured tunneling conductances on an under-doped trilayer cuprate Bi2.1Sr1.9Ca2Cu3O10+≏ (Bi2223) with TC ∼ 101K by a point contact method, which has three CuO2 planes in a unit cell. The tunneling conductances on Bi2223 exhibited two sizes of gaps originated from outer and inner CuO2 plane (OP and IP). The estimated size of superconducting gap from OP ΔOP is 34 ± 6 meV, and the ΔIP from IP is 51 ± 5 meV, respectively. We also observed tunneling conductances which simultaneously displayed two superconducting peaks of OP and IP. Moreover, we propose the model of two superconductor-insulator-normal metal junctions which exhibit two sizes gaps of OP and IP

Chemical characterization of water-soluble organic carbon aerosols at a rural site in the Pearl River Delta, China, in the summer of 2006

Online measurements of water-soluble organic carbon (WSOC) aerosols were made using a particle-into-liquid sampler (PILS) combined with a total organic carbon (TOC) analyzer at a rural site in the Pearl River Delta region, China, in July 2006. A macroporous nonionic (DAX-8) resin was used to quantify hydrophilic and hydrophobic WSOC, which are defined as the fractions of WSOC that penetrated through and retained on the DAX-8 column, respectively. Laboratory calibrations showed that hydrophilic WSOC (WSOCHPI) included low-molecular aliphatic dicarboxylic acids and carbonyls, saccharides, and amines, while hydrophobic WSOC (WSOCHPO) included longer-chain aliphatic dicarboxylic acids and carbonyls, aromatic acids, phenols, organic nitrates, cyclic acids, and fulvic acids. On average, total WSOC (TWSOC) accounted for 60% of OC, and WSOCHPO accounted for 60% of TWSOC. Both WSOC HIP and WSOCHPO increased with photochemical aging determined from the NOx/NOy ratio. In particular, the average WSOCHPO mass was found to increase by a factor of five within a timescale of ∼10 hours, which was substantially larger than that of WSOCHPI (by a factor of 2-3). The total increase in OC mass with photochemical aging was associated with the large increase in WSOCHPO mass. These results, combined with the laboratory calibrations, suggest that significant amounts of hydrophobic organic compounds (likely containing large carbon numbers) were produced by photochemical processing. By contrast, water-insoluble OC (WIOC) mass did not exhibit significant changes with photochemical aging, suggesting that chemical transformation of WIOC to WSOC was not a dominant process for the production of WSOC during the study period. Copyright 2009 by the American Geophysical Union

Random-phase approximation study of collective excitations in the Bose-Fermi mixed condensate of alkali-metal gases

We perform Random Phase Approximation (RPA) study of collective excitations in the bose-fermi mixed degenerate gas of Alkali-metal atoms at T=0. The calculation is done by diagonalization in a model space composed of particle-hole type excitations from the ground state, the latter being obtained from the coupled Gross-Pitaevskii and Thomas-Fermi equations. We investigate strength distributions for different combinations of bose and fermi multipole ($L$) operators with $L=0,1,2,3$. Transition densities and dynamical structure factors are calculated for collective excitations. Comparison with the sum rule prediction for the collective frequency is given. Time dependent behavior of the system after an external impulse is studied.Comment: 28 pages, 13 figures, submitted to Phys. Rev.

Control sideband generation for dual-recycled laser interferometric gravitational wave detectors

We present a discussion of the problems associated with generation of multiple control sidebands for length sensing and control of dual-recycled, cavity-enhanced Michelson interferometers and the motivation behind more complicated sideband generation methods. We focus on the Mach–Zehnder interferometer as a topological solution to the problem and present results from tests carried out at the Caltech 40 m prototype gravitational wave detector. The consequences for sensing and control for advanced interferometry are discussed, as are the implications for future interferometers such as Advanced LIGO