ABSTRACT
Inspired by the growing interest in miniaturized NMR devices and their applications in material science as well as in chemical and biological research, low power rf excitation is explored. 1H NMR spectra have been measured with low power Frank excitation and are compared to spectra obtained by single-pulse excitation. Frank excitation consists of a large number of phase-modulated, constant-amplitude rf-pulses. A Frank sequence is divided into packages of discrete phase wavelets that correspond to a scan across a spectral frequency range. The largely coherent excitation is found experimentally to require less power than white noise excitation. The package structure suggests that individual wavelets can be omitted to skip individual frequency regions in the excitation, converting the white Frank excitation into colored Frank excitation. This work explores different approaches of colored, selective Frank excitation for spectroscopy and imaging. It is motivated by the aim to eliminate the rf amplifier from the NMR spectrometer so as to enable further miniaturization of NMR instruments. Colored Frank excitation bears promise as a low-power modality for solvent signal suppression in spectroscopy and motion tagging in magnetic resonance imaging.
ABSTRACT
In a secondary care hospital in Germany with an in-house microbiology laboratory, an 84-year-old female patient with candidemia was selected for determination of the time periods required for each diagnostic step preceding the application of the first dose of antimycotic treatment. The total time from the beginning of fever to the first dose of fluconazole was 25 hours and 10 minutes. The largest delay occurred between the positive signal of the blood culture bottle during the night and the start of the work-up of the positive blood culture bottle in the morning. Improvements appear to be possible in both clinical and laboratory settings by optimizing pre-analytical, analytical, and post-analytical procedures.
