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  • 1985-1989  (2)
  • 1975-1979  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Modification to the HP 4274/75A LCR meters for investigation of device admittance under heavy forward bias conditions (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1265-1268 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The HP 4274A and HP 4275A LCR meters are widely used in the fields of semiconductor device characterization and component test. A bias voltage can be applied to the test samples either from an external power supply or from the built-in HP-IB controllable voltage source. The total series resistance of the bias filtering circuit should be in the range of about 100 Ω (HP 4275A). Detailed measurements and checking the measuring circuit diagrams revealed that the effective series resistance can be much higher, depending on the measuring range of the bridge. Therefore, admittance measurements on low-ohmic samples, especially Schottky or pn junctions under heavy forward bias conditions, are seriously affected by bias voltage reduction between the front HI/LOW terminals. Thus, e.g., a reduced apparent capacitance is measured. Consequently, the doping concentration near the pn junction will be determined erroneously. To avoid these effects, a bias regulating circuit is inserted into the LCR meters to guarantee the feedthrough of the bias voltage without any attenuation. Examples of admittance vs frequency and doping profiles near the pn junction of quaternary (Ga0.046In0.954As0.1P0.9) diodes are given for explanation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1137989
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic field dependence of the elastic constants in Nd3Se4(abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3933-3933 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Most of the metallic rare-earth chalcogenides of RE3X4 type, where X stands for S, Se, Te, show marked elastic anomalies which appear either in conjunction with a structural transformation or with a magnetic ordering transition. In this contribution we report on results obtained from Nd3Se4 where the elastic constants display a particular magnetic field dependence. Single crystals were grown by a Bridgman–Stockbarger method and the three cubic elastic constants were measured by ultrasonic techniques as function of temperature and in an external magnetic field. The occurrence of magnetic ordering was proved independently by susceptibility measurements. Nd3Se4 has been found to order ferromagnetically at Tc =52 K. In the absence of an external magnetic field approaching Tc from above, the shear elastic constants (C11−C12)/2 softens by about 40%. Below Tc the elastic constants harden again where the increment of C11 follows the Brillouin function of the magnetization. An external magnetic field parallel to the propagation direction of the sound waves affects the elastic anomalies in the paramagnetic as well as in the ferromagnetic phase. Above Tc the sound velocities exhibit a H2 field dependence, as is expected from a magnetoelastic coupling mechanism. At temperatures smaller Tc the field-dependent elastic anomalies are related to the hysteresis loop M(H). The change of the elastic constants as a function of the magnetic field is proportional to the field derivative dM/dH. The coupling coefficient has an opposite sign for the C44 and (C11−C12)/2 shear elastic constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340610
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Cadmium diiodate (1978)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 34 (1978), S. 263-265 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567740878002745
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  • 4
    Electronic Resource
    Electronic Resource
    Continuous determination of ethanol during aerobic cultivation of yeasts (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 20 (1978), S. 799-807 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new sensor for the continuous determination of ethanol during the production of yeasts, growing aerobically on fermentable sugars, is described. The operating principle is based on the detection of ethanol vapor in the exit air. A description of the sensor with a diagram of the measuring electronics is supplied. It was designed for the determination of ethanol contents up to 3 g/liter in aqueous solutions at 30°C. The sensitivity is very high  -  1 ppm ethanol being detectable under these conditions. The aeration rate dose not affect the output signal in a wide range (0.5-2 v/v/m). Besides the unspecific sensitivity of the sensor to other easily oxidizable substances, the influence of the pO2 in the exit air, however, must be taken into account. The application of the sensor is shown in a fed-batch culture of bakers' yeast where aerobic fermentation is caused by increasing the glucose feed rate.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260200603
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