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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1741-1743 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a low threshold current density and high power for λ∼9 μmAlInAs/GaInAs quantum cascade lasers operating at room temperature. The threshold current density is 1.95 kA/cm2 at 300 K and 0.61 kA/cm2 at 80 K for 5 μs pulses at 200 Hz repetition rate. The peak output power is 700 mW at room temperature and 1.3 W at 80 K per two facets for cavity length is 3 mm with a stripe width of 20 μm. The characteristic temperature T0 is 185 °C. The slope efficiency is 450 and 800 mW/A at 300 and 80 K, respectively. In continuous wave operation, the output power is more than 150 mW at 80 K and 25 mW at 140 K. This high performance was achieved by improving the material growth and processing technology. © 2000 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4559-4561 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: With Bi3TiNbO9 (BTN) ferroelectric samples, in situ electrical-field-induced growth of ferroelectric thin films was demonstrated to control the films' microstructure and manipulate their ferroelectric properties. BTN films on Ti/SiO2/Si substrates were grown at a relatively low temperature (650 °C) with a biased electrical field during pulsed-laser deposition. The (001) orientation of the films, which makes no contribution to their polarization, was effectively reduced by the in situ electrical field of strength of 70 V/cm. This results in a large increase of remnant polarization from 1.1 to 6.2 μC/cm2, and reduction of the coercive field from 70 to 50 kV/cm, comparing the films grown freely under the same condition. Furthermore, the films showed an excellent fatigue-free property of up to 1010 switching cycles. © 2001 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2973-2975 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To understand and improve the applications of titanium-oxide nanoparticles, it is extremely important to perform a detailed investigation of the surface and the interior structural properties of nanocrystalline materials, such as rutile and anatase with diameter of few nanometers. Here, x-ray absorption spectroscopy has been used to identify the local Ti environment and characterize the related electronic structure. We combine experimental results at the Ti K edge in both bulk and nanocrystal samples to determine the lattice distortion via the characteristic pre-edge features and the variation in the multiple-scattering region of the x-ray absorption near-edge structure spectra. The correlation between peak intensities and surface-to-volume ratio of nanoparticles is also discussed. © 2002 American Institute of Physics.
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  • 4
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Long-term adrenalectomy (ADX) is associated with marked down-regulation of pituitary corticotropin releasing factor type-1 receptors (CRF-R1) but normal CRF-R1 mRNA levels, suggesting that regulation of receptor levels occurs at post-transcriptional sites. We have reported that adrenal cytosolic proteins, which bind to cis elements in the 5′ leader sequence (5′LS) of the rat angiotensin II type 1a receptor (AT1aR) mRNA, participate in the regulation of AT1aR density by inhibiting AT1aR mRNA translation. In this study, we examined anterior pituitary cytosolic proteins that form RNA protein complexes (RPC) with the 5′LS of the CRF-R1 and the AT1aR. Competition studies and ultraviolet-crosslinking analysis suggest that formation of CRF-R1 and AT1aR 5′LS RPC require at least some proteins that are common to both receptor mRNAs. Pituitaries isolated from male Sprague-Dawley rats six days after ADX showed significant (P 〈 0.05) increases of 2.9-fold in CRF-R1 5′LS RNA binding protein (BP) activity compared to pituitaries from sham-operated rats; this effect of ADX was prevented by glucocorticoid replacement. By contrast, no differences in the number of pituitary AT1aR binding sites or pituitary AT1aR 5′LS BP activity were observed between sham and ADX rats, indicating that the effect of ADX on RPC formation was specific for CRF-R1 mRNA. Addition of pituitary cytosolic extracts inhibited in vitro translation of CRF-R1 mRNA by 79% under conditions that had no significant effects on the translation of a control mRNA. The data suggest that CRF-R1 translation is regulated by modulation of the HPA axis through pituitary cytosolic proteins binding to the CRF-R1 5′LS.
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Pseudomonas aeruginosa is a ubiquitous environmental bacterium that is one of the top three causes of opportunistic human infections. A major factor in its prominence as a pathogen is its intrinsic resistance to antibiotics and disinfectants. Here we report the complete sequence of P. ...
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  • 6
    Electronic Resource
    Electronic Resource
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 719-721 
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Since many years the oxidation of alkali metals has being attracted much interest due to the catalytic properties of metal promoters and the simple electronic structure of alkali atoms. The alkali-oxides phase diagram indicates that the interaction of oxygen with alkali metals can lead to the formation of different atomic O2- ions and molecular O2- and O22- ions. Potassium superoxide has been prepared in situ and high resolution O k-edge absorption NEXAFS spectra have been measured at the VUV beam-line at ELETTRA facility. The experimental data have been analyzed by multiple scattering approach deriving many geometrical and electronic details. In particular, we have found that the growth material structure is of the KO2 type with an O-O distance of about 1.35Å and that the transition involving single π molecular empty state of the superoxide O2- anion has a fine structure. Multiple Scattering self consistent calculation indicates that the bond between oxygen anion and K atom is totally ionic and that the fine structure is essentially due to solid state effects.
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  • 7
    ISSN: 1420-9136
    Keywords: Key Words: Sichuan-Qinghai-Xizang (Tibet), seismic source, rupture, earthquake activity, single-link cluster.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —The Chinese provinces of Sichuan, Qinghai and Xizang (Tibet) are situated in a very active seismic zone. From 1988 to 1990, nine strong earthquakes (M 〉 5.9) occurred in these provinces. A method of analyzing seismic waveforms using apparent source time functions (aSTF) and apparent time differences (aTD) is adopted to derive rupture characteristics for the strong earthquakes. Combining the source characteristics with aftershock data, regional tectonics and geology, this paper examines the migration of strong earthquakes. The Qinghai earthquakes in this study were found to have strong reverse-slip faulting, which is different from the strike-slip focal mechanisms of past earthquakes in the region. The steepness of compressional axes of Sichuan earthquakes is related to the local complicated tectonics. Finally, the single-link cluster (SLC) method is used to analyze the spatial-temporal behavior of the all strong earthquakes that occurred in the region since 1970. The SLC analysis suggests that the patterns of earthquake activity can be identified well and that continental earthquakes occur seemingly with basic regularity.
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  • 8
    ISSN: 1432-1238
    Keywords: Key words Sepsis ; Endotoxin ; Nitric oxide ; Pulmonary surfactant ; Acute respiratory distress syndrome ; Respiratory therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: To evaluate the efficacy of surfactant and inhaled nitric oxide (iNO) in endotoxin-induced acute lung injury (ALI).¶Design: Prospective, randomised, controlled experimental study.¶Setting: A medical university hospital research laboratory.¶Intervention: Twenty-nine adult rabbits (2.4–3.4 kg) were given two doses of intravenous endotoxin (Escherichia coli) (0.01 mg/kg and, 12 h later, 0.1 mg/kg), and then subjected to mechanical ventilation. After 8 h these animals were allocated to four treatment groups: (1) control, (2) iNO at 20 ppm (NO), (3) surfactant at 100 mg/kg (Surf) and (4) both surfactant and iNO as in groups 2 and 3 (SNO), and ventilated for a further 6 h followed by broncho-alveolar lavage (BAL), analysis of surfactant contents in BAL fluid and histological examination of the lungs.¶Measurements and results: All the animals had developed ALI with respiratory failure 8 h after the second dose of endotoxin as evidenced by a decrease of PaO2/FIO2 from 520 ± 30 to 395 ± 19 mmHg and dynamic compliance (Cdyn) from 1.20 ± 0.11 to 0.73 ± 0.05 ml/cmH2O × kg, and an increase of intrapulmonary shunting (Qs/Qt) from 7.5 ± 0.8 % to 12.9 ± 1.0 % (all measurements p 〈 0.01 versus baseline). In the SNO group, values for PaO2/FIO2, Cdyn and Qs/Qt after 6 h were 301 ± 15 mmHg, 0.67 ± 0.05 ml/cmH2O × kg and 16.5 ± 0.8 %, compared to 224 ± 26 mmHg, 0.53 ± 0.04 ml/cmH2O × kg and 24.1 ± 2.0 %, respectively, in the control group (all measurements p 〈 0.01). Both Surf and NO groups showed intermediate levels of these parameters. In both Surf and SNO groups, the minimum surface tension of BAL fluid was lower, and the content of disaturated phosphatidylcholine/total protein higher, than in the control and NO groups (p 〈 0.01). Histological features of lung injury were less prominent and wet/dry lung weight ratio lower in the NO, Surf and SNO groups. Decreased surfactant protein A (SP-A) and its mRNA expression were found in all endotoxin-exposed groups, but the SP-A content of the SNO group was moderately improved in comparison to the control group. Surfactant aggregate size was not affected.¶Conclusion: Early application of surfactant and iNO moderately mitigated ALI as reflected by improvement of lung mechanics, pulmonary perfusion and morphology.
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  • 9
    ISSN: 1572-8943
    Keywords: heterocyclic polymers ; mechanical properties ; thermal degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal mechanical properties and degradation behaviors were studied on fibers prepared from two high-performance, heterocyclic polymers, poly(p-phenylenebenzobisthiazole) (PBZT) and poly(p-phenylenebenzobisoxazole) (PBZO). Our research demonstrated that these two fibers exhibited excellent mechanical properties and outstanding thermal and thermo-oxidative stability. Their long-term mechanical tensile performance at high temperatures was found to be critically associated with the stability of the C—O or C—S linkage at the heterocyclic rings on these polymers' backbones. PBZO fibers with the C—O linkages displayed substantially higher thermal stability compared to PBZT containing C—S linkages. High resolution pyrolysis-gas chromatography/mass spectrometry provided the information of the pyrolyzates' compositions and distributions as well as their relationships with the structures of PBZT and PBZO. Based on the analysis of the compositions and distributions of all pyrolyzates at different temperatures, it was found that the thermal degradation mechanisms for both of these heterocyclic polymers were identical. Kevlar®-49 fibers were also studied under the same experimental conditions in order to make a comparison of thermo-oxidative stability and long-term mechanical performance at high temperatures with PBZO and PBZT fibers. The data of two high-performance aromatic polyimide fibers were also included as references.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 145 (2000), S. 19-34 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A hybrid inviscid/viscous flow problem is considered in this paper. The interface treatment is uniformly valid for problems with smooth and discontinuous solutions at the interface. It satisfies the requirement of conservation and nonlinear uniqueness for cases where the interface coincides with a shock. The well-posedness in the linear sense is studied for a two-dimensional hybrid inviscid/viscous flow problem.
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