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101.
We have studied transverse momentum distributions for exclusive
0 muoproduction on protons and heavier nuclei at 2Q
2<25>25>2. TheQ
2 dependence of the slopes of thep
t
2
andt distributions is discussed. The influence of the non-exclusive background is investigated. Thep
t
2
-slope for exclusive events is 4.3±0.6±0.7 GeV–2 at largeQ
2. Thep
t
2
spectra are much softer than inclusivep
t
2
spectra of leading hadrons produced in deep inelastic scattering.Supported by Bundesministerium für Forschung und Technologie 相似文献
102.
Masella R Straface E Giovannini C Di Benedetto R Scazzocchio B Viora M Cantafora A Malorni W 《Photochemistry and photobiology》2000,71(1):97-102
Oxidized LDL (ox-LDL) have been involved in the pathogenesis of several human diseases including dermatological pathologies. Oxidative modification of low-density lipoproteins (LDL) is accompanied by both extensive degradation of its polyunsaturated fatty acids and production of lipoperoxides. These highly reactive products induce an intracellular oxidative stress with a variety of cytotoxic effects. In order to evaluate cellular damage induced by oxidative stress in epidermal cells, a human epidermoid carcinoma cell line in culture (A 431) was used as experimental model. Cell treatment with UV-oxidized LDL resulted in cytostatic and cytotoxic effects characterized by morphological and functional alterations: inhibition of cell proliferation, modifications of cytoskeleton network, microtubular derangement, loss of cell–cell and cell–substrate contacts, cell detachment and cell death by apoptosis. The ox-LDL-induced alterations were almost completely prevented by pre-incubating cells with α-tocopherol. The results presented here could be of relevance for a better comprehension of the pathogenic mechanisms of several human diseases, including dermatological pathologies, and could indicate that antioxidants such as α-tocopherol could represent an important therapeutic challenge in the maintenance of cell and tissue homeostasis in the long run. 相似文献
103.
104.
105.
P. Krötz D. Stupar J. Krieg G. Sonnabend M. Sornig F. Giorgetta E. Baumann M. Giovannini N. Hoyler D. Hofstetter R. Schieder 《Applied physics. B, Lasers and optics》2008,90(2):187-190
Quantum cascade (QC) structures, for both emitting and detecting mid-infrared radiation, are powerful devices for spectroscopy.
QC lasers (QCLs), which have been built for nearly 15 years, already play the leading role in certain wavelength regions.
QC detectors (QCDs) are a fairly new development, which has been evolving from the QCL research. In high-resolution heterodyne
spectrometers for astronomy, such as the Cologne tuneable heterodyne infrared spectrometer (THIS), QC devices help to open
new windows to space as discussed in this paper. We will briefly review the use of QC devices in THIS, show recent results
in measuring planetary atmospheric dynamics and give an outlook to astronomical goals for the future.
PACS 33.70.Jg 相似文献
106.
Widely tunable mode-hop free external cavity quantum cascade lasers for high resolution spectroscopy and chemical sensing 总被引:1,自引:0,他引:1
G. Wysocki R. Lewicki R.F. Curl F.K. Tittel L. Diehl F. Capasso M. Troccoli G. Hofler D. Bour S. Corzine R. Maulini M. Giovannini J. Faist 《Applied physics. B, Lasers and optics》2008,92(3):305-311
Recent progress in the development of room temperature, continuous wave, widely tunable, mode-hop-free mid-infrared external
cavity quantum cascade laser (EC-QCL) spectroscopic sources is reported. A single mode tuning range of 155 cm-1 (∼ 8% of the center wavelength) with a maximum power of 11.1 mW and 182 cm-1 (∼ 15% of the center wavelength) with a maximum power of 50 mW was obtained for 5.3 and 8.4 μm EC-QCLs respectively. This
technology is particularly suitable for high resolution spectroscopic applications, multi species trace-gas detection and
spectroscopic measurements of broadband absorbers. Several examples of spectroscopic measurements performed using EC-QCL based
spectrometers are demonstrated.
PACS 42.55.Px; 42.60.-v; 42.62.Fi; 07.07.Df 相似文献
107.
Choi H Diehl L Wu ZK Giovannini M Faist J Capasso F Norris TB 《Physical review letters》2008,100(16):167401
Quantum cascade lasers are semiconductor devices based on the interplay of perpendicular transport through the heterostructure and the intracavity lasing field. We employ femtosecond time-resolved pump-probe measurements to investigate the nature of the transport through the laser structure via the dynamics of the gain. The gain recovery is determined by the time-dependent transport of electrons through both the active regions and the superlattice regions connecting them. As the laser approaches and exceeds threshold, the component of the gain recovery due to the nonzero lifetime of the upper lasing state in the active region shows a dramatic reduction due to the onset of quantum stimulated emission; the drift of the electrons is thus driven by the cavity photon density. The gain recovery is qualitatively different from that in conventional lasers due to the superlattice transport in the cascade. 相似文献
108.
Continuous-wave operation of an external cavity quantum-cascade laser on a thermoelectric cooler is reported. The active region of the gain element was based on a bound-to-continuum design emitting near 5.15 microm. The external cavity setup was arranged in a Littrow configuration. The front facet of the gain chip was antireflection coated. The laser could be tuned over more than 170 cm(-1) from 4.94 to 5.4 microm and was single mode over more than 140 cm(-1). The output power was in excess of 10 mW over approximately 100 cm(-1) and in excess of 5 mW over approximately 130 cm(-1) at -30 degrees C. 相似文献
109.
Photoinduzierte nucleophile Substitution von 3-substituierten 2,1-Benzisoxazolen (unter Ringöffnung)
On UV.-irradiation in strongly acidic solution 3-alkyl- and 3-aryl-2,1 benzisoxazoles, respectively, yield 5-substituted 2-aminophenylketons. 相似文献
110.