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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 4267-4272 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, low-temperature photoluminescence (PL) is used for the investigation of beryllium (Be) dopant outdiffusion in AlGaAs/GaAs single-heterojunction bipolar transistors (HBTs). Near the typical emission peak at ∼1.92 eV which is due to the band-to-band transition from AlGaAs emitter, an additional emission peak is found in the PL spectrum. This peak is found to be caused by the Be-related transition from AlGaAs emitter due to the Be outdiffusion from the GaAs base to the AlGaAs emitter. The concentration of Be outdiffused into the emitter can be estimated from the energy separation between these two emission peaks in AlGaAs range based on the band gap narrowing effect. The measured dc current gain and the emitter-base turn-on voltage of the HBTs fabricated on different wafers with different growth conditions were found to correlate well with the PL results. Our results demonstrate that low temperature PL technique is an efficient method in identifying Be outdiffusion in HBTs and is useful in HBT growth and device structure optimization. © 1999 American Institute of Physics.
    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 86 (1999), S. 6468-6473 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: AlGaAs/GaAs single heterojunction bipolar transistor (HBT) structures with Be- and C-doped bases have been annealed at different temperatures using rapid thermal processing (RTP). Both electrical and low-temperature photoluminescence measurements were used to investigate their thermal stability. We found that the conventional AlGaAs/GaAs abrupt HBT structures could undergo significant degradation at temperatures commonly encountered in typical RTP for device fabrication. The decrease of current gain was observed in both molecular beam epitaxy-grown HBTs with a Be-doped base and metalorganic chemical vapor deposition-grown HBTs with a C-doped base after RTP at temperatures greater than 600 °C. Our studies show that high-temperature RTP could induce undesirable degradation in AlGaAs/GaAs HBTs. Different degradation mechanisms, which are similar to those for the degradation of the Be- and C-doped base HBTs under current-induced stress, are responsible for the degradation of the Be- and C-doped HBTs subjected to RTP. The degradation of Be-doped HBTs is believed to be due to the outdiffusion of Be from the highly doped base, whereas the decrease of current gain for C-doped HBTs is closely related to the unintentionally incorporated hydrogen during material growth. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1523-5378
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background. Bismuth triple therapy provides consistently good results in Helicobacter pylori eradication worldwide, whereas quadruple therapy using a combination of omeprazole and bismuth triple regimen has produced cure rates in excess of 90%. The prevalence of metronidazole-resistant strains was 26.8% in our area. Colloidal bismuth pectin (CBP) is a new, lower-priced bismuth salt made in China. The purpose of this study was to investigate the efficacy and safety of CBP triple and quadruple regimens in the treatment of H. pylori–positive duodenal ulcer.Materials and Methods. In this prospective trial, 205 patients with H. pylori–positive duodenal ulcer were allocated randomly to receive one of four regimens: metronidazole, 200 mg; amoxicillin, 250 mg; and colloidal bismuth subcitrate (CBS), 120 mg (group 1), or CBP, 100 mg qid (group 2) for 2 weeks, then continued CBS, 240 mg, or CBP, 200 mg bid for a further 2 weeks. A quadruple regimen using a combination of omeprazole, 20 mg bid, and CBS triple therapy (group 3) or CBP triple therapy (group 4), respectively, was given to patients for 1 week, followed by omeprazole, 20 mg once daily for a further 3 weeks. Further endoscopy was performed at least 4 weeks after cessation of the treatment. H. pylori status was determined by histology, a 14C urea breath test, and a urease test.Results. The per-protocol H. pylori cure rates were 85% (22 of 26 patients), 90% (35 of 39), 96% (46 of 48), and 95% (75 of 79) for groups 1 through 4. In the intention-to-treat analysis, cure rates were 79% (22 of 28), 83% (35 of 42), 90% (46 of 51), and 89% (75 of 84), respectively. The cure rates of quadruple therapy were higher than those of triple therapy; an 8.2% difference was not statistically significant (95% confidence interval [CI], 2.3–18.7%). The ulcer-healing rates were 88%, 87%, 98%, and 97%, respectively, for groups 1 through 4. The ulcer pain was relieved more rapidly in quadruple- than in triple-therapy regimens. Two patients discontinued treatment prematurely owing to drug-related side effects.Conclusion. One-week quadruple therapy is highly effective and safe in H. pylori eradication in Chinese patients. CBP is as effective as CBS.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 34 (1995), S. 6863-6868 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2711-2718 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We compare CO's response to electric fields at edge and terrace sites on the stepped Pt(335) surface. The comparison is made at zero frequency and at the frequency of the C–O stretch vibration. Atop-bonded CO is observed with reflection–absorption ir spectroscopy (RAIRS), electroreflectance vibrational spectroscopy (EVS), and high-resolution electron energy loss spectroscopy (HREELS). Coadsorbed H or O is used to control the CO adsorption site. With both RAIRS and HREELS the measured vibrational cross-section of atop CO at the step edge is 2.0±0.2 times greater than for CO on the terrace. The vibrational Stark effect—the change of CO's vibrational frequency with externally applied electrostatic field—is also a factor 2.0±0.2 larger for atop CO at the step edge than it is for atop CO on the terrace. Because the vibrational cross section varies as the square of the field while the Stark effect is linear, a model in which CO responds to the screened local field at a single point cannot simultaneously explain the observed site dependence of both the vibrational Stark effect and the vibrational cross section. The most plausible explanation is that CO's response to electric fields is nonlocal. A simple model is presented that can account for our data. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 2981-2991 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 9569-9576 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: As part of a study of species important in automotive exhaust chemistry, the reactivity of atomic N and NO on Pt(335) at low temperature has been studied. The atomic N was produced by dissociating adsorbed NO with a 76 eV electron beam. Cross sections for electron-stimulated desorption and dissociation are estimated for NO on terrace and step sites. Terrace NO is at least five times more likely to desorb than to dissociate. Step NO has a lower desorption cross section than terrace NO, but probably a higher dissociation cross section. Temperature-programmed desorption was used to monitor desorption, dissociation, and the formation of N2 and N2O from adsorbed N and NO. Five distinct desorption states of N2 formed by NO dissociation are identified. The dominant N2 peak (435 K) comes from electron-dissociated step NO; its desorption temperature is higher than the N2 peaks from electron-dissociated terrace NO. Coadsorbed N and NO react to form N2O even below 100 K, with an activation barrier of ∼6 kcal/mol. Only terrace NO participates in this reaction; step NO does not react to form N2O. This site dependence resembles that for CO oxidation on Pt(112) and Pt(335) and can be rationalized with simple steric considerations. All of the forms of atomic N participate in N2O formation, but that formed by the dissociation of step NO exhibits the lowest reaction temperature. Hence, the same N atoms that only recombine to form N2 at 435 K, react with NO to form N2O at 100 K. We found no evidence for an NO reaction with N atoms to form N2 and adsorbed O, or for NO formation from the recombination of adsorbed N and adsorbed O2. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 799 (1996), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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