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  • 1
    Electronic Resource
    Electronic Resource
    Quasidivergency-free extraction of a slow positron beam from high magnetic fields (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 3819-3825 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In a hybrid slow positron beam, extraction of the positrons from the magnetic field (∼1 T for the PSI beam) to field-free space is a necessary operation. A theoretical and experimental demonstration is given which shows that the following proposed beam extraction method works as predicted: magnetic transport of the slow positrons down to field strengths of ∼100 G and passage through an aperture grid of ∼10 cm diameter in a field termination shield followed by some brightness enhancement stages. The simulation and measurement of the magnetic-field distributions along the beam axis show a steep drop down of the field from ∼100 G to a few gauss within 1 cm of shield thickness and a quasiuniform spreading of the transverse field strength across the grid opening. Measurement of transmission and divergency (transverse energy) of the beam exiting the extraction aperture confirmed theoretical estimations and ray tracing calculations for the aperture design used to be of the order of 75% and 20 eV, respectively. These data as a function of field strength and beam energy are used for optimization of the final extraction aperture design ((approximately-greater-than)85% transmission) to be used in the PSI high intensity beam facility. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145443
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  • 2
    Electronic Resource
    Electronic Resource
    Free volume and ionic conductivity of poly(ether urethane)-LiClO4 polymeric electrolyte studied by positron annihilation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 334-338 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The positron lifetime spectra and ionic conductivity have been measured for poly(ether urethane)-LiClO4 polymeric electrolyte as a function of temperature. The glass transition temperature Tg, free-volume Vf, and fractional free-volume f were derived from the positron annihilation parameters. A correlation between fractional free-volume f(T) and conductivity σ above Tg, log[σ/σ(Tg)]=C1[f(T)−f(Tg)]/f[T], was first experimentally confirmed using measured positron annihilation results. The comparison of the value of the obtained constant C1 with the universal values for the segmental diffusion of amorphous polymers indicated that the critical free volume required for the ion transport is much smaller than that required for polymer chain segment mobility. Carrier transport and the segmental motion are discussed in terms of the free-volume theory. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359326
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  • 3
    Electronic Resource
    Electronic Resource
    Observation of negative differential resistance phenomenon in a two-step barrier diode (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3320-3322 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, the realization of AlxGa1−xAs/GaAs two-step barrier diode is presented. Experimental observation on the current–voltage characteristics of the two-step barrier diode is reported. At both room temperature and 77 K, it shows a strong negative differential resistance under forward bias while no similar phenomenon was observed under reverse bias. Such an asymmetric current–voltage characteristic would open the possibility of negative differential resistance in an ac field in the absence of a dc bias. Theoretical simulation and experimental current–voltage characteristics are compared and discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116044
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  • 4
    Electronic Resource
    Electronic Resource
    Relationship between hole trapping and interface state generation in metal-oxide-silicon structures (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1431-1433 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have discovered a general relationship between the location of trapped holes and the subsequent generation of interface states. Experimentally, we find that a hole can become an interface state, but it must first be trapped between 20 and 70 A(ring) from the Si/SiO2 interface (near-interfacial hole trap) and then transfer to within 18 A(ring) of the interface (interfacial trapped holes). Finally, the hole captures an electron and becomes an interface state. The transfer process between near-interfacial and interfacial trapped holes does not seem to be a simple release-capture process. Rather it appears to involve a complicated migration of the trapped hole defect towards the interface. Radiation-hardened oxides are shown to have a similar number of near-interfacial traps, but these traps are shallower than those in the soft oxides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99690
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  • 5
    Electronic Resource
    Electronic Resource
    Inversion criteria for the metal-insulator-semiconductor tunnel structures (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1080-1086 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The conditions of strong surface inversion in the semiconductor surface of a metal-insulator-semiconductor (MIS) tunnel structure are studied. By employing the voltage equation which governs the potential distribution in the MIS diode and by defining a parameter θ which indicates the energy separation between the semiconductor minority-carrier quasi-Fermi level and the metal Fermi level at the insulator–semiconductor interface, the values of θ(inv) under strong surface inversion are calculated in terms of oxide thickness, metal work function, oxide and interface state charges, semiconductor doping concentration, and reverse bias voltage. There are three conditions, namely, (1) without the external injection of the minority-carrier current density Jinj (i.e., Jinj=0), (2) with it (i.e., Jinj is positive), and (3) where Jinj is negative (i.e., carrier extraction). The second condition can be attributed to the critical insulator thickness dcri below which the semiconductor surface cannot be inverted solely by applying a reverse bias voltage, hence an externally injected minority-carrier current Jinj(inv) is required to achieve strong surface inversion at certain bias and oxide thickness. It also reveals that Jinj(inv) increases with decreasing insulator layer thickness and is strongly dependent on the oxide and interface state charges. For the Al–SiO2–Si tunnel structure, the calculated value of dcri is about 30 A(ring), which is in good agreement with the reported experimental results of 28–35 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337776
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  • 6
    Electronic Resource
    Electronic Resource
    Capture-emission process in double Poole–Frenkel well traps: Theory and experiments (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1042-1045 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The field-dependent capture-emission process has been studied for double Poole–Frenkel well traps compared with that of single Poole–Frenkel well trap. The emission rate increases with increasing field strength for a single trap. However, for a double trap, it increases to a maximum then decreases with further increasing field due to the barrier lowering and interstate interactions between these two wells. Experimental capacitance deep-level transient spectroscopic data of GaAs samples grown by molecular-beam epitaxy show that when there is a delay in the capacitance transient then there always appear two levels, namely, 0.4 and 0.5 eV. In addition, for both levels, the emission rate increases first to a maximum and then decreases with increasing electric field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337395
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  • 7
    Electronic Resource
    Electronic Resource
    Wide-bandwidth and high-power InGaAsP distributed feedback lasers (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4640-4644 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fabrication and performance characteristics of a wide-bandwidth InGaAsP laser diode structure are described. The wide bandwidth is achieved using semi-insulating Fe-doped InP current blocking layers around the active region. The lasers have a bandwidth of 18 GHz at 20 mW, emit 50 mW in a single transverse and longitudinal mode, have rise and fall times of less than 40 ps, have low chirp (FWHM〈1 A(ring)) under modulation, and exhibit harmonic distortion characteristics in agreement with fundamental calculations using a rate equation model. Error-free transmission with no dispersion penalty has been obtained using these lasers in a transmission experiment at 8 Gb/s over 76 km of fiber.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343820
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  • 8
    Electronic Resource
    Electronic Resource
    Normal Data for Lumbar Spine Bone Mineral Content in Healthy Chinese Men (1997)
    Springer
    Calcified tissue international 61 (1997), S. 114 -116 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Age — Bone mineral density — Chinese men.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The aim of this study was to evaluate the influence of age on bone mineral density (BMD) of the lumbar spine for healthy Chinese men. In 430 healthy Chinese men (ages 20–92 years) living on Taiwan, BMD at the level of the 2nd to 4th lumbar vertebraes (L2–L4) was determined with a commercial dual-energy X-ray absorptiometer (DXA). Our study found that the peak BMD value of lumbar spines of healthy Chinese men was 1.056 ± 0.127 g/cm2 which occurs from age 20 to 29. The results show that a linear correlation between the age and BMD of lumbar vertebraes for healthy Chinese is notable. Only slight decreases of BMD values in the different age groups are found. In comparison with the normal data of white men and Asian men from Japan and Korea, the mean BMD values of lumbar spines of Chinese men seem to be lower than those of the white, Japanese, and Korean men of the same ages. Our findings indicate that the influence of age and ethnicity may exist in the BMD values for healthy Chinese males.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900306
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  • 9
    Electronic Resource
    Electronic Resource
    Comparison technetium of Tc-99m disofenin cholescintigraphy with ultrasonography in the differentiation of biliary atresia from other forms of neonatal jaundice (1996)
    Springer
    Pediatric surgery international 12 (1996), S. 30-33 
    Details
    ISSN: 1437-9813
    Keywords: Key words Technetium Tc-99m disofenin ; cholescintigraphy ; Biliary atresia ; Ultrasonography ; Neonatal hepatitis ; Neonatal jaundice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Technetium Tc-99m disofenin cholescintigraphy (CS) and ultrasonography (US) are two major clinical methods used in differentiating biliary atresia (BA) from neonatal jaundice. To compare the diagnostic utility of these two modalities, 66 patients with neonatal cholestasis (15 BA, 3 choledochal cyst (CC), 32 neonatal hepatitis, 13 prolonged jaundice, 2 total parenteral nutrition, and 1 sepsis) underwent Tc-99m disofenin CS and US. The diagnostic sensitivity, specificity, and accuracy of CS in differentiating BA from other forms of neonatal jaundice was 100%, 87.5%, and 90.5%, respectively, and for US 86.7%, 77.1%, and 79.4%, respectively. Tc-99m disofenin CS after premedication with phenobarbital and cholestyramine is a convenient and reliable method of differentiating BA from neonatal hepatitis, with a diagnostic accuracy superior to that of US. However, US is the initial imaging procedure of choice in patients presenting with jaundice to rule out anatomic anomalies such as CC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01194798
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  • 10
    Electronic Resource
    Electronic Resource
    Comparison technetium of Tc-99m disofenin cholescintigraphy with ultrasonography in the differentiation of biliary atresia from other forms of neonatal jaundice (1996)
    Springer
    Pediatric surgery international 12 (1996), S. 30-33 
    Details
    ISSN: 1437-9813
    Keywords: Technetium Tc-99m disofenin cholescintigraphy ; Biliary atresia ; Ultrasonography Neonatal hepatitis ; Neonatal jaundice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Technetium Tc-99m disofenin cholescintigraphy (CS) and ultrasonography (US) are two major clinical methods used in differentiating biliary atresia (BA) from neonatal jaundice. To compare the diagnostic utility of these two modalities, 66 patients with neonatal cholestasis (15 BA, 3 choledochal cyst (CC), 32 neonatal hepatitis, 13 prolonged jaundice, 2 total parenteral nutrition, and 1 sepsis) underwent Tc-99m disofenin CS and US. The diagnostic sensitivity, specificity, and accuracy of CS in differentiating BA from other forms of neonatal jaundice was 100%, 87.5%, and 90.5%, respectively, and for US 86.7%, 77.1%, and 79.4%, respectively. Tc-99m disofenin CS after premedication with phenobarbital and cholestyramine is a convenient and reliable method of differentiating BA from neonatal hepatitis, with a diagnostic accuracy superior to that of US. However, US is the initial imaging procedure of choice in patients presenting with jaundice to rule out anatomic anomalies such as CC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01194798
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