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  • Artikel  (164)
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  • Artikel  (164)
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  • 1
    Digitale Medien
    Digitale Medien
    The effects of aqueous solvent structure on the mutarotation kinetics of glucose (1977)
    Springer
    Journal of solution chemistry 6 (1977), S. 203-216 
    Details
    ISSN: 1572-8927
    Schlagwort(e): Glucose ; kinetics ; mixed solvent ; kinetic isotope effect ; enthalpy of activation ; entropy of activation ; tetrahydrofuran ; tert-butanol ; mutarotation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The mutarotation rates of glucose in aqueous mixtures of tetrahydrofuran andtert-butanol in the mole fraction (xi) range 0〈xi〈0.2 have been measured at 5° intervals in the range 5–35°C. The kinetic deuterium isotope effects have been determined for the same solvent compositions at 25 and 35°C. A statistical analysis of the Arrhenius plots indicates that the experimental errors, although small, are too large for the establishment of any compensation behavior between ΔH
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00646739
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  • 2
    Digitale Medien
    Digitale Medien
    Solvent effects on the acid-catalyzed hydrolysis of tetramethylurea (1976)
    Springer
    Journal of solution chemistry 5 (1976), S. 163-169 
    Details
    ISSN: 1572-8927
    Schlagwort(e): Solvent effects ; tetramethylurea ; hydrolysis ; hydrogen bonding ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Tetramethylurea was hydrolyzed in aqueous hydrochloric acid at temperatures of 80, 90, and 100°C. All reactions were carried out in an excess of both tetramethylurea and water, with first-order dependence on acid concentration being observed. As the concentration of water was increased, the rate of hydrolysis decreased until equimolar amounts of water and tetramethylurea were present. Subsequent addition of water had no effect on the observed rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00654333
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  • 3
    Digitale Medien
    Digitale Medien
    Excimer ArF/XeF lasers providing high-power stimulated radiation in Ar/Xe and F lines (1977)
    Springer
    Applied physics 14 (1977), S. 231-233 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Lasing in atomic lines of noble gases and fluorine, prior to excimer radiation, was observed in an electric discharge ArF/XeF excimer laser. Some Ar/Xe lines end at metastable levels, which are very important for the formation of ArF/XeF excimer molecules. Five new lasing lines of atomic fluorine have been obtained. Consideration is given to the use of lasing in atomic and molecular lines, that occurs in one burst, in investigations of the excitation kinetics of excimer states under the conditions of a high-pressure electric discharge.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00883096
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  • 4
    Digitale Medien
    Digitale Medien
    Properties and current-voltage characteristics of discharges in waveguide gas lasers (1977)
    Springer
    Applied physics 14 (1977), S. 277-282 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 52
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The paper deals with the properties andI-V characteristics of discharges in narrow capillaries used, for example, for He−Ne waveguide lasers. It has been observed that discharges in He−Ne waveguide lasers are unstable because of the strongly falling characteristic. A theory is presented which assumes that at low currents wall charges restrict the positive column to a narrow plasma channel and are the main reason for the observed falling characteristic. A numerical evaluation for helium gives results which agree well with experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00882732
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  • 5
    Digitale Medien
    Digitale Medien
    Models of DNA-dye-complexes: Energy transfer and molecular structures as evaluated by laser excitation (1979)
    Springer
    Applied physics 18 (1979), S. 333-338 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 87 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Energy transfer in DNA-dye-complexes after excitation in the UV down to 220 nm by means of a tunable laser was investigated. DNA of different base composition and polynucleotides were compared. The dyes proflavine, acridine orange and ethidium bromide were used. The energy transfer from DNA-bases to dye molecules was measured in dependence of the excitation wavelength and the base composition of the DNA. Models of the energy transfer from DNA to dye and of the molecular structures of the DNA-dye-complex (intercalation) could be deduced.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00899685
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  • 6
    Digitale Medien
    Digitale Medien
    Free-electron lasers and masers on curved paths (1979)
    Springer
    Applied physics 19 (1979), S. 47-51 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The possibility of building free-electron lasers and masers with quasi-circular undulators is considered. The two-mirror cavity is replaced by a suitable waveguide. The magnetic field along the orbit has a continuous component superimposed on the alternating one. Besides allowing large freedom for electron guiding and focusing, the structure allows effective negative mass conditions, which may enhance the electron beam modulation when space charge effect are important. Furthermore the radiation frequency can be higher than that in a linear undulator with the same electron energy, and long interaction times are possible in a compact structure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00900537
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  • 7
    Digitale Medien
    Digitale Medien
    Laser properties of praseodymium pentaphosphate single crystals (1979)
    Springer
    Applied physics 19 (1979), S. 345-351 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 78.55 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract PrP5O14, PrxLa1−xP5O14, and PrxY1−xP5O14 (0≦x≦1) single crystals of laser quality were synthesized and their crystallographic and optical parameters measured. Laser emissions in the visible (λ=637.4 nm) with no mirrors in place (superradiance) and also in various optical resonators have been observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00900479
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  • 8
    Digitale Medien
    Digitale Medien
    Continuous laser oscillation in diatomic molecular sodium (1977)
    Springer
    Applied physics 13 (1977), S. 97-99 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract First cw laser oscillation with thresholds below 1 mW was observed for various B1Пu → X1 ∑ g + transitions of diatomic molecular sodium excited by different argon laser lines in the range of 454–488 nm. For pump powers of 0.5 W output powers up to 3 mW and single-pass gain up to 0.1 cm−1 were obtained. Some properties of the heat pipe laser system are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00890727
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  • 9
    Digitale Medien
    Digitale Medien
    Optically pumped FIR-laser with variable Fabry-Perot output coupler (1977)
    Springer
    Applied physics 13 (1977), S. 383-385 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract An optically pumped FIR laser was operated with a copper mesh Fabr-Perot output coupler. With this device a Gaussian output beam was obtained andthe degree of coupling could be varied continuously, thus allowing optimum coupling. From the measured properties of the wire mesches grains of two FIR laser lines are calculated and the saturation intensities estimated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00882614
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  • 10
    Digitale Medien
    Digitale Medien
    A magnetic tuning system for dye lasers (1977)
    Springer
    Applied physics 14 (1977), S. 25-28 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A new device for magnetically displacing the output mirror of a laser resonator and synchronously tilting an etalon in order to obtain single-mode tuning of a dye laser over a tuning range of at least 10 GHz is described. Comparatively large displacements with good linearity of a coil mounted on a membrane and placed inside the strong magnetic field of a ring magnet are obtained for currents in the order of several hundred milliamperes. Together with etalon flats of appropriate thickness and reflection mounted in the resonator of the laser a versatile instrument for application in intra and extra cavity spectroscopy has been developed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00882629
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  • 11
    Digitale Medien
    Digitale Medien
    Measurements of some reaction rates of importance in KrF lasers (1977)
    Springer
    Applied physics 14 (1977), S. 393-398 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 34 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A flowing afterglow method has been used to study a number of reactions of importance in KrF lasers using NF3 as the fluorine donor. Total rate constants are reported for Kr*(3 P 2)+NF3 and Kr++NF3. The thermal energy attachment coefficient has been measured for NF3 and the cross section for the electron excitation process Kr*(3 P 2) +e→Kr*(3 P 1)+e has been estimated. The relevance of these results to discharge pumped KrF lasers is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00883445
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  • 12
    Digitale Medien
    Digitale Medien
    Argon laser with wall stabilized transverse discharge (1977)
    Springer
    Applied physics 14 (1977), S. 193-197 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 52
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Planar and cylindrical discharges for argon lasers are compared by plasmatheoretical calculations. The maximum laser output power available in the two arrangements is computed in dependence of various parameters neglecting saturation mechanisms. A transverse discharge arrangement confining the positive column by two parallel walls is described and experimental laser threshold values for the current and pressure are reported.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00883089
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  • 13
    Digitale Medien
    Digitale Medien
    Modulation behavior of semiconductor injection lasers (1977)
    Springer
    Applied physics 14 (1977), S. 255-268 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.80 ; 42.55 ; 85.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract GaAs double heterostructure semiconductor injection lasers which now exhibit more than 25000 h cw room temperature lifetime are of great interest for future use as directly modulated transmitters for high bit-rate fiber optical communications. The effects limiting this application are modulation distortions, spectral width and additional spectral broadening in the case of modulation and spontaneous fluctuations of the output power. The dynamic and spectral behavior of injection lasers, the methods of high bit-rate modulation and the improvement of the high bit-rate modulation capability by coupling two lasers are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00882730
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  • 14
    Digitale Medien
    Digitale Medien
    Electron energy loss spectra of dye vapors (1978)
    Springer
    Applied physics 15 (1978), S. 185-190 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Electron energy loss studies of POPOP andp-terphenyl in the vapor phase at an incident electron energy of 25 eV have been performed. The spectra covering an energy loss between 0 and 9 eV revealed a considerable initial triplet population under electron impact excitation. The implications for electron-beam pumped vapor phase dye lasers are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00928206
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  • 15
    Digitale Medien
    Digitale Medien
    High-power argon-ion laser with titanium covered beryllia discharge tube (1978)
    Springer
    Applied physics 15 (1978), S. 229-232 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A new type of discharge tube for high-power argon-ion lasers constructed of a segmented metal-ceramic compound system is described. Up to date, the system has been operating for 1500 h without failure. The maximum cw output is 140 W, limited by the destruction of the mirrors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00928214
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  • 16
    Digitale Medien
    Digitale Medien
    Ultrashort-pulse generation by lasers with saturable absorbers (1978)
    Springer
    Applied physics 15 (1978), S. 439-450 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A theoretical model for the ultrashort-pulse (USP) generation by lasers with saturable absorbers is presented. The gain medium is assumed to be a two-level system whereas the absorber is described by a four-level system which is characterized by a two-stage absorption process and the pertinent relaxation times. Laser dynamical equations are developed in the rate-equation approximation and boundary conditions appropriate for an unidirectional ring cavity are established. Evolution of USP is investigated for different combinations of parameter values appropriate for solid-state laser systems by computer simulation, employing a finite difference approximation for the dynamical equations. It is shown that USP output is attainable even if the cross-section of the excited-state absorption isgreater than that of the ground-state absorption and the laser is operating just above threshold. In fact, it is found that through the participation of a strong excited-state absorption the discrimination against satellite pulses is enhanced so that single-pulse output is more achievable. Furthermore, it is proposed that single picosecond pulses may be obtainable from relatively broad initial peaks by utilizing the high pulse-selection and pulse-shortening efficiency of the absorber due to the contribution of the excited-state absorption. The applicability of the present model to singlet-triplet crossing and photoisomer formation is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886165
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  • 17
    Digitale Medien
    Digitale Medien
    Efficient spectral narrowing and tuning of a cw dye laser with a low-loss diffraction grating (1978)
    Springer
    Applied physics 16 (1978), S. 297-301 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A grating-tuned cw dye laser with an emission bandwidth of less than 1 GHz and output power in excess of 400 mW has been constructed. This was accomplished using a newly developed holographic grating with sinusoidal groove profile, which resulted in an enhanced spectral efficiency up to 94%. The low losses and the broad spectral working range (more than 1000 Å) which can be easily covered by simple rotation make these gratings an attractive single-stage tuning element for low-gain cw lasers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00885125
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  • 18
    Digitale Medien
    Digitale Medien
    Tunable UV-radiation by stimulated Raman scattering in hydrogen (1978)
    Springer
    Applied physics 16 (1978), S. 151-154 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.65 ; 42.55 ; 33
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract We observed tunable UV radiation down to 175 nm by SRS of the output of a frequency-doubled dye laser in H2. The high power output of the 4th anti-Stokes to 5th Stokes line generated by the frequency doubled dye laser and the 8th anti-Stokes to 3rd Stokes line generated by the undoubled dye laser represents a broadly tunable coherent radiation source between 189 nm and 2064 nm.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00930379
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  • 19
    Digitale Medien
    Digitale Medien
    A simple and reliable short-pulse dye laser (1977)
    Springer
    Applied physics 13 (1977), S. 109-110 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A simple technique is described that allows the generation of a short pulses (1 ns) from dye lasers pumped by a much longer (7 ns) N2-laser pulse. Dye-laser pulses, either with a narrow bandwidth or a short duration, can thus be obtained with the same N2-laser pump.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00890731
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  • 20
    Digitale Medien
    Digitale Medien
    Quasi-cw laser action in K5Nd(MoO4)4 (1978)
    Springer
    Applied physics 17 (1978), S. 367-370 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 78.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract We report on room temperature quasi-cw laser action in K5Nd(MoO4)4 at a wavelength of 1.067 μm. The crystal was pumped with the 5140 Å line of an argon ion laser. Due to thermal effects actual cw lasing was not possible. Chopping the pump light with a low duty cycle of 1∶1000 leads to quasi-cw laser action and stable output power. We have determined the fundamental laser parameters: threshold pump powerA T=15 mW, slope efficiency η=22%, and internal lossesL=2.5%. In order to explain the measured relaxation oscillations, diffusion of the excited 4f-excitons is considered. According to a recently developed theory, a diffusion constant ofD=2×10−6cm2/s explains the observed results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886207
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  • 21
    Digitale Medien
    Digitale Medien
    Tunable laser via F 2 + and F 2 − colour centers in the spectral region 0.88–1.25 μm (1977)
    Springer
    Applied physics 14 (1977), S. 121-122 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Frequency-tunable generation by means of F 2 + and F 2 − colour centers in a LiF crystal is reported. Colour centers were created by illuminating LiF crystals with electrons of 3 meV energy at the electron current density of 1 μA/cm2. The pumping source was a ruby laser with a peak power of 20 MW, a pulse duration of 20 ns, and a repetition rate of 1 Hz. The frequency tuning is obtained in the range of 0.88–1.25 μm. Discussed are the ways of pumping of colour centers and the possibility of lasing in the spectral region of 0.85 to 2 μm in the type of colour centers under investigation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00882641
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  • 22
    Digitale Medien
    Digitale Medien
    Polarization spectroscopy with ultrashort light pulses (1979)
    Springer
    Applied physics 18 (1979), S. 257-260 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 32 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract We have demonstrated the feasibility of Doppler-free polarization spectroscopy with a train of ultrashort pulses from a synchronously pumped mode-locked dye laser. The sensitivity of the method is compared with saturation spectroscopy with a single-mode laser.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00885511
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  • 23
    Digitale Medien
    Digitale Medien
    High-energy dye laser pumped by wall-ablation lamps (1978)
    Springer
    Applied physics 15 (1978), S. 191-196 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A guideline for the optimum design of linear wall-ablation lamps is presented with a simple empirical formula which describes the luminescent characteristics of lamps. The absolute luminescent efficiency of the wall-ablation lamp was measured. A high-energy dye laser with a quadruple-elliptical cylindrical cavity was constructed using these lamps, and an output energy of 23.3 J (11.6 MW) was obtained with an overall efficiency of 0.31 %. The energy-flow diagram of this laser system was computed with a rate-equation analysis, and the conversion efficiency from electrical input to laser output was determined. One can expect an overall efficiency of about 2 %.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00928207
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  • 24
    Digitale Medien
    Digitale Medien
    Threshold singularities of optically pumped dye lasers (1978)
    Springer
    Applied physics 17 (1978), S. 181-187 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A complete theoretical model for optically pumped dye lasers is studied using the rate equation approach which includes excited singlet and triplet state absorption effects. Closed-form solutions under steady-state conditions reveal a novel nonlinear threshold phenomenon: partial reabsorption of the excited laser light can lead to a discontinuous onset of laser oscillation above laser threshold. Theoretical and experimental results for a transversely and longitudinally pumped rhodamine 6G laser are presented in terms of softmode and hardmode behavior at threshold.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00885253
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  • 25
    Digitale Medien
    Digitale Medien
    The external-resonator cw spin-flip Raman laser; output characteristics and spectroscopic applications (1979)
    Springer
    Applied physics 19 (1979), S. 205-212 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The characteristics of a stable, external-resonator spin-flip Raman laser (SFRL), pumped by a cw carbon monoxide laser of controlled mode quality and spectral content, are determined using a combination of molecular spectroscopy, Raman amplifier and confocal Fabry-Perot interferometer measurements, and heterodyne detection. Single-frequency output of a free-running external-resonator is demonstrated with an inherent linewidth of 〈10 kHz and a short-term frequency jitter of ≃100 kHz. With the resonator length actively controlled to lock an axial mode frequency to the peak of the spontaneous gain, the linewidth of the SFRL output was maintained below 2 MHz. In this mode of operation, small variations in the output tuning rate, corresponding to the magnetic field dependence of the conduction-electrong-factor, were calibrated. Molecular absorption spectra obtained using gas cells both inside and outside the resonator have been used to illustrate the high resolution, wide-range tuning capability and sensitivity of the system. Lambda-doubling of the $$^2 \pi _{3/2} $$ of the Q-branch head of nitric oxide was measured for values ofJ down to 13/2, below which the splitting is less than the Doppler width. The splittings agreed with predictions using parameters obtained by conventional spectra for higherJ-values.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00932399
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  • 26
    Digitale Medien
    Digitale Medien
    New FIR laser lines from optically pumped methanol analogues (1979)
    Springer
    Applied physics 19 (1979), S. 241-242 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Several new laser lines using optically pumped deuterated methanol molecules have been discovered. These not only increase the spectral coverage of pumped methanol isotopes but may assist in the assignment of a molecular structure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00932405
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  • 27
    Digitale Medien
    Digitale Medien
    Efficient single-mode operation of a standing-wave dye laser (1979)
    Springer
    Applied physics 19 (1979), S. 399-403 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The selection of a single longitudinal mode of a dye laser can be achieved with double or triple Michelson reflectors instead of Fabry-Perot etalons inside the laser cavity. These systems can be adapted to commercial multimode dye lasers. They provide a high efficiency and a good geometrical quality of the output beam. With a 7 watt pump power (λ=514.5 nm line of the Ar+ laser), a tunable output power of 1 watt was obtained at the peak of R6G, in the main output beam; the total single-mode power, including the auxiliary output beams, exceeded 1.4 watt. These results correspond to efficiencies of 14% and 20%, respectively (24% and 30% slope efficiencies). We discuss in the text why these efficiencies are comparable to those of ring lasers. In the infrared, with a 4.5 watt pump power (red lines of a Kr+ laser), 250 mW of single-mode output power in the main output beam was obtained at 780 nm with Oxazine 750.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00930103
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  • 28
    Digitale Medien
    Digitale Medien
    Spectral coincidences between CO-Laser and nitric-oxide. A reinvestigation (1979)
    Springer
    Applied physics 19 (1979), S. 427-429 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 33 ; 35 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Spectral coincidences between CO-laser lines and NO fundamental absorption lines were reinvestigated in order to resolve discrepancies between recently published papers. The absorption of CO laser radiation by NO and NO/Ar mixtures was measured and fitted by calculations using a Voigt profile for the NO line shapes. A new coincidence with a frequency offset of less than the NO Doppler width was found.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00930107
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  • 29
    Digitale Medien
    Digitale Medien
    Extended spectral distribution of lasing transitions in a liquid-nitrogen cooled CO-laser (1979)
    Springer
    Applied physics 19 (1979), S. 439-440 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 07 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A liquid-nitrogen cooled12C16O laser was operated both Q-switched and cw. A total of 276 lasing transitions were observed in cw using an intracavity grating for line selection. In the Q-switch mode, 230 lines occurred without dispersive element in the cavity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00930109
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  • 30
    Digitale Medien
    Digitale Medien
    A broadly tunable IR waveguide Raman laser pumped by a dye laser (1979)
    Springer
    Applied physics 18 (1979), S. 235-241 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.65C ; 42.55 ; 33.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Design and performance characteristics of a tunable ir waveguide Raman laser pumped by a high power dye laser are described. Using SRS up to third Stokes order in compressed H2, the wavelength range from 0.7 to 7 μm has been covered without gaps. Taking advantage of a waveguide structure in the scattering chamber, energy conversion efficiencies better than 1% with power levels in excess of 80 kW for the third Stokes component have been achieved. The experimental results support the theoretical predictions that a 4-wave parametric process is responsible for the production of the third Stokes component.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00885508
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  • 31
    Digitale Medien
    Digitale Medien
    A free-electron laser in a uniform magnetic field (1979)
    Springer
    Applied physics 20 (1979), S. 41-50 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 41 ; 42.55 ; 95
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The interaction of free electrons and free electromagnetic radiation, in the presence of a uniform magnetic field, can result in stimulated emission or absorption. We analyze the dynamics of single electrons by solving the classical, relativistic Lorentz force equations of motion in these combined fields. An electron may gain energy from, or lose energy to, the radiation field, depending crucially on the phase and oscillation frequency of the electron's helical motion within the superposed, circularly polarized light wave. To first order in the radiation field strength, electrons in a monoenergetic, uniformly distributed beam become spatially bunched, but there is no net energy change. To second order, however, the beam may experience a gain or loss of energy, corresponding to attenuation or amplification of radiation. We compare the bunching of this laser process to the bunching processes involved in 1) the Stanford free-electron laser and 2) the cyclotron maser, and find significant differences in each case. Our analytic results provide a clear, simple picture of the interaction process, and can be useful in exploring light amplification in astrophysical magnetic fields, the magnetosphere, or in laboratory devices.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00901785
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  • 32
    Digitale Medien
    Digitale Medien
    A laser accelerator (1979)
    Springer
    Applied physics 20 (1979), S. 61-65 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract We show that a laser can efficiently accelerate charged particles if a magnetic field is introduced to improve the coupling between the particle and the wave. Solving the relativistic equations of motion for an electron in a uniform magnetic field and superposed, circularly polarized electromagnetic wave, we find that in energy-position phase space an electron traces out a curtate cycloid: it alternately gains and loses energy. If, however, the parameters are chosen so that the electron's oscillations in the two fields are resonant, it will continually accelerate or decelerate depending on its initial position within a wavelength of light. A laboratory accelerator operating under these resonant conditions appears attractive: in a magnetic field of 105 Gauss, and the fields of a 5×1012 W, 10 μm wavelength laser, an optimally positioned electron would accelerate to 700 MeV in only 10m.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00901788
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  • 33
    Digitale Medien
    Digitale Medien
    A double-wavelength nitrogen-laser-pumped dye laser (1979)
    Springer
    Applied physics 20 (1979), S. 97-99 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A narrow-band tunable double-wavelength dye laser with a bandwidth of 0.1 cm−1 is described. The output at one of the wavelengths is found to be completely linearly polarized in the plane of incidence.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00901793
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  • 34
    Digitale Medien
    Digitale Medien
    Excimer gas-discharge tunable ArF laser (1977)
    Springer
    Applied physics 13 (1977), S. 107-108 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Intense laser oscillation has been observed from ArF molecules at 1933 Å. Excitation of the gas mixture NF3:Ar:He=1:55:630 at total pressures above 2.1 atm was produced by a transverse electric discharge. The range of fine tuning was from 1927 Å to 1936 Å. An output energy of 0.8 mJ was measured from a laser pulse 15 ns in duration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00890730
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  • 35
    Digitale Medien
    Digitale Medien
    Polarization properties of a single-mode gas laser in transverse magnetic fields (1978)
    Springer
    Applied physics 17 (1978), S. 257-267 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 32.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The effect of transversally applied magnetic fields on the polarization behavior of a single-mode gas laser is theoretically investigated, stressing the importance of the additivity of respective contributions influencing the time evolution of polarization parameters. By adding a new element to the existing theory, namely the contribution of magnetic-field-free regions in the active medium, and by considering the relatively large effects that small cavity anisotropies can cause, several apparent discrepancies between experiments and existing theory are resolved.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886954
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  • 36
    Digitale Medien
    Digitale Medien
    Feedback controlled self-excitation of optical pulses in a CW dye ring laser (1978)
    Springer
    Applied physics 15 (1978), S. 59-63 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Feedback controlled self-excitation of optical pulses of nanosecond duration has been observed to occur rather reliably in a CW dye ring laser, oscillating in a traveling mode. These observations are described analytically by means of a direct time domain approach. It is shown that a steady-state Gaussian pulse whose time duration determined from the self consistency condition in terms of system characteristics describes accurately the observed pulse behaviors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00896891
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  • 37
    Digitale Medien
    Digitale Medien
    Intrapulse thermally induced wavelength shift in a distributed feedback dye laser (1979)
    Springer
    Applied physics 19 (1979), S. 39-41 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract It is shown that when a distributed feedback dye laser is used to generate a train of picosecond pulses, the narrow lines observed in the spectrum are not longitudinal modes, but are due to the intrapulse refractive index changes caused by the heating effect of the pumping pulse.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00900535
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  • 38
    Digitale Medien
    Digitale Medien
    Laser-fluctuation measurements in a bath of strong Gaussian noise (1979)
    Springer
    Applied physics 18 (1979), S. 415-419 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Remarkable intensity fluctuations were observed in the LiNdP4O12 (LNP) laser by placing a moving ground-glass plate across the ouput beam. Resonance-like behaviors were also observed by tuning the moving velocity of the ground-glass plate, with respect to relaxation oscillations. Classical rate equations including the modulation term were given to explain the observed phenomena. Similar intensity fluctuations corresponding to relaxation oscillations were observed when the LNP laser light beam was coupled to an optical fiber.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00899696
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  • 39
    Digitale Medien
    Digitale Medien
    Efficient dye lasers pumped by a XeCl excimer laser (1979)
    Springer
    Applied physics 19 (1979), S. 35-37 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Results of an investigation of 19 organic dyes pumped by a 1.7 MW discharge-pumped XeCl excimer laser are reported. The dye-laser emission covered a wide wavelength range from 340 nm to 710 nm.P-terphenyl shows efficient laser action. The highest energy conversion efficiency exceeds 40% in visible region. In comparison with 250 kW nitrogen laser pumping, higher efficiencies are obtained for most of these dyes in the same dye-laser configuration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00900534
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  • 40
    Digitale Medien
    Digitale Medien
    On the interaction of stimulated spin-flip raman scattering and stimulated recombination radiation in InSb (1979)
    Springer
    Applied physics 19 (1979), S. 185-189 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract We have studied the interaction of stimulated spin-flip Raman scattering and stimulated recombination radiation in n-InSb using a CW CO pump laser. A change in linewidth and output power of second Stokes spin-flip radiation is observed when the tuning curve of the first Stokes stimulated spin-flip radiation and the stimulated recombination radiation cross. The observations are explained using a simple rate equation model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00932395
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  • 41
    Digitale Medien
    Digitale Medien
    NdP5O14 and NdAl3(BO3)4 lasers at 1.3 μm (1979)
    Springer
    Applied physics 18 (1979), S. 77-80 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 78.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract We report, for the first time, on room temperature cw laser action of NdP5O14 and NdAl3(BO3)4 at 1.3 μm wavelength. The emission cross sections of the transition4 F 3/2→4 I 13/2 are 0.24·10−19 cm2 and 1.74·10−19 cm2, respectively. The lowest observed threshold was 45 mW and the slope efficiency was nearly 10%. The minimum threshold is expected to be about 5 mW of absorbed pump light for both materials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00935906
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  • 42
    Digitale Medien
    Digitale Medien
    Collisional effects upon optical coherences: Experimental study in a xenon three-level system (1979)
    Springer
    Applied physics 20 (1979), S. 83-88 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 32 ; 34 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Laser induced nonlinear absorption profiles in a three-level system have been recorded to study the effect of elastic collisions upon optical coherences. In our particular system, the signal is due to a pure double-quantum term, where we have separated the effect of phase-interrupting collisions from the effect of velocity-changing collisions. Experimental results show that the effect of velocity-changing collisions is very small, and that broadening of the signal is due to phase-interrupting collisions mainly. We are able to determine the increase of the decay rate of the coherent superposition (the “coherence”) of two levels of same parity [Dγ 13/dp=(6.5±1) MHz/Torr] and an upper limit for the mean velocity change (ũ≲5m/s).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00901791
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  • 43
    Digitale Medien
    Digitale Medien
    Dye lasers and intermolecular and intramolecular energy transfer processes (1979)
    Springer
    Applied physics 19 (1979), S. 165-170 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Computer calculations of ETDL performance indicate that dye laser output can be manipulated by an appropriate choice of a donor (absorber)-acceptor (dye) couple. Studies of relevant laser induced inter- and intramolecular energy transfer processes are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00932391
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  • 44
    Digitale Medien
    Digitale Medien
    Small-scale instability of a pulse front traversing a resonant saturable absorber (1979)
    Springer
    Applied physics 19 (1979), S. 221-224 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.10 ; 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Wave front of a light pulse is shown to be unstable as it propagates through a resonant saturable absorber, if its frequency is higher than the resonance frequency of the absorber. When ΔωT 2∼1, a small-scale transverse instability with the dimension of (λl abs)1/2 grows rapidly. Its growth-rate is of the order of the small-signal-absorption length of the medium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00932401
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  • 45
    Digitale Medien
    Digitale Medien
    A simple transition-locked and polarization-forced multi-line oscillator for high-power CO2-laser systems (1979)
    Springer
    Applied physics 19 (1979), S. 257-264 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Employing injection-locking techniques an oscillator configuration was found comprising in a simple way all the features required for fusion directed high-power CO2 laser systems. The oscillator provides emission in single axial modes on rotational transitions which can be freely selected by feeding fluencies of a few mW/cm2 at the particular transition into the oscillator cavity. In the same way simultaneous emission on selectable lines can be achieved. By the same principle the oscillator can be forced to emit in any orientation of polarization. The set up is relatively simple, the alignment rather uncritical, and the operation reliable. Gaussian-shaped nanosecond pulses with low forepulse power are produced with the help of a pulse cutter and saturable multiline absorber. The set up is described and its features are demonstrated by measurements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00900468
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  • 46
    Digitale Medien
    Digitale Medien
    Reaction kinetics of excimer lasers using NF3 (1977)
    Springer
    Applied physics 13 (1977), S. 1-3 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Disappearance of NF3 and appearance of NF2 and N2F2 in an excimer laser is followed quantitatively with a mass spectrometer. A model for the kinetics is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00890711
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  • 47
    Digitale Medien
    Digitale Medien
    Performance of NdLa pentaphosphate laser pumped by nanosecond pulses (1977)
    Springer
    Applied physics 13 (1977), S. 55-58 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 78.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract NdxLa1−xP5O14 (0.25≦x≦1) single crystals, placed within a confocal optical resonator, were pumped with ruby laser fundamental and second-harmonic nanosecond pulses. In both cases laser oscillations at 1.05 μm exceeding in duration many times the pumping pulse were obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00890721
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  • 48
    Digitale Medien
    Digitale Medien
    Nonlinear absorption spectroscopy of the ethane molecule (1977)
    Springer
    Applied physics 14 (1977), S. 343-350 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract By means of nonlinear absorption spectroscopy data necessary for the interpretation of molecular spectra can be obtained in such spectral regions, where conventional spectroscopic methods yield only a quasi-continuous absorption curve. Using a Zeeman-tuned He−Ne laser at the wavelength of 3.39μm we have measured significant differences in the intensity and temperature behaviour for several ethane absorption lines, the analysis of which made possible a preliminary qualitative assignment of these lines.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00883437
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  • 49
    Digitale Medien
    Digitale Medien
    A high-power single-mode cw dye ring laser (1977)
    Springer
    Applied physics 14 (1977), S. 377-380 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Due to spatial hole burning, standing-wave dye lasers require a large amount of selectivity inside the cavity for single-mode operation. The output power of these lasers is limited by losses caused by the frequency selecting elements. In a travelling-wave laser, on the other hand, spatial hole burning does not exist, thereby eliminating the need for high selectivity. A travelling-wave cw dye laser was realized by unidirectional operation of a ring laser, yielding single mode output powers of 1.2 W at 595 nm and of 55 mW in the UV-region with intracavity frequency doubling.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00883442
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  • 50
    Digitale Medien
    Digitale Medien
    Instability of laser cw oscillation in the presence of a passive medium (1978)
    Springer
    Applied physics 15 (1978), S. 265-270 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract For a homogeneously broadened two-level ring laser model the stability of the cw laser oscillation in the presence of a passive medium is investigated. The passive material is treated similar to the active material, but without an external pumping mechanism. Stable and unstable regions are shown for various parameters. The stability region of the cw solution becomes extremly small for certain parameters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00896107
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  • 51
    Digitale Medien
    Digitale Medien
    Dynamic mode interaction in multi-mode laser diodes (1978)
    Springer
    Applied physics 16 (1978), S. 155-158 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 78.60 ; 85.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Dynamic characteristics of laser diodes are numerically calculated on multi-mode rate equations, including spatial relaxing interaction causing mode competitions or jumps. It is revealed that the interaction effect is classified into three cases [“independent (or inhomogeneous)”, “competition (or intermediate)”, and “monopoly (or ideally homogeneous)”], that an optimum relaxing coefficient value exists to minimize relaxation oscillations in rise and decay transients, and that the optimum value is related to the relaxation period. Calculated results are discussed in comparison with the experimental results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00930380
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  • 52
    Digitale Medien
    Digitale Medien
    Cw oscillation at 1.05 and 1.32 μm of LiNd(PO3)4 lasers in external resonator and in resonator with directly applied mirrors (1979)
    Springer
    Applied physics 20 (1979), S. 329-334 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The room temperature cw oscillation at 1.05 and 1.32 μm of lithium neodymium tetraphosphate [LiNd(PO3)4, LNP] lasers in an external resonator and, for the first time, also in a Fabry-Perot resonator with directly applied mirrors is reported. The growth and fluorescence properties of the LNP crystals are briefly described. Laser parameters such as threshold pump power, output power, differential efficiency, optical gain, emission cross section and laser modes are both measured and calculated. Laser experiments show the threshold pump power to be lower for 1.05 μm than for 1.32 μm emission because of the smaller emission cross section; the pump power density is lower for the external resonator than for the Fabry-Perot resonator because of its higher mode losses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00895005
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  • 53
    Digitale Medien
    Digitale Medien
    Effect of laser dye deterioration on performance (1977)
    Springer
    Applied physics 14 (1977), S. 199-203 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Loss of gain in a dye medium as a result of decomposition by pump photons is considered in terms of disappearance of dye molecules and the appearance of a new, single chemical product having absorption in the fluorescence band. The cases of small signal gain and saturated gain are applied to a single pass through a transversely excited amplifier. Loss of output, defined as “quantum yield of laser deterioration”,Q L , is related to the true quantum yield of molecular destruction of the dye,Q M , and other known parameters. For the experimentally common, saturated gain condition, the smallestQ L can be isQ M , which requires a photochemically bleachable dye with high gain, preferably at high concentration, in a long cavity, operating at high injection and pumping fluxes. Reversing these conditions, the highest valueQ L can be, compared withQ M , is unrestricted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00883090
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  • 54
    Digitale Medien
    Digitale Medien
    Measurement of the diameter of a laser beam (1978)
    Springer
    Applied physics 17 (1978), S. 303-307 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A new and simple technique for measuring the effective diameter of a laser beam used in material processing is described. The time for the temperature of a spot heated by the laser beam to rise to 90% of equilibrium is compared with that predicted theoretically for a Gaussian TEM00 laser beam. A Gaussian beam diameter equivalent is thus deduced. This calculated diameter is of particular relevance to applications where the laser is used as a heat source.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886959
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  • 55
    Digitale Medien
    Digitale Medien
    Nonstationary intracavity stimulated raman scattering by polaritons (1978)
    Springer
    Applied physics 17 (1978), S. 393-400 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Stimulated Raman scattering by polaritons when employing a nonlinear crystal inside the cavity of the laser with Q-switching and locked to fundamental frequency was theoretically studied. The equations were formulated describing the dynamics of the fundamental, Stokes and polariton waves under the assumption of instant Q-switching and uniformity of radiation except in the longitudinal direction. Numerical solutions of the equations were found and analysed. We demonstrate the influence, on generation characteristics, of the most important parameters, such as the effective nonlinearity, the initial level of population inversion, the feedback of the Stokes wave and the group mismatch between a Stokes and a pump wave. Optimum generation conditions are determined. Possibilities of the method are discussed for the generation of a) giant pulses which are controllable with regard to carrier frequency and duration but are unachievable with other methods, b) Stokes pulses of very small duration and high energy having sharp trailing edges, and c) analogous polariton pulses in the middle and far infrared range. The generation using a number of polariton branches in LiNbO3 was considered as an example. Calculations are in qualitative agreement with experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886211
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  • 56
    Digitale Medien
    Digitale Medien
    High-power tunable IR Raman lasers (1978)
    Springer
    Applied physics 17 (1978), S. 211-232 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Physical principles, new ways and means of creation, schemes, characteristics and features of efficient high-power tunable pulse Raman lasers, operating in the near and middle ir are reviewed. The paper includes: tunable dye and Nd lasers as pump sources; promising active media and their optimal excitation methods; optical systems for producing spatially homogeneous pumping; the physics of Raman oscillators and their practical schemes, efficient high pulse energy liquid N2 and compressed H2 Raman oscillators, covering several bands in the range between 1.4 and 9.2 μm; the physics and construction of efficient tunable Raman amplifiers-convertors, amplifying in the saturation regime of spontaneously scattered or beforehand produced and collimated external Stokes signals, obtained in the spectral range between 0.83 μm and 18 μm. Raman laser using a, so-called, broadband pump where the linewidth of pumping light is broader than the spontaneous scattering linewidth, are also discussed. Features of both amplification and oscillation regimes of such broadband pumped Raman lasers are reported, and conditions for the efficient frequency conversion are determined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886950
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  • 57
    Digitale Medien
    Digitale Medien
    Multiwatt optically pumped ammonia laser operation in the 12–13 μm (1978)
    Springer
    Applied physics 17 (1978), S. 317-320 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Design and operating caracteristics of high pulse repetition rate NH3 laser producing up to 20 W of average output power are described. The NH3 laser, operating in the 12–13 μm region was optically pumped with a high pulse repetition rate TEA CO2 laser. Dependences of the NH3 laser output on the pump energy, ammonia and buffer gas pressures and pulse repetition rate have been studied. The conversion efficiency of up to 16% has been received.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886961
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  • 58
    Digitale Medien
    Digitale Medien
    Measurement of the transition strength of the 00o2 9.4 μm sequence band in CO2 using a tunable diode laser (1978)
    Springer
    Applied physics 17 (1978), S. 349-353 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 35 ; 42.55 ; 42.68
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract We report the first accurate measurements of the transition strengths and linewidths of the 00o2 9.4 μm sequence lines of CO2. This sequence band is found to be very similar to the regular 00o1 laser band, except for an experimentally determined factor of 1.89±0.12 increase in transition strength (if the CO2 molecule is treated as a simple harmonic oscillator the theoretical increase in transition strength is 2.0). The laser absorption spectrometer used for these measurements can detect absorption coefficients in CO2 of ≈10−7 m−1, and we discuss the feasibility of using this sensitivity to monitor rare isotopic forms of CO2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886204
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  • 59
    Digitale Medien
    Digitale Medien
    Tunable simultaneous double-wavelength operation of a cw CO2 laser (1979)
    Springer
    Applied physics 19 (1979), S. 243-245 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Stable step-tunable simultaneous double-wavelength emission from any branch combination of the 9.6 and 10.6 μm bands of a cw CO2 laser is reported in which the relative strengths of the two signals may be controlled.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00932406
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  • 60
    Digitale Medien
    Digitale Medien
    Tunable coherent radiation source covering a spectral range from 185 to 880 nm (1979)
    Springer
    Applied physics 18 (1979), S. 177-181 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65 ; 33
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract We have studied experimentally stimulated Raman scattering and 4-wave-interaction processes occuring in hydrogen gas, which is excited by a Nd:YAG-pumped dye laser. The tuning ranges of the various Stokes and anti-Stokes lines, which are generated with high efficiency, cover the spectrum from 185 to 880 nm without a gap.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00934413
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  • 61
    Digitale Medien
    Digitale Medien
    Influence of collisional coupling on the energy extraction from theB, C, andD state in KrF (1979)
    Springer
    Applied physics 20 (1979), S. 129-134 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 33 ; 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Collisional coupling between theB, C, andD states of KrF is measured in a discharge pumped KrF laser. Detection of the time resolved populations in the three states via measurement of the side fluorescence in theB→X, C→A, andD→X bands is used to record the collisional relaxation from theC andD state to theB state during laser emission. The experimentally determined limits for the collisional coupling times are τB-C≦1 ns and τB-D,τC-D〈20 ns at total pressures of 2 bar. Investigation of theB→X fluorescence band shows that the vibrational manifold of theB state is not thermalized during laser emission. TheV-V,T coupling time is estimated to be τV-V,T=4±2 ns. The influence of collisional coupling on energy extraction in the KrF laser is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00885933
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  • 62
    Digitale Medien
    Digitale Medien
    Influence of the inversion depletion in the active medium on the evolution of ultrashort pulses in passively mode-locked solid-state lasers (1979)
    Springer
    Applied physics 20 (1979), S. 237-245 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract An analytical treatment of the ultrashort-pulse generation in a solid-state laser is given taking into account gain saturation. The probability for the breakdown of the picosecond-pulse evolution caused by the amplification depletion is calculated. The influence of the active medium saturation on the satellite-pulse probability is investigated. Both probabilities characterize the mode-locking behaviour of the laser system and are calculated for various laser parameters to find an optimum laser regime.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886024
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  • 63
    Digitale Medien
    Digitale Medien
    Coherent γ-emission by stimulated annihilation of electron-positron pairs (1979)
    Springer
    Applied physics 19 (1979), S. 127-130 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The possibility of using stimulated emission from the recombination of electron-positron pairs for obtaining coherent γ-rays is considered. The critical number of pairs needed for the process is calculated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00900548
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  • 64
    Digitale Medien
    Digitale Medien
    CW HCN laser gain in a hollow dielectric rectangular cross-section discharge tube (1979)
    Springer
    Applied physics 19 (1979), S. 359-361 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract This paper describes a 1 m-long CW HCN discharge laser with a hollow dielectric rectangular discharge tube of 5×20 cm2 cross-section. For optimum working conditions, the characteristics of the amplifying medium have been made constant over the cross-section, by using an additional magnetic field. Then, the unsaturated gain for the 337 μm line is 6.8% m−1. It is shown to be dependent on the smaller dimension of the cross-section rather than on the other dimension. By using the tube as a waveguide, laser output power of 1 Watt might be obtained with a discharge length of 4 m, instead of the 12m-long discharge required to get the same output power from a cylindrical waveguide laser.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00900481
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  • 65
    Digitale Medien
    Digitale Medien
    Selective laser excitation of bases in nucleic acids (1979)
    Springer
    Applied physics 20 (1979), S. 257-259 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 87 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Selective electronic excitation of single kinds of DNA bases were performed with dye lasers. Different DNA-dye-complexes were used and the selective excitation could be proved by the varying strength of the interaction between the bases and the dye molecules.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886028
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  • 66
    Digitale Medien
    Digitale Medien
    Powerful laser systems with phase conjugation by SMBS mirror (1979)
    Springer
    Applied physics 20 (1979), S. 261-264 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.65 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The method of Stimulated Mandelshtam-Brillouin Scattering (SMBS) is utilized in a powerful laser to obtain better transverse beam quality by phase conjugation. The principle is explained, and the conclusions are substantiated by experimental results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00886029
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  • 67
    Digitale Medien
    Digitale Medien
    Localization of cells capable of transdetermination in a specific region of the male foreleg disk ofDrosophila (1977)
    Springer
    Development genes and evolution 182 (1977), S. 69-74 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Drosophila melanogaster ; Male foreleg disk ; Capacity of transdetermination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In the male foreleg disk ofDrosophila melanogaster the cells capable of transdetermination are clustered in a specific region within the upper half of the disk. Cells outside this region cannot transdetermine under any of the experimental conditions thus far applied. Transdetermination occurs when cells capable of transdetermination are stimulated to a certain extent of additional proliferation. This can be achieved either by exposing these cells at a wound surface of an intact fragment, or by dissociation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848088
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  • 68
    Digitale Medien
    Digitale Medien
    Localized synthesis of specific proteins during oogenesis and early embryogenesis inDrosophila melanogaster (1979)
    Springer
    Development genes and evolution 187 (1979), S. 151-165 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Oogenesis ; Embryogenesis ; Two-dimensional gels ; Protein synthesis ; Drosophila melanogaster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Protein synthesis in egg follicles and blastoderm embryos ofDrosophila melanogaster has been studied by means of two-dimensional gel electrophoresis. Up to 400 polypeptide spots have been resolved on autoradiographs. Stage 10 follicles (for stages see King, 1970) were labelled in vitro for 10 to 60 min with35S-methionine and cut with tungsten needles into an anterior fragment containing the nurse cells and a posterior fragment containing the oocyte and follicle cells. The nurse cells were found to synthesize a complex pattern of proteins. At least two proteins were detected only in nurse cells but not in the oocyte even after a one hour labelling period. Nurse cells isolated from stages 9, 10 and 12 follicles were shown to synthesize stage specific patterns of proteins. Several proteins are synthesized in posterior fragments of stage 10 follicles but not in anterior fragments. These proteins are only found in follicle cells. No oocyte specific proteins have been detected. Striking differences between the protein patterns of anterior and posterior fragments persist until the nurse cells degenerate. In mature stage 14 follicles, labelled in vivo, no significant differences in the protein patterns of isolated anterior and posterior fragments could be detected; this may be due to technical limitations. At the blastoderm stage localized synthesis of specific proteins becomes detectable again. When blastoderm embryos, labelled in vivo, are cut with tungsten needles and the cells are isolated from anterior and posterior halves, differences become apparent. The pole cells located at the posterior pole are highly active in protein synthesis and contribute several specific proteins which are found exclusively in the posterior region of the embryo. In this study synthesis of specific proteins could only be demonstrated at those developmental stages which are characterized by the presence of different cell types within the egg chamber, while no differences were detected when stage 14 follicles were cut and anterior and posterior fragments analyzed separately. The differences in the pattern of protein synthesis by pole cells and blastoderm cells indicate that even the earliest stages of determination are reflected by marked changes at the biochemical level.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848268
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  • 69
    Digitale Medien
    Digitale Medien
    Genetic analysis of pattern-formation in the embryo ofDrosophila melanogaster (1977)
    Springer
    Development genes and evolution 183 (1977), S. 249-268 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Pattern-formation ; Embryogenesis ; Maternal-effect mutants ; Drosophila melanogaster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The mutationbicaudal (Bull, 1966) causes embryos to develop a longitudinal mirror image duplication of the posteriormost abdominal segments, while head and thorax are missing. These embryos occur with varying frequencies among eggs laid by mutant females, irrespective of the paternal genotype. Recombination and deletion mapping indicate thatbicaudal (bic) is a recessive, hypomorphic, maternal-effect mutation mapping at a single locus on the second chromosome ofDrosophila melanogaster close tovg (67.0±0.1). The frequency of bicaudal embryos depends on the age of the mother, her genetic constitution and the temperature at which she is raised. Best producers are very young females hemizygous forbic (bic/Df(2)vg B ) at 28° C. Under these conditions 80% to 90% of the eggs which differentiate can show the bicaudal embryo phenotype. Upon ageing of the mother the frequency of bicaudal embryos declines rapidly, and most of the eggs develop the normal body pattern. Temperature shift experiments suggest a temperature-sensitive period at the onset of vitellogenesis. The mutation causes several types of abnormalities in the segment pattern of theDrosophila embryo, which are interpreted as various degrees of expression of the mutant character. The most frequent abnormal phenotype is the symmetrical bicaudal embryo with one to five abdominal segments duplicated. Less frequent are asymmetrical types, in which the smaller number of segments is always in the anterior reversed part. Other phenotypes are embryos with missing or rudimentary heads, and embryos with irregular gaps in the segment pattern. In bicaudal embryos, the pole cells, formed at the posterior pole of the egg prior to blastoderm formation, are not duplicated at the anterior. The significance of thebicaudal phenotypes for embryonic pattern-formation inDrosophila is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00867325
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  • 70
    Digitale Medien
    Digitale Medien
    Detection of clones in the nervous system ofDrosophila melanogaster (1977)
    Springer
    Development genes and evolution 183 (1977), S. 165-169 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Clones ; Nervous system ; Shibire ; Drosophila melanogaster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Mitotic recombination was induced, by X-irradiation at the blastoderm stage, in flies heterozygous for one of the temperature-sensitive paralytic mutationsshibire andtp-2. The results show that these mutations can be used to detect the presence of clones in the central nervous system through the temperature-sensitive paralysis of individual legs. Mitotic recombination can also be used to examine the effects of these mutations in the peripheral nervous system; shibire is thus shown to affect the function of sensory neurons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848786
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  • 71
    Digitale Medien
    Digitale Medien
    Isozymic patterns and functional states of cell lines ofDrosophila melanogaster cultured in vitro. II (1976)
    Springer
    Development genes and evolution 180 (1976), S. 107-119 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Drosophila melanogaster ; Cell lines ; Isoenzymes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Our previous isoenzyme investigation ofDrosophila melanogaster cell lines in vitro has been completed with twelve further enzyme systems. The “enzyme profiles” seem to be in good agreement with a previous hypothesis concerning the precise origin of these cell lines (probably from imaginal discs or nervous tissues). Our results have been summarized with reference to the biochemical genetic map ofDrosophila melanogaster in order to consider a possible functional organization of the genome.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848101
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  • 72
    Digitale Medien
    Digitale Medien
    A study of the female germ line in mosaics ofDrosophila (1978)
    Springer
    Development genes and evolution 184 (1978), S. 41-56 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Drosophila melanogaster ; Female germ line ; Mosaics ; Stem cell divisions ; Metafemale ; Sterility
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Our report presents an analysis of the development and dynamics of the female germ line inDrosophila. Females were produced that were mosaic either for attached-X chromosomes $$(\widehat{XX})$$ and a ring-X (triplo-X-diplo-X), or for $$\widehat{XX}$$ and a marked Y-chromosome $$(\widehat{XX}/Y - \widehat{XX}/O)$$ . The germ-line and genitalia of these females were analysed by direct microscopic observation or by examination of the progeny. Eggs derived from triplo-X germ cells were hardly capable of supporting development, with most of the zygotes dying during embryonic development. The analysis of the germ line was therefore carried out mainly by direct observation of histochemically stained developing oocytes in the ovaries of mosaic females. The total germ cell population of both ovaries of a female was mosaic in 22–29% of the tested animals. From this frequency of mosaicism we estimated the number of functional primordial germ cells to be betwen 3 and 6 cells at the blastoderm stage. At this stage the cell lineages for the left and right ovary are not yet separated. The germ cell population of individual ovarioles was frequently mosaic which shows that the few stem cells in an ovariole are recruited as a group and are not clonal descendants of a single ancestor cell per ovariole. An analysis of the sequential pattern of oocyte-nurse cell cysts in mosaic ovarioles revealed that neighbouring cysts tend to be of the same genotype. This suggests that the stem cells of the adult ovaries preferentially divide in bursts, one of them giving rise to two, three and sometimes even more cystocytes in a row. In addition, the foci for lethality and sterility of the triplo-X condition were determined. Non-mosaic triplo-X females (metafemales) are hardly viable and invariably sterile. Using our mosaics, the focus forlethality could be mapped to a region very near the ventral prothoracic discs. The focus forsterility resides in the genitalia, since flies with triplo-X genitalia never laid any eggs, regardless of the genotype of their ovaries.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848668
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  • 73
    Digitale Medien
    Digitale Medien
    Rudimentary mutants ofDrosophila melanogaster (1979)
    Springer
    Development genes and evolution 187 (1979), S. 167-177 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Pyrimidine biosynthesis ; rudimentary mutants ; Drosophila melanogaster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The X-linkedrudimentary (r) mutants ofDrosophila melanogaster are pyrimidine auxotrophs and require exogenous pyrimidines (Nørby, 1970; Falk, 1976). We have established a set ofrudimentary cell lines that are derived from embryos, homozygous for eitherr 1 orr 36. The enzymatic activities of the pyrimidine synthesizing enzymes were measured in the mutant lines. We have further investigated the nutritional requirements of the mutant cells in vitro by using a pyrimidine free culture medium. Ther 1 cell lines were found to express 3–7%dihydroorotase (DHOase) activity as compared to a wildtype cell line. Reducedaspartate transcarbamylase (ATCase) activity was measured in somer 1 cell lines whereas wildtypecarbamylphosphate synthetase (CPSase) activity is expressed in allr 1 cell lines. Ther 36 cell line expresses wildtype activity ofDHOase andCPSase. ATCase activity was found to be reduced to 10% of the wildtype activity. The mutant cell lines do not proliferate in pyrimidine free minimal medium and cell proliferation is obtained by the addition of crude RNA. Proliferation of ther 1 cells is restored by the supplementation of the minimal medium withdihydroorotate whereas proliferation of ther 36 cells is restored by supplementation with eitherdihydroorotate orcarbamylaspartate. The results demonstrate that therudimentary phenotypesr 1 andr 36 are expressed at the cellular level and that the two mutant cell types behave as cellular pyrimidine auxotrophs in vitro.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848269
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  • 74
    Digitale Medien
    Digitale Medien
    The effect of fat body on the differentiation in vitro of wing imaginal discs ofDrosophila melanogaster (1976)
    Springer
    Development genes and evolution 180 (1976), S. 73-77 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Ecdysones ; Imaginal discs ; Fat body ; Drosophila melanogaster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The effect of suboptimal levels of α-ecdysone on the differentiation in vitro ofDrosophila melanogaster wing discs was enhanced by the addition of larval fat body to the cultures. However, similar experiments with β-ecdysome showed no enhancement. It is suggested that a partial conversion of α-ecdysone to β-ecdysone by the fat body may well account for these results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848885
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  • 75
    Digitale Medien
    Digitale Medien
    Developmental potentials of the cells of the male foreleg disc ofDrosophila (1977)
    Springer
    Development genes and evolution 181 (1977), S. 309-320 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Drosophila melanogaster ; Male foreleg disc ; Pattern regulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary 1. The developmental potentials of the four quadrants of the male foreleg disc ofDrosophila melanogaster were analysed by culturing excised quadrants for 3 days and 10 days in adult hosts prior to metamorphosis. 2. The cultured pieces underwent different types of pattern regulation in a circular direction. The upper medial piece was able to regenerate the missing structures of the disc, thus confirming the findings of earlier reports. The three remaining pieces could undergo pattern duplication in mirror-image symmetry. The lower medial piece revealed in addition a slight capacity for regeneration from the vertical cut surface. 3. The duplicating pieces differed markedly in their frequencies of pattern duplication: duplications occurred with very high frequencies in lower medial pieces, with intermediate frequencies in upper lateral pieces, and with very low frequencies in lower lateral pieces. 4. Both lower lateral and upper lateral pieces underwent a progressive loss of most markers with increasing culture time. 5. Claws were regenerated solely by upper medial pieces. 6. Transdetermined structures, too, were encountered only in upper medial pieces. 7. The results are discussed with respect to the two major current models of pattern regulation in imaginal discs, the “gradient model” and the “clock model”. 8. It is suggested that the differences in the frequencies of pattern duplication reflect the unequal spacing of circular positional values within the three duplicating quadrants. Under this assumption the data indicate a progressive decrease in the density of circular positional values with increasing distance from the upper medial quadrant of the disc.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00848058
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  • 76
    Digitale Medien
    Digitale Medien
    Influence of acetylsalicylic acid on the renal handling of a spironolactone metabolite in healthy subjects (1976)
    Springer
    European journal of clinical pharmacology 10 (1976), S. 43-48 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Spironolactone ; acetylsalicylic acid ; fludrocortisone ; kinetics ; pharmacology ; interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of 600 mg acetylsalicylic acid (ASA) on the renal excretion and clearance of canrenone, the principal unconjugated metabolite of spironolactone, was examined in a double-blind crossover study in six healthy subjects. ASA significantly reduced the urinary excretion, and the fractional excretion, of canrenone between 4 — 6 hours after administration of 50 mg spironolactone. The pharmacological activity of spironolactone, assessed simultaneously by alterations in fludrocortisone-induced urinary electrolyte changes, was slightly but not significantly reduced. The reductions in urinary canrenone excretion correlated with changes in the urinary log 10 Na/K ratio. The results suggest that canrenone may be actively secreted at the proximal renal tubule, and that secretion is blocked by ASA or its conjugates. This is a possible mechanism for the pharmacological interaction between ASA and spironolactone which has been described previously.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00561548
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  • 77
    Digitale Medien
    Digitale Medien
    Kinetics and efficacy of theophylline in the treatment of apnea in the premature newborn (1978)
    Springer
    European journal of clinical pharmacology 13 (1978), S. 203-207 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Theophylline ; kinetics ; apnea ; premature newborns ; developmental pharmacology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Aminophylline (theophylline-ethylenediamine) was administered to 27 premature newborns to prevent apneic spells. Of the 22 patients monitored for theophylline concentration, a therapeutic blood level was reached in 19 in 1–2 days, and 3 stayed below it. ‘Toxic’ blood levels (≥20 µg/ml) were reached in 3 cases, one of whom showed signs of toxicity. Theophylline treatment was not efficient in the prevention of apnea when a serious underlying disease was present. Theophylline blood half-life (mean : 27.0 h) and clearance (mean 12.9 ml/h/kg) confirmed the slow elimination pattern of the drug in the premature infant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00609983
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  • 78
    Digitale Medien
    Digitale Medien
    Dissolution kinetics of small amounts of oxygen in tantalum alloy T-111 and internal oxide displacement reactions during annealing (1976)
    Springer
    Oxidation of metals 10 (1976), S. 291-309 
    Details
    ISSN: 1573-4889
    Schlagwort(e): tantalum alloy ; oxygen ; dissolution ; kinetics ; oxides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Oxygen was added to T-111 (Ta-8W-2Hf, wt.%) at 820 and 990°C at an oxygen pressure of about 3×10−4 Torr (4×10−2N/m2). The technique employed permitted predetermined and reproducible doping of T-111 up to 3.0 at% oxygen. Based on the temperature dependence of the doping reaction, it is concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the latter oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and of other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high-temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990°C. The vaporization of WO3 has no apparent affect on the doping reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00612028
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  • 79
    Digitale Medien
    Digitale Medien
    The formation of a double oxide layer on pure copper (1977)
    Springer
    Oxidation of metals 11 (1977), S. 127-132 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Duplex oxides ; copper oxidation ; kinetics ; oxygen partitioning
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The theory for the growth of a double oxide layer proposed by Yurek, Hirth, and Rapp, has been applied to copper using experimental rate-constant data obtained by Valensi. Calculated thicknesses of the layers agree very well with experimentally measured values.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00606399
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  • 80
    Digitale Medien
    Digitale Medien
    Effect of oxide grain structure on the high-temperature oxidation of Cr (1975)
    Springer
    Oxidation of metals 9 (1975), S. 459-472 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Cr ; oxidation ; kinetics ; Cr2O3 grain size ; short-circuit diffusion ; surface ; preparation ; Fe-Cr
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Cr was oxidized in 1 aim O2 at 980, 1090, and 1200°C. ElectropolishedCr and some orientations of etched Cr oxidize rapidly and develop compressive stress in the growing Cr2O3; other orientations oxidize slowly, apparently free of stress. SEM examination of fracture sections shows that the thick oxide is polycrystalline whereas the thin oxide on etched Cr is monocrystalline. It is deduced that the monocrystalline oxide grows by lattice diffusion of cations outward, and the polycrystalline layer by the two-way transport of cation diffusion outward and anion diffusion inward along oxide grain boundaries. The consequent formation of oxide within the body of the polycrystalline layer generates compressive stress and leads to wrinkling by plastic deformation. The activation energy for oxidation of Cr by cation lattice transport is 58 kcal/mole. Polycrystalline Cr2O3 forms on Fe-26Cr alloy, whether electropolished or etched; oxidation is accordingly rapid and accompanied by compressive stress.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00611694
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  • 81
    Digitale Medien
    Digitale Medien
    Nutritional control of xanthine dehydrogenase. II. Effects on xanthine dehydrogenase and aldehyde oxidase of culturing wild-type and mutant Drosophila on different levels of molybdenum (1975)
    Springer
    Biochemical genetics 13 (1975), S. 53-64 
    Details
    ISSN: 1573-4927
    Schlagwort(e): aldehyde oxidase ; xanthine dehydrogenase ; Drosophila melanogaster ; molybdenum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Two new mutants, deficient in aldehyde oxidase and xanthine dehydrogenase, have been isolated from a wild-type stock of Drosophila melanogaster and have been provisionally termed lxd c and lxd d, respectively, as both mutants appear to be allelic with lxd (low xanthine dehydrogenase). An analysis has been made of the effects of dietary molybdenum on lxd, lxd c, lxdd, lao (low aldehyde oxidase), mal (maroon-like eye color), and pac (Pacific) wild-type flies. On the lower dietary levels of 10 −3 M and 10 −2 M molybdenum, increases in specific activity of both enzymes were observed only in lxd. Furthermore, two- to three-fold increases in specific activity of both enzymes occurred in all strains, except mal, when cultured on 5×10 −2 M molybdenum. The lxd and lxd c strains failed to survive on this high concentration of the ion. Similar concentrations of molybdenum had no effect in vitro. An extra electrophoretic band of xanthine dehydrogenase was observed on polyacrylamide gel from extracts of wild-type flies cultured on certain levels of molybdenum, but its appearance was not always correlated with the increases in specific activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00486006
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  • 82
    Digitale Medien
    Digitale Medien
    The size of poly(A)-containing RNAs in Drosophila melanogaster embryos (1976)
    Springer
    Biochemical genetics 14 (1976), S. 357-371 
    Details
    ISSN: 1573-4927
    Schlagwort(e): Drosophila melanogaster ; poly(A)-containing RNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The size range of poly(A)-containing RNA from Drosophila melanogaster embryos has been estimated by hybridization with 3H-labeled poly(U) and subsequent fractionation on sucrose gradients. The median size of nuclear poly(A)-containing RNA is about 30 S (6000 nucleotides), and the median size of cytoplasmic poly(A)-containing RNA is about 17 S (1800 nucleotides). The relationship of these sizes to messenger RNA needed to code for protein and to the length of DNA contained in a chromomere is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00484774
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  • 83
    Digitale Medien
    Digitale Medien
    Partial purification and properties of guanosine triphosphate cyclohydrolase from Drosophila melanogaster (1976)
    Springer
    Biochemical genetics 14 (1976), S. 259-270 
    Details
    ISSN: 1573-4927
    Schlagwort(e): GTP cyclohydrolase ; Drosophila melanogaster ; pteridines ; dihydroneopterin triphosphate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The first enzyme (named GTP cyclohydrolase) in the pathway for the biosynthesis of pteridines has been partially purified from extracts of late pupae and young adults of Drosophila melanogaster. This enzyme catalyzes the hydrolytic removal from GTP of carbon 8 as formate and the synthesis of 2-amino-4-hydroxy-6-(d-erythro-1′,2′,3′-trihydroxypropyl)-7,8-dihydropteridine triphosphate (dihydroneopterin triphosphate). Some of the properties of the enzyme are as follows: it functions optimally at pH 7.8 and at 42 C; activity is unaffected by KCl and NaCl, but divalent cations (Mg2+, Mn2+, Zn2+, and Ca2+) are inhibitory; the K m for GTP is 22 μm; and the molecular weight is estimated at 345,000 from gel filtration experiments. Of a number of nucleotides tested, only GDP and dGTP were used to any extent as substrate in place of GTP, and these respective compounds were used only 1.8% and 1.5% as well as GTP.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00484765
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  • 84
    Digitale Medien
    Digitale Medien
    The suppressor of forked mutation in Drosophila melanogaster: Interactions with the lozenge gene (1976)
    Springer
    Biochemical genetics 14 (1976), S. 611-617 
    Details
    ISSN: 1573-4927
    Schlagwort(e): Drosophila melanogaster ; phenol oxidases ; spectrophotometry ; electrophoresis ; suppression ; ribosomal proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract An interaction between the lozenge gene and the suppressor of forked gene of Drosophila melanogaster has been investigated both spectrophotometrically and electrophoretically. The nature of this interaction is such that certain lozenge alleles appear to be phenotypically suppressed while others are enhanced or unaffected, and the results reported demonstrate that the effect can clearly be observed at the biochemical level. Earlier observations have suggested that the suppressor of forked gene codes for a ribosomal protein, and this hypothesis is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00485839
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  • 85
    Digitale Medien
    Digitale Medien
    Selection against homozygotes in the ADH polymorphic system of Drosophila melanogaster associated with the lethal factor l(2) Stm (1977)
    Springer
    Biochemical genetics 15 (1977), S. 93-100 
    Details
    ISSN: 1573-4927
    Schlagwort(e): alcohol dehydrogenase (ADH) ; genetic polymorphism ; selection ; Drosophila melanogaster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract In the natural populations +Tüb, +Prov, and +Rov, similar Adh F allele frequencies occur (q F=0.11, 0.18, and 0.08, respectively). However, there is a discrepancy in that the Adh F allele in +Tüb is closely linked to the lethal factor 1(2)Stm, which reduces relative fitness of the F phenotype to zero. In spite of this, polymorphism is maintained also in +Tüb, because the heterozygotes are superior to the homozygous S type (relative fitness=0.88). Under laboratory culture conditions, in +Tüb the relative fitness of the S genotype further decreases to 0.6. After outcrossing the lethal factor, relative fitnesses for S, FS, and F become 0.6, 1, and 0.48, respectively, implying that fitness for S remains the same. Relative values for S, FS, and F in +Prov, not affected by the lethal factor, are calculated by the maximum average fitness method to be 1, 1.2, and 0.2 under the assumption that heterozygous FS are similarly superior to S as in the natural +Tüb population and all allele frequencies found are stable equilibrium values.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00484551
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  • 86
    Digitale Medien
    Digitale Medien
    Origin of α-glycerophosphate dehydrogenase isozymes in Drosophila melanogaster and their functional relationship in the α-glycerophosphate cycle (1977)
    Springer
    Biochemical genetics 15 (1977), S. 235-251 
    Details
    ISSN: 1573-4927
    Schlagwort(e): l-glycerol-3-phosphate dehydrogenase (α-GPDH) ; isozymes ; development ; Drosophila melanogaster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The basis for the differentiation of l-glycerol-3-phosphate dehydrogenase (α-GPDH) into larval and adult isozymes in Drosophila melanogaster was investigated by the correlation of a lack of appearance of each isozyme during development within Drosophila bearing α-GPDH “null” alleles and by the study of a putative conversion factor. Conversion studies indicate the presence of a heat-labile RNase-resistant conversion factor present in crude larval extracts with the ability to convert GPDH-1 to GPDH-2 and GPDH-3 but not vice versa. In addition, “null” mutations at the Gpdh locus obliterate all isozymatic species of α-GPDH in all developmental stages. These observations suggest that all α-GPDH isozymes are the product of a single structural gene and that the multiple forms of this enzyme arise during successive developmental stages through an epigenetic modification of the primary Gpdh + polypeptide. Finally, observations are reported which bear on the functional divergence of the α-glycerophosphate cycle in the adult and larval stage of development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00484456
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  • 87
    Digitale Medien
    Digitale Medien
    Isolation and genetic characterization of alcohol dehydrogenase thermostability variants occurring in natural populations of Drosophila melanogaster (1977)
    Springer
    Biochemical genetics 15 (1977), S. 971-988 
    Details
    ISSN: 1573-4927
    Schlagwort(e): allozymes ; thermostability ; alcohol dehydrogenase ; Drosophila melanogaster ; natural populations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Drosophila melanogaster collected from natural populations were examined fo thermostability variants within electrophoretic mobility classes of two enzymes. In alcohol dehydrogenase, two discrete forms of the “slow” allozyme and three discrete forms of the “fast” allozyme were revealed by postelectrophoretic treatments ranging from 15 sec at 40 C to 40 sec at 43 C. All variants have been mapped to within 0.7 unit of the Adh locus. Results of a geographic survey indicate that two alleles giving rise to fast-moderate and slow-moderate allozymes are common everywhere; other variants have a collective frequency ranging from 0% to 7%. In a test of the possibility that the rare Adh alleles could be generated by intragenic recombination between the two common alleles, electrophoresis and heat treatment of progeny recombinant for flanking markers of Adh revealed no new allozymes. Among 27 stocks containing slow α-glycerophosphate dehydrogenase allozymes and 109 fast stocks, heat treatments revealed no additional variation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00483992
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  • 88
    Digitale Medien
    Digitale Medien
    Control of drosopterin synthesis in Drosophila melanogaster: Mutants showing an altered pattern of GTP cyclohydrolase activity during development (1978)
    Springer
    Biochemical genetics 16 (1978), S. 13-26 
    Details
    ISSN: 1573-4927
    Schlagwort(e): Drosophila melanogaster ; GTP cyclohydrolase ; development ; pteridine biosynthesis ; mutants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The reaction catalyzed by GTP cyclohydrolase is the first unique step of pteridine biosynthesis in Drosophila melanogaster and is therefore likely to be an important control point. GTP cyclohydrolase activity varies during development, showing two distinct peaks of activity—one at pupariation and a much larger peak at emergence. Most of the early pupal enzyme is located in the body region, whereas in late pupal and early adult life most of the activity is found in the head. Mixing experiments indicate that developmental changes in activity are not due to changes in the level of a direct effector of GTP cyclohydrolase. The mutants raspberry and prune show an increased GTP cyclohydrolase activity at pupariation relative to wild type, but a decreased enzyme activity at emergence. The changes in GTP cyclohydrolase activity are reflected in changes in pteridine levels in these mutants. Several lines of evidence suggest that neither locus is the structural gene for GTP cyclohydrolase. The raspberry and prune gene products may play a specific role in regulating GTP cyclohydrolase activity during development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00484381
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  • 89
    Digitale Medien
    Digitale Medien
    A genetic and developmental analysis of an acid deoxyribonuclease in Drosophila melanogaster (1978)
    Springer
    Biochemical genetics 16 (1978), S. 1113-1134 
    Details
    ISSN: 1573-4927
    Schlagwort(e): Drosophila melanogaster ; isozymes ; position effect ; segmental aneuploidy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract A deoxyribonuclease, called DNase-1, that is active at acid pH in the presence of EDTA has been studied in Drosophila melanogaster. The locus for the enzyme maps genetically to 61.8 on the right arm of the third chromosome. Cytogenetically, DNase-1 has been localized to within five to ten bands between 90C-2 and 90E. This analysis utilizes both electrophoretic variants and the Y-autosome translocations of Lindsley et al. (1972). DNase-1 is present in all stages of the life cycle, and the paternal genome actively contributes DNase-1 to the embryo between 0 and 1 hr after fertilization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00484532
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  • 90
    Digitale Medien
    Digitale Medien
    Variation in amount of enzyme protein in natural populations (1978)
    Springer
    Biochemical genetics 16 (1978), S. 159-170 
    Details
    ISSN: 1573-4927
    Schlagwort(e): alcohol dehydrogenase ; allozyme properties and amounts ; Drosophila melanogaster
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Among strains of Drosophila melanogaster each derived from a single fertilized female taken from natural populations, there is variation in both alcohol dehydrogenase (ADH) activity and the amount of ADH protein. The correlation between ADH activity and number of molecules over all strains examined is 0.87 or 0.96 in late third instar larvae depending on whether the substrate is 2-propanol or ethanol. With respect to the two common electrophoretic allozymic forms, F and S, segregating in these populations, the FF strains on the whole have higher ADH activities and numbers of ADH molecules than the SS strains. Over all strains examined, enzyme extracts from FF strains have a mean catalytic efficiency per enzyme molecule higher than that of enzyme extracts from SS strains when ethanol is the substrate, and much higher when 2-propanol is the substrate. One FF strain had an ADH activity/ADH protein ratio characteristic of SS strains.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00484075
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  • 91
    Digitale Medien
    Digitale Medien
    Alcohol metabolism in Drosophila melanogaster: Uselessness of the most active aldehyde oxidase produced by the Aldox locus (1978)
    Springer
    Biochemical genetics 16 (1978), S. 203-211 
    Details
    ISSN: 1573-4927
    Schlagwort(e): Drosophila melanogaster ; alcohol tolerance ; alcohol utilization ; alcohol dehydrogenase ; aldehyde oxidase ; allozymes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Alcohol dehydrogenase is necessary for ethanol detoxification and metabolic utilization. It has been generally assumed that aldehyde oxidase (AO) produced by the Aldox locus (3–56.7) is necessary for a further transformation of acetaldehyde into acetate. We find that various mutant strains (ma-l or Aldox n) which do not produce an active enzyme show about the same tolerance to alcohol as do wild strains. This physiological paradox is probably to be explained by the discovery of another locus (not localized) which produced a small amount of AO in all tested strains. The adaptive significance of the genetically polymorphic Aldox locus is probably to be looked for in physiological pathways other than ethanol metabolism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00484078
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  • 92
    Digitale Medien
    Digitale Medien
    A simple approach for discovering common nonelectrophoretic enzyme variability: A heat denaturation study in Drosophila melanogaster (1978)
    Springer
    Biochemical genetics 16 (1978), S. 299-305 
    Details
    ISSN: 1573-4927
    Schlagwort(e): nonelectrophoretic structural variability ; Drosophila melanogaster ; phosphoglucomutase ; genetic polymorphism ; heat denaturation study
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract A simple procedure is described to detect genetic heterogeneity within electrophoretic classes at a locus in Drosophila, based on electrophoresis and heat denaturation studies. Temperature-resistant (tr) and temperature-sensitive (ts) isoelectrophoretic alleles at the phosphoglucomutase locus (Pgm) are present at polymorphic frequencies in natural and in laboratory populations of Drosophila melanogaster.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00484086
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  • 93
    Digitale Medien
    Digitale Medien
    Developmental changes of sepiapterin synthase activity associated with a variegated purple gene in Drosophila melanogaster (1979)
    Springer
    Biochemical genetics 17 (1979), S. 197-206 
    Details
    ISSN: 1573-4927
    Schlagwort(e): sepiapterin synthase ; variegation ; purple ; Drosophila melanogaster ; pteridine eye pigments ; drosopterin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract A variegated position effect on the autonomous gene, purple, has been studied enzymologically in Drosophila melanogaster. Sepiapterin synthase, the enzyme system associated with pr +, was examined for activity in different developmental stages of the fly. The results indicate that T(Y:2) pr c5, cn/prc4 cn flies (flies in which pr + has been translocated and which exhibit variegation) have a reduced amount of enzyme activity as compared with both Oregon-R and pr 1 flies. This reduction in activity was not found in larval stages, which suggests that the inactivation process probably occurs in late larval or early pupal stages. The phenotype of the variegated adult has white eyes with red-colored spots and patches where drosopterins occur. The phenotype of the fly carrying the translocation is modified by the presence of additional Y chromosomes. This extends the observation from other systems that extra heterochromatin acts to suppress the variegated position effect. The advantages of studying the variegation by measuring enzyme activity, as well as the phenotypic expression, are several; for example, the developmental time at which variegation occurs may be estimated even though drosopterin synthesis is not occurring.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00484485
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  • 94
    Digitale Medien
    Digitale Medien
    Polymorphism at the G6pd and 6Pgd loci in Drosophila melanogaster. III. Developmental and biochemical aspects (1979)
    Springer
    Biochemical genetics 17 (1979), S. 1131-1144 
    Details
    ISSN: 1573-4927
    Schlagwort(e): Drosophila melanogaster ; enzyme polymorphism ; G6PD ; 6PGD ; enzyme activity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The electrophoretic variants of G6PD and 6PGD isolated from the Bogota Drosophila melanogaster population were characterized developmentally and biochemically. Changes in in vitro enzyme activity during development were comparable to those found for other dehydrogenases: an increase in the larval and adult stage and a decrease in the pupal stage. During the whole life cycle the “S” enzyme of both loci showed a higher activity than the “F” enzyme. MgCl2 had a stimulating effect on the activity of both enzymes whereas their heat stability was decreased. The allozymes of 6PGD had different Vmax's but were comparable with respect to Km values, pH optimum, and stability at 45 C. the allozymes of G6PD showed different Vmax's and differed in stability at 35 C, but had similar Km values and pH optima. As the difference in stability was probably due to differences in molecular structure of the allozymes, the differences in activity found at high pH and high MgCl2 concentration were most probably due to this difference in stability.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00504350
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  • 95
    Digitale Medien
    Digitale Medien
    Kinetics of high-temperature oxidation of boron carbide in oxygen (1976)
    Springer
    Oxidation of metals 10 (1976), S. 85-95 
    Details
    ISSN: 1573-4889
    Schlagwort(e): boron carbide ; oxidation ; kinetics ; chromatography method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Thermogravimetry and gas-adsorption chromatography were used to study the kinetics of formation of solid and gaseous products during the hightemperature oxidation of compact boron carbide in oxygen at 740 Torr. Oxidation resistance was observed at temperatures up to 1200°C. The main oxidation products were B2O3 and CO2. Oxidation was paralinear; the carbon consumption exceeded the consumption of boron as compared to the ratio of these elements in the compound B4C. This difference resulted in carbon depletion of the carbide layer in the substrate near the scale〉.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00614238
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  • 96
    Digitale Medien
    Digitale Medien
    Influence on the oxidation kinetics of metals by control of the structure of oxide scales (1976)
    Springer
    Oxidation of metals 10 (1976), S. 361-376 
    Details
    ISSN: 1573-4889
    Schlagwort(e): metals ; scale structure ; epitaxy ; kinetics ; diffusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract An explanation of the deviation from the parabolic law is the treatment which considers both shortcircuit and lattice diffusion in the oxide scale. In this study we examine how the oxidation kinetics are influenced by changing the structure of the scale of copper oxide in order to confirm the role of short-circuit diffusion in determining the oxidation rate. In addition we explain the oxidation kinetics of copper and nickel by using a model of the scale structure which includes recrystallization and grain growth. Results are as follows: (1) The nucleation and growth behavior of oxide have a direct effect on the structure and in turn the oxidation kinetics due to short-circuit diffusion. (2) A modified treatment is valid in the region where volume diffusion and short-circuit diffusion play an important role in which it is necessary to consider the scale structure such as the grain size distribution and the boundary width. (3) When recrystallization takes place it is necessary to consider the model of a two-layered scale structure which is different in properties and morphology. (4) In this region the rate curves are S-shaped when oxide recrystallization takes place and exhibit a transition from a parabolic to an nth-power relationship (n〉2) when grain growth takes place.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00612048
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Oxidation of tantalum in oxygen-nitrogen and oxygen-inert gas mixtures (1977)
    Springer
    Oxidation of metals 11 (1977), S. 225-239 
    Details
    ISSN: 1573-4889
    Schlagwort(e): tantalum ; oxidation ; high temperature ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of tantalum in oxygen-nitrogen and oxygen-inert gas mixtures at925°C has been studied. The oxygen pressure was close to 0.5 atm in all experiments, and partial pressures of the second component of from 0 to 180 Torr were employed. Spherical specimens were used to provide quantitatively significant kinetic data. A model has been proposed which suggests that the oxygen pressure at the reaction interface close to the metal surface is lower than the external pressure because of the finite permeability of the porous outer oxide layer, and that the inert gas effectively reduces the permeability. The model gives good quantitative agreement with the experimental results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00606059
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Oxidation of cobalt at high temperature (1977)
    Springer
    Oxidation of metals 11 (1977), S. 365-381 
    Details
    ISSN: 1573-4889
    Schlagwort(e): cobalt oxidation ; kinetics ; parabolic rate constant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Precise values of parabolic rate constants of cobalt oxidation have been determined over a wide range of temperature (950–1300°C) and oxygen pressure (6.58× 10−4−0.658 atm). The dependence of the calculated values of parabolic rate constants k″p on oxygen pressure and temperature can be described by the following empirical equation: $$k''_p = const. \cdot {\text{p}}_{O_2 }^{{\text{1/n}}} \cdot exp ( - {\text{E}}_{\text{k}} /RT)$$ The exponent 1/n decreases with an increase in temperature from 1/3.40 at 950°C to 1/3.96 at 1300°C, whereas the activation energy Ek decreases with an increase in the oxygen pressure from 41.7 to 38.1 kcal/mole.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00608018
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Solid-solid reactions, I: Experimental study of barium metatitanate synthesis (1979)
    Springer
    Oxidation of metals 13 (1979), S. 77-88 
    Details
    ISSN: 1573-4889
    Schlagwort(e): BaTiO3 ; kinetics ; solid state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The solid-state reaction between barium carbonate and rutile powders to form barium metatitanate BaTiO3 was studied by thermogravimetric analysis, X rays, and microscopy. Phase-stability domains were drawn in a temperature— $${\text{p}}_{CO_2 } $$ , diagram. The dependence of the reaction kinetics on $${\text{p}}_{CO_2 } $$ , $${\text{p}}_{O_2 } $$ or $${\text{p}}_{N_2 } $$ is discussed. In particular, the rate continuously decreases when $${\text{p}}_{CO_2 } $$ , or $${\text{p}}_{N_2 } $$ increases, but it reaches a maximum as a function of $${\text{p}}_{O_2 } $$ .
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00715871
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    High-temperature oxidation kinetics of Cu-Si alloys containing up to 4.75 wt.% Si in $$p_{{\text{O}}_{\text{2}} } $$ =0.01 atm and pure CO2 (1978)
    Springer
    Oxidation of metals 12 (1978), S. 323-329 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Cu-Si alloys ; oxidation ; kinetics ; silica
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of Cu-Si alloys (containing up to 4.75 wt. % Si) in $${\text{p}}_{O_2 } $$ =0.01 atm from 800 to 1000°C has been investigated using thermogravimetry and other techniques. A 0.04% Si alloy followed a parabolic oxidation law with a rate similar to that of pure Cu. As the Si concentration increased the rate decreased and became irregular owing to SiO2 particles or flakes at the alloy-scale interface. It is considered that sintering of SiO2 particles and rupture of the sinter because of contraction during sintering are responsible for the irregular kinetics. A SiO2 layer forms directly on the 4.75% Si alloy which oxidizes uniformly. The SiO2 was always amorphous. In pure CO2 a similar pattern of amorphous SiO2 particles, flakes, and layers occurs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00603576
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