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  • 1
    Digitale Medien
    Digitale Medien
    Absence of anaplastic lymphoma kinase (ALK) and Epstein–Barr virus gene products in primary cutaneous anaplastic large cell lymphoma and lymphomatoid papulosis (1997)
    Oxford, UK : Blackwell Publishing Ltd
    British journal of dermatology 137 (1997), S. 0 
    Details
    ISSN: 1365-2133
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Summary The prevalence of the t(2:5)(p23;q35) and/or anaplastic lymphoma kinase (ALK) gene products in cutaneous anaplastic large cell (ALC) lymphomas and a potential precursor lesion, lymphomatoid papulosis (LyP). is controversial. ALK gene products, which are absent from normal lymphohae-matopoietic cells, are a phenotypic marker of lymphomas carrying the t(2:5). We used in situ hybridization and immunohistology to screen 14 cutaneous ALC lymphomas, 21 cases of LyP, and one nodal ALC lymphoma associated with LyP for ALK gene products. ALK gene products were not detectable in these cases. In contrast, ALK gene products were found in a lymphonodal ALC lymphoma with subsequent extension to the skin and in t(2:5)-positive cell lines. Detection of the Epstein-Barr virus (EBV)-encoded small nuclear transcripts (EBER), and of immunoglobulin light chain transcripts served to check for the presence of cellular RNA in the tissue sections. EBER transcripts were found in scattered reactive lymphoid cells, but not in atypical or tumour cells. ALK gene expression and EBV infection seem to be a rare finding in cutaneous ALC lymphomas and LyP. This points to a molecular aetiology of primary cutaneous ALC lymphomas and LyP distinct from that of extracutaneous CD30+ lymphoproliferative disease. Detection of the t(2;5) or ALK gene products in cutaneous lymphoproliferative lesions therefore requires exclusion of extracutaneous ALC lymphoma in such patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2133.1997.19352050.x
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  • 2
    Digitale Medien
    Digitale Medien
    CO2 laser light absorption characteristics of metal powders (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3835-3841 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Absorption characteristics of metal powders for 10.6 μm CO2 laser radiation were examined. Using a calorimetric method, absorptance measurements were performed on four different powder materials, including aluminum, copper, iron, and titanium aluminide. The experimental results showed that laser absorptance depends on powder porosity and material. The measured absorptance values at low laser intensities ranged between 28% and 43%. The titanium aluminide powders showed the highest absorptance values, and aluminum powders the lowest. As laser intensity was increased, the copper and iron powders showed strong signs of oxidation when irradiated in air, resulting in an increase in absorptance. Neither oxidation nor increased absorptance were observed when helium or argon were used as shielding gas. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.361811
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  • 3
    Digitale Medien
    Digitale Medien
    High-precision laser cutting of high-temperature superconductors (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2568-2570 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A laser-cutting technique was used to pattern high-temperature superconducting single crystals with high precision into various shapes. The low mean power of 135 mW of the laser enables one to produce cuts of arbitrary shape without affecting the superconducting parameters. This was proven by local observations of the magnetic flux distribution using the magnetooptical Faraday effect. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.116186
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  • 4
    Digitale Medien
    Digitale Medien
    Laser processing integrated into machine tools — design, applications, economy (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 1149-1164 
    Details
    ISSN: 1572-817X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract In the last few years, lasers have found new applications in production engineering as tools for surface treatment, cutting, welding, drilling and marking. So far, the laser has mainly been used in special laser processing machines (‘laser-only’) directly integrated into a production line or serving as stand-alone stations in the workshop. By combining conventional metal cutting technologies with laser processes in one machine, complete processing of a workpiece with different technologies in one setting can be realized. The main advantages are a reduction of the material flow between the production machines, which leads to a reduction in processing time and logistics, and an enhancement of manufacturing quality due to the processing in one setting. In addition to this approach, new processing technologies such as laser-assisted machining are possible. Applications of laser caving, hardening, welding and drilling of production parts in combination with the cutting process in one setting have been investigated with the aim of adapting these technologies to the characteristics of the machines and the typical parts spectra. Furthermore, various technical solutions for the integration of lasers into milling centres and lathes have been elaborated. In both situations the laser tool is handled like a standard tool and can be exchanged automatically. The main results will be reported, together with a brief discussion of the economic aspects of laser processing integrated into machine tools.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00326472
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  • 5
    Digitale Medien
    Digitale Medien
    Laser welding of aluminium lightweight materials: problems, solutions, readiness for application (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 1203-1211 
    Details
    ISSN: 1572-817X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract Using high-power CO2 and Nd:YAG lasers of high beam quality, high process efficiencies and excellent seam qualities are achieved. A particular method for obtaining almost pore-free weld seams without blowholes is the combining of the beams of two CO2 lasers. Without the need for filler material, crack-free welds can be produced in sheets of hot-crack susceptible, precipitation hardened alloys up to a welding speed of 5–7m min-1 for full penetration and up to 3–4m min-1 for partial penetration. In contrast, AlMg alloys containing more than 2.5wt% Mg and AlSi cast alloys are insensitive to hot-cracking even at high processing speeds. Laser welds possess much better static mechanical properties than gas tungsten arc (GTA) or gas metal arc (GMA) butt welds. For the alloys AlMgSi1 and AlMg5Mn the maximum static strength which can be achieved in laser welding is determined by the alloy type, i.e. the hardening mechanism and the heat-treated condition. Laser butt welded car body sheets without filler material exhibit the same load-bearing capacity under dynamical load as GMA welds with filler material. The latest research work has demonstrated that high-quality ‘tailored blanks’ with good mechanical properties can also be made out of different aluminium plates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00326476
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  • 6
    Digitale Medien
    Digitale Medien
    Scalable concept for diode-pumped high-power solid-state lasers (1994)
    Springer
    Applied physics 58 (1994), S. 365-372 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.55.Rz
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new, scalable concept for diode-pumped high-power solid-state lasers is presented. The basic idea of our approach is a very thin laser crystal disc with one face mounted on a heat sink. This allows very high pump power densities without high temperature rises within the crystal. Together with a flat-top pump-beam profile this geometry leads to an almost homogeneous and one-dimensional heat flux perpendicular to the surface. This design dramatically reduces thermal distortions compared to conventional cooling schemes and is particularly suited for quasi-three-level systems which need high pump power densities. Starting from the results obtained with a Ti:Sapphire-pumped Yb:YAG laser at various temperatures, the design was proved by operating a diode-pumped Yb:YAG laser with an output power of 4.4 W and a maximum slope efficiency of 68%. From these first results we predict an exctracted cw power of 100 W at 300 K (140 W at 200 K) with high beam quality from a single longitudinally pumped Yb: YAG crystal with an active volume of 2 mm3. Compact diode-pumped solid-state lasers in the kilowatt range seem to be possible by increasing the pump-beam diameter and/or by using several crystal discs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081875
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  • 7
    Digitale Medien
    Digitale Medien
    Excimer laser beam homogenizer with low divergence (1999)
    Springer
    Applied physics 69 (1999), S. S315 
    Details
    ISSN: 1432-0630
    Schlagwort(e): PACS: 42.62.C; 42.55.L; 42.79
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract. A new beam homogenizer device which leaves the beam parameter product almost unaffected is presented. Excimer laser beams usually show a nearly Gaussian beam profile along the short beam axis whereas along the long beam axis a nearly flat-top profile is provided. The new beam homogenizer efficiently converts the short beam axis into a top-hat profile featuring nearly the same divergence as the incoming laser beam. Depending on the output beam profile of the excimer laser the homogenizer presented provides a beam profile with a homogeneity of ±5% to ±10% within an area covering 65% to 70% of the total pulse energy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003390051407
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  • 8
    Digitale Medien
    Digitale Medien
    Shadowgraphic and interferometric investigations on Nd:YAG laser-induced vapor/plasma plumes for different processing wavelengths (1999)
    Springer
    Applied physics 69 (1999), S. S505 
    Details
    ISSN: 1432-0630
    Schlagwort(e): PACS: 52.40.Nk; 52.50.Jm; 52.70.Kz
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract. Shadowgraphic and interferometric images of vapor/plasma plumes generated by pulses of a ns-Nd:YAG laser reveal the distinctive behavior of the shock wave expansion for each of three processing wavelengths (1064 nm, 532 nm, and 355 nm), indicating that different mechanisms dominate the interaction between the optical fields and the material vapor/plasma. Electron density distributions within the plasma plumes calculated from interferometrically obtained refractive index distributions allow us to describe the regions of absorption and the absorption mechanisms using a simple model of inverse bremsstrahlung and photoionization, which allows us to estimate absorption coefficients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003390051454
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  • 9
    Digitale Medien
    Digitale Medien
    CO2 laser-induced plasma CVD synthesis of diamond (1998)
    Springer
    Applied physics 66 (1998), S. 575-578 
    Details
    ISSN: 1432-0630
    Schlagwort(e): PACS: 81.51.Gh+; 52.80.Tn
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 2 laser maintenance of a stationary optical discharge in a gas stream, exhausting over a substrate into the air (laser plasmatron). Nano- and polycrystalline-diamond films were deposited on tungsten substrates from atmospheric-pressure Xe(Ar):H2:CH4 gas mixtures at flow rates of 2 ?/min. A 2.5-kW CO2 laser focused beam produced plasma. The deposition area was about 1 cm2 and growth rates were up to 30–50 μm/h. Peculiarities and advantages of laser plasmatrons are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003390050716
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  • 10
    Digitale Medien
    Digitale Medien
    Phase investigation in laser surface alloyed steels with TiC (1995)
    Springer
    Journal of materials science 30 (1995), S. 1849-1853 
    Details
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Laser technology enables melting and alloying specimen surfaces without the substrate itself being heated, whereby surfaces with special attributes are obtained with the properties of the substrate remaining unaffected. The surfaces of Armco iron and AISI 1045 steel were laser-alloyed with TiC powder, a CO2 laser of 2.5 kW maximum power being used. Optimal laser and powder-feed parameters were established. Particles of TiC were injected into the molten surface layer, forming a composite material, steel + TiC. The microstructures were investigated metallographically. Some of the particles had partially melted during their passage through the laser beam and had re-solidified, forming small and fine dendrites. Phase identification by X-ray diffraction revealed the presence of α-Fe, martensite, and Fe3C phases, as well as amounts of stochiometric TiC and unknown phases. Identification of phases by TEM and diffraction of electrons revealed the presence of unknown phases, such as tetragonal TiC and (FeTi)C. Mössbauer results show ternary Fe-Ti-C phases, which can be related to the TEM and X-ray diffraction results. A correlation was found between the substrate's composition, microstructures, and the different phases present.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00351621
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