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  • 1
    Electronic Resource
    Electronic Resource
    Bridged loop–gap resonator: A resonant structure for pulsed ESR transparent to high-frequency radiation (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 752-760 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new and inexpensive X-band resonator structure for pulsed electron-spin resonance and electron-nuclear-double-resonance applications is introduced. The resonator consists of a bridged loop structure and is distinguished by a good reproducibility and reliability. It has a high filling factor and an adjustable Q value and is transparent to radio frequency fields with an upper limit 〉100 MHz. The inner diameter of 5 mm allows convenient sample access of standard 4-mm quartz tubes in the temperature range between 4 and 300 K. Numerical computations of the resonant frequencies, the Q values, and the three-dimensional distributions of the electromagnetic fields are presented. They are based on a discretization method for the solution of Maxwell's equations and include all dielectric elements of the resonator structure. The field homogeneity in the sample area and the influence of the dimensions and the thickness of the metallic layers on field intensity, quality factor, and resonant frequency are determined experimentally. The performance of the resonator is demonstrated by a novel field-swept echo-induced electron-spin-resonance experiment with jumping magnetic field vectors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139822
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  • 2
    Electronic Resource
    Electronic Resource
    General method for adjusting the quality factor of EPR resonators (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4857-4865 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Instrumentation for remote control of the unloaded quality factor, Q0, of a loop-gap resonator is described. The value of Q0 can be lowered by weak inductive coupling of the resonator to a loop of wire that contains a carbon resistor. Replacement of the resistor by a PIN diode permits remote control. Theoretical analysis and experiments are carried out in a context of electron paramagnetic resonance (EPR) spectroscopy at X band. Equivalent circuits are solved numerically and predicted performance confirmed experimentally. Two applications are demonstrated: (a) superfine control of critical coupling of the incoming transmission line to the resonator in excess of −80 dB, and (b) dynamic Q spoiling for reduction of the dead time after a microwave pulse. Possible degradation of EPR system performance by shot noise from the PIN diode is considered. Scant literature suggests that it is very low, and noise from this source could not be detected experimentally. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146165
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  • 3
    Electronic Resource
    Electronic Resource
    A pulsed ENDOR probehead with the bridged loop-gap resonator: Construction and performance (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3360-3367 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A probehead for pulsed electron-nuclear double resonance (ENDOR) experiments with radio-frequency fields up to 20 mT is introduced. The probehead consists of a bridged loop-gap resonator for X-band microwave frequencies surrounded by a solenoidal rf coil that generates the radio-frequency field, and serves as microwave radiation shield. A broad band and a tuned circuit for pulsed ENDOR experiments between 1–200 and 1.5–26 MHz, respectively, are described. Details of the probehead design and characteristics of the rf circuits are given. The performance of the probehead is demonstrated by pulsed ENDOR spectra in solids and liquids between 8 and 150 MHz and by an ENDOR experiment that requires a stepping of the static magnetic field strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141584
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and Opiate Activity in vitro of Five New p-Nitrophenylalanine4-Enkephalin-like Peptides (1983)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 66 (1983), S. 1053-1060 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Converging data obtained in biochemical and pharmacological bioassays for opiate activity are presented for five new enkephalin-like peptides. The main structural features of the analogues, the synthesis of which is described in detail, were the presence of D-alanine or D-serine in position 2, p-nitrophenylalanine in position 4 and of a free C-terminal carboxylic function. Confirming our previous observations [1], the substitution of phenylalanine by p-nitrophenylalanine enhanced the overall opiate activity but decreased the selectivity towards m̈/δ-receptor sites. Tyrosyl-D-alanyl-glycyl-p-nitrophenylalanyl-adamantylalanine was particularly potent in all assays while tyrosyl-D-seryl-glycyl-p-nitrophenylalanyl-leucyl-threonine was very selective in the bioassays on isolated tissues and moderately selective in the binding assay. These results will have to be taken into account in future photoaffinity labelling and quantitative structure-activity relationships (QSAR) studies.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19830660408
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