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  • 1
    Digitale Medien
    Digitale Medien
    Low-temperature dependence of midinfrared optical constants of lead–germanium–telluride thin film (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3556-3561 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The design and manufacture of diode lasers for gas analysis or multilayer thin-film optical devices used at low-temperature require the refractive index and the temperature coefficient of IV–VI compound over a significant temperature range. In this article, the refractive index and the absorption coefficient of Pb0.94Ge0.06Te thin film have been determined from transmission spectra measured at temperature between 80 and 300 K in the spectral range of 2.5–8.5 μm by fitting based on a Lorentz-oscillator model. It is found that the maximum refractive index occurs at 150 K, which corresponds to the structural phase transition from rocksalt to rhombohedrally distorted structure and reflects an increase of lattice polarizability. The value of the index of refraction is 5.350–6.000 in the spectral range of 4.0–8.5 μm for all measured temperatures, which reveals that Pb1−xGexTe is a highly refractive infrared material. The temperature coefficient of refractive index, dn/dT, is found to be −0.006–0.002 K−1 in the spectral range of 3.0–8.5 μm for all measured temperature. An empirical formula that fits the temperature coefficient in the spectral range of 4.0-8.5 μm is presented. The dependence of the transmission and absorption spectra on decreasing temperature can be explained by the modification of the energy-band structure due to rhombohedral distortions. The conclusion can be drawn that anomalies corresponding to the ferroelectric phase transition occur in both refractive index and absorption coefficient of Pb1−xGexTe alloy. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1448866
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  • 2
    Digitale Medien
    Digitale Medien
    Molecular dynamics simulation of stick-slip (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3090-3094 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Molecular dynamics simulation was carried out to investigate the stick-slip on an atomic scale by using the embedded atom method potential for Ni–Al. The analyses of the dynamic features of the atoms in the sliding block clearly show that the elastic deformation of the surface layers is the main cause for the stick-slip phenomenon, which is consistent with the macroscopic stick-slip. The simulation results also indicate that phonons are emitted during stick-slip, and a commensurate fit between the contacting surfaces is not significant for the stick-slip friction. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1394916
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  • 3
    Digitale Medien
    Digitale Medien
    Bubble dynamics and shock waves generated by laser absorption of a photoacoustic sphere (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 2352-2362 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Theoretical analysis and extensive numerical simulations are performed on the system of a spherical absorber illuminated by a pulsed laser. Both bubble formation and shock wave generation are investigated. We find that a strong shock front forms just outside the absorber and attenuates quickly into an acoustic wave as it propagates away from the absorber. The formation and growth of the bubble is shown to have a gentle threshold dependence and to be a continuous function of the energy of the laser pulse with no explosive threshold. There is a weak dependence of the threshold fluence for bubble formation on the pulse duration of the laser. The bubble growth dynamics are also pulse-duration dependent for pulse lengths shorter than the thermal conduction time. For ultrashort pulses (shorter than the acoustic transit time across the absorber), the bubble dynamics approach a limiting growth trajectory. The process is a cooperative effect of both thermal and pressure interactions. We also find that variation of the absorber's mechanical parameters, such as the thermal expansion coefficient, can significantly alter not only the shock waves but also the bubble growth dynamics. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1288507
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  • 4
    Digitale Medien
    Digitale Medien
    Pulsed laser induced mode-mismatched crossed-beam thermal lens measurements (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2741-2749 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In this article, an accurate Fresnel diffraction model for a pulsed laser induced thermal lens effect in mode-mismatched crossed-beam configuration is presented. The effect of a lateral offset between the two beams is included in the model. This model is used to calculate the diffraction field of the probe beam at the detection plane from the very near- to the far-field, therefore the evolution of the intensity profile of the probe beam from the near- to the far-field is clearly illustrated. Numerical calculations predict and experimental results demonstrate that the thermal lens (TL) signal maximum is obtained when the probe beam propagates about a characteristic distance away from the sample position, while the characteristic distance is determined by the radius of the excitation beam in the sample and the wavelength of the probe beam. At large size mismatch of two beams and near-field detection cases, the TL signal is approximately independent on the sample location relative to the waist of the probe beam. The theoretical and experimental results are of great importance to configuration optimization of an extremely sensitive and compact TL instrument, which is the trend in the development of analytical instruments. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1148189
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  • 5
    Digitale Medien
    Digitale Medien
    Integrating Software into PRA: A Test-Based Approach (2005)
    350 Main Street , Malden , MA 02148 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Publishing, Inc.
    Risk analysis 25 (2005), S. 0 
    Details
    ISSN: 1539-6924
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Energietechnik
    Notizen: Probabilistic risk assessment (PRA) is a methodology to assess the probability of failure or success of a system's operation. PRA has been proved to be a systematic, logical, and comprehensive technique for risk assessment. Software plays an increasing role in modern safety critical systems. A significant number of failures can be attributed to software failures. Unfortunately, current probabilistic risk assessment concentrates on representing the behavior of hardware systems, humans, and their contributions (to a limited extent) to risk but neglects the contributions of software due to a lack of understanding of software failure phenomena. It is thus imperative to consider and model the impact of software to reflect the risk in current and future systems. The objective of our research is to develop a methodology to account for the impact of software on system failure that can be used in the classical PRA analysis process. A test-based approach for integrating software into PRA is discussed in this article. This approach includes identification of software functions to be modeled in the PRA, modeling of the software contributions in the ESD, and fault tree. The approach also introduces the concepts of input tree and output tree and proposes a quantification strategy that uses a software safety testing technique. The method is applied to an example system, PACS.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1539-6924.2005.00638.x
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  • 6
    Digitale Medien
    Digitale Medien
    Abundant Tissue Butyrylcholinesterase and Its Possible Function in the Acetylcholinesterase Knockout Mouse (2000)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 75 (2000), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: We have described recently an acetylcholinesterase (AChE) knockout mouse. While comparing the tissue distribution of AChE and butyrylcholinesterase (BChE), we found that extraction buffers containing Triton X-100 strongly inhibited mouse BChE activity. In contrast, buffers with Tween 20 caused no inhibition of BChE. Conventional techniques grossly underestimated BChE activity by up to 15-fold. In Tween 20 buffer, the intestine, serum, lung, liver, and heart had higher BChE than AChE activity. Only brain had higher AChE than BChE activity in AChE +/+ mice. These findings contradict the dogma, based mainly on observations in Triton X-100 extracts, that BChE is a minor cholinesterase in animal tissues. AChE +/- mice had 50% of normal AChE activity and AChE -/- mice had none, but all mice had similar levels of BChE activity. BChE was inhibited by Triton X-100 in all species tested, except rat and chicken. Inhibition was reversible and competitive with substrate binding. The active site of rat BChE was unique, having an arginine in place of leucine at position 286 (human BChE numbering) in the acyl-binding pocket of the active site, thus explaining the lack of inhibition of rat BChE by Triton X-100. The generally high levels of BChE activity in tissues, including the motor endplate, and the observation that mice live without AChE, suggest that BChE has an essential function in nullizygous mice and probably in wild-type mice as well.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1471-4159.2000.751320.x
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  • 7
    Digitale Medien
    Digitale Medien
    Inactivation of a Cytosolic Phospholipase A2 by Thiol-Modifying Reagents: Cysteine Residues as Potential Targets of Phospholipase A2 (1994)
    s.l. : American Chemical Society
    Biochemistry 33 (1994), S. 8594-8603 
    Details
    ISSN: 1520-4995
    Quelle: ACS Legacy Archives
    Thema: Biologie , Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/bi00194a026
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  • 8
    Digitale Medien
    Digitale Medien
    Inhibition of Escherichia coli glutamine synthetase by .alpha.- and .gamma.-substituted phosphinothricins (1990)
    s.l. : American Chemical Society
    Biochemistry 29 (1990), S. 366-372 
    Details
    ISSN: 1520-4995
    Quelle: ACS Legacy Archives
    Thema: Biologie , Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/bi00454a009
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  • 9
    Digitale Medien
    Digitale Medien
    Self-assembly of one-dimensional molecular and atomic chains using striped alkanethiol structures as templates (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1685-1687 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Well-ordered striped structures are developed from alkanethiol self-assembled monolayers on an Au(111) surface following well-controlled annealing processes. We demonstrate here that such regular concave–convex molecular structures can be used as the templates for growing one-dimensional molecular and atomic chains. By depositing C60 molecules onto the striped surface, C60 bimolecular chains are self-assembled. Due to the breaking of C–S bonds under certain conditions, residual S atoms can form a S monoatomic chain between two adjacent stripe pairs of thoroughly lying-down molecules. Possible growth mechanisms are discussed. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1402648
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  • 10
    Digitale Medien
    Digitale Medien
    Laser Pulse-Induced Photochemical Strand Cleavage of Site-Specifically and Covalently Modified (+)-anti-Benzo[a]pyrene Diol Epoxide-Oligonucleotide Adducts (1995)
    s.l. : American Chemical Society
    Chemical research in toxicology 8 (1995), S. 396-402 
    Details
    ISSN: 1520-5010
    Quelle: ACS Legacy Archives
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/tx00045a011
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