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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 51 (1979), S. 844-851 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5021-5031 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The current–voltage (I–V) characteristics in the ballistic limit of metal-oxide tunnel transistors are calculated as a function of temperature, potential barrier height, gate insulator thickness, aspect ratio, and oxide-channel shape. The saturation (‘knee') point and three modes of current transport across the device are discussed. For a given aspect ratio, the output impedance improves with increase in tunnel-oxide width, accompanied by slight decrease of gate transconductance. The net result is a significant improvement in the transistor gain. The gate transconductance improves with decrease in gate-insulator thickness, while approximately maintaining the output impedance. The net result is also a significant improvement in the transistor gain. Thus for a given aspect ratio, further device optimization to increase the transistor gain can be carried out by either increasing the tunnel oxide width or decreasing the gate insulator thickness. In practice, one preferably does both. A numerical study of the device performance of tapered-oxide devices is undertaken. We find that uniform-oxide channel design is generally superior to tapered-oxide channel designs. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiac surgery 9 (1994), S. 0 
    ISSN: 1540-8191
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We report our initial experience from April 1992 to November 1993 with a stentless porcine valve (Toronto SPVTM Valve, St. Jude Medical) for aortic valve replacement (AVR) in 21 consecutive patients and compare this group to a matched cohort that underwent AVR with a Hancock II (Medtronic) bloprosthesis. There were no hospital deaths in either group. Postoperative hospitalization was 5.5 ± 0.8 versus 7.0 ± 2.3 days (p = 0.004). Aortic cross-clamp time was 114.5 ± 15.7 min In the SPV group and 96.0 ± 25.0 min in the Hancock II group (p = 0.003). Complications in the SPV group were: one patient suffered perioperative infarction, one patient required late reoperation for left main stenosis, and one patient died suddenly following femoral thrombectomy at another center. Complications in the Hancock II group included: one patient with postoperative low output syndrome, and two late deaths (one from an aortic dissection and the other from chronic liver disease secondary to alcohol abuse). Comparison data indicate that the average size valve implanted in the SPV group was higher than in the Hancock II group (26.3 ± 1.9 vs 24.0 ± 1.9, p = 0.001). In the SPV group, 16 patients had 0 or trivial regurgitation and 1+ regurgitation was seen in 5 patients; regurgitation did not change over a 12-month follow-up. We observed a decrease in gradients over time (p 〈 0.01). Our results are compatible with a hypothesis that the ventricle undergoes remodeling over time, once the obstruction is relieved. We think the stentiess design is an important feature that allows this to occur. Furthermore, this design allows for the implantation of a larger size valve for the same body size, as well as for decreased shear forces during diastole, with accompanying better hemodynamics, and potential improvement in longevity. These results indicate that the SPV valve has excellent hemodynamic characteristics that do not appear to change over a short follow-up period.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 117-119 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented on a new type of extremely quiet and sensitive GaAs/AlGaAs photodetector. The photoresponse of the device is controlled by a hole trap in a tunnel barrier. Capture of a single photoinjected hole by the trap gates the device and produces an easily measured current pulse which can be counted by a conventional pulse-counting apparatus. There is only one detectable trap in a photoactive area of (approximately-equal-to)400 μm2. However, due to electric field channeling effects the trap collects photoinjected holes with a 1% efficiency in the active region. The absence of measurable dark counts in a 25 h period at 77 K establishes a minimum detectable photon flux 〈0.001 photons/s at 8200 A(ring).
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1133-1139 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The design criteria for large transconductance/high output impedance or high-gain operation of metal-oxide tunneling transistors is given. The dependence of the gate control on the aspect ratio of thickness to width of the tunneling oxide is investigated by computer simulation. This device structure can only operate similar to conventional semiconductor transistors for aspect ratio considerably less than one. It ceases to function as a transistor for larger aspect ratio due to insufficient penetration of the gate control field into the tunneling oxide. To demonstrate this, the current–voltage characteristics are computed for aspect ratios equal to 7/30, 1, 21/10, and the different tunneling-current behaviors compared with our experimental results on Ti/TiOx/Ti and Nb/NbOx/Nb tunnel transistors.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2124-2126 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Efficient band-gap electroluminescence has been observed in n+-n−-n+ single-barrier tunneling devices. The electroluminescence arises from holes created by the impact ionization of electrons in large electric fields. From the voltage dependence of the electroluminescence the electric field dependence of the impact ionization rate is determined. Comparisons to theory are made.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1378-1382 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Voltage pulsed modification of surfaces in air with a scanning tunneling microscope has been studied with a view to understanding the physical processes involved. Incremented negative pulses have been applied to a tungsten tip to determine the threshold for feature writing on gold. The primary event observed with virgin tips is pit formation, which is interpreted as due to the transfer of gold cations from sample to tip. Subsequent pulsing establishes a threshold for a secondary process in which hillocks form on the gold surface and which are thought to be the result of gold anion retransfer from tip to sample. The thresholds are 4.16 and 3.92 V, respectively, for the two processes. For one particular tip, which gave rise to a Y-shaped pit, a three-dimensional profile was subsequently obtained by crashing it at a remote site on the surface and imaging the crater formed. The geometrical parameters of the tip, so elaborated, allowed a model of the electrostatic potential between tip and sample during pulsing to be numerically evaluated by solution of Laplace's equation and the field pattern over the surface to be determined. For the blunt pyramid involved, there is substantial anisotropy though modest field reduction at positions some nm from the projection of the tip on the surface. It is then a straightforward matter to understand the Y shape of the pit formed on the surface by the initial pulse. Field evaporation is thereby confirmed as the operative process. Reference experiments using gold tips showed no threshold difference between primary and secondary modification, a result consistent with the field evaporation mechanism. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1388-1390 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fabrication of nanometer-scale side-gated silicon field effect transistors using an atomic force microscope is reported. The probe tip was used to define nanometer-scale source, gate, and drain patterns by the local anodic oxidation of a passivated silicon (100) surface. These thin oxide patterns were used as etch masks for selective etching of the silicon to form the finished devices. Devices with critical features as small as 30 nm have been fabricated with this technique. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1932-1934 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method for fabricating Si nanostructures with an air-operated atomic force microscope (AFM) is presented. An electrically conducting AFM tip is used to oxidize regions of size 10–30 nm of a H-passivated Si (100) surface at write speeds up to 1 mm/s. This oxide serves as an effective mask for pattern transfer into the substrate by selective liquid etching. The initial oxide growth rate depends exponentially on the applied voltage which produces an effective "tip sharpening'' that allows small features to be produced by a relatively large diameter tip.
    Type of Medium: Electronic Resource
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